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Message-ID: <20081107145036.GF21884@redhat.com>
Date: Fri, 7 Nov 2008 09:50:36 -0500
From: Vivek Goyal <vgoyal@...hat.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: linux-kernel@...r.kernel.org,
containers@...ts.linux-foundation.org,
virtualization@...ts.linux-foundation.org, jens.axboe@...cle.com,
Hirokazu Takahashi <taka@...inux.co.jp>,
Ryo Tsuruta <ryov@...inux.co.jp>,
Andrea Righi <righi.andrea@...il.com>,
Satoshi UCHIDA <s-uchida@...jp.nec.com>,
Rik van Riel <riel@...hat.com>, fernando@....ntt.co.jp,
Jeff Moyer <jmoyer@...hat.com>, menage@...gle.com,
ngupta@...gle.com, Andrew Morton <akpm@...ux-foundation.org>,
balbir@...ux.vnet.ibm.com
Subject: Re: [patch 3/4] io controller: Core IO controller implementation
logic
On Fri, Nov 07, 2008 at 12:21:45PM +0900, KAMEZAWA Hiroyuki wrote:
> On Thu, 06 Nov 2008 10:30:25 -0500
> vgoyal@...hat.com wrote:
>
> >
> > o Core IO controller implementation
> >
> > Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
> >
>
> 2 comments after a quick look.
>
> - I don't recommend generic work queue. More stacked dependency between "work"
> is not good. (I think disk-driver uses "work" for their jobs.)
Sorry, I did not get this. Are you recommending that don't create a new
work queue, instead use existing work queue (say kblockd) to submit the bios
here?
I will look into it. I was little worried about a kblockd being overworked
in case of too many logical devices enabling IO controller.
>
> - It seems this bio-cgroup can queue the bio to infinite. Then, a process can submit
> io unitl cause OOM.
> (IIUC, Dirty bit of the page is cleared at submitting I/O.
> Then dirty_ratio can't help us.)
> please add "wait for congestion by sleeping" code in bio-cgroup.
Yes, you are right. I need to put some kind of control on max number of
bios I can queue on a cgroup and after crossing the limit, I should put
the submitting task to sleep. (Something like request descriptor kind of
flow control implememented by elevators).
Thanks
Vivek
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