linux-kernel - Re: [PATCH v4 24/25] memcg/slub: shrink dead caches

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Message-ID: <alpine.DEB.2.00.1207061015030.28648@router.home>
Date:	Fri, 6 Jul 2012 10:16:36 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Glauber Costa <glommer@...allels.com>
cc:	linux-mm@...ck.org, Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>, cgroups@...r.kernel.org,
	devel@...nvz.org, kamezawa.hiroyu@...fujitsu.com,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v4 24/25] memcg/slub: shrink dead caches

On Mon, 18 Jun 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.

This is the same btw in SLAB which keeps objects in per cpu caches and
keeps empty slab pages on special queues.

> This patch marks all memcg caches as dead. kmem_cache_shrink is called
> for the ones who are not yet dead - this will force internal cache
> reorganization, and then all references to empty pages will be removed.

You need to call this also for slab to drain the caches and free the pages
on the empty list.

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