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 unsigned long capacity_orig_of(int cpu);
4148 static int cpu_util(int cpu);
4150 static void update_capacity_of(int cpu)
4152 unsigned long req_cap;
4157 /* Convert scale-invariant capacity to cpu. */
4158 req_cap = cpu_util(cpu) * SCHED_CAPACITY_SCALE / capacity_orig_of(cpu);
4159 set_cfs_cpu_capacity(cpu, true, req_cap);
4162 static bool cpu_overutilized(int cpu);
4165 * The enqueue_task method is called before nr_running is
4166 * increased. Here we update the fair scheduling stats and
4167 * then put the task into the rbtree:
4170 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4172 struct cfs_rq *cfs_rq;
4173 struct sched_entity *se = &p->se;
4174 int task_new = !(flags & ENQUEUE_WAKEUP);
4176 for_each_sched_entity(se) {
4179 cfs_rq = cfs_rq_of(se);
4180 enqueue_entity(cfs_rq, se, flags);
4183 * end evaluation on encountering a throttled cfs_rq
4185 * note: in the case of encountering a throttled cfs_rq we will
4186 * post the final h_nr_running increment below.
4188 if (cfs_rq_throttled(cfs_rq))
4190 cfs_rq->h_nr_running++;
4192 flags = ENQUEUE_WAKEUP;
4195 for_each_sched_entity(se) {
4196 cfs_rq = cfs_rq_of(se);
4197 cfs_rq->h_nr_running++;
4199 if (cfs_rq_throttled(cfs_rq))
4202 update_load_avg(se, 1);
4203 update_cfs_shares(cfs_rq);
4207 add_nr_running(rq, 1);
4208 if (!task_new && !rq->rd->overutilized &&
4209 cpu_overutilized(rq->cpu))
4210 rq->rd->overutilized = true;
4213 * We want to potentially trigger a freq switch
4214 * request only for tasks that are waking up; this is
4215 * because we get here also during load balancing, but
4216 * in these cases it seems wise to trigger as single
4217 * request after load balancing is done.
4219 * XXX: how about fork()? Do we need a special
4220 * flag/something to tell if we are here after a
4221 * fork() (wakeup_task_new)?
4224 update_capacity_of(cpu_of(rq));
4229 static void set_next_buddy(struct sched_entity *se);
4232 * The dequeue_task method is called before nr_running is
4233 * decreased. We remove the task from the rbtree and
4234 * update the fair scheduling stats:
4236 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4238 struct cfs_rq *cfs_rq;
4239 struct sched_entity *se = &p->se;
4240 int task_sleep = flags & DEQUEUE_SLEEP;
4242 for_each_sched_entity(se) {
4243 cfs_rq = cfs_rq_of(se);
4244 dequeue_entity(cfs_rq, se, flags);
4247 * end evaluation on encountering a throttled cfs_rq
4249 * note: in the case of encountering a throttled cfs_rq we will
4250 * post the final h_nr_running decrement below.
4252 if (cfs_rq_throttled(cfs_rq))
4254 cfs_rq->h_nr_running--;
4256 /* Don't dequeue parent if it has other entities besides us */
4257 if (cfs_rq->load.weight) {
4259 * Bias pick_next to pick a task from this cfs_rq, as
4260 * p is sleeping when it is within its sched_slice.
4262 if (task_sleep && parent_entity(se))
4263 set_next_buddy(parent_entity(se));
4265 /* avoid re-evaluating load for this entity */
4266 se = parent_entity(se);
4269 flags |= DEQUEUE_SLEEP;
4272 for_each_sched_entity(se) {
4273 cfs_rq = cfs_rq_of(se);
4274 cfs_rq->h_nr_running--;
4276 if (cfs_rq_throttled(cfs_rq))
4279 update_load_avg(se, 1);
4280 update_cfs_shares(cfs_rq);
4284 sub_nr_running(rq, 1);
4287 * We want to potentially trigger a freq switch
4288 * request only for tasks that are going to sleep;
4289 * this is because we get here also during load
4290 * balancing, but in these cases it seems wise to
4291 * trigger as single request after load balancing is
4295 if (rq->cfs.nr_running)
4296 update_capacity_of(cpu_of(rq));
4297 else if (sched_freq())
4298 set_cfs_cpu_capacity(cpu_of(rq), false, 0);
4307 * per rq 'load' arrray crap; XXX kill this.
4311 * The exact cpuload at various idx values, calculated at every tick would be
4312 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4314 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4315 * on nth tick when cpu may be busy, then we have:
4316 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4317 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4319 * decay_load_missed() below does efficient calculation of
4320 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4321 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4323 * The calculation is approximated on a 128 point scale.
4324 * degrade_zero_ticks is the number of ticks after which load at any
4325 * particular idx is approximated to be zero.
4326 * degrade_factor is a precomputed table, a row for each load idx.
4327 * Each column corresponds to degradation factor for a power of two ticks,
4328 * based on 128 point scale.
4330 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4331 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4333 * With this power of 2 load factors, we can degrade the load n times
4334 * by looking at 1 bits in n and doing as many mult/shift instead of
4335 * n mult/shifts needed by the exact degradation.
4337 #define DEGRADE_SHIFT 7
4338 static const unsigned char
4339 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4340 static const unsigned char
4341 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4342 {0, 0, 0, 0, 0, 0, 0, 0},
4343 {64, 32, 8, 0, 0, 0, 0, 0},
4344 {96, 72, 40, 12, 1, 0, 0},
4345 {112, 98, 75, 43, 15, 1, 0},
4346 {120, 112, 98, 76, 45, 16, 2} };
4349 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4350 * would be when CPU is idle and so we just decay the old load without
4351 * adding any new load.
4353 static unsigned long
4354 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4358 if (!missed_updates)
4361 if (missed_updates >= degrade_zero_ticks[idx])
4365 return load >> missed_updates;
4367 while (missed_updates) {
4368 if (missed_updates % 2)
4369 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4371 missed_updates >>= 1;
4378 * Update rq->cpu_load[] statistics. This function is usually called every
4379 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4380 * every tick. We fix it up based on jiffies.
4382 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4383 unsigned long pending_updates)
4387 this_rq->nr_load_updates++;
4389 /* Update our load: */
4390 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4391 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4392 unsigned long old_load, new_load;
4394 /* scale is effectively 1 << i now, and >> i divides by scale */
4396 old_load = this_rq->cpu_load[i];
4397 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4398 new_load = this_load;
4400 * Round up the averaging division if load is increasing. This
4401 * prevents us from getting stuck on 9 if the load is 10, for
4404 if (new_load > old_load)
4405 new_load += scale - 1;
4407 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4410 sched_avg_update(this_rq);
4413 /* Used instead of source_load when we know the type == 0 */
4414 static unsigned long weighted_cpuload(const int cpu)
4416 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4419 #ifdef CONFIG_NO_HZ_COMMON
4421 * There is no sane way to deal with nohz on smp when using jiffies because the
4422 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4423 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4425 * Therefore we cannot use the delta approach from the regular tick since that
4426 * would seriously skew the load calculation. However we'll make do for those
4427 * updates happening while idle (nohz_idle_balance) or coming out of idle
4428 * (tick_nohz_idle_exit).
4430 * This means we might still be one tick off for nohz periods.
4434 * Called from nohz_idle_balance() to update the load ratings before doing the
4437 static void update_idle_cpu_load(struct rq *this_rq)
4439 unsigned long curr_jiffies = READ_ONCE(jiffies);
4440 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4441 unsigned long pending_updates;
4444 * bail if there's load or we're actually up-to-date.
4446 if (load || curr_jiffies == this_rq->last_load_update_tick)
4449 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4450 this_rq->last_load_update_tick = curr_jiffies;
4452 __update_cpu_load(this_rq, load, pending_updates);
4456 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4458 void update_cpu_load_nohz(void)
4460 struct rq *this_rq = this_rq();
4461 unsigned long curr_jiffies = READ_ONCE(jiffies);
4462 unsigned long pending_updates;
4464 if (curr_jiffies == this_rq->last_load_update_tick)
4467 raw_spin_lock(&this_rq->lock);
4468 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4469 if (pending_updates) {
4470 this_rq->last_load_update_tick = curr_jiffies;
4472 * We were idle, this means load 0, the current load might be
4473 * !0 due to remote wakeups and the sort.
4475 __update_cpu_load(this_rq, 0, pending_updates);
4477 raw_spin_unlock(&this_rq->lock);
4479 #endif /* CONFIG_NO_HZ */
4482 * Called from scheduler_tick()
4484 void update_cpu_load_active(struct rq *this_rq)
4486 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4488 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4490 this_rq->last_load_update_tick = jiffies;
4491 __update_cpu_load(this_rq, load, 1);
4495 * Return a low guess at the load of a migration-source cpu weighted
4496 * according to the scheduling class and "nice" value.
4498 * We want to under-estimate the load of migration sources, to
4499 * balance conservatively.
4501 static unsigned long source_load(int cpu, int type)
4503 struct rq *rq = cpu_rq(cpu);
4504 unsigned long total = weighted_cpuload(cpu);
4506 if (type == 0 || !sched_feat(LB_BIAS))
4509 return min(rq->cpu_load[type-1], total);
4513 * Return a high guess at the load of a migration-target cpu weighted
4514 * according to the scheduling class and "nice" value.
4516 static unsigned long target_load(int cpu, int type)
4518 struct rq *rq = cpu_rq(cpu);
4519 unsigned long total = weighted_cpuload(cpu);
4521 if (type == 0 || !sched_feat(LB_BIAS))
4524 return max(rq->cpu_load[type-1], total);
4527 static unsigned long capacity_of(int cpu)
4529 return cpu_rq(cpu)->cpu_capacity;
4532 static unsigned long capacity_orig_of(int cpu)
4534 return cpu_rq(cpu)->cpu_capacity_orig;
4537 static unsigned long cpu_avg_load_per_task(int cpu)
4539 struct rq *rq = cpu_rq(cpu);
4540 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4541 unsigned long load_avg = weighted_cpuload(cpu);
4544 return load_avg / nr_running;
4549 static void record_wakee(struct task_struct *p)
4552 * Rough decay (wiping) for cost saving, don't worry
4553 * about the boundary, really active task won't care
4556 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4557 current->wakee_flips >>= 1;
4558 current->wakee_flip_decay_ts = jiffies;
4561 if (current->last_wakee != p) {
4562 current->last_wakee = p;
4563 current->wakee_flips++;
4567 static void task_waking_fair(struct task_struct *p)
4569 struct sched_entity *se = &p->se;
4570 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4573 #ifndef CONFIG_64BIT
4574 u64 min_vruntime_copy;
4577 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4579 min_vruntime = cfs_rq->min_vruntime;
4580 } while (min_vruntime != min_vruntime_copy);
4582 min_vruntime = cfs_rq->min_vruntime;
4585 se->vruntime -= min_vruntime;
4589 #ifdef CONFIG_FAIR_GROUP_SCHED
4591 * effective_load() calculates the load change as seen from the root_task_group
4593 * Adding load to a group doesn't make a group heavier, but can cause movement
4594 * of group shares between cpus. Assuming the shares were perfectly aligned one
4595 * can calculate the shift in shares.
4597 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4598 * on this @cpu and results in a total addition (subtraction) of @wg to the
4599 * total group weight.
4601 * Given a runqueue weight distribution (rw_i) we can compute a shares
4602 * distribution (s_i) using:
4604 * s_i = rw_i / \Sum rw_j (1)
4606 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4607 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4608 * shares distribution (s_i):
4610 * rw_i = { 2, 4, 1, 0 }
4611 * s_i = { 2/7, 4/7, 1/7, 0 }
4613 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4614 * task used to run on and the CPU the waker is running on), we need to
4615 * compute the effect of waking a task on either CPU and, in case of a sync
4616 * wakeup, compute the effect of the current task going to sleep.
4618 * So for a change of @wl to the local @cpu with an overall group weight change
4619 * of @wl we can compute the new shares distribution (s'_i) using:
4621 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4623 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4624 * differences in waking a task to CPU 0. The additional task changes the
4625 * weight and shares distributions like:
4627 * rw'_i = { 3, 4, 1, 0 }
4628 * s'_i = { 3/8, 4/8, 1/8, 0 }
4630 * We can then compute the difference in effective weight by using:
4632 * dw_i = S * (s'_i - s_i) (3)
4634 * Where 'S' is the group weight as seen by its parent.
4636 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4637 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4638 * 4/7) times the weight of the group.
4640 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4642 struct sched_entity *se = tg->se[cpu];
4644 if (!tg->parent) /* the trivial, non-cgroup case */
4647 for_each_sched_entity(se) {
4653 * W = @wg + \Sum rw_j
4655 W = wg + calc_tg_weight(tg, se->my_q);
4660 w = cfs_rq_load_avg(se->my_q) + wl;
4663 * wl = S * s'_i; see (2)
4666 wl = (w * (long)tg->shares) / W;
4671 * Per the above, wl is the new se->load.weight value; since
4672 * those are clipped to [MIN_SHARES, ...) do so now. See
4673 * calc_cfs_shares().
4675 if (wl < MIN_SHARES)
4679 * wl = dw_i = S * (s'_i - s_i); see (3)
4681 wl -= se->avg.load_avg;
4684 * Recursively apply this logic to all parent groups to compute
4685 * the final effective load change on the root group. Since
4686 * only the @tg group gets extra weight, all parent groups can
4687 * only redistribute existing shares. @wl is the shift in shares
4688 * resulting from this level per the above.
4697 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4705 * Returns the current capacity of cpu after applying both
4706 * cpu and freq scaling.
4708 static unsigned long capacity_curr_of(int cpu)
4710 return cpu_rq(cpu)->cpu_capacity_orig *
4711 arch_scale_freq_capacity(NULL, cpu)
4712 >> SCHED_CAPACITY_SHIFT;
4716 * cpu_util returns the amount of capacity of a CPU that is used by CFS
4717 * tasks. The unit of the return value must be the one of capacity so we can
4718 * compare the utilization with the capacity of the CPU that is available for
4719 * CFS task (ie cpu_capacity).
4721 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
4722 * recent utilization of currently non-runnable tasks on a CPU. It represents
4723 * the amount of utilization of a CPU in the range [0..capacity_orig] where
4724 * capacity_orig is the cpu_capacity available at the highest frequency
4725 * (arch_scale_freq_capacity()).
4726 * The utilization of a CPU converges towards a sum equal to or less than the
4727 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
4728 * the running time on this CPU scaled by capacity_curr.
4730 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
4731 * higher than capacity_orig because of unfortunate rounding in
4732 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
4733 * the average stabilizes with the new running time. We need to check that the
4734 * utilization stays within the range of [0..capacity_orig] and cap it if
4735 * necessary. Without utilization capping, a group could be seen as overloaded
4736 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
4737 * available capacity. We allow utilization to overshoot capacity_curr (but not
4738 * capacity_orig) as it useful for predicting the capacity required after task
4739 * migrations (scheduler-driven DVFS).
4741 static unsigned long __cpu_util(int cpu, int delta)
4743 unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
4744 unsigned long capacity = capacity_orig_of(cpu);
4750 return (delta >= capacity) ? capacity : delta;
4753 static unsigned long cpu_util(int cpu)
4755 return __cpu_util(cpu, 0);
4758 static inline bool energy_aware(void)
4760 return sched_feat(ENERGY_AWARE);
4764 struct sched_group *sg_top;
4765 struct sched_group *sg_cap;
4774 * __cpu_norm_util() returns the cpu util relative to a specific capacity,
4775 * i.e. it's busy ratio, in the range [0..SCHED_LOAD_SCALE] which is useful for
4776 * energy calculations. Using the scale-invariant util returned by
4777 * cpu_util() and approximating scale-invariant util by:
4779 * util ~ (curr_freq/max_freq)*1024 * capacity_orig/1024 * running_time/time
4781 * the normalized util can be found using the specific capacity.
4783 * capacity = capacity_orig * curr_freq/max_freq
4785 * norm_util = running_time/time ~ util/capacity
4787 static unsigned long __cpu_norm_util(int cpu, unsigned long capacity, int delta)
4789 int util = __cpu_util(cpu, delta);
4791 if (util >= capacity)
4792 return SCHED_CAPACITY_SCALE;
4794 return (util << SCHED_CAPACITY_SHIFT)/capacity;
4797 static int calc_util_delta(struct energy_env *eenv, int cpu)
4799 if (cpu == eenv->src_cpu)
4800 return -eenv->util_delta;
4801 if (cpu == eenv->dst_cpu)
4802 return eenv->util_delta;
4807 unsigned long group_max_util(struct energy_env *eenv)
4810 unsigned long max_util = 0;
4812 for_each_cpu(i, sched_group_cpus(eenv->sg_cap)) {
4813 delta = calc_util_delta(eenv, i);
4814 max_util = max(max_util, __cpu_util(i, delta));
4821 * group_norm_util() returns the approximated group util relative to it's
4822 * current capacity (busy ratio) in the range [0..SCHED_LOAD_SCALE] for use in
4823 * energy calculations. Since task executions may or may not overlap in time in
4824 * the group the true normalized util is between max(cpu_norm_util(i)) and
4825 * sum(cpu_norm_util(i)) when iterating over all cpus in the group, i. The
4826 * latter is used as the estimate as it leads to a more pessimistic energy
4827 * estimate (more busy).
4830 long group_norm_util(struct energy_env *eenv, struct sched_group *sg)
4833 unsigned long util_sum = 0;
4834 unsigned long capacity = sg->sge->cap_states[eenv->cap_idx].cap;
4836 for_each_cpu(i, sched_group_cpus(sg)) {
4837 delta = calc_util_delta(eenv, i);
4838 util_sum += __cpu_norm_util(i, capacity, delta);
4841 if (util_sum > SCHED_CAPACITY_SCALE)
4842 return SCHED_CAPACITY_SCALE;
4846 static int find_new_capacity(struct energy_env *eenv,
4847 const struct sched_group_energy const *sge)
4850 unsigned long util = group_max_util(eenv);
4852 for (idx = 0; idx < sge->nr_cap_states; idx++) {
4853 if (sge->cap_states[idx].cap >= util)
4857 eenv->cap_idx = idx;
4862 static int group_idle_state(struct sched_group *sg)
4864 int i, state = INT_MAX;
4866 /* Find the shallowest idle state in the sched group. */
4867 for_each_cpu(i, sched_group_cpus(sg))
4868 state = min(state, idle_get_state_idx(cpu_rq(i)));
4870 /* Take non-cpuidle idling into account (active idle/arch_cpu_idle()) */
4877 * sched_group_energy(): Computes the absolute energy consumption of cpus
4878 * belonging to the sched_group including shared resources shared only by
4879 * members of the group. Iterates over all cpus in the hierarchy below the
4880 * sched_group starting from the bottom working it's way up before going to
4881 * the next cpu until all cpus are covered at all levels. The current
4882 * implementation is likely to gather the same util statistics multiple times.
4883 * This can probably be done in a faster but more complex way.
4884 * Note: sched_group_energy() may fail when racing with sched_domain updates.
4886 static int sched_group_energy(struct energy_env *eenv)
4888 struct sched_domain *sd;
4889 int cpu, total_energy = 0;
4890 struct cpumask visit_cpus;
4891 struct sched_group *sg;
4893 WARN_ON(!eenv->sg_top->sge);
4895 cpumask_copy(&visit_cpus, sched_group_cpus(eenv->sg_top));
4897 while (!cpumask_empty(&visit_cpus)) {
4898 struct sched_group *sg_shared_cap = NULL;
4900 cpu = cpumask_first(&visit_cpus);
4903 * Is the group utilization affected by cpus outside this
4906 sd = rcu_dereference(per_cpu(sd_scs, cpu));
4910 * We most probably raced with hotplug; returning a
4911 * wrong energy estimation is better than entering an
4917 sg_shared_cap = sd->parent->groups;
4919 for_each_domain(cpu, sd) {
4922 /* Has this sched_domain already been visited? */
4923 if (sd->child && group_first_cpu(sg) != cpu)
4927 unsigned long group_util;
4928 int sg_busy_energy, sg_idle_energy;
4929 int cap_idx, idle_idx;
4931 if (sg_shared_cap && sg_shared_cap->group_weight >= sg->group_weight)
4932 eenv->sg_cap = sg_shared_cap;
4936 cap_idx = find_new_capacity(eenv, sg->sge);
4937 idle_idx = group_idle_state(sg);
4938 group_util = group_norm_util(eenv, sg);
4939 sg_busy_energy = (group_util * sg->sge->cap_states[cap_idx].power)
4940 >> SCHED_CAPACITY_SHIFT;
4941 sg_idle_energy = ((SCHED_LOAD_SCALE-group_util)
4942 * sg->sge->idle_states[idle_idx].power)
4943 >> SCHED_CAPACITY_SHIFT;
4945 total_energy += sg_busy_energy + sg_idle_energy;
4948 cpumask_xor(&visit_cpus, &visit_cpus, sched_group_cpus(sg));
4950 if (cpumask_equal(sched_group_cpus(sg), sched_group_cpus(eenv->sg_top)))
4953 } while (sg = sg->next, sg != sd->groups);
4959 eenv->energy = total_energy;
4963 static inline bool cpu_in_sg(struct sched_group *sg, int cpu)
4965 return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));
4969 * energy_diff(): Estimate the energy impact of changing the utilization
4970 * distribution. eenv specifies the change: utilisation amount, source, and
4971 * destination cpu. Source or destination cpu may be -1 in which case the
4972 * utilization is removed from or added to the system (e.g. task wake-up). If
4973 * both are specified, the utilization is migrated.
4975 static int energy_diff(struct energy_env *eenv)
4977 struct sched_domain *sd;
4978 struct sched_group *sg;
4979 int sd_cpu = -1, energy_before = 0, energy_after = 0;
4981 struct energy_env eenv_before = {
4983 .src_cpu = eenv->src_cpu,
4984 .dst_cpu = eenv->dst_cpu,
4987 if (eenv->src_cpu == eenv->dst_cpu)
4990 sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu;
4991 sd = rcu_dereference(per_cpu(sd_ea, sd_cpu));
4994 return 0; /* Error */
4999 if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) {
5000 eenv_before.sg_top = eenv->sg_top = sg;
5002 if (sched_group_energy(&eenv_before))
5003 return 0; /* Invalid result abort */
5004 energy_before += eenv_before.energy;
5006 if (sched_group_energy(eenv))
5007 return 0; /* Invalid result abort */
5008 energy_after += eenv->energy;
5010 } while (sg = sg->next, sg != sd->groups);
5012 return energy_after-energy_before;
5016 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5017 * A waker of many should wake a different task than the one last awakened
5018 * at a frequency roughly N times higher than one of its wakees. In order
5019 * to determine whether we should let the load spread vs consolodating to
5020 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
5021 * partner, and a factor of lls_size higher frequency in the other. With
5022 * both conditions met, we can be relatively sure that the relationship is
5023 * non-monogamous, with partner count exceeding socket size. Waker/wakee
5024 * being client/server, worker/dispatcher, interrupt source or whatever is
5025 * irrelevant, spread criteria is apparent partner count exceeds socket size.
5027 static int wake_wide(struct task_struct *p)
5029 unsigned int master = current->wakee_flips;
5030 unsigned int slave = p->wakee_flips;
5031 int factor = this_cpu_read(sd_llc_size);
5034 swap(master, slave);
5035 if (slave < factor || master < slave * factor)
5040 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
5042 s64 this_load, load;
5043 s64 this_eff_load, prev_eff_load;
5044 int idx, this_cpu, prev_cpu;
5045 struct task_group *tg;
5046 unsigned long weight;
5050 this_cpu = smp_processor_id();
5051 prev_cpu = task_cpu(p);
5052 load = source_load(prev_cpu, idx);
5053 this_load = target_load(this_cpu, idx);
5056 * If sync wakeup then subtract the (maximum possible)
5057 * effect of the currently running task from the load
5058 * of the current CPU:
5061 tg = task_group(current);
5062 weight = current->se.avg.load_avg;
5064 this_load += effective_load(tg, this_cpu, -weight, -weight);
5065 load += effective_load(tg, prev_cpu, 0, -weight);
5069 weight = p->se.avg.load_avg;
5072 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5073 * due to the sync cause above having dropped this_load to 0, we'll
5074 * always have an imbalance, but there's really nothing you can do
5075 * about that, so that's good too.
5077 * Otherwise check if either cpus are near enough in load to allow this
5078 * task to be woken on this_cpu.
5080 this_eff_load = 100;
5081 this_eff_load *= capacity_of(prev_cpu);
5083 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5084 prev_eff_load *= capacity_of(this_cpu);
5086 if (this_load > 0) {
5087 this_eff_load *= this_load +
5088 effective_load(tg, this_cpu, weight, weight);
5090 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5093 balanced = this_eff_load <= prev_eff_load;
5095 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5100 schedstat_inc(sd, ttwu_move_affine);
5101 schedstat_inc(p, se.statistics.nr_wakeups_affine);
5106 static inline unsigned long task_util(struct task_struct *p)
5108 return p->se.avg.util_avg;
5111 unsigned int capacity_margin = 1280; /* ~20% margin */
5113 static inline bool __task_fits(struct task_struct *p, int cpu, int util)
5115 unsigned long capacity = capacity_of(cpu);
5117 util += task_util(p);
5119 return (capacity * 1024) > (util * capacity_margin);
5122 static inline bool task_fits_max(struct task_struct *p, int cpu)
5124 unsigned long capacity = capacity_of(cpu);
5125 unsigned long max_capacity = cpu_rq(cpu)->rd->max_cpu_capacity.val;
5127 if (capacity == max_capacity)
5130 if (capacity * capacity_margin > max_capacity * 1024)
5133 return __task_fits(p, cpu, 0);
5136 static inline bool task_fits_spare(struct task_struct *p, int cpu)
5138 return __task_fits(p, cpu, cpu_util(cpu));
5141 static bool cpu_overutilized(int cpu)
5143 return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
5147 * find_idlest_group finds and returns the least busy CPU group within the
5150 static struct sched_group *
5151 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5152 int this_cpu, int sd_flag)
5154 struct sched_group *idlest = NULL, *group = sd->groups;
5155 struct sched_group *fit_group = NULL, *spare_group = NULL;
5156 unsigned long min_load = ULONG_MAX, this_load = 0;
5157 unsigned long fit_capacity = ULONG_MAX;
5158 unsigned long max_spare_capacity = capacity_margin - SCHED_LOAD_SCALE;
5159 int load_idx = sd->forkexec_idx;
5160 int imbalance = 100 + (sd->imbalance_pct-100)/2;
5162 if (sd_flag & SD_BALANCE_WAKE)
5163 load_idx = sd->wake_idx;
5166 unsigned long load, avg_load, spare_capacity;
5170 /* Skip over this group if it has no CPUs allowed */
5171 if (!cpumask_intersects(sched_group_cpus(group),
5172 tsk_cpus_allowed(p)))
5175 local_group = cpumask_test_cpu(this_cpu,
5176 sched_group_cpus(group));
5178 /* Tally up the load of all CPUs in the group */
5181 for_each_cpu(i, sched_group_cpus(group)) {
5182 /* Bias balancing toward cpus of our domain */
5184 load = source_load(i, load_idx);
5186 load = target_load(i, load_idx);
5191 * Look for most energy-efficient group that can fit
5192 * that can fit the task.
5194 if (capacity_of(i) < fit_capacity && task_fits_spare(p, i)) {
5195 fit_capacity = capacity_of(i);
5200 * Look for group which has most spare capacity on a
5203 spare_capacity = capacity_of(i) - cpu_util(i);
5204 if (spare_capacity > max_spare_capacity) {
5205 max_spare_capacity = spare_capacity;
5206 spare_group = group;
5210 /* Adjust by relative CPU capacity of the group */
5211 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5214 this_load = avg_load;
5215 } else if (avg_load < min_load) {
5216 min_load = avg_load;
5219 } while (group = group->next, group != sd->groups);
5227 if (!idlest || 100*this_load < imbalance*min_load)
5233 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5236 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5238 unsigned long load, min_load = ULONG_MAX;
5239 unsigned int min_exit_latency = UINT_MAX;
5240 u64 latest_idle_timestamp = 0;
5241 int least_loaded_cpu = this_cpu;
5242 int shallowest_idle_cpu = -1;
5245 /* Traverse only the allowed CPUs */
5246 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5247 if (task_fits_spare(p, i)) {
5248 struct rq *rq = cpu_rq(i);
5249 struct cpuidle_state *idle = idle_get_state(rq);
5250 if (idle && idle->exit_latency < min_exit_latency) {
5252 * We give priority to a CPU whose idle state
5253 * has the smallest exit latency irrespective
5254 * of any idle timestamp.
5256 min_exit_latency = idle->exit_latency;
5257 latest_idle_timestamp = rq->idle_stamp;
5258 shallowest_idle_cpu = i;
5259 } else if (idle_cpu(i) &&
5260 (!idle || idle->exit_latency == min_exit_latency) &&
5261 rq->idle_stamp > latest_idle_timestamp) {
5263 * If equal or no active idle state, then
5264 * the most recently idled CPU might have
5267 latest_idle_timestamp = rq->idle_stamp;
5268 shallowest_idle_cpu = i;
5269 } else if (shallowest_idle_cpu == -1) {
5271 * If we haven't found an idle CPU yet
5272 * pick a non-idle one that can fit the task as
5275 shallowest_idle_cpu = i;
5277 } else if (shallowest_idle_cpu == -1) {
5278 load = weighted_cpuload(i);
5279 if (load < min_load || (load == min_load && i == this_cpu)) {
5281 least_loaded_cpu = i;
5286 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5290 * Try and locate an idle CPU in the sched_domain.
5292 static int select_idle_sibling(struct task_struct *p, int target)
5294 struct sched_domain *sd;
5295 struct sched_group *sg;
5296 int i = task_cpu(p);
5298 if (idle_cpu(target))
5302 * If the prevous cpu is cache affine and idle, don't be stupid.
5304 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5308 * Otherwise, iterate the domains and find an elegible idle cpu.
5310 sd = rcu_dereference(per_cpu(sd_llc, target));
5311 for_each_lower_domain(sd) {
5314 if (!cpumask_intersects(sched_group_cpus(sg),
5315 tsk_cpus_allowed(p)))
5318 for_each_cpu(i, sched_group_cpus(sg)) {
5319 if (i == target || !idle_cpu(i))
5323 target = cpumask_first_and(sched_group_cpus(sg),
5324 tsk_cpus_allowed(p));
5328 } while (sg != sd->groups);
5334 static int energy_aware_wake_cpu(struct task_struct *p, int target)
5336 struct sched_domain *sd;
5337 struct sched_group *sg, *sg_target;
5338 int target_max_cap = INT_MAX;
5339 int target_cpu = task_cpu(p);
5342 sd = rcu_dereference(per_cpu(sd_ea, task_cpu(p)));
5351 * Find group with sufficient capacity. We only get here if no cpu is
5352 * overutilized. We may end up overutilizing a cpu by adding the task,
5353 * but that should not be any worse than select_idle_sibling().
5354 * load_balance() should sort it out later as we get above the tipping
5358 /* Assuming all cpus are the same in group */
5359 int max_cap_cpu = group_first_cpu(sg);
5362 * Assume smaller max capacity means more energy-efficient.
5363 * Ideally we should query the energy model for the right
5364 * answer but it easily ends up in an exhaustive search.
5366 if (capacity_of(max_cap_cpu) < target_max_cap &&
5367 task_fits_max(p, max_cap_cpu)) {
5369 target_max_cap = capacity_of(max_cap_cpu);
5371 } while (sg = sg->next, sg != sd->groups);
5373 /* Find cpu with sufficient capacity */
5374 for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg_target)) {
5376 * p's blocked utilization is still accounted for on prev_cpu
5377 * so prev_cpu will receive a negative bias due to the double
5378 * accounting. However, the blocked utilization may be zero.
5380 int new_util = cpu_util(i) + task_util(p);
5382 if (new_util > capacity_orig_of(i))
5385 if (new_util < capacity_curr_of(i)) {
5387 if (cpu_rq(i)->nr_running)
5391 /* cpu has capacity at higher OPP, keep it as fallback */
5392 if (target_cpu == task_cpu(p))
5396 if (target_cpu != task_cpu(p)) {
5397 struct energy_env eenv = {
5398 .util_delta = task_util(p),
5399 .src_cpu = task_cpu(p),
5400 .dst_cpu = target_cpu,
5403 /* Not enough spare capacity on previous cpu */
5404 if (cpu_overutilized(task_cpu(p)))
5407 if (energy_diff(&eenv) >= 0)
5415 * select_task_rq_fair: Select target runqueue for the waking task in domains
5416 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5417 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5419 * Balances load by selecting the idlest cpu in the idlest group, or under
5420 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5422 * Returns the target cpu number.
5424 * preempt must be disabled.
5427 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5429 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5430 int cpu = smp_processor_id();
5431 int new_cpu = prev_cpu;
5432 int want_affine = 0;
5433 int sync = wake_flags & WF_SYNC;
5435 if (sd_flag & SD_BALANCE_WAKE)
5436 want_affine = (!wake_wide(p) && task_fits_max(p, cpu) &&
5437 cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) ||
5441 for_each_domain(cpu, tmp) {
5442 if (!(tmp->flags & SD_LOAD_BALANCE))
5446 * If both cpu and prev_cpu are part of this domain,
5447 * cpu is a valid SD_WAKE_AFFINE target.
5449 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5450 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5455 if (tmp->flags & sd_flag)
5457 else if (!want_affine)
5462 sd = NULL; /* Prefer wake_affine over balance flags */
5463 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5468 if (energy_aware() && !cpu_rq(cpu)->rd->overutilized)
5469 new_cpu = energy_aware_wake_cpu(p, prev_cpu);
5470 else if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5471 new_cpu = select_idle_sibling(p, new_cpu);
5474 struct sched_group *group;
5477 if (!(sd->flags & sd_flag)) {
5482 group = find_idlest_group(sd, p, cpu, sd_flag);
5488 new_cpu = find_idlest_cpu(group, p, cpu);
5489 if (new_cpu == -1 || new_cpu == cpu) {
5490 /* Now try balancing at a lower domain level of cpu */
5495 /* Now try balancing at a lower domain level of new_cpu */
5497 weight = sd->span_weight;
5499 for_each_domain(cpu, tmp) {
5500 if (weight <= tmp->span_weight)
5502 if (tmp->flags & sd_flag)
5505 /* while loop will break here if sd == NULL */
5513 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5514 * cfs_rq_of(p) references at time of call are still valid and identify the
5515 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5516 * other assumptions, including the state of rq->lock, should be made.
5518 static void migrate_task_rq_fair(struct task_struct *p)
5521 * We are supposed to update the task to "current" time, then its up to date
5522 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5523 * what current time is, so simply throw away the out-of-date time. This
5524 * will result in the wakee task is less decayed, but giving the wakee more
5525 * load sounds not bad.
5527 remove_entity_load_avg(&p->se);
5529 /* Tell new CPU we are migrated */
5530 p->se.avg.last_update_time = 0;
5532 /* We have migrated, no longer consider this task hot */
5533 p->se.exec_start = 0;
5536 static void task_dead_fair(struct task_struct *p)
5538 remove_entity_load_avg(&p->se);
5540 #endif /* CONFIG_SMP */
5542 static unsigned long
5543 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5545 unsigned long gran = sysctl_sched_wakeup_granularity;
5548 * Since its curr running now, convert the gran from real-time
5549 * to virtual-time in his units.
5551 * By using 'se' instead of 'curr' we penalize light tasks, so
5552 * they get preempted easier. That is, if 'se' < 'curr' then
5553 * the resulting gran will be larger, therefore penalizing the
5554 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5555 * be smaller, again penalizing the lighter task.
5557 * This is especially important for buddies when the leftmost
5558 * task is higher priority than the buddy.
5560 return calc_delta_fair(gran, se);
5564 * Should 'se' preempt 'curr'.
5578 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5580 s64 gran, vdiff = curr->vruntime - se->vruntime;
5585 gran = wakeup_gran(curr, se);
5592 static void set_last_buddy(struct sched_entity *se)
5594 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5597 for_each_sched_entity(se)
5598 cfs_rq_of(se)->last = se;
5601 static void set_next_buddy(struct sched_entity *se)
5603 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5606 for_each_sched_entity(se)
5607 cfs_rq_of(se)->next = se;
5610 static void set_skip_buddy(struct sched_entity *se)
5612 for_each_sched_entity(se)
5613 cfs_rq_of(se)->skip = se;
5617 * Preempt the current task with a newly woken task if needed:
5619 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5621 struct task_struct *curr = rq->curr;
5622 struct sched_entity *se = &curr->se, *pse = &p->se;
5623 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5624 int scale = cfs_rq->nr_running >= sched_nr_latency;
5625 int next_buddy_marked = 0;
5627 if (unlikely(se == pse))
5631 * This is possible from callers such as attach_tasks(), in which we
5632 * unconditionally check_prempt_curr() after an enqueue (which may have
5633 * lead to a throttle). This both saves work and prevents false
5634 * next-buddy nomination below.
5636 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5639 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5640 set_next_buddy(pse);
5641 next_buddy_marked = 1;
5645 * We can come here with TIF_NEED_RESCHED already set from new task
5648 * Note: this also catches the edge-case of curr being in a throttled
5649 * group (e.g. via set_curr_task), since update_curr() (in the
5650 * enqueue of curr) will have resulted in resched being set. This
5651 * prevents us from potentially nominating it as a false LAST_BUDDY
5654 if (test_tsk_need_resched(curr))
5657 /* Idle tasks are by definition preempted by non-idle tasks. */
5658 if (unlikely(curr->policy == SCHED_IDLE) &&
5659 likely(p->policy != SCHED_IDLE))
5663 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5664 * is driven by the tick):
5666 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5669 find_matching_se(&se, &pse);
5670 update_curr(cfs_rq_of(se));
5672 if (wakeup_preempt_entity(se, pse) == 1) {
5674 * Bias pick_next to pick the sched entity that is
5675 * triggering this preemption.
5677 if (!next_buddy_marked)
5678 set_next_buddy(pse);
5687 * Only set the backward buddy when the current task is still
5688 * on the rq. This can happen when a wakeup gets interleaved
5689 * with schedule on the ->pre_schedule() or idle_balance()
5690 * point, either of which can * drop the rq lock.
5692 * Also, during early boot the idle thread is in the fair class,
5693 * for obvious reasons its a bad idea to schedule back to it.
5695 if (unlikely(!se->on_rq || curr == rq->idle))
5698 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5702 static struct task_struct *
5703 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5705 struct cfs_rq *cfs_rq = &rq->cfs;
5706 struct sched_entity *se;
5707 struct task_struct *p;
5711 #ifdef CONFIG_FAIR_GROUP_SCHED
5712 if (!cfs_rq->nr_running)
5715 if (prev->sched_class != &fair_sched_class)
5719 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5720 * likely that a next task is from the same cgroup as the current.
5722 * Therefore attempt to avoid putting and setting the entire cgroup
5723 * hierarchy, only change the part that actually changes.
5727 struct sched_entity *curr = cfs_rq->curr;
5730 * Since we got here without doing put_prev_entity() we also
5731 * have to consider cfs_rq->curr. If it is still a runnable
5732 * entity, update_curr() will update its vruntime, otherwise
5733 * forget we've ever seen it.
5737 update_curr(cfs_rq);
5742 * This call to check_cfs_rq_runtime() will do the
5743 * throttle and dequeue its entity in the parent(s).
5744 * Therefore the 'simple' nr_running test will indeed
5747 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5751 se = pick_next_entity(cfs_rq, curr);
5752 cfs_rq = group_cfs_rq(se);
5758 * Since we haven't yet done put_prev_entity and if the selected task
5759 * is a different task than we started out with, try and touch the
5760 * least amount of cfs_rqs.
5763 struct sched_entity *pse = &prev->se;
5765 while (!(cfs_rq = is_same_group(se, pse))) {
5766 int se_depth = se->depth;
5767 int pse_depth = pse->depth;
5769 if (se_depth <= pse_depth) {
5770 put_prev_entity(cfs_rq_of(pse), pse);
5771 pse = parent_entity(pse);
5773 if (se_depth >= pse_depth) {
5774 set_next_entity(cfs_rq_of(se), se);
5775 se = parent_entity(se);
5779 put_prev_entity(cfs_rq, pse);
5780 set_next_entity(cfs_rq, se);
5783 if (hrtick_enabled(rq))
5784 hrtick_start_fair(rq, p);
5786 rq->misfit_task = !task_fits_max(p, rq->cpu);
5793 if (!cfs_rq->nr_running)
5796 put_prev_task(rq, prev);
5799 se = pick_next_entity(cfs_rq, NULL);
5800 set_next_entity(cfs_rq, se);
5801 cfs_rq = group_cfs_rq(se);
5806 if (hrtick_enabled(rq))
5807 hrtick_start_fair(rq, p);
5809 rq->misfit_task = !task_fits_max(p, rq->cpu);
5814 rq->misfit_task = 0;
5816 * This is OK, because current is on_cpu, which avoids it being picked
5817 * for load-balance and preemption/IRQs are still disabled avoiding
5818 * further scheduler activity on it and we're being very careful to
5819 * re-start the picking loop.
5821 lockdep_unpin_lock(&rq->lock);
5822 new_tasks = idle_balance(rq);
5823 lockdep_pin_lock(&rq->lock);
5825 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5826 * possible for any higher priority task to appear. In that case we
5827 * must re-start the pick_next_entity() loop.
5839 * Account for a descheduled task:
5841 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5843 struct sched_entity *se = &prev->se;
5844 struct cfs_rq *cfs_rq;
5846 for_each_sched_entity(se) {
5847 cfs_rq = cfs_rq_of(se);
5848 put_prev_entity(cfs_rq, se);
5853 * sched_yield() is very simple
5855 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5857 static void yield_task_fair(struct rq *rq)
5859 struct task_struct *curr = rq->curr;
5860 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5861 struct sched_entity *se = &curr->se;
5864 * Are we the only task in the tree?
5866 if (unlikely(rq->nr_running == 1))
5869 clear_buddies(cfs_rq, se);
5871 if (curr->policy != SCHED_BATCH) {
5872 update_rq_clock(rq);
5874 * Update run-time statistics of the 'current'.
5876 update_curr(cfs_rq);
5878 * Tell update_rq_clock() that we've just updated,
5879 * so we don't do microscopic update in schedule()
5880 * and double the fastpath cost.
5882 rq_clock_skip_update(rq, true);
5888 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5890 struct sched_entity *se = &p->se;
5892 /* throttled hierarchies are not runnable */
5893 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5896 /* Tell the scheduler that we'd really like pse to run next. */
5899 yield_task_fair(rq);
5905 /**************************************************
5906 * Fair scheduling class load-balancing methods.
5910 * The purpose of load-balancing is to achieve the same basic fairness the
5911 * per-cpu scheduler provides, namely provide a proportional amount of compute
5912 * time to each task. This is expressed in the following equation:
5914 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5916 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5917 * W_i,0 is defined as:
5919 * W_i,0 = \Sum_j w_i,j (2)
5921 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5922 * is derived from the nice value as per prio_to_weight[].
5924 * The weight average is an exponential decay average of the instantaneous
5927 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5929 * C_i is the compute capacity of cpu i, typically it is the
5930 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5931 * can also include other factors [XXX].
5933 * To achieve this balance we define a measure of imbalance which follows
5934 * directly from (1):
5936 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5938 * We them move tasks around to minimize the imbalance. In the continuous
5939 * function space it is obvious this converges, in the discrete case we get
5940 * a few fun cases generally called infeasible weight scenarios.
5943 * - infeasible weights;
5944 * - local vs global optima in the discrete case. ]
5949 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5950 * for all i,j solution, we create a tree of cpus that follows the hardware
5951 * topology where each level pairs two lower groups (or better). This results
5952 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5953 * tree to only the first of the previous level and we decrease the frequency
5954 * of load-balance at each level inv. proportional to the number of cpus in
5960 * \Sum { --- * --- * 2^i } = O(n) (5)
5962 * `- size of each group
5963 * | | `- number of cpus doing load-balance
5965 * `- sum over all levels
5967 * Coupled with a limit on how many tasks we can migrate every balance pass,
5968 * this makes (5) the runtime complexity of the balancer.
5970 * An important property here is that each CPU is still (indirectly) connected
5971 * to every other cpu in at most O(log n) steps:
5973 * The adjacency matrix of the resulting graph is given by:
5976 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5979 * And you'll find that:
5981 * A^(log_2 n)_i,j != 0 for all i,j (7)
5983 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5984 * The task movement gives a factor of O(m), giving a convergence complexity
5987 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5992 * In order to avoid CPUs going idle while there's still work to do, new idle
5993 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5994 * tree itself instead of relying on other CPUs to bring it work.
5996 * This adds some complexity to both (5) and (8) but it reduces the total idle
6004 * Cgroups make a horror show out of (2), instead of a simple sum we get:
6007 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
6012 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
6014 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
6016 * The big problem is S_k, its a global sum needed to compute a local (W_i)
6019 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
6020 * rewrite all of this once again.]
6023 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
6025 enum fbq_type { regular, remote, all };
6034 #define LBF_ALL_PINNED 0x01
6035 #define LBF_NEED_BREAK 0x02
6036 #define LBF_DST_PINNED 0x04
6037 #define LBF_SOME_PINNED 0x08
6040 struct sched_domain *sd;
6048 struct cpumask *dst_grpmask;
6050 enum cpu_idle_type idle;
6052 unsigned int src_grp_nr_running;
6053 /* The set of CPUs under consideration for load-balancing */
6054 struct cpumask *cpus;
6059 unsigned int loop_break;
6060 unsigned int loop_max;
6062 enum fbq_type fbq_type;
6063 enum group_type busiest_group_type;
6064 struct list_head tasks;
6068 * Is this task likely cache-hot:
6070 static int task_hot(struct task_struct *p, struct lb_env *env)
6074 lockdep_assert_held(&env->src_rq->lock);
6076 if (p->sched_class != &fair_sched_class)
6079 if (unlikely(p->policy == SCHED_IDLE))
6083 * Buddy candidates are cache hot:
6085 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6086 (&p->se == cfs_rq_of(&p->se)->next ||
6087 &p->se == cfs_rq_of(&p->se)->last))
6090 if (sysctl_sched_migration_cost == -1)
6092 if (sysctl_sched_migration_cost == 0)
6095 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6097 return delta < (s64)sysctl_sched_migration_cost;
6100 #ifdef CONFIG_NUMA_BALANCING
6102 * Returns 1, if task migration degrades locality
6103 * Returns 0, if task migration improves locality i.e migration preferred.
6104 * Returns -1, if task migration is not affected by locality.
6106 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6108 struct numa_group *numa_group = rcu_dereference(p->numa_group);
6109 unsigned long src_faults, dst_faults;
6110 int src_nid, dst_nid;
6112 if (!static_branch_likely(&sched_numa_balancing))
6115 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6118 src_nid = cpu_to_node(env->src_cpu);
6119 dst_nid = cpu_to_node(env->dst_cpu);
6121 if (src_nid == dst_nid)
6124 /* Migrating away from the preferred node is always bad. */
6125 if (src_nid == p->numa_preferred_nid) {
6126 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6132 /* Encourage migration to the preferred node. */
6133 if (dst_nid == p->numa_preferred_nid)
6137 src_faults = group_faults(p, src_nid);
6138 dst_faults = group_faults(p, dst_nid);
6140 src_faults = task_faults(p, src_nid);
6141 dst_faults = task_faults(p, dst_nid);
6144 return dst_faults < src_faults;
6148 static inline int migrate_degrades_locality(struct task_struct *p,
6156 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6159 int can_migrate_task(struct task_struct *p, struct lb_env *env)
6163 lockdep_assert_held(&env->src_rq->lock);
6166 * We do not migrate tasks that are:
6167 * 1) throttled_lb_pair, or
6168 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6169 * 3) running (obviously), or
6170 * 4) are cache-hot on their current CPU.
6172 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6175 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6178 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6180 env->flags |= LBF_SOME_PINNED;
6183 * Remember if this task can be migrated to any other cpu in
6184 * our sched_group. We may want to revisit it if we couldn't
6185 * meet load balance goals by pulling other tasks on src_cpu.
6187 * Also avoid computing new_dst_cpu if we have already computed
6188 * one in current iteration.
6190 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6193 /* Prevent to re-select dst_cpu via env's cpus */
6194 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6195 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6196 env->flags |= LBF_DST_PINNED;
6197 env->new_dst_cpu = cpu;
6205 /* Record that we found atleast one task that could run on dst_cpu */
6206 env->flags &= ~LBF_ALL_PINNED;
6208 if (task_running(env->src_rq, p)) {
6209 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6214 * Aggressive migration if:
6215 * 1) destination numa is preferred
6216 * 2) task is cache cold, or
6217 * 3) too many balance attempts have failed.
6219 tsk_cache_hot = migrate_degrades_locality(p, env);
6220 if (tsk_cache_hot == -1)
6221 tsk_cache_hot = task_hot(p, env);
6223 if (tsk_cache_hot <= 0 ||
6224 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6225 if (tsk_cache_hot == 1) {
6226 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
6227 schedstat_inc(p, se.statistics.nr_forced_migrations);
6232 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
6237 * detach_task() -- detach the task for the migration specified in env
6239 static void detach_task(struct task_struct *p, struct lb_env *env)
6241 lockdep_assert_held(&env->src_rq->lock);
6243 deactivate_task(env->src_rq, p, 0);
6244 p->on_rq = TASK_ON_RQ_MIGRATING;
6245 set_task_cpu(p, env->dst_cpu);
6249 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6250 * part of active balancing operations within "domain".
6252 * Returns a task if successful and NULL otherwise.
6254 static struct task_struct *detach_one_task(struct lb_env *env)
6256 struct task_struct *p, *n;
6258 lockdep_assert_held(&env->src_rq->lock);
6260 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
6261 if (!can_migrate_task(p, env))
6264 detach_task(p, env);
6267 * Right now, this is only the second place where
6268 * lb_gained[env->idle] is updated (other is detach_tasks)
6269 * so we can safely collect stats here rather than
6270 * inside detach_tasks().
6272 schedstat_inc(env->sd, lb_gained[env->idle]);
6278 static const unsigned int sched_nr_migrate_break = 32;
6281 * detach_tasks() -- tries to detach up to imbalance weighted load from
6282 * busiest_rq, as part of a balancing operation within domain "sd".
6284 * Returns number of detached tasks if successful and 0 otherwise.
6286 static int detach_tasks(struct lb_env *env)
6288 struct list_head *tasks = &env->src_rq->cfs_tasks;
6289 struct task_struct *p;
6293 lockdep_assert_held(&env->src_rq->lock);
6295 if (env->imbalance <= 0)
6298 while (!list_empty(tasks)) {
6300 * We don't want to steal all, otherwise we may be treated likewise,
6301 * which could at worst lead to a livelock crash.
6303 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6306 p = list_first_entry(tasks, struct task_struct, se.group_node);
6309 /* We've more or less seen every task there is, call it quits */
6310 if (env->loop > env->loop_max)
6313 /* take a breather every nr_migrate tasks */
6314 if (env->loop > env->loop_break) {
6315 env->loop_break += sched_nr_migrate_break;
6316 env->flags |= LBF_NEED_BREAK;
6320 if (!can_migrate_task(p, env))
6323 load = task_h_load(p);
6325 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6328 if ((load / 2) > env->imbalance)
6331 detach_task(p, env);
6332 list_add(&p->se.group_node, &env->tasks);
6335 env->imbalance -= load;
6337 #ifdef CONFIG_PREEMPT
6339 * NEWIDLE balancing is a source of latency, so preemptible
6340 * kernels will stop after the first task is detached to minimize
6341 * the critical section.
6343 if (env->idle == CPU_NEWLY_IDLE)
6348 * We only want to steal up to the prescribed amount of
6351 if (env->imbalance <= 0)
6356 list_move_tail(&p->se.group_node, tasks);
6360 * Right now, this is one of only two places we collect this stat
6361 * so we can safely collect detach_one_task() stats here rather
6362 * than inside detach_one_task().
6364 schedstat_add(env->sd, lb_gained[env->idle], detached);
6370 * attach_task() -- attach the task detached by detach_task() to its new rq.
6372 static void attach_task(struct rq *rq, struct task_struct *p)
6374 lockdep_assert_held(&rq->lock);
6376 BUG_ON(task_rq(p) != rq);
6377 p->on_rq = TASK_ON_RQ_QUEUED;
6378 activate_task(rq, p, 0);
6379 check_preempt_curr(rq, p, 0);
6383 * attach_one_task() -- attaches the task returned from detach_one_task() to
6386 static void attach_one_task(struct rq *rq, struct task_struct *p)
6388 raw_spin_lock(&rq->lock);
6390 raw_spin_unlock(&rq->lock);
6394 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6397 static void attach_tasks(struct lb_env *env)
6399 struct list_head *tasks = &env->tasks;
6400 struct task_struct *p;
6402 raw_spin_lock(&env->dst_rq->lock);
6404 while (!list_empty(tasks)) {
6405 p = list_first_entry(tasks, struct task_struct, se.group_node);
6406 list_del_init(&p->se.group_node);
6408 attach_task(env->dst_rq, p);
6411 raw_spin_unlock(&env->dst_rq->lock);
6414 #ifdef CONFIG_FAIR_GROUP_SCHED
6415 static void update_blocked_averages(int cpu)
6417 struct rq *rq = cpu_rq(cpu);
6418 struct cfs_rq *cfs_rq;
6419 unsigned long flags;
6421 raw_spin_lock_irqsave(&rq->lock, flags);
6422 update_rq_clock(rq);
6425 * Iterates the task_group tree in a bottom up fashion, see
6426 * list_add_leaf_cfs_rq() for details.
6428 for_each_leaf_cfs_rq(rq, cfs_rq) {
6429 /* throttled entities do not contribute to load */
6430 if (throttled_hierarchy(cfs_rq))
6433 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6434 update_tg_load_avg(cfs_rq, 0);
6436 raw_spin_unlock_irqrestore(&rq->lock, flags);
6440 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6441 * This needs to be done in a top-down fashion because the load of a child
6442 * group is a fraction of its parents load.
6444 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6446 struct rq *rq = rq_of(cfs_rq);
6447 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6448 unsigned long now = jiffies;
6451 if (cfs_rq->last_h_load_update == now)
6454 cfs_rq->h_load_next = NULL;
6455 for_each_sched_entity(se) {
6456 cfs_rq = cfs_rq_of(se);
6457 cfs_rq->h_load_next = se;
6458 if (cfs_rq->last_h_load_update == now)
6463 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6464 cfs_rq->last_h_load_update = now;
6467 while ((se = cfs_rq->h_load_next) != NULL) {
6468 load = cfs_rq->h_load;
6469 load = div64_ul(load * se->avg.load_avg,
6470 cfs_rq_load_avg(cfs_rq) + 1);
6471 cfs_rq = group_cfs_rq(se);
6472 cfs_rq->h_load = load;
6473 cfs_rq->last_h_load_update = now;
6477 static unsigned long task_h_load(struct task_struct *p)
6479 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6481 update_cfs_rq_h_load(cfs_rq);
6482 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6483 cfs_rq_load_avg(cfs_rq) + 1);
6486 static inline void update_blocked_averages(int cpu)
6488 struct rq *rq = cpu_rq(cpu);
6489 struct cfs_rq *cfs_rq = &rq->cfs;
6490 unsigned long flags;
6492 raw_spin_lock_irqsave(&rq->lock, flags);
6493 update_rq_clock(rq);
6494 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6495 raw_spin_unlock_irqrestore(&rq->lock, flags);
6498 static unsigned long task_h_load(struct task_struct *p)
6500 return p->se.avg.load_avg;
6504 /********** Helpers for find_busiest_group ************************/
6507 * sg_lb_stats - stats of a sched_group required for load_balancing
6509 struct sg_lb_stats {
6510 unsigned long avg_load; /*Avg load across the CPUs of the group */
6511 unsigned long group_load; /* Total load over the CPUs of the group */
6512 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6513 unsigned long load_per_task;
6514 unsigned long group_capacity;
6515 unsigned long group_util; /* Total utilization of the group */
6516 unsigned int sum_nr_running; /* Nr tasks running in the group */
6517 unsigned int idle_cpus;
6518 unsigned int group_weight;
6519 enum group_type group_type;
6520 int group_no_capacity;
6521 int group_misfit_task; /* A cpu has a task too big for its capacity */
6522 #ifdef CONFIG_NUMA_BALANCING
6523 unsigned int nr_numa_running;
6524 unsigned int nr_preferred_running;
6529 * sd_lb_stats - Structure to store the statistics of a sched_domain
6530 * during load balancing.
6532 struct sd_lb_stats {
6533 struct sched_group *busiest; /* Busiest group in this sd */
6534 struct sched_group *local; /* Local group in this sd */
6535 unsigned long total_load; /* Total load of all groups in sd */
6536 unsigned long total_capacity; /* Total capacity of all groups in sd */
6537 unsigned long avg_load; /* Average load across all groups in sd */
6539 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6540 struct sg_lb_stats local_stat; /* Statistics of the local group */
6543 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6546 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6547 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6548 * We must however clear busiest_stat::avg_load because
6549 * update_sd_pick_busiest() reads this before assignment.
6551 *sds = (struct sd_lb_stats){
6555 .total_capacity = 0UL,
6558 .sum_nr_running = 0,
6559 .group_type = group_other,
6565 * get_sd_load_idx - Obtain the load index for a given sched domain.
6566 * @sd: The sched_domain whose load_idx is to be obtained.
6567 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6569 * Return: The load index.
6571 static inline int get_sd_load_idx(struct sched_domain *sd,
6572 enum cpu_idle_type idle)
6578 load_idx = sd->busy_idx;
6581 case CPU_NEWLY_IDLE:
6582 load_idx = sd->newidle_idx;
6585 load_idx = sd->idle_idx;
6592 static unsigned long scale_rt_capacity(int cpu)
6594 struct rq *rq = cpu_rq(cpu);
6595 u64 total, used, age_stamp, avg;
6599 * Since we're reading these variables without serialization make sure
6600 * we read them once before doing sanity checks on them.
6602 age_stamp = READ_ONCE(rq->age_stamp);
6603 avg = READ_ONCE(rq->rt_avg);
6604 delta = __rq_clock_broken(rq) - age_stamp;
6606 if (unlikely(delta < 0))
6609 total = sched_avg_period() + delta;
6611 used = div_u64(avg, total);
6613 if (likely(used < SCHED_CAPACITY_SCALE))
6614 return SCHED_CAPACITY_SCALE - used;
6619 void init_max_cpu_capacity(struct max_cpu_capacity *mcc)
6621 raw_spin_lock_init(&mcc->lock);
6626 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6628 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6629 struct sched_group *sdg = sd->groups;
6630 struct max_cpu_capacity *mcc;
6631 unsigned long max_capacity;
6633 unsigned long flags;
6635 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6637 mcc = &cpu_rq(cpu)->rd->max_cpu_capacity;
6639 raw_spin_lock_irqsave(&mcc->lock, flags);
6640 max_capacity = mcc->val;
6641 max_cap_cpu = mcc->cpu;
6643 if ((max_capacity > capacity && max_cap_cpu == cpu) ||
6644 (max_capacity < capacity)) {
6645 mcc->val = capacity;
6647 #ifdef CONFIG_SCHED_DEBUG
6648 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6649 pr_info("CPU%d: update max cpu_capacity %lu\n", cpu, capacity);
6653 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6655 skip_unlock: __attribute__ ((unused));
6656 capacity *= scale_rt_capacity(cpu);
6657 capacity >>= SCHED_CAPACITY_SHIFT;
6662 cpu_rq(cpu)->cpu_capacity = capacity;
6663 sdg->sgc->capacity = capacity;
6664 sdg->sgc->max_capacity = capacity;
6667 void update_group_capacity(struct sched_domain *sd, int cpu)
6669 struct sched_domain *child = sd->child;
6670 struct sched_group *group, *sdg = sd->groups;
6671 unsigned long capacity, max_capacity;
6672 unsigned long interval;
6674 interval = msecs_to_jiffies(sd->balance_interval);
6675 interval = clamp(interval, 1UL, max_load_balance_interval);
6676 sdg->sgc->next_update = jiffies + interval;
6679 update_cpu_capacity(sd, cpu);
6686 if (child->flags & SD_OVERLAP) {
6688 * SD_OVERLAP domains cannot assume that child groups
6689 * span the current group.
6692 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6693 struct sched_group_capacity *sgc;
6694 struct rq *rq = cpu_rq(cpu);
6697 * build_sched_domains() -> init_sched_groups_capacity()
6698 * gets here before we've attached the domains to the
6701 * Use capacity_of(), which is set irrespective of domains
6702 * in update_cpu_capacity().
6704 * This avoids capacity from being 0 and
6705 * causing divide-by-zero issues on boot.
6707 if (unlikely(!rq->sd)) {
6708 capacity += capacity_of(cpu);
6710 sgc = rq->sd->groups->sgc;
6711 capacity += sgc->capacity;
6714 max_capacity = max(capacity, max_capacity);
6718 * !SD_OVERLAP domains can assume that child groups
6719 * span the current group.
6722 group = child->groups;
6724 struct sched_group_capacity *sgc = group->sgc;
6726 capacity += sgc->capacity;
6727 max_capacity = max(sgc->max_capacity, max_capacity);
6728 group = group->next;
6729 } while (group != child->groups);
6732 sdg->sgc->capacity = capacity;
6733 sdg->sgc->max_capacity = max_capacity;
6737 * Check whether the capacity of the rq has been noticeably reduced by side
6738 * activity. The imbalance_pct is used for the threshold.
6739 * Return true is the capacity is reduced
6742 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6744 return ((rq->cpu_capacity * sd->imbalance_pct) <
6745 (rq->cpu_capacity_orig * 100));
6749 * Group imbalance indicates (and tries to solve) the problem where balancing
6750 * groups is inadequate due to tsk_cpus_allowed() constraints.
6752 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6753 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6756 * { 0 1 2 3 } { 4 5 6 7 }
6759 * If we were to balance group-wise we'd place two tasks in the first group and
6760 * two tasks in the second group. Clearly this is undesired as it will overload
6761 * cpu 3 and leave one of the cpus in the second group unused.
6763 * The current solution to this issue is detecting the skew in the first group
6764 * by noticing the lower domain failed to reach balance and had difficulty
6765 * moving tasks due to affinity constraints.
6767 * When this is so detected; this group becomes a candidate for busiest; see
6768 * update_sd_pick_busiest(). And calculate_imbalance() and
6769 * find_busiest_group() avoid some of the usual balance conditions to allow it
6770 * to create an effective group imbalance.
6772 * This is a somewhat tricky proposition since the next run might not find the
6773 * group imbalance and decide the groups need to be balanced again. A most
6774 * subtle and fragile situation.
6777 static inline int sg_imbalanced(struct sched_group *group)
6779 return group->sgc->imbalance;
6783 * group_has_capacity returns true if the group has spare capacity that could
6784 * be used by some tasks.
6785 * We consider that a group has spare capacity if the * number of task is
6786 * smaller than the number of CPUs or if the utilization is lower than the
6787 * available capacity for CFS tasks.
6788 * For the latter, we use a threshold to stabilize the state, to take into
6789 * account the variance of the tasks' load and to return true if the available
6790 * capacity in meaningful for the load balancer.
6791 * As an example, an available capacity of 1% can appear but it doesn't make
6792 * any benefit for the load balance.
6795 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6797 if (sgs->sum_nr_running < sgs->group_weight)
6800 if ((sgs->group_capacity * 100) >
6801 (sgs->group_util * env->sd->imbalance_pct))
6808 * group_is_overloaded returns true if the group has more tasks than it can
6810 * group_is_overloaded is not equals to !group_has_capacity because a group
6811 * with the exact right number of tasks, has no more spare capacity but is not
6812 * overloaded so both group_has_capacity and group_is_overloaded return
6816 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6818 if (sgs->sum_nr_running <= sgs->group_weight)
6821 if ((sgs->group_capacity * 100) <
6822 (sgs->group_util * env->sd->imbalance_pct))
6830 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
6831 * per-cpu capacity than sched_group ref.
6834 group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
6836 return sg->sgc->max_capacity + capacity_margin - SCHED_LOAD_SCALE <
6837 ref->sgc->max_capacity;
6841 group_type group_classify(struct sched_group *group,
6842 struct sg_lb_stats *sgs)
6844 if (sgs->group_no_capacity)
6845 return group_overloaded;
6847 if (sg_imbalanced(group))
6848 return group_imbalanced;
6850 if (sgs->group_misfit_task)
6851 return group_misfit_task;
6857 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6858 * @env: The load balancing environment.
6859 * @group: sched_group whose statistics are to be updated.
6860 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6861 * @local_group: Does group contain this_cpu.
6862 * @sgs: variable to hold the statistics for this group.
6863 * @overload: Indicate more than one runnable task for any CPU.
6864 * @overutilized: Indicate overutilization for any CPU.
6866 static inline void update_sg_lb_stats(struct lb_env *env,
6867 struct sched_group *group, int load_idx,
6868 int local_group, struct sg_lb_stats *sgs,
6869 bool *overload, bool *overutilized)
6874 memset(sgs, 0, sizeof(*sgs));
6876 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6877 struct rq *rq = cpu_rq(i);
6879 /* Bias balancing toward cpus of our domain */
6881 load = target_load(i, load_idx);
6883 load = source_load(i, load_idx);
6885 sgs->group_load += load;
6886 sgs->group_util += cpu_util(i);
6887 sgs->sum_nr_running += rq->cfs.h_nr_running;
6889 if (rq->nr_running > 1)
6892 #ifdef CONFIG_NUMA_BALANCING
6893 sgs->nr_numa_running += rq->nr_numa_running;
6894 sgs->nr_preferred_running += rq->nr_preferred_running;
6896 sgs->sum_weighted_load += weighted_cpuload(i);
6900 if (cpu_overutilized(i)) {
6901 *overutilized = true;
6902 if (!sgs->group_misfit_task && rq->misfit_task)
6903 sgs->group_misfit_task = capacity_of(i);
6907 /* Adjust by relative CPU capacity of the group */
6908 sgs->group_capacity = group->sgc->capacity;
6909 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6911 if (sgs->sum_nr_running)
6912 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6914 sgs->group_weight = group->group_weight;
6916 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6917 sgs->group_type = group_classify(group, sgs);
6921 * update_sd_pick_busiest - return 1 on busiest group
6922 * @env: The load balancing environment.
6923 * @sds: sched_domain statistics
6924 * @sg: sched_group candidate to be checked for being the busiest
6925 * @sgs: sched_group statistics
6927 * Determine if @sg is a busier group than the previously selected
6930 * Return: %true if @sg is a busier group than the previously selected
6931 * busiest group. %false otherwise.
6933 static bool update_sd_pick_busiest(struct lb_env *env,
6934 struct sd_lb_stats *sds,
6935 struct sched_group *sg,
6936 struct sg_lb_stats *sgs)
6938 struct sg_lb_stats *busiest = &sds->busiest_stat;
6940 if (sgs->group_type > busiest->group_type)
6943 if (sgs->group_type < busiest->group_type)
6947 * Candidate sg doesn't face any serious load-balance problems
6948 * so don't pick it if the local sg is already filled up.
6950 if (sgs->group_type == group_other &&
6951 !group_has_capacity(env, &sds->local_stat))
6954 if (sgs->avg_load <= busiest->avg_load)
6958 * Candiate sg has no more than one task per cpu and has higher
6959 * per-cpu capacity. No reason to pull tasks to less capable cpus.
6961 if (sgs->sum_nr_running <= sgs->group_weight &&
6962 group_smaller_cpu_capacity(sds->local, sg))
6965 /* This is the busiest node in its class. */
6966 if (!(env->sd->flags & SD_ASYM_PACKING))
6970 * ASYM_PACKING needs to move all the work to the lowest
6971 * numbered CPUs in the group, therefore mark all groups
6972 * higher than ourself as busy.
6974 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6978 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6985 #ifdef CONFIG_NUMA_BALANCING
6986 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6988 if (sgs->sum_nr_running > sgs->nr_numa_running)
6990 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6995 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6997 if (rq->nr_running > rq->nr_numa_running)
6999 if (rq->nr_running > rq->nr_preferred_running)
7004 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7009 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7013 #endif /* CONFIG_NUMA_BALANCING */
7016 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7017 * @env: The load balancing environment.
7018 * @sds: variable to hold the statistics for this sched_domain.
7020 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7022 struct sched_domain *child = env->sd->child;
7023 struct sched_group *sg = env->sd->groups;
7024 struct sg_lb_stats tmp_sgs;
7025 int load_idx, prefer_sibling = 0;
7026 bool overload = false, overutilized = false;
7028 if (child && child->flags & SD_PREFER_SIBLING)
7031 load_idx = get_sd_load_idx(env->sd, env->idle);
7034 struct sg_lb_stats *sgs = &tmp_sgs;
7037 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
7040 sgs = &sds->local_stat;
7042 if (env->idle != CPU_NEWLY_IDLE ||
7043 time_after_eq(jiffies, sg->sgc->next_update))
7044 update_group_capacity(env->sd, env->dst_cpu);
7047 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
7048 &overload, &overutilized);
7054 * In case the child domain prefers tasks go to siblings
7055 * first, lower the sg capacity so that we'll try
7056 * and move all the excess tasks away. We lower the capacity
7057 * of a group only if the local group has the capacity to fit
7058 * these excess tasks. The extra check prevents the case where
7059 * you always pull from the heaviest group when it is already
7060 * under-utilized (possible with a large weight task outweighs
7061 * the tasks on the system).
7063 if (prefer_sibling && sds->local &&
7064 group_has_capacity(env, &sds->local_stat) &&
7065 (sgs->sum_nr_running > 1)) {
7066 sgs->group_no_capacity = 1;
7067 sgs->group_type = group_classify(sg, sgs);
7071 * Ignore task groups with misfit tasks if local group has no
7072 * capacity or if per-cpu capacity isn't higher.
7074 if (sgs->group_type == group_misfit_task &&
7075 (!group_has_capacity(env, &sds->local_stat) ||
7076 !group_smaller_cpu_capacity(sg, sds->local)))
7077 sgs->group_type = group_other;
7079 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7081 sds->busiest_stat = *sgs;
7085 /* Now, start updating sd_lb_stats */
7086 sds->total_load += sgs->group_load;
7087 sds->total_capacity += sgs->group_capacity;
7090 } while (sg != env->sd->groups);
7092 if (env->sd->flags & SD_NUMA)
7093 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7095 env->src_grp_nr_running = sds->busiest_stat.sum_nr_running;
7097 if (!env->sd->parent) {
7098 /* update overload indicator if we are at root domain */
7099 if (env->dst_rq->rd->overload != overload)
7100 env->dst_rq->rd->overload = overload;
7102 /* Update over-utilization (tipping point, U >= 0) indicator */
7103 if (env->dst_rq->rd->overutilized != overutilized)
7104 env->dst_rq->rd->overutilized = overutilized;
7106 if (!env->dst_rq->rd->overutilized && overutilized)
7107 env->dst_rq->rd->overutilized = true;
7112 * check_asym_packing - Check to see if the group is packed into the
7115 * This is primarily intended to used at the sibling level. Some
7116 * cores like POWER7 prefer to use lower numbered SMT threads. In the
7117 * case of POWER7, it can move to lower SMT modes only when higher
7118 * threads are idle. When in lower SMT modes, the threads will
7119 * perform better since they share less core resources. Hence when we
7120 * have idle threads, we want them to be the higher ones.
7122 * This packing function is run on idle threads. It checks to see if
7123 * the busiest CPU in this domain (core in the P7 case) has a higher
7124 * CPU number than the packing function is being run on. Here we are
7125 * assuming lower CPU number will be equivalent to lower a SMT thread
7128 * Return: 1 when packing is required and a task should be moved to
7129 * this CPU. The amount of the imbalance is returned in *imbalance.
7131 * @env: The load balancing environment.
7132 * @sds: Statistics of the sched_domain which is to be packed
7134 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7138 if (!(env->sd->flags & SD_ASYM_PACKING))
7144 busiest_cpu = group_first_cpu(sds->busiest);
7145 if (env->dst_cpu > busiest_cpu)
7148 env->imbalance = DIV_ROUND_CLOSEST(
7149 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7150 SCHED_CAPACITY_SCALE);
7156 * fix_small_imbalance - Calculate the minor imbalance that exists
7157 * amongst the groups of a sched_domain, during
7159 * @env: The load balancing environment.
7160 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7163 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7165 unsigned long tmp, capa_now = 0, capa_move = 0;
7166 unsigned int imbn = 2;
7167 unsigned long scaled_busy_load_per_task;
7168 struct sg_lb_stats *local, *busiest;
7170 local = &sds->local_stat;
7171 busiest = &sds->busiest_stat;
7173 if (!local->sum_nr_running)
7174 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
7175 else if (busiest->load_per_task > local->load_per_task)
7178 scaled_busy_load_per_task =
7179 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7180 busiest->group_capacity;
7182 if (busiest->avg_load + scaled_busy_load_per_task >=
7183 local->avg_load + (scaled_busy_load_per_task * imbn)) {
7184 env->imbalance = busiest->load_per_task;
7189 * OK, we don't have enough imbalance to justify moving tasks,
7190 * however we may be able to increase total CPU capacity used by
7194 capa_now += busiest->group_capacity *
7195 min(busiest->load_per_task, busiest->avg_load);
7196 capa_now += local->group_capacity *
7197 min(local->load_per_task, local->avg_load);
7198 capa_now /= SCHED_CAPACITY_SCALE;
7200 /* Amount of load we'd subtract */
7201 if (busiest->avg_load > scaled_busy_load_per_task) {
7202 capa_move += busiest->group_capacity *
7203 min(busiest->load_per_task,
7204 busiest->avg_load - scaled_busy_load_per_task);
7207 /* Amount of load we'd add */
7208 if (busiest->avg_load * busiest->group_capacity <
7209 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7210 tmp = (busiest->avg_load * busiest->group_capacity) /
7211 local->group_capacity;
7213 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7214 local->group_capacity;
7216 capa_move += local->group_capacity *
7217 min(local->load_per_task, local->avg_load + tmp);
7218 capa_move /= SCHED_CAPACITY_SCALE;
7220 /* Move if we gain throughput */
7221 if (capa_move > capa_now)
7222 env->imbalance = busiest->load_per_task;
7226 * calculate_imbalance - Calculate the amount of imbalance present within the
7227 * groups of a given sched_domain during load balance.
7228 * @env: load balance environment
7229 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7231 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7233 unsigned long max_pull, load_above_capacity = ~0UL;
7234 struct sg_lb_stats *local, *busiest;
7236 local = &sds->local_stat;
7237 busiest = &sds->busiest_stat;
7239 if (busiest->group_type == group_imbalanced) {
7241 * In the group_imb case we cannot rely on group-wide averages
7242 * to ensure cpu-load equilibrium, look at wider averages. XXX
7244 busiest->load_per_task =
7245 min(busiest->load_per_task, sds->avg_load);
7249 * In the presence of smp nice balancing, certain scenarios can have
7250 * max load less than avg load(as we skip the groups at or below
7251 * its cpu_capacity, while calculating max_load..)
7253 if (busiest->avg_load <= sds->avg_load ||
7254 local->avg_load >= sds->avg_load) {
7255 /* Misfitting tasks should be migrated in any case */
7256 if (busiest->group_type == group_misfit_task) {
7257 env->imbalance = busiest->group_misfit_task;
7262 * Busiest group is overloaded, local is not, use the spare
7263 * cycles to maximize throughput
7265 if (busiest->group_type == group_overloaded &&
7266 local->group_type <= group_misfit_task) {
7267 env->imbalance = busiest->load_per_task;
7272 return fix_small_imbalance(env, sds);
7276 * If there aren't any idle cpus, avoid creating some.
7278 if (busiest->group_type == group_overloaded &&
7279 local->group_type == group_overloaded) {
7280 load_above_capacity = busiest->sum_nr_running *
7282 if (load_above_capacity > busiest->group_capacity)
7283 load_above_capacity -= busiest->group_capacity;
7285 load_above_capacity = ~0UL;
7289 * We're trying to get all the cpus to the average_load, so we don't
7290 * want to push ourselves above the average load, nor do we wish to
7291 * reduce the max loaded cpu below the average load. At the same time,
7292 * we also don't want to reduce the group load below the group capacity
7293 * (so that we can implement power-savings policies etc). Thus we look
7294 * for the minimum possible imbalance.
7296 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7298 /* How much load to actually move to equalise the imbalance */
7299 env->imbalance = min(
7300 max_pull * busiest->group_capacity,
7301 (sds->avg_load - local->avg_load) * local->group_capacity
7302 ) / SCHED_CAPACITY_SCALE;
7304 /* Boost imbalance to allow misfit task to be balanced. */
7305 if (busiest->group_type == group_misfit_task)
7306 env->imbalance = max_t(long, env->imbalance,
7307 busiest->group_misfit_task);
7310 * if *imbalance is less than the average load per runnable task
7311 * there is no guarantee that any tasks will be moved so we'll have
7312 * a think about bumping its value to force at least one task to be
7315 if (env->imbalance < busiest->load_per_task)
7316 return fix_small_imbalance(env, sds);
7319 /******* find_busiest_group() helpers end here *********************/
7322 * find_busiest_group - Returns the busiest group within the sched_domain
7323 * if there is an imbalance. If there isn't an imbalance, and
7324 * the user has opted for power-savings, it returns a group whose
7325 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
7326 * such a group exists.
7328 * Also calculates the amount of weighted load which should be moved
7329 * to restore balance.
7331 * @env: The load balancing environment.
7333 * Return: - The busiest group if imbalance exists.
7334 * - If no imbalance and user has opted for power-savings balance,
7335 * return the least loaded group whose CPUs can be
7336 * put to idle by rebalancing its tasks onto our group.
7338 static struct sched_group *find_busiest_group(struct lb_env *env)
7340 struct sg_lb_stats *local, *busiest;
7341 struct sd_lb_stats sds;
7343 init_sd_lb_stats(&sds);
7346 * Compute the various statistics relavent for load balancing at
7349 update_sd_lb_stats(env, &sds);
7351 if (energy_aware() && !env->dst_rq->rd->overutilized)
7354 local = &sds.local_stat;
7355 busiest = &sds.busiest_stat;
7357 /* ASYM feature bypasses nice load balance check */
7358 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
7359 check_asym_packing(env, &sds))
7362 /* There is no busy sibling group to pull tasks from */
7363 if (!sds.busiest || busiest->sum_nr_running == 0)
7366 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7367 / sds.total_capacity;
7370 * If the busiest group is imbalanced the below checks don't
7371 * work because they assume all things are equal, which typically
7372 * isn't true due to cpus_allowed constraints and the like.
7374 if (busiest->group_type == group_imbalanced)
7377 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7378 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7379 busiest->group_no_capacity)
7382 /* Misfitting tasks should be dealt with regardless of the avg load */
7383 if (busiest->group_type == group_misfit_task) {
7388 * If the local group is busier than the selected busiest group
7389 * don't try and pull any tasks.
7391 if (local->avg_load >= busiest->avg_load)
7395 * Don't pull any tasks if this group is already above the domain
7398 if (local->avg_load >= sds.avg_load)
7401 if (env->idle == CPU_IDLE) {
7403 * This cpu is idle. If the busiest group is not overloaded
7404 * and there is no imbalance between this and busiest group
7405 * wrt idle cpus, it is balanced. The imbalance becomes
7406 * significant if the diff is greater than 1 otherwise we
7407 * might end up to just move the imbalance on another group
7409 if ((busiest->group_type != group_overloaded) &&
7410 (local->idle_cpus <= (busiest->idle_cpus + 1)) &&
7411 !group_smaller_cpu_capacity(sds.busiest, sds.local))
7415 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7416 * imbalance_pct to be conservative.
7418 if (100 * busiest->avg_load <=
7419 env->sd->imbalance_pct * local->avg_load)
7424 env->busiest_group_type = busiest->group_type;
7425 /* Looks like there is an imbalance. Compute it */
7426 calculate_imbalance(env, &sds);
7435 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7437 static struct rq *find_busiest_queue(struct lb_env *env,
7438 struct sched_group *group)
7440 struct rq *busiest = NULL, *rq;
7441 unsigned long busiest_load = 0, busiest_capacity = 1;
7444 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7445 unsigned long capacity, wl;
7449 rt = fbq_classify_rq(rq);
7452 * We classify groups/runqueues into three groups:
7453 * - regular: there are !numa tasks
7454 * - remote: there are numa tasks that run on the 'wrong' node
7455 * - all: there is no distinction
7457 * In order to avoid migrating ideally placed numa tasks,
7458 * ignore those when there's better options.
7460 * If we ignore the actual busiest queue to migrate another
7461 * task, the next balance pass can still reduce the busiest
7462 * queue by moving tasks around inside the node.
7464 * If we cannot move enough load due to this classification
7465 * the next pass will adjust the group classification and
7466 * allow migration of more tasks.
7468 * Both cases only affect the total convergence complexity.
7470 if (rt > env->fbq_type)
7473 capacity = capacity_of(i);
7475 wl = weighted_cpuload(i);
7478 * When comparing with imbalance, use weighted_cpuload()
7479 * which is not scaled with the cpu capacity.
7482 if (rq->nr_running == 1 && wl > env->imbalance &&
7483 !check_cpu_capacity(rq, env->sd) &&
7484 env->busiest_group_type != group_misfit_task)
7488 * For the load comparisons with the other cpu's, consider
7489 * the weighted_cpuload() scaled with the cpu capacity, so
7490 * that the load can be moved away from the cpu that is
7491 * potentially running at a lower capacity.
7493 * Thus we're looking for max(wl_i / capacity_i), crosswise
7494 * multiplication to rid ourselves of the division works out
7495 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7496 * our previous maximum.
7498 if (wl * busiest_capacity > busiest_load * capacity) {
7500 busiest_capacity = capacity;
7509 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7510 * so long as it is large enough.
7512 #define MAX_PINNED_INTERVAL 512
7514 /* Working cpumask for load_balance and load_balance_newidle. */
7515 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7517 static int need_active_balance(struct lb_env *env)
7519 struct sched_domain *sd = env->sd;
7521 if (env->idle == CPU_NEWLY_IDLE) {
7524 * ASYM_PACKING needs to force migrate tasks from busy but
7525 * higher numbered CPUs in order to pack all tasks in the
7526 * lowest numbered CPUs.
7528 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7533 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7534 * It's worth migrating the task if the src_cpu's capacity is reduced
7535 * because of other sched_class or IRQs if more capacity stays
7536 * available on dst_cpu.
7538 if ((env->idle != CPU_NOT_IDLE) &&
7539 (env->src_rq->cfs.h_nr_running == 1)) {
7540 if ((check_cpu_capacity(env->src_rq, sd)) &&
7541 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7545 if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
7546 env->src_rq->cfs.h_nr_running == 1 &&
7547 cpu_overutilized(env->src_cpu) &&
7548 !cpu_overutilized(env->dst_cpu)) {
7552 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7555 static int active_load_balance_cpu_stop(void *data);
7557 static int should_we_balance(struct lb_env *env)
7559 struct sched_group *sg = env->sd->groups;
7560 struct cpumask *sg_cpus, *sg_mask;
7561 int cpu, balance_cpu = -1;
7564 * In the newly idle case, we will allow all the cpu's
7565 * to do the newly idle load balance.
7567 if (env->idle == CPU_NEWLY_IDLE)
7570 sg_cpus = sched_group_cpus(sg);
7571 sg_mask = sched_group_mask(sg);
7572 /* Try to find first idle cpu */
7573 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7574 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7581 if (balance_cpu == -1)
7582 balance_cpu = group_balance_cpu(sg);
7585 * First idle cpu or the first cpu(busiest) in this sched group
7586 * is eligible for doing load balancing at this and above domains.
7588 return balance_cpu == env->dst_cpu;
7592 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7593 * tasks if there is an imbalance.
7595 static int load_balance(int this_cpu, struct rq *this_rq,
7596 struct sched_domain *sd, enum cpu_idle_type idle,
7597 int *continue_balancing)
7599 int ld_moved, cur_ld_moved, active_balance = 0;
7600 struct sched_domain *sd_parent = sd->parent;
7601 struct sched_group *group;
7603 unsigned long flags;
7604 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7606 struct lb_env env = {
7608 .dst_cpu = this_cpu,
7610 .dst_grpmask = sched_group_cpus(sd->groups),
7612 .loop_break = sched_nr_migrate_break,
7615 .tasks = LIST_HEAD_INIT(env.tasks),
7619 * For NEWLY_IDLE load_balancing, we don't need to consider
7620 * other cpus in our group
7622 if (idle == CPU_NEWLY_IDLE)
7623 env.dst_grpmask = NULL;
7625 cpumask_copy(cpus, cpu_active_mask);
7627 schedstat_inc(sd, lb_count[idle]);
7630 if (!should_we_balance(&env)) {
7631 *continue_balancing = 0;
7635 group = find_busiest_group(&env);
7637 schedstat_inc(sd, lb_nobusyg[idle]);
7641 busiest = find_busiest_queue(&env, group);
7643 schedstat_inc(sd, lb_nobusyq[idle]);
7647 BUG_ON(busiest == env.dst_rq);
7649 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7651 env.src_cpu = busiest->cpu;
7652 env.src_rq = busiest;
7655 if (busiest->nr_running > 1) {
7657 * Attempt to move tasks. If find_busiest_group has found
7658 * an imbalance but busiest->nr_running <= 1, the group is
7659 * still unbalanced. ld_moved simply stays zero, so it is
7660 * correctly treated as an imbalance.
7662 env.flags |= LBF_ALL_PINNED;
7663 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7666 raw_spin_lock_irqsave(&busiest->lock, flags);
7669 * cur_ld_moved - load moved in current iteration
7670 * ld_moved - cumulative load moved across iterations
7672 cur_ld_moved = detach_tasks(&env);
7675 * We've detached some tasks from busiest_rq. Every
7676 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7677 * unlock busiest->lock, and we are able to be sure
7678 * that nobody can manipulate the tasks in parallel.
7679 * See task_rq_lock() family for the details.
7682 raw_spin_unlock(&busiest->lock);
7686 ld_moved += cur_ld_moved;
7689 local_irq_restore(flags);
7691 if (env.flags & LBF_NEED_BREAK) {
7692 env.flags &= ~LBF_NEED_BREAK;
7697 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7698 * us and move them to an alternate dst_cpu in our sched_group
7699 * where they can run. The upper limit on how many times we
7700 * iterate on same src_cpu is dependent on number of cpus in our
7703 * This changes load balance semantics a bit on who can move
7704 * load to a given_cpu. In addition to the given_cpu itself
7705 * (or a ilb_cpu acting on its behalf where given_cpu is
7706 * nohz-idle), we now have balance_cpu in a position to move
7707 * load to given_cpu. In rare situations, this may cause
7708 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7709 * _independently_ and at _same_ time to move some load to
7710 * given_cpu) causing exceess load to be moved to given_cpu.
7711 * This however should not happen so much in practice and
7712 * moreover subsequent load balance cycles should correct the
7713 * excess load moved.
7715 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7717 /* Prevent to re-select dst_cpu via env's cpus */
7718 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7720 env.dst_rq = cpu_rq(env.new_dst_cpu);
7721 env.dst_cpu = env.new_dst_cpu;
7722 env.flags &= ~LBF_DST_PINNED;
7724 env.loop_break = sched_nr_migrate_break;
7727 * Go back to "more_balance" rather than "redo" since we
7728 * need to continue with same src_cpu.
7734 * We failed to reach balance because of affinity.
7737 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7739 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7740 *group_imbalance = 1;
7743 /* All tasks on this runqueue were pinned by CPU affinity */
7744 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7745 cpumask_clear_cpu(cpu_of(busiest), cpus);
7746 if (!cpumask_empty(cpus)) {
7748 env.loop_break = sched_nr_migrate_break;
7751 goto out_all_pinned;
7756 schedstat_inc(sd, lb_failed[idle]);
7758 * Increment the failure counter only on periodic balance.
7759 * We do not want newidle balance, which can be very
7760 * frequent, pollute the failure counter causing
7761 * excessive cache_hot migrations and active balances.
7763 if (idle != CPU_NEWLY_IDLE)
7764 if (env.src_grp_nr_running > 1)
7765 sd->nr_balance_failed++;
7767 if (need_active_balance(&env)) {
7768 raw_spin_lock_irqsave(&busiest->lock, flags);
7770 /* don't kick the active_load_balance_cpu_stop,
7771 * if the curr task on busiest cpu can't be
7774 if (!cpumask_test_cpu(this_cpu,
7775 tsk_cpus_allowed(busiest->curr))) {
7776 raw_spin_unlock_irqrestore(&busiest->lock,
7778 env.flags |= LBF_ALL_PINNED;
7779 goto out_one_pinned;
7783 * ->active_balance synchronizes accesses to
7784 * ->active_balance_work. Once set, it's cleared
7785 * only after active load balance is finished.
7787 if (!busiest->active_balance) {
7788 busiest->active_balance = 1;
7789 busiest->push_cpu = this_cpu;
7792 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7794 if (active_balance) {
7795 stop_one_cpu_nowait(cpu_of(busiest),
7796 active_load_balance_cpu_stop, busiest,
7797 &busiest->active_balance_work);
7801 * We've kicked active balancing, reset the failure
7804 sd->nr_balance_failed = sd->cache_nice_tries+1;
7807 sd->nr_balance_failed = 0;
7809 if (likely(!active_balance)) {
7810 /* We were unbalanced, so reset the balancing interval */
7811 sd->balance_interval = sd->min_interval;
7814 * If we've begun active balancing, start to back off. This
7815 * case may not be covered by the all_pinned logic if there
7816 * is only 1 task on the busy runqueue (because we don't call
7819 if (sd->balance_interval < sd->max_interval)
7820 sd->balance_interval *= 2;
7827 * We reach balance although we may have faced some affinity
7828 * constraints. Clear the imbalance flag if it was set.
7831 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7833 if (*group_imbalance)
7834 *group_imbalance = 0;
7839 * We reach balance because all tasks are pinned at this level so
7840 * we can't migrate them. Let the imbalance flag set so parent level
7841 * can try to migrate them.
7843 schedstat_inc(sd, lb_balanced[idle]);
7845 sd->nr_balance_failed = 0;
7848 /* tune up the balancing interval */
7849 if (((env.flags & LBF_ALL_PINNED) &&
7850 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7851 (sd->balance_interval < sd->max_interval))
7852 sd->balance_interval *= 2;
7859 static inline unsigned long
7860 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7862 unsigned long interval = sd->balance_interval;
7865 interval *= sd->busy_factor;
7867 /* scale ms to jiffies */
7868 interval = msecs_to_jiffies(interval);
7869 interval = clamp(interval, 1UL, max_load_balance_interval);
7875 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7877 unsigned long interval, next;
7879 interval = get_sd_balance_interval(sd, cpu_busy);
7880 next = sd->last_balance + interval;
7882 if (time_after(*next_balance, next))
7883 *next_balance = next;
7887 * idle_balance is called by schedule() if this_cpu is about to become
7888 * idle. Attempts to pull tasks from other CPUs.
7890 static int idle_balance(struct rq *this_rq)
7892 unsigned long next_balance = jiffies + HZ;
7893 int this_cpu = this_rq->cpu;
7894 struct sched_domain *sd;
7895 int pulled_task = 0;
7898 idle_enter_fair(this_rq);
7901 * We must set idle_stamp _before_ calling idle_balance(), such that we
7902 * measure the duration of idle_balance() as idle time.
7904 this_rq->idle_stamp = rq_clock(this_rq);
7906 if (!energy_aware() &&
7907 (this_rq->avg_idle < sysctl_sched_migration_cost ||
7908 !this_rq->rd->overload)) {
7910 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7912 update_next_balance(sd, 0, &next_balance);
7918 raw_spin_unlock(&this_rq->lock);
7920 update_blocked_averages(this_cpu);
7922 for_each_domain(this_cpu, sd) {
7923 int continue_balancing = 1;
7924 u64 t0, domain_cost;
7926 if (!(sd->flags & SD_LOAD_BALANCE))
7929 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7930 update_next_balance(sd, 0, &next_balance);
7934 if (sd->flags & SD_BALANCE_NEWIDLE) {
7935 t0 = sched_clock_cpu(this_cpu);
7937 pulled_task = load_balance(this_cpu, this_rq,
7939 &continue_balancing);
7941 domain_cost = sched_clock_cpu(this_cpu) - t0;
7942 if (domain_cost > sd->max_newidle_lb_cost)
7943 sd->max_newidle_lb_cost = domain_cost;
7945 curr_cost += domain_cost;
7948 update_next_balance(sd, 0, &next_balance);
7951 * Stop searching for tasks to pull if there are
7952 * now runnable tasks on this rq.
7954 if (pulled_task || this_rq->nr_running > 0)
7959 raw_spin_lock(&this_rq->lock);
7961 if (curr_cost > this_rq->max_idle_balance_cost)
7962 this_rq->max_idle_balance_cost = curr_cost;
7965 * While browsing the domains, we released the rq lock, a task could
7966 * have been enqueued in the meantime. Since we're not going idle,
7967 * pretend we pulled a task.
7969 if (this_rq->cfs.h_nr_running && !pulled_task)
7973 /* Move the next balance forward */
7974 if (time_after(this_rq->next_balance, next_balance))
7975 this_rq->next_balance = next_balance;
7977 /* Is there a task of a high priority class? */
7978 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7982 idle_exit_fair(this_rq);
7983 this_rq->idle_stamp = 0;
7990 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7991 * running tasks off the busiest CPU onto idle CPUs. It requires at
7992 * least 1 task to be running on each physical CPU where possible, and
7993 * avoids physical / logical imbalances.
7995 static int active_load_balance_cpu_stop(void *data)
7997 struct rq *busiest_rq = data;
7998 int busiest_cpu = cpu_of(busiest_rq);
7999 int target_cpu = busiest_rq->push_cpu;
8000 struct rq *target_rq = cpu_rq(target_cpu);
8001 struct sched_domain *sd;
8002 struct task_struct *p = NULL;
8004 raw_spin_lock_irq(&busiest_rq->lock);
8006 /* make sure the requested cpu hasn't gone down in the meantime */
8007 if (unlikely(busiest_cpu != smp_processor_id() ||
8008 !busiest_rq->active_balance))
8011 /* Is there any task to move? */
8012 if (busiest_rq->nr_running <= 1)
8016 * This condition is "impossible", if it occurs
8017 * we need to fix it. Originally reported by
8018 * Bjorn Helgaas on a 128-cpu setup.
8020 BUG_ON(busiest_rq == target_rq);
8022 /* Search for an sd spanning us and the target CPU. */
8024 for_each_domain(target_cpu, sd) {
8025 if ((sd->flags & SD_LOAD_BALANCE) &&
8026 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
8031 struct lb_env env = {
8033 .dst_cpu = target_cpu,
8034 .dst_rq = target_rq,
8035 .src_cpu = busiest_rq->cpu,
8036 .src_rq = busiest_rq,
8040 schedstat_inc(sd, alb_count);
8042 p = detach_one_task(&env);
8044 schedstat_inc(sd, alb_pushed);
8046 schedstat_inc(sd, alb_failed);
8050 busiest_rq->active_balance = 0;
8051 raw_spin_unlock(&busiest_rq->lock);
8054 attach_one_task(target_rq, p);
8061 static inline int on_null_domain(struct rq *rq)
8063 return unlikely(!rcu_dereference_sched(rq->sd));
8066 #ifdef CONFIG_NO_HZ_COMMON
8068 * idle load balancing details
8069 * - When one of the busy CPUs notice that there may be an idle rebalancing
8070 * needed, they will kick the idle load balancer, which then does idle
8071 * load balancing for all the idle CPUs.
8074 cpumask_var_t idle_cpus_mask;
8076 unsigned long next_balance; /* in jiffy units */
8077 } nohz ____cacheline_aligned;
8079 static inline int find_new_ilb(void)
8081 int ilb = cpumask_first(nohz.idle_cpus_mask);
8083 if (ilb < nr_cpu_ids && idle_cpu(ilb))
8090 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
8091 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
8092 * CPU (if there is one).
8094 static void nohz_balancer_kick(void)
8098 nohz.next_balance++;
8100 ilb_cpu = find_new_ilb();
8102 if (ilb_cpu >= nr_cpu_ids)
8105 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8108 * Use smp_send_reschedule() instead of resched_cpu().
8109 * This way we generate a sched IPI on the target cpu which
8110 * is idle. And the softirq performing nohz idle load balance
8111 * will be run before returning from the IPI.
8113 smp_send_reschedule(ilb_cpu);
8117 static inline void nohz_balance_exit_idle(int cpu)
8119 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8121 * Completely isolated CPUs don't ever set, so we must test.
8123 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
8124 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
8125 atomic_dec(&nohz.nr_cpus);
8127 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8131 static inline void set_cpu_sd_state_busy(void)
8133 struct sched_domain *sd;
8134 int cpu = smp_processor_id();
8137 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8139 if (!sd || !sd->nohz_idle)
8143 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
8148 void set_cpu_sd_state_idle(void)
8150 struct sched_domain *sd;
8151 int cpu = smp_processor_id();
8154 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8156 if (!sd || sd->nohz_idle)
8160 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
8166 * This routine will record that the cpu is going idle with tick stopped.
8167 * This info will be used in performing idle load balancing in the future.
8169 void nohz_balance_enter_idle(int cpu)
8172 * If this cpu is going down, then nothing needs to be done.
8174 if (!cpu_active(cpu))
8177 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
8181 * If we're a completely isolated CPU, we don't play.
8183 if (on_null_domain(cpu_rq(cpu)))
8186 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
8187 atomic_inc(&nohz.nr_cpus);
8188 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8191 static int sched_ilb_notifier(struct notifier_block *nfb,
8192 unsigned long action, void *hcpu)
8194 switch (action & ~CPU_TASKS_FROZEN) {
8196 nohz_balance_exit_idle(smp_processor_id());
8204 static DEFINE_SPINLOCK(balancing);
8207 * Scale the max load_balance interval with the number of CPUs in the system.
8208 * This trades load-balance latency on larger machines for less cross talk.
8210 void update_max_interval(void)
8212 max_load_balance_interval = HZ*num_online_cpus()/10;
8216 * It checks each scheduling domain to see if it is due to be balanced,
8217 * and initiates a balancing operation if so.
8219 * Balancing parameters are set up in init_sched_domains.
8221 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8223 int continue_balancing = 1;
8225 unsigned long interval;
8226 struct sched_domain *sd;
8227 /* Earliest time when we have to do rebalance again */
8228 unsigned long next_balance = jiffies + 60*HZ;
8229 int update_next_balance = 0;
8230 int need_serialize, need_decay = 0;
8233 update_blocked_averages(cpu);
8236 for_each_domain(cpu, sd) {
8238 * Decay the newidle max times here because this is a regular
8239 * visit to all the domains. Decay ~1% per second.
8241 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
8242 sd->max_newidle_lb_cost =
8243 (sd->max_newidle_lb_cost * 253) / 256;
8244 sd->next_decay_max_lb_cost = jiffies + HZ;
8247 max_cost += sd->max_newidle_lb_cost;
8249 if (!(sd->flags & SD_LOAD_BALANCE))
8253 * Stop the load balance at this level. There is another
8254 * CPU in our sched group which is doing load balancing more
8257 if (!continue_balancing) {
8263 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8265 need_serialize = sd->flags & SD_SERIALIZE;
8266 if (need_serialize) {
8267 if (!spin_trylock(&balancing))
8271 if (time_after_eq(jiffies, sd->last_balance + interval)) {
8272 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8274 * The LBF_DST_PINNED logic could have changed
8275 * env->dst_cpu, so we can't know our idle
8276 * state even if we migrated tasks. Update it.
8278 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8280 sd->last_balance = jiffies;
8281 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8284 spin_unlock(&balancing);
8286 if (time_after(next_balance, sd->last_balance + interval)) {
8287 next_balance = sd->last_balance + interval;
8288 update_next_balance = 1;
8293 * Ensure the rq-wide value also decays but keep it at a
8294 * reasonable floor to avoid funnies with rq->avg_idle.
8296 rq->max_idle_balance_cost =
8297 max((u64)sysctl_sched_migration_cost, max_cost);
8302 * next_balance will be updated only when there is a need.
8303 * When the cpu is attached to null domain for ex, it will not be
8306 if (likely(update_next_balance)) {
8307 rq->next_balance = next_balance;
8309 #ifdef CONFIG_NO_HZ_COMMON
8311 * If this CPU has been elected to perform the nohz idle
8312 * balance. Other idle CPUs have already rebalanced with
8313 * nohz_idle_balance() and nohz.next_balance has been
8314 * updated accordingly. This CPU is now running the idle load
8315 * balance for itself and we need to update the
8316 * nohz.next_balance accordingly.
8318 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8319 nohz.next_balance = rq->next_balance;
8324 #ifdef CONFIG_NO_HZ_COMMON
8326 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8327 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8329 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8331 int this_cpu = this_rq->cpu;
8334 /* Earliest time when we have to do rebalance again */
8335 unsigned long next_balance = jiffies + 60*HZ;
8336 int update_next_balance = 0;
8338 if (idle != CPU_IDLE ||
8339 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8342 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8343 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8347 * If this cpu gets work to do, stop the load balancing
8348 * work being done for other cpus. Next load
8349 * balancing owner will pick it up.
8354 rq = cpu_rq(balance_cpu);
8357 * If time for next balance is due,
8360 if (time_after_eq(jiffies, rq->next_balance)) {
8361 raw_spin_lock_irq(&rq->lock);
8362 update_rq_clock(rq);
8363 update_idle_cpu_load(rq);
8364 raw_spin_unlock_irq(&rq->lock);
8365 rebalance_domains(rq, CPU_IDLE);
8368 if (time_after(next_balance, rq->next_balance)) {
8369 next_balance = rq->next_balance;
8370 update_next_balance = 1;
8375 * next_balance will be updated only when there is a need.
8376 * When the CPU is attached to null domain for ex, it will not be
8379 if (likely(update_next_balance))
8380 nohz.next_balance = next_balance;
8382 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8386 * Current heuristic for kicking the idle load balancer in the presence
8387 * of an idle cpu in the system.
8388 * - This rq has more than one task.
8389 * - This rq has at least one CFS task and the capacity of the CPU is
8390 * significantly reduced because of RT tasks or IRQs.
8391 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8392 * multiple busy cpu.
8393 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8394 * domain span are idle.
8396 static inline bool nohz_kick_needed(struct rq *rq)
8398 unsigned long now = jiffies;
8399 struct sched_domain *sd;
8400 struct sched_group_capacity *sgc;
8401 int nr_busy, cpu = rq->cpu;
8404 if (unlikely(rq->idle_balance))
8408 * We may be recently in ticked or tickless idle mode. At the first
8409 * busy tick after returning from idle, we will update the busy stats.
8411 set_cpu_sd_state_busy();
8412 nohz_balance_exit_idle(cpu);
8415 * None are in tickless mode and hence no need for NOHZ idle load
8418 if (likely(!atomic_read(&nohz.nr_cpus)))
8421 if (time_before(now, nohz.next_balance))
8424 if (rq->nr_running >= 2 &&
8425 (!energy_aware() || cpu_overutilized(cpu)))
8429 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8430 if (sd && !energy_aware()) {
8431 sgc = sd->groups->sgc;
8432 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8441 sd = rcu_dereference(rq->sd);
8443 if ((rq->cfs.h_nr_running >= 1) &&
8444 check_cpu_capacity(rq, sd)) {
8450 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8451 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8452 sched_domain_span(sd)) < cpu)) {
8462 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8466 * run_rebalance_domains is triggered when needed from the scheduler tick.
8467 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8469 static void run_rebalance_domains(struct softirq_action *h)
8471 struct rq *this_rq = this_rq();
8472 enum cpu_idle_type idle = this_rq->idle_balance ?
8473 CPU_IDLE : CPU_NOT_IDLE;
8476 * If this cpu has a pending nohz_balance_kick, then do the
8477 * balancing on behalf of the other idle cpus whose ticks are
8478 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8479 * give the idle cpus a chance to load balance. Else we may
8480 * load balance only within the local sched_domain hierarchy
8481 * and abort nohz_idle_balance altogether if we pull some load.
8483 nohz_idle_balance(this_rq, idle);
8484 rebalance_domains(this_rq, idle);
8488 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8490 void trigger_load_balance(struct rq *rq)
8492 /* Don't need to rebalance while attached to NULL domain */
8493 if (unlikely(on_null_domain(rq)))
8496 if (time_after_eq(jiffies, rq->next_balance))
8497 raise_softirq(SCHED_SOFTIRQ);
8498 #ifdef CONFIG_NO_HZ_COMMON
8499 if (nohz_kick_needed(rq))
8500 nohz_balancer_kick();
8504 static void rq_online_fair(struct rq *rq)
8508 update_runtime_enabled(rq);
8511 static void rq_offline_fair(struct rq *rq)
8515 /* Ensure any throttled groups are reachable by pick_next_task */
8516 unthrottle_offline_cfs_rqs(rq);
8519 #endif /* CONFIG_SMP */
8522 * scheduler tick hitting a task of our scheduling class:
8524 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8526 struct cfs_rq *cfs_rq;
8527 struct sched_entity *se = &curr->se;
8529 for_each_sched_entity(se) {
8530 cfs_rq = cfs_rq_of(se);
8531 entity_tick(cfs_rq, se, queued);
8534 if (static_branch_unlikely(&sched_numa_balancing))
8535 task_tick_numa(rq, curr);
8537 if (!rq->rd->overutilized && cpu_overutilized(task_cpu(curr)))
8538 rq->rd->overutilized = true;
8540 rq->misfit_task = !task_fits_max(curr, rq->cpu);
8544 * called on fork with the child task as argument from the parent's context
8545 * - child not yet on the tasklist
8546 * - preemption disabled
8548 static void task_fork_fair(struct task_struct *p)
8550 struct cfs_rq *cfs_rq;
8551 struct sched_entity *se = &p->se, *curr;
8552 int this_cpu = smp_processor_id();
8553 struct rq *rq = this_rq();
8554 unsigned long flags;
8556 raw_spin_lock_irqsave(&rq->lock, flags);
8558 update_rq_clock(rq);
8560 cfs_rq = task_cfs_rq(current);
8561 curr = cfs_rq->curr;
8564 * Not only the cpu but also the task_group of the parent might have
8565 * been changed after parent->se.parent,cfs_rq were copied to
8566 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8567 * of child point to valid ones.
8570 __set_task_cpu(p, this_cpu);
8573 update_curr(cfs_rq);
8576 se->vruntime = curr->vruntime;
8577 place_entity(cfs_rq, se, 1);
8579 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8581 * Upon rescheduling, sched_class::put_prev_task() will place
8582 * 'current' within the tree based on its new key value.
8584 swap(curr->vruntime, se->vruntime);
8588 se->vruntime -= cfs_rq->min_vruntime;
8590 raw_spin_unlock_irqrestore(&rq->lock, flags);
8594 * Priority of the task has changed. Check to see if we preempt
8598 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8600 if (!task_on_rq_queued(p))
8604 * Reschedule if we are currently running on this runqueue and
8605 * our priority decreased, or if we are not currently running on
8606 * this runqueue and our priority is higher than the current's
8608 if (rq->curr == p) {
8609 if (p->prio > oldprio)
8612 check_preempt_curr(rq, p, 0);
8615 static inline bool vruntime_normalized(struct task_struct *p)
8617 struct sched_entity *se = &p->se;
8620 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8621 * the dequeue_entity(.flags=0) will already have normalized the
8628 * When !on_rq, vruntime of the task has usually NOT been normalized.
8629 * But there are some cases where it has already been normalized:
8631 * - A forked child which is waiting for being woken up by
8632 * wake_up_new_task().
8633 * - A task which has been woken up by try_to_wake_up() and
8634 * waiting for actually being woken up by sched_ttwu_pending().
8636 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8642 static void detach_task_cfs_rq(struct task_struct *p)
8644 struct sched_entity *se = &p->se;
8645 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8647 if (!vruntime_normalized(p)) {
8649 * Fix up our vruntime so that the current sleep doesn't
8650 * cause 'unlimited' sleep bonus.
8652 place_entity(cfs_rq, se, 0);
8653 se->vruntime -= cfs_rq->min_vruntime;
8656 /* Catch up with the cfs_rq and remove our load when we leave */
8657 detach_entity_load_avg(cfs_rq, se);
8660 static void attach_task_cfs_rq(struct task_struct *p)
8662 struct sched_entity *se = &p->se;
8663 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8665 #ifdef CONFIG_FAIR_GROUP_SCHED
8667 * Since the real-depth could have been changed (only FAIR
8668 * class maintain depth value), reset depth properly.
8670 se->depth = se->parent ? se->parent->depth + 1 : 0;
8673 /* Synchronize task with its cfs_rq */
8674 attach_entity_load_avg(cfs_rq, se);
8676 if (!vruntime_normalized(p))
8677 se->vruntime += cfs_rq->min_vruntime;
8680 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8682 detach_task_cfs_rq(p);
8685 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8687 attach_task_cfs_rq(p);
8689 if (task_on_rq_queued(p)) {
8691 * We were most likely switched from sched_rt, so
8692 * kick off the schedule if running, otherwise just see
8693 * if we can still preempt the current task.
8698 check_preempt_curr(rq, p, 0);
8702 /* Account for a task changing its policy or group.
8704 * This routine is mostly called to set cfs_rq->curr field when a task
8705 * migrates between groups/classes.
8707 static void set_curr_task_fair(struct rq *rq)
8709 struct sched_entity *se = &rq->curr->se;
8711 for_each_sched_entity(se) {
8712 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8714 set_next_entity(cfs_rq, se);
8715 /* ensure bandwidth has been allocated on our new cfs_rq */
8716 account_cfs_rq_runtime(cfs_rq, 0);
8720 void init_cfs_rq(struct cfs_rq *cfs_rq)
8722 cfs_rq->tasks_timeline = RB_ROOT;
8723 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8724 #ifndef CONFIG_64BIT
8725 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8728 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8729 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8733 #ifdef CONFIG_FAIR_GROUP_SCHED
8734 static void task_move_group_fair(struct task_struct *p)
8736 detach_task_cfs_rq(p);
8737 set_task_rq(p, task_cpu(p));
8740 /* Tell se's cfs_rq has been changed -- migrated */
8741 p->se.avg.last_update_time = 0;
8743 attach_task_cfs_rq(p);
8746 void free_fair_sched_group(struct task_group *tg)
8750 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8752 for_each_possible_cpu(i) {
8754 kfree(tg->cfs_rq[i]);
8757 remove_entity_load_avg(tg->se[i]);
8766 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8768 struct cfs_rq *cfs_rq;
8769 struct sched_entity *se;
8772 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8775 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8779 tg->shares = NICE_0_LOAD;
8781 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8783 for_each_possible_cpu(i) {
8784 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8785 GFP_KERNEL, cpu_to_node(i));
8789 se = kzalloc_node(sizeof(struct sched_entity),
8790 GFP_KERNEL, cpu_to_node(i));
8794 init_cfs_rq(cfs_rq);
8795 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8796 init_entity_runnable_average(se);
8807 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8809 struct rq *rq = cpu_rq(cpu);
8810 unsigned long flags;
8813 * Only empty task groups can be destroyed; so we can speculatively
8814 * check on_list without danger of it being re-added.
8816 if (!tg->cfs_rq[cpu]->on_list)
8819 raw_spin_lock_irqsave(&rq->lock, flags);
8820 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8821 raw_spin_unlock_irqrestore(&rq->lock, flags);
8824 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8825 struct sched_entity *se, int cpu,
8826 struct sched_entity *parent)
8828 struct rq *rq = cpu_rq(cpu);
8832 init_cfs_rq_runtime(cfs_rq);
8834 tg->cfs_rq[cpu] = cfs_rq;
8837 /* se could be NULL for root_task_group */
8842 se->cfs_rq = &rq->cfs;
8845 se->cfs_rq = parent->my_q;
8846 se->depth = parent->depth + 1;
8850 /* guarantee group entities always have weight */
8851 update_load_set(&se->load, NICE_0_LOAD);
8852 se->parent = parent;
8855 static DEFINE_MUTEX(shares_mutex);
8857 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8860 unsigned long flags;
8863 * We can't change the weight of the root cgroup.
8868 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8870 mutex_lock(&shares_mutex);
8871 if (tg->shares == shares)
8874 tg->shares = shares;
8875 for_each_possible_cpu(i) {
8876 struct rq *rq = cpu_rq(i);
8877 struct sched_entity *se;
8880 /* Propagate contribution to hierarchy */
8881 raw_spin_lock_irqsave(&rq->lock, flags);
8883 /* Possible calls to update_curr() need rq clock */
8884 update_rq_clock(rq);
8885 for_each_sched_entity(se)
8886 update_cfs_shares(group_cfs_rq(se));
8887 raw_spin_unlock_irqrestore(&rq->lock, flags);
8891 mutex_unlock(&shares_mutex);
8894 #else /* CONFIG_FAIR_GROUP_SCHED */
8896 void free_fair_sched_group(struct task_group *tg) { }
8898 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8903 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
8905 #endif /* CONFIG_FAIR_GROUP_SCHED */
8908 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8910 struct sched_entity *se = &task->se;
8911 unsigned int rr_interval = 0;
8914 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8917 if (rq->cfs.load.weight)
8918 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8924 * All the scheduling class methods:
8926 const struct sched_class fair_sched_class = {
8927 .next = &idle_sched_class,
8928 .enqueue_task = enqueue_task_fair,
8929 .dequeue_task = dequeue_task_fair,
8930 .yield_task = yield_task_fair,
8931 .yield_to_task = yield_to_task_fair,
8933 .check_preempt_curr = check_preempt_wakeup,
8935 .pick_next_task = pick_next_task_fair,
8936 .put_prev_task = put_prev_task_fair,
8939 .select_task_rq = select_task_rq_fair,
8940 .migrate_task_rq = migrate_task_rq_fair,
8942 .rq_online = rq_online_fair,
8943 .rq_offline = rq_offline_fair,
8945 .task_waking = task_waking_fair,
8946 .task_dead = task_dead_fair,
8947 .set_cpus_allowed = set_cpus_allowed_common,
8950 .set_curr_task = set_curr_task_fair,
8951 .task_tick = task_tick_fair,
8952 .task_fork = task_fork_fair,
8954 .prio_changed = prio_changed_fair,
8955 .switched_from = switched_from_fair,
8956 .switched_to = switched_to_fair,
8958 .get_rr_interval = get_rr_interval_fair,
8960 .update_curr = update_curr_fair,
8962 #ifdef CONFIG_FAIR_GROUP_SCHED
8963 .task_move_group = task_move_group_fair,
8967 #ifdef CONFIG_SCHED_DEBUG
8968 void print_cfs_stats(struct seq_file *m, int cpu)
8970 struct cfs_rq *cfs_rq;
8973 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8974 print_cfs_rq(m, cpu, cfs_rq);
8978 #ifdef CONFIG_NUMA_BALANCING
8979 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8982 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8984 for_each_online_node(node) {
8985 if (p->numa_faults) {
8986 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8987 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8989 if (p->numa_group) {
8990 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8991 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8993 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8996 #endif /* CONFIG_NUMA_BALANCING */
8997 #endif /* CONFIG_SCHED_DEBUG */
8999 __init void init_sched_fair_class(void)
9002 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
9004 #ifdef CONFIG_NO_HZ_COMMON
9005 nohz.next_balance = jiffies;
9006 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
9007 cpu_notifier(sched_ilb_notifier, 0);