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

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Message-ID: <20070604175436.GC30274@elte.hu>
Date:	Mon, 4 Jun 2007 19:54:36 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Matt Mackall <mpm@...enic.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>, akpm@...ux-foundation.org,
	Linux-kernel@...r.kernel.org
Subject: Re: Interesting interaction between lguest and CFS


* Matt Mackall <mpm@...enic.com> 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.
> 
> The system isn't swapping and has basically no I/O load.

could you send me the /proc/PID/sched file of that task which shows this 
2-3 seconds delay? (if it's a shell and a graphical terminal then please 
send the sched-debug file of both.) I suspect the latency goes away if 
you strace -f the shell task(s)? If not then please send the strace 
output too.

	Ingo
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