linux-kernel - Re: [PATCH] mm, oom: Give __GFP_NOFAIL allocations access to memory reserves

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Message-ID: <20151112085125.GD1174@dhcp22.suse.cz>
Date:	Thu, 12 Nov 2015 09:51:25 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm, oom: Give __GFP_NOFAIL allocations access to memory
 reserves

On Wed 11-11-15 10:54:46, Johannes Weiner wrote:
> On Wed, Nov 11, 2015 at 02:48:17PM +0100, mhocko@...nel.org wrote:
> > From: Michal Hocko <mhocko@...e.com>
> > 
> > __GFP_NOFAIL is a big hammer used to ensure that the allocation
> > request can never fail. This is a strong requirement and as such
> > it also deserves a special treatment when the system is OOM. The
> > primary problem here is that the allocation request might have
> > come with some locks held and the oom victim might be blocked
> > on the same locks. This is basically an OOM deadlock situation.
> > 
> > This patch tries to reduce the risk of such a deadlocks by giving
> > __GFP_NOFAIL allocations a special treatment and let them dive into
> > memory reserves after oom killer invocation. This should help them
> > to make a progress and release resources they are holding. The OOM
> > victim should compensate for the reserves consumption.
> > 
> > Signed-off-by: Michal Hocko <mhocko@...e.com>
> > ---
> > 
> > Hi,
> > this has been posted previously as a part of larger GFP_NOFS related
> > patch set (http://lkml.kernel.org/r/1438768284-30927-1-git-send-email-mhocko%40kernel.org)
> > but Andrea was asking basically the same thing at LSF early this year
> > (I cannot seem to find it in any public archive though). I think the
> > patch makes some sense on its own.
> 
> I sent this right after LSF based on Andrea's suggestion:
> 
> https://lkml.org/lkml/2015/3/25/37

Ohh, I completely forgot as it was part of a larger series.
Thanks for the pointer.

-- 
Michal Hocko
SUSE Labs
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