Date: Tue, 19 Aug 2008 21:46:35 +0900 (JST)
Message-Id: <20080819.214635.70071441.taka@valinux.co.jp>
To: balbir@linux.vnet.ibm.com
Cc: ryov@valinux.co.jp, kamezawa.hiroyu@jp.fujitsu.com,
       xen-devel@lists.xensource.com, containers@lists.linux-foundation.org,
       linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org,
       dm-devel@redhat.com, agk@sourceware.org, xemul@openvz.org,
       fernando@oss.ntt.co.jp
Subject: Re: [PATCH 4/7] bio-cgroup: Split the cgroup memory subsystem into
 two parts
From: Hirokazu Takahashi <taka@valinux.co.jp>
In-Reply-To: <48AA4594.1000908@linux.vnet.ibm.com>
References: <20080818103938.8b4e8bfa.kamezawa.hiroyu@jp.fujitsu.com>
	<20080819.122811.59660409.ryov@valinux.co.jp>
	<48AA4594.1000908@linux.vnet.ibm.com>
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Hi,

> >> I'm now writing remove-lock-page-cgroup patches. it works well.
> >> please wait for a while...
> > 
> > I'm looking forward to those patches.
> > 
> > By the way, I'm glad if memory-cgroup has a feature which can make a
> > page_cgroup move between cgroups with small overhead. It makes
> > bio-cgroup improve the accuracy of tracking down pages.
> 
> Page movement can be a very expensive operation and is proportional to the size
> of the control group. I think movement should be an optional feature, if we ever
> add it.

Yes, we should avoid moving pages as far as it is balanced fairly well
between groups.

But I want to move pages between bio-cgoups in case it started charging
quite a few I/O requests to a wrong bio-cgroup. I think it will be okay
if pages moves between bio-cgroups, but they don't need to move between
memory cgroups. I know the latter is really heavy and the effect seems
to be so limited.

Thanks,
Hirokazu Takahashi.
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