From 98fbc798533339be802c6dcd48c2293c712e87db Mon Sep 17 00:00:00 2001 From: Dmitry Adamushko Date: Fri, 24 Aug 2007 20:39:10 +0200 Subject: [PATCH] sched: optimize task_tick_rt() a bit 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 Signed-off-by: Ingo Molnar --- kernel/sched_rt.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index dcdcad6..4b87476 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -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 = { -- 2.7.4