linux-kernel - Re: [RFC PATCH] page_cgroup: Reduce allocation overhead for page_cgroup array for CONFIG

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Message-ID: <20110224093304.GA20922@tiehlicka.suse.cz>
Date:	Thu, 24 Feb 2011 10:33:04 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	linux-mm@...ck.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] page_cgroup: Reduce allocation overhead for
 page_cgroup array for CONFIG_SPARSEMEM

On Wed 23-02-11 10:19:22, Dave Hansen wrote:
> On Wed, 2011-02-23 at 16:10 +0100, Michal Hocko wrote:
> > We can reduce this internal fragmentation by splitting the single
> > page_cgroup array into more arrays where each one is well kmalloc
> > aligned. This patch implements this idea. 
> 
> How about using alloc_pages_exact()?  These things aren't allocated
> often enough to really get most of the benefits of being in a slab.

Yes, you are right. alloc_pages_exact (which I wasn't aware of) is much
simpler solution and it gets comparable results. I will prepare the
patch for review.

Thanks for pointing this out.
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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