x86: ucode-amd: Don't warn when no ucode is available for a CPU revision
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / sched_fair.c
blob4e777b47eedac1f5f779c002091e2dc8b696abe1
1 /*
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>
26 * Targeted preemption latency for CPU-bound tasks:
27 * (default: 5ms * (1 + ilog(ncpus)), units: nanoseconds)
29 * NOTE: this latency value is not the same as the concept of
30 * 'timeslice length' - timeslices in CFS are of variable length
31 * and have no persistent notion like in traditional, time-slice
32 * based scheduling concepts.
34 * (to see the precise effective timeslice length of your workload,
35 * run vmstat and monitor the context-switches (cs) field)
37 unsigned int sysctl_sched_latency = 5000000ULL;
40 * Minimal preemption granularity for CPU-bound tasks:
41 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
43 unsigned int sysctl_sched_min_granularity = 1000000ULL;
46 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
48 static unsigned int sched_nr_latency = 5;
51 * After fork, child runs first. If set to 0 (default) then
52 * parent will (try to) run first.
54 unsigned int sysctl_sched_child_runs_first __read_mostly;
57 * sys_sched_yield() compat mode
59 * This option switches the agressive yield implementation of the
60 * old scheduler back on.
62 unsigned int __read_mostly sysctl_sched_compat_yield;
65 * SCHED_OTHER wake-up granularity.
66 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
68 * This option delays the preemption effects of decoupled workloads
69 * and reduces their over-scheduling. Synchronous workloads will still
70 * have immediate wakeup/sleep latencies.
72 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
74 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
76 static const struct sched_class fair_sched_class;
78 /**************************************************************
79 * CFS operations on generic schedulable entities:
82 #ifdef CONFIG_FAIR_GROUP_SCHED
84 /* cpu runqueue to which this cfs_rq is attached */
85 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
87 return cfs_rq->rq;
90 /* An entity is a task if it doesn't "own" a runqueue */
91 #define entity_is_task(se) (!se->my_q)
93 static inline struct task_struct *task_of(struct sched_entity *se)
95 #ifdef CONFIG_SCHED_DEBUG
96 WARN_ON_ONCE(!entity_is_task(se));
97 #endif
98 return container_of(se, struct task_struct, se);
101 /* Walk up scheduling entities hierarchy */
102 #define for_each_sched_entity(se) \
103 for (; se; se = se->parent)
105 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
107 return p->se.cfs_rq;
110 /* runqueue on which this entity is (to be) queued */
111 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
113 return se->cfs_rq;
116 /* runqueue "owned" by this group */
117 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
119 return grp->my_q;
122 /* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
123 * another cpu ('this_cpu')
125 static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
127 return cfs_rq->tg->cfs_rq[this_cpu];
130 /* Iterate thr' all leaf cfs_rq's on a runqueue */
131 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
132 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
134 /* Do the two (enqueued) entities belong to the same group ? */
135 static inline int
136 is_same_group(struct sched_entity *se, struct sched_entity *pse)
138 if (se->cfs_rq == pse->cfs_rq)
139 return 1;
141 return 0;
144 static inline struct sched_entity *parent_entity(struct sched_entity *se)
146 return se->parent;
149 /* return depth at which a sched entity is present in the hierarchy */
150 static inline int depth_se(struct sched_entity *se)
152 int depth = 0;
154 for_each_sched_entity(se)
155 depth++;
157 return depth;
160 static void
161 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
163 int se_depth, pse_depth;
166 * preemption test can be made between sibling entities who are in the
167 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
168 * both tasks until we find their ancestors who are siblings of common
169 * parent.
172 /* First walk up until both entities are at same depth */
173 se_depth = depth_se(*se);
174 pse_depth = depth_se(*pse);
176 while (se_depth > pse_depth) {
177 se_depth--;
178 *se = parent_entity(*se);
181 while (pse_depth > se_depth) {
182 pse_depth--;
183 *pse = parent_entity(*pse);
186 while (!is_same_group(*se, *pse)) {
187 *se = parent_entity(*se);
188 *pse = parent_entity(*pse);
192 #else /* !CONFIG_FAIR_GROUP_SCHED */
194 static inline struct task_struct *task_of(struct sched_entity *se)
196 return container_of(se, struct task_struct, se);
199 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
201 return container_of(cfs_rq, struct rq, cfs);
204 #define entity_is_task(se) 1
206 #define for_each_sched_entity(se) \
207 for (; se; se = NULL)
209 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
211 return &task_rq(p)->cfs;
214 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
216 struct task_struct *p = task_of(se);
217 struct rq *rq = task_rq(p);
219 return &rq->cfs;
222 /* runqueue "owned" by this group */
223 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
225 return NULL;
228 static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
230 return &cpu_rq(this_cpu)->cfs;
233 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
234 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
236 static inline int
237 is_same_group(struct sched_entity *se, struct sched_entity *pse)
239 return 1;
242 static inline struct sched_entity *parent_entity(struct sched_entity *se)
244 return NULL;
247 static inline void
248 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
252 #endif /* CONFIG_FAIR_GROUP_SCHED */
255 /**************************************************************
256 * Scheduling class tree data structure manipulation methods:
259 static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
261 s64 delta = (s64)(vruntime - min_vruntime);
262 if (delta > 0)
263 min_vruntime = vruntime;
265 return min_vruntime;
268 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
270 s64 delta = (s64)(vruntime - min_vruntime);
271 if (delta < 0)
272 min_vruntime = vruntime;
274 return min_vruntime;
277 static inline int entity_before(struct sched_entity *a,
278 struct sched_entity *b)
280 return (s64)(a->vruntime - b->vruntime) < 0;
283 static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
285 return se->vruntime - cfs_rq->min_vruntime;
288 static void update_min_vruntime(struct cfs_rq *cfs_rq)
290 u64 vruntime = cfs_rq->min_vruntime;
292 if (cfs_rq->curr)
293 vruntime = cfs_rq->curr->vruntime;
295 if (cfs_rq->rb_leftmost) {
296 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
297 struct sched_entity,
298 run_node);
300 if (!cfs_rq->curr)
301 vruntime = se->vruntime;
302 else
303 vruntime = min_vruntime(vruntime, se->vruntime);
306 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
310 * Enqueue an entity into the rb-tree:
312 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
314 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
315 struct rb_node *parent = NULL;
316 struct sched_entity *entry;
317 s64 key = entity_key(cfs_rq, se);
318 int leftmost = 1;
321 * Find the right place in the rbtree:
323 while (*link) {
324 parent = *link;
325 entry = rb_entry(parent, struct sched_entity, run_node);
327 * We dont care about collisions. Nodes with
328 * the same key stay together.
330 if (key < entity_key(cfs_rq, entry)) {
331 link = &parent->rb_left;
332 } else {
333 link = &parent->rb_right;
334 leftmost = 0;
339 * Maintain a cache of leftmost tree entries (it is frequently
340 * used):
342 if (leftmost)
343 cfs_rq->rb_leftmost = &se->run_node;
345 rb_link_node(&se->run_node, parent, link);
346 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
349 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
351 if (cfs_rq->rb_leftmost == &se->run_node) {
352 struct rb_node *next_node;
354 next_node = rb_next(&se->run_node);
355 cfs_rq->rb_leftmost = next_node;
358 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
361 static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
363 struct rb_node *left = cfs_rq->rb_leftmost;
365 if (!left)
366 return NULL;
368 return rb_entry(left, struct sched_entity, run_node);
371 static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
373 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
375 if (!last)
376 return NULL;
378 return rb_entry(last, struct sched_entity, run_node);
381 /**************************************************************
382 * Scheduling class statistics methods:
385 #ifdef CONFIG_SCHED_DEBUG
386 int sched_nr_latency_handler(struct ctl_table *table, int write,
387 void __user *buffer, size_t *lenp,
388 loff_t *ppos)
390 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
392 if (ret || !write)
393 return ret;
395 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
396 sysctl_sched_min_granularity);
398 return 0;
400 #endif
403 * delta /= w
405 static inline unsigned long
406 calc_delta_fair(unsigned long delta, struct sched_entity *se)
408 if (unlikely(se->load.weight != NICE_0_LOAD))
409 delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
411 return delta;
415 * The idea is to set a period in which each task runs once.
417 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
418 * this period because otherwise the slices get too small.
420 * p = (nr <= nl) ? l : l*nr/nl
422 static u64 __sched_period(unsigned long nr_running)
424 u64 period = sysctl_sched_latency;
425 unsigned long nr_latency = sched_nr_latency;
427 if (unlikely(nr_running > nr_latency)) {
428 period = sysctl_sched_min_granularity;
429 period *= nr_running;
432 return period;
436 * We calculate the wall-time slice from the period by taking a part
437 * proportional to the weight.
439 * s = p*P[w/rw]
441 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
443 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
445 for_each_sched_entity(se) {
446 struct load_weight *load;
447 struct load_weight lw;
449 cfs_rq = cfs_rq_of(se);
450 load = &cfs_rq->load;
452 if (unlikely(!se->on_rq)) {
453 lw = cfs_rq->load;
455 update_load_add(&lw, se->load.weight);
456 load = &lw;
458 slice = calc_delta_mine(slice, se->load.weight, load);
460 return slice;
464 * We calculate the vruntime slice of a to be inserted task
466 * vs = s/w
468 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
470 return calc_delta_fair(sched_slice(cfs_rq, se), se);
474 * Update the current task's runtime statistics. Skip current tasks that
475 * are not in our scheduling class.
477 static inline void
478 __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
479 unsigned long delta_exec)
481 unsigned long delta_exec_weighted;
483 schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
485 curr->sum_exec_runtime += delta_exec;
486 schedstat_add(cfs_rq, exec_clock, delta_exec);
487 delta_exec_weighted = calc_delta_fair(delta_exec, curr);
488 curr->vruntime += delta_exec_weighted;
489 update_min_vruntime(cfs_rq);
492 static void update_curr(struct cfs_rq *cfs_rq)
494 struct sched_entity *curr = cfs_rq->curr;
495 u64 now = rq_of(cfs_rq)->clock;
496 unsigned long delta_exec;
498 if (unlikely(!curr))
499 return;
502 * Get the amount of time the current task was running
503 * since the last time we changed load (this cannot
504 * overflow on 32 bits):
506 delta_exec = (unsigned long)(now - curr->exec_start);
507 if (!delta_exec)
508 return;
510 __update_curr(cfs_rq, curr, delta_exec);
511 curr->exec_start = now;
513 if (entity_is_task(curr)) {
514 struct task_struct *curtask = task_of(curr);
516 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
517 cpuacct_charge(curtask, delta_exec);
518 account_group_exec_runtime(curtask, delta_exec);
522 static inline void
523 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
525 schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
529 * Task is being enqueued - update stats:
531 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
534 * Are we enqueueing a waiting task? (for current tasks
535 * a dequeue/enqueue event is a NOP)
537 if (se != cfs_rq->curr)
538 update_stats_wait_start(cfs_rq, se);
541 static void
542 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
544 schedstat_set(se->wait_max, max(se->wait_max,
545 rq_of(cfs_rq)->clock - se->wait_start));
546 schedstat_set(se->wait_count, se->wait_count + 1);
547 schedstat_set(se->wait_sum, se->wait_sum +
548 rq_of(cfs_rq)->clock - se->wait_start);
549 #ifdef CONFIG_SCHEDSTATS
550 if (entity_is_task(se)) {
551 trace_sched_stat_wait(task_of(se),
552 rq_of(cfs_rq)->clock - se->wait_start);
554 #endif
555 schedstat_set(se->wait_start, 0);
558 static inline void
559 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
562 * Mark the end of the wait period if dequeueing a
563 * waiting task:
565 if (se != cfs_rq->curr)
566 update_stats_wait_end(cfs_rq, se);
570 * We are picking a new current task - update its stats:
572 static inline void
573 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
576 * We are starting a new run period:
578 se->exec_start = rq_of(cfs_rq)->clock;
581 /**************************************************
582 * Scheduling class queueing methods:
585 #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
586 static void
587 add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
589 cfs_rq->task_weight += weight;
591 #else
592 static inline void
593 add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
596 #endif
598 static void
599 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
601 update_load_add(&cfs_rq->load, se->load.weight);
602 if (!parent_entity(se))
603 inc_cpu_load(rq_of(cfs_rq), se->load.weight);
604 if (entity_is_task(se)) {
605 add_cfs_task_weight(cfs_rq, se->load.weight);
606 list_add(&se->group_node, &cfs_rq->tasks);
608 cfs_rq->nr_running++;
609 se->on_rq = 1;
612 static void
613 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
615 update_load_sub(&cfs_rq->load, se->load.weight);
616 if (!parent_entity(se))
617 dec_cpu_load(rq_of(cfs_rq), se->load.weight);
618 if (entity_is_task(se)) {
619 add_cfs_task_weight(cfs_rq, -se->load.weight);
620 list_del_init(&se->group_node);
622 cfs_rq->nr_running--;
623 se->on_rq = 0;
626 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
628 #ifdef CONFIG_SCHEDSTATS
629 struct task_struct *tsk = NULL;
631 if (entity_is_task(se))
632 tsk = task_of(se);
634 if (se->sleep_start) {
635 u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
637 if ((s64)delta < 0)
638 delta = 0;
640 if (unlikely(delta > se->sleep_max))
641 se->sleep_max = delta;
643 se->sleep_start = 0;
644 se->sum_sleep_runtime += delta;
646 if (tsk) {
647 account_scheduler_latency(tsk, delta >> 10, 1);
648 trace_sched_stat_sleep(tsk, delta);
651 if (se->block_start) {
652 u64 delta = rq_of(cfs_rq)->clock - se->block_start;
654 if ((s64)delta < 0)
655 delta = 0;
657 if (unlikely(delta > se->block_max))
658 se->block_max = delta;
660 se->block_start = 0;
661 se->sum_sleep_runtime += delta;
663 if (tsk) {
664 if (tsk->in_iowait) {
665 se->iowait_sum += delta;
666 se->iowait_count++;
667 trace_sched_stat_iowait(tsk, delta);
671 * Blocking time is in units of nanosecs, so shift by
672 * 20 to get a milliseconds-range estimation of the
673 * amount of time that the task spent sleeping:
675 if (unlikely(prof_on == SLEEP_PROFILING)) {
676 profile_hits(SLEEP_PROFILING,
677 (void *)get_wchan(tsk),
678 delta >> 20);
680 account_scheduler_latency(tsk, delta >> 10, 0);
683 #endif
686 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
688 #ifdef CONFIG_SCHED_DEBUG
689 s64 d = se->vruntime - cfs_rq->min_vruntime;
691 if (d < 0)
692 d = -d;
694 if (d > 3*sysctl_sched_latency)
695 schedstat_inc(cfs_rq, nr_spread_over);
696 #endif
699 static void
700 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
702 u64 vruntime = cfs_rq->min_vruntime;
705 * The 'current' period is already promised to the current tasks,
706 * however the extra weight of the new task will slow them down a
707 * little, place the new task so that it fits in the slot that
708 * stays open at the end.
710 if (initial && sched_feat(START_DEBIT))
711 vruntime += sched_vslice(cfs_rq, se);
713 /* sleeps up to a single latency don't count. */
714 if (!initial && sched_feat(FAIR_SLEEPERS)) {
715 unsigned long thresh = sysctl_sched_latency;
718 * Convert the sleeper threshold into virtual time.
719 * SCHED_IDLE is a special sub-class. We care about
720 * fairness only relative to other SCHED_IDLE tasks,
721 * all of which have the same weight.
723 if (sched_feat(NORMALIZED_SLEEPER) && (!entity_is_task(se) ||
724 task_of(se)->policy != SCHED_IDLE))
725 thresh = calc_delta_fair(thresh, se);
728 * Halve their sleep time's effect, to allow
729 * for a gentler effect of sleepers:
731 if (sched_feat(GENTLE_FAIR_SLEEPERS))
732 thresh >>= 1;
734 vruntime -= thresh;
737 /* ensure we never gain time by being placed backwards. */
738 vruntime = max_vruntime(se->vruntime, vruntime);
740 se->vruntime = vruntime;
743 static void
744 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
747 * Update run-time statistics of the 'current'.
749 update_curr(cfs_rq);
750 account_entity_enqueue(cfs_rq, se);
752 if (wakeup) {
753 place_entity(cfs_rq, se, 0);
754 enqueue_sleeper(cfs_rq, se);
757 update_stats_enqueue(cfs_rq, se);
758 check_spread(cfs_rq, se);
759 if (se != cfs_rq->curr)
760 __enqueue_entity(cfs_rq, se);
763 static void __clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
765 if (!se || cfs_rq->last == se)
766 cfs_rq->last = NULL;
768 if (!se || cfs_rq->next == se)
769 cfs_rq->next = NULL;
772 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
774 for_each_sched_entity(se)
775 __clear_buddies(cfs_rq_of(se), se);
778 static void
779 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
782 * Update run-time statistics of the 'current'.
784 update_curr(cfs_rq);
786 update_stats_dequeue(cfs_rq, se);
787 if (sleep) {
788 #ifdef CONFIG_SCHEDSTATS
789 if (entity_is_task(se)) {
790 struct task_struct *tsk = task_of(se);
792 if (tsk->state & TASK_INTERRUPTIBLE)
793 se->sleep_start = rq_of(cfs_rq)->clock;
794 if (tsk->state & TASK_UNINTERRUPTIBLE)
795 se->block_start = rq_of(cfs_rq)->clock;
797 #endif
800 clear_buddies(cfs_rq, se);
802 if (se != cfs_rq->curr)
803 __dequeue_entity(cfs_rq, se);
804 account_entity_dequeue(cfs_rq, se);
805 update_min_vruntime(cfs_rq);
809 * Preempt the current task with a newly woken task if needed:
811 static void
812 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
814 unsigned long ideal_runtime, delta_exec;
816 ideal_runtime = sched_slice(cfs_rq, curr);
817 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
818 if (delta_exec > ideal_runtime) {
819 resched_task(rq_of(cfs_rq)->curr);
821 * The current task ran long enough, ensure it doesn't get
822 * re-elected due to buddy favours.
824 clear_buddies(cfs_rq, curr);
828 static void
829 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
831 /* 'current' is not kept within the tree. */
832 if (se->on_rq) {
834 * Any task has to be enqueued before it get to execute on
835 * a CPU. So account for the time it spent waiting on the
836 * runqueue.
838 update_stats_wait_end(cfs_rq, se);
839 __dequeue_entity(cfs_rq, se);
842 update_stats_curr_start(cfs_rq, se);
843 cfs_rq->curr = se;
844 #ifdef CONFIG_SCHEDSTATS
846 * Track our maximum slice length, if the CPU's load is at
847 * least twice that of our own weight (i.e. dont track it
848 * when there are only lesser-weight tasks around):
850 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
851 se->slice_max = max(se->slice_max,
852 se->sum_exec_runtime - se->prev_sum_exec_runtime);
854 #endif
855 se->prev_sum_exec_runtime = se->sum_exec_runtime;
858 static int
859 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
861 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
863 struct sched_entity *se = __pick_next_entity(cfs_rq);
865 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, se) < 1)
866 return cfs_rq->next;
868 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, se) < 1)
869 return cfs_rq->last;
871 return se;
874 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
877 * If still on the runqueue then deactivate_task()
878 * was not called and update_curr() has to be done:
880 if (prev->on_rq)
881 update_curr(cfs_rq);
883 check_spread(cfs_rq, prev);
884 if (prev->on_rq) {
885 update_stats_wait_start(cfs_rq, prev);
886 /* Put 'current' back into the tree. */
887 __enqueue_entity(cfs_rq, prev);
889 cfs_rq->curr = NULL;
892 static void
893 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
896 * Update run-time statistics of the 'current'.
898 update_curr(cfs_rq);
900 #ifdef CONFIG_SCHED_HRTICK
902 * queued ticks are scheduled to match the slice, so don't bother
903 * validating it and just reschedule.
905 if (queued) {
906 resched_task(rq_of(cfs_rq)->curr);
907 return;
910 * don't let the period tick interfere with the hrtick preemption
912 if (!sched_feat(DOUBLE_TICK) &&
913 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
914 return;
915 #endif
917 if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
918 check_preempt_tick(cfs_rq, curr);
921 /**************************************************
922 * CFS operations on tasks:
925 #ifdef CONFIG_SCHED_HRTICK
926 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
928 struct sched_entity *se = &p->se;
929 struct cfs_rq *cfs_rq = cfs_rq_of(se);
931 WARN_ON(task_rq(p) != rq);
933 if (hrtick_enabled(rq) && cfs_rq->nr_running > 1) {
934 u64 slice = sched_slice(cfs_rq, se);
935 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
936 s64 delta = slice - ran;
938 if (delta < 0) {
939 if (rq->curr == p)
940 resched_task(p);
941 return;
945 * Don't schedule slices shorter than 10000ns, that just
946 * doesn't make sense. Rely on vruntime for fairness.
948 if (rq->curr != p)
949 delta = max_t(s64, 10000LL, delta);
951 hrtick_start(rq, delta);
956 * called from enqueue/dequeue and updates the hrtick when the
957 * current task is from our class and nr_running is low enough
958 * to matter.
960 static void hrtick_update(struct rq *rq)
962 struct task_struct *curr = rq->curr;
964 if (curr->sched_class != &fair_sched_class)
965 return;
967 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
968 hrtick_start_fair(rq, curr);
970 #else /* !CONFIG_SCHED_HRTICK */
971 static inline void
972 hrtick_start_fair(struct rq *rq, struct task_struct *p)
976 static inline void hrtick_update(struct rq *rq)
979 #endif
982 * The enqueue_task method is called before nr_running is
983 * increased. Here we update the fair scheduling stats and
984 * then put the task into the rbtree:
986 static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
988 struct cfs_rq *cfs_rq;
989 struct sched_entity *se = &p->se;
991 for_each_sched_entity(se) {
992 if (se->on_rq)
993 break;
994 cfs_rq = cfs_rq_of(se);
995 enqueue_entity(cfs_rq, se, wakeup);
996 wakeup = 1;
999 hrtick_update(rq);
1003 * The dequeue_task method is called before nr_running is
1004 * decreased. We remove the task from the rbtree and
1005 * update the fair scheduling stats:
1007 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
1009 struct cfs_rq *cfs_rq;
1010 struct sched_entity *se = &p->se;
1012 for_each_sched_entity(se) {
1013 cfs_rq = cfs_rq_of(se);
1014 dequeue_entity(cfs_rq, se, sleep);
1015 /* Don't dequeue parent if it has other entities besides us */
1016 if (cfs_rq->load.weight)
1017 break;
1018 sleep = 1;
1021 hrtick_update(rq);
1025 * sched_yield() support is very simple - we dequeue and enqueue.
1027 * If compat_yield is turned on then we requeue to the end of the tree.
1029 static void yield_task_fair(struct rq *rq)
1031 struct task_struct *curr = rq->curr;
1032 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1033 struct sched_entity *rightmost, *se = &curr->se;
1036 * Are we the only task in the tree?
1038 if (unlikely(cfs_rq->nr_running == 1))
1039 return;
1041 clear_buddies(cfs_rq, se);
1043 if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
1044 update_rq_clock(rq);
1046 * Update run-time statistics of the 'current'.
1048 update_curr(cfs_rq);
1050 return;
1053 * Find the rightmost entry in the rbtree:
1055 rightmost = __pick_last_entity(cfs_rq);
1057 * Already in the rightmost position?
1059 if (unlikely(!rightmost || entity_before(rightmost, se)))
1060 return;
1063 * Minimally necessary key value to be last in the tree:
1064 * Upon rescheduling, sched_class::put_prev_task() will place
1065 * 'current' within the tree based on its new key value.
1067 se->vruntime = rightmost->vruntime + 1;
1070 #ifdef CONFIG_SMP
1072 #ifdef CONFIG_FAIR_GROUP_SCHED
1074 * effective_load() calculates the load change as seen from the root_task_group
1076 * Adding load to a group doesn't make a group heavier, but can cause movement
1077 * of group shares between cpus. Assuming the shares were perfectly aligned one
1078 * can calculate the shift in shares.
1080 * The problem is that perfectly aligning the shares is rather expensive, hence
1081 * we try to avoid doing that too often - see update_shares(), which ratelimits
1082 * this change.
1084 * We compensate this by not only taking the current delta into account, but
1085 * also considering the delta between when the shares were last adjusted and
1086 * now.
1088 * We still saw a performance dip, some tracing learned us that between
1089 * cgroup:/ and cgroup:/foo balancing the number of affine wakeups increased
1090 * significantly. Therefore try to bias the error in direction of failing
1091 * the affine wakeup.
1094 static long effective_load(struct task_group *tg, int cpu,
1095 long wl, long wg)
1097 struct sched_entity *se = tg->se[cpu];
1099 if (!tg->parent)
1100 return wl;
1103 * By not taking the decrease of shares on the other cpu into
1104 * account our error leans towards reducing the affine wakeups.
1106 if (!wl && sched_feat(ASYM_EFF_LOAD))
1107 return wl;
1109 for_each_sched_entity(se) {
1110 long S, rw, s, a, b;
1111 long more_w;
1114 * Instead of using this increment, also add the difference
1115 * between when the shares were last updated and now.
1117 more_w = se->my_q->load.weight - se->my_q->rq_weight;
1118 wl += more_w;
1119 wg += more_w;
1121 S = se->my_q->tg->shares;
1122 s = se->my_q->shares;
1123 rw = se->my_q->rq_weight;
1125 a = S*(rw + wl);
1126 b = S*rw + s*wg;
1128 wl = s*(a-b);
1130 if (likely(b))
1131 wl /= b;
1134 * Assume the group is already running and will
1135 * thus already be accounted for in the weight.
1137 * That is, moving shares between CPUs, does not
1138 * alter the group weight.
1140 wg = 0;
1143 return wl;
1146 #else
1148 static inline unsigned long effective_load(struct task_group *tg, int cpu,
1149 unsigned long wl, unsigned long wg)
1151 return wl;
1154 #endif
1156 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
1158 struct task_struct *curr = current;
1159 unsigned long this_load, load;
1160 int idx, this_cpu, prev_cpu;
1161 unsigned long tl_per_task;
1162 unsigned int imbalance;
1163 struct task_group *tg;
1164 unsigned long weight;
1165 int balanced;
1167 idx = sd->wake_idx;
1168 this_cpu = smp_processor_id();
1169 prev_cpu = task_cpu(p);
1170 load = source_load(prev_cpu, idx);
1171 this_load = target_load(this_cpu, idx);
1173 if (sync) {
1174 if (sched_feat(SYNC_LESS) &&
1175 (curr->se.avg_overlap > sysctl_sched_migration_cost ||
1176 p->se.avg_overlap > sysctl_sched_migration_cost))
1177 sync = 0;
1178 } else {
1179 if (sched_feat(SYNC_MORE) &&
1180 (curr->se.avg_overlap < sysctl_sched_migration_cost &&
1181 p->se.avg_overlap < sysctl_sched_migration_cost))
1182 sync = 1;
1186 * If sync wakeup then subtract the (maximum possible)
1187 * effect of the currently running task from the load
1188 * of the current CPU:
1190 if (sync) {
1191 tg = task_group(current);
1192 weight = current->se.load.weight;
1194 this_load += effective_load(tg, this_cpu, -weight, -weight);
1195 load += effective_load(tg, prev_cpu, 0, -weight);
1198 tg = task_group(p);
1199 weight = p->se.load.weight;
1201 imbalance = 100 + (sd->imbalance_pct - 100) / 2;
1204 * In low-load situations, where prev_cpu is idle and this_cpu is idle
1205 * due to the sync cause above having dropped this_load to 0, we'll
1206 * always have an imbalance, but there's really nothing you can do
1207 * about that, so that's good too.
1209 * Otherwise check if either cpus are near enough in load to allow this
1210 * task to be woken on this_cpu.
1212 balanced = !this_load ||
1213 100*(this_load + effective_load(tg, this_cpu, weight, weight)) <=
1214 imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
1217 * If the currently running task will sleep within
1218 * a reasonable amount of time then attract this newly
1219 * woken task:
1221 if (sync && balanced)
1222 return 1;
1224 schedstat_inc(p, se.nr_wakeups_affine_attempts);
1225 tl_per_task = cpu_avg_load_per_task(this_cpu);
1227 if (balanced ||
1228 (this_load <= load &&
1229 this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
1231 * This domain has SD_WAKE_AFFINE and
1232 * p is cache cold in this domain, and
1233 * there is no bad imbalance.
1235 schedstat_inc(sd, ttwu_move_affine);
1236 schedstat_inc(p, se.nr_wakeups_affine);
1238 return 1;
1240 return 0;
1244 * find_idlest_group finds and returns the least busy CPU group within the
1245 * domain.
1247 static struct sched_group *
1248 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
1249 int this_cpu, int load_idx)
1251 struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups;
1252 unsigned long min_load = ULONG_MAX, this_load = 0;
1253 int imbalance = 100 + (sd->imbalance_pct-100)/2;
1255 do {
1256 unsigned long load, avg_load;
1257 int local_group;
1258 int i;
1260 /* Skip over this group if it has no CPUs allowed */
1261 if (!cpumask_intersects(sched_group_cpus(group),
1262 &p->cpus_allowed))
1263 continue;
1265 local_group = cpumask_test_cpu(this_cpu,
1266 sched_group_cpus(group));
1268 /* Tally up the load of all CPUs in the group */
1269 avg_load = 0;
1271 for_each_cpu(i, sched_group_cpus(group)) {
1272 /* Bias balancing toward cpus of our domain */
1273 if (local_group)
1274 load = source_load(i, load_idx);
1275 else
1276 load = target_load(i, load_idx);
1278 avg_load += load;
1281 /* Adjust by relative CPU power of the group */
1282 avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
1284 if (local_group) {
1285 this_load = avg_load;
1286 this = group;
1287 } else if (avg_load < min_load) {
1288 min_load = avg_load;
1289 idlest = group;
1291 } while (group = group->next, group != sd->groups);
1293 if (!idlest || 100*this_load < imbalance*min_load)
1294 return NULL;
1295 return idlest;
1299 * find_idlest_cpu - find the idlest cpu among the cpus in group.
1301 static int
1302 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
1304 unsigned long load, min_load = ULONG_MAX;
1305 int idlest = -1;
1306 int i;
1308 /* Traverse only the allowed CPUs */
1309 for_each_cpu_and(i, sched_group_cpus(group), &p->cpus_allowed) {
1310 load = weighted_cpuload(i);
1312 if (load < min_load || (load == min_load && i == this_cpu)) {
1313 min_load = load;
1314 idlest = i;
1318 return idlest;
1322 * sched_balance_self: balance the current task (running on cpu) in domains
1323 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
1324 * SD_BALANCE_EXEC.
1326 * Balance, ie. select the least loaded group.
1328 * Returns the target CPU number, or the same CPU if no balancing is needed.
1330 * preempt must be disabled.
1332 static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
1334 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
1335 int cpu = smp_processor_id();
1336 int prev_cpu = task_cpu(p);
1337 int new_cpu = cpu;
1338 int want_affine = 0;
1339 int want_sd = 1;
1340 int sync = wake_flags & WF_SYNC;
1342 if (sd_flag & SD_BALANCE_WAKE) {
1343 if (sched_feat(AFFINE_WAKEUPS) &&
1344 cpumask_test_cpu(cpu, &p->cpus_allowed))
1345 want_affine = 1;
1346 new_cpu = prev_cpu;
1349 rcu_read_lock();
1350 for_each_domain(cpu, tmp) {
1352 * If power savings logic is enabled for a domain, see if we
1353 * are not overloaded, if so, don't balance wider.
1355 if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
1356 unsigned long power = 0;
1357 unsigned long nr_running = 0;
1358 unsigned long capacity;
1359 int i;
1361 for_each_cpu(i, sched_domain_span(tmp)) {
1362 power += power_of(i);
1363 nr_running += cpu_rq(i)->cfs.nr_running;
1366 capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
1368 if (tmp->flags & SD_POWERSAVINGS_BALANCE)
1369 nr_running /= 2;
1371 if (nr_running < capacity)
1372 want_sd = 0;
1375 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
1376 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
1378 affine_sd = tmp;
1379 want_affine = 0;
1382 if (!want_sd && !want_affine)
1383 break;
1385 if (!(tmp->flags & sd_flag))
1386 continue;
1388 if (want_sd)
1389 sd = tmp;
1392 if (sched_feat(LB_SHARES_UPDATE)) {
1394 * Pick the largest domain to update shares over
1396 tmp = sd;
1397 if (affine_sd && (!tmp ||
1398 cpumask_weight(sched_domain_span(affine_sd)) >
1399 cpumask_weight(sched_domain_span(sd))))
1400 tmp = affine_sd;
1402 if (tmp)
1403 update_shares(tmp);
1406 if (affine_sd && wake_affine(affine_sd, p, sync)) {
1407 new_cpu = cpu;
1408 goto out;
1411 while (sd) {
1412 int load_idx = sd->forkexec_idx;
1413 struct sched_group *group;
1414 int weight;
1416 if (!(sd->flags & sd_flag)) {
1417 sd = sd->child;
1418 continue;
1421 if (sd_flag & SD_BALANCE_WAKE)
1422 load_idx = sd->wake_idx;
1424 group = find_idlest_group(sd, p, cpu, load_idx);
1425 if (!group) {
1426 sd = sd->child;
1427 continue;
1430 new_cpu = find_idlest_cpu(group, p, cpu);
1431 if (new_cpu == -1 || new_cpu == cpu) {
1432 /* Now try balancing at a lower domain level of cpu */
1433 sd = sd->child;
1434 continue;
1437 /* Now try balancing at a lower domain level of new_cpu */
1438 cpu = new_cpu;
1439 weight = cpumask_weight(sched_domain_span(sd));
1440 sd = NULL;
1441 for_each_domain(cpu, tmp) {
1442 if (weight <= cpumask_weight(sched_domain_span(tmp)))
1443 break;
1444 if (tmp->flags & sd_flag)
1445 sd = tmp;
1447 /* while loop will break here if sd == NULL */
1450 out:
1451 rcu_read_unlock();
1452 return new_cpu;
1454 #endif /* CONFIG_SMP */
1457 * Adaptive granularity
1459 * se->avg_wakeup gives the average time a task runs until it does a wakeup,
1460 * with the limit of wakeup_gran -- when it never does a wakeup.
1462 * So the smaller avg_wakeup is the faster we want this task to preempt,
1463 * but we don't want to treat the preemptee unfairly and therefore allow it
1464 * to run for at least the amount of time we'd like to run.
1466 * NOTE: we use 2*avg_wakeup to increase the probability of actually doing one
1468 * NOTE: we use *nr_running to scale with load, this nicely matches the
1469 * degrading latency on load.
1471 static unsigned long
1472 adaptive_gran(struct sched_entity *curr, struct sched_entity *se)
1474 u64 this_run = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1475 u64 expected_wakeup = 2*se->avg_wakeup * cfs_rq_of(se)->nr_running;
1476 u64 gran = 0;
1478 if (this_run < expected_wakeup)
1479 gran = expected_wakeup - this_run;
1481 return min_t(s64, gran, sysctl_sched_wakeup_granularity);
1484 static unsigned long
1485 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
1487 unsigned long gran = sysctl_sched_wakeup_granularity;
1489 if (cfs_rq_of(curr)->curr && sched_feat(ADAPTIVE_GRAN))
1490 gran = adaptive_gran(curr, se);
1493 * Since its curr running now, convert the gran from real-time
1494 * to virtual-time in his units.
1496 if (sched_feat(ASYM_GRAN)) {
1498 * By using 'se' instead of 'curr' we penalize light tasks, so
1499 * they get preempted easier. That is, if 'se' < 'curr' then
1500 * the resulting gran will be larger, therefore penalizing the
1501 * lighter, if otoh 'se' > 'curr' then the resulting gran will
1502 * be smaller, again penalizing the lighter task.
1504 * This is especially important for buddies when the leftmost
1505 * task is higher priority than the buddy.
1507 if (unlikely(se->load.weight != NICE_0_LOAD))
1508 gran = calc_delta_fair(gran, se);
1509 } else {
1510 if (unlikely(curr->load.weight != NICE_0_LOAD))
1511 gran = calc_delta_fair(gran, curr);
1514 return gran;
1518 * Should 'se' preempt 'curr'.
1520 * |s1
1521 * |s2
1522 * |s3
1524 * |<--->|c
1526 * w(c, s1) = -1
1527 * w(c, s2) = 0
1528 * w(c, s3) = 1
1531 static int
1532 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
1534 s64 gran, vdiff = curr->vruntime - se->vruntime;
1536 if (vdiff <= 0)
1537 return -1;
1539 gran = wakeup_gran(curr, se);
1540 if (vdiff > gran)
1541 return 1;
1543 return 0;
1546 static void set_last_buddy(struct sched_entity *se)
1548 if (likely(task_of(se)->policy != SCHED_IDLE)) {
1549 for_each_sched_entity(se)
1550 cfs_rq_of(se)->last = se;
1554 static void set_next_buddy(struct sched_entity *se)
1556 if (likely(task_of(se)->policy != SCHED_IDLE)) {
1557 for_each_sched_entity(se)
1558 cfs_rq_of(se)->next = se;
1563 * Preempt the current task with a newly woken task if needed:
1565 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
1567 struct task_struct *curr = rq->curr;
1568 struct sched_entity *se = &curr->se, *pse = &p->se;
1569 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1570 int sync = wake_flags & WF_SYNC;
1572 update_curr(cfs_rq);
1574 if (unlikely(rt_prio(p->prio))) {
1575 resched_task(curr);
1576 return;
1579 if (unlikely(p->sched_class != &fair_sched_class))
1580 return;
1582 if (unlikely(se == pse))
1583 return;
1586 * Only set the backward buddy when the current task is still on the
1587 * rq. This can happen when a wakeup gets interleaved with schedule on
1588 * the ->pre_schedule() or idle_balance() point, either of which can
1589 * drop the rq lock.
1591 * Also, during early boot the idle thread is in the fair class, for
1592 * obvious reasons its a bad idea to schedule back to the idle thread.
1594 if (sched_feat(LAST_BUDDY) && likely(se->on_rq && curr != rq->idle))
1595 set_last_buddy(se);
1596 if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK))
1597 set_next_buddy(pse);
1600 * We can come here with TIF_NEED_RESCHED already set from new task
1601 * wake up path.
1603 if (test_tsk_need_resched(curr))
1604 return;
1607 * Batch and idle tasks do not preempt (their preemption is driven by
1608 * the tick):
1610 if (unlikely(p->policy != SCHED_NORMAL))
1611 return;
1613 /* Idle tasks are by definition preempted by everybody. */
1614 if (unlikely(curr->policy == SCHED_IDLE)) {
1615 resched_task(curr);
1616 return;
1619 if ((sched_feat(WAKEUP_SYNC) && sync) ||
1620 (sched_feat(WAKEUP_OVERLAP) &&
1621 (se->avg_overlap < sysctl_sched_migration_cost &&
1622 pse->avg_overlap < sysctl_sched_migration_cost))) {
1623 resched_task(curr);
1624 return;
1627 if (sched_feat(WAKEUP_RUNNING)) {
1628 if (pse->avg_running < se->avg_running) {
1629 set_next_buddy(pse);
1630 resched_task(curr);
1631 return;
1635 if (!sched_feat(WAKEUP_PREEMPT))
1636 return;
1638 find_matching_se(&se, &pse);
1640 BUG_ON(!pse);
1642 if (wakeup_preempt_entity(se, pse) == 1)
1643 resched_task(curr);
1646 static struct task_struct *pick_next_task_fair(struct rq *rq)
1648 struct task_struct *p;
1649 struct cfs_rq *cfs_rq = &rq->cfs;
1650 struct sched_entity *se;
1652 if (unlikely(!cfs_rq->nr_running))
1653 return NULL;
1655 do {
1656 se = pick_next_entity(cfs_rq);
1658 * If se was a buddy, clear it so that it will have to earn
1659 * the favour again.
1661 * If se was not a buddy, clear the buddies because neither
1662 * was elegible to run, let them earn it again.
1664 * IOW. unconditionally clear buddies.
1666 __clear_buddies(cfs_rq, NULL);
1667 set_next_entity(cfs_rq, se);
1668 cfs_rq = group_cfs_rq(se);
1669 } while (cfs_rq);
1671 p = task_of(se);
1672 hrtick_start_fair(rq, p);
1674 return p;
1678 * Account for a descheduled task:
1680 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1682 struct sched_entity *se = &prev->se;
1683 struct cfs_rq *cfs_rq;
1685 for_each_sched_entity(se) {
1686 cfs_rq = cfs_rq_of(se);
1687 put_prev_entity(cfs_rq, se);
1691 #ifdef CONFIG_SMP
1692 /**************************************************
1693 * Fair scheduling class load-balancing methods:
1697 * Load-balancing iterator. Note: while the runqueue stays locked
1698 * during the whole iteration, the current task might be
1699 * dequeued so the iterator has to be dequeue-safe. Here we
1700 * achieve that by always pre-iterating before returning
1701 * the current task:
1703 static struct task_struct *
1704 __load_balance_iterator(struct cfs_rq *cfs_rq, struct list_head *next)
1706 struct task_struct *p = NULL;
1707 struct sched_entity *se;
1709 if (next == &cfs_rq->tasks)
1710 return NULL;
1712 se = list_entry(next, struct sched_entity, group_node);
1713 p = task_of(se);
1714 cfs_rq->balance_iterator = next->next;
1716 return p;
1719 static struct task_struct *load_balance_start_fair(void *arg)
1721 struct cfs_rq *cfs_rq = arg;
1723 return __load_balance_iterator(cfs_rq, cfs_rq->tasks.next);
1726 static struct task_struct *load_balance_next_fair(void *arg)
1728 struct cfs_rq *cfs_rq = arg;
1730 return __load_balance_iterator(cfs_rq, cfs_rq->balance_iterator);
1733 static unsigned long
1734 __load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1735 unsigned long max_load_move, struct sched_domain *sd,
1736 enum cpu_idle_type idle, int *all_pinned, int *this_best_prio,
1737 struct cfs_rq *cfs_rq)
1739 struct rq_iterator cfs_rq_iterator;
1741 cfs_rq_iterator.start = load_balance_start_fair;
1742 cfs_rq_iterator.next = load_balance_next_fair;
1743 cfs_rq_iterator.arg = cfs_rq;
1745 return balance_tasks(this_rq, this_cpu, busiest,
1746 max_load_move, sd, idle, all_pinned,
1747 this_best_prio, &cfs_rq_iterator);
1750 #ifdef CONFIG_FAIR_GROUP_SCHED
1751 static unsigned long
1752 load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1753 unsigned long max_load_move,
1754 struct sched_domain *sd, enum cpu_idle_type idle,
1755 int *all_pinned, int *this_best_prio)
1757 long rem_load_move = max_load_move;
1758 int busiest_cpu = cpu_of(busiest);
1759 struct task_group *tg;
1761 rcu_read_lock();
1762 update_h_load(busiest_cpu);
1764 list_for_each_entry_rcu(tg, &task_groups, list) {
1765 struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu];
1766 unsigned long busiest_h_load = busiest_cfs_rq->h_load;
1767 unsigned long busiest_weight = busiest_cfs_rq->load.weight;
1768 u64 rem_load, moved_load;
1771 * empty group
1773 if (!busiest_cfs_rq->task_weight)
1774 continue;
1776 rem_load = (u64)rem_load_move * busiest_weight;
1777 rem_load = div_u64(rem_load, busiest_h_load + 1);
1779 moved_load = __load_balance_fair(this_rq, this_cpu, busiest,
1780 rem_load, sd, idle, all_pinned, this_best_prio,
1781 tg->cfs_rq[busiest_cpu]);
1783 if (!moved_load)
1784 continue;
1786 moved_load *= busiest_h_load;
1787 moved_load = div_u64(moved_load, busiest_weight + 1);
1789 rem_load_move -= moved_load;
1790 if (rem_load_move < 0)
1791 break;
1793 rcu_read_unlock();
1795 return max_load_move - rem_load_move;
1797 #else
1798 static unsigned long
1799 load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1800 unsigned long max_load_move,
1801 struct sched_domain *sd, enum cpu_idle_type idle,
1802 int *all_pinned, int *this_best_prio)
1804 return __load_balance_fair(this_rq, this_cpu, busiest,
1805 max_load_move, sd, idle, all_pinned,
1806 this_best_prio, &busiest->cfs);
1808 #endif
1810 static int
1811 move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1812 struct sched_domain *sd, enum cpu_idle_type idle)
1814 struct cfs_rq *busy_cfs_rq;
1815 struct rq_iterator cfs_rq_iterator;
1817 cfs_rq_iterator.start = load_balance_start_fair;
1818 cfs_rq_iterator.next = load_balance_next_fair;
1820 for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
1822 * pass busy_cfs_rq argument into
1823 * load_balance_[start|next]_fair iterators
1825 cfs_rq_iterator.arg = busy_cfs_rq;
1826 if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
1827 &cfs_rq_iterator))
1828 return 1;
1831 return 0;
1833 #endif /* CONFIG_SMP */
1836 * scheduler tick hitting a task of our scheduling class:
1838 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
1840 struct cfs_rq *cfs_rq;
1841 struct sched_entity *se = &curr->se;
1843 for_each_sched_entity(se) {
1844 cfs_rq = cfs_rq_of(se);
1845 entity_tick(cfs_rq, se, queued);
1850 * Share the fairness runtime between parent and child, thus the
1851 * total amount of pressure for CPU stays equal - new tasks
1852 * get a chance to run but frequent forkers are not allowed to
1853 * monopolize the CPU. Note: the parent runqueue is locked,
1854 * the child is not running yet.
1856 static void task_new_fair(struct rq *rq, struct task_struct *p)
1858 struct cfs_rq *cfs_rq = task_cfs_rq(p);
1859 struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
1860 int this_cpu = smp_processor_id();
1862 sched_info_queued(p);
1864 update_curr(cfs_rq);
1865 if (curr)
1866 se->vruntime = curr->vruntime;
1867 place_entity(cfs_rq, se, 1);
1869 /* 'curr' will be NULL if the child belongs to a different group */
1870 if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
1871 curr && entity_before(curr, se)) {
1873 * Upon rescheduling, sched_class::put_prev_task() will place
1874 * 'current' within the tree based on its new key value.
1876 swap(curr->vruntime, se->vruntime);
1877 resched_task(rq->curr);
1880 enqueue_task_fair(rq, p, 0);
1884 * Priority of the task has changed. Check to see if we preempt
1885 * the current task.
1887 static void prio_changed_fair(struct rq *rq, struct task_struct *p,
1888 int oldprio, int running)
1891 * Reschedule if we are currently running on this runqueue and
1892 * our priority decreased, or if we are not currently running on
1893 * this runqueue and our priority is higher than the current's
1895 if (running) {
1896 if (p->prio > oldprio)
1897 resched_task(rq->curr);
1898 } else
1899 check_preempt_curr(rq, p, 0);
1903 * We switched to the sched_fair class.
1905 static void switched_to_fair(struct rq *rq, struct task_struct *p,
1906 int running)
1909 * We were most likely switched from sched_rt, so
1910 * kick off the schedule if running, otherwise just see
1911 * if we can still preempt the current task.
1913 if (running)
1914 resched_task(rq->curr);
1915 else
1916 check_preempt_curr(rq, p, 0);
1919 /* Account for a task changing its policy or group.
1921 * This routine is mostly called to set cfs_rq->curr field when a task
1922 * migrates between groups/classes.
1924 static void set_curr_task_fair(struct rq *rq)
1926 struct sched_entity *se = &rq->curr->se;
1928 for_each_sched_entity(se)
1929 set_next_entity(cfs_rq_of(se), se);
1932 #ifdef CONFIG_FAIR_GROUP_SCHED
1933 static void moved_group_fair(struct task_struct *p)
1935 struct cfs_rq *cfs_rq = task_cfs_rq(p);
1937 update_curr(cfs_rq);
1938 place_entity(cfs_rq, &p->se, 1);
1940 #endif
1942 unsigned int get_rr_interval_fair(struct task_struct *task)
1944 struct sched_entity *se = &task->se;
1945 unsigned long flags;
1946 struct rq *rq;
1947 unsigned int rr_interval = 0;
1950 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
1951 * idle runqueue:
1953 rq = task_rq_lock(task, &flags);
1954 if (rq->cfs.load.weight)
1955 rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));
1956 task_rq_unlock(rq, &flags);
1958 return rr_interval;
1962 * All the scheduling class methods:
1964 static const struct sched_class fair_sched_class = {
1965 .next = &idle_sched_class,
1966 .enqueue_task = enqueue_task_fair,
1967 .dequeue_task = dequeue_task_fair,
1968 .yield_task = yield_task_fair,
1970 .check_preempt_curr = check_preempt_wakeup,
1972 .pick_next_task = pick_next_task_fair,
1973 .put_prev_task = put_prev_task_fair,
1975 #ifdef CONFIG_SMP
1976 .select_task_rq = select_task_rq_fair,
1978 .load_balance = load_balance_fair,
1979 .move_one_task = move_one_task_fair,
1980 #endif
1982 .set_curr_task = set_curr_task_fair,
1983 .task_tick = task_tick_fair,
1984 .task_new = task_new_fair,
1986 .prio_changed = prio_changed_fair,
1987 .switched_to = switched_to_fair,
1989 .get_rr_interval = get_rr_interval_fair,
1991 #ifdef CONFIG_FAIR_GROUP_SCHED
1992 .moved_group = moved_group_fair,
1993 #endif
1996 #ifdef CONFIG_SCHED_DEBUG
1997 static void print_cfs_stats(struct seq_file *m, int cpu)
1999 struct cfs_rq *cfs_rq;
2001 rcu_read_lock();
2002 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
2003 print_cfs_rq(m, cpu, cfs_rq);
2004 rcu_read_unlock();
2006 #endif