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: 20ms * (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
= 20000000ULL;
40 * Minimal preemption granularity for CPU-bound tasks:
41 * (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds)
43 unsigned int sysctl_sched_min_granularity
= 4000000ULL;
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. (default) If set to 0 then
52 * parent will (try to) run first.
54 const_debug
unsigned int sysctl_sched_child_runs_first
= 1;
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_BATCH wake-up granularity.
66 * (default: 10 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_batch_wakeup_granularity
= 10000000UL;
75 * SCHED_OTHER wake-up granularity.
76 * (default: 10 msec * (1 + ilog(ncpus)), units: nanoseconds)
78 * This option delays the preemption effects of decoupled workloads
79 * and reduces their over-scheduling. Synchronous workloads will still
80 * have immediate wakeup/sleep latencies.
82 unsigned int sysctl_sched_wakeup_granularity
= 10000000UL;
84 const_debug
unsigned int sysctl_sched_migration_cost
= 500000UL;
86 /**************************************************************
87 * CFS operations on generic schedulable entities:
90 #ifdef CONFIG_FAIR_GROUP_SCHED
92 /* cpu runqueue to which this cfs_rq is attached */
93 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
98 /* An entity is a task if it doesn't "own" a runqueue */
99 #define entity_is_task(se) (!se->my_q)
101 #else /* CONFIG_FAIR_GROUP_SCHED */
103 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
105 return container_of(cfs_rq
, struct rq
, cfs
);
108 #define entity_is_task(se) 1
110 #endif /* CONFIG_FAIR_GROUP_SCHED */
112 static inline struct task_struct
*task_of(struct sched_entity
*se
)
114 return container_of(se
, struct task_struct
, se
);
118 /**************************************************************
119 * Scheduling class tree data structure manipulation methods:
122 static inline u64
max_vruntime(u64 min_vruntime
, u64 vruntime
)
124 s64 delta
= (s64
)(vruntime
- min_vruntime
);
126 min_vruntime
= vruntime
;
131 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
133 s64 delta
= (s64
)(vruntime
- min_vruntime
);
135 min_vruntime
= vruntime
;
140 static inline s64
entity_key(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
142 return se
->vruntime
- cfs_rq
->min_vruntime
;
146 * Enqueue an entity into the rb-tree:
148 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
150 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
151 struct rb_node
*parent
= NULL
;
152 struct sched_entity
*entry
;
153 s64 key
= entity_key(cfs_rq
, se
);
157 * Find the right place in the rbtree:
161 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
163 * We dont care about collisions. Nodes with
164 * the same key stay together.
166 if (key
< entity_key(cfs_rq
, entry
)) {
167 link
= &parent
->rb_left
;
169 link
= &parent
->rb_right
;
175 * Maintain a cache of leftmost tree entries (it is frequently
179 cfs_rq
->rb_leftmost
= &se
->run_node
;
181 * maintain cfs_rq->min_vruntime to be a monotonic increasing
182 * value tracking the leftmost vruntime in the tree.
184 cfs_rq
->min_vruntime
=
185 max_vruntime(cfs_rq
->min_vruntime
, se
->vruntime
);
188 rb_link_node(&se
->run_node
, parent
, link
);
189 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
192 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
194 if (cfs_rq
->rb_leftmost
== &se
->run_node
) {
195 struct rb_node
*next_node
;
196 struct sched_entity
*next
;
198 next_node
= rb_next(&se
->run_node
);
199 cfs_rq
->rb_leftmost
= next_node
;
202 next
= rb_entry(next_node
,
203 struct sched_entity
, run_node
);
204 cfs_rq
->min_vruntime
=
205 max_vruntime(cfs_rq
->min_vruntime
,
210 if (cfs_rq
->next
== se
)
213 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
216 static inline struct rb_node
*first_fair(struct cfs_rq
*cfs_rq
)
218 return cfs_rq
->rb_leftmost
;
221 static struct sched_entity
*__pick_next_entity(struct cfs_rq
*cfs_rq
)
223 return rb_entry(first_fair(cfs_rq
), struct sched_entity
, run_node
);
226 static inline struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
228 struct rb_node
*last
= rb_last(&cfs_rq
->tasks_timeline
);
233 return rb_entry(last
, struct sched_entity
, run_node
);
236 /**************************************************************
237 * Scheduling class statistics methods:
240 #ifdef CONFIG_SCHED_DEBUG
241 int sched_nr_latency_handler(struct ctl_table
*table
, int write
,
242 struct file
*filp
, void __user
*buffer
, size_t *lenp
,
245 int ret
= proc_dointvec_minmax(table
, write
, filp
, buffer
, lenp
, ppos
);
250 sched_nr_latency
= DIV_ROUND_UP(sysctl_sched_latency
,
251 sysctl_sched_min_granularity
);
258 * The idea is to set a period in which each task runs once.
260 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
261 * this period because otherwise the slices get too small.
263 * p = (nr <= nl) ? l : l*nr/nl
265 static u64
__sched_period(unsigned long nr_running
)
267 u64 period
= sysctl_sched_latency
;
268 unsigned long nr_latency
= sched_nr_latency
;
270 if (unlikely(nr_running
> nr_latency
)) {
271 period
= sysctl_sched_min_granularity
;
272 period
*= nr_running
;
279 * We calculate the wall-time slice from the period by taking a part
280 * proportional to the weight.
284 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
286 u64 slice
= __sched_period(cfs_rq
->nr_running
);
288 slice
*= se
->load
.weight
;
289 do_div(slice
, cfs_rq
->load
.weight
);
295 * We calculate the vruntime slice.
299 static u64
__sched_vslice(unsigned long rq_weight
, unsigned long nr_running
)
301 u64 vslice
= __sched_period(nr_running
);
303 vslice
*= NICE_0_LOAD
;
304 do_div(vslice
, rq_weight
);
309 static u64
sched_vslice(struct cfs_rq
*cfs_rq
)
311 return __sched_vslice(cfs_rq
->load
.weight
, cfs_rq
->nr_running
);
314 static u64
sched_vslice_add(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
316 return __sched_vslice(cfs_rq
->load
.weight
+ se
->load
.weight
,
317 cfs_rq
->nr_running
+ 1);
321 * Update the current task's runtime statistics. Skip current tasks that
322 * are not in our scheduling class.
325 __update_curr(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
,
326 unsigned long delta_exec
)
328 unsigned long delta_exec_weighted
;
330 schedstat_set(curr
->exec_max
, max((u64
)delta_exec
, curr
->exec_max
));
332 curr
->sum_exec_runtime
+= delta_exec
;
333 schedstat_add(cfs_rq
, exec_clock
, delta_exec
);
334 delta_exec_weighted
= delta_exec
;
335 if (unlikely(curr
->load
.weight
!= NICE_0_LOAD
)) {
336 delta_exec_weighted
= calc_delta_fair(delta_exec_weighted
,
339 curr
->vruntime
+= delta_exec_weighted
;
342 static void update_curr(struct cfs_rq
*cfs_rq
)
344 struct sched_entity
*curr
= cfs_rq
->curr
;
345 u64 now
= rq_of(cfs_rq
)->clock
;
346 unsigned long delta_exec
;
352 * Get the amount of time the current task was running
353 * since the last time we changed load (this cannot
354 * overflow on 32 bits):
356 delta_exec
= (unsigned long)(now
- curr
->exec_start
);
358 __update_curr(cfs_rq
, curr
, delta_exec
);
359 curr
->exec_start
= now
;
361 if (entity_is_task(curr
)) {
362 struct task_struct
*curtask
= task_of(curr
);
364 cpuacct_charge(curtask
, delta_exec
);
369 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
371 schedstat_set(se
->wait_start
, rq_of(cfs_rq
)->clock
);
375 * Task is being enqueued - update stats:
377 static void update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
380 * Are we enqueueing a waiting task? (for current tasks
381 * a dequeue/enqueue event is a NOP)
383 if (se
!= cfs_rq
->curr
)
384 update_stats_wait_start(cfs_rq
, se
);
388 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
390 schedstat_set(se
->wait_max
, max(se
->wait_max
,
391 rq_of(cfs_rq
)->clock
- se
->wait_start
));
392 schedstat_set(se
->wait_count
, se
->wait_count
+ 1);
393 schedstat_set(se
->wait_sum
, se
->wait_sum
+
394 rq_of(cfs_rq
)->clock
- se
->wait_start
);
395 schedstat_set(se
->wait_start
, 0);
399 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
402 * Mark the end of the wait period if dequeueing a
405 if (se
!= cfs_rq
->curr
)
406 update_stats_wait_end(cfs_rq
, se
);
410 * We are picking a new current task - update its stats:
413 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
416 * We are starting a new run period:
418 se
->exec_start
= rq_of(cfs_rq
)->clock
;
421 /**************************************************
422 * Scheduling class queueing methods:
426 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
428 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
429 cfs_rq
->nr_running
++;
434 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
436 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
437 cfs_rq
->nr_running
--;
441 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
443 #ifdef CONFIG_SCHEDSTATS
444 if (se
->sleep_start
) {
445 u64 delta
= rq_of(cfs_rq
)->clock
- se
->sleep_start
;
446 struct task_struct
*tsk
= task_of(se
);
451 if (unlikely(delta
> se
->sleep_max
))
452 se
->sleep_max
= delta
;
455 se
->sum_sleep_runtime
+= delta
;
457 account_scheduler_latency(tsk
, delta
>> 10, 1);
459 if (se
->block_start
) {
460 u64 delta
= rq_of(cfs_rq
)->clock
- se
->block_start
;
461 struct task_struct
*tsk
= task_of(se
);
466 if (unlikely(delta
> se
->block_max
))
467 se
->block_max
= delta
;
470 se
->sum_sleep_runtime
+= delta
;
473 * Blocking time is in units of nanosecs, so shift by 20 to
474 * get a milliseconds-range estimation of the amount of
475 * time that the task spent sleeping:
477 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
479 profile_hits(SLEEP_PROFILING
, (void *)get_wchan(tsk
),
482 account_scheduler_latency(tsk
, delta
>> 10, 0);
487 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
489 #ifdef CONFIG_SCHED_DEBUG
490 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
495 if (d
> 3*sysctl_sched_latency
)
496 schedstat_inc(cfs_rq
, nr_spread_over
);
501 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
505 if (first_fair(cfs_rq
)) {
506 vruntime
= min_vruntime(cfs_rq
->min_vruntime
,
507 __pick_next_entity(cfs_rq
)->vruntime
);
509 vruntime
= cfs_rq
->min_vruntime
;
511 if (sched_feat(TREE_AVG
)) {
512 struct sched_entity
*last
= __pick_last_entity(cfs_rq
);
514 vruntime
+= last
->vruntime
;
517 } else if (sched_feat(APPROX_AVG
) && cfs_rq
->nr_running
)
518 vruntime
+= sched_vslice(cfs_rq
)/2;
521 * The 'current' period is already promised to the current tasks,
522 * however the extra weight of the new task will slow them down a
523 * little, place the new task so that it fits in the slot that
524 * stays open at the end.
526 if (initial
&& sched_feat(START_DEBIT
))
527 vruntime
+= sched_vslice_add(cfs_rq
, se
);
530 /* sleeps upto a single latency don't count. */
531 if (sched_feat(NEW_FAIR_SLEEPERS
)) {
532 vruntime
-= calc_delta_fair(sysctl_sched_latency
,
536 /* ensure we never gain time by being placed backwards. */
537 vruntime
= max_vruntime(se
->vruntime
, vruntime
);
540 se
->vruntime
= vruntime
;
544 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int wakeup
)
547 * Update run-time statistics of the 'current'.
552 place_entity(cfs_rq
, se
, 0);
553 enqueue_sleeper(cfs_rq
, se
);
556 update_stats_enqueue(cfs_rq
, se
);
557 check_spread(cfs_rq
, se
);
558 if (se
!= cfs_rq
->curr
)
559 __enqueue_entity(cfs_rq
, se
);
560 account_entity_enqueue(cfs_rq
, se
);
564 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int sleep
)
567 * Update run-time statistics of the 'current'.
571 update_stats_dequeue(cfs_rq
, se
);
573 #ifdef CONFIG_SCHEDSTATS
574 if (entity_is_task(se
)) {
575 struct task_struct
*tsk
= task_of(se
);
577 if (tsk
->state
& TASK_INTERRUPTIBLE
)
578 se
->sleep_start
= rq_of(cfs_rq
)->clock
;
579 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
580 se
->block_start
= rq_of(cfs_rq
)->clock
;
585 if (se
!= cfs_rq
->curr
)
586 __dequeue_entity(cfs_rq
, se
);
587 account_entity_dequeue(cfs_rq
, se
);
591 * Preempt the current task with a newly woken task if needed:
594 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
596 unsigned long ideal_runtime
, delta_exec
;
598 ideal_runtime
= sched_slice(cfs_rq
, curr
);
599 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
600 if (delta_exec
> ideal_runtime
)
601 resched_task(rq_of(cfs_rq
)->curr
);
605 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
607 /* 'current' is not kept within the tree. */
610 * Any task has to be enqueued before it get to execute on
611 * a CPU. So account for the time it spent waiting on the
614 update_stats_wait_end(cfs_rq
, se
);
615 __dequeue_entity(cfs_rq
, se
);
618 update_stats_curr_start(cfs_rq
, se
);
620 #ifdef CONFIG_SCHEDSTATS
622 * Track our maximum slice length, if the CPU's load is at
623 * least twice that of our own weight (i.e. dont track it
624 * when there are only lesser-weight tasks around):
626 if (rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
627 se
->slice_max
= max(se
->slice_max
,
628 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
631 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
634 static struct sched_entity
*
635 pick_next(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
642 diff
= cfs_rq
->next
->vruntime
- se
->vruntime
;
646 gran
= calc_delta_fair(sysctl_sched_wakeup_granularity
, &cfs_rq
->load
);
653 static struct sched_entity
*pick_next_entity(struct cfs_rq
*cfs_rq
)
655 struct sched_entity
*se
= NULL
;
657 if (first_fair(cfs_rq
)) {
658 se
= __pick_next_entity(cfs_rq
);
659 se
= pick_next(cfs_rq
, se
);
660 set_next_entity(cfs_rq
, se
);
666 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
669 * If still on the runqueue then deactivate_task()
670 * was not called and update_curr() has to be done:
675 check_spread(cfs_rq
, prev
);
677 update_stats_wait_start(cfs_rq
, prev
);
678 /* Put 'current' back into the tree. */
679 __enqueue_entity(cfs_rq
, prev
);
685 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
688 * Update run-time statistics of the 'current'.
692 #ifdef CONFIG_SCHED_HRTICK
694 * queued ticks are scheduled to match the slice, so don't bother
695 * validating it and just reschedule.
698 return resched_task(rq_of(cfs_rq
)->curr
);
700 * don't let the period tick interfere with the hrtick preemption
702 if (!sched_feat(DOUBLE_TICK
) &&
703 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
707 if (cfs_rq
->nr_running
> 1 || !sched_feat(WAKEUP_PREEMPT
))
708 check_preempt_tick(cfs_rq
, curr
);
711 /**************************************************
712 * CFS operations on tasks:
715 #ifdef CONFIG_FAIR_GROUP_SCHED
717 /* Walk up scheduling entities hierarchy */
718 #define for_each_sched_entity(se) \
719 for (; se; se = se->parent)
721 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
726 /* runqueue on which this entity is (to be) queued */
727 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
732 /* runqueue "owned" by this group */
733 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
738 /* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
739 * another cpu ('this_cpu')
741 static inline struct cfs_rq
*cpu_cfs_rq(struct cfs_rq
*cfs_rq
, int this_cpu
)
743 return cfs_rq
->tg
->cfs_rq
[this_cpu
];
746 /* Iterate thr' all leaf cfs_rq's on a runqueue */
747 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
748 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
750 /* Do the two (enqueued) entities belong to the same group ? */
752 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
754 if (se
->cfs_rq
== pse
->cfs_rq
)
760 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
765 #else /* CONFIG_FAIR_GROUP_SCHED */
767 #define for_each_sched_entity(se) \
768 for (; se; se = NULL)
770 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
772 return &task_rq(p
)->cfs
;
775 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
777 struct task_struct
*p
= task_of(se
);
778 struct rq
*rq
= task_rq(p
);
783 /* runqueue "owned" by this group */
784 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
789 static inline struct cfs_rq
*cpu_cfs_rq(struct cfs_rq
*cfs_rq
, int this_cpu
)
791 return &cpu_rq(this_cpu
)->cfs
;
794 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
795 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
798 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
803 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
808 #endif /* CONFIG_FAIR_GROUP_SCHED */
810 #ifdef CONFIG_SCHED_HRTICK
811 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
813 int requeue
= rq
->curr
== p
;
814 struct sched_entity
*se
= &p
->se
;
815 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
817 WARN_ON(task_rq(p
) != rq
);
819 if (hrtick_enabled(rq
) && cfs_rq
->nr_running
> 1) {
820 u64 slice
= sched_slice(cfs_rq
, se
);
821 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
822 s64 delta
= slice
- ran
;
831 * Don't schedule slices shorter than 10000ns, that just
832 * doesn't make sense. Rely on vruntime for fairness.
835 delta
= max(10000LL, delta
);
837 hrtick_start(rq
, delta
, requeue
);
842 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
848 * The enqueue_task method is called before nr_running is
849 * increased. Here we update the fair scheduling stats and
850 * then put the task into the rbtree:
852 static void enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int wakeup
)
854 struct cfs_rq
*cfs_rq
;
855 struct sched_entity
*se
= &p
->se
;
857 for_each_sched_entity(se
) {
860 cfs_rq
= cfs_rq_of(se
);
861 enqueue_entity(cfs_rq
, se
, wakeup
);
865 hrtick_start_fair(rq
, rq
->curr
);
869 * The dequeue_task method is called before nr_running is
870 * decreased. We remove the task from the rbtree and
871 * update the fair scheduling stats:
873 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int sleep
)
875 struct cfs_rq
*cfs_rq
;
876 struct sched_entity
*se
= &p
->se
;
878 for_each_sched_entity(se
) {
879 cfs_rq
= cfs_rq_of(se
);
880 dequeue_entity(cfs_rq
, se
, sleep
);
881 /* Don't dequeue parent if it has other entities besides us */
882 if (cfs_rq
->load
.weight
)
887 hrtick_start_fair(rq
, rq
->curr
);
891 * sched_yield() support is very simple - we dequeue and enqueue.
893 * If compat_yield is turned on then we requeue to the end of the tree.
895 static void yield_task_fair(struct rq
*rq
)
897 struct task_struct
*curr
= rq
->curr
;
898 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
899 struct sched_entity
*rightmost
, *se
= &curr
->se
;
902 * Are we the only task in the tree?
904 if (unlikely(cfs_rq
->nr_running
== 1))
907 if (likely(!sysctl_sched_compat_yield
) && curr
->policy
!= SCHED_BATCH
) {
908 __update_rq_clock(rq
);
910 * Update run-time statistics of the 'current'.
917 * Find the rightmost entry in the rbtree:
919 rightmost
= __pick_last_entity(cfs_rq
);
921 * Already in the rightmost position?
923 if (unlikely(rightmost
->vruntime
< se
->vruntime
))
927 * Minimally necessary key value to be last in the tree:
928 * Upon rescheduling, sched_class::put_prev_task() will place
929 * 'current' within the tree based on its new key value.
931 se
->vruntime
= rightmost
->vruntime
+ 1;
935 * wake_idle() will wake a task on an idle cpu if task->cpu is
936 * not idle and an idle cpu is available. The span of cpus to
937 * search starts with cpus closest then further out as needed,
938 * so we always favor a closer, idle cpu.
940 * Returns the CPU we should wake onto.
942 #if defined(ARCH_HAS_SCHED_WAKE_IDLE)
943 static int wake_idle(int cpu
, struct task_struct
*p
)
946 struct sched_domain
*sd
;
950 * If it is idle, then it is the best cpu to run this task.
952 * This cpu is also the best, if it has more than one task already.
953 * Siblings must be also busy(in most cases) as they didn't already
954 * pickup the extra load from this cpu and hence we need not check
955 * sibling runqueue info. This will avoid the checks and cache miss
956 * penalities associated with that.
958 if (idle_cpu(cpu
) || cpu_rq(cpu
)->nr_running
> 1)
961 for_each_domain(cpu
, sd
) {
962 if (sd
->flags
& SD_WAKE_IDLE
) {
963 cpus_and(tmp
, sd
->span
, p
->cpus_allowed
);
964 for_each_cpu_mask(i
, tmp
) {
966 if (i
!= task_cpu(p
)) {
980 static inline int wake_idle(int cpu
, struct task_struct
*p
)
987 static int select_task_rq_fair(struct task_struct
*p
, int sync
)
991 struct sched_domain
*sd
, *this_sd
= NULL
;
996 this_cpu
= smp_processor_id();
1002 for_each_domain(this_cpu
, sd
) {
1003 if (cpu_isset(cpu
, sd
->span
)) {
1009 if (unlikely(!cpu_isset(this_cpu
, p
->cpus_allowed
)))
1013 * Check for affine wakeup and passive balancing possibilities.
1016 int idx
= this_sd
->wake_idx
;
1017 unsigned int imbalance
;
1018 unsigned long load
, this_load
;
1020 imbalance
= 100 + (this_sd
->imbalance_pct
- 100) / 2;
1022 load
= source_load(cpu
, idx
);
1023 this_load
= target_load(this_cpu
, idx
);
1025 new_cpu
= this_cpu
; /* Wake to this CPU if we can */
1027 if (this_sd
->flags
& SD_WAKE_AFFINE
) {
1028 unsigned long tl
= this_load
;
1029 unsigned long tl_per_task
;
1032 * Attract cache-cold tasks on sync wakeups:
1034 if (sync
&& !task_hot(p
, rq
->clock
, this_sd
))
1037 schedstat_inc(p
, se
.nr_wakeups_affine_attempts
);
1038 tl_per_task
= cpu_avg_load_per_task(this_cpu
);
1041 * If sync wakeup then subtract the (maximum possible)
1042 * effect of the currently running task from the load
1043 * of the current CPU:
1046 tl
-= current
->se
.load
.weight
;
1049 tl
+ target_load(cpu
, idx
) <= tl_per_task
) ||
1050 100*(tl
+ p
->se
.load
.weight
) <= imbalance
*load
) {
1052 * This domain has SD_WAKE_AFFINE and
1053 * p is cache cold in this domain, and
1054 * there is no bad imbalance.
1056 schedstat_inc(this_sd
, ttwu_move_affine
);
1057 schedstat_inc(p
, se
.nr_wakeups_affine
);
1063 * Start passive balancing when half the imbalance_pct
1066 if (this_sd
->flags
& SD_WAKE_BALANCE
) {
1067 if (imbalance
*this_load
<= 100*load
) {
1068 schedstat_inc(this_sd
, ttwu_move_balance
);
1069 schedstat_inc(p
, se
.nr_wakeups_passive
);
1075 new_cpu
= cpu
; /* Could not wake to this_cpu. Wake to cpu instead */
1077 return wake_idle(new_cpu
, p
);
1079 #endif /* CONFIG_SMP */
1083 * Preempt the current task with a newly woken task if needed:
1085 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
)
1087 struct task_struct
*curr
= rq
->curr
;
1088 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
1089 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
1092 if (unlikely(rt_prio(p
->prio
))) {
1093 update_rq_clock(rq
);
1094 update_curr(cfs_rq
);
1099 cfs_rq_of(pse
)->next
= pse
;
1102 * Batch tasks do not preempt (their preemption is driven by
1105 if (unlikely(p
->policy
== SCHED_BATCH
))
1108 if (!sched_feat(WAKEUP_PREEMPT
))
1111 while (!is_same_group(se
, pse
)) {
1112 se
= parent_entity(se
);
1113 pse
= parent_entity(pse
);
1116 gran
= sysctl_sched_wakeup_granularity
;
1118 * More easily preempt - nice tasks, while not making
1119 * it harder for + nice tasks.
1121 if (unlikely(se
->load
.weight
> NICE_0_LOAD
))
1122 gran
= calc_delta_fair(gran
, &se
->load
);
1124 if (pse
->vruntime
+ gran
< se
->vruntime
)
1128 static struct task_struct
*pick_next_task_fair(struct rq
*rq
)
1130 struct task_struct
*p
;
1131 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
1132 struct sched_entity
*se
;
1134 if (unlikely(!cfs_rq
->nr_running
))
1138 se
= pick_next_entity(cfs_rq
);
1139 cfs_rq
= group_cfs_rq(se
);
1143 hrtick_start_fair(rq
, p
);
1149 * Account for a descheduled task:
1151 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
1153 struct sched_entity
*se
= &prev
->se
;
1154 struct cfs_rq
*cfs_rq
;
1156 for_each_sched_entity(se
) {
1157 cfs_rq
= cfs_rq_of(se
);
1158 put_prev_entity(cfs_rq
, se
);
1163 /**************************************************
1164 * Fair scheduling class load-balancing methods:
1168 * Load-balancing iterator. Note: while the runqueue stays locked
1169 * during the whole iteration, the current task might be
1170 * dequeued so the iterator has to be dequeue-safe. Here we
1171 * achieve that by always pre-iterating before returning
1174 static struct task_struct
*
1175 __load_balance_iterator(struct cfs_rq
*cfs_rq
, struct rb_node
*curr
)
1177 struct task_struct
*p
;
1182 p
= rb_entry(curr
, struct task_struct
, se
.run_node
);
1183 cfs_rq
->rb_load_balance_curr
= rb_next(curr
);
1188 static struct task_struct
*load_balance_start_fair(void *arg
)
1190 struct cfs_rq
*cfs_rq
= arg
;
1192 return __load_balance_iterator(cfs_rq
, first_fair(cfs_rq
));
1195 static struct task_struct
*load_balance_next_fair(void *arg
)
1197 struct cfs_rq
*cfs_rq
= arg
;
1199 return __load_balance_iterator(cfs_rq
, cfs_rq
->rb_load_balance_curr
);
1202 #ifdef CONFIG_FAIR_GROUP_SCHED
1203 static int cfs_rq_best_prio(struct cfs_rq
*cfs_rq
)
1205 struct sched_entity
*curr
;
1206 struct task_struct
*p
;
1208 if (!cfs_rq
->nr_running
|| !first_fair(cfs_rq
))
1211 curr
= cfs_rq
->curr
;
1213 curr
= __pick_next_entity(cfs_rq
);
1221 static unsigned long
1222 load_balance_fair(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
1223 unsigned long max_load_move
,
1224 struct sched_domain
*sd
, enum cpu_idle_type idle
,
1225 int *all_pinned
, int *this_best_prio
)
1227 struct cfs_rq
*busy_cfs_rq
;
1228 long rem_load_move
= max_load_move
;
1229 struct rq_iterator cfs_rq_iterator
;
1231 cfs_rq_iterator
.start
= load_balance_start_fair
;
1232 cfs_rq_iterator
.next
= load_balance_next_fair
;
1234 for_each_leaf_cfs_rq(busiest
, busy_cfs_rq
) {
1235 #ifdef CONFIG_FAIR_GROUP_SCHED
1236 struct cfs_rq
*this_cfs_rq
;
1238 unsigned long maxload
;
1240 this_cfs_rq
= cpu_cfs_rq(busy_cfs_rq
, this_cpu
);
1242 imbalance
= busy_cfs_rq
->load
.weight
- this_cfs_rq
->load
.weight
;
1243 /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
1247 /* Don't pull more than imbalance/2 */
1249 maxload
= min(rem_load_move
, imbalance
);
1251 *this_best_prio
= cfs_rq_best_prio(this_cfs_rq
);
1253 # define maxload rem_load_move
1256 * pass busy_cfs_rq argument into
1257 * load_balance_[start|next]_fair iterators
1259 cfs_rq_iterator
.arg
= busy_cfs_rq
;
1260 rem_load_move
-= balance_tasks(this_rq
, this_cpu
, busiest
,
1261 maxload
, sd
, idle
, all_pinned
,
1265 if (rem_load_move
<= 0)
1269 return max_load_move
- rem_load_move
;
1273 move_one_task_fair(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
1274 struct sched_domain
*sd
, enum cpu_idle_type idle
)
1276 struct cfs_rq
*busy_cfs_rq
;
1277 struct rq_iterator cfs_rq_iterator
;
1279 cfs_rq_iterator
.start
= load_balance_start_fair
;
1280 cfs_rq_iterator
.next
= load_balance_next_fair
;
1282 for_each_leaf_cfs_rq(busiest
, busy_cfs_rq
) {
1284 * pass busy_cfs_rq argument into
1285 * load_balance_[start|next]_fair iterators
1287 cfs_rq_iterator
.arg
= busy_cfs_rq
;
1288 if (iter_move_one_task(this_rq
, this_cpu
, busiest
, sd
, idle
,
1298 * scheduler tick hitting a task of our scheduling class:
1300 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
1302 struct cfs_rq
*cfs_rq
;
1303 struct sched_entity
*se
= &curr
->se
;
1305 for_each_sched_entity(se
) {
1306 cfs_rq
= cfs_rq_of(se
);
1307 entity_tick(cfs_rq
, se
, queued
);
1311 #define swap(a, b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
1314 * Share the fairness runtime between parent and child, thus the
1315 * total amount of pressure for CPU stays equal - new tasks
1316 * get a chance to run but frequent forkers are not allowed to
1317 * monopolize the CPU. Note: the parent runqueue is locked,
1318 * the child is not running yet.
1320 static void task_new_fair(struct rq
*rq
, struct task_struct
*p
)
1322 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
1323 struct sched_entity
*se
= &p
->se
, *curr
= cfs_rq
->curr
;
1324 int this_cpu
= smp_processor_id();
1326 sched_info_queued(p
);
1328 update_curr(cfs_rq
);
1329 place_entity(cfs_rq
, se
, 1);
1331 /* 'curr' will be NULL if the child belongs to a different group */
1332 if (sysctl_sched_child_runs_first
&& this_cpu
== task_cpu(p
) &&
1333 curr
&& curr
->vruntime
< se
->vruntime
) {
1335 * Upon rescheduling, sched_class::put_prev_task() will place
1336 * 'current' within the tree based on its new key value.
1338 swap(curr
->vruntime
, se
->vruntime
);
1341 enqueue_task_fair(rq
, p
, 0);
1342 resched_task(rq
->curr
);
1346 * Priority of the task has changed. Check to see if we preempt
1349 static void prio_changed_fair(struct rq
*rq
, struct task_struct
*p
,
1350 int oldprio
, int running
)
1353 * Reschedule if we are currently running on this runqueue and
1354 * our priority decreased, or if we are not currently running on
1355 * this runqueue and our priority is higher than the current's
1358 if (p
->prio
> oldprio
)
1359 resched_task(rq
->curr
);
1361 check_preempt_curr(rq
, p
);
1365 * We switched to the sched_fair class.
1367 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
,
1371 * We were most likely switched from sched_rt, so
1372 * kick off the schedule if running, otherwise just see
1373 * if we can still preempt the current task.
1376 resched_task(rq
->curr
);
1378 check_preempt_curr(rq
, p
);
1381 /* Account for a task changing its policy or group.
1383 * This routine is mostly called to set cfs_rq->curr field when a task
1384 * migrates between groups/classes.
1386 static void set_curr_task_fair(struct rq
*rq
)
1388 struct sched_entity
*se
= &rq
->curr
->se
;
1390 for_each_sched_entity(se
)
1391 set_next_entity(cfs_rq_of(se
), se
);
1394 #ifdef CONFIG_FAIR_GROUP_SCHED
1395 static void moved_group_fair(struct task_struct
*p
)
1397 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
1399 update_curr(cfs_rq
);
1400 place_entity(cfs_rq
, &p
->se
, 1);
1405 * All the scheduling class methods:
1407 static const struct sched_class fair_sched_class
= {
1408 .next
= &idle_sched_class
,
1409 .enqueue_task
= enqueue_task_fair
,
1410 .dequeue_task
= dequeue_task_fair
,
1411 .yield_task
= yield_task_fair
,
1413 .select_task_rq
= select_task_rq_fair
,
1414 #endif /* CONFIG_SMP */
1416 .check_preempt_curr
= check_preempt_wakeup
,
1418 .pick_next_task
= pick_next_task_fair
,
1419 .put_prev_task
= put_prev_task_fair
,
1422 .load_balance
= load_balance_fair
,
1423 .move_one_task
= move_one_task_fair
,
1426 .set_curr_task
= set_curr_task_fair
,
1427 .task_tick
= task_tick_fair
,
1428 .task_new
= task_new_fair
,
1430 .prio_changed
= prio_changed_fair
,
1431 .switched_to
= switched_to_fair
,
1433 #ifdef CONFIG_FAIR_GROUP_SCHED
1434 .moved_group
= moved_group_fair
,
1438 #ifdef CONFIG_SCHED_DEBUG
1439 static void print_cfs_stats(struct seq_file
*m
, int cpu
)
1441 struct cfs_rq
*cfs_rq
;
1443 #ifdef CONFIG_FAIR_GROUP_SCHED
1444 print_cfs_rq(m
, cpu
, &cpu_rq(cpu
)->cfs
);
1447 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
1448 print_cfs_rq(m
, cpu
, cfs_rq
);