linux-kernel - Re: [patch 3/9] mm: memcontrol: retry reclaim for oom-disabled and __GFP

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Message-ID: <20140508182848.GP19914@cmpxchg.org>
Date:	Thu, 8 May 2014 14:28:48 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	linux-mm@...ck.org, Hugh Dickins <hughd@...gle.com>,
	Tejun Heo <tj@...nel.org>, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 3/9] mm: memcontrol: retry reclaim for oom-disabled and
 __GFP_NOFAIL charges

On Wed, May 07, 2014 at 04:43:39PM +0200, Michal Hocko wrote:
> On Wed 30-04-14 16:25:37, Johannes Weiner wrote:
> > There is no reason why oom-disabled and __GFP_NOFAIL charges should
> > try to reclaim only once when every other charge tries several times
> > before giving up.  Make them all retry the same number of times.
> 
> I guess the idea whas that oom disabled (THP) allocation can fallback to
> a smaller allocation. I would suspect this would increase latency for
> THP page faults.

If it does, we should probably teach THP to use __GFP_NORETRY.

On that note, __GFP_NORETRY is currently useless for memcg because it
has !__GFP_WAIT semantics...  I'll include a fix for that in v2.
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