linux-kernel - Re: [RFC][2/3] Account and control virtual address space allocations

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Date:	Mon, 17 Mar 2008 09:53:10 -0700
From:	Dave Hansen <haveblue@...ibm.com>
To:	Balbir Singh <balbir@...ux.vnet.ibm.com>
Cc:	linux-mm@...ck.org, Hugh Dickins <hugh@...itas.com>,
	Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
	YAMAMOTO Takashi <yamamoto@...inux.co.jp>,
	Paul Menage <menage@...gle.com>, lizf@...fujitsu.com,
	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][2/3] Account and control virtual address space
	allocations

On Sun, 2008-03-16 at 23:00 +0530, Balbir Singh wrote:
> @@ -787,6 +788,8 @@ static int ptrace_bts_realloc(struct tas
>         current->mm->total_vm  -= old_size;
>         current->mm->locked_vm -= old_size;
>  
> +       mem_cgroup_update_as(current->mm, -old_size);
> +
>         if (size == 0)
>                 goto out;

I think splattering these things all over is probably a bad idea.

If you're going to do this, I think you need a couple of phases.  

1. update the vm_(un)acct_memory() functions to take an mm
2. start using them (or some other abstracted functions in place)
3. update the new functions for cgroups

It's a bit non-obvious why you do the mem_cgroup_update_as() calls in
the places that you do from context.

Having some other vm-abstracted functions will also keep you from
splattering mem_cgroup_update_as() across the tree.  That's a pretty bad
name. :)  ...update_mapped() or ...update_vm() might be a wee bit
better. 

-- Dave

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