linux-kernel - Re: [RFC] oom-kill: give the dying task a higher priority

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Message-ID: <alpine.DEB.2.00.1006031327480.10856@chino.kir.corp.google.com>
Date:	Thu, 3 Jun 2010 13:32:03 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Minchan Kim <minchan.kim@...il.com>, balbir@...ux.vnet.ibm.com,
	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Thomas Gleixner <tglx@...utronix.de>,
	Mel Gorman <mel@....ul.ie>, williams@...hat.com
Subject: Re: [RFC] oom-kill: give the dying task a higher priority

On Thu, 3 Jun 2010, Peter Zijlstra wrote:

> > And that can reduce the runtime of the thread holding a writelock on 
> > mm->mmap_sem, making the exit actually take longer than without the patch 
> > if its priority is significantly higher, especially on smaller machines. 
> 
> /me smells an inversion... on -rt we solved those ;-)
> 

Right, but I don't see how increasing an oom killed tasks priority to a 
divine priority doesn't impact the priorities of other tasks which may be 
blocking the exit of that task, namely a coredumper or holder of 
mm->mmap_sem.  This patch also doesn't address how it negatively impacts 
the priorities of jobs running in different cpusets (although sharing the 
same cpus) because one cpuset is oom.
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