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 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;
685 sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
686 sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
687 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
690 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
691 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
693 void init_entity_runnable_average(struct sched_entity *se)
699 * Update the current task's runtime statistics.
701 static void update_curr(struct cfs_rq *cfs_rq)
703 struct sched_entity *curr = cfs_rq->curr;
704 u64 now = rq_clock_task(rq_of(cfs_rq));
710 delta_exec = now - curr->exec_start;
711 if (unlikely((s64)delta_exec <= 0))
714 curr->exec_start = now;
716 schedstat_set(curr->statistics.exec_max,
717 max(delta_exec, curr->statistics.exec_max));
719 curr->sum_exec_runtime += delta_exec;
720 schedstat_add(cfs_rq, exec_clock, delta_exec);
722 curr->vruntime += calc_delta_fair(delta_exec, curr);
723 update_min_vruntime(cfs_rq);
725 if (entity_is_task(curr)) {
726 struct task_struct *curtask = task_of(curr);
728 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
729 cpuacct_charge(curtask, delta_exec);
730 account_group_exec_runtime(curtask, delta_exec);
733 account_cfs_rq_runtime(cfs_rq, delta_exec);
736 static void update_curr_fair(struct rq *rq)
738 update_curr(cfs_rq_of(&rq->curr->se));
741 #ifdef CONFIG_SCHEDSTATS
743 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
745 u64 wait_start = rq_clock(rq_of(cfs_rq));
747 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
748 likely(wait_start > se->statistics.wait_start))
749 wait_start -= se->statistics.wait_start;
751 se->statistics.wait_start = wait_start;
755 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
757 struct task_struct *p;
760 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;
762 if (entity_is_task(se)) {
764 if (task_on_rq_migrating(p)) {
766 * Preserve migrating task's wait time so wait_start
767 * time stamp can be adjusted to accumulate wait time
768 * prior to migration.
770 se->statistics.wait_start = delta;
773 trace_sched_stat_wait(p, delta);
776 se->statistics.wait_max = max(se->statistics.wait_max, delta);
777 se->statistics.wait_count++;
778 se->statistics.wait_sum += delta;
779 se->statistics.wait_start = 0;
783 * Task is being enqueued - update stats:
786 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
789 * Are we enqueueing a waiting task? (for current tasks
790 * a dequeue/enqueue event is a NOP)
792 if (se != cfs_rq->curr)
793 update_stats_wait_start(cfs_rq, se);
797 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
800 * Mark the end of the wait period if dequeueing a
803 if (se != cfs_rq->curr)
804 update_stats_wait_end(cfs_rq, se);
806 if (flags & DEQUEUE_SLEEP) {
807 if (entity_is_task(se)) {
808 struct task_struct *tsk = task_of(se);
810 if (tsk->state & TASK_INTERRUPTIBLE)
811 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
812 if (tsk->state & TASK_UNINTERRUPTIBLE)
813 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
820 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
825 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
830 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
835 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
841 * We are picking a new current task - update its stats:
844 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
847 * We are starting a new run period:
849 se->exec_start = rq_clock_task(rq_of(cfs_rq));
852 /**************************************************
853 * Scheduling class queueing methods:
856 #ifdef CONFIG_NUMA_BALANCING
858 * Approximate time to scan a full NUMA task in ms. The task scan period is
859 * calculated based on the tasks virtual memory size and
860 * numa_balancing_scan_size.
862 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
863 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
865 /* Portion of address space to scan in MB */
866 unsigned int sysctl_numa_balancing_scan_size = 256;
868 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
869 unsigned int sysctl_numa_balancing_scan_delay = 1000;
871 static unsigned int task_nr_scan_windows(struct task_struct *p)
873 unsigned long rss = 0;
874 unsigned long nr_scan_pages;
877 * Calculations based on RSS as non-present and empty pages are skipped
878 * by the PTE scanner and NUMA hinting faults should be trapped based
881 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
882 rss = get_mm_rss(p->mm);
886 rss = round_up(rss, nr_scan_pages);
887 return rss / nr_scan_pages;
890 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
891 #define MAX_SCAN_WINDOW 2560
893 static unsigned int task_scan_min(struct task_struct *p)
895 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
896 unsigned int scan, floor;
897 unsigned int windows = 1;
899 if (scan_size < MAX_SCAN_WINDOW)
900 windows = MAX_SCAN_WINDOW / scan_size;
901 floor = 1000 / windows;
903 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
904 return max_t(unsigned int, floor, scan);
907 static unsigned int task_scan_max(struct task_struct *p)
909 unsigned int smin = task_scan_min(p);
912 /* Watch for min being lower than max due to floor calculations */
913 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
914 return max(smin, smax);
917 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
919 rq->nr_numa_running += (p->numa_preferred_nid != -1);
920 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
923 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
925 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
926 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
932 spinlock_t lock; /* nr_tasks, tasks */
938 unsigned long total_faults;
939 unsigned long max_faults_cpu;
941 * Faults_cpu is used to decide whether memory should move
942 * towards the CPU. As a consequence, these stats are weighted
943 * more by CPU use than by memory faults.
945 unsigned long *faults_cpu;
946 unsigned long faults[0];
949 /* Shared or private faults. */
950 #define NR_NUMA_HINT_FAULT_TYPES 2
952 /* Memory and CPU locality */
953 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
955 /* Averaged statistics, and temporary buffers. */
956 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
958 pid_t task_numa_group_id(struct task_struct *p)
960 return p->numa_group ? p->numa_group->gid : 0;
964 * The averaged statistics, shared & private, memory & cpu,
965 * occupy the first half of the array. The second half of the
966 * array is for current counters, which are averaged into the
967 * first set by task_numa_placement.
969 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
971 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
974 static inline unsigned long task_faults(struct task_struct *p, int nid)
979 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
980 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
983 static inline unsigned long group_faults(struct task_struct *p, int nid)
988 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
989 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
992 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
994 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
995 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
999 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1000 * considered part of a numa group's pseudo-interleaving set. Migrations
1001 * between these nodes are slowed down, to allow things to settle down.
1003 #define ACTIVE_NODE_FRACTION 3
1005 static bool numa_is_active_node(int nid, struct numa_group *ng)
1007 return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
1010 /* Handle placement on systems where not all nodes are directly connected. */
1011 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
1012 int maxdist, bool task)
1014 unsigned long score = 0;
1018 * All nodes are directly connected, and the same distance
1019 * from each other. No need for fancy placement algorithms.
1021 if (sched_numa_topology_type == NUMA_DIRECT)
1025 * This code is called for each node, introducing N^2 complexity,
1026 * which should be ok given the number of nodes rarely exceeds 8.
1028 for_each_online_node(node) {
1029 unsigned long faults;
1030 int dist = node_distance(nid, node);
1033 * The furthest away nodes in the system are not interesting
1034 * for placement; nid was already counted.
1036 if (dist == sched_max_numa_distance || node == nid)
1040 * On systems with a backplane NUMA topology, compare groups
1041 * of nodes, and move tasks towards the group with the most
1042 * memory accesses. When comparing two nodes at distance
1043 * "hoplimit", only nodes closer by than "hoplimit" are part
1044 * of each group. Skip other nodes.
1046 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1050 /* Add up the faults from nearby nodes. */
1052 faults = task_faults(p, node);
1054 faults = group_faults(p, node);
1057 * On systems with a glueless mesh NUMA topology, there are
1058 * no fixed "groups of nodes". Instead, nodes that are not
1059 * directly connected bounce traffic through intermediate
1060 * nodes; a numa_group can occupy any set of nodes.
1061 * The further away a node is, the less the faults count.
1062 * This seems to result in good task placement.
1064 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1065 faults *= (sched_max_numa_distance - dist);
1066 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1076 * These return the fraction of accesses done by a particular task, or
1077 * task group, on a particular numa node. The group weight is given a
1078 * larger multiplier, in order to group tasks together that are almost
1079 * evenly spread out between numa nodes.
1081 static inline unsigned long task_weight(struct task_struct *p, int nid,
1084 unsigned long faults, total_faults;
1086 if (!p->numa_faults)
1089 total_faults = p->total_numa_faults;
1094 faults = task_faults(p, nid);
1095 faults += score_nearby_nodes(p, nid, dist, true);
1097 return 1000 * faults / total_faults;
1100 static inline unsigned long group_weight(struct task_struct *p, int nid,
1103 unsigned long faults, total_faults;
1108 total_faults = p->numa_group->total_faults;
1113 faults = group_faults(p, nid);
1114 faults += score_nearby_nodes(p, nid, dist, false);
1116 return 1000 * faults / total_faults;
1119 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1120 int src_nid, int dst_cpu)
1122 struct numa_group *ng = p->numa_group;
1123 int dst_nid = cpu_to_node(dst_cpu);
1124 int last_cpupid, this_cpupid;
1126 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1129 * Multi-stage node selection is used in conjunction with a periodic
1130 * migration fault to build a temporal task<->page relation. By using
1131 * a two-stage filter we remove short/unlikely relations.
1133 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1134 * a task's usage of a particular page (n_p) per total usage of this
1135 * page (n_t) (in a given time-span) to a probability.
1137 * Our periodic faults will sample this probability and getting the
1138 * same result twice in a row, given these samples are fully
1139 * independent, is then given by P(n)^2, provided our sample period
1140 * is sufficiently short compared to the usage pattern.
1142 * This quadric squishes small probabilities, making it less likely we
1143 * act on an unlikely task<->page relation.
1145 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1146 if (!cpupid_pid_unset(last_cpupid) &&
1147 cpupid_to_nid(last_cpupid) != dst_nid)
1150 /* Always allow migrate on private faults */
1151 if (cpupid_match_pid(p, last_cpupid))
1154 /* A shared fault, but p->numa_group has not been set up yet. */
1159 * Destination node is much more heavily used than the source
1160 * node? Allow migration.
1162 if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
1163 ACTIVE_NODE_FRACTION)
1167 * Distribute memory according to CPU & memory use on each node,
1168 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1170 * faults_cpu(dst) 3 faults_cpu(src)
1171 * --------------- * - > ---------------
1172 * faults_mem(dst) 4 faults_mem(src)
1174 return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
1175 group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1178 static unsigned long weighted_cpuload(const int cpu);
1179 static unsigned long source_load(int cpu, int type);
1180 static unsigned long target_load(int cpu, int type);
1181 static unsigned long capacity_of(int cpu);
1182 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1184 /* Cached statistics for all CPUs within a node */
1186 unsigned long nr_running;
1189 /* Total compute capacity of CPUs on a node */
1190 unsigned long compute_capacity;
1192 /* Approximate capacity in terms of runnable tasks on a node */
1193 unsigned long task_capacity;
1194 int has_free_capacity;
1198 * XXX borrowed from update_sg_lb_stats
1200 static void update_numa_stats(struct numa_stats *ns, int nid)
1202 int smt, cpu, cpus = 0;
1203 unsigned long capacity;
1205 memset(ns, 0, sizeof(*ns));
1206 for_each_cpu(cpu, cpumask_of_node(nid)) {
1207 struct rq *rq = cpu_rq(cpu);
1209 ns->nr_running += rq->nr_running;
1210 ns->load += weighted_cpuload(cpu);
1211 ns->compute_capacity += capacity_of(cpu);
1217 * If we raced with hotplug and there are no CPUs left in our mask
1218 * the @ns structure is NULL'ed and task_numa_compare() will
1219 * not find this node attractive.
1221 * We'll either bail at !has_free_capacity, or we'll detect a huge
1222 * imbalance and bail there.
1227 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1228 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1229 capacity = cpus / smt; /* cores */
1231 ns->task_capacity = min_t(unsigned, capacity,
1232 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1233 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1236 struct task_numa_env {
1237 struct task_struct *p;
1239 int src_cpu, src_nid;
1240 int dst_cpu, dst_nid;
1242 struct numa_stats src_stats, dst_stats;
1247 struct task_struct *best_task;
1252 static void task_numa_assign(struct task_numa_env *env,
1253 struct task_struct *p, long imp)
1256 put_task_struct(env->best_task);
1259 env->best_imp = imp;
1260 env->best_cpu = env->dst_cpu;
1263 static bool load_too_imbalanced(long src_load, long dst_load,
1264 struct task_numa_env *env)
1267 long orig_src_load, orig_dst_load;
1268 long src_capacity, dst_capacity;
1271 * The load is corrected for the CPU capacity available on each node.
1274 * ------------ vs ---------
1275 * src_capacity dst_capacity
1277 src_capacity = env->src_stats.compute_capacity;
1278 dst_capacity = env->dst_stats.compute_capacity;
1280 /* We care about the slope of the imbalance, not the direction. */
1281 if (dst_load < src_load)
1282 swap(dst_load, src_load);
1284 /* Is the difference below the threshold? */
1285 imb = dst_load * src_capacity * 100 -
1286 src_load * dst_capacity * env->imbalance_pct;
1291 * The imbalance is above the allowed threshold.
1292 * Compare it with the old imbalance.
1294 orig_src_load = env->src_stats.load;
1295 orig_dst_load = env->dst_stats.load;
1297 if (orig_dst_load < orig_src_load)
1298 swap(orig_dst_load, orig_src_load);
1300 old_imb = orig_dst_load * src_capacity * 100 -
1301 orig_src_load * dst_capacity * env->imbalance_pct;
1303 /* Would this change make things worse? */
1304 return (imb > old_imb);
1308 * This checks if the overall compute and NUMA accesses of the system would
1309 * be improved if the source tasks was migrated to the target dst_cpu taking
1310 * into account that it might be best if task running on the dst_cpu should
1311 * be exchanged with the source task
1313 static void task_numa_compare(struct task_numa_env *env,
1314 long taskimp, long groupimp)
1316 struct rq *src_rq = cpu_rq(env->src_cpu);
1317 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1318 struct task_struct *cur;
1319 long src_load, dst_load;
1321 long imp = env->p->numa_group ? groupimp : taskimp;
1323 int dist = env->dist;
1324 bool assigned = false;
1328 raw_spin_lock_irq(&dst_rq->lock);
1331 * No need to move the exiting task or idle task.
1333 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1337 * The task_struct must be protected here to protect the
1338 * p->numa_faults access in the task_weight since the
1339 * numa_faults could already be freed in the following path:
1340 * finish_task_switch()
1341 * --> put_task_struct()
1342 * --> __put_task_struct()
1343 * --> task_numa_free()
1345 get_task_struct(cur);
1348 raw_spin_unlock_irq(&dst_rq->lock);
1351 * Because we have preemption enabled we can get migrated around and
1352 * end try selecting ourselves (current == env->p) as a swap candidate.
1358 * "imp" is the fault differential for the source task between the
1359 * source and destination node. Calculate the total differential for
1360 * the source task and potential destination task. The more negative
1361 * the value is, the more rmeote accesses that would be expected to
1362 * be incurred if the tasks were swapped.
1365 /* Skip this swap candidate if cannot move to the source cpu */
1366 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1370 * If dst and source tasks are in the same NUMA group, or not
1371 * in any group then look only at task weights.
1373 if (cur->numa_group == env->p->numa_group) {
1374 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1375 task_weight(cur, env->dst_nid, dist);
1377 * Add some hysteresis to prevent swapping the
1378 * tasks within a group over tiny differences.
1380 if (cur->numa_group)
1384 * Compare the group weights. If a task is all by
1385 * itself (not part of a group), use the task weight
1388 if (cur->numa_group)
1389 imp += group_weight(cur, env->src_nid, dist) -
1390 group_weight(cur, env->dst_nid, dist);
1392 imp += task_weight(cur, env->src_nid, dist) -
1393 task_weight(cur, env->dst_nid, dist);
1397 if (imp <= env->best_imp && moveimp <= env->best_imp)
1401 /* Is there capacity at our destination? */
1402 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1403 !env->dst_stats.has_free_capacity)
1409 /* Balance doesn't matter much if we're running a task per cpu */
1410 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1411 dst_rq->nr_running == 1)
1415 * In the overloaded case, try and keep the load balanced.
1418 load = task_h_load(env->p);
1419 dst_load = env->dst_stats.load + load;
1420 src_load = env->src_stats.load - load;
1422 if (moveimp > imp && moveimp > env->best_imp) {
1424 * If the improvement from just moving env->p direction is
1425 * better than swapping tasks around, check if a move is
1426 * possible. Store a slightly smaller score than moveimp,
1427 * so an actually idle CPU will win.
1429 if (!load_too_imbalanced(src_load, dst_load, env)) {
1431 put_task_struct(cur);
1437 if (imp <= env->best_imp)
1441 load = task_h_load(cur);
1446 if (load_too_imbalanced(src_load, dst_load, env))
1450 * One idle CPU per node is evaluated for a task numa move.
1451 * Call select_idle_sibling to maybe find a better one.
1454 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1458 task_numa_assign(env, cur, imp);
1462 * The dst_rq->curr isn't assigned. The protection for task_struct is
1465 if (cur && !assigned)
1466 put_task_struct(cur);
1469 static void task_numa_find_cpu(struct task_numa_env *env,
1470 long taskimp, long groupimp)
1474 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1475 /* Skip this CPU if the source task cannot migrate */
1476 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1480 task_numa_compare(env, taskimp, groupimp);
1484 /* Only move tasks to a NUMA node less busy than the current node. */
1485 static bool numa_has_capacity(struct task_numa_env *env)
1487 struct numa_stats *src = &env->src_stats;
1488 struct numa_stats *dst = &env->dst_stats;
1490 if (src->has_free_capacity && !dst->has_free_capacity)
1494 * Only consider a task move if the source has a higher load
1495 * than the destination, corrected for CPU capacity on each node.
1497 * src->load dst->load
1498 * --------------------- vs ---------------------
1499 * src->compute_capacity dst->compute_capacity
1501 if (src->load * dst->compute_capacity * env->imbalance_pct >
1503 dst->load * src->compute_capacity * 100)
1509 static int task_numa_migrate(struct task_struct *p)
1511 struct task_numa_env env = {
1514 .src_cpu = task_cpu(p),
1515 .src_nid = task_node(p),
1517 .imbalance_pct = 112,
1523 struct sched_domain *sd;
1524 unsigned long taskweight, groupweight;
1526 long taskimp, groupimp;
1529 * Pick the lowest SD_NUMA domain, as that would have the smallest
1530 * imbalance and would be the first to start moving tasks about.
1532 * And we want to avoid any moving of tasks about, as that would create
1533 * random movement of tasks -- counter the numa conditions we're trying
1537 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1539 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1543 * Cpusets can break the scheduler domain tree into smaller
1544 * balance domains, some of which do not cross NUMA boundaries.
1545 * Tasks that are "trapped" in such domains cannot be migrated
1546 * elsewhere, so there is no point in (re)trying.
1548 if (unlikely(!sd)) {
1549 p->numa_preferred_nid = task_node(p);
1553 env.dst_nid = p->numa_preferred_nid;
1554 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1555 taskweight = task_weight(p, env.src_nid, dist);
1556 groupweight = group_weight(p, env.src_nid, dist);
1557 update_numa_stats(&env.src_stats, env.src_nid);
1558 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1559 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1560 update_numa_stats(&env.dst_stats, env.dst_nid);
1562 /* Try to find a spot on the preferred nid. */
1563 if (numa_has_capacity(&env))
1564 task_numa_find_cpu(&env, taskimp, groupimp);
1567 * Look at other nodes in these cases:
1568 * - there is no space available on the preferred_nid
1569 * - the task is part of a numa_group that is interleaved across
1570 * multiple NUMA nodes; in order to better consolidate the group,
1571 * we need to check other locations.
1573 if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1574 for_each_online_node(nid) {
1575 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1578 dist = node_distance(env.src_nid, env.dst_nid);
1579 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1581 taskweight = task_weight(p, env.src_nid, dist);
1582 groupweight = group_weight(p, env.src_nid, dist);
1585 /* Only consider nodes where both task and groups benefit */
1586 taskimp = task_weight(p, nid, dist) - taskweight;
1587 groupimp = group_weight(p, nid, dist) - groupweight;
1588 if (taskimp < 0 && groupimp < 0)
1593 update_numa_stats(&env.dst_stats, env.dst_nid);
1594 if (numa_has_capacity(&env))
1595 task_numa_find_cpu(&env, taskimp, groupimp);
1600 * If the task is part of a workload that spans multiple NUMA nodes,
1601 * and is migrating into one of the workload's active nodes, remember
1602 * this node as the task's preferred numa node, so the workload can
1604 * A task that migrated to a second choice node will be better off
1605 * trying for a better one later. Do not set the preferred node here.
1607 if (p->numa_group) {
1608 struct numa_group *ng = p->numa_group;
1610 if (env.best_cpu == -1)
1615 if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1616 sched_setnuma(p, env.dst_nid);
1619 /* No better CPU than the current one was found. */
1620 if (env.best_cpu == -1)
1624 * Reset the scan period if the task is being rescheduled on an
1625 * alternative node to recheck if the tasks is now properly placed.
1627 p->numa_scan_period = task_scan_min(p);
1629 if (env.best_task == NULL) {
1630 ret = migrate_task_to(p, env.best_cpu);
1632 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1636 ret = migrate_swap(p, env.best_task);
1638 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1639 put_task_struct(env.best_task);
1643 /* Attempt to migrate a task to a CPU on the preferred node. */
1644 static void numa_migrate_preferred(struct task_struct *p)
1646 unsigned long interval = HZ;
1648 /* This task has no NUMA fault statistics yet */
1649 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1652 /* Periodically retry migrating the task to the preferred node */
1653 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1654 p->numa_migrate_retry = jiffies + interval;
1656 /* Success if task is already running on preferred CPU */
1657 if (task_node(p) == p->numa_preferred_nid)
1660 /* Otherwise, try migrate to a CPU on the preferred node */
1661 task_numa_migrate(p);
1665 * Find out how many nodes on the workload is actively running on. Do this by
1666 * tracking the nodes from which NUMA hinting faults are triggered. This can
1667 * be different from the set of nodes where the workload's memory is currently
1670 static void numa_group_count_active_nodes(struct numa_group *numa_group)
1672 unsigned long faults, max_faults = 0;
1673 int nid, active_nodes = 0;
1675 for_each_online_node(nid) {
1676 faults = group_faults_cpu(numa_group, nid);
1677 if (faults > max_faults)
1678 max_faults = faults;
1681 for_each_online_node(nid) {
1682 faults = group_faults_cpu(numa_group, nid);
1683 if (faults * ACTIVE_NODE_FRACTION > max_faults)
1687 numa_group->max_faults_cpu = max_faults;
1688 numa_group->active_nodes = active_nodes;
1692 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1693 * increments. The more local the fault statistics are, the higher the scan
1694 * period will be for the next scan window. If local/(local+remote) ratio is
1695 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1696 * the scan period will decrease. Aim for 70% local accesses.
1698 #define NUMA_PERIOD_SLOTS 10
1699 #define NUMA_PERIOD_THRESHOLD 7
1702 * Increase the scan period (slow down scanning) if the majority of
1703 * our memory is already on our local node, or if the majority of
1704 * the page accesses are shared with other processes.
1705 * Otherwise, decrease the scan period.
1707 static void update_task_scan_period(struct task_struct *p,
1708 unsigned long shared, unsigned long private)
1710 unsigned int period_slot;
1714 unsigned long remote = p->numa_faults_locality[0];
1715 unsigned long local = p->numa_faults_locality[1];
1718 * If there were no record hinting faults then either the task is
1719 * completely idle or all activity is areas that are not of interest
1720 * to automatic numa balancing. Related to that, if there were failed
1721 * migration then it implies we are migrating too quickly or the local
1722 * node is overloaded. In either case, scan slower
1724 if (local + shared == 0 || p->numa_faults_locality[2]) {
1725 p->numa_scan_period = min(p->numa_scan_period_max,
1726 p->numa_scan_period << 1);
1728 p->mm->numa_next_scan = jiffies +
1729 msecs_to_jiffies(p->numa_scan_period);
1735 * Prepare to scale scan period relative to the current period.
1736 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1737 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1738 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1740 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1741 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1742 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1743 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1746 diff = slot * period_slot;
1748 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1751 * Scale scan rate increases based on sharing. There is an
1752 * inverse relationship between the degree of sharing and
1753 * the adjustment made to the scanning period. Broadly
1754 * speaking the intent is that there is little point
1755 * scanning faster if shared accesses dominate as it may
1756 * simply bounce migrations uselessly
1758 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1759 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1762 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1763 task_scan_min(p), task_scan_max(p));
1764 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1768 * Get the fraction of time the task has been running since the last
1769 * NUMA placement cycle. The scheduler keeps similar statistics, but
1770 * decays those on a 32ms period, which is orders of magnitude off
1771 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1772 * stats only if the task is so new there are no NUMA statistics yet.
1774 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1776 u64 runtime, delta, now;
1777 /* Use the start of this time slice to avoid calculations. */
1778 now = p->se.exec_start;
1779 runtime = p->se.sum_exec_runtime;
1781 if (p->last_task_numa_placement) {
1782 delta = runtime - p->last_sum_exec_runtime;
1783 *period = now - p->last_task_numa_placement;
1785 delta = p->se.avg.load_sum / p->se.load.weight;
1786 *period = LOAD_AVG_MAX;
1789 p->last_sum_exec_runtime = runtime;
1790 p->last_task_numa_placement = now;
1796 * Determine the preferred nid for a task in a numa_group. This needs to
1797 * be done in a way that produces consistent results with group_weight,
1798 * otherwise workloads might not converge.
1800 static int preferred_group_nid(struct task_struct *p, int nid)
1805 /* Direct connections between all NUMA nodes. */
1806 if (sched_numa_topology_type == NUMA_DIRECT)
1810 * On a system with glueless mesh NUMA topology, group_weight
1811 * scores nodes according to the number of NUMA hinting faults on
1812 * both the node itself, and on nearby nodes.
1814 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1815 unsigned long score, max_score = 0;
1816 int node, max_node = nid;
1818 dist = sched_max_numa_distance;
1820 for_each_online_node(node) {
1821 score = group_weight(p, node, dist);
1822 if (score > max_score) {
1831 * Finding the preferred nid in a system with NUMA backplane
1832 * interconnect topology is more involved. The goal is to locate
1833 * tasks from numa_groups near each other in the system, and
1834 * untangle workloads from different sides of the system. This requires
1835 * searching down the hierarchy of node groups, recursively searching
1836 * inside the highest scoring group of nodes. The nodemask tricks
1837 * keep the complexity of the search down.
1839 nodes = node_online_map;
1840 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1841 unsigned long max_faults = 0;
1842 nodemask_t max_group = NODE_MASK_NONE;
1845 /* Are there nodes at this distance from each other? */
1846 if (!find_numa_distance(dist))
1849 for_each_node_mask(a, nodes) {
1850 unsigned long faults = 0;
1851 nodemask_t this_group;
1852 nodes_clear(this_group);
1854 /* Sum group's NUMA faults; includes a==b case. */
1855 for_each_node_mask(b, nodes) {
1856 if (node_distance(a, b) < dist) {
1857 faults += group_faults(p, b);
1858 node_set(b, this_group);
1859 node_clear(b, nodes);
1863 /* Remember the top group. */
1864 if (faults > max_faults) {
1865 max_faults = faults;
1866 max_group = this_group;
1868 * subtle: at the smallest distance there is
1869 * just one node left in each "group", the
1870 * winner is the preferred nid.
1875 /* Next round, evaluate the nodes within max_group. */
1883 static void task_numa_placement(struct task_struct *p)
1885 int seq, nid, max_nid = -1, max_group_nid = -1;
1886 unsigned long max_faults = 0, max_group_faults = 0;
1887 unsigned long fault_types[2] = { 0, 0 };
1888 unsigned long total_faults;
1889 u64 runtime, period;
1890 spinlock_t *group_lock = NULL;
1893 * The p->mm->numa_scan_seq field gets updated without
1894 * exclusive access. Use READ_ONCE() here to ensure
1895 * that the field is read in a single access:
1897 seq = READ_ONCE(p->mm->numa_scan_seq);
1898 if (p->numa_scan_seq == seq)
1900 p->numa_scan_seq = seq;
1901 p->numa_scan_period_max = task_scan_max(p);
1903 total_faults = p->numa_faults_locality[0] +
1904 p->numa_faults_locality[1];
1905 runtime = numa_get_avg_runtime(p, &period);
1907 /* If the task is part of a group prevent parallel updates to group stats */
1908 if (p->numa_group) {
1909 group_lock = &p->numa_group->lock;
1910 spin_lock_irq(group_lock);
1913 /* Find the node with the highest number of faults */
1914 for_each_online_node(nid) {
1915 /* Keep track of the offsets in numa_faults array */
1916 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1917 unsigned long faults = 0, group_faults = 0;
1920 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1921 long diff, f_diff, f_weight;
1923 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1924 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1925 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1926 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1928 /* Decay existing window, copy faults since last scan */
1929 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1930 fault_types[priv] += p->numa_faults[membuf_idx];
1931 p->numa_faults[membuf_idx] = 0;
1934 * Normalize the faults_from, so all tasks in a group
1935 * count according to CPU use, instead of by the raw
1936 * number of faults. Tasks with little runtime have
1937 * little over-all impact on throughput, and thus their
1938 * faults are less important.
1940 f_weight = div64_u64(runtime << 16, period + 1);
1941 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1943 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1944 p->numa_faults[cpubuf_idx] = 0;
1946 p->numa_faults[mem_idx] += diff;
1947 p->numa_faults[cpu_idx] += f_diff;
1948 faults += p->numa_faults[mem_idx];
1949 p->total_numa_faults += diff;
1950 if (p->numa_group) {
1952 * safe because we can only change our own group
1954 * mem_idx represents the offset for a given
1955 * nid and priv in a specific region because it
1956 * is at the beginning of the numa_faults array.
1958 p->numa_group->faults[mem_idx] += diff;
1959 p->numa_group->faults_cpu[mem_idx] += f_diff;
1960 p->numa_group->total_faults += diff;
1961 group_faults += p->numa_group->faults[mem_idx];
1965 if (faults > max_faults) {
1966 max_faults = faults;
1970 if (group_faults > max_group_faults) {
1971 max_group_faults = group_faults;
1972 max_group_nid = nid;
1976 update_task_scan_period(p, fault_types[0], fault_types[1]);
1978 if (p->numa_group) {
1979 numa_group_count_active_nodes(p->numa_group);
1980 spin_unlock_irq(group_lock);
1981 max_nid = preferred_group_nid(p, max_group_nid);
1985 /* Set the new preferred node */
1986 if (max_nid != p->numa_preferred_nid)
1987 sched_setnuma(p, max_nid);
1989 if (task_node(p) != p->numa_preferred_nid)
1990 numa_migrate_preferred(p);
1994 static inline int get_numa_group(struct numa_group *grp)
1996 return atomic_inc_not_zero(&grp->refcount);
1999 static inline void put_numa_group(struct numa_group *grp)
2001 if (atomic_dec_and_test(&grp->refcount))
2002 kfree_rcu(grp, rcu);
2005 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
2008 struct numa_group *grp, *my_grp;
2009 struct task_struct *tsk;
2011 int cpu = cpupid_to_cpu(cpupid);
2014 if (unlikely(!p->numa_group)) {
2015 unsigned int size = sizeof(struct numa_group) +
2016 4*nr_node_ids*sizeof(unsigned long);
2018 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
2022 atomic_set(&grp->refcount, 1);
2023 grp->active_nodes = 1;
2024 grp->max_faults_cpu = 0;
2025 spin_lock_init(&grp->lock);
2027 /* Second half of the array tracks nids where faults happen */
2028 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
2031 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2032 grp->faults[i] = p->numa_faults[i];
2034 grp->total_faults = p->total_numa_faults;
2037 rcu_assign_pointer(p->numa_group, grp);
2041 tsk = READ_ONCE(cpu_rq(cpu)->curr);
2043 if (!cpupid_match_pid(tsk, cpupid))
2046 grp = rcu_dereference(tsk->numa_group);
2050 my_grp = p->numa_group;
2055 * Only join the other group if its bigger; if we're the bigger group,
2056 * the other task will join us.
2058 if (my_grp->nr_tasks > grp->nr_tasks)
2062 * Tie-break on the grp address.
2064 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2067 /* Always join threads in the same process. */
2068 if (tsk->mm == current->mm)
2071 /* Simple filter to avoid false positives due to PID collisions */
2072 if (flags & TNF_SHARED)
2075 /* Update priv based on whether false sharing was detected */
2078 if (join && !get_numa_group(grp))
2086 BUG_ON(irqs_disabled());
2087 double_lock_irq(&my_grp->lock, &grp->lock);
2089 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2090 my_grp->faults[i] -= p->numa_faults[i];
2091 grp->faults[i] += p->numa_faults[i];
2093 my_grp->total_faults -= p->total_numa_faults;
2094 grp->total_faults += p->total_numa_faults;
2099 spin_unlock(&my_grp->lock);
2100 spin_unlock_irq(&grp->lock);
2102 rcu_assign_pointer(p->numa_group, grp);
2104 put_numa_group(my_grp);
2112 void task_numa_free(struct task_struct *p)
2114 struct numa_group *grp = p->numa_group;
2115 void *numa_faults = p->numa_faults;
2116 unsigned long flags;
2120 spin_lock_irqsave(&grp->lock, flags);
2121 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2122 grp->faults[i] -= p->numa_faults[i];
2123 grp->total_faults -= p->total_numa_faults;
2126 spin_unlock_irqrestore(&grp->lock, flags);
2127 RCU_INIT_POINTER(p->numa_group, NULL);
2128 put_numa_group(grp);
2131 p->numa_faults = NULL;
2136 * Got a PROT_NONE fault for a page on @node.
2138 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2140 struct task_struct *p = current;
2141 bool migrated = flags & TNF_MIGRATED;
2142 int cpu_node = task_node(current);
2143 int local = !!(flags & TNF_FAULT_LOCAL);
2144 struct numa_group *ng;
2147 if (!static_branch_likely(&sched_numa_balancing))
2150 /* for example, ksmd faulting in a user's mm */
2154 /* Allocate buffer to track faults on a per-node basis */
2155 if (unlikely(!p->numa_faults)) {
2156 int size = sizeof(*p->numa_faults) *
2157 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2159 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2160 if (!p->numa_faults)
2163 p->total_numa_faults = 0;
2164 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2168 * First accesses are treated as private, otherwise consider accesses
2169 * to be private if the accessing pid has not changed
2171 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2174 priv = cpupid_match_pid(p, last_cpupid);
2175 if (!priv && !(flags & TNF_NO_GROUP))
2176 task_numa_group(p, last_cpupid, flags, &priv);
2180 * If a workload spans multiple NUMA nodes, a shared fault that
2181 * occurs wholly within the set of nodes that the workload is
2182 * actively using should be counted as local. This allows the
2183 * scan rate to slow down when a workload has settled down.
2186 if (!priv && !local && ng && ng->active_nodes > 1 &&
2187 numa_is_active_node(cpu_node, ng) &&
2188 numa_is_active_node(mem_node, ng))
2191 task_numa_placement(p);
2194 * Retry task to preferred node migration periodically, in case it
2195 * case it previously failed, or the scheduler moved us.
2197 if (time_after(jiffies, p->numa_migrate_retry))
2198 numa_migrate_preferred(p);
2201 p->numa_pages_migrated += pages;
2202 if (flags & TNF_MIGRATE_FAIL)
2203 p->numa_faults_locality[2] += pages;
2205 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2206 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2207 p->numa_faults_locality[local] += pages;
2210 static void reset_ptenuma_scan(struct task_struct *p)
2213 * We only did a read acquisition of the mmap sem, so
2214 * p->mm->numa_scan_seq is written to without exclusive access
2215 * and the update is not guaranteed to be atomic. That's not
2216 * much of an issue though, since this is just used for
2217 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2218 * expensive, to avoid any form of compiler optimizations:
2220 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2221 p->mm->numa_scan_offset = 0;
2225 * The expensive part of numa migration is done from task_work context.
2226 * Triggered from task_tick_numa().
2228 void task_numa_work(struct callback_head *work)
2230 unsigned long migrate, next_scan, now = jiffies;
2231 struct task_struct *p = current;
2232 struct mm_struct *mm = p->mm;
2233 u64 runtime = p->se.sum_exec_runtime;
2234 struct vm_area_struct *vma;
2235 unsigned long start, end;
2236 unsigned long nr_pte_updates = 0;
2237 long pages, virtpages;
2239 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2241 work->next = work; /* protect against double add */
2243 * Who cares about NUMA placement when they're dying.
2245 * NOTE: make sure not to dereference p->mm before this check,
2246 * exit_task_work() happens _after_ exit_mm() so we could be called
2247 * without p->mm even though we still had it when we enqueued this
2250 if (p->flags & PF_EXITING)
2253 if (!mm->numa_next_scan) {
2254 mm->numa_next_scan = now +
2255 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2259 * Enforce maximal scan/migration frequency..
2261 migrate = mm->numa_next_scan;
2262 if (time_before(now, migrate))
2265 if (p->numa_scan_period == 0) {
2266 p->numa_scan_period_max = task_scan_max(p);
2267 p->numa_scan_period = task_scan_min(p);
2270 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2271 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2275 * Delay this task enough that another task of this mm will likely win
2276 * the next time around.
2278 p->node_stamp += 2 * TICK_NSEC;
2280 start = mm->numa_scan_offset;
2281 pages = sysctl_numa_balancing_scan_size;
2282 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2283 virtpages = pages * 8; /* Scan up to this much virtual space */
2288 down_read(&mm->mmap_sem);
2289 vma = find_vma(mm, start);
2291 reset_ptenuma_scan(p);
2295 for (; vma; vma = vma->vm_next) {
2296 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2297 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2302 * Shared library pages mapped by multiple processes are not
2303 * migrated as it is expected they are cache replicated. Avoid
2304 * hinting faults in read-only file-backed mappings or the vdso
2305 * as migrating the pages will be of marginal benefit.
2308 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2312 * Skip inaccessible VMAs to avoid any confusion between
2313 * PROT_NONE and NUMA hinting ptes
2315 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2319 start = max(start, vma->vm_start);
2320 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2321 end = min(end, vma->vm_end);
2322 nr_pte_updates = change_prot_numa(vma, start, end);
2325 * Try to scan sysctl_numa_balancing_size worth of
2326 * hpages that have at least one present PTE that
2327 * is not already pte-numa. If the VMA contains
2328 * areas that are unused or already full of prot_numa
2329 * PTEs, scan up to virtpages, to skip through those
2333 pages -= (end - start) >> PAGE_SHIFT;
2334 virtpages -= (end - start) >> PAGE_SHIFT;
2337 if (pages <= 0 || virtpages <= 0)
2341 } while (end != vma->vm_end);
2346 * It is possible to reach the end of the VMA list but the last few
2347 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2348 * would find the !migratable VMA on the next scan but not reset the
2349 * scanner to the start so check it now.
2352 mm->numa_scan_offset = start;
2354 reset_ptenuma_scan(p);
2355 up_read(&mm->mmap_sem);
2358 * Make sure tasks use at least 32x as much time to run other code
2359 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2360 * Usually update_task_scan_period slows down scanning enough; on an
2361 * overloaded system we need to limit overhead on a per task basis.
2363 if (unlikely(p->se.sum_exec_runtime != runtime)) {
2364 u64 diff = p->se.sum_exec_runtime - runtime;
2365 p->node_stamp += 32 * diff;
2370 * Drive the periodic memory faults..
2372 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2374 struct callback_head *work = &curr->numa_work;
2378 * We don't care about NUMA placement if we don't have memory.
2380 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2384 * Using runtime rather than walltime has the dual advantage that
2385 * we (mostly) drive the selection from busy threads and that the
2386 * task needs to have done some actual work before we bother with
2389 now = curr->se.sum_exec_runtime;
2390 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2392 if (now > curr->node_stamp + period) {
2393 if (!curr->node_stamp)
2394 curr->numa_scan_period = task_scan_min(curr);
2395 curr->node_stamp += period;
2397 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2398 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2399 task_work_add(curr, work, true);
2404 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2408 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2412 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2415 #endif /* CONFIG_NUMA_BALANCING */
2418 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2420 update_load_add(&cfs_rq->load, se->load.weight);
2421 if (!parent_entity(se))
2422 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2424 if (entity_is_task(se)) {
2425 struct rq *rq = rq_of(cfs_rq);
2427 account_numa_enqueue(rq, task_of(se));
2428 list_add(&se->group_node, &rq->cfs_tasks);
2431 cfs_rq->nr_running++;
2435 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2437 update_load_sub(&cfs_rq->load, se->load.weight);
2438 if (!parent_entity(se))
2439 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2440 if (entity_is_task(se)) {
2441 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2442 list_del_init(&se->group_node);
2444 cfs_rq->nr_running--;
2447 #ifdef CONFIG_FAIR_GROUP_SCHED
2449 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2454 * Use this CPU's real-time load instead of the last load contribution
2455 * as the updating of the contribution is delayed, and we will use the
2456 * the real-time load to calc the share. See update_tg_load_avg().
2458 tg_weight = atomic_long_read(&tg->load_avg);
2459 tg_weight -= cfs_rq->tg_load_avg_contrib;
2460 tg_weight += cfs_rq->load.weight;
2465 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2467 long tg_weight, load, shares;
2469 tg_weight = calc_tg_weight(tg, cfs_rq);
2470 load = cfs_rq->load.weight;
2472 shares = (tg->shares * load);
2474 shares /= tg_weight;
2476 if (shares < MIN_SHARES)
2477 shares = MIN_SHARES;
2478 if (shares > tg->shares)
2479 shares = tg->shares;
2483 # else /* CONFIG_SMP */
2484 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2488 # endif /* CONFIG_SMP */
2489 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2490 unsigned long weight)
2493 /* commit outstanding execution time */
2494 if (cfs_rq->curr == se)
2495 update_curr(cfs_rq);
2496 account_entity_dequeue(cfs_rq, se);
2499 update_load_set(&se->load, weight);
2502 account_entity_enqueue(cfs_rq, se);
2505 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2507 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2509 struct task_group *tg;
2510 struct sched_entity *se;
2514 se = tg->se[cpu_of(rq_of(cfs_rq))];
2515 if (!se || throttled_hierarchy(cfs_rq))
2518 if (likely(se->load.weight == tg->shares))
2521 shares = calc_cfs_shares(cfs_rq, tg);
2523 reweight_entity(cfs_rq_of(se), se, shares);
2525 #else /* CONFIG_FAIR_GROUP_SCHED */
2526 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2529 #endif /* CONFIG_FAIR_GROUP_SCHED */
2532 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2533 static const u32 runnable_avg_yN_inv[] = {
2534 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2535 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2536 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2537 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2538 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2539 0x85aac367, 0x82cd8698,
2543 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2544 * over-estimates when re-combining.
2546 static const u32 runnable_avg_yN_sum[] = {
2547 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2548 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2549 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2554 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2556 static __always_inline u64 decay_load(u64 val, u64 n)
2558 unsigned int local_n;
2562 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2565 /* after bounds checking we can collapse to 32-bit */
2569 * As y^PERIOD = 1/2, we can combine
2570 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2571 * With a look-up table which covers y^n (n<PERIOD)
2573 * To achieve constant time decay_load.
2575 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2576 val >>= local_n / LOAD_AVG_PERIOD;
2577 local_n %= LOAD_AVG_PERIOD;
2580 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2585 * For updates fully spanning n periods, the contribution to runnable
2586 * average will be: \Sum 1024*y^n
2588 * We can compute this reasonably efficiently by combining:
2589 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2591 static u32 __compute_runnable_contrib(u64 n)
2595 if (likely(n <= LOAD_AVG_PERIOD))
2596 return runnable_avg_yN_sum[n];
2597 else if (unlikely(n >= LOAD_AVG_MAX_N))
2598 return LOAD_AVG_MAX;
2600 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2602 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2603 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2605 n -= LOAD_AVG_PERIOD;
2606 } while (n > LOAD_AVG_PERIOD);
2608 contrib = decay_load(contrib, n);
2609 return contrib + runnable_avg_yN_sum[n];
2612 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2613 #error "load tracking assumes 2^10 as unit"
2616 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2619 * We can represent the historical contribution to runnable average as the
2620 * coefficients of a geometric series. To do this we sub-divide our runnable
2621 * history into segments of approximately 1ms (1024us); label the segment that
2622 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2624 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2626 * (now) (~1ms ago) (~2ms ago)
2628 * Let u_i denote the fraction of p_i that the entity was runnable.
2630 * We then designate the fractions u_i as our co-efficients, yielding the
2631 * following representation of historical load:
2632 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2634 * We choose y based on the with of a reasonably scheduling period, fixing:
2637 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2638 * approximately half as much as the contribution to load within the last ms
2641 * When a period "rolls over" and we have new u_0`, multiplying the previous
2642 * sum again by y is sufficient to update:
2643 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2644 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2646 static __always_inline int
2647 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2648 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2650 u64 delta, scaled_delta, periods;
2652 unsigned int delta_w, scaled_delta_w, decayed = 0;
2653 unsigned long scale_freq, scale_cpu;
2655 delta = now - sa->last_update_time;
2657 * This should only happen when time goes backwards, which it
2658 * unfortunately does during sched clock init when we swap over to TSC.
2660 if ((s64)delta < 0) {
2661 sa->last_update_time = now;
2666 * Use 1024ns as the unit of measurement since it's a reasonable
2667 * approximation of 1us and fast to compute.
2672 sa->last_update_time = now;
2674 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2675 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2677 /* delta_w is the amount already accumulated against our next period */
2678 delta_w = sa->period_contrib;
2679 if (delta + delta_w >= 1024) {
2682 /* how much left for next period will start over, we don't know yet */
2683 sa->period_contrib = 0;
2686 * Now that we know we're crossing a period boundary, figure
2687 * out how much from delta we need to complete the current
2688 * period and accrue it.
2690 delta_w = 1024 - delta_w;
2691 scaled_delta_w = cap_scale(delta_w, scale_freq);
2693 sa->load_sum += weight * scaled_delta_w;
2695 cfs_rq->runnable_load_sum +=
2696 weight * scaled_delta_w;
2700 sa->util_sum += scaled_delta_w * scale_cpu;
2704 /* Figure out how many additional periods this update spans */
2705 periods = delta / 1024;
2708 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2710 cfs_rq->runnable_load_sum =
2711 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2713 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2715 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2716 contrib = __compute_runnable_contrib(periods);
2717 contrib = cap_scale(contrib, scale_freq);
2719 sa->load_sum += weight * contrib;
2721 cfs_rq->runnable_load_sum += weight * contrib;
2724 sa->util_sum += contrib * scale_cpu;
2727 /* Remainder of delta accrued against u_0` */
2728 scaled_delta = cap_scale(delta, scale_freq);
2730 sa->load_sum += weight * scaled_delta;
2732 cfs_rq->runnable_load_sum += weight * scaled_delta;
2735 sa->util_sum += scaled_delta * scale_cpu;
2737 sa->period_contrib += delta;
2740 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2742 cfs_rq->runnable_load_avg =
2743 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2745 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2751 #ifdef CONFIG_FAIR_GROUP_SCHED
2753 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2754 * and effective_load (which is not done because it is too costly).
2756 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2758 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2761 * No need to update load_avg for root_task_group as it is not used.
2763 if (cfs_rq->tg == &root_task_group)
2766 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2767 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2768 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2773 * Called within set_task_rq() right before setting a task's cpu. The
2774 * caller only guarantees p->pi_lock is held; no other assumptions,
2775 * including the state of rq->lock, should be made.
2777 void set_task_rq_fair(struct sched_entity *se,
2778 struct cfs_rq *prev, struct cfs_rq *next)
2780 if (!sched_feat(ATTACH_AGE_LOAD))
2784 * We are supposed to update the task to "current" time, then its up to
2785 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
2786 * getting what current time is, so simply throw away the out-of-date
2787 * time. This will result in the wakee task is less decayed, but giving
2788 * the wakee more load sounds not bad.
2790 if (se->avg.last_update_time && prev) {
2791 u64 p_last_update_time;
2792 u64 n_last_update_time;
2794 #ifndef CONFIG_64BIT
2795 u64 p_last_update_time_copy;
2796 u64 n_last_update_time_copy;
2799 p_last_update_time_copy = prev->load_last_update_time_copy;
2800 n_last_update_time_copy = next->load_last_update_time_copy;
2804 p_last_update_time = prev->avg.last_update_time;
2805 n_last_update_time = next->avg.last_update_time;
2807 } while (p_last_update_time != p_last_update_time_copy ||
2808 n_last_update_time != n_last_update_time_copy);
2810 p_last_update_time = prev->avg.last_update_time;
2811 n_last_update_time = next->avg.last_update_time;
2813 __update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
2814 &se->avg, 0, 0, NULL);
2815 se->avg.last_update_time = n_last_update_time;
2818 #else /* CONFIG_FAIR_GROUP_SCHED */
2819 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2820 #endif /* CONFIG_FAIR_GROUP_SCHED */
2822 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2824 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2825 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2827 struct sched_avg *sa = &cfs_rq->avg;
2828 int decayed, removed = 0;
2830 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2831 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2832 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2833 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2837 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2838 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2839 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2840 sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2843 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2844 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2846 #ifndef CONFIG_64BIT
2848 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2851 return decayed || removed;
2854 /* Update task and its cfs_rq load average */
2855 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2857 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2858 u64 now = cfs_rq_clock_task(cfs_rq);
2859 int cpu = cpu_of(rq_of(cfs_rq));
2862 * Track task load average for carrying it to new CPU after migrated, and
2863 * track group sched_entity load average for task_h_load calc in migration
2865 __update_load_avg(now, cpu, &se->avg,
2866 se->on_rq * scale_load_down(se->load.weight),
2867 cfs_rq->curr == se, NULL);
2869 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2870 update_tg_load_avg(cfs_rq, 0);
2873 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2875 if (!sched_feat(ATTACH_AGE_LOAD))
2879 * If we got migrated (either between CPUs or between cgroups) we'll
2880 * have aged the average right before clearing @last_update_time.
2882 if (se->avg.last_update_time) {
2883 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2884 &se->avg, 0, 0, NULL);
2887 * XXX: we could have just aged the entire load away if we've been
2888 * absent from the fair class for too long.
2893 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2894 cfs_rq->avg.load_avg += se->avg.load_avg;
2895 cfs_rq->avg.load_sum += se->avg.load_sum;
2896 cfs_rq->avg.util_avg += se->avg.util_avg;
2897 cfs_rq->avg.util_sum += se->avg.util_sum;
2900 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2902 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2903 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2904 cfs_rq->curr == se, NULL);
2906 cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
2907 cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
2908 cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
2909 cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
2912 /* Add the load generated by se into cfs_rq's load average */
2914 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2916 struct sched_avg *sa = &se->avg;
2917 u64 now = cfs_rq_clock_task(cfs_rq);
2918 int migrated, decayed;
2920 migrated = !sa->last_update_time;
2922 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2923 se->on_rq * scale_load_down(se->load.weight),
2924 cfs_rq->curr == se, NULL);
2927 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2929 cfs_rq->runnable_load_avg += sa->load_avg;
2930 cfs_rq->runnable_load_sum += sa->load_sum;
2933 attach_entity_load_avg(cfs_rq, se);
2935 if (decayed || migrated)
2936 update_tg_load_avg(cfs_rq, 0);
2939 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2941 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2943 update_load_avg(se, 1);
2945 cfs_rq->runnable_load_avg =
2946 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2947 cfs_rq->runnable_load_sum =
2948 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2951 #ifndef CONFIG_64BIT
2952 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2954 u64 last_update_time_copy;
2955 u64 last_update_time;
2958 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2960 last_update_time = cfs_rq->avg.last_update_time;
2961 } while (last_update_time != last_update_time_copy);
2963 return last_update_time;
2966 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2968 return cfs_rq->avg.last_update_time;
2973 * Task first catches up with cfs_rq, and then subtract
2974 * itself from the cfs_rq (task must be off the queue now).
2976 void remove_entity_load_avg(struct sched_entity *se)
2978 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2979 u64 last_update_time;
2982 * Newly created task or never used group entity should not be removed
2983 * from its (source) cfs_rq
2985 if (se->avg.last_update_time == 0)
2988 last_update_time = cfs_rq_last_update_time(cfs_rq);
2990 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2991 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2992 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2995 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2997 return cfs_rq->runnable_load_avg;
3000 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
3002 return cfs_rq->avg.load_avg;
3005 static int idle_balance(struct rq *this_rq);
3007 #else /* CONFIG_SMP */
3009 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
3011 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3013 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3014 static inline void remove_entity_load_avg(struct sched_entity *se) {}
3017 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3019 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3021 static inline int idle_balance(struct rq *rq)
3026 #endif /* CONFIG_SMP */
3028 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
3030 #ifdef CONFIG_SCHEDSTATS
3031 struct task_struct *tsk = NULL;
3033 if (entity_is_task(se))
3036 if (se->statistics.sleep_start) {
3037 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
3042 if (unlikely(delta > se->statistics.sleep_max))
3043 se->statistics.sleep_max = delta;
3045 se->statistics.sleep_start = 0;
3046 se->statistics.sum_sleep_runtime += delta;
3049 account_scheduler_latency(tsk, delta >> 10, 1);
3050 trace_sched_stat_sleep(tsk, delta);
3053 if (se->statistics.block_start) {
3054 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
3059 if (unlikely(delta > se->statistics.block_max))
3060 se->statistics.block_max = delta;
3062 se->statistics.block_start = 0;
3063 se->statistics.sum_sleep_runtime += delta;
3066 if (tsk->in_iowait) {
3067 se->statistics.iowait_sum += delta;
3068 se->statistics.iowait_count++;
3069 trace_sched_stat_iowait(tsk, delta);
3072 trace_sched_stat_blocked(tsk, delta);
3075 * Blocking time is in units of nanosecs, so shift by
3076 * 20 to get a milliseconds-range estimation of the
3077 * amount of time that the task spent sleeping:
3079 if (unlikely(prof_on == SLEEP_PROFILING)) {
3080 profile_hits(SLEEP_PROFILING,
3081 (void *)get_wchan(tsk),
3084 account_scheduler_latency(tsk, delta >> 10, 0);
3090 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
3092 #ifdef CONFIG_SCHED_DEBUG
3093 s64 d = se->vruntime - cfs_rq->min_vruntime;
3098 if (d > 3*sysctl_sched_latency)
3099 schedstat_inc(cfs_rq, nr_spread_over);
3104 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
3106 u64 vruntime = cfs_rq->min_vruntime;
3109 * The 'current' period is already promised to the current tasks,
3110 * however the extra weight of the new task will slow them down a
3111 * little, place the new task so that it fits in the slot that
3112 * stays open at the end.
3114 if (initial && sched_feat(START_DEBIT))
3115 vruntime += sched_vslice(cfs_rq, se);
3117 /* sleeps up to a single latency don't count. */
3119 unsigned long thresh = sysctl_sched_latency;
3122 * Halve their sleep time's effect, to allow
3123 * for a gentler effect of sleepers:
3125 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3131 /* ensure we never gain time by being placed backwards. */
3132 se->vruntime = max_vruntime(se->vruntime, vruntime);
3135 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3137 static inline void check_schedstat_required(void)
3139 #ifdef CONFIG_SCHEDSTATS
3140 if (schedstat_enabled())
3143 /* Force schedstat enabled if a dependent tracepoint is active */
3144 if (trace_sched_stat_wait_enabled() ||
3145 trace_sched_stat_sleep_enabled() ||
3146 trace_sched_stat_iowait_enabled() ||
3147 trace_sched_stat_blocked_enabled() ||
3148 trace_sched_stat_runtime_enabled()) {
3149 pr_warn_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3150 "stat_blocked and stat_runtime require the "
3151 "kernel parameter schedstats=enabled or "
3152 "kernel.sched_schedstats=1\n");
3158 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3160 bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING);
3161 bool curr = cfs_rq->curr == se;
3164 * If we're the current task, we must renormalise before calling
3168 se->vruntime += cfs_rq->min_vruntime;
3170 update_curr(cfs_rq);
3173 * Otherwise, renormalise after, such that we're placed at the current
3174 * moment in time, instead of some random moment in the past.
3176 if (renorm && !curr)
3177 se->vruntime += cfs_rq->min_vruntime;
3179 enqueue_entity_load_avg(cfs_rq, se);
3180 account_entity_enqueue(cfs_rq, se);
3181 update_cfs_shares(cfs_rq);
3183 if (flags & ENQUEUE_WAKEUP) {
3184 place_entity(cfs_rq, se, 0);
3185 if (schedstat_enabled())
3186 enqueue_sleeper(cfs_rq, se);
3189 check_schedstat_required();
3190 if (schedstat_enabled()) {
3191 update_stats_enqueue(cfs_rq, se);
3192 check_spread(cfs_rq, se);
3195 __enqueue_entity(cfs_rq, se);
3198 if (cfs_rq->nr_running == 1) {
3199 list_add_leaf_cfs_rq(cfs_rq);
3200 check_enqueue_throttle(cfs_rq);
3204 static void __clear_buddies_last(struct sched_entity *se)
3206 for_each_sched_entity(se) {
3207 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3208 if (cfs_rq->last != se)
3211 cfs_rq->last = NULL;
3215 static void __clear_buddies_next(struct sched_entity *se)
3217 for_each_sched_entity(se) {
3218 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3219 if (cfs_rq->next != se)
3222 cfs_rq->next = NULL;
3226 static void __clear_buddies_skip(struct sched_entity *se)
3228 for_each_sched_entity(se) {
3229 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3230 if (cfs_rq->skip != se)
3233 cfs_rq->skip = NULL;
3237 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3239 if (cfs_rq->last == se)
3240 __clear_buddies_last(se);
3242 if (cfs_rq->next == se)
3243 __clear_buddies_next(se);
3245 if (cfs_rq->skip == se)
3246 __clear_buddies_skip(se);
3249 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3252 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3255 * Update run-time statistics of the 'current'.
3257 update_curr(cfs_rq);
3258 dequeue_entity_load_avg(cfs_rq, se);
3260 if (schedstat_enabled())
3261 update_stats_dequeue(cfs_rq, se, flags);
3263 clear_buddies(cfs_rq, se);
3265 if (se != cfs_rq->curr)
3266 __dequeue_entity(cfs_rq, se);
3268 account_entity_dequeue(cfs_rq, se);
3271 * Normalize the entity after updating the min_vruntime because the
3272 * update can refer to the ->curr item and we need to reflect this
3273 * movement in our normalized position.
3275 if (!(flags & DEQUEUE_SLEEP))
3276 se->vruntime -= cfs_rq->min_vruntime;
3278 /* return excess runtime on last dequeue */
3279 return_cfs_rq_runtime(cfs_rq);
3281 update_min_vruntime(cfs_rq);
3282 update_cfs_shares(cfs_rq);
3286 * Preempt the current task with a newly woken task if needed:
3289 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3291 unsigned long ideal_runtime, delta_exec;
3292 struct sched_entity *se;
3295 ideal_runtime = sched_slice(cfs_rq, curr);
3296 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3297 if (delta_exec > ideal_runtime) {
3298 resched_curr(rq_of(cfs_rq));
3300 * The current task ran long enough, ensure it doesn't get
3301 * re-elected due to buddy favours.
3303 clear_buddies(cfs_rq, curr);
3308 * Ensure that a task that missed wakeup preemption by a
3309 * narrow margin doesn't have to wait for a full slice.
3310 * This also mitigates buddy induced latencies under load.
3312 if (delta_exec < sysctl_sched_min_granularity)
3315 se = __pick_first_entity(cfs_rq);
3316 delta = curr->vruntime - se->vruntime;
3321 if (delta > ideal_runtime)
3322 resched_curr(rq_of(cfs_rq));
3326 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3328 /* 'current' is not kept within the tree. */
3331 * Any task has to be enqueued before it get to execute on
3332 * a CPU. So account for the time it spent waiting on the
3335 if (schedstat_enabled())
3336 update_stats_wait_end(cfs_rq, se);
3337 __dequeue_entity(cfs_rq, se);
3338 update_load_avg(se, 1);
3341 update_stats_curr_start(cfs_rq, se);
3343 #ifdef CONFIG_SCHEDSTATS
3345 * Track our maximum slice length, if the CPU's load is at
3346 * least twice that of our own weight (i.e. dont track it
3347 * when there are only lesser-weight tasks around):
3349 if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3350 se->statistics.slice_max = max(se->statistics.slice_max,
3351 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3354 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3358 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3361 * Pick the next process, keeping these things in mind, in this order:
3362 * 1) keep things fair between processes/task groups
3363 * 2) pick the "next" process, since someone really wants that to run
3364 * 3) pick the "last" process, for cache locality
3365 * 4) do not run the "skip" process, if something else is available
3367 static struct sched_entity *
3368 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3370 struct sched_entity *left = __pick_first_entity(cfs_rq);
3371 struct sched_entity *se;
3374 * If curr is set we have to see if its left of the leftmost entity
3375 * still in the tree, provided there was anything in the tree at all.
3377 if (!left || (curr && entity_before(curr, left)))
3380 se = left; /* ideally we run the leftmost entity */
3383 * Avoid running the skip buddy, if running something else can
3384 * be done without getting too unfair.
3386 if (cfs_rq->skip == se) {
3387 struct sched_entity *second;
3390 second = __pick_first_entity(cfs_rq);
3392 second = __pick_next_entity(se);
3393 if (!second || (curr && entity_before(curr, second)))
3397 if (second && wakeup_preempt_entity(second, left) < 1)
3402 * Prefer last buddy, try to return the CPU to a preempted task.
3404 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3408 * Someone really wants this to run. If it's not unfair, run it.
3410 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3413 clear_buddies(cfs_rq, se);
3418 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3420 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3423 * If still on the runqueue then deactivate_task()
3424 * was not called and update_curr() has to be done:
3427 update_curr(cfs_rq);
3429 /* throttle cfs_rqs exceeding runtime */
3430 check_cfs_rq_runtime(cfs_rq);
3432 if (schedstat_enabled()) {
3433 check_spread(cfs_rq, prev);
3435 update_stats_wait_start(cfs_rq, prev);
3439 /* Put 'current' back into the tree. */
3440 __enqueue_entity(cfs_rq, prev);
3441 /* in !on_rq case, update occurred at dequeue */
3442 update_load_avg(prev, 0);
3444 cfs_rq->curr = NULL;
3448 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3451 * Update run-time statistics of the 'current'.
3453 update_curr(cfs_rq);
3456 * Ensure that runnable average is periodically updated.
3458 update_load_avg(curr, 1);
3459 update_cfs_shares(cfs_rq);
3461 #ifdef CONFIG_SCHED_HRTICK
3463 * queued ticks are scheduled to match the slice, so don't bother
3464 * validating it and just reschedule.
3467 resched_curr(rq_of(cfs_rq));
3471 * don't let the period tick interfere with the hrtick preemption
3473 if (!sched_feat(DOUBLE_TICK) &&
3474 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3478 if (cfs_rq->nr_running > 1)
3479 check_preempt_tick(cfs_rq, curr);
3483 /**************************************************
3484 * CFS bandwidth control machinery
3487 #ifdef CONFIG_CFS_BANDWIDTH
3489 #ifdef HAVE_JUMP_LABEL
3490 static struct static_key __cfs_bandwidth_used;
3492 static inline bool cfs_bandwidth_used(void)
3494 return static_key_false(&__cfs_bandwidth_used);
3497 void cfs_bandwidth_usage_inc(void)
3499 static_key_slow_inc(&__cfs_bandwidth_used);
3502 void cfs_bandwidth_usage_dec(void)
3504 static_key_slow_dec(&__cfs_bandwidth_used);
3506 #else /* HAVE_JUMP_LABEL */
3507 static bool cfs_bandwidth_used(void)
3512 void cfs_bandwidth_usage_inc(void) {}
3513 void cfs_bandwidth_usage_dec(void) {}
3514 #endif /* HAVE_JUMP_LABEL */
3517 * default period for cfs group bandwidth.
3518 * default: 0.1s, units: nanoseconds
3520 static inline u64 default_cfs_period(void)
3522 return 100000000ULL;
3525 static inline u64 sched_cfs_bandwidth_slice(void)
3527 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3531 * Replenish runtime according to assigned quota and update expiration time.
3532 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3533 * additional synchronization around rq->lock.
3535 * requires cfs_b->lock
3537 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3541 if (cfs_b->quota == RUNTIME_INF)
3544 now = sched_clock_cpu(smp_processor_id());
3545 cfs_b->runtime = cfs_b->quota;
3546 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3549 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3551 return &tg->cfs_bandwidth;
3554 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3555 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3557 if (unlikely(cfs_rq->throttle_count))
3558 return cfs_rq->throttled_clock_task;
3560 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3563 /* returns 0 on failure to allocate runtime */
3564 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3566 struct task_group *tg = cfs_rq->tg;
3567 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3568 u64 amount = 0, min_amount, expires;
3570 /* note: this is a positive sum as runtime_remaining <= 0 */
3571 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3573 raw_spin_lock(&cfs_b->lock);
3574 if (cfs_b->quota == RUNTIME_INF)
3575 amount = min_amount;
3577 start_cfs_bandwidth(cfs_b);
3579 if (cfs_b->runtime > 0) {
3580 amount = min(cfs_b->runtime, min_amount);
3581 cfs_b->runtime -= amount;
3585 expires = cfs_b->runtime_expires;
3586 raw_spin_unlock(&cfs_b->lock);
3588 cfs_rq->runtime_remaining += amount;
3590 * we may have advanced our local expiration to account for allowed
3591 * spread between our sched_clock and the one on which runtime was
3594 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3595 cfs_rq->runtime_expires = expires;
3597 return cfs_rq->runtime_remaining > 0;
3601 * Note: This depends on the synchronization provided by sched_clock and the
3602 * fact that rq->clock snapshots this value.
3604 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3606 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3608 /* if the deadline is ahead of our clock, nothing to do */
3609 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3612 if (cfs_rq->runtime_remaining < 0)
3616 * If the local deadline has passed we have to consider the
3617 * possibility that our sched_clock is 'fast' and the global deadline
3618 * has not truly expired.
3620 * Fortunately we can check determine whether this the case by checking
3621 * whether the global deadline has advanced. It is valid to compare
3622 * cfs_b->runtime_expires without any locks since we only care about
3623 * exact equality, so a partial write will still work.
3626 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3627 /* extend local deadline, drift is bounded above by 2 ticks */
3628 cfs_rq->runtime_expires += TICK_NSEC;
3630 /* global deadline is ahead, expiration has passed */
3631 cfs_rq->runtime_remaining = 0;
3635 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3637 /* dock delta_exec before expiring quota (as it could span periods) */
3638 cfs_rq->runtime_remaining -= delta_exec;
3639 expire_cfs_rq_runtime(cfs_rq);
3641 if (likely(cfs_rq->runtime_remaining > 0))
3645 * if we're unable to extend our runtime we resched so that the active
3646 * hierarchy can be throttled
3648 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3649 resched_curr(rq_of(cfs_rq));
3652 static __always_inline
3653 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3655 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3658 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3661 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3663 return cfs_bandwidth_used() && cfs_rq->throttled;
3666 /* check whether cfs_rq, or any parent, is throttled */
3667 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3669 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3673 * Ensure that neither of the group entities corresponding to src_cpu or
3674 * dest_cpu are members of a throttled hierarchy when performing group
3675 * load-balance operations.
3677 static inline int throttled_lb_pair(struct task_group *tg,
3678 int src_cpu, int dest_cpu)
3680 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3682 src_cfs_rq = tg->cfs_rq[src_cpu];
3683 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3685 return throttled_hierarchy(src_cfs_rq) ||
3686 throttled_hierarchy(dest_cfs_rq);
3689 /* updated child weight may affect parent so we have to do this bottom up */
3690 static int tg_unthrottle_up(struct task_group *tg, void *data)
3692 struct rq *rq = data;
3693 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3695 cfs_rq->throttle_count--;
3697 if (!cfs_rq->throttle_count) {
3698 /* adjust cfs_rq_clock_task() */
3699 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3700 cfs_rq->throttled_clock_task;
3707 static int tg_throttle_down(struct task_group *tg, void *data)
3709 struct rq *rq = data;
3710 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3712 /* group is entering throttled state, stop time */
3713 if (!cfs_rq->throttle_count)
3714 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3715 cfs_rq->throttle_count++;
3720 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3722 struct rq *rq = rq_of(cfs_rq);
3723 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3724 struct sched_entity *se;
3725 long task_delta, dequeue = 1;
3728 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3730 /* freeze hierarchy runnable averages while throttled */
3732 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3735 task_delta = cfs_rq->h_nr_running;
3736 for_each_sched_entity(se) {
3737 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3738 /* throttled entity or throttle-on-deactivate */
3743 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3744 qcfs_rq->h_nr_running -= task_delta;
3746 if (qcfs_rq->load.weight)
3751 sub_nr_running(rq, task_delta);
3753 cfs_rq->throttled = 1;
3754 cfs_rq->throttled_clock = rq_clock(rq);
3755 raw_spin_lock(&cfs_b->lock);
3756 empty = list_empty(&cfs_b->throttled_cfs_rq);
3759 * Add to the _head_ of the list, so that an already-started
3760 * distribute_cfs_runtime will not see us
3762 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3765 * If we're the first throttled task, make sure the bandwidth
3769 start_cfs_bandwidth(cfs_b);
3771 raw_spin_unlock(&cfs_b->lock);
3774 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3776 struct rq *rq = rq_of(cfs_rq);
3777 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3778 struct sched_entity *se;
3782 se = cfs_rq->tg->se[cpu_of(rq)];
3784 cfs_rq->throttled = 0;
3786 update_rq_clock(rq);
3788 raw_spin_lock(&cfs_b->lock);
3789 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3790 list_del_rcu(&cfs_rq->throttled_list);
3791 raw_spin_unlock(&cfs_b->lock);
3793 /* update hierarchical throttle state */
3794 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3796 if (!cfs_rq->load.weight)
3799 task_delta = cfs_rq->h_nr_running;
3800 for_each_sched_entity(se) {
3804 cfs_rq = cfs_rq_of(se);
3806 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3807 cfs_rq->h_nr_running += task_delta;
3809 if (cfs_rq_throttled(cfs_rq))
3814 add_nr_running(rq, task_delta);
3816 /* determine whether we need to wake up potentially idle cpu */
3817 if (rq->curr == rq->idle && rq->cfs.nr_running)
3821 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3822 u64 remaining, u64 expires)
3824 struct cfs_rq *cfs_rq;
3826 u64 starting_runtime = remaining;
3829 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3831 struct rq *rq = rq_of(cfs_rq);
3833 raw_spin_lock(&rq->lock);
3834 if (!cfs_rq_throttled(cfs_rq))
3837 runtime = -cfs_rq->runtime_remaining + 1;
3838 if (runtime > remaining)
3839 runtime = remaining;
3840 remaining -= runtime;
3842 cfs_rq->runtime_remaining += runtime;
3843 cfs_rq->runtime_expires = expires;
3845 /* we check whether we're throttled above */
3846 if (cfs_rq->runtime_remaining > 0)
3847 unthrottle_cfs_rq(cfs_rq);
3850 raw_spin_unlock(&rq->lock);
3857 return starting_runtime - remaining;
3861 * Responsible for refilling a task_group's bandwidth and unthrottling its
3862 * cfs_rqs as appropriate. If there has been no activity within the last
3863 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3864 * used to track this state.
3866 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3868 u64 runtime, runtime_expires;
3871 /* no need to continue the timer with no bandwidth constraint */
3872 if (cfs_b->quota == RUNTIME_INF)
3873 goto out_deactivate;
3875 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3876 cfs_b->nr_periods += overrun;
3879 * idle depends on !throttled (for the case of a large deficit), and if
3880 * we're going inactive then everything else can be deferred
3882 if (cfs_b->idle && !throttled)
3883 goto out_deactivate;
3885 __refill_cfs_bandwidth_runtime(cfs_b);
3888 /* mark as potentially idle for the upcoming period */
3893 /* account preceding periods in which throttling occurred */
3894 cfs_b->nr_throttled += overrun;
3896 runtime_expires = cfs_b->runtime_expires;
3899 * This check is repeated as we are holding onto the new bandwidth while
3900 * we unthrottle. This can potentially race with an unthrottled group
3901 * trying to acquire new bandwidth from the global pool. This can result
3902 * in us over-using our runtime if it is all used during this loop, but
3903 * only by limited amounts in that extreme case.
3905 while (throttled && cfs_b->runtime > 0) {
3906 runtime = cfs_b->runtime;
3907 raw_spin_unlock(&cfs_b->lock);
3908 /* we can't nest cfs_b->lock while distributing bandwidth */
3909 runtime = distribute_cfs_runtime(cfs_b, runtime,
3911 raw_spin_lock(&cfs_b->lock);
3913 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3915 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3919 * While we are ensured activity in the period following an
3920 * unthrottle, this also covers the case in which the new bandwidth is
3921 * insufficient to cover the existing bandwidth deficit. (Forcing the
3922 * timer to remain active while there are any throttled entities.)
3932 /* a cfs_rq won't donate quota below this amount */
3933 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3934 /* minimum remaining period time to redistribute slack quota */
3935 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3936 /* how long we wait to gather additional slack before distributing */
3937 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3940 * Are we near the end of the current quota period?
3942 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3943 * hrtimer base being cleared by hrtimer_start. In the case of
3944 * migrate_hrtimers, base is never cleared, so we are fine.
3946 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3948 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3951 /* if the call-back is running a quota refresh is already occurring */
3952 if (hrtimer_callback_running(refresh_timer))
3955 /* is a quota refresh about to occur? */
3956 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3957 if (remaining < min_expire)
3963 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3965 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3967 /* if there's a quota refresh soon don't bother with slack */
3968 if (runtime_refresh_within(cfs_b, min_left))
3971 hrtimer_start(&cfs_b->slack_timer,
3972 ns_to_ktime(cfs_bandwidth_slack_period),
3976 /* we know any runtime found here is valid as update_curr() precedes return */
3977 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3979 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3980 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3982 if (slack_runtime <= 0)
3985 raw_spin_lock(&cfs_b->lock);
3986 if (cfs_b->quota != RUNTIME_INF &&
3987 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3988 cfs_b->runtime += slack_runtime;
3990 /* we are under rq->lock, defer unthrottling using a timer */
3991 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3992 !list_empty(&cfs_b->throttled_cfs_rq))
3993 start_cfs_slack_bandwidth(cfs_b);
3995 raw_spin_unlock(&cfs_b->lock);
3997 /* even if it's not valid for return we don't want to try again */
3998 cfs_rq->runtime_remaining -= slack_runtime;
4001 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4003 if (!cfs_bandwidth_used())
4006 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4009 __return_cfs_rq_runtime(cfs_rq);
4013 * This is done with a timer (instead of inline with bandwidth return) since
4014 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4016 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
4018 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
4021 /* confirm we're still not at a refresh boundary */
4022 raw_spin_lock(&cfs_b->lock);
4023 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
4024 raw_spin_unlock(&cfs_b->lock);
4028 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4029 runtime = cfs_b->runtime;
4031 expires = cfs_b->runtime_expires;
4032 raw_spin_unlock(&cfs_b->lock);
4037 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
4039 raw_spin_lock(&cfs_b->lock);
4040 if (expires == cfs_b->runtime_expires)
4041 cfs_b->runtime -= min(runtime, cfs_b->runtime);
4042 raw_spin_unlock(&cfs_b->lock);
4046 * When a group wakes up we want to make sure that its quota is not already
4047 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4048 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4050 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
4052 if (!cfs_bandwidth_used())
4055 /* an active group must be handled by the update_curr()->put() path */
4056 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
4059 /* ensure the group is not already throttled */
4060 if (cfs_rq_throttled(cfs_rq))
4063 /* update runtime allocation */
4064 account_cfs_rq_runtime(cfs_rq, 0);
4065 if (cfs_rq->runtime_remaining <= 0)
4066 throttle_cfs_rq(cfs_rq);
4069 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4070 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4072 if (!cfs_bandwidth_used())
4075 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4079 * it's possible for a throttled entity to be forced into a running
4080 * state (e.g. set_curr_task), in this case we're finished.
4082 if (cfs_rq_throttled(cfs_rq))
4085 throttle_cfs_rq(cfs_rq);
4089 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
4091 struct cfs_bandwidth *cfs_b =
4092 container_of(timer, struct cfs_bandwidth, slack_timer);
4094 do_sched_cfs_slack_timer(cfs_b);
4096 return HRTIMER_NORESTART;
4099 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
4101 struct cfs_bandwidth *cfs_b =
4102 container_of(timer, struct cfs_bandwidth, period_timer);
4106 raw_spin_lock(&cfs_b->lock);
4108 overrun = hrtimer_forward_now(timer, cfs_b->period);
4112 idle = do_sched_cfs_period_timer(cfs_b, overrun);
4115 cfs_b->period_active = 0;
4116 raw_spin_unlock(&cfs_b->lock);
4118 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
4121 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4123 raw_spin_lock_init(&cfs_b->lock);
4125 cfs_b->quota = RUNTIME_INF;
4126 cfs_b->period = ns_to_ktime(default_cfs_period());
4128 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
4129 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4130 cfs_b->period_timer.function = sched_cfs_period_timer;
4131 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
4132 cfs_b->slack_timer.function = sched_cfs_slack_timer;
4135 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4137 cfs_rq->runtime_enabled = 0;
4138 INIT_LIST_HEAD(&cfs_rq->throttled_list);
4141 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4143 lockdep_assert_held(&cfs_b->lock);
4145 if (!cfs_b->period_active) {
4146 cfs_b->period_active = 1;
4147 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4148 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4152 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4154 /* init_cfs_bandwidth() was not called */
4155 if (!cfs_b->throttled_cfs_rq.next)
4158 hrtimer_cancel(&cfs_b->period_timer);
4159 hrtimer_cancel(&cfs_b->slack_timer);
4162 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4164 struct cfs_rq *cfs_rq;
4166 for_each_leaf_cfs_rq(rq, cfs_rq) {
4167 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4169 raw_spin_lock(&cfs_b->lock);
4170 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4171 raw_spin_unlock(&cfs_b->lock);
4175 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4177 struct cfs_rq *cfs_rq;
4179 for_each_leaf_cfs_rq(rq, cfs_rq) {
4180 if (!cfs_rq->runtime_enabled)
4184 * clock_task is not advancing so we just need to make sure
4185 * there's some valid quota amount
4187 cfs_rq->runtime_remaining = 1;
4189 * Offline rq is schedulable till cpu is completely disabled
4190 * in take_cpu_down(), so we prevent new cfs throttling here.
4192 cfs_rq->runtime_enabled = 0;
4194 if (cfs_rq_throttled(cfs_rq))
4195 unthrottle_cfs_rq(cfs_rq);
4199 #else /* CONFIG_CFS_BANDWIDTH */
4200 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4202 return rq_clock_task(rq_of(cfs_rq));
4205 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4206 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4207 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4208 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4210 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4215 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4220 static inline int throttled_lb_pair(struct task_group *tg,
4221 int src_cpu, int dest_cpu)
4226 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4228 #ifdef CONFIG_FAIR_GROUP_SCHED
4229 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4232 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4236 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4237 static inline void update_runtime_enabled(struct rq *rq) {}
4238 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4240 #endif /* CONFIG_CFS_BANDWIDTH */
4242 /**************************************************
4243 * CFS operations on tasks:
4246 #ifdef CONFIG_SCHED_HRTICK
4247 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4249 struct sched_entity *se = &p->se;
4250 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4252 WARN_ON(task_rq(p) != rq);
4254 if (cfs_rq->nr_running > 1) {
4255 u64 slice = sched_slice(cfs_rq, se);
4256 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4257 s64 delta = slice - ran;
4264 hrtick_start(rq, delta);
4269 * called from enqueue/dequeue and updates the hrtick when the
4270 * current task is from our class and nr_running is low enough
4273 static void hrtick_update(struct rq *rq)
4275 struct task_struct *curr = rq->curr;
4277 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4280 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4281 hrtick_start_fair(rq, curr);
4283 #else /* !CONFIG_SCHED_HRTICK */
4285 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4289 static inline void hrtick_update(struct rq *rq)
4295 * The enqueue_task method is called before nr_running is
4296 * increased. Here we update the fair scheduling stats and
4297 * then put the task into the rbtree:
4300 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4302 struct cfs_rq *cfs_rq;
4303 struct sched_entity *se = &p->se;
4305 for_each_sched_entity(se) {
4308 cfs_rq = cfs_rq_of(se);
4309 enqueue_entity(cfs_rq, se, flags);
4312 * end evaluation on encountering a throttled cfs_rq
4314 * note: in the case of encountering a throttled cfs_rq we will
4315 * post the final h_nr_running increment below.
4317 if (cfs_rq_throttled(cfs_rq))
4319 cfs_rq->h_nr_running++;
4321 flags = ENQUEUE_WAKEUP;
4324 for_each_sched_entity(se) {
4325 cfs_rq = cfs_rq_of(se);
4326 cfs_rq->h_nr_running++;
4328 if (cfs_rq_throttled(cfs_rq))
4331 update_load_avg(se, 1);
4332 update_cfs_shares(cfs_rq);
4336 add_nr_running(rq, 1);
4341 static void set_next_buddy(struct sched_entity *se);
4344 * The dequeue_task method is called before nr_running is
4345 * decreased. We remove the task from the rbtree and
4346 * update the fair scheduling stats:
4348 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4350 struct cfs_rq *cfs_rq;
4351 struct sched_entity *se = &p->se;
4352 int task_sleep = flags & DEQUEUE_SLEEP;
4354 for_each_sched_entity(se) {
4355 cfs_rq = cfs_rq_of(se);
4356 dequeue_entity(cfs_rq, se, flags);
4359 * end evaluation on encountering a throttled cfs_rq
4361 * note: in the case of encountering a throttled cfs_rq we will
4362 * post the final h_nr_running decrement below.
4364 if (cfs_rq_throttled(cfs_rq))
4366 cfs_rq->h_nr_running--;
4368 /* Don't dequeue parent if it has other entities besides us */
4369 if (cfs_rq->load.weight) {
4371 * Bias pick_next to pick a task from this cfs_rq, as
4372 * p is sleeping when it is within its sched_slice.
4374 if (task_sleep && parent_entity(se))
4375 set_next_buddy(parent_entity(se));
4377 /* avoid re-evaluating load for this entity */
4378 se = parent_entity(se);
4381 flags |= DEQUEUE_SLEEP;
4384 for_each_sched_entity(se) {
4385 cfs_rq = cfs_rq_of(se);
4386 cfs_rq->h_nr_running--;
4388 if (cfs_rq_throttled(cfs_rq))
4391 update_load_avg(se, 1);
4392 update_cfs_shares(cfs_rq);
4396 sub_nr_running(rq, 1);
4404 * per rq 'load' arrray crap; XXX kill this.
4408 * The exact cpuload calculated at every tick would be:
4410 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4412 * If a cpu misses updates for n ticks (as it was idle) and update gets
4413 * called on the n+1-th tick when cpu may be busy, then we have:
4415 * load_n = (1 - 1/2^i)^n * load_0
4416 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
4418 * decay_load_missed() below does efficient calculation of
4420 * load' = (1 - 1/2^i)^n * load
4422 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4423 * This allows us to precompute the above in said factors, thereby allowing the
4424 * reduction of an arbitrary n in O(log_2 n) steps. (See also
4425 * fixed_power_int())
4427 * The calculation is approximated on a 128 point scale.
4429 #define DEGRADE_SHIFT 7
4431 static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4432 static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4433 { 0, 0, 0, 0, 0, 0, 0, 0 },
4434 { 64, 32, 8, 0, 0, 0, 0, 0 },
4435 { 96, 72, 40, 12, 1, 0, 0, 0 },
4436 { 112, 98, 75, 43, 15, 1, 0, 0 },
4437 { 120, 112, 98, 76, 45, 16, 2, 0 }
4441 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4442 * would be when CPU is idle and so we just decay the old load without
4443 * adding any new load.
4445 static unsigned long
4446 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4450 if (!missed_updates)
4453 if (missed_updates >= degrade_zero_ticks[idx])
4457 return load >> missed_updates;
4459 while (missed_updates) {
4460 if (missed_updates % 2)
4461 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4463 missed_updates >>= 1;
4470 * __update_cpu_load - update the rq->cpu_load[] statistics
4471 * @this_rq: The rq to update statistics for
4472 * @this_load: The current load
4473 * @pending_updates: The number of missed updates
4474 * @active: !0 for NOHZ_FULL
4476 * Update rq->cpu_load[] statistics. This function is usually called every
4477 * scheduler tick (TICK_NSEC).
4479 * This function computes a decaying average:
4481 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4483 * Because of NOHZ it might not get called on every tick which gives need for
4484 * the @pending_updates argument.
4486 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4487 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4488 * = A * (A * load[i]_n-2 + B) + B
4489 * = A * (A * (A * load[i]_n-3 + B) + B) + B
4490 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4491 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4492 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4493 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4495 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4496 * any change in load would have resulted in the tick being turned back on.
4498 * For regular NOHZ, this reduces to:
4500 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
4502 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4503 * term. See the @active paramter.
4505 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4506 unsigned long pending_updates, int active)
4508 unsigned long tickless_load = active ? this_rq->cpu_load[0] : 0;
4511 this_rq->nr_load_updates++;
4513 /* Update our load: */
4514 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4515 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4516 unsigned long old_load, new_load;
4518 /* scale is effectively 1 << i now, and >> i divides by scale */
4520 old_load = this_rq->cpu_load[i];
4521 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4522 if (tickless_load) {
4523 old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
4525 * old_load can never be a negative value because a
4526 * decayed tickless_load cannot be greater than the
4527 * original tickless_load.
4529 old_load += tickless_load;
4531 new_load = this_load;
4533 * Round up the averaging division if load is increasing. This
4534 * prevents us from getting stuck on 9 if the load is 10, for
4537 if (new_load > old_load)
4538 new_load += scale - 1;
4540 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4543 sched_avg_update(this_rq);
4546 /* Used instead of source_load when we know the type == 0 */
4547 static unsigned long weighted_cpuload(const int cpu)
4549 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4552 #ifdef CONFIG_NO_HZ_COMMON
4553 static void __update_cpu_load_nohz(struct rq *this_rq,
4554 unsigned long curr_jiffies,
4558 unsigned long pending_updates;
4560 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4561 if (pending_updates) {
4562 this_rq->last_load_update_tick = curr_jiffies;
4564 * In the regular NOHZ case, we were idle, this means load 0.
4565 * In the NOHZ_FULL case, we were non-idle, we should consider
4566 * its weighted load.
4568 __update_cpu_load(this_rq, load, pending_updates, active);
4573 * There is no sane way to deal with nohz on smp when using jiffies because the
4574 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4575 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4577 * Therefore we cannot use the delta approach from the regular tick since that
4578 * would seriously skew the load calculation. However we'll make do for those
4579 * updates happening while idle (nohz_idle_balance) or coming out of idle
4580 * (tick_nohz_idle_exit).
4582 * This means we might still be one tick off for nohz periods.
4586 * Called from nohz_idle_balance() to update the load ratings before doing the
4589 static void update_cpu_load_idle(struct rq *this_rq)
4592 * bail if there's load or we're actually up-to-date.
4594 if (weighted_cpuload(cpu_of(this_rq)))
4597 __update_cpu_load_nohz(this_rq, READ_ONCE(jiffies), 0, 0);
4601 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4603 void update_cpu_load_nohz(int active)
4605 struct rq *this_rq = this_rq();
4606 unsigned long curr_jiffies = READ_ONCE(jiffies);
4607 unsigned long load = active ? weighted_cpuload(cpu_of(this_rq)) : 0;
4609 if (curr_jiffies == this_rq->last_load_update_tick)
4612 raw_spin_lock(&this_rq->lock);
4613 __update_cpu_load_nohz(this_rq, curr_jiffies, load, active);
4614 raw_spin_unlock(&this_rq->lock);
4616 #endif /* CONFIG_NO_HZ */
4619 * Called from scheduler_tick()
4621 void update_cpu_load_active(struct rq *this_rq)
4623 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4625 * See the mess around update_cpu_load_idle() / update_cpu_load_nohz().
4627 this_rq->last_load_update_tick = jiffies;
4628 __update_cpu_load(this_rq, load, 1, 1);
4632 * Return a low guess at the load of a migration-source cpu weighted
4633 * according to the scheduling class and "nice" value.
4635 * We want to under-estimate the load of migration sources, to
4636 * balance conservatively.
4638 static unsigned long source_load(int cpu, int type)
4640 struct rq *rq = cpu_rq(cpu);
4641 unsigned long total = weighted_cpuload(cpu);
4643 if (type == 0 || !sched_feat(LB_BIAS))
4646 return min(rq->cpu_load[type-1], total);
4650 * Return a high guess at the load of a migration-target cpu weighted
4651 * according to the scheduling class and "nice" value.
4653 static unsigned long target_load(int cpu, int type)
4655 struct rq *rq = cpu_rq(cpu);
4656 unsigned long total = weighted_cpuload(cpu);
4658 if (type == 0 || !sched_feat(LB_BIAS))
4661 return max(rq->cpu_load[type-1], total);
4664 static unsigned long capacity_of(int cpu)
4666 return cpu_rq(cpu)->cpu_capacity;
4669 static unsigned long capacity_orig_of(int cpu)
4671 return cpu_rq(cpu)->cpu_capacity_orig;
4674 static unsigned long cpu_avg_load_per_task(int cpu)
4676 struct rq *rq = cpu_rq(cpu);
4677 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4678 unsigned long load_avg = weighted_cpuload(cpu);
4681 return load_avg / nr_running;
4686 static void record_wakee(struct task_struct *p)
4689 * Rough decay (wiping) for cost saving, don't worry
4690 * about the boundary, really active task won't care
4693 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4694 current->wakee_flips >>= 1;
4695 current->wakee_flip_decay_ts = jiffies;
4698 if (current->last_wakee != p) {
4699 current->last_wakee = p;
4700 current->wakee_flips++;
4704 static void task_waking_fair(struct task_struct *p)
4706 struct sched_entity *se = &p->se;
4707 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4710 #ifndef CONFIG_64BIT
4711 u64 min_vruntime_copy;
4714 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4716 min_vruntime = cfs_rq->min_vruntime;
4717 } while (min_vruntime != min_vruntime_copy);
4719 min_vruntime = cfs_rq->min_vruntime;
4722 se->vruntime -= min_vruntime;
4726 #ifdef CONFIG_FAIR_GROUP_SCHED
4728 * effective_load() calculates the load change as seen from the root_task_group
4730 * Adding load to a group doesn't make a group heavier, but can cause movement
4731 * of group shares between cpus. Assuming the shares were perfectly aligned one
4732 * can calculate the shift in shares.
4734 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4735 * on this @cpu and results in a total addition (subtraction) of @wg to the
4736 * total group weight.
4738 * Given a runqueue weight distribution (rw_i) we can compute a shares
4739 * distribution (s_i) using:
4741 * s_i = rw_i / \Sum rw_j (1)
4743 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4744 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4745 * shares distribution (s_i):
4747 * rw_i = { 2, 4, 1, 0 }
4748 * s_i = { 2/7, 4/7, 1/7, 0 }
4750 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4751 * task used to run on and the CPU the waker is running on), we need to
4752 * compute the effect of waking a task on either CPU and, in case of a sync
4753 * wakeup, compute the effect of the current task going to sleep.
4755 * So for a change of @wl to the local @cpu with an overall group weight change
4756 * of @wl we can compute the new shares distribution (s'_i) using:
4758 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4760 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4761 * differences in waking a task to CPU 0. The additional task changes the
4762 * weight and shares distributions like:
4764 * rw'_i = { 3, 4, 1, 0 }
4765 * s'_i = { 3/8, 4/8, 1/8, 0 }
4767 * We can then compute the difference in effective weight by using:
4769 * dw_i = S * (s'_i - s_i) (3)
4771 * Where 'S' is the group weight as seen by its parent.
4773 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4774 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4775 * 4/7) times the weight of the group.
4777 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4779 struct sched_entity *se = tg->se[cpu];
4781 if (!tg->parent) /* the trivial, non-cgroup case */
4784 for_each_sched_entity(se) {
4790 * W = @wg + \Sum rw_j
4792 W = wg + calc_tg_weight(tg, se->my_q);
4797 w = cfs_rq_load_avg(se->my_q) + wl;
4800 * wl = S * s'_i; see (2)
4803 wl = (w * (long)tg->shares) / W;
4808 * Per the above, wl is the new se->load.weight value; since
4809 * those are clipped to [MIN_SHARES, ...) do so now. See
4810 * calc_cfs_shares().
4812 if (wl < MIN_SHARES)
4816 * wl = dw_i = S * (s'_i - s_i); see (3)
4818 wl -= se->avg.load_avg;
4821 * Recursively apply this logic to all parent groups to compute
4822 * the final effective load change on the root group. Since
4823 * only the @tg group gets extra weight, all parent groups can
4824 * only redistribute existing shares. @wl is the shift in shares
4825 * resulting from this level per the above.
4834 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4842 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4843 * A waker of many should wake a different task than the one last awakened
4844 * at a frequency roughly N times higher than one of its wakees. In order
4845 * to determine whether we should let the load spread vs consolodating to
4846 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4847 * partner, and a factor of lls_size higher frequency in the other. With
4848 * both conditions met, we can be relatively sure that the relationship is
4849 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4850 * being client/server, worker/dispatcher, interrupt source or whatever is
4851 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4853 static int wake_wide(struct task_struct *p)
4855 unsigned int master = current->wakee_flips;
4856 unsigned int slave = p->wakee_flips;
4857 int factor = this_cpu_read(sd_llc_size);
4860 swap(master, slave);
4861 if (slave < factor || master < slave * factor)
4866 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4868 s64 this_load, load;
4869 s64 this_eff_load, prev_eff_load;
4870 int idx, this_cpu, prev_cpu;
4871 struct task_group *tg;
4872 unsigned long weight;
4876 this_cpu = smp_processor_id();
4877 prev_cpu = task_cpu(p);
4878 load = source_load(prev_cpu, idx);
4879 this_load = target_load(this_cpu, idx);
4882 * If sync wakeup then subtract the (maximum possible)
4883 * effect of the currently running task from the load
4884 * of the current CPU:
4887 tg = task_group(current);
4888 weight = current->se.avg.load_avg;
4890 this_load += effective_load(tg, this_cpu, -weight, -weight);
4891 load += effective_load(tg, prev_cpu, 0, -weight);
4895 weight = p->se.avg.load_avg;
4898 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4899 * due to the sync cause above having dropped this_load to 0, we'll
4900 * always have an imbalance, but there's really nothing you can do
4901 * about that, so that's good too.
4903 * Otherwise check if either cpus are near enough in load to allow this
4904 * task to be woken on this_cpu.
4906 this_eff_load = 100;
4907 this_eff_load *= capacity_of(prev_cpu);
4909 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4910 prev_eff_load *= capacity_of(this_cpu);
4912 if (this_load > 0) {
4913 this_eff_load *= this_load +
4914 effective_load(tg, this_cpu, weight, weight);
4916 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4919 balanced = this_eff_load <= prev_eff_load;
4921 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4926 schedstat_inc(sd, ttwu_move_affine);
4927 schedstat_inc(p, se.statistics.nr_wakeups_affine);
4933 * find_idlest_group finds and returns the least busy CPU group within the
4936 static struct sched_group *
4937 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4938 int this_cpu, int sd_flag)
4940 struct sched_group *idlest = NULL, *group = sd->groups;
4941 unsigned long min_load = ULONG_MAX, this_load = 0;
4942 int load_idx = sd->forkexec_idx;
4943 int imbalance = 100 + (sd->imbalance_pct-100)/2;
4945 if (sd_flag & SD_BALANCE_WAKE)
4946 load_idx = sd->wake_idx;
4949 unsigned long load, avg_load;
4953 /* Skip over this group if it has no CPUs allowed */
4954 if (!cpumask_intersects(sched_group_cpus(group),
4955 tsk_cpus_allowed(p)))
4958 local_group = cpumask_test_cpu(this_cpu,
4959 sched_group_cpus(group));
4961 /* Tally up the load of all CPUs in the group */
4964 for_each_cpu(i, sched_group_cpus(group)) {
4965 /* Bias balancing toward cpus of our domain */
4967 load = source_load(i, load_idx);
4969 load = target_load(i, load_idx);
4974 /* Adjust by relative CPU capacity of the group */
4975 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4978 this_load = avg_load;
4979 } else if (avg_load < min_load) {
4980 min_load = avg_load;
4983 } while (group = group->next, group != sd->groups);
4985 if (!idlest || 100*this_load < imbalance*min_load)
4991 * find_idlest_cpu - find the idlest cpu among the cpus in group.
4994 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4996 unsigned long load, min_load = ULONG_MAX;
4997 unsigned int min_exit_latency = UINT_MAX;
4998 u64 latest_idle_timestamp = 0;
4999 int least_loaded_cpu = this_cpu;
5000 int shallowest_idle_cpu = -1;
5003 /* Traverse only the allowed CPUs */
5004 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5006 struct rq *rq = cpu_rq(i);
5007 struct cpuidle_state *idle = idle_get_state(rq);
5008 if (idle && idle->exit_latency < min_exit_latency) {
5010 * We give priority to a CPU whose idle state
5011 * has the smallest exit latency irrespective
5012 * of any idle timestamp.
5014 min_exit_latency = idle->exit_latency;
5015 latest_idle_timestamp = rq->idle_stamp;
5016 shallowest_idle_cpu = i;
5017 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
5018 rq->idle_stamp > latest_idle_timestamp) {
5020 * If equal or no active idle state, then
5021 * the most recently idled CPU might have
5024 latest_idle_timestamp = rq->idle_stamp;
5025 shallowest_idle_cpu = i;
5027 } else if (shallowest_idle_cpu == -1) {
5028 load = weighted_cpuload(i);
5029 if (load < min_load || (load == min_load && i == this_cpu)) {
5031 least_loaded_cpu = i;
5036 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5040 * Try and locate an idle CPU in the sched_domain.
5042 static int select_idle_sibling(struct task_struct *p, int target)
5044 struct sched_domain *sd;
5045 struct sched_group *sg;
5046 int i = task_cpu(p);
5048 if (idle_cpu(target))
5052 * If the prevous cpu is cache affine and idle, don't be stupid.
5054 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5058 * Otherwise, iterate the domains and find an eligible idle cpu.
5060 * A completely idle sched group at higher domains is more
5061 * desirable than an idle group at a lower level, because lower
5062 * domains have smaller groups and usually share hardware
5063 * resources which causes tasks to contend on them, e.g. x86
5064 * hyperthread siblings in the lowest domain (SMT) can contend
5065 * on the shared cpu pipeline.
5067 * However, while we prefer idle groups at higher domains
5068 * finding an idle cpu at the lowest domain is still better than
5069 * returning 'target', which we've already established, isn't
5072 sd = rcu_dereference(per_cpu(sd_llc, target));
5073 for_each_lower_domain(sd) {
5076 if (!cpumask_intersects(sched_group_cpus(sg),
5077 tsk_cpus_allowed(p)))
5080 /* Ensure the entire group is idle */
5081 for_each_cpu(i, sched_group_cpus(sg)) {
5082 if (i == target || !idle_cpu(i))
5087 * It doesn't matter which cpu we pick, the
5088 * whole group is idle.
5090 target = cpumask_first_and(sched_group_cpus(sg),
5091 tsk_cpus_allowed(p));
5095 } while (sg != sd->groups);
5102 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5103 * tasks. The unit of the return value must be the one of capacity so we can
5104 * compare the utilization with the capacity of the CPU that is available for
5105 * CFS task (ie cpu_capacity).
5107 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5108 * recent utilization of currently non-runnable tasks on a CPU. It represents
5109 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5110 * capacity_orig is the cpu_capacity available at the highest frequency
5111 * (arch_scale_freq_capacity()).
5112 * The utilization of a CPU converges towards a sum equal to or less than the
5113 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5114 * the running time on this CPU scaled by capacity_curr.
5116 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5117 * higher than capacity_orig because of unfortunate rounding in
5118 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5119 * the average stabilizes with the new running time. We need to check that the
5120 * utilization stays within the range of [0..capacity_orig] and cap it if
5121 * necessary. Without utilization capping, a group could be seen as overloaded
5122 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5123 * available capacity. We allow utilization to overshoot capacity_curr (but not
5124 * capacity_orig) as it useful for predicting the capacity required after task
5125 * migrations (scheduler-driven DVFS).
5127 static int cpu_util(int cpu)
5129 unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5130 unsigned long capacity = capacity_orig_of(cpu);
5132 return (util >= capacity) ? capacity : util;
5136 * select_task_rq_fair: Select target runqueue for the waking task in domains
5137 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5138 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5140 * Balances load by selecting the idlest cpu in the idlest group, or under
5141 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5143 * Returns the target cpu number.
5145 * preempt must be disabled.
5148 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5150 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5151 int cpu = smp_processor_id();
5152 int new_cpu = prev_cpu;
5153 int want_affine = 0;
5154 int sync = wake_flags & WF_SYNC;
5156 if (sd_flag & SD_BALANCE_WAKE)
5157 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
5160 for_each_domain(cpu, tmp) {
5161 if (!(tmp->flags & SD_LOAD_BALANCE))
5165 * If both cpu and prev_cpu are part of this domain,
5166 * cpu is a valid SD_WAKE_AFFINE target.
5168 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5169 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5174 if (tmp->flags & sd_flag)
5176 else if (!want_affine)
5181 sd = NULL; /* Prefer wake_affine over balance flags */
5182 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5187 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5188 new_cpu = select_idle_sibling(p, new_cpu);
5191 struct sched_group *group;
5194 if (!(sd->flags & sd_flag)) {
5199 group = find_idlest_group(sd, p, cpu, sd_flag);
5205 new_cpu = find_idlest_cpu(group, p, cpu);
5206 if (new_cpu == -1 || new_cpu == cpu) {
5207 /* Now try balancing at a lower domain level of cpu */
5212 /* Now try balancing at a lower domain level of new_cpu */
5214 weight = sd->span_weight;
5216 for_each_domain(cpu, tmp) {
5217 if (weight <= tmp->span_weight)
5219 if (tmp->flags & sd_flag)
5222 /* while loop will break here if sd == NULL */
5230 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5231 * cfs_rq_of(p) references at time of call are still valid and identify the
5232 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5234 static void migrate_task_rq_fair(struct task_struct *p)
5237 * We are supposed to update the task to "current" time, then its up to date
5238 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5239 * what current time is, so simply throw away the out-of-date time. This
5240 * will result in the wakee task is less decayed, but giving the wakee more
5241 * load sounds not bad.
5243 remove_entity_load_avg(&p->se);
5245 /* Tell new CPU we are migrated */
5246 p->se.avg.last_update_time = 0;
5248 /* We have migrated, no longer consider this task hot */
5249 p->se.exec_start = 0;
5252 static void task_dead_fair(struct task_struct *p)
5254 remove_entity_load_avg(&p->se);
5256 #endif /* CONFIG_SMP */
5258 static unsigned long
5259 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5261 unsigned long gran = sysctl_sched_wakeup_granularity;
5264 * Since its curr running now, convert the gran from real-time
5265 * to virtual-time in his units.
5267 * By using 'se' instead of 'curr' we penalize light tasks, so
5268 * they get preempted easier. That is, if 'se' < 'curr' then
5269 * the resulting gran will be larger, therefore penalizing the
5270 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5271 * be smaller, again penalizing the lighter task.
5273 * This is especially important for buddies when the leftmost
5274 * task is higher priority than the buddy.
5276 return calc_delta_fair(gran, se);
5280 * Should 'se' preempt 'curr'.
5294 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5296 s64 gran, vdiff = curr->vruntime - se->vruntime;
5301 gran = wakeup_gran(curr, se);
5308 static void set_last_buddy(struct sched_entity *se)
5310 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5313 for_each_sched_entity(se)
5314 cfs_rq_of(se)->last = se;
5317 static void set_next_buddy(struct sched_entity *se)
5319 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5322 for_each_sched_entity(se)
5323 cfs_rq_of(se)->next = se;
5326 static void set_skip_buddy(struct sched_entity *se)
5328 for_each_sched_entity(se)
5329 cfs_rq_of(se)->skip = se;
5333 * Preempt the current task with a newly woken task if needed:
5335 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5337 struct task_struct *curr = rq->curr;
5338 struct sched_entity *se = &curr->se, *pse = &p->se;
5339 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5340 int scale = cfs_rq->nr_running >= sched_nr_latency;
5341 int next_buddy_marked = 0;
5343 if (unlikely(se == pse))
5347 * This is possible from callers such as attach_tasks(), in which we
5348 * unconditionally check_prempt_curr() after an enqueue (which may have
5349 * lead to a throttle). This both saves work and prevents false
5350 * next-buddy nomination below.
5352 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5355 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5356 set_next_buddy(pse);
5357 next_buddy_marked = 1;
5361 * We can come here with TIF_NEED_RESCHED already set from new task
5364 * Note: this also catches the edge-case of curr being in a throttled
5365 * group (e.g. via set_curr_task), since update_curr() (in the
5366 * enqueue of curr) will have resulted in resched being set. This
5367 * prevents us from potentially nominating it as a false LAST_BUDDY
5370 if (test_tsk_need_resched(curr))
5373 /* Idle tasks are by definition preempted by non-idle tasks. */
5374 if (unlikely(curr->policy == SCHED_IDLE) &&
5375 likely(p->policy != SCHED_IDLE))
5379 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5380 * is driven by the tick):
5382 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5385 find_matching_se(&se, &pse);
5386 update_curr(cfs_rq_of(se));
5388 if (wakeup_preempt_entity(se, pse) == 1) {
5390 * Bias pick_next to pick the sched entity that is
5391 * triggering this preemption.
5393 if (!next_buddy_marked)
5394 set_next_buddy(pse);
5403 * Only set the backward buddy when the current task is still
5404 * on the rq. This can happen when a wakeup gets interleaved
5405 * with schedule on the ->pre_schedule() or idle_balance()
5406 * point, either of which can * drop the rq lock.
5408 * Also, during early boot the idle thread is in the fair class,
5409 * for obvious reasons its a bad idea to schedule back to it.
5411 if (unlikely(!se->on_rq || curr == rq->idle))
5414 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5418 static struct task_struct *
5419 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5421 struct cfs_rq *cfs_rq = &rq->cfs;
5422 struct sched_entity *se;
5423 struct task_struct *p;
5427 #ifdef CONFIG_FAIR_GROUP_SCHED
5428 if (!cfs_rq->nr_running)
5431 if (prev->sched_class != &fair_sched_class)
5435 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5436 * likely that a next task is from the same cgroup as the current.
5438 * Therefore attempt to avoid putting and setting the entire cgroup
5439 * hierarchy, only change the part that actually changes.
5443 struct sched_entity *curr = cfs_rq->curr;
5446 * Since we got here without doing put_prev_entity() we also
5447 * have to consider cfs_rq->curr. If it is still a runnable
5448 * entity, update_curr() will update its vruntime, otherwise
5449 * forget we've ever seen it.
5453 update_curr(cfs_rq);
5458 * This call to check_cfs_rq_runtime() will do the
5459 * throttle and dequeue its entity in the parent(s).
5460 * Therefore the 'simple' nr_running test will indeed
5463 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5467 se = pick_next_entity(cfs_rq, curr);
5468 cfs_rq = group_cfs_rq(se);
5474 * Since we haven't yet done put_prev_entity and if the selected task
5475 * is a different task than we started out with, try and touch the
5476 * least amount of cfs_rqs.
5479 struct sched_entity *pse = &prev->se;
5481 while (!(cfs_rq = is_same_group(se, pse))) {
5482 int se_depth = se->depth;
5483 int pse_depth = pse->depth;
5485 if (se_depth <= pse_depth) {
5486 put_prev_entity(cfs_rq_of(pse), pse);
5487 pse = parent_entity(pse);
5489 if (se_depth >= pse_depth) {
5490 set_next_entity(cfs_rq_of(se), se);
5491 se = parent_entity(se);
5495 put_prev_entity(cfs_rq, pse);
5496 set_next_entity(cfs_rq, se);
5499 if (hrtick_enabled(rq))
5500 hrtick_start_fair(rq, p);
5507 if (!cfs_rq->nr_running)
5510 put_prev_task(rq, prev);
5513 se = pick_next_entity(cfs_rq, NULL);
5514 set_next_entity(cfs_rq, se);
5515 cfs_rq = group_cfs_rq(se);
5520 if (hrtick_enabled(rq))
5521 hrtick_start_fair(rq, p);
5527 * This is OK, because current is on_cpu, which avoids it being picked
5528 * for load-balance and preemption/IRQs are still disabled avoiding
5529 * further scheduler activity on it and we're being very careful to
5530 * re-start the picking loop.
5532 lockdep_unpin_lock(&rq->lock);
5533 new_tasks = idle_balance(rq);
5534 lockdep_pin_lock(&rq->lock);
5536 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5537 * possible for any higher priority task to appear. In that case we
5538 * must re-start the pick_next_entity() loop.
5550 * Account for a descheduled task:
5552 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5554 struct sched_entity *se = &prev->se;
5555 struct cfs_rq *cfs_rq;
5557 for_each_sched_entity(se) {
5558 cfs_rq = cfs_rq_of(se);
5559 put_prev_entity(cfs_rq, se);
5564 * sched_yield() is very simple
5566 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5568 static void yield_task_fair(struct rq *rq)
5570 struct task_struct *curr = rq->curr;
5571 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5572 struct sched_entity *se = &curr->se;
5575 * Are we the only task in the tree?
5577 if (unlikely(rq->nr_running == 1))
5580 clear_buddies(cfs_rq, se);
5582 if (curr->policy != SCHED_BATCH) {
5583 update_rq_clock(rq);
5585 * Update run-time statistics of the 'current'.
5587 update_curr(cfs_rq);
5589 * Tell update_rq_clock() that we've just updated,
5590 * so we don't do microscopic update in schedule()
5591 * and double the fastpath cost.
5593 rq_clock_skip_update(rq, true);
5599 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5601 struct sched_entity *se = &p->se;
5603 /* throttled hierarchies are not runnable */
5604 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5607 /* Tell the scheduler that we'd really like pse to run next. */
5610 yield_task_fair(rq);
5616 /**************************************************
5617 * Fair scheduling class load-balancing methods.
5621 * The purpose of load-balancing is to achieve the same basic fairness the
5622 * per-cpu scheduler provides, namely provide a proportional amount of compute
5623 * time to each task. This is expressed in the following equation:
5625 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5627 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5628 * W_i,0 is defined as:
5630 * W_i,0 = \Sum_j w_i,j (2)
5632 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5633 * is derived from the nice value as per prio_to_weight[].
5635 * The weight average is an exponential decay average of the instantaneous
5638 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5640 * C_i is the compute capacity of cpu i, typically it is the
5641 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5642 * can also include other factors [XXX].
5644 * To achieve this balance we define a measure of imbalance which follows
5645 * directly from (1):
5647 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5649 * We them move tasks around to minimize the imbalance. In the continuous
5650 * function space it is obvious this converges, in the discrete case we get
5651 * a few fun cases generally called infeasible weight scenarios.
5654 * - infeasible weights;
5655 * - local vs global optima in the discrete case. ]
5660 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5661 * for all i,j solution, we create a tree of cpus that follows the hardware
5662 * topology where each level pairs two lower groups (or better). This results
5663 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5664 * tree to only the first of the previous level and we decrease the frequency
5665 * of load-balance at each level inv. proportional to the number of cpus in
5671 * \Sum { --- * --- * 2^i } = O(n) (5)
5673 * `- size of each group
5674 * | | `- number of cpus doing load-balance
5676 * `- sum over all levels
5678 * Coupled with a limit on how many tasks we can migrate every balance pass,
5679 * this makes (5) the runtime complexity of the balancer.
5681 * An important property here is that each CPU is still (indirectly) connected
5682 * to every other cpu in at most O(log n) steps:
5684 * The adjacency matrix of the resulting graph is given by:
5687 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5690 * And you'll find that:
5692 * A^(log_2 n)_i,j != 0 for all i,j (7)
5694 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5695 * The task movement gives a factor of O(m), giving a convergence complexity
5698 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5703 * In order to avoid CPUs going idle while there's still work to do, new idle
5704 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5705 * tree itself instead of relying on other CPUs to bring it work.
5707 * This adds some complexity to both (5) and (8) but it reduces the total idle
5715 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5718 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5723 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5725 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5727 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5730 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5731 * rewrite all of this once again.]
5734 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5736 enum fbq_type { regular, remote, all };
5738 #define LBF_ALL_PINNED 0x01
5739 #define LBF_NEED_BREAK 0x02
5740 #define LBF_DST_PINNED 0x04
5741 #define LBF_SOME_PINNED 0x08
5744 struct sched_domain *sd;
5752 struct cpumask *dst_grpmask;
5754 enum cpu_idle_type idle;
5756 /* The set of CPUs under consideration for load-balancing */
5757 struct cpumask *cpus;
5762 unsigned int loop_break;
5763 unsigned int loop_max;
5765 enum fbq_type fbq_type;
5766 struct list_head tasks;
5770 * Is this task likely cache-hot:
5772 static int task_hot(struct task_struct *p, struct lb_env *env)
5776 lockdep_assert_held(&env->src_rq->lock);
5778 if (p->sched_class != &fair_sched_class)
5781 if (unlikely(p->policy == SCHED_IDLE))
5785 * Buddy candidates are cache hot:
5787 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5788 (&p->se == cfs_rq_of(&p->se)->next ||
5789 &p->se == cfs_rq_of(&p->se)->last))
5792 if (sysctl_sched_migration_cost == -1)
5794 if (sysctl_sched_migration_cost == 0)
5797 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5799 return delta < (s64)sysctl_sched_migration_cost;
5802 #ifdef CONFIG_NUMA_BALANCING
5804 * Returns 1, if task migration degrades locality
5805 * Returns 0, if task migration improves locality i.e migration preferred.
5806 * Returns -1, if task migration is not affected by locality.
5808 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5810 struct numa_group *numa_group = rcu_dereference(p->numa_group);
5811 unsigned long src_faults, dst_faults;
5812 int src_nid, dst_nid;
5814 if (!static_branch_likely(&sched_numa_balancing))
5817 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5820 src_nid = cpu_to_node(env->src_cpu);
5821 dst_nid = cpu_to_node(env->dst_cpu);
5823 if (src_nid == dst_nid)
5826 /* Migrating away from the preferred node is always bad. */
5827 if (src_nid == p->numa_preferred_nid) {
5828 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
5834 /* Encourage migration to the preferred node. */
5835 if (dst_nid == p->numa_preferred_nid)
5839 src_faults = group_faults(p, src_nid);
5840 dst_faults = group_faults(p, dst_nid);
5842 src_faults = task_faults(p, src_nid);
5843 dst_faults = task_faults(p, dst_nid);
5846 return dst_faults < src_faults;
5850 static inline int migrate_degrades_locality(struct task_struct *p,
5858 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5861 int can_migrate_task(struct task_struct *p, struct lb_env *env)
5865 lockdep_assert_held(&env->src_rq->lock);
5868 * We do not migrate tasks that are:
5869 * 1) throttled_lb_pair, or
5870 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5871 * 3) running (obviously), or
5872 * 4) are cache-hot on their current CPU.
5874 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5877 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5880 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5882 env->flags |= LBF_SOME_PINNED;
5885 * Remember if this task can be migrated to any other cpu in
5886 * our sched_group. We may want to revisit it if we couldn't
5887 * meet load balance goals by pulling other tasks on src_cpu.
5889 * Also avoid computing new_dst_cpu if we have already computed
5890 * one in current iteration.
5892 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5895 /* Prevent to re-select dst_cpu via env's cpus */
5896 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5897 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5898 env->flags |= LBF_DST_PINNED;
5899 env->new_dst_cpu = cpu;
5907 /* Record that we found atleast one task that could run on dst_cpu */
5908 env->flags &= ~LBF_ALL_PINNED;
5910 if (task_running(env->src_rq, p)) {
5911 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5916 * Aggressive migration if:
5917 * 1) destination numa is preferred
5918 * 2) task is cache cold, or
5919 * 3) too many balance attempts have failed.
5921 tsk_cache_hot = migrate_degrades_locality(p, env);
5922 if (tsk_cache_hot == -1)
5923 tsk_cache_hot = task_hot(p, env);
5925 if (tsk_cache_hot <= 0 ||
5926 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5927 if (tsk_cache_hot == 1) {
5928 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5929 schedstat_inc(p, se.statistics.nr_forced_migrations);
5934 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5939 * detach_task() -- detach the task for the migration specified in env
5941 static void detach_task(struct task_struct *p, struct lb_env *env)
5943 lockdep_assert_held(&env->src_rq->lock);
5945 p->on_rq = TASK_ON_RQ_MIGRATING;
5946 deactivate_task(env->src_rq, p, 0);
5947 set_task_cpu(p, env->dst_cpu);
5951 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5952 * part of active balancing operations within "domain".
5954 * Returns a task if successful and NULL otherwise.
5956 static struct task_struct *detach_one_task(struct lb_env *env)
5958 struct task_struct *p, *n;
5960 lockdep_assert_held(&env->src_rq->lock);
5962 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5963 if (!can_migrate_task(p, env))
5966 detach_task(p, env);
5969 * Right now, this is only the second place where
5970 * lb_gained[env->idle] is updated (other is detach_tasks)
5971 * so we can safely collect stats here rather than
5972 * inside detach_tasks().
5974 schedstat_inc(env->sd, lb_gained[env->idle]);
5980 static const unsigned int sched_nr_migrate_break = 32;
5983 * detach_tasks() -- tries to detach up to imbalance weighted load from
5984 * busiest_rq, as part of a balancing operation within domain "sd".
5986 * Returns number of detached tasks if successful and 0 otherwise.
5988 static int detach_tasks(struct lb_env *env)
5990 struct list_head *tasks = &env->src_rq->cfs_tasks;
5991 struct task_struct *p;
5995 lockdep_assert_held(&env->src_rq->lock);
5997 if (env->imbalance <= 0)
6000 while (!list_empty(tasks)) {
6002 * We don't want to steal all, otherwise we may be treated likewise,
6003 * which could at worst lead to a livelock crash.
6005 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6008 p = list_first_entry(tasks, struct task_struct, se.group_node);
6011 /* We've more or less seen every task there is, call it quits */
6012 if (env->loop > env->loop_max)
6015 /* take a breather every nr_migrate tasks */
6016 if (env->loop > env->loop_break) {
6017 env->loop_break += sched_nr_migrate_break;
6018 env->flags |= LBF_NEED_BREAK;
6022 if (!can_migrate_task(p, env))
6025 load = task_h_load(p);
6027 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6030 if ((load / 2) > env->imbalance)
6033 detach_task(p, env);
6034 list_add(&p->se.group_node, &env->tasks);
6037 env->imbalance -= load;
6039 #ifdef CONFIG_PREEMPT
6041 * NEWIDLE balancing is a source of latency, so preemptible
6042 * kernels will stop after the first task is detached to minimize
6043 * the critical section.
6045 if (env->idle == CPU_NEWLY_IDLE)
6050 * We only want to steal up to the prescribed amount of
6053 if (env->imbalance <= 0)
6058 list_move_tail(&p->se.group_node, tasks);
6062 * Right now, this is one of only two places we collect this stat
6063 * so we can safely collect detach_one_task() stats here rather
6064 * than inside detach_one_task().
6066 schedstat_add(env->sd, lb_gained[env->idle], detached);
6072 * attach_task() -- attach the task detached by detach_task() to its new rq.
6074 static void attach_task(struct rq *rq, struct task_struct *p)
6076 lockdep_assert_held(&rq->lock);
6078 BUG_ON(task_rq(p) != rq);
6079 activate_task(rq, p, 0);
6080 p->on_rq = TASK_ON_RQ_QUEUED;
6081 check_preempt_curr(rq, p, 0);
6085 * attach_one_task() -- attaches the task returned from detach_one_task() to
6088 static void attach_one_task(struct rq *rq, struct task_struct *p)
6090 raw_spin_lock(&rq->lock);
6092 raw_spin_unlock(&rq->lock);
6096 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6099 static void attach_tasks(struct lb_env *env)
6101 struct list_head *tasks = &env->tasks;
6102 struct task_struct *p;
6104 raw_spin_lock(&env->dst_rq->lock);
6106 while (!list_empty(tasks)) {
6107 p = list_first_entry(tasks, struct task_struct, se.group_node);
6108 list_del_init(&p->se.group_node);
6110 attach_task(env->dst_rq, p);
6113 raw_spin_unlock(&env->dst_rq->lock);
6116 #ifdef CONFIG_FAIR_GROUP_SCHED
6117 static void update_blocked_averages(int cpu)
6119 struct rq *rq = cpu_rq(cpu);
6120 struct cfs_rq *cfs_rq;
6121 unsigned long flags;
6123 raw_spin_lock_irqsave(&rq->lock, flags);
6124 update_rq_clock(rq);
6127 * Iterates the task_group tree in a bottom up fashion, see
6128 * list_add_leaf_cfs_rq() for details.
6130 for_each_leaf_cfs_rq(rq, cfs_rq) {
6131 /* throttled entities do not contribute to load */
6132 if (throttled_hierarchy(cfs_rq))
6135 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6136 update_tg_load_avg(cfs_rq, 0);
6138 raw_spin_unlock_irqrestore(&rq->lock, flags);
6142 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6143 * This needs to be done in a top-down fashion because the load of a child
6144 * group is a fraction of its parents load.
6146 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6148 struct rq *rq = rq_of(cfs_rq);
6149 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6150 unsigned long now = jiffies;
6153 if (cfs_rq->last_h_load_update == now)
6156 cfs_rq->h_load_next = NULL;
6157 for_each_sched_entity(se) {
6158 cfs_rq = cfs_rq_of(se);
6159 cfs_rq->h_load_next = se;
6160 if (cfs_rq->last_h_load_update == now)
6165 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6166 cfs_rq->last_h_load_update = now;
6169 while ((se = cfs_rq->h_load_next) != NULL) {
6170 load = cfs_rq->h_load;
6171 load = div64_ul(load * se->avg.load_avg,
6172 cfs_rq_load_avg(cfs_rq) + 1);
6173 cfs_rq = group_cfs_rq(se);
6174 cfs_rq->h_load = load;
6175 cfs_rq->last_h_load_update = now;
6179 static unsigned long task_h_load(struct task_struct *p)
6181 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6183 update_cfs_rq_h_load(cfs_rq);
6184 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6185 cfs_rq_load_avg(cfs_rq) + 1);
6188 static inline void update_blocked_averages(int cpu)
6190 struct rq *rq = cpu_rq(cpu);
6191 struct cfs_rq *cfs_rq = &rq->cfs;
6192 unsigned long flags;
6194 raw_spin_lock_irqsave(&rq->lock, flags);
6195 update_rq_clock(rq);
6196 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6197 raw_spin_unlock_irqrestore(&rq->lock, flags);
6200 static unsigned long task_h_load(struct task_struct *p)
6202 return p->se.avg.load_avg;
6206 /********** Helpers for find_busiest_group ************************/
6215 * sg_lb_stats - stats of a sched_group required for load_balancing
6217 struct sg_lb_stats {
6218 unsigned long avg_load; /*Avg load across the CPUs of the group */
6219 unsigned long group_load; /* Total load over the CPUs of the group */
6220 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6221 unsigned long load_per_task;
6222 unsigned long group_capacity;
6223 unsigned long group_util; /* Total utilization of the group */
6224 unsigned int sum_nr_running; /* Nr tasks running in the group */
6225 unsigned int idle_cpus;
6226 unsigned int group_weight;
6227 enum group_type group_type;
6228 int group_no_capacity;
6229 #ifdef CONFIG_NUMA_BALANCING
6230 unsigned int nr_numa_running;
6231 unsigned int nr_preferred_running;
6236 * sd_lb_stats - Structure to store the statistics of a sched_domain
6237 * during load balancing.
6239 struct sd_lb_stats {
6240 struct sched_group *busiest; /* Busiest group in this sd */
6241 struct sched_group *local; /* Local group in this sd */
6242 unsigned long total_load; /* Total load of all groups in sd */
6243 unsigned long total_capacity; /* Total capacity of all groups in sd */
6244 unsigned long avg_load; /* Average load across all groups in sd */
6246 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6247 struct sg_lb_stats local_stat; /* Statistics of the local group */
6250 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6253 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6254 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6255 * We must however clear busiest_stat::avg_load because
6256 * update_sd_pick_busiest() reads this before assignment.
6258 *sds = (struct sd_lb_stats){
6262 .total_capacity = 0UL,
6265 .sum_nr_running = 0,
6266 .group_type = group_other,
6272 * get_sd_load_idx - Obtain the load index for a given sched domain.
6273 * @sd: The sched_domain whose load_idx is to be obtained.
6274 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6276 * Return: The load index.
6278 static inline int get_sd_load_idx(struct sched_domain *sd,
6279 enum cpu_idle_type idle)
6285 load_idx = sd->busy_idx;
6288 case CPU_NEWLY_IDLE:
6289 load_idx = sd->newidle_idx;
6292 load_idx = sd->idle_idx;
6299 static unsigned long scale_rt_capacity(int cpu)
6301 struct rq *rq = cpu_rq(cpu);
6302 u64 total, used, age_stamp, avg;
6306 * Since we're reading these variables without serialization make sure
6307 * we read them once before doing sanity checks on them.
6309 age_stamp = READ_ONCE(rq->age_stamp);
6310 avg = READ_ONCE(rq->rt_avg);
6311 delta = __rq_clock_broken(rq) - age_stamp;
6313 if (unlikely(delta < 0))
6316 total = sched_avg_period() + delta;
6318 used = div_u64(avg, total);
6320 if (likely(used < SCHED_CAPACITY_SCALE))
6321 return SCHED_CAPACITY_SCALE - used;
6326 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6328 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6329 struct sched_group *sdg = sd->groups;
6331 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6333 capacity *= scale_rt_capacity(cpu);
6334 capacity >>= SCHED_CAPACITY_SHIFT;
6339 cpu_rq(cpu)->cpu_capacity = capacity;
6340 sdg->sgc->capacity = capacity;
6343 void update_group_capacity(struct sched_domain *sd, int cpu)
6345 struct sched_domain *child = sd->child;
6346 struct sched_group *group, *sdg = sd->groups;
6347 unsigned long capacity;
6348 unsigned long interval;
6350 interval = msecs_to_jiffies(sd->balance_interval);
6351 interval = clamp(interval, 1UL, max_load_balance_interval);
6352 sdg->sgc->next_update = jiffies + interval;
6355 update_cpu_capacity(sd, cpu);
6361 if (child->flags & SD_OVERLAP) {
6363 * SD_OVERLAP domains cannot assume that child groups
6364 * span the current group.
6367 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6368 struct sched_group_capacity *sgc;
6369 struct rq *rq = cpu_rq(cpu);
6372 * build_sched_domains() -> init_sched_groups_capacity()
6373 * gets here before we've attached the domains to the
6376 * Use capacity_of(), which is set irrespective of domains
6377 * in update_cpu_capacity().
6379 * This avoids capacity from being 0 and
6380 * causing divide-by-zero issues on boot.
6382 if (unlikely(!rq->sd)) {
6383 capacity += capacity_of(cpu);
6387 sgc = rq->sd->groups->sgc;
6388 capacity += sgc->capacity;
6392 * !SD_OVERLAP domains can assume that child groups
6393 * span the current group.
6396 group = child->groups;
6398 capacity += group->sgc->capacity;
6399 group = group->next;
6400 } while (group != child->groups);
6403 sdg->sgc->capacity = capacity;
6407 * Check whether the capacity of the rq has been noticeably reduced by side
6408 * activity. The imbalance_pct is used for the threshold.
6409 * Return true is the capacity is reduced
6412 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6414 return ((rq->cpu_capacity * sd->imbalance_pct) <
6415 (rq->cpu_capacity_orig * 100));
6419 * Group imbalance indicates (and tries to solve) the problem where balancing
6420 * groups is inadequate due to tsk_cpus_allowed() constraints.
6422 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6423 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6426 * { 0 1 2 3 } { 4 5 6 7 }
6429 * If we were to balance group-wise we'd place two tasks in the first group and
6430 * two tasks in the second group. Clearly this is undesired as it will overload
6431 * cpu 3 and leave one of the cpus in the second group unused.
6433 * The current solution to this issue is detecting the skew in the first group
6434 * by noticing the lower domain failed to reach balance and had difficulty
6435 * moving tasks due to affinity constraints.
6437 * When this is so detected; this group becomes a candidate for busiest; see
6438 * update_sd_pick_busiest(). And calculate_imbalance() and
6439 * find_busiest_group() avoid some of the usual balance conditions to allow it
6440 * to create an effective group imbalance.
6442 * This is a somewhat tricky proposition since the next run might not find the
6443 * group imbalance and decide the groups need to be balanced again. A most
6444 * subtle and fragile situation.
6447 static inline int sg_imbalanced(struct sched_group *group)
6449 return group->sgc->imbalance;
6453 * group_has_capacity returns true if the group has spare capacity that could
6454 * be used by some tasks.
6455 * We consider that a group has spare capacity if the * number of task is
6456 * smaller than the number of CPUs or if the utilization is lower than the
6457 * available capacity for CFS tasks.
6458 * For the latter, we use a threshold to stabilize the state, to take into
6459 * account the variance of the tasks' load and to return true if the available
6460 * capacity in meaningful for the load balancer.
6461 * As an example, an available capacity of 1% can appear but it doesn't make
6462 * any benefit for the load balance.
6465 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6467 if (sgs->sum_nr_running < sgs->group_weight)
6470 if ((sgs->group_capacity * 100) >
6471 (sgs->group_util * env->sd->imbalance_pct))
6478 * group_is_overloaded returns true if the group has more tasks than it can
6480 * group_is_overloaded is not equals to !group_has_capacity because a group
6481 * with the exact right number of tasks, has no more spare capacity but is not
6482 * overloaded so both group_has_capacity and group_is_overloaded return
6486 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6488 if (sgs->sum_nr_running <= sgs->group_weight)
6491 if ((sgs->group_capacity * 100) <
6492 (sgs->group_util * env->sd->imbalance_pct))
6499 group_type group_classify(struct sched_group *group,
6500 struct sg_lb_stats *sgs)
6502 if (sgs->group_no_capacity)
6503 return group_overloaded;
6505 if (sg_imbalanced(group))
6506 return group_imbalanced;
6512 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6513 * @env: The load balancing environment.
6514 * @group: sched_group whose statistics are to be updated.
6515 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6516 * @local_group: Does group contain this_cpu.
6517 * @sgs: variable to hold the statistics for this group.
6518 * @overload: Indicate more than one runnable task for any CPU.
6520 static inline void update_sg_lb_stats(struct lb_env *env,
6521 struct sched_group *group, int load_idx,
6522 int local_group, struct sg_lb_stats *sgs,
6528 memset(sgs, 0, sizeof(*sgs));
6530 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6531 struct rq *rq = cpu_rq(i);
6533 /* Bias balancing toward cpus of our domain */
6535 load = target_load(i, load_idx);
6537 load = source_load(i, load_idx);
6539 sgs->group_load += load;
6540 sgs->group_util += cpu_util(i);
6541 sgs->sum_nr_running += rq->cfs.h_nr_running;
6543 nr_running = rq->nr_running;
6547 #ifdef CONFIG_NUMA_BALANCING
6548 sgs->nr_numa_running += rq->nr_numa_running;
6549 sgs->nr_preferred_running += rq->nr_preferred_running;
6551 sgs->sum_weighted_load += weighted_cpuload(i);
6553 * No need to call idle_cpu() if nr_running is not 0
6555 if (!nr_running && idle_cpu(i))
6559 /* Adjust by relative CPU capacity of the group */
6560 sgs->group_capacity = group->sgc->capacity;
6561 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6563 if (sgs->sum_nr_running)
6564 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6566 sgs->group_weight = group->group_weight;
6568 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6569 sgs->group_type = group_classify(group, sgs);
6573 * update_sd_pick_busiest - return 1 on busiest group
6574 * @env: The load balancing environment.
6575 * @sds: sched_domain statistics
6576 * @sg: sched_group candidate to be checked for being the busiest
6577 * @sgs: sched_group statistics
6579 * Determine if @sg is a busier group than the previously selected
6582 * Return: %true if @sg is a busier group than the previously selected
6583 * busiest group. %false otherwise.
6585 static bool update_sd_pick_busiest(struct lb_env *env,
6586 struct sd_lb_stats *sds,
6587 struct sched_group *sg,
6588 struct sg_lb_stats *sgs)
6590 struct sg_lb_stats *busiest = &sds->busiest_stat;
6592 if (sgs->group_type > busiest->group_type)
6595 if (sgs->group_type < busiest->group_type)
6598 if (sgs->avg_load <= busiest->avg_load)
6601 /* This is the busiest node in its class. */
6602 if (!(env->sd->flags & SD_ASYM_PACKING))
6606 * ASYM_PACKING needs to move all the work to the lowest
6607 * numbered CPUs in the group, therefore mark all groups
6608 * higher than ourself as busy.
6610 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6614 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6621 #ifdef CONFIG_NUMA_BALANCING
6622 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6624 if (sgs->sum_nr_running > sgs->nr_numa_running)
6626 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6631 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6633 if (rq->nr_running > rq->nr_numa_running)
6635 if (rq->nr_running > rq->nr_preferred_running)
6640 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6645 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6649 #endif /* CONFIG_NUMA_BALANCING */
6652 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6653 * @env: The load balancing environment.
6654 * @sds: variable to hold the statistics for this sched_domain.
6656 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6658 struct sched_domain *child = env->sd->child;
6659 struct sched_group *sg = env->sd->groups;
6660 struct sg_lb_stats tmp_sgs;
6661 int load_idx, prefer_sibling = 0;
6662 bool overload = false;
6664 if (child && child->flags & SD_PREFER_SIBLING)
6667 load_idx = get_sd_load_idx(env->sd, env->idle);
6670 struct sg_lb_stats *sgs = &tmp_sgs;
6673 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6676 sgs = &sds->local_stat;
6678 if (env->idle != CPU_NEWLY_IDLE ||
6679 time_after_eq(jiffies, sg->sgc->next_update))
6680 update_group_capacity(env->sd, env->dst_cpu);
6683 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6690 * In case the child domain prefers tasks go to siblings
6691 * first, lower the sg capacity so that we'll try
6692 * and move all the excess tasks away. We lower the capacity
6693 * of a group only if the local group has the capacity to fit
6694 * these excess tasks. The extra check prevents the case where
6695 * you always pull from the heaviest group when it is already
6696 * under-utilized (possible with a large weight task outweighs
6697 * the tasks on the system).
6699 if (prefer_sibling && sds->local &&
6700 group_has_capacity(env, &sds->local_stat) &&
6701 (sgs->sum_nr_running > 1)) {
6702 sgs->group_no_capacity = 1;
6703 sgs->group_type = group_classify(sg, sgs);
6706 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6708 sds->busiest_stat = *sgs;
6712 /* Now, start updating sd_lb_stats */
6713 sds->total_load += sgs->group_load;
6714 sds->total_capacity += sgs->group_capacity;
6717 } while (sg != env->sd->groups);
6719 if (env->sd->flags & SD_NUMA)
6720 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6722 if (!env->sd->parent) {
6723 /* update overload indicator if we are at root domain */
6724 if (env->dst_rq->rd->overload != overload)
6725 env->dst_rq->rd->overload = overload;
6731 * check_asym_packing - Check to see if the group is packed into the
6734 * This is primarily intended to used at the sibling level. Some
6735 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6736 * case of POWER7, it can move to lower SMT modes only when higher
6737 * threads are idle. When in lower SMT modes, the threads will
6738 * perform better since they share less core resources. Hence when we
6739 * have idle threads, we want them to be the higher ones.
6741 * This packing function is run on idle threads. It checks to see if
6742 * the busiest CPU in this domain (core in the P7 case) has a higher
6743 * CPU number than the packing function is being run on. Here we are
6744 * assuming lower CPU number will be equivalent to lower a SMT thread
6747 * Return: 1 when packing is required and a task should be moved to
6748 * this CPU. The amount of the imbalance is returned in *imbalance.
6750 * @env: The load balancing environment.
6751 * @sds: Statistics of the sched_domain which is to be packed
6753 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6757 if (!(env->sd->flags & SD_ASYM_PACKING))
6763 busiest_cpu = group_first_cpu(sds->busiest);
6764 if (env->dst_cpu > busiest_cpu)
6767 env->imbalance = DIV_ROUND_CLOSEST(
6768 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6769 SCHED_CAPACITY_SCALE);
6775 * fix_small_imbalance - Calculate the minor imbalance that exists
6776 * amongst the groups of a sched_domain, during
6778 * @env: The load balancing environment.
6779 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6782 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6784 unsigned long tmp, capa_now = 0, capa_move = 0;
6785 unsigned int imbn = 2;
6786 unsigned long scaled_busy_load_per_task;
6787 struct sg_lb_stats *local, *busiest;
6789 local = &sds->local_stat;
6790 busiest = &sds->busiest_stat;
6792 if (!local->sum_nr_running)
6793 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6794 else if (busiest->load_per_task > local->load_per_task)
6797 scaled_busy_load_per_task =
6798 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6799 busiest->group_capacity;
6801 if (busiest->avg_load + scaled_busy_load_per_task >=
6802 local->avg_load + (scaled_busy_load_per_task * imbn)) {
6803 env->imbalance = busiest->load_per_task;
6808 * OK, we don't have enough imbalance to justify moving tasks,
6809 * however we may be able to increase total CPU capacity used by
6813 capa_now += busiest->group_capacity *
6814 min(busiest->load_per_task, busiest->avg_load);
6815 capa_now += local->group_capacity *
6816 min(local->load_per_task, local->avg_load);
6817 capa_now /= SCHED_CAPACITY_SCALE;
6819 /* Amount of load we'd subtract */
6820 if (busiest->avg_load > scaled_busy_load_per_task) {
6821 capa_move += busiest->group_capacity *
6822 min(busiest->load_per_task,
6823 busiest->avg_load - scaled_busy_load_per_task);
6826 /* Amount of load we'd add */
6827 if (busiest->avg_load * busiest->group_capacity <
6828 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6829 tmp = (busiest->avg_load * busiest->group_capacity) /
6830 local->group_capacity;
6832 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6833 local->group_capacity;
6835 capa_move += local->group_capacity *
6836 min(local->load_per_task, local->avg_load + tmp);
6837 capa_move /= SCHED_CAPACITY_SCALE;
6839 /* Move if we gain throughput */
6840 if (capa_move > capa_now)
6841 env->imbalance = busiest->load_per_task;
6845 * calculate_imbalance - Calculate the amount of imbalance present within the
6846 * groups of a given sched_domain during load balance.
6847 * @env: load balance environment
6848 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6850 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6852 unsigned long max_pull, load_above_capacity = ~0UL;
6853 struct sg_lb_stats *local, *busiest;
6855 local = &sds->local_stat;
6856 busiest = &sds->busiest_stat;
6858 if (busiest->group_type == group_imbalanced) {
6860 * In the group_imb case we cannot rely on group-wide averages
6861 * to ensure cpu-load equilibrium, look at wider averages. XXX
6863 busiest->load_per_task =
6864 min(busiest->load_per_task, sds->avg_load);
6868 * In the presence of smp nice balancing, certain scenarios can have
6869 * max load less than avg load(as we skip the groups at or below
6870 * its cpu_capacity, while calculating max_load..)
6872 if (busiest->avg_load <= sds->avg_load ||
6873 local->avg_load >= sds->avg_load) {
6875 return fix_small_imbalance(env, sds);
6879 * If there aren't any idle cpus, avoid creating some.
6881 if (busiest->group_type == group_overloaded &&
6882 local->group_type == group_overloaded) {
6883 load_above_capacity = busiest->sum_nr_running *
6885 if (load_above_capacity > busiest->group_capacity)
6886 load_above_capacity -= busiest->group_capacity;
6888 load_above_capacity = ~0UL;
6892 * We're trying to get all the cpus to the average_load, so we don't
6893 * want to push ourselves above the average load, nor do we wish to
6894 * reduce the max loaded cpu below the average load. At the same time,
6895 * we also don't want to reduce the group load below the group capacity
6896 * (so that we can implement power-savings policies etc). Thus we look
6897 * for the minimum possible imbalance.
6899 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6901 /* How much load to actually move to equalise the imbalance */
6902 env->imbalance = min(
6903 max_pull * busiest->group_capacity,
6904 (sds->avg_load - local->avg_load) * local->group_capacity
6905 ) / SCHED_CAPACITY_SCALE;
6908 * if *imbalance is less than the average load per runnable task
6909 * there is no guarantee that any tasks will be moved so we'll have
6910 * a think about bumping its value to force at least one task to be
6913 if (env->imbalance < busiest->load_per_task)
6914 return fix_small_imbalance(env, sds);
6917 /******* find_busiest_group() helpers end here *********************/
6920 * find_busiest_group - Returns the busiest group within the sched_domain
6921 * if there is an imbalance. If there isn't an imbalance, and
6922 * the user has opted for power-savings, it returns a group whose
6923 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6924 * such a group exists.
6926 * Also calculates the amount of weighted load which should be moved
6927 * to restore balance.
6929 * @env: The load balancing environment.
6931 * Return: - The busiest group if imbalance exists.
6932 * - If no imbalance and user has opted for power-savings balance,
6933 * return the least loaded group whose CPUs can be
6934 * put to idle by rebalancing its tasks onto our group.
6936 static struct sched_group *find_busiest_group(struct lb_env *env)
6938 struct sg_lb_stats *local, *busiest;
6939 struct sd_lb_stats sds;
6941 init_sd_lb_stats(&sds);
6944 * Compute the various statistics relavent for load balancing at
6947 update_sd_lb_stats(env, &sds);
6948 local = &sds.local_stat;
6949 busiest = &sds.busiest_stat;
6951 /* ASYM feature bypasses nice load balance check */
6952 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6953 check_asym_packing(env, &sds))
6956 /* There is no busy sibling group to pull tasks from */
6957 if (!sds.busiest || busiest->sum_nr_running == 0)
6960 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
6961 / sds.total_capacity;
6964 * If the busiest group is imbalanced the below checks don't
6965 * work because they assume all things are equal, which typically
6966 * isn't true due to cpus_allowed constraints and the like.
6968 if (busiest->group_type == group_imbalanced)
6971 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6972 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
6973 busiest->group_no_capacity)
6977 * If the local group is busier than the selected busiest group
6978 * don't try and pull any tasks.
6980 if (local->avg_load >= busiest->avg_load)
6984 * Don't pull any tasks if this group is already above the domain
6987 if (local->avg_load >= sds.avg_load)
6990 if (env->idle == CPU_IDLE) {
6992 * This cpu is idle. If the busiest group is not overloaded
6993 * and there is no imbalance between this and busiest group
6994 * wrt idle cpus, it is balanced. The imbalance becomes
6995 * significant if the diff is greater than 1 otherwise we
6996 * might end up to just move the imbalance on another group
6998 if ((busiest->group_type != group_overloaded) &&
6999 (local->idle_cpus <= (busiest->idle_cpus + 1)))
7003 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7004 * imbalance_pct to be conservative.
7006 if (100 * busiest->avg_load <=
7007 env->sd->imbalance_pct * local->avg_load)
7012 /* Looks like there is an imbalance. Compute it */
7013 calculate_imbalance(env, &sds);
7022 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7024 static struct rq *find_busiest_queue(struct lb_env *env,
7025 struct sched_group *group)
7027 struct rq *busiest = NULL, *rq;
7028 unsigned long busiest_load = 0, busiest_capacity = 1;
7031 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7032 unsigned long capacity, wl;
7036 rt = fbq_classify_rq(rq);
7039 * We classify groups/runqueues into three groups:
7040 * - regular: there are !numa tasks
7041 * - remote: there are numa tasks that run on the 'wrong' node
7042 * - all: there is no distinction
7044 * In order to avoid migrating ideally placed numa tasks,
7045 * ignore those when there's better options.
7047 * If we ignore the actual busiest queue to migrate another
7048 * task, the next balance pass can still reduce the busiest
7049 * queue by moving tasks around inside the node.
7051 * If we cannot move enough load due to this classification
7052 * the next pass will adjust the group classification and
7053 * allow migration of more tasks.
7055 * Both cases only affect the total convergence complexity.
7057 if (rt > env->fbq_type)
7060 capacity = capacity_of(i);
7062 wl = weighted_cpuload(i);
7065 * When comparing with imbalance, use weighted_cpuload()
7066 * which is not scaled with the cpu capacity.
7069 if (rq->nr_running == 1 && wl > env->imbalance &&
7070 !check_cpu_capacity(rq, env->sd))
7074 * For the load comparisons with the other cpu's, consider
7075 * the weighted_cpuload() scaled with the cpu capacity, so
7076 * that the load can be moved away from the cpu that is
7077 * potentially running at a lower capacity.
7079 * Thus we're looking for max(wl_i / capacity_i), crosswise
7080 * multiplication to rid ourselves of the division works out
7081 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7082 * our previous maximum.
7084 if (wl * busiest_capacity > busiest_load * capacity) {
7086 busiest_capacity = capacity;
7095 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7096 * so long as it is large enough.
7098 #define MAX_PINNED_INTERVAL 512
7100 /* Working cpumask for load_balance and load_balance_newidle. */
7101 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7103 static int need_active_balance(struct lb_env *env)
7105 struct sched_domain *sd = env->sd;
7107 if (env->idle == CPU_NEWLY_IDLE) {
7110 * ASYM_PACKING needs to force migrate tasks from busy but
7111 * higher numbered CPUs in order to pack all tasks in the
7112 * lowest numbered CPUs.
7114 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7119 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7120 * It's worth migrating the task if the src_cpu's capacity is reduced
7121 * because of other sched_class or IRQs if more capacity stays
7122 * available on dst_cpu.
7124 if ((env->idle != CPU_NOT_IDLE) &&
7125 (env->src_rq->cfs.h_nr_running == 1)) {
7126 if ((check_cpu_capacity(env->src_rq, sd)) &&
7127 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7131 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7134 static int active_load_balance_cpu_stop(void *data);
7136 static int should_we_balance(struct lb_env *env)
7138 struct sched_group *sg = env->sd->groups;
7139 struct cpumask *sg_cpus, *sg_mask;
7140 int cpu, balance_cpu = -1;
7143 * In the newly idle case, we will allow all the cpu's
7144 * to do the newly idle load balance.
7146 if (env->idle == CPU_NEWLY_IDLE)
7149 sg_cpus = sched_group_cpus(sg);
7150 sg_mask = sched_group_mask(sg);
7151 /* Try to find first idle cpu */
7152 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7153 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7160 if (balance_cpu == -1)
7161 balance_cpu = group_balance_cpu(sg);
7164 * First idle cpu or the first cpu(busiest) in this sched group
7165 * is eligible for doing load balancing at this and above domains.
7167 return balance_cpu == env->dst_cpu;
7171 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7172 * tasks if there is an imbalance.
7174 static int load_balance(int this_cpu, struct rq *this_rq,
7175 struct sched_domain *sd, enum cpu_idle_type idle,
7176 int *continue_balancing)
7178 int ld_moved, cur_ld_moved, active_balance = 0;
7179 struct sched_domain *sd_parent = sd->parent;
7180 struct sched_group *group;
7182 unsigned long flags;
7183 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7185 struct lb_env env = {
7187 .dst_cpu = this_cpu,
7189 .dst_grpmask = sched_group_cpus(sd->groups),
7191 .loop_break = sched_nr_migrate_break,
7194 .tasks = LIST_HEAD_INIT(env.tasks),
7198 * For NEWLY_IDLE load_balancing, we don't need to consider
7199 * other cpus in our group
7201 if (idle == CPU_NEWLY_IDLE)
7202 env.dst_grpmask = NULL;
7204 cpumask_copy(cpus, cpu_active_mask);
7206 schedstat_inc(sd, lb_count[idle]);
7209 if (!should_we_balance(&env)) {
7210 *continue_balancing = 0;
7214 group = find_busiest_group(&env);
7216 schedstat_inc(sd, lb_nobusyg[idle]);
7220 busiest = find_busiest_queue(&env, group);
7222 schedstat_inc(sd, lb_nobusyq[idle]);
7226 BUG_ON(busiest == env.dst_rq);
7228 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7230 env.src_cpu = busiest->cpu;
7231 env.src_rq = busiest;
7234 if (busiest->nr_running > 1) {
7236 * Attempt to move tasks. If find_busiest_group has found
7237 * an imbalance but busiest->nr_running <= 1, the group is
7238 * still unbalanced. ld_moved simply stays zero, so it is
7239 * correctly treated as an imbalance.
7241 env.flags |= LBF_ALL_PINNED;
7242 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7245 raw_spin_lock_irqsave(&busiest->lock, flags);
7248 * cur_ld_moved - load moved in current iteration
7249 * ld_moved - cumulative load moved across iterations
7251 cur_ld_moved = detach_tasks(&env);
7254 * We've detached some tasks from busiest_rq. Every
7255 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7256 * unlock busiest->lock, and we are able to be sure
7257 * that nobody can manipulate the tasks in parallel.
7258 * See task_rq_lock() family for the details.
7261 raw_spin_unlock(&busiest->lock);
7265 ld_moved += cur_ld_moved;
7268 local_irq_restore(flags);
7270 if (env.flags & LBF_NEED_BREAK) {
7271 env.flags &= ~LBF_NEED_BREAK;
7276 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7277 * us and move them to an alternate dst_cpu in our sched_group
7278 * where they can run. The upper limit on how many times we
7279 * iterate on same src_cpu is dependent on number of cpus in our
7282 * This changes load balance semantics a bit on who can move
7283 * load to a given_cpu. In addition to the given_cpu itself
7284 * (or a ilb_cpu acting on its behalf where given_cpu is
7285 * nohz-idle), we now have balance_cpu in a position to move
7286 * load to given_cpu. In rare situations, this may cause
7287 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7288 * _independently_ and at _same_ time to move some load to
7289 * given_cpu) causing exceess load to be moved to given_cpu.
7290 * This however should not happen so much in practice and
7291 * moreover subsequent load balance cycles should correct the
7292 * excess load moved.
7294 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7296 /* Prevent to re-select dst_cpu via env's cpus */
7297 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7299 env.dst_rq = cpu_rq(env.new_dst_cpu);
7300 env.dst_cpu = env.new_dst_cpu;
7301 env.flags &= ~LBF_DST_PINNED;
7303 env.loop_break = sched_nr_migrate_break;
7306 * Go back to "more_balance" rather than "redo" since we
7307 * need to continue with same src_cpu.
7313 * We failed to reach balance because of affinity.
7316 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7318 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7319 *group_imbalance = 1;
7322 /* All tasks on this runqueue were pinned by CPU affinity */
7323 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7324 cpumask_clear_cpu(cpu_of(busiest), cpus);
7325 if (!cpumask_empty(cpus)) {
7327 env.loop_break = sched_nr_migrate_break;
7330 goto out_all_pinned;
7335 schedstat_inc(sd, lb_failed[idle]);
7337 * Increment the failure counter only on periodic balance.
7338 * We do not want newidle balance, which can be very
7339 * frequent, pollute the failure counter causing
7340 * excessive cache_hot migrations and active balances.
7342 if (idle != CPU_NEWLY_IDLE)
7343 sd->nr_balance_failed++;
7345 if (need_active_balance(&env)) {
7346 raw_spin_lock_irqsave(&busiest->lock, flags);
7348 /* don't kick the active_load_balance_cpu_stop,
7349 * if the curr task on busiest cpu can't be
7352 if (!cpumask_test_cpu(this_cpu,
7353 tsk_cpus_allowed(busiest->curr))) {
7354 raw_spin_unlock_irqrestore(&busiest->lock,
7356 env.flags |= LBF_ALL_PINNED;
7357 goto out_one_pinned;
7361 * ->active_balance synchronizes accesses to
7362 * ->active_balance_work. Once set, it's cleared
7363 * only after active load balance is finished.
7365 if (!busiest->active_balance) {
7366 busiest->active_balance = 1;
7367 busiest->push_cpu = this_cpu;
7370 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7372 if (active_balance) {
7373 stop_one_cpu_nowait(cpu_of(busiest),
7374 active_load_balance_cpu_stop, busiest,
7375 &busiest->active_balance_work);
7379 * We've kicked active balancing, reset the failure
7382 sd->nr_balance_failed = sd->cache_nice_tries+1;
7385 sd->nr_balance_failed = 0;
7387 if (likely(!active_balance)) {
7388 /* We were unbalanced, so reset the balancing interval */
7389 sd->balance_interval = sd->min_interval;
7392 * If we've begun active balancing, start to back off. This
7393 * case may not be covered by the all_pinned logic if there
7394 * is only 1 task on the busy runqueue (because we don't call
7397 if (sd->balance_interval < sd->max_interval)
7398 sd->balance_interval *= 2;
7405 * We reach balance although we may have faced some affinity
7406 * constraints. Clear the imbalance flag if it was set.
7409 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7411 if (*group_imbalance)
7412 *group_imbalance = 0;
7417 * We reach balance because all tasks are pinned at this level so
7418 * we can't migrate them. Let the imbalance flag set so parent level
7419 * can try to migrate them.
7421 schedstat_inc(sd, lb_balanced[idle]);
7423 sd->nr_balance_failed = 0;
7426 /* tune up the balancing interval */
7427 if (((env.flags & LBF_ALL_PINNED) &&
7428 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7429 (sd->balance_interval < sd->max_interval))
7430 sd->balance_interval *= 2;
7437 static inline unsigned long
7438 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7440 unsigned long interval = sd->balance_interval;
7443 interval *= sd->busy_factor;
7445 /* scale ms to jiffies */
7446 interval = msecs_to_jiffies(interval);
7447 interval = clamp(interval, 1UL, max_load_balance_interval);
7453 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7455 unsigned long interval, next;
7457 interval = get_sd_balance_interval(sd, cpu_busy);
7458 next = sd->last_balance + interval;
7460 if (time_after(*next_balance, next))
7461 *next_balance = next;
7465 * idle_balance is called by schedule() if this_cpu is about to become
7466 * idle. Attempts to pull tasks from other CPUs.
7468 static int idle_balance(struct rq *this_rq)
7470 unsigned long next_balance = jiffies + HZ;
7471 int this_cpu = this_rq->cpu;
7472 struct sched_domain *sd;
7473 int pulled_task = 0;
7477 * We must set idle_stamp _before_ calling idle_balance(), such that we
7478 * measure the duration of idle_balance() as idle time.
7480 this_rq->idle_stamp = rq_clock(this_rq);
7482 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7483 !this_rq->rd->overload) {
7485 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7487 update_next_balance(sd, 0, &next_balance);
7493 raw_spin_unlock(&this_rq->lock);
7495 update_blocked_averages(this_cpu);
7497 for_each_domain(this_cpu, sd) {
7498 int continue_balancing = 1;
7499 u64 t0, domain_cost;
7501 if (!(sd->flags & SD_LOAD_BALANCE))
7504 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7505 update_next_balance(sd, 0, &next_balance);
7509 if (sd->flags & SD_BALANCE_NEWIDLE) {
7510 t0 = sched_clock_cpu(this_cpu);
7512 pulled_task = load_balance(this_cpu, this_rq,
7514 &continue_balancing);
7516 domain_cost = sched_clock_cpu(this_cpu) - t0;
7517 if (domain_cost > sd->max_newidle_lb_cost)
7518 sd->max_newidle_lb_cost = domain_cost;
7520 curr_cost += domain_cost;
7523 update_next_balance(sd, 0, &next_balance);
7526 * Stop searching for tasks to pull if there are
7527 * now runnable tasks on this rq.
7529 if (pulled_task || this_rq->nr_running > 0)
7534 raw_spin_lock(&this_rq->lock);
7536 if (curr_cost > this_rq->max_idle_balance_cost)
7537 this_rq->max_idle_balance_cost = curr_cost;
7540 * While browsing the domains, we released the rq lock, a task could
7541 * have been enqueued in the meantime. Since we're not going idle,
7542 * pretend we pulled a task.
7544 if (this_rq->cfs.h_nr_running && !pulled_task)
7548 /* Move the next balance forward */
7549 if (time_after(this_rq->next_balance, next_balance))
7550 this_rq->next_balance = next_balance;
7552 /* Is there a task of a high priority class? */
7553 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7557 this_rq->idle_stamp = 0;
7563 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7564 * running tasks off the busiest CPU onto idle CPUs. It requires at
7565 * least 1 task to be running on each physical CPU where possible, and
7566 * avoids physical / logical imbalances.
7568 static int active_load_balance_cpu_stop(void *data)
7570 struct rq *busiest_rq = data;
7571 int busiest_cpu = cpu_of(busiest_rq);
7572 int target_cpu = busiest_rq->push_cpu;
7573 struct rq *target_rq = cpu_rq(target_cpu);
7574 struct sched_domain *sd;
7575 struct task_struct *p = NULL;
7577 raw_spin_lock_irq(&busiest_rq->lock);
7579 /* make sure the requested cpu hasn't gone down in the meantime */
7580 if (unlikely(busiest_cpu != smp_processor_id() ||
7581 !busiest_rq->active_balance))
7584 /* Is there any task to move? */
7585 if (busiest_rq->nr_running <= 1)
7589 * This condition is "impossible", if it occurs
7590 * we need to fix it. Originally reported by
7591 * Bjorn Helgaas on a 128-cpu setup.
7593 BUG_ON(busiest_rq == target_rq);
7595 /* Search for an sd spanning us and the target CPU. */
7597 for_each_domain(target_cpu, sd) {
7598 if ((sd->flags & SD_LOAD_BALANCE) &&
7599 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7604 struct lb_env env = {
7606 .dst_cpu = target_cpu,
7607 .dst_rq = target_rq,
7608 .src_cpu = busiest_rq->cpu,
7609 .src_rq = busiest_rq,
7613 schedstat_inc(sd, alb_count);
7615 p = detach_one_task(&env);
7617 schedstat_inc(sd, alb_pushed);
7619 schedstat_inc(sd, alb_failed);
7623 busiest_rq->active_balance = 0;
7624 raw_spin_unlock(&busiest_rq->lock);
7627 attach_one_task(target_rq, p);
7634 static inline int on_null_domain(struct rq *rq)
7636 return unlikely(!rcu_dereference_sched(rq->sd));
7639 #ifdef CONFIG_NO_HZ_COMMON
7641 * idle load balancing details
7642 * - When one of the busy CPUs notice that there may be an idle rebalancing
7643 * needed, they will kick the idle load balancer, which then does idle
7644 * load balancing for all the idle CPUs.
7647 cpumask_var_t idle_cpus_mask;
7649 unsigned long next_balance; /* in jiffy units */
7650 } nohz ____cacheline_aligned;
7652 static inline int find_new_ilb(void)
7654 int ilb = cpumask_first(nohz.idle_cpus_mask);
7656 if (ilb < nr_cpu_ids && idle_cpu(ilb))
7663 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7664 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7665 * CPU (if there is one).
7667 static void nohz_balancer_kick(void)
7671 nohz.next_balance++;
7673 ilb_cpu = find_new_ilb();
7675 if (ilb_cpu >= nr_cpu_ids)
7678 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7681 * Use smp_send_reschedule() instead of resched_cpu().
7682 * This way we generate a sched IPI on the target cpu which
7683 * is idle. And the softirq performing nohz idle load balance
7684 * will be run before returning from the IPI.
7686 smp_send_reschedule(ilb_cpu);
7690 static inline void nohz_balance_exit_idle(int cpu)
7692 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7694 * Completely isolated CPUs don't ever set, so we must test.
7696 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7697 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7698 atomic_dec(&nohz.nr_cpus);
7700 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7704 static inline void set_cpu_sd_state_busy(void)
7706 struct sched_domain *sd;
7707 int cpu = smp_processor_id();
7710 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7712 if (!sd || !sd->nohz_idle)
7716 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7721 void set_cpu_sd_state_idle(void)
7723 struct sched_domain *sd;
7724 int cpu = smp_processor_id();
7727 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7729 if (!sd || sd->nohz_idle)
7733 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7739 * This routine will record that the cpu is going idle with tick stopped.
7740 * This info will be used in performing idle load balancing in the future.
7742 void nohz_balance_enter_idle(int cpu)
7745 * If this cpu is going down, then nothing needs to be done.
7747 if (!cpu_active(cpu))
7750 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7754 * If we're a completely isolated CPU, we don't play.
7756 if (on_null_domain(cpu_rq(cpu)))
7759 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7760 atomic_inc(&nohz.nr_cpus);
7761 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7764 static int sched_ilb_notifier(struct notifier_block *nfb,
7765 unsigned long action, void *hcpu)
7767 switch (action & ~CPU_TASKS_FROZEN) {
7769 nohz_balance_exit_idle(smp_processor_id());
7777 static DEFINE_SPINLOCK(balancing);
7780 * Scale the max load_balance interval with the number of CPUs in the system.
7781 * This trades load-balance latency on larger machines for less cross talk.
7783 void update_max_interval(void)
7785 max_load_balance_interval = HZ*num_online_cpus()/10;
7789 * It checks each scheduling domain to see if it is due to be balanced,
7790 * and initiates a balancing operation if so.
7792 * Balancing parameters are set up in init_sched_domains.
7794 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7796 int continue_balancing = 1;
7798 unsigned long interval;
7799 struct sched_domain *sd;
7800 /* Earliest time when we have to do rebalance again */
7801 unsigned long next_balance = jiffies + 60*HZ;
7802 int update_next_balance = 0;
7803 int need_serialize, need_decay = 0;
7806 update_blocked_averages(cpu);
7809 for_each_domain(cpu, sd) {
7811 * Decay the newidle max times here because this is a regular
7812 * visit to all the domains. Decay ~1% per second.
7814 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7815 sd->max_newidle_lb_cost =
7816 (sd->max_newidle_lb_cost * 253) / 256;
7817 sd->next_decay_max_lb_cost = jiffies + HZ;
7820 max_cost += sd->max_newidle_lb_cost;
7822 if (!(sd->flags & SD_LOAD_BALANCE))
7826 * Stop the load balance at this level. There is another
7827 * CPU in our sched group which is doing load balancing more
7830 if (!continue_balancing) {
7836 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7838 need_serialize = sd->flags & SD_SERIALIZE;
7839 if (need_serialize) {
7840 if (!spin_trylock(&balancing))
7844 if (time_after_eq(jiffies, sd->last_balance + interval)) {
7845 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7847 * The LBF_DST_PINNED logic could have changed
7848 * env->dst_cpu, so we can't know our idle
7849 * state even if we migrated tasks. Update it.
7851 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7853 sd->last_balance = jiffies;
7854 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7857 spin_unlock(&balancing);
7859 if (time_after(next_balance, sd->last_balance + interval)) {
7860 next_balance = sd->last_balance + interval;
7861 update_next_balance = 1;
7866 * Ensure the rq-wide value also decays but keep it at a
7867 * reasonable floor to avoid funnies with rq->avg_idle.
7869 rq->max_idle_balance_cost =
7870 max((u64)sysctl_sched_migration_cost, max_cost);
7875 * next_balance will be updated only when there is a need.
7876 * When the cpu is attached to null domain for ex, it will not be
7879 if (likely(update_next_balance)) {
7880 rq->next_balance = next_balance;
7882 #ifdef CONFIG_NO_HZ_COMMON
7884 * If this CPU has been elected to perform the nohz idle
7885 * balance. Other idle CPUs have already rebalanced with
7886 * nohz_idle_balance() and nohz.next_balance has been
7887 * updated accordingly. This CPU is now running the idle load
7888 * balance for itself and we need to update the
7889 * nohz.next_balance accordingly.
7891 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
7892 nohz.next_balance = rq->next_balance;
7897 #ifdef CONFIG_NO_HZ_COMMON
7899 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7900 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7902 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7904 int this_cpu = this_rq->cpu;
7907 /* Earliest time when we have to do rebalance again */
7908 unsigned long next_balance = jiffies + 60*HZ;
7909 int update_next_balance = 0;
7911 if (idle != CPU_IDLE ||
7912 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7915 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7916 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7920 * If this cpu gets work to do, stop the load balancing
7921 * work being done for other cpus. Next load
7922 * balancing owner will pick it up.
7927 rq = cpu_rq(balance_cpu);
7930 * If time for next balance is due,
7933 if (time_after_eq(jiffies, rq->next_balance)) {
7934 raw_spin_lock_irq(&rq->lock);
7935 update_rq_clock(rq);
7936 update_cpu_load_idle(rq);
7937 raw_spin_unlock_irq(&rq->lock);
7938 rebalance_domains(rq, CPU_IDLE);
7941 if (time_after(next_balance, rq->next_balance)) {
7942 next_balance = rq->next_balance;
7943 update_next_balance = 1;
7948 * next_balance will be updated only when there is a need.
7949 * When the CPU is attached to null domain for ex, it will not be
7952 if (likely(update_next_balance))
7953 nohz.next_balance = next_balance;
7955 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7959 * Current heuristic for kicking the idle load balancer in the presence
7960 * of an idle cpu in the system.
7961 * - This rq has more than one task.
7962 * - This rq has at least one CFS task and the capacity of the CPU is
7963 * significantly reduced because of RT tasks or IRQs.
7964 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
7965 * multiple busy cpu.
7966 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7967 * domain span are idle.
7969 static inline bool nohz_kick_needed(struct rq *rq)
7971 unsigned long now = jiffies;
7972 struct sched_domain *sd;
7973 struct sched_group_capacity *sgc;
7974 int nr_busy, cpu = rq->cpu;
7977 if (unlikely(rq->idle_balance))
7981 * We may be recently in ticked or tickless idle mode. At the first
7982 * busy tick after returning from idle, we will update the busy stats.
7984 set_cpu_sd_state_busy();
7985 nohz_balance_exit_idle(cpu);
7988 * None are in tickless mode and hence no need for NOHZ idle load
7991 if (likely(!atomic_read(&nohz.nr_cpus)))
7994 if (time_before(now, nohz.next_balance))
7997 if (rq->nr_running >= 2)
8001 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8003 sgc = sd->groups->sgc;
8004 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8013 sd = rcu_dereference(rq->sd);
8015 if ((rq->cfs.h_nr_running >= 1) &&
8016 check_cpu_capacity(rq, sd)) {
8022 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8023 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8024 sched_domain_span(sd)) < cpu)) {
8034 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8038 * run_rebalance_domains is triggered when needed from the scheduler tick.
8039 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8041 static void run_rebalance_domains(struct softirq_action *h)
8043 struct rq *this_rq = this_rq();
8044 enum cpu_idle_type idle = this_rq->idle_balance ?
8045 CPU_IDLE : CPU_NOT_IDLE;
8048 * If this cpu has a pending nohz_balance_kick, then do the
8049 * balancing on behalf of the other idle cpus whose ticks are
8050 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8051 * give the idle cpus a chance to load balance. Else we may
8052 * load balance only within the local sched_domain hierarchy
8053 * and abort nohz_idle_balance altogether if we pull some load.
8055 nohz_idle_balance(this_rq, idle);
8056 rebalance_domains(this_rq, idle);
8060 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8062 void trigger_load_balance(struct rq *rq)
8064 /* Don't need to rebalance while attached to NULL domain */
8065 if (unlikely(on_null_domain(rq)))
8068 if (time_after_eq(jiffies, rq->next_balance))
8069 raise_softirq(SCHED_SOFTIRQ);
8070 #ifdef CONFIG_NO_HZ_COMMON
8071 if (nohz_kick_needed(rq))
8072 nohz_balancer_kick();
8076 static void rq_online_fair(struct rq *rq)
8080 update_runtime_enabled(rq);
8083 static void rq_offline_fair(struct rq *rq)
8087 /* Ensure any throttled groups are reachable by pick_next_task */
8088 unthrottle_offline_cfs_rqs(rq);
8091 #endif /* CONFIG_SMP */
8094 * scheduler tick hitting a task of our scheduling class:
8096 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8098 struct cfs_rq *cfs_rq;
8099 struct sched_entity *se = &curr->se;
8101 for_each_sched_entity(se) {
8102 cfs_rq = cfs_rq_of(se);
8103 entity_tick(cfs_rq, se, queued);
8106 if (static_branch_unlikely(&sched_numa_balancing))
8107 task_tick_numa(rq, curr);
8111 * called on fork with the child task as argument from the parent's context
8112 * - child not yet on the tasklist
8113 * - preemption disabled
8115 static void task_fork_fair(struct task_struct *p)
8117 struct cfs_rq *cfs_rq;
8118 struct sched_entity *se = &p->se, *curr;
8119 int this_cpu = smp_processor_id();
8120 struct rq *rq = this_rq();
8121 unsigned long flags;
8123 raw_spin_lock_irqsave(&rq->lock, flags);
8125 update_rq_clock(rq);
8127 cfs_rq = task_cfs_rq(current);
8128 curr = cfs_rq->curr;
8131 * Not only the cpu but also the task_group of the parent might have
8132 * been changed after parent->se.parent,cfs_rq were copied to
8133 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8134 * of child point to valid ones.
8137 __set_task_cpu(p, this_cpu);
8140 update_curr(cfs_rq);
8143 se->vruntime = curr->vruntime;
8144 place_entity(cfs_rq, se, 1);
8146 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8148 * Upon rescheduling, sched_class::put_prev_task() will place
8149 * 'current' within the tree based on its new key value.
8151 swap(curr->vruntime, se->vruntime);
8155 se->vruntime -= cfs_rq->min_vruntime;
8157 raw_spin_unlock_irqrestore(&rq->lock, flags);
8161 * Priority of the task has changed. Check to see if we preempt
8165 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8167 if (!task_on_rq_queued(p))
8171 * Reschedule if we are currently running on this runqueue and
8172 * our priority decreased, or if we are not currently running on
8173 * this runqueue and our priority is higher than the current's
8175 if (rq->curr == p) {
8176 if (p->prio > oldprio)
8179 check_preempt_curr(rq, p, 0);
8182 static inline bool vruntime_normalized(struct task_struct *p)
8184 struct sched_entity *se = &p->se;
8187 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8188 * the dequeue_entity(.flags=0) will already have normalized the
8195 * When !on_rq, vruntime of the task has usually NOT been normalized.
8196 * But there are some cases where it has already been normalized:
8198 * - A forked child which is waiting for being woken up by
8199 * wake_up_new_task().
8200 * - A task which has been woken up by try_to_wake_up() and
8201 * waiting for actually being woken up by sched_ttwu_pending().
8203 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8209 static void detach_task_cfs_rq(struct task_struct *p)
8211 struct sched_entity *se = &p->se;
8212 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8214 if (!vruntime_normalized(p)) {
8216 * Fix up our vruntime so that the current sleep doesn't
8217 * cause 'unlimited' sleep bonus.
8219 place_entity(cfs_rq, se, 0);
8220 se->vruntime -= cfs_rq->min_vruntime;
8223 /* Catch up with the cfs_rq and remove our load when we leave */
8224 detach_entity_load_avg(cfs_rq, se);
8227 static void attach_task_cfs_rq(struct task_struct *p)
8229 struct sched_entity *se = &p->se;
8230 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8232 #ifdef CONFIG_FAIR_GROUP_SCHED
8234 * Since the real-depth could have been changed (only FAIR
8235 * class maintain depth value), reset depth properly.
8237 se->depth = se->parent ? se->parent->depth + 1 : 0;
8240 /* Synchronize task with its cfs_rq */
8241 attach_entity_load_avg(cfs_rq, se);
8243 if (!vruntime_normalized(p))
8244 se->vruntime += cfs_rq->min_vruntime;
8247 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8249 detach_task_cfs_rq(p);
8252 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8254 attach_task_cfs_rq(p);
8256 if (task_on_rq_queued(p)) {
8258 * We were most likely switched from sched_rt, so
8259 * kick off the schedule if running, otherwise just see
8260 * if we can still preempt the current task.
8265 check_preempt_curr(rq, p, 0);
8269 /* Account for a task changing its policy or group.
8271 * This routine is mostly called to set cfs_rq->curr field when a task
8272 * migrates between groups/classes.
8274 static void set_curr_task_fair(struct rq *rq)
8276 struct sched_entity *se = &rq->curr->se;
8278 for_each_sched_entity(se) {
8279 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8281 set_next_entity(cfs_rq, se);
8282 /* ensure bandwidth has been allocated on our new cfs_rq */
8283 account_cfs_rq_runtime(cfs_rq, 0);
8287 void init_cfs_rq(struct cfs_rq *cfs_rq)
8289 cfs_rq->tasks_timeline = RB_ROOT;
8290 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8291 #ifndef CONFIG_64BIT
8292 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8295 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8296 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8300 #ifdef CONFIG_FAIR_GROUP_SCHED
8301 static void task_move_group_fair(struct task_struct *p)
8303 detach_task_cfs_rq(p);
8304 set_task_rq(p, task_cpu(p));
8307 /* Tell se's cfs_rq has been changed -- migrated */
8308 p->se.avg.last_update_time = 0;
8310 attach_task_cfs_rq(p);
8313 void free_fair_sched_group(struct task_group *tg)
8317 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8319 for_each_possible_cpu(i) {
8321 kfree(tg->cfs_rq[i]);
8330 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8332 struct cfs_rq *cfs_rq;
8333 struct sched_entity *se;
8336 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8339 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8343 tg->shares = NICE_0_LOAD;
8345 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8347 for_each_possible_cpu(i) {
8348 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8349 GFP_KERNEL, cpu_to_node(i));
8353 se = kzalloc_node(sizeof(struct sched_entity),
8354 GFP_KERNEL, cpu_to_node(i));
8358 init_cfs_rq(cfs_rq);
8359 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8360 init_entity_runnable_average(se);
8371 void unregister_fair_sched_group(struct task_group *tg)
8373 unsigned long flags;
8377 for_each_possible_cpu(cpu) {
8379 remove_entity_load_avg(tg->se[cpu]);
8382 * Only empty task groups can be destroyed; so we can speculatively
8383 * check on_list without danger of it being re-added.
8385 if (!tg->cfs_rq[cpu]->on_list)
8390 raw_spin_lock_irqsave(&rq->lock, flags);
8391 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8392 raw_spin_unlock_irqrestore(&rq->lock, flags);
8396 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8397 struct sched_entity *se, int cpu,
8398 struct sched_entity *parent)
8400 struct rq *rq = cpu_rq(cpu);
8404 init_cfs_rq_runtime(cfs_rq);
8406 tg->cfs_rq[cpu] = cfs_rq;
8409 /* se could be NULL for root_task_group */
8414 se->cfs_rq = &rq->cfs;
8417 se->cfs_rq = parent->my_q;
8418 se->depth = parent->depth + 1;
8422 /* guarantee group entities always have weight */
8423 update_load_set(&se->load, NICE_0_LOAD);
8424 se->parent = parent;
8427 static DEFINE_MUTEX(shares_mutex);
8429 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8432 unsigned long flags;
8435 * We can't change the weight of the root cgroup.
8440 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8442 mutex_lock(&shares_mutex);
8443 if (tg->shares == shares)
8446 tg->shares = shares;
8447 for_each_possible_cpu(i) {
8448 struct rq *rq = cpu_rq(i);
8449 struct sched_entity *se;
8452 /* Propagate contribution to hierarchy */
8453 raw_spin_lock_irqsave(&rq->lock, flags);
8455 /* Possible calls to update_curr() need rq clock */
8456 update_rq_clock(rq);
8457 for_each_sched_entity(se)
8458 update_cfs_shares(group_cfs_rq(se));
8459 raw_spin_unlock_irqrestore(&rq->lock, flags);
8463 mutex_unlock(&shares_mutex);
8466 #else /* CONFIG_FAIR_GROUP_SCHED */
8468 void free_fair_sched_group(struct task_group *tg) { }
8470 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8475 void unregister_fair_sched_group(struct task_group *tg) { }
8477 #endif /* CONFIG_FAIR_GROUP_SCHED */
8480 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8482 struct sched_entity *se = &task->se;
8483 unsigned int rr_interval = 0;
8486 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8489 if (rq->cfs.load.weight)
8490 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8496 * All the scheduling class methods:
8498 const struct sched_class fair_sched_class = {
8499 .next = &idle_sched_class,
8500 .enqueue_task = enqueue_task_fair,
8501 .dequeue_task = dequeue_task_fair,
8502 .yield_task = yield_task_fair,
8503 .yield_to_task = yield_to_task_fair,
8505 .check_preempt_curr = check_preempt_wakeup,
8507 .pick_next_task = pick_next_task_fair,
8508 .put_prev_task = put_prev_task_fair,
8511 .select_task_rq = select_task_rq_fair,
8512 .migrate_task_rq = migrate_task_rq_fair,
8514 .rq_online = rq_online_fair,
8515 .rq_offline = rq_offline_fair,
8517 .task_waking = task_waking_fair,
8518 .task_dead = task_dead_fair,
8519 .set_cpus_allowed = set_cpus_allowed_common,
8522 .set_curr_task = set_curr_task_fair,
8523 .task_tick = task_tick_fair,
8524 .task_fork = task_fork_fair,
8526 .prio_changed = prio_changed_fair,
8527 .switched_from = switched_from_fair,
8528 .switched_to = switched_to_fair,
8530 .get_rr_interval = get_rr_interval_fair,
8532 .update_curr = update_curr_fair,
8534 #ifdef CONFIG_FAIR_GROUP_SCHED
8535 .task_move_group = task_move_group_fair,
8539 #ifdef CONFIG_SCHED_DEBUG
8540 void print_cfs_stats(struct seq_file *m, int cpu)
8542 struct cfs_rq *cfs_rq;
8545 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8546 print_cfs_rq(m, cpu, cfs_rq);
8550 #ifdef CONFIG_NUMA_BALANCING
8551 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8554 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8556 for_each_online_node(node) {
8557 if (p->numa_faults) {
8558 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8559 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8561 if (p->numa_group) {
8562 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8563 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8565 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8568 #endif /* CONFIG_NUMA_BALANCING */
8569 #endif /* CONFIG_SCHED_DEBUG */
8571 __init void init_sched_fair_class(void)
8574 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
8576 #ifdef CONFIG_NO_HZ_COMMON
8577 nohz.next_balance = jiffies;
8578 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8579 cpu_notifier(sched_ilb_notifier, 0);