linux-kernel - Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache

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Date:	Mon, 24 Sep 2012 12:17:37 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Tejun Heo <tj@...nel.org>
CC:	<linux-kernel@...r.kernel.org>, <cgroups@...r.kernel.org>,
	<kamezawa.hiroyu@...fujitsu.com>, <devel@...nvz.org>,
	<linux-mm@...ck.org>, Suleiman Souhlal <suleiman@...gle.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation
 to the right cache

On 09/22/2012 12:52 AM, Tejun Heo wrote:
> Missed some stuff.
> 
> On Tue, Sep 18, 2012 at 06:12:00PM +0400, Glauber Costa wrote:
>> +static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
>> +						  struct kmem_cache *cachep)
>> +{
> ...
>> +	memcg->slabs[idx] = new_cachep;
> ...
>> +struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
>> +					  gfp_t gfp)
>> +{
> ...
>> +	return memcg->slabs[idx];
> 
> I think you need memory barriers for the above pair.
> 
> Thanks.
> 

Why is that?

We'll either see a value, or NULL. If we see NULL, we assume the cache
is not yet created. Not a big deal.

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