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

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Date:	Tue, 08 Apr 2008 08:09:57 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	menage@...gle.com, xemul@...nvz.org, hugh@...itas.com,
	skumar@...ux.vnet.ibm.com, yamamoto@...inux.co.jp,
	lizf@...fujitsu.com, linux-kernel@...r.kernel.org,
	taka@...inux.co.jp, linux-mm@...ck.org, rientjes@...gle.com,
	kamezawa.hiroyu@...fujitsu.com
Subject: Re: [-mm] Add an owner to the mm_struct (v8)

Andrew Morton wrote:
> On Fri, 04 Apr 2008 13:35:44 +0530
> Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> 
>> 1. Add mm->owner change callbacks using cgroups
>>
>> ...
>>
>> +config MM_OWNER
>> +	bool "Enable ownership of mm structure"
>> +	help
>> +	  This option enables mm_struct's to have an owner. The advantage
>> +	  of this approach is that it allows for several independent memory
>> +	  based cgroup controllers to co-exist independently without too
>> +	  much space overhead
>> +
>> +	  This feature adds fork/exit overhead. So enable this only if
>> +	  you need resource controllers
> 
> Do we really want to offer this option to people?  It's rather a low-level
> thing and it's likely to cause more confusion than it's worth.  Remember
> that most kernels get to our users via kernel vendors - to what will they
> be setting this config option?
> 

I suspect that this kernel option will not be explicitly set it. This option
will be selected by other config options (memory controller, swap namespace,
revoke*)

>>  config CGROUP_MEM_RES_CTLR
>>  	bool "Memory Resource Controller for Control Groups"
>>  	depends on CGROUPS && RESOURCE_COUNTERS
>> +	select MM_OWNER
> 
> Presumably they'll always be setting it to "y" if they are enabling cgroups
> at all.
> 
>> --- linux-2.6.25-rc8/kernel/cgroup.c~memory-controller-add-mm-owner	2008-04-03 22:43:27.000000000 +0530
>> +++ linux-2.6.25-rc8-balbir/kernel/cgroup.c	2008-04-03 22:43:27.000000000 +0530
>> @@ -118,6 +118,7 @@ static int root_count;
>>   * be called.
>>   */
>>  static int need_forkexit_callback;
>> +static int need_mm_owner_callback;
> 
> I suppose these should be __read_mostly.
> 

Yes, good point. I'll send out v9 with this fix.

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