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Date: Fri, 17 Apr 2009 11:40:42 +0200
From: Andrea Righi <righi.andrea@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: menage@google.com, balbir@linux.vnet.ibm.com, guijianfeng@cn.fujitsu.com,
       kamezawa.hiroyu@jp.fujitsu.com, agk@sourceware.org, axboe@kernel.dk,
       baramsori72@gmail.com, chlunde@ping.uio.no, dave@linux.vnet.ibm.com,
       dpshah@google.com, eric.rannaud@gmail.com, fernando@oss.ntt.co.jp,
       taka@valinux.co.jp, lizf@cn.fujitsu.com, matt@bluehost.com,
       dradford@bluehost.com, ngupta@google.com, randy.dunlap@oracle.com,
       roberto@unbit.it, ryov@valinux.co.jp, 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 3/9] bio-cgroup controller
Message-ID: <20090417094042.GB8689@linux>
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References: <1239740480-28125-1-git-send-email-righi.andrea@gmail.com> <1239740480-28125-4-git-send-email-righi.andrea@gmail.com> <20090416152937.b2188370.akpm@linux-foundation.org>
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On Thu, Apr 16, 2009 at 03:29:37PM -0700, Andrew Morton wrote:
> On Tue, 14 Apr 2009 22:21:14 +0200
> Andrea Righi <righi.andrea@gmail.com> wrote:
> 
> > Subject: [PATCH 3/9] bio-cgroup controller
> 
> Sorry, but I have to register extreme distress at the name of this. 
> The term "bio" is well-established in the kernel and here we have a new
> definition for the same term: "block I/O".
> 
> "bio" was a fine term for you to have chosen from the user's
> perspective, but from the kernel developer perspective it is quite
> horrid.  The patch adds a vast number of new symbols all into the
> existing "bio_" namespace, many of which aren't related to `struct bio'
> at all.
> 
> At least, I think that's what's happening.  Perhaps the controller
> really _is_ designed to track `struct bio'?  If so, that's an odd thing
> to tell userspace about.
> 
> 
> > The controller bio-cgroup is used by io-throttle to track writeback IO
> > and for properly apply throttling.
> 
> Presumably it tracks all forms of block-based I/O and not just delayed
> writeback.

For the general case bio-cgroup tracks all forms of block IO, in this
particular case (only for the io-throttle controller) I used bio-cgroup
to track writeback IO. Synchronous IO is accounted directly in
submit_bio() and throttled as well, imposing explicit sleeps via
schedule_timeout_killable().

-Andrea
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