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sched: Add yield_to(task, preempt) functionality

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Currently only implemented for fair class tasks.

Add a yield_to_task method() to the fair scheduling class. allowing the
caller of yield_to() to accelerate another thread in it's thread group,
task group.

Implemented via a scheduler hint, using cfs_rq->next to encourage the
target being selected.  We can rely on pick_next_entity to keep things
fair, so noone can accelerate a thread that has already used its fair
share of CPU time.

This also means callers should only call yield_to when they really
mean it.  Calling it too often can result in the scheduler just
ignoring the hint.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110201095051.4ddb7738@annuminas.surriel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mike Galbraith
2011-02-01 09:50:51 -05:00
committed by Ingo Molnar
parent ac53db596c
commit d95f412200
3 changed files with 107 additions and 0 deletions
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20
kernel/sched_fair.c
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@@ -1975,6 +1975,25 @@ static void yield_task_fair(struct rq *rq)
set_skip_buddy(se);
}
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
struct sched_entity *se = &p->se;
if (!se->on_rq)
return false;
/* Tell the scheduler that we'd really like pse to run next. */
set_next_buddy(se);
/* Make p's CPU reschedule; pick_next_entity takes care of fairness. */
if (preempt)
resched_task(rq->curr);
yield_task_fair(rq);
return true;
}
#ifdef CONFIG_SMP
/**************************************************
* Fair scheduling class load-balancing methods:
@@ -4243,6 +4262,7 @@ static const struct sched_class fair_sched_class = {
.enqueue_task = enqueue_task_fair,
.dequeue_task = dequeue_task_fair,
.yield_task = yield_task_fair,
.yield_to_task = yield_to_task_fair,
.check_preempt_curr = check_preempt_wakeup,