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Date: Mon, 7 Mar 2011 16:51:19 -0800
From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [patch] memcg: add oom killer delay
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To: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Balbir Singh <balbir@linux.vnet.ibm.com>, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>, linux-mm@kvack.org

On Mon, 7 Mar 2011 16:36:47 -0800 (PST)
David Rientjes <rientjes@google.com> wrote:

> On Mon, 7 Mar 2011, Andrew Morton wrote:
> 
> > > So the question I'd ask is
> > 
> > What about my question?  Why is your usersapce oom-handler "unresponsive"?
> > 
> 
> If we have a per-memcg userspace oom handler, then it's absolutely 
> required that it either increase the hard limit of the oom memcg or kill a 
> task to free memory; anything else risks livelocking that memcg.  At 
> the same time, the oom handler's memcg isn't really important: it may be 
> in a different memcg but it may be oom at the same time.  If we risk 
> livelocking the memcg when it is oom and the oom killer cannot respond 
> (the only reason for the oom killer to exist in the first place), then 
> there's no guarantee that a userspace oom handler could respond under 
> livelock.

So you're saying that your userspace oom-handler is in a memcg which is
also oom?  That this is the only situation you've observed in which the
userspace oom-handler is "unresponsive"?

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