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

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Message-ID: <4FE9755B.1040905@parallels.com>
Date:	Tue, 26 Jun 2012 12:39:55 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Suleiman Souhlal <suleiman@...gle.com>
CC:	<cgroups@...r.kernel.org>, <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Lameter <cl@...ux.com>, <devel@...nvz.org>,
	<kamezawa.hiroyu@...fujitsu.com>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 02/11] memcg: Reclaim when more than one page needed.

On 06/26/2012 03:33 AM, Suleiman Souhlal wrote:
> On Mon, Jun 25, 2012 at 7:15 AM, Glauber Costa <glommer@...allels.com> wrote:
>> From: Suleiman Souhlal <ssouhlal@...eBSD.org>
>>
>> mem_cgroup_do_charge() was written before slab 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 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), stay safe with a cond_resched(),
>> and make sure not to do it if __GFP_NORETRY.
>
> The commit description mentions COSTLY_ORDER, but it's not actually
> used in the patch.
>
> -- Suleiman
>
Yeah, forgot to update the changelog =(

But much more importantly, are you still happy with those changes?

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