linux-kernel - Re: Interesting interaction between lguest and CFS

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Message-ID: <20070604202405.GA27632@elte.hu>
Date:	Mon, 4 Jun 2007 22:24:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	James Morris <jmorris@...ei.org>
Cc:	Matt Mackall <mpm@...enic.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	akpm@...ux-foundation.org, Linux-kernel@...r.kernel.org
Subject: Re: Interesting interaction between lguest and CFS


* James Morris <jmorris@...ei.org> wrote:

> On Mon, 4 Jun 2007, Ingo Molnar wrote:
> 
> > perhaps lguest does something unusual when it idles? Does it fiddle 
> > sched_clock() in any way?
> 
> One of the lguest processes calls nice(2), which seems like a long 
> shot, but also not impossibly related.  (Note that newer patches in 
> the lguest queue remove this, so it'll depend on exactly which patches 
> you have applied).

i've got 2.6.22-rc3-mm1's lguest (with a trivial boot-time crash fix in 
sched_clock that i ran into). But nice(2) should only cause a gentle, 
20% smaller CPU bandwidth to be allocated by CFS to that thread, nothing 
more drastic like user-visible delays.

	Ingo
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