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);
2591 /* delta_w is the amount already accumulated against our next period */
2592 delta_w = sa->period_contrib;
2593 if (delta + delta_w >= 1024) {
2596 /* how much left for next period will start over, we don't know yet */
2597 sa->period_contrib = 0;
2600 * Now that we know we're crossing a period boundary, figure
2601 * out how much from delta we need to complete the current
2602 * period and accrue it.
2604 delta_w = 1024 - delta_w;
2605 scaled_delta_w = cap_scale(delta_w, scale_freq);
2607 sa->load_sum += weight * scaled_delta_w;
2609 cfs_rq->runnable_load_sum +=
2610 weight * scaled_delta_w;
2614 sa->util_sum += scaled_delta_w * scale_cpu;
2618 /* Figure out how many additional periods this update spans */
2619 periods = delta / 1024;
2622 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2624 cfs_rq->runnable_load_sum =
2625 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2627 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2629 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2630 contrib = __compute_runnable_contrib(periods);
2631 contrib = cap_scale(contrib, scale_freq);
2633 sa->load_sum += weight * contrib;
2635 cfs_rq->runnable_load_sum += weight * contrib;
2638 sa->util_sum += contrib * scale_cpu;
2641 /* Remainder of delta accrued against u_0` */
2642 scaled_delta = cap_scale(delta, scale_freq);
2644 sa->load_sum += weight * scaled_delta;
2646 cfs_rq->runnable_load_sum += weight * scaled_delta;
2649 sa->util_sum += scaled_delta * scale_cpu;
2651 sa->period_contrib += delta;
2654 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2656 cfs_rq->runnable_load_avg =
2657 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2659 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2665 #ifdef CONFIG_FAIR_GROUP_SCHED
2667 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2668 * and effective_load (which is not done because it is too costly).
2670 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2672 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2674 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2675 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2676 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2680 #else /* CONFIG_FAIR_GROUP_SCHED */
2681 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2682 #endif /* CONFIG_FAIR_GROUP_SCHED */
2684 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2686 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2687 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2689 struct sched_avg *sa = &cfs_rq->avg;
2690 int decayed, removed = 0;
2692 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2693 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2694 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2695 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2699 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2700 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2701 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2702 sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2705 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2706 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2708 #ifndef CONFIG_64BIT
2710 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2713 return decayed || removed;
2716 /* Update task and its cfs_rq load average */
2717 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2719 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2720 u64 now = cfs_rq_clock_task(cfs_rq);
2721 int cpu = cpu_of(rq_of(cfs_rq));
2724 * Track task load average for carrying it to new CPU after migrated, and
2725 * track group sched_entity load average for task_h_load calc in migration
2727 __update_load_avg(now, cpu, &se->avg,
2728 se->on_rq * scale_load_down(se->load.weight),
2729 cfs_rq->curr == se, NULL);
2731 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2732 update_tg_load_avg(cfs_rq, 0);
2735 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2737 if (!sched_feat(ATTACH_AGE_LOAD))
2741 * If we got migrated (either between CPUs or between cgroups) we'll
2742 * have aged the average right before clearing @last_update_time.
2744 if (se->avg.last_update_time) {
2745 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2746 &se->avg, 0, 0, NULL);
2749 * XXX: we could have just aged the entire load away if we've been
2750 * absent from the fair class for too long.
2755 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2756 cfs_rq->avg.load_avg += se->avg.load_avg;
2757 cfs_rq->avg.load_sum += se->avg.load_sum;
2758 cfs_rq->avg.util_avg += se->avg.util_avg;
2759 cfs_rq->avg.util_sum += se->avg.util_sum;
2762 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2764 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2765 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2766 cfs_rq->curr == se, NULL);
2768 cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
2769 cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
2770 cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
2771 cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
2774 /* Add the load generated by se into cfs_rq's load average */
2776 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2778 struct sched_avg *sa = &se->avg;
2779 u64 now = cfs_rq_clock_task(cfs_rq);
2780 int migrated, decayed;
2782 migrated = !sa->last_update_time;
2784 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2785 se->on_rq * scale_load_down(se->load.weight),
2786 cfs_rq->curr == se, NULL);
2789 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2791 cfs_rq->runnable_load_avg += sa->load_avg;
2792 cfs_rq->runnable_load_sum += sa->load_sum;
2795 attach_entity_load_avg(cfs_rq, se);
2797 if (decayed || migrated)
2798 update_tg_load_avg(cfs_rq, 0);
2801 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2803 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2805 update_load_avg(se, 1);
2807 cfs_rq->runnable_load_avg =
2808 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2809 cfs_rq->runnable_load_sum =
2810 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2813 #ifndef CONFIG_64BIT
2814 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2816 u64 last_update_time_copy;
2817 u64 last_update_time;
2820 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2822 last_update_time = cfs_rq->avg.last_update_time;
2823 } while (last_update_time != last_update_time_copy);
2825 return last_update_time;
2828 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2830 return cfs_rq->avg.last_update_time;
2835 * Task first catches up with cfs_rq, and then subtract
2836 * itself from the cfs_rq (task must be off the queue now).
2838 void remove_entity_load_avg(struct sched_entity *se)
2840 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2841 u64 last_update_time;
2844 * Newly created task or never used group entity should not be removed
2845 * from its (source) cfs_rq
2847 if (se->avg.last_update_time == 0)
2850 last_update_time = cfs_rq_last_update_time(cfs_rq);
2852 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2853 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2854 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2858 * Update the rq's load with the elapsed running time before entering
2859 * idle. if the last scheduled task is not a CFS task, idle_enter will
2860 * be the only way to update the runnable statistic.
2862 void idle_enter_fair(struct rq *this_rq)
2867 * Update the rq's load with the elapsed idle time before a task is
2868 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2869 * be the only way to update the runnable statistic.
2871 void idle_exit_fair(struct rq *this_rq)
2875 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2877 return cfs_rq->runnable_load_avg;
2880 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2882 return cfs_rq->avg.load_avg;
2885 static int idle_balance(struct rq *this_rq);
2887 #else /* CONFIG_SMP */
2889 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2891 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2893 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2894 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2897 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2899 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2901 static inline int idle_balance(struct rq *rq)
2906 #endif /* CONFIG_SMP */
2908 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2910 #ifdef CONFIG_SCHEDSTATS
2911 struct task_struct *tsk = NULL;
2913 if (entity_is_task(se))
2916 if (se->statistics.sleep_start) {
2917 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2922 if (unlikely(delta > se->statistics.sleep_max))
2923 se->statistics.sleep_max = delta;
2925 se->statistics.sleep_start = 0;
2926 se->statistics.sum_sleep_runtime += delta;
2929 account_scheduler_latency(tsk, delta >> 10, 1);
2930 trace_sched_stat_sleep(tsk, delta);
2933 if (se->statistics.block_start) {
2934 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2939 if (unlikely(delta > se->statistics.block_max))
2940 se->statistics.block_max = delta;
2942 se->statistics.block_start = 0;
2943 se->statistics.sum_sleep_runtime += delta;
2946 if (tsk->in_iowait) {
2947 se->statistics.iowait_sum += delta;
2948 se->statistics.iowait_count++;
2949 trace_sched_stat_iowait(tsk, delta);
2952 trace_sched_stat_blocked(tsk, delta);
2955 * Blocking time is in units of nanosecs, so shift by
2956 * 20 to get a milliseconds-range estimation of the
2957 * amount of time that the task spent sleeping:
2959 if (unlikely(prof_on == SLEEP_PROFILING)) {
2960 profile_hits(SLEEP_PROFILING,
2961 (void *)get_wchan(tsk),
2964 account_scheduler_latency(tsk, delta >> 10, 0);
2970 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2972 #ifdef CONFIG_SCHED_DEBUG
2973 s64 d = se->vruntime - cfs_rq->min_vruntime;
2978 if (d > 3*sysctl_sched_latency)
2979 schedstat_inc(cfs_rq, nr_spread_over);
2984 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2986 u64 vruntime = cfs_rq->min_vruntime;
2989 * The 'current' period is already promised to the current tasks,
2990 * however the extra weight of the new task will slow them down a
2991 * little, place the new task so that it fits in the slot that
2992 * stays open at the end.
2994 if (initial && sched_feat(START_DEBIT))
2995 vruntime += sched_vslice(cfs_rq, se);
2997 /* sleeps up to a single latency don't count. */
2999 unsigned long thresh = sysctl_sched_latency;
3002 * Halve their sleep time's effect, to allow
3003 * for a gentler effect of sleepers:
3005 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3011 /* ensure we never gain time by being placed backwards. */
3012 se->vruntime = max_vruntime(se->vruntime, vruntime);
3015 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3018 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3021 * Update the normalized vruntime before updating min_vruntime
3022 * through calling update_curr().
3024 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3025 se->vruntime += cfs_rq->min_vruntime;
3028 * Update run-time statistics of the 'current'.
3030 update_curr(cfs_rq);
3031 enqueue_entity_load_avg(cfs_rq, se);
3032 account_entity_enqueue(cfs_rq, se);
3033 update_cfs_shares(cfs_rq);
3035 if (flags & ENQUEUE_WAKEUP) {
3036 place_entity(cfs_rq, se, 0);
3037 enqueue_sleeper(cfs_rq, se);
3040 update_stats_enqueue(cfs_rq, se);
3041 check_spread(cfs_rq, se);
3042 if (se != cfs_rq->curr)
3043 __enqueue_entity(cfs_rq, se);
3046 if (cfs_rq->nr_running == 1) {
3047 list_add_leaf_cfs_rq(cfs_rq);
3048 check_enqueue_throttle(cfs_rq);
3052 static void __clear_buddies_last(struct sched_entity *se)
3054 for_each_sched_entity(se) {
3055 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3056 if (cfs_rq->last != se)
3059 cfs_rq->last = NULL;
3063 static void __clear_buddies_next(struct sched_entity *se)
3065 for_each_sched_entity(se) {
3066 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3067 if (cfs_rq->next != se)
3070 cfs_rq->next = NULL;
3074 static void __clear_buddies_skip(struct sched_entity *se)
3076 for_each_sched_entity(se) {
3077 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3078 if (cfs_rq->skip != se)
3081 cfs_rq->skip = NULL;
3085 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3087 if (cfs_rq->last == se)
3088 __clear_buddies_last(se);
3090 if (cfs_rq->next == se)
3091 __clear_buddies_next(se);
3093 if (cfs_rq->skip == se)
3094 __clear_buddies_skip(se);
3097 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3100 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3103 * Update run-time statistics of the 'current'.
3105 update_curr(cfs_rq);
3106 dequeue_entity_load_avg(cfs_rq, se);
3108 update_stats_dequeue(cfs_rq, se);
3109 if (flags & DEQUEUE_SLEEP) {
3110 #ifdef CONFIG_SCHEDSTATS
3111 if (entity_is_task(se)) {
3112 struct task_struct *tsk = task_of(se);
3114 if (tsk->state & TASK_INTERRUPTIBLE)
3115 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3116 if (tsk->state & TASK_UNINTERRUPTIBLE)
3117 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3122 clear_buddies(cfs_rq, se);
3124 if (se != cfs_rq->curr)
3125 __dequeue_entity(cfs_rq, se);
3127 account_entity_dequeue(cfs_rq, se);
3130 * Normalize the entity after updating the min_vruntime because the
3131 * update can refer to the ->curr item and we need to reflect this
3132 * movement in our normalized position.
3134 if (!(flags & DEQUEUE_SLEEP))
3135 se->vruntime -= cfs_rq->min_vruntime;
3137 /* return excess runtime on last dequeue */
3138 return_cfs_rq_runtime(cfs_rq);
3140 update_min_vruntime(cfs_rq);
3141 update_cfs_shares(cfs_rq);
3145 * Preempt the current task with a newly woken task if needed:
3148 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3150 unsigned long ideal_runtime, delta_exec;
3151 struct sched_entity *se;
3154 ideal_runtime = sched_slice(cfs_rq, curr);
3155 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3156 if (delta_exec > ideal_runtime) {
3157 resched_curr(rq_of(cfs_rq));
3159 * The current task ran long enough, ensure it doesn't get
3160 * re-elected due to buddy favours.
3162 clear_buddies(cfs_rq, curr);
3167 * Ensure that a task that missed wakeup preemption by a
3168 * narrow margin doesn't have to wait for a full slice.
3169 * This also mitigates buddy induced latencies under load.
3171 if (delta_exec < sysctl_sched_min_granularity)
3174 se = __pick_first_entity(cfs_rq);
3175 delta = curr->vruntime - se->vruntime;
3180 if (delta > ideal_runtime)
3181 resched_curr(rq_of(cfs_rq));
3185 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3187 /* 'current' is not kept within the tree. */
3190 * Any task has to be enqueued before it get to execute on
3191 * a CPU. So account for the time it spent waiting on the
3194 update_stats_wait_end(cfs_rq, se);
3195 __dequeue_entity(cfs_rq, se);
3196 update_load_avg(se, 1);
3199 update_stats_curr_start(cfs_rq, se);
3201 #ifdef CONFIG_SCHEDSTATS
3203 * Track our maximum slice length, if the CPU's load is at
3204 * least twice that of our own weight (i.e. dont track it
3205 * when there are only lesser-weight tasks around):
3207 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3208 se->statistics.slice_max = max(se->statistics.slice_max,
3209 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3212 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3216 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3219 * Pick the next process, keeping these things in mind, in this order:
3220 * 1) keep things fair between processes/task groups
3221 * 2) pick the "next" process, since someone really wants that to run
3222 * 3) pick the "last" process, for cache locality
3223 * 4) do not run the "skip" process, if something else is available
3225 static struct sched_entity *
3226 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3228 struct sched_entity *left = __pick_first_entity(cfs_rq);
3229 struct sched_entity *se;
3232 * If curr is set we have to see if its left of the leftmost entity
3233 * still in the tree, provided there was anything in the tree at all.
3235 if (!left || (curr && entity_before(curr, left)))
3238 se = left; /* ideally we run the leftmost entity */
3241 * Avoid running the skip buddy, if running something else can
3242 * be done without getting too unfair.
3244 if (cfs_rq->skip == se) {
3245 struct sched_entity *second;
3248 second = __pick_first_entity(cfs_rq);
3250 second = __pick_next_entity(se);
3251 if (!second || (curr && entity_before(curr, second)))
3255 if (second && wakeup_preempt_entity(second, left) < 1)
3260 * Prefer last buddy, try to return the CPU to a preempted task.
3262 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3266 * Someone really wants this to run. If it's not unfair, run it.
3268 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3271 clear_buddies(cfs_rq, se);
3276 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3278 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3281 * If still on the runqueue then deactivate_task()
3282 * was not called and update_curr() has to be done:
3285 update_curr(cfs_rq);
3287 /* throttle cfs_rqs exceeding runtime */
3288 check_cfs_rq_runtime(cfs_rq);
3290 check_spread(cfs_rq, prev);
3292 update_stats_wait_start(cfs_rq, prev);
3293 /* Put 'current' back into the tree. */
3294 __enqueue_entity(cfs_rq, prev);
3295 /* in !on_rq case, update occurred at dequeue */
3296 update_load_avg(prev, 0);
3298 cfs_rq->curr = NULL;
3302 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3305 * Update run-time statistics of the 'current'.
3307 update_curr(cfs_rq);
3310 * Ensure that runnable average is periodically updated.
3312 update_load_avg(curr, 1);
3313 update_cfs_shares(cfs_rq);
3315 #ifdef CONFIG_SCHED_HRTICK
3317 * queued ticks are scheduled to match the slice, so don't bother
3318 * validating it and just reschedule.
3321 resched_curr(rq_of(cfs_rq));
3325 * don't let the period tick interfere with the hrtick preemption
3327 if (!sched_feat(DOUBLE_TICK) &&
3328 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3332 if (cfs_rq->nr_running > 1)
3333 check_preempt_tick(cfs_rq, curr);
3337 /**************************************************
3338 * CFS bandwidth control machinery
3341 #ifdef CONFIG_CFS_BANDWIDTH
3343 #ifdef HAVE_JUMP_LABEL
3344 static struct static_key __cfs_bandwidth_used;
3346 static inline bool cfs_bandwidth_used(void)
3348 return static_key_false(&__cfs_bandwidth_used);
3351 void cfs_bandwidth_usage_inc(void)
3353 static_key_slow_inc(&__cfs_bandwidth_used);
3356 void cfs_bandwidth_usage_dec(void)
3358 static_key_slow_dec(&__cfs_bandwidth_used);
3360 #else /* HAVE_JUMP_LABEL */
3361 static bool cfs_bandwidth_used(void)
3366 void cfs_bandwidth_usage_inc(void) {}
3367 void cfs_bandwidth_usage_dec(void) {}
3368 #endif /* HAVE_JUMP_LABEL */
3371 * default period for cfs group bandwidth.
3372 * default: 0.1s, units: nanoseconds
3374 static inline u64 default_cfs_period(void)
3376 return 100000000ULL;
3379 static inline u64 sched_cfs_bandwidth_slice(void)
3381 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3385 * Replenish runtime according to assigned quota and update expiration time.
3386 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3387 * additional synchronization around rq->lock.
3389 * requires cfs_b->lock
3391 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3395 if (cfs_b->quota == RUNTIME_INF)
3398 now = sched_clock_cpu(smp_processor_id());
3399 cfs_b->runtime = cfs_b->quota;
3400 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3403 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3405 return &tg->cfs_bandwidth;
3408 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3409 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3411 if (unlikely(cfs_rq->throttle_count))
3412 return cfs_rq->throttled_clock_task;
3414 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3417 /* returns 0 on failure to allocate runtime */
3418 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3420 struct task_group *tg = cfs_rq->tg;
3421 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3422 u64 amount = 0, min_amount, expires;
3424 /* note: this is a positive sum as runtime_remaining <= 0 */
3425 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3427 raw_spin_lock(&cfs_b->lock);
3428 if (cfs_b->quota == RUNTIME_INF)
3429 amount = min_amount;
3431 start_cfs_bandwidth(cfs_b);
3433 if (cfs_b->runtime > 0) {
3434 amount = min(cfs_b->runtime, min_amount);
3435 cfs_b->runtime -= amount;
3439 expires = cfs_b->runtime_expires;
3440 raw_spin_unlock(&cfs_b->lock);
3442 cfs_rq->runtime_remaining += amount;
3444 * we may have advanced our local expiration to account for allowed
3445 * spread between our sched_clock and the one on which runtime was
3448 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3449 cfs_rq->runtime_expires = expires;
3451 return cfs_rq->runtime_remaining > 0;
3455 * Note: This depends on the synchronization provided by sched_clock and the
3456 * fact that rq->clock snapshots this value.
3458 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3460 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3462 /* if the deadline is ahead of our clock, nothing to do */
3463 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3466 if (cfs_rq->runtime_remaining < 0)
3470 * If the local deadline has passed we have to consider the
3471 * possibility that our sched_clock is 'fast' and the global deadline
3472 * has not truly expired.
3474 * Fortunately we can check determine whether this the case by checking
3475 * whether the global deadline has advanced. It is valid to compare
3476 * cfs_b->runtime_expires without any locks since we only care about
3477 * exact equality, so a partial write will still work.
3480 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3481 /* extend local deadline, drift is bounded above by 2 ticks */
3482 cfs_rq->runtime_expires += TICK_NSEC;
3484 /* global deadline is ahead, expiration has passed */
3485 cfs_rq->runtime_remaining = 0;
3489 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3491 /* dock delta_exec before expiring quota (as it could span periods) */
3492 cfs_rq->runtime_remaining -= delta_exec;
3493 expire_cfs_rq_runtime(cfs_rq);
3495 if (likely(cfs_rq->runtime_remaining > 0))
3499 * if we're unable to extend our runtime we resched so that the active
3500 * hierarchy can be throttled
3502 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3503 resched_curr(rq_of(cfs_rq));
3506 static __always_inline
3507 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3509 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3512 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3515 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3517 return cfs_bandwidth_used() && cfs_rq->throttled;
3520 /* check whether cfs_rq, or any parent, is throttled */
3521 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3523 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3527 * Ensure that neither of the group entities corresponding to src_cpu or
3528 * dest_cpu are members of a throttled hierarchy when performing group
3529 * load-balance operations.
3531 static inline int throttled_lb_pair(struct task_group *tg,
3532 int src_cpu, int dest_cpu)
3534 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3536 src_cfs_rq = tg->cfs_rq[src_cpu];
3537 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3539 return throttled_hierarchy(src_cfs_rq) ||
3540 throttled_hierarchy(dest_cfs_rq);
3543 /* updated child weight may affect parent so we have to do this bottom up */
3544 static int tg_unthrottle_up(struct task_group *tg, void *data)
3546 struct rq *rq = data;
3547 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3549 cfs_rq->throttle_count--;
3551 if (!cfs_rq->throttle_count) {
3552 /* adjust cfs_rq_clock_task() */
3553 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3554 cfs_rq->throttled_clock_task;
3561 static int tg_throttle_down(struct task_group *tg, void *data)
3563 struct rq *rq = data;
3564 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3566 /* group is entering throttled state, stop time */
3567 if (!cfs_rq->throttle_count)
3568 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3569 cfs_rq->throttle_count++;
3574 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3576 struct rq *rq = rq_of(cfs_rq);
3577 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3578 struct sched_entity *se;
3579 long task_delta, dequeue = 1;
3582 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3584 /* freeze hierarchy runnable averages while throttled */
3586 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3589 task_delta = cfs_rq->h_nr_running;
3590 for_each_sched_entity(se) {
3591 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3592 /* throttled entity or throttle-on-deactivate */
3597 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3598 qcfs_rq->h_nr_running -= task_delta;
3600 if (qcfs_rq->load.weight)
3605 sub_nr_running(rq, task_delta);
3607 cfs_rq->throttled = 1;
3608 cfs_rq->throttled_clock = rq_clock(rq);
3609 raw_spin_lock(&cfs_b->lock);
3610 empty = list_empty(&cfs_b->throttled_cfs_rq);
3613 * Add to the _head_ of the list, so that an already-started
3614 * distribute_cfs_runtime will not see us
3616 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3619 * If we're the first throttled task, make sure the bandwidth
3623 start_cfs_bandwidth(cfs_b);
3625 raw_spin_unlock(&cfs_b->lock);
3628 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3630 struct rq *rq = rq_of(cfs_rq);
3631 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3632 struct sched_entity *se;
3636 se = cfs_rq->tg->se[cpu_of(rq)];
3638 cfs_rq->throttled = 0;
3640 update_rq_clock(rq);
3642 raw_spin_lock(&cfs_b->lock);
3643 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3644 list_del_rcu(&cfs_rq->throttled_list);
3645 raw_spin_unlock(&cfs_b->lock);
3647 /* update hierarchical throttle state */
3648 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3650 if (!cfs_rq->load.weight)
3653 task_delta = cfs_rq->h_nr_running;
3654 for_each_sched_entity(se) {
3658 cfs_rq = cfs_rq_of(se);
3660 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3661 cfs_rq->h_nr_running += task_delta;
3663 if (cfs_rq_throttled(cfs_rq))
3668 add_nr_running(rq, task_delta);
3670 /* determine whether we need to wake up potentially idle cpu */
3671 if (rq->curr == rq->idle && rq->cfs.nr_running)
3675 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3676 u64 remaining, u64 expires)
3678 struct cfs_rq *cfs_rq;
3680 u64 starting_runtime = remaining;
3683 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3685 struct rq *rq = rq_of(cfs_rq);
3687 raw_spin_lock(&rq->lock);
3688 if (!cfs_rq_throttled(cfs_rq))
3691 runtime = -cfs_rq->runtime_remaining + 1;
3692 if (runtime > remaining)
3693 runtime = remaining;
3694 remaining -= runtime;
3696 cfs_rq->runtime_remaining += runtime;
3697 cfs_rq->runtime_expires = expires;
3699 /* we check whether we're throttled above */
3700 if (cfs_rq->runtime_remaining > 0)
3701 unthrottle_cfs_rq(cfs_rq);
3704 raw_spin_unlock(&rq->lock);
3711 return starting_runtime - remaining;
3715 * Responsible for refilling a task_group's bandwidth and unthrottling its
3716 * cfs_rqs as appropriate. If there has been no activity within the last
3717 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3718 * used to track this state.
3720 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3722 u64 runtime, runtime_expires;
3725 /* no need to continue the timer with no bandwidth constraint */
3726 if (cfs_b->quota == RUNTIME_INF)
3727 goto out_deactivate;
3729 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3730 cfs_b->nr_periods += overrun;
3733 * idle depends on !throttled (for the case of a large deficit), and if
3734 * we're going inactive then everything else can be deferred
3736 if (cfs_b->idle && !throttled)
3737 goto out_deactivate;
3739 __refill_cfs_bandwidth_runtime(cfs_b);
3742 /* mark as potentially idle for the upcoming period */
3747 /* account preceding periods in which throttling occurred */
3748 cfs_b->nr_throttled += overrun;
3750 runtime_expires = cfs_b->runtime_expires;
3753 * This check is repeated as we are holding onto the new bandwidth while
3754 * we unthrottle. This can potentially race with an unthrottled group
3755 * trying to acquire new bandwidth from the global pool. This can result
3756 * in us over-using our runtime if it is all used during this loop, but
3757 * only by limited amounts in that extreme case.
3759 while (throttled && cfs_b->runtime > 0) {
3760 runtime = cfs_b->runtime;
3761 raw_spin_unlock(&cfs_b->lock);
3762 /* we can't nest cfs_b->lock while distributing bandwidth */
3763 runtime = distribute_cfs_runtime(cfs_b, runtime,
3765 raw_spin_lock(&cfs_b->lock);
3767 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3769 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3773 * While we are ensured activity in the period following an
3774 * unthrottle, this also covers the case in which the new bandwidth is
3775 * insufficient to cover the existing bandwidth deficit. (Forcing the
3776 * timer to remain active while there are any throttled entities.)
3786 /* a cfs_rq won't donate quota below this amount */
3787 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3788 /* minimum remaining period time to redistribute slack quota */
3789 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3790 /* how long we wait to gather additional slack before distributing */
3791 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3794 * Are we near the end of the current quota period?
3796 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3797 * hrtimer base being cleared by hrtimer_start. In the case of
3798 * migrate_hrtimers, base is never cleared, so we are fine.
3800 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3802 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3805 /* if the call-back is running a quota refresh is already occurring */
3806 if (hrtimer_callback_running(refresh_timer))
3809 /* is a quota refresh about to occur? */
3810 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3811 if (remaining < min_expire)
3817 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3819 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3821 /* if there's a quota refresh soon don't bother with slack */
3822 if (runtime_refresh_within(cfs_b, min_left))
3825 hrtimer_start(&cfs_b->slack_timer,
3826 ns_to_ktime(cfs_bandwidth_slack_period),
3830 /* we know any runtime found here is valid as update_curr() precedes return */
3831 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3833 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3834 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3836 if (slack_runtime <= 0)
3839 raw_spin_lock(&cfs_b->lock);
3840 if (cfs_b->quota != RUNTIME_INF &&
3841 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3842 cfs_b->runtime += slack_runtime;
3844 /* we are under rq->lock, defer unthrottling using a timer */
3845 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3846 !list_empty(&cfs_b->throttled_cfs_rq))
3847 start_cfs_slack_bandwidth(cfs_b);
3849 raw_spin_unlock(&cfs_b->lock);
3851 /* even if it's not valid for return we don't want to try again */
3852 cfs_rq->runtime_remaining -= slack_runtime;
3855 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3857 if (!cfs_bandwidth_used())
3860 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3863 __return_cfs_rq_runtime(cfs_rq);
3867 * This is done with a timer (instead of inline with bandwidth return) since
3868 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3870 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3872 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3875 /* confirm we're still not at a refresh boundary */
3876 raw_spin_lock(&cfs_b->lock);
3877 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3878 raw_spin_unlock(&cfs_b->lock);
3882 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3883 runtime = cfs_b->runtime;
3885 expires = cfs_b->runtime_expires;
3886 raw_spin_unlock(&cfs_b->lock);
3891 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3893 raw_spin_lock(&cfs_b->lock);
3894 if (expires == cfs_b->runtime_expires)
3895 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3896 raw_spin_unlock(&cfs_b->lock);
3900 * When a group wakes up we want to make sure that its quota is not already
3901 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3902 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3904 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3906 if (!cfs_bandwidth_used())
3909 /* an active group must be handled by the update_curr()->put() path */
3910 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3913 /* ensure the group is not already throttled */
3914 if (cfs_rq_throttled(cfs_rq))
3917 /* update runtime allocation */
3918 account_cfs_rq_runtime(cfs_rq, 0);
3919 if (cfs_rq->runtime_remaining <= 0)
3920 throttle_cfs_rq(cfs_rq);
3923 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3924 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3926 if (!cfs_bandwidth_used())
3929 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3933 * it's possible for a throttled entity to be forced into a running
3934 * state (e.g. set_curr_task), in this case we're finished.
3936 if (cfs_rq_throttled(cfs_rq))
3939 throttle_cfs_rq(cfs_rq);
3943 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3945 struct cfs_bandwidth *cfs_b =
3946 container_of(timer, struct cfs_bandwidth, slack_timer);
3948 do_sched_cfs_slack_timer(cfs_b);
3950 return HRTIMER_NORESTART;
3953 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3955 struct cfs_bandwidth *cfs_b =
3956 container_of(timer, struct cfs_bandwidth, period_timer);
3960 raw_spin_lock(&cfs_b->lock);
3962 overrun = hrtimer_forward_now(timer, cfs_b->period);
3966 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3969 cfs_b->period_active = 0;
3970 raw_spin_unlock(&cfs_b->lock);
3972 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3975 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3977 raw_spin_lock_init(&cfs_b->lock);
3979 cfs_b->quota = RUNTIME_INF;
3980 cfs_b->period = ns_to_ktime(default_cfs_period());
3982 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3983 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3984 cfs_b->period_timer.function = sched_cfs_period_timer;
3985 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3986 cfs_b->slack_timer.function = sched_cfs_slack_timer;
3989 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3991 cfs_rq->runtime_enabled = 0;
3992 INIT_LIST_HEAD(&cfs_rq->throttled_list);
3995 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3997 lockdep_assert_held(&cfs_b->lock);
3999 if (!cfs_b->period_active) {
4000 cfs_b->period_active = 1;
4001 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4002 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4006 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4008 /* init_cfs_bandwidth() was not called */
4009 if (!cfs_b->throttled_cfs_rq.next)
4012 hrtimer_cancel(&cfs_b->period_timer);
4013 hrtimer_cancel(&cfs_b->slack_timer);
4016 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4018 struct cfs_rq *cfs_rq;
4020 for_each_leaf_cfs_rq(rq, cfs_rq) {
4021 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4023 raw_spin_lock(&cfs_b->lock);
4024 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4025 raw_spin_unlock(&cfs_b->lock);
4029 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4031 struct cfs_rq *cfs_rq;
4033 for_each_leaf_cfs_rq(rq, cfs_rq) {
4034 if (!cfs_rq->runtime_enabled)
4038 * clock_task is not advancing so we just need to make sure
4039 * there's some valid quota amount
4041 cfs_rq->runtime_remaining = 1;
4043 * Offline rq is schedulable till cpu is completely disabled
4044 * in take_cpu_down(), so we prevent new cfs throttling here.
4046 cfs_rq->runtime_enabled = 0;
4048 if (cfs_rq_throttled(cfs_rq))
4049 unthrottle_cfs_rq(cfs_rq);
4053 #else /* CONFIG_CFS_BANDWIDTH */
4054 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4056 return rq_clock_task(rq_of(cfs_rq));
4059 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4060 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4061 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4062 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4064 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4069 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4074 static inline int throttled_lb_pair(struct task_group *tg,
4075 int src_cpu, int dest_cpu)
4080 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4082 #ifdef CONFIG_FAIR_GROUP_SCHED
4083 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4086 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4090 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4091 static inline void update_runtime_enabled(struct rq *rq) {}
4092 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4094 #endif /* CONFIG_CFS_BANDWIDTH */
4096 /**************************************************
4097 * CFS operations on tasks:
4100 #ifdef CONFIG_SCHED_HRTICK
4101 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4103 struct sched_entity *se = &p->se;
4104 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4106 WARN_ON(task_rq(p) != rq);
4108 if (cfs_rq->nr_running > 1) {
4109 u64 slice = sched_slice(cfs_rq, se);
4110 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4111 s64 delta = slice - ran;
4118 hrtick_start(rq, delta);
4123 * called from enqueue/dequeue and updates the hrtick when the
4124 * current task is from our class and nr_running is low enough
4127 static void hrtick_update(struct rq *rq)
4129 struct task_struct *curr = rq->curr;
4131 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4134 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4135 hrtick_start_fair(rq, curr);
4137 #else /* !CONFIG_SCHED_HRTICK */
4139 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4143 static inline void hrtick_update(struct rq *rq)
4148 static inline unsigned long boosted_cpu_util(int cpu);
4150 static void update_capacity_of(int cpu)
4152 unsigned long req_cap;
4157 /* Convert scale-invariant capacity to cpu. */
4158 req_cap = boosted_cpu_util(cpu);
4159 req_cap = req_cap * SCHED_CAPACITY_SCALE / capacity_orig_of(cpu);
4160 set_cfs_cpu_capacity(cpu, true, req_cap);
4163 static bool cpu_overutilized(int cpu);
4166 * The enqueue_task method is called before nr_running is
4167 * increased. Here we update the fair scheduling stats and
4168 * then put the task into the rbtree:
4171 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4173 struct cfs_rq *cfs_rq;
4174 struct sched_entity *se = &p->se;
4175 int task_new = flags & ENQUEUE_WAKEUP_NEW;
4176 int task_wakeup = flags & ENQUEUE_WAKEUP;
4178 for_each_sched_entity(se) {
4181 cfs_rq = cfs_rq_of(se);
4182 enqueue_entity(cfs_rq, se, flags);
4185 * end evaluation on encountering a throttled cfs_rq
4187 * note: in the case of encountering a throttled cfs_rq we will
4188 * post the final h_nr_running increment below.
4190 if (cfs_rq_throttled(cfs_rq))
4192 cfs_rq->h_nr_running++;
4194 flags = ENQUEUE_WAKEUP;
4197 for_each_sched_entity(se) {
4198 cfs_rq = cfs_rq_of(se);
4199 cfs_rq->h_nr_running++;
4201 if (cfs_rq_throttled(cfs_rq))
4204 update_load_avg(se, 1);
4205 update_cfs_shares(cfs_rq);
4209 add_nr_running(rq, 1);
4210 if (!task_new && !rq->rd->overutilized &&
4211 cpu_overutilized(rq->cpu))
4212 rq->rd->overutilized = true;
4214 schedtune_enqueue_task(p, cpu_of(rq));
4217 * We want to potentially trigger a freq switch
4218 * request only for tasks that are waking up; this is
4219 * because we get here also during load balancing, but
4220 * in these cases it seems wise to trigger as single
4221 * request after load balancing is done.
4223 if (task_new || task_wakeup)
4224 update_capacity_of(cpu_of(rq));
4229 static void set_next_buddy(struct sched_entity *se);
4232 * The dequeue_task method is called before nr_running is
4233 * decreased. We remove the task from the rbtree and
4234 * update the fair scheduling stats:
4236 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4238 struct cfs_rq *cfs_rq;
4239 struct sched_entity *se = &p->se;
4240 int task_sleep = flags & DEQUEUE_SLEEP;
4242 for_each_sched_entity(se) {
4243 cfs_rq = cfs_rq_of(se);
4244 dequeue_entity(cfs_rq, se, flags);
4247 * end evaluation on encountering a throttled cfs_rq
4249 * note: in the case of encountering a throttled cfs_rq we will
4250 * post the final h_nr_running decrement below.
4252 if (cfs_rq_throttled(cfs_rq))
4254 cfs_rq->h_nr_running--;
4256 /* Don't dequeue parent if it has other entities besides us */
4257 if (cfs_rq->load.weight) {
4259 * Bias pick_next to pick a task from this cfs_rq, as
4260 * p is sleeping when it is within its sched_slice.
4262 if (task_sleep && parent_entity(se))
4263 set_next_buddy(parent_entity(se));
4265 /* avoid re-evaluating load for this entity */
4266 se = parent_entity(se);
4269 flags |= DEQUEUE_SLEEP;
4272 for_each_sched_entity(se) {
4273 cfs_rq = cfs_rq_of(se);
4274 cfs_rq->h_nr_running--;
4276 if (cfs_rq_throttled(cfs_rq))
4279 update_load_avg(se, 1);
4280 update_cfs_shares(cfs_rq);
4284 sub_nr_running(rq, 1);
4285 schedtune_dequeue_task(p, cpu_of(rq));
4288 * We want to potentially trigger a freq switch
4289 * request only for tasks that are going to sleep;
4290 * this is because we get here also during load
4291 * balancing, but in these cases it seems wise to
4292 * trigger as single request after load balancing is
4296 if (rq->cfs.nr_running)
4297 update_capacity_of(cpu_of(rq));
4298 else if (sched_freq())
4299 set_cfs_cpu_capacity(cpu_of(rq), false, 0);
4308 * per rq 'load' arrray crap; XXX kill this.
4312 * The exact cpuload at various idx values, calculated at every tick would be
4313 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4315 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4316 * on nth tick when cpu may be busy, then we have:
4317 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4318 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4320 * decay_load_missed() below does efficient calculation of
4321 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4322 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4324 * The calculation is approximated on a 128 point scale.
4325 * degrade_zero_ticks is the number of ticks after which load at any
4326 * particular idx is approximated to be zero.
4327 * degrade_factor is a precomputed table, a row for each load idx.
4328 * Each column corresponds to degradation factor for a power of two ticks,
4329 * based on 128 point scale.
4331 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4332 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4334 * With this power of 2 load factors, we can degrade the load n times
4335 * by looking at 1 bits in n and doing as many mult/shift instead of
4336 * n mult/shifts needed by the exact degradation.
4338 #define DEGRADE_SHIFT 7
4339 static const unsigned char
4340 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4341 static const unsigned char
4342 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4343 {0, 0, 0, 0, 0, 0, 0, 0},
4344 {64, 32, 8, 0, 0, 0, 0, 0},
4345 {96, 72, 40, 12, 1, 0, 0},
4346 {112, 98, 75, 43, 15, 1, 0},
4347 {120, 112, 98, 76, 45, 16, 2} };
4350 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4351 * would be when CPU is idle and so we just decay the old load without
4352 * adding any new load.
4354 static unsigned long
4355 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4359 if (!missed_updates)
4362 if (missed_updates >= degrade_zero_ticks[idx])
4366 return load >> missed_updates;
4368 while (missed_updates) {
4369 if (missed_updates % 2)
4370 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4372 missed_updates >>= 1;
4379 * Update rq->cpu_load[] statistics. This function is usually called every
4380 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4381 * every tick. We fix it up based on jiffies.
4383 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4384 unsigned long pending_updates)
4388 this_rq->nr_load_updates++;
4390 /* Update our load: */
4391 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4392 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4393 unsigned long old_load, new_load;
4395 /* scale is effectively 1 << i now, and >> i divides by scale */
4397 old_load = this_rq->cpu_load[i];
4398 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4399 new_load = this_load;
4401 * Round up the averaging division if load is increasing. This
4402 * prevents us from getting stuck on 9 if the load is 10, for
4405 if (new_load > old_load)
4406 new_load += scale - 1;
4408 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4411 sched_avg_update(this_rq);
4414 /* Used instead of source_load when we know the type == 0 */
4415 static unsigned long weighted_cpuload(const int cpu)
4417 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4420 #ifdef CONFIG_NO_HZ_COMMON
4422 * There is no sane way to deal with nohz on smp when using jiffies because the
4423 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4424 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4426 * Therefore we cannot use the delta approach from the regular tick since that
4427 * would seriously skew the load calculation. However we'll make do for those
4428 * updates happening while idle (nohz_idle_balance) or coming out of idle
4429 * (tick_nohz_idle_exit).
4431 * This means we might still be one tick off for nohz periods.
4435 * Called from nohz_idle_balance() to update the load ratings before doing the
4438 static void update_idle_cpu_load(struct rq *this_rq)
4440 unsigned long curr_jiffies = READ_ONCE(jiffies);
4441 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4442 unsigned long pending_updates;
4445 * bail if there's load or we're actually up-to-date.
4447 if (load || curr_jiffies == this_rq->last_load_update_tick)
4450 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4451 this_rq->last_load_update_tick = curr_jiffies;
4453 __update_cpu_load(this_rq, load, pending_updates);
4457 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4459 void update_cpu_load_nohz(void)
4461 struct rq *this_rq = this_rq();
4462 unsigned long curr_jiffies = READ_ONCE(jiffies);
4463 unsigned long pending_updates;
4465 if (curr_jiffies == this_rq->last_load_update_tick)
4468 raw_spin_lock(&this_rq->lock);
4469 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4470 if (pending_updates) {
4471 this_rq->last_load_update_tick = curr_jiffies;
4473 * We were idle, this means load 0, the current load might be
4474 * !0 due to remote wakeups and the sort.
4476 __update_cpu_load(this_rq, 0, pending_updates);
4478 raw_spin_unlock(&this_rq->lock);
4480 #endif /* CONFIG_NO_HZ */
4483 * Called from scheduler_tick()
4485 void update_cpu_load_active(struct rq *this_rq)
4487 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4489 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4491 this_rq->last_load_update_tick = jiffies;
4492 __update_cpu_load(this_rq, load, 1);
4496 * Return a low guess at the load of a migration-source cpu weighted
4497 * according to the scheduling class and "nice" value.
4499 * We want to under-estimate the load of migration sources, to
4500 * balance conservatively.
4502 static unsigned long source_load(int cpu, int type)
4504 struct rq *rq = cpu_rq(cpu);
4505 unsigned long total = weighted_cpuload(cpu);
4507 if (type == 0 || !sched_feat(LB_BIAS))
4510 return min(rq->cpu_load[type-1], total);
4514 * Return a high guess at the load of a migration-target cpu weighted
4515 * according to the scheduling class and "nice" value.
4517 static unsigned long target_load(int cpu, int type)
4519 struct rq *rq = cpu_rq(cpu);
4520 unsigned long total = weighted_cpuload(cpu);
4522 if (type == 0 || !sched_feat(LB_BIAS))
4525 return max(rq->cpu_load[type-1], total);
4529 static unsigned long cpu_avg_load_per_task(int cpu)
4531 struct rq *rq = cpu_rq(cpu);
4532 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4533 unsigned long load_avg = weighted_cpuload(cpu);
4536 return load_avg / nr_running;
4541 static void record_wakee(struct task_struct *p)
4544 * Rough decay (wiping) for cost saving, don't worry
4545 * about the boundary, really active task won't care
4548 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4549 current->wakee_flips >>= 1;
4550 current->wakee_flip_decay_ts = jiffies;
4553 if (current->last_wakee != p) {
4554 current->last_wakee = p;
4555 current->wakee_flips++;
4559 static void task_waking_fair(struct task_struct *p)
4561 struct sched_entity *se = &p->se;
4562 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4565 #ifndef CONFIG_64BIT
4566 u64 min_vruntime_copy;
4569 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4571 min_vruntime = cfs_rq->min_vruntime;
4572 } while (min_vruntime != min_vruntime_copy);
4574 min_vruntime = cfs_rq->min_vruntime;
4577 se->vruntime -= min_vruntime;
4581 #ifdef CONFIG_FAIR_GROUP_SCHED
4583 * effective_load() calculates the load change as seen from the root_task_group
4585 * Adding load to a group doesn't make a group heavier, but can cause movement
4586 * of group shares between cpus. Assuming the shares were perfectly aligned one
4587 * can calculate the shift in shares.
4589 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4590 * on this @cpu and results in a total addition (subtraction) of @wg to the
4591 * total group weight.
4593 * Given a runqueue weight distribution (rw_i) we can compute a shares
4594 * distribution (s_i) using:
4596 * s_i = rw_i / \Sum rw_j (1)
4598 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4599 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4600 * shares distribution (s_i):
4602 * rw_i = { 2, 4, 1, 0 }
4603 * s_i = { 2/7, 4/7, 1/7, 0 }
4605 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4606 * task used to run on and the CPU the waker is running on), we need to
4607 * compute the effect of waking a task on either CPU and, in case of a sync
4608 * wakeup, compute the effect of the current task going to sleep.
4610 * So for a change of @wl to the local @cpu with an overall group weight change
4611 * of @wl we can compute the new shares distribution (s'_i) using:
4613 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4615 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4616 * differences in waking a task to CPU 0. The additional task changes the
4617 * weight and shares distributions like:
4619 * rw'_i = { 3, 4, 1, 0 }
4620 * s'_i = { 3/8, 4/8, 1/8, 0 }
4622 * We can then compute the difference in effective weight by using:
4624 * dw_i = S * (s'_i - s_i) (3)
4626 * Where 'S' is the group weight as seen by its parent.
4628 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4629 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4630 * 4/7) times the weight of the group.
4632 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4634 struct sched_entity *se = tg->se[cpu];
4636 if (!tg->parent) /* the trivial, non-cgroup case */
4639 for_each_sched_entity(se) {
4645 * W = @wg + \Sum rw_j
4647 W = wg + calc_tg_weight(tg, se->my_q);
4652 w = cfs_rq_load_avg(se->my_q) + wl;
4655 * wl = S * s'_i; see (2)
4658 wl = (w * (long)tg->shares) / W;
4663 * Per the above, wl is the new se->load.weight value; since
4664 * those are clipped to [MIN_SHARES, ...) do so now. See
4665 * calc_cfs_shares().
4667 if (wl < MIN_SHARES)
4671 * wl = dw_i = S * (s'_i - s_i); see (3)
4673 wl -= se->avg.load_avg;
4676 * Recursively apply this logic to all parent groups to compute
4677 * the final effective load change on the root group. Since
4678 * only the @tg group gets extra weight, all parent groups can
4679 * only redistribute existing shares. @wl is the shift in shares
4680 * resulting from this level per the above.
4689 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4696 static inline bool energy_aware(void)
4698 return sched_feat(ENERGY_AWARE);
4702 struct sched_group *sg_top;
4703 struct sched_group *sg_cap;
4712 * __cpu_norm_util() returns the cpu util relative to a specific capacity,
4713 * i.e. it's busy ratio, in the range [0..SCHED_LOAD_SCALE] which is useful for
4714 * energy calculations. Using the scale-invariant util returned by
4715 * cpu_util() and approximating scale-invariant util by:
4717 * util ~ (curr_freq/max_freq)*1024 * capacity_orig/1024 * running_time/time
4719 * the normalized util can be found using the specific capacity.
4721 * capacity = capacity_orig * curr_freq/max_freq
4723 * norm_util = running_time/time ~ util/capacity
4725 static unsigned long __cpu_norm_util(int cpu, unsigned long capacity, int delta)
4727 int util = __cpu_util(cpu, delta);
4729 if (util >= capacity)
4730 return SCHED_CAPACITY_SCALE;
4732 return (util << SCHED_CAPACITY_SHIFT)/capacity;
4735 static int calc_util_delta(struct energy_env *eenv, int cpu)
4737 if (cpu == eenv->src_cpu)
4738 return -eenv->util_delta;
4739 if (cpu == eenv->dst_cpu)
4740 return eenv->util_delta;
4745 unsigned long group_max_util(struct energy_env *eenv)
4748 unsigned long max_util = 0;
4750 for_each_cpu(i, sched_group_cpus(eenv->sg_cap)) {
4751 delta = calc_util_delta(eenv, i);
4752 max_util = max(max_util, __cpu_util(i, delta));
4759 * group_norm_util() returns the approximated group util relative to it's
4760 * current capacity (busy ratio) in the range [0..SCHED_LOAD_SCALE] for use in
4761 * energy calculations. Since task executions may or may not overlap in time in
4762 * the group the true normalized util is between max(cpu_norm_util(i)) and
4763 * sum(cpu_norm_util(i)) when iterating over all cpus in the group, i. The
4764 * latter is used as the estimate as it leads to a more pessimistic energy
4765 * estimate (more busy).
4768 long group_norm_util(struct energy_env *eenv, struct sched_group *sg)
4771 unsigned long util_sum = 0;
4772 unsigned long capacity = sg->sge->cap_states[eenv->cap_idx].cap;
4774 for_each_cpu(i, sched_group_cpus(sg)) {
4775 delta = calc_util_delta(eenv, i);
4776 util_sum += __cpu_norm_util(i, capacity, delta);
4779 if (util_sum > SCHED_CAPACITY_SCALE)
4780 return SCHED_CAPACITY_SCALE;
4784 static int find_new_capacity(struct energy_env *eenv,
4785 const struct sched_group_energy const *sge)
4788 unsigned long util = group_max_util(eenv);
4790 for (idx = 0; idx < sge->nr_cap_states; idx++) {
4791 if (sge->cap_states[idx].cap >= util)
4795 eenv->cap_idx = idx;
4800 static int group_idle_state(struct sched_group *sg)
4802 int i, state = INT_MAX;
4804 /* Find the shallowest idle state in the sched group. */
4805 for_each_cpu(i, sched_group_cpus(sg))
4806 state = min(state, idle_get_state_idx(cpu_rq(i)));
4808 /* Take non-cpuidle idling into account (active idle/arch_cpu_idle()) */
4815 * sched_group_energy(): Computes the absolute energy consumption of cpus
4816 * belonging to the sched_group including shared resources shared only by
4817 * members of the group. Iterates over all cpus in the hierarchy below the
4818 * sched_group starting from the bottom working it's way up before going to
4819 * the next cpu until all cpus are covered at all levels. The current
4820 * implementation is likely to gather the same util statistics multiple times.
4821 * This can probably be done in a faster but more complex way.
4822 * Note: sched_group_energy() may fail when racing with sched_domain updates.
4824 static int sched_group_energy(struct energy_env *eenv)
4826 struct sched_domain *sd;
4827 int cpu, total_energy = 0;
4828 struct cpumask visit_cpus;
4829 struct sched_group *sg;
4831 WARN_ON(!eenv->sg_top->sge);
4833 cpumask_copy(&visit_cpus, sched_group_cpus(eenv->sg_top));
4835 while (!cpumask_empty(&visit_cpus)) {
4836 struct sched_group *sg_shared_cap = NULL;
4838 cpu = cpumask_first(&visit_cpus);
4841 * Is the group utilization affected by cpus outside this
4844 sd = rcu_dereference(per_cpu(sd_scs, cpu));
4848 * We most probably raced with hotplug; returning a
4849 * wrong energy estimation is better than entering an
4855 sg_shared_cap = sd->parent->groups;
4857 for_each_domain(cpu, sd) {
4860 /* Has this sched_domain already been visited? */
4861 if (sd->child && group_first_cpu(sg) != cpu)
4865 unsigned long group_util;
4866 int sg_busy_energy, sg_idle_energy;
4867 int cap_idx, idle_idx;
4869 if (sg_shared_cap && sg_shared_cap->group_weight >= sg->group_weight)
4870 eenv->sg_cap = sg_shared_cap;
4874 cap_idx = find_new_capacity(eenv, sg->sge);
4875 idle_idx = group_idle_state(sg);
4876 group_util = group_norm_util(eenv, sg);
4877 sg_busy_energy = (group_util * sg->sge->cap_states[cap_idx].power)
4878 >> SCHED_CAPACITY_SHIFT;
4879 sg_idle_energy = ((SCHED_LOAD_SCALE-group_util)
4880 * sg->sge->idle_states[idle_idx].power)
4881 >> SCHED_CAPACITY_SHIFT;
4883 total_energy += sg_busy_energy + sg_idle_energy;
4886 cpumask_xor(&visit_cpus, &visit_cpus, sched_group_cpus(sg));
4888 if (cpumask_equal(sched_group_cpus(sg), sched_group_cpus(eenv->sg_top)))
4891 } while (sg = sg->next, sg != sd->groups);
4897 eenv->energy = total_energy;
4901 static inline bool cpu_in_sg(struct sched_group *sg, int cpu)
4903 return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));
4907 * energy_diff(): Estimate the energy impact of changing the utilization
4908 * distribution. eenv specifies the change: utilisation amount, source, and
4909 * destination cpu. Source or destination cpu may be -1 in which case the
4910 * utilization is removed from or added to the system (e.g. task wake-up). If
4911 * both are specified, the utilization is migrated.
4913 static int energy_diff(struct energy_env *eenv)
4915 struct sched_domain *sd;
4916 struct sched_group *sg;
4917 int sd_cpu = -1, energy_before = 0, energy_after = 0;
4919 struct energy_env eenv_before = {
4921 .src_cpu = eenv->src_cpu,
4922 .dst_cpu = eenv->dst_cpu,
4925 if (eenv->src_cpu == eenv->dst_cpu)
4928 sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu;
4929 sd = rcu_dereference(per_cpu(sd_ea, sd_cpu));
4932 return 0; /* Error */
4937 if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) {
4938 eenv_before.sg_top = eenv->sg_top = sg;
4940 if (sched_group_energy(&eenv_before))
4941 return 0; /* Invalid result abort */
4942 energy_before += eenv_before.energy;
4944 if (sched_group_energy(eenv))
4945 return 0; /* Invalid result abort */
4946 energy_after += eenv->energy;
4948 } while (sg = sg->next, sg != sd->groups);
4950 return energy_after-energy_before;
4954 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4955 * A waker of many should wake a different task than the one last awakened
4956 * at a frequency roughly N times higher than one of its wakees. In order
4957 * to determine whether we should let the load spread vs consolodating to
4958 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4959 * partner, and a factor of lls_size higher frequency in the other. With
4960 * both conditions met, we can be relatively sure that the relationship is
4961 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4962 * being client/server, worker/dispatcher, interrupt source or whatever is
4963 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4965 static int wake_wide(struct task_struct *p)
4967 unsigned int master = current->wakee_flips;
4968 unsigned int slave = p->wakee_flips;
4969 int factor = this_cpu_read(sd_llc_size);
4972 swap(master, slave);
4973 if (slave < factor || master < slave * factor)
4978 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4980 s64 this_load, load;
4981 s64 this_eff_load, prev_eff_load;
4982 int idx, this_cpu, prev_cpu;
4983 struct task_group *tg;
4984 unsigned long weight;
4988 this_cpu = smp_processor_id();
4989 prev_cpu = task_cpu(p);
4990 load = source_load(prev_cpu, idx);
4991 this_load = target_load(this_cpu, idx);
4994 * If sync wakeup then subtract the (maximum possible)
4995 * effect of the currently running task from the load
4996 * of the current CPU:
4999 tg = task_group(current);
5000 weight = current->se.avg.load_avg;
5002 this_load += effective_load(tg, this_cpu, -weight, -weight);
5003 load += effective_load(tg, prev_cpu, 0, -weight);
5007 weight = p->se.avg.load_avg;
5010 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5011 * due to the sync cause above having dropped this_load to 0, we'll
5012 * always have an imbalance, but there's really nothing you can do
5013 * about that, so that's good too.
5015 * Otherwise check if either cpus are near enough in load to allow this
5016 * task to be woken on this_cpu.
5018 this_eff_load = 100;
5019 this_eff_load *= capacity_of(prev_cpu);
5021 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5022 prev_eff_load *= capacity_of(this_cpu);
5024 if (this_load > 0) {
5025 this_eff_load *= this_load +
5026 effective_load(tg, this_cpu, weight, weight);
5028 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5031 balanced = this_eff_load <= prev_eff_load;
5033 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5038 schedstat_inc(sd, ttwu_move_affine);
5039 schedstat_inc(p, se.statistics.nr_wakeups_affine);
5044 static inline unsigned long task_util(struct task_struct *p)
5046 return p->se.avg.util_avg;
5049 unsigned int capacity_margin = 1280; /* ~20% margin */
5051 static inline bool __task_fits(struct task_struct *p, int cpu, int util)
5053 unsigned long capacity = capacity_of(cpu);
5055 util += task_util(p);
5057 return (capacity * 1024) > (util * capacity_margin);
5060 static inline bool task_fits_max(struct task_struct *p, int cpu)
5062 unsigned long capacity = capacity_of(cpu);
5063 unsigned long max_capacity = cpu_rq(cpu)->rd->max_cpu_capacity.val;
5065 if (capacity == max_capacity)
5068 if (capacity * capacity_margin > max_capacity * 1024)
5071 return __task_fits(p, cpu, 0);
5074 static inline bool task_fits_spare(struct task_struct *p, int cpu)
5076 return __task_fits(p, cpu, cpu_util(cpu));
5079 static bool cpu_overutilized(int cpu)
5081 return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
5084 #ifdef CONFIG_SCHED_TUNE
5086 static unsigned long
5087 schedtune_margin(unsigned long signal, unsigned long boost)
5089 unsigned long long margin = 0;
5092 * Signal proportional compensation (SPC)
5094 * The Boost (B) value is used to compute a Margin (M) which is
5095 * proportional to the complement of the original Signal (S):
5096 * M = B * (SCHED_LOAD_SCALE - S)
5097 * The obtained M could be used by the caller to "boost" S.
5099 margin = SCHED_LOAD_SCALE - signal;
5103 * Fast integer division by constant:
5104 * Constant : (C) = 100
5105 * Precision : 0.1% (P) = 0.1
5106 * Reference : C * 100 / P (R) = 100000
5109 * Shift bits : ceil(log(R,2)) (S) = 17
5110 * Mult const : round(2^S/C) (M) = 1311
5120 static inline unsigned int
5121 schedtune_cpu_margin(unsigned long util, int cpu)
5125 #ifdef CONFIG_CGROUP_SCHEDTUNE
5126 boost = schedtune_cpu_boost(cpu);
5128 boost = get_sysctl_sched_cfs_boost();
5133 return schedtune_margin(util, boost);
5136 #else /* CONFIG_SCHED_TUNE */
5138 static inline unsigned int
5139 schedtune_cpu_margin(unsigned long util, int cpu)
5144 #endif /* CONFIG_SCHED_TUNE */
5146 static inline unsigned long
5147 boosted_cpu_util(int cpu)
5149 unsigned long util = cpu_util(cpu);
5150 unsigned long margin = schedtune_cpu_margin(util, cpu);
5152 return util + margin;
5156 * find_idlest_group finds and returns the least busy CPU group within the
5159 static struct sched_group *
5160 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5161 int this_cpu, int sd_flag)
5163 struct sched_group *idlest = NULL, *group = sd->groups;
5164 struct sched_group *fit_group = NULL, *spare_group = NULL;
5165 unsigned long min_load = ULONG_MAX, this_load = 0;
5166 unsigned long fit_capacity = ULONG_MAX;
5167 unsigned long max_spare_capacity = capacity_margin - SCHED_LOAD_SCALE;
5168 int load_idx = sd->forkexec_idx;
5169 int imbalance = 100 + (sd->imbalance_pct-100)/2;
5171 if (sd_flag & SD_BALANCE_WAKE)
5172 load_idx = sd->wake_idx;
5175 unsigned long load, avg_load, spare_capacity;
5179 /* Skip over this group if it has no CPUs allowed */
5180 if (!cpumask_intersects(sched_group_cpus(group),
5181 tsk_cpus_allowed(p)))
5184 local_group = cpumask_test_cpu(this_cpu,
5185 sched_group_cpus(group));
5187 /* Tally up the load of all CPUs in the group */
5190 for_each_cpu(i, sched_group_cpus(group)) {
5191 /* Bias balancing toward cpus of our domain */
5193 load = source_load(i, load_idx);
5195 load = target_load(i, load_idx);
5200 * Look for most energy-efficient group that can fit
5201 * that can fit the task.
5203 if (capacity_of(i) < fit_capacity && task_fits_spare(p, i)) {
5204 fit_capacity = capacity_of(i);
5209 * Look for group which has most spare capacity on a
5212 spare_capacity = capacity_of(i) - cpu_util(i);
5213 if (spare_capacity > max_spare_capacity) {
5214 max_spare_capacity = spare_capacity;
5215 spare_group = group;
5219 /* Adjust by relative CPU capacity of the group */
5220 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5223 this_load = avg_load;
5224 } else if (avg_load < min_load) {
5225 min_load = avg_load;
5228 } while (group = group->next, group != sd->groups);
5236 if (!idlest || 100*this_load < imbalance*min_load)
5242 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5245 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5247 unsigned long load, min_load = ULONG_MAX;
5248 unsigned int min_exit_latency = UINT_MAX;
5249 u64 latest_idle_timestamp = 0;
5250 int least_loaded_cpu = this_cpu;
5251 int shallowest_idle_cpu = -1;
5254 /* Traverse only the allowed CPUs */
5255 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5256 if (task_fits_spare(p, i)) {
5257 struct rq *rq = cpu_rq(i);
5258 struct cpuidle_state *idle = idle_get_state(rq);
5259 if (idle && idle->exit_latency < min_exit_latency) {
5261 * We give priority to a CPU whose idle state
5262 * has the smallest exit latency irrespective
5263 * of any idle timestamp.
5265 min_exit_latency = idle->exit_latency;
5266 latest_idle_timestamp = rq->idle_stamp;
5267 shallowest_idle_cpu = i;
5268 } else if (idle_cpu(i) &&
5269 (!idle || idle->exit_latency == min_exit_latency) &&
5270 rq->idle_stamp > latest_idle_timestamp) {
5272 * If equal or no active idle state, then
5273 * the most recently idled CPU might have
5276 latest_idle_timestamp = rq->idle_stamp;
5277 shallowest_idle_cpu = i;
5278 } else if (shallowest_idle_cpu == -1) {
5280 * If we haven't found an idle CPU yet
5281 * pick a non-idle one that can fit the task as
5284 shallowest_idle_cpu = i;
5286 } else if (shallowest_idle_cpu == -1) {
5287 load = weighted_cpuload(i);
5288 if (load < min_load || (load == min_load && i == this_cpu)) {
5290 least_loaded_cpu = i;
5295 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5299 * Try and locate an idle CPU in the sched_domain.
5301 static int select_idle_sibling(struct task_struct *p, int target)
5303 struct sched_domain *sd;
5304 struct sched_group *sg;
5305 int i = task_cpu(p);
5307 if (idle_cpu(target))
5311 * If the prevous cpu is cache affine and idle, don't be stupid.
5313 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5317 * Otherwise, iterate the domains and find an elegible idle cpu.
5319 sd = rcu_dereference(per_cpu(sd_llc, target));
5320 for_each_lower_domain(sd) {
5323 if (!cpumask_intersects(sched_group_cpus(sg),
5324 tsk_cpus_allowed(p)))
5327 for_each_cpu(i, sched_group_cpus(sg)) {
5328 if (i == target || !idle_cpu(i))
5332 target = cpumask_first_and(sched_group_cpus(sg),
5333 tsk_cpus_allowed(p));
5337 } while (sg != sd->groups);
5343 static int energy_aware_wake_cpu(struct task_struct *p, int target)
5345 struct sched_domain *sd;
5346 struct sched_group *sg, *sg_target;
5347 int target_max_cap = INT_MAX;
5348 int target_cpu = task_cpu(p);
5351 sd = rcu_dereference(per_cpu(sd_ea, task_cpu(p)));
5360 * Find group with sufficient capacity. We only get here if no cpu is
5361 * overutilized. We may end up overutilizing a cpu by adding the task,
5362 * but that should not be any worse than select_idle_sibling().
5363 * load_balance() should sort it out later as we get above the tipping
5367 /* Assuming all cpus are the same in group */
5368 int max_cap_cpu = group_first_cpu(sg);
5371 * Assume smaller max capacity means more energy-efficient.
5372 * Ideally we should query the energy model for the right
5373 * answer but it easily ends up in an exhaustive search.
5375 if (capacity_of(max_cap_cpu) < target_max_cap &&
5376 task_fits_max(p, max_cap_cpu)) {
5378 target_max_cap = capacity_of(max_cap_cpu);
5380 } while (sg = sg->next, sg != sd->groups);
5382 /* Find cpu with sufficient capacity */
5383 for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg_target)) {
5385 * p's blocked utilization is still accounted for on prev_cpu
5386 * so prev_cpu will receive a negative bias due to the double
5387 * accounting. However, the blocked utilization may be zero.
5389 int new_util = cpu_util(i) + task_util(p);
5391 if (new_util > capacity_orig_of(i))
5394 if (new_util < capacity_curr_of(i)) {
5396 if (cpu_rq(i)->nr_running)
5400 /* cpu has capacity at higher OPP, keep it as fallback */
5401 if (target_cpu == task_cpu(p))
5405 if (target_cpu != task_cpu(p)) {
5406 struct energy_env eenv = {
5407 .util_delta = task_util(p),
5408 .src_cpu = task_cpu(p),
5409 .dst_cpu = target_cpu,
5412 /* Not enough spare capacity on previous cpu */
5413 if (cpu_overutilized(task_cpu(p)))
5416 if (energy_diff(&eenv) >= 0)
5424 * select_task_rq_fair: Select target runqueue for the waking task in domains
5425 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5426 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5428 * Balances load by selecting the idlest cpu in the idlest group, or under
5429 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5431 * Returns the target cpu number.
5433 * preempt must be disabled.
5436 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5438 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5439 int cpu = smp_processor_id();
5440 int new_cpu = prev_cpu;
5441 int want_affine = 0;
5442 int sync = wake_flags & WF_SYNC;
5444 if (sd_flag & SD_BALANCE_WAKE)
5445 want_affine = (!wake_wide(p) && task_fits_max(p, cpu) &&
5446 cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) ||
5450 for_each_domain(cpu, tmp) {
5451 if (!(tmp->flags & SD_LOAD_BALANCE))
5455 * If both cpu and prev_cpu are part of this domain,
5456 * cpu is a valid SD_WAKE_AFFINE target.
5458 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5459 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5464 if (tmp->flags & sd_flag)
5466 else if (!want_affine)
5471 sd = NULL; /* Prefer wake_affine over balance flags */
5472 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5477 if (energy_aware() && !cpu_rq(cpu)->rd->overutilized)
5478 new_cpu = energy_aware_wake_cpu(p, prev_cpu);
5479 else if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5480 new_cpu = select_idle_sibling(p, new_cpu);
5483 struct sched_group *group;
5486 if (!(sd->flags & sd_flag)) {
5491 group = find_idlest_group(sd, p, cpu, sd_flag);
5497 new_cpu = find_idlest_cpu(group, p, cpu);
5498 if (new_cpu == -1 || new_cpu == cpu) {
5499 /* Now try balancing at a lower domain level of cpu */
5504 /* Now try balancing at a lower domain level of new_cpu */
5506 weight = sd->span_weight;
5508 for_each_domain(cpu, tmp) {
5509 if (weight <= tmp->span_weight)
5511 if (tmp->flags & sd_flag)
5514 /* while loop will break here if sd == NULL */
5522 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5523 * cfs_rq_of(p) references at time of call are still valid and identify the
5524 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5525 * other assumptions, including the state of rq->lock, should be made.
5527 static void migrate_task_rq_fair(struct task_struct *p)
5530 * We are supposed to update the task to "current" time, then its up to date
5531 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5532 * what current time is, so simply throw away the out-of-date time. This
5533 * will result in the wakee task is less decayed, but giving the wakee more
5534 * load sounds not bad.
5536 remove_entity_load_avg(&p->se);
5538 /* Tell new CPU we are migrated */
5539 p->se.avg.last_update_time = 0;
5541 /* We have migrated, no longer consider this task hot */
5542 p->se.exec_start = 0;
5545 static void task_dead_fair(struct task_struct *p)
5547 remove_entity_load_avg(&p->se);
5549 #endif /* CONFIG_SMP */
5551 static unsigned long
5552 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5554 unsigned long gran = sysctl_sched_wakeup_granularity;
5557 * Since its curr running now, convert the gran from real-time
5558 * to virtual-time in his units.
5560 * By using 'se' instead of 'curr' we penalize light tasks, so
5561 * they get preempted easier. That is, if 'se' < 'curr' then
5562 * the resulting gran will be larger, therefore penalizing the
5563 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5564 * be smaller, again penalizing the lighter task.
5566 * This is especially important for buddies when the leftmost
5567 * task is higher priority than the buddy.
5569 return calc_delta_fair(gran, se);
5573 * Should 'se' preempt 'curr'.
5587 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5589 s64 gran, vdiff = curr->vruntime - se->vruntime;
5594 gran = wakeup_gran(curr, se);
5601 static void set_last_buddy(struct sched_entity *se)
5603 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5606 for_each_sched_entity(se)
5607 cfs_rq_of(se)->last = se;
5610 static void set_next_buddy(struct sched_entity *se)
5612 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5615 for_each_sched_entity(se)
5616 cfs_rq_of(se)->next = se;
5619 static void set_skip_buddy(struct sched_entity *se)
5621 for_each_sched_entity(se)
5622 cfs_rq_of(se)->skip = se;
5626 * Preempt the current task with a newly woken task if needed:
5628 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5630 struct task_struct *curr = rq->curr;
5631 struct sched_entity *se = &curr->se, *pse = &p->se;
5632 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5633 int scale = cfs_rq->nr_running >= sched_nr_latency;
5634 int next_buddy_marked = 0;
5636 if (unlikely(se == pse))
5640 * This is possible from callers such as attach_tasks(), in which we
5641 * unconditionally check_prempt_curr() after an enqueue (which may have
5642 * lead to a throttle). This both saves work and prevents false
5643 * next-buddy nomination below.
5645 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5648 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5649 set_next_buddy(pse);
5650 next_buddy_marked = 1;
5654 * We can come here with TIF_NEED_RESCHED already set from new task
5657 * Note: this also catches the edge-case of curr being in a throttled
5658 * group (e.g. via set_curr_task), since update_curr() (in the
5659 * enqueue of curr) will have resulted in resched being set. This
5660 * prevents us from potentially nominating it as a false LAST_BUDDY
5663 if (test_tsk_need_resched(curr))
5666 /* Idle tasks are by definition preempted by non-idle tasks. */
5667 if (unlikely(curr->policy == SCHED_IDLE) &&
5668 likely(p->policy != SCHED_IDLE))
5672 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5673 * is driven by the tick):
5675 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5678 find_matching_se(&se, &pse);
5679 update_curr(cfs_rq_of(se));
5681 if (wakeup_preempt_entity(se, pse) == 1) {
5683 * Bias pick_next to pick the sched entity that is
5684 * triggering this preemption.
5686 if (!next_buddy_marked)
5687 set_next_buddy(pse);
5696 * Only set the backward buddy when the current task is still
5697 * on the rq. This can happen when a wakeup gets interleaved
5698 * with schedule on the ->pre_schedule() or idle_balance()
5699 * point, either of which can * drop the rq lock.
5701 * Also, during early boot the idle thread is in the fair class,
5702 * for obvious reasons its a bad idea to schedule back to it.
5704 if (unlikely(!se->on_rq || curr == rq->idle))
5707 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5711 static struct task_struct *
5712 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5714 struct cfs_rq *cfs_rq = &rq->cfs;
5715 struct sched_entity *se;
5716 struct task_struct *p;
5720 #ifdef CONFIG_FAIR_GROUP_SCHED
5721 if (!cfs_rq->nr_running)
5724 if (prev->sched_class != &fair_sched_class)
5728 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5729 * likely that a next task is from the same cgroup as the current.
5731 * Therefore attempt to avoid putting and setting the entire cgroup
5732 * hierarchy, only change the part that actually changes.
5736 struct sched_entity *curr = cfs_rq->curr;
5739 * Since we got here without doing put_prev_entity() we also
5740 * have to consider cfs_rq->curr. If it is still a runnable
5741 * entity, update_curr() will update its vruntime, otherwise
5742 * forget we've ever seen it.
5746 update_curr(cfs_rq);
5751 * This call to check_cfs_rq_runtime() will do the
5752 * throttle and dequeue its entity in the parent(s).
5753 * Therefore the 'simple' nr_running test will indeed
5756 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5760 se = pick_next_entity(cfs_rq, curr);
5761 cfs_rq = group_cfs_rq(se);
5767 * Since we haven't yet done put_prev_entity and if the selected task
5768 * is a different task than we started out with, try and touch the
5769 * least amount of cfs_rqs.
5772 struct sched_entity *pse = &prev->se;
5774 while (!(cfs_rq = is_same_group(se, pse))) {
5775 int se_depth = se->depth;
5776 int pse_depth = pse->depth;
5778 if (se_depth <= pse_depth) {
5779 put_prev_entity(cfs_rq_of(pse), pse);
5780 pse = parent_entity(pse);
5782 if (se_depth >= pse_depth) {
5783 set_next_entity(cfs_rq_of(se), se);
5784 se = parent_entity(se);
5788 put_prev_entity(cfs_rq, pse);
5789 set_next_entity(cfs_rq, se);
5792 if (hrtick_enabled(rq))
5793 hrtick_start_fair(rq, p);
5795 rq->misfit_task = !task_fits_max(p, rq->cpu);
5802 if (!cfs_rq->nr_running)
5805 put_prev_task(rq, prev);
5808 se = pick_next_entity(cfs_rq, NULL);
5809 set_next_entity(cfs_rq, se);
5810 cfs_rq = group_cfs_rq(se);
5815 if (hrtick_enabled(rq))
5816 hrtick_start_fair(rq, p);
5818 rq->misfit_task = !task_fits_max(p, rq->cpu);
5823 rq->misfit_task = 0;
5825 * This is OK, because current is on_cpu, which avoids it being picked
5826 * for load-balance and preemption/IRQs are still disabled avoiding
5827 * further scheduler activity on it and we're being very careful to
5828 * re-start the picking loop.
5830 lockdep_unpin_lock(&rq->lock);
5831 new_tasks = idle_balance(rq);
5832 lockdep_pin_lock(&rq->lock);
5834 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5835 * possible for any higher priority task to appear. In that case we
5836 * must re-start the pick_next_entity() loop.
5848 * Account for a descheduled task:
5850 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5852 struct sched_entity *se = &prev->se;
5853 struct cfs_rq *cfs_rq;
5855 for_each_sched_entity(se) {
5856 cfs_rq = cfs_rq_of(se);
5857 put_prev_entity(cfs_rq, se);
5862 * sched_yield() is very simple
5864 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5866 static void yield_task_fair(struct rq *rq)
5868 struct task_struct *curr = rq->curr;
5869 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5870 struct sched_entity *se = &curr->se;
5873 * Are we the only task in the tree?
5875 if (unlikely(rq->nr_running == 1))
5878 clear_buddies(cfs_rq, se);
5880 if (curr->policy != SCHED_BATCH) {
5881 update_rq_clock(rq);
5883 * Update run-time statistics of the 'current'.
5885 update_curr(cfs_rq);
5887 * Tell update_rq_clock() that we've just updated,
5888 * so we don't do microscopic update in schedule()
5889 * and double the fastpath cost.
5891 rq_clock_skip_update(rq, true);
5897 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5899 struct sched_entity *se = &p->se;
5901 /* throttled hierarchies are not runnable */
5902 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5905 /* Tell the scheduler that we'd really like pse to run next. */
5908 yield_task_fair(rq);
5914 /**************************************************
5915 * Fair scheduling class load-balancing methods.
5919 * The purpose of load-balancing is to achieve the same basic fairness the
5920 * per-cpu scheduler provides, namely provide a proportional amount of compute
5921 * time to each task. This is expressed in the following equation:
5923 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5925 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5926 * W_i,0 is defined as:
5928 * W_i,0 = \Sum_j w_i,j (2)
5930 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5931 * is derived from the nice value as per prio_to_weight[].
5933 * The weight average is an exponential decay average of the instantaneous
5936 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5938 * C_i is the compute capacity of cpu i, typically it is the
5939 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5940 * can also include other factors [XXX].
5942 * To achieve this balance we define a measure of imbalance which follows
5943 * directly from (1):
5945 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5947 * We them move tasks around to minimize the imbalance. In the continuous
5948 * function space it is obvious this converges, in the discrete case we get
5949 * a few fun cases generally called infeasible weight scenarios.
5952 * - infeasible weights;
5953 * - local vs global optima in the discrete case. ]
5958 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5959 * for all i,j solution, we create a tree of cpus that follows the hardware
5960 * topology where each level pairs two lower groups (or better). This results
5961 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5962 * tree to only the first of the previous level and we decrease the frequency
5963 * of load-balance at each level inv. proportional to the number of cpus in
5969 * \Sum { --- * --- * 2^i } = O(n) (5)
5971 * `- size of each group
5972 * | | `- number of cpus doing load-balance
5974 * `- sum over all levels
5976 * Coupled with a limit on how many tasks we can migrate every balance pass,
5977 * this makes (5) the runtime complexity of the balancer.
5979 * An important property here is that each CPU is still (indirectly) connected
5980 * to every other cpu in at most O(log n) steps:
5982 * The adjacency matrix of the resulting graph is given by:
5985 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5988 * And you'll find that:
5990 * A^(log_2 n)_i,j != 0 for all i,j (7)
5992 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5993 * The task movement gives a factor of O(m), giving a convergence complexity
5996 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
6001 * In order to avoid CPUs going idle while there's still work to do, new idle
6002 * balancing is more aggressive and has the newly idle cpu iterate up the domain
6003 * tree itself instead of relying on other CPUs to bring it work.
6005 * This adds some complexity to both (5) and (8) but it reduces the total idle
6013 * Cgroups make a horror show out of (2), instead of a simple sum we get:
6016 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
6021 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
6023 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
6025 * The big problem is S_k, its a global sum needed to compute a local (W_i)
6028 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
6029 * rewrite all of this once again.]
6032 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
6034 enum fbq_type { regular, remote, all };
6043 #define LBF_ALL_PINNED 0x01
6044 #define LBF_NEED_BREAK 0x02
6045 #define LBF_DST_PINNED 0x04
6046 #define LBF_SOME_PINNED 0x08
6049 struct sched_domain *sd;
6057 struct cpumask *dst_grpmask;
6059 enum cpu_idle_type idle;
6061 unsigned int src_grp_nr_running;
6062 /* The set of CPUs under consideration for load-balancing */
6063 struct cpumask *cpus;
6068 unsigned int loop_break;
6069 unsigned int loop_max;
6071 enum fbq_type fbq_type;
6072 enum group_type busiest_group_type;
6073 struct list_head tasks;
6077 * Is this task likely cache-hot:
6079 static int task_hot(struct task_struct *p, struct lb_env *env)
6083 lockdep_assert_held(&env->src_rq->lock);
6085 if (p->sched_class != &fair_sched_class)
6088 if (unlikely(p->policy == SCHED_IDLE))
6092 * Buddy candidates are cache hot:
6094 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6095 (&p->se == cfs_rq_of(&p->se)->next ||
6096 &p->se == cfs_rq_of(&p->se)->last))
6099 if (sysctl_sched_migration_cost == -1)
6101 if (sysctl_sched_migration_cost == 0)
6104 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6106 return delta < (s64)sysctl_sched_migration_cost;
6109 #ifdef CONFIG_NUMA_BALANCING
6111 * Returns 1, if task migration degrades locality
6112 * Returns 0, if task migration improves locality i.e migration preferred.
6113 * Returns -1, if task migration is not affected by locality.
6115 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6117 struct numa_group *numa_group = rcu_dereference(p->numa_group);
6118 unsigned long src_faults, dst_faults;
6119 int src_nid, dst_nid;
6121 if (!static_branch_likely(&sched_numa_balancing))
6124 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6127 src_nid = cpu_to_node(env->src_cpu);
6128 dst_nid = cpu_to_node(env->dst_cpu);
6130 if (src_nid == dst_nid)
6133 /* Migrating away from the preferred node is always bad. */
6134 if (src_nid == p->numa_preferred_nid) {
6135 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6141 /* Encourage migration to the preferred node. */
6142 if (dst_nid == p->numa_preferred_nid)
6146 src_faults = group_faults(p, src_nid);
6147 dst_faults = group_faults(p, dst_nid);
6149 src_faults = task_faults(p, src_nid);
6150 dst_faults = task_faults(p, dst_nid);
6153 return dst_faults < src_faults;
6157 static inline int migrate_degrades_locality(struct task_struct *p,
6165 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6168 int can_migrate_task(struct task_struct *p, struct lb_env *env)
6172 lockdep_assert_held(&env->src_rq->lock);
6175 * We do not migrate tasks that are:
6176 * 1) throttled_lb_pair, or
6177 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6178 * 3) running (obviously), or
6179 * 4) are cache-hot on their current CPU.
6181 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6184 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6187 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6189 env->flags |= LBF_SOME_PINNED;
6192 * Remember if this task can be migrated to any other cpu in
6193 * our sched_group. We may want to revisit it if we couldn't
6194 * meet load balance goals by pulling other tasks on src_cpu.
6196 * Also avoid computing new_dst_cpu if we have already computed
6197 * one in current iteration.
6199 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6202 /* Prevent to re-select dst_cpu via env's cpus */
6203 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6204 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6205 env->flags |= LBF_DST_PINNED;
6206 env->new_dst_cpu = cpu;
6214 /* Record that we found atleast one task that could run on dst_cpu */
6215 env->flags &= ~LBF_ALL_PINNED;
6217 if (task_running(env->src_rq, p)) {
6218 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6223 * Aggressive migration if:
6224 * 1) destination numa is preferred
6225 * 2) task is cache cold, or
6226 * 3) too many balance attempts have failed.
6228 tsk_cache_hot = migrate_degrades_locality(p, env);
6229 if (tsk_cache_hot == -1)
6230 tsk_cache_hot = task_hot(p, env);
6232 if (tsk_cache_hot <= 0 ||
6233 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6234 if (tsk_cache_hot == 1) {
6235 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
6236 schedstat_inc(p, se.statistics.nr_forced_migrations);
6241 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
6246 * detach_task() -- detach the task for the migration specified in env
6248 static void detach_task(struct task_struct *p, struct lb_env *env)
6250 lockdep_assert_held(&env->src_rq->lock);
6252 deactivate_task(env->src_rq, p, 0);
6253 p->on_rq = TASK_ON_RQ_MIGRATING;
6254 set_task_cpu(p, env->dst_cpu);
6258 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6259 * part of active balancing operations within "domain".
6261 * Returns a task if successful and NULL otherwise.
6263 static struct task_struct *detach_one_task(struct lb_env *env)
6265 struct task_struct *p, *n;
6267 lockdep_assert_held(&env->src_rq->lock);
6269 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
6270 if (!can_migrate_task(p, env))
6273 detach_task(p, env);
6276 * Right now, this is only the second place where
6277 * lb_gained[env->idle] is updated (other is detach_tasks)
6278 * so we can safely collect stats here rather than
6279 * inside detach_tasks().
6281 schedstat_inc(env->sd, lb_gained[env->idle]);
6287 static const unsigned int sched_nr_migrate_break = 32;
6290 * detach_tasks() -- tries to detach up to imbalance weighted load from
6291 * busiest_rq, as part of a balancing operation within domain "sd".
6293 * Returns number of detached tasks if successful and 0 otherwise.
6295 static int detach_tasks(struct lb_env *env)
6297 struct list_head *tasks = &env->src_rq->cfs_tasks;
6298 struct task_struct *p;
6302 lockdep_assert_held(&env->src_rq->lock);
6304 if (env->imbalance <= 0)
6307 while (!list_empty(tasks)) {
6309 * We don't want to steal all, otherwise we may be treated likewise,
6310 * which could at worst lead to a livelock crash.
6312 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6315 p = list_first_entry(tasks, struct task_struct, se.group_node);
6318 /* We've more or less seen every task there is, call it quits */
6319 if (env->loop > env->loop_max)
6322 /* take a breather every nr_migrate tasks */
6323 if (env->loop > env->loop_break) {
6324 env->loop_break += sched_nr_migrate_break;
6325 env->flags |= LBF_NEED_BREAK;
6329 if (!can_migrate_task(p, env))
6332 load = task_h_load(p);
6334 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6337 if ((load / 2) > env->imbalance)
6340 detach_task(p, env);
6341 list_add(&p->se.group_node, &env->tasks);
6344 env->imbalance -= load;
6346 #ifdef CONFIG_PREEMPT
6348 * NEWIDLE balancing is a source of latency, so preemptible
6349 * kernels will stop after the first task is detached to minimize
6350 * the critical section.
6352 if (env->idle == CPU_NEWLY_IDLE)
6357 * We only want to steal up to the prescribed amount of
6360 if (env->imbalance <= 0)
6365 list_move_tail(&p->se.group_node, tasks);
6369 * Right now, this is one of only two places we collect this stat
6370 * so we can safely collect detach_one_task() stats here rather
6371 * than inside detach_one_task().
6373 schedstat_add(env->sd, lb_gained[env->idle], detached);
6379 * attach_task() -- attach the task detached by detach_task() to its new rq.
6381 static void attach_task(struct rq *rq, struct task_struct *p)
6383 lockdep_assert_held(&rq->lock);
6385 BUG_ON(task_rq(p) != rq);
6386 p->on_rq = TASK_ON_RQ_QUEUED;
6387 activate_task(rq, p, 0);
6388 check_preempt_curr(rq, p, 0);
6392 * attach_one_task() -- attaches the task returned from detach_one_task() to
6395 static void attach_one_task(struct rq *rq, struct task_struct *p)
6397 raw_spin_lock(&rq->lock);
6400 * We want to potentially raise target_cpu's OPP.
6402 update_capacity_of(cpu_of(rq));
6403 raw_spin_unlock(&rq->lock);
6407 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6410 static void attach_tasks(struct lb_env *env)
6412 struct list_head *tasks = &env->tasks;
6413 struct task_struct *p;
6415 raw_spin_lock(&env->dst_rq->lock);
6417 while (!list_empty(tasks)) {
6418 p = list_first_entry(tasks, struct task_struct, se.group_node);
6419 list_del_init(&p->se.group_node);
6421 attach_task(env->dst_rq, p);
6425 * We want to potentially raise env.dst_cpu's OPP.
6427 update_capacity_of(env->dst_cpu);
6429 raw_spin_unlock(&env->dst_rq->lock);
6432 #ifdef CONFIG_FAIR_GROUP_SCHED
6433 static void update_blocked_averages(int cpu)
6435 struct rq *rq = cpu_rq(cpu);
6436 struct cfs_rq *cfs_rq;
6437 unsigned long flags;
6439 raw_spin_lock_irqsave(&rq->lock, flags);
6440 update_rq_clock(rq);
6443 * Iterates the task_group tree in a bottom up fashion, see
6444 * list_add_leaf_cfs_rq() for details.
6446 for_each_leaf_cfs_rq(rq, cfs_rq) {
6447 /* throttled entities do not contribute to load */
6448 if (throttled_hierarchy(cfs_rq))
6451 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6452 update_tg_load_avg(cfs_rq, 0);
6454 raw_spin_unlock_irqrestore(&rq->lock, flags);
6458 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6459 * This needs to be done in a top-down fashion because the load of a child
6460 * group is a fraction of its parents load.
6462 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6464 struct rq *rq = rq_of(cfs_rq);
6465 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6466 unsigned long now = jiffies;
6469 if (cfs_rq->last_h_load_update == now)
6472 cfs_rq->h_load_next = NULL;
6473 for_each_sched_entity(se) {
6474 cfs_rq = cfs_rq_of(se);
6475 cfs_rq->h_load_next = se;
6476 if (cfs_rq->last_h_load_update == now)
6481 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6482 cfs_rq->last_h_load_update = now;
6485 while ((se = cfs_rq->h_load_next) != NULL) {
6486 load = cfs_rq->h_load;
6487 load = div64_ul(load * se->avg.load_avg,
6488 cfs_rq_load_avg(cfs_rq) + 1);
6489 cfs_rq = group_cfs_rq(se);
6490 cfs_rq->h_load = load;
6491 cfs_rq->last_h_load_update = now;
6495 static unsigned long task_h_load(struct task_struct *p)
6497 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6499 update_cfs_rq_h_load(cfs_rq);
6500 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6501 cfs_rq_load_avg(cfs_rq) + 1);
6504 static inline void update_blocked_averages(int cpu)
6506 struct rq *rq = cpu_rq(cpu);
6507 struct cfs_rq *cfs_rq = &rq->cfs;
6508 unsigned long flags;
6510 raw_spin_lock_irqsave(&rq->lock, flags);
6511 update_rq_clock(rq);
6512 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6513 raw_spin_unlock_irqrestore(&rq->lock, flags);
6516 static unsigned long task_h_load(struct task_struct *p)
6518 return p->se.avg.load_avg;
6522 /********** Helpers for find_busiest_group ************************/
6525 * sg_lb_stats - stats of a sched_group required for load_balancing
6527 struct sg_lb_stats {
6528 unsigned long avg_load; /*Avg load across the CPUs of the group */
6529 unsigned long group_load; /* Total load over the CPUs of the group */
6530 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6531 unsigned long load_per_task;
6532 unsigned long group_capacity;
6533 unsigned long group_util; /* Total utilization of the group */
6534 unsigned int sum_nr_running; /* Nr tasks running in the group */
6535 unsigned int idle_cpus;
6536 unsigned int group_weight;
6537 enum group_type group_type;
6538 int group_no_capacity;
6539 int group_misfit_task; /* A cpu has a task too big for its capacity */
6540 #ifdef CONFIG_NUMA_BALANCING
6541 unsigned int nr_numa_running;
6542 unsigned int nr_preferred_running;
6547 * sd_lb_stats - Structure to store the statistics of a sched_domain
6548 * during load balancing.
6550 struct sd_lb_stats {
6551 struct sched_group *busiest; /* Busiest group in this sd */
6552 struct sched_group *local; /* Local group in this sd */
6553 unsigned long total_load; /* Total load of all groups in sd */
6554 unsigned long total_capacity; /* Total capacity of all groups in sd */
6555 unsigned long avg_load; /* Average load across all groups in sd */
6557 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6558 struct sg_lb_stats local_stat; /* Statistics of the local group */
6561 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6564 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6565 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6566 * We must however clear busiest_stat::avg_load because
6567 * update_sd_pick_busiest() reads this before assignment.
6569 *sds = (struct sd_lb_stats){
6573 .total_capacity = 0UL,
6576 .sum_nr_running = 0,
6577 .group_type = group_other,
6583 * get_sd_load_idx - Obtain the load index for a given sched domain.
6584 * @sd: The sched_domain whose load_idx is to be obtained.
6585 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6587 * Return: The load index.
6589 static inline int get_sd_load_idx(struct sched_domain *sd,
6590 enum cpu_idle_type idle)
6596 load_idx = sd->busy_idx;
6599 case CPU_NEWLY_IDLE:
6600 load_idx = sd->newidle_idx;
6603 load_idx = sd->idle_idx;
6610 static unsigned long scale_rt_capacity(int cpu)
6612 struct rq *rq = cpu_rq(cpu);
6613 u64 total, used, age_stamp, avg;
6617 * Since we're reading these variables without serialization make sure
6618 * we read them once before doing sanity checks on them.
6620 age_stamp = READ_ONCE(rq->age_stamp);
6621 avg = READ_ONCE(rq->rt_avg);
6622 delta = __rq_clock_broken(rq) - age_stamp;
6624 if (unlikely(delta < 0))
6627 total = sched_avg_period() + delta;
6629 used = div_u64(avg, total);
6632 * deadline bandwidth is defined at system level so we must
6633 * weight this bandwidth with the max capacity of the system.
6634 * As a reminder, avg_bw is 20bits width and
6635 * scale_cpu_capacity is 10 bits width
6637 used += div_u64(rq->dl.avg_bw, arch_scale_cpu_capacity(NULL, cpu));
6639 if (likely(used < SCHED_CAPACITY_SCALE))
6640 return SCHED_CAPACITY_SCALE - used;
6645 void init_max_cpu_capacity(struct max_cpu_capacity *mcc)
6647 raw_spin_lock_init(&mcc->lock);
6652 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6654 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6655 struct sched_group *sdg = sd->groups;
6656 struct max_cpu_capacity *mcc;
6657 unsigned long max_capacity;
6659 unsigned long flags;
6661 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6663 mcc = &cpu_rq(cpu)->rd->max_cpu_capacity;
6665 raw_spin_lock_irqsave(&mcc->lock, flags);
6666 max_capacity = mcc->val;
6667 max_cap_cpu = mcc->cpu;
6669 if ((max_capacity > capacity && max_cap_cpu == cpu) ||
6670 (max_capacity < capacity)) {
6671 mcc->val = capacity;
6673 #ifdef CONFIG_SCHED_DEBUG
6674 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6675 pr_info("CPU%d: update max cpu_capacity %lu\n", cpu, capacity);
6679 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6681 skip_unlock: __attribute__ ((unused));
6682 capacity *= scale_rt_capacity(cpu);
6683 capacity >>= SCHED_CAPACITY_SHIFT;
6688 cpu_rq(cpu)->cpu_capacity = capacity;
6689 sdg->sgc->capacity = capacity;
6690 sdg->sgc->max_capacity = capacity;
6693 void update_group_capacity(struct sched_domain *sd, int cpu)
6695 struct sched_domain *child = sd->child;
6696 struct sched_group *group, *sdg = sd->groups;
6697 unsigned long capacity, max_capacity;
6698 unsigned long interval;
6700 interval = msecs_to_jiffies(sd->balance_interval);
6701 interval = clamp(interval, 1UL, max_load_balance_interval);
6702 sdg->sgc->next_update = jiffies + interval;
6705 update_cpu_capacity(sd, cpu);
6712 if (child->flags & SD_OVERLAP) {
6714 * SD_OVERLAP domains cannot assume that child groups
6715 * span the current group.
6718 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6719 struct sched_group_capacity *sgc;
6720 struct rq *rq = cpu_rq(cpu);
6723 * build_sched_domains() -> init_sched_groups_capacity()
6724 * gets here before we've attached the domains to the
6727 * Use capacity_of(), which is set irrespective of domains
6728 * in update_cpu_capacity().
6730 * This avoids capacity from being 0 and
6731 * causing divide-by-zero issues on boot.
6733 if (unlikely(!rq->sd)) {
6734 capacity += capacity_of(cpu);
6736 sgc = rq->sd->groups->sgc;
6737 capacity += sgc->capacity;
6740 max_capacity = max(capacity, max_capacity);
6744 * !SD_OVERLAP domains can assume that child groups
6745 * span the current group.
6748 group = child->groups;
6750 struct sched_group_capacity *sgc = group->sgc;
6752 capacity += sgc->capacity;
6753 max_capacity = max(sgc->max_capacity, max_capacity);
6754 group = group->next;
6755 } while (group != child->groups);
6758 sdg->sgc->capacity = capacity;
6759 sdg->sgc->max_capacity = max_capacity;
6763 * Check whether the capacity of the rq has been noticeably reduced by side
6764 * activity. The imbalance_pct is used for the threshold.
6765 * Return true is the capacity is reduced
6768 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6770 return ((rq->cpu_capacity * sd->imbalance_pct) <
6771 (rq->cpu_capacity_orig * 100));
6775 * Group imbalance indicates (and tries to solve) the problem where balancing
6776 * groups is inadequate due to tsk_cpus_allowed() constraints.
6778 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6779 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6782 * { 0 1 2 3 } { 4 5 6 7 }
6785 * If we were to balance group-wise we'd place two tasks in the first group and
6786 * two tasks in the second group. Clearly this is undesired as it will overload
6787 * cpu 3 and leave one of the cpus in the second group unused.
6789 * The current solution to this issue is detecting the skew in the first group
6790 * by noticing the lower domain failed to reach balance and had difficulty
6791 * moving tasks due to affinity constraints.
6793 * When this is so detected; this group becomes a candidate for busiest; see
6794 * update_sd_pick_busiest(). And calculate_imbalance() and
6795 * find_busiest_group() avoid some of the usual balance conditions to allow it
6796 * to create an effective group imbalance.
6798 * This is a somewhat tricky proposition since the next run might not find the
6799 * group imbalance and decide the groups need to be balanced again. A most
6800 * subtle and fragile situation.
6803 static inline int sg_imbalanced(struct sched_group *group)
6805 return group->sgc->imbalance;
6809 * group_has_capacity returns true if the group has spare capacity that could
6810 * be used by some tasks.
6811 * We consider that a group has spare capacity if the * number of task is
6812 * smaller than the number of CPUs or if the utilization is lower than the
6813 * available capacity for CFS tasks.
6814 * For the latter, we use a threshold to stabilize the state, to take into
6815 * account the variance of the tasks' load and to return true if the available
6816 * capacity in meaningful for the load balancer.
6817 * As an example, an available capacity of 1% can appear but it doesn't make
6818 * any benefit for the load balance.
6821 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6823 if (sgs->sum_nr_running < sgs->group_weight)
6826 if ((sgs->group_capacity * 100) >
6827 (sgs->group_util * env->sd->imbalance_pct))
6834 * group_is_overloaded returns true if the group has more tasks than it can
6836 * group_is_overloaded is not equals to !group_has_capacity because a group
6837 * with the exact right number of tasks, has no more spare capacity but is not
6838 * overloaded so both group_has_capacity and group_is_overloaded return
6842 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6844 if (sgs->sum_nr_running <= sgs->group_weight)
6847 if ((sgs->group_capacity * 100) <
6848 (sgs->group_util * env->sd->imbalance_pct))
6856 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
6857 * per-cpu capacity than sched_group ref.
6860 group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
6862 return sg->sgc->max_capacity + capacity_margin - SCHED_LOAD_SCALE <
6863 ref->sgc->max_capacity;
6867 group_type group_classify(struct sched_group *group,
6868 struct sg_lb_stats *sgs)
6870 if (sgs->group_no_capacity)
6871 return group_overloaded;
6873 if (sg_imbalanced(group))
6874 return group_imbalanced;
6876 if (sgs->group_misfit_task)
6877 return group_misfit_task;
6883 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6884 * @env: The load balancing environment.
6885 * @group: sched_group whose statistics are to be updated.
6886 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6887 * @local_group: Does group contain this_cpu.
6888 * @sgs: variable to hold the statistics for this group.
6889 * @overload: Indicate more than one runnable task for any CPU.
6890 * @overutilized: Indicate overutilization for any CPU.
6892 static inline void update_sg_lb_stats(struct lb_env *env,
6893 struct sched_group *group, int load_idx,
6894 int local_group, struct sg_lb_stats *sgs,
6895 bool *overload, bool *overutilized)
6900 memset(sgs, 0, sizeof(*sgs));
6902 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6903 struct rq *rq = cpu_rq(i);
6905 /* Bias balancing toward cpus of our domain */
6907 load = target_load(i, load_idx);
6909 load = source_load(i, load_idx);
6911 sgs->group_load += load;
6912 sgs->group_util += cpu_util(i);
6913 sgs->sum_nr_running += rq->cfs.h_nr_running;
6915 if (rq->nr_running > 1)
6918 #ifdef CONFIG_NUMA_BALANCING
6919 sgs->nr_numa_running += rq->nr_numa_running;
6920 sgs->nr_preferred_running += rq->nr_preferred_running;
6922 sgs->sum_weighted_load += weighted_cpuload(i);
6926 if (cpu_overutilized(i)) {
6927 *overutilized = true;
6928 if (!sgs->group_misfit_task && rq->misfit_task)
6929 sgs->group_misfit_task = capacity_of(i);
6933 /* Adjust by relative CPU capacity of the group */
6934 sgs->group_capacity = group->sgc->capacity;
6935 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6937 if (sgs->sum_nr_running)
6938 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6940 sgs->group_weight = group->group_weight;
6942 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6943 sgs->group_type = group_classify(group, sgs);
6947 * update_sd_pick_busiest - return 1 on busiest group
6948 * @env: The load balancing environment.
6949 * @sds: sched_domain statistics
6950 * @sg: sched_group candidate to be checked for being the busiest
6951 * @sgs: sched_group statistics
6953 * Determine if @sg is a busier group than the previously selected
6956 * Return: %true if @sg is a busier group than the previously selected
6957 * busiest group. %false otherwise.
6959 static bool update_sd_pick_busiest(struct lb_env *env,
6960 struct sd_lb_stats *sds,
6961 struct sched_group *sg,
6962 struct sg_lb_stats *sgs)
6964 struct sg_lb_stats *busiest = &sds->busiest_stat;
6966 if (sgs->group_type > busiest->group_type)
6969 if (sgs->group_type < busiest->group_type)
6973 * Candidate sg doesn't face any serious load-balance problems
6974 * so don't pick it if the local sg is already filled up.
6976 if (sgs->group_type == group_other &&
6977 !group_has_capacity(env, &sds->local_stat))
6980 if (sgs->avg_load <= busiest->avg_load)
6984 * Candiate sg has no more than one task per cpu and has higher
6985 * per-cpu capacity. No reason to pull tasks to less capable cpus.
6987 if (sgs->sum_nr_running <= sgs->group_weight &&
6988 group_smaller_cpu_capacity(sds->local, sg))
6991 /* This is the busiest node in its class. */
6992 if (!(env->sd->flags & SD_ASYM_PACKING))
6996 * ASYM_PACKING needs to move all the work to the lowest
6997 * numbered CPUs in the group, therefore mark all groups
6998 * higher than ourself as busy.
7000 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
7004 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
7011 #ifdef CONFIG_NUMA_BALANCING
7012 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7014 if (sgs->sum_nr_running > sgs->nr_numa_running)
7016 if (sgs->sum_nr_running > sgs->nr_preferred_running)
7021 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7023 if (rq->nr_running > rq->nr_numa_running)
7025 if (rq->nr_running > rq->nr_preferred_running)
7030 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7035 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7039 #endif /* CONFIG_NUMA_BALANCING */
7042 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7043 * @env: The load balancing environment.
7044 * @sds: variable to hold the statistics for this sched_domain.
7046 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7048 struct sched_domain *child = env->sd->child;
7049 struct sched_group *sg = env->sd->groups;
7050 struct sg_lb_stats tmp_sgs;
7051 int load_idx, prefer_sibling = 0;
7052 bool overload = false, overutilized = false;
7054 if (child && child->flags & SD_PREFER_SIBLING)
7057 load_idx = get_sd_load_idx(env->sd, env->idle);
7060 struct sg_lb_stats *sgs = &tmp_sgs;
7063 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
7066 sgs = &sds->local_stat;
7068 if (env->idle != CPU_NEWLY_IDLE ||
7069 time_after_eq(jiffies, sg->sgc->next_update))
7070 update_group_capacity(env->sd, env->dst_cpu);
7073 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
7074 &overload, &overutilized);
7080 * In case the child domain prefers tasks go to siblings
7081 * first, lower the sg capacity so that we'll try
7082 * and move all the excess tasks away. We lower the capacity
7083 * of a group only if the local group has the capacity to fit
7084 * these excess tasks. The extra check prevents the case where
7085 * you always pull from the heaviest group when it is already
7086 * under-utilized (possible with a large weight task outweighs
7087 * the tasks on the system).
7089 if (prefer_sibling && sds->local &&
7090 group_has_capacity(env, &sds->local_stat) &&
7091 (sgs->sum_nr_running > 1)) {
7092 sgs->group_no_capacity = 1;
7093 sgs->group_type = group_classify(sg, sgs);
7097 * Ignore task groups with misfit tasks if local group has no
7098 * capacity or if per-cpu capacity isn't higher.
7100 if (sgs->group_type == group_misfit_task &&
7101 (!group_has_capacity(env, &sds->local_stat) ||
7102 !group_smaller_cpu_capacity(sg, sds->local)))
7103 sgs->group_type = group_other;
7105 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7107 sds->busiest_stat = *sgs;
7111 /* Now, start updating sd_lb_stats */
7112 sds->total_load += sgs->group_load;
7113 sds->total_capacity += sgs->group_capacity;
7116 } while (sg != env->sd->groups);
7118 if (env->sd->flags & SD_NUMA)
7119 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7121 env->src_grp_nr_running = sds->busiest_stat.sum_nr_running;
7123 if (!env->sd->parent) {
7124 /* update overload indicator if we are at root domain */
7125 if (env->dst_rq->rd->overload != overload)
7126 env->dst_rq->rd->overload = overload;
7128 /* Update over-utilization (tipping point, U >= 0) indicator */
7129 if (env->dst_rq->rd->overutilized != overutilized)
7130 env->dst_rq->rd->overutilized = overutilized;
7132 if (!env->dst_rq->rd->overutilized && overutilized)
7133 env->dst_rq->rd->overutilized = true;
7138 * check_asym_packing - Check to see if the group is packed into the
7141 * This is primarily intended to used at the sibling level. Some
7142 * cores like POWER7 prefer to use lower numbered SMT threads. In the
7143 * case of POWER7, it can move to lower SMT modes only when higher
7144 * threads are idle. When in lower SMT modes, the threads will
7145 * perform better since they share less core resources. Hence when we
7146 * have idle threads, we want them to be the higher ones.
7148 * This packing function is run on idle threads. It checks to see if
7149 * the busiest CPU in this domain (core in the P7 case) has a higher
7150 * CPU number than the packing function is being run on. Here we are
7151 * assuming lower CPU number will be equivalent to lower a SMT thread
7154 * Return: 1 when packing is required and a task should be moved to
7155 * this CPU. The amount of the imbalance is returned in *imbalance.
7157 * @env: The load balancing environment.
7158 * @sds: Statistics of the sched_domain which is to be packed
7160 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7164 if (!(env->sd->flags & SD_ASYM_PACKING))
7170 busiest_cpu = group_first_cpu(sds->busiest);
7171 if (env->dst_cpu > busiest_cpu)
7174 env->imbalance = DIV_ROUND_CLOSEST(
7175 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7176 SCHED_CAPACITY_SCALE);
7182 * fix_small_imbalance - Calculate the minor imbalance that exists
7183 * amongst the groups of a sched_domain, during
7185 * @env: The load balancing environment.
7186 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7189 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7191 unsigned long tmp, capa_now = 0, capa_move = 0;
7192 unsigned int imbn = 2;
7193 unsigned long scaled_busy_load_per_task;
7194 struct sg_lb_stats *local, *busiest;
7196 local = &sds->local_stat;
7197 busiest = &sds->busiest_stat;
7199 if (!local->sum_nr_running)
7200 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
7201 else if (busiest->load_per_task > local->load_per_task)
7204 scaled_busy_load_per_task =
7205 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7206 busiest->group_capacity;
7208 if (busiest->avg_load + scaled_busy_load_per_task >=
7209 local->avg_load + (scaled_busy_load_per_task * imbn)) {
7210 env->imbalance = busiest->load_per_task;
7215 * OK, we don't have enough imbalance to justify moving tasks,
7216 * however we may be able to increase total CPU capacity used by
7220 capa_now += busiest->group_capacity *
7221 min(busiest->load_per_task, busiest->avg_load);
7222 capa_now += local->group_capacity *
7223 min(local->load_per_task, local->avg_load);
7224 capa_now /= SCHED_CAPACITY_SCALE;
7226 /* Amount of load we'd subtract */
7227 if (busiest->avg_load > scaled_busy_load_per_task) {
7228 capa_move += busiest->group_capacity *
7229 min(busiest->load_per_task,
7230 busiest->avg_load - scaled_busy_load_per_task);
7233 /* Amount of load we'd add */
7234 if (busiest->avg_load * busiest->group_capacity <
7235 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7236 tmp = (busiest->avg_load * busiest->group_capacity) /
7237 local->group_capacity;
7239 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7240 local->group_capacity;
7242 capa_move += local->group_capacity *
7243 min(local->load_per_task, local->avg_load + tmp);
7244 capa_move /= SCHED_CAPACITY_SCALE;
7246 /* Move if we gain throughput */
7247 if (capa_move > capa_now)
7248 env->imbalance = busiest->load_per_task;
7252 * calculate_imbalance - Calculate the amount of imbalance present within the
7253 * groups of a given sched_domain during load balance.
7254 * @env: load balance environment
7255 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7257 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7259 unsigned long max_pull, load_above_capacity = ~0UL;
7260 struct sg_lb_stats *local, *busiest;
7262 local = &sds->local_stat;
7263 busiest = &sds->busiest_stat;
7265 if (busiest->group_type == group_imbalanced) {
7267 * In the group_imb case we cannot rely on group-wide averages
7268 * to ensure cpu-load equilibrium, look at wider averages. XXX
7270 busiest->load_per_task =
7271 min(busiest->load_per_task, sds->avg_load);
7275 * In the presence of smp nice balancing, certain scenarios can have
7276 * max load less than avg load(as we skip the groups at or below
7277 * its cpu_capacity, while calculating max_load..)
7279 if (busiest->avg_load <= sds->avg_load ||
7280 local->avg_load >= sds->avg_load) {
7281 /* Misfitting tasks should be migrated in any case */
7282 if (busiest->group_type == group_misfit_task) {
7283 env->imbalance = busiest->group_misfit_task;
7288 * Busiest group is overloaded, local is not, use the spare
7289 * cycles to maximize throughput
7291 if (busiest->group_type == group_overloaded &&
7292 local->group_type <= group_misfit_task) {
7293 env->imbalance = busiest->load_per_task;
7298 return fix_small_imbalance(env, sds);
7302 * If there aren't any idle cpus, avoid creating some.
7304 if (busiest->group_type == group_overloaded &&
7305 local->group_type == group_overloaded) {
7306 load_above_capacity = busiest->sum_nr_running *
7308 if (load_above_capacity > busiest->group_capacity)
7309 load_above_capacity -= busiest->group_capacity;
7311 load_above_capacity = ~0UL;
7315 * We're trying to get all the cpus to the average_load, so we don't
7316 * want to push ourselves above the average load, nor do we wish to
7317 * reduce the max loaded cpu below the average load. At the same time,
7318 * we also don't want to reduce the group load below the group capacity
7319 * (so that we can implement power-savings policies etc). Thus we look
7320 * for the minimum possible imbalance.
7322 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7324 /* How much load to actually move to equalise the imbalance */
7325 env->imbalance = min(
7326 max_pull * busiest->group_capacity,
7327 (sds->avg_load - local->avg_load) * local->group_capacity
7328 ) / SCHED_CAPACITY_SCALE;
7330 /* Boost imbalance to allow misfit task to be balanced. */
7331 if (busiest->group_type == group_misfit_task)
7332 env->imbalance = max_t(long, env->imbalance,
7333 busiest->group_misfit_task);
7336 * if *imbalance is less than the average load per runnable task
7337 * there is no guarantee that any tasks will be moved so we'll have
7338 * a think about bumping its value to force at least one task to be
7341 if (env->imbalance < busiest->load_per_task)
7342 return fix_small_imbalance(env, sds);
7345 /******* find_busiest_group() helpers end here *********************/
7348 * find_busiest_group - Returns the busiest group within the sched_domain
7349 * if there is an imbalance. If there isn't an imbalance, and
7350 * the user has opted for power-savings, it returns a group whose
7351 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
7352 * such a group exists.
7354 * Also calculates the amount of weighted load which should be moved
7355 * to restore balance.
7357 * @env: The load balancing environment.
7359 * Return: - The busiest group if imbalance exists.
7360 * - If no imbalance and user has opted for power-savings balance,
7361 * return the least loaded group whose CPUs can be
7362 * put to idle by rebalancing its tasks onto our group.
7364 static struct sched_group *find_busiest_group(struct lb_env *env)
7366 struct sg_lb_stats *local, *busiest;
7367 struct sd_lb_stats sds;
7369 init_sd_lb_stats(&sds);
7372 * Compute the various statistics relavent for load balancing at
7375 update_sd_lb_stats(env, &sds);
7377 if (energy_aware() && !env->dst_rq->rd->overutilized)
7380 local = &sds.local_stat;
7381 busiest = &sds.busiest_stat;
7383 /* ASYM feature bypasses nice load balance check */
7384 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
7385 check_asym_packing(env, &sds))
7388 /* There is no busy sibling group to pull tasks from */
7389 if (!sds.busiest || busiest->sum_nr_running == 0)
7392 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7393 / sds.total_capacity;
7396 * If the busiest group is imbalanced the below checks don't
7397 * work because they assume all things are equal, which typically
7398 * isn't true due to cpus_allowed constraints and the like.
7400 if (busiest->group_type == group_imbalanced)
7403 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7404 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7405 busiest->group_no_capacity)
7408 /* Misfitting tasks should be dealt with regardless of the avg load */
7409 if (busiest->group_type == group_misfit_task) {
7414 * If the local group is busier than the selected busiest group
7415 * don't try and pull any tasks.
7417 if (local->avg_load >= busiest->avg_load)
7421 * Don't pull any tasks if this group is already above the domain
7424 if (local->avg_load >= sds.avg_load)
7427 if (env->idle == CPU_IDLE) {
7429 * This cpu is idle. If the busiest group is not overloaded
7430 * and there is no imbalance between this and busiest group
7431 * wrt idle cpus, it is balanced. The imbalance becomes
7432 * significant if the diff is greater than 1 otherwise we
7433 * might end up to just move the imbalance on another group
7435 if ((busiest->group_type != group_overloaded) &&
7436 (local->idle_cpus <= (busiest->idle_cpus + 1)) &&
7437 !group_smaller_cpu_capacity(sds.busiest, sds.local))
7441 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7442 * imbalance_pct to be conservative.
7444 if (100 * busiest->avg_load <=
7445 env->sd->imbalance_pct * local->avg_load)
7450 env->busiest_group_type = busiest->group_type;
7451 /* Looks like there is an imbalance. Compute it */
7452 calculate_imbalance(env, &sds);
7461 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7463 static struct rq *find_busiest_queue(struct lb_env *env,
7464 struct sched_group *group)
7466 struct rq *busiest = NULL, *rq;
7467 unsigned long busiest_load = 0, busiest_capacity = 1;
7470 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7471 unsigned long capacity, wl;
7475 rt = fbq_classify_rq(rq);
7478 * We classify groups/runqueues into three groups:
7479 * - regular: there are !numa tasks
7480 * - remote: there are numa tasks that run on the 'wrong' node
7481 * - all: there is no distinction
7483 * In order to avoid migrating ideally placed numa tasks,
7484 * ignore those when there's better options.
7486 * If we ignore the actual busiest queue to migrate another
7487 * task, the next balance pass can still reduce the busiest
7488 * queue by moving tasks around inside the node.
7490 * If we cannot move enough load due to this classification
7491 * the next pass will adjust the group classification and
7492 * allow migration of more tasks.
7494 * Both cases only affect the total convergence complexity.
7496 if (rt > env->fbq_type)
7499 capacity = capacity_of(i);
7501 wl = weighted_cpuload(i);
7504 * When comparing with imbalance, use weighted_cpuload()
7505 * which is not scaled with the cpu capacity.
7508 if (rq->nr_running == 1 && wl > env->imbalance &&
7509 !check_cpu_capacity(rq, env->sd) &&
7510 env->busiest_group_type != group_misfit_task)
7514 * For the load comparisons with the other cpu's, consider
7515 * the weighted_cpuload() scaled with the cpu capacity, so
7516 * that the load can be moved away from the cpu that is
7517 * potentially running at a lower capacity.
7519 * Thus we're looking for max(wl_i / capacity_i), crosswise
7520 * multiplication to rid ourselves of the division works out
7521 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7522 * our previous maximum.
7524 if (wl * busiest_capacity > busiest_load * capacity) {
7526 busiest_capacity = capacity;
7535 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7536 * so long as it is large enough.
7538 #define MAX_PINNED_INTERVAL 512
7540 /* Working cpumask for load_balance and load_balance_newidle. */
7541 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7543 static int need_active_balance(struct lb_env *env)
7545 struct sched_domain *sd = env->sd;
7547 if (env->idle == CPU_NEWLY_IDLE) {
7550 * ASYM_PACKING needs to force migrate tasks from busy but
7551 * higher numbered CPUs in order to pack all tasks in the
7552 * lowest numbered CPUs.
7554 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7559 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7560 * It's worth migrating the task if the src_cpu's capacity is reduced
7561 * because of other sched_class or IRQs if more capacity stays
7562 * available on dst_cpu.
7564 if ((env->idle != CPU_NOT_IDLE) &&
7565 (env->src_rq->cfs.h_nr_running == 1)) {
7566 if ((check_cpu_capacity(env->src_rq, sd)) &&
7567 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7571 if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
7572 env->src_rq->cfs.h_nr_running == 1 &&
7573 cpu_overutilized(env->src_cpu) &&
7574 !cpu_overutilized(env->dst_cpu)) {
7578 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7581 static int active_load_balance_cpu_stop(void *data);
7583 static int should_we_balance(struct lb_env *env)
7585 struct sched_group *sg = env->sd->groups;
7586 struct cpumask *sg_cpus, *sg_mask;
7587 int cpu, balance_cpu = -1;
7590 * In the newly idle case, we will allow all the cpu's
7591 * to do the newly idle load balance.
7593 if (env->idle == CPU_NEWLY_IDLE)
7596 sg_cpus = sched_group_cpus(sg);
7597 sg_mask = sched_group_mask(sg);
7598 /* Try to find first idle cpu */
7599 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7600 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7607 if (balance_cpu == -1)
7608 balance_cpu = group_balance_cpu(sg);
7611 * First idle cpu or the first cpu(busiest) in this sched group
7612 * is eligible for doing load balancing at this and above domains.
7614 return balance_cpu == env->dst_cpu;
7618 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7619 * tasks if there is an imbalance.
7621 static int load_balance(int this_cpu, struct rq *this_rq,
7622 struct sched_domain *sd, enum cpu_idle_type idle,
7623 int *continue_balancing)
7625 int ld_moved, cur_ld_moved, active_balance = 0;
7626 struct sched_domain *sd_parent = sd->parent;
7627 struct sched_group *group;
7629 unsigned long flags;
7630 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7632 struct lb_env env = {
7634 .dst_cpu = this_cpu,
7636 .dst_grpmask = sched_group_cpus(sd->groups),
7638 .loop_break = sched_nr_migrate_break,
7641 .tasks = LIST_HEAD_INIT(env.tasks),
7645 * For NEWLY_IDLE load_balancing, we don't need to consider
7646 * other cpus in our group
7648 if (idle == CPU_NEWLY_IDLE)
7649 env.dst_grpmask = NULL;
7651 cpumask_copy(cpus, cpu_active_mask);
7653 schedstat_inc(sd, lb_count[idle]);
7656 if (!should_we_balance(&env)) {
7657 *continue_balancing = 0;
7661 group = find_busiest_group(&env);
7663 schedstat_inc(sd, lb_nobusyg[idle]);
7667 busiest = find_busiest_queue(&env, group);
7669 schedstat_inc(sd, lb_nobusyq[idle]);
7673 BUG_ON(busiest == env.dst_rq);
7675 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7677 env.src_cpu = busiest->cpu;
7678 env.src_rq = busiest;
7681 if (busiest->nr_running > 1) {
7683 * Attempt to move tasks. If find_busiest_group has found
7684 * an imbalance but busiest->nr_running <= 1, the group is
7685 * still unbalanced. ld_moved simply stays zero, so it is
7686 * correctly treated as an imbalance.
7688 env.flags |= LBF_ALL_PINNED;
7689 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7692 raw_spin_lock_irqsave(&busiest->lock, flags);
7695 * cur_ld_moved - load moved in current iteration
7696 * ld_moved - cumulative load moved across iterations
7698 cur_ld_moved = detach_tasks(&env);
7700 * We want to potentially lower env.src_cpu's OPP.
7703 update_capacity_of(env.src_cpu);
7706 * We've detached some tasks from busiest_rq. Every
7707 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7708 * unlock busiest->lock, and we are able to be sure
7709 * that nobody can manipulate the tasks in parallel.
7710 * See task_rq_lock() family for the details.
7713 raw_spin_unlock(&busiest->lock);
7717 ld_moved += cur_ld_moved;
7720 local_irq_restore(flags);
7722 if (env.flags & LBF_NEED_BREAK) {
7723 env.flags &= ~LBF_NEED_BREAK;
7728 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7729 * us and move them to an alternate dst_cpu in our sched_group
7730 * where they can run. The upper limit on how many times we
7731 * iterate on same src_cpu is dependent on number of cpus in our
7734 * This changes load balance semantics a bit on who can move
7735 * load to a given_cpu. In addition to the given_cpu itself
7736 * (or a ilb_cpu acting on its behalf where given_cpu is
7737 * nohz-idle), we now have balance_cpu in a position to move
7738 * load to given_cpu. In rare situations, this may cause
7739 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7740 * _independently_ and at _same_ time to move some load to
7741 * given_cpu) causing exceess load to be moved to given_cpu.
7742 * This however should not happen so much in practice and
7743 * moreover subsequent load balance cycles should correct the
7744 * excess load moved.
7746 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7748 /* Prevent to re-select dst_cpu via env's cpus */
7749 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7751 env.dst_rq = cpu_rq(env.new_dst_cpu);
7752 env.dst_cpu = env.new_dst_cpu;
7753 env.flags &= ~LBF_DST_PINNED;
7755 env.loop_break = sched_nr_migrate_break;
7758 * Go back to "more_balance" rather than "redo" since we
7759 * need to continue with same src_cpu.
7765 * We failed to reach balance because of affinity.
7768 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7770 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7771 *group_imbalance = 1;
7774 /* All tasks on this runqueue were pinned by CPU affinity */
7775 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7776 cpumask_clear_cpu(cpu_of(busiest), cpus);
7777 if (!cpumask_empty(cpus)) {
7779 env.loop_break = sched_nr_migrate_break;
7782 goto out_all_pinned;
7787 schedstat_inc(sd, lb_failed[idle]);
7789 * Increment the failure counter only on periodic balance.
7790 * We do not want newidle balance, which can be very
7791 * frequent, pollute the failure counter causing
7792 * excessive cache_hot migrations and active balances.
7794 if (idle != CPU_NEWLY_IDLE)
7795 if (env.src_grp_nr_running > 1)
7796 sd->nr_balance_failed++;
7798 if (need_active_balance(&env)) {
7799 raw_spin_lock_irqsave(&busiest->lock, flags);
7801 /* don't kick the active_load_balance_cpu_stop,
7802 * if the curr task on busiest cpu can't be
7805 if (!cpumask_test_cpu(this_cpu,
7806 tsk_cpus_allowed(busiest->curr))) {
7807 raw_spin_unlock_irqrestore(&busiest->lock,
7809 env.flags |= LBF_ALL_PINNED;
7810 goto out_one_pinned;
7814 * ->active_balance synchronizes accesses to
7815 * ->active_balance_work. Once set, it's cleared
7816 * only after active load balance is finished.
7818 if (!busiest->active_balance) {
7819 busiest->active_balance = 1;
7820 busiest->push_cpu = this_cpu;
7823 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7825 if (active_balance) {
7826 stop_one_cpu_nowait(cpu_of(busiest),
7827 active_load_balance_cpu_stop, busiest,
7828 &busiest->active_balance_work);
7832 * We've kicked active balancing, reset the failure
7835 sd->nr_balance_failed = sd->cache_nice_tries+1;
7838 sd->nr_balance_failed = 0;
7840 if (likely(!active_balance)) {
7841 /* We were unbalanced, so reset the balancing interval */
7842 sd->balance_interval = sd->min_interval;
7845 * If we've begun active balancing, start to back off. This
7846 * case may not be covered by the all_pinned logic if there
7847 * is only 1 task on the busy runqueue (because we don't call
7850 if (sd->balance_interval < sd->max_interval)
7851 sd->balance_interval *= 2;
7858 * We reach balance although we may have faced some affinity
7859 * constraints. Clear the imbalance flag if it was set.
7862 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7864 if (*group_imbalance)
7865 *group_imbalance = 0;
7870 * We reach balance because all tasks are pinned at this level so
7871 * we can't migrate them. Let the imbalance flag set so parent level
7872 * can try to migrate them.
7874 schedstat_inc(sd, lb_balanced[idle]);
7876 sd->nr_balance_failed = 0;
7879 /* tune up the balancing interval */
7880 if (((env.flags & LBF_ALL_PINNED) &&
7881 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7882 (sd->balance_interval < sd->max_interval))
7883 sd->balance_interval *= 2;
7890 static inline unsigned long
7891 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7893 unsigned long interval = sd->balance_interval;
7896 interval *= sd->busy_factor;
7898 /* scale ms to jiffies */
7899 interval = msecs_to_jiffies(interval);
7900 interval = clamp(interval, 1UL, max_load_balance_interval);
7906 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7908 unsigned long interval, next;
7910 interval = get_sd_balance_interval(sd, cpu_busy);
7911 next = sd->last_balance + interval;
7913 if (time_after(*next_balance, next))
7914 *next_balance = next;
7918 * idle_balance is called by schedule() if this_cpu is about to become
7919 * idle. Attempts to pull tasks from other CPUs.
7921 static int idle_balance(struct rq *this_rq)
7923 unsigned long next_balance = jiffies + HZ;
7924 int this_cpu = this_rq->cpu;
7925 struct sched_domain *sd;
7926 int pulled_task = 0;
7929 idle_enter_fair(this_rq);
7932 * We must set idle_stamp _before_ calling idle_balance(), such that we
7933 * measure the duration of idle_balance() as idle time.
7935 this_rq->idle_stamp = rq_clock(this_rq);
7937 if (!energy_aware() &&
7938 (this_rq->avg_idle < sysctl_sched_migration_cost ||
7939 !this_rq->rd->overload)) {
7941 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7943 update_next_balance(sd, 0, &next_balance);
7949 raw_spin_unlock(&this_rq->lock);
7951 update_blocked_averages(this_cpu);
7953 for_each_domain(this_cpu, sd) {
7954 int continue_balancing = 1;
7955 u64 t0, domain_cost;
7957 if (!(sd->flags & SD_LOAD_BALANCE))
7960 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7961 update_next_balance(sd, 0, &next_balance);
7965 if (sd->flags & SD_BALANCE_NEWIDLE) {
7966 t0 = sched_clock_cpu(this_cpu);
7968 pulled_task = load_balance(this_cpu, this_rq,
7970 &continue_balancing);
7972 domain_cost = sched_clock_cpu(this_cpu) - t0;
7973 if (domain_cost > sd->max_newidle_lb_cost)
7974 sd->max_newidle_lb_cost = domain_cost;
7976 curr_cost += domain_cost;
7979 update_next_balance(sd, 0, &next_balance);
7982 * Stop searching for tasks to pull if there are
7983 * now runnable tasks on this rq.
7985 if (pulled_task || this_rq->nr_running > 0)
7990 raw_spin_lock(&this_rq->lock);
7992 if (curr_cost > this_rq->max_idle_balance_cost)
7993 this_rq->max_idle_balance_cost = curr_cost;
7996 * While browsing the domains, we released the rq lock, a task could
7997 * have been enqueued in the meantime. Since we're not going idle,
7998 * pretend we pulled a task.
8000 if (this_rq->cfs.h_nr_running && !pulled_task)
8004 /* Move the next balance forward */
8005 if (time_after(this_rq->next_balance, next_balance))
8006 this_rq->next_balance = next_balance;
8008 /* Is there a task of a high priority class? */
8009 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8013 idle_exit_fair(this_rq);
8014 this_rq->idle_stamp = 0;
8021 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
8022 * running tasks off the busiest CPU onto idle CPUs. It requires at
8023 * least 1 task to be running on each physical CPU where possible, and
8024 * avoids physical / logical imbalances.
8026 static int active_load_balance_cpu_stop(void *data)
8028 struct rq *busiest_rq = data;
8029 int busiest_cpu = cpu_of(busiest_rq);
8030 int target_cpu = busiest_rq->push_cpu;
8031 struct rq *target_rq = cpu_rq(target_cpu);
8032 struct sched_domain *sd;
8033 struct task_struct *p = NULL;
8035 raw_spin_lock_irq(&busiest_rq->lock);
8037 /* make sure the requested cpu hasn't gone down in the meantime */
8038 if (unlikely(busiest_cpu != smp_processor_id() ||
8039 !busiest_rq->active_balance))
8042 /* Is there any task to move? */
8043 if (busiest_rq->nr_running <= 1)
8047 * This condition is "impossible", if it occurs
8048 * we need to fix it. Originally reported by
8049 * Bjorn Helgaas on a 128-cpu setup.
8051 BUG_ON(busiest_rq == target_rq);
8053 /* Search for an sd spanning us and the target CPU. */
8055 for_each_domain(target_cpu, sd) {
8056 if ((sd->flags & SD_LOAD_BALANCE) &&
8057 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
8062 struct lb_env env = {
8064 .dst_cpu = target_cpu,
8065 .dst_rq = target_rq,
8066 .src_cpu = busiest_rq->cpu,
8067 .src_rq = busiest_rq,
8071 schedstat_inc(sd, alb_count);
8073 p = detach_one_task(&env);
8075 schedstat_inc(sd, alb_pushed);
8077 * We want to potentially lower env.src_cpu's OPP.
8079 update_capacity_of(env.src_cpu);
8082 schedstat_inc(sd, alb_failed);
8086 busiest_rq->active_balance = 0;
8087 raw_spin_unlock(&busiest_rq->lock);
8090 attach_one_task(target_rq, p);
8097 static inline int on_null_domain(struct rq *rq)
8099 return unlikely(!rcu_dereference_sched(rq->sd));
8102 #ifdef CONFIG_NO_HZ_COMMON
8104 * idle load balancing details
8105 * - When one of the busy CPUs notice that there may be an idle rebalancing
8106 * needed, they will kick the idle load balancer, which then does idle
8107 * load balancing for all the idle CPUs.
8110 cpumask_var_t idle_cpus_mask;
8112 unsigned long next_balance; /* in jiffy units */
8113 } nohz ____cacheline_aligned;
8115 static inline int find_new_ilb(void)
8117 int ilb = cpumask_first(nohz.idle_cpus_mask);
8119 if (ilb < nr_cpu_ids && idle_cpu(ilb))
8126 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
8127 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
8128 * CPU (if there is one).
8130 static void nohz_balancer_kick(void)
8134 nohz.next_balance++;
8136 ilb_cpu = find_new_ilb();
8138 if (ilb_cpu >= nr_cpu_ids)
8141 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8144 * Use smp_send_reschedule() instead of resched_cpu().
8145 * This way we generate a sched IPI on the target cpu which
8146 * is idle. And the softirq performing nohz idle load balance
8147 * will be run before returning from the IPI.
8149 smp_send_reschedule(ilb_cpu);
8153 static inline void nohz_balance_exit_idle(int cpu)
8155 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8157 * Completely isolated CPUs don't ever set, so we must test.
8159 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
8160 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
8161 atomic_dec(&nohz.nr_cpus);
8163 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8167 static inline void set_cpu_sd_state_busy(void)
8169 struct sched_domain *sd;
8170 int cpu = smp_processor_id();
8173 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8175 if (!sd || !sd->nohz_idle)
8179 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
8184 void set_cpu_sd_state_idle(void)
8186 struct sched_domain *sd;
8187 int cpu = smp_processor_id();
8190 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8192 if (!sd || sd->nohz_idle)
8196 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
8202 * This routine will record that the cpu is going idle with tick stopped.
8203 * This info will be used in performing idle load balancing in the future.
8205 void nohz_balance_enter_idle(int cpu)
8208 * If this cpu is going down, then nothing needs to be done.
8210 if (!cpu_active(cpu))
8213 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
8217 * If we're a completely isolated CPU, we don't play.
8219 if (on_null_domain(cpu_rq(cpu)))
8222 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
8223 atomic_inc(&nohz.nr_cpus);
8224 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8227 static int sched_ilb_notifier(struct notifier_block *nfb,
8228 unsigned long action, void *hcpu)
8230 switch (action & ~CPU_TASKS_FROZEN) {
8232 nohz_balance_exit_idle(smp_processor_id());
8240 static DEFINE_SPINLOCK(balancing);
8243 * Scale the max load_balance interval with the number of CPUs in the system.
8244 * This trades load-balance latency on larger machines for less cross talk.
8246 void update_max_interval(void)
8248 max_load_balance_interval = HZ*num_online_cpus()/10;
8252 * It checks each scheduling domain to see if it is due to be balanced,
8253 * and initiates a balancing operation if so.
8255 * Balancing parameters are set up in init_sched_domains.
8257 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8259 int continue_balancing = 1;
8261 unsigned long interval;
8262 struct sched_domain *sd;
8263 /* Earliest time when we have to do rebalance again */
8264 unsigned long next_balance = jiffies + 60*HZ;
8265 int update_next_balance = 0;
8266 int need_serialize, need_decay = 0;
8269 update_blocked_averages(cpu);
8272 for_each_domain(cpu, sd) {
8274 * Decay the newidle max times here because this is a regular
8275 * visit to all the domains. Decay ~1% per second.
8277 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
8278 sd->max_newidle_lb_cost =
8279 (sd->max_newidle_lb_cost * 253) / 256;
8280 sd->next_decay_max_lb_cost = jiffies + HZ;
8283 max_cost += sd->max_newidle_lb_cost;
8285 if (!(sd->flags & SD_LOAD_BALANCE))
8289 * Stop the load balance at this level. There is another
8290 * CPU in our sched group which is doing load balancing more
8293 if (!continue_balancing) {
8299 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8301 need_serialize = sd->flags & SD_SERIALIZE;
8302 if (need_serialize) {
8303 if (!spin_trylock(&balancing))
8307 if (time_after_eq(jiffies, sd->last_balance + interval)) {
8308 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8310 * The LBF_DST_PINNED logic could have changed
8311 * env->dst_cpu, so we can't know our idle
8312 * state even if we migrated tasks. Update it.
8314 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8316 sd->last_balance = jiffies;
8317 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8320 spin_unlock(&balancing);
8322 if (time_after(next_balance, sd->last_balance + interval)) {
8323 next_balance = sd->last_balance + interval;
8324 update_next_balance = 1;
8329 * Ensure the rq-wide value also decays but keep it at a
8330 * reasonable floor to avoid funnies with rq->avg_idle.
8332 rq->max_idle_balance_cost =
8333 max((u64)sysctl_sched_migration_cost, max_cost);
8338 * next_balance will be updated only when there is a need.
8339 * When the cpu is attached to null domain for ex, it will not be
8342 if (likely(update_next_balance)) {
8343 rq->next_balance = next_balance;
8345 #ifdef CONFIG_NO_HZ_COMMON
8347 * If this CPU has been elected to perform the nohz idle
8348 * balance. Other idle CPUs have already rebalanced with
8349 * nohz_idle_balance() and nohz.next_balance has been
8350 * updated accordingly. This CPU is now running the idle load
8351 * balance for itself and we need to update the
8352 * nohz.next_balance accordingly.
8354 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8355 nohz.next_balance = rq->next_balance;
8360 #ifdef CONFIG_NO_HZ_COMMON
8362 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8363 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8365 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8367 int this_cpu = this_rq->cpu;
8370 /* Earliest time when we have to do rebalance again */
8371 unsigned long next_balance = jiffies + 60*HZ;
8372 int update_next_balance = 0;
8374 if (idle != CPU_IDLE ||
8375 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8378 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8379 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8383 * If this cpu gets work to do, stop the load balancing
8384 * work being done for other cpus. Next load
8385 * balancing owner will pick it up.
8390 rq = cpu_rq(balance_cpu);
8393 * If time for next balance is due,
8396 if (time_after_eq(jiffies, rq->next_balance)) {
8397 raw_spin_lock_irq(&rq->lock);
8398 update_rq_clock(rq);
8399 update_idle_cpu_load(rq);
8400 raw_spin_unlock_irq(&rq->lock);
8401 rebalance_domains(rq, CPU_IDLE);
8404 if (time_after(next_balance, rq->next_balance)) {
8405 next_balance = rq->next_balance;
8406 update_next_balance = 1;
8411 * next_balance will be updated only when there is a need.
8412 * When the CPU is attached to null domain for ex, it will not be
8415 if (likely(update_next_balance))
8416 nohz.next_balance = next_balance;
8418 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8422 * Current heuristic for kicking the idle load balancer in the presence
8423 * of an idle cpu in the system.
8424 * - This rq has more than one task.
8425 * - This rq has at least one CFS task and the capacity of the CPU is
8426 * significantly reduced because of RT tasks or IRQs.
8427 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8428 * multiple busy cpu.
8429 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8430 * domain span are idle.
8432 static inline bool nohz_kick_needed(struct rq *rq)
8434 unsigned long now = jiffies;
8435 struct sched_domain *sd;
8436 struct sched_group_capacity *sgc;
8437 int nr_busy, cpu = rq->cpu;
8440 if (unlikely(rq->idle_balance))
8444 * We may be recently in ticked or tickless idle mode. At the first
8445 * busy tick after returning from idle, we will update the busy stats.
8447 set_cpu_sd_state_busy();
8448 nohz_balance_exit_idle(cpu);
8451 * None are in tickless mode and hence no need for NOHZ idle load
8454 if (likely(!atomic_read(&nohz.nr_cpus)))
8457 if (time_before(now, nohz.next_balance))
8460 if (rq->nr_running >= 2 &&
8461 (!energy_aware() || cpu_overutilized(cpu)))
8465 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8466 if (sd && !energy_aware()) {
8467 sgc = sd->groups->sgc;
8468 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8477 sd = rcu_dereference(rq->sd);
8479 if ((rq->cfs.h_nr_running >= 1) &&
8480 check_cpu_capacity(rq, sd)) {
8486 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8487 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8488 sched_domain_span(sd)) < cpu)) {
8498 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8502 * run_rebalance_domains is triggered when needed from the scheduler tick.
8503 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8505 static void run_rebalance_domains(struct softirq_action *h)
8507 struct rq *this_rq = this_rq();
8508 enum cpu_idle_type idle = this_rq->idle_balance ?
8509 CPU_IDLE : CPU_NOT_IDLE;
8512 * If this cpu has a pending nohz_balance_kick, then do the
8513 * balancing on behalf of the other idle cpus whose ticks are
8514 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8515 * give the idle cpus a chance to load balance. Else we may
8516 * load balance only within the local sched_domain hierarchy
8517 * and abort nohz_idle_balance altogether if we pull some load.
8519 nohz_idle_balance(this_rq, idle);
8520 rebalance_domains(this_rq, idle);
8524 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8526 void trigger_load_balance(struct rq *rq)
8528 /* Don't need to rebalance while attached to NULL domain */
8529 if (unlikely(on_null_domain(rq)))
8532 if (time_after_eq(jiffies, rq->next_balance))
8533 raise_softirq(SCHED_SOFTIRQ);
8534 #ifdef CONFIG_NO_HZ_COMMON
8535 if (nohz_kick_needed(rq))
8536 nohz_balancer_kick();
8540 static void rq_online_fair(struct rq *rq)
8544 update_runtime_enabled(rq);
8547 static void rq_offline_fair(struct rq *rq)
8551 /* Ensure any throttled groups are reachable by pick_next_task */
8552 unthrottle_offline_cfs_rqs(rq);
8555 #endif /* CONFIG_SMP */
8558 * scheduler tick hitting a task of our scheduling class:
8560 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8562 struct cfs_rq *cfs_rq;
8563 struct sched_entity *se = &curr->se;
8565 for_each_sched_entity(se) {
8566 cfs_rq = cfs_rq_of(se);
8567 entity_tick(cfs_rq, se, queued);
8570 if (static_branch_unlikely(&sched_numa_balancing))
8571 task_tick_numa(rq, curr);
8573 if (!rq->rd->overutilized && cpu_overutilized(task_cpu(curr)))
8574 rq->rd->overutilized = true;
8576 rq->misfit_task = !task_fits_max(curr, rq->cpu);
8580 * called on fork with the child task as argument from the parent's context
8581 * - child not yet on the tasklist
8582 * - preemption disabled
8584 static void task_fork_fair(struct task_struct *p)
8586 struct cfs_rq *cfs_rq;
8587 struct sched_entity *se = &p->se, *curr;
8588 int this_cpu = smp_processor_id();
8589 struct rq *rq = this_rq();
8590 unsigned long flags;
8592 raw_spin_lock_irqsave(&rq->lock, flags);
8594 update_rq_clock(rq);
8596 cfs_rq = task_cfs_rq(current);
8597 curr = cfs_rq->curr;
8600 * Not only the cpu but also the task_group of the parent might have
8601 * been changed after parent->se.parent,cfs_rq were copied to
8602 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8603 * of child point to valid ones.
8606 __set_task_cpu(p, this_cpu);
8609 update_curr(cfs_rq);
8612 se->vruntime = curr->vruntime;
8613 place_entity(cfs_rq, se, 1);
8615 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8617 * Upon rescheduling, sched_class::put_prev_task() will place
8618 * 'current' within the tree based on its new key value.
8620 swap(curr->vruntime, se->vruntime);
8624 se->vruntime -= cfs_rq->min_vruntime;
8626 raw_spin_unlock_irqrestore(&rq->lock, flags);
8630 * Priority of the task has changed. Check to see if we preempt
8634 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8636 if (!task_on_rq_queued(p))
8640 * Reschedule if we are currently running on this runqueue and
8641 * our priority decreased, or if we are not currently running on
8642 * this runqueue and our priority is higher than the current's
8644 if (rq->curr == p) {
8645 if (p->prio > oldprio)
8648 check_preempt_curr(rq, p, 0);
8651 static inline bool vruntime_normalized(struct task_struct *p)
8653 struct sched_entity *se = &p->se;
8656 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8657 * the dequeue_entity(.flags=0) will already have normalized the
8664 * When !on_rq, vruntime of the task has usually NOT been normalized.
8665 * But there are some cases where it has already been normalized:
8667 * - A forked child which is waiting for being woken up by
8668 * wake_up_new_task().
8669 * - A task which has been woken up by try_to_wake_up() and
8670 * waiting for actually being woken up by sched_ttwu_pending().
8672 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8678 static void detach_task_cfs_rq(struct task_struct *p)
8680 struct sched_entity *se = &p->se;
8681 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8683 if (!vruntime_normalized(p)) {
8685 * Fix up our vruntime so that the current sleep doesn't
8686 * cause 'unlimited' sleep bonus.
8688 place_entity(cfs_rq, se, 0);
8689 se->vruntime -= cfs_rq->min_vruntime;
8692 /* Catch up with the cfs_rq and remove our load when we leave */
8693 detach_entity_load_avg(cfs_rq, se);
8696 static void attach_task_cfs_rq(struct task_struct *p)
8698 struct sched_entity *se = &p->se;
8699 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8701 #ifdef CONFIG_FAIR_GROUP_SCHED
8703 * Since the real-depth could have been changed (only FAIR
8704 * class maintain depth value), reset depth properly.
8706 se->depth = se->parent ? se->parent->depth + 1 : 0;
8709 /* Synchronize task with its cfs_rq */
8710 attach_entity_load_avg(cfs_rq, se);
8712 if (!vruntime_normalized(p))
8713 se->vruntime += cfs_rq->min_vruntime;
8716 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8718 detach_task_cfs_rq(p);
8721 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8723 attach_task_cfs_rq(p);
8725 if (task_on_rq_queued(p)) {
8727 * We were most likely switched from sched_rt, so
8728 * kick off the schedule if running, otherwise just see
8729 * if we can still preempt the current task.
8734 check_preempt_curr(rq, p, 0);
8738 /* Account for a task changing its policy or group.
8740 * This routine is mostly called to set cfs_rq->curr field when a task
8741 * migrates between groups/classes.
8743 static void set_curr_task_fair(struct rq *rq)
8745 struct sched_entity *se = &rq->curr->se;
8747 for_each_sched_entity(se) {
8748 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8750 set_next_entity(cfs_rq, se);
8751 /* ensure bandwidth has been allocated on our new cfs_rq */
8752 account_cfs_rq_runtime(cfs_rq, 0);
8756 void init_cfs_rq(struct cfs_rq *cfs_rq)
8758 cfs_rq->tasks_timeline = RB_ROOT;
8759 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8760 #ifndef CONFIG_64BIT
8761 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8764 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8765 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8769 #ifdef CONFIG_FAIR_GROUP_SCHED
8770 static void task_move_group_fair(struct task_struct *p)
8772 detach_task_cfs_rq(p);
8773 set_task_rq(p, task_cpu(p));
8776 /* Tell se's cfs_rq has been changed -- migrated */
8777 p->se.avg.last_update_time = 0;
8779 attach_task_cfs_rq(p);
8782 void free_fair_sched_group(struct task_group *tg)
8786 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8788 for_each_possible_cpu(i) {
8790 kfree(tg->cfs_rq[i]);
8793 remove_entity_load_avg(tg->se[i]);
8802 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8804 struct cfs_rq *cfs_rq;
8805 struct sched_entity *se;
8808 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8811 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8815 tg->shares = NICE_0_LOAD;
8817 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8819 for_each_possible_cpu(i) {
8820 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8821 GFP_KERNEL, cpu_to_node(i));
8825 se = kzalloc_node(sizeof(struct sched_entity),
8826 GFP_KERNEL, cpu_to_node(i));
8830 init_cfs_rq(cfs_rq);
8831 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8832 init_entity_runnable_average(se);
8843 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8845 struct rq *rq = cpu_rq(cpu);
8846 unsigned long flags;
8849 * Only empty task groups can be destroyed; so we can speculatively
8850 * check on_list without danger of it being re-added.
8852 if (!tg->cfs_rq[cpu]->on_list)
8855 raw_spin_lock_irqsave(&rq->lock, flags);
8856 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8857 raw_spin_unlock_irqrestore(&rq->lock, flags);
8860 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8861 struct sched_entity *se, int cpu,
8862 struct sched_entity *parent)
8864 struct rq *rq = cpu_rq(cpu);
8868 init_cfs_rq_runtime(cfs_rq);
8870 tg->cfs_rq[cpu] = cfs_rq;
8873 /* se could be NULL for root_task_group */
8878 se->cfs_rq = &rq->cfs;
8881 se->cfs_rq = parent->my_q;
8882 se->depth = parent->depth + 1;
8886 /* guarantee group entities always have weight */
8887 update_load_set(&se->load, NICE_0_LOAD);
8888 se->parent = parent;
8891 static DEFINE_MUTEX(shares_mutex);
8893 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8896 unsigned long flags;
8899 * We can't change the weight of the root cgroup.
8904 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8906 mutex_lock(&shares_mutex);
8907 if (tg->shares == shares)
8910 tg->shares = shares;
8911 for_each_possible_cpu(i) {
8912 struct rq *rq = cpu_rq(i);
8913 struct sched_entity *se;
8916 /* Propagate contribution to hierarchy */
8917 raw_spin_lock_irqsave(&rq->lock, flags);
8919 /* Possible calls to update_curr() need rq clock */
8920 update_rq_clock(rq);
8921 for_each_sched_entity(se)
8922 update_cfs_shares(group_cfs_rq(se));
8923 raw_spin_unlock_irqrestore(&rq->lock, flags);
8927 mutex_unlock(&shares_mutex);
8930 #else /* CONFIG_FAIR_GROUP_SCHED */
8932 void free_fair_sched_group(struct task_group *tg) { }
8934 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8939 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
8941 #endif /* CONFIG_FAIR_GROUP_SCHED */
8944 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8946 struct sched_entity *se = &task->se;
8947 unsigned int rr_interval = 0;
8950 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8953 if (rq->cfs.load.weight)
8954 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8960 * All the scheduling class methods:
8962 const struct sched_class fair_sched_class = {
8963 .next = &idle_sched_class,
8964 .enqueue_task = enqueue_task_fair,
8965 .dequeue_task = dequeue_task_fair,
8966 .yield_task = yield_task_fair,
8967 .yield_to_task = yield_to_task_fair,
8969 .check_preempt_curr = check_preempt_wakeup,
8971 .pick_next_task = pick_next_task_fair,
8972 .put_prev_task = put_prev_task_fair,
8975 .select_task_rq = select_task_rq_fair,
8976 .migrate_task_rq = migrate_task_rq_fair,
8978 .rq_online = rq_online_fair,
8979 .rq_offline = rq_offline_fair,
8981 .task_waking = task_waking_fair,
8982 .task_dead = task_dead_fair,
8983 .set_cpus_allowed = set_cpus_allowed_common,
8986 .set_curr_task = set_curr_task_fair,
8987 .task_tick = task_tick_fair,
8988 .task_fork = task_fork_fair,
8990 .prio_changed = prio_changed_fair,
8991 .switched_from = switched_from_fair,
8992 .switched_to = switched_to_fair,
8994 .get_rr_interval = get_rr_interval_fair,
8996 .update_curr = update_curr_fair,
8998 #ifdef CONFIG_FAIR_GROUP_SCHED
8999 .task_move_group = task_move_group_fair,
9003 #ifdef CONFIG_SCHED_DEBUG
9004 void print_cfs_stats(struct seq_file *m, int cpu)
9006 struct cfs_rq *cfs_rq;
9009 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
9010 print_cfs_rq(m, cpu, cfs_rq);
9014 #ifdef CONFIG_NUMA_BALANCING
9015 void show_numa_stats(struct task_struct *p, struct seq_file *m)
9018 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
9020 for_each_online_node(node) {
9021 if (p->numa_faults) {
9022 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
9023 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
9025 if (p->numa_group) {
9026 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
9027 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
9029 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
9032 #endif /* CONFIG_NUMA_BALANCING */
9033 #endif /* CONFIG_SCHED_DEBUG */
9035 __init void init_sched_fair_class(void)
9038 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
9040 #ifdef CONFIG_NO_HZ_COMMON
9041 nohz.next_balance = jiffies;
9042 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
9043 cpu_notifier(sched_ilb_notifier, 0);