2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
23 #include <linux/latencytop.h>
24 #include <linux/sched.h>
25 #include <linux/cpumask.h>
26 #include <linux/slab.h>
27 #include <linux/profile.h>
28 #include <linux/interrupt.h>
29 #include <linux/mempolicy.h>
30 #include <linux/migrate.h>
31 #include <linux/task_work.h>
33 #include <trace/events/sched.h>
38 * Targeted preemption latency for CPU-bound tasks:
39 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
41 * NOTE: this latency value is not the same as the concept of
42 * 'timeslice length' - timeslices in CFS are of variable length
43 * and have no persistent notion like in traditional, time-slice
44 * based scheduling concepts.
46 * (to see the precise effective timeslice length of your workload,
47 * run vmstat and monitor the context-switches (cs) field)
49 unsigned int sysctl_sched_latency
= 6000000ULL;
50 unsigned int normalized_sysctl_sched_latency
= 6000000ULL;
53 * The initial- and re-scaling of tunables is configurable
54 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
57 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
58 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
59 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
61 enum sched_tunable_scaling sysctl_sched_tunable_scaling
62 = SCHED_TUNABLESCALING_LOG
;
65 * Minimal preemption granularity for CPU-bound tasks:
66 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
68 unsigned int sysctl_sched_min_granularity
= 750000ULL;
69 unsigned int normalized_sysctl_sched_min_granularity
= 750000ULL;
72 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
74 static unsigned int sched_nr_latency
= 8;
77 * After fork, child runs first. If set to 0 (default) then
78 * parent will (try to) run first.
80 unsigned int sysctl_sched_child_runs_first __read_mostly
;
83 * SCHED_OTHER wake-up granularity.
84 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
86 * This option delays the preemption effects of decoupled workloads
87 * and reduces their over-scheduling. Synchronous workloads will still
88 * have immediate wakeup/sleep latencies.
90 unsigned int sysctl_sched_wakeup_granularity
= 1000000UL;
91 unsigned int normalized_sysctl_sched_wakeup_granularity
= 1000000UL;
93 const_debug
unsigned int sysctl_sched_migration_cost
= 500000UL;
96 * The exponential sliding window over which load is averaged for shares
100 unsigned int __read_mostly sysctl_sched_shares_window
= 10000000UL;
102 #ifdef CONFIG_CFS_BANDWIDTH
104 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
105 * each time a cfs_rq requests quota.
107 * Note: in the case that the slice exceeds the runtime remaining (either due
108 * to consumption or the quota being specified to be smaller than the slice)
109 * we will always only issue the remaining available time.
111 * default: 5 msec, units: microseconds
113 unsigned int sysctl_sched_cfs_bandwidth_slice
= 5000UL;
116 static inline void update_load_add(struct load_weight
*lw
, unsigned long inc
)
122 static inline void update_load_sub(struct load_weight
*lw
, unsigned long dec
)
128 static inline void update_load_set(struct load_weight
*lw
, unsigned long w
)
135 * Increase the granularity value when there are more CPUs,
136 * because with more CPUs the 'effective latency' as visible
137 * to users decreases. But the relationship is not linear,
138 * so pick a second-best guess by going with the log2 of the
141 * This idea comes from the SD scheduler of Con Kolivas:
143 static int get_update_sysctl_factor(void)
145 unsigned int cpus
= min_t(int, num_online_cpus(), 8);
148 switch (sysctl_sched_tunable_scaling
) {
149 case SCHED_TUNABLESCALING_NONE
:
152 case SCHED_TUNABLESCALING_LINEAR
:
155 case SCHED_TUNABLESCALING_LOG
:
157 factor
= 1 + ilog2(cpus
);
164 static void update_sysctl(void)
166 unsigned int factor
= get_update_sysctl_factor();
168 #define SET_SYSCTL(name) \
169 (sysctl_##name = (factor) * normalized_sysctl_##name)
170 SET_SYSCTL(sched_min_granularity
);
171 SET_SYSCTL(sched_latency
);
172 SET_SYSCTL(sched_wakeup_granularity
);
176 void sched_init_granularity(void)
181 #define WMULT_CONST (~0U)
182 #define WMULT_SHIFT 32
184 static void __update_inv_weight(struct load_weight
*lw
)
188 if (likely(lw
->inv_weight
))
191 w
= scale_load_down(lw
->weight
);
193 if (BITS_PER_LONG
> 32 && unlikely(w
>= WMULT_CONST
))
195 else if (unlikely(!w
))
196 lw
->inv_weight
= WMULT_CONST
;
198 lw
->inv_weight
= WMULT_CONST
/ w
;
202 * delta_exec * weight / lw.weight
204 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
206 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
207 * we're guaranteed shift stays positive because inv_weight is guaranteed to
208 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
210 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
211 * weight/lw.weight <= 1, and therefore our shift will also be positive.
213 static u64
__calc_delta(u64 delta_exec
, unsigned long weight
, struct load_weight
*lw
)
215 u64 fact
= scale_load_down(weight
);
216 int shift
= WMULT_SHIFT
;
218 __update_inv_weight(lw
);
220 if (unlikely(fact
>> 32)) {
227 /* hint to use a 32x32->64 mul */
228 fact
= (u64
)(u32
)fact
* lw
->inv_weight
;
235 return mul_u64_u32_shr(delta_exec
, fact
, shift
);
239 const struct sched_class fair_sched_class
;
241 /**************************************************************
242 * CFS operations on generic schedulable entities:
245 #ifdef CONFIG_FAIR_GROUP_SCHED
247 /* cpu runqueue to which this cfs_rq is attached */
248 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
253 /* An entity is a task if it doesn't "own" a runqueue */
254 #define entity_is_task(se) (!se->my_q)
256 static inline struct task_struct
*task_of(struct sched_entity
*se
)
258 #ifdef CONFIG_SCHED_DEBUG
259 WARN_ON_ONCE(!entity_is_task(se
));
261 return container_of(se
, struct task_struct
, se
);
264 /* Walk up scheduling entities hierarchy */
265 #define for_each_sched_entity(se) \
266 for (; se; se = se->parent)
268 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
273 /* runqueue on which this entity is (to be) queued */
274 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
279 /* runqueue "owned" by this group */
280 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
285 static void update_cfs_rq_blocked_load(struct cfs_rq
*cfs_rq
,
288 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
290 if (!cfs_rq
->on_list
) {
292 * Ensure we either appear before our parent (if already
293 * enqueued) or force our parent to appear after us when it is
294 * enqueued. The fact that we always enqueue bottom-up
295 * reduces this to two cases.
297 if (cfs_rq
->tg
->parent
&&
298 cfs_rq
->tg
->parent
->cfs_rq
[cpu_of(rq_of(cfs_rq
))]->on_list
) {
299 list_add_rcu(&cfs_rq
->leaf_cfs_rq_list
,
300 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
302 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
303 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
307 /* We should have no load, but we need to update last_decay. */
308 update_cfs_rq_blocked_load(cfs_rq
, 0);
312 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
314 if (cfs_rq
->on_list
) {
315 list_del_rcu(&cfs_rq
->leaf_cfs_rq_list
);
320 /* Iterate thr' all leaf cfs_rq's on a runqueue */
321 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
322 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
324 /* Do the two (enqueued) entities belong to the same group ? */
325 static inline struct cfs_rq
*
326 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
328 if (se
->cfs_rq
== pse
->cfs_rq
)
334 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
340 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
342 int se_depth
, pse_depth
;
345 * preemption test can be made between sibling entities who are in the
346 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
347 * both tasks until we find their ancestors who are siblings of common
351 /* First walk up until both entities are at same depth */
352 se_depth
= (*se
)->depth
;
353 pse_depth
= (*pse
)->depth
;
355 while (se_depth
> pse_depth
) {
357 *se
= parent_entity(*se
);
360 while (pse_depth
> se_depth
) {
362 *pse
= parent_entity(*pse
);
365 while (!is_same_group(*se
, *pse
)) {
366 *se
= parent_entity(*se
);
367 *pse
= parent_entity(*pse
);
371 #else /* !CONFIG_FAIR_GROUP_SCHED */
373 static inline struct task_struct
*task_of(struct sched_entity
*se
)
375 return container_of(se
, struct task_struct
, se
);
378 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
380 return container_of(cfs_rq
, struct rq
, cfs
);
383 #define entity_is_task(se) 1
385 #define for_each_sched_entity(se) \
386 for (; se; se = NULL)
388 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
390 return &task_rq(p
)->cfs
;
393 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
395 struct task_struct
*p
= task_of(se
);
396 struct rq
*rq
= task_rq(p
);
401 /* runqueue "owned" by this group */
402 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
407 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
411 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
415 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
416 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
418 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
424 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
428 #endif /* CONFIG_FAIR_GROUP_SCHED */
430 static __always_inline
431 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
);
433 /**************************************************************
434 * Scheduling class tree data structure manipulation methods:
437 static inline u64
max_vruntime(u64 max_vruntime
, u64 vruntime
)
439 s64 delta
= (s64
)(vruntime
- max_vruntime
);
441 max_vruntime
= vruntime
;
446 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
448 s64 delta
= (s64
)(vruntime
- min_vruntime
);
450 min_vruntime
= vruntime
;
455 static inline int entity_before(struct sched_entity
*a
,
456 struct sched_entity
*b
)
458 return (s64
)(a
->vruntime
- b
->vruntime
) < 0;
461 static void update_min_vruntime(struct cfs_rq
*cfs_rq
)
463 u64 vruntime
= cfs_rq
->min_vruntime
;
466 vruntime
= cfs_rq
->curr
->vruntime
;
468 if (cfs_rq
->rb_leftmost
) {
469 struct sched_entity
*se
= rb_entry(cfs_rq
->rb_leftmost
,
474 vruntime
= se
->vruntime
;
476 vruntime
= min_vruntime(vruntime
, se
->vruntime
);
479 /* ensure we never gain time by being placed backwards. */
480 cfs_rq
->min_vruntime
= max_vruntime(cfs_rq
->min_vruntime
, vruntime
);
483 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
488 * Enqueue an entity into the rb-tree:
490 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
492 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
493 struct rb_node
*parent
= NULL
;
494 struct sched_entity
*entry
;
498 * Find the right place in the rbtree:
502 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
504 * We dont care about collisions. Nodes with
505 * the same key stay together.
507 if (entity_before(se
, entry
)) {
508 link
= &parent
->rb_left
;
510 link
= &parent
->rb_right
;
516 * Maintain a cache of leftmost tree entries (it is frequently
520 cfs_rq
->rb_leftmost
= &se
->run_node
;
522 rb_link_node(&se
->run_node
, parent
, link
);
523 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
526 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
528 if (cfs_rq
->rb_leftmost
== &se
->run_node
) {
529 struct rb_node
*next_node
;
531 next_node
= rb_next(&se
->run_node
);
532 cfs_rq
->rb_leftmost
= next_node
;
535 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
538 struct sched_entity
*__pick_first_entity(struct cfs_rq
*cfs_rq
)
540 struct rb_node
*left
= cfs_rq
->rb_leftmost
;
545 return rb_entry(left
, struct sched_entity
, run_node
);
548 static struct sched_entity
*__pick_next_entity(struct sched_entity
*se
)
550 struct rb_node
*next
= rb_next(&se
->run_node
);
555 return rb_entry(next
, struct sched_entity
, run_node
);
558 #ifdef CONFIG_SCHED_DEBUG
559 struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
561 struct rb_node
*last
= rb_last(&cfs_rq
->tasks_timeline
);
566 return rb_entry(last
, struct sched_entity
, run_node
);
569 /**************************************************************
570 * Scheduling class statistics methods:
573 int sched_proc_update_handler(struct ctl_table
*table
, int write
,
574 void __user
*buffer
, size_t *lenp
,
577 int ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
578 int factor
= get_update_sysctl_factor();
583 sched_nr_latency
= DIV_ROUND_UP(sysctl_sched_latency
,
584 sysctl_sched_min_granularity
);
586 #define WRT_SYSCTL(name) \
587 (normalized_sysctl_##name = sysctl_##name / (factor))
588 WRT_SYSCTL(sched_min_granularity
);
589 WRT_SYSCTL(sched_latency
);
590 WRT_SYSCTL(sched_wakeup_granularity
);
600 static inline u64
calc_delta_fair(u64 delta
, struct sched_entity
*se
)
602 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
603 delta
= __calc_delta(delta
, NICE_0_LOAD
, &se
->load
);
609 * The idea is to set a period in which each task runs once.
611 * When there are too many tasks (sched_nr_latency) we have to stretch
612 * this period because otherwise the slices get too small.
614 * p = (nr <= nl) ? l : l*nr/nl
616 static u64
__sched_period(unsigned long nr_running
)
618 u64 period
= sysctl_sched_latency
;
619 unsigned long nr_latency
= sched_nr_latency
;
621 if (unlikely(nr_running
> nr_latency
)) {
622 period
= sysctl_sched_min_granularity
;
623 period
*= nr_running
;
630 * We calculate the wall-time slice from the period by taking a part
631 * proportional to the weight.
635 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
637 u64 slice
= __sched_period(cfs_rq
->nr_running
+ !se
->on_rq
);
639 for_each_sched_entity(se
) {
640 struct load_weight
*load
;
641 struct load_weight lw
;
643 cfs_rq
= cfs_rq_of(se
);
644 load
= &cfs_rq
->load
;
646 if (unlikely(!se
->on_rq
)) {
649 update_load_add(&lw
, se
->load
.weight
);
652 slice
= __calc_delta(slice
, se
->load
.weight
, load
);
658 * We calculate the vruntime slice of a to-be-inserted task.
662 static u64
sched_vslice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
664 return calc_delta_fair(sched_slice(cfs_rq
, se
), se
);
668 static unsigned long task_h_load(struct task_struct
*p
);
670 static inline void __update_task_entity_contrib(struct sched_entity
*se
);
672 /* Give new task start runnable values to heavy its load in infant time */
673 void init_task_runnable_average(struct task_struct
*p
)
677 p
->se
.avg
.decay_count
= 0;
678 slice
= sched_slice(task_cfs_rq(p
), &p
->se
) >> 10;
679 p
->se
.avg
.runnable_avg_sum
= slice
;
680 p
->se
.avg
.runnable_avg_period
= slice
;
681 __update_task_entity_contrib(&p
->se
);
684 void init_task_runnable_average(struct task_struct
*p
)
690 * Update the current task's runtime statistics.
692 static void update_curr(struct cfs_rq
*cfs_rq
)
694 struct sched_entity
*curr
= cfs_rq
->curr
;
695 u64 now
= rq_clock_task(rq_of(cfs_rq
));
701 delta_exec
= now
- curr
->exec_start
;
702 if (unlikely((s64
)delta_exec
<= 0))
705 curr
->exec_start
= now
;
707 schedstat_set(curr
->statistics
.exec_max
,
708 max(delta_exec
, curr
->statistics
.exec_max
));
710 curr
->sum_exec_runtime
+= delta_exec
;
711 schedstat_add(cfs_rq
, exec_clock
, delta_exec
);
713 curr
->vruntime
+= calc_delta_fair(delta_exec
, curr
);
714 update_min_vruntime(cfs_rq
);
716 if (entity_is_task(curr
)) {
717 struct task_struct
*curtask
= task_of(curr
);
719 trace_sched_stat_runtime(curtask
, delta_exec
, curr
->vruntime
);
720 cpuacct_charge(curtask
, delta_exec
);
721 account_group_exec_runtime(curtask
, delta_exec
);
724 account_cfs_rq_runtime(cfs_rq
, delta_exec
);
728 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
730 schedstat_set(se
->statistics
.wait_start
, rq_clock(rq_of(cfs_rq
)));
734 * Task is being enqueued - update stats:
736 static void update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
739 * Are we enqueueing a waiting task? (for current tasks
740 * a dequeue/enqueue event is a NOP)
742 if (se
!= cfs_rq
->curr
)
743 update_stats_wait_start(cfs_rq
, se
);
747 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
749 schedstat_set(se
->statistics
.wait_max
, max(se
->statistics
.wait_max
,
750 rq_clock(rq_of(cfs_rq
)) - se
->statistics
.wait_start
));
751 schedstat_set(se
->statistics
.wait_count
, se
->statistics
.wait_count
+ 1);
752 schedstat_set(se
->statistics
.wait_sum
, se
->statistics
.wait_sum
+
753 rq_clock(rq_of(cfs_rq
)) - se
->statistics
.wait_start
);
754 #ifdef CONFIG_SCHEDSTATS
755 if (entity_is_task(se
)) {
756 trace_sched_stat_wait(task_of(se
),
757 rq_clock(rq_of(cfs_rq
)) - se
->statistics
.wait_start
);
760 schedstat_set(se
->statistics
.wait_start
, 0);
764 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
767 * Mark the end of the wait period if dequeueing a
770 if (se
!= cfs_rq
->curr
)
771 update_stats_wait_end(cfs_rq
, se
);
775 * We are picking a new current task - update its stats:
778 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
781 * We are starting a new run period:
783 se
->exec_start
= rq_clock_task(rq_of(cfs_rq
));
786 /**************************************************
787 * Scheduling class queueing methods:
790 #ifdef CONFIG_NUMA_BALANCING
792 * Approximate time to scan a full NUMA task in ms. The task scan period is
793 * calculated based on the tasks virtual memory size and
794 * numa_balancing_scan_size.
796 unsigned int sysctl_numa_balancing_scan_period_min
= 1000;
797 unsigned int sysctl_numa_balancing_scan_period_max
= 60000;
799 /* Portion of address space to scan in MB */
800 unsigned int sysctl_numa_balancing_scan_size
= 256;
802 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
803 unsigned int sysctl_numa_balancing_scan_delay
= 1000;
805 static unsigned int task_nr_scan_windows(struct task_struct
*p
)
807 unsigned long rss
= 0;
808 unsigned long nr_scan_pages
;
811 * Calculations based on RSS as non-present and empty pages are skipped
812 * by the PTE scanner and NUMA hinting faults should be trapped based
815 nr_scan_pages
= sysctl_numa_balancing_scan_size
<< (20 - PAGE_SHIFT
);
816 rss
= get_mm_rss(p
->mm
);
820 rss
= round_up(rss
, nr_scan_pages
);
821 return rss
/ nr_scan_pages
;
824 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
825 #define MAX_SCAN_WINDOW 2560
827 static unsigned int task_scan_min(struct task_struct
*p
)
829 unsigned int scan
, floor
;
830 unsigned int windows
= 1;
832 if (sysctl_numa_balancing_scan_size
< MAX_SCAN_WINDOW
)
833 windows
= MAX_SCAN_WINDOW
/ sysctl_numa_balancing_scan_size
;
834 floor
= 1000 / windows
;
836 scan
= sysctl_numa_balancing_scan_period_min
/ task_nr_scan_windows(p
);
837 return max_t(unsigned int, floor
, scan
);
840 static unsigned int task_scan_max(struct task_struct
*p
)
842 unsigned int smin
= task_scan_min(p
);
845 /* Watch for min being lower than max due to floor calculations */
846 smax
= sysctl_numa_balancing_scan_period_max
/ task_nr_scan_windows(p
);
847 return max(smin
, smax
);
850 static void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
852 rq
->nr_numa_running
+= (p
->numa_preferred_nid
!= -1);
853 rq
->nr_preferred_running
+= (p
->numa_preferred_nid
== task_node(p
));
856 static void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
858 rq
->nr_numa_running
-= (p
->numa_preferred_nid
!= -1);
859 rq
->nr_preferred_running
-= (p
->numa_preferred_nid
== task_node(p
));
865 spinlock_t lock
; /* nr_tasks, tasks */
868 struct list_head task_list
;
871 nodemask_t active_nodes
;
872 unsigned long total_faults
;
874 * Faults_cpu is used to decide whether memory should move
875 * towards the CPU. As a consequence, these stats are weighted
876 * more by CPU use than by memory faults.
878 unsigned long *faults_cpu
;
879 unsigned long faults
[0];
882 /* Shared or private faults. */
883 #define NR_NUMA_HINT_FAULT_TYPES 2
885 /* Memory and CPU locality */
886 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
888 /* Averaged statistics, and temporary buffers. */
889 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
891 pid_t
task_numa_group_id(struct task_struct
*p
)
893 return p
->numa_group
? p
->numa_group
->gid
: 0;
896 static inline int task_faults_idx(int nid
, int priv
)
898 return NR_NUMA_HINT_FAULT_TYPES
* nid
+ priv
;
901 static inline unsigned long task_faults(struct task_struct
*p
, int nid
)
903 if (!p
->numa_faults_memory
)
906 return p
->numa_faults_memory
[task_faults_idx(nid
, 0)] +
907 p
->numa_faults_memory
[task_faults_idx(nid
, 1)];
910 static inline unsigned long group_faults(struct task_struct
*p
, int nid
)
915 return p
->numa_group
->faults
[task_faults_idx(nid
, 0)] +
916 p
->numa_group
->faults
[task_faults_idx(nid
, 1)];
919 static inline unsigned long group_faults_cpu(struct numa_group
*group
, int nid
)
921 return group
->faults_cpu
[task_faults_idx(nid
, 0)] +
922 group
->faults_cpu
[task_faults_idx(nid
, 1)];
926 * These return the fraction of accesses done by a particular task, or
927 * task group, on a particular numa node. The group weight is given a
928 * larger multiplier, in order to group tasks together that are almost
929 * evenly spread out between numa nodes.
931 static inline unsigned long task_weight(struct task_struct
*p
, int nid
)
933 unsigned long total_faults
;
935 if (!p
->numa_faults_memory
)
938 total_faults
= p
->total_numa_faults
;
943 return 1000 * task_faults(p
, nid
) / total_faults
;
946 static inline unsigned long group_weight(struct task_struct
*p
, int nid
)
948 if (!p
->numa_group
|| !p
->numa_group
->total_faults
)
951 return 1000 * group_faults(p
, nid
) / p
->numa_group
->total_faults
;
954 bool should_numa_migrate_memory(struct task_struct
*p
, struct page
* page
,
955 int src_nid
, int dst_cpu
)
957 struct numa_group
*ng
= p
->numa_group
;
958 int dst_nid
= cpu_to_node(dst_cpu
);
959 int last_cpupid
, this_cpupid
;
961 this_cpupid
= cpu_pid_to_cpupid(dst_cpu
, current
->pid
);
964 * Multi-stage node selection is used in conjunction with a periodic
965 * migration fault to build a temporal task<->page relation. By using
966 * a two-stage filter we remove short/unlikely relations.
968 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
969 * a task's usage of a particular page (n_p) per total usage of this
970 * page (n_t) (in a given time-span) to a probability.
972 * Our periodic faults will sample this probability and getting the
973 * same result twice in a row, given these samples are fully
974 * independent, is then given by P(n)^2, provided our sample period
975 * is sufficiently short compared to the usage pattern.
977 * This quadric squishes small probabilities, making it less likely we
978 * act on an unlikely task<->page relation.
980 last_cpupid
= page_cpupid_xchg_last(page
, this_cpupid
);
981 if (!cpupid_pid_unset(last_cpupid
) &&
982 cpupid_to_nid(last_cpupid
) != dst_nid
)
985 /* Always allow migrate on private faults */
986 if (cpupid_match_pid(p
, last_cpupid
))
989 /* A shared fault, but p->numa_group has not been set up yet. */
994 * Do not migrate if the destination is not a node that
995 * is actively used by this numa group.
997 if (!node_isset(dst_nid
, ng
->active_nodes
))
1001 * Source is a node that is not actively used by this
1002 * numa group, while the destination is. Migrate.
1004 if (!node_isset(src_nid
, ng
->active_nodes
))
1008 * Both source and destination are nodes in active
1009 * use by this numa group. Maximize memory bandwidth
1010 * by migrating from more heavily used groups, to less
1011 * heavily used ones, spreading the load around.
1012 * Use a 1/4 hysteresis to avoid spurious page movement.
1014 return group_faults(p
, dst_nid
) < (group_faults(p
, src_nid
) * 3 / 4);
1017 static unsigned long weighted_cpuload(const int cpu
);
1018 static unsigned long source_load(int cpu
, int type
);
1019 static unsigned long target_load(int cpu
, int type
);
1020 static unsigned long power_of(int cpu
);
1021 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
);
1023 /* Cached statistics for all CPUs within a node */
1025 unsigned long nr_running
;
1028 /* Total compute capacity of CPUs on a node */
1029 unsigned long power
;
1031 /* Approximate capacity in terms of runnable tasks on a node */
1032 unsigned long capacity
;
1037 * XXX borrowed from update_sg_lb_stats
1039 static void update_numa_stats(struct numa_stats
*ns
, int nid
)
1043 memset(ns
, 0, sizeof(*ns
));
1044 for_each_cpu(cpu
, cpumask_of_node(nid
)) {
1045 struct rq
*rq
= cpu_rq(cpu
);
1047 ns
->nr_running
+= rq
->nr_running
;
1048 ns
->load
+= weighted_cpuload(cpu
);
1049 ns
->power
+= power_of(cpu
);
1055 * If we raced with hotplug and there are no CPUs left in our mask
1056 * the @ns structure is NULL'ed and task_numa_compare() will
1057 * not find this node attractive.
1059 * We'll either bail at !has_capacity, or we'll detect a huge imbalance
1065 ns
->load
= (ns
->load
* SCHED_POWER_SCALE
) / ns
->power
;
1066 ns
->capacity
= DIV_ROUND_CLOSEST(ns
->power
, SCHED_POWER_SCALE
);
1067 ns
->has_capacity
= (ns
->nr_running
< ns
->capacity
);
1070 struct task_numa_env
{
1071 struct task_struct
*p
;
1073 int src_cpu
, src_nid
;
1074 int dst_cpu
, dst_nid
;
1076 struct numa_stats src_stats
, dst_stats
;
1080 struct task_struct
*best_task
;
1085 static void task_numa_assign(struct task_numa_env
*env
,
1086 struct task_struct
*p
, long imp
)
1089 put_task_struct(env
->best_task
);
1094 env
->best_imp
= imp
;
1095 env
->best_cpu
= env
->dst_cpu
;
1099 * This checks if the overall compute and NUMA accesses of the system would
1100 * be improved if the source tasks was migrated to the target dst_cpu taking
1101 * into account that it might be best if task running on the dst_cpu should
1102 * be exchanged with the source task
1104 static void task_numa_compare(struct task_numa_env
*env
,
1105 long taskimp
, long groupimp
)
1107 struct rq
*src_rq
= cpu_rq(env
->src_cpu
);
1108 struct rq
*dst_rq
= cpu_rq(env
->dst_cpu
);
1109 struct task_struct
*cur
;
1110 long dst_load
, src_load
;
1112 long imp
= (groupimp
> 0) ? groupimp
: taskimp
;
1115 cur
= ACCESS_ONCE(dst_rq
->curr
);
1116 if (cur
->pid
== 0) /* idle */
1120 * "imp" is the fault differential for the source task between the
1121 * source and destination node. Calculate the total differential for
1122 * the source task and potential destination task. The more negative
1123 * the value is, the more rmeote accesses that would be expected to
1124 * be incurred if the tasks were swapped.
1127 /* Skip this swap candidate if cannot move to the source cpu */
1128 if (!cpumask_test_cpu(env
->src_cpu
, tsk_cpus_allowed(cur
)))
1132 * If dst and source tasks are in the same NUMA group, or not
1133 * in any group then look only at task weights.
1135 if (cur
->numa_group
== env
->p
->numa_group
) {
1136 imp
= taskimp
+ task_weight(cur
, env
->src_nid
) -
1137 task_weight(cur
, env
->dst_nid
);
1139 * Add some hysteresis to prevent swapping the
1140 * tasks within a group over tiny differences.
1142 if (cur
->numa_group
)
1146 * Compare the group weights. If a task is all by
1147 * itself (not part of a group), use the task weight
1150 if (env
->p
->numa_group
)
1155 if (cur
->numa_group
)
1156 imp
+= group_weight(cur
, env
->src_nid
) -
1157 group_weight(cur
, env
->dst_nid
);
1159 imp
+= task_weight(cur
, env
->src_nid
) -
1160 task_weight(cur
, env
->dst_nid
);
1164 if (imp
< env
->best_imp
)
1168 /* Is there capacity at our destination? */
1169 if (env
->src_stats
.has_capacity
&&
1170 !env
->dst_stats
.has_capacity
)
1176 /* Balance doesn't matter much if we're running a task per cpu */
1177 if (src_rq
->nr_running
== 1 && dst_rq
->nr_running
== 1)
1181 * In the overloaded case, try and keep the load balanced.
1184 dst_load
= env
->dst_stats
.load
;
1185 src_load
= env
->src_stats
.load
;
1187 /* XXX missing power terms */
1188 load
= task_h_load(env
->p
);
1193 load
= task_h_load(cur
);
1198 /* make src_load the smaller */
1199 if (dst_load
< src_load
)
1200 swap(dst_load
, src_load
);
1202 if (src_load
* env
->imbalance_pct
< dst_load
* 100)
1206 task_numa_assign(env
, cur
, imp
);
1211 static void task_numa_find_cpu(struct task_numa_env
*env
,
1212 long taskimp
, long groupimp
)
1216 for_each_cpu(cpu
, cpumask_of_node(env
->dst_nid
)) {
1217 /* Skip this CPU if the source task cannot migrate */
1218 if (!cpumask_test_cpu(cpu
, tsk_cpus_allowed(env
->p
)))
1222 task_numa_compare(env
, taskimp
, groupimp
);
1226 static int task_numa_migrate(struct task_struct
*p
)
1228 struct task_numa_env env
= {
1231 .src_cpu
= task_cpu(p
),
1232 .src_nid
= task_node(p
),
1234 .imbalance_pct
= 112,
1240 struct sched_domain
*sd
;
1241 unsigned long taskweight
, groupweight
;
1243 long taskimp
, groupimp
;
1246 * Pick the lowest SD_NUMA domain, as that would have the smallest
1247 * imbalance and would be the first to start moving tasks about.
1249 * And we want to avoid any moving of tasks about, as that would create
1250 * random movement of tasks -- counter the numa conditions we're trying
1254 sd
= rcu_dereference(per_cpu(sd_numa
, env
.src_cpu
));
1256 env
.imbalance_pct
= 100 + (sd
->imbalance_pct
- 100) / 2;
1260 * Cpusets can break the scheduler domain tree into smaller
1261 * balance domains, some of which do not cross NUMA boundaries.
1262 * Tasks that are "trapped" in such domains cannot be migrated
1263 * elsewhere, so there is no point in (re)trying.
1265 if (unlikely(!sd
)) {
1266 p
->numa_preferred_nid
= task_node(p
);
1270 taskweight
= task_weight(p
, env
.src_nid
);
1271 groupweight
= group_weight(p
, env
.src_nid
);
1272 update_numa_stats(&env
.src_stats
, env
.src_nid
);
1273 env
.dst_nid
= p
->numa_preferred_nid
;
1274 taskimp
= task_weight(p
, env
.dst_nid
) - taskweight
;
1275 groupimp
= group_weight(p
, env
.dst_nid
) - groupweight
;
1276 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1278 /* If the preferred nid has capacity, try to use it. */
1279 if (env
.dst_stats
.has_capacity
)
1280 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1282 /* No space available on the preferred nid. Look elsewhere. */
1283 if (env
.best_cpu
== -1) {
1284 for_each_online_node(nid
) {
1285 if (nid
== env
.src_nid
|| nid
== p
->numa_preferred_nid
)
1288 /* Only consider nodes where both task and groups benefit */
1289 taskimp
= task_weight(p
, nid
) - taskweight
;
1290 groupimp
= group_weight(p
, nid
) - groupweight
;
1291 if (taskimp
< 0 && groupimp
< 0)
1295 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1296 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1300 /* No better CPU than the current one was found. */
1301 if (env
.best_cpu
== -1)
1304 sched_setnuma(p
, env
.dst_nid
);
1307 * Reset the scan period if the task is being rescheduled on an
1308 * alternative node to recheck if the tasks is now properly placed.
1310 p
->numa_scan_period
= task_scan_min(p
);
1312 if (env
.best_task
== NULL
) {
1313 ret
= migrate_task_to(p
, env
.best_cpu
);
1315 trace_sched_stick_numa(p
, env
.src_cpu
, env
.best_cpu
);
1319 ret
= migrate_swap(p
, env
.best_task
);
1321 trace_sched_stick_numa(p
, env
.src_cpu
, task_cpu(env
.best_task
));
1322 put_task_struct(env
.best_task
);
1326 /* Attempt to migrate a task to a CPU on the preferred node. */
1327 static void numa_migrate_preferred(struct task_struct
*p
)
1329 /* This task has no NUMA fault statistics yet */
1330 if (unlikely(p
->numa_preferred_nid
== -1 || !p
->numa_faults_memory
))
1333 /* Periodically retry migrating the task to the preferred node */
1334 p
->numa_migrate_retry
= jiffies
+ HZ
;
1336 /* Success if task is already running on preferred CPU */
1337 if (task_node(p
) == p
->numa_preferred_nid
)
1340 /* Otherwise, try migrate to a CPU on the preferred node */
1341 task_numa_migrate(p
);
1345 * Find the nodes on which the workload is actively running. We do this by
1346 * tracking the nodes from which NUMA hinting faults are triggered. This can
1347 * be different from the set of nodes where the workload's memory is currently
1350 * The bitmask is used to make smarter decisions on when to do NUMA page
1351 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1352 * are added when they cause over 6/16 of the maximum number of faults, but
1353 * only removed when they drop below 3/16.
1355 static void update_numa_active_node_mask(struct numa_group
*numa_group
)
1357 unsigned long faults
, max_faults
= 0;
1360 for_each_online_node(nid
) {
1361 faults
= group_faults_cpu(numa_group
, nid
);
1362 if (faults
> max_faults
)
1363 max_faults
= faults
;
1366 for_each_online_node(nid
) {
1367 faults
= group_faults_cpu(numa_group
, nid
);
1368 if (!node_isset(nid
, numa_group
->active_nodes
)) {
1369 if (faults
> max_faults
* 6 / 16)
1370 node_set(nid
, numa_group
->active_nodes
);
1371 } else if (faults
< max_faults
* 3 / 16)
1372 node_clear(nid
, numa_group
->active_nodes
);
1377 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1378 * increments. The more local the fault statistics are, the higher the scan
1379 * period will be for the next scan window. If local/remote ratio is below
1380 * NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the
1381 * scan period will decrease
1383 #define NUMA_PERIOD_SLOTS 10
1384 #define NUMA_PERIOD_THRESHOLD 3
1387 * Increase the scan period (slow down scanning) if the majority of
1388 * our memory is already on our local node, or if the majority of
1389 * the page accesses are shared with other processes.
1390 * Otherwise, decrease the scan period.
1392 static void update_task_scan_period(struct task_struct
*p
,
1393 unsigned long shared
, unsigned long private)
1395 unsigned int period_slot
;
1399 unsigned long remote
= p
->numa_faults_locality
[0];
1400 unsigned long local
= p
->numa_faults_locality
[1];
1403 * If there were no record hinting faults then either the task is
1404 * completely idle or all activity is areas that are not of interest
1405 * to automatic numa balancing. Scan slower
1407 if (local
+ shared
== 0) {
1408 p
->numa_scan_period
= min(p
->numa_scan_period_max
,
1409 p
->numa_scan_period
<< 1);
1411 p
->mm
->numa_next_scan
= jiffies
+
1412 msecs_to_jiffies(p
->numa_scan_period
);
1418 * Prepare to scale scan period relative to the current period.
1419 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1420 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1421 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1423 period_slot
= DIV_ROUND_UP(p
->numa_scan_period
, NUMA_PERIOD_SLOTS
);
1424 ratio
= (local
* NUMA_PERIOD_SLOTS
) / (local
+ remote
);
1425 if (ratio
>= NUMA_PERIOD_THRESHOLD
) {
1426 int slot
= ratio
- NUMA_PERIOD_THRESHOLD
;
1429 diff
= slot
* period_slot
;
1431 diff
= -(NUMA_PERIOD_THRESHOLD
- ratio
) * period_slot
;
1434 * Scale scan rate increases based on sharing. There is an
1435 * inverse relationship between the degree of sharing and
1436 * the adjustment made to the scanning period. Broadly
1437 * speaking the intent is that there is little point
1438 * scanning faster if shared accesses dominate as it may
1439 * simply bounce migrations uselessly
1441 ratio
= DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS
, (private + shared
));
1442 diff
= (diff
* ratio
) / NUMA_PERIOD_SLOTS
;
1445 p
->numa_scan_period
= clamp(p
->numa_scan_period
+ diff
,
1446 task_scan_min(p
), task_scan_max(p
));
1447 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
1451 * Get the fraction of time the task has been running since the last
1452 * NUMA placement cycle. The scheduler keeps similar statistics, but
1453 * decays those on a 32ms period, which is orders of magnitude off
1454 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1455 * stats only if the task is so new there are no NUMA statistics yet.
1457 static u64
numa_get_avg_runtime(struct task_struct
*p
, u64
*period
)
1459 u64 runtime
, delta
, now
;
1460 /* Use the start of this time slice to avoid calculations. */
1461 now
= p
->se
.exec_start
;
1462 runtime
= p
->se
.sum_exec_runtime
;
1464 if (p
->last_task_numa_placement
) {
1465 delta
= runtime
- p
->last_sum_exec_runtime
;
1466 *period
= now
- p
->last_task_numa_placement
;
1468 delta
= p
->se
.avg
.runnable_avg_sum
;
1469 *period
= p
->se
.avg
.runnable_avg_period
;
1472 p
->last_sum_exec_runtime
= runtime
;
1473 p
->last_task_numa_placement
= now
;
1478 static void task_numa_placement(struct task_struct
*p
)
1480 int seq
, nid
, max_nid
= -1, max_group_nid
= -1;
1481 unsigned long max_faults
= 0, max_group_faults
= 0;
1482 unsigned long fault_types
[2] = { 0, 0 };
1483 unsigned long total_faults
;
1484 u64 runtime
, period
;
1485 spinlock_t
*group_lock
= NULL
;
1487 seq
= ACCESS_ONCE(p
->mm
->numa_scan_seq
);
1488 if (p
->numa_scan_seq
== seq
)
1490 p
->numa_scan_seq
= seq
;
1491 p
->numa_scan_period_max
= task_scan_max(p
);
1493 total_faults
= p
->numa_faults_locality
[0] +
1494 p
->numa_faults_locality
[1];
1495 runtime
= numa_get_avg_runtime(p
, &period
);
1497 /* If the task is part of a group prevent parallel updates to group stats */
1498 if (p
->numa_group
) {
1499 group_lock
= &p
->numa_group
->lock
;
1500 spin_lock_irq(group_lock
);
1503 /* Find the node with the highest number of faults */
1504 for_each_online_node(nid
) {
1505 unsigned long faults
= 0, group_faults
= 0;
1508 for (priv
= 0; priv
< NR_NUMA_HINT_FAULT_TYPES
; priv
++) {
1509 long diff
, f_diff
, f_weight
;
1511 i
= task_faults_idx(nid
, priv
);
1513 /* Decay existing window, copy faults since last scan */
1514 diff
= p
->numa_faults_buffer_memory
[i
] - p
->numa_faults_memory
[i
] / 2;
1515 fault_types
[priv
] += p
->numa_faults_buffer_memory
[i
];
1516 p
->numa_faults_buffer_memory
[i
] = 0;
1519 * Normalize the faults_from, so all tasks in a group
1520 * count according to CPU use, instead of by the raw
1521 * number of faults. Tasks with little runtime have
1522 * little over-all impact on throughput, and thus their
1523 * faults are less important.
1525 f_weight
= div64_u64(runtime
<< 16, period
+ 1);
1526 f_weight
= (f_weight
* p
->numa_faults_buffer_cpu
[i
]) /
1528 f_diff
= f_weight
- p
->numa_faults_cpu
[i
] / 2;
1529 p
->numa_faults_buffer_cpu
[i
] = 0;
1531 p
->numa_faults_memory
[i
] += diff
;
1532 p
->numa_faults_cpu
[i
] += f_diff
;
1533 faults
+= p
->numa_faults_memory
[i
];
1534 p
->total_numa_faults
+= diff
;
1535 if (p
->numa_group
) {
1536 /* safe because we can only change our own group */
1537 p
->numa_group
->faults
[i
] += diff
;
1538 p
->numa_group
->faults_cpu
[i
] += f_diff
;
1539 p
->numa_group
->total_faults
+= diff
;
1540 group_faults
+= p
->numa_group
->faults
[i
];
1544 if (faults
> max_faults
) {
1545 max_faults
= faults
;
1549 if (group_faults
> max_group_faults
) {
1550 max_group_faults
= group_faults
;
1551 max_group_nid
= nid
;
1555 update_task_scan_period(p
, fault_types
[0], fault_types
[1]);
1557 if (p
->numa_group
) {
1558 update_numa_active_node_mask(p
->numa_group
);
1560 * If the preferred task and group nids are different,
1561 * iterate over the nodes again to find the best place.
1563 if (max_nid
!= max_group_nid
) {
1564 unsigned long weight
, max_weight
= 0;
1566 for_each_online_node(nid
) {
1567 weight
= task_weight(p
, nid
) + group_weight(p
, nid
);
1568 if (weight
> max_weight
) {
1569 max_weight
= weight
;
1575 spin_unlock_irq(group_lock
);
1578 /* Preferred node as the node with the most faults */
1579 if (max_faults
&& max_nid
!= p
->numa_preferred_nid
) {
1580 /* Update the preferred nid and migrate task if possible */
1581 sched_setnuma(p
, max_nid
);
1582 numa_migrate_preferred(p
);
1586 static inline int get_numa_group(struct numa_group
*grp
)
1588 return atomic_inc_not_zero(&grp
->refcount
);
1591 static inline void put_numa_group(struct numa_group
*grp
)
1593 if (atomic_dec_and_test(&grp
->refcount
))
1594 kfree_rcu(grp
, rcu
);
1597 static void task_numa_group(struct task_struct
*p
, int cpupid
, int flags
,
1600 struct numa_group
*grp
, *my_grp
;
1601 struct task_struct
*tsk
;
1603 int cpu
= cpupid_to_cpu(cpupid
);
1606 if (unlikely(!p
->numa_group
)) {
1607 unsigned int size
= sizeof(struct numa_group
) +
1608 4*nr_node_ids
*sizeof(unsigned long);
1610 grp
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
1614 atomic_set(&grp
->refcount
, 1);
1615 spin_lock_init(&grp
->lock
);
1616 INIT_LIST_HEAD(&grp
->task_list
);
1618 /* Second half of the array tracks nids where faults happen */
1619 grp
->faults_cpu
= grp
->faults
+ NR_NUMA_HINT_FAULT_TYPES
*
1622 node_set(task_node(current
), grp
->active_nodes
);
1624 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
1625 grp
->faults
[i
] = p
->numa_faults_memory
[i
];
1627 grp
->total_faults
= p
->total_numa_faults
;
1629 list_add(&p
->numa_entry
, &grp
->task_list
);
1631 rcu_assign_pointer(p
->numa_group
, grp
);
1635 tsk
= ACCESS_ONCE(cpu_rq(cpu
)->curr
);
1637 if (!cpupid_match_pid(tsk
, cpupid
))
1640 grp
= rcu_dereference(tsk
->numa_group
);
1644 my_grp
= p
->numa_group
;
1649 * Only join the other group if its bigger; if we're the bigger group,
1650 * the other task will join us.
1652 if (my_grp
->nr_tasks
> grp
->nr_tasks
)
1656 * Tie-break on the grp address.
1658 if (my_grp
->nr_tasks
== grp
->nr_tasks
&& my_grp
> grp
)
1661 /* Always join threads in the same process. */
1662 if (tsk
->mm
== current
->mm
)
1665 /* Simple filter to avoid false positives due to PID collisions */
1666 if (flags
& TNF_SHARED
)
1669 /* Update priv based on whether false sharing was detected */
1672 if (join
&& !get_numa_group(grp
))
1680 BUG_ON(irqs_disabled());
1681 double_lock_irq(&my_grp
->lock
, &grp
->lock
);
1683 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++) {
1684 my_grp
->faults
[i
] -= p
->numa_faults_memory
[i
];
1685 grp
->faults
[i
] += p
->numa_faults_memory
[i
];
1687 my_grp
->total_faults
-= p
->total_numa_faults
;
1688 grp
->total_faults
+= p
->total_numa_faults
;
1690 list_move(&p
->numa_entry
, &grp
->task_list
);
1694 spin_unlock(&my_grp
->lock
);
1695 spin_unlock_irq(&grp
->lock
);
1697 rcu_assign_pointer(p
->numa_group
, grp
);
1699 put_numa_group(my_grp
);
1707 void task_numa_free(struct task_struct
*p
)
1709 struct numa_group
*grp
= p
->numa_group
;
1710 void *numa_faults
= p
->numa_faults_memory
;
1711 unsigned long flags
;
1715 spin_lock_irqsave(&grp
->lock
, flags
);
1716 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
1717 grp
->faults
[i
] -= p
->numa_faults_memory
[i
];
1718 grp
->total_faults
-= p
->total_numa_faults
;
1720 list_del(&p
->numa_entry
);
1722 spin_unlock_irqrestore(&grp
->lock
, flags
);
1723 rcu_assign_pointer(p
->numa_group
, NULL
);
1724 put_numa_group(grp
);
1727 p
->numa_faults_memory
= NULL
;
1728 p
->numa_faults_buffer_memory
= NULL
;
1729 p
->numa_faults_cpu
= NULL
;
1730 p
->numa_faults_buffer_cpu
= NULL
;
1735 * Got a PROT_NONE fault for a page on @node.
1737 void task_numa_fault(int last_cpupid
, int mem_node
, int pages
, int flags
)
1739 struct task_struct
*p
= current
;
1740 bool migrated
= flags
& TNF_MIGRATED
;
1741 int cpu_node
= task_node(current
);
1744 if (!numabalancing_enabled
)
1747 /* for example, ksmd faulting in a user's mm */
1751 /* Do not worry about placement if exiting */
1752 if (p
->state
== TASK_DEAD
)
1755 /* Allocate buffer to track faults on a per-node basis */
1756 if (unlikely(!p
->numa_faults_memory
)) {
1757 int size
= sizeof(*p
->numa_faults_memory
) *
1758 NR_NUMA_HINT_FAULT_BUCKETS
* nr_node_ids
;
1760 p
->numa_faults_memory
= kzalloc(size
, GFP_KERNEL
|__GFP_NOWARN
);
1761 if (!p
->numa_faults_memory
)
1764 BUG_ON(p
->numa_faults_buffer_memory
);
1766 * The averaged statistics, shared & private, memory & cpu,
1767 * occupy the first half of the array. The second half of the
1768 * array is for current counters, which are averaged into the
1769 * first set by task_numa_placement.
1771 p
->numa_faults_cpu
= p
->numa_faults_memory
+ (2 * nr_node_ids
);
1772 p
->numa_faults_buffer_memory
= p
->numa_faults_memory
+ (4 * nr_node_ids
);
1773 p
->numa_faults_buffer_cpu
= p
->numa_faults_memory
+ (6 * nr_node_ids
);
1774 p
->total_numa_faults
= 0;
1775 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
1779 * First accesses are treated as private, otherwise consider accesses
1780 * to be private if the accessing pid has not changed
1782 if (unlikely(last_cpupid
== (-1 & LAST_CPUPID_MASK
))) {
1785 priv
= cpupid_match_pid(p
, last_cpupid
);
1786 if (!priv
&& !(flags
& TNF_NO_GROUP
))
1787 task_numa_group(p
, last_cpupid
, flags
, &priv
);
1790 task_numa_placement(p
);
1793 * Retry task to preferred node migration periodically, in case it
1794 * case it previously failed, or the scheduler moved us.
1796 if (time_after(jiffies
, p
->numa_migrate_retry
))
1797 numa_migrate_preferred(p
);
1800 p
->numa_pages_migrated
+= pages
;
1802 p
->numa_faults_buffer_memory
[task_faults_idx(mem_node
, priv
)] += pages
;
1803 p
->numa_faults_buffer_cpu
[task_faults_idx(cpu_node
, priv
)] += pages
;
1804 p
->numa_faults_locality
[!!(flags
& TNF_FAULT_LOCAL
)] += pages
;
1807 static void reset_ptenuma_scan(struct task_struct
*p
)
1809 ACCESS_ONCE(p
->mm
->numa_scan_seq
)++;
1810 p
->mm
->numa_scan_offset
= 0;
1814 * The expensive part of numa migration is done from task_work context.
1815 * Triggered from task_tick_numa().
1817 void task_numa_work(struct callback_head
*work
)
1819 unsigned long migrate
, next_scan
, now
= jiffies
;
1820 struct task_struct
*p
= current
;
1821 struct mm_struct
*mm
= p
->mm
;
1822 struct vm_area_struct
*vma
;
1823 unsigned long start
, end
;
1824 unsigned long nr_pte_updates
= 0;
1827 WARN_ON_ONCE(p
!= container_of(work
, struct task_struct
, numa_work
));
1829 work
->next
= work
; /* protect against double add */
1831 * Who cares about NUMA placement when they're dying.
1833 * NOTE: make sure not to dereference p->mm before this check,
1834 * exit_task_work() happens _after_ exit_mm() so we could be called
1835 * without p->mm even though we still had it when we enqueued this
1838 if (p
->flags
& PF_EXITING
)
1841 if (!mm
->numa_next_scan
) {
1842 mm
->numa_next_scan
= now
+
1843 msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
1847 * Enforce maximal scan/migration frequency..
1849 migrate
= mm
->numa_next_scan
;
1850 if (time_before(now
, migrate
))
1853 if (p
->numa_scan_period
== 0) {
1854 p
->numa_scan_period_max
= task_scan_max(p
);
1855 p
->numa_scan_period
= task_scan_min(p
);
1858 next_scan
= now
+ msecs_to_jiffies(p
->numa_scan_period
);
1859 if (cmpxchg(&mm
->numa_next_scan
, migrate
, next_scan
) != migrate
)
1863 * Delay this task enough that another task of this mm will likely win
1864 * the next time around.
1866 p
->node_stamp
+= 2 * TICK_NSEC
;
1868 start
= mm
->numa_scan_offset
;
1869 pages
= sysctl_numa_balancing_scan_size
;
1870 pages
<<= 20 - PAGE_SHIFT
; /* MB in pages */
1874 down_read(&mm
->mmap_sem
);
1875 vma
= find_vma(mm
, start
);
1877 reset_ptenuma_scan(p
);
1881 for (; vma
; vma
= vma
->vm_next
) {
1882 if (!vma_migratable(vma
) || !vma_policy_mof(p
, vma
))
1886 * Shared library pages mapped by multiple processes are not
1887 * migrated as it is expected they are cache replicated. Avoid
1888 * hinting faults in read-only file-backed mappings or the vdso
1889 * as migrating the pages will be of marginal benefit.
1892 (vma
->vm_file
&& (vma
->vm_flags
& (VM_READ
|VM_WRITE
)) == (VM_READ
)))
1896 * Skip inaccessible VMAs to avoid any confusion between
1897 * PROT_NONE and NUMA hinting ptes
1899 if (!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)))
1903 start
= max(start
, vma
->vm_start
);
1904 end
= ALIGN(start
+ (pages
<< PAGE_SHIFT
), HPAGE_SIZE
);
1905 end
= min(end
, vma
->vm_end
);
1906 nr_pte_updates
+= change_prot_numa(vma
, start
, end
);
1909 * Scan sysctl_numa_balancing_scan_size but ensure that
1910 * at least one PTE is updated so that unused virtual
1911 * address space is quickly skipped.
1914 pages
-= (end
- start
) >> PAGE_SHIFT
;
1921 } while (end
!= vma
->vm_end
);
1926 * It is possible to reach the end of the VMA list but the last few
1927 * VMAs are not guaranteed to the vma_migratable. If they are not, we
1928 * would find the !migratable VMA on the next scan but not reset the
1929 * scanner to the start so check it now.
1932 mm
->numa_scan_offset
= start
;
1934 reset_ptenuma_scan(p
);
1935 up_read(&mm
->mmap_sem
);
1939 * Drive the periodic memory faults..
1941 void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
1943 struct callback_head
*work
= &curr
->numa_work
;
1947 * We don't care about NUMA placement if we don't have memory.
1949 if (!curr
->mm
|| (curr
->flags
& PF_EXITING
) || work
->next
!= work
)
1953 * Using runtime rather than walltime has the dual advantage that
1954 * we (mostly) drive the selection from busy threads and that the
1955 * task needs to have done some actual work before we bother with
1958 now
= curr
->se
.sum_exec_runtime
;
1959 period
= (u64
)curr
->numa_scan_period
* NSEC_PER_MSEC
;
1961 if (now
- curr
->node_stamp
> period
) {
1962 if (!curr
->node_stamp
)
1963 curr
->numa_scan_period
= task_scan_min(curr
);
1964 curr
->node_stamp
+= period
;
1966 if (!time_before(jiffies
, curr
->mm
->numa_next_scan
)) {
1967 init_task_work(work
, task_numa_work
); /* TODO: move this into sched_fork() */
1968 task_work_add(curr
, work
, true);
1973 static void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
1977 static inline void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
1981 static inline void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
1984 #endif /* CONFIG_NUMA_BALANCING */
1987 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
1989 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
1990 if (!parent_entity(se
))
1991 update_load_add(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
1993 if (entity_is_task(se
)) {
1994 struct rq
*rq
= rq_of(cfs_rq
);
1996 account_numa_enqueue(rq
, task_of(se
));
1997 list_add(&se
->group_node
, &rq
->cfs_tasks
);
2000 cfs_rq
->nr_running
++;
2004 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2006 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
2007 if (!parent_entity(se
))
2008 update_load_sub(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2009 if (entity_is_task(se
)) {
2010 account_numa_dequeue(rq_of(cfs_rq
), task_of(se
));
2011 list_del_init(&se
->group_node
);
2013 cfs_rq
->nr_running
--;
2016 #ifdef CONFIG_FAIR_GROUP_SCHED
2018 static inline long calc_tg_weight(struct task_group
*tg
, struct cfs_rq
*cfs_rq
)
2023 * Use this CPU's actual weight instead of the last load_contribution
2024 * to gain a more accurate current total weight. See
2025 * update_cfs_rq_load_contribution().
2027 tg_weight
= atomic_long_read(&tg
->load_avg
);
2028 tg_weight
-= cfs_rq
->tg_load_contrib
;
2029 tg_weight
+= cfs_rq
->load
.weight
;
2034 static long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2036 long tg_weight
, load
, shares
;
2038 tg_weight
= calc_tg_weight(tg
, cfs_rq
);
2039 load
= cfs_rq
->load
.weight
;
2041 shares
= (tg
->shares
* load
);
2043 shares
/= tg_weight
;
2045 if (shares
< MIN_SHARES
)
2046 shares
= MIN_SHARES
;
2047 if (shares
> tg
->shares
)
2048 shares
= tg
->shares
;
2052 # else /* CONFIG_SMP */
2053 static inline long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2057 # endif /* CONFIG_SMP */
2058 static void reweight_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
2059 unsigned long weight
)
2062 /* commit outstanding execution time */
2063 if (cfs_rq
->curr
== se
)
2064 update_curr(cfs_rq
);
2065 account_entity_dequeue(cfs_rq
, se
);
2068 update_load_set(&se
->load
, weight
);
2071 account_entity_enqueue(cfs_rq
, se
);
2074 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
);
2076 static void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2078 struct task_group
*tg
;
2079 struct sched_entity
*se
;
2083 se
= tg
->se
[cpu_of(rq_of(cfs_rq
))];
2084 if (!se
|| throttled_hierarchy(cfs_rq
))
2087 if (likely(se
->load
.weight
== tg
->shares
))
2090 shares
= calc_cfs_shares(cfs_rq
, tg
);
2092 reweight_entity(cfs_rq_of(se
), se
, shares
);
2094 #else /* CONFIG_FAIR_GROUP_SCHED */
2095 static inline void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2098 #endif /* CONFIG_FAIR_GROUP_SCHED */
2102 * We choose a half-life close to 1 scheduling period.
2103 * Note: The tables below are dependent on this value.
2105 #define LOAD_AVG_PERIOD 32
2106 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
2107 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
2109 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2110 static const u32 runnable_avg_yN_inv
[] = {
2111 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2112 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2113 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2114 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2115 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2116 0x85aac367, 0x82cd8698,
2120 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2121 * over-estimates when re-combining.
2123 static const u32 runnable_avg_yN_sum
[] = {
2124 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2125 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2126 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2131 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2133 static __always_inline u64
decay_load(u64 val
, u64 n
)
2135 unsigned int local_n
;
2139 else if (unlikely(n
> LOAD_AVG_PERIOD
* 63))
2142 /* after bounds checking we can collapse to 32-bit */
2146 * As y^PERIOD = 1/2, we can combine
2147 * y^n = 1/2^(n/PERIOD) * k^(n%PERIOD)
2148 * With a look-up table which covers k^n (n<PERIOD)
2150 * To achieve constant time decay_load.
2152 if (unlikely(local_n
>= LOAD_AVG_PERIOD
)) {
2153 val
>>= local_n
/ LOAD_AVG_PERIOD
;
2154 local_n
%= LOAD_AVG_PERIOD
;
2157 val
*= runnable_avg_yN_inv
[local_n
];
2158 /* We don't use SRR here since we always want to round down. */
2163 * For updates fully spanning n periods, the contribution to runnable
2164 * average will be: \Sum 1024*y^n
2166 * We can compute this reasonably efficiently by combining:
2167 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2169 static u32
__compute_runnable_contrib(u64 n
)
2173 if (likely(n
<= LOAD_AVG_PERIOD
))
2174 return runnable_avg_yN_sum
[n
];
2175 else if (unlikely(n
>= LOAD_AVG_MAX_N
))
2176 return LOAD_AVG_MAX
;
2178 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2180 contrib
/= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2181 contrib
+= runnable_avg_yN_sum
[LOAD_AVG_PERIOD
];
2183 n
-= LOAD_AVG_PERIOD
;
2184 } while (n
> LOAD_AVG_PERIOD
);
2186 contrib
= decay_load(contrib
, n
);
2187 return contrib
+ runnable_avg_yN_sum
[n
];
2191 * We can represent the historical contribution to runnable average as the
2192 * coefficients of a geometric series. To do this we sub-divide our runnable
2193 * history into segments of approximately 1ms (1024us); label the segment that
2194 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2196 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2198 * (now) (~1ms ago) (~2ms ago)
2200 * Let u_i denote the fraction of p_i that the entity was runnable.
2202 * We then designate the fractions u_i as our co-efficients, yielding the
2203 * following representation of historical load:
2204 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2206 * We choose y based on the with of a reasonably scheduling period, fixing:
2209 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2210 * approximately half as much as the contribution to load within the last ms
2213 * When a period "rolls over" and we have new u_0`, multiplying the previous
2214 * sum again by y is sufficient to update:
2215 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2216 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2218 static __always_inline
int __update_entity_runnable_avg(u64 now
,
2219 struct sched_avg
*sa
,
2223 u32 runnable_contrib
;
2224 int delta_w
, decayed
= 0;
2226 delta
= now
- sa
->last_runnable_update
;
2228 * This should only happen when time goes backwards, which it
2229 * unfortunately does during sched clock init when we swap over to TSC.
2231 if ((s64
)delta
< 0) {
2232 sa
->last_runnable_update
= now
;
2237 * Use 1024ns as the unit of measurement since it's a reasonable
2238 * approximation of 1us and fast to compute.
2243 sa
->last_runnable_update
= now
;
2245 /* delta_w is the amount already accumulated against our next period */
2246 delta_w
= sa
->runnable_avg_period
% 1024;
2247 if (delta
+ delta_w
>= 1024) {
2248 /* period roll-over */
2252 * Now that we know we're crossing a period boundary, figure
2253 * out how much from delta we need to complete the current
2254 * period and accrue it.
2256 delta_w
= 1024 - delta_w
;
2258 sa
->runnable_avg_sum
+= delta_w
;
2259 sa
->runnable_avg_period
+= delta_w
;
2263 /* Figure out how many additional periods this update spans */
2264 periods
= delta
/ 1024;
2267 sa
->runnable_avg_sum
= decay_load(sa
->runnable_avg_sum
,
2269 sa
->runnable_avg_period
= decay_load(sa
->runnable_avg_period
,
2272 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2273 runnable_contrib
= __compute_runnable_contrib(periods
);
2275 sa
->runnable_avg_sum
+= runnable_contrib
;
2276 sa
->runnable_avg_period
+= runnable_contrib
;
2279 /* Remainder of delta accrued against u_0` */
2281 sa
->runnable_avg_sum
+= delta
;
2282 sa
->runnable_avg_period
+= delta
;
2287 /* Synchronize an entity's decay with its parenting cfs_rq.*/
2288 static inline u64
__synchronize_entity_decay(struct sched_entity
*se
)
2290 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2291 u64 decays
= atomic64_read(&cfs_rq
->decay_counter
);
2293 decays
-= se
->avg
.decay_count
;
2297 se
->avg
.load_avg_contrib
= decay_load(se
->avg
.load_avg_contrib
, decays
);
2298 se
->avg
.decay_count
= 0;
2303 #ifdef CONFIG_FAIR_GROUP_SCHED
2304 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq
*cfs_rq
,
2307 struct task_group
*tg
= cfs_rq
->tg
;
2310 tg_contrib
= cfs_rq
->runnable_load_avg
+ cfs_rq
->blocked_load_avg
;
2311 tg_contrib
-= cfs_rq
->tg_load_contrib
;
2313 if (force_update
|| abs(tg_contrib
) > cfs_rq
->tg_load_contrib
/ 8) {
2314 atomic_long_add(tg_contrib
, &tg
->load_avg
);
2315 cfs_rq
->tg_load_contrib
+= tg_contrib
;
2320 * Aggregate cfs_rq runnable averages into an equivalent task_group
2321 * representation for computing load contributions.
2323 static inline void __update_tg_runnable_avg(struct sched_avg
*sa
,
2324 struct cfs_rq
*cfs_rq
)
2326 struct task_group
*tg
= cfs_rq
->tg
;
2329 /* The fraction of a cpu used by this cfs_rq */
2330 contrib
= div_u64((u64
)sa
->runnable_avg_sum
<< NICE_0_SHIFT
,
2331 sa
->runnable_avg_period
+ 1);
2332 contrib
-= cfs_rq
->tg_runnable_contrib
;
2334 if (abs(contrib
) > cfs_rq
->tg_runnable_contrib
/ 64) {
2335 atomic_add(contrib
, &tg
->runnable_avg
);
2336 cfs_rq
->tg_runnable_contrib
+= contrib
;
2340 static inline void __update_group_entity_contrib(struct sched_entity
*se
)
2342 struct cfs_rq
*cfs_rq
= group_cfs_rq(se
);
2343 struct task_group
*tg
= cfs_rq
->tg
;
2348 contrib
= cfs_rq
->tg_load_contrib
* tg
->shares
;
2349 se
->avg
.load_avg_contrib
= div_u64(contrib
,
2350 atomic_long_read(&tg
->load_avg
) + 1);
2353 * For group entities we need to compute a correction term in the case
2354 * that they are consuming <1 cpu so that we would contribute the same
2355 * load as a task of equal weight.
2357 * Explicitly co-ordinating this measurement would be expensive, but
2358 * fortunately the sum of each cpus contribution forms a usable
2359 * lower-bound on the true value.
2361 * Consider the aggregate of 2 contributions. Either they are disjoint
2362 * (and the sum represents true value) or they are disjoint and we are
2363 * understating by the aggregate of their overlap.
2365 * Extending this to N cpus, for a given overlap, the maximum amount we
2366 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
2367 * cpus that overlap for this interval and w_i is the interval width.
2369 * On a small machine; the first term is well-bounded which bounds the
2370 * total error since w_i is a subset of the period. Whereas on a
2371 * larger machine, while this first term can be larger, if w_i is the
2372 * of consequential size guaranteed to see n_i*w_i quickly converge to
2373 * our upper bound of 1-cpu.
2375 runnable_avg
= atomic_read(&tg
->runnable_avg
);
2376 if (runnable_avg
< NICE_0_LOAD
) {
2377 se
->avg
.load_avg_contrib
*= runnable_avg
;
2378 se
->avg
.load_avg_contrib
>>= NICE_0_SHIFT
;
2382 static inline void update_rq_runnable_avg(struct rq
*rq
, int runnable
)
2384 __update_entity_runnable_avg(rq_clock_task(rq
), &rq
->avg
, runnable
);
2385 __update_tg_runnable_avg(&rq
->avg
, &rq
->cfs
);
2387 #else /* CONFIG_FAIR_GROUP_SCHED */
2388 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq
*cfs_rq
,
2389 int force_update
) {}
2390 static inline void __update_tg_runnable_avg(struct sched_avg
*sa
,
2391 struct cfs_rq
*cfs_rq
) {}
2392 static inline void __update_group_entity_contrib(struct sched_entity
*se
) {}
2393 static inline void update_rq_runnable_avg(struct rq
*rq
, int runnable
) {}
2394 #endif /* CONFIG_FAIR_GROUP_SCHED */
2396 static inline void __update_task_entity_contrib(struct sched_entity
*se
)
2400 /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
2401 contrib
= se
->avg
.runnable_avg_sum
* scale_load_down(se
->load
.weight
);
2402 contrib
/= (se
->avg
.runnable_avg_period
+ 1);
2403 se
->avg
.load_avg_contrib
= scale_load(contrib
);
2406 /* Compute the current contribution to load_avg by se, return any delta */
2407 static long __update_entity_load_avg_contrib(struct sched_entity
*se
)
2409 long old_contrib
= se
->avg
.load_avg_contrib
;
2411 if (entity_is_task(se
)) {
2412 __update_task_entity_contrib(se
);
2414 __update_tg_runnable_avg(&se
->avg
, group_cfs_rq(se
));
2415 __update_group_entity_contrib(se
);
2418 return se
->avg
.load_avg_contrib
- old_contrib
;
2421 static inline void subtract_blocked_load_contrib(struct cfs_rq
*cfs_rq
,
2424 if (likely(load_contrib
< cfs_rq
->blocked_load_avg
))
2425 cfs_rq
->blocked_load_avg
-= load_contrib
;
2427 cfs_rq
->blocked_load_avg
= 0;
2430 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
);
2432 /* Update a sched_entity's runnable average */
2433 static inline void update_entity_load_avg(struct sched_entity
*se
,
2436 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2441 * For a group entity we need to use their owned cfs_rq_clock_task() in
2442 * case they are the parent of a throttled hierarchy.
2444 if (entity_is_task(se
))
2445 now
= cfs_rq_clock_task(cfs_rq
);
2447 now
= cfs_rq_clock_task(group_cfs_rq(se
));
2449 if (!__update_entity_runnable_avg(now
, &se
->avg
, se
->on_rq
))
2452 contrib_delta
= __update_entity_load_avg_contrib(se
);
2458 cfs_rq
->runnable_load_avg
+= contrib_delta
;
2460 subtract_blocked_load_contrib(cfs_rq
, -contrib_delta
);
2464 * Decay the load contributed by all blocked children and account this so that
2465 * their contribution may appropriately discounted when they wake up.
2467 static void update_cfs_rq_blocked_load(struct cfs_rq
*cfs_rq
, int force_update
)
2469 u64 now
= cfs_rq_clock_task(cfs_rq
) >> 20;
2472 decays
= now
- cfs_rq
->last_decay
;
2473 if (!decays
&& !force_update
)
2476 if (atomic_long_read(&cfs_rq
->removed_load
)) {
2477 unsigned long removed_load
;
2478 removed_load
= atomic_long_xchg(&cfs_rq
->removed_load
, 0);
2479 subtract_blocked_load_contrib(cfs_rq
, removed_load
);
2483 cfs_rq
->blocked_load_avg
= decay_load(cfs_rq
->blocked_load_avg
,
2485 atomic64_add(decays
, &cfs_rq
->decay_counter
);
2486 cfs_rq
->last_decay
= now
;
2489 __update_cfs_rq_tg_load_contrib(cfs_rq
, force_update
);
2492 /* Add the load generated by se into cfs_rq's child load-average */
2493 static inline void enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
,
2494 struct sched_entity
*se
,
2498 * We track migrations using entity decay_count <= 0, on a wake-up
2499 * migration we use a negative decay count to track the remote decays
2500 * accumulated while sleeping.
2502 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
2503 * are seen by enqueue_entity_load_avg() as a migration with an already
2504 * constructed load_avg_contrib.
2506 if (unlikely(se
->avg
.decay_count
<= 0)) {
2507 se
->avg
.last_runnable_update
= rq_clock_task(rq_of(cfs_rq
));
2508 if (se
->avg
.decay_count
) {
2510 * In a wake-up migration we have to approximate the
2511 * time sleeping. This is because we can't synchronize
2512 * clock_task between the two cpus, and it is not
2513 * guaranteed to be read-safe. Instead, we can
2514 * approximate this using our carried decays, which are
2515 * explicitly atomically readable.
2517 se
->avg
.last_runnable_update
-= (-se
->avg
.decay_count
)
2519 update_entity_load_avg(se
, 0);
2520 /* Indicate that we're now synchronized and on-rq */
2521 se
->avg
.decay_count
= 0;
2525 __synchronize_entity_decay(se
);
2528 /* migrated tasks did not contribute to our blocked load */
2530 subtract_blocked_load_contrib(cfs_rq
, se
->avg
.load_avg_contrib
);
2531 update_entity_load_avg(se
, 0);
2534 cfs_rq
->runnable_load_avg
+= se
->avg
.load_avg_contrib
;
2535 /* we force update consideration on load-balancer moves */
2536 update_cfs_rq_blocked_load(cfs_rq
, !wakeup
);
2540 * Remove se's load from this cfs_rq child load-average, if the entity is
2541 * transitioning to a blocked state we track its projected decay using
2544 static inline void dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
,
2545 struct sched_entity
*se
,
2548 update_entity_load_avg(se
, 1);
2549 /* we force update consideration on load-balancer moves */
2550 update_cfs_rq_blocked_load(cfs_rq
, !sleep
);
2552 cfs_rq
->runnable_load_avg
-= se
->avg
.load_avg_contrib
;
2554 cfs_rq
->blocked_load_avg
+= se
->avg
.load_avg_contrib
;
2555 se
->avg
.decay_count
= atomic64_read(&cfs_rq
->decay_counter
);
2556 } /* migrations, e.g. sleep=0 leave decay_count == 0 */
2560 * Update the rq's load with the elapsed running time before entering
2561 * idle. if the last scheduled task is not a CFS task, idle_enter will
2562 * be the only way to update the runnable statistic.
2564 void idle_enter_fair(struct rq
*this_rq
)
2566 update_rq_runnable_avg(this_rq
, 1);
2570 * Update the rq's load with the elapsed idle time before a task is
2571 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2572 * be the only way to update the runnable statistic.
2574 void idle_exit_fair(struct rq
*this_rq
)
2576 update_rq_runnable_avg(this_rq
, 0);
2579 static int idle_balance(struct rq
*this_rq
);
2581 #else /* CONFIG_SMP */
2583 static inline void update_entity_load_avg(struct sched_entity
*se
,
2584 int update_cfs_rq
) {}
2585 static inline void update_rq_runnable_avg(struct rq
*rq
, int runnable
) {}
2586 static inline void enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
,
2587 struct sched_entity
*se
,
2589 static inline void dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
,
2590 struct sched_entity
*se
,
2592 static inline void update_cfs_rq_blocked_load(struct cfs_rq
*cfs_rq
,
2593 int force_update
) {}
2595 static inline int idle_balance(struct rq
*rq
)
2600 #endif /* CONFIG_SMP */
2602 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2604 #ifdef CONFIG_SCHEDSTATS
2605 struct task_struct
*tsk
= NULL
;
2607 if (entity_is_task(se
))
2610 if (se
->statistics
.sleep_start
) {
2611 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.sleep_start
;
2616 if (unlikely(delta
> se
->statistics
.sleep_max
))
2617 se
->statistics
.sleep_max
= delta
;
2619 se
->statistics
.sleep_start
= 0;
2620 se
->statistics
.sum_sleep_runtime
+= delta
;
2623 account_scheduler_latency(tsk
, delta
>> 10, 1);
2624 trace_sched_stat_sleep(tsk
, delta
);
2627 if (se
->statistics
.block_start
) {
2628 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.block_start
;
2633 if (unlikely(delta
> se
->statistics
.block_max
))
2634 se
->statistics
.block_max
= delta
;
2636 se
->statistics
.block_start
= 0;
2637 se
->statistics
.sum_sleep_runtime
+= delta
;
2640 if (tsk
->in_iowait
) {
2641 se
->statistics
.iowait_sum
+= delta
;
2642 se
->statistics
.iowait_count
++;
2643 trace_sched_stat_iowait(tsk
, delta
);
2646 trace_sched_stat_blocked(tsk
, delta
);
2649 * Blocking time is in units of nanosecs, so shift by
2650 * 20 to get a milliseconds-range estimation of the
2651 * amount of time that the task spent sleeping:
2653 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
2654 profile_hits(SLEEP_PROFILING
,
2655 (void *)get_wchan(tsk
),
2658 account_scheduler_latency(tsk
, delta
>> 10, 0);
2664 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2666 #ifdef CONFIG_SCHED_DEBUG
2667 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
2672 if (d
> 3*sysctl_sched_latency
)
2673 schedstat_inc(cfs_rq
, nr_spread_over
);
2678 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
2680 u64 vruntime
= cfs_rq
->min_vruntime
;
2683 * The 'current' period is already promised to the current tasks,
2684 * however the extra weight of the new task will slow them down a
2685 * little, place the new task so that it fits in the slot that
2686 * stays open at the end.
2688 if (initial
&& sched_feat(START_DEBIT
))
2689 vruntime
+= sched_vslice(cfs_rq
, se
);
2691 /* sleeps up to a single latency don't count. */
2693 unsigned long thresh
= sysctl_sched_latency
;
2696 * Halve their sleep time's effect, to allow
2697 * for a gentler effect of sleepers:
2699 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
2705 /* ensure we never gain time by being placed backwards. */
2706 se
->vruntime
= max_vruntime(se
->vruntime
, vruntime
);
2709 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
);
2712 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
2715 * Update the normalized vruntime before updating min_vruntime
2716 * through calling update_curr().
2718 if (!(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_WAKING
))
2719 se
->vruntime
+= cfs_rq
->min_vruntime
;
2722 * Update run-time statistics of the 'current'.
2724 update_curr(cfs_rq
);
2725 enqueue_entity_load_avg(cfs_rq
, se
, flags
& ENQUEUE_WAKEUP
);
2726 account_entity_enqueue(cfs_rq
, se
);
2727 update_cfs_shares(cfs_rq
);
2729 if (flags
& ENQUEUE_WAKEUP
) {
2730 place_entity(cfs_rq
, se
, 0);
2731 enqueue_sleeper(cfs_rq
, se
);
2734 update_stats_enqueue(cfs_rq
, se
);
2735 check_spread(cfs_rq
, se
);
2736 if (se
!= cfs_rq
->curr
)
2737 __enqueue_entity(cfs_rq
, se
);
2740 if (cfs_rq
->nr_running
== 1) {
2741 list_add_leaf_cfs_rq(cfs_rq
);
2742 check_enqueue_throttle(cfs_rq
);
2746 static void __clear_buddies_last(struct sched_entity
*se
)
2748 for_each_sched_entity(se
) {
2749 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2750 if (cfs_rq
->last
!= se
)
2753 cfs_rq
->last
= NULL
;
2757 static void __clear_buddies_next(struct sched_entity
*se
)
2759 for_each_sched_entity(se
) {
2760 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2761 if (cfs_rq
->next
!= se
)
2764 cfs_rq
->next
= NULL
;
2768 static void __clear_buddies_skip(struct sched_entity
*se
)
2770 for_each_sched_entity(se
) {
2771 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2772 if (cfs_rq
->skip
!= se
)
2775 cfs_rq
->skip
= NULL
;
2779 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2781 if (cfs_rq
->last
== se
)
2782 __clear_buddies_last(se
);
2784 if (cfs_rq
->next
== se
)
2785 __clear_buddies_next(se
);
2787 if (cfs_rq
->skip
== se
)
2788 __clear_buddies_skip(se
);
2791 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
2794 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
2797 * Update run-time statistics of the 'current'.
2799 update_curr(cfs_rq
);
2800 dequeue_entity_load_avg(cfs_rq
, se
, flags
& DEQUEUE_SLEEP
);
2802 update_stats_dequeue(cfs_rq
, se
);
2803 if (flags
& DEQUEUE_SLEEP
) {
2804 #ifdef CONFIG_SCHEDSTATS
2805 if (entity_is_task(se
)) {
2806 struct task_struct
*tsk
= task_of(se
);
2808 if (tsk
->state
& TASK_INTERRUPTIBLE
)
2809 se
->statistics
.sleep_start
= rq_clock(rq_of(cfs_rq
));
2810 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
2811 se
->statistics
.block_start
= rq_clock(rq_of(cfs_rq
));
2816 clear_buddies(cfs_rq
, se
);
2818 if (se
!= cfs_rq
->curr
)
2819 __dequeue_entity(cfs_rq
, se
);
2821 account_entity_dequeue(cfs_rq
, se
);
2824 * Normalize the entity after updating the min_vruntime because the
2825 * update can refer to the ->curr item and we need to reflect this
2826 * movement in our normalized position.
2828 if (!(flags
& DEQUEUE_SLEEP
))
2829 se
->vruntime
-= cfs_rq
->min_vruntime
;
2831 /* return excess runtime on last dequeue */
2832 return_cfs_rq_runtime(cfs_rq
);
2834 update_min_vruntime(cfs_rq
);
2835 update_cfs_shares(cfs_rq
);
2839 * Preempt the current task with a newly woken task if needed:
2842 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
2844 unsigned long ideal_runtime
, delta_exec
;
2845 struct sched_entity
*se
;
2848 ideal_runtime
= sched_slice(cfs_rq
, curr
);
2849 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
2850 if (delta_exec
> ideal_runtime
) {
2851 resched_task(rq_of(cfs_rq
)->curr
);
2853 * The current task ran long enough, ensure it doesn't get
2854 * re-elected due to buddy favours.
2856 clear_buddies(cfs_rq
, curr
);
2861 * Ensure that a task that missed wakeup preemption by a
2862 * narrow margin doesn't have to wait for a full slice.
2863 * This also mitigates buddy induced latencies under load.
2865 if (delta_exec
< sysctl_sched_min_granularity
)
2868 se
= __pick_first_entity(cfs_rq
);
2869 delta
= curr
->vruntime
- se
->vruntime
;
2874 if (delta
> ideal_runtime
)
2875 resched_task(rq_of(cfs_rq
)->curr
);
2879 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2881 /* 'current' is not kept within the tree. */
2884 * Any task has to be enqueued before it get to execute on
2885 * a CPU. So account for the time it spent waiting on the
2888 update_stats_wait_end(cfs_rq
, se
);
2889 __dequeue_entity(cfs_rq
, se
);
2892 update_stats_curr_start(cfs_rq
, se
);
2894 #ifdef CONFIG_SCHEDSTATS
2896 * Track our maximum slice length, if the CPU's load is at
2897 * least twice that of our own weight (i.e. dont track it
2898 * when there are only lesser-weight tasks around):
2900 if (rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
2901 se
->statistics
.slice_max
= max(se
->statistics
.slice_max
,
2902 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
2905 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
2909 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
2912 * Pick the next process, keeping these things in mind, in this order:
2913 * 1) keep things fair between processes/task groups
2914 * 2) pick the "next" process, since someone really wants that to run
2915 * 3) pick the "last" process, for cache locality
2916 * 4) do not run the "skip" process, if something else is available
2918 static struct sched_entity
*
2919 pick_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
2921 struct sched_entity
*left
= __pick_first_entity(cfs_rq
);
2922 struct sched_entity
*se
;
2925 * If curr is set we have to see if its left of the leftmost entity
2926 * still in the tree, provided there was anything in the tree at all.
2928 if (!left
|| (curr
&& entity_before(curr
, left
)))
2931 se
= left
; /* ideally we run the leftmost entity */
2934 * Avoid running the skip buddy, if running something else can
2935 * be done without getting too unfair.
2937 if (cfs_rq
->skip
== se
) {
2938 struct sched_entity
*second
;
2941 second
= __pick_first_entity(cfs_rq
);
2943 second
= __pick_next_entity(se
);
2944 if (!second
|| (curr
&& entity_before(curr
, second
)))
2948 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
2953 * Prefer last buddy, try to return the CPU to a preempted task.
2955 if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1)
2959 * Someone really wants this to run. If it's not unfair, run it.
2961 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1)
2964 clear_buddies(cfs_rq
, se
);
2969 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
2971 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
2974 * If still on the runqueue then deactivate_task()
2975 * was not called and update_curr() has to be done:
2978 update_curr(cfs_rq
);
2980 /* throttle cfs_rqs exceeding runtime */
2981 check_cfs_rq_runtime(cfs_rq
);
2983 check_spread(cfs_rq
, prev
);
2985 update_stats_wait_start(cfs_rq
, prev
);
2986 /* Put 'current' back into the tree. */
2987 __enqueue_entity(cfs_rq
, prev
);
2988 /* in !on_rq case, update occurred at dequeue */
2989 update_entity_load_avg(prev
, 1);
2991 cfs_rq
->curr
= NULL
;
2995 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
2998 * Update run-time statistics of the 'current'.
3000 update_curr(cfs_rq
);
3003 * Ensure that runnable average is periodically updated.
3005 update_entity_load_avg(curr
, 1);
3006 update_cfs_rq_blocked_load(cfs_rq
, 1);
3007 update_cfs_shares(cfs_rq
);
3009 #ifdef CONFIG_SCHED_HRTICK
3011 * queued ticks are scheduled to match the slice, so don't bother
3012 * validating it and just reschedule.
3015 resched_task(rq_of(cfs_rq
)->curr
);
3019 * don't let the period tick interfere with the hrtick preemption
3021 if (!sched_feat(DOUBLE_TICK
) &&
3022 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
3026 if (cfs_rq
->nr_running
> 1)
3027 check_preempt_tick(cfs_rq
, curr
);
3031 /**************************************************
3032 * CFS bandwidth control machinery
3035 #ifdef CONFIG_CFS_BANDWIDTH
3037 #ifdef HAVE_JUMP_LABEL
3038 static struct static_key __cfs_bandwidth_used
;
3040 static inline bool cfs_bandwidth_used(void)
3042 return static_key_false(&__cfs_bandwidth_used
);
3045 void cfs_bandwidth_usage_inc(void)
3047 static_key_slow_inc(&__cfs_bandwidth_used
);
3050 void cfs_bandwidth_usage_dec(void)
3052 static_key_slow_dec(&__cfs_bandwidth_used
);
3054 #else /* HAVE_JUMP_LABEL */
3055 static bool cfs_bandwidth_used(void)
3060 void cfs_bandwidth_usage_inc(void) {}
3061 void cfs_bandwidth_usage_dec(void) {}
3062 #endif /* HAVE_JUMP_LABEL */
3065 * default period for cfs group bandwidth.
3066 * default: 0.1s, units: nanoseconds
3068 static inline u64
default_cfs_period(void)
3070 return 100000000ULL;
3073 static inline u64
sched_cfs_bandwidth_slice(void)
3075 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
3079 * Replenish runtime according to assigned quota and update expiration time.
3080 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3081 * additional synchronization around rq->lock.
3083 * requires cfs_b->lock
3085 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
3089 if (cfs_b
->quota
== RUNTIME_INF
)
3092 now
= sched_clock_cpu(smp_processor_id());
3093 cfs_b
->runtime
= cfs_b
->quota
;
3094 cfs_b
->runtime_expires
= now
+ ktime_to_ns(cfs_b
->period
);
3097 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
3099 return &tg
->cfs_bandwidth
;
3102 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3103 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
3105 if (unlikely(cfs_rq
->throttle_count
))
3106 return cfs_rq
->throttled_clock_task
;
3108 return rq_clock_task(rq_of(cfs_rq
)) - cfs_rq
->throttled_clock_task_time
;
3111 /* returns 0 on failure to allocate runtime */
3112 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3114 struct task_group
*tg
= cfs_rq
->tg
;
3115 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(tg
);
3116 u64 amount
= 0, min_amount
, expires
;
3118 /* note: this is a positive sum as runtime_remaining <= 0 */
3119 min_amount
= sched_cfs_bandwidth_slice() - cfs_rq
->runtime_remaining
;
3121 raw_spin_lock(&cfs_b
->lock
);
3122 if (cfs_b
->quota
== RUNTIME_INF
)
3123 amount
= min_amount
;
3126 * If the bandwidth pool has become inactive, then at least one
3127 * period must have elapsed since the last consumption.
3128 * Refresh the global state and ensure bandwidth timer becomes
3131 if (!cfs_b
->timer_active
) {
3132 __refill_cfs_bandwidth_runtime(cfs_b
);
3133 __start_cfs_bandwidth(cfs_b
, false);
3136 if (cfs_b
->runtime
> 0) {
3137 amount
= min(cfs_b
->runtime
, min_amount
);
3138 cfs_b
->runtime
-= amount
;
3142 expires
= cfs_b
->runtime_expires
;
3143 raw_spin_unlock(&cfs_b
->lock
);
3145 cfs_rq
->runtime_remaining
+= amount
;
3147 * we may have advanced our local expiration to account for allowed
3148 * spread between our sched_clock and the one on which runtime was
3151 if ((s64
)(expires
- cfs_rq
->runtime_expires
) > 0)
3152 cfs_rq
->runtime_expires
= expires
;
3154 return cfs_rq
->runtime_remaining
> 0;
3158 * Note: This depends on the synchronization provided by sched_clock and the
3159 * fact that rq->clock snapshots this value.
3161 static void expire_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3163 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3165 /* if the deadline is ahead of our clock, nothing to do */
3166 if (likely((s64
)(rq_clock(rq_of(cfs_rq
)) - cfs_rq
->runtime_expires
) < 0))
3169 if (cfs_rq
->runtime_remaining
< 0)
3173 * If the local deadline has passed we have to consider the
3174 * possibility that our sched_clock is 'fast' and the global deadline
3175 * has not truly expired.
3177 * Fortunately we can check determine whether this the case by checking
3178 * whether the global deadline has advanced.
3181 if ((s64
)(cfs_rq
->runtime_expires
- cfs_b
->runtime_expires
) >= 0) {
3182 /* extend local deadline, drift is bounded above by 2 ticks */
3183 cfs_rq
->runtime_expires
+= TICK_NSEC
;
3185 /* global deadline is ahead, expiration has passed */
3186 cfs_rq
->runtime_remaining
= 0;
3190 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3192 /* dock delta_exec before expiring quota (as it could span periods) */
3193 cfs_rq
->runtime_remaining
-= delta_exec
;
3194 expire_cfs_rq_runtime(cfs_rq
);
3196 if (likely(cfs_rq
->runtime_remaining
> 0))
3200 * if we're unable to extend our runtime we resched so that the active
3201 * hierarchy can be throttled
3203 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
3204 resched_task(rq_of(cfs_rq
)->curr
);
3207 static __always_inline
3208 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3210 if (!cfs_bandwidth_used() || !cfs_rq
->runtime_enabled
)
3213 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
3216 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
3218 return cfs_bandwidth_used() && cfs_rq
->throttled
;
3221 /* check whether cfs_rq, or any parent, is throttled */
3222 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
3224 return cfs_bandwidth_used() && cfs_rq
->throttle_count
;
3228 * Ensure that neither of the group entities corresponding to src_cpu or
3229 * dest_cpu are members of a throttled hierarchy when performing group
3230 * load-balance operations.
3232 static inline int throttled_lb_pair(struct task_group
*tg
,
3233 int src_cpu
, int dest_cpu
)
3235 struct cfs_rq
*src_cfs_rq
, *dest_cfs_rq
;
3237 src_cfs_rq
= tg
->cfs_rq
[src_cpu
];
3238 dest_cfs_rq
= tg
->cfs_rq
[dest_cpu
];
3240 return throttled_hierarchy(src_cfs_rq
) ||
3241 throttled_hierarchy(dest_cfs_rq
);
3244 /* updated child weight may affect parent so we have to do this bottom up */
3245 static int tg_unthrottle_up(struct task_group
*tg
, void *data
)
3247 struct rq
*rq
= data
;
3248 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3250 cfs_rq
->throttle_count
--;
3252 if (!cfs_rq
->throttle_count
) {
3253 /* adjust cfs_rq_clock_task() */
3254 cfs_rq
->throttled_clock_task_time
+= rq_clock_task(rq
) -
3255 cfs_rq
->throttled_clock_task
;
3262 static int tg_throttle_down(struct task_group
*tg
, void *data
)
3264 struct rq
*rq
= data
;
3265 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3267 /* group is entering throttled state, stop time */
3268 if (!cfs_rq
->throttle_count
)
3269 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
3270 cfs_rq
->throttle_count
++;
3275 static void throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
3277 struct rq
*rq
= rq_of(cfs_rq
);
3278 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3279 struct sched_entity
*se
;
3280 long task_delta
, dequeue
= 1;
3282 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
3284 /* freeze hierarchy runnable averages while throttled */
3286 walk_tg_tree_from(cfs_rq
->tg
, tg_throttle_down
, tg_nop
, (void *)rq
);
3289 task_delta
= cfs_rq
->h_nr_running
;
3290 for_each_sched_entity(se
) {
3291 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
3292 /* throttled entity or throttle-on-deactivate */
3297 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
3298 qcfs_rq
->h_nr_running
-= task_delta
;
3300 if (qcfs_rq
->load
.weight
)
3305 rq
->nr_running
-= task_delta
;
3307 cfs_rq
->throttled
= 1;
3308 cfs_rq
->throttled_clock
= rq_clock(rq
);
3309 raw_spin_lock(&cfs_b
->lock
);
3310 list_add_tail_rcu(&cfs_rq
->throttled_list
, &cfs_b
->throttled_cfs_rq
);
3311 if (!cfs_b
->timer_active
)
3312 __start_cfs_bandwidth(cfs_b
, false);
3313 raw_spin_unlock(&cfs_b
->lock
);
3316 void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
3318 struct rq
*rq
= rq_of(cfs_rq
);
3319 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3320 struct sched_entity
*se
;
3324 se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
3326 cfs_rq
->throttled
= 0;
3328 update_rq_clock(rq
);
3330 raw_spin_lock(&cfs_b
->lock
);
3331 cfs_b
->throttled_time
+= rq_clock(rq
) - cfs_rq
->throttled_clock
;
3332 list_del_rcu(&cfs_rq
->throttled_list
);
3333 raw_spin_unlock(&cfs_b
->lock
);
3335 /* update hierarchical throttle state */
3336 walk_tg_tree_from(cfs_rq
->tg
, tg_nop
, tg_unthrottle_up
, (void *)rq
);
3338 if (!cfs_rq
->load
.weight
)
3341 task_delta
= cfs_rq
->h_nr_running
;
3342 for_each_sched_entity(se
) {
3346 cfs_rq
= cfs_rq_of(se
);
3348 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
3349 cfs_rq
->h_nr_running
+= task_delta
;
3351 if (cfs_rq_throttled(cfs_rq
))
3356 rq
->nr_running
+= task_delta
;
3358 /* determine whether we need to wake up potentially idle cpu */
3359 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
3360 resched_task(rq
->curr
);
3363 static u64
distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
,
3364 u64 remaining
, u64 expires
)
3366 struct cfs_rq
*cfs_rq
;
3367 u64 runtime
= remaining
;
3370 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
3372 struct rq
*rq
= rq_of(cfs_rq
);
3374 raw_spin_lock(&rq
->lock
);
3375 if (!cfs_rq_throttled(cfs_rq
))
3378 runtime
= -cfs_rq
->runtime_remaining
+ 1;
3379 if (runtime
> remaining
)
3380 runtime
= remaining
;
3381 remaining
-= runtime
;
3383 cfs_rq
->runtime_remaining
+= runtime
;
3384 cfs_rq
->runtime_expires
= expires
;
3386 /* we check whether we're throttled above */
3387 if (cfs_rq
->runtime_remaining
> 0)
3388 unthrottle_cfs_rq(cfs_rq
);
3391 raw_spin_unlock(&rq
->lock
);
3402 * Responsible for refilling a task_group's bandwidth and unthrottling its
3403 * cfs_rqs as appropriate. If there has been no activity within the last
3404 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3405 * used to track this state.
3407 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
)
3409 u64 runtime
, runtime_expires
;
3410 int idle
= 1, throttled
;
3412 raw_spin_lock(&cfs_b
->lock
);
3413 /* no need to continue the timer with no bandwidth constraint */
3414 if (cfs_b
->quota
== RUNTIME_INF
)
3417 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
3418 /* idle depends on !throttled (for the case of a large deficit) */
3419 idle
= cfs_b
->idle
&& !throttled
;
3420 cfs_b
->nr_periods
+= overrun
;
3422 /* if we're going inactive then everything else can be deferred */
3427 * if we have relooped after returning idle once, we need to update our
3428 * status as actually running, so that other cpus doing
3429 * __start_cfs_bandwidth will stop trying to cancel us.
3431 cfs_b
->timer_active
= 1;
3433 __refill_cfs_bandwidth_runtime(cfs_b
);
3436 /* mark as potentially idle for the upcoming period */
3441 /* account preceding periods in which throttling occurred */
3442 cfs_b
->nr_throttled
+= overrun
;
3445 * There are throttled entities so we must first use the new bandwidth
3446 * to unthrottle them before making it generally available. This
3447 * ensures that all existing debts will be paid before a new cfs_rq is
3450 runtime
= cfs_b
->runtime
;
3451 runtime_expires
= cfs_b
->runtime_expires
;
3455 * This check is repeated as we are holding onto the new bandwidth
3456 * while we unthrottle. This can potentially race with an unthrottled
3457 * group trying to acquire new bandwidth from the global pool.
3459 while (throttled
&& runtime
> 0) {
3460 raw_spin_unlock(&cfs_b
->lock
);
3461 /* we can't nest cfs_b->lock while distributing bandwidth */
3462 runtime
= distribute_cfs_runtime(cfs_b
, runtime
,
3464 raw_spin_lock(&cfs_b
->lock
);
3466 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
3469 /* return (any) remaining runtime */
3470 cfs_b
->runtime
= runtime
;
3472 * While we are ensured activity in the period following an
3473 * unthrottle, this also covers the case in which the new bandwidth is
3474 * insufficient to cover the existing bandwidth deficit. (Forcing the
3475 * timer to remain active while there are any throttled entities.)
3480 cfs_b
->timer_active
= 0;
3481 raw_spin_unlock(&cfs_b
->lock
);
3486 /* a cfs_rq won't donate quota below this amount */
3487 static const u64 min_cfs_rq_runtime
= 1 * NSEC_PER_MSEC
;
3488 /* minimum remaining period time to redistribute slack quota */
3489 static const u64 min_bandwidth_expiration
= 2 * NSEC_PER_MSEC
;
3490 /* how long we wait to gather additional slack before distributing */
3491 static const u64 cfs_bandwidth_slack_period
= 5 * NSEC_PER_MSEC
;
3494 * Are we near the end of the current quota period?
3496 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3497 * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
3498 * migrate_hrtimers, base is never cleared, so we are fine.
3500 static int runtime_refresh_within(struct cfs_bandwidth
*cfs_b
, u64 min_expire
)
3502 struct hrtimer
*refresh_timer
= &cfs_b
->period_timer
;
3505 /* if the call-back is running a quota refresh is already occurring */
3506 if (hrtimer_callback_running(refresh_timer
))
3509 /* is a quota refresh about to occur? */
3510 remaining
= ktime_to_ns(hrtimer_expires_remaining(refresh_timer
));
3511 if (remaining
< min_expire
)
3517 static void start_cfs_slack_bandwidth(struct cfs_bandwidth
*cfs_b
)
3519 u64 min_left
= cfs_bandwidth_slack_period
+ min_bandwidth_expiration
;
3521 /* if there's a quota refresh soon don't bother with slack */
3522 if (runtime_refresh_within(cfs_b
, min_left
))
3525 start_bandwidth_timer(&cfs_b
->slack_timer
,
3526 ns_to_ktime(cfs_bandwidth_slack_period
));
3529 /* we know any runtime found here is valid as update_curr() precedes return */
3530 static void __return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3532 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3533 s64 slack_runtime
= cfs_rq
->runtime_remaining
- min_cfs_rq_runtime
;
3535 if (slack_runtime
<= 0)
3538 raw_spin_lock(&cfs_b
->lock
);
3539 if (cfs_b
->quota
!= RUNTIME_INF
&&
3540 cfs_rq
->runtime_expires
== cfs_b
->runtime_expires
) {
3541 cfs_b
->runtime
+= slack_runtime
;
3543 /* we are under rq->lock, defer unthrottling using a timer */
3544 if (cfs_b
->runtime
> sched_cfs_bandwidth_slice() &&
3545 !list_empty(&cfs_b
->throttled_cfs_rq
))
3546 start_cfs_slack_bandwidth(cfs_b
);
3548 raw_spin_unlock(&cfs_b
->lock
);
3550 /* even if it's not valid for return we don't want to try again */
3551 cfs_rq
->runtime_remaining
-= slack_runtime
;
3554 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3556 if (!cfs_bandwidth_used())
3559 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->nr_running
)
3562 __return_cfs_rq_runtime(cfs_rq
);
3566 * This is done with a timer (instead of inline with bandwidth return) since
3567 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3569 static void do_sched_cfs_slack_timer(struct cfs_bandwidth
*cfs_b
)
3571 u64 runtime
= 0, slice
= sched_cfs_bandwidth_slice();
3574 /* confirm we're still not at a refresh boundary */
3575 raw_spin_lock(&cfs_b
->lock
);
3576 if (runtime_refresh_within(cfs_b
, min_bandwidth_expiration
)) {
3577 raw_spin_unlock(&cfs_b
->lock
);
3581 if (cfs_b
->quota
!= RUNTIME_INF
&& cfs_b
->runtime
> slice
) {
3582 runtime
= cfs_b
->runtime
;
3585 expires
= cfs_b
->runtime_expires
;
3586 raw_spin_unlock(&cfs_b
->lock
);
3591 runtime
= distribute_cfs_runtime(cfs_b
, runtime
, expires
);
3593 raw_spin_lock(&cfs_b
->lock
);
3594 if (expires
== cfs_b
->runtime_expires
)
3595 cfs_b
->runtime
= runtime
;
3596 raw_spin_unlock(&cfs_b
->lock
);
3600 * When a group wakes up we want to make sure that its quota is not already
3601 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3602 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3604 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
)
3606 if (!cfs_bandwidth_used())
3609 /* an active group must be handled by the update_curr()->put() path */
3610 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->curr
)
3613 /* ensure the group is not already throttled */
3614 if (cfs_rq_throttled(cfs_rq
))
3617 /* update runtime allocation */
3618 account_cfs_rq_runtime(cfs_rq
, 0);
3619 if (cfs_rq
->runtime_remaining
<= 0)
3620 throttle_cfs_rq(cfs_rq
);
3623 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3624 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3626 if (!cfs_bandwidth_used())
3629 if (likely(!cfs_rq
->runtime_enabled
|| cfs_rq
->runtime_remaining
> 0))
3633 * it's possible for a throttled entity to be forced into a running
3634 * state (e.g. set_curr_task), in this case we're finished.
3636 if (cfs_rq_throttled(cfs_rq
))
3639 throttle_cfs_rq(cfs_rq
);
3643 static enum hrtimer_restart
sched_cfs_slack_timer(struct hrtimer
*timer
)
3645 struct cfs_bandwidth
*cfs_b
=
3646 container_of(timer
, struct cfs_bandwidth
, slack_timer
);
3647 do_sched_cfs_slack_timer(cfs_b
);
3649 return HRTIMER_NORESTART
;
3652 static enum hrtimer_restart
sched_cfs_period_timer(struct hrtimer
*timer
)
3654 struct cfs_bandwidth
*cfs_b
=
3655 container_of(timer
, struct cfs_bandwidth
, period_timer
);
3661 now
= hrtimer_cb_get_time(timer
);
3662 overrun
= hrtimer_forward(timer
, now
, cfs_b
->period
);
3667 idle
= do_sched_cfs_period_timer(cfs_b
, overrun
);
3670 return idle
? HRTIMER_NORESTART
: HRTIMER_RESTART
;
3673 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
3675 raw_spin_lock_init(&cfs_b
->lock
);
3677 cfs_b
->quota
= RUNTIME_INF
;
3678 cfs_b
->period
= ns_to_ktime(default_cfs_period());
3680 INIT_LIST_HEAD(&cfs_b
->throttled_cfs_rq
);
3681 hrtimer_init(&cfs_b
->period_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
3682 cfs_b
->period_timer
.function
= sched_cfs_period_timer
;
3683 hrtimer_init(&cfs_b
->slack_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
3684 cfs_b
->slack_timer
.function
= sched_cfs_slack_timer
;
3687 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3689 cfs_rq
->runtime_enabled
= 0;
3690 INIT_LIST_HEAD(&cfs_rq
->throttled_list
);
3693 /* requires cfs_b->lock, may release to reprogram timer */
3694 void __start_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
, bool force
)
3697 * The timer may be active because we're trying to set a new bandwidth
3698 * period or because we're racing with the tear-down path
3699 * (timer_active==0 becomes visible before the hrtimer call-back
3700 * terminates). In either case we ensure that it's re-programmed
3702 while (unlikely(hrtimer_active(&cfs_b
->period_timer
)) &&
3703 hrtimer_try_to_cancel(&cfs_b
->period_timer
) < 0) {
3704 /* bounce the lock to allow do_sched_cfs_period_timer to run */
3705 raw_spin_unlock(&cfs_b
->lock
);
3707 raw_spin_lock(&cfs_b
->lock
);
3708 /* if someone else restarted the timer then we're done */
3709 if (!force
&& cfs_b
->timer_active
)
3713 cfs_b
->timer_active
= 1;
3714 start_bandwidth_timer(&cfs_b
->period_timer
, cfs_b
->period
);
3717 static void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
3719 hrtimer_cancel(&cfs_b
->period_timer
);
3720 hrtimer_cancel(&cfs_b
->slack_timer
);
3723 static void __maybe_unused
unthrottle_offline_cfs_rqs(struct rq
*rq
)
3725 struct cfs_rq
*cfs_rq
;
3727 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
3728 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3730 if (!cfs_rq
->runtime_enabled
)
3734 * clock_task is not advancing so we just need to make sure
3735 * there's some valid quota amount
3737 cfs_rq
->runtime_remaining
= cfs_b
->quota
;
3738 if (cfs_rq_throttled(cfs_rq
))
3739 unthrottle_cfs_rq(cfs_rq
);
3743 #else /* CONFIG_CFS_BANDWIDTH */
3744 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
3746 return rq_clock_task(rq_of(cfs_rq
));
3749 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
) {}
3750 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) { return false; }
3751 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
) {}
3752 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
3754 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
3759 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
3764 static inline int throttled_lb_pair(struct task_group
*tg
,
3765 int src_cpu
, int dest_cpu
)
3770 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
3772 #ifdef CONFIG_FAIR_GROUP_SCHED
3773 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
3776 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
3780 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
3781 static inline void unthrottle_offline_cfs_rqs(struct rq
*rq
) {}
3783 #endif /* CONFIG_CFS_BANDWIDTH */
3785 /**************************************************
3786 * CFS operations on tasks:
3789 #ifdef CONFIG_SCHED_HRTICK
3790 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
3792 struct sched_entity
*se
= &p
->se
;
3793 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3795 WARN_ON(task_rq(p
) != rq
);
3797 if (cfs_rq
->nr_running
> 1) {
3798 u64 slice
= sched_slice(cfs_rq
, se
);
3799 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
3800 s64 delta
= slice
- ran
;
3809 * Don't schedule slices shorter than 10000ns, that just
3810 * doesn't make sense. Rely on vruntime for fairness.
3813 delta
= max_t(s64
, 10000LL, delta
);
3815 hrtick_start(rq
, delta
);
3820 * called from enqueue/dequeue and updates the hrtick when the
3821 * current task is from our class and nr_running is low enough
3824 static void hrtick_update(struct rq
*rq
)
3826 struct task_struct
*curr
= rq
->curr
;
3828 if (!hrtick_enabled(rq
) || curr
->sched_class
!= &fair_sched_class
)
3831 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
3832 hrtick_start_fair(rq
, curr
);
3834 #else /* !CONFIG_SCHED_HRTICK */
3836 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
3840 static inline void hrtick_update(struct rq
*rq
)
3846 * The enqueue_task method is called before nr_running is
3847 * increased. Here we update the fair scheduling stats and
3848 * then put the task into the rbtree:
3851 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
3853 struct cfs_rq
*cfs_rq
;
3854 struct sched_entity
*se
= &p
->se
;
3856 for_each_sched_entity(se
) {
3859 cfs_rq
= cfs_rq_of(se
);
3860 enqueue_entity(cfs_rq
, se
, flags
);
3863 * end evaluation on encountering a throttled cfs_rq
3865 * note: in the case of encountering a throttled cfs_rq we will
3866 * post the final h_nr_running increment below.
3868 if (cfs_rq_throttled(cfs_rq
))
3870 cfs_rq
->h_nr_running
++;
3872 flags
= ENQUEUE_WAKEUP
;
3875 for_each_sched_entity(se
) {
3876 cfs_rq
= cfs_rq_of(se
);
3877 cfs_rq
->h_nr_running
++;
3879 if (cfs_rq_throttled(cfs_rq
))
3882 update_cfs_shares(cfs_rq
);
3883 update_entity_load_avg(se
, 1);
3887 update_rq_runnable_avg(rq
, rq
->nr_running
);
3893 static void set_next_buddy(struct sched_entity
*se
);
3896 * The dequeue_task method is called before nr_running is
3897 * decreased. We remove the task from the rbtree and
3898 * update the fair scheduling stats:
3900 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
3902 struct cfs_rq
*cfs_rq
;
3903 struct sched_entity
*se
= &p
->se
;
3904 int task_sleep
= flags
& DEQUEUE_SLEEP
;
3906 for_each_sched_entity(se
) {
3907 cfs_rq
= cfs_rq_of(se
);
3908 dequeue_entity(cfs_rq
, se
, flags
);
3911 * end evaluation on encountering a throttled cfs_rq
3913 * note: in the case of encountering a throttled cfs_rq we will
3914 * post the final h_nr_running decrement below.
3916 if (cfs_rq_throttled(cfs_rq
))
3918 cfs_rq
->h_nr_running
--;
3920 /* Don't dequeue parent if it has other entities besides us */
3921 if (cfs_rq
->load
.weight
) {
3923 * Bias pick_next to pick a task from this cfs_rq, as
3924 * p is sleeping when it is within its sched_slice.
3926 if (task_sleep
&& parent_entity(se
))
3927 set_next_buddy(parent_entity(se
));
3929 /* avoid re-evaluating load for this entity */
3930 se
= parent_entity(se
);
3933 flags
|= DEQUEUE_SLEEP
;
3936 for_each_sched_entity(se
) {
3937 cfs_rq
= cfs_rq_of(se
);
3938 cfs_rq
->h_nr_running
--;
3940 if (cfs_rq_throttled(cfs_rq
))
3943 update_cfs_shares(cfs_rq
);
3944 update_entity_load_avg(se
, 1);
3949 update_rq_runnable_avg(rq
, 1);
3955 /* Used instead of source_load when we know the type == 0 */
3956 static unsigned long weighted_cpuload(const int cpu
)
3958 return cpu_rq(cpu
)->cfs
.runnable_load_avg
;
3962 * Return a low guess at the load of a migration-source cpu weighted
3963 * according to the scheduling class and "nice" value.
3965 * We want to under-estimate the load of migration sources, to
3966 * balance conservatively.
3968 static unsigned long source_load(int cpu
, int type
)
3970 struct rq
*rq
= cpu_rq(cpu
);
3971 unsigned long total
= weighted_cpuload(cpu
);
3973 if (type
== 0 || !sched_feat(LB_BIAS
))
3976 return min(rq
->cpu_load
[type
-1], total
);
3980 * Return a high guess at the load of a migration-target cpu weighted
3981 * according to the scheduling class and "nice" value.
3983 static unsigned long target_load(int cpu
, int type
)
3985 struct rq
*rq
= cpu_rq(cpu
);
3986 unsigned long total
= weighted_cpuload(cpu
);
3988 if (type
== 0 || !sched_feat(LB_BIAS
))
3991 return max(rq
->cpu_load
[type
-1], total
);
3994 static unsigned long power_of(int cpu
)
3996 return cpu_rq(cpu
)->cpu_power
;
3999 static unsigned long cpu_avg_load_per_task(int cpu
)
4001 struct rq
*rq
= cpu_rq(cpu
);
4002 unsigned long nr_running
= ACCESS_ONCE(rq
->nr_running
);
4003 unsigned long load_avg
= rq
->cfs
.runnable_load_avg
;
4006 return load_avg
/ nr_running
;
4011 static void record_wakee(struct task_struct
*p
)
4014 * Rough decay (wiping) for cost saving, don't worry
4015 * about the boundary, really active task won't care
4018 if (jiffies
> current
->wakee_flip_decay_ts
+ HZ
) {
4019 current
->wakee_flips
= 0;
4020 current
->wakee_flip_decay_ts
= jiffies
;
4023 if (current
->last_wakee
!= p
) {
4024 current
->last_wakee
= p
;
4025 current
->wakee_flips
++;
4029 static void task_waking_fair(struct task_struct
*p
)
4031 struct sched_entity
*se
= &p
->se
;
4032 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4035 #ifndef CONFIG_64BIT
4036 u64 min_vruntime_copy
;
4039 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
4041 min_vruntime
= cfs_rq
->min_vruntime
;
4042 } while (min_vruntime
!= min_vruntime_copy
);
4044 min_vruntime
= cfs_rq
->min_vruntime
;
4047 se
->vruntime
-= min_vruntime
;
4051 #ifdef CONFIG_FAIR_GROUP_SCHED
4053 * effective_load() calculates the load change as seen from the root_task_group
4055 * Adding load to a group doesn't make a group heavier, but can cause movement
4056 * of group shares between cpus. Assuming the shares were perfectly aligned one
4057 * can calculate the shift in shares.
4059 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4060 * on this @cpu and results in a total addition (subtraction) of @wg to the
4061 * total group weight.
4063 * Given a runqueue weight distribution (rw_i) we can compute a shares
4064 * distribution (s_i) using:
4066 * s_i = rw_i / \Sum rw_j (1)
4068 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4069 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4070 * shares distribution (s_i):
4072 * rw_i = { 2, 4, 1, 0 }
4073 * s_i = { 2/7, 4/7, 1/7, 0 }
4075 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4076 * task used to run on and the CPU the waker is running on), we need to
4077 * compute the effect of waking a task on either CPU and, in case of a sync
4078 * wakeup, compute the effect of the current task going to sleep.
4080 * So for a change of @wl to the local @cpu with an overall group weight change
4081 * of @wl we can compute the new shares distribution (s'_i) using:
4083 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4085 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4086 * differences in waking a task to CPU 0. The additional task changes the
4087 * weight and shares distributions like:
4089 * rw'_i = { 3, 4, 1, 0 }
4090 * s'_i = { 3/8, 4/8, 1/8, 0 }
4092 * We can then compute the difference in effective weight by using:
4094 * dw_i = S * (s'_i - s_i) (3)
4096 * Where 'S' is the group weight as seen by its parent.
4098 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4099 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4100 * 4/7) times the weight of the group.
4102 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4104 struct sched_entity
*se
= tg
->se
[cpu
];
4106 if (!tg
->parent
) /* the trivial, non-cgroup case */
4109 for_each_sched_entity(se
) {
4115 * W = @wg + \Sum rw_j
4117 W
= wg
+ calc_tg_weight(tg
, se
->my_q
);
4122 w
= se
->my_q
->load
.weight
+ wl
;
4125 * wl = S * s'_i; see (2)
4128 wl
= (w
* tg
->shares
) / W
;
4133 * Per the above, wl is the new se->load.weight value; since
4134 * those are clipped to [MIN_SHARES, ...) do so now. See
4135 * calc_cfs_shares().
4137 if (wl
< MIN_SHARES
)
4141 * wl = dw_i = S * (s'_i - s_i); see (3)
4143 wl
-= se
->load
.weight
;
4146 * Recursively apply this logic to all parent groups to compute
4147 * the final effective load change on the root group. Since
4148 * only the @tg group gets extra weight, all parent groups can
4149 * only redistribute existing shares. @wl is the shift in shares
4150 * resulting from this level per the above.
4159 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4166 static int wake_wide(struct task_struct
*p
)
4168 int factor
= this_cpu_read(sd_llc_size
);
4171 * Yeah, it's the switching-frequency, could means many wakee or
4172 * rapidly switch, use factor here will just help to automatically
4173 * adjust the loose-degree, so bigger node will lead to more pull.
4175 if (p
->wakee_flips
> factor
) {
4177 * wakee is somewhat hot, it needs certain amount of cpu
4178 * resource, so if waker is far more hot, prefer to leave
4181 if (current
->wakee_flips
> (factor
* p
->wakee_flips
))
4188 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
, int sync
)
4190 s64 this_load
, load
;
4191 int idx
, this_cpu
, prev_cpu
;
4192 unsigned long tl_per_task
;
4193 struct task_group
*tg
;
4194 unsigned long weight
;
4198 * If we wake multiple tasks be careful to not bounce
4199 * ourselves around too much.
4205 this_cpu
= smp_processor_id();
4206 prev_cpu
= task_cpu(p
);
4207 load
= source_load(prev_cpu
, idx
);
4208 this_load
= target_load(this_cpu
, idx
);
4211 * If sync wakeup then subtract the (maximum possible)
4212 * effect of the currently running task from the load
4213 * of the current CPU:
4216 tg
= task_group(current
);
4217 weight
= current
->se
.load
.weight
;
4219 this_load
+= effective_load(tg
, this_cpu
, -weight
, -weight
);
4220 load
+= effective_load(tg
, prev_cpu
, 0, -weight
);
4224 weight
= p
->se
.load
.weight
;
4227 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4228 * due to the sync cause above having dropped this_load to 0, we'll
4229 * always have an imbalance, but there's really nothing you can do
4230 * about that, so that's good too.
4232 * Otherwise check if either cpus are near enough in load to allow this
4233 * task to be woken on this_cpu.
4235 if (this_load
> 0) {
4236 s64 this_eff_load
, prev_eff_load
;
4238 this_eff_load
= 100;
4239 this_eff_load
*= power_of(prev_cpu
);
4240 this_eff_load
*= this_load
+
4241 effective_load(tg
, this_cpu
, weight
, weight
);
4243 prev_eff_load
= 100 + (sd
->imbalance_pct
- 100) / 2;
4244 prev_eff_load
*= power_of(this_cpu
);
4245 prev_eff_load
*= load
+ effective_load(tg
, prev_cpu
, 0, weight
);
4247 balanced
= this_eff_load
<= prev_eff_load
;
4252 * If the currently running task will sleep within
4253 * a reasonable amount of time then attract this newly
4256 if (sync
&& balanced
)
4259 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine_attempts
);
4260 tl_per_task
= cpu_avg_load_per_task(this_cpu
);
4263 (this_load
<= load
&&
4264 this_load
+ target_load(prev_cpu
, idx
) <= tl_per_task
)) {
4266 * This domain has SD_WAKE_AFFINE and
4267 * p is cache cold in this domain, and
4268 * there is no bad imbalance.
4270 schedstat_inc(sd
, ttwu_move_affine
);
4271 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine
);
4279 * find_idlest_group finds and returns the least busy CPU group within the
4282 static struct sched_group
*
4283 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
,
4284 int this_cpu
, int sd_flag
)
4286 struct sched_group
*idlest
= NULL
, *group
= sd
->groups
;
4287 unsigned long min_load
= ULONG_MAX
, this_load
= 0;
4288 int load_idx
= sd
->forkexec_idx
;
4289 int imbalance
= 100 + (sd
->imbalance_pct
-100)/2;
4291 if (sd_flag
& SD_BALANCE_WAKE
)
4292 load_idx
= sd
->wake_idx
;
4295 unsigned long load
, avg_load
;
4299 /* Skip over this group if it has no CPUs allowed */
4300 if (!cpumask_intersects(sched_group_cpus(group
),
4301 tsk_cpus_allowed(p
)))
4304 local_group
= cpumask_test_cpu(this_cpu
,
4305 sched_group_cpus(group
));
4307 /* Tally up the load of all CPUs in the group */
4310 for_each_cpu(i
, sched_group_cpus(group
)) {
4311 /* Bias balancing toward cpus of our domain */
4313 load
= source_load(i
, load_idx
);
4315 load
= target_load(i
, load_idx
);
4320 /* Adjust by relative CPU power of the group */
4321 avg_load
= (avg_load
* SCHED_POWER_SCALE
) / group
->sgp
->power
;
4324 this_load
= avg_load
;
4325 } else if (avg_load
< min_load
) {
4326 min_load
= avg_load
;
4329 } while (group
= group
->next
, group
!= sd
->groups
);
4331 if (!idlest
|| 100*this_load
< imbalance
*min_load
)
4337 * find_idlest_cpu - find the idlest cpu among the cpus in group.
4340 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
4342 unsigned long load
, min_load
= ULONG_MAX
;
4346 /* Traverse only the allowed CPUs */
4347 for_each_cpu_and(i
, sched_group_cpus(group
), tsk_cpus_allowed(p
)) {
4348 load
= weighted_cpuload(i
);
4350 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
4360 * Try and locate an idle CPU in the sched_domain.
4362 static int select_idle_sibling(struct task_struct
*p
, int target
)
4364 struct sched_domain
*sd
;
4365 struct sched_group
*sg
;
4366 int i
= task_cpu(p
);
4368 if (idle_cpu(target
))
4372 * If the prevous cpu is cache affine and idle, don't be stupid.
4374 if (i
!= target
&& cpus_share_cache(i
, target
) && idle_cpu(i
))
4378 * Otherwise, iterate the domains and find an elegible idle cpu.
4380 sd
= rcu_dereference(per_cpu(sd_llc
, target
));
4381 for_each_lower_domain(sd
) {
4384 if (!cpumask_intersects(sched_group_cpus(sg
),
4385 tsk_cpus_allowed(p
)))
4388 for_each_cpu(i
, sched_group_cpus(sg
)) {
4389 if (i
== target
|| !idle_cpu(i
))
4393 target
= cpumask_first_and(sched_group_cpus(sg
),
4394 tsk_cpus_allowed(p
));
4398 } while (sg
!= sd
->groups
);
4405 * select_task_rq_fair: Select target runqueue for the waking task in domains
4406 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
4407 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
4409 * Balances load by selecting the idlest cpu in the idlest group, or under
4410 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
4412 * Returns the target cpu number.
4414 * preempt must be disabled.
4417 select_task_rq_fair(struct task_struct
*p
, int prev_cpu
, int sd_flag
, int wake_flags
)
4419 struct sched_domain
*tmp
, *affine_sd
= NULL
, *sd
= NULL
;
4420 int cpu
= smp_processor_id();
4422 int want_affine
= 0;
4423 int sync
= wake_flags
& WF_SYNC
;
4425 if (p
->nr_cpus_allowed
== 1)
4428 if (sd_flag
& SD_BALANCE_WAKE
) {
4429 if (cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
)))
4435 for_each_domain(cpu
, tmp
) {
4436 if (!(tmp
->flags
& SD_LOAD_BALANCE
))
4440 * If both cpu and prev_cpu are part of this domain,
4441 * cpu is a valid SD_WAKE_AFFINE target.
4443 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
4444 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
4449 if (tmp
->flags
& sd_flag
)
4454 if (cpu
!= prev_cpu
&& wake_affine(affine_sd
, p
, sync
))
4457 new_cpu
= select_idle_sibling(p
, prev_cpu
);
4462 struct sched_group
*group
;
4465 if (!(sd
->flags
& sd_flag
)) {
4470 group
= find_idlest_group(sd
, p
, cpu
, sd_flag
);
4476 new_cpu
= find_idlest_cpu(group
, p
, cpu
);
4477 if (new_cpu
== -1 || new_cpu
== cpu
) {
4478 /* Now try balancing at a lower domain level of cpu */
4483 /* Now try balancing at a lower domain level of new_cpu */
4485 weight
= sd
->span_weight
;
4487 for_each_domain(cpu
, tmp
) {
4488 if (weight
<= tmp
->span_weight
)
4490 if (tmp
->flags
& sd_flag
)
4493 /* while loop will break here if sd == NULL */
4502 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
4503 * cfs_rq_of(p) references at time of call are still valid and identify the
4504 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
4505 * other assumptions, including the state of rq->lock, should be made.
4508 migrate_task_rq_fair(struct task_struct
*p
, int next_cpu
)
4510 struct sched_entity
*se
= &p
->se
;
4511 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4514 * Load tracking: accumulate removed load so that it can be processed
4515 * when we next update owning cfs_rq under rq->lock. Tasks contribute
4516 * to blocked load iff they have a positive decay-count. It can never
4517 * be negative here since on-rq tasks have decay-count == 0.
4519 if (se
->avg
.decay_count
) {
4520 se
->avg
.decay_count
= -__synchronize_entity_decay(se
);
4521 atomic_long_add(se
->avg
.load_avg_contrib
,
4522 &cfs_rq
->removed_load
);
4525 #endif /* CONFIG_SMP */
4527 static unsigned long
4528 wakeup_gran(struct sched_entity
*curr
, struct sched_entity
*se
)
4530 unsigned long gran
= sysctl_sched_wakeup_granularity
;
4533 * Since its curr running now, convert the gran from real-time
4534 * to virtual-time in his units.
4536 * By using 'se' instead of 'curr' we penalize light tasks, so
4537 * they get preempted easier. That is, if 'se' < 'curr' then
4538 * the resulting gran will be larger, therefore penalizing the
4539 * lighter, if otoh 'se' > 'curr' then the resulting gran will
4540 * be smaller, again penalizing the lighter task.
4542 * This is especially important for buddies when the leftmost
4543 * task is higher priority than the buddy.
4545 return calc_delta_fair(gran
, se
);
4549 * Should 'se' preempt 'curr'.
4563 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
4565 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
4570 gran
= wakeup_gran(curr
, se
);
4577 static void set_last_buddy(struct sched_entity
*se
)
4579 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
4582 for_each_sched_entity(se
)
4583 cfs_rq_of(se
)->last
= se
;
4586 static void set_next_buddy(struct sched_entity
*se
)
4588 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
4591 for_each_sched_entity(se
)
4592 cfs_rq_of(se
)->next
= se
;
4595 static void set_skip_buddy(struct sched_entity
*se
)
4597 for_each_sched_entity(se
)
4598 cfs_rq_of(se
)->skip
= se
;
4602 * Preempt the current task with a newly woken task if needed:
4604 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
4606 struct task_struct
*curr
= rq
->curr
;
4607 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
4608 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
4609 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
4610 int next_buddy_marked
= 0;
4612 if (unlikely(se
== pse
))
4616 * This is possible from callers such as move_task(), in which we
4617 * unconditionally check_prempt_curr() after an enqueue (which may have
4618 * lead to a throttle). This both saves work and prevents false
4619 * next-buddy nomination below.
4621 if (unlikely(throttled_hierarchy(cfs_rq_of(pse
))))
4624 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
4625 set_next_buddy(pse
);
4626 next_buddy_marked
= 1;
4630 * We can come here with TIF_NEED_RESCHED already set from new task
4633 * Note: this also catches the edge-case of curr being in a throttled
4634 * group (e.g. via set_curr_task), since update_curr() (in the
4635 * enqueue of curr) will have resulted in resched being set. This
4636 * prevents us from potentially nominating it as a false LAST_BUDDY
4639 if (test_tsk_need_resched(curr
))
4642 /* Idle tasks are by definition preempted by non-idle tasks. */
4643 if (unlikely(curr
->policy
== SCHED_IDLE
) &&
4644 likely(p
->policy
!= SCHED_IDLE
))
4648 * Batch and idle tasks do not preempt non-idle tasks (their preemption
4649 * is driven by the tick):
4651 if (unlikely(p
->policy
!= SCHED_NORMAL
) || !sched_feat(WAKEUP_PREEMPTION
))
4654 find_matching_se(&se
, &pse
);
4655 update_curr(cfs_rq_of(se
));
4657 if (wakeup_preempt_entity(se
, pse
) == 1) {
4659 * Bias pick_next to pick the sched entity that is
4660 * triggering this preemption.
4662 if (!next_buddy_marked
)
4663 set_next_buddy(pse
);
4672 * Only set the backward buddy when the current task is still
4673 * on the rq. This can happen when a wakeup gets interleaved
4674 * with schedule on the ->pre_schedule() or idle_balance()
4675 * point, either of which can * drop the rq lock.
4677 * Also, during early boot the idle thread is in the fair class,
4678 * for obvious reasons its a bad idea to schedule back to it.
4680 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
4683 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
4687 static struct task_struct
*
4688 pick_next_task_fair(struct rq
*rq
, struct task_struct
*prev
)
4690 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
4691 struct sched_entity
*se
;
4692 struct task_struct
*p
;
4696 #ifdef CONFIG_FAIR_GROUP_SCHED
4697 if (!cfs_rq
->nr_running
)
4700 if (prev
->sched_class
!= &fair_sched_class
)
4704 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
4705 * likely that a next task is from the same cgroup as the current.
4707 * Therefore attempt to avoid putting and setting the entire cgroup
4708 * hierarchy, only change the part that actually changes.
4712 struct sched_entity
*curr
= cfs_rq
->curr
;
4715 * Since we got here without doing put_prev_entity() we also
4716 * have to consider cfs_rq->curr. If it is still a runnable
4717 * entity, update_curr() will update its vruntime, otherwise
4718 * forget we've ever seen it.
4720 if (curr
&& curr
->on_rq
)
4721 update_curr(cfs_rq
);
4726 * This call to check_cfs_rq_runtime() will do the throttle and
4727 * dequeue its entity in the parent(s). Therefore the 'simple'
4728 * nr_running test will indeed be correct.
4730 if (unlikely(check_cfs_rq_runtime(cfs_rq
)))
4733 se
= pick_next_entity(cfs_rq
, curr
);
4734 cfs_rq
= group_cfs_rq(se
);
4740 * Since we haven't yet done put_prev_entity and if the selected task
4741 * is a different task than we started out with, try and touch the
4742 * least amount of cfs_rqs.
4745 struct sched_entity
*pse
= &prev
->se
;
4747 while (!(cfs_rq
= is_same_group(se
, pse
))) {
4748 int se_depth
= se
->depth
;
4749 int pse_depth
= pse
->depth
;
4751 if (se_depth
<= pse_depth
) {
4752 put_prev_entity(cfs_rq_of(pse
), pse
);
4753 pse
= parent_entity(pse
);
4755 if (se_depth
>= pse_depth
) {
4756 set_next_entity(cfs_rq_of(se
), se
);
4757 se
= parent_entity(se
);
4761 put_prev_entity(cfs_rq
, pse
);
4762 set_next_entity(cfs_rq
, se
);
4765 if (hrtick_enabled(rq
))
4766 hrtick_start_fair(rq
, p
);
4773 if (!cfs_rq
->nr_running
)
4776 put_prev_task(rq
, prev
);
4779 se
= pick_next_entity(cfs_rq
, NULL
);
4780 set_next_entity(cfs_rq
, se
);
4781 cfs_rq
= group_cfs_rq(se
);
4786 if (hrtick_enabled(rq
))
4787 hrtick_start_fair(rq
, p
);
4792 new_tasks
= idle_balance(rq
);
4794 * Because idle_balance() releases (and re-acquires) rq->lock, it is
4795 * possible for any higher priority task to appear. In that case we
4796 * must re-start the pick_next_entity() loop.
4808 * Account for a descheduled task:
4810 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
4812 struct sched_entity
*se
= &prev
->se
;
4813 struct cfs_rq
*cfs_rq
;
4815 for_each_sched_entity(se
) {
4816 cfs_rq
= cfs_rq_of(se
);
4817 put_prev_entity(cfs_rq
, se
);
4822 * sched_yield() is very simple
4824 * The magic of dealing with the ->skip buddy is in pick_next_entity.
4826 static void yield_task_fair(struct rq
*rq
)
4828 struct task_struct
*curr
= rq
->curr
;
4829 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
4830 struct sched_entity
*se
= &curr
->se
;
4833 * Are we the only task in the tree?
4835 if (unlikely(rq
->nr_running
== 1))
4838 clear_buddies(cfs_rq
, se
);
4840 if (curr
->policy
!= SCHED_BATCH
) {
4841 update_rq_clock(rq
);
4843 * Update run-time statistics of the 'current'.
4845 update_curr(cfs_rq
);
4847 * Tell update_rq_clock() that we've just updated,
4848 * so we don't do microscopic update in schedule()
4849 * and double the fastpath cost.
4851 rq
->skip_clock_update
= 1;
4857 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
, bool preempt
)
4859 struct sched_entity
*se
= &p
->se
;
4861 /* throttled hierarchies are not runnable */
4862 if (!se
->on_rq
|| throttled_hierarchy(cfs_rq_of(se
)))
4865 /* Tell the scheduler that we'd really like pse to run next. */
4868 yield_task_fair(rq
);
4874 /**************************************************
4875 * Fair scheduling class load-balancing methods.
4879 * The purpose of load-balancing is to achieve the same basic fairness the
4880 * per-cpu scheduler provides, namely provide a proportional amount of compute
4881 * time to each task. This is expressed in the following equation:
4883 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
4885 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
4886 * W_i,0 is defined as:
4888 * W_i,0 = \Sum_j w_i,j (2)
4890 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
4891 * is derived from the nice value as per prio_to_weight[].
4893 * The weight average is an exponential decay average of the instantaneous
4896 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
4898 * P_i is the cpu power (or compute capacity) of cpu i, typically it is the
4899 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
4900 * can also include other factors [XXX].
4902 * To achieve this balance we define a measure of imbalance which follows
4903 * directly from (1):
4905 * imb_i,j = max{ avg(W/P), W_i/P_i } - min{ avg(W/P), W_j/P_j } (4)
4907 * We them move tasks around to minimize the imbalance. In the continuous
4908 * function space it is obvious this converges, in the discrete case we get
4909 * a few fun cases generally called infeasible weight scenarios.
4912 * - infeasible weights;
4913 * - local vs global optima in the discrete case. ]
4918 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
4919 * for all i,j solution, we create a tree of cpus that follows the hardware
4920 * topology where each level pairs two lower groups (or better). This results
4921 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
4922 * tree to only the first of the previous level and we decrease the frequency
4923 * of load-balance at each level inv. proportional to the number of cpus in
4929 * \Sum { --- * --- * 2^i } = O(n) (5)
4931 * `- size of each group
4932 * | | `- number of cpus doing load-balance
4934 * `- sum over all levels
4936 * Coupled with a limit on how many tasks we can migrate every balance pass,
4937 * this makes (5) the runtime complexity of the balancer.
4939 * An important property here is that each CPU is still (indirectly) connected
4940 * to every other cpu in at most O(log n) steps:
4942 * The adjacency matrix of the resulting graph is given by:
4945 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
4948 * And you'll find that:
4950 * A^(log_2 n)_i,j != 0 for all i,j (7)
4952 * Showing there's indeed a path between every cpu in at most O(log n) steps.
4953 * The task movement gives a factor of O(m), giving a convergence complexity
4956 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
4961 * In order to avoid CPUs going idle while there's still work to do, new idle
4962 * balancing is more aggressive and has the newly idle cpu iterate up the domain
4963 * tree itself instead of relying on other CPUs to bring it work.
4965 * This adds some complexity to both (5) and (8) but it reduces the total idle
4973 * Cgroups make a horror show out of (2), instead of a simple sum we get:
4976 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
4981 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
4983 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
4985 * The big problem is S_k, its a global sum needed to compute a local (W_i)
4988 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
4989 * rewrite all of this once again.]
4992 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
4994 enum fbq_type
{ regular
, remote
, all
};
4996 #define LBF_ALL_PINNED 0x01
4997 #define LBF_NEED_BREAK 0x02
4998 #define LBF_DST_PINNED 0x04
4999 #define LBF_SOME_PINNED 0x08
5002 struct sched_domain
*sd
;
5010 struct cpumask
*dst_grpmask
;
5012 enum cpu_idle_type idle
;
5014 /* The set of CPUs under consideration for load-balancing */
5015 struct cpumask
*cpus
;
5020 unsigned int loop_break
;
5021 unsigned int loop_max
;
5023 enum fbq_type fbq_type
;
5027 * move_task - move a task from one runqueue to another runqueue.
5028 * Both runqueues must be locked.
5030 static void move_task(struct task_struct
*p
, struct lb_env
*env
)
5032 deactivate_task(env
->src_rq
, p
, 0);
5033 set_task_cpu(p
, env
->dst_cpu
);
5034 activate_task(env
->dst_rq
, p
, 0);
5035 check_preempt_curr(env
->dst_rq
, p
, 0);
5039 * Is this task likely cache-hot:
5042 task_hot(struct task_struct
*p
, u64 now
)
5046 if (p
->sched_class
!= &fair_sched_class
)
5049 if (unlikely(p
->policy
== SCHED_IDLE
))
5053 * Buddy candidates are cache hot:
5055 if (sched_feat(CACHE_HOT_BUDDY
) && this_rq()->nr_running
&&
5056 (&p
->se
== cfs_rq_of(&p
->se
)->next
||
5057 &p
->se
== cfs_rq_of(&p
->se
)->last
))
5060 if (sysctl_sched_migration_cost
== -1)
5062 if (sysctl_sched_migration_cost
== 0)
5065 delta
= now
- p
->se
.exec_start
;
5067 return delta
< (s64
)sysctl_sched_migration_cost
;
5070 #ifdef CONFIG_NUMA_BALANCING
5071 /* Returns true if the destination node has incurred more faults */
5072 static bool migrate_improves_locality(struct task_struct
*p
, struct lb_env
*env
)
5074 int src_nid
, dst_nid
;
5076 if (!sched_feat(NUMA_FAVOUR_HIGHER
) || !p
->numa_faults_memory
||
5077 !(env
->sd
->flags
& SD_NUMA
)) {
5081 src_nid
= cpu_to_node(env
->src_cpu
);
5082 dst_nid
= cpu_to_node(env
->dst_cpu
);
5084 if (src_nid
== dst_nid
)
5087 /* Always encourage migration to the preferred node. */
5088 if (dst_nid
== p
->numa_preferred_nid
)
5091 /* If both task and group weight improve, this move is a winner. */
5092 if (task_weight(p
, dst_nid
) > task_weight(p
, src_nid
) &&
5093 group_weight(p
, dst_nid
) > group_weight(p
, src_nid
))
5100 static bool migrate_degrades_locality(struct task_struct
*p
, struct lb_env
*env
)
5102 int src_nid
, dst_nid
;
5104 if (!sched_feat(NUMA
) || !sched_feat(NUMA_RESIST_LOWER
))
5107 if (!p
->numa_faults_memory
|| !(env
->sd
->flags
& SD_NUMA
))
5110 src_nid
= cpu_to_node(env
->src_cpu
);
5111 dst_nid
= cpu_to_node(env
->dst_cpu
);
5113 if (src_nid
== dst_nid
)
5116 /* Migrating away from the preferred node is always bad. */
5117 if (src_nid
== p
->numa_preferred_nid
)
5120 /* If either task or group weight get worse, don't do it. */
5121 if (task_weight(p
, dst_nid
) < task_weight(p
, src_nid
) ||
5122 group_weight(p
, dst_nid
) < group_weight(p
, src_nid
))
5129 static inline bool migrate_improves_locality(struct task_struct
*p
,
5135 static inline bool migrate_degrades_locality(struct task_struct
*p
,
5143 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5146 int can_migrate_task(struct task_struct
*p
, struct lb_env
*env
)
5148 int tsk_cache_hot
= 0;
5150 * We do not migrate tasks that are:
5151 * 1) throttled_lb_pair, or
5152 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5153 * 3) running (obviously), or
5154 * 4) are cache-hot on their current CPU.
5156 if (throttled_lb_pair(task_group(p
), env
->src_cpu
, env
->dst_cpu
))
5159 if (!cpumask_test_cpu(env
->dst_cpu
, tsk_cpus_allowed(p
))) {
5162 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_affine
);
5164 env
->flags
|= LBF_SOME_PINNED
;
5167 * Remember if this task can be migrated to any other cpu in
5168 * our sched_group. We may want to revisit it if we couldn't
5169 * meet load balance goals by pulling other tasks on src_cpu.
5171 * Also avoid computing new_dst_cpu if we have already computed
5172 * one in current iteration.
5174 if (!env
->dst_grpmask
|| (env
->flags
& LBF_DST_PINNED
))
5177 /* Prevent to re-select dst_cpu via env's cpus */
5178 for_each_cpu_and(cpu
, env
->dst_grpmask
, env
->cpus
) {
5179 if (cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
))) {
5180 env
->flags
|= LBF_DST_PINNED
;
5181 env
->new_dst_cpu
= cpu
;
5189 /* Record that we found atleast one task that could run on dst_cpu */
5190 env
->flags
&= ~LBF_ALL_PINNED
;
5192 if (task_running(env
->src_rq
, p
)) {
5193 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_running
);
5198 * Aggressive migration if:
5199 * 1) destination numa is preferred
5200 * 2) task is cache cold, or
5201 * 3) too many balance attempts have failed.
5203 tsk_cache_hot
= task_hot(p
, rq_clock_task(env
->src_rq
));
5205 tsk_cache_hot
= migrate_degrades_locality(p
, env
);
5207 if (migrate_improves_locality(p
, env
)) {
5208 #ifdef CONFIG_SCHEDSTATS
5209 if (tsk_cache_hot
) {
5210 schedstat_inc(env
->sd
, lb_hot_gained
[env
->idle
]);
5211 schedstat_inc(p
, se
.statistics
.nr_forced_migrations
);
5217 if (!tsk_cache_hot
||
5218 env
->sd
->nr_balance_failed
> env
->sd
->cache_nice_tries
) {
5220 if (tsk_cache_hot
) {
5221 schedstat_inc(env
->sd
, lb_hot_gained
[env
->idle
]);
5222 schedstat_inc(p
, se
.statistics
.nr_forced_migrations
);
5228 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_hot
);
5233 * move_one_task tries to move exactly one task from busiest to this_rq, as
5234 * part of active balancing operations within "domain".
5235 * Returns 1 if successful and 0 otherwise.
5237 * Called with both runqueues locked.
5239 static int move_one_task(struct lb_env
*env
)
5241 struct task_struct
*p
, *n
;
5243 list_for_each_entry_safe(p
, n
, &env
->src_rq
->cfs_tasks
, se
.group_node
) {
5244 if (!can_migrate_task(p
, env
))
5249 * Right now, this is only the second place move_task()
5250 * is called, so we can safely collect move_task()
5251 * stats here rather than inside move_task().
5253 schedstat_inc(env
->sd
, lb_gained
[env
->idle
]);
5259 static const unsigned int sched_nr_migrate_break
= 32;
5262 * move_tasks tries to move up to imbalance weighted load from busiest to
5263 * this_rq, as part of a balancing operation within domain "sd".
5264 * Returns 1 if successful and 0 otherwise.
5266 * Called with both runqueues locked.
5268 static int move_tasks(struct lb_env
*env
)
5270 struct list_head
*tasks
= &env
->src_rq
->cfs_tasks
;
5271 struct task_struct
*p
;
5275 if (env
->imbalance
<= 0)
5278 while (!list_empty(tasks
)) {
5279 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
5282 /* We've more or less seen every task there is, call it quits */
5283 if (env
->loop
> env
->loop_max
)
5286 /* take a breather every nr_migrate tasks */
5287 if (env
->loop
> env
->loop_break
) {
5288 env
->loop_break
+= sched_nr_migrate_break
;
5289 env
->flags
|= LBF_NEED_BREAK
;
5293 if (!can_migrate_task(p
, env
))
5296 load
= task_h_load(p
);
5298 if (sched_feat(LB_MIN
) && load
< 16 && !env
->sd
->nr_balance_failed
)
5301 if ((load
/ 2) > env
->imbalance
)
5306 env
->imbalance
-= load
;
5308 #ifdef CONFIG_PREEMPT
5310 * NEWIDLE balancing is a source of latency, so preemptible
5311 * kernels will stop after the first task is pulled to minimize
5312 * the critical section.
5314 if (env
->idle
== CPU_NEWLY_IDLE
)
5319 * We only want to steal up to the prescribed amount of
5322 if (env
->imbalance
<= 0)
5327 list_move_tail(&p
->se
.group_node
, tasks
);
5331 * Right now, this is one of only two places move_task() is called,
5332 * so we can safely collect move_task() stats here rather than
5333 * inside move_task().
5335 schedstat_add(env
->sd
, lb_gained
[env
->idle
], pulled
);
5340 #ifdef CONFIG_FAIR_GROUP_SCHED
5342 * update tg->load_weight by folding this cpu's load_avg
5344 static void __update_blocked_averages_cpu(struct task_group
*tg
, int cpu
)
5346 struct sched_entity
*se
= tg
->se
[cpu
];
5347 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu
];
5349 /* throttled entities do not contribute to load */
5350 if (throttled_hierarchy(cfs_rq
))
5353 update_cfs_rq_blocked_load(cfs_rq
, 1);
5356 update_entity_load_avg(se
, 1);
5358 * We pivot on our runnable average having decayed to zero for
5359 * list removal. This generally implies that all our children
5360 * have also been removed (modulo rounding error or bandwidth
5361 * control); however, such cases are rare and we can fix these
5364 * TODO: fix up out-of-order children on enqueue.
5366 if (!se
->avg
.runnable_avg_sum
&& !cfs_rq
->nr_running
)
5367 list_del_leaf_cfs_rq(cfs_rq
);
5369 struct rq
*rq
= rq_of(cfs_rq
);
5370 update_rq_runnable_avg(rq
, rq
->nr_running
);
5374 static void update_blocked_averages(int cpu
)
5376 struct rq
*rq
= cpu_rq(cpu
);
5377 struct cfs_rq
*cfs_rq
;
5378 unsigned long flags
;
5380 raw_spin_lock_irqsave(&rq
->lock
, flags
);
5381 update_rq_clock(rq
);
5383 * Iterates the task_group tree in a bottom up fashion, see
5384 * list_add_leaf_cfs_rq() for details.
5386 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
5388 * Note: We may want to consider periodically releasing
5389 * rq->lock about these updates so that creating many task
5390 * groups does not result in continually extending hold time.
5392 __update_blocked_averages_cpu(cfs_rq
->tg
, rq
->cpu
);
5395 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
5399 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5400 * This needs to be done in a top-down fashion because the load of a child
5401 * group is a fraction of its parents load.
5403 static void update_cfs_rq_h_load(struct cfs_rq
*cfs_rq
)
5405 struct rq
*rq
= rq_of(cfs_rq
);
5406 struct sched_entity
*se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
5407 unsigned long now
= jiffies
;
5410 if (cfs_rq
->last_h_load_update
== now
)
5413 cfs_rq
->h_load_next
= NULL
;
5414 for_each_sched_entity(se
) {
5415 cfs_rq
= cfs_rq_of(se
);
5416 cfs_rq
->h_load_next
= se
;
5417 if (cfs_rq
->last_h_load_update
== now
)
5422 cfs_rq
->h_load
= cfs_rq
->runnable_load_avg
;
5423 cfs_rq
->last_h_load_update
= now
;
5426 while ((se
= cfs_rq
->h_load_next
) != NULL
) {
5427 load
= cfs_rq
->h_load
;
5428 load
= div64_ul(load
* se
->avg
.load_avg_contrib
,
5429 cfs_rq
->runnable_load_avg
+ 1);
5430 cfs_rq
= group_cfs_rq(se
);
5431 cfs_rq
->h_load
= load
;
5432 cfs_rq
->last_h_load_update
= now
;
5436 static unsigned long task_h_load(struct task_struct
*p
)
5438 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
5440 update_cfs_rq_h_load(cfs_rq
);
5441 return div64_ul(p
->se
.avg
.load_avg_contrib
* cfs_rq
->h_load
,
5442 cfs_rq
->runnable_load_avg
+ 1);
5445 static inline void update_blocked_averages(int cpu
)
5449 static unsigned long task_h_load(struct task_struct
*p
)
5451 return p
->se
.avg
.load_avg_contrib
;
5455 /********** Helpers for find_busiest_group ************************/
5457 * sg_lb_stats - stats of a sched_group required for load_balancing
5459 struct sg_lb_stats
{
5460 unsigned long avg_load
; /*Avg load across the CPUs of the group */
5461 unsigned long group_load
; /* Total load over the CPUs of the group */
5462 unsigned long sum_weighted_load
; /* Weighted load of group's tasks */
5463 unsigned long load_per_task
;
5464 unsigned long group_power
;
5465 unsigned int sum_nr_running
; /* Nr tasks running in the group */
5466 unsigned int group_capacity
;
5467 unsigned int idle_cpus
;
5468 unsigned int group_weight
;
5469 int group_imb
; /* Is there an imbalance in the group ? */
5470 int group_has_capacity
; /* Is there extra capacity in the group? */
5471 #ifdef CONFIG_NUMA_BALANCING
5472 unsigned int nr_numa_running
;
5473 unsigned int nr_preferred_running
;
5478 * sd_lb_stats - Structure to store the statistics of a sched_domain
5479 * during load balancing.
5481 struct sd_lb_stats
{
5482 struct sched_group
*busiest
; /* Busiest group in this sd */
5483 struct sched_group
*local
; /* Local group in this sd */
5484 unsigned long total_load
; /* Total load of all groups in sd */
5485 unsigned long total_pwr
; /* Total power of all groups in sd */
5486 unsigned long avg_load
; /* Average load across all groups in sd */
5488 struct sg_lb_stats busiest_stat
;/* Statistics of the busiest group */
5489 struct sg_lb_stats local_stat
; /* Statistics of the local group */
5492 static inline void init_sd_lb_stats(struct sd_lb_stats
*sds
)
5495 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
5496 * local_stat because update_sg_lb_stats() does a full clear/assignment.
5497 * We must however clear busiest_stat::avg_load because
5498 * update_sd_pick_busiest() reads this before assignment.
5500 *sds
= (struct sd_lb_stats
){
5512 * get_sd_load_idx - Obtain the load index for a given sched domain.
5513 * @sd: The sched_domain whose load_idx is to be obtained.
5514 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5516 * Return: The load index.
5518 static inline int get_sd_load_idx(struct sched_domain
*sd
,
5519 enum cpu_idle_type idle
)
5525 load_idx
= sd
->busy_idx
;
5528 case CPU_NEWLY_IDLE
:
5529 load_idx
= sd
->newidle_idx
;
5532 load_idx
= sd
->idle_idx
;
5539 static unsigned long default_scale_freq_power(struct sched_domain
*sd
, int cpu
)
5541 return SCHED_POWER_SCALE
;
5544 unsigned long __weak
arch_scale_freq_power(struct sched_domain
*sd
, int cpu
)
5546 return default_scale_freq_power(sd
, cpu
);
5549 static unsigned long default_scale_smt_power(struct sched_domain
*sd
, int cpu
)
5551 unsigned long weight
= sd
->span_weight
;
5552 unsigned long smt_gain
= sd
->smt_gain
;
5559 unsigned long __weak
arch_scale_smt_power(struct sched_domain
*sd
, int cpu
)
5561 return default_scale_smt_power(sd
, cpu
);
5564 static unsigned long scale_rt_power(int cpu
)
5566 struct rq
*rq
= cpu_rq(cpu
);
5567 u64 total
, available
, age_stamp
, avg
;
5570 * Since we're reading these variables without serialization make sure
5571 * we read them once before doing sanity checks on them.
5573 age_stamp
= ACCESS_ONCE(rq
->age_stamp
);
5574 avg
= ACCESS_ONCE(rq
->rt_avg
);
5576 total
= sched_avg_period() + (rq_clock(rq
) - age_stamp
);
5578 if (unlikely(total
< avg
)) {
5579 /* Ensures that power won't end up being negative */
5582 available
= total
- avg
;
5585 if (unlikely((s64
)total
< SCHED_POWER_SCALE
))
5586 total
= SCHED_POWER_SCALE
;
5588 total
>>= SCHED_POWER_SHIFT
;
5590 return div_u64(available
, total
);
5593 static void update_cpu_power(struct sched_domain
*sd
, int cpu
)
5595 unsigned long weight
= sd
->span_weight
;
5596 unsigned long power
= SCHED_POWER_SCALE
;
5597 struct sched_group
*sdg
= sd
->groups
;
5599 if ((sd
->flags
& SD_SHARE_CPUPOWER
) && weight
> 1) {
5600 if (sched_feat(ARCH_POWER
))
5601 power
*= arch_scale_smt_power(sd
, cpu
);
5603 power
*= default_scale_smt_power(sd
, cpu
);
5605 power
>>= SCHED_POWER_SHIFT
;
5608 sdg
->sgp
->power_orig
= power
;
5610 if (sched_feat(ARCH_POWER
))
5611 power
*= arch_scale_freq_power(sd
, cpu
);
5613 power
*= default_scale_freq_power(sd
, cpu
);
5615 power
>>= SCHED_POWER_SHIFT
;
5617 power
*= scale_rt_power(cpu
);
5618 power
>>= SCHED_POWER_SHIFT
;
5623 cpu_rq(cpu
)->cpu_power
= power
;
5624 sdg
->sgp
->power
= power
;
5627 void update_group_power(struct sched_domain
*sd
, int cpu
)
5629 struct sched_domain
*child
= sd
->child
;
5630 struct sched_group
*group
, *sdg
= sd
->groups
;
5631 unsigned long power
, power_orig
;
5632 unsigned long interval
;
5634 interval
= msecs_to_jiffies(sd
->balance_interval
);
5635 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
5636 sdg
->sgp
->next_update
= jiffies
+ interval
;
5639 update_cpu_power(sd
, cpu
);
5643 power_orig
= power
= 0;
5645 if (child
->flags
& SD_OVERLAP
) {
5647 * SD_OVERLAP domains cannot assume that child groups
5648 * span the current group.
5651 for_each_cpu(cpu
, sched_group_cpus(sdg
)) {
5652 struct sched_group_power
*sgp
;
5653 struct rq
*rq
= cpu_rq(cpu
);
5656 * build_sched_domains() -> init_sched_groups_power()
5657 * gets here before we've attached the domains to the
5660 * Use power_of(), which is set irrespective of domains
5661 * in update_cpu_power().
5663 * This avoids power/power_orig from being 0 and
5664 * causing divide-by-zero issues on boot.
5666 * Runtime updates will correct power_orig.
5668 if (unlikely(!rq
->sd
)) {
5669 power_orig
+= power_of(cpu
);
5670 power
+= power_of(cpu
);
5674 sgp
= rq
->sd
->groups
->sgp
;
5675 power_orig
+= sgp
->power_orig
;
5676 power
+= sgp
->power
;
5680 * !SD_OVERLAP domains can assume that child groups
5681 * span the current group.
5684 group
= child
->groups
;
5686 power_orig
+= group
->sgp
->power_orig
;
5687 power
+= group
->sgp
->power
;
5688 group
= group
->next
;
5689 } while (group
!= child
->groups
);
5692 sdg
->sgp
->power_orig
= power_orig
;
5693 sdg
->sgp
->power
= power
;
5697 * Try and fix up capacity for tiny siblings, this is needed when
5698 * things like SD_ASYM_PACKING need f_b_g to select another sibling
5699 * which on its own isn't powerful enough.
5701 * See update_sd_pick_busiest() and check_asym_packing().
5704 fix_small_capacity(struct sched_domain
*sd
, struct sched_group
*group
)
5707 * Only siblings can have significantly less than SCHED_POWER_SCALE
5709 if (!(sd
->flags
& SD_SHARE_CPUPOWER
))
5713 * If ~90% of the cpu_power is still there, we're good.
5715 if (group
->sgp
->power
* 32 > group
->sgp
->power_orig
* 29)
5722 * Group imbalance indicates (and tries to solve) the problem where balancing
5723 * groups is inadequate due to tsk_cpus_allowed() constraints.
5725 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
5726 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
5729 * { 0 1 2 3 } { 4 5 6 7 }
5732 * If we were to balance group-wise we'd place two tasks in the first group and
5733 * two tasks in the second group. Clearly this is undesired as it will overload
5734 * cpu 3 and leave one of the cpus in the second group unused.
5736 * The current solution to this issue is detecting the skew in the first group
5737 * by noticing the lower domain failed to reach balance and had difficulty
5738 * moving tasks due to affinity constraints.
5740 * When this is so detected; this group becomes a candidate for busiest; see
5741 * update_sd_pick_busiest(). And calculate_imbalance() and
5742 * find_busiest_group() avoid some of the usual balance conditions to allow it
5743 * to create an effective group imbalance.
5745 * This is a somewhat tricky proposition since the next run might not find the
5746 * group imbalance and decide the groups need to be balanced again. A most
5747 * subtle and fragile situation.
5750 static inline int sg_imbalanced(struct sched_group
*group
)
5752 return group
->sgp
->imbalance
;
5756 * Compute the group capacity.
5758 * Avoid the issue where N*frac(smt_power) >= 1 creates 'phantom' cores by
5759 * first dividing out the smt factor and computing the actual number of cores
5760 * and limit power unit capacity with that.
5762 static inline int sg_capacity(struct lb_env
*env
, struct sched_group
*group
)
5764 unsigned int capacity
, smt
, cpus
;
5765 unsigned int power
, power_orig
;
5767 power
= group
->sgp
->power
;
5768 power_orig
= group
->sgp
->power_orig
;
5769 cpus
= group
->group_weight
;
5771 /* smt := ceil(cpus / power), assumes: 1 < smt_power < 2 */
5772 smt
= DIV_ROUND_UP(SCHED_POWER_SCALE
* cpus
, power_orig
);
5773 capacity
= cpus
/ smt
; /* cores */
5775 capacity
= min_t(unsigned, capacity
, DIV_ROUND_CLOSEST(power
, SCHED_POWER_SCALE
));
5777 capacity
= fix_small_capacity(env
->sd
, group
);
5783 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
5784 * @env: The load balancing environment.
5785 * @group: sched_group whose statistics are to be updated.
5786 * @load_idx: Load index of sched_domain of this_cpu for load calc.
5787 * @local_group: Does group contain this_cpu.
5788 * @sgs: variable to hold the statistics for this group.
5790 static inline void update_sg_lb_stats(struct lb_env
*env
,
5791 struct sched_group
*group
, int load_idx
,
5792 int local_group
, struct sg_lb_stats
*sgs
)
5797 memset(sgs
, 0, sizeof(*sgs
));
5799 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
5800 struct rq
*rq
= cpu_rq(i
);
5802 /* Bias balancing toward cpus of our domain */
5804 load
= target_load(i
, load_idx
);
5806 load
= source_load(i
, load_idx
);
5808 sgs
->group_load
+= load
;
5809 sgs
->sum_nr_running
+= rq
->nr_running
;
5810 #ifdef CONFIG_NUMA_BALANCING
5811 sgs
->nr_numa_running
+= rq
->nr_numa_running
;
5812 sgs
->nr_preferred_running
+= rq
->nr_preferred_running
;
5814 sgs
->sum_weighted_load
+= weighted_cpuload(i
);
5819 /* Adjust by relative CPU power of the group */
5820 sgs
->group_power
= group
->sgp
->power
;
5821 sgs
->avg_load
= (sgs
->group_load
*SCHED_POWER_SCALE
) / sgs
->group_power
;
5823 if (sgs
->sum_nr_running
)
5824 sgs
->load_per_task
= sgs
->sum_weighted_load
/ sgs
->sum_nr_running
;
5826 sgs
->group_weight
= group
->group_weight
;
5828 sgs
->group_imb
= sg_imbalanced(group
);
5829 sgs
->group_capacity
= sg_capacity(env
, group
);
5831 if (sgs
->group_capacity
> sgs
->sum_nr_running
)
5832 sgs
->group_has_capacity
= 1;
5836 * update_sd_pick_busiest - return 1 on busiest group
5837 * @env: The load balancing environment.
5838 * @sds: sched_domain statistics
5839 * @sg: sched_group candidate to be checked for being the busiest
5840 * @sgs: sched_group statistics
5842 * Determine if @sg is a busier group than the previously selected
5845 * Return: %true if @sg is a busier group than the previously selected
5846 * busiest group. %false otherwise.
5848 static bool update_sd_pick_busiest(struct lb_env
*env
,
5849 struct sd_lb_stats
*sds
,
5850 struct sched_group
*sg
,
5851 struct sg_lb_stats
*sgs
)
5853 if (sgs
->avg_load
<= sds
->busiest_stat
.avg_load
)
5856 if (sgs
->sum_nr_running
> sgs
->group_capacity
)
5863 * ASYM_PACKING needs to move all the work to the lowest
5864 * numbered CPUs in the group, therefore mark all groups
5865 * higher than ourself as busy.
5867 if ((env
->sd
->flags
& SD_ASYM_PACKING
) && sgs
->sum_nr_running
&&
5868 env
->dst_cpu
< group_first_cpu(sg
)) {
5872 if (group_first_cpu(sds
->busiest
) > group_first_cpu(sg
))
5879 #ifdef CONFIG_NUMA_BALANCING
5880 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
5882 if (sgs
->sum_nr_running
> sgs
->nr_numa_running
)
5884 if (sgs
->sum_nr_running
> sgs
->nr_preferred_running
)
5889 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
5891 if (rq
->nr_running
> rq
->nr_numa_running
)
5893 if (rq
->nr_running
> rq
->nr_preferred_running
)
5898 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
5903 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
5907 #endif /* CONFIG_NUMA_BALANCING */
5910 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
5911 * @env: The load balancing environment.
5912 * @sds: variable to hold the statistics for this sched_domain.
5914 static inline void update_sd_lb_stats(struct lb_env
*env
, struct sd_lb_stats
*sds
)
5916 struct sched_domain
*child
= env
->sd
->child
;
5917 struct sched_group
*sg
= env
->sd
->groups
;
5918 struct sg_lb_stats tmp_sgs
;
5919 int load_idx
, prefer_sibling
= 0;
5921 if (child
&& child
->flags
& SD_PREFER_SIBLING
)
5924 load_idx
= get_sd_load_idx(env
->sd
, env
->idle
);
5927 struct sg_lb_stats
*sgs
= &tmp_sgs
;
5930 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_cpus(sg
));
5933 sgs
= &sds
->local_stat
;
5935 if (env
->idle
!= CPU_NEWLY_IDLE
||
5936 time_after_eq(jiffies
, sg
->sgp
->next_update
))
5937 update_group_power(env
->sd
, env
->dst_cpu
);
5940 update_sg_lb_stats(env
, sg
, load_idx
, local_group
, sgs
);
5946 * In case the child domain prefers tasks go to siblings
5947 * first, lower the sg capacity to one so that we'll try
5948 * and move all the excess tasks away. We lower the capacity
5949 * of a group only if the local group has the capacity to fit
5950 * these excess tasks, i.e. nr_running < group_capacity. The
5951 * extra check prevents the case where you always pull from the
5952 * heaviest group when it is already under-utilized (possible
5953 * with a large weight task outweighs the tasks on the system).
5955 if (prefer_sibling
&& sds
->local
&&
5956 sds
->local_stat
.group_has_capacity
)
5957 sgs
->group_capacity
= min(sgs
->group_capacity
, 1U);
5959 if (update_sd_pick_busiest(env
, sds
, sg
, sgs
)) {
5961 sds
->busiest_stat
= *sgs
;
5965 /* Now, start updating sd_lb_stats */
5966 sds
->total_load
+= sgs
->group_load
;
5967 sds
->total_pwr
+= sgs
->group_power
;
5970 } while (sg
!= env
->sd
->groups
);
5972 if (env
->sd
->flags
& SD_NUMA
)
5973 env
->fbq_type
= fbq_classify_group(&sds
->busiest_stat
);
5977 * check_asym_packing - Check to see if the group is packed into the
5980 * This is primarily intended to used at the sibling level. Some
5981 * cores like POWER7 prefer to use lower numbered SMT threads. In the
5982 * case of POWER7, it can move to lower SMT modes only when higher
5983 * threads are idle. When in lower SMT modes, the threads will
5984 * perform better since they share less core resources. Hence when we
5985 * have idle threads, we want them to be the higher ones.
5987 * This packing function is run on idle threads. It checks to see if
5988 * the busiest CPU in this domain (core in the P7 case) has a higher
5989 * CPU number than the packing function is being run on. Here we are
5990 * assuming lower CPU number will be equivalent to lower a SMT thread
5993 * Return: 1 when packing is required and a task should be moved to
5994 * this CPU. The amount of the imbalance is returned in *imbalance.
5996 * @env: The load balancing environment.
5997 * @sds: Statistics of the sched_domain which is to be packed
5999 static int check_asym_packing(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6003 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6009 busiest_cpu
= group_first_cpu(sds
->busiest
);
6010 if (env
->dst_cpu
> busiest_cpu
)
6013 env
->imbalance
= DIV_ROUND_CLOSEST(
6014 sds
->busiest_stat
.avg_load
* sds
->busiest_stat
.group_power
,
6021 * fix_small_imbalance - Calculate the minor imbalance that exists
6022 * amongst the groups of a sched_domain, during
6024 * @env: The load balancing environment.
6025 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6028 void fix_small_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6030 unsigned long tmp
, pwr_now
= 0, pwr_move
= 0;
6031 unsigned int imbn
= 2;
6032 unsigned long scaled_busy_load_per_task
;
6033 struct sg_lb_stats
*local
, *busiest
;
6035 local
= &sds
->local_stat
;
6036 busiest
= &sds
->busiest_stat
;
6038 if (!local
->sum_nr_running
)
6039 local
->load_per_task
= cpu_avg_load_per_task(env
->dst_cpu
);
6040 else if (busiest
->load_per_task
> local
->load_per_task
)
6043 scaled_busy_load_per_task
=
6044 (busiest
->load_per_task
* SCHED_POWER_SCALE
) /
6045 busiest
->group_power
;
6047 if (busiest
->avg_load
+ scaled_busy_load_per_task
>=
6048 local
->avg_load
+ (scaled_busy_load_per_task
* imbn
)) {
6049 env
->imbalance
= busiest
->load_per_task
;
6054 * OK, we don't have enough imbalance to justify moving tasks,
6055 * however we may be able to increase total CPU power used by
6059 pwr_now
+= busiest
->group_power
*
6060 min(busiest
->load_per_task
, busiest
->avg_load
);
6061 pwr_now
+= local
->group_power
*
6062 min(local
->load_per_task
, local
->avg_load
);
6063 pwr_now
/= SCHED_POWER_SCALE
;
6065 /* Amount of load we'd subtract */
6066 if (busiest
->avg_load
> scaled_busy_load_per_task
) {
6067 pwr_move
+= busiest
->group_power
*
6068 min(busiest
->load_per_task
,
6069 busiest
->avg_load
- scaled_busy_load_per_task
);
6072 /* Amount of load we'd add */
6073 if (busiest
->avg_load
* busiest
->group_power
<
6074 busiest
->load_per_task
* SCHED_POWER_SCALE
) {
6075 tmp
= (busiest
->avg_load
* busiest
->group_power
) /
6078 tmp
= (busiest
->load_per_task
* SCHED_POWER_SCALE
) /
6081 pwr_move
+= local
->group_power
*
6082 min(local
->load_per_task
, local
->avg_load
+ tmp
);
6083 pwr_move
/= SCHED_POWER_SCALE
;
6085 /* Move if we gain throughput */
6086 if (pwr_move
> pwr_now
)
6087 env
->imbalance
= busiest
->load_per_task
;
6091 * calculate_imbalance - Calculate the amount of imbalance present within the
6092 * groups of a given sched_domain during load balance.
6093 * @env: load balance environment
6094 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6096 static inline void calculate_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6098 unsigned long max_pull
, load_above_capacity
= ~0UL;
6099 struct sg_lb_stats
*local
, *busiest
;
6101 local
= &sds
->local_stat
;
6102 busiest
= &sds
->busiest_stat
;
6104 if (busiest
->group_imb
) {
6106 * In the group_imb case we cannot rely on group-wide averages
6107 * to ensure cpu-load equilibrium, look at wider averages. XXX
6109 busiest
->load_per_task
=
6110 min(busiest
->load_per_task
, sds
->avg_load
);
6114 * In the presence of smp nice balancing, certain scenarios can have
6115 * max load less than avg load(as we skip the groups at or below
6116 * its cpu_power, while calculating max_load..)
6118 if (busiest
->avg_load
<= sds
->avg_load
||
6119 local
->avg_load
>= sds
->avg_load
) {
6121 return fix_small_imbalance(env
, sds
);
6124 if (!busiest
->group_imb
) {
6126 * Don't want to pull so many tasks that a group would go idle.
6127 * Except of course for the group_imb case, since then we might
6128 * have to drop below capacity to reach cpu-load equilibrium.
6130 load_above_capacity
=
6131 (busiest
->sum_nr_running
- busiest
->group_capacity
);
6133 load_above_capacity
*= (SCHED_LOAD_SCALE
* SCHED_POWER_SCALE
);
6134 load_above_capacity
/= busiest
->group_power
;
6138 * We're trying to get all the cpus to the average_load, so we don't
6139 * want to push ourselves above the average load, nor do we wish to
6140 * reduce the max loaded cpu below the average load. At the same time,
6141 * we also don't want to reduce the group load below the group capacity
6142 * (so that we can implement power-savings policies etc). Thus we look
6143 * for the minimum possible imbalance.
6145 max_pull
= min(busiest
->avg_load
- sds
->avg_load
, load_above_capacity
);
6147 /* How much load to actually move to equalise the imbalance */
6148 env
->imbalance
= min(
6149 max_pull
* busiest
->group_power
,
6150 (sds
->avg_load
- local
->avg_load
) * local
->group_power
6151 ) / SCHED_POWER_SCALE
;
6154 * if *imbalance is less than the average load per runnable task
6155 * there is no guarantee that any tasks will be moved so we'll have
6156 * a think about bumping its value to force at least one task to be
6159 if (env
->imbalance
< busiest
->load_per_task
)
6160 return fix_small_imbalance(env
, sds
);
6163 /******* find_busiest_group() helpers end here *********************/
6166 * find_busiest_group - Returns the busiest group within the sched_domain
6167 * if there is an imbalance. If there isn't an imbalance, and
6168 * the user has opted for power-savings, it returns a group whose
6169 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6170 * such a group exists.
6172 * Also calculates the amount of weighted load which should be moved
6173 * to restore balance.
6175 * @env: The load balancing environment.
6177 * Return: - The busiest group if imbalance exists.
6178 * - If no imbalance and user has opted for power-savings balance,
6179 * return the least loaded group whose CPUs can be
6180 * put to idle by rebalancing its tasks onto our group.
6182 static struct sched_group
*find_busiest_group(struct lb_env
*env
)
6184 struct sg_lb_stats
*local
, *busiest
;
6185 struct sd_lb_stats sds
;
6187 init_sd_lb_stats(&sds
);
6190 * Compute the various statistics relavent for load balancing at
6193 update_sd_lb_stats(env
, &sds
);
6194 local
= &sds
.local_stat
;
6195 busiest
= &sds
.busiest_stat
;
6197 if ((env
->idle
== CPU_IDLE
|| env
->idle
== CPU_NEWLY_IDLE
) &&
6198 check_asym_packing(env
, &sds
))
6201 /* There is no busy sibling group to pull tasks from */
6202 if (!sds
.busiest
|| busiest
->sum_nr_running
== 0)
6205 sds
.avg_load
= (SCHED_POWER_SCALE
* sds
.total_load
) / sds
.total_pwr
;
6208 * If the busiest group is imbalanced the below checks don't
6209 * work because they assume all things are equal, which typically
6210 * isn't true due to cpus_allowed constraints and the like.
6212 if (busiest
->group_imb
)
6215 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6216 if (env
->idle
== CPU_NEWLY_IDLE
&& local
->group_has_capacity
&&
6217 !busiest
->group_has_capacity
)
6221 * If the local group is more busy than the selected busiest group
6222 * don't try and pull any tasks.
6224 if (local
->avg_load
>= busiest
->avg_load
)
6228 * Don't pull any tasks if this group is already above the domain
6231 if (local
->avg_load
>= sds
.avg_load
)
6234 if (env
->idle
== CPU_IDLE
) {
6236 * This cpu is idle. If the busiest group load doesn't
6237 * have more tasks than the number of available cpu's and
6238 * there is no imbalance between this and busiest group
6239 * wrt to idle cpu's, it is balanced.
6241 if ((local
->idle_cpus
< busiest
->idle_cpus
) &&
6242 busiest
->sum_nr_running
<= busiest
->group_weight
)
6246 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6247 * imbalance_pct to be conservative.
6249 if (100 * busiest
->avg_load
<=
6250 env
->sd
->imbalance_pct
* local
->avg_load
)
6255 /* Looks like there is an imbalance. Compute it */
6256 calculate_imbalance(env
, &sds
);
6265 * find_busiest_queue - find the busiest runqueue among the cpus in group.
6267 static struct rq
*find_busiest_queue(struct lb_env
*env
,
6268 struct sched_group
*group
)
6270 struct rq
*busiest
= NULL
, *rq
;
6271 unsigned long busiest_load
= 0, busiest_power
= 1;
6274 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
6275 unsigned long power
, capacity
, wl
;
6279 rt
= fbq_classify_rq(rq
);
6282 * We classify groups/runqueues into three groups:
6283 * - regular: there are !numa tasks
6284 * - remote: there are numa tasks that run on the 'wrong' node
6285 * - all: there is no distinction
6287 * In order to avoid migrating ideally placed numa tasks,
6288 * ignore those when there's better options.
6290 * If we ignore the actual busiest queue to migrate another
6291 * task, the next balance pass can still reduce the busiest
6292 * queue by moving tasks around inside the node.
6294 * If we cannot move enough load due to this classification
6295 * the next pass will adjust the group classification and
6296 * allow migration of more tasks.
6298 * Both cases only affect the total convergence complexity.
6300 if (rt
> env
->fbq_type
)
6303 power
= power_of(i
);
6304 capacity
= DIV_ROUND_CLOSEST(power
, SCHED_POWER_SCALE
);
6306 capacity
= fix_small_capacity(env
->sd
, group
);
6308 wl
= weighted_cpuload(i
);
6311 * When comparing with imbalance, use weighted_cpuload()
6312 * which is not scaled with the cpu power.
6314 if (capacity
&& rq
->nr_running
== 1 && wl
> env
->imbalance
)
6318 * For the load comparisons with the other cpu's, consider
6319 * the weighted_cpuload() scaled with the cpu power, so that
6320 * the load can be moved away from the cpu that is potentially
6321 * running at a lower capacity.
6323 * Thus we're looking for max(wl_i / power_i), crosswise
6324 * multiplication to rid ourselves of the division works out
6325 * to: wl_i * power_j > wl_j * power_i; where j is our
6328 if (wl
* busiest_power
> busiest_load
* power
) {
6330 busiest_power
= power
;
6339 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6340 * so long as it is large enough.
6342 #define MAX_PINNED_INTERVAL 512
6344 /* Working cpumask for load_balance and load_balance_newidle. */
6345 DEFINE_PER_CPU(cpumask_var_t
, load_balance_mask
);
6347 static int need_active_balance(struct lb_env
*env
)
6349 struct sched_domain
*sd
= env
->sd
;
6351 if (env
->idle
== CPU_NEWLY_IDLE
) {
6354 * ASYM_PACKING needs to force migrate tasks from busy but
6355 * higher numbered CPUs in order to pack all tasks in the
6356 * lowest numbered CPUs.
6358 if ((sd
->flags
& SD_ASYM_PACKING
) && env
->src_cpu
> env
->dst_cpu
)
6362 return unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2);
6365 static int active_load_balance_cpu_stop(void *data
);
6367 static int should_we_balance(struct lb_env
*env
)
6369 struct sched_group
*sg
= env
->sd
->groups
;
6370 struct cpumask
*sg_cpus
, *sg_mask
;
6371 int cpu
, balance_cpu
= -1;
6374 * In the newly idle case, we will allow all the cpu's
6375 * to do the newly idle load balance.
6377 if (env
->idle
== CPU_NEWLY_IDLE
)
6380 sg_cpus
= sched_group_cpus(sg
);
6381 sg_mask
= sched_group_mask(sg
);
6382 /* Try to find first idle cpu */
6383 for_each_cpu_and(cpu
, sg_cpus
, env
->cpus
) {
6384 if (!cpumask_test_cpu(cpu
, sg_mask
) || !idle_cpu(cpu
))
6391 if (balance_cpu
== -1)
6392 balance_cpu
= group_balance_cpu(sg
);
6395 * First idle cpu or the first cpu(busiest) in this sched group
6396 * is eligible for doing load balancing at this and above domains.
6398 return balance_cpu
== env
->dst_cpu
;
6402 * Check this_cpu to ensure it is balanced within domain. Attempt to move
6403 * tasks if there is an imbalance.
6405 static int load_balance(int this_cpu
, struct rq
*this_rq
,
6406 struct sched_domain
*sd
, enum cpu_idle_type idle
,
6407 int *continue_balancing
)
6409 int ld_moved
, cur_ld_moved
, active_balance
= 0;
6410 struct sched_domain
*sd_parent
= sd
->parent
;
6411 struct sched_group
*group
;
6413 unsigned long flags
;
6414 struct cpumask
*cpus
= __get_cpu_var(load_balance_mask
);
6416 struct lb_env env
= {
6418 .dst_cpu
= this_cpu
,
6420 .dst_grpmask
= sched_group_cpus(sd
->groups
),
6422 .loop_break
= sched_nr_migrate_break
,
6428 * For NEWLY_IDLE load_balancing, we don't need to consider
6429 * other cpus in our group
6431 if (idle
== CPU_NEWLY_IDLE
)
6432 env
.dst_grpmask
= NULL
;
6434 cpumask_copy(cpus
, cpu_active_mask
);
6436 schedstat_inc(sd
, lb_count
[idle
]);
6439 if (!should_we_balance(&env
)) {
6440 *continue_balancing
= 0;
6444 group
= find_busiest_group(&env
);
6446 schedstat_inc(sd
, lb_nobusyg
[idle
]);
6450 busiest
= find_busiest_queue(&env
, group
);
6452 schedstat_inc(sd
, lb_nobusyq
[idle
]);
6456 BUG_ON(busiest
== env
.dst_rq
);
6458 schedstat_add(sd
, lb_imbalance
[idle
], env
.imbalance
);
6461 if (busiest
->nr_running
> 1) {
6463 * Attempt to move tasks. If find_busiest_group has found
6464 * an imbalance but busiest->nr_running <= 1, the group is
6465 * still unbalanced. ld_moved simply stays zero, so it is
6466 * correctly treated as an imbalance.
6468 env
.flags
|= LBF_ALL_PINNED
;
6469 env
.src_cpu
= busiest
->cpu
;
6470 env
.src_rq
= busiest
;
6471 env
.loop_max
= min(sysctl_sched_nr_migrate
, busiest
->nr_running
);
6474 local_irq_save(flags
);
6475 double_rq_lock(env
.dst_rq
, busiest
);
6478 * cur_ld_moved - load moved in current iteration
6479 * ld_moved - cumulative load moved across iterations
6481 cur_ld_moved
= move_tasks(&env
);
6482 ld_moved
+= cur_ld_moved
;
6483 double_rq_unlock(env
.dst_rq
, busiest
);
6484 local_irq_restore(flags
);
6487 * some other cpu did the load balance for us.
6489 if (cur_ld_moved
&& env
.dst_cpu
!= smp_processor_id())
6490 resched_cpu(env
.dst_cpu
);
6492 if (env
.flags
& LBF_NEED_BREAK
) {
6493 env
.flags
&= ~LBF_NEED_BREAK
;
6498 * Revisit (affine) tasks on src_cpu that couldn't be moved to
6499 * us and move them to an alternate dst_cpu in our sched_group
6500 * where they can run. The upper limit on how many times we
6501 * iterate on same src_cpu is dependent on number of cpus in our
6504 * This changes load balance semantics a bit on who can move
6505 * load to a given_cpu. In addition to the given_cpu itself
6506 * (or a ilb_cpu acting on its behalf where given_cpu is
6507 * nohz-idle), we now have balance_cpu in a position to move
6508 * load to given_cpu. In rare situations, this may cause
6509 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
6510 * _independently_ and at _same_ time to move some load to
6511 * given_cpu) causing exceess load to be moved to given_cpu.
6512 * This however should not happen so much in practice and
6513 * moreover subsequent load balance cycles should correct the
6514 * excess load moved.
6516 if ((env
.flags
& LBF_DST_PINNED
) && env
.imbalance
> 0) {
6518 /* Prevent to re-select dst_cpu via env's cpus */
6519 cpumask_clear_cpu(env
.dst_cpu
, env
.cpus
);
6521 env
.dst_rq
= cpu_rq(env
.new_dst_cpu
);
6522 env
.dst_cpu
= env
.new_dst_cpu
;
6523 env
.flags
&= ~LBF_DST_PINNED
;
6525 env
.loop_break
= sched_nr_migrate_break
;
6528 * Go back to "more_balance" rather than "redo" since we
6529 * need to continue with same src_cpu.
6535 * We failed to reach balance because of affinity.
6538 int *group_imbalance
= &sd_parent
->groups
->sgp
->imbalance
;
6540 if ((env
.flags
& LBF_SOME_PINNED
) && env
.imbalance
> 0) {
6541 *group_imbalance
= 1;
6542 } else if (*group_imbalance
)
6543 *group_imbalance
= 0;
6546 /* All tasks on this runqueue were pinned by CPU affinity */
6547 if (unlikely(env
.flags
& LBF_ALL_PINNED
)) {
6548 cpumask_clear_cpu(cpu_of(busiest
), cpus
);
6549 if (!cpumask_empty(cpus
)) {
6551 env
.loop_break
= sched_nr_migrate_break
;
6559 schedstat_inc(sd
, lb_failed
[idle
]);
6561 * Increment the failure counter only on periodic balance.
6562 * We do not want newidle balance, which can be very
6563 * frequent, pollute the failure counter causing
6564 * excessive cache_hot migrations and active balances.
6566 if (idle
!= CPU_NEWLY_IDLE
)
6567 sd
->nr_balance_failed
++;
6569 if (need_active_balance(&env
)) {
6570 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
6572 /* don't kick the active_load_balance_cpu_stop,
6573 * if the curr task on busiest cpu can't be
6576 if (!cpumask_test_cpu(this_cpu
,
6577 tsk_cpus_allowed(busiest
->curr
))) {
6578 raw_spin_unlock_irqrestore(&busiest
->lock
,
6580 env
.flags
|= LBF_ALL_PINNED
;
6581 goto out_one_pinned
;
6585 * ->active_balance synchronizes accesses to
6586 * ->active_balance_work. Once set, it's cleared
6587 * only after active load balance is finished.
6589 if (!busiest
->active_balance
) {
6590 busiest
->active_balance
= 1;
6591 busiest
->push_cpu
= this_cpu
;
6594 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
6596 if (active_balance
) {
6597 stop_one_cpu_nowait(cpu_of(busiest
),
6598 active_load_balance_cpu_stop
, busiest
,
6599 &busiest
->active_balance_work
);
6603 * We've kicked active balancing, reset the failure
6606 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
6609 sd
->nr_balance_failed
= 0;
6611 if (likely(!active_balance
)) {
6612 /* We were unbalanced, so reset the balancing interval */
6613 sd
->balance_interval
= sd
->min_interval
;
6616 * If we've begun active balancing, start to back off. This
6617 * case may not be covered by the all_pinned logic if there
6618 * is only 1 task on the busy runqueue (because we don't call
6621 if (sd
->balance_interval
< sd
->max_interval
)
6622 sd
->balance_interval
*= 2;
6628 schedstat_inc(sd
, lb_balanced
[idle
]);
6630 sd
->nr_balance_failed
= 0;
6633 /* tune up the balancing interval */
6634 if (((env
.flags
& LBF_ALL_PINNED
) &&
6635 sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
6636 (sd
->balance_interval
< sd
->max_interval
))
6637 sd
->balance_interval
*= 2;
6645 * idle_balance is called by schedule() if this_cpu is about to become
6646 * idle. Attempts to pull tasks from other CPUs.
6648 static int idle_balance(struct rq
*this_rq
)
6650 struct sched_domain
*sd
;
6651 int pulled_task
= 0;
6652 unsigned long next_balance
= jiffies
+ HZ
;
6654 int this_cpu
= this_rq
->cpu
;
6656 idle_enter_fair(this_rq
);
6659 * We must set idle_stamp _before_ calling idle_balance(), such that we
6660 * measure the duration of idle_balance() as idle time.
6662 this_rq
->idle_stamp
= rq_clock(this_rq
);
6664 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
)
6668 * Drop the rq->lock, but keep IRQ/preempt disabled.
6670 raw_spin_unlock(&this_rq
->lock
);
6672 update_blocked_averages(this_cpu
);
6674 for_each_domain(this_cpu
, sd
) {
6675 unsigned long interval
;
6676 int continue_balancing
= 1;
6677 u64 t0
, domain_cost
;
6679 if (!(sd
->flags
& SD_LOAD_BALANCE
))
6682 if (this_rq
->avg_idle
< curr_cost
+ sd
->max_newidle_lb_cost
)
6685 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
6686 t0
= sched_clock_cpu(this_cpu
);
6688 /* If we've pulled tasks over stop searching: */
6689 pulled_task
= load_balance(this_cpu
, this_rq
,
6691 &continue_balancing
);
6693 domain_cost
= sched_clock_cpu(this_cpu
) - t0
;
6694 if (domain_cost
> sd
->max_newidle_lb_cost
)
6695 sd
->max_newidle_lb_cost
= domain_cost
;
6697 curr_cost
+= domain_cost
;
6700 interval
= msecs_to_jiffies(sd
->balance_interval
);
6701 if (time_after(next_balance
, sd
->last_balance
+ interval
))
6702 next_balance
= sd
->last_balance
+ interval
;
6708 raw_spin_lock(&this_rq
->lock
);
6710 if (curr_cost
> this_rq
->max_idle_balance_cost
)
6711 this_rq
->max_idle_balance_cost
= curr_cost
;
6714 * While browsing the domains, we released the rq lock, a task could
6715 * have been enqueued in the meantime. Since we're not going idle,
6716 * pretend we pulled a task.
6718 if (this_rq
->cfs
.h_nr_running
&& !pulled_task
)
6721 if (pulled_task
|| time_after(jiffies
, this_rq
->next_balance
)) {
6723 * We are going idle. next_balance may be set based on
6724 * a busy processor. So reset next_balance.
6726 this_rq
->next_balance
= next_balance
;
6730 /* Is there a task of a high priority class? */
6731 if (this_rq
->nr_running
!= this_rq
->cfs
.h_nr_running
&&
6732 ((this_rq
->stop
&& this_rq
->stop
->on_rq
) ||
6733 this_rq
->dl
.dl_nr_running
||
6734 (this_rq
->rt
.rt_nr_running
&& !rt_rq_throttled(&this_rq
->rt
))))
6738 idle_exit_fair(this_rq
);
6739 this_rq
->idle_stamp
= 0;
6746 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
6747 * running tasks off the busiest CPU onto idle CPUs. It requires at
6748 * least 1 task to be running on each physical CPU where possible, and
6749 * avoids physical / logical imbalances.
6751 static int active_load_balance_cpu_stop(void *data
)
6753 struct rq
*busiest_rq
= data
;
6754 int busiest_cpu
= cpu_of(busiest_rq
);
6755 int target_cpu
= busiest_rq
->push_cpu
;
6756 struct rq
*target_rq
= cpu_rq(target_cpu
);
6757 struct sched_domain
*sd
;
6759 raw_spin_lock_irq(&busiest_rq
->lock
);
6761 /* make sure the requested cpu hasn't gone down in the meantime */
6762 if (unlikely(busiest_cpu
!= smp_processor_id() ||
6763 !busiest_rq
->active_balance
))
6766 /* Is there any task to move? */
6767 if (busiest_rq
->nr_running
<= 1)
6771 * This condition is "impossible", if it occurs
6772 * we need to fix it. Originally reported by
6773 * Bjorn Helgaas on a 128-cpu setup.
6775 BUG_ON(busiest_rq
== target_rq
);
6777 /* move a task from busiest_rq to target_rq */
6778 double_lock_balance(busiest_rq
, target_rq
);
6780 /* Search for an sd spanning us and the target CPU. */
6782 for_each_domain(target_cpu
, sd
) {
6783 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
6784 cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
6789 struct lb_env env
= {
6791 .dst_cpu
= target_cpu
,
6792 .dst_rq
= target_rq
,
6793 .src_cpu
= busiest_rq
->cpu
,
6794 .src_rq
= busiest_rq
,
6798 schedstat_inc(sd
, alb_count
);
6800 if (move_one_task(&env
))
6801 schedstat_inc(sd
, alb_pushed
);
6803 schedstat_inc(sd
, alb_failed
);
6806 double_unlock_balance(busiest_rq
, target_rq
);
6808 busiest_rq
->active_balance
= 0;
6809 raw_spin_unlock_irq(&busiest_rq
->lock
);
6813 static inline int on_null_domain(struct rq
*rq
)
6815 return unlikely(!rcu_dereference_sched(rq
->sd
));
6818 #ifdef CONFIG_NO_HZ_COMMON
6820 * idle load balancing details
6821 * - When one of the busy CPUs notice that there may be an idle rebalancing
6822 * needed, they will kick the idle load balancer, which then does idle
6823 * load balancing for all the idle CPUs.
6826 cpumask_var_t idle_cpus_mask
;
6828 unsigned long next_balance
; /* in jiffy units */
6829 } nohz ____cacheline_aligned
;
6831 static inline int find_new_ilb(void)
6833 int ilb
= cpumask_first(nohz
.idle_cpus_mask
);
6835 if (ilb
< nr_cpu_ids
&& idle_cpu(ilb
))
6842 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
6843 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
6844 * CPU (if there is one).
6846 static void nohz_balancer_kick(void)
6850 nohz
.next_balance
++;
6852 ilb_cpu
= find_new_ilb();
6854 if (ilb_cpu
>= nr_cpu_ids
)
6857 if (test_and_set_bit(NOHZ_BALANCE_KICK
, nohz_flags(ilb_cpu
)))
6860 * Use smp_send_reschedule() instead of resched_cpu().
6861 * This way we generate a sched IPI on the target cpu which
6862 * is idle. And the softirq performing nohz idle load balance
6863 * will be run before returning from the IPI.
6865 smp_send_reschedule(ilb_cpu
);
6869 static inline void nohz_balance_exit_idle(int cpu
)
6871 if (unlikely(test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))) {
6873 * Completely isolated CPUs don't ever set, so we must test.
6875 if (likely(cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))) {
6876 cpumask_clear_cpu(cpu
, nohz
.idle_cpus_mask
);
6877 atomic_dec(&nohz
.nr_cpus
);
6879 clear_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
6883 static inline void set_cpu_sd_state_busy(void)
6885 struct sched_domain
*sd
;
6886 int cpu
= smp_processor_id();
6889 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
6891 if (!sd
|| !sd
->nohz_idle
)
6895 atomic_inc(&sd
->groups
->sgp
->nr_busy_cpus
);
6900 void set_cpu_sd_state_idle(void)
6902 struct sched_domain
*sd
;
6903 int cpu
= smp_processor_id();
6906 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
6908 if (!sd
|| sd
->nohz_idle
)
6912 atomic_dec(&sd
->groups
->sgp
->nr_busy_cpus
);
6918 * This routine will record that the cpu is going idle with tick stopped.
6919 * This info will be used in performing idle load balancing in the future.
6921 void nohz_balance_enter_idle(int cpu
)
6924 * If this cpu is going down, then nothing needs to be done.
6926 if (!cpu_active(cpu
))
6929 if (test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))
6933 * If we're a completely isolated CPU, we don't play.
6935 if (on_null_domain(cpu_rq(cpu
)))
6938 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
6939 atomic_inc(&nohz
.nr_cpus
);
6940 set_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
6943 static int sched_ilb_notifier(struct notifier_block
*nfb
,
6944 unsigned long action
, void *hcpu
)
6946 switch (action
& ~CPU_TASKS_FROZEN
) {
6948 nohz_balance_exit_idle(smp_processor_id());
6956 static DEFINE_SPINLOCK(balancing
);
6959 * Scale the max load_balance interval with the number of CPUs in the system.
6960 * This trades load-balance latency on larger machines for less cross talk.
6962 void update_max_interval(void)
6964 max_load_balance_interval
= HZ
*num_online_cpus()/10;
6968 * It checks each scheduling domain to see if it is due to be balanced,
6969 * and initiates a balancing operation if so.
6971 * Balancing parameters are set up in init_sched_domains.
6973 static void rebalance_domains(struct rq
*rq
, enum cpu_idle_type idle
)
6975 int continue_balancing
= 1;
6977 unsigned long interval
;
6978 struct sched_domain
*sd
;
6979 /* Earliest time when we have to do rebalance again */
6980 unsigned long next_balance
= jiffies
+ 60*HZ
;
6981 int update_next_balance
= 0;
6982 int need_serialize
, need_decay
= 0;
6985 update_blocked_averages(cpu
);
6988 for_each_domain(cpu
, sd
) {
6990 * Decay the newidle max times here because this is a regular
6991 * visit to all the domains. Decay ~1% per second.
6993 if (time_after(jiffies
, sd
->next_decay_max_lb_cost
)) {
6994 sd
->max_newidle_lb_cost
=
6995 (sd
->max_newidle_lb_cost
* 253) / 256;
6996 sd
->next_decay_max_lb_cost
= jiffies
+ HZ
;
6999 max_cost
+= sd
->max_newidle_lb_cost
;
7001 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7005 * Stop the load balance at this level. There is another
7006 * CPU in our sched group which is doing load balancing more
7009 if (!continue_balancing
) {
7015 interval
= sd
->balance_interval
;
7016 if (idle
!= CPU_IDLE
)
7017 interval
*= sd
->busy_factor
;
7019 /* scale ms to jiffies */
7020 interval
= msecs_to_jiffies(interval
);
7021 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
7023 need_serialize
= sd
->flags
& SD_SERIALIZE
;
7025 if (need_serialize
) {
7026 if (!spin_trylock(&balancing
))
7030 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
7031 if (load_balance(cpu
, rq
, sd
, idle
, &continue_balancing
)) {
7033 * The LBF_DST_PINNED logic could have changed
7034 * env->dst_cpu, so we can't know our idle
7035 * state even if we migrated tasks. Update it.
7037 idle
= idle_cpu(cpu
) ? CPU_IDLE
: CPU_NOT_IDLE
;
7039 sd
->last_balance
= jiffies
;
7042 spin_unlock(&balancing
);
7044 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
7045 next_balance
= sd
->last_balance
+ interval
;
7046 update_next_balance
= 1;
7051 * Ensure the rq-wide value also decays but keep it at a
7052 * reasonable floor to avoid funnies with rq->avg_idle.
7054 rq
->max_idle_balance_cost
=
7055 max((u64
)sysctl_sched_migration_cost
, max_cost
);
7060 * next_balance will be updated only when there is a need.
7061 * When the cpu is attached to null domain for ex, it will not be
7064 if (likely(update_next_balance
))
7065 rq
->next_balance
= next_balance
;
7068 #ifdef CONFIG_NO_HZ_COMMON
7070 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7071 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7073 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
7075 int this_cpu
= this_rq
->cpu
;
7079 if (idle
!= CPU_IDLE
||
7080 !test_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
)))
7083 for_each_cpu(balance_cpu
, nohz
.idle_cpus_mask
) {
7084 if (balance_cpu
== this_cpu
|| !idle_cpu(balance_cpu
))
7088 * If this cpu gets work to do, stop the load balancing
7089 * work being done for other cpus. Next load
7090 * balancing owner will pick it up.
7095 rq
= cpu_rq(balance_cpu
);
7097 raw_spin_lock_irq(&rq
->lock
);
7098 update_rq_clock(rq
);
7099 update_idle_cpu_load(rq
);
7100 raw_spin_unlock_irq(&rq
->lock
);
7102 rebalance_domains(rq
, CPU_IDLE
);
7104 if (time_after(this_rq
->next_balance
, rq
->next_balance
))
7105 this_rq
->next_balance
= rq
->next_balance
;
7107 nohz
.next_balance
= this_rq
->next_balance
;
7109 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
));
7113 * Current heuristic for kicking the idle load balancer in the presence
7114 * of an idle cpu is the system.
7115 * - This rq has more than one task.
7116 * - At any scheduler domain level, this cpu's scheduler group has multiple
7117 * busy cpu's exceeding the group's power.
7118 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7119 * domain span are idle.
7121 static inline int nohz_kick_needed(struct rq
*rq
)
7123 unsigned long now
= jiffies
;
7124 struct sched_domain
*sd
;
7125 struct sched_group_power
*sgp
;
7126 int nr_busy
, cpu
= rq
->cpu
;
7128 if (unlikely(rq
->idle_balance
))
7132 * We may be recently in ticked or tickless idle mode. At the first
7133 * busy tick after returning from idle, we will update the busy stats.
7135 set_cpu_sd_state_busy();
7136 nohz_balance_exit_idle(cpu
);
7139 * None are in tickless mode and hence no need for NOHZ idle load
7142 if (likely(!atomic_read(&nohz
.nr_cpus
)))
7145 if (time_before(now
, nohz
.next_balance
))
7148 if (rq
->nr_running
>= 2)
7152 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7155 sgp
= sd
->groups
->sgp
;
7156 nr_busy
= atomic_read(&sgp
->nr_busy_cpus
);
7159 goto need_kick_unlock
;
7162 sd
= rcu_dereference(per_cpu(sd_asym
, cpu
));
7164 if (sd
&& (cpumask_first_and(nohz
.idle_cpus_mask
,
7165 sched_domain_span(sd
)) < cpu
))
7166 goto need_kick_unlock
;
7177 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
) { }
7181 * run_rebalance_domains is triggered when needed from the scheduler tick.
7182 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7184 static void run_rebalance_domains(struct softirq_action
*h
)
7186 struct rq
*this_rq
= this_rq();
7187 enum cpu_idle_type idle
= this_rq
->idle_balance
?
7188 CPU_IDLE
: CPU_NOT_IDLE
;
7190 rebalance_domains(this_rq
, idle
);
7193 * If this cpu has a pending nohz_balance_kick, then do the
7194 * balancing on behalf of the other idle cpus whose ticks are
7197 nohz_idle_balance(this_rq
, idle
);
7201 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7203 void trigger_load_balance(struct rq
*rq
)
7205 /* Don't need to rebalance while attached to NULL domain */
7206 if (unlikely(on_null_domain(rq
)))
7209 if (time_after_eq(jiffies
, rq
->next_balance
))
7210 raise_softirq(SCHED_SOFTIRQ
);
7211 #ifdef CONFIG_NO_HZ_COMMON
7212 if (nohz_kick_needed(rq
))
7213 nohz_balancer_kick();
7217 static void rq_online_fair(struct rq
*rq
)
7222 static void rq_offline_fair(struct rq
*rq
)
7226 /* Ensure any throttled groups are reachable by pick_next_task */
7227 unthrottle_offline_cfs_rqs(rq
);
7230 #endif /* CONFIG_SMP */
7233 * scheduler tick hitting a task of our scheduling class:
7235 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
7237 struct cfs_rq
*cfs_rq
;
7238 struct sched_entity
*se
= &curr
->se
;
7240 for_each_sched_entity(se
) {
7241 cfs_rq
= cfs_rq_of(se
);
7242 entity_tick(cfs_rq
, se
, queued
);
7245 if (numabalancing_enabled
)
7246 task_tick_numa(rq
, curr
);
7248 update_rq_runnable_avg(rq
, 1);
7252 * called on fork with the child task as argument from the parent's context
7253 * - child not yet on the tasklist
7254 * - preemption disabled
7256 static void task_fork_fair(struct task_struct
*p
)
7258 struct cfs_rq
*cfs_rq
;
7259 struct sched_entity
*se
= &p
->se
, *curr
;
7260 int this_cpu
= smp_processor_id();
7261 struct rq
*rq
= this_rq();
7262 unsigned long flags
;
7264 raw_spin_lock_irqsave(&rq
->lock
, flags
);
7266 update_rq_clock(rq
);
7268 cfs_rq
= task_cfs_rq(current
);
7269 curr
= cfs_rq
->curr
;
7272 * Not only the cpu but also the task_group of the parent might have
7273 * been changed after parent->se.parent,cfs_rq were copied to
7274 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
7275 * of child point to valid ones.
7278 __set_task_cpu(p
, this_cpu
);
7281 update_curr(cfs_rq
);
7284 se
->vruntime
= curr
->vruntime
;
7285 place_entity(cfs_rq
, se
, 1);
7287 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
7289 * Upon rescheduling, sched_class::put_prev_task() will place
7290 * 'current' within the tree based on its new key value.
7292 swap(curr
->vruntime
, se
->vruntime
);
7293 resched_task(rq
->curr
);
7296 se
->vruntime
-= cfs_rq
->min_vruntime
;
7298 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
7302 * Priority of the task has changed. Check to see if we preempt
7306 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
7312 * Reschedule if we are currently running on this runqueue and
7313 * our priority decreased, or if we are not currently running on
7314 * this runqueue and our priority is higher than the current's
7316 if (rq
->curr
== p
) {
7317 if (p
->prio
> oldprio
)
7318 resched_task(rq
->curr
);
7320 check_preempt_curr(rq
, p
, 0);
7323 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
7325 struct sched_entity
*se
= &p
->se
;
7326 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
7329 * Ensure the task's vruntime is normalized, so that when it's
7330 * switched back to the fair class the enqueue_entity(.flags=0) will
7331 * do the right thing.
7333 * If it's on_rq, then the dequeue_entity(.flags=0) will already
7334 * have normalized the vruntime, if it's !on_rq, then only when
7335 * the task is sleeping will it still have non-normalized vruntime.
7337 if (!p
->on_rq
&& p
->state
!= TASK_RUNNING
) {
7339 * Fix up our vruntime so that the current sleep doesn't
7340 * cause 'unlimited' sleep bonus.
7342 place_entity(cfs_rq
, se
, 0);
7343 se
->vruntime
-= cfs_rq
->min_vruntime
;
7348 * Remove our load from contribution when we leave sched_fair
7349 * and ensure we don't carry in an old decay_count if we
7352 if (se
->avg
.decay_count
) {
7353 __synchronize_entity_decay(se
);
7354 subtract_blocked_load_contrib(cfs_rq
, se
->avg
.load_avg_contrib
);
7360 * We switched to the sched_fair class.
7362 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
7364 struct sched_entity
*se
= &p
->se
;
7365 #ifdef CONFIG_FAIR_GROUP_SCHED
7367 * Since the real-depth could have been changed (only FAIR
7368 * class maintain depth value), reset depth properly.
7370 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
7376 * We were most likely switched from sched_rt, so
7377 * kick off the schedule if running, otherwise just see
7378 * if we can still preempt the current task.
7381 resched_task(rq
->curr
);
7383 check_preempt_curr(rq
, p
, 0);
7386 /* Account for a task changing its policy or group.
7388 * This routine is mostly called to set cfs_rq->curr field when a task
7389 * migrates between groups/classes.
7391 static void set_curr_task_fair(struct rq
*rq
)
7393 struct sched_entity
*se
= &rq
->curr
->se
;
7395 for_each_sched_entity(se
) {
7396 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
7398 set_next_entity(cfs_rq
, se
);
7399 /* ensure bandwidth has been allocated on our new cfs_rq */
7400 account_cfs_rq_runtime(cfs_rq
, 0);
7404 void init_cfs_rq(struct cfs_rq
*cfs_rq
)
7406 cfs_rq
->tasks_timeline
= RB_ROOT
;
7407 cfs_rq
->min_vruntime
= (u64
)(-(1LL << 20));
7408 #ifndef CONFIG_64BIT
7409 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
7412 atomic64_set(&cfs_rq
->decay_counter
, 1);
7413 atomic_long_set(&cfs_rq
->removed_load
, 0);
7417 #ifdef CONFIG_FAIR_GROUP_SCHED
7418 static void task_move_group_fair(struct task_struct
*p
, int on_rq
)
7420 struct sched_entity
*se
= &p
->se
;
7421 struct cfs_rq
*cfs_rq
;
7424 * If the task was not on the rq at the time of this cgroup movement
7425 * it must have been asleep, sleeping tasks keep their ->vruntime
7426 * absolute on their old rq until wakeup (needed for the fair sleeper
7427 * bonus in place_entity()).
7429 * If it was on the rq, we've just 'preempted' it, which does convert
7430 * ->vruntime to a relative base.
7432 * Make sure both cases convert their relative position when migrating
7433 * to another cgroup's rq. This does somewhat interfere with the
7434 * fair sleeper stuff for the first placement, but who cares.
7437 * When !on_rq, vruntime of the task has usually NOT been normalized.
7438 * But there are some cases where it has already been normalized:
7440 * - Moving a forked child which is waiting for being woken up by
7441 * wake_up_new_task().
7442 * - Moving a task which has been woken up by try_to_wake_up() and
7443 * waiting for actually being woken up by sched_ttwu_pending().
7445 * To prevent boost or penalty in the new cfs_rq caused by delta
7446 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
7448 if (!on_rq
&& (!se
->sum_exec_runtime
|| p
->state
== TASK_WAKING
))
7452 se
->vruntime
-= cfs_rq_of(se
)->min_vruntime
;
7453 set_task_rq(p
, task_cpu(p
));
7454 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
7456 cfs_rq
= cfs_rq_of(se
);
7457 se
->vruntime
+= cfs_rq
->min_vruntime
;
7460 * migrate_task_rq_fair() will have removed our previous
7461 * contribution, but we must synchronize for ongoing future
7464 se
->avg
.decay_count
= atomic64_read(&cfs_rq
->decay_counter
);
7465 cfs_rq
->blocked_load_avg
+= se
->avg
.load_avg_contrib
;
7470 void free_fair_sched_group(struct task_group
*tg
)
7474 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg
));
7476 for_each_possible_cpu(i
) {
7478 kfree(tg
->cfs_rq
[i
]);
7487 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
7489 struct cfs_rq
*cfs_rq
;
7490 struct sched_entity
*se
;
7493 tg
->cfs_rq
= kzalloc(sizeof(cfs_rq
) * nr_cpu_ids
, GFP_KERNEL
);
7496 tg
->se
= kzalloc(sizeof(se
) * nr_cpu_ids
, GFP_KERNEL
);
7500 tg
->shares
= NICE_0_LOAD
;
7502 init_cfs_bandwidth(tg_cfs_bandwidth(tg
));
7504 for_each_possible_cpu(i
) {
7505 cfs_rq
= kzalloc_node(sizeof(struct cfs_rq
),
7506 GFP_KERNEL
, cpu_to_node(i
));
7510 se
= kzalloc_node(sizeof(struct sched_entity
),
7511 GFP_KERNEL
, cpu_to_node(i
));
7515 init_cfs_rq(cfs_rq
);
7516 init_tg_cfs_entry(tg
, cfs_rq
, se
, i
, parent
->se
[i
]);
7527 void unregister_fair_sched_group(struct task_group
*tg
, int cpu
)
7529 struct rq
*rq
= cpu_rq(cpu
);
7530 unsigned long flags
;
7533 * Only empty task groups can be destroyed; so we can speculatively
7534 * check on_list without danger of it being re-added.
7536 if (!tg
->cfs_rq
[cpu
]->on_list
)
7539 raw_spin_lock_irqsave(&rq
->lock
, flags
);
7540 list_del_leaf_cfs_rq(tg
->cfs_rq
[cpu
]);
7541 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
7544 void init_tg_cfs_entry(struct task_group
*tg
, struct cfs_rq
*cfs_rq
,
7545 struct sched_entity
*se
, int cpu
,
7546 struct sched_entity
*parent
)
7548 struct rq
*rq
= cpu_rq(cpu
);
7552 init_cfs_rq_runtime(cfs_rq
);
7554 tg
->cfs_rq
[cpu
] = cfs_rq
;
7557 /* se could be NULL for root_task_group */
7562 se
->cfs_rq
= &rq
->cfs
;
7565 se
->cfs_rq
= parent
->my_q
;
7566 se
->depth
= parent
->depth
+ 1;
7570 /* guarantee group entities always have weight */
7571 update_load_set(&se
->load
, NICE_0_LOAD
);
7572 se
->parent
= parent
;
7575 static DEFINE_MUTEX(shares_mutex
);
7577 int sched_group_set_shares(struct task_group
*tg
, unsigned long shares
)
7580 unsigned long flags
;
7583 * We can't change the weight of the root cgroup.
7588 shares
= clamp(shares
, scale_load(MIN_SHARES
), scale_load(MAX_SHARES
));
7590 mutex_lock(&shares_mutex
);
7591 if (tg
->shares
== shares
)
7594 tg
->shares
= shares
;
7595 for_each_possible_cpu(i
) {
7596 struct rq
*rq
= cpu_rq(i
);
7597 struct sched_entity
*se
;
7600 /* Propagate contribution to hierarchy */
7601 raw_spin_lock_irqsave(&rq
->lock
, flags
);
7603 /* Possible calls to update_curr() need rq clock */
7604 update_rq_clock(rq
);
7605 for_each_sched_entity(se
)
7606 update_cfs_shares(group_cfs_rq(se
));
7607 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
7611 mutex_unlock(&shares_mutex
);
7614 #else /* CONFIG_FAIR_GROUP_SCHED */
7616 void free_fair_sched_group(struct task_group
*tg
) { }
7618 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
7623 void unregister_fair_sched_group(struct task_group
*tg
, int cpu
) { }
7625 #endif /* CONFIG_FAIR_GROUP_SCHED */
7628 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
7630 struct sched_entity
*se
= &task
->se
;
7631 unsigned int rr_interval
= 0;
7634 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
7637 if (rq
->cfs
.load
.weight
)
7638 rr_interval
= NS_TO_JIFFIES(sched_slice(cfs_rq_of(se
), se
));
7644 * All the scheduling class methods:
7646 const struct sched_class fair_sched_class
= {
7647 .next
= &idle_sched_class
,
7648 .enqueue_task
= enqueue_task_fair
,
7649 .dequeue_task
= dequeue_task_fair
,
7650 .yield_task
= yield_task_fair
,
7651 .yield_to_task
= yield_to_task_fair
,
7653 .check_preempt_curr
= check_preempt_wakeup
,
7655 .pick_next_task
= pick_next_task_fair
,
7656 .put_prev_task
= put_prev_task_fair
,
7659 .select_task_rq
= select_task_rq_fair
,
7660 .migrate_task_rq
= migrate_task_rq_fair
,
7662 .rq_online
= rq_online_fair
,
7663 .rq_offline
= rq_offline_fair
,
7665 .task_waking
= task_waking_fair
,
7668 .set_curr_task
= set_curr_task_fair
,
7669 .task_tick
= task_tick_fair
,
7670 .task_fork
= task_fork_fair
,
7672 .prio_changed
= prio_changed_fair
,
7673 .switched_from
= switched_from_fair
,
7674 .switched_to
= switched_to_fair
,
7676 .get_rr_interval
= get_rr_interval_fair
,
7678 #ifdef CONFIG_FAIR_GROUP_SCHED
7679 .task_move_group
= task_move_group_fair
,
7683 #ifdef CONFIG_SCHED_DEBUG
7684 void print_cfs_stats(struct seq_file
*m
, int cpu
)
7686 struct cfs_rq
*cfs_rq
;
7689 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
7690 print_cfs_rq(m
, cpu
, cfs_rq
);
7695 __init
void init_sched_fair_class(void)
7698 open_softirq(SCHED_SOFTIRQ
, run_rebalance_domains
);
7700 #ifdef CONFIG_NO_HZ_COMMON
7701 nohz
.next_balance
= jiffies
;
7702 zalloc_cpumask_var(&nohz
.idle_cpus_mask
, GFP_NOWAIT
);
7703 cpu_notifier(sched_ilb_notifier
, 0);