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

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Message-ID: <47F1EE8F.2050508@linux.vnet.ibm.com>
Date:	Tue, 01 Apr 2008 13:43:03 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Paul Menage <menage@...gle.com>,
	YAMAMOTO Takashi <yamamoto@...inux.co.jp>
CC:	balbir@...ux.vnet.ibm.com, Pavel Emelianov <xemul@...nvz.org>,
	Hugh Dickins <hugh@...itas.com>,
	Sudhir Kumar <skumar@...ux.vnet.ibm.com>, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org, taka@...inux.co.jp,
	linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [RFC][-mm] Add an owner to the mm_struct (v3)

Balbir Singh wrote:
> Paul Menage wrote:
>> On Mon, Mar 31, 2008 at 11:23 PM, Balbir Singh
>> <balbir@...ux.vnet.ibm.com> wrote:
>>>  > Here we'll want to call vm_cgroup_update_mm_owner(), to adjust the
>>>  > accounting. (Or if in future we end up with more than a couple of
>>>  > subsystems that want notification at this time, we'll want to call
>>>  > cgroup_update_mm_owner() and have it call any interested subsystems.
>>>  >
>>>
>>>  I don't think we need to adjust accounting, since only mm->owner is changing and
>>>  not the cgroup to which the task/mm belongs. Do we really need to notify? I
>>>  don't want to do any notifications under task_lock().
>> It's possible but unlikely that the new owner is in a different cgroup.
> 
> Hmmm... that can never happen with thread groups, since mm->owner is
> p->group_leader and that never exits unless all threads are gone (it can
> explicitly change groups though). Without thread groups, the new owner can
> belong to a different cgroup, so we might need notification.
> 
> 

Thinking out aloud

If mm->owner changes and belongs to a different cgroup, we have a whole new
problem. We need to determine all tasks that share the mm and belong to a
particular cgroup, which changed since the new owner belongs to a different
cgroup and then update the charge.


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