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 <pzijlstr@redhat.com>
23 #include <linux/latencytop.h>
24 #include <linux/sched.h>
25 #include <linux/cpumask.h>
26 #include <linux/cpuidle.h>
27 #include <linux/slab.h>
28 #include <linux/profile.h>
29 #include <linux/interrupt.h>
30 #include <linux/mempolicy.h>
31 #include <linux/migrate.h>
32 #include <linux/task_work.h>
34 #include <trace/events/sched.h>
39 * Targeted preemption latency for CPU-bound tasks:
40 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
42 * NOTE: this latency value is not the same as the concept of
43 * 'timeslice length' - timeslices in CFS are of variable length
44 * and have no persistent notion like in traditional, time-slice
45 * based scheduling concepts.
47 * (to see the precise effective timeslice length of your workload,
48 * run vmstat and monitor the context-switches (cs) field)
50 unsigned int sysctl_sched_latency = 6000000ULL;
51 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
54 * The initial- and re-scaling of tunables is configurable
55 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
58 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
59 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
60 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
62 enum sched_tunable_scaling sysctl_sched_tunable_scaling
63 = SCHED_TUNABLESCALING_LOG;
66 * Minimal preemption granularity for CPU-bound tasks:
67 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
69 unsigned int sysctl_sched_min_granularity = 750000ULL;
70 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
73 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
75 static unsigned int sched_nr_latency = 8;
78 * After fork, child runs first. If set to 0 (default) then
79 * parent will (try to) run first.
81 unsigned int sysctl_sched_child_runs_first __read_mostly;
84 * SCHED_OTHER wake-up granularity.
85 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
87 * This option delays the preemption effects of decoupled workloads
88 * and reduces their over-scheduling. Synchronous workloads will still
89 * have immediate wakeup/sleep latencies.
91 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
92 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
94 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
97 * The exponential sliding window over which load is averaged for shares
101 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
103 #ifdef CONFIG_CFS_BANDWIDTH
105 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
106 * each time a cfs_rq requests quota.
108 * Note: in the case that the slice exceeds the runtime remaining (either due
109 * to consumption or the quota being specified to be smaller than the slice)
110 * we will always only issue the remaining available time.
112 * default: 5 msec, units: microseconds
114 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
117 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
123 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
129 static inline void update_load_set(struct load_weight *lw, unsigned long w)
136 * Increase the granularity value when there are more CPUs,
137 * because with more CPUs the 'effective latency' as visible
138 * to users decreases. But the relationship is not linear,
139 * so pick a second-best guess by going with the log2 of the
142 * This idea comes from the SD scheduler of Con Kolivas:
144 static unsigned int get_update_sysctl_factor(void)
146 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
149 switch (sysctl_sched_tunable_scaling) {
150 case SCHED_TUNABLESCALING_NONE:
153 case SCHED_TUNABLESCALING_LINEAR:
156 case SCHED_TUNABLESCALING_LOG:
158 factor = 1 + ilog2(cpus);
165 static void update_sysctl(void)
167 unsigned int factor = get_update_sysctl_factor();
169 #define SET_SYSCTL(name) \
170 (sysctl_##name = (factor) * normalized_sysctl_##name)
171 SET_SYSCTL(sched_min_granularity);
172 SET_SYSCTL(sched_latency);
173 SET_SYSCTL(sched_wakeup_granularity);
177 void sched_init_granularity(void)
182 #define WMULT_CONST (~0U)
183 #define WMULT_SHIFT 32
185 static void __update_inv_weight(struct load_weight *lw)
189 if (likely(lw->inv_weight))
192 w = scale_load_down(lw->weight);
194 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
196 else if (unlikely(!w))
197 lw->inv_weight = WMULT_CONST;
199 lw->inv_weight = WMULT_CONST / w;
203 * delta_exec * weight / lw.weight
205 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
207 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
208 * we're guaranteed shift stays positive because inv_weight is guaranteed to
209 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
211 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
212 * weight/lw.weight <= 1, and therefore our shift will also be positive.
214 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
216 u64 fact = scale_load_down(weight);
217 int shift = WMULT_SHIFT;
219 __update_inv_weight(lw);
221 if (unlikely(fact >> 32)) {
228 /* hint to use a 32x32->64 mul */
229 fact = (u64)(u32)fact * lw->inv_weight;
236 return mul_u64_u32_shr(delta_exec, fact, shift);
240 const struct sched_class fair_sched_class;
242 /**************************************************************
243 * CFS operations on generic schedulable entities:
246 #ifdef CONFIG_FAIR_GROUP_SCHED
248 /* cpu runqueue to which this cfs_rq is attached */
249 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
254 /* An entity is a task if it doesn't "own" a runqueue */
255 #define entity_is_task(se) (!se->my_q)
257 static inline struct task_struct *task_of(struct sched_entity *se)
259 #ifdef CONFIG_SCHED_DEBUG
260 WARN_ON_ONCE(!entity_is_task(se));
262 return container_of(se, struct task_struct, se);
265 /* Walk up scheduling entities hierarchy */
266 #define for_each_sched_entity(se) \
267 for (; se; se = se->parent)
269 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
274 /* runqueue on which this entity is (to be) queued */
275 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
280 /* runqueue "owned" by this group */
281 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
286 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
288 if (!cfs_rq->on_list) {
290 * Ensure we either appear before our parent (if already
291 * enqueued) or force our parent to appear after us when it is
292 * enqueued. The fact that we always enqueue bottom-up
293 * reduces this to two cases.
295 if (cfs_rq->tg->parent &&
296 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
297 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
298 &rq_of(cfs_rq)->leaf_cfs_rq_list);
300 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
301 &rq_of(cfs_rq)->leaf_cfs_rq_list);
308 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
310 if (cfs_rq->on_list) {
311 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
316 /* Iterate thr' all leaf cfs_rq's on a runqueue */
317 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
318 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
320 /* Do the two (enqueued) entities belong to the same group ? */
321 static inline struct cfs_rq *
322 is_same_group(struct sched_entity *se, struct sched_entity *pse)
324 if (se->cfs_rq == pse->cfs_rq)
330 static inline struct sched_entity *parent_entity(struct sched_entity *se)
336 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
338 int se_depth, pse_depth;
341 * preemption test can be made between sibling entities who are in the
342 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
343 * both tasks until we find their ancestors who are siblings of common
347 /* First walk up until both entities are at same depth */
348 se_depth = (*se)->depth;
349 pse_depth = (*pse)->depth;
351 while (se_depth > pse_depth) {
353 *se = parent_entity(*se);
356 while (pse_depth > se_depth) {
358 *pse = parent_entity(*pse);
361 while (!is_same_group(*se, *pse)) {
362 *se = parent_entity(*se);
363 *pse = parent_entity(*pse);
367 #else /* !CONFIG_FAIR_GROUP_SCHED */
369 static inline struct task_struct *task_of(struct sched_entity *se)
371 return container_of(se, struct task_struct, se);
374 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
376 return container_of(cfs_rq, struct rq, cfs);
379 #define entity_is_task(se) 1
381 #define for_each_sched_entity(se) \
382 for (; se; se = NULL)
384 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
386 return &task_rq(p)->cfs;
389 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
391 struct task_struct *p = task_of(se);
392 struct rq *rq = task_rq(p);
397 /* runqueue "owned" by this group */
398 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
403 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
407 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
411 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
412 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
414 static inline struct sched_entity *parent_entity(struct sched_entity *se)
420 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
424 #endif /* CONFIG_FAIR_GROUP_SCHED */
426 static __always_inline
427 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
429 /**************************************************************
430 * Scheduling class tree data structure manipulation methods:
433 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
435 s64 delta = (s64)(vruntime - max_vruntime);
437 max_vruntime = vruntime;
442 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
444 s64 delta = (s64)(vruntime - min_vruntime);
446 min_vruntime = vruntime;
451 static inline int entity_before(struct sched_entity *a,
452 struct sched_entity *b)
454 return (s64)(a->vruntime - b->vruntime) < 0;
457 static void update_min_vruntime(struct cfs_rq *cfs_rq)
459 u64 vruntime = cfs_rq->min_vruntime;
462 vruntime = cfs_rq->curr->vruntime;
464 if (cfs_rq->rb_leftmost) {
465 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
470 vruntime = se->vruntime;
472 vruntime = min_vruntime(vruntime, se->vruntime);
475 /* ensure we never gain time by being placed backwards. */
476 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
479 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
484 * Enqueue an entity into the rb-tree:
486 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
488 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
489 struct rb_node *parent = NULL;
490 struct sched_entity *entry;
494 * Find the right place in the rbtree:
498 entry = rb_entry(parent, struct sched_entity, run_node);
500 * We dont care about collisions. Nodes with
501 * the same key stay together.
503 if (entity_before(se, entry)) {
504 link = &parent->rb_left;
506 link = &parent->rb_right;
512 * Maintain a cache of leftmost tree entries (it is frequently
516 cfs_rq->rb_leftmost = &se->run_node;
518 rb_link_node(&se->run_node, parent, link);
519 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
522 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
524 if (cfs_rq->rb_leftmost == &se->run_node) {
525 struct rb_node *next_node;
527 next_node = rb_next(&se->run_node);
528 cfs_rq->rb_leftmost = next_node;
531 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
534 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
536 struct rb_node *left = cfs_rq->rb_leftmost;
541 return rb_entry(left, struct sched_entity, run_node);
544 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
546 struct rb_node *next = rb_next(&se->run_node);
551 return rb_entry(next, struct sched_entity, run_node);
554 #ifdef CONFIG_SCHED_DEBUG
555 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
557 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
562 return rb_entry(last, struct sched_entity, run_node);
565 /**************************************************************
566 * Scheduling class statistics methods:
569 int sched_proc_update_handler(struct ctl_table *table, int write,
570 void __user *buffer, size_t *lenp,
573 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
574 unsigned int factor = get_update_sysctl_factor();
579 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
580 sysctl_sched_min_granularity);
582 #define WRT_SYSCTL(name) \
583 (normalized_sysctl_##name = sysctl_##name / (factor))
584 WRT_SYSCTL(sched_min_granularity);
585 WRT_SYSCTL(sched_latency);
586 WRT_SYSCTL(sched_wakeup_granularity);
596 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
598 if (unlikely(se->load.weight != NICE_0_LOAD))
599 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
605 * The idea is to set a period in which each task runs once.
607 * When there are too many tasks (sched_nr_latency) we have to stretch
608 * this period because otherwise the slices get too small.
610 * p = (nr <= nl) ? l : l*nr/nl
612 static u64 __sched_period(unsigned long nr_running)
614 if (unlikely(nr_running > sched_nr_latency))
615 return nr_running * sysctl_sched_min_granularity;
617 return sysctl_sched_latency;
621 * We calculate the wall-time slice from the period by taking a part
622 * proportional to the weight.
626 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
628 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
630 for_each_sched_entity(se) {
631 struct load_weight *load;
632 struct load_weight lw;
634 cfs_rq = cfs_rq_of(se);
635 load = &cfs_rq->load;
637 if (unlikely(!se->on_rq)) {
640 update_load_add(&lw, se->load.weight);
643 slice = __calc_delta(slice, se->load.weight, load);
649 * We calculate the vruntime slice of a to-be-inserted task.
653 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
655 return calc_delta_fair(sched_slice(cfs_rq, se), se);
659 static int select_idle_sibling(struct task_struct *p, int cpu);
660 static unsigned long task_h_load(struct task_struct *p);
663 * We choose a half-life close to 1 scheduling period.
664 * Note: The tables below are dependent on this value.
666 #define LOAD_AVG_PERIOD 32
667 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
668 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
670 /* Give new sched_entity start runnable values to heavy its load in infant time */
671 void init_entity_runnable_average(struct sched_entity *se)
673 struct sched_avg *sa = &se->avg;
675 sa->last_update_time = 0;
677 * sched_avg's period_contrib should be strictly less then 1024, so
678 * we give it 1023 to make sure it is almost a period (1024us), and
679 * will definitely be update (after enqueue).
681 sa->period_contrib = 1023;
682 sa->load_avg = scale_load_down(se->load.weight);
683 sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
684 sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
685 sa->util_sum = LOAD_AVG_MAX;
686 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
689 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
690 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
692 void init_entity_runnable_average(struct sched_entity *se)
698 * Update the current task's runtime statistics.
700 static void update_curr(struct cfs_rq *cfs_rq)
702 struct sched_entity *curr = cfs_rq->curr;
703 u64 now = rq_clock_task(rq_of(cfs_rq));
709 delta_exec = now - curr->exec_start;
710 if (unlikely((s64)delta_exec <= 0))
713 curr->exec_start = now;
715 schedstat_set(curr->statistics.exec_max,
716 max(delta_exec, curr->statistics.exec_max));
718 curr->sum_exec_runtime += delta_exec;
719 schedstat_add(cfs_rq, exec_clock, delta_exec);
721 curr->vruntime += calc_delta_fair(delta_exec, curr);
722 update_min_vruntime(cfs_rq);
724 if (entity_is_task(curr)) {
725 struct task_struct *curtask = task_of(curr);
727 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
728 cpuacct_charge(curtask, delta_exec);
729 account_group_exec_runtime(curtask, delta_exec);
732 account_cfs_rq_runtime(cfs_rq, delta_exec);
735 static void update_curr_fair(struct rq *rq)
737 update_curr(cfs_rq_of(&rq->curr->se));
741 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
743 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
747 * Task is being enqueued - update stats:
749 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
752 * Are we enqueueing a waiting task? (for current tasks
753 * a dequeue/enqueue event is a NOP)
755 if (se != cfs_rq->curr)
756 update_stats_wait_start(cfs_rq, se);
760 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
762 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
763 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
764 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
765 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
766 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
767 #ifdef CONFIG_SCHEDSTATS
768 if (entity_is_task(se)) {
769 trace_sched_stat_wait(task_of(se),
770 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
773 schedstat_set(se->statistics.wait_start, 0);
777 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
780 * Mark the end of the wait period if dequeueing a
783 if (se != cfs_rq->curr)
784 update_stats_wait_end(cfs_rq, se);
788 * We are picking a new current task - update its stats:
791 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
794 * We are starting a new run period:
796 se->exec_start = rq_clock_task(rq_of(cfs_rq));
799 /**************************************************
800 * Scheduling class queueing methods:
803 #ifdef CONFIG_NUMA_BALANCING
805 * Approximate time to scan a full NUMA task in ms. The task scan period is
806 * calculated based on the tasks virtual memory size and
807 * numa_balancing_scan_size.
809 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
810 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
812 /* Portion of address space to scan in MB */
813 unsigned int sysctl_numa_balancing_scan_size = 256;
815 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
816 unsigned int sysctl_numa_balancing_scan_delay = 1000;
818 static unsigned int task_nr_scan_windows(struct task_struct *p)
820 unsigned long rss = 0;
821 unsigned long nr_scan_pages;
824 * Calculations based on RSS as non-present and empty pages are skipped
825 * by the PTE scanner and NUMA hinting faults should be trapped based
828 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
829 rss = get_mm_rss(p->mm);
833 rss = round_up(rss, nr_scan_pages);
834 return rss / nr_scan_pages;
837 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
838 #define MAX_SCAN_WINDOW 2560
840 static unsigned int task_scan_min(struct task_struct *p)
842 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
843 unsigned int scan, floor;
844 unsigned int windows = 1;
846 if (scan_size < MAX_SCAN_WINDOW)
847 windows = MAX_SCAN_WINDOW / scan_size;
848 floor = 1000 / windows;
850 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
851 return max_t(unsigned int, floor, scan);
854 static unsigned int task_scan_max(struct task_struct *p)
856 unsigned int smin = task_scan_min(p);
859 /* Watch for min being lower than max due to floor calculations */
860 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
861 return max(smin, smax);
864 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
866 rq->nr_numa_running += (p->numa_preferred_nid != -1);
867 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
870 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
872 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
873 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
879 spinlock_t lock; /* nr_tasks, tasks */
884 nodemask_t active_nodes;
885 unsigned long total_faults;
887 * Faults_cpu is used to decide whether memory should move
888 * towards the CPU. As a consequence, these stats are weighted
889 * more by CPU use than by memory faults.
891 unsigned long *faults_cpu;
892 unsigned long faults[0];
895 /* Shared or private faults. */
896 #define NR_NUMA_HINT_FAULT_TYPES 2
898 /* Memory and CPU locality */
899 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
901 /* Averaged statistics, and temporary buffers. */
902 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
904 pid_t task_numa_group_id(struct task_struct *p)
906 return p->numa_group ? p->numa_group->gid : 0;
910 * The averaged statistics, shared & private, memory & cpu,
911 * occupy the first half of the array. The second half of the
912 * array is for current counters, which are averaged into the
913 * first set by task_numa_placement.
915 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
917 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
920 static inline unsigned long task_faults(struct task_struct *p, int nid)
925 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
926 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
929 static inline unsigned long group_faults(struct task_struct *p, int nid)
934 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
935 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
938 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
940 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
941 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
944 /* Handle placement on systems where not all nodes are directly connected. */
945 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
946 int maxdist, bool task)
948 unsigned long score = 0;
952 * All nodes are directly connected, and the same distance
953 * from each other. No need for fancy placement algorithms.
955 if (sched_numa_topology_type == NUMA_DIRECT)
959 * This code is called for each node, introducing N^2 complexity,
960 * which should be ok given the number of nodes rarely exceeds 8.
962 for_each_online_node(node) {
963 unsigned long faults;
964 int dist = node_distance(nid, node);
967 * The furthest away nodes in the system are not interesting
968 * for placement; nid was already counted.
970 if (dist == sched_max_numa_distance || node == nid)
974 * On systems with a backplane NUMA topology, compare groups
975 * of nodes, and move tasks towards the group with the most
976 * memory accesses. When comparing two nodes at distance
977 * "hoplimit", only nodes closer by than "hoplimit" are part
978 * of each group. Skip other nodes.
980 if (sched_numa_topology_type == NUMA_BACKPLANE &&
984 /* Add up the faults from nearby nodes. */
986 faults = task_faults(p, node);
988 faults = group_faults(p, node);
991 * On systems with a glueless mesh NUMA topology, there are
992 * no fixed "groups of nodes". Instead, nodes that are not
993 * directly connected bounce traffic through intermediate
994 * nodes; a numa_group can occupy any set of nodes.
995 * The further away a node is, the less the faults count.
996 * This seems to result in good task placement.
998 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
999 faults *= (sched_max_numa_distance - dist);
1000 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1010 * These return the fraction of accesses done by a particular task, or
1011 * task group, on a particular numa node. The group weight is given a
1012 * larger multiplier, in order to group tasks together that are almost
1013 * evenly spread out between numa nodes.
1015 static inline unsigned long task_weight(struct task_struct *p, int nid,
1018 unsigned long faults, total_faults;
1020 if (!p->numa_faults)
1023 total_faults = p->total_numa_faults;
1028 faults = task_faults(p, nid);
1029 faults += score_nearby_nodes(p, nid, dist, true);
1031 return 1000 * faults / total_faults;
1034 static inline unsigned long group_weight(struct task_struct *p, int nid,
1037 unsigned long faults, total_faults;
1042 total_faults = p->numa_group->total_faults;
1047 faults = group_faults(p, nid);
1048 faults += score_nearby_nodes(p, nid, dist, false);
1050 return 1000 * faults / total_faults;
1053 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1054 int src_nid, int dst_cpu)
1056 struct numa_group *ng = p->numa_group;
1057 int dst_nid = cpu_to_node(dst_cpu);
1058 int last_cpupid, this_cpupid;
1060 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1063 * Multi-stage node selection is used in conjunction with a periodic
1064 * migration fault to build a temporal task<->page relation. By using
1065 * a two-stage filter we remove short/unlikely relations.
1067 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1068 * a task's usage of a particular page (n_p) per total usage of this
1069 * page (n_t) (in a given time-span) to a probability.
1071 * Our periodic faults will sample this probability and getting the
1072 * same result twice in a row, given these samples are fully
1073 * independent, is then given by P(n)^2, provided our sample period
1074 * is sufficiently short compared to the usage pattern.
1076 * This quadric squishes small probabilities, making it less likely we
1077 * act on an unlikely task<->page relation.
1079 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1080 if (!cpupid_pid_unset(last_cpupid) &&
1081 cpupid_to_nid(last_cpupid) != dst_nid)
1084 /* Always allow migrate on private faults */
1085 if (cpupid_match_pid(p, last_cpupid))
1088 /* A shared fault, but p->numa_group has not been set up yet. */
1093 * Do not migrate if the destination is not a node that
1094 * is actively used by this numa group.
1096 if (!node_isset(dst_nid, ng->active_nodes))
1100 * Source is a node that is not actively used by this
1101 * numa group, while the destination is. Migrate.
1103 if (!node_isset(src_nid, ng->active_nodes))
1107 * Both source and destination are nodes in active
1108 * use by this numa group. Maximize memory bandwidth
1109 * by migrating from more heavily used groups, to less
1110 * heavily used ones, spreading the load around.
1111 * Use a 1/4 hysteresis to avoid spurious page movement.
1113 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1116 static unsigned long weighted_cpuload(const int cpu);
1117 static unsigned long source_load(int cpu, int type);
1118 static unsigned long target_load(int cpu, int type);
1119 static unsigned long capacity_of(int cpu);
1120 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1122 /* Cached statistics for all CPUs within a node */
1124 unsigned long nr_running;
1127 /* Total compute capacity of CPUs on a node */
1128 unsigned long compute_capacity;
1130 /* Approximate capacity in terms of runnable tasks on a node */
1131 unsigned long task_capacity;
1132 int has_free_capacity;
1136 * XXX borrowed from update_sg_lb_stats
1138 static void update_numa_stats(struct numa_stats *ns, int nid)
1140 int smt, cpu, cpus = 0;
1141 unsigned long capacity;
1143 memset(ns, 0, sizeof(*ns));
1144 for_each_cpu(cpu, cpumask_of_node(nid)) {
1145 struct rq *rq = cpu_rq(cpu);
1147 ns->nr_running += rq->nr_running;
1148 ns->load += weighted_cpuload(cpu);
1149 ns->compute_capacity += capacity_of(cpu);
1155 * If we raced with hotplug and there are no CPUs left in our mask
1156 * the @ns structure is NULL'ed and task_numa_compare() will
1157 * not find this node attractive.
1159 * We'll either bail at !has_free_capacity, or we'll detect a huge
1160 * imbalance and bail there.
1165 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1166 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1167 capacity = cpus / smt; /* cores */
1169 ns->task_capacity = min_t(unsigned, capacity,
1170 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1171 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1174 struct task_numa_env {
1175 struct task_struct *p;
1177 int src_cpu, src_nid;
1178 int dst_cpu, dst_nid;
1180 struct numa_stats src_stats, dst_stats;
1185 struct task_struct *best_task;
1190 static void task_numa_assign(struct task_numa_env *env,
1191 struct task_struct *p, long imp)
1194 put_task_struct(env->best_task);
1199 env->best_imp = imp;
1200 env->best_cpu = env->dst_cpu;
1203 static bool load_too_imbalanced(long src_load, long dst_load,
1204 struct task_numa_env *env)
1207 long orig_src_load, orig_dst_load;
1208 long src_capacity, dst_capacity;
1211 * The load is corrected for the CPU capacity available on each node.
1214 * ------------ vs ---------
1215 * src_capacity dst_capacity
1217 src_capacity = env->src_stats.compute_capacity;
1218 dst_capacity = env->dst_stats.compute_capacity;
1220 /* We care about the slope of the imbalance, not the direction. */
1221 if (dst_load < src_load)
1222 swap(dst_load, src_load);
1224 /* Is the difference below the threshold? */
1225 imb = dst_load * src_capacity * 100 -
1226 src_load * dst_capacity * env->imbalance_pct;
1231 * The imbalance is above the allowed threshold.
1232 * Compare it with the old imbalance.
1234 orig_src_load = env->src_stats.load;
1235 orig_dst_load = env->dst_stats.load;
1237 if (orig_dst_load < orig_src_load)
1238 swap(orig_dst_load, orig_src_load);
1240 old_imb = orig_dst_load * src_capacity * 100 -
1241 orig_src_load * dst_capacity * env->imbalance_pct;
1243 /* Would this change make things worse? */
1244 return (imb > old_imb);
1248 * This checks if the overall compute and NUMA accesses of the system would
1249 * be improved if the source tasks was migrated to the target dst_cpu taking
1250 * into account that it might be best if task running on the dst_cpu should
1251 * be exchanged with the source task
1253 static void task_numa_compare(struct task_numa_env *env,
1254 long taskimp, long groupimp)
1256 struct rq *src_rq = cpu_rq(env->src_cpu);
1257 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1258 struct task_struct *cur;
1259 long src_load, dst_load;
1261 long imp = env->p->numa_group ? groupimp : taskimp;
1263 int dist = env->dist;
1267 raw_spin_lock_irq(&dst_rq->lock);
1270 * No need to move the exiting task, and this ensures that ->curr
1271 * wasn't reaped and thus get_task_struct() in task_numa_assign()
1272 * is safe under RCU read lock.
1273 * Note that rcu_read_lock() itself can't protect from the final
1274 * put_task_struct() after the last schedule().
1276 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1278 raw_spin_unlock_irq(&dst_rq->lock);
1281 * Because we have preemption enabled we can get migrated around and
1282 * end try selecting ourselves (current == env->p) as a swap candidate.
1288 * "imp" is the fault differential for the source task between the
1289 * source and destination node. Calculate the total differential for
1290 * the source task and potential destination task. The more negative
1291 * the value is, the more rmeote accesses that would be expected to
1292 * be incurred if the tasks were swapped.
1295 /* Skip this swap candidate if cannot move to the source cpu */
1296 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1300 * If dst and source tasks are in the same NUMA group, or not
1301 * in any group then look only at task weights.
1303 if (cur->numa_group == env->p->numa_group) {
1304 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1305 task_weight(cur, env->dst_nid, dist);
1307 * Add some hysteresis to prevent swapping the
1308 * tasks within a group over tiny differences.
1310 if (cur->numa_group)
1314 * Compare the group weights. If a task is all by
1315 * itself (not part of a group), use the task weight
1318 if (cur->numa_group)
1319 imp += group_weight(cur, env->src_nid, dist) -
1320 group_weight(cur, env->dst_nid, dist);
1322 imp += task_weight(cur, env->src_nid, dist) -
1323 task_weight(cur, env->dst_nid, dist);
1327 if (imp <= env->best_imp && moveimp <= env->best_imp)
1331 /* Is there capacity at our destination? */
1332 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1333 !env->dst_stats.has_free_capacity)
1339 /* Balance doesn't matter much if we're running a task per cpu */
1340 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1341 dst_rq->nr_running == 1)
1345 * In the overloaded case, try and keep the load balanced.
1348 load = task_h_load(env->p);
1349 dst_load = env->dst_stats.load + load;
1350 src_load = env->src_stats.load - load;
1352 if (moveimp > imp && moveimp > env->best_imp) {
1354 * If the improvement from just moving env->p direction is
1355 * better than swapping tasks around, check if a move is
1356 * possible. Store a slightly smaller score than moveimp,
1357 * so an actually idle CPU will win.
1359 if (!load_too_imbalanced(src_load, dst_load, env)) {
1366 if (imp <= env->best_imp)
1370 load = task_h_load(cur);
1375 if (load_too_imbalanced(src_load, dst_load, env))
1379 * One idle CPU per node is evaluated for a task numa move.
1380 * Call select_idle_sibling to maybe find a better one.
1383 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1386 task_numa_assign(env, cur, imp);
1391 static void task_numa_find_cpu(struct task_numa_env *env,
1392 long taskimp, long groupimp)
1396 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1397 /* Skip this CPU if the source task cannot migrate */
1398 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1402 task_numa_compare(env, taskimp, groupimp);
1406 /* Only move tasks to a NUMA node less busy than the current node. */
1407 static bool numa_has_capacity(struct task_numa_env *env)
1409 struct numa_stats *src = &env->src_stats;
1410 struct numa_stats *dst = &env->dst_stats;
1412 if (src->has_free_capacity && !dst->has_free_capacity)
1416 * Only consider a task move if the source has a higher load
1417 * than the destination, corrected for CPU capacity on each node.
1419 * src->load dst->load
1420 * --------------------- vs ---------------------
1421 * src->compute_capacity dst->compute_capacity
1423 if (src->load * dst->compute_capacity * env->imbalance_pct >
1425 dst->load * src->compute_capacity * 100)
1431 static int task_numa_migrate(struct task_struct *p)
1433 struct task_numa_env env = {
1436 .src_cpu = task_cpu(p),
1437 .src_nid = task_node(p),
1439 .imbalance_pct = 112,
1445 struct sched_domain *sd;
1446 unsigned long taskweight, groupweight;
1448 long taskimp, groupimp;
1451 * Pick the lowest SD_NUMA domain, as that would have the smallest
1452 * imbalance and would be the first to start moving tasks about.
1454 * And we want to avoid any moving of tasks about, as that would create
1455 * random movement of tasks -- counter the numa conditions we're trying
1459 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1461 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1465 * Cpusets can break the scheduler domain tree into smaller
1466 * balance domains, some of which do not cross NUMA boundaries.
1467 * Tasks that are "trapped" in such domains cannot be migrated
1468 * elsewhere, so there is no point in (re)trying.
1470 if (unlikely(!sd)) {
1471 p->numa_preferred_nid = task_node(p);
1475 env.dst_nid = p->numa_preferred_nid;
1476 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1477 taskweight = task_weight(p, env.src_nid, dist);
1478 groupweight = group_weight(p, env.src_nid, dist);
1479 update_numa_stats(&env.src_stats, env.src_nid);
1480 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1481 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1482 update_numa_stats(&env.dst_stats, env.dst_nid);
1484 /* Try to find a spot on the preferred nid. */
1485 if (numa_has_capacity(&env))
1486 task_numa_find_cpu(&env, taskimp, groupimp);
1489 * Look at other nodes in these cases:
1490 * - there is no space available on the preferred_nid
1491 * - the task is part of a numa_group that is interleaved across
1492 * multiple NUMA nodes; in order to better consolidate the group,
1493 * we need to check other locations.
1495 if (env.best_cpu == -1 || (p->numa_group &&
1496 nodes_weight(p->numa_group->active_nodes) > 1)) {
1497 for_each_online_node(nid) {
1498 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1501 dist = node_distance(env.src_nid, env.dst_nid);
1502 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1504 taskweight = task_weight(p, env.src_nid, dist);
1505 groupweight = group_weight(p, env.src_nid, dist);
1508 /* Only consider nodes where both task and groups benefit */
1509 taskimp = task_weight(p, nid, dist) - taskweight;
1510 groupimp = group_weight(p, nid, dist) - groupweight;
1511 if (taskimp < 0 && groupimp < 0)
1516 update_numa_stats(&env.dst_stats, env.dst_nid);
1517 if (numa_has_capacity(&env))
1518 task_numa_find_cpu(&env, taskimp, groupimp);
1523 * If the task is part of a workload that spans multiple NUMA nodes,
1524 * and is migrating into one of the workload's active nodes, remember
1525 * this node as the task's preferred numa node, so the workload can
1527 * A task that migrated to a second choice node will be better off
1528 * trying for a better one later. Do not set the preferred node here.
1530 if (p->numa_group) {
1531 if (env.best_cpu == -1)
1536 if (node_isset(nid, p->numa_group->active_nodes))
1537 sched_setnuma(p, env.dst_nid);
1540 /* No better CPU than the current one was found. */
1541 if (env.best_cpu == -1)
1545 * Reset the scan period if the task is being rescheduled on an
1546 * alternative node to recheck if the tasks is now properly placed.
1548 p->numa_scan_period = task_scan_min(p);
1550 if (env.best_task == NULL) {
1551 ret = migrate_task_to(p, env.best_cpu);
1553 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1557 ret = migrate_swap(p, env.best_task);
1559 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1560 put_task_struct(env.best_task);
1564 /* Attempt to migrate a task to a CPU on the preferred node. */
1565 static void numa_migrate_preferred(struct task_struct *p)
1567 unsigned long interval = HZ;
1569 /* This task has no NUMA fault statistics yet */
1570 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1573 /* Periodically retry migrating the task to the preferred node */
1574 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1575 p->numa_migrate_retry = jiffies + interval;
1577 /* Success if task is already running on preferred CPU */
1578 if (task_node(p) == p->numa_preferred_nid)
1581 /* Otherwise, try migrate to a CPU on the preferred node */
1582 task_numa_migrate(p);
1586 * Find the nodes on which the workload is actively running. We do this by
1587 * tracking the nodes from which NUMA hinting faults are triggered. This can
1588 * be different from the set of nodes where the workload's memory is currently
1591 * The bitmask is used to make smarter decisions on when to do NUMA page
1592 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1593 * are added when they cause over 6/16 of the maximum number of faults, but
1594 * only removed when they drop below 3/16.
1596 static void update_numa_active_node_mask(struct numa_group *numa_group)
1598 unsigned long faults, max_faults = 0;
1601 for_each_online_node(nid) {
1602 faults = group_faults_cpu(numa_group, nid);
1603 if (faults > max_faults)
1604 max_faults = faults;
1607 for_each_online_node(nid) {
1608 faults = group_faults_cpu(numa_group, nid);
1609 if (!node_isset(nid, numa_group->active_nodes)) {
1610 if (faults > max_faults * 6 / 16)
1611 node_set(nid, numa_group->active_nodes);
1612 } else if (faults < max_faults * 3 / 16)
1613 node_clear(nid, numa_group->active_nodes);
1618 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1619 * increments. The more local the fault statistics are, the higher the scan
1620 * period will be for the next scan window. If local/(local+remote) ratio is
1621 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1622 * the scan period will decrease. Aim for 70% local accesses.
1624 #define NUMA_PERIOD_SLOTS 10
1625 #define NUMA_PERIOD_THRESHOLD 7
1628 * Increase the scan period (slow down scanning) if the majority of
1629 * our memory is already on our local node, or if the majority of
1630 * the page accesses are shared with other processes.
1631 * Otherwise, decrease the scan period.
1633 static void update_task_scan_period(struct task_struct *p,
1634 unsigned long shared, unsigned long private)
1636 unsigned int period_slot;
1640 unsigned long remote = p->numa_faults_locality[0];
1641 unsigned long local = p->numa_faults_locality[1];
1644 * If there were no record hinting faults then either the task is
1645 * completely idle or all activity is areas that are not of interest
1646 * to automatic numa balancing. Related to that, if there were failed
1647 * migration then it implies we are migrating too quickly or the local
1648 * node is overloaded. In either case, scan slower
1650 if (local + shared == 0 || p->numa_faults_locality[2]) {
1651 p->numa_scan_period = min(p->numa_scan_period_max,
1652 p->numa_scan_period << 1);
1654 p->mm->numa_next_scan = jiffies +
1655 msecs_to_jiffies(p->numa_scan_period);
1661 * Prepare to scale scan period relative to the current period.
1662 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1663 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1664 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1666 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1667 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1668 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1669 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1672 diff = slot * period_slot;
1674 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1677 * Scale scan rate increases based on sharing. There is an
1678 * inverse relationship between the degree of sharing and
1679 * the adjustment made to the scanning period. Broadly
1680 * speaking the intent is that there is little point
1681 * scanning faster if shared accesses dominate as it may
1682 * simply bounce migrations uselessly
1684 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1685 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1688 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1689 task_scan_min(p), task_scan_max(p));
1690 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1694 * Get the fraction of time the task has been running since the last
1695 * NUMA placement cycle. The scheduler keeps similar statistics, but
1696 * decays those on a 32ms period, which is orders of magnitude off
1697 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1698 * stats only if the task is so new there are no NUMA statistics yet.
1700 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1702 u64 runtime, delta, now;
1703 /* Use the start of this time slice to avoid calculations. */
1704 now = p->se.exec_start;
1705 runtime = p->se.sum_exec_runtime;
1707 if (p->last_task_numa_placement) {
1708 delta = runtime - p->last_sum_exec_runtime;
1709 *period = now - p->last_task_numa_placement;
1711 delta = p->se.avg.load_sum / p->se.load.weight;
1712 *period = LOAD_AVG_MAX;
1715 p->last_sum_exec_runtime = runtime;
1716 p->last_task_numa_placement = now;
1722 * Determine the preferred nid for a task in a numa_group. This needs to
1723 * be done in a way that produces consistent results with group_weight,
1724 * otherwise workloads might not converge.
1726 static int preferred_group_nid(struct task_struct *p, int nid)
1731 /* Direct connections between all NUMA nodes. */
1732 if (sched_numa_topology_type == NUMA_DIRECT)
1736 * On a system with glueless mesh NUMA topology, group_weight
1737 * scores nodes according to the number of NUMA hinting faults on
1738 * both the node itself, and on nearby nodes.
1740 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1741 unsigned long score, max_score = 0;
1742 int node, max_node = nid;
1744 dist = sched_max_numa_distance;
1746 for_each_online_node(node) {
1747 score = group_weight(p, node, dist);
1748 if (score > max_score) {
1757 * Finding the preferred nid in a system with NUMA backplane
1758 * interconnect topology is more involved. The goal is to locate
1759 * tasks from numa_groups near each other in the system, and
1760 * untangle workloads from different sides of the system. This requires
1761 * searching down the hierarchy of node groups, recursively searching
1762 * inside the highest scoring group of nodes. The nodemask tricks
1763 * keep the complexity of the search down.
1765 nodes = node_online_map;
1766 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1767 unsigned long max_faults = 0;
1768 nodemask_t max_group = NODE_MASK_NONE;
1771 /* Are there nodes at this distance from each other? */
1772 if (!find_numa_distance(dist))
1775 for_each_node_mask(a, nodes) {
1776 unsigned long faults = 0;
1777 nodemask_t this_group;
1778 nodes_clear(this_group);
1780 /* Sum group's NUMA faults; includes a==b case. */
1781 for_each_node_mask(b, nodes) {
1782 if (node_distance(a, b) < dist) {
1783 faults += group_faults(p, b);
1784 node_set(b, this_group);
1785 node_clear(b, nodes);
1789 /* Remember the top group. */
1790 if (faults > max_faults) {
1791 max_faults = faults;
1792 max_group = this_group;
1794 * subtle: at the smallest distance there is
1795 * just one node left in each "group", the
1796 * winner is the preferred nid.
1801 /* Next round, evaluate the nodes within max_group. */
1809 static void task_numa_placement(struct task_struct *p)
1811 int seq, nid, max_nid = -1, max_group_nid = -1;
1812 unsigned long max_faults = 0, max_group_faults = 0;
1813 unsigned long fault_types[2] = { 0, 0 };
1814 unsigned long total_faults;
1815 u64 runtime, period;
1816 spinlock_t *group_lock = NULL;
1819 * The p->mm->numa_scan_seq field gets updated without
1820 * exclusive access. Use READ_ONCE() here to ensure
1821 * that the field is read in a single access:
1823 seq = READ_ONCE(p->mm->numa_scan_seq);
1824 if (p->numa_scan_seq == seq)
1826 p->numa_scan_seq = seq;
1827 p->numa_scan_period_max = task_scan_max(p);
1829 total_faults = p->numa_faults_locality[0] +
1830 p->numa_faults_locality[1];
1831 runtime = numa_get_avg_runtime(p, &period);
1833 /* If the task is part of a group prevent parallel updates to group stats */
1834 if (p->numa_group) {
1835 group_lock = &p->numa_group->lock;
1836 spin_lock_irq(group_lock);
1839 /* Find the node with the highest number of faults */
1840 for_each_online_node(nid) {
1841 /* Keep track of the offsets in numa_faults array */
1842 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1843 unsigned long faults = 0, group_faults = 0;
1846 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1847 long diff, f_diff, f_weight;
1849 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1850 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1851 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1852 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1854 /* Decay existing window, copy faults since last scan */
1855 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1856 fault_types[priv] += p->numa_faults[membuf_idx];
1857 p->numa_faults[membuf_idx] = 0;
1860 * Normalize the faults_from, so all tasks in a group
1861 * count according to CPU use, instead of by the raw
1862 * number of faults. Tasks with little runtime have
1863 * little over-all impact on throughput, and thus their
1864 * faults are less important.
1866 f_weight = div64_u64(runtime << 16, period + 1);
1867 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1869 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1870 p->numa_faults[cpubuf_idx] = 0;
1872 p->numa_faults[mem_idx] += diff;
1873 p->numa_faults[cpu_idx] += f_diff;
1874 faults += p->numa_faults[mem_idx];
1875 p->total_numa_faults += diff;
1876 if (p->numa_group) {
1878 * safe because we can only change our own group
1880 * mem_idx represents the offset for a given
1881 * nid and priv in a specific region because it
1882 * is at the beginning of the numa_faults array.
1884 p->numa_group->faults[mem_idx] += diff;
1885 p->numa_group->faults_cpu[mem_idx] += f_diff;
1886 p->numa_group->total_faults += diff;
1887 group_faults += p->numa_group->faults[mem_idx];
1891 if (faults > max_faults) {
1892 max_faults = faults;
1896 if (group_faults > max_group_faults) {
1897 max_group_faults = group_faults;
1898 max_group_nid = nid;
1902 update_task_scan_period(p, fault_types[0], fault_types[1]);
1904 if (p->numa_group) {
1905 update_numa_active_node_mask(p->numa_group);
1906 spin_unlock_irq(group_lock);
1907 max_nid = preferred_group_nid(p, max_group_nid);
1911 /* Set the new preferred node */
1912 if (max_nid != p->numa_preferred_nid)
1913 sched_setnuma(p, max_nid);
1915 if (task_node(p) != p->numa_preferred_nid)
1916 numa_migrate_preferred(p);
1920 static inline int get_numa_group(struct numa_group *grp)
1922 return atomic_inc_not_zero(&grp->refcount);
1925 static inline void put_numa_group(struct numa_group *grp)
1927 if (atomic_dec_and_test(&grp->refcount))
1928 kfree_rcu(grp, rcu);
1931 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1934 struct numa_group *grp, *my_grp;
1935 struct task_struct *tsk;
1937 int cpu = cpupid_to_cpu(cpupid);
1940 if (unlikely(!p->numa_group)) {
1941 unsigned int size = sizeof(struct numa_group) +
1942 4*nr_node_ids*sizeof(unsigned long);
1944 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1948 atomic_set(&grp->refcount, 1);
1949 spin_lock_init(&grp->lock);
1951 /* Second half of the array tracks nids where faults happen */
1952 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1955 node_set(task_node(current), grp->active_nodes);
1957 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1958 grp->faults[i] = p->numa_faults[i];
1960 grp->total_faults = p->total_numa_faults;
1963 rcu_assign_pointer(p->numa_group, grp);
1967 tsk = READ_ONCE(cpu_rq(cpu)->curr);
1969 if (!cpupid_match_pid(tsk, cpupid))
1972 grp = rcu_dereference(tsk->numa_group);
1976 my_grp = p->numa_group;
1981 * Only join the other group if its bigger; if we're the bigger group,
1982 * the other task will join us.
1984 if (my_grp->nr_tasks > grp->nr_tasks)
1988 * Tie-break on the grp address.
1990 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1993 /* Always join threads in the same process. */
1994 if (tsk->mm == current->mm)
1997 /* Simple filter to avoid false positives due to PID collisions */
1998 if (flags & TNF_SHARED)
2001 /* Update priv based on whether false sharing was detected */
2004 if (join && !get_numa_group(grp))
2012 BUG_ON(irqs_disabled());
2013 double_lock_irq(&my_grp->lock, &grp->lock);
2015 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2016 my_grp->faults[i] -= p->numa_faults[i];
2017 grp->faults[i] += p->numa_faults[i];
2019 my_grp->total_faults -= p->total_numa_faults;
2020 grp->total_faults += p->total_numa_faults;
2025 spin_unlock(&my_grp->lock);
2026 spin_unlock_irq(&grp->lock);
2028 rcu_assign_pointer(p->numa_group, grp);
2030 put_numa_group(my_grp);
2038 void task_numa_free(struct task_struct *p)
2040 struct numa_group *grp = p->numa_group;
2041 void *numa_faults = p->numa_faults;
2042 unsigned long flags;
2046 spin_lock_irqsave(&grp->lock, flags);
2047 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2048 grp->faults[i] -= p->numa_faults[i];
2049 grp->total_faults -= p->total_numa_faults;
2052 spin_unlock_irqrestore(&grp->lock, flags);
2053 RCU_INIT_POINTER(p->numa_group, NULL);
2054 put_numa_group(grp);
2057 p->numa_faults = NULL;
2062 * Got a PROT_NONE fault for a page on @node.
2064 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2066 struct task_struct *p = current;
2067 bool migrated = flags & TNF_MIGRATED;
2068 int cpu_node = task_node(current);
2069 int local = !!(flags & TNF_FAULT_LOCAL);
2072 if (!numabalancing_enabled)
2075 /* for example, ksmd faulting in a user's mm */
2079 /* Allocate buffer to track faults on a per-node basis */
2080 if (unlikely(!p->numa_faults)) {
2081 int size = sizeof(*p->numa_faults) *
2082 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2084 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2085 if (!p->numa_faults)
2088 p->total_numa_faults = 0;
2089 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2093 * First accesses are treated as private, otherwise consider accesses
2094 * to be private if the accessing pid has not changed
2096 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2099 priv = cpupid_match_pid(p, last_cpupid);
2100 if (!priv && !(flags & TNF_NO_GROUP))
2101 task_numa_group(p, last_cpupid, flags, &priv);
2105 * If a workload spans multiple NUMA nodes, a shared fault that
2106 * occurs wholly within the set of nodes that the workload is
2107 * actively using should be counted as local. This allows the
2108 * scan rate to slow down when a workload has settled down.
2110 if (!priv && !local && p->numa_group &&
2111 node_isset(cpu_node, p->numa_group->active_nodes) &&
2112 node_isset(mem_node, p->numa_group->active_nodes))
2115 task_numa_placement(p);
2118 * Retry task to preferred node migration periodically, in case it
2119 * case it previously failed, or the scheduler moved us.
2121 if (time_after(jiffies, p->numa_migrate_retry))
2122 numa_migrate_preferred(p);
2125 p->numa_pages_migrated += pages;
2126 if (flags & TNF_MIGRATE_FAIL)
2127 p->numa_faults_locality[2] += pages;
2129 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2130 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2131 p->numa_faults_locality[local] += pages;
2134 static void reset_ptenuma_scan(struct task_struct *p)
2137 * We only did a read acquisition of the mmap sem, so
2138 * p->mm->numa_scan_seq is written to without exclusive access
2139 * and the update is not guaranteed to be atomic. That's not
2140 * much of an issue though, since this is just used for
2141 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2142 * expensive, to avoid any form of compiler optimizations:
2144 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2145 p->mm->numa_scan_offset = 0;
2149 * The expensive part of numa migration is done from task_work context.
2150 * Triggered from task_tick_numa().
2152 void task_numa_work(struct callback_head *work)
2154 unsigned long migrate, next_scan, now = jiffies;
2155 struct task_struct *p = current;
2156 struct mm_struct *mm = p->mm;
2157 struct vm_area_struct *vma;
2158 unsigned long start, end;
2159 unsigned long nr_pte_updates = 0;
2162 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2164 work->next = work; /* protect against double add */
2166 * Who cares about NUMA placement when they're dying.
2168 * NOTE: make sure not to dereference p->mm before this check,
2169 * exit_task_work() happens _after_ exit_mm() so we could be called
2170 * without p->mm even though we still had it when we enqueued this
2173 if (p->flags & PF_EXITING)
2176 if (!mm->numa_next_scan) {
2177 mm->numa_next_scan = now +
2178 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2182 * Enforce maximal scan/migration frequency..
2184 migrate = mm->numa_next_scan;
2185 if (time_before(now, migrate))
2188 if (p->numa_scan_period == 0) {
2189 p->numa_scan_period_max = task_scan_max(p);
2190 p->numa_scan_period = task_scan_min(p);
2193 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2194 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2198 * Delay this task enough that another task of this mm will likely win
2199 * the next time around.
2201 p->node_stamp += 2 * TICK_NSEC;
2203 start = mm->numa_scan_offset;
2204 pages = sysctl_numa_balancing_scan_size;
2205 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2209 down_read(&mm->mmap_sem);
2210 vma = find_vma(mm, start);
2212 reset_ptenuma_scan(p);
2216 for (; vma; vma = vma->vm_next) {
2217 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2218 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2223 * Shared library pages mapped by multiple processes are not
2224 * migrated as it is expected they are cache replicated. Avoid
2225 * hinting faults in read-only file-backed mappings or the vdso
2226 * as migrating the pages will be of marginal benefit.
2229 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2233 * Skip inaccessible VMAs to avoid any confusion between
2234 * PROT_NONE and NUMA hinting ptes
2236 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2240 start = max(start, vma->vm_start);
2241 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2242 end = min(end, vma->vm_end);
2243 nr_pte_updates += change_prot_numa(vma, start, end);
2246 * Scan sysctl_numa_balancing_scan_size but ensure that
2247 * at least one PTE is updated so that unused virtual
2248 * address space is quickly skipped.
2251 pages -= (end - start) >> PAGE_SHIFT;
2258 } while (end != vma->vm_end);
2263 * It is possible to reach the end of the VMA list but the last few
2264 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2265 * would find the !migratable VMA on the next scan but not reset the
2266 * scanner to the start so check it now.
2269 mm->numa_scan_offset = start;
2271 reset_ptenuma_scan(p);
2272 up_read(&mm->mmap_sem);
2276 * Drive the periodic memory faults..
2278 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2280 struct callback_head *work = &curr->numa_work;
2284 * We don't care about NUMA placement if we don't have memory.
2286 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2290 * Using runtime rather than walltime has the dual advantage that
2291 * we (mostly) drive the selection from busy threads and that the
2292 * task needs to have done some actual work before we bother with
2295 now = curr->se.sum_exec_runtime;
2296 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2298 if (now - curr->node_stamp > period) {
2299 if (!curr->node_stamp)
2300 curr->numa_scan_period = task_scan_min(curr);
2301 curr->node_stamp += period;
2303 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2304 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2305 task_work_add(curr, work, true);
2310 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2314 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2318 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2321 #endif /* CONFIG_NUMA_BALANCING */
2324 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2326 update_load_add(&cfs_rq->load, se->load.weight);
2327 if (!parent_entity(se))
2328 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2330 if (entity_is_task(se)) {
2331 struct rq *rq = rq_of(cfs_rq);
2333 account_numa_enqueue(rq, task_of(se));
2334 list_add(&se->group_node, &rq->cfs_tasks);
2337 cfs_rq->nr_running++;
2341 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2343 update_load_sub(&cfs_rq->load, se->load.weight);
2344 if (!parent_entity(se))
2345 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2346 if (entity_is_task(se)) {
2347 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2348 list_del_init(&se->group_node);
2350 cfs_rq->nr_running--;
2353 #ifdef CONFIG_FAIR_GROUP_SCHED
2355 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2360 * Use this CPU's real-time load instead of the last load contribution
2361 * as the updating of the contribution is delayed, and we will use the
2362 * the real-time load to calc the share. See update_tg_load_avg().
2364 tg_weight = atomic_long_read(&tg->load_avg);
2365 tg_weight -= cfs_rq->tg_load_avg_contrib;
2366 tg_weight += cfs_rq_load_avg(cfs_rq);
2371 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2373 long tg_weight, load, shares;
2375 tg_weight = calc_tg_weight(tg, cfs_rq);
2376 load = cfs_rq_load_avg(cfs_rq);
2378 shares = (tg->shares * load);
2380 shares /= tg_weight;
2382 if (shares < MIN_SHARES)
2383 shares = MIN_SHARES;
2384 if (shares > tg->shares)
2385 shares = tg->shares;
2389 # else /* CONFIG_SMP */
2390 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2394 # endif /* CONFIG_SMP */
2395 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2396 unsigned long weight)
2399 /* commit outstanding execution time */
2400 if (cfs_rq->curr == se)
2401 update_curr(cfs_rq);
2402 account_entity_dequeue(cfs_rq, se);
2405 update_load_set(&se->load, weight);
2408 account_entity_enqueue(cfs_rq, se);
2411 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2413 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2415 struct task_group *tg;
2416 struct sched_entity *se;
2420 se = tg->se[cpu_of(rq_of(cfs_rq))];
2421 if (!se || throttled_hierarchy(cfs_rq))
2424 if (likely(se->load.weight == tg->shares))
2427 shares = calc_cfs_shares(cfs_rq, tg);
2429 reweight_entity(cfs_rq_of(se), se, shares);
2431 #else /* CONFIG_FAIR_GROUP_SCHED */
2432 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2435 #endif /* CONFIG_FAIR_GROUP_SCHED */
2438 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2439 static const u32 runnable_avg_yN_inv[] = {
2440 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2441 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2442 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2443 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2444 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2445 0x85aac367, 0x82cd8698,
2449 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2450 * over-estimates when re-combining.
2452 static const u32 runnable_avg_yN_sum[] = {
2453 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2454 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2455 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2460 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2462 static __always_inline u64 decay_load(u64 val, u64 n)
2464 unsigned int local_n;
2468 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2471 /* after bounds checking we can collapse to 32-bit */
2475 * As y^PERIOD = 1/2, we can combine
2476 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2477 * With a look-up table which covers y^n (n<PERIOD)
2479 * To achieve constant time decay_load.
2481 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2482 val >>= local_n / LOAD_AVG_PERIOD;
2483 local_n %= LOAD_AVG_PERIOD;
2486 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2491 * For updates fully spanning n periods, the contribution to runnable
2492 * average will be: \Sum 1024*y^n
2494 * We can compute this reasonably efficiently by combining:
2495 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2497 static u32 __compute_runnable_contrib(u64 n)
2501 if (likely(n <= LOAD_AVG_PERIOD))
2502 return runnable_avg_yN_sum[n];
2503 else if (unlikely(n >= LOAD_AVG_MAX_N))
2504 return LOAD_AVG_MAX;
2506 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2508 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2509 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2511 n -= LOAD_AVG_PERIOD;
2512 } while (n > LOAD_AVG_PERIOD);
2514 contrib = decay_load(contrib, n);
2515 return contrib + runnable_avg_yN_sum[n];
2519 * We can represent the historical contribution to runnable average as the
2520 * coefficients of a geometric series. To do this we sub-divide our runnable
2521 * history into segments of approximately 1ms (1024us); label the segment that
2522 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2524 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2526 * (now) (~1ms ago) (~2ms ago)
2528 * Let u_i denote the fraction of p_i that the entity was runnable.
2530 * We then designate the fractions u_i as our co-efficients, yielding the
2531 * following representation of historical load:
2532 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2534 * We choose y based on the with of a reasonably scheduling period, fixing:
2537 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2538 * approximately half as much as the contribution to load within the last ms
2541 * When a period "rolls over" and we have new u_0`, multiplying the previous
2542 * sum again by y is sufficient to update:
2543 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2544 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2546 static __always_inline int
2547 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2548 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2552 int delta_w, decayed = 0;
2553 unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu);
2555 delta = now - sa->last_update_time;
2557 * This should only happen when time goes backwards, which it
2558 * unfortunately does during sched clock init when we swap over to TSC.
2560 if ((s64)delta < 0) {
2561 sa->last_update_time = now;
2566 * Use 1024ns as the unit of measurement since it's a reasonable
2567 * approximation of 1us and fast to compute.
2572 sa->last_update_time = now;
2574 /* delta_w is the amount already accumulated against our next period */
2575 delta_w = sa->period_contrib;
2576 if (delta + delta_w >= 1024) {
2579 /* how much left for next period will start over, we don't know yet */
2580 sa->period_contrib = 0;
2583 * Now that we know we're crossing a period boundary, figure
2584 * out how much from delta we need to complete the current
2585 * period and accrue it.
2587 delta_w = 1024 - delta_w;
2589 sa->load_sum += weight * delta_w;
2591 cfs_rq->runnable_load_sum += weight * delta_w;
2594 sa->util_sum += delta_w * scale_freq >> SCHED_CAPACITY_SHIFT;
2598 /* Figure out how many additional periods this update spans */
2599 periods = delta / 1024;
2602 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2604 cfs_rq->runnable_load_sum =
2605 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2607 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2609 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2610 contrib = __compute_runnable_contrib(periods);
2612 sa->load_sum += weight * contrib;
2614 cfs_rq->runnable_load_sum += weight * contrib;
2617 sa->util_sum += contrib * scale_freq >> SCHED_CAPACITY_SHIFT;
2620 /* Remainder of delta accrued against u_0` */
2622 sa->load_sum += weight * delta;
2624 cfs_rq->runnable_load_sum += weight * delta;
2627 sa->util_sum += delta * scale_freq >> SCHED_CAPACITY_SHIFT;
2629 sa->period_contrib += delta;
2632 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2634 cfs_rq->runnable_load_avg =
2635 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2637 sa->util_avg = (sa->util_sum << SCHED_LOAD_SHIFT) / LOAD_AVG_MAX;
2643 #ifdef CONFIG_FAIR_GROUP_SCHED
2645 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2646 * and effective_load (which is not done because it is too costly).
2648 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2650 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2652 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2653 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2654 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2658 #else /* CONFIG_FAIR_GROUP_SCHED */
2659 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2660 #endif /* CONFIG_FAIR_GROUP_SCHED */
2662 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2664 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2665 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2667 struct sched_avg *sa = &cfs_rq->avg;
2670 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2671 long r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2672 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2673 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2676 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2677 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2678 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2679 sa->util_sum = max_t(s32, sa->util_sum -
2680 ((r * LOAD_AVG_MAX) >> SCHED_LOAD_SHIFT), 0);
2683 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2684 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2686 #ifndef CONFIG_64BIT
2688 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2694 /* Update task and its cfs_rq load average */
2695 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2697 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2698 u64 now = cfs_rq_clock_task(cfs_rq);
2699 int cpu = cpu_of(rq_of(cfs_rq));
2702 * Track task load average for carrying it to new CPU after migrated, and
2703 * track group sched_entity load average for task_h_load calc in migration
2705 __update_load_avg(now, cpu, &se->avg,
2706 se->on_rq * scale_load_down(se->load.weight),
2707 cfs_rq->curr == se, NULL);
2709 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2710 update_tg_load_avg(cfs_rq, 0);
2713 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2715 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2716 cfs_rq->avg.load_avg += se->avg.load_avg;
2717 cfs_rq->avg.load_sum += se->avg.load_sum;
2718 cfs_rq->avg.util_avg += se->avg.util_avg;
2719 cfs_rq->avg.util_sum += se->avg.util_sum;
2722 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2724 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2725 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2726 cfs_rq->curr == se, NULL);
2728 cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
2729 cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
2730 cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
2731 cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
2734 /* Add the load generated by se into cfs_rq's load average */
2736 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2738 struct sched_avg *sa = &se->avg;
2739 u64 now = cfs_rq_clock_task(cfs_rq);
2740 int migrated, decayed;
2742 migrated = !sa->last_update_time;
2744 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2745 se->on_rq * scale_load_down(se->load.weight),
2746 cfs_rq->curr == se, NULL);
2749 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2751 cfs_rq->runnable_load_avg += sa->load_avg;
2752 cfs_rq->runnable_load_sum += sa->load_sum;
2755 attach_entity_load_avg(cfs_rq, se);
2757 if (decayed || migrated)
2758 update_tg_load_avg(cfs_rq, 0);
2761 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2763 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2765 update_load_avg(se, 1);
2767 cfs_rq->runnable_load_avg =
2768 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2769 cfs_rq->runnable_load_sum =
2770 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2774 * Task first catches up with cfs_rq, and then subtract
2775 * itself from the cfs_rq (task must be off the queue now).
2777 void remove_entity_load_avg(struct sched_entity *se)
2779 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2780 u64 last_update_time;
2782 #ifndef CONFIG_64BIT
2783 u64 last_update_time_copy;
2786 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2788 last_update_time = cfs_rq->avg.last_update_time;
2789 } while (last_update_time != last_update_time_copy);
2791 last_update_time = cfs_rq->avg.last_update_time;
2794 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2795 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2796 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2800 * Update the rq's load with the elapsed running time before entering
2801 * idle. if the last scheduled task is not a CFS task, idle_enter will
2802 * be the only way to update the runnable statistic.
2804 void idle_enter_fair(struct rq *this_rq)
2809 * Update the rq's load with the elapsed idle time before a task is
2810 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2811 * be the only way to update the runnable statistic.
2813 void idle_exit_fair(struct rq *this_rq)
2817 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2819 return cfs_rq->runnable_load_avg;
2822 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2824 return cfs_rq->avg.load_avg;
2827 static int idle_balance(struct rq *this_rq);
2829 #else /* CONFIG_SMP */
2831 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2833 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2835 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2836 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2839 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2841 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2843 static inline int idle_balance(struct rq *rq)
2848 #endif /* CONFIG_SMP */
2850 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2852 #ifdef CONFIG_SCHEDSTATS
2853 struct task_struct *tsk = NULL;
2855 if (entity_is_task(se))
2858 if (se->statistics.sleep_start) {
2859 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2864 if (unlikely(delta > se->statistics.sleep_max))
2865 se->statistics.sleep_max = delta;
2867 se->statistics.sleep_start = 0;
2868 se->statistics.sum_sleep_runtime += delta;
2871 account_scheduler_latency(tsk, delta >> 10, 1);
2872 trace_sched_stat_sleep(tsk, delta);
2875 if (se->statistics.block_start) {
2876 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2881 if (unlikely(delta > se->statistics.block_max))
2882 se->statistics.block_max = delta;
2884 se->statistics.block_start = 0;
2885 se->statistics.sum_sleep_runtime += delta;
2888 if (tsk->in_iowait) {
2889 se->statistics.iowait_sum += delta;
2890 se->statistics.iowait_count++;
2891 trace_sched_stat_iowait(tsk, delta);
2894 trace_sched_stat_blocked(tsk, delta);
2897 * Blocking time is in units of nanosecs, so shift by
2898 * 20 to get a milliseconds-range estimation of the
2899 * amount of time that the task spent sleeping:
2901 if (unlikely(prof_on == SLEEP_PROFILING)) {
2902 profile_hits(SLEEP_PROFILING,
2903 (void *)get_wchan(tsk),
2906 account_scheduler_latency(tsk, delta >> 10, 0);
2912 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2914 #ifdef CONFIG_SCHED_DEBUG
2915 s64 d = se->vruntime - cfs_rq->min_vruntime;
2920 if (d > 3*sysctl_sched_latency)
2921 schedstat_inc(cfs_rq, nr_spread_over);
2926 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2928 u64 vruntime = cfs_rq->min_vruntime;
2931 * The 'current' period is already promised to the current tasks,
2932 * however the extra weight of the new task will slow them down a
2933 * little, place the new task so that it fits in the slot that
2934 * stays open at the end.
2936 if (initial && sched_feat(START_DEBIT))
2937 vruntime += sched_vslice(cfs_rq, se);
2939 /* sleeps up to a single latency don't count. */
2941 unsigned long thresh = sysctl_sched_latency;
2944 * Halve their sleep time's effect, to allow
2945 * for a gentler effect of sleepers:
2947 if (sched_feat(GENTLE_FAIR_SLEEPERS))
2953 /* ensure we never gain time by being placed backwards. */
2954 se->vruntime = max_vruntime(se->vruntime, vruntime);
2957 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
2960 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2963 * Update the normalized vruntime before updating min_vruntime
2964 * through calling update_curr().
2966 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
2967 se->vruntime += cfs_rq->min_vruntime;
2970 * Update run-time statistics of the 'current'.
2972 update_curr(cfs_rq);
2973 enqueue_entity_load_avg(cfs_rq, se);
2974 account_entity_enqueue(cfs_rq, se);
2975 update_cfs_shares(cfs_rq);
2977 if (flags & ENQUEUE_WAKEUP) {
2978 place_entity(cfs_rq, se, 0);
2979 enqueue_sleeper(cfs_rq, se);
2982 update_stats_enqueue(cfs_rq, se);
2983 check_spread(cfs_rq, se);
2984 if (se != cfs_rq->curr)
2985 __enqueue_entity(cfs_rq, se);
2988 if (cfs_rq->nr_running == 1) {
2989 list_add_leaf_cfs_rq(cfs_rq);
2990 check_enqueue_throttle(cfs_rq);
2994 static void __clear_buddies_last(struct sched_entity *se)
2996 for_each_sched_entity(se) {
2997 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2998 if (cfs_rq->last != se)
3001 cfs_rq->last = NULL;
3005 static void __clear_buddies_next(struct sched_entity *se)
3007 for_each_sched_entity(se) {
3008 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3009 if (cfs_rq->next != se)
3012 cfs_rq->next = NULL;
3016 static void __clear_buddies_skip(struct sched_entity *se)
3018 for_each_sched_entity(se) {
3019 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3020 if (cfs_rq->skip != se)
3023 cfs_rq->skip = NULL;
3027 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3029 if (cfs_rq->last == se)
3030 __clear_buddies_last(se);
3032 if (cfs_rq->next == se)
3033 __clear_buddies_next(se);
3035 if (cfs_rq->skip == se)
3036 __clear_buddies_skip(se);
3039 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3042 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3045 * Update run-time statistics of the 'current'.
3047 update_curr(cfs_rq);
3048 dequeue_entity_load_avg(cfs_rq, se);
3050 update_stats_dequeue(cfs_rq, se);
3051 if (flags & DEQUEUE_SLEEP) {
3052 #ifdef CONFIG_SCHEDSTATS
3053 if (entity_is_task(se)) {
3054 struct task_struct *tsk = task_of(se);
3056 if (tsk->state & TASK_INTERRUPTIBLE)
3057 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3058 if (tsk->state & TASK_UNINTERRUPTIBLE)
3059 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3064 clear_buddies(cfs_rq, se);
3066 if (se != cfs_rq->curr)
3067 __dequeue_entity(cfs_rq, se);
3069 account_entity_dequeue(cfs_rq, se);
3072 * Normalize the entity after updating the min_vruntime because the
3073 * update can refer to the ->curr item and we need to reflect this
3074 * movement in our normalized position.
3076 if (!(flags & DEQUEUE_SLEEP))
3077 se->vruntime -= cfs_rq->min_vruntime;
3079 /* return excess runtime on last dequeue */
3080 return_cfs_rq_runtime(cfs_rq);
3082 update_min_vruntime(cfs_rq);
3083 update_cfs_shares(cfs_rq);
3087 * Preempt the current task with a newly woken task if needed:
3090 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3092 unsigned long ideal_runtime, delta_exec;
3093 struct sched_entity *se;
3096 ideal_runtime = sched_slice(cfs_rq, curr);
3097 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3098 if (delta_exec > ideal_runtime) {
3099 resched_curr(rq_of(cfs_rq));
3101 * The current task ran long enough, ensure it doesn't get
3102 * re-elected due to buddy favours.
3104 clear_buddies(cfs_rq, curr);
3109 * Ensure that a task that missed wakeup preemption by a
3110 * narrow margin doesn't have to wait for a full slice.
3111 * This also mitigates buddy induced latencies under load.
3113 if (delta_exec < sysctl_sched_min_granularity)
3116 se = __pick_first_entity(cfs_rq);
3117 delta = curr->vruntime - se->vruntime;
3122 if (delta > ideal_runtime)
3123 resched_curr(rq_of(cfs_rq));
3127 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3129 /* 'current' is not kept within the tree. */
3132 * Any task has to be enqueued before it get to execute on
3133 * a CPU. So account for the time it spent waiting on the
3136 update_stats_wait_end(cfs_rq, se);
3137 __dequeue_entity(cfs_rq, se);
3138 update_load_avg(se, 1);
3141 update_stats_curr_start(cfs_rq, se);
3143 #ifdef CONFIG_SCHEDSTATS
3145 * Track our maximum slice length, if the CPU's load is at
3146 * least twice that of our own weight (i.e. dont track it
3147 * when there are only lesser-weight tasks around):
3149 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3150 se->statistics.slice_max = max(se->statistics.slice_max,
3151 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3154 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3158 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3161 * Pick the next process, keeping these things in mind, in this order:
3162 * 1) keep things fair between processes/task groups
3163 * 2) pick the "next" process, since someone really wants that to run
3164 * 3) pick the "last" process, for cache locality
3165 * 4) do not run the "skip" process, if something else is available
3167 static struct sched_entity *
3168 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3170 struct sched_entity *left = __pick_first_entity(cfs_rq);
3171 struct sched_entity *se;
3174 * If curr is set we have to see if its left of the leftmost entity
3175 * still in the tree, provided there was anything in the tree at all.
3177 if (!left || (curr && entity_before(curr, left)))
3180 se = left; /* ideally we run the leftmost entity */
3183 * Avoid running the skip buddy, if running something else can
3184 * be done without getting too unfair.
3186 if (cfs_rq->skip == se) {
3187 struct sched_entity *second;
3190 second = __pick_first_entity(cfs_rq);
3192 second = __pick_next_entity(se);
3193 if (!second || (curr && entity_before(curr, second)))
3197 if (second && wakeup_preempt_entity(second, left) < 1)
3202 * Prefer last buddy, try to return the CPU to a preempted task.
3204 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3208 * Someone really wants this to run. If it's not unfair, run it.
3210 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3213 clear_buddies(cfs_rq, se);
3218 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3220 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3223 * If still on the runqueue then deactivate_task()
3224 * was not called and update_curr() has to be done:
3227 update_curr(cfs_rq);
3229 /* throttle cfs_rqs exceeding runtime */
3230 check_cfs_rq_runtime(cfs_rq);
3232 check_spread(cfs_rq, prev);
3234 update_stats_wait_start(cfs_rq, prev);
3235 /* Put 'current' back into the tree. */
3236 __enqueue_entity(cfs_rq, prev);
3237 /* in !on_rq case, update occurred at dequeue */
3238 update_load_avg(prev, 0);
3240 cfs_rq->curr = NULL;
3244 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3247 * Update run-time statistics of the 'current'.
3249 update_curr(cfs_rq);
3252 * Ensure that runnable average is periodically updated.
3254 update_load_avg(curr, 1);
3255 update_cfs_shares(cfs_rq);
3257 #ifdef CONFIG_SCHED_HRTICK
3259 * queued ticks are scheduled to match the slice, so don't bother
3260 * validating it and just reschedule.
3263 resched_curr(rq_of(cfs_rq));
3267 * don't let the period tick interfere with the hrtick preemption
3269 if (!sched_feat(DOUBLE_TICK) &&
3270 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3274 if (cfs_rq->nr_running > 1)
3275 check_preempt_tick(cfs_rq, curr);
3279 /**************************************************
3280 * CFS bandwidth control machinery
3283 #ifdef CONFIG_CFS_BANDWIDTH
3285 #ifdef HAVE_JUMP_LABEL
3286 static struct static_key __cfs_bandwidth_used;
3288 static inline bool cfs_bandwidth_used(void)
3290 return static_key_false(&__cfs_bandwidth_used);
3293 void cfs_bandwidth_usage_inc(void)
3295 static_key_slow_inc(&__cfs_bandwidth_used);
3298 void cfs_bandwidth_usage_dec(void)
3300 static_key_slow_dec(&__cfs_bandwidth_used);
3302 #else /* HAVE_JUMP_LABEL */
3303 static bool cfs_bandwidth_used(void)
3308 void cfs_bandwidth_usage_inc(void) {}
3309 void cfs_bandwidth_usage_dec(void) {}
3310 #endif /* HAVE_JUMP_LABEL */
3313 * default period for cfs group bandwidth.
3314 * default: 0.1s, units: nanoseconds
3316 static inline u64 default_cfs_period(void)
3318 return 100000000ULL;
3321 static inline u64 sched_cfs_bandwidth_slice(void)
3323 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3327 * Replenish runtime according to assigned quota and update expiration time.
3328 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3329 * additional synchronization around rq->lock.
3331 * requires cfs_b->lock
3333 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3337 if (cfs_b->quota == RUNTIME_INF)
3340 now = sched_clock_cpu(smp_processor_id());
3341 cfs_b->runtime = cfs_b->quota;
3342 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3345 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3347 return &tg->cfs_bandwidth;
3350 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3351 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3353 if (unlikely(cfs_rq->throttle_count))
3354 return cfs_rq->throttled_clock_task;
3356 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3359 /* returns 0 on failure to allocate runtime */
3360 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3362 struct task_group *tg = cfs_rq->tg;
3363 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3364 u64 amount = 0, min_amount, expires;
3366 /* note: this is a positive sum as runtime_remaining <= 0 */
3367 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3369 raw_spin_lock(&cfs_b->lock);
3370 if (cfs_b->quota == RUNTIME_INF)
3371 amount = min_amount;
3373 start_cfs_bandwidth(cfs_b);
3375 if (cfs_b->runtime > 0) {
3376 amount = min(cfs_b->runtime, min_amount);
3377 cfs_b->runtime -= amount;
3381 expires = cfs_b->runtime_expires;
3382 raw_spin_unlock(&cfs_b->lock);
3384 cfs_rq->runtime_remaining += amount;
3386 * we may have advanced our local expiration to account for allowed
3387 * spread between our sched_clock and the one on which runtime was
3390 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3391 cfs_rq->runtime_expires = expires;
3393 return cfs_rq->runtime_remaining > 0;
3397 * Note: This depends on the synchronization provided by sched_clock and the
3398 * fact that rq->clock snapshots this value.
3400 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3402 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3404 /* if the deadline is ahead of our clock, nothing to do */
3405 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3408 if (cfs_rq->runtime_remaining < 0)
3412 * If the local deadline has passed we have to consider the
3413 * possibility that our sched_clock is 'fast' and the global deadline
3414 * has not truly expired.
3416 * Fortunately we can check determine whether this the case by checking
3417 * whether the global deadline has advanced. It is valid to compare
3418 * cfs_b->runtime_expires without any locks since we only care about
3419 * exact equality, so a partial write will still work.
3422 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3423 /* extend local deadline, drift is bounded above by 2 ticks */
3424 cfs_rq->runtime_expires += TICK_NSEC;
3426 /* global deadline is ahead, expiration has passed */
3427 cfs_rq->runtime_remaining = 0;
3431 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3433 /* dock delta_exec before expiring quota (as it could span periods) */
3434 cfs_rq->runtime_remaining -= delta_exec;
3435 expire_cfs_rq_runtime(cfs_rq);
3437 if (likely(cfs_rq->runtime_remaining > 0))
3441 * if we're unable to extend our runtime we resched so that the active
3442 * hierarchy can be throttled
3444 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3445 resched_curr(rq_of(cfs_rq));
3448 static __always_inline
3449 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3451 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3454 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3457 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3459 return cfs_bandwidth_used() && cfs_rq->throttled;
3462 /* check whether cfs_rq, or any parent, is throttled */
3463 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3465 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3469 * Ensure that neither of the group entities corresponding to src_cpu or
3470 * dest_cpu are members of a throttled hierarchy when performing group
3471 * load-balance operations.
3473 static inline int throttled_lb_pair(struct task_group *tg,
3474 int src_cpu, int dest_cpu)
3476 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3478 src_cfs_rq = tg->cfs_rq[src_cpu];
3479 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3481 return throttled_hierarchy(src_cfs_rq) ||
3482 throttled_hierarchy(dest_cfs_rq);
3485 /* updated child weight may affect parent so we have to do this bottom up */
3486 static int tg_unthrottle_up(struct task_group *tg, void *data)
3488 struct rq *rq = data;
3489 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3491 cfs_rq->throttle_count--;
3493 if (!cfs_rq->throttle_count) {
3494 /* adjust cfs_rq_clock_task() */
3495 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3496 cfs_rq->throttled_clock_task;
3503 static int tg_throttle_down(struct task_group *tg, void *data)
3505 struct rq *rq = data;
3506 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3508 /* group is entering throttled state, stop time */
3509 if (!cfs_rq->throttle_count)
3510 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3511 cfs_rq->throttle_count++;
3516 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3518 struct rq *rq = rq_of(cfs_rq);
3519 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3520 struct sched_entity *se;
3521 long task_delta, dequeue = 1;
3524 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3526 /* freeze hierarchy runnable averages while throttled */
3528 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3531 task_delta = cfs_rq->h_nr_running;
3532 for_each_sched_entity(se) {
3533 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3534 /* throttled entity or throttle-on-deactivate */
3539 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3540 qcfs_rq->h_nr_running -= task_delta;
3542 if (qcfs_rq->load.weight)
3547 sub_nr_running(rq, task_delta);
3549 cfs_rq->throttled = 1;
3550 cfs_rq->throttled_clock = rq_clock(rq);
3551 raw_spin_lock(&cfs_b->lock);
3552 empty = list_empty(&cfs_b->throttled_cfs_rq);
3555 * Add to the _head_ of the list, so that an already-started
3556 * distribute_cfs_runtime will not see us
3558 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3561 * If we're the first throttled task, make sure the bandwidth
3565 start_cfs_bandwidth(cfs_b);
3567 raw_spin_unlock(&cfs_b->lock);
3570 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3572 struct rq *rq = rq_of(cfs_rq);
3573 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3574 struct sched_entity *se;
3578 se = cfs_rq->tg->se[cpu_of(rq)];
3580 cfs_rq->throttled = 0;
3582 update_rq_clock(rq);
3584 raw_spin_lock(&cfs_b->lock);
3585 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3586 list_del_rcu(&cfs_rq->throttled_list);
3587 raw_spin_unlock(&cfs_b->lock);
3589 /* update hierarchical throttle state */
3590 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3592 if (!cfs_rq->load.weight)
3595 task_delta = cfs_rq->h_nr_running;
3596 for_each_sched_entity(se) {
3600 cfs_rq = cfs_rq_of(se);
3602 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3603 cfs_rq->h_nr_running += task_delta;
3605 if (cfs_rq_throttled(cfs_rq))
3610 add_nr_running(rq, task_delta);
3612 /* determine whether we need to wake up potentially idle cpu */
3613 if (rq->curr == rq->idle && rq->cfs.nr_running)
3617 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3618 u64 remaining, u64 expires)
3620 struct cfs_rq *cfs_rq;
3622 u64 starting_runtime = remaining;
3625 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3627 struct rq *rq = rq_of(cfs_rq);
3629 raw_spin_lock(&rq->lock);
3630 if (!cfs_rq_throttled(cfs_rq))
3633 runtime = -cfs_rq->runtime_remaining + 1;
3634 if (runtime > remaining)
3635 runtime = remaining;
3636 remaining -= runtime;
3638 cfs_rq->runtime_remaining += runtime;
3639 cfs_rq->runtime_expires = expires;
3641 /* we check whether we're throttled above */
3642 if (cfs_rq->runtime_remaining > 0)
3643 unthrottle_cfs_rq(cfs_rq);
3646 raw_spin_unlock(&rq->lock);
3653 return starting_runtime - remaining;
3657 * Responsible for refilling a task_group's bandwidth and unthrottling its
3658 * cfs_rqs as appropriate. If there has been no activity within the last
3659 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3660 * used to track this state.
3662 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3664 u64 runtime, runtime_expires;
3667 /* no need to continue the timer with no bandwidth constraint */
3668 if (cfs_b->quota == RUNTIME_INF)
3669 goto out_deactivate;
3671 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3672 cfs_b->nr_periods += overrun;
3675 * idle depends on !throttled (for the case of a large deficit), and if
3676 * we're going inactive then everything else can be deferred
3678 if (cfs_b->idle && !throttled)
3679 goto out_deactivate;
3681 __refill_cfs_bandwidth_runtime(cfs_b);
3684 /* mark as potentially idle for the upcoming period */
3689 /* account preceding periods in which throttling occurred */
3690 cfs_b->nr_throttled += overrun;
3692 runtime_expires = cfs_b->runtime_expires;
3695 * This check is repeated as we are holding onto the new bandwidth while
3696 * we unthrottle. This can potentially race with an unthrottled group
3697 * trying to acquire new bandwidth from the global pool. This can result
3698 * in us over-using our runtime if it is all used during this loop, but
3699 * only by limited amounts in that extreme case.
3701 while (throttled && cfs_b->runtime > 0) {
3702 runtime = cfs_b->runtime;
3703 raw_spin_unlock(&cfs_b->lock);
3704 /* we can't nest cfs_b->lock while distributing bandwidth */
3705 runtime = distribute_cfs_runtime(cfs_b, runtime,
3707 raw_spin_lock(&cfs_b->lock);
3709 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3711 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3715 * While we are ensured activity in the period following an
3716 * unthrottle, this also covers the case in which the new bandwidth is
3717 * insufficient to cover the existing bandwidth deficit. (Forcing the
3718 * timer to remain active while there are any throttled entities.)
3728 /* a cfs_rq won't donate quota below this amount */
3729 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3730 /* minimum remaining period time to redistribute slack quota */
3731 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3732 /* how long we wait to gather additional slack before distributing */
3733 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3736 * Are we near the end of the current quota period?
3738 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3739 * hrtimer base being cleared by hrtimer_start. In the case of
3740 * migrate_hrtimers, base is never cleared, so we are fine.
3742 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3744 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3747 /* if the call-back is running a quota refresh is already occurring */
3748 if (hrtimer_callback_running(refresh_timer))
3751 /* is a quota refresh about to occur? */
3752 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3753 if (remaining < min_expire)
3759 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3761 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3763 /* if there's a quota refresh soon don't bother with slack */
3764 if (runtime_refresh_within(cfs_b, min_left))
3767 hrtimer_start(&cfs_b->slack_timer,
3768 ns_to_ktime(cfs_bandwidth_slack_period),
3772 /* we know any runtime found here is valid as update_curr() precedes return */
3773 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3775 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3776 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3778 if (slack_runtime <= 0)
3781 raw_spin_lock(&cfs_b->lock);
3782 if (cfs_b->quota != RUNTIME_INF &&
3783 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3784 cfs_b->runtime += slack_runtime;
3786 /* we are under rq->lock, defer unthrottling using a timer */
3787 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3788 !list_empty(&cfs_b->throttled_cfs_rq))
3789 start_cfs_slack_bandwidth(cfs_b);
3791 raw_spin_unlock(&cfs_b->lock);
3793 /* even if it's not valid for return we don't want to try again */
3794 cfs_rq->runtime_remaining -= slack_runtime;
3797 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3799 if (!cfs_bandwidth_used())
3802 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3805 __return_cfs_rq_runtime(cfs_rq);
3809 * This is done with a timer (instead of inline with bandwidth return) since
3810 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3812 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3814 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3817 /* confirm we're still not at a refresh boundary */
3818 raw_spin_lock(&cfs_b->lock);
3819 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3820 raw_spin_unlock(&cfs_b->lock);
3824 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3825 runtime = cfs_b->runtime;
3827 expires = cfs_b->runtime_expires;
3828 raw_spin_unlock(&cfs_b->lock);
3833 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3835 raw_spin_lock(&cfs_b->lock);
3836 if (expires == cfs_b->runtime_expires)
3837 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3838 raw_spin_unlock(&cfs_b->lock);
3842 * When a group wakes up we want to make sure that its quota is not already
3843 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3844 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3846 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3848 if (!cfs_bandwidth_used())
3851 /* an active group must be handled by the update_curr()->put() path */
3852 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3855 /* ensure the group is not already throttled */
3856 if (cfs_rq_throttled(cfs_rq))
3859 /* update runtime allocation */
3860 account_cfs_rq_runtime(cfs_rq, 0);
3861 if (cfs_rq->runtime_remaining <= 0)
3862 throttle_cfs_rq(cfs_rq);
3865 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3866 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3868 if (!cfs_bandwidth_used())
3871 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3875 * it's possible for a throttled entity to be forced into a running
3876 * state (e.g. set_curr_task), in this case we're finished.
3878 if (cfs_rq_throttled(cfs_rq))
3881 throttle_cfs_rq(cfs_rq);
3885 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3887 struct cfs_bandwidth *cfs_b =
3888 container_of(timer, struct cfs_bandwidth, slack_timer);
3890 do_sched_cfs_slack_timer(cfs_b);
3892 return HRTIMER_NORESTART;
3895 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3897 struct cfs_bandwidth *cfs_b =
3898 container_of(timer, struct cfs_bandwidth, period_timer);
3902 raw_spin_lock(&cfs_b->lock);
3904 overrun = hrtimer_forward_now(timer, cfs_b->period);
3908 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3911 cfs_b->period_active = 0;
3912 raw_spin_unlock(&cfs_b->lock);
3914 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3917 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3919 raw_spin_lock_init(&cfs_b->lock);
3921 cfs_b->quota = RUNTIME_INF;
3922 cfs_b->period = ns_to_ktime(default_cfs_period());
3924 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3925 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3926 cfs_b->period_timer.function = sched_cfs_period_timer;
3927 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3928 cfs_b->slack_timer.function = sched_cfs_slack_timer;
3931 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3933 cfs_rq->runtime_enabled = 0;
3934 INIT_LIST_HEAD(&cfs_rq->throttled_list);
3937 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3939 lockdep_assert_held(&cfs_b->lock);
3941 if (!cfs_b->period_active) {
3942 cfs_b->period_active = 1;
3943 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
3944 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
3948 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3950 /* init_cfs_bandwidth() was not called */
3951 if (!cfs_b->throttled_cfs_rq.next)
3954 hrtimer_cancel(&cfs_b->period_timer);
3955 hrtimer_cancel(&cfs_b->slack_timer);
3958 static void __maybe_unused update_runtime_enabled(struct rq *rq)
3960 struct cfs_rq *cfs_rq;
3962 for_each_leaf_cfs_rq(rq, cfs_rq) {
3963 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
3965 raw_spin_lock(&cfs_b->lock);
3966 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
3967 raw_spin_unlock(&cfs_b->lock);
3971 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
3973 struct cfs_rq *cfs_rq;
3975 for_each_leaf_cfs_rq(rq, cfs_rq) {
3976 if (!cfs_rq->runtime_enabled)
3980 * clock_task is not advancing so we just need to make sure
3981 * there's some valid quota amount
3983 cfs_rq->runtime_remaining = 1;
3985 * Offline rq is schedulable till cpu is completely disabled
3986 * in take_cpu_down(), so we prevent new cfs throttling here.
3988 cfs_rq->runtime_enabled = 0;
3990 if (cfs_rq_throttled(cfs_rq))
3991 unthrottle_cfs_rq(cfs_rq);
3995 #else /* CONFIG_CFS_BANDWIDTH */
3996 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3998 return rq_clock_task(rq_of(cfs_rq));
4001 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4002 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4003 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4004 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4006 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4011 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4016 static inline int throttled_lb_pair(struct task_group *tg,
4017 int src_cpu, int dest_cpu)
4022 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4024 #ifdef CONFIG_FAIR_GROUP_SCHED
4025 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4028 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4032 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4033 static inline void update_runtime_enabled(struct rq *rq) {}
4034 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4036 #endif /* CONFIG_CFS_BANDWIDTH */
4038 /**************************************************
4039 * CFS operations on tasks:
4042 #ifdef CONFIG_SCHED_HRTICK
4043 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4045 struct sched_entity *se = &p->se;
4046 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4048 WARN_ON(task_rq(p) != rq);
4050 if (cfs_rq->nr_running > 1) {
4051 u64 slice = sched_slice(cfs_rq, se);
4052 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4053 s64 delta = slice - ran;
4060 hrtick_start(rq, delta);
4065 * called from enqueue/dequeue and updates the hrtick when the
4066 * current task is from our class and nr_running is low enough
4069 static void hrtick_update(struct rq *rq)
4071 struct task_struct *curr = rq->curr;
4073 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4076 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4077 hrtick_start_fair(rq, curr);
4079 #else /* !CONFIG_SCHED_HRTICK */
4081 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4085 static inline void hrtick_update(struct rq *rq)
4091 * The enqueue_task method is called before nr_running is
4092 * increased. Here we update the fair scheduling stats and
4093 * then put the task into the rbtree:
4096 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4098 struct cfs_rq *cfs_rq;
4099 struct sched_entity *se = &p->se;
4101 for_each_sched_entity(se) {
4104 cfs_rq = cfs_rq_of(se);
4105 enqueue_entity(cfs_rq, se, flags);
4108 * end evaluation on encountering a throttled cfs_rq
4110 * note: in the case of encountering a throttled cfs_rq we will
4111 * post the final h_nr_running increment below.
4113 if (cfs_rq_throttled(cfs_rq))
4115 cfs_rq->h_nr_running++;
4117 flags = ENQUEUE_WAKEUP;
4120 for_each_sched_entity(se) {
4121 cfs_rq = cfs_rq_of(se);
4122 cfs_rq->h_nr_running++;
4124 if (cfs_rq_throttled(cfs_rq))
4127 update_load_avg(se, 1);
4128 update_cfs_shares(cfs_rq);
4132 add_nr_running(rq, 1);
4137 static void set_next_buddy(struct sched_entity *se);
4140 * The dequeue_task method is called before nr_running is
4141 * decreased. We remove the task from the rbtree and
4142 * update the fair scheduling stats:
4144 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4146 struct cfs_rq *cfs_rq;
4147 struct sched_entity *se = &p->se;
4148 int task_sleep = flags & DEQUEUE_SLEEP;
4150 for_each_sched_entity(se) {
4151 cfs_rq = cfs_rq_of(se);
4152 dequeue_entity(cfs_rq, se, flags);
4155 * end evaluation on encountering a throttled cfs_rq
4157 * note: in the case of encountering a throttled cfs_rq we will
4158 * post the final h_nr_running decrement below.
4160 if (cfs_rq_throttled(cfs_rq))
4162 cfs_rq->h_nr_running--;
4164 /* Don't dequeue parent if it has other entities besides us */
4165 if (cfs_rq->load.weight) {
4167 * Bias pick_next to pick a task from this cfs_rq, as
4168 * p is sleeping when it is within its sched_slice.
4170 if (task_sleep && parent_entity(se))
4171 set_next_buddy(parent_entity(se));
4173 /* avoid re-evaluating load for this entity */
4174 se = parent_entity(se);
4177 flags |= DEQUEUE_SLEEP;
4180 for_each_sched_entity(se) {
4181 cfs_rq = cfs_rq_of(se);
4182 cfs_rq->h_nr_running--;
4184 if (cfs_rq_throttled(cfs_rq))
4187 update_load_avg(se, 1);
4188 update_cfs_shares(cfs_rq);
4192 sub_nr_running(rq, 1);
4200 * per rq 'load' arrray crap; XXX kill this.
4204 * The exact cpuload at various idx values, calculated at every tick would be
4205 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4207 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4208 * on nth tick when cpu may be busy, then we have:
4209 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4210 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4212 * decay_load_missed() below does efficient calculation of
4213 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4214 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4216 * The calculation is approximated on a 128 point scale.
4217 * degrade_zero_ticks is the number of ticks after which load at any
4218 * particular idx is approximated to be zero.
4219 * degrade_factor is a precomputed table, a row for each load idx.
4220 * Each column corresponds to degradation factor for a power of two ticks,
4221 * based on 128 point scale.
4223 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4224 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4226 * With this power of 2 load factors, we can degrade the load n times
4227 * by looking at 1 bits in n and doing as many mult/shift instead of
4228 * n mult/shifts needed by the exact degradation.
4230 #define DEGRADE_SHIFT 7
4231 static const unsigned char
4232 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4233 static const unsigned char
4234 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4235 {0, 0, 0, 0, 0, 0, 0, 0},
4236 {64, 32, 8, 0, 0, 0, 0, 0},
4237 {96, 72, 40, 12, 1, 0, 0},
4238 {112, 98, 75, 43, 15, 1, 0},
4239 {120, 112, 98, 76, 45, 16, 2} };
4242 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4243 * would be when CPU is idle and so we just decay the old load without
4244 * adding any new load.
4246 static unsigned long
4247 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4251 if (!missed_updates)
4254 if (missed_updates >= degrade_zero_ticks[idx])
4258 return load >> missed_updates;
4260 while (missed_updates) {
4261 if (missed_updates % 2)
4262 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4264 missed_updates >>= 1;
4271 * Update rq->cpu_load[] statistics. This function is usually called every
4272 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4273 * every tick. We fix it up based on jiffies.
4275 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4276 unsigned long pending_updates)
4280 this_rq->nr_load_updates++;
4282 /* Update our load: */
4283 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4284 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4285 unsigned long old_load, new_load;
4287 /* scale is effectively 1 << i now, and >> i divides by scale */
4289 old_load = this_rq->cpu_load[i];
4290 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4291 new_load = this_load;
4293 * Round up the averaging division if load is increasing. This
4294 * prevents us from getting stuck on 9 if the load is 10, for
4297 if (new_load > old_load)
4298 new_load += scale - 1;
4300 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4303 sched_avg_update(this_rq);
4306 /* Used instead of source_load when we know the type == 0 */
4307 static unsigned long weighted_cpuload(const int cpu)
4309 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4312 #ifdef CONFIG_NO_HZ_COMMON
4314 * There is no sane way to deal with nohz on smp when using jiffies because the
4315 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4316 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4318 * Therefore we cannot use the delta approach from the regular tick since that
4319 * would seriously skew the load calculation. However we'll make do for those
4320 * updates happening while idle (nohz_idle_balance) or coming out of idle
4321 * (tick_nohz_idle_exit).
4323 * This means we might still be one tick off for nohz periods.
4327 * Called from nohz_idle_balance() to update the load ratings before doing the
4330 static void update_idle_cpu_load(struct rq *this_rq)
4332 unsigned long curr_jiffies = READ_ONCE(jiffies);
4333 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4334 unsigned long pending_updates;
4337 * bail if there's load or we're actually up-to-date.
4339 if (load || curr_jiffies == this_rq->last_load_update_tick)
4342 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4343 this_rq->last_load_update_tick = curr_jiffies;
4345 __update_cpu_load(this_rq, load, pending_updates);
4349 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4351 void update_cpu_load_nohz(void)
4353 struct rq *this_rq = this_rq();
4354 unsigned long curr_jiffies = READ_ONCE(jiffies);
4355 unsigned long pending_updates;
4357 if (curr_jiffies == this_rq->last_load_update_tick)
4360 raw_spin_lock(&this_rq->lock);
4361 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4362 if (pending_updates) {
4363 this_rq->last_load_update_tick = curr_jiffies;
4365 * We were idle, this means load 0, the current load might be
4366 * !0 due to remote wakeups and the sort.
4368 __update_cpu_load(this_rq, 0, pending_updates);
4370 raw_spin_unlock(&this_rq->lock);
4372 #endif /* CONFIG_NO_HZ */
4375 * Called from scheduler_tick()
4377 void update_cpu_load_active(struct rq *this_rq)
4379 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4381 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4383 this_rq->last_load_update_tick = jiffies;
4384 __update_cpu_load(this_rq, load, 1);
4388 * Return a low guess at the load of a migration-source cpu weighted
4389 * according to the scheduling class and "nice" value.
4391 * We want to under-estimate the load of migration sources, to
4392 * balance conservatively.
4394 static unsigned long source_load(int cpu, int type)
4396 struct rq *rq = cpu_rq(cpu);
4397 unsigned long total = weighted_cpuload(cpu);
4399 if (type == 0 || !sched_feat(LB_BIAS))
4402 return min(rq->cpu_load[type-1], total);
4406 * Return a high guess at the load of a migration-target cpu weighted
4407 * according to the scheduling class and "nice" value.
4409 static unsigned long target_load(int cpu, int type)
4411 struct rq *rq = cpu_rq(cpu);
4412 unsigned long total = weighted_cpuload(cpu);
4414 if (type == 0 || !sched_feat(LB_BIAS))
4417 return max(rq->cpu_load[type-1], total);
4420 static unsigned long capacity_of(int cpu)
4422 return cpu_rq(cpu)->cpu_capacity;
4425 static unsigned long capacity_orig_of(int cpu)
4427 return cpu_rq(cpu)->cpu_capacity_orig;
4430 static unsigned long cpu_avg_load_per_task(int cpu)
4432 struct rq *rq = cpu_rq(cpu);
4433 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4434 unsigned long load_avg = weighted_cpuload(cpu);
4437 return load_avg / nr_running;
4442 static void record_wakee(struct task_struct *p)
4445 * Rough decay (wiping) for cost saving, don't worry
4446 * about the boundary, really active task won't care
4449 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4450 current->wakee_flips >>= 1;
4451 current->wakee_flip_decay_ts = jiffies;
4454 if (current->last_wakee != p) {
4455 current->last_wakee = p;
4456 current->wakee_flips++;
4460 static void task_waking_fair(struct task_struct *p)
4462 struct sched_entity *se = &p->se;
4463 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4466 #ifndef CONFIG_64BIT
4467 u64 min_vruntime_copy;
4470 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4472 min_vruntime = cfs_rq->min_vruntime;
4473 } while (min_vruntime != min_vruntime_copy);
4475 min_vruntime = cfs_rq->min_vruntime;
4478 se->vruntime -= min_vruntime;
4482 #ifdef CONFIG_FAIR_GROUP_SCHED
4484 * effective_load() calculates the load change as seen from the root_task_group
4486 * Adding load to a group doesn't make a group heavier, but can cause movement
4487 * of group shares between cpus. Assuming the shares were perfectly aligned one
4488 * can calculate the shift in shares.
4490 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4491 * on this @cpu and results in a total addition (subtraction) of @wg to the
4492 * total group weight.
4494 * Given a runqueue weight distribution (rw_i) we can compute a shares
4495 * distribution (s_i) using:
4497 * s_i = rw_i / \Sum rw_j (1)
4499 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4500 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4501 * shares distribution (s_i):
4503 * rw_i = { 2, 4, 1, 0 }
4504 * s_i = { 2/7, 4/7, 1/7, 0 }
4506 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4507 * task used to run on and the CPU the waker is running on), we need to
4508 * compute the effect of waking a task on either CPU and, in case of a sync
4509 * wakeup, compute the effect of the current task going to sleep.
4511 * So for a change of @wl to the local @cpu with an overall group weight change
4512 * of @wl we can compute the new shares distribution (s'_i) using:
4514 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4516 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4517 * differences in waking a task to CPU 0. The additional task changes the
4518 * weight and shares distributions like:
4520 * rw'_i = { 3, 4, 1, 0 }
4521 * s'_i = { 3/8, 4/8, 1/8, 0 }
4523 * We can then compute the difference in effective weight by using:
4525 * dw_i = S * (s'_i - s_i) (3)
4527 * Where 'S' is the group weight as seen by its parent.
4529 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4530 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4531 * 4/7) times the weight of the group.
4533 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4535 struct sched_entity *se = tg->se[cpu];
4537 if (!tg->parent) /* the trivial, non-cgroup case */
4540 for_each_sched_entity(se) {
4546 * W = @wg + \Sum rw_j
4548 W = wg + calc_tg_weight(tg, se->my_q);
4553 w = cfs_rq_load_avg(se->my_q) + wl;
4556 * wl = S * s'_i; see (2)
4559 wl = (w * (long)tg->shares) / W;
4564 * Per the above, wl is the new se->load.weight value; since
4565 * those are clipped to [MIN_SHARES, ...) do so now. See
4566 * calc_cfs_shares().
4568 if (wl < MIN_SHARES)
4572 * wl = dw_i = S * (s'_i - s_i); see (3)
4574 wl -= se->avg.load_avg;
4577 * Recursively apply this logic to all parent groups to compute
4578 * the final effective load change on the root group. Since
4579 * only the @tg group gets extra weight, all parent groups can
4580 * only redistribute existing shares. @wl is the shift in shares
4581 * resulting from this level per the above.
4590 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4598 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4599 * A waker of many should wake a different task than the one last awakened
4600 * at a frequency roughly N times higher than one of its wakees. In order
4601 * to determine whether we should let the load spread vs consolodating to
4602 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4603 * partner, and a factor of lls_size higher frequency in the other. With
4604 * both conditions met, we can be relatively sure that the relationship is
4605 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4606 * being client/server, worker/dispatcher, interrupt source or whatever is
4607 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4609 static int wake_wide(struct task_struct *p)
4611 unsigned int master = current->wakee_flips;
4612 unsigned int slave = p->wakee_flips;
4613 int factor = this_cpu_read(sd_llc_size);
4616 swap(master, slave);
4617 if (slave < factor || master < slave * factor)
4622 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4624 s64 this_load, load;
4625 s64 this_eff_load, prev_eff_load;
4626 int idx, this_cpu, prev_cpu;
4627 struct task_group *tg;
4628 unsigned long weight;
4632 this_cpu = smp_processor_id();
4633 prev_cpu = task_cpu(p);
4634 load = source_load(prev_cpu, idx);
4635 this_load = target_load(this_cpu, idx);
4638 * If sync wakeup then subtract the (maximum possible)
4639 * effect of the currently running task from the load
4640 * of the current CPU:
4643 tg = task_group(current);
4644 weight = current->se.avg.load_avg;
4646 this_load += effective_load(tg, this_cpu, -weight, -weight);
4647 load += effective_load(tg, prev_cpu, 0, -weight);
4651 weight = p->se.avg.load_avg;
4654 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4655 * due to the sync cause above having dropped this_load to 0, we'll
4656 * always have an imbalance, but there's really nothing you can do
4657 * about that, so that's good too.
4659 * Otherwise check if either cpus are near enough in load to allow this
4660 * task to be woken on this_cpu.
4662 this_eff_load = 100;
4663 this_eff_load *= capacity_of(prev_cpu);
4665 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4666 prev_eff_load *= capacity_of(this_cpu);
4668 if (this_load > 0) {
4669 this_eff_load *= this_load +
4670 effective_load(tg, this_cpu, weight, weight);
4672 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4675 balanced = this_eff_load <= prev_eff_load;
4677 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4682 schedstat_inc(sd, ttwu_move_affine);
4683 schedstat_inc(p, se.statistics.nr_wakeups_affine);
4689 * find_idlest_group finds and returns the least busy CPU group within the
4692 static struct sched_group *
4693 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4694 int this_cpu, int sd_flag)
4696 struct sched_group *idlest = NULL, *group = sd->groups;
4697 unsigned long min_load = ULONG_MAX, this_load = 0;
4698 int load_idx = sd->forkexec_idx;
4699 int imbalance = 100 + (sd->imbalance_pct-100)/2;
4701 if (sd_flag & SD_BALANCE_WAKE)
4702 load_idx = sd->wake_idx;
4705 unsigned long load, avg_load;
4709 /* Skip over this group if it has no CPUs allowed */
4710 if (!cpumask_intersects(sched_group_cpus(group),
4711 tsk_cpus_allowed(p)))
4714 local_group = cpumask_test_cpu(this_cpu,
4715 sched_group_cpus(group));
4717 /* Tally up the load of all CPUs in the group */
4720 for_each_cpu(i, sched_group_cpus(group)) {
4721 /* Bias balancing toward cpus of our domain */
4723 load = source_load(i, load_idx);
4725 load = target_load(i, load_idx);
4730 /* Adjust by relative CPU capacity of the group */
4731 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4734 this_load = avg_load;
4735 } else if (avg_load < min_load) {
4736 min_load = avg_load;
4739 } while (group = group->next, group != sd->groups);
4741 if (!idlest || 100*this_load < imbalance*min_load)
4747 * find_idlest_cpu - find the idlest cpu among the cpus in group.
4750 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4752 unsigned long load, min_load = ULONG_MAX;
4753 unsigned int min_exit_latency = UINT_MAX;
4754 u64 latest_idle_timestamp = 0;
4755 int least_loaded_cpu = this_cpu;
4756 int shallowest_idle_cpu = -1;
4759 /* Traverse only the allowed CPUs */
4760 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4762 struct rq *rq = cpu_rq(i);
4763 struct cpuidle_state *idle = idle_get_state(rq);
4764 if (idle && idle->exit_latency < min_exit_latency) {
4766 * We give priority to a CPU whose idle state
4767 * has the smallest exit latency irrespective
4768 * of any idle timestamp.
4770 min_exit_latency = idle->exit_latency;
4771 latest_idle_timestamp = rq->idle_stamp;
4772 shallowest_idle_cpu = i;
4773 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
4774 rq->idle_stamp > latest_idle_timestamp) {
4776 * If equal or no active idle state, then
4777 * the most recently idled CPU might have
4780 latest_idle_timestamp = rq->idle_stamp;
4781 shallowest_idle_cpu = i;
4783 } else if (shallowest_idle_cpu == -1) {
4784 load = weighted_cpuload(i);
4785 if (load < min_load || (load == min_load && i == this_cpu)) {
4787 least_loaded_cpu = i;
4792 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4796 * Try and locate an idle CPU in the sched_domain.
4798 static int select_idle_sibling(struct task_struct *p, int target)
4800 struct sched_domain *sd;
4801 struct sched_group *sg;
4802 int i = task_cpu(p);
4804 if (idle_cpu(target))
4808 * If the prevous cpu is cache affine and idle, don't be stupid.
4810 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
4814 * Otherwise, iterate the domains and find an elegible idle cpu.
4816 sd = rcu_dereference(per_cpu(sd_llc, target));
4817 for_each_lower_domain(sd) {
4820 if (!cpumask_intersects(sched_group_cpus(sg),
4821 tsk_cpus_allowed(p)))
4824 for_each_cpu(i, sched_group_cpus(sg)) {
4825 if (i == target || !idle_cpu(i))
4829 target = cpumask_first_and(sched_group_cpus(sg),
4830 tsk_cpus_allowed(p));
4834 } while (sg != sd->groups);
4840 * get_cpu_usage returns the amount of capacity of a CPU that is used by CFS
4841 * tasks. The unit of the return value must be the one of capacity so we can
4842 * compare the usage with the capacity of the CPU that is available for CFS
4843 * task (ie cpu_capacity).
4844 * cfs.avg.util_avg is the sum of running time of runnable tasks on a
4845 * CPU. It represents the amount of utilization of a CPU in the range
4846 * [0..SCHED_LOAD_SCALE]. The usage of a CPU can't be higher than the full
4847 * capacity of the CPU because it's about the running time on this CPU.
4848 * Nevertheless, cfs.avg.util_avg can be higher than SCHED_LOAD_SCALE
4849 * because of unfortunate rounding in util_avg or just
4850 * after migrating tasks until the average stabilizes with the new running
4851 * time. So we need to check that the usage stays into the range
4852 * [0..cpu_capacity_orig] and cap if necessary.
4853 * Without capping the usage, a group could be seen as overloaded (CPU0 usage
4854 * at 121% + CPU1 usage at 80%) whereas CPU1 has 20% of available capacity
4856 static int get_cpu_usage(int cpu)
4858 unsigned long usage = cpu_rq(cpu)->cfs.avg.util_avg;
4859 unsigned long capacity = capacity_orig_of(cpu);
4861 if (usage >= SCHED_LOAD_SCALE)
4864 return (usage * capacity) >> SCHED_LOAD_SHIFT;
4868 * select_task_rq_fair: Select target runqueue for the waking task in domains
4869 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
4870 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
4872 * Balances load by selecting the idlest cpu in the idlest group, or under
4873 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
4875 * Returns the target cpu number.
4877 * preempt must be disabled.
4880 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4882 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4883 int cpu = smp_processor_id();
4884 int new_cpu = prev_cpu;
4885 int want_affine = 0;
4886 int sync = wake_flags & WF_SYNC;
4888 if (sd_flag & SD_BALANCE_WAKE)
4889 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4892 for_each_domain(cpu, tmp) {
4893 if (!(tmp->flags & SD_LOAD_BALANCE))
4897 * If both cpu and prev_cpu are part of this domain,
4898 * cpu is a valid SD_WAKE_AFFINE target.
4900 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
4901 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
4906 if (tmp->flags & sd_flag)
4908 else if (!want_affine)
4913 sd = NULL; /* Prefer wake_affine over balance flags */
4914 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
4919 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
4920 new_cpu = select_idle_sibling(p, new_cpu);
4923 struct sched_group *group;
4926 if (!(sd->flags & sd_flag)) {
4931 group = find_idlest_group(sd, p, cpu, sd_flag);
4937 new_cpu = find_idlest_cpu(group, p, cpu);
4938 if (new_cpu == -1 || new_cpu == cpu) {
4939 /* Now try balancing at a lower domain level of cpu */
4944 /* Now try balancing at a lower domain level of new_cpu */
4946 weight = sd->span_weight;
4948 for_each_domain(cpu, tmp) {
4949 if (weight <= tmp->span_weight)
4951 if (tmp->flags & sd_flag)
4954 /* while loop will break here if sd == NULL */
4962 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
4963 * cfs_rq_of(p) references at time of call are still valid and identify the
4964 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
4965 * other assumptions, including the state of rq->lock, should be made.
4967 static void migrate_task_rq_fair(struct task_struct *p, int next_cpu)
4970 * We are supposed to update the task to "current" time, then its up to date
4971 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
4972 * what current time is, so simply throw away the out-of-date time. This
4973 * will result in the wakee task is less decayed, but giving the wakee more
4974 * load sounds not bad.
4976 remove_entity_load_avg(&p->se);
4978 /* Tell new CPU we are migrated */
4979 p->se.avg.last_update_time = 0;
4981 /* We have migrated, no longer consider this task hot */
4982 p->se.exec_start = 0;
4985 static void task_dead_fair(struct task_struct *p)
4987 remove_entity_load_avg(&p->se);
4989 #endif /* CONFIG_SMP */
4991 static unsigned long
4992 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4994 unsigned long gran = sysctl_sched_wakeup_granularity;
4997 * Since its curr running now, convert the gran from real-time
4998 * to virtual-time in his units.
5000 * By using 'se' instead of 'curr' we penalize light tasks, so
5001 * they get preempted easier. That is, if 'se' < 'curr' then
5002 * the resulting gran will be larger, therefore penalizing the
5003 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5004 * be smaller, again penalizing the lighter task.
5006 * This is especially important for buddies when the leftmost
5007 * task is higher priority than the buddy.
5009 return calc_delta_fair(gran, se);
5013 * Should 'se' preempt 'curr'.
5027 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5029 s64 gran, vdiff = curr->vruntime - se->vruntime;
5034 gran = wakeup_gran(curr, se);
5041 static void set_last_buddy(struct sched_entity *se)
5043 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5046 for_each_sched_entity(se)
5047 cfs_rq_of(se)->last = se;
5050 static void set_next_buddy(struct sched_entity *se)
5052 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5055 for_each_sched_entity(se)
5056 cfs_rq_of(se)->next = se;
5059 static void set_skip_buddy(struct sched_entity *se)
5061 for_each_sched_entity(se)
5062 cfs_rq_of(se)->skip = se;
5066 * Preempt the current task with a newly woken task if needed:
5068 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5070 struct task_struct *curr = rq->curr;
5071 struct sched_entity *se = &curr->se, *pse = &p->se;
5072 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5073 int scale = cfs_rq->nr_running >= sched_nr_latency;
5074 int next_buddy_marked = 0;
5076 if (unlikely(se == pse))
5080 * This is possible from callers such as attach_tasks(), in which we
5081 * unconditionally check_prempt_curr() after an enqueue (which may have
5082 * lead to a throttle). This both saves work and prevents false
5083 * next-buddy nomination below.
5085 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5088 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5089 set_next_buddy(pse);
5090 next_buddy_marked = 1;
5094 * We can come here with TIF_NEED_RESCHED already set from new task
5097 * Note: this also catches the edge-case of curr being in a throttled
5098 * group (e.g. via set_curr_task), since update_curr() (in the
5099 * enqueue of curr) will have resulted in resched being set. This
5100 * prevents us from potentially nominating it as a false LAST_BUDDY
5103 if (test_tsk_need_resched(curr))
5106 /* Idle tasks are by definition preempted by non-idle tasks. */
5107 if (unlikely(curr->policy == SCHED_IDLE) &&
5108 likely(p->policy != SCHED_IDLE))
5112 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5113 * is driven by the tick):
5115 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5118 find_matching_se(&se, &pse);
5119 update_curr(cfs_rq_of(se));
5121 if (wakeup_preempt_entity(se, pse) == 1) {
5123 * Bias pick_next to pick the sched entity that is
5124 * triggering this preemption.
5126 if (!next_buddy_marked)
5127 set_next_buddy(pse);
5136 * Only set the backward buddy when the current task is still
5137 * on the rq. This can happen when a wakeup gets interleaved
5138 * with schedule on the ->pre_schedule() or idle_balance()
5139 * point, either of which can * drop the rq lock.
5141 * Also, during early boot the idle thread is in the fair class,
5142 * for obvious reasons its a bad idea to schedule back to it.
5144 if (unlikely(!se->on_rq || curr == rq->idle))
5147 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5151 static struct task_struct *
5152 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5154 struct cfs_rq *cfs_rq = &rq->cfs;
5155 struct sched_entity *se;
5156 struct task_struct *p;
5160 #ifdef CONFIG_FAIR_GROUP_SCHED
5161 if (!cfs_rq->nr_running)
5164 if (prev->sched_class != &fair_sched_class)
5168 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5169 * likely that a next task is from the same cgroup as the current.
5171 * Therefore attempt to avoid putting and setting the entire cgroup
5172 * hierarchy, only change the part that actually changes.
5176 struct sched_entity *curr = cfs_rq->curr;
5179 * Since we got here without doing put_prev_entity() we also
5180 * have to consider cfs_rq->curr. If it is still a runnable
5181 * entity, update_curr() will update its vruntime, otherwise
5182 * forget we've ever seen it.
5186 update_curr(cfs_rq);
5191 * This call to check_cfs_rq_runtime() will do the
5192 * throttle and dequeue its entity in the parent(s).
5193 * Therefore the 'simple' nr_running test will indeed
5196 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5200 se = pick_next_entity(cfs_rq, curr);
5201 cfs_rq = group_cfs_rq(se);
5207 * Since we haven't yet done put_prev_entity and if the selected task
5208 * is a different task than we started out with, try and touch the
5209 * least amount of cfs_rqs.
5212 struct sched_entity *pse = &prev->se;
5214 while (!(cfs_rq = is_same_group(se, pse))) {
5215 int se_depth = se->depth;
5216 int pse_depth = pse->depth;
5218 if (se_depth <= pse_depth) {
5219 put_prev_entity(cfs_rq_of(pse), pse);
5220 pse = parent_entity(pse);
5222 if (se_depth >= pse_depth) {
5223 set_next_entity(cfs_rq_of(se), se);
5224 se = parent_entity(se);
5228 put_prev_entity(cfs_rq, pse);
5229 set_next_entity(cfs_rq, se);
5232 if (hrtick_enabled(rq))
5233 hrtick_start_fair(rq, p);
5240 if (!cfs_rq->nr_running)
5243 put_prev_task(rq, prev);
5246 se = pick_next_entity(cfs_rq, NULL);
5247 set_next_entity(cfs_rq, se);
5248 cfs_rq = group_cfs_rq(se);
5253 if (hrtick_enabled(rq))
5254 hrtick_start_fair(rq, p);
5260 * This is OK, because current is on_cpu, which avoids it being picked
5261 * for load-balance and preemption/IRQs are still disabled avoiding
5262 * further scheduler activity on it and we're being very careful to
5263 * re-start the picking loop.
5265 lockdep_unpin_lock(&rq->lock);
5266 new_tasks = idle_balance(rq);
5267 lockdep_pin_lock(&rq->lock);
5269 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5270 * possible for any higher priority task to appear. In that case we
5271 * must re-start the pick_next_entity() loop.
5283 * Account for a descheduled task:
5285 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5287 struct sched_entity *se = &prev->se;
5288 struct cfs_rq *cfs_rq;
5290 for_each_sched_entity(se) {
5291 cfs_rq = cfs_rq_of(se);
5292 put_prev_entity(cfs_rq, se);
5297 * sched_yield() is very simple
5299 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5301 static void yield_task_fair(struct rq *rq)
5303 struct task_struct *curr = rq->curr;
5304 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5305 struct sched_entity *se = &curr->se;
5308 * Are we the only task in the tree?
5310 if (unlikely(rq->nr_running == 1))
5313 clear_buddies(cfs_rq, se);
5315 if (curr->policy != SCHED_BATCH) {
5316 update_rq_clock(rq);
5318 * Update run-time statistics of the 'current'.
5320 update_curr(cfs_rq);
5322 * Tell update_rq_clock() that we've just updated,
5323 * so we don't do microscopic update in schedule()
5324 * and double the fastpath cost.
5326 rq_clock_skip_update(rq, true);
5332 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5334 struct sched_entity *se = &p->se;
5336 /* throttled hierarchies are not runnable */
5337 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5340 /* Tell the scheduler that we'd really like pse to run next. */
5343 yield_task_fair(rq);
5349 /**************************************************
5350 * Fair scheduling class load-balancing methods.
5354 * The purpose of load-balancing is to achieve the same basic fairness the
5355 * per-cpu scheduler provides, namely provide a proportional amount of compute
5356 * time to each task. This is expressed in the following equation:
5358 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5360 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5361 * W_i,0 is defined as:
5363 * W_i,0 = \Sum_j w_i,j (2)
5365 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5366 * is derived from the nice value as per prio_to_weight[].
5368 * The weight average is an exponential decay average of the instantaneous
5371 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5373 * C_i is the compute capacity of cpu i, typically it is the
5374 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5375 * can also include other factors [XXX].
5377 * To achieve this balance we define a measure of imbalance which follows
5378 * directly from (1):
5380 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5382 * We them move tasks around to minimize the imbalance. In the continuous
5383 * function space it is obvious this converges, in the discrete case we get
5384 * a few fun cases generally called infeasible weight scenarios.
5387 * - infeasible weights;
5388 * - local vs global optima in the discrete case. ]
5393 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5394 * for all i,j solution, we create a tree of cpus that follows the hardware
5395 * topology where each level pairs two lower groups (or better). This results
5396 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5397 * tree to only the first of the previous level and we decrease the frequency
5398 * of load-balance at each level inv. proportional to the number of cpus in
5404 * \Sum { --- * --- * 2^i } = O(n) (5)
5406 * `- size of each group
5407 * | | `- number of cpus doing load-balance
5409 * `- sum over all levels
5411 * Coupled with a limit on how many tasks we can migrate every balance pass,
5412 * this makes (5) the runtime complexity of the balancer.
5414 * An important property here is that each CPU is still (indirectly) connected
5415 * to every other cpu in at most O(log n) steps:
5417 * The adjacency matrix of the resulting graph is given by:
5420 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5423 * And you'll find that:
5425 * A^(log_2 n)_i,j != 0 for all i,j (7)
5427 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5428 * The task movement gives a factor of O(m), giving a convergence complexity
5431 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5436 * In order to avoid CPUs going idle while there's still work to do, new idle
5437 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5438 * tree itself instead of relying on other CPUs to bring it work.
5440 * This adds some complexity to both (5) and (8) but it reduces the total idle
5448 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5451 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5456 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5458 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5460 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5463 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5464 * rewrite all of this once again.]
5467 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5469 enum fbq_type { regular, remote, all };
5471 #define LBF_ALL_PINNED 0x01
5472 #define LBF_NEED_BREAK 0x02
5473 #define LBF_DST_PINNED 0x04
5474 #define LBF_SOME_PINNED 0x08
5477 struct sched_domain *sd;
5485 struct cpumask *dst_grpmask;
5487 enum cpu_idle_type idle;
5489 /* The set of CPUs under consideration for load-balancing */
5490 struct cpumask *cpus;
5495 unsigned int loop_break;
5496 unsigned int loop_max;
5498 enum fbq_type fbq_type;
5499 struct list_head tasks;
5503 * Is this task likely cache-hot:
5505 static int task_hot(struct task_struct *p, struct lb_env *env)
5509 lockdep_assert_held(&env->src_rq->lock);
5511 if (p->sched_class != &fair_sched_class)
5514 if (unlikely(p->policy == SCHED_IDLE))
5518 * Buddy candidates are cache hot:
5520 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5521 (&p->se == cfs_rq_of(&p->se)->next ||
5522 &p->se == cfs_rq_of(&p->se)->last))
5525 if (sysctl_sched_migration_cost == -1)
5527 if (sysctl_sched_migration_cost == 0)
5530 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5532 return delta < (s64)sysctl_sched_migration_cost;
5535 #ifdef CONFIG_NUMA_BALANCING
5537 * Returns 1, if task migration degrades locality
5538 * Returns 0, if task migration improves locality i.e migration preferred.
5539 * Returns -1, if task migration is not affected by locality.
5541 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5543 struct numa_group *numa_group = rcu_dereference(p->numa_group);
5544 unsigned long src_faults, dst_faults;
5545 int src_nid, dst_nid;
5547 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5550 if (!sched_feat(NUMA))
5553 src_nid = cpu_to_node(env->src_cpu);
5554 dst_nid = cpu_to_node(env->dst_cpu);
5556 if (src_nid == dst_nid)
5559 /* Migrating away from the preferred node is always bad. */
5560 if (src_nid == p->numa_preferred_nid) {
5561 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
5567 /* Encourage migration to the preferred node. */
5568 if (dst_nid == p->numa_preferred_nid)
5572 src_faults = group_faults(p, src_nid);
5573 dst_faults = group_faults(p, dst_nid);
5575 src_faults = task_faults(p, src_nid);
5576 dst_faults = task_faults(p, dst_nid);
5579 return dst_faults < src_faults;
5583 static inline int migrate_degrades_locality(struct task_struct *p,
5591 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5594 int can_migrate_task(struct task_struct *p, struct lb_env *env)
5598 lockdep_assert_held(&env->src_rq->lock);
5601 * We do not migrate tasks that are:
5602 * 1) throttled_lb_pair, or
5603 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5604 * 3) running (obviously), or
5605 * 4) are cache-hot on their current CPU.
5607 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5610 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5613 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5615 env->flags |= LBF_SOME_PINNED;
5618 * Remember if this task can be migrated to any other cpu in
5619 * our sched_group. We may want to revisit it if we couldn't
5620 * meet load balance goals by pulling other tasks on src_cpu.
5622 * Also avoid computing new_dst_cpu if we have already computed
5623 * one in current iteration.
5625 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5628 /* Prevent to re-select dst_cpu via env's cpus */
5629 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5630 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5631 env->flags |= LBF_DST_PINNED;
5632 env->new_dst_cpu = cpu;
5640 /* Record that we found atleast one task that could run on dst_cpu */
5641 env->flags &= ~LBF_ALL_PINNED;
5643 if (task_running(env->src_rq, p)) {
5644 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5649 * Aggressive migration if:
5650 * 1) destination numa is preferred
5651 * 2) task is cache cold, or
5652 * 3) too many balance attempts have failed.
5654 tsk_cache_hot = migrate_degrades_locality(p, env);
5655 if (tsk_cache_hot == -1)
5656 tsk_cache_hot = task_hot(p, env);
5658 if (tsk_cache_hot <= 0 ||
5659 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5660 if (tsk_cache_hot == 1) {
5661 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5662 schedstat_inc(p, se.statistics.nr_forced_migrations);
5667 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5672 * detach_task() -- detach the task for the migration specified in env
5674 static void detach_task(struct task_struct *p, struct lb_env *env)
5676 lockdep_assert_held(&env->src_rq->lock);
5678 deactivate_task(env->src_rq, p, 0);
5679 p->on_rq = TASK_ON_RQ_MIGRATING;
5680 set_task_cpu(p, env->dst_cpu);
5684 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5685 * part of active balancing operations within "domain".
5687 * Returns a task if successful and NULL otherwise.
5689 static struct task_struct *detach_one_task(struct lb_env *env)
5691 struct task_struct *p, *n;
5693 lockdep_assert_held(&env->src_rq->lock);
5695 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5696 if (!can_migrate_task(p, env))
5699 detach_task(p, env);
5702 * Right now, this is only the second place where
5703 * lb_gained[env->idle] is updated (other is detach_tasks)
5704 * so we can safely collect stats here rather than
5705 * inside detach_tasks().
5707 schedstat_inc(env->sd, lb_gained[env->idle]);
5713 static const unsigned int sched_nr_migrate_break = 32;
5716 * detach_tasks() -- tries to detach up to imbalance weighted load from
5717 * busiest_rq, as part of a balancing operation within domain "sd".
5719 * Returns number of detached tasks if successful and 0 otherwise.
5721 static int detach_tasks(struct lb_env *env)
5723 struct list_head *tasks = &env->src_rq->cfs_tasks;
5724 struct task_struct *p;
5728 lockdep_assert_held(&env->src_rq->lock);
5730 if (env->imbalance <= 0)
5733 while (!list_empty(tasks)) {
5735 * We don't want to steal all, otherwise we may be treated likewise,
5736 * which could at worst lead to a livelock crash.
5738 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
5741 p = list_first_entry(tasks, struct task_struct, se.group_node);
5744 /* We've more or less seen every task there is, call it quits */
5745 if (env->loop > env->loop_max)
5748 /* take a breather every nr_migrate tasks */
5749 if (env->loop > env->loop_break) {
5750 env->loop_break += sched_nr_migrate_break;
5751 env->flags |= LBF_NEED_BREAK;
5755 if (!can_migrate_task(p, env))
5758 load = task_h_load(p);
5760 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5763 if ((load / 2) > env->imbalance)
5766 detach_task(p, env);
5767 list_add(&p->se.group_node, &env->tasks);
5770 env->imbalance -= load;
5772 #ifdef CONFIG_PREEMPT
5774 * NEWIDLE balancing is a source of latency, so preemptible
5775 * kernels will stop after the first task is detached to minimize
5776 * the critical section.
5778 if (env->idle == CPU_NEWLY_IDLE)
5783 * We only want to steal up to the prescribed amount of
5786 if (env->imbalance <= 0)
5791 list_move_tail(&p->se.group_node, tasks);
5795 * Right now, this is one of only two places we collect this stat
5796 * so we can safely collect detach_one_task() stats here rather
5797 * than inside detach_one_task().
5799 schedstat_add(env->sd, lb_gained[env->idle], detached);
5805 * attach_task() -- attach the task detached by detach_task() to its new rq.
5807 static void attach_task(struct rq *rq, struct task_struct *p)
5809 lockdep_assert_held(&rq->lock);
5811 BUG_ON(task_rq(p) != rq);
5812 p->on_rq = TASK_ON_RQ_QUEUED;
5813 activate_task(rq, p, 0);
5814 check_preempt_curr(rq, p, 0);
5818 * attach_one_task() -- attaches the task returned from detach_one_task() to
5821 static void attach_one_task(struct rq *rq, struct task_struct *p)
5823 raw_spin_lock(&rq->lock);
5825 raw_spin_unlock(&rq->lock);
5829 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
5832 static void attach_tasks(struct lb_env *env)
5834 struct list_head *tasks = &env->tasks;
5835 struct task_struct *p;
5837 raw_spin_lock(&env->dst_rq->lock);
5839 while (!list_empty(tasks)) {
5840 p = list_first_entry(tasks, struct task_struct, se.group_node);
5841 list_del_init(&p->se.group_node);
5843 attach_task(env->dst_rq, p);
5846 raw_spin_unlock(&env->dst_rq->lock);
5849 #ifdef CONFIG_FAIR_GROUP_SCHED
5850 static void update_blocked_averages(int cpu)
5852 struct rq *rq = cpu_rq(cpu);
5853 struct cfs_rq *cfs_rq;
5854 unsigned long flags;
5856 raw_spin_lock_irqsave(&rq->lock, flags);
5857 update_rq_clock(rq);
5860 * Iterates the task_group tree in a bottom up fashion, see
5861 * list_add_leaf_cfs_rq() for details.
5863 for_each_leaf_cfs_rq(rq, cfs_rq) {
5864 /* throttled entities do not contribute to load */
5865 if (throttled_hierarchy(cfs_rq))
5868 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
5869 update_tg_load_avg(cfs_rq, 0);
5871 raw_spin_unlock_irqrestore(&rq->lock, flags);
5875 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5876 * This needs to be done in a top-down fashion because the load of a child
5877 * group is a fraction of its parents load.
5879 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5881 struct rq *rq = rq_of(cfs_rq);
5882 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5883 unsigned long now = jiffies;
5886 if (cfs_rq->last_h_load_update == now)
5889 cfs_rq->h_load_next = NULL;
5890 for_each_sched_entity(se) {
5891 cfs_rq = cfs_rq_of(se);
5892 cfs_rq->h_load_next = se;
5893 if (cfs_rq->last_h_load_update == now)
5898 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
5899 cfs_rq->last_h_load_update = now;
5902 while ((se = cfs_rq->h_load_next) != NULL) {
5903 load = cfs_rq->h_load;
5904 load = div64_ul(load * se->avg.load_avg,
5905 cfs_rq_load_avg(cfs_rq) + 1);
5906 cfs_rq = group_cfs_rq(se);
5907 cfs_rq->h_load = load;
5908 cfs_rq->last_h_load_update = now;
5912 static unsigned long task_h_load(struct task_struct *p)
5914 struct cfs_rq *cfs_rq = task_cfs_rq(p);
5916 update_cfs_rq_h_load(cfs_rq);
5917 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
5918 cfs_rq_load_avg(cfs_rq) + 1);
5921 static inline void update_blocked_averages(int cpu)
5923 struct rq *rq = cpu_rq(cpu);
5924 struct cfs_rq *cfs_rq = &rq->cfs;
5925 unsigned long flags;
5927 raw_spin_lock_irqsave(&rq->lock, flags);
5928 update_rq_clock(rq);
5929 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
5930 raw_spin_unlock_irqrestore(&rq->lock, flags);
5933 static unsigned long task_h_load(struct task_struct *p)
5935 return p->se.avg.load_avg;
5939 /********** Helpers for find_busiest_group ************************/
5948 * sg_lb_stats - stats of a sched_group required for load_balancing
5950 struct sg_lb_stats {
5951 unsigned long avg_load; /*Avg load across the CPUs of the group */
5952 unsigned long group_load; /* Total load over the CPUs of the group */
5953 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
5954 unsigned long load_per_task;
5955 unsigned long group_capacity;
5956 unsigned long group_usage; /* Total usage of the group */
5957 unsigned int sum_nr_running; /* Nr tasks running in the group */
5958 unsigned int idle_cpus;
5959 unsigned int group_weight;
5960 enum group_type group_type;
5961 int group_no_capacity;
5962 #ifdef CONFIG_NUMA_BALANCING
5963 unsigned int nr_numa_running;
5964 unsigned int nr_preferred_running;
5969 * sd_lb_stats - Structure to store the statistics of a sched_domain
5970 * during load balancing.
5972 struct sd_lb_stats {
5973 struct sched_group *busiest; /* Busiest group in this sd */
5974 struct sched_group *local; /* Local group in this sd */
5975 unsigned long total_load; /* Total load of all groups in sd */
5976 unsigned long total_capacity; /* Total capacity of all groups in sd */
5977 unsigned long avg_load; /* Average load across all groups in sd */
5979 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5980 struct sg_lb_stats local_stat; /* Statistics of the local group */
5983 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
5986 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
5987 * local_stat because update_sg_lb_stats() does a full clear/assignment.
5988 * We must however clear busiest_stat::avg_load because
5989 * update_sd_pick_busiest() reads this before assignment.
5991 *sds = (struct sd_lb_stats){
5995 .total_capacity = 0UL,
5998 .sum_nr_running = 0,
5999 .group_type = group_other,
6005 * get_sd_load_idx - Obtain the load index for a given sched domain.
6006 * @sd: The sched_domain whose load_idx is to be obtained.
6007 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6009 * Return: The load index.
6011 static inline int get_sd_load_idx(struct sched_domain *sd,
6012 enum cpu_idle_type idle)
6018 load_idx = sd->busy_idx;
6021 case CPU_NEWLY_IDLE:
6022 load_idx = sd->newidle_idx;
6025 load_idx = sd->idle_idx;
6032 static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu)
6034 if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
6035 return sd->smt_gain / sd->span_weight;
6037 return SCHED_CAPACITY_SCALE;
6040 unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
6042 return default_scale_cpu_capacity(sd, cpu);
6045 static unsigned long scale_rt_capacity(int cpu)
6047 struct rq *rq = cpu_rq(cpu);
6048 u64 total, used, age_stamp, avg;
6052 * Since we're reading these variables without serialization make sure
6053 * we read them once before doing sanity checks on them.
6055 age_stamp = READ_ONCE(rq->age_stamp);
6056 avg = READ_ONCE(rq->rt_avg);
6057 delta = __rq_clock_broken(rq) - age_stamp;
6059 if (unlikely(delta < 0))
6062 total = sched_avg_period() + delta;
6064 used = div_u64(avg, total);
6066 if (likely(used < SCHED_CAPACITY_SCALE))
6067 return SCHED_CAPACITY_SCALE - used;
6072 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6074 unsigned long capacity = SCHED_CAPACITY_SCALE;
6075 struct sched_group *sdg = sd->groups;
6077 if (sched_feat(ARCH_CAPACITY))
6078 capacity *= arch_scale_cpu_capacity(sd, cpu);
6080 capacity *= default_scale_cpu_capacity(sd, cpu);
6082 capacity >>= SCHED_CAPACITY_SHIFT;
6084 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6086 capacity *= scale_rt_capacity(cpu);
6087 capacity >>= SCHED_CAPACITY_SHIFT;
6092 cpu_rq(cpu)->cpu_capacity = capacity;
6093 sdg->sgc->capacity = capacity;
6096 void update_group_capacity(struct sched_domain *sd, int cpu)
6098 struct sched_domain *child = sd->child;
6099 struct sched_group *group, *sdg = sd->groups;
6100 unsigned long capacity;
6101 unsigned long interval;
6103 interval = msecs_to_jiffies(sd->balance_interval);
6104 interval = clamp(interval, 1UL, max_load_balance_interval);
6105 sdg->sgc->next_update = jiffies + interval;
6108 update_cpu_capacity(sd, cpu);
6114 if (child->flags & SD_OVERLAP) {
6116 * SD_OVERLAP domains cannot assume that child groups
6117 * span the current group.
6120 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6121 struct sched_group_capacity *sgc;
6122 struct rq *rq = cpu_rq(cpu);
6125 * build_sched_domains() -> init_sched_groups_capacity()
6126 * gets here before we've attached the domains to the
6129 * Use capacity_of(), which is set irrespective of domains
6130 * in update_cpu_capacity().
6132 * This avoids capacity from being 0 and
6133 * causing divide-by-zero issues on boot.
6135 if (unlikely(!rq->sd)) {
6136 capacity += capacity_of(cpu);
6140 sgc = rq->sd->groups->sgc;
6141 capacity += sgc->capacity;
6145 * !SD_OVERLAP domains can assume that child groups
6146 * span the current group.
6149 group = child->groups;
6151 capacity += group->sgc->capacity;
6152 group = group->next;
6153 } while (group != child->groups);
6156 sdg->sgc->capacity = capacity;
6160 * Check whether the capacity of the rq has been noticeably reduced by side
6161 * activity. The imbalance_pct is used for the threshold.
6162 * Return true is the capacity is reduced
6165 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6167 return ((rq->cpu_capacity * sd->imbalance_pct) <
6168 (rq->cpu_capacity_orig * 100));
6172 * Group imbalance indicates (and tries to solve) the problem where balancing
6173 * groups is inadequate due to tsk_cpus_allowed() constraints.
6175 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6176 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6179 * { 0 1 2 3 } { 4 5 6 7 }
6182 * If we were to balance group-wise we'd place two tasks in the first group and
6183 * two tasks in the second group. Clearly this is undesired as it will overload
6184 * cpu 3 and leave one of the cpus in the second group unused.
6186 * The current solution to this issue is detecting the skew in the first group
6187 * by noticing the lower domain failed to reach balance and had difficulty
6188 * moving tasks due to affinity constraints.
6190 * When this is so detected; this group becomes a candidate for busiest; see
6191 * update_sd_pick_busiest(). And calculate_imbalance() and
6192 * find_busiest_group() avoid some of the usual balance conditions to allow it
6193 * to create an effective group imbalance.
6195 * This is a somewhat tricky proposition since the next run might not find the
6196 * group imbalance and decide the groups need to be balanced again. A most
6197 * subtle and fragile situation.
6200 static inline int sg_imbalanced(struct sched_group *group)
6202 return group->sgc->imbalance;
6206 * group_has_capacity returns true if the group has spare capacity that could
6207 * be used by some tasks.
6208 * We consider that a group has spare capacity if the * number of task is
6209 * smaller than the number of CPUs or if the usage is lower than the available
6210 * capacity for CFS tasks.
6211 * For the latter, we use a threshold to stabilize the state, to take into
6212 * account the variance of the tasks' load and to return true if the available
6213 * capacity in meaningful for the load balancer.
6214 * As an example, an available capacity of 1% can appear but it doesn't make
6215 * any benefit for the load balance.
6218 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6220 if (sgs->sum_nr_running < sgs->group_weight)
6223 if ((sgs->group_capacity * 100) >
6224 (sgs->group_usage * env->sd->imbalance_pct))
6231 * group_is_overloaded returns true if the group has more tasks than it can
6233 * group_is_overloaded is not equals to !group_has_capacity because a group
6234 * with the exact right number of tasks, has no more spare capacity but is not
6235 * overloaded so both group_has_capacity and group_is_overloaded return
6239 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6241 if (sgs->sum_nr_running <= sgs->group_weight)
6244 if ((sgs->group_capacity * 100) <
6245 (sgs->group_usage * env->sd->imbalance_pct))
6251 static enum group_type group_classify(struct lb_env *env,
6252 struct sched_group *group,
6253 struct sg_lb_stats *sgs)
6255 if (sgs->group_no_capacity)
6256 return group_overloaded;
6258 if (sg_imbalanced(group))
6259 return group_imbalanced;
6265 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6266 * @env: The load balancing environment.
6267 * @group: sched_group whose statistics are to be updated.
6268 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6269 * @local_group: Does group contain this_cpu.
6270 * @sgs: variable to hold the statistics for this group.
6271 * @overload: Indicate more than one runnable task for any CPU.
6273 static inline void update_sg_lb_stats(struct lb_env *env,
6274 struct sched_group *group, int load_idx,
6275 int local_group, struct sg_lb_stats *sgs,
6281 memset(sgs, 0, sizeof(*sgs));
6283 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6284 struct rq *rq = cpu_rq(i);
6286 /* Bias balancing toward cpus of our domain */
6288 load = target_load(i, load_idx);
6290 load = source_load(i, load_idx);
6292 sgs->group_load += load;
6293 sgs->group_usage += get_cpu_usage(i);
6294 sgs->sum_nr_running += rq->cfs.h_nr_running;
6296 if (rq->nr_running > 1)
6299 #ifdef CONFIG_NUMA_BALANCING
6300 sgs->nr_numa_running += rq->nr_numa_running;
6301 sgs->nr_preferred_running += rq->nr_preferred_running;
6303 sgs->sum_weighted_load += weighted_cpuload(i);
6308 /* Adjust by relative CPU capacity of the group */
6309 sgs->group_capacity = group->sgc->capacity;
6310 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6312 if (sgs->sum_nr_running)
6313 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6315 sgs->group_weight = group->group_weight;
6317 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6318 sgs->group_type = group_classify(env, group, sgs);
6322 * update_sd_pick_busiest - return 1 on busiest group
6323 * @env: The load balancing environment.
6324 * @sds: sched_domain statistics
6325 * @sg: sched_group candidate to be checked for being the busiest
6326 * @sgs: sched_group statistics
6328 * Determine if @sg is a busier group than the previously selected
6331 * Return: %true if @sg is a busier group than the previously selected
6332 * busiest group. %false otherwise.
6334 static bool update_sd_pick_busiest(struct lb_env *env,
6335 struct sd_lb_stats *sds,
6336 struct sched_group *sg,
6337 struct sg_lb_stats *sgs)
6339 struct sg_lb_stats *busiest = &sds->busiest_stat;
6341 if (sgs->group_type > busiest->group_type)
6344 if (sgs->group_type < busiest->group_type)
6347 if (sgs->avg_load <= busiest->avg_load)
6350 /* This is the busiest node in its class. */
6351 if (!(env->sd->flags & SD_ASYM_PACKING))
6355 * ASYM_PACKING needs to move all the work to the lowest
6356 * numbered CPUs in the group, therefore mark all groups
6357 * higher than ourself as busy.
6359 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6363 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6370 #ifdef CONFIG_NUMA_BALANCING
6371 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6373 if (sgs->sum_nr_running > sgs->nr_numa_running)
6375 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6380 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6382 if (rq->nr_running > rq->nr_numa_running)
6384 if (rq->nr_running > rq->nr_preferred_running)
6389 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6394 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6398 #endif /* CONFIG_NUMA_BALANCING */
6401 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6402 * @env: The load balancing environment.
6403 * @sds: variable to hold the statistics for this sched_domain.
6405 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6407 struct sched_domain *child = env->sd->child;
6408 struct sched_group *sg = env->sd->groups;
6409 struct sg_lb_stats tmp_sgs;
6410 int load_idx, prefer_sibling = 0;
6411 bool overload = false;
6413 if (child && child->flags & SD_PREFER_SIBLING)
6416 load_idx = get_sd_load_idx(env->sd, env->idle);
6419 struct sg_lb_stats *sgs = &tmp_sgs;
6422 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6425 sgs = &sds->local_stat;
6427 if (env->idle != CPU_NEWLY_IDLE ||
6428 time_after_eq(jiffies, sg->sgc->next_update))
6429 update_group_capacity(env->sd, env->dst_cpu);
6432 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6439 * In case the child domain prefers tasks go to siblings
6440 * first, lower the sg capacity so that we'll try
6441 * and move all the excess tasks away. We lower the capacity
6442 * of a group only if the local group has the capacity to fit
6443 * these excess tasks. The extra check prevents the case where
6444 * you always pull from the heaviest group when it is already
6445 * under-utilized (possible with a large weight task outweighs
6446 * the tasks on the system).
6448 if (prefer_sibling && sds->local &&
6449 group_has_capacity(env, &sds->local_stat) &&
6450 (sgs->sum_nr_running > 1)) {
6451 sgs->group_no_capacity = 1;
6452 sgs->group_type = group_overloaded;
6455 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6457 sds->busiest_stat = *sgs;
6461 /* Now, start updating sd_lb_stats */
6462 sds->total_load += sgs->group_load;
6463 sds->total_capacity += sgs->group_capacity;
6466 } while (sg != env->sd->groups);
6468 if (env->sd->flags & SD_NUMA)
6469 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6471 if (!env->sd->parent) {
6472 /* update overload indicator if we are at root domain */
6473 if (env->dst_rq->rd->overload != overload)
6474 env->dst_rq->rd->overload = overload;
6480 * check_asym_packing - Check to see if the group is packed into the
6483 * This is primarily intended to used at the sibling level. Some
6484 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6485 * case of POWER7, it can move to lower SMT modes only when higher
6486 * threads are idle. When in lower SMT modes, the threads will
6487 * perform better since they share less core resources. Hence when we
6488 * have idle threads, we want them to be the higher ones.
6490 * This packing function is run on idle threads. It checks to see if
6491 * the busiest CPU in this domain (core in the P7 case) has a higher
6492 * CPU number than the packing function is being run on. Here we are
6493 * assuming lower CPU number will be equivalent to lower a SMT thread
6496 * Return: 1 when packing is required and a task should be moved to
6497 * this CPU. The amount of the imbalance is returned in *imbalance.
6499 * @env: The load balancing environment.
6500 * @sds: Statistics of the sched_domain which is to be packed
6502 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6506 if (!(env->sd->flags & SD_ASYM_PACKING))
6512 busiest_cpu = group_first_cpu(sds->busiest);
6513 if (env->dst_cpu > busiest_cpu)
6516 env->imbalance = DIV_ROUND_CLOSEST(
6517 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6518 SCHED_CAPACITY_SCALE);
6524 * fix_small_imbalance - Calculate the minor imbalance that exists
6525 * amongst the groups of a sched_domain, during
6527 * @env: The load balancing environment.
6528 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6531 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6533 unsigned long tmp, capa_now = 0, capa_move = 0;
6534 unsigned int imbn = 2;
6535 unsigned long scaled_busy_load_per_task;
6536 struct sg_lb_stats *local, *busiest;
6538 local = &sds->local_stat;
6539 busiest = &sds->busiest_stat;
6541 if (!local->sum_nr_running)
6542 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6543 else if (busiest->load_per_task > local->load_per_task)
6546 scaled_busy_load_per_task =
6547 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6548 busiest->group_capacity;
6550 if (busiest->avg_load + scaled_busy_load_per_task >=
6551 local->avg_load + (scaled_busy_load_per_task * imbn)) {
6552 env->imbalance = busiest->load_per_task;
6557 * OK, we don't have enough imbalance to justify moving tasks,
6558 * however we may be able to increase total CPU capacity used by
6562 capa_now += busiest->group_capacity *
6563 min(busiest->load_per_task, busiest->avg_load);
6564 capa_now += local->group_capacity *
6565 min(local->load_per_task, local->avg_load);
6566 capa_now /= SCHED_CAPACITY_SCALE;
6568 /* Amount of load we'd subtract */
6569 if (busiest->avg_load > scaled_busy_load_per_task) {
6570 capa_move += busiest->group_capacity *
6571 min(busiest->load_per_task,
6572 busiest->avg_load - scaled_busy_load_per_task);
6575 /* Amount of load we'd add */
6576 if (busiest->avg_load * busiest->group_capacity <
6577 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6578 tmp = (busiest->avg_load * busiest->group_capacity) /
6579 local->group_capacity;
6581 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6582 local->group_capacity;
6584 capa_move += local->group_capacity *
6585 min(local->load_per_task, local->avg_load + tmp);
6586 capa_move /= SCHED_CAPACITY_SCALE;
6588 /* Move if we gain throughput */
6589 if (capa_move > capa_now)
6590 env->imbalance = busiest->load_per_task;
6594 * calculate_imbalance - Calculate the amount of imbalance present within the
6595 * groups of a given sched_domain during load balance.
6596 * @env: load balance environment
6597 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6599 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6601 unsigned long max_pull, load_above_capacity = ~0UL;
6602 struct sg_lb_stats *local, *busiest;
6604 local = &sds->local_stat;
6605 busiest = &sds->busiest_stat;
6607 if (busiest->group_type == group_imbalanced) {
6609 * In the group_imb case we cannot rely on group-wide averages
6610 * to ensure cpu-load equilibrium, look at wider averages. XXX
6612 busiest->load_per_task =
6613 min(busiest->load_per_task, sds->avg_load);
6617 * In the presence of smp nice balancing, certain scenarios can have
6618 * max load less than avg load(as we skip the groups at or below
6619 * its cpu_capacity, while calculating max_load..)
6621 if (busiest->avg_load <= sds->avg_load ||
6622 local->avg_load >= sds->avg_load) {
6624 return fix_small_imbalance(env, sds);
6628 * If there aren't any idle cpus, avoid creating some.
6630 if (busiest->group_type == group_overloaded &&
6631 local->group_type == group_overloaded) {
6632 load_above_capacity = busiest->sum_nr_running *
6634 if (load_above_capacity > busiest->group_capacity)
6635 load_above_capacity -= busiest->group_capacity;
6637 load_above_capacity = ~0UL;
6641 * We're trying to get all the cpus to the average_load, so we don't
6642 * want to push ourselves above the average load, nor do we wish to
6643 * reduce the max loaded cpu below the average load. At the same time,
6644 * we also don't want to reduce the group load below the group capacity
6645 * (so that we can implement power-savings policies etc). Thus we look
6646 * for the minimum possible imbalance.
6648 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6650 /* How much load to actually move to equalise the imbalance */
6651 env->imbalance = min(
6652 max_pull * busiest->group_capacity,
6653 (sds->avg_load - local->avg_load) * local->group_capacity
6654 ) / SCHED_CAPACITY_SCALE;
6657 * if *imbalance is less than the average load per runnable task
6658 * there is no guarantee that any tasks will be moved so we'll have
6659 * a think about bumping its value to force at least one task to be
6662 if (env->imbalance < busiest->load_per_task)
6663 return fix_small_imbalance(env, sds);
6666 /******* find_busiest_group() helpers end here *********************/
6669 * find_busiest_group - Returns the busiest group within the sched_domain
6670 * if there is an imbalance. If there isn't an imbalance, and
6671 * the user has opted for power-savings, it returns a group whose
6672 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6673 * such a group exists.
6675 * Also calculates the amount of weighted load which should be moved
6676 * to restore balance.
6678 * @env: The load balancing environment.
6680 * Return: - The busiest group if imbalance exists.
6681 * - If no imbalance and user has opted for power-savings balance,
6682 * return the least loaded group whose CPUs can be
6683 * put to idle by rebalancing its tasks onto our group.
6685 static struct sched_group *find_busiest_group(struct lb_env *env)
6687 struct sg_lb_stats *local, *busiest;
6688 struct sd_lb_stats sds;
6690 init_sd_lb_stats(&sds);
6693 * Compute the various statistics relavent for load balancing at
6696 update_sd_lb_stats(env, &sds);
6697 local = &sds.local_stat;
6698 busiest = &sds.busiest_stat;
6700 /* ASYM feature bypasses nice load balance check */
6701 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6702 check_asym_packing(env, &sds))
6705 /* There is no busy sibling group to pull tasks from */
6706 if (!sds.busiest || busiest->sum_nr_running == 0)
6709 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
6710 / sds.total_capacity;
6713 * If the busiest group is imbalanced the below checks don't
6714 * work because they assume all things are equal, which typically
6715 * isn't true due to cpus_allowed constraints and the like.
6717 if (busiest->group_type == group_imbalanced)
6720 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6721 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
6722 busiest->group_no_capacity)
6726 * If the local group is busier than the selected busiest group
6727 * don't try and pull any tasks.
6729 if (local->avg_load >= busiest->avg_load)
6733 * Don't pull any tasks if this group is already above the domain
6736 if (local->avg_load >= sds.avg_load)
6739 if (env->idle == CPU_IDLE) {
6741 * This cpu is idle. If the busiest group is not overloaded
6742 * and there is no imbalance between this and busiest group
6743 * wrt idle cpus, it is balanced. The imbalance becomes
6744 * significant if the diff is greater than 1 otherwise we
6745 * might end up to just move the imbalance on another group
6747 if ((busiest->group_type != group_overloaded) &&
6748 (local->idle_cpus <= (busiest->idle_cpus + 1)))
6752 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6753 * imbalance_pct to be conservative.
6755 if (100 * busiest->avg_load <=
6756 env->sd->imbalance_pct * local->avg_load)
6761 /* Looks like there is an imbalance. Compute it */
6762 calculate_imbalance(env, &sds);
6771 * find_busiest_queue - find the busiest runqueue among the cpus in group.
6773 static struct rq *find_busiest_queue(struct lb_env *env,
6774 struct sched_group *group)
6776 struct rq *busiest = NULL, *rq;
6777 unsigned long busiest_load = 0, busiest_capacity = 1;
6780 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6781 unsigned long capacity, wl;
6785 rt = fbq_classify_rq(rq);
6788 * We classify groups/runqueues into three groups:
6789 * - regular: there are !numa tasks
6790 * - remote: there are numa tasks that run on the 'wrong' node
6791 * - all: there is no distinction
6793 * In order to avoid migrating ideally placed numa tasks,
6794 * ignore those when there's better options.
6796 * If we ignore the actual busiest queue to migrate another
6797 * task, the next balance pass can still reduce the busiest
6798 * queue by moving tasks around inside the node.
6800 * If we cannot move enough load due to this classification
6801 * the next pass will adjust the group classification and
6802 * allow migration of more tasks.
6804 * Both cases only affect the total convergence complexity.
6806 if (rt > env->fbq_type)
6809 capacity = capacity_of(i);
6811 wl = weighted_cpuload(i);
6814 * When comparing with imbalance, use weighted_cpuload()
6815 * which is not scaled with the cpu capacity.
6818 if (rq->nr_running == 1 && wl > env->imbalance &&
6819 !check_cpu_capacity(rq, env->sd))
6823 * For the load comparisons with the other cpu's, consider
6824 * the weighted_cpuload() scaled with the cpu capacity, so
6825 * that the load can be moved away from the cpu that is
6826 * potentially running at a lower capacity.
6828 * Thus we're looking for max(wl_i / capacity_i), crosswise
6829 * multiplication to rid ourselves of the division works out
6830 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
6831 * our previous maximum.
6833 if (wl * busiest_capacity > busiest_load * capacity) {
6835 busiest_capacity = capacity;
6844 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6845 * so long as it is large enough.
6847 #define MAX_PINNED_INTERVAL 512
6849 /* Working cpumask for load_balance and load_balance_newidle. */
6850 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6852 static int need_active_balance(struct lb_env *env)
6854 struct sched_domain *sd = env->sd;
6856 if (env->idle == CPU_NEWLY_IDLE) {
6859 * ASYM_PACKING needs to force migrate tasks from busy but
6860 * higher numbered CPUs in order to pack all tasks in the
6861 * lowest numbered CPUs.
6863 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6868 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
6869 * It's worth migrating the task if the src_cpu's capacity is reduced
6870 * because of other sched_class or IRQs if more capacity stays
6871 * available on dst_cpu.
6873 if ((env->idle != CPU_NOT_IDLE) &&
6874 (env->src_rq->cfs.h_nr_running == 1)) {
6875 if ((check_cpu_capacity(env->src_rq, sd)) &&
6876 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
6880 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
6883 static int active_load_balance_cpu_stop(void *data);
6885 static int should_we_balance(struct lb_env *env)
6887 struct sched_group *sg = env->sd->groups;
6888 struct cpumask *sg_cpus, *sg_mask;
6889 int cpu, balance_cpu = -1;
6892 * In the newly idle case, we will allow all the cpu's
6893 * to do the newly idle load balance.
6895 if (env->idle == CPU_NEWLY_IDLE)
6898 sg_cpus = sched_group_cpus(sg);
6899 sg_mask = sched_group_mask(sg);
6900 /* Try to find first idle cpu */
6901 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
6902 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
6909 if (balance_cpu == -1)
6910 balance_cpu = group_balance_cpu(sg);
6913 * First idle cpu or the first cpu(busiest) in this sched group
6914 * is eligible for doing load balancing at this and above domains.
6916 return balance_cpu == env->dst_cpu;
6920 * Check this_cpu to ensure it is balanced within domain. Attempt to move
6921 * tasks if there is an imbalance.
6923 static int load_balance(int this_cpu, struct rq *this_rq,
6924 struct sched_domain *sd, enum cpu_idle_type idle,
6925 int *continue_balancing)
6927 int ld_moved, cur_ld_moved, active_balance = 0;
6928 struct sched_domain *sd_parent = sd->parent;
6929 struct sched_group *group;
6931 unsigned long flags;
6932 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
6934 struct lb_env env = {
6936 .dst_cpu = this_cpu,
6938 .dst_grpmask = sched_group_cpus(sd->groups),
6940 .loop_break = sched_nr_migrate_break,
6943 .tasks = LIST_HEAD_INIT(env.tasks),
6947 * For NEWLY_IDLE load_balancing, we don't need to consider
6948 * other cpus in our group
6950 if (idle == CPU_NEWLY_IDLE)
6951 env.dst_grpmask = NULL;
6953 cpumask_copy(cpus, cpu_active_mask);
6955 schedstat_inc(sd, lb_count[idle]);
6958 if (!should_we_balance(&env)) {
6959 *continue_balancing = 0;
6963 group = find_busiest_group(&env);
6965 schedstat_inc(sd, lb_nobusyg[idle]);
6969 busiest = find_busiest_queue(&env, group);
6971 schedstat_inc(sd, lb_nobusyq[idle]);
6975 BUG_ON(busiest == env.dst_rq);
6977 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6979 env.src_cpu = busiest->cpu;
6980 env.src_rq = busiest;
6983 if (busiest->nr_running > 1) {
6985 * Attempt to move tasks. If find_busiest_group has found
6986 * an imbalance but busiest->nr_running <= 1, the group is
6987 * still unbalanced. ld_moved simply stays zero, so it is
6988 * correctly treated as an imbalance.
6990 env.flags |= LBF_ALL_PINNED;
6991 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
6994 raw_spin_lock_irqsave(&busiest->lock, flags);
6997 * cur_ld_moved - load moved in current iteration
6998 * ld_moved - cumulative load moved across iterations
7000 cur_ld_moved = detach_tasks(&env);
7003 * We've detached some tasks from busiest_rq. Every
7004 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7005 * unlock busiest->lock, and we are able to be sure
7006 * that nobody can manipulate the tasks in parallel.
7007 * See task_rq_lock() family for the details.
7010 raw_spin_unlock(&busiest->lock);
7014 ld_moved += cur_ld_moved;
7017 local_irq_restore(flags);
7019 if (env.flags & LBF_NEED_BREAK) {
7020 env.flags &= ~LBF_NEED_BREAK;
7025 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7026 * us and move them to an alternate dst_cpu in our sched_group
7027 * where they can run. The upper limit on how many times we
7028 * iterate on same src_cpu is dependent on number of cpus in our
7031 * This changes load balance semantics a bit on who can move
7032 * load to a given_cpu. In addition to the given_cpu itself
7033 * (or a ilb_cpu acting on its behalf where given_cpu is
7034 * nohz-idle), we now have balance_cpu in a position to move
7035 * load to given_cpu. In rare situations, this may cause
7036 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7037 * _independently_ and at _same_ time to move some load to
7038 * given_cpu) causing exceess load to be moved to given_cpu.
7039 * This however should not happen so much in practice and
7040 * moreover subsequent load balance cycles should correct the
7041 * excess load moved.
7043 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7045 /* Prevent to re-select dst_cpu via env's cpus */
7046 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7048 env.dst_rq = cpu_rq(env.new_dst_cpu);
7049 env.dst_cpu = env.new_dst_cpu;
7050 env.flags &= ~LBF_DST_PINNED;
7052 env.loop_break = sched_nr_migrate_break;
7055 * Go back to "more_balance" rather than "redo" since we
7056 * need to continue with same src_cpu.
7062 * We failed to reach balance because of affinity.
7065 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7067 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7068 *group_imbalance = 1;
7071 /* All tasks on this runqueue were pinned by CPU affinity */
7072 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7073 cpumask_clear_cpu(cpu_of(busiest), cpus);
7074 if (!cpumask_empty(cpus)) {
7076 env.loop_break = sched_nr_migrate_break;
7079 goto out_all_pinned;
7084 schedstat_inc(sd, lb_failed[idle]);
7086 * Increment the failure counter only on periodic balance.
7087 * We do not want newidle balance, which can be very
7088 * frequent, pollute the failure counter causing
7089 * excessive cache_hot migrations and active balances.
7091 if (idle != CPU_NEWLY_IDLE)
7092 sd->nr_balance_failed++;
7094 if (need_active_balance(&env)) {
7095 raw_spin_lock_irqsave(&busiest->lock, flags);
7097 /* don't kick the active_load_balance_cpu_stop,
7098 * if the curr task on busiest cpu can't be
7101 if (!cpumask_test_cpu(this_cpu,
7102 tsk_cpus_allowed(busiest->curr))) {
7103 raw_spin_unlock_irqrestore(&busiest->lock,
7105 env.flags |= LBF_ALL_PINNED;
7106 goto out_one_pinned;
7110 * ->active_balance synchronizes accesses to
7111 * ->active_balance_work. Once set, it's cleared
7112 * only after active load balance is finished.
7114 if (!busiest->active_balance) {
7115 busiest->active_balance = 1;
7116 busiest->push_cpu = this_cpu;
7119 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7121 if (active_balance) {
7122 stop_one_cpu_nowait(cpu_of(busiest),
7123 active_load_balance_cpu_stop, busiest,
7124 &busiest->active_balance_work);
7128 * We've kicked active balancing, reset the failure
7131 sd->nr_balance_failed = sd->cache_nice_tries+1;
7134 sd->nr_balance_failed = 0;
7136 if (likely(!active_balance)) {
7137 /* We were unbalanced, so reset the balancing interval */
7138 sd->balance_interval = sd->min_interval;
7141 * If we've begun active balancing, start to back off. This
7142 * case may not be covered by the all_pinned logic if there
7143 * is only 1 task on the busy runqueue (because we don't call
7146 if (sd->balance_interval < sd->max_interval)
7147 sd->balance_interval *= 2;
7154 * We reach balance although we may have faced some affinity
7155 * constraints. Clear the imbalance flag if it was set.
7158 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7160 if (*group_imbalance)
7161 *group_imbalance = 0;
7166 * We reach balance because all tasks are pinned at this level so
7167 * we can't migrate them. Let the imbalance flag set so parent level
7168 * can try to migrate them.
7170 schedstat_inc(sd, lb_balanced[idle]);
7172 sd->nr_balance_failed = 0;
7175 /* tune up the balancing interval */
7176 if (((env.flags & LBF_ALL_PINNED) &&
7177 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7178 (sd->balance_interval < sd->max_interval))
7179 sd->balance_interval *= 2;
7186 static inline unsigned long
7187 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7189 unsigned long interval = sd->balance_interval;
7192 interval *= sd->busy_factor;
7194 /* scale ms to jiffies */
7195 interval = msecs_to_jiffies(interval);
7196 interval = clamp(interval, 1UL, max_load_balance_interval);
7202 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7204 unsigned long interval, next;
7206 interval = get_sd_balance_interval(sd, cpu_busy);
7207 next = sd->last_balance + interval;
7209 if (time_after(*next_balance, next))
7210 *next_balance = next;
7214 * idle_balance is called by schedule() if this_cpu is about to become
7215 * idle. Attempts to pull tasks from other CPUs.
7217 static int idle_balance(struct rq *this_rq)
7219 unsigned long next_balance = jiffies + HZ;
7220 int this_cpu = this_rq->cpu;
7221 struct sched_domain *sd;
7222 int pulled_task = 0;
7225 idle_enter_fair(this_rq);
7228 * We must set idle_stamp _before_ calling idle_balance(), such that we
7229 * measure the duration of idle_balance() as idle time.
7231 this_rq->idle_stamp = rq_clock(this_rq);
7233 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7234 !this_rq->rd->overload) {
7236 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7238 update_next_balance(sd, 0, &next_balance);
7244 raw_spin_unlock(&this_rq->lock);
7246 update_blocked_averages(this_cpu);
7248 for_each_domain(this_cpu, sd) {
7249 int continue_balancing = 1;
7250 u64 t0, domain_cost;
7252 if (!(sd->flags & SD_LOAD_BALANCE))
7255 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7256 update_next_balance(sd, 0, &next_balance);
7260 if (sd->flags & SD_BALANCE_NEWIDLE) {
7261 t0 = sched_clock_cpu(this_cpu);
7263 pulled_task = load_balance(this_cpu, this_rq,
7265 &continue_balancing);
7267 domain_cost = sched_clock_cpu(this_cpu) - t0;
7268 if (domain_cost > sd->max_newidle_lb_cost)
7269 sd->max_newidle_lb_cost = domain_cost;
7271 curr_cost += domain_cost;
7274 update_next_balance(sd, 0, &next_balance);
7277 * Stop searching for tasks to pull if there are
7278 * now runnable tasks on this rq.
7280 if (pulled_task || this_rq->nr_running > 0)
7285 raw_spin_lock(&this_rq->lock);
7287 if (curr_cost > this_rq->max_idle_balance_cost)
7288 this_rq->max_idle_balance_cost = curr_cost;
7291 * While browsing the domains, we released the rq lock, a task could
7292 * have been enqueued in the meantime. Since we're not going idle,
7293 * pretend we pulled a task.
7295 if (this_rq->cfs.h_nr_running && !pulled_task)
7299 /* Move the next balance forward */
7300 if (time_after(this_rq->next_balance, next_balance))
7301 this_rq->next_balance = next_balance;
7303 /* Is there a task of a high priority class? */
7304 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7308 idle_exit_fair(this_rq);
7309 this_rq->idle_stamp = 0;
7316 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7317 * running tasks off the busiest CPU onto idle CPUs. It requires at
7318 * least 1 task to be running on each physical CPU where possible, and
7319 * avoids physical / logical imbalances.
7321 static int active_load_balance_cpu_stop(void *data)
7323 struct rq *busiest_rq = data;
7324 int busiest_cpu = cpu_of(busiest_rq);
7325 int target_cpu = busiest_rq->push_cpu;
7326 struct rq *target_rq = cpu_rq(target_cpu);
7327 struct sched_domain *sd;
7328 struct task_struct *p = NULL;
7330 raw_spin_lock_irq(&busiest_rq->lock);
7332 /* make sure the requested cpu hasn't gone down in the meantime */
7333 if (unlikely(busiest_cpu != smp_processor_id() ||
7334 !busiest_rq->active_balance))
7337 /* Is there any task to move? */
7338 if (busiest_rq->nr_running <= 1)
7342 * This condition is "impossible", if it occurs
7343 * we need to fix it. Originally reported by
7344 * Bjorn Helgaas on a 128-cpu setup.
7346 BUG_ON(busiest_rq == target_rq);
7348 /* Search for an sd spanning us and the target CPU. */
7350 for_each_domain(target_cpu, sd) {
7351 if ((sd->flags & SD_LOAD_BALANCE) &&
7352 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7357 struct lb_env env = {
7359 .dst_cpu = target_cpu,
7360 .dst_rq = target_rq,
7361 .src_cpu = busiest_rq->cpu,
7362 .src_rq = busiest_rq,
7366 schedstat_inc(sd, alb_count);
7368 p = detach_one_task(&env);
7370 schedstat_inc(sd, alb_pushed);
7372 schedstat_inc(sd, alb_failed);
7376 busiest_rq->active_balance = 0;
7377 raw_spin_unlock(&busiest_rq->lock);
7380 attach_one_task(target_rq, p);
7387 static inline int on_null_domain(struct rq *rq)
7389 return unlikely(!rcu_dereference_sched(rq->sd));
7392 #ifdef CONFIG_NO_HZ_COMMON
7394 * idle load balancing details
7395 * - When one of the busy CPUs notice that there may be an idle rebalancing
7396 * needed, they will kick the idle load balancer, which then does idle
7397 * load balancing for all the idle CPUs.
7400 cpumask_var_t idle_cpus_mask;
7402 unsigned long next_balance; /* in jiffy units */
7403 } nohz ____cacheline_aligned;
7405 static inline int find_new_ilb(void)
7407 int ilb = cpumask_first(nohz.idle_cpus_mask);
7409 if (ilb < nr_cpu_ids && idle_cpu(ilb))
7416 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7417 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7418 * CPU (if there is one).
7420 static void nohz_balancer_kick(void)
7424 nohz.next_balance++;
7426 ilb_cpu = find_new_ilb();
7428 if (ilb_cpu >= nr_cpu_ids)
7431 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7434 * Use smp_send_reschedule() instead of resched_cpu().
7435 * This way we generate a sched IPI on the target cpu which
7436 * is idle. And the softirq performing nohz idle load balance
7437 * will be run before returning from the IPI.
7439 smp_send_reschedule(ilb_cpu);
7443 static inline void nohz_balance_exit_idle(int cpu)
7445 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7447 * Completely isolated CPUs don't ever set, so we must test.
7449 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7450 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7451 atomic_dec(&nohz.nr_cpus);
7453 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7457 static inline void set_cpu_sd_state_busy(void)
7459 struct sched_domain *sd;
7460 int cpu = smp_processor_id();
7463 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7465 if (!sd || !sd->nohz_idle)
7469 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7474 void set_cpu_sd_state_idle(void)
7476 struct sched_domain *sd;
7477 int cpu = smp_processor_id();
7480 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7482 if (!sd || sd->nohz_idle)
7486 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7492 * This routine will record that the cpu is going idle with tick stopped.
7493 * This info will be used in performing idle load balancing in the future.
7495 void nohz_balance_enter_idle(int cpu)
7498 * If this cpu is going down, then nothing needs to be done.
7500 if (!cpu_active(cpu))
7503 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7507 * If we're a completely isolated CPU, we don't play.
7509 if (on_null_domain(cpu_rq(cpu)))
7512 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7513 atomic_inc(&nohz.nr_cpus);
7514 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7517 static int sched_ilb_notifier(struct notifier_block *nfb,
7518 unsigned long action, void *hcpu)
7520 switch (action & ~CPU_TASKS_FROZEN) {
7522 nohz_balance_exit_idle(smp_processor_id());
7530 static DEFINE_SPINLOCK(balancing);
7533 * Scale the max load_balance interval with the number of CPUs in the system.
7534 * This trades load-balance latency on larger machines for less cross talk.
7536 void update_max_interval(void)
7538 max_load_balance_interval = HZ*num_online_cpus()/10;
7542 * It checks each scheduling domain to see if it is due to be balanced,
7543 * and initiates a balancing operation if so.
7545 * Balancing parameters are set up in init_sched_domains.
7547 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7549 int continue_balancing = 1;
7551 unsigned long interval;
7552 struct sched_domain *sd;
7553 /* Earliest time when we have to do rebalance again */
7554 unsigned long next_balance = jiffies + 60*HZ;
7555 int update_next_balance = 0;
7556 int need_serialize, need_decay = 0;
7559 update_blocked_averages(cpu);
7562 for_each_domain(cpu, sd) {
7564 * Decay the newidle max times here because this is a regular
7565 * visit to all the domains. Decay ~1% per second.
7567 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7568 sd->max_newidle_lb_cost =
7569 (sd->max_newidle_lb_cost * 253) / 256;
7570 sd->next_decay_max_lb_cost = jiffies + HZ;
7573 max_cost += sd->max_newidle_lb_cost;
7575 if (!(sd->flags & SD_LOAD_BALANCE))
7579 * Stop the load balance at this level. There is another
7580 * CPU in our sched group which is doing load balancing more
7583 if (!continue_balancing) {
7589 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7591 need_serialize = sd->flags & SD_SERIALIZE;
7592 if (need_serialize) {
7593 if (!spin_trylock(&balancing))
7597 if (time_after_eq(jiffies, sd->last_balance + interval)) {
7598 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7600 * The LBF_DST_PINNED logic could have changed
7601 * env->dst_cpu, so we can't know our idle
7602 * state even if we migrated tasks. Update it.
7604 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7606 sd->last_balance = jiffies;
7607 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7610 spin_unlock(&balancing);
7612 if (time_after(next_balance, sd->last_balance + interval)) {
7613 next_balance = sd->last_balance + interval;
7614 update_next_balance = 1;
7619 * Ensure the rq-wide value also decays but keep it at a
7620 * reasonable floor to avoid funnies with rq->avg_idle.
7622 rq->max_idle_balance_cost =
7623 max((u64)sysctl_sched_migration_cost, max_cost);
7628 * next_balance will be updated only when there is a need.
7629 * When the cpu is attached to null domain for ex, it will not be
7632 if (likely(update_next_balance))
7633 rq->next_balance = next_balance;
7636 #ifdef CONFIG_NO_HZ_COMMON
7638 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7639 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7641 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7643 int this_cpu = this_rq->cpu;
7647 if (idle != CPU_IDLE ||
7648 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7651 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7652 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7656 * If this cpu gets work to do, stop the load balancing
7657 * work being done for other cpus. Next load
7658 * balancing owner will pick it up.
7663 rq = cpu_rq(balance_cpu);
7666 * If time for next balance is due,
7669 if (time_after_eq(jiffies, rq->next_balance)) {
7670 raw_spin_lock_irq(&rq->lock);
7671 update_rq_clock(rq);
7672 update_idle_cpu_load(rq);
7673 raw_spin_unlock_irq(&rq->lock);
7674 rebalance_domains(rq, CPU_IDLE);
7677 if (time_after(this_rq->next_balance, rq->next_balance))
7678 this_rq->next_balance = rq->next_balance;
7680 nohz.next_balance = this_rq->next_balance;
7682 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7686 * Current heuristic for kicking the idle load balancer in the presence
7687 * of an idle cpu in the system.
7688 * - This rq has more than one task.
7689 * - This rq has at least one CFS task and the capacity of the CPU is
7690 * significantly reduced because of RT tasks or IRQs.
7691 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
7692 * multiple busy cpu.
7693 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7694 * domain span are idle.
7696 static inline bool nohz_kick_needed(struct rq *rq)
7698 unsigned long now = jiffies;
7699 struct sched_domain *sd;
7700 struct sched_group_capacity *sgc;
7701 int nr_busy, cpu = rq->cpu;
7704 if (unlikely(rq->idle_balance))
7708 * We may be recently in ticked or tickless idle mode. At the first
7709 * busy tick after returning from idle, we will update the busy stats.
7711 set_cpu_sd_state_busy();
7712 nohz_balance_exit_idle(cpu);
7715 * None are in tickless mode and hence no need for NOHZ idle load
7718 if (likely(!atomic_read(&nohz.nr_cpus)))
7721 if (time_before(now, nohz.next_balance))
7724 if (rq->nr_running >= 2)
7728 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7730 sgc = sd->groups->sgc;
7731 nr_busy = atomic_read(&sgc->nr_busy_cpus);
7740 sd = rcu_dereference(rq->sd);
7742 if ((rq->cfs.h_nr_running >= 1) &&
7743 check_cpu_capacity(rq, sd)) {
7749 sd = rcu_dereference(per_cpu(sd_asym, cpu));
7750 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7751 sched_domain_span(sd)) < cpu)) {
7761 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7765 * run_rebalance_domains is triggered when needed from the scheduler tick.
7766 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7768 static void run_rebalance_domains(struct softirq_action *h)
7770 struct rq *this_rq = this_rq();
7771 enum cpu_idle_type idle = this_rq->idle_balance ?
7772 CPU_IDLE : CPU_NOT_IDLE;
7775 * If this cpu has a pending nohz_balance_kick, then do the
7776 * balancing on behalf of the other idle cpus whose ticks are
7777 * stopped. Do nohz_idle_balance *before* rebalance_domains to
7778 * give the idle cpus a chance to load balance. Else we may
7779 * load balance only within the local sched_domain hierarchy
7780 * and abort nohz_idle_balance altogether if we pull some load.
7782 nohz_idle_balance(this_rq, idle);
7783 rebalance_domains(this_rq, idle);
7787 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7789 void trigger_load_balance(struct rq *rq)
7791 /* Don't need to rebalance while attached to NULL domain */
7792 if (unlikely(on_null_domain(rq)))
7795 if (time_after_eq(jiffies, rq->next_balance))
7796 raise_softirq(SCHED_SOFTIRQ);
7797 #ifdef CONFIG_NO_HZ_COMMON
7798 if (nohz_kick_needed(rq))
7799 nohz_balancer_kick();
7803 static void rq_online_fair(struct rq *rq)
7807 update_runtime_enabled(rq);
7810 static void rq_offline_fair(struct rq *rq)
7814 /* Ensure any throttled groups are reachable by pick_next_task */
7815 unthrottle_offline_cfs_rqs(rq);
7818 #endif /* CONFIG_SMP */
7821 * scheduler tick hitting a task of our scheduling class:
7823 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7825 struct cfs_rq *cfs_rq;
7826 struct sched_entity *se = &curr->se;
7828 for_each_sched_entity(se) {
7829 cfs_rq = cfs_rq_of(se);
7830 entity_tick(cfs_rq, se, queued);
7833 if (numabalancing_enabled)
7834 task_tick_numa(rq, curr);
7838 * called on fork with the child task as argument from the parent's context
7839 * - child not yet on the tasklist
7840 * - preemption disabled
7842 static void task_fork_fair(struct task_struct *p)
7844 struct cfs_rq *cfs_rq;
7845 struct sched_entity *se = &p->se, *curr;
7846 int this_cpu = smp_processor_id();
7847 struct rq *rq = this_rq();
7848 unsigned long flags;
7850 raw_spin_lock_irqsave(&rq->lock, flags);
7852 update_rq_clock(rq);
7854 cfs_rq = task_cfs_rq(current);
7855 curr = cfs_rq->curr;
7858 * Not only the cpu but also the task_group of the parent might have
7859 * been changed after parent->se.parent,cfs_rq were copied to
7860 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
7861 * of child point to valid ones.
7864 __set_task_cpu(p, this_cpu);
7867 update_curr(cfs_rq);
7870 se->vruntime = curr->vruntime;
7871 place_entity(cfs_rq, se, 1);
7873 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
7875 * Upon rescheduling, sched_class::put_prev_task() will place
7876 * 'current' within the tree based on its new key value.
7878 swap(curr->vruntime, se->vruntime);
7882 se->vruntime -= cfs_rq->min_vruntime;
7884 raw_spin_unlock_irqrestore(&rq->lock, flags);
7888 * Priority of the task has changed. Check to see if we preempt
7892 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7894 if (!task_on_rq_queued(p))
7898 * Reschedule if we are currently running on this runqueue and
7899 * our priority decreased, or if we are not currently running on
7900 * this runqueue and our priority is higher than the current's
7902 if (rq->curr == p) {
7903 if (p->prio > oldprio)
7906 check_preempt_curr(rq, p, 0);
7909 static void switched_from_fair(struct rq *rq, struct task_struct *p)
7911 struct sched_entity *se = &p->se;
7912 struct cfs_rq *cfs_rq = cfs_rq_of(se);
7915 * Ensure the task's vruntime is normalized, so that when it's
7916 * switched back to the fair class the enqueue_entity(.flags=0) will
7917 * do the right thing.
7919 * If it's queued, then the dequeue_entity(.flags=0) will already
7920 * have normalized the vruntime, if it's !queued, then only when
7921 * the task is sleeping will it still have non-normalized vruntime.
7923 if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) {
7925 * Fix up our vruntime so that the current sleep doesn't
7926 * cause 'unlimited' sleep bonus.
7928 place_entity(cfs_rq, se, 0);
7929 se->vruntime -= cfs_rq->min_vruntime;
7932 /* Catch up with the cfs_rq and remove our load when we leave */
7933 detach_entity_load_avg(cfs_rq, se);
7936 static void switched_to_fair(struct rq *rq, struct task_struct *p)
7938 struct sched_entity *se = &p->se;
7940 #ifdef CONFIG_FAIR_GROUP_SCHED
7942 * Since the real-depth could have been changed (only FAIR
7943 * class maintain depth value), reset depth properly.
7945 se->depth = se->parent ? se->parent->depth + 1 : 0;
7948 if (!task_on_rq_queued(p)) {
7951 * Ensure the task has a non-normalized vruntime when it is switched
7952 * back to the fair class with !queued, so that enqueue_entity() at
7953 * wake-up time will do the right thing.
7955 * If it's queued, then the enqueue_entity(.flags=0) makes the task
7956 * has non-normalized vruntime, if it's !queued, then it still has
7957 * normalized vruntime.
7959 if (p->state != TASK_RUNNING)
7960 se->vruntime += cfs_rq_of(se)->min_vruntime;
7965 * We were most likely switched from sched_rt, so
7966 * kick off the schedule if running, otherwise just see
7967 * if we can still preempt the current task.
7972 check_preempt_curr(rq, p, 0);
7975 /* Account for a task changing its policy or group.
7977 * This routine is mostly called to set cfs_rq->curr field when a task
7978 * migrates between groups/classes.
7980 static void set_curr_task_fair(struct rq *rq)
7982 struct sched_entity *se = &rq->curr->se;
7984 for_each_sched_entity(se) {
7985 struct cfs_rq *cfs_rq = cfs_rq_of(se);
7987 set_next_entity(cfs_rq, se);
7988 /* ensure bandwidth has been allocated on our new cfs_rq */
7989 account_cfs_rq_runtime(cfs_rq, 0);
7993 void init_cfs_rq(struct cfs_rq *cfs_rq)
7995 cfs_rq->tasks_timeline = RB_ROOT;
7996 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
7997 #ifndef CONFIG_64BIT
7998 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8001 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8002 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8006 #ifdef CONFIG_FAIR_GROUP_SCHED
8007 static void task_move_group_fair(struct task_struct *p, int queued)
8009 struct sched_entity *se = &p->se;
8010 struct cfs_rq *cfs_rq;
8013 * If the task was not on the rq at the time of this cgroup movement
8014 * it must have been asleep, sleeping tasks keep their ->vruntime
8015 * absolute on their old rq until wakeup (needed for the fair sleeper
8016 * bonus in place_entity()).
8018 * If it was on the rq, we've just 'preempted' it, which does convert
8019 * ->vruntime to a relative base.
8021 * Make sure both cases convert their relative position when migrating
8022 * to another cgroup's rq. This does somewhat interfere with the
8023 * fair sleeper stuff for the first placement, but who cares.
8026 * When !queued, vruntime of the task has usually NOT been normalized.
8027 * But there are some cases where it has already been normalized:
8029 * - Moving a forked child which is waiting for being woken up by
8030 * wake_up_new_task().
8031 * - Moving a task which has been woken up by try_to_wake_up() and
8032 * waiting for actually being woken up by sched_ttwu_pending().
8034 * To prevent boost or penalty in the new cfs_rq caused by delta
8035 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
8037 if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
8041 se->vruntime -= cfs_rq_of(se)->min_vruntime;
8042 set_task_rq(p, task_cpu(p));
8043 se->depth = se->parent ? se->parent->depth + 1 : 0;
8045 cfs_rq = cfs_rq_of(se);
8046 se->vruntime += cfs_rq->min_vruntime;
8048 /* Virtually synchronize task with its new cfs_rq */
8049 attach_entity_load_avg(cfs_rq, se);
8053 void free_fair_sched_group(struct task_group *tg)
8057 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8059 for_each_possible_cpu(i) {
8061 kfree(tg->cfs_rq[i]);
8064 remove_entity_load_avg(tg->se[i]);
8073 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8075 struct cfs_rq *cfs_rq;
8076 struct sched_entity *se;
8079 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8082 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8086 tg->shares = NICE_0_LOAD;
8088 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8090 for_each_possible_cpu(i) {
8091 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8092 GFP_KERNEL, cpu_to_node(i));
8096 se = kzalloc_node(sizeof(struct sched_entity),
8097 GFP_KERNEL, cpu_to_node(i));
8101 init_cfs_rq(cfs_rq);
8102 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8103 init_entity_runnable_average(se);
8114 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8116 struct rq *rq = cpu_rq(cpu);
8117 unsigned long flags;
8120 * Only empty task groups can be destroyed; so we can speculatively
8121 * check on_list without danger of it being re-added.
8123 if (!tg->cfs_rq[cpu]->on_list)
8126 raw_spin_lock_irqsave(&rq->lock, flags);
8127 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8128 raw_spin_unlock_irqrestore(&rq->lock, flags);
8131 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8132 struct sched_entity *se, int cpu,
8133 struct sched_entity *parent)
8135 struct rq *rq = cpu_rq(cpu);
8139 init_cfs_rq_runtime(cfs_rq);
8141 tg->cfs_rq[cpu] = cfs_rq;
8144 /* se could be NULL for root_task_group */
8149 se->cfs_rq = &rq->cfs;
8152 se->cfs_rq = parent->my_q;
8153 se->depth = parent->depth + 1;
8157 /* guarantee group entities always have weight */
8158 update_load_set(&se->load, NICE_0_LOAD);
8159 se->parent = parent;
8162 static DEFINE_MUTEX(shares_mutex);
8164 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8167 unsigned long flags;
8170 * We can't change the weight of the root cgroup.
8175 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8177 mutex_lock(&shares_mutex);
8178 if (tg->shares == shares)
8181 tg->shares = shares;
8182 for_each_possible_cpu(i) {
8183 struct rq *rq = cpu_rq(i);
8184 struct sched_entity *se;
8187 /* Propagate contribution to hierarchy */
8188 raw_spin_lock_irqsave(&rq->lock, flags);
8190 /* Possible calls to update_curr() need rq clock */
8191 update_rq_clock(rq);
8192 for_each_sched_entity(se)
8193 update_cfs_shares(group_cfs_rq(se));
8194 raw_spin_unlock_irqrestore(&rq->lock, flags);
8198 mutex_unlock(&shares_mutex);
8201 #else /* CONFIG_FAIR_GROUP_SCHED */
8203 void free_fair_sched_group(struct task_group *tg) { }
8205 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8210 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
8212 #endif /* CONFIG_FAIR_GROUP_SCHED */
8215 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8217 struct sched_entity *se = &task->se;
8218 unsigned int rr_interval = 0;
8221 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8224 if (rq->cfs.load.weight)
8225 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8231 * All the scheduling class methods:
8233 const struct sched_class fair_sched_class = {
8234 .next = &idle_sched_class,
8235 .enqueue_task = enqueue_task_fair,
8236 .dequeue_task = dequeue_task_fair,
8237 .yield_task = yield_task_fair,
8238 .yield_to_task = yield_to_task_fair,
8240 .check_preempt_curr = check_preempt_wakeup,
8242 .pick_next_task = pick_next_task_fair,
8243 .put_prev_task = put_prev_task_fair,
8246 .select_task_rq = select_task_rq_fair,
8247 .migrate_task_rq = migrate_task_rq_fair,
8249 .rq_online = rq_online_fair,
8250 .rq_offline = rq_offline_fair,
8252 .task_waking = task_waking_fair,
8253 .task_dead = task_dead_fair,
8254 .set_cpus_allowed = set_cpus_allowed_common,
8257 .set_curr_task = set_curr_task_fair,
8258 .task_tick = task_tick_fair,
8259 .task_fork = task_fork_fair,
8261 .prio_changed = prio_changed_fair,
8262 .switched_from = switched_from_fair,
8263 .switched_to = switched_to_fair,
8265 .get_rr_interval = get_rr_interval_fair,
8267 .update_curr = update_curr_fair,
8269 #ifdef CONFIG_FAIR_GROUP_SCHED
8270 .task_move_group = task_move_group_fair,
8274 #ifdef CONFIG_SCHED_DEBUG
8275 void print_cfs_stats(struct seq_file *m, int cpu)
8277 struct cfs_rq *cfs_rq;
8280 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8281 print_cfs_rq(m, cpu, cfs_rq);
8285 #ifdef CONFIG_NUMA_BALANCING
8286 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8289 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8291 for_each_online_node(node) {
8292 if (p->numa_faults) {
8293 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8294 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8296 if (p->numa_group) {
8297 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8298 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8300 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8303 #endif /* CONFIG_NUMA_BALANCING */
8304 #endif /* CONFIG_SCHED_DEBUG */
8306 __init void init_sched_fair_class(void)
8309 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
8311 #ifdef CONFIG_NO_HZ_COMMON
8312 nohz.next_balance = jiffies;
8313 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8314 cpu_notifier(sched_ilb_notifier, 0);