Messages in this thread Patch in this message | | | Date | Wed, 15 Feb 2017 09:25:07 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task() |
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On Wed, 15 Feb 2017 10:47:49 +0000 Juri Lelli <juri.lelli@arm.com> wrote:
> [+Steve, Luca] > > Hi, > > On 15/02/17 14:11, Byungchul Park wrote: > > Once pick_next_pushable_dl_task(rq) return a task, it guarantees that > > the task's cpu is rq->cpu, so task_cpu(next_task) is always rq->cpu if > > task == next_task. Remove a redundant condition and make code simpler. > > > > Signed-off-by: Byungchul Park <byungchul.park@lge.com> > > --- > > kernel/sched/deadline.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > > index 27737f3..ad8d577 100644 > > --- a/kernel/sched/deadline.c > > +++ b/kernel/sched/deadline.c > > @@ -1483,7 +1483,7 @@ static int push_dl_task(struct rq *rq) > > * then possible that next_task has migrated. > > */ > > task = pick_next_pushable_dl_task(rq); > > - if (task_cpu(next_task) == rq->cpu && task == next_task) { > > + if (task == next_task) { > > Seems a sensible optimization to me. Actually, we are doing the same for > rt.c; Steve, Peter, do you think we should optimize that as well? >
Are we doing the same for push_rt_task()? I don't see it, and I don't see it in tip/sched/core either. What I have is:
if (task_cpu(next_task) == rq->cpu && task == next_task) {
But that said, I believe this patch is correct, and we should change rt.c as well.
task = pick_next_pushable_dl_task(rq); Which has:
BUG_ON(rq->cpu != task_cpu(task))
when it returns a task other than NULL. Which means that task_cpu(task) must be rq->cpu. Then if task == next_task, then task_cpu(next_task) must be rq->cpu as well.
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Mind fixing rt.c if it hasn't been fixed already.
-- Steve
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