linux-kernel - Re: [PATCH v2 02/11] memcg: Reclaim when more than one page needed.

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Message-ID: <20120813131014.GB24248@dhcp22.suse.cz>
Date:	Mon, 13 Aug 2012 15:10:14 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	cgroups@...r.kernel.org, devel@...nvz.org,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kamezawa.hiroyu@...fujitsu.com, Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [PATCH v2 02/11] memcg: Reclaim when more than one page needed.

On Mon 13-08-12 12:05:38, Glauber Costa wrote:
> On 08/10/2012 10:54 PM, Michal Hocko wrote:
> > On Thu 09-08-12 17:01:10, Glauber Costa wrote:
> >> From: Suleiman Souhlal <ssouhlal@...eBSD.org>
> >>
> >> mem_cgroup_do_charge() was written before kmem accounting, and expects
> >> three cases: being called for 1 page, being called for a stock of 32
> >> pages, or being called for a hugepage.  If we call for 2 or 3 pages (and
> >> both the stack and several slabs used in process creation are such, at
> >> least with the debug options I had), it assumed it's being called for
> >> stock and just retried without reclaiming.
> >>
> >> Fix that by passing down a minsize argument in addition to the csize.
> >>
> >> And what to do about that (csize == PAGE_SIZE && ret) retry?  If it's
> >> needed at all (and presumably is since it's there, perhaps to handle
> >> races), then it should be extended to more than PAGE_SIZE, yet how far?
> >> And should there be a retry count limit, of what?  For now retry up to
> >> COSTLY_ORDER (as page_alloc.c does) and make sure not to do it if
> >> __GFP_NORETRY.
> >>
> >> [v4: fixed nr pages calculation pointed out by Christoph Lameter ]
> >>
> >> Signed-off-by: Suleiman Souhlal <suleiman@...gle.com>
> >> Signed-off-by: Glauber Costa <glommer@...allels.com>
> >> Reviewed-by: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > 
> > I am not happy with the min_pages argument but we can do something more
> > clever  later.
> > 
> > Acked-by: Michal Hocko <mhocko@...e.cz>
> > 
> 
> I am a bit confused here. Does your ack come before or after your other
> comments on this patch?

Heh, it was hard Friday ;) Yes, it was after the mind fart...
-- 
Michal Hocko
SUSE Labs
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