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/slab.h>
27 #include <linux/profile.h>
28 #include <linux/interrupt.h>
29 #include <linux/mempolicy.h>
30 #include <linux/migrate.h>
31 #include <linux/task_work.h>
33 #include <trace/events/sched.h>
38 * Targeted preemption latency for CPU-bound tasks:
39 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
41 * NOTE: this latency value is not the same as the concept of
42 * 'timeslice length' - timeslices in CFS are of variable length
43 * and have no persistent notion like in traditional, time-slice
44 * based scheduling concepts.
46 * (to see the precise effective timeslice length of your workload,
47 * run vmstat and monitor the context-switches (cs) field)
49 unsigned int sysctl_sched_latency = 6000000ULL;
50 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
53 * The initial- and re-scaling of tunables is configurable
54 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
57 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
58 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
59 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
61 enum sched_tunable_scaling sysctl_sched_tunable_scaling
62 = SCHED_TUNABLESCALING_LOG;
65 * Minimal preemption granularity for CPU-bound tasks:
66 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
68 unsigned int sysctl_sched_min_granularity = 750000ULL;
69 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
72 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
74 static unsigned int sched_nr_latency = 8;
77 * After fork, child runs first. If set to 0 (default) then
78 * parent will (try to) run first.
80 unsigned int sysctl_sched_child_runs_first __read_mostly;
83 * SCHED_OTHER wake-up granularity.
84 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
86 * This option delays the preemption effects of decoupled workloads
87 * and reduces their over-scheduling. Synchronous workloads will still
88 * have immediate wakeup/sleep latencies.
90 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
91 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
93 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
96 * The exponential sliding window over which load is averaged for shares
100 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
102 #ifdef CONFIG_CFS_BANDWIDTH
104 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
105 * each time a cfs_rq requests quota.
107 * Note: in the case that the slice exceeds the runtime remaining (either due
108 * to consumption or the quota being specified to be smaller than the slice)
109 * we will always only issue the remaining available time.
111 * default: 5 msec, units: microseconds
113 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
116 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
122 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
128 static inline void update_load_set(struct load_weight *lw, unsigned long w)
135 * Increase the granularity value when there are more CPUs,
136 * because with more CPUs the 'effective latency' as visible
137 * to users decreases. But the relationship is not linear,
138 * so pick a second-best guess by going with the log2 of the
141 * This idea comes from the SD scheduler of Con Kolivas:
143 static int get_update_sysctl_factor(void)
145 unsigned int cpus = min_t(int, num_online_cpus(), 8);
148 switch (sysctl_sched_tunable_scaling) {
149 case SCHED_TUNABLESCALING_NONE:
152 case SCHED_TUNABLESCALING_LINEAR:
155 case SCHED_TUNABLESCALING_LOG:
157 factor = 1 + ilog2(cpus);
164 static void update_sysctl(void)
166 unsigned int factor = get_update_sysctl_factor();
168 #define SET_SYSCTL(name) \
169 (sysctl_##name = (factor) * normalized_sysctl_##name)
170 SET_SYSCTL(sched_min_granularity);
171 SET_SYSCTL(sched_latency);
172 SET_SYSCTL(sched_wakeup_granularity);
176 void sched_init_granularity(void)
181 #if BITS_PER_LONG == 32
182 # define WMULT_CONST (~0UL)
184 # define WMULT_CONST (1UL << 32)
187 #define WMULT_SHIFT 32
190 * Shift right and round:
192 #define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))
195 * delta *= weight / lw
198 calc_delta_mine(unsigned long delta_exec, unsigned long weight,
199 struct load_weight *lw)
204 * weight can be less than 2^SCHED_LOAD_RESOLUTION for task group sched
205 * entities since MIN_SHARES = 2. Treat weight as 1 if less than
206 * 2^SCHED_LOAD_RESOLUTION.
208 if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION)))
209 tmp = (u64)delta_exec * scale_load_down(weight);
211 tmp = (u64)delta_exec;
213 if (!lw->inv_weight) {
214 unsigned long w = scale_load_down(lw->weight);
216 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
218 else if (unlikely(!w))
219 lw->inv_weight = WMULT_CONST;
221 lw->inv_weight = WMULT_CONST / w;
225 * Check whether we'd overflow the 64-bit multiplication:
227 if (unlikely(tmp > WMULT_CONST))
228 tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
231 tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);
233 return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
237 const struct sched_class fair_sched_class;
239 /**************************************************************
240 * CFS operations on generic schedulable entities:
243 #ifdef CONFIG_FAIR_GROUP_SCHED
245 /* cpu runqueue to which this cfs_rq is attached */
246 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
251 /* An entity is a task if it doesn't "own" a runqueue */
252 #define entity_is_task(se) (!se->my_q)
254 static inline struct task_struct *task_of(struct sched_entity *se)
256 #ifdef CONFIG_SCHED_DEBUG
257 WARN_ON_ONCE(!entity_is_task(se));
259 return container_of(se, struct task_struct, se);
262 /* Walk up scheduling entities hierarchy */
263 #define for_each_sched_entity(se) \
264 for (; se; se = se->parent)
266 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
271 /* runqueue on which this entity is (to be) queued */
272 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
277 /* runqueue "owned" by this group */
278 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
283 static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
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);
305 /* We should have no load, but we need to update last_decay. */
306 update_cfs_rq_blocked_load(cfs_rq, 0);
310 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
312 if (cfs_rq->on_list) {
313 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
318 /* Iterate thr' all leaf cfs_rq's on a runqueue */
319 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
320 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
322 /* Do the two (enqueued) entities belong to the same group ? */
324 is_same_group(struct sched_entity *se, struct sched_entity *pse)
326 if (se->cfs_rq == pse->cfs_rq)
332 static inline struct sched_entity *parent_entity(struct sched_entity *se)
337 /* return depth at which a sched entity is present in the hierarchy */
338 static inline int depth_se(struct sched_entity *se)
342 for_each_sched_entity(se)
349 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
351 int se_depth, pse_depth;
354 * preemption test can be made between sibling entities who are in the
355 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
356 * both tasks until we find their ancestors who are siblings of common
360 /* First walk up until both entities are at same depth */
361 se_depth = depth_se(*se);
362 pse_depth = depth_se(*pse);
364 while (se_depth > pse_depth) {
366 *se = parent_entity(*se);
369 while (pse_depth > se_depth) {
371 *pse = parent_entity(*pse);
374 while (!is_same_group(*se, *pse)) {
375 *se = parent_entity(*se);
376 *pse = parent_entity(*pse);
380 #else /* !CONFIG_FAIR_GROUP_SCHED */
382 static inline struct task_struct *task_of(struct sched_entity *se)
384 return container_of(se, struct task_struct, se);
387 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
389 return container_of(cfs_rq, struct rq, cfs);
392 #define entity_is_task(se) 1
394 #define for_each_sched_entity(se) \
395 for (; se; se = NULL)
397 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
399 return &task_rq(p)->cfs;
402 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
404 struct task_struct *p = task_of(se);
405 struct rq *rq = task_rq(p);
410 /* runqueue "owned" by this group */
411 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
416 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
420 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
424 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
425 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
428 is_same_group(struct sched_entity *se, struct sched_entity *pse)
433 static inline struct sched_entity *parent_entity(struct sched_entity *se)
439 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
443 #endif /* CONFIG_FAIR_GROUP_SCHED */
445 static __always_inline
446 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec);
448 /**************************************************************
449 * Scheduling class tree data structure manipulation methods:
452 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
454 s64 delta = (s64)(vruntime - max_vruntime);
456 max_vruntime = vruntime;
461 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
463 s64 delta = (s64)(vruntime - min_vruntime);
465 min_vruntime = vruntime;
470 static inline int entity_before(struct sched_entity *a,
471 struct sched_entity *b)
473 return (s64)(a->vruntime - b->vruntime) < 0;
476 static void update_min_vruntime(struct cfs_rq *cfs_rq)
478 u64 vruntime = cfs_rq->min_vruntime;
481 vruntime = cfs_rq->curr->vruntime;
483 if (cfs_rq->rb_leftmost) {
484 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
489 vruntime = se->vruntime;
491 vruntime = min_vruntime(vruntime, se->vruntime);
494 /* ensure we never gain time by being placed backwards. */
495 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
498 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
503 * Enqueue an entity into the rb-tree:
505 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
507 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
508 struct rb_node *parent = NULL;
509 struct sched_entity *entry;
513 * Find the right place in the rbtree:
517 entry = rb_entry(parent, struct sched_entity, run_node);
519 * We dont care about collisions. Nodes with
520 * the same key stay together.
522 if (entity_before(se, entry)) {
523 link = &parent->rb_left;
525 link = &parent->rb_right;
531 * Maintain a cache of leftmost tree entries (it is frequently
535 cfs_rq->rb_leftmost = &se->run_node;
537 rb_link_node(&se->run_node, parent, link);
538 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
541 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
543 if (cfs_rq->rb_leftmost == &se->run_node) {
544 struct rb_node *next_node;
546 next_node = rb_next(&se->run_node);
547 cfs_rq->rb_leftmost = next_node;
550 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
553 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
555 struct rb_node *left = cfs_rq->rb_leftmost;
560 return rb_entry(left, struct sched_entity, run_node);
563 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
565 struct rb_node *next = rb_next(&se->run_node);
570 return rb_entry(next, struct sched_entity, run_node);
573 #ifdef CONFIG_SCHED_DEBUG
574 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
576 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
581 return rb_entry(last, struct sched_entity, run_node);
584 /**************************************************************
585 * Scheduling class statistics methods:
588 int sched_proc_update_handler(struct ctl_table *table, int write,
589 void __user *buffer, size_t *lenp,
592 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
593 int factor = get_update_sysctl_factor();
598 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
599 sysctl_sched_min_granularity);
601 #define WRT_SYSCTL(name) \
602 (normalized_sysctl_##name = sysctl_##name / (factor))
603 WRT_SYSCTL(sched_min_granularity);
604 WRT_SYSCTL(sched_latency);
605 WRT_SYSCTL(sched_wakeup_granularity);
615 static inline unsigned long
616 calc_delta_fair(unsigned long delta, struct sched_entity *se)
618 if (unlikely(se->load.weight != NICE_0_LOAD))
619 delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
625 * The idea is to set a period in which each task runs once.
627 * When there are too many tasks (sched_nr_latency) we have to stretch
628 * this period because otherwise the slices get too small.
630 * p = (nr <= nl) ? l : l*nr/nl
632 static u64 __sched_period(unsigned long nr_running)
634 u64 period = sysctl_sched_latency;
635 unsigned long nr_latency = sched_nr_latency;
637 if (unlikely(nr_running > nr_latency)) {
638 period = sysctl_sched_min_granularity;
639 period *= nr_running;
646 * We calculate the wall-time slice from the period by taking a part
647 * proportional to the weight.
651 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
653 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
655 for_each_sched_entity(se) {
656 struct load_weight *load;
657 struct load_weight lw;
659 cfs_rq = cfs_rq_of(se);
660 load = &cfs_rq->load;
662 if (unlikely(!se->on_rq)) {
665 update_load_add(&lw, se->load.weight);
668 slice = calc_delta_mine(slice, se->load.weight, load);
674 * We calculate the vruntime slice of a to-be-inserted task.
678 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
680 return calc_delta_fair(sched_slice(cfs_rq, se), se);
684 static inline void __update_task_entity_contrib(struct sched_entity *se);
686 /* Give new task start runnable values to heavy its load in infant time */
687 void init_task_runnable_average(struct task_struct *p)
691 p->se.avg.decay_count = 0;
692 slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
693 p->se.avg.runnable_avg_sum = slice;
694 p->se.avg.runnable_avg_period = slice;
695 __update_task_entity_contrib(&p->se);
698 void init_task_runnable_average(struct task_struct *p)
704 * Update the current task's runtime statistics. Skip current tasks that
705 * are not in our scheduling class.
708 __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
709 unsigned long delta_exec)
711 unsigned long delta_exec_weighted;
713 schedstat_set(curr->statistics.exec_max,
714 max((u64)delta_exec, curr->statistics.exec_max));
716 curr->sum_exec_runtime += delta_exec;
717 schedstat_add(cfs_rq, exec_clock, delta_exec);
718 delta_exec_weighted = calc_delta_fair(delta_exec, curr);
720 curr->vruntime += delta_exec_weighted;
721 update_min_vruntime(cfs_rq);
724 static void update_curr(struct cfs_rq *cfs_rq)
726 struct sched_entity *curr = cfs_rq->curr;
727 u64 now = rq_clock_task(rq_of(cfs_rq));
728 unsigned long delta_exec;
734 * Get the amount of time the current task was running
735 * since the last time we changed load (this cannot
736 * overflow on 32 bits):
738 delta_exec = (unsigned long)(now - curr->exec_start);
742 __update_curr(cfs_rq, curr, delta_exec);
743 curr->exec_start = now;
745 if (entity_is_task(curr)) {
746 struct task_struct *curtask = task_of(curr);
748 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
749 cpuacct_charge(curtask, delta_exec);
750 account_group_exec_runtime(curtask, delta_exec);
753 account_cfs_rq_runtime(cfs_rq, delta_exec);
757 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
759 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
763 * Task is being enqueued - update stats:
765 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
768 * Are we enqueueing a waiting task? (for current tasks
769 * a dequeue/enqueue event is a NOP)
771 if (se != cfs_rq->curr)
772 update_stats_wait_start(cfs_rq, se);
776 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
778 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
779 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
780 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
781 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
782 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
783 #ifdef CONFIG_SCHEDSTATS
784 if (entity_is_task(se)) {
785 trace_sched_stat_wait(task_of(se),
786 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
789 schedstat_set(se->statistics.wait_start, 0);
793 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
796 * Mark the end of the wait period if dequeueing a
799 if (se != cfs_rq->curr)
800 update_stats_wait_end(cfs_rq, se);
804 * We are picking a new current task - update its stats:
807 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
810 * We are starting a new run period:
812 se->exec_start = rq_clock_task(rq_of(cfs_rq));
815 /**************************************************
816 * Scheduling class queueing methods:
819 #ifdef CONFIG_NUMA_BALANCING
821 * numa task sample period in ms
823 unsigned int sysctl_numa_balancing_scan_period_min = 100;
824 unsigned int sysctl_numa_balancing_scan_period_max = 100*50;
825 unsigned int sysctl_numa_balancing_scan_period_reset = 100*600;
827 /* Portion of address space to scan in MB */
828 unsigned int sysctl_numa_balancing_scan_size = 256;
830 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
831 unsigned int sysctl_numa_balancing_scan_delay = 1000;
833 static void task_numa_placement(struct task_struct *p)
837 if (!p->mm) /* for example, ksmd faulting in a user's mm */
839 seq = ACCESS_ONCE(p->mm->numa_scan_seq);
840 if (p->numa_scan_seq == seq)
842 p->numa_scan_seq = seq;
844 /* FIXME: Scheduling placement policy hints go here */
848 * Got a PROT_NONE fault for a page on @node.
850 void task_numa_fault(int node, int pages, bool migrated)
852 struct task_struct *p = current;
854 if (!sched_feat_numa(NUMA))
857 /* FIXME: Allocate task-specific structure for placement policy here */
860 * If pages are properly placed (did not migrate) then scan slower.
861 * This is reset periodically in case of phase changes
864 p->numa_scan_period = min(sysctl_numa_balancing_scan_period_max,
865 p->numa_scan_period + jiffies_to_msecs(10));
867 task_numa_placement(p);
870 static void reset_ptenuma_scan(struct task_struct *p)
872 ACCESS_ONCE(p->mm->numa_scan_seq)++;
873 p->mm->numa_scan_offset = 0;
877 * The expensive part of numa migration is done from task_work context.
878 * Triggered from task_tick_numa().
880 void task_numa_work(struct callback_head *work)
882 unsigned long migrate, next_scan, now = jiffies;
883 struct task_struct *p = current;
884 struct mm_struct *mm = p->mm;
885 struct vm_area_struct *vma;
886 unsigned long start, end;
889 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
891 work->next = work; /* protect against double add */
893 * Who cares about NUMA placement when they're dying.
895 * NOTE: make sure not to dereference p->mm before this check,
896 * exit_task_work() happens _after_ exit_mm() so we could be called
897 * without p->mm even though we still had it when we enqueued this
900 if (p->flags & PF_EXITING)
904 * We do not care about task placement until a task runs on a node
905 * other than the first one used by the address space. This is
906 * largely because migrations are driven by what CPU the task
907 * is running on. If it's never scheduled on another node, it'll
908 * not migrate so why bother trapping the fault.
910 if (mm->first_nid == NUMA_PTE_SCAN_INIT)
911 mm->first_nid = numa_node_id();
912 if (mm->first_nid != NUMA_PTE_SCAN_ACTIVE) {
913 /* Are we running on a new node yet? */
914 if (numa_node_id() == mm->first_nid &&
915 !sched_feat_numa(NUMA_FORCE))
918 mm->first_nid = NUMA_PTE_SCAN_ACTIVE;
922 * Reset the scan period if enough time has gone by. Objective is that
923 * scanning will be reduced if pages are properly placed. As tasks
924 * can enter different phases this needs to be re-examined. Lacking
925 * proper tracking of reference behaviour, this blunt hammer is used.
927 migrate = mm->numa_next_reset;
928 if (time_after(now, migrate)) {
929 p->numa_scan_period = sysctl_numa_balancing_scan_period_min;
930 next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
931 xchg(&mm->numa_next_reset, next_scan);
935 * Enforce maximal scan/migration frequency..
937 migrate = mm->numa_next_scan;
938 if (time_before(now, migrate))
941 if (p->numa_scan_period == 0)
942 p->numa_scan_period = sysctl_numa_balancing_scan_period_min;
944 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
945 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
949 * Do not set pte_numa if the current running node is rate-limited.
950 * This loses statistics on the fault but if we are unwilling to
951 * migrate to this node, it is less likely we can do useful work
953 if (migrate_ratelimited(numa_node_id()))
956 start = mm->numa_scan_offset;
957 pages = sysctl_numa_balancing_scan_size;
958 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
962 down_read(&mm->mmap_sem);
963 vma = find_vma(mm, start);
965 reset_ptenuma_scan(p);
969 for (; vma; vma = vma->vm_next) {
970 if (!vma_migratable(vma))
973 /* Skip small VMAs. They are not likely to be of relevance */
974 if (vma->vm_end - vma->vm_start < HPAGE_SIZE)
978 start = max(start, vma->vm_start);
979 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
980 end = min(end, vma->vm_end);
981 pages -= change_prot_numa(vma, start, end);
986 } while (end != vma->vm_end);
991 * It is possible to reach the end of the VMA list but the last few VMAs are
992 * not guaranteed to the vma_migratable. If they are not, we would find the
993 * !migratable VMA on the next scan but not reset the scanner to the start
997 mm->numa_scan_offset = start;
999 reset_ptenuma_scan(p);
1000 up_read(&mm->mmap_sem);
1004 * Drive the periodic memory faults..
1006 void task_tick_numa(struct rq *rq, struct task_struct *curr)
1008 struct callback_head *work = &curr->numa_work;
1012 * We don't care about NUMA placement if we don't have memory.
1014 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
1018 * Using runtime rather than walltime has the dual advantage that
1019 * we (mostly) drive the selection from busy threads and that the
1020 * task needs to have done some actual work before we bother with
1023 now = curr->se.sum_exec_runtime;
1024 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
1026 if (now - curr->node_stamp > period) {
1027 if (!curr->node_stamp)
1028 curr->numa_scan_period = sysctl_numa_balancing_scan_period_min;
1029 curr->node_stamp = now;
1031 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
1032 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
1033 task_work_add(curr, work, true);
1038 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
1041 #endif /* CONFIG_NUMA_BALANCING */
1044 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
1046 update_load_add(&cfs_rq->load, se->load.weight);
1047 if (!parent_entity(se))
1048 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1050 if (entity_is_task(se))
1051 list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
1053 cfs_rq->nr_running++;
1057 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
1059 update_load_sub(&cfs_rq->load, se->load.weight);
1060 if (!parent_entity(se))
1061 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
1062 if (entity_is_task(se))
1063 list_del_init(&se->group_node);
1064 cfs_rq->nr_running--;
1067 #ifdef CONFIG_FAIR_GROUP_SCHED
1069 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
1074 * Use this CPU's actual weight instead of the last load_contribution
1075 * to gain a more accurate current total weight. See
1076 * update_cfs_rq_load_contribution().
1078 tg_weight = atomic_long_read(&tg->load_avg);
1079 tg_weight -= cfs_rq->tg_load_contrib;
1080 tg_weight += cfs_rq->load.weight;
1085 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1087 long tg_weight, load, shares;
1089 tg_weight = calc_tg_weight(tg, cfs_rq);
1090 load = cfs_rq->load.weight;
1092 shares = (tg->shares * load);
1094 shares /= tg_weight;
1096 if (shares < MIN_SHARES)
1097 shares = MIN_SHARES;
1098 if (shares > tg->shares)
1099 shares = tg->shares;
1103 # else /* CONFIG_SMP */
1104 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1108 # endif /* CONFIG_SMP */
1109 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
1110 unsigned long weight)
1113 /* commit outstanding execution time */
1114 if (cfs_rq->curr == se)
1115 update_curr(cfs_rq);
1116 account_entity_dequeue(cfs_rq, se);
1119 update_load_set(&se->load, weight);
1122 account_entity_enqueue(cfs_rq, se);
1125 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
1127 static void update_cfs_shares(struct cfs_rq *cfs_rq)
1129 struct task_group *tg;
1130 struct sched_entity *se;
1134 se = tg->se[cpu_of(rq_of(cfs_rq))];
1135 if (!se || throttled_hierarchy(cfs_rq))
1138 if (likely(se->load.weight == tg->shares))
1141 shares = calc_cfs_shares(cfs_rq, tg);
1143 reweight_entity(cfs_rq_of(se), se, shares);
1145 #else /* CONFIG_FAIR_GROUP_SCHED */
1146 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
1149 #endif /* CONFIG_FAIR_GROUP_SCHED */
1153 * We choose a half-life close to 1 scheduling period.
1154 * Note: The tables below are dependent on this value.
1156 #define LOAD_AVG_PERIOD 32
1157 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
1158 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
1160 /* Precomputed fixed inverse multiplies for multiplication by y^n */
1161 static const u32 runnable_avg_yN_inv[] = {
1162 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
1163 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
1164 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
1165 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
1166 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
1167 0x85aac367, 0x82cd8698,
1171 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
1172 * over-estimates when re-combining.
1174 static const u32 runnable_avg_yN_sum[] = {
1175 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
1176 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
1177 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
1182 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
1184 static __always_inline u64 decay_load(u64 val, u64 n)
1186 unsigned int local_n;
1190 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
1193 /* after bounds checking we can collapse to 32-bit */
1197 * As y^PERIOD = 1/2, we can combine
1198 * y^n = 1/2^(n/PERIOD) * k^(n%PERIOD)
1199 * With a look-up table which covers k^n (n<PERIOD)
1201 * To achieve constant time decay_load.
1203 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
1204 val >>= local_n / LOAD_AVG_PERIOD;
1205 local_n %= LOAD_AVG_PERIOD;
1208 val *= runnable_avg_yN_inv[local_n];
1209 /* We don't use SRR here since we always want to round down. */
1214 * For updates fully spanning n periods, the contribution to runnable
1215 * average will be: \Sum 1024*y^n
1217 * We can compute this reasonably efficiently by combining:
1218 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
1220 static u32 __compute_runnable_contrib(u64 n)
1224 if (likely(n <= LOAD_AVG_PERIOD))
1225 return runnable_avg_yN_sum[n];
1226 else if (unlikely(n >= LOAD_AVG_MAX_N))
1227 return LOAD_AVG_MAX;
1229 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
1231 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
1232 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
1234 n -= LOAD_AVG_PERIOD;
1235 } while (n > LOAD_AVG_PERIOD);
1237 contrib = decay_load(contrib, n);
1238 return contrib + runnable_avg_yN_sum[n];
1242 * We can represent the historical contribution to runnable average as the
1243 * coefficients of a geometric series. To do this we sub-divide our runnable
1244 * history into segments of approximately 1ms (1024us); label the segment that
1245 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
1247 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
1249 * (now) (~1ms ago) (~2ms ago)
1251 * Let u_i denote the fraction of p_i that the entity was runnable.
1253 * We then designate the fractions u_i as our co-efficients, yielding the
1254 * following representation of historical load:
1255 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
1257 * We choose y based on the with of a reasonably scheduling period, fixing:
1260 * This means that the contribution to load ~32ms ago (u_32) will be weighted
1261 * approximately half as much as the contribution to load within the last ms
1264 * When a period "rolls over" and we have new u_0`, multiplying the previous
1265 * sum again by y is sufficient to update:
1266 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
1267 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
1269 static __always_inline int __update_entity_runnable_avg(u64 now,
1270 struct sched_avg *sa,
1274 u32 runnable_contrib;
1275 int delta_w, decayed = 0;
1277 delta = now - sa->last_runnable_update;
1279 * This should only happen when time goes backwards, which it
1280 * unfortunately does during sched clock init when we swap over to TSC.
1282 if ((s64)delta < 0) {
1283 sa->last_runnable_update = now;
1288 * Use 1024ns as the unit of measurement since it's a reasonable
1289 * approximation of 1us and fast to compute.
1294 sa->last_runnable_update = now;
1296 /* delta_w is the amount already accumulated against our next period */
1297 delta_w = sa->runnable_avg_period % 1024;
1298 if (delta + delta_w >= 1024) {
1299 /* period roll-over */
1303 * Now that we know we're crossing a period boundary, figure
1304 * out how much from delta we need to complete the current
1305 * period and accrue it.
1307 delta_w = 1024 - delta_w;
1309 sa->runnable_avg_sum += delta_w;
1310 sa->runnable_avg_period += delta_w;
1314 /* Figure out how many additional periods this update spans */
1315 periods = delta / 1024;
1318 sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
1320 sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
1323 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
1324 runnable_contrib = __compute_runnable_contrib(periods);
1326 sa->runnable_avg_sum += runnable_contrib;
1327 sa->runnable_avg_period += runnable_contrib;
1330 /* Remainder of delta accrued against u_0` */
1332 sa->runnable_avg_sum += delta;
1333 sa->runnable_avg_period += delta;
1338 /* Synchronize an entity's decay with its parenting cfs_rq.*/
1339 static inline u64 __synchronize_entity_decay(struct sched_entity *se)
1341 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1342 u64 decays = atomic64_read(&cfs_rq->decay_counter);
1344 decays -= se->avg.decay_count;
1348 se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
1349 se->avg.decay_count = 0;
1354 #ifdef CONFIG_FAIR_GROUP_SCHED
1355 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
1358 struct task_group *tg = cfs_rq->tg;
1361 tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg;
1362 tg_contrib -= cfs_rq->tg_load_contrib;
1364 if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
1365 atomic_long_add(tg_contrib, &tg->load_avg);
1366 cfs_rq->tg_load_contrib += tg_contrib;
1371 * Aggregate cfs_rq runnable averages into an equivalent task_group
1372 * representation for computing load contributions.
1374 static inline void __update_tg_runnable_avg(struct sched_avg *sa,
1375 struct cfs_rq *cfs_rq)
1377 struct task_group *tg = cfs_rq->tg;
1380 /* The fraction of a cpu used by this cfs_rq */
1381 contrib = div_u64(sa->runnable_avg_sum << NICE_0_SHIFT,
1382 sa->runnable_avg_period + 1);
1383 contrib -= cfs_rq->tg_runnable_contrib;
1385 if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
1386 atomic_add(contrib, &tg->runnable_avg);
1387 cfs_rq->tg_runnable_contrib += contrib;
1391 static inline void __update_group_entity_contrib(struct sched_entity *se)
1393 struct cfs_rq *cfs_rq = group_cfs_rq(se);
1394 struct task_group *tg = cfs_rq->tg;
1399 contrib = cfs_rq->tg_load_contrib * tg->shares;
1400 se->avg.load_avg_contrib = div_u64(contrib,
1401 atomic_long_read(&tg->load_avg) + 1);
1404 * For group entities we need to compute a correction term in the case
1405 * that they are consuming <1 cpu so that we would contribute the same
1406 * load as a task of equal weight.
1408 * Explicitly co-ordinating this measurement would be expensive, but
1409 * fortunately the sum of each cpus contribution forms a usable
1410 * lower-bound on the true value.
1412 * Consider the aggregate of 2 contributions. Either they are disjoint
1413 * (and the sum represents true value) or they are disjoint and we are
1414 * understating by the aggregate of their overlap.
1416 * Extending this to N cpus, for a given overlap, the maximum amount we
1417 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
1418 * cpus that overlap for this interval and w_i is the interval width.
1420 * On a small machine; the first term is well-bounded which bounds the
1421 * total error since w_i is a subset of the period. Whereas on a
1422 * larger machine, while this first term can be larger, if w_i is the
1423 * of consequential size guaranteed to see n_i*w_i quickly converge to
1424 * our upper bound of 1-cpu.
1426 runnable_avg = atomic_read(&tg->runnable_avg);
1427 if (runnable_avg < NICE_0_LOAD) {
1428 se->avg.load_avg_contrib *= runnable_avg;
1429 se->avg.load_avg_contrib >>= NICE_0_SHIFT;
1433 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
1434 int force_update) {}
1435 static inline void __update_tg_runnable_avg(struct sched_avg *sa,
1436 struct cfs_rq *cfs_rq) {}
1437 static inline void __update_group_entity_contrib(struct sched_entity *se) {}
1440 static inline void __update_task_entity_contrib(struct sched_entity *se)
1444 /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
1445 contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
1446 contrib /= (se->avg.runnable_avg_period + 1);
1447 se->avg.load_avg_contrib = scale_load(contrib);
1450 /* Compute the current contribution to load_avg by se, return any delta */
1451 static long __update_entity_load_avg_contrib(struct sched_entity *se)
1453 long old_contrib = se->avg.load_avg_contrib;
1455 if (entity_is_task(se)) {
1456 __update_task_entity_contrib(se);
1458 __update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
1459 __update_group_entity_contrib(se);
1462 return se->avg.load_avg_contrib - old_contrib;
1465 static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
1468 if (likely(load_contrib < cfs_rq->blocked_load_avg))
1469 cfs_rq->blocked_load_avg -= load_contrib;
1471 cfs_rq->blocked_load_avg = 0;
1474 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
1476 /* Update a sched_entity's runnable average */
1477 static inline void update_entity_load_avg(struct sched_entity *se,
1480 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1485 * For a group entity we need to use their owned cfs_rq_clock_task() in
1486 * case they are the parent of a throttled hierarchy.
1488 if (entity_is_task(se))
1489 now = cfs_rq_clock_task(cfs_rq);
1491 now = cfs_rq_clock_task(group_cfs_rq(se));
1493 if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
1496 contrib_delta = __update_entity_load_avg_contrib(se);
1502 cfs_rq->runnable_load_avg += contrib_delta;
1504 subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
1508 * Decay the load contributed by all blocked children and account this so that
1509 * their contribution may appropriately discounted when they wake up.
1511 static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
1513 u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
1516 decays = now - cfs_rq->last_decay;
1517 if (!decays && !force_update)
1520 if (atomic_long_read(&cfs_rq->removed_load)) {
1521 unsigned long removed_load;
1522 removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
1523 subtract_blocked_load_contrib(cfs_rq, removed_load);
1527 cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
1529 atomic64_add(decays, &cfs_rq->decay_counter);
1530 cfs_rq->last_decay = now;
1533 __update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
1536 static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
1538 __update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
1539 __update_tg_runnable_avg(&rq->avg, &rq->cfs);
1542 /* Add the load generated by se into cfs_rq's child load-average */
1543 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
1544 struct sched_entity *se,
1548 * We track migrations using entity decay_count <= 0, on a wake-up
1549 * migration we use a negative decay count to track the remote decays
1550 * accumulated while sleeping.
1552 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
1553 * are seen by enqueue_entity_load_avg() as a migration with an already
1554 * constructed load_avg_contrib.
1556 if (unlikely(se->avg.decay_count <= 0)) {
1557 se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
1558 if (se->avg.decay_count) {
1560 * In a wake-up migration we have to approximate the
1561 * time sleeping. This is because we can't synchronize
1562 * clock_task between the two cpus, and it is not
1563 * guaranteed to be read-safe. Instead, we can
1564 * approximate this using our carried decays, which are
1565 * explicitly atomically readable.
1567 se->avg.last_runnable_update -= (-se->avg.decay_count)
1569 update_entity_load_avg(se, 0);
1570 /* Indicate that we're now synchronized and on-rq */
1571 se->avg.decay_count = 0;
1576 * Task re-woke on same cpu (or else migrate_task_rq_fair()
1577 * would have made count negative); we must be careful to avoid
1578 * double-accounting blocked time after synchronizing decays.
1580 se->avg.last_runnable_update += __synchronize_entity_decay(se)
1584 /* migrated tasks did not contribute to our blocked load */
1586 subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
1587 update_entity_load_avg(se, 0);
1590 cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
1591 /* we force update consideration on load-balancer moves */
1592 update_cfs_rq_blocked_load(cfs_rq, !wakeup);
1596 * Remove se's load from this cfs_rq child load-average, if the entity is
1597 * transitioning to a blocked state we track its projected decay using
1600 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1601 struct sched_entity *se,
1604 update_entity_load_avg(se, 1);
1605 /* we force update consideration on load-balancer moves */
1606 update_cfs_rq_blocked_load(cfs_rq, !sleep);
1608 cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
1610 cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
1611 se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
1612 } /* migrations, e.g. sleep=0 leave decay_count == 0 */
1616 * Update the rq's load with the elapsed running time before entering
1617 * idle. if the last scheduled task is not a CFS task, idle_enter will
1618 * be the only way to update the runnable statistic.
1620 void idle_enter_fair(struct rq *this_rq)
1622 update_rq_runnable_avg(this_rq, 1);
1626 * Update the rq's load with the elapsed idle time before a task is
1627 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
1628 * be the only way to update the runnable statistic.
1630 void idle_exit_fair(struct rq *this_rq)
1632 update_rq_runnable_avg(this_rq, 0);
1636 static inline void update_entity_load_avg(struct sched_entity *se,
1637 int update_cfs_rq) {}
1638 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
1639 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
1640 struct sched_entity *se,
1642 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1643 struct sched_entity *se,
1645 static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
1646 int force_update) {}
1649 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
1651 #ifdef CONFIG_SCHEDSTATS
1652 struct task_struct *tsk = NULL;
1654 if (entity_is_task(se))
1657 if (se->statistics.sleep_start) {
1658 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
1663 if (unlikely(delta > se->statistics.sleep_max))
1664 se->statistics.sleep_max = delta;
1666 se->statistics.sleep_start = 0;
1667 se->statistics.sum_sleep_runtime += delta;
1670 account_scheduler_latency(tsk, delta >> 10, 1);
1671 trace_sched_stat_sleep(tsk, delta);
1674 if (se->statistics.block_start) {
1675 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
1680 if (unlikely(delta > se->statistics.block_max))
1681 se->statistics.block_max = delta;
1683 se->statistics.block_start = 0;
1684 se->statistics.sum_sleep_runtime += delta;
1687 if (tsk->in_iowait) {
1688 se->statistics.iowait_sum += delta;
1689 se->statistics.iowait_count++;
1690 trace_sched_stat_iowait(tsk, delta);
1693 trace_sched_stat_blocked(tsk, delta);
1696 * Blocking time is in units of nanosecs, so shift by
1697 * 20 to get a milliseconds-range estimation of the
1698 * amount of time that the task spent sleeping:
1700 if (unlikely(prof_on == SLEEP_PROFILING)) {
1701 profile_hits(SLEEP_PROFILING,
1702 (void *)get_wchan(tsk),
1705 account_scheduler_latency(tsk, delta >> 10, 0);
1711 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
1713 #ifdef CONFIG_SCHED_DEBUG
1714 s64 d = se->vruntime - cfs_rq->min_vruntime;
1719 if (d > 3*sysctl_sched_latency)
1720 schedstat_inc(cfs_rq, nr_spread_over);
1725 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
1727 u64 vruntime = cfs_rq->min_vruntime;
1730 * The 'current' period is already promised to the current tasks,
1731 * however the extra weight of the new task will slow them down a
1732 * little, place the new task so that it fits in the slot that
1733 * stays open at the end.
1735 if (initial && sched_feat(START_DEBIT))
1736 vruntime += sched_vslice(cfs_rq, se);
1738 /* sleeps up to a single latency don't count. */
1740 unsigned long thresh = sysctl_sched_latency;
1743 * Halve their sleep time's effect, to allow
1744 * for a gentler effect of sleepers:
1746 if (sched_feat(GENTLE_FAIR_SLEEPERS))
1752 /* ensure we never gain time by being placed backwards. */
1753 se->vruntime = max_vruntime(se->vruntime, vruntime);
1756 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
1759 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1762 * Update the normalized vruntime before updating min_vruntime
1763 * through calling update_curr().
1765 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
1766 se->vruntime += cfs_rq->min_vruntime;
1769 * Update run-time statistics of the 'current'.
1771 update_curr(cfs_rq);
1772 enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
1773 account_entity_enqueue(cfs_rq, se);
1774 update_cfs_shares(cfs_rq);
1776 if (flags & ENQUEUE_WAKEUP) {
1777 place_entity(cfs_rq, se, 0);
1778 enqueue_sleeper(cfs_rq, se);
1781 update_stats_enqueue(cfs_rq, se);
1782 check_spread(cfs_rq, se);
1783 if (se != cfs_rq->curr)
1784 __enqueue_entity(cfs_rq, se);
1787 if (cfs_rq->nr_running == 1) {
1788 list_add_leaf_cfs_rq(cfs_rq);
1789 check_enqueue_throttle(cfs_rq);
1793 static void __clear_buddies_last(struct sched_entity *se)
1795 for_each_sched_entity(se) {
1796 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1797 if (cfs_rq->last == se)
1798 cfs_rq->last = NULL;
1804 static void __clear_buddies_next(struct sched_entity *se)
1806 for_each_sched_entity(se) {
1807 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1808 if (cfs_rq->next == se)
1809 cfs_rq->next = NULL;
1815 static void __clear_buddies_skip(struct sched_entity *se)
1817 for_each_sched_entity(se) {
1818 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1819 if (cfs_rq->skip == se)
1820 cfs_rq->skip = NULL;
1826 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
1828 if (cfs_rq->last == se)
1829 __clear_buddies_last(se);
1831 if (cfs_rq->next == se)
1832 __clear_buddies_next(se);
1834 if (cfs_rq->skip == se)
1835 __clear_buddies_skip(se);
1838 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
1841 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1844 * Update run-time statistics of the 'current'.
1846 update_curr(cfs_rq);
1847 dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
1849 update_stats_dequeue(cfs_rq, se);
1850 if (flags & DEQUEUE_SLEEP) {
1851 #ifdef CONFIG_SCHEDSTATS
1852 if (entity_is_task(se)) {
1853 struct task_struct *tsk = task_of(se);
1855 if (tsk->state & TASK_INTERRUPTIBLE)
1856 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
1857 if (tsk->state & TASK_UNINTERRUPTIBLE)
1858 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
1863 clear_buddies(cfs_rq, se);
1865 if (se != cfs_rq->curr)
1866 __dequeue_entity(cfs_rq, se);
1868 account_entity_dequeue(cfs_rq, se);
1871 * Normalize the entity after updating the min_vruntime because the
1872 * update can refer to the ->curr item and we need to reflect this
1873 * movement in our normalized position.
1875 if (!(flags & DEQUEUE_SLEEP))
1876 se->vruntime -= cfs_rq->min_vruntime;
1878 /* return excess runtime on last dequeue */
1879 return_cfs_rq_runtime(cfs_rq);
1881 update_min_vruntime(cfs_rq);
1882 update_cfs_shares(cfs_rq);
1886 * Preempt the current task with a newly woken task if needed:
1889 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1891 unsigned long ideal_runtime, delta_exec;
1892 struct sched_entity *se;
1895 ideal_runtime = sched_slice(cfs_rq, curr);
1896 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1897 if (delta_exec > ideal_runtime) {
1898 resched_task(rq_of(cfs_rq)->curr);
1900 * The current task ran long enough, ensure it doesn't get
1901 * re-elected due to buddy favours.
1903 clear_buddies(cfs_rq, curr);
1908 * Ensure that a task that missed wakeup preemption by a
1909 * narrow margin doesn't have to wait for a full slice.
1910 * This also mitigates buddy induced latencies under load.
1912 if (delta_exec < sysctl_sched_min_granularity)
1915 se = __pick_first_entity(cfs_rq);
1916 delta = curr->vruntime - se->vruntime;
1921 if (delta > ideal_runtime)
1922 resched_task(rq_of(cfs_rq)->curr);
1926 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1928 /* 'current' is not kept within the tree. */
1931 * Any task has to be enqueued before it get to execute on
1932 * a CPU. So account for the time it spent waiting on the
1935 update_stats_wait_end(cfs_rq, se);
1936 __dequeue_entity(cfs_rq, se);
1939 update_stats_curr_start(cfs_rq, se);
1941 #ifdef CONFIG_SCHEDSTATS
1943 * Track our maximum slice length, if the CPU's load is at
1944 * least twice that of our own weight (i.e. dont track it
1945 * when there are only lesser-weight tasks around):
1947 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1948 se->statistics.slice_max = max(se->statistics.slice_max,
1949 se->sum_exec_runtime - se->prev_sum_exec_runtime);
1952 se->prev_sum_exec_runtime = se->sum_exec_runtime;
1956 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
1959 * Pick the next process, keeping these things in mind, in this order:
1960 * 1) keep things fair between processes/task groups
1961 * 2) pick the "next" process, since someone really wants that to run
1962 * 3) pick the "last" process, for cache locality
1963 * 4) do not run the "skip" process, if something else is available
1965 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1967 struct sched_entity *se = __pick_first_entity(cfs_rq);
1968 struct sched_entity *left = se;
1971 * Avoid running the skip buddy, if running something else can
1972 * be done without getting too unfair.
1974 if (cfs_rq->skip == se) {
1975 struct sched_entity *second = __pick_next_entity(se);
1976 if (second && wakeup_preempt_entity(second, left) < 1)
1981 * Prefer last buddy, try to return the CPU to a preempted task.
1983 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
1987 * Someone really wants this to run. If it's not unfair, run it.
1989 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
1992 clear_buddies(cfs_rq, se);
1997 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
1999 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
2002 * If still on the runqueue then deactivate_task()
2003 * was not called and update_curr() has to be done:
2006 update_curr(cfs_rq);
2008 /* throttle cfs_rqs exceeding runtime */
2009 check_cfs_rq_runtime(cfs_rq);
2011 check_spread(cfs_rq, prev);
2013 update_stats_wait_start(cfs_rq, prev);
2014 /* Put 'current' back into the tree. */
2015 __enqueue_entity(cfs_rq, prev);
2016 /* in !on_rq case, update occurred at dequeue */
2017 update_entity_load_avg(prev, 1);
2019 cfs_rq->curr = NULL;
2023 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
2026 * Update run-time statistics of the 'current'.
2028 update_curr(cfs_rq);
2031 * Ensure that runnable average is periodically updated.
2033 update_entity_load_avg(curr, 1);
2034 update_cfs_rq_blocked_load(cfs_rq, 1);
2036 #ifdef CONFIG_SCHED_HRTICK
2038 * queued ticks are scheduled to match the slice, so don't bother
2039 * validating it and just reschedule.
2042 resched_task(rq_of(cfs_rq)->curr);
2046 * don't let the period tick interfere with the hrtick preemption
2048 if (!sched_feat(DOUBLE_TICK) &&
2049 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
2053 if (cfs_rq->nr_running > 1)
2054 check_preempt_tick(cfs_rq, curr);
2058 /**************************************************
2059 * CFS bandwidth control machinery
2062 #ifdef CONFIG_CFS_BANDWIDTH
2064 #ifdef HAVE_JUMP_LABEL
2065 static struct static_key __cfs_bandwidth_used;
2067 static inline bool cfs_bandwidth_used(void)
2069 return static_key_false(&__cfs_bandwidth_used);
2072 void account_cfs_bandwidth_used(int enabled, int was_enabled)
2074 /* only need to count groups transitioning between enabled/!enabled */
2075 if (enabled && !was_enabled)
2076 static_key_slow_inc(&__cfs_bandwidth_used);
2077 else if (!enabled && was_enabled)
2078 static_key_slow_dec(&__cfs_bandwidth_used);
2080 #else /* HAVE_JUMP_LABEL */
2081 static bool cfs_bandwidth_used(void)
2086 void account_cfs_bandwidth_used(int enabled, int was_enabled) {}
2087 #endif /* HAVE_JUMP_LABEL */
2090 * default period for cfs group bandwidth.
2091 * default: 0.1s, units: nanoseconds
2093 static inline u64 default_cfs_period(void)
2095 return 100000000ULL;
2098 static inline u64 sched_cfs_bandwidth_slice(void)
2100 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
2104 * Replenish runtime according to assigned quota and update expiration time.
2105 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
2106 * additional synchronization around rq->lock.
2108 * requires cfs_b->lock
2110 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
2114 if (cfs_b->quota == RUNTIME_INF)
2117 now = sched_clock_cpu(smp_processor_id());
2118 cfs_b->runtime = cfs_b->quota;
2119 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
2122 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
2124 return &tg->cfs_bandwidth;
2127 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
2128 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
2130 if (unlikely(cfs_rq->throttle_count))
2131 return cfs_rq->throttled_clock_task;
2133 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
2136 /* returns 0 on failure to allocate runtime */
2137 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2139 struct task_group *tg = cfs_rq->tg;
2140 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
2141 u64 amount = 0, min_amount, expires;
2143 /* note: this is a positive sum as runtime_remaining <= 0 */
2144 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
2146 raw_spin_lock(&cfs_b->lock);
2147 if (cfs_b->quota == RUNTIME_INF)
2148 amount = min_amount;
2151 * If the bandwidth pool has become inactive, then at least one
2152 * period must have elapsed since the last consumption.
2153 * Refresh the global state and ensure bandwidth timer becomes
2156 if (!cfs_b->timer_active) {
2157 __refill_cfs_bandwidth_runtime(cfs_b);
2158 __start_cfs_bandwidth(cfs_b);
2161 if (cfs_b->runtime > 0) {
2162 amount = min(cfs_b->runtime, min_amount);
2163 cfs_b->runtime -= amount;
2167 expires = cfs_b->runtime_expires;
2168 raw_spin_unlock(&cfs_b->lock);
2170 cfs_rq->runtime_remaining += amount;
2172 * we may have advanced our local expiration to account for allowed
2173 * spread between our sched_clock and the one on which runtime was
2176 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
2177 cfs_rq->runtime_expires = expires;
2179 return cfs_rq->runtime_remaining > 0;
2183 * Note: This depends on the synchronization provided by sched_clock and the
2184 * fact that rq->clock snapshots this value.
2186 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2188 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
2190 /* if the deadline is ahead of our clock, nothing to do */
2191 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
2194 if (cfs_rq->runtime_remaining < 0)
2198 * If the local deadline has passed we have to consider the
2199 * possibility that our sched_clock is 'fast' and the global deadline
2200 * has not truly expired.
2202 * Fortunately we can check determine whether this the case by checking
2203 * whether the global deadline has advanced.
2206 if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
2207 /* extend local deadline, drift is bounded above by 2 ticks */
2208 cfs_rq->runtime_expires += TICK_NSEC;
2210 /* global deadline is ahead, expiration has passed */
2211 cfs_rq->runtime_remaining = 0;
2215 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
2216 unsigned long delta_exec)
2218 /* dock delta_exec before expiring quota (as it could span periods) */
2219 cfs_rq->runtime_remaining -= delta_exec;
2220 expire_cfs_rq_runtime(cfs_rq);
2222 if (likely(cfs_rq->runtime_remaining > 0))
2226 * if we're unable to extend our runtime we resched so that the active
2227 * hierarchy can be throttled
2229 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
2230 resched_task(rq_of(cfs_rq)->curr);
2233 static __always_inline
2234 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
2236 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
2239 __account_cfs_rq_runtime(cfs_rq, delta_exec);
2242 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
2244 return cfs_bandwidth_used() && cfs_rq->throttled;
2247 /* check whether cfs_rq, or any parent, is throttled */
2248 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
2250 return cfs_bandwidth_used() && cfs_rq->throttle_count;
2254 * Ensure that neither of the group entities corresponding to src_cpu or
2255 * dest_cpu are members of a throttled hierarchy when performing group
2256 * load-balance operations.
2258 static inline int throttled_lb_pair(struct task_group *tg,
2259 int src_cpu, int dest_cpu)
2261 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
2263 src_cfs_rq = tg->cfs_rq[src_cpu];
2264 dest_cfs_rq = tg->cfs_rq[dest_cpu];
2266 return throttled_hierarchy(src_cfs_rq) ||
2267 throttled_hierarchy(dest_cfs_rq);
2270 /* updated child weight may affect parent so we have to do this bottom up */
2271 static int tg_unthrottle_up(struct task_group *tg, void *data)
2273 struct rq *rq = data;
2274 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
2276 cfs_rq->throttle_count--;
2278 if (!cfs_rq->throttle_count) {
2279 /* adjust cfs_rq_clock_task() */
2280 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
2281 cfs_rq->throttled_clock_task;
2288 static int tg_throttle_down(struct task_group *tg, void *data)
2290 struct rq *rq = data;
2291 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
2293 /* group is entering throttled state, stop time */
2294 if (!cfs_rq->throttle_count)
2295 cfs_rq->throttled_clock_task = rq_clock_task(rq);
2296 cfs_rq->throttle_count++;
2301 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
2303 struct rq *rq = rq_of(cfs_rq);
2304 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
2305 struct sched_entity *se;
2306 long task_delta, dequeue = 1;
2308 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
2310 /* freeze hierarchy runnable averages while throttled */
2312 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
2315 task_delta = cfs_rq->h_nr_running;
2316 for_each_sched_entity(se) {
2317 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
2318 /* throttled entity or throttle-on-deactivate */
2323 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
2324 qcfs_rq->h_nr_running -= task_delta;
2326 if (qcfs_rq->load.weight)
2331 rq->nr_running -= task_delta;
2333 cfs_rq->throttled = 1;
2334 cfs_rq->throttled_clock = rq_clock(rq);
2335 raw_spin_lock(&cfs_b->lock);
2336 list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
2337 raw_spin_unlock(&cfs_b->lock);
2340 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
2342 struct rq *rq = rq_of(cfs_rq);
2343 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
2344 struct sched_entity *se;
2348 se = cfs_rq->tg->se[cpu_of(rq)];
2350 cfs_rq->throttled = 0;
2352 update_rq_clock(rq);
2354 raw_spin_lock(&cfs_b->lock);
2355 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
2356 list_del_rcu(&cfs_rq->throttled_list);
2357 raw_spin_unlock(&cfs_b->lock);
2359 /* update hierarchical throttle state */
2360 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
2362 if (!cfs_rq->load.weight)
2365 task_delta = cfs_rq->h_nr_running;
2366 for_each_sched_entity(se) {
2370 cfs_rq = cfs_rq_of(se);
2372 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
2373 cfs_rq->h_nr_running += task_delta;
2375 if (cfs_rq_throttled(cfs_rq))
2380 rq->nr_running += task_delta;
2382 /* determine whether we need to wake up potentially idle cpu */
2383 if (rq->curr == rq->idle && rq->cfs.nr_running)
2384 resched_task(rq->curr);
2387 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
2388 u64 remaining, u64 expires)
2390 struct cfs_rq *cfs_rq;
2391 u64 runtime = remaining;
2394 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
2396 struct rq *rq = rq_of(cfs_rq);
2398 raw_spin_lock(&rq->lock);
2399 if (!cfs_rq_throttled(cfs_rq))
2402 runtime = -cfs_rq->runtime_remaining + 1;
2403 if (runtime > remaining)
2404 runtime = remaining;
2405 remaining -= runtime;
2407 cfs_rq->runtime_remaining += runtime;
2408 cfs_rq->runtime_expires = expires;
2410 /* we check whether we're throttled above */
2411 if (cfs_rq->runtime_remaining > 0)
2412 unthrottle_cfs_rq(cfs_rq);
2415 raw_spin_unlock(&rq->lock);
2426 * Responsible for refilling a task_group's bandwidth and unthrottling its
2427 * cfs_rqs as appropriate. If there has been no activity within the last
2428 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
2429 * used to track this state.
2431 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
2433 u64 runtime, runtime_expires;
2434 int idle = 1, throttled;
2436 raw_spin_lock(&cfs_b->lock);
2437 /* no need to continue the timer with no bandwidth constraint */
2438 if (cfs_b->quota == RUNTIME_INF)
2441 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
2442 /* idle depends on !throttled (for the case of a large deficit) */
2443 idle = cfs_b->idle && !throttled;
2444 cfs_b->nr_periods += overrun;
2446 /* if we're going inactive then everything else can be deferred */
2450 __refill_cfs_bandwidth_runtime(cfs_b);
2453 /* mark as potentially idle for the upcoming period */
2458 /* account preceding periods in which throttling occurred */
2459 cfs_b->nr_throttled += overrun;
2462 * There are throttled entities so we must first use the new bandwidth
2463 * to unthrottle them before making it generally available. This
2464 * ensures that all existing debts will be paid before a new cfs_rq is
2467 runtime = cfs_b->runtime;
2468 runtime_expires = cfs_b->runtime_expires;
2472 * This check is repeated as we are holding onto the new bandwidth
2473 * while we unthrottle. This can potentially race with an unthrottled
2474 * group trying to acquire new bandwidth from the global pool.
2476 while (throttled && runtime > 0) {
2477 raw_spin_unlock(&cfs_b->lock);
2478 /* we can't nest cfs_b->lock while distributing bandwidth */
2479 runtime = distribute_cfs_runtime(cfs_b, runtime,
2481 raw_spin_lock(&cfs_b->lock);
2483 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
2486 /* return (any) remaining runtime */
2487 cfs_b->runtime = runtime;
2489 * While we are ensured activity in the period following an
2490 * unthrottle, this also covers the case in which the new bandwidth is
2491 * insufficient to cover the existing bandwidth deficit. (Forcing the
2492 * timer to remain active while there are any throttled entities.)
2497 cfs_b->timer_active = 0;
2498 raw_spin_unlock(&cfs_b->lock);
2503 /* a cfs_rq won't donate quota below this amount */
2504 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
2505 /* minimum remaining period time to redistribute slack quota */
2506 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
2507 /* how long we wait to gather additional slack before distributing */
2508 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
2510 /* are we near the end of the current quota period? */
2511 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
2513 struct hrtimer *refresh_timer = &cfs_b->period_timer;
2516 /* if the call-back is running a quota refresh is already occurring */
2517 if (hrtimer_callback_running(refresh_timer))
2520 /* is a quota refresh about to occur? */
2521 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
2522 if (remaining < min_expire)
2528 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
2530 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
2532 /* if there's a quota refresh soon don't bother with slack */
2533 if (runtime_refresh_within(cfs_b, min_left))
2536 start_bandwidth_timer(&cfs_b->slack_timer,
2537 ns_to_ktime(cfs_bandwidth_slack_period));
2540 /* we know any runtime found here is valid as update_curr() precedes return */
2541 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2543 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
2544 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
2546 if (slack_runtime <= 0)
2549 raw_spin_lock(&cfs_b->lock);
2550 if (cfs_b->quota != RUNTIME_INF &&
2551 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
2552 cfs_b->runtime += slack_runtime;
2554 /* we are under rq->lock, defer unthrottling using a timer */
2555 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
2556 !list_empty(&cfs_b->throttled_cfs_rq))
2557 start_cfs_slack_bandwidth(cfs_b);
2559 raw_spin_unlock(&cfs_b->lock);
2561 /* even if it's not valid for return we don't want to try again */
2562 cfs_rq->runtime_remaining -= slack_runtime;
2565 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2567 if (!cfs_bandwidth_used())
2570 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
2573 __return_cfs_rq_runtime(cfs_rq);
2577 * This is done with a timer (instead of inline with bandwidth return) since
2578 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
2580 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
2582 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
2585 /* confirm we're still not at a refresh boundary */
2586 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration))
2589 raw_spin_lock(&cfs_b->lock);
2590 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
2591 runtime = cfs_b->runtime;
2594 expires = cfs_b->runtime_expires;
2595 raw_spin_unlock(&cfs_b->lock);
2600 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
2602 raw_spin_lock(&cfs_b->lock);
2603 if (expires == cfs_b->runtime_expires)
2604 cfs_b->runtime = runtime;
2605 raw_spin_unlock(&cfs_b->lock);
2609 * When a group wakes up we want to make sure that its quota is not already
2610 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
2611 * runtime as update_curr() throttling can not not trigger until it's on-rq.
2613 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
2615 if (!cfs_bandwidth_used())
2618 /* an active group must be handled by the update_curr()->put() path */
2619 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
2622 /* ensure the group is not already throttled */
2623 if (cfs_rq_throttled(cfs_rq))
2626 /* update runtime allocation */
2627 account_cfs_rq_runtime(cfs_rq, 0);
2628 if (cfs_rq->runtime_remaining <= 0)
2629 throttle_cfs_rq(cfs_rq);
2632 /* conditionally throttle active cfs_rq's from put_prev_entity() */
2633 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2635 if (!cfs_bandwidth_used())
2638 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
2642 * it's possible for a throttled entity to be forced into a running
2643 * state (e.g. set_curr_task), in this case we're finished.
2645 if (cfs_rq_throttled(cfs_rq))
2648 throttle_cfs_rq(cfs_rq);
2651 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
2653 struct cfs_bandwidth *cfs_b =
2654 container_of(timer, struct cfs_bandwidth, slack_timer);
2655 do_sched_cfs_slack_timer(cfs_b);
2657 return HRTIMER_NORESTART;
2660 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
2662 struct cfs_bandwidth *cfs_b =
2663 container_of(timer, struct cfs_bandwidth, period_timer);
2669 now = hrtimer_cb_get_time(timer);
2670 overrun = hrtimer_forward(timer, now, cfs_b->period);
2675 idle = do_sched_cfs_period_timer(cfs_b, overrun);
2678 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
2681 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
2683 raw_spin_lock_init(&cfs_b->lock);
2685 cfs_b->quota = RUNTIME_INF;
2686 cfs_b->period = ns_to_ktime(default_cfs_period());
2688 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
2689 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
2690 cfs_b->period_timer.function = sched_cfs_period_timer;
2691 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
2692 cfs_b->slack_timer.function = sched_cfs_slack_timer;
2695 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2697 cfs_rq->runtime_enabled = 0;
2698 INIT_LIST_HEAD(&cfs_rq->throttled_list);
2701 /* requires cfs_b->lock, may release to reprogram timer */
2702 void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
2705 * The timer may be active because we're trying to set a new bandwidth
2706 * period or because we're racing with the tear-down path
2707 * (timer_active==0 becomes visible before the hrtimer call-back
2708 * terminates). In either case we ensure that it's re-programmed
2710 while (unlikely(hrtimer_active(&cfs_b->period_timer))) {
2711 raw_spin_unlock(&cfs_b->lock);
2712 /* ensure cfs_b->lock is available while we wait */
2713 hrtimer_cancel(&cfs_b->period_timer);
2715 raw_spin_lock(&cfs_b->lock);
2716 /* if someone else restarted the timer then we're done */
2717 if (cfs_b->timer_active)
2721 cfs_b->timer_active = 1;
2722 start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
2725 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
2727 hrtimer_cancel(&cfs_b->period_timer);
2728 hrtimer_cancel(&cfs_b->slack_timer);
2731 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
2733 struct cfs_rq *cfs_rq;
2735 for_each_leaf_cfs_rq(rq, cfs_rq) {
2736 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
2738 if (!cfs_rq->runtime_enabled)
2742 * clock_task is not advancing so we just need to make sure
2743 * there's some valid quota amount
2745 cfs_rq->runtime_remaining = cfs_b->quota;
2746 if (cfs_rq_throttled(cfs_rq))
2747 unthrottle_cfs_rq(cfs_rq);
2751 #else /* CONFIG_CFS_BANDWIDTH */
2752 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
2754 return rq_clock_task(rq_of(cfs_rq));
2757 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
2758 unsigned long delta_exec) {}
2759 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2760 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
2761 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2763 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
2768 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
2773 static inline int throttled_lb_pair(struct task_group *tg,
2774 int src_cpu, int dest_cpu)
2779 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
2781 #ifdef CONFIG_FAIR_GROUP_SCHED
2782 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2785 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
2789 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
2790 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
2792 #endif /* CONFIG_CFS_BANDWIDTH */
2794 /**************************************************
2795 * CFS operations on tasks:
2798 #ifdef CONFIG_SCHED_HRTICK
2799 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
2801 struct sched_entity *se = &p->se;
2802 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2804 WARN_ON(task_rq(p) != rq);
2806 if (cfs_rq->nr_running > 1) {
2807 u64 slice = sched_slice(cfs_rq, se);
2808 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
2809 s64 delta = slice - ran;
2818 * Don't schedule slices shorter than 10000ns, that just
2819 * doesn't make sense. Rely on vruntime for fairness.
2822 delta = max_t(s64, 10000LL, delta);
2824 hrtick_start(rq, delta);
2829 * called from enqueue/dequeue and updates the hrtick when the
2830 * current task is from our class and nr_running is low enough
2833 static void hrtick_update(struct rq *rq)
2835 struct task_struct *curr = rq->curr;
2837 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
2840 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
2841 hrtick_start_fair(rq, curr);
2843 #else /* !CONFIG_SCHED_HRTICK */
2845 hrtick_start_fair(struct rq *rq, struct task_struct *p)
2849 static inline void hrtick_update(struct rq *rq)
2855 * The enqueue_task method is called before nr_running is
2856 * increased. Here we update the fair scheduling stats and
2857 * then put the task into the rbtree:
2860 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2862 struct cfs_rq *cfs_rq;
2863 struct sched_entity *se = &p->se;
2865 for_each_sched_entity(se) {
2868 cfs_rq = cfs_rq_of(se);
2869 enqueue_entity(cfs_rq, se, flags);
2872 * end evaluation on encountering a throttled cfs_rq
2874 * note: in the case of encountering a throttled cfs_rq we will
2875 * post the final h_nr_running increment below.
2877 if (cfs_rq_throttled(cfs_rq))
2879 cfs_rq->h_nr_running++;
2881 flags = ENQUEUE_WAKEUP;
2884 for_each_sched_entity(se) {
2885 cfs_rq = cfs_rq_of(se);
2886 cfs_rq->h_nr_running++;
2888 if (cfs_rq_throttled(cfs_rq))
2891 update_cfs_shares(cfs_rq);
2892 update_entity_load_avg(se, 1);
2896 update_rq_runnable_avg(rq, rq->nr_running);
2902 static void set_next_buddy(struct sched_entity *se);
2905 * The dequeue_task method is called before nr_running is
2906 * decreased. We remove the task from the rbtree and
2907 * update the fair scheduling stats:
2909 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2911 struct cfs_rq *cfs_rq;
2912 struct sched_entity *se = &p->se;
2913 int task_sleep = flags & DEQUEUE_SLEEP;
2915 for_each_sched_entity(se) {
2916 cfs_rq = cfs_rq_of(se);
2917 dequeue_entity(cfs_rq, se, flags);
2920 * end evaluation on encountering a throttled cfs_rq
2922 * note: in the case of encountering a throttled cfs_rq we will
2923 * post the final h_nr_running decrement below.
2925 if (cfs_rq_throttled(cfs_rq))
2927 cfs_rq->h_nr_running--;
2929 /* Don't dequeue parent if it has other entities besides us */
2930 if (cfs_rq->load.weight) {
2932 * Bias pick_next to pick a task from this cfs_rq, as
2933 * p is sleeping when it is within its sched_slice.
2935 if (task_sleep && parent_entity(se))
2936 set_next_buddy(parent_entity(se));
2938 /* avoid re-evaluating load for this entity */
2939 se = parent_entity(se);
2942 flags |= DEQUEUE_SLEEP;
2945 for_each_sched_entity(se) {
2946 cfs_rq = cfs_rq_of(se);
2947 cfs_rq->h_nr_running--;
2949 if (cfs_rq_throttled(cfs_rq))
2952 update_cfs_shares(cfs_rq);
2953 update_entity_load_avg(se, 1);
2958 update_rq_runnable_avg(rq, 1);
2964 /* Used instead of source_load when we know the type == 0 */
2965 static unsigned long weighted_cpuload(const int cpu)
2967 return cpu_rq(cpu)->cfs.runnable_load_avg;
2971 * Return a low guess at the load of a migration-source cpu weighted
2972 * according to the scheduling class and "nice" value.
2974 * We want to under-estimate the load of migration sources, to
2975 * balance conservatively.
2977 static unsigned long source_load(int cpu, int type)
2979 struct rq *rq = cpu_rq(cpu);
2980 unsigned long total = weighted_cpuload(cpu);
2982 if (type == 0 || !sched_feat(LB_BIAS))
2985 return min(rq->cpu_load[type-1], total);
2989 * Return a high guess at the load of a migration-target cpu weighted
2990 * according to the scheduling class and "nice" value.
2992 static unsigned long target_load(int cpu, int type)
2994 struct rq *rq = cpu_rq(cpu);
2995 unsigned long total = weighted_cpuload(cpu);
2997 if (type == 0 || !sched_feat(LB_BIAS))
3000 return max(rq->cpu_load[type-1], total);
3003 static unsigned long power_of(int cpu)
3005 return cpu_rq(cpu)->cpu_power;
3008 static unsigned long cpu_avg_load_per_task(int cpu)
3010 struct rq *rq = cpu_rq(cpu);
3011 unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
3012 unsigned long load_avg = rq->cfs.runnable_load_avg;
3015 return load_avg / nr_running;
3020 static void record_wakee(struct task_struct *p)
3023 * Rough decay (wiping) for cost saving, don't worry
3024 * about the boundary, really active task won't care
3027 if (jiffies > current->wakee_flip_decay_ts + HZ) {
3028 current->wakee_flips = 0;
3029 current->wakee_flip_decay_ts = jiffies;
3032 if (current->last_wakee != p) {
3033 current->last_wakee = p;
3034 current->wakee_flips++;
3038 static void task_waking_fair(struct task_struct *p)
3040 struct sched_entity *se = &p->se;
3041 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3044 #ifndef CONFIG_64BIT
3045 u64 min_vruntime_copy;
3048 min_vruntime_copy = cfs_rq->min_vruntime_copy;
3050 min_vruntime = cfs_rq->min_vruntime;
3051 } while (min_vruntime != min_vruntime_copy);
3053 min_vruntime = cfs_rq->min_vruntime;
3056 se->vruntime -= min_vruntime;
3060 #ifdef CONFIG_FAIR_GROUP_SCHED
3062 * effective_load() calculates the load change as seen from the root_task_group
3064 * Adding load to a group doesn't make a group heavier, but can cause movement
3065 * of group shares between cpus. Assuming the shares were perfectly aligned one
3066 * can calculate the shift in shares.
3068 * Calculate the effective load difference if @wl is added (subtracted) to @tg
3069 * on this @cpu and results in a total addition (subtraction) of @wg to the
3070 * total group weight.
3072 * Given a runqueue weight distribution (rw_i) we can compute a shares
3073 * distribution (s_i) using:
3075 * s_i = rw_i / \Sum rw_j (1)
3077 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
3078 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
3079 * shares distribution (s_i):
3081 * rw_i = { 2, 4, 1, 0 }
3082 * s_i = { 2/7, 4/7, 1/7, 0 }
3084 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
3085 * task used to run on and the CPU the waker is running on), we need to
3086 * compute the effect of waking a task on either CPU and, in case of a sync
3087 * wakeup, compute the effect of the current task going to sleep.
3089 * So for a change of @wl to the local @cpu with an overall group weight change
3090 * of @wl we can compute the new shares distribution (s'_i) using:
3092 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
3094 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
3095 * differences in waking a task to CPU 0. The additional task changes the
3096 * weight and shares distributions like:
3098 * rw'_i = { 3, 4, 1, 0 }
3099 * s'_i = { 3/8, 4/8, 1/8, 0 }
3101 * We can then compute the difference in effective weight by using:
3103 * dw_i = S * (s'_i - s_i) (3)
3105 * Where 'S' is the group weight as seen by its parent.
3107 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
3108 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
3109 * 4/7) times the weight of the group.
3111 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
3113 struct sched_entity *se = tg->se[cpu];
3115 if (!tg->parent) /* the trivial, non-cgroup case */
3118 for_each_sched_entity(se) {
3124 * W = @wg + \Sum rw_j
3126 W = wg + calc_tg_weight(tg, se->my_q);
3131 w = se->my_q->load.weight + wl;
3134 * wl = S * s'_i; see (2)
3137 wl = (w * tg->shares) / W;
3142 * Per the above, wl is the new se->load.weight value; since
3143 * those are clipped to [MIN_SHARES, ...) do so now. See
3144 * calc_cfs_shares().
3146 if (wl < MIN_SHARES)
3150 * wl = dw_i = S * (s'_i - s_i); see (3)
3152 wl -= se->load.weight;
3155 * Recursively apply this logic to all parent groups to compute
3156 * the final effective load change on the root group. Since
3157 * only the @tg group gets extra weight, all parent groups can
3158 * only redistribute existing shares. @wl is the shift in shares
3159 * resulting from this level per the above.
3168 static inline unsigned long effective_load(struct task_group *tg, int cpu,
3169 unsigned long wl, unsigned long wg)
3176 static int wake_wide(struct task_struct *p)
3178 int factor = nr_cpus_node(cpu_to_node(smp_processor_id()));
3181 * Yeah, it's the switching-frequency, could means many wakee or
3182 * rapidly switch, use factor here will just help to automatically
3183 * adjust the loose-degree, so bigger node will lead to more pull.
3185 if (p->wakee_flips > factor) {
3187 * wakee is somewhat hot, it needs certain amount of cpu
3188 * resource, so if waker is far more hot, prefer to leave
3191 if (current->wakee_flips > (factor * p->wakee_flips))
3198 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
3200 s64 this_load, load;
3201 int idx, this_cpu, prev_cpu;
3202 unsigned long tl_per_task;
3203 struct task_group *tg;
3204 unsigned long weight;
3208 * If we wake multiple tasks be careful to not bounce
3209 * ourselves around too much.
3215 this_cpu = smp_processor_id();
3216 prev_cpu = task_cpu(p);
3217 load = source_load(prev_cpu, idx);
3218 this_load = target_load(this_cpu, idx);
3221 * If sync wakeup then subtract the (maximum possible)
3222 * effect of the currently running task from the load
3223 * of the current CPU:
3226 tg = task_group(current);
3227 weight = current->se.load.weight;
3229 this_load += effective_load(tg, this_cpu, -weight, -weight);
3230 load += effective_load(tg, prev_cpu, 0, -weight);
3234 weight = p->se.load.weight;
3237 * In low-load situations, where prev_cpu is idle and this_cpu is idle
3238 * due to the sync cause above having dropped this_load to 0, we'll
3239 * always have an imbalance, but there's really nothing you can do
3240 * about that, so that's good too.
3242 * Otherwise check if either cpus are near enough in load to allow this
3243 * task to be woken on this_cpu.
3245 if (this_load > 0) {
3246 s64 this_eff_load, prev_eff_load;
3248 this_eff_load = 100;
3249 this_eff_load *= power_of(prev_cpu);
3250 this_eff_load *= this_load +
3251 effective_load(tg, this_cpu, weight, weight);
3253 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
3254 prev_eff_load *= power_of(this_cpu);
3255 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
3257 balanced = this_eff_load <= prev_eff_load;
3262 * If the currently running task will sleep within
3263 * a reasonable amount of time then attract this newly
3266 if (sync && balanced)
3269 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
3270 tl_per_task = cpu_avg_load_per_task(this_cpu);
3273 (this_load <= load &&
3274 this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
3276 * This domain has SD_WAKE_AFFINE and
3277 * p is cache cold in this domain, and
3278 * there is no bad imbalance.
3280 schedstat_inc(sd, ttwu_move_affine);
3281 schedstat_inc(p, se.statistics.nr_wakeups_affine);
3289 * find_idlest_group finds and returns the least busy CPU group within the
3292 static struct sched_group *
3293 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
3294 int this_cpu, int load_idx)
3296 struct sched_group *idlest = NULL, *group = sd->groups;
3297 unsigned long min_load = ULONG_MAX, this_load = 0;
3298 int imbalance = 100 + (sd->imbalance_pct-100)/2;
3301 unsigned long load, avg_load;
3305 /* Skip over this group if it has no CPUs allowed */
3306 if (!cpumask_intersects(sched_group_cpus(group),
3307 tsk_cpus_allowed(p)))
3310 local_group = cpumask_test_cpu(this_cpu,
3311 sched_group_cpus(group));
3313 /* Tally up the load of all CPUs in the group */
3316 for_each_cpu(i, sched_group_cpus(group)) {
3317 /* Bias balancing toward cpus of our domain */
3319 load = source_load(i, load_idx);
3321 load = target_load(i, load_idx);
3326 /* Adjust by relative CPU power of the group */
3327 avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
3330 this_load = avg_load;
3331 } else if (avg_load < min_load) {
3332 min_load = avg_load;
3335 } while (group = group->next, group != sd->groups);
3337 if (!idlest || 100*this_load < imbalance*min_load)
3343 * find_idlest_cpu - find the idlest cpu among the cpus in group.
3346 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
3348 unsigned long load, min_load = ULONG_MAX;
3352 /* Traverse only the allowed CPUs */
3353 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
3354 load = weighted_cpuload(i);
3356 if (load < min_load || (load == min_load && i == this_cpu)) {
3366 * Try and locate an idle CPU in the sched_domain.
3368 static int select_idle_sibling(struct task_struct *p, int target)
3370 struct sched_domain *sd;
3371 struct sched_group *sg;
3372 int i = task_cpu(p);
3374 if (idle_cpu(target))
3378 * If the prevous cpu is cache affine and idle, don't be stupid.
3380 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
3384 * Otherwise, iterate the domains and find an elegible idle cpu.
3386 sd = rcu_dereference(per_cpu(sd_llc, target));
3387 for_each_lower_domain(sd) {
3390 if (!cpumask_intersects(sched_group_cpus(sg),
3391 tsk_cpus_allowed(p)))
3394 for_each_cpu(i, sched_group_cpus(sg)) {
3395 if (i == target || !idle_cpu(i))
3399 target = cpumask_first_and(sched_group_cpus(sg),
3400 tsk_cpus_allowed(p));
3404 } while (sg != sd->groups);
3411 * sched_balance_self: balance the current task (running on cpu) in domains
3412 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
3415 * Balance, ie. select the least loaded group.
3417 * Returns the target CPU number, or the same CPU if no balancing is needed.
3419 * preempt must be disabled.
3422 select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
3424 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
3425 int cpu = smp_processor_id();
3426 int prev_cpu = task_cpu(p);
3428 int want_affine = 0;
3429 int sync = wake_flags & WF_SYNC;
3431 if (p->nr_cpus_allowed == 1)
3434 if (sd_flag & SD_BALANCE_WAKE) {
3435 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
3441 for_each_domain(cpu, tmp) {
3442 if (!(tmp->flags & SD_LOAD_BALANCE))
3446 * If both cpu and prev_cpu are part of this domain,
3447 * cpu is a valid SD_WAKE_AFFINE target.
3449 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
3450 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
3455 if (tmp->flags & sd_flag)
3460 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
3463 new_cpu = select_idle_sibling(p, prev_cpu);
3468 int load_idx = sd->forkexec_idx;
3469 struct sched_group *group;
3472 if (!(sd->flags & sd_flag)) {
3477 if (sd_flag & SD_BALANCE_WAKE)
3478 load_idx = sd->wake_idx;
3480 group = find_idlest_group(sd, p, cpu, load_idx);
3486 new_cpu = find_idlest_cpu(group, p, cpu);
3487 if (new_cpu == -1 || new_cpu == cpu) {
3488 /* Now try balancing at a lower domain level of cpu */
3493 /* Now try balancing at a lower domain level of new_cpu */
3495 weight = sd->span_weight;
3497 for_each_domain(cpu, tmp) {
3498 if (weight <= tmp->span_weight)
3500 if (tmp->flags & sd_flag)
3503 /* while loop will break here if sd == NULL */
3512 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
3513 * cfs_rq_of(p) references at time of call are still valid and identify the
3514 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
3515 * other assumptions, including the state of rq->lock, should be made.
3518 migrate_task_rq_fair(struct task_struct *p, int next_cpu)
3520 struct sched_entity *se = &p->se;
3521 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3524 * Load tracking: accumulate removed load so that it can be processed
3525 * when we next update owning cfs_rq under rq->lock. Tasks contribute
3526 * to blocked load iff they have a positive decay-count. It can never
3527 * be negative here since on-rq tasks have decay-count == 0.
3529 if (se->avg.decay_count) {
3530 se->avg.decay_count = -__synchronize_entity_decay(se);
3531 atomic_long_add(se->avg.load_avg_contrib,
3532 &cfs_rq->removed_load);
3535 #endif /* CONFIG_SMP */
3537 static unsigned long
3538 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
3540 unsigned long gran = sysctl_sched_wakeup_granularity;
3543 * Since its curr running now, convert the gran from real-time
3544 * to virtual-time in his units.
3546 * By using 'se' instead of 'curr' we penalize light tasks, so
3547 * they get preempted easier. That is, if 'se' < 'curr' then
3548 * the resulting gran will be larger, therefore penalizing the
3549 * lighter, if otoh 'se' > 'curr' then the resulting gran will
3550 * be smaller, again penalizing the lighter task.
3552 * This is especially important for buddies when the leftmost
3553 * task is higher priority than the buddy.
3555 return calc_delta_fair(gran, se);
3559 * Should 'se' preempt 'curr'.
3573 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
3575 s64 gran, vdiff = curr->vruntime - se->vruntime;
3580 gran = wakeup_gran(curr, se);
3587 static void set_last_buddy(struct sched_entity *se)
3589 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
3592 for_each_sched_entity(se)
3593 cfs_rq_of(se)->last = se;
3596 static void set_next_buddy(struct sched_entity *se)
3598 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
3601 for_each_sched_entity(se)
3602 cfs_rq_of(se)->next = se;
3605 static void set_skip_buddy(struct sched_entity *se)
3607 for_each_sched_entity(se)
3608 cfs_rq_of(se)->skip = se;
3612 * Preempt the current task with a newly woken task if needed:
3614 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
3616 struct task_struct *curr = rq->curr;
3617 struct sched_entity *se = &curr->se, *pse = &p->se;
3618 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3619 int scale = cfs_rq->nr_running >= sched_nr_latency;
3620 int next_buddy_marked = 0;
3622 if (unlikely(se == pse))
3626 * This is possible from callers such as move_task(), in which we
3627 * unconditionally check_prempt_curr() after an enqueue (which may have
3628 * lead to a throttle). This both saves work and prevents false
3629 * next-buddy nomination below.
3631 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
3634 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
3635 set_next_buddy(pse);
3636 next_buddy_marked = 1;
3640 * We can come here with TIF_NEED_RESCHED already set from new task
3643 * Note: this also catches the edge-case of curr being in a throttled
3644 * group (e.g. via set_curr_task), since update_curr() (in the
3645 * enqueue of curr) will have resulted in resched being set. This
3646 * prevents us from potentially nominating it as a false LAST_BUDDY
3649 if (test_tsk_need_resched(curr))
3652 /* Idle tasks are by definition preempted by non-idle tasks. */
3653 if (unlikely(curr->policy == SCHED_IDLE) &&
3654 likely(p->policy != SCHED_IDLE))
3658 * Batch and idle tasks do not preempt non-idle tasks (their preemption
3659 * is driven by the tick):
3661 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
3664 find_matching_se(&se, &pse);
3665 update_curr(cfs_rq_of(se));
3667 if (wakeup_preempt_entity(se, pse) == 1) {
3669 * Bias pick_next to pick the sched entity that is
3670 * triggering this preemption.
3672 if (!next_buddy_marked)
3673 set_next_buddy(pse);
3682 * Only set the backward buddy when the current task is still
3683 * on the rq. This can happen when a wakeup gets interleaved
3684 * with schedule on the ->pre_schedule() or idle_balance()
3685 * point, either of which can * drop the rq lock.
3687 * Also, during early boot the idle thread is in the fair class,
3688 * for obvious reasons its a bad idea to schedule back to it.
3690 if (unlikely(!se->on_rq || curr == rq->idle))
3693 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
3697 static struct task_struct *pick_next_task_fair(struct rq *rq)
3699 struct task_struct *p;
3700 struct cfs_rq *cfs_rq = &rq->cfs;
3701 struct sched_entity *se;
3703 if (!cfs_rq->nr_running)
3707 se = pick_next_entity(cfs_rq);
3708 set_next_entity(cfs_rq, se);
3709 cfs_rq = group_cfs_rq(se);
3713 if (hrtick_enabled(rq))
3714 hrtick_start_fair(rq, p);
3720 * Account for a descheduled task:
3722 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
3724 struct sched_entity *se = &prev->se;
3725 struct cfs_rq *cfs_rq;
3727 for_each_sched_entity(se) {
3728 cfs_rq = cfs_rq_of(se);
3729 put_prev_entity(cfs_rq, se);
3734 * sched_yield() is very simple
3736 * The magic of dealing with the ->skip buddy is in pick_next_entity.
3738 static void yield_task_fair(struct rq *rq)
3740 struct task_struct *curr = rq->curr;
3741 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3742 struct sched_entity *se = &curr->se;
3745 * Are we the only task in the tree?
3747 if (unlikely(rq->nr_running == 1))
3750 clear_buddies(cfs_rq, se);
3752 if (curr->policy != SCHED_BATCH) {
3753 update_rq_clock(rq);
3755 * Update run-time statistics of the 'current'.
3757 update_curr(cfs_rq);
3759 * Tell update_rq_clock() that we've just updated,
3760 * so we don't do microscopic update in schedule()
3761 * and double the fastpath cost.
3763 rq->skip_clock_update = 1;
3769 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
3771 struct sched_entity *se = &p->se;
3773 /* throttled hierarchies are not runnable */
3774 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
3777 /* Tell the scheduler that we'd really like pse to run next. */
3780 yield_task_fair(rq);
3786 /**************************************************
3787 * Fair scheduling class load-balancing methods.
3791 * The purpose of load-balancing is to achieve the same basic fairness the
3792 * per-cpu scheduler provides, namely provide a proportional amount of compute
3793 * time to each task. This is expressed in the following equation:
3795 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
3797 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
3798 * W_i,0 is defined as:
3800 * W_i,0 = \Sum_j w_i,j (2)
3802 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
3803 * is derived from the nice value as per prio_to_weight[].
3805 * The weight average is an exponential decay average of the instantaneous
3808 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
3810 * P_i is the cpu power (or compute capacity) of cpu i, typically it is the
3811 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
3812 * can also include other factors [XXX].
3814 * To achieve this balance we define a measure of imbalance which follows
3815 * directly from (1):
3817 * imb_i,j = max{ avg(W/P), W_i/P_i } - min{ avg(W/P), W_j/P_j } (4)
3819 * We them move tasks around to minimize the imbalance. In the continuous
3820 * function space it is obvious this converges, in the discrete case we get
3821 * a few fun cases generally called infeasible weight scenarios.
3824 * - infeasible weights;
3825 * - local vs global optima in the discrete case. ]
3830 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
3831 * for all i,j solution, we create a tree of cpus that follows the hardware
3832 * topology where each level pairs two lower groups (or better). This results
3833 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
3834 * tree to only the first of the previous level and we decrease the frequency
3835 * of load-balance at each level inv. proportional to the number of cpus in
3841 * \Sum { --- * --- * 2^i } = O(n) (5)
3843 * `- size of each group
3844 * | | `- number of cpus doing load-balance
3846 * `- sum over all levels
3848 * Coupled with a limit on how many tasks we can migrate every balance pass,
3849 * this makes (5) the runtime complexity of the balancer.
3851 * An important property here is that each CPU is still (indirectly) connected
3852 * to every other cpu in at most O(log n) steps:
3854 * The adjacency matrix of the resulting graph is given by:
3857 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
3860 * And you'll find that:
3862 * A^(log_2 n)_i,j != 0 for all i,j (7)
3864 * Showing there's indeed a path between every cpu in at most O(log n) steps.
3865 * The task movement gives a factor of O(m), giving a convergence complexity
3868 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
3873 * In order to avoid CPUs going idle while there's still work to do, new idle
3874 * balancing is more aggressive and has the newly idle cpu iterate up the domain
3875 * tree itself instead of relying on other CPUs to bring it work.
3877 * This adds some complexity to both (5) and (8) but it reduces the total idle
3885 * Cgroups make a horror show out of (2), instead of a simple sum we get:
3888 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
3893 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
3895 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
3897 * The big problem is S_k, its a global sum needed to compute a local (W_i)
3900 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
3901 * rewrite all of this once again.]
3904 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
3906 #define LBF_ALL_PINNED 0x01
3907 #define LBF_NEED_BREAK 0x02
3908 #define LBF_SOME_PINNED 0x04
3911 struct sched_domain *sd;
3919 struct cpumask *dst_grpmask;
3921 enum cpu_idle_type idle;
3923 /* The set of CPUs under consideration for load-balancing */
3924 struct cpumask *cpus;
3929 unsigned int loop_break;
3930 unsigned int loop_max;
3934 * move_task - move a task from one runqueue to another runqueue.
3935 * Both runqueues must be locked.
3937 static void move_task(struct task_struct *p, struct lb_env *env)
3939 deactivate_task(env->src_rq, p, 0);
3940 set_task_cpu(p, env->dst_cpu);
3941 activate_task(env->dst_rq, p, 0);
3942 check_preempt_curr(env->dst_rq, p, 0);
3946 * Is this task likely cache-hot:
3949 task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
3953 if (p->sched_class != &fair_sched_class)
3956 if (unlikely(p->policy == SCHED_IDLE))
3960 * Buddy candidates are cache hot:
3962 if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
3963 (&p->se == cfs_rq_of(&p->se)->next ||
3964 &p->se == cfs_rq_of(&p->se)->last))
3967 if (sysctl_sched_migration_cost == -1)
3969 if (sysctl_sched_migration_cost == 0)
3972 delta = now - p->se.exec_start;
3974 return delta < (s64)sysctl_sched_migration_cost;
3978 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
3981 int can_migrate_task(struct task_struct *p, struct lb_env *env)
3983 int tsk_cache_hot = 0;
3985 * We do not migrate tasks that are:
3986 * 1) throttled_lb_pair, or
3987 * 2) cannot be migrated to this CPU due to cpus_allowed, or
3988 * 3) running (obviously), or
3989 * 4) are cache-hot on their current CPU.
3991 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
3994 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
3997 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
4000 * Remember if this task can be migrated to any other cpu in
4001 * our sched_group. We may want to revisit it if we couldn't
4002 * meet load balance goals by pulling other tasks on src_cpu.
4004 * Also avoid computing new_dst_cpu if we have already computed
4005 * one in current iteration.
4007 if (!env->dst_grpmask || (env->flags & LBF_SOME_PINNED))
4010 /* Prevent to re-select dst_cpu via env's cpus */
4011 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
4012 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
4013 env->flags |= LBF_SOME_PINNED;
4014 env->new_dst_cpu = cpu;
4022 /* Record that we found atleast one task that could run on dst_cpu */
4023 env->flags &= ~LBF_ALL_PINNED;
4025 if (task_running(env->src_rq, p)) {
4026 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
4031 * Aggressive migration if:
4032 * 1) task is cache cold, or
4033 * 2) too many balance attempts have failed.
4036 tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
4037 if (!tsk_cache_hot ||
4038 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
4040 if (tsk_cache_hot) {
4041 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
4042 schedstat_inc(p, se.statistics.nr_forced_migrations);
4048 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
4053 * move_one_task tries to move exactly one task from busiest to this_rq, as
4054 * part of active balancing operations within "domain".
4055 * Returns 1 if successful and 0 otherwise.
4057 * Called with both runqueues locked.
4059 static int move_one_task(struct lb_env *env)
4061 struct task_struct *p, *n;
4063 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
4064 if (!can_migrate_task(p, env))
4069 * Right now, this is only the second place move_task()
4070 * is called, so we can safely collect move_task()
4071 * stats here rather than inside move_task().
4073 schedstat_inc(env->sd, lb_gained[env->idle]);
4079 static unsigned long task_h_load(struct task_struct *p);
4081 static const unsigned int sched_nr_migrate_break = 32;
4084 * move_tasks tries to move up to imbalance weighted load from busiest to
4085 * this_rq, as part of a balancing operation within domain "sd".
4086 * Returns 1 if successful and 0 otherwise.
4088 * Called with both runqueues locked.
4090 static int move_tasks(struct lb_env *env)
4092 struct list_head *tasks = &env->src_rq->cfs_tasks;
4093 struct task_struct *p;
4097 if (env->imbalance <= 0)
4100 while (!list_empty(tasks)) {
4101 p = list_first_entry(tasks, struct task_struct, se.group_node);
4104 /* We've more or less seen every task there is, call it quits */
4105 if (env->loop > env->loop_max)
4108 /* take a breather every nr_migrate tasks */
4109 if (env->loop > env->loop_break) {
4110 env->loop_break += sched_nr_migrate_break;
4111 env->flags |= LBF_NEED_BREAK;
4115 if (!can_migrate_task(p, env))
4118 load = task_h_load(p);
4120 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
4123 if ((load / 2) > env->imbalance)
4128 env->imbalance -= load;
4130 #ifdef CONFIG_PREEMPT
4132 * NEWIDLE balancing is a source of latency, so preemptible
4133 * kernels will stop after the first task is pulled to minimize
4134 * the critical section.
4136 if (env->idle == CPU_NEWLY_IDLE)
4141 * We only want to steal up to the prescribed amount of
4144 if (env->imbalance <= 0)
4149 list_move_tail(&p->se.group_node, tasks);
4153 * Right now, this is one of only two places move_task() is called,
4154 * so we can safely collect move_task() stats here rather than
4155 * inside move_task().
4157 schedstat_add(env->sd, lb_gained[env->idle], pulled);
4162 #ifdef CONFIG_FAIR_GROUP_SCHED
4164 * update tg->load_weight by folding this cpu's load_avg
4166 static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
4168 struct sched_entity *se = tg->se[cpu];
4169 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
4171 /* throttled entities do not contribute to load */
4172 if (throttled_hierarchy(cfs_rq))
4175 update_cfs_rq_blocked_load(cfs_rq, 1);
4178 update_entity_load_avg(se, 1);
4180 * We pivot on our runnable average having decayed to zero for
4181 * list removal. This generally implies that all our children
4182 * have also been removed (modulo rounding error or bandwidth
4183 * control); however, such cases are rare and we can fix these
4186 * TODO: fix up out-of-order children on enqueue.
4188 if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
4189 list_del_leaf_cfs_rq(cfs_rq);
4191 struct rq *rq = rq_of(cfs_rq);
4192 update_rq_runnable_avg(rq, rq->nr_running);
4196 static void update_blocked_averages(int cpu)
4198 struct rq *rq = cpu_rq(cpu);
4199 struct cfs_rq *cfs_rq;
4200 unsigned long flags;
4202 raw_spin_lock_irqsave(&rq->lock, flags);
4203 update_rq_clock(rq);
4205 * Iterates the task_group tree in a bottom up fashion, see
4206 * list_add_leaf_cfs_rq() for details.
4208 for_each_leaf_cfs_rq(rq, cfs_rq) {
4210 * Note: We may want to consider periodically releasing
4211 * rq->lock about these updates so that creating many task
4212 * groups does not result in continually extending hold time.
4214 __update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
4217 raw_spin_unlock_irqrestore(&rq->lock, flags);
4221 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
4222 * This needs to be done in a top-down fashion because the load of a child
4223 * group is a fraction of its parents load.
4225 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
4227 struct rq *rq = rq_of(cfs_rq);
4228 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
4229 unsigned long now = jiffies;
4232 if (cfs_rq->last_h_load_update == now)
4235 cfs_rq->h_load_next = NULL;
4236 for_each_sched_entity(se) {
4237 cfs_rq = cfs_rq_of(se);
4238 cfs_rq->h_load_next = se;
4239 if (cfs_rq->last_h_load_update == now)
4244 cfs_rq->h_load = rq->avg.load_avg_contrib;
4245 cfs_rq->last_h_load_update = now;
4248 while ((se = cfs_rq->h_load_next) != NULL) {
4249 load = cfs_rq->h_load;
4250 load = div64_ul(load * se->avg.load_avg_contrib,
4251 cfs_rq->runnable_load_avg + 1);
4252 cfs_rq = group_cfs_rq(se);
4253 cfs_rq->h_load = load;
4254 cfs_rq->last_h_load_update = now;
4258 static unsigned long task_h_load(struct task_struct *p)
4260 struct cfs_rq *cfs_rq = task_cfs_rq(p);
4262 update_cfs_rq_h_load(cfs_rq);
4263 return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
4264 cfs_rq->runnable_load_avg + 1);
4267 static inline void update_blocked_averages(int cpu)
4271 static unsigned long task_h_load(struct task_struct *p)
4273 return p->se.avg.load_avg_contrib;
4277 /********** Helpers for find_busiest_group ************************/
4279 * sd_lb_stats - Structure to store the statistics of a sched_domain
4280 * during load balancing.
4282 struct sd_lb_stats {
4283 struct sched_group *busiest; /* Busiest group in this sd */
4284 struct sched_group *this; /* Local group in this sd */
4285 unsigned long total_load; /* Total load of all groups in sd */
4286 unsigned long total_pwr; /* Total power of all groups in sd */
4287 unsigned long avg_load; /* Average load across all groups in sd */
4289 /** Statistics of this group */
4290 unsigned long this_load;
4291 unsigned long this_load_per_task;
4292 unsigned long this_nr_running;
4293 unsigned long this_has_capacity;
4294 unsigned int this_idle_cpus;
4296 /* Statistics of the busiest group */
4297 unsigned int busiest_idle_cpus;
4298 unsigned long max_load;
4299 unsigned long busiest_load_per_task;
4300 unsigned long busiest_nr_running;
4301 unsigned long busiest_group_capacity;
4302 unsigned long busiest_has_capacity;
4303 unsigned int busiest_group_weight;
4305 int group_imb; /* Is there imbalance in this sd */
4309 * sg_lb_stats - stats of a sched_group required for load_balancing
4311 struct sg_lb_stats {
4312 unsigned long avg_load; /*Avg load across the CPUs of the group */
4313 unsigned long group_load; /* Total load over the CPUs of the group */
4314 unsigned long sum_nr_running; /* Nr tasks running in the group */
4315 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
4316 unsigned long group_capacity;
4317 unsigned long idle_cpus;
4318 unsigned long group_weight;
4319 int group_imb; /* Is there an imbalance in the group ? */
4320 int group_has_capacity; /* Is there extra capacity in the group? */
4324 * get_sd_load_idx - Obtain the load index for a given sched domain.
4325 * @sd: The sched_domain whose load_idx is to be obtained.
4326 * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
4328 static inline int get_sd_load_idx(struct sched_domain *sd,
4329 enum cpu_idle_type idle)
4335 load_idx = sd->busy_idx;
4338 case CPU_NEWLY_IDLE:
4339 load_idx = sd->newidle_idx;
4342 load_idx = sd->idle_idx;
4349 static unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
4351 return SCHED_POWER_SCALE;
4354 unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
4356 return default_scale_freq_power(sd, cpu);
4359 static unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
4361 unsigned long weight = sd->span_weight;
4362 unsigned long smt_gain = sd->smt_gain;
4369 unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
4371 return default_scale_smt_power(sd, cpu);
4374 static unsigned long scale_rt_power(int cpu)
4376 struct rq *rq = cpu_rq(cpu);
4377 u64 total, available, age_stamp, avg;
4380 * Since we're reading these variables without serialization make sure
4381 * we read them once before doing sanity checks on them.
4383 age_stamp = ACCESS_ONCE(rq->age_stamp);
4384 avg = ACCESS_ONCE(rq->rt_avg);
4386 total = sched_avg_period() + (rq_clock(rq) - age_stamp);
4388 if (unlikely(total < avg)) {
4389 /* Ensures that power won't end up being negative */
4392 available = total - avg;
4395 if (unlikely((s64)total < SCHED_POWER_SCALE))
4396 total = SCHED_POWER_SCALE;
4398 total >>= SCHED_POWER_SHIFT;
4400 return div_u64(available, total);
4403 static void update_cpu_power(struct sched_domain *sd, int cpu)
4405 unsigned long weight = sd->span_weight;
4406 unsigned long power = SCHED_POWER_SCALE;
4407 struct sched_group *sdg = sd->groups;
4409 if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
4410 if (sched_feat(ARCH_POWER))
4411 power *= arch_scale_smt_power(sd, cpu);
4413 power *= default_scale_smt_power(sd, cpu);
4415 power >>= SCHED_POWER_SHIFT;
4418 sdg->sgp->power_orig = power;
4420 if (sched_feat(ARCH_POWER))
4421 power *= arch_scale_freq_power(sd, cpu);
4423 power *= default_scale_freq_power(sd, cpu);
4425 power >>= SCHED_POWER_SHIFT;
4427 power *= scale_rt_power(cpu);
4428 power >>= SCHED_POWER_SHIFT;
4433 cpu_rq(cpu)->cpu_power = power;
4434 sdg->sgp->power = power;
4437 void update_group_power(struct sched_domain *sd, int cpu)
4439 struct sched_domain *child = sd->child;
4440 struct sched_group *group, *sdg = sd->groups;
4441 unsigned long power;
4442 unsigned long interval;
4444 interval = msecs_to_jiffies(sd->balance_interval);
4445 interval = clamp(interval, 1UL, max_load_balance_interval);
4446 sdg->sgp->next_update = jiffies + interval;
4449 update_cpu_power(sd, cpu);
4455 if (child->flags & SD_OVERLAP) {
4457 * SD_OVERLAP domains cannot assume that child groups
4458 * span the current group.
4461 for_each_cpu(cpu, sched_group_cpus(sdg))
4462 power += power_of(cpu);
4465 * !SD_OVERLAP domains can assume that child groups
4466 * span the current group.
4469 group = child->groups;
4471 power += group->sgp->power;
4472 group = group->next;
4473 } while (group != child->groups);
4476 sdg->sgp->power_orig = sdg->sgp->power = power;
4480 * Try and fix up capacity for tiny siblings, this is needed when
4481 * things like SD_ASYM_PACKING need f_b_g to select another sibling
4482 * which on its own isn't powerful enough.
4484 * See update_sd_pick_busiest() and check_asym_packing().
4487 fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
4490 * Only siblings can have significantly less than SCHED_POWER_SCALE
4492 if (!(sd->flags & SD_SHARE_CPUPOWER))
4496 * If ~90% of the cpu_power is still there, we're good.
4498 if (group->sgp->power * 32 > group->sgp->power_orig * 29)
4505 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
4506 * @env: The load balancing environment.
4507 * @group: sched_group whose statistics are to be updated.
4508 * @load_idx: Load index of sched_domain of this_cpu for load calc.
4509 * @local_group: Does group contain this_cpu.
4510 * @balance: Should we balance.
4511 * @sgs: variable to hold the statistics for this group.
4513 static inline void update_sg_lb_stats(struct lb_env *env,
4514 struct sched_group *group, int load_idx,
4515 int local_group, int *balance, struct sg_lb_stats *sgs)
4517 unsigned long nr_running, max_nr_running, min_nr_running;
4518 unsigned long load, max_cpu_load, min_cpu_load;
4519 unsigned int balance_cpu = -1, first_idle_cpu = 0;
4520 unsigned long avg_load_per_task = 0;
4524 balance_cpu = group_balance_cpu(group);
4526 /* Tally up the load of all CPUs in the group */
4528 min_cpu_load = ~0UL;
4530 min_nr_running = ~0UL;
4532 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
4533 struct rq *rq = cpu_rq(i);
4535 nr_running = rq->nr_running;
4537 /* Bias balancing toward cpus of our domain */
4539 if (idle_cpu(i) && !first_idle_cpu &&
4540 cpumask_test_cpu(i, sched_group_mask(group))) {
4545 load = target_load(i, load_idx);
4547 load = source_load(i, load_idx);
4548 if (load > max_cpu_load)
4549 max_cpu_load = load;
4550 if (min_cpu_load > load)
4551 min_cpu_load = load;
4553 if (nr_running > max_nr_running)
4554 max_nr_running = nr_running;
4555 if (min_nr_running > nr_running)
4556 min_nr_running = nr_running;
4559 sgs->group_load += load;
4560 sgs->sum_nr_running += nr_running;
4561 sgs->sum_weighted_load += weighted_cpuload(i);
4567 * First idle cpu or the first cpu(busiest) in this sched group
4568 * is eligible for doing load balancing at this and above
4569 * domains. In the newly idle case, we will allow all the cpu's
4570 * to do the newly idle load balance.
4573 if (env->idle != CPU_NEWLY_IDLE) {
4574 if (balance_cpu != env->dst_cpu) {
4578 update_group_power(env->sd, env->dst_cpu);
4579 } else if (time_after_eq(jiffies, group->sgp->next_update))
4580 update_group_power(env->sd, env->dst_cpu);
4583 /* Adjust by relative CPU power of the group */
4584 sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power;
4587 * Consider the group unbalanced when the imbalance is larger
4588 * than the average weight of a task.
4590 * APZ: with cgroup the avg task weight can vary wildly and
4591 * might not be a suitable number - should we keep a
4592 * normalized nr_running number somewhere that negates
4595 if (sgs->sum_nr_running)
4596 avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
4598 if ((max_cpu_load - min_cpu_load) >= avg_load_per_task &&
4599 (max_nr_running - min_nr_running) > 1)
4602 sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
4604 if (!sgs->group_capacity)
4605 sgs->group_capacity = fix_small_capacity(env->sd, group);
4606 sgs->group_weight = group->group_weight;
4608 if (sgs->group_capacity > sgs->sum_nr_running)
4609 sgs->group_has_capacity = 1;
4613 * update_sd_pick_busiest - return 1 on busiest group
4614 * @env: The load balancing environment.
4615 * @sds: sched_domain statistics
4616 * @sg: sched_group candidate to be checked for being the busiest
4617 * @sgs: sched_group statistics
4619 * Determine if @sg is a busier group than the previously selected
4622 static bool update_sd_pick_busiest(struct lb_env *env,
4623 struct sd_lb_stats *sds,
4624 struct sched_group *sg,
4625 struct sg_lb_stats *sgs)
4627 if (sgs->avg_load <= sds->max_load)
4630 if (sgs->sum_nr_running > sgs->group_capacity)
4637 * ASYM_PACKING needs to move all the work to the lowest
4638 * numbered CPUs in the group, therefore mark all groups
4639 * higher than ourself as busy.
4641 if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
4642 env->dst_cpu < group_first_cpu(sg)) {
4646 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
4654 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
4655 * @env: The load balancing environment.
4656 * @balance: Should we balance.
4657 * @sds: variable to hold the statistics for this sched_domain.
4659 static inline void update_sd_lb_stats(struct lb_env *env,
4660 int *balance, struct sd_lb_stats *sds)
4662 struct sched_domain *child = env->sd->child;
4663 struct sched_group *sg = env->sd->groups;
4664 struct sg_lb_stats sgs;
4665 int load_idx, prefer_sibling = 0;
4667 if (child && child->flags & SD_PREFER_SIBLING)
4670 load_idx = get_sd_load_idx(env->sd, env->idle);
4675 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
4676 memset(&sgs, 0, sizeof(sgs));
4677 update_sg_lb_stats(env, sg, load_idx, local_group, balance, &sgs);
4679 if (local_group && !(*balance))
4682 sds->total_load += sgs.group_load;
4683 sds->total_pwr += sg->sgp->power;
4686 * In case the child domain prefers tasks go to siblings
4687 * first, lower the sg capacity to one so that we'll try
4688 * and move all the excess tasks away. We lower the capacity
4689 * of a group only if the local group has the capacity to fit
4690 * these excess tasks, i.e. nr_running < group_capacity. The
4691 * extra check prevents the case where you always pull from the
4692 * heaviest group when it is already under-utilized (possible
4693 * with a large weight task outweighs the tasks on the system).
4695 if (prefer_sibling && !local_group && sds->this_has_capacity)
4696 sgs.group_capacity = min(sgs.group_capacity, 1UL);
4699 sds->this_load = sgs.avg_load;
4701 sds->this_nr_running = sgs.sum_nr_running;
4702 sds->this_load_per_task = sgs.sum_weighted_load;
4703 sds->this_has_capacity = sgs.group_has_capacity;
4704 sds->this_idle_cpus = sgs.idle_cpus;
4705 } else if (update_sd_pick_busiest(env, sds, sg, &sgs)) {
4706 sds->max_load = sgs.avg_load;
4708 sds->busiest_nr_running = sgs.sum_nr_running;
4709 sds->busiest_idle_cpus = sgs.idle_cpus;
4710 sds->busiest_group_capacity = sgs.group_capacity;
4711 sds->busiest_load_per_task = sgs.sum_weighted_load;
4712 sds->busiest_has_capacity = sgs.group_has_capacity;
4713 sds->busiest_group_weight = sgs.group_weight;
4714 sds->group_imb = sgs.group_imb;
4718 } while (sg != env->sd->groups);
4722 * check_asym_packing - Check to see if the group is packed into the
4725 * This is primarily intended to used at the sibling level. Some
4726 * cores like POWER7 prefer to use lower numbered SMT threads. In the
4727 * case of POWER7, it can move to lower SMT modes only when higher
4728 * threads are idle. When in lower SMT modes, the threads will
4729 * perform better since they share less core resources. Hence when we
4730 * have idle threads, we want them to be the higher ones.
4732 * This packing function is run on idle threads. It checks to see if
4733 * the busiest CPU in this domain (core in the P7 case) has a higher
4734 * CPU number than the packing function is being run on. Here we are
4735 * assuming lower CPU number will be equivalent to lower a SMT thread
4738 * Returns 1 when packing is required and a task should be moved to
4739 * this CPU. The amount of the imbalance is returned in *imbalance.
4741 * @env: The load balancing environment.
4742 * @sds: Statistics of the sched_domain which is to be packed
4744 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
4748 if (!(env->sd->flags & SD_ASYM_PACKING))
4754 busiest_cpu = group_first_cpu(sds->busiest);
4755 if (env->dst_cpu > busiest_cpu)
4758 env->imbalance = DIV_ROUND_CLOSEST(
4759 sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE);
4765 * fix_small_imbalance - Calculate the minor imbalance that exists
4766 * amongst the groups of a sched_domain, during
4768 * @env: The load balancing environment.
4769 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
4772 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4774 unsigned long tmp, pwr_now = 0, pwr_move = 0;
4775 unsigned int imbn = 2;
4776 unsigned long scaled_busy_load_per_task;
4778 if (sds->this_nr_running) {
4779 sds->this_load_per_task /= sds->this_nr_running;
4780 if (sds->busiest_load_per_task >
4781 sds->this_load_per_task)
4784 sds->this_load_per_task =
4785 cpu_avg_load_per_task(env->dst_cpu);
4788 scaled_busy_load_per_task = sds->busiest_load_per_task
4789 * SCHED_POWER_SCALE;
4790 scaled_busy_load_per_task /= sds->busiest->sgp->power;
4792 if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
4793 (scaled_busy_load_per_task * imbn)) {
4794 env->imbalance = sds->busiest_load_per_task;
4799 * OK, we don't have enough imbalance to justify moving tasks,
4800 * however we may be able to increase total CPU power used by
4804 pwr_now += sds->busiest->sgp->power *
4805 min(sds->busiest_load_per_task, sds->max_load);
4806 pwr_now += sds->this->sgp->power *
4807 min(sds->this_load_per_task, sds->this_load);
4808 pwr_now /= SCHED_POWER_SCALE;
4810 /* Amount of load we'd subtract */
4811 tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4812 sds->busiest->sgp->power;
4813 if (sds->max_load > tmp)
4814 pwr_move += sds->busiest->sgp->power *
4815 min(sds->busiest_load_per_task, sds->max_load - tmp);
4817 /* Amount of load we'd add */
4818 if (sds->max_load * sds->busiest->sgp->power <
4819 sds->busiest_load_per_task * SCHED_POWER_SCALE)
4820 tmp = (sds->max_load * sds->busiest->sgp->power) /
4821 sds->this->sgp->power;
4823 tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4824 sds->this->sgp->power;
4825 pwr_move += sds->this->sgp->power *
4826 min(sds->this_load_per_task, sds->this_load + tmp);
4827 pwr_move /= SCHED_POWER_SCALE;
4829 /* Move if we gain throughput */
4830 if (pwr_move > pwr_now)
4831 env->imbalance = sds->busiest_load_per_task;
4835 * calculate_imbalance - Calculate the amount of imbalance present within the
4836 * groups of a given sched_domain during load balance.
4837 * @env: load balance environment
4838 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
4840 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4842 unsigned long max_pull, load_above_capacity = ~0UL;
4844 sds->busiest_load_per_task /= sds->busiest_nr_running;
4845 if (sds->group_imb) {
4846 sds->busiest_load_per_task =
4847 min(sds->busiest_load_per_task, sds->avg_load);
4851 * In the presence of smp nice balancing, certain scenarios can have
4852 * max load less than avg load(as we skip the groups at or below
4853 * its cpu_power, while calculating max_load..)
4855 if (sds->max_load < sds->avg_load) {
4857 return fix_small_imbalance(env, sds);
4860 if (!sds->group_imb) {
4862 * Don't want to pull so many tasks that a group would go idle.
4864 load_above_capacity = (sds->busiest_nr_running -
4865 sds->busiest_group_capacity);
4867 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
4869 load_above_capacity /= sds->busiest->sgp->power;
4873 * We're trying to get all the cpus to the average_load, so we don't
4874 * want to push ourselves above the average load, nor do we wish to
4875 * reduce the max loaded cpu below the average load. At the same time,
4876 * we also don't want to reduce the group load below the group capacity
4877 * (so that we can implement power-savings policies etc). Thus we look
4878 * for the minimum possible imbalance.
4879 * Be careful of negative numbers as they'll appear as very large values
4880 * with unsigned longs.
4882 max_pull = min(sds->max_load - sds->avg_load, load_above_capacity);
4884 /* How much load to actually move to equalise the imbalance */
4885 env->imbalance = min(max_pull * sds->busiest->sgp->power,
4886 (sds->avg_load - sds->this_load) * sds->this->sgp->power)
4887 / SCHED_POWER_SCALE;
4890 * if *imbalance is less than the average load per runnable task
4891 * there is no guarantee that any tasks will be moved so we'll have
4892 * a think about bumping its value to force at least one task to be
4895 if (env->imbalance < sds->busiest_load_per_task)
4896 return fix_small_imbalance(env, sds);
4900 /******* find_busiest_group() helpers end here *********************/
4903 * find_busiest_group - Returns the busiest group within the sched_domain
4904 * if there is an imbalance. If there isn't an imbalance, and
4905 * the user has opted for power-savings, it returns a group whose
4906 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
4907 * such a group exists.
4909 * Also calculates the amount of weighted load which should be moved
4910 * to restore balance.
4912 * @env: The load balancing environment.
4913 * @balance: Pointer to a variable indicating if this_cpu
4914 * is the appropriate cpu to perform load balancing at this_level.
4916 * Returns: - the busiest group if imbalance exists.
4917 * - If no imbalance and user has opted for power-savings balance,
4918 * return the least loaded group whose CPUs can be
4919 * put to idle by rebalancing its tasks onto our group.
4921 static struct sched_group *
4922 find_busiest_group(struct lb_env *env, int *balance)
4924 struct sd_lb_stats sds;
4926 memset(&sds, 0, sizeof(sds));
4929 * Compute the various statistics relavent for load balancing at
4932 update_sd_lb_stats(env, balance, &sds);
4935 * this_cpu is not the appropriate cpu to perform load balancing at
4941 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
4942 check_asym_packing(env, &sds))
4945 /* There is no busy sibling group to pull tasks from */
4946 if (!sds.busiest || sds.busiest_nr_running == 0)
4949 sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
4952 * If the busiest group is imbalanced the below checks don't
4953 * work because they assumes all things are equal, which typically
4954 * isn't true due to cpus_allowed constraints and the like.
4959 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
4960 if (env->idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
4961 !sds.busiest_has_capacity)
4965 * If the local group is more busy than the selected busiest group
4966 * don't try and pull any tasks.
4968 if (sds.this_load >= sds.max_load)
4972 * Don't pull any tasks if this group is already above the domain
4975 if (sds.this_load >= sds.avg_load)
4978 if (env->idle == CPU_IDLE) {
4980 * This cpu is idle. If the busiest group load doesn't
4981 * have more tasks than the number of available cpu's and
4982 * there is no imbalance between this and busiest group
4983 * wrt to idle cpu's, it is balanced.
4985 if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
4986 sds.busiest_nr_running <= sds.busiest_group_weight)
4990 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
4991 * imbalance_pct to be conservative.
4993 if (100 * sds.max_load <= env->sd->imbalance_pct * sds.this_load)
4998 /* Looks like there is an imbalance. Compute it */
4999 calculate_imbalance(env, &sds);
5009 * find_busiest_queue - find the busiest runqueue among the cpus in group.
5011 static struct rq *find_busiest_queue(struct lb_env *env,
5012 struct sched_group *group)
5014 struct rq *busiest = NULL, *rq;
5015 unsigned long max_load = 0;
5018 for_each_cpu(i, sched_group_cpus(group)) {
5019 unsigned long power = power_of(i);
5020 unsigned long capacity = DIV_ROUND_CLOSEST(power,
5025 capacity = fix_small_capacity(env->sd, group);
5027 if (!cpumask_test_cpu(i, env->cpus))
5031 wl = weighted_cpuload(i);
5034 * When comparing with imbalance, use weighted_cpuload()
5035 * which is not scaled with the cpu power.
5037 if (capacity && rq->nr_running == 1 && wl > env->imbalance)
5041 * For the load comparisons with the other cpu's, consider
5042 * the weighted_cpuload() scaled with the cpu power, so that
5043 * the load can be moved away from the cpu that is potentially
5044 * running at a lower capacity.
5046 wl = (wl * SCHED_POWER_SCALE) / power;
5048 if (wl > max_load) {
5058 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
5059 * so long as it is large enough.
5061 #define MAX_PINNED_INTERVAL 512
5063 /* Working cpumask for load_balance and load_balance_newidle. */
5064 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5066 static int need_active_balance(struct lb_env *env)
5068 struct sched_domain *sd = env->sd;
5070 if (env->idle == CPU_NEWLY_IDLE) {
5073 * ASYM_PACKING needs to force migrate tasks from busy but
5074 * higher numbered CPUs in order to pack all tasks in the
5075 * lowest numbered CPUs.
5077 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
5081 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
5084 static int active_load_balance_cpu_stop(void *data);
5087 * Check this_cpu to ensure it is balanced within domain. Attempt to move
5088 * tasks if there is an imbalance.
5090 static int load_balance(int this_cpu, struct rq *this_rq,
5091 struct sched_domain *sd, enum cpu_idle_type idle,
5094 int ld_moved, cur_ld_moved, active_balance = 0;
5095 struct sched_group *group;
5097 unsigned long flags;
5098 struct cpumask *cpus = __get_cpu_var(load_balance_mask);
5100 struct lb_env env = {
5102 .dst_cpu = this_cpu,
5104 .dst_grpmask = sched_group_cpus(sd->groups),
5106 .loop_break = sched_nr_migrate_break,
5111 * For NEWLY_IDLE load_balancing, we don't need to consider
5112 * other cpus in our group
5114 if (idle == CPU_NEWLY_IDLE)
5115 env.dst_grpmask = NULL;
5117 cpumask_copy(cpus, cpu_active_mask);
5119 schedstat_inc(sd, lb_count[idle]);
5122 group = find_busiest_group(&env, balance);
5128 schedstat_inc(sd, lb_nobusyg[idle]);
5132 busiest = find_busiest_queue(&env, group);
5134 schedstat_inc(sd, lb_nobusyq[idle]);
5138 BUG_ON(busiest == env.dst_rq);
5140 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
5143 if (busiest->nr_running > 1) {
5145 * Attempt to move tasks. If find_busiest_group has found
5146 * an imbalance but busiest->nr_running <= 1, the group is
5147 * still unbalanced. ld_moved simply stays zero, so it is
5148 * correctly treated as an imbalance.
5150 env.flags |= LBF_ALL_PINNED;
5151 env.src_cpu = busiest->cpu;
5152 env.src_rq = busiest;
5153 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
5156 local_irq_save(flags);
5157 double_rq_lock(env.dst_rq, busiest);
5160 * cur_ld_moved - load moved in current iteration
5161 * ld_moved - cumulative load moved across iterations
5163 cur_ld_moved = move_tasks(&env);
5164 ld_moved += cur_ld_moved;
5165 double_rq_unlock(env.dst_rq, busiest);
5166 local_irq_restore(flags);
5169 * some other cpu did the load balance for us.
5171 if (cur_ld_moved && env.dst_cpu != smp_processor_id())
5172 resched_cpu(env.dst_cpu);
5174 if (env.flags & LBF_NEED_BREAK) {
5175 env.flags &= ~LBF_NEED_BREAK;
5180 * Revisit (affine) tasks on src_cpu that couldn't be moved to
5181 * us and move them to an alternate dst_cpu in our sched_group
5182 * where they can run. The upper limit on how many times we
5183 * iterate on same src_cpu is dependent on number of cpus in our
5186 * This changes load balance semantics a bit on who can move
5187 * load to a given_cpu. In addition to the given_cpu itself
5188 * (or a ilb_cpu acting on its behalf where given_cpu is
5189 * nohz-idle), we now have balance_cpu in a position to move
5190 * load to given_cpu. In rare situations, this may cause
5191 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
5192 * _independently_ and at _same_ time to move some load to
5193 * given_cpu) causing exceess load to be moved to given_cpu.
5194 * This however should not happen so much in practice and
5195 * moreover subsequent load balance cycles should correct the
5196 * excess load moved.
5198 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
5200 env.dst_rq = cpu_rq(env.new_dst_cpu);
5201 env.dst_cpu = env.new_dst_cpu;
5202 env.flags &= ~LBF_SOME_PINNED;
5204 env.loop_break = sched_nr_migrate_break;
5206 /* Prevent to re-select dst_cpu via env's cpus */
5207 cpumask_clear_cpu(env.dst_cpu, env.cpus);
5210 * Go back to "more_balance" rather than "redo" since we
5211 * need to continue with same src_cpu.
5216 /* All tasks on this runqueue were pinned by CPU affinity */
5217 if (unlikely(env.flags & LBF_ALL_PINNED)) {
5218 cpumask_clear_cpu(cpu_of(busiest), cpus);
5219 if (!cpumask_empty(cpus)) {
5221 env.loop_break = sched_nr_migrate_break;
5229 schedstat_inc(sd, lb_failed[idle]);
5231 * Increment the failure counter only on periodic balance.
5232 * We do not want newidle balance, which can be very
5233 * frequent, pollute the failure counter causing
5234 * excessive cache_hot migrations and active balances.
5236 if (idle != CPU_NEWLY_IDLE)
5237 sd->nr_balance_failed++;
5239 if (need_active_balance(&env)) {
5240 raw_spin_lock_irqsave(&busiest->lock, flags);
5242 /* don't kick the active_load_balance_cpu_stop,
5243 * if the curr task on busiest cpu can't be
5246 if (!cpumask_test_cpu(this_cpu,
5247 tsk_cpus_allowed(busiest->curr))) {
5248 raw_spin_unlock_irqrestore(&busiest->lock,
5250 env.flags |= LBF_ALL_PINNED;
5251 goto out_one_pinned;
5255 * ->active_balance synchronizes accesses to
5256 * ->active_balance_work. Once set, it's cleared
5257 * only after active load balance is finished.
5259 if (!busiest->active_balance) {
5260 busiest->active_balance = 1;
5261 busiest->push_cpu = this_cpu;
5264 raw_spin_unlock_irqrestore(&busiest->lock, flags);
5266 if (active_balance) {
5267 stop_one_cpu_nowait(cpu_of(busiest),
5268 active_load_balance_cpu_stop, busiest,
5269 &busiest->active_balance_work);
5273 * We've kicked active balancing, reset the failure
5276 sd->nr_balance_failed = sd->cache_nice_tries+1;
5279 sd->nr_balance_failed = 0;
5281 if (likely(!active_balance)) {
5282 /* We were unbalanced, so reset the balancing interval */
5283 sd->balance_interval = sd->min_interval;
5286 * If we've begun active balancing, start to back off. This
5287 * case may not be covered by the all_pinned logic if there
5288 * is only 1 task on the busy runqueue (because we don't call
5291 if (sd->balance_interval < sd->max_interval)
5292 sd->balance_interval *= 2;
5298 schedstat_inc(sd, lb_balanced[idle]);
5300 sd->nr_balance_failed = 0;
5303 /* tune up the balancing interval */
5304 if (((env.flags & LBF_ALL_PINNED) &&
5305 sd->balance_interval < MAX_PINNED_INTERVAL) ||
5306 (sd->balance_interval < sd->max_interval))
5307 sd->balance_interval *= 2;
5315 * idle_balance is called by schedule() if this_cpu is about to become
5316 * idle. Attempts to pull tasks from other CPUs.
5318 void idle_balance(int this_cpu, struct rq *this_rq)
5320 struct sched_domain *sd;
5321 int pulled_task = 0;
5322 unsigned long next_balance = jiffies + HZ;
5324 this_rq->idle_stamp = rq_clock(this_rq);
5326 if (this_rq->avg_idle < sysctl_sched_migration_cost)
5330 * Drop the rq->lock, but keep IRQ/preempt disabled.
5332 raw_spin_unlock(&this_rq->lock);
5334 update_blocked_averages(this_cpu);
5336 for_each_domain(this_cpu, sd) {
5337 unsigned long interval;
5340 if (!(sd->flags & SD_LOAD_BALANCE))
5343 if (sd->flags & SD_BALANCE_NEWIDLE) {
5344 /* If we've pulled tasks over stop searching: */
5345 pulled_task = load_balance(this_cpu, this_rq,
5346 sd, CPU_NEWLY_IDLE, &balance);
5349 interval = msecs_to_jiffies(sd->balance_interval);
5350 if (time_after(next_balance, sd->last_balance + interval))
5351 next_balance = sd->last_balance + interval;
5353 this_rq->idle_stamp = 0;
5359 raw_spin_lock(&this_rq->lock);
5361 if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
5363 * We are going idle. next_balance may be set based on
5364 * a busy processor. So reset next_balance.
5366 this_rq->next_balance = next_balance;
5371 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
5372 * running tasks off the busiest CPU onto idle CPUs. It requires at
5373 * least 1 task to be running on each physical CPU where possible, and
5374 * avoids physical / logical imbalances.
5376 static int active_load_balance_cpu_stop(void *data)
5378 struct rq *busiest_rq = data;
5379 int busiest_cpu = cpu_of(busiest_rq);
5380 int target_cpu = busiest_rq->push_cpu;
5381 struct rq *target_rq = cpu_rq(target_cpu);
5382 struct sched_domain *sd;
5384 raw_spin_lock_irq(&busiest_rq->lock);
5386 /* make sure the requested cpu hasn't gone down in the meantime */
5387 if (unlikely(busiest_cpu != smp_processor_id() ||
5388 !busiest_rq->active_balance))
5391 /* Is there any task to move? */
5392 if (busiest_rq->nr_running <= 1)
5396 * This condition is "impossible", if it occurs
5397 * we need to fix it. Originally reported by
5398 * Bjorn Helgaas on a 128-cpu setup.
5400 BUG_ON(busiest_rq == target_rq);
5402 /* move a task from busiest_rq to target_rq */
5403 double_lock_balance(busiest_rq, target_rq);
5405 /* Search for an sd spanning us and the target CPU. */
5407 for_each_domain(target_cpu, sd) {
5408 if ((sd->flags & SD_LOAD_BALANCE) &&
5409 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
5414 struct lb_env env = {
5416 .dst_cpu = target_cpu,
5417 .dst_rq = target_rq,
5418 .src_cpu = busiest_rq->cpu,
5419 .src_rq = busiest_rq,
5423 schedstat_inc(sd, alb_count);
5425 if (move_one_task(&env))
5426 schedstat_inc(sd, alb_pushed);
5428 schedstat_inc(sd, alb_failed);
5431 double_unlock_balance(busiest_rq, target_rq);
5433 busiest_rq->active_balance = 0;
5434 raw_spin_unlock_irq(&busiest_rq->lock);
5438 #ifdef CONFIG_NO_HZ_COMMON
5440 * idle load balancing details
5441 * - When one of the busy CPUs notice that there may be an idle rebalancing
5442 * needed, they will kick the idle load balancer, which then does idle
5443 * load balancing for all the idle CPUs.
5446 cpumask_var_t idle_cpus_mask;
5448 unsigned long next_balance; /* in jiffy units */
5449 } nohz ____cacheline_aligned;
5451 static inline int find_new_ilb(int call_cpu)
5453 int ilb = cpumask_first(nohz.idle_cpus_mask);
5455 if (ilb < nr_cpu_ids && idle_cpu(ilb))
5462 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
5463 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
5464 * CPU (if there is one).
5466 static void nohz_balancer_kick(int cpu)
5470 nohz.next_balance++;
5472 ilb_cpu = find_new_ilb(cpu);
5474 if (ilb_cpu >= nr_cpu_ids)
5477 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
5480 * Use smp_send_reschedule() instead of resched_cpu().
5481 * This way we generate a sched IPI on the target cpu which
5482 * is idle. And the softirq performing nohz idle load balance
5483 * will be run before returning from the IPI.
5485 smp_send_reschedule(ilb_cpu);
5489 static inline void nohz_balance_exit_idle(int cpu)
5491 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
5492 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
5493 atomic_dec(&nohz.nr_cpus);
5494 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5498 static inline void set_cpu_sd_state_busy(void)
5500 struct sched_domain *sd;
5503 sd = rcu_dereference_check_sched_domain(this_rq()->sd);
5505 if (!sd || !sd->nohz_idle)
5509 for (; sd; sd = sd->parent)
5510 atomic_inc(&sd->groups->sgp->nr_busy_cpus);
5515 void set_cpu_sd_state_idle(void)
5517 struct sched_domain *sd;
5520 sd = rcu_dereference_check_sched_domain(this_rq()->sd);
5522 if (!sd || sd->nohz_idle)
5526 for (; sd; sd = sd->parent)
5527 atomic_dec(&sd->groups->sgp->nr_busy_cpus);
5533 * This routine will record that the cpu is going idle with tick stopped.
5534 * This info will be used in performing idle load balancing in the future.
5536 void nohz_balance_enter_idle(int cpu)
5539 * If this cpu is going down, then nothing needs to be done.
5541 if (!cpu_active(cpu))
5544 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
5547 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
5548 atomic_inc(&nohz.nr_cpus);
5549 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5552 static int sched_ilb_notifier(struct notifier_block *nfb,
5553 unsigned long action, void *hcpu)
5555 switch (action & ~CPU_TASKS_FROZEN) {
5557 nohz_balance_exit_idle(smp_processor_id());
5565 static DEFINE_SPINLOCK(balancing);
5568 * Scale the max load_balance interval with the number of CPUs in the system.
5569 * This trades load-balance latency on larger machines for less cross talk.
5571 void update_max_interval(void)
5573 max_load_balance_interval = HZ*num_online_cpus()/10;
5577 * It checks each scheduling domain to see if it is due to be balanced,
5578 * and initiates a balancing operation if so.
5580 * Balancing parameters are set up in init_sched_domains.
5582 static void rebalance_domains(int cpu, enum cpu_idle_type idle)
5585 struct rq *rq = cpu_rq(cpu);
5586 unsigned long interval;
5587 struct sched_domain *sd;
5588 /* Earliest time when we have to do rebalance again */
5589 unsigned long next_balance = jiffies + 60*HZ;
5590 int update_next_balance = 0;
5593 update_blocked_averages(cpu);
5596 for_each_domain(cpu, sd) {
5597 if (!(sd->flags & SD_LOAD_BALANCE))
5600 interval = sd->balance_interval;
5601 if (idle != CPU_IDLE)
5602 interval *= sd->busy_factor;
5604 /* scale ms to jiffies */
5605 interval = msecs_to_jiffies(interval);
5606 interval = clamp(interval, 1UL, max_load_balance_interval);
5608 need_serialize = sd->flags & SD_SERIALIZE;
5610 if (need_serialize) {
5611 if (!spin_trylock(&balancing))
5615 if (time_after_eq(jiffies, sd->last_balance + interval)) {
5616 if (load_balance(cpu, rq, sd, idle, &balance)) {
5618 * The LBF_SOME_PINNED logic could have changed
5619 * env->dst_cpu, so we can't know our idle
5620 * state even if we migrated tasks. Update it.
5622 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
5624 sd->last_balance = jiffies;
5627 spin_unlock(&balancing);
5629 if (time_after(next_balance, sd->last_balance + interval)) {
5630 next_balance = sd->last_balance + interval;
5631 update_next_balance = 1;
5635 * Stop the load balance at this level. There is another
5636 * CPU in our sched group which is doing load balancing more
5645 * next_balance will be updated only when there is a need.
5646 * When the cpu is attached to null domain for ex, it will not be
5649 if (likely(update_next_balance))
5650 rq->next_balance = next_balance;
5653 #ifdef CONFIG_NO_HZ_COMMON
5655 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
5656 * rebalancing for all the cpus for whom scheduler ticks are stopped.
5658 static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle)
5660 struct rq *this_rq = cpu_rq(this_cpu);
5664 if (idle != CPU_IDLE ||
5665 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
5668 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
5669 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
5673 * If this cpu gets work to do, stop the load balancing
5674 * work being done for other cpus. Next load
5675 * balancing owner will pick it up.
5680 rq = cpu_rq(balance_cpu);
5682 raw_spin_lock_irq(&rq->lock);
5683 update_rq_clock(rq);
5684 update_idle_cpu_load(rq);
5685 raw_spin_unlock_irq(&rq->lock);
5687 rebalance_domains(balance_cpu, CPU_IDLE);
5689 if (time_after(this_rq->next_balance, rq->next_balance))
5690 this_rq->next_balance = rq->next_balance;
5692 nohz.next_balance = this_rq->next_balance;
5694 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
5698 * Current heuristic for kicking the idle load balancer in the presence
5699 * of an idle cpu is the system.
5700 * - This rq has more than one task.
5701 * - At any scheduler domain level, this cpu's scheduler group has multiple
5702 * busy cpu's exceeding the group's power.
5703 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
5704 * domain span are idle.
5706 static inline int nohz_kick_needed(struct rq *rq, int cpu)
5708 unsigned long now = jiffies;
5709 struct sched_domain *sd;
5711 if (unlikely(idle_cpu(cpu)))
5715 * We may be recently in ticked or tickless idle mode. At the first
5716 * busy tick after returning from idle, we will update the busy stats.
5718 set_cpu_sd_state_busy();
5719 nohz_balance_exit_idle(cpu);
5722 * None are in tickless mode and hence no need for NOHZ idle load
5725 if (likely(!atomic_read(&nohz.nr_cpus)))
5728 if (time_before(now, nohz.next_balance))
5731 if (rq->nr_running >= 2)
5735 for_each_domain(cpu, sd) {
5736 struct sched_group *sg = sd->groups;
5737 struct sched_group_power *sgp = sg->sgp;
5738 int nr_busy = atomic_read(&sgp->nr_busy_cpus);
5740 if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
5741 goto need_kick_unlock;
5743 if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
5744 && (cpumask_first_and(nohz.idle_cpus_mask,
5745 sched_domain_span(sd)) < cpu))
5746 goto need_kick_unlock;
5748 if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
5760 static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { }
5764 * run_rebalance_domains is triggered when needed from the scheduler tick.
5765 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
5767 static void run_rebalance_domains(struct softirq_action *h)
5769 int this_cpu = smp_processor_id();
5770 struct rq *this_rq = cpu_rq(this_cpu);
5771 enum cpu_idle_type idle = this_rq->idle_balance ?
5772 CPU_IDLE : CPU_NOT_IDLE;
5774 rebalance_domains(this_cpu, idle);
5777 * If this cpu has a pending nohz_balance_kick, then do the
5778 * balancing on behalf of the other idle cpus whose ticks are
5781 nohz_idle_balance(this_cpu, idle);
5784 static inline int on_null_domain(int cpu)
5786 return !rcu_dereference_sched(cpu_rq(cpu)->sd);
5790 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
5792 void trigger_load_balance(struct rq *rq, int cpu)
5794 /* Don't need to rebalance while attached to NULL domain */
5795 if (time_after_eq(jiffies, rq->next_balance) &&
5796 likely(!on_null_domain(cpu)))
5797 raise_softirq(SCHED_SOFTIRQ);
5798 #ifdef CONFIG_NO_HZ_COMMON
5799 if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
5800 nohz_balancer_kick(cpu);
5804 static void rq_online_fair(struct rq *rq)
5809 static void rq_offline_fair(struct rq *rq)
5813 /* Ensure any throttled groups are reachable by pick_next_task */
5814 unthrottle_offline_cfs_rqs(rq);
5817 #endif /* CONFIG_SMP */
5820 * scheduler tick hitting a task of our scheduling class:
5822 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
5824 struct cfs_rq *cfs_rq;
5825 struct sched_entity *se = &curr->se;
5827 for_each_sched_entity(se) {
5828 cfs_rq = cfs_rq_of(se);
5829 entity_tick(cfs_rq, se, queued);
5832 if (sched_feat_numa(NUMA))
5833 task_tick_numa(rq, curr);
5835 update_rq_runnable_avg(rq, 1);
5839 * called on fork with the child task as argument from the parent's context
5840 * - child not yet on the tasklist
5841 * - preemption disabled
5843 static void task_fork_fair(struct task_struct *p)
5845 struct cfs_rq *cfs_rq;
5846 struct sched_entity *se = &p->se, *curr;
5847 int this_cpu = smp_processor_id();
5848 struct rq *rq = this_rq();
5849 unsigned long flags;
5851 raw_spin_lock_irqsave(&rq->lock, flags);
5853 update_rq_clock(rq);
5855 cfs_rq = task_cfs_rq(current);
5856 curr = cfs_rq->curr;
5858 if (unlikely(task_cpu(p) != this_cpu)) {
5860 __set_task_cpu(p, this_cpu);
5864 update_curr(cfs_rq);
5867 se->vruntime = curr->vruntime;
5868 place_entity(cfs_rq, se, 1);
5870 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
5872 * Upon rescheduling, sched_class::put_prev_task() will place
5873 * 'current' within the tree based on its new key value.
5875 swap(curr->vruntime, se->vruntime);
5876 resched_task(rq->curr);
5879 se->vruntime -= cfs_rq->min_vruntime;
5881 raw_spin_unlock_irqrestore(&rq->lock, flags);
5885 * Priority of the task has changed. Check to see if we preempt
5889 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
5895 * Reschedule if we are currently running on this runqueue and
5896 * our priority decreased, or if we are not currently running on
5897 * this runqueue and our priority is higher than the current's
5899 if (rq->curr == p) {
5900 if (p->prio > oldprio)
5901 resched_task(rq->curr);
5903 check_preempt_curr(rq, p, 0);
5906 static void switched_from_fair(struct rq *rq, struct task_struct *p)
5908 struct sched_entity *se = &p->se;
5909 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5912 * Ensure the task's vruntime is normalized, so that when its
5913 * switched back to the fair class the enqueue_entity(.flags=0) will
5914 * do the right thing.
5916 * If it was on_rq, then the dequeue_entity(.flags=0) will already
5917 * have normalized the vruntime, if it was !on_rq, then only when
5918 * the task is sleeping will it still have non-normalized vruntime.
5920 if (!se->on_rq && p->state != TASK_RUNNING) {
5922 * Fix up our vruntime so that the current sleep doesn't
5923 * cause 'unlimited' sleep bonus.
5925 place_entity(cfs_rq, se, 0);
5926 se->vruntime -= cfs_rq->min_vruntime;
5931 * Remove our load from contribution when we leave sched_fair
5932 * and ensure we don't carry in an old decay_count if we
5935 if (p->se.avg.decay_count) {
5936 struct cfs_rq *cfs_rq = cfs_rq_of(&p->se);
5937 __synchronize_entity_decay(&p->se);
5938 subtract_blocked_load_contrib(cfs_rq,
5939 p->se.avg.load_avg_contrib);
5945 * We switched to the sched_fair class.
5947 static void switched_to_fair(struct rq *rq, struct task_struct *p)
5953 * We were most likely switched from sched_rt, so
5954 * kick off the schedule if running, otherwise just see
5955 * if we can still preempt the current task.
5958 resched_task(rq->curr);
5960 check_preempt_curr(rq, p, 0);
5963 /* Account for a task changing its policy or group.
5965 * This routine is mostly called to set cfs_rq->curr field when a task
5966 * migrates between groups/classes.
5968 static void set_curr_task_fair(struct rq *rq)
5970 struct sched_entity *se = &rq->curr->se;
5972 for_each_sched_entity(se) {
5973 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5975 set_next_entity(cfs_rq, se);
5976 /* ensure bandwidth has been allocated on our new cfs_rq */
5977 account_cfs_rq_runtime(cfs_rq, 0);
5981 void init_cfs_rq(struct cfs_rq *cfs_rq)
5983 cfs_rq->tasks_timeline = RB_ROOT;
5984 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
5985 #ifndef CONFIG_64BIT
5986 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
5989 atomic64_set(&cfs_rq->decay_counter, 1);
5990 atomic_long_set(&cfs_rq->removed_load, 0);
5994 #ifdef CONFIG_FAIR_GROUP_SCHED
5995 static void task_move_group_fair(struct task_struct *p, int on_rq)
5997 struct cfs_rq *cfs_rq;
5999 * If the task was not on the rq at the time of this cgroup movement
6000 * it must have been asleep, sleeping tasks keep their ->vruntime
6001 * absolute on their old rq until wakeup (needed for the fair sleeper
6002 * bonus in place_entity()).
6004 * If it was on the rq, we've just 'preempted' it, which does convert
6005 * ->vruntime to a relative base.
6007 * Make sure both cases convert their relative position when migrating
6008 * to another cgroup's rq. This does somewhat interfere with the
6009 * fair sleeper stuff for the first placement, but who cares.
6012 * When !on_rq, vruntime of the task has usually NOT been normalized.
6013 * But there are some cases where it has already been normalized:
6015 * - Moving a forked child which is waiting for being woken up by
6016 * wake_up_new_task().
6017 * - Moving a task which has been woken up by try_to_wake_up() and
6018 * waiting for actually being woken up by sched_ttwu_pending().
6020 * To prevent boost or penalty in the new cfs_rq caused by delta
6021 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
6023 if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
6027 p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
6028 set_task_rq(p, task_cpu(p));
6030 cfs_rq = cfs_rq_of(&p->se);
6031 p->se.vruntime += cfs_rq->min_vruntime;
6034 * migrate_task_rq_fair() will have removed our previous
6035 * contribution, but we must synchronize for ongoing future
6038 p->se.avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
6039 cfs_rq->blocked_load_avg += p->se.avg.load_avg_contrib;
6044 void free_fair_sched_group(struct task_group *tg)
6048 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
6050 for_each_possible_cpu(i) {
6052 kfree(tg->cfs_rq[i]);
6061 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
6063 struct cfs_rq *cfs_rq;
6064 struct sched_entity *se;
6067 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
6070 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
6074 tg->shares = NICE_0_LOAD;
6076 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
6078 for_each_possible_cpu(i) {
6079 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
6080 GFP_KERNEL, cpu_to_node(i));
6084 se = kzalloc_node(sizeof(struct sched_entity),
6085 GFP_KERNEL, cpu_to_node(i));
6089 init_cfs_rq(cfs_rq);
6090 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
6101 void unregister_fair_sched_group(struct task_group *tg, int cpu)
6103 struct rq *rq = cpu_rq(cpu);
6104 unsigned long flags;
6107 * Only empty task groups can be destroyed; so we can speculatively
6108 * check on_list without danger of it being re-added.
6110 if (!tg->cfs_rq[cpu]->on_list)
6113 raw_spin_lock_irqsave(&rq->lock, flags);
6114 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
6115 raw_spin_unlock_irqrestore(&rq->lock, flags);
6118 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
6119 struct sched_entity *se, int cpu,
6120 struct sched_entity *parent)
6122 struct rq *rq = cpu_rq(cpu);
6126 init_cfs_rq_runtime(cfs_rq);
6128 tg->cfs_rq[cpu] = cfs_rq;
6131 /* se could be NULL for root_task_group */
6136 se->cfs_rq = &rq->cfs;
6138 se->cfs_rq = parent->my_q;
6141 update_load_set(&se->load, 0);
6142 se->parent = parent;
6145 static DEFINE_MUTEX(shares_mutex);
6147 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
6150 unsigned long flags;
6153 * We can't change the weight of the root cgroup.
6158 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
6160 mutex_lock(&shares_mutex);
6161 if (tg->shares == shares)
6164 tg->shares = shares;
6165 for_each_possible_cpu(i) {
6166 struct rq *rq = cpu_rq(i);
6167 struct sched_entity *se;
6170 /* Propagate contribution to hierarchy */
6171 raw_spin_lock_irqsave(&rq->lock, flags);
6173 /* Possible calls to update_curr() need rq clock */
6174 update_rq_clock(rq);
6175 for_each_sched_entity(se)
6176 update_cfs_shares(group_cfs_rq(se));
6177 raw_spin_unlock_irqrestore(&rq->lock, flags);
6181 mutex_unlock(&shares_mutex);
6184 #else /* CONFIG_FAIR_GROUP_SCHED */
6186 void free_fair_sched_group(struct task_group *tg) { }
6188 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
6193 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
6195 #endif /* CONFIG_FAIR_GROUP_SCHED */
6198 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
6200 struct sched_entity *se = &task->se;
6201 unsigned int rr_interval = 0;
6204 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
6207 if (rq->cfs.load.weight)
6208 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
6214 * All the scheduling class methods:
6216 const struct sched_class fair_sched_class = {
6217 .next = &idle_sched_class,
6218 .enqueue_task = enqueue_task_fair,
6219 .dequeue_task = dequeue_task_fair,
6220 .yield_task = yield_task_fair,
6221 .yield_to_task = yield_to_task_fair,
6223 .check_preempt_curr = check_preempt_wakeup,
6225 .pick_next_task = pick_next_task_fair,
6226 .put_prev_task = put_prev_task_fair,
6229 .select_task_rq = select_task_rq_fair,
6230 .migrate_task_rq = migrate_task_rq_fair,
6232 .rq_online = rq_online_fair,
6233 .rq_offline = rq_offline_fair,
6235 .task_waking = task_waking_fair,
6238 .set_curr_task = set_curr_task_fair,
6239 .task_tick = task_tick_fair,
6240 .task_fork = task_fork_fair,
6242 .prio_changed = prio_changed_fair,
6243 .switched_from = switched_from_fair,
6244 .switched_to = switched_to_fair,
6246 .get_rr_interval = get_rr_interval_fair,
6248 #ifdef CONFIG_FAIR_GROUP_SCHED
6249 .task_move_group = task_move_group_fair,
6253 #ifdef CONFIG_SCHED_DEBUG
6254 void print_cfs_stats(struct seq_file *m, int cpu)
6256 struct cfs_rq *cfs_rq;
6259 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
6260 print_cfs_rq(m, cpu, cfs_rq);
6265 __init void init_sched_fair_class(void)
6268 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
6270 #ifdef CONFIG_NO_HZ_COMMON
6271 nohz.next_balance = jiffies;
6272 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
6273 cpu_notifier(sched_ilb_notifier, 0);