linux-kernel - Re: [RFC] [PATCH] Cgroup based OOM killer controller

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Date:	Thu, 22 Jan 2009 01:39:28 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Nikanth Karthikesan <knikanth@...e.de>
cc:	Evgeniy Polyakov <zbr@...emap.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Chris Snook <csnook@...hat.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Paul Menage <menage@...gle.com>,
	containers@...ts.linux-foundation.org
Subject: Re: [RFC] [PATCH] Cgroup based OOM killer controller

On Thu, 22 Jan 2009, Nikanth Karthikesan wrote:

> > You can't specify different behavior for an oom cgroup depending on what
> > type of oom it is, which is the problem with this proposal.
> >
> 
> No. This does not disable any such special selection criteria which is used 
> without this controller.
> 

I didn't say it disabled it; the cpuset preference is actually implemented 
in the badness() score and not specifically excluded in 
select_bad_process().  That's because it's quite possible that a task has 
allocated memory in a cpuset and then either moved to a separate cpuset or 
had it's mems_allowed changed.

Please try it and you'll see.  Create two cpusets, cpuset A and cpuset B.  
Elevate cpuset A's oom.victim value and then trigger an oom in cpuset B.  
Your patch will cause a task from cpuset A to be killed for a cpuset B 
triggered oom which, more often than not, will not lead to future memory 
freeing.

It's quite possible that cpuset A would be preferred to be killed in a 
global unconstrained oom condition, however.  That's the only reason why 
one would elevate its oom.victim score to begin with.  But it doesn't work 
for cpuset-constrained ooms.

It's not going to help if it I explain it further and you don't try it out 
on your own.  Thanks.
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