linux-kernel - Re: [patch 2/2] mm, memcg: add memory.oom

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Date:	Mon, 18 Nov 2013 17:25:13 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Michal Hocko <mhocko@...e.cz>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	cgroups@...r.kernel.org
Subject: Re: [patch 2/2] mm, memcg: add memory.oom_control notification for
 system oom

On Mon, 18 Nov 2013, Michal Hocko wrote:

> > A subset of applications that wait on memory.oom_control don't disable
> > the oom killer for that memcg and simply log or cleanup after the kernel
> > oom killer kills a process to free memory.
> > 
> > We need the ability to do this for system oom conditions as well, i.e.
> > when the system is depleted of all memory and must kill a process.  For
> > convenience, this can use memcg since oom notifiers are already present.
> 
> Using the memcg interface for "read-only" interface without any plan for
> the "write" is only halfway solution. We want to handle global OOM in a
> more user defined ways but we have to agree on the proper interface
> first. I do not want to end up with something half baked with memcg and
> a different interface to do the real thing just because memcg turns out
> to be unsuitable.
> 

This patch isn't really a halfway solution, you can still determine if the 
open(O_WRONLY) succeeds or not to determine if that feature has been 
implemented.  I'm concerned about disabling the oom killer entirely for 
system oom conditions, though, so I didn't implement it to be writable.  I 
don't think we should be doing anything special in terms of "write" 
behavior for the root memcg memory.oom_control, so I'd argue against doing 
anything other than disabling the oom killer.  That's scary.
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