linux-kernel - Re: [PATCH v5 14/18] memcg/sl[au]b: shrink dead caches

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Message-ID: <5084F7B2.7000105@parallels.com>
Date:	Mon, 22 Oct 2012 11:37:22 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	<cgroups@...r.kernel.org>, Mel Gorman <mgorman@...e.de>,
	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	<kamezawa.hiroyu@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>, <devel@...nvz.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [PATCH v5 14/18] memcg/sl[au]b: shrink dead caches

On 10/19/2012 11:47 PM, Christoph Lameter wrote:
> On Fri, 19 Oct 2012, Glauber Costa wrote:
> 
>> An unlikely branch is used to make sure this case does not affect
>> performance in the usual slab_free path.
>>
>> The slab allocator has a time based reaper that would eventually get rid
>> of the objects, but we can also call it explicitly, since dead caches
>> are not a likely event.
> 
> This is also something that could be done from slab_common since all
> allocators have kmem_cache_shrink and kmem_cache_shrink can be used to
> drain the caches and free up empty slab pages.
> 

The changelog needs to be updated. I updated the code, forgot the
changelog =(

I am actually now following Tejun's last suggestion, and no longer using
my old verify_dead code.

So I am basically calling shrink_slab every once in a while until the
cache disappears.

The only change I still need in the allocators is to count the amount of
pages they have, so I can differentiate between need-to-shrink and
need-to-destroy

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