linux-kernel - Re: [PATCH 10/10] memcg/sl[au]b: shrink dead caches

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Message-ID: <alpine.DEB.2.00.1207251207180.3543@router.home>
Date:	Wed, 25 Jul 2012 12:13:23 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Glauber Costa <glommer@...allels.com>
cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>,
	Greg Thelen <gthelen@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>, devel@...nvz.org,
	cgroups@...r.kernel.org, Pekka Enberg <penberg@...helsinki.fi>,
	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [PATCH 10/10] memcg/sl[au]b: shrink dead caches

On Wed, 25 Jul 2012, Glauber Costa wrote:

> In the slub allocator, when the last object of a page goes away, we
> don't necessarily free it - there is not necessarily a test for empty
> page in any slab_free path.

That is true for the slab allocator as well. In either case calling
kmem_cache_shrink() will make the objects go away by draining the cached
objects and freeing the pages used for the objects back to the page
allocator. You do not need this patch. Just call the proper functions to
drop the objecgts in the caches in either allocator.

> 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.

So this is already for both allocators?
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