linux-kernel - Re: [PATCH mmotm] memcg use generic percpu allocator instead of private one

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Date:	Wed, 20 Jan 2010 18:16:43 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	kirill@...temov.name
Subject: Re: [PATCH mmotm] memcg use generic percpu allocator instead of private
 one

On Wednesday 20 January 2010 03:17 PM, KAMEZAWA Hiroyuki wrote:
> On Wed, 20 Jan 2010 15:07:52 +0530
> Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> 
>> On Wednesday 20 January 2010 12:48 PM, KAMEZAWA Hiroyuki wrote:
>>> This patch is onto mmotm Jan/15.
>>> =
>>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>>
>>> When per-cpu counter for memcg was implemneted, dynamic percpu allocator
>>> was not very good. But now, we have good one and useful macros.
>>> This patch replaces memcg's private percpu counter implementation with
>>> generic dynamic percpu allocator and macros.
>>>
>>> The benefits are
>>> 	- We can remove private implementation.
>>> 	- The counters will be NUMA-aware. (Current one is not...)
>>> 	- This patch reduces sizeof(struct mem_cgroup). Then,
>>> 	  struct mem_cgroup may be fit in page size on small config.
>>>
>>> By this, size of text is reduced.
>>>  [Before]
>>>  [kamezawa@...extal mmotm-2.6.33-Jan15]$ size mm/memcontrol.o
>>>    text    data     bss     dec     hex filename
>>>   24373    2528    4132   31033    7939 mm/memcontrol.o
>>>  [After]
>>>  [kamezawa@...extal mmotm-2.6.33-Jan15]$ size mm/memcontrol.o
>>>    text    data     bss     dec     hex filename
>>>   23913    2528    4132   30573    776d mm/memcontrol.o
>>>
>>> This includes no functional changes.
>>>
>>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>
>>
>> Before review, could you please post parallel pagefault data on a large
>> system, since root now uses these per cpu counters and its overhead is
>> now dependent on these counters. Also the data read from root cgroup is
>> also dependent on these, could you make sure that is not broken.
>>
> No number difference before/after patch on my SMP quick test.
> But I don't have NUMA. Could you test on NUMA ?
> 
> I'll measure again tomorrow if I have machine time.

I'll do the same as well if possible.

Balbir
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