linux-kernel - Re: massive_intr on CFS, BFS, and EDF

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Message-Id: <1253948171.4924.14.camel@Palantir>
Date:	Sat, 26 Sep 2009 08:56:11 +0200
From:	Raistlin <raistlin@...ux.it>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Chris Friesen <cfriesen@...tel.com>,
	Michael Trimarchi <trimarchi@...dalf.sssup.it>,
	sat <takeuchi_satoru@...fujitsu.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Con Kolivas <kernel@...ivas.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: massive_intr on CFS, BFS, and EDF

On Sat, 2009-09-26 at 00:37 +0200, Peter Zijlstra wrote:
> On Fri, 2009-09-25 at 15:31 -0600, Chris Friesen wrote: 
> > Do you allow oversubscription with EDF?  It would seem so based on these
> > results.  Would it maybe make sense to disallow oversubscription, or
> > make it an option?
> 
> afaiu he doesn't, 
yeaah, as explained in the previous mail, this is in place only if group
scheduling is on since now, but I'll add these bits to non-group
solution, aalready planned that. :-)

> he simply splits the task's wcet between parent and
> child and (intends?) to feed back on child exit.
> 
yes again, that's what the submitted patch does, which is an arbitrary
choice among all the non-optimal solutions I'm able to think of, as
explained in the first e-mail! :-(

Now, I'm going to give your suggestion of assigning children 0 bandwidth
a shot, and ask the parent (they can't they have no bandwidth!) to give
them some runtime/deadline to make them run.
This also has some issues, I think, but looks more natural... At least
does not affect parent's bandwidth, possibly reducing it to (almost)
0!! :-(

Regards,
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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