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

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Message-Id: <1253949740.4924.34.camel@Palantir>
Date:	Sat, 26 Sep 2009 09:22:20 +0200
From:	Raistlin <raistlin@...ux.it>
To:	Chris Friesen <cfriesen@...tel.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	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 Fri, 2009-09-25 at 16:46 -0600, Chris Friesen wrote:
> On 09/25/2009 04:37 PM, Peter Zijlstra wrote: 
> > afaiu he doesn't, he simply splits the task's wcet between parent and
> > child and (intends?) to feed back on child exit.
> 
> How does this work if we have one parent task that forks off a bunch of
> kids like massive_intr?  Does each child get half the bandwidth of the
> previous child?
> 
Yes, that's exactly how I think it goes... Moreover, also the parent's
bandwidth is halved at each fork, which make things very odd in
workloads like massive_intr! :-(

> Right...so would it perhaps be more interesting to try a modified test
> where each child's bandwidth is equal and small enough that there is no
> oversubscription?
> 
So right! I think that should be the way to go, and I'll try to do
something like this as soon as I can... I promise... :-D

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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