linux-kernel - Re: [PATCH v6 00/29] kmem controller for memcg.

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Date:	Mon, 5 Nov 2012 09:18:25 +0100
From:	Glauber Costa <glommer@...allels.com>
To:	JoonSoo Kim <js1304@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Tejun Heo <tj@...nel.org>, Michal Hocko <mhocko@...e.cz>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Greg Thelen <gthelen@...gle.com>
Subject: Re: [PATCH v6 00/29] kmem controller for memcg.

On 11/02/2012 08:25 PM, JoonSoo Kim wrote:
> Hello, Glauber.
> 
> 2012/11/2 Glauber Costa <glommer@...allels.com>:
>> On 11/02/2012 04:04 AM, Andrew Morton wrote:
>>> On Thu,  1 Nov 2012 16:07:16 +0400
>>> Glauber Costa <glommer@...allels.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> This work introduces the kernel memory controller for memcg. Unlike previous
>>>> submissions, this includes the whole controller, comprised of slab and stack
>>>> memory.
>>>
>>> I'm in the middle of (re)reading all this.  Meanwhile I'll push it all
>>> out to http://ozlabs.org/~akpm/mmots/ for the crazier testers.
>>>
>>> One thing:
>>>
>>>> Numbers can be found at https://lkml.org/lkml/2012/9/13/239
>>>
>>> You claim in the above that the fork worload is 'slab intensive".  Or
>>> at least, you seem to - it's a bit fuzzy.
>>>
>>> But how slab intensive is it, really?
>>>
>>> What is extremely slab intensive is networking.  The networking guys
>>> are very sensitive to slab performance.  If this hasn't already been
>>> done, could you please determine what impact this has upon networking?
>>> I expect Eric Dumazet, Dave Miller and Tom Herbert could suggest
>>> testing approaches.
>>>
>>
>> I can test it, but unfortunately I am unlikely to get to prepare a good
>> environment before Barcelona.
>>
>> I know, however, that Greg Thelen was testing netperf in his setup.
>> Greg, do you have any publishable numbers you could share?
> 
> Below is my humble opinion.
> I am worrying about data cache footprint which is possibly caused by
> this patchset, especially slab implementation.
> If there are several memcg cgroups, each cgroup has it's own kmem_caches.

I answered the performance part in response to Tejun's response.

Let me just add something here: Just keep in mind this is not "per
memcg", this is "per memcg that are kernel-memory limited". So in a
sense, you are only paying this, and allocate from different caches, if
you runtime enable this.

This should all be documented in the Documentation/ patch. But let me
know if there is anything that needs further clarification
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