Date: Thu, 23 Apr 2009 14:37:30 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Theodore Tso <tytso@mit.edu>, Andrea Righi <righi.andrea@gmail.com>,
       randy.dunlap@oracle.com, Carl Henrik Lunde <chlunde@ping.uio.no>,
       Jens Axboe <jens.axboe@oracle.com>, eric.rannaud@gmail.com,
       Balbir Singh <balbir@linux.vnet.ibm.com>, fernando@oss.ntt.co.jp,
       dradford@bluehost.com, Gui@smtp1.linux-foundation.org,
       agk@sourceware.org, subrata@linux.vnet.ibm.com,
       Paul Menage <menage@google.com>, containers@lists.linux-foundation.org,
       linux-kernel@vger.kernel.org, dave@linux.vnet.ibm.com,
       matt@bluehost.com, roberto@unbit.it, ngupta@google.com
Subject: Re: [PATCH 9/9] ext3: do not throttle metadata and journal IO
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On Wed, 22 Apr 2009 21:58:25 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:
> >  Or at least that *someone* is
> > doing so and can perhaps document how all of these knobs interact.
> > After all, if they are going to be separate, and someone turns the I/O
> > throttling knob without bothering to turn the write throttling knob
> > --- what's going to happen?  An OOM?  That's not going to be very safe
> > or friendly for the sysadmin who plans to be configuring the system.
> 
> ... this problem.
> 
Considering that low-io-limit cgroup as very slow device,
the problem itself is not far from that the current kernel has.
If per-bdi-dirty-ratio works well, we can write per-cgroup-dirty-ratio, I think.
(I'll do if I find time.)

But yes, configuration-how-to should be documented, finally.
I hope sysadmins will not use some acrobatic configuration ;)


Thanks,
-Kame

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