2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
23 #include <linux/sched.h>
24 #include <linux/latencytop.h>
25 #include <linux/cpumask.h>
26 #include <linux/cpuidle.h>
27 #include <linux/slab.h>
28 #include <linux/profile.h>
29 #include <linux/interrupt.h>
30 #include <linux/mempolicy.h>
31 #include <linux/migrate.h>
32 #include <linux/task_work.h>
34 #include <trace/events/sched.h>
39 * Targeted preemption latency for CPU-bound tasks:
40 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
42 * NOTE: this latency value is not the same as the concept of
43 * 'timeslice length' - timeslices in CFS are of variable length
44 * and have no persistent notion like in traditional, time-slice
45 * based scheduling concepts.
47 * (to see the precise effective timeslice length of your workload,
48 * run vmstat and monitor the context-switches (cs) field)
50 unsigned int sysctl_sched_latency = 6000000ULL;
51 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
54 * The initial- and re-scaling of tunables is configurable
55 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
58 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
59 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
60 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
62 enum sched_tunable_scaling sysctl_sched_tunable_scaling
63 = SCHED_TUNABLESCALING_LOG;
66 * Minimal preemption granularity for CPU-bound tasks:
67 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
69 unsigned int sysctl_sched_min_granularity = 750000ULL;
70 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
73 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
75 static unsigned int sched_nr_latency = 8;
78 * After fork, child runs first. If set to 0 (default) then
79 * parent will (try to) run first.
81 unsigned int sysctl_sched_child_runs_first __read_mostly;
84 * SCHED_OTHER wake-up granularity.
85 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
87 * This option delays the preemption effects of decoupled workloads
88 * and reduces their over-scheduling. Synchronous workloads will still
89 * have immediate wakeup/sleep latencies.
91 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
92 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
94 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
97 * The exponential sliding window over which load is averaged for shares
101 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
103 #ifdef CONFIG_CFS_BANDWIDTH
105 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
106 * each time a cfs_rq requests quota.
108 * Note: in the case that the slice exceeds the runtime remaining (either due
109 * to consumption or the quota being specified to be smaller than the slice)
110 * we will always only issue the remaining available time.
112 * default: 5 msec, units: microseconds
114 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
117 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
123 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
129 static inline void update_load_set(struct load_weight *lw, unsigned long w)
136 * Increase the granularity value when there are more CPUs,
137 * because with more CPUs the 'effective latency' as visible
138 * to users decreases. But the relationship is not linear,
139 * so pick a second-best guess by going with the log2 of the
142 * This idea comes from the SD scheduler of Con Kolivas:
144 static unsigned int get_update_sysctl_factor(void)
146 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
149 switch (sysctl_sched_tunable_scaling) {
150 case SCHED_TUNABLESCALING_NONE:
153 case SCHED_TUNABLESCALING_LINEAR:
156 case SCHED_TUNABLESCALING_LOG:
158 factor = 1 + ilog2(cpus);
165 static void update_sysctl(void)
167 unsigned int factor = get_update_sysctl_factor();
169 #define SET_SYSCTL(name) \
170 (sysctl_##name = (factor) * normalized_sysctl_##name)
171 SET_SYSCTL(sched_min_granularity);
172 SET_SYSCTL(sched_latency);
173 SET_SYSCTL(sched_wakeup_granularity);
177 void sched_init_granularity(void)
182 #define WMULT_CONST (~0U)
183 #define WMULT_SHIFT 32
185 static void __update_inv_weight(struct load_weight *lw)
189 if (likely(lw->inv_weight))
192 w = scale_load_down(lw->weight);
194 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
196 else if (unlikely(!w))
197 lw->inv_weight = WMULT_CONST;
199 lw->inv_weight = WMULT_CONST / w;
203 * delta_exec * weight / lw.weight
205 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
207 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
208 * we're guaranteed shift stays positive because inv_weight is guaranteed to
209 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
211 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
212 * weight/lw.weight <= 1, and therefore our shift will also be positive.
214 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
216 u64 fact = scale_load_down(weight);
217 int shift = WMULT_SHIFT;
219 __update_inv_weight(lw);
221 if (unlikely(fact >> 32)) {
228 /* hint to use a 32x32->64 mul */
229 fact = (u64)(u32)fact * lw->inv_weight;
236 return mul_u64_u32_shr(delta_exec, fact, shift);
240 const struct sched_class fair_sched_class;
242 /**************************************************************
243 * CFS operations on generic schedulable entities:
246 #ifdef CONFIG_FAIR_GROUP_SCHED
248 /* cpu runqueue to which this cfs_rq is attached */
249 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
254 /* An entity is a task if it doesn't "own" a runqueue */
255 #define entity_is_task(se) (!se->my_q)
257 static inline struct task_struct *task_of(struct sched_entity *se)
259 #ifdef CONFIG_SCHED_DEBUG
260 WARN_ON_ONCE(!entity_is_task(se));
262 return container_of(se, struct task_struct, se);
265 /* Walk up scheduling entities hierarchy */
266 #define for_each_sched_entity(se) \
267 for (; se; se = se->parent)
269 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
274 /* runqueue on which this entity is (to be) queued */
275 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
280 /* runqueue "owned" by this group */
281 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
286 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
288 if (!cfs_rq->on_list) {
290 * Ensure we either appear before our parent (if already
291 * enqueued) or force our parent to appear after us when it is
292 * enqueued. The fact that we always enqueue bottom-up
293 * reduces this to two cases.
295 if (cfs_rq->tg->parent &&
296 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
297 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
298 &rq_of(cfs_rq)->leaf_cfs_rq_list);
300 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
301 &rq_of(cfs_rq)->leaf_cfs_rq_list);
308 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
310 if (cfs_rq->on_list) {
311 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
316 /* Iterate thr' all leaf cfs_rq's on a runqueue */
317 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
318 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
320 /* Do the two (enqueued) entities belong to the same group ? */
321 static inline struct cfs_rq *
322 is_same_group(struct sched_entity *se, struct sched_entity *pse)
324 if (se->cfs_rq == pse->cfs_rq)
330 static inline struct sched_entity *parent_entity(struct sched_entity *se)
336 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
338 int se_depth, pse_depth;
341 * preemption test can be made between sibling entities who are in the
342 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
343 * both tasks until we find their ancestors who are siblings of common
347 /* First walk up until both entities are at same depth */
348 se_depth = (*se)->depth;
349 pse_depth = (*pse)->depth;
351 while (se_depth > pse_depth) {
353 *se = parent_entity(*se);
356 while (pse_depth > se_depth) {
358 *pse = parent_entity(*pse);
361 while (!is_same_group(*se, *pse)) {
362 *se = parent_entity(*se);
363 *pse = parent_entity(*pse);
367 #else /* !CONFIG_FAIR_GROUP_SCHED */
369 static inline struct task_struct *task_of(struct sched_entity *se)
371 return container_of(se, struct task_struct, se);
374 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
376 return container_of(cfs_rq, struct rq, cfs);
379 #define entity_is_task(se) 1
381 #define for_each_sched_entity(se) \
382 for (; se; se = NULL)
384 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
386 return &task_rq(p)->cfs;
389 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
391 struct task_struct *p = task_of(se);
392 struct rq *rq = task_rq(p);
397 /* runqueue "owned" by this group */
398 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
403 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
407 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
411 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
412 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
414 static inline struct sched_entity *parent_entity(struct sched_entity *se)
420 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
424 #endif /* CONFIG_FAIR_GROUP_SCHED */
426 static __always_inline
427 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
429 /**************************************************************
430 * Scheduling class tree data structure manipulation methods:
433 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
435 s64 delta = (s64)(vruntime - max_vruntime);
437 max_vruntime = vruntime;
442 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
444 s64 delta = (s64)(vruntime - min_vruntime);
446 min_vruntime = vruntime;
451 static inline int entity_before(struct sched_entity *a,
452 struct sched_entity *b)
454 return (s64)(a->vruntime - b->vruntime) < 0;
457 static void update_min_vruntime(struct cfs_rq *cfs_rq)
459 u64 vruntime = cfs_rq->min_vruntime;
462 vruntime = cfs_rq->curr->vruntime;
464 if (cfs_rq->rb_leftmost) {
465 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
470 vruntime = se->vruntime;
472 vruntime = min_vruntime(vruntime, se->vruntime);
475 /* ensure we never gain time by being placed backwards. */
476 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
479 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
484 * Enqueue an entity into the rb-tree:
486 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
488 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
489 struct rb_node *parent = NULL;
490 struct sched_entity *entry;
494 * Find the right place in the rbtree:
498 entry = rb_entry(parent, struct sched_entity, run_node);
500 * We dont care about collisions. Nodes with
501 * the same key stay together.
503 if (entity_before(se, entry)) {
504 link = &parent->rb_left;
506 link = &parent->rb_right;
512 * Maintain a cache of leftmost tree entries (it is frequently
516 cfs_rq->rb_leftmost = &se->run_node;
518 rb_link_node(&se->run_node, parent, link);
519 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
522 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
524 if (cfs_rq->rb_leftmost == &se->run_node) {
525 struct rb_node *next_node;
527 next_node = rb_next(&se->run_node);
528 cfs_rq->rb_leftmost = next_node;
531 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
534 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
536 struct rb_node *left = cfs_rq->rb_leftmost;
541 return rb_entry(left, struct sched_entity, run_node);
544 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
546 struct rb_node *next = rb_next(&se->run_node);
551 return rb_entry(next, struct sched_entity, run_node);
554 #ifdef CONFIG_SCHED_DEBUG
555 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
557 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
562 return rb_entry(last, struct sched_entity, run_node);
565 /**************************************************************
566 * Scheduling class statistics methods:
569 int sched_proc_update_handler(struct ctl_table *table, int write,
570 void __user *buffer, size_t *lenp,
573 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
574 unsigned int factor = get_update_sysctl_factor();
579 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
580 sysctl_sched_min_granularity);
582 #define WRT_SYSCTL(name) \
583 (normalized_sysctl_##name = sysctl_##name / (factor))
584 WRT_SYSCTL(sched_min_granularity);
585 WRT_SYSCTL(sched_latency);
586 WRT_SYSCTL(sched_wakeup_granularity);
596 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
598 if (unlikely(se->load.weight != NICE_0_LOAD))
599 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
605 * The idea is to set a period in which each task runs once.
607 * When there are too many tasks (sched_nr_latency) we have to stretch
608 * this period because otherwise the slices get too small.
610 * p = (nr <= nl) ? l : l*nr/nl
612 static u64 __sched_period(unsigned long nr_running)
614 if (unlikely(nr_running > sched_nr_latency))
615 return nr_running * sysctl_sched_min_granularity;
617 return sysctl_sched_latency;
621 * We calculate the wall-time slice from the period by taking a part
622 * proportional to the weight.
626 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
628 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
630 for_each_sched_entity(se) {
631 struct load_weight *load;
632 struct load_weight lw;
634 cfs_rq = cfs_rq_of(se);
635 load = &cfs_rq->load;
637 if (unlikely(!se->on_rq)) {
640 update_load_add(&lw, se->load.weight);
643 slice = __calc_delta(slice, se->load.weight, load);
649 * We calculate the vruntime slice of a to-be-inserted task.
653 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
655 return calc_delta_fair(sched_slice(cfs_rq, se), se);
659 static int select_idle_sibling(struct task_struct *p, int cpu);
660 static unsigned long task_h_load(struct task_struct *p);
663 * We choose a half-life close to 1 scheduling period.
664 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
665 * dependent on this value.
667 #define LOAD_AVG_PERIOD 32
668 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
669 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
671 /* Give new sched_entity start runnable values to heavy its load in infant time */
672 void init_entity_runnable_average(struct sched_entity *se)
674 struct sched_avg *sa = &se->avg;
676 sa->last_update_time = 0;
678 * sched_avg's period_contrib should be strictly less then 1024, so
679 * we give it 1023 to make sure it is almost a period (1024us), and
680 * will definitely be update (after enqueue).
682 sa->period_contrib = 1023;
683 sa->load_avg = scale_load_down(se->load.weight);
684 sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
686 * At this point, util_avg won't be used in select_task_rq_fair anyway
690 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
694 * With new tasks being created, their initial util_avgs are extrapolated
695 * based on the cfs_rq's current util_avg:
697 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
699 * However, in many cases, the above util_avg does not give a desired
700 * value. Moreover, the sum of the util_avgs may be divergent, such
701 * as when the series is a harmonic series.
703 * To solve this problem, we also cap the util_avg of successive tasks to
704 * only 1/2 of the left utilization budget:
706 * util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
708 * where n denotes the nth task.
710 * For example, a simplest series from the beginning would be like:
712 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
713 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
715 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
716 * if util_avg > util_avg_cap.
718 void post_init_entity_util_avg(struct sched_entity *se)
720 struct cfs_rq *cfs_rq = cfs_rq_of(se);
721 struct sched_avg *sa = &se->avg;
722 long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
725 if (cfs_rq->avg.util_avg != 0) {
726 sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
727 sa->util_avg /= (cfs_rq->avg.load_avg + 1);
729 if (sa->util_avg > cap)
734 sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
738 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
739 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
741 void init_entity_runnable_average(struct sched_entity *se)
744 void post_init_entity_util_avg(struct sched_entity *se)
750 * Update the current task's runtime statistics.
752 static void update_curr(struct cfs_rq *cfs_rq)
754 struct sched_entity *curr = cfs_rq->curr;
755 u64 now = rq_clock_task(rq_of(cfs_rq));
761 delta_exec = now - curr->exec_start;
762 if (unlikely((s64)delta_exec <= 0))
765 curr->exec_start = now;
767 schedstat_set(curr->statistics.exec_max,
768 max(delta_exec, curr->statistics.exec_max));
770 curr->sum_exec_runtime += delta_exec;
771 schedstat_add(cfs_rq, exec_clock, delta_exec);
773 curr->vruntime += calc_delta_fair(delta_exec, curr);
774 update_min_vruntime(cfs_rq);
776 if (entity_is_task(curr)) {
777 struct task_struct *curtask = task_of(curr);
779 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
780 cpuacct_charge(curtask, delta_exec);
781 account_group_exec_runtime(curtask, delta_exec);
784 account_cfs_rq_runtime(cfs_rq, delta_exec);
787 static void update_curr_fair(struct rq *rq)
789 update_curr(cfs_rq_of(&rq->curr->se));
792 #ifdef CONFIG_SCHEDSTATS
794 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
796 u64 wait_start = rq_clock(rq_of(cfs_rq));
798 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
799 likely(wait_start > se->statistics.wait_start))
800 wait_start -= se->statistics.wait_start;
802 se->statistics.wait_start = wait_start;
806 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
808 struct task_struct *p;
811 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;
813 if (entity_is_task(se)) {
815 if (task_on_rq_migrating(p)) {
817 * Preserve migrating task's wait time so wait_start
818 * time stamp can be adjusted to accumulate wait time
819 * prior to migration.
821 se->statistics.wait_start = delta;
824 trace_sched_stat_wait(p, delta);
827 se->statistics.wait_max = max(se->statistics.wait_max, delta);
828 se->statistics.wait_count++;
829 se->statistics.wait_sum += delta;
830 se->statistics.wait_start = 0;
834 * Task is being enqueued - update stats:
837 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
840 * Are we enqueueing a waiting task? (for current tasks
841 * a dequeue/enqueue event is a NOP)
843 if (se != cfs_rq->curr)
844 update_stats_wait_start(cfs_rq, se);
848 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
851 * Mark the end of the wait period if dequeueing a
854 if (se != cfs_rq->curr)
855 update_stats_wait_end(cfs_rq, se);
857 if (flags & DEQUEUE_SLEEP) {
858 if (entity_is_task(se)) {
859 struct task_struct *tsk = task_of(se);
861 if (tsk->state & TASK_INTERRUPTIBLE)
862 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
863 if (tsk->state & TASK_UNINTERRUPTIBLE)
864 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
871 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
876 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
881 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
886 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
892 * We are picking a new current task - update its stats:
895 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
898 * We are starting a new run period:
900 se->exec_start = rq_clock_task(rq_of(cfs_rq));
903 /**************************************************
904 * Scheduling class queueing methods:
907 #ifdef CONFIG_NUMA_BALANCING
909 * Approximate time to scan a full NUMA task in ms. The task scan period is
910 * calculated based on the tasks virtual memory size and
911 * numa_balancing_scan_size.
913 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
914 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
916 /* Portion of address space to scan in MB */
917 unsigned int sysctl_numa_balancing_scan_size = 256;
919 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
920 unsigned int sysctl_numa_balancing_scan_delay = 1000;
922 static unsigned int task_nr_scan_windows(struct task_struct *p)
924 unsigned long rss = 0;
925 unsigned long nr_scan_pages;
928 * Calculations based on RSS as non-present and empty pages are skipped
929 * by the PTE scanner and NUMA hinting faults should be trapped based
932 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
933 rss = get_mm_rss(p->mm);
937 rss = round_up(rss, nr_scan_pages);
938 return rss / nr_scan_pages;
941 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
942 #define MAX_SCAN_WINDOW 2560
944 static unsigned int task_scan_min(struct task_struct *p)
946 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
947 unsigned int scan, floor;
948 unsigned int windows = 1;
950 if (scan_size < MAX_SCAN_WINDOW)
951 windows = MAX_SCAN_WINDOW / scan_size;
952 floor = 1000 / windows;
954 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
955 return max_t(unsigned int, floor, scan);
958 static unsigned int task_scan_max(struct task_struct *p)
960 unsigned int smin = task_scan_min(p);
963 /* Watch for min being lower than max due to floor calculations */
964 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
965 return max(smin, smax);
968 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
970 rq->nr_numa_running += (p->numa_preferred_nid != -1);
971 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
974 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
976 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
977 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
983 spinlock_t lock; /* nr_tasks, tasks */
989 unsigned long total_faults;
990 unsigned long max_faults_cpu;
992 * Faults_cpu is used to decide whether memory should move
993 * towards the CPU. As a consequence, these stats are weighted
994 * more by CPU use than by memory faults.
996 unsigned long *faults_cpu;
997 unsigned long faults[0];
1000 /* Shared or private faults. */
1001 #define NR_NUMA_HINT_FAULT_TYPES 2
1003 /* Memory and CPU locality */
1004 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1006 /* Averaged statistics, and temporary buffers. */
1007 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1009 pid_t task_numa_group_id(struct task_struct *p)
1011 return p->numa_group ? p->numa_group->gid : 0;
1015 * The averaged statistics, shared & private, memory & cpu,
1016 * occupy the first half of the array. The second half of the
1017 * array is for current counters, which are averaged into the
1018 * first set by task_numa_placement.
1020 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1022 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1025 static inline unsigned long task_faults(struct task_struct *p, int nid)
1027 if (!p->numa_faults)
1030 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1031 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1034 static inline unsigned long group_faults(struct task_struct *p, int nid)
1039 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1040 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1043 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
1045 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
1046 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1050 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1051 * considered part of a numa group's pseudo-interleaving set. Migrations
1052 * between these nodes are slowed down, to allow things to settle down.
1054 #define ACTIVE_NODE_FRACTION 3
1056 static bool numa_is_active_node(int nid, struct numa_group *ng)
1058 return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
1061 /* Handle placement on systems where not all nodes are directly connected. */
1062 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
1063 int maxdist, bool task)
1065 unsigned long score = 0;
1069 * All nodes are directly connected, and the same distance
1070 * from each other. No need for fancy placement algorithms.
1072 if (sched_numa_topology_type == NUMA_DIRECT)
1076 * This code is called for each node, introducing N^2 complexity,
1077 * which should be ok given the number of nodes rarely exceeds 8.
1079 for_each_online_node(node) {
1080 unsigned long faults;
1081 int dist = node_distance(nid, node);
1084 * The furthest away nodes in the system are not interesting
1085 * for placement; nid was already counted.
1087 if (dist == sched_max_numa_distance || node == nid)
1091 * On systems with a backplane NUMA topology, compare groups
1092 * of nodes, and move tasks towards the group with the most
1093 * memory accesses. When comparing two nodes at distance
1094 * "hoplimit", only nodes closer by than "hoplimit" are part
1095 * of each group. Skip other nodes.
1097 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1101 /* Add up the faults from nearby nodes. */
1103 faults = task_faults(p, node);
1105 faults = group_faults(p, node);
1108 * On systems with a glueless mesh NUMA topology, there are
1109 * no fixed "groups of nodes". Instead, nodes that are not
1110 * directly connected bounce traffic through intermediate
1111 * nodes; a numa_group can occupy any set of nodes.
1112 * The further away a node is, the less the faults count.
1113 * This seems to result in good task placement.
1115 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1116 faults *= (sched_max_numa_distance - dist);
1117 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1127 * These return the fraction of accesses done by a particular task, or
1128 * task group, on a particular numa node. The group weight is given a
1129 * larger multiplier, in order to group tasks together that are almost
1130 * evenly spread out between numa nodes.
1132 static inline unsigned long task_weight(struct task_struct *p, int nid,
1135 unsigned long faults, total_faults;
1137 if (!p->numa_faults)
1140 total_faults = p->total_numa_faults;
1145 faults = task_faults(p, nid);
1146 faults += score_nearby_nodes(p, nid, dist, true);
1148 return 1000 * faults / total_faults;
1151 static inline unsigned long group_weight(struct task_struct *p, int nid,
1154 unsigned long faults, total_faults;
1159 total_faults = p->numa_group->total_faults;
1164 faults = group_faults(p, nid);
1165 faults += score_nearby_nodes(p, nid, dist, false);
1167 return 1000 * faults / total_faults;
1170 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1171 int src_nid, int dst_cpu)
1173 struct numa_group *ng = p->numa_group;
1174 int dst_nid = cpu_to_node(dst_cpu);
1175 int last_cpupid, this_cpupid;
1177 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1180 * Multi-stage node selection is used in conjunction with a periodic
1181 * migration fault to build a temporal task<->page relation. By using
1182 * a two-stage filter we remove short/unlikely relations.
1184 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1185 * a task's usage of a particular page (n_p) per total usage of this
1186 * page (n_t) (in a given time-span) to a probability.
1188 * Our periodic faults will sample this probability and getting the
1189 * same result twice in a row, given these samples are fully
1190 * independent, is then given by P(n)^2, provided our sample period
1191 * is sufficiently short compared to the usage pattern.
1193 * This quadric squishes small probabilities, making it less likely we
1194 * act on an unlikely task<->page relation.
1196 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1197 if (!cpupid_pid_unset(last_cpupid) &&
1198 cpupid_to_nid(last_cpupid) != dst_nid)
1201 /* Always allow migrate on private faults */
1202 if (cpupid_match_pid(p, last_cpupid))
1205 /* A shared fault, but p->numa_group has not been set up yet. */
1210 * Destination node is much more heavily used than the source
1211 * node? Allow migration.
1213 if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
1214 ACTIVE_NODE_FRACTION)
1218 * Distribute memory according to CPU & memory use on each node,
1219 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1221 * faults_cpu(dst) 3 faults_cpu(src)
1222 * --------------- * - > ---------------
1223 * faults_mem(dst) 4 faults_mem(src)
1225 return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
1226 group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1229 static unsigned long weighted_cpuload(const int cpu);
1230 static unsigned long source_load(int cpu, int type);
1231 static unsigned long target_load(int cpu, int type);
1232 static unsigned long capacity_of(int cpu);
1233 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1235 /* Cached statistics for all CPUs within a node */
1237 unsigned long nr_running;
1240 /* Total compute capacity of CPUs on a node */
1241 unsigned long compute_capacity;
1243 /* Approximate capacity in terms of runnable tasks on a node */
1244 unsigned long task_capacity;
1245 int has_free_capacity;
1249 * XXX borrowed from update_sg_lb_stats
1251 static void update_numa_stats(struct numa_stats *ns, int nid)
1253 int smt, cpu, cpus = 0;
1254 unsigned long capacity;
1256 memset(ns, 0, sizeof(*ns));
1257 for_each_cpu(cpu, cpumask_of_node(nid)) {
1258 struct rq *rq = cpu_rq(cpu);
1260 ns->nr_running += rq->nr_running;
1261 ns->load += weighted_cpuload(cpu);
1262 ns->compute_capacity += capacity_of(cpu);
1268 * If we raced with hotplug and there are no CPUs left in our mask
1269 * the @ns structure is NULL'ed and task_numa_compare() will
1270 * not find this node attractive.
1272 * We'll either bail at !has_free_capacity, or we'll detect a huge
1273 * imbalance and bail there.
1278 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1279 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1280 capacity = cpus / smt; /* cores */
1282 ns->task_capacity = min_t(unsigned, capacity,
1283 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1284 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1287 struct task_numa_env {
1288 struct task_struct *p;
1290 int src_cpu, src_nid;
1291 int dst_cpu, dst_nid;
1293 struct numa_stats src_stats, dst_stats;
1298 struct task_struct *best_task;
1303 static void task_numa_assign(struct task_numa_env *env,
1304 struct task_struct *p, long imp)
1307 put_task_struct(env->best_task);
1310 env->best_imp = imp;
1311 env->best_cpu = env->dst_cpu;
1314 static bool load_too_imbalanced(long src_load, long dst_load,
1315 struct task_numa_env *env)
1318 long orig_src_load, orig_dst_load;
1319 long src_capacity, dst_capacity;
1322 * The load is corrected for the CPU capacity available on each node.
1325 * ------------ vs ---------
1326 * src_capacity dst_capacity
1328 src_capacity = env->src_stats.compute_capacity;
1329 dst_capacity = env->dst_stats.compute_capacity;
1331 /* We care about the slope of the imbalance, not the direction. */
1332 if (dst_load < src_load)
1333 swap(dst_load, src_load);
1335 /* Is the difference below the threshold? */
1336 imb = dst_load * src_capacity * 100 -
1337 src_load * dst_capacity * env->imbalance_pct;
1342 * The imbalance is above the allowed threshold.
1343 * Compare it with the old imbalance.
1345 orig_src_load = env->src_stats.load;
1346 orig_dst_load = env->dst_stats.load;
1348 if (orig_dst_load < orig_src_load)
1349 swap(orig_dst_load, orig_src_load);
1351 old_imb = orig_dst_load * src_capacity * 100 -
1352 orig_src_load * dst_capacity * env->imbalance_pct;
1354 /* Would this change make things worse? */
1355 return (imb > old_imb);
1359 * This checks if the overall compute and NUMA accesses of the system would
1360 * be improved if the source tasks was migrated to the target dst_cpu taking
1361 * into account that it might be best if task running on the dst_cpu should
1362 * be exchanged with the source task
1364 static void task_numa_compare(struct task_numa_env *env,
1365 long taskimp, long groupimp)
1367 struct rq *src_rq = cpu_rq(env->src_cpu);
1368 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1369 struct task_struct *cur;
1370 long src_load, dst_load;
1372 long imp = env->p->numa_group ? groupimp : taskimp;
1374 int dist = env->dist;
1375 bool assigned = false;
1379 raw_spin_lock_irq(&dst_rq->lock);
1382 * No need to move the exiting task or idle task.
1384 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1388 * The task_struct must be protected here to protect the
1389 * p->numa_faults access in the task_weight since the
1390 * numa_faults could already be freed in the following path:
1391 * finish_task_switch()
1392 * --> put_task_struct()
1393 * --> __put_task_struct()
1394 * --> task_numa_free()
1396 get_task_struct(cur);
1399 raw_spin_unlock_irq(&dst_rq->lock);
1402 * Because we have preemption enabled we can get migrated around and
1403 * end try selecting ourselves (current == env->p) as a swap candidate.
1409 * "imp" is the fault differential for the source task between the
1410 * source and destination node. Calculate the total differential for
1411 * the source task and potential destination task. The more negative
1412 * the value is, the more rmeote accesses that would be expected to
1413 * be incurred if the tasks were swapped.
1416 /* Skip this swap candidate if cannot move to the source cpu */
1417 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1421 * If dst and source tasks are in the same NUMA group, or not
1422 * in any group then look only at task weights.
1424 if (cur->numa_group == env->p->numa_group) {
1425 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1426 task_weight(cur, env->dst_nid, dist);
1428 * Add some hysteresis to prevent swapping the
1429 * tasks within a group over tiny differences.
1431 if (cur->numa_group)
1435 * Compare the group weights. If a task is all by
1436 * itself (not part of a group), use the task weight
1439 if (cur->numa_group)
1440 imp += group_weight(cur, env->src_nid, dist) -
1441 group_weight(cur, env->dst_nid, dist);
1443 imp += task_weight(cur, env->src_nid, dist) -
1444 task_weight(cur, env->dst_nid, dist);
1448 if (imp <= env->best_imp && moveimp <= env->best_imp)
1452 /* Is there capacity at our destination? */
1453 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1454 !env->dst_stats.has_free_capacity)
1460 /* Balance doesn't matter much if we're running a task per cpu */
1461 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1462 dst_rq->nr_running == 1)
1466 * In the overloaded case, try and keep the load balanced.
1469 load = task_h_load(env->p);
1470 dst_load = env->dst_stats.load + load;
1471 src_load = env->src_stats.load - load;
1473 if (moveimp > imp && moveimp > env->best_imp) {
1475 * If the improvement from just moving env->p direction is
1476 * better than swapping tasks around, check if a move is
1477 * possible. Store a slightly smaller score than moveimp,
1478 * so an actually idle CPU will win.
1480 if (!load_too_imbalanced(src_load, dst_load, env)) {
1482 put_task_struct(cur);
1488 if (imp <= env->best_imp)
1492 load = task_h_load(cur);
1497 if (load_too_imbalanced(src_load, dst_load, env))
1501 * One idle CPU per node is evaluated for a task numa move.
1502 * Call select_idle_sibling to maybe find a better one.
1505 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1509 task_numa_assign(env, cur, imp);
1513 * The dst_rq->curr isn't assigned. The protection for task_struct is
1516 if (cur && !assigned)
1517 put_task_struct(cur);
1520 static void task_numa_find_cpu(struct task_numa_env *env,
1521 long taskimp, long groupimp)
1525 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1526 /* Skip this CPU if the source task cannot migrate */
1527 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1531 task_numa_compare(env, taskimp, groupimp);
1535 /* Only move tasks to a NUMA node less busy than the current node. */
1536 static bool numa_has_capacity(struct task_numa_env *env)
1538 struct numa_stats *src = &env->src_stats;
1539 struct numa_stats *dst = &env->dst_stats;
1541 if (src->has_free_capacity && !dst->has_free_capacity)
1545 * Only consider a task move if the source has a higher load
1546 * than the destination, corrected for CPU capacity on each node.
1548 * src->load dst->load
1549 * --------------------- vs ---------------------
1550 * src->compute_capacity dst->compute_capacity
1552 if (src->load * dst->compute_capacity * env->imbalance_pct >
1554 dst->load * src->compute_capacity * 100)
1560 static int task_numa_migrate(struct task_struct *p)
1562 struct task_numa_env env = {
1565 .src_cpu = task_cpu(p),
1566 .src_nid = task_node(p),
1568 .imbalance_pct = 112,
1574 struct sched_domain *sd;
1575 unsigned long taskweight, groupweight;
1577 long taskimp, groupimp;
1580 * Pick the lowest SD_NUMA domain, as that would have the smallest
1581 * imbalance and would be the first to start moving tasks about.
1583 * And we want to avoid any moving of tasks about, as that would create
1584 * random movement of tasks -- counter the numa conditions we're trying
1588 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1590 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1594 * Cpusets can break the scheduler domain tree into smaller
1595 * balance domains, some of which do not cross NUMA boundaries.
1596 * Tasks that are "trapped" in such domains cannot be migrated
1597 * elsewhere, so there is no point in (re)trying.
1599 if (unlikely(!sd)) {
1600 p->numa_preferred_nid = task_node(p);
1604 env.dst_nid = p->numa_preferred_nid;
1605 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1606 taskweight = task_weight(p, env.src_nid, dist);
1607 groupweight = group_weight(p, env.src_nid, dist);
1608 update_numa_stats(&env.src_stats, env.src_nid);
1609 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1610 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1611 update_numa_stats(&env.dst_stats, env.dst_nid);
1613 /* Try to find a spot on the preferred nid. */
1614 if (numa_has_capacity(&env))
1615 task_numa_find_cpu(&env, taskimp, groupimp);
1618 * Look at other nodes in these cases:
1619 * - there is no space available on the preferred_nid
1620 * - the task is part of a numa_group that is interleaved across
1621 * multiple NUMA nodes; in order to better consolidate the group,
1622 * we need to check other locations.
1624 if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1625 for_each_online_node(nid) {
1626 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1629 dist = node_distance(env.src_nid, env.dst_nid);
1630 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1632 taskweight = task_weight(p, env.src_nid, dist);
1633 groupweight = group_weight(p, env.src_nid, dist);
1636 /* Only consider nodes where both task and groups benefit */
1637 taskimp = task_weight(p, nid, dist) - taskweight;
1638 groupimp = group_weight(p, nid, dist) - groupweight;
1639 if (taskimp < 0 && groupimp < 0)
1644 update_numa_stats(&env.dst_stats, env.dst_nid);
1645 if (numa_has_capacity(&env))
1646 task_numa_find_cpu(&env, taskimp, groupimp);
1651 * If the task is part of a workload that spans multiple NUMA nodes,
1652 * and is migrating into one of the workload's active nodes, remember
1653 * this node as the task's preferred numa node, so the workload can
1655 * A task that migrated to a second choice node will be better off
1656 * trying for a better one later. Do not set the preferred node here.
1658 if (p->numa_group) {
1659 struct numa_group *ng = p->numa_group;
1661 if (env.best_cpu == -1)
1666 if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1667 sched_setnuma(p, env.dst_nid);
1670 /* No better CPU than the current one was found. */
1671 if (env.best_cpu == -1)
1675 * Reset the scan period if the task is being rescheduled on an
1676 * alternative node to recheck if the tasks is now properly placed.
1678 p->numa_scan_period = task_scan_min(p);
1680 if (env.best_task == NULL) {
1681 ret = migrate_task_to(p, env.best_cpu);
1683 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1687 ret = migrate_swap(p, env.best_task);
1689 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1690 put_task_struct(env.best_task);
1694 /* Attempt to migrate a task to a CPU on the preferred node. */
1695 static void numa_migrate_preferred(struct task_struct *p)
1697 unsigned long interval = HZ;
1699 /* This task has no NUMA fault statistics yet */
1700 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1703 /* Periodically retry migrating the task to the preferred node */
1704 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1705 p->numa_migrate_retry = jiffies + interval;
1707 /* Success if task is already running on preferred CPU */
1708 if (task_node(p) == p->numa_preferred_nid)
1711 /* Otherwise, try migrate to a CPU on the preferred node */
1712 task_numa_migrate(p);
1716 * Find out how many nodes on the workload is actively running on. Do this by
1717 * tracking the nodes from which NUMA hinting faults are triggered. This can
1718 * be different from the set of nodes where the workload's memory is currently
1721 static void numa_group_count_active_nodes(struct numa_group *numa_group)
1723 unsigned long faults, max_faults = 0;
1724 int nid, active_nodes = 0;
1726 for_each_online_node(nid) {
1727 faults = group_faults_cpu(numa_group, nid);
1728 if (faults > max_faults)
1729 max_faults = faults;
1732 for_each_online_node(nid) {
1733 faults = group_faults_cpu(numa_group, nid);
1734 if (faults * ACTIVE_NODE_FRACTION > max_faults)
1738 numa_group->max_faults_cpu = max_faults;
1739 numa_group->active_nodes = active_nodes;
1743 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1744 * increments. The more local the fault statistics are, the higher the scan
1745 * period will be for the next scan window. If local/(local+remote) ratio is
1746 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1747 * the scan period will decrease. Aim for 70% local accesses.
1749 #define NUMA_PERIOD_SLOTS 10
1750 #define NUMA_PERIOD_THRESHOLD 7
1753 * Increase the scan period (slow down scanning) if the majority of
1754 * our memory is already on our local node, or if the majority of
1755 * the page accesses are shared with other processes.
1756 * Otherwise, decrease the scan period.
1758 static void update_task_scan_period(struct task_struct *p,
1759 unsigned long shared, unsigned long private)
1761 unsigned int period_slot;
1765 unsigned long remote = p->numa_faults_locality[0];
1766 unsigned long local = p->numa_faults_locality[1];
1769 * If there were no record hinting faults then either the task is
1770 * completely idle or all activity is areas that are not of interest
1771 * to automatic numa balancing. Related to that, if there were failed
1772 * migration then it implies we are migrating too quickly or the local
1773 * node is overloaded. In either case, scan slower
1775 if (local + shared == 0 || p->numa_faults_locality[2]) {
1776 p->numa_scan_period = min(p->numa_scan_period_max,
1777 p->numa_scan_period << 1);
1779 p->mm->numa_next_scan = jiffies +
1780 msecs_to_jiffies(p->numa_scan_period);
1786 * Prepare to scale scan period relative to the current period.
1787 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1788 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1789 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1791 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1792 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1793 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1794 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1797 diff = slot * period_slot;
1799 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1802 * Scale scan rate increases based on sharing. There is an
1803 * inverse relationship between the degree of sharing and
1804 * the adjustment made to the scanning period. Broadly
1805 * speaking the intent is that there is little point
1806 * scanning faster if shared accesses dominate as it may
1807 * simply bounce migrations uselessly
1809 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1810 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1813 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1814 task_scan_min(p), task_scan_max(p));
1815 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1819 * Get the fraction of time the task has been running since the last
1820 * NUMA placement cycle. The scheduler keeps similar statistics, but
1821 * decays those on a 32ms period, which is orders of magnitude off
1822 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1823 * stats only if the task is so new there are no NUMA statistics yet.
1825 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1827 u64 runtime, delta, now;
1828 /* Use the start of this time slice to avoid calculations. */
1829 now = p->se.exec_start;
1830 runtime = p->se.sum_exec_runtime;
1832 if (p->last_task_numa_placement) {
1833 delta = runtime - p->last_sum_exec_runtime;
1834 *period = now - p->last_task_numa_placement;
1836 delta = p->se.avg.load_sum / p->se.load.weight;
1837 *period = LOAD_AVG_MAX;
1840 p->last_sum_exec_runtime = runtime;
1841 p->last_task_numa_placement = now;
1847 * Determine the preferred nid for a task in a numa_group. This needs to
1848 * be done in a way that produces consistent results with group_weight,
1849 * otherwise workloads might not converge.
1851 static int preferred_group_nid(struct task_struct *p, int nid)
1856 /* Direct connections between all NUMA nodes. */
1857 if (sched_numa_topology_type == NUMA_DIRECT)
1861 * On a system with glueless mesh NUMA topology, group_weight
1862 * scores nodes according to the number of NUMA hinting faults on
1863 * both the node itself, and on nearby nodes.
1865 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1866 unsigned long score, max_score = 0;
1867 int node, max_node = nid;
1869 dist = sched_max_numa_distance;
1871 for_each_online_node(node) {
1872 score = group_weight(p, node, dist);
1873 if (score > max_score) {
1882 * Finding the preferred nid in a system with NUMA backplane
1883 * interconnect topology is more involved. The goal is to locate
1884 * tasks from numa_groups near each other in the system, and
1885 * untangle workloads from different sides of the system. This requires
1886 * searching down the hierarchy of node groups, recursively searching
1887 * inside the highest scoring group of nodes. The nodemask tricks
1888 * keep the complexity of the search down.
1890 nodes = node_online_map;
1891 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1892 unsigned long max_faults = 0;
1893 nodemask_t max_group = NODE_MASK_NONE;
1896 /* Are there nodes at this distance from each other? */
1897 if (!find_numa_distance(dist))
1900 for_each_node_mask(a, nodes) {
1901 unsigned long faults = 0;
1902 nodemask_t this_group;
1903 nodes_clear(this_group);
1905 /* Sum group's NUMA faults; includes a==b case. */
1906 for_each_node_mask(b, nodes) {
1907 if (node_distance(a, b) < dist) {
1908 faults += group_faults(p, b);
1909 node_set(b, this_group);
1910 node_clear(b, nodes);
1914 /* Remember the top group. */
1915 if (faults > max_faults) {
1916 max_faults = faults;
1917 max_group = this_group;
1919 * subtle: at the smallest distance there is
1920 * just one node left in each "group", the
1921 * winner is the preferred nid.
1926 /* Next round, evaluate the nodes within max_group. */
1934 static void task_numa_placement(struct task_struct *p)
1936 int seq, nid, max_nid = -1, max_group_nid = -1;
1937 unsigned long max_faults = 0, max_group_faults = 0;
1938 unsigned long fault_types[2] = { 0, 0 };
1939 unsigned long total_faults;
1940 u64 runtime, period;
1941 spinlock_t *group_lock = NULL;
1944 * The p->mm->numa_scan_seq field gets updated without
1945 * exclusive access. Use READ_ONCE() here to ensure
1946 * that the field is read in a single access:
1948 seq = READ_ONCE(p->mm->numa_scan_seq);
1949 if (p->numa_scan_seq == seq)
1951 p->numa_scan_seq = seq;
1952 p->numa_scan_period_max = task_scan_max(p);
1954 total_faults = p->numa_faults_locality[0] +
1955 p->numa_faults_locality[1];
1956 runtime = numa_get_avg_runtime(p, &period);
1958 /* If the task is part of a group prevent parallel updates to group stats */
1959 if (p->numa_group) {
1960 group_lock = &p->numa_group->lock;
1961 spin_lock_irq(group_lock);
1964 /* Find the node with the highest number of faults */
1965 for_each_online_node(nid) {
1966 /* Keep track of the offsets in numa_faults array */
1967 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1968 unsigned long faults = 0, group_faults = 0;
1971 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1972 long diff, f_diff, f_weight;
1974 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1975 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1976 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1977 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1979 /* Decay existing window, copy faults since last scan */
1980 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1981 fault_types[priv] += p->numa_faults[membuf_idx];
1982 p->numa_faults[membuf_idx] = 0;
1985 * Normalize the faults_from, so all tasks in a group
1986 * count according to CPU use, instead of by the raw
1987 * number of faults. Tasks with little runtime have
1988 * little over-all impact on throughput, and thus their
1989 * faults are less important.
1991 f_weight = div64_u64(runtime << 16, period + 1);
1992 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1994 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1995 p->numa_faults[cpubuf_idx] = 0;
1997 p->numa_faults[mem_idx] += diff;
1998 p->numa_faults[cpu_idx] += f_diff;
1999 faults += p->numa_faults[mem_idx];
2000 p->total_numa_faults += diff;
2001 if (p->numa_group) {
2003 * safe because we can only change our own group
2005 * mem_idx represents the offset for a given
2006 * nid and priv in a specific region because it
2007 * is at the beginning of the numa_faults array.
2009 p->numa_group->faults[mem_idx] += diff;
2010 p->numa_group->faults_cpu[mem_idx] += f_diff;
2011 p->numa_group->total_faults += diff;
2012 group_faults += p->numa_group->faults[mem_idx];
2016 if (faults > max_faults) {
2017 max_faults = faults;
2021 if (group_faults > max_group_faults) {
2022 max_group_faults = group_faults;
2023 max_group_nid = nid;
2027 update_task_scan_period(p, fault_types[0], fault_types[1]);
2029 if (p->numa_group) {
2030 numa_group_count_active_nodes(p->numa_group);
2031 spin_unlock_irq(group_lock);
2032 max_nid = preferred_group_nid(p, max_group_nid);
2036 /* Set the new preferred node */
2037 if (max_nid != p->numa_preferred_nid)
2038 sched_setnuma(p, max_nid);
2040 if (task_node(p) != p->numa_preferred_nid)
2041 numa_migrate_preferred(p);
2045 static inline int get_numa_group(struct numa_group *grp)
2047 return atomic_inc_not_zero(&grp->refcount);
2050 static inline void put_numa_group(struct numa_group *grp)
2052 if (atomic_dec_and_test(&grp->refcount))
2053 kfree_rcu(grp, rcu);
2056 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
2059 struct numa_group *grp, *my_grp;
2060 struct task_struct *tsk;
2062 int cpu = cpupid_to_cpu(cpupid);
2065 if (unlikely(!p->numa_group)) {
2066 unsigned int size = sizeof(struct numa_group) +
2067 4*nr_node_ids*sizeof(unsigned long);
2069 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
2073 atomic_set(&grp->refcount, 1);
2074 grp->active_nodes = 1;
2075 grp->max_faults_cpu = 0;
2076 spin_lock_init(&grp->lock);
2078 /* Second half of the array tracks nids where faults happen */
2079 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
2082 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2083 grp->faults[i] = p->numa_faults[i];
2085 grp->total_faults = p->total_numa_faults;
2088 rcu_assign_pointer(p->numa_group, grp);
2092 tsk = READ_ONCE(cpu_rq(cpu)->curr);
2094 if (!cpupid_match_pid(tsk, cpupid))
2097 grp = rcu_dereference(tsk->numa_group);
2101 my_grp = p->numa_group;
2106 * Only join the other group if its bigger; if we're the bigger group,
2107 * the other task will join us.
2109 if (my_grp->nr_tasks > grp->nr_tasks)
2113 * Tie-break on the grp address.
2115 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2118 /* Always join threads in the same process. */
2119 if (tsk->mm == current->mm)
2122 /* Simple filter to avoid false positives due to PID collisions */
2123 if (flags & TNF_SHARED)
2126 /* Update priv based on whether false sharing was detected */
2129 if (join && !get_numa_group(grp))
2137 BUG_ON(irqs_disabled());
2138 double_lock_irq(&my_grp->lock, &grp->lock);
2140 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2141 my_grp->faults[i] -= p->numa_faults[i];
2142 grp->faults[i] += p->numa_faults[i];
2144 my_grp->total_faults -= p->total_numa_faults;
2145 grp->total_faults += p->total_numa_faults;
2150 spin_unlock(&my_grp->lock);
2151 spin_unlock_irq(&grp->lock);
2153 rcu_assign_pointer(p->numa_group, grp);
2155 put_numa_group(my_grp);
2163 void task_numa_free(struct task_struct *p)
2165 struct numa_group *grp = p->numa_group;
2166 void *numa_faults = p->numa_faults;
2167 unsigned long flags;
2171 spin_lock_irqsave(&grp->lock, flags);
2172 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2173 grp->faults[i] -= p->numa_faults[i];
2174 grp->total_faults -= p->total_numa_faults;
2177 spin_unlock_irqrestore(&grp->lock, flags);
2178 RCU_INIT_POINTER(p->numa_group, NULL);
2179 put_numa_group(grp);
2182 p->numa_faults = NULL;
2187 * Got a PROT_NONE fault for a page on @node.
2189 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2191 struct task_struct *p = current;
2192 bool migrated = flags & TNF_MIGRATED;
2193 int cpu_node = task_node(current);
2194 int local = !!(flags & TNF_FAULT_LOCAL);
2195 struct numa_group *ng;
2198 if (!static_branch_likely(&sched_numa_balancing))
2201 /* for example, ksmd faulting in a user's mm */
2205 /* Allocate buffer to track faults on a per-node basis */
2206 if (unlikely(!p->numa_faults)) {
2207 int size = sizeof(*p->numa_faults) *
2208 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2210 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2211 if (!p->numa_faults)
2214 p->total_numa_faults = 0;
2215 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2219 * First accesses are treated as private, otherwise consider accesses
2220 * to be private if the accessing pid has not changed
2222 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2225 priv = cpupid_match_pid(p, last_cpupid);
2226 if (!priv && !(flags & TNF_NO_GROUP))
2227 task_numa_group(p, last_cpupid, flags, &priv);
2231 * If a workload spans multiple NUMA nodes, a shared fault that
2232 * occurs wholly within the set of nodes that the workload is
2233 * actively using should be counted as local. This allows the
2234 * scan rate to slow down when a workload has settled down.
2237 if (!priv && !local && ng && ng->active_nodes > 1 &&
2238 numa_is_active_node(cpu_node, ng) &&
2239 numa_is_active_node(mem_node, ng))
2242 task_numa_placement(p);
2245 * Retry task to preferred node migration periodically, in case it
2246 * case it previously failed, or the scheduler moved us.
2248 if (time_after(jiffies, p->numa_migrate_retry))
2249 numa_migrate_preferred(p);
2252 p->numa_pages_migrated += pages;
2253 if (flags & TNF_MIGRATE_FAIL)
2254 p->numa_faults_locality[2] += pages;
2256 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2257 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2258 p->numa_faults_locality[local] += pages;
2261 static void reset_ptenuma_scan(struct task_struct *p)
2264 * We only did a read acquisition of the mmap sem, so
2265 * p->mm->numa_scan_seq is written to without exclusive access
2266 * and the update is not guaranteed to be atomic. That's not
2267 * much of an issue though, since this is just used for
2268 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2269 * expensive, to avoid any form of compiler optimizations:
2271 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2272 p->mm->numa_scan_offset = 0;
2276 * The expensive part of numa migration is done from task_work context.
2277 * Triggered from task_tick_numa().
2279 void task_numa_work(struct callback_head *work)
2281 unsigned long migrate, next_scan, now = jiffies;
2282 struct task_struct *p = current;
2283 struct mm_struct *mm = p->mm;
2284 u64 runtime = p->se.sum_exec_runtime;
2285 struct vm_area_struct *vma;
2286 unsigned long start, end;
2287 unsigned long nr_pte_updates = 0;
2288 long pages, virtpages;
2290 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2292 work->next = work; /* protect against double add */
2294 * Who cares about NUMA placement when they're dying.
2296 * NOTE: make sure not to dereference p->mm before this check,
2297 * exit_task_work() happens _after_ exit_mm() so we could be called
2298 * without p->mm even though we still had it when we enqueued this
2301 if (p->flags & PF_EXITING)
2304 if (!mm->numa_next_scan) {
2305 mm->numa_next_scan = now +
2306 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2310 * Enforce maximal scan/migration frequency..
2312 migrate = mm->numa_next_scan;
2313 if (time_before(now, migrate))
2316 if (p->numa_scan_period == 0) {
2317 p->numa_scan_period_max = task_scan_max(p);
2318 p->numa_scan_period = task_scan_min(p);
2321 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2322 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2326 * Delay this task enough that another task of this mm will likely win
2327 * the next time around.
2329 p->node_stamp += 2 * TICK_NSEC;
2331 start = mm->numa_scan_offset;
2332 pages = sysctl_numa_balancing_scan_size;
2333 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2334 virtpages = pages * 8; /* Scan up to this much virtual space */
2339 down_read(&mm->mmap_sem);
2340 vma = find_vma(mm, start);
2342 reset_ptenuma_scan(p);
2346 for (; vma; vma = vma->vm_next) {
2347 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2348 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2353 * Shared library pages mapped by multiple processes are not
2354 * migrated as it is expected they are cache replicated. Avoid
2355 * hinting faults in read-only file-backed mappings or the vdso
2356 * as migrating the pages will be of marginal benefit.
2359 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2363 * Skip inaccessible VMAs to avoid any confusion between
2364 * PROT_NONE and NUMA hinting ptes
2366 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2370 start = max(start, vma->vm_start);
2371 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2372 end = min(end, vma->vm_end);
2373 nr_pte_updates = change_prot_numa(vma, start, end);
2376 * Try to scan sysctl_numa_balancing_size worth of
2377 * hpages that have at least one present PTE that
2378 * is not already pte-numa. If the VMA contains
2379 * areas that are unused or already full of prot_numa
2380 * PTEs, scan up to virtpages, to skip through those
2384 pages -= (end - start) >> PAGE_SHIFT;
2385 virtpages -= (end - start) >> PAGE_SHIFT;
2388 if (pages <= 0 || virtpages <= 0)
2392 } while (end != vma->vm_end);
2397 * It is possible to reach the end of the VMA list but the last few
2398 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2399 * would find the !migratable VMA on the next scan but not reset the
2400 * scanner to the start so check it now.
2403 mm->numa_scan_offset = start;
2405 reset_ptenuma_scan(p);
2406 up_read(&mm->mmap_sem);
2409 * Make sure tasks use at least 32x as much time to run other code
2410 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2411 * Usually update_task_scan_period slows down scanning enough; on an
2412 * overloaded system we need to limit overhead on a per task basis.
2414 if (unlikely(p->se.sum_exec_runtime != runtime)) {
2415 u64 diff = p->se.sum_exec_runtime - runtime;
2416 p->node_stamp += 32 * diff;
2421 * Drive the periodic memory faults..
2423 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2425 struct callback_head *work = &curr->numa_work;
2429 * We don't care about NUMA placement if we don't have memory.
2431 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2435 * Using runtime rather than walltime has the dual advantage that
2436 * we (mostly) drive the selection from busy threads and that the
2437 * task needs to have done some actual work before we bother with
2440 now = curr->se.sum_exec_runtime;
2441 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2443 if (now > curr->node_stamp + period) {
2444 if (!curr->node_stamp)
2445 curr->numa_scan_period = task_scan_min(curr);
2446 curr->node_stamp += period;
2448 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2449 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2450 task_work_add(curr, work, true);
2455 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2459 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2463 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2466 #endif /* CONFIG_NUMA_BALANCING */
2469 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2471 update_load_add(&cfs_rq->load, se->load.weight);
2472 if (!parent_entity(se))
2473 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2475 if (entity_is_task(se)) {
2476 struct rq *rq = rq_of(cfs_rq);
2478 account_numa_enqueue(rq, task_of(se));
2479 list_add(&se->group_node, &rq->cfs_tasks);
2482 cfs_rq->nr_running++;
2486 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2488 update_load_sub(&cfs_rq->load, se->load.weight);
2489 if (!parent_entity(se))
2490 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2492 if (entity_is_task(se)) {
2493 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2494 list_del_init(&se->group_node);
2497 cfs_rq->nr_running--;
2500 #ifdef CONFIG_FAIR_GROUP_SCHED
2502 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2507 * Use this CPU's real-time load instead of the last load contribution
2508 * as the updating of the contribution is delayed, and we will use the
2509 * the real-time load to calc the share. See update_tg_load_avg().
2511 tg_weight = atomic_long_read(&tg->load_avg);
2512 tg_weight -= cfs_rq->tg_load_avg_contrib;
2513 tg_weight += cfs_rq->load.weight;
2518 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2520 long tg_weight, load, shares;
2522 tg_weight = calc_tg_weight(tg, cfs_rq);
2523 load = cfs_rq->load.weight;
2525 shares = (tg->shares * load);
2527 shares /= tg_weight;
2529 if (shares < MIN_SHARES)
2530 shares = MIN_SHARES;
2531 if (shares > tg->shares)
2532 shares = tg->shares;
2536 # else /* CONFIG_SMP */
2537 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2541 # endif /* CONFIG_SMP */
2542 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2543 unsigned long weight)
2546 /* commit outstanding execution time */
2547 if (cfs_rq->curr == se)
2548 update_curr(cfs_rq);
2549 account_entity_dequeue(cfs_rq, se);
2552 update_load_set(&se->load, weight);
2555 account_entity_enqueue(cfs_rq, se);
2558 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2560 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2562 struct task_group *tg;
2563 struct sched_entity *se;
2567 se = tg->se[cpu_of(rq_of(cfs_rq))];
2568 if (!se || throttled_hierarchy(cfs_rq))
2571 if (likely(se->load.weight == tg->shares))
2574 shares = calc_cfs_shares(cfs_rq, tg);
2576 reweight_entity(cfs_rq_of(se), se, shares);
2578 #else /* CONFIG_FAIR_GROUP_SCHED */
2579 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2582 #endif /* CONFIG_FAIR_GROUP_SCHED */
2585 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2586 static const u32 runnable_avg_yN_inv[] = {
2587 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2588 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2589 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2590 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2591 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2592 0x85aac367, 0x82cd8698,
2596 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2597 * over-estimates when re-combining.
2599 static const u32 runnable_avg_yN_sum[] = {
2600 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2601 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2602 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2606 * Precomputed \Sum y^k { 1<=k<=n, where n%32=0). Values are rolled down to
2607 * lower integers. See Documentation/scheduler/sched-avg.txt how these
2610 static const u32 __accumulated_sum_N32[] = {
2611 0, 23371, 35056, 40899, 43820, 45281,
2612 46011, 46376, 46559, 46650, 46696, 46719,
2617 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2619 static __always_inline u64 decay_load(u64 val, u64 n)
2621 unsigned int local_n;
2625 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2628 /* after bounds checking we can collapse to 32-bit */
2632 * As y^PERIOD = 1/2, we can combine
2633 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2634 * With a look-up table which covers y^n (n<PERIOD)
2636 * To achieve constant time decay_load.
2638 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2639 val >>= local_n / LOAD_AVG_PERIOD;
2640 local_n %= LOAD_AVG_PERIOD;
2643 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2648 * For updates fully spanning n periods, the contribution to runnable
2649 * average will be: \Sum 1024*y^n
2651 * We can compute this reasonably efficiently by combining:
2652 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2654 static u32 __compute_runnable_contrib(u64 n)
2658 if (likely(n <= LOAD_AVG_PERIOD))
2659 return runnable_avg_yN_sum[n];
2660 else if (unlikely(n >= LOAD_AVG_MAX_N))
2661 return LOAD_AVG_MAX;
2663 /* Since n < LOAD_AVG_MAX_N, n/LOAD_AVG_PERIOD < 11 */
2664 contrib = __accumulated_sum_N32[n/LOAD_AVG_PERIOD];
2665 n %= LOAD_AVG_PERIOD;
2666 contrib = decay_load(contrib, n);
2667 return contrib + runnable_avg_yN_sum[n];
2670 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2673 * We can represent the historical contribution to runnable average as the
2674 * coefficients of a geometric series. To do this we sub-divide our runnable
2675 * history into segments of approximately 1ms (1024us); label the segment that
2676 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2678 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2680 * (now) (~1ms ago) (~2ms ago)
2682 * Let u_i denote the fraction of p_i that the entity was runnable.
2684 * We then designate the fractions u_i as our co-efficients, yielding the
2685 * following representation of historical load:
2686 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2688 * We choose y based on the with of a reasonably scheduling period, fixing:
2691 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2692 * approximately half as much as the contribution to load within the last ms
2695 * When a period "rolls over" and we have new u_0`, multiplying the previous
2696 * sum again by y is sufficient to update:
2697 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2698 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2700 static __always_inline int
2701 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2702 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2704 u64 delta, scaled_delta, periods;
2706 unsigned int delta_w, scaled_delta_w, decayed = 0;
2707 unsigned long scale_freq, scale_cpu;
2709 delta = now - sa->last_update_time;
2711 * This should only happen when time goes backwards, which it
2712 * unfortunately does during sched clock init when we swap over to TSC.
2714 if ((s64)delta < 0) {
2715 sa->last_update_time = now;
2720 * Use 1024ns as the unit of measurement since it's a reasonable
2721 * approximation of 1us and fast to compute.
2726 sa->last_update_time = now;
2728 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2729 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2731 /* delta_w is the amount already accumulated against our next period */
2732 delta_w = sa->period_contrib;
2733 if (delta + delta_w >= 1024) {
2736 /* how much left for next period will start over, we don't know yet */
2737 sa->period_contrib = 0;
2740 * Now that we know we're crossing a period boundary, figure
2741 * out how much from delta we need to complete the current
2742 * period and accrue it.
2744 delta_w = 1024 - delta_w;
2745 scaled_delta_w = cap_scale(delta_w, scale_freq);
2747 sa->load_sum += weight * scaled_delta_w;
2749 cfs_rq->runnable_load_sum +=
2750 weight * scaled_delta_w;
2754 sa->util_sum += scaled_delta_w * scale_cpu;
2758 /* Figure out how many additional periods this update spans */
2759 periods = delta / 1024;
2762 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2764 cfs_rq->runnable_load_sum =
2765 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2767 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2769 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2770 contrib = __compute_runnable_contrib(periods);
2771 contrib = cap_scale(contrib, scale_freq);
2773 sa->load_sum += weight * contrib;
2775 cfs_rq->runnable_load_sum += weight * contrib;
2778 sa->util_sum += contrib * scale_cpu;
2781 /* Remainder of delta accrued against u_0` */
2782 scaled_delta = cap_scale(delta, scale_freq);
2784 sa->load_sum += weight * scaled_delta;
2786 cfs_rq->runnable_load_sum += weight * scaled_delta;
2789 sa->util_sum += scaled_delta * scale_cpu;
2791 sa->period_contrib += delta;
2794 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2796 cfs_rq->runnable_load_avg =
2797 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2799 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2805 #ifdef CONFIG_FAIR_GROUP_SCHED
2807 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2808 * and effective_load (which is not done because it is too costly).
2810 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2812 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2815 * No need to update load_avg for root_task_group as it is not used.
2817 if (cfs_rq->tg == &root_task_group)
2820 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2821 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2822 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2827 * Called within set_task_rq() right before setting a task's cpu. The
2828 * caller only guarantees p->pi_lock is held; no other assumptions,
2829 * including the state of rq->lock, should be made.
2831 void set_task_rq_fair(struct sched_entity *se,
2832 struct cfs_rq *prev, struct cfs_rq *next)
2834 if (!sched_feat(ATTACH_AGE_LOAD))
2838 * We are supposed to update the task to "current" time, then its up to
2839 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
2840 * getting what current time is, so simply throw away the out-of-date
2841 * time. This will result in the wakee task is less decayed, but giving
2842 * the wakee more load sounds not bad.
2844 if (se->avg.last_update_time && prev) {
2845 u64 p_last_update_time;
2846 u64 n_last_update_time;
2848 #ifndef CONFIG_64BIT
2849 u64 p_last_update_time_copy;
2850 u64 n_last_update_time_copy;
2853 p_last_update_time_copy = prev->load_last_update_time_copy;
2854 n_last_update_time_copy = next->load_last_update_time_copy;
2858 p_last_update_time = prev->avg.last_update_time;
2859 n_last_update_time = next->avg.last_update_time;
2861 } while (p_last_update_time != p_last_update_time_copy ||
2862 n_last_update_time != n_last_update_time_copy);
2864 p_last_update_time = prev->avg.last_update_time;
2865 n_last_update_time = next->avg.last_update_time;
2867 __update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
2868 &se->avg, 0, 0, NULL);
2869 se->avg.last_update_time = n_last_update_time;
2872 #else /* CONFIG_FAIR_GROUP_SCHED */
2873 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2874 #endif /* CONFIG_FAIR_GROUP_SCHED */
2876 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2878 static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
2880 struct rq *rq = rq_of(cfs_rq);
2881 int cpu = cpu_of(rq);
2883 if (cpu == smp_processor_id() && &rq->cfs == cfs_rq) {
2884 unsigned long max = rq->cpu_capacity_orig;
2887 * There are a few boundary cases this might miss but it should
2888 * get called often enough that that should (hopefully) not be
2889 * a real problem -- added to that it only calls on the local
2890 * CPU, so if we enqueue remotely we'll miss an update, but
2891 * the next tick/schedule should update.
2893 * It will not get called when we go idle, because the idle
2894 * thread is a different class (!fair), nor will the utilization
2895 * number include things like RT tasks.
2897 * As is, the util number is not freq-invariant (we'd have to
2898 * implement arch_scale_freq_capacity() for that).
2902 cpufreq_update_util(rq_clock(rq),
2903 min(cfs_rq->avg.util_avg, max), max);
2907 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2909 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
2911 struct sched_avg *sa = &cfs_rq->avg;
2912 int decayed, removed_load = 0, removed_util = 0;
2914 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2915 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2916 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2917 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2921 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2922 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2923 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2924 sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2928 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2929 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2931 #ifndef CONFIG_64BIT
2933 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2936 if (update_freq && (decayed || removed_util))
2937 cfs_rq_util_change(cfs_rq);
2939 return decayed || removed_load;
2942 /* Update task and its cfs_rq load average */
2943 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2945 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2946 u64 now = cfs_rq_clock_task(cfs_rq);
2947 struct rq *rq = rq_of(cfs_rq);
2948 int cpu = cpu_of(rq);
2951 * Track task load average for carrying it to new CPU after migrated, and
2952 * track group sched_entity load average for task_h_load calc in migration
2954 __update_load_avg(now, cpu, &se->avg,
2955 se->on_rq * scale_load_down(se->load.weight),
2956 cfs_rq->curr == se, NULL);
2958 if (update_cfs_rq_load_avg(now, cfs_rq, true) && update_tg)
2959 update_tg_load_avg(cfs_rq, 0);
2962 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2964 if (!sched_feat(ATTACH_AGE_LOAD))
2968 * If we got migrated (either between CPUs or between cgroups) we'll
2969 * have aged the average right before clearing @last_update_time.
2971 if (se->avg.last_update_time) {
2972 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2973 &se->avg, 0, 0, NULL);
2976 * XXX: we could have just aged the entire load away if we've been
2977 * absent from the fair class for too long.
2982 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2983 cfs_rq->avg.load_avg += se->avg.load_avg;
2984 cfs_rq->avg.load_sum += se->avg.load_sum;
2985 cfs_rq->avg.util_avg += se->avg.util_avg;
2986 cfs_rq->avg.util_sum += se->avg.util_sum;
2988 cfs_rq_util_change(cfs_rq);
2991 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2993 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2994 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2995 cfs_rq->curr == se, NULL);
2997 cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
2998 cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
2999 cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
3000 cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
3002 cfs_rq_util_change(cfs_rq);
3005 /* Add the load generated by se into cfs_rq's load average */
3007 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3009 struct sched_avg *sa = &se->avg;
3010 u64 now = cfs_rq_clock_task(cfs_rq);
3011 int migrated, decayed;
3013 migrated = !sa->last_update_time;
3015 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
3016 se->on_rq * scale_load_down(se->load.weight),
3017 cfs_rq->curr == se, NULL);
3020 decayed = update_cfs_rq_load_avg(now, cfs_rq, !migrated);
3022 cfs_rq->runnable_load_avg += sa->load_avg;
3023 cfs_rq->runnable_load_sum += sa->load_sum;
3026 attach_entity_load_avg(cfs_rq, se);
3028 if (decayed || migrated)
3029 update_tg_load_avg(cfs_rq, 0);
3032 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
3034 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3036 update_load_avg(se, 1);
3038 cfs_rq->runnable_load_avg =
3039 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
3040 cfs_rq->runnable_load_sum =
3041 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
3044 #ifndef CONFIG_64BIT
3045 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3047 u64 last_update_time_copy;
3048 u64 last_update_time;
3051 last_update_time_copy = cfs_rq->load_last_update_time_copy;
3053 last_update_time = cfs_rq->avg.last_update_time;
3054 } while (last_update_time != last_update_time_copy);
3056 return last_update_time;
3059 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3061 return cfs_rq->avg.last_update_time;
3066 * Task first catches up with cfs_rq, and then subtract
3067 * itself from the cfs_rq (task must be off the queue now).
3069 void remove_entity_load_avg(struct sched_entity *se)
3071 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3072 u64 last_update_time;
3075 * Newly created task or never used group entity should not be removed
3076 * from its (source) cfs_rq
3078 if (se->avg.last_update_time == 0)
3081 last_update_time = cfs_rq_last_update_time(cfs_rq);
3083 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
3084 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
3085 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
3088 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
3090 return cfs_rq->runnable_load_avg;
3093 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
3095 return cfs_rq->avg.load_avg;
3098 static int idle_balance(struct rq *this_rq);
3100 #else /* CONFIG_SMP */
3102 static inline void update_load_avg(struct sched_entity *se, int not_used)
3104 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3105 struct rq *rq = rq_of(cfs_rq);
3107 cpufreq_trigger_update(rq_clock(rq));
3111 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3113 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3114 static inline void remove_entity_load_avg(struct sched_entity *se) {}
3117 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3119 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3121 static inline int idle_balance(struct rq *rq)
3126 #endif /* CONFIG_SMP */
3128 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
3130 #ifdef CONFIG_SCHEDSTATS
3131 struct task_struct *tsk = NULL;
3133 if (entity_is_task(se))
3136 if (se->statistics.sleep_start) {
3137 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
3142 if (unlikely(delta > se->statistics.sleep_max))
3143 se->statistics.sleep_max = delta;
3145 se->statistics.sleep_start = 0;
3146 se->statistics.sum_sleep_runtime += delta;
3149 account_scheduler_latency(tsk, delta >> 10, 1);
3150 trace_sched_stat_sleep(tsk, delta);
3153 if (se->statistics.block_start) {
3154 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
3159 if (unlikely(delta > se->statistics.block_max))
3160 se->statistics.block_max = delta;
3162 se->statistics.block_start = 0;
3163 se->statistics.sum_sleep_runtime += delta;
3166 if (tsk->in_iowait) {
3167 se->statistics.iowait_sum += delta;
3168 se->statistics.iowait_count++;
3169 trace_sched_stat_iowait(tsk, delta);
3172 trace_sched_stat_blocked(tsk, delta);
3175 * Blocking time is in units of nanosecs, so shift by
3176 * 20 to get a milliseconds-range estimation of the
3177 * amount of time that the task spent sleeping:
3179 if (unlikely(prof_on == SLEEP_PROFILING)) {
3180 profile_hits(SLEEP_PROFILING,
3181 (void *)get_wchan(tsk),
3184 account_scheduler_latency(tsk, delta >> 10, 0);
3190 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
3192 #ifdef CONFIG_SCHED_DEBUG
3193 s64 d = se->vruntime - cfs_rq->min_vruntime;
3198 if (d > 3*sysctl_sched_latency)
3199 schedstat_inc(cfs_rq, nr_spread_over);
3204 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
3206 u64 vruntime = cfs_rq->min_vruntime;
3209 * The 'current' period is already promised to the current tasks,
3210 * however the extra weight of the new task will slow them down a
3211 * little, place the new task so that it fits in the slot that
3212 * stays open at the end.
3214 if (initial && sched_feat(START_DEBIT))
3215 vruntime += sched_vslice(cfs_rq, se);
3217 /* sleeps up to a single latency don't count. */
3219 unsigned long thresh = sysctl_sched_latency;
3222 * Halve their sleep time's effect, to allow
3223 * for a gentler effect of sleepers:
3225 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3231 /* ensure we never gain time by being placed backwards. */
3232 se->vruntime = max_vruntime(se->vruntime, vruntime);
3235 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3237 static inline void check_schedstat_required(void)
3239 #ifdef CONFIG_SCHEDSTATS
3240 if (schedstat_enabled())
3243 /* Force schedstat enabled if a dependent tracepoint is active */
3244 if (trace_sched_stat_wait_enabled() ||
3245 trace_sched_stat_sleep_enabled() ||
3246 trace_sched_stat_iowait_enabled() ||
3247 trace_sched_stat_blocked_enabled() ||
3248 trace_sched_stat_runtime_enabled()) {
3249 pr_warn_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3250 "stat_blocked and stat_runtime require the "
3251 "kernel parameter schedstats=enabled or "
3252 "kernel.sched_schedstats=1\n");
3263 * update_min_vruntime()
3264 * vruntime -= min_vruntime
3268 * update_min_vruntime()
3269 * vruntime += min_vruntime
3271 * this way the vruntime transition between RQs is done when both
3272 * min_vruntime are up-to-date.
3276 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
3277 * vruntime -= min_vruntime
3281 * update_min_vruntime()
3282 * vruntime += min_vruntime
3284 * this way we don't have the most up-to-date min_vruntime on the originating
3285 * CPU and an up-to-date min_vruntime on the destination CPU.
3289 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3291 bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
3292 bool curr = cfs_rq->curr == se;
3295 * If we're the current task, we must renormalise before calling
3299 se->vruntime += cfs_rq->min_vruntime;
3301 update_curr(cfs_rq);
3304 * Otherwise, renormalise after, such that we're placed at the current
3305 * moment in time, instead of some random moment in the past. Being
3306 * placed in the past could significantly boost this task to the
3307 * fairness detriment of existing tasks.
3309 if (renorm && !curr)
3310 se->vruntime += cfs_rq->min_vruntime;
3312 enqueue_entity_load_avg(cfs_rq, se);
3313 account_entity_enqueue(cfs_rq, se);
3314 update_cfs_shares(cfs_rq);
3316 if (flags & ENQUEUE_WAKEUP) {
3317 place_entity(cfs_rq, se, 0);
3318 if (schedstat_enabled())
3319 enqueue_sleeper(cfs_rq, se);
3322 check_schedstat_required();
3323 if (schedstat_enabled()) {
3324 update_stats_enqueue(cfs_rq, se);
3325 check_spread(cfs_rq, se);
3328 __enqueue_entity(cfs_rq, se);
3331 if (cfs_rq->nr_running == 1) {
3332 list_add_leaf_cfs_rq(cfs_rq);
3333 check_enqueue_throttle(cfs_rq);
3337 static void __clear_buddies_last(struct sched_entity *se)
3339 for_each_sched_entity(se) {
3340 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3341 if (cfs_rq->last != se)
3344 cfs_rq->last = NULL;
3348 static void __clear_buddies_next(struct sched_entity *se)
3350 for_each_sched_entity(se) {
3351 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3352 if (cfs_rq->next != se)
3355 cfs_rq->next = NULL;
3359 static void __clear_buddies_skip(struct sched_entity *se)
3361 for_each_sched_entity(se) {
3362 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3363 if (cfs_rq->skip != se)
3366 cfs_rq->skip = NULL;
3370 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3372 if (cfs_rq->last == se)
3373 __clear_buddies_last(se);
3375 if (cfs_rq->next == se)
3376 __clear_buddies_next(se);
3378 if (cfs_rq->skip == se)
3379 __clear_buddies_skip(se);
3382 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3385 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3388 * Update run-time statistics of the 'current'.
3390 update_curr(cfs_rq);
3391 dequeue_entity_load_avg(cfs_rq, se);
3393 if (schedstat_enabled())
3394 update_stats_dequeue(cfs_rq, se, flags);
3396 clear_buddies(cfs_rq, se);
3398 if (se != cfs_rq->curr)
3399 __dequeue_entity(cfs_rq, se);
3401 account_entity_dequeue(cfs_rq, se);
3404 * Normalize the entity after updating the min_vruntime because the
3405 * update can refer to the ->curr item and we need to reflect this
3406 * movement in our normalized position.
3408 if (!(flags & DEQUEUE_SLEEP))
3409 se->vruntime -= cfs_rq->min_vruntime;
3411 /* return excess runtime on last dequeue */
3412 return_cfs_rq_runtime(cfs_rq);
3414 update_min_vruntime(cfs_rq);
3415 update_cfs_shares(cfs_rq);
3419 * Preempt the current task with a newly woken task if needed:
3422 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3424 unsigned long ideal_runtime, delta_exec;
3425 struct sched_entity *se;
3428 ideal_runtime = sched_slice(cfs_rq, curr);
3429 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3430 if (delta_exec > ideal_runtime) {
3431 resched_curr(rq_of(cfs_rq));
3433 * The current task ran long enough, ensure it doesn't get
3434 * re-elected due to buddy favours.
3436 clear_buddies(cfs_rq, curr);
3441 * Ensure that a task that missed wakeup preemption by a
3442 * narrow margin doesn't have to wait for a full slice.
3443 * This also mitigates buddy induced latencies under load.
3445 if (delta_exec < sysctl_sched_min_granularity)
3448 se = __pick_first_entity(cfs_rq);
3449 delta = curr->vruntime - se->vruntime;
3454 if (delta > ideal_runtime)
3455 resched_curr(rq_of(cfs_rq));
3459 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3461 /* 'current' is not kept within the tree. */
3464 * Any task has to be enqueued before it get to execute on
3465 * a CPU. So account for the time it spent waiting on the
3468 if (schedstat_enabled())
3469 update_stats_wait_end(cfs_rq, se);
3470 __dequeue_entity(cfs_rq, se);
3471 update_load_avg(se, 1);
3474 update_stats_curr_start(cfs_rq, se);
3476 #ifdef CONFIG_SCHEDSTATS
3478 * Track our maximum slice length, if the CPU's load is at
3479 * least twice that of our own weight (i.e. dont track it
3480 * when there are only lesser-weight tasks around):
3482 if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3483 se->statistics.slice_max = max(se->statistics.slice_max,
3484 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3487 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3491 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3494 * Pick the next process, keeping these things in mind, in this order:
3495 * 1) keep things fair between processes/task groups
3496 * 2) pick the "next" process, since someone really wants that to run
3497 * 3) pick the "last" process, for cache locality
3498 * 4) do not run the "skip" process, if something else is available
3500 static struct sched_entity *
3501 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3503 struct sched_entity *left = __pick_first_entity(cfs_rq);
3504 struct sched_entity *se;
3507 * If curr is set we have to see if its left of the leftmost entity
3508 * still in the tree, provided there was anything in the tree at all.
3510 if (!left || (curr && entity_before(curr, left)))
3513 se = left; /* ideally we run the leftmost entity */
3516 * Avoid running the skip buddy, if running something else can
3517 * be done without getting too unfair.
3519 if (cfs_rq->skip == se) {
3520 struct sched_entity *second;
3523 second = __pick_first_entity(cfs_rq);
3525 second = __pick_next_entity(se);
3526 if (!second || (curr && entity_before(curr, second)))
3530 if (second && wakeup_preempt_entity(second, left) < 1)
3535 * Prefer last buddy, try to return the CPU to a preempted task.
3537 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3541 * Someone really wants this to run. If it's not unfair, run it.
3543 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3546 clear_buddies(cfs_rq, se);
3551 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3553 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3556 * If still on the runqueue then deactivate_task()
3557 * was not called and update_curr() has to be done:
3560 update_curr(cfs_rq);
3562 /* throttle cfs_rqs exceeding runtime */
3563 check_cfs_rq_runtime(cfs_rq);
3565 if (schedstat_enabled()) {
3566 check_spread(cfs_rq, prev);
3568 update_stats_wait_start(cfs_rq, prev);
3572 /* Put 'current' back into the tree. */
3573 __enqueue_entity(cfs_rq, prev);
3574 /* in !on_rq case, update occurred at dequeue */
3575 update_load_avg(prev, 0);
3577 cfs_rq->curr = NULL;
3581 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3584 * Update run-time statistics of the 'current'.
3586 update_curr(cfs_rq);
3589 * Ensure that runnable average is periodically updated.
3591 update_load_avg(curr, 1);
3592 update_cfs_shares(cfs_rq);
3594 #ifdef CONFIG_SCHED_HRTICK
3596 * queued ticks are scheduled to match the slice, so don't bother
3597 * validating it and just reschedule.
3600 resched_curr(rq_of(cfs_rq));
3604 * don't let the period tick interfere with the hrtick preemption
3606 if (!sched_feat(DOUBLE_TICK) &&
3607 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3611 if (cfs_rq->nr_running > 1)
3612 check_preempt_tick(cfs_rq, curr);
3616 /**************************************************
3617 * CFS bandwidth control machinery
3620 #ifdef CONFIG_CFS_BANDWIDTH
3622 #ifdef HAVE_JUMP_LABEL
3623 static struct static_key __cfs_bandwidth_used;
3625 static inline bool cfs_bandwidth_used(void)
3627 return static_key_false(&__cfs_bandwidth_used);
3630 void cfs_bandwidth_usage_inc(void)
3632 static_key_slow_inc(&__cfs_bandwidth_used);
3635 void cfs_bandwidth_usage_dec(void)
3637 static_key_slow_dec(&__cfs_bandwidth_used);
3639 #else /* HAVE_JUMP_LABEL */
3640 static bool cfs_bandwidth_used(void)
3645 void cfs_bandwidth_usage_inc(void) {}
3646 void cfs_bandwidth_usage_dec(void) {}
3647 #endif /* HAVE_JUMP_LABEL */
3650 * default period for cfs group bandwidth.
3651 * default: 0.1s, units: nanoseconds
3653 static inline u64 default_cfs_period(void)
3655 return 100000000ULL;
3658 static inline u64 sched_cfs_bandwidth_slice(void)
3660 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3664 * Replenish runtime according to assigned quota and update expiration time.
3665 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3666 * additional synchronization around rq->lock.
3668 * requires cfs_b->lock
3670 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3674 if (cfs_b->quota == RUNTIME_INF)
3677 now = sched_clock_cpu(smp_processor_id());
3678 cfs_b->runtime = cfs_b->quota;
3679 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3682 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3684 return &tg->cfs_bandwidth;
3687 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3688 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3690 if (unlikely(cfs_rq->throttle_count))
3691 return cfs_rq->throttled_clock_task;
3693 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3696 /* returns 0 on failure to allocate runtime */
3697 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3699 struct task_group *tg = cfs_rq->tg;
3700 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3701 u64 amount = 0, min_amount, expires;
3703 /* note: this is a positive sum as runtime_remaining <= 0 */
3704 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3706 raw_spin_lock(&cfs_b->lock);
3707 if (cfs_b->quota == RUNTIME_INF)
3708 amount = min_amount;
3710 start_cfs_bandwidth(cfs_b);
3712 if (cfs_b->runtime > 0) {
3713 amount = min(cfs_b->runtime, min_amount);
3714 cfs_b->runtime -= amount;
3718 expires = cfs_b->runtime_expires;
3719 raw_spin_unlock(&cfs_b->lock);
3721 cfs_rq->runtime_remaining += amount;
3723 * we may have advanced our local expiration to account for allowed
3724 * spread between our sched_clock and the one on which runtime was
3727 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3728 cfs_rq->runtime_expires = expires;
3730 return cfs_rq->runtime_remaining > 0;
3734 * Note: This depends on the synchronization provided by sched_clock and the
3735 * fact that rq->clock snapshots this value.
3737 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3739 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3741 /* if the deadline is ahead of our clock, nothing to do */
3742 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3745 if (cfs_rq->runtime_remaining < 0)
3749 * If the local deadline has passed we have to consider the
3750 * possibility that our sched_clock is 'fast' and the global deadline
3751 * has not truly expired.
3753 * Fortunately we can check determine whether this the case by checking
3754 * whether the global deadline has advanced. It is valid to compare
3755 * cfs_b->runtime_expires without any locks since we only care about
3756 * exact equality, so a partial write will still work.
3759 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3760 /* extend local deadline, drift is bounded above by 2 ticks */
3761 cfs_rq->runtime_expires += TICK_NSEC;
3763 /* global deadline is ahead, expiration has passed */
3764 cfs_rq->runtime_remaining = 0;
3768 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3770 /* dock delta_exec before expiring quota (as it could span periods) */
3771 cfs_rq->runtime_remaining -= delta_exec;
3772 expire_cfs_rq_runtime(cfs_rq);
3774 if (likely(cfs_rq->runtime_remaining > 0))
3778 * if we're unable to extend our runtime we resched so that the active
3779 * hierarchy can be throttled
3781 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3782 resched_curr(rq_of(cfs_rq));
3785 static __always_inline
3786 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3788 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3791 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3794 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3796 return cfs_bandwidth_used() && cfs_rq->throttled;
3799 /* check whether cfs_rq, or any parent, is throttled */
3800 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3802 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3806 * Ensure that neither of the group entities corresponding to src_cpu or
3807 * dest_cpu are members of a throttled hierarchy when performing group
3808 * load-balance operations.
3810 static inline int throttled_lb_pair(struct task_group *tg,
3811 int src_cpu, int dest_cpu)
3813 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3815 src_cfs_rq = tg->cfs_rq[src_cpu];
3816 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3818 return throttled_hierarchy(src_cfs_rq) ||
3819 throttled_hierarchy(dest_cfs_rq);
3822 /* updated child weight may affect parent so we have to do this bottom up */
3823 static int tg_unthrottle_up(struct task_group *tg, void *data)
3825 struct rq *rq = data;
3826 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3828 cfs_rq->throttle_count--;
3830 if (!cfs_rq->throttle_count) {
3831 /* adjust cfs_rq_clock_task() */
3832 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3833 cfs_rq->throttled_clock_task;
3840 static int tg_throttle_down(struct task_group *tg, void *data)
3842 struct rq *rq = data;
3843 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3845 /* group is entering throttled state, stop time */
3846 if (!cfs_rq->throttle_count)
3847 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3848 cfs_rq->throttle_count++;
3853 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3855 struct rq *rq = rq_of(cfs_rq);
3856 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3857 struct sched_entity *se;
3858 long task_delta, dequeue = 1;
3861 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3863 /* freeze hierarchy runnable averages while throttled */
3865 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3868 task_delta = cfs_rq->h_nr_running;
3869 for_each_sched_entity(se) {
3870 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3871 /* throttled entity or throttle-on-deactivate */
3876 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3877 qcfs_rq->h_nr_running -= task_delta;
3879 if (qcfs_rq->load.weight)
3884 sub_nr_running(rq, task_delta);
3886 cfs_rq->throttled = 1;
3887 cfs_rq->throttled_clock = rq_clock(rq);
3888 raw_spin_lock(&cfs_b->lock);
3889 empty = list_empty(&cfs_b->throttled_cfs_rq);
3892 * Add to the _head_ of the list, so that an already-started
3893 * distribute_cfs_runtime will not see us
3895 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3898 * If we're the first throttled task, make sure the bandwidth
3902 start_cfs_bandwidth(cfs_b);
3904 raw_spin_unlock(&cfs_b->lock);
3907 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3909 struct rq *rq = rq_of(cfs_rq);
3910 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3911 struct sched_entity *se;
3915 se = cfs_rq->tg->se[cpu_of(rq)];
3917 cfs_rq->throttled = 0;
3919 update_rq_clock(rq);
3921 raw_spin_lock(&cfs_b->lock);
3922 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3923 list_del_rcu(&cfs_rq->throttled_list);
3924 raw_spin_unlock(&cfs_b->lock);
3926 /* update hierarchical throttle state */
3927 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3929 if (!cfs_rq->load.weight)
3932 task_delta = cfs_rq->h_nr_running;
3933 for_each_sched_entity(se) {
3937 cfs_rq = cfs_rq_of(se);
3939 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3940 cfs_rq->h_nr_running += task_delta;
3942 if (cfs_rq_throttled(cfs_rq))
3947 add_nr_running(rq, task_delta);
3949 /* determine whether we need to wake up potentially idle cpu */
3950 if (rq->curr == rq->idle && rq->cfs.nr_running)
3954 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3955 u64 remaining, u64 expires)
3957 struct cfs_rq *cfs_rq;
3959 u64 starting_runtime = remaining;
3962 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3964 struct rq *rq = rq_of(cfs_rq);
3966 raw_spin_lock(&rq->lock);
3967 if (!cfs_rq_throttled(cfs_rq))
3970 runtime = -cfs_rq->runtime_remaining + 1;
3971 if (runtime > remaining)
3972 runtime = remaining;
3973 remaining -= runtime;
3975 cfs_rq->runtime_remaining += runtime;
3976 cfs_rq->runtime_expires = expires;
3978 /* we check whether we're throttled above */
3979 if (cfs_rq->runtime_remaining > 0)
3980 unthrottle_cfs_rq(cfs_rq);
3983 raw_spin_unlock(&rq->lock);
3990 return starting_runtime - remaining;
3994 * Responsible for refilling a task_group's bandwidth and unthrottling its
3995 * cfs_rqs as appropriate. If there has been no activity within the last
3996 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3997 * used to track this state.
3999 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
4001 u64 runtime, runtime_expires;
4004 /* no need to continue the timer with no bandwidth constraint */
4005 if (cfs_b->quota == RUNTIME_INF)
4006 goto out_deactivate;
4008 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4009 cfs_b->nr_periods += overrun;
4012 * idle depends on !throttled (for the case of a large deficit), and if
4013 * we're going inactive then everything else can be deferred
4015 if (cfs_b->idle && !throttled)
4016 goto out_deactivate;
4018 __refill_cfs_bandwidth_runtime(cfs_b);
4021 /* mark as potentially idle for the upcoming period */
4026 /* account preceding periods in which throttling occurred */
4027 cfs_b->nr_throttled += overrun;
4029 runtime_expires = cfs_b->runtime_expires;
4032 * This check is repeated as we are holding onto the new bandwidth while
4033 * we unthrottle. This can potentially race with an unthrottled group
4034 * trying to acquire new bandwidth from the global pool. This can result
4035 * in us over-using our runtime if it is all used during this loop, but
4036 * only by limited amounts in that extreme case.
4038 while (throttled && cfs_b->runtime > 0) {
4039 runtime = cfs_b->runtime;
4040 raw_spin_unlock(&cfs_b->lock);
4041 /* we can't nest cfs_b->lock while distributing bandwidth */
4042 runtime = distribute_cfs_runtime(cfs_b, runtime,
4044 raw_spin_lock(&cfs_b->lock);
4046 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4048 cfs_b->runtime -= min(runtime, cfs_b->runtime);
4052 * While we are ensured activity in the period following an
4053 * unthrottle, this also covers the case in which the new bandwidth is
4054 * insufficient to cover the existing bandwidth deficit. (Forcing the
4055 * timer to remain active while there are any throttled entities.)
4065 /* a cfs_rq won't donate quota below this amount */
4066 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
4067 /* minimum remaining period time to redistribute slack quota */
4068 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
4069 /* how long we wait to gather additional slack before distributing */
4070 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
4073 * Are we near the end of the current quota period?
4075 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4076 * hrtimer base being cleared by hrtimer_start. In the case of
4077 * migrate_hrtimers, base is never cleared, so we are fine.
4079 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
4081 struct hrtimer *refresh_timer = &cfs_b->period_timer;
4084 /* if the call-back is running a quota refresh is already occurring */
4085 if (hrtimer_callback_running(refresh_timer))
4088 /* is a quota refresh about to occur? */
4089 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
4090 if (remaining < min_expire)
4096 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
4098 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
4100 /* if there's a quota refresh soon don't bother with slack */
4101 if (runtime_refresh_within(cfs_b, min_left))
4104 hrtimer_start(&cfs_b->slack_timer,
4105 ns_to_ktime(cfs_bandwidth_slack_period),
4109 /* we know any runtime found here is valid as update_curr() precedes return */
4110 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4112 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4113 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
4115 if (slack_runtime <= 0)
4118 raw_spin_lock(&cfs_b->lock);
4119 if (cfs_b->quota != RUNTIME_INF &&
4120 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
4121 cfs_b->runtime += slack_runtime;
4123 /* we are under rq->lock, defer unthrottling using a timer */
4124 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
4125 !list_empty(&cfs_b->throttled_cfs_rq))
4126 start_cfs_slack_bandwidth(cfs_b);
4128 raw_spin_unlock(&cfs_b->lock);
4130 /* even if it's not valid for return we don't want to try again */
4131 cfs_rq->runtime_remaining -= slack_runtime;
4134 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4136 if (!cfs_bandwidth_used())
4139 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4142 __return_cfs_rq_runtime(cfs_rq);
4146 * This is done with a timer (instead of inline with bandwidth return) since
4147 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4149 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
4151 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
4154 /* confirm we're still not at a refresh boundary */
4155 raw_spin_lock(&cfs_b->lock);
4156 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
4157 raw_spin_unlock(&cfs_b->lock);
4161 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4162 runtime = cfs_b->runtime;
4164 expires = cfs_b->runtime_expires;
4165 raw_spin_unlock(&cfs_b->lock);
4170 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
4172 raw_spin_lock(&cfs_b->lock);
4173 if (expires == cfs_b->runtime_expires)
4174 cfs_b->runtime -= min(runtime, cfs_b->runtime);
4175 raw_spin_unlock(&cfs_b->lock);
4179 * When a group wakes up we want to make sure that its quota is not already
4180 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4181 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4183 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
4185 if (!cfs_bandwidth_used())
4188 /* an active group must be handled by the update_curr()->put() path */
4189 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
4192 /* ensure the group is not already throttled */
4193 if (cfs_rq_throttled(cfs_rq))
4196 /* update runtime allocation */
4197 account_cfs_rq_runtime(cfs_rq, 0);
4198 if (cfs_rq->runtime_remaining <= 0)
4199 throttle_cfs_rq(cfs_rq);
4202 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4203 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4205 if (!cfs_bandwidth_used())
4208 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4212 * it's possible for a throttled entity to be forced into a running
4213 * state (e.g. set_curr_task), in this case we're finished.
4215 if (cfs_rq_throttled(cfs_rq))
4218 throttle_cfs_rq(cfs_rq);
4222 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
4224 struct cfs_bandwidth *cfs_b =
4225 container_of(timer, struct cfs_bandwidth, slack_timer);
4227 do_sched_cfs_slack_timer(cfs_b);
4229 return HRTIMER_NORESTART;
4232 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
4234 struct cfs_bandwidth *cfs_b =
4235 container_of(timer, struct cfs_bandwidth, period_timer);
4239 raw_spin_lock(&cfs_b->lock);
4241 overrun = hrtimer_forward_now(timer, cfs_b->period);
4245 idle = do_sched_cfs_period_timer(cfs_b, overrun);
4248 cfs_b->period_active = 0;
4249 raw_spin_unlock(&cfs_b->lock);
4251 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
4254 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4256 raw_spin_lock_init(&cfs_b->lock);
4258 cfs_b->quota = RUNTIME_INF;
4259 cfs_b->period = ns_to_ktime(default_cfs_period());
4261 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
4262 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4263 cfs_b->period_timer.function = sched_cfs_period_timer;
4264 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
4265 cfs_b->slack_timer.function = sched_cfs_slack_timer;
4268 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4270 cfs_rq->runtime_enabled = 0;
4271 INIT_LIST_HEAD(&cfs_rq->throttled_list);
4274 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4276 lockdep_assert_held(&cfs_b->lock);
4278 if (!cfs_b->period_active) {
4279 cfs_b->period_active = 1;
4280 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4281 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4285 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4287 /* init_cfs_bandwidth() was not called */
4288 if (!cfs_b->throttled_cfs_rq.next)
4291 hrtimer_cancel(&cfs_b->period_timer);
4292 hrtimer_cancel(&cfs_b->slack_timer);
4295 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4297 struct cfs_rq *cfs_rq;
4299 for_each_leaf_cfs_rq(rq, cfs_rq) {
4300 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4302 raw_spin_lock(&cfs_b->lock);
4303 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4304 raw_spin_unlock(&cfs_b->lock);
4308 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4310 struct cfs_rq *cfs_rq;
4312 for_each_leaf_cfs_rq(rq, cfs_rq) {
4313 if (!cfs_rq->runtime_enabled)
4317 * clock_task is not advancing so we just need to make sure
4318 * there's some valid quota amount
4320 cfs_rq->runtime_remaining = 1;
4322 * Offline rq is schedulable till cpu is completely disabled
4323 * in take_cpu_down(), so we prevent new cfs throttling here.
4325 cfs_rq->runtime_enabled = 0;
4327 if (cfs_rq_throttled(cfs_rq))
4328 unthrottle_cfs_rq(cfs_rq);
4332 #else /* CONFIG_CFS_BANDWIDTH */
4333 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4335 return rq_clock_task(rq_of(cfs_rq));
4338 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4339 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4340 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4341 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4343 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4348 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4353 static inline int throttled_lb_pair(struct task_group *tg,
4354 int src_cpu, int dest_cpu)
4359 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4361 #ifdef CONFIG_FAIR_GROUP_SCHED
4362 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4365 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4369 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4370 static inline void update_runtime_enabled(struct rq *rq) {}
4371 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4373 #endif /* CONFIG_CFS_BANDWIDTH */
4375 /**************************************************
4376 * CFS operations on tasks:
4379 #ifdef CONFIG_SCHED_HRTICK
4380 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4382 struct sched_entity *se = &p->se;
4383 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4385 WARN_ON(task_rq(p) != rq);
4387 if (cfs_rq->nr_running > 1) {
4388 u64 slice = sched_slice(cfs_rq, se);
4389 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4390 s64 delta = slice - ran;
4397 hrtick_start(rq, delta);
4402 * called from enqueue/dequeue and updates the hrtick when the
4403 * current task is from our class and nr_running is low enough
4406 static void hrtick_update(struct rq *rq)
4408 struct task_struct *curr = rq->curr;
4410 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4413 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4414 hrtick_start_fair(rq, curr);
4416 #else /* !CONFIG_SCHED_HRTICK */
4418 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4422 static inline void hrtick_update(struct rq *rq)
4428 * The enqueue_task method is called before nr_running is
4429 * increased. Here we update the fair scheduling stats and
4430 * then put the task into the rbtree:
4433 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4435 struct cfs_rq *cfs_rq;
4436 struct sched_entity *se = &p->se;
4438 for_each_sched_entity(se) {
4441 cfs_rq = cfs_rq_of(se);
4442 enqueue_entity(cfs_rq, se, flags);
4445 * end evaluation on encountering a throttled cfs_rq
4447 * note: in the case of encountering a throttled cfs_rq we will
4448 * post the final h_nr_running increment below.
4450 if (cfs_rq_throttled(cfs_rq))
4452 cfs_rq->h_nr_running++;
4454 flags = ENQUEUE_WAKEUP;
4457 for_each_sched_entity(se) {
4458 cfs_rq = cfs_rq_of(se);
4459 cfs_rq->h_nr_running++;
4461 if (cfs_rq_throttled(cfs_rq))
4464 update_load_avg(se, 1);
4465 update_cfs_shares(cfs_rq);
4469 add_nr_running(rq, 1);
4474 static void set_next_buddy(struct sched_entity *se);
4477 * The dequeue_task method is called before nr_running is
4478 * decreased. We remove the task from the rbtree and
4479 * update the fair scheduling stats:
4481 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4483 struct cfs_rq *cfs_rq;
4484 struct sched_entity *se = &p->se;
4485 int task_sleep = flags & DEQUEUE_SLEEP;
4487 for_each_sched_entity(se) {
4488 cfs_rq = cfs_rq_of(se);
4489 dequeue_entity(cfs_rq, se, flags);
4492 * end evaluation on encountering a throttled cfs_rq
4494 * note: in the case of encountering a throttled cfs_rq we will
4495 * post the final h_nr_running decrement below.
4497 if (cfs_rq_throttled(cfs_rq))
4499 cfs_rq->h_nr_running--;
4501 /* Don't dequeue parent if it has other entities besides us */
4502 if (cfs_rq->load.weight) {
4504 * Bias pick_next to pick a task from this cfs_rq, as
4505 * p is sleeping when it is within its sched_slice.
4507 if (task_sleep && parent_entity(se))
4508 set_next_buddy(parent_entity(se));
4510 /* avoid re-evaluating load for this entity */
4511 se = parent_entity(se);
4514 flags |= DEQUEUE_SLEEP;
4517 for_each_sched_entity(se) {
4518 cfs_rq = cfs_rq_of(se);
4519 cfs_rq->h_nr_running--;
4521 if (cfs_rq_throttled(cfs_rq))
4524 update_load_avg(se, 1);
4525 update_cfs_shares(cfs_rq);
4529 sub_nr_running(rq, 1);
4535 #ifdef CONFIG_NO_HZ_COMMON
4537 * per rq 'load' arrray crap; XXX kill this.
4541 * The exact cpuload calculated at every tick would be:
4543 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4545 * If a cpu misses updates for n ticks (as it was idle) and update gets
4546 * called on the n+1-th tick when cpu may be busy, then we have:
4548 * load_n = (1 - 1/2^i)^n * load_0
4549 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
4551 * decay_load_missed() below does efficient calculation of
4553 * load' = (1 - 1/2^i)^n * load
4555 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4556 * This allows us to precompute the above in said factors, thereby allowing the
4557 * reduction of an arbitrary n in O(log_2 n) steps. (See also
4558 * fixed_power_int())
4560 * The calculation is approximated on a 128 point scale.
4562 #define DEGRADE_SHIFT 7
4564 static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4565 static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4566 { 0, 0, 0, 0, 0, 0, 0, 0 },
4567 { 64, 32, 8, 0, 0, 0, 0, 0 },
4568 { 96, 72, 40, 12, 1, 0, 0, 0 },
4569 { 112, 98, 75, 43, 15, 1, 0, 0 },
4570 { 120, 112, 98, 76, 45, 16, 2, 0 }
4574 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4575 * would be when CPU is idle and so we just decay the old load without
4576 * adding any new load.
4578 static unsigned long
4579 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4583 if (!missed_updates)
4586 if (missed_updates >= degrade_zero_ticks[idx])
4590 return load >> missed_updates;
4592 while (missed_updates) {
4593 if (missed_updates % 2)
4594 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4596 missed_updates >>= 1;
4601 #endif /* CONFIG_NO_HZ_COMMON */
4604 * __cpu_load_update - update the rq->cpu_load[] statistics
4605 * @this_rq: The rq to update statistics for
4606 * @this_load: The current load
4607 * @pending_updates: The number of missed updates
4609 * Update rq->cpu_load[] statistics. This function is usually called every
4610 * scheduler tick (TICK_NSEC).
4612 * This function computes a decaying average:
4614 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4616 * Because of NOHZ it might not get called on every tick which gives need for
4617 * the @pending_updates argument.
4619 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4620 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4621 * = A * (A * load[i]_n-2 + B) + B
4622 * = A * (A * (A * load[i]_n-3 + B) + B) + B
4623 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4624 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4625 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4626 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4628 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4629 * any change in load would have resulted in the tick being turned back on.
4631 * For regular NOHZ, this reduces to:
4633 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
4635 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4638 static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
4639 unsigned long pending_updates)
4641 unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
4644 this_rq->nr_load_updates++;
4646 /* Update our load: */
4647 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4648 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4649 unsigned long old_load, new_load;
4651 /* scale is effectively 1 << i now, and >> i divides by scale */
4653 old_load = this_rq->cpu_load[i];
4654 #ifdef CONFIG_NO_HZ_COMMON
4655 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4656 if (tickless_load) {
4657 old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
4659 * old_load can never be a negative value because a
4660 * decayed tickless_load cannot be greater than the
4661 * original tickless_load.
4663 old_load += tickless_load;
4666 new_load = this_load;
4668 * Round up the averaging division if load is increasing. This
4669 * prevents us from getting stuck on 9 if the load is 10, for
4672 if (new_load > old_load)
4673 new_load += scale - 1;
4675 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4678 sched_avg_update(this_rq);
4681 /* Used instead of source_load when we know the type == 0 */
4682 static unsigned long weighted_cpuload(const int cpu)
4684 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4687 #ifdef CONFIG_NO_HZ_COMMON
4689 * There is no sane way to deal with nohz on smp when using jiffies because the
4690 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4691 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4693 * Therefore we need to avoid the delta approach from the regular tick when
4694 * possible since that would seriously skew the load calculation. This is why we
4695 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
4696 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
4697 * loop exit, nohz_idle_balance, nohz full exit...)
4699 * This means we might still be one tick off for nohz periods.
4702 static void cpu_load_update_nohz(struct rq *this_rq,
4703 unsigned long curr_jiffies,
4706 unsigned long pending_updates;
4708 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4709 if (pending_updates) {
4710 this_rq->last_load_update_tick = curr_jiffies;
4712 * In the regular NOHZ case, we were idle, this means load 0.
4713 * In the NOHZ_FULL case, we were non-idle, we should consider
4714 * its weighted load.
4716 cpu_load_update(this_rq, load, pending_updates);
4721 * Called from nohz_idle_balance() to update the load ratings before doing the
4724 static void cpu_load_update_idle(struct rq *this_rq)
4727 * bail if there's load or we're actually up-to-date.
4729 if (weighted_cpuload(cpu_of(this_rq)))
4732 cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
4736 * Record CPU load on nohz entry so we know the tickless load to account
4737 * on nohz exit. cpu_load[0] happens then to be updated more frequently
4738 * than other cpu_load[idx] but it should be fine as cpu_load readers
4739 * shouldn't rely into synchronized cpu_load[*] updates.
4741 void cpu_load_update_nohz_start(void)
4743 struct rq *this_rq = this_rq();
4746 * This is all lockless but should be fine. If weighted_cpuload changes
4747 * concurrently we'll exit nohz. And cpu_load write can race with
4748 * cpu_load_update_idle() but both updater would be writing the same.
4750 this_rq->cpu_load[0] = weighted_cpuload(cpu_of(this_rq));
4754 * Account the tickless load in the end of a nohz frame.
4756 void cpu_load_update_nohz_stop(void)
4758 unsigned long curr_jiffies = READ_ONCE(jiffies);
4759 struct rq *this_rq = this_rq();
4762 if (curr_jiffies == this_rq->last_load_update_tick)
4765 load = weighted_cpuload(cpu_of(this_rq));
4766 raw_spin_lock(&this_rq->lock);
4767 update_rq_clock(this_rq);
4768 cpu_load_update_nohz(this_rq, curr_jiffies, load);
4769 raw_spin_unlock(&this_rq->lock);
4771 #else /* !CONFIG_NO_HZ_COMMON */
4772 static inline void cpu_load_update_nohz(struct rq *this_rq,
4773 unsigned long curr_jiffies,
4774 unsigned long load) { }
4775 #endif /* CONFIG_NO_HZ_COMMON */
4777 static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
4779 #ifdef CONFIG_NO_HZ_COMMON
4780 /* See the mess around cpu_load_update_nohz(). */
4781 this_rq->last_load_update_tick = READ_ONCE(jiffies);
4783 cpu_load_update(this_rq, load, 1);
4787 * Called from scheduler_tick()
4789 void cpu_load_update_active(struct rq *this_rq)
4791 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4793 if (tick_nohz_tick_stopped())
4794 cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
4796 cpu_load_update_periodic(this_rq, load);
4800 * Return a low guess at the load of a migration-source cpu weighted
4801 * according to the scheduling class and "nice" value.
4803 * We want to under-estimate the load of migration sources, to
4804 * balance conservatively.
4806 static unsigned long source_load(int cpu, int type)
4808 struct rq *rq = cpu_rq(cpu);
4809 unsigned long total = weighted_cpuload(cpu);
4811 if (type == 0 || !sched_feat(LB_BIAS))
4814 return min(rq->cpu_load[type-1], total);
4818 * Return a high guess at the load of a migration-target cpu weighted
4819 * according to the scheduling class and "nice" value.
4821 static unsigned long target_load(int cpu, int type)
4823 struct rq *rq = cpu_rq(cpu);
4824 unsigned long total = weighted_cpuload(cpu);
4826 if (type == 0 || !sched_feat(LB_BIAS))
4829 return max(rq->cpu_load[type-1], total);
4832 static unsigned long capacity_of(int cpu)
4834 return cpu_rq(cpu)->cpu_capacity;
4837 static unsigned long capacity_orig_of(int cpu)
4839 return cpu_rq(cpu)->cpu_capacity_orig;
4842 static unsigned long cpu_avg_load_per_task(int cpu)
4844 struct rq *rq = cpu_rq(cpu);
4845 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4846 unsigned long load_avg = weighted_cpuload(cpu);
4849 return load_avg / nr_running;
4854 #ifdef CONFIG_FAIR_GROUP_SCHED
4856 * effective_load() calculates the load change as seen from the root_task_group
4858 * Adding load to a group doesn't make a group heavier, but can cause movement
4859 * of group shares between cpus. Assuming the shares were perfectly aligned one
4860 * can calculate the shift in shares.
4862 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4863 * on this @cpu and results in a total addition (subtraction) of @wg to the
4864 * total group weight.
4866 * Given a runqueue weight distribution (rw_i) we can compute a shares
4867 * distribution (s_i) using:
4869 * s_i = rw_i / \Sum rw_j (1)
4871 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4872 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4873 * shares distribution (s_i):
4875 * rw_i = { 2, 4, 1, 0 }
4876 * s_i = { 2/7, 4/7, 1/7, 0 }
4878 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4879 * task used to run on and the CPU the waker is running on), we need to
4880 * compute the effect of waking a task on either CPU and, in case of a sync
4881 * wakeup, compute the effect of the current task going to sleep.
4883 * So for a change of @wl to the local @cpu with an overall group weight change
4884 * of @wl we can compute the new shares distribution (s'_i) using:
4886 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4888 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4889 * differences in waking a task to CPU 0. The additional task changes the
4890 * weight and shares distributions like:
4892 * rw'_i = { 3, 4, 1, 0 }
4893 * s'_i = { 3/8, 4/8, 1/8, 0 }
4895 * We can then compute the difference in effective weight by using:
4897 * dw_i = S * (s'_i - s_i) (3)
4899 * Where 'S' is the group weight as seen by its parent.
4901 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4902 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4903 * 4/7) times the weight of the group.
4905 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4907 struct sched_entity *se = tg->se[cpu];
4909 if (!tg->parent) /* the trivial, non-cgroup case */
4912 for_each_sched_entity(se) {
4918 * W = @wg + \Sum rw_j
4920 W = wg + calc_tg_weight(tg, se->my_q);
4925 w = cfs_rq_load_avg(se->my_q) + wl;
4928 * wl = S * s'_i; see (2)
4931 wl = (w * (long)tg->shares) / W;
4936 * Per the above, wl is the new se->load.weight value; since
4937 * those are clipped to [MIN_SHARES, ...) do so now. See
4938 * calc_cfs_shares().
4940 if (wl < MIN_SHARES)
4944 * wl = dw_i = S * (s'_i - s_i); see (3)
4946 wl -= se->avg.load_avg;
4949 * Recursively apply this logic to all parent groups to compute
4950 * the final effective load change on the root group. Since
4951 * only the @tg group gets extra weight, all parent groups can
4952 * only redistribute existing shares. @wl is the shift in shares
4953 * resulting from this level per the above.
4962 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4969 static void record_wakee(struct task_struct *p)
4972 * Only decay a single time; tasks that have less then 1 wakeup per
4973 * jiffy will not have built up many flips.
4975 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4976 current->wakee_flips >>= 1;
4977 current->wakee_flip_decay_ts = jiffies;
4980 if (current->last_wakee != p) {
4981 current->last_wakee = p;
4982 current->wakee_flips++;
4987 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4989 * A waker of many should wake a different task than the one last awakened
4990 * at a frequency roughly N times higher than one of its wakees.
4992 * In order to determine whether we should let the load spread vs consolidating
4993 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
4994 * partner, and a factor of lls_size higher frequency in the other.
4996 * With both conditions met, we can be relatively sure that the relationship is
4997 * non-monogamous, with partner count exceeding socket size.
4999 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5000 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5003 static int wake_wide(struct task_struct *p)
5005 unsigned int master = current->wakee_flips;
5006 unsigned int slave = p->wakee_flips;
5007 int factor = this_cpu_read(sd_llc_size);
5010 swap(master, slave);
5011 if (slave < factor || master < slave * factor)
5016 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
5018 s64 this_load, load;
5019 s64 this_eff_load, prev_eff_load;
5020 int idx, this_cpu, prev_cpu;
5021 struct task_group *tg;
5022 unsigned long weight;
5026 this_cpu = smp_processor_id();
5027 prev_cpu = task_cpu(p);
5028 load = source_load(prev_cpu, idx);
5029 this_load = target_load(this_cpu, idx);
5032 * If sync wakeup then subtract the (maximum possible)
5033 * effect of the currently running task from the load
5034 * of the current CPU:
5037 tg = task_group(current);
5038 weight = current->se.avg.load_avg;
5040 this_load += effective_load(tg, this_cpu, -weight, -weight);
5041 load += effective_load(tg, prev_cpu, 0, -weight);
5045 weight = p->se.avg.load_avg;
5048 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5049 * due to the sync cause above having dropped this_load to 0, we'll
5050 * always have an imbalance, but there's really nothing you can do
5051 * about that, so that's good too.
5053 * Otherwise check if either cpus are near enough in load to allow this
5054 * task to be woken on this_cpu.
5056 this_eff_load = 100;
5057 this_eff_load *= capacity_of(prev_cpu);
5059 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5060 prev_eff_load *= capacity_of(this_cpu);
5062 if (this_load > 0) {
5063 this_eff_load *= this_load +
5064 effective_load(tg, this_cpu, weight, weight);
5066 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5069 balanced = this_eff_load <= prev_eff_load;
5071 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5076 schedstat_inc(sd, ttwu_move_affine);
5077 schedstat_inc(p, se.statistics.nr_wakeups_affine);
5083 * find_idlest_group finds and returns the least busy CPU group within the
5086 static struct sched_group *
5087 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5088 int this_cpu, int sd_flag)
5090 struct sched_group *idlest = NULL, *group = sd->groups;
5091 unsigned long min_load = ULONG_MAX, this_load = 0;
5092 int load_idx = sd->forkexec_idx;
5093 int imbalance = 100 + (sd->imbalance_pct-100)/2;
5095 if (sd_flag & SD_BALANCE_WAKE)
5096 load_idx = sd->wake_idx;
5099 unsigned long load, avg_load;
5103 /* Skip over this group if it has no CPUs allowed */
5104 if (!cpumask_intersects(sched_group_cpus(group),
5105 tsk_cpus_allowed(p)))
5108 local_group = cpumask_test_cpu(this_cpu,
5109 sched_group_cpus(group));
5111 /* Tally up the load of all CPUs in the group */
5114 for_each_cpu(i, sched_group_cpus(group)) {
5115 /* Bias balancing toward cpus of our domain */
5117 load = source_load(i, load_idx);
5119 load = target_load(i, load_idx);
5124 /* Adjust by relative CPU capacity of the group */
5125 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5128 this_load = avg_load;
5129 } else if (avg_load < min_load) {
5130 min_load = avg_load;
5133 } while (group = group->next, group != sd->groups);
5135 if (!idlest || 100*this_load < imbalance*min_load)
5141 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5144 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5146 unsigned long load, min_load = ULONG_MAX;
5147 unsigned int min_exit_latency = UINT_MAX;
5148 u64 latest_idle_timestamp = 0;
5149 int least_loaded_cpu = this_cpu;
5150 int shallowest_idle_cpu = -1;
5153 /* Traverse only the allowed CPUs */
5154 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5156 struct rq *rq = cpu_rq(i);
5157 struct cpuidle_state *idle = idle_get_state(rq);
5158 if (idle && idle->exit_latency < min_exit_latency) {
5160 * We give priority to a CPU whose idle state
5161 * has the smallest exit latency irrespective
5162 * of any idle timestamp.
5164 min_exit_latency = idle->exit_latency;
5165 latest_idle_timestamp = rq->idle_stamp;
5166 shallowest_idle_cpu = i;
5167 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
5168 rq->idle_stamp > latest_idle_timestamp) {
5170 * If equal or no active idle state, then
5171 * the most recently idled CPU might have
5174 latest_idle_timestamp = rq->idle_stamp;
5175 shallowest_idle_cpu = i;
5177 } else if (shallowest_idle_cpu == -1) {
5178 load = weighted_cpuload(i);
5179 if (load < min_load || (load == min_load && i == this_cpu)) {
5181 least_loaded_cpu = i;
5186 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5190 * Try and locate an idle CPU in the sched_domain.
5192 static int select_idle_sibling(struct task_struct *p, int target)
5194 struct sched_domain *sd;
5195 struct sched_group *sg;
5196 int i = task_cpu(p);
5198 if (idle_cpu(target))
5202 * If the prevous cpu is cache affine and idle, don't be stupid.
5204 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5208 * Otherwise, iterate the domains and find an eligible idle cpu.
5210 * A completely idle sched group at higher domains is more
5211 * desirable than an idle group at a lower level, because lower
5212 * domains have smaller groups and usually share hardware
5213 * resources which causes tasks to contend on them, e.g. x86
5214 * hyperthread siblings in the lowest domain (SMT) can contend
5215 * on the shared cpu pipeline.
5217 * However, while we prefer idle groups at higher domains
5218 * finding an idle cpu at the lowest domain is still better than
5219 * returning 'target', which we've already established, isn't
5222 sd = rcu_dereference(per_cpu(sd_llc, target));
5223 for_each_lower_domain(sd) {
5226 if (!cpumask_intersects(sched_group_cpus(sg),
5227 tsk_cpus_allowed(p)))
5230 /* Ensure the entire group is idle */
5231 for_each_cpu(i, sched_group_cpus(sg)) {
5232 if (i == target || !idle_cpu(i))
5237 * It doesn't matter which cpu we pick, the
5238 * whole group is idle.
5240 target = cpumask_first_and(sched_group_cpus(sg),
5241 tsk_cpus_allowed(p));
5245 } while (sg != sd->groups);
5252 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5253 * tasks. The unit of the return value must be the one of capacity so we can
5254 * compare the utilization with the capacity of the CPU that is available for
5255 * CFS task (ie cpu_capacity).
5257 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5258 * recent utilization of currently non-runnable tasks on a CPU. It represents
5259 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5260 * capacity_orig is the cpu_capacity available at the highest frequency
5261 * (arch_scale_freq_capacity()).
5262 * The utilization of a CPU converges towards a sum equal to or less than the
5263 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5264 * the running time on this CPU scaled by capacity_curr.
5266 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5267 * higher than capacity_orig because of unfortunate rounding in
5268 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5269 * the average stabilizes with the new running time. We need to check that the
5270 * utilization stays within the range of [0..capacity_orig] and cap it if
5271 * necessary. Without utilization capping, a group could be seen as overloaded
5272 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5273 * available capacity. We allow utilization to overshoot capacity_curr (but not
5274 * capacity_orig) as it useful for predicting the capacity required after task
5275 * migrations (scheduler-driven DVFS).
5277 static int cpu_util(int cpu)
5279 unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5280 unsigned long capacity = capacity_orig_of(cpu);
5282 return (util >= capacity) ? capacity : util;
5286 * select_task_rq_fair: Select target runqueue for the waking task in domains
5287 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5288 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5290 * Balances load by selecting the idlest cpu in the idlest group, or under
5291 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5293 * Returns the target cpu number.
5295 * preempt must be disabled.
5298 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5300 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5301 int cpu = smp_processor_id();
5302 int new_cpu = prev_cpu;
5303 int want_affine = 0;
5304 int sync = wake_flags & WF_SYNC;
5306 if (sd_flag & SD_BALANCE_WAKE) {
5308 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
5312 for_each_domain(cpu, tmp) {
5313 if (!(tmp->flags & SD_LOAD_BALANCE))
5317 * If both cpu and prev_cpu are part of this domain,
5318 * cpu is a valid SD_WAKE_AFFINE target.
5320 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5321 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5326 if (tmp->flags & sd_flag)
5328 else if (!want_affine)
5333 sd = NULL; /* Prefer wake_affine over balance flags */
5334 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5339 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5340 new_cpu = select_idle_sibling(p, new_cpu);
5343 struct sched_group *group;
5346 if (!(sd->flags & sd_flag)) {
5351 group = find_idlest_group(sd, p, cpu, sd_flag);
5357 new_cpu = find_idlest_cpu(group, p, cpu);
5358 if (new_cpu == -1 || new_cpu == cpu) {
5359 /* Now try balancing at a lower domain level of cpu */
5364 /* Now try balancing at a lower domain level of new_cpu */
5366 weight = sd->span_weight;
5368 for_each_domain(cpu, tmp) {
5369 if (weight <= tmp->span_weight)
5371 if (tmp->flags & sd_flag)
5374 /* while loop will break here if sd == NULL */
5382 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5383 * cfs_rq_of(p) references at time of call are still valid and identify the
5384 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5386 static void migrate_task_rq_fair(struct task_struct *p)
5389 * As blocked tasks retain absolute vruntime the migration needs to
5390 * deal with this by subtracting the old and adding the new
5391 * min_vruntime -- the latter is done by enqueue_entity() when placing
5392 * the task on the new runqueue.
5394 if (p->state == TASK_WAKING) {
5395 struct sched_entity *se = &p->se;
5396 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5399 #ifndef CONFIG_64BIT
5400 u64 min_vruntime_copy;
5403 min_vruntime_copy = cfs_rq->min_vruntime_copy;
5405 min_vruntime = cfs_rq->min_vruntime;
5406 } while (min_vruntime != min_vruntime_copy);
5408 min_vruntime = cfs_rq->min_vruntime;
5411 se->vruntime -= min_vruntime;
5415 * We are supposed to update the task to "current" time, then its up to date
5416 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5417 * what current time is, so simply throw away the out-of-date time. This
5418 * will result in the wakee task is less decayed, but giving the wakee more
5419 * load sounds not bad.
5421 remove_entity_load_avg(&p->se);
5423 /* Tell new CPU we are migrated */
5424 p->se.avg.last_update_time = 0;
5426 /* We have migrated, no longer consider this task hot */
5427 p->se.exec_start = 0;
5430 static void task_dead_fair(struct task_struct *p)
5432 remove_entity_load_avg(&p->se);
5434 #endif /* CONFIG_SMP */
5436 static unsigned long
5437 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5439 unsigned long gran = sysctl_sched_wakeup_granularity;
5442 * Since its curr running now, convert the gran from real-time
5443 * to virtual-time in his units.
5445 * By using 'se' instead of 'curr' we penalize light tasks, so
5446 * they get preempted easier. That is, if 'se' < 'curr' then
5447 * the resulting gran will be larger, therefore penalizing the
5448 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5449 * be smaller, again penalizing the lighter task.
5451 * This is especially important for buddies when the leftmost
5452 * task is higher priority than the buddy.
5454 return calc_delta_fair(gran, se);
5458 * Should 'se' preempt 'curr'.
5472 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5474 s64 gran, vdiff = curr->vruntime - se->vruntime;
5479 gran = wakeup_gran(curr, se);
5486 static void set_last_buddy(struct sched_entity *se)
5488 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5491 for_each_sched_entity(se)
5492 cfs_rq_of(se)->last = se;
5495 static void set_next_buddy(struct sched_entity *se)
5497 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5500 for_each_sched_entity(se)
5501 cfs_rq_of(se)->next = se;
5504 static void set_skip_buddy(struct sched_entity *se)
5506 for_each_sched_entity(se)
5507 cfs_rq_of(se)->skip = se;
5511 * Preempt the current task with a newly woken task if needed:
5513 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5515 struct task_struct *curr = rq->curr;
5516 struct sched_entity *se = &curr->se, *pse = &p->se;
5517 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5518 int scale = cfs_rq->nr_running >= sched_nr_latency;
5519 int next_buddy_marked = 0;
5521 if (unlikely(se == pse))
5525 * This is possible from callers such as attach_tasks(), in which we
5526 * unconditionally check_prempt_curr() after an enqueue (which may have
5527 * lead to a throttle). This both saves work and prevents false
5528 * next-buddy nomination below.
5530 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5533 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5534 set_next_buddy(pse);
5535 next_buddy_marked = 1;
5539 * We can come here with TIF_NEED_RESCHED already set from new task
5542 * Note: this also catches the edge-case of curr being in a throttled
5543 * group (e.g. via set_curr_task), since update_curr() (in the
5544 * enqueue of curr) will have resulted in resched being set. This
5545 * prevents us from potentially nominating it as a false LAST_BUDDY
5548 if (test_tsk_need_resched(curr))
5551 /* Idle tasks are by definition preempted by non-idle tasks. */
5552 if (unlikely(curr->policy == SCHED_IDLE) &&
5553 likely(p->policy != SCHED_IDLE))
5557 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5558 * is driven by the tick):
5560 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5563 find_matching_se(&se, &pse);
5564 update_curr(cfs_rq_of(se));
5566 if (wakeup_preempt_entity(se, pse) == 1) {
5568 * Bias pick_next to pick the sched entity that is
5569 * triggering this preemption.
5571 if (!next_buddy_marked)
5572 set_next_buddy(pse);
5581 * Only set the backward buddy when the current task is still
5582 * on the rq. This can happen when a wakeup gets interleaved
5583 * with schedule on the ->pre_schedule() or idle_balance()
5584 * point, either of which can * drop the rq lock.
5586 * Also, during early boot the idle thread is in the fair class,
5587 * for obvious reasons its a bad idea to schedule back to it.
5589 if (unlikely(!se->on_rq || curr == rq->idle))
5592 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5596 static struct task_struct *
5597 pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie)
5599 struct cfs_rq *cfs_rq = &rq->cfs;
5600 struct sched_entity *se;
5601 struct task_struct *p;
5605 #ifdef CONFIG_FAIR_GROUP_SCHED
5606 if (!cfs_rq->nr_running)
5609 if (prev->sched_class != &fair_sched_class)
5613 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5614 * likely that a next task is from the same cgroup as the current.
5616 * Therefore attempt to avoid putting and setting the entire cgroup
5617 * hierarchy, only change the part that actually changes.
5621 struct sched_entity *curr = cfs_rq->curr;
5624 * Since we got here without doing put_prev_entity() we also
5625 * have to consider cfs_rq->curr. If it is still a runnable
5626 * entity, update_curr() will update its vruntime, otherwise
5627 * forget we've ever seen it.
5631 update_curr(cfs_rq);
5636 * This call to check_cfs_rq_runtime() will do the
5637 * throttle and dequeue its entity in the parent(s).
5638 * Therefore the 'simple' nr_running test will indeed
5641 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5645 se = pick_next_entity(cfs_rq, curr);
5646 cfs_rq = group_cfs_rq(se);
5652 * Since we haven't yet done put_prev_entity and if the selected task
5653 * is a different task than we started out with, try and touch the
5654 * least amount of cfs_rqs.
5657 struct sched_entity *pse = &prev->se;
5659 while (!(cfs_rq = is_same_group(se, pse))) {
5660 int se_depth = se->depth;
5661 int pse_depth = pse->depth;
5663 if (se_depth <= pse_depth) {
5664 put_prev_entity(cfs_rq_of(pse), pse);
5665 pse = parent_entity(pse);
5667 if (se_depth >= pse_depth) {
5668 set_next_entity(cfs_rq_of(se), se);
5669 se = parent_entity(se);
5673 put_prev_entity(cfs_rq, pse);
5674 set_next_entity(cfs_rq, se);
5677 if (hrtick_enabled(rq))
5678 hrtick_start_fair(rq, p);
5685 if (!cfs_rq->nr_running)
5688 put_prev_task(rq, prev);
5691 se = pick_next_entity(cfs_rq, NULL);
5692 set_next_entity(cfs_rq, se);
5693 cfs_rq = group_cfs_rq(se);
5698 if (hrtick_enabled(rq))
5699 hrtick_start_fair(rq, p);
5705 * This is OK, because current is on_cpu, which avoids it being picked
5706 * for load-balance and preemption/IRQs are still disabled avoiding
5707 * further scheduler activity on it and we're being very careful to
5708 * re-start the picking loop.
5710 lockdep_unpin_lock(&rq->lock, cookie);
5711 new_tasks = idle_balance(rq);
5712 lockdep_repin_lock(&rq->lock, cookie);
5714 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5715 * possible for any higher priority task to appear. In that case we
5716 * must re-start the pick_next_entity() loop.
5728 * Account for a descheduled task:
5730 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5732 struct sched_entity *se = &prev->se;
5733 struct cfs_rq *cfs_rq;
5735 for_each_sched_entity(se) {
5736 cfs_rq = cfs_rq_of(se);
5737 put_prev_entity(cfs_rq, se);
5742 * sched_yield() is very simple
5744 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5746 static void yield_task_fair(struct rq *rq)
5748 struct task_struct *curr = rq->curr;
5749 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5750 struct sched_entity *se = &curr->se;
5753 * Are we the only task in the tree?
5755 if (unlikely(rq->nr_running == 1))
5758 clear_buddies(cfs_rq, se);
5760 if (curr->policy != SCHED_BATCH) {
5761 update_rq_clock(rq);
5763 * Update run-time statistics of the 'current'.
5765 update_curr(cfs_rq);
5767 * Tell update_rq_clock() that we've just updated,
5768 * so we don't do microscopic update in schedule()
5769 * and double the fastpath cost.
5771 rq_clock_skip_update(rq, true);
5777 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5779 struct sched_entity *se = &p->se;
5781 /* throttled hierarchies are not runnable */
5782 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5785 /* Tell the scheduler that we'd really like pse to run next. */
5788 yield_task_fair(rq);
5794 /**************************************************
5795 * Fair scheduling class load-balancing methods.
5799 * The purpose of load-balancing is to achieve the same basic fairness the
5800 * per-cpu scheduler provides, namely provide a proportional amount of compute
5801 * time to each task. This is expressed in the following equation:
5803 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5805 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5806 * W_i,0 is defined as:
5808 * W_i,0 = \Sum_j w_i,j (2)
5810 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5811 * is derived from the nice value as per sched_prio_to_weight[].
5813 * The weight average is an exponential decay average of the instantaneous
5816 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5818 * C_i is the compute capacity of cpu i, typically it is the
5819 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5820 * can also include other factors [XXX].
5822 * To achieve this balance we define a measure of imbalance which follows
5823 * directly from (1):
5825 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5827 * We them move tasks around to minimize the imbalance. In the continuous
5828 * function space it is obvious this converges, in the discrete case we get
5829 * a few fun cases generally called infeasible weight scenarios.
5832 * - infeasible weights;
5833 * - local vs global optima in the discrete case. ]
5838 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5839 * for all i,j solution, we create a tree of cpus that follows the hardware
5840 * topology where each level pairs two lower groups (or better). This results
5841 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5842 * tree to only the first of the previous level and we decrease the frequency
5843 * of load-balance at each level inv. proportional to the number of cpus in
5849 * \Sum { --- * --- * 2^i } = O(n) (5)
5851 * `- size of each group
5852 * | | `- number of cpus doing load-balance
5854 * `- sum over all levels
5856 * Coupled with a limit on how many tasks we can migrate every balance pass,
5857 * this makes (5) the runtime complexity of the balancer.
5859 * An important property here is that each CPU is still (indirectly) connected
5860 * to every other cpu in at most O(log n) steps:
5862 * The adjacency matrix of the resulting graph is given by:
5865 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5868 * And you'll find that:
5870 * A^(log_2 n)_i,j != 0 for all i,j (7)
5872 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5873 * The task movement gives a factor of O(m), giving a convergence complexity
5876 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5881 * In order to avoid CPUs going idle while there's still work to do, new idle
5882 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5883 * tree itself instead of relying on other CPUs to bring it work.
5885 * This adds some complexity to both (5) and (8) but it reduces the total idle
5893 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5896 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5901 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5903 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5905 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5908 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5909 * rewrite all of this once again.]
5912 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5914 enum fbq_type { regular, remote, all };
5916 #define LBF_ALL_PINNED 0x01
5917 #define LBF_NEED_BREAK 0x02
5918 #define LBF_DST_PINNED 0x04
5919 #define LBF_SOME_PINNED 0x08
5922 struct sched_domain *sd;
5930 struct cpumask *dst_grpmask;
5932 enum cpu_idle_type idle;
5934 /* The set of CPUs under consideration for load-balancing */
5935 struct cpumask *cpus;
5940 unsigned int loop_break;
5941 unsigned int loop_max;
5943 enum fbq_type fbq_type;
5944 struct list_head tasks;
5948 * Is this task likely cache-hot:
5950 static int task_hot(struct task_struct *p, struct lb_env *env)
5954 lockdep_assert_held(&env->src_rq->lock);
5956 if (p->sched_class != &fair_sched_class)
5959 if (unlikely(p->policy == SCHED_IDLE))
5963 * Buddy candidates are cache hot:
5965 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5966 (&p->se == cfs_rq_of(&p->se)->next ||
5967 &p->se == cfs_rq_of(&p->se)->last))
5970 if (sysctl_sched_migration_cost == -1)
5972 if (sysctl_sched_migration_cost == 0)
5975 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5977 return delta < (s64)sysctl_sched_migration_cost;
5980 #ifdef CONFIG_NUMA_BALANCING
5982 * Returns 1, if task migration degrades locality
5983 * Returns 0, if task migration improves locality i.e migration preferred.
5984 * Returns -1, if task migration is not affected by locality.
5986 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5988 struct numa_group *numa_group = rcu_dereference(p->numa_group);
5989 unsigned long src_faults, dst_faults;
5990 int src_nid, dst_nid;
5992 if (!static_branch_likely(&sched_numa_balancing))
5995 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5998 src_nid = cpu_to_node(env->src_cpu);
5999 dst_nid = cpu_to_node(env->dst_cpu);
6001 if (src_nid == dst_nid)
6004 /* Migrating away from the preferred node is always bad. */
6005 if (src_nid == p->numa_preferred_nid) {
6006 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6012 /* Encourage migration to the preferred node. */
6013 if (dst_nid == p->numa_preferred_nid)
6017 src_faults = group_faults(p, src_nid);
6018 dst_faults = group_faults(p, dst_nid);
6020 src_faults = task_faults(p, src_nid);
6021 dst_faults = task_faults(p, dst_nid);
6024 return dst_faults < src_faults;
6028 static inline int migrate_degrades_locality(struct task_struct *p,
6036 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6039 int can_migrate_task(struct task_struct *p, struct lb_env *env)
6043 lockdep_assert_held(&env->src_rq->lock);
6046 * We do not migrate tasks that are:
6047 * 1) throttled_lb_pair, or
6048 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6049 * 3) running (obviously), or
6050 * 4) are cache-hot on their current CPU.
6052 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6055 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6058 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6060 env->flags |= LBF_SOME_PINNED;
6063 * Remember if this task can be migrated to any other cpu in
6064 * our sched_group. We may want to revisit it if we couldn't
6065 * meet load balance goals by pulling other tasks on src_cpu.
6067 * Also avoid computing new_dst_cpu if we have already computed
6068 * one in current iteration.
6070 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6073 /* Prevent to re-select dst_cpu via env's cpus */
6074 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6075 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6076 env->flags |= LBF_DST_PINNED;
6077 env->new_dst_cpu = cpu;
6085 /* Record that we found atleast one task that could run on dst_cpu */
6086 env->flags &= ~LBF_ALL_PINNED;
6088 if (task_running(env->src_rq, p)) {
6089 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6094 * Aggressive migration if:
6095 * 1) destination numa is preferred
6096 * 2) task is cache cold, or
6097 * 3) too many balance attempts have failed.
6099 tsk_cache_hot = migrate_degrades_locality(p, env);
6100 if (tsk_cache_hot == -1)
6101 tsk_cache_hot = task_hot(p, env);
6103 if (tsk_cache_hot <= 0 ||
6104 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6105 if (tsk_cache_hot == 1) {
6106 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
6107 schedstat_inc(p, se.statistics.nr_forced_migrations);
6112 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
6117 * detach_task() -- detach the task for the migration specified in env
6119 static void detach_task(struct task_struct *p, struct lb_env *env)
6121 lockdep_assert_held(&env->src_rq->lock);
6123 p->on_rq = TASK_ON_RQ_MIGRATING;
6124 deactivate_task(env->src_rq, p, 0);
6125 set_task_cpu(p, env->dst_cpu);
6129 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6130 * part of active balancing operations within "domain".
6132 * Returns a task if successful and NULL otherwise.
6134 static struct task_struct *detach_one_task(struct lb_env *env)
6136 struct task_struct *p, *n;
6138 lockdep_assert_held(&env->src_rq->lock);
6140 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
6141 if (!can_migrate_task(p, env))
6144 detach_task(p, env);
6147 * Right now, this is only the second place where
6148 * lb_gained[env->idle] is updated (other is detach_tasks)
6149 * so we can safely collect stats here rather than
6150 * inside detach_tasks().
6152 schedstat_inc(env->sd, lb_gained[env->idle]);
6158 static const unsigned int sched_nr_migrate_break = 32;
6161 * detach_tasks() -- tries to detach up to imbalance weighted load from
6162 * busiest_rq, as part of a balancing operation within domain "sd".
6164 * Returns number of detached tasks if successful and 0 otherwise.
6166 static int detach_tasks(struct lb_env *env)
6168 struct list_head *tasks = &env->src_rq->cfs_tasks;
6169 struct task_struct *p;
6173 lockdep_assert_held(&env->src_rq->lock);
6175 if (env->imbalance <= 0)
6178 while (!list_empty(tasks)) {
6180 * We don't want to steal all, otherwise we may be treated likewise,
6181 * which could at worst lead to a livelock crash.
6183 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6186 p = list_first_entry(tasks, struct task_struct, se.group_node);
6189 /* We've more or less seen every task there is, call it quits */
6190 if (env->loop > env->loop_max)
6193 /* take a breather every nr_migrate tasks */
6194 if (env->loop > env->loop_break) {
6195 env->loop_break += sched_nr_migrate_break;
6196 env->flags |= LBF_NEED_BREAK;
6200 if (!can_migrate_task(p, env))
6203 load = task_h_load(p);
6205 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6208 if ((load / 2) > env->imbalance)
6211 detach_task(p, env);
6212 list_add(&p->se.group_node, &env->tasks);
6215 env->imbalance -= load;
6217 #ifdef CONFIG_PREEMPT
6219 * NEWIDLE balancing is a source of latency, so preemptible
6220 * kernels will stop after the first task is detached to minimize
6221 * the critical section.
6223 if (env->idle == CPU_NEWLY_IDLE)
6228 * We only want to steal up to the prescribed amount of
6231 if (env->imbalance <= 0)
6236 list_move_tail(&p->se.group_node, tasks);
6240 * Right now, this is one of only two places we collect this stat
6241 * so we can safely collect detach_one_task() stats here rather
6242 * than inside detach_one_task().
6244 schedstat_add(env->sd, lb_gained[env->idle], detached);
6250 * attach_task() -- attach the task detached by detach_task() to its new rq.
6252 static void attach_task(struct rq *rq, struct task_struct *p)
6254 lockdep_assert_held(&rq->lock);
6256 BUG_ON(task_rq(p) != rq);
6257 activate_task(rq, p, 0);
6258 p->on_rq = TASK_ON_RQ_QUEUED;
6259 check_preempt_curr(rq, p, 0);
6263 * attach_one_task() -- attaches the task returned from detach_one_task() to
6266 static void attach_one_task(struct rq *rq, struct task_struct *p)
6268 raw_spin_lock(&rq->lock);
6270 raw_spin_unlock(&rq->lock);
6274 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6277 static void attach_tasks(struct lb_env *env)
6279 struct list_head *tasks = &env->tasks;
6280 struct task_struct *p;
6282 raw_spin_lock(&env->dst_rq->lock);
6284 while (!list_empty(tasks)) {
6285 p = list_first_entry(tasks, struct task_struct, se.group_node);
6286 list_del_init(&p->se.group_node);
6288 attach_task(env->dst_rq, p);
6291 raw_spin_unlock(&env->dst_rq->lock);
6294 #ifdef CONFIG_FAIR_GROUP_SCHED
6295 static void update_blocked_averages(int cpu)
6297 struct rq *rq = cpu_rq(cpu);
6298 struct cfs_rq *cfs_rq;
6299 unsigned long flags;
6301 raw_spin_lock_irqsave(&rq->lock, flags);
6302 update_rq_clock(rq);
6305 * Iterates the task_group tree in a bottom up fashion, see
6306 * list_add_leaf_cfs_rq() for details.
6308 for_each_leaf_cfs_rq(rq, cfs_rq) {
6309 /* throttled entities do not contribute to load */
6310 if (throttled_hierarchy(cfs_rq))
6313 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true))
6314 update_tg_load_avg(cfs_rq, 0);
6316 raw_spin_unlock_irqrestore(&rq->lock, flags);
6320 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6321 * This needs to be done in a top-down fashion because the load of a child
6322 * group is a fraction of its parents load.
6324 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6326 struct rq *rq = rq_of(cfs_rq);
6327 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6328 unsigned long now = jiffies;
6331 if (cfs_rq->last_h_load_update == now)
6334 cfs_rq->h_load_next = NULL;
6335 for_each_sched_entity(se) {
6336 cfs_rq = cfs_rq_of(se);
6337 cfs_rq->h_load_next = se;
6338 if (cfs_rq->last_h_load_update == now)
6343 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6344 cfs_rq->last_h_load_update = now;
6347 while ((se = cfs_rq->h_load_next) != NULL) {
6348 load = cfs_rq->h_load;
6349 load = div64_ul(load * se->avg.load_avg,
6350 cfs_rq_load_avg(cfs_rq) + 1);
6351 cfs_rq = group_cfs_rq(se);
6352 cfs_rq->h_load = load;
6353 cfs_rq->last_h_load_update = now;
6357 static unsigned long task_h_load(struct task_struct *p)
6359 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6361 update_cfs_rq_h_load(cfs_rq);
6362 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6363 cfs_rq_load_avg(cfs_rq) + 1);
6366 static inline void update_blocked_averages(int cpu)
6368 struct rq *rq = cpu_rq(cpu);
6369 struct cfs_rq *cfs_rq = &rq->cfs;
6370 unsigned long flags;
6372 raw_spin_lock_irqsave(&rq->lock, flags);
6373 update_rq_clock(rq);
6374 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true);
6375 raw_spin_unlock_irqrestore(&rq->lock, flags);
6378 static unsigned long task_h_load(struct task_struct *p)
6380 return p->se.avg.load_avg;
6384 /********** Helpers for find_busiest_group ************************/
6393 * sg_lb_stats - stats of a sched_group required for load_balancing
6395 struct sg_lb_stats {
6396 unsigned long avg_load; /*Avg load across the CPUs of the group */
6397 unsigned long group_load; /* Total load over the CPUs of the group */
6398 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6399 unsigned long load_per_task;
6400 unsigned long group_capacity;
6401 unsigned long group_util; /* Total utilization of the group */
6402 unsigned int sum_nr_running; /* Nr tasks running in the group */
6403 unsigned int idle_cpus;
6404 unsigned int group_weight;
6405 enum group_type group_type;
6406 int group_no_capacity;
6407 #ifdef CONFIG_NUMA_BALANCING
6408 unsigned int nr_numa_running;
6409 unsigned int nr_preferred_running;
6414 * sd_lb_stats - Structure to store the statistics of a sched_domain
6415 * during load balancing.
6417 struct sd_lb_stats {
6418 struct sched_group *busiest; /* Busiest group in this sd */
6419 struct sched_group *local; /* Local group in this sd */
6420 unsigned long total_load; /* Total load of all groups in sd */
6421 unsigned long total_capacity; /* Total capacity of all groups in sd */
6422 unsigned long avg_load; /* Average load across all groups in sd */
6424 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6425 struct sg_lb_stats local_stat; /* Statistics of the local group */
6428 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6431 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6432 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6433 * We must however clear busiest_stat::avg_load because
6434 * update_sd_pick_busiest() reads this before assignment.
6436 *sds = (struct sd_lb_stats){
6440 .total_capacity = 0UL,
6443 .sum_nr_running = 0,
6444 .group_type = group_other,
6450 * get_sd_load_idx - Obtain the load index for a given sched domain.
6451 * @sd: The sched_domain whose load_idx is to be obtained.
6452 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6454 * Return: The load index.
6456 static inline int get_sd_load_idx(struct sched_domain *sd,
6457 enum cpu_idle_type idle)
6463 load_idx = sd->busy_idx;
6466 case CPU_NEWLY_IDLE:
6467 load_idx = sd->newidle_idx;
6470 load_idx = sd->idle_idx;
6477 static unsigned long scale_rt_capacity(int cpu)
6479 struct rq *rq = cpu_rq(cpu);
6480 u64 total, used, age_stamp, avg;
6484 * Since we're reading these variables without serialization make sure
6485 * we read them once before doing sanity checks on them.
6487 age_stamp = READ_ONCE(rq->age_stamp);
6488 avg = READ_ONCE(rq->rt_avg);
6489 delta = __rq_clock_broken(rq) - age_stamp;
6491 if (unlikely(delta < 0))
6494 total = sched_avg_period() + delta;
6496 used = div_u64(avg, total);
6498 if (likely(used < SCHED_CAPACITY_SCALE))
6499 return SCHED_CAPACITY_SCALE - used;
6504 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6506 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6507 struct sched_group *sdg = sd->groups;
6509 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6511 capacity *= scale_rt_capacity(cpu);
6512 capacity >>= SCHED_CAPACITY_SHIFT;
6517 cpu_rq(cpu)->cpu_capacity = capacity;
6518 sdg->sgc->capacity = capacity;
6521 void update_group_capacity(struct sched_domain *sd, int cpu)
6523 struct sched_domain *child = sd->child;
6524 struct sched_group *group, *sdg = sd->groups;
6525 unsigned long capacity;
6526 unsigned long interval;
6528 interval = msecs_to_jiffies(sd->balance_interval);
6529 interval = clamp(interval, 1UL, max_load_balance_interval);
6530 sdg->sgc->next_update = jiffies + interval;
6533 update_cpu_capacity(sd, cpu);
6539 if (child->flags & SD_OVERLAP) {
6541 * SD_OVERLAP domains cannot assume that child groups
6542 * span the current group.
6545 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6546 struct sched_group_capacity *sgc;
6547 struct rq *rq = cpu_rq(cpu);
6550 * build_sched_domains() -> init_sched_groups_capacity()
6551 * gets here before we've attached the domains to the
6554 * Use capacity_of(), which is set irrespective of domains
6555 * in update_cpu_capacity().
6557 * This avoids capacity from being 0 and
6558 * causing divide-by-zero issues on boot.
6560 if (unlikely(!rq->sd)) {
6561 capacity += capacity_of(cpu);
6565 sgc = rq->sd->groups->sgc;
6566 capacity += sgc->capacity;
6570 * !SD_OVERLAP domains can assume that child groups
6571 * span the current group.
6574 group = child->groups;
6576 capacity += group->sgc->capacity;
6577 group = group->next;
6578 } while (group != child->groups);
6581 sdg->sgc->capacity = capacity;
6585 * Check whether the capacity of the rq has been noticeably reduced by side
6586 * activity. The imbalance_pct is used for the threshold.
6587 * Return true is the capacity is reduced
6590 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6592 return ((rq->cpu_capacity * sd->imbalance_pct) <
6593 (rq->cpu_capacity_orig * 100));
6597 * Group imbalance indicates (and tries to solve) the problem where balancing
6598 * groups is inadequate due to tsk_cpus_allowed() constraints.
6600 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6601 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6604 * { 0 1 2 3 } { 4 5 6 7 }
6607 * If we were to balance group-wise we'd place two tasks in the first group and
6608 * two tasks in the second group. Clearly this is undesired as it will overload
6609 * cpu 3 and leave one of the cpus in the second group unused.
6611 * The current solution to this issue is detecting the skew in the first group
6612 * by noticing the lower domain failed to reach balance and had difficulty
6613 * moving tasks due to affinity constraints.
6615 * When this is so detected; this group becomes a candidate for busiest; see
6616 * update_sd_pick_busiest(). And calculate_imbalance() and
6617 * find_busiest_group() avoid some of the usual balance conditions to allow it
6618 * to create an effective group imbalance.
6620 * This is a somewhat tricky proposition since the next run might not find the
6621 * group imbalance and decide the groups need to be balanced again. A most
6622 * subtle and fragile situation.
6625 static inline int sg_imbalanced(struct sched_group *group)
6627 return group->sgc->imbalance;
6631 * group_has_capacity returns true if the group has spare capacity that could
6632 * be used by some tasks.
6633 * We consider that a group has spare capacity if the * number of task is
6634 * smaller than the number of CPUs or if the utilization is lower than the
6635 * available capacity for CFS tasks.
6636 * For the latter, we use a threshold to stabilize the state, to take into
6637 * account the variance of the tasks' load and to return true if the available
6638 * capacity in meaningful for the load balancer.
6639 * As an example, an available capacity of 1% can appear but it doesn't make
6640 * any benefit for the load balance.
6643 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6645 if (sgs->sum_nr_running < sgs->group_weight)
6648 if ((sgs->group_capacity * 100) >
6649 (sgs->group_util * env->sd->imbalance_pct))
6656 * group_is_overloaded returns true if the group has more tasks than it can
6658 * group_is_overloaded is not equals to !group_has_capacity because a group
6659 * with the exact right number of tasks, has no more spare capacity but is not
6660 * overloaded so both group_has_capacity and group_is_overloaded return
6664 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6666 if (sgs->sum_nr_running <= sgs->group_weight)
6669 if ((sgs->group_capacity * 100) <
6670 (sgs->group_util * env->sd->imbalance_pct))
6677 group_type group_classify(struct sched_group *group,
6678 struct sg_lb_stats *sgs)
6680 if (sgs->group_no_capacity)
6681 return group_overloaded;
6683 if (sg_imbalanced(group))
6684 return group_imbalanced;
6690 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6691 * @env: The load balancing environment.
6692 * @group: sched_group whose statistics are to be updated.
6693 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6694 * @local_group: Does group contain this_cpu.
6695 * @sgs: variable to hold the statistics for this group.
6696 * @overload: Indicate more than one runnable task for any CPU.
6698 static inline void update_sg_lb_stats(struct lb_env *env,
6699 struct sched_group *group, int load_idx,
6700 int local_group, struct sg_lb_stats *sgs,
6706 memset(sgs, 0, sizeof(*sgs));
6708 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6709 struct rq *rq = cpu_rq(i);
6711 /* Bias balancing toward cpus of our domain */
6713 load = target_load(i, load_idx);
6715 load = source_load(i, load_idx);
6717 sgs->group_load += load;
6718 sgs->group_util += cpu_util(i);
6719 sgs->sum_nr_running += rq->cfs.h_nr_running;
6721 nr_running = rq->nr_running;
6725 #ifdef CONFIG_NUMA_BALANCING
6726 sgs->nr_numa_running += rq->nr_numa_running;
6727 sgs->nr_preferred_running += rq->nr_preferred_running;
6729 sgs->sum_weighted_load += weighted_cpuload(i);
6731 * No need to call idle_cpu() if nr_running is not 0
6733 if (!nr_running && idle_cpu(i))
6737 /* Adjust by relative CPU capacity of the group */
6738 sgs->group_capacity = group->sgc->capacity;
6739 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6741 if (sgs->sum_nr_running)
6742 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6744 sgs->group_weight = group->group_weight;
6746 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6747 sgs->group_type = group_classify(group, sgs);
6751 * update_sd_pick_busiest - return 1 on busiest group
6752 * @env: The load balancing environment.
6753 * @sds: sched_domain statistics
6754 * @sg: sched_group candidate to be checked for being the busiest
6755 * @sgs: sched_group statistics
6757 * Determine if @sg is a busier group than the previously selected
6760 * Return: %true if @sg is a busier group than the previously selected
6761 * busiest group. %false otherwise.
6763 static bool update_sd_pick_busiest(struct lb_env *env,
6764 struct sd_lb_stats *sds,
6765 struct sched_group *sg,
6766 struct sg_lb_stats *sgs)
6768 struct sg_lb_stats *busiest = &sds->busiest_stat;
6770 if (sgs->group_type > busiest->group_type)
6773 if (sgs->group_type < busiest->group_type)
6776 if (sgs->avg_load <= busiest->avg_load)
6779 /* This is the busiest node in its class. */
6780 if (!(env->sd->flags & SD_ASYM_PACKING))
6783 /* No ASYM_PACKING if target cpu is already busy */
6784 if (env->idle == CPU_NOT_IDLE)
6787 * ASYM_PACKING needs to move all the work to the lowest
6788 * numbered CPUs in the group, therefore mark all groups
6789 * higher than ourself as busy.
6791 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6795 /* Prefer to move from highest possible cpu's work */
6796 if (group_first_cpu(sds->busiest) < group_first_cpu(sg))
6803 #ifdef CONFIG_NUMA_BALANCING
6804 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6806 if (sgs->sum_nr_running > sgs->nr_numa_running)
6808 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6813 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6815 if (rq->nr_running > rq->nr_numa_running)
6817 if (rq->nr_running > rq->nr_preferred_running)
6822 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6827 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6831 #endif /* CONFIG_NUMA_BALANCING */
6834 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6835 * @env: The load balancing environment.
6836 * @sds: variable to hold the statistics for this sched_domain.
6838 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6840 struct sched_domain *child = env->sd->child;
6841 struct sched_group *sg = env->sd->groups;
6842 struct sg_lb_stats tmp_sgs;
6843 int load_idx, prefer_sibling = 0;
6844 bool overload = false;
6846 if (child && child->flags & SD_PREFER_SIBLING)
6849 load_idx = get_sd_load_idx(env->sd, env->idle);
6852 struct sg_lb_stats *sgs = &tmp_sgs;
6855 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6858 sgs = &sds->local_stat;
6860 if (env->idle != CPU_NEWLY_IDLE ||
6861 time_after_eq(jiffies, sg->sgc->next_update))
6862 update_group_capacity(env->sd, env->dst_cpu);
6865 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6872 * In case the child domain prefers tasks go to siblings
6873 * first, lower the sg capacity so that we'll try
6874 * and move all the excess tasks away. We lower the capacity
6875 * of a group only if the local group has the capacity to fit
6876 * these excess tasks. The extra check prevents the case where
6877 * you always pull from the heaviest group when it is already
6878 * under-utilized (possible with a large weight task outweighs
6879 * the tasks on the system).
6881 if (prefer_sibling && sds->local &&
6882 group_has_capacity(env, &sds->local_stat) &&
6883 (sgs->sum_nr_running > 1)) {
6884 sgs->group_no_capacity = 1;
6885 sgs->group_type = group_classify(sg, sgs);
6888 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6890 sds->busiest_stat = *sgs;
6894 /* Now, start updating sd_lb_stats */
6895 sds->total_load += sgs->group_load;
6896 sds->total_capacity += sgs->group_capacity;
6899 } while (sg != env->sd->groups);
6901 if (env->sd->flags & SD_NUMA)
6902 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6904 if (!env->sd->parent) {
6905 /* update overload indicator if we are at root domain */
6906 if (env->dst_rq->rd->overload != overload)
6907 env->dst_rq->rd->overload = overload;
6913 * check_asym_packing - Check to see if the group is packed into the
6916 * This is primarily intended to used at the sibling level. Some
6917 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6918 * case of POWER7, it can move to lower SMT modes only when higher
6919 * threads are idle. When in lower SMT modes, the threads will
6920 * perform better since they share less core resources. Hence when we
6921 * have idle threads, we want them to be the higher ones.
6923 * This packing function is run on idle threads. It checks to see if
6924 * the busiest CPU in this domain (core in the P7 case) has a higher
6925 * CPU number than the packing function is being run on. Here we are
6926 * assuming lower CPU number will be equivalent to lower a SMT thread
6929 * Return: 1 when packing is required and a task should be moved to
6930 * this CPU. The amount of the imbalance is returned in *imbalance.
6932 * @env: The load balancing environment.
6933 * @sds: Statistics of the sched_domain which is to be packed
6935 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6939 if (!(env->sd->flags & SD_ASYM_PACKING))
6942 if (env->idle == CPU_NOT_IDLE)
6948 busiest_cpu = group_first_cpu(sds->busiest);
6949 if (env->dst_cpu > busiest_cpu)
6952 env->imbalance = DIV_ROUND_CLOSEST(
6953 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6954 SCHED_CAPACITY_SCALE);
6960 * fix_small_imbalance - Calculate the minor imbalance that exists
6961 * amongst the groups of a sched_domain, during
6963 * @env: The load balancing environment.
6964 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6967 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6969 unsigned long tmp, capa_now = 0, capa_move = 0;
6970 unsigned int imbn = 2;
6971 unsigned long scaled_busy_load_per_task;
6972 struct sg_lb_stats *local, *busiest;
6974 local = &sds->local_stat;
6975 busiest = &sds->busiest_stat;
6977 if (!local->sum_nr_running)
6978 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6979 else if (busiest->load_per_task > local->load_per_task)
6982 scaled_busy_load_per_task =
6983 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6984 busiest->group_capacity;
6986 if (busiest->avg_load + scaled_busy_load_per_task >=
6987 local->avg_load + (scaled_busy_load_per_task * imbn)) {
6988 env->imbalance = busiest->load_per_task;
6993 * OK, we don't have enough imbalance to justify moving tasks,
6994 * however we may be able to increase total CPU capacity used by
6998 capa_now += busiest->group_capacity *
6999 min(busiest->load_per_task, busiest->avg_load);
7000 capa_now += local->group_capacity *
7001 min(local->load_per_task, local->avg_load);
7002 capa_now /= SCHED_CAPACITY_SCALE;
7004 /* Amount of load we'd subtract */
7005 if (busiest->avg_load > scaled_busy_load_per_task) {
7006 capa_move += busiest->group_capacity *
7007 min(busiest->load_per_task,
7008 busiest->avg_load - scaled_busy_load_per_task);
7011 /* Amount of load we'd add */
7012 if (busiest->avg_load * busiest->group_capacity <
7013 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7014 tmp = (busiest->avg_load * busiest->group_capacity) /
7015 local->group_capacity;
7017 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7018 local->group_capacity;
7020 capa_move += local->group_capacity *
7021 min(local->load_per_task, local->avg_load + tmp);
7022 capa_move /= SCHED_CAPACITY_SCALE;
7024 /* Move if we gain throughput */
7025 if (capa_move > capa_now)
7026 env->imbalance = busiest->load_per_task;
7030 * calculate_imbalance - Calculate the amount of imbalance present within the
7031 * groups of a given sched_domain during load balance.
7032 * @env: load balance environment
7033 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7035 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7037 unsigned long max_pull, load_above_capacity = ~0UL;
7038 struct sg_lb_stats *local, *busiest;
7040 local = &sds->local_stat;
7041 busiest = &sds->busiest_stat;
7043 if (busiest->group_type == group_imbalanced) {
7045 * In the group_imb case we cannot rely on group-wide averages
7046 * to ensure cpu-load equilibrium, look at wider averages. XXX
7048 busiest->load_per_task =
7049 min(busiest->load_per_task, sds->avg_load);
7053 * Avg load of busiest sg can be less and avg load of local sg can
7054 * be greater than avg load across all sgs of sd because avg load
7055 * factors in sg capacity and sgs with smaller group_type are
7056 * skipped when updating the busiest sg:
7058 if (busiest->avg_load <= sds->avg_load ||
7059 local->avg_load >= sds->avg_load) {
7061 return fix_small_imbalance(env, sds);
7065 * If there aren't any idle cpus, avoid creating some.
7067 if (busiest->group_type == group_overloaded &&
7068 local->group_type == group_overloaded) {
7069 load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
7070 if (load_above_capacity > busiest->group_capacity) {
7071 load_above_capacity -= busiest->group_capacity;
7072 load_above_capacity *= NICE_0_LOAD;
7073 load_above_capacity /= busiest->group_capacity;
7075 load_above_capacity = ~0UL;
7079 * We're trying to get all the cpus to the average_load, so we don't
7080 * want to push ourselves above the average load, nor do we wish to
7081 * reduce the max loaded cpu below the average load. At the same time,
7082 * we also don't want to reduce the group load below the group
7083 * capacity. Thus we look for the minimum possible imbalance.
7085 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7087 /* How much load to actually move to equalise the imbalance */
7088 env->imbalance = min(
7089 max_pull * busiest->group_capacity,
7090 (sds->avg_load - local->avg_load) * local->group_capacity
7091 ) / SCHED_CAPACITY_SCALE;
7094 * if *imbalance is less than the average load per runnable task
7095 * there is no guarantee that any tasks will be moved so we'll have
7096 * a think about bumping its value to force at least one task to be
7099 if (env->imbalance < busiest->load_per_task)
7100 return fix_small_imbalance(env, sds);
7103 /******* find_busiest_group() helpers end here *********************/
7106 * find_busiest_group - Returns the busiest group within the sched_domain
7107 * if there is an imbalance.
7109 * Also calculates the amount of weighted load which should be moved
7110 * to restore balance.
7112 * @env: The load balancing environment.
7114 * Return: - The busiest group if imbalance exists.
7116 static struct sched_group *find_busiest_group(struct lb_env *env)
7118 struct sg_lb_stats *local, *busiest;
7119 struct sd_lb_stats sds;
7121 init_sd_lb_stats(&sds);
7124 * Compute the various statistics relavent for load balancing at
7127 update_sd_lb_stats(env, &sds);
7128 local = &sds.local_stat;
7129 busiest = &sds.busiest_stat;
7131 /* ASYM feature bypasses nice load balance check */
7132 if (check_asym_packing(env, &sds))
7135 /* There is no busy sibling group to pull tasks from */
7136 if (!sds.busiest || busiest->sum_nr_running == 0)
7139 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7140 / sds.total_capacity;
7143 * If the busiest group is imbalanced the below checks don't
7144 * work because they assume all things are equal, which typically
7145 * isn't true due to cpus_allowed constraints and the like.
7147 if (busiest->group_type == group_imbalanced)
7150 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7151 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7152 busiest->group_no_capacity)
7156 * If the local group is busier than the selected busiest group
7157 * don't try and pull any tasks.
7159 if (local->avg_load >= busiest->avg_load)
7163 * Don't pull any tasks if this group is already above the domain
7166 if (local->avg_load >= sds.avg_load)
7169 if (env->idle == CPU_IDLE) {
7171 * This cpu is idle. If the busiest group is not overloaded
7172 * and there is no imbalance between this and busiest group
7173 * wrt idle cpus, it is balanced. The imbalance becomes
7174 * significant if the diff is greater than 1 otherwise we
7175 * might end up to just move the imbalance on another group
7177 if ((busiest->group_type != group_overloaded) &&
7178 (local->idle_cpus <= (busiest->idle_cpus + 1)))
7182 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7183 * imbalance_pct to be conservative.
7185 if (100 * busiest->avg_load <=
7186 env->sd->imbalance_pct * local->avg_load)
7191 /* Looks like there is an imbalance. Compute it */
7192 calculate_imbalance(env, &sds);
7201 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7203 static struct rq *find_busiest_queue(struct lb_env *env,
7204 struct sched_group *group)
7206 struct rq *busiest = NULL, *rq;
7207 unsigned long busiest_load = 0, busiest_capacity = 1;
7210 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7211 unsigned long capacity, wl;
7215 rt = fbq_classify_rq(rq);
7218 * We classify groups/runqueues into three groups:
7219 * - regular: there are !numa tasks
7220 * - remote: there are numa tasks that run on the 'wrong' node
7221 * - all: there is no distinction
7223 * In order to avoid migrating ideally placed numa tasks,
7224 * ignore those when there's better options.
7226 * If we ignore the actual busiest queue to migrate another
7227 * task, the next balance pass can still reduce the busiest
7228 * queue by moving tasks around inside the node.
7230 * If we cannot move enough load due to this classification
7231 * the next pass will adjust the group classification and
7232 * allow migration of more tasks.
7234 * Both cases only affect the total convergence complexity.
7236 if (rt > env->fbq_type)
7239 capacity = capacity_of(i);
7241 wl = weighted_cpuload(i);
7244 * When comparing with imbalance, use weighted_cpuload()
7245 * which is not scaled with the cpu capacity.
7248 if (rq->nr_running == 1 && wl > env->imbalance &&
7249 !check_cpu_capacity(rq, env->sd))
7253 * For the load comparisons with the other cpu's, consider
7254 * the weighted_cpuload() scaled with the cpu capacity, so
7255 * that the load can be moved away from the cpu that is
7256 * potentially running at a lower capacity.
7258 * Thus we're looking for max(wl_i / capacity_i), crosswise
7259 * multiplication to rid ourselves of the division works out
7260 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7261 * our previous maximum.
7263 if (wl * busiest_capacity > busiest_load * capacity) {
7265 busiest_capacity = capacity;
7274 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7275 * so long as it is large enough.
7277 #define MAX_PINNED_INTERVAL 512
7279 /* Working cpumask for load_balance and load_balance_newidle. */
7280 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7282 static int need_active_balance(struct lb_env *env)
7284 struct sched_domain *sd = env->sd;
7286 if (env->idle == CPU_NEWLY_IDLE) {
7289 * ASYM_PACKING needs to force migrate tasks from busy but
7290 * higher numbered CPUs in order to pack all tasks in the
7291 * lowest numbered CPUs.
7293 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7298 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7299 * It's worth migrating the task if the src_cpu's capacity is reduced
7300 * because of other sched_class or IRQs if more capacity stays
7301 * available on dst_cpu.
7303 if ((env->idle != CPU_NOT_IDLE) &&
7304 (env->src_rq->cfs.h_nr_running == 1)) {
7305 if ((check_cpu_capacity(env->src_rq, sd)) &&
7306 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7310 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7313 static int active_load_balance_cpu_stop(void *data);
7315 static int should_we_balance(struct lb_env *env)
7317 struct sched_group *sg = env->sd->groups;
7318 struct cpumask *sg_cpus, *sg_mask;
7319 int cpu, balance_cpu = -1;
7322 * In the newly idle case, we will allow all the cpu's
7323 * to do the newly idle load balance.
7325 if (env->idle == CPU_NEWLY_IDLE)
7328 sg_cpus = sched_group_cpus(sg);
7329 sg_mask = sched_group_mask(sg);
7330 /* Try to find first idle cpu */
7331 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7332 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7339 if (balance_cpu == -1)
7340 balance_cpu = group_balance_cpu(sg);
7343 * First idle cpu or the first cpu(busiest) in this sched group
7344 * is eligible for doing load balancing at this and above domains.
7346 return balance_cpu == env->dst_cpu;
7350 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7351 * tasks if there is an imbalance.
7353 static int load_balance(int this_cpu, struct rq *this_rq,
7354 struct sched_domain *sd, enum cpu_idle_type idle,
7355 int *continue_balancing)
7357 int ld_moved, cur_ld_moved, active_balance = 0;
7358 struct sched_domain *sd_parent = sd->parent;
7359 struct sched_group *group;
7361 unsigned long flags;
7362 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7364 struct lb_env env = {
7366 .dst_cpu = this_cpu,
7368 .dst_grpmask = sched_group_cpus(sd->groups),
7370 .loop_break = sched_nr_migrate_break,
7373 .tasks = LIST_HEAD_INIT(env.tasks),
7377 * For NEWLY_IDLE load_balancing, we don't need to consider
7378 * other cpus in our group
7380 if (idle == CPU_NEWLY_IDLE)
7381 env.dst_grpmask = NULL;
7383 cpumask_copy(cpus, cpu_active_mask);
7385 schedstat_inc(sd, lb_count[idle]);
7388 if (!should_we_balance(&env)) {
7389 *continue_balancing = 0;
7393 group = find_busiest_group(&env);
7395 schedstat_inc(sd, lb_nobusyg[idle]);
7399 busiest = find_busiest_queue(&env, group);
7401 schedstat_inc(sd, lb_nobusyq[idle]);
7405 BUG_ON(busiest == env.dst_rq);
7407 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7409 env.src_cpu = busiest->cpu;
7410 env.src_rq = busiest;
7413 if (busiest->nr_running > 1) {
7415 * Attempt to move tasks. If find_busiest_group has found
7416 * an imbalance but busiest->nr_running <= 1, the group is
7417 * still unbalanced. ld_moved simply stays zero, so it is
7418 * correctly treated as an imbalance.
7420 env.flags |= LBF_ALL_PINNED;
7421 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7424 raw_spin_lock_irqsave(&busiest->lock, flags);
7427 * cur_ld_moved - load moved in current iteration
7428 * ld_moved - cumulative load moved across iterations
7430 cur_ld_moved = detach_tasks(&env);
7433 * We've detached some tasks from busiest_rq. Every
7434 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7435 * unlock busiest->lock, and we are able to be sure
7436 * that nobody can manipulate the tasks in parallel.
7437 * See task_rq_lock() family for the details.
7440 raw_spin_unlock(&busiest->lock);
7444 ld_moved += cur_ld_moved;
7447 local_irq_restore(flags);
7449 if (env.flags & LBF_NEED_BREAK) {
7450 env.flags &= ~LBF_NEED_BREAK;
7455 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7456 * us and move them to an alternate dst_cpu in our sched_group
7457 * where they can run. The upper limit on how many times we
7458 * iterate on same src_cpu is dependent on number of cpus in our
7461 * This changes load balance semantics a bit on who can move
7462 * load to a given_cpu. In addition to the given_cpu itself
7463 * (or a ilb_cpu acting on its behalf where given_cpu is
7464 * nohz-idle), we now have balance_cpu in a position to move
7465 * load to given_cpu. In rare situations, this may cause
7466 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7467 * _independently_ and at _same_ time to move some load to
7468 * given_cpu) causing exceess load to be moved to given_cpu.
7469 * This however should not happen so much in practice and
7470 * moreover subsequent load balance cycles should correct the
7471 * excess load moved.
7473 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7475 /* Prevent to re-select dst_cpu via env's cpus */
7476 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7478 env.dst_rq = cpu_rq(env.new_dst_cpu);
7479 env.dst_cpu = env.new_dst_cpu;
7480 env.flags &= ~LBF_DST_PINNED;
7482 env.loop_break = sched_nr_migrate_break;
7485 * Go back to "more_balance" rather than "redo" since we
7486 * need to continue with same src_cpu.
7492 * We failed to reach balance because of affinity.
7495 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7497 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7498 *group_imbalance = 1;
7501 /* All tasks on this runqueue were pinned by CPU affinity */
7502 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7503 cpumask_clear_cpu(cpu_of(busiest), cpus);
7504 if (!cpumask_empty(cpus)) {
7506 env.loop_break = sched_nr_migrate_break;
7509 goto out_all_pinned;
7514 schedstat_inc(sd, lb_failed[idle]);
7516 * Increment the failure counter only on periodic balance.
7517 * We do not want newidle balance, which can be very
7518 * frequent, pollute the failure counter causing
7519 * excessive cache_hot migrations and active balances.
7521 if (idle != CPU_NEWLY_IDLE)
7522 sd->nr_balance_failed++;
7524 if (need_active_balance(&env)) {
7525 raw_spin_lock_irqsave(&busiest->lock, flags);
7527 /* don't kick the active_load_balance_cpu_stop,
7528 * if the curr task on busiest cpu can't be
7531 if (!cpumask_test_cpu(this_cpu,
7532 tsk_cpus_allowed(busiest->curr))) {
7533 raw_spin_unlock_irqrestore(&busiest->lock,
7535 env.flags |= LBF_ALL_PINNED;
7536 goto out_one_pinned;
7540 * ->active_balance synchronizes accesses to
7541 * ->active_balance_work. Once set, it's cleared
7542 * only after active load balance is finished.
7544 if (!busiest->active_balance) {
7545 busiest->active_balance = 1;
7546 busiest->push_cpu = this_cpu;
7549 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7551 if (active_balance) {
7552 stop_one_cpu_nowait(cpu_of(busiest),
7553 active_load_balance_cpu_stop, busiest,
7554 &busiest->active_balance_work);
7557 /* We've kicked active balancing, force task migration. */
7558 sd->nr_balance_failed = sd->cache_nice_tries+1;
7561 sd->nr_balance_failed = 0;
7563 if (likely(!active_balance)) {
7564 /* We were unbalanced, so reset the balancing interval */
7565 sd->balance_interval = sd->min_interval;
7568 * If we've begun active balancing, start to back off. This
7569 * case may not be covered by the all_pinned logic if there
7570 * is only 1 task on the busy runqueue (because we don't call
7573 if (sd->balance_interval < sd->max_interval)
7574 sd->balance_interval *= 2;
7581 * We reach balance although we may have faced some affinity
7582 * constraints. Clear the imbalance flag if it was set.
7585 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7587 if (*group_imbalance)
7588 *group_imbalance = 0;
7593 * We reach balance because all tasks are pinned at this level so
7594 * we can't migrate them. Let the imbalance flag set so parent level
7595 * can try to migrate them.
7597 schedstat_inc(sd, lb_balanced[idle]);
7599 sd->nr_balance_failed = 0;
7602 /* tune up the balancing interval */
7603 if (((env.flags & LBF_ALL_PINNED) &&
7604 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7605 (sd->balance_interval < sd->max_interval))
7606 sd->balance_interval *= 2;
7613 static inline unsigned long
7614 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7616 unsigned long interval = sd->balance_interval;
7619 interval *= sd->busy_factor;
7621 /* scale ms to jiffies */
7622 interval = msecs_to_jiffies(interval);
7623 interval = clamp(interval, 1UL, max_load_balance_interval);
7629 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7631 unsigned long interval, next;
7633 interval = get_sd_balance_interval(sd, cpu_busy);
7634 next = sd->last_balance + interval;
7636 if (time_after(*next_balance, next))
7637 *next_balance = next;
7641 * idle_balance is called by schedule() if this_cpu is about to become
7642 * idle. Attempts to pull tasks from other CPUs.
7644 static int idle_balance(struct rq *this_rq)
7646 unsigned long next_balance = jiffies + HZ;
7647 int this_cpu = this_rq->cpu;
7648 struct sched_domain *sd;
7649 int pulled_task = 0;
7653 * We must set idle_stamp _before_ calling idle_balance(), such that we
7654 * measure the duration of idle_balance() as idle time.
7656 this_rq->idle_stamp = rq_clock(this_rq);
7658 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7659 !this_rq->rd->overload) {
7661 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7663 update_next_balance(sd, 0, &next_balance);
7669 raw_spin_unlock(&this_rq->lock);
7671 update_blocked_averages(this_cpu);
7673 for_each_domain(this_cpu, sd) {
7674 int continue_balancing = 1;
7675 u64 t0, domain_cost;
7677 if (!(sd->flags & SD_LOAD_BALANCE))
7680 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7681 update_next_balance(sd, 0, &next_balance);
7685 if (sd->flags & SD_BALANCE_NEWIDLE) {
7686 t0 = sched_clock_cpu(this_cpu);
7688 pulled_task = load_balance(this_cpu, this_rq,
7690 &continue_balancing);
7692 domain_cost = sched_clock_cpu(this_cpu) - t0;
7693 if (domain_cost > sd->max_newidle_lb_cost)
7694 sd->max_newidle_lb_cost = domain_cost;
7696 curr_cost += domain_cost;
7699 update_next_balance(sd, 0, &next_balance);
7702 * Stop searching for tasks to pull if there are
7703 * now runnable tasks on this rq.
7705 if (pulled_task || this_rq->nr_running > 0)
7710 raw_spin_lock(&this_rq->lock);
7712 if (curr_cost > this_rq->max_idle_balance_cost)
7713 this_rq->max_idle_balance_cost = curr_cost;
7716 * While browsing the domains, we released the rq lock, a task could
7717 * have been enqueued in the meantime. Since we're not going idle,
7718 * pretend we pulled a task.
7720 if (this_rq->cfs.h_nr_running && !pulled_task)
7724 /* Move the next balance forward */
7725 if (time_after(this_rq->next_balance, next_balance))
7726 this_rq->next_balance = next_balance;
7728 /* Is there a task of a high priority class? */
7729 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7733 this_rq->idle_stamp = 0;
7739 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7740 * running tasks off the busiest CPU onto idle CPUs. It requires at
7741 * least 1 task to be running on each physical CPU where possible, and
7742 * avoids physical / logical imbalances.
7744 static int active_load_balance_cpu_stop(void *data)
7746 struct rq *busiest_rq = data;
7747 int busiest_cpu = cpu_of(busiest_rq);
7748 int target_cpu = busiest_rq->push_cpu;
7749 struct rq *target_rq = cpu_rq(target_cpu);
7750 struct sched_domain *sd;
7751 struct task_struct *p = NULL;
7753 raw_spin_lock_irq(&busiest_rq->lock);
7755 /* make sure the requested cpu hasn't gone down in the meantime */
7756 if (unlikely(busiest_cpu != smp_processor_id() ||
7757 !busiest_rq->active_balance))
7760 /* Is there any task to move? */
7761 if (busiest_rq->nr_running <= 1)
7765 * This condition is "impossible", if it occurs
7766 * we need to fix it. Originally reported by
7767 * Bjorn Helgaas on a 128-cpu setup.
7769 BUG_ON(busiest_rq == target_rq);
7771 /* Search for an sd spanning us and the target CPU. */
7773 for_each_domain(target_cpu, sd) {
7774 if ((sd->flags & SD_LOAD_BALANCE) &&
7775 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7780 struct lb_env env = {
7782 .dst_cpu = target_cpu,
7783 .dst_rq = target_rq,
7784 .src_cpu = busiest_rq->cpu,
7785 .src_rq = busiest_rq,
7789 schedstat_inc(sd, alb_count);
7791 p = detach_one_task(&env);
7793 schedstat_inc(sd, alb_pushed);
7794 /* Active balancing done, reset the failure counter. */
7795 sd->nr_balance_failed = 0;
7797 schedstat_inc(sd, alb_failed);
7802 busiest_rq->active_balance = 0;
7803 raw_spin_unlock(&busiest_rq->lock);
7806 attach_one_task(target_rq, p);
7813 static inline int on_null_domain(struct rq *rq)
7815 return unlikely(!rcu_dereference_sched(rq->sd));
7818 #ifdef CONFIG_NO_HZ_COMMON
7820 * idle load balancing details
7821 * - When one of the busy CPUs notice that there may be an idle rebalancing
7822 * needed, they will kick the idle load balancer, which then does idle
7823 * load balancing for all the idle CPUs.
7826 cpumask_var_t idle_cpus_mask;
7828 unsigned long next_balance; /* in jiffy units */
7829 } nohz ____cacheline_aligned;
7831 static inline int find_new_ilb(void)
7833 int ilb = cpumask_first(nohz.idle_cpus_mask);
7835 if (ilb < nr_cpu_ids && idle_cpu(ilb))
7842 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7843 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7844 * CPU (if there is one).
7846 static void nohz_balancer_kick(void)
7850 nohz.next_balance++;
7852 ilb_cpu = find_new_ilb();
7854 if (ilb_cpu >= nr_cpu_ids)
7857 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7860 * Use smp_send_reschedule() instead of resched_cpu().
7861 * This way we generate a sched IPI on the target cpu which
7862 * is idle. And the softirq performing nohz idle load balance
7863 * will be run before returning from the IPI.
7865 smp_send_reschedule(ilb_cpu);
7869 void nohz_balance_exit_idle(unsigned int cpu)
7871 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7873 * Completely isolated CPUs don't ever set, so we must test.
7875 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7876 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7877 atomic_dec(&nohz.nr_cpus);
7879 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7883 static inline void set_cpu_sd_state_busy(void)
7885 struct sched_domain *sd;
7886 int cpu = smp_processor_id();
7889 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7891 if (!sd || !sd->nohz_idle)
7895 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7900 void set_cpu_sd_state_idle(void)
7902 struct sched_domain *sd;
7903 int cpu = smp_processor_id();
7906 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7908 if (!sd || sd->nohz_idle)
7912 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7918 * This routine will record that the cpu is going idle with tick stopped.
7919 * This info will be used in performing idle load balancing in the future.
7921 void nohz_balance_enter_idle(int cpu)
7924 * If this cpu is going down, then nothing needs to be done.
7926 if (!cpu_active(cpu))
7929 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7933 * If we're a completely isolated CPU, we don't play.
7935 if (on_null_domain(cpu_rq(cpu)))
7938 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7939 atomic_inc(&nohz.nr_cpus);
7940 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7944 static DEFINE_SPINLOCK(balancing);
7947 * Scale the max load_balance interval with the number of CPUs in the system.
7948 * This trades load-balance latency on larger machines for less cross talk.
7950 void update_max_interval(void)
7952 max_load_balance_interval = HZ*num_online_cpus()/10;
7956 * It checks each scheduling domain to see if it is due to be balanced,
7957 * and initiates a balancing operation if so.
7959 * Balancing parameters are set up in init_sched_domains.
7961 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7963 int continue_balancing = 1;
7965 unsigned long interval;
7966 struct sched_domain *sd;
7967 /* Earliest time when we have to do rebalance again */
7968 unsigned long next_balance = jiffies + 60*HZ;
7969 int update_next_balance = 0;
7970 int need_serialize, need_decay = 0;
7973 update_blocked_averages(cpu);
7976 for_each_domain(cpu, sd) {
7978 * Decay the newidle max times here because this is a regular
7979 * visit to all the domains. Decay ~1% per second.
7981 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7982 sd->max_newidle_lb_cost =
7983 (sd->max_newidle_lb_cost * 253) / 256;
7984 sd->next_decay_max_lb_cost = jiffies + HZ;
7987 max_cost += sd->max_newidle_lb_cost;
7989 if (!(sd->flags & SD_LOAD_BALANCE))
7993 * Stop the load balance at this level. There is another
7994 * CPU in our sched group which is doing load balancing more
7997 if (!continue_balancing) {
8003 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8005 need_serialize = sd->flags & SD_SERIALIZE;
8006 if (need_serialize) {
8007 if (!spin_trylock(&balancing))
8011 if (time_after_eq(jiffies, sd->last_balance + interval)) {
8012 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8014 * The LBF_DST_PINNED logic could have changed
8015 * env->dst_cpu, so we can't know our idle
8016 * state even if we migrated tasks. Update it.
8018 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8020 sd->last_balance = jiffies;
8021 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8024 spin_unlock(&balancing);
8026 if (time_after(next_balance, sd->last_balance + interval)) {
8027 next_balance = sd->last_balance + interval;
8028 update_next_balance = 1;
8033 * Ensure the rq-wide value also decays but keep it at a
8034 * reasonable floor to avoid funnies with rq->avg_idle.
8036 rq->max_idle_balance_cost =
8037 max((u64)sysctl_sched_migration_cost, max_cost);
8042 * next_balance will be updated only when there is a need.
8043 * When the cpu is attached to null domain for ex, it will not be
8046 if (likely(update_next_balance)) {
8047 rq->next_balance = next_balance;
8049 #ifdef CONFIG_NO_HZ_COMMON
8051 * If this CPU has been elected to perform the nohz idle
8052 * balance. Other idle CPUs have already rebalanced with
8053 * nohz_idle_balance() and nohz.next_balance has been
8054 * updated accordingly. This CPU is now running the idle load
8055 * balance for itself and we need to update the
8056 * nohz.next_balance accordingly.
8058 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8059 nohz.next_balance = rq->next_balance;
8064 #ifdef CONFIG_NO_HZ_COMMON
8066 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8067 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8069 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8071 int this_cpu = this_rq->cpu;
8074 /* Earliest time when we have to do rebalance again */
8075 unsigned long next_balance = jiffies + 60*HZ;
8076 int update_next_balance = 0;
8078 if (idle != CPU_IDLE ||
8079 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8082 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8083 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8087 * If this cpu gets work to do, stop the load balancing
8088 * work being done for other cpus. Next load
8089 * balancing owner will pick it up.
8094 rq = cpu_rq(balance_cpu);
8097 * If time for next balance is due,
8100 if (time_after_eq(jiffies, rq->next_balance)) {
8101 raw_spin_lock_irq(&rq->lock);
8102 update_rq_clock(rq);
8103 cpu_load_update_idle(rq);
8104 raw_spin_unlock_irq(&rq->lock);
8105 rebalance_domains(rq, CPU_IDLE);
8108 if (time_after(next_balance, rq->next_balance)) {
8109 next_balance = rq->next_balance;
8110 update_next_balance = 1;
8115 * next_balance will be updated only when there is a need.
8116 * When the CPU is attached to null domain for ex, it will not be
8119 if (likely(update_next_balance))
8120 nohz.next_balance = next_balance;
8122 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8126 * Current heuristic for kicking the idle load balancer in the presence
8127 * of an idle cpu in the system.
8128 * - This rq has more than one task.
8129 * - This rq has at least one CFS task and the capacity of the CPU is
8130 * significantly reduced because of RT tasks or IRQs.
8131 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8132 * multiple busy cpu.
8133 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8134 * domain span are idle.
8136 static inline bool nohz_kick_needed(struct rq *rq)
8138 unsigned long now = jiffies;
8139 struct sched_domain *sd;
8140 struct sched_group_capacity *sgc;
8141 int nr_busy, cpu = rq->cpu;
8144 if (unlikely(rq->idle_balance))
8148 * We may be recently in ticked or tickless idle mode. At the first
8149 * busy tick after returning from idle, we will update the busy stats.
8151 set_cpu_sd_state_busy();
8152 nohz_balance_exit_idle(cpu);
8155 * None are in tickless mode and hence no need for NOHZ idle load
8158 if (likely(!atomic_read(&nohz.nr_cpus)))
8161 if (time_before(now, nohz.next_balance))
8164 if (rq->nr_running >= 2)
8168 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8170 sgc = sd->groups->sgc;
8171 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8180 sd = rcu_dereference(rq->sd);
8182 if ((rq->cfs.h_nr_running >= 1) &&
8183 check_cpu_capacity(rq, sd)) {
8189 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8190 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8191 sched_domain_span(sd)) < cpu)) {
8201 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8205 * run_rebalance_domains is triggered when needed from the scheduler tick.
8206 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8208 static void run_rebalance_domains(struct softirq_action *h)
8210 struct rq *this_rq = this_rq();
8211 enum cpu_idle_type idle = this_rq->idle_balance ?
8212 CPU_IDLE : CPU_NOT_IDLE;
8215 * If this cpu has a pending nohz_balance_kick, then do the
8216 * balancing on behalf of the other idle cpus whose ticks are
8217 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8218 * give the idle cpus a chance to load balance. Else we may
8219 * load balance only within the local sched_domain hierarchy
8220 * and abort nohz_idle_balance altogether if we pull some load.
8222 nohz_idle_balance(this_rq, idle);
8223 rebalance_domains(this_rq, idle);
8227 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8229 void trigger_load_balance(struct rq *rq)
8231 /* Don't need to rebalance while attached to NULL domain */
8232 if (unlikely(on_null_domain(rq)))
8235 if (time_after_eq(jiffies, rq->next_balance))
8236 raise_softirq(SCHED_SOFTIRQ);
8237 #ifdef CONFIG_NO_HZ_COMMON
8238 if (nohz_kick_needed(rq))
8239 nohz_balancer_kick();
8243 static void rq_online_fair(struct rq *rq)
8247 update_runtime_enabled(rq);
8250 static void rq_offline_fair(struct rq *rq)
8254 /* Ensure any throttled groups are reachable by pick_next_task */
8255 unthrottle_offline_cfs_rqs(rq);
8258 #endif /* CONFIG_SMP */
8261 * scheduler tick hitting a task of our scheduling class:
8263 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8265 struct cfs_rq *cfs_rq;
8266 struct sched_entity *se = &curr->se;
8268 for_each_sched_entity(se) {
8269 cfs_rq = cfs_rq_of(se);
8270 entity_tick(cfs_rq, se, queued);
8273 if (static_branch_unlikely(&sched_numa_balancing))
8274 task_tick_numa(rq, curr);
8278 * called on fork with the child task as argument from the parent's context
8279 * - child not yet on the tasklist
8280 * - preemption disabled
8282 static void task_fork_fair(struct task_struct *p)
8284 struct cfs_rq *cfs_rq;
8285 struct sched_entity *se = &p->se, *curr;
8286 int this_cpu = smp_processor_id();
8287 struct rq *rq = this_rq();
8288 unsigned long flags;
8290 raw_spin_lock_irqsave(&rq->lock, flags);
8292 update_rq_clock(rq);
8294 cfs_rq = task_cfs_rq(current);
8295 curr = cfs_rq->curr;
8298 * Not only the cpu but also the task_group of the parent might have
8299 * been changed after parent->se.parent,cfs_rq were copied to
8300 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8301 * of child point to valid ones.
8304 __set_task_cpu(p, this_cpu);
8307 update_curr(cfs_rq);
8310 se->vruntime = curr->vruntime;
8311 place_entity(cfs_rq, se, 1);
8313 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8315 * Upon rescheduling, sched_class::put_prev_task() will place
8316 * 'current' within the tree based on its new key value.
8318 swap(curr->vruntime, se->vruntime);
8322 se->vruntime -= cfs_rq->min_vruntime;
8324 raw_spin_unlock_irqrestore(&rq->lock, flags);
8328 * Priority of the task has changed. Check to see if we preempt
8332 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8334 if (!task_on_rq_queued(p))
8338 * Reschedule if we are currently running on this runqueue and
8339 * our priority decreased, or if we are not currently running on
8340 * this runqueue and our priority is higher than the current's
8342 if (rq->curr == p) {
8343 if (p->prio > oldprio)
8346 check_preempt_curr(rq, p, 0);
8349 static inline bool vruntime_normalized(struct task_struct *p)
8351 struct sched_entity *se = &p->se;
8354 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8355 * the dequeue_entity(.flags=0) will already have normalized the
8362 * When !on_rq, vruntime of the task has usually NOT been normalized.
8363 * But there are some cases where it has already been normalized:
8365 * - A forked child which is waiting for being woken up by
8366 * wake_up_new_task().
8367 * - A task which has been woken up by try_to_wake_up() and
8368 * waiting for actually being woken up by sched_ttwu_pending().
8370 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8376 static void detach_task_cfs_rq(struct task_struct *p)
8378 struct sched_entity *se = &p->se;
8379 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8381 if (!vruntime_normalized(p)) {
8383 * Fix up our vruntime so that the current sleep doesn't
8384 * cause 'unlimited' sleep bonus.
8386 place_entity(cfs_rq, se, 0);
8387 se->vruntime -= cfs_rq->min_vruntime;
8390 /* Catch up with the cfs_rq and remove our load when we leave */
8391 detach_entity_load_avg(cfs_rq, se);
8394 static void attach_task_cfs_rq(struct task_struct *p)
8396 struct sched_entity *se = &p->se;
8397 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8399 #ifdef CONFIG_FAIR_GROUP_SCHED
8401 * Since the real-depth could have been changed (only FAIR
8402 * class maintain depth value), reset depth properly.
8404 se->depth = se->parent ? se->parent->depth + 1 : 0;
8407 /* Synchronize task with its cfs_rq */
8408 attach_entity_load_avg(cfs_rq, se);
8410 if (!vruntime_normalized(p))
8411 se->vruntime += cfs_rq->min_vruntime;
8414 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8416 detach_task_cfs_rq(p);
8419 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8421 attach_task_cfs_rq(p);
8423 if (task_on_rq_queued(p)) {
8425 * We were most likely switched from sched_rt, so
8426 * kick off the schedule if running, otherwise just see
8427 * if we can still preempt the current task.
8432 check_preempt_curr(rq, p, 0);
8436 /* Account for a task changing its policy or group.
8438 * This routine is mostly called to set cfs_rq->curr field when a task
8439 * migrates between groups/classes.
8441 static void set_curr_task_fair(struct rq *rq)
8443 struct sched_entity *se = &rq->curr->se;
8445 for_each_sched_entity(se) {
8446 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8448 set_next_entity(cfs_rq, se);
8449 /* ensure bandwidth has been allocated on our new cfs_rq */
8450 account_cfs_rq_runtime(cfs_rq, 0);
8454 void init_cfs_rq(struct cfs_rq *cfs_rq)
8456 cfs_rq->tasks_timeline = RB_ROOT;
8457 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8458 #ifndef CONFIG_64BIT
8459 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8462 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8463 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8467 #ifdef CONFIG_FAIR_GROUP_SCHED
8468 static void task_move_group_fair(struct task_struct *p)
8470 detach_task_cfs_rq(p);
8471 set_task_rq(p, task_cpu(p));
8474 /* Tell se's cfs_rq has been changed -- migrated */
8475 p->se.avg.last_update_time = 0;
8477 attach_task_cfs_rq(p);
8480 void free_fair_sched_group(struct task_group *tg)
8484 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8486 for_each_possible_cpu(i) {
8488 kfree(tg->cfs_rq[i]);
8497 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8499 struct cfs_rq *cfs_rq;
8500 struct sched_entity *se;
8503 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8506 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8510 tg->shares = NICE_0_LOAD;
8512 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8514 for_each_possible_cpu(i) {
8515 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8516 GFP_KERNEL, cpu_to_node(i));
8520 se = kzalloc_node(sizeof(struct sched_entity),
8521 GFP_KERNEL, cpu_to_node(i));
8525 init_cfs_rq(cfs_rq);
8526 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8527 init_entity_runnable_average(se);
8528 post_init_entity_util_avg(se);
8539 void unregister_fair_sched_group(struct task_group *tg)
8541 unsigned long flags;
8545 for_each_possible_cpu(cpu) {
8547 remove_entity_load_avg(tg->se[cpu]);
8550 * Only empty task groups can be destroyed; so we can speculatively
8551 * check on_list without danger of it being re-added.
8553 if (!tg->cfs_rq[cpu]->on_list)
8558 raw_spin_lock_irqsave(&rq->lock, flags);
8559 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8560 raw_spin_unlock_irqrestore(&rq->lock, flags);
8564 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8565 struct sched_entity *se, int cpu,
8566 struct sched_entity *parent)
8568 struct rq *rq = cpu_rq(cpu);
8572 init_cfs_rq_runtime(cfs_rq);
8574 tg->cfs_rq[cpu] = cfs_rq;
8577 /* se could be NULL for root_task_group */
8582 se->cfs_rq = &rq->cfs;
8585 se->cfs_rq = parent->my_q;
8586 se->depth = parent->depth + 1;
8590 /* guarantee group entities always have weight */
8591 update_load_set(&se->load, NICE_0_LOAD);
8592 se->parent = parent;
8595 static DEFINE_MUTEX(shares_mutex);
8597 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8600 unsigned long flags;
8603 * We can't change the weight of the root cgroup.
8608 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8610 mutex_lock(&shares_mutex);
8611 if (tg->shares == shares)
8614 tg->shares = shares;
8615 for_each_possible_cpu(i) {
8616 struct rq *rq = cpu_rq(i);
8617 struct sched_entity *se;
8620 /* Propagate contribution to hierarchy */
8621 raw_spin_lock_irqsave(&rq->lock, flags);
8623 /* Possible calls to update_curr() need rq clock */
8624 update_rq_clock(rq);
8625 for_each_sched_entity(se)
8626 update_cfs_shares(group_cfs_rq(se));
8627 raw_spin_unlock_irqrestore(&rq->lock, flags);
8631 mutex_unlock(&shares_mutex);
8634 #else /* CONFIG_FAIR_GROUP_SCHED */
8636 void free_fair_sched_group(struct task_group *tg) { }
8638 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8643 void unregister_fair_sched_group(struct task_group *tg) { }
8645 #endif /* CONFIG_FAIR_GROUP_SCHED */
8648 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8650 struct sched_entity *se = &task->se;
8651 unsigned int rr_interval = 0;
8654 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8657 if (rq->cfs.load.weight)
8658 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8664 * All the scheduling class methods:
8666 const struct sched_class fair_sched_class = {
8667 .next = &idle_sched_class,
8668 .enqueue_task = enqueue_task_fair,
8669 .dequeue_task = dequeue_task_fair,
8670 .yield_task = yield_task_fair,
8671 .yield_to_task = yield_to_task_fair,
8673 .check_preempt_curr = check_preempt_wakeup,
8675 .pick_next_task = pick_next_task_fair,
8676 .put_prev_task = put_prev_task_fair,
8679 .select_task_rq = select_task_rq_fair,
8680 .migrate_task_rq = migrate_task_rq_fair,
8682 .rq_online = rq_online_fair,
8683 .rq_offline = rq_offline_fair,
8685 .task_dead = task_dead_fair,
8686 .set_cpus_allowed = set_cpus_allowed_common,
8689 .set_curr_task = set_curr_task_fair,
8690 .task_tick = task_tick_fair,
8691 .task_fork = task_fork_fair,
8693 .prio_changed = prio_changed_fair,
8694 .switched_from = switched_from_fair,
8695 .switched_to = switched_to_fair,
8697 .get_rr_interval = get_rr_interval_fair,
8699 .update_curr = update_curr_fair,
8701 #ifdef CONFIG_FAIR_GROUP_SCHED
8702 .task_move_group = task_move_group_fair,
8706 #ifdef CONFIG_SCHED_DEBUG
8707 void print_cfs_stats(struct seq_file *m, int cpu)
8709 struct cfs_rq *cfs_rq;
8712 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8713 print_cfs_rq(m, cpu, cfs_rq);
8717 #ifdef CONFIG_NUMA_BALANCING
8718 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8721 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8723 for_each_online_node(node) {
8724 if (p->numa_faults) {
8725 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8726 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8728 if (p->numa_group) {
8729 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8730 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8732 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8735 #endif /* CONFIG_NUMA_BALANCING */
8736 #endif /* CONFIG_SCHED_DEBUG */
8738 __init void init_sched_fair_class(void)
8741 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
8743 #ifdef CONFIG_NO_HZ_COMMON
8744 nohz.next_balance = jiffies;
8745 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);