linux-kernel - Re: Misleading OOM messages

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Message-ID: <20090515181951.GI4451@balbir.in.ibm.com>
Date:	Fri, 15 May 2009 23:49:51 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Pavel Machek <pavel@....cz>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Nick Piggin <npiggin@...e.de>, Mel Gorman <mel@....ul.ie>,
	Peter Ziljstra <a.p.ziljstra@...llo.nl>,
	San Mehat <san@...roid.com>, Arve Hj?nnev?g <arve@...roid.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Misleading OOM messages

* Dave Hansen <dave@...ux.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
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