linux-kernel - Re: [RFC][3/3] Update documentation for virtual address space control

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Date:	Mon, 17 Mar 2008 07:03:31 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Randy Dunlap <randy.dunlap@...cle.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][3/3] Update documentation for virtual address space control

Randy Dunlap wrote:
> On Sun, 16 Mar 2008 23:00:17 +0530 Balbir Singh wrote:
> 
>> This patch adds documentation for virtual address space control.
>>
>> Signed-off-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
>> ---
>>
>>  Documentation/controllers/memory.txt |   26 +++++++++++++++++++++++++-
>>  1 file changed, 25 insertions(+), 1 deletion(-)
>>
>> diff -puN Documentation/controllers/memory.txt~memory-controller-virtual-address-control-documentation Documentation/controllers/memory.txt
>> --- linux-2.6.25-rc5/Documentation/controllers/memory.txt~memory-controller-virtual-address-control-documentation	2008-03-16 22:57:44.000000000 +0530
>> +++ linux-2.6.25-rc5-balbir/Documentation/controllers/memory.txt	2008-03-16 22:57:44.000000000 +0530
>> @@ -237,7 +237,31 @@ cgroup might have some charge associated
>>  tasks have migrated away from it. Such charges are automatically dropped at
>>  rmdir() if there are no tasks.
>>  
>> -5. TODO
>> +5. Virtual address space accounting
>> +
>> +A new resource counter controls the address space expansion of the tasks in
>> +the cgroup. Address space control is provided along the same lines as
>> +RLIMIT_AS control, which is available via getrlimit(2)/setrlimit(2).
>> +The interface for controlling address space is provided through
>> +"as_limit_in_bytes". The file is similar to "limit_in_bytes" w.r.t the user
> 
>                                                                 w.r.t.
>   or even spelled out.
> 

Will spell out.

>> +interface. Please see section 3 for more details on how to use the user
>> +interface to get and set values.
>> +
>> +The "as_usage_in_bytes" file provides information about the total address
>> +space usage of the cgroup in bytes.
>> +
>> +5.1 Advantages of providing this feature
>> +
>> +1. Control over virtual address space allows for a cgroup to fail gracefully
>> +   i.e, via a malloc or mmap failure as compared to OOM kill when no
> 
>       i.e.,
> 
>> +   pages can be reclaimed
> 
> end with period.

Will fix

> 
>> +2. It provides better control over how many pages can be swapped out when
>> +   the cgroup goes over it's limit. A badly setup cgroup can cause excessive
> 
>                            its (not "it is")
> 

Will fix :)

>> +   swapping. Providing control over the address space allocations ensures
>> +   that the system administrator has control over the total swapping that
>> +   can take place.
>> +
>> +6. TODO
>>  
>>  1. Add support for accounting huge pages (as a separate controller)
>>  2. Make per-cgroup scanner reclaim not-shared pages first
>> _
> 
> ---
> ~Randy
> 
> --
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-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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