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sched: optimize task_tick_rt() a bit

Browse source 
Mitchell Erblich suggested a quality-of-implementation change to
not requeue SCHED_RR tasks if there's only a single task on the
runqueue, by checking for rq->nr_running == 1.

provide a more efficient implementation of that, to check that
particular RT priority-queue only.

[ From: mingo@elte.hu ]

Also first requeue the task then set need_resched - results in slightly
better machine-instruction ordering. Also clean up the code a bit.

Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Dmitry Adamushko 2007-08-24 20:39:10 +02:00 committed by Ingo Molnar
parent deac4ee65a
commit 98fbc79853
1 changed files with 8 additions and 3 deletions
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11
kernel/sched_rt.c
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@ -207,10 +207,15 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p)
return;
p->time_slice = static_prio_timeslice(p->static_prio);
set_tsk_need_resched(p);
/* put it at the end of the queue: */
requeue_task_rt(rq, p);
/*
* Requeue to the end of queue if we are not the only element
* on the queue:
*/
if (p->run_list.prev != p->run_list.next) {
requeue_task_rt(rq, p);
set_tsk_need_resched(p);
}
}
static struct sched_class rt_sched_class __read_mostly = {