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

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Message-ID: <20070604225827.GA4280@lixom.net>
Date:	Mon, 4 Jun 2007 17:58:27 -0500
From:	olof@...om.net (Olof Johansson)
To:	Matt Mackall <mpm@...enic.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Rusty Russell <rusty@...tcorp.com.au>,
	akpm@...ux-foundation.org, Linux-kernel@...r.kernel.org
Subject: Re: Interesting interaction between lguest and CFS

On Mon, Jun 04, 2007 at 12:37:10PM -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.
> 
> The system isn't swapping and has basically no I/O load.

Is this on hvc console? The hvc driver was recently modified to back off
it's timing interval when there's no input, the max value is 2 seconds.

See b791072ba3c3b29bab1890963bde52eb944a8451 for the changes in question.


-Olof

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