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Message-Id: <20080918140043.9ce73713.kamezawa.hiroyu@jp.fujitsu.com>
Date: Thu, 18 Sep 2008 14:00:43 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: balbir@...ux.vnet.ibm.com
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Dave Hansen <dave@...ux.vnet.ibm.com>,
Nick Piggin <nickpiggin@...oo.com.au>, hugh@...itas.com,
menage@...gle.com, xemul@...nvz.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [RFC][PATCH] Remove cgroup member from struct page (v3)
On Wed, 17 Sep 2008 20:57:54 -0700
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> Andrew Morton wrote:
> > someone somewhere decided that (Aa + Bb) / Cc < 1.0. What are the values
> > of A, B and C and where did they come from? ;)
> >
> > (IOW, your changelog is in the category "sucky", along with 90% of the others)
>
> Yes, I agree, to be honest we discussed the reasons on the mailing list and
> those should go to the changelog. I'll do that in the next version of the
> patches. These are early RFC patches, but the changelog does suck.
>
IIRC, (Aa + Bb) / Cc < 1.0 discussion was following.
Because we have to maintain pointer to page_cgroup in radix-tree (ZONE_NORMAL)
1. memory usage will increase when memory cgroup is enabled.
The amount memory usage increase just depends on the height of radix-tree.
2. memory usage will decrease when memory cgroup is disabled.
This saves 4bytes per 4096bytes. (on x86-32)
Thanks,
-Kame
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