linux-kernel - Re: [PATCH v3 05/16] consider a memcg parameter in kmem_create

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Message-ID: <506015E7.8030900@parallels.com>
Date:	Mon, 24 Sep 2012 12:12:23 +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 05/16] consider a memcg parameter in kmem_create_cache

On 09/21/2012 10:14 PM, Tejun Heo wrote:
> Hello, Glauber.
> 
> On Tue, Sep 18, 2012 at 06:11:59PM +0400, Glauber Costa wrote:
>> +void memcg_register_cache(struct mem_cgroup *memcg, struct kmem_cache *cachep)
>> +{
>> +	int id = -1;
>> +
>> +	if (!memcg)
>> +		id = ida_simple_get(&cache_types, 0, MAX_KMEM_CACHE_TYPES,
>> +				    GFP_KERNEL);
>> +	cachep->memcg_params.id = id;
>> +}
> 
> I'm a bit confused.  Why is id allocated only when memcg is NULL?
> 

I think you figured that out already from your answer in another patch,
right? But I'll add a comment here since it seems to be a a natural
search point for people, explaining the mechanism.

> Also, how would the per-memcg slab/slubs appear in slabinfo?  If they
> appear separately it might be better to give them readable cgroup
> names.
>

The new caches will appear under /proc/slabinfo with the rest, with a
string appended that identifies the group.

> Thanks.
> 

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