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

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Message-ID: <47DF1760.9030908@linux.vnet.ibm.com>
Date:	Tue, 18 Mar 2008 06:44:08 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Dave Hansen <haveblue@...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

Dave Hansen wrote:
> 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.
> 

I agree and I tried to avoid the splattering

> 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

There are other problems

1. vm_(un)acct_memory is conditionally dependent on VM_ACCOUNT. Look at
shmem_(un)acct_size for example
2. These routines are not called from all contexts that we care about (look at
insert_special_mapping())

> 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. 
> 

I am going to split mem_cgroup_update_as() to two routines with a better name. I
agree with you in principle about splattering, but please see my comments above

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