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>
40 * Targeted preemption latency for CPU-bound tasks:
41 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
43 * NOTE: this latency value is not the same as the concept of
44 * 'timeslice length' - timeslices in CFS are of variable length
45 * and have no persistent notion like in traditional, time-slice
46 * based scheduling concepts.
48 * (to see the precise effective timeslice length of your workload,
49 * run vmstat and monitor the context-switches (cs) field)
51 unsigned int sysctl_sched_latency = 6000000ULL;
52 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
55 * The initial- and re-scaling of tunables is configurable
56 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
59 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
60 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
61 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
63 enum sched_tunable_scaling sysctl_sched_tunable_scaling
64 = SCHED_TUNABLESCALING_LOG;
67 * Minimal preemption granularity for CPU-bound tasks:
68 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
70 unsigned int sysctl_sched_min_granularity = 750000ULL;
71 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
74 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
76 static unsigned int sched_nr_latency = 8;
79 * After fork, child runs first. If set to 0 (default) then
80 * parent will (try to) run first.
82 unsigned int sysctl_sched_child_runs_first __read_mostly;
85 * SCHED_OTHER wake-up granularity.
86 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
88 * This option delays the preemption effects of decoupled workloads
89 * and reduces their over-scheduling. Synchronous workloads will still
90 * have immediate wakeup/sleep latencies.
92 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
93 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
95 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
98 * The exponential sliding window over which load is averaged for shares
102 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
104 #ifdef CONFIG_CFS_BANDWIDTH
106 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
107 * each time a cfs_rq requests quota.
109 * Note: in the case that the slice exceeds the runtime remaining (either due
110 * to consumption or the quota being specified to be smaller than the slice)
111 * we will always only issue the remaining available time.
113 * default: 5 msec, units: microseconds
115 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
118 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
124 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
130 static inline void update_load_set(struct load_weight *lw, unsigned long w)
137 * Increase the granularity value when there are more CPUs,
138 * because with more CPUs the 'effective latency' as visible
139 * to users decreases. But the relationship is not linear,
140 * so pick a second-best guess by going with the log2 of the
143 * This idea comes from the SD scheduler of Con Kolivas:
145 static unsigned int get_update_sysctl_factor(void)
147 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
150 switch (sysctl_sched_tunable_scaling) {
151 case SCHED_TUNABLESCALING_NONE:
154 case SCHED_TUNABLESCALING_LINEAR:
157 case SCHED_TUNABLESCALING_LOG:
159 factor = 1 + ilog2(cpus);
166 static void update_sysctl(void)
168 unsigned int factor = get_update_sysctl_factor();
170 #define SET_SYSCTL(name) \
171 (sysctl_##name = (factor) * normalized_sysctl_##name)
172 SET_SYSCTL(sched_min_granularity);
173 SET_SYSCTL(sched_latency);
174 SET_SYSCTL(sched_wakeup_granularity);
178 void sched_init_granularity(void)
183 #define WMULT_CONST (~0U)
184 #define WMULT_SHIFT 32
186 static void __update_inv_weight(struct load_weight *lw)
190 if (likely(lw->inv_weight))
193 w = scale_load_down(lw->weight);
195 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
197 else if (unlikely(!w))
198 lw->inv_weight = WMULT_CONST;
200 lw->inv_weight = WMULT_CONST / w;
204 * delta_exec * weight / lw.weight
206 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
208 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
209 * we're guaranteed shift stays positive because inv_weight is guaranteed to
210 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
212 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
213 * weight/lw.weight <= 1, and therefore our shift will also be positive.
215 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
217 u64 fact = scale_load_down(weight);
218 int shift = WMULT_SHIFT;
220 __update_inv_weight(lw);
222 if (unlikely(fact >> 32)) {
229 /* hint to use a 32x32->64 mul */
230 fact = (u64)(u32)fact * lw->inv_weight;
237 return mul_u64_u32_shr(delta_exec, fact, shift);
241 const struct sched_class fair_sched_class;
243 /**************************************************************
244 * CFS operations on generic schedulable entities:
247 #ifdef CONFIG_FAIR_GROUP_SCHED
249 /* cpu runqueue to which this cfs_rq is attached */
250 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
255 /* An entity is a task if it doesn't "own" a runqueue */
256 #define entity_is_task(se) (!se->my_q)
258 static inline struct task_struct *task_of(struct sched_entity *se)
260 #ifdef CONFIG_SCHED_DEBUG
261 WARN_ON_ONCE(!entity_is_task(se));
263 return container_of(se, struct task_struct, se);
266 /* Walk up scheduling entities hierarchy */
267 #define for_each_sched_entity(se) \
268 for (; se; se = se->parent)
270 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
275 /* runqueue on which this entity is (to be) queued */
276 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
281 /* runqueue "owned" by this group */
282 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
287 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
289 if (!cfs_rq->on_list) {
291 * Ensure we either appear before our parent (if already
292 * enqueued) or force our parent to appear after us when it is
293 * enqueued. The fact that we always enqueue bottom-up
294 * reduces this to two cases.
296 if (cfs_rq->tg->parent &&
297 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
298 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
299 &rq_of(cfs_rq)->leaf_cfs_rq_list);
301 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
302 &rq_of(cfs_rq)->leaf_cfs_rq_list);
309 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
311 if (cfs_rq->on_list) {
312 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
317 /* Iterate thr' all leaf cfs_rq's on a runqueue */
318 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
319 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
321 /* Do the two (enqueued) entities belong to the same group ? */
322 static inline struct cfs_rq *
323 is_same_group(struct sched_entity *se, struct sched_entity *pse)
325 if (se->cfs_rq == pse->cfs_rq)
331 static inline struct sched_entity *parent_entity(struct sched_entity *se)
337 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
339 int se_depth, pse_depth;
342 * preemption test can be made between sibling entities who are in the
343 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
344 * both tasks until we find their ancestors who are siblings of common
348 /* First walk up until both entities are at same depth */
349 se_depth = (*se)->depth;
350 pse_depth = (*pse)->depth;
352 while (se_depth > pse_depth) {
354 *se = parent_entity(*se);
357 while (pse_depth > se_depth) {
359 *pse = parent_entity(*pse);
362 while (!is_same_group(*se, *pse)) {
363 *se = parent_entity(*se);
364 *pse = parent_entity(*pse);
368 #else /* !CONFIG_FAIR_GROUP_SCHED */
370 static inline struct task_struct *task_of(struct sched_entity *se)
372 return container_of(se, struct task_struct, se);
375 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
377 return container_of(cfs_rq, struct rq, cfs);
380 #define entity_is_task(se) 1
382 #define for_each_sched_entity(se) \
383 for (; se; se = NULL)
385 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
387 return &task_rq(p)->cfs;
390 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
392 struct task_struct *p = task_of(se);
393 struct rq *rq = task_rq(p);
398 /* runqueue "owned" by this group */
399 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
404 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
408 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
412 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
413 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
415 static inline struct sched_entity *parent_entity(struct sched_entity *se)
421 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
425 #endif /* CONFIG_FAIR_GROUP_SCHED */
427 static __always_inline
428 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
430 /**************************************************************
431 * Scheduling class tree data structure manipulation methods:
434 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
436 s64 delta = (s64)(vruntime - max_vruntime);
438 max_vruntime = vruntime;
443 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
445 s64 delta = (s64)(vruntime - min_vruntime);
447 min_vruntime = vruntime;
452 static inline int entity_before(struct sched_entity *a,
453 struct sched_entity *b)
455 return (s64)(a->vruntime - b->vruntime) < 0;
458 static void update_min_vruntime(struct cfs_rq *cfs_rq)
460 u64 vruntime = cfs_rq->min_vruntime;
463 vruntime = cfs_rq->curr->vruntime;
465 if (cfs_rq->rb_leftmost) {
466 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
471 vruntime = se->vruntime;
473 vruntime = min_vruntime(vruntime, se->vruntime);
476 /* ensure we never gain time by being placed backwards. */
477 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
480 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
485 * Enqueue an entity into the rb-tree:
487 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
489 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
490 struct rb_node *parent = NULL;
491 struct sched_entity *entry;
495 * Find the right place in the rbtree:
499 entry = rb_entry(parent, struct sched_entity, run_node);
501 * We dont care about collisions. Nodes with
502 * the same key stay together.
504 if (entity_before(se, entry)) {
505 link = &parent->rb_left;
507 link = &parent->rb_right;
513 * Maintain a cache of leftmost tree entries (it is frequently
517 cfs_rq->rb_leftmost = &se->run_node;
519 rb_link_node(&se->run_node, parent, link);
520 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
523 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
525 if (cfs_rq->rb_leftmost == &se->run_node) {
526 struct rb_node *next_node;
528 next_node = rb_next(&se->run_node);
529 cfs_rq->rb_leftmost = next_node;
532 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
535 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
537 struct rb_node *left = cfs_rq->rb_leftmost;
542 return rb_entry(left, struct sched_entity, run_node);
545 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
547 struct rb_node *next = rb_next(&se->run_node);
552 return rb_entry(next, struct sched_entity, run_node);
555 #ifdef CONFIG_SCHED_DEBUG
556 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
558 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
563 return rb_entry(last, struct sched_entity, run_node);
566 /**************************************************************
567 * Scheduling class statistics methods:
570 int sched_proc_update_handler(struct ctl_table *table, int write,
571 void __user *buffer, size_t *lenp,
574 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
575 unsigned int factor = get_update_sysctl_factor();
580 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
581 sysctl_sched_min_granularity);
583 #define WRT_SYSCTL(name) \
584 (normalized_sysctl_##name = sysctl_##name / (factor))
585 WRT_SYSCTL(sched_min_granularity);
586 WRT_SYSCTL(sched_latency);
587 WRT_SYSCTL(sched_wakeup_granularity);
597 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
599 if (unlikely(se->load.weight != NICE_0_LOAD))
600 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
606 * The idea is to set a period in which each task runs once.
608 * When there are too many tasks (sched_nr_latency) we have to stretch
609 * this period because otherwise the slices get too small.
611 * p = (nr <= nl) ? l : l*nr/nl
613 static u64 __sched_period(unsigned long nr_running)
615 if (unlikely(nr_running > sched_nr_latency))
616 return nr_running * sysctl_sched_min_granularity;
618 return sysctl_sched_latency;
622 * We calculate the wall-time slice from the period by taking a part
623 * proportional to the weight.
627 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
629 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
631 for_each_sched_entity(se) {
632 struct load_weight *load;
633 struct load_weight lw;
635 cfs_rq = cfs_rq_of(se);
636 load = &cfs_rq->load;
638 if (unlikely(!se->on_rq)) {
641 update_load_add(&lw, se->load.weight);
644 slice = __calc_delta(slice, se->load.weight, load);
650 * We calculate the vruntime slice of a to-be-inserted task.
654 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
656 return calc_delta_fair(sched_slice(cfs_rq, se), se);
660 static int select_idle_sibling(struct task_struct *p, int cpu);
661 static unsigned long task_h_load(struct task_struct *p);
664 * We choose a half-life close to 1 scheduling period.
665 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
666 * dependent on this value.
668 #define LOAD_AVG_PERIOD 32
669 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
670 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
672 /* Give new sched_entity start runnable values to heavy its load in infant time */
673 void init_entity_runnable_average(struct sched_entity *se)
675 struct sched_avg *sa = &se->avg;
677 sa->last_update_time = 0;
679 * sched_avg's period_contrib should be strictly less then 1024, so
680 * we give it 1023 to make sure it is almost a period (1024us), and
681 * will definitely be update (after enqueue).
683 sa->period_contrib = 1023;
684 sa->load_avg = scale_load_down(se->load.weight);
685 sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
686 sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
687 sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
688 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
691 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
692 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
694 void init_entity_runnable_average(struct sched_entity *se)
700 * Update the current task's runtime statistics.
702 static void update_curr(struct cfs_rq *cfs_rq)
704 struct sched_entity *curr = cfs_rq->curr;
705 u64 now = rq_clock_task(rq_of(cfs_rq));
711 delta_exec = now - curr->exec_start;
712 if (unlikely((s64)delta_exec <= 0))
715 curr->exec_start = now;
717 schedstat_set(curr->statistics.exec_max,
718 max(delta_exec, curr->statistics.exec_max));
720 curr->sum_exec_runtime += delta_exec;
721 schedstat_add(cfs_rq, exec_clock, delta_exec);
723 curr->vruntime += calc_delta_fair(delta_exec, curr);
724 update_min_vruntime(cfs_rq);
726 if (entity_is_task(curr)) {
727 struct task_struct *curtask = task_of(curr);
729 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
730 cpuacct_charge(curtask, delta_exec);
731 account_group_exec_runtime(curtask, delta_exec);
734 account_cfs_rq_runtime(cfs_rq, delta_exec);
737 static void update_curr_fair(struct rq *rq)
739 update_curr(cfs_rq_of(&rq->curr->se));
743 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
745 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
749 * Task is being enqueued - update stats:
751 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
754 * Are we enqueueing a waiting task? (for current tasks
755 * a dequeue/enqueue event is a NOP)
757 if (se != cfs_rq->curr)
758 update_stats_wait_start(cfs_rq, se);
762 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
764 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
765 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
766 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
767 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
768 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
769 #ifdef CONFIG_SCHEDSTATS
770 if (entity_is_task(se)) {
771 trace_sched_stat_wait(task_of(se),
772 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
775 schedstat_set(se->statistics.wait_start, 0);
779 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
782 * Mark the end of the wait period if dequeueing a
785 if (se != cfs_rq->curr)
786 update_stats_wait_end(cfs_rq, se);
790 * We are picking a new current task - update its stats:
793 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
796 * We are starting a new run period:
798 se->exec_start = rq_clock_task(rq_of(cfs_rq));
801 /**************************************************
802 * Scheduling class queueing methods:
805 #ifdef CONFIG_NUMA_BALANCING
807 * Approximate time to scan a full NUMA task in ms. The task scan period is
808 * calculated based on the tasks virtual memory size and
809 * numa_balancing_scan_size.
811 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
812 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
814 /* Portion of address space to scan in MB */
815 unsigned int sysctl_numa_balancing_scan_size = 256;
817 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
818 unsigned int sysctl_numa_balancing_scan_delay = 1000;
820 static unsigned int task_nr_scan_windows(struct task_struct *p)
822 unsigned long rss = 0;
823 unsigned long nr_scan_pages;
826 * Calculations based on RSS as non-present and empty pages are skipped
827 * by the PTE scanner and NUMA hinting faults should be trapped based
830 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
831 rss = get_mm_rss(p->mm);
835 rss = round_up(rss, nr_scan_pages);
836 return rss / nr_scan_pages;
839 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
840 #define MAX_SCAN_WINDOW 2560
842 static unsigned int task_scan_min(struct task_struct *p)
844 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
845 unsigned int scan, floor;
846 unsigned int windows = 1;
848 if (scan_size < MAX_SCAN_WINDOW)
849 windows = MAX_SCAN_WINDOW / scan_size;
850 floor = 1000 / windows;
852 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
853 return max_t(unsigned int, floor, scan);
856 static unsigned int task_scan_max(struct task_struct *p)
858 unsigned int smin = task_scan_min(p);
861 /* Watch for min being lower than max due to floor calculations */
862 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
863 return max(smin, smax);
866 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
868 rq->nr_numa_running += (p->numa_preferred_nid != -1);
869 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
872 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
874 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
875 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
881 spinlock_t lock; /* nr_tasks, tasks */
886 nodemask_t active_nodes;
887 unsigned long total_faults;
889 * Faults_cpu is used to decide whether memory should move
890 * towards the CPU. As a consequence, these stats are weighted
891 * more by CPU use than by memory faults.
893 unsigned long *faults_cpu;
894 unsigned long faults[0];
897 /* Shared or private faults. */
898 #define NR_NUMA_HINT_FAULT_TYPES 2
900 /* Memory and CPU locality */
901 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
903 /* Averaged statistics, and temporary buffers. */
904 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
906 pid_t task_numa_group_id(struct task_struct *p)
908 return p->numa_group ? p->numa_group->gid : 0;
912 * The averaged statistics, shared & private, memory & cpu,
913 * occupy the first half of the array. The second half of the
914 * array is for current counters, which are averaged into the
915 * first set by task_numa_placement.
917 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
919 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
922 static inline unsigned long task_faults(struct task_struct *p, int nid)
927 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
928 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
931 static inline unsigned long group_faults(struct task_struct *p, int nid)
936 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
937 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
940 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
942 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
943 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
946 /* Handle placement on systems where not all nodes are directly connected. */
947 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
948 int maxdist, bool task)
950 unsigned long score = 0;
954 * All nodes are directly connected, and the same distance
955 * from each other. No need for fancy placement algorithms.
957 if (sched_numa_topology_type == NUMA_DIRECT)
961 * This code is called for each node, introducing N^2 complexity,
962 * which should be ok given the number of nodes rarely exceeds 8.
964 for_each_online_node(node) {
965 unsigned long faults;
966 int dist = node_distance(nid, node);
969 * The furthest away nodes in the system are not interesting
970 * for placement; nid was already counted.
972 if (dist == sched_max_numa_distance || node == nid)
976 * On systems with a backplane NUMA topology, compare groups
977 * of nodes, and move tasks towards the group with the most
978 * memory accesses. When comparing two nodes at distance
979 * "hoplimit", only nodes closer by than "hoplimit" are part
980 * of each group. Skip other nodes.
982 if (sched_numa_topology_type == NUMA_BACKPLANE &&
986 /* Add up the faults from nearby nodes. */
988 faults = task_faults(p, node);
990 faults = group_faults(p, node);
993 * On systems with a glueless mesh NUMA topology, there are
994 * no fixed "groups of nodes". Instead, nodes that are not
995 * directly connected bounce traffic through intermediate
996 * nodes; a numa_group can occupy any set of nodes.
997 * The further away a node is, the less the faults count.
998 * This seems to result in good task placement.
1000 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1001 faults *= (sched_max_numa_distance - dist);
1002 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1012 * These return the fraction of accesses done by a particular task, or
1013 * task group, on a particular numa node. The group weight is given a
1014 * larger multiplier, in order to group tasks together that are almost
1015 * evenly spread out between numa nodes.
1017 static inline unsigned long task_weight(struct task_struct *p, int nid,
1020 unsigned long faults, total_faults;
1022 if (!p->numa_faults)
1025 total_faults = p->total_numa_faults;
1030 faults = task_faults(p, nid);
1031 faults += score_nearby_nodes(p, nid, dist, true);
1033 return 1000 * faults / total_faults;
1036 static inline unsigned long group_weight(struct task_struct *p, int nid,
1039 unsigned long faults, total_faults;
1044 total_faults = p->numa_group->total_faults;
1049 faults = group_faults(p, nid);
1050 faults += score_nearby_nodes(p, nid, dist, false);
1052 return 1000 * faults / total_faults;
1055 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1056 int src_nid, int dst_cpu)
1058 struct numa_group *ng = p->numa_group;
1059 int dst_nid = cpu_to_node(dst_cpu);
1060 int last_cpupid, this_cpupid;
1062 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1065 * Multi-stage node selection is used in conjunction with a periodic
1066 * migration fault to build a temporal task<->page relation. By using
1067 * a two-stage filter we remove short/unlikely relations.
1069 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1070 * a task's usage of a particular page (n_p) per total usage of this
1071 * page (n_t) (in a given time-span) to a probability.
1073 * Our periodic faults will sample this probability and getting the
1074 * same result twice in a row, given these samples are fully
1075 * independent, is then given by P(n)^2, provided our sample period
1076 * is sufficiently short compared to the usage pattern.
1078 * This quadric squishes small probabilities, making it less likely we
1079 * act on an unlikely task<->page relation.
1081 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1082 if (!cpupid_pid_unset(last_cpupid) &&
1083 cpupid_to_nid(last_cpupid) != dst_nid)
1086 /* Always allow migrate on private faults */
1087 if (cpupid_match_pid(p, last_cpupid))
1090 /* A shared fault, but p->numa_group has not been set up yet. */
1095 * Do not migrate if the destination is not a node that
1096 * is actively used by this numa group.
1098 if (!node_isset(dst_nid, ng->active_nodes))
1102 * Source is a node that is not actively used by this
1103 * numa group, while the destination is. Migrate.
1105 if (!node_isset(src_nid, ng->active_nodes))
1109 * Both source and destination are nodes in active
1110 * use by this numa group. Maximize memory bandwidth
1111 * by migrating from more heavily used groups, to less
1112 * heavily used ones, spreading the load around.
1113 * Use a 1/4 hysteresis to avoid spurious page movement.
1115 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1118 static unsigned long weighted_cpuload(const int cpu);
1119 static unsigned long source_load(int cpu, int type);
1120 static unsigned long target_load(int cpu, int type);
1121 static unsigned long capacity_of(int cpu);
1122 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1124 /* Cached statistics for all CPUs within a node */
1126 unsigned long nr_running;
1129 /* Total compute capacity of CPUs on a node */
1130 unsigned long compute_capacity;
1132 /* Approximate capacity in terms of runnable tasks on a node */
1133 unsigned long task_capacity;
1134 int has_free_capacity;
1138 * XXX borrowed from update_sg_lb_stats
1140 static void update_numa_stats(struct numa_stats *ns, int nid)
1142 int smt, cpu, cpus = 0;
1143 unsigned long capacity;
1145 memset(ns, 0, sizeof(*ns));
1146 for_each_cpu(cpu, cpumask_of_node(nid)) {
1147 struct rq *rq = cpu_rq(cpu);
1149 ns->nr_running += rq->nr_running;
1150 ns->load += weighted_cpuload(cpu);
1151 ns->compute_capacity += capacity_of(cpu);
1157 * If we raced with hotplug and there are no CPUs left in our mask
1158 * the @ns structure is NULL'ed and task_numa_compare() will
1159 * not find this node attractive.
1161 * We'll either bail at !has_free_capacity, or we'll detect a huge
1162 * imbalance and bail there.
1167 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1168 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1169 capacity = cpus / smt; /* cores */
1171 ns->task_capacity = min_t(unsigned, capacity,
1172 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1173 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1176 struct task_numa_env {
1177 struct task_struct *p;
1179 int src_cpu, src_nid;
1180 int dst_cpu, dst_nid;
1182 struct numa_stats src_stats, dst_stats;
1187 struct task_struct *best_task;
1192 static void task_numa_assign(struct task_numa_env *env,
1193 struct task_struct *p, long imp)
1196 put_task_struct(env->best_task);
1201 env->best_imp = imp;
1202 env->best_cpu = env->dst_cpu;
1205 static bool load_too_imbalanced(long src_load, long dst_load,
1206 struct task_numa_env *env)
1209 long orig_src_load, orig_dst_load;
1210 long src_capacity, dst_capacity;
1213 * The load is corrected for the CPU capacity available on each node.
1216 * ------------ vs ---------
1217 * src_capacity dst_capacity
1219 src_capacity = env->src_stats.compute_capacity;
1220 dst_capacity = env->dst_stats.compute_capacity;
1222 /* We care about the slope of the imbalance, not the direction. */
1223 if (dst_load < src_load)
1224 swap(dst_load, src_load);
1226 /* Is the difference below the threshold? */
1227 imb = dst_load * src_capacity * 100 -
1228 src_load * dst_capacity * env->imbalance_pct;
1233 * The imbalance is above the allowed threshold.
1234 * Compare it with the old imbalance.
1236 orig_src_load = env->src_stats.load;
1237 orig_dst_load = env->dst_stats.load;
1239 if (orig_dst_load < orig_src_load)
1240 swap(orig_dst_load, orig_src_load);
1242 old_imb = orig_dst_load * src_capacity * 100 -
1243 orig_src_load * dst_capacity * env->imbalance_pct;
1245 /* Would this change make things worse? */
1246 return (imb > old_imb);
1250 * This checks if the overall compute and NUMA accesses of the system would
1251 * be improved if the source tasks was migrated to the target dst_cpu taking
1252 * into account that it might be best if task running on the dst_cpu should
1253 * be exchanged with the source task
1255 static void task_numa_compare(struct task_numa_env *env,
1256 long taskimp, long groupimp)
1258 struct rq *src_rq = cpu_rq(env->src_cpu);
1259 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1260 struct task_struct *cur;
1261 long src_load, dst_load;
1263 long imp = env->p->numa_group ? groupimp : taskimp;
1265 int dist = env->dist;
1269 raw_spin_lock_irq(&dst_rq->lock);
1272 * No need to move the exiting task, and this ensures that ->curr
1273 * wasn't reaped and thus get_task_struct() in task_numa_assign()
1274 * is safe under RCU read lock.
1275 * Note that rcu_read_lock() itself can't protect from the final
1276 * put_task_struct() after the last schedule().
1278 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1280 raw_spin_unlock_irq(&dst_rq->lock);
1283 * Because we have preemption enabled we can get migrated around and
1284 * end try selecting ourselves (current == env->p) as a swap candidate.
1290 * "imp" is the fault differential for the source task between the
1291 * source and destination node. Calculate the total differential for
1292 * the source task and potential destination task. The more negative
1293 * the value is, the more rmeote accesses that would be expected to
1294 * be incurred if the tasks were swapped.
1297 /* Skip this swap candidate if cannot move to the source cpu */
1298 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1302 * If dst and source tasks are in the same NUMA group, or not
1303 * in any group then look only at task weights.
1305 if (cur->numa_group == env->p->numa_group) {
1306 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1307 task_weight(cur, env->dst_nid, dist);
1309 * Add some hysteresis to prevent swapping the
1310 * tasks within a group over tiny differences.
1312 if (cur->numa_group)
1316 * Compare the group weights. If a task is all by
1317 * itself (not part of a group), use the task weight
1320 if (cur->numa_group)
1321 imp += group_weight(cur, env->src_nid, dist) -
1322 group_weight(cur, env->dst_nid, dist);
1324 imp += task_weight(cur, env->src_nid, dist) -
1325 task_weight(cur, env->dst_nid, dist);
1329 if (imp <= env->best_imp && moveimp <= env->best_imp)
1333 /* Is there capacity at our destination? */
1334 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1335 !env->dst_stats.has_free_capacity)
1341 /* Balance doesn't matter much if we're running a task per cpu */
1342 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1343 dst_rq->nr_running == 1)
1347 * In the overloaded case, try and keep the load balanced.
1350 load = task_h_load(env->p);
1351 dst_load = env->dst_stats.load + load;
1352 src_load = env->src_stats.load - load;
1354 if (moveimp > imp && moveimp > env->best_imp) {
1356 * If the improvement from just moving env->p direction is
1357 * better than swapping tasks around, check if a move is
1358 * possible. Store a slightly smaller score than moveimp,
1359 * so an actually idle CPU will win.
1361 if (!load_too_imbalanced(src_load, dst_load, env)) {
1368 if (imp <= env->best_imp)
1372 load = task_h_load(cur);
1377 if (load_too_imbalanced(src_load, dst_load, env))
1381 * One idle CPU per node is evaluated for a task numa move.
1382 * Call select_idle_sibling to maybe find a better one.
1385 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1388 task_numa_assign(env, cur, imp);
1393 static void task_numa_find_cpu(struct task_numa_env *env,
1394 long taskimp, long groupimp)
1398 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1399 /* Skip this CPU if the source task cannot migrate */
1400 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1404 task_numa_compare(env, taskimp, groupimp);
1408 /* Only move tasks to a NUMA node less busy than the current node. */
1409 static bool numa_has_capacity(struct task_numa_env *env)
1411 struct numa_stats *src = &env->src_stats;
1412 struct numa_stats *dst = &env->dst_stats;
1414 if (src->has_free_capacity && !dst->has_free_capacity)
1418 * Only consider a task move if the source has a higher load
1419 * than the destination, corrected for CPU capacity on each node.
1421 * src->load dst->load
1422 * --------------------- vs ---------------------
1423 * src->compute_capacity dst->compute_capacity
1425 if (src->load * dst->compute_capacity * env->imbalance_pct >
1427 dst->load * src->compute_capacity * 100)
1433 static int task_numa_migrate(struct task_struct *p)
1435 struct task_numa_env env = {
1438 .src_cpu = task_cpu(p),
1439 .src_nid = task_node(p),
1441 .imbalance_pct = 112,
1447 struct sched_domain *sd;
1448 unsigned long taskweight, groupweight;
1450 long taskimp, groupimp;
1453 * Pick the lowest SD_NUMA domain, as that would have the smallest
1454 * imbalance and would be the first to start moving tasks about.
1456 * And we want to avoid any moving of tasks about, as that would create
1457 * random movement of tasks -- counter the numa conditions we're trying
1461 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1463 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1467 * Cpusets can break the scheduler domain tree into smaller
1468 * balance domains, some of which do not cross NUMA boundaries.
1469 * Tasks that are "trapped" in such domains cannot be migrated
1470 * elsewhere, so there is no point in (re)trying.
1472 if (unlikely(!sd)) {
1473 p->numa_preferred_nid = task_node(p);
1477 env.dst_nid = p->numa_preferred_nid;
1478 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1479 taskweight = task_weight(p, env.src_nid, dist);
1480 groupweight = group_weight(p, env.src_nid, dist);
1481 update_numa_stats(&env.src_stats, env.src_nid);
1482 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1483 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1484 update_numa_stats(&env.dst_stats, env.dst_nid);
1486 /* Try to find a spot on the preferred nid. */
1487 if (numa_has_capacity(&env))
1488 task_numa_find_cpu(&env, taskimp, groupimp);
1491 * Look at other nodes in these cases:
1492 * - there is no space available on the preferred_nid
1493 * - the task is part of a numa_group that is interleaved across
1494 * multiple NUMA nodes; in order to better consolidate the group,
1495 * we need to check other locations.
1497 if (env.best_cpu == -1 || (p->numa_group &&
1498 nodes_weight(p->numa_group->active_nodes) > 1)) {
1499 for_each_online_node(nid) {
1500 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1503 dist = node_distance(env.src_nid, env.dst_nid);
1504 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1506 taskweight = task_weight(p, env.src_nid, dist);
1507 groupweight = group_weight(p, env.src_nid, dist);
1510 /* Only consider nodes where both task and groups benefit */
1511 taskimp = task_weight(p, nid, dist) - taskweight;
1512 groupimp = group_weight(p, nid, dist) - groupweight;
1513 if (taskimp < 0 && groupimp < 0)
1518 update_numa_stats(&env.dst_stats, env.dst_nid);
1519 if (numa_has_capacity(&env))
1520 task_numa_find_cpu(&env, taskimp, groupimp);
1525 * If the task is part of a workload that spans multiple NUMA nodes,
1526 * and is migrating into one of the workload's active nodes, remember
1527 * this node as the task's preferred numa node, so the workload can
1529 * A task that migrated to a second choice node will be better off
1530 * trying for a better one later. Do not set the preferred node here.
1532 if (p->numa_group) {
1533 if (env.best_cpu == -1)
1538 if (node_isset(nid, p->numa_group->active_nodes))
1539 sched_setnuma(p, env.dst_nid);
1542 /* No better CPU than the current one was found. */
1543 if (env.best_cpu == -1)
1547 * Reset the scan period if the task is being rescheduled on an
1548 * alternative node to recheck if the tasks is now properly placed.
1550 p->numa_scan_period = task_scan_min(p);
1552 if (env.best_task == NULL) {
1553 ret = migrate_task_to(p, env.best_cpu);
1555 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1559 ret = migrate_swap(p, env.best_task);
1561 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1562 put_task_struct(env.best_task);
1566 /* Attempt to migrate a task to a CPU on the preferred node. */
1567 static void numa_migrate_preferred(struct task_struct *p)
1569 unsigned long interval = HZ;
1571 /* This task has no NUMA fault statistics yet */
1572 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1575 /* Periodically retry migrating the task to the preferred node */
1576 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1577 p->numa_migrate_retry = jiffies + interval;
1579 /* Success if task is already running on preferred CPU */
1580 if (task_node(p) == p->numa_preferred_nid)
1583 /* Otherwise, try migrate to a CPU on the preferred node */
1584 task_numa_migrate(p);
1588 * Find the nodes on which the workload is actively running. We do this by
1589 * tracking the nodes from which NUMA hinting faults are triggered. This can
1590 * be different from the set of nodes where the workload's memory is currently
1593 * The bitmask is used to make smarter decisions on when to do NUMA page
1594 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1595 * are added when they cause over 6/16 of the maximum number of faults, but
1596 * only removed when they drop below 3/16.
1598 static void update_numa_active_node_mask(struct numa_group *numa_group)
1600 unsigned long faults, max_faults = 0;
1603 for_each_online_node(nid) {
1604 faults = group_faults_cpu(numa_group, nid);
1605 if (faults > max_faults)
1606 max_faults = faults;
1609 for_each_online_node(nid) {
1610 faults = group_faults_cpu(numa_group, nid);
1611 if (!node_isset(nid, numa_group->active_nodes)) {
1612 if (faults > max_faults * 6 / 16)
1613 node_set(nid, numa_group->active_nodes);
1614 } else if (faults < max_faults * 3 / 16)
1615 node_clear(nid, numa_group->active_nodes);
1620 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1621 * increments. The more local the fault statistics are, the higher the scan
1622 * period will be for the next scan window. If local/(local+remote) ratio is
1623 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1624 * the scan period will decrease. Aim for 70% local accesses.
1626 #define NUMA_PERIOD_SLOTS 10
1627 #define NUMA_PERIOD_THRESHOLD 7
1630 * Increase the scan period (slow down scanning) if the majority of
1631 * our memory is already on our local node, or if the majority of
1632 * the page accesses are shared with other processes.
1633 * Otherwise, decrease the scan period.
1635 static void update_task_scan_period(struct task_struct *p,
1636 unsigned long shared, unsigned long private)
1638 unsigned int period_slot;
1642 unsigned long remote = p->numa_faults_locality[0];
1643 unsigned long local = p->numa_faults_locality[1];
1646 * If there were no record hinting faults then either the task is
1647 * completely idle or all activity is areas that are not of interest
1648 * to automatic numa balancing. Related to that, if there were failed
1649 * migration then it implies we are migrating too quickly or the local
1650 * node is overloaded. In either case, scan slower
1652 if (local + shared == 0 || p->numa_faults_locality[2]) {
1653 p->numa_scan_period = min(p->numa_scan_period_max,
1654 p->numa_scan_period << 1);
1656 p->mm->numa_next_scan = jiffies +
1657 msecs_to_jiffies(p->numa_scan_period);
1663 * Prepare to scale scan period relative to the current period.
1664 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1665 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1666 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1668 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1669 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1670 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1671 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1674 diff = slot * period_slot;
1676 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1679 * Scale scan rate increases based on sharing. There is an
1680 * inverse relationship between the degree of sharing and
1681 * the adjustment made to the scanning period. Broadly
1682 * speaking the intent is that there is little point
1683 * scanning faster if shared accesses dominate as it may
1684 * simply bounce migrations uselessly
1686 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1687 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1690 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1691 task_scan_min(p), task_scan_max(p));
1692 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1696 * Get the fraction of time the task has been running since the last
1697 * NUMA placement cycle. The scheduler keeps similar statistics, but
1698 * decays those on a 32ms period, which is orders of magnitude off
1699 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1700 * stats only if the task is so new there are no NUMA statistics yet.
1702 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1704 u64 runtime, delta, now;
1705 /* Use the start of this time slice to avoid calculations. */
1706 now = p->se.exec_start;
1707 runtime = p->se.sum_exec_runtime;
1709 if (p->last_task_numa_placement) {
1710 delta = runtime - p->last_sum_exec_runtime;
1711 *period = now - p->last_task_numa_placement;
1713 delta = p->se.avg.load_sum / p->se.load.weight;
1714 *period = LOAD_AVG_MAX;
1717 p->last_sum_exec_runtime = runtime;
1718 p->last_task_numa_placement = now;
1724 * Determine the preferred nid for a task in a numa_group. This needs to
1725 * be done in a way that produces consistent results with group_weight,
1726 * otherwise workloads might not converge.
1728 static int preferred_group_nid(struct task_struct *p, int nid)
1733 /* Direct connections between all NUMA nodes. */
1734 if (sched_numa_topology_type == NUMA_DIRECT)
1738 * On a system with glueless mesh NUMA topology, group_weight
1739 * scores nodes according to the number of NUMA hinting faults on
1740 * both the node itself, and on nearby nodes.
1742 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1743 unsigned long score, max_score = 0;
1744 int node, max_node = nid;
1746 dist = sched_max_numa_distance;
1748 for_each_online_node(node) {
1749 score = group_weight(p, node, dist);
1750 if (score > max_score) {
1759 * Finding the preferred nid in a system with NUMA backplane
1760 * interconnect topology is more involved. The goal is to locate
1761 * tasks from numa_groups near each other in the system, and
1762 * untangle workloads from different sides of the system. This requires
1763 * searching down the hierarchy of node groups, recursively searching
1764 * inside the highest scoring group of nodes. The nodemask tricks
1765 * keep the complexity of the search down.
1767 nodes = node_online_map;
1768 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1769 unsigned long max_faults = 0;
1770 nodemask_t max_group = NODE_MASK_NONE;
1773 /* Are there nodes at this distance from each other? */
1774 if (!find_numa_distance(dist))
1777 for_each_node_mask(a, nodes) {
1778 unsigned long faults = 0;
1779 nodemask_t this_group;
1780 nodes_clear(this_group);
1782 /* Sum group's NUMA faults; includes a==b case. */
1783 for_each_node_mask(b, nodes) {
1784 if (node_distance(a, b) < dist) {
1785 faults += group_faults(p, b);
1786 node_set(b, this_group);
1787 node_clear(b, nodes);
1791 /* Remember the top group. */
1792 if (faults > max_faults) {
1793 max_faults = faults;
1794 max_group = this_group;
1796 * subtle: at the smallest distance there is
1797 * just one node left in each "group", the
1798 * winner is the preferred nid.
1803 /* Next round, evaluate the nodes within max_group. */
1811 static void task_numa_placement(struct task_struct *p)
1813 int seq, nid, max_nid = -1, max_group_nid = -1;
1814 unsigned long max_faults = 0, max_group_faults = 0;
1815 unsigned long fault_types[2] = { 0, 0 };
1816 unsigned long total_faults;
1817 u64 runtime, period;
1818 spinlock_t *group_lock = NULL;
1821 * The p->mm->numa_scan_seq field gets updated without
1822 * exclusive access. Use READ_ONCE() here to ensure
1823 * that the field is read in a single access:
1825 seq = READ_ONCE(p->mm->numa_scan_seq);
1826 if (p->numa_scan_seq == seq)
1828 p->numa_scan_seq = seq;
1829 p->numa_scan_period_max = task_scan_max(p);
1831 total_faults = p->numa_faults_locality[0] +
1832 p->numa_faults_locality[1];
1833 runtime = numa_get_avg_runtime(p, &period);
1835 /* If the task is part of a group prevent parallel updates to group stats */
1836 if (p->numa_group) {
1837 group_lock = &p->numa_group->lock;
1838 spin_lock_irq(group_lock);
1841 /* Find the node with the highest number of faults */
1842 for_each_online_node(nid) {
1843 /* Keep track of the offsets in numa_faults array */
1844 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1845 unsigned long faults = 0, group_faults = 0;
1848 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1849 long diff, f_diff, f_weight;
1851 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1852 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1853 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1854 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1856 /* Decay existing window, copy faults since last scan */
1857 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1858 fault_types[priv] += p->numa_faults[membuf_idx];
1859 p->numa_faults[membuf_idx] = 0;
1862 * Normalize the faults_from, so all tasks in a group
1863 * count according to CPU use, instead of by the raw
1864 * number of faults. Tasks with little runtime have
1865 * little over-all impact on throughput, and thus their
1866 * faults are less important.
1868 f_weight = div64_u64(runtime << 16, period + 1);
1869 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1871 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1872 p->numa_faults[cpubuf_idx] = 0;
1874 p->numa_faults[mem_idx] += diff;
1875 p->numa_faults[cpu_idx] += f_diff;
1876 faults += p->numa_faults[mem_idx];
1877 p->total_numa_faults += diff;
1878 if (p->numa_group) {
1880 * safe because we can only change our own group
1882 * mem_idx represents the offset for a given
1883 * nid and priv in a specific region because it
1884 * is at the beginning of the numa_faults array.
1886 p->numa_group->faults[mem_idx] += diff;
1887 p->numa_group->faults_cpu[mem_idx] += f_diff;
1888 p->numa_group->total_faults += diff;
1889 group_faults += p->numa_group->faults[mem_idx];
1893 if (faults > max_faults) {
1894 max_faults = faults;
1898 if (group_faults > max_group_faults) {
1899 max_group_faults = group_faults;
1900 max_group_nid = nid;
1904 update_task_scan_period(p, fault_types[0], fault_types[1]);
1906 if (p->numa_group) {
1907 update_numa_active_node_mask(p->numa_group);
1908 spin_unlock_irq(group_lock);
1909 max_nid = preferred_group_nid(p, max_group_nid);
1913 /* Set the new preferred node */
1914 if (max_nid != p->numa_preferred_nid)
1915 sched_setnuma(p, max_nid);
1917 if (task_node(p) != p->numa_preferred_nid)
1918 numa_migrate_preferred(p);
1922 static inline int get_numa_group(struct numa_group *grp)
1924 return atomic_inc_not_zero(&grp->refcount);
1927 static inline void put_numa_group(struct numa_group *grp)
1929 if (atomic_dec_and_test(&grp->refcount))
1930 kfree_rcu(grp, rcu);
1933 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1936 struct numa_group *grp, *my_grp;
1937 struct task_struct *tsk;
1939 int cpu = cpupid_to_cpu(cpupid);
1942 if (unlikely(!p->numa_group)) {
1943 unsigned int size = sizeof(struct numa_group) +
1944 4*nr_node_ids*sizeof(unsigned long);
1946 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1950 atomic_set(&grp->refcount, 1);
1951 spin_lock_init(&grp->lock);
1953 /* Second half of the array tracks nids where faults happen */
1954 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1957 node_set(task_node(current), grp->active_nodes);
1959 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1960 grp->faults[i] = p->numa_faults[i];
1962 grp->total_faults = p->total_numa_faults;
1965 rcu_assign_pointer(p->numa_group, grp);
1969 tsk = READ_ONCE(cpu_rq(cpu)->curr);
1971 if (!cpupid_match_pid(tsk, cpupid))
1974 grp = rcu_dereference(tsk->numa_group);
1978 my_grp = p->numa_group;
1983 * Only join the other group if its bigger; if we're the bigger group,
1984 * the other task will join us.
1986 if (my_grp->nr_tasks > grp->nr_tasks)
1990 * Tie-break on the grp address.
1992 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1995 /* Always join threads in the same process. */
1996 if (tsk->mm == current->mm)
1999 /* Simple filter to avoid false positives due to PID collisions */
2000 if (flags & TNF_SHARED)
2003 /* Update priv based on whether false sharing was detected */
2006 if (join && !get_numa_group(grp))
2014 BUG_ON(irqs_disabled());
2015 double_lock_irq(&my_grp->lock, &grp->lock);
2017 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2018 my_grp->faults[i] -= p->numa_faults[i];
2019 grp->faults[i] += p->numa_faults[i];
2021 my_grp->total_faults -= p->total_numa_faults;
2022 grp->total_faults += p->total_numa_faults;
2027 spin_unlock(&my_grp->lock);
2028 spin_unlock_irq(&grp->lock);
2030 rcu_assign_pointer(p->numa_group, grp);
2032 put_numa_group(my_grp);
2040 void task_numa_free(struct task_struct *p)
2042 struct numa_group *grp = p->numa_group;
2043 void *numa_faults = p->numa_faults;
2044 unsigned long flags;
2048 spin_lock_irqsave(&grp->lock, flags);
2049 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2050 grp->faults[i] -= p->numa_faults[i];
2051 grp->total_faults -= p->total_numa_faults;
2054 spin_unlock_irqrestore(&grp->lock, flags);
2055 RCU_INIT_POINTER(p->numa_group, NULL);
2056 put_numa_group(grp);
2059 p->numa_faults = NULL;
2064 * Got a PROT_NONE fault for a page on @node.
2066 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2068 struct task_struct *p = current;
2069 bool migrated = flags & TNF_MIGRATED;
2070 int cpu_node = task_node(current);
2071 int local = !!(flags & TNF_FAULT_LOCAL);
2074 if (!static_branch_likely(&sched_numa_balancing))
2077 /* for example, ksmd faulting in a user's mm */
2081 /* Allocate buffer to track faults on a per-node basis */
2082 if (unlikely(!p->numa_faults)) {
2083 int size = sizeof(*p->numa_faults) *
2084 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2086 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2087 if (!p->numa_faults)
2090 p->total_numa_faults = 0;
2091 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2095 * First accesses are treated as private, otherwise consider accesses
2096 * to be private if the accessing pid has not changed
2098 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2101 priv = cpupid_match_pid(p, last_cpupid);
2102 if (!priv && !(flags & TNF_NO_GROUP))
2103 task_numa_group(p, last_cpupid, flags, &priv);
2107 * If a workload spans multiple NUMA nodes, a shared fault that
2108 * occurs wholly within the set of nodes that the workload is
2109 * actively using should be counted as local. This allows the
2110 * scan rate to slow down when a workload has settled down.
2112 if (!priv && !local && p->numa_group &&
2113 node_isset(cpu_node, p->numa_group->active_nodes) &&
2114 node_isset(mem_node, p->numa_group->active_nodes))
2117 task_numa_placement(p);
2120 * Retry task to preferred node migration periodically, in case it
2121 * case it previously failed, or the scheduler moved us.
2123 if (time_after(jiffies, p->numa_migrate_retry))
2124 numa_migrate_preferred(p);
2127 p->numa_pages_migrated += pages;
2128 if (flags & TNF_MIGRATE_FAIL)
2129 p->numa_faults_locality[2] += pages;
2131 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2132 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2133 p->numa_faults_locality[local] += pages;
2136 static void reset_ptenuma_scan(struct task_struct *p)
2139 * We only did a read acquisition of the mmap sem, so
2140 * p->mm->numa_scan_seq is written to without exclusive access
2141 * and the update is not guaranteed to be atomic. That's not
2142 * much of an issue though, since this is just used for
2143 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2144 * expensive, to avoid any form of compiler optimizations:
2146 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2147 p->mm->numa_scan_offset = 0;
2151 * The expensive part of numa migration is done from task_work context.
2152 * Triggered from task_tick_numa().
2154 void task_numa_work(struct callback_head *work)
2156 unsigned long migrate, next_scan, now = jiffies;
2157 struct task_struct *p = current;
2158 struct mm_struct *mm = p->mm;
2159 struct vm_area_struct *vma;
2160 unsigned long start, end;
2161 unsigned long nr_pte_updates = 0;
2162 long pages, virtpages;
2164 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2166 work->next = work; /* protect against double add */
2168 * Who cares about NUMA placement when they're dying.
2170 * NOTE: make sure not to dereference p->mm before this check,
2171 * exit_task_work() happens _after_ exit_mm() so we could be called
2172 * without p->mm even though we still had it when we enqueued this
2175 if (p->flags & PF_EXITING)
2178 if (!mm->numa_next_scan) {
2179 mm->numa_next_scan = now +
2180 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2184 * Enforce maximal scan/migration frequency..
2186 migrate = mm->numa_next_scan;
2187 if (time_before(now, migrate))
2190 if (p->numa_scan_period == 0) {
2191 p->numa_scan_period_max = task_scan_max(p);
2192 p->numa_scan_period = task_scan_min(p);
2195 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2196 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2200 * Delay this task enough that another task of this mm will likely win
2201 * the next time around.
2203 p->node_stamp += 2 * TICK_NSEC;
2205 start = mm->numa_scan_offset;
2206 pages = sysctl_numa_balancing_scan_size;
2207 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2208 virtpages = pages * 8; /* Scan up to this much virtual space */
2213 down_read(&mm->mmap_sem);
2214 vma = find_vma(mm, start);
2216 reset_ptenuma_scan(p);
2220 for (; vma; vma = vma->vm_next) {
2221 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2222 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2227 * Shared library pages mapped by multiple processes are not
2228 * migrated as it is expected they are cache replicated. Avoid
2229 * hinting faults in read-only file-backed mappings or the vdso
2230 * as migrating the pages will be of marginal benefit.
2233 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2237 * Skip inaccessible VMAs to avoid any confusion between
2238 * PROT_NONE and NUMA hinting ptes
2240 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2244 start = max(start, vma->vm_start);
2245 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2246 end = min(end, vma->vm_end);
2247 nr_pte_updates = change_prot_numa(vma, start, end);
2250 * Try to scan sysctl_numa_balancing_size worth of
2251 * hpages that have at least one present PTE that
2252 * is not already pte-numa. If the VMA contains
2253 * areas that are unused or already full of prot_numa
2254 * PTEs, scan up to virtpages, to skip through those
2258 pages -= (end - start) >> PAGE_SHIFT;
2259 virtpages -= (end - start) >> PAGE_SHIFT;
2262 if (pages <= 0 || virtpages <= 0)
2266 } while (end != vma->vm_end);
2271 * It is possible to reach the end of the VMA list but the last few
2272 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2273 * would find the !migratable VMA on the next scan but not reset the
2274 * scanner to the start so check it now.
2277 mm->numa_scan_offset = start;
2279 reset_ptenuma_scan(p);
2280 up_read(&mm->mmap_sem);
2284 * Drive the periodic memory faults..
2286 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2288 struct callback_head *work = &curr->numa_work;
2292 * We don't care about NUMA placement if we don't have memory.
2294 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2298 * Using runtime rather than walltime has the dual advantage that
2299 * we (mostly) drive the selection from busy threads and that the
2300 * task needs to have done some actual work before we bother with
2303 now = curr->se.sum_exec_runtime;
2304 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2306 if (now > curr->node_stamp + period) {
2307 if (!curr->node_stamp)
2308 curr->numa_scan_period = task_scan_min(curr);
2309 curr->node_stamp += period;
2311 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2312 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2313 task_work_add(curr, work, true);
2318 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2322 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2326 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2329 #endif /* CONFIG_NUMA_BALANCING */
2332 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2334 update_load_add(&cfs_rq->load, se->load.weight);
2335 if (!parent_entity(se))
2336 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2338 if (entity_is_task(se)) {
2339 struct rq *rq = rq_of(cfs_rq);
2341 account_numa_enqueue(rq, task_of(se));
2342 list_add(&se->group_node, &rq->cfs_tasks);
2345 cfs_rq->nr_running++;
2349 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2351 update_load_sub(&cfs_rq->load, se->load.weight);
2352 if (!parent_entity(se))
2353 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2354 if (entity_is_task(se)) {
2355 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2356 list_del_init(&se->group_node);
2358 cfs_rq->nr_running--;
2361 #ifdef CONFIG_FAIR_GROUP_SCHED
2363 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2368 * Use this CPU's real-time load instead of the last load contribution
2369 * as the updating of the contribution is delayed, and we will use the
2370 * the real-time load to calc the share. See update_tg_load_avg().
2372 tg_weight = atomic_long_read(&tg->load_avg);
2373 tg_weight -= cfs_rq->tg_load_avg_contrib;
2374 tg_weight += cfs_rq->load.weight;
2379 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2381 long tg_weight, load, shares;
2383 tg_weight = calc_tg_weight(tg, cfs_rq);
2384 load = cfs_rq->load.weight;
2386 shares = (tg->shares * load);
2388 shares /= tg_weight;
2390 if (shares < MIN_SHARES)
2391 shares = MIN_SHARES;
2392 if (shares > tg->shares)
2393 shares = tg->shares;
2397 # else /* CONFIG_SMP */
2398 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2402 # endif /* CONFIG_SMP */
2403 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2404 unsigned long weight)
2407 /* commit outstanding execution time */
2408 if (cfs_rq->curr == se)
2409 update_curr(cfs_rq);
2410 account_entity_dequeue(cfs_rq, se);
2413 update_load_set(&se->load, weight);
2416 account_entity_enqueue(cfs_rq, se);
2419 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2421 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2423 struct task_group *tg;
2424 struct sched_entity *se;
2428 se = tg->se[cpu_of(rq_of(cfs_rq))];
2429 if (!se || throttled_hierarchy(cfs_rq))
2432 if (likely(se->load.weight == tg->shares))
2435 shares = calc_cfs_shares(cfs_rq, tg);
2437 reweight_entity(cfs_rq_of(se), se, shares);
2439 #else /* CONFIG_FAIR_GROUP_SCHED */
2440 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2443 #endif /* CONFIG_FAIR_GROUP_SCHED */
2446 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2447 static const u32 runnable_avg_yN_inv[] = {
2448 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2449 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2450 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2451 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2452 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2453 0x85aac367, 0x82cd8698,
2457 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2458 * over-estimates when re-combining.
2460 static const u32 runnable_avg_yN_sum[] = {
2461 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2462 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2463 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2468 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2470 static __always_inline u64 decay_load(u64 val, u64 n)
2472 unsigned int local_n;
2476 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2479 /* after bounds checking we can collapse to 32-bit */
2483 * As y^PERIOD = 1/2, we can combine
2484 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2485 * With a look-up table which covers y^n (n<PERIOD)
2487 * To achieve constant time decay_load.
2489 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2490 val >>= local_n / LOAD_AVG_PERIOD;
2491 local_n %= LOAD_AVG_PERIOD;
2494 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2499 * For updates fully spanning n periods, the contribution to runnable
2500 * average will be: \Sum 1024*y^n
2502 * We can compute this reasonably efficiently by combining:
2503 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2505 static u32 __compute_runnable_contrib(u64 n)
2509 if (likely(n <= LOAD_AVG_PERIOD))
2510 return runnable_avg_yN_sum[n];
2511 else if (unlikely(n >= LOAD_AVG_MAX_N))
2512 return LOAD_AVG_MAX;
2514 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2516 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2517 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2519 n -= LOAD_AVG_PERIOD;
2520 } while (n > LOAD_AVG_PERIOD);
2522 contrib = decay_load(contrib, n);
2523 return contrib + runnable_avg_yN_sum[n];
2526 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2527 #error "load tracking assumes 2^10 as unit"
2530 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2533 * We can represent the historical contribution to runnable average as the
2534 * coefficients of a geometric series. To do this we sub-divide our runnable
2535 * history into segments of approximately 1ms (1024us); label the segment that
2536 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2538 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2540 * (now) (~1ms ago) (~2ms ago)
2542 * Let u_i denote the fraction of p_i that the entity was runnable.
2544 * We then designate the fractions u_i as our co-efficients, yielding the
2545 * following representation of historical load:
2546 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2548 * We choose y based on the with of a reasonably scheduling period, fixing:
2551 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2552 * approximately half as much as the contribution to load within the last ms
2555 * When a period "rolls over" and we have new u_0`, multiplying the previous
2556 * sum again by y is sufficient to update:
2557 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2558 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2560 static __always_inline int
2561 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2562 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2564 u64 delta, scaled_delta, periods;
2566 unsigned int delta_w, scaled_delta_w, decayed = 0;
2567 unsigned long scale_freq, scale_cpu;
2569 delta = now - sa->last_update_time;
2571 * This should only happen when time goes backwards, which it
2572 * unfortunately does during sched clock init when we swap over to TSC.
2574 if ((s64)delta < 0) {
2575 sa->last_update_time = now;
2580 * Use 1024ns as the unit of measurement since it's a reasonable
2581 * approximation of 1us and fast to compute.
2586 sa->last_update_time = now;
2588 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2589 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2590 trace_sched_contrib_scale_f(cpu, scale_freq, scale_cpu);
2592 /* delta_w is the amount already accumulated against our next period */
2593 delta_w = sa->period_contrib;
2594 if (delta + delta_w >= 1024) {
2597 /* how much left for next period will start over, we don't know yet */
2598 sa->period_contrib = 0;
2601 * Now that we know we're crossing a period boundary, figure
2602 * out how much from delta we need to complete the current
2603 * period and accrue it.
2605 delta_w = 1024 - delta_w;
2606 scaled_delta_w = cap_scale(delta_w, scale_freq);
2608 sa->load_sum += weight * scaled_delta_w;
2610 cfs_rq->runnable_load_sum +=
2611 weight * scaled_delta_w;
2615 sa->util_sum += scaled_delta_w * scale_cpu;
2619 /* Figure out how many additional periods this update spans */
2620 periods = delta / 1024;
2623 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2625 cfs_rq->runnable_load_sum =
2626 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2628 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2630 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2631 contrib = __compute_runnable_contrib(periods);
2632 contrib = cap_scale(contrib, scale_freq);
2634 sa->load_sum += weight * contrib;
2636 cfs_rq->runnable_load_sum += weight * contrib;
2639 sa->util_sum += contrib * scale_cpu;
2642 /* Remainder of delta accrued against u_0` */
2643 scaled_delta = cap_scale(delta, scale_freq);
2645 sa->load_sum += weight * scaled_delta;
2647 cfs_rq->runnable_load_sum += weight * scaled_delta;
2650 sa->util_sum += scaled_delta * scale_cpu;
2652 sa->period_contrib += delta;
2655 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2657 cfs_rq->runnable_load_avg =
2658 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2660 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2666 #ifdef CONFIG_FAIR_GROUP_SCHED
2668 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2669 * and effective_load (which is not done because it is too costly).
2671 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2673 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2675 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2676 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2677 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2681 #else /* CONFIG_FAIR_GROUP_SCHED */
2682 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2683 #endif /* CONFIG_FAIR_GROUP_SCHED */
2685 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2687 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2688 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2690 struct sched_avg *sa = &cfs_rq->avg;
2691 int decayed, removed = 0;
2693 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2694 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2695 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2696 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2700 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2701 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2702 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2703 sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2706 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2707 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2709 #ifndef CONFIG_64BIT
2711 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2714 return decayed || removed;
2717 /* Update task and its cfs_rq load average */
2718 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2720 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2721 u64 now = cfs_rq_clock_task(cfs_rq);
2722 int cpu = cpu_of(rq_of(cfs_rq));
2725 * Track task load average for carrying it to new CPU after migrated, and
2726 * track group sched_entity load average for task_h_load calc in migration
2728 __update_load_avg(now, cpu, &se->avg,
2729 se->on_rq * scale_load_down(se->load.weight),
2730 cfs_rq->curr == se, NULL);
2732 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2733 update_tg_load_avg(cfs_rq, 0);
2736 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2738 if (!sched_feat(ATTACH_AGE_LOAD))
2742 * If we got migrated (either between CPUs or between cgroups) we'll
2743 * have aged the average right before clearing @last_update_time.
2745 if (se->avg.last_update_time) {
2746 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2747 &se->avg, 0, 0, NULL);
2750 * XXX: we could have just aged the entire load away if we've been
2751 * absent from the fair class for too long.
2756 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2757 cfs_rq->avg.load_avg += se->avg.load_avg;
2758 cfs_rq->avg.load_sum += se->avg.load_sum;
2759 cfs_rq->avg.util_avg += se->avg.util_avg;
2760 cfs_rq->avg.util_sum += se->avg.util_sum;
2763 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2765 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2766 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2767 cfs_rq->curr == se, NULL);
2769 cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
2770 cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
2771 cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
2772 cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
2775 /* Add the load generated by se into cfs_rq's load average */
2777 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2779 struct sched_avg *sa = &se->avg;
2780 u64 now = cfs_rq_clock_task(cfs_rq);
2781 int migrated, decayed;
2783 migrated = !sa->last_update_time;
2785 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2786 se->on_rq * scale_load_down(se->load.weight),
2787 cfs_rq->curr == se, NULL);
2790 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2792 cfs_rq->runnable_load_avg += sa->load_avg;
2793 cfs_rq->runnable_load_sum += sa->load_sum;
2796 attach_entity_load_avg(cfs_rq, se);
2798 if (decayed || migrated)
2799 update_tg_load_avg(cfs_rq, 0);
2802 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2804 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2806 update_load_avg(se, 1);
2808 cfs_rq->runnable_load_avg =
2809 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2810 cfs_rq->runnable_load_sum =
2811 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2814 #ifndef CONFIG_64BIT
2815 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2817 u64 last_update_time_copy;
2818 u64 last_update_time;
2821 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2823 last_update_time = cfs_rq->avg.last_update_time;
2824 } while (last_update_time != last_update_time_copy);
2826 return last_update_time;
2829 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2831 return cfs_rq->avg.last_update_time;
2836 * Task first catches up with cfs_rq, and then subtract
2837 * itself from the cfs_rq (task must be off the queue now).
2839 void remove_entity_load_avg(struct sched_entity *se)
2841 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2842 u64 last_update_time;
2845 * Newly created task or never used group entity should not be removed
2846 * from its (source) cfs_rq
2848 if (se->avg.last_update_time == 0)
2851 last_update_time = cfs_rq_last_update_time(cfs_rq);
2853 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2854 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2855 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2859 * Update the rq's load with the elapsed running time before entering
2860 * idle. if the last scheduled task is not a CFS task, idle_enter will
2861 * be the only way to update the runnable statistic.
2863 void idle_enter_fair(struct rq *this_rq)
2868 * Update the rq's load with the elapsed idle time before a task is
2869 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2870 * be the only way to update the runnable statistic.
2872 void idle_exit_fair(struct rq *this_rq)
2876 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2878 return cfs_rq->runnable_load_avg;
2881 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2883 return cfs_rq->avg.load_avg;
2886 static int idle_balance(struct rq *this_rq);
2888 #else /* CONFIG_SMP */
2890 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2892 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2894 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2895 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2898 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2900 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2902 static inline int idle_balance(struct rq *rq)
2907 #endif /* CONFIG_SMP */
2909 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2911 #ifdef CONFIG_SCHEDSTATS
2912 struct task_struct *tsk = NULL;
2914 if (entity_is_task(se))
2917 if (se->statistics.sleep_start) {
2918 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2923 if (unlikely(delta > se->statistics.sleep_max))
2924 se->statistics.sleep_max = delta;
2926 se->statistics.sleep_start = 0;
2927 se->statistics.sum_sleep_runtime += delta;
2930 account_scheduler_latency(tsk, delta >> 10, 1);
2931 trace_sched_stat_sleep(tsk, delta);
2934 if (se->statistics.block_start) {
2935 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2940 if (unlikely(delta > se->statistics.block_max))
2941 se->statistics.block_max = delta;
2943 se->statistics.block_start = 0;
2944 se->statistics.sum_sleep_runtime += delta;
2947 if (tsk->in_iowait) {
2948 se->statistics.iowait_sum += delta;
2949 se->statistics.iowait_count++;
2950 trace_sched_stat_iowait(tsk, delta);
2953 trace_sched_stat_blocked(tsk, delta);
2956 * Blocking time is in units of nanosecs, so shift by
2957 * 20 to get a milliseconds-range estimation of the
2958 * amount of time that the task spent sleeping:
2960 if (unlikely(prof_on == SLEEP_PROFILING)) {
2961 profile_hits(SLEEP_PROFILING,
2962 (void *)get_wchan(tsk),
2965 account_scheduler_latency(tsk, delta >> 10, 0);
2971 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2973 #ifdef CONFIG_SCHED_DEBUG
2974 s64 d = se->vruntime - cfs_rq->min_vruntime;
2979 if (d > 3*sysctl_sched_latency)
2980 schedstat_inc(cfs_rq, nr_spread_over);
2985 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2987 u64 vruntime = cfs_rq->min_vruntime;
2990 * The 'current' period is already promised to the current tasks,
2991 * however the extra weight of the new task will slow them down a
2992 * little, place the new task so that it fits in the slot that
2993 * stays open at the end.
2995 if (initial && sched_feat(START_DEBIT))
2996 vruntime += sched_vslice(cfs_rq, se);
2998 /* sleeps up to a single latency don't count. */
3000 unsigned long thresh = sysctl_sched_latency;
3003 * Halve their sleep time's effect, to allow
3004 * for a gentler effect of sleepers:
3006 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3012 /* ensure we never gain time by being placed backwards. */
3013 se->vruntime = max_vruntime(se->vruntime, vruntime);
3016 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3019 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3022 * Update the normalized vruntime before updating min_vruntime
3023 * through calling update_curr().
3025 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3026 se->vruntime += cfs_rq->min_vruntime;
3029 * Update run-time statistics of the 'current'.
3031 update_curr(cfs_rq);
3032 enqueue_entity_load_avg(cfs_rq, se);
3033 account_entity_enqueue(cfs_rq, se);
3034 update_cfs_shares(cfs_rq);
3036 if (flags & ENQUEUE_WAKEUP) {
3037 place_entity(cfs_rq, se, 0);
3038 enqueue_sleeper(cfs_rq, se);
3041 update_stats_enqueue(cfs_rq, se);
3042 check_spread(cfs_rq, se);
3043 if (se != cfs_rq->curr)
3044 __enqueue_entity(cfs_rq, se);
3047 if (cfs_rq->nr_running == 1) {
3048 list_add_leaf_cfs_rq(cfs_rq);
3049 check_enqueue_throttle(cfs_rq);
3053 static void __clear_buddies_last(struct sched_entity *se)
3055 for_each_sched_entity(se) {
3056 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3057 if (cfs_rq->last != se)
3060 cfs_rq->last = NULL;
3064 static void __clear_buddies_next(struct sched_entity *se)
3066 for_each_sched_entity(se) {
3067 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3068 if (cfs_rq->next != se)
3071 cfs_rq->next = NULL;
3075 static void __clear_buddies_skip(struct sched_entity *se)
3077 for_each_sched_entity(se) {
3078 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3079 if (cfs_rq->skip != se)
3082 cfs_rq->skip = NULL;
3086 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3088 if (cfs_rq->last == se)
3089 __clear_buddies_last(se);
3091 if (cfs_rq->next == se)
3092 __clear_buddies_next(se);
3094 if (cfs_rq->skip == se)
3095 __clear_buddies_skip(se);
3098 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3101 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3104 * Update run-time statistics of the 'current'.
3106 update_curr(cfs_rq);
3107 dequeue_entity_load_avg(cfs_rq, se);
3109 update_stats_dequeue(cfs_rq, se);
3110 if (flags & DEQUEUE_SLEEP) {
3111 #ifdef CONFIG_SCHEDSTATS
3112 if (entity_is_task(se)) {
3113 struct task_struct *tsk = task_of(se);
3115 if (tsk->state & TASK_INTERRUPTIBLE)
3116 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3117 if (tsk->state & TASK_UNINTERRUPTIBLE)
3118 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3123 clear_buddies(cfs_rq, se);
3125 if (se != cfs_rq->curr)
3126 __dequeue_entity(cfs_rq, se);
3128 account_entity_dequeue(cfs_rq, se);
3131 * Normalize the entity after updating the min_vruntime because the
3132 * update can refer to the ->curr item and we need to reflect this
3133 * movement in our normalized position.
3135 if (!(flags & DEQUEUE_SLEEP))
3136 se->vruntime -= cfs_rq->min_vruntime;
3138 /* return excess runtime on last dequeue */
3139 return_cfs_rq_runtime(cfs_rq);
3141 update_min_vruntime(cfs_rq);
3142 update_cfs_shares(cfs_rq);
3146 * Preempt the current task with a newly woken task if needed:
3149 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3151 unsigned long ideal_runtime, delta_exec;
3152 struct sched_entity *se;
3155 ideal_runtime = sched_slice(cfs_rq, curr);
3156 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3157 if (delta_exec > ideal_runtime) {
3158 resched_curr(rq_of(cfs_rq));
3160 * The current task ran long enough, ensure it doesn't get
3161 * re-elected due to buddy favours.
3163 clear_buddies(cfs_rq, curr);
3168 * Ensure that a task that missed wakeup preemption by a
3169 * narrow margin doesn't have to wait for a full slice.
3170 * This also mitigates buddy induced latencies under load.
3172 if (delta_exec < sysctl_sched_min_granularity)
3175 se = __pick_first_entity(cfs_rq);
3176 delta = curr->vruntime - se->vruntime;
3181 if (delta > ideal_runtime)
3182 resched_curr(rq_of(cfs_rq));
3186 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3188 /* 'current' is not kept within the tree. */
3191 * Any task has to be enqueued before it get to execute on
3192 * a CPU. So account for the time it spent waiting on the
3195 update_stats_wait_end(cfs_rq, se);
3196 __dequeue_entity(cfs_rq, se);
3197 update_load_avg(se, 1);
3200 update_stats_curr_start(cfs_rq, se);
3202 #ifdef CONFIG_SCHEDSTATS
3204 * Track our maximum slice length, if the CPU's load is at
3205 * least twice that of our own weight (i.e. dont track it
3206 * when there are only lesser-weight tasks around):
3208 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3209 se->statistics.slice_max = max(se->statistics.slice_max,
3210 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3213 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3217 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3220 * Pick the next process, keeping these things in mind, in this order:
3221 * 1) keep things fair between processes/task groups
3222 * 2) pick the "next" process, since someone really wants that to run
3223 * 3) pick the "last" process, for cache locality
3224 * 4) do not run the "skip" process, if something else is available
3226 static struct sched_entity *
3227 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3229 struct sched_entity *left = __pick_first_entity(cfs_rq);
3230 struct sched_entity *se;
3233 * If curr is set we have to see if its left of the leftmost entity
3234 * still in the tree, provided there was anything in the tree at all.
3236 if (!left || (curr && entity_before(curr, left)))
3239 se = left; /* ideally we run the leftmost entity */
3242 * Avoid running the skip buddy, if running something else can
3243 * be done without getting too unfair.
3245 if (cfs_rq->skip == se) {
3246 struct sched_entity *second;
3249 second = __pick_first_entity(cfs_rq);
3251 second = __pick_next_entity(se);
3252 if (!second || (curr && entity_before(curr, second)))
3256 if (second && wakeup_preempt_entity(second, left) < 1)
3261 * Prefer last buddy, try to return the CPU to a preempted task.
3263 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3267 * Someone really wants this to run. If it's not unfair, run it.
3269 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3272 clear_buddies(cfs_rq, se);
3277 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3279 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3282 * If still on the runqueue then deactivate_task()
3283 * was not called and update_curr() has to be done:
3286 update_curr(cfs_rq);
3288 /* throttle cfs_rqs exceeding runtime */
3289 check_cfs_rq_runtime(cfs_rq);
3291 check_spread(cfs_rq, prev);
3293 update_stats_wait_start(cfs_rq, prev);
3294 /* Put 'current' back into the tree. */
3295 __enqueue_entity(cfs_rq, prev);
3296 /* in !on_rq case, update occurred at dequeue */
3297 update_load_avg(prev, 0);
3299 cfs_rq->curr = NULL;
3303 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3306 * Update run-time statistics of the 'current'.
3308 update_curr(cfs_rq);
3311 * Ensure that runnable average is periodically updated.
3313 update_load_avg(curr, 1);
3314 update_cfs_shares(cfs_rq);
3316 #ifdef CONFIG_SCHED_HRTICK
3318 * queued ticks are scheduled to match the slice, so don't bother
3319 * validating it and just reschedule.
3322 resched_curr(rq_of(cfs_rq));
3326 * don't let the period tick interfere with the hrtick preemption
3328 if (!sched_feat(DOUBLE_TICK) &&
3329 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3333 if (cfs_rq->nr_running > 1)
3334 check_preempt_tick(cfs_rq, curr);
3338 /**************************************************
3339 * CFS bandwidth control machinery
3342 #ifdef CONFIG_CFS_BANDWIDTH
3344 #ifdef HAVE_JUMP_LABEL
3345 static struct static_key __cfs_bandwidth_used;
3347 static inline bool cfs_bandwidth_used(void)
3349 return static_key_false(&__cfs_bandwidth_used);
3352 void cfs_bandwidth_usage_inc(void)
3354 static_key_slow_inc(&__cfs_bandwidth_used);
3357 void cfs_bandwidth_usage_dec(void)
3359 static_key_slow_dec(&__cfs_bandwidth_used);
3361 #else /* HAVE_JUMP_LABEL */
3362 static bool cfs_bandwidth_used(void)
3367 void cfs_bandwidth_usage_inc(void) {}
3368 void cfs_bandwidth_usage_dec(void) {}
3369 #endif /* HAVE_JUMP_LABEL */
3372 * default period for cfs group bandwidth.
3373 * default: 0.1s, units: nanoseconds
3375 static inline u64 default_cfs_period(void)
3377 return 100000000ULL;
3380 static inline u64 sched_cfs_bandwidth_slice(void)
3382 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3386 * Replenish runtime according to assigned quota and update expiration time.
3387 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3388 * additional synchronization around rq->lock.
3390 * requires cfs_b->lock
3392 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3396 if (cfs_b->quota == RUNTIME_INF)
3399 now = sched_clock_cpu(smp_processor_id());
3400 cfs_b->runtime = cfs_b->quota;
3401 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3404 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3406 return &tg->cfs_bandwidth;
3409 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3410 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3412 if (unlikely(cfs_rq->throttle_count))
3413 return cfs_rq->throttled_clock_task;
3415 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3418 /* returns 0 on failure to allocate runtime */
3419 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3421 struct task_group *tg = cfs_rq->tg;
3422 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3423 u64 amount = 0, min_amount, expires;
3425 /* note: this is a positive sum as runtime_remaining <= 0 */
3426 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3428 raw_spin_lock(&cfs_b->lock);
3429 if (cfs_b->quota == RUNTIME_INF)
3430 amount = min_amount;
3432 start_cfs_bandwidth(cfs_b);
3434 if (cfs_b->runtime > 0) {
3435 amount = min(cfs_b->runtime, min_amount);
3436 cfs_b->runtime -= amount;
3440 expires = cfs_b->runtime_expires;
3441 raw_spin_unlock(&cfs_b->lock);
3443 cfs_rq->runtime_remaining += amount;
3445 * we may have advanced our local expiration to account for allowed
3446 * spread between our sched_clock and the one on which runtime was
3449 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3450 cfs_rq->runtime_expires = expires;
3452 return cfs_rq->runtime_remaining > 0;
3456 * Note: This depends on the synchronization provided by sched_clock and the
3457 * fact that rq->clock snapshots this value.
3459 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3461 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3463 /* if the deadline is ahead of our clock, nothing to do */
3464 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3467 if (cfs_rq->runtime_remaining < 0)
3471 * If the local deadline has passed we have to consider the
3472 * possibility that our sched_clock is 'fast' and the global deadline
3473 * has not truly expired.
3475 * Fortunately we can check determine whether this the case by checking
3476 * whether the global deadline has advanced. It is valid to compare
3477 * cfs_b->runtime_expires without any locks since we only care about
3478 * exact equality, so a partial write will still work.
3481 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3482 /* extend local deadline, drift is bounded above by 2 ticks */
3483 cfs_rq->runtime_expires += TICK_NSEC;
3485 /* global deadline is ahead, expiration has passed */
3486 cfs_rq->runtime_remaining = 0;
3490 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3492 /* dock delta_exec before expiring quota (as it could span periods) */
3493 cfs_rq->runtime_remaining -= delta_exec;
3494 expire_cfs_rq_runtime(cfs_rq);
3496 if (likely(cfs_rq->runtime_remaining > 0))
3500 * if we're unable to extend our runtime we resched so that the active
3501 * hierarchy can be throttled
3503 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3504 resched_curr(rq_of(cfs_rq));
3507 static __always_inline
3508 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3510 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3513 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3516 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3518 return cfs_bandwidth_used() && cfs_rq->throttled;
3521 /* check whether cfs_rq, or any parent, is throttled */
3522 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3524 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3528 * Ensure that neither of the group entities corresponding to src_cpu or
3529 * dest_cpu are members of a throttled hierarchy when performing group
3530 * load-balance operations.
3532 static inline int throttled_lb_pair(struct task_group *tg,
3533 int src_cpu, int dest_cpu)
3535 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3537 src_cfs_rq = tg->cfs_rq[src_cpu];
3538 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3540 return throttled_hierarchy(src_cfs_rq) ||
3541 throttled_hierarchy(dest_cfs_rq);
3544 /* updated child weight may affect parent so we have to do this bottom up */
3545 static int tg_unthrottle_up(struct task_group *tg, void *data)
3547 struct rq *rq = data;
3548 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3550 cfs_rq->throttle_count--;
3552 if (!cfs_rq->throttle_count) {
3553 /* adjust cfs_rq_clock_task() */
3554 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3555 cfs_rq->throttled_clock_task;
3562 static int tg_throttle_down(struct task_group *tg, void *data)
3564 struct rq *rq = data;
3565 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3567 /* group is entering throttled state, stop time */
3568 if (!cfs_rq->throttle_count)
3569 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3570 cfs_rq->throttle_count++;
3575 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3577 struct rq *rq = rq_of(cfs_rq);
3578 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3579 struct sched_entity *se;
3580 long task_delta, dequeue = 1;
3583 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3585 /* freeze hierarchy runnable averages while throttled */
3587 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3590 task_delta = cfs_rq->h_nr_running;
3591 for_each_sched_entity(se) {
3592 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3593 /* throttled entity or throttle-on-deactivate */
3598 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3599 qcfs_rq->h_nr_running -= task_delta;
3601 if (qcfs_rq->load.weight)
3606 sub_nr_running(rq, task_delta);
3608 cfs_rq->throttled = 1;
3609 cfs_rq->throttled_clock = rq_clock(rq);
3610 raw_spin_lock(&cfs_b->lock);
3611 empty = list_empty(&cfs_b->throttled_cfs_rq);
3614 * Add to the _head_ of the list, so that an already-started
3615 * distribute_cfs_runtime will not see us
3617 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3620 * If we're the first throttled task, make sure the bandwidth
3624 start_cfs_bandwidth(cfs_b);
3626 raw_spin_unlock(&cfs_b->lock);
3629 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3631 struct rq *rq = rq_of(cfs_rq);
3632 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3633 struct sched_entity *se;
3637 se = cfs_rq->tg->se[cpu_of(rq)];
3639 cfs_rq->throttled = 0;
3641 update_rq_clock(rq);
3643 raw_spin_lock(&cfs_b->lock);
3644 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3645 list_del_rcu(&cfs_rq->throttled_list);
3646 raw_spin_unlock(&cfs_b->lock);
3648 /* update hierarchical throttle state */
3649 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3651 if (!cfs_rq->load.weight)
3654 task_delta = cfs_rq->h_nr_running;
3655 for_each_sched_entity(se) {
3659 cfs_rq = cfs_rq_of(se);
3661 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3662 cfs_rq->h_nr_running += task_delta;
3664 if (cfs_rq_throttled(cfs_rq))
3669 add_nr_running(rq, task_delta);
3671 /* determine whether we need to wake up potentially idle cpu */
3672 if (rq->curr == rq->idle && rq->cfs.nr_running)
3676 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3677 u64 remaining, u64 expires)
3679 struct cfs_rq *cfs_rq;
3681 u64 starting_runtime = remaining;
3684 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3686 struct rq *rq = rq_of(cfs_rq);
3688 raw_spin_lock(&rq->lock);
3689 if (!cfs_rq_throttled(cfs_rq))
3692 runtime = -cfs_rq->runtime_remaining + 1;
3693 if (runtime > remaining)
3694 runtime = remaining;
3695 remaining -= runtime;
3697 cfs_rq->runtime_remaining += runtime;
3698 cfs_rq->runtime_expires = expires;
3700 /* we check whether we're throttled above */
3701 if (cfs_rq->runtime_remaining > 0)
3702 unthrottle_cfs_rq(cfs_rq);
3705 raw_spin_unlock(&rq->lock);
3712 return starting_runtime - remaining;
3716 * Responsible for refilling a task_group's bandwidth and unthrottling its
3717 * cfs_rqs as appropriate. If there has been no activity within the last
3718 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3719 * used to track this state.
3721 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3723 u64 runtime, runtime_expires;
3726 /* no need to continue the timer with no bandwidth constraint */
3727 if (cfs_b->quota == RUNTIME_INF)
3728 goto out_deactivate;
3730 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3731 cfs_b->nr_periods += overrun;
3734 * idle depends on !throttled (for the case of a large deficit), and if
3735 * we're going inactive then everything else can be deferred
3737 if (cfs_b->idle && !throttled)
3738 goto out_deactivate;
3740 __refill_cfs_bandwidth_runtime(cfs_b);
3743 /* mark as potentially idle for the upcoming period */
3748 /* account preceding periods in which throttling occurred */
3749 cfs_b->nr_throttled += overrun;
3751 runtime_expires = cfs_b->runtime_expires;
3754 * This check is repeated as we are holding onto the new bandwidth while
3755 * we unthrottle. This can potentially race with an unthrottled group
3756 * trying to acquire new bandwidth from the global pool. This can result
3757 * in us over-using our runtime if it is all used during this loop, but
3758 * only by limited amounts in that extreme case.
3760 while (throttled && cfs_b->runtime > 0) {
3761 runtime = cfs_b->runtime;
3762 raw_spin_unlock(&cfs_b->lock);
3763 /* we can't nest cfs_b->lock while distributing bandwidth */
3764 runtime = distribute_cfs_runtime(cfs_b, runtime,
3766 raw_spin_lock(&cfs_b->lock);
3768 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3770 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3774 * While we are ensured activity in the period following an
3775 * unthrottle, this also covers the case in which the new bandwidth is
3776 * insufficient to cover the existing bandwidth deficit. (Forcing the
3777 * timer to remain active while there are any throttled entities.)
3787 /* a cfs_rq won't donate quota below this amount */
3788 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3789 /* minimum remaining period time to redistribute slack quota */
3790 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3791 /* how long we wait to gather additional slack before distributing */
3792 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3795 * Are we near the end of the current quota period?
3797 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3798 * hrtimer base being cleared by hrtimer_start. In the case of
3799 * migrate_hrtimers, base is never cleared, so we are fine.
3801 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3803 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3806 /* if the call-back is running a quota refresh is already occurring */
3807 if (hrtimer_callback_running(refresh_timer))
3810 /* is a quota refresh about to occur? */
3811 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3812 if (remaining < min_expire)
3818 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3820 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3822 /* if there's a quota refresh soon don't bother with slack */
3823 if (runtime_refresh_within(cfs_b, min_left))
3826 hrtimer_start(&cfs_b->slack_timer,
3827 ns_to_ktime(cfs_bandwidth_slack_period),
3831 /* we know any runtime found here is valid as update_curr() precedes return */
3832 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3834 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3835 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3837 if (slack_runtime <= 0)
3840 raw_spin_lock(&cfs_b->lock);
3841 if (cfs_b->quota != RUNTIME_INF &&
3842 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3843 cfs_b->runtime += slack_runtime;
3845 /* we are under rq->lock, defer unthrottling using a timer */
3846 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3847 !list_empty(&cfs_b->throttled_cfs_rq))
3848 start_cfs_slack_bandwidth(cfs_b);
3850 raw_spin_unlock(&cfs_b->lock);
3852 /* even if it's not valid for return we don't want to try again */
3853 cfs_rq->runtime_remaining -= slack_runtime;
3856 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3858 if (!cfs_bandwidth_used())
3861 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3864 __return_cfs_rq_runtime(cfs_rq);
3868 * This is done with a timer (instead of inline with bandwidth return) since
3869 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3871 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3873 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3876 /* confirm we're still not at a refresh boundary */
3877 raw_spin_lock(&cfs_b->lock);
3878 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3879 raw_spin_unlock(&cfs_b->lock);
3883 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3884 runtime = cfs_b->runtime;
3886 expires = cfs_b->runtime_expires;
3887 raw_spin_unlock(&cfs_b->lock);
3892 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3894 raw_spin_lock(&cfs_b->lock);
3895 if (expires == cfs_b->runtime_expires)
3896 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3897 raw_spin_unlock(&cfs_b->lock);
3901 * When a group wakes up we want to make sure that its quota is not already
3902 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3903 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3905 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3907 if (!cfs_bandwidth_used())
3910 /* an active group must be handled by the update_curr()->put() path */
3911 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3914 /* ensure the group is not already throttled */
3915 if (cfs_rq_throttled(cfs_rq))
3918 /* update runtime allocation */
3919 account_cfs_rq_runtime(cfs_rq, 0);
3920 if (cfs_rq->runtime_remaining <= 0)
3921 throttle_cfs_rq(cfs_rq);
3924 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3925 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3927 if (!cfs_bandwidth_used())
3930 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3934 * it's possible for a throttled entity to be forced into a running
3935 * state (e.g. set_curr_task), in this case we're finished.
3937 if (cfs_rq_throttled(cfs_rq))
3940 throttle_cfs_rq(cfs_rq);
3944 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3946 struct cfs_bandwidth *cfs_b =
3947 container_of(timer, struct cfs_bandwidth, slack_timer);
3949 do_sched_cfs_slack_timer(cfs_b);
3951 return HRTIMER_NORESTART;
3954 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3956 struct cfs_bandwidth *cfs_b =
3957 container_of(timer, struct cfs_bandwidth, period_timer);
3961 raw_spin_lock(&cfs_b->lock);
3963 overrun = hrtimer_forward_now(timer, cfs_b->period);
3967 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3970 cfs_b->period_active = 0;
3971 raw_spin_unlock(&cfs_b->lock);
3973 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3976 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3978 raw_spin_lock_init(&cfs_b->lock);
3980 cfs_b->quota = RUNTIME_INF;
3981 cfs_b->period = ns_to_ktime(default_cfs_period());
3983 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3984 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3985 cfs_b->period_timer.function = sched_cfs_period_timer;
3986 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3987 cfs_b->slack_timer.function = sched_cfs_slack_timer;
3990 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3992 cfs_rq->runtime_enabled = 0;
3993 INIT_LIST_HEAD(&cfs_rq->throttled_list);
3996 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3998 lockdep_assert_held(&cfs_b->lock);
4000 if (!cfs_b->period_active) {
4001 cfs_b->period_active = 1;
4002 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4003 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4007 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4009 /* init_cfs_bandwidth() was not called */
4010 if (!cfs_b->throttled_cfs_rq.next)
4013 hrtimer_cancel(&cfs_b->period_timer);
4014 hrtimer_cancel(&cfs_b->slack_timer);
4017 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4019 struct cfs_rq *cfs_rq;
4021 for_each_leaf_cfs_rq(rq, cfs_rq) {
4022 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4024 raw_spin_lock(&cfs_b->lock);
4025 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4026 raw_spin_unlock(&cfs_b->lock);
4030 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4032 struct cfs_rq *cfs_rq;
4034 for_each_leaf_cfs_rq(rq, cfs_rq) {
4035 if (!cfs_rq->runtime_enabled)
4039 * clock_task is not advancing so we just need to make sure
4040 * there's some valid quota amount
4042 cfs_rq->runtime_remaining = 1;
4044 * Offline rq is schedulable till cpu is completely disabled
4045 * in take_cpu_down(), so we prevent new cfs throttling here.
4047 cfs_rq->runtime_enabled = 0;
4049 if (cfs_rq_throttled(cfs_rq))
4050 unthrottle_cfs_rq(cfs_rq);
4054 #else /* CONFIG_CFS_BANDWIDTH */
4055 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4057 return rq_clock_task(rq_of(cfs_rq));
4060 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4061 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4062 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4063 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4065 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4070 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4075 static inline int throttled_lb_pair(struct task_group *tg,
4076 int src_cpu, int dest_cpu)
4081 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4083 #ifdef CONFIG_FAIR_GROUP_SCHED
4084 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4087 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4091 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4092 static inline void update_runtime_enabled(struct rq *rq) {}
4093 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4095 #endif /* CONFIG_CFS_BANDWIDTH */
4097 /**************************************************
4098 * CFS operations on tasks:
4101 #ifdef CONFIG_SCHED_HRTICK
4102 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4104 struct sched_entity *se = &p->se;
4105 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4107 WARN_ON(task_rq(p) != rq);
4109 if (cfs_rq->nr_running > 1) {
4110 u64 slice = sched_slice(cfs_rq, se);
4111 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4112 s64 delta = slice - ran;
4119 hrtick_start(rq, delta);
4124 * called from enqueue/dequeue and updates the hrtick when the
4125 * current task is from our class and nr_running is low enough
4128 static void hrtick_update(struct rq *rq)
4130 struct task_struct *curr = rq->curr;
4132 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4135 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4136 hrtick_start_fair(rq, curr);
4138 #else /* !CONFIG_SCHED_HRTICK */
4140 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4144 static inline void hrtick_update(struct rq *rq)
4149 static inline unsigned long boosted_cpu_util(int cpu);
4151 static void update_capacity_of(int cpu)
4153 unsigned long req_cap;
4158 /* Convert scale-invariant capacity to cpu. */
4159 req_cap = boosted_cpu_util(cpu);
4160 req_cap = req_cap * SCHED_CAPACITY_SCALE / capacity_orig_of(cpu);
4161 set_cfs_cpu_capacity(cpu, true, req_cap);
4164 static bool cpu_overutilized(int cpu);
4167 * The enqueue_task method is called before nr_running is
4168 * increased. Here we update the fair scheduling stats and
4169 * then put the task into the rbtree:
4172 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4174 struct cfs_rq *cfs_rq;
4175 struct sched_entity *se = &p->se;
4176 int task_new = flags & ENQUEUE_WAKEUP_NEW;
4177 int task_wakeup = flags & ENQUEUE_WAKEUP;
4179 for_each_sched_entity(se) {
4182 cfs_rq = cfs_rq_of(se);
4183 enqueue_entity(cfs_rq, se, flags);
4186 * end evaluation on encountering a throttled cfs_rq
4188 * note: in the case of encountering a throttled cfs_rq we will
4189 * post the final h_nr_running increment below.
4191 if (cfs_rq_throttled(cfs_rq))
4193 cfs_rq->h_nr_running++;
4195 flags = ENQUEUE_WAKEUP;
4198 for_each_sched_entity(se) {
4199 cfs_rq = cfs_rq_of(se);
4200 cfs_rq->h_nr_running++;
4202 if (cfs_rq_throttled(cfs_rq))
4205 update_load_avg(se, 1);
4206 update_cfs_shares(cfs_rq);
4210 add_nr_running(rq, 1);
4211 if (!task_new && !rq->rd->overutilized &&
4212 cpu_overutilized(rq->cpu))
4213 rq->rd->overutilized = true;
4215 schedtune_enqueue_task(p, cpu_of(rq));
4218 * We want to potentially trigger a freq switch
4219 * request only for tasks that are waking up; this is
4220 * because we get here also during load balancing, but
4221 * in these cases it seems wise to trigger as single
4222 * request after load balancing is done.
4224 if (task_new || task_wakeup)
4225 update_capacity_of(cpu_of(rq));
4230 static void set_next_buddy(struct sched_entity *se);
4233 * The dequeue_task method is called before nr_running is
4234 * decreased. We remove the task from the rbtree and
4235 * update the fair scheduling stats:
4237 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4239 struct cfs_rq *cfs_rq;
4240 struct sched_entity *se = &p->se;
4241 int task_sleep = flags & DEQUEUE_SLEEP;
4243 for_each_sched_entity(se) {
4244 cfs_rq = cfs_rq_of(se);
4245 dequeue_entity(cfs_rq, se, flags);
4248 * end evaluation on encountering a throttled cfs_rq
4250 * note: in the case of encountering a throttled cfs_rq we will
4251 * post the final h_nr_running decrement below.
4253 if (cfs_rq_throttled(cfs_rq))
4255 cfs_rq->h_nr_running--;
4257 /* Don't dequeue parent if it has other entities besides us */
4258 if (cfs_rq->load.weight) {
4260 * Bias pick_next to pick a task from this cfs_rq, as
4261 * p is sleeping when it is within its sched_slice.
4263 if (task_sleep && parent_entity(se))
4264 set_next_buddy(parent_entity(se));
4266 /* avoid re-evaluating load for this entity */
4267 se = parent_entity(se);
4270 flags |= DEQUEUE_SLEEP;
4273 for_each_sched_entity(se) {
4274 cfs_rq = cfs_rq_of(se);
4275 cfs_rq->h_nr_running--;
4277 if (cfs_rq_throttled(cfs_rq))
4280 update_load_avg(se, 1);
4281 update_cfs_shares(cfs_rq);
4285 sub_nr_running(rq, 1);
4286 schedtune_dequeue_task(p, cpu_of(rq));
4289 * We want to potentially trigger a freq switch
4290 * request only for tasks that are going to sleep;
4291 * this is because we get here also during load
4292 * balancing, but in these cases it seems wise to
4293 * trigger as single request after load balancing is
4297 if (rq->cfs.nr_running)
4298 update_capacity_of(cpu_of(rq));
4299 else if (sched_freq())
4300 set_cfs_cpu_capacity(cpu_of(rq), false, 0);
4309 * per rq 'load' arrray crap; XXX kill this.
4313 * The exact cpuload at various idx values, calculated at every tick would be
4314 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4316 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4317 * on nth tick when cpu may be busy, then we have:
4318 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4319 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4321 * decay_load_missed() below does efficient calculation of
4322 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4323 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4325 * The calculation is approximated on a 128 point scale.
4326 * degrade_zero_ticks is the number of ticks after which load at any
4327 * particular idx is approximated to be zero.
4328 * degrade_factor is a precomputed table, a row for each load idx.
4329 * Each column corresponds to degradation factor for a power of two ticks,
4330 * based on 128 point scale.
4332 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4333 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4335 * With this power of 2 load factors, we can degrade the load n times
4336 * by looking at 1 bits in n and doing as many mult/shift instead of
4337 * n mult/shifts needed by the exact degradation.
4339 #define DEGRADE_SHIFT 7
4340 static const unsigned char
4341 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4342 static const unsigned char
4343 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4344 {0, 0, 0, 0, 0, 0, 0, 0},
4345 {64, 32, 8, 0, 0, 0, 0, 0},
4346 {96, 72, 40, 12, 1, 0, 0},
4347 {112, 98, 75, 43, 15, 1, 0},
4348 {120, 112, 98, 76, 45, 16, 2} };
4351 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4352 * would be when CPU is idle and so we just decay the old load without
4353 * adding any new load.
4355 static unsigned long
4356 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4360 if (!missed_updates)
4363 if (missed_updates >= degrade_zero_ticks[idx])
4367 return load >> missed_updates;
4369 while (missed_updates) {
4370 if (missed_updates % 2)
4371 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4373 missed_updates >>= 1;
4380 * Update rq->cpu_load[] statistics. This function is usually called every
4381 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4382 * every tick. We fix it up based on jiffies.
4384 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4385 unsigned long pending_updates)
4389 this_rq->nr_load_updates++;
4391 /* Update our load: */
4392 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4393 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4394 unsigned long old_load, new_load;
4396 /* scale is effectively 1 << i now, and >> i divides by scale */
4398 old_load = this_rq->cpu_load[i];
4399 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4400 new_load = this_load;
4402 * Round up the averaging division if load is increasing. This
4403 * prevents us from getting stuck on 9 if the load is 10, for
4406 if (new_load > old_load)
4407 new_load += scale - 1;
4409 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4412 sched_avg_update(this_rq);
4415 /* Used instead of source_load when we know the type == 0 */
4416 static unsigned long weighted_cpuload(const int cpu)
4418 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4421 #ifdef CONFIG_NO_HZ_COMMON
4423 * There is no sane way to deal with nohz on smp when using jiffies because the
4424 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4425 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4427 * Therefore we cannot use the delta approach from the regular tick since that
4428 * would seriously skew the load calculation. However we'll make do for those
4429 * updates happening while idle (nohz_idle_balance) or coming out of idle
4430 * (tick_nohz_idle_exit).
4432 * This means we might still be one tick off for nohz periods.
4436 * Called from nohz_idle_balance() to update the load ratings before doing the
4439 static void update_idle_cpu_load(struct rq *this_rq)
4441 unsigned long curr_jiffies = READ_ONCE(jiffies);
4442 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4443 unsigned long pending_updates;
4446 * bail if there's load or we're actually up-to-date.
4448 if (load || curr_jiffies == this_rq->last_load_update_tick)
4451 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4452 this_rq->last_load_update_tick = curr_jiffies;
4454 __update_cpu_load(this_rq, load, pending_updates);
4458 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4460 void update_cpu_load_nohz(void)
4462 struct rq *this_rq = this_rq();
4463 unsigned long curr_jiffies = READ_ONCE(jiffies);
4464 unsigned long pending_updates;
4466 if (curr_jiffies == this_rq->last_load_update_tick)
4469 raw_spin_lock(&this_rq->lock);
4470 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4471 if (pending_updates) {
4472 this_rq->last_load_update_tick = curr_jiffies;
4474 * We were idle, this means load 0, the current load might be
4475 * !0 due to remote wakeups and the sort.
4477 __update_cpu_load(this_rq, 0, pending_updates);
4479 raw_spin_unlock(&this_rq->lock);
4481 #endif /* CONFIG_NO_HZ */
4484 * Called from scheduler_tick()
4486 void update_cpu_load_active(struct rq *this_rq)
4488 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4490 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4492 this_rq->last_load_update_tick = jiffies;
4493 __update_cpu_load(this_rq, load, 1);
4497 * Return a low guess at the load of a migration-source cpu weighted
4498 * according to the scheduling class and "nice" value.
4500 * We want to under-estimate the load of migration sources, to
4501 * balance conservatively.
4503 static unsigned long source_load(int cpu, int type)
4505 struct rq *rq = cpu_rq(cpu);
4506 unsigned long total = weighted_cpuload(cpu);
4508 if (type == 0 || !sched_feat(LB_BIAS))
4511 return min(rq->cpu_load[type-1], total);
4515 * Return a high guess at the load of a migration-target cpu weighted
4516 * according to the scheduling class and "nice" value.
4518 static unsigned long target_load(int cpu, int type)
4520 struct rq *rq = cpu_rq(cpu);
4521 unsigned long total = weighted_cpuload(cpu);
4523 if (type == 0 || !sched_feat(LB_BIAS))
4526 return max(rq->cpu_load[type-1], total);
4530 static unsigned long cpu_avg_load_per_task(int cpu)
4532 struct rq *rq = cpu_rq(cpu);
4533 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4534 unsigned long load_avg = weighted_cpuload(cpu);
4537 return load_avg / nr_running;
4542 static void record_wakee(struct task_struct *p)
4545 * Rough decay (wiping) for cost saving, don't worry
4546 * about the boundary, really active task won't care
4549 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4550 current->wakee_flips >>= 1;
4551 current->wakee_flip_decay_ts = jiffies;
4554 if (current->last_wakee != p) {
4555 current->last_wakee = p;
4556 current->wakee_flips++;
4560 static void task_waking_fair(struct task_struct *p)
4562 struct sched_entity *se = &p->se;
4563 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4566 #ifndef CONFIG_64BIT
4567 u64 min_vruntime_copy;
4570 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4572 min_vruntime = cfs_rq->min_vruntime;
4573 } while (min_vruntime != min_vruntime_copy);
4575 min_vruntime = cfs_rq->min_vruntime;
4578 se->vruntime -= min_vruntime;
4582 #ifdef CONFIG_FAIR_GROUP_SCHED
4584 * effective_load() calculates the load change as seen from the root_task_group
4586 * Adding load to a group doesn't make a group heavier, but can cause movement
4587 * of group shares between cpus. Assuming the shares were perfectly aligned one
4588 * can calculate the shift in shares.
4590 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4591 * on this @cpu and results in a total addition (subtraction) of @wg to the
4592 * total group weight.
4594 * Given a runqueue weight distribution (rw_i) we can compute a shares
4595 * distribution (s_i) using:
4597 * s_i = rw_i / \Sum rw_j (1)
4599 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4600 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4601 * shares distribution (s_i):
4603 * rw_i = { 2, 4, 1, 0 }
4604 * s_i = { 2/7, 4/7, 1/7, 0 }
4606 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4607 * task used to run on and the CPU the waker is running on), we need to
4608 * compute the effect of waking a task on either CPU and, in case of a sync
4609 * wakeup, compute the effect of the current task going to sleep.
4611 * So for a change of @wl to the local @cpu with an overall group weight change
4612 * of @wl we can compute the new shares distribution (s'_i) using:
4614 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4616 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4617 * differences in waking a task to CPU 0. The additional task changes the
4618 * weight and shares distributions like:
4620 * rw'_i = { 3, 4, 1, 0 }
4621 * s'_i = { 3/8, 4/8, 1/8, 0 }
4623 * We can then compute the difference in effective weight by using:
4625 * dw_i = S * (s'_i - s_i) (3)
4627 * Where 'S' is the group weight as seen by its parent.
4629 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4630 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4631 * 4/7) times the weight of the group.
4633 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4635 struct sched_entity *se = tg->se[cpu];
4637 if (!tg->parent) /* the trivial, non-cgroup case */
4640 for_each_sched_entity(se) {
4646 * W = @wg + \Sum rw_j
4648 W = wg + calc_tg_weight(tg, se->my_q);
4653 w = cfs_rq_load_avg(se->my_q) + wl;
4656 * wl = S * s'_i; see (2)
4659 wl = (w * (long)tg->shares) / W;
4664 * Per the above, wl is the new se->load.weight value; since
4665 * those are clipped to [MIN_SHARES, ...) do so now. See
4666 * calc_cfs_shares().
4668 if (wl < MIN_SHARES)
4672 * wl = dw_i = S * (s'_i - s_i); see (3)
4674 wl -= se->avg.load_avg;
4677 * Recursively apply this logic to all parent groups to compute
4678 * the final effective load change on the root group. Since
4679 * only the @tg group gets extra weight, all parent groups can
4680 * only redistribute existing shares. @wl is the shift in shares
4681 * resulting from this level per the above.
4690 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4697 static inline bool energy_aware(void)
4699 return sched_feat(ENERGY_AWARE);
4703 struct sched_group *sg_top;
4704 struct sched_group *sg_cap;
4711 struct task_struct *task;
4726 * __cpu_norm_util() returns the cpu util relative to a specific capacity,
4727 * i.e. it's busy ratio, in the range [0..SCHED_LOAD_SCALE] which is useful for
4728 * energy calculations. Using the scale-invariant util returned by
4729 * cpu_util() and approximating scale-invariant util by:
4731 * util ~ (curr_freq/max_freq)*1024 * capacity_orig/1024 * running_time/time
4733 * the normalized util can be found using the specific capacity.
4735 * capacity = capacity_orig * curr_freq/max_freq
4737 * norm_util = running_time/time ~ util/capacity
4739 static unsigned long __cpu_norm_util(int cpu, unsigned long capacity, int delta)
4741 int util = __cpu_util(cpu, delta);
4743 if (util >= capacity)
4744 return SCHED_CAPACITY_SCALE;
4746 return (util << SCHED_CAPACITY_SHIFT)/capacity;
4749 static int calc_util_delta(struct energy_env *eenv, int cpu)
4751 if (cpu == eenv->src_cpu)
4752 return -eenv->util_delta;
4753 if (cpu == eenv->dst_cpu)
4754 return eenv->util_delta;
4759 unsigned long group_max_util(struct energy_env *eenv)
4762 unsigned long max_util = 0;
4764 for_each_cpu(i, sched_group_cpus(eenv->sg_cap)) {
4765 delta = calc_util_delta(eenv, i);
4766 max_util = max(max_util, __cpu_util(i, delta));
4773 * group_norm_util() returns the approximated group util relative to it's
4774 * current capacity (busy ratio) in the range [0..SCHED_LOAD_SCALE] for use in
4775 * energy calculations. Since task executions may or may not overlap in time in
4776 * the group the true normalized util is between max(cpu_norm_util(i)) and
4777 * sum(cpu_norm_util(i)) when iterating over all cpus in the group, i. The
4778 * latter is used as the estimate as it leads to a more pessimistic energy
4779 * estimate (more busy).
4782 long group_norm_util(struct energy_env *eenv, struct sched_group *sg)
4785 unsigned long util_sum = 0;
4786 unsigned long capacity = sg->sge->cap_states[eenv->cap_idx].cap;
4788 for_each_cpu(i, sched_group_cpus(sg)) {
4789 delta = calc_util_delta(eenv, i);
4790 util_sum += __cpu_norm_util(i, capacity, delta);
4793 if (util_sum > SCHED_CAPACITY_SCALE)
4794 return SCHED_CAPACITY_SCALE;
4798 static int find_new_capacity(struct energy_env *eenv,
4799 const struct sched_group_energy const *sge)
4802 unsigned long util = group_max_util(eenv);
4804 for (idx = 0; idx < sge->nr_cap_states; idx++) {
4805 if (sge->cap_states[idx].cap >= util)
4809 eenv->cap_idx = idx;
4814 static int group_idle_state(struct sched_group *sg)
4816 int i, state = INT_MAX;
4818 /* Find the shallowest idle state in the sched group. */
4819 for_each_cpu(i, sched_group_cpus(sg))
4820 state = min(state, idle_get_state_idx(cpu_rq(i)));
4822 /* Take non-cpuidle idling into account (active idle/arch_cpu_idle()) */
4829 * sched_group_energy(): Computes the absolute energy consumption of cpus
4830 * belonging to the sched_group including shared resources shared only by
4831 * members of the group. Iterates over all cpus in the hierarchy below the
4832 * sched_group starting from the bottom working it's way up before going to
4833 * the next cpu until all cpus are covered at all levels. The current
4834 * implementation is likely to gather the same util statistics multiple times.
4835 * This can probably be done in a faster but more complex way.
4836 * Note: sched_group_energy() may fail when racing with sched_domain updates.
4838 static int sched_group_energy(struct energy_env *eenv)
4840 struct sched_domain *sd;
4841 int cpu, total_energy = 0;
4842 struct cpumask visit_cpus;
4843 struct sched_group *sg;
4845 WARN_ON(!eenv->sg_top->sge);
4847 cpumask_copy(&visit_cpus, sched_group_cpus(eenv->sg_top));
4849 while (!cpumask_empty(&visit_cpus)) {
4850 struct sched_group *sg_shared_cap = NULL;
4852 cpu = cpumask_first(&visit_cpus);
4855 * Is the group utilization affected by cpus outside this
4858 sd = rcu_dereference(per_cpu(sd_scs, cpu));
4862 * We most probably raced with hotplug; returning a
4863 * wrong energy estimation is better than entering an
4869 sg_shared_cap = sd->parent->groups;
4871 for_each_domain(cpu, sd) {
4874 /* Has this sched_domain already been visited? */
4875 if (sd->child && group_first_cpu(sg) != cpu)
4879 unsigned long group_util;
4880 int sg_busy_energy, sg_idle_energy;
4881 int cap_idx, idle_idx;
4883 if (sg_shared_cap && sg_shared_cap->group_weight >= sg->group_weight)
4884 eenv->sg_cap = sg_shared_cap;
4888 cap_idx = find_new_capacity(eenv, sg->sge);
4890 if (sg->group_weight == 1) {
4891 /* Remove capacity of src CPU (before task move) */
4892 if (eenv->util_delta == 0 &&
4893 cpumask_test_cpu(eenv->src_cpu, sched_group_cpus(sg))) {
4894 eenv->cap.before = sg->sge->cap_states[cap_idx].cap;
4895 eenv->cap.delta -= eenv->cap.before;
4897 /* Add capacity of dst CPU (after task move) */
4898 if (eenv->util_delta != 0 &&
4899 cpumask_test_cpu(eenv->dst_cpu, sched_group_cpus(sg))) {
4900 eenv->cap.after = sg->sge->cap_states[cap_idx].cap;
4901 eenv->cap.delta += eenv->cap.after;
4905 idle_idx = group_idle_state(sg);
4906 group_util = group_norm_util(eenv, sg);
4907 sg_busy_energy = (group_util * sg->sge->cap_states[cap_idx].power)
4908 >> SCHED_CAPACITY_SHIFT;
4909 sg_idle_energy = ((SCHED_LOAD_SCALE-group_util)
4910 * sg->sge->idle_states[idle_idx].power)
4911 >> SCHED_CAPACITY_SHIFT;
4913 total_energy += sg_busy_energy + sg_idle_energy;
4916 cpumask_xor(&visit_cpus, &visit_cpus, sched_group_cpus(sg));
4918 if (cpumask_equal(sched_group_cpus(sg), sched_group_cpus(eenv->sg_top)))
4921 } while (sg = sg->next, sg != sd->groups);
4927 eenv->energy = total_energy;
4931 static inline bool cpu_in_sg(struct sched_group *sg, int cpu)
4933 return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));
4936 #ifdef CONFIG_SCHED_TUNE
4937 static int energy_diff_evaluate(struct energy_env *eenv)
4942 /* Return energy diff when boost margin is 0 */
4943 #ifdef CONFIG_CGROUP_SCHEDTUNE
4944 boost = schedtune_task_boost(eenv->task);
4946 boost = get_sysctl_sched_cfs_boost();
4949 return eenv->nrg.diff;
4951 /* Compute normalized energy diff */
4952 nrg_delta = schedtune_normalize_energy(eenv->nrg.diff);
4953 eenv->nrg.delta = nrg_delta;
4955 eenv->payoff = schedtune_accept_deltas(
4961 * When SchedTune is enabled, the energy_diff() function will return
4962 * the computed energy payoff value. Since the energy_diff() return
4963 * value is expected to be negative by its callers, this evaluation
4964 * function return a negative value each time the evaluation return a
4965 * positive payoff, which is the condition for the acceptance of
4966 * a scheduling decision
4968 return -eenv->payoff;
4970 #else /* CONFIG_SCHED_TUNE */
4971 #define energy_diff_evaluate(eenv) eenv->nrg.diff
4975 * energy_diff(): Estimate the energy impact of changing the utilization
4976 * distribution. eenv specifies the change: utilisation amount, source, and
4977 * destination cpu. Source or destination cpu may be -1 in which case the
4978 * utilization is removed from or added to the system (e.g. task wake-up). If
4979 * both are specified, the utilization is migrated.
4981 static int energy_diff(struct energy_env *eenv)
4983 struct sched_domain *sd;
4984 struct sched_group *sg;
4985 int sd_cpu = -1, energy_before = 0, energy_after = 0;
4987 struct energy_env eenv_before = {
4989 .src_cpu = eenv->src_cpu,
4990 .dst_cpu = eenv->dst_cpu,
4991 .nrg = { 0, 0, 0, 0},
4995 if (eenv->src_cpu == eenv->dst_cpu)
4998 sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu;
4999 sd = rcu_dereference(per_cpu(sd_ea, sd_cpu));
5002 return 0; /* Error */
5007 if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) {
5008 eenv_before.sg_top = eenv->sg_top = sg;
5010 if (sched_group_energy(&eenv_before))
5011 return 0; /* Invalid result abort */
5012 energy_before += eenv_before.energy;
5014 /* Keep track of SRC cpu (before) capacity */
5015 eenv->cap.before = eenv_before.cap.before;
5016 eenv->cap.delta = eenv_before.cap.delta;
5018 if (sched_group_energy(eenv))
5019 return 0; /* Invalid result abort */
5020 energy_after += eenv->energy;
5022 } while (sg = sg->next, sg != sd->groups);
5024 eenv->nrg.before = energy_before;
5025 eenv->nrg.after = energy_after;
5026 eenv->nrg.diff = eenv->nrg.after - eenv->nrg.before;
5029 return energy_diff_evaluate(eenv);
5033 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5034 * A waker of many should wake a different task than the one last awakened
5035 * at a frequency roughly N times higher than one of its wakees. In order
5036 * to determine whether we should let the load spread vs consolodating to
5037 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
5038 * partner, and a factor of lls_size higher frequency in the other. With
5039 * both conditions met, we can be relatively sure that the relationship is
5040 * non-monogamous, with partner count exceeding socket size. Waker/wakee
5041 * being client/server, worker/dispatcher, interrupt source or whatever is
5042 * irrelevant, spread criteria is apparent partner count exceeds socket size.
5044 static int wake_wide(struct task_struct *p)
5046 unsigned int master = current->wakee_flips;
5047 unsigned int slave = p->wakee_flips;
5048 int factor = this_cpu_read(sd_llc_size);
5051 swap(master, slave);
5052 if (slave < factor || master < slave * factor)
5057 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
5059 s64 this_load, load;
5060 s64 this_eff_load, prev_eff_load;
5061 int idx, this_cpu, prev_cpu;
5062 struct task_group *tg;
5063 unsigned long weight;
5067 this_cpu = smp_processor_id();
5068 prev_cpu = task_cpu(p);
5069 load = source_load(prev_cpu, idx);
5070 this_load = target_load(this_cpu, idx);
5073 * If sync wakeup then subtract the (maximum possible)
5074 * effect of the currently running task from the load
5075 * of the current CPU:
5078 tg = task_group(current);
5079 weight = current->se.avg.load_avg;
5081 this_load += effective_load(tg, this_cpu, -weight, -weight);
5082 load += effective_load(tg, prev_cpu, 0, -weight);
5086 weight = p->se.avg.load_avg;
5089 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5090 * due to the sync cause above having dropped this_load to 0, we'll
5091 * always have an imbalance, but there's really nothing you can do
5092 * about that, so that's good too.
5094 * Otherwise check if either cpus are near enough in load to allow this
5095 * task to be woken on this_cpu.
5097 this_eff_load = 100;
5098 this_eff_load *= capacity_of(prev_cpu);
5100 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5101 prev_eff_load *= capacity_of(this_cpu);
5103 if (this_load > 0) {
5104 this_eff_load *= this_load +
5105 effective_load(tg, this_cpu, weight, weight);
5107 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5110 balanced = this_eff_load <= prev_eff_load;
5112 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5117 schedstat_inc(sd, ttwu_move_affine);
5118 schedstat_inc(p, se.statistics.nr_wakeups_affine);
5123 static inline unsigned long task_util(struct task_struct *p)
5125 return p->se.avg.util_avg;
5128 unsigned int capacity_margin = 1280; /* ~20% margin */
5130 static inline unsigned long boosted_task_util(struct task_struct *task);
5132 static inline bool __task_fits(struct task_struct *p, int cpu, int util)
5134 unsigned long capacity = capacity_of(cpu);
5136 util += boosted_task_util(p);
5138 return (capacity * 1024) > (util * capacity_margin);
5141 static inline bool task_fits_max(struct task_struct *p, int cpu)
5143 unsigned long capacity = capacity_of(cpu);
5144 unsigned long max_capacity = cpu_rq(cpu)->rd->max_cpu_capacity.val;
5146 if (capacity == max_capacity)
5149 if (capacity * capacity_margin > max_capacity * 1024)
5152 return __task_fits(p, cpu, 0);
5155 static inline bool task_fits_spare(struct task_struct *p, int cpu)
5157 return __task_fits(p, cpu, cpu_util(cpu));
5160 static bool cpu_overutilized(int cpu)
5162 return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
5165 #ifdef CONFIG_SCHED_TUNE
5167 static unsigned long
5168 schedtune_margin(unsigned long signal, unsigned long boost)
5170 unsigned long long margin = 0;
5173 * Signal proportional compensation (SPC)
5175 * The Boost (B) value is used to compute a Margin (M) which is
5176 * proportional to the complement of the original Signal (S):
5177 * M = B * (SCHED_LOAD_SCALE - S)
5178 * The obtained M could be used by the caller to "boost" S.
5180 margin = SCHED_LOAD_SCALE - signal;
5184 * Fast integer division by constant:
5185 * Constant : (C) = 100
5186 * Precision : 0.1% (P) = 0.1
5187 * Reference : C * 100 / P (R) = 100000
5190 * Shift bits : ceil(log(R,2)) (S) = 17
5191 * Mult const : round(2^S/C) (M) = 1311
5201 static inline unsigned int
5202 schedtune_cpu_margin(unsigned long util, int cpu)
5206 #ifdef CONFIG_CGROUP_SCHEDTUNE
5207 boost = schedtune_cpu_boost(cpu);
5209 boost = get_sysctl_sched_cfs_boost();
5214 return schedtune_margin(util, boost);
5217 static inline unsigned long
5218 schedtune_task_margin(struct task_struct *task)
5222 unsigned long margin;
5224 #ifdef CONFIG_CGROUP_SCHEDTUNE
5225 boost = schedtune_task_boost(task);
5227 boost = get_sysctl_sched_cfs_boost();
5232 util = task_util(task);
5233 margin = schedtune_margin(util, boost);
5238 #else /* CONFIG_SCHED_TUNE */
5240 static inline unsigned int
5241 schedtune_cpu_margin(unsigned long util, int cpu)
5246 static inline unsigned int
5247 schedtune_task_margin(struct task_struct *task)
5252 #endif /* CONFIG_SCHED_TUNE */
5254 static inline unsigned long
5255 boosted_cpu_util(int cpu)
5257 unsigned long util = cpu_util(cpu);
5258 unsigned long margin = schedtune_cpu_margin(util, cpu);
5260 return util + margin;
5263 static inline unsigned long
5264 boosted_task_util(struct task_struct *task)
5266 unsigned long util = task_util(task);
5267 unsigned long margin = schedtune_task_margin(task);
5269 return util + margin;
5273 * find_idlest_group finds and returns the least busy CPU group within the
5276 static struct sched_group *
5277 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5278 int this_cpu, int sd_flag)
5280 struct sched_group *idlest = NULL, *group = sd->groups;
5281 struct sched_group *fit_group = NULL, *spare_group = NULL;
5282 unsigned long min_load = ULONG_MAX, this_load = 0;
5283 unsigned long fit_capacity = ULONG_MAX;
5284 unsigned long max_spare_capacity = capacity_margin - SCHED_LOAD_SCALE;
5285 int load_idx = sd->forkexec_idx;
5286 int imbalance = 100 + (sd->imbalance_pct-100)/2;
5288 if (sd_flag & SD_BALANCE_WAKE)
5289 load_idx = sd->wake_idx;
5292 unsigned long load, avg_load, spare_capacity;
5296 /* Skip over this group if it has no CPUs allowed */
5297 if (!cpumask_intersects(sched_group_cpus(group),
5298 tsk_cpus_allowed(p)))
5301 local_group = cpumask_test_cpu(this_cpu,
5302 sched_group_cpus(group));
5304 /* Tally up the load of all CPUs in the group */
5307 for_each_cpu(i, sched_group_cpus(group)) {
5308 /* Bias balancing toward cpus of our domain */
5310 load = source_load(i, load_idx);
5312 load = target_load(i, load_idx);
5317 * Look for most energy-efficient group that can fit
5318 * that can fit the task.
5320 if (capacity_of(i) < fit_capacity && task_fits_spare(p, i)) {
5321 fit_capacity = capacity_of(i);
5326 * Look for group which has most spare capacity on a
5329 spare_capacity = capacity_of(i) - cpu_util(i);
5330 if (spare_capacity > max_spare_capacity) {
5331 max_spare_capacity = spare_capacity;
5332 spare_group = group;
5336 /* Adjust by relative CPU capacity of the group */
5337 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5340 this_load = avg_load;
5341 } else if (avg_load < min_load) {
5342 min_load = avg_load;
5345 } while (group = group->next, group != sd->groups);
5353 if (!idlest || 100*this_load < imbalance*min_load)
5359 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5362 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5364 unsigned long load, min_load = ULONG_MAX;
5365 unsigned int min_exit_latency = UINT_MAX;
5366 u64 latest_idle_timestamp = 0;
5367 int least_loaded_cpu = this_cpu;
5368 int shallowest_idle_cpu = -1;
5371 /* Traverse only the allowed CPUs */
5372 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5373 if (task_fits_spare(p, i)) {
5374 struct rq *rq = cpu_rq(i);
5375 struct cpuidle_state *idle = idle_get_state(rq);
5376 if (idle && idle->exit_latency < min_exit_latency) {
5378 * We give priority to a CPU whose idle state
5379 * has the smallest exit latency irrespective
5380 * of any idle timestamp.
5382 min_exit_latency = idle->exit_latency;
5383 latest_idle_timestamp = rq->idle_stamp;
5384 shallowest_idle_cpu = i;
5385 } else if (idle_cpu(i) &&
5386 (!idle || idle->exit_latency == min_exit_latency) &&
5387 rq->idle_stamp > latest_idle_timestamp) {
5389 * If equal or no active idle state, then
5390 * the most recently idled CPU might have
5393 latest_idle_timestamp = rq->idle_stamp;
5394 shallowest_idle_cpu = i;
5395 } else if (shallowest_idle_cpu == -1) {
5397 * If we haven't found an idle CPU yet
5398 * pick a non-idle one that can fit the task as
5401 shallowest_idle_cpu = i;
5403 } else if (shallowest_idle_cpu == -1) {
5404 load = weighted_cpuload(i);
5405 if (load < min_load || (load == min_load && i == this_cpu)) {
5407 least_loaded_cpu = i;
5412 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5416 * Try and locate an idle CPU in the sched_domain.
5418 static int select_idle_sibling(struct task_struct *p, int target)
5420 struct sched_domain *sd;
5421 struct sched_group *sg;
5422 int i = task_cpu(p);
5424 if (idle_cpu(target))
5428 * If the prevous cpu is cache affine and idle, don't be stupid.
5430 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5434 * Otherwise, iterate the domains and find an elegible idle cpu.
5436 sd = rcu_dereference(per_cpu(sd_llc, target));
5437 for_each_lower_domain(sd) {
5440 if (!cpumask_intersects(sched_group_cpus(sg),
5441 tsk_cpus_allowed(p)))
5444 for_each_cpu(i, sched_group_cpus(sg)) {
5445 if (i == target || !idle_cpu(i))
5449 target = cpumask_first_and(sched_group_cpus(sg),
5450 tsk_cpus_allowed(p));
5454 } while (sg != sd->groups);
5460 static int energy_aware_wake_cpu(struct task_struct *p, int target)
5462 struct sched_domain *sd;
5463 struct sched_group *sg, *sg_target;
5464 int target_max_cap = INT_MAX;
5465 int target_cpu = task_cpu(p);
5468 sd = rcu_dereference(per_cpu(sd_ea, task_cpu(p)));
5477 * Find group with sufficient capacity. We only get here if no cpu is
5478 * overutilized. We may end up overutilizing a cpu by adding the task,
5479 * but that should not be any worse than select_idle_sibling().
5480 * load_balance() should sort it out later as we get above the tipping
5484 /* Assuming all cpus are the same in group */
5485 int max_cap_cpu = group_first_cpu(sg);
5488 * Assume smaller max capacity means more energy-efficient.
5489 * Ideally we should query the energy model for the right
5490 * answer but it easily ends up in an exhaustive search.
5492 if (capacity_of(max_cap_cpu) < target_max_cap &&
5493 task_fits_max(p, max_cap_cpu)) {
5495 target_max_cap = capacity_of(max_cap_cpu);
5497 } while (sg = sg->next, sg != sd->groups);
5499 /* Find cpu with sufficient capacity */
5500 for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg_target)) {
5502 * p's blocked utilization is still accounted for on prev_cpu
5503 * so prev_cpu will receive a negative bias due to the double
5504 * accounting. However, the blocked utilization may be zero.
5506 int new_util = cpu_util(i) + boosted_task_util(p);
5508 if (new_util > capacity_orig_of(i))
5511 if (new_util < capacity_curr_of(i)) {
5513 if (cpu_rq(i)->nr_running)
5517 /* cpu has capacity at higher OPP, keep it as fallback */
5518 if (target_cpu == task_cpu(p))
5522 if (target_cpu != task_cpu(p)) {
5523 struct energy_env eenv = {
5524 .util_delta = task_util(p),
5525 .src_cpu = task_cpu(p),
5526 .dst_cpu = target_cpu,
5530 /* Not enough spare capacity on previous cpu */
5531 if (cpu_overutilized(task_cpu(p)))
5534 if (energy_diff(&eenv) >= 0)
5542 * select_task_rq_fair: Select target runqueue for the waking task in domains
5543 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5544 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5546 * Balances load by selecting the idlest cpu in the idlest group, or under
5547 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5549 * Returns the target cpu number.
5551 * preempt must be disabled.
5554 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5556 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5557 int cpu = smp_processor_id();
5558 int new_cpu = prev_cpu;
5559 int want_affine = 0;
5560 int sync = wake_flags & WF_SYNC;
5562 if (sd_flag & SD_BALANCE_WAKE)
5563 want_affine = (!wake_wide(p) && task_fits_max(p, cpu) &&
5564 cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) ||
5568 for_each_domain(cpu, tmp) {
5569 if (!(tmp->flags & SD_LOAD_BALANCE))
5573 * If both cpu and prev_cpu are part of this domain,
5574 * cpu is a valid SD_WAKE_AFFINE target.
5576 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5577 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5582 if (tmp->flags & sd_flag)
5584 else if (!want_affine)
5589 sd = NULL; /* Prefer wake_affine over balance flags */
5590 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5595 if (energy_aware() && !cpu_rq(cpu)->rd->overutilized)
5596 new_cpu = energy_aware_wake_cpu(p, prev_cpu);
5597 else if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5598 new_cpu = select_idle_sibling(p, new_cpu);
5601 struct sched_group *group;
5604 if (!(sd->flags & sd_flag)) {
5609 group = find_idlest_group(sd, p, cpu, sd_flag);
5615 new_cpu = find_idlest_cpu(group, p, cpu);
5616 if (new_cpu == -1 || new_cpu == cpu) {
5617 /* Now try balancing at a lower domain level of cpu */
5622 /* Now try balancing at a lower domain level of new_cpu */
5624 weight = sd->span_weight;
5626 for_each_domain(cpu, tmp) {
5627 if (weight <= tmp->span_weight)
5629 if (tmp->flags & sd_flag)
5632 /* while loop will break here if sd == NULL */
5640 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5641 * cfs_rq_of(p) references at time of call are still valid and identify the
5642 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5643 * other assumptions, including the state of rq->lock, should be made.
5645 static void migrate_task_rq_fair(struct task_struct *p)
5648 * We are supposed to update the task to "current" time, then its up to date
5649 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5650 * what current time is, so simply throw away the out-of-date time. This
5651 * will result in the wakee task is less decayed, but giving the wakee more
5652 * load sounds not bad.
5654 remove_entity_load_avg(&p->se);
5656 /* Tell new CPU we are migrated */
5657 p->se.avg.last_update_time = 0;
5659 /* We have migrated, no longer consider this task hot */
5660 p->se.exec_start = 0;
5663 static void task_dead_fair(struct task_struct *p)
5665 remove_entity_load_avg(&p->se);
5667 #endif /* CONFIG_SMP */
5669 static unsigned long
5670 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5672 unsigned long gran = sysctl_sched_wakeup_granularity;
5675 * Since its curr running now, convert the gran from real-time
5676 * to virtual-time in his units.
5678 * By using 'se' instead of 'curr' we penalize light tasks, so
5679 * they get preempted easier. That is, if 'se' < 'curr' then
5680 * the resulting gran will be larger, therefore penalizing the
5681 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5682 * be smaller, again penalizing the lighter task.
5684 * This is especially important for buddies when the leftmost
5685 * task is higher priority than the buddy.
5687 return calc_delta_fair(gran, se);
5691 * Should 'se' preempt 'curr'.
5705 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5707 s64 gran, vdiff = curr->vruntime - se->vruntime;
5712 gran = wakeup_gran(curr, se);
5719 static void set_last_buddy(struct sched_entity *se)
5721 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5724 for_each_sched_entity(se)
5725 cfs_rq_of(se)->last = se;
5728 static void set_next_buddy(struct sched_entity *se)
5730 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5733 for_each_sched_entity(se)
5734 cfs_rq_of(se)->next = se;
5737 static void set_skip_buddy(struct sched_entity *se)
5739 for_each_sched_entity(se)
5740 cfs_rq_of(se)->skip = se;
5744 * Preempt the current task with a newly woken task if needed:
5746 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5748 struct task_struct *curr = rq->curr;
5749 struct sched_entity *se = &curr->se, *pse = &p->se;
5750 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5751 int scale = cfs_rq->nr_running >= sched_nr_latency;
5752 int next_buddy_marked = 0;
5754 if (unlikely(se == pse))
5758 * This is possible from callers such as attach_tasks(), in which we
5759 * unconditionally check_prempt_curr() after an enqueue (which may have
5760 * lead to a throttle). This both saves work and prevents false
5761 * next-buddy nomination below.
5763 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5766 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5767 set_next_buddy(pse);
5768 next_buddy_marked = 1;
5772 * We can come here with TIF_NEED_RESCHED already set from new task
5775 * Note: this also catches the edge-case of curr being in a throttled
5776 * group (e.g. via set_curr_task), since update_curr() (in the
5777 * enqueue of curr) will have resulted in resched being set. This
5778 * prevents us from potentially nominating it as a false LAST_BUDDY
5781 if (test_tsk_need_resched(curr))
5784 /* Idle tasks are by definition preempted by non-idle tasks. */
5785 if (unlikely(curr->policy == SCHED_IDLE) &&
5786 likely(p->policy != SCHED_IDLE))
5790 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5791 * is driven by the tick):
5793 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5796 find_matching_se(&se, &pse);
5797 update_curr(cfs_rq_of(se));
5799 if (wakeup_preempt_entity(se, pse) == 1) {
5801 * Bias pick_next to pick the sched entity that is
5802 * triggering this preemption.
5804 if (!next_buddy_marked)
5805 set_next_buddy(pse);
5814 * Only set the backward buddy when the current task is still
5815 * on the rq. This can happen when a wakeup gets interleaved
5816 * with schedule on the ->pre_schedule() or idle_balance()
5817 * point, either of which can * drop the rq lock.
5819 * Also, during early boot the idle thread is in the fair class,
5820 * for obvious reasons its a bad idea to schedule back to it.
5822 if (unlikely(!se->on_rq || curr == rq->idle))
5825 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5829 static struct task_struct *
5830 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5832 struct cfs_rq *cfs_rq = &rq->cfs;
5833 struct sched_entity *se;
5834 struct task_struct *p;
5838 #ifdef CONFIG_FAIR_GROUP_SCHED
5839 if (!cfs_rq->nr_running)
5842 if (prev->sched_class != &fair_sched_class)
5846 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5847 * likely that a next task is from the same cgroup as the current.
5849 * Therefore attempt to avoid putting and setting the entire cgroup
5850 * hierarchy, only change the part that actually changes.
5854 struct sched_entity *curr = cfs_rq->curr;
5857 * Since we got here without doing put_prev_entity() we also
5858 * have to consider cfs_rq->curr. If it is still a runnable
5859 * entity, update_curr() will update its vruntime, otherwise
5860 * forget we've ever seen it.
5864 update_curr(cfs_rq);
5869 * This call to check_cfs_rq_runtime() will do the
5870 * throttle and dequeue its entity in the parent(s).
5871 * Therefore the 'simple' nr_running test will indeed
5874 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5878 se = pick_next_entity(cfs_rq, curr);
5879 cfs_rq = group_cfs_rq(se);
5885 * Since we haven't yet done put_prev_entity and if the selected task
5886 * is a different task than we started out with, try and touch the
5887 * least amount of cfs_rqs.
5890 struct sched_entity *pse = &prev->se;
5892 while (!(cfs_rq = is_same_group(se, pse))) {
5893 int se_depth = se->depth;
5894 int pse_depth = pse->depth;
5896 if (se_depth <= pse_depth) {
5897 put_prev_entity(cfs_rq_of(pse), pse);
5898 pse = parent_entity(pse);
5900 if (se_depth >= pse_depth) {
5901 set_next_entity(cfs_rq_of(se), se);
5902 se = parent_entity(se);
5906 put_prev_entity(cfs_rq, pse);
5907 set_next_entity(cfs_rq, se);
5910 if (hrtick_enabled(rq))
5911 hrtick_start_fair(rq, p);
5913 rq->misfit_task = !task_fits_max(p, rq->cpu);
5920 if (!cfs_rq->nr_running)
5923 put_prev_task(rq, prev);
5926 se = pick_next_entity(cfs_rq, NULL);
5927 set_next_entity(cfs_rq, se);
5928 cfs_rq = group_cfs_rq(se);
5933 if (hrtick_enabled(rq))
5934 hrtick_start_fair(rq, p);
5936 rq->misfit_task = !task_fits_max(p, rq->cpu);
5941 rq->misfit_task = 0;
5943 * This is OK, because current is on_cpu, which avoids it being picked
5944 * for load-balance and preemption/IRQs are still disabled avoiding
5945 * further scheduler activity on it and we're being very careful to
5946 * re-start the picking loop.
5948 lockdep_unpin_lock(&rq->lock);
5949 new_tasks = idle_balance(rq);
5950 lockdep_pin_lock(&rq->lock);
5952 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5953 * possible for any higher priority task to appear. In that case we
5954 * must re-start the pick_next_entity() loop.
5966 * Account for a descheduled task:
5968 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5970 struct sched_entity *se = &prev->se;
5971 struct cfs_rq *cfs_rq;
5973 for_each_sched_entity(se) {
5974 cfs_rq = cfs_rq_of(se);
5975 put_prev_entity(cfs_rq, se);
5980 * sched_yield() is very simple
5982 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5984 static void yield_task_fair(struct rq *rq)
5986 struct task_struct *curr = rq->curr;
5987 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5988 struct sched_entity *se = &curr->se;
5991 * Are we the only task in the tree?
5993 if (unlikely(rq->nr_running == 1))
5996 clear_buddies(cfs_rq, se);
5998 if (curr->policy != SCHED_BATCH) {
5999 update_rq_clock(rq);
6001 * Update run-time statistics of the 'current'.
6003 update_curr(cfs_rq);
6005 * Tell update_rq_clock() that we've just updated,
6006 * so we don't do microscopic update in schedule()
6007 * and double the fastpath cost.
6009 rq_clock_skip_update(rq, true);
6015 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
6017 struct sched_entity *se = &p->se;
6019 /* throttled hierarchies are not runnable */
6020 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6023 /* Tell the scheduler that we'd really like pse to run next. */
6026 yield_task_fair(rq);
6032 /**************************************************
6033 * Fair scheduling class load-balancing methods.
6037 * The purpose of load-balancing is to achieve the same basic fairness the
6038 * per-cpu scheduler provides, namely provide a proportional amount of compute
6039 * time to each task. This is expressed in the following equation:
6041 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
6043 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
6044 * W_i,0 is defined as:
6046 * W_i,0 = \Sum_j w_i,j (2)
6048 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
6049 * is derived from the nice value as per prio_to_weight[].
6051 * The weight average is an exponential decay average of the instantaneous
6054 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
6056 * C_i is the compute capacity of cpu i, typically it is the
6057 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
6058 * can also include other factors [XXX].
6060 * To achieve this balance we define a measure of imbalance which follows
6061 * directly from (1):
6063 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
6065 * We them move tasks around to minimize the imbalance. In the continuous
6066 * function space it is obvious this converges, in the discrete case we get
6067 * a few fun cases generally called infeasible weight scenarios.
6070 * - infeasible weights;
6071 * - local vs global optima in the discrete case. ]
6076 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
6077 * for all i,j solution, we create a tree of cpus that follows the hardware
6078 * topology where each level pairs two lower groups (or better). This results
6079 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
6080 * tree to only the first of the previous level and we decrease the frequency
6081 * of load-balance at each level inv. proportional to the number of cpus in
6087 * \Sum { --- * --- * 2^i } = O(n) (5)
6089 * `- size of each group
6090 * | | `- number of cpus doing load-balance
6092 * `- sum over all levels
6094 * Coupled with a limit on how many tasks we can migrate every balance pass,
6095 * this makes (5) the runtime complexity of the balancer.
6097 * An important property here is that each CPU is still (indirectly) connected
6098 * to every other cpu in at most O(log n) steps:
6100 * The adjacency matrix of the resulting graph is given by:
6103 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
6106 * And you'll find that:
6108 * A^(log_2 n)_i,j != 0 for all i,j (7)
6110 * Showing there's indeed a path between every cpu in at most O(log n) steps.
6111 * The task movement gives a factor of O(m), giving a convergence complexity
6114 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
6119 * In order to avoid CPUs going idle while there's still work to do, new idle
6120 * balancing is more aggressive and has the newly idle cpu iterate up the domain
6121 * tree itself instead of relying on other CPUs to bring it work.
6123 * This adds some complexity to both (5) and (8) but it reduces the total idle
6131 * Cgroups make a horror show out of (2), instead of a simple sum we get:
6134 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
6139 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
6141 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
6143 * The big problem is S_k, its a global sum needed to compute a local (W_i)
6146 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
6147 * rewrite all of this once again.]
6150 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
6152 enum fbq_type { regular, remote, all };
6161 #define LBF_ALL_PINNED 0x01
6162 #define LBF_NEED_BREAK 0x02
6163 #define LBF_DST_PINNED 0x04
6164 #define LBF_SOME_PINNED 0x08
6167 struct sched_domain *sd;
6175 struct cpumask *dst_grpmask;
6177 enum cpu_idle_type idle;
6179 unsigned int src_grp_nr_running;
6180 /* The set of CPUs under consideration for load-balancing */
6181 struct cpumask *cpus;
6186 unsigned int loop_break;
6187 unsigned int loop_max;
6189 enum fbq_type fbq_type;
6190 enum group_type busiest_group_type;
6191 struct list_head tasks;
6195 * Is this task likely cache-hot:
6197 static int task_hot(struct task_struct *p, struct lb_env *env)
6201 lockdep_assert_held(&env->src_rq->lock);
6203 if (p->sched_class != &fair_sched_class)
6206 if (unlikely(p->policy == SCHED_IDLE))
6210 * Buddy candidates are cache hot:
6212 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6213 (&p->se == cfs_rq_of(&p->se)->next ||
6214 &p->se == cfs_rq_of(&p->se)->last))
6217 if (sysctl_sched_migration_cost == -1)
6219 if (sysctl_sched_migration_cost == 0)
6222 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6224 return delta < (s64)sysctl_sched_migration_cost;
6227 #ifdef CONFIG_NUMA_BALANCING
6229 * Returns 1, if task migration degrades locality
6230 * Returns 0, if task migration improves locality i.e migration preferred.
6231 * Returns -1, if task migration is not affected by locality.
6233 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6235 struct numa_group *numa_group = rcu_dereference(p->numa_group);
6236 unsigned long src_faults, dst_faults;
6237 int src_nid, dst_nid;
6239 if (!static_branch_likely(&sched_numa_balancing))
6242 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6245 src_nid = cpu_to_node(env->src_cpu);
6246 dst_nid = cpu_to_node(env->dst_cpu);
6248 if (src_nid == dst_nid)
6251 /* Migrating away from the preferred node is always bad. */
6252 if (src_nid == p->numa_preferred_nid) {
6253 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6259 /* Encourage migration to the preferred node. */
6260 if (dst_nid == p->numa_preferred_nid)
6264 src_faults = group_faults(p, src_nid);
6265 dst_faults = group_faults(p, dst_nid);
6267 src_faults = task_faults(p, src_nid);
6268 dst_faults = task_faults(p, dst_nid);
6271 return dst_faults < src_faults;
6275 static inline int migrate_degrades_locality(struct task_struct *p,
6283 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6286 int can_migrate_task(struct task_struct *p, struct lb_env *env)
6290 lockdep_assert_held(&env->src_rq->lock);
6293 * We do not migrate tasks that are:
6294 * 1) throttled_lb_pair, or
6295 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6296 * 3) running (obviously), or
6297 * 4) are cache-hot on their current CPU.
6299 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6302 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6305 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6307 env->flags |= LBF_SOME_PINNED;
6310 * Remember if this task can be migrated to any other cpu in
6311 * our sched_group. We may want to revisit it if we couldn't
6312 * meet load balance goals by pulling other tasks on src_cpu.
6314 * Also avoid computing new_dst_cpu if we have already computed
6315 * one in current iteration.
6317 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6320 /* Prevent to re-select dst_cpu via env's cpus */
6321 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6322 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6323 env->flags |= LBF_DST_PINNED;
6324 env->new_dst_cpu = cpu;
6332 /* Record that we found atleast one task that could run on dst_cpu */
6333 env->flags &= ~LBF_ALL_PINNED;
6335 if (task_running(env->src_rq, p)) {
6336 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6341 * Aggressive migration if:
6342 * 1) destination numa is preferred
6343 * 2) task is cache cold, or
6344 * 3) too many balance attempts have failed.
6346 tsk_cache_hot = migrate_degrades_locality(p, env);
6347 if (tsk_cache_hot == -1)
6348 tsk_cache_hot = task_hot(p, env);
6350 if (tsk_cache_hot <= 0 ||
6351 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6352 if (tsk_cache_hot == 1) {
6353 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
6354 schedstat_inc(p, se.statistics.nr_forced_migrations);
6359 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
6364 * detach_task() -- detach the task for the migration specified in env
6366 static void detach_task(struct task_struct *p, struct lb_env *env)
6368 lockdep_assert_held(&env->src_rq->lock);
6370 deactivate_task(env->src_rq, p, 0);
6371 p->on_rq = TASK_ON_RQ_MIGRATING;
6372 set_task_cpu(p, env->dst_cpu);
6376 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6377 * part of active balancing operations within "domain".
6379 * Returns a task if successful and NULL otherwise.
6381 static struct task_struct *detach_one_task(struct lb_env *env)
6383 struct task_struct *p, *n;
6385 lockdep_assert_held(&env->src_rq->lock);
6387 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
6388 if (!can_migrate_task(p, env))
6391 detach_task(p, env);
6394 * Right now, this is only the second place where
6395 * lb_gained[env->idle] is updated (other is detach_tasks)
6396 * so we can safely collect stats here rather than
6397 * inside detach_tasks().
6399 schedstat_inc(env->sd, lb_gained[env->idle]);
6405 static const unsigned int sched_nr_migrate_break = 32;
6408 * detach_tasks() -- tries to detach up to imbalance weighted load from
6409 * busiest_rq, as part of a balancing operation within domain "sd".
6411 * Returns number of detached tasks if successful and 0 otherwise.
6413 static int detach_tasks(struct lb_env *env)
6415 struct list_head *tasks = &env->src_rq->cfs_tasks;
6416 struct task_struct *p;
6420 lockdep_assert_held(&env->src_rq->lock);
6422 if (env->imbalance <= 0)
6425 while (!list_empty(tasks)) {
6427 * We don't want to steal all, otherwise we may be treated likewise,
6428 * which could at worst lead to a livelock crash.
6430 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6433 p = list_first_entry(tasks, struct task_struct, se.group_node);
6436 /* We've more or less seen every task there is, call it quits */
6437 if (env->loop > env->loop_max)
6440 /* take a breather every nr_migrate tasks */
6441 if (env->loop > env->loop_break) {
6442 env->loop_break += sched_nr_migrate_break;
6443 env->flags |= LBF_NEED_BREAK;
6447 if (!can_migrate_task(p, env))
6450 load = task_h_load(p);
6452 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6455 if ((load / 2) > env->imbalance)
6458 detach_task(p, env);
6459 list_add(&p->se.group_node, &env->tasks);
6462 env->imbalance -= load;
6464 #ifdef CONFIG_PREEMPT
6466 * NEWIDLE balancing is a source of latency, so preemptible
6467 * kernels will stop after the first task is detached to minimize
6468 * the critical section.
6470 if (env->idle == CPU_NEWLY_IDLE)
6475 * We only want to steal up to the prescribed amount of
6478 if (env->imbalance <= 0)
6483 list_move_tail(&p->se.group_node, tasks);
6487 * Right now, this is one of only two places we collect this stat
6488 * so we can safely collect detach_one_task() stats here rather
6489 * than inside detach_one_task().
6491 schedstat_add(env->sd, lb_gained[env->idle], detached);
6497 * attach_task() -- attach the task detached by detach_task() to its new rq.
6499 static void attach_task(struct rq *rq, struct task_struct *p)
6501 lockdep_assert_held(&rq->lock);
6503 BUG_ON(task_rq(p) != rq);
6504 p->on_rq = TASK_ON_RQ_QUEUED;
6505 activate_task(rq, p, 0);
6506 check_preempt_curr(rq, p, 0);
6510 * attach_one_task() -- attaches the task returned from detach_one_task() to
6513 static void attach_one_task(struct rq *rq, struct task_struct *p)
6515 raw_spin_lock(&rq->lock);
6518 * We want to potentially raise target_cpu's OPP.
6520 update_capacity_of(cpu_of(rq));
6521 raw_spin_unlock(&rq->lock);
6525 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6528 static void attach_tasks(struct lb_env *env)
6530 struct list_head *tasks = &env->tasks;
6531 struct task_struct *p;
6533 raw_spin_lock(&env->dst_rq->lock);
6535 while (!list_empty(tasks)) {
6536 p = list_first_entry(tasks, struct task_struct, se.group_node);
6537 list_del_init(&p->se.group_node);
6539 attach_task(env->dst_rq, p);
6543 * We want to potentially raise env.dst_cpu's OPP.
6545 update_capacity_of(env->dst_cpu);
6547 raw_spin_unlock(&env->dst_rq->lock);
6550 #ifdef CONFIG_FAIR_GROUP_SCHED
6551 static void update_blocked_averages(int cpu)
6553 struct rq *rq = cpu_rq(cpu);
6554 struct cfs_rq *cfs_rq;
6555 unsigned long flags;
6557 raw_spin_lock_irqsave(&rq->lock, flags);
6558 update_rq_clock(rq);
6561 * Iterates the task_group tree in a bottom up fashion, see
6562 * list_add_leaf_cfs_rq() for details.
6564 for_each_leaf_cfs_rq(rq, cfs_rq) {
6565 /* throttled entities do not contribute to load */
6566 if (throttled_hierarchy(cfs_rq))
6569 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6570 update_tg_load_avg(cfs_rq, 0);
6572 raw_spin_unlock_irqrestore(&rq->lock, flags);
6576 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6577 * This needs to be done in a top-down fashion because the load of a child
6578 * group is a fraction of its parents load.
6580 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6582 struct rq *rq = rq_of(cfs_rq);
6583 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6584 unsigned long now = jiffies;
6587 if (cfs_rq->last_h_load_update == now)
6590 cfs_rq->h_load_next = NULL;
6591 for_each_sched_entity(se) {
6592 cfs_rq = cfs_rq_of(se);
6593 cfs_rq->h_load_next = se;
6594 if (cfs_rq->last_h_load_update == now)
6599 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6600 cfs_rq->last_h_load_update = now;
6603 while ((se = cfs_rq->h_load_next) != NULL) {
6604 load = cfs_rq->h_load;
6605 load = div64_ul(load * se->avg.load_avg,
6606 cfs_rq_load_avg(cfs_rq) + 1);
6607 cfs_rq = group_cfs_rq(se);
6608 cfs_rq->h_load = load;
6609 cfs_rq->last_h_load_update = now;
6613 static unsigned long task_h_load(struct task_struct *p)
6615 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6617 update_cfs_rq_h_load(cfs_rq);
6618 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6619 cfs_rq_load_avg(cfs_rq) + 1);
6622 static inline void update_blocked_averages(int cpu)
6624 struct rq *rq = cpu_rq(cpu);
6625 struct cfs_rq *cfs_rq = &rq->cfs;
6626 unsigned long flags;
6628 raw_spin_lock_irqsave(&rq->lock, flags);
6629 update_rq_clock(rq);
6630 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6631 raw_spin_unlock_irqrestore(&rq->lock, flags);
6634 static unsigned long task_h_load(struct task_struct *p)
6636 return p->se.avg.load_avg;
6640 /********** Helpers for find_busiest_group ************************/
6643 * sg_lb_stats - stats of a sched_group required for load_balancing
6645 struct sg_lb_stats {
6646 unsigned long avg_load; /*Avg load across the CPUs of the group */
6647 unsigned long group_load; /* Total load over the CPUs of the group */
6648 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6649 unsigned long load_per_task;
6650 unsigned long group_capacity;
6651 unsigned long group_util; /* Total utilization of the group */
6652 unsigned int sum_nr_running; /* Nr tasks running in the group */
6653 unsigned int idle_cpus;
6654 unsigned int group_weight;
6655 enum group_type group_type;
6656 int group_no_capacity;
6657 int group_misfit_task; /* A cpu has a task too big for its capacity */
6658 #ifdef CONFIG_NUMA_BALANCING
6659 unsigned int nr_numa_running;
6660 unsigned int nr_preferred_running;
6665 * sd_lb_stats - Structure to store the statistics of a sched_domain
6666 * during load balancing.
6668 struct sd_lb_stats {
6669 struct sched_group *busiest; /* Busiest group in this sd */
6670 struct sched_group *local; /* Local group in this sd */
6671 unsigned long total_load; /* Total load of all groups in sd */
6672 unsigned long total_capacity; /* Total capacity of all groups in sd */
6673 unsigned long avg_load; /* Average load across all groups in sd */
6675 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6676 struct sg_lb_stats local_stat; /* Statistics of the local group */
6679 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6682 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6683 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6684 * We must however clear busiest_stat::avg_load because
6685 * update_sd_pick_busiest() reads this before assignment.
6687 *sds = (struct sd_lb_stats){
6691 .total_capacity = 0UL,
6694 .sum_nr_running = 0,
6695 .group_type = group_other,
6701 * get_sd_load_idx - Obtain the load index for a given sched domain.
6702 * @sd: The sched_domain whose load_idx is to be obtained.
6703 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6705 * Return: The load index.
6707 static inline int get_sd_load_idx(struct sched_domain *sd,
6708 enum cpu_idle_type idle)
6714 load_idx = sd->busy_idx;
6717 case CPU_NEWLY_IDLE:
6718 load_idx = sd->newidle_idx;
6721 load_idx = sd->idle_idx;
6728 static unsigned long scale_rt_capacity(int cpu)
6730 struct rq *rq = cpu_rq(cpu);
6731 u64 total, used, age_stamp, avg;
6735 * Since we're reading these variables without serialization make sure
6736 * we read them once before doing sanity checks on them.
6738 age_stamp = READ_ONCE(rq->age_stamp);
6739 avg = READ_ONCE(rq->rt_avg);
6740 delta = __rq_clock_broken(rq) - age_stamp;
6742 if (unlikely(delta < 0))
6745 total = sched_avg_period() + delta;
6747 used = div_u64(avg, total);
6750 * deadline bandwidth is defined at system level so we must
6751 * weight this bandwidth with the max capacity of the system.
6752 * As a reminder, avg_bw is 20bits width and
6753 * scale_cpu_capacity is 10 bits width
6755 used += div_u64(rq->dl.avg_bw, arch_scale_cpu_capacity(NULL, cpu));
6757 if (likely(used < SCHED_CAPACITY_SCALE))
6758 return SCHED_CAPACITY_SCALE - used;
6763 void init_max_cpu_capacity(struct max_cpu_capacity *mcc)
6765 raw_spin_lock_init(&mcc->lock);
6770 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6772 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6773 struct sched_group *sdg = sd->groups;
6774 struct max_cpu_capacity *mcc;
6775 unsigned long max_capacity;
6777 unsigned long flags;
6779 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6781 mcc = &cpu_rq(cpu)->rd->max_cpu_capacity;
6783 raw_spin_lock_irqsave(&mcc->lock, flags);
6784 max_capacity = mcc->val;
6785 max_cap_cpu = mcc->cpu;
6787 if ((max_capacity > capacity && max_cap_cpu == cpu) ||
6788 (max_capacity < capacity)) {
6789 mcc->val = capacity;
6791 #ifdef CONFIG_SCHED_DEBUG
6792 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6793 pr_info("CPU%d: update max cpu_capacity %lu\n", cpu, capacity);
6797 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6799 skip_unlock: __attribute__ ((unused));
6800 capacity *= scale_rt_capacity(cpu);
6801 capacity >>= SCHED_CAPACITY_SHIFT;
6806 cpu_rq(cpu)->cpu_capacity = capacity;
6807 sdg->sgc->capacity = capacity;
6808 sdg->sgc->max_capacity = capacity;
6811 void update_group_capacity(struct sched_domain *sd, int cpu)
6813 struct sched_domain *child = sd->child;
6814 struct sched_group *group, *sdg = sd->groups;
6815 unsigned long capacity, max_capacity;
6816 unsigned long interval;
6818 interval = msecs_to_jiffies(sd->balance_interval);
6819 interval = clamp(interval, 1UL, max_load_balance_interval);
6820 sdg->sgc->next_update = jiffies + interval;
6823 update_cpu_capacity(sd, cpu);
6830 if (child->flags & SD_OVERLAP) {
6832 * SD_OVERLAP domains cannot assume that child groups
6833 * span the current group.
6836 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6837 struct sched_group_capacity *sgc;
6838 struct rq *rq = cpu_rq(cpu);
6841 * build_sched_domains() -> init_sched_groups_capacity()
6842 * gets here before we've attached the domains to the
6845 * Use capacity_of(), which is set irrespective of domains
6846 * in update_cpu_capacity().
6848 * This avoids capacity from being 0 and
6849 * causing divide-by-zero issues on boot.
6851 if (unlikely(!rq->sd)) {
6852 capacity += capacity_of(cpu);
6854 sgc = rq->sd->groups->sgc;
6855 capacity += sgc->capacity;
6858 max_capacity = max(capacity, max_capacity);
6862 * !SD_OVERLAP domains can assume that child groups
6863 * span the current group.
6866 group = child->groups;
6868 struct sched_group_capacity *sgc = group->sgc;
6870 capacity += sgc->capacity;
6871 max_capacity = max(sgc->max_capacity, max_capacity);
6872 group = group->next;
6873 } while (group != child->groups);
6876 sdg->sgc->capacity = capacity;
6877 sdg->sgc->max_capacity = max_capacity;
6881 * Check whether the capacity of the rq has been noticeably reduced by side
6882 * activity. The imbalance_pct is used for the threshold.
6883 * Return true is the capacity is reduced
6886 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6888 return ((rq->cpu_capacity * sd->imbalance_pct) <
6889 (rq->cpu_capacity_orig * 100));
6893 * Group imbalance indicates (and tries to solve) the problem where balancing
6894 * groups is inadequate due to tsk_cpus_allowed() constraints.
6896 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6897 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6900 * { 0 1 2 3 } { 4 5 6 7 }
6903 * If we were to balance group-wise we'd place two tasks in the first group and
6904 * two tasks in the second group. Clearly this is undesired as it will overload
6905 * cpu 3 and leave one of the cpus in the second group unused.
6907 * The current solution to this issue is detecting the skew in the first group
6908 * by noticing the lower domain failed to reach balance and had difficulty
6909 * moving tasks due to affinity constraints.
6911 * When this is so detected; this group becomes a candidate for busiest; see
6912 * update_sd_pick_busiest(). And calculate_imbalance() and
6913 * find_busiest_group() avoid some of the usual balance conditions to allow it
6914 * to create an effective group imbalance.
6916 * This is a somewhat tricky proposition since the next run might not find the
6917 * group imbalance and decide the groups need to be balanced again. A most
6918 * subtle and fragile situation.
6921 static inline int sg_imbalanced(struct sched_group *group)
6923 return group->sgc->imbalance;
6927 * group_has_capacity returns true if the group has spare capacity that could
6928 * be used by some tasks.
6929 * We consider that a group has spare capacity if the * number of task is
6930 * smaller than the number of CPUs or if the utilization is lower than the
6931 * available capacity for CFS tasks.
6932 * For the latter, we use a threshold to stabilize the state, to take into
6933 * account the variance of the tasks' load and to return true if the available
6934 * capacity in meaningful for the load balancer.
6935 * As an example, an available capacity of 1% can appear but it doesn't make
6936 * any benefit for the load balance.
6939 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6941 if (sgs->sum_nr_running < sgs->group_weight)
6944 if ((sgs->group_capacity * 100) >
6945 (sgs->group_util * env->sd->imbalance_pct))
6952 * group_is_overloaded returns true if the group has more tasks than it can
6954 * group_is_overloaded is not equals to !group_has_capacity because a group
6955 * with the exact right number of tasks, has no more spare capacity but is not
6956 * overloaded so both group_has_capacity and group_is_overloaded return
6960 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6962 if (sgs->sum_nr_running <= sgs->group_weight)
6965 if ((sgs->group_capacity * 100) <
6966 (sgs->group_util * env->sd->imbalance_pct))
6974 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
6975 * per-cpu capacity than sched_group ref.
6978 group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
6980 return sg->sgc->max_capacity + capacity_margin - SCHED_LOAD_SCALE <
6981 ref->sgc->max_capacity;
6985 group_type group_classify(struct sched_group *group,
6986 struct sg_lb_stats *sgs)
6988 if (sgs->group_no_capacity)
6989 return group_overloaded;
6991 if (sg_imbalanced(group))
6992 return group_imbalanced;
6994 if (sgs->group_misfit_task)
6995 return group_misfit_task;
7001 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7002 * @env: The load balancing environment.
7003 * @group: sched_group whose statistics are to be updated.
7004 * @load_idx: Load index of sched_domain of this_cpu for load calc.
7005 * @local_group: Does group contain this_cpu.
7006 * @sgs: variable to hold the statistics for this group.
7007 * @overload: Indicate more than one runnable task for any CPU.
7008 * @overutilized: Indicate overutilization for any CPU.
7010 static inline void update_sg_lb_stats(struct lb_env *env,
7011 struct sched_group *group, int load_idx,
7012 int local_group, struct sg_lb_stats *sgs,
7013 bool *overload, bool *overutilized)
7018 memset(sgs, 0, sizeof(*sgs));
7020 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7021 struct rq *rq = cpu_rq(i);
7023 /* Bias balancing toward cpus of our domain */
7025 load = target_load(i, load_idx);
7027 load = source_load(i, load_idx);
7029 sgs->group_load += load;
7030 sgs->group_util += cpu_util(i);
7031 sgs->sum_nr_running += rq->cfs.h_nr_running;
7033 if (rq->nr_running > 1)
7036 #ifdef CONFIG_NUMA_BALANCING
7037 sgs->nr_numa_running += rq->nr_numa_running;
7038 sgs->nr_preferred_running += rq->nr_preferred_running;
7040 sgs->sum_weighted_load += weighted_cpuload(i);
7044 if (cpu_overutilized(i)) {
7045 *overutilized = true;
7046 if (!sgs->group_misfit_task && rq->misfit_task)
7047 sgs->group_misfit_task = capacity_of(i);
7051 /* Adjust by relative CPU capacity of the group */
7052 sgs->group_capacity = group->sgc->capacity;
7053 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7055 if (sgs->sum_nr_running)
7056 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7058 sgs->group_weight = group->group_weight;
7060 sgs->group_no_capacity = group_is_overloaded(env, sgs);
7061 sgs->group_type = group_classify(group, sgs);
7065 * update_sd_pick_busiest - return 1 on busiest group
7066 * @env: The load balancing environment.
7067 * @sds: sched_domain statistics
7068 * @sg: sched_group candidate to be checked for being the busiest
7069 * @sgs: sched_group statistics
7071 * Determine if @sg is a busier group than the previously selected
7074 * Return: %true if @sg is a busier group than the previously selected
7075 * busiest group. %false otherwise.
7077 static bool update_sd_pick_busiest(struct lb_env *env,
7078 struct sd_lb_stats *sds,
7079 struct sched_group *sg,
7080 struct sg_lb_stats *sgs)
7082 struct sg_lb_stats *busiest = &sds->busiest_stat;
7084 if (sgs->group_type > busiest->group_type)
7087 if (sgs->group_type < busiest->group_type)
7091 * Candidate sg doesn't face any serious load-balance problems
7092 * so don't pick it if the local sg is already filled up.
7094 if (sgs->group_type == group_other &&
7095 !group_has_capacity(env, &sds->local_stat))
7098 if (sgs->avg_load <= busiest->avg_load)
7102 * Candiate sg has no more than one task per cpu and has higher
7103 * per-cpu capacity. No reason to pull tasks to less capable cpus.
7105 if (sgs->sum_nr_running <= sgs->group_weight &&
7106 group_smaller_cpu_capacity(sds->local, sg))
7109 /* This is the busiest node in its class. */
7110 if (!(env->sd->flags & SD_ASYM_PACKING))
7114 * ASYM_PACKING needs to move all the work to the lowest
7115 * numbered CPUs in the group, therefore mark all groups
7116 * higher than ourself as busy.
7118 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
7122 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
7129 #ifdef CONFIG_NUMA_BALANCING
7130 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7132 if (sgs->sum_nr_running > sgs->nr_numa_running)
7134 if (sgs->sum_nr_running > sgs->nr_preferred_running)
7139 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7141 if (rq->nr_running > rq->nr_numa_running)
7143 if (rq->nr_running > rq->nr_preferred_running)
7148 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7153 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7157 #endif /* CONFIG_NUMA_BALANCING */
7160 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7161 * @env: The load balancing environment.
7162 * @sds: variable to hold the statistics for this sched_domain.
7164 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7166 struct sched_domain *child = env->sd->child;
7167 struct sched_group *sg = env->sd->groups;
7168 struct sg_lb_stats tmp_sgs;
7169 int load_idx, prefer_sibling = 0;
7170 bool overload = false, overutilized = false;
7172 if (child && child->flags & SD_PREFER_SIBLING)
7175 load_idx = get_sd_load_idx(env->sd, env->idle);
7178 struct sg_lb_stats *sgs = &tmp_sgs;
7181 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
7184 sgs = &sds->local_stat;
7186 if (env->idle != CPU_NEWLY_IDLE ||
7187 time_after_eq(jiffies, sg->sgc->next_update))
7188 update_group_capacity(env->sd, env->dst_cpu);
7191 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
7192 &overload, &overutilized);
7198 * In case the child domain prefers tasks go to siblings
7199 * first, lower the sg capacity so that we'll try
7200 * and move all the excess tasks away. We lower the capacity
7201 * of a group only if the local group has the capacity to fit
7202 * these excess tasks. The extra check prevents the case where
7203 * you always pull from the heaviest group when it is already
7204 * under-utilized (possible with a large weight task outweighs
7205 * the tasks on the system).
7207 if (prefer_sibling && sds->local &&
7208 group_has_capacity(env, &sds->local_stat) &&
7209 (sgs->sum_nr_running > 1)) {
7210 sgs->group_no_capacity = 1;
7211 sgs->group_type = group_classify(sg, sgs);
7215 * Ignore task groups with misfit tasks if local group has no
7216 * capacity or if per-cpu capacity isn't higher.
7218 if (sgs->group_type == group_misfit_task &&
7219 (!group_has_capacity(env, &sds->local_stat) ||
7220 !group_smaller_cpu_capacity(sg, sds->local)))
7221 sgs->group_type = group_other;
7223 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7225 sds->busiest_stat = *sgs;
7229 /* Now, start updating sd_lb_stats */
7230 sds->total_load += sgs->group_load;
7231 sds->total_capacity += sgs->group_capacity;
7234 } while (sg != env->sd->groups);
7236 if (env->sd->flags & SD_NUMA)
7237 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7239 env->src_grp_nr_running = sds->busiest_stat.sum_nr_running;
7241 if (!env->sd->parent) {
7242 /* update overload indicator if we are at root domain */
7243 if (env->dst_rq->rd->overload != overload)
7244 env->dst_rq->rd->overload = overload;
7246 /* Update over-utilization (tipping point, U >= 0) indicator */
7247 if (env->dst_rq->rd->overutilized != overutilized)
7248 env->dst_rq->rd->overutilized = overutilized;
7250 if (!env->dst_rq->rd->overutilized && overutilized)
7251 env->dst_rq->rd->overutilized = true;
7256 * check_asym_packing - Check to see if the group is packed into the
7259 * This is primarily intended to used at the sibling level. Some
7260 * cores like POWER7 prefer to use lower numbered SMT threads. In the
7261 * case of POWER7, it can move to lower SMT modes only when higher
7262 * threads are idle. When in lower SMT modes, the threads will
7263 * perform better since they share less core resources. Hence when we
7264 * have idle threads, we want them to be the higher ones.
7266 * This packing function is run on idle threads. It checks to see if
7267 * the busiest CPU in this domain (core in the P7 case) has a higher
7268 * CPU number than the packing function is being run on. Here we are
7269 * assuming lower CPU number will be equivalent to lower a SMT thread
7272 * Return: 1 when packing is required and a task should be moved to
7273 * this CPU. The amount of the imbalance is returned in *imbalance.
7275 * @env: The load balancing environment.
7276 * @sds: Statistics of the sched_domain which is to be packed
7278 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7282 if (!(env->sd->flags & SD_ASYM_PACKING))
7288 busiest_cpu = group_first_cpu(sds->busiest);
7289 if (env->dst_cpu > busiest_cpu)
7292 env->imbalance = DIV_ROUND_CLOSEST(
7293 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7294 SCHED_CAPACITY_SCALE);
7300 * fix_small_imbalance - Calculate the minor imbalance that exists
7301 * amongst the groups of a sched_domain, during
7303 * @env: The load balancing environment.
7304 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7307 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7309 unsigned long tmp, capa_now = 0, capa_move = 0;
7310 unsigned int imbn = 2;
7311 unsigned long scaled_busy_load_per_task;
7312 struct sg_lb_stats *local, *busiest;
7314 local = &sds->local_stat;
7315 busiest = &sds->busiest_stat;
7317 if (!local->sum_nr_running)
7318 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
7319 else if (busiest->load_per_task > local->load_per_task)
7322 scaled_busy_load_per_task =
7323 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7324 busiest->group_capacity;
7326 if (busiest->avg_load + scaled_busy_load_per_task >=
7327 local->avg_load + (scaled_busy_load_per_task * imbn)) {
7328 env->imbalance = busiest->load_per_task;
7333 * OK, we don't have enough imbalance to justify moving tasks,
7334 * however we may be able to increase total CPU capacity used by
7338 capa_now += busiest->group_capacity *
7339 min(busiest->load_per_task, busiest->avg_load);
7340 capa_now += local->group_capacity *
7341 min(local->load_per_task, local->avg_load);
7342 capa_now /= SCHED_CAPACITY_SCALE;
7344 /* Amount of load we'd subtract */
7345 if (busiest->avg_load > scaled_busy_load_per_task) {
7346 capa_move += busiest->group_capacity *
7347 min(busiest->load_per_task,
7348 busiest->avg_load - scaled_busy_load_per_task);
7351 /* Amount of load we'd add */
7352 if (busiest->avg_load * busiest->group_capacity <
7353 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7354 tmp = (busiest->avg_load * busiest->group_capacity) /
7355 local->group_capacity;
7357 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7358 local->group_capacity;
7360 capa_move += local->group_capacity *
7361 min(local->load_per_task, local->avg_load + tmp);
7362 capa_move /= SCHED_CAPACITY_SCALE;
7364 /* Move if we gain throughput */
7365 if (capa_move > capa_now)
7366 env->imbalance = busiest->load_per_task;
7370 * calculate_imbalance - Calculate the amount of imbalance present within the
7371 * groups of a given sched_domain during load balance.
7372 * @env: load balance environment
7373 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7375 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7377 unsigned long max_pull, load_above_capacity = ~0UL;
7378 struct sg_lb_stats *local, *busiest;
7380 local = &sds->local_stat;
7381 busiest = &sds->busiest_stat;
7383 if (busiest->group_type == group_imbalanced) {
7385 * In the group_imb case we cannot rely on group-wide averages
7386 * to ensure cpu-load equilibrium, look at wider averages. XXX
7388 busiest->load_per_task =
7389 min(busiest->load_per_task, sds->avg_load);
7393 * In the presence of smp nice balancing, certain scenarios can have
7394 * max load less than avg load(as we skip the groups at or below
7395 * its cpu_capacity, while calculating max_load..)
7397 if (busiest->avg_load <= sds->avg_load ||
7398 local->avg_load >= sds->avg_load) {
7399 /* Misfitting tasks should be migrated in any case */
7400 if (busiest->group_type == group_misfit_task) {
7401 env->imbalance = busiest->group_misfit_task;
7406 * Busiest group is overloaded, local is not, use the spare
7407 * cycles to maximize throughput
7409 if (busiest->group_type == group_overloaded &&
7410 local->group_type <= group_misfit_task) {
7411 env->imbalance = busiest->load_per_task;
7416 return fix_small_imbalance(env, sds);
7420 * If there aren't any idle cpus, avoid creating some.
7422 if (busiest->group_type == group_overloaded &&
7423 local->group_type == group_overloaded) {
7424 load_above_capacity = busiest->sum_nr_running *
7426 if (load_above_capacity > busiest->group_capacity)
7427 load_above_capacity -= busiest->group_capacity;
7429 load_above_capacity = ~0UL;
7433 * We're trying to get all the cpus to the average_load, so we don't
7434 * want to push ourselves above the average load, nor do we wish to
7435 * reduce the max loaded cpu below the average load. At the same time,
7436 * we also don't want to reduce the group load below the group capacity
7437 * (so that we can implement power-savings policies etc). Thus we look
7438 * for the minimum possible imbalance.
7440 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7442 /* How much load to actually move to equalise the imbalance */
7443 env->imbalance = min(
7444 max_pull * busiest->group_capacity,
7445 (sds->avg_load - local->avg_load) * local->group_capacity
7446 ) / SCHED_CAPACITY_SCALE;
7448 /* Boost imbalance to allow misfit task to be balanced. */
7449 if (busiest->group_type == group_misfit_task)
7450 env->imbalance = max_t(long, env->imbalance,
7451 busiest->group_misfit_task);
7454 * if *imbalance is less than the average load per runnable task
7455 * there is no guarantee that any tasks will be moved so we'll have
7456 * a think about bumping its value to force at least one task to be
7459 if (env->imbalance < busiest->load_per_task)
7460 return fix_small_imbalance(env, sds);
7463 /******* find_busiest_group() helpers end here *********************/
7466 * find_busiest_group - Returns the busiest group within the sched_domain
7467 * if there is an imbalance. If there isn't an imbalance, and
7468 * the user has opted for power-savings, it returns a group whose
7469 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
7470 * such a group exists.
7472 * Also calculates the amount of weighted load which should be moved
7473 * to restore balance.
7475 * @env: The load balancing environment.
7477 * Return: - The busiest group if imbalance exists.
7478 * - If no imbalance and user has opted for power-savings balance,
7479 * return the least loaded group whose CPUs can be
7480 * put to idle by rebalancing its tasks onto our group.
7482 static struct sched_group *find_busiest_group(struct lb_env *env)
7484 struct sg_lb_stats *local, *busiest;
7485 struct sd_lb_stats sds;
7487 init_sd_lb_stats(&sds);
7490 * Compute the various statistics relavent for load balancing at
7493 update_sd_lb_stats(env, &sds);
7495 if (energy_aware() && !env->dst_rq->rd->overutilized)
7498 local = &sds.local_stat;
7499 busiest = &sds.busiest_stat;
7501 /* ASYM feature bypasses nice load balance check */
7502 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
7503 check_asym_packing(env, &sds))
7506 /* There is no busy sibling group to pull tasks from */
7507 if (!sds.busiest || busiest->sum_nr_running == 0)
7510 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7511 / sds.total_capacity;
7514 * If the busiest group is imbalanced the below checks don't
7515 * work because they assume all things are equal, which typically
7516 * isn't true due to cpus_allowed constraints and the like.
7518 if (busiest->group_type == group_imbalanced)
7521 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7522 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7523 busiest->group_no_capacity)
7526 /* Misfitting tasks should be dealt with regardless of the avg load */
7527 if (busiest->group_type == group_misfit_task) {
7532 * If the local group is busier than the selected busiest group
7533 * don't try and pull any tasks.
7535 if (local->avg_load >= busiest->avg_load)
7539 * Don't pull any tasks if this group is already above the domain
7542 if (local->avg_load >= sds.avg_load)
7545 if (env->idle == CPU_IDLE) {
7547 * This cpu is idle. If the busiest group is not overloaded
7548 * and there is no imbalance between this and busiest group
7549 * wrt idle cpus, it is balanced. The imbalance becomes
7550 * significant if the diff is greater than 1 otherwise we
7551 * might end up to just move the imbalance on another group
7553 if ((busiest->group_type != group_overloaded) &&
7554 (local->idle_cpus <= (busiest->idle_cpus + 1)) &&
7555 !group_smaller_cpu_capacity(sds.busiest, sds.local))
7559 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7560 * imbalance_pct to be conservative.
7562 if (100 * busiest->avg_load <=
7563 env->sd->imbalance_pct * local->avg_load)
7568 env->busiest_group_type = busiest->group_type;
7569 /* Looks like there is an imbalance. Compute it */
7570 calculate_imbalance(env, &sds);
7579 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7581 static struct rq *find_busiest_queue(struct lb_env *env,
7582 struct sched_group *group)
7584 struct rq *busiest = NULL, *rq;
7585 unsigned long busiest_load = 0, busiest_capacity = 1;
7588 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7589 unsigned long capacity, wl;
7593 rt = fbq_classify_rq(rq);
7596 * We classify groups/runqueues into three groups:
7597 * - regular: there are !numa tasks
7598 * - remote: there are numa tasks that run on the 'wrong' node
7599 * - all: there is no distinction
7601 * In order to avoid migrating ideally placed numa tasks,
7602 * ignore those when there's better options.
7604 * If we ignore the actual busiest queue to migrate another
7605 * task, the next balance pass can still reduce the busiest
7606 * queue by moving tasks around inside the node.
7608 * If we cannot move enough load due to this classification
7609 * the next pass will adjust the group classification and
7610 * allow migration of more tasks.
7612 * Both cases only affect the total convergence complexity.
7614 if (rt > env->fbq_type)
7617 capacity = capacity_of(i);
7619 wl = weighted_cpuload(i);
7622 * When comparing with imbalance, use weighted_cpuload()
7623 * which is not scaled with the cpu capacity.
7626 if (rq->nr_running == 1 && wl > env->imbalance &&
7627 !check_cpu_capacity(rq, env->sd) &&
7628 env->busiest_group_type != group_misfit_task)
7632 * For the load comparisons with the other cpu's, consider
7633 * the weighted_cpuload() scaled with the cpu capacity, so
7634 * that the load can be moved away from the cpu that is
7635 * potentially running at a lower capacity.
7637 * Thus we're looking for max(wl_i / capacity_i), crosswise
7638 * multiplication to rid ourselves of the division works out
7639 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7640 * our previous maximum.
7642 if (wl * busiest_capacity > busiest_load * capacity) {
7644 busiest_capacity = capacity;
7653 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7654 * so long as it is large enough.
7656 #define MAX_PINNED_INTERVAL 512
7658 /* Working cpumask for load_balance and load_balance_newidle. */
7659 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7661 static int need_active_balance(struct lb_env *env)
7663 struct sched_domain *sd = env->sd;
7665 if (env->idle == CPU_NEWLY_IDLE) {
7668 * ASYM_PACKING needs to force migrate tasks from busy but
7669 * higher numbered CPUs in order to pack all tasks in the
7670 * lowest numbered CPUs.
7672 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7677 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7678 * It's worth migrating the task if the src_cpu's capacity is reduced
7679 * because of other sched_class or IRQs if more capacity stays
7680 * available on dst_cpu.
7682 if ((env->idle != CPU_NOT_IDLE) &&
7683 (env->src_rq->cfs.h_nr_running == 1)) {
7684 if ((check_cpu_capacity(env->src_rq, sd)) &&
7685 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7689 if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
7690 env->src_rq->cfs.h_nr_running == 1 &&
7691 cpu_overutilized(env->src_cpu) &&
7692 !cpu_overutilized(env->dst_cpu)) {
7696 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7699 static int active_load_balance_cpu_stop(void *data);
7701 static int should_we_balance(struct lb_env *env)
7703 struct sched_group *sg = env->sd->groups;
7704 struct cpumask *sg_cpus, *sg_mask;
7705 int cpu, balance_cpu = -1;
7708 * In the newly idle case, we will allow all the cpu's
7709 * to do the newly idle load balance.
7711 if (env->idle == CPU_NEWLY_IDLE)
7714 sg_cpus = sched_group_cpus(sg);
7715 sg_mask = sched_group_mask(sg);
7716 /* Try to find first idle cpu */
7717 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7718 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7725 if (balance_cpu == -1)
7726 balance_cpu = group_balance_cpu(sg);
7729 * First idle cpu or the first cpu(busiest) in this sched group
7730 * is eligible for doing load balancing at this and above domains.
7732 return balance_cpu == env->dst_cpu;
7736 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7737 * tasks if there is an imbalance.
7739 static int load_balance(int this_cpu, struct rq *this_rq,
7740 struct sched_domain *sd, enum cpu_idle_type idle,
7741 int *continue_balancing)
7743 int ld_moved, cur_ld_moved, active_balance = 0;
7744 struct sched_domain *sd_parent = sd->parent;
7745 struct sched_group *group;
7747 unsigned long flags;
7748 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7750 struct lb_env env = {
7752 .dst_cpu = this_cpu,
7754 .dst_grpmask = sched_group_cpus(sd->groups),
7756 .loop_break = sched_nr_migrate_break,
7759 .tasks = LIST_HEAD_INIT(env.tasks),
7763 * For NEWLY_IDLE load_balancing, we don't need to consider
7764 * other cpus in our group
7766 if (idle == CPU_NEWLY_IDLE)
7767 env.dst_grpmask = NULL;
7769 cpumask_copy(cpus, cpu_active_mask);
7771 schedstat_inc(sd, lb_count[idle]);
7774 if (!should_we_balance(&env)) {
7775 *continue_balancing = 0;
7779 group = find_busiest_group(&env);
7781 schedstat_inc(sd, lb_nobusyg[idle]);
7785 busiest = find_busiest_queue(&env, group);
7787 schedstat_inc(sd, lb_nobusyq[idle]);
7791 BUG_ON(busiest == env.dst_rq);
7793 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7795 env.src_cpu = busiest->cpu;
7796 env.src_rq = busiest;
7799 if (busiest->nr_running > 1) {
7801 * Attempt to move tasks. If find_busiest_group has found
7802 * an imbalance but busiest->nr_running <= 1, the group is
7803 * still unbalanced. ld_moved simply stays zero, so it is
7804 * correctly treated as an imbalance.
7806 env.flags |= LBF_ALL_PINNED;
7807 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7810 raw_spin_lock_irqsave(&busiest->lock, flags);
7813 * cur_ld_moved - load moved in current iteration
7814 * ld_moved - cumulative load moved across iterations
7816 cur_ld_moved = detach_tasks(&env);
7818 * We want to potentially lower env.src_cpu's OPP.
7821 update_capacity_of(env.src_cpu);
7824 * We've detached some tasks from busiest_rq. Every
7825 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7826 * unlock busiest->lock, and we are able to be sure
7827 * that nobody can manipulate the tasks in parallel.
7828 * See task_rq_lock() family for the details.
7831 raw_spin_unlock(&busiest->lock);
7835 ld_moved += cur_ld_moved;
7838 local_irq_restore(flags);
7840 if (env.flags & LBF_NEED_BREAK) {
7841 env.flags &= ~LBF_NEED_BREAK;
7846 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7847 * us and move them to an alternate dst_cpu in our sched_group
7848 * where they can run. The upper limit on how many times we
7849 * iterate on same src_cpu is dependent on number of cpus in our
7852 * This changes load balance semantics a bit on who can move
7853 * load to a given_cpu. In addition to the given_cpu itself
7854 * (or a ilb_cpu acting on its behalf where given_cpu is
7855 * nohz-idle), we now have balance_cpu in a position to move
7856 * load to given_cpu. In rare situations, this may cause
7857 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7858 * _independently_ and at _same_ time to move some load to
7859 * given_cpu) causing exceess load to be moved to given_cpu.
7860 * This however should not happen so much in practice and
7861 * moreover subsequent load balance cycles should correct the
7862 * excess load moved.
7864 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7866 /* Prevent to re-select dst_cpu via env's cpus */
7867 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7869 env.dst_rq = cpu_rq(env.new_dst_cpu);
7870 env.dst_cpu = env.new_dst_cpu;
7871 env.flags &= ~LBF_DST_PINNED;
7873 env.loop_break = sched_nr_migrate_break;
7876 * Go back to "more_balance" rather than "redo" since we
7877 * need to continue with same src_cpu.
7883 * We failed to reach balance because of affinity.
7886 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7888 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7889 *group_imbalance = 1;
7892 /* All tasks on this runqueue were pinned by CPU affinity */
7893 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7894 cpumask_clear_cpu(cpu_of(busiest), cpus);
7895 if (!cpumask_empty(cpus)) {
7897 env.loop_break = sched_nr_migrate_break;
7900 goto out_all_pinned;
7905 schedstat_inc(sd, lb_failed[idle]);
7907 * Increment the failure counter only on periodic balance.
7908 * We do not want newidle balance, which can be very
7909 * frequent, pollute the failure counter causing
7910 * excessive cache_hot migrations and active balances.
7912 if (idle != CPU_NEWLY_IDLE)
7913 if (env.src_grp_nr_running > 1)
7914 sd->nr_balance_failed++;
7916 if (need_active_balance(&env)) {
7917 raw_spin_lock_irqsave(&busiest->lock, flags);
7919 /* don't kick the active_load_balance_cpu_stop,
7920 * if the curr task on busiest cpu can't be
7923 if (!cpumask_test_cpu(this_cpu,
7924 tsk_cpus_allowed(busiest->curr))) {
7925 raw_spin_unlock_irqrestore(&busiest->lock,
7927 env.flags |= LBF_ALL_PINNED;
7928 goto out_one_pinned;
7932 * ->active_balance synchronizes accesses to
7933 * ->active_balance_work. Once set, it's cleared
7934 * only after active load balance is finished.
7936 if (!busiest->active_balance) {
7937 busiest->active_balance = 1;
7938 busiest->push_cpu = this_cpu;
7941 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7943 if (active_balance) {
7944 stop_one_cpu_nowait(cpu_of(busiest),
7945 active_load_balance_cpu_stop, busiest,
7946 &busiest->active_balance_work);
7950 * We've kicked active balancing, reset the failure
7953 sd->nr_balance_failed = sd->cache_nice_tries+1;
7956 sd->nr_balance_failed = 0;
7958 if (likely(!active_balance)) {
7959 /* We were unbalanced, so reset the balancing interval */
7960 sd->balance_interval = sd->min_interval;
7963 * If we've begun active balancing, start to back off. This
7964 * case may not be covered by the all_pinned logic if there
7965 * is only 1 task on the busy runqueue (because we don't call
7968 if (sd->balance_interval < sd->max_interval)
7969 sd->balance_interval *= 2;
7976 * We reach balance although we may have faced some affinity
7977 * constraints. Clear the imbalance flag if it was set.
7980 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7982 if (*group_imbalance)
7983 *group_imbalance = 0;
7988 * We reach balance because all tasks are pinned at this level so
7989 * we can't migrate them. Let the imbalance flag set so parent level
7990 * can try to migrate them.
7992 schedstat_inc(sd, lb_balanced[idle]);
7994 sd->nr_balance_failed = 0;
7997 /* tune up the balancing interval */
7998 if (((env.flags & LBF_ALL_PINNED) &&
7999 sd->balance_interval < MAX_PINNED_INTERVAL) ||
8000 (sd->balance_interval < sd->max_interval))
8001 sd->balance_interval *= 2;
8008 static inline unsigned long
8009 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
8011 unsigned long interval = sd->balance_interval;
8014 interval *= sd->busy_factor;
8016 /* scale ms to jiffies */
8017 interval = msecs_to_jiffies(interval);
8018 interval = clamp(interval, 1UL, max_load_balance_interval);
8024 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
8026 unsigned long interval, next;
8028 interval = get_sd_balance_interval(sd, cpu_busy);
8029 next = sd->last_balance + interval;
8031 if (time_after(*next_balance, next))
8032 *next_balance = next;
8036 * idle_balance is called by schedule() if this_cpu is about to become
8037 * idle. Attempts to pull tasks from other CPUs.
8039 static int idle_balance(struct rq *this_rq)
8041 unsigned long next_balance = jiffies + HZ;
8042 int this_cpu = this_rq->cpu;
8043 struct sched_domain *sd;
8044 int pulled_task = 0;
8047 idle_enter_fair(this_rq);
8050 * We must set idle_stamp _before_ calling idle_balance(), such that we
8051 * measure the duration of idle_balance() as idle time.
8053 this_rq->idle_stamp = rq_clock(this_rq);
8055 if (!energy_aware() &&
8056 (this_rq->avg_idle < sysctl_sched_migration_cost ||
8057 !this_rq->rd->overload)) {
8059 sd = rcu_dereference_check_sched_domain(this_rq->sd);
8061 update_next_balance(sd, 0, &next_balance);
8067 raw_spin_unlock(&this_rq->lock);
8069 update_blocked_averages(this_cpu);
8071 for_each_domain(this_cpu, sd) {
8072 int continue_balancing = 1;
8073 u64 t0, domain_cost;
8075 if (!(sd->flags & SD_LOAD_BALANCE))
8078 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8079 update_next_balance(sd, 0, &next_balance);
8083 if (sd->flags & SD_BALANCE_NEWIDLE) {
8084 t0 = sched_clock_cpu(this_cpu);
8086 pulled_task = load_balance(this_cpu, this_rq,
8088 &continue_balancing);
8090 domain_cost = sched_clock_cpu(this_cpu) - t0;
8091 if (domain_cost > sd->max_newidle_lb_cost)
8092 sd->max_newidle_lb_cost = domain_cost;
8094 curr_cost += domain_cost;
8097 update_next_balance(sd, 0, &next_balance);
8100 * Stop searching for tasks to pull if there are
8101 * now runnable tasks on this rq.
8103 if (pulled_task || this_rq->nr_running > 0)
8108 raw_spin_lock(&this_rq->lock);
8110 if (curr_cost > this_rq->max_idle_balance_cost)
8111 this_rq->max_idle_balance_cost = curr_cost;
8114 * While browsing the domains, we released the rq lock, a task could
8115 * have been enqueued in the meantime. Since we're not going idle,
8116 * pretend we pulled a task.
8118 if (this_rq->cfs.h_nr_running && !pulled_task)
8122 /* Move the next balance forward */
8123 if (time_after(this_rq->next_balance, next_balance))
8124 this_rq->next_balance = next_balance;
8126 /* Is there a task of a high priority class? */
8127 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8131 idle_exit_fair(this_rq);
8132 this_rq->idle_stamp = 0;
8139 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
8140 * running tasks off the busiest CPU onto idle CPUs. It requires at
8141 * least 1 task to be running on each physical CPU where possible, and
8142 * avoids physical / logical imbalances.
8144 static int active_load_balance_cpu_stop(void *data)
8146 struct rq *busiest_rq = data;
8147 int busiest_cpu = cpu_of(busiest_rq);
8148 int target_cpu = busiest_rq->push_cpu;
8149 struct rq *target_rq = cpu_rq(target_cpu);
8150 struct sched_domain *sd;
8151 struct task_struct *p = NULL;
8153 raw_spin_lock_irq(&busiest_rq->lock);
8155 /* make sure the requested cpu hasn't gone down in the meantime */
8156 if (unlikely(busiest_cpu != smp_processor_id() ||
8157 !busiest_rq->active_balance))
8160 /* Is there any task to move? */
8161 if (busiest_rq->nr_running <= 1)
8165 * This condition is "impossible", if it occurs
8166 * we need to fix it. Originally reported by
8167 * Bjorn Helgaas on a 128-cpu setup.
8169 BUG_ON(busiest_rq == target_rq);
8171 /* Search for an sd spanning us and the target CPU. */
8173 for_each_domain(target_cpu, sd) {
8174 if ((sd->flags & SD_LOAD_BALANCE) &&
8175 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
8180 struct lb_env env = {
8182 .dst_cpu = target_cpu,
8183 .dst_rq = target_rq,
8184 .src_cpu = busiest_rq->cpu,
8185 .src_rq = busiest_rq,
8189 schedstat_inc(sd, alb_count);
8191 p = detach_one_task(&env);
8193 schedstat_inc(sd, alb_pushed);
8195 * We want to potentially lower env.src_cpu's OPP.
8197 update_capacity_of(env.src_cpu);
8200 schedstat_inc(sd, alb_failed);
8204 busiest_rq->active_balance = 0;
8205 raw_spin_unlock(&busiest_rq->lock);
8208 attach_one_task(target_rq, p);
8215 static inline int on_null_domain(struct rq *rq)
8217 return unlikely(!rcu_dereference_sched(rq->sd));
8220 #ifdef CONFIG_NO_HZ_COMMON
8222 * idle load balancing details
8223 * - When one of the busy CPUs notice that there may be an idle rebalancing
8224 * needed, they will kick the idle load balancer, which then does idle
8225 * load balancing for all the idle CPUs.
8228 cpumask_var_t idle_cpus_mask;
8230 unsigned long next_balance; /* in jiffy units */
8231 } nohz ____cacheline_aligned;
8233 static inline int find_new_ilb(void)
8235 int ilb = cpumask_first(nohz.idle_cpus_mask);
8237 if (ilb < nr_cpu_ids && idle_cpu(ilb))
8244 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
8245 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
8246 * CPU (if there is one).
8248 static void nohz_balancer_kick(void)
8252 nohz.next_balance++;
8254 ilb_cpu = find_new_ilb();
8256 if (ilb_cpu >= nr_cpu_ids)
8259 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8262 * Use smp_send_reschedule() instead of resched_cpu().
8263 * This way we generate a sched IPI on the target cpu which
8264 * is idle. And the softirq performing nohz idle load balance
8265 * will be run before returning from the IPI.
8267 smp_send_reschedule(ilb_cpu);
8271 static inline void nohz_balance_exit_idle(int cpu)
8273 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8275 * Completely isolated CPUs don't ever set, so we must test.
8277 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
8278 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
8279 atomic_dec(&nohz.nr_cpus);
8281 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8285 static inline void set_cpu_sd_state_busy(void)
8287 struct sched_domain *sd;
8288 int cpu = smp_processor_id();
8291 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8293 if (!sd || !sd->nohz_idle)
8297 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
8302 void set_cpu_sd_state_idle(void)
8304 struct sched_domain *sd;
8305 int cpu = smp_processor_id();
8308 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8310 if (!sd || sd->nohz_idle)
8314 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
8320 * This routine will record that the cpu is going idle with tick stopped.
8321 * This info will be used in performing idle load balancing in the future.
8323 void nohz_balance_enter_idle(int cpu)
8326 * If this cpu is going down, then nothing needs to be done.
8328 if (!cpu_active(cpu))
8331 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
8335 * If we're a completely isolated CPU, we don't play.
8337 if (on_null_domain(cpu_rq(cpu)))
8340 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
8341 atomic_inc(&nohz.nr_cpus);
8342 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8345 static int sched_ilb_notifier(struct notifier_block *nfb,
8346 unsigned long action, void *hcpu)
8348 switch (action & ~CPU_TASKS_FROZEN) {
8350 nohz_balance_exit_idle(smp_processor_id());
8358 static DEFINE_SPINLOCK(balancing);
8361 * Scale the max load_balance interval with the number of CPUs in the system.
8362 * This trades load-balance latency on larger machines for less cross talk.
8364 void update_max_interval(void)
8366 max_load_balance_interval = HZ*num_online_cpus()/10;
8370 * It checks each scheduling domain to see if it is due to be balanced,
8371 * and initiates a balancing operation if so.
8373 * Balancing parameters are set up in init_sched_domains.
8375 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8377 int continue_balancing = 1;
8379 unsigned long interval;
8380 struct sched_domain *sd;
8381 /* Earliest time when we have to do rebalance again */
8382 unsigned long next_balance = jiffies + 60*HZ;
8383 int update_next_balance = 0;
8384 int need_serialize, need_decay = 0;
8387 update_blocked_averages(cpu);
8390 for_each_domain(cpu, sd) {
8392 * Decay the newidle max times here because this is a regular
8393 * visit to all the domains. Decay ~1% per second.
8395 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
8396 sd->max_newidle_lb_cost =
8397 (sd->max_newidle_lb_cost * 253) / 256;
8398 sd->next_decay_max_lb_cost = jiffies + HZ;
8401 max_cost += sd->max_newidle_lb_cost;
8403 if (!(sd->flags & SD_LOAD_BALANCE))
8407 * Stop the load balance at this level. There is another
8408 * CPU in our sched group which is doing load balancing more
8411 if (!continue_balancing) {
8417 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8419 need_serialize = sd->flags & SD_SERIALIZE;
8420 if (need_serialize) {
8421 if (!spin_trylock(&balancing))
8425 if (time_after_eq(jiffies, sd->last_balance + interval)) {
8426 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8428 * The LBF_DST_PINNED logic could have changed
8429 * env->dst_cpu, so we can't know our idle
8430 * state even if we migrated tasks. Update it.
8432 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8434 sd->last_balance = jiffies;
8435 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8438 spin_unlock(&balancing);
8440 if (time_after(next_balance, sd->last_balance + interval)) {
8441 next_balance = sd->last_balance + interval;
8442 update_next_balance = 1;
8447 * Ensure the rq-wide value also decays but keep it at a
8448 * reasonable floor to avoid funnies with rq->avg_idle.
8450 rq->max_idle_balance_cost =
8451 max((u64)sysctl_sched_migration_cost, max_cost);
8456 * next_balance will be updated only when there is a need.
8457 * When the cpu is attached to null domain for ex, it will not be
8460 if (likely(update_next_balance)) {
8461 rq->next_balance = next_balance;
8463 #ifdef CONFIG_NO_HZ_COMMON
8465 * If this CPU has been elected to perform the nohz idle
8466 * balance. Other idle CPUs have already rebalanced with
8467 * nohz_idle_balance() and nohz.next_balance has been
8468 * updated accordingly. This CPU is now running the idle load
8469 * balance for itself and we need to update the
8470 * nohz.next_balance accordingly.
8472 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8473 nohz.next_balance = rq->next_balance;
8478 #ifdef CONFIG_NO_HZ_COMMON
8480 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8481 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8483 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8485 int this_cpu = this_rq->cpu;
8488 /* Earliest time when we have to do rebalance again */
8489 unsigned long next_balance = jiffies + 60*HZ;
8490 int update_next_balance = 0;
8492 if (idle != CPU_IDLE ||
8493 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8496 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8497 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8501 * If this cpu gets work to do, stop the load balancing
8502 * work being done for other cpus. Next load
8503 * balancing owner will pick it up.
8508 rq = cpu_rq(balance_cpu);
8511 * If time for next balance is due,
8514 if (time_after_eq(jiffies, rq->next_balance)) {
8515 raw_spin_lock_irq(&rq->lock);
8516 update_rq_clock(rq);
8517 update_idle_cpu_load(rq);
8518 raw_spin_unlock_irq(&rq->lock);
8519 rebalance_domains(rq, CPU_IDLE);
8522 if (time_after(next_balance, rq->next_balance)) {
8523 next_balance = rq->next_balance;
8524 update_next_balance = 1;
8529 * next_balance will be updated only when there is a need.
8530 * When the CPU is attached to null domain for ex, it will not be
8533 if (likely(update_next_balance))
8534 nohz.next_balance = next_balance;
8536 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8540 * Current heuristic for kicking the idle load balancer in the presence
8541 * of an idle cpu in the system.
8542 * - This rq has more than one task.
8543 * - This rq has at least one CFS task and the capacity of the CPU is
8544 * significantly reduced because of RT tasks or IRQs.
8545 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8546 * multiple busy cpu.
8547 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8548 * domain span are idle.
8550 static inline bool nohz_kick_needed(struct rq *rq)
8552 unsigned long now = jiffies;
8553 struct sched_domain *sd;
8554 struct sched_group_capacity *sgc;
8555 int nr_busy, cpu = rq->cpu;
8558 if (unlikely(rq->idle_balance))
8562 * We may be recently in ticked or tickless idle mode. At the first
8563 * busy tick after returning from idle, we will update the busy stats.
8565 set_cpu_sd_state_busy();
8566 nohz_balance_exit_idle(cpu);
8569 * None are in tickless mode and hence no need for NOHZ idle load
8572 if (likely(!atomic_read(&nohz.nr_cpus)))
8575 if (time_before(now, nohz.next_balance))
8578 if (rq->nr_running >= 2 &&
8579 (!energy_aware() || cpu_overutilized(cpu)))
8583 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8584 if (sd && !energy_aware()) {
8585 sgc = sd->groups->sgc;
8586 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8595 sd = rcu_dereference(rq->sd);
8597 if ((rq->cfs.h_nr_running >= 1) &&
8598 check_cpu_capacity(rq, sd)) {
8604 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8605 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8606 sched_domain_span(sd)) < cpu)) {
8616 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8620 * run_rebalance_domains is triggered when needed from the scheduler tick.
8621 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8623 static void run_rebalance_domains(struct softirq_action *h)
8625 struct rq *this_rq = this_rq();
8626 enum cpu_idle_type idle = this_rq->idle_balance ?
8627 CPU_IDLE : CPU_NOT_IDLE;
8630 * If this cpu has a pending nohz_balance_kick, then do the
8631 * balancing on behalf of the other idle cpus whose ticks are
8632 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8633 * give the idle cpus a chance to load balance. Else we may
8634 * load balance only within the local sched_domain hierarchy
8635 * and abort nohz_idle_balance altogether if we pull some load.
8637 nohz_idle_balance(this_rq, idle);
8638 rebalance_domains(this_rq, idle);
8642 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8644 void trigger_load_balance(struct rq *rq)
8646 /* Don't need to rebalance while attached to NULL domain */
8647 if (unlikely(on_null_domain(rq)))
8650 if (time_after_eq(jiffies, rq->next_balance))
8651 raise_softirq(SCHED_SOFTIRQ);
8652 #ifdef CONFIG_NO_HZ_COMMON
8653 if (nohz_kick_needed(rq))
8654 nohz_balancer_kick();
8658 static void rq_online_fair(struct rq *rq)
8662 update_runtime_enabled(rq);
8665 static void rq_offline_fair(struct rq *rq)
8669 /* Ensure any throttled groups are reachable by pick_next_task */
8670 unthrottle_offline_cfs_rqs(rq);
8673 #endif /* CONFIG_SMP */
8676 * scheduler tick hitting a task of our scheduling class:
8678 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8680 struct cfs_rq *cfs_rq;
8681 struct sched_entity *se = &curr->se;
8683 for_each_sched_entity(se) {
8684 cfs_rq = cfs_rq_of(se);
8685 entity_tick(cfs_rq, se, queued);
8688 if (static_branch_unlikely(&sched_numa_balancing))
8689 task_tick_numa(rq, curr);
8691 if (!rq->rd->overutilized && cpu_overutilized(task_cpu(curr)))
8692 rq->rd->overutilized = true;
8694 rq->misfit_task = !task_fits_max(curr, rq->cpu);
8698 * called on fork with the child task as argument from the parent's context
8699 * - child not yet on the tasklist
8700 * - preemption disabled
8702 static void task_fork_fair(struct task_struct *p)
8704 struct cfs_rq *cfs_rq;
8705 struct sched_entity *se = &p->se, *curr;
8706 int this_cpu = smp_processor_id();
8707 struct rq *rq = this_rq();
8708 unsigned long flags;
8710 raw_spin_lock_irqsave(&rq->lock, flags);
8712 update_rq_clock(rq);
8714 cfs_rq = task_cfs_rq(current);
8715 curr = cfs_rq->curr;
8718 * Not only the cpu but also the task_group of the parent might have
8719 * been changed after parent->se.parent,cfs_rq were copied to
8720 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8721 * of child point to valid ones.
8724 __set_task_cpu(p, this_cpu);
8727 update_curr(cfs_rq);
8730 se->vruntime = curr->vruntime;
8731 place_entity(cfs_rq, se, 1);
8733 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8735 * Upon rescheduling, sched_class::put_prev_task() will place
8736 * 'current' within the tree based on its new key value.
8738 swap(curr->vruntime, se->vruntime);
8742 se->vruntime -= cfs_rq->min_vruntime;
8744 raw_spin_unlock_irqrestore(&rq->lock, flags);
8748 * Priority of the task has changed. Check to see if we preempt
8752 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8754 if (!task_on_rq_queued(p))
8758 * Reschedule if we are currently running on this runqueue and
8759 * our priority decreased, or if we are not currently running on
8760 * this runqueue and our priority is higher than the current's
8762 if (rq->curr == p) {
8763 if (p->prio > oldprio)
8766 check_preempt_curr(rq, p, 0);
8769 static inline bool vruntime_normalized(struct task_struct *p)
8771 struct sched_entity *se = &p->se;
8774 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8775 * the dequeue_entity(.flags=0) will already have normalized the
8782 * When !on_rq, vruntime of the task has usually NOT been normalized.
8783 * But there are some cases where it has already been normalized:
8785 * - A forked child which is waiting for being woken up by
8786 * wake_up_new_task().
8787 * - A task which has been woken up by try_to_wake_up() and
8788 * waiting for actually being woken up by sched_ttwu_pending().
8790 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8796 static void detach_task_cfs_rq(struct task_struct *p)
8798 struct sched_entity *se = &p->se;
8799 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8801 if (!vruntime_normalized(p)) {
8803 * Fix up our vruntime so that the current sleep doesn't
8804 * cause 'unlimited' sleep bonus.
8806 place_entity(cfs_rq, se, 0);
8807 se->vruntime -= cfs_rq->min_vruntime;
8810 /* Catch up with the cfs_rq and remove our load when we leave */
8811 detach_entity_load_avg(cfs_rq, se);
8814 static void attach_task_cfs_rq(struct task_struct *p)
8816 struct sched_entity *se = &p->se;
8817 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8819 #ifdef CONFIG_FAIR_GROUP_SCHED
8821 * Since the real-depth could have been changed (only FAIR
8822 * class maintain depth value), reset depth properly.
8824 se->depth = se->parent ? se->parent->depth + 1 : 0;
8827 /* Synchronize task with its cfs_rq */
8828 attach_entity_load_avg(cfs_rq, se);
8830 if (!vruntime_normalized(p))
8831 se->vruntime += cfs_rq->min_vruntime;
8834 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8836 detach_task_cfs_rq(p);
8839 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8841 attach_task_cfs_rq(p);
8843 if (task_on_rq_queued(p)) {
8845 * We were most likely switched from sched_rt, so
8846 * kick off the schedule if running, otherwise just see
8847 * if we can still preempt the current task.
8852 check_preempt_curr(rq, p, 0);
8856 /* Account for a task changing its policy or group.
8858 * This routine is mostly called to set cfs_rq->curr field when a task
8859 * migrates between groups/classes.
8861 static void set_curr_task_fair(struct rq *rq)
8863 struct sched_entity *se = &rq->curr->se;
8865 for_each_sched_entity(se) {
8866 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8868 set_next_entity(cfs_rq, se);
8869 /* ensure bandwidth has been allocated on our new cfs_rq */
8870 account_cfs_rq_runtime(cfs_rq, 0);
8874 void init_cfs_rq(struct cfs_rq *cfs_rq)
8876 cfs_rq->tasks_timeline = RB_ROOT;
8877 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8878 #ifndef CONFIG_64BIT
8879 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8882 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8883 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8887 #ifdef CONFIG_FAIR_GROUP_SCHED
8888 static void task_move_group_fair(struct task_struct *p)
8890 detach_task_cfs_rq(p);
8891 set_task_rq(p, task_cpu(p));
8894 /* Tell se's cfs_rq has been changed -- migrated */
8895 p->se.avg.last_update_time = 0;
8897 attach_task_cfs_rq(p);
8900 void free_fair_sched_group(struct task_group *tg)
8904 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8906 for_each_possible_cpu(i) {
8908 kfree(tg->cfs_rq[i]);
8911 remove_entity_load_avg(tg->se[i]);
8920 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8922 struct cfs_rq *cfs_rq;
8923 struct sched_entity *se;
8926 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8929 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8933 tg->shares = NICE_0_LOAD;
8935 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8937 for_each_possible_cpu(i) {
8938 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8939 GFP_KERNEL, cpu_to_node(i));
8943 se = kzalloc_node(sizeof(struct sched_entity),
8944 GFP_KERNEL, cpu_to_node(i));
8948 init_cfs_rq(cfs_rq);
8949 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8950 init_entity_runnable_average(se);
8961 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8963 struct rq *rq = cpu_rq(cpu);
8964 unsigned long flags;
8967 * Only empty task groups can be destroyed; so we can speculatively
8968 * check on_list without danger of it being re-added.
8970 if (!tg->cfs_rq[cpu]->on_list)
8973 raw_spin_lock_irqsave(&rq->lock, flags);
8974 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8975 raw_spin_unlock_irqrestore(&rq->lock, flags);
8978 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8979 struct sched_entity *se, int cpu,
8980 struct sched_entity *parent)
8982 struct rq *rq = cpu_rq(cpu);
8986 init_cfs_rq_runtime(cfs_rq);
8988 tg->cfs_rq[cpu] = cfs_rq;
8991 /* se could be NULL for root_task_group */
8996 se->cfs_rq = &rq->cfs;
8999 se->cfs_rq = parent->my_q;
9000 se->depth = parent->depth + 1;
9004 /* guarantee group entities always have weight */
9005 update_load_set(&se->load, NICE_0_LOAD);
9006 se->parent = parent;
9009 static DEFINE_MUTEX(shares_mutex);
9011 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
9014 unsigned long flags;
9017 * We can't change the weight of the root cgroup.
9022 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
9024 mutex_lock(&shares_mutex);
9025 if (tg->shares == shares)
9028 tg->shares = shares;
9029 for_each_possible_cpu(i) {
9030 struct rq *rq = cpu_rq(i);
9031 struct sched_entity *se;
9034 /* Propagate contribution to hierarchy */
9035 raw_spin_lock_irqsave(&rq->lock, flags);
9037 /* Possible calls to update_curr() need rq clock */
9038 update_rq_clock(rq);
9039 for_each_sched_entity(se)
9040 update_cfs_shares(group_cfs_rq(se));
9041 raw_spin_unlock_irqrestore(&rq->lock, flags);
9045 mutex_unlock(&shares_mutex);
9048 #else /* CONFIG_FAIR_GROUP_SCHED */
9050 void free_fair_sched_group(struct task_group *tg) { }
9052 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
9057 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
9059 #endif /* CONFIG_FAIR_GROUP_SCHED */
9062 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
9064 struct sched_entity *se = &task->se;
9065 unsigned int rr_interval = 0;
9068 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
9071 if (rq->cfs.load.weight)
9072 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
9078 * All the scheduling class methods:
9080 const struct sched_class fair_sched_class = {
9081 .next = &idle_sched_class,
9082 .enqueue_task = enqueue_task_fair,
9083 .dequeue_task = dequeue_task_fair,
9084 .yield_task = yield_task_fair,
9085 .yield_to_task = yield_to_task_fair,
9087 .check_preempt_curr = check_preempt_wakeup,
9089 .pick_next_task = pick_next_task_fair,
9090 .put_prev_task = put_prev_task_fair,
9093 .select_task_rq = select_task_rq_fair,
9094 .migrate_task_rq = migrate_task_rq_fair,
9096 .rq_online = rq_online_fair,
9097 .rq_offline = rq_offline_fair,
9099 .task_waking = task_waking_fair,
9100 .task_dead = task_dead_fair,
9101 .set_cpus_allowed = set_cpus_allowed_common,
9104 .set_curr_task = set_curr_task_fair,
9105 .task_tick = task_tick_fair,
9106 .task_fork = task_fork_fair,
9108 .prio_changed = prio_changed_fair,
9109 .switched_from = switched_from_fair,
9110 .switched_to = switched_to_fair,
9112 .get_rr_interval = get_rr_interval_fair,
9114 .update_curr = update_curr_fair,
9116 #ifdef CONFIG_FAIR_GROUP_SCHED
9117 .task_move_group = task_move_group_fair,
9121 #ifdef CONFIG_SCHED_DEBUG
9122 void print_cfs_stats(struct seq_file *m, int cpu)
9124 struct cfs_rq *cfs_rq;
9127 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
9128 print_cfs_rq(m, cpu, cfs_rq);
9132 #ifdef CONFIG_NUMA_BALANCING
9133 void show_numa_stats(struct task_struct *p, struct seq_file *m)
9136 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
9138 for_each_online_node(node) {
9139 if (p->numa_faults) {
9140 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
9141 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
9143 if (p->numa_group) {
9144 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
9145 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
9147 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
9150 #endif /* CONFIG_NUMA_BALANCING */
9151 #endif /* CONFIG_SCHED_DEBUG */
9153 __init void init_sched_fair_class(void)
9156 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
9158 #ifdef CONFIG_NO_HZ_COMMON
9159 nohz.next_balance = jiffies;
9160 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
9161 cpu_notifier(sched_ilb_notifier, 0);