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sched: fix wakeup granularity for buddies

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The wakeup buddy logic didn't use the same wakeup granularity logic as the
wakeup preemption did, this might cause the ->next buddy to be selected past
the point where we would have preempted had the task been a single running
instance.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-04-19 19:44:57 +02:00 committed by Ingo Molnar
parent 15934a3732
commit 0bbd3336ee
1 changed files with 49 additions and 20 deletions
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69
kernel/sched_fair.c
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@ -73,13 +73,13 @@ unsigned int sysctl_sched_batch_wakeup_granularity = 10000000UL;
/*
* SCHED_OTHER wake-up granularity.
* (default: 5 msec * (1 + ilog(ncpus)), units: nanoseconds)
* (default: 10 msec * (1 + ilog(ncpus)), units: nanoseconds)
*
* This option delays the preemption effects of decoupled workloads
* and reduces their over-scheduling. Synchronous workloads will still
* have immediate wakeup/sleep latencies.
*/
unsigned int sysctl_sched_wakeup_granularity = 5000000UL;
unsigned int sysctl_sched_wakeup_granularity = 10000000UL;
const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
@ -629,20 +629,16 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
se->prev_sum_exec_runtime = se->sum_exec_runtime;
}
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
static struct sched_entity *
pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
s64 diff, gran;
if (!cfs_rq->next)
return se;
diff = cfs_rq->next->vruntime - se->vruntime;
if (diff < 0)
return se;
gran = calc_delta_fair(sysctl_sched_wakeup_granularity, &cfs_rq->load);
if (diff > gran)
if (wakeup_preempt_entity(cfs_rq->next, se) != 0)
return se;
return cfs_rq->next;
@ -1101,6 +1097,48 @@ static int select_task_rq_fair(struct task_struct *p, int sync)
}
#endif /* CONFIG_SMP */
static unsigned long wakeup_gran(struct sched_entity *se)
{
unsigned long gran = sysctl_sched_wakeup_granularity;
/*
* More easily preempt - nice tasks, while not making
* it harder for + nice tasks.
*/
if (unlikely(se->load.weight > NICE_0_LOAD))
gran = calc_delta_fair(gran, &se->load);
return gran;
}
/*
* Should 'se' preempt 'curr'.
*
* |s1
* |s2
* |s3
* g
* |<--->|c
*
* w(c, s1) = -1
* w(c, s2) = 0
* w(c, s3) = 1
*
*/
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
{
s64 gran, vdiff = curr->vruntime - se->vruntime;
if (vdiff < 0)
return -1;
gran = wakeup_gran(curr);
if (vdiff > gran)
return 1;
return 0;
}
/*
* Preempt the current task with a newly woken task if needed:
@ -1110,7 +1148,6 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
struct task_struct *curr = rq->curr;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
struct sched_entity *se = &curr->se, *pse = &p->se;
unsigned long gran;
if (unlikely(rt_prio(p->prio))) {
update_rq_clock(rq);
@ -1140,15 +1177,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
pse = parent_entity(pse);
}
gran = sysctl_sched_wakeup_granularity;
/*
* More easily preempt - nice tasks, while not making
* it harder for + nice tasks.
*/
if (unlikely(se->load.weight > NICE_0_LOAD))
gran = calc_delta_fair(gran, &se->load);
if (pse->vruntime + gran < se->vruntime)
if (wakeup_preempt_entity(se, pse) == 1)
resched_task(curr);
}