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To: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>, Vegard Nossum <vegard.nossum@gmail.com>,
       Dmitry Adamushko <dmitry.adamushko@gmail.com>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Keith Packard <keith.packard@intel.com>
Subject: Re: [patch] CFS scheduler, -v18
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From: Andi Kleen <andi@firstfloor.org>
Date: 04 Jul 2007 14:11:54 +0200
In-Reply-To: <20070703072252.GB29984@elte.hu>
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Ingo Molnar <mingo@elte.hu> writes:
> 
> ah. That indeed makes sense. It seems like the xterm doesnt process the 
> Ctrl-C/Z keypresses _at all_ when it is 'spammed' with output. Normally, 
> output 'spam' is throttled by the scroll buffer's overhead. But in 
> Vegard's case, the printout involves a \r carriage return:
> 
>        printf("%ld\r", 1000 * clock() / CLOCKS_PER_SEC);
> 
> which allows xterm-spam (attached) to easily flood the xterm (without 
> any scrolling that would act as a throttle) and the xterm to flood Xorg. 
> 
> I suspect we need the help of an xterm/Xorg expert? (maybe Keith can 
> give us further pointers? I can reproduce the problem on a T60 with i940 
> and Core2Duo running Fedora 7 + Xorg 7.1.)

Xorg seems to have a couple of starvation issues. e.g. I found
the Gantt view in icemon during a busy compile session can starve all
other X clients for tenths of seconds.

-Andi