Message-ID: <4FC4F5A8.9060506@parallels.com>
Date: Tue, 29 May 2012 20:13:28 +0400
From: Glauber Costa <glommer@parallels.com>
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To: Christoph Lameter <cl@linux.com>
CC: <linux-kernel@vger.kernel.org>, <cgroups@vger.kernel.org>,
        <linux-mm@kvack.org>, <kamezawa.hiroyu@jp.fujitsu.com>,
        Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Greg Thelen <gthelen@google.com>,
        Suleiman Souhlal <suleiman@google.com>, Michal Hocko <mhocko@suse.cz>,
        Johannes Weiner <hannes@cmpxchg.org>, <devel@openvz.org>,
        David Rientjes <rientjes@google.com>,
        Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [PATCH v3 19/28] slab: per-memcg accounting of slab caches
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On 05/29/2012 08:07 PM, Glauber Costa wrote:
> On 05/29/2012 06:52 PM, Christoph Lameter wrote:
>> On Fri, 25 May 2012, Glauber Costa wrote:
>>
>>> > This patch charges allocation of a slab object to a particular
>>> > memcg.
>> Ok so a requirement is to support tracking of individual slab
>> objects to cgroups? That is going to be quite expensive since it will
>> touch the hotpaths.
>>
>
> No, we track pages. But all the objects in the page belong to the same
> cgroup.
>

Also, please note the following:

The code that relays us to the right cache, is wrapped inside a static 
branch. Whoever is not using more than the root cgroup, will not suffer 
a single bit.

If you are, but your process is in the right cgroup, you will 
unfortunately pay function call penalty(*), but the code will make and 
effort to detect that as early as possible and resume.


(*) Not even then if you fall in the following categories, that are 
resolved inline:

+       if (!current->mm)
+               return cachep;
+       if (in_interrupt())
+               return cachep;
+       if (gfp & __GFP_NOFAIL)
+               return cachep;

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