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Message-ID: <1262097422.7135.152.camel@laptop>
Date: Tue, 29 Dec 2009 15:37:02 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Raistlin <raistlin@...ux.it>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
michael trimarchi <michael@...dence.eu.com>,
Fabio Checconi <fabio@...dalf.sssup.it>,
Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
Dhaval Giani <dhaval.giani@...il.com>,
Johan Eker <johan.eker@...csson.com>,
"p.faure" <p.faure@...tech.ch>,
Chris Friesen <cfriesen@...tel.com>,
Steven Rostedt <rostedt@...dmis.org>,
Henrik Austad <henrik@...tad.us>,
Frederic Weisbecker <fweisbec@...il.com>,
Darren Hart <darren@...art.com>,
Sven-Thorsten Dietrich <sven@...bigcorporation.com>,
Bjoern Brandenburg <bbb@...unc.edu>,
Tommaso Cucinotta <tommaso.cucinotta@...up.it>,
"giuseppe.lipari" <giuseppe.lipari@...up.it>,
Juri Lelli <juri.lelli@...il.com>
Subject: Re: [RFC 0/12][PATCH] SCHED_DEADLINE: core of the scheduling class
On Tue, 2009-12-29 at 15:30 +0100, Peter Zijlstra wrote:
> On Fri, 2009-10-16 at 17:40 +0200, Raistlin wrote:
> > +struct task_struct *pick_next_task_deadline(struct rq *rq)
> > +{
> > + struct sched_dl_entity *dl_se;
> > + struct task_struct *p;
> > + struct dl_rq *dl_rq;
> > +
> > + dl_rq = &rq->dl;
> > +
> > + if (likely(!dl_rq->dl_nr_running))
> > + return NULL;
> > +
> > + dl_se = pick_next_deadline_entity(rq, dl_rq);
> > + BUG_ON(!dl_se);
> > +
> > + p = deadline_task_of(dl_se);
> > + p->se.exec_start = rq->clock;
> > +#ifdef CONFIG_SCHED_HRTICK
> > + if (hrtick_enabled(rq))
> > + start_hrtick_deadline(rq, p);
> > +#endif
> > + return p;
> > +}
>
> I'm not sure about actually using hrtick like this, I'd expect
> SCHED_DEADLINE to always use hrtimers when available. The only reason
> to use some of the hrtick infrastructure is to re-use the hrtick_start()
> logic which uses IPIs to ensure we program the timer on the right cpu
> (so we can schedule from it).
Hmm I suppose we could ignore all that CONFIG_SCHED_HRTICK stuff and
simply bounce the schedule event using the resched ipi when we find
we're on the wrong cpu. Not ideal though.. frigging mess all this :-)
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