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Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency mask model

From	Juri Lelli <juri.lelli@arm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency mask model
Date	2015-08-10 16:10 +0200
Message-ID	<pVVW1-7v-3@gated-at.bofh.it> (permalink)
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Hi,

On 04/08/15 08:41, Peter Zijlstra wrote:
> On Mon, Aug 03, 2015 at 07:30:32PM +0200, Frederic Weisbecker wrote:
>>> But you've forgotten about SCHED_DEADLINE, we count those in:
>>> rq->dl.dl_nr_running.
>>
>> Indeed. Hmm, there is no preemption between SCHED_DEALINE tasks, right?
>> So I can treat it like SCHED_FIFO.
> 
> Sadly no. Even though EDF has static job priority (once a job is
> activated its priority doesn't change anymore) DEADLINE also has a CBS
> component and that needs the tick regardless, even with a single task.
> 
> So any deadline task running means we cannot stop the tick.

Well, couldn't we stop it when we use hrtick? As start_hrtick_dl() sets
the hrtick to fire at tasks runtime depletion instant.

Thanks,

- Juri

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Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency  mask model Juri Lelli <juri.lelli@arm.com> - 2015-08-10 16:10 +0200
  Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency  mask model Frederic Weisbecker <fweisbec@gmail.com> - 2015-08-10 16:20 +0200
    Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency  mask model Peter Zijlstra <peterz@infradead.org> - 2015-08-10 16:30 +0200
      Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency  mask model Peter Zijlstra <peterz@infradead.org> - 2015-08-10 17:20 +0200
        Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency  mask model Frederic Weisbecker <fweisbec@gmail.com> - 2015-08-10 17:30 +0200
          Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency  mask model Juri Lelli <juri.lelli@arm.com> - 2015-08-10 17:50 +0200
          Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency  mask model Peter Zijlstra <peterz@infradead.org> - 2015-08-10 18:50 +0200
    Re: [PATCH 07/10] sched: Migrate sched to use new tick dependency  mask model Christoph Lameter <cl@linux.com> - 2015-08-10 17:40 +0200

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