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
25 #include <trace/events/sched.h>
28 * Targeted preemption latency for CPU-bound tasks:
30 * NOTE: this latency value is not the same as the concept of
31 * 'timeslice length' - timeslices in CFS are of variable length
32 * and have no persistent notion like in traditional, time-slice
33 * based scheduling concepts.
35 * (to see the precise effective timeslice length of your workload,
36 * run vmstat and monitor the context-switches (cs) field)
38 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
40 unsigned int sysctl_sched_latency = 6000000ULL;
41 static unsigned int normalized_sysctl_sched_latency = 6000000ULL;
44 * The initial- and re-scaling of tunables is configurable
48 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
49 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
50 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
52 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
54 enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
57 * Minimal preemption granularity for CPU-bound tasks:
59 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
61 unsigned int sysctl_sched_min_granularity = 750000ULL;
62 static unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
65 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
67 static unsigned int sched_nr_latency = 8;
70 * After fork, child runs first. If set to 0 (default) then
71 * parent will (try to) run first.
73 unsigned int sysctl_sched_child_runs_first __read_mostly;
76 * SCHED_OTHER wake-up granularity.
78 * This option delays the preemption effects of decoupled workloads
79 * and reduces their over-scheduling. Synchronous workloads will still
80 * have immediate wakeup/sleep latencies.
82 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
84 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
85 static unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
87 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
89 int sched_thermal_decay_shift;
90 static int __init setup_sched_thermal_decay_shift(char *str)
94 if (kstrtoint(str, 0, &_shift))
95 pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
97 sched_thermal_decay_shift = clamp(_shift, 0, 10);
100 __setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
104 * For asym packing, by default the lower numbered CPU has higher priority.
106 int __weak arch_asym_cpu_priority(int cpu)
112 * The margin used when comparing utilization with CPU capacity.
116 #define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024)
120 #ifdef CONFIG_CFS_BANDWIDTH
122 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
123 * each time a cfs_rq requests quota.
125 * Note: in the case that the slice exceeds the runtime remaining (either due
126 * to consumption or the quota being specified to be smaller than the slice)
127 * we will always only issue the remaining available time.
129 * (default: 5 msec, units: microseconds)
131 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
134 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
140 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
146 static inline void update_load_set(struct load_weight *lw, unsigned long w)
153 * Increase the granularity value when there are more CPUs,
154 * because with more CPUs the 'effective latency' as visible
155 * to users decreases. But the relationship is not linear,
156 * so pick a second-best guess by going with the log2 of the
159 * This idea comes from the SD scheduler of Con Kolivas:
161 static unsigned int get_update_sysctl_factor(void)
163 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
166 switch (sysctl_sched_tunable_scaling) {
167 case SCHED_TUNABLESCALING_NONE:
170 case SCHED_TUNABLESCALING_LINEAR:
173 case SCHED_TUNABLESCALING_LOG:
175 factor = 1 + ilog2(cpus);
182 static void update_sysctl(void)
184 unsigned int factor = get_update_sysctl_factor();
186 #define SET_SYSCTL(name) \
187 (sysctl_##name = (factor) * normalized_sysctl_##name)
188 SET_SYSCTL(sched_min_granularity);
189 SET_SYSCTL(sched_latency);
190 SET_SYSCTL(sched_wakeup_granularity);
194 void __init sched_init_granularity(void)
199 #define WMULT_CONST (~0U)
200 #define WMULT_SHIFT 32
202 static void __update_inv_weight(struct load_weight *lw)
206 if (likely(lw->inv_weight))
209 w = scale_load_down(lw->weight);
211 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
213 else if (unlikely(!w))
214 lw->inv_weight = WMULT_CONST;
216 lw->inv_weight = WMULT_CONST / w;
220 * delta_exec * weight / lw.weight
222 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
224 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
225 * we're guaranteed shift stays positive because inv_weight is guaranteed to
226 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
228 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
229 * weight/lw.weight <= 1, and therefore our shift will also be positive.
231 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
233 u64 fact = scale_load_down(weight);
234 int shift = WMULT_SHIFT;
236 __update_inv_weight(lw);
238 if (unlikely(fact >> 32)) {
245 fact = mul_u32_u32(fact, lw->inv_weight);
252 return mul_u64_u32_shr(delta_exec, fact, shift);
256 const struct sched_class fair_sched_class;
258 /**************************************************************
259 * CFS operations on generic schedulable entities:
262 #ifdef CONFIG_FAIR_GROUP_SCHED
263 static inline struct task_struct *task_of(struct sched_entity *se)
265 SCHED_WARN_ON(!entity_is_task(se));
266 return container_of(se, struct task_struct, se);
269 /* Walk up scheduling entities hierarchy */
270 #define for_each_sched_entity(se) \
271 for (; se; se = se->parent)
273 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
278 /* runqueue on which this entity is (to be) queued */
279 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
284 /* runqueue "owned" by this group */
285 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
290 static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
295 if (cfs_rq && task_group_is_autogroup(cfs_rq->tg))
296 autogroup_path(cfs_rq->tg, path, len);
297 else if (cfs_rq && cfs_rq->tg->css.cgroup)
298 cgroup_path(cfs_rq->tg->css.cgroup, path, len);
300 strlcpy(path, "(null)", len);
303 static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
305 struct rq *rq = rq_of(cfs_rq);
306 int cpu = cpu_of(rq);
309 return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
314 * Ensure we either appear before our parent (if already
315 * enqueued) or force our parent to appear after us when it is
316 * enqueued. The fact that we always enqueue bottom-up
317 * reduces this to two cases and a special case for the root
318 * cfs_rq. Furthermore, it also means that we will always reset
319 * tmp_alone_branch either when the branch is connected
320 * to a tree or when we reach the top of the tree
322 if (cfs_rq->tg->parent &&
323 cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
325 * If parent is already on the list, we add the child
326 * just before. Thanks to circular linked property of
327 * the list, this means to put the child at the tail
328 * of the list that starts by parent.
330 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
331 &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
333 * The branch is now connected to its tree so we can
334 * reset tmp_alone_branch to the beginning of the
337 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
341 if (!cfs_rq->tg->parent) {
343 * cfs rq without parent should be put
344 * at the tail of the list.
346 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
347 &rq->leaf_cfs_rq_list);
349 * We have reach the top of a tree so we can reset
350 * tmp_alone_branch to the beginning of the list.
352 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
357 * The parent has not already been added so we want to
358 * make sure that it will be put after us.
359 * tmp_alone_branch points to the begin of the branch
360 * where we will add parent.
362 list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch);
364 * update tmp_alone_branch to points to the new begin
367 rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
371 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
373 if (cfs_rq->on_list) {
374 struct rq *rq = rq_of(cfs_rq);
377 * With cfs_rq being unthrottled/throttled during an enqueue,
378 * it can happen the tmp_alone_branch points the a leaf that
379 * we finally want to del. In this case, tmp_alone_branch moves
380 * to the prev element but it will point to rq->leaf_cfs_rq_list
381 * at the end of the enqueue.
383 if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list)
384 rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev;
386 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
391 static inline void assert_list_leaf_cfs_rq(struct rq *rq)
393 SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list);
396 /* Iterate thr' all leaf cfs_rq's on a runqueue */
397 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
398 list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, \
401 /* Do the two (enqueued) entities belong to the same group ? */
402 static inline struct cfs_rq *
403 is_same_group(struct sched_entity *se, struct sched_entity *pse)
405 if (se->cfs_rq == pse->cfs_rq)
411 static inline struct sched_entity *parent_entity(struct sched_entity *se)
417 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
419 int se_depth, pse_depth;
422 * preemption test can be made between sibling entities who are in the
423 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
424 * both tasks until we find their ancestors who are siblings of common
428 /* First walk up until both entities are at same depth */
429 se_depth = (*se)->depth;
430 pse_depth = (*pse)->depth;
432 while (se_depth > pse_depth) {
434 *se = parent_entity(*se);
437 while (pse_depth > se_depth) {
439 *pse = parent_entity(*pse);
442 while (!is_same_group(*se, *pse)) {
443 *se = parent_entity(*se);
444 *pse = parent_entity(*pse);
448 #else /* !CONFIG_FAIR_GROUP_SCHED */
450 static inline struct task_struct *task_of(struct sched_entity *se)
452 return container_of(se, struct task_struct, se);
455 #define for_each_sched_entity(se) \
456 for (; se; se = NULL)
458 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
460 return &task_rq(p)->cfs;
463 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
465 struct task_struct *p = task_of(se);
466 struct rq *rq = task_rq(p);
471 /* runqueue "owned" by this group */
472 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
477 static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
480 strlcpy(path, "(null)", len);
483 static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
488 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
492 static inline void assert_list_leaf_cfs_rq(struct rq *rq)
496 #define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) \
497 for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
499 static inline struct sched_entity *parent_entity(struct sched_entity *se)
505 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
509 #endif /* CONFIG_FAIR_GROUP_SCHED */
511 static __always_inline
512 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
514 /**************************************************************
515 * Scheduling class tree data structure manipulation methods:
518 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
520 s64 delta = (s64)(vruntime - max_vruntime);
522 max_vruntime = vruntime;
527 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
529 s64 delta = (s64)(vruntime - min_vruntime);
531 min_vruntime = vruntime;
536 static inline int entity_before(struct sched_entity *a,
537 struct sched_entity *b)
539 return (s64)(a->vruntime - b->vruntime) < 0;
542 static void update_min_vruntime(struct cfs_rq *cfs_rq)
544 struct sched_entity *curr = cfs_rq->curr;
545 struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
547 u64 vruntime = cfs_rq->min_vruntime;
551 vruntime = curr->vruntime;
556 if (leftmost) { /* non-empty tree */
557 struct sched_entity *se;
558 se = rb_entry(leftmost, struct sched_entity, run_node);
561 vruntime = se->vruntime;
563 vruntime = min_vruntime(vruntime, se->vruntime);
566 /* ensure we never gain time by being placed backwards. */
567 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
570 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
575 * Enqueue an entity into the rb-tree:
577 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
579 struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
580 struct rb_node *parent = NULL;
581 struct sched_entity *entry;
582 bool leftmost = true;
585 * Find the right place in the rbtree:
589 entry = rb_entry(parent, struct sched_entity, run_node);
591 * We dont care about collisions. Nodes with
592 * the same key stay together.
594 if (entity_before(se, entry)) {
595 link = &parent->rb_left;
597 link = &parent->rb_right;
602 rb_link_node(&se->run_node, parent, link);
603 rb_insert_color_cached(&se->run_node,
604 &cfs_rq->tasks_timeline, leftmost);
607 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
609 rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
612 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
614 struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
619 return rb_entry(left, struct sched_entity, run_node);
622 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
624 struct rb_node *next = rb_next(&se->run_node);
629 return rb_entry(next, struct sched_entity, run_node);
632 #ifdef CONFIG_SCHED_DEBUG
633 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
635 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
640 return rb_entry(last, struct sched_entity, run_node);
643 /**************************************************************
644 * Scheduling class statistics methods:
647 int sched_proc_update_handler(struct ctl_table *table, int write,
648 void __user *buffer, size_t *lenp,
651 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
652 unsigned int factor = get_update_sysctl_factor();
657 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
658 sysctl_sched_min_granularity);
660 #define WRT_SYSCTL(name) \
661 (normalized_sysctl_##name = sysctl_##name / (factor))
662 WRT_SYSCTL(sched_min_granularity);
663 WRT_SYSCTL(sched_latency);
664 WRT_SYSCTL(sched_wakeup_granularity);
674 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
676 if (unlikely(se->load.weight != NICE_0_LOAD))
677 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
683 * The idea is to set a period in which each task runs once.
685 * When there are too many tasks (sched_nr_latency) we have to stretch
686 * this period because otherwise the slices get too small.
688 * p = (nr <= nl) ? l : l*nr/nl
690 static u64 __sched_period(unsigned long nr_running)
692 if (unlikely(nr_running > sched_nr_latency))
693 return nr_running * sysctl_sched_min_granularity;
695 return sysctl_sched_latency;
699 * We calculate the wall-time slice from the period by taking a part
700 * proportional to the weight.
704 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
706 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
708 for_each_sched_entity(se) {
709 struct load_weight *load;
710 struct load_weight lw;
712 cfs_rq = cfs_rq_of(se);
713 load = &cfs_rq->load;
715 if (unlikely(!se->on_rq)) {
718 update_load_add(&lw, se->load.weight);
721 slice = __calc_delta(slice, se->load.weight, load);
727 * We calculate the vruntime slice of a to-be-inserted task.
731 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
733 return calc_delta_fair(sched_slice(cfs_rq, se), se);
739 static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
740 static unsigned long task_h_load(struct task_struct *p);
741 static unsigned long capacity_of(int cpu);
743 /* Give new sched_entity start runnable values to heavy its load in infant time */
744 void init_entity_runnable_average(struct sched_entity *se)
746 struct sched_avg *sa = &se->avg;
748 memset(sa, 0, sizeof(*sa));
751 * Tasks are initialized with full load to be seen as heavy tasks until
752 * they get a chance to stabilize to their real load level.
753 * Group entities are initialized with zero load to reflect the fact that
754 * nothing has been attached to the task group yet.
756 if (entity_is_task(se))
757 sa->load_avg = scale_load_down(se->load.weight);
759 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
762 static void attach_entity_cfs_rq(struct sched_entity *se);
765 * With new tasks being created, their initial util_avgs are extrapolated
766 * based on the cfs_rq's current util_avg:
768 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
770 * However, in many cases, the above util_avg does not give a desired
771 * value. Moreover, the sum of the util_avgs may be divergent, such
772 * as when the series is a harmonic series.
774 * To solve this problem, we also cap the util_avg of successive tasks to
775 * only 1/2 of the left utilization budget:
777 * util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
779 * where n denotes the nth task and cpu_scale the CPU capacity.
781 * For example, for a CPU with 1024 of capacity, a simplest series from
782 * the beginning would be like:
784 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
785 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
787 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
788 * if util_avg > util_avg_cap.
790 void post_init_entity_util_avg(struct task_struct *p)
792 struct sched_entity *se = &p->se;
793 struct cfs_rq *cfs_rq = cfs_rq_of(se);
794 struct sched_avg *sa = &se->avg;
795 long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)));
796 long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
799 if (cfs_rq->avg.util_avg != 0) {
800 sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
801 sa->util_avg /= (cfs_rq->avg.load_avg + 1);
803 if (sa->util_avg > cap)
810 sa->runnable_avg = cpu_scale;
812 if (p->sched_class != &fair_sched_class) {
814 * For !fair tasks do:
816 update_cfs_rq_load_avg(now, cfs_rq);
817 attach_entity_load_avg(cfs_rq, se);
818 switched_from_fair(rq, p);
820 * such that the next switched_to_fair() has the
823 se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
827 attach_entity_cfs_rq(se);
830 #else /* !CONFIG_SMP */
831 void init_entity_runnable_average(struct sched_entity *se)
834 void post_init_entity_util_avg(struct task_struct *p)
837 static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
840 #endif /* CONFIG_SMP */
843 * Update the current task's runtime statistics.
845 static void update_curr(struct cfs_rq *cfs_rq)
847 struct sched_entity *curr = cfs_rq->curr;
848 u64 now = rq_clock_task(rq_of(cfs_rq));
854 delta_exec = now - curr->exec_start;
855 if (unlikely((s64)delta_exec <= 0))
858 curr->exec_start = now;
860 schedstat_set(curr->statistics.exec_max,
861 max(delta_exec, curr->statistics.exec_max));
863 curr->sum_exec_runtime += delta_exec;
864 schedstat_add(cfs_rq->exec_clock, delta_exec);
866 curr->vruntime += calc_delta_fair(delta_exec, curr);
867 update_min_vruntime(cfs_rq);
869 if (entity_is_task(curr)) {
870 struct task_struct *curtask = task_of(curr);
872 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
873 cgroup_account_cputime(curtask, delta_exec);
874 account_group_exec_runtime(curtask, delta_exec);
877 account_cfs_rq_runtime(cfs_rq, delta_exec);
880 static void update_curr_fair(struct rq *rq)
882 update_curr(cfs_rq_of(&rq->curr->se));
886 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
888 u64 wait_start, prev_wait_start;
890 if (!schedstat_enabled())
893 wait_start = rq_clock(rq_of(cfs_rq));
894 prev_wait_start = schedstat_val(se->statistics.wait_start);
896 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
897 likely(wait_start > prev_wait_start))
898 wait_start -= prev_wait_start;
900 __schedstat_set(se->statistics.wait_start, wait_start);
904 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
906 struct task_struct *p;
909 if (!schedstat_enabled())
912 delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
914 if (entity_is_task(se)) {
916 if (task_on_rq_migrating(p)) {
918 * Preserve migrating task's wait time so wait_start
919 * time stamp can be adjusted to accumulate wait time
920 * prior to migration.
922 __schedstat_set(se->statistics.wait_start, delta);
925 trace_sched_stat_wait(p, delta);
928 __schedstat_set(se->statistics.wait_max,
929 max(schedstat_val(se->statistics.wait_max), delta));
930 __schedstat_inc(se->statistics.wait_count);
931 __schedstat_add(se->statistics.wait_sum, delta);
932 __schedstat_set(se->statistics.wait_start, 0);
936 update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
938 struct task_struct *tsk = NULL;
939 u64 sleep_start, block_start;
941 if (!schedstat_enabled())
944 sleep_start = schedstat_val(se->statistics.sleep_start);
945 block_start = schedstat_val(se->statistics.block_start);
947 if (entity_is_task(se))
951 u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
956 if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
957 __schedstat_set(se->statistics.sleep_max, delta);
959 __schedstat_set(se->statistics.sleep_start, 0);
960 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
963 account_scheduler_latency(tsk, delta >> 10, 1);
964 trace_sched_stat_sleep(tsk, delta);
968 u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
973 if (unlikely(delta > schedstat_val(se->statistics.block_max)))
974 __schedstat_set(se->statistics.block_max, delta);
976 __schedstat_set(se->statistics.block_start, 0);
977 __schedstat_add(se->statistics.sum_sleep_runtime, delta);
980 if (tsk->in_iowait) {
981 __schedstat_add(se->statistics.iowait_sum, delta);
982 __schedstat_inc(se->statistics.iowait_count);
983 trace_sched_stat_iowait(tsk, delta);
986 trace_sched_stat_blocked(tsk, delta);
989 * Blocking time is in units of nanosecs, so shift by
990 * 20 to get a milliseconds-range estimation of the
991 * amount of time that the task spent sleeping:
993 if (unlikely(prof_on == SLEEP_PROFILING)) {
994 profile_hits(SLEEP_PROFILING,
995 (void *)get_wchan(tsk),
998 account_scheduler_latency(tsk, delta >> 10, 0);
1004 * Task is being enqueued - update stats:
1007 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1009 if (!schedstat_enabled())
1013 * Are we enqueueing a waiting task? (for current tasks
1014 * a dequeue/enqueue event is a NOP)
1016 if (se != cfs_rq->curr)
1017 update_stats_wait_start(cfs_rq, se);
1019 if (flags & ENQUEUE_WAKEUP)
1020 update_stats_enqueue_sleeper(cfs_rq, se);
1024 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1027 if (!schedstat_enabled())
1031 * Mark the end of the wait period if dequeueing a
1034 if (se != cfs_rq->curr)
1035 update_stats_wait_end(cfs_rq, se);
1037 if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
1038 struct task_struct *tsk = task_of(se);
1040 if (tsk->state & TASK_INTERRUPTIBLE)
1041 __schedstat_set(se->statistics.sleep_start,
1042 rq_clock(rq_of(cfs_rq)));
1043 if (tsk->state & TASK_UNINTERRUPTIBLE)
1044 __schedstat_set(se->statistics.block_start,
1045 rq_clock(rq_of(cfs_rq)));
1050 * We are picking a new current task - update its stats:
1053 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1056 * We are starting a new run period:
1058 se->exec_start = rq_clock_task(rq_of(cfs_rq));
1061 /**************************************************
1062 * Scheduling class queueing methods:
1065 #ifdef CONFIG_NUMA_BALANCING
1067 * Approximate time to scan a full NUMA task in ms. The task scan period is
1068 * calculated based on the tasks virtual memory size and
1069 * numa_balancing_scan_size.
1071 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
1072 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1074 /* Portion of address space to scan in MB */
1075 unsigned int sysctl_numa_balancing_scan_size = 256;
1077 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
1078 unsigned int sysctl_numa_balancing_scan_delay = 1000;
1081 refcount_t refcount;
1083 spinlock_t lock; /* nr_tasks, tasks */
1088 struct rcu_head rcu;
1089 unsigned long total_faults;
1090 unsigned long max_faults_cpu;
1092 * Faults_cpu is used to decide whether memory should move
1093 * towards the CPU. As a consequence, these stats are weighted
1094 * more by CPU use than by memory faults.
1096 unsigned long *faults_cpu;
1097 unsigned long faults[0];
1101 * For functions that can be called in multiple contexts that permit reading
1102 * ->numa_group (see struct task_struct for locking rules).
1104 static struct numa_group *deref_task_numa_group(struct task_struct *p)
1106 return rcu_dereference_check(p->numa_group, p == current ||
1107 (lockdep_is_held(&task_rq(p)->lock) && !READ_ONCE(p->on_cpu)));
1110 static struct numa_group *deref_curr_numa_group(struct task_struct *p)
1112 return rcu_dereference_protected(p->numa_group, p == current);
1115 static inline unsigned long group_faults_priv(struct numa_group *ng);
1116 static inline unsigned long group_faults_shared(struct numa_group *ng);
1118 static unsigned int task_nr_scan_windows(struct task_struct *p)
1120 unsigned long rss = 0;
1121 unsigned long nr_scan_pages;
1124 * Calculations based on RSS as non-present and empty pages are skipped
1125 * by the PTE scanner and NUMA hinting faults should be trapped based
1128 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
1129 rss = get_mm_rss(p->mm);
1131 rss = nr_scan_pages;
1133 rss = round_up(rss, nr_scan_pages);
1134 return rss / nr_scan_pages;
1137 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
1138 #define MAX_SCAN_WINDOW 2560
1140 static unsigned int task_scan_min(struct task_struct *p)
1142 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1143 unsigned int scan, floor;
1144 unsigned int windows = 1;
1146 if (scan_size < MAX_SCAN_WINDOW)
1147 windows = MAX_SCAN_WINDOW / scan_size;
1148 floor = 1000 / windows;
1150 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
1151 return max_t(unsigned int, floor, scan);
1154 static unsigned int task_scan_start(struct task_struct *p)
1156 unsigned long smin = task_scan_min(p);
1157 unsigned long period = smin;
1158 struct numa_group *ng;
1160 /* Scale the maximum scan period with the amount of shared memory. */
1162 ng = rcu_dereference(p->numa_group);
1164 unsigned long shared = group_faults_shared(ng);
1165 unsigned long private = group_faults_priv(ng);
1167 period *= refcount_read(&ng->refcount);
1168 period *= shared + 1;
1169 period /= private + shared + 1;
1173 return max(smin, period);
1176 static unsigned int task_scan_max(struct task_struct *p)
1178 unsigned long smin = task_scan_min(p);
1180 struct numa_group *ng;
1182 /* Watch for min being lower than max due to floor calculations */
1183 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1185 /* Scale the maximum scan period with the amount of shared memory. */
1186 ng = deref_curr_numa_group(p);
1188 unsigned long shared = group_faults_shared(ng);
1189 unsigned long private = group_faults_priv(ng);
1190 unsigned long period = smax;
1192 period *= refcount_read(&ng->refcount);
1193 period *= shared + 1;
1194 period /= private + shared + 1;
1196 smax = max(smax, period);
1199 return max(smin, smax);
1202 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
1204 rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE);
1205 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
1208 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
1210 rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE);
1211 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
1214 /* Shared or private faults. */
1215 #define NR_NUMA_HINT_FAULT_TYPES 2
1217 /* Memory and CPU locality */
1218 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1220 /* Averaged statistics, and temporary buffers. */
1221 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1223 pid_t task_numa_group_id(struct task_struct *p)
1225 struct numa_group *ng;
1229 ng = rcu_dereference(p->numa_group);
1238 * The averaged statistics, shared & private, memory & CPU,
1239 * occupy the first half of the array. The second half of the
1240 * array is for current counters, which are averaged into the
1241 * first set by task_numa_placement.
1243 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1245 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1248 static inline unsigned long task_faults(struct task_struct *p, int nid)
1250 if (!p->numa_faults)
1253 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1254 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1257 static inline unsigned long group_faults(struct task_struct *p, int nid)
1259 struct numa_group *ng = deref_task_numa_group(p);
1264 return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1265 ng->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1268 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
1270 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
1271 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1274 static inline unsigned long group_faults_priv(struct numa_group *ng)
1276 unsigned long faults = 0;
1279 for_each_online_node(node) {
1280 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
1286 static inline unsigned long group_faults_shared(struct numa_group *ng)
1288 unsigned long faults = 0;
1291 for_each_online_node(node) {
1292 faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
1299 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1300 * considered part of a numa group's pseudo-interleaving set. Migrations
1301 * between these nodes are slowed down, to allow things to settle down.
1303 #define ACTIVE_NODE_FRACTION 3
1305 static bool numa_is_active_node(int nid, struct numa_group *ng)
1307 return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
1310 /* Handle placement on systems where not all nodes are directly connected. */
1311 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
1312 int maxdist, bool task)
1314 unsigned long score = 0;
1318 * All nodes are directly connected, and the same distance
1319 * from each other. No need for fancy placement algorithms.
1321 if (sched_numa_topology_type == NUMA_DIRECT)
1325 * This code is called for each node, introducing N^2 complexity,
1326 * which should be ok given the number of nodes rarely exceeds 8.
1328 for_each_online_node(node) {
1329 unsigned long faults;
1330 int dist = node_distance(nid, node);
1333 * The furthest away nodes in the system are not interesting
1334 * for placement; nid was already counted.
1336 if (dist == sched_max_numa_distance || node == nid)
1340 * On systems with a backplane NUMA topology, compare groups
1341 * of nodes, and move tasks towards the group with the most
1342 * memory accesses. When comparing two nodes at distance
1343 * "hoplimit", only nodes closer by than "hoplimit" are part
1344 * of each group. Skip other nodes.
1346 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1350 /* Add up the faults from nearby nodes. */
1352 faults = task_faults(p, node);
1354 faults = group_faults(p, node);
1357 * On systems with a glueless mesh NUMA topology, there are
1358 * no fixed "groups of nodes". Instead, nodes that are not
1359 * directly connected bounce traffic through intermediate
1360 * nodes; a numa_group can occupy any set of nodes.
1361 * The further away a node is, the less the faults count.
1362 * This seems to result in good task placement.
1364 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1365 faults *= (sched_max_numa_distance - dist);
1366 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1376 * These return the fraction of accesses done by a particular task, or
1377 * task group, on a particular numa node. The group weight is given a
1378 * larger multiplier, in order to group tasks together that are almost
1379 * evenly spread out between numa nodes.
1381 static inline unsigned long task_weight(struct task_struct *p, int nid,
1384 unsigned long faults, total_faults;
1386 if (!p->numa_faults)
1389 total_faults = p->total_numa_faults;
1394 faults = task_faults(p, nid);
1395 faults += score_nearby_nodes(p, nid, dist, true);
1397 return 1000 * faults / total_faults;
1400 static inline unsigned long group_weight(struct task_struct *p, int nid,
1403 struct numa_group *ng = deref_task_numa_group(p);
1404 unsigned long faults, total_faults;
1409 total_faults = ng->total_faults;
1414 faults = group_faults(p, nid);
1415 faults += score_nearby_nodes(p, nid, dist, false);
1417 return 1000 * faults / total_faults;
1420 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1421 int src_nid, int dst_cpu)
1423 struct numa_group *ng = deref_curr_numa_group(p);
1424 int dst_nid = cpu_to_node(dst_cpu);
1425 int last_cpupid, this_cpupid;
1427 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1428 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1431 * Allow first faults or private faults to migrate immediately early in
1432 * the lifetime of a task. The magic number 4 is based on waiting for
1433 * two full passes of the "multi-stage node selection" test that is
1436 if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= 4) &&
1437 (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid)))
1441 * Multi-stage node selection is used in conjunction with a periodic
1442 * migration fault to build a temporal task<->page relation. By using
1443 * a two-stage filter we remove short/unlikely relations.
1445 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1446 * a task's usage of a particular page (n_p) per total usage of this
1447 * page (n_t) (in a given time-span) to a probability.
1449 * Our periodic faults will sample this probability and getting the
1450 * same result twice in a row, given these samples are fully
1451 * independent, is then given by P(n)^2, provided our sample period
1452 * is sufficiently short compared to the usage pattern.
1454 * This quadric squishes small probabilities, making it less likely we
1455 * act on an unlikely task<->page relation.
1457 if (!cpupid_pid_unset(last_cpupid) &&
1458 cpupid_to_nid(last_cpupid) != dst_nid)
1461 /* Always allow migrate on private faults */
1462 if (cpupid_match_pid(p, last_cpupid))
1465 /* A shared fault, but p->numa_group has not been set up yet. */
1470 * Destination node is much more heavily used than the source
1471 * node? Allow migration.
1473 if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
1474 ACTIVE_NODE_FRACTION)
1478 * Distribute memory according to CPU & memory use on each node,
1479 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1481 * faults_cpu(dst) 3 faults_cpu(src)
1482 * --------------- * - > ---------------
1483 * faults_mem(dst) 4 faults_mem(src)
1485 return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
1486 group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1490 * 'numa_type' describes the node at the moment of load balancing.
1493 /* The node has spare capacity that can be used to run more tasks. */
1496 * The node is fully used and the tasks don't compete for more CPU
1497 * cycles. Nevertheless, some tasks might wait before running.
1501 * The node is overloaded and can't provide expected CPU cycles to all
1507 /* Cached statistics for all CPUs within a node */
1511 /* Total compute capacity of CPUs on a node */
1512 unsigned long compute_capacity;
1513 unsigned int nr_running;
1514 unsigned int weight;
1515 enum numa_type node_type;
1519 static inline bool is_core_idle(int cpu)
1521 #ifdef CONFIG_SCHED_SMT
1524 for_each_cpu(sibling, cpu_smt_mask(cpu)) {
1536 struct task_numa_env {
1537 struct task_struct *p;
1539 int src_cpu, src_nid;
1540 int dst_cpu, dst_nid;
1542 struct numa_stats src_stats, dst_stats;
1547 struct task_struct *best_task;
1552 static unsigned long cpu_load(struct rq *rq);
1553 static unsigned long cpu_util(int cpu);
1554 static inline long adjust_numa_imbalance(int imbalance, int src_nr_running);
1557 numa_type numa_classify(unsigned int imbalance_pct,
1558 struct numa_stats *ns)
1560 if ((ns->nr_running > ns->weight) &&
1561 ((ns->compute_capacity * 100) < (ns->util * imbalance_pct)))
1562 return node_overloaded;
1564 if ((ns->nr_running < ns->weight) ||
1565 ((ns->compute_capacity * 100) > (ns->util * imbalance_pct)))
1566 return node_has_spare;
1568 return node_fully_busy;
1571 #ifdef CONFIG_SCHED_SMT
1572 /* Forward declarations of select_idle_sibling helpers */
1573 static inline bool test_idle_cores(int cpu, bool def);
1574 static inline int numa_idle_core(int idle_core, int cpu)
1576 if (!static_branch_likely(&sched_smt_present) ||
1577 idle_core >= 0 || !test_idle_cores(cpu, false))
1581 * Prefer cores instead of packing HT siblings
1582 * and triggering future load balancing.
1584 if (is_core_idle(cpu))
1590 static inline int numa_idle_core(int idle_core, int cpu)
1597 * Gather all necessary information to make NUMA balancing placement
1598 * decisions that are compatible with standard load balancer. This
1599 * borrows code and logic from update_sg_lb_stats but sharing a
1600 * common implementation is impractical.
1602 static void update_numa_stats(struct task_numa_env *env,
1603 struct numa_stats *ns, int nid,
1606 int cpu, idle_core = -1;
1608 memset(ns, 0, sizeof(*ns));
1612 for_each_cpu(cpu, cpumask_of_node(nid)) {
1613 struct rq *rq = cpu_rq(cpu);
1615 ns->load += cpu_load(rq);
1616 ns->util += cpu_util(cpu);
1617 ns->nr_running += rq->cfs.h_nr_running;
1618 ns->compute_capacity += capacity_of(cpu);
1620 if (find_idle && !rq->nr_running && idle_cpu(cpu)) {
1621 if (READ_ONCE(rq->numa_migrate_on) ||
1622 !cpumask_test_cpu(cpu, env->p->cpus_ptr))
1625 if (ns->idle_cpu == -1)
1628 idle_core = numa_idle_core(idle_core, cpu);
1633 ns->weight = cpumask_weight(cpumask_of_node(nid));
1635 ns->node_type = numa_classify(env->imbalance_pct, ns);
1638 ns->idle_cpu = idle_core;
1641 static void task_numa_assign(struct task_numa_env *env,
1642 struct task_struct *p, long imp)
1644 struct rq *rq = cpu_rq(env->dst_cpu);
1646 /* Check if run-queue part of active NUMA balance. */
1647 if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1)) {
1649 int start = env->dst_cpu;
1651 /* Find alternative idle CPU. */
1652 for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start) {
1653 if (cpu == env->best_cpu || !idle_cpu(cpu) ||
1654 !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
1659 rq = cpu_rq(env->dst_cpu);
1660 if (!xchg(&rq->numa_migrate_on, 1))
1664 /* Failed to find an alternative idle CPU */
1670 * Clear previous best_cpu/rq numa-migrate flag, since task now
1671 * found a better CPU to move/swap.
1673 if (env->best_cpu != -1 && env->best_cpu != env->dst_cpu) {
1674 rq = cpu_rq(env->best_cpu);
1675 WRITE_ONCE(rq->numa_migrate_on, 0);
1679 put_task_struct(env->best_task);
1684 env->best_imp = imp;
1685 env->best_cpu = env->dst_cpu;
1688 static bool load_too_imbalanced(long src_load, long dst_load,
1689 struct task_numa_env *env)
1692 long orig_src_load, orig_dst_load;
1693 long src_capacity, dst_capacity;
1696 * The load is corrected for the CPU capacity available on each node.
1699 * ------------ vs ---------
1700 * src_capacity dst_capacity
1702 src_capacity = env->src_stats.compute_capacity;
1703 dst_capacity = env->dst_stats.compute_capacity;
1705 imb = abs(dst_load * src_capacity - src_load * dst_capacity);
1707 orig_src_load = env->src_stats.load;
1708 orig_dst_load = env->dst_stats.load;
1710 old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
1712 /* Would this change make things worse? */
1713 return (imb > old_imb);
1717 * Maximum NUMA importance can be 1998 (2*999);
1718 * SMALLIMP @ 30 would be close to 1998/64.
1719 * Used to deter task migration.
1724 * This checks if the overall compute and NUMA accesses of the system would
1725 * be improved if the source tasks was migrated to the target dst_cpu taking
1726 * into account that it might be best if task running on the dst_cpu should
1727 * be exchanged with the source task
1729 static bool task_numa_compare(struct task_numa_env *env,
1730 long taskimp, long groupimp, bool maymove)
1732 struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p);
1733 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1734 long imp = p_ng ? groupimp : taskimp;
1735 struct task_struct *cur;
1736 long src_load, dst_load;
1737 int dist = env->dist;
1740 bool stopsearch = false;
1742 if (READ_ONCE(dst_rq->numa_migrate_on))
1746 cur = rcu_dereference(dst_rq->curr);
1747 if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1751 * Because we have preemption enabled we can get migrated around and
1752 * end try selecting ourselves (current == env->p) as a swap candidate.
1754 if (cur == env->p) {
1760 if (maymove && moveimp >= env->best_imp)
1766 /* Skip this swap candidate if cannot move to the source cpu. */
1767 if (!cpumask_test_cpu(env->src_cpu, cur->cpus_ptr))
1771 * Skip this swap candidate if it is not moving to its preferred
1772 * node and the best task is.
1774 if (env->best_task &&
1775 env->best_task->numa_preferred_nid == env->src_nid &&
1776 cur->numa_preferred_nid != env->src_nid) {
1781 * "imp" is the fault differential for the source task between the
1782 * source and destination node. Calculate the total differential for
1783 * the source task and potential destination task. The more negative
1784 * the value is, the more remote accesses that would be expected to
1785 * be incurred if the tasks were swapped.
1787 * If dst and source tasks are in the same NUMA group, or not
1788 * in any group then look only at task weights.
1790 cur_ng = rcu_dereference(cur->numa_group);
1791 if (cur_ng == p_ng) {
1792 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1793 task_weight(cur, env->dst_nid, dist);
1795 * Add some hysteresis to prevent swapping the
1796 * tasks within a group over tiny differences.
1802 * Compare the group weights. If a task is all by itself
1803 * (not part of a group), use the task weight instead.
1806 imp += group_weight(cur, env->src_nid, dist) -
1807 group_weight(cur, env->dst_nid, dist);
1809 imp += task_weight(cur, env->src_nid, dist) -
1810 task_weight(cur, env->dst_nid, dist);
1813 /* Discourage picking a task already on its preferred node */
1814 if (cur->numa_preferred_nid == env->dst_nid)
1818 * Encourage picking a task that moves to its preferred node.
1819 * This potentially makes imp larger than it's maximum of
1820 * 1998 (see SMALLIMP and task_weight for why) but in this
1821 * case, it does not matter.
1823 if (cur->numa_preferred_nid == env->src_nid)
1826 if (maymove && moveimp > imp && moveimp > env->best_imp) {
1833 * Prefer swapping with a task moving to its preferred node over a
1836 if (env->best_task && cur->numa_preferred_nid == env->src_nid &&
1837 env->best_task->numa_preferred_nid != env->src_nid) {
1842 * If the NUMA importance is less than SMALLIMP,
1843 * task migration might only result in ping pong
1844 * of tasks and also hurt performance due to cache
1847 if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
1851 * In the overloaded case, try and keep the load balanced.
1853 load = task_h_load(env->p) - task_h_load(cur);
1857 dst_load = env->dst_stats.load + load;
1858 src_load = env->src_stats.load - load;
1860 if (load_too_imbalanced(src_load, dst_load, env))
1864 /* Evaluate an idle CPU for a task numa move. */
1866 int cpu = env->dst_stats.idle_cpu;
1868 /* Nothing cached so current CPU went idle since the search. */
1873 * If the CPU is no longer truly idle and the previous best CPU
1874 * is, keep using it.
1876 if (!idle_cpu(cpu) && env->best_cpu >= 0 &&
1877 idle_cpu(env->best_cpu)) {
1878 cpu = env->best_cpu;
1884 task_numa_assign(env, cur, imp);
1887 * If a move to idle is allowed because there is capacity or load
1888 * balance improves then stop the search. While a better swap
1889 * candidate may exist, a search is not free.
1891 if (maymove && !cur && env->best_cpu >= 0 && idle_cpu(env->best_cpu))
1895 * If a swap candidate must be identified and the current best task
1896 * moves its preferred node then stop the search.
1898 if (!maymove && env->best_task &&
1899 env->best_task->numa_preferred_nid == env->src_nid) {
1908 static void task_numa_find_cpu(struct task_numa_env *env,
1909 long taskimp, long groupimp)
1911 bool maymove = false;
1915 * If dst node has spare capacity, then check if there is an
1916 * imbalance that would be overruled by the load balancer.
1918 if (env->dst_stats.node_type == node_has_spare) {
1919 unsigned int imbalance;
1920 int src_running, dst_running;
1923 * Would movement cause an imbalance? Note that if src has
1924 * more running tasks that the imbalance is ignored as the
1925 * move improves the imbalance from the perspective of the
1926 * CPU load balancer.
1928 src_running = env->src_stats.nr_running - 1;
1929 dst_running = env->dst_stats.nr_running + 1;
1930 imbalance = max(0, dst_running - src_running);
1931 imbalance = adjust_numa_imbalance(imbalance, src_running);
1933 /* Use idle CPU if there is no imbalance */
1936 if (env->dst_stats.idle_cpu >= 0) {
1937 env->dst_cpu = env->dst_stats.idle_cpu;
1938 task_numa_assign(env, NULL, 0);
1943 long src_load, dst_load, load;
1945 * If the improvement from just moving env->p direction is better
1946 * than swapping tasks around, check if a move is possible.
1948 load = task_h_load(env->p);
1949 dst_load = env->dst_stats.load + load;
1950 src_load = env->src_stats.load - load;
1951 maymove = !load_too_imbalanced(src_load, dst_load, env);
1954 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1955 /* Skip this CPU if the source task cannot migrate */
1956 if (!cpumask_test_cpu(cpu, env->p->cpus_ptr))
1960 if (task_numa_compare(env, taskimp, groupimp, maymove))
1965 static int task_numa_migrate(struct task_struct *p)
1967 struct task_numa_env env = {
1970 .src_cpu = task_cpu(p),
1971 .src_nid = task_node(p),
1973 .imbalance_pct = 112,
1979 unsigned long taskweight, groupweight;
1980 struct sched_domain *sd;
1981 long taskimp, groupimp;
1982 struct numa_group *ng;
1987 * Pick the lowest SD_NUMA domain, as that would have the smallest
1988 * imbalance and would be the first to start moving tasks about.
1990 * And we want to avoid any moving of tasks about, as that would create
1991 * random movement of tasks -- counter the numa conditions we're trying
1995 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1997 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
2001 * Cpusets can break the scheduler domain tree into smaller
2002 * balance domains, some of which do not cross NUMA boundaries.
2003 * Tasks that are "trapped" in such domains cannot be migrated
2004 * elsewhere, so there is no point in (re)trying.
2006 if (unlikely(!sd)) {
2007 sched_setnuma(p, task_node(p));
2011 env.dst_nid = p->numa_preferred_nid;
2012 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
2013 taskweight = task_weight(p, env.src_nid, dist);
2014 groupweight = group_weight(p, env.src_nid, dist);
2015 update_numa_stats(&env, &env.src_stats, env.src_nid, false);
2016 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
2017 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
2018 update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
2020 /* Try to find a spot on the preferred nid. */
2021 task_numa_find_cpu(&env, taskimp, groupimp);
2024 * Look at other nodes in these cases:
2025 * - there is no space available on the preferred_nid
2026 * - the task is part of a numa_group that is interleaved across
2027 * multiple NUMA nodes; in order to better consolidate the group,
2028 * we need to check other locations.
2030 ng = deref_curr_numa_group(p);
2031 if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) {
2032 for_each_online_node(nid) {
2033 if (nid == env.src_nid || nid == p->numa_preferred_nid)
2036 dist = node_distance(env.src_nid, env.dst_nid);
2037 if (sched_numa_topology_type == NUMA_BACKPLANE &&
2039 taskweight = task_weight(p, env.src_nid, dist);
2040 groupweight = group_weight(p, env.src_nid, dist);
2043 /* Only consider nodes where both task and groups benefit */
2044 taskimp = task_weight(p, nid, dist) - taskweight;
2045 groupimp = group_weight(p, nid, dist) - groupweight;
2046 if (taskimp < 0 && groupimp < 0)
2051 update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
2052 task_numa_find_cpu(&env, taskimp, groupimp);
2057 * If the task is part of a workload that spans multiple NUMA nodes,
2058 * and is migrating into one of the workload's active nodes, remember
2059 * this node as the task's preferred numa node, so the workload can
2061 * A task that migrated to a second choice node will be better off
2062 * trying for a better one later. Do not set the preferred node here.
2065 if (env.best_cpu == -1)
2068 nid = cpu_to_node(env.best_cpu);
2070 if (nid != p->numa_preferred_nid)
2071 sched_setnuma(p, nid);
2074 /* No better CPU than the current one was found. */
2075 if (env.best_cpu == -1) {
2076 trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
2080 best_rq = cpu_rq(env.best_cpu);
2081 if (env.best_task == NULL) {
2082 ret = migrate_task_to(p, env.best_cpu);
2083 WRITE_ONCE(best_rq->numa_migrate_on, 0);
2085 trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
2089 ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
2090 WRITE_ONCE(best_rq->numa_migrate_on, 0);
2093 trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
2094 put_task_struct(env.best_task);
2098 /* Attempt to migrate a task to a CPU on the preferred node. */
2099 static void numa_migrate_preferred(struct task_struct *p)
2101 unsigned long interval = HZ;
2103 /* This task has no NUMA fault statistics yet */
2104 if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults))
2107 /* Periodically retry migrating the task to the preferred node */
2108 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
2109 p->numa_migrate_retry = jiffies + interval;
2111 /* Success if task is already running on preferred CPU */
2112 if (task_node(p) == p->numa_preferred_nid)
2115 /* Otherwise, try migrate to a CPU on the preferred node */
2116 task_numa_migrate(p);
2120 * Find out how many nodes on the workload is actively running on. Do this by
2121 * tracking the nodes from which NUMA hinting faults are triggered. This can
2122 * be different from the set of nodes where the workload's memory is currently
2125 static void numa_group_count_active_nodes(struct numa_group *numa_group)
2127 unsigned long faults, max_faults = 0;
2128 int nid, active_nodes = 0;
2130 for_each_online_node(nid) {
2131 faults = group_faults_cpu(numa_group, nid);
2132 if (faults > max_faults)
2133 max_faults = faults;
2136 for_each_online_node(nid) {
2137 faults = group_faults_cpu(numa_group, nid);
2138 if (faults * ACTIVE_NODE_FRACTION > max_faults)
2142 numa_group->max_faults_cpu = max_faults;
2143 numa_group->active_nodes = active_nodes;
2147 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
2148 * increments. The more local the fault statistics are, the higher the scan
2149 * period will be for the next scan window. If local/(local+remote) ratio is
2150 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
2151 * the scan period will decrease. Aim for 70% local accesses.
2153 #define NUMA_PERIOD_SLOTS 10
2154 #define NUMA_PERIOD_THRESHOLD 7
2157 * Increase the scan period (slow down scanning) if the majority of
2158 * our memory is already on our local node, or if the majority of
2159 * the page accesses are shared with other processes.
2160 * Otherwise, decrease the scan period.
2162 static void update_task_scan_period(struct task_struct *p,
2163 unsigned long shared, unsigned long private)
2165 unsigned int period_slot;
2166 int lr_ratio, ps_ratio;
2169 unsigned long remote = p->numa_faults_locality[0];
2170 unsigned long local = p->numa_faults_locality[1];
2173 * If there were no record hinting faults then either the task is
2174 * completely idle or all activity is areas that are not of interest
2175 * to automatic numa balancing. Related to that, if there were failed
2176 * migration then it implies we are migrating too quickly or the local
2177 * node is overloaded. In either case, scan slower
2179 if (local + shared == 0 || p->numa_faults_locality[2]) {
2180 p->numa_scan_period = min(p->numa_scan_period_max,
2181 p->numa_scan_period << 1);
2183 p->mm->numa_next_scan = jiffies +
2184 msecs_to_jiffies(p->numa_scan_period);
2190 * Prepare to scale scan period relative to the current period.
2191 * == NUMA_PERIOD_THRESHOLD scan period stays the same
2192 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
2193 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
2195 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
2196 lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
2197 ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
2199 if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
2201 * Most memory accesses are local. There is no need to
2202 * do fast NUMA scanning, since memory is already local.
2204 int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
2207 diff = slot * period_slot;
2208 } else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
2210 * Most memory accesses are shared with other tasks.
2211 * There is no point in continuing fast NUMA scanning,
2212 * since other tasks may just move the memory elsewhere.
2214 int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
2217 diff = slot * period_slot;
2220 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
2221 * yet they are not on the local NUMA node. Speed up
2222 * NUMA scanning to get the memory moved over.
2224 int ratio = max(lr_ratio, ps_ratio);
2225 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
2228 p->numa_scan_period = clamp(p->numa_scan_period + diff,
2229 task_scan_min(p), task_scan_max(p));
2230 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2234 * Get the fraction of time the task has been running since the last
2235 * NUMA placement cycle. The scheduler keeps similar statistics, but
2236 * decays those on a 32ms period, which is orders of magnitude off
2237 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
2238 * stats only if the task is so new there are no NUMA statistics yet.
2240 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
2242 u64 runtime, delta, now;
2243 /* Use the start of this time slice to avoid calculations. */
2244 now = p->se.exec_start;
2245 runtime = p->se.sum_exec_runtime;
2247 if (p->last_task_numa_placement) {
2248 delta = runtime - p->last_sum_exec_runtime;
2249 *period = now - p->last_task_numa_placement;
2251 /* Avoid time going backwards, prevent potential divide error: */
2252 if (unlikely((s64)*period < 0))
2255 delta = p->se.avg.load_sum;
2256 *period = LOAD_AVG_MAX;
2259 p->last_sum_exec_runtime = runtime;
2260 p->last_task_numa_placement = now;
2266 * Determine the preferred nid for a task in a numa_group. This needs to
2267 * be done in a way that produces consistent results with group_weight,
2268 * otherwise workloads might not converge.
2270 static int preferred_group_nid(struct task_struct *p, int nid)
2275 /* Direct connections between all NUMA nodes. */
2276 if (sched_numa_topology_type == NUMA_DIRECT)
2280 * On a system with glueless mesh NUMA topology, group_weight
2281 * scores nodes according to the number of NUMA hinting faults on
2282 * both the node itself, and on nearby nodes.
2284 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
2285 unsigned long score, max_score = 0;
2286 int node, max_node = nid;
2288 dist = sched_max_numa_distance;
2290 for_each_online_node(node) {
2291 score = group_weight(p, node, dist);
2292 if (score > max_score) {
2301 * Finding the preferred nid in a system with NUMA backplane
2302 * interconnect topology is more involved. The goal is to locate
2303 * tasks from numa_groups near each other in the system, and
2304 * untangle workloads from different sides of the system. This requires
2305 * searching down the hierarchy of node groups, recursively searching
2306 * inside the highest scoring group of nodes. The nodemask tricks
2307 * keep the complexity of the search down.
2309 nodes = node_online_map;
2310 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
2311 unsigned long max_faults = 0;
2312 nodemask_t max_group = NODE_MASK_NONE;
2315 /* Are there nodes at this distance from each other? */
2316 if (!find_numa_distance(dist))
2319 for_each_node_mask(a, nodes) {
2320 unsigned long faults = 0;
2321 nodemask_t this_group;
2322 nodes_clear(this_group);
2324 /* Sum group's NUMA faults; includes a==b case. */
2325 for_each_node_mask(b, nodes) {
2326 if (node_distance(a, b) < dist) {
2327 faults += group_faults(p, b);
2328 node_set(b, this_group);
2329 node_clear(b, nodes);
2333 /* Remember the top group. */
2334 if (faults > max_faults) {
2335 max_faults = faults;
2336 max_group = this_group;
2338 * subtle: at the smallest distance there is
2339 * just one node left in each "group", the
2340 * winner is the preferred nid.
2345 /* Next round, evaluate the nodes within max_group. */
2353 static void task_numa_placement(struct task_struct *p)
2355 int seq, nid, max_nid = NUMA_NO_NODE;
2356 unsigned long max_faults = 0;
2357 unsigned long fault_types[2] = { 0, 0 };
2358 unsigned long total_faults;
2359 u64 runtime, period;
2360 spinlock_t *group_lock = NULL;
2361 struct numa_group *ng;
2364 * The p->mm->numa_scan_seq field gets updated without
2365 * exclusive access. Use READ_ONCE() here to ensure
2366 * that the field is read in a single access:
2368 seq = READ_ONCE(p->mm->numa_scan_seq);
2369 if (p->numa_scan_seq == seq)
2371 p->numa_scan_seq = seq;
2372 p->numa_scan_period_max = task_scan_max(p);
2374 total_faults = p->numa_faults_locality[0] +
2375 p->numa_faults_locality[1];
2376 runtime = numa_get_avg_runtime(p, &period);
2378 /* If the task is part of a group prevent parallel updates to group stats */
2379 ng = deref_curr_numa_group(p);
2381 group_lock = &ng->lock;
2382 spin_lock_irq(group_lock);
2385 /* Find the node with the highest number of faults */
2386 for_each_online_node(nid) {
2387 /* Keep track of the offsets in numa_faults array */
2388 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2389 unsigned long faults = 0, group_faults = 0;
2392 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2393 long diff, f_diff, f_weight;
2395 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
2396 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
2397 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
2398 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
2400 /* Decay existing window, copy faults since last scan */
2401 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
2402 fault_types[priv] += p->numa_faults[membuf_idx];
2403 p->numa_faults[membuf_idx] = 0;
2406 * Normalize the faults_from, so all tasks in a group
2407 * count according to CPU use, instead of by the raw
2408 * number of faults. Tasks with little runtime have
2409 * little over-all impact on throughput, and thus their
2410 * faults are less important.
2412 f_weight = div64_u64(runtime << 16, period + 1);
2413 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2415 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
2416 p->numa_faults[cpubuf_idx] = 0;
2418 p->numa_faults[mem_idx] += diff;
2419 p->numa_faults[cpu_idx] += f_diff;
2420 faults += p->numa_faults[mem_idx];
2421 p->total_numa_faults += diff;
2424 * safe because we can only change our own group
2426 * mem_idx represents the offset for a given
2427 * nid and priv in a specific region because it
2428 * is at the beginning of the numa_faults array.
2430 ng->faults[mem_idx] += diff;
2431 ng->faults_cpu[mem_idx] += f_diff;
2432 ng->total_faults += diff;
2433 group_faults += ng->faults[mem_idx];
2438 if (faults > max_faults) {
2439 max_faults = faults;
2442 } else if (group_faults > max_faults) {
2443 max_faults = group_faults;
2449 numa_group_count_active_nodes(ng);
2450 spin_unlock_irq(group_lock);
2451 max_nid = preferred_group_nid(p, max_nid);
2455 /* Set the new preferred node */
2456 if (max_nid != p->numa_preferred_nid)
2457 sched_setnuma(p, max_nid);
2460 update_task_scan_period(p, fault_types[0], fault_types[1]);
2463 static inline int get_numa_group(struct numa_group *grp)
2465 return refcount_inc_not_zero(&grp->refcount);
2468 static inline void put_numa_group(struct numa_group *grp)
2470 if (refcount_dec_and_test(&grp->refcount))
2471 kfree_rcu(grp, rcu);
2474 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
2477 struct numa_group *grp, *my_grp;
2478 struct task_struct *tsk;
2480 int cpu = cpupid_to_cpu(cpupid);
2483 if (unlikely(!deref_curr_numa_group(p))) {
2484 unsigned int size = sizeof(struct numa_group) +
2485 4*nr_node_ids*sizeof(unsigned long);
2487 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
2491 refcount_set(&grp->refcount, 1);
2492 grp->active_nodes = 1;
2493 grp->max_faults_cpu = 0;
2494 spin_lock_init(&grp->lock);
2496 /* Second half of the array tracks nids where faults happen */
2497 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
2500 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2501 grp->faults[i] = p->numa_faults[i];
2503 grp->total_faults = p->total_numa_faults;
2506 rcu_assign_pointer(p->numa_group, grp);
2510 tsk = READ_ONCE(cpu_rq(cpu)->curr);
2512 if (!cpupid_match_pid(tsk, cpupid))
2515 grp = rcu_dereference(tsk->numa_group);
2519 my_grp = deref_curr_numa_group(p);
2524 * Only join the other group if its bigger; if we're the bigger group,
2525 * the other task will join us.
2527 if (my_grp->nr_tasks > grp->nr_tasks)
2531 * Tie-break on the grp address.
2533 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2536 /* Always join threads in the same process. */
2537 if (tsk->mm == current->mm)
2540 /* Simple filter to avoid false positives due to PID collisions */
2541 if (flags & TNF_SHARED)
2544 /* Update priv based on whether false sharing was detected */
2547 if (join && !get_numa_group(grp))
2555 BUG_ON(irqs_disabled());
2556 double_lock_irq(&my_grp->lock, &grp->lock);
2558 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2559 my_grp->faults[i] -= p->numa_faults[i];
2560 grp->faults[i] += p->numa_faults[i];
2562 my_grp->total_faults -= p->total_numa_faults;
2563 grp->total_faults += p->total_numa_faults;
2568 spin_unlock(&my_grp->lock);
2569 spin_unlock_irq(&grp->lock);
2571 rcu_assign_pointer(p->numa_group, grp);
2573 put_numa_group(my_grp);
2582 * Get rid of NUMA staticstics associated with a task (either current or dead).
2583 * If @final is set, the task is dead and has reached refcount zero, so we can
2584 * safely free all relevant data structures. Otherwise, there might be
2585 * concurrent reads from places like load balancing and procfs, and we should
2586 * reset the data back to default state without freeing ->numa_faults.
2588 void task_numa_free(struct task_struct *p, bool final)
2590 /* safe: p either is current or is being freed by current */
2591 struct numa_group *grp = rcu_dereference_raw(p->numa_group);
2592 unsigned long *numa_faults = p->numa_faults;
2593 unsigned long flags;
2600 spin_lock_irqsave(&grp->lock, flags);
2601 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2602 grp->faults[i] -= p->numa_faults[i];
2603 grp->total_faults -= p->total_numa_faults;
2606 spin_unlock_irqrestore(&grp->lock, flags);
2607 RCU_INIT_POINTER(p->numa_group, NULL);
2608 put_numa_group(grp);
2612 p->numa_faults = NULL;
2615 p->total_numa_faults = 0;
2616 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2622 * Got a PROT_NONE fault for a page on @node.
2624 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2626 struct task_struct *p = current;
2627 bool migrated = flags & TNF_MIGRATED;
2628 int cpu_node = task_node(current);
2629 int local = !!(flags & TNF_FAULT_LOCAL);
2630 struct numa_group *ng;
2633 if (!static_branch_likely(&sched_numa_balancing))
2636 /* for example, ksmd faulting in a user's mm */
2640 /* Allocate buffer to track faults on a per-node basis */
2641 if (unlikely(!p->numa_faults)) {
2642 int size = sizeof(*p->numa_faults) *
2643 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2645 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2646 if (!p->numa_faults)
2649 p->total_numa_faults = 0;
2650 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2654 * First accesses are treated as private, otherwise consider accesses
2655 * to be private if the accessing pid has not changed
2657 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2660 priv = cpupid_match_pid(p, last_cpupid);
2661 if (!priv && !(flags & TNF_NO_GROUP))
2662 task_numa_group(p, last_cpupid, flags, &priv);
2666 * If a workload spans multiple NUMA nodes, a shared fault that
2667 * occurs wholly within the set of nodes that the workload is
2668 * actively using should be counted as local. This allows the
2669 * scan rate to slow down when a workload has settled down.
2671 ng = deref_curr_numa_group(p);
2672 if (!priv && !local && ng && ng->active_nodes > 1 &&
2673 numa_is_active_node(cpu_node, ng) &&
2674 numa_is_active_node(mem_node, ng))
2678 * Retry to migrate task to preferred node periodically, in case it
2679 * previously failed, or the scheduler moved us.
2681 if (time_after(jiffies, p->numa_migrate_retry)) {
2682 task_numa_placement(p);
2683 numa_migrate_preferred(p);
2687 p->numa_pages_migrated += pages;
2688 if (flags & TNF_MIGRATE_FAIL)
2689 p->numa_faults_locality[2] += pages;
2691 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2692 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2693 p->numa_faults_locality[local] += pages;
2696 static void reset_ptenuma_scan(struct task_struct *p)
2699 * We only did a read acquisition of the mmap sem, so
2700 * p->mm->numa_scan_seq is written to without exclusive access
2701 * and the update is not guaranteed to be atomic. That's not
2702 * much of an issue though, since this is just used for
2703 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2704 * expensive, to avoid any form of compiler optimizations:
2706 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2707 p->mm->numa_scan_offset = 0;
2711 * The expensive part of numa migration is done from task_work context.
2712 * Triggered from task_tick_numa().
2714 static void task_numa_work(struct callback_head *work)
2716 unsigned long migrate, next_scan, now = jiffies;
2717 struct task_struct *p = current;
2718 struct mm_struct *mm = p->mm;
2719 u64 runtime = p->se.sum_exec_runtime;
2720 struct vm_area_struct *vma;
2721 unsigned long start, end;
2722 unsigned long nr_pte_updates = 0;
2723 long pages, virtpages;
2725 SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2729 * Who cares about NUMA placement when they're dying.
2731 * NOTE: make sure not to dereference p->mm before this check,
2732 * exit_task_work() happens _after_ exit_mm() so we could be called
2733 * without p->mm even though we still had it when we enqueued this
2736 if (p->flags & PF_EXITING)
2739 if (!mm->numa_next_scan) {
2740 mm->numa_next_scan = now +
2741 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2745 * Enforce maximal scan/migration frequency..
2747 migrate = mm->numa_next_scan;
2748 if (time_before(now, migrate))
2751 if (p->numa_scan_period == 0) {
2752 p->numa_scan_period_max = task_scan_max(p);
2753 p->numa_scan_period = task_scan_start(p);
2756 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2757 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2761 * Delay this task enough that another task of this mm will likely win
2762 * the next time around.
2764 p->node_stamp += 2 * TICK_NSEC;
2766 start = mm->numa_scan_offset;
2767 pages = sysctl_numa_balancing_scan_size;
2768 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2769 virtpages = pages * 8; /* Scan up to this much virtual space */
2774 if (!down_read_trylock(&mm->mmap_sem))
2776 vma = find_vma(mm, start);
2778 reset_ptenuma_scan(p);
2782 for (; vma; vma = vma->vm_next) {
2783 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2784 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2789 * Shared library pages mapped by multiple processes are not
2790 * migrated as it is expected they are cache replicated. Avoid
2791 * hinting faults in read-only file-backed mappings or the vdso
2792 * as migrating the pages will be of marginal benefit.
2795 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2799 * Skip inaccessible VMAs to avoid any confusion between
2800 * PROT_NONE and NUMA hinting ptes
2802 if (!vma_is_accessible(vma))
2806 start = max(start, vma->vm_start);
2807 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2808 end = min(end, vma->vm_end);
2809 nr_pte_updates = change_prot_numa(vma, start, end);
2812 * Try to scan sysctl_numa_balancing_size worth of
2813 * hpages that have at least one present PTE that
2814 * is not already pte-numa. If the VMA contains
2815 * areas that are unused or already full of prot_numa
2816 * PTEs, scan up to virtpages, to skip through those
2820 pages -= (end - start) >> PAGE_SHIFT;
2821 virtpages -= (end - start) >> PAGE_SHIFT;
2824 if (pages <= 0 || virtpages <= 0)
2828 } while (end != vma->vm_end);
2833 * It is possible to reach the end of the VMA list but the last few
2834 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2835 * would find the !migratable VMA on the next scan but not reset the
2836 * scanner to the start so check it now.
2839 mm->numa_scan_offset = start;
2841 reset_ptenuma_scan(p);
2842 up_read(&mm->mmap_sem);
2845 * Make sure tasks use at least 32x as much time to run other code
2846 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2847 * Usually update_task_scan_period slows down scanning enough; on an
2848 * overloaded system we need to limit overhead on a per task basis.
2850 if (unlikely(p->se.sum_exec_runtime != runtime)) {
2851 u64 diff = p->se.sum_exec_runtime - runtime;
2852 p->node_stamp += 32 * diff;
2856 void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
2859 struct mm_struct *mm = p->mm;
2862 mm_users = atomic_read(&mm->mm_users);
2863 if (mm_users == 1) {
2864 mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2865 mm->numa_scan_seq = 0;
2869 p->numa_scan_seq = mm ? mm->numa_scan_seq : 0;
2870 p->numa_scan_period = sysctl_numa_balancing_scan_delay;
2871 /* Protect against double add, see task_tick_numa and task_numa_work */
2872 p->numa_work.next = &p->numa_work;
2873 p->numa_faults = NULL;
2874 RCU_INIT_POINTER(p->numa_group, NULL);
2875 p->last_task_numa_placement = 0;
2876 p->last_sum_exec_runtime = 0;
2878 init_task_work(&p->numa_work, task_numa_work);
2880 /* New address space, reset the preferred nid */
2881 if (!(clone_flags & CLONE_VM)) {
2882 p->numa_preferred_nid = NUMA_NO_NODE;
2887 * New thread, keep existing numa_preferred_nid which should be copied
2888 * already by arch_dup_task_struct but stagger when scans start.
2893 delay = min_t(unsigned int, task_scan_max(current),
2894 current->numa_scan_period * mm_users * NSEC_PER_MSEC);
2895 delay += 2 * TICK_NSEC;
2896 p->node_stamp = delay;
2901 * Drive the periodic memory faults..
2903 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2905 struct callback_head *work = &curr->numa_work;
2909 * We don't care about NUMA placement if we don't have memory.
2911 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2915 * Using runtime rather than walltime has the dual advantage that
2916 * we (mostly) drive the selection from busy threads and that the
2917 * task needs to have done some actual work before we bother with
2920 now = curr->se.sum_exec_runtime;
2921 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2923 if (now > curr->node_stamp + period) {
2924 if (!curr->node_stamp)
2925 curr->numa_scan_period = task_scan_start(curr);
2926 curr->node_stamp += period;
2928 if (!time_before(jiffies, curr->mm->numa_next_scan))
2929 task_work_add(curr, work, true);
2933 static void update_scan_period(struct task_struct *p, int new_cpu)
2935 int src_nid = cpu_to_node(task_cpu(p));
2936 int dst_nid = cpu_to_node(new_cpu);
2938 if (!static_branch_likely(&sched_numa_balancing))
2941 if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
2944 if (src_nid == dst_nid)
2948 * Allow resets if faults have been trapped before one scan
2949 * has completed. This is most likely due to a new task that
2950 * is pulled cross-node due to wakeups or load balancing.
2952 if (p->numa_scan_seq) {
2954 * Avoid scan adjustments if moving to the preferred
2955 * node or if the task was not previously running on
2956 * the preferred node.
2958 if (dst_nid == p->numa_preferred_nid ||
2959 (p->numa_preferred_nid != NUMA_NO_NODE &&
2960 src_nid != p->numa_preferred_nid))
2964 p->numa_scan_period = task_scan_start(p);
2968 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2972 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2976 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2980 static inline void update_scan_period(struct task_struct *p, int new_cpu)
2984 #endif /* CONFIG_NUMA_BALANCING */
2987 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2989 update_load_add(&cfs_rq->load, se->load.weight);
2991 if (entity_is_task(se)) {
2992 struct rq *rq = rq_of(cfs_rq);
2994 account_numa_enqueue(rq, task_of(se));
2995 list_add(&se->group_node, &rq->cfs_tasks);
2998 cfs_rq->nr_running++;
3002 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
3004 update_load_sub(&cfs_rq->load, se->load.weight);
3006 if (entity_is_task(se)) {
3007 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
3008 list_del_init(&se->group_node);
3011 cfs_rq->nr_running--;
3015 * Signed add and clamp on underflow.
3017 * Explicitly do a load-store to ensure the intermediate value never hits
3018 * memory. This allows lockless observations without ever seeing the negative
3021 #define add_positive(_ptr, _val) do { \
3022 typeof(_ptr) ptr = (_ptr); \
3023 typeof(_val) val = (_val); \
3024 typeof(*ptr) res, var = READ_ONCE(*ptr); \
3028 if (val < 0 && res > var) \
3031 WRITE_ONCE(*ptr, res); \
3035 * Unsigned subtract and clamp on underflow.
3037 * Explicitly do a load-store to ensure the intermediate value never hits
3038 * memory. This allows lockless observations without ever seeing the negative
3041 #define sub_positive(_ptr, _val) do { \
3042 typeof(_ptr) ptr = (_ptr); \
3043 typeof(*ptr) val = (_val); \
3044 typeof(*ptr) res, var = READ_ONCE(*ptr); \
3048 WRITE_ONCE(*ptr, res); \
3052 * Remove and clamp on negative, from a local variable.
3054 * A variant of sub_positive(), which does not use explicit load-store
3055 * and is thus optimized for local variable updates.
3057 #define lsub_positive(_ptr, _val) do { \
3058 typeof(_ptr) ptr = (_ptr); \
3059 *ptr -= min_t(typeof(*ptr), *ptr, _val); \
3064 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3066 cfs_rq->avg.load_avg += se->avg.load_avg;
3067 cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
3071 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3073 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
3074 sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
3078 enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
3080 dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
3083 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
3084 unsigned long weight)
3087 /* commit outstanding execution time */
3088 if (cfs_rq->curr == se)
3089 update_curr(cfs_rq);
3090 account_entity_dequeue(cfs_rq, se);
3092 dequeue_load_avg(cfs_rq, se);
3094 update_load_set(&se->load, weight);
3098 u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib;
3100 se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
3104 enqueue_load_avg(cfs_rq, se);
3106 account_entity_enqueue(cfs_rq, se);
3110 void reweight_task(struct task_struct *p, int prio)
3112 struct sched_entity *se = &p->se;
3113 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3114 struct load_weight *load = &se->load;
3115 unsigned long weight = scale_load(sched_prio_to_weight[prio]);
3117 reweight_entity(cfs_rq, se, weight);
3118 load->inv_weight = sched_prio_to_wmult[prio];
3121 #ifdef CONFIG_FAIR_GROUP_SCHED
3124 * All this does is approximate the hierarchical proportion which includes that
3125 * global sum we all love to hate.
3127 * That is, the weight of a group entity, is the proportional share of the
3128 * group weight based on the group runqueue weights. That is:
3130 * tg->weight * grq->load.weight
3131 * ge->load.weight = ----------------------------- (1)
3132 * \Sum grq->load.weight
3134 * Now, because computing that sum is prohibitively expensive to compute (been
3135 * there, done that) we approximate it with this average stuff. The average
3136 * moves slower and therefore the approximation is cheaper and more stable.
3138 * So instead of the above, we substitute:
3140 * grq->load.weight -> grq->avg.load_avg (2)
3142 * which yields the following:
3144 * tg->weight * grq->avg.load_avg
3145 * ge->load.weight = ------------------------------ (3)
3148 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
3150 * That is shares_avg, and it is right (given the approximation (2)).
3152 * The problem with it is that because the average is slow -- it was designed
3153 * to be exactly that of course -- this leads to transients in boundary
3154 * conditions. In specific, the case where the group was idle and we start the
3155 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
3156 * yielding bad latency etc..
3158 * Now, in that special case (1) reduces to:
3160 * tg->weight * grq->load.weight
3161 * ge->load.weight = ----------------------------- = tg->weight (4)
3164 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
3166 * So what we do is modify our approximation (3) to approach (4) in the (near)
3171 * tg->weight * grq->load.weight
3172 * --------------------------------------------------- (5)
3173 * tg->load_avg - grq->avg.load_avg + grq->load.weight
3175 * But because grq->load.weight can drop to 0, resulting in a divide by zero,
3176 * we need to use grq->avg.load_avg as its lower bound, which then gives:
3179 * tg->weight * grq->load.weight
3180 * ge->load.weight = ----------------------------- (6)
3185 * tg_load_avg' = tg->load_avg - grq->avg.load_avg +
3186 * max(grq->load.weight, grq->avg.load_avg)
3188 * And that is shares_weight and is icky. In the (near) UP case it approaches
3189 * (4) while in the normal case it approaches (3). It consistently
3190 * overestimates the ge->load.weight and therefore:
3192 * \Sum ge->load.weight >= tg->weight
3196 static long calc_group_shares(struct cfs_rq *cfs_rq)
3198 long tg_weight, tg_shares, load, shares;
3199 struct task_group *tg = cfs_rq->tg;
3201 tg_shares = READ_ONCE(tg->shares);
3203 load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
3205 tg_weight = atomic_long_read(&tg->load_avg);
3207 /* Ensure tg_weight >= load */
3208 tg_weight -= cfs_rq->tg_load_avg_contrib;
3211 shares = (tg_shares * load);
3213 shares /= tg_weight;
3216 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
3217 * of a group with small tg->shares value. It is a floor value which is
3218 * assigned as a minimum load.weight to the sched_entity representing
3219 * the group on a CPU.
3221 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
3222 * on an 8-core system with 8 tasks each runnable on one CPU shares has
3223 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
3224 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
3227 return clamp_t(long, shares, MIN_SHARES, tg_shares);
3229 #endif /* CONFIG_SMP */
3231 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
3234 * Recomputes the group entity based on the current state of its group
3237 static void update_cfs_group(struct sched_entity *se)
3239 struct cfs_rq *gcfs_rq = group_cfs_rq(se);
3245 if (throttled_hierarchy(gcfs_rq))
3249 shares = READ_ONCE(gcfs_rq->tg->shares);
3251 if (likely(se->load.weight == shares))
3254 shares = calc_group_shares(gcfs_rq);
3257 reweight_entity(cfs_rq_of(se), se, shares);
3260 #else /* CONFIG_FAIR_GROUP_SCHED */
3261 static inline void update_cfs_group(struct sched_entity *se)
3264 #endif /* CONFIG_FAIR_GROUP_SCHED */
3266 static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
3268 struct rq *rq = rq_of(cfs_rq);
3270 if (&rq->cfs == cfs_rq) {
3272 * There are a few boundary cases this might miss but it should
3273 * get called often enough that that should (hopefully) not be
3276 * It will not get called when we go idle, because the idle
3277 * thread is a different class (!fair), nor will the utilization
3278 * number include things like RT tasks.
3280 * As is, the util number is not freq-invariant (we'd have to
3281 * implement arch_scale_freq_capacity() for that).
3285 cpufreq_update_util(rq, flags);
3290 #ifdef CONFIG_FAIR_GROUP_SCHED
3292 * update_tg_load_avg - update the tg's load avg
3293 * @cfs_rq: the cfs_rq whose avg changed
3294 * @force: update regardless of how small the difference
3296 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
3297 * However, because tg->load_avg is a global value there are performance
3300 * In order to avoid having to look at the other cfs_rq's, we use a
3301 * differential update where we store the last value we propagated. This in
3302 * turn allows skipping updates if the differential is 'small'.
3304 * Updating tg's load_avg is necessary before update_cfs_share().
3306 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3308 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3311 * No need to update load_avg for root_task_group as it is not used.
3313 if (cfs_rq->tg == &root_task_group)
3316 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
3317 atomic_long_add(delta, &cfs_rq->tg->load_avg);
3318 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
3323 * Called within set_task_rq() right before setting a task's CPU. The
3324 * caller only guarantees p->pi_lock is held; no other assumptions,
3325 * including the state of rq->lock, should be made.
3327 void set_task_rq_fair(struct sched_entity *se,
3328 struct cfs_rq *prev, struct cfs_rq *next)
3330 u64 p_last_update_time;
3331 u64 n_last_update_time;
3333 if (!sched_feat(ATTACH_AGE_LOAD))
3337 * We are supposed to update the task to "current" time, then its up to
3338 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
3339 * getting what current time is, so simply throw away the out-of-date
3340 * time. This will result in the wakee task is less decayed, but giving
3341 * the wakee more load sounds not bad.
3343 if (!(se->avg.last_update_time && prev))
3346 #ifndef CONFIG_64BIT
3348 u64 p_last_update_time_copy;
3349 u64 n_last_update_time_copy;
3352 p_last_update_time_copy = prev->load_last_update_time_copy;
3353 n_last_update_time_copy = next->load_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 } while (p_last_update_time != p_last_update_time_copy ||
3361 n_last_update_time != n_last_update_time_copy);
3364 p_last_update_time = prev->avg.last_update_time;
3365 n_last_update_time = next->avg.last_update_time;
3367 __update_load_avg_blocked_se(p_last_update_time, se);
3368 se->avg.last_update_time = n_last_update_time;
3373 * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
3374 * propagate its contribution. The key to this propagation is the invariant
3375 * that for each group:
3377 * ge->avg == grq->avg (1)
3379 * _IFF_ we look at the pure running and runnable sums. Because they
3380 * represent the very same entity, just at different points in the hierarchy.
3382 * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
3383 * and simply copies the running/runnable sum over (but still wrong, because
3384 * the group entity and group rq do not have their PELT windows aligned).
3386 * However, update_tg_cfs_load() is more complex. So we have:
3388 * ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg (2)
3390 * And since, like util, the runnable part should be directly transferable,
3391 * the following would _appear_ to be the straight forward approach:
3393 * grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg (3)
3395 * And per (1) we have:
3397 * ge->avg.runnable_avg == grq->avg.runnable_avg
3401 * ge->load.weight * grq->avg.load_avg
3402 * ge->avg.load_avg = ----------------------------------- (4)
3405 * Except that is wrong!
3407 * Because while for entities historical weight is not important and we
3408 * really only care about our future and therefore can consider a pure
3409 * runnable sum, runqueues can NOT do this.
3411 * We specifically want runqueues to have a load_avg that includes
3412 * historical weights. Those represent the blocked load, the load we expect
3413 * to (shortly) return to us. This only works by keeping the weights as
3414 * integral part of the sum. We therefore cannot decompose as per (3).
3416 * Another reason this doesn't work is that runnable isn't a 0-sum entity.
3417 * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
3418 * rq itself is runnable anywhere between 2/3 and 1 depending on how the
3419 * runnable section of these tasks overlap (or not). If they were to perfectly
3420 * align the rq as a whole would be runnable 2/3 of the time. If however we
3421 * always have at least 1 runnable task, the rq as a whole is always runnable.
3423 * So we'll have to approximate.. :/
3425 * Given the constraint:
3427 * ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3429 * We can construct a rule that adds runnable to a rq by assuming minimal
3432 * On removal, we'll assume each task is equally runnable; which yields:
3434 * grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3436 * XXX: only do this for the part of runnable > running ?
3441 update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3443 long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
3445 /* Nothing to update */
3450 * The relation between sum and avg is:
3452 * LOAD_AVG_MAX - 1024 + sa->period_contrib
3454 * however, the PELT windows are not aligned between grq and gse.
3457 /* Set new sched_entity's utilization */
3458 se->avg.util_avg = gcfs_rq->avg.util_avg;
3459 se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;
3461 /* Update parent cfs_rq utilization */
3462 add_positive(&cfs_rq->avg.util_avg, delta);
3463 cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
3467 update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3469 long delta = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
3471 /* Nothing to update */
3476 * The relation between sum and avg is:
3478 * LOAD_AVG_MAX - 1024 + sa->period_contrib
3480 * however, the PELT windows are not aligned between grq and gse.
3483 /* Set new sched_entity's runnable */
3484 se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
3485 se->avg.runnable_sum = se->avg.runnable_avg * LOAD_AVG_MAX;
3487 /* Update parent cfs_rq runnable */
3488 add_positive(&cfs_rq->avg.runnable_avg, delta);
3489 cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * LOAD_AVG_MAX;
3493 update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3495 long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
3496 unsigned long load_avg;
3503 gcfs_rq->prop_runnable_sum = 0;
3505 if (runnable_sum >= 0) {
3507 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
3508 * the CPU is saturated running == runnable.
3510 runnable_sum += se->avg.load_sum;
3511 runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
3514 * Estimate the new unweighted runnable_sum of the gcfs_rq by
3515 * assuming all tasks are equally runnable.
3517 if (scale_load_down(gcfs_rq->load.weight)) {
3518 load_sum = div_s64(gcfs_rq->avg.load_sum,
3519 scale_load_down(gcfs_rq->load.weight));
3522 /* But make sure to not inflate se's runnable */
3523 runnable_sum = min(se->avg.load_sum, load_sum);
3527 * runnable_sum can't be lower than running_sum
3528 * Rescale running sum to be in the same range as runnable sum
3529 * running_sum is in [0 : LOAD_AVG_MAX << SCHED_CAPACITY_SHIFT]
3530 * runnable_sum is in [0 : LOAD_AVG_MAX]
3532 running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
3533 runnable_sum = max(runnable_sum, running_sum);
3535 load_sum = (s64)se_weight(se) * runnable_sum;
3536 load_avg = div_s64(load_sum, LOAD_AVG_MAX);
3538 delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
3539 delta_avg = load_avg - se->avg.load_avg;
3541 se->avg.load_sum = runnable_sum;
3542 se->avg.load_avg = load_avg;
3543 add_positive(&cfs_rq->avg.load_avg, delta_avg);
3544 add_positive(&cfs_rq->avg.load_sum, delta_sum);
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, int force) {}
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 = LOAD_AVG_MAX - 1024 + sa->period_contrib;
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 sub_positive(&sa->load_sum, r * divider);
3663 sub_positive(&sa->util_avg, r);
3664 sub_positive(&sa->util_sum, r * divider);
3666 r = removed_runnable;
3667 sub_positive(&sa->runnable_avg, r);
3668 sub_positive(&sa->runnable_sum, r * 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)
3700 u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
3703 * When we attach the @se to the @cfs_rq, we must align the decay
3704 * window because without that, really weird and wonderful things can
3709 se->avg.last_update_time = cfs_rq->avg.last_update_time;
3710 se->avg.period_contrib = cfs_rq->avg.period_contrib;
3713 * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
3714 * period_contrib. This isn't strictly correct, but since we're
3715 * entirely outside of the PELT hierarchy, nobody cares if we truncate
3718 se->avg.util_sum = se->avg.util_avg * divider;
3720 se->avg.runnable_sum = se->avg.runnable_avg * divider;
3722 se->avg.load_sum = divider;
3723 if (se_weight(se)) {
3725 div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
3728 enqueue_load_avg(cfs_rq, se);
3729 cfs_rq->avg.util_avg += se->avg.util_avg;
3730 cfs_rq->avg.util_sum += se->avg.util_sum;
3731 cfs_rq->avg.runnable_avg += se->avg.runnable_avg;
3732 cfs_rq->avg.runnable_sum += se->avg.runnable_sum;
3734 add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3736 cfs_rq_util_change(cfs_rq, 0);
3738 trace_pelt_cfs_tp(cfs_rq);
3742 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3743 * @cfs_rq: cfs_rq to detach from
3744 * @se: sched_entity to detach
3746 * Must call update_cfs_rq_load_avg() before this, since we rely on
3747 * cfs_rq->avg.last_update_time being current.
3749 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3751 dequeue_load_avg(cfs_rq, se);
3752 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
3753 sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3754 sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
3755 sub_positive(&cfs_rq->avg.runnable_sum, se->avg.runnable_sum);
3757 add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3759 cfs_rq_util_change(cfs_rq, 0);
3761 trace_pelt_cfs_tp(cfs_rq);
3765 * Optional action to be done while updating the load average
3767 #define UPDATE_TG 0x1
3768 #define SKIP_AGE_LOAD 0x2
3769 #define DO_ATTACH 0x4
3771 /* Update task and its cfs_rq load average */
3772 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3774 u64 now = cfs_rq_clock_pelt(cfs_rq);
3778 * Track task load average for carrying it to new CPU after migrated, and
3779 * track group sched_entity load average for task_h_load calc in migration
3781 if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
3782 __update_load_avg_se(now, cfs_rq, se);
3784 decayed = update_cfs_rq_load_avg(now, cfs_rq);
3785 decayed |= propagate_entity_load_avg(se);
3787 if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
3790 * DO_ATTACH means we're here from enqueue_entity().
3791 * !last_update_time means we've passed through
3792 * migrate_task_rq_fair() indicating we migrated.
3794 * IOW we're enqueueing a task on a new CPU.
3796 attach_entity_load_avg(cfs_rq, se);
3797 update_tg_load_avg(cfs_rq, 0);
3799 } else if (decayed) {
3800 cfs_rq_util_change(cfs_rq, 0);
3802 if (flags & UPDATE_TG)
3803 update_tg_load_avg(cfs_rq, 0);
3807 #ifndef CONFIG_64BIT
3808 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3810 u64 last_update_time_copy;
3811 u64 last_update_time;
3814 last_update_time_copy = cfs_rq->load_last_update_time_copy;
3816 last_update_time = cfs_rq->avg.last_update_time;
3817 } while (last_update_time != last_update_time_copy);
3819 return last_update_time;
3822 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3824 return cfs_rq->avg.last_update_time;
3829 * Synchronize entity load avg of dequeued entity without locking
3832 static void sync_entity_load_avg(struct sched_entity *se)
3834 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3835 u64 last_update_time;
3837 last_update_time = cfs_rq_last_update_time(cfs_rq);
3838 __update_load_avg_blocked_se(last_update_time, se);
3842 * Task first catches up with cfs_rq, and then subtract
3843 * itself from the cfs_rq (task must be off the queue now).
3845 static void remove_entity_load_avg(struct sched_entity *se)
3847 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3848 unsigned long flags;
3851 * tasks cannot exit without having gone through wake_up_new_task() ->
3852 * post_init_entity_util_avg() which will have added things to the
3853 * cfs_rq, so we can remove unconditionally.
3856 sync_entity_load_avg(se);
3858 raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
3859 ++cfs_rq->removed.nr;
3860 cfs_rq->removed.util_avg += se->avg.util_avg;
3861 cfs_rq->removed.load_avg += se->avg.load_avg;
3862 cfs_rq->removed.runnable_avg += se->avg.runnable_avg;
3863 raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3866 static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq)
3868 return cfs_rq->avg.runnable_avg;
3871 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
3873 return cfs_rq->avg.load_avg;
3876 static int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
3878 static inline unsigned long task_util(struct task_struct *p)
3880 return READ_ONCE(p->se.avg.util_avg);
3883 static inline unsigned long _task_util_est(struct task_struct *p)
3885 struct util_est ue = READ_ONCE(p->se.avg.util_est);
3887 return (max(ue.ewma, ue.enqueued) | UTIL_AVG_UNCHANGED);
3890 static inline unsigned long task_util_est(struct task_struct *p)
3892 return max(task_util(p), _task_util_est(p));
3895 #ifdef CONFIG_UCLAMP_TASK
3896 static inline unsigned long uclamp_task_util(struct task_struct *p)
3898 return clamp(task_util_est(p),
3899 uclamp_eff_value(p, UCLAMP_MIN),
3900 uclamp_eff_value(p, UCLAMP_MAX));
3903 static inline unsigned long uclamp_task_util(struct task_struct *p)
3905 return task_util_est(p);
3909 static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
3910 struct task_struct *p)
3912 unsigned int enqueued;
3914 if (!sched_feat(UTIL_EST))
3917 /* Update root cfs_rq's estimated utilization */
3918 enqueued = cfs_rq->avg.util_est.enqueued;
3919 enqueued += _task_util_est(p);
3920 WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
3924 * Check if a (signed) value is within a specified (unsigned) margin,
3925 * based on the observation that:
3927 * abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
3929 * NOTE: this only works when value + maring < INT_MAX.
3931 static inline bool within_margin(int value, int margin)
3933 return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
3937 util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
3939 long last_ewma_diff;
3943 if (!sched_feat(UTIL_EST))
3946 /* Update root cfs_rq's estimated utilization */
3947 ue.enqueued = cfs_rq->avg.util_est.enqueued;
3948 ue.enqueued -= min_t(unsigned int, ue.enqueued, _task_util_est(p));
3949 WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);
3952 * Skip update of task's estimated utilization when the task has not
3953 * yet completed an activation, e.g. being migrated.
3959 * If the PELT values haven't changed since enqueue time,
3960 * skip the util_est update.
3962 ue = p->se.avg.util_est;
3963 if (ue.enqueued & UTIL_AVG_UNCHANGED)
3967 * Reset EWMA on utilization increases, the moving average is used only
3968 * to smooth utilization decreases.
3970 ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
3971 if (sched_feat(UTIL_EST_FASTUP)) {
3972 if (ue.ewma < ue.enqueued) {
3973 ue.ewma = ue.enqueued;
3979 * Skip update of task's estimated utilization when its EWMA is
3980 * already ~1% close to its last activation value.
3982 last_ewma_diff = ue.enqueued - ue.ewma;
3983 if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100)))
3987 * To avoid overestimation of actual task utilization, skip updates if
3988 * we cannot grant there is idle time in this CPU.
3990 cpu = cpu_of(rq_of(cfs_rq));
3991 if (task_util(p) > capacity_orig_of(cpu))
3995 * Update Task's estimated utilization
3997 * When *p completes an activation we can consolidate another sample
3998 * of the task size. This is done by storing the current PELT value
3999 * as ue.enqueued and by using this value to update the Exponential
4000 * Weighted Moving Average (EWMA):
4002 * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
4003 * = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
4004 * = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
4005 * = w * ( last_ewma_diff ) + ewma(t-1)
4006 * = w * (last_ewma_diff + ewma(t-1) / w)
4008 * Where 'w' is the weight of new samples, which is configured to be
4009 * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
4011 ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
4012 ue.ewma += last_ewma_diff;
4013 ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
4015 WRITE_ONCE(p->se.avg.util_est, ue);
4018 static inline int task_fits_capacity(struct task_struct *p, long capacity)
4020 return fits_capacity(uclamp_task_util(p), capacity);
4023 static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
4025 if (!static_branch_unlikely(&sched_asym_cpucapacity))
4029 rq->misfit_task_load = 0;
4033 if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) {
4034 rq->misfit_task_load = 0;
4038 rq->misfit_task_load = task_h_load(p);
4041 #else /* CONFIG_SMP */
4043 #define UPDATE_TG 0x0
4044 #define SKIP_AGE_LOAD 0x0
4045 #define DO_ATTACH 0x0
4047 static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
4049 cfs_rq_util_change(cfs_rq, 0);
4052 static inline void remove_entity_load_avg(struct sched_entity *se) {}
4055 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
4057 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
4059 static inline int newidle_balance(struct rq *rq, struct rq_flags *rf)
4065 util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
4068 util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p,
4070 static inline void update_misfit_status(struct task_struct *p, struct rq *rq) {}
4072 #endif /* CONFIG_SMP */
4074 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
4076 #ifdef CONFIG_SCHED_DEBUG
4077 s64 d = se->vruntime - cfs_rq->min_vruntime;
4082 if (d > 3*sysctl_sched_latency)
4083 schedstat_inc(cfs_rq->nr_spread_over);
4088 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
4090 u64 vruntime = cfs_rq->min_vruntime;
4093 * The 'current' period is already promised to the current tasks,
4094 * however the extra weight of the new task will slow them down a
4095 * little, place the new task so that it fits in the slot that
4096 * stays open at the end.
4098 if (initial && sched_feat(START_DEBIT))
4099 vruntime += sched_vslice(cfs_rq, se);
4101 /* sleeps up to a single latency don't count. */
4103 unsigned long thresh = sysctl_sched_latency;
4106 * Halve their sleep time's effect, to allow
4107 * for a gentler effect of sleepers:
4109 if (sched_feat(GENTLE_FAIR_SLEEPERS))
4115 /* ensure we never gain time by being placed backwards. */
4116 se->vruntime = max_vruntime(se->vruntime, vruntime);
4119 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
4121 static inline void check_schedstat_required(void)
4123 #ifdef CONFIG_SCHEDSTATS
4124 if (schedstat_enabled())
4127 /* Force schedstat enabled if a dependent tracepoint is active */
4128 if (trace_sched_stat_wait_enabled() ||
4129 trace_sched_stat_sleep_enabled() ||
4130 trace_sched_stat_iowait_enabled() ||
4131 trace_sched_stat_blocked_enabled() ||
4132 trace_sched_stat_runtime_enabled()) {
4133 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
4134 "stat_blocked and stat_runtime require the "
4135 "kernel parameter schedstats=enable or "
4136 "kernel.sched_schedstats=1\n");
4141 static inline bool cfs_bandwidth_used(void);
4148 * update_min_vruntime()
4149 * vruntime -= min_vruntime
4153 * update_min_vruntime()
4154 * vruntime += min_vruntime
4156 * this way the vruntime transition between RQs is done when both
4157 * min_vruntime are up-to-date.
4161 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
4162 * vruntime -= min_vruntime
4166 * update_min_vruntime()
4167 * vruntime += min_vruntime
4169 * this way we don't have the most up-to-date min_vruntime on the originating
4170 * CPU and an up-to-date min_vruntime on the destination CPU.
4174 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4176 bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
4177 bool curr = cfs_rq->curr == se;
4180 * If we're the current task, we must renormalise before calling
4184 se->vruntime += cfs_rq->min_vruntime;
4186 update_curr(cfs_rq);
4189 * Otherwise, renormalise after, such that we're placed at the current
4190 * moment in time, instead of some random moment in the past. Being
4191 * placed in the past could significantly boost this task to the
4192 * fairness detriment of existing tasks.
4194 if (renorm && !curr)
4195 se->vruntime += cfs_rq->min_vruntime;
4198 * When enqueuing a sched_entity, we must:
4199 * - Update loads to have both entity and cfs_rq synced with now.
4200 * - Add its load to cfs_rq->runnable_avg
4201 * - For group_entity, update its weight to reflect the new share of
4203 * - Add its new weight to cfs_rq->load.weight
4205 update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
4206 se_update_runnable(se);
4207 update_cfs_group(se);
4208 account_entity_enqueue(cfs_rq, se);
4210 if (flags & ENQUEUE_WAKEUP)
4211 place_entity(cfs_rq, se, 0);
4213 check_schedstat_required();
4214 update_stats_enqueue(cfs_rq, se, flags);
4215 check_spread(cfs_rq, se);
4217 __enqueue_entity(cfs_rq, se);
4221 * When bandwidth control is enabled, cfs might have been removed
4222 * because of a parent been throttled but cfs->nr_running > 1. Try to
4223 * add it unconditionnally.
4225 if (cfs_rq->nr_running == 1 || cfs_bandwidth_used())
4226 list_add_leaf_cfs_rq(cfs_rq);
4228 if (cfs_rq->nr_running == 1)
4229 check_enqueue_throttle(cfs_rq);
4232 static void __clear_buddies_last(struct sched_entity *se)
4234 for_each_sched_entity(se) {
4235 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4236 if (cfs_rq->last != se)
4239 cfs_rq->last = NULL;
4243 static void __clear_buddies_next(struct sched_entity *se)
4245 for_each_sched_entity(se) {
4246 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4247 if (cfs_rq->next != se)
4250 cfs_rq->next = NULL;
4254 static void __clear_buddies_skip(struct sched_entity *se)
4256 for_each_sched_entity(se) {
4257 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4258 if (cfs_rq->skip != se)
4261 cfs_rq->skip = NULL;
4265 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
4267 if (cfs_rq->last == se)
4268 __clear_buddies_last(se);
4270 if (cfs_rq->next == se)
4271 __clear_buddies_next(se);
4273 if (cfs_rq->skip == se)
4274 __clear_buddies_skip(se);
4277 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4280 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4283 * Update run-time statistics of the 'current'.
4285 update_curr(cfs_rq);
4288 * When dequeuing a sched_entity, we must:
4289 * - Update loads to have both entity and cfs_rq synced with now.
4290 * - Subtract its load from the cfs_rq->runnable_avg.
4291 * - Subtract its previous weight from cfs_rq->load.weight.
4292 * - For group entity, update its weight to reflect the new share
4293 * of its group cfs_rq.
4295 update_load_avg(cfs_rq, se, UPDATE_TG);
4296 se_update_runnable(se);
4298 update_stats_dequeue(cfs_rq, se, flags);
4300 clear_buddies(cfs_rq, se);
4302 if (se != cfs_rq->curr)
4303 __dequeue_entity(cfs_rq, se);
4305 account_entity_dequeue(cfs_rq, se);
4308 * Normalize after update_curr(); which will also have moved
4309 * min_vruntime if @se is the one holding it back. But before doing
4310 * update_min_vruntime() again, which will discount @se's position and
4311 * can move min_vruntime forward still more.
4313 if (!(flags & DEQUEUE_SLEEP))
4314 se->vruntime -= cfs_rq->min_vruntime;
4316 /* return excess runtime on last dequeue */
4317 return_cfs_rq_runtime(cfs_rq);
4319 update_cfs_group(se);
4322 * Now advance min_vruntime if @se was the entity holding it back,
4323 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
4324 * put back on, and if we advance min_vruntime, we'll be placed back
4325 * further than we started -- ie. we'll be penalized.
4327 if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
4328 update_min_vruntime(cfs_rq);
4332 * Preempt the current task with a newly woken task if needed:
4335 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4337 unsigned long ideal_runtime, delta_exec;
4338 struct sched_entity *se;
4341 ideal_runtime = sched_slice(cfs_rq, curr);
4342 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4343 if (delta_exec > ideal_runtime) {
4344 resched_curr(rq_of(cfs_rq));
4346 * The current task ran long enough, ensure it doesn't get
4347 * re-elected due to buddy favours.
4349 clear_buddies(cfs_rq, curr);
4354 * Ensure that a task that missed wakeup preemption by a
4355 * narrow margin doesn't have to wait for a full slice.
4356 * This also mitigates buddy induced latencies under load.
4358 if (delta_exec < sysctl_sched_min_granularity)
4361 se = __pick_first_entity(cfs_rq);
4362 delta = curr->vruntime - se->vruntime;
4367 if (delta > ideal_runtime)
4368 resched_curr(rq_of(cfs_rq));
4372 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4374 /* 'current' is not kept within the tree. */
4377 * Any task has to be enqueued before it get to execute on
4378 * a CPU. So account for the time it spent waiting on the
4381 update_stats_wait_end(cfs_rq, se);
4382 __dequeue_entity(cfs_rq, se);
4383 update_load_avg(cfs_rq, se, UPDATE_TG);
4386 update_stats_curr_start(cfs_rq, se);
4390 * Track our maximum slice length, if the CPU's load is at
4391 * least twice that of our own weight (i.e. dont track it
4392 * when there are only lesser-weight tasks around):
4394 if (schedstat_enabled() &&
4395 rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
4396 schedstat_set(se->statistics.slice_max,
4397 max((u64)schedstat_val(se->statistics.slice_max),
4398 se->sum_exec_runtime - se->prev_sum_exec_runtime));
4401 se->prev_sum_exec_runtime = se->sum_exec_runtime;
4405 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
4408 * Pick the next process, keeping these things in mind, in this order:
4409 * 1) keep things fair between processes/task groups
4410 * 2) pick the "next" process, since someone really wants that to run
4411 * 3) pick the "last" process, for cache locality
4412 * 4) do not run the "skip" process, if something else is available
4414 static struct sched_entity *
4415 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4417 struct sched_entity *left = __pick_first_entity(cfs_rq);
4418 struct sched_entity *se;
4421 * If curr is set we have to see if its left of the leftmost entity
4422 * still in the tree, provided there was anything in the tree at all.
4424 if (!left || (curr && entity_before(curr, left)))
4427 se = left; /* ideally we run the leftmost entity */
4430 * Avoid running the skip buddy, if running something else can
4431 * be done without getting too unfair.
4433 if (cfs_rq->skip == se) {
4434 struct sched_entity *second;
4437 second = __pick_first_entity(cfs_rq);
4439 second = __pick_next_entity(se);
4440 if (!second || (curr && entity_before(curr, second)))
4444 if (second && wakeup_preempt_entity(second, left) < 1)
4449 * Prefer last buddy, try to return the CPU to a preempted task.
4451 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
4455 * Someone really wants this to run. If it's not unfair, run it.
4457 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
4460 clear_buddies(cfs_rq, se);
4465 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4467 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4470 * If still on the runqueue then deactivate_task()
4471 * was not called and update_curr() has to be done:
4474 update_curr(cfs_rq);
4476 /* throttle cfs_rqs exceeding runtime */
4477 check_cfs_rq_runtime(cfs_rq);
4479 check_spread(cfs_rq, prev);
4482 update_stats_wait_start(cfs_rq, prev);
4483 /* Put 'current' back into the tree. */
4484 __enqueue_entity(cfs_rq, prev);
4485 /* in !on_rq case, update occurred at dequeue */
4486 update_load_avg(cfs_rq, prev, 0);
4488 cfs_rq->curr = NULL;
4492 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4495 * Update run-time statistics of the 'current'.
4497 update_curr(cfs_rq);
4500 * Ensure that runnable average is periodically updated.
4502 update_load_avg(cfs_rq, curr, UPDATE_TG);
4503 update_cfs_group(curr);
4505 #ifdef CONFIG_SCHED_HRTICK
4507 * queued ticks are scheduled to match the slice, so don't bother
4508 * validating it and just reschedule.
4511 resched_curr(rq_of(cfs_rq));
4515 * don't let the period tick interfere with the hrtick preemption
4517 if (!sched_feat(DOUBLE_TICK) &&
4518 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
4522 if (cfs_rq->nr_running > 1)
4523 check_preempt_tick(cfs_rq, curr);
4527 /**************************************************
4528 * CFS bandwidth control machinery
4531 #ifdef CONFIG_CFS_BANDWIDTH
4533 #ifdef CONFIG_JUMP_LABEL
4534 static struct static_key __cfs_bandwidth_used;
4536 static inline bool cfs_bandwidth_used(void)
4538 return static_key_false(&__cfs_bandwidth_used);
4541 void cfs_bandwidth_usage_inc(void)
4543 static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4546 void cfs_bandwidth_usage_dec(void)
4548 static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4550 #else /* CONFIG_JUMP_LABEL */
4551 static bool cfs_bandwidth_used(void)
4556 void cfs_bandwidth_usage_inc(void) {}
4557 void cfs_bandwidth_usage_dec(void) {}
4558 #endif /* CONFIG_JUMP_LABEL */
4561 * default period for cfs group bandwidth.
4562 * default: 0.1s, units: nanoseconds
4564 static inline u64 default_cfs_period(void)
4566 return 100000000ULL;
4569 static inline u64 sched_cfs_bandwidth_slice(void)
4571 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
4575 * Replenish runtime according to assigned quota. We use sched_clock_cpu
4576 * directly instead of rq->clock to avoid adding additional synchronization
4579 * requires cfs_b->lock
4581 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
4583 if (cfs_b->quota != RUNTIME_INF)
4584 cfs_b->runtime = cfs_b->quota;
4587 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4589 return &tg->cfs_bandwidth;
4592 /* returns 0 on failure to allocate runtime */
4593 static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b,
4594 struct cfs_rq *cfs_rq, u64 target_runtime)
4596 u64 min_amount, amount = 0;
4598 lockdep_assert_held(&cfs_b->lock);
4600 /* note: this is a positive sum as runtime_remaining <= 0 */
4601 min_amount = target_runtime - cfs_rq->runtime_remaining;
4603 if (cfs_b->quota == RUNTIME_INF)
4604 amount = min_amount;
4606 start_cfs_bandwidth(cfs_b);
4608 if (cfs_b->runtime > 0) {
4609 amount = min(cfs_b->runtime, min_amount);
4610 cfs_b->runtime -= amount;
4615 cfs_rq->runtime_remaining += amount;
4617 return cfs_rq->runtime_remaining > 0;
4620 /* returns 0 on failure to allocate runtime */
4621 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4623 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4626 raw_spin_lock(&cfs_b->lock);
4627 ret = __assign_cfs_rq_runtime(cfs_b, cfs_rq, sched_cfs_bandwidth_slice());
4628 raw_spin_unlock(&cfs_b->lock);
4633 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4635 /* dock delta_exec before expiring quota (as it could span periods) */
4636 cfs_rq->runtime_remaining -= delta_exec;
4638 if (likely(cfs_rq->runtime_remaining > 0))
4641 if (cfs_rq->throttled)
4644 * if we're unable to extend our runtime we resched so that the active
4645 * hierarchy can be throttled
4647 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
4648 resched_curr(rq_of(cfs_rq));
4651 static __always_inline
4652 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4654 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4657 __account_cfs_rq_runtime(cfs_rq, delta_exec);
4660 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4662 return cfs_bandwidth_used() && cfs_rq->throttled;
4665 /* check whether cfs_rq, or any parent, is throttled */
4666 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4668 return cfs_bandwidth_used() && cfs_rq->throttle_count;
4672 * Ensure that neither of the group entities corresponding to src_cpu or
4673 * dest_cpu are members of a throttled hierarchy when performing group
4674 * load-balance operations.
4676 static inline int throttled_lb_pair(struct task_group *tg,
4677 int src_cpu, int dest_cpu)
4679 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
4681 src_cfs_rq = tg->cfs_rq[src_cpu];
4682 dest_cfs_rq = tg->cfs_rq[dest_cpu];
4684 return throttled_hierarchy(src_cfs_rq) ||
4685 throttled_hierarchy(dest_cfs_rq);
4688 static int tg_unthrottle_up(struct task_group *tg, void *data)
4690 struct rq *rq = data;
4691 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4693 cfs_rq->throttle_count--;
4694 if (!cfs_rq->throttle_count) {
4695 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4696 cfs_rq->throttled_clock_task;
4698 /* Add cfs_rq with already running entity in the list */
4699 if (cfs_rq->nr_running >= 1)
4700 list_add_leaf_cfs_rq(cfs_rq);
4706 static int tg_throttle_down(struct task_group *tg, void *data)
4708 struct rq *rq = data;
4709 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4711 /* group is entering throttled state, stop time */
4712 if (!cfs_rq->throttle_count) {
4713 cfs_rq->throttled_clock_task = rq_clock_task(rq);
4714 list_del_leaf_cfs_rq(cfs_rq);
4716 cfs_rq->throttle_count++;
4721 static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
4723 struct rq *rq = rq_of(cfs_rq);
4724 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4725 struct sched_entity *se;
4726 long task_delta, idle_task_delta, dequeue = 1;
4728 raw_spin_lock(&cfs_b->lock);
4729 /* This will start the period timer if necessary */
4730 if (__assign_cfs_rq_runtime(cfs_b, cfs_rq, 1)) {
4732 * We have raced with bandwidth becoming available, and if we
4733 * actually throttled the timer might not unthrottle us for an
4734 * entire period. We additionally needed to make sure that any
4735 * subsequent check_cfs_rq_runtime calls agree not to throttle
4736 * us, as we may commit to do cfs put_prev+pick_next, so we ask
4737 * for 1ns of runtime rather than just check cfs_b.
4741 list_add_tail_rcu(&cfs_rq->throttled_list,
4742 &cfs_b->throttled_cfs_rq);
4744 raw_spin_unlock(&cfs_b->lock);
4747 return false; /* Throttle no longer required. */
4749 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
4751 /* freeze hierarchy runnable averages while throttled */
4753 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
4756 task_delta = cfs_rq->h_nr_running;
4757 idle_task_delta = cfs_rq->idle_h_nr_running;
4758 for_each_sched_entity(se) {
4759 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
4760 /* throttled entity or throttle-on-deactivate */
4765 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
4767 update_load_avg(qcfs_rq, se, 0);
4768 se_update_runnable(se);
4771 qcfs_rq->h_nr_running -= task_delta;
4772 qcfs_rq->idle_h_nr_running -= idle_task_delta;
4774 if (qcfs_rq->load.weight)
4779 sub_nr_running(rq, task_delta);
4782 * Note: distribution will already see us throttled via the
4783 * throttled-list. rq->lock protects completion.
4785 cfs_rq->throttled = 1;
4786 cfs_rq->throttled_clock = rq_clock(rq);
4790 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4792 struct rq *rq = rq_of(cfs_rq);
4793 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4794 struct sched_entity *se;
4795 long task_delta, idle_task_delta;
4797 se = cfs_rq->tg->se[cpu_of(rq)];
4799 cfs_rq->throttled = 0;
4801 update_rq_clock(rq);
4803 raw_spin_lock(&cfs_b->lock);
4804 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4805 list_del_rcu(&cfs_rq->throttled_list);
4806 raw_spin_unlock(&cfs_b->lock);
4808 /* update hierarchical throttle state */
4809 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
4811 if (!cfs_rq->load.weight)
4814 task_delta = cfs_rq->h_nr_running;
4815 idle_task_delta = cfs_rq->idle_h_nr_running;
4816 for_each_sched_entity(se) {
4819 cfs_rq = cfs_rq_of(se);
4820 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
4822 cfs_rq->h_nr_running += task_delta;
4823 cfs_rq->idle_h_nr_running += idle_task_delta;
4825 /* end evaluation on encountering a throttled cfs_rq */
4826 if (cfs_rq_throttled(cfs_rq))
4827 goto unthrottle_throttle;
4830 for_each_sched_entity(se) {
4831 cfs_rq = cfs_rq_of(se);
4833 update_load_avg(cfs_rq, se, UPDATE_TG);
4834 se_update_runnable(se);
4836 cfs_rq->h_nr_running += task_delta;
4837 cfs_rq->idle_h_nr_running += idle_task_delta;
4840 /* end evaluation on encountering a throttled cfs_rq */
4841 if (cfs_rq_throttled(cfs_rq))
4842 goto unthrottle_throttle;
4845 * One parent has been throttled and cfs_rq removed from the
4846 * list. Add it back to not break the leaf list.
4848 if (throttled_hierarchy(cfs_rq))
4849 list_add_leaf_cfs_rq(cfs_rq);
4852 /* At this point se is NULL and we are at root level*/
4853 add_nr_running(rq, task_delta);
4855 unthrottle_throttle:
4857 * The cfs_rq_throttled() breaks in the above iteration can result in
4858 * incomplete leaf list maintenance, resulting in triggering the
4861 for_each_sched_entity(se) {
4862 cfs_rq = cfs_rq_of(se);
4864 if (list_add_leaf_cfs_rq(cfs_rq))
4868 assert_list_leaf_cfs_rq(rq);
4870 /* Determine whether we need to wake up potentially idle CPU: */
4871 if (rq->curr == rq->idle && rq->cfs.nr_running)
4875 static void distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
4877 struct cfs_rq *cfs_rq;
4878 u64 runtime, remaining = 1;
4881 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
4883 struct rq *rq = rq_of(cfs_rq);
4886 rq_lock_irqsave(rq, &rf);
4887 if (!cfs_rq_throttled(cfs_rq))
4890 /* By the above check, this should never be true */
4891 SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);
4893 raw_spin_lock(&cfs_b->lock);
4894 runtime = -cfs_rq->runtime_remaining + 1;
4895 if (runtime > cfs_b->runtime)
4896 runtime = cfs_b->runtime;
4897 cfs_b->runtime -= runtime;
4898 remaining = cfs_b->runtime;
4899 raw_spin_unlock(&cfs_b->lock);
4901 cfs_rq->runtime_remaining += runtime;
4903 /* we check whether we're throttled above */
4904 if (cfs_rq->runtime_remaining > 0)
4905 unthrottle_cfs_rq(cfs_rq);
4908 rq_unlock_irqrestore(rq, &rf);
4917 * Responsible for refilling a task_group's bandwidth and unthrottling its
4918 * cfs_rqs as appropriate. If there has been no activity within the last
4919 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4920 * used to track this state.
4922 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
4926 /* no need to continue the timer with no bandwidth constraint */
4927 if (cfs_b->quota == RUNTIME_INF)
4928 goto out_deactivate;
4930 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4931 cfs_b->nr_periods += overrun;
4934 * idle depends on !throttled (for the case of a large deficit), and if
4935 * we're going inactive then everything else can be deferred
4937 if (cfs_b->idle && !throttled)
4938 goto out_deactivate;
4940 __refill_cfs_bandwidth_runtime(cfs_b);
4943 /* mark as potentially idle for the upcoming period */
4948 /* account preceding periods in which throttling occurred */
4949 cfs_b->nr_throttled += overrun;
4952 * This check is repeated as we release cfs_b->lock while we unthrottle.
4954 while (throttled && cfs_b->runtime > 0) {
4955 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
4956 /* we can't nest cfs_b->lock while distributing bandwidth */
4957 distribute_cfs_runtime(cfs_b);
4958 raw_spin_lock_irqsave(&cfs_b->lock, flags);
4960 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4964 * While we are ensured activity in the period following an
4965 * unthrottle, this also covers the case in which the new bandwidth is
4966 * insufficient to cover the existing bandwidth deficit. (Forcing the
4967 * timer to remain active while there are any throttled entities.)
4977 /* a cfs_rq won't donate quota below this amount */
4978 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
4979 /* minimum remaining period time to redistribute slack quota */
4980 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
4981 /* how long we wait to gather additional slack before distributing */
4982 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
4985 * Are we near the end of the current quota period?
4987 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4988 * hrtimer base being cleared by hrtimer_start. In the case of
4989 * migrate_hrtimers, base is never cleared, so we are fine.
4991 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
4993 struct hrtimer *refresh_timer = &cfs_b->period_timer;
4996 /* if the call-back is running a quota refresh is already occurring */
4997 if (hrtimer_callback_running(refresh_timer))
5000 /* is a quota refresh about to occur? */
5001 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
5002 if (remaining < min_expire)
5008 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
5010 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
5012 /* if there's a quota refresh soon don't bother with slack */
5013 if (runtime_refresh_within(cfs_b, min_left))
5016 /* don't push forwards an existing deferred unthrottle */
5017 if (cfs_b->slack_started)
5019 cfs_b->slack_started = true;
5021 hrtimer_start(&cfs_b->slack_timer,
5022 ns_to_ktime(cfs_bandwidth_slack_period),
5026 /* we know any runtime found here is valid as update_curr() precedes return */
5027 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5029 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
5030 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
5032 if (slack_runtime <= 0)
5035 raw_spin_lock(&cfs_b->lock);
5036 if (cfs_b->quota != RUNTIME_INF) {
5037 cfs_b->runtime += slack_runtime;
5039 /* we are under rq->lock, defer unthrottling using a timer */
5040 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
5041 !list_empty(&cfs_b->throttled_cfs_rq))
5042 start_cfs_slack_bandwidth(cfs_b);
5044 raw_spin_unlock(&cfs_b->lock);
5046 /* even if it's not valid for return we don't want to try again */
5047 cfs_rq->runtime_remaining -= slack_runtime;
5050 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5052 if (!cfs_bandwidth_used())
5055 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
5058 __return_cfs_rq_runtime(cfs_rq);
5062 * This is done with a timer (instead of inline with bandwidth return) since
5063 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
5065 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
5067 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
5068 unsigned long flags;
5070 /* confirm we're still not at a refresh boundary */
5071 raw_spin_lock_irqsave(&cfs_b->lock, flags);
5072 cfs_b->slack_started = false;
5074 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
5075 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5079 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
5080 runtime = cfs_b->runtime;
5082 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5087 distribute_cfs_runtime(cfs_b);
5089 raw_spin_lock_irqsave(&cfs_b->lock, flags);
5090 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5094 * When a group wakes up we want to make sure that its quota is not already
5095 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
5096 * runtime as update_curr() throttling can not not trigger until it's on-rq.
5098 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
5100 if (!cfs_bandwidth_used())
5103 /* an active group must be handled by the update_curr()->put() path */
5104 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
5107 /* ensure the group is not already throttled */
5108 if (cfs_rq_throttled(cfs_rq))
5111 /* update runtime allocation */
5112 account_cfs_rq_runtime(cfs_rq, 0);
5113 if (cfs_rq->runtime_remaining <= 0)
5114 throttle_cfs_rq(cfs_rq);
5117 static void sync_throttle(struct task_group *tg, int cpu)
5119 struct cfs_rq *pcfs_rq, *cfs_rq;
5121 if (!cfs_bandwidth_used())
5127 cfs_rq = tg->cfs_rq[cpu];
5128 pcfs_rq = tg->parent->cfs_rq[cpu];
5130 cfs_rq->throttle_count = pcfs_rq->throttle_count;
5131 cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
5134 /* conditionally throttle active cfs_rq's from put_prev_entity() */
5135 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5137 if (!cfs_bandwidth_used())
5140 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
5144 * it's possible for a throttled entity to be forced into a running
5145 * state (e.g. set_curr_task), in this case we're finished.
5147 if (cfs_rq_throttled(cfs_rq))
5150 return throttle_cfs_rq(cfs_rq);
5153 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
5155 struct cfs_bandwidth *cfs_b =
5156 container_of(timer, struct cfs_bandwidth, slack_timer);
5158 do_sched_cfs_slack_timer(cfs_b);
5160 return HRTIMER_NORESTART;
5163 extern const u64 max_cfs_quota_period;
5165 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
5167 struct cfs_bandwidth *cfs_b =
5168 container_of(timer, struct cfs_bandwidth, period_timer);
5169 unsigned long flags;
5174 raw_spin_lock_irqsave(&cfs_b->lock, flags);
5176 overrun = hrtimer_forward_now(timer, cfs_b->period);
5180 idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);
5183 u64 new, old = ktime_to_ns(cfs_b->period);
5186 * Grow period by a factor of 2 to avoid losing precision.
5187 * Precision loss in the quota/period ratio can cause __cfs_schedulable
5191 if (new < max_cfs_quota_period) {
5192 cfs_b->period = ns_to_ktime(new);
5195 pr_warn_ratelimited(
5196 "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5198 div_u64(new, NSEC_PER_USEC),
5199 div_u64(cfs_b->quota, NSEC_PER_USEC));
5201 pr_warn_ratelimited(
5202 "cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
5204 div_u64(old, NSEC_PER_USEC),
5205 div_u64(cfs_b->quota, NSEC_PER_USEC));
5208 /* reset count so we don't come right back in here */
5213 cfs_b->period_active = 0;
5214 raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
5216 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
5219 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5221 raw_spin_lock_init(&cfs_b->lock);
5223 cfs_b->quota = RUNTIME_INF;
5224 cfs_b->period = ns_to_ktime(default_cfs_period());
5226 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
5227 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
5228 cfs_b->period_timer.function = sched_cfs_period_timer;
5229 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
5230 cfs_b->slack_timer.function = sched_cfs_slack_timer;
5231 cfs_b->slack_started = false;
5234 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
5236 cfs_rq->runtime_enabled = 0;
5237 INIT_LIST_HEAD(&cfs_rq->throttled_list);
5240 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5242 lockdep_assert_held(&cfs_b->lock);
5244 if (cfs_b->period_active)
5247 cfs_b->period_active = 1;
5248 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
5249 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
5252 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5254 /* init_cfs_bandwidth() was not called */
5255 if (!cfs_b->throttled_cfs_rq.next)
5258 hrtimer_cancel(&cfs_b->period_timer);
5259 hrtimer_cancel(&cfs_b->slack_timer);
5263 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
5265 * The race is harmless, since modifying bandwidth settings of unhooked group
5266 * bits doesn't do much.
5269 /* cpu online calback */
5270 static void __maybe_unused update_runtime_enabled(struct rq *rq)
5272 struct task_group *tg;
5274 lockdep_assert_held(&rq->lock);
5277 list_for_each_entry_rcu(tg, &task_groups, list) {
5278 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
5279 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5281 raw_spin_lock(&cfs_b->lock);
5282 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
5283 raw_spin_unlock(&cfs_b->lock);
5288 /* cpu offline callback */
5289 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
5291 struct task_group *tg;
5293 lockdep_assert_held(&rq->lock);
5296 list_for_each_entry_rcu(tg, &task_groups, list) {
5297 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
5299 if (!cfs_rq->runtime_enabled)
5303 * clock_task is not advancing so we just need to make sure
5304 * there's some valid quota amount
5306 cfs_rq->runtime_remaining = 1;
5308 * Offline rq is schedulable till CPU is completely disabled
5309 * in take_cpu_down(), so we prevent new cfs throttling here.
5311 cfs_rq->runtime_enabled = 0;
5313 if (cfs_rq_throttled(cfs_rq))
5314 unthrottle_cfs_rq(cfs_rq);
5319 #else /* CONFIG_CFS_BANDWIDTH */
5321 static inline bool cfs_bandwidth_used(void)
5326 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5327 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5328 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5329 static inline void sync_throttle(struct task_group *tg, int cpu) {}
5330 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5332 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
5337 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
5342 static inline int throttled_lb_pair(struct task_group *tg,
5343 int src_cpu, int dest_cpu)
5348 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5350 #ifdef CONFIG_FAIR_GROUP_SCHED
5351 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5354 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
5358 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5359 static inline void update_runtime_enabled(struct rq *rq) {}
5360 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5362 #endif /* CONFIG_CFS_BANDWIDTH */
5364 /**************************************************
5365 * CFS operations on tasks:
5368 #ifdef CONFIG_SCHED_HRTICK
5369 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
5371 struct sched_entity *se = &p->se;
5372 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5374 SCHED_WARN_ON(task_rq(p) != rq);
5376 if (rq->cfs.h_nr_running > 1) {
5377 u64 slice = sched_slice(cfs_rq, se);
5378 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
5379 s64 delta = slice - ran;
5386 hrtick_start(rq, delta);
5391 * called from enqueue/dequeue and updates the hrtick when the
5392 * current task is from our class and nr_running is low enough
5395 static void hrtick_update(struct rq *rq)
5397 struct task_struct *curr = rq->curr;
5399 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
5402 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
5403 hrtick_start_fair(rq, curr);
5405 #else /* !CONFIG_SCHED_HRTICK */
5407 hrtick_start_fair(struct rq *rq, struct task_struct *p)
5411 static inline void hrtick_update(struct rq *rq)
5417 static inline unsigned long cpu_util(int cpu);
5419 static inline bool cpu_overutilized(int cpu)
5421 return !fits_capacity(cpu_util(cpu), capacity_of(cpu));
5424 static inline void update_overutilized_status(struct rq *rq)
5426 if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) {
5427 WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
5428 trace_sched_overutilized_tp(rq->rd, SG_OVERUTILIZED);
5432 static inline void update_overutilized_status(struct rq *rq) { }
5435 /* Runqueue only has SCHED_IDLE tasks enqueued */
5436 static int sched_idle_rq(struct rq *rq)
5438 return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running &&
5443 static int sched_idle_cpu(int cpu)
5445 return sched_idle_rq(cpu_rq(cpu));
5450 * The enqueue_task method is called before nr_running is
5451 * increased. Here we update the fair scheduling stats and
5452 * then put the task into the rbtree:
5455 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5457 struct cfs_rq *cfs_rq;
5458 struct sched_entity *se = &p->se;
5459 int idle_h_nr_running = task_has_idle_policy(p);
5462 * The code below (indirectly) updates schedutil which looks at
5463 * the cfs_rq utilization to select a frequency.
5464 * Let's add the task's estimated utilization to the cfs_rq's
5465 * estimated utilization, before we update schedutil.
5467 util_est_enqueue(&rq->cfs, p);
5470 * If in_iowait is set, the code below may not trigger any cpufreq
5471 * utilization updates, so do it here explicitly with the IOWAIT flag
5475 cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5477 for_each_sched_entity(se) {
5480 cfs_rq = cfs_rq_of(se);
5481 enqueue_entity(cfs_rq, se, flags);
5483 cfs_rq->h_nr_running++;
5484 cfs_rq->idle_h_nr_running += idle_h_nr_running;
5486 /* end evaluation on encountering a throttled cfs_rq */
5487 if (cfs_rq_throttled(cfs_rq))
5488 goto enqueue_throttle;
5490 flags = ENQUEUE_WAKEUP;
5493 for_each_sched_entity(se) {
5494 cfs_rq = cfs_rq_of(se);
5496 update_load_avg(cfs_rq, se, UPDATE_TG);
5497 se_update_runnable(se);
5498 update_cfs_group(se);
5500 cfs_rq->h_nr_running++;
5501 cfs_rq->idle_h_nr_running += idle_h_nr_running;
5503 /* end evaluation on encountering a throttled cfs_rq */
5504 if (cfs_rq_throttled(cfs_rq))
5505 goto enqueue_throttle;
5508 * One parent has been throttled and cfs_rq removed from the
5509 * list. Add it back to not break the leaf list.
5511 if (throttled_hierarchy(cfs_rq))
5512 list_add_leaf_cfs_rq(cfs_rq);
5515 /* At this point se is NULL and we are at root level*/
5516 add_nr_running(rq, 1);
5519 * Since new tasks are assigned an initial util_avg equal to
5520 * half of the spare capacity of their CPU, tiny tasks have the
5521 * ability to cross the overutilized threshold, which will
5522 * result in the load balancer ruining all the task placement
5523 * done by EAS. As a way to mitigate that effect, do not account
5524 * for the first enqueue operation of new tasks during the
5525 * overutilized flag detection.
5527 * A better way of solving this problem would be to wait for
5528 * the PELT signals of tasks to converge before taking them
5529 * into account, but that is not straightforward to implement,
5530 * and the following generally works well enough in practice.
5532 if (flags & ENQUEUE_WAKEUP)
5533 update_overutilized_status(rq);
5536 if (cfs_bandwidth_used()) {
5538 * When bandwidth control is enabled; the cfs_rq_throttled()
5539 * breaks in the above iteration can result in incomplete
5540 * leaf list maintenance, resulting in triggering the assertion
5543 for_each_sched_entity(se) {
5544 cfs_rq = cfs_rq_of(se);
5546 if (list_add_leaf_cfs_rq(cfs_rq))
5551 assert_list_leaf_cfs_rq(rq);
5556 static void set_next_buddy(struct sched_entity *se);
5559 * The dequeue_task method is called before nr_running is
5560 * decreased. We remove the task from the rbtree and
5561 * update the fair scheduling stats:
5563 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5565 struct cfs_rq *cfs_rq;
5566 struct sched_entity *se = &p->se;
5567 int task_sleep = flags & DEQUEUE_SLEEP;
5568 int idle_h_nr_running = task_has_idle_policy(p);
5569 bool was_sched_idle = sched_idle_rq(rq);
5571 for_each_sched_entity(se) {
5572 cfs_rq = cfs_rq_of(se);
5573 dequeue_entity(cfs_rq, se, flags);
5575 cfs_rq->h_nr_running--;
5576 cfs_rq->idle_h_nr_running -= idle_h_nr_running;
5578 /* end evaluation on encountering a throttled cfs_rq */
5579 if (cfs_rq_throttled(cfs_rq))
5580 goto dequeue_throttle;
5582 /* Don't dequeue parent if it has other entities besides us */
5583 if (cfs_rq->load.weight) {
5584 /* Avoid re-evaluating load for this entity: */
5585 se = parent_entity(se);
5587 * Bias pick_next to pick a task from this cfs_rq, as
5588 * p is sleeping when it is within its sched_slice.
5590 if (task_sleep && se && !throttled_hierarchy(cfs_rq))
5594 flags |= DEQUEUE_SLEEP;
5597 for_each_sched_entity(se) {
5598 cfs_rq = cfs_rq_of(se);
5600 update_load_avg(cfs_rq, se, UPDATE_TG);
5601 se_update_runnable(se);
5602 update_cfs_group(se);
5604 cfs_rq->h_nr_running--;
5605 cfs_rq->idle_h_nr_running -= idle_h_nr_running;
5607 /* end evaluation on encountering a throttled cfs_rq */
5608 if (cfs_rq_throttled(cfs_rq))
5609 goto dequeue_throttle;
5615 sub_nr_running(rq, 1);
5617 /* balance early to pull high priority tasks */
5618 if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
5619 rq->next_balance = jiffies;
5621 util_est_dequeue(&rq->cfs, p, task_sleep);
5627 /* Working cpumask for: load_balance, load_balance_newidle. */
5628 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5629 DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
5631 #ifdef CONFIG_NO_HZ_COMMON
5634 cpumask_var_t idle_cpus_mask;
5636 int has_blocked; /* Idle CPUS has blocked load */
5637 unsigned long next_balance; /* in jiffy units */
5638 unsigned long next_blocked; /* Next update of blocked load in jiffies */
5639 } nohz ____cacheline_aligned;
5641 #endif /* CONFIG_NO_HZ_COMMON */
5643 static unsigned long cpu_load(struct rq *rq)
5645 return cfs_rq_load_avg(&rq->cfs);
5649 * cpu_load_without - compute CPU load without any contributions from *p
5650 * @cpu: the CPU which load is requested
5651 * @p: the task which load should be discounted
5653 * The load of a CPU is defined by the load of tasks currently enqueued on that
5654 * CPU as well as tasks which are currently sleeping after an execution on that
5657 * This method returns the load of the specified CPU by discounting the load of
5658 * the specified task, whenever the task is currently contributing to the CPU
5661 static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p)
5663 struct cfs_rq *cfs_rq;
5666 /* Task has no contribution or is new */
5667 if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
5668 return cpu_load(rq);
5671 load = READ_ONCE(cfs_rq->avg.load_avg);
5673 /* Discount task's util from CPU's util */
5674 lsub_positive(&load, task_h_load(p));
5679 static unsigned long cpu_runnable(struct rq *rq)
5681 return cfs_rq_runnable_avg(&rq->cfs);
5684 static unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p)
5686 struct cfs_rq *cfs_rq;
5687 unsigned int runnable;
5689 /* Task has no contribution or is new */
5690 if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
5691 return cpu_runnable(rq);
5694 runnable = READ_ONCE(cfs_rq->avg.runnable_avg);
5696 /* Discount task's runnable from CPU's runnable */
5697 lsub_positive(&runnable, p->se.avg.runnable_avg);
5702 static unsigned long capacity_of(int cpu)
5704 return cpu_rq(cpu)->cpu_capacity;
5707 static void record_wakee(struct task_struct *p)
5710 * Only decay a single time; tasks that have less then 1 wakeup per
5711 * jiffy will not have built up many flips.
5713 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
5714 current->wakee_flips >>= 1;
5715 current->wakee_flip_decay_ts = jiffies;
5718 if (current->last_wakee != p) {
5719 current->last_wakee = p;
5720 current->wakee_flips++;
5725 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5727 * A waker of many should wake a different task than the one last awakened
5728 * at a frequency roughly N times higher than one of its wakees.
5730 * In order to determine whether we should let the load spread vs consolidating
5731 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5732 * partner, and a factor of lls_size higher frequency in the other.
5734 * With both conditions met, we can be relatively sure that the relationship is
5735 * non-monogamous, with partner count exceeding socket size.
5737 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5738 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5741 static int wake_wide(struct task_struct *p)
5743 unsigned int master = current->wakee_flips;
5744 unsigned int slave = p->wakee_flips;
5745 int factor = __this_cpu_read(sd_llc_size);
5748 swap(master, slave);
5749 if (slave < factor || master < slave * factor)
5755 * The purpose of wake_affine() is to quickly determine on which CPU we can run
5756 * soonest. For the purpose of speed we only consider the waking and previous
5759 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
5760 * cache-affine and is (or will be) idle.
5762 * wake_affine_weight() - considers the weight to reflect the average
5763 * scheduling latency of the CPUs. This seems to work
5764 * for the overloaded case.
5767 wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5770 * If this_cpu is idle, it implies the wakeup is from interrupt
5771 * context. Only allow the move if cache is shared. Otherwise an
5772 * interrupt intensive workload could force all tasks onto one
5773 * node depending on the IO topology or IRQ affinity settings.
5775 * If the prev_cpu is idle and cache affine then avoid a migration.
5776 * There is no guarantee that the cache hot data from an interrupt
5777 * is more important than cache hot data on the prev_cpu and from
5778 * a cpufreq perspective, it's better to have higher utilisation
5781 if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
5782 return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5784 if (sync && cpu_rq(this_cpu)->nr_running == 1)
5787 return nr_cpumask_bits;
5791 wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
5792 int this_cpu, int prev_cpu, int sync)
5794 s64 this_eff_load, prev_eff_load;
5795 unsigned long task_load;
5797 this_eff_load = cpu_load(cpu_rq(this_cpu));
5800 unsigned long current_load = task_h_load(current);
5802 if (current_load > this_eff_load)
5805 this_eff_load -= current_load;
5808 task_load = task_h_load(p);
5810 this_eff_load += task_load;
5811 if (sched_feat(WA_BIAS))
5812 this_eff_load *= 100;
5813 this_eff_load *= capacity_of(prev_cpu);
5815 prev_eff_load = cpu_load(cpu_rq(prev_cpu));
5816 prev_eff_load -= task_load;
5817 if (sched_feat(WA_BIAS))
5818 prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
5819 prev_eff_load *= capacity_of(this_cpu);
5822 * If sync, adjust the weight of prev_eff_load such that if
5823 * prev_eff == this_eff that select_idle_sibling() will consider
5824 * stacking the wakee on top of the waker if no other CPU is
5830 return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
5833 static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5834 int this_cpu, int prev_cpu, int sync)
5836 int target = nr_cpumask_bits;
5838 if (sched_feat(WA_IDLE))
5839 target = wake_affine_idle(this_cpu, prev_cpu, sync);
5841 if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
5842 target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5844 schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5845 if (target == nr_cpumask_bits)
5848 schedstat_inc(sd->ttwu_move_affine);
5849 schedstat_inc(p->se.statistics.nr_wakeups_affine);
5853 static struct sched_group *
5854 find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu);
5857 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5860 find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5862 unsigned long load, min_load = ULONG_MAX;
5863 unsigned int min_exit_latency = UINT_MAX;
5864 u64 latest_idle_timestamp = 0;
5865 int least_loaded_cpu = this_cpu;
5866 int shallowest_idle_cpu = -1;
5869 /* Check if we have any choice: */
5870 if (group->group_weight == 1)
5871 return cpumask_first(sched_group_span(group));
5873 /* Traverse only the allowed CPUs */
5874 for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) {
5875 if (sched_idle_cpu(i))
5878 if (available_idle_cpu(i)) {
5879 struct rq *rq = cpu_rq(i);
5880 struct cpuidle_state *idle = idle_get_state(rq);
5881 if (idle && idle->exit_latency < min_exit_latency) {
5883 * We give priority to a CPU whose idle state
5884 * has the smallest exit latency irrespective
5885 * of any idle timestamp.
5887 min_exit_latency = idle->exit_latency;
5888 latest_idle_timestamp = rq->idle_stamp;
5889 shallowest_idle_cpu = i;
5890 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
5891 rq->idle_stamp > latest_idle_timestamp) {
5893 * If equal or no active idle state, then
5894 * the most recently idled CPU might have
5897 latest_idle_timestamp = rq->idle_stamp;
5898 shallowest_idle_cpu = i;
5900 } else if (shallowest_idle_cpu == -1) {
5901 load = cpu_load(cpu_rq(i));
5902 if (load < min_load) {
5904 least_loaded_cpu = i;
5909 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5912 static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
5913 int cpu, int prev_cpu, int sd_flag)
5917 if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
5921 * We need task's util for cpu_util_without, sync it up to
5922 * prev_cpu's last_update_time.
5924 if (!(sd_flag & SD_BALANCE_FORK))
5925 sync_entity_load_avg(&p->se);
5928 struct sched_group *group;
5929 struct sched_domain *tmp;
5932 if (!(sd->flags & sd_flag)) {
5937 group = find_idlest_group(sd, p, cpu);
5943 new_cpu = find_idlest_group_cpu(group, p, cpu);
5944 if (new_cpu == cpu) {
5945 /* Now try balancing at a lower domain level of 'cpu': */
5950 /* Now try balancing at a lower domain level of 'new_cpu': */
5952 weight = sd->span_weight;
5954 for_each_domain(cpu, tmp) {
5955 if (weight <= tmp->span_weight)
5957 if (tmp->flags & sd_flag)
5965 #ifdef CONFIG_SCHED_SMT
5966 DEFINE_STATIC_KEY_FALSE(sched_smt_present);
5967 EXPORT_SYMBOL_GPL(sched_smt_present);
5969 static inline void set_idle_cores(int cpu, int val)
5971 struct sched_domain_shared *sds;
5973 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
5975 WRITE_ONCE(sds->has_idle_cores, val);
5978 static inline bool test_idle_cores(int cpu, bool def)
5980 struct sched_domain_shared *sds;
5982 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
5984 return READ_ONCE(sds->has_idle_cores);
5990 * Scans the local SMT mask to see if the entire core is idle, and records this
5991 * information in sd_llc_shared->has_idle_cores.
5993 * Since SMT siblings share all cache levels, inspecting this limited remote
5994 * state should be fairly cheap.
5996 void __update_idle_core(struct rq *rq)
5998 int core = cpu_of(rq);
6002 if (test_idle_cores(core, true))
6005 for_each_cpu(cpu, cpu_smt_mask(core)) {
6009 if (!available_idle_cpu(cpu))
6013 set_idle_cores(core, 1);
6019 * Scan the entire LLC domain for idle cores; this dynamically switches off if
6020 * there are no idle cores left in the system; tracked through
6021 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
6023 static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
6025 struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6028 if (!static_branch_likely(&sched_smt_present))
6031 if (!test_idle_cores(target, false))
6034 cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6036 for_each_cpu_wrap(core, cpus, target) {
6039 for_each_cpu(cpu, cpu_smt_mask(core)) {
6040 if (!available_idle_cpu(cpu)) {
6045 cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
6052 * Failed to find an idle core; stop looking for one.
6054 set_idle_cores(target, 0);
6060 * Scan the local SMT mask for idle CPUs.
6062 static int select_idle_smt(struct task_struct *p, int target)
6066 if (!static_branch_likely(&sched_smt_present))
6069 for_each_cpu(cpu, cpu_smt_mask(target)) {
6070 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
6072 if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
6079 #else /* CONFIG_SCHED_SMT */
6081 static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
6086 static inline int select_idle_smt(struct task_struct *p, int target)
6091 #endif /* CONFIG_SCHED_SMT */
6094 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
6095 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
6096 * average idle time for this rq (as found in rq->avg_idle).
6098 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
6100 struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6101 struct sched_domain *this_sd;
6102 u64 avg_cost, avg_idle;
6104 int this = smp_processor_id();
6105 int cpu, nr = INT_MAX;
6107 this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
6112 * Due to large variance we need a large fuzz factor; hackbench in
6113 * particularly is sensitive here.
6115 avg_idle = this_rq()->avg_idle / 512;
6116 avg_cost = this_sd->avg_scan_cost + 1;
6118 if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
6121 if (sched_feat(SIS_PROP)) {
6122 u64 span_avg = sd->span_weight * avg_idle;
6123 if (span_avg > 4*avg_cost)
6124 nr = div_u64(span_avg, avg_cost);
6129 time = cpu_clock(this);
6131 cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6133 for_each_cpu_wrap(cpu, cpus, target) {
6136 if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
6140 time = cpu_clock(this) - time;
6141 update_avg(&this_sd->avg_scan_cost, time);
6147 * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
6148 * the task fits. If no CPU is big enough, but there are idle ones, try to
6149 * maximize capacity.
6152 select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
6154 unsigned long best_cap = 0;
6155 int cpu, best_cpu = -1;
6156 struct cpumask *cpus;
6158 sync_entity_load_avg(&p->se);
6160 cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6161 cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
6163 for_each_cpu_wrap(cpu, cpus, target) {
6164 unsigned long cpu_cap = capacity_of(cpu);
6166 if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
6168 if (task_fits_capacity(p, cpu_cap))
6171 if (cpu_cap > best_cap) {
6181 * Try and locate an idle core/thread in the LLC cache domain.
6183 static int select_idle_sibling(struct task_struct *p, int prev, int target)
6185 struct sched_domain *sd;
6186 int i, recent_used_cpu;
6189 * For asymmetric CPU capacity systems, our domain of interest is
6190 * sd_asym_cpucapacity rather than sd_llc.
6192 if (static_branch_unlikely(&sched_asym_cpucapacity)) {
6193 sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
6195 * On an asymmetric CPU capacity system where an exclusive
6196 * cpuset defines a symmetric island (i.e. one unique
6197 * capacity_orig value through the cpuset), the key will be set
6198 * but the CPUs within that cpuset will not have a domain with
6199 * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
6205 i = select_idle_capacity(p, sd, target);
6206 return ((unsigned)i < nr_cpumask_bits) ? i : target;
6210 if (available_idle_cpu(target) || sched_idle_cpu(target))
6214 * If the previous CPU is cache affine and idle, don't be stupid:
6216 if (prev != target && cpus_share_cache(prev, target) &&
6217 (available_idle_cpu(prev) || sched_idle_cpu(prev)))
6221 * Allow a per-cpu kthread to stack with the wakee if the
6222 * kworker thread and the tasks previous CPUs are the same.
6223 * The assumption is that the wakee queued work for the
6224 * per-cpu kthread that is now complete and the wakeup is
6225 * essentially a sync wakeup. An obvious example of this
6226 * pattern is IO completions.
6228 if (is_per_cpu_kthread(current) &&
6229 prev == smp_processor_id() &&
6230 this_rq()->nr_running <= 1) {
6234 /* Check a recently used CPU as a potential idle candidate: */
6235 recent_used_cpu = p->recent_used_cpu;
6236 if (recent_used_cpu != prev &&
6237 recent_used_cpu != target &&
6238 cpus_share_cache(recent_used_cpu, target) &&
6239 (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
6240 cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr)) {
6242 * Replace recent_used_cpu with prev as it is a potential
6243 * candidate for the next wake:
6245 p->recent_used_cpu = prev;
6246 return recent_used_cpu;
6249 sd = rcu_dereference(per_cpu(sd_llc, target));
6253 i = select_idle_core(p, sd, target);
6254 if ((unsigned)i < nr_cpumask_bits)
6257 i = select_idle_cpu(p, sd, target);
6258 if ((unsigned)i < nr_cpumask_bits)
6261 i = select_idle_smt(p, target);
6262 if ((unsigned)i < nr_cpumask_bits)
6269 * Amount of capacity of a CPU that is (estimated to be) used by CFS tasks
6270 * @cpu: the CPU to get the utilization of
6272 * The unit of the return value must be the one of capacity so we can compare
6273 * the utilization with the capacity of the CPU that is available for CFS task
6274 * (ie cpu_capacity).
6276 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
6277 * recent utilization of currently non-runnable tasks on a CPU. It represents
6278 * the amount of utilization of a CPU in the range [0..capacity_orig] where
6279 * capacity_orig is the cpu_capacity available at the highest frequency
6280 * (arch_scale_freq_capacity()).
6281 * The utilization of a CPU converges towards a sum equal to or less than the
6282 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
6283 * the running time on this CPU scaled by capacity_curr.
6285 * The estimated utilization of a CPU is defined to be the maximum between its
6286 * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
6287 * currently RUNNABLE on that CPU.
6288 * This allows to properly represent the expected utilization of a CPU which
6289 * has just got a big task running since a long sleep period. At the same time
6290 * however it preserves the benefits of the "blocked utilization" in
6291 * describing the potential for other tasks waking up on the same CPU.
6293 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
6294 * higher than capacity_orig because of unfortunate rounding in
6295 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
6296 * the average stabilizes with the new running time. We need to check that the
6297 * utilization stays within the range of [0..capacity_orig] and cap it if
6298 * necessary. Without utilization capping, a group could be seen as overloaded
6299 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
6300 * available capacity. We allow utilization to overshoot capacity_curr (but not
6301 * capacity_orig) as it useful for predicting the capacity required after task
6302 * migrations (scheduler-driven DVFS).
6304 * Return: the (estimated) utilization for the specified CPU
6306 static inline unsigned long cpu_util(int cpu)
6308 struct cfs_rq *cfs_rq;
6311 cfs_rq = &cpu_rq(cpu)->cfs;
6312 util = READ_ONCE(cfs_rq->avg.util_avg);
6314 if (sched_feat(UTIL_EST))
6315 util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
6317 return min_t(unsigned long, util, capacity_orig_of(cpu));
6321 * cpu_util_without: compute cpu utilization without any contributions from *p
6322 * @cpu: the CPU which utilization is requested
6323 * @p: the task which utilization should be discounted
6325 * The utilization of a CPU is defined by the utilization of tasks currently
6326 * enqueued on that CPU as well as tasks which are currently sleeping after an
6327 * execution on that CPU.
6329 * This method returns the utilization of the specified CPU by discounting the
6330 * utilization of the specified task, whenever the task is currently
6331 * contributing to the CPU utilization.
6333 static unsigned long cpu_util_without(int cpu, struct task_struct *p)
6335 struct cfs_rq *cfs_rq;
6338 /* Task has no contribution or is new */
6339 if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
6340 return cpu_util(cpu);
6342 cfs_rq = &cpu_rq(cpu)->cfs;
6343 util = READ_ONCE(cfs_rq->avg.util_avg);
6345 /* Discount task's util from CPU's util */
6346 lsub_positive(&util, task_util(p));
6351 * a) if *p is the only task sleeping on this CPU, then:
6352 * cpu_util (== task_util) > util_est (== 0)
6353 * and thus we return:
6354 * cpu_util_without = (cpu_util - task_util) = 0
6356 * b) if other tasks are SLEEPING on this CPU, which is now exiting
6358 * cpu_util >= task_util
6359 * cpu_util > util_est (== 0)
6360 * and thus we discount *p's blocked utilization to return:
6361 * cpu_util_without = (cpu_util - task_util) >= 0
6363 * c) if other tasks are RUNNABLE on that CPU and
6364 * util_est > cpu_util
6365 * then we use util_est since it returns a more restrictive
6366 * estimation of the spare capacity on that CPU, by just
6367 * considering the expected utilization of tasks already
6368 * runnable on that CPU.
6370 * Cases a) and b) are covered by the above code, while case c) is
6371 * covered by the following code when estimated utilization is
6374 if (sched_feat(UTIL_EST)) {
6375 unsigned int estimated =
6376 READ_ONCE(cfs_rq->avg.util_est.enqueued);
6379 * Despite the following checks we still have a small window
6380 * for a possible race, when an execl's select_task_rq_fair()
6381 * races with LB's detach_task():
6384 * p->on_rq = TASK_ON_RQ_MIGRATING;
6385 * ---------------------------------- A
6386 * deactivate_task() \
6387 * dequeue_task() + RaceTime
6388 * util_est_dequeue() /
6389 * ---------------------------------- B
6391 * The additional check on "current == p" it's required to
6392 * properly fix the execl regression and it helps in further
6393 * reducing the chances for the above race.
6395 if (unlikely(task_on_rq_queued(p) || current == p))
6396 lsub_positive(&estimated, _task_util_est(p));
6398 util = max(util, estimated);
6402 * Utilization (estimated) can exceed the CPU capacity, thus let's
6403 * clamp to the maximum CPU capacity to ensure consistency with
6404 * the cpu_util call.
6406 return min_t(unsigned long, util, capacity_orig_of(cpu));
6410 * Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued)
6413 static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
6415 struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
6416 unsigned long util_est, util = READ_ONCE(cfs_rq->avg.util_avg);
6419 * If @p migrates from @cpu to another, remove its contribution. Or,
6420 * if @p migrates from another CPU to @cpu, add its contribution. In
6421 * the other cases, @cpu is not impacted by the migration, so the
6422 * util_avg should already be correct.
6424 if (task_cpu(p) == cpu && dst_cpu != cpu)
6425 sub_positive(&util, task_util(p));
6426 else if (task_cpu(p) != cpu && dst_cpu == cpu)
6427 util += task_util(p);
6429 if (sched_feat(UTIL_EST)) {
6430 util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);
6433 * During wake-up, the task isn't enqueued yet and doesn't
6434 * appear in the cfs_rq->avg.util_est.enqueued of any rq,
6435 * so just add it (if needed) to "simulate" what will be
6436 * cpu_util() after the task has been enqueued.
6439 util_est += _task_util_est(p);
6441 util = max(util, util_est);
6444 return min(util, capacity_orig_of(cpu));
6448 * compute_energy(): Estimates the energy that @pd would consume if @p was
6449 * migrated to @dst_cpu. compute_energy() predicts what will be the utilization
6450 * landscape of @pd's CPUs after the task migration, and uses the Energy Model
6451 * to compute what would be the energy if we decided to actually migrate that
6455 compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
6457 struct cpumask *pd_mask = perf_domain_span(pd);
6458 unsigned long cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask));
6459 unsigned long max_util = 0, sum_util = 0;
6463 * The capacity state of CPUs of the current rd can be driven by CPUs
6464 * of another rd if they belong to the same pd. So, account for the
6465 * utilization of these CPUs too by masking pd with cpu_online_mask
6466 * instead of the rd span.
6468 * If an entire pd is outside of the current rd, it will not appear in
6469 * its pd list and will not be accounted by compute_energy().
6471 for_each_cpu_and(cpu, pd_mask, cpu_online_mask) {
6472 unsigned long cpu_util, util_cfs = cpu_util_next(cpu, p, dst_cpu);
6473 struct task_struct *tsk = cpu == dst_cpu ? p : NULL;
6476 * Busy time computation: utilization clamping is not
6477 * required since the ratio (sum_util / cpu_capacity)
6478 * is already enough to scale the EM reported power
6479 * consumption at the (eventually clamped) cpu_capacity.
6481 sum_util += schedutil_cpu_util(cpu, util_cfs, cpu_cap,
6485 * Performance domain frequency: utilization clamping
6486 * must be considered since it affects the selection
6487 * of the performance domain frequency.
6488 * NOTE: in case RT tasks are running, by default the
6489 * FREQUENCY_UTIL's utilization can be max OPP.
6491 cpu_util = schedutil_cpu_util(cpu, util_cfs, cpu_cap,
6492 FREQUENCY_UTIL, tsk);
6493 max_util = max(max_util, cpu_util);
6496 return em_pd_energy(pd->em_pd, max_util, sum_util);
6500 * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
6501 * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
6502 * spare capacity in each performance domain and uses it as a potential
6503 * candidate to execute the task. Then, it uses the Energy Model to figure
6504 * out which of the CPU candidates is the most energy-efficient.
6506 * The rationale for this heuristic is as follows. In a performance domain,
6507 * all the most energy efficient CPU candidates (according to the Energy
6508 * Model) are those for which we'll request a low frequency. When there are
6509 * several CPUs for which the frequency request will be the same, we don't
6510 * have enough data to break the tie between them, because the Energy Model
6511 * only includes active power costs. With this model, if we assume that
6512 * frequency requests follow utilization (e.g. using schedutil), the CPU with
6513 * the maximum spare capacity in a performance domain is guaranteed to be among
6514 * the best candidates of the performance domain.
6516 * In practice, it could be preferable from an energy standpoint to pack
6517 * small tasks on a CPU in order to let other CPUs go in deeper idle states,
6518 * but that could also hurt our chances to go cluster idle, and we have no
6519 * ways to tell with the current Energy Model if this is actually a good
6520 * idea or not. So, find_energy_efficient_cpu() basically favors
6521 * cluster-packing, and spreading inside a cluster. That should at least be
6522 * a good thing for latency, and this is consistent with the idea that most
6523 * of the energy savings of EAS come from the asymmetry of the system, and
6524 * not so much from breaking the tie between identical CPUs. That's also the
6525 * reason why EAS is enabled in the topology code only for systems where
6526 * SD_ASYM_CPUCAPACITY is set.
6528 * NOTE: Forkees are not accepted in the energy-aware wake-up path because
6529 * they don't have any useful utilization data yet and it's not possible to
6530 * forecast their impact on energy consumption. Consequently, they will be
6531 * placed by find_idlest_cpu() on the least loaded CPU, which might turn out
6532 * to be energy-inefficient in some use-cases. The alternative would be to
6533 * bias new tasks towards specific types of CPUs first, or to try to infer
6534 * their util_avg from the parent task, but those heuristics could hurt
6535 * other use-cases too. So, until someone finds a better way to solve this,
6536 * let's keep things simple by re-using the existing slow path.
6538 static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
6540 unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
6541 struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
6542 unsigned long cpu_cap, util, base_energy = 0;
6543 int cpu, best_energy_cpu = prev_cpu;
6544 struct sched_domain *sd;
6545 struct perf_domain *pd;
6548 pd = rcu_dereference(rd->pd);
6549 if (!pd || READ_ONCE(rd->overutilized))
6553 * Energy-aware wake-up happens on the lowest sched_domain starting
6554 * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
6556 sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
6557 while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
6562 sync_entity_load_avg(&p->se);
6563 if (!task_util_est(p))
6566 for (; pd; pd = pd->next) {
6567 unsigned long cur_delta, spare_cap, max_spare_cap = 0;
6568 unsigned long base_energy_pd;
6569 int max_spare_cap_cpu = -1;
6571 /* Compute the 'base' energy of the pd, without @p */
6572 base_energy_pd = compute_energy(p, -1, pd);
6573 base_energy += base_energy_pd;
6575 for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) {
6576 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
6579 util = cpu_util_next(cpu, p, cpu);
6580 cpu_cap = capacity_of(cpu);
6581 spare_cap = cpu_cap - util;
6584 * Skip CPUs that cannot satisfy the capacity request.
6585 * IOW, placing the task there would make the CPU
6586 * overutilized. Take uclamp into account to see how
6587 * much capacity we can get out of the CPU; this is
6588 * aligned with schedutil_cpu_util().
6590 util = uclamp_rq_util_with(cpu_rq(cpu), util, p);
6591 if (!fits_capacity(util, cpu_cap))
6594 /* Always use prev_cpu as a candidate. */
6595 if (cpu == prev_cpu) {
6596 prev_delta = compute_energy(p, prev_cpu, pd);
6597 prev_delta -= base_energy_pd;
6598 best_delta = min(best_delta, prev_delta);
6602 * Find the CPU with the maximum spare capacity in
6603 * the performance domain
6605 if (spare_cap > max_spare_cap) {
6606 max_spare_cap = spare_cap;
6607 max_spare_cap_cpu = cpu;
6611 /* Evaluate the energy impact of using this CPU. */
6612 if (max_spare_cap_cpu >= 0 && max_spare_cap_cpu != prev_cpu) {
6613 cur_delta = compute_energy(p, max_spare_cap_cpu, pd);
6614 cur_delta -= base_energy_pd;
6615 if (cur_delta < best_delta) {
6616 best_delta = cur_delta;
6617 best_energy_cpu = max_spare_cap_cpu;
6625 * Pick the best CPU if prev_cpu cannot be used, or if it saves at
6626 * least 6% of the energy used by prev_cpu.
6628 if (prev_delta == ULONG_MAX)
6629 return best_energy_cpu;
6631 if ((prev_delta - best_delta) > ((prev_delta + base_energy) >> 4))
6632 return best_energy_cpu;
6643 * select_task_rq_fair: Select target runqueue for the waking task in domains
6644 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
6645 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
6647 * Balances load by selecting the idlest CPU in the idlest group, or under
6648 * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
6650 * Returns the target CPU number.
6652 * preempt must be disabled.
6655 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6657 struct sched_domain *tmp, *sd = NULL;
6658 int cpu = smp_processor_id();
6659 int new_cpu = prev_cpu;
6660 int want_affine = 0;
6661 int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6663 if (sd_flag & SD_BALANCE_WAKE) {
6666 if (sched_energy_enabled()) {
6667 new_cpu = find_energy_efficient_cpu(p, prev_cpu);
6673 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
6677 for_each_domain(cpu, tmp) {
6679 * If both 'cpu' and 'prev_cpu' are part of this domain,
6680 * cpu is a valid SD_WAKE_AFFINE target.
6682 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
6683 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
6684 if (cpu != prev_cpu)
6685 new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
6687 sd = NULL; /* Prefer wake_affine over balance flags */
6691 if (tmp->flags & sd_flag)
6693 else if (!want_affine)
6699 new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6700 } else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
6703 new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
6706 current->recent_used_cpu = cpu;
6713 static void detach_entity_cfs_rq(struct sched_entity *se);
6716 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6717 * cfs_rq_of(p) references at time of call are still valid and identify the
6718 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6720 static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
6723 * As blocked tasks retain absolute vruntime the migration needs to
6724 * deal with this by subtracting the old and adding the new
6725 * min_vruntime -- the latter is done by enqueue_entity() when placing
6726 * the task on the new runqueue.
6728 if (p->state == TASK_WAKING) {
6729 struct sched_entity *se = &p->se;
6730 struct cfs_rq *cfs_rq = cfs_rq_of(se);
6733 #ifndef CONFIG_64BIT
6734 u64 min_vruntime_copy;
6737 min_vruntime_copy = cfs_rq->min_vruntime_copy;
6739 min_vruntime = cfs_rq->min_vruntime;
6740 } while (min_vruntime != min_vruntime_copy);
6742 min_vruntime = cfs_rq->min_vruntime;
6745 se->vruntime -= min_vruntime;
6748 if (p->on_rq == TASK_ON_RQ_MIGRATING) {
6750 * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
6751 * rq->lock and can modify state directly.
6753 lockdep_assert_held(&task_rq(p)->lock);
6754 detach_entity_cfs_rq(&p->se);
6758 * We are supposed to update the task to "current" time, then
6759 * its up to date and ready to go to new CPU/cfs_rq. But we
6760 * have difficulty in getting what current time is, so simply
6761 * throw away the out-of-date time. This will result in the
6762 * wakee task is less decayed, but giving the wakee more load
6765 remove_entity_load_avg(&p->se);
6768 /* Tell new CPU we are migrated */
6769 p->se.avg.last_update_time = 0;
6771 /* We have migrated, no longer consider this task hot */
6772 p->se.exec_start = 0;
6774 update_scan_period(p, new_cpu);
6777 static void task_dead_fair(struct task_struct *p)
6779 remove_entity_load_avg(&p->se);
6783 balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6788 return newidle_balance(rq, rf) != 0;
6790 #endif /* CONFIG_SMP */
6792 static unsigned long wakeup_gran(struct sched_entity *se)
6794 unsigned long gran = sysctl_sched_wakeup_granularity;
6797 * Since its curr running now, convert the gran from real-time
6798 * to virtual-time in his units.
6800 * By using 'se' instead of 'curr' we penalize light tasks, so
6801 * they get preempted easier. That is, if 'se' < 'curr' then
6802 * the resulting gran will be larger, therefore penalizing the
6803 * lighter, if otoh 'se' > 'curr' then the resulting gran will
6804 * be smaller, again penalizing the lighter task.
6806 * This is especially important for buddies when the leftmost
6807 * task is higher priority than the buddy.
6809 return calc_delta_fair(gran, se);
6813 * Should 'se' preempt 'curr'.
6827 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
6829 s64 gran, vdiff = curr->vruntime - se->vruntime;
6834 gran = wakeup_gran(se);
6841 static void set_last_buddy(struct sched_entity *se)
6843 if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
6846 for_each_sched_entity(se) {
6847 if (SCHED_WARN_ON(!se->on_rq))
6849 cfs_rq_of(se)->last = se;
6853 static void set_next_buddy(struct sched_entity *se)
6855 if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se))))
6858 for_each_sched_entity(se) {
6859 if (SCHED_WARN_ON(!se->on_rq))
6861 cfs_rq_of(se)->next = se;
6865 static void set_skip_buddy(struct sched_entity *se)
6867 for_each_sched_entity(se)
6868 cfs_rq_of(se)->skip = se;
6872 * Preempt the current task with a newly woken task if needed:
6874 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6876 struct task_struct *curr = rq->curr;
6877 struct sched_entity *se = &curr->se, *pse = &p->se;
6878 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6879 int scale = cfs_rq->nr_running >= sched_nr_latency;
6880 int next_buddy_marked = 0;
6882 if (unlikely(se == pse))
6886 * This is possible from callers such as attach_tasks(), in which we
6887 * unconditionally check_prempt_curr() after an enqueue (which may have
6888 * lead to a throttle). This both saves work and prevents false
6889 * next-buddy nomination below.
6891 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
6894 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
6895 set_next_buddy(pse);
6896 next_buddy_marked = 1;
6900 * We can come here with TIF_NEED_RESCHED already set from new task
6903 * Note: this also catches the edge-case of curr being in a throttled
6904 * group (e.g. via set_curr_task), since update_curr() (in the
6905 * enqueue of curr) will have resulted in resched being set. This
6906 * prevents us from potentially nominating it as a false LAST_BUDDY
6909 if (test_tsk_need_resched(curr))
6912 /* Idle tasks are by definition preempted by non-idle tasks. */
6913 if (unlikely(task_has_idle_policy(curr)) &&
6914 likely(!task_has_idle_policy(p)))
6918 * Batch and idle tasks do not preempt non-idle tasks (their preemption
6919 * is driven by the tick):
6921 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6924 find_matching_se(&se, &pse);
6925 update_curr(cfs_rq_of(se));
6927 if (wakeup_preempt_entity(se, pse) == 1) {
6929 * Bias pick_next to pick the sched entity that is
6930 * triggering this preemption.
6932 if (!next_buddy_marked)
6933 set_next_buddy(pse);
6942 * Only set the backward buddy when the current task is still
6943 * on the rq. This can happen when a wakeup gets interleaved
6944 * with schedule on the ->pre_schedule() or idle_balance()
6945 * point, either of which can * drop the rq lock.
6947 * Also, during early boot the idle thread is in the fair class,
6948 * for obvious reasons its a bad idea to schedule back to it.
6950 if (unlikely(!se->on_rq || curr == rq->idle))
6953 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
6957 struct task_struct *
6958 pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6960 struct cfs_rq *cfs_rq = &rq->cfs;
6961 struct sched_entity *se;
6962 struct task_struct *p;
6966 if (!sched_fair_runnable(rq))
6969 #ifdef CONFIG_FAIR_GROUP_SCHED
6970 if (!prev || prev->sched_class != &fair_sched_class)
6974 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
6975 * likely that a next task is from the same cgroup as the current.
6977 * Therefore attempt to avoid putting and setting the entire cgroup
6978 * hierarchy, only change the part that actually changes.
6982 struct sched_entity *curr = cfs_rq->curr;
6985 * Since we got here without doing put_prev_entity() we also
6986 * have to consider cfs_rq->curr. If it is still a runnable
6987 * entity, update_curr() will update its vruntime, otherwise
6988 * forget we've ever seen it.
6992 update_curr(cfs_rq);
6997 * This call to check_cfs_rq_runtime() will do the
6998 * throttle and dequeue its entity in the parent(s).
6999 * Therefore the nr_running test will indeed
7002 if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
7005 if (!cfs_rq->nr_running)
7012 se = pick_next_entity(cfs_rq, curr);
7013 cfs_rq = group_cfs_rq(se);
7019 * Since we haven't yet done put_prev_entity and if the selected task
7020 * is a different task than we started out with, try and touch the
7021 * least amount of cfs_rqs.
7024 struct sched_entity *pse = &prev->se;
7026 while (!(cfs_rq = is_same_group(se, pse))) {
7027 int se_depth = se->depth;
7028 int pse_depth = pse->depth;
7030 if (se_depth <= pse_depth) {
7031 put_prev_entity(cfs_rq_of(pse), pse);
7032 pse = parent_entity(pse);
7034 if (se_depth >= pse_depth) {
7035 set_next_entity(cfs_rq_of(se), se);
7036 se = parent_entity(se);
7040 put_prev_entity(cfs_rq, pse);
7041 set_next_entity(cfs_rq, se);
7048 put_prev_task(rq, prev);
7051 se = pick_next_entity(cfs_rq, NULL);
7052 set_next_entity(cfs_rq, se);
7053 cfs_rq = group_cfs_rq(se);
7058 done: __maybe_unused;
7061 * Move the next running task to the front of
7062 * the list, so our cfs_tasks list becomes MRU
7065 list_move(&p->se.group_node, &rq->cfs_tasks);
7068 if (hrtick_enabled(rq))
7069 hrtick_start_fair(rq, p);
7071 update_misfit_status(p, rq);
7079 new_tasks = newidle_balance(rq, rf);
7082 * Because newidle_balance() releases (and re-acquires) rq->lock, it is
7083 * possible for any higher priority task to appear. In that case we
7084 * must re-start the pick_next_entity() loop.
7093 * rq is about to be idle, check if we need to update the
7094 * lost_idle_time of clock_pelt
7096 update_idle_rq_clock_pelt(rq);
7101 static struct task_struct *__pick_next_task_fair(struct rq *rq)
7103 return pick_next_task_fair(rq, NULL, NULL);
7107 * Account for a descheduled task:
7109 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
7111 struct sched_entity *se = &prev->se;
7112 struct cfs_rq *cfs_rq;
7114 for_each_sched_entity(se) {
7115 cfs_rq = cfs_rq_of(se);
7116 put_prev_entity(cfs_rq, se);
7121 * sched_yield() is very simple
7123 * The magic of dealing with the ->skip buddy is in pick_next_entity.
7125 static void yield_task_fair(struct rq *rq)
7127 struct task_struct *curr = rq->curr;
7128 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
7129 struct sched_entity *se = &curr->se;
7132 * Are we the only task in the tree?
7134 if (unlikely(rq->nr_running == 1))
7137 clear_buddies(cfs_rq, se);
7139 if (curr->policy != SCHED_BATCH) {
7140 update_rq_clock(rq);
7142 * Update run-time statistics of the 'current'.
7144 update_curr(cfs_rq);
7146 * Tell update_rq_clock() that we've just updated,
7147 * so we don't do microscopic update in schedule()
7148 * and double the fastpath cost.
7150 rq_clock_skip_update(rq);
7156 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
7158 struct sched_entity *se = &p->se;
7160 /* throttled hierarchies are not runnable */
7161 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
7164 /* Tell the scheduler that we'd really like pse to run next. */
7167 yield_task_fair(rq);
7173 /**************************************************
7174 * Fair scheduling class load-balancing methods.
7178 * The purpose of load-balancing is to achieve the same basic fairness the
7179 * per-CPU scheduler provides, namely provide a proportional amount of compute
7180 * time to each task. This is expressed in the following equation:
7182 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
7184 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
7185 * W_i,0 is defined as:
7187 * W_i,0 = \Sum_j w_i,j (2)
7189 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
7190 * is derived from the nice value as per sched_prio_to_weight[].
7192 * The weight average is an exponential decay average of the instantaneous
7195 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
7197 * C_i is the compute capacity of CPU i, typically it is the
7198 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
7199 * can also include other factors [XXX].
7201 * To achieve this balance we define a measure of imbalance which follows
7202 * directly from (1):
7204 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
7206 * We them move tasks around to minimize the imbalance. In the continuous
7207 * function space it is obvious this converges, in the discrete case we get
7208 * a few fun cases generally called infeasible weight scenarios.
7211 * - infeasible weights;
7212 * - local vs global optima in the discrete case. ]
7217 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
7218 * for all i,j solution, we create a tree of CPUs that follows the hardware
7219 * topology where each level pairs two lower groups (or better). This results
7220 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
7221 * tree to only the first of the previous level and we decrease the frequency
7222 * of load-balance at each level inv. proportional to the number of CPUs in
7228 * \Sum { --- * --- * 2^i } = O(n) (5)
7230 * `- size of each group
7231 * | | `- number of CPUs doing load-balance
7233 * `- sum over all levels
7235 * Coupled with a limit on how many tasks we can migrate every balance pass,
7236 * this makes (5) the runtime complexity of the balancer.
7238 * An important property here is that each CPU is still (indirectly) connected
7239 * to every other CPU in at most O(log n) steps:
7241 * The adjacency matrix of the resulting graph is given by:
7244 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
7247 * And you'll find that:
7249 * A^(log_2 n)_i,j != 0 for all i,j (7)
7251 * Showing there's indeed a path between every CPU in at most O(log n) steps.
7252 * The task movement gives a factor of O(m), giving a convergence complexity
7255 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
7260 * In order to avoid CPUs going idle while there's still work to do, new idle
7261 * balancing is more aggressive and has the newly idle CPU iterate up the domain
7262 * tree itself instead of relying on other CPUs to bring it work.
7264 * This adds some complexity to both (5) and (8) but it reduces the total idle
7272 * Cgroups make a horror show out of (2), instead of a simple sum we get:
7275 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
7280 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
7282 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
7284 * The big problem is S_k, its a global sum needed to compute a local (W_i)
7287 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
7288 * rewrite all of this once again.]
7291 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
7293 enum fbq_type { regular, remote, all };
7296 * 'group_type' describes the group of CPUs at the moment of load balancing.
7298 * The enum is ordered by pulling priority, with the group with lowest priority
7299 * first so the group_type can simply be compared when selecting the busiest
7300 * group. See update_sd_pick_busiest().
7303 /* The group has spare capacity that can be used to run more tasks. */
7304 group_has_spare = 0,
7306 * The group is fully used and the tasks don't compete for more CPU
7307 * cycles. Nevertheless, some tasks might wait before running.
7311 * SD_ASYM_CPUCAPACITY only: One task doesn't fit with CPU's capacity
7312 * and must be migrated to a more powerful CPU.
7316 * SD_ASYM_PACKING only: One local CPU with higher capacity is available,
7317 * and the task should be migrated to it instead of running on the
7322 * The tasks' affinity constraints previously prevented the scheduler
7323 * from balancing the load across the system.
7327 * The CPU is overloaded and can't provide expected CPU cycles to all
7333 enum migration_type {
7340 #define LBF_ALL_PINNED 0x01
7341 #define LBF_NEED_BREAK 0x02
7342 #define LBF_DST_PINNED 0x04
7343 #define LBF_SOME_PINNED 0x08
7344 #define LBF_NOHZ_STATS 0x10
7345 #define LBF_NOHZ_AGAIN 0x20
7348 struct sched_domain *sd;
7356 struct cpumask *dst_grpmask;
7358 enum cpu_idle_type idle;
7360 /* The set of CPUs under consideration for load-balancing */
7361 struct cpumask *cpus;
7366 unsigned int loop_break;
7367 unsigned int loop_max;
7369 enum fbq_type fbq_type;
7370 enum migration_type migration_type;
7371 struct list_head tasks;
7375 * Is this task likely cache-hot:
7377 static int task_hot(struct task_struct *p, struct lb_env *env)
7381 lockdep_assert_held(&env->src_rq->lock);
7383 if (p->sched_class != &fair_sched_class)
7386 if (unlikely(task_has_idle_policy(p)))
7390 * Buddy candidates are cache hot:
7392 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
7393 (&p->se == cfs_rq_of(&p->se)->next ||
7394 &p->se == cfs_rq_of(&p->se)->last))
7397 if (sysctl_sched_migration_cost == -1)
7399 if (sysctl_sched_migration_cost == 0)
7402 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
7404 return delta < (s64)sysctl_sched_migration_cost;
7407 #ifdef CONFIG_NUMA_BALANCING
7409 * Returns 1, if task migration degrades locality
7410 * Returns 0, if task migration improves locality i.e migration preferred.
7411 * Returns -1, if task migration is not affected by locality.
7413 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
7415 struct numa_group *numa_group = rcu_dereference(p->numa_group);
7416 unsigned long src_weight, dst_weight;
7417 int src_nid, dst_nid, dist;
7419 if (!static_branch_likely(&sched_numa_balancing))
7422 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
7425 src_nid = cpu_to_node(env->src_cpu);
7426 dst_nid = cpu_to_node(env->dst_cpu);
7428 if (src_nid == dst_nid)
7431 /* Migrating away from the preferred node is always bad. */
7432 if (src_nid == p->numa_preferred_nid) {
7433 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
7439 /* Encourage migration to the preferred node. */
7440 if (dst_nid == p->numa_preferred_nid)
7443 /* Leaving a core idle is often worse than degrading locality. */
7444 if (env->idle == CPU_IDLE)
7447 dist = node_distance(src_nid, dst_nid);
7449 src_weight = group_weight(p, src_nid, dist);
7450 dst_weight = group_weight(p, dst_nid, dist);
7452 src_weight = task_weight(p, src_nid, dist);
7453 dst_weight = task_weight(p, dst_nid, dist);
7456 return dst_weight < src_weight;
7460 static inline int migrate_degrades_locality(struct task_struct *p,
7468 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
7471 int can_migrate_task(struct task_struct *p, struct lb_env *env)
7475 lockdep_assert_held(&env->src_rq->lock);
7478 * We do not migrate tasks that are:
7479 * 1) throttled_lb_pair, or
7480 * 2) cannot be migrated to this CPU due to cpus_ptr, or
7481 * 3) running (obviously), or
7482 * 4) are cache-hot on their current CPU.
7484 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
7487 if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) {
7490 schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7492 env->flags |= LBF_SOME_PINNED;
7495 * Remember if this task can be migrated to any other CPU in
7496 * our sched_group. We may want to revisit it if we couldn't
7497 * meet load balance goals by pulling other tasks on src_cpu.
7499 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
7500 * already computed one in current iteration.
7502 if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
7505 /* Prevent to re-select dst_cpu via env's CPUs: */
7506 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7507 if (cpumask_test_cpu(cpu, p->cpus_ptr)) {
7508 env->flags |= LBF_DST_PINNED;
7509 env->new_dst_cpu = cpu;
7517 /* Record that we found atleast one task that could run on dst_cpu */
7518 env->flags &= ~LBF_ALL_PINNED;
7520 if (task_running(env->src_rq, p)) {
7521 schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7526 * Aggressive migration if:
7527 * 1) destination numa is preferred
7528 * 2) task is cache cold, or
7529 * 3) too many balance attempts have failed.
7531 tsk_cache_hot = migrate_degrades_locality(p, env);
7532 if (tsk_cache_hot == -1)
7533 tsk_cache_hot = task_hot(p, env);
7535 if (tsk_cache_hot <= 0 ||
7536 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7537 if (tsk_cache_hot == 1) {
7538 schedstat_inc(env->sd->lb_hot_gained[env->idle]);
7539 schedstat_inc(p->se.statistics.nr_forced_migrations);
7544 schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
7549 * detach_task() -- detach the task for the migration specified in env
7551 static void detach_task(struct task_struct *p, struct lb_env *env)
7553 lockdep_assert_held(&env->src_rq->lock);
7555 deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7556 set_task_cpu(p, env->dst_cpu);
7560 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7561 * part of active balancing operations within "domain".
7563 * Returns a task if successful and NULL otherwise.
7565 static struct task_struct *detach_one_task(struct lb_env *env)
7567 struct task_struct *p;
7569 lockdep_assert_held(&env->src_rq->lock);
7571 list_for_each_entry_reverse(p,
7572 &env->src_rq->cfs_tasks, se.group_node) {
7573 if (!can_migrate_task(p, env))
7576 detach_task(p, env);
7579 * Right now, this is only the second place where
7580 * lb_gained[env->idle] is updated (other is detach_tasks)
7581 * so we can safely collect stats here rather than
7582 * inside detach_tasks().
7584 schedstat_inc(env->sd->lb_gained[env->idle]);
7590 static const unsigned int sched_nr_migrate_break = 32;
7593 * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
7594 * busiest_rq, as part of a balancing operation within domain "sd".
7596 * Returns number of detached tasks if successful and 0 otherwise.
7598 static int detach_tasks(struct lb_env *env)
7600 struct list_head *tasks = &env->src_rq->cfs_tasks;
7601 unsigned long util, load;
7602 struct task_struct *p;
7605 lockdep_assert_held(&env->src_rq->lock);
7607 if (env->imbalance <= 0)
7610 while (!list_empty(tasks)) {
7612 * We don't want to steal all, otherwise we may be treated likewise,
7613 * which could at worst lead to a livelock crash.
7615 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
7618 p = list_last_entry(tasks, struct task_struct, se.group_node);
7621 /* We've more or less seen every task there is, call it quits */
7622 if (env->loop > env->loop_max)
7625 /* take a breather every nr_migrate tasks */
7626 if (env->loop > env->loop_break) {
7627 env->loop_break += sched_nr_migrate_break;
7628 env->flags |= LBF_NEED_BREAK;
7632 if (!can_migrate_task(p, env))
7635 switch (env->migration_type) {
7637 load = task_h_load(p);
7639 if (sched_feat(LB_MIN) &&
7640 load < 16 && !env->sd->nr_balance_failed)
7644 * Make sure that we don't migrate too much load.
7645 * Nevertheless, let relax the constraint if
7646 * scheduler fails to find a good waiting task to
7649 if (load/2 > env->imbalance &&
7650 env->sd->nr_balance_failed <= env->sd->cache_nice_tries)
7653 env->imbalance -= load;
7657 util = task_util_est(p);
7659 if (util > env->imbalance)
7662 env->imbalance -= util;
7669 case migrate_misfit:
7670 /* This is not a misfit task */
7671 if (task_fits_capacity(p, capacity_of(env->src_cpu)))
7678 detach_task(p, env);
7679 list_add(&p->se.group_node, &env->tasks);
7683 #ifdef CONFIG_PREEMPTION
7685 * NEWIDLE balancing is a source of latency, so preemptible
7686 * kernels will stop after the first task is detached to minimize
7687 * the critical section.
7689 if (env->idle == CPU_NEWLY_IDLE)
7694 * We only want to steal up to the prescribed amount of
7697 if (env->imbalance <= 0)
7702 list_move(&p->se.group_node, tasks);
7706 * Right now, this is one of only two places we collect this stat
7707 * so we can safely collect detach_one_task() stats here rather
7708 * than inside detach_one_task().
7710 schedstat_add(env->sd->lb_gained[env->idle], detached);
7716 * attach_task() -- attach the task detached by detach_task() to its new rq.
7718 static void attach_task(struct rq *rq, struct task_struct *p)
7720 lockdep_assert_held(&rq->lock);
7722 BUG_ON(task_rq(p) != rq);
7723 activate_task(rq, p, ENQUEUE_NOCLOCK);
7724 check_preempt_curr(rq, p, 0);
7728 * attach_one_task() -- attaches the task returned from detach_one_task() to
7731 static void attach_one_task(struct rq *rq, struct task_struct *p)
7736 update_rq_clock(rq);
7742 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
7745 static void attach_tasks(struct lb_env *env)
7747 struct list_head *tasks = &env->tasks;
7748 struct task_struct *p;
7751 rq_lock(env->dst_rq, &rf);
7752 update_rq_clock(env->dst_rq);
7754 while (!list_empty(tasks)) {
7755 p = list_first_entry(tasks, struct task_struct, se.group_node);
7756 list_del_init(&p->se.group_node);
7758 attach_task(env->dst_rq, p);
7761 rq_unlock(env->dst_rq, &rf);
7764 #ifdef CONFIG_NO_HZ_COMMON
7765 static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
7767 if (cfs_rq->avg.load_avg)
7770 if (cfs_rq->avg.util_avg)
7776 static inline bool others_have_blocked(struct rq *rq)
7778 if (READ_ONCE(rq->avg_rt.util_avg))
7781 if (READ_ONCE(rq->avg_dl.util_avg))
7784 if (thermal_load_avg(rq))
7787 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
7788 if (READ_ONCE(rq->avg_irq.util_avg))
7795 static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
7797 rq->last_blocked_load_update_tick = jiffies;
7800 rq->has_blocked_load = 0;
7803 static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq) { return false; }
7804 static inline bool others_have_blocked(struct rq *rq) { return false; }
7805 static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {}
7808 static bool __update_blocked_others(struct rq *rq, bool *done)
7810 const struct sched_class *curr_class;
7811 u64 now = rq_clock_pelt(rq);
7812 unsigned long thermal_pressure;
7816 * update_load_avg() can call cpufreq_update_util(). Make sure that RT,
7817 * DL and IRQ signals have been updated before updating CFS.
7819 curr_class = rq->curr->sched_class;
7821 thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
7823 decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
7824 update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
7825 update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
7826 update_irq_load_avg(rq, 0);
7828 if (others_have_blocked(rq))
7834 #ifdef CONFIG_FAIR_GROUP_SCHED
7836 static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
7838 if (cfs_rq->load.weight)
7841 if (cfs_rq->avg.load_sum)
7844 if (cfs_rq->avg.util_sum)
7847 if (cfs_rq->avg.runnable_sum)
7853 static bool __update_blocked_fair(struct rq *rq, bool *done)
7855 struct cfs_rq *cfs_rq, *pos;
7856 bool decayed = false;
7857 int cpu = cpu_of(rq);
7860 * Iterates the task_group tree in a bottom up fashion, see
7861 * list_add_leaf_cfs_rq() for details.
7863 for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
7864 struct sched_entity *se;
7866 if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
7867 update_tg_load_avg(cfs_rq, 0);
7869 if (cfs_rq == &rq->cfs)
7873 /* Propagate pending load changes to the parent, if any: */
7874 se = cfs_rq->tg->se[cpu];
7875 if (se && !skip_blocked_update(se))
7876 update_load_avg(cfs_rq_of(se), se, 0);
7879 * There can be a lot of idle CPU cgroups. Don't let fully
7880 * decayed cfs_rqs linger on the list.
7882 if (cfs_rq_is_decayed(cfs_rq))
7883 list_del_leaf_cfs_rq(cfs_rq);
7885 /* Don't need periodic decay once load/util_avg are null */
7886 if (cfs_rq_has_blocked(cfs_rq))
7894 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7895 * This needs to be done in a top-down fashion because the load of a child
7896 * group is a fraction of its parents load.
7898 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7900 struct rq *rq = rq_of(cfs_rq);
7901 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7902 unsigned long now = jiffies;
7905 if (cfs_rq->last_h_load_update == now)
7908 WRITE_ONCE(cfs_rq->h_load_next, NULL);
7909 for_each_sched_entity(se) {
7910 cfs_rq = cfs_rq_of(se);
7911 WRITE_ONCE(cfs_rq->h_load_next, se);
7912 if (cfs_rq->last_h_load_update == now)
7917 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7918 cfs_rq->last_h_load_update = now;
7921 while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
7922 load = cfs_rq->h_load;
7923 load = div64_ul(load * se->avg.load_avg,
7924 cfs_rq_load_avg(cfs_rq) + 1);
7925 cfs_rq = group_cfs_rq(se);
7926 cfs_rq->h_load = load;
7927 cfs_rq->last_h_load_update = now;
7931 static unsigned long task_h_load(struct task_struct *p)
7933 struct cfs_rq *cfs_rq = task_cfs_rq(p);
7935 update_cfs_rq_h_load(cfs_rq);
7936 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7937 cfs_rq_load_avg(cfs_rq) + 1);
7940 static bool __update_blocked_fair(struct rq *rq, bool *done)
7942 struct cfs_rq *cfs_rq = &rq->cfs;
7945 decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
7946 if (cfs_rq_has_blocked(cfs_rq))
7952 static unsigned long task_h_load(struct task_struct *p)
7954 return p->se.avg.load_avg;
7958 static void update_blocked_averages(int cpu)
7960 bool decayed = false, done = true;
7961 struct rq *rq = cpu_rq(cpu);
7964 rq_lock_irqsave(rq, &rf);
7965 update_rq_clock(rq);
7967 decayed |= __update_blocked_others(rq, &done);
7968 decayed |= __update_blocked_fair(rq, &done);
7970 update_blocked_load_status(rq, !done);
7972 cpufreq_update_util(rq, 0);
7973 rq_unlock_irqrestore(rq, &rf);
7976 /********** Helpers for find_busiest_group ************************/
7979 * sg_lb_stats - stats of a sched_group required for load_balancing
7981 struct sg_lb_stats {
7982 unsigned long avg_load; /*Avg load across the CPUs of the group */
7983 unsigned long group_load; /* Total load over the CPUs of the group */
7984 unsigned long group_capacity;
7985 unsigned long group_util; /* Total utilization over the CPUs of the group */
7986 unsigned long group_runnable; /* Total runnable time over the CPUs of the group */
7987 unsigned int sum_nr_running; /* Nr of tasks running in the group */
7988 unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
7989 unsigned int idle_cpus;
7990 unsigned int group_weight;
7991 enum group_type group_type;
7992 unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
7993 unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
7994 #ifdef CONFIG_NUMA_BALANCING
7995 unsigned int nr_numa_running;
7996 unsigned int nr_preferred_running;
8001 * sd_lb_stats - Structure to store the statistics of a sched_domain
8002 * during load balancing.
8004 struct sd_lb_stats {
8005 struct sched_group *busiest; /* Busiest group in this sd */
8006 struct sched_group *local; /* Local group in this sd */
8007 unsigned long total_load; /* Total load of all groups in sd */
8008 unsigned long total_capacity; /* Total capacity of all groups in sd */
8009 unsigned long avg_load; /* Average load across all groups in sd */
8010 unsigned int prefer_sibling; /* tasks should go to sibling first */
8012 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
8013 struct sg_lb_stats local_stat; /* Statistics of the local group */
8016 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
8019 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
8020 * local_stat because update_sg_lb_stats() does a full clear/assignment.
8021 * We must however set busiest_stat::group_type and
8022 * busiest_stat::idle_cpus to the worst busiest group because
8023 * update_sd_pick_busiest() reads these before assignment.
8025 *sds = (struct sd_lb_stats){
8029 .total_capacity = 0UL,
8031 .idle_cpus = UINT_MAX,
8032 .group_type = group_has_spare,
8037 static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
8039 struct rq *rq = cpu_rq(cpu);
8040 unsigned long max = arch_scale_cpu_capacity(cpu);
8041 unsigned long used, free;
8044 irq = cpu_util_irq(rq);
8046 if (unlikely(irq >= max))
8050 * avg_rt.util_avg and avg_dl.util_avg track binary signals
8051 * (running and not running) with weights 0 and 1024 respectively.
8052 * avg_thermal.load_avg tracks thermal pressure and the weighted
8053 * average uses the actual delta max capacity(load).
8055 used = READ_ONCE(rq->avg_rt.util_avg);
8056 used += READ_ONCE(rq->avg_dl.util_avg);
8057 used += thermal_load_avg(rq);
8059 if (unlikely(used >= max))
8064 return scale_irq_capacity(free, irq, max);
8067 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
8069 unsigned long capacity = scale_rt_capacity(sd, cpu);
8070 struct sched_group *sdg = sd->groups;
8072 cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);
8077 cpu_rq(cpu)->cpu_capacity = capacity;
8078 sdg->sgc->capacity = capacity;
8079 sdg->sgc->min_capacity = capacity;
8080 sdg->sgc->max_capacity = capacity;
8083 void update_group_capacity(struct sched_domain *sd, int cpu)
8085 struct sched_domain *child = sd->child;
8086 struct sched_group *group, *sdg = sd->groups;
8087 unsigned long capacity, min_capacity, max_capacity;
8088 unsigned long interval;
8090 interval = msecs_to_jiffies(sd->balance_interval);
8091 interval = clamp(interval, 1UL, max_load_balance_interval);
8092 sdg->sgc->next_update = jiffies + interval;
8095 update_cpu_capacity(sd, cpu);
8100 min_capacity = ULONG_MAX;
8103 if (child->flags & SD_OVERLAP) {
8105 * SD_OVERLAP domains cannot assume that child groups
8106 * span the current group.
8109 for_each_cpu(cpu, sched_group_span(sdg)) {
8110 unsigned long cpu_cap = capacity_of(cpu);
8112 capacity += cpu_cap;
8113 min_capacity = min(cpu_cap, min_capacity);
8114 max_capacity = max(cpu_cap, max_capacity);
8118 * !SD_OVERLAP domains can assume that child groups
8119 * span the current group.
8122 group = child->groups;
8124 struct sched_group_capacity *sgc = group->sgc;
8126 capacity += sgc->capacity;
8127 min_capacity = min(sgc->min_capacity, min_capacity);
8128 max_capacity = max(sgc->max_capacity, max_capacity);
8129 group = group->next;
8130 } while (group != child->groups);
8133 sdg->sgc->capacity = capacity;
8134 sdg->sgc->min_capacity = min_capacity;
8135 sdg->sgc->max_capacity = max_capacity;
8139 * Check whether the capacity of the rq has been noticeably reduced by side
8140 * activity. The imbalance_pct is used for the threshold.
8141 * Return true is the capacity is reduced
8144 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
8146 return ((rq->cpu_capacity * sd->imbalance_pct) <
8147 (rq->cpu_capacity_orig * 100));
8151 * Check whether a rq has a misfit task and if it looks like we can actually
8152 * help that task: we can migrate the task to a CPU of higher capacity, or
8153 * the task's current CPU is heavily pressured.
8155 static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
8157 return rq->misfit_task_load &&
8158 (rq->cpu_capacity_orig < rq->rd->max_cpu_capacity ||
8159 check_cpu_capacity(rq, sd));
8163 * Group imbalance indicates (and tries to solve) the problem where balancing
8164 * groups is inadequate due to ->cpus_ptr constraints.
8166 * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
8167 * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
8170 * { 0 1 2 3 } { 4 5 6 7 }
8173 * If we were to balance group-wise we'd place two tasks in the first group and
8174 * two tasks in the second group. Clearly this is undesired as it will overload
8175 * cpu 3 and leave one of the CPUs in the second group unused.
8177 * The current solution to this issue is detecting the skew in the first group
8178 * by noticing the lower domain failed to reach balance and had difficulty
8179 * moving tasks due to affinity constraints.
8181 * When this is so detected; this group becomes a candidate for busiest; see
8182 * update_sd_pick_busiest(). And calculate_imbalance() and
8183 * find_busiest_group() avoid some of the usual balance conditions to allow it
8184 * to create an effective group imbalance.
8186 * This is a somewhat tricky proposition since the next run might not find the
8187 * group imbalance and decide the groups need to be balanced again. A most
8188 * subtle and fragile situation.
8191 static inline int sg_imbalanced(struct sched_group *group)
8193 return group->sgc->imbalance;
8197 * group_has_capacity returns true if the group has spare capacity that could
8198 * be used by some tasks.
8199 * We consider that a group has spare capacity if the * number of task is
8200 * smaller than the number of CPUs or if the utilization is lower than the
8201 * available capacity for CFS tasks.
8202 * For the latter, we use a threshold to stabilize the state, to take into
8203 * account the variance of the tasks' load and to return true if the available
8204 * capacity in meaningful for the load balancer.
8205 * As an example, an available capacity of 1% can appear but it doesn't make
8206 * any benefit for the load balance.
8209 group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
8211 if (sgs->sum_nr_running < sgs->group_weight)
8214 if ((sgs->group_capacity * imbalance_pct) <
8215 (sgs->group_runnable * 100))
8218 if ((sgs->group_capacity * 100) >
8219 (sgs->group_util * imbalance_pct))
8226 * group_is_overloaded returns true if the group has more tasks than it can
8228 * group_is_overloaded is not equals to !group_has_capacity because a group
8229 * with the exact right number of tasks, has no more spare capacity but is not
8230 * overloaded so both group_has_capacity and group_is_overloaded return
8234 group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
8236 if (sgs->sum_nr_running <= sgs->group_weight)
8239 if ((sgs->group_capacity * 100) <
8240 (sgs->group_util * imbalance_pct))
8243 if ((sgs->group_capacity * imbalance_pct) <
8244 (sgs->group_runnable * 100))
8251 * group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller
8252 * per-CPU capacity than sched_group ref.
8255 group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
8257 return fits_capacity(sg->sgc->min_capacity, ref->sgc->min_capacity);
8261 * group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller
8262 * per-CPU capacity_orig than sched_group ref.
8265 group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
8267 return fits_capacity(sg->sgc->max_capacity, ref->sgc->max_capacity);
8271 group_type group_classify(unsigned int imbalance_pct,
8272 struct sched_group *group,
8273 struct sg_lb_stats *sgs)
8275 if (group_is_overloaded(imbalance_pct, sgs))
8276 return group_overloaded;
8278 if (sg_imbalanced(group))
8279 return group_imbalanced;
8281 if (sgs->group_asym_packing)
8282 return group_asym_packing;
8284 if (sgs->group_misfit_task_load)
8285 return group_misfit_task;
8287 if (!group_has_capacity(imbalance_pct, sgs))
8288 return group_fully_busy;
8290 return group_has_spare;
8293 static bool update_nohz_stats(struct rq *rq, bool force)
8295 #ifdef CONFIG_NO_HZ_COMMON
8296 unsigned int cpu = rq->cpu;
8298 if (!rq->has_blocked_load)
8301 if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
8304 if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
8307 update_blocked_averages(cpu);
8309 return rq->has_blocked_load;
8316 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
8317 * @env: The load balancing environment.
8318 * @group: sched_group whose statistics are to be updated.
8319 * @sgs: variable to hold the statistics for this group.
8320 * @sg_status: Holds flag indicating the status of the sched_group
8322 static inline void update_sg_lb_stats(struct lb_env *env,
8323 struct sched_group *group,
8324 struct sg_lb_stats *sgs,
8327 int i, nr_running, local_group;
8329 memset(sgs, 0, sizeof(*sgs));
8331 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(group));
8333 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8334 struct rq *rq = cpu_rq(i);
8336 if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
8337 env->flags |= LBF_NOHZ_AGAIN;
8339 sgs->group_load += cpu_load(rq);
8340 sgs->group_util += cpu_util(i);
8341 sgs->group_runnable += cpu_runnable(rq);
8342 sgs->sum_h_nr_running += rq->cfs.h_nr_running;
8344 nr_running = rq->nr_running;
8345 sgs->sum_nr_running += nr_running;
8348 *sg_status |= SG_OVERLOAD;
8350 if (cpu_overutilized(i))
8351 *sg_status |= SG_OVERUTILIZED;
8353 #ifdef CONFIG_NUMA_BALANCING
8354 sgs->nr_numa_running += rq->nr_numa_running;
8355 sgs->nr_preferred_running += rq->nr_preferred_running;
8358 * No need to call idle_cpu() if nr_running is not 0
8360 if (!nr_running && idle_cpu(i)) {
8362 /* Idle cpu can't have misfit task */
8369 /* Check for a misfit task on the cpu */
8370 if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
8371 sgs->group_misfit_task_load < rq->misfit_task_load) {
8372 sgs->group_misfit_task_load = rq->misfit_task_load;
8373 *sg_status |= SG_OVERLOAD;
8377 /* Check if dst CPU is idle and preferred to this group */
8378 if (env->sd->flags & SD_ASYM_PACKING &&
8379 env->idle != CPU_NOT_IDLE &&
8380 sgs->sum_h_nr_running &&
8381 sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) {
8382 sgs->group_asym_packing = 1;
8385 sgs->group_capacity = group->sgc->capacity;
8387 sgs->group_weight = group->group_weight;
8389 sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);
8391 /* Computing avg_load makes sense only when group is overloaded */
8392 if (sgs->group_type == group_overloaded)
8393 sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
8394 sgs->group_capacity;
8398 * update_sd_pick_busiest - return 1 on busiest group
8399 * @env: The load balancing environment.
8400 * @sds: sched_domain statistics
8401 * @sg: sched_group candidate to be checked for being the busiest
8402 * @sgs: sched_group statistics
8404 * Determine if @sg is a busier group than the previously selected
8407 * Return: %true if @sg is a busier group than the previously selected
8408 * busiest group. %false otherwise.
8410 static bool update_sd_pick_busiest(struct lb_env *env,
8411 struct sd_lb_stats *sds,
8412 struct sched_group *sg,
8413 struct sg_lb_stats *sgs)
8415 struct sg_lb_stats *busiest = &sds->busiest_stat;
8417 /* Make sure that there is at least one task to pull */
8418 if (!sgs->sum_h_nr_running)
8422 * Don't try to pull misfit tasks we can't help.
8423 * We can use max_capacity here as reduction in capacity on some
8424 * CPUs in the group should either be possible to resolve
8425 * internally or be covered by avg_load imbalance (eventually).
8427 if (sgs->group_type == group_misfit_task &&
8428 (!group_smaller_max_cpu_capacity(sg, sds->local) ||
8429 sds->local_stat.group_type != group_has_spare))
8432 if (sgs->group_type > busiest->group_type)
8435 if (sgs->group_type < busiest->group_type)
8439 * The candidate and the current busiest group are the same type of
8440 * group. Let check which one is the busiest according to the type.
8443 switch (sgs->group_type) {
8444 case group_overloaded:
8445 /* Select the overloaded group with highest avg_load. */
8446 if (sgs->avg_load <= busiest->avg_load)
8450 case group_imbalanced:
8452 * Select the 1st imbalanced group as we don't have any way to
8453 * choose one more than another.
8457 case group_asym_packing:
8458 /* Prefer to move from lowest priority CPU's work */
8459 if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu))
8463 case group_misfit_task:
8465 * If we have more than one misfit sg go with the biggest
8468 if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
8472 case group_fully_busy:
8474 * Select the fully busy group with highest avg_load. In
8475 * theory, there is no need to pull task from such kind of
8476 * group because tasks have all compute capacity that they need
8477 * but we can still improve the overall throughput by reducing
8478 * contention when accessing shared HW resources.
8480 * XXX for now avg_load is not computed and always 0 so we
8481 * select the 1st one.
8483 if (sgs->avg_load <= busiest->avg_load)
8487 case group_has_spare:
8489 * Select not overloaded group with lowest number of idle cpus
8490 * and highest number of running tasks. We could also compare
8491 * the spare capacity which is more stable but it can end up
8492 * that the group has less spare capacity but finally more idle
8493 * CPUs which means less opportunity to pull tasks.
8495 if (sgs->idle_cpus > busiest->idle_cpus)
8497 else if ((sgs->idle_cpus == busiest->idle_cpus) &&
8498 (sgs->sum_nr_running <= busiest->sum_nr_running))
8505 * Candidate sg has no more than one task per CPU and has higher
8506 * per-CPU capacity. Migrating tasks to less capable CPUs may harm
8507 * throughput. Maximize throughput, power/energy consequences are not
8510 if ((env->sd->flags & SD_ASYM_CPUCAPACITY) &&
8511 (sgs->group_type <= group_fully_busy) &&
8512 (group_smaller_min_cpu_capacity(sds->local, sg)))
8518 #ifdef CONFIG_NUMA_BALANCING
8519 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8521 if (sgs->sum_h_nr_running > sgs->nr_numa_running)
8523 if (sgs->sum_h_nr_running > sgs->nr_preferred_running)
8528 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8530 if (rq->nr_running > rq->nr_numa_running)
8532 if (rq->nr_running > rq->nr_preferred_running)
8537 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
8542 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
8546 #endif /* CONFIG_NUMA_BALANCING */
8552 * task_running_on_cpu - return 1 if @p is running on @cpu.
8555 static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
8557 /* Task has no contribution or is new */
8558 if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
8561 if (task_on_rq_queued(p))
8568 * idle_cpu_without - would a given CPU be idle without p ?
8569 * @cpu: the processor on which idleness is tested.
8570 * @p: task which should be ignored.
8572 * Return: 1 if the CPU would be idle. 0 otherwise.
8574 static int idle_cpu_without(int cpu, struct task_struct *p)
8576 struct rq *rq = cpu_rq(cpu);
8578 if (rq->curr != rq->idle && rq->curr != p)
8582 * rq->nr_running can't be used but an updated version without the
8583 * impact of p on cpu must be used instead. The updated nr_running
8584 * be computed and tested before calling idle_cpu_without().
8588 if (!llist_empty(&rq->wake_list))
8596 * update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
8597 * @sd: The sched_domain level to look for idlest group.
8598 * @group: sched_group whose statistics are to be updated.
8599 * @sgs: variable to hold the statistics for this group.
8600 * @p: The task for which we look for the idlest group/CPU.
8602 static inline void update_sg_wakeup_stats(struct sched_domain *sd,
8603 struct sched_group *group,
8604 struct sg_lb_stats *sgs,
8605 struct task_struct *p)
8609 memset(sgs, 0, sizeof(*sgs));
8611 for_each_cpu(i, sched_group_span(group)) {
8612 struct rq *rq = cpu_rq(i);
8615 sgs->group_load += cpu_load_without(rq, p);
8616 sgs->group_util += cpu_util_without(i, p);
8617 sgs->group_runnable += cpu_runnable_without(rq, p);
8618 local = task_running_on_cpu(i, p);
8619 sgs->sum_h_nr_running += rq->cfs.h_nr_running - local;
8621 nr_running = rq->nr_running - local;
8622 sgs->sum_nr_running += nr_running;
8625 * No need to call idle_cpu_without() if nr_running is not 0
8627 if (!nr_running && idle_cpu_without(i, p))
8632 /* Check if task fits in the group */
8633 if (sd->flags & SD_ASYM_CPUCAPACITY &&
8634 !task_fits_capacity(p, group->sgc->max_capacity)) {
8635 sgs->group_misfit_task_load = 1;
8638 sgs->group_capacity = group->sgc->capacity;
8640 sgs->group_weight = group->group_weight;
8642 sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
8645 * Computing avg_load makes sense only when group is fully busy or
8648 if (sgs->group_type == group_fully_busy ||
8649 sgs->group_type == group_overloaded)
8650 sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) /
8651 sgs->group_capacity;
8654 static bool update_pick_idlest(struct sched_group *idlest,
8655 struct sg_lb_stats *idlest_sgs,
8656 struct sched_group *group,
8657 struct sg_lb_stats *sgs)
8659 if (sgs->group_type < idlest_sgs->group_type)
8662 if (sgs->group_type > idlest_sgs->group_type)
8666 * The candidate and the current idlest group are the same type of
8667 * group. Let check which one is the idlest according to the type.
8670 switch (sgs->group_type) {
8671 case group_overloaded:
8672 case group_fully_busy:
8673 /* Select the group with lowest avg_load. */
8674 if (idlest_sgs->avg_load <= sgs->avg_load)
8678 case group_imbalanced:
8679 case group_asym_packing:
8680 /* Those types are not used in the slow wakeup path */
8683 case group_misfit_task:
8684 /* Select group with the highest max capacity */
8685 if (idlest->sgc->max_capacity >= group->sgc->max_capacity)
8689 case group_has_spare:
8690 /* Select group with most idle CPUs */
8691 if (idlest_sgs->idle_cpus >= sgs->idle_cpus)
8700 * find_idlest_group() finds and returns the least busy CPU group within the
8703 * Assumes p is allowed on at least one CPU in sd.
8705 static struct sched_group *
8706 find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
8708 struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups;
8709 struct sg_lb_stats local_sgs, tmp_sgs;
8710 struct sg_lb_stats *sgs;
8711 unsigned long imbalance;
8712 struct sg_lb_stats idlest_sgs = {
8713 .avg_load = UINT_MAX,
8714 .group_type = group_overloaded,
8717 imbalance = scale_load_down(NICE_0_LOAD) *
8718 (sd->imbalance_pct-100) / 100;
8723 /* Skip over this group if it has no CPUs allowed */
8724 if (!cpumask_intersects(sched_group_span(group),
8728 local_group = cpumask_test_cpu(this_cpu,
8729 sched_group_span(group));
8738 update_sg_wakeup_stats(sd, group, sgs, p);
8740 if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) {
8745 } while (group = group->next, group != sd->groups);
8748 /* There is no idlest group to push tasks to */
8752 /* The local group has been skipped because of CPU affinity */
8757 * If the local group is idler than the selected idlest group
8758 * don't try and push the task.
8760 if (local_sgs.group_type < idlest_sgs.group_type)
8764 * If the local group is busier than the selected idlest group
8765 * try and push the task.
8767 if (local_sgs.group_type > idlest_sgs.group_type)
8770 switch (local_sgs.group_type) {
8771 case group_overloaded:
8772 case group_fully_busy:
8774 * When comparing groups across NUMA domains, it's possible for
8775 * the local domain to be very lightly loaded relative to the
8776 * remote domains but "imbalance" skews the comparison making
8777 * remote CPUs look much more favourable. When considering
8778 * cross-domain, add imbalance to the load on the remote node
8779 * and consider staying local.
8782 if ((sd->flags & SD_NUMA) &&
8783 ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load))
8787 * If the local group is less loaded than the selected
8788 * idlest group don't try and push any tasks.
8790 if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance))
8793 if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load)
8797 case group_imbalanced:
8798 case group_asym_packing:
8799 /* Those type are not used in the slow wakeup path */
8802 case group_misfit_task:
8803 /* Select group with the highest max capacity */
8804 if (local->sgc->max_capacity >= idlest->sgc->max_capacity)
8808 case group_has_spare:
8809 if (sd->flags & SD_NUMA) {
8810 #ifdef CONFIG_NUMA_BALANCING
8813 * If there is spare capacity at NUMA, try to select
8814 * the preferred node
8816 if (cpu_to_node(this_cpu) == p->numa_preferred_nid)
8819 idlest_cpu = cpumask_first(sched_group_span(idlest));
8820 if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid)
8824 * Otherwise, keep the task on this node to stay close
8825 * its wakeup source and improve locality. If there is
8826 * a real need of migration, periodic load balance will
8829 if (local_sgs.idle_cpus)
8834 * Select group with highest number of idle CPUs. We could also
8835 * compare the utilization which is more stable but it can end
8836 * up that the group has less spare capacity but finally more
8837 * idle CPUs which means more opportunity to run task.
8839 if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus)
8848 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
8849 * @env: The load balancing environment.
8850 * @sds: variable to hold the statistics for this sched_domain.
8853 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
8855 struct sched_domain *child = env->sd->child;
8856 struct sched_group *sg = env->sd->groups;
8857 struct sg_lb_stats *local = &sds->local_stat;
8858 struct sg_lb_stats tmp_sgs;
8861 #ifdef CONFIG_NO_HZ_COMMON
8862 if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
8863 env->flags |= LBF_NOHZ_STATS;
8867 struct sg_lb_stats *sgs = &tmp_sgs;
8870 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
8875 if (env->idle != CPU_NEWLY_IDLE ||
8876 time_after_eq(jiffies, sg->sgc->next_update))
8877 update_group_capacity(env->sd, env->dst_cpu);
8880 update_sg_lb_stats(env, sg, sgs, &sg_status);
8886 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
8888 sds->busiest_stat = *sgs;
8892 /* Now, start updating sd_lb_stats */
8893 sds->total_load += sgs->group_load;
8894 sds->total_capacity += sgs->group_capacity;
8897 } while (sg != env->sd->groups);
8899 /* Tag domain that child domain prefers tasks go to siblings first */
8900 sds->prefer_sibling = child && child->flags & SD_PREFER_SIBLING;
8902 #ifdef CONFIG_NO_HZ_COMMON
8903 if ((env->flags & LBF_NOHZ_AGAIN) &&
8904 cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) {
8906 WRITE_ONCE(nohz.next_blocked,
8907 jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD));
8911 if (env->sd->flags & SD_NUMA)
8912 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
8914 if (!env->sd->parent) {
8915 struct root_domain *rd = env->dst_rq->rd;
8917 /* update overload indicator if we are at root domain */
8918 WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD);
8920 /* Update over-utilization (tipping point, U >= 0) indicator */
8921 WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
8922 trace_sched_overutilized_tp(rd, sg_status & SG_OVERUTILIZED);
8923 } else if (sg_status & SG_OVERUTILIZED) {
8924 struct root_domain *rd = env->dst_rq->rd;
8926 WRITE_ONCE(rd->overutilized, SG_OVERUTILIZED);
8927 trace_sched_overutilized_tp(rd, SG_OVERUTILIZED);
8931 static inline long adjust_numa_imbalance(int imbalance, int src_nr_running)
8933 unsigned int imbalance_min;
8936 * Allow a small imbalance based on a simple pair of communicating
8937 * tasks that remain local when the source domain is almost idle.
8940 if (src_nr_running <= imbalance_min)
8947 * calculate_imbalance - Calculate the amount of imbalance present within the
8948 * groups of a given sched_domain during load balance.
8949 * @env: load balance environment
8950 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
8952 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8954 struct sg_lb_stats *local, *busiest;
8956 local = &sds->local_stat;
8957 busiest = &sds->busiest_stat;
8959 if (busiest->group_type == group_misfit_task) {
8960 /* Set imbalance to allow misfit tasks to be balanced. */
8961 env->migration_type = migrate_misfit;
8966 if (busiest->group_type == group_asym_packing) {
8968 * In case of asym capacity, we will try to migrate all load to
8969 * the preferred CPU.
8971 env->migration_type = migrate_task;
8972 env->imbalance = busiest->sum_h_nr_running;
8976 if (busiest->group_type == group_imbalanced) {
8978 * In the group_imb case we cannot rely on group-wide averages
8979 * to ensure CPU-load equilibrium, try to move any task to fix
8980 * the imbalance. The next load balance will take care of
8981 * balancing back the system.
8983 env->migration_type = migrate_task;
8989 * Try to use spare capacity of local group without overloading it or
8992 if (local->group_type == group_has_spare) {
8993 if (busiest->group_type > group_fully_busy) {
8995 * If busiest is overloaded, try to fill spare
8996 * capacity. This might end up creating spare capacity
8997 * in busiest or busiest still being overloaded but
8998 * there is no simple way to directly compute the
8999 * amount of load to migrate in order to balance the
9002 env->migration_type = migrate_util;
9003 env->imbalance = max(local->group_capacity, local->group_util) -
9007 * In some cases, the group's utilization is max or even
9008 * higher than capacity because of migrations but the
9009 * local CPU is (newly) idle. There is at least one
9010 * waiting task in this overloaded busiest group. Let's
9013 if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) {
9014 env->migration_type = migrate_task;
9021 if (busiest->group_weight == 1 || sds->prefer_sibling) {
9022 unsigned int nr_diff = busiest->sum_nr_running;
9024 * When prefer sibling, evenly spread running tasks on
9027 env->migration_type = migrate_task;
9028 lsub_positive(&nr_diff, local->sum_nr_running);
9029 env->imbalance = nr_diff >> 1;
9033 * If there is no overload, we just want to even the number of
9036 env->migration_type = migrate_task;
9037 env->imbalance = max_t(long, 0, (local->idle_cpus -
9038 busiest->idle_cpus) >> 1);
9041 /* Consider allowing a small imbalance between NUMA groups */
9042 if (env->sd->flags & SD_NUMA)
9043 env->imbalance = adjust_numa_imbalance(env->imbalance,
9044 busiest->sum_nr_running);
9050 * Local is fully busy but has to take more load to relieve the
9053 if (local->group_type < group_overloaded) {
9055 * Local will become overloaded so the avg_load metrics are
9059 local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) /
9060 local->group_capacity;
9062 sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) /
9063 sds->total_capacity;
9065 * If the local group is more loaded than the selected
9066 * busiest group don't try to pull any tasks.
9068 if (local->avg_load >= busiest->avg_load) {
9075 * Both group are or will become overloaded and we're trying to get all
9076 * the CPUs to the average_load, so we don't want to push ourselves
9077 * above the average load, nor do we wish to reduce the max loaded CPU
9078 * below the average load. At the same time, we also don't want to
9079 * reduce the group load below the group capacity. Thus we look for
9080 * the minimum possible imbalance.
9082 env->migration_type = migrate_load;
9083 env->imbalance = min(
9084 (busiest->avg_load - sds->avg_load) * busiest->group_capacity,
9085 (sds->avg_load - local->avg_load) * local->group_capacity
9086 ) / SCHED_CAPACITY_SCALE;
9089 /******* find_busiest_group() helpers end here *********************/
9092 * Decision matrix according to the local and busiest group type:
9094 * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
9095 * has_spare nr_idle balanced N/A N/A balanced balanced
9096 * fully_busy nr_idle nr_idle N/A N/A balanced balanced
9097 * misfit_task force N/A N/A N/A force force
9098 * asym_packing force force N/A N/A force force
9099 * imbalanced force force N/A N/A force force
9100 * overloaded force force N/A N/A force avg_load
9102 * N/A : Not Applicable because already filtered while updating
9104 * balanced : The system is balanced for these 2 groups.
9105 * force : Calculate the imbalance as load migration is probably needed.
9106 * avg_load : Only if imbalance is significant enough.
9107 * nr_idle : dst_cpu is not busy and the number of idle CPUs is quite
9108 * different in groups.
9112 * find_busiest_group - Returns the busiest group within the sched_domain
9113 * if there is an imbalance.
9115 * Also calculates the amount of runnable load which should be moved
9116 * to restore balance.
9118 * @env: The load balancing environment.
9120 * Return: - The busiest group if imbalance exists.
9122 static struct sched_group *find_busiest_group(struct lb_env *env)
9124 struct sg_lb_stats *local, *busiest;
9125 struct sd_lb_stats sds;
9127 init_sd_lb_stats(&sds);
9130 * Compute the various statistics relevant for load balancing at
9133 update_sd_lb_stats(env, &sds);
9135 if (sched_energy_enabled()) {
9136 struct root_domain *rd = env->dst_rq->rd;
9138 if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
9142 local = &sds.local_stat;
9143 busiest = &sds.busiest_stat;
9145 /* There is no busy sibling group to pull tasks from */
9149 /* Misfit tasks should be dealt with regardless of the avg load */
9150 if (busiest->group_type == group_misfit_task)
9153 /* ASYM feature bypasses nice load balance check */
9154 if (busiest->group_type == group_asym_packing)
9158 * If the busiest group is imbalanced the below checks don't
9159 * work because they assume all things are equal, which typically
9160 * isn't true due to cpus_ptr constraints and the like.
9162 if (busiest->group_type == group_imbalanced)
9166 * If the local group is busier than the selected busiest group
9167 * don't try and pull any tasks.
9169 if (local->group_type > busiest->group_type)
9173 * When groups are overloaded, use the avg_load to ensure fairness
9176 if (local->group_type == group_overloaded) {
9178 * If the local group is more loaded than the selected
9179 * busiest group don't try to pull any tasks.
9181 if (local->avg_load >= busiest->avg_load)
9184 /* XXX broken for overlapping NUMA groups */
9185 sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) /
9189 * Don't pull any tasks if this group is already above the
9190 * domain average load.
9192 if (local->avg_load >= sds.avg_load)
9196 * If the busiest group is more loaded, use imbalance_pct to be
9199 if (100 * busiest->avg_load <=
9200 env->sd->imbalance_pct * local->avg_load)
9204 /* Try to move all excess tasks to child's sibling domain */
9205 if (sds.prefer_sibling && local->group_type == group_has_spare &&
9206 busiest->sum_nr_running > local->sum_nr_running + 1)
9209 if (busiest->group_type != group_overloaded) {
9210 if (env->idle == CPU_NOT_IDLE)
9212 * If the busiest group is not overloaded (and as a
9213 * result the local one too) but this CPU is already
9214 * busy, let another idle CPU try to pull task.
9218 if (busiest->group_weight > 1 &&
9219 local->idle_cpus <= (busiest->idle_cpus + 1))
9221 * If the busiest group is not overloaded
9222 * and there is no imbalance between this and busiest
9223 * group wrt idle CPUs, it is balanced. The imbalance
9224 * becomes significant if the diff is greater than 1
9225 * otherwise we might end up to just move the imbalance
9226 * on another group. Of course this applies only if
9227 * there is more than 1 CPU per group.
9231 if (busiest->sum_h_nr_running == 1)
9233 * busiest doesn't have any tasks waiting to run
9239 /* Looks like there is an imbalance. Compute it */
9240 calculate_imbalance(env, &sds);
9241 return env->imbalance ? sds.busiest : NULL;
9249 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
9251 static struct rq *find_busiest_queue(struct lb_env *env,
9252 struct sched_group *group)
9254 struct rq *busiest = NULL, *rq;
9255 unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
9256 unsigned int busiest_nr = 0;
9259 for_each_cpu_and(i, sched_group_span(group), env->cpus) {
9260 unsigned long capacity, load, util;
9261 unsigned int nr_running;
9265 rt = fbq_classify_rq(rq);
9268 * We classify groups/runqueues into three groups:
9269 * - regular: there are !numa tasks
9270 * - remote: there are numa tasks that run on the 'wrong' node
9271 * - all: there is no distinction
9273 * In order to avoid migrating ideally placed numa tasks,
9274 * ignore those when there's better options.
9276 * If we ignore the actual busiest queue to migrate another
9277 * task, the next balance pass can still reduce the busiest
9278 * queue by moving tasks around inside the node.
9280 * If we cannot move enough load due to this classification
9281 * the next pass will adjust the group classification and
9282 * allow migration of more tasks.
9284 * Both cases only affect the total convergence complexity.
9286 if (rt > env->fbq_type)
9289 capacity = capacity_of(i);
9290 nr_running = rq->cfs.h_nr_running;
9293 * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
9294 * eventually lead to active_balancing high->low capacity.
9295 * Higher per-CPU capacity is considered better than balancing
9298 if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
9299 capacity_of(env->dst_cpu) < capacity &&
9303 switch (env->migration_type) {
9306 * When comparing with load imbalance, use cpu_load()
9307 * which is not scaled with the CPU capacity.
9309 load = cpu_load(rq);
9311 if (nr_running == 1 && load > env->imbalance &&
9312 !check_cpu_capacity(rq, env->sd))
9316 * For the load comparisons with the other CPUs,
9317 * consider the cpu_load() scaled with the CPU
9318 * capacity, so that the load can be moved away
9319 * from the CPU that is potentially running at a
9322 * Thus we're looking for max(load_i / capacity_i),
9323 * crosswise multiplication to rid ourselves of the
9324 * division works out to:
9325 * load_i * capacity_j > load_j * capacity_i;
9326 * where j is our previous maximum.
9328 if (load * busiest_capacity > busiest_load * capacity) {
9329 busiest_load = load;
9330 busiest_capacity = capacity;
9336 util = cpu_util(cpu_of(rq));
9339 * Don't try to pull utilization from a CPU with one
9340 * running task. Whatever its utilization, we will fail
9343 if (nr_running <= 1)
9346 if (busiest_util < util) {
9347 busiest_util = util;
9353 if (busiest_nr < nr_running) {
9354 busiest_nr = nr_running;
9359 case migrate_misfit:
9361 * For ASYM_CPUCAPACITY domains with misfit tasks we
9362 * simply seek the "biggest" misfit task.
9364 if (rq->misfit_task_load > busiest_load) {
9365 busiest_load = rq->misfit_task_load;
9378 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
9379 * so long as it is large enough.
9381 #define MAX_PINNED_INTERVAL 512
9384 asym_active_balance(struct lb_env *env)
9387 * ASYM_PACKING needs to force migrate tasks from busy but
9388 * lower priority CPUs in order to pack all tasks in the
9389 * highest priority CPUs.
9391 return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
9392 sched_asym_prefer(env->dst_cpu, env->src_cpu);
9396 voluntary_active_balance(struct lb_env *env)
9398 struct sched_domain *sd = env->sd;
9400 if (asym_active_balance(env))
9404 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
9405 * It's worth migrating the task if the src_cpu's capacity is reduced
9406 * because of other sched_class or IRQs if more capacity stays
9407 * available on dst_cpu.
9409 if ((env->idle != CPU_NOT_IDLE) &&
9410 (env->src_rq->cfs.h_nr_running == 1)) {
9411 if ((check_cpu_capacity(env->src_rq, sd)) &&
9412 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
9416 if (env->migration_type == migrate_misfit)
9422 static int need_active_balance(struct lb_env *env)
9424 struct sched_domain *sd = env->sd;
9426 if (voluntary_active_balance(env))
9429 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
9432 static int active_load_balance_cpu_stop(void *data);
9434 static int should_we_balance(struct lb_env *env)
9436 struct sched_group *sg = env->sd->groups;
9440 * Ensure the balancing environment is consistent; can happen
9441 * when the softirq triggers 'during' hotplug.
9443 if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
9447 * In the newly idle case, we will allow all the CPUs
9448 * to do the newly idle load balance.
9450 if (env->idle == CPU_NEWLY_IDLE)
9453 /* Try to find first idle CPU */
9454 for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
9458 /* Are we the first idle CPU? */
9459 return cpu == env->dst_cpu;
9462 /* Are we the first CPU of this group ? */
9463 return group_balance_cpu(sg) == env->dst_cpu;
9467 * Check this_cpu to ensure it is balanced within domain. Attempt to move
9468 * tasks if there is an imbalance.
9470 static int load_balance(int this_cpu, struct rq *this_rq,
9471 struct sched_domain *sd, enum cpu_idle_type idle,
9472 int *continue_balancing)
9474 int ld_moved, cur_ld_moved, active_balance = 0;
9475 struct sched_domain *sd_parent = sd->parent;
9476 struct sched_group *group;
9479 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
9481 struct lb_env env = {
9483 .dst_cpu = this_cpu,
9485 .dst_grpmask = sched_group_span(sd->groups),
9487 .loop_break = sched_nr_migrate_break,
9490 .tasks = LIST_HEAD_INIT(env.tasks),
9493 cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
9495 schedstat_inc(sd->lb_count[idle]);
9498 if (!should_we_balance(&env)) {
9499 *continue_balancing = 0;
9503 group = find_busiest_group(&env);
9505 schedstat_inc(sd->lb_nobusyg[idle]);
9509 busiest = find_busiest_queue(&env, group);
9511 schedstat_inc(sd->lb_nobusyq[idle]);
9515 BUG_ON(busiest == env.dst_rq);
9517 schedstat_add(sd->lb_imbalance[idle], env.imbalance);
9519 env.src_cpu = busiest->cpu;
9520 env.src_rq = busiest;
9523 if (busiest->nr_running > 1) {
9525 * Attempt to move tasks. If find_busiest_group has found
9526 * an imbalance but busiest->nr_running <= 1, the group is
9527 * still unbalanced. ld_moved simply stays zero, so it is
9528 * correctly treated as an imbalance.
9530 env.flags |= LBF_ALL_PINNED;
9531 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
9534 rq_lock_irqsave(busiest, &rf);
9535 update_rq_clock(busiest);
9538 * cur_ld_moved - load moved in current iteration
9539 * ld_moved - cumulative load moved across iterations
9541 cur_ld_moved = detach_tasks(&env);
9544 * We've detached some tasks from busiest_rq. Every
9545 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
9546 * unlock busiest->lock, and we are able to be sure
9547 * that nobody can manipulate the tasks in parallel.
9548 * See task_rq_lock() family for the details.
9551 rq_unlock(busiest, &rf);
9555 ld_moved += cur_ld_moved;
9558 local_irq_restore(rf.flags);
9560 if (env.flags & LBF_NEED_BREAK) {
9561 env.flags &= ~LBF_NEED_BREAK;
9566 * Revisit (affine) tasks on src_cpu that couldn't be moved to
9567 * us and move them to an alternate dst_cpu in our sched_group
9568 * where they can run. The upper limit on how many times we
9569 * iterate on same src_cpu is dependent on number of CPUs in our
9572 * This changes load balance semantics a bit on who can move
9573 * load to a given_cpu. In addition to the given_cpu itself
9574 * (or a ilb_cpu acting on its behalf where given_cpu is
9575 * nohz-idle), we now have balance_cpu in a position to move
9576 * load to given_cpu. In rare situations, this may cause
9577 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
9578 * _independently_ and at _same_ time to move some load to
9579 * given_cpu) causing exceess load to be moved to given_cpu.
9580 * This however should not happen so much in practice and
9581 * moreover subsequent load balance cycles should correct the
9582 * excess load moved.
9584 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
9586 /* Prevent to re-select dst_cpu via env's CPUs */
9587 __cpumask_clear_cpu(env.dst_cpu, env.cpus);
9589 env.dst_rq = cpu_rq(env.new_dst_cpu);
9590 env.dst_cpu = env.new_dst_cpu;
9591 env.flags &= ~LBF_DST_PINNED;
9593 env.loop_break = sched_nr_migrate_break;
9596 * Go back to "more_balance" rather than "redo" since we
9597 * need to continue with same src_cpu.
9603 * We failed to reach balance because of affinity.
9606 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
9608 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
9609 *group_imbalance = 1;
9612 /* All tasks on this runqueue were pinned by CPU affinity */
9613 if (unlikely(env.flags & LBF_ALL_PINNED)) {
9614 __cpumask_clear_cpu(cpu_of(busiest), cpus);
9616 * Attempting to continue load balancing at the current
9617 * sched_domain level only makes sense if there are
9618 * active CPUs remaining as possible busiest CPUs to
9619 * pull load from which are not contained within the
9620 * destination group that is receiving any migrated
9623 if (!cpumask_subset(cpus, env.dst_grpmask)) {
9625 env.loop_break = sched_nr_migrate_break;
9628 goto out_all_pinned;
9633 schedstat_inc(sd->lb_failed[idle]);
9635 * Increment the failure counter only on periodic balance.
9636 * We do not want newidle balance, which can be very
9637 * frequent, pollute the failure counter causing
9638 * excessive cache_hot migrations and active balances.
9640 if (idle != CPU_NEWLY_IDLE)
9641 sd->nr_balance_failed++;
9643 if (need_active_balance(&env)) {
9644 unsigned long flags;
9646 raw_spin_lock_irqsave(&busiest->lock, flags);
9649 * Don't kick the active_load_balance_cpu_stop,
9650 * if the curr task on busiest CPU can't be
9651 * moved to this_cpu:
9653 if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
9654 raw_spin_unlock_irqrestore(&busiest->lock,
9656 env.flags |= LBF_ALL_PINNED;
9657 goto out_one_pinned;
9661 * ->active_balance synchronizes accesses to
9662 * ->active_balance_work. Once set, it's cleared
9663 * only after active load balance is finished.
9665 if (!busiest->active_balance) {
9666 busiest->active_balance = 1;
9667 busiest->push_cpu = this_cpu;
9670 raw_spin_unlock_irqrestore(&busiest->lock, flags);
9672 if (active_balance) {
9673 stop_one_cpu_nowait(cpu_of(busiest),
9674 active_load_balance_cpu_stop, busiest,
9675 &busiest->active_balance_work);
9678 /* We've kicked active balancing, force task migration. */
9679 sd->nr_balance_failed = sd->cache_nice_tries+1;
9682 sd->nr_balance_failed = 0;
9684 if (likely(!active_balance) || voluntary_active_balance(&env)) {
9685 /* We were unbalanced, so reset the balancing interval */
9686 sd->balance_interval = sd->min_interval;
9689 * If we've begun active balancing, start to back off. This
9690 * case may not be covered by the all_pinned logic if there
9691 * is only 1 task on the busy runqueue (because we don't call
9694 if (sd->balance_interval < sd->max_interval)
9695 sd->balance_interval *= 2;
9702 * We reach balance although we may have faced some affinity
9703 * constraints. Clear the imbalance flag only if other tasks got
9704 * a chance to move and fix the imbalance.
9706 if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
9707 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
9709 if (*group_imbalance)
9710 *group_imbalance = 0;
9715 * We reach balance because all tasks are pinned at this level so
9716 * we can't migrate them. Let the imbalance flag set so parent level
9717 * can try to migrate them.
9719 schedstat_inc(sd->lb_balanced[idle]);
9721 sd->nr_balance_failed = 0;
9727 * newidle_balance() disregards balance intervals, so we could
9728 * repeatedly reach this code, which would lead to balance_interval
9729 * skyrocketting in a short amount of time. Skip the balance_interval
9730 * increase logic to avoid that.
9732 if (env.idle == CPU_NEWLY_IDLE)
9735 /* tune up the balancing interval */
9736 if ((env.flags & LBF_ALL_PINNED &&
9737 sd->balance_interval < MAX_PINNED_INTERVAL) ||
9738 sd->balance_interval < sd->max_interval)
9739 sd->balance_interval *= 2;
9744 static inline unsigned long
9745 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
9747 unsigned long interval = sd->balance_interval;
9750 interval *= sd->busy_factor;
9752 /* scale ms to jiffies */
9753 interval = msecs_to_jiffies(interval);
9754 interval = clamp(interval, 1UL, max_load_balance_interval);
9760 update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
9762 unsigned long interval, next;
9764 /* used by idle balance, so cpu_busy = 0 */
9765 interval = get_sd_balance_interval(sd, 0);
9766 next = sd->last_balance + interval;
9768 if (time_after(*next_balance, next))
9769 *next_balance = next;
9773 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
9774 * running tasks off the busiest CPU onto idle CPUs. It requires at
9775 * least 1 task to be running on each physical CPU where possible, and
9776 * avoids physical / logical imbalances.
9778 static int active_load_balance_cpu_stop(void *data)
9780 struct rq *busiest_rq = data;
9781 int busiest_cpu = cpu_of(busiest_rq);
9782 int target_cpu = busiest_rq->push_cpu;
9783 struct rq *target_rq = cpu_rq(target_cpu);
9784 struct sched_domain *sd;
9785 struct task_struct *p = NULL;
9788 rq_lock_irq(busiest_rq, &rf);
9790 * Between queueing the stop-work and running it is a hole in which
9791 * CPUs can become inactive. We should not move tasks from or to
9794 if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
9797 /* Make sure the requested CPU hasn't gone down in the meantime: */
9798 if (unlikely(busiest_cpu != smp_processor_id() ||
9799 !busiest_rq->active_balance))
9802 /* Is there any task to move? */
9803 if (busiest_rq->nr_running <= 1)
9807 * This condition is "impossible", if it occurs
9808 * we need to fix it. Originally reported by
9809 * Bjorn Helgaas on a 128-CPU setup.
9811 BUG_ON(busiest_rq == target_rq);
9813 /* Search for an sd spanning us and the target CPU. */
9815 for_each_domain(target_cpu, sd) {
9816 if (cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
9821 struct lb_env env = {
9823 .dst_cpu = target_cpu,
9824 .dst_rq = target_rq,
9825 .src_cpu = busiest_rq->cpu,
9826 .src_rq = busiest_rq,
9829 * can_migrate_task() doesn't need to compute new_dst_cpu
9830 * for active balancing. Since we have CPU_IDLE, but no
9831 * @dst_grpmask we need to make that test go away with lying
9834 .flags = LBF_DST_PINNED,
9837 schedstat_inc(sd->alb_count);
9838 update_rq_clock(busiest_rq);
9840 p = detach_one_task(&env);
9842 schedstat_inc(sd->alb_pushed);
9843 /* Active balancing done, reset the failure counter. */
9844 sd->nr_balance_failed = 0;
9846 schedstat_inc(sd->alb_failed);
9851 busiest_rq->active_balance = 0;
9852 rq_unlock(busiest_rq, &rf);
9855 attach_one_task(target_rq, p);
9862 static DEFINE_SPINLOCK(balancing);
9865 * Scale the max load_balance interval with the number of CPUs in the system.
9866 * This trades load-balance latency on larger machines for less cross talk.
9868 void update_max_interval(void)
9870 max_load_balance_interval = HZ*num_online_cpus()/10;
9874 * It checks each scheduling domain to see if it is due to be balanced,
9875 * and initiates a balancing operation if so.
9877 * Balancing parameters are set up in init_sched_domains.
9879 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
9881 int continue_balancing = 1;
9883 int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
9884 unsigned long interval;
9885 struct sched_domain *sd;
9886 /* Earliest time when we have to do rebalance again */
9887 unsigned long next_balance = jiffies + 60*HZ;
9888 int update_next_balance = 0;
9889 int need_serialize, need_decay = 0;
9893 for_each_domain(cpu, sd) {
9895 * Decay the newidle max times here because this is a regular
9896 * visit to all the domains. Decay ~1% per second.
9898 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
9899 sd->max_newidle_lb_cost =
9900 (sd->max_newidle_lb_cost * 253) / 256;
9901 sd->next_decay_max_lb_cost = jiffies + HZ;
9904 max_cost += sd->max_newidle_lb_cost;
9907 * Stop the load balance at this level. There is another
9908 * CPU in our sched group which is doing load balancing more
9911 if (!continue_balancing) {
9917 interval = get_sd_balance_interval(sd, busy);
9919 need_serialize = sd->flags & SD_SERIALIZE;
9920 if (need_serialize) {
9921 if (!spin_trylock(&balancing))
9925 if (time_after_eq(jiffies, sd->last_balance + interval)) {
9926 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
9928 * The LBF_DST_PINNED logic could have changed
9929 * env->dst_cpu, so we can't know our idle
9930 * state even if we migrated tasks. Update it.
9932 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
9933 busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
9935 sd->last_balance = jiffies;
9936 interval = get_sd_balance_interval(sd, busy);
9939 spin_unlock(&balancing);
9941 if (time_after(next_balance, sd->last_balance + interval)) {
9942 next_balance = sd->last_balance + interval;
9943 update_next_balance = 1;
9948 * Ensure the rq-wide value also decays but keep it at a
9949 * reasonable floor to avoid funnies with rq->avg_idle.
9951 rq->max_idle_balance_cost =
9952 max((u64)sysctl_sched_migration_cost, max_cost);
9957 * next_balance will be updated only when there is a need.
9958 * When the cpu is attached to null domain for ex, it will not be
9961 if (likely(update_next_balance)) {
9962 rq->next_balance = next_balance;
9964 #ifdef CONFIG_NO_HZ_COMMON
9966 * If this CPU has been elected to perform the nohz idle
9967 * balance. Other idle CPUs have already rebalanced with
9968 * nohz_idle_balance() and nohz.next_balance has been
9969 * updated accordingly. This CPU is now running the idle load
9970 * balance for itself and we need to update the
9971 * nohz.next_balance accordingly.
9973 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
9974 nohz.next_balance = rq->next_balance;
9979 static inline int on_null_domain(struct rq *rq)
9981 return unlikely(!rcu_dereference_sched(rq->sd));
9984 #ifdef CONFIG_NO_HZ_COMMON
9986 * idle load balancing details
9987 * - When one of the busy CPUs notice that there may be an idle rebalancing
9988 * needed, they will kick the idle load balancer, which then does idle
9989 * load balancing for all the idle CPUs.
9990 * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set
9994 static inline int find_new_ilb(void)
9998 for_each_cpu_and(ilb, nohz.idle_cpus_mask,
9999 housekeeping_cpumask(HK_FLAG_MISC)) {
10008 * Kick a CPU to do the nohz balancing, if it is time for it. We pick any
10009 * idle CPU in the HK_FLAG_MISC housekeeping set (if there is one).
10011 static void kick_ilb(unsigned int flags)
10015 nohz.next_balance++;
10017 ilb_cpu = find_new_ilb();
10019 if (ilb_cpu >= nr_cpu_ids)
10022 flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
10023 if (flags & NOHZ_KICK_MASK)
10027 * This way we generate an IPI on the target CPU which
10028 * is idle. And the softirq performing nohz idle load balance
10029 * will be run before returning from the IPI.
10031 smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd);
10035 * Current decision point for kicking the idle load balancer in the presence
10036 * of idle CPUs in the system.
10038 static void nohz_balancer_kick(struct rq *rq)
10040 unsigned long now = jiffies;
10041 struct sched_domain_shared *sds;
10042 struct sched_domain *sd;
10043 int nr_busy, i, cpu = rq->cpu;
10044 unsigned int flags = 0;
10046 if (unlikely(rq->idle_balance))
10050 * We may be recently in ticked or tickless idle mode. At the first
10051 * busy tick after returning from idle, we will update the busy stats.
10053 nohz_balance_exit_idle(rq);
10056 * None are in tickless mode and hence no need for NOHZ idle load
10059 if (likely(!atomic_read(&nohz.nr_cpus)))
10062 if (READ_ONCE(nohz.has_blocked) &&
10063 time_after(now, READ_ONCE(nohz.next_blocked)))
10064 flags = NOHZ_STATS_KICK;
10066 if (time_before(now, nohz.next_balance))
10069 if (rq->nr_running >= 2) {
10070 flags = NOHZ_KICK_MASK;
10076 sd = rcu_dereference(rq->sd);
10079 * If there's a CFS task and the current CPU has reduced
10080 * capacity; kick the ILB to see if there's a better CPU to run
10083 if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
10084 flags = NOHZ_KICK_MASK;
10089 sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
10092 * When ASYM_PACKING; see if there's a more preferred CPU
10093 * currently idle; in which case, kick the ILB to move tasks
10096 for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
10097 if (sched_asym_prefer(i, cpu)) {
10098 flags = NOHZ_KICK_MASK;
10104 sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
10107 * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
10108 * to run the misfit task on.
10110 if (check_misfit_status(rq, sd)) {
10111 flags = NOHZ_KICK_MASK;
10116 * For asymmetric systems, we do not want to nicely balance
10117 * cache use, instead we want to embrace asymmetry and only
10118 * ensure tasks have enough CPU capacity.
10120 * Skip the LLC logic because it's not relevant in that case.
10125 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
10128 * If there is an imbalance between LLC domains (IOW we could
10129 * increase the overall cache use), we need some less-loaded LLC
10130 * domain to pull some load. Likewise, we may need to spread
10131 * load within the current LLC domain (e.g. packed SMT cores but
10132 * other CPUs are idle). We can't really know from here how busy
10133 * the others are - so just get a nohz balance going if it looks
10134 * like this LLC domain has tasks we could move.
10136 nr_busy = atomic_read(&sds->nr_busy_cpus);
10138 flags = NOHZ_KICK_MASK;
10149 static void set_cpu_sd_state_busy(int cpu)
10151 struct sched_domain *sd;
10154 sd = rcu_dereference(per_cpu(sd_llc, cpu));
10156 if (!sd || !sd->nohz_idle)
10160 atomic_inc(&sd->shared->nr_busy_cpus);
10165 void nohz_balance_exit_idle(struct rq *rq)
10167 SCHED_WARN_ON(rq != this_rq());
10169 if (likely(!rq->nohz_tick_stopped))
10172 rq->nohz_tick_stopped = 0;
10173 cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
10174 atomic_dec(&nohz.nr_cpus);
10176 set_cpu_sd_state_busy(rq->cpu);
10179 static void set_cpu_sd_state_idle(int cpu)
10181 struct sched_domain *sd;
10184 sd = rcu_dereference(per_cpu(sd_llc, cpu));
10186 if (!sd || sd->nohz_idle)
10190 atomic_dec(&sd->shared->nr_busy_cpus);
10196 * This routine will record that the CPU is going idle with tick stopped.
10197 * This info will be used in performing idle load balancing in the future.
10199 void nohz_balance_enter_idle(int cpu)
10201 struct rq *rq = cpu_rq(cpu);
10203 SCHED_WARN_ON(cpu != smp_processor_id());
10205 /* If this CPU is going down, then nothing needs to be done: */
10206 if (!cpu_active(cpu))
10209 /* Spare idle load balancing on CPUs that don't want to be disturbed: */
10210 if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
10214 * Can be set safely without rq->lock held
10215 * If a clear happens, it will have evaluated last additions because
10216 * rq->lock is held during the check and the clear
10218 rq->has_blocked_load = 1;
10221 * The tick is still stopped but load could have been added in the
10222 * meantime. We set the nohz.has_blocked flag to trig a check of the
10223 * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
10224 * of nohz.has_blocked can only happen after checking the new load
10226 if (rq->nohz_tick_stopped)
10229 /* If we're a completely isolated CPU, we don't play: */
10230 if (on_null_domain(rq))
10233 rq->nohz_tick_stopped = 1;
10235 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
10236 atomic_inc(&nohz.nr_cpus);
10239 * Ensures that if nohz_idle_balance() fails to observe our
10240 * @idle_cpus_mask store, it must observe the @has_blocked
10243 smp_mb__after_atomic();
10245 set_cpu_sd_state_idle(cpu);
10249 * Each time a cpu enter idle, we assume that it has blocked load and
10250 * enable the periodic update of the load of idle cpus
10252 WRITE_ONCE(nohz.has_blocked, 1);
10256 * Internal function that runs load balance for all idle cpus. The load balance
10257 * can be a simple update of blocked load or a complete load balance with
10258 * tasks movement depending of flags.
10259 * The function returns false if the loop has stopped before running
10260 * through all idle CPUs.
10262 static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
10263 enum cpu_idle_type idle)
10265 /* Earliest time when we have to do rebalance again */
10266 unsigned long now = jiffies;
10267 unsigned long next_balance = now + 60*HZ;
10268 bool has_blocked_load = false;
10269 int update_next_balance = 0;
10270 int this_cpu = this_rq->cpu;
10275 SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
10278 * We assume there will be no idle load after this update and clear
10279 * the has_blocked flag. If a cpu enters idle in the mean time, it will
10280 * set the has_blocked flag and trig another update of idle load.
10281 * Because a cpu that becomes idle, is added to idle_cpus_mask before
10282 * setting the flag, we are sure to not clear the state and not
10283 * check the load of an idle cpu.
10285 WRITE_ONCE(nohz.has_blocked, 0);
10288 * Ensures that if we miss the CPU, we must see the has_blocked
10289 * store from nohz_balance_enter_idle().
10293 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
10294 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
10298 * If this CPU gets work to do, stop the load balancing
10299 * work being done for other CPUs. Next load
10300 * balancing owner will pick it up.
10302 if (need_resched()) {
10303 has_blocked_load = true;
10307 rq = cpu_rq(balance_cpu);
10309 has_blocked_load |= update_nohz_stats(rq, true);
10312 * If time for next balance is due,
10315 if (time_after_eq(jiffies, rq->next_balance)) {
10316 struct rq_flags rf;
10318 rq_lock_irqsave(rq, &rf);
10319 update_rq_clock(rq);
10320 rq_unlock_irqrestore(rq, &rf);
10322 if (flags & NOHZ_BALANCE_KICK)
10323 rebalance_domains(rq, CPU_IDLE);
10326 if (time_after(next_balance, rq->next_balance)) {
10327 next_balance = rq->next_balance;
10328 update_next_balance = 1;
10332 /* Newly idle CPU doesn't need an update */
10333 if (idle != CPU_NEWLY_IDLE) {
10334 update_blocked_averages(this_cpu);
10335 has_blocked_load |= this_rq->has_blocked_load;
10338 if (flags & NOHZ_BALANCE_KICK)
10339 rebalance_domains(this_rq, CPU_IDLE);
10341 WRITE_ONCE(nohz.next_blocked,
10342 now + msecs_to_jiffies(LOAD_AVG_PERIOD));
10344 /* The full idle balance loop has been done */
10348 /* There is still blocked load, enable periodic update */
10349 if (has_blocked_load)
10350 WRITE_ONCE(nohz.has_blocked, 1);
10353 * next_balance will be updated only when there is a need.
10354 * When the CPU is attached to null domain for ex, it will not be
10357 if (likely(update_next_balance))
10358 nohz.next_balance = next_balance;
10364 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
10365 * rebalancing for all the cpus for whom scheduler ticks are stopped.
10367 static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
10369 int this_cpu = this_rq->cpu;
10370 unsigned int flags;
10372 if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK))
10375 if (idle != CPU_IDLE) {
10376 atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
10380 /* could be _relaxed() */
10381 flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
10382 if (!(flags & NOHZ_KICK_MASK))
10385 _nohz_idle_balance(this_rq, flags, idle);
10390 static void nohz_newidle_balance(struct rq *this_rq)
10392 int this_cpu = this_rq->cpu;
10395 * This CPU doesn't want to be disturbed by scheduler
10398 if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED))
10401 /* Will wake up very soon. No time for doing anything else*/
10402 if (this_rq->avg_idle < sysctl_sched_migration_cost)
10405 /* Don't need to update blocked load of idle CPUs*/
10406 if (!READ_ONCE(nohz.has_blocked) ||
10407 time_before(jiffies, READ_ONCE(nohz.next_blocked)))
10410 raw_spin_unlock(&this_rq->lock);
10412 * This CPU is going to be idle and blocked load of idle CPUs
10413 * need to be updated. Run the ilb locally as it is a good
10414 * candidate for ilb instead of waking up another idle CPU.
10415 * Kick an normal ilb if we failed to do the update.
10417 if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE))
10418 kick_ilb(NOHZ_STATS_KICK);
10419 raw_spin_lock(&this_rq->lock);
10422 #else /* !CONFIG_NO_HZ_COMMON */
10423 static inline void nohz_balancer_kick(struct rq *rq) { }
10425 static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
10430 static inline void nohz_newidle_balance(struct rq *this_rq) { }
10431 #endif /* CONFIG_NO_HZ_COMMON */
10434 * idle_balance is called by schedule() if this_cpu is about to become
10435 * idle. Attempts to pull tasks from other CPUs.
10438 * < 0 - we released the lock and there are !fair tasks present
10439 * 0 - failed, no new tasks
10440 * > 0 - success, new (fair) tasks present
10442 static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
10444 unsigned long next_balance = jiffies + HZ;
10445 int this_cpu = this_rq->cpu;
10446 struct sched_domain *sd;
10447 int pulled_task = 0;
10450 update_misfit_status(NULL, this_rq);
10452 * We must set idle_stamp _before_ calling idle_balance(), such that we
10453 * measure the duration of idle_balance() as idle time.
10455 this_rq->idle_stamp = rq_clock(this_rq);
10458 * Do not pull tasks towards !active CPUs...
10460 if (!cpu_active(this_cpu))
10464 * This is OK, because current is on_cpu, which avoids it being picked
10465 * for load-balance and preemption/IRQs are still disabled avoiding
10466 * further scheduler activity on it and we're being very careful to
10467 * re-start the picking loop.
10469 rq_unpin_lock(this_rq, rf);
10471 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
10472 !READ_ONCE(this_rq->rd->overload)) {
10475 sd = rcu_dereference_check_sched_domain(this_rq->sd);
10477 update_next_balance(sd, &next_balance);
10480 nohz_newidle_balance(this_rq);
10485 raw_spin_unlock(&this_rq->lock);
10487 update_blocked_averages(this_cpu);
10489 for_each_domain(this_cpu, sd) {
10490 int continue_balancing = 1;
10491 u64 t0, domain_cost;
10493 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
10494 update_next_balance(sd, &next_balance);
10498 if (sd->flags & SD_BALANCE_NEWIDLE) {
10499 t0 = sched_clock_cpu(this_cpu);
10501 pulled_task = load_balance(this_cpu, this_rq,
10502 sd, CPU_NEWLY_IDLE,
10503 &continue_balancing);
10505 domain_cost = sched_clock_cpu(this_cpu) - t0;
10506 if (domain_cost > sd->max_newidle_lb_cost)
10507 sd->max_newidle_lb_cost = domain_cost;
10509 curr_cost += domain_cost;
10512 update_next_balance(sd, &next_balance);
10515 * Stop searching for tasks to pull if there are
10516 * now runnable tasks on this rq.
10518 if (pulled_task || this_rq->nr_running > 0)
10523 raw_spin_lock(&this_rq->lock);
10525 if (curr_cost > this_rq->max_idle_balance_cost)
10526 this_rq->max_idle_balance_cost = curr_cost;
10530 * While browsing the domains, we released the rq lock, a task could
10531 * have been enqueued in the meantime. Since we're not going idle,
10532 * pretend we pulled a task.
10534 if (this_rq->cfs.h_nr_running && !pulled_task)
10537 /* Move the next balance forward */
10538 if (time_after(this_rq->next_balance, next_balance))
10539 this_rq->next_balance = next_balance;
10541 /* Is there a task of a high priority class? */
10542 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
10546 this_rq->idle_stamp = 0;
10548 rq_repin_lock(this_rq, rf);
10550 return pulled_task;
10554 * run_rebalance_domains is triggered when needed from the scheduler tick.
10555 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
10557 static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
10559 struct rq *this_rq = this_rq();
10560 enum cpu_idle_type idle = this_rq->idle_balance ?
10561 CPU_IDLE : CPU_NOT_IDLE;
10564 * If this CPU has a pending nohz_balance_kick, then do the
10565 * balancing on behalf of the other idle CPUs whose ticks are
10566 * stopped. Do nohz_idle_balance *before* rebalance_domains to
10567 * give the idle CPUs a chance to load balance. Else we may
10568 * load balance only within the local sched_domain hierarchy
10569 * and abort nohz_idle_balance altogether if we pull some load.
10571 if (nohz_idle_balance(this_rq, idle))
10574 /* normal load balance */
10575 update_blocked_averages(this_rq->cpu);
10576 rebalance_domains(this_rq, idle);
10580 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
10582 void trigger_load_balance(struct rq *rq)
10584 /* Don't need to rebalance while attached to NULL domain */
10585 if (unlikely(on_null_domain(rq)))
10588 if (time_after_eq(jiffies, rq->next_balance))
10589 raise_softirq(SCHED_SOFTIRQ);
10591 nohz_balancer_kick(rq);
10594 static void rq_online_fair(struct rq *rq)
10598 update_runtime_enabled(rq);
10601 static void rq_offline_fair(struct rq *rq)
10605 /* Ensure any throttled groups are reachable by pick_next_task */
10606 unthrottle_offline_cfs_rqs(rq);
10609 #endif /* CONFIG_SMP */
10612 * scheduler tick hitting a task of our scheduling class.
10614 * NOTE: This function can be called remotely by the tick offload that
10615 * goes along full dynticks. Therefore no local assumption can be made
10616 * and everything must be accessed through the @rq and @curr passed in
10619 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
10621 struct cfs_rq *cfs_rq;
10622 struct sched_entity *se = &curr->se;
10624 for_each_sched_entity(se) {
10625 cfs_rq = cfs_rq_of(se);
10626 entity_tick(cfs_rq, se, queued);
10629 if (static_branch_unlikely(&sched_numa_balancing))
10630 task_tick_numa(rq, curr);
10632 update_misfit_status(curr, rq);
10633 update_overutilized_status(task_rq(curr));
10637 * called on fork with the child task as argument from the parent's context
10638 * - child not yet on the tasklist
10639 * - preemption disabled
10641 static void task_fork_fair(struct task_struct *p)
10643 struct cfs_rq *cfs_rq;
10644 struct sched_entity *se = &p->se, *curr;
10645 struct rq *rq = this_rq();
10646 struct rq_flags rf;
10649 update_rq_clock(rq);
10651 cfs_rq = task_cfs_rq(current);
10652 curr = cfs_rq->curr;
10654 update_curr(cfs_rq);
10655 se->vruntime = curr->vruntime;
10657 place_entity(cfs_rq, se, 1);
10659 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
10661 * Upon rescheduling, sched_class::put_prev_task() will place
10662 * 'current' within the tree based on its new key value.
10664 swap(curr->vruntime, se->vruntime);
10668 se->vruntime -= cfs_rq->min_vruntime;
10669 rq_unlock(rq, &rf);
10673 * Priority of the task has changed. Check to see if we preempt
10674 * the current task.
10677 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
10679 if (!task_on_rq_queued(p))
10682 if (rq->cfs.nr_running == 1)
10686 * Reschedule if we are currently running on this runqueue and
10687 * our priority decreased, or if we are not currently running on
10688 * this runqueue and our priority is higher than the current's
10690 if (rq->curr == p) {
10691 if (p->prio > oldprio)
10694 check_preempt_curr(rq, p, 0);
10697 static inline bool vruntime_normalized(struct task_struct *p)
10699 struct sched_entity *se = &p->se;
10702 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
10703 * the dequeue_entity(.flags=0) will already have normalized the
10710 * When !on_rq, vruntime of the task has usually NOT been normalized.
10711 * But there are some cases where it has already been normalized:
10713 * - A forked child which is waiting for being woken up by
10714 * wake_up_new_task().
10715 * - A task which has been woken up by try_to_wake_up() and
10716 * waiting for actually being woken up by sched_ttwu_pending().
10718 if (!se->sum_exec_runtime ||
10719 (p->state == TASK_WAKING && p->sched_remote_wakeup))
10725 #ifdef CONFIG_FAIR_GROUP_SCHED
10727 * Propagate the changes of the sched_entity across the tg tree to make it
10728 * visible to the root
10730 static void propagate_entity_cfs_rq(struct sched_entity *se)
10732 struct cfs_rq *cfs_rq;
10734 /* Start to propagate at parent */
10737 for_each_sched_entity(se) {
10738 cfs_rq = cfs_rq_of(se);
10740 if (cfs_rq_throttled(cfs_rq))
10743 update_load_avg(cfs_rq, se, UPDATE_TG);
10747 static void propagate_entity_cfs_rq(struct sched_entity *se) { }
10750 static void detach_entity_cfs_rq(struct sched_entity *se)
10752 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10754 /* Catch up with the cfs_rq and remove our load when we leave */
10755 update_load_avg(cfs_rq, se, 0);
10756 detach_entity_load_avg(cfs_rq, se);
10757 update_tg_load_avg(cfs_rq, false);
10758 propagate_entity_cfs_rq(se);
10761 static void attach_entity_cfs_rq(struct sched_entity *se)
10763 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10765 #ifdef CONFIG_FAIR_GROUP_SCHED
10767 * Since the real-depth could have been changed (only FAIR
10768 * class maintain depth value), reset depth properly.
10770 se->depth = se->parent ? se->parent->depth + 1 : 0;
10773 /* Synchronize entity with its cfs_rq */
10774 update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
10775 attach_entity_load_avg(cfs_rq, se);
10776 update_tg_load_avg(cfs_rq, false);
10777 propagate_entity_cfs_rq(se);
10780 static void detach_task_cfs_rq(struct task_struct *p)
10782 struct sched_entity *se = &p->se;
10783 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10785 if (!vruntime_normalized(p)) {
10787 * Fix up our vruntime so that the current sleep doesn't
10788 * cause 'unlimited' sleep bonus.
10790 place_entity(cfs_rq, se, 0);
10791 se->vruntime -= cfs_rq->min_vruntime;
10794 detach_entity_cfs_rq(se);
10797 static void attach_task_cfs_rq(struct task_struct *p)
10799 struct sched_entity *se = &p->se;
10800 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10802 attach_entity_cfs_rq(se);
10804 if (!vruntime_normalized(p))
10805 se->vruntime += cfs_rq->min_vruntime;
10808 static void switched_from_fair(struct rq *rq, struct task_struct *p)
10810 detach_task_cfs_rq(p);
10813 static void switched_to_fair(struct rq *rq, struct task_struct *p)
10815 attach_task_cfs_rq(p);
10817 if (task_on_rq_queued(p)) {
10819 * We were most likely switched from sched_rt, so
10820 * kick off the schedule if running, otherwise just see
10821 * if we can still preempt the current task.
10826 check_preempt_curr(rq, p, 0);
10830 /* Account for a task changing its policy or group.
10832 * This routine is mostly called to set cfs_rq->curr field when a task
10833 * migrates between groups/classes.
10835 static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
10837 struct sched_entity *se = &p->se;
10840 if (task_on_rq_queued(p)) {
10842 * Move the next running task to the front of the list, so our
10843 * cfs_tasks list becomes MRU one.
10845 list_move(&se->group_node, &rq->cfs_tasks);
10849 for_each_sched_entity(se) {
10850 struct cfs_rq *cfs_rq = cfs_rq_of(se);
10852 set_next_entity(cfs_rq, se);
10853 /* ensure bandwidth has been allocated on our new cfs_rq */
10854 account_cfs_rq_runtime(cfs_rq, 0);
10858 void init_cfs_rq(struct cfs_rq *cfs_rq)
10860 cfs_rq->tasks_timeline = RB_ROOT_CACHED;
10861 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
10862 #ifndef CONFIG_64BIT
10863 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
10866 raw_spin_lock_init(&cfs_rq->removed.lock);
10870 #ifdef CONFIG_FAIR_GROUP_SCHED
10871 static void task_set_group_fair(struct task_struct *p)
10873 struct sched_entity *se = &p->se;
10875 set_task_rq(p, task_cpu(p));
10876 se->depth = se->parent ? se->parent->depth + 1 : 0;
10879 static void task_move_group_fair(struct task_struct *p)
10881 detach_task_cfs_rq(p);
10882 set_task_rq(p, task_cpu(p));
10885 /* Tell se's cfs_rq has been changed -- migrated */
10886 p->se.avg.last_update_time = 0;
10888 attach_task_cfs_rq(p);
10891 static void task_change_group_fair(struct task_struct *p, int type)
10894 case TASK_SET_GROUP:
10895 task_set_group_fair(p);
10898 case TASK_MOVE_GROUP:
10899 task_move_group_fair(p);
10904 void free_fair_sched_group(struct task_group *tg)
10908 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
10910 for_each_possible_cpu(i) {
10912 kfree(tg->cfs_rq[i]);
10921 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
10923 struct sched_entity *se;
10924 struct cfs_rq *cfs_rq;
10927 tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
10930 tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
10934 tg->shares = NICE_0_LOAD;
10936 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
10938 for_each_possible_cpu(i) {
10939 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
10940 GFP_KERNEL, cpu_to_node(i));
10944 se = kzalloc_node(sizeof(struct sched_entity),
10945 GFP_KERNEL, cpu_to_node(i));
10949 init_cfs_rq(cfs_rq);
10950 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
10951 init_entity_runnable_average(se);
10962 void online_fair_sched_group(struct task_group *tg)
10964 struct sched_entity *se;
10965 struct rq_flags rf;
10969 for_each_possible_cpu(i) {
10972 rq_lock_irq(rq, &rf);
10973 update_rq_clock(rq);
10974 attach_entity_cfs_rq(se);
10975 sync_throttle(tg, i);
10976 rq_unlock_irq(rq, &rf);
10980 void unregister_fair_sched_group(struct task_group *tg)
10982 unsigned long flags;
10986 for_each_possible_cpu(cpu) {
10988 remove_entity_load_avg(tg->se[cpu]);
10991 * Only empty task groups can be destroyed; so we can speculatively
10992 * check on_list without danger of it being re-added.
10994 if (!tg->cfs_rq[cpu]->on_list)
10999 raw_spin_lock_irqsave(&rq->lock, flags);
11000 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
11001 raw_spin_unlock_irqrestore(&rq->lock, flags);
11005 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
11006 struct sched_entity *se, int cpu,
11007 struct sched_entity *parent)
11009 struct rq *rq = cpu_rq(cpu);
11013 init_cfs_rq_runtime(cfs_rq);
11015 tg->cfs_rq[cpu] = cfs_rq;
11018 /* se could be NULL for root_task_group */
11023 se->cfs_rq = &rq->cfs;
11026 se->cfs_rq = parent->my_q;
11027 se->depth = parent->depth + 1;
11031 /* guarantee group entities always have weight */
11032 update_load_set(&se->load, NICE_0_LOAD);
11033 se->parent = parent;
11036 static DEFINE_MUTEX(shares_mutex);
11038 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
11043 * We can't change the weight of the root cgroup.
11048 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
11050 mutex_lock(&shares_mutex);
11051 if (tg->shares == shares)
11054 tg->shares = shares;
11055 for_each_possible_cpu(i) {
11056 struct rq *rq = cpu_rq(i);
11057 struct sched_entity *se = tg->se[i];
11058 struct rq_flags rf;
11060 /* Propagate contribution to hierarchy */
11061 rq_lock_irqsave(rq, &rf);
11062 update_rq_clock(rq);
11063 for_each_sched_entity(se) {
11064 update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
11065 update_cfs_group(se);
11067 rq_unlock_irqrestore(rq, &rf);
11071 mutex_unlock(&shares_mutex);
11074 #else /* CONFIG_FAIR_GROUP_SCHED */
11076 void free_fair_sched_group(struct task_group *tg) { }
11078 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
11083 void online_fair_sched_group(struct task_group *tg) { }
11085 void unregister_fair_sched_group(struct task_group *tg) { }
11087 #endif /* CONFIG_FAIR_GROUP_SCHED */
11090 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
11092 struct sched_entity *se = &task->se;
11093 unsigned int rr_interval = 0;
11096 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
11099 if (rq->cfs.load.weight)
11100 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
11102 return rr_interval;
11106 * All the scheduling class methods:
11108 const struct sched_class fair_sched_class = {
11109 .next = &idle_sched_class,
11110 .enqueue_task = enqueue_task_fair,
11111 .dequeue_task = dequeue_task_fair,
11112 .yield_task = yield_task_fair,
11113 .yield_to_task = yield_to_task_fair,
11115 .check_preempt_curr = check_preempt_wakeup,
11117 .pick_next_task = __pick_next_task_fair,
11118 .put_prev_task = put_prev_task_fair,
11119 .set_next_task = set_next_task_fair,
11122 .balance = balance_fair,
11123 .select_task_rq = select_task_rq_fair,
11124 .migrate_task_rq = migrate_task_rq_fair,
11126 .rq_online = rq_online_fair,
11127 .rq_offline = rq_offline_fair,
11129 .task_dead = task_dead_fair,
11130 .set_cpus_allowed = set_cpus_allowed_common,
11133 .task_tick = task_tick_fair,
11134 .task_fork = task_fork_fair,
11136 .prio_changed = prio_changed_fair,
11137 .switched_from = switched_from_fair,
11138 .switched_to = switched_to_fair,
11140 .get_rr_interval = get_rr_interval_fair,
11142 .update_curr = update_curr_fair,
11144 #ifdef CONFIG_FAIR_GROUP_SCHED
11145 .task_change_group = task_change_group_fair,
11148 #ifdef CONFIG_UCLAMP_TASK
11149 .uclamp_enabled = 1,
11153 #ifdef CONFIG_SCHED_DEBUG
11154 void print_cfs_stats(struct seq_file *m, int cpu)
11156 struct cfs_rq *cfs_rq, *pos;
11159 for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
11160 print_cfs_rq(m, cpu, cfs_rq);
11164 #ifdef CONFIG_NUMA_BALANCING
11165 void show_numa_stats(struct task_struct *p, struct seq_file *m)
11168 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
11169 struct numa_group *ng;
11172 ng = rcu_dereference(p->numa_group);
11173 for_each_online_node(node) {
11174 if (p->numa_faults) {
11175 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
11176 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
11179 gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)],
11180 gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
11182 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
11186 #endif /* CONFIG_NUMA_BALANCING */
11187 #endif /* CONFIG_SCHED_DEBUG */
11189 __init void init_sched_fair_class(void)
11192 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
11194 #ifdef CONFIG_NO_HZ_COMMON
11195 nohz.next_balance = jiffies;
11196 nohz.next_blocked = jiffies;
11197 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
11204 * Helper functions to facilitate extracting info from tracepoints.
11207 const struct sched_avg *sched_trace_cfs_rq_avg(struct cfs_rq *cfs_rq)
11210 return cfs_rq ? &cfs_rq->avg : NULL;
11215 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_avg);
11217 char *sched_trace_cfs_rq_path(struct cfs_rq *cfs_rq, char *str, int len)
11221 strlcpy(str, "(null)", len);
11226 cfs_rq_tg_path(cfs_rq, str, len);
11229 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_path);
11231 int sched_trace_cfs_rq_cpu(struct cfs_rq *cfs_rq)
11233 return cfs_rq ? cpu_of(rq_of(cfs_rq)) : -1;
11235 EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_cpu);
11237 const struct sched_avg *sched_trace_rq_avg_rt(struct rq *rq)
11240 return rq ? &rq->avg_rt : NULL;
11245 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_rt);
11247 const struct sched_avg *sched_trace_rq_avg_dl(struct rq *rq)
11250 return rq ? &rq->avg_dl : NULL;
11255 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_dl);
11257 const struct sched_avg *sched_trace_rq_avg_irq(struct rq *rq)
11259 #if defined(CONFIG_SMP) && defined(CONFIG_HAVE_SCHED_AVG_IRQ)
11260 return rq ? &rq->avg_irq : NULL;
11265 EXPORT_SYMBOL_GPL(sched_trace_rq_avg_irq);
11267 int sched_trace_rq_cpu(struct rq *rq)
11269 return rq ? cpu_of(rq) : -1;
11271 EXPORT_SYMBOL_GPL(sched_trace_rq_cpu);
11273 const struct cpumask *sched_trace_rd_span(struct root_domain *rd)
11276 return rd ? rd->span : NULL;
11281 EXPORT_SYMBOL_GPL(sched_trace_rd_span);