Messages in this thread | | | Date | Wed, 15 Feb 2017 14:45:03 +0000 | From | Juri Lelli <> | Subject | Re: [PATCH] sched/deadline: Remove unnecessary condition in push_dl_task() |
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On 15/02/17 09:25, Steven Rostedt wrote: > 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) {
Sorry, bad wording on my side. I meant the are currently checking the same conditions both for DL and for RT, and we should probably optimize RT as well if we are going to take this patch.
> > But that said, I believe this patch is correct, and we should change > rt.c as well. >
That's what I meant. :)
> > 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.
Right.
> > Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> >
You can also add mine
Reviewed-by: Juri Lelli <juri.lelli@arm.com>
> Mind fixing rt.c if it hasn't been fixed already. > > -- Steve
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