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sched: add vslice

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add vslice: the load-dependent "virtual slice" a task should
run ideally, so that the observed latency stays within the
sched_latency window.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Peter Zijlstra 2007-10-15 17:00:10 +02:00 committed by Ingo Molnar
parent 1aa4731eff
commit 67e9fb2a39
3 changed files with 32 additions and 15 deletions
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1
include/linux/sched.h
View file

@ -908,6 +908,7 @@ struct sched_entity {
u64 sum_exec_runtime;
u64 vruntime;
u64 prev_sum_exec_runtime;
u64 last_min_vruntime;
#ifdef CONFIG_SCHEDSTATS
u64 wait_start;

2
kernel/sched.c
View file

@ -1615,6 +1615,7 @@ static void __sched_fork(struct task_struct *p)
p->se.exec_start = 0;
p->se.sum_exec_runtime = 0;
p->se.prev_sum_exec_runtime = 0;
p->se.last_min_vruntime = 0;
#ifdef CONFIG_SCHEDSTATS
p->se.wait_start = 0;
@ -6495,6 +6496,7 @@ static inline void init_cfs_rq(struct cfs_rq *cfs_rq, struct rq *rq)
#ifdef CONFIG_FAIR_GROUP_SCHED
cfs_rq->rq = rq;
#endif
cfs_rq->min_vruntime = (u64)(-(1LL << 20));
}
void __init sched_init(void)

44
kernel/sched_fair.c
View file

@ -243,6 +243,15 @@ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
return period;
}
static u64 __sched_vslice(unsigned long nr_running)
{
u64 period = __sched_period(nr_running);
do_div(period, nr_running);
return period;
}
/*
* Update the current task's runtime statistics. Skip current tasks that
* are not in our scheduling class.
@ -441,32 +450,33 @@ static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
u64 min_runtime, latency;
u64 vruntime;
min_runtime = cfs_rq->min_vruntime;
vruntime = cfs_rq->min_vruntime;
if (sched_feat(USE_TREE_AVG)) {
struct sched_entity *last = __pick_last_entity(cfs_rq);
if (last) {
min_runtime = __pick_next_entity(cfs_rq)->vruntime;
min_runtime += last->vruntime;
min_runtime >>= 1;
vruntime += last->vruntime;
vruntime >>= 1;
}
} else if (sched_feat(APPROX_AVG))
min_runtime += sysctl_sched_latency/2;
} else if (sched_feat(APPROX_AVG) && cfs_rq->nr_running)
vruntime += __sched_vslice(cfs_rq->nr_running)/2;
if (initial && sched_feat(START_DEBIT))
min_runtime += sched_slice(cfs_rq, se);
vruntime += __sched_vslice(cfs_rq->nr_running + 1);
if (!initial && sched_feat(NEW_FAIR_SLEEPERS)) {
latency = sysctl_sched_latency;
if (min_runtime > latency)
min_runtime -= latency;
s64 latency = cfs_rq->min_vruntime - se->last_min_vruntime;
if (latency < 0 || !cfs_rq->nr_running)
latency = 0;
else
min_runtime = 0;
latency = min_t(s64, latency, sysctl_sched_latency);
vruntime -= latency;
}
se->vruntime = max(se->vruntime, min_runtime);
se->vruntime = vruntime;
}
static void
@ -478,6 +488,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
update_curr(cfs_rq);
if (wakeup) {
/* se->vruntime += cfs_rq->min_vruntime; */
place_entity(cfs_rq, se, 0);
enqueue_sleeper(cfs_rq, se);
}
@ -492,8 +503,8 @@ static void
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
{
update_stats_dequeue(cfs_rq, se);
#ifdef CONFIG_SCHEDSTATS
if (sleep) {
#ifdef CONFIG_SCHEDSTATS
if (entity_is_task(se)) {
struct task_struct *tsk = task_of(se);
@ -502,8 +513,11 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
if (tsk->state & TASK_UNINTERRUPTIBLE)
se->block_start = rq_of(cfs_rq)->clock;
}
}
#endif
/* se->vruntime = entity_key(cfs_rq, se); */
se->last_min_vruntime = cfs_rq->min_vruntime;
}
if (se != cfs_rq->curr)
__dequeue_entity(cfs_rq, se);
account_entity_dequeue(cfs_rq, se);