linux-kernel - Re: [REPORT] cfs-v4 vs sd-0.44

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Date:	Sun, 22 Apr 2007 15:27:32 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mark Lord <lkml@....ca>
Cc:	Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	Con Kolivas <kernel@...ivas.org>, Willy Tarreau <w@....eu>,
	William Lee Irwin III <wli@...omorphy.com>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Williams <pwil3058@...pond.net.au>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr,
	Gene Heskett <gene.heskett@...il.com>
Subject: Re: [REPORT] cfs-v4 vs sd-0.44


* Mark Lord <lkml@....ca> wrote:

> > i've not experienced a 'runaway X' personally, at most it would 
> > crash or lock up ;) The value is boot-time and sysctl configurable 
> > as well back to 0.
> 
> Mmmm.. I've had to kill off the odd X that was locking in 100% CPU 
> usage. In the past, this has happened maybe 1-3 times a year or so on 
> my notebook.
> 
> Now mind you, that usage could have been due to some client process, 
> but X is where the 100% showed up, so X is what I nuked.

well, i just simulated a runaway X at nice -19 on CFS (on a UP box), and 
while the box was a tad laggy, i was able to killall it without 
problems, within 2 seconds that also included a 'su'. So it's not an 
issue in CFS, it can be turned off, and because every distro has another 
way to renice Xorg, this is a convenience hack until Xorg standardizes 
it into some xorg.conf field. (It also makes sure that X isnt preempted 
by other userspace stuff while it does timing-sensitive operations like 
setting the video modes up or switching video modes, etc.)

	Ingo
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