Messages in this thread | | | Date | Thu, 9 Aug 2007 10:39:13 +0200 | From | "Dmitry Adamushko" <> | Subject | Re: Question: RT schedular : task_tick_rt(struct rq *rq, struct task_struct *p) : decreases overhead when rq->nr_running == 1 |
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On 09/08/07, Ingo Molnar <mingo@elte.hu> wrote: > > FYI, that's the patch i applied:
Thanks. Added my SOB below.
> > ---------------------------> > Subject: sched: optimize task_tick_rt() a bit > From: Dmitry Adamushko <dmitry.adamushko@gmail.com> > > Mitchell Erblich suggested a 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: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
> --- > kernel/sched_rt.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > Index: linux/kernel/sched_rt.c > =================================================================== > --- linux.orig/kernel/sched_rt.c > +++ linux/kernel/sched_rt.c > @@ -207,10 +207,15 @@ static void task_tick_rt(struct rq *rq, > 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 = { >
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