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Message-ID: <20070605071011.GA25163@elte.hu>
Date: Tue, 5 Jun 2007 09:10:11 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Rusty Russell <rusty@...tcorp.com.au>
Cc: Matt Mackall <mpm@...enic.com>, akpm@...ux-foundation.org,
Linux-kernel@...r.kernel.org
Subject: Re: Interesting interaction between lguest and CFS
* Rusty Russell <rusty@...tcorp.com.au> wrote:
> This sounds like the waker process (nice 19) not getting a chance to
> run. You can hack around it for the moment by changing "nice(19)" in
> Documentation/lguest/lguest.c to something less aggressive.
even if the waker runs at nice+19, under CFS (which schedules
deterministically) it should not be delayed by a single nice-0 task by
more than ~70 msecs. That is a far cry from the 'seconds' that Matt saw
- and the sched stats he sent look anomalous too. Also, i'm not able to
reproduce it at all - while any nice+19 related problem should be
readily reproducable on my box too. So my current take is that this is
some sort of host-side CFS related problem and that the lguest host
threads somehow were the first ones that managed to trigger it in some
really bad way.
OTOH i do agree with your patch, that nice+19 thing is quite hacky :-)
Ingo
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