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Date: Fri, 17 Apr 2009 11:55:56 +0200
From: Andrea Righi <righi.andrea@gmail.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Menage <menage@google.com>, Balbir Singh <balbir@linux.vnet.ibm.com>,
       Gui Jianfeng <guijianfeng@cn.fujitsu.com>, agk@sourceware.org,
       akpm@linux-foundation.org, axboe@kernel.dk, baramsori72@gmail.com,
       Carl Henrik Lunde <chlunde@ping.uio.no>, dave@linux.vnet.ibm.com,
       Divyesh Shah <dpshah@google.com>, eric.rannaud@gmail.com,
       fernando@oss.ntt.co.jp, Hirokazu Takahashi <taka@valinux.co.jp>,
       Li Zefan <lizf@cn.fujitsu.com>, matt@bluehost.com,
       dradford@bluehost.com, ngupta@google.com, randy.dunlap@oracle.com,
       roberto@unbit.it, Ryo Tsuruta <ryov@valinux.co.jp>,
       Satoshi UCHIDA <s-uchida@ap.jp.nec.com>, subrata@linux.vnet.ibm.com,
       yoshikawa.takuya@oss.ntt.co.jp, containers@lists.linux-foundation.org,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/9] io-throttle documentation
Message-ID: <20090417095555.GD8689@linux>
Mail-Followup-To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	Paul Menage <menage@google.com>,
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On Fri, Apr 17, 2009 at 10:24:17AM +0900, KAMEZAWA Hiroyuki wrote:
> On Tue, 14 Apr 2009 22:21:12 +0200
> Andrea Righi <righi.andrea@gmail.com> wrote:
> 
> > +Example:
> > +* Create an association between an io-throttle group and a bio-cgroup group
> > +  with "bio" and "blockio" subsystems mounted in different mount points:
> > +  # mount -t cgroup -o bio bio-cgroup /mnt/bio-cgroup/
> > +  # cd /mnt/bio-cgroup/
> > +  # mkdir bio-grp
> > +  # cat bio-grp/bio.id
> > +  1
> > +  # mount -t cgroup -o blockio blockio /mnt/io-throttle
> > +  # cd /mnt/io-throttle
> > +  # mkdir foo
> > +  # echo 1 > foo/blockio.bio_id
> 
> Why do we need multiple cgroups at once to track I/O ?
> Seems complicated to me.
> 
> Thanks,
> -Kame

I totally agree. I could easily merge the bio-cgroup functionality in
io-throttle or implement this as an infrastructure framework, using a
single controller and remove this complication.

For now, since the decisions on IO controllers are not definitive at
all, I privileged flexibility and I simply decided to be a plain user of
bio-cgroup to quickly adapt my patch to the future bio-cgroup
development.

Thanks,
-Andrea