From: Christoph Hellwig <hch@lst.de>
To: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>,
xfs@oss.sgi.com, hch@infradead.org,
Jeff Moyer <jmoyer@redhat.com>, Al Viro <viro@ZenIV.linux.org.uk>,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/2] direct-io: Implement generic deferred AIO completions
Date: Thu, 1 Aug 2013 10:17:20 +0200 [thread overview]
Message-ID: <20130801081720.GA29497@lst.de> (raw)
In-Reply-To: <20130712004421.GE3438@dastard>
On Fri, Jul 12, 2013 at 10:44:21AM +1000, Dave Chinner wrote:
> On Thu, Jul 11, 2013 at 12:02:18AM +0200, Jan Kara wrote:
> > From: Christoph Hellwig <hch@infradead.org>
> >
> > Add support to the core direct-io code to defer AIO completions to user
> > context using a workqueue. This replaces opencoded and less efficient
> > code in XFS and ext4 and will be needed to properly support O_(D)SYNC
> > for AIO.
>
> I don't see how this is any more efficient than the deferral
> that XFS already does for direct IO completion - it just changes
> what queues IO for completions. And on that topic:
It avoided a memory allocation for each dіrect I/O write.
> FWIW, in XFS we queue unwritten extent conversion completions on a
> different workqueue to EOF size update completions because the
> latter are small, fast and rarely require IO or get blocked. The
> data IO completion workqueue for EOF updates has the same
> concurrency and depth as the unwritten extent work queue (i.e. 256
> workers per cpu per superblock). So pushing all of this DIO and EOF
> completion work into a single threaded global workqueue that can
> block in every IO completion doesn't seem like a very smart idea to
> me...
Currently the direct I/O code doesn't support async extending writes.
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next prev parent reply other threads:[~2013-08-01 8:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-10 22:02 [PATCH 1/2] direct-io: Implement generic deferred AIO completions Jan Kara
2013-07-10 22:02 ` [PATCH 2/2] direct-io: Handle O_(D)SYNC AIO Jan Kara
2013-07-12 0:44 ` [PATCH 1/2] direct-io: Implement generic deferred AIO completions Dave Chinner
2013-07-16 21:00 ` Jan Kara
2013-08-12 16:14 ` Jan Kara
2013-08-13 0:11 ` Dave Chinner
2013-08-01 8:17 ` Christoph Hellwig [this message]
-- strict thread matches above, loose matches on Subject: below --
2013-08-14 9:10 [PATCH 0/2 v2] Fix O_SYNC AIO DIO Jan Kara
2013-08-14 9:10 ` [PATCH 1/2] direct-io: Implement generic deferred AIO completions Jan Kara
2013-09-04 13:04 [PATCH 0/2 v3] Fix O_SYNC AIO DIO Jan Kara
2013-09-04 13:04 ` [PATCH 1/2] direct-io: Implement generic deferred AIO completions Jan Kara
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