linux-kernel - Re: [patch 09/11] mm, page_alloc: allow system oom handlers to use memory reserves

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Message-ID: <20140306211337.GC17902@htj.dyndns.org>
Date:	Thu, 6 Mar 2014 16:13:37 -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 09/11] mm, page_alloc: allow system oom handlers to use
 memory reserves

On Tue, Mar 04, 2014 at 07:59:35PM -0800, David Rientjes wrote:
> The root memcg allows unlimited memory charging, so no memory may be
> reserved for userspace oom handlers that are responsible for dealing
> with system oom conditions.
> 
> Instead, this memory must come from per-zone memory reserves.  This
> allows the memory allocation to succeed, and the memcg charge will
> naturally succeed afterwards.
> 
> This patch introduces per-zone oom watermarks that aren't really
> watermarks in the traditional sense.  The oom watermark is the root
> memcg's oom reserve proportional to the size of the zone.  When a page
> allocation is done, the effective watermark is
> 
> 	[min/low/high watermark] - [oom watermark]
> 
> For the [min watermark] case, this is effectively the oom reserve.
> However, it also adjusts the low and high watermark accordingly so
> memory is actually only allocated from min reserves when appropriate.
> 
> Signed-off-by: David Rientjes <rientjes@...gle.com>

Until consensus on the whole approach can be reached,

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

Thanks.

-- 
tejun
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