linux-kernel - Re: [RFC][0/3] Virtual address space control for cgroups

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Date:	Mon, 17 Mar 2008 10:38:58 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Paul Menage <menage@...gle.com>
CC:	Li Zefan <lizf@...fujitsu.com>, linux-mm@...ck.org,
	Hugh Dickins <hugh@...itas.com>,
	Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
	YAMAMOTO Takashi <yamamoto@...inux.co.jp>,
	linux-kernel@...r.kernel.org, taka@...inux.co.jp,
	David Rientjes <rientjes@...gle.com>,
	Pavel Emelianov <xemul@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [RFC][0/3] Virtual address space control for cgroups

Paul Menage wrote:
> On Mon, Mar 17, 2008 at 9:47 AM, Li Zefan <lizf@...fujitsu.com> wrote:
>>  It will be code duplication to make it a new subsystem,
> 
> Would it? Other than the basic cgroup boilerplate, the only real
> duplication that I could see would be that there'd need to be an
> additional per-mm pointer back to the cgroup. (Which could be avoided
> if we added a single per-mm pointer back to the "owning" task, which
> would generally be the mm's thread group leader, so that you could go
> quickly from an mm to a set of cgroup subsystems).
> 

I understand the per-mm pointer overhead back to the cgroup. I don't understand
the part about adding a per-mm pointer back to the "owning" task. We already
have task->mm. BTW, the reason by we directly add the mm_struct to mem_cgroup
mapping is that there are contexts from where only the mm_struct is known (when
we charge/uncharge). Assuming that current->mm's mem_cgorup is the one we want
to charge/uncharge is incorrect.

> And the advantage would that you'd be able to more easily pick/choose
> which bits of control you use (and pay for).

I am not sure I understand your proposal fully. But, if it can help provide the
flexibility you are referring to, I am all ears.

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