linux-kernel - Re: dm-ioband + bio-cgroup benchmarks

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Message-Id: <20080924.193414.22923673.taka@valinux.co.jp>
Date:	Wed, 24 Sep 2008 19:34:14 +0900 (JST)
From:	Hirokazu Takahashi <taka@...inux.co.jp>
To:	vgoyal@...hat.com
Cc:	ryov@...inux.co.jp, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com, containers@...ts.linux-foundation.org,
	virtualization@...ts.linux-foundation.org,
	xen-devel@...ts.xensource.com, fernando@....ntt.co.jp,
	balbir@...ux.vnet.ibm.com, xemul@...nvz.org, agk@...rceware.org,
	righi.andrea@...il.com, jens.axboe@...cle.com
Subject: Re: dm-ioband + bio-cgroup benchmarks

Hi,

> > It's possible the algorithm of dm-ioband can be placed in the block layer
> > if it is really a big problem.
> > But I doubt it can control every control block I/O as we wish since
> > the interface the cgroup supports is quite poor.
> 
> Had a question regarding cgroup interface. I am assuming that in a system,
> one will be using other controllers as well apart from IO-controller.
> Other controllers will be using cgroup as a grouping mechanism.
> Now coming up with additional grouping mechanism for only io-controller seems
> little odd to me. It will make the job of higher level management software
> harder.
> 
> Looking at the dm-ioband grouping examples given in patches, I think cases
> of grouping based  in pid, pgrp, uid and kvm can be handled by creating right
> cgroup and making sure applications are launched/moved into right cgroup by
> user space tools. 

Grouping in pid, pgrp and uid is not the point, which I've been thinking
can be replaced with cgroup once the implementation of bio-cgroup is done.

I think problems of cgroup are that they can't support lots of storages
and hotplug devices, it just handle them as if they were just one resource.
I don't insist the interface of dm-ioband is the best. I just hope the
cgroup infrastructure support this kind of resources.

> I think keeping grouping mechanism in line with rest of the controllers
> should help because a uniform grouping mechanism should make life simpler.
> 
> I am not very sure about moving dm-ioband algorithm in block layer. Looks
> like it will make life simpler at least in terms of configuration. 


Thanks,
Hirokazu Takahashi.
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