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

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Date:	Mon, 13 Aug 2012 12:36:51 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<cgroups@...r.kernel.org>, <devel@...nvz.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: Re: [PATCH v2 04/11] kmem accounting basic infrastructure

On 08/10/2012 09:02 PM, Kamezawa Hiroyuki wrote:
> (2012/08/09 22:01), Glauber Costa wrote:
>> This patch adds the basic infrastructure for the accounting of the slab
>> caches. To control that, the following files are created:
>>
>>   * memory.kmem.usage_in_bytes
>>   * memory.kmem.limit_in_bytes
>>   * memory.kmem.failcnt
>>   * memory.kmem.max_usage_in_bytes
>>
>> They have the same meaning of their user memory counterparts. They
>> reflect the state of the "kmem" res_counter.
>>
>> The code is not enabled until a limit is set. This can be tested by the
>> flag "kmem_accounted". This means that after the patch is applied, no
>> behavioral changes exists for whoever is still using memcg to control
>> their memory usage.
>>
>> We always account to both user and kernel resource_counters. This
>> effectively means that an independent kernel limit is in place when the
>> limit is set to a lower value than the user memory. A equal or higher
>> value means that the user limit will always hit first, meaning that kmem
>> is effectively unlimited.
>>
>> People who want to track kernel memory but not limit it, can set this
>> limit to a very high number (like RESOURCE_MAX - 1page - that no one
>> will ever hit, or equal to the user memory)
>>
>> Signed-off-by: Glauber Costa <glommer@...allels.com>
>> CC: Michal Hocko <mhocko@...e.cz>
>> CC: Johannes Weiner <hannes@...xchg.org>
>> Reviewed-by: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> Could you add  a patch for documentation of this new interface and a text
> explaining the behavior of "kmem_accounting" ?
> 
> Hm, my concern is the difference of behavior between user page accounting and
> kmem accounting...but this is how tcp-accounting is working.
> 
> Once you add Documentation, it's okay to add my Ack.
> 
I plan to add documentation in a separate patch. Due to that, can I add
your ack to this patch here?

Also, I find that the description text in patch0 grew to be quite
informative and complete. I plan to add that to the documentation
if that is ok with you


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