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

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Message-ID: <20070424072408.GA27769@elte.hu>
Date:	Tue, 24 Apr 2007 09:24:08 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	David Lang <david.lang@...italinsight.com>
Cc:	Gene Heskett <gene.heskett@...il.com>,
	Peter Williams <pwil3058@...pond.net.au>,
	Arjan van de Ven <arjan@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Juliusz Chroboczek <jch@....jussieu.fr>,
	Con Kolivas <kernel@...ivas.org>, ck list <ck@....kolivas.org>,
	Bill Davidsen <davidsen@....com>, Willy Tarreau <w@....eu>,
	William Lee Irwin III <wli@...omorphy.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Galbraith <efault@....de>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr
Subject: Re: [REPORT] cfs-v4 vs sd-0.44


* David Lang <david.lang@...italinsight.com> wrote:

> > (Btw., to protect against such mishaps in the future i have changed 
> > the SysRq-N [SysRq-Nice] implementation in my tree to not only 
> > change real-time tasks to SCHED_OTHER, but to also renice negative 
> > nice levels back to 0 - this will show up in -v6. That way you'd 
> > only have had to hit SysRq-N to get the system out of the wedge.)
> 
> if you are trying to unwedge a system it may be a good idea to renice 
> all tasks to 0, it could be that a task at +19 is holding a lock that 
> something else is waiting for.

Yeah, that's possible too, but +19 tasks are getting a small but 
guaranteed share of the CPU so eventually it ought to release it. It's 
still a possibility, but i think i'll wait for a specific incident to 
happen first, and then react to that incident :-)

	Ingo
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