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/latencytop.h>
24 #include <linux/sched.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));
742 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
744 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
748 * Task is being enqueued - update stats:
750 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
753 * Are we enqueueing a waiting task? (for current tasks
754 * a dequeue/enqueue event is a NOP)
756 if (se != cfs_rq->curr)
757 update_stats_wait_start(cfs_rq, se);
761 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
763 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
764 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
765 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
766 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
767 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
768 #ifdef CONFIG_SCHEDSTATS
769 if (entity_is_task(se)) {
770 trace_sched_stat_wait(task_of(se),
771 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
774 schedstat_set(se->statistics.wait_start, 0);
778 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
781 * Mark the end of the wait period if dequeueing a
784 if (se != cfs_rq->curr)
785 update_stats_wait_end(cfs_rq, se);
789 * We are picking a new current task - update its stats:
792 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
795 * We are starting a new run period:
797 se->exec_start = rq_clock_task(rq_of(cfs_rq));
800 /**************************************************
801 * Scheduling class queueing methods:
804 #ifdef CONFIG_NUMA_BALANCING
806 * Approximate time to scan a full NUMA task in ms. The task scan period is
807 * calculated based on the tasks virtual memory size and
808 * numa_balancing_scan_size.
810 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
811 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
813 /* Portion of address space to scan in MB */
814 unsigned int sysctl_numa_balancing_scan_size = 256;
816 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
817 unsigned int sysctl_numa_balancing_scan_delay = 1000;
819 static unsigned int task_nr_scan_windows(struct task_struct *p)
821 unsigned long rss = 0;
822 unsigned long nr_scan_pages;
825 * Calculations based on RSS as non-present and empty pages are skipped
826 * by the PTE scanner and NUMA hinting faults should be trapped based
829 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
830 rss = get_mm_rss(p->mm);
834 rss = round_up(rss, nr_scan_pages);
835 return rss / nr_scan_pages;
838 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
839 #define MAX_SCAN_WINDOW 2560
841 static unsigned int task_scan_min(struct task_struct *p)
843 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
844 unsigned int scan, floor;
845 unsigned int windows = 1;
847 if (scan_size < MAX_SCAN_WINDOW)
848 windows = MAX_SCAN_WINDOW / scan_size;
849 floor = 1000 / windows;
851 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
852 return max_t(unsigned int, floor, scan);
855 static unsigned int task_scan_max(struct task_struct *p)
857 unsigned int smin = task_scan_min(p);
860 /* Watch for min being lower than max due to floor calculations */
861 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
862 return max(smin, smax);
865 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
867 rq->nr_numa_running += (p->numa_preferred_nid != -1);
868 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
871 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
873 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
874 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
880 spinlock_t lock; /* nr_tasks, tasks */
885 nodemask_t active_nodes;
886 unsigned long total_faults;
888 * Faults_cpu is used to decide whether memory should move
889 * towards the CPU. As a consequence, these stats are weighted
890 * more by CPU use than by memory faults.
892 unsigned long *faults_cpu;
893 unsigned long faults[0];
896 /* Shared or private faults. */
897 #define NR_NUMA_HINT_FAULT_TYPES 2
899 /* Memory and CPU locality */
900 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
902 /* Averaged statistics, and temporary buffers. */
903 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
905 pid_t task_numa_group_id(struct task_struct *p)
907 return p->numa_group ? p->numa_group->gid : 0;
911 * The averaged statistics, shared & private, memory & cpu,
912 * occupy the first half of the array. The second half of the
913 * array is for current counters, which are averaged into the
914 * first set by task_numa_placement.
916 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
918 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
921 static inline unsigned long task_faults(struct task_struct *p, int nid)
926 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
927 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
930 static inline unsigned long group_faults(struct task_struct *p, int nid)
935 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
936 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
939 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
941 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
942 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
945 /* Handle placement on systems where not all nodes are directly connected. */
946 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
947 int maxdist, bool task)
949 unsigned long score = 0;
953 * All nodes are directly connected, and the same distance
954 * from each other. No need for fancy placement algorithms.
956 if (sched_numa_topology_type == NUMA_DIRECT)
960 * This code is called for each node, introducing N^2 complexity,
961 * which should be ok given the number of nodes rarely exceeds 8.
963 for_each_online_node(node) {
964 unsigned long faults;
965 int dist = node_distance(nid, node);
968 * The furthest away nodes in the system are not interesting
969 * for placement; nid was already counted.
971 if (dist == sched_max_numa_distance || node == nid)
975 * On systems with a backplane NUMA topology, compare groups
976 * of nodes, and move tasks towards the group with the most
977 * memory accesses. When comparing two nodes at distance
978 * "hoplimit", only nodes closer by than "hoplimit" are part
979 * of each group. Skip other nodes.
981 if (sched_numa_topology_type == NUMA_BACKPLANE &&
985 /* Add up the faults from nearby nodes. */
987 faults = task_faults(p, node);
989 faults = group_faults(p, node);
992 * On systems with a glueless mesh NUMA topology, there are
993 * no fixed "groups of nodes". Instead, nodes that are not
994 * directly connected bounce traffic through intermediate
995 * nodes; a numa_group can occupy any set of nodes.
996 * The further away a node is, the less the faults count.
997 * This seems to result in good task placement.
999 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1000 faults *= (sched_max_numa_distance - dist);
1001 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1011 * These return the fraction of accesses done by a particular task, or
1012 * task group, on a particular numa node. The group weight is given a
1013 * larger multiplier, in order to group tasks together that are almost
1014 * evenly spread out between numa nodes.
1016 static inline unsigned long task_weight(struct task_struct *p, int nid,
1019 unsigned long faults, total_faults;
1021 if (!p->numa_faults)
1024 total_faults = p->total_numa_faults;
1029 faults = task_faults(p, nid);
1030 faults += score_nearby_nodes(p, nid, dist, true);
1032 return 1000 * faults / total_faults;
1035 static inline unsigned long group_weight(struct task_struct *p, int nid,
1038 unsigned long faults, total_faults;
1043 total_faults = p->numa_group->total_faults;
1048 faults = group_faults(p, nid);
1049 faults += score_nearby_nodes(p, nid, dist, false);
1051 return 1000 * faults / total_faults;
1054 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1055 int src_nid, int dst_cpu)
1057 struct numa_group *ng = p->numa_group;
1058 int dst_nid = cpu_to_node(dst_cpu);
1059 int last_cpupid, this_cpupid;
1061 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1064 * Multi-stage node selection is used in conjunction with a periodic
1065 * migration fault to build a temporal task<->page relation. By using
1066 * a two-stage filter we remove short/unlikely relations.
1068 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1069 * a task's usage of a particular page (n_p) per total usage of this
1070 * page (n_t) (in a given time-span) to a probability.
1072 * Our periodic faults will sample this probability and getting the
1073 * same result twice in a row, given these samples are fully
1074 * independent, is then given by P(n)^2, provided our sample period
1075 * is sufficiently short compared to the usage pattern.
1077 * This quadric squishes small probabilities, making it less likely we
1078 * act on an unlikely task<->page relation.
1080 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1081 if (!cpupid_pid_unset(last_cpupid) &&
1082 cpupid_to_nid(last_cpupid) != dst_nid)
1085 /* Always allow migrate on private faults */
1086 if (cpupid_match_pid(p, last_cpupid))
1089 /* A shared fault, but p->numa_group has not been set up yet. */
1094 * Do not migrate if the destination is not a node that
1095 * is actively used by this numa group.
1097 if (!node_isset(dst_nid, ng->active_nodes))
1101 * Source is a node that is not actively used by this
1102 * numa group, while the destination is. Migrate.
1104 if (!node_isset(src_nid, ng->active_nodes))
1108 * Both source and destination are nodes in active
1109 * use by this numa group. Maximize memory bandwidth
1110 * by migrating from more heavily used groups, to less
1111 * heavily used ones, spreading the load around.
1112 * Use a 1/4 hysteresis to avoid spurious page movement.
1114 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1117 static unsigned long weighted_cpuload(const int cpu);
1118 static unsigned long source_load(int cpu, int type);
1119 static unsigned long target_load(int cpu, int type);
1120 static unsigned long capacity_of(int cpu);
1121 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1123 /* Cached statistics for all CPUs within a node */
1125 unsigned long nr_running;
1128 /* Total compute capacity of CPUs on a node */
1129 unsigned long compute_capacity;
1131 /* Approximate capacity in terms of runnable tasks on a node */
1132 unsigned long task_capacity;
1133 int has_free_capacity;
1137 * XXX borrowed from update_sg_lb_stats
1139 static void update_numa_stats(struct numa_stats *ns, int nid)
1141 int smt, cpu, cpus = 0;
1142 unsigned long capacity;
1144 memset(ns, 0, sizeof(*ns));
1145 for_each_cpu(cpu, cpumask_of_node(nid)) {
1146 struct rq *rq = cpu_rq(cpu);
1148 ns->nr_running += rq->nr_running;
1149 ns->load += weighted_cpuload(cpu);
1150 ns->compute_capacity += capacity_of(cpu);
1156 * If we raced with hotplug and there are no CPUs left in our mask
1157 * the @ns structure is NULL'ed and task_numa_compare() will
1158 * not find this node attractive.
1160 * We'll either bail at !has_free_capacity, or we'll detect a huge
1161 * imbalance and bail there.
1166 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1167 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1168 capacity = cpus / smt; /* cores */
1170 ns->task_capacity = min_t(unsigned, capacity,
1171 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1172 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1175 struct task_numa_env {
1176 struct task_struct *p;
1178 int src_cpu, src_nid;
1179 int dst_cpu, dst_nid;
1181 struct numa_stats src_stats, dst_stats;
1186 struct task_struct *best_task;
1191 static void task_numa_assign(struct task_numa_env *env,
1192 struct task_struct *p, long imp)
1195 put_task_struct(env->best_task);
1200 env->best_imp = imp;
1201 env->best_cpu = env->dst_cpu;
1204 static bool load_too_imbalanced(long src_load, long dst_load,
1205 struct task_numa_env *env)
1208 long orig_src_load, orig_dst_load;
1209 long src_capacity, dst_capacity;
1212 * The load is corrected for the CPU capacity available on each node.
1215 * ------------ vs ---------
1216 * src_capacity dst_capacity
1218 src_capacity = env->src_stats.compute_capacity;
1219 dst_capacity = env->dst_stats.compute_capacity;
1221 /* We care about the slope of the imbalance, not the direction. */
1222 if (dst_load < src_load)
1223 swap(dst_load, src_load);
1225 /* Is the difference below the threshold? */
1226 imb = dst_load * src_capacity * 100 -
1227 src_load * dst_capacity * env->imbalance_pct;
1232 * The imbalance is above the allowed threshold.
1233 * Compare it with the old imbalance.
1235 orig_src_load = env->src_stats.load;
1236 orig_dst_load = env->dst_stats.load;
1238 if (orig_dst_load < orig_src_load)
1239 swap(orig_dst_load, orig_src_load);
1241 old_imb = orig_dst_load * src_capacity * 100 -
1242 orig_src_load * dst_capacity * env->imbalance_pct;
1244 /* Would this change make things worse? */
1245 return (imb > old_imb);
1249 * This checks if the overall compute and NUMA accesses of the system would
1250 * be improved if the source tasks was migrated to the target dst_cpu taking
1251 * into account that it might be best if task running on the dst_cpu should
1252 * be exchanged with the source task
1254 static void task_numa_compare(struct task_numa_env *env,
1255 long taskimp, long groupimp)
1257 struct rq *src_rq = cpu_rq(env->src_cpu);
1258 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1259 struct task_struct *cur;
1260 long src_load, dst_load;
1262 long imp = env->p->numa_group ? groupimp : taskimp;
1264 int dist = env->dist;
1268 raw_spin_lock_irq(&dst_rq->lock);
1271 * No need to move the exiting task, and this ensures that ->curr
1272 * wasn't reaped and thus get_task_struct() in task_numa_assign()
1273 * is safe under RCU read lock.
1274 * Note that rcu_read_lock() itself can't protect from the final
1275 * put_task_struct() after the last schedule().
1277 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1279 raw_spin_unlock_irq(&dst_rq->lock);
1282 * Because we have preemption enabled we can get migrated around and
1283 * end try selecting ourselves (current == env->p) as a swap candidate.
1289 * "imp" is the fault differential for the source task between the
1290 * source and destination node. Calculate the total differential for
1291 * the source task and potential destination task. The more negative
1292 * the value is, the more rmeote accesses that would be expected to
1293 * be incurred if the tasks were swapped.
1296 /* Skip this swap candidate if cannot move to the source cpu */
1297 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1301 * If dst and source tasks are in the same NUMA group, or not
1302 * in any group then look only at task weights.
1304 if (cur->numa_group == env->p->numa_group) {
1305 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1306 task_weight(cur, env->dst_nid, dist);
1308 * Add some hysteresis to prevent swapping the
1309 * tasks within a group over tiny differences.
1311 if (cur->numa_group)
1315 * Compare the group weights. If a task is all by
1316 * itself (not part of a group), use the task weight
1319 if (cur->numa_group)
1320 imp += group_weight(cur, env->src_nid, dist) -
1321 group_weight(cur, env->dst_nid, dist);
1323 imp += task_weight(cur, env->src_nid, dist) -
1324 task_weight(cur, env->dst_nid, dist);
1328 if (imp <= env->best_imp && moveimp <= env->best_imp)
1332 /* Is there capacity at our destination? */
1333 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1334 !env->dst_stats.has_free_capacity)
1340 /* Balance doesn't matter much if we're running a task per cpu */
1341 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1342 dst_rq->nr_running == 1)
1346 * In the overloaded case, try and keep the load balanced.
1349 load = task_h_load(env->p);
1350 dst_load = env->dst_stats.load + load;
1351 src_load = env->src_stats.load - load;
1353 if (moveimp > imp && moveimp > env->best_imp) {
1355 * If the improvement from just moving env->p direction is
1356 * better than swapping tasks around, check if a move is
1357 * possible. Store a slightly smaller score than moveimp,
1358 * so an actually idle CPU will win.
1360 if (!load_too_imbalanced(src_load, dst_load, env)) {
1367 if (imp <= env->best_imp)
1371 load = task_h_load(cur);
1376 if (load_too_imbalanced(src_load, dst_load, env))
1380 * One idle CPU per node is evaluated for a task numa move.
1381 * Call select_idle_sibling to maybe find a better one.
1384 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1387 task_numa_assign(env, cur, imp);
1392 static void task_numa_find_cpu(struct task_numa_env *env,
1393 long taskimp, long groupimp)
1397 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1398 /* Skip this CPU if the source task cannot migrate */
1399 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1403 task_numa_compare(env, taskimp, groupimp);
1407 /* Only move tasks to a NUMA node less busy than the current node. */
1408 static bool numa_has_capacity(struct task_numa_env *env)
1410 struct numa_stats *src = &env->src_stats;
1411 struct numa_stats *dst = &env->dst_stats;
1413 if (src->has_free_capacity && !dst->has_free_capacity)
1417 * Only consider a task move if the source has a higher load
1418 * than the destination, corrected for CPU capacity on each node.
1420 * src->load dst->load
1421 * --------------------- vs ---------------------
1422 * src->compute_capacity dst->compute_capacity
1424 if (src->load * dst->compute_capacity * env->imbalance_pct >
1426 dst->load * src->compute_capacity * 100)
1432 static int task_numa_migrate(struct task_struct *p)
1434 struct task_numa_env env = {
1437 .src_cpu = task_cpu(p),
1438 .src_nid = task_node(p),
1440 .imbalance_pct = 112,
1446 struct sched_domain *sd;
1447 unsigned long taskweight, groupweight;
1449 long taskimp, groupimp;
1452 * Pick the lowest SD_NUMA domain, as that would have the smallest
1453 * imbalance and would be the first to start moving tasks about.
1455 * And we want to avoid any moving of tasks about, as that would create
1456 * random movement of tasks -- counter the numa conditions we're trying
1460 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1462 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1466 * Cpusets can break the scheduler domain tree into smaller
1467 * balance domains, some of which do not cross NUMA boundaries.
1468 * Tasks that are "trapped" in such domains cannot be migrated
1469 * elsewhere, so there is no point in (re)trying.
1471 if (unlikely(!sd)) {
1472 p->numa_preferred_nid = task_node(p);
1476 env.dst_nid = p->numa_preferred_nid;
1477 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1478 taskweight = task_weight(p, env.src_nid, dist);
1479 groupweight = group_weight(p, env.src_nid, dist);
1480 update_numa_stats(&env.src_stats, env.src_nid);
1481 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1482 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1483 update_numa_stats(&env.dst_stats, env.dst_nid);
1485 /* Try to find a spot on the preferred nid. */
1486 if (numa_has_capacity(&env))
1487 task_numa_find_cpu(&env, taskimp, groupimp);
1490 * Look at other nodes in these cases:
1491 * - there is no space available on the preferred_nid
1492 * - the task is part of a numa_group that is interleaved across
1493 * multiple NUMA nodes; in order to better consolidate the group,
1494 * we need to check other locations.
1496 if (env.best_cpu == -1 || (p->numa_group &&
1497 nodes_weight(p->numa_group->active_nodes) > 1)) {
1498 for_each_online_node(nid) {
1499 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1502 dist = node_distance(env.src_nid, env.dst_nid);
1503 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1505 taskweight = task_weight(p, env.src_nid, dist);
1506 groupweight = group_weight(p, env.src_nid, dist);
1509 /* Only consider nodes where both task and groups benefit */
1510 taskimp = task_weight(p, nid, dist) - taskweight;
1511 groupimp = group_weight(p, nid, dist) - groupweight;
1512 if (taskimp < 0 && groupimp < 0)
1517 update_numa_stats(&env.dst_stats, env.dst_nid);
1518 if (numa_has_capacity(&env))
1519 task_numa_find_cpu(&env, taskimp, groupimp);
1524 * If the task is part of a workload that spans multiple NUMA nodes,
1525 * and is migrating into one of the workload's active nodes, remember
1526 * this node as the task's preferred numa node, so the workload can
1528 * A task that migrated to a second choice node will be better off
1529 * trying for a better one later. Do not set the preferred node here.
1531 if (p->numa_group) {
1532 if (env.best_cpu == -1)
1537 if (node_isset(nid, p->numa_group->active_nodes))
1538 sched_setnuma(p, env.dst_nid);
1541 /* No better CPU than the current one was found. */
1542 if (env.best_cpu == -1)
1546 * Reset the scan period if the task is being rescheduled on an
1547 * alternative node to recheck if the tasks is now properly placed.
1549 p->numa_scan_period = task_scan_min(p);
1551 if (env.best_task == NULL) {
1552 ret = migrate_task_to(p, env.best_cpu);
1554 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1558 ret = migrate_swap(p, env.best_task);
1560 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1561 put_task_struct(env.best_task);
1565 /* Attempt to migrate a task to a CPU on the preferred node. */
1566 static void numa_migrate_preferred(struct task_struct *p)
1568 unsigned long interval = HZ;
1570 /* This task has no NUMA fault statistics yet */
1571 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1574 /* Periodically retry migrating the task to the preferred node */
1575 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1576 p->numa_migrate_retry = jiffies + interval;
1578 /* Success if task is already running on preferred CPU */
1579 if (task_node(p) == p->numa_preferred_nid)
1582 /* Otherwise, try migrate to a CPU on the preferred node */
1583 task_numa_migrate(p);
1587 * Find the nodes on which the workload is actively running. We do this by
1588 * tracking the nodes from which NUMA hinting faults are triggered. This can
1589 * be different from the set of nodes where the workload's memory is currently
1592 * The bitmask is used to make smarter decisions on when to do NUMA page
1593 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1594 * are added when they cause over 6/16 of the maximum number of faults, but
1595 * only removed when they drop below 3/16.
1597 static void update_numa_active_node_mask(struct numa_group *numa_group)
1599 unsigned long faults, max_faults = 0;
1602 for_each_online_node(nid) {
1603 faults = group_faults_cpu(numa_group, nid);
1604 if (faults > max_faults)
1605 max_faults = faults;
1608 for_each_online_node(nid) {
1609 faults = group_faults_cpu(numa_group, nid);
1610 if (!node_isset(nid, numa_group->active_nodes)) {
1611 if (faults > max_faults * 6 / 16)
1612 node_set(nid, numa_group->active_nodes);
1613 } else if (faults < max_faults * 3 / 16)
1614 node_clear(nid, numa_group->active_nodes);
1619 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1620 * increments. The more local the fault statistics are, the higher the scan
1621 * period will be for the next scan window. If local/(local+remote) ratio is
1622 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1623 * the scan period will decrease. Aim for 70% local accesses.
1625 #define NUMA_PERIOD_SLOTS 10
1626 #define NUMA_PERIOD_THRESHOLD 7
1629 * Increase the scan period (slow down scanning) if the majority of
1630 * our memory is already on our local node, or if the majority of
1631 * the page accesses are shared with other processes.
1632 * Otherwise, decrease the scan period.
1634 static void update_task_scan_period(struct task_struct *p,
1635 unsigned long shared, unsigned long private)
1637 unsigned int period_slot;
1641 unsigned long remote = p->numa_faults_locality[0];
1642 unsigned long local = p->numa_faults_locality[1];
1645 * If there were no record hinting faults then either the task is
1646 * completely idle or all activity is areas that are not of interest
1647 * to automatic numa balancing. Related to that, if there were failed
1648 * migration then it implies we are migrating too quickly or the local
1649 * node is overloaded. In either case, scan slower
1651 if (local + shared == 0 || p->numa_faults_locality[2]) {
1652 p->numa_scan_period = min(p->numa_scan_period_max,
1653 p->numa_scan_period << 1);
1655 p->mm->numa_next_scan = jiffies +
1656 msecs_to_jiffies(p->numa_scan_period);
1662 * Prepare to scale scan period relative to the current period.
1663 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1664 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1665 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1667 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1668 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1669 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1670 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1673 diff = slot * period_slot;
1675 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1678 * Scale scan rate increases based on sharing. There is an
1679 * inverse relationship between the degree of sharing and
1680 * the adjustment made to the scanning period. Broadly
1681 * speaking the intent is that there is little point
1682 * scanning faster if shared accesses dominate as it may
1683 * simply bounce migrations uselessly
1685 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1686 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1689 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1690 task_scan_min(p), task_scan_max(p));
1691 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1695 * Get the fraction of time the task has been running since the last
1696 * NUMA placement cycle. The scheduler keeps similar statistics, but
1697 * decays those on a 32ms period, which is orders of magnitude off
1698 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1699 * stats only if the task is so new there are no NUMA statistics yet.
1701 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1703 u64 runtime, delta, now;
1704 /* Use the start of this time slice to avoid calculations. */
1705 now = p->se.exec_start;
1706 runtime = p->se.sum_exec_runtime;
1708 if (p->last_task_numa_placement) {
1709 delta = runtime - p->last_sum_exec_runtime;
1710 *period = now - p->last_task_numa_placement;
1712 delta = p->se.avg.load_sum / p->se.load.weight;
1713 *period = LOAD_AVG_MAX;
1716 p->last_sum_exec_runtime = runtime;
1717 p->last_task_numa_placement = now;
1723 * Determine the preferred nid for a task in a numa_group. This needs to
1724 * be done in a way that produces consistent results with group_weight,
1725 * otherwise workloads might not converge.
1727 static int preferred_group_nid(struct task_struct *p, int nid)
1732 /* Direct connections between all NUMA nodes. */
1733 if (sched_numa_topology_type == NUMA_DIRECT)
1737 * On a system with glueless mesh NUMA topology, group_weight
1738 * scores nodes according to the number of NUMA hinting faults on
1739 * both the node itself, and on nearby nodes.
1741 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1742 unsigned long score, max_score = 0;
1743 int node, max_node = nid;
1745 dist = sched_max_numa_distance;
1747 for_each_online_node(node) {
1748 score = group_weight(p, node, dist);
1749 if (score > max_score) {
1758 * Finding the preferred nid in a system with NUMA backplane
1759 * interconnect topology is more involved. The goal is to locate
1760 * tasks from numa_groups near each other in the system, and
1761 * untangle workloads from different sides of the system. This requires
1762 * searching down the hierarchy of node groups, recursively searching
1763 * inside the highest scoring group of nodes. The nodemask tricks
1764 * keep the complexity of the search down.
1766 nodes = node_online_map;
1767 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1768 unsigned long max_faults = 0;
1769 nodemask_t max_group = NODE_MASK_NONE;
1772 /* Are there nodes at this distance from each other? */
1773 if (!find_numa_distance(dist))
1776 for_each_node_mask(a, nodes) {
1777 unsigned long faults = 0;
1778 nodemask_t this_group;
1779 nodes_clear(this_group);
1781 /* Sum group's NUMA faults; includes a==b case. */
1782 for_each_node_mask(b, nodes) {
1783 if (node_distance(a, b) < dist) {
1784 faults += group_faults(p, b);
1785 node_set(b, this_group);
1786 node_clear(b, nodes);
1790 /* Remember the top group. */
1791 if (faults > max_faults) {
1792 max_faults = faults;
1793 max_group = this_group;
1795 * subtle: at the smallest distance there is
1796 * just one node left in each "group", the
1797 * winner is the preferred nid.
1802 /* Next round, evaluate the nodes within max_group. */
1810 static void task_numa_placement(struct task_struct *p)
1812 int seq, nid, max_nid = -1, max_group_nid = -1;
1813 unsigned long max_faults = 0, max_group_faults = 0;
1814 unsigned long fault_types[2] = { 0, 0 };
1815 unsigned long total_faults;
1816 u64 runtime, period;
1817 spinlock_t *group_lock = NULL;
1820 * The p->mm->numa_scan_seq field gets updated without
1821 * exclusive access. Use READ_ONCE() here to ensure
1822 * that the field is read in a single access:
1824 seq = READ_ONCE(p->mm->numa_scan_seq);
1825 if (p->numa_scan_seq == seq)
1827 p->numa_scan_seq = seq;
1828 p->numa_scan_period_max = task_scan_max(p);
1830 total_faults = p->numa_faults_locality[0] +
1831 p->numa_faults_locality[1];
1832 runtime = numa_get_avg_runtime(p, &period);
1834 /* If the task is part of a group prevent parallel updates to group stats */
1835 if (p->numa_group) {
1836 group_lock = &p->numa_group->lock;
1837 spin_lock_irq(group_lock);
1840 /* Find the node with the highest number of faults */
1841 for_each_online_node(nid) {
1842 /* Keep track of the offsets in numa_faults array */
1843 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1844 unsigned long faults = 0, group_faults = 0;
1847 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1848 long diff, f_diff, f_weight;
1850 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1851 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1852 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1853 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1855 /* Decay existing window, copy faults since last scan */
1856 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1857 fault_types[priv] += p->numa_faults[membuf_idx];
1858 p->numa_faults[membuf_idx] = 0;
1861 * Normalize the faults_from, so all tasks in a group
1862 * count according to CPU use, instead of by the raw
1863 * number of faults. Tasks with little runtime have
1864 * little over-all impact on throughput, and thus their
1865 * faults are less important.
1867 f_weight = div64_u64(runtime << 16, period + 1);
1868 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1870 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1871 p->numa_faults[cpubuf_idx] = 0;
1873 p->numa_faults[mem_idx] += diff;
1874 p->numa_faults[cpu_idx] += f_diff;
1875 faults += p->numa_faults[mem_idx];
1876 p->total_numa_faults += diff;
1877 if (p->numa_group) {
1879 * safe because we can only change our own group
1881 * mem_idx represents the offset for a given
1882 * nid and priv in a specific region because it
1883 * is at the beginning of the numa_faults array.
1885 p->numa_group->faults[mem_idx] += diff;
1886 p->numa_group->faults_cpu[mem_idx] += f_diff;
1887 p->numa_group->total_faults += diff;
1888 group_faults += p->numa_group->faults[mem_idx];
1892 if (faults > max_faults) {
1893 max_faults = faults;
1897 if (group_faults > max_group_faults) {
1898 max_group_faults = group_faults;
1899 max_group_nid = nid;
1903 update_task_scan_period(p, fault_types[0], fault_types[1]);
1905 if (p->numa_group) {
1906 update_numa_active_node_mask(p->numa_group);
1907 spin_unlock_irq(group_lock);
1908 max_nid = preferred_group_nid(p, max_group_nid);
1912 /* Set the new preferred node */
1913 if (max_nid != p->numa_preferred_nid)
1914 sched_setnuma(p, max_nid);
1916 if (task_node(p) != p->numa_preferred_nid)
1917 numa_migrate_preferred(p);
1921 static inline int get_numa_group(struct numa_group *grp)
1923 return atomic_inc_not_zero(&grp->refcount);
1926 static inline void put_numa_group(struct numa_group *grp)
1928 if (atomic_dec_and_test(&grp->refcount))
1929 kfree_rcu(grp, rcu);
1932 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1935 struct numa_group *grp, *my_grp;
1936 struct task_struct *tsk;
1938 int cpu = cpupid_to_cpu(cpupid);
1941 if (unlikely(!p->numa_group)) {
1942 unsigned int size = sizeof(struct numa_group) +
1943 4*nr_node_ids*sizeof(unsigned long);
1945 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1949 atomic_set(&grp->refcount, 1);
1950 spin_lock_init(&grp->lock);
1952 /* Second half of the array tracks nids where faults happen */
1953 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1956 node_set(task_node(current), grp->active_nodes);
1958 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1959 grp->faults[i] = p->numa_faults[i];
1961 grp->total_faults = p->total_numa_faults;
1964 rcu_assign_pointer(p->numa_group, grp);
1968 tsk = READ_ONCE(cpu_rq(cpu)->curr);
1970 if (!cpupid_match_pid(tsk, cpupid))
1973 grp = rcu_dereference(tsk->numa_group);
1977 my_grp = p->numa_group;
1982 * Only join the other group if its bigger; if we're the bigger group,
1983 * the other task will join us.
1985 if (my_grp->nr_tasks > grp->nr_tasks)
1989 * Tie-break on the grp address.
1991 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1994 /* Always join threads in the same process. */
1995 if (tsk->mm == current->mm)
1998 /* Simple filter to avoid false positives due to PID collisions */
1999 if (flags & TNF_SHARED)
2002 /* Update priv based on whether false sharing was detected */
2005 if (join && !get_numa_group(grp))
2013 BUG_ON(irqs_disabled());
2014 double_lock_irq(&my_grp->lock, &grp->lock);
2016 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2017 my_grp->faults[i] -= p->numa_faults[i];
2018 grp->faults[i] += p->numa_faults[i];
2020 my_grp->total_faults -= p->total_numa_faults;
2021 grp->total_faults += p->total_numa_faults;
2026 spin_unlock(&my_grp->lock);
2027 spin_unlock_irq(&grp->lock);
2029 rcu_assign_pointer(p->numa_group, grp);
2031 put_numa_group(my_grp);
2039 void task_numa_free(struct task_struct *p)
2041 struct numa_group *grp = p->numa_group;
2042 void *numa_faults = p->numa_faults;
2043 unsigned long flags;
2047 spin_lock_irqsave(&grp->lock, flags);
2048 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2049 grp->faults[i] -= p->numa_faults[i];
2050 grp->total_faults -= p->total_numa_faults;
2053 spin_unlock_irqrestore(&grp->lock, flags);
2054 RCU_INIT_POINTER(p->numa_group, NULL);
2055 put_numa_group(grp);
2058 p->numa_faults = NULL;
2063 * Got a PROT_NONE fault for a page on @node.
2065 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2067 struct task_struct *p = current;
2068 bool migrated = flags & TNF_MIGRATED;
2069 int cpu_node = task_node(current);
2070 int local = !!(flags & TNF_FAULT_LOCAL);
2073 if (!static_branch_likely(&sched_numa_balancing))
2076 /* for example, ksmd faulting in a user's mm */
2080 /* Allocate buffer to track faults on a per-node basis */
2081 if (unlikely(!p->numa_faults)) {
2082 int size = sizeof(*p->numa_faults) *
2083 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2085 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2086 if (!p->numa_faults)
2089 p->total_numa_faults = 0;
2090 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2094 * First accesses are treated as private, otherwise consider accesses
2095 * to be private if the accessing pid has not changed
2097 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2100 priv = cpupid_match_pid(p, last_cpupid);
2101 if (!priv && !(flags & TNF_NO_GROUP))
2102 task_numa_group(p, last_cpupid, flags, &priv);
2106 * If a workload spans multiple NUMA nodes, a shared fault that
2107 * occurs wholly within the set of nodes that the workload is
2108 * actively using should be counted as local. This allows the
2109 * scan rate to slow down when a workload has settled down.
2111 if (!priv && !local && p->numa_group &&
2112 node_isset(cpu_node, p->numa_group->active_nodes) &&
2113 node_isset(mem_node, p->numa_group->active_nodes))
2116 task_numa_placement(p);
2119 * Retry task to preferred node migration periodically, in case it
2120 * case it previously failed, or the scheduler moved us.
2122 if (time_after(jiffies, p->numa_migrate_retry))
2123 numa_migrate_preferred(p);
2126 p->numa_pages_migrated += pages;
2127 if (flags & TNF_MIGRATE_FAIL)
2128 p->numa_faults_locality[2] += pages;
2130 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2131 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2132 p->numa_faults_locality[local] += pages;
2135 static void reset_ptenuma_scan(struct task_struct *p)
2138 * We only did a read acquisition of the mmap sem, so
2139 * p->mm->numa_scan_seq is written to without exclusive access
2140 * and the update is not guaranteed to be atomic. That's not
2141 * much of an issue though, since this is just used for
2142 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2143 * expensive, to avoid any form of compiler optimizations:
2145 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2146 p->mm->numa_scan_offset = 0;
2150 * The expensive part of numa migration is done from task_work context.
2151 * Triggered from task_tick_numa().
2153 void task_numa_work(struct callback_head *work)
2155 unsigned long migrate, next_scan, now = jiffies;
2156 struct task_struct *p = current;
2157 struct mm_struct *mm = p->mm;
2158 struct vm_area_struct *vma;
2159 unsigned long start, end;
2160 unsigned long nr_pte_updates = 0;
2161 long pages, virtpages;
2163 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2165 work->next = work; /* protect against double add */
2167 * Who cares about NUMA placement when they're dying.
2169 * NOTE: make sure not to dereference p->mm before this check,
2170 * exit_task_work() happens _after_ exit_mm() so we could be called
2171 * without p->mm even though we still had it when we enqueued this
2174 if (p->flags & PF_EXITING)
2177 if (!mm->numa_next_scan) {
2178 mm->numa_next_scan = now +
2179 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2183 * Enforce maximal scan/migration frequency..
2185 migrate = mm->numa_next_scan;
2186 if (time_before(now, migrate))
2189 if (p->numa_scan_period == 0) {
2190 p->numa_scan_period_max = task_scan_max(p);
2191 p->numa_scan_period = task_scan_min(p);
2194 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2195 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2199 * Delay this task enough that another task of this mm will likely win
2200 * the next time around.
2202 p->node_stamp += 2 * TICK_NSEC;
2204 start = mm->numa_scan_offset;
2205 pages = sysctl_numa_balancing_scan_size;
2206 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2207 virtpages = pages * 8; /* Scan up to this much virtual space */
2212 down_read(&mm->mmap_sem);
2213 vma = find_vma(mm, start);
2215 reset_ptenuma_scan(p);
2219 for (; vma; vma = vma->vm_next) {
2220 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2221 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2226 * Shared library pages mapped by multiple processes are not
2227 * migrated as it is expected they are cache replicated. Avoid
2228 * hinting faults in read-only file-backed mappings or the vdso
2229 * as migrating the pages will be of marginal benefit.
2232 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2236 * Skip inaccessible VMAs to avoid any confusion between
2237 * PROT_NONE and NUMA hinting ptes
2239 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2243 start = max(start, vma->vm_start);
2244 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2245 end = min(end, vma->vm_end);
2246 nr_pte_updates = change_prot_numa(vma, start, end);
2249 * Try to scan sysctl_numa_balancing_size worth of
2250 * hpages that have at least one present PTE that
2251 * is not already pte-numa. If the VMA contains
2252 * areas that are unused or already full of prot_numa
2253 * PTEs, scan up to virtpages, to skip through those
2257 pages -= (end - start) >> PAGE_SHIFT;
2258 virtpages -= (end - start) >> PAGE_SHIFT;
2261 if (pages <= 0 || virtpages <= 0)
2265 } while (end != vma->vm_end);
2270 * It is possible to reach the end of the VMA list but the last few
2271 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2272 * would find the !migratable VMA on the next scan but not reset the
2273 * scanner to the start so check it now.
2276 mm->numa_scan_offset = start;
2278 reset_ptenuma_scan(p);
2279 up_read(&mm->mmap_sem);
2283 * Drive the periodic memory faults..
2285 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2287 struct callback_head *work = &curr->numa_work;
2291 * We don't care about NUMA placement if we don't have memory.
2293 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2297 * Using runtime rather than walltime has the dual advantage that
2298 * we (mostly) drive the selection from busy threads and that the
2299 * task needs to have done some actual work before we bother with
2302 now = curr->se.sum_exec_runtime;
2303 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2305 if (now > curr->node_stamp + period) {
2306 if (!curr->node_stamp)
2307 curr->numa_scan_period = task_scan_min(curr);
2308 curr->node_stamp += period;
2310 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2311 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2312 task_work_add(curr, work, true);
2317 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2321 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2325 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2328 #endif /* CONFIG_NUMA_BALANCING */
2331 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2333 update_load_add(&cfs_rq->load, se->load.weight);
2334 if (!parent_entity(se))
2335 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2337 if (entity_is_task(se)) {
2338 struct rq *rq = rq_of(cfs_rq);
2340 account_numa_enqueue(rq, task_of(se));
2341 list_add(&se->group_node, &rq->cfs_tasks);
2344 cfs_rq->nr_running++;
2348 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2350 update_load_sub(&cfs_rq->load, se->load.weight);
2351 if (!parent_entity(se))
2352 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2353 if (entity_is_task(se)) {
2354 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2355 list_del_init(&se->group_node);
2357 cfs_rq->nr_running--;
2360 #ifdef CONFIG_FAIR_GROUP_SCHED
2362 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2367 * Use this CPU's real-time load instead of the last load contribution
2368 * as the updating of the contribution is delayed, and we will use the
2369 * the real-time load to calc the share. See update_tg_load_avg().
2371 tg_weight = atomic_long_read(&tg->load_avg);
2372 tg_weight -= cfs_rq->tg_load_avg_contrib;
2373 tg_weight += cfs_rq->load.weight;
2378 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2380 long tg_weight, load, shares;
2382 tg_weight = calc_tg_weight(tg, cfs_rq);
2383 load = cfs_rq->load.weight;
2385 shares = (tg->shares * load);
2387 shares /= tg_weight;
2389 if (shares < MIN_SHARES)
2390 shares = MIN_SHARES;
2391 if (shares > tg->shares)
2392 shares = tg->shares;
2396 # else /* CONFIG_SMP */
2397 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2401 # endif /* CONFIG_SMP */
2402 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2403 unsigned long weight)
2406 /* commit outstanding execution time */
2407 if (cfs_rq->curr == se)
2408 update_curr(cfs_rq);
2409 account_entity_dequeue(cfs_rq, se);
2412 update_load_set(&se->load, weight);
2415 account_entity_enqueue(cfs_rq, se);
2418 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2420 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2422 struct task_group *tg;
2423 struct sched_entity *se;
2427 se = tg->se[cpu_of(rq_of(cfs_rq))];
2428 if (!se || throttled_hierarchy(cfs_rq))
2431 if (likely(se->load.weight == tg->shares))
2434 shares = calc_cfs_shares(cfs_rq, tg);
2436 reweight_entity(cfs_rq_of(se), se, shares);
2438 #else /* CONFIG_FAIR_GROUP_SCHED */
2439 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2442 #endif /* CONFIG_FAIR_GROUP_SCHED */
2445 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2446 static const u32 runnable_avg_yN_inv[] = {
2447 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2448 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2449 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2450 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2451 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2452 0x85aac367, 0x82cd8698,
2456 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2457 * over-estimates when re-combining.
2459 static const u32 runnable_avg_yN_sum[] = {
2460 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2461 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2462 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2467 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2469 static __always_inline u64 decay_load(u64 val, u64 n)
2471 unsigned int local_n;
2475 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2478 /* after bounds checking we can collapse to 32-bit */
2482 * As y^PERIOD = 1/2, we can combine
2483 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2484 * With a look-up table which covers y^n (n<PERIOD)
2486 * To achieve constant time decay_load.
2488 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2489 val >>= local_n / LOAD_AVG_PERIOD;
2490 local_n %= LOAD_AVG_PERIOD;
2493 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2498 * For updates fully spanning n periods, the contribution to runnable
2499 * average will be: \Sum 1024*y^n
2501 * We can compute this reasonably efficiently by combining:
2502 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2504 static u32 __compute_runnable_contrib(u64 n)
2508 if (likely(n <= LOAD_AVG_PERIOD))
2509 return runnable_avg_yN_sum[n];
2510 else if (unlikely(n >= LOAD_AVG_MAX_N))
2511 return LOAD_AVG_MAX;
2513 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2515 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2516 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2518 n -= LOAD_AVG_PERIOD;
2519 } while (n > LOAD_AVG_PERIOD);
2521 contrib = decay_load(contrib, n);
2522 return contrib + runnable_avg_yN_sum[n];
2525 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2526 #error "load tracking assumes 2^10 as unit"
2529 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2532 * We can represent the historical contribution to runnable average as the
2533 * coefficients of a geometric series. To do this we sub-divide our runnable
2534 * history into segments of approximately 1ms (1024us); label the segment that
2535 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2537 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2539 * (now) (~1ms ago) (~2ms ago)
2541 * Let u_i denote the fraction of p_i that the entity was runnable.
2543 * We then designate the fractions u_i as our co-efficients, yielding the
2544 * following representation of historical load:
2545 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2547 * We choose y based on the with of a reasonably scheduling period, fixing:
2550 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2551 * approximately half as much as the contribution to load within the last ms
2554 * When a period "rolls over" and we have new u_0`, multiplying the previous
2555 * sum again by y is sufficient to update:
2556 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2557 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2559 static __always_inline int
2560 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2561 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2563 u64 delta, scaled_delta, periods;
2565 unsigned int delta_w, scaled_delta_w, decayed = 0;
2566 unsigned long scale_freq, scale_cpu;
2568 delta = now - sa->last_update_time;
2570 * This should only happen when time goes backwards, which it
2571 * unfortunately does during sched clock init when we swap over to TSC.
2573 if ((s64)delta < 0) {
2574 sa->last_update_time = now;
2579 * Use 1024ns as the unit of measurement since it's a reasonable
2580 * approximation of 1us and fast to compute.
2585 sa->last_update_time = now;
2587 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2588 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2590 /* delta_w is the amount already accumulated against our next period */
2591 delta_w = sa->period_contrib;
2592 if (delta + delta_w >= 1024) {
2595 /* how much left for next period will start over, we don't know yet */
2596 sa->period_contrib = 0;
2599 * Now that we know we're crossing a period boundary, figure
2600 * out how much from delta we need to complete the current
2601 * period and accrue it.
2603 delta_w = 1024 - delta_w;
2604 scaled_delta_w = cap_scale(delta_w, scale_freq);
2606 sa->load_sum += weight * scaled_delta_w;
2608 cfs_rq->runnable_load_sum +=
2609 weight * scaled_delta_w;
2613 sa->util_sum += scaled_delta_w * scale_cpu;
2617 /* Figure out how many additional periods this update spans */
2618 periods = delta / 1024;
2621 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2623 cfs_rq->runnable_load_sum =
2624 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2626 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2628 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2629 contrib = __compute_runnable_contrib(periods);
2630 contrib = cap_scale(contrib, scale_freq);
2632 sa->load_sum += weight * contrib;
2634 cfs_rq->runnable_load_sum += weight * contrib;
2637 sa->util_sum += contrib * scale_cpu;
2640 /* Remainder of delta accrued against u_0` */
2641 scaled_delta = cap_scale(delta, scale_freq);
2643 sa->load_sum += weight * scaled_delta;
2645 cfs_rq->runnable_load_sum += weight * scaled_delta;
2648 sa->util_sum += scaled_delta * scale_cpu;
2650 sa->period_contrib += delta;
2653 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2655 cfs_rq->runnable_load_avg =
2656 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2658 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2664 #ifdef CONFIG_FAIR_GROUP_SCHED
2666 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2667 * and effective_load (which is not done because it is too costly).
2669 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2671 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2673 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2674 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2675 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2679 #else /* CONFIG_FAIR_GROUP_SCHED */
2680 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2681 #endif /* CONFIG_FAIR_GROUP_SCHED */
2683 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2685 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2686 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2688 struct sched_avg *sa = &cfs_rq->avg;
2689 int decayed, removed = 0;
2691 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2692 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2693 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2694 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2698 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2699 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2700 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2701 sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2704 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2705 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2707 #ifndef CONFIG_64BIT
2709 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2712 return decayed || removed;
2715 /* Update task and its cfs_rq load average */
2716 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2718 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2719 u64 now = cfs_rq_clock_task(cfs_rq);
2720 int cpu = cpu_of(rq_of(cfs_rq));
2723 * Track task load average for carrying it to new CPU after migrated, and
2724 * track group sched_entity load average for task_h_load calc in migration
2726 __update_load_avg(now, cpu, &se->avg,
2727 se->on_rq * scale_load_down(se->load.weight),
2728 cfs_rq->curr == se, NULL);
2730 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2731 update_tg_load_avg(cfs_rq, 0);
2734 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2736 if (!sched_feat(ATTACH_AGE_LOAD))
2740 * If we got migrated (either between CPUs or between cgroups) we'll
2741 * have aged the average right before clearing @last_update_time.
2743 if (se->avg.last_update_time) {
2744 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2745 &se->avg, 0, 0, NULL);
2748 * XXX: we could have just aged the entire load away if we've been
2749 * absent from the fair class for too long.
2754 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2755 cfs_rq->avg.load_avg += se->avg.load_avg;
2756 cfs_rq->avg.load_sum += se->avg.load_sum;
2757 cfs_rq->avg.util_avg += se->avg.util_avg;
2758 cfs_rq->avg.util_sum += se->avg.util_sum;
2761 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2763 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2764 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2765 cfs_rq->curr == se, NULL);
2767 cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
2768 cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
2769 cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
2770 cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
2773 /* Add the load generated by se into cfs_rq's load average */
2775 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2777 struct sched_avg *sa = &se->avg;
2778 u64 now = cfs_rq_clock_task(cfs_rq);
2779 int migrated, decayed;
2781 migrated = !sa->last_update_time;
2783 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2784 se->on_rq * scale_load_down(se->load.weight),
2785 cfs_rq->curr == se, NULL);
2788 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2790 cfs_rq->runnable_load_avg += sa->load_avg;
2791 cfs_rq->runnable_load_sum += sa->load_sum;
2794 attach_entity_load_avg(cfs_rq, se);
2796 if (decayed || migrated)
2797 update_tg_load_avg(cfs_rq, 0);
2800 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2802 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2804 update_load_avg(se, 1);
2806 cfs_rq->runnable_load_avg =
2807 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2808 cfs_rq->runnable_load_sum =
2809 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2812 #ifndef CONFIG_64BIT
2813 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2815 u64 last_update_time_copy;
2816 u64 last_update_time;
2819 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2821 last_update_time = cfs_rq->avg.last_update_time;
2822 } while (last_update_time != last_update_time_copy);
2824 return last_update_time;
2827 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2829 return cfs_rq->avg.last_update_time;
2834 * Task first catches up with cfs_rq, and then subtract
2835 * itself from the cfs_rq (task must be off the queue now).
2837 void remove_entity_load_avg(struct sched_entity *se)
2839 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2840 u64 last_update_time;
2843 * Newly created task or never used group entity should not be removed
2844 * from its (source) cfs_rq
2846 if (se->avg.last_update_time == 0)
2849 last_update_time = cfs_rq_last_update_time(cfs_rq);
2851 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2852 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2853 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2857 * Update the rq's load with the elapsed running time before entering
2858 * idle. if the last scheduled task is not a CFS task, idle_enter will
2859 * be the only way to update the runnable statistic.
2861 void idle_enter_fair(struct rq *this_rq)
2866 * Update the rq's load with the elapsed idle time before a task is
2867 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2868 * be the only way to update the runnable statistic.
2870 void idle_exit_fair(struct rq *this_rq)
2874 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2876 return cfs_rq->runnable_load_avg;
2879 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2881 return cfs_rq->avg.load_avg;
2884 static int idle_balance(struct rq *this_rq);
2886 #else /* CONFIG_SMP */
2888 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2890 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2892 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2893 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2896 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2898 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2900 static inline int idle_balance(struct rq *rq)
2905 #endif /* CONFIG_SMP */
2907 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2909 #ifdef CONFIG_SCHEDSTATS
2910 struct task_struct *tsk = NULL;
2912 if (entity_is_task(se))
2915 if (se->statistics.sleep_start) {
2916 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2921 if (unlikely(delta > se->statistics.sleep_max))
2922 se->statistics.sleep_max = delta;
2924 se->statistics.sleep_start = 0;
2925 se->statistics.sum_sleep_runtime += delta;
2928 account_scheduler_latency(tsk, delta >> 10, 1);
2929 trace_sched_stat_sleep(tsk, delta);
2932 if (se->statistics.block_start) {
2933 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2938 if (unlikely(delta > se->statistics.block_max))
2939 se->statistics.block_max = delta;
2941 se->statistics.block_start = 0;
2942 se->statistics.sum_sleep_runtime += delta;
2945 if (tsk->in_iowait) {
2946 se->statistics.iowait_sum += delta;
2947 se->statistics.iowait_count++;
2948 trace_sched_stat_iowait(tsk, delta);
2951 trace_sched_stat_blocked(tsk, delta);
2954 * Blocking time is in units of nanosecs, so shift by
2955 * 20 to get a milliseconds-range estimation of the
2956 * amount of time that the task spent sleeping:
2958 if (unlikely(prof_on == SLEEP_PROFILING)) {
2959 profile_hits(SLEEP_PROFILING,
2960 (void *)get_wchan(tsk),
2963 account_scheduler_latency(tsk, delta >> 10, 0);
2969 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2971 #ifdef CONFIG_SCHED_DEBUG
2972 s64 d = se->vruntime - cfs_rq->min_vruntime;
2977 if (d > 3*sysctl_sched_latency)
2978 schedstat_inc(cfs_rq, nr_spread_over);
2983 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2985 u64 vruntime = cfs_rq->min_vruntime;
2988 * The 'current' period is already promised to the current tasks,
2989 * however the extra weight of the new task will slow them down a
2990 * little, place the new task so that it fits in the slot that
2991 * stays open at the end.
2993 if (initial && sched_feat(START_DEBIT))
2994 vruntime += sched_vslice(cfs_rq, se);
2996 /* sleeps up to a single latency don't count. */
2998 unsigned long thresh = sysctl_sched_latency;
3001 * Halve their sleep time's effect, to allow
3002 * for a gentler effect of sleepers:
3004 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3010 /* ensure we never gain time by being placed backwards. */
3011 se->vruntime = max_vruntime(se->vruntime, vruntime);
3014 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3017 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3020 * Update the normalized vruntime before updating min_vruntime
3021 * through calling update_curr().
3023 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3024 se->vruntime += cfs_rq->min_vruntime;
3027 * Update run-time statistics of the 'current'.
3029 update_curr(cfs_rq);
3030 enqueue_entity_load_avg(cfs_rq, se);
3031 account_entity_enqueue(cfs_rq, se);
3032 update_cfs_shares(cfs_rq);
3034 if (flags & ENQUEUE_WAKEUP) {
3035 place_entity(cfs_rq, se, 0);
3036 enqueue_sleeper(cfs_rq, se);
3039 update_stats_enqueue(cfs_rq, se);
3040 check_spread(cfs_rq, se);
3041 if (se != cfs_rq->curr)
3042 __enqueue_entity(cfs_rq, se);
3045 if (cfs_rq->nr_running == 1) {
3046 list_add_leaf_cfs_rq(cfs_rq);
3047 check_enqueue_throttle(cfs_rq);
3051 static void __clear_buddies_last(struct sched_entity *se)
3053 for_each_sched_entity(se) {
3054 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3055 if (cfs_rq->last != se)
3058 cfs_rq->last = NULL;
3062 static void __clear_buddies_next(struct sched_entity *se)
3064 for_each_sched_entity(se) {
3065 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3066 if (cfs_rq->next != se)
3069 cfs_rq->next = NULL;
3073 static void __clear_buddies_skip(struct sched_entity *se)
3075 for_each_sched_entity(se) {
3076 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3077 if (cfs_rq->skip != se)
3080 cfs_rq->skip = NULL;
3084 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3086 if (cfs_rq->last == se)
3087 __clear_buddies_last(se);
3089 if (cfs_rq->next == se)
3090 __clear_buddies_next(se);
3092 if (cfs_rq->skip == se)
3093 __clear_buddies_skip(se);
3096 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3099 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3102 * Update run-time statistics of the 'current'.
3104 update_curr(cfs_rq);
3105 dequeue_entity_load_avg(cfs_rq, se);
3107 update_stats_dequeue(cfs_rq, se);
3108 if (flags & DEQUEUE_SLEEP) {
3109 #ifdef CONFIG_SCHEDSTATS
3110 if (entity_is_task(se)) {
3111 struct task_struct *tsk = task_of(se);
3113 if (tsk->state & TASK_INTERRUPTIBLE)
3114 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3115 if (tsk->state & TASK_UNINTERRUPTIBLE)
3116 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3121 clear_buddies(cfs_rq, se);
3123 if (se != cfs_rq->curr)
3124 __dequeue_entity(cfs_rq, se);
3126 account_entity_dequeue(cfs_rq, se);
3129 * Normalize the entity after updating the min_vruntime because the
3130 * update can refer to the ->curr item and we need to reflect this
3131 * movement in our normalized position.
3133 if (!(flags & DEQUEUE_SLEEP))
3134 se->vruntime -= cfs_rq->min_vruntime;
3136 /* return excess runtime on last dequeue */
3137 return_cfs_rq_runtime(cfs_rq);
3139 update_min_vruntime(cfs_rq);
3140 update_cfs_shares(cfs_rq);
3144 * Preempt the current task with a newly woken task if needed:
3147 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3149 unsigned long ideal_runtime, delta_exec;
3150 struct sched_entity *se;
3153 ideal_runtime = sched_slice(cfs_rq, curr);
3154 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3155 if (delta_exec > ideal_runtime) {
3156 resched_curr(rq_of(cfs_rq));
3158 * The current task ran long enough, ensure it doesn't get
3159 * re-elected due to buddy favours.
3161 clear_buddies(cfs_rq, curr);
3166 * Ensure that a task that missed wakeup preemption by a
3167 * narrow margin doesn't have to wait for a full slice.
3168 * This also mitigates buddy induced latencies under load.
3170 if (delta_exec < sysctl_sched_min_granularity)
3173 se = __pick_first_entity(cfs_rq);
3174 delta = curr->vruntime - se->vruntime;
3179 if (delta > ideal_runtime)
3180 resched_curr(rq_of(cfs_rq));
3184 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3186 /* 'current' is not kept within the tree. */
3189 * Any task has to be enqueued before it get to execute on
3190 * a CPU. So account for the time it spent waiting on the
3193 update_stats_wait_end(cfs_rq, se);
3194 __dequeue_entity(cfs_rq, se);
3195 update_load_avg(se, 1);
3198 update_stats_curr_start(cfs_rq, se);
3200 #ifdef CONFIG_SCHEDSTATS
3202 * Track our maximum slice length, if the CPU's load is at
3203 * least twice that of our own weight (i.e. dont track it
3204 * when there are only lesser-weight tasks around):
3206 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3207 se->statistics.slice_max = max(se->statistics.slice_max,
3208 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3211 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3215 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3218 * Pick the next process, keeping these things in mind, in this order:
3219 * 1) keep things fair between processes/task groups
3220 * 2) pick the "next" process, since someone really wants that to run
3221 * 3) pick the "last" process, for cache locality
3222 * 4) do not run the "skip" process, if something else is available
3224 static struct sched_entity *
3225 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3227 struct sched_entity *left = __pick_first_entity(cfs_rq);
3228 struct sched_entity *se;
3231 * If curr is set we have to see if its left of the leftmost entity
3232 * still in the tree, provided there was anything in the tree at all.
3234 if (!left || (curr && entity_before(curr, left)))
3237 se = left; /* ideally we run the leftmost entity */
3240 * Avoid running the skip buddy, if running something else can
3241 * be done without getting too unfair.
3243 if (cfs_rq->skip == se) {
3244 struct sched_entity *second;
3247 second = __pick_first_entity(cfs_rq);
3249 second = __pick_next_entity(se);
3250 if (!second || (curr && entity_before(curr, second)))
3254 if (second && wakeup_preempt_entity(second, left) < 1)
3259 * Prefer last buddy, try to return the CPU to a preempted task.
3261 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3265 * Someone really wants this to run. If it's not unfair, run it.
3267 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3270 clear_buddies(cfs_rq, se);
3275 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3277 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3280 * If still on the runqueue then deactivate_task()
3281 * was not called and update_curr() has to be done:
3284 update_curr(cfs_rq);
3286 /* throttle cfs_rqs exceeding runtime */
3287 check_cfs_rq_runtime(cfs_rq);
3289 check_spread(cfs_rq, prev);
3291 update_stats_wait_start(cfs_rq, prev);
3292 /* Put 'current' back into the tree. */
3293 __enqueue_entity(cfs_rq, prev);
3294 /* in !on_rq case, update occurred at dequeue */
3295 update_load_avg(prev, 0);
3297 cfs_rq->curr = NULL;
3301 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3304 * Update run-time statistics of the 'current'.
3306 update_curr(cfs_rq);
3309 * Ensure that runnable average is periodically updated.
3311 update_load_avg(curr, 1);
3312 update_cfs_shares(cfs_rq);
3314 #ifdef CONFIG_SCHED_HRTICK
3316 * queued ticks are scheduled to match the slice, so don't bother
3317 * validating it and just reschedule.
3320 resched_curr(rq_of(cfs_rq));
3324 * don't let the period tick interfere with the hrtick preemption
3326 if (!sched_feat(DOUBLE_TICK) &&
3327 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3331 if (cfs_rq->nr_running > 1)
3332 check_preempt_tick(cfs_rq, curr);
3336 /**************************************************
3337 * CFS bandwidth control machinery
3340 #ifdef CONFIG_CFS_BANDWIDTH
3342 #ifdef HAVE_JUMP_LABEL
3343 static struct static_key __cfs_bandwidth_used;
3345 static inline bool cfs_bandwidth_used(void)
3347 return static_key_false(&__cfs_bandwidth_used);
3350 void cfs_bandwidth_usage_inc(void)
3352 static_key_slow_inc(&__cfs_bandwidth_used);
3355 void cfs_bandwidth_usage_dec(void)
3357 static_key_slow_dec(&__cfs_bandwidth_used);
3359 #else /* HAVE_JUMP_LABEL */
3360 static bool cfs_bandwidth_used(void)
3365 void cfs_bandwidth_usage_inc(void) {}
3366 void cfs_bandwidth_usage_dec(void) {}
3367 #endif /* HAVE_JUMP_LABEL */
3370 * default period for cfs group bandwidth.
3371 * default: 0.1s, units: nanoseconds
3373 static inline u64 default_cfs_period(void)
3375 return 100000000ULL;
3378 static inline u64 sched_cfs_bandwidth_slice(void)
3380 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3384 * Replenish runtime according to assigned quota and update expiration time.
3385 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3386 * additional synchronization around rq->lock.
3388 * requires cfs_b->lock
3390 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3394 if (cfs_b->quota == RUNTIME_INF)
3397 now = sched_clock_cpu(smp_processor_id());
3398 cfs_b->runtime = cfs_b->quota;
3399 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3402 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3404 return &tg->cfs_bandwidth;
3407 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3408 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3410 if (unlikely(cfs_rq->throttle_count))
3411 return cfs_rq->throttled_clock_task;
3413 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3416 /* returns 0 on failure to allocate runtime */
3417 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3419 struct task_group *tg = cfs_rq->tg;
3420 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3421 u64 amount = 0, min_amount, expires;
3423 /* note: this is a positive sum as runtime_remaining <= 0 */
3424 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3426 raw_spin_lock(&cfs_b->lock);
3427 if (cfs_b->quota == RUNTIME_INF)
3428 amount = min_amount;
3430 start_cfs_bandwidth(cfs_b);
3432 if (cfs_b->runtime > 0) {
3433 amount = min(cfs_b->runtime, min_amount);
3434 cfs_b->runtime -= amount;
3438 expires = cfs_b->runtime_expires;
3439 raw_spin_unlock(&cfs_b->lock);
3441 cfs_rq->runtime_remaining += amount;
3443 * we may have advanced our local expiration to account for allowed
3444 * spread between our sched_clock and the one on which runtime was
3447 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3448 cfs_rq->runtime_expires = expires;
3450 return cfs_rq->runtime_remaining > 0;
3454 * Note: This depends on the synchronization provided by sched_clock and the
3455 * fact that rq->clock snapshots this value.
3457 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3459 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3461 /* if the deadline is ahead of our clock, nothing to do */
3462 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3465 if (cfs_rq->runtime_remaining < 0)
3469 * If the local deadline has passed we have to consider the
3470 * possibility that our sched_clock is 'fast' and the global deadline
3471 * has not truly expired.
3473 * Fortunately we can check determine whether this the case by checking
3474 * whether the global deadline has advanced. It is valid to compare
3475 * cfs_b->runtime_expires without any locks since we only care about
3476 * exact equality, so a partial write will still work.
3479 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3480 /* extend local deadline, drift is bounded above by 2 ticks */
3481 cfs_rq->runtime_expires += TICK_NSEC;
3483 /* global deadline is ahead, expiration has passed */
3484 cfs_rq->runtime_remaining = 0;
3488 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3490 /* dock delta_exec before expiring quota (as it could span periods) */
3491 cfs_rq->runtime_remaining -= delta_exec;
3492 expire_cfs_rq_runtime(cfs_rq);
3494 if (likely(cfs_rq->runtime_remaining > 0))
3498 * if we're unable to extend our runtime we resched so that the active
3499 * hierarchy can be throttled
3501 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3502 resched_curr(rq_of(cfs_rq));
3505 static __always_inline
3506 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3508 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3511 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3514 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3516 return cfs_bandwidth_used() && cfs_rq->throttled;
3519 /* check whether cfs_rq, or any parent, is throttled */
3520 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3522 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3526 * Ensure that neither of the group entities corresponding to src_cpu or
3527 * dest_cpu are members of a throttled hierarchy when performing group
3528 * load-balance operations.
3530 static inline int throttled_lb_pair(struct task_group *tg,
3531 int src_cpu, int dest_cpu)
3533 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3535 src_cfs_rq = tg->cfs_rq[src_cpu];
3536 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3538 return throttled_hierarchy(src_cfs_rq) ||
3539 throttled_hierarchy(dest_cfs_rq);
3542 /* updated child weight may affect parent so we have to do this bottom up */
3543 static int tg_unthrottle_up(struct task_group *tg, void *data)
3545 struct rq *rq = data;
3546 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3548 cfs_rq->throttle_count--;
3550 if (!cfs_rq->throttle_count) {
3551 /* adjust cfs_rq_clock_task() */
3552 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3553 cfs_rq->throttled_clock_task;
3560 static int tg_throttle_down(struct task_group *tg, void *data)
3562 struct rq *rq = data;
3563 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3565 /* group is entering throttled state, stop time */
3566 if (!cfs_rq->throttle_count)
3567 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3568 cfs_rq->throttle_count++;
3573 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3575 struct rq *rq = rq_of(cfs_rq);
3576 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3577 struct sched_entity *se;
3578 long task_delta, dequeue = 1;
3581 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3583 /* freeze hierarchy runnable averages while throttled */
3585 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3588 task_delta = cfs_rq->h_nr_running;
3589 for_each_sched_entity(se) {
3590 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3591 /* throttled entity or throttle-on-deactivate */
3596 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3597 qcfs_rq->h_nr_running -= task_delta;
3599 if (qcfs_rq->load.weight)
3604 sub_nr_running(rq, task_delta);
3606 cfs_rq->throttled = 1;
3607 cfs_rq->throttled_clock = rq_clock(rq);
3608 raw_spin_lock(&cfs_b->lock);
3609 empty = list_empty(&cfs_b->throttled_cfs_rq);
3612 * Add to the _head_ of the list, so that an already-started
3613 * distribute_cfs_runtime will not see us
3615 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3618 * If we're the first throttled task, make sure the bandwidth
3622 start_cfs_bandwidth(cfs_b);
3624 raw_spin_unlock(&cfs_b->lock);
3627 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3629 struct rq *rq = rq_of(cfs_rq);
3630 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3631 struct sched_entity *se;
3635 se = cfs_rq->tg->se[cpu_of(rq)];
3637 cfs_rq->throttled = 0;
3639 update_rq_clock(rq);
3641 raw_spin_lock(&cfs_b->lock);
3642 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3643 list_del_rcu(&cfs_rq->throttled_list);
3644 raw_spin_unlock(&cfs_b->lock);
3646 /* update hierarchical throttle state */
3647 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3649 if (!cfs_rq->load.weight)
3652 task_delta = cfs_rq->h_nr_running;
3653 for_each_sched_entity(se) {
3657 cfs_rq = cfs_rq_of(se);
3659 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3660 cfs_rq->h_nr_running += task_delta;
3662 if (cfs_rq_throttled(cfs_rq))
3667 add_nr_running(rq, task_delta);
3669 /* determine whether we need to wake up potentially idle cpu */
3670 if (rq->curr == rq->idle && rq->cfs.nr_running)
3674 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3675 u64 remaining, u64 expires)
3677 struct cfs_rq *cfs_rq;
3679 u64 starting_runtime = remaining;
3682 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3684 struct rq *rq = rq_of(cfs_rq);
3686 raw_spin_lock(&rq->lock);
3687 if (!cfs_rq_throttled(cfs_rq))
3690 runtime = -cfs_rq->runtime_remaining + 1;
3691 if (runtime > remaining)
3692 runtime = remaining;
3693 remaining -= runtime;
3695 cfs_rq->runtime_remaining += runtime;
3696 cfs_rq->runtime_expires = expires;
3698 /* we check whether we're throttled above */
3699 if (cfs_rq->runtime_remaining > 0)
3700 unthrottle_cfs_rq(cfs_rq);
3703 raw_spin_unlock(&rq->lock);
3710 return starting_runtime - remaining;
3714 * Responsible for refilling a task_group's bandwidth and unthrottling its
3715 * cfs_rqs as appropriate. If there has been no activity within the last
3716 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3717 * used to track this state.
3719 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3721 u64 runtime, runtime_expires;
3724 /* no need to continue the timer with no bandwidth constraint */
3725 if (cfs_b->quota == RUNTIME_INF)
3726 goto out_deactivate;
3728 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3729 cfs_b->nr_periods += overrun;
3732 * idle depends on !throttled (for the case of a large deficit), and if
3733 * we're going inactive then everything else can be deferred
3735 if (cfs_b->idle && !throttled)
3736 goto out_deactivate;
3738 __refill_cfs_bandwidth_runtime(cfs_b);
3741 /* mark as potentially idle for the upcoming period */
3746 /* account preceding periods in which throttling occurred */
3747 cfs_b->nr_throttled += overrun;
3749 runtime_expires = cfs_b->runtime_expires;
3752 * This check is repeated as we are holding onto the new bandwidth while
3753 * we unthrottle. This can potentially race with an unthrottled group
3754 * trying to acquire new bandwidth from the global pool. This can result
3755 * in us over-using our runtime if it is all used during this loop, but
3756 * only by limited amounts in that extreme case.
3758 while (throttled && cfs_b->runtime > 0) {
3759 runtime = cfs_b->runtime;
3760 raw_spin_unlock(&cfs_b->lock);
3761 /* we can't nest cfs_b->lock while distributing bandwidth */
3762 runtime = distribute_cfs_runtime(cfs_b, runtime,
3764 raw_spin_lock(&cfs_b->lock);
3766 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3768 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3772 * While we are ensured activity in the period following an
3773 * unthrottle, this also covers the case in which the new bandwidth is
3774 * insufficient to cover the existing bandwidth deficit. (Forcing the
3775 * timer to remain active while there are any throttled entities.)
3785 /* a cfs_rq won't donate quota below this amount */
3786 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3787 /* minimum remaining period time to redistribute slack quota */
3788 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3789 /* how long we wait to gather additional slack before distributing */
3790 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3793 * Are we near the end of the current quota period?
3795 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3796 * hrtimer base being cleared by hrtimer_start. In the case of
3797 * migrate_hrtimers, base is never cleared, so we are fine.
3799 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3801 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3804 /* if the call-back is running a quota refresh is already occurring */
3805 if (hrtimer_callback_running(refresh_timer))
3808 /* is a quota refresh about to occur? */
3809 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3810 if (remaining < min_expire)
3816 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3818 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3820 /* if there's a quota refresh soon don't bother with slack */
3821 if (runtime_refresh_within(cfs_b, min_left))
3824 hrtimer_start(&cfs_b->slack_timer,
3825 ns_to_ktime(cfs_bandwidth_slack_period),
3829 /* we know any runtime found here is valid as update_curr() precedes return */
3830 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3832 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3833 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3835 if (slack_runtime <= 0)
3838 raw_spin_lock(&cfs_b->lock);
3839 if (cfs_b->quota != RUNTIME_INF &&
3840 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3841 cfs_b->runtime += slack_runtime;
3843 /* we are under rq->lock, defer unthrottling using a timer */
3844 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3845 !list_empty(&cfs_b->throttled_cfs_rq))
3846 start_cfs_slack_bandwidth(cfs_b);
3848 raw_spin_unlock(&cfs_b->lock);
3850 /* even if it's not valid for return we don't want to try again */
3851 cfs_rq->runtime_remaining -= slack_runtime;
3854 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3856 if (!cfs_bandwidth_used())
3859 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3862 __return_cfs_rq_runtime(cfs_rq);
3866 * This is done with a timer (instead of inline with bandwidth return) since
3867 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3869 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3871 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3874 /* confirm we're still not at a refresh boundary */
3875 raw_spin_lock(&cfs_b->lock);
3876 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3877 raw_spin_unlock(&cfs_b->lock);
3881 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3882 runtime = cfs_b->runtime;
3884 expires = cfs_b->runtime_expires;
3885 raw_spin_unlock(&cfs_b->lock);
3890 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3892 raw_spin_lock(&cfs_b->lock);
3893 if (expires == cfs_b->runtime_expires)
3894 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3895 raw_spin_unlock(&cfs_b->lock);
3899 * When a group wakes up we want to make sure that its quota is not already
3900 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3901 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3903 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3905 if (!cfs_bandwidth_used())
3908 /* an active group must be handled by the update_curr()->put() path */
3909 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3912 /* ensure the group is not already throttled */
3913 if (cfs_rq_throttled(cfs_rq))
3916 /* update runtime allocation */
3917 account_cfs_rq_runtime(cfs_rq, 0);
3918 if (cfs_rq->runtime_remaining <= 0)
3919 throttle_cfs_rq(cfs_rq);
3922 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3923 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3925 if (!cfs_bandwidth_used())
3928 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3932 * it's possible for a throttled entity to be forced into a running
3933 * state (e.g. set_curr_task), in this case we're finished.
3935 if (cfs_rq_throttled(cfs_rq))
3938 throttle_cfs_rq(cfs_rq);
3942 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3944 struct cfs_bandwidth *cfs_b =
3945 container_of(timer, struct cfs_bandwidth, slack_timer);
3947 do_sched_cfs_slack_timer(cfs_b);
3949 return HRTIMER_NORESTART;
3952 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3954 struct cfs_bandwidth *cfs_b =
3955 container_of(timer, struct cfs_bandwidth, period_timer);
3959 raw_spin_lock(&cfs_b->lock);
3961 overrun = hrtimer_forward_now(timer, cfs_b->period);
3965 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3968 cfs_b->period_active = 0;
3969 raw_spin_unlock(&cfs_b->lock);
3971 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3974 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3976 raw_spin_lock_init(&cfs_b->lock);
3978 cfs_b->quota = RUNTIME_INF;
3979 cfs_b->period = ns_to_ktime(default_cfs_period());
3981 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3982 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3983 cfs_b->period_timer.function = sched_cfs_period_timer;
3984 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3985 cfs_b->slack_timer.function = sched_cfs_slack_timer;
3988 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3990 cfs_rq->runtime_enabled = 0;
3991 INIT_LIST_HEAD(&cfs_rq->throttled_list);
3994 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3996 lockdep_assert_held(&cfs_b->lock);
3998 if (!cfs_b->period_active) {
3999 cfs_b->period_active = 1;
4000 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4001 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4005 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4007 /* init_cfs_bandwidth() was not called */
4008 if (!cfs_b->throttled_cfs_rq.next)
4011 hrtimer_cancel(&cfs_b->period_timer);
4012 hrtimer_cancel(&cfs_b->slack_timer);
4015 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4017 struct cfs_rq *cfs_rq;
4019 for_each_leaf_cfs_rq(rq, cfs_rq) {
4020 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4022 raw_spin_lock(&cfs_b->lock);
4023 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4024 raw_spin_unlock(&cfs_b->lock);
4028 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4030 struct cfs_rq *cfs_rq;
4032 for_each_leaf_cfs_rq(rq, cfs_rq) {
4033 if (!cfs_rq->runtime_enabled)
4037 * clock_task is not advancing so we just need to make sure
4038 * there's some valid quota amount
4040 cfs_rq->runtime_remaining = 1;
4042 * Offline rq is schedulable till cpu is completely disabled
4043 * in take_cpu_down(), so we prevent new cfs throttling here.
4045 cfs_rq->runtime_enabled = 0;
4047 if (cfs_rq_throttled(cfs_rq))
4048 unthrottle_cfs_rq(cfs_rq);
4052 #else /* CONFIG_CFS_BANDWIDTH */
4053 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4055 return rq_clock_task(rq_of(cfs_rq));
4058 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4059 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4060 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4061 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4063 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4068 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4073 static inline int throttled_lb_pair(struct task_group *tg,
4074 int src_cpu, int dest_cpu)
4079 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4081 #ifdef CONFIG_FAIR_GROUP_SCHED
4082 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4085 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4089 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4090 static inline void update_runtime_enabled(struct rq *rq) {}
4091 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4093 #endif /* CONFIG_CFS_BANDWIDTH */
4095 /**************************************************
4096 * CFS operations on tasks:
4099 #ifdef CONFIG_SCHED_HRTICK
4100 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4102 struct sched_entity *se = &p->se;
4103 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4105 WARN_ON(task_rq(p) != rq);
4107 if (cfs_rq->nr_running > 1) {
4108 u64 slice = sched_slice(cfs_rq, se);
4109 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4110 s64 delta = slice - ran;
4117 hrtick_start(rq, delta);
4122 * called from enqueue/dequeue and updates the hrtick when the
4123 * current task is from our class and nr_running is low enough
4126 static void hrtick_update(struct rq *rq)
4128 struct task_struct *curr = rq->curr;
4130 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4133 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4134 hrtick_start_fair(rq, curr);
4136 #else /* !CONFIG_SCHED_HRTICK */
4138 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4142 static inline void hrtick_update(struct rq *rq)
4147 static bool cpu_overutilized(int cpu);
4150 * The enqueue_task method is called before nr_running is
4151 * increased. Here we update the fair scheduling stats and
4152 * then put the task into the rbtree:
4155 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4157 struct cfs_rq *cfs_rq;
4158 struct sched_entity *se = &p->se;
4159 int task_new = !(flags & ENQUEUE_WAKEUP);
4161 for_each_sched_entity(se) {
4164 cfs_rq = cfs_rq_of(se);
4165 enqueue_entity(cfs_rq, se, flags);
4168 * end evaluation on encountering a throttled cfs_rq
4170 * note: in the case of encountering a throttled cfs_rq we will
4171 * post the final h_nr_running increment below.
4173 if (cfs_rq_throttled(cfs_rq))
4175 cfs_rq->h_nr_running++;
4177 flags = ENQUEUE_WAKEUP;
4180 for_each_sched_entity(se) {
4181 cfs_rq = cfs_rq_of(se);
4182 cfs_rq->h_nr_running++;
4184 if (cfs_rq_throttled(cfs_rq))
4187 update_load_avg(se, 1);
4188 update_cfs_shares(cfs_rq);
4192 add_nr_running(rq, 1);
4193 if (!task_new && !rq->rd->overutilized &&
4194 cpu_overutilized(rq->cpu))
4195 rq->rd->overutilized = true;
4200 static void set_next_buddy(struct sched_entity *se);
4203 * The dequeue_task method is called before nr_running is
4204 * decreased. We remove the task from the rbtree and
4205 * update the fair scheduling stats:
4207 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4209 struct cfs_rq *cfs_rq;
4210 struct sched_entity *se = &p->se;
4211 int task_sleep = flags & DEQUEUE_SLEEP;
4213 for_each_sched_entity(se) {
4214 cfs_rq = cfs_rq_of(se);
4215 dequeue_entity(cfs_rq, se, flags);
4218 * end evaluation on encountering a throttled cfs_rq
4220 * note: in the case of encountering a throttled cfs_rq we will
4221 * post the final h_nr_running decrement below.
4223 if (cfs_rq_throttled(cfs_rq))
4225 cfs_rq->h_nr_running--;
4227 /* Don't dequeue parent if it has other entities besides us */
4228 if (cfs_rq->load.weight) {
4230 * Bias pick_next to pick a task from this cfs_rq, as
4231 * p is sleeping when it is within its sched_slice.
4233 if (task_sleep && parent_entity(se))
4234 set_next_buddy(parent_entity(se));
4236 /* avoid re-evaluating load for this entity */
4237 se = parent_entity(se);
4240 flags |= DEQUEUE_SLEEP;
4243 for_each_sched_entity(se) {
4244 cfs_rq = cfs_rq_of(se);
4245 cfs_rq->h_nr_running--;
4247 if (cfs_rq_throttled(cfs_rq))
4250 update_load_avg(se, 1);
4251 update_cfs_shares(cfs_rq);
4255 sub_nr_running(rq, 1);
4263 * per rq 'load' arrray crap; XXX kill this.
4267 * The exact cpuload at various idx values, calculated at every tick would be
4268 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4270 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4271 * on nth tick when cpu may be busy, then we have:
4272 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4273 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4275 * decay_load_missed() below does efficient calculation of
4276 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4277 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4279 * The calculation is approximated on a 128 point scale.
4280 * degrade_zero_ticks is the number of ticks after which load at any
4281 * particular idx is approximated to be zero.
4282 * degrade_factor is a precomputed table, a row for each load idx.
4283 * Each column corresponds to degradation factor for a power of two ticks,
4284 * based on 128 point scale.
4286 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4287 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4289 * With this power of 2 load factors, we can degrade the load n times
4290 * by looking at 1 bits in n and doing as many mult/shift instead of
4291 * n mult/shifts needed by the exact degradation.
4293 #define DEGRADE_SHIFT 7
4294 static const unsigned char
4295 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4296 static const unsigned char
4297 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4298 {0, 0, 0, 0, 0, 0, 0, 0},
4299 {64, 32, 8, 0, 0, 0, 0, 0},
4300 {96, 72, 40, 12, 1, 0, 0},
4301 {112, 98, 75, 43, 15, 1, 0},
4302 {120, 112, 98, 76, 45, 16, 2} };
4305 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4306 * would be when CPU is idle and so we just decay the old load without
4307 * adding any new load.
4309 static unsigned long
4310 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4314 if (!missed_updates)
4317 if (missed_updates >= degrade_zero_ticks[idx])
4321 return load >> missed_updates;
4323 while (missed_updates) {
4324 if (missed_updates % 2)
4325 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4327 missed_updates >>= 1;
4334 * Update rq->cpu_load[] statistics. This function is usually called every
4335 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4336 * every tick. We fix it up based on jiffies.
4338 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4339 unsigned long pending_updates)
4343 this_rq->nr_load_updates++;
4345 /* Update our load: */
4346 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4347 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4348 unsigned long old_load, new_load;
4350 /* scale is effectively 1 << i now, and >> i divides by scale */
4352 old_load = this_rq->cpu_load[i];
4353 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4354 new_load = this_load;
4356 * Round up the averaging division if load is increasing. This
4357 * prevents us from getting stuck on 9 if the load is 10, for
4360 if (new_load > old_load)
4361 new_load += scale - 1;
4363 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4366 sched_avg_update(this_rq);
4369 /* Used instead of source_load when we know the type == 0 */
4370 static unsigned long weighted_cpuload(const int cpu)
4372 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4375 #ifdef CONFIG_NO_HZ_COMMON
4377 * There is no sane way to deal with nohz on smp when using jiffies because the
4378 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4379 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4381 * Therefore we cannot use the delta approach from the regular tick since that
4382 * would seriously skew the load calculation. However we'll make do for those
4383 * updates happening while idle (nohz_idle_balance) or coming out of idle
4384 * (tick_nohz_idle_exit).
4386 * This means we might still be one tick off for nohz periods.
4390 * Called from nohz_idle_balance() to update the load ratings before doing the
4393 static void update_idle_cpu_load(struct rq *this_rq)
4395 unsigned long curr_jiffies = READ_ONCE(jiffies);
4396 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4397 unsigned long pending_updates;
4400 * bail if there's load or we're actually up-to-date.
4402 if (load || curr_jiffies == this_rq->last_load_update_tick)
4405 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4406 this_rq->last_load_update_tick = curr_jiffies;
4408 __update_cpu_load(this_rq, load, pending_updates);
4412 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4414 void update_cpu_load_nohz(void)
4416 struct rq *this_rq = this_rq();
4417 unsigned long curr_jiffies = READ_ONCE(jiffies);
4418 unsigned long pending_updates;
4420 if (curr_jiffies == this_rq->last_load_update_tick)
4423 raw_spin_lock(&this_rq->lock);
4424 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4425 if (pending_updates) {
4426 this_rq->last_load_update_tick = curr_jiffies;
4428 * We were idle, this means load 0, the current load might be
4429 * !0 due to remote wakeups and the sort.
4431 __update_cpu_load(this_rq, 0, pending_updates);
4433 raw_spin_unlock(&this_rq->lock);
4435 #endif /* CONFIG_NO_HZ */
4438 * Called from scheduler_tick()
4440 void update_cpu_load_active(struct rq *this_rq)
4442 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4444 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4446 this_rq->last_load_update_tick = jiffies;
4447 __update_cpu_load(this_rq, load, 1);
4451 * Return a low guess at the load of a migration-source cpu weighted
4452 * according to the scheduling class and "nice" value.
4454 * We want to under-estimate the load of migration sources, to
4455 * balance conservatively.
4457 static unsigned long source_load(int cpu, int type)
4459 struct rq *rq = cpu_rq(cpu);
4460 unsigned long total = weighted_cpuload(cpu);
4462 if (type == 0 || !sched_feat(LB_BIAS))
4465 return min(rq->cpu_load[type-1], total);
4469 * Return a high guess at the load of a migration-target cpu weighted
4470 * according to the scheduling class and "nice" value.
4472 static unsigned long target_load(int cpu, int type)
4474 struct rq *rq = cpu_rq(cpu);
4475 unsigned long total = weighted_cpuload(cpu);
4477 if (type == 0 || !sched_feat(LB_BIAS))
4480 return max(rq->cpu_load[type-1], total);
4483 static unsigned long capacity_of(int cpu)
4485 return cpu_rq(cpu)->cpu_capacity;
4488 static unsigned long capacity_orig_of(int cpu)
4490 return cpu_rq(cpu)->cpu_capacity_orig;
4493 static unsigned long cpu_avg_load_per_task(int cpu)
4495 struct rq *rq = cpu_rq(cpu);
4496 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4497 unsigned long load_avg = weighted_cpuload(cpu);
4500 return load_avg / nr_running;
4505 static void record_wakee(struct task_struct *p)
4508 * Rough decay (wiping) for cost saving, don't worry
4509 * about the boundary, really active task won't care
4512 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4513 current->wakee_flips >>= 1;
4514 current->wakee_flip_decay_ts = jiffies;
4517 if (current->last_wakee != p) {
4518 current->last_wakee = p;
4519 current->wakee_flips++;
4523 static void task_waking_fair(struct task_struct *p)
4525 struct sched_entity *se = &p->se;
4526 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4529 #ifndef CONFIG_64BIT
4530 u64 min_vruntime_copy;
4533 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4535 min_vruntime = cfs_rq->min_vruntime;
4536 } while (min_vruntime != min_vruntime_copy);
4538 min_vruntime = cfs_rq->min_vruntime;
4541 se->vruntime -= min_vruntime;
4545 #ifdef CONFIG_FAIR_GROUP_SCHED
4547 * effective_load() calculates the load change as seen from the root_task_group
4549 * Adding load to a group doesn't make a group heavier, but can cause movement
4550 * of group shares between cpus. Assuming the shares were perfectly aligned one
4551 * can calculate the shift in shares.
4553 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4554 * on this @cpu and results in a total addition (subtraction) of @wg to the
4555 * total group weight.
4557 * Given a runqueue weight distribution (rw_i) we can compute a shares
4558 * distribution (s_i) using:
4560 * s_i = rw_i / \Sum rw_j (1)
4562 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4563 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4564 * shares distribution (s_i):
4566 * rw_i = { 2, 4, 1, 0 }
4567 * s_i = { 2/7, 4/7, 1/7, 0 }
4569 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4570 * task used to run on and the CPU the waker is running on), we need to
4571 * compute the effect of waking a task on either CPU and, in case of a sync
4572 * wakeup, compute the effect of the current task going to sleep.
4574 * So for a change of @wl to the local @cpu with an overall group weight change
4575 * of @wl we can compute the new shares distribution (s'_i) using:
4577 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4579 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4580 * differences in waking a task to CPU 0. The additional task changes the
4581 * weight and shares distributions like:
4583 * rw'_i = { 3, 4, 1, 0 }
4584 * s'_i = { 3/8, 4/8, 1/8, 0 }
4586 * We can then compute the difference in effective weight by using:
4588 * dw_i = S * (s'_i - s_i) (3)
4590 * Where 'S' is the group weight as seen by its parent.
4592 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4593 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4594 * 4/7) times the weight of the group.
4596 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4598 struct sched_entity *se = tg->se[cpu];
4600 if (!tg->parent) /* the trivial, non-cgroup case */
4603 for_each_sched_entity(se) {
4609 * W = @wg + \Sum rw_j
4611 W = wg + calc_tg_weight(tg, se->my_q);
4616 w = cfs_rq_load_avg(se->my_q) + wl;
4619 * wl = S * s'_i; see (2)
4622 wl = (w * (long)tg->shares) / W;
4627 * Per the above, wl is the new se->load.weight value; since
4628 * those are clipped to [MIN_SHARES, ...) do so now. See
4629 * calc_cfs_shares().
4631 if (wl < MIN_SHARES)
4635 * wl = dw_i = S * (s'_i - s_i); see (3)
4637 wl -= se->avg.load_avg;
4640 * Recursively apply this logic to all parent groups to compute
4641 * the final effective load change on the root group. Since
4642 * only the @tg group gets extra weight, all parent groups can
4643 * only redistribute existing shares. @wl is the shift in shares
4644 * resulting from this level per the above.
4653 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4661 * Returns the current capacity of cpu after applying both
4662 * cpu and freq scaling.
4664 static unsigned long capacity_curr_of(int cpu)
4666 return cpu_rq(cpu)->cpu_capacity_orig *
4667 arch_scale_freq_capacity(NULL, cpu)
4668 >> SCHED_CAPACITY_SHIFT;
4672 * cpu_util returns the amount of capacity of a CPU that is used by CFS
4673 * tasks. The unit of the return value must be the one of capacity so we can
4674 * compare the utilization with the capacity of the CPU that is available for
4675 * CFS task (ie cpu_capacity).
4677 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
4678 * recent utilization of currently non-runnable tasks on a CPU. It represents
4679 * the amount of utilization of a CPU in the range [0..capacity_orig] where
4680 * capacity_orig is the cpu_capacity available at the highest frequency
4681 * (arch_scale_freq_capacity()).
4682 * The utilization of a CPU converges towards a sum equal to or less than the
4683 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
4684 * the running time on this CPU scaled by capacity_curr.
4686 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
4687 * higher than capacity_orig because of unfortunate rounding in
4688 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
4689 * the average stabilizes with the new running time. We need to check that the
4690 * utilization stays within the range of [0..capacity_orig] and cap it if
4691 * necessary. Without utilization capping, a group could be seen as overloaded
4692 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
4693 * available capacity. We allow utilization to overshoot capacity_curr (but not
4694 * capacity_orig) as it useful for predicting the capacity required after task
4695 * migrations (scheduler-driven DVFS).
4697 static unsigned long __cpu_util(int cpu, int delta)
4699 unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
4700 unsigned long capacity = capacity_orig_of(cpu);
4706 return (delta >= capacity) ? capacity : delta;
4709 static unsigned long cpu_util(int cpu)
4711 return __cpu_util(cpu, 0);
4714 static inline bool energy_aware(void)
4716 return sched_feat(ENERGY_AWARE);
4720 struct sched_group *sg_top;
4721 struct sched_group *sg_cap;
4730 * __cpu_norm_util() returns the cpu util relative to a specific capacity,
4731 * i.e. it's busy ratio, in the range [0..SCHED_LOAD_SCALE] which is useful for
4732 * energy calculations. Using the scale-invariant util returned by
4733 * cpu_util() and approximating scale-invariant util by:
4735 * util ~ (curr_freq/max_freq)*1024 * capacity_orig/1024 * running_time/time
4737 * the normalized util can be found using the specific capacity.
4739 * capacity = capacity_orig * curr_freq/max_freq
4741 * norm_util = running_time/time ~ util/capacity
4743 static unsigned long __cpu_norm_util(int cpu, unsigned long capacity, int delta)
4745 int util = __cpu_util(cpu, delta);
4747 if (util >= capacity)
4748 return SCHED_CAPACITY_SCALE;
4750 return (util << SCHED_CAPACITY_SHIFT)/capacity;
4753 static int calc_util_delta(struct energy_env *eenv, int cpu)
4755 if (cpu == eenv->src_cpu)
4756 return -eenv->util_delta;
4757 if (cpu == eenv->dst_cpu)
4758 return eenv->util_delta;
4763 unsigned long group_max_util(struct energy_env *eenv)
4766 unsigned long max_util = 0;
4768 for_each_cpu(i, sched_group_cpus(eenv->sg_cap)) {
4769 delta = calc_util_delta(eenv, i);
4770 max_util = max(max_util, __cpu_util(i, delta));
4777 * group_norm_util() returns the approximated group util relative to it's
4778 * current capacity (busy ratio) in the range [0..SCHED_LOAD_SCALE] for use in
4779 * energy calculations. Since task executions may or may not overlap in time in
4780 * the group the true normalized util is between max(cpu_norm_util(i)) and
4781 * sum(cpu_norm_util(i)) when iterating over all cpus in the group, i. The
4782 * latter is used as the estimate as it leads to a more pessimistic energy
4783 * estimate (more busy).
4786 long group_norm_util(struct energy_env *eenv, struct sched_group *sg)
4789 unsigned long util_sum = 0;
4790 unsigned long capacity = sg->sge->cap_states[eenv->cap_idx].cap;
4792 for_each_cpu(i, sched_group_cpus(sg)) {
4793 delta = calc_util_delta(eenv, i);
4794 util_sum += __cpu_norm_util(i, capacity, delta);
4797 if (util_sum > SCHED_CAPACITY_SCALE)
4798 return SCHED_CAPACITY_SCALE;
4802 static int find_new_capacity(struct energy_env *eenv,
4803 const struct sched_group_energy const *sge)
4806 unsigned long util = group_max_util(eenv);
4808 for (idx = 0; idx < sge->nr_cap_states; idx++) {
4809 if (sge->cap_states[idx].cap >= util)
4813 eenv->cap_idx = idx;
4818 static int group_idle_state(struct sched_group *sg)
4820 int i, state = INT_MAX;
4822 /* Find the shallowest idle state in the sched group. */
4823 for_each_cpu(i, sched_group_cpus(sg))
4824 state = min(state, idle_get_state_idx(cpu_rq(i)));
4826 /* Take non-cpuidle idling into account (active idle/arch_cpu_idle()) */
4833 * sched_group_energy(): Computes the absolute energy consumption of cpus
4834 * belonging to the sched_group including shared resources shared only by
4835 * members of the group. Iterates over all cpus in the hierarchy below the
4836 * sched_group starting from the bottom working it's way up before going to
4837 * the next cpu until all cpus are covered at all levels. The current
4838 * implementation is likely to gather the same util statistics multiple times.
4839 * This can probably be done in a faster but more complex way.
4840 * Note: sched_group_energy() may fail when racing with sched_domain updates.
4842 static int sched_group_energy(struct energy_env *eenv)
4844 struct sched_domain *sd;
4845 int cpu, total_energy = 0;
4846 struct cpumask visit_cpus;
4847 struct sched_group *sg;
4849 WARN_ON(!eenv->sg_top->sge);
4851 cpumask_copy(&visit_cpus, sched_group_cpus(eenv->sg_top));
4853 while (!cpumask_empty(&visit_cpus)) {
4854 struct sched_group *sg_shared_cap = NULL;
4856 cpu = cpumask_first(&visit_cpus);
4859 * Is the group utilization affected by cpus outside this
4862 sd = rcu_dereference(per_cpu(sd_scs, cpu));
4866 * We most probably raced with hotplug; returning a
4867 * wrong energy estimation is better than entering an
4873 sg_shared_cap = sd->parent->groups;
4875 for_each_domain(cpu, sd) {
4878 /* Has this sched_domain already been visited? */
4879 if (sd->child && group_first_cpu(sg) != cpu)
4883 unsigned long group_util;
4884 int sg_busy_energy, sg_idle_energy;
4885 int cap_idx, idle_idx;
4887 if (sg_shared_cap && sg_shared_cap->group_weight >= sg->group_weight)
4888 eenv->sg_cap = sg_shared_cap;
4892 cap_idx = find_new_capacity(eenv, sg->sge);
4893 idle_idx = group_idle_state(sg);
4894 group_util = group_norm_util(eenv, sg);
4895 sg_busy_energy = (group_util * sg->sge->cap_states[cap_idx].power)
4896 >> SCHED_CAPACITY_SHIFT;
4897 sg_idle_energy = ((SCHED_LOAD_SCALE-group_util)
4898 * sg->sge->idle_states[idle_idx].power)
4899 >> SCHED_CAPACITY_SHIFT;
4901 total_energy += sg_busy_energy + sg_idle_energy;
4904 cpumask_xor(&visit_cpus, &visit_cpus, sched_group_cpus(sg));
4906 if (cpumask_equal(sched_group_cpus(sg), sched_group_cpus(eenv->sg_top)))
4909 } while (sg = sg->next, sg != sd->groups);
4915 eenv->energy = total_energy;
4919 static inline bool cpu_in_sg(struct sched_group *sg, int cpu)
4921 return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));
4925 * energy_diff(): Estimate the energy impact of changing the utilization
4926 * distribution. eenv specifies the change: utilisation amount, source, and
4927 * destination cpu. Source or destination cpu may be -1 in which case the
4928 * utilization is removed from or added to the system (e.g. task wake-up). If
4929 * both are specified, the utilization is migrated.
4931 static int energy_diff(struct energy_env *eenv)
4933 struct sched_domain *sd;
4934 struct sched_group *sg;
4935 int sd_cpu = -1, energy_before = 0, energy_after = 0;
4937 struct energy_env eenv_before = {
4939 .src_cpu = eenv->src_cpu,
4940 .dst_cpu = eenv->dst_cpu,
4943 if (eenv->src_cpu == eenv->dst_cpu)
4946 sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu;
4947 sd = rcu_dereference(per_cpu(sd_ea, sd_cpu));
4950 return 0; /* Error */
4955 if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) {
4956 eenv_before.sg_top = eenv->sg_top = sg;
4958 if (sched_group_energy(&eenv_before))
4959 return 0; /* Invalid result abort */
4960 energy_before += eenv_before.energy;
4962 if (sched_group_energy(eenv))
4963 return 0; /* Invalid result abort */
4964 energy_after += eenv->energy;
4966 } while (sg = sg->next, sg != sd->groups);
4968 return energy_after-energy_before;
4972 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4973 * A waker of many should wake a different task than the one last awakened
4974 * at a frequency roughly N times higher than one of its wakees. In order
4975 * to determine whether we should let the load spread vs consolodating to
4976 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4977 * partner, and a factor of lls_size higher frequency in the other. With
4978 * both conditions met, we can be relatively sure that the relationship is
4979 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4980 * being client/server, worker/dispatcher, interrupt source or whatever is
4981 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4983 static int wake_wide(struct task_struct *p)
4985 unsigned int master = current->wakee_flips;
4986 unsigned int slave = p->wakee_flips;
4987 int factor = this_cpu_read(sd_llc_size);
4990 swap(master, slave);
4991 if (slave < factor || master < slave * factor)
4996 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4998 s64 this_load, load;
4999 s64 this_eff_load, prev_eff_load;
5000 int idx, this_cpu, prev_cpu;
5001 struct task_group *tg;
5002 unsigned long weight;
5006 this_cpu = smp_processor_id();
5007 prev_cpu = task_cpu(p);
5008 load = source_load(prev_cpu, idx);
5009 this_load = target_load(this_cpu, idx);
5012 * If sync wakeup then subtract the (maximum possible)
5013 * effect of the currently running task from the load
5014 * of the current CPU:
5017 tg = task_group(current);
5018 weight = current->se.avg.load_avg;
5020 this_load += effective_load(tg, this_cpu, -weight, -weight);
5021 load += effective_load(tg, prev_cpu, 0, -weight);
5025 weight = p->se.avg.load_avg;
5028 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5029 * due to the sync cause above having dropped this_load to 0, we'll
5030 * always have an imbalance, but there's really nothing you can do
5031 * about that, so that's good too.
5033 * Otherwise check if either cpus are near enough in load to allow this
5034 * task to be woken on this_cpu.
5036 this_eff_load = 100;
5037 this_eff_load *= capacity_of(prev_cpu);
5039 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5040 prev_eff_load *= capacity_of(this_cpu);
5042 if (this_load > 0) {
5043 this_eff_load *= this_load +
5044 effective_load(tg, this_cpu, weight, weight);
5046 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5049 balanced = this_eff_load <= prev_eff_load;
5051 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5056 schedstat_inc(sd, ttwu_move_affine);
5057 schedstat_inc(p, se.statistics.nr_wakeups_affine);
5062 static inline unsigned long task_util(struct task_struct *p)
5064 return p->se.avg.util_avg;
5067 static unsigned int capacity_margin = 1280; /* ~20% margin */
5069 static inline bool __task_fits(struct task_struct *p, int cpu, int util)
5071 unsigned long capacity = capacity_of(cpu);
5073 util += task_util(p);
5075 return (capacity * 1024) > (util * capacity_margin);
5078 static inline bool task_fits_max(struct task_struct *p, int cpu)
5080 unsigned long capacity = capacity_of(cpu);
5081 unsigned long max_capacity = cpu_rq(cpu)->rd->max_cpu_capacity;
5083 if (capacity == max_capacity)
5086 if (capacity * capacity_margin > max_capacity * 1024)
5089 return __task_fits(p, cpu, 0);
5092 static inline bool task_fits_spare(struct task_struct *p, int cpu)
5094 return __task_fits(p, cpu, cpu_util(cpu));
5097 static bool cpu_overutilized(int cpu)
5099 return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
5103 * find_idlest_group finds and returns the least busy CPU group within the
5106 static struct sched_group *
5107 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5108 int this_cpu, int sd_flag)
5110 struct sched_group *idlest = NULL, *group = sd->groups;
5111 struct sched_group *fit_group = NULL, *spare_group = NULL;
5112 unsigned long min_load = ULONG_MAX, this_load = 0;
5113 unsigned long fit_capacity = ULONG_MAX;
5114 unsigned long max_spare_capacity = capacity_margin - SCHED_LOAD_SCALE;
5115 int load_idx = sd->forkexec_idx;
5116 int imbalance = 100 + (sd->imbalance_pct-100)/2;
5118 if (sd_flag & SD_BALANCE_WAKE)
5119 load_idx = sd->wake_idx;
5122 unsigned long load, avg_load, spare_capacity;
5126 /* Skip over this group if it has no CPUs allowed */
5127 if (!cpumask_intersects(sched_group_cpus(group),
5128 tsk_cpus_allowed(p)))
5131 local_group = cpumask_test_cpu(this_cpu,
5132 sched_group_cpus(group));
5134 /* Tally up the load of all CPUs in the group */
5137 for_each_cpu(i, sched_group_cpus(group)) {
5138 /* Bias balancing toward cpus of our domain */
5140 load = source_load(i, load_idx);
5142 load = target_load(i, load_idx);
5147 * Look for most energy-efficient group that can fit
5148 * that can fit the task.
5150 if (capacity_of(i) < fit_capacity && task_fits_spare(p, i)) {
5151 fit_capacity = capacity_of(i);
5156 * Look for group which has most spare capacity on a
5159 spare_capacity = capacity_of(i) - cpu_util(i);
5160 if (spare_capacity > max_spare_capacity) {
5161 max_spare_capacity = spare_capacity;
5162 spare_group = group;
5166 /* Adjust by relative CPU capacity of the group */
5167 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5170 this_load = avg_load;
5171 } else if (avg_load < min_load) {
5172 min_load = avg_load;
5175 } while (group = group->next, group != sd->groups);
5183 if (!idlest || 100*this_load < imbalance*min_load)
5189 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5192 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5194 unsigned long load, min_load = ULONG_MAX;
5195 unsigned int min_exit_latency = UINT_MAX;
5196 u64 latest_idle_timestamp = 0;
5197 int least_loaded_cpu = this_cpu;
5198 int shallowest_idle_cpu = -1;
5201 /* Traverse only the allowed CPUs */
5202 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5203 if (task_fits_spare(p, i)) {
5204 struct rq *rq = cpu_rq(i);
5205 struct cpuidle_state *idle = idle_get_state(rq);
5206 if (idle && idle->exit_latency < min_exit_latency) {
5208 * We give priority to a CPU whose idle state
5209 * has the smallest exit latency irrespective
5210 * of any idle timestamp.
5212 min_exit_latency = idle->exit_latency;
5213 latest_idle_timestamp = rq->idle_stamp;
5214 shallowest_idle_cpu = i;
5215 } else if (idle_cpu(i) &&
5216 (!idle || idle->exit_latency == min_exit_latency) &&
5217 rq->idle_stamp > latest_idle_timestamp) {
5219 * If equal or no active idle state, then
5220 * the most recently idled CPU might have
5223 latest_idle_timestamp = rq->idle_stamp;
5224 shallowest_idle_cpu = i;
5225 } else if (shallowest_idle_cpu == -1) {
5227 * If we haven't found an idle CPU yet
5228 * pick a non-idle one that can fit the task as
5231 shallowest_idle_cpu = i;
5233 } else if (shallowest_idle_cpu == -1) {
5234 load = weighted_cpuload(i);
5235 if (load < min_load || (load == min_load && i == this_cpu)) {
5237 least_loaded_cpu = i;
5242 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5246 * Try and locate an idle CPU in the sched_domain.
5248 static int select_idle_sibling(struct task_struct *p, int target)
5250 struct sched_domain *sd;
5251 struct sched_group *sg;
5252 int i = task_cpu(p);
5254 if (idle_cpu(target))
5258 * If the prevous cpu is cache affine and idle, don't be stupid.
5260 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5264 * Otherwise, iterate the domains and find an elegible idle cpu.
5266 sd = rcu_dereference(per_cpu(sd_llc, target));
5267 for_each_lower_domain(sd) {
5270 if (!cpumask_intersects(sched_group_cpus(sg),
5271 tsk_cpus_allowed(p)))
5274 for_each_cpu(i, sched_group_cpus(sg)) {
5275 if (i == target || !idle_cpu(i))
5279 target = cpumask_first_and(sched_group_cpus(sg),
5280 tsk_cpus_allowed(p));
5284 } while (sg != sd->groups);
5290 static int energy_aware_wake_cpu(struct task_struct *p, int target)
5292 struct sched_domain *sd;
5293 struct sched_group *sg, *sg_target;
5294 int target_max_cap = INT_MAX;
5295 int target_cpu = task_cpu(p);
5298 sd = rcu_dereference(per_cpu(sd_ea, task_cpu(p)));
5307 * Find group with sufficient capacity. We only get here if no cpu is
5308 * overutilized. We may end up overutilizing a cpu by adding the task,
5309 * but that should not be any worse than select_idle_sibling().
5310 * load_balance() should sort it out later as we get above the tipping
5314 /* Assuming all cpus are the same in group */
5315 int max_cap_cpu = group_first_cpu(sg);
5318 * Assume smaller max capacity means more energy-efficient.
5319 * Ideally we should query the energy model for the right
5320 * answer but it easily ends up in an exhaustive search.
5322 if (capacity_of(max_cap_cpu) < target_max_cap &&
5323 task_fits_max(p, max_cap_cpu)) {
5325 target_max_cap = capacity_of(max_cap_cpu);
5327 } while (sg = sg->next, sg != sd->groups);
5329 /* Find cpu with sufficient capacity */
5330 for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg_target)) {
5332 * p's blocked utilization is still accounted for on prev_cpu
5333 * so prev_cpu will receive a negative bias due to the double
5334 * accounting. However, the blocked utilization may be zero.
5336 int new_util = cpu_util(i) + task_util(p);
5338 if (new_util > capacity_orig_of(i))
5341 if (new_util < capacity_curr_of(i)) {
5343 if (cpu_rq(i)->nr_running)
5347 /* cpu has capacity at higher OPP, keep it as fallback */
5348 if (target_cpu == task_cpu(p))
5352 if (target_cpu != task_cpu(p)) {
5353 struct energy_env eenv = {
5354 .util_delta = task_util(p),
5355 .src_cpu = task_cpu(p),
5356 .dst_cpu = target_cpu,
5359 /* Not enough spare capacity on previous cpu */
5360 if (cpu_overutilized(task_cpu(p)))
5363 if (energy_diff(&eenv) >= 0)
5371 * select_task_rq_fair: Select target runqueue for the waking task in domains
5372 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5373 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5375 * Balances load by selecting the idlest cpu in the idlest group, or under
5376 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5378 * Returns the target cpu number.
5380 * preempt must be disabled.
5383 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5385 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5386 int cpu = smp_processor_id();
5387 int new_cpu = prev_cpu;
5388 int want_affine = 0;
5389 int sync = wake_flags & WF_SYNC;
5391 if (sd_flag & SD_BALANCE_WAKE)
5392 want_affine = (!wake_wide(p) && task_fits_max(p, cpu) &&
5393 cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) ||
5397 for_each_domain(cpu, tmp) {
5398 if (!(tmp->flags & SD_LOAD_BALANCE))
5402 * If both cpu and prev_cpu are part of this domain,
5403 * cpu is a valid SD_WAKE_AFFINE target.
5405 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5406 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5411 if (tmp->flags & sd_flag)
5413 else if (!want_affine)
5418 sd = NULL; /* Prefer wake_affine over balance flags */
5419 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5424 if (energy_aware() && !cpu_rq(cpu)->rd->overutilized)
5425 new_cpu = energy_aware_wake_cpu(p, prev_cpu);
5426 else if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5427 new_cpu = select_idle_sibling(p, new_cpu);
5430 struct sched_group *group;
5433 if (!(sd->flags & sd_flag)) {
5438 group = find_idlest_group(sd, p, cpu, sd_flag);
5444 new_cpu = find_idlest_cpu(group, p, cpu);
5445 if (new_cpu == -1 || new_cpu == cpu) {
5446 /* Now try balancing at a lower domain level of cpu */
5451 /* Now try balancing at a lower domain level of new_cpu */
5453 weight = sd->span_weight;
5455 for_each_domain(cpu, tmp) {
5456 if (weight <= tmp->span_weight)
5458 if (tmp->flags & sd_flag)
5461 /* while loop will break here if sd == NULL */
5469 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5470 * cfs_rq_of(p) references at time of call are still valid and identify the
5471 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5472 * other assumptions, including the state of rq->lock, should be made.
5474 static void migrate_task_rq_fair(struct task_struct *p)
5477 * We are supposed to update the task to "current" time, then its up to date
5478 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5479 * what current time is, so simply throw away the out-of-date time. This
5480 * will result in the wakee task is less decayed, but giving the wakee more
5481 * load sounds not bad.
5483 remove_entity_load_avg(&p->se);
5485 /* Tell new CPU we are migrated */
5486 p->se.avg.last_update_time = 0;
5488 /* We have migrated, no longer consider this task hot */
5489 p->se.exec_start = 0;
5492 static void task_dead_fair(struct task_struct *p)
5494 remove_entity_load_avg(&p->se);
5496 #endif /* CONFIG_SMP */
5498 static unsigned long
5499 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5501 unsigned long gran = sysctl_sched_wakeup_granularity;
5504 * Since its curr running now, convert the gran from real-time
5505 * to virtual-time in his units.
5507 * By using 'se' instead of 'curr' we penalize light tasks, so
5508 * they get preempted easier. That is, if 'se' < 'curr' then
5509 * the resulting gran will be larger, therefore penalizing the
5510 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5511 * be smaller, again penalizing the lighter task.
5513 * This is especially important for buddies when the leftmost
5514 * task is higher priority than the buddy.
5516 return calc_delta_fair(gran, se);
5520 * Should 'se' preempt 'curr'.
5534 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5536 s64 gran, vdiff = curr->vruntime - se->vruntime;
5541 gran = wakeup_gran(curr, se);
5548 static void set_last_buddy(struct sched_entity *se)
5550 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5553 for_each_sched_entity(se)
5554 cfs_rq_of(se)->last = se;
5557 static void set_next_buddy(struct sched_entity *se)
5559 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5562 for_each_sched_entity(se)
5563 cfs_rq_of(se)->next = se;
5566 static void set_skip_buddy(struct sched_entity *se)
5568 for_each_sched_entity(se)
5569 cfs_rq_of(se)->skip = se;
5573 * Preempt the current task with a newly woken task if needed:
5575 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5577 struct task_struct *curr = rq->curr;
5578 struct sched_entity *se = &curr->se, *pse = &p->se;
5579 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5580 int scale = cfs_rq->nr_running >= sched_nr_latency;
5581 int next_buddy_marked = 0;
5583 if (unlikely(se == pse))
5587 * This is possible from callers such as attach_tasks(), in which we
5588 * unconditionally check_prempt_curr() after an enqueue (which may have
5589 * lead to a throttle). This both saves work and prevents false
5590 * next-buddy nomination below.
5592 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5595 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5596 set_next_buddy(pse);
5597 next_buddy_marked = 1;
5601 * We can come here with TIF_NEED_RESCHED already set from new task
5604 * Note: this also catches the edge-case of curr being in a throttled
5605 * group (e.g. via set_curr_task), since update_curr() (in the
5606 * enqueue of curr) will have resulted in resched being set. This
5607 * prevents us from potentially nominating it as a false LAST_BUDDY
5610 if (test_tsk_need_resched(curr))
5613 /* Idle tasks are by definition preempted by non-idle tasks. */
5614 if (unlikely(curr->policy == SCHED_IDLE) &&
5615 likely(p->policy != SCHED_IDLE))
5619 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5620 * is driven by the tick):
5622 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5625 find_matching_se(&se, &pse);
5626 update_curr(cfs_rq_of(se));
5628 if (wakeup_preempt_entity(se, pse) == 1) {
5630 * Bias pick_next to pick the sched entity that is
5631 * triggering this preemption.
5633 if (!next_buddy_marked)
5634 set_next_buddy(pse);
5643 * Only set the backward buddy when the current task is still
5644 * on the rq. This can happen when a wakeup gets interleaved
5645 * with schedule on the ->pre_schedule() or idle_balance()
5646 * point, either of which can * drop the rq lock.
5648 * Also, during early boot the idle thread is in the fair class,
5649 * for obvious reasons its a bad idea to schedule back to it.
5651 if (unlikely(!se->on_rq || curr == rq->idle))
5654 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5658 static struct task_struct *
5659 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5661 struct cfs_rq *cfs_rq = &rq->cfs;
5662 struct sched_entity *se;
5663 struct task_struct *p;
5667 #ifdef CONFIG_FAIR_GROUP_SCHED
5668 if (!cfs_rq->nr_running)
5671 if (prev->sched_class != &fair_sched_class)
5675 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5676 * likely that a next task is from the same cgroup as the current.
5678 * Therefore attempt to avoid putting and setting the entire cgroup
5679 * hierarchy, only change the part that actually changes.
5683 struct sched_entity *curr = cfs_rq->curr;
5686 * Since we got here without doing put_prev_entity() we also
5687 * have to consider cfs_rq->curr. If it is still a runnable
5688 * entity, update_curr() will update its vruntime, otherwise
5689 * forget we've ever seen it.
5693 update_curr(cfs_rq);
5698 * This call to check_cfs_rq_runtime() will do the
5699 * throttle and dequeue its entity in the parent(s).
5700 * Therefore the 'simple' nr_running test will indeed
5703 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5707 se = pick_next_entity(cfs_rq, curr);
5708 cfs_rq = group_cfs_rq(se);
5714 * Since we haven't yet done put_prev_entity and if the selected task
5715 * is a different task than we started out with, try and touch the
5716 * least amount of cfs_rqs.
5719 struct sched_entity *pse = &prev->se;
5721 while (!(cfs_rq = is_same_group(se, pse))) {
5722 int se_depth = se->depth;
5723 int pse_depth = pse->depth;
5725 if (se_depth <= pse_depth) {
5726 put_prev_entity(cfs_rq_of(pse), pse);
5727 pse = parent_entity(pse);
5729 if (se_depth >= pse_depth) {
5730 set_next_entity(cfs_rq_of(se), se);
5731 se = parent_entity(se);
5735 put_prev_entity(cfs_rq, pse);
5736 set_next_entity(cfs_rq, se);
5739 if (hrtick_enabled(rq))
5740 hrtick_start_fair(rq, p);
5747 if (!cfs_rq->nr_running)
5750 put_prev_task(rq, prev);
5753 se = pick_next_entity(cfs_rq, NULL);
5754 set_next_entity(cfs_rq, se);
5755 cfs_rq = group_cfs_rq(se);
5760 if (hrtick_enabled(rq))
5761 hrtick_start_fair(rq, p);
5767 * This is OK, because current is on_cpu, which avoids it being picked
5768 * for load-balance and preemption/IRQs are still disabled avoiding
5769 * further scheduler activity on it and we're being very careful to
5770 * re-start the picking loop.
5772 lockdep_unpin_lock(&rq->lock);
5773 new_tasks = idle_balance(rq);
5774 lockdep_pin_lock(&rq->lock);
5776 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5777 * possible for any higher priority task to appear. In that case we
5778 * must re-start the pick_next_entity() loop.
5790 * Account for a descheduled task:
5792 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5794 struct sched_entity *se = &prev->se;
5795 struct cfs_rq *cfs_rq;
5797 for_each_sched_entity(se) {
5798 cfs_rq = cfs_rq_of(se);
5799 put_prev_entity(cfs_rq, se);
5804 * sched_yield() is very simple
5806 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5808 static void yield_task_fair(struct rq *rq)
5810 struct task_struct *curr = rq->curr;
5811 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5812 struct sched_entity *se = &curr->se;
5815 * Are we the only task in the tree?
5817 if (unlikely(rq->nr_running == 1))
5820 clear_buddies(cfs_rq, se);
5822 if (curr->policy != SCHED_BATCH) {
5823 update_rq_clock(rq);
5825 * Update run-time statistics of the 'current'.
5827 update_curr(cfs_rq);
5829 * Tell update_rq_clock() that we've just updated,
5830 * so we don't do microscopic update in schedule()
5831 * and double the fastpath cost.
5833 rq_clock_skip_update(rq, true);
5839 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5841 struct sched_entity *se = &p->se;
5843 /* throttled hierarchies are not runnable */
5844 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5847 /* Tell the scheduler that we'd really like pse to run next. */
5850 yield_task_fair(rq);
5856 /**************************************************
5857 * Fair scheduling class load-balancing methods.
5861 * The purpose of load-balancing is to achieve the same basic fairness the
5862 * per-cpu scheduler provides, namely provide a proportional amount of compute
5863 * time to each task. This is expressed in the following equation:
5865 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5867 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5868 * W_i,0 is defined as:
5870 * W_i,0 = \Sum_j w_i,j (2)
5872 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5873 * is derived from the nice value as per prio_to_weight[].
5875 * The weight average is an exponential decay average of the instantaneous
5878 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5880 * C_i is the compute capacity of cpu i, typically it is the
5881 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5882 * can also include other factors [XXX].
5884 * To achieve this balance we define a measure of imbalance which follows
5885 * directly from (1):
5887 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5889 * We them move tasks around to minimize the imbalance. In the continuous
5890 * function space it is obvious this converges, in the discrete case we get
5891 * a few fun cases generally called infeasible weight scenarios.
5894 * - infeasible weights;
5895 * - local vs global optima in the discrete case. ]
5900 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5901 * for all i,j solution, we create a tree of cpus that follows the hardware
5902 * topology where each level pairs two lower groups (or better). This results
5903 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5904 * tree to only the first of the previous level and we decrease the frequency
5905 * of load-balance at each level inv. proportional to the number of cpus in
5911 * \Sum { --- * --- * 2^i } = O(n) (5)
5913 * `- size of each group
5914 * | | `- number of cpus doing load-balance
5916 * `- sum over all levels
5918 * Coupled with a limit on how many tasks we can migrate every balance pass,
5919 * this makes (5) the runtime complexity of the balancer.
5921 * An important property here is that each CPU is still (indirectly) connected
5922 * to every other cpu in at most O(log n) steps:
5924 * The adjacency matrix of the resulting graph is given by:
5927 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5930 * And you'll find that:
5932 * A^(log_2 n)_i,j != 0 for all i,j (7)
5934 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5935 * The task movement gives a factor of O(m), giving a convergence complexity
5938 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5943 * In order to avoid CPUs going idle while there's still work to do, new idle
5944 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5945 * tree itself instead of relying on other CPUs to bring it work.
5947 * This adds some complexity to both (5) and (8) but it reduces the total idle
5955 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5958 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5963 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5965 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5967 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5970 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5971 * rewrite all of this once again.]
5974 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5976 enum fbq_type { regular, remote, all };
5978 #define LBF_ALL_PINNED 0x01
5979 #define LBF_NEED_BREAK 0x02
5980 #define LBF_DST_PINNED 0x04
5981 #define LBF_SOME_PINNED 0x08
5984 struct sched_domain *sd;
5992 struct cpumask *dst_grpmask;
5994 enum cpu_idle_type idle;
5996 unsigned int src_grp_nr_running;
5997 /* The set of CPUs under consideration for load-balancing */
5998 struct cpumask *cpus;
6003 unsigned int loop_break;
6004 unsigned int loop_max;
6006 enum fbq_type fbq_type;
6007 struct list_head tasks;
6011 * Is this task likely cache-hot:
6013 static int task_hot(struct task_struct *p, struct lb_env *env)
6017 lockdep_assert_held(&env->src_rq->lock);
6019 if (p->sched_class != &fair_sched_class)
6022 if (unlikely(p->policy == SCHED_IDLE))
6026 * Buddy candidates are cache hot:
6028 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6029 (&p->se == cfs_rq_of(&p->se)->next ||
6030 &p->se == cfs_rq_of(&p->se)->last))
6033 if (sysctl_sched_migration_cost == -1)
6035 if (sysctl_sched_migration_cost == 0)
6038 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6040 return delta < (s64)sysctl_sched_migration_cost;
6043 #ifdef CONFIG_NUMA_BALANCING
6045 * Returns 1, if task migration degrades locality
6046 * Returns 0, if task migration improves locality i.e migration preferred.
6047 * Returns -1, if task migration is not affected by locality.
6049 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6051 struct numa_group *numa_group = rcu_dereference(p->numa_group);
6052 unsigned long src_faults, dst_faults;
6053 int src_nid, dst_nid;
6055 if (!static_branch_likely(&sched_numa_balancing))
6058 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6061 src_nid = cpu_to_node(env->src_cpu);
6062 dst_nid = cpu_to_node(env->dst_cpu);
6064 if (src_nid == dst_nid)
6067 /* Migrating away from the preferred node is always bad. */
6068 if (src_nid == p->numa_preferred_nid) {
6069 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6075 /* Encourage migration to the preferred node. */
6076 if (dst_nid == p->numa_preferred_nid)
6080 src_faults = group_faults(p, src_nid);
6081 dst_faults = group_faults(p, dst_nid);
6083 src_faults = task_faults(p, src_nid);
6084 dst_faults = task_faults(p, dst_nid);
6087 return dst_faults < src_faults;
6091 static inline int migrate_degrades_locality(struct task_struct *p,
6099 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6102 int can_migrate_task(struct task_struct *p, struct lb_env *env)
6106 lockdep_assert_held(&env->src_rq->lock);
6109 * We do not migrate tasks that are:
6110 * 1) throttled_lb_pair, or
6111 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6112 * 3) running (obviously), or
6113 * 4) are cache-hot on their current CPU.
6115 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6118 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6121 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6123 env->flags |= LBF_SOME_PINNED;
6126 * Remember if this task can be migrated to any other cpu in
6127 * our sched_group. We may want to revisit it if we couldn't
6128 * meet load balance goals by pulling other tasks on src_cpu.
6130 * Also avoid computing new_dst_cpu if we have already computed
6131 * one in current iteration.
6133 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6136 /* Prevent to re-select dst_cpu via env's cpus */
6137 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6138 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6139 env->flags |= LBF_DST_PINNED;
6140 env->new_dst_cpu = cpu;
6148 /* Record that we found atleast one task that could run on dst_cpu */
6149 env->flags &= ~LBF_ALL_PINNED;
6151 if (task_running(env->src_rq, p)) {
6152 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6157 * Aggressive migration if:
6158 * 1) destination numa is preferred
6159 * 2) task is cache cold, or
6160 * 3) too many balance attempts have failed.
6162 tsk_cache_hot = migrate_degrades_locality(p, env);
6163 if (tsk_cache_hot == -1)
6164 tsk_cache_hot = task_hot(p, env);
6166 if (tsk_cache_hot <= 0 ||
6167 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6168 if (tsk_cache_hot == 1) {
6169 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
6170 schedstat_inc(p, se.statistics.nr_forced_migrations);
6175 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
6180 * detach_task() -- detach the task for the migration specified in env
6182 static void detach_task(struct task_struct *p, struct lb_env *env)
6184 lockdep_assert_held(&env->src_rq->lock);
6186 deactivate_task(env->src_rq, p, 0);
6187 p->on_rq = TASK_ON_RQ_MIGRATING;
6188 set_task_cpu(p, env->dst_cpu);
6192 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6193 * part of active balancing operations within "domain".
6195 * Returns a task if successful and NULL otherwise.
6197 static struct task_struct *detach_one_task(struct lb_env *env)
6199 struct task_struct *p, *n;
6201 lockdep_assert_held(&env->src_rq->lock);
6203 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
6204 if (!can_migrate_task(p, env))
6207 detach_task(p, env);
6210 * Right now, this is only the second place where
6211 * lb_gained[env->idle] is updated (other is detach_tasks)
6212 * so we can safely collect stats here rather than
6213 * inside detach_tasks().
6215 schedstat_inc(env->sd, lb_gained[env->idle]);
6221 static const unsigned int sched_nr_migrate_break = 32;
6224 * detach_tasks() -- tries to detach up to imbalance weighted load from
6225 * busiest_rq, as part of a balancing operation within domain "sd".
6227 * Returns number of detached tasks if successful and 0 otherwise.
6229 static int detach_tasks(struct lb_env *env)
6231 struct list_head *tasks = &env->src_rq->cfs_tasks;
6232 struct task_struct *p;
6236 lockdep_assert_held(&env->src_rq->lock);
6238 if (env->imbalance <= 0)
6241 while (!list_empty(tasks)) {
6243 * We don't want to steal all, otherwise we may be treated likewise,
6244 * which could at worst lead to a livelock crash.
6246 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6249 p = list_first_entry(tasks, struct task_struct, se.group_node);
6252 /* We've more or less seen every task there is, call it quits */
6253 if (env->loop > env->loop_max)
6256 /* take a breather every nr_migrate tasks */
6257 if (env->loop > env->loop_break) {
6258 env->loop_break += sched_nr_migrate_break;
6259 env->flags |= LBF_NEED_BREAK;
6263 if (!can_migrate_task(p, env))
6266 load = task_h_load(p);
6268 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6271 if ((load / 2) > env->imbalance)
6274 detach_task(p, env);
6275 list_add(&p->se.group_node, &env->tasks);
6278 env->imbalance -= load;
6280 #ifdef CONFIG_PREEMPT
6282 * NEWIDLE balancing is a source of latency, so preemptible
6283 * kernels will stop after the first task is detached to minimize
6284 * the critical section.
6286 if (env->idle == CPU_NEWLY_IDLE)
6291 * We only want to steal up to the prescribed amount of
6294 if (env->imbalance <= 0)
6299 list_move_tail(&p->se.group_node, tasks);
6303 * Right now, this is one of only two places we collect this stat
6304 * so we can safely collect detach_one_task() stats here rather
6305 * than inside detach_one_task().
6307 schedstat_add(env->sd, lb_gained[env->idle], detached);
6313 * attach_task() -- attach the task detached by detach_task() to its new rq.
6315 static void attach_task(struct rq *rq, struct task_struct *p)
6317 lockdep_assert_held(&rq->lock);
6319 BUG_ON(task_rq(p) != rq);
6320 p->on_rq = TASK_ON_RQ_QUEUED;
6321 activate_task(rq, p, 0);
6322 check_preempt_curr(rq, p, 0);
6326 * attach_one_task() -- attaches the task returned from detach_one_task() to
6329 static void attach_one_task(struct rq *rq, struct task_struct *p)
6331 raw_spin_lock(&rq->lock);
6333 raw_spin_unlock(&rq->lock);
6337 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6340 static void attach_tasks(struct lb_env *env)
6342 struct list_head *tasks = &env->tasks;
6343 struct task_struct *p;
6345 raw_spin_lock(&env->dst_rq->lock);
6347 while (!list_empty(tasks)) {
6348 p = list_first_entry(tasks, struct task_struct, se.group_node);
6349 list_del_init(&p->se.group_node);
6351 attach_task(env->dst_rq, p);
6354 raw_spin_unlock(&env->dst_rq->lock);
6357 #ifdef CONFIG_FAIR_GROUP_SCHED
6358 static void update_blocked_averages(int cpu)
6360 struct rq *rq = cpu_rq(cpu);
6361 struct cfs_rq *cfs_rq;
6362 unsigned long flags;
6364 raw_spin_lock_irqsave(&rq->lock, flags);
6365 update_rq_clock(rq);
6368 * Iterates the task_group tree in a bottom up fashion, see
6369 * list_add_leaf_cfs_rq() for details.
6371 for_each_leaf_cfs_rq(rq, cfs_rq) {
6372 /* throttled entities do not contribute to load */
6373 if (throttled_hierarchy(cfs_rq))
6376 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6377 update_tg_load_avg(cfs_rq, 0);
6379 raw_spin_unlock_irqrestore(&rq->lock, flags);
6383 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6384 * This needs to be done in a top-down fashion because the load of a child
6385 * group is a fraction of its parents load.
6387 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6389 struct rq *rq = rq_of(cfs_rq);
6390 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6391 unsigned long now = jiffies;
6394 if (cfs_rq->last_h_load_update == now)
6397 cfs_rq->h_load_next = NULL;
6398 for_each_sched_entity(se) {
6399 cfs_rq = cfs_rq_of(se);
6400 cfs_rq->h_load_next = se;
6401 if (cfs_rq->last_h_load_update == now)
6406 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6407 cfs_rq->last_h_load_update = now;
6410 while ((se = cfs_rq->h_load_next) != NULL) {
6411 load = cfs_rq->h_load;
6412 load = div64_ul(load * se->avg.load_avg,
6413 cfs_rq_load_avg(cfs_rq) + 1);
6414 cfs_rq = group_cfs_rq(se);
6415 cfs_rq->h_load = load;
6416 cfs_rq->last_h_load_update = now;
6420 static unsigned long task_h_load(struct task_struct *p)
6422 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6424 update_cfs_rq_h_load(cfs_rq);
6425 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6426 cfs_rq_load_avg(cfs_rq) + 1);
6429 static inline void update_blocked_averages(int cpu)
6431 struct rq *rq = cpu_rq(cpu);
6432 struct cfs_rq *cfs_rq = &rq->cfs;
6433 unsigned long flags;
6435 raw_spin_lock_irqsave(&rq->lock, flags);
6436 update_rq_clock(rq);
6437 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6438 raw_spin_unlock_irqrestore(&rq->lock, flags);
6441 static unsigned long task_h_load(struct task_struct *p)
6443 return p->se.avg.load_avg;
6447 /********** Helpers for find_busiest_group ************************/
6456 * sg_lb_stats - stats of a sched_group required for load_balancing
6458 struct sg_lb_stats {
6459 unsigned long avg_load; /*Avg load across the CPUs of the group */
6460 unsigned long group_load; /* Total load over the CPUs of the group */
6461 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6462 unsigned long load_per_task;
6463 unsigned long group_capacity;
6464 unsigned long group_util; /* Total utilization of the group */
6465 unsigned int sum_nr_running; /* Nr tasks running in the group */
6466 unsigned int idle_cpus;
6467 unsigned int group_weight;
6468 enum group_type group_type;
6469 int group_no_capacity;
6470 #ifdef CONFIG_NUMA_BALANCING
6471 unsigned int nr_numa_running;
6472 unsigned int nr_preferred_running;
6477 * sd_lb_stats - Structure to store the statistics of a sched_domain
6478 * during load balancing.
6480 struct sd_lb_stats {
6481 struct sched_group *busiest; /* Busiest group in this sd */
6482 struct sched_group *local; /* Local group in this sd */
6483 unsigned long total_load; /* Total load of all groups in sd */
6484 unsigned long total_capacity; /* Total capacity of all groups in sd */
6485 unsigned long avg_load; /* Average load across all groups in sd */
6487 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6488 struct sg_lb_stats local_stat; /* Statistics of the local group */
6491 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6494 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6495 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6496 * We must however clear busiest_stat::avg_load because
6497 * update_sd_pick_busiest() reads this before assignment.
6499 *sds = (struct sd_lb_stats){
6503 .total_capacity = 0UL,
6506 .sum_nr_running = 0,
6507 .group_type = group_other,
6513 * get_sd_load_idx - Obtain the load index for a given sched domain.
6514 * @sd: The sched_domain whose load_idx is to be obtained.
6515 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6517 * Return: The load index.
6519 static inline int get_sd_load_idx(struct sched_domain *sd,
6520 enum cpu_idle_type idle)
6526 load_idx = sd->busy_idx;
6529 case CPU_NEWLY_IDLE:
6530 load_idx = sd->newidle_idx;
6533 load_idx = sd->idle_idx;
6540 static unsigned long scale_rt_capacity(int cpu)
6542 struct rq *rq = cpu_rq(cpu);
6543 u64 total, used, age_stamp, avg;
6547 * Since we're reading these variables without serialization make sure
6548 * we read them once before doing sanity checks on them.
6550 age_stamp = READ_ONCE(rq->age_stamp);
6551 avg = READ_ONCE(rq->rt_avg);
6552 delta = __rq_clock_broken(rq) - age_stamp;
6554 if (unlikely(delta < 0))
6557 total = sched_avg_period() + delta;
6559 used = div_u64(avg, total);
6561 if (likely(used < SCHED_CAPACITY_SCALE))
6562 return SCHED_CAPACITY_SCALE - used;
6567 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6569 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6570 struct sched_group *sdg = sd->groups;
6572 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6574 capacity *= scale_rt_capacity(cpu);
6575 capacity >>= SCHED_CAPACITY_SHIFT;
6580 cpu_rq(cpu)->cpu_capacity = capacity;
6581 sdg->sgc->capacity = capacity;
6584 void update_group_capacity(struct sched_domain *sd, int cpu)
6586 struct sched_domain *child = sd->child;
6587 struct sched_group *group, *sdg = sd->groups;
6588 unsigned long capacity;
6589 unsigned long interval;
6591 interval = msecs_to_jiffies(sd->balance_interval);
6592 interval = clamp(interval, 1UL, max_load_balance_interval);
6593 sdg->sgc->next_update = jiffies + interval;
6596 update_cpu_capacity(sd, cpu);
6602 if (child->flags & SD_OVERLAP) {
6604 * SD_OVERLAP domains cannot assume that child groups
6605 * span the current group.
6608 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6609 struct sched_group_capacity *sgc;
6610 struct rq *rq = cpu_rq(cpu);
6613 * build_sched_domains() -> init_sched_groups_capacity()
6614 * gets here before we've attached the domains to the
6617 * Use capacity_of(), which is set irrespective of domains
6618 * in update_cpu_capacity().
6620 * This avoids capacity from being 0 and
6621 * causing divide-by-zero issues on boot.
6623 if (unlikely(!rq->sd)) {
6624 capacity += capacity_of(cpu);
6628 sgc = rq->sd->groups->sgc;
6629 capacity += sgc->capacity;
6633 * !SD_OVERLAP domains can assume that child groups
6634 * span the current group.
6637 group = child->groups;
6639 capacity += group->sgc->capacity;
6640 group = group->next;
6641 } while (group != child->groups);
6644 sdg->sgc->capacity = capacity;
6648 * Check whether the capacity of the rq has been noticeably reduced by side
6649 * activity. The imbalance_pct is used for the threshold.
6650 * Return true is the capacity is reduced
6653 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6655 return ((rq->cpu_capacity * sd->imbalance_pct) <
6656 (rq->cpu_capacity_orig * 100));
6660 * Group imbalance indicates (and tries to solve) the problem where balancing
6661 * groups is inadequate due to tsk_cpus_allowed() constraints.
6663 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6664 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6667 * { 0 1 2 3 } { 4 5 6 7 }
6670 * If we were to balance group-wise we'd place two tasks in the first group and
6671 * two tasks in the second group. Clearly this is undesired as it will overload
6672 * cpu 3 and leave one of the cpus in the second group unused.
6674 * The current solution to this issue is detecting the skew in the first group
6675 * by noticing the lower domain failed to reach balance and had difficulty
6676 * moving tasks due to affinity constraints.
6678 * When this is so detected; this group becomes a candidate for busiest; see
6679 * update_sd_pick_busiest(). And calculate_imbalance() and
6680 * find_busiest_group() avoid some of the usual balance conditions to allow it
6681 * to create an effective group imbalance.
6683 * This is a somewhat tricky proposition since the next run might not find the
6684 * group imbalance and decide the groups need to be balanced again. A most
6685 * subtle and fragile situation.
6688 static inline int sg_imbalanced(struct sched_group *group)
6690 return group->sgc->imbalance;
6694 * group_has_capacity returns true if the group has spare capacity that could
6695 * be used by some tasks.
6696 * We consider that a group has spare capacity if the * number of task is
6697 * smaller than the number of CPUs or if the utilization is lower than the
6698 * available capacity for CFS tasks.
6699 * For the latter, we use a threshold to stabilize the state, to take into
6700 * account the variance of the tasks' load and to return true if the available
6701 * capacity in meaningful for the load balancer.
6702 * As an example, an available capacity of 1% can appear but it doesn't make
6703 * any benefit for the load balance.
6706 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6708 if (sgs->sum_nr_running < sgs->group_weight)
6711 if ((sgs->group_capacity * 100) >
6712 (sgs->group_util * env->sd->imbalance_pct))
6719 * group_is_overloaded returns true if the group has more tasks than it can
6721 * group_is_overloaded is not equals to !group_has_capacity because a group
6722 * with the exact right number of tasks, has no more spare capacity but is not
6723 * overloaded so both group_has_capacity and group_is_overloaded return
6727 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6729 if (sgs->sum_nr_running <= sgs->group_weight)
6732 if ((sgs->group_capacity * 100) <
6733 (sgs->group_util * env->sd->imbalance_pct))
6740 group_type group_classify(struct sched_group *group,
6741 struct sg_lb_stats *sgs)
6743 if (sgs->group_no_capacity)
6744 return group_overloaded;
6746 if (sg_imbalanced(group))
6747 return group_imbalanced;
6753 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6754 * @env: The load balancing environment.
6755 * @group: sched_group whose statistics are to be updated.
6756 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6757 * @local_group: Does group contain this_cpu.
6758 * @sgs: variable to hold the statistics for this group.
6759 * @overload: Indicate more than one runnable task for any CPU.
6760 * @overutilized: Indicate overutilization for any CPU.
6762 static inline void update_sg_lb_stats(struct lb_env *env,
6763 struct sched_group *group, int load_idx,
6764 int local_group, struct sg_lb_stats *sgs,
6765 bool *overload, bool *overutilized)
6770 memset(sgs, 0, sizeof(*sgs));
6772 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6773 struct rq *rq = cpu_rq(i);
6775 /* Bias balancing toward cpus of our domain */
6777 load = target_load(i, load_idx);
6779 load = source_load(i, load_idx);
6781 sgs->group_load += load;
6782 sgs->group_util += cpu_util(i);
6783 sgs->sum_nr_running += rq->cfs.h_nr_running;
6785 if (rq->nr_running > 1)
6788 #ifdef CONFIG_NUMA_BALANCING
6789 sgs->nr_numa_running += rq->nr_numa_running;
6790 sgs->nr_preferred_running += rq->nr_preferred_running;
6792 sgs->sum_weighted_load += weighted_cpuload(i);
6796 if (cpu_overutilized(i))
6797 *overutilized = true;
6800 /* Adjust by relative CPU capacity of the group */
6801 sgs->group_capacity = group->sgc->capacity;
6802 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6804 if (sgs->sum_nr_running)
6805 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6807 sgs->group_weight = group->group_weight;
6809 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6810 sgs->group_type = group_classify(group, sgs);
6814 * update_sd_pick_busiest - return 1 on busiest group
6815 * @env: The load balancing environment.
6816 * @sds: sched_domain statistics
6817 * @sg: sched_group candidate to be checked for being the busiest
6818 * @sgs: sched_group statistics
6820 * Determine if @sg is a busier group than the previously selected
6823 * Return: %true if @sg is a busier group than the previously selected
6824 * busiest group. %false otherwise.
6826 static bool update_sd_pick_busiest(struct lb_env *env,
6827 struct sd_lb_stats *sds,
6828 struct sched_group *sg,
6829 struct sg_lb_stats *sgs)
6831 struct sg_lb_stats *busiest = &sds->busiest_stat;
6833 if (sgs->group_type > busiest->group_type)
6836 if (sgs->group_type < busiest->group_type)
6839 if (sgs->avg_load <= busiest->avg_load)
6842 /* This is the busiest node in its class. */
6843 if (!(env->sd->flags & SD_ASYM_PACKING))
6847 * ASYM_PACKING needs to move all the work to the lowest
6848 * numbered CPUs in the group, therefore mark all groups
6849 * higher than ourself as busy.
6851 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6855 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6862 #ifdef CONFIG_NUMA_BALANCING
6863 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6865 if (sgs->sum_nr_running > sgs->nr_numa_running)
6867 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6872 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6874 if (rq->nr_running > rq->nr_numa_running)
6876 if (rq->nr_running > rq->nr_preferred_running)
6881 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6886 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6890 #endif /* CONFIG_NUMA_BALANCING */
6893 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6894 * @env: The load balancing environment.
6895 * @sds: variable to hold the statistics for this sched_domain.
6897 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6899 struct sched_domain *child = env->sd->child;
6900 struct sched_group *sg = env->sd->groups;
6901 struct sg_lb_stats tmp_sgs;
6902 int load_idx, prefer_sibling = 0;
6903 bool overload = false, overutilized = false;
6905 if (child && child->flags & SD_PREFER_SIBLING)
6908 load_idx = get_sd_load_idx(env->sd, env->idle);
6911 struct sg_lb_stats *sgs = &tmp_sgs;
6914 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6917 sgs = &sds->local_stat;
6919 if (env->idle != CPU_NEWLY_IDLE ||
6920 time_after_eq(jiffies, sg->sgc->next_update))
6921 update_group_capacity(env->sd, env->dst_cpu);
6924 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6925 &overload, &overutilized);
6931 * In case the child domain prefers tasks go to siblings
6932 * first, lower the sg capacity so that we'll try
6933 * and move all the excess tasks away. We lower the capacity
6934 * of a group only if the local group has the capacity to fit
6935 * these excess tasks. The extra check prevents the case where
6936 * you always pull from the heaviest group when it is already
6937 * under-utilized (possible with a large weight task outweighs
6938 * the tasks on the system).
6940 if (prefer_sibling && sds->local &&
6941 group_has_capacity(env, &sds->local_stat) &&
6942 (sgs->sum_nr_running > 1)) {
6943 sgs->group_no_capacity = 1;
6944 sgs->group_type = group_classify(sg, sgs);
6947 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6949 sds->busiest_stat = *sgs;
6953 /* Now, start updating sd_lb_stats */
6954 sds->total_load += sgs->group_load;
6955 sds->total_capacity += sgs->group_capacity;
6958 } while (sg != env->sd->groups);
6960 if (env->sd->flags & SD_NUMA)
6961 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6963 env->src_grp_nr_running = sds->busiest_stat.sum_nr_running;
6965 if (!env->sd->parent) {
6966 /* update overload indicator if we are at root domain */
6967 if (env->dst_rq->rd->overload != overload)
6968 env->dst_rq->rd->overload = overload;
6970 /* Update over-utilization (tipping point, U >= 0) indicator */
6971 if (env->dst_rq->rd->overutilized != overutilized)
6972 env->dst_rq->rd->overutilized = overutilized;
6974 if (!env->dst_rq->rd->overutilized && overutilized)
6975 env->dst_rq->rd->overutilized = true;
6980 * check_asym_packing - Check to see if the group is packed into the
6983 * This is primarily intended to used at the sibling level. Some
6984 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6985 * case of POWER7, it can move to lower SMT modes only when higher
6986 * threads are idle. When in lower SMT modes, the threads will
6987 * perform better since they share less core resources. Hence when we
6988 * have idle threads, we want them to be the higher ones.
6990 * This packing function is run on idle threads. It checks to see if
6991 * the busiest CPU in this domain (core in the P7 case) has a higher
6992 * CPU number than the packing function is being run on. Here we are
6993 * assuming lower CPU number will be equivalent to lower a SMT thread
6996 * Return: 1 when packing is required and a task should be moved to
6997 * this CPU. The amount of the imbalance is returned in *imbalance.
6999 * @env: The load balancing environment.
7000 * @sds: Statistics of the sched_domain which is to be packed
7002 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7006 if (!(env->sd->flags & SD_ASYM_PACKING))
7012 busiest_cpu = group_first_cpu(sds->busiest);
7013 if (env->dst_cpu > busiest_cpu)
7016 env->imbalance = DIV_ROUND_CLOSEST(
7017 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7018 SCHED_CAPACITY_SCALE);
7024 * fix_small_imbalance - Calculate the minor imbalance that exists
7025 * amongst the groups of a sched_domain, during
7027 * @env: The load balancing environment.
7028 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7031 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7033 unsigned long tmp, capa_now = 0, capa_move = 0;
7034 unsigned int imbn = 2;
7035 unsigned long scaled_busy_load_per_task;
7036 struct sg_lb_stats *local, *busiest;
7038 local = &sds->local_stat;
7039 busiest = &sds->busiest_stat;
7041 if (!local->sum_nr_running)
7042 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
7043 else if (busiest->load_per_task > local->load_per_task)
7046 scaled_busy_load_per_task =
7047 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7048 busiest->group_capacity;
7050 if (busiest->avg_load + scaled_busy_load_per_task >=
7051 local->avg_load + (scaled_busy_load_per_task * imbn)) {
7052 env->imbalance = busiest->load_per_task;
7057 * OK, we don't have enough imbalance to justify moving tasks,
7058 * however we may be able to increase total CPU capacity used by
7062 capa_now += busiest->group_capacity *
7063 min(busiest->load_per_task, busiest->avg_load);
7064 capa_now += local->group_capacity *
7065 min(local->load_per_task, local->avg_load);
7066 capa_now /= SCHED_CAPACITY_SCALE;
7068 /* Amount of load we'd subtract */
7069 if (busiest->avg_load > scaled_busy_load_per_task) {
7070 capa_move += busiest->group_capacity *
7071 min(busiest->load_per_task,
7072 busiest->avg_load - scaled_busy_load_per_task);
7075 /* Amount of load we'd add */
7076 if (busiest->avg_load * busiest->group_capacity <
7077 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7078 tmp = (busiest->avg_load * busiest->group_capacity) /
7079 local->group_capacity;
7081 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7082 local->group_capacity;
7084 capa_move += local->group_capacity *
7085 min(local->load_per_task, local->avg_load + tmp);
7086 capa_move /= SCHED_CAPACITY_SCALE;
7088 /* Move if we gain throughput */
7089 if (capa_move > capa_now)
7090 env->imbalance = busiest->load_per_task;
7094 * calculate_imbalance - Calculate the amount of imbalance present within the
7095 * groups of a given sched_domain during load balance.
7096 * @env: load balance environment
7097 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7099 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7101 unsigned long max_pull, load_above_capacity = ~0UL;
7102 struct sg_lb_stats *local, *busiest;
7104 local = &sds->local_stat;
7105 busiest = &sds->busiest_stat;
7107 if (busiest->group_type == group_imbalanced) {
7109 * In the group_imb case we cannot rely on group-wide averages
7110 * to ensure cpu-load equilibrium, look at wider averages. XXX
7112 busiest->load_per_task =
7113 min(busiest->load_per_task, sds->avg_load);
7117 * In the presence of smp nice balancing, certain scenarios can have
7118 * max load less than avg load(as we skip the groups at or below
7119 * its cpu_capacity, while calculating max_load..)
7121 if (busiest->avg_load <= sds->avg_load ||
7122 local->avg_load >= sds->avg_load) {
7124 return fix_small_imbalance(env, sds);
7128 * If there aren't any idle cpus, avoid creating some.
7130 if (busiest->group_type == group_overloaded &&
7131 local->group_type == group_overloaded) {
7132 load_above_capacity = busiest->sum_nr_running *
7134 if (load_above_capacity > busiest->group_capacity)
7135 load_above_capacity -= busiest->group_capacity;
7137 load_above_capacity = ~0UL;
7141 * We're trying to get all the cpus to the average_load, so we don't
7142 * want to push ourselves above the average load, nor do we wish to
7143 * reduce the max loaded cpu below the average load. At the same time,
7144 * we also don't want to reduce the group load below the group capacity
7145 * (so that we can implement power-savings policies etc). Thus we look
7146 * for the minimum possible imbalance.
7148 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7150 /* How much load to actually move to equalise the imbalance */
7151 env->imbalance = min(
7152 max_pull * busiest->group_capacity,
7153 (sds->avg_load - local->avg_load) * local->group_capacity
7154 ) / SCHED_CAPACITY_SCALE;
7157 * if *imbalance is less than the average load per runnable task
7158 * there is no guarantee that any tasks will be moved so we'll have
7159 * a think about bumping its value to force at least one task to be
7162 if (env->imbalance < busiest->load_per_task)
7163 return fix_small_imbalance(env, sds);
7166 /******* find_busiest_group() helpers end here *********************/
7169 * find_busiest_group - Returns the busiest group within the sched_domain
7170 * if there is an imbalance. If there isn't an imbalance, and
7171 * the user has opted for power-savings, it returns a group whose
7172 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
7173 * such a group exists.
7175 * Also calculates the amount of weighted load which should be moved
7176 * to restore balance.
7178 * @env: The load balancing environment.
7180 * Return: - The busiest group if imbalance exists.
7181 * - If no imbalance and user has opted for power-savings balance,
7182 * return the least loaded group whose CPUs can be
7183 * put to idle by rebalancing its tasks onto our group.
7185 static struct sched_group *find_busiest_group(struct lb_env *env)
7187 struct sg_lb_stats *local, *busiest;
7188 struct sd_lb_stats sds;
7190 init_sd_lb_stats(&sds);
7193 * Compute the various statistics relavent for load balancing at
7196 update_sd_lb_stats(env, &sds);
7198 if (energy_aware() && !env->dst_rq->rd->overutilized)
7201 local = &sds.local_stat;
7202 busiest = &sds.busiest_stat;
7204 /* ASYM feature bypasses nice load balance check */
7205 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
7206 check_asym_packing(env, &sds))
7209 /* There is no busy sibling group to pull tasks from */
7210 if (!sds.busiest || busiest->sum_nr_running == 0)
7213 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7214 / sds.total_capacity;
7217 * If the busiest group is imbalanced the below checks don't
7218 * work because they assume all things are equal, which typically
7219 * isn't true due to cpus_allowed constraints and the like.
7221 if (busiest->group_type == group_imbalanced)
7224 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7225 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7226 busiest->group_no_capacity)
7230 * If the local group is busier than the selected busiest group
7231 * don't try and pull any tasks.
7233 if (local->avg_load >= busiest->avg_load)
7237 * Don't pull any tasks if this group is already above the domain
7240 if (local->avg_load >= sds.avg_load)
7243 if (env->idle == CPU_IDLE) {
7245 * This cpu is idle. If the busiest group is not overloaded
7246 * and there is no imbalance between this and busiest group
7247 * wrt idle cpus, it is balanced. The imbalance becomes
7248 * significant if the diff is greater than 1 otherwise we
7249 * might end up to just move the imbalance on another group
7251 if ((busiest->group_type != group_overloaded) &&
7252 (local->idle_cpus <= (busiest->idle_cpus + 1)))
7256 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7257 * imbalance_pct to be conservative.
7259 if (100 * busiest->avg_load <=
7260 env->sd->imbalance_pct * local->avg_load)
7265 /* Looks like there is an imbalance. Compute it */
7266 calculate_imbalance(env, &sds);
7275 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7277 static struct rq *find_busiest_queue(struct lb_env *env,
7278 struct sched_group *group)
7280 struct rq *busiest = NULL, *rq;
7281 unsigned long busiest_load = 0, busiest_capacity = 1;
7284 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7285 unsigned long capacity, wl;
7289 rt = fbq_classify_rq(rq);
7292 * We classify groups/runqueues into three groups:
7293 * - regular: there are !numa tasks
7294 * - remote: there are numa tasks that run on the 'wrong' node
7295 * - all: there is no distinction
7297 * In order to avoid migrating ideally placed numa tasks,
7298 * ignore those when there's better options.
7300 * If we ignore the actual busiest queue to migrate another
7301 * task, the next balance pass can still reduce the busiest
7302 * queue by moving tasks around inside the node.
7304 * If we cannot move enough load due to this classification
7305 * the next pass will adjust the group classification and
7306 * allow migration of more tasks.
7308 * Both cases only affect the total convergence complexity.
7310 if (rt > env->fbq_type)
7313 capacity = capacity_of(i);
7315 wl = weighted_cpuload(i);
7318 * When comparing with imbalance, use weighted_cpuload()
7319 * which is not scaled with the cpu capacity.
7322 if (rq->nr_running == 1 && wl > env->imbalance &&
7323 !check_cpu_capacity(rq, env->sd))
7327 * For the load comparisons with the other cpu's, consider
7328 * the weighted_cpuload() scaled with the cpu capacity, so
7329 * that the load can be moved away from the cpu that is
7330 * potentially running at a lower capacity.
7332 * Thus we're looking for max(wl_i / capacity_i), crosswise
7333 * multiplication to rid ourselves of the division works out
7334 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7335 * our previous maximum.
7337 if (wl * busiest_capacity > busiest_load * capacity) {
7339 busiest_capacity = capacity;
7348 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7349 * so long as it is large enough.
7351 #define MAX_PINNED_INTERVAL 512
7353 /* Working cpumask for load_balance and load_balance_newidle. */
7354 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7356 static int need_active_balance(struct lb_env *env)
7358 struct sched_domain *sd = env->sd;
7360 if (env->idle == CPU_NEWLY_IDLE) {
7363 * ASYM_PACKING needs to force migrate tasks from busy but
7364 * higher numbered CPUs in order to pack all tasks in the
7365 * lowest numbered CPUs.
7367 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7372 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7373 * It's worth migrating the task if the src_cpu's capacity is reduced
7374 * because of other sched_class or IRQs if more capacity stays
7375 * available on dst_cpu.
7377 if ((env->idle != CPU_NOT_IDLE) &&
7378 (env->src_rq->cfs.h_nr_running == 1)) {
7379 if ((check_cpu_capacity(env->src_rq, sd)) &&
7380 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7384 if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
7385 env->src_rq->cfs.h_nr_running == 1 &&
7386 cpu_overutilized(env->src_cpu) &&
7387 !cpu_overutilized(env->dst_cpu)) {
7391 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7394 static int active_load_balance_cpu_stop(void *data);
7396 static int should_we_balance(struct lb_env *env)
7398 struct sched_group *sg = env->sd->groups;
7399 struct cpumask *sg_cpus, *sg_mask;
7400 int cpu, balance_cpu = -1;
7403 * In the newly idle case, we will allow all the cpu's
7404 * to do the newly idle load balance.
7406 if (env->idle == CPU_NEWLY_IDLE)
7409 sg_cpus = sched_group_cpus(sg);
7410 sg_mask = sched_group_mask(sg);
7411 /* Try to find first idle cpu */
7412 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7413 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7420 if (balance_cpu == -1)
7421 balance_cpu = group_balance_cpu(sg);
7424 * First idle cpu or the first cpu(busiest) in this sched group
7425 * is eligible for doing load balancing at this and above domains.
7427 return balance_cpu == env->dst_cpu;
7431 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7432 * tasks if there is an imbalance.
7434 static int load_balance(int this_cpu, struct rq *this_rq,
7435 struct sched_domain *sd, enum cpu_idle_type idle,
7436 int *continue_balancing)
7438 int ld_moved, cur_ld_moved, active_balance = 0;
7439 struct sched_domain *sd_parent = sd->parent;
7440 struct sched_group *group;
7442 unsigned long flags;
7443 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7445 struct lb_env env = {
7447 .dst_cpu = this_cpu,
7449 .dst_grpmask = sched_group_cpus(sd->groups),
7451 .loop_break = sched_nr_migrate_break,
7454 .tasks = LIST_HEAD_INIT(env.tasks),
7458 * For NEWLY_IDLE load_balancing, we don't need to consider
7459 * other cpus in our group
7461 if (idle == CPU_NEWLY_IDLE)
7462 env.dst_grpmask = NULL;
7464 cpumask_copy(cpus, cpu_active_mask);
7466 schedstat_inc(sd, lb_count[idle]);
7469 if (!should_we_balance(&env)) {
7470 *continue_balancing = 0;
7474 group = find_busiest_group(&env);
7476 schedstat_inc(sd, lb_nobusyg[idle]);
7480 busiest = find_busiest_queue(&env, group);
7482 schedstat_inc(sd, lb_nobusyq[idle]);
7486 BUG_ON(busiest == env.dst_rq);
7488 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7490 env.src_cpu = busiest->cpu;
7491 env.src_rq = busiest;
7494 if (busiest->nr_running > 1) {
7496 * Attempt to move tasks. If find_busiest_group has found
7497 * an imbalance but busiest->nr_running <= 1, the group is
7498 * still unbalanced. ld_moved simply stays zero, so it is
7499 * correctly treated as an imbalance.
7501 env.flags |= LBF_ALL_PINNED;
7502 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7505 raw_spin_lock_irqsave(&busiest->lock, flags);
7508 * cur_ld_moved - load moved in current iteration
7509 * ld_moved - cumulative load moved across iterations
7511 cur_ld_moved = detach_tasks(&env);
7514 * We've detached some tasks from busiest_rq. Every
7515 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7516 * unlock busiest->lock, and we are able to be sure
7517 * that nobody can manipulate the tasks in parallel.
7518 * See task_rq_lock() family for the details.
7521 raw_spin_unlock(&busiest->lock);
7525 ld_moved += cur_ld_moved;
7528 local_irq_restore(flags);
7530 if (env.flags & LBF_NEED_BREAK) {
7531 env.flags &= ~LBF_NEED_BREAK;
7536 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7537 * us and move them to an alternate dst_cpu in our sched_group
7538 * where they can run. The upper limit on how many times we
7539 * iterate on same src_cpu is dependent on number of cpus in our
7542 * This changes load balance semantics a bit on who can move
7543 * load to a given_cpu. In addition to the given_cpu itself
7544 * (or a ilb_cpu acting on its behalf where given_cpu is
7545 * nohz-idle), we now have balance_cpu in a position to move
7546 * load to given_cpu. In rare situations, this may cause
7547 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7548 * _independently_ and at _same_ time to move some load to
7549 * given_cpu) causing exceess load to be moved to given_cpu.
7550 * This however should not happen so much in practice and
7551 * moreover subsequent load balance cycles should correct the
7552 * excess load moved.
7554 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7556 /* Prevent to re-select dst_cpu via env's cpus */
7557 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7559 env.dst_rq = cpu_rq(env.new_dst_cpu);
7560 env.dst_cpu = env.new_dst_cpu;
7561 env.flags &= ~LBF_DST_PINNED;
7563 env.loop_break = sched_nr_migrate_break;
7566 * Go back to "more_balance" rather than "redo" since we
7567 * need to continue with same src_cpu.
7573 * We failed to reach balance because of affinity.
7576 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7578 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7579 *group_imbalance = 1;
7582 /* All tasks on this runqueue were pinned by CPU affinity */
7583 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7584 cpumask_clear_cpu(cpu_of(busiest), cpus);
7585 if (!cpumask_empty(cpus)) {
7587 env.loop_break = sched_nr_migrate_break;
7590 goto out_all_pinned;
7595 schedstat_inc(sd, lb_failed[idle]);
7597 * Increment the failure counter only on periodic balance.
7598 * We do not want newidle balance, which can be very
7599 * frequent, pollute the failure counter causing
7600 * excessive cache_hot migrations and active balances.
7602 if (idle != CPU_NEWLY_IDLE)
7603 if (env.src_grp_nr_running > 1)
7604 sd->nr_balance_failed++;
7606 if (need_active_balance(&env)) {
7607 raw_spin_lock_irqsave(&busiest->lock, flags);
7609 /* don't kick the active_load_balance_cpu_stop,
7610 * if the curr task on busiest cpu can't be
7613 if (!cpumask_test_cpu(this_cpu,
7614 tsk_cpus_allowed(busiest->curr))) {
7615 raw_spin_unlock_irqrestore(&busiest->lock,
7617 env.flags |= LBF_ALL_PINNED;
7618 goto out_one_pinned;
7622 * ->active_balance synchronizes accesses to
7623 * ->active_balance_work. Once set, it's cleared
7624 * only after active load balance is finished.
7626 if (!busiest->active_balance) {
7627 busiest->active_balance = 1;
7628 busiest->push_cpu = this_cpu;
7631 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7633 if (active_balance) {
7634 stop_one_cpu_nowait(cpu_of(busiest),
7635 active_load_balance_cpu_stop, busiest,
7636 &busiest->active_balance_work);
7640 * We've kicked active balancing, reset the failure
7643 sd->nr_balance_failed = sd->cache_nice_tries+1;
7646 sd->nr_balance_failed = 0;
7648 if (likely(!active_balance)) {
7649 /* We were unbalanced, so reset the balancing interval */
7650 sd->balance_interval = sd->min_interval;
7653 * If we've begun active balancing, start to back off. This
7654 * case may not be covered by the all_pinned logic if there
7655 * is only 1 task on the busy runqueue (because we don't call
7658 if (sd->balance_interval < sd->max_interval)
7659 sd->balance_interval *= 2;
7666 * We reach balance although we may have faced some affinity
7667 * constraints. Clear the imbalance flag if it was set.
7670 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7672 if (*group_imbalance)
7673 *group_imbalance = 0;
7678 * We reach balance because all tasks are pinned at this level so
7679 * we can't migrate them. Let the imbalance flag set so parent level
7680 * can try to migrate them.
7682 schedstat_inc(sd, lb_balanced[idle]);
7684 sd->nr_balance_failed = 0;
7687 /* tune up the balancing interval */
7688 if (((env.flags & LBF_ALL_PINNED) &&
7689 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7690 (sd->balance_interval < sd->max_interval))
7691 sd->balance_interval *= 2;
7698 static inline unsigned long
7699 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7701 unsigned long interval = sd->balance_interval;
7704 interval *= sd->busy_factor;
7706 /* scale ms to jiffies */
7707 interval = msecs_to_jiffies(interval);
7708 interval = clamp(interval, 1UL, max_load_balance_interval);
7714 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7716 unsigned long interval, next;
7718 interval = get_sd_balance_interval(sd, cpu_busy);
7719 next = sd->last_balance + interval;
7721 if (time_after(*next_balance, next))
7722 *next_balance = next;
7726 * idle_balance is called by schedule() if this_cpu is about to become
7727 * idle. Attempts to pull tasks from other CPUs.
7729 static int idle_balance(struct rq *this_rq)
7731 unsigned long next_balance = jiffies + HZ;
7732 int this_cpu = this_rq->cpu;
7733 struct sched_domain *sd;
7734 int pulled_task = 0;
7737 idle_enter_fair(this_rq);
7740 * We must set idle_stamp _before_ calling idle_balance(), such that we
7741 * measure the duration of idle_balance() as idle time.
7743 this_rq->idle_stamp = rq_clock(this_rq);
7745 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7746 !this_rq->rd->overload) {
7748 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7750 update_next_balance(sd, 0, &next_balance);
7756 raw_spin_unlock(&this_rq->lock);
7758 update_blocked_averages(this_cpu);
7760 for_each_domain(this_cpu, sd) {
7761 int continue_balancing = 1;
7762 u64 t0, domain_cost;
7764 if (!(sd->flags & SD_LOAD_BALANCE))
7767 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7768 update_next_balance(sd, 0, &next_balance);
7772 if (sd->flags & SD_BALANCE_NEWIDLE) {
7773 t0 = sched_clock_cpu(this_cpu);
7775 pulled_task = load_balance(this_cpu, this_rq,
7777 &continue_balancing);
7779 domain_cost = sched_clock_cpu(this_cpu) - t0;
7780 if (domain_cost > sd->max_newidle_lb_cost)
7781 sd->max_newidle_lb_cost = domain_cost;
7783 curr_cost += domain_cost;
7786 update_next_balance(sd, 0, &next_balance);
7789 * Stop searching for tasks to pull if there are
7790 * now runnable tasks on this rq.
7792 if (pulled_task || this_rq->nr_running > 0)
7797 raw_spin_lock(&this_rq->lock);
7799 if (curr_cost > this_rq->max_idle_balance_cost)
7800 this_rq->max_idle_balance_cost = curr_cost;
7803 * While browsing the domains, we released the rq lock, a task could
7804 * have been enqueued in the meantime. Since we're not going idle,
7805 * pretend we pulled a task.
7807 if (this_rq->cfs.h_nr_running && !pulled_task)
7811 /* Move the next balance forward */
7812 if (time_after(this_rq->next_balance, next_balance))
7813 this_rq->next_balance = next_balance;
7815 /* Is there a task of a high priority class? */
7816 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7820 idle_exit_fair(this_rq);
7821 this_rq->idle_stamp = 0;
7828 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7829 * running tasks off the busiest CPU onto idle CPUs. It requires at
7830 * least 1 task to be running on each physical CPU where possible, and
7831 * avoids physical / logical imbalances.
7833 static int active_load_balance_cpu_stop(void *data)
7835 struct rq *busiest_rq = data;
7836 int busiest_cpu = cpu_of(busiest_rq);
7837 int target_cpu = busiest_rq->push_cpu;
7838 struct rq *target_rq = cpu_rq(target_cpu);
7839 struct sched_domain *sd;
7840 struct task_struct *p = NULL;
7842 raw_spin_lock_irq(&busiest_rq->lock);
7844 /* make sure the requested cpu hasn't gone down in the meantime */
7845 if (unlikely(busiest_cpu != smp_processor_id() ||
7846 !busiest_rq->active_balance))
7849 /* Is there any task to move? */
7850 if (busiest_rq->nr_running <= 1)
7854 * This condition is "impossible", if it occurs
7855 * we need to fix it. Originally reported by
7856 * Bjorn Helgaas on a 128-cpu setup.
7858 BUG_ON(busiest_rq == target_rq);
7860 /* Search for an sd spanning us and the target CPU. */
7862 for_each_domain(target_cpu, sd) {
7863 if ((sd->flags & SD_LOAD_BALANCE) &&
7864 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7869 struct lb_env env = {
7871 .dst_cpu = target_cpu,
7872 .dst_rq = target_rq,
7873 .src_cpu = busiest_rq->cpu,
7874 .src_rq = busiest_rq,
7878 schedstat_inc(sd, alb_count);
7880 p = detach_one_task(&env);
7882 schedstat_inc(sd, alb_pushed);
7884 schedstat_inc(sd, alb_failed);
7888 busiest_rq->active_balance = 0;
7889 raw_spin_unlock(&busiest_rq->lock);
7892 attach_one_task(target_rq, p);
7899 static inline int on_null_domain(struct rq *rq)
7901 return unlikely(!rcu_dereference_sched(rq->sd));
7904 #ifdef CONFIG_NO_HZ_COMMON
7906 * idle load balancing details
7907 * - When one of the busy CPUs notice that there may be an idle rebalancing
7908 * needed, they will kick the idle load balancer, which then does idle
7909 * load balancing for all the idle CPUs.
7912 cpumask_var_t idle_cpus_mask;
7914 unsigned long next_balance; /* in jiffy units */
7915 } nohz ____cacheline_aligned;
7917 static inline int find_new_ilb(void)
7919 int ilb = cpumask_first(nohz.idle_cpus_mask);
7921 if (ilb < nr_cpu_ids && idle_cpu(ilb))
7928 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7929 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7930 * CPU (if there is one).
7932 static void nohz_balancer_kick(void)
7936 nohz.next_balance++;
7938 ilb_cpu = find_new_ilb();
7940 if (ilb_cpu >= nr_cpu_ids)
7943 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7946 * Use smp_send_reschedule() instead of resched_cpu().
7947 * This way we generate a sched IPI on the target cpu which
7948 * is idle. And the softirq performing nohz idle load balance
7949 * will be run before returning from the IPI.
7951 smp_send_reschedule(ilb_cpu);
7955 static inline void nohz_balance_exit_idle(int cpu)
7957 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7959 * Completely isolated CPUs don't ever set, so we must test.
7961 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7962 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7963 atomic_dec(&nohz.nr_cpus);
7965 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7969 static inline void set_cpu_sd_state_busy(void)
7971 struct sched_domain *sd;
7972 int cpu = smp_processor_id();
7975 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7977 if (!sd || !sd->nohz_idle)
7981 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7986 void set_cpu_sd_state_idle(void)
7988 struct sched_domain *sd;
7989 int cpu = smp_processor_id();
7992 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7994 if (!sd || sd->nohz_idle)
7998 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
8004 * This routine will record that the cpu is going idle with tick stopped.
8005 * This info will be used in performing idle load balancing in the future.
8007 void nohz_balance_enter_idle(int cpu)
8010 * If this cpu is going down, then nothing needs to be done.
8012 if (!cpu_active(cpu))
8015 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
8019 * If we're a completely isolated CPU, we don't play.
8021 if (on_null_domain(cpu_rq(cpu)))
8024 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
8025 atomic_inc(&nohz.nr_cpus);
8026 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8029 static int sched_ilb_notifier(struct notifier_block *nfb,
8030 unsigned long action, void *hcpu)
8032 switch (action & ~CPU_TASKS_FROZEN) {
8034 nohz_balance_exit_idle(smp_processor_id());
8042 static DEFINE_SPINLOCK(balancing);
8045 * Scale the max load_balance interval with the number of CPUs in the system.
8046 * This trades load-balance latency on larger machines for less cross talk.
8048 void update_max_interval(void)
8050 max_load_balance_interval = HZ*num_online_cpus()/10;
8054 * It checks each scheduling domain to see if it is due to be balanced,
8055 * and initiates a balancing operation if so.
8057 * Balancing parameters are set up in init_sched_domains.
8059 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8061 int continue_balancing = 1;
8063 unsigned long interval;
8064 struct sched_domain *sd;
8065 /* Earliest time when we have to do rebalance again */
8066 unsigned long next_balance = jiffies + 60*HZ;
8067 int update_next_balance = 0;
8068 int need_serialize, need_decay = 0;
8071 update_blocked_averages(cpu);
8074 for_each_domain(cpu, sd) {
8076 * Decay the newidle max times here because this is a regular
8077 * visit to all the domains. Decay ~1% per second.
8079 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
8080 sd->max_newidle_lb_cost =
8081 (sd->max_newidle_lb_cost * 253) / 256;
8082 sd->next_decay_max_lb_cost = jiffies + HZ;
8085 max_cost += sd->max_newidle_lb_cost;
8087 if (!(sd->flags & SD_LOAD_BALANCE))
8091 * Stop the load balance at this level. There is another
8092 * CPU in our sched group which is doing load balancing more
8095 if (!continue_balancing) {
8101 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8103 need_serialize = sd->flags & SD_SERIALIZE;
8104 if (need_serialize) {
8105 if (!spin_trylock(&balancing))
8109 if (time_after_eq(jiffies, sd->last_balance + interval)) {
8110 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8112 * The LBF_DST_PINNED logic could have changed
8113 * env->dst_cpu, so we can't know our idle
8114 * state even if we migrated tasks. Update it.
8116 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8118 sd->last_balance = jiffies;
8119 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8122 spin_unlock(&balancing);
8124 if (time_after(next_balance, sd->last_balance + interval)) {
8125 next_balance = sd->last_balance + interval;
8126 update_next_balance = 1;
8131 * Ensure the rq-wide value also decays but keep it at a
8132 * reasonable floor to avoid funnies with rq->avg_idle.
8134 rq->max_idle_balance_cost =
8135 max((u64)sysctl_sched_migration_cost, max_cost);
8140 * next_balance will be updated only when there is a need.
8141 * When the cpu is attached to null domain for ex, it will not be
8144 if (likely(update_next_balance)) {
8145 rq->next_balance = next_balance;
8147 #ifdef CONFIG_NO_HZ_COMMON
8149 * If this CPU has been elected to perform the nohz idle
8150 * balance. Other idle CPUs have already rebalanced with
8151 * nohz_idle_balance() and nohz.next_balance has been
8152 * updated accordingly. This CPU is now running the idle load
8153 * balance for itself and we need to update the
8154 * nohz.next_balance accordingly.
8156 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8157 nohz.next_balance = rq->next_balance;
8162 #ifdef CONFIG_NO_HZ_COMMON
8164 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8165 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8167 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8169 int this_cpu = this_rq->cpu;
8172 /* Earliest time when we have to do rebalance again */
8173 unsigned long next_balance = jiffies + 60*HZ;
8174 int update_next_balance = 0;
8176 if (idle != CPU_IDLE ||
8177 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8180 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8181 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8185 * If this cpu gets work to do, stop the load balancing
8186 * work being done for other cpus. Next load
8187 * balancing owner will pick it up.
8192 rq = cpu_rq(balance_cpu);
8195 * If time for next balance is due,
8198 if (time_after_eq(jiffies, rq->next_balance)) {
8199 raw_spin_lock_irq(&rq->lock);
8200 update_rq_clock(rq);
8201 update_idle_cpu_load(rq);
8202 raw_spin_unlock_irq(&rq->lock);
8203 rebalance_domains(rq, CPU_IDLE);
8206 if (time_after(next_balance, rq->next_balance)) {
8207 next_balance = rq->next_balance;
8208 update_next_balance = 1;
8213 * next_balance will be updated only when there is a need.
8214 * When the CPU is attached to null domain for ex, it will not be
8217 if (likely(update_next_balance))
8218 nohz.next_balance = next_balance;
8220 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8224 * Current heuristic for kicking the idle load balancer in the presence
8225 * of an idle cpu in the system.
8226 * - This rq has more than one task.
8227 * - This rq has at least one CFS task and the capacity of the CPU is
8228 * significantly reduced because of RT tasks or IRQs.
8229 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8230 * multiple busy cpu.
8231 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8232 * domain span are idle.
8234 static inline bool nohz_kick_needed(struct rq *rq)
8236 unsigned long now = jiffies;
8237 struct sched_domain *sd;
8238 struct sched_group_capacity *sgc;
8239 int nr_busy, cpu = rq->cpu;
8242 if (unlikely(rq->idle_balance))
8246 * We may be recently in ticked or tickless idle mode. At the first
8247 * busy tick after returning from idle, we will update the busy stats.
8249 set_cpu_sd_state_busy();
8250 nohz_balance_exit_idle(cpu);
8253 * None are in tickless mode and hence no need for NOHZ idle load
8256 if (likely(!atomic_read(&nohz.nr_cpus)))
8259 if (time_before(now, nohz.next_balance))
8262 if (rq->nr_running >= 2 &&
8263 (!energy_aware() || cpu_overutilized(cpu)))
8267 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8268 if (sd && !energy_aware()) {
8269 sgc = sd->groups->sgc;
8270 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8279 sd = rcu_dereference(rq->sd);
8281 if ((rq->cfs.h_nr_running >= 1) &&
8282 check_cpu_capacity(rq, sd)) {
8288 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8289 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8290 sched_domain_span(sd)) < cpu)) {
8300 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8304 * run_rebalance_domains is triggered when needed from the scheduler tick.
8305 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8307 static void run_rebalance_domains(struct softirq_action *h)
8309 struct rq *this_rq = this_rq();
8310 enum cpu_idle_type idle = this_rq->idle_balance ?
8311 CPU_IDLE : CPU_NOT_IDLE;
8314 * If this cpu has a pending nohz_balance_kick, then do the
8315 * balancing on behalf of the other idle cpus whose ticks are
8316 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8317 * give the idle cpus a chance to load balance. Else we may
8318 * load balance only within the local sched_domain hierarchy
8319 * and abort nohz_idle_balance altogether if we pull some load.
8321 nohz_idle_balance(this_rq, idle);
8322 rebalance_domains(this_rq, idle);
8326 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8328 void trigger_load_balance(struct rq *rq)
8330 /* Don't need to rebalance while attached to NULL domain */
8331 if (unlikely(on_null_domain(rq)))
8334 if (time_after_eq(jiffies, rq->next_balance))
8335 raise_softirq(SCHED_SOFTIRQ);
8336 #ifdef CONFIG_NO_HZ_COMMON
8337 if (nohz_kick_needed(rq))
8338 nohz_balancer_kick();
8342 static void rq_online_fair(struct rq *rq)
8346 update_runtime_enabled(rq);
8349 static void rq_offline_fair(struct rq *rq)
8353 /* Ensure any throttled groups are reachable by pick_next_task */
8354 unthrottle_offline_cfs_rqs(rq);
8357 #endif /* CONFIG_SMP */
8360 * scheduler tick hitting a task of our scheduling class:
8362 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8364 struct cfs_rq *cfs_rq;
8365 struct sched_entity *se = &curr->se;
8367 for_each_sched_entity(se) {
8368 cfs_rq = cfs_rq_of(se);
8369 entity_tick(cfs_rq, se, queued);
8372 if (static_branch_unlikely(&sched_numa_balancing))
8373 task_tick_numa(rq, curr);
8375 if (!rq->rd->overutilized && cpu_overutilized(task_cpu(curr)))
8376 rq->rd->overutilized = true;
8380 * called on fork with the child task as argument from the parent's context
8381 * - child not yet on the tasklist
8382 * - preemption disabled
8384 static void task_fork_fair(struct task_struct *p)
8386 struct cfs_rq *cfs_rq;
8387 struct sched_entity *se = &p->se, *curr;
8388 int this_cpu = smp_processor_id();
8389 struct rq *rq = this_rq();
8390 unsigned long flags;
8392 raw_spin_lock_irqsave(&rq->lock, flags);
8394 update_rq_clock(rq);
8396 cfs_rq = task_cfs_rq(current);
8397 curr = cfs_rq->curr;
8400 * Not only the cpu but also the task_group of the parent might have
8401 * been changed after parent->se.parent,cfs_rq were copied to
8402 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8403 * of child point to valid ones.
8406 __set_task_cpu(p, this_cpu);
8409 update_curr(cfs_rq);
8412 se->vruntime = curr->vruntime;
8413 place_entity(cfs_rq, se, 1);
8415 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8417 * Upon rescheduling, sched_class::put_prev_task() will place
8418 * 'current' within the tree based on its new key value.
8420 swap(curr->vruntime, se->vruntime);
8424 se->vruntime -= cfs_rq->min_vruntime;
8426 raw_spin_unlock_irqrestore(&rq->lock, flags);
8430 * Priority of the task has changed. Check to see if we preempt
8434 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8436 if (!task_on_rq_queued(p))
8440 * Reschedule if we are currently running on this runqueue and
8441 * our priority decreased, or if we are not currently running on
8442 * this runqueue and our priority is higher than the current's
8444 if (rq->curr == p) {
8445 if (p->prio > oldprio)
8448 check_preempt_curr(rq, p, 0);
8451 static inline bool vruntime_normalized(struct task_struct *p)
8453 struct sched_entity *se = &p->se;
8456 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8457 * the dequeue_entity(.flags=0) will already have normalized the
8464 * When !on_rq, vruntime of the task has usually NOT been normalized.
8465 * But there are some cases where it has already been normalized:
8467 * - A forked child which is waiting for being woken up by
8468 * wake_up_new_task().
8469 * - A task which has been woken up by try_to_wake_up() and
8470 * waiting for actually being woken up by sched_ttwu_pending().
8472 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8478 static void detach_task_cfs_rq(struct task_struct *p)
8480 struct sched_entity *se = &p->se;
8481 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8483 if (!vruntime_normalized(p)) {
8485 * Fix up our vruntime so that the current sleep doesn't
8486 * cause 'unlimited' sleep bonus.
8488 place_entity(cfs_rq, se, 0);
8489 se->vruntime -= cfs_rq->min_vruntime;
8492 /* Catch up with the cfs_rq and remove our load when we leave */
8493 detach_entity_load_avg(cfs_rq, se);
8496 static void attach_task_cfs_rq(struct task_struct *p)
8498 struct sched_entity *se = &p->se;
8499 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8501 #ifdef CONFIG_FAIR_GROUP_SCHED
8503 * Since the real-depth could have been changed (only FAIR
8504 * class maintain depth value), reset depth properly.
8506 se->depth = se->parent ? se->parent->depth + 1 : 0;
8509 /* Synchronize task with its cfs_rq */
8510 attach_entity_load_avg(cfs_rq, se);
8512 if (!vruntime_normalized(p))
8513 se->vruntime += cfs_rq->min_vruntime;
8516 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8518 detach_task_cfs_rq(p);
8521 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8523 attach_task_cfs_rq(p);
8525 if (task_on_rq_queued(p)) {
8527 * We were most likely switched from sched_rt, so
8528 * kick off the schedule if running, otherwise just see
8529 * if we can still preempt the current task.
8534 check_preempt_curr(rq, p, 0);
8538 /* Account for a task changing its policy or group.
8540 * This routine is mostly called to set cfs_rq->curr field when a task
8541 * migrates between groups/classes.
8543 static void set_curr_task_fair(struct rq *rq)
8545 struct sched_entity *se = &rq->curr->se;
8547 for_each_sched_entity(se) {
8548 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8550 set_next_entity(cfs_rq, se);
8551 /* ensure bandwidth has been allocated on our new cfs_rq */
8552 account_cfs_rq_runtime(cfs_rq, 0);
8556 void init_cfs_rq(struct cfs_rq *cfs_rq)
8558 cfs_rq->tasks_timeline = RB_ROOT;
8559 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8560 #ifndef CONFIG_64BIT
8561 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8564 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8565 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8569 #ifdef CONFIG_FAIR_GROUP_SCHED
8570 static void task_move_group_fair(struct task_struct *p)
8572 detach_task_cfs_rq(p);
8573 set_task_rq(p, task_cpu(p));
8576 /* Tell se's cfs_rq has been changed -- migrated */
8577 p->se.avg.last_update_time = 0;
8579 attach_task_cfs_rq(p);
8582 void free_fair_sched_group(struct task_group *tg)
8586 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8588 for_each_possible_cpu(i) {
8590 kfree(tg->cfs_rq[i]);
8593 remove_entity_load_avg(tg->se[i]);
8602 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8604 struct cfs_rq *cfs_rq;
8605 struct sched_entity *se;
8608 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8611 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8615 tg->shares = NICE_0_LOAD;
8617 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8619 for_each_possible_cpu(i) {
8620 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8621 GFP_KERNEL, cpu_to_node(i));
8625 se = kzalloc_node(sizeof(struct sched_entity),
8626 GFP_KERNEL, cpu_to_node(i));
8630 init_cfs_rq(cfs_rq);
8631 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8632 init_entity_runnable_average(se);
8643 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8645 struct rq *rq = cpu_rq(cpu);
8646 unsigned long flags;
8649 * Only empty task groups can be destroyed; so we can speculatively
8650 * check on_list without danger of it being re-added.
8652 if (!tg->cfs_rq[cpu]->on_list)
8655 raw_spin_lock_irqsave(&rq->lock, flags);
8656 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8657 raw_spin_unlock_irqrestore(&rq->lock, flags);
8660 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8661 struct sched_entity *se, int cpu,
8662 struct sched_entity *parent)
8664 struct rq *rq = cpu_rq(cpu);
8668 init_cfs_rq_runtime(cfs_rq);
8670 tg->cfs_rq[cpu] = cfs_rq;
8673 /* se could be NULL for root_task_group */
8678 se->cfs_rq = &rq->cfs;
8681 se->cfs_rq = parent->my_q;
8682 se->depth = parent->depth + 1;
8686 /* guarantee group entities always have weight */
8687 update_load_set(&se->load, NICE_0_LOAD);
8688 se->parent = parent;
8691 static DEFINE_MUTEX(shares_mutex);
8693 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8696 unsigned long flags;
8699 * We can't change the weight of the root cgroup.
8704 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8706 mutex_lock(&shares_mutex);
8707 if (tg->shares == shares)
8710 tg->shares = shares;
8711 for_each_possible_cpu(i) {
8712 struct rq *rq = cpu_rq(i);
8713 struct sched_entity *se;
8716 /* Propagate contribution to hierarchy */
8717 raw_spin_lock_irqsave(&rq->lock, flags);
8719 /* Possible calls to update_curr() need rq clock */
8720 update_rq_clock(rq);
8721 for_each_sched_entity(se)
8722 update_cfs_shares(group_cfs_rq(se));
8723 raw_spin_unlock_irqrestore(&rq->lock, flags);
8727 mutex_unlock(&shares_mutex);
8730 #else /* CONFIG_FAIR_GROUP_SCHED */
8732 void free_fair_sched_group(struct task_group *tg) { }
8734 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8739 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
8741 #endif /* CONFIG_FAIR_GROUP_SCHED */
8744 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8746 struct sched_entity *se = &task->se;
8747 unsigned int rr_interval = 0;
8750 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8753 if (rq->cfs.load.weight)
8754 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8760 * All the scheduling class methods:
8762 const struct sched_class fair_sched_class = {
8763 .next = &idle_sched_class,
8764 .enqueue_task = enqueue_task_fair,
8765 .dequeue_task = dequeue_task_fair,
8766 .yield_task = yield_task_fair,
8767 .yield_to_task = yield_to_task_fair,
8769 .check_preempt_curr = check_preempt_wakeup,
8771 .pick_next_task = pick_next_task_fair,
8772 .put_prev_task = put_prev_task_fair,
8775 .select_task_rq = select_task_rq_fair,
8776 .migrate_task_rq = migrate_task_rq_fair,
8778 .rq_online = rq_online_fair,
8779 .rq_offline = rq_offline_fair,
8781 .task_waking = task_waking_fair,
8782 .task_dead = task_dead_fair,
8783 .set_cpus_allowed = set_cpus_allowed_common,
8786 .set_curr_task = set_curr_task_fair,
8787 .task_tick = task_tick_fair,
8788 .task_fork = task_fork_fair,
8790 .prio_changed = prio_changed_fair,
8791 .switched_from = switched_from_fair,
8792 .switched_to = switched_to_fair,
8794 .get_rr_interval = get_rr_interval_fair,
8796 .update_curr = update_curr_fair,
8798 #ifdef CONFIG_FAIR_GROUP_SCHED
8799 .task_move_group = task_move_group_fair,
8803 #ifdef CONFIG_SCHED_DEBUG
8804 void print_cfs_stats(struct seq_file *m, int cpu)
8806 struct cfs_rq *cfs_rq;
8809 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8810 print_cfs_rq(m, cpu, cfs_rq);
8814 #ifdef CONFIG_NUMA_BALANCING
8815 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8818 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8820 for_each_online_node(node) {
8821 if (p->numa_faults) {
8822 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8823 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8825 if (p->numa_group) {
8826 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8827 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8829 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8832 #endif /* CONFIG_NUMA_BALANCING */
8833 #endif /* CONFIG_SCHED_DEBUG */
8835 __init void init_sched_fair_class(void)
8838 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
8840 #ifdef CONFIG_NO_HZ_COMMON
8841 nohz.next_balance = jiffies;
8842 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8843 cpu_notifier(sched_ilb_notifier, 0);