linux-kernel - Re: [patch 7/8] mm, memcg: allow processes handling oom notifications to access reserves

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Date:	Thu, 12 Dec 2013 17:32:22 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	Tim Hockin <thockin@...kin.org>,
	David Rientjes <rientjes@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Pekka Enberg <penberg@...nel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Li Zefan <lizefan@...wei.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, Cgroups <cgroups@...r.kernel.org>
Subject: Re: [patch 7/8] mm, memcg: allow processes handling oom
 notifications to access reserves

On Thu 12-12-13 09:21:56, Tejun Heo wrote:
[...]
> There'd still be all the bells and whistles to configure and monitor
> system-level OOM and if there's justified need for improvements, we
> surely can and should do that;

You weren't on the CC of the original thread which has started here
https://lkml.org/lkml/2013/11/19/191. And the original request for
discussion was more about user defined _policies_ for the global
OOM rather than user space global OOM handler. I feel that there
are usacases where the current "kill a single task based on some
calculations" is far from optimal which leads to hacks which try to cope
with after oom condition somehow gracefully.

I do agree with you that pulling oom handling sounds too dangerous
even with all the code that it would need and I feel we should go a
different path than (ab)using memcg.oom_control interface for that.
I still think we need to have a way to tell the global OOM killer what
to do.

[...]
-- 
Michal Hocko
SUSE Labs
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