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

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Message-ID: <5028B552.2070708@parallels.com>
Date:	Mon, 13 Aug 2012 12:05:38 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Michal Hocko <mhocko@...e.cz>
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 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?


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