linux-kernel - Re: [PATCH v2 04/11] kmem accounting basic infrastructure

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Date:	Wed, 15 Aug 2012 11:07:09 -0700
From:	Ying Han <yinghan@...gle.com>
To:	Glauber Costa <glommer@...allels.com>
Cc:	Christoph Lameter <cl@...ux.com>, Michal Hocko <mhocko@...e.cz>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	cgroups@...r.kernel.org, devel@...nvz.org,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kamezawa.hiroyu@...fujitsu.com,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH v2 04/11] kmem accounting basic infrastructure

On Wed, Aug 15, 2012 at 8:11 AM, Glauber Costa <glommer@...allels.com> wrote:
> On 08/15/2012 06:47 PM, Christoph Lameter wrote:
>> On Wed, 15 Aug 2012, Michal Hocko wrote:
>>
>>>> That is not what the kernel does, in general. We assume that if he wants
>>>> that memory and we can serve it, we should. Also, not all kernel memory
>>>> is unreclaimable. We can shrink the slabs, for instance. Ying Han
>>>> claims she has patches for that already...
>>>
>>> Are those patches somewhere around?
>>
>> You can already shrink the reclaimable slabs (dentries / inodes) via
>> calls to the subsystem specific shrinkers. Did Ying Han do anything to
>> go beyond that?
>>
> That is not enough for us.
> We would like to make sure that the objects being discarded belong to
> the memcg which is under pressure. We don't need to be perfect here, and
> an occasional slip is totally fine. But if in general, shrinking from
> memcg A will mostly wipe out objects from memcg B, we harmed the system
> in return for nothing good.

Correct. For example, we have per-superblock shrinker today for vfs
caches. That is not enough since we need to isolate the dentry caches
per-memcg basis.

--Ying
>
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