1 // SPDX-License-Identifier: GPL-2.0
3 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
5 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
7 * Interactivity improvements by Mike Galbraith
8 * (C) 2007 Mike Galbraith <efault@gmx.de>
10 * Various enhancements by Dmitry Adamushko.
11 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
13 * Group scheduling enhancements by Srivatsa Vaddagiri
14 * Copyright IBM Corporation, 2007
15 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
17 * Scaled math optimizations by Thomas Gleixner
18 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
20 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
21 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
26 * Targeted preemption latency for CPU-bound tasks:
28 * NOTE: this latency value is not the same as the concept of
29 * 'timeslice length' - timeslices in CFS are of variable length
30 * and have no persistent notion like in traditional, time-slice
31 * based scheduling concepts.
33 * (to see the precise effective timeslice length of your workload,
34 * run vmstat and monitor the context-switches (cs) field)
36 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
38 unsigned int sysctl_sched_latency = 6000000ULL;
39 static unsigned int normalized_sysctl_sched_latency = 6000000ULL;
42 * The initial- and re-scaling of tunables is configurable
46 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
47 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
48 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
50 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
52 unsigned int sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
55 * Minimal preemption granularity for CPU-bound tasks:
57 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
59 unsigned int sysctl_sched_min_granularity = 750000ULL;
60 static unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
63 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
65 static unsigned int sched_nr_latency = 8;
68 * After fork, child runs first. If set to 0 (default) then
69 * parent will (try to) run first.
71 unsigned int sysctl_sched_child_runs_first __read_mostly;
74 * SCHED_OTHER wake-up granularity.
76 * This option delays the preemption effects of decoupled workloads
77 * and reduces their over-scheduling. Synchronous workloads will still
78 * have immediate wakeup/sleep latencies.
80 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
82 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
83 static unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
85 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
87 int sched_thermal_decay_shift;
88 static int __init setup_sched_thermal_decay_shift(char *str)
92 if (kstrtoint(str, 0, &_shift))
93 pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
95 sched_thermal_decay_shift = clamp(_shift, 0, 10);
98 __setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
102 * For asym packing, by default the lower numbered CPU has higher priority.
104 int __weak arch_asym_cpu_priority(int cpu)
110 * The margin used when comparing utilization with CPU capacity.
114 #define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024)
117 * The margin used when comparing CPU capacities.
118 * is 'cap1' noticeably greater than 'cap2'
122 #define capacity_greater(cap1, cap2) ((cap1) * 1024 > (cap2) * 1078)
125 #ifdef CONFIG_CFS_BANDWIDTH
127 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
128 * each time a cfs_rq requests quota.
130 * Note: in the case that the slice exceeds the runtime remaining (either due
131 * to consumption or the quota being specified to be smaller than the slice)
132 * we will always only issue the remaining available time.
134 * (default: 5 msec, units: microseconds)
136 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
139 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
145 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
151 static inline void update_load_set(struct load_weight *lw, unsigned long w)
158 * Increase the granularity value when there are more CPUs,
159 * because with more CPUs the 'effective latency' as visible
160 * to users decreases. But the relationship is not linear,
161 * so pick a second-best guess by going with the log2 of the
164 * This idea comes from the SD scheduler of Con Kolivas:
166 static unsigned int get_update_sysctl_factor(void)
168 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
171 switch (sysctl_sched_tunable_scaling) {
172 case SCHED_TUNABLESCALING_NONE:
175 case SCHED_TUNABLESCALING_LINEAR:
178 case SCHED_TUNABLESCALING_LOG:
180 factor = 1 + ilog2(cpus);
187 static void update_sysctl(void)
189 unsigned int factor = get_update_sysctl_factor();
191 #define SET_SYSCTL(name) \
192 (sysctl_##name = (factor) * normalized_sysctl_##name)
193 SET_SYSCTL(sched_min_granularity);
194 SET_SYSCTL(sched_latency);
195 SET_SYSCTL(sched_wakeup_granularity);
199 void __init sched_init_granularity(void)
204 #define WMULT_CONST (~0U)
205 #define WMULT_SHIFT 32
207 static void __update_inv_weight(struct load_weight *lw)
211 if (likely(lw->inv_weight))
214 w = scale_load_down(lw->weight);
216 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
218 else if (unlikely(!w))
219 lw->inv_weight = WMULT_CONST;
221 lw->inv_weight = WMULT_CONST / w;
225 * delta_exec * weight / lw.weight
227 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
229 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
230 * we're guaranteed shift stays positive because inv_weight is guaranteed to
231 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
233 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
234 * weight/lw.weight <= 1, and therefore our shift will also be positive.
236 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
238 u64 fact = scale_load_down(weight);
239 u32 fact_hi = (u32)(fact >> 32);
240 int shift = WMULT_SHIFT;
243 __update_inv_weight(lw);
245 if (unlikely(fact_hi)) {
251 fact = mul_u32_u32(fact, lw->inv_weight);
253 fact_hi = (u32)(fact >> 32);
260 return mul_u64_u32_shr(delta_exec, fact, shift);
264 const struct sched_class fair_sched_class;
266 /**************************************************************
267 * CFS operations on generic schedulable entities:
270 #ifdef CONFIG_FAIR_GROUP_SCHED
272 /* Walk up scheduling entities hierarchy */
273 #define for_each_sched_entity(se) \
274 for (; se; se = se->parent)
276 static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
281 if (cfs_rq && task_group_is_autogroup(cfs_rq->tg))
282 autogroup_path(cfs_rq->tg, path, len);
283 else if (cfs_rq && cfs_rq->tg->css.cgroup)
284 cgroup_path(cfs_rq->tg->css.cgroup, path, len);
286 strlcpy(path, "(null)", len);
289 static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
291 struct rq *rq = rq_of(cfs_rq);
292 int cpu = cpu_of(rq);
295 return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
300 * Ensure we either appear before our parent (if already
301 * enqueued) or force our parent to appear after us when it is
302 * enqueued. The fact that we always enqueue bottom-up
303 * reduces this to two cases and a special case for the root
304 * cfs_rq. Furthermore, it also means that we will always reset
305 * tmp_alone_branch either when the branch is connected
306 * to a tree or when we reach the top of the tree
308 if (cfs_rq->tg->parent &&
309 cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
311 * If parent is already on the list, we add the child
312 * just before. Thanks to circular linked property of
313 * the list, this means to put the child at the tail
314 * of the list that starts by parent.
316 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
317 &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
319 * The branch is now connected to its tree so we can
320 * reset tmp_alone_branch to the beginning of the
323 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
327 if (!cfs_rq->tg->parent) {
329 * cfs rq without parent should be put
330 * at the tail of the list.
332 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
333 &rq->leaf_cfs_rq_list);
335 * We have reach the top of a tree so we can reset
336 * tmp_alone_branch to the beginning of the list.
338 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
343 * The parent has not already been added so we want to
344 * make sure that it will be put after us.
345 * tmp_alone_branch points to the begin of the branch
346 * where we will add parent.
348 list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch);
350 * update tmp_alone_branch to points to the new begin
353 rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
357 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
359 if (cfs_rq->on_list) {
360 struct rq *rq = rq_of(cfs_rq);
363 * With cfs_rq being unthrottled/throttled during an enqueue,
364 * it can happen the tmp_alone_branch points the a leaf that
365 * we finally want to del. In this case, tmp_alone_branch moves
366 * to the prev element but it will point to rq->leaf_cfs_rq_list
367 * at the end of the enqueue.
369 if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list)
370 rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev;
372 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
377 static inline void assert_list_leaf_cfs_rq(struct rq *rq)
379 SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list);
382 /* Iterate thr' all leaf cfs_rq's on a runqueue */
383 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
384 list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
387 /* Do the two (enqueued) entities belong to the same group ? */
388 static inline struct cfs_rq *
389 is_same_group(struct sched_entity *se, struct sched_entity *pse)
391 if (se->cfs_rq == pse->cfs_rq)
397 static inline struct sched_entity *parent_entity(struct sched_entity *se)
403 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
405 int se_depth, pse_depth;
408 * preemption test can be made between sibling entities who are in the
409 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
410 * both tasks until we find their ancestors who are siblings of common
414 /* First walk up until both entities are at same depth */
415 se_depth = (*se)->depth;
416 pse_depth = (*pse)->depth;
418 while (se_depth > pse_depth) {
420 *se = parent_entity(*se);
423 while (pse_depth > se_depth) {
425 *pse = parent_entity(*pse);
428 while (!is_same_group(*se, *pse)) {
429 *se = parent_entity(*se);
430 *pse = parent_entity(*pse);
434 #else /* !CONFIG_FAIR_GROUP_SCHED */
436 #define for_each_sched_entity(se) \
437 for (; se; se = NULL)
439 static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
442 strlcpy(path, "(null)", len);
445 static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
450 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
454 static inline void assert_list_leaf_cfs_rq(struct rq *rq)
458 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
459 for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
461 static inline struct sched_entity *parent_entity(struct sched_entity *se)
467 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
471 #endif /* CONFIG_FAIR_GROUP_SCHED */
473 static __always_inline
474 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
476 /**************************************************************
477 * Scheduling class tree data structure manipulation methods:
480 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
482 s64 delta = (s64)(vruntime - max_vruntime);
484 max_vruntime = vruntime;
489 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
491 s64 delta = (s64)(vruntime - min_vruntime);
493 min_vruntime = vruntime;
498 static inline bool entity_before(struct sched_entity *a,
499 struct sched_entity *b)
501 return (s64)(a->vruntime - b->vruntime) < 0;
504 #define __node_2_se(node) \
505 rb_entry((node), struct sched_entity, run_node)
507 static void update_min_vruntime(struct cfs_rq *cfs_rq)
509 struct sched_entity *curr = cfs_rq->curr;
510 struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
512 u64 vruntime = cfs_rq->min_vruntime;
516 vruntime = curr->vruntime;
521 if (leftmost) { /* non-empty tree */
522 struct sched_entity *se = __node_2_se(leftmost);
525 vruntime = se->vruntime;
527 vruntime = min_vruntime(vruntime, se->vruntime);
530 /* ensure we never gain time by being placed backwards. */
531 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
534 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
538 static inline bool __entity_less(struct rb_node *a, const struct rb_node *b)
540 return entity_before(__node_2_se(a), __node_2_se(b));
544 * Enqueue an entity into the rb-tree:
546 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
548 rb_add_cached(&se->run_node, &cfs_rq->tasks_timeline, __entity_less);
551 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
553 rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
556 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
558 struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
563 return __node_2_se(left);
566 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
568 struct rb_node *next = rb_next(&se->run_node);
573 return __node_2_se(next);
576 #ifdef CONFIG_SCHED_DEBUG
577 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
579 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
584 return __node_2_se(last);
587 /**************************************************************
588 * Scheduling class statistics methods:
591 int sched_update_scaling(void)
593 unsigned int factor = get_update_sysctl_factor();
595 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
596 sysctl_sched_min_granularity);
598 #define WRT_SYSCTL(name) \
599 (normalized_sysctl_##name = sysctl_##name / (factor))
600 WRT_SYSCTL(sched_min_granularity);
601 WRT_SYSCTL(sched_latency);
602 WRT_SYSCTL(sched_wakeup_granularity);
612 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
614 if (unlikely(se->load.weight != NICE_0_LOAD))
615 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
621 * The idea is to set a period in which each task runs once.
623 * When there are too many tasks (sched_nr_latency) we have to stretch
624 * this period because otherwise the slices get too small.
626 * p = (nr <= nl) ? l : l*nr/nl
628 static u64 __sched_period(unsigned long nr_running)
630 if (unlikely(nr_running > sched_nr_latency))
631 return nr_running * sysctl_sched_min_granularity;
633 return sysctl_sched_latency;
637 * We calculate the wall-time slice from the period by taking a part
638 * proportional to the weight.
642 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
644 unsigned int nr_running = cfs_rq->nr_running;
647 if (sched_feat(ALT_PERIOD))
648 nr_running = rq_of(cfs_rq)->cfs.h_nr_running;
650 slice = __sched_period(nr_running + !se->on_rq);
652 for_each_sched_entity(se) {
653 struct load_weight *load;
654 struct load_weight lw;
656 cfs_rq = cfs_rq_of(se);
657 load = &cfs_rq->load;
659 if (unlikely(!se->on_rq)) {
662 update_load_add(&lw, se->load.weight);
665 slice = __calc_delta(slice, se->load.weight, load);
668 if (sched_feat(BASE_SLICE))
669 slice = max(slice, (u64)sysctl_sched_min_granularity);
675 * We calculate the vruntime slice of a to-be-inserted task.
679 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
681 return calc_delta_fair(sched_slice(cfs_rq, se), se);
687 static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
688 static unsigned long task_h_load(struct task_struct *p);
689 static unsigned long capacity_of(int cpu);
691 /* Give new sched_entity start runnable values to heavy its load in infant time */
692 void init_entity_runnable_average(struct sched_entity *se)
694 struct sched_avg *sa = &se->avg;
696 memset(sa, 0, sizeof(*sa));
699 * Tasks are initialized with full load to be seen as heavy tasks until
700 * they get a chance to stabilize to their real load level.
701 * Group entities are initialized with zero load to reflect the fact that
702 * nothing has been attached to the task group yet.
704 if (entity_is_task(se))
705 sa->load_avg = scale_load_down(se->load.weight);
707 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
710 static void attach_entity_cfs_rq(struct sched_entity *se);
713 * With new tasks being created, their initial util_avgs are extrapolated
714 * based on the cfs_rq's current util_avg:
716 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
718 * However, in many cases, the above util_avg does not give a desired
719 * value. Moreover, the sum of the util_avgs may be divergent, such
720 * as when the series is a harmonic series.
722 * To solve this problem, we also cap the util_avg of successive tasks to
723 * only 1/2 of the left utilization budget:
725 * util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
727 * where n denotes the nth task and cpu_scale the CPU capacity.
729 * For example, for a CPU with 1024 of capacity, a simplest series from
730 * the beginning would be like:
732 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
733 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
735 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
736 * if util_avg > util_avg_cap.
738 void post_init_entity_util_avg(struct task_struct *p)
740 struct sched_entity *se = &p->se;
741 struct cfs_rq *cfs_rq = cfs_rq_of(se);
742 struct sched_avg *sa = &se->avg;
743 long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)));
744 long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
747 if (cfs_rq->avg.util_avg != 0) {
748 sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
749 sa->util_avg /= (cfs_rq->avg.load_avg + 1);
751 if (sa->util_avg > cap)
758 sa->runnable_avg = sa->util_avg;
760 if (p->sched_class != &fair_sched_class) {
762 * For !fair tasks do:
764 update_cfs_rq_load_avg(now, cfs_rq);
765 attach_entity_load_avg(cfs_rq, se);
766 switched_from_fair(rq, p);
768 * such that the next switched_to_fair() has the
771 se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
775 attach_entity_cfs_rq(se);
778 #else /* !CONFIG_SMP */
779 void init_entity_runnable_average(struct sched_entity *se)
782 void post_init_entity_util_avg(struct task_struct *p)
785 static void update_tg_load_avg(struct cfs_rq *cfs_rq)
788 #endif /* CONFIG_SMP */
791 * Update the current task's runtime statistics.
793 static void update_curr(struct cfs_rq *cfs_rq)
795 struct sched_entity *curr = cfs_rq->curr;
796 u64 now = rq_clock_task(rq_of(cfs_rq));
802 delta_exec = now - curr->exec_start;
803 if (unlikely((s64)delta_exec <= 0))
806 curr->exec_start = now;
808 schedstat_set(curr->statistics.exec_max,
809 max(delta_exec, curr->statistics.exec_max));
811 curr->sum_exec_runtime += delta_exec;
812 schedstat_add(cfs_rq->exec_clock, delta_exec);
814 curr->vruntime += calc_delta_fair(delta_exec, curr);
815 update_min_vruntime(cfs_rq);
817 if (entity_is_task(curr)) {
818 struct task_struct *curtask = task_of(curr);
820 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
821 cgroup_account_cputime(curtask, delta_exec);
822 account_group_exec_runtime(curtask, delta_exec);
825 account_cfs_rq_runtime(cfs_rq, delta_exec);
828 static void update_curr_fair(struct rq *rq)
830 update_curr(cfs_rq_of(&rq->curr->se));
834 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
836 u64 wait_start, prev_wait_start;
838 if (!schedstat_enabled())
841 wait_start = rq_clock(rq_of(cfs_rq));
842 prev_wait_start = schedstat_val(se->statistics.wait_start);
844 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
845 likely(wait_start > prev_wait_start))
846 wait_start -= prev_wait_start;
848 __schedstat_set(se->statistics.wait_start, wait_start);
852 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
854 struct task_struct *p;
857 if (!schedstat_enabled())
861 * When the sched_schedstat changes from 0 to 1, some sched se
862 * maybe already in the runqueue, the se->statistics.wait_start
863 * will be 0.So it will let the delta wrong. We need to avoid this
866 if (unlikely(!schedstat_val(se->statistics.wait_start)))
869 delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
871 if (entity_is_task(se)) {
873 if (task_on_rq_migrating(p)) {
875 * Preserve migrating task's wait time so wait_start
876 * time stamp can be adjusted to accumulate wait time
877 * prior to migration.
879 __schedstat_set(se->statistics.wait_start, delta);
882 trace_sched_stat_wait(p, delta);
885 __schedstat_set(se->statistics.wait_max,
886 max(schedstat_val(se->statistics.wait_max), delta));
887 __schedstat_inc(se->statistics.wait_count);
888 __schedstat_add(se->statistics.wait_sum, delta);
889 __schedstat_set(se->statistics.wait_start, 0);
893 update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
895 struct task_struct *tsk = NULL;
896 u64 sleep_start, block_start;
898 if (!schedstat_enabled())
901 sleep_start = schedstat_val(se->statistics.sleep_start);
902 block_start = schedstat_val(se->statistics.block_start);
904 if (entity_is_task(se))
908 u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
913 if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
914 __schedstat_set(se->statistics.sleep_max, delta);
916 __schedstat_set(se->statistics.sleep_start, 0);
917 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
920 account_scheduler_latency(tsk, delta >> 10, 1);
921 trace_sched_stat_sleep(tsk, delta);
925 u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
930 if (unlikely(delta > schedstat_val(se->statistics.block_max)))
931 __schedstat_set(se->statistics.block_max, delta);
933 __schedstat_set(se->statistics.block_start, 0);
934 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
937 if (tsk->in_iowait) {
938 __schedstat_add(se->statistics.iowait_sum, delta);
939 __schedstat_inc(se->statistics.iowait_count);
940 trace_sched_stat_iowait(tsk, delta);
943 trace_sched_stat_blocked(tsk, delta);
946 * Blocking time is in units of nanosecs, so shift by
947 * 20 to get a milliseconds-range estimation of the
948 * amount of time that the task spent sleeping:
950 if (unlikely(prof_on == SLEEP_PROFILING)) {
951 profile_hits(SLEEP_PROFILING,
952 (void *)get_wchan(tsk),
955 account_scheduler_latency(tsk, delta >> 10, 0);
961 * Task is being enqueued - update stats:
964 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
966 if (!schedstat_enabled())
970 * Are we enqueueing a waiting task? (for current tasks
971 * a dequeue/enqueue event is a NOP)
973 if (se != cfs_rq->curr)
974 update_stats_wait_start(cfs_rq, se);
976 if (flags & ENQUEUE_WAKEUP)
977 update_stats_enqueue_sleeper(cfs_rq, se);
981 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
984 if (!schedstat_enabled())
988 * Mark the end of the wait period if dequeueing a
991 if (se != cfs_rq->curr)
992 update_stats_wait_end(cfs_rq, se);
994 if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
995 struct task_struct *tsk = task_of(se);
998 /* XXX racy against TTWU */
999 state = READ_ONCE(tsk->__state);
1000 if (state & TASK_INTERRUPTIBLE)
1001 __schedstat_set(se->statistics.sleep_start,
1002 rq_clock(rq_of(cfs_rq)));
1003 if (state & TASK_UNINTERRUPTIBLE)
1004 __schedstat_set(se->statistics.block_start,
1005 rq_clock(rq_of(cfs_rq)));
1010 * We are picking a new current task - update its stats:
1013 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1016 * We are starting a new run period:
1018 se->exec_start = rq_clock_task(rq_of(cfs_rq));
1021 /**************************************************
1022 * Scheduling class queueing methods:
1025 #ifdef CONFIG_NUMA_BALANCING
1027 * Approximate time to scan a full NUMA task in ms. The task scan period is
1028 * calculated based on the tasks virtual memory size and
1029 * numa_balancing_scan_size.
1031 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
1032 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1034 /* Portion of address space to scan in MB */
1035 unsigned int sysctl_numa_balancing_scan_size = 256;
1037 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
1038 unsigned int sysctl_numa_balancing_scan_delay = 1000;
1041 refcount_t refcount;
1043 spinlock_t lock; /* nr_tasks, tasks */
1048 struct rcu_head rcu;
1049 unsigned long total_faults;
1050 unsigned long max_faults_cpu;
1052 * Faults_cpu is used to decide whether memory should move
1053 * towards the CPU. As a consequence, these stats are weighted
1054 * more by CPU use than by memory faults.
1056 unsigned long *faults_cpu;
1057 unsigned long faults[];
1061 * For functions that can be called in multiple contexts that permit reading
1062 * ->numa_group (see struct task_struct for locking rules).
1064 static struct numa_group *deref_task_numa_group(struct task_struct *p)
1066 return rcu_dereference_check(p->numa_group, p == current ||
1067 (lockdep_is_held(__rq_lockp(task_rq(p))) && !READ_ONCE(p->on_cpu)));
1070 static struct numa_group *deref_curr_numa_group(struct task_struct *p)
1072 return rcu_dereference_protected(p->numa_group, p == current);
1075 static inline unsigned long group_faults_priv(struct numa_group *ng);
1076 static inline unsigned long group_faults_shared(struct numa_group *ng);
1078 static unsigned int task_nr_scan_windows(struct task_struct *p)
1080 unsigned long rss = 0;
1081 unsigned long nr_scan_pages;
1084 * Calculations based on RSS as non-present and empty pages are skipped
1085 * by the PTE scanner and NUMA hinting faults should be trapped based
1088 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
1089 rss = get_mm_rss(p->mm);
1091 rss = nr_scan_pages;
1093 rss = round_up(rss, nr_scan_pages);
1094 return rss / nr_scan_pages;
1097 /* For sanity's sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
1098 #define MAX_SCAN_WINDOW 2560
1100 static unsigned int task_scan_min(struct task_struct *p)
1102 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1103 unsigned int scan, floor;
1104 unsigned int windows = 1;
1106 if (scan_size < MAX_SCAN_WINDOW)
1107 windows = MAX_SCAN_WINDOW / scan_size;
1108 floor = 1000 / windows;
1110 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
1111 return max_t(unsigned int, floor, scan);
1114 static unsigned int task_scan_start(struct task_struct *p)
1116 unsigned long smin = task_scan_min(p);
1117 unsigned long period = smin;
1118 struct numa_group *ng;
1120 /* Scale the maximum scan period with the amount of shared memory. */
1122 ng = rcu_dereference(p->numa_group);
1124 unsigned long shared = group_faults_shared(ng);
1125 unsigned long private = group_faults_priv(ng);
1127 period *= refcount_read(&ng->refcount);
1128 period *= shared + 1;
1129 period /= private + shared + 1;
1133 return max(smin, period);
1136 static unsigned int task_scan_max(struct task_struct *p)
1138 unsigned long smin = task_scan_min(p);
1140 struct numa_group *ng;
1142 /* Watch for min being lower than max due to floor calculations */
1143 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1145 /* Scale the maximum scan period with the amount of shared memory. */
1146 ng = deref_curr_numa_group(p);
1148 unsigned long shared = group_faults_shared(ng);
1149 unsigned long private = group_faults_priv(ng);
1150 unsigned long period = smax;
1152 period *= refcount_read(&ng->refcount);
1153 period *= shared + 1;
1154 period /= private + shared + 1;
1156 smax = max(smax, period);
1159 return max(smin, smax);
1162 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
1164 rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE);
1165 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
1168 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
1170 rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE);
1171 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
1174 /* Shared or private faults. */
1175 #define NR_NUMA_HINT_FAULT_TYPES 2
1177 /* Memory and CPU locality */
1178 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1180 /* Averaged statistics, and temporary buffers. */
1181 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1183 pid_t task_numa_group_id(struct task_struct *p)
1185 struct numa_group *ng;
1189 ng = rcu_dereference(p->numa_group);
1198 * The averaged statistics, shared & private, memory & CPU,
1199 * occupy the first half of the array. The second half of the
1200 * array is for current counters, which are averaged into the
1201 * first set by task_numa_placement.
1203 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1205 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1208 static inline unsigned long task_faults(struct task_struct *p, int nid)
1210 if (!p->numa_faults)
1213 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1214 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1217 static inline unsigned long group_faults(struct task_struct *p, int nid)
1219 struct numa_group *ng = deref_task_numa_group(p);
1224 return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1225 ng->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1228 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
1230 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
1231 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1234 static inline unsigned long group_faults_priv(struct numa_group *ng)
1236 unsigned long faults = 0;
1239 for_each_online_node(node) {
1240 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
1246 static inline unsigned long group_faults_shared(struct numa_group *ng)
1248 unsigned long faults = 0;
1251 for_each_online_node(node) {
1252 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
1259 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1260 * considered part of a numa group's pseudo-interleaving set. Migrations
1261 * between these nodes are slowed down, to allow things to settle down.
1263 #define ACTIVE_NODE_FRACTION 3
1265 static bool numa_is_active_node(int nid, struct numa_group *ng)
1267 return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
1270 /* Handle placement on systems where not all nodes are directly connected. */
1271 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
1272 int maxdist, bool task)
1274 unsigned long score = 0;
1278 * All nodes are directly connected, and the same distance
1279 * from each other. No need for fancy placement algorithms.
1281 if (sched_numa_topology_type == NUMA_DIRECT)
1285 * This code is called for each node, introducing N^2 complexity,
1286 * which should be ok given the number of nodes rarely exceeds 8.
1288 for_each_online_node(node) {
1289 unsigned long faults;
1290 int dist = node_distance(nid, node);
1293 * The furthest away nodes in the system are not interesting
1294 * for placement; nid was already counted.
1296 if (dist == sched_max_numa_distance || node == nid)
1300 * On systems with a backplane NUMA topology, compare groups
1301 * of nodes, and move tasks towards the group with the most
1302 * memory accesses. When comparing two nodes at distance
1303 * "hoplimit", only nodes closer by than "hoplimit" are part
1304 * of each group. Skip other nodes.
1306 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1310 /* Add up the faults from nearby nodes. */
1312 faults = task_faults(p, node);
1314 faults = group_faults(p, node);
1317 * On systems with a glueless mesh NUMA topology, there are
1318 * no fixed "groups of nodes". Instead, nodes that are not
1319 * directly connected bounce traffic through intermediate
1320 * nodes; a numa_group can occupy any set of nodes.
1321 * The further away a node is, the less the faults count.
1322 * This seems to result in good task placement.
1324 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1325 faults *= (sched_max_numa_distance - dist);
1326 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1336 * These return the fraction of accesses done by a particular task, or
1337 * task group, on a particular numa node. The group weight is given a
1338 * larger multiplier, in order to group tasks together that are almost
1339 * evenly spread out between numa nodes.
1341 static inline unsigned long task_weight(struct task_struct *p, int nid,
1344 unsigned long faults, total_faults;
1346 if (!p->numa_faults)
1349 total_faults = p->total_numa_faults;
1354 faults = task_faults(p, nid);
1355 faults += score_nearby_nodes(p, nid, dist, true);
1357 return 1000 * faults / total_faults;
1360 static inline unsigned long group_weight(struct task_struct *p, int nid,
1363 struct numa_group *ng = deref_task_numa_group(p);
1364 unsigned long faults, total_faults;
1369 total_faults = ng->total_faults;
1374 faults = group_faults(p, nid);
1375 faults += score_nearby_nodes(p, nid, dist, false);
1377 return 1000 * faults / total_faults;
1380 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1381 int src_nid, int dst_cpu)
1383 struct numa_group *ng = deref_curr_numa_group(p);
1384 int dst_nid = cpu_to_node(dst_cpu);
1385 int last_cpupid, this_cpupid;
1387 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1388 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1391 * Allow first faults or private faults to migrate immediately early in
1392 * the lifetime of a task. The magic number 4 is based on waiting for
1393 * two full passes of the "multi-stage node selection" test that is
1396 if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= 4) &&
1397 (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid)))
1401 * Multi-stage node selection is used in conjunction with a periodic
1402 * migration fault to build a temporal task<->page relation. By using
1403 * a two-stage filter we remove short/unlikely relations.
1405 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1406 * a task's usage of a particular page (n_p) per total usage of this
1407 * page (n_t) (in a given time-span) to a probability.
1409 * Our periodic faults will sample this probability and getting the
1410 * same result twice in a row, given these samples are fully
1411 * independent, is then given by P(n)^2, provided our sample period
1412 * is sufficiently short compared to the usage pattern.
1414 * This quadric squishes small probabilities, making it less likely we
1415 * act on an unlikely task<->page relation.
1417 if (!cpupid_pid_unset(last_cpupid) &&
1418 cpupid_to_nid(last_cpupid) != dst_nid)
1421 /* Always allow migrate on private faults */
1422 if (cpupid_match_pid(p, last_cpupid))
1425 /* A shared fault, but p->numa_group has not been set up yet. */
1430 * Destination node is much more heavily used than the source
1431 * node? Allow migration.
1433 if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
1434 ACTIVE_NODE_FRACTION)
1438 * Distribute memory according to CPU & memory use on each node,
1439 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1441 * faults_cpu(dst) 3 faults_cpu(src)
1442 * --------------- * - > ---------------
1443 * faults_mem(dst) 4 faults_mem(src)
1445 return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
1446 group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1450 * 'numa_type' describes the node at the moment of load balancing.
1453 /* The node has spare capacity that can be used to run more tasks. */
1456 * The node is fully used and the tasks don't compete for more CPU
1457 * cycles. Nevertheless, some tasks might wait before running.
1461 * The node is overloaded and can't provide expected CPU cycles to all
1467 /* Cached statistics for all CPUs within a node */
1470 unsigned long runnable;
1472 /* Total compute capacity of CPUs on a node */
1473 unsigned long compute_capacity;
1474 unsigned int nr_running;
1475 unsigned int weight;
1476 enum numa_type node_type;
1480 static inline bool is_core_idle(int cpu)
1482 #ifdef CONFIG_SCHED_SMT
1485 for_each_cpu(sibling, cpu_smt_mask(cpu)) {
1489 if (!idle_cpu(sibling))
1497 struct task_numa_env {
1498 struct task_struct *p;
1500 int src_cpu, src_nid;
1501 int dst_cpu, dst_nid;
1503 struct numa_stats src_stats, dst_stats;
1508 struct task_struct *best_task;
1513 static unsigned long cpu_load(struct rq *rq);
1514 static unsigned long cpu_runnable(struct rq *rq);
1515 static unsigned long cpu_util(int cpu);
1516 static inline long adjust_numa_imbalance(int imbalance,
1517 int dst_running, int dst_weight);
1520 numa_type numa_classify(unsigned int imbalance_pct,
1521 struct numa_stats *ns)
1523 if ((ns->nr_running > ns->weight) &&
1524 (((ns->compute_capacity * 100) < (ns->util * imbalance_pct)) ||
1525 ((ns->compute_capacity * imbalance_pct) < (ns->runnable * 100))))
1526 return node_overloaded;
1528 if ((ns->nr_running < ns->weight) ||
1529 (((ns->compute_capacity * 100) > (ns->util * imbalance_pct)) &&
1530 ((ns->compute_capacity * imbalance_pct) > (ns->runnable * 100))))
1531 return node_has_spare;
1533 return node_fully_busy;
1536 #ifdef CONFIG_SCHED_SMT
1537 /* Forward declarations of select_idle_sibling helpers */
1538 static inline bool test_idle_cores(int cpu, bool def);
1539 static inline int numa_idle_core(int idle_core, int cpu)
1541 if (!static_branch_likely(&sched_smt_present) ||
1542 idle_core >= 0 || !test_idle_cores(cpu, false))
1546 * Prefer cores instead of packing HT siblings
1547 * and triggering future load balancing.
1549 if (is_core_idle(cpu))
1555 static inline int numa_idle_core(int idle_core, int cpu)
1562 * Gather all necessary information to make NUMA balancing placement
1563 * decisions that are compatible with standard load balancer. This
1564 * borrows code and logic from update_sg_lb_stats but sharing a
1565 * common implementation is impractical.
1567 static void update_numa_stats(struct task_numa_env *env,
1568 struct numa_stats *ns, int nid,
1571 int cpu, idle_core = -1;
1573 memset(ns, 0, sizeof(*ns));
1577 for_each_cpu(cpu, cpumask_of_node(nid)) {
1578 struct rq *rq = cpu_rq(cpu);
1580 ns->load += cpu_load(rq);
1581 ns->runnable += cpu_runnable(rq);
1582 ns->util += cpu_util(cpu);
1583 ns->nr_running += rq->cfs.h_nr_running;
1584 ns->compute_capacity += capacity_of(cpu);
1586 if (find_idle && !rq->nr_running && idle_cpu(cpu)) {
1587 if (READ_ONCE(rq->numa_migrate_on) ||
1588 !cpumask_test_cpu(cpu, env->p->cpus_ptr))
1591 if (ns->idle_cpu == -1)
1594 idle_core = numa_idle_core(idle_core, cpu);
1599 ns->weight = cpumask_weight(cpumask_of_node(nid));
1601 ns->node_type = numa_classify(env->imbalance_pct, ns);
1604 ns->idle_cpu = idle_core;
1607 static void task_numa_assign(struct task_numa_env *env,
1608 struct task_struct *p, long imp)
1610 struct rq *rq = cpu_rq(env->dst_cpu);
1612 /* Check if run-queue part of active NUMA balance. */
1613 if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1)) {
1615 int start = env->dst_cpu;
1617 /* Find alternative idle CPU. */
1618 for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start) {
1619 if (cpu == env->best_cpu || !idle_cpu(cpu) ||
1620 !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
1625 rq = cpu_rq(env->dst_cpu);
1626 if (!xchg(&rq->numa_migrate_on, 1))
1630 /* Failed to find an alternative idle CPU */
1636 * Clear previous best_cpu/rq numa-migrate flag, since task now
1637 * found a better CPU to move/swap.
1639 if (env->best_cpu != -1 && env->best_cpu != env->dst_cpu) {
1640 rq = cpu_rq(env->best_cpu);
1641 WRITE_ONCE(rq->numa_migrate_on, 0);
1645 put_task_struct(env->best_task);
1650 env->best_imp = imp;
1651 env->best_cpu = env->dst_cpu;
1654 static bool load_too_imbalanced(long src_load, long dst_load,
1655 struct task_numa_env *env)
1658 long orig_src_load, orig_dst_load;
1659 long src_capacity, dst_capacity;
1662 * The load is corrected for the CPU capacity available on each node.
1665 * ------------ vs ---------
1666 * src_capacity dst_capacity
1668 src_capacity = env->src_stats.compute_capacity;
1669 dst_capacity = env->dst_stats.compute_capacity;
1671 imb = abs(dst_load * src_capacity - src_load * dst_capacity);
1673 orig_src_load = env->src_stats.load;
1674 orig_dst_load = env->dst_stats.load;
1676 old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
1678 /* Would this change make things worse? */
1679 return (imb > old_imb);
1683 * Maximum NUMA importance can be 1998 (2*999);
1684 * SMALLIMP @ 30 would be close to 1998/64.
1685 * Used to deter task migration.
1690 * This checks if the overall compute and NUMA accesses of the system would
1691 * be improved if the source tasks was migrated to the target dst_cpu taking
1692 * into account that it might be best if task running on the dst_cpu should
1693 * be exchanged with the source task
1695 static bool task_numa_compare(struct task_numa_env *env,
1696 long taskimp, long groupimp, bool maymove)
1698 struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p);
1699 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1700 long imp = p_ng ? groupimp : taskimp;
1701 struct task_struct *cur;
1702 long src_load, dst_load;
1703 int dist = env->dist;
1706 bool stopsearch = false;
1708 if (READ_ONCE(dst_rq->numa_migrate_on))
1712 cur = rcu_dereference(dst_rq->curr);
1713 if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1717 * Because we have preemption enabled we can get migrated around and
1718 * end try selecting ourselves (current == env->p) as a swap candidate.
1720 if (cur == env->p) {
1726 if (maymove && moveimp >= env->best_imp)
1732 /* Skip this swap candidate if cannot move to the source cpu. */
1733 if (!cpumask_test_cpu(env->src_cpu, cur->cpus_ptr))
1737 * Skip this swap candidate if it is not moving to its preferred
1738 * node and the best task is.
1740 if (env->best_task &&
1741 env->best_task->numa_preferred_nid == env->src_nid &&
1742 cur->numa_preferred_nid != env->src_nid) {
1747 * "imp" is the fault differential for the source task between the
1748 * source and destination node. Calculate the total differential for
1749 * the source task and potential destination task. The more negative
1750 * the value is, the more remote accesses that would be expected to
1751 * be incurred if the tasks were swapped.
1753 * If dst and source tasks are in the same NUMA group, or not
1754 * in any group then look only at task weights.
1756 cur_ng = rcu_dereference(cur->numa_group);
1757 if (cur_ng == p_ng) {
1758 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1759 task_weight(cur, env->dst_nid, dist);
1761 * Add some hysteresis to prevent swapping the
1762 * tasks within a group over tiny differences.
1768 * Compare the group weights. If a task is all by itself
1769 * (not part of a group), use the task weight instead.
1772 imp += group_weight(cur, env->src_nid, dist) -
1773 group_weight(cur, env->dst_nid, dist);
1775 imp += task_weight(cur, env->src_nid, dist) -
1776 task_weight(cur, env->dst_nid, dist);
1779 /* Discourage picking a task already on its preferred node */
1780 if (cur->numa_preferred_nid == env->dst_nid)
1784 * Encourage picking a task that moves to its preferred node.
1785 * This potentially makes imp larger than it's maximum of
1786 * 1998 (see SMALLIMP and task_weight for why) but in this
1787 * case, it does not matter.
1789 if (cur->numa_preferred_nid == env->src_nid)
1792 if (maymove && moveimp > imp && moveimp > env->best_imp) {
1799 * Prefer swapping with a task moving to its preferred node over a
1802 if (env->best_task && cur->numa_preferred_nid == env->src_nid &&
1803 env->best_task->numa_preferred_nid != env->src_nid) {
1808 * If the NUMA importance is less than SMALLIMP,
1809 * task migration might only result in ping pong
1810 * of tasks and also hurt performance due to cache
1813 if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
1817 * In the overloaded case, try and keep the load balanced.
1819 load = task_h_load(env->p) - task_h_load(cur);
1823 dst_load = env->dst_stats.load + load;
1824 src_load = env->src_stats.load - load;
1826 if (load_too_imbalanced(src_load, dst_load, env))
1830 /* Evaluate an idle CPU for a task numa move. */
1832 int cpu = env->dst_stats.idle_cpu;
1834 /* Nothing cached so current CPU went idle since the search. */
1839 * If the CPU is no longer truly idle and the previous best CPU
1840 * is, keep using it.
1842 if (!idle_cpu(cpu) && env->best_cpu >= 0 &&
1843 idle_cpu(env->best_cpu)) {
1844 cpu = env->best_cpu;
1850 task_numa_assign(env, cur, imp);
1853 * If a move to idle is allowed because there is capacity or load
1854 * balance improves then stop the search. While a better swap
1855 * candidate may exist, a search is not free.
1857 if (maymove && !cur && env->best_cpu >= 0 && idle_cpu(env->best_cpu))
1861 * If a swap candidate must be identified and the current best task
1862 * moves its preferred node then stop the search.
1864 if (!maymove && env->best_task &&
1865 env->best_task->numa_preferred_nid == env->src_nid) {
1874 static void task_numa_find_cpu(struct task_numa_env *env,
1875 long taskimp, long groupimp)
1877 bool maymove = false;
1881 * If dst node has spare capacity, then check if there is an
1882 * imbalance that would be overruled by the load balancer.
1884 if (env->dst_stats.node_type == node_has_spare) {
1885 unsigned int imbalance;
1886 int src_running, dst_running;
1889 * Would movement cause an imbalance? Note that if src has
1890 * more running tasks that the imbalance is ignored as the
1891 * move improves the imbalance from the perspective of the
1892 * CPU load balancer.
1894 src_running = env->src_stats.nr_running - 1;
1895 dst_running = env->dst_stats.nr_running + 1;
1896 imbalance = max(0, dst_running - src_running);
1897 imbalance = adjust_numa_imbalance(imbalance, dst_running,
1898 env->dst_stats.weight);
1900 /* Use idle CPU if there is no imbalance */
1903 if (env->dst_stats.idle_cpu >= 0) {
1904 env->dst_cpu = env->dst_stats.idle_cpu;
1905 task_numa_assign(env, NULL, 0);
1910 long src_load, dst_load, load;
1912 * If the improvement from just moving env->p direction is better
1913 * than swapping tasks around, check if a move is possible.
1915 load = task_h_load(env->p);
1916 dst_load = env->dst_stats.load + load;
1917 src_load = env->src_stats.load - load;
1918 maymove = !load_too_imbalanced(src_load, dst_load, env);
1921 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1922 /* Skip this CPU if the source task cannot migrate */
1923 if (!cpumask_test_cpu(cpu, env->p->cpus_ptr))
1927 if (task_numa_compare(env, taskimp, groupimp, maymove))
1932 static int task_numa_migrate(struct task_struct *p)
1934 struct task_numa_env env = {
1937 .src_cpu = task_cpu(p),
1938 .src_nid = task_node(p),
1940 .imbalance_pct = 112,
1946 unsigned long taskweight, groupweight;
1947 struct sched_domain *sd;
1948 long taskimp, groupimp;
1949 struct numa_group *ng;
1954 * Pick the lowest SD_NUMA domain, as that would have the smallest
1955 * imbalance and would be the first to start moving tasks about.
1957 * And we want to avoid any moving of tasks about, as that would create
1958 * random movement of tasks -- counter the numa conditions we're trying
1962 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1964 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1968 * Cpusets can break the scheduler domain tree into smaller
1969 * balance domains, some of which do not cross NUMA boundaries.
1970 * Tasks that are "trapped" in such domains cannot be migrated
1971 * elsewhere, so there is no point in (re)trying.
1973 if (unlikely(!sd)) {
1974 sched_setnuma(p, task_node(p));
1978 env.dst_nid = p->numa_preferred_nid;
1979 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1980 taskweight = task_weight(p, env.src_nid, dist);
1981 groupweight = group_weight(p, env.src_nid, dist);
1982 update_numa_stats(&env, &env.src_stats, env.src_nid, false);
1983 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1984 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1985 update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
1987 /* Try to find a spot on the preferred nid. */
1988 task_numa_find_cpu(&env, taskimp, groupimp);
1991 * Look at other nodes in these cases:
1992 * - there is no space available on the preferred_nid
1993 * - the task is part of a numa_group that is interleaved across
1994 * multiple NUMA nodes; in order to better consolidate the group,
1995 * we need to check other locations.
1997 ng = deref_curr_numa_group(p);
1998 if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) {
1999 for_each_online_node(nid) {
2000 if (nid == env.src_nid || nid == p->numa_preferred_nid)
2003 dist = node_distance(env.src_nid, env.dst_nid);
2004 if (sched_numa_topology_type == NUMA_BACKPLANE &&
2006 taskweight = task_weight(p, env.src_nid, dist);
2007 groupweight = group_weight(p, env.src_nid, dist);
2010 /* Only consider nodes where both task and groups benefit */
2011 taskimp = task_weight(p, nid, dist) - taskweight;
2012 groupimp = group_weight(p, nid, dist) - groupweight;
2013 if (taskimp < 0 && groupimp < 0)
2018 update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
2019 task_numa_find_cpu(&env, taskimp, groupimp);
2024 * If the task is part of a workload that spans multiple NUMA nodes,
2025 * and is migrating into one of the workload's active nodes, remember
2026 * this node as the task's preferred numa node, so the workload can
2028 * A task that migrated to a second choice node will be better off
2029 * trying for a better one later. Do not set the preferred node here.
2032 if (env.best_cpu == -1)
2035 nid = cpu_to_node(env.best_cpu);
2037 if (nid != p->numa_preferred_nid)
2038 sched_setnuma(p, nid);
2041 /* No better CPU than the current one was found. */
2042 if (env.best_cpu == -1) {
2043 trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
2047 best_rq = cpu_rq(env.best_cpu);
2048 if (env.best_task == NULL) {
2049 ret = migrate_task_to(p, env.best_cpu);
2050 WRITE_ONCE(best_rq->numa_migrate_on, 0);
2052 trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
2056 ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
2057 WRITE_ONCE(best_rq->numa_migrate_on, 0);
2060 trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
2061 put_task_struct(env.best_task);
2065 /* Attempt to migrate a task to a CPU on the preferred node. */
2066 static void numa_migrate_preferred(struct task_struct *p)
2068 unsigned long interval = HZ;
2070 /* This task has no NUMA fault statistics yet */
2071 if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults))
2074 /* Periodically retry migrating the task to the preferred node */
2075 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
2076 p->numa_migrate_retry = jiffies + interval;
2078 /* Success if task is already running on preferred CPU */
2079 if (task_node(p) == p->numa_preferred_nid)
2082 /* Otherwise, try migrate to a CPU on the preferred node */
2083 task_numa_migrate(p);
2087 * Find out how many nodes on the workload is actively running on. Do this by
2088 * tracking the nodes from which NUMA hinting faults are triggered. This can
2089 * be different from the set of nodes where the workload's memory is currently
2092 static void numa_group_count_active_nodes(struct numa_group *numa_group)
2094 unsigned long faults, max_faults = 0;
2095 int nid, active_nodes = 0;
2097 for_each_online_node(nid) {
2098 faults = group_faults_cpu(numa_group, nid);
2099 if (faults > max_faults)
2100 max_faults = faults;
2103 for_each_online_node(nid) {
2104 faults = group_faults_cpu(numa_group, nid);
2105 if (faults * ACTIVE_NODE_FRACTION > max_faults)
2109 numa_group->max_faults_cpu = max_faults;
2110 numa_group->active_nodes = active_nodes;
2114 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
2115 * increments. The more local the fault statistics are, the higher the scan
2116 * period will be for the next scan window. If local/(local+remote) ratio is
2117 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
2118 * the scan period will decrease. Aim for 70% local accesses.
2120 #define NUMA_PERIOD_SLOTS 10
2121 #define NUMA_PERIOD_THRESHOLD 7
2124 * Increase the scan period (slow down scanning) if the majority of
2125 * our memory is already on our local node, or if the majority of
2126 * the page accesses are shared with other processes.
2127 * Otherwise, decrease the scan period.
2129 static void update_task_scan_period(struct task_struct *p,
2130 unsigned long shared, unsigned long private)
2132 unsigned int period_slot;
2133 int lr_ratio, ps_ratio;
2136 unsigned long remote = p->numa_faults_locality[0];
2137 unsigned long local = p->numa_faults_locality[1];
2140 * If there were no record hinting faults then either the task is
2141 * completely idle or all activity is areas that are not of interest
2142 * to automatic numa balancing. Related to that, if there were failed
2143 * migration then it implies we are migrating too quickly or the local
2144 * node is overloaded. In either case, scan slower
2146 if (local + shared == 0 || p->numa_faults_locality[2]) {
2147 p->numa_scan_period = min(p->numa_scan_period_max,
2148 p->numa_scan_period << 1);
2150 p->mm->numa_next_scan = jiffies +
2151 msecs_to_jiffies(p->numa_scan_period);
2157 * Prepare to scale scan period relative to the current period.
2158 * == NUMA_PERIOD_THRESHOLD scan period stays the same
2159 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
2160 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
2162 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
2163 lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
2164 ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
2166 if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
2168 * Most memory accesses are local. There is no need to
2169 * do fast NUMA scanning, since memory is already local.
2171 int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
2174 diff = slot * period_slot;
2175 } else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
2177 * Most memory accesses are shared with other tasks.
2178 * There is no point in continuing fast NUMA scanning,
2179 * since other tasks may just move the memory elsewhere.
2181 int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
2184 diff = slot * period_slot;
2187 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
2188 * yet they are not on the local NUMA node. Speed up
2189 * NUMA scanning to get the memory moved over.
2191 int ratio = max(lr_ratio, ps_ratio);
2192 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
2195 p->numa_scan_period = clamp(p->numa_scan_period + diff,
2196 task_scan_min(p), task_scan_max(p));
2197 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2201 * Get the fraction of time the task has been running since the last
2202 * NUMA placement cycle. The scheduler keeps similar statistics, but
2203 * decays those on a 32ms period, which is orders of magnitude off
2204 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
2205 * stats only if the task is so new there are no NUMA statistics yet.
2207 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
2209 u64 runtime, delta, now;
2210 /* Use the start of this time slice to avoid calculations. */
2211 now = p->se.exec_start;
2212 runtime = p->se.sum_exec_runtime;
2214 if (p->last_task_numa_placement) {
2215 delta = runtime - p->last_sum_exec_runtime;
2216 *period = now - p->last_task_numa_placement;
2218 /* Avoid time going backwards, prevent potential divide error: */
2219 if (unlikely((s64)*period < 0))
2222 delta = p->se.avg.load_sum;
2223 *period = LOAD_AVG_MAX;
2226 p->last_sum_exec_runtime = runtime;
2227 p->last_task_numa_placement = now;
2233 * Determine the preferred nid for a task in a numa_group. This needs to
2234 * be done in a way that produces consistent results with group_weight,
2235 * otherwise workloads might not converge.
2237 static int preferred_group_nid(struct task_struct *p, int nid)
2242 /* Direct connections between all NUMA nodes. */
2243 if (sched_numa_topology_type == NUMA_DIRECT)
2247 * On a system with glueless mesh NUMA topology, group_weight
2248 * scores nodes according to the number of NUMA hinting faults on
2249 * both the node itself, and on nearby nodes.
2251 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
2252 unsigned long score, max_score = 0;
2253 int node, max_node = nid;
2255 dist = sched_max_numa_distance;
2257 for_each_online_node(node) {
2258 score = group_weight(p, node, dist);
2259 if (score > max_score) {
2268 * Finding the preferred nid in a system with NUMA backplane
2269 * interconnect topology is more involved. The goal is to locate
2270 * tasks from numa_groups near each other in the system, and
2271 * untangle workloads from different sides of the system. This requires
2272 * searching down the hierarchy of node groups, recursively searching
2273 * inside the highest scoring group of nodes. The nodemask tricks
2274 * keep the complexity of the search down.
2276 nodes = node_online_map;
2277 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
2278 unsigned long max_faults = 0;
2279 nodemask_t max_group = NODE_MASK_NONE;
2282 /* Are there nodes at this distance from each other? */
2283 if (!find_numa_distance(dist))
2286 for_each_node_mask(a, nodes) {
2287 unsigned long faults = 0;
2288 nodemask_t this_group;
2289 nodes_clear(this_group);
2291 /* Sum group's NUMA faults; includes a==b case. */
2292 for_each_node_mask(b, nodes) {
2293 if (node_distance(a, b) < dist) {
2294 faults += group_faults(p, b);
2295 node_set(b, this_group);
2296 node_clear(b, nodes);
2300 /* Remember the top group. */
2301 if (faults > max_faults) {
2302 max_faults = faults;
2303 max_group = this_group;
2305 * subtle: at the smallest distance there is
2306 * just one node left in each "group", the
2307 * winner is the preferred nid.
2312 /* Next round, evaluate the nodes within max_group. */
2320 static void task_numa_placement(struct task_struct *p)
2322 int seq, nid, max_nid = NUMA_NO_NODE;
2323 unsigned long max_faults = 0;
2324 unsigned long fault_types[2] = { 0, 0 };
2325 unsigned long total_faults;
2326 u64 runtime, period;
2327 spinlock_t *group_lock = NULL;
2328 struct numa_group *ng;
2331 * The p->mm->numa_scan_seq field gets updated without
2332 * exclusive access. Use READ_ONCE() here to ensure
2333 * that the field is read in a single access:
2335 seq = READ_ONCE(p->mm->numa_scan_seq);
2336 if (p->numa_scan_seq == seq)
2338 p->numa_scan_seq = seq;
2339 p->numa_scan_period_max = task_scan_max(p);
2341 total_faults = p->numa_faults_locality[0] +
2342 p->numa_faults_locality[1];
2343 runtime = numa_get_avg_runtime(p, &period);
2345 /* If the task is part of a group prevent parallel updates to group stats */
2346 ng = deref_curr_numa_group(p);
2348 group_lock = &ng->lock;
2349 spin_lock_irq(group_lock);
2352 /* Find the node with the highest number of faults */
2353 for_each_online_node(nid) {
2354 /* Keep track of the offsets in numa_faults array */
2355 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2356 unsigned long faults = 0, group_faults = 0;
2359 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2360 long diff, f_diff, f_weight;
2362 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
2363 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
2364 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
2365 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
2367 /* Decay existing window, copy faults since last scan */
2368 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
2369 fault_types[priv] += p->numa_faults[membuf_idx];
2370 p->numa_faults[membuf_idx] = 0;
2373 * Normalize the faults_from, so all tasks in a group
2374 * count according to CPU use, instead of by the raw
2375 * number of faults. Tasks with little runtime have
2376 * little over-all impact on throughput, and thus their
2377 * faults are less important.
2379 f_weight = div64_u64(runtime << 16, period + 1);
2380 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2382 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
2383 p->numa_faults[cpubuf_idx] = 0;
2385 p->numa_faults[mem_idx] += diff;
2386 p->numa_faults[cpu_idx] += f_diff;
2387 faults += p->numa_faults[mem_idx];
2388 p->total_numa_faults += diff;
2391 * safe because we can only change our own group
2393 * mem_idx represents the offset for a given
2394 * nid and priv in a specific region because it
2395 * is at the beginning of the numa_faults array.
2397 ng->faults[mem_idx] += diff;
2398 ng->faults_cpu[mem_idx] += f_diff;
2399 ng->total_faults += diff;
2400 group_faults += ng->faults[mem_idx];
2405 if (faults > max_faults) {
2406 max_faults = faults;
2409 } else if (group_faults > max_faults) {
2410 max_faults = group_faults;
2416 numa_group_count_active_nodes(ng);
2417 spin_unlock_irq(group_lock);
2418 max_nid = preferred_group_nid(p, max_nid);
2422 /* Set the new preferred node */
2423 if (max_nid != p->numa_preferred_nid)
2424 sched_setnuma(p, max_nid);
2427 update_task_scan_period(p, fault_types[0], fault_types[1]);
2430 static inline int get_numa_group(struct numa_group *grp)
2432 return refcount_inc_not_zero(&grp->refcount);
2435 static inline void put_numa_group(struct numa_group *grp)
2437 if (refcount_dec_and_test(&grp->refcount))
2438 kfree_rcu(grp, rcu);
2441 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
2444 struct numa_group *grp, *my_grp;
2445 struct task_struct *tsk;
2447 int cpu = cpupid_to_cpu(cpupid);
2450 if (unlikely(!deref_curr_numa_group(p))) {
2451 unsigned int size = sizeof(struct numa_group) +
2452 4*nr_node_ids*sizeof(unsigned long);
2454 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
2458 refcount_set(&grp->refcount, 1);
2459 grp->active_nodes = 1;
2460 grp->max_faults_cpu = 0;
2461 spin_lock_init(&grp->lock);
2463 /* Second half of the array tracks nids where faults happen */
2464 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
2467 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2468 grp->faults[i] = p->numa_faults[i];
2470 grp->total_faults = p->total_numa_faults;
2473 rcu_assign_pointer(p->numa_group, grp);
2477 tsk = READ_ONCE(cpu_rq(cpu)->curr);
2479 if (!cpupid_match_pid(tsk, cpupid))
2482 grp = rcu_dereference(tsk->numa_group);
2486 my_grp = deref_curr_numa_group(p);
2491 * Only join the other group if its bigger; if we're the bigger group,
2492 * the other task will join us.
2494 if (my_grp->nr_tasks > grp->nr_tasks)
2498 * Tie-break on the grp address.
2500 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2503 /* Always join threads in the same process. */
2504 if (tsk->mm == current->mm)
2507 /* Simple filter to avoid false positives due to PID collisions */
2508 if (flags & TNF_SHARED)
2511 /* Update priv based on whether false sharing was detected */
2514 if (join && !get_numa_group(grp))
2522 BUG_ON(irqs_disabled());
2523 double_lock_irq(&my_grp->lock, &grp->lock);
2525 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2526 my_grp->faults[i] -= p->numa_faults[i];
2527 grp->faults[i] += p->numa_faults[i];
2529 my_grp->total_faults -= p->total_numa_faults;
2530 grp->total_faults += p->total_numa_faults;
2535 spin_unlock(&my_grp->lock);
2536 spin_unlock_irq(&grp->lock);
2538 rcu_assign_pointer(p->numa_group, grp);
2540 put_numa_group(my_grp);
2549 * Get rid of NUMA statistics associated with a task (either current or dead).
2550 * If @final is set, the task is dead and has reached refcount zero, so we can
2551 * safely free all relevant data structures. Otherwise, there might be
2552 * concurrent reads from places like load balancing and procfs, and we should
2553 * reset the data back to default state without freeing ->numa_faults.
2555 void task_numa_free(struct task_struct *p, bool final)
2557 /* safe: p either is current or is being freed by current */
2558 struct numa_group *grp = rcu_dereference_raw(p->numa_group);
2559 unsigned long *numa_faults = p->numa_faults;
2560 unsigned long flags;
2567 spin_lock_irqsave(&grp->lock, flags);
2568 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2569 grp->faults[i] -= p->numa_faults[i];
2570 grp->total_faults -= p->total_numa_faults;
2573 spin_unlock_irqrestore(&grp->lock, flags);
2574 RCU_INIT_POINTER(p->numa_group, NULL);
2575 put_numa_group(grp);
2579 p->numa_faults = NULL;
2582 p->total_numa_faults = 0;
2583 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2589 * Got a PROT_NONE fault for a page on @node.
2591 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2593 struct task_struct *p = current;
2594 bool migrated = flags & TNF_MIGRATED;
2595 int cpu_node = task_node(current);
2596 int local = !!(flags & TNF_FAULT_LOCAL);
2597 struct numa_group *ng;
2600 if (!static_branch_likely(&sched_numa_balancing))
2603 /* for example, ksmd faulting in a user's mm */
2607 /* Allocate buffer to track faults on a per-node basis */
2608 if (unlikely(!p->numa_faults)) {
2609 int size = sizeof(*p->numa_faults) *
2610 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2612 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2613 if (!p->numa_faults)
2616 p->total_numa_faults = 0;
2617 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2621 * First accesses are treated as private, otherwise consider accesses
2622 * to be private if the accessing pid has not changed
2624 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2627 priv = cpupid_match_pid(p, last_cpupid);
2628 if (!priv && !(flags & TNF_NO_GROUP))
2629 task_numa_group(p, last_cpupid, flags, &priv);
2633 * If a workload spans multiple NUMA nodes, a shared fault that
2634 * occurs wholly within the set of nodes that the workload is
2635 * actively using should be counted as local. This allows the
2636 * scan rate to slow down when a workload has settled down.
2638 ng = deref_curr_numa_group(p);
2639 if (!priv && !local && ng && ng->active_nodes > 1 &&
2640 numa_is_active_node(cpu_node, ng) &&
2641 numa_is_active_node(mem_node, ng))
2645 * Retry to migrate task to preferred node periodically, in case it
2646 * previously failed, or the scheduler moved us.
2648 if (time_after(jiffies, p->numa_migrate_retry)) {
2649 task_numa_placement(p);
2650 numa_migrate_preferred(p);
2654 p->numa_pages_migrated += pages;
2655 if (flags & TNF_MIGRATE_FAIL)
2656 p->numa_faults_locality[2] += pages;
2658 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2659 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2660 p->numa_faults_locality[local] += pages;
2663 static void reset_ptenuma_scan(struct task_struct *p)
2666 * We only did a read acquisition of the mmap sem, so
2667 * p->mm->numa_scan_seq is written to without exclusive access
2668 * and the update is not guaranteed to be atomic. That's not
2669 * much of an issue though, since this is just used for
2670 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2671 * expensive, to avoid any form of compiler optimizations:
2673 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2674 p->mm->numa_scan_offset = 0;
2678 * The expensive part of numa migration is done from task_work context.
2679 * Triggered from task_tick_numa().
2681 static void task_numa_work(struct callback_head *work)
2683 unsigned long migrate, next_scan, now = jiffies;
2684 struct task_struct *p = current;
2685 struct mm_struct *mm = p->mm;
2686 u64 runtime = p->se.sum_exec_runtime;
2687 struct vm_area_struct *vma;
2688 unsigned long start, end;
2689 unsigned long nr_pte_updates = 0;
2690 long pages, virtpages;
2692 SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2696 * Who cares about NUMA placement when they're dying.
2698 * NOTE: make sure not to dereference p->mm before this check,
2699 * exit_task_work() happens _after_ exit_mm() so we could be called
2700 * without p->mm even though we still had it when we enqueued this
2703 if (p->flags & PF_EXITING)
2706 if (!mm->numa_next_scan) {
2707 mm->numa_next_scan = now +
2708 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2712 * Enforce maximal scan/migration frequency..
2714 migrate = mm->numa_next_scan;
2715 if (time_before(now, migrate))
2718 if (p->numa_scan_period == 0) {
2719 p->numa_scan_period_max = task_scan_max(p);
2720 p->numa_scan_period = task_scan_start(p);
2723 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2724 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2728 * Delay this task enough that another task of this mm will likely win
2729 * the next time around.
2731 p->node_stamp += 2 * TICK_NSEC;
2733 start = mm->numa_scan_offset;
2734 pages = sysctl_numa_balancing_scan_size;
2735 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2736 virtpages = pages * 8; /* Scan up to this much virtual space */
2741 if (!mmap_read_trylock(mm))
2743 vma = find_vma(mm, start);
2745 reset_ptenuma_scan(p);
2749 for (; vma; vma = vma->vm_next) {
2750 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2751 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2756 * Shared library pages mapped by multiple processes are not
2757 * migrated as it is expected they are cache replicated. Avoid
2758 * hinting faults in read-only file-backed mappings or the vdso
2759 * as migrating the pages will be of marginal benefit.
2762 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2766 * Skip inaccessible VMAs to avoid any confusion between
2767 * PROT_NONE and NUMA hinting ptes
2769 if (!vma_is_accessible(vma))
2773 start = max(start, vma->vm_start);
2774 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2775 end = min(end, vma->vm_end);
2776 nr_pte_updates = change_prot_numa(vma, start, end);
2779 * Try to scan sysctl_numa_balancing_size worth of
2780 * hpages that have at least one present PTE that
2781 * is not already pte-numa. If the VMA contains
2782 * areas that are unused or already full of prot_numa
2783 * PTEs, scan up to virtpages, to skip through those
2787 pages -= (end - start) >> PAGE_SHIFT;
2788 virtpages -= (end - start) >> PAGE_SHIFT;
2791 if (pages <= 0 || virtpages <= 0)
2795 } while (end != vma->vm_end);
2800 * It is possible to reach the end of the VMA list but the last few
2801 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2802 * would find the !migratable VMA on the next scan but not reset the
2803 * scanner to the start so check it now.
2806 mm->numa_scan_offset = start;
2808 reset_ptenuma_scan(p);
2809 mmap_read_unlock(mm);
2812 * Make sure tasks use at least 32x as much time to run other code
2813 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2814 * Usually update_task_scan_period slows down scanning enough; on an
2815 * overloaded system we need to limit overhead on a per task basis.
2817 if (unlikely(p->se.sum_exec_runtime != runtime)) {
2818 u64 diff = p->se.sum_exec_runtime - runtime;
2819 p->node_stamp += 32 * diff;
2823 void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
2826 struct mm_struct *mm = p->mm;
2829 mm_users = atomic_read(&mm->mm_users);
2830 if (mm_users == 1) {
2831 mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2832 mm->numa_scan_seq = 0;
2836 p->numa_scan_seq = mm ? mm->numa_scan_seq : 0;
2837 p->numa_scan_period = sysctl_numa_balancing_scan_delay;
2838 /* Protect against double add, see task_tick_numa and task_numa_work */
2839 p->numa_work.next = &p->numa_work;
2840 p->numa_faults = NULL;
2841 RCU_INIT_POINTER(p->numa_group, NULL);
2842 p->last_task_numa_placement = 0;
2843 p->last_sum_exec_runtime = 0;
2845 init_task_work(&p->numa_work, task_numa_work);
2847 /* New address space, reset the preferred nid */
2848 if (!(clone_flags & CLONE_VM)) {
2849 p->numa_preferred_nid = NUMA_NO_NODE;
2854 * New thread, keep existing numa_preferred_nid which should be copied
2855 * already by arch_dup_task_struct but stagger when scans start.
2860 delay = min_t(unsigned int, task_scan_max(current),
2861 current->numa_scan_period * mm_users * NSEC_PER_MSEC);
2862 delay += 2 * TICK_NSEC;
2863 p->node_stamp = delay;
2868 * Drive the periodic memory faults..
2870 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2872 struct callback_head *work = &curr->numa_work;
2876 * We don't care about NUMA placement if we don't have memory.
2878 if ((curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work)
2882 * Using runtime rather than walltime has the dual advantage that
2883 * we (mostly) drive the selection from busy threads and that the
2884 * task needs to have done some actual work before we bother with
2887 now = curr->se.sum_exec_runtime;
2888 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2890 if (now > curr->node_stamp + period) {
2891 if (!curr->node_stamp)
2892 curr->numa_scan_period = task_scan_start(curr);
2893 curr->node_stamp += period;
2895 if (!time_before(jiffies, curr->mm->numa_next_scan))
2896 task_work_add(curr, work, TWA_RESUME);
2900 static void update_scan_period(struct task_struct *p, int new_cpu)
2902 int src_nid = cpu_to_node(task_cpu(p));
2903 int dst_nid = cpu_to_node(new_cpu);
2905 if (!static_branch_likely(&sched_numa_balancing))
2908 if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
2911 if (src_nid == dst_nid)
2915 * Allow resets if faults have been trapped before one scan
2916 * has completed. This is most likely due to a new task that
2917 * is pulled cross-node due to wakeups or load balancing.
2919 if (p->numa_scan_seq) {
2921 * Avoid scan adjustments if moving to the preferred
2922 * node or if the task was not previously running on
2923 * the preferred node.
2925 if (dst_nid == p->numa_preferred_nid ||
2926 (p->numa_preferred_nid != NUMA_NO_NODE &&
2927 src_nid != p->numa_preferred_nid))
2931 p->numa_scan_period = task_scan_start(p);
2935 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2939 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2943 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2947 static inline void update_scan_period(struct task_struct *p, int new_cpu)
2951 #endif /* CONFIG_NUMA_BALANCING */
2954 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2956 update_load_add(&cfs_rq->load, se->load.weight);
2958 if (entity_is_task(se)) {
2959 struct rq *rq = rq_of(cfs_rq);
2961 account_numa_enqueue(rq, task_of(se));
2962 list_add(&se->group_node, &rq->cfs_tasks);
2965 cfs_rq->nr_running++;
2969 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2971 update_load_sub(&cfs_rq->load, se->load.weight);
2973 if (entity_is_task(se)) {
2974 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2975 list_del_init(&se->group_node);
2978 cfs_rq->nr_running--;
2982 * Signed add and clamp on underflow.
2984 * Explicitly do a load-store to ensure the intermediate value never hits
2985 * memory. This allows lockless observations without ever seeing the negative
2988 #define add_positive(_ptr, _val) do { \
2989 typeof(_ptr) ptr = (_ptr); \
2990 typeof(_val) val = (_val); \
2991 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2995 if (val < 0 && res > var) \
2998 WRITE_ONCE(*ptr, res); \
3002 * Unsigned subtract and clamp on underflow.
3004 * Explicitly do a load-store to ensure the intermediate value never hits
3005 * memory. This allows lockless observations without ever seeing the negative
3008 #define sub_positive(_ptr, _val) do { \
3009 typeof(_ptr) ptr = (_ptr); \
3010 typeof(*ptr) val = (_val); \
3011 typeof(*ptr) res, var = READ_ONCE(*ptr); \
3015 WRITE_ONCE(*ptr, res); \
3019 * Remove and clamp on negative, from a local variable.
3021 * A variant of sub_positive(), which does not use explicit load-store
3022 * and is thus optimized for local variable updates.
3024 #define lsub_positive(_ptr, _val) do { \
3025 typeof(_ptr) ptr = (_ptr); \
3026 *ptr -= min_t(typeof(*ptr), *ptr, _val); \
3031 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3033 cfs_rq->avg.load_avg += se->avg.load_avg;
3034 cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
3038 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3040 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
3041 sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
3045 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
3047 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
3050 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
3051 unsigned long weight)
3054 /* commit outstanding execution time */
3055 if (cfs_rq->curr == se)
3056 update_curr(cfs_rq);
3057 update_load_sub(&cfs_rq->load, se->load.weight);
3059 dequeue_load_avg(cfs_rq, se);
3061 update_load_set(&se->load, weight);
3065 u32 divider = get_pelt_divider(&se->avg);
3067 se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
3071 enqueue_load_avg(cfs_rq, se);
3073 update_load_add(&cfs_rq->load, se->load.weight);
3077 void reweight_task(struct task_struct *p, int prio)
3079 struct sched_entity *se = &p->se;
3080 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3081 struct load_weight *load = &se->load;
3082 unsigned long weight = scale_load(sched_prio_to_weight[prio]);
3084 reweight_entity(cfs_rq, se, weight);
3085 load->inv_weight = sched_prio_to_wmult[prio];
3088 #ifdef CONFIG_FAIR_GROUP_SCHED
3091 * All this does is approximate the hierarchical proportion which includes that
3092 * global sum we all love to hate.
3094 * That is, the weight of a group entity, is the proportional share of the
3095 * group weight based on the group runqueue weights. That is:
3097 * tg->weight * grq->load.weight
3098 * ge->load.weight = ----------------------------- (1)
3099 * \Sum grq->load.weight
3101 * Now, because computing that sum is prohibitively expensive to compute (been
3102 * there, done that) we approximate it with this average stuff. The average
3103 * moves slower and therefore the approximation is cheaper and more stable.
3105 * So instead of the above, we substitute:
3107 * grq->load.weight -> grq->avg.load_avg (2)
3109 * which yields the following:
3111 * tg->weight * grq->avg.load_avg
3112 * ge->load.weight = ------------------------------ (3)
3115 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
3117 * That is shares_avg, and it is right (given the approximation (2)).
3119 * The problem with it is that because the average is slow -- it was designed
3120 * to be exactly that of course -- this leads to transients in boundary
3121 * conditions. In specific, the case where the group was idle and we start the
3122 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
3123 * yielding bad latency etc..
3125 * Now, in that special case (1) reduces to:
3127 * tg->weight * grq->load.weight
3128 * ge->load.weight = ----------------------------- = tg->weight (4)
3131 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
3133 * So what we do is modify our approximation (3) to approach (4) in the (near)
3138 * tg->weight * grq->load.weight
3139 * --------------------------------------------------- (5)
3140 * tg->load_avg - grq->avg.load_avg + grq->load.weight
3142 * But because grq->load.weight can drop to 0, resulting in a divide by zero,
3143 * we need to use grq->avg.load_avg as its lower bound, which then gives:
3146 * tg->weight * grq->load.weight
3147 * ge->load.weight = ----------------------------- (6)
3152 * tg_load_avg' = tg->load_avg - grq->avg.load_avg +
3153 * max(grq->load.weight, grq->avg.load_avg)
3155 * And that is shares_weight and is icky. In the (near) UP case it approaches
3156 * (4) while in the normal case it approaches (3). It consistently
3157 * overestimates the ge->load.weight and therefore:
3159 * \Sum ge->load.weight >= tg->weight
3163 static long calc_group_shares(struct cfs_rq *cfs_rq)
3165 long tg_weight, tg_shares, load, shares;
3166 struct task_group *tg = cfs_rq->tg;
3168 tg_shares = READ_ONCE(tg->shares);
3170 load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
3172 tg_weight = atomic_long_read(&tg->load_avg);
3174 /* Ensure tg_weight >= load */
3175 tg_weight -= cfs_rq->tg_load_avg_contrib;
3178 shares = (tg_shares * load);
3180 shares /= tg_weight;
3183 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
3184 * of a group with small tg->shares value. It is a floor value which is
3185 * assigned as a minimum load.weight to the sched_entity representing
3186 * the group on a CPU.
3188 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
3189 * on an 8-core system with 8 tasks each runnable on one CPU shares has
3190 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
3191 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
3194 return clamp_t(long, shares, MIN_SHARES, tg_shares);
3196 #endif /* CONFIG_SMP */
3198 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
3201 * Recomputes the group entity based on the current state of its group
3204 static void update_cfs_group(struct sched_entity *se)
3206 struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3212 if (throttled_hierarchy(gcfs_rq))
3216 shares = READ_ONCE(gcfs_rq->tg->shares);
3218 if (likely(se->load.weight == shares))
3221 shares = calc_group_shares(gcfs_rq);
3224 reweight_entity(cfs_rq_of(se), se, shares);
3227 #else /* CONFIG_FAIR_GROUP_SCHED */
3228 static inline void update_cfs_group(struct sched_entity *se)
3231 #endif /* CONFIG_FAIR_GROUP_SCHED */
3233 static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
3235 struct rq *rq = rq_of(cfs_rq);
3237 if (&rq->cfs == cfs_rq) {
3239 * There are a few boundary cases this might miss but it should
3240 * get called often enough that that should (hopefully) not be
3243 * It will not get called when we go idle, because the idle
3244 * thread is a different class (!fair), nor will the utilization
3245 * number include things like RT tasks.
3247 * As is, the util number is not freq-invariant (we'd have to
3248 * implement arch_scale_freq_capacity() for that).
3252 cpufreq_update_util(rq, flags);
3257 #ifdef CONFIG_FAIR_GROUP_SCHED
3259 static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
3261 if (cfs_rq->load.weight)
3264 if (cfs_rq->avg.load_sum)
3267 if (cfs_rq->avg.util_sum)
3270 if (cfs_rq->avg.runnable_sum)
3274 * _avg must be null when _sum are null because _avg = _sum / divider
3275 * Make sure that rounding and/or propagation of PELT values never
3278 SCHED_WARN_ON(cfs_rq->avg.load_avg ||
3279 cfs_rq->avg.util_avg ||
3280 cfs_rq->avg.runnable_avg);
3286 * update_tg_load_avg - update the tg's load avg
3287 * @cfs_rq: the cfs_rq whose avg changed
3289 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
3290 * However, because tg->load_avg is a global value there are performance
3293 * In order to avoid having to look at the other cfs_rq's, we use a
3294 * differential update where we store the last value we propagated. This in
3295 * turn allows skipping updates if the differential is 'small'.
3297 * Updating tg's load_avg is necessary before update_cfs_share().
3299 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq)
3301 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3304 * No need to update load_avg for root_task_group as it is not used.
3306 if (cfs_rq->tg == &root_task_group)
3309 if (abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
3310 atomic_long_add(delta, &cfs_rq->tg->load_avg);
3311 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
3316 * Called within set_task_rq() right before setting a task's CPU. The
3317 * caller only guarantees p->pi_lock is held; no other assumptions,
3318 * including the state of rq->lock, should be made.
3320 void set_task_rq_fair(struct sched_entity *se,
3321 struct cfs_rq *prev, struct cfs_rq *next)
3323 u64 p_last_update_time;
3324 u64 n_last_update_time;
3326 if (!sched_feat(ATTACH_AGE_LOAD))
3330 * We are supposed to update the task to "current" time, then its up to
3331 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
3332 * getting what current time is, so simply throw away the out-of-date
3333 * time. This will result in the wakee task is less decayed, but giving
3334 * the wakee more load sounds not bad.
3336 if (!(se->avg.last_update_time && prev))
3339 #ifndef CONFIG_64BIT
3341 u64 p_last_update_time_copy;
3342 u64 n_last_update_time_copy;
3345 p_last_update_time_copy = prev->load_last_update_time_copy;
3346 n_last_update_time_copy = next->load_last_update_time_copy;
3350 p_last_update_time = prev->avg.last_update_time;
3351 n_last_update_time = next->avg.last_update_time;
3353 } while (p_last_update_time != p_last_update_time_copy ||
3354 n_last_update_time != n_last_update_time_copy);
3357 p_last_update_time = prev->avg.last_update_time;
3358 n_last_update_time = next->avg.last_update_time;
3360 __update_load_avg_blocked_se(p_last_update_time, se);
3361 se->avg.last_update_time = n_last_update_time;
3366 * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
3367 * propagate its contribution. The key to this propagation is the invariant
3368 * that for each group:
3370 * ge->avg == grq->avg (1)
3372 * _IFF_ we look at the pure running and runnable sums. Because they
3373 * represent the very same entity, just at different points in the hierarchy.
3375 * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
3376 * and simply copies the running/runnable sum over (but still wrong, because
3377 * the group entity and group rq do not have their PELT windows aligned).
3379 * However, update_tg_cfs_load() is more complex. So we have:
3381 * ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2)
3383 * And since, like util, the runnable part should be directly transferable,
3384 * the following would _appear_ to be the straight forward approach:
3386 * grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3)
3388 * And per (1) we have:
3390 * ge->avg.runnable_avg == grq->avg.runnable_avg
3394 * ge->load.weight * grq->avg.load_avg
3395 * ge->avg.load_avg = ----------------------------------- (4)
3398 * Except that is wrong!
3400 * Because while for entities historical weight is not important and we
3401 * really only care about our future and therefore can consider a pure
3402 * runnable sum, runqueues can NOT do this.
3404 * We specifically want runqueues to have a load_avg that includes
3405 * historical weights. Those represent the blocked load, the load we expect
3406 * to (shortly) return to us. This only works by keeping the weights as
3407 * integral part of the sum. We therefore cannot decompose as per (3).
3409 * Another reason this doesn't work is that runnable isn't a 0-sum entity.
3410 * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
3411 * rq itself is runnable anywhere between 2/3 and 1 depending on how the
3412 * runnable section of these tasks overlap (or not). If they were to perfectly
3413 * align the rq as a whole would be runnable 2/3 of the time. If however we
3414 * always have at least 1 runnable task, the rq as a whole is always runnable.
3416 * So we'll have to approximate.. :/
3418 * Given the constraint:
3420 * ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3422 * We can construct a rule that adds runnable to a rq by assuming minimal
3425 * On removal, we'll assume each task is equally runnable; which yields:
3427 * grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3429 * XXX: only do this for the part of runnable > running ?
3434 update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3436 long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
3439 /* Nothing to update */
3444 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3445 * See ___update_load_avg() for details.
3447 divider = get_pelt_divider(&cfs_rq->avg);
3449 /* Set new sched_entity's utilization */
3450 se->avg.util_avg = gcfs_rq->avg.util_avg;
3451 se->avg.util_sum = se->avg.util_avg * divider;
3453 /* Update parent cfs_rq utilization */
3454 add_positive(&cfs_rq->avg.util_avg, delta);
3455 cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider;
3459 update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3461 long delta = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
3464 /* Nothing to update */
3469 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3470 * See ___update_load_avg() for details.
3472 divider = get_pelt_divider(&cfs_rq->avg);
3474 /* Set new sched_entity's runnable */
3475 se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
3476 se->avg.runnable_sum = se->avg.runnable_avg * divider;
3478 /* Update parent cfs_rq runnable */
3479 add_positive(&cfs_rq->avg.runnable_avg, delta);
3480 cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * divider;
3484 update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3486 long delta, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
3487 unsigned long load_avg;
3494 gcfs_rq->prop_runnable_sum = 0;
3497 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3498 * See ___update_load_avg() for details.
3500 divider = get_pelt_divider(&cfs_rq->avg);
3502 if (runnable_sum >= 0) {
3504 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
3505 * the CPU is saturated running == runnable.
3507 runnable_sum += se->avg.load_sum;
3508 runnable_sum = min_t(long, runnable_sum, divider);
3511 * Estimate the new unweighted runnable_sum of the gcfs_rq by
3512 * assuming all tasks are equally runnable.
3514 if (scale_load_down(gcfs_rq->load.weight)) {
3515 load_sum = div_s64(gcfs_rq->avg.load_sum,
3516 scale_load_down(gcfs_rq->load.weight));
3519 /* But make sure to not inflate se's runnable */
3520 runnable_sum = min(se->avg.load_sum, load_sum);
3524 * runnable_sum can't be lower than running_sum
3525 * Rescale running sum to be in the same range as runnable sum
3526 * running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT]
3527 * runnable_sum is in [0 : LOAD_AVG_MAX]
3529 running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
3530 runnable_sum = max(runnable_sum, running_sum);
3532 load_sum = (s64)se_weight(se) * runnable_sum;
3533 load_avg = div_s64(load_sum, divider);
3535 se->avg.load_sum = runnable_sum;
3537 delta = load_avg - se->avg.load_avg;
3541 se->avg.load_avg = load_avg;
3543 add_positive(&cfs_rq->avg.load_avg, delta);
3544 cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * divider;
3547 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
3549 cfs_rq->propagate = 1;
3550 cfs_rq->prop_runnable_sum += runnable_sum;
3553 /* Update task and its cfs_rq load average */
3554 static inline int propagate_entity_load_avg(struct sched_entity *se)
3556 struct cfs_rq *cfs_rq, *gcfs_rq;
3558 if (entity_is_task(se))
3561 gcfs_rq = group_cfs_rq(se);
3562 if (!gcfs_rq->propagate)
3565 gcfs_rq->propagate = 0;
3567 cfs_rq = cfs_rq_of(se);
3569 add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
3571 update_tg_cfs_util(cfs_rq, se, gcfs_rq);
3572 update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
3573 update_tg_cfs_load(cfs_rq, se, gcfs_rq);
3575 trace_pelt_cfs_tp(cfs_rq);
3576 trace_pelt_se_tp(se);
3582 * Check if we need to update the load and the utilization of a blocked
3585 static inline bool skip_blocked_update(struct sched_entity *se)
3587 struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3590 * If sched_entity still have not zero load or utilization, we have to
3593 if (se->avg.load_avg || se->avg.util_avg)
3597 * If there is a pending propagation, we have to update the load and
3598 * the utilization of the sched_entity:
3600 if (gcfs_rq->propagate)
3604 * Otherwise, the load and the utilization of the sched_entity is
3605 * already zero and there is no pending propagation, so it will be a
3606 * waste of time to try to decay it:
3611 #else /* CONFIG_FAIR_GROUP_SCHED */
3613 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) {}
3615 static inline int propagate_entity_load_avg(struct sched_entity *se)
3620 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3622 #endif /* CONFIG_FAIR_GROUP_SCHED */
3625 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
3626 * @now: current time, as per cfs_rq_clock_pelt()
3627 * @cfs_rq: cfs_rq to update
3629 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
3630 * avg. The immediate corollary is that all (fair) tasks must be attached, see
3631 * post_init_entity_util_avg().
3633 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
3635 * Returns true if the load decayed or we removed load.
3637 * Since both these conditions indicate a changed cfs_rq->avg.load we should
3638 * call update_tg_load_avg() when this function returns true.
3641 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3643 unsigned long removed_load = 0, removed_util = 0, removed_runnable = 0;
3644 struct sched_avg *sa = &cfs_rq->avg;
3647 if (cfs_rq->removed.nr) {
3649 u32 divider = get_pelt_divider(&cfs_rq->avg);
3651 raw_spin_lock(&cfs_rq->removed.lock);
3652 swap(cfs_rq->removed.util_avg, removed_util);
3653 swap(cfs_rq->removed.load_avg, removed_load);
3654 swap(cfs_rq->removed.runnable_avg, removed_runnable);
3655 cfs_rq->removed.nr = 0;
3656 raw_spin_unlock(&cfs_rq->removed.lock);
3659 sub_positive(&sa->load_avg, r);
3660 sa->load_sum = sa->load_avg * divider;
3663 sub_positive(&sa->util_avg, r);
3664 sa->util_sum = sa->util_avg * divider;
3666 r = removed_runnable;
3667 sub_positive(&sa->runnable_avg, r);
3668 sa->runnable_sum = sa->runnable_avg * divider;
3671 * removed_runnable is the unweighted version of removed_load so we
3672 * can use it to estimate removed_load_sum.
3674 add_tg_cfs_propagate(cfs_rq,
3675 -(long)(removed_runnable * divider) >> SCHED_CAPACITY_SHIFT);
3680 decayed |= __update_load_avg_cfs_rq(now, cfs_rq);
3682 #ifndef CONFIG_64BIT
3684 cfs_rq->load_last_update_time_copy = sa->last_update_time;
3691 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
3692 * @cfs_rq: cfs_rq to attach to
3693 * @se: sched_entity to attach
3695 * Must call update_cfs_rq_load_avg() before this, since we rely on
3696 * cfs_rq->avg.last_update_time being current.
3698 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3701 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3702 * See ___update_load_avg() for details.
3704 u32 divider = get_pelt_divider(&cfs_rq->avg);
3707 * When we attach the @se to the @cfs_rq, we must align the decay
3708 * window because without that, really weird and wonderful things can
3713 se->avg.last_update_time = cfs_rq->avg.last_update_time;
3714 se->avg.period_contrib = cfs_rq->avg.period_contrib;
3717 * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
3718 * period_contrib. This isn't strictly correct, but since we're
3719 * entirely outside of the PELT hierarchy, nobody cares if we truncate
3722 se->avg.util_sum = se->avg.util_avg * divider;
3724 se->avg.runnable_sum = se->avg.runnable_avg * divider;
3726 se->avg.load_sum = divider;
3727 if (se_weight(se)) {
3729 div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
3732 enqueue_load_avg(cfs_rq, se);
3733 cfs_rq->avg.util_avg += se->avg.util_avg;
3734 cfs_rq->avg.util_sum += se->avg.util_sum;
3735 cfs_rq->avg.runnable_avg += se->avg.runnable_avg;
3736 cfs_rq->avg.runnable_sum += se->avg.runnable_sum;
3738 add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3740 cfs_rq_util_change(cfs_rq, 0);
3742 trace_pelt_cfs_tp(cfs_rq);
3746 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3747 * @cfs_rq: cfs_rq to detach from
3748 * @se: sched_entity to detach
3750 * Must call update_cfs_rq_load_avg() before this, since we rely on
3751 * cfs_rq->avg.last_update_time being current.
3753 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3756 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
3757 * See ___update_load_avg() for details.
3759 u32 divider = get_pelt_divider(&cfs_rq->avg);
3761 dequeue_load_avg(cfs_rq, se);
3762 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
3763 cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider;
3764 sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
3765 cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * divider;
3767 add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3769 cfs_rq_util_change(cfs_rq, 0);
3771 trace_pelt_cfs_tp(cfs_rq);
3775 * Optional action to be done while updating the load average
3777 #define UPDATE_TG 0x1
3778 #define SKIP_AGE_LOAD 0x2
3779 #define DO_ATTACH 0x4
3781 /* Update task and its cfs_rq load average */
3782 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3784 u64 now = cfs_rq_clock_pelt(cfs_rq);
3788 * Track task load average for carrying it to new CPU after migrated, and
3789 * track group sched_entity load average for task_h_load calc in migration
3791 if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
3792 __update_load_avg_se(now, cfs_rq, se);
3794 decayed = update_cfs_rq_load_avg(now, cfs_rq);
3795 decayed |= propagate_entity_load_avg(se);
3797 if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
3800 * DO_ATTACH means we're here from enqueue_entity().
3801 * !last_update_time means we've passed through
3802 * migrate_task_rq_fair() indicating we migrated.
3804 * IOW we're enqueueing a task on a new CPU.
3806 attach_entity_load_avg(cfs_rq, se);
3807 update_tg_load_avg(cfs_rq);
3809 } else if (decayed) {
3810 cfs_rq_util_change(cfs_rq, 0);
3812 if (flags & UPDATE_TG)
3813 update_tg_load_avg(cfs_rq);
3817 #ifndef CONFIG_64BIT
3818 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3820 u64 last_update_time_copy;
3821 u64 last_update_time;
3824 last_update_time_copy = cfs_rq->load_last_update_time_copy;
3826 last_update_time = cfs_rq->avg.last_update_time;
3827 } while (last_update_time != last_update_time_copy);
3829 return last_update_time;
3832 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3834 return cfs_rq->avg.last_update_time;
3839 * Synchronize entity load avg of dequeued entity without locking
3842 static void sync_entity_load_avg(struct sched_entity *se)
3844 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3845 u64 last_update_time;
3847 last_update_time = cfs_rq_last_update_time(cfs_rq);
3848 __update_load_avg_blocked_se(last_update_time, se);
3852 * Task first catches up with cfs_rq, and then subtract
3853 * itself from the cfs_rq (task must be off the queue now).
3855 static void remove_entity_load_avg(struct sched_entity *se)
3857 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3858 unsigned long flags;
3861 * tasks cannot exit without having gone through wake_up_new_task() ->
3862 * post_init_entity_util_avg() which will have added things to the
3863 * cfs_rq, so we can remove unconditionally.
3866 sync_entity_load_avg(se);
3868 raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
3869 ++cfs_rq->removed.nr;
3870 cfs_rq->removed.util_avg += se->avg.util_avg;
3871 cfs_rq->removed.load_avg += se->avg.load_avg;
3872 cfs_rq->removed.runnable_avg += se->avg.runnable_avg;
3873 raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3876 static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq)
3878 return cfs_rq->avg.runnable_avg;
3881 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
3883 return cfs_rq->avg.load_avg;
3886 static int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
3888 static inline unsigned long task_util(struct task_struct *p)
3890 return READ_ONCE(p->se.avg.util_avg);
3893 static inline unsigned long _task_util_est(struct task_struct *p)
3895 struct util_est ue = READ_ONCE(p->se.avg.util_est);
3897 return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED));
3900 static inline unsigned long task_util_est(struct task_struct *p)
3902 return max(task_util(p), _task_util_est(p));
3905 #ifdef CONFIG_UCLAMP_TASK
3906 static inline unsigned long uclamp_task_util(struct task_struct *p)
3908 return clamp(task_util_est(p),
3909 uclamp_eff_value(p, UCLAMP_MIN),
3910 uclamp_eff_value(p, UCLAMP_MAX));
3913 static inline unsigned long uclamp_task_util(struct task_struct *p)
3915 return task_util_est(p);
3919 static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
3920 struct task_struct *p)
3922 unsigned int enqueued;
3924 if (!sched_feat(UTIL_EST))
3927 /* Update root cfs_rq's estimated utilization */
3928 enqueued = cfs_rq->avg.util_est.enqueued;
3929 enqueued += _task_util_est(p);
3930 WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
3932 trace_sched_util_est_cfs_tp(cfs_rq);
3935 static inline void util_est_dequeue(struct cfs_rq *cfs_rq,
3936 struct task_struct *p)
3938 unsigned int enqueued;
3940 if (!sched_feat(UTIL_EST))
3943 /* Update root cfs_rq's estimated utilization */
3944 enqueued = cfs_rq->avg.util_est.enqueued;
3945 enqueued -= min_t(unsigned int, enqueued, _task_util_est(p));
3946 WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
3948 trace_sched_util_est_cfs_tp(cfs_rq);
3951 #define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / 100)
3954 * Check if a (signed) value is within a specified (unsigned) margin,
3955 * based on the observation that:
3957 * abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
3959 * NOTE: this only works when value + margin < INT_MAX.
3961 static inline bool within_margin(int value, int margin)
3963 return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
3966 static inline void util_est_update(struct cfs_rq *cfs_rq,
3967 struct task_struct *p,
3970 long last_ewma_diff, last_enqueued_diff;
3973 if (!sched_feat(UTIL_EST))
3977 * Skip update of task's estimated utilization when the task has not
3978 * yet completed an activation, e.g. being migrated.
3984 * If the PELT values haven't changed since enqueue time,
3985 * skip the util_est update.
3987 ue = p->se.avg.util_est;
3988 if (ue.enqueued & UTIL_AVG_UNCHANGED)
3991 last_enqueued_diff = ue.enqueued;
3994 * Reset EWMA on utilization increases, the moving average is used only
3995 * to smooth utilization decreases.
3997 ue.enqueued = task_util(p);
3998 if (sched_feat(UTIL_EST_FASTUP)) {
3999 if (ue.ewma < ue.enqueued) {
4000 ue.ewma = ue.enqueued;
4006 * Skip update of task's estimated utilization when its members are
4007 * already ~1% close to its last activation value.
4009 last_ewma_diff = ue.enqueued - ue.ewma;
4010 last_enqueued_diff -= ue.enqueued;
4011 if (within_margin(last_ewma_diff, UTIL_EST_MARGIN)) {
4012 if (!within_margin(last_enqueued_diff, UTIL_EST_MARGIN))
4019 * To avoid overestimation of actual task utilization, skip updates if
4020 * we cannot grant there is idle time in this CPU.
4022 if (task_util(p) > capacity_orig_of(cpu_of(rq_of(cfs_rq))))
4026 * Update Task's estimated utilization
4028 * When *p completes an activation we can consolidate another sample
4029 * of the task size. This is done by storing the current PELT value
4030 * as ue.enqueued and by using this value to update the Exponential
4031 * Weighted Moving Average (EWMA):
4033 * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
4034 * = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
4035 * = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
4036 * = w * ( last_ewma_diff ) + ewma(t-1)
4037 * = w * (last_ewma_diff + ewma(t-1) / w)
4039 * Where 'w' is the weight of new samples, which is configured to be
4040 * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
4042 ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
4043 ue.ewma += last_ewma_diff;
4044 ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
4046 ue.enqueued |= UTIL_AVG_UNCHANGED;
4047 WRITE_ONCE(p->se.avg.util_est, ue);
4049 trace_sched_util_est_se_tp(&p->se);
4052 static inline int task_fits_capacity(struct task_struct *p, long capacity)
4054 return fits_capacity(uclamp_task_util(p), capacity);
4057 static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
4059 if (!static_branch_unlikely(&sched_asym_cpucapacity))
4062 if (!p || p->nr_cpus_allowed == 1) {
4063 rq->misfit_task_load = 0;
4067 if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) {
4068 rq->misfit_task_load = 0;
4073 * Make sure that misfit_task_load will not be null even if
4074 * task_h_load() returns 0.
4076 rq->misfit_task_load = max_t(unsigned long, task_h_load(p), 1);
4079 #else /* CONFIG_SMP */
4081 static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
4086 #define UPDATE_TG 0x0
4087 #define SKIP_AGE_LOAD 0x0
4088 #define DO_ATTACH 0x0
4090 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
4092 cfs_rq_util_change(cfs_rq, 0);
4095 static inline void remove_entity_load_avg(struct sched_entity *se) {}
4098 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
4100 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
4102 static inline int newidle_balance(struct rq *rq, struct rq_flags *rf)
4108 util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
4111 util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
4114 util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p,
4116 static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {}
4118 #endif /* CONFIG_SMP */
4120 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
4122 #ifdef CONFIG_SCHED_DEBUG
4123 s64 d = se->vruntime - cfs_rq->min_vruntime;
4128 if (d > 3*sysctl_sched_latency)
4129 schedstat_inc(cfs_rq->nr_spread_over);
4134 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
4136 u64 vruntime = cfs_rq->min_vruntime;
4139 * The 'current' period is already promised to the current tasks,
4140 * however the extra weight of the new task will slow them down a
4141 * little, place the new task so that it fits in the slot that
4142 * stays open at the end.
4144 if (initial && sched_feat(START_DEBIT))
4145 vruntime += sched_vslice(cfs_rq, se);
4147 /* sleeps up to a single latency don't count. */
4149 unsigned long thresh = sysctl_sched_latency;
4152 * Halve their sleep time's effect, to allow
4153 * for a gentler effect of sleepers:
4155 if (sched_feat(GENTLE_FAIR_SLEEPERS))
4161 /* ensure we never gain time by being placed backwards. */
4162 se->vruntime = max_vruntime(se->vruntime, vruntime);
4165 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
4167 static inline void check_schedstat_required(void)
4169 #ifdef CONFIG_SCHEDSTATS
4170 if (schedstat_enabled())
4173 /* Force schedstat enabled if a dependent tracepoint is active */
4174 if (trace_sched_stat_wait_enabled() ||
4175 trace_sched_stat_sleep_enabled() ||
4176 trace_sched_stat_iowait_enabled() ||
4177 trace_sched_stat_blocked_enabled() ||
4178 trace_sched_stat_runtime_enabled()) {
4179 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
4180 "stat_blocked and stat_runtime require the "
4181 "kernel parameter schedstats=enable or "
4182 "kernel.sched_schedstats=1\n");
4187 static inline bool cfs_bandwidth_used(void);
4194 * update_min_vruntime()
4195 * vruntime -= min_vruntime
4199 * update_min_vruntime()
4200 * vruntime += min_vruntime
4202 * this way the vruntime transition between RQs is done when both
4203 * min_vruntime are up-to-date.
4207 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
4208 * vruntime -= min_vruntime
4212 * update_min_vruntime()
4213 * vruntime += min_vruntime
4215 * this way we don't have the most up-to-date min_vruntime on the originating
4216 * CPU and an up-to-date min_vruntime on the destination CPU.
4220 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4222 bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
4223 bool curr = cfs_rq->curr == se;
4226 * If we're the current task, we must renormalise before calling
4230 se->vruntime += cfs_rq->min_vruntime;
4232 update_curr(cfs_rq);
4235 * Otherwise, renormalise after, such that we're placed at the current
4236 * moment in time, instead of some random moment in the past. Being
4237 * placed in the past could significantly boost this task to the
4238 * fairness detriment of existing tasks.
4240 if (renorm && !curr)
4241 se->vruntime += cfs_rq->min_vruntime;
4244 * When enqueuing a sched_entity, we must:
4245 * - Update loads to have both entity and cfs_rq synced with now.
4246 * - Add its load to cfs_rq->runnable_avg
4247 * - For group_entity, update its weight to reflect the new share of
4249 * - Add its new weight to cfs_rq->load.weight
4251 update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
4252 se_update_runnable(se);
4253 update_cfs_group(se);
4254 account_entity_enqueue(cfs_rq, se);
4256 if (flags & ENQUEUE_WAKEUP)
4257 place_entity(cfs_rq, se, 0);
4259 check_schedstat_required();
4260 update_stats_enqueue(cfs_rq, se, flags);
4261 check_spread(cfs_rq, se);
4263 __enqueue_entity(cfs_rq, se);
4267 * When bandwidth control is enabled, cfs might have been removed
4268 * because of a parent been throttled but cfs->nr_running > 1. Try to
4269 * add it unconditionally.
4271 if (cfs_rq->nr_running == 1 || cfs_bandwidth_used())
4272 list_add_leaf_cfs_rq(cfs_rq);
4274 if (cfs_rq->nr_running == 1)
4275 check_enqueue_throttle(cfs_rq);
4278 static void __clear_buddies_last(struct sched_entity *se)
4280 for_each_sched_entity(se) {
4281 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4282 if (cfs_rq->last != se)
4285 cfs_rq->last = NULL;
4289 static void __clear_buddies_next(struct sched_entity *se)
4291 for_each_sched_entity(se) {
4292 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4293 if (cfs_rq->next != se)
4296 cfs_rq->next = NULL;
4300 static void __clear_buddies_skip(struct sched_entity *se)
4302 for_each_sched_entity(se) {
4303 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4304 if (cfs_rq->skip != se)
4307 cfs_rq->skip = NULL;
4311 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
4313 if (cfs_rq->last == se)
4314 __clear_buddies_last(se);
4316 if (cfs_rq->next == se)
4317 __clear_buddies_next(se);
4319 if (cfs_rq->skip == se)
4320 __clear_buddies_skip(se);
4323 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4326 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4329 * Update run-time statistics of the 'current'.
4331 update_curr(cfs_rq);
4334 * When dequeuing a sched_entity, we must:
4335 * - Update loads to have both entity and cfs_rq synced with now.
4336 * - Subtract its load from the cfs_rq->runnable_avg.
4337 * - Subtract its previous weight from cfs_rq->load.weight.
4338 * - For group entity, update its weight to reflect the new share
4339 * of its group cfs_rq.
4341 update_load_avg(cfs_rq, se, UPDATE_TG);
4342 se_update_runnable(se);
4344 update_stats_dequeue(cfs_rq, se, flags);
4346 clear_buddies(cfs_rq, se);
4348 if (se != cfs_rq->curr)
4349 __dequeue_entity(cfs_rq, se);
4351 account_entity_dequeue(cfs_rq, se);
4354 * Normalize after update_curr(); which will also have moved
4355 * min_vruntime if @se is the one holding it back. But before doing
4356 * update_min_vruntime() again, which will discount @se's position and
4357 * can move min_vruntime forward still more.
4359 if (!(flags & DEQUEUE_SLEEP))
4360 se->vruntime -= cfs_rq->min_vruntime;
4362 /* return excess runtime on last dequeue */
4363 return_cfs_rq_runtime(cfs_rq);
4365 update_cfs_group(se);
4368 * Now advance min_vruntime if @se was the entity holding it back,
4369 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
4370 * put back on, and if we advance min_vruntime, we'll be placed back
4371 * further than we started -- ie. we'll be penalized.
4373 if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
4374 update_min_vruntime(cfs_rq);
4378 * Preempt the current task with a newly woken task if needed:
4381 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4383 unsigned long ideal_runtime, delta_exec;
4384 struct sched_entity *se;
4387 ideal_runtime = sched_slice(cfs_rq, curr);
4388 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4389 if (delta_exec > ideal_runtime) {
4390 resched_curr(rq_of(cfs_rq));
4392 * The current task ran long enough, ensure it doesn't get
4393 * re-elected due to buddy favours.
4395 clear_buddies(cfs_rq, curr);
4400 * Ensure that a task that missed wakeup preemption by a
4401 * narrow margin doesn't have to wait for a full slice.
4402 * This also mitigates buddy induced latencies under load.
4404 if (delta_exec < sysctl_sched_min_granularity)
4407 se = __pick_first_entity(cfs_rq);
4408 delta = curr->vruntime - se->vruntime;
4413 if (delta > ideal_runtime)
4414 resched_curr(rq_of(cfs_rq));
4418 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4420 clear_buddies(cfs_rq, se);
4422 /* 'current' is not kept within the tree. */
4425 * Any task has to be enqueued before it get to execute on
4426 * a CPU. So account for the time it spent waiting on the
4429 update_stats_wait_end(cfs_rq, se);
4430 __dequeue_entity(cfs_rq, se);
4431 update_load_avg(cfs_rq, se, UPDATE_TG);
4434 update_stats_curr_start(cfs_rq, se);
4438 * Track our maximum slice length, if the CPU's load is at
4439 * least twice that of our own weight (i.e. dont track it
4440 * when there are only lesser-weight tasks around):
4442 if (schedstat_enabled() &&
4443 rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
4444 schedstat_set(se->statistics.slice_max,
4445 max((u64)schedstat_val(se->statistics.slice_max),
4446 se->sum_exec_runtime - se->prev_sum_exec_runtime));
4449 se->prev_sum_exec_runtime = se->sum_exec_runtime;
4453 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
4456 * Pick the next process, keeping these things in mind, in this order:
4457 * 1) keep things fair between processes/task groups
4458 * 2) pick the "next" process, since someone really wants that to run
4459 * 3) pick the "last" process, for cache locality
4460 * 4) do not run the "skip" process, if something else is available
4462 static struct sched_entity *
4463 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4465 struct sched_entity *left = __pick_first_entity(cfs_rq);
4466 struct sched_entity *se;
4469 * If curr is set we have to see if its left of the leftmost entity
4470 * still in the tree, provided there was anything in the tree at all.
4472 if (!left || (curr && entity_before(curr, left)))
4475 se = left; /* ideally we run the leftmost entity */
4478 * Avoid running the skip buddy, if running something else can
4479 * be done without getting too unfair.
4481 if (cfs_rq->skip && cfs_rq->skip == se) {
4482 struct sched_entity *second;
4485 second = __pick_first_entity(cfs_rq);
4487 second = __pick_next_entity(se);
4488 if (!second || (curr && entity_before(curr, second)))
4492 if (second && wakeup_preempt_entity(second, left) < 1)
4496 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) {
4498 * Someone really wants this to run. If it's not unfair, run it.
4501 } else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) {
4503 * Prefer last buddy, try to return the CPU to a preempted task.
4511 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4513 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4516 * If still on the runqueue then deactivate_task()
4517 * was not called and update_curr() has to be done:
4520 update_curr(cfs_rq);
4522 /* throttle cfs_rqs exceeding runtime */
4523 check_cfs_rq_runtime(cfs_rq);
4525 check_spread(cfs_rq, prev);
4528 update_stats_wait_start(cfs_rq, prev);
4529 /* Put 'current' back into the tree. */
4530 __enqueue_entity(cfs_rq, prev);
4531 /* in !on_rq case, update occurred at dequeue */
4532 update_load_avg(cfs_rq, prev, 0);
4534 cfs_rq->curr = NULL;
4538 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4541 * Update run-time statistics of the 'current'.
4543 update_curr(cfs_rq);
4546 * Ensure that runnable average is periodically updated.
4548 update_load_avg(cfs_rq, curr, UPDATE_TG);
4549 update_cfs_group(curr);
4551 #ifdef CONFIG_SCHED_HRTICK
4553 * queued ticks are scheduled to match the slice, so don't bother
4554 * validating it and just reschedule.
4557 resched_curr(rq_of(cfs_rq));
4561 * don't let the period tick interfere with the hrtick preemption
4563 if (!sched_feat(DOUBLE_TICK) &&
4564 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
4568 if (cfs_rq->nr_running > 1)
4569 check_preempt_tick(cfs_rq, curr);
4573 /**************************************************
4574 * CFS bandwidth control machinery
4577 #ifdef CONFIG_CFS_BANDWIDTH
4579 #ifdef CONFIG_JUMP_LABEL
4580 static struct static_key __cfs_bandwidth_used;
4582 static inline bool cfs_bandwidth_used(void)
4584 return static_key_false(&__cfs_bandwidth_used);
4587 void cfs_bandwidth_usage_inc(void)
4589 static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4592 void cfs_bandwidth_usage_dec(void)
4594 static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4596 #else /* CONFIG_JUMP_LABEL */
4597 static bool cfs_bandwidth_used(void)
4602 void cfs_bandwidth_usage_inc(void) {}
4603 void cfs_bandwidth_usage_dec(void) {}
4604 #endif /* CONFIG_JUMP_LABEL */
4607 * default period for cfs group bandwidth.
4608 * default: 0.1s, units: nanoseconds
4610 static inline u64 default_cfs_period(void)
4612 return 100000000ULL;
4615 static inline u64 sched_cfs_bandwidth_slice(void)
4617 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
4621 * Replenish runtime according to assigned quota. We use sched_clock_cpu
4622 * directly instead of rq->clock to avoid adding additional synchronization
4625 * requires cfs_b->lock
4627 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
4629 if (unlikely(cfs_b->quota == RUNTIME_INF))
4632 cfs_b->runtime += cfs_b->quota;
4633 cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst);
4636 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4638 return &tg->cfs_bandwidth;
4641 /* returns 0 on failure to allocate runtime */
4642 static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
4643 struct cfs_rq *cfs_rq, u64 target_runtime)
4645 u64 min_amount, amount = 0;
4647 lockdep_assert_held(&cfs_b->lock);
4649 /* note: this is a positive sum as runtime_remaining <= 0 */
4650 min_amount = target_runtime - cfs_rq->runtime_remaining;
4652 if (cfs_b->quota == RUNTIME_INF)
4653 amount = min_amount;
4655 start_cfs_bandwidth(cfs_b);
4657 if (cfs_b->runtime > 0) {
4658 amount = min(cfs_b->runtime, min_amount);
4659 cfs_b->runtime -= amount;
4664 cfs_rq->runtime_remaining += amount;
4666 return cfs_rq->runtime_remaining > 0;
4669 /* returns 0 on failure to allocate runtime */
4670 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4672 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4675 raw_spin_lock(&cfs_b->lock);
4676 ret = __assign_cfs_rq_runtime(cfs_b, cfs_rq, sched_cfs_bandwidth_slice());
4677 raw_spin_unlock(&cfs_b->lock);
4682 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4684 /* dock delta_exec before expiring quota (as it could span periods) */
4685 cfs_rq->runtime_remaining -= delta_exec;
4687 if (likely(cfs_rq->runtime_remaining > 0))
4690 if (cfs_rq->throttled)
4693 * if we're unable to extend our runtime we resched so that the active
4694 * hierarchy can be throttled
4696 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
4697 resched_curr(rq_of(cfs_rq));
4700 static __always_inline
4701 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4703 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4706 __account_cfs_rq_runtime(cfs_rq, delta_exec);
4709 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4711 return cfs_bandwidth_used() && cfs_rq->throttled;
4714 /* check whether cfs_rq, or any parent, is throttled */
4715 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4717 return cfs_bandwidth_used() && cfs_rq->throttle_count;
4721 * Ensure that neither of the group entities corresponding to src_cpu or
4722 * dest_cpu are members of a throttled hierarchy when performing group
4723 * load-balance operations.
4725 static inline int throttled_lb_pair(struct task_group *tg,
4726 int src_cpu, int dest_cpu)
4728 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
4730 src_cfs_rq = tg->cfs_rq[src_cpu];
4731 dest_cfs_rq = tg->cfs_rq[dest_cpu];
4733 return throttled_hierarchy(src_cfs_rq) ||
4734 throttled_hierarchy(dest_cfs_rq);
4737 static int tg_unthrottle_up(struct task_group *tg, void *data)
4739 struct rq *rq = data;
4740 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4742 cfs_rq->throttle_count--;
4743 if (!cfs_rq->throttle_count) {
4744 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4745 cfs_rq->throttled_clock_task;
4747 /* Add cfs_rq with load or one or more already running entities to the list */
4748 if (!cfs_rq_is_decayed(cfs_rq) || cfs_rq->nr_running)
4749 list_add_leaf_cfs_rq(cfs_rq);
4755 static int tg_throttle_down(struct task_group *tg, void *data)
4757 struct rq *rq = data;
4758 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4760 /* group is entering throttled state, stop time */
4761 if (!cfs_rq->throttle_count) {
4762 cfs_rq->throttled_clock_task = rq_clock_task(rq);
4763 list_del_leaf_cfs_rq(cfs_rq);
4765 cfs_rq->throttle_count++;
4770 static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
4772 struct rq *rq = rq_of(cfs_rq);
4773 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4774 struct sched_entity *se;
4775 long task_delta, idle_task_delta, dequeue = 1;
4777 raw_spin_lock(&cfs_b->lock);
4778 /* This will start the period timer if necessary */
4779 if (__assign_cfs_rq_runtime(cfs_b, cfs_rq, 1)) {
4781 * We have raced with bandwidth becoming available, and if we
4782 * actually throttled the timer might not unthrottle us for an
4783 * entire period. We additionally needed to make sure that any
4784 * subsequent check_cfs_rq_runtime calls agree not to throttle
4785 * us, as we may commit to do cfs put_prev+pick_next, so we ask
4786 * for 1ns of runtime rather than just check cfs_b.
4790 list_add_tail_rcu(&cfs_rq->throttled_list,
4791 &cfs_b->throttled_cfs_rq);
4793 raw_spin_unlock(&cfs_b->lock);
4796 return false; /* Throttle no longer required. */
4798 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
4800 /* freeze hierarchy runnable averages while throttled */
4802 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
4805 task_delta = cfs_rq->h_nr_running;
4806 idle_task_delta = cfs_rq->idle_h_nr_running;
4807 for_each_sched_entity(se) {
4808 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
4809 /* throttled entity or throttle-on-deactivate */
4813 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
4815 qcfs_rq->h_nr_running -= task_delta;
4816 qcfs_rq->idle_h_nr_running -= idle_task_delta;
4818 if (qcfs_rq->load.weight) {
4819 /* Avoid re-evaluating load for this entity: */
4820 se = parent_entity(se);
4825 for_each_sched_entity(se) {
4826 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
4827 /* throttled entity or throttle-on-deactivate */
4831 update_load_avg(qcfs_rq, se, 0);
4832 se_update_runnable(se);
4834 qcfs_rq->h_nr_running -= task_delta;
4835 qcfs_rq->idle_h_nr_running -= idle_task_delta;
4838 /* At this point se is NULL and we are at root level*/
4839 sub_nr_running(rq, task_delta);
4843 * Note: distribution will already see us throttled via the
4844 * throttled-list. rq->lock protects completion.
4846 cfs_rq->throttled = 1;
4847 cfs_rq->throttled_clock = rq_clock(rq);
4851 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4853 struct rq *rq = rq_of(cfs_rq);
4854 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4855 struct sched_entity *se;
4856 long task_delta, idle_task_delta;
4858 se = cfs_rq->tg->se[cpu_of(rq)];
4860 cfs_rq->throttled = 0;
4862 update_rq_clock(rq);
4864 raw_spin_lock(&cfs_b->lock);
4865 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4866 list_del_rcu(&cfs_rq->throttled_list);
4867 raw_spin_unlock(&cfs_b->lock);
4869 /* update hierarchical throttle state */
4870 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
4872 if (!cfs_rq->load.weight)
4875 task_delta = cfs_rq->h_nr_running;
4876 idle_task_delta = cfs_rq->idle_h_nr_running;
4877 for_each_sched_entity(se) {
4880 cfs_rq = cfs_rq_of(se);
4881 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
4883 cfs_rq->h_nr_running += task_delta;
4884 cfs_rq->idle_h_nr_running += idle_task_delta;
4886 /* end evaluation on encountering a throttled cfs_rq */
4887 if (cfs_rq_throttled(cfs_rq))
4888 goto unthrottle_throttle;
4891 for_each_sched_entity(se) {
4892 cfs_rq = cfs_rq_of(se);
4894 update_load_avg(cfs_rq, se, UPDATE_TG);
4895 se_update_runnable(se);
4897 cfs_rq->h_nr_running += task_delta;
4898 cfs_rq->idle_h_nr_running += idle_task_delta;
4901 /* end evaluation on encountering a throttled cfs_rq */
4902 if (cfs_rq_throttled(cfs_rq))
4903 goto unthrottle_throttle;
4906 * One parent has been throttled and cfs_rq removed from the
4907 * list. Add it back to not break the leaf list.
4909 if (throttled_hierarchy(cfs_rq))
4910 list_add_leaf_cfs_rq(cfs_rq);
4913 /* At this point se is NULL and we are at root level*/
4914 add_nr_running(rq, task_delta);
4916 unthrottle_throttle:
4918 * The cfs_rq_throttled() breaks in the above iteration can result in
4919 * incomplete leaf list maintenance, resulting in triggering the
4922 for_each_sched_entity(se) {
4923 cfs_rq = cfs_rq_of(se);
4925 if (list_add_leaf_cfs_rq(cfs_rq))
4929 assert_list_leaf_cfs_rq(rq);
4931 /* Determine whether we need to wake up potentially idle CPU: */
4932 if (rq->curr == rq->idle && rq->cfs.nr_running)
4936 static void distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
4938 struct cfs_rq *cfs_rq;
4939 u64 runtime, remaining = 1;
4942 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
4944 struct rq *rq = rq_of(cfs_rq);
4947 rq_lock_irqsave(rq, &rf);
4948 if (!cfs_rq_throttled(cfs_rq))
4951 /* By the above check, this should never be true */
4952 SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);
4954 raw_spin_lock(&cfs_b->lock);
4955 runtime = -cfs_rq->runtime_remaining + 1;
4956 if (runtime > cfs_b->runtime)
4957 runtime = cfs_b->runtime;
4958 cfs_b->runtime -= runtime;
4959 remaining = cfs_b->runtime;
4960 raw_spin_unlock(&cfs_b->lock);
4962 cfs_rq->runtime_remaining += runtime;
4964 /* we check whether we're throttled above */
4965 if (cfs_rq->runtime_remaining > 0)
4966 unthrottle_cfs_rq(cfs_rq);
4969 rq_unlock_irqrestore(rq, &rf);
4978 * Responsible for refilling a task_group's bandwidth and unthrottling its
4979 * cfs_rqs as appropriate. If there has been no activity within the last
4980 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4981 * used to track this state.
4983 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
4987 /* no need to continue the timer with no bandwidth constraint */
4988 if (cfs_b->quota == RUNTIME_INF)
4989 goto out_deactivate;
4991 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4992 cfs_b->nr_periods += overrun;
4994 /* Refill extra burst quota even if cfs_b->idle */
4995 __refill_cfs_bandwidth_runtime(cfs_b);
4998 * idle depends on !throttled (for the case of a large deficit), and if
4999 * we're going inactive then everything else can be deferred
5001 if (cfs_b->idle && !throttled)
5002 goto out_deactivate;
5005 /* mark as potentially idle for the upcoming period */
5010 /* account preceding periods in which throttling occurred */
5011 cfs_b->nr_throttled += overrun;
5014 * This check is repeated as we release cfs_b->lock while we unthrottle.
5016 while (throttled && cfs_b->runtime > 0) {
5017 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5018 /* we can't nest cfs_b->lock while distributing bandwidth */
5019 distribute_cfs_runtime(cfs_b);
5020 raw_spin_lock_irqsave(&cfs_b->lock, flags);
5022 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
5026 * While we are ensured activity in the period following an
5027 * unthrottle, this also covers the case in which the new bandwidth is
5028 * insufficient to cover the existing bandwidth deficit. (Forcing the
5029 * timer to remain active while there are any throttled entities.)
5039 /* a cfs_rq won't donate quota below this amount */
5040 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
5041 /* minimum remaining period time to redistribute slack quota */
5042 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
5043 /* how long we wait to gather additional slack before distributing */
5044 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
5047 * Are we near the end of the current quota period?
5049 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
5050 * hrtimer base being cleared by hrtimer_start. In the case of
5051 * migrate_hrtimers, base is never cleared, so we are fine.
5053 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
5055 struct hrtimer *refresh_timer = &cfs_b->period_timer;
5058 /* if the call-back is running a quota refresh is already occurring */
5059 if (hrtimer_callback_running(refresh_timer))
5062 /* is a quota refresh about to occur? */
5063 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
5064 if (remaining < min_expire)
5070 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
5072 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
5074 /* if there's a quota refresh soon don't bother with slack */
5075 if (runtime_refresh_within(cfs_b, min_left))
5078 /* don't push forwards an existing deferred unthrottle */
5079 if (cfs_b->slack_started)
5081 cfs_b->slack_started = true;
5083 hrtimer_start(&cfs_b->slack_timer,
5084 ns_to_ktime(cfs_bandwidth_slack_period),
5088 /* we know any runtime found here is valid as update_curr() precedes return */
5089 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5091 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
5092 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
5094 if (slack_runtime <= 0)
5097 raw_spin_lock(&cfs_b->lock);
5098 if (cfs_b->quota != RUNTIME_INF) {
5099 cfs_b->runtime += slack_runtime;
5101 /* we are under rq->lock, defer unthrottling using a timer */
5102 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
5103 !list_empty(&cfs_b->throttled_cfs_rq))
5104 start_cfs_slack_bandwidth(cfs_b);
5106 raw_spin_unlock(&cfs_b->lock);
5108 /* even if it's not valid for return we don't want to try again */
5109 cfs_rq->runtime_remaining -= slack_runtime;
5112 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5114 if (!cfs_bandwidth_used())
5117 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
5120 __return_cfs_rq_runtime(cfs_rq);
5124 * This is done with a timer (instead of inline with bandwidth return) since
5125 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
5127 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
5129 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
5130 unsigned long flags;
5132 /* confirm we're still not at a refresh boundary */
5133 raw_spin_lock_irqsave(&cfs_b->lock, flags);
5134 cfs_b->slack_started = false;
5136 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
5137 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5141 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
5142 runtime = cfs_b->runtime;
5144 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5149 distribute_cfs_runtime(cfs_b);
5153 * When a group wakes up we want to make sure that its quota is not already
5154 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
5155 * runtime as update_curr() throttling can not trigger until it's on-rq.
5157 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
5159 if (!cfs_bandwidth_used())
5162 /* an active group must be handled by the update_curr()->put() path */
5163 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
5166 /* ensure the group is not already throttled */
5167 if (cfs_rq_throttled(cfs_rq))
5170 /* update runtime allocation */
5171 account_cfs_rq_runtime(cfs_rq, 0);
5172 if (cfs_rq->runtime_remaining <= 0)
5173 throttle_cfs_rq(cfs_rq);
5176 static void sync_throttle(struct task_group *tg, int cpu)
5178 struct cfs_rq *pcfs_rq, *cfs_rq;
5180 if (!cfs_bandwidth_used())
5186 cfs_rq = tg->cfs_rq[cpu];
5187 pcfs_rq = tg->parent->cfs_rq[cpu];
5189 cfs_rq->throttle_count = pcfs_rq->throttle_count;
5190 cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
5193 /* conditionally throttle active cfs_rq's from put_prev_entity() */
5194 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5196 if (!cfs_bandwidth_used())
5199 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
5203 * it's possible for a throttled entity to be forced into a running
5204 * state (e.g. set_curr_task), in this case we're finished.
5206 if (cfs_rq_throttled(cfs_rq))
5209 return throttle_cfs_rq(cfs_rq);
5212 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
5214 struct cfs_bandwidth *cfs_b =
5215 container_of(timer, struct cfs_bandwidth, slack_timer);
5217 do_sched_cfs_slack_timer(cfs_b);
5219 return HRTIMER_NORESTART;
5222 extern const u64 max_cfs_quota_period;
5224 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
5226 struct cfs_bandwidth *cfs_b =
5227 container_of(timer, struct cfs_bandwidth, period_timer);
5228 unsigned long flags;
5233 raw_spin_lock_irqsave(&cfs_b->lock, flags);
5235 overrun = hrtimer_forward_now(timer, cfs_b->period);
5239 idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
5242 u64 new, old = ktime_to_ns(cfs_b->period);
5245 * Grow period by a factor of 2 to avoid losing precision.
5246 * Precision loss in the quota/period ratio can cause __cfs_schedulable
5250 if (new < max_cfs_quota_period) {
5251 cfs_b->period = ns_to_ktime(new);
5255 pr_warn_ratelimited(
5256 "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5258 div_u64(new, NSEC_PER_USEC),
5259 div_u64(cfs_b->quota, NSEC_PER_USEC));
5261 pr_warn_ratelimited(
5262 "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5264 div_u64(old, NSEC_PER_USEC),
5265 div_u64(cfs_b->quota, NSEC_PER_USEC));
5268 /* reset count so we don't come right back in here */
5273 cfs_b->period_active = 0;
5274 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5276 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
5279 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5281 raw_spin_lock_init(&cfs_b->lock);
5283 cfs_b->quota = RUNTIME_INF;
5284 cfs_b->period = ns_to_ktime(default_cfs_period());
5287 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
5288 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
5289 cfs_b->period_timer.function = sched_cfs_period_timer;
5290 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
5291 cfs_b->slack_timer.function = sched_cfs_slack_timer;
5292 cfs_b->slack_started = false;
5295 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5297 cfs_rq->runtime_enabled = 0;
5298 INIT_LIST_HEAD(&cfs_rq->throttled_list);
5301 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5303 lockdep_assert_held(&cfs_b->lock);
5305 if (cfs_b->period_active)
5308 cfs_b->period_active = 1;
5309 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
5310 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
5313 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5315 /* init_cfs_bandwidth() was not called */
5316 if (!cfs_b->throttled_cfs_rq.next)
5319 hrtimer_cancel(&cfs_b->period_timer);
5320 hrtimer_cancel(&cfs_b->slack_timer);
5324 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
5326 * The race is harmless, since modifying bandwidth settings of unhooked group
5327 * bits doesn't do much.
5330 /* cpu online callback */
5331 static void __maybe_unused update_runtime_enabled(struct rq *rq)
5333 struct task_group *tg;
5335 lockdep_assert_rq_held(rq);
5338 list_for_each_entry_rcu(tg, &task_groups, list) {
5339 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
5340 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5342 raw_spin_lock(&cfs_b->lock);
5343 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
5344 raw_spin_unlock(&cfs_b->lock);
5349 /* cpu offline callback */
5350 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
5352 struct task_group *tg;
5354 lockdep_assert_rq_held(rq);
5357 list_for_each_entry_rcu(tg, &task_groups, list) {
5358 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5360 if (!cfs_rq->runtime_enabled)
5364 * clock_task is not advancing so we just need to make sure
5365 * there's some valid quota amount
5367 cfs_rq->runtime_remaining = 1;
5369 * Offline rq is schedulable till CPU is completely disabled
5370 * in take_cpu_down(), so we prevent new cfs throttling here.
5372 cfs_rq->runtime_enabled = 0;
5374 if (cfs_rq_throttled(cfs_rq))
5375 unthrottle_cfs_rq(cfs_rq);
5380 #else /* CONFIG_CFS_BANDWIDTH */
5382 static inline bool cfs_bandwidth_used(void)
5387 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5388 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5389 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5390 static inline void sync_throttle(struct task_group *tg, int cpu) {}
5391 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5393 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
5398 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
5403 static inline int throttled_lb_pair(struct task_group *tg,
5404 int src_cpu, int dest_cpu)
5409 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5411 #ifdef CONFIG_FAIR_GROUP_SCHED
5412 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5415 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
5419 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5420 static inline void update_runtime_enabled(struct rq *rq) {}
5421 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5423 #endif /* CONFIG_CFS_BANDWIDTH */
5425 /**************************************************
5426 * CFS operations on tasks:
5429 #ifdef CONFIG_SCHED_HRTICK
5430 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
5432 struct sched_entity *se = &p->se;
5433 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5435 SCHED_WARN_ON(task_rq(p) != rq);
5437 if (rq->cfs.h_nr_running > 1) {
5438 u64 slice = sched_slice(cfs_rq, se);
5439 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
5440 s64 delta = slice - ran;
5443 if (task_current(rq, p))
5447 hrtick_start(rq, delta);
5452 * called from enqueue/dequeue and updates the hrtick when the
5453 * current task is from our class and nr_running is low enough
5456 static void hrtick_update(struct rq *rq)
5458 struct task_struct *curr = rq->curr;
5460 if (!hrtick_enabled_fair(rq) || curr->sched_class != &fair_sched_class)
5463 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
5464 hrtick_start_fair(rq, curr);
5466 #else /* !CONFIG_SCHED_HRTICK */
5468 hrtick_start_fair(struct rq *rq, struct task_struct *p)
5472 static inline void hrtick_update(struct rq *rq)
5478 static inline unsigned long cpu_util(int cpu);
5480 static inline bool cpu_overutilized(int cpu)
5482 return !fits_capacity(cpu_util(cpu), capacity_of(cpu));
5485 static inline void update_overutilized_status(struct rq *rq)
5487 if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) {
5488 WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
5489 trace_sched_overutilized_tp(rq->rd, SG_OVERUTILIZED);
5493 static inline void update_overutilized_status(struct rq *rq) { }
5496 /* Runqueue only has SCHED_IDLE tasks enqueued */
5497 static int sched_idle_rq(struct rq *rq)
5499 return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running &&
5504 static int sched_idle_cpu(int cpu)
5506 return sched_idle_rq(cpu_rq(cpu));
5511 * The enqueue_task method is called before nr_running is
5512 * increased. Here we update the fair scheduling stats and
5513 * then put the task into the rbtree:
5516 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5518 struct cfs_rq *cfs_rq;
5519 struct sched_entity *se = &p->se;
5520 int idle_h_nr_running = task_has_idle_policy(p);
5521 int task_new = !(flags & ENQUEUE_WAKEUP);
5524 * The code below (indirectly) updates schedutil which looks at
5525 * the cfs_rq utilization to select a frequency.
5526 * Let's add the task's estimated utilization to the cfs_rq's
5527 * estimated utilization, before we update schedutil.
5529 util_est_enqueue(&rq->cfs, p);
5532 * If in_iowait is set, the code below may not trigger any cpufreq
5533 * utilization updates, so do it here explicitly with the IOWAIT flag
5537 cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5539 for_each_sched_entity(se) {
5542 cfs_rq = cfs_rq_of(se);
5543 enqueue_entity(cfs_rq, se, flags);
5545 cfs_rq->h_nr_running++;
5546 cfs_rq->idle_h_nr_running += idle_h_nr_running;
5548 /* end evaluation on encountering a throttled cfs_rq */
5549 if (cfs_rq_throttled(cfs_rq))
5550 goto enqueue_throttle;
5552 flags = ENQUEUE_WAKEUP;
5555 for_each_sched_entity(se) {
5556 cfs_rq = cfs_rq_of(se);
5558 update_load_avg(cfs_rq, se, UPDATE_TG);
5559 se_update_runnable(se);
5560 update_cfs_group(se);
5562 cfs_rq->h_nr_running++;
5563 cfs_rq->idle_h_nr_running += idle_h_nr_running;
5565 /* end evaluation on encountering a throttled cfs_rq */
5566 if (cfs_rq_throttled(cfs_rq))
5567 goto enqueue_throttle;
5570 * One parent has been throttled and cfs_rq removed from the
5571 * list. Add it back to not break the leaf list.
5573 if (throttled_hierarchy(cfs_rq))
5574 list_add_leaf_cfs_rq(cfs_rq);
5577 /* At this point se is NULL and we are at root level*/
5578 add_nr_running(rq, 1);
5581 * Since new tasks are assigned an initial util_avg equal to
5582 * half of the spare capacity of their CPU, tiny tasks have the
5583 * ability to cross the overutilized threshold, which will
5584 * result in the load balancer ruining all the task placement
5585 * done by EAS. As a way to mitigate that effect, do not account
5586 * for the first enqueue operation of new tasks during the
5587 * overutilized flag detection.
5589 * A better way of solving this problem would be to wait for
5590 * the PELT signals of tasks to converge before taking them
5591 * into account, but that is not straightforward to implement,
5592 * and the following generally works well enough in practice.
5595 update_overutilized_status(rq);
5598 if (cfs_bandwidth_used()) {
5600 * When bandwidth control is enabled; the cfs_rq_throttled()
5601 * breaks in the above iteration can result in incomplete
5602 * leaf list maintenance, resulting in triggering the assertion
5605 for_each_sched_entity(se) {
5606 cfs_rq = cfs_rq_of(se);
5608 if (list_add_leaf_cfs_rq(cfs_rq))
5613 assert_list_leaf_cfs_rq(rq);
5618 static void set_next_buddy(struct sched_entity *se);
5621 * The dequeue_task method is called before nr_running is
5622 * decreased. We remove the task from the rbtree and
5623 * update the fair scheduling stats:
5625 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5627 struct cfs_rq *cfs_rq;
5628 struct sched_entity *se = &p->se;
5629 int task_sleep = flags & DEQUEUE_SLEEP;
5630 int idle_h_nr_running = task_has_idle_policy(p);
5631 bool was_sched_idle = sched_idle_rq(rq);
5633 util_est_dequeue(&rq->cfs, p);
5635 for_each_sched_entity(se) {
5636 cfs_rq = cfs_rq_of(se);
5637 dequeue_entity(cfs_rq, se, flags);
5639 cfs_rq->h_nr_running--;
5640 cfs_rq->idle_h_nr_running -= idle_h_nr_running;
5642 /* end evaluation on encountering a throttled cfs_rq */
5643 if (cfs_rq_throttled(cfs_rq))
5644 goto dequeue_throttle;
5646 /* Don't dequeue parent if it has other entities besides us */
5647 if (cfs_rq->load.weight) {
5648 /* Avoid re-evaluating load for this entity: */
5649 se = parent_entity(se);
5651 * Bias pick_next to pick a task from this cfs_rq, as
5652 * p is sleeping when it is within its sched_slice.
5654 if (task_sleep && se && !throttled_hierarchy(cfs_rq))
5658 flags |= DEQUEUE_SLEEP;
5661 for_each_sched_entity(se) {
5662 cfs_rq = cfs_rq_of(se);
5664 update_load_avg(cfs_rq, se, UPDATE_TG);
5665 se_update_runnable(se);
5666 update_cfs_group(se);
5668 cfs_rq->h_nr_running--;
5669 cfs_rq->idle_h_nr_running -= idle_h_nr_running;
5671 /* end evaluation on encountering a throttled cfs_rq */
5672 if (cfs_rq_throttled(cfs_rq))
5673 goto dequeue_throttle;
5677 /* At this point se is NULL and we are at root level*/
5678 sub_nr_running(rq, 1);
5680 /* balance early to pull high priority tasks */
5681 if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
5682 rq->next_balance = jiffies;
5685 util_est_update(&rq->cfs, p, task_sleep);
5691 /* Working cpumask for: load_balance, load_balance_newidle. */
5692 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5693 DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
5695 #ifdef CONFIG_NO_HZ_COMMON
5698 cpumask_var_t idle_cpus_mask;
5700 int has_blocked; /* Idle CPUS has blocked load */
5701 unsigned long next_balance; /* in jiffy units */
5702 unsigned long next_blocked; /* Next update of blocked load in jiffies */
5703 } nohz ____cacheline_aligned;
5705 #endif /* CONFIG_NO_HZ_COMMON */
5707 static unsigned long cpu_load(struct rq *rq)
5709 return cfs_rq_load_avg(&rq->cfs);
5713 * cpu_load_without - compute CPU load without any contributions from *p
5714 * @cpu: the CPU which load is requested
5715 * @p: the task which load should be discounted
5717 * The load of a CPU is defined by the load of tasks currently enqueued on that
5718 * CPU as well as tasks which are currently sleeping after an execution on that
5721 * This method returns the load of the specified CPU by discounting the load of
5722 * the specified task, whenever the task is currently contributing to the CPU
5725 static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p)
5727 struct cfs_rq *cfs_rq;
5730 /* Task has no contribution or is new */
5731 if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
5732 return cpu_load(rq);
5735 load = READ_ONCE(cfs_rq->avg.load_avg);
5737 /* Discount task's util from CPU's util */
5738 lsub_positive(&load, task_h_load(p));
5743 static unsigned long cpu_runnable(struct rq *rq)
5745 return cfs_rq_runnable_avg(&rq->cfs);
5748 static unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p)
5750 struct cfs_rq *cfs_rq;
5751 unsigned int runnable;
5753 /* Task has no contribution or is new */
5754 if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
5755 return cpu_runnable(rq);
5758 runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
5760 /* Discount task's runnable from CPU's runnable */
5761 lsub_positive(&runnable, p->se.avg.runnable_avg);
5766 static unsigned long capacity_of(int cpu)
5768 return cpu_rq(cpu)->cpu_capacity;
5771 static void record_wakee(struct task_struct *p)
5774 * Only decay a single time; tasks that have less then 1 wakeup per
5775 * jiffy will not have built up many flips.
5777 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
5778 current->wakee_flips >>= 1;
5779 current->wakee_flip_decay_ts = jiffies;
5782 if (current->last_wakee != p) {
5783 current->last_wakee = p;
5784 current->wakee_flips++;
5789 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5791 * A waker of many should wake a different task than the one last awakened
5792 * at a frequency roughly N times higher than one of its wakees.
5794 * In order to determine whether we should let the load spread vs consolidating
5795 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5796 * partner, and a factor of lls_size higher frequency in the other.
5798 * With both conditions met, we can be relatively sure that the relationship is
5799 * non-monogamous, with partner count exceeding socket size.
5801 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5802 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5805 static int wake_wide(struct task_struct *p)
5807 unsigned int master = current->wakee_flips;
5808 unsigned int slave = p->wakee_flips;
5809 int factor = __this_cpu_read(sd_llc_size);
5812 swap(master, slave);
5813 if (slave < factor || master < slave * factor)
5819 * The purpose of wake_affine() is to quickly determine on which CPU we can run
5820 * soonest. For the purpose of speed we only consider the waking and previous
5823 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
5824 * cache-affine and is (or will be) idle.
5826 * wake_affine_weight() - considers the weight to reflect the average
5827 * scheduling latency of the CPUs. This seems to work
5828 * for the overloaded case.
5831 wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5834 * If this_cpu is idle, it implies the wakeup is from interrupt
5835 * context. Only allow the move if cache is shared. Otherwise an
5836 * interrupt intensive workload could force all tasks onto one
5837 * node depending on the IO topology or IRQ affinity settings.
5839 * If the prev_cpu is idle and cache affine then avoid a migration.
5840 * There is no guarantee that the cache hot data from an interrupt
5841 * is more important than cache hot data on the prev_cpu and from
5842 * a cpufreq perspective, it's better to have higher utilisation
5845 if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
5846 return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5848 if (sync && cpu_rq(this_cpu)->nr_running == 1)
5851 if (available_idle_cpu(prev_cpu))
5854 return nr_cpumask_bits;
5858 wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
5859 int this_cpu, int prev_cpu, int sync)
5861 s64 this_eff_load, prev_eff_load;
5862 unsigned long task_load;
5864 this_eff_load = cpu_load(cpu_rq(this_cpu));
5867 unsigned long current_load = task_h_load(current);
5869 if (current_load > this_eff_load)
5872 this_eff_load -= current_load;
5875 task_load = task_h_load(p);
5877 this_eff_load += task_load;
5878 if (sched_feat(WA_BIAS))
5879 this_eff_load *= 100;
5880 this_eff_load *= capacity_of(prev_cpu);
5882 prev_eff_load = cpu_load(cpu_rq(prev_cpu));
5883 prev_eff_load -= task_load;
5884 if (sched_feat(WA_BIAS))
5885 prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
5886 prev_eff_load *= capacity_of(this_cpu);
5889 * If sync, adjust the weight of prev_eff_load such that if
5890 * prev_eff == this_eff that select_idle_sibling() will consider
5891 * stacking the wakee on top of the waker if no other CPU is
5897 return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
5900 static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5901 int this_cpu, int prev_cpu, int sync)
5903 int target = nr_cpumask_bits;
5905 if (sched_feat(WA_IDLE))
5906 target = wake_affine_idle(this_cpu, prev_cpu, sync);
5908 if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
5909 target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5911 schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5912 if (target == nr_cpumask_bits)
5915 schedstat_inc(sd->ttwu_move_affine);
5916 schedstat_inc(p->se.statistics.nr_wakeups_affine);
5920 static struct sched_group *
5921 find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu);
5924 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5927 find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5929 unsigned long load, min_load = ULONG_MAX;
5930 unsigned int min_exit_latency = UINT_MAX;
5931 u64 latest_idle_timestamp = 0;
5932 int least_loaded_cpu = this_cpu;
5933 int shallowest_idle_cpu = -1;
5936 /* Check if we have any choice: */
5937 if (group->group_weight == 1)
5938 return cpumask_first(sched_group_span(group));
5940 /* Traverse only the allowed CPUs */
5941 for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) {
5942 struct rq *rq = cpu_rq(i);
5944 if (!sched_core_cookie_match(rq, p))
5947 if (sched_idle_cpu(i))
5950 if (available_idle_cpu(i)) {
5951 struct cpuidle_state *idle = idle_get_state(rq);
5952 if (idle && idle->exit_latency < min_exit_latency) {
5954 * We give priority to a CPU whose idle state
5955 * has the smallest exit latency irrespective
5956 * of any idle timestamp.
5958 min_exit_latency = idle->exit_latency;
5959 latest_idle_timestamp = rq->idle_stamp;
5960 shallowest_idle_cpu = i;
5961 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
5962 rq->idle_stamp > latest_idle_timestamp) {
5964 * If equal or no active idle state, then
5965 * the most recently idled CPU might have
5968 latest_idle_timestamp = rq->idle_stamp;
5969 shallowest_idle_cpu = i;
5971 } else if (shallowest_idle_cpu == -1) {
5972 load = cpu_load(cpu_rq(i));
5973 if (load < min_load) {
5975 least_loaded_cpu = i;
5980 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5983 static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
5984 int cpu, int prev_cpu, int sd_flag)
5988 if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
5992 * We need task's util for cpu_util_without, sync it up to
5993 * prev_cpu's last_update_time.
5995 if (!(sd_flag & SD_BALANCE_FORK))
5996 sync_entity_load_avg(&p->se);
5999 struct sched_group *group;
6000 struct sched_domain *tmp;
6003 if (!(sd->flags & sd_flag)) {
6008 group = find_idlest_group(sd, p, cpu);
6014 new_cpu = find_idlest_group_cpu(group, p, cpu);
6015 if (new_cpu == cpu) {
6016 /* Now try balancing at a lower domain level of 'cpu': */
6021 /* Now try balancing at a lower domain level of 'new_cpu': */
6023 weight = sd->span_weight;
6025 for_each_domain(cpu, tmp) {
6026 if (weight <= tmp->span_weight)
6028 if (tmp->flags & sd_flag)
6036 static inline int __select_idle_cpu(int cpu, struct task_struct *p)
6038 if ((available_idle_cpu(cpu) || sched_idle_cpu(cpu)) &&
6039 sched_cpu_cookie_match(cpu_rq(cpu), p))
6045 #ifdef CONFIG_SCHED_SMT
6046 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
6047 EXPORT_SYMBOL_GPL(sched_smt_present);
6049 static inline void set_idle_cores(int cpu, int val)
6051 struct sched_domain_shared *sds;
6053 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
6055 WRITE_ONCE(sds->has_idle_cores, val);
6058 static inline bool test_idle_cores(int cpu, bool def)
6060 struct sched_domain_shared *sds;
6062 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
6064 return READ_ONCE(sds->has_idle_cores);
6070 * Scans the local SMT mask to see if the entire core is idle, and records this
6071 * information in sd_llc_shared->has_idle_cores.
6073 * Since SMT siblings share all cache levels, inspecting this limited remote
6074 * state should be fairly cheap.
6076 void __update_idle_core(struct rq *rq)
6078 int core = cpu_of(rq);
6082 if (test_idle_cores(core, true))
6085 for_each_cpu(cpu, cpu_smt_mask(core)) {
6089 if (!available_idle_cpu(cpu))
6093 set_idle_cores(core, 1);
6099 * Scan the entire LLC domain for idle cores; this dynamically switches off if
6100 * there are no idle cores left in the system; tracked through
6101 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
6103 static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
6108 if (!static_branch_likely(&sched_smt_present))
6109 return __select_idle_cpu(core, p);
6111 for_each_cpu(cpu, cpu_smt_mask(core)) {
6112 if (!available_idle_cpu(cpu)) {
6114 if (*idle_cpu == -1) {
6115 if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
6123 if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
6130 cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
6135 * Scan the local SMT mask for idle CPUs.
6137 static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
6141 for_each_cpu(cpu, cpu_smt_mask(target)) {
6142 if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
6143 !cpumask_test_cpu(cpu, sched_domain_span(sd)))
6145 if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
6152 #else /* CONFIG_SCHED_SMT */
6154 static inline void set_idle_cores(int cpu, int val)
6158 static inline bool test_idle_cores(int cpu, bool def)
6163 static inline int select_idle_core(struct task_struct *p, int core, struct cpumask *cpus, int *idle_cpu)
6165 return __select_idle_cpu(core, p);
6168 static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
6173 #endif /* CONFIG_SCHED_SMT */
6176 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
6177 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
6178 * average idle time for this rq (as found in rq->avg_idle).
6180 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool has_idle_core, int target)
6182 struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6183 int i, cpu, idle_cpu = -1, nr = INT_MAX;
6184 struct rq *this_rq = this_rq();
6185 int this = smp_processor_id();
6186 struct sched_domain *this_sd;
6189 this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
6193 cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6195 if (sched_feat(SIS_PROP) && !has_idle_core) {
6196 u64 avg_cost, avg_idle, span_avg;
6197 unsigned long now = jiffies;
6200 * If we're busy, the assumption that the last idle period
6201 * predicts the future is flawed; age away the remaining
6202 * predicted idle time.
6204 if (unlikely(this_rq->wake_stamp < now)) {
6205 while (this_rq->wake_stamp < now && this_rq->wake_avg_idle) {
6206 this_rq->wake_stamp++;
6207 this_rq->wake_avg_idle >>= 1;
6211 avg_idle = this_rq->wake_avg_idle;
6212 avg_cost = this_sd->avg_scan_cost + 1;
6214 span_avg = sd->span_weight * avg_idle;
6215 if (span_avg > 4*avg_cost)
6216 nr = div_u64(span_avg, avg_cost);
6220 time = cpu_clock(this);
6223 for_each_cpu_wrap(cpu, cpus, target + 1) {
6224 if (has_idle_core) {
6225 i = select_idle_core(p, cpu, cpus, &idle_cpu);
6226 if ((unsigned int)i < nr_cpumask_bits)
6232 idle_cpu = __select_idle_cpu(cpu, p);
6233 if ((unsigned int)idle_cpu < nr_cpumask_bits)
6239 set_idle_cores(target, false);
6241 if (sched_feat(SIS_PROP) && !has_idle_core) {
6242 time = cpu_clock(this) - time;
6245 * Account for the scan cost of wakeups against the average
6248 this_rq->wake_avg_idle -= min(this_rq->wake_avg_idle, time);
6250 update_avg(&this_sd->avg_scan_cost, time);
6257 * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
6258 * the task fits. If no CPU is big enough, but there are idle ones, try to
6259 * maximize capacity.
6262 select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
6264 unsigned long task_util, best_cap = 0;
6265 int cpu, best_cpu = -1;
6266 struct cpumask *cpus;
6268 cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6269 cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6271 task_util = uclamp_task_util(p);
6273 for_each_cpu_wrap(cpu, cpus, target) {
6274 unsigned long cpu_cap = capacity_of(cpu);
6276 if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
6278 if (fits_capacity(task_util, cpu_cap))
6281 if (cpu_cap > best_cap) {
6290 static inline bool asym_fits_capacity(int task_util, int cpu)
6292 if (static_branch_unlikely(&sched_asym_cpucapacity))
6293 return fits_capacity(task_util, capacity_of(cpu));
6299 * Try and locate an idle core/thread in the LLC cache domain.
6301 static int select_idle_sibling(struct task_struct *p, int prev, int target)
6303 bool has_idle_core = false;
6304 struct sched_domain *sd;
6305 unsigned long task_util;
6306 int i, recent_used_cpu;
6309 * On asymmetric system, update task utilization because we will check
6310 * that the task fits with cpu's capacity.
6312 if (static_branch_unlikely(&sched_asym_cpucapacity)) {
6313 sync_entity_load_avg(&p->se);
6314 task_util = uclamp_task_util(p);
6318 * per-cpu select_idle_mask usage
6320 lockdep_assert_irqs_disabled();
6322 if ((available_idle_cpu(target) || sched_idle_cpu(target)) &&
6323 asym_fits_capacity(task_util, target))
6327 * If the previous CPU is cache affine and idle, don't be stupid:
6329 if (prev != target && cpus_share_cache(prev, target) &&
6330 (available_idle_cpu(prev) || sched_idle_cpu(prev)) &&
6331 asym_fits_capacity(task_util, prev))
6335 * Allow a per-cpu kthread to stack with the wakee if the
6336 * kworker thread and the tasks previous CPUs are the same.
6337 * The assumption is that the wakee queued work for the
6338 * per-cpu kthread that is now complete and the wakeup is
6339 * essentially a sync wakeup. An obvious example of this
6340 * pattern is IO completions.
6342 if (is_per_cpu_kthread(current) &&
6343 prev == smp_processor_id() &&
6344 this_rq()->nr_running <= 1) {
6348 /* Check a recently used CPU as a potential idle candidate: */
6349 recent_used_cpu = p->recent_used_cpu;
6350 p->recent_used_cpu = prev;
6351 if (recent_used_cpu != prev &&
6352 recent_used_cpu != target &&
6353 cpus_share_cache(recent_used_cpu, target) &&
6354 (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
6355 cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) &&
6356 asym_fits_capacity(task_util, recent_used_cpu)) {
6358 * Replace recent_used_cpu with prev as it is a potential
6359 * candidate for the next wake:
6361 p->recent_used_cpu = prev;
6362 return recent_used_cpu;
6366 * For asymmetric CPU capacity systems, our domain of interest is
6367 * sd_asym_cpucapacity rather than sd_llc.
6369 if (static_branch_unlikely(&sched_asym_cpucapacity)) {
6370 sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
6372 * On an asymmetric CPU capacity system where an exclusive
6373 * cpuset defines a symmetric island (i.e. one unique
6374 * capacity_orig value through the cpuset), the key will be set
6375 * but the CPUs within that cpuset will not have a domain with
6376 * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
6380 i = select_idle_capacity(p, sd, target);
6381 return ((unsigned)i < nr_cpumask_bits) ? i : target;
6385 sd = rcu_dereference(per_cpu(sd_llc, target));
6389 if (sched_smt_active()) {
6390 has_idle_core = test_idle_cores(target, false);
6392 if (!has_idle_core && cpus_share_cache(prev, target)) {
6393 i = select_idle_smt(p, sd, prev);
6394 if ((unsigned int)i < nr_cpumask_bits)
6399 i = select_idle_cpu(p, sd, has_idle_core, target);
6400 if ((unsigned)i < nr_cpumask_bits)
6407 * cpu_util - Estimates the amount of capacity of a CPU used by CFS tasks.
6408 * @cpu: the CPU to get the utilization of
6410 * The unit of the return value must be the one of capacity so we can compare
6411 * the utilization with the capacity of the CPU that is available for CFS task
6412 * (ie cpu_capacity).
6414 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
6415 * recent utilization of currently non-runnable tasks on a CPU. It represents
6416 * the amount of utilization of a CPU in the range [0..capacity_orig] where
6417 * capacity_orig is the cpu_capacity available at the highest frequency
6418 * (arch_scale_freq_capacity()).
6419 * The utilization of a CPU converges towards a sum equal to or less than the
6420 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
6421 * the running time on this CPU scaled by capacity_curr.
6423 * The estimated utilization of a CPU is defined to be the maximum between its
6424 * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
6425 * currently RUNNABLE on that CPU.
6426 * This allows to properly represent the expected utilization of a CPU which
6427 * has just got a big task running since a long sleep period. At the same time
6428 * however it preserves the benefits of the "blocked utilization" in
6429 * describing the potential for other tasks waking up on the same CPU.
6431 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
6432 * higher than capacity_orig because of unfortunate rounding in
6433 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
6434 * the average stabilizes with the new running time. We need to check that the
6435 * utilization stays within the range of [0..capacity_orig] and cap it if
6436 * necessary. Without utilization capping, a group could be seen as overloaded
6437 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
6438 * available capacity. We allow utilization to overshoot capacity_curr (but not
6439 * capacity_orig) as it useful for predicting the capacity required after task
6440 * migrations (scheduler-driven DVFS).
6442 * Return: the (estimated) utilization for the specified CPU
6444 static inline unsigned long cpu_util(int cpu)
6446 struct cfs_rq *cfs_rq;
6449 cfs_rq = &cpu_rq(cpu)->cfs;
6450 util = READ_ONCE(cfs_rq->avg.util_avg);
6452 if (sched_feat(UTIL_EST))
6453 util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
6455 return min_t(unsigned long, util, capacity_orig_of(cpu));
6459 * cpu_util_without: compute cpu utilization without any contributions from *p
6460 * @cpu: the CPU which utilization is requested
6461 * @p: the task which utilization should be discounted
6463 * The utilization of a CPU is defined by the utilization of tasks currently
6464 * enqueued on that CPU as well as tasks which are currently sleeping after an
6465 * execution on that CPU.
6467 * This method returns the utilization of the specified CPU by discounting the
6468 * utilization of the specified task, whenever the task is currently
6469 * contributing to the CPU utilization.
6471 static unsigned long cpu_util_without(int cpu, struct task_struct *p)
6473 struct cfs_rq *cfs_rq;
6476 /* Task has no contribution or is new */
6477 if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
6478 return cpu_util(cpu);
6480 cfs_rq = &cpu_rq(cpu)->cfs;
6481 util = READ_ONCE(cfs_rq->avg.util_avg);
6483 /* Discount task's util from CPU's util */
6484 lsub_positive(&util, task_util(p));
6489 * a) if *p is the only task sleeping on this CPU, then:
6490 * cpu_util (== task_util) > util_est (== 0)
6491 * and thus we return:
6492 * cpu_util_without = (cpu_util - task_util) = 0
6494 * b) if other tasks are SLEEPING on this CPU, which is now exiting
6496 * cpu_util >= task_util
6497 * cpu_util > util_est (== 0)
6498 * and thus we discount *p's blocked utilization to return:
6499 * cpu_util_without = (cpu_util - task_util) >= 0
6501 * c) if other tasks are RUNNABLE on that CPU and
6502 * util_est > cpu_util
6503 * then we use util_est since it returns a more restrictive
6504 * estimation of the spare capacity on that CPU, by just
6505 * considering the expected utilization of tasks already
6506 * runnable on that CPU.
6508 * Cases a) and b) are covered by the above code, while case c) is
6509 * covered by the following code when estimated utilization is
6512 if (sched_feat(UTIL_EST)) {
6513 unsigned int estimated =
6514 READ_ONCE(cfs_rq->avg.util_est.enqueued);
6517 * Despite the following checks we still have a small window
6518 * for a possible race, when an execl's select_task_rq_fair()
6519 * races with LB's detach_task():
6522 * p->on_rq = TASK_ON_RQ_MIGRATING;
6523 * ---------------------------------- A
6524 * deactivate_task() \
6525 * dequeue_task() + RaceTime
6526 * util_est_dequeue() /
6527 * ---------------------------------- B
6529 * The additional check on "current == p" it's required to
6530 * properly fix the execl regression and it helps in further
6531 * reducing the chances for the above race.
6533 if (unlikely(task_on_rq_queued(p) || current == p))
6534 lsub_positive(&estimated, _task_util_est(p));
6536 util = max(util, estimated);
6540 * Utilization (estimated) can exceed the CPU capacity, thus let's
6541 * clamp to the maximum CPU capacity to ensure consistency with
6542 * the cpu_util call.
6544 return min_t(unsigned long, util, capacity_orig_of(cpu));
6548 * Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued)
6551 static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
6553 struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
6554 unsigned long util_est, util = READ_ONCE(cfs_rq->avg.util_avg);
6557 * If @p migrates from @cpu to another, remove its contribution. Or,
6558 * if @p migrates from another CPU to @cpu, add its contribution. In
6559 * the other cases, @cpu is not impacted by the migration, so the
6560 * util_avg should already be correct.
6562 if (task_cpu(p) == cpu && dst_cpu != cpu)
6563 lsub_positive(&util, task_util(p));
6564 else if (task_cpu(p) != cpu && dst_cpu == cpu)
6565 util += task_util(p);
6567 if (sched_feat(UTIL_EST)) {
6568 util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);
6571 * During wake-up, the task isn't enqueued yet and doesn't
6572 * appear in the cfs_rq->avg.util_est.enqueued of any rq,
6573 * so just add it (if needed) to "simulate" what will be
6574 * cpu_util() after the task has been enqueued.
6577 util_est += _task_util_est(p);
6579 util = max(util, util_est);
6582 return min(util, capacity_orig_of(cpu));
6586 * compute_energy(): Estimates the energy that @pd would consume if @p was
6587 * migrated to @dst_cpu. compute_energy() predicts what will be the utilization
6588 * landscape of @pd's CPUs after the task migration, and uses the Energy Model
6589 * to compute what would be the energy if we decided to actually migrate that
6593 compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
6595 struct cpumask *pd_mask = perf_domain_span(pd);
6596 unsigned long cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask));
6597 unsigned long max_util = 0, sum_util = 0;
6598 unsigned long _cpu_cap = cpu_cap;
6601 _cpu_cap -= arch_scale_thermal_pressure(cpumask_first(pd_mask));
6604 * The capacity state of CPUs of the current rd can be driven by CPUs
6605 * of another rd if they belong to the same pd. So, account for the
6606 * utilization of these CPUs too by masking pd with cpu_online_mask
6607 * instead of the rd span.
6609 * If an entire pd is outside of the current rd, it will not appear in
6610 * its pd list and will not be accounted by compute_energy().
6612 for_each_cpu_and(cpu, pd_mask, cpu_online_mask) {
6613 unsigned long util_freq = cpu_util_next(cpu, p, dst_cpu);
6614 unsigned long cpu_util, util_running = util_freq;
6615 struct task_struct *tsk = NULL;
6618 * When @p is placed on @cpu:
6620 * util_running = max(cpu_util, cpu_util_est) +
6621 * max(task_util, _task_util_est)
6623 * while cpu_util_next is: max(cpu_util + task_util,
6624 * cpu_util_est + _task_util_est)
6626 if (cpu == dst_cpu) {
6629 cpu_util_next(cpu, p, -1) + task_util_est(p);
6633 * Busy time computation: utilization clamping is not
6634 * required since the ratio (sum_util / cpu_capacity)
6635 * is already enough to scale the EM reported power
6636 * consumption at the (eventually clamped) cpu_capacity.
6638 cpu_util = effective_cpu_util(cpu, util_running, cpu_cap,
6641 sum_util += min(cpu_util, _cpu_cap);
6644 * Performance domain frequency: utilization clamping
6645 * must be considered since it affects the selection
6646 * of the performance domain frequency.
6647 * NOTE: in case RT tasks are running, by default the
6648 * FREQUENCY_UTIL's utilization can be max OPP.
6650 cpu_util = effective_cpu_util(cpu, util_freq, cpu_cap,
6651 FREQUENCY_UTIL, tsk);
6652 max_util = max(max_util, min(cpu_util, _cpu_cap));
6655 return em_cpu_energy(pd->em_pd, max_util, sum_util, _cpu_cap);
6659 * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
6660 * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
6661 * spare capacity in each performance domain and uses it as a potential
6662 * candidate to execute the task. Then, it uses the Energy Model to figure
6663 * out which of the CPU candidates is the most energy-efficient.
6665 * The rationale for this heuristic is as follows. In a performance domain,
6666 * all the most energy efficient CPU candidates (according to the Energy
6667 * Model) are those for which we'll request a low frequency. When there are
6668 * several CPUs for which the frequency request will be the same, we don't
6669 * have enough data to break the tie between them, because the Energy Model
6670 * only includes active power costs. With this model, if we assume that
6671 * frequency requests follow utilization (e.g. using schedutil), the CPU with
6672 * the maximum spare capacity in a performance domain is guaranteed to be among
6673 * the best candidates of the performance domain.
6675 * In practice, it could be preferable from an energy standpoint to pack
6676 * small tasks on a CPU in order to let other CPUs go in deeper idle states,
6677 * but that could also hurt our chances to go cluster idle, and we have no
6678 * ways to tell with the current Energy Model if this is actually a good
6679 * idea or not. So, find_energy_efficient_cpu() basically favors
6680 * cluster-packing, and spreading inside a cluster. That should at least be
6681 * a good thing for latency, and this is consistent with the idea that most
6682 * of the energy savings of EAS come from the asymmetry of the system, and
6683 * not so much from breaking the tie between identical CPUs. That's also the
6684 * reason why EAS is enabled in the topology code only for systems where
6685 * SD_ASYM_CPUCAPACITY is set.
6687 * NOTE: Forkees are not accepted in the energy-aware wake-up path because
6688 * they don't have any useful utilization data yet and it's not possible to
6689 * forecast their impact on energy consumption. Consequently, they will be
6690 * placed by find_idlest_cpu() on the least loaded CPU, which might turn out
6691 * to be energy-inefficient in some use-cases. The alternative would be to
6692 * bias new tasks towards specific types of CPUs first, or to try to infer
6693 * their util_avg from the parent task, but those heuristics could hurt
6694 * other use-cases too. So, until someone finds a better way to solve this,
6695 * let's keep things simple by re-using the existing slow path.
6697 static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
6699 unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
6700 struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
6701 int cpu, best_energy_cpu = prev_cpu, target = -1;
6702 unsigned long cpu_cap, util, base_energy = 0;
6703 struct sched_domain *sd;
6704 struct perf_domain *pd;
6707 pd = rcu_dereference(rd->pd);
6708 if (!pd || READ_ONCE(rd->overutilized))
6712 * Energy-aware wake-up happens on the lowest sched_domain starting
6713 * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
6715 sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
6716 while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
6723 sync_entity_load_avg(&p->se);
6724 if (!task_util_est(p))
6727 for (; pd; pd = pd->next) {
6728 unsigned long cur_delta, spare_cap, max_spare_cap = 0;
6729 bool compute_prev_delta = false;
6730 unsigned long base_energy_pd;
6731 int max_spare_cap_cpu = -1;
6733 for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) {
6734 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
6737 util = cpu_util_next(cpu, p, cpu);
6738 cpu_cap = capacity_of(cpu);
6739 spare_cap = cpu_cap;
6740 lsub_positive(&spare_cap, util);
6743 * Skip CPUs that cannot satisfy the capacity request.
6744 * IOW, placing the task there would make the CPU
6745 * overutilized. Take uclamp into account to see how
6746 * much capacity we can get out of the CPU; this is
6747 * aligned with sched_cpu_util().
6749 util = uclamp_rq_util_with(cpu_rq(cpu), util, p);
6750 if (!fits_capacity(util, cpu_cap))
6753 if (cpu == prev_cpu) {
6754 /* Always use prev_cpu as a candidate. */
6755 compute_prev_delta = true;
6756 } else if (spare_cap > max_spare_cap) {
6758 * Find the CPU with the maximum spare capacity
6759 * in the performance domain.
6761 max_spare_cap = spare_cap;
6762 max_spare_cap_cpu = cpu;
6766 if (max_spare_cap_cpu < 0 && !compute_prev_delta)
6769 /* Compute the 'base' energy of the pd, without @p */
6770 base_energy_pd = compute_energy(p, -1, pd);
6771 base_energy += base_energy_pd;
6773 /* Evaluate the energy impact of using prev_cpu. */
6774 if (compute_prev_delta) {
6775 prev_delta = compute_energy(p, prev_cpu, pd);
6776 if (prev_delta < base_energy_pd)
6778 prev_delta -= base_energy_pd;
6779 best_delta = min(best_delta, prev_delta);
6782 /* Evaluate the energy impact of using max_spare_cap_cpu. */
6783 if (max_spare_cap_cpu >= 0) {
6784 cur_delta = compute_energy(p, max_spare_cap_cpu, pd);
6785 if (cur_delta < base_energy_pd)
6787 cur_delta -= base_energy_pd;
6788 if (cur_delta < best_delta) {
6789 best_delta = cur_delta;
6790 best_energy_cpu = max_spare_cap_cpu;
6797 * Pick the best CPU if prev_cpu cannot be used, or if it saves at
6798 * least 6% of the energy used by prev_cpu.
6800 if ((prev_delta == ULONG_MAX) ||
6801 (prev_delta - best_delta) > ((prev_delta + base_energy) >> 4))
6802 target = best_energy_cpu;
6813 * select_task_rq_fair: Select target runqueue for the waking task in domains
6814 * that have the relevant SD flag set. In practice, this is SD_BALANCE_WAKE,
6815 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
6817 * Balances load by selecting the idlest CPU in the idlest group, or under
6818 * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
6820 * Returns the target CPU number.
6823 select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
6825 int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6826 struct sched_domain *tmp, *sd = NULL;
6827 int cpu = smp_processor_id();
6828 int new_cpu = prev_cpu;
6829 int want_affine = 0;
6830 /* SD_flags and WF_flags share the first nibble */
6831 int sd_flag = wake_flags & 0xF;
6834 * required for stable ->cpus_allowed
6836 lockdep_assert_held(&p->pi_lock);
6837 if (wake_flags & WF_TTWU) {
6840 if (sched_energy_enabled()) {
6841 new_cpu = find_energy_efficient_cpu(p, prev_cpu);
6847 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
6851 for_each_domain(cpu, tmp) {
6853 * If both 'cpu' and 'prev_cpu' are part of this domain,
6854 * cpu is a valid SD_WAKE_AFFINE target.
6856 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
6857 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
6858 if (cpu != prev_cpu)
6859 new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
6861 sd = NULL; /* Prefer wake_affine over balance flags */
6865 if (tmp->flags & sd_flag)
6867 else if (!want_affine)
6873 new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6874 } else if (wake_flags & WF_TTWU) { /* XXX always ? */
6876 new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
6883 static void detach_entity_cfs_rq(struct sched_entity *se);
6886 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6887 * cfs_rq_of(p) references at time of call are still valid and identify the
6888 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6890 static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
6893 * As blocked tasks retain absolute vruntime the migration needs to
6894 * deal with this by subtracting the old and adding the new
6895 * min_vruntime -- the latter is done by enqueue_entity() when placing
6896 * the task on the new runqueue.
6898 if (READ_ONCE(p->__state) == TASK_WAKING) {
6899 struct sched_entity *se = &p->se;
6900 struct cfs_rq *cfs_rq = cfs_rq_of(se);
6903 #ifndef CONFIG_64BIT
6904 u64 min_vruntime_copy;
6907 min_vruntime_copy = cfs_rq->min_vruntime_copy;
6909 min_vruntime = cfs_rq->min_vruntime;
6910 } while (min_vruntime != min_vruntime_copy);
6912 min_vruntime = cfs_rq->min_vruntime;
6915 se->vruntime -= min_vruntime;
6918 if (p->on_rq == TASK_ON_RQ_MIGRATING) {
6920 * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
6921 * rq->lock and can modify state directly.
6923 lockdep_assert_rq_held(task_rq(p));
6924 detach_entity_cfs_rq(&p->se);
6928 * We are supposed to update the task to "current" time, then
6929 * its up to date and ready to go to new CPU/cfs_rq. But we
6930 * have difficulty in getting what current time is, so simply
6931 * throw away the out-of-date time. This will result in the
6932 * wakee task is less decayed, but giving the wakee more load
6935 remove_entity_load_avg(&p->se);
6938 /* Tell new CPU we are migrated */
6939 p->se.avg.last_update_time = 0;
6941 /* We have migrated, no longer consider this task hot */
6942 p->se.exec_start = 0;
6944 update_scan_period(p, new_cpu);
6947 static void task_dead_fair(struct task_struct *p)
6949 remove_entity_load_avg(&p->se);
6953 balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6958 return newidle_balance(rq, rf) != 0;
6960 #endif /* CONFIG_SMP */
6962 static unsigned long wakeup_gran(struct sched_entity *se)
6964 unsigned long gran = sysctl_sched_wakeup_granularity;
6967 * Since its curr running now, convert the gran from real-time
6968 * to virtual-time in his units.
6970 * By using 'se' instead of 'curr' we penalize light tasks, so
6971 * they get preempted easier. That is, if 'se' < 'curr' then
6972 * the resulting gran will be larger, therefore penalizing the
6973 * lighter, if otoh 'se' > 'curr' then the resulting gran will
6974 * be smaller, again penalizing the lighter task.
6976 * This is especially important for buddies when the leftmost
6977 * task is higher priority than the buddy.
6979 return calc_delta_fair(gran, se);
6983 * Should 'se' preempt 'curr'.
6997 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
6999 s64 gran, vdiff = curr->vruntime - se->vruntime;
7004 gran = wakeup_gran(se);
7011 static void set_last_buddy(struct sched_entity *se)
7013 if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
7016 for_each_sched_entity(se) {
7017 if (SCHED_WARN_ON(!se->on_rq))
7019 cfs_rq_of(se)->last = se;
7023 static void set_next_buddy(struct sched_entity *se)
7025 if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
7028 for_each_sched_entity(se) {
7029 if (SCHED_WARN_ON(!se->on_rq))
7031 cfs_rq_of(se)->next = se;
7035 static void set_skip_buddy(struct sched_entity *se)
7037 for_each_sched_entity(se)
7038 cfs_rq_of(se)->skip = se;
7042 * Preempt the current task with a newly woken task if needed:
7044 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
7046 struct task_struct *curr = rq->curr;
7047 struct sched_entity *se = &curr->se, *pse = &p->se;
7048 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
7049 int scale = cfs_rq->nr_running >= sched_nr_latency;
7050 int next_buddy_marked = 0;
7052 if (unlikely(se == pse))
7056 * This is possible from callers such as attach_tasks(), in which we
7057 * unconditionally check_preempt_curr() after an enqueue (which may have
7058 * lead to a throttle). This both saves work and prevents false
7059 * next-buddy nomination below.
7061 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
7064 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
7065 set_next_buddy(pse);
7066 next_buddy_marked = 1;
7070 * We can come here with TIF_NEED_RESCHED already set from new task
7073 * Note: this also catches the edge-case of curr being in a throttled
7074 * group (e.g. via set_curr_task), since update_curr() (in the
7075 * enqueue of curr) will have resulted in resched being set. This
7076 * prevents us from potentially nominating it as a false LAST_BUDDY
7079 if (test_tsk_need_resched(curr))
7082 /* Idle tasks are by definition preempted by non-idle tasks. */
7083 if (unlikely(task_has_idle_policy(curr)) &&
7084 likely(!task_has_idle_policy(p)))
7088 * Batch and idle tasks do not preempt non-idle tasks (their preemption
7089 * is driven by the tick):
7091 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
7094 find_matching_se(&se, &pse);
7095 update_curr(cfs_rq_of(se));
7097 if (wakeup_preempt_entity(se, pse) == 1) {
7099 * Bias pick_next to pick the sched entity that is
7100 * triggering this preemption.
7102 if (!next_buddy_marked)
7103 set_next_buddy(pse);
7112 * Only set the backward buddy when the current task is still
7113 * on the rq. This can happen when a wakeup gets interleaved
7114 * with schedule on the ->pre_schedule() or idle_balance()
7115 * point, either of which can * drop the rq lock.
7117 * Also, during early boot the idle thread is in the fair class,
7118 * for obvious reasons its a bad idea to schedule back to it.
7120 if (unlikely(!se->on_rq || curr == rq->idle))
7123 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
7128 static struct task_struct *pick_task_fair(struct rq *rq)
7130 struct sched_entity *se;
7131 struct cfs_rq *cfs_rq;
7135 if (!cfs_rq->nr_running)
7139 struct sched_entity *curr = cfs_rq->curr;
7141 /* When we pick for a remote RQ, we'll not have done put_prev_entity() */
7144 update_curr(cfs_rq);
7148 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
7152 se = pick_next_entity(cfs_rq, curr);
7153 cfs_rq = group_cfs_rq(se);
7160 struct task_struct *
7161 pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
7163 struct cfs_rq *cfs_rq = &rq->cfs;
7164 struct sched_entity *se;
7165 struct task_struct *p;
7169 if (!sched_fair_runnable(rq))
7172 #ifdef CONFIG_FAIR_GROUP_SCHED
7173 if (!prev || prev->sched_class != &fair_sched_class)
7177 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
7178 * likely that a next task is from the same cgroup as the current.
7180 * Therefore attempt to avoid putting and setting the entire cgroup
7181 * hierarchy, only change the part that actually changes.
7185 struct sched_entity *curr = cfs_rq->curr;
7188 * Since we got here without doing put_prev_entity() we also
7189 * have to consider cfs_rq->curr. If it is still a runnable
7190 * entity, update_curr() will update its vruntime, otherwise
7191 * forget we've ever seen it.
7195 update_curr(cfs_rq);
7200 * This call to check_cfs_rq_runtime() will do the
7201 * throttle and dequeue its entity in the parent(s).
7202 * Therefore the nr_running test will indeed
7205 if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
7208 if (!cfs_rq->nr_running)
7215 se = pick_next_entity(cfs_rq, curr);
7216 cfs_rq = group_cfs_rq(se);
7222 * Since we haven't yet done put_prev_entity and if the selected task
7223 * is a different task than we started out with, try and touch the
7224 * least amount of cfs_rqs.
7227 struct sched_entity *pse = &prev->se;
7229 while (!(cfs_rq = is_same_group(se, pse))) {
7230 int se_depth = se->depth;
7231 int pse_depth = pse->depth;
7233 if (se_depth <= pse_depth) {
7234 put_prev_entity(cfs_rq_of(pse), pse);
7235 pse = parent_entity(pse);
7237 if (se_depth >= pse_depth) {
7238 set_next_entity(cfs_rq_of(se), se);
7239 se = parent_entity(se);
7243 put_prev_entity(cfs_rq, pse);
7244 set_next_entity(cfs_rq, se);
7251 put_prev_task(rq, prev);
7254 se = pick_next_entity(cfs_rq, NULL);
7255 set_next_entity(cfs_rq, se);
7256 cfs_rq = group_cfs_rq(se);
7261 done: __maybe_unused;
7264 * Move the next running task to the front of
7265 * the list, so our cfs_tasks list becomes MRU
7268 list_move(&p->se.group_node, &rq->cfs_tasks);
7271 if (hrtick_enabled_fair(rq))
7272 hrtick_start_fair(rq, p);
7274 update_misfit_status(p, rq);
7282 new_tasks = newidle_balance(rq, rf);
7285 * Because newidle_balance() releases (and re-acquires) rq->lock, it is
7286 * possible for any higher priority task to appear. In that case we
7287 * must re-start the pick_next_entity() loop.
7296 * rq is about to be idle, check if we need to update the
7297 * lost_idle_time of clock_pelt
7299 update_idle_rq_clock_pelt(rq);
7304 static struct task_struct *__pick_next_task_fair(struct rq *rq)
7306 return pick_next_task_fair(rq, NULL, NULL);
7310 * Account for a descheduled task:
7312 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
7314 struct sched_entity *se = &prev->se;
7315 struct cfs_rq *cfs_rq;
7317 for_each_sched_entity(se) {
7318 cfs_rq = cfs_rq_of(se);
7319 put_prev_entity(cfs_rq, se);
7324 * sched_yield() is very simple
7326 * The magic of dealing with the ->skip buddy is in pick_next_entity.
7328 static void yield_task_fair(struct rq *rq)
7330 struct task_struct *curr = rq->curr;
7331 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
7332 struct sched_entity *se = &curr->se;
7335 * Are we the only task in the tree?
7337 if (unlikely(rq->nr_running == 1))
7340 clear_buddies(cfs_rq, se);
7342 if (curr->policy != SCHED_BATCH) {
7343 update_rq_clock(rq);
7345 * Update run-time statistics of the 'current'.
7347 update_curr(cfs_rq);
7349 * Tell update_rq_clock() that we've just updated,
7350 * so we don't do microscopic update in schedule()
7351 * and double the fastpath cost.
7353 rq_clock_skip_update(rq);
7359 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p)
7361 struct sched_entity *se = &p->se;
7363 /* throttled hierarchies are not runnable */
7364 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
7367 /* Tell the scheduler that we'd really like pse to run next. */
7370 yield_task_fair(rq);
7376 /**************************************************
7377 * Fair scheduling class load-balancing methods.
7381 * The purpose of load-balancing is to achieve the same basic fairness the
7382 * per-CPU scheduler provides, namely provide a proportional amount of compute
7383 * time to each task. This is expressed in the following equation:
7385 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
7387 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
7388 * W_i,0 is defined as:
7390 * W_i,0 = \Sum_j w_i,j (2)
7392 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
7393 * is derived from the nice value as per sched_prio_to_weight[].
7395 * The weight average is an exponential decay average of the instantaneous
7398 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
7400 * C_i is the compute capacity of CPU i, typically it is the
7401 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
7402 * can also include other factors [XXX].
7404 * To achieve this balance we define a measure of imbalance which follows
7405 * directly from (1):
7407 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
7409 * We them move tasks around to minimize the imbalance. In the continuous
7410 * function space it is obvious this converges, in the discrete case we get
7411 * a few fun cases generally called infeasible weight scenarios.
7414 * - infeasible weights;
7415 * - local vs global optima in the discrete case. ]
7420 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
7421 * for all i,j solution, we create a tree of CPUs that follows the hardware
7422 * topology where each level pairs two lower groups (or better). This results
7423 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
7424 * tree to only the first of the previous level and we decrease the frequency
7425 * of load-balance at each level inv. proportional to the number of CPUs in
7431 * \Sum { --- * --- * 2^i } = O(n) (5)
7433 * `- size of each group
7434 * | | `- number of CPUs doing load-balance
7436 * `- sum over all levels
7438 * Coupled with a limit on how many tasks we can migrate every balance pass,
7439 * this makes (5) the runtime complexity of the balancer.
7441 * An important property here is that each CPU is still (indirectly) connected
7442 * to every other CPU in at most O(log n) steps:
7444 * The adjacency matrix of the resulting graph is given by:
7447 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
7450 * And you'll find that:
7452 * A^(log_2 n)_i,j != 0 for all i,j (7)
7454 * Showing there's indeed a path between every CPU in at most O(log n) steps.
7455 * The task movement gives a factor of O(m), giving a convergence complexity
7458 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
7463 * In order to avoid CPUs going idle while there's still work to do, new idle
7464 * balancing is more aggressive and has the newly idle CPU iterate up the domain
7465 * tree itself instead of relying on other CPUs to bring it work.
7467 * This adds some complexity to both (5) and (8) but it reduces the total idle
7475 * Cgroups make a horror show out of (2), instead of a simple sum we get:
7478 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
7483 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
7485 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
7487 * The big problem is S_k, its a global sum needed to compute a local (W_i)
7490 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
7491 * rewrite all of this once again.]
7494 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
7496 enum fbq_type { regular, remote, all };
7499 * 'group_type' describes the group of CPUs at the moment of load balancing.
7501 * The enum is ordered by pulling priority, with the group with lowest priority
7502 * first so the group_type can simply be compared when selecting the busiest
7503 * group. See update_sd_pick_busiest().
7506 /* The group has spare capacity that can be used to run more tasks. */
7507 group_has_spare = 0,
7509 * The group is fully used and the tasks don't compete for more CPU
7510 * cycles. Nevertheless, some tasks might wait before running.
7514 * SD_ASYM_CPUCAPACITY only: One task doesn't fit with CPU's capacity
7515 * and must be migrated to a more powerful CPU.
7519 * SD_ASYM_PACKING only: One local CPU with higher capacity is available,
7520 * and the task should be migrated to it instead of running on the
7525 * The tasks' affinity constraints previously prevented the scheduler
7526 * from balancing the load across the system.
7530 * The CPU is overloaded and can't provide expected CPU cycles to all
7536 enum migration_type {
7543 #define LBF_ALL_PINNED 0x01
7544 #define LBF_NEED_BREAK 0x02
7545 #define LBF_DST_PINNED 0x04
7546 #define LBF_SOME_PINNED 0x08
7547 #define LBF_ACTIVE_LB 0x10
7550 struct sched_domain *sd;
7558 struct cpumask *dst_grpmask;
7560 enum cpu_idle_type idle;
7562 /* The set of CPUs under consideration for load-balancing */
7563 struct cpumask *cpus;
7568 unsigned int loop_break;
7569 unsigned int loop_max;
7571 enum fbq_type fbq_type;
7572 enum migration_type migration_type;
7573 struct list_head tasks;
7577 * Is this task likely cache-hot:
7579 static int task_hot(struct task_struct *p, struct lb_env *env)
7583 lockdep_assert_rq_held(env->src_rq);
7585 if (p->sched_class != &fair_sched_class)
7588 if (unlikely(task_has_idle_policy(p)))
7591 /* SMT siblings share cache */
7592 if (env->sd->flags & SD_SHARE_CPUCAPACITY)
7596 * Buddy candidates are cache hot:
7598 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
7599 (&p->se == cfs_rq_of(&p->se)->next ||
7600 &p->se == cfs_rq_of(&p->se)->last))
7603 if (sysctl_sched_migration_cost == -1)
7607 * Don't migrate task if the task's cookie does not match
7608 * with the destination CPU's core cookie.
7610 if (!sched_core_cookie_match(cpu_rq(env->dst_cpu), p))
7613 if (sysctl_sched_migration_cost == 0)
7616 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
7618 return delta < (s64)sysctl_sched_migration_cost;
7621 #ifdef CONFIG_NUMA_BALANCING
7623 * Returns 1, if task migration degrades locality
7624 * Returns 0, if task migration improves locality i.e migration preferred.
7625 * Returns -1, if task migration is not affected by locality.
7627 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
7629 struct numa_group *numa_group = rcu_dereference(p->numa_group);
7630 unsigned long src_weight, dst_weight;
7631 int src_nid, dst_nid, dist;
7633 if (!static_branch_likely(&sched_numa_balancing))
7636 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
7639 src_nid = cpu_to_node(env->src_cpu);
7640 dst_nid = cpu_to_node(env->dst_cpu);
7642 if (src_nid == dst_nid)
7645 /* Migrating away from the preferred node is always bad. */
7646 if (src_nid == p->numa_preferred_nid) {
7647 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
7653 /* Encourage migration to the preferred node. */
7654 if (dst_nid == p->numa_preferred_nid)
7657 /* Leaving a core idle is often worse than degrading locality. */
7658 if (env->idle == CPU_IDLE)
7661 dist = node_distance(src_nid, dst_nid);
7663 src_weight = group_weight(p, src_nid, dist);
7664 dst_weight = group_weight(p, dst_nid, dist);
7666 src_weight = task_weight(p, src_nid, dist);
7667 dst_weight = task_weight(p, dst_nid, dist);
7670 return dst_weight < src_weight;
7674 static inline int migrate_degrades_locality(struct task_struct *p,
7682 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
7685 int can_migrate_task(struct task_struct *p, struct lb_env *env)
7689 lockdep_assert_rq_held(env->src_rq);
7692 * We do not migrate tasks that are:
7693 * 1) throttled_lb_pair, or
7694 * 2) cannot be migrated to this CPU due to cpus_ptr, or
7695 * 3) running (obviously), or
7696 * 4) are cache-hot on their current CPU.
7698 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
7701 /* Disregard pcpu kthreads; they are where they need to be. */
7702 if (kthread_is_per_cpu(p))
7705 if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) {
7708 schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7710 env->flags |= LBF_SOME_PINNED;
7713 * Remember if this task can be migrated to any other CPU in
7714 * our sched_group. We may want to revisit it if we couldn't
7715 * meet load balance goals by pulling other tasks on src_cpu.
7717 * Avoid computing new_dst_cpu
7719 * - if we have already computed one in current iteration
7720 * - if it's an active balance
7722 if (env->idle == CPU_NEWLY_IDLE ||
7723 env->flags & (LBF_DST_PINNED | LBF_ACTIVE_LB))
7726 /* Prevent to re-select dst_cpu via env's CPUs: */
7727 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7728 if (cpumask_test_cpu(cpu, p->cpus_ptr)) {
7729 env->flags |= LBF_DST_PINNED;
7730 env->new_dst_cpu = cpu;
7738 /* Record that we found at least one task that could run on dst_cpu */
7739 env->flags &= ~LBF_ALL_PINNED;
7741 if (task_running(env->src_rq, p)) {
7742 schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7747 * Aggressive migration if:
7749 * 2) destination numa is preferred
7750 * 3) task is cache cold, or
7751 * 4) too many balance attempts have failed.
7753 if (env->flags & LBF_ACTIVE_LB)
7756 tsk_cache_hot = migrate_degrades_locality(p, env);
7757 if (tsk_cache_hot == -1)
7758 tsk_cache_hot = task_hot(p, env);
7760 if (tsk_cache_hot <= 0 ||
7761 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7762 if (tsk_cache_hot == 1) {
7763 schedstat_inc(env->sd->lb_hot_gained[env->idle]);
7764 schedstat_inc(p->se.statistics.nr_forced_migrations);
7769 schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
7774 * detach_task() -- detach the task for the migration specified in env
7776 static void detach_task(struct task_struct *p, struct lb_env *env)
7778 lockdep_assert_rq_held(env->src_rq);
7780 deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7781 set_task_cpu(p, env->dst_cpu);
7785 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7786 * part of active balancing operations within "domain".
7788 * Returns a task if successful and NULL otherwise.
7790 static struct task_struct *detach_one_task(struct lb_env *env)
7792 struct task_struct *p;
7794 lockdep_assert_rq_held(env->src_rq);
7796 list_for_each_entry_reverse(p,
7797 &env->src_rq->cfs_tasks, se.group_node) {
7798 if (!can_migrate_task(p, env))
7801 detach_task(p, env);
7804 * Right now, this is only the second place where
7805 * lb_gained[env->idle] is updated (other is detach_tasks)
7806 * so we can safely collect stats here rather than
7807 * inside detach_tasks().
7809 schedstat_inc(env->sd->lb_gained[env->idle]);
7815 static const unsigned int sched_nr_migrate_break = 32;
7818 * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
7819 * busiest_rq, as part of a balancing operation within domain "sd".
7821 * Returns number of detached tasks if successful and 0 otherwise.
7823 static int detach_tasks(struct lb_env *env)
7825 struct list_head *tasks = &env->src_rq->cfs_tasks;
7826 unsigned long util, load;
7827 struct task_struct *p;
7830 lockdep_assert_rq_held(env->src_rq);
7833 * Source run queue has been emptied by another CPU, clear
7834 * LBF_ALL_PINNED flag as we will not test any task.
7836 if (env->src_rq->nr_running <= 1) {
7837 env->flags &= ~LBF_ALL_PINNED;
7841 if (env->imbalance <= 0)
7844 while (!list_empty(tasks)) {
7846 * We don't want to steal all, otherwise we may be treated likewise,
7847 * which could at worst lead to a livelock crash.
7849 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
7852 p = list_last_entry(tasks, struct task_struct, se.group_node);
7855 /* We've more or less seen every task there is, call it quits */
7856 if (env->loop > env->loop_max)
7859 /* take a breather every nr_migrate tasks */
7860 if (env->loop > env->loop_break) {
7861 env->loop_break += sched_nr_migrate_break;
7862 env->flags |= LBF_NEED_BREAK;
7866 if (!can_migrate_task(p, env))
7869 switch (env->migration_type) {
7872 * Depending of the number of CPUs and tasks and the
7873 * cgroup hierarchy, task_h_load() can return a null
7874 * value. Make sure that env->imbalance decreases
7875 * otherwise detach_tasks() will stop only after
7876 * detaching up to loop_max tasks.
7878 load = max_t(unsigned long, task_h_load(p), 1);
7880 if (sched_feat(LB_MIN) &&
7881 load < 16 && !env->sd->nr_balance_failed)
7885 * Make sure that we don't migrate too much load.
7886 * Nevertheless, let relax the constraint if
7887 * scheduler fails to find a good waiting task to
7890 if (shr_bound(load, env->sd->nr_balance_failed) > env->imbalance)
7893 env->imbalance -= load;
7897 util = task_util_est(p);
7899 if (util > env->imbalance)
7902 env->imbalance -= util;
7909 case migrate_misfit:
7910 /* This is not a misfit task */
7911 if (task_fits_capacity(p, capacity_of(env->src_cpu)))
7918 detach_task(p, env);
7919 list_add(&p->se.group_node, &env->tasks);
7923 #ifdef CONFIG_PREEMPTION
7925 * NEWIDLE balancing is a source of latency, so preemptible
7926 * kernels will stop after the first task is detached to minimize
7927 * the critical section.
7929 if (env->idle == CPU_NEWLY_IDLE)
7934 * We only want to steal up to the prescribed amount of
7937 if (env->imbalance <= 0)
7942 list_move(&p->se.group_node, tasks);
7946 * Right now, this is one of only two places we collect this stat
7947 * so we can safely collect detach_one_task() stats here rather
7948 * than inside detach_one_task().
7950 schedstat_add(env->sd->lb_gained[env->idle], detached);
7956 * attach_task() -- attach the task detached by detach_task() to its new rq.
7958 static void attach_task(struct rq *rq, struct task_struct *p)
7960 lockdep_assert_rq_held(rq);
7962 BUG_ON(task_rq(p) != rq);
7963 activate_task(rq, p, ENQUEUE_NOCLOCK);
7964 check_preempt_curr(rq, p, 0);
7968 * attach_one_task() -- attaches the task returned from detach_one_task() to
7971 static void attach_one_task(struct rq *rq, struct task_struct *p)
7976 update_rq_clock(rq);
7982 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
7985 static void attach_tasks(struct lb_env *env)
7987 struct list_head *tasks = &env->tasks;
7988 struct task_struct *p;
7991 rq_lock(env->dst_rq, &rf);
7992 update_rq_clock(env->dst_rq);
7994 while (!list_empty(tasks)) {
7995 p = list_first_entry(tasks, struct task_struct, se.group_node);
7996 list_del_init(&p->se.group_node);
7998 attach_task(env->dst_rq, p);
8001 rq_unlock(env->dst_rq, &rf);
8004 #ifdef CONFIG_NO_HZ_COMMON
8005 static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
8007 if (cfs_rq->avg.load_avg)
8010 if (cfs_rq->avg.util_avg)
8016 static inline bool others_have_blocked(struct rq *rq)
8018 if (READ_ONCE(rq->avg_rt.util_avg))
8021 if (READ_ONCE(rq->avg_dl.util_avg))
8024 if (thermal_load_avg(rq))
8027 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
8028 if (READ_ONCE(rq->avg_irq.util_avg))
8035 static inline void update_blocked_load_tick(struct rq *rq)
8037 WRITE_ONCE(rq->last_blocked_load_update_tick, jiffies);
8040 static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
8043 rq->has_blocked_load = 0;
8046 static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; }
8047 static inline bool others_have_blocked(struct rq *rq) { return false; }
8048 static inline void update_blocked_load_tick(struct rq *rq) {}
8049 static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {}
8052 static bool __update_blocked_others(struct rq *rq, bool *done)
8054 const struct sched_class *curr_class;
8055 u64 now = rq_clock_pelt(rq);
8056 unsigned long thermal_pressure;
8060 * update_load_avg() can call cpufreq_update_util(). Make sure that RT,
8061 * DL and IRQ signals have been updated before updating CFS.
8063 curr_class = rq->curr->sched_class;
8065 thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
8067 decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
8068 update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
8069 update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
8070 update_irq_load_avg(rq, 0);
8072 if (others_have_blocked(rq))
8078 #ifdef CONFIG_FAIR_GROUP_SCHED
8080 static bool __update_blocked_fair(struct rq *rq, bool *done)
8082 struct cfs_rq *cfs_rq, *pos;
8083 bool decayed = false;
8084 int cpu = cpu_of(rq);
8087 * Iterates the task_group tree in a bottom up fashion, see
8088 * list_add_leaf_cfs_rq() for details.
8090 for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
8091 struct sched_entity *se;
8093 if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
8094 update_tg_load_avg(cfs_rq);
8096 if (cfs_rq == &rq->cfs)
8100 /* Propagate pending load changes to the parent, if any: */
8101 se = cfs_rq->tg->se[cpu];
8102 if (se && !skip_blocked_update(se))
8103 update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
8106 * There can be a lot of idle CPU cgroups. Don't let fully
8107 * decayed cfs_rqs linger on the list.
8109 if (cfs_rq_is_decayed(cfs_rq))
8110 list_del_leaf_cfs_rq(cfs_rq);
8112 /* Don't need periodic decay once load/util_avg are null */
8113 if (cfs_rq_has_blocked(cfs_rq))
8121 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
8122 * This needs to be done in a top-down fashion because the load of a child
8123 * group is a fraction of its parents load.
8125 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
8127 struct rq *rq = rq_of(cfs_rq);
8128 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
8129 unsigned long now = jiffies;
8132 if (cfs_rq->last_h_load_update == now)
8135 WRITE_ONCE(cfs_rq->h_load_next, NULL);
8136 for_each_sched_entity(se) {
8137 cfs_rq = cfs_rq_of(se);
8138 WRITE_ONCE(cfs_rq->h_load_next, se);
8139 if (cfs_rq->last_h_load_update == now)
8144 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
8145 cfs_rq->last_h_load_update = now;
8148 while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
8149 load = cfs_rq->h_load;
8150 load = div64_ul(load * se->avg.load_avg,
8151 cfs_rq_load_avg(cfs_rq) + 1);
8152 cfs_rq = group_cfs_rq(se);
8153 cfs_rq->h_load = load;
8154 cfs_rq->last_h_load_update = now;
8158 static unsigned long task_h_load(struct task_struct *p)
8160 struct cfs_rq *cfs_rq = task_cfs_rq(p);
8162 update_cfs_rq_h_load(cfs_rq);
8163 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
8164 cfs_rq_load_avg(cfs_rq) + 1);
8167 static bool __update_blocked_fair(struct rq *rq, bool *done)
8169 struct cfs_rq *cfs_rq = &rq->cfs;
8172 decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
8173 if (cfs_rq_has_blocked(cfs_rq))
8179 static unsigned long task_h_load(struct task_struct *p)
8181 return p->se.avg.load_avg;
8185 static void update_blocked_averages(int cpu)
8187 bool decayed = false, done = true;
8188 struct rq *rq = cpu_rq(cpu);
8191 rq_lock_irqsave(rq, &rf);
8192 update_blocked_load_tick(rq);
8193 update_rq_clock(rq);
8195 decayed |= __update_blocked_others(rq, &done);
8196 decayed |= __update_blocked_fair(rq, &done);
8198 update_blocked_load_status(rq, !done);
8200 cpufreq_update_util(rq, 0);
8201 rq_unlock_irqrestore(rq, &rf);
8204 /********** Helpers for find_busiest_group ************************/
8207 * sg_lb_stats - stats of a sched_group required for load_balancing
8209 struct sg_lb_stats {
8210 unsigned long avg_load; /*Avg load across the CPUs of the group */
8211 unsigned long group_load; /* Total load over the CPUs of the group */
8212 unsigned long group_capacity;
8213 unsigned long group_util; /* Total utilization over the CPUs of the group */
8214 unsigned long group_runnable; /* Total runnable time over the CPUs of the group */
8215 unsigned int sum_nr_running; /* Nr of tasks running in the group */
8216 unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
8217 unsigned int idle_cpus;
8218 unsigned int group_weight;
8219 enum group_type group_type;
8220 unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
8221 unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
8222 #ifdef CONFIG_NUMA_BALANCING
8223 unsigned int nr_numa_running;
8224 unsigned int nr_preferred_running;
8229 * sd_lb_stats - Structure to store the statistics of a sched_domain
8230 * during load balancing.
8232 struct sd_lb_stats {
8233 struct sched_group *busiest; /* Busiest group in this sd */
8234 struct sched_group *local; /* Local group in this sd */
8235 unsigned long total_load; /* Total load of all groups in sd */
8236 unsigned long total_capacity; /* Total capacity of all groups in sd */
8237 unsigned long avg_load; /* Average load across all groups in sd */
8238 unsigned int prefer_sibling; /* tasks should go to sibling first */
8240 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
8241 struct sg_lb_stats local_stat; /* Statistics of the local group */
8244 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
8247 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
8248 * local_stat because update_sg_lb_stats() does a full clear/assignment.
8249 * We must however set busiest_stat::group_type and
8250 * busiest_stat::idle_cpus to the worst busiest group because
8251 * update_sd_pick_busiest() reads these before assignment.
8253 *sds = (struct sd_lb_stats){
8257 .total_capacity = 0UL,
8259 .idle_cpus = UINT_MAX,
8260 .group_type = group_has_spare,
8265 static unsigned long scale_rt_capacity(int cpu)
8267 struct rq *rq = cpu_rq(cpu);
8268 unsigned long max = arch_scale_cpu_capacity(cpu);
8269 unsigned long used, free;
8272 irq = cpu_util_irq(rq);
8274 if (unlikely(irq >= max))
8278 * avg_rt.util_avg and avg_dl.util_avg track binary signals
8279 * (running and not running) with weights 0 and 1024 respectively.
8280 * avg_thermal.load_avg tracks thermal pressure and the weighted
8281 * average uses the actual delta max capacity(load).
8283 used = READ_ONCE(rq->avg_rt.util_avg);
8284 used += READ_ONCE(rq->avg_dl.util_avg);
8285 used += thermal_load_avg(rq);
8287 if (unlikely(used >= max))
8292 return scale_irq_capacity(free, irq, max);
8295 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
8297 unsigned long capacity = scale_rt_capacity(cpu);
8298 struct sched_group *sdg = sd->groups;
8300 cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
8305 cpu_rq(cpu)->cpu_capacity = capacity;
8306 trace_sched_cpu_capacity_tp(cpu_rq(cpu));
8308 sdg->sgc->capacity = capacity;
8309 sdg->sgc->min_capacity = capacity;
8310 sdg->sgc->max_capacity = capacity;
8313 void update_group_capacity(struct sched_domain *sd, int cpu)
8315 struct sched_domain *child = sd->child;
8316 struct sched_group *group, *sdg = sd->groups;
8317 unsigned long capacity, min_capacity, max_capacity;
8318 unsigned long interval;
8320 interval = msecs_to_jiffies(sd->balance_interval);
8321 interval = clamp(interval, 1UL, max_load_balance_interval);
8322 sdg->sgc->next_update = jiffies + interval;
8325 update_cpu_capacity(sd, cpu);
8330 min_capacity = ULONG_MAX;
8333 if (child->flags & SD_OVERLAP) {
8335 * SD_OVERLAP domains cannot assume that child groups
8336 * span the current group.
8339 for_each_cpu(cpu, sched_group_span(sdg)) {
8340 unsigned long cpu_cap = capacity_of(cpu);
8342 capacity += cpu_cap;
8343 min_capacity = min(cpu_cap, min_capacity);
8344 max_capacity = max(cpu_cap, max_capacity);
8348 * !SD_OVERLAP domains can assume that child groups
8349 * span the current group.
8352 group = child->groups;
8354 struct sched_group_capacity *sgc = group->sgc;
8356 capacity += sgc->capacity;
8357 min_capacity = min(sgc->min_capacity, min_capacity);
8358 max_capacity = max(sgc->max_capacity, max_capacity);
8359 group = group->next;
8360 } while (group != child->groups);
8363 sdg->sgc->capacity = capacity;
8364 sdg->sgc->min_capacity = min_capacity;
8365 sdg->sgc->max_capacity = max_capacity;
8369 * Check whether the capacity of the rq has been noticeably reduced by side
8370 * activity. The imbalance_pct is used for the threshold.
8371 * Return true is the capacity is reduced
8374 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
8376 return ((rq->cpu_capacity * sd->imbalance_pct) <
8377 (rq->cpu_capacity_orig * 100));
8381 * Check whether a rq has a misfit task and if it looks like we can actually
8382 * help that task: we can migrate the task to a CPU of higher capacity, or
8383 * the task's current CPU is heavily pressured.
8385 static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
8387 return rq->misfit_task_load &&
8388 (rq->cpu_capacity_orig < rq->rd->max_cpu_capacity ||
8389 check_cpu_capacity(rq, sd));
8393 * Group imbalance indicates (and tries to solve) the problem where balancing
8394 * groups is inadequate due to ->cpus_ptr constraints.
8396 * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
8397 * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
8400 * { 0 1 2 3 } { 4 5 6 7 }
8403 * If we were to balance group-wise we'd place two tasks in the first group and
8404 * two tasks in the second group. Clearly this is undesired as it will overload
8405 * cpu 3 and leave one of the CPUs in the second group unused.
8407 * The current solution to this issue is detecting the skew in the first group
8408 * by noticing the lower domain failed to reach balance and had difficulty
8409 * moving tasks due to affinity constraints.
8411 * When this is so detected; this group becomes a candidate for busiest; see
8412 * update_sd_pick_busiest(). And calculate_imbalance() and
8413 * find_busiest_group() avoid some of the usual balance conditions to allow it
8414 * to create an effective group imbalance.
8416 * This is a somewhat tricky proposition since the next run might not find the
8417 * group imbalance and decide the groups need to be balanced again. A most
8418 * subtle and fragile situation.
8421 static inline int sg_imbalanced(struct sched_group *group)
8423 return group->sgc->imbalance;
8427 * group_has_capacity returns true if the group has spare capacity that could
8428 * be used by some tasks.
8429 * We consider that a group has spare capacity if the * number of task is
8430 * smaller than the number of CPUs or if the utilization is lower than the
8431 * available capacity for CFS tasks.
8432 * For the latter, we use a threshold to stabilize the state, to take into
8433 * account the variance of the tasks' load and to return true if the available
8434 * capacity in meaningful for the load balancer.
8435 * As an example, an available capacity of 1% can appear but it doesn't make
8436 * any benefit for the load balance.
8439 group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
8441 if (sgs->sum_nr_running < sgs->group_weight)
8444 if ((sgs->group_capacity * imbalance_pct) <
8445 (sgs->group_runnable * 100))
8448 if ((sgs->group_capacity * 100) >
8449 (sgs->group_util * imbalance_pct))
8456 * group_is_overloaded returns true if the group has more tasks than it can
8458 * group_is_overloaded is not equals to !group_has_capacity because a group
8459 * with the exact right number of tasks, has no more spare capacity but is not
8460 * overloaded so both group_has_capacity and group_is_overloaded return
8464 group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
8466 if (sgs->sum_nr_running <= sgs->group_weight)
8469 if ((sgs->group_capacity * 100) <
8470 (sgs->group_util * imbalance_pct))
8473 if ((sgs->group_capacity * imbalance_pct) <
8474 (sgs->group_runnable * 100))
8481 group_type group_classify(unsigned int imbalance_pct,
8482 struct sched_group *group,
8483 struct sg_lb_stats *sgs)
8485 if (group_is_overloaded(imbalance_pct, sgs))
8486 return group_overloaded;
8488 if (sg_imbalanced(group))
8489 return group_imbalanced;
8491 if (sgs->group_asym_packing)
8492 return group_asym_packing;
8494 if (sgs->group_misfit_task_load)
8495 return group_misfit_task;
8497 if (!group_has_capacity(imbalance_pct, sgs))
8498 return group_fully_busy;
8500 return group_has_spare;
8504 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
8505 * @env: The load balancing environment.
8506 * @group: sched_group whose statistics are to be updated.
8507 * @sgs: variable to hold the statistics for this group.
8508 * @sg_status: Holds flag indicating the status of the sched_group
8510 static inline void update_sg_lb_stats(struct lb_env *env,
8511 struct sched_group *group,
8512 struct sg_lb_stats *sgs,
8515 int i, nr_running, local_group;
8517 memset(sgs, 0, sizeof(*sgs));
8519 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(group));
8521 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8522 struct rq *rq = cpu_rq(i);
8524 sgs->group_load += cpu_load(rq);
8525 sgs->group_util += cpu_util(i);
8526 sgs->group_runnable += cpu_runnable(rq);
8527 sgs->sum_h_nr_running += rq->cfs.h_nr_running;
8529 nr_running = rq->nr_running;
8530 sgs->sum_nr_running += nr_running;
8533 *sg_status |= SG_OVERLOAD;
8535 if (cpu_overutilized(i))
8536 *sg_status |= SG_OVERUTILIZED;
8538 #ifdef CONFIG_NUMA_BALANCING
8539 sgs->nr_numa_running += rq->nr_numa_running;
8540 sgs->nr_preferred_running += rq->nr_preferred_running;
8543 * No need to call idle_cpu() if nr_running is not 0
8545 if (!nr_running && idle_cpu(i)) {
8547 /* Idle cpu can't have misfit task */
8554 /* Check for a misfit task on the cpu */
8555 if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
8556 sgs->group_misfit_task_load < rq->misfit_task_load) {
8557 sgs->group_misfit_task_load = rq->misfit_task_load;
8558 *sg_status |= SG_OVERLOAD;
8562 /* Check if dst CPU is idle and preferred to this group */
8563 if (env->sd->flags & SD_ASYM_PACKING &&
8564 env->idle != CPU_NOT_IDLE &&
8565 sgs->sum_h_nr_running &&
8566 sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) {
8567 sgs->group_asym_packing = 1;
8570 sgs->group_capacity = group->sgc->capacity;
8572 sgs->group_weight = group->group_weight;
8574 sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
8576 /* Computing avg_load makes sense only when group is overloaded */
8577 if (sgs->group_type == group_overloaded)
8578 sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
8579 sgs->group_capacity;
8583 * update_sd_pick_busiest - return 1 on busiest group
8584 * @env: The load balancing environment.
8585 * @sds: sched_domain statistics
8586 * @sg: sched_group candidate to be checked for being the busiest
8587 * @sgs: sched_group statistics
8589 * Determine if @sg is a busier group than the previously selected
8592 * Return: %true if @sg is a busier group than the previously selected
8593 * busiest group. %false otherwise.
8595 static bool update_sd_pick_busiest(struct lb_env *env,
8596 struct sd_lb_stats *sds,
8597 struct sched_group *sg,
8598 struct sg_lb_stats *sgs)
8600 struct sg_lb_stats *busiest = &sds->busiest_stat;
8602 /* Make sure that there is at least one task to pull */
8603 if (!sgs->sum_h_nr_running)
8607 * Don't try to pull misfit tasks we can't help.
8608 * We can use max_capacity here as reduction in capacity on some
8609 * CPUs in the group should either be possible to resolve
8610 * internally or be covered by avg_load imbalance (eventually).
8612 if (sgs->group_type == group_misfit_task &&
8613 (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
8614 sds->local_stat.group_type != group_has_spare))
8617 if (sgs->group_type > busiest->group_type)
8620 if (sgs->group_type < busiest->group_type)
8624 * The candidate and the current busiest group are the same type of
8625 * group. Let check which one is the busiest according to the type.
8628 switch (sgs->group_type) {
8629 case group_overloaded:
8630 /* Select the overloaded group with highest avg_load. */
8631 if (sgs->avg_load <= busiest->avg_load)
8635 case group_imbalanced:
8637 * Select the 1st imbalanced group as we don't have any way to
8638 * choose one more than another.
8642 case group_asym_packing:
8643 /* Prefer to move from lowest priority CPU's work */
8644 if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu))
8648 case group_misfit_task:
8650 * If we have more than one misfit sg go with the biggest
8653 if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
8657 case group_fully_busy:
8659 * Select the fully busy group with highest avg_load. In
8660 * theory, there is no need to pull task from such kind of
8661 * group because tasks have all compute capacity that they need
8662 * but we can still improve the overall throughput by reducing
8663 * contention when accessing shared HW resources.
8665 * XXX for now avg_load is not computed and always 0 so we
8666 * select the 1st one.
8668 if (sgs->avg_load <= busiest->avg_load)
8672 case group_has_spare:
8674 * Select not overloaded group with lowest number of idle cpus
8675 * and highest number of running tasks. We could also compare
8676 * the spare capacity which is more stable but it can end up
8677 * that the group has less spare capacity but finally more idle
8678 * CPUs which means less opportunity to pull tasks.
8680 if (sgs->idle_cpus > busiest->idle_cpus)
8682 else if ((sgs->idle_cpus == busiest->idle_cpus) &&
8683 (sgs->sum_nr_running <= busiest->sum_nr_running))
8690 * Candidate sg has no more than one task per CPU and has higher
8691 * per-CPU capacity. Migrating tasks to less capable CPUs may harm
8692 * throughput. Maximize throughput, power/energy consequences are not
8695 if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
8696 (sgs->group_type <= group_fully_busy) &&
8697 (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu))))
8703 #ifdef CONFIG_NUMA_BALANCING
8704 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8706 if (sgs->sum_h_nr_running > sgs->nr_numa_running)
8708 if (sgs->sum_h_nr_running > sgs->nr_preferred_running)
8713 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8715 if (rq->nr_running > rq->nr_numa_running)
8717 if (rq->nr_running > rq->nr_preferred_running)
8722 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8727 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8731 #endif /* CONFIG_NUMA_BALANCING */
8737 * task_running_on_cpu - return 1 if @p is running on @cpu.
8740 static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
8742 /* Task has no contribution or is new */
8743 if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
8746 if (task_on_rq_queued(p))
8753 * idle_cpu_without - would a given CPU be idle without p ?
8754 * @cpu: the processor on which idleness is tested.
8755 * @p: task which should be ignored.
8757 * Return: 1 if the CPU would be idle. 0 otherwise.
8759 static int idle_cpu_without(int cpu, struct task_struct *p)
8761 struct rq *rq = cpu_rq(cpu);
8763 if (rq->curr != rq->idle && rq->curr != p)
8767 * rq->nr_running can't be used but an updated version without the
8768 * impact of p on cpu must be used instead. The updated nr_running
8769 * be computed and tested before calling idle_cpu_without().
8773 if (rq->ttwu_pending)
8781 * update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
8782 * @sd: The sched_domain level to look for idlest group.
8783 * @group: sched_group whose statistics are to be updated.
8784 * @sgs: variable to hold the statistics for this group.
8785 * @p: The task for which we look for the idlest group/CPU.
8787 static inline void update_sg_wakeup_stats(struct sched_domain *sd,
8788 struct sched_group *group,
8789 struct sg_lb_stats *sgs,
8790 struct task_struct *p)
8794 memset(sgs, 0, sizeof(*sgs));
8796 for_each_cpu(i, sched_group_span(group)) {
8797 struct rq *rq = cpu_rq(i);
8800 sgs->group_load += cpu_load_without(rq, p);
8801 sgs->group_util += cpu_util_without(i, p);
8802 sgs->group_runnable += cpu_runnable_without(rq, p);
8803 local = task_running_on_cpu(i, p);
8804 sgs->sum_h_nr_running += rq->cfs.h_nr_running - local;
8806 nr_running = rq->nr_running - local;
8807 sgs->sum_nr_running += nr_running;
8810 * No need to call idle_cpu_without() if nr_running is not 0
8812 if (!nr_running && idle_cpu_without(i, p))
8817 /* Check if task fits in the group */
8818 if (sd->flags & SD_ASYM_CPUCAPACITY &&
8819 !task_fits_capacity(p, group->sgc->max_capacity)) {
8820 sgs->group_misfit_task_load = 1;
8823 sgs->group_capacity = group->sgc->capacity;
8825 sgs->group_weight = group->group_weight;
8827 sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
8830 * Computing avg_load makes sense only when group is fully busy or
8833 if (sgs->group_type == group_fully_busy ||
8834 sgs->group_type == group_overloaded)
8835 sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
8836 sgs->group_capacity;
8839 static bool update_pick_idlest(struct sched_group *idlest,
8840 struct sg_lb_stats *idlest_sgs,
8841 struct sched_group *group,
8842 struct sg_lb_stats *sgs)
8844 if (sgs->group_type < idlest_sgs->group_type)
8847 if (sgs->group_type > idlest_sgs->group_type)
8851 * The candidate and the current idlest group are the same type of
8852 * group. Let check which one is the idlest according to the type.
8855 switch (sgs->group_type) {
8856 case group_overloaded:
8857 case group_fully_busy:
8858 /* Select the group with lowest avg_load. */
8859 if (idlest_sgs->avg_load <= sgs->avg_load)
8863 case group_imbalanced:
8864 case group_asym_packing:
8865 /* Those types are not used in the slow wakeup path */
8868 case group_misfit_task:
8869 /* Select group with the highest max capacity */
8870 if (idlest->sgc->max_capacity >= group->sgc->max_capacity)
8874 case group_has_spare:
8875 /* Select group with most idle CPUs */
8876 if (idlest_sgs->idle_cpus > sgs->idle_cpus)
8879 /* Select group with lowest group_util */
8880 if (idlest_sgs->idle_cpus == sgs->idle_cpus &&
8881 idlest_sgs->group_util <= sgs->group_util)
8891 * Allow a NUMA imbalance if busy CPUs is less than 25% of the domain.
8892 * This is an approximation as the number of running tasks may not be
8893 * related to the number of busy CPUs due to sched_setaffinity.
8895 static inline bool allow_numa_imbalance(int dst_running, int dst_weight)
8897 return (dst_running < (dst_weight >> 2));
8901 * find_idlest_group() finds and returns the least busy CPU group within the
8904 * Assumes p is allowed on at least one CPU in sd.
8906 static struct sched_group *
8907 find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
8909 struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups;
8910 struct sg_lb_stats local_sgs, tmp_sgs;
8911 struct sg_lb_stats *sgs;
8912 unsigned long imbalance;
8913 struct sg_lb_stats idlest_sgs = {
8914 .avg_load = UINT_MAX,
8915 .group_type = group_overloaded,
8921 /* Skip over this group if it has no CPUs allowed */
8922 if (!cpumask_intersects(sched_group_span(group),
8926 /* Skip over this group if no cookie matched */
8927 if (!sched_group_cookie_match(cpu_rq(this_cpu), p, group))
8930 local_group = cpumask_test_cpu(this_cpu,
8931 sched_group_span(group));
8940 update_sg_wakeup_stats(sd, group, sgs, p);
8942 if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) {
8947 } while (group = group->next, group != sd->groups);
8950 /* There is no idlest group to push tasks to */
8954 /* The local group has been skipped because of CPU affinity */
8959 * If the local group is idler than the selected idlest group
8960 * don't try and push the task.
8962 if (local_sgs.group_type < idlest_sgs.group_type)
8966 * If the local group is busier than the selected idlest group
8967 * try and push the task.
8969 if (local_sgs.group_type > idlest_sgs.group_type)
8972 switch (local_sgs.group_type) {
8973 case group_overloaded:
8974 case group_fully_busy:
8976 /* Calculate allowed imbalance based on load */
8977 imbalance = scale_load_down(NICE_0_LOAD) *
8978 (sd->imbalance_pct-100) / 100;
8981 * When comparing groups across NUMA domains, it's possible for
8982 * the local domain to be very lightly loaded relative to the
8983 * remote domains but "imbalance" skews the comparison making
8984 * remote CPUs look much more favourable. When considering
8985 * cross-domain, add imbalance to the load on the remote node
8986 * and consider staying local.
8989 if ((sd->flags & SD_NUMA) &&
8990 ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load))
8994 * If the local group is less loaded than the selected
8995 * idlest group don't try and push any tasks.
8997 if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance))
9000 if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load)
9004 case group_imbalanced:
9005 case group_asym_packing:
9006 /* Those type are not used in the slow wakeup path */
9009 case group_misfit_task:
9010 /* Select group with the highest max capacity */
9011 if (local->sgc->max_capacity >= idlest->sgc->max_capacity)
9015 case group_has_spare:
9016 if (sd->flags & SD_NUMA) {
9017 #ifdef CONFIG_NUMA_BALANCING
9020 * If there is spare capacity at NUMA, try to select
9021 * the preferred node
9023 if (cpu_to_node(this_cpu) == p->numa_preferred_nid)
9026 idlest_cpu = cpumask_first(sched_group_span(idlest));
9027 if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid)
9031 * Otherwise, keep the task on this node to stay close
9032 * its wakeup source and improve locality. If there is
9033 * a real need of migration, periodic load balance will
9036 if (allow_numa_imbalance(local_sgs.sum_nr_running, sd->span_weight))
9041 * Select group with highest number of idle CPUs. We could also
9042 * compare the utilization which is more stable but it can end
9043 * up that the group has less spare capacity but finally more
9044 * idle CPUs which means more opportunity to run task.
9046 if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus)
9055 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
9056 * @env: The load balancing environment.
9057 * @sds: variable to hold the statistics for this sched_domain.
9060 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
9062 struct sched_domain *child = env->sd->child;
9063 struct sched_group *sg = env->sd->groups;
9064 struct sg_lb_stats *local = &sds->local_stat;
9065 struct sg_lb_stats tmp_sgs;
9069 struct sg_lb_stats *sgs = &tmp_sgs;
9072 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
9077 if (env->idle != CPU_NEWLY_IDLE ||
9078 time_after_eq(jiffies, sg->sgc->next_update))
9079 update_group_capacity(env->sd, env->dst_cpu);
9082 update_sg_lb_stats(env, sg, sgs, &sg_status);
9088 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
9090 sds->busiest_stat = *sgs;
9094 /* Now, start updating sd_lb_stats */
9095 sds->total_load += sgs->group_load;
9096 sds->total_capacity += sgs->group_capacity;
9099 } while (sg != env->sd->groups);
9101 /* Tag domain that child domain prefers tasks go to siblings first */
9102 sds->prefer_sibling = child && child->flags & SD_PREFER_SIBLING;
9105 if (env->sd->flags & SD_NUMA)
9106 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
9108 if (!env->sd->parent) {
9109 struct root_domain *rd = env->dst_rq->rd;
9111 /* update overload indicator if we are at root domain */
9112 WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD);
9114 /* Update over-utilization (tipping point, U >= 0) indicator */
9115 WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
9116 trace_sched_overutilized_tp(rd, sg_status & SG_OVERUTILIZED);
9117 } else if (sg_status & SG_OVERUTILIZED) {
9118 struct root_domain *rd = env->dst_rq->rd;
9120 WRITE_ONCE(rd->overutilized, SG_OVERUTILIZED);
9121 trace_sched_overutilized_tp(rd, SG_OVERUTILIZED);
9125 #define NUMA_IMBALANCE_MIN 2
9127 static inline long adjust_numa_imbalance(int imbalance,
9128 int dst_running, int dst_weight)
9130 if (!allow_numa_imbalance(dst_running, dst_weight))
9134 * Allow a small imbalance based on a simple pair of communicating
9135 * tasks that remain local when the destination is lightly loaded.
9137 if (imbalance <= NUMA_IMBALANCE_MIN)
9144 * calculate_imbalance - Calculate the amount of imbalance present within the
9145 * groups of a given sched_domain during load balance.
9146 * @env: load balance environment
9147 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
9149 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
9151 struct sg_lb_stats *local, *busiest;
9153 local = &sds->local_stat;
9154 busiest = &sds->busiest_stat;
9156 if (busiest->group_type == group_misfit_task) {
9157 /* Set imbalance to allow misfit tasks to be balanced. */
9158 env->migration_type = migrate_misfit;
9163 if (busiest->group_type == group_asym_packing) {
9165 * In case of asym capacity, we will try to migrate all load to
9166 * the preferred CPU.
9168 env->migration_type = migrate_task;
9169 env->imbalance = busiest->sum_h_nr_running;
9173 if (busiest->group_type == group_imbalanced) {
9175 * In the group_imb case we cannot rely on group-wide averages
9176 * to ensure CPU-load equilibrium, try to move any task to fix
9177 * the imbalance. The next load balance will take care of
9178 * balancing back the system.
9180 env->migration_type = migrate_task;
9186 * Try to use spare capacity of local group without overloading it or
9189 if (local->group_type == group_has_spare) {
9190 if ((busiest->group_type > group_fully_busy) &&
9191 !(env->sd->flags & SD_SHARE_PKG_RESOURCES)) {
9193 * If busiest is overloaded, try to fill spare
9194 * capacity. This might end up creating spare capacity
9195 * in busiest or busiest still being overloaded but
9196 * there is no simple way to directly compute the
9197 * amount of load to migrate in order to balance the
9200 env->migration_type = migrate_util;
9201 env->imbalance = max(local->group_capacity, local->group_util) -
9205 * In some cases, the group's utilization is max or even
9206 * higher than capacity because of migrations but the
9207 * local CPU is (newly) idle. There is at least one
9208 * waiting task in this overloaded busiest group. Let's
9211 if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) {
9212 env->migration_type = migrate_task;
9219 if (busiest->group_weight == 1 || sds->prefer_sibling) {
9220 unsigned int nr_diff = busiest->sum_nr_running;
9222 * When prefer sibling, evenly spread running tasks on
9225 env->migration_type = migrate_task;
9226 lsub_positive(&nr_diff, local->sum_nr_running);
9227 env->imbalance = nr_diff >> 1;
9231 * If there is no overload, we just want to even the number of
9234 env->migration_type = migrate_task;
9235 env->imbalance = max_t(long, 0, (local->idle_cpus -
9236 busiest->idle_cpus) >> 1);
9239 /* Consider allowing a small imbalance between NUMA groups */
9240 if (env->sd->flags & SD_NUMA) {
9241 env->imbalance = adjust_numa_imbalance(env->imbalance,
9242 busiest->sum_nr_running, busiest->group_weight);
9249 * Local is fully busy but has to take more load to relieve the
9252 if (local->group_type < group_overloaded) {
9254 * Local will become overloaded so the avg_load metrics are
9258 local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) /
9259 local->group_capacity;
9261 sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
9262 sds->total_capacity;
9264 * If the local group is more loaded than the selected
9265 * busiest group don't try to pull any tasks.
9267 if (local->avg_load >= busiest->avg_load) {
9274 * Both group are or will become overloaded and we're trying to get all
9275 * the CPUs to the average_load, so we don't want to push ourselves
9276 * above the average load, nor do we wish to reduce the max loaded CPU
9277 * below the average load. At the same time, we also don't want to
9278 * reduce the group load below the group capacity. Thus we look for
9279 * the minimum possible imbalance.
9281 env->migration_type = migrate_load;
9282 env->imbalance = min(
9283 (busiest->avg_load - sds->avg_load) * busiest->group_capacity,
9284 (sds->avg_load - local->avg_load) * local->group_capacity
9285 ) / SCHED_CAPACITY_SCALE;
9288 /******* find_busiest_group() helpers end here *********************/
9291 * Decision matrix according to the local and busiest group type:
9293 * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
9294 * has_spare nr_idle balanced N/A N/A balanced balanced
9295 * fully_busy nr_idle nr_idle N/A N/A balanced balanced
9296 * misfit_task force N/A N/A N/A force force
9297 * asym_packing force force N/A N/A force force
9298 * imbalanced force force N/A N/A force force
9299 * overloaded force force N/A N/A force avg_load
9301 * N/A : Not Applicable because already filtered while updating
9303 * balanced : The system is balanced for these 2 groups.
9304 * force : Calculate the imbalance as load migration is probably needed.
9305 * avg_load : Only if imbalance is significant enough.
9306 * nr_idle : dst_cpu is not busy and the number of idle CPUs is quite
9307 * different in groups.
9311 * find_busiest_group - Returns the busiest group within the sched_domain
9312 * if there is an imbalance.
9314 * Also calculates the amount of runnable load which should be moved
9315 * to restore balance.
9317 * @env: The load balancing environment.
9319 * Return: - The busiest group if imbalance exists.
9321 static struct sched_group *find_busiest_group(struct lb_env *env)
9323 struct sg_lb_stats *local, *busiest;
9324 struct sd_lb_stats sds;
9326 init_sd_lb_stats(&sds);
9329 * Compute the various statistics relevant for load balancing at
9332 update_sd_lb_stats(env, &sds);
9334 if (sched_energy_enabled()) {
9335 struct root_domain *rd = env->dst_rq->rd;
9337 if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
9341 local = &sds.local_stat;
9342 busiest = &sds.busiest_stat;
9344 /* There is no busy sibling group to pull tasks from */
9348 /* Misfit tasks should be dealt with regardless of the avg load */
9349 if (busiest->group_type == group_misfit_task)
9352 /* ASYM feature bypasses nice load balance check */
9353 if (busiest->group_type == group_asym_packing)
9357 * If the busiest group is imbalanced the below checks don't
9358 * work because they assume all things are equal, which typically
9359 * isn't true due to cpus_ptr constraints and the like.
9361 if (busiest->group_type == group_imbalanced)
9365 * If the local group is busier than the selected busiest group
9366 * don't try and pull any tasks.
9368 if (local->group_type > busiest->group_type)
9372 * When groups are overloaded, use the avg_load to ensure fairness
9375 if (local->group_type == group_overloaded) {
9377 * If the local group is more loaded than the selected
9378 * busiest group don't try to pull any tasks.
9380 if (local->avg_load >= busiest->avg_load)
9383 /* XXX broken for overlapping NUMA groups */
9384 sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) /
9388 * Don't pull any tasks if this group is already above the
9389 * domain average load.
9391 if (local->avg_load >= sds.avg_load)
9395 * If the busiest group is more loaded, use imbalance_pct to be
9398 if (100 * busiest->avg_load <=
9399 env->sd->imbalance_pct * local->avg_load)
9403 /* Try to move all excess tasks to child's sibling domain */
9404 if (sds.prefer_sibling && local->group_type == group_has_spare &&
9405 busiest->sum_nr_running > local->sum_nr_running + 1)
9408 if (busiest->group_type != group_overloaded) {
9409 if (env->idle == CPU_NOT_IDLE)
9411 * If the busiest group is not overloaded (and as a
9412 * result the local one too) but this CPU is already
9413 * busy, let another idle CPU try to pull task.
9417 if (busiest->group_weight > 1 &&
9418 local->idle_cpus <= (busiest->idle_cpus + 1))
9420 * If the busiest group is not overloaded
9421 * and there is no imbalance between this and busiest
9422 * group wrt idle CPUs, it is balanced. The imbalance
9423 * becomes significant if the diff is greater than 1
9424 * otherwise we might end up to just move the imbalance
9425 * on another group. Of course this applies only if
9426 * there is more than 1 CPU per group.
9430 if (busiest->sum_h_nr_running == 1)
9432 * busiest doesn't have any tasks waiting to run
9438 /* Looks like there is an imbalance. Compute it */
9439 calculate_imbalance(env, &sds);
9440 return env->imbalance ? sds.busiest : NULL;
9448 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
9450 static struct rq *find_busiest_queue(struct lb_env *env,
9451 struct sched_group *group)
9453 struct rq *busiest = NULL, *rq;
9454 unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
9455 unsigned int busiest_nr = 0;
9458 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
9459 unsigned long capacity, load, util;
9460 unsigned int nr_running;
9464 rt = fbq_classify_rq(rq);
9467 * We classify groups/runqueues into three groups:
9468 * - regular: there are !numa tasks
9469 * - remote: there are numa tasks that run on the 'wrong' node
9470 * - all: there is no distinction
9472 * In order to avoid migrating ideally placed numa tasks,
9473 * ignore those when there's better options.
9475 * If we ignore the actual busiest queue to migrate another
9476 * task, the next balance pass can still reduce the busiest
9477 * queue by moving tasks around inside the node.
9479 * If we cannot move enough load due to this classification
9480 * the next pass will adjust the group classification and
9481 * allow migration of more tasks.
9483 * Both cases only affect the total convergence complexity.
9485 if (rt > env->fbq_type)
9488 nr_running = rq->cfs.h_nr_running;
9492 capacity = capacity_of(i);
9495 * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
9496 * eventually lead to active_balancing high->low capacity.
9497 * Higher per-CPU capacity is considered better than balancing
9500 if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
9501 !capacity_greater(capacity_of(env->dst_cpu), capacity) &&
9505 switch (env->migration_type) {
9508 * When comparing with load imbalance, use cpu_load()
9509 * which is not scaled with the CPU capacity.
9511 load = cpu_load(rq);
9513 if (nr_running == 1 && load > env->imbalance &&
9514 !check_cpu_capacity(rq, env->sd))
9518 * For the load comparisons with the other CPUs,
9519 * consider the cpu_load() scaled with the CPU
9520 * capacity, so that the load can be moved away
9521 * from the CPU that is potentially running at a
9524 * Thus we're looking for max(load_i / capacity_i),
9525 * crosswise multiplication to rid ourselves of the
9526 * division works out to:
9527 * load_i * capacity_j > load_j * capacity_i;
9528 * where j is our previous maximum.
9530 if (load * busiest_capacity > busiest_load * capacity) {
9531 busiest_load = load;
9532 busiest_capacity = capacity;
9538 util = cpu_util(cpu_of(rq));
9541 * Don't try to pull utilization from a CPU with one
9542 * running task. Whatever its utilization, we will fail
9545 if (nr_running <= 1)
9548 if (busiest_util < util) {
9549 busiest_util = util;
9555 if (busiest_nr < nr_running) {
9556 busiest_nr = nr_running;
9561 case migrate_misfit:
9563 * For ASYM_CPUCAPACITY domains with misfit tasks we
9564 * simply seek the "biggest" misfit task.
9566 if (rq->misfit_task_load > busiest_load) {
9567 busiest_load = rq->misfit_task_load;
9580 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
9581 * so long as it is large enough.
9583 #define MAX_PINNED_INTERVAL 512
9586 asym_active_balance(struct lb_env *env)
9589 * ASYM_PACKING needs to force migrate tasks from busy but
9590 * lower priority CPUs in order to pack all tasks in the
9591 * highest priority CPUs.
9593 return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
9594 sched_asym_prefer(env->dst_cpu, env->src_cpu);
9598 imbalanced_active_balance(struct lb_env *env)
9600 struct sched_domain *sd = env->sd;
9603 * The imbalanced case includes the case of pinned tasks preventing a fair
9604 * distribution of the load on the system but also the even distribution of the
9605 * threads on a system with spare capacity
9607 if ((env->migration_type == migrate_task) &&
9608 (sd->nr_balance_failed > sd->cache_nice_tries+2))
9614 static int need_active_balance(struct lb_env *env)
9616 struct sched_domain *sd = env->sd;
9618 if (asym_active_balance(env))
9621 if (imbalanced_active_balance(env))
9625 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
9626 * It's worth migrating the task if the src_cpu's capacity is reduced
9627 * because of other sched_class or IRQs if more capacity stays
9628 * available on dst_cpu.
9630 if ((env->idle != CPU_NOT_IDLE) &&
9631 (env->src_rq->cfs.h_nr_running == 1)) {
9632 if ((check_cpu_capacity(env->src_rq, sd)) &&
9633 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
9637 if (env->migration_type == migrate_misfit)
9643 static int active_load_balance_cpu_stop(void *data);
9645 static int should_we_balance(struct lb_env *env)
9647 struct sched_group *sg = env->sd->groups;
9651 * Ensure the balancing environment is consistent; can happen
9652 * when the softirq triggers 'during' hotplug.
9654 if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
9658 * In the newly idle case, we will allow all the CPUs
9659 * to do the newly idle load balance.
9661 if (env->idle == CPU_NEWLY_IDLE)
9664 /* Try to find first idle CPU */
9665 for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
9669 /* Are we the first idle CPU? */
9670 return cpu == env->dst_cpu;
9673 /* Are we the first CPU of this group ? */
9674 return group_balance_cpu(sg) == env->dst_cpu;
9678 * Check this_cpu to ensure it is balanced within domain. Attempt to move
9679 * tasks if there is an imbalance.
9681 static int load_balance(int this_cpu, struct rq *this_rq,
9682 struct sched_domain *sd, enum cpu_idle_type idle,
9683 int *continue_balancing)
9685 int ld_moved, cur_ld_moved, active_balance = 0;
9686 struct sched_domain *sd_parent = sd->parent;
9687 struct sched_group *group;
9690 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
9692 struct lb_env env = {
9694 .dst_cpu = this_cpu,
9696 .dst_grpmask = sched_group_span(sd->groups),
9698 .loop_break = sched_nr_migrate_break,
9701 .tasks = LIST_HEAD_INIT(env.tasks),
9704 cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
9706 schedstat_inc(sd->lb_count[idle]);
9709 if (!should_we_balance(&env)) {
9710 *continue_balancing = 0;
9714 group = find_busiest_group(&env);
9716 schedstat_inc(sd->lb_nobusyg[idle]);
9720 busiest = find_busiest_queue(&env, group);
9722 schedstat_inc(sd->lb_nobusyq[idle]);
9726 BUG_ON(busiest == env.dst_rq);
9728 schedstat_add(sd->lb_imbalance[idle], env.imbalance);
9730 env.src_cpu = busiest->cpu;
9731 env.src_rq = busiest;
9734 /* Clear this flag as soon as we find a pullable task */
9735 env.flags |= LBF_ALL_PINNED;
9736 if (busiest->nr_running > 1) {
9738 * Attempt to move tasks. If find_busiest_group has found
9739 * an imbalance but busiest->nr_running <= 1, the group is
9740 * still unbalanced. ld_moved simply stays zero, so it is
9741 * correctly treated as an imbalance.
9743 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
9746 rq_lock_irqsave(busiest, &rf);
9747 update_rq_clock(busiest);
9750 * cur_ld_moved - load moved in current iteration
9751 * ld_moved - cumulative load moved across iterations
9753 cur_ld_moved = detach_tasks(&env);
9756 * We've detached some tasks from busiest_rq. Every
9757 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
9758 * unlock busiest->lock, and we are able to be sure
9759 * that nobody can manipulate the tasks in parallel.
9760 * See task_rq_lock() family for the details.
9763 rq_unlock(busiest, &rf);
9767 ld_moved += cur_ld_moved;
9770 local_irq_restore(rf.flags);
9772 if (env.flags & LBF_NEED_BREAK) {
9773 env.flags &= ~LBF_NEED_BREAK;
9778 * Revisit (affine) tasks on src_cpu that couldn't be moved to
9779 * us and move them to an alternate dst_cpu in our sched_group
9780 * where they can run. The upper limit on how many times we
9781 * iterate on same src_cpu is dependent on number of CPUs in our
9784 * This changes load balance semantics a bit on who can move
9785 * load to a given_cpu. In addition to the given_cpu itself
9786 * (or a ilb_cpu acting on its behalf where given_cpu is
9787 * nohz-idle), we now have balance_cpu in a position to move
9788 * load to given_cpu. In rare situations, this may cause
9789 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
9790 * _independently_ and at _same_ time to move some load to
9791 * given_cpu) causing excess load to be moved to given_cpu.
9792 * This however should not happen so much in practice and
9793 * moreover subsequent load balance cycles should correct the
9794 * excess load moved.
9796 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
9798 /* Prevent to re-select dst_cpu via env's CPUs */
9799 __cpumask_clear_cpu(env.dst_cpu, env.cpus);
9801 env.dst_rq = cpu_rq(env.new_dst_cpu);
9802 env.dst_cpu = env.new_dst_cpu;
9803 env.flags &= ~LBF_DST_PINNED;
9805 env.loop_break = sched_nr_migrate_break;
9808 * Go back to "more_balance" rather than "redo" since we
9809 * need to continue with same src_cpu.
9815 * We failed to reach balance because of affinity.
9818 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
9820 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
9821 *group_imbalance = 1;
9824 /* All tasks on this runqueue were pinned by CPU affinity */
9825 if (unlikely(env.flags & LBF_ALL_PINNED)) {
9826 __cpumask_clear_cpu(cpu_of(busiest), cpus);
9828 * Attempting to continue load balancing at the current
9829 * sched_domain level only makes sense if there are
9830 * active CPUs remaining as possible busiest CPUs to
9831 * pull load from which are not contained within the
9832 * destination group that is receiving any migrated
9835 if (!cpumask_subset(cpus, env.dst_grpmask)) {
9837 env.loop_break = sched_nr_migrate_break;
9840 goto out_all_pinned;
9845 schedstat_inc(sd->lb_failed[idle]);
9847 * Increment the failure counter only on periodic balance.
9848 * We do not want newidle balance, which can be very
9849 * frequent, pollute the failure counter causing
9850 * excessive cache_hot migrations and active balances.
9852 if (idle != CPU_NEWLY_IDLE)
9853 sd->nr_balance_failed++;
9855 if (need_active_balance(&env)) {
9856 unsigned long flags;
9858 raw_spin_rq_lock_irqsave(busiest, flags);
9861 * Don't kick the active_load_balance_cpu_stop,
9862 * if the curr task on busiest CPU can't be
9863 * moved to this_cpu:
9865 if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
9866 raw_spin_rq_unlock_irqrestore(busiest, flags);
9867 goto out_one_pinned;
9870 /* Record that we found at least one task that could run on this_cpu */
9871 env.flags &= ~LBF_ALL_PINNED;
9874 * ->active_balance synchronizes accesses to
9875 * ->active_balance_work. Once set, it's cleared
9876 * only after active load balance is finished.
9878 if (!busiest->active_balance) {
9879 busiest->active_balance = 1;
9880 busiest->push_cpu = this_cpu;
9883 raw_spin_rq_unlock_irqrestore(busiest, flags);
9885 if (active_balance) {
9886 stop_one_cpu_nowait(cpu_of(busiest),
9887 active_load_balance_cpu_stop, busiest,
9888 &busiest->active_balance_work);
9892 sd->nr_balance_failed = 0;
9895 if (likely(!active_balance) || need_active_balance(&env)) {
9896 /* We were unbalanced, so reset the balancing interval */
9897 sd->balance_interval = sd->min_interval;
9904 * We reach balance although we may have faced some affinity
9905 * constraints. Clear the imbalance flag only if other tasks got
9906 * a chance to move and fix the imbalance.
9908 if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
9909 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
9911 if (*group_imbalance)
9912 *group_imbalance = 0;
9917 * We reach balance because all tasks are pinned at this level so
9918 * we can't migrate them. Let the imbalance flag set so parent level
9919 * can try to migrate them.
9921 schedstat_inc(sd->lb_balanced[idle]);
9923 sd->nr_balance_failed = 0;
9929 * newidle_balance() disregards balance intervals, so we could
9930 * repeatedly reach this code, which would lead to balance_interval
9931 * skyrocketing in a short amount of time. Skip the balance_interval
9932 * increase logic to avoid that.
9934 if (env.idle == CPU_NEWLY_IDLE)
9937 /* tune up the balancing interval */
9938 if ((env.flags & LBF_ALL_PINNED &&
9939 sd->balance_interval < MAX_PINNED_INTERVAL) ||
9940 sd->balance_interval < sd->max_interval)
9941 sd->balance_interval *= 2;
9946 static inline unsigned long
9947 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
9949 unsigned long interval = sd->balance_interval;
9952 interval *= sd->busy_factor;
9954 /* scale ms to jiffies */
9955 interval = msecs_to_jiffies(interval);
9958 * Reduce likelihood of busy balancing at higher domains racing with
9959 * balancing at lower domains by preventing their balancing periods
9960 * from being multiples of each other.
9965 interval = clamp(interval, 1UL, max_load_balance_interval);
9971 update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
9973 unsigned long interval, next;
9975 /* used by idle balance, so cpu_busy = 0 */
9976 interval = get_sd_balance_interval(sd, 0);
9977 next = sd->last_balance + interval;
9979 if (time_after(*next_balance, next))
9980 *next_balance = next;
9984 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
9985 * running tasks off the busiest CPU onto idle CPUs. It requires at
9986 * least 1 task to be running on each physical CPU where possible, and
9987 * avoids physical / logical imbalances.
9989 static int active_load_balance_cpu_stop(void *data)
9991 struct rq *busiest_rq = data;
9992 int busiest_cpu = cpu_of(busiest_rq);
9993 int target_cpu = busiest_rq->push_cpu;
9994 struct rq *target_rq = cpu_rq(target_cpu);
9995 struct sched_domain *sd;
9996 struct task_struct *p = NULL;
9999 rq_lock_irq(busiest_rq, &rf);
10001 * Between queueing the stop-work and running it is a hole in which
10002 * CPUs can become inactive. We should not move tasks from or to
10005 if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
10008 /* Make sure the requested CPU hasn't gone down in the meantime: */
10009 if (unlikely(busiest_cpu != smp_processor_id() ||
10010 !busiest_rq->active_balance))
10013 /* Is there any task to move? */
10014 if (busiest_rq->nr_running <= 1)
10018 * This condition is "impossible", if it occurs
10019 * we need to fix it. Originally reported by
10020 * Bjorn Helgaas on a 128-CPU setup.
10022 BUG_ON(busiest_rq == target_rq);
10024 /* Search for an sd spanning us and the target CPU. */
10026 for_each_domain(target_cpu, sd) {
10027 if (cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
10032 struct lb_env env = {
10034 .dst_cpu = target_cpu,
10035 .dst_rq = target_rq,
10036 .src_cpu = busiest_rq->cpu,
10037 .src_rq = busiest_rq,
10039 .flags = LBF_ACTIVE_LB,
10042 schedstat_inc(sd->alb_count);
10043 update_rq_clock(busiest_rq);
10045 p = detach_one_task(&env);
10047 schedstat_inc(sd->alb_pushed);
10048 /* Active balancing done, reset the failure counter. */
10049 sd->nr_balance_failed = 0;
10051 schedstat_inc(sd->alb_failed);
10056 busiest_rq->active_balance = 0;
10057 rq_unlock(busiest_rq, &rf);
10060 attach_one_task(target_rq, p);
10062 local_irq_enable();
10067 static DEFINE_SPINLOCK(balancing);
10070 * Scale the max load_balance interval with the number of CPUs in the system.
10071 * This trades load-balance latency on larger machines for less cross talk.
10073 void update_max_interval(void)
10075 max_load_balance_interval = HZ*num_online_cpus()/10;
10079 * It checks each scheduling domain to see if it is due to be balanced,
10080 * and initiates a balancing operation if so.
10082 * Balancing parameters are set up in init_sched_domains.
10084 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
10086 int continue_balancing = 1;
10088 int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
10089 unsigned long interval;
10090 struct sched_domain *sd;
10091 /* Earliest time when we have to do rebalance again */
10092 unsigned long next_balance = jiffies + 60*HZ;
10093 int update_next_balance = 0;
10094 int need_serialize, need_decay = 0;
10098 for_each_domain(cpu, sd) {
10100 * Decay the newidle max times here because this is a regular
10101 * visit to all the domains. Decay ~1% per second.
10103 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
10104 sd->max_newidle_lb_cost =
10105 (sd->max_newidle_lb_cost * 253) / 256;
10106 sd->next_decay_max_lb_cost = jiffies + HZ;
10109 max_cost += sd->max_newidle_lb_cost;
10112 * Stop the load balance at this level. There is another
10113 * CPU in our sched group which is doing load balancing more
10116 if (!continue_balancing) {
10122 interval = get_sd_balance_interval(sd, busy);
10124 need_serialize = sd->flags & SD_SERIALIZE;
10125 if (need_serialize) {
10126 if (!spin_trylock(&balancing))
10130 if (time_after_eq(jiffies, sd->last_balance + interval)) {
10131 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
10133 * The LBF_DST_PINNED logic could have changed
10134 * env->dst_cpu, so we can't know our idle
10135 * state even if we migrated tasks. Update it.
10137 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
10138 busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
10140 sd->last_balance = jiffies;
10141 interval = get_sd_balance_interval(sd, busy);
10143 if (need_serialize)
10144 spin_unlock(&balancing);
10146 if (time_after(next_balance, sd->last_balance + interval)) {
10147 next_balance = sd->last_balance + interval;
10148 update_next_balance = 1;
10153 * Ensure the rq-wide value also decays but keep it at a
10154 * reasonable floor to avoid funnies with rq->avg_idle.
10156 rq->max_idle_balance_cost =
10157 max((u64)sysctl_sched_migration_cost, max_cost);
10162 * next_balance will be updated only when there is a need.
10163 * When the cpu is attached to null domain for ex, it will not be
10166 if (likely(update_next_balance))
10167 rq->next_balance = next_balance;
10171 static inline int on_null_domain(struct rq *rq)
10173 return unlikely(!rcu_dereference_sched(rq->sd));
10176 #ifdef CONFIG_NO_HZ_COMMON
10178 * idle load balancing details
10179 * - When one of the busy CPUs notice that there may be an idle rebalancing
10180 * needed, they will kick the idle load balancer, which then does idle
10181 * load balancing for all the idle CPUs.
10182 * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set
10186 static inline int find_new_ilb(void)
10189 const struct cpumask *hk_mask;
10191 hk_mask = housekeeping_cpumask(HK_FLAG_MISC);
10193 for_each_cpu_and(ilb, nohz.idle_cpus_mask, hk_mask) {
10195 if (ilb == smp_processor_id())
10206 * Kick a CPU to do the nohz balancing, if it is time for it. We pick any
10207 * idle CPU in the HK_FLAG_MISC housekeeping set (if there is one).
10209 static void kick_ilb(unsigned int flags)
10214 * Increase nohz.next_balance only when if full ilb is triggered but
10215 * not if we only update stats.
10217 if (flags & NOHZ_BALANCE_KICK)
10218 nohz.next_balance = jiffies+1;
10220 ilb_cpu = find_new_ilb();
10222 if (ilb_cpu >= nr_cpu_ids)
10226 * Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets
10227 * the first flag owns it; cleared by nohz_csd_func().
10229 flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
10230 if (flags & NOHZ_KICK_MASK)
10234 * This way we generate an IPI on the target CPU which
10235 * is idle. And the softirq performing nohz idle load balance
10236 * will be run before returning from the IPI.
10238 smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd);
10242 * Current decision point for kicking the idle load balancer in the presence
10243 * of idle CPUs in the system.
10245 static void nohz_balancer_kick(struct rq *rq)
10247 unsigned long now = jiffies;
10248 struct sched_domain_shared *sds;
10249 struct sched_domain *sd;
10250 int nr_busy, i, cpu = rq->cpu;
10251 unsigned int flags = 0;
10253 if (unlikely(rq->idle_balance))
10257 * We may be recently in ticked or tickless idle mode. At the first
10258 * busy tick after returning from idle, we will update the busy stats.
10260 nohz_balance_exit_idle(rq);
10263 * None are in tickless mode and hence no need for NOHZ idle load
10266 if (likely(!atomic_read(&nohz.nr_cpus)))
10269 if (READ_ONCE(nohz.has_blocked) &&
10270 time_after(now, READ_ONCE(nohz.next_blocked)))
10271 flags = NOHZ_STATS_KICK;
10273 if (time_before(now, nohz.next_balance))
10276 if (rq->nr_running >= 2) {
10277 flags = NOHZ_KICK_MASK;
10283 sd = rcu_dereference(rq->sd);
10286 * If there's a CFS task and the current CPU has reduced
10287 * capacity; kick the ILB to see if there's a better CPU to run
10290 if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
10291 flags = NOHZ_KICK_MASK;
10296 sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
10299 * When ASYM_PACKING; see if there's a more preferred CPU
10300 * currently idle; in which case, kick the ILB to move tasks
10303 for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
10304 if (sched_asym_prefer(i, cpu)) {
10305 flags = NOHZ_KICK_MASK;
10311 sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
10314 * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
10315 * to run the misfit task on.
10317 if (check_misfit_status(rq, sd)) {
10318 flags = NOHZ_KICK_MASK;
10323 * For asymmetric systems, we do not want to nicely balance
10324 * cache use, instead we want to embrace asymmetry and only
10325 * ensure tasks have enough CPU capacity.
10327 * Skip the LLC logic because it's not relevant in that case.
10332 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
10335 * If there is an imbalance between LLC domains (IOW we could
10336 * increase the overall cache use), we need some less-loaded LLC
10337 * domain to pull some load. Likewise, we may need to spread
10338 * load within the current LLC domain (e.g. packed SMT cores but
10339 * other CPUs are idle). We can't really know from here how busy
10340 * the others are - so just get a nohz balance going if it looks
10341 * like this LLC domain has tasks we could move.
10343 nr_busy = atomic_read(&sds->nr_busy_cpus);
10345 flags = NOHZ_KICK_MASK;
10356 static void set_cpu_sd_state_busy(int cpu)
10358 struct sched_domain *sd;
10361 sd = rcu_dereference(per_cpu(sd_llc, cpu));
10363 if (!sd || !sd->nohz_idle)
10367 atomic_inc(&sd->shared->nr_busy_cpus);
10372 void nohz_balance_exit_idle(struct rq *rq)
10374 SCHED_WARN_ON(rq != this_rq());
10376 if (likely(!rq->nohz_tick_stopped))
10379 rq->nohz_tick_stopped = 0;
10380 cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
10381 atomic_dec(&nohz.nr_cpus);
10383 set_cpu_sd_state_busy(rq->cpu);
10386 static void set_cpu_sd_state_idle(int cpu)
10388 struct sched_domain *sd;
10391 sd = rcu_dereference(per_cpu(sd_llc, cpu));
10393 if (!sd || sd->nohz_idle)
10397 atomic_dec(&sd->shared->nr_busy_cpus);
10403 * This routine will record that the CPU is going idle with tick stopped.
10404 * This info will be used in performing idle load balancing in the future.
10406 void nohz_balance_enter_idle(int cpu)
10408 struct rq *rq = cpu_rq(cpu);
10410 SCHED_WARN_ON(cpu != smp_processor_id());
10412 /* If this CPU is going down, then nothing needs to be done: */
10413 if (!cpu_active(cpu))
10416 /* Spare idle load balancing on CPUs that don't want to be disturbed: */
10417 if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
10421 * Can be set safely without rq->lock held
10422 * If a clear happens, it will have evaluated last additions because
10423 * rq->lock is held during the check and the clear
10425 rq->has_blocked_load = 1;
10428 * The tick is still stopped but load could have been added in the
10429 * meantime. We set the nohz.has_blocked flag to trig a check of the
10430 * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
10431 * of nohz.has_blocked can only happen after checking the new load
10433 if (rq->nohz_tick_stopped)
10436 /* If we're a completely isolated CPU, we don't play: */
10437 if (on_null_domain(rq))
10440 rq->nohz_tick_stopped = 1;
10442 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
10443 atomic_inc(&nohz.nr_cpus);
10446 * Ensures that if nohz_idle_balance() fails to observe our
10447 * @idle_cpus_mask store, it must observe the @has_blocked
10450 smp_mb__after_atomic();
10452 set_cpu_sd_state_idle(cpu);
10456 * Each time a cpu enter idle, we assume that it has blocked load and
10457 * enable the periodic update of the load of idle cpus
10459 WRITE_ONCE(nohz.has_blocked, 1);
10462 static bool update_nohz_stats(struct rq *rq)
10464 unsigned int cpu = rq->cpu;
10466 if (!rq->has_blocked_load)
10469 if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
10472 if (!time_after(jiffies, READ_ONCE(rq->last_blocked_load_update_tick)))
10475 update_blocked_averages(cpu);
10477 return rq->has_blocked_load;
10481 * Internal function that runs load balance for all idle cpus. The load balance
10482 * can be a simple update of blocked load or a complete load balance with
10483 * tasks movement depending of flags.
10485 static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
10486 enum cpu_idle_type idle)
10488 /* Earliest time when we have to do rebalance again */
10489 unsigned long now = jiffies;
10490 unsigned long next_balance = now + 60*HZ;
10491 bool has_blocked_load = false;
10492 int update_next_balance = 0;
10493 int this_cpu = this_rq->cpu;
10497 SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
10500 * We assume there will be no idle load after this update and clear
10501 * the has_blocked flag. If a cpu enters idle in the mean time, it will
10502 * set the has_blocked flag and trig another update of idle load.
10503 * Because a cpu that becomes idle, is added to idle_cpus_mask before
10504 * setting the flag, we are sure to not clear the state and not
10505 * check the load of an idle cpu.
10507 WRITE_ONCE(nohz.has_blocked, 0);
10510 * Ensures that if we miss the CPU, we must see the has_blocked
10511 * store from nohz_balance_enter_idle().
10516 * Start with the next CPU after this_cpu so we will end with this_cpu and let a
10517 * chance for other idle cpu to pull load.
10519 for_each_cpu_wrap(balance_cpu, nohz.idle_cpus_mask, this_cpu+1) {
10520 if (!idle_cpu(balance_cpu))
10524 * If this CPU gets work to do, stop the load balancing
10525 * work being done for other CPUs. Next load
10526 * balancing owner will pick it up.
10528 if (need_resched()) {
10529 has_blocked_load = true;
10533 rq = cpu_rq(balance_cpu);
10535 has_blocked_load |= update_nohz_stats(rq);
10538 * If time for next balance is due,
10541 if (time_after_eq(jiffies, rq->next_balance)) {
10542 struct rq_flags rf;
10544 rq_lock_irqsave(rq, &rf);
10545 update_rq_clock(rq);
10546 rq_unlock_irqrestore(rq, &rf);
10548 if (flags & NOHZ_BALANCE_KICK)
10549 rebalance_domains(rq, CPU_IDLE);
10552 if (time_after(next_balance, rq->next_balance)) {
10553 next_balance = rq->next_balance;
10554 update_next_balance = 1;
10559 * next_balance will be updated only when there is a need.
10560 * When the CPU is attached to null domain for ex, it will not be
10563 if (likely(update_next_balance))
10564 nohz.next_balance = next_balance;
10566 WRITE_ONCE(nohz.next_blocked,
10567 now + msecs_to_jiffies(LOAD_AVG_PERIOD));
10570 /* There is still blocked load, enable periodic update */
10571 if (has_blocked_load)
10572 WRITE_ONCE(nohz.has_blocked, 1);
10576 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
10577 * rebalancing for all the cpus for whom scheduler ticks are stopped.
10579 static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
10581 unsigned int flags = this_rq->nohz_idle_balance;
10586 this_rq->nohz_idle_balance = 0;
10588 if (idle != CPU_IDLE)
10591 _nohz_idle_balance(this_rq, flags, idle);
10597 * Check if we need to run the ILB for updating blocked load before entering
10600 void nohz_run_idle_balance(int cpu)
10602 unsigned int flags;
10604 flags = atomic_fetch_andnot(NOHZ_NEWILB_KICK, nohz_flags(cpu));
10607 * Update the blocked load only if no SCHED_SOFTIRQ is about to happen
10608 * (ie NOHZ_STATS_KICK set) and will do the same.
10610 if ((flags == NOHZ_NEWILB_KICK) && !need_resched())
10611 _nohz_idle_balance(cpu_rq(cpu), NOHZ_STATS_KICK, CPU_IDLE);
10614 static void nohz_newidle_balance(struct rq *this_rq)
10616 int this_cpu = this_rq->cpu;
10619 * This CPU doesn't want to be disturbed by scheduler
10622 if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED))
10625 /* Will wake up very soon. No time for doing anything else*/
10626 if (this_rq->avg_idle < sysctl_sched_migration_cost)
10629 /* Don't need to update blocked load of idle CPUs*/
10630 if (!READ_ONCE(nohz.has_blocked) ||
10631 time_before(jiffies, READ_ONCE(nohz.next_blocked)))
10635 * Set the need to trigger ILB in order to update blocked load
10636 * before entering idle state.
10638 atomic_or(NOHZ_NEWILB_KICK, nohz_flags(this_cpu));
10641 #else /* !CONFIG_NO_HZ_COMMON */
10642 static inline void nohz_balancer_kick(struct rq *rq) { }
10644 static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
10649 static inline void nohz_newidle_balance(struct rq *this_rq) { }
10650 #endif /* CONFIG_NO_HZ_COMMON */
10653 * newidle_balance is called by schedule() if this_cpu is about to become
10654 * idle. Attempts to pull tasks from other CPUs.
10657 * < 0 - we released the lock and there are !fair tasks present
10658 * 0 - failed, no new tasks
10659 * > 0 - success, new (fair) tasks present
10661 static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
10663 unsigned long next_balance = jiffies + HZ;
10664 int this_cpu = this_rq->cpu;
10665 struct sched_domain *sd;
10666 int pulled_task = 0;
10669 update_misfit_status(NULL, this_rq);
10672 * There is a task waiting to run. No need to search for one.
10673 * Return 0; the task will be enqueued when switching to idle.
10675 if (this_rq->ttwu_pending)
10679 * We must set idle_stamp _before_ calling idle_balance(), such that we
10680 * measure the duration of idle_balance() as idle time.
10682 this_rq->idle_stamp = rq_clock(this_rq);
10685 * Do not pull tasks towards !active CPUs...
10687 if (!cpu_active(this_cpu))
10691 * This is OK, because current is on_cpu, which avoids it being picked
10692 * for load-balance and preemption/IRQs are still disabled avoiding
10693 * further scheduler activity on it and we're being very careful to
10694 * re-start the picking loop.
10696 rq_unpin_lock(this_rq, rf);
10698 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
10699 !READ_ONCE(this_rq->rd->overload)) {
10702 sd = rcu_dereference_check_sched_domain(this_rq->sd);
10704 update_next_balance(sd, &next_balance);
10710 raw_spin_rq_unlock(this_rq);
10712 update_blocked_averages(this_cpu);
10714 for_each_domain(this_cpu, sd) {
10715 int continue_balancing = 1;
10716 u64 t0, domain_cost;
10718 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
10719 update_next_balance(sd, &next_balance);
10723 if (sd->flags & SD_BALANCE_NEWIDLE) {
10724 t0 = sched_clock_cpu(this_cpu);
10726 pulled_task = load_balance(this_cpu, this_rq,
10727 sd, CPU_NEWLY_IDLE,
10728 &continue_balancing);
10730 domain_cost = sched_clock_cpu(this_cpu) - t0;
10731 if (domain_cost > sd->max_newidle_lb_cost)
10732 sd->max_newidle_lb_cost = domain_cost;
10734 curr_cost += domain_cost;
10737 update_next_balance(sd, &next_balance);
10740 * Stop searching for tasks to pull if there are
10741 * now runnable tasks on this rq.
10743 if (pulled_task || this_rq->nr_running > 0 ||
10744 this_rq->ttwu_pending)
10749 raw_spin_rq_lock(this_rq);
10751 if (curr_cost > this_rq->max_idle_balance_cost)
10752 this_rq->max_idle_balance_cost = curr_cost;
10755 * While browsing the domains, we released the rq lock, a task could
10756 * have been enqueued in the meantime. Since we're not going idle,
10757 * pretend we pulled a task.
10759 if (this_rq->cfs.h_nr_running && !pulled_task)
10762 /* Is there a task of a high priority class? */
10763 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
10767 /* Move the next balance forward */
10768 if (time_after(this_rq->next_balance, next_balance))
10769 this_rq->next_balance = next_balance;
10772 this_rq->idle_stamp = 0;
10774 nohz_newidle_balance(this_rq);
10776 rq_repin_lock(this_rq, rf);
10778 return pulled_task;
10782 * run_rebalance_domains is triggered when needed from the scheduler tick.
10783 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
10785 static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
10787 struct rq *this_rq = this_rq();
10788 enum cpu_idle_type idle = this_rq->idle_balance ?
10789 CPU_IDLE : CPU_NOT_IDLE;
10792 * If this CPU has a pending nohz_balance_kick, then do the
10793 * balancing on behalf of the other idle CPUs whose ticks are
10794 * stopped. Do nohz_idle_balance *before* rebalance_domains to
10795 * give the idle CPUs a chance to load balance. Else we may
10796 * load balance only within the local sched_domain hierarchy
10797 * and abort nohz_idle_balance altogether if we pull some load.
10799 if (nohz_idle_balance(this_rq, idle))
10802 /* normal load balance */
10803 update_blocked_averages(this_rq->cpu);
10804 rebalance_domains(this_rq, idle);
10808 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
10810 void trigger_load_balance(struct rq *rq)
10813 * Don't need to rebalance while attached to NULL domain or
10814 * runqueue CPU is not active
10816 if (unlikely(on_null_domain(rq) || !cpu_active(cpu_of(rq))))
10819 if (time_after_eq(jiffies, rq->next_balance))
10820 raise_softirq(SCHED_SOFTIRQ);
10822 nohz_balancer_kick(rq);
10825 static void rq_online_fair(struct rq *rq)
10829 update_runtime_enabled(rq);
10832 static void rq_offline_fair(struct rq *rq)
10836 /* Ensure any throttled groups are reachable by pick_next_task */
10837 unthrottle_offline_cfs_rqs(rq);
10840 #endif /* CONFIG_SMP */
10842 #ifdef CONFIG_SCHED_CORE
10844 __entity_slice_used(struct sched_entity *se, int min_nr_tasks)
10846 u64 slice = sched_slice(cfs_rq_of(se), se);
10847 u64 rtime = se->sum_exec_runtime - se->prev_sum_exec_runtime;
10849 return (rtime * min_nr_tasks > slice);
10852 #define MIN_NR_TASKS_DURING_FORCEIDLE 2
10853 static inline void task_tick_core(struct rq *rq, struct task_struct *curr)
10855 if (!sched_core_enabled(rq))
10859 * If runqueue has only one task which used up its slice and
10860 * if the sibling is forced idle, then trigger schedule to
10861 * give forced idle task a chance.
10863 * sched_slice() considers only this active rq and it gets the
10864 * whole slice. But during force idle, we have siblings acting
10865 * like a single runqueue and hence we need to consider runnable
10866 * tasks on this CPU and the forced idle CPU. Ideally, we should
10867 * go through the forced idle rq, but that would be a perf hit.
10868 * We can assume that the forced idle CPU has at least
10869 * MIN_NR_TASKS_DURING_FORCEIDLE - 1 tasks and use that to check
10870 * if we need to give up the CPU.
10872 if (rq->core->core_forceidle && rq->cfs.nr_running == 1 &&
10873 __entity_slice_used(&curr->se, MIN_NR_TASKS_DURING_FORCEIDLE))
10878 * se_fi_update - Update the cfs_rq->min_vruntime_fi in a CFS hierarchy if needed.
10880 static void se_fi_update(struct sched_entity *se, unsigned int fi_seq, bool forceidle)
10882 for_each_sched_entity(se) {
10883 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10886 if (cfs_rq->forceidle_seq == fi_seq)
10888 cfs_rq->forceidle_seq = fi_seq;
10891 cfs_rq->min_vruntime_fi = cfs_rq->min_vruntime;
10895 void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi)
10897 struct sched_entity *se = &p->se;
10899 if (p->sched_class != &fair_sched_class)
10902 se_fi_update(se, rq->core->core_forceidle_seq, in_fi);
10905 bool cfs_prio_less(struct task_struct *a, struct task_struct *b, bool in_fi)
10907 struct rq *rq = task_rq(a);
10908 struct sched_entity *sea = &a->se;
10909 struct sched_entity *seb = &b->se;
10910 struct cfs_rq *cfs_rqa;
10911 struct cfs_rq *cfs_rqb;
10914 SCHED_WARN_ON(task_rq(b)->core != rq->core);
10916 #ifdef CONFIG_FAIR_GROUP_SCHED
10918 * Find an se in the hierarchy for tasks a and b, such that the se's
10919 * are immediate siblings.
10921 while (sea->cfs_rq->tg != seb->cfs_rq->tg) {
10922 int sea_depth = sea->depth;
10923 int seb_depth = seb->depth;
10925 if (sea_depth >= seb_depth)
10926 sea = parent_entity(sea);
10927 if (sea_depth <= seb_depth)
10928 seb = parent_entity(seb);
10931 se_fi_update(sea, rq->core->core_forceidle_seq, in_fi);
10932 se_fi_update(seb, rq->core->core_forceidle_seq, in_fi);
10934 cfs_rqa = sea->cfs_rq;
10935 cfs_rqb = seb->cfs_rq;
10937 cfs_rqa = &task_rq(a)->cfs;
10938 cfs_rqb = &task_rq(b)->cfs;
10942 * Find delta after normalizing se's vruntime with its cfs_rq's
10943 * min_vruntime_fi, which would have been updated in prior calls
10944 * to se_fi_update().
10946 delta = (s64)(sea->vruntime - seb->vruntime) +
10947 (s64)(cfs_rqb->min_vruntime_fi - cfs_rqa->min_vruntime_fi);
10952 static inline void task_tick_core(struct rq *rq, struct task_struct *curr) {}
10956 * scheduler tick hitting a task of our scheduling class.
10958 * NOTE: This function can be called remotely by the tick offload that
10959 * goes along full dynticks. Therefore no local assumption can be made
10960 * and everything must be accessed through the @rq and @curr passed in
10963 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
10965 struct cfs_rq *cfs_rq;
10966 struct sched_entity *se = &curr->se;
10968 for_each_sched_entity(se) {
10969 cfs_rq = cfs_rq_of(se);
10970 entity_tick(cfs_rq, se, queued);
10973 if (static_branch_unlikely(&sched_numa_balancing))
10974 task_tick_numa(rq, curr);
10976 update_misfit_status(curr, rq);
10977 update_overutilized_status(task_rq(curr));
10979 task_tick_core(rq, curr);
10983 * called on fork with the child task as argument from the parent's context
10984 * - child not yet on the tasklist
10985 * - preemption disabled
10987 static void task_fork_fair(struct task_struct *p)
10989 struct cfs_rq *cfs_rq;
10990 struct sched_entity *se = &p->se, *curr;
10991 struct rq *rq = this_rq();
10992 struct rq_flags rf;
10995 update_rq_clock(rq);
10997 cfs_rq = task_cfs_rq(current);
10998 curr = cfs_rq->curr;
11000 update_curr(cfs_rq);
11001 se->vruntime = curr->vruntime;
11003 place_entity(cfs_rq, se, 1);
11005 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
11007 * Upon rescheduling, sched_class::put_prev_task() will place
11008 * 'current' within the tree based on its new key value.
11010 swap(curr->vruntime, se->vruntime);
11014 se->vruntime -= cfs_rq->min_vruntime;
11015 rq_unlock(rq, &rf);
11019 * Priority of the task has changed. Check to see if we preempt
11020 * the current task.
11023 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
11025 if (!task_on_rq_queued(p))
11028 if (rq->cfs.nr_running == 1)
11032 * Reschedule if we are currently running on this runqueue and
11033 * our priority decreased, or if we are not currently running on
11034 * this runqueue and our priority is higher than the current's
11036 if (task_current(rq, p)) {
11037 if (p->prio > oldprio)
11040 check_preempt_curr(rq, p, 0);
11043 static inline bool vruntime_normalized(struct task_struct *p)
11045 struct sched_entity *se = &p->se;
11048 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
11049 * the dequeue_entity(.flags=0) will already have normalized the
11056 * When !on_rq, vruntime of the task has usually NOT been normalized.
11057 * But there are some cases where it has already been normalized:
11059 * - A forked child which is waiting for being woken up by
11060 * wake_up_new_task().
11061 * - A task which has been woken up by try_to_wake_up() and
11062 * waiting for actually being woken up by sched_ttwu_pending().
11064 if (!se->sum_exec_runtime ||
11065 (READ_ONCE(p->__state) == TASK_WAKING && p->sched_remote_wakeup))
11071 #ifdef CONFIG_FAIR_GROUP_SCHED
11073 * Propagate the changes of the sched_entity across the tg tree to make it
11074 * visible to the root
11076 static void propagate_entity_cfs_rq(struct sched_entity *se)
11078 struct cfs_rq *cfs_rq;
11080 list_add_leaf_cfs_rq(cfs_rq_of(se));
11082 /* Start to propagate at parent */
11085 for_each_sched_entity(se) {
11086 cfs_rq = cfs_rq_of(se);
11088 if (!cfs_rq_throttled(cfs_rq)){
11089 update_load_avg(cfs_rq, se, UPDATE_TG);
11090 list_add_leaf_cfs_rq(cfs_rq);
11094 if (list_add_leaf_cfs_rq(cfs_rq))
11099 static void propagate_entity_cfs_rq(struct sched_entity *se) { }
11102 static void detach_entity_cfs_rq(struct sched_entity *se)
11104 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11106 /* Catch up with the cfs_rq and remove our load when we leave */
11107 update_load_avg(cfs_rq, se, 0);
11108 detach_entity_load_avg(cfs_rq, se);
11109 update_tg_load_avg(cfs_rq);
11110 propagate_entity_cfs_rq(se);
11113 static void attach_entity_cfs_rq(struct sched_entity *se)
11115 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11117 #ifdef CONFIG_FAIR_GROUP_SCHED
11119 * Since the real-depth could have been changed (only FAIR
11120 * class maintain depth value), reset depth properly.
11122 se->depth = se->parent ? se->parent->depth + 1 : 0;
11125 /* Synchronize entity with its cfs_rq */
11126 update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
11127 attach_entity_load_avg(cfs_rq, se);
11128 update_tg_load_avg(cfs_rq);
11129 propagate_entity_cfs_rq(se);
11132 static void detach_task_cfs_rq(struct task_struct *p)
11134 struct sched_entity *se = &p->se;
11135 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11137 if (!vruntime_normalized(p)) {
11139 * Fix up our vruntime so that the current sleep doesn't
11140 * cause 'unlimited' sleep bonus.
11142 place_entity(cfs_rq, se, 0);
11143 se->vruntime -= cfs_rq->min_vruntime;
11146 detach_entity_cfs_rq(se);
11149 static void attach_task_cfs_rq(struct task_struct *p)
11151 struct sched_entity *se = &p->se;
11152 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11154 attach_entity_cfs_rq(se);
11156 if (!vruntime_normalized(p))
11157 se->vruntime += cfs_rq->min_vruntime;
11160 static void switched_from_fair(struct rq *rq, struct task_struct *p)
11162 detach_task_cfs_rq(p);
11165 static void switched_to_fair(struct rq *rq, struct task_struct *p)
11167 attach_task_cfs_rq(p);
11169 if (task_on_rq_queued(p)) {
11171 * We were most likely switched from sched_rt, so
11172 * kick off the schedule if running, otherwise just see
11173 * if we can still preempt the current task.
11175 if (task_current(rq, p))
11178 check_preempt_curr(rq, p, 0);
11182 /* Account for a task changing its policy or group.
11184 * This routine is mostly called to set cfs_rq->curr field when a task
11185 * migrates between groups/classes.
11187 static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
11189 struct sched_entity *se = &p->se;
11192 if (task_on_rq_queued(p)) {
11194 * Move the next running task to the front of the list, so our
11195 * cfs_tasks list becomes MRU one.
11197 list_move(&se->group_node, &rq->cfs_tasks);
11201 for_each_sched_entity(se) {
11202 struct cfs_rq *cfs_rq = cfs_rq_of(se);
11204 set_next_entity(cfs_rq, se);
11205 /* ensure bandwidth has been allocated on our new cfs_rq */
11206 account_cfs_rq_runtime(cfs_rq, 0);
11210 void init_cfs_rq(struct cfs_rq *cfs_rq)
11212 cfs_rq->tasks_timeline = RB_ROOT_CACHED;
11213 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
11214 #ifndef CONFIG_64BIT
11215 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
11218 raw_spin_lock_init(&cfs_rq->removed.lock);
11222 #ifdef CONFIG_FAIR_GROUP_SCHED
11223 static void task_set_group_fair(struct task_struct *p)
11225 struct sched_entity *se = &p->se;
11227 set_task_rq(p, task_cpu(p));
11228 se->depth = se->parent ? se->parent->depth + 1 : 0;
11231 static void task_move_group_fair(struct task_struct *p)
11233 detach_task_cfs_rq(p);
11234 set_task_rq(p, task_cpu(p));
11237 /* Tell se's cfs_rq has been changed -- migrated */
11238 p->se.avg.last_update_time = 0;
11240 attach_task_cfs_rq(p);
11243 static void task_change_group_fair(struct task_struct *p, int type)
11246 case TASK_SET_GROUP:
11247 task_set_group_fair(p);
11250 case TASK_MOVE_GROUP:
11251 task_move_group_fair(p);
11256 void free_fair_sched_group(struct task_group *tg)
11260 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
11262 for_each_possible_cpu(i) {
11264 kfree(tg->cfs_rq[i]);
11273 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
11275 struct sched_entity *se;
11276 struct cfs_rq *cfs_rq;
11279 tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
11282 tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
11286 tg->shares = NICE_0_LOAD;
11288 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
11290 for_each_possible_cpu(i) {
11291 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
11292 GFP_KERNEL, cpu_to_node(i));
11296 se = kzalloc_node(sizeof(struct sched_entity),
11297 GFP_KERNEL, cpu_to_node(i));
11301 init_cfs_rq(cfs_rq);
11302 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
11303 init_entity_runnable_average(se);
11314 void online_fair_sched_group(struct task_group *tg)
11316 struct sched_entity *se;
11317 struct rq_flags rf;
11321 for_each_possible_cpu(i) {
11324 rq_lock_irq(rq, &rf);
11325 update_rq_clock(rq);
11326 attach_entity_cfs_rq(se);
11327 sync_throttle(tg, i);
11328 rq_unlock_irq(rq, &rf);
11332 void unregister_fair_sched_group(struct task_group *tg)
11334 unsigned long flags;
11338 for_each_possible_cpu(cpu) {
11340 remove_entity_load_avg(tg->se[cpu]);
11343 * Only empty task groups can be destroyed; so we can speculatively
11344 * check on_list without danger of it being re-added.
11346 if (!tg->cfs_rq[cpu]->on_list)
11351 raw_spin_rq_lock_irqsave(rq, flags);
11352 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
11353 raw_spin_rq_unlock_irqrestore(rq, flags);
11357 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
11358 struct sched_entity *se, int cpu,
11359 struct sched_entity *parent)
11361 struct rq *rq = cpu_rq(cpu);
11365 init_cfs_rq_runtime(cfs_rq);
11367 tg->cfs_rq[cpu] = cfs_rq;
11370 /* se could be NULL for root_task_group */
11375 se->cfs_rq = &rq->cfs;
11378 se->cfs_rq = parent->my_q;
11379 se->depth = parent->depth + 1;
11383 /* guarantee group entities always have weight */
11384 update_load_set(&se->load, NICE_0_LOAD);
11385 se->parent = parent;
11388 static DEFINE_MUTEX(shares_mutex);
11390 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
11395 * We can't change the weight of the root cgroup.
11400 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
11402 mutex_lock(&shares_mutex);
11403 if (tg->shares == shares)
11406 tg->shares = shares;
11407 for_each_possible_cpu(i) {
11408 struct rq *rq = cpu_rq(i);
11409 struct sched_entity *se = tg->se[i];
11410 struct rq_flags rf;
11412 /* Propagate contribution to hierarchy */
11413 rq_lock_irqsave(rq, &rf);
11414 update_rq_clock(rq);
11415 for_each_sched_entity(se) {
11416 update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
11417 update_cfs_group(se);
11419 rq_unlock_irqrestore(rq, &rf);
11423 mutex_unlock(&shares_mutex);
11426 #else /* CONFIG_FAIR_GROUP_SCHED */
11428 void free_fair_sched_group(struct task_group *tg) { }
11430 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
11435 void online_fair_sched_group(struct task_group *tg) { }
11437 void unregister_fair_sched_group(struct task_group *tg) { }
11439 #endif /* CONFIG_FAIR_GROUP_SCHED */
11442 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
11444 struct sched_entity *se = &task->se;
11445 unsigned int rr_interval = 0;
11448 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
11451 if (rq->cfs.load.weight)
11452 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
11454 return rr_interval;
11458 * All the scheduling class methods:
11460 DEFINE_SCHED_CLASS(fair) = {
11462 .enqueue_task = enqueue_task_fair,
11463 .dequeue_task = dequeue_task_fair,
11464 .yield_task = yield_task_fair,
11465 .yield_to_task = yield_to_task_fair,
11467 .check_preempt_curr = check_preempt_wakeup,
11469 .pick_next_task = __pick_next_task_fair,
11470 .put_prev_task = put_prev_task_fair,
11471 .set_next_task = set_next_task_fair,
11474 .balance = balance_fair,
11475 .pick_task = pick_task_fair,
11476 .select_task_rq = select_task_rq_fair,
11477 .migrate_task_rq = migrate_task_rq_fair,
11479 .rq_online = rq_online_fair,
11480 .rq_offline = rq_offline_fair,
11482 .task_dead = task_dead_fair,
11483 .set_cpus_allowed = set_cpus_allowed_common,
11486 .task_tick = task_tick_fair,
11487 .task_fork = task_fork_fair,
11489 .prio_changed = prio_changed_fair,
11490 .switched_from = switched_from_fair,
11491 .switched_to = switched_to_fair,
11493 .get_rr_interval = get_rr_interval_fair,
11495 .update_curr = update_curr_fair,
11497 #ifdef CONFIG_FAIR_GROUP_SCHED
11498 .task_change_group = task_change_group_fair,
11501 #ifdef CONFIG_UCLAMP_TASK
11502 .uclamp_enabled = 1,
11506 #ifdef CONFIG_SCHED_DEBUG
11507 void print_cfs_stats(struct seq_file *m, int cpu)
11509 struct cfs_rq *cfs_rq, *pos;
11512 for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
11513 print_cfs_rq(m, cpu, cfs_rq);
11517 #ifdef CONFIG_NUMA_BALANCING
11518 void show_numa_stats(struct task_struct *p, struct seq_file *m)
11521 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
11522 struct numa_group *ng;
11525 ng = rcu_dereference(p->numa_group);
11526 for_each_online_node(node) {
11527 if (p->numa_faults) {
11528 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
11529 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
11532 gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)],
11533 gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
11535 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
11539 #endif /* CONFIG_NUMA_BALANCING */
11540 #endif /* CONFIG_SCHED_DEBUG */
11542 __init void init_sched_fair_class(void)
11545 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
11547 #ifdef CONFIG_NO_HZ_COMMON
11548 nohz.next_balance = jiffies;
11549 nohz.next_blocked = jiffies;
11550 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
11557 * Helper functions to facilitate extracting info from tracepoints.
11560 const struct sched_avg *sched_trace_cfs_rq_avg(struct cfs_rq *cfs_rq)
11563 return cfs_rq ? &cfs_rq->avg : NULL;
11568 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_avg);
11570 char *sched_trace_cfs_rq_path(struct cfs_rq *cfs_rq, char *str, int len)
11574 strlcpy(str, "(null)", len);
11579 cfs_rq_tg_path(cfs_rq, str, len);
11582 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_path);
11584 int sched_trace_cfs_rq_cpu(struct cfs_rq *cfs_rq)
11586 return cfs_rq ? cpu_of(rq_of(cfs_rq)) : -1;
11588 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_cpu);
11590 const struct sched_avg *sched_trace_rq_avg_rt(struct rq *rq)
11593 return rq ? &rq->avg_rt : NULL;
11598 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_rt);
11600 const struct sched_avg *sched_trace_rq_avg_dl(struct rq *rq)
11603 return rq ? &rq->avg_dl : NULL;
11608 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_dl);
11610 const struct sched_avg *sched_trace_rq_avg_irq(struct rq *rq)
11612 #if defined(CONFIG_SMP) && defined(CONFIG_HAVE_SCHED_AVG_IRQ)
11613 return rq ? &rq->avg_irq : NULL;
11618 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_irq);
11620 int sched_trace_rq_cpu(struct rq *rq)
11622 return rq ? cpu_of(rq) : -1;
11624 EXPORT_SYMBOL_GPL(sched_trace_rq_cpu);
11626 int sched_trace_rq_cpu_capacity(struct rq *rq)
11632 SCHED_CAPACITY_SCALE
11636 EXPORT_SYMBOL_GPL(sched_trace_rq_cpu_capacity);
11638 const struct cpumask *sched_trace_rd_span(struct root_domain *rd)
11641 return rd ? rd->span : NULL;
11646 EXPORT_SYMBOL_GPL(sched_trace_rd_span);
11648 int sched_trace_rq_nr_running(struct rq *rq)
11650 return rq ? rq->nr_running : -1;
11652 EXPORT_SYMBOL_GPL(sched_trace_rq_nr_running);