linux-kernel - Re: [PATCH -mm] slab: use cgroup ino for naming per memcg caches

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Message-ID: <20150408181911.GA18199@esperanza>
Date:	Wed, 8 Apr 2015 21:19:11 +0300
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, <linux-mm@...ck.org>,
	<cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -mm] slab: use cgroup ino for naming per memcg caches

On Wed, Apr 08, 2015 at 08:46:22AM -0500, Christoph Lameter wrote:
> On Wed, 8 Apr 2015, Vladimir Davydov wrote:
> 
> > has its own copy of kmem cache. What if we decide to share the same kmem
> > cache among all memory cgroups one day? Of course, this will hardly ever
> > happen, but it is an alternative approach to implementing the same
> 
> /sys/kernel/slab already supports the use of symlinks. And both SLAB and
> SLUB do slab merging which means effectively an aliasing of multiple slab
> caches to the same name.

Yeah, I think cache merging is a good argument for grouping memcg caches
under /sys/kernel/slab/<slab-name>/cgroup/. We cannot maintain symlinks
for merged memcg caches, because when a memcg cache is created we do not
have names of caches the new cache is merged with. If memcg caches were
listed under /sys/kernel/slab/ along with global ones, absence of the
symlinks would lead to confusion.

Thanks,
Vladimir
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