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Subject: Re: [RFC][PATCH 05/22] sched: SCHED_DEADLINE policy implementation
From: Peter Zijlstra <peterz@infradead.org>
To: Raistlin <raistlin@linux.it>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
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Date: Thu, 11 Nov 2010 14:13:38 +0100
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On Thu, 2010-11-11 at 02:18 +0100, Raistlin wrote:
> On Wed, 2010-11-10 at 21:21 +0100, Peter Zijlstra wrote:
> > > +       if (dl_time_before(dl_se->deadline, rq->clock) ||
> > > +           dl_entity_overflow(dl_se, rq->clock)) {
> > > +               dl_se->deadline = rq->clock + dl_se->dl_deadline;
> > > +               dl_se->runtime = dl_se->dl_runtime;
> > > +       }
> > > +} 
> > 
> > Can't we loose runtime deficit this way?

>  - if unblocking happens _before_ it becomes eligible again, the 
>    enqueue will be later handled by the dl_timer itself, when it'll
>    fire, and the task will be given a replenishment starting from its
>    negative runtime;
>  - if unblocking happens _later_ than the firing of dl_timer, resetting
>    the scheduling parameters should be just fine, from the bandwidth
>    point of view.
> 
> Does it make sense?

Yes, I think so. Thanks!