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

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Date:	Wed, 20 Jan 2010 18:47:07 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.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 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.

Thanks,
-Kame



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