linux-kernel - Re: [RFC][-mm] Add an owner to the mm

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Message-ID: <47F1D576.608@linux.vnet.ibm.com>
Date:	Tue, 01 Apr 2008 11:55:58 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	YAMAMOTO Takashi <yamamoto@...inux.co.jp>
CC:	menage@...gle.com, xemul@...nvz.org, hugh@...itas.com,
	skumar@...ux.vnet.ibm.com, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org, taka@...inux.co.jp,
	linux-mm@...ck.org, rientjes@...gle.com, akpm@...ux-foundation.org,
	kamezawa.hiroyu@...fujitsu.com
Subject: Re: [RFC][-mm] Add an owner to the mm_struct (v3)

YAMAMOTO Takashi wrote:
>> This patch removes the mem_cgroup member from mm_struct and instead adds
>> an owner. This approach was suggested by Paul Menage. The advantage of
>> this approach is that, once the mm->owner is known, using the subsystem
>> id, the cgroup can be determined. It also allows several control groups
>> that are virtually grouped by mm_struct, to exist independent of the memory
>> controller i.e., without adding mem_cgroup's for each controller,
>> to mm_struct.
>>
>> A new config option CONFIG_MM_OWNER is added and the memory resource
>> controller selects this config option.
>>
>> NOTE: This patch was developed on top of 2.6.25-rc5-mm1 and is applied on top
>> of the memory-controller-move-to-own-slab patch (which is already present
>> in the Andrew's patchset).
>>
>> I am indebted to Paul Menage for the several reviews of this patchset
>> and helping me make it lighter and simpler.
>>
>> This patch was tested on a powerpc box, by running a task under the memory
>> resource controller and moving it across groups at a constant interval.
>>
>> Signed-off-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
>> ---
> 
> changing mm->owner without notifying controllers makes it difficult to use.
> can you provide a notification mechanism?

But mm->owner is just a way to get to the correct cgroup and that does not
change when mm->owner changes. Do we really need this notification? For the
virtual memory controller, move_task() is sufficient, not sure why mm->owner is
required.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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