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>
24 * Targeted preemption latency for CPU-bound tasks:
25 * (default: 20ms, units: nanoseconds)
27 * NOTE: this latency value is not the same as the concept of
28 * 'timeslice length' - timeslices in CFS are of variable length
29 * and have no persistent notion like in traditional, time-slice
30 * based scheduling concepts.
32 * (to see the precise effective timeslice length of your workload,
33 * run vmstat and monitor the context-switches (cs) field)
35 const_debug
unsigned int sysctl_sched_latency
= 20000000ULL;
38 * After fork, child runs first. (default) If set to 0 then
39 * parent will (try to) run first.
41 const_debug
unsigned int sysctl_sched_child_runs_first
= 1;
44 * Minimal preemption granularity for CPU-bound tasks:
45 * (default: 2 msec, units: nanoseconds)
47 const_debug
unsigned int sysctl_sched_nr_latency
= 20;
50 * sys_sched_yield() compat mode
52 * This option switches the agressive yield implementation of the
53 * old scheduler back on.
55 unsigned int __read_mostly sysctl_sched_compat_yield
;
58 * SCHED_BATCH wake-up granularity.
59 * (default: 10 msec, units: nanoseconds)
61 * This option delays the preemption effects of decoupled workloads
62 * and reduces their over-scheduling. Synchronous workloads will still
63 * have immediate wakeup/sleep latencies.
65 const_debug
unsigned int sysctl_sched_batch_wakeup_granularity
= 10000000UL;
68 * SCHED_OTHER wake-up granularity.
69 * (default: 10 msec, units: nanoseconds)
71 * This option delays the preemption effects of decoupled workloads
72 * and reduces their over-scheduling. Synchronous workloads will still
73 * have immediate wakeup/sleep latencies.
75 const_debug
unsigned int sysctl_sched_wakeup_granularity
= 10000000UL;
77 const_debug
unsigned int sysctl_sched_migration_cost
= 500000UL;
79 /**************************************************************
80 * CFS operations on generic schedulable entities:
83 #ifdef CONFIG_FAIR_GROUP_SCHED
85 /* cpu runqueue to which this cfs_rq is attached */
86 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
91 /* An entity is a task if it doesn't "own" a runqueue */
92 #define entity_is_task(se) (!se->my_q)
94 #else /* CONFIG_FAIR_GROUP_SCHED */
96 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
98 return container_of(cfs_rq
, struct rq
, cfs
);
101 #define entity_is_task(se) 1
103 #endif /* CONFIG_FAIR_GROUP_SCHED */
105 static inline struct task_struct
*task_of(struct sched_entity
*se
)
107 return container_of(se
, struct task_struct
, se
);
111 /**************************************************************
112 * Scheduling class tree data structure manipulation methods:
115 static inline u64
max_vruntime(u64 min_vruntime
, u64 vruntime
)
117 s64 delta
= (s64
)(vruntime
- min_vruntime
);
119 min_vruntime
= vruntime
;
124 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
126 s64 delta
= (s64
)(vruntime
- min_vruntime
);
128 min_vruntime
= vruntime
;
133 static inline s64
entity_key(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
135 return se
->vruntime
- cfs_rq
->min_vruntime
;
139 * Enqueue an entity into the rb-tree:
141 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
143 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
144 struct rb_node
*parent
= NULL
;
145 struct sched_entity
*entry
;
146 s64 key
= entity_key(cfs_rq
, se
);
150 * Find the right place in the rbtree:
154 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
156 * We dont care about collisions. Nodes with
157 * the same key stay together.
159 if (key
< entity_key(cfs_rq
, entry
)) {
160 link
= &parent
->rb_left
;
162 link
= &parent
->rb_right
;
168 * Maintain a cache of leftmost tree entries (it is frequently
172 cfs_rq
->rb_leftmost
= &se
->run_node
;
174 rb_link_node(&se
->run_node
, parent
, link
);
175 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
178 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
180 if (cfs_rq
->rb_leftmost
== &se
->run_node
)
181 cfs_rq
->rb_leftmost
= rb_next(&se
->run_node
);
183 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
186 static inline struct rb_node
*first_fair(struct cfs_rq
*cfs_rq
)
188 return cfs_rq
->rb_leftmost
;
191 static struct sched_entity
*__pick_next_entity(struct cfs_rq
*cfs_rq
)
193 return rb_entry(first_fair(cfs_rq
), struct sched_entity
, run_node
);
196 static inline struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
198 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
199 struct sched_entity
*se
= NULL
;
200 struct rb_node
*parent
;
204 se
= rb_entry(parent
, struct sched_entity
, run_node
);
205 link
= &parent
->rb_right
;
211 /**************************************************************
212 * Scheduling class statistics methods:
217 * The idea is to set a period in which each task runs once.
219 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
220 * this period because otherwise the slices get too small.
222 * p = (nr <= nl) ? l : l*nr/nl
224 static u64
__sched_period(unsigned long nr_running
)
226 u64 period
= sysctl_sched_latency
;
227 unsigned long nr_latency
= sysctl_sched_nr_latency
;
229 if (unlikely(nr_running
> nr_latency
)) {
230 period
*= nr_running
;
231 do_div(period
, nr_latency
);
238 * We calculate the wall-time slice from the period by taking a part
239 * proportional to the weight.
243 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
245 u64 slice
= __sched_period(cfs_rq
->nr_running
);
247 slice
*= se
->load
.weight
;
248 do_div(slice
, cfs_rq
->load
.weight
);
254 * We calculate the vruntime slice.
258 static u64
__sched_vslice(unsigned long rq_weight
, unsigned long nr_running
)
260 u64 vslice
= __sched_period(nr_running
);
262 vslice
*= NICE_0_LOAD
;
263 do_div(vslice
, rq_weight
);
268 static u64
sched_vslice(struct cfs_rq
*cfs_rq
)
270 return __sched_vslice(cfs_rq
->load
.weight
, cfs_rq
->nr_running
);
273 static u64
sched_vslice_add(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
275 return __sched_vslice(cfs_rq
->load
.weight
+ se
->load
.weight
,
276 cfs_rq
->nr_running
+ 1);
280 * Update the current task's runtime statistics. Skip current tasks that
281 * are not in our scheduling class.
284 __update_curr(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
,
285 unsigned long delta_exec
)
287 unsigned long delta_exec_weighted
;
290 schedstat_set(curr
->exec_max
, max((u64
)delta_exec
, curr
->exec_max
));
292 curr
->sum_exec_runtime
+= delta_exec
;
293 schedstat_add(cfs_rq
, exec_clock
, delta_exec
);
294 delta_exec_weighted
= delta_exec
;
295 if (unlikely(curr
->load
.weight
!= NICE_0_LOAD
)) {
296 delta_exec_weighted
= calc_delta_fair(delta_exec_weighted
,
299 curr
->vruntime
+= delta_exec_weighted
;
302 * maintain cfs_rq->min_vruntime to be a monotonic increasing
303 * value tracking the leftmost vruntime in the tree.
305 if (first_fair(cfs_rq
)) {
306 vruntime
= min_vruntime(curr
->vruntime
,
307 __pick_next_entity(cfs_rq
)->vruntime
);
309 vruntime
= curr
->vruntime
;
311 cfs_rq
->min_vruntime
=
312 max_vruntime(cfs_rq
->min_vruntime
, vruntime
);
315 static void update_curr(struct cfs_rq
*cfs_rq
)
317 struct sched_entity
*curr
= cfs_rq
->curr
;
318 u64 now
= rq_of(cfs_rq
)->clock
;
319 unsigned long delta_exec
;
325 * Get the amount of time the current task was running
326 * since the last time we changed load (this cannot
327 * overflow on 32 bits):
329 delta_exec
= (unsigned long)(now
- curr
->exec_start
);
331 __update_curr(cfs_rq
, curr
, delta_exec
);
332 curr
->exec_start
= now
;
336 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
338 schedstat_set(se
->wait_start
, rq_of(cfs_rq
)->clock
);
342 * Task is being enqueued - update stats:
344 static void update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
347 * Are we enqueueing a waiting task? (for current tasks
348 * a dequeue/enqueue event is a NOP)
350 if (se
!= cfs_rq
->curr
)
351 update_stats_wait_start(cfs_rq
, se
);
355 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
357 schedstat_set(se
->wait_max
, max(se
->wait_max
,
358 rq_of(cfs_rq
)->clock
- se
->wait_start
));
359 schedstat_set(se
->wait_start
, 0);
363 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
366 * Mark the end of the wait period if dequeueing a
369 if (se
!= cfs_rq
->curr
)
370 update_stats_wait_end(cfs_rq
, se
);
374 * We are picking a new current task - update its stats:
377 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
380 * We are starting a new run period:
382 se
->exec_start
= rq_of(cfs_rq
)->clock
;
385 /**************************************************
386 * Scheduling class queueing methods:
390 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
392 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
393 cfs_rq
->nr_running
++;
398 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
400 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
401 cfs_rq
->nr_running
--;
405 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
407 #ifdef CONFIG_SCHEDSTATS
408 if (se
->sleep_start
) {
409 u64 delta
= rq_of(cfs_rq
)->clock
- se
->sleep_start
;
414 if (unlikely(delta
> se
->sleep_max
))
415 se
->sleep_max
= delta
;
418 se
->sum_sleep_runtime
+= delta
;
420 if (se
->block_start
) {
421 u64 delta
= rq_of(cfs_rq
)->clock
- se
->block_start
;
426 if (unlikely(delta
> se
->block_max
))
427 se
->block_max
= delta
;
430 se
->sum_sleep_runtime
+= delta
;
433 * Blocking time is in units of nanosecs, so shift by 20 to
434 * get a milliseconds-range estimation of the amount of
435 * time that the task spent sleeping:
437 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
438 struct task_struct
*tsk
= task_of(se
);
440 profile_hits(SLEEP_PROFILING
, (void *)get_wchan(tsk
),
447 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
449 #ifdef CONFIG_SCHED_DEBUG
450 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
455 if (d
> 3*sysctl_sched_latency
)
456 schedstat_inc(cfs_rq
, nr_spread_over
);
461 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
465 vruntime
= cfs_rq
->min_vruntime
;
467 if (sched_feat(TREE_AVG
)) {
468 struct sched_entity
*last
= __pick_last_entity(cfs_rq
);
470 vruntime
+= last
->vruntime
;
473 } else if (sched_feat(APPROX_AVG
) && cfs_rq
->nr_running
)
474 vruntime
+= sched_vslice(cfs_rq
)/2;
477 * The 'current' period is already promised to the current tasks,
478 * however the extra weight of the new task will slow them down a
479 * little, place the new task so that it fits in the slot that
480 * stays open at the end.
482 if (initial
&& sched_feat(START_DEBIT
))
483 vruntime
+= sched_vslice_add(cfs_rq
, se
);
486 /* sleeps upto a single latency don't count. */
487 if (sched_feat(NEW_FAIR_SLEEPERS
) && entity_is_task(se
) &&
488 task_of(se
)->policy
!= SCHED_BATCH
)
489 vruntime
-= sysctl_sched_latency
;
491 /* ensure we never gain time by being placed backwards. */
492 vruntime
= max_vruntime(se
->vruntime
, vruntime
);
495 se
->vruntime
= vruntime
;
499 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int wakeup
)
502 * Update run-time statistics of the 'current'.
507 place_entity(cfs_rq
, se
, 0);
508 enqueue_sleeper(cfs_rq
, se
);
511 update_stats_enqueue(cfs_rq
, se
);
512 check_spread(cfs_rq
, se
);
513 if (se
!= cfs_rq
->curr
)
514 __enqueue_entity(cfs_rq
, se
);
515 account_entity_enqueue(cfs_rq
, se
);
519 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int sleep
)
522 * Update run-time statistics of the 'current'.
526 update_stats_dequeue(cfs_rq
, se
);
528 se
->peer_preempt
= 0;
529 #ifdef CONFIG_SCHEDSTATS
530 if (entity_is_task(se
)) {
531 struct task_struct
*tsk
= task_of(se
);
533 if (tsk
->state
& TASK_INTERRUPTIBLE
)
534 se
->sleep_start
= rq_of(cfs_rq
)->clock
;
535 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
536 se
->block_start
= rq_of(cfs_rq
)->clock
;
541 if (se
!= cfs_rq
->curr
)
542 __dequeue_entity(cfs_rq
, se
);
543 account_entity_dequeue(cfs_rq
, se
);
547 * Preempt the current task with a newly woken task if needed:
550 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
552 unsigned long ideal_runtime
, delta_exec
;
554 ideal_runtime
= sched_slice(cfs_rq
, curr
);
555 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
556 if (delta_exec
> ideal_runtime
||
557 (sched_feat(PREEMPT_RESTRICT
) && curr
->peer_preempt
))
558 resched_task(rq_of(cfs_rq
)->curr
);
559 curr
->peer_preempt
= 0;
563 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
565 /* 'current' is not kept within the tree. */
568 * Any task has to be enqueued before it get to execute on
569 * a CPU. So account for the time it spent waiting on the
572 update_stats_wait_end(cfs_rq
, se
);
573 __dequeue_entity(cfs_rq
, se
);
576 update_stats_curr_start(cfs_rq
, se
);
578 #ifdef CONFIG_SCHEDSTATS
580 * Track our maximum slice length, if the CPU's load is at
581 * least twice that of our own weight (i.e. dont track it
582 * when there are only lesser-weight tasks around):
584 if (rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
585 se
->slice_max
= max(se
->slice_max
,
586 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
589 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
592 static struct sched_entity
*pick_next_entity(struct cfs_rq
*cfs_rq
)
594 struct sched_entity
*se
= NULL
;
596 if (first_fair(cfs_rq
)) {
597 se
= __pick_next_entity(cfs_rq
);
598 set_next_entity(cfs_rq
, se
);
604 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
607 * If still on the runqueue then deactivate_task()
608 * was not called and update_curr() has to be done:
613 check_spread(cfs_rq
, prev
);
615 update_stats_wait_start(cfs_rq
, prev
);
616 /* Put 'current' back into the tree. */
617 __enqueue_entity(cfs_rq
, prev
);
622 static void entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
625 * Update run-time statistics of the 'current'.
629 if (cfs_rq
->nr_running
> 1 || !sched_feat(WAKEUP_PREEMPT
))
630 check_preempt_tick(cfs_rq
, curr
);
633 /**************************************************
634 * CFS operations on tasks:
637 #ifdef CONFIG_FAIR_GROUP_SCHED
639 /* Walk up scheduling entities hierarchy */
640 #define for_each_sched_entity(se) \
641 for (; se; se = se->parent)
643 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
648 /* runqueue on which this entity is (to be) queued */
649 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
654 /* runqueue "owned" by this group */
655 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
660 /* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
661 * another cpu ('this_cpu')
663 static inline struct cfs_rq
*cpu_cfs_rq(struct cfs_rq
*cfs_rq
, int this_cpu
)
665 return cfs_rq
->tg
->cfs_rq
[this_cpu
];
668 /* Iterate thr' all leaf cfs_rq's on a runqueue */
669 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
670 list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
672 /* Do the two (enqueued) entities belong to the same group ? */
674 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
676 if (se
->cfs_rq
== pse
->cfs_rq
)
682 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
687 #else /* CONFIG_FAIR_GROUP_SCHED */
689 #define for_each_sched_entity(se) \
690 for (; se; se = NULL)
692 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
694 return &task_rq(p
)->cfs
;
697 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
699 struct task_struct
*p
= task_of(se
);
700 struct rq
*rq
= task_rq(p
);
705 /* runqueue "owned" by this group */
706 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
711 static inline struct cfs_rq
*cpu_cfs_rq(struct cfs_rq
*cfs_rq
, int this_cpu
)
713 return &cpu_rq(this_cpu
)->cfs
;
716 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
717 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
720 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
725 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
730 #endif /* CONFIG_FAIR_GROUP_SCHED */
733 * The enqueue_task method is called before nr_running is
734 * increased. Here we update the fair scheduling stats and
735 * then put the task into the rbtree:
737 static void enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int wakeup
)
739 struct cfs_rq
*cfs_rq
;
740 struct sched_entity
*se
= &p
->se
;
742 for_each_sched_entity(se
) {
745 cfs_rq
= cfs_rq_of(se
);
746 enqueue_entity(cfs_rq
, se
, wakeup
);
752 * The dequeue_task method is called before nr_running is
753 * decreased. We remove the task from the rbtree and
754 * update the fair scheduling stats:
756 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int sleep
)
758 struct cfs_rq
*cfs_rq
;
759 struct sched_entity
*se
= &p
->se
;
761 for_each_sched_entity(se
) {
762 cfs_rq
= cfs_rq_of(se
);
763 dequeue_entity(cfs_rq
, se
, sleep
);
764 /* Don't dequeue parent if it has other entities besides us */
765 if (cfs_rq
->load
.weight
)
772 * sched_yield() support is very simple - we dequeue and enqueue.
774 * If compat_yield is turned on then we requeue to the end of the tree.
776 static void yield_task_fair(struct rq
*rq
)
778 struct cfs_rq
*cfs_rq
= task_cfs_rq(rq
->curr
);
779 struct sched_entity
*rightmost
, *se
= &rq
->curr
->se
;
782 * Are we the only task in the tree?
784 if (unlikely(cfs_rq
->nr_running
== 1))
787 if (likely(!sysctl_sched_compat_yield
)) {
788 __update_rq_clock(rq
);
790 * Update run-time statistics of the 'current'.
797 * Find the rightmost entry in the rbtree:
799 rightmost
= __pick_last_entity(cfs_rq
);
801 * Already in the rightmost position?
803 if (unlikely(rightmost
->vruntime
< se
->vruntime
))
807 * Minimally necessary key value to be last in the tree:
808 * Upon rescheduling, sched_class::put_prev_task() will place
809 * 'current' within the tree based on its new key value.
811 se
->vruntime
= rightmost
->vruntime
+ 1;
815 * Preempt the current task with a newly woken task if needed:
817 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
)
819 struct task_struct
*curr
= rq
->curr
;
820 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
821 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
824 if (unlikely(rt_prio(p
->prio
))) {
831 * Batch tasks do not preempt (their preemption is driven by
834 if (unlikely(p
->policy
== SCHED_BATCH
))
837 if (sched_feat(WAKEUP_PREEMPT
)) {
838 while (!is_same_group(se
, pse
)) {
839 se
= parent_entity(se
);
840 pse
= parent_entity(pse
);
843 delta
= se
->vruntime
- pse
->vruntime
;
844 gran
= sysctl_sched_wakeup_granularity
;
845 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
846 gran
= calc_delta_fair(gran
, &se
->load
);
849 int now
= !sched_feat(PREEMPT_RESTRICT
);
851 if (now
|| p
->prio
< curr
->prio
|| !se
->peer_preempt
++)
857 static struct task_struct
*pick_next_task_fair(struct rq
*rq
)
859 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
860 struct sched_entity
*se
;
862 if (unlikely(!cfs_rq
->nr_running
))
866 se
= pick_next_entity(cfs_rq
);
867 cfs_rq
= group_cfs_rq(se
);
874 * Account for a descheduled task:
876 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
878 struct sched_entity
*se
= &prev
->se
;
879 struct cfs_rq
*cfs_rq
;
881 for_each_sched_entity(se
) {
882 cfs_rq
= cfs_rq_of(se
);
883 put_prev_entity(cfs_rq
, se
);
888 /**************************************************
889 * Fair scheduling class load-balancing methods:
893 * Load-balancing iterator. Note: while the runqueue stays locked
894 * during the whole iteration, the current task might be
895 * dequeued so the iterator has to be dequeue-safe. Here we
896 * achieve that by always pre-iterating before returning
899 static struct task_struct
*
900 __load_balance_iterator(struct cfs_rq
*cfs_rq
, struct rb_node
*curr
)
902 struct task_struct
*p
;
907 p
= rb_entry(curr
, struct task_struct
, se
.run_node
);
908 cfs_rq
->rb_load_balance_curr
= rb_next(curr
);
913 static struct task_struct
*load_balance_start_fair(void *arg
)
915 struct cfs_rq
*cfs_rq
= arg
;
917 return __load_balance_iterator(cfs_rq
, first_fair(cfs_rq
));
920 static struct task_struct
*load_balance_next_fair(void *arg
)
922 struct cfs_rq
*cfs_rq
= arg
;
924 return __load_balance_iterator(cfs_rq
, cfs_rq
->rb_load_balance_curr
);
927 #ifdef CONFIG_FAIR_GROUP_SCHED
928 static int cfs_rq_best_prio(struct cfs_rq
*cfs_rq
)
930 struct sched_entity
*curr
;
931 struct task_struct
*p
;
933 if (!cfs_rq
->nr_running
)
938 curr
= __pick_next_entity(cfs_rq
);
947 load_balance_fair(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
948 unsigned long max_load_move
,
949 struct sched_domain
*sd
, enum cpu_idle_type idle
,
950 int *all_pinned
, int *this_best_prio
)
952 struct cfs_rq
*busy_cfs_rq
;
953 long rem_load_move
= max_load_move
;
954 struct rq_iterator cfs_rq_iterator
;
956 cfs_rq_iterator
.start
= load_balance_start_fair
;
957 cfs_rq_iterator
.next
= load_balance_next_fair
;
959 for_each_leaf_cfs_rq(busiest
, busy_cfs_rq
) {
960 #ifdef CONFIG_FAIR_GROUP_SCHED
961 struct cfs_rq
*this_cfs_rq
;
963 unsigned long maxload
;
965 this_cfs_rq
= cpu_cfs_rq(busy_cfs_rq
, this_cpu
);
967 imbalance
= busy_cfs_rq
->load
.weight
- this_cfs_rq
->load
.weight
;
968 /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
972 /* Don't pull more than imbalance/2 */
974 maxload
= min(rem_load_move
, imbalance
);
976 *this_best_prio
= cfs_rq_best_prio(this_cfs_rq
);
978 # define maxload rem_load_move
981 * pass busy_cfs_rq argument into
982 * load_balance_[start|next]_fair iterators
984 cfs_rq_iterator
.arg
= busy_cfs_rq
;
985 rem_load_move
-= balance_tasks(this_rq
, this_cpu
, busiest
,
986 maxload
, sd
, idle
, all_pinned
,
990 if (rem_load_move
<= 0)
994 return max_load_move
- rem_load_move
;
998 move_one_task_fair(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
999 struct sched_domain
*sd
, enum cpu_idle_type idle
)
1001 struct cfs_rq
*busy_cfs_rq
;
1002 struct rq_iterator cfs_rq_iterator
;
1004 cfs_rq_iterator
.start
= load_balance_start_fair
;
1005 cfs_rq_iterator
.next
= load_balance_next_fair
;
1007 for_each_leaf_cfs_rq(busiest
, busy_cfs_rq
) {
1009 * pass busy_cfs_rq argument into
1010 * load_balance_[start|next]_fair iterators
1012 cfs_rq_iterator
.arg
= busy_cfs_rq
;
1013 if (iter_move_one_task(this_rq
, this_cpu
, busiest
, sd
, idle
,
1023 * scheduler tick hitting a task of our scheduling class:
1025 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
)
1027 struct cfs_rq
*cfs_rq
;
1028 struct sched_entity
*se
= &curr
->se
;
1030 for_each_sched_entity(se
) {
1031 cfs_rq
= cfs_rq_of(se
);
1032 entity_tick(cfs_rq
, se
);
1036 #define swap(a, b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
1039 * Share the fairness runtime between parent and child, thus the
1040 * total amount of pressure for CPU stays equal - new tasks
1041 * get a chance to run but frequent forkers are not allowed to
1042 * monopolize the CPU. Note: the parent runqueue is locked,
1043 * the child is not running yet.
1045 static void task_new_fair(struct rq
*rq
, struct task_struct
*p
)
1047 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
1048 struct sched_entity
*se
= &p
->se
, *curr
= cfs_rq
->curr
;
1049 int this_cpu
= smp_processor_id();
1051 sched_info_queued(p
);
1053 update_curr(cfs_rq
);
1054 place_entity(cfs_rq
, se
, 1);
1056 if (sysctl_sched_child_runs_first
&& this_cpu
== task_cpu(p
) &&
1057 curr
->vruntime
< se
->vruntime
) {
1059 * Upon rescheduling, sched_class::put_prev_task() will place
1060 * 'current' within the tree based on its new key value.
1062 swap(curr
->vruntime
, se
->vruntime
);
1065 se
->peer_preempt
= 0;
1066 enqueue_task_fair(rq
, p
, 0);
1067 resched_task(rq
->curr
);
1070 /* Account for a task changing its policy or group.
1072 * This routine is mostly called to set cfs_rq->curr field when a task
1073 * migrates between groups/classes.
1075 static void set_curr_task_fair(struct rq
*rq
)
1077 struct sched_entity
*se
= &rq
->curr
->se
;
1079 for_each_sched_entity(se
)
1080 set_next_entity(cfs_rq_of(se
), se
);
1084 * All the scheduling class methods:
1086 static const struct sched_class fair_sched_class
= {
1087 .next
= &idle_sched_class
,
1088 .enqueue_task
= enqueue_task_fair
,
1089 .dequeue_task
= dequeue_task_fair
,
1090 .yield_task
= yield_task_fair
,
1092 .check_preempt_curr
= check_preempt_wakeup
,
1094 .pick_next_task
= pick_next_task_fair
,
1095 .put_prev_task
= put_prev_task_fair
,
1098 .load_balance
= load_balance_fair
,
1099 .move_one_task
= move_one_task_fair
,
1102 .set_curr_task
= set_curr_task_fair
,
1103 .task_tick
= task_tick_fair
,
1104 .task_new
= task_new_fair
,
1107 #ifdef CONFIG_SCHED_DEBUG
1108 static void print_cfs_stats(struct seq_file
*m
, int cpu
)
1110 struct cfs_rq
*cfs_rq
;
1112 #ifdef CONFIG_FAIR_GROUP_SCHED
1113 print_cfs_rq(m
, cpu
, &cpu_rq(cpu
)->cfs
);
1115 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
1116 print_cfs_rq(m
, cpu
, cfs_rq
);