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

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Message-ID: <20070605023412.GN11115@waste.org>
Date:	Mon, 4 Jun 2007 21:34:12 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org,
	Linux-kernel@...r.kernel.org
Subject: Re: Interesting interaction between lguest and CFS

On Tue, Jun 05, 2007 at 10:18:54AM +1000, Rusty Russell wrote:
> On Mon, 2007-06-04 at 12:37 -0500, Matt Mackall wrote:
> > With 2.6.22-rc3-mm1, I've got a long-running video transcoding going
> > on. In other windows, I'm compiling, reading email, etc. with no
> > noticeable problems.
> > 
> > If I fire up lguest and leave it sitting at a shell prompt for a
> > couple moments, when I return to type something at the prompt, it can
> > take 2-3 seconds for my input to echo. Once it starts responding,
> > typing latency disappears. Suspend the other app and the latency
> > disappears.
> 
> 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.

Manual renicing seems to have done the trick.

This is still a little suspicious though. Why does it take two seconds
to wake up and then behave responsively for a long interval after that?

-- 
Mathematics is the supreme nostalgia of our time.
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