2 * Scheduler topology setup/handling methods
4 #include <linux/sched.h>
5 #include <linux/mutex.h>
9 DEFINE_MUTEX(sched_domains_mutex);
11 /* Protected by sched_domains_mutex: */
12 cpumask_var_t sched_domains_tmpmask;
13 cpumask_var_t sched_domains_tmpmask2;
15 #ifdef CONFIG_SCHED_DEBUG
17 static __read_mostly int sched_debug_enabled;
19 static int __init sched_debug_setup(char *str)
21 sched_debug_enabled = 1;
25 early_param("sched_debug", sched_debug_setup);
27 static inline bool sched_debug(void)
29 return sched_debug_enabled;
32 static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
33 struct cpumask *groupmask)
35 struct sched_group *group = sd->groups;
37 cpumask_clear(groupmask);
39 printk(KERN_DEBUG "%*s domain-%d: ", level, "", level);
41 if (!(sd->flags & SD_LOAD_BALANCE)) {
42 printk("does not load-balance\n");
44 printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
49 printk(KERN_CONT "span=%*pbl level=%s\n",
50 cpumask_pr_args(sched_domain_span(sd)), sd->name);
52 if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
53 printk(KERN_ERR "ERROR: domain->span does not contain "
56 if (!cpumask_test_cpu(cpu, sched_group_span(group))) {
57 printk(KERN_ERR "ERROR: domain->groups does not contain"
61 printk(KERN_DEBUG "%*s groups:", level + 1, "");
65 printk(KERN_ERR "ERROR: group is NULL\n");
69 if (!cpumask_weight(sched_group_span(group))) {
70 printk(KERN_CONT "\n");
71 printk(KERN_ERR "ERROR: empty group\n");
75 if (!(sd->flags & SD_OVERLAP) &&
76 cpumask_intersects(groupmask, sched_group_span(group))) {
77 printk(KERN_CONT "\n");
78 printk(KERN_ERR "ERROR: repeated CPUs\n");
82 cpumask_or(groupmask, groupmask, sched_group_span(group));
84 printk(KERN_CONT " %d:{ span=%*pbl",
86 cpumask_pr_args(sched_group_span(group)));
88 if ((sd->flags & SD_OVERLAP) &&
89 !cpumask_equal(group_balance_mask(group), sched_group_span(group))) {
90 printk(KERN_CONT " mask=%*pbl",
91 cpumask_pr_args(group_balance_mask(group)));
94 if (group->sgc->capacity != SCHED_CAPACITY_SCALE)
95 printk(KERN_CONT " cap=%lu", group->sgc->capacity);
97 if (group == sd->groups && sd->child &&
98 !cpumask_equal(sched_domain_span(sd->child),
99 sched_group_span(group))) {
100 printk(KERN_ERR "ERROR: domain->groups does not match domain->child\n");
103 printk(KERN_CONT " }");
107 if (group != sd->groups)
108 printk(KERN_CONT ",");
110 } while (group != sd->groups);
111 printk(KERN_CONT "\n");
113 if (!cpumask_equal(sched_domain_span(sd), groupmask))
114 printk(KERN_ERR "ERROR: groups don't span domain->span\n");
117 !cpumask_subset(groupmask, sched_domain_span(sd->parent)))
118 printk(KERN_ERR "ERROR: parent span is not a superset "
119 "of domain->span\n");
123 static void sched_domain_debug(struct sched_domain *sd, int cpu)
127 if (!sched_debug_enabled)
131 printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
135 printk(KERN_DEBUG "CPU%d attaching sched-domain(s):\n", cpu);
138 if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask))
146 #else /* !CONFIG_SCHED_DEBUG */
148 # define sched_debug_enabled 0
149 # define sched_domain_debug(sd, cpu) do { } while (0)
150 static inline bool sched_debug(void)
154 #endif /* CONFIG_SCHED_DEBUG */
156 static int sd_degenerate(struct sched_domain *sd)
158 if (cpumask_weight(sched_domain_span(sd)) == 1)
161 /* Following flags need at least 2 groups */
162 if (sd->flags & (SD_LOAD_BALANCE |
166 SD_SHARE_CPUCAPACITY |
167 SD_ASYM_CPUCAPACITY |
168 SD_SHARE_PKG_RESOURCES |
169 SD_SHARE_POWERDOMAIN)) {
170 if (sd->groups != sd->groups->next)
174 /* Following flags don't use groups */
175 if (sd->flags & (SD_WAKE_AFFINE))
182 sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
184 unsigned long cflags = sd->flags, pflags = parent->flags;
186 if (sd_degenerate(parent))
189 if (!cpumask_equal(sched_domain_span(sd), sched_domain_span(parent)))
192 /* Flags needing groups don't count if only 1 group in parent */
193 if (parent->groups == parent->groups->next) {
194 pflags &= ~(SD_LOAD_BALANCE |
198 SD_ASYM_CPUCAPACITY |
199 SD_SHARE_CPUCAPACITY |
200 SD_SHARE_PKG_RESOURCES |
202 SD_SHARE_POWERDOMAIN);
203 if (nr_node_ids == 1)
204 pflags &= ~SD_SERIALIZE;
206 if (~cflags & pflags)
212 static void free_rootdomain(struct rcu_head *rcu)
214 struct root_domain *rd = container_of(rcu, struct root_domain, rcu);
216 cpupri_cleanup(&rd->cpupri);
217 cpudl_cleanup(&rd->cpudl);
218 free_cpumask_var(rd->dlo_mask);
219 free_cpumask_var(rd->rto_mask);
220 free_cpumask_var(rd->online);
221 free_cpumask_var(rd->span);
225 void rq_attach_root(struct rq *rq, struct root_domain *rd)
227 struct root_domain *old_rd = NULL;
230 raw_spin_lock_irqsave(&rq->lock, flags);
235 if (cpumask_test_cpu(rq->cpu, old_rd->online))
238 cpumask_clear_cpu(rq->cpu, old_rd->span);
241 * If we dont want to free the old_rd yet then
242 * set old_rd to NULL to skip the freeing later
245 if (!atomic_dec_and_test(&old_rd->refcount))
249 atomic_inc(&rd->refcount);
252 cpumask_set_cpu(rq->cpu, rd->span);
253 if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
256 raw_spin_unlock_irqrestore(&rq->lock, flags);
259 call_rcu_sched(&old_rd->rcu, free_rootdomain);
262 static int init_rootdomain(struct root_domain *rd)
264 memset(rd, 0, sizeof(*rd));
266 if (!zalloc_cpumask_var(&rd->span, GFP_KERNEL))
268 if (!zalloc_cpumask_var(&rd->online, GFP_KERNEL))
270 if (!zalloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
272 if (!zalloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
275 init_dl_bw(&rd->dl_bw);
276 if (cpudl_init(&rd->cpudl) != 0)
279 if (cpupri_init(&rd->cpupri) != 0)
284 cpudl_cleanup(&rd->cpudl);
286 free_cpumask_var(rd->rto_mask);
288 free_cpumask_var(rd->dlo_mask);
290 free_cpumask_var(rd->online);
292 free_cpumask_var(rd->span);
298 * By default the system creates a single root-domain with all CPUs as
299 * members (mimicking the global state we have today).
301 struct root_domain def_root_domain;
303 void init_defrootdomain(void)
305 init_rootdomain(&def_root_domain);
307 atomic_set(&def_root_domain.refcount, 1);
310 static struct root_domain *alloc_rootdomain(void)
312 struct root_domain *rd;
314 rd = kmalloc(sizeof(*rd), GFP_KERNEL);
318 if (init_rootdomain(rd) != 0) {
326 static void free_sched_groups(struct sched_group *sg, int free_sgc)
328 struct sched_group *tmp, *first;
337 if (free_sgc && atomic_dec_and_test(&sg->sgc->ref))
342 } while (sg != first);
345 static void destroy_sched_domain(struct sched_domain *sd)
348 * If its an overlapping domain it has private groups, iterate and
351 if (sd->flags & SD_OVERLAP) {
352 free_sched_groups(sd->groups, 1);
353 } else if (atomic_dec_and_test(&sd->groups->ref)) {
354 kfree(sd->groups->sgc);
357 if (sd->shared && atomic_dec_and_test(&sd->shared->ref))
362 static void destroy_sched_domains_rcu(struct rcu_head *rcu)
364 struct sched_domain *sd = container_of(rcu, struct sched_domain, rcu);
367 struct sched_domain *parent = sd->parent;
368 destroy_sched_domain(sd);
373 static void destroy_sched_domains(struct sched_domain *sd)
376 call_rcu(&sd->rcu, destroy_sched_domains_rcu);
380 * Keep a special pointer to the highest sched_domain that has
381 * SD_SHARE_PKG_RESOURCE set (Last Level Cache Domain) for this
382 * allows us to avoid some pointer chasing select_idle_sibling().
384 * Also keep a unique ID per domain (we use the first CPU number in
385 * the cpumask of the domain), this allows us to quickly tell if
386 * two CPUs are in the same cache domain, see cpus_share_cache().
388 DEFINE_PER_CPU(struct sched_domain *, sd_llc);
389 DEFINE_PER_CPU(int, sd_llc_size);
390 DEFINE_PER_CPU(int, sd_llc_id);
391 DEFINE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);
392 DEFINE_PER_CPU(struct sched_domain *, sd_numa);
393 DEFINE_PER_CPU(struct sched_domain *, sd_asym);
395 static void update_top_cache_domain(int cpu)
397 struct sched_domain_shared *sds = NULL;
398 struct sched_domain *sd;
402 sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
404 id = cpumask_first(sched_domain_span(sd));
405 size = cpumask_weight(sched_domain_span(sd));
409 rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
410 per_cpu(sd_llc_size, cpu) = size;
411 per_cpu(sd_llc_id, cpu) = id;
412 rcu_assign_pointer(per_cpu(sd_llc_shared, cpu), sds);
414 sd = lowest_flag_domain(cpu, SD_NUMA);
415 rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
417 sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
418 rcu_assign_pointer(per_cpu(sd_asym, cpu), sd);
422 * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
423 * hold the hotplug lock.
426 cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
428 struct rq *rq = cpu_rq(cpu);
429 struct sched_domain *tmp;
431 /* Remove the sched domains which do not contribute to scheduling. */
432 for (tmp = sd; tmp; ) {
433 struct sched_domain *parent = tmp->parent;
437 if (sd_parent_degenerate(tmp, parent)) {
438 tmp->parent = parent->parent;
440 parent->parent->child = tmp;
442 * Transfer SD_PREFER_SIBLING down in case of a
443 * degenerate parent; the spans match for this
444 * so the property transfers.
446 if (parent->flags & SD_PREFER_SIBLING)
447 tmp->flags |= SD_PREFER_SIBLING;
448 destroy_sched_domain(parent);
453 if (sd && sd_degenerate(sd)) {
456 destroy_sched_domain(tmp);
461 sched_domain_debug(sd, cpu);
463 rq_attach_root(rq, rd);
465 rcu_assign_pointer(rq->sd, sd);
466 destroy_sched_domains(tmp);
468 update_top_cache_domain(cpu);
471 /* Setup the mask of CPUs configured for isolated domains */
472 static int __init isolated_cpu_setup(char *str)
476 alloc_bootmem_cpumask_var(&cpu_isolated_map);
477 ret = cpulist_parse(str, cpu_isolated_map);
479 pr_err("sched: Error, all isolcpus= values must be between 0 and %d\n", nr_cpu_ids);
484 __setup("isolcpus=", isolated_cpu_setup);
487 struct sched_domain ** __percpu sd;
488 struct root_domain *rd;
499 * Return the canonical balance CPU for this group, this is the first CPU
500 * of this group that's also in the balance mask.
502 * The balance mask are all those CPUs that could actually end up at this
503 * group. See build_balance_mask().
505 * Also see should_we_balance().
507 int group_balance_cpu(struct sched_group *sg)
509 return cpumask_first(group_balance_mask(sg));
514 * NUMA topology (first read the regular topology blurb below)
516 * Given a node-distance table, for example:
524 * which represents a 4 node ring topology like:
532 * We want to construct domains and groups to represent this. The way we go
533 * about doing this is to build the domains on 'hops'. For each NUMA level we
534 * construct the mask of all nodes reachable in @level hops.
536 * For the above NUMA topology that gives 3 levels:
538 * NUMA-2 0-3 0-3 0-3 0-3
539 * groups: {0-1,3},{1-3} {0-2},{0,2-3} {1-3},{0-1,3} {0,2-3},{0-2}
541 * NUMA-1 0-1,3 0-2 1-3 0,2-3
542 * groups: {0},{1},{3} {0},{1},{2} {1},{2},{3} {0},{2},{3}
547 * As can be seen; things don't nicely line up as with the regular topology.
548 * When we iterate a domain in child domain chunks some nodes can be
549 * represented multiple times -- hence the "overlap" naming for this part of
552 * In order to minimize this overlap, we only build enough groups to cover the
553 * domain. For instance Node-0 NUMA-2 would only get groups: 0-1,3 and 1-3.
557 * - the first group of each domain is its child domain; this
558 * gets us the first 0-1,3
559 * - the only uncovered node is 2, who's child domain is 1-3.
561 * However, because of the overlap, computing a unique CPU for each group is
562 * more complicated. Consider for instance the groups of NODE-1 NUMA-2, both
563 * groups include the CPUs of Node-0, while those CPUs would not in fact ever
564 * end up at those groups (they would end up in group: 0-1,3).
566 * To correct this we have to introduce the group balance mask. This mask
567 * will contain those CPUs in the group that can reach this group given the
568 * (child) domain tree.
570 * With this we can once again compute balance_cpu and sched_group_capacity
573 * XXX include words on how balance_cpu is unique and therefore can be
574 * used for sched_group_capacity links.
577 * Another 'interesting' topology is:
585 * Which looks a little like:
593 * This topology is asymmetric, nodes 1,2 are fully connected, but nodes 0,3
596 * This leads to a few particularly weird cases where the sched_domain's are
597 * not of the same number for each cpu. Consider:
600 * groups: {0-2},{1-3} {1-3},{0-2}
602 * NUMA-1 0-2 0-3 0-3 1-3
610 * Build the balance mask; it contains only those CPUs that can arrive at this
611 * group and should be considered to continue balancing.
613 * We do this during the group creation pass, therefore the group information
614 * isn't complete yet, however since each group represents a (child) domain we
615 * can fully construct this using the sched_domain bits (which are already
619 build_balance_mask(struct sched_domain *sd, struct sched_group *sg, struct cpumask *mask)
621 const struct cpumask *sg_span = sched_group_span(sg);
622 struct sd_data *sdd = sd->private;
623 struct sched_domain *sibling;
628 for_each_cpu(i, sg_span) {
629 sibling = *per_cpu_ptr(sdd->sd, i);
632 * Can happen in the asymmetric case, where these siblings are
633 * unused. The mask will not be empty because those CPUs that
634 * do have the top domain _should_ span the domain.
639 /* If we would not end up here, we can't continue from here */
640 if (!cpumask_equal(sg_span, sched_domain_span(sibling->child)))
643 cpumask_set_cpu(i, mask);
646 /* We must not have empty masks here */
647 WARN_ON_ONCE(cpumask_empty(mask));
651 * XXX: This creates per-node group entries; since the load-balancer will
652 * immediately access remote memory to construct this group's load-balance
653 * statistics having the groups node local is of dubious benefit.
655 static struct sched_group *
656 build_group_from_child_sched_domain(struct sched_domain *sd, int cpu)
658 struct sched_group *sg;
659 struct cpumask *sg_span;
661 sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
662 GFP_KERNEL, cpu_to_node(cpu));
667 sg_span = sched_group_span(sg);
669 cpumask_copy(sg_span, sched_domain_span(sd->child));
671 cpumask_copy(sg_span, sched_domain_span(sd));
676 static void init_overlap_sched_group(struct sched_domain *sd,
677 struct sched_group *sg)
679 struct cpumask *mask = sched_domains_tmpmask2;
680 struct sd_data *sdd = sd->private;
681 struct cpumask *sg_span;
684 build_balance_mask(sd, sg, mask);
685 cpu = cpumask_first_and(sched_group_span(sg), mask);
687 sg->sgc = *per_cpu_ptr(sdd->sgc, cpu);
688 if (atomic_inc_return(&sg->sgc->ref) == 1)
689 cpumask_copy(group_balance_mask(sg), mask);
691 WARN_ON_ONCE(!cpumask_equal(group_balance_mask(sg), mask));
694 * Initialize sgc->capacity such that even if we mess up the
695 * domains and no possible iteration will get us here, we won't
698 sg_span = sched_group_span(sg);
699 sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);
700 sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;
704 build_overlap_sched_groups(struct sched_domain *sd, int cpu)
706 struct sched_group *first = NULL, *last = NULL, *sg;
707 const struct cpumask *span = sched_domain_span(sd);
708 struct cpumask *covered = sched_domains_tmpmask;
709 struct sd_data *sdd = sd->private;
710 struct sched_domain *sibling;
713 cpumask_clear(covered);
715 for_each_cpu_wrap(i, span, cpu) {
716 struct cpumask *sg_span;
718 if (cpumask_test_cpu(i, covered))
721 sibling = *per_cpu_ptr(sdd->sd, i);
724 * Asymmetric node setups can result in situations where the
725 * domain tree is of unequal depth, make sure to skip domains
726 * that already cover the entire range.
728 * In that case build_sched_domains() will have terminated the
729 * iteration early and our sibling sd spans will be empty.
730 * Domains should always include the CPU they're built on, so
733 if (!cpumask_test_cpu(i, sched_domain_span(sibling)))
736 sg = build_group_from_child_sched_domain(sibling, cpu);
740 sg_span = sched_group_span(sg);
741 cpumask_or(covered, covered, sg_span);
743 init_overlap_sched_group(sd, sg);
757 free_sched_groups(first, 0);
764 * Package topology (also see the load-balance blurb in fair.c)
766 * The scheduler builds a tree structure to represent a number of important
767 * topology features. By default (default_topology[]) these include:
769 * - Simultaneous multithreading (SMT)
770 * - Multi-Core Cache (MC)
773 * Where the last one more or less denotes everything up to a NUMA node.
775 * The tree consists of 3 primary data structures:
777 * sched_domain -> sched_group -> sched_group_capacity
781 * The sched_domains are per-cpu and have a two way link (parent & child) and
782 * denote the ever growing mask of CPUs belonging to that level of topology.
784 * Each sched_domain has a circular (double) linked list of sched_group's, each
785 * denoting the domains of the level below (or individual CPUs in case of the
786 * first domain level). The sched_group linked by a sched_domain includes the
787 * CPU of that sched_domain [*].
789 * Take for instance a 2 threaded, 2 core, 2 cache cluster part:
791 * CPU 0 1 2 3 4 5 6 7
795 * SMT [ ] [ ] [ ] [ ]
799 * DIE 0-7 0-7 0-7 0-7 0-7 0-7 0-7 0-7
800 * MC 0-3 0-3 0-3 0-3 4-7 4-7 4-7 4-7
801 * SMT 0-1 0-1 2-3 2-3 4-5 4-5 6-7 6-7
803 * CPU 0 1 2 3 4 5 6 7
805 * One way to think about it is: sched_domain moves you up and down among these
806 * topology levels, while sched_group moves you sideways through it, at child
807 * domain granularity.
809 * sched_group_capacity ensures each unique sched_group has shared storage.
811 * There are two related construction problems, both require a CPU that
812 * uniquely identify each group (for a given domain):
814 * - The first is the balance_cpu (see should_we_balance() and the
815 * load-balance blub in fair.c); for each group we only want 1 CPU to
816 * continue balancing at a higher domain.
818 * - The second is the sched_group_capacity; we want all identical groups
819 * to share a single sched_group_capacity.
821 * Since these topologies are exclusive by construction. That is, its
822 * impossible for an SMT thread to belong to multiple cores, and cores to
823 * be part of multiple caches. There is a very clear and unique location
824 * for each CPU in the hierarchy.
826 * Therefore computing a unique CPU for each group is trivial (the iteration
827 * mask is redundant and set all 1s; all CPUs in a group will end up at _that_
828 * group), we can simply pick the first CPU in each group.
831 * [*] in other words, the first group of each domain is its child domain.
834 static struct sched_group *get_group(int cpu, struct sd_data *sdd)
836 struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
837 struct sched_domain *child = sd->child;
838 struct sched_group *sg;
841 cpu = cpumask_first(sched_domain_span(child));
843 sg = *per_cpu_ptr(sdd->sg, cpu);
844 sg->sgc = *per_cpu_ptr(sdd->sgc, cpu);
846 /* For claim_allocations: */
847 atomic_inc(&sg->ref);
848 atomic_inc(&sg->sgc->ref);
851 cpumask_copy(sched_group_span(sg), sched_domain_span(child));
852 cpumask_copy(group_balance_mask(sg), sched_group_span(sg));
854 cpumask_set_cpu(cpu, sched_group_span(sg));
855 cpumask_set_cpu(cpu, group_balance_mask(sg));
858 sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sched_group_span(sg));
859 sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;
865 * build_sched_groups will build a circular linked list of the groups
866 * covered by the given span, and will set each group's ->cpumask correctly,
867 * and ->cpu_capacity to 0.
869 * Assumes the sched_domain tree is fully constructed
872 build_sched_groups(struct sched_domain *sd, int cpu)
874 struct sched_group *first = NULL, *last = NULL;
875 struct sd_data *sdd = sd->private;
876 const struct cpumask *span = sched_domain_span(sd);
877 struct cpumask *covered;
880 lockdep_assert_held(&sched_domains_mutex);
881 covered = sched_domains_tmpmask;
883 cpumask_clear(covered);
885 for_each_cpu_wrap(i, span, cpu) {
886 struct sched_group *sg;
888 if (cpumask_test_cpu(i, covered))
891 sg = get_group(i, sdd);
893 cpumask_or(covered, covered, sched_group_span(sg));
908 * Initialize sched groups cpu_capacity.
910 * cpu_capacity indicates the capacity of sched group, which is used while
911 * distributing the load between different sched groups in a sched domain.
912 * Typically cpu_capacity for all the groups in a sched domain will be same
913 * unless there are asymmetries in the topology. If there are asymmetries,
914 * group having more cpu_capacity will pickup more load compared to the
915 * group having less cpu_capacity.
917 static void init_sched_groups_capacity(int cpu, struct sched_domain *sd)
919 struct sched_group *sg = sd->groups;
924 int cpu, max_cpu = -1;
926 sg->group_weight = cpumask_weight(sched_group_span(sg));
928 if (!(sd->flags & SD_ASYM_PACKING))
931 for_each_cpu(cpu, sched_group_span(sg)) {
934 else if (sched_asym_prefer(cpu, max_cpu))
937 sg->asym_prefer_cpu = max_cpu;
941 } while (sg != sd->groups);
943 if (cpu != group_balance_cpu(sg))
946 update_group_capacity(sd, cpu);
950 * Initializers for schedule domains
951 * Non-inlined to reduce accumulated stack pressure in build_sched_domains()
954 static int default_relax_domain_level = -1;
955 int sched_domain_level_max;
957 static int __init setup_relax_domain_level(char *str)
959 if (kstrtoint(str, 0, &default_relax_domain_level))
960 pr_warn("Unable to set relax_domain_level\n");
964 __setup("relax_domain_level=", setup_relax_domain_level);
966 static void set_domain_attribute(struct sched_domain *sd,
967 struct sched_domain_attr *attr)
971 if (!attr || attr->relax_domain_level < 0) {
972 if (default_relax_domain_level < 0)
975 request = default_relax_domain_level;
977 request = attr->relax_domain_level;
978 if (request < sd->level) {
979 /* Turn off idle balance on this domain: */
980 sd->flags &= ~(SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
982 /* Turn on idle balance on this domain: */
983 sd->flags |= (SD_BALANCE_WAKE|SD_BALANCE_NEWIDLE);
987 static void __sdt_free(const struct cpumask *cpu_map);
988 static int __sdt_alloc(const struct cpumask *cpu_map);
990 static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
991 const struct cpumask *cpu_map)
995 if (!atomic_read(&d->rd->refcount))
996 free_rootdomain(&d->rd->rcu);
1002 __sdt_free(cpu_map);
1010 __visit_domain_allocation_hell(struct s_data *d, const struct cpumask *cpu_map)
1012 memset(d, 0, sizeof(*d));
1014 if (__sdt_alloc(cpu_map))
1015 return sa_sd_storage;
1016 d->sd = alloc_percpu(struct sched_domain *);
1018 return sa_sd_storage;
1019 d->rd = alloc_rootdomain();
1022 return sa_rootdomain;
1026 * NULL the sd_data elements we've used to build the sched_domain and
1027 * sched_group structure so that the subsequent __free_domain_allocs()
1028 * will not free the data we're using.
1030 static void claim_allocations(int cpu, struct sched_domain *sd)
1032 struct sd_data *sdd = sd->private;
1034 WARN_ON_ONCE(*per_cpu_ptr(sdd->sd, cpu) != sd);
1035 *per_cpu_ptr(sdd->sd, cpu) = NULL;
1037 if (atomic_read(&(*per_cpu_ptr(sdd->sds, cpu))->ref))
1038 *per_cpu_ptr(sdd->sds, cpu) = NULL;
1040 if (atomic_read(&(*per_cpu_ptr(sdd->sg, cpu))->ref))
1041 *per_cpu_ptr(sdd->sg, cpu) = NULL;
1043 if (atomic_read(&(*per_cpu_ptr(sdd->sgc, cpu))->ref))
1044 *per_cpu_ptr(sdd->sgc, cpu) = NULL;
1048 static int sched_domains_numa_levels;
1049 enum numa_topology_type sched_numa_topology_type;
1050 static int *sched_domains_numa_distance;
1051 int sched_max_numa_distance;
1052 static struct cpumask ***sched_domains_numa_masks;
1053 static int sched_domains_curr_level;
1057 * SD_flags allowed in topology descriptions.
1059 * These flags are purely descriptive of the topology and do not prescribe
1060 * behaviour. Behaviour is artificial and mapped in the below sd_init()
1063 * SD_SHARE_CPUCAPACITY - describes SMT topologies
1064 * SD_SHARE_PKG_RESOURCES - describes shared caches
1065 * SD_NUMA - describes NUMA topologies
1066 * SD_SHARE_POWERDOMAIN - describes shared power domain
1067 * SD_ASYM_CPUCAPACITY - describes mixed capacity topologies
1069 * Odd one out, which beside describing the topology has a quirk also
1070 * prescribes the desired behaviour that goes along with it:
1072 * SD_ASYM_PACKING - describes SMT quirks
1074 #define TOPOLOGY_SD_FLAGS \
1075 (SD_SHARE_CPUCAPACITY | \
1076 SD_SHARE_PKG_RESOURCES | \
1079 SD_ASYM_CPUCAPACITY | \
1080 SD_SHARE_POWERDOMAIN)
1082 static struct sched_domain *
1083 sd_init(struct sched_domain_topology_level *tl,
1084 const struct cpumask *cpu_map,
1085 struct sched_domain *child, int cpu)
1087 struct sd_data *sdd = &tl->data;
1088 struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu);
1089 int sd_id, sd_weight, sd_flags = 0;
1093 * Ugly hack to pass state to sd_numa_mask()...
1095 sched_domains_curr_level = tl->numa_level;
1098 sd_weight = cpumask_weight(tl->mask(cpu));
1101 sd_flags = (*tl->sd_flags)();
1102 if (WARN_ONCE(sd_flags & ~TOPOLOGY_SD_FLAGS,
1103 "wrong sd_flags in topology description\n"))
1104 sd_flags &= ~TOPOLOGY_SD_FLAGS;
1106 *sd = (struct sched_domain){
1107 .min_interval = sd_weight,
1108 .max_interval = 2*sd_weight,
1110 .imbalance_pct = 125,
1112 .cache_nice_tries = 0,
1119 .flags = 1*SD_LOAD_BALANCE
1120 | 1*SD_BALANCE_NEWIDLE
1125 | 0*SD_SHARE_CPUCAPACITY
1126 | 0*SD_SHARE_PKG_RESOURCES
1128 | 0*SD_PREFER_SIBLING
1133 .last_balance = jiffies,
1134 .balance_interval = sd_weight,
1136 .max_newidle_lb_cost = 0,
1137 .next_decay_max_lb_cost = jiffies,
1139 #ifdef CONFIG_SCHED_DEBUG
1144 cpumask_and(sched_domain_span(sd), cpu_map, tl->mask(cpu));
1145 sd_id = cpumask_first(sched_domain_span(sd));
1148 * Convert topological properties into behaviour.
1151 if (sd->flags & SD_ASYM_CPUCAPACITY) {
1152 struct sched_domain *t = sd;
1154 for_each_lower_domain(t)
1155 t->flags |= SD_BALANCE_WAKE;
1158 if (sd->flags & SD_SHARE_CPUCAPACITY) {
1159 sd->flags |= SD_PREFER_SIBLING;
1160 sd->imbalance_pct = 110;
1161 sd->smt_gain = 1178; /* ~15% */
1163 } else if (sd->flags & SD_SHARE_PKG_RESOURCES) {
1164 sd->imbalance_pct = 117;
1165 sd->cache_nice_tries = 1;
1169 } else if (sd->flags & SD_NUMA) {
1170 sd->cache_nice_tries = 2;
1174 sd->flags |= SD_SERIALIZE;
1175 if (sched_domains_numa_distance[tl->numa_level] > RECLAIM_DISTANCE) {
1176 sd->flags &= ~(SD_BALANCE_EXEC |
1183 sd->flags |= SD_PREFER_SIBLING;
1184 sd->cache_nice_tries = 1;
1190 * For all levels sharing cache; connect a sched_domain_shared
1193 if (sd->flags & SD_SHARE_PKG_RESOURCES) {
1194 sd->shared = *per_cpu_ptr(sdd->sds, sd_id);
1195 atomic_inc(&sd->shared->ref);
1196 atomic_set(&sd->shared->nr_busy_cpus, sd_weight);
1205 * Topology list, bottom-up.
1207 static struct sched_domain_topology_level default_topology[] = {
1208 #ifdef CONFIG_SCHED_SMT
1209 { cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT) },
1211 #ifdef CONFIG_SCHED_MC
1212 { cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
1214 { cpu_cpu_mask, SD_INIT_NAME(DIE) },
1218 static struct sched_domain_topology_level *sched_domain_topology =
1221 #define for_each_sd_topology(tl) \
1222 for (tl = sched_domain_topology; tl->mask; tl++)
1224 void set_sched_topology(struct sched_domain_topology_level *tl)
1226 if (WARN_ON_ONCE(sched_smp_initialized))
1229 sched_domain_topology = tl;
1234 static const struct cpumask *sd_numa_mask(int cpu)
1236 return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)];
1239 static void sched_numa_warn(const char *str)
1241 static int done = false;
1249 printk(KERN_WARNING "ERROR: %s\n\n", str);
1251 for (i = 0; i < nr_node_ids; i++) {
1252 printk(KERN_WARNING " ");
1253 for (j = 0; j < nr_node_ids; j++)
1254 printk(KERN_CONT "%02d ", node_distance(i,j));
1255 printk(KERN_CONT "\n");
1257 printk(KERN_WARNING "\n");
1260 bool find_numa_distance(int distance)
1264 if (distance == node_distance(0, 0))
1267 for (i = 0; i < sched_domains_numa_levels; i++) {
1268 if (sched_domains_numa_distance[i] == distance)
1276 * A system can have three types of NUMA topology:
1277 * NUMA_DIRECT: all nodes are directly connected, or not a NUMA system
1278 * NUMA_GLUELESS_MESH: some nodes reachable through intermediary nodes
1279 * NUMA_BACKPLANE: nodes can reach other nodes through a backplane
1281 * The difference between a glueless mesh topology and a backplane
1282 * topology lies in whether communication between not directly
1283 * connected nodes goes through intermediary nodes (where programs
1284 * could run), or through backplane controllers. This affects
1285 * placement of programs.
1287 * The type of topology can be discerned with the following tests:
1288 * - If the maximum distance between any nodes is 1 hop, the system
1289 * is directly connected.
1290 * - If for two nodes A and B, located N > 1 hops away from each other,
1291 * there is an intermediary node C, which is < N hops away from both
1292 * nodes A and B, the system is a glueless mesh.
1294 static void init_numa_topology_type(void)
1298 n = sched_max_numa_distance;
1300 if (sched_domains_numa_levels <= 1) {
1301 sched_numa_topology_type = NUMA_DIRECT;
1305 for_each_online_node(a) {
1306 for_each_online_node(b) {
1307 /* Find two nodes furthest removed from each other. */
1308 if (node_distance(a, b) < n)
1311 /* Is there an intermediary node between a and b? */
1312 for_each_online_node(c) {
1313 if (node_distance(a, c) < n &&
1314 node_distance(b, c) < n) {
1315 sched_numa_topology_type =
1321 sched_numa_topology_type = NUMA_BACKPLANE;
1327 void sched_init_numa(void)
1329 int next_distance, curr_distance = node_distance(0, 0);
1330 struct sched_domain_topology_level *tl;
1334 sched_domains_numa_distance = kzalloc(sizeof(int) * nr_node_ids, GFP_KERNEL);
1335 if (!sched_domains_numa_distance)
1339 * O(nr_nodes^2) deduplicating selection sort -- in order to find the
1340 * unique distances in the node_distance() table.
1342 * Assumes node_distance(0,j) includes all distances in
1343 * node_distance(i,j) in order to avoid cubic time.
1345 next_distance = curr_distance;
1346 for (i = 0; i < nr_node_ids; i++) {
1347 for (j = 0; j < nr_node_ids; j++) {
1348 for (k = 0; k < nr_node_ids; k++) {
1349 int distance = node_distance(i, k);
1351 if (distance > curr_distance &&
1352 (distance < next_distance ||
1353 next_distance == curr_distance))
1354 next_distance = distance;
1357 * While not a strong assumption it would be nice to know
1358 * about cases where if node A is connected to B, B is not
1359 * equally connected to A.
1361 if (sched_debug() && node_distance(k, i) != distance)
1362 sched_numa_warn("Node-distance not symmetric");
1364 if (sched_debug() && i && !find_numa_distance(distance))
1365 sched_numa_warn("Node-0 not representative");
1367 if (next_distance != curr_distance) {
1368 sched_domains_numa_distance[level++] = next_distance;
1369 sched_domains_numa_levels = level;
1370 curr_distance = next_distance;
1375 * In case of sched_debug() we verify the above assumption.
1385 * 'level' contains the number of unique distances, excluding the
1386 * identity distance node_distance(i,i).
1388 * The sched_domains_numa_distance[] array includes the actual distance
1393 * Here, we should temporarily reset sched_domains_numa_levels to 0.
1394 * If it fails to allocate memory for array sched_domains_numa_masks[][],
1395 * the array will contain less then 'level' members. This could be
1396 * dangerous when we use it to iterate array sched_domains_numa_masks[][]
1397 * in other functions.
1399 * We reset it to 'level' at the end of this function.
1401 sched_domains_numa_levels = 0;
1403 sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL);
1404 if (!sched_domains_numa_masks)
1408 * Now for each level, construct a mask per node which contains all
1409 * CPUs of nodes that are that many hops away from us.
1411 for (i = 0; i < level; i++) {
1412 sched_domains_numa_masks[i] =
1413 kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
1414 if (!sched_domains_numa_masks[i])
1417 for (j = 0; j < nr_node_ids; j++) {
1418 struct cpumask *mask = kzalloc(cpumask_size(), GFP_KERNEL);
1422 sched_domains_numa_masks[i][j] = mask;
1425 if (node_distance(j, k) > sched_domains_numa_distance[i])
1428 cpumask_or(mask, mask, cpumask_of_node(k));
1433 /* Compute default topology size */
1434 for (i = 0; sched_domain_topology[i].mask; i++);
1436 tl = kzalloc((i + level + 1) *
1437 sizeof(struct sched_domain_topology_level), GFP_KERNEL);
1442 * Copy the default topology bits..
1444 for (i = 0; sched_domain_topology[i].mask; i++)
1445 tl[i] = sched_domain_topology[i];
1448 * .. and append 'j' levels of NUMA goodness.
1450 for (j = 0; j < level; i++, j++) {
1451 tl[i] = (struct sched_domain_topology_level){
1452 .mask = sd_numa_mask,
1453 .sd_flags = cpu_numa_flags,
1454 .flags = SDTL_OVERLAP,
1460 sched_domain_topology = tl;
1462 sched_domains_numa_levels = level;
1463 sched_max_numa_distance = sched_domains_numa_distance[level - 1];
1465 init_numa_topology_type();
1468 void sched_domains_numa_masks_set(unsigned int cpu)
1470 int node = cpu_to_node(cpu);
1473 for (i = 0; i < sched_domains_numa_levels; i++) {
1474 for (j = 0; j < nr_node_ids; j++) {
1475 if (node_distance(j, node) <= sched_domains_numa_distance[i])
1476 cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]);
1481 void sched_domains_numa_masks_clear(unsigned int cpu)
1485 for (i = 0; i < sched_domains_numa_levels; i++) {
1486 for (j = 0; j < nr_node_ids; j++)
1487 cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]);
1491 #endif /* CONFIG_NUMA */
1493 static int __sdt_alloc(const struct cpumask *cpu_map)
1495 struct sched_domain_topology_level *tl;
1498 for_each_sd_topology(tl) {
1499 struct sd_data *sdd = &tl->data;
1501 sdd->sd = alloc_percpu(struct sched_domain *);
1505 sdd->sds = alloc_percpu(struct sched_domain_shared *);
1509 sdd->sg = alloc_percpu(struct sched_group *);
1513 sdd->sgc = alloc_percpu(struct sched_group_capacity *);
1517 for_each_cpu(j, cpu_map) {
1518 struct sched_domain *sd;
1519 struct sched_domain_shared *sds;
1520 struct sched_group *sg;
1521 struct sched_group_capacity *sgc;
1523 sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(),
1524 GFP_KERNEL, cpu_to_node(j));
1528 *per_cpu_ptr(sdd->sd, j) = sd;
1530 sds = kzalloc_node(sizeof(struct sched_domain_shared),
1531 GFP_KERNEL, cpu_to_node(j));
1535 *per_cpu_ptr(sdd->sds, j) = sds;
1537 sg = kzalloc_node(sizeof(struct sched_group) + cpumask_size(),
1538 GFP_KERNEL, cpu_to_node(j));
1544 *per_cpu_ptr(sdd->sg, j) = sg;
1546 sgc = kzalloc_node(sizeof(struct sched_group_capacity) + cpumask_size(),
1547 GFP_KERNEL, cpu_to_node(j));
1551 #ifdef CONFIG_SCHED_DEBUG
1555 *per_cpu_ptr(sdd->sgc, j) = sgc;
1562 static void __sdt_free(const struct cpumask *cpu_map)
1564 struct sched_domain_topology_level *tl;
1567 for_each_sd_topology(tl) {
1568 struct sd_data *sdd = &tl->data;
1570 for_each_cpu(j, cpu_map) {
1571 struct sched_domain *sd;
1574 sd = *per_cpu_ptr(sdd->sd, j);
1575 if (sd && (sd->flags & SD_OVERLAP))
1576 free_sched_groups(sd->groups, 0);
1577 kfree(*per_cpu_ptr(sdd->sd, j));
1581 kfree(*per_cpu_ptr(sdd->sds, j));
1583 kfree(*per_cpu_ptr(sdd->sg, j));
1585 kfree(*per_cpu_ptr(sdd->sgc, j));
1587 free_percpu(sdd->sd);
1589 free_percpu(sdd->sds);
1591 free_percpu(sdd->sg);
1593 free_percpu(sdd->sgc);
1598 struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
1599 const struct cpumask *cpu_map, struct sched_domain_attr *attr,
1600 struct sched_domain *child, int cpu)
1602 struct sched_domain *sd = sd_init(tl, cpu_map, child, cpu);
1605 sd->level = child->level + 1;
1606 sched_domain_level_max = max(sched_domain_level_max, sd->level);
1609 if (!cpumask_subset(sched_domain_span(child),
1610 sched_domain_span(sd))) {
1611 pr_err("BUG: arch topology borken\n");
1612 #ifdef CONFIG_SCHED_DEBUG
1613 pr_err(" the %s domain not a subset of the %s domain\n",
1614 child->name, sd->name);
1616 /* Fixup, ensure @sd has at least @child cpus. */
1617 cpumask_or(sched_domain_span(sd),
1618 sched_domain_span(sd),
1619 sched_domain_span(child));
1623 set_domain_attribute(sd, attr);
1629 * Build sched domains for a given set of CPUs and attach the sched domains
1630 * to the individual CPUs
1633 build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *attr)
1635 enum s_alloc alloc_state;
1636 struct sched_domain *sd;
1638 struct rq *rq = NULL;
1639 int i, ret = -ENOMEM;
1641 alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
1642 if (alloc_state != sa_rootdomain)
1645 /* Set up domains for CPUs specified by the cpu_map: */
1646 for_each_cpu(i, cpu_map) {
1647 struct sched_domain_topology_level *tl;
1650 for_each_sd_topology(tl) {
1651 sd = build_sched_domain(tl, cpu_map, attr, sd, i);
1652 if (tl == sched_domain_topology)
1653 *per_cpu_ptr(d.sd, i) = sd;
1654 if (tl->flags & SDTL_OVERLAP)
1655 sd->flags |= SD_OVERLAP;
1656 if (cpumask_equal(cpu_map, sched_domain_span(sd)))
1661 /* Build the groups for the domains */
1662 for_each_cpu(i, cpu_map) {
1663 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
1664 sd->span_weight = cpumask_weight(sched_domain_span(sd));
1665 if (sd->flags & SD_OVERLAP) {
1666 if (build_overlap_sched_groups(sd, i))
1669 if (build_sched_groups(sd, i))
1675 /* Calculate CPU capacity for physical packages and nodes */
1676 for (i = nr_cpumask_bits-1; i >= 0; i--) {
1677 if (!cpumask_test_cpu(i, cpu_map))
1680 for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) {
1681 claim_allocations(i, sd);
1682 init_sched_groups_capacity(i, sd);
1686 /* Attach the domains */
1688 for_each_cpu(i, cpu_map) {
1690 sd = *per_cpu_ptr(d.sd, i);
1692 /* Use READ_ONCE()/WRITE_ONCE() to avoid load/store tearing: */
1693 if (rq->cpu_capacity_orig > READ_ONCE(d.rd->max_cpu_capacity))
1694 WRITE_ONCE(d.rd->max_cpu_capacity, rq->cpu_capacity_orig);
1696 cpu_attach_domain(sd, d.rd, i);
1700 if (rq && sched_debug_enabled) {
1701 pr_info("span: %*pbl (max cpu_capacity = %lu)\n",
1702 cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity);
1707 __free_domain_allocs(&d, alloc_state, cpu_map);
1711 /* Current sched domains: */
1712 static cpumask_var_t *doms_cur;
1714 /* Number of sched domains in 'doms_cur': */
1715 static int ndoms_cur;
1717 /* Attribues of custom domains in 'doms_cur' */
1718 static struct sched_domain_attr *dattr_cur;
1721 * Special case: If a kmalloc() of a doms_cur partition (array of
1722 * cpumask) fails, then fallback to a single sched domain,
1723 * as determined by the single cpumask fallback_doms.
1725 static cpumask_var_t fallback_doms;
1728 * arch_update_cpu_topology lets virtualized architectures update the
1729 * CPU core maps. It is supposed to return 1 if the topology changed
1730 * or 0 if it stayed the same.
1732 int __weak arch_update_cpu_topology(void)
1737 cpumask_var_t *alloc_sched_domains(unsigned int ndoms)
1740 cpumask_var_t *doms;
1742 doms = kmalloc(sizeof(*doms) * ndoms, GFP_KERNEL);
1745 for (i = 0; i < ndoms; i++) {
1746 if (!alloc_cpumask_var(&doms[i], GFP_KERNEL)) {
1747 free_sched_domains(doms, i);
1754 void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms)
1757 for (i = 0; i < ndoms; i++)
1758 free_cpumask_var(doms[i]);
1763 * Set up scheduler domains and groups. Callers must hold the hotplug lock.
1764 * For now this just excludes isolated CPUs, but could be used to
1765 * exclude other special cases in the future.
1767 int sched_init_domains(const struct cpumask *cpu_map)
1771 zalloc_cpumask_var(&sched_domains_tmpmask, GFP_KERNEL);
1772 zalloc_cpumask_var(&sched_domains_tmpmask2, GFP_KERNEL);
1773 zalloc_cpumask_var(&fallback_doms, GFP_KERNEL);
1775 arch_update_cpu_topology();
1777 doms_cur = alloc_sched_domains(ndoms_cur);
1779 doms_cur = &fallback_doms;
1780 cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
1781 err = build_sched_domains(doms_cur[0], NULL);
1782 register_sched_domain_sysctl();
1788 * Detach sched domains from a group of CPUs specified in cpu_map
1789 * These CPUs will now be attached to the NULL domain
1791 static void detach_destroy_domains(const struct cpumask *cpu_map)
1796 for_each_cpu(i, cpu_map)
1797 cpu_attach_domain(NULL, &def_root_domain, i);
1801 /* handle null as "default" */
1802 static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
1803 struct sched_domain_attr *new, int idx_new)
1805 struct sched_domain_attr tmp;
1812 return !memcmp(cur ? (cur + idx_cur) : &tmp,
1813 new ? (new + idx_new) : &tmp,
1814 sizeof(struct sched_domain_attr));
1818 * Partition sched domains as specified by the 'ndoms_new'
1819 * cpumasks in the array doms_new[] of cpumasks. This compares
1820 * doms_new[] to the current sched domain partitioning, doms_cur[].
1821 * It destroys each deleted domain and builds each new domain.
1823 * 'doms_new' is an array of cpumask_var_t's of length 'ndoms_new'.
1824 * The masks don't intersect (don't overlap.) We should setup one
1825 * sched domain for each mask. CPUs not in any of the cpumasks will
1826 * not be load balanced. If the same cpumask appears both in the
1827 * current 'doms_cur' domains and in the new 'doms_new', we can leave
1830 * The passed in 'doms_new' should be allocated using
1831 * alloc_sched_domains. This routine takes ownership of it and will
1832 * free_sched_domains it when done with it. If the caller failed the
1833 * alloc call, then it can pass in doms_new == NULL && ndoms_new == 1,
1834 * and partition_sched_domains() will fallback to the single partition
1835 * 'fallback_doms', it also forces the domains to be rebuilt.
1837 * If doms_new == NULL it will be replaced with cpu_online_mask.
1838 * ndoms_new == 0 is a special case for destroying existing domains,
1839 * and it will not create the default domain.
1841 * Call with hotplug lock held
1843 void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
1844 struct sched_domain_attr *dattr_new)
1849 mutex_lock(&sched_domains_mutex);
1851 /* Always unregister in case we don't destroy any domains: */
1852 unregister_sched_domain_sysctl();
1854 /* Let the architecture update CPU core mappings: */
1855 new_topology = arch_update_cpu_topology();
1857 n = doms_new ? ndoms_new : 0;
1859 /* Destroy deleted domains: */
1860 for (i = 0; i < ndoms_cur; i++) {
1861 for (j = 0; j < n && !new_topology; j++) {
1862 if (cpumask_equal(doms_cur[i], doms_new[j])
1863 && dattrs_equal(dattr_cur, i, dattr_new, j))
1866 /* No match - a current sched domain not in new doms_new[] */
1867 detach_destroy_domains(doms_cur[i]);
1873 if (doms_new == NULL) {
1875 doms_new = &fallback_doms;
1876 cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
1877 WARN_ON_ONCE(dattr_new);
1880 /* Build new domains: */
1881 for (i = 0; i < ndoms_new; i++) {
1882 for (j = 0; j < n && !new_topology; j++) {
1883 if (cpumask_equal(doms_new[i], doms_cur[j])
1884 && dattrs_equal(dattr_new, i, dattr_cur, j))
1887 /* No match - add a new doms_new */
1888 build_sched_domains(doms_new[i], dattr_new ? dattr_new + i : NULL);
1893 /* Remember the new sched domains: */
1894 if (doms_cur != &fallback_doms)
1895 free_sched_domains(doms_cur, ndoms_cur);
1898 doms_cur = doms_new;
1899 dattr_cur = dattr_new;
1900 ndoms_cur = ndoms_new;
1902 register_sched_domain_sysctl();
1904 mutex_unlock(&sched_domains_mutex);