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SubjectRe: [PATCH V2 3/3] sched/deadline: Tracepoints for deadline scheduler
On Tue, 29 Mar 2016 13:10:34 -0300
Daniel Bristot de Oliveira <bristot@redhat.com> wrote:

> On 03/29/2016 12:16 PM, Peter Zijlstra wrote:
> >> + trace_sched_deadline_yield(&rq->curr->dl);
>
> ouch, it should be trace_sched_deadline_yield(dl_se). It works
> as is, but it is really very sad, my bad, sorry.
>
> >> > dl_se->dl_throttled = 1;
> >> > + trace_sched_deadline_throttle(dl_se);
> > This is just really very sad.
>
> Am I missing any other really very sad thing here?

Well, we shouldn't have two tracepoints back to back.

>
> >> > __dequeue_task_dl(rq, curr, 0);
> >> > if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr)))
> >> > enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
> >> > @@ -910,6 +917,7 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se,
> >> > static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
> >> > {
> >> > __dequeue_dl_entity(dl_se);
> >> > + trace_sched_deadline_block(dl_se);
> >> > }
> > And that's just not going to happen.
>
> It will, if a task goes to sleep during the activation,
> e.g., when blocking on a system call. For example:
>
> <idle>-0 [007] d..3 78377.688969: sched_switch: prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=b next_pid=18973 next_prio=-1
> b-18973 [007] d..3 78377.688979: sched_deadline_block: now=78377.688976271 deadline=78377.718945137 remaining_runtime=9968866
> b-18973 [007] d..3 78377.688981: sched_switch: prev_comm=b prev_pid=18973 prev_prio=-1 prev_state=S ==> next_comm=swapper/7 next_pid=0 next_prio=120

Why did it go to sleep? The above is still not very useful. What do you
mean "blocking on a system call"?

-- Steve

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