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Message-ID: <alpine.DEB.2.00.1006011132130.32024@chino.kir.corp.google.com>
Date: Tue, 1 Jun 2010 11:36:05 -0700 (PDT)
From: David Rientjes <rientjes@...gle.com>
To: Minchan Kim <minchan.kim@...il.com>
cc: "Luis Claudio R. Goncalves" <lclaudio@...g.org>,
Peter Zijlstra <peterz@...radead.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.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 Tue, 1 Jun 2010, Minchan Kim wrote:
> Secondly, as Kame pointed out, we have to raise whole thread's
> priority to kill victim process for reclaiming pages. But I think it
> has deadlock problem.
Agreed, this has the potential to actually increase the amount of time for
an oom killed task to fully exit: the exit path takes mm->mmap_sem on exit
and if that is held by another thread waiting for the oom killed task to
exit (i.e. reclaim has failed and the oom killer becomes a no-op because
it sees an already killed task) then there's a livelock. That's always
been a problem, but is compounded with increasing the priority of a task
not holding mm->mmap_sem if the thread holding the writelock actually
isn't looking for memory but simply doesn't get a chance to release
because it fails to run.
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