linux-kernel - Re: [RFC][PATCH 07/22] sched: SCHED

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Date:	Fri, 12 Nov 2010 22:11:05 +0100
From:	Raistlin <raistlin@...ux.it>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Chris Friesen <cfriesen@...tel.com>, oleg@...hat.com,
	Frederic Weisbecker <fweisbec@...il.com>,
	Darren Hart <darren@...art.com>,
	Johan Eker <johan.eker@...csson.com>,
	"p.faure" <p.faure@...tech.ch>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Claudio Scordino <claudio@...dence.eu.com>,
	michael trimarchi <trimarchi@...is.sssup.it>,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	Tommaso Cucinotta <cucinotta@...up.it>,
	Juri Lelli <juri.lelli@...il.com>,
	Nicola Manica <nicola.manica@...i.unitn.it>,
	Luca Abeni <luca.abeni@...tn.it>,
	Dhaval Giani <dhaval@...is.sssup.it>,
	Harald Gustafsson <hgu1972@...il.com>,
	paulmck <paulmck@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 07/22] sched: SCHED_DEADLINE push and pull logic

On Fri, 2010-11-12 at 17:17 +0100, Peter Zijlstra wrote:
> On Fri, 2010-10-29 at 08:32 +0200, Raistlin wrote:
> > Add dynamic migrations to SCHED_DEADLINE, so that tasks can
> > be moved among CPUs when necessary. It is also possible to bind a
> > task to a (set of) CPU(s), thus restricting its capability of
> > migrating, or forbidding migrations at all.
> > 
> > The very same approach used in sched_rt is utilised:
> >  - -deadline tasks are kept into CPU-specific runqueues,
> >  - -deadline tasks are migrated among runqueues to achieve the
> >    following:
> >     * on an M-CPU system the M earliest deadline ready tasks
> >       are always running;
> >     * affinity/cpusets settings of all the -deadline tasks is
> >       always respected. 
> 
> I haven't fully digested the patch, I keep getting side-tracked and its
> a large patch.. 
>
Yeah, I know, take your time. :-)

> however, I thought we would only allow 2 affinities,
> strict per-cpu and full root-domain?
> 
Yes, we do! Writing a better changelog for this already noted for next
version.

> Keep 2 per-cpu utilization counts, a hard-rt and a soft-rt, and ensure
> the sum stays <= 1. Use the hard-rt one for the planned SF_HARD_RT flag,
> use the soft-rt one for !SF_HARD_RT with nr_cpus_allowed == 1, and use
> \Sum (1-h-s) over the root domain for nr_cpus_allowed != 1.
> 
As agreed during LPC, that's exactly what I'll do. Let's hope to don't
screw up while trying to do the math! :-P

Thanks,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)

http://blog.linux.it/raistlin / raistlin@...ga.net /
dario.faggioli@...ber.org

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