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Date: Fri, 15 May 2009 23:49:51 +0530
From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux-foundation.org>, Pavel Machek <pavel@ucw.cz>,
       David Rientjes <rientjes@google.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Greg Kroah-Hartman <gregkh@suse.de>, Nick Piggin <npiggin@suse.de>,
       Mel Gorman <mel@csn.ul.ie>, Peter Ziljstra <a.p.ziljstra@chello.nl>,
       San Mehat <san@android.com>, Arve Hj?nnev?g <arve@android.com>,
       linux-kernel@vger.kernel.org
Subject: Re: Misleading OOM messages
Message-ID: <20090515181951.GI4451@balbir.in.ibm.com>
Reply-To: balbir@linux.vnet.ibm.com
References: <alpine.DEB.1.10.0905121708470.14226@qirst.com> <20090514092909.GG1365@ucw.cz> <alpine.DEB.1.10.0905141546040.1381@qirst.com> <1242333519.15391.210.camel@nimitz> <alpine.DEB.2.00.0905141346030.28074@chino.kir.corp.google.com> <1242335120.15391.242.camel@nimitz> <alpine.DEB.1.10.0905141729180.30187@qirst.com> <20090514213403.GB14741@elf.ucw.cz> <alpine.DEB.1.10.0905151346550.26559@qirst.com> <1242411307.28257.25.camel@nimitz>
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* Dave Hansen <dave@linux.vnet.ibm.com> [2009-05-15 11:15:07]:

> On Fri, 2009-05-15 at 13:57 -0400, Christoph Lameter wrote:
> > > If you misconfigured cgroups, you give more memory to them.
> > 
> > If you do not have enough memory in a cgroup then your application should
> > slow down (because of page evictions) but the system should not OOM.
> > Are cgroups broken or why are you getting OOMs when using them?
> 
> See mm/oom_kill.c::mem_cgroup_out_of_memory().  A group itself can have
> an OOM done on it.  It's not a system-wide oom.  We just need to ensure
> that we continue to differentiate the cgroup-specific oom message from
> the general one.  Maybe also include some more cgroup info in the debug
> outbut.
>

A long pending action item is to allow user space to handle cgroup
OOM. A cgroup can OOM, if the tasks in the group is way over their limit
and reclaim fails. I'll look to see if we enhance the output.

-- 
	Balbir