linux-kernel - Re: [patch 07/11] mm, memcg: allow processes handling oom notifications to access reserves

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Message-ID: <20140306211246.GB17902@htj.dyndns.org>
Date:	Thu, 6 Mar 2014 16:12:46 -0500
From:	Tejun Heo <tj@...nel.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Mel Gorman <mgorman@...e.de>, Oleg Nesterov <oleg@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Jianguo Wu <wujianguo@...wei.com>,
	Tim Hockin <thockin@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, cgroups@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [patch 07/11] mm, memcg: allow processes handling oom
 notifications to access reserves

On Tue, Mar 04, 2014 at 07:59:29PM -0800, David Rientjes wrote:
> Now that a per-process flag is available, define it for processes that
> handle userspace oom notifications.  This is an optimization to avoid
> mantaining a list of such processes attached to a memcg at any given time
> and iterating it at charge time.
> 
> This flag gets set whenever a process has registered for an oom
> notification and is cleared whenever it unregisters.
> 
> When memcg reclaim has failed to free any memory, it is necessary for
> userspace oom handlers to be able to dip into reserves to pagefault text,
> allocate kernel memory to read the "tasks" file, allocate heap, etc.
> 
> System oom conditions are not addressed at this time, but the same per-
> process flag can be used in the page allocator to determine if access
> should be given to userspace oom handlers to per-zone memory reserves at
> a later time once there is consensus.
> 
> Signed-off-by: David Rientjes <rientjes@...gle.com>

ntil consensus on the whole approach can be reached,

 Nacked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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