From: Jens Axboe <axboe@suse.de>
To: Ben LaHaise <bcrl@redhat.com>
Cc: "Stephen C. Tweedie" <sct@redhat.com>,
Linus Torvalds <torvalds@transmeta.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Manfred Spraul <manfred@colorfullife.com>,
Steve Lord <lord@sgi.com>,
linux-kernel@vger.kernel.org,
kiobuf-io-devel@lists.sourceforge.net,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait
Date: Tue, 6 Feb 2001 19:00:18 +0100 [thread overview]
Message-ID: <20010206190018.E580@suse.de> (raw)
In-Reply-To: <20010206170506.H1167@redhat.com> <Pine.LNX.4.30.0102061225330.15204-100000@today.toronto.redhat.com>
In-Reply-To: <Pine.LNX.4.30.0102061225330.15204-100000@today.toronto.redhat.com>; from bcrl@redhat.com on Tue, Feb 06, 2001 at 12:37:26PM -0500
On Tue, Feb 06 2001, Ben LaHaise wrote:
> > The whole point of the post was that it is merging, not splitting,
> > which is troublesome. How are you going to merge requests without
> > having chains of scatter-gather entities each with their own
> > completion callbacks?
>
> Let me just emphasize what Stephen is pointing out: if requests are
> properly merged at higher layers, then merging is neither required nor
> desired. Traditionally, ext2 has not done merging because the underlying
> system doesn't support it. This leads to rather convoluted code for
> readahead which doesn't result in appropriately merged requests on
> indirect block boundries, and in fact leads to suboptimal performance.
> The only case I see where merging of requests can improve things is when
> dealing with lots of small files. But we already know that small files
> need to be treated differently (fe tail merging). Besides, most of the
> benefit of merging can be had by doing readaround for these small files.
Stephen already covered this point, the merging is not a problem
to deal with for read-ahead. The underlying system can easily
queue that in nice big chunks. Delayed allocation makes it
easier to to flush big chunks as well. I seem to recall the xfs people
having problems with the lack of merging causing a performance hit
on smaller I/O.
Of course merging doesn't have to happen in ll_rw_blk.
> As for io completion, can't we just issue seperate requests for the
> critical data and the readahead? That way for SCSI disks, the important
> io should be finished while the readahead can continue. Thoughts?
Priorities?
--
Jens Axboe
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next prev parent reply other threads:[~2001-02-06 18:01 UTC|newest]
Thread overview: 186+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-02-01 14:44 [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait /notify + callback chains bsuparna
2001-02-01 15:09 ` Christoph Hellwig
2001-02-01 16:08 ` Steve Lord
2001-02-01 16:49 ` Stephen C. Tweedie
2001-02-01 17:02 ` Christoph Hellwig
2001-02-01 17:34 ` Alan Cox
2001-02-01 17:49 ` Stephen C. Tweedie
2001-02-01 17:09 ` Chaitanya Tumuluri
2001-02-01 20:33 ` Christoph Hellwig
2001-02-01 20:56 ` Steve Lord
2001-02-01 20:59 ` Christoph Hellwig
2001-02-01 21:17 ` Steve Lord
2001-02-01 21:44 ` Stephen C. Tweedie
2001-02-01 22:07 ` Stephen C. Tweedie
2001-02-02 12:02 ` Christoph Hellwig
2001-02-05 12:19 ` Stephen C. Tweedie
2001-02-05 21:28 ` Ingo Molnar
2001-02-05 22:58 ` Stephen C. Tweedie
2001-02-05 23:06 ` Alan Cox
2001-02-05 23:16 ` Stephen C. Tweedie
2001-02-06 0:19 ` Manfred Spraul
2001-02-03 20:28 ` Linus Torvalds
2001-02-05 11:03 ` Stephen C. Tweedie
2001-02-05 12:00 ` Manfred Spraul
2001-02-05 15:03 ` Stephen C. Tweedie
2001-02-05 15:19 ` Alan Cox
2001-02-05 17:20 ` Stephen C. Tweedie
2001-02-05 17:29 ` Alan Cox
2001-02-05 18:49 ` Stephen C. Tweedie
2001-02-05 19:04 ` Alan Cox
2001-02-05 19:09 ` Linus Torvalds
2001-02-05 19:16 ` [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait Alan Cox
2001-02-05 19:28 ` Linus Torvalds
2001-02-05 20:54 ` Stephen C. Tweedie
2001-02-05 21:08 ` David Lang
2001-02-05 21:51 ` Alan Cox
2001-02-06 0:07 ` Stephen C. Tweedie
2001-02-06 17:00 ` Christoph Hellwig
2001-02-06 17:05 ` Stephen C. Tweedie
2001-02-06 17:14 ` Jens Axboe
2001-02-06 17:22 ` Christoph Hellwig
2001-02-06 18:26 ` Stephen C. Tweedie
2001-02-06 17:37 ` Ben LaHaise
2001-02-06 18:00 ` Jens Axboe [this message]
2001-02-06 18:09 ` Ben LaHaise
2001-02-06 19:35 ` Jens Axboe
2001-02-06 18:14 ` Linus Torvalds
2001-02-08 11:21 ` Andi Kleen
2001-02-08 14:11 ` Martin Dalecki
2001-02-08 17:59 ` Linus Torvalds
2001-02-06 18:18 ` Ingo Molnar
2001-02-06 18:25 ` Ben LaHaise
2001-02-06 18:35 ` Ingo Molnar
2001-02-06 18:54 ` Ben LaHaise
2001-02-06 18:58 ` Ingo Molnar
2001-02-06 19:11 ` Ben LaHaise
2001-02-06 19:32 ` Jens Axboe
2001-02-06 19:32 ` Ingo Molnar
2001-02-06 19:32 ` Linus Torvalds
2001-02-06 19:44 ` Ingo Molnar
2001-02-06 19:49 ` Ben LaHaise
2001-02-06 19:57 ` Ingo Molnar
2001-02-06 20:07 ` Jens Axboe
2001-02-06 20:25 ` Ben LaHaise
2001-02-06 20:41 ` Manfred Spraul
2001-02-06 20:50 ` Jens Axboe
2001-02-06 21:26 ` Manfred Spraul
2001-02-06 21:42 ` Linus Torvalds
2001-02-06 20:16 ` Marcelo Tosatti
2001-02-06 22:09 ` Jens Axboe
2001-02-06 22:26 ` Linus Torvalds
2001-02-06 21:13 ` Marcelo Tosatti
2001-02-06 23:26 ` Linus Torvalds
2001-02-07 23:17 ` select() returning busy for regular files [was Re: [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait] Pavel Machek
2001-02-08 13:57 ` Ben LaHaise
2001-02-08 17:52 ` Linus Torvalds
2001-02-08 15:06 ` [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait Ben LaHaise
2001-02-08 13:44 ` Marcelo Tosatti
2001-02-08 13:45 ` Marcelo Tosatti
2001-02-07 23:15 ` Pavel Machek
2001-02-08 13:22 ` Stephen C. Tweedie
2001-02-08 12:03 ` Marcelo Tosatti
2001-02-08 15:46 ` Mikulas Patocka
2001-02-08 14:05 ` Marcelo Tosatti
2001-02-08 16:11 ` Mikulas Patocka
2001-02-08 14:44 ` Marcelo Tosatti
2001-02-08 16:57 ` Rik van Riel
2001-02-08 17:13 ` James Sutherland
2001-02-08 18:38 ` Linus Torvalds
2001-02-09 12:17 ` Martin Dalecki
2001-02-08 15:55 ` Jens Axboe
2001-02-08 18:09 ` Linus Torvalds
2001-02-08 14:52 ` Mikulas Patocka
2001-02-08 19:50 ` Stephen C. Tweedie
2001-02-11 21:30 ` Pavel Machek
2001-02-06 21:57 ` Manfred Spraul
2001-02-06 22:13 ` Linus Torvalds
2001-02-06 22:26 ` Andre Hedrick
2001-02-06 20:49 ` Jens Axboe
2001-02-07 0:21 ` Stephen C. Tweedie
2001-02-07 0:25 ` Ingo Molnar
2001-02-07 0:36 ` Stephen C. Tweedie
2001-02-07 0:50 ` Linus Torvalds
2001-02-07 1:49 ` Stephen C. Tweedie
2001-02-07 2:37 ` Linus Torvalds
2001-02-07 14:52 ` Stephen C. Tweedie
2001-02-07 19:12 ` Richard Gooch
2001-02-07 20:03 ` Stephen C. Tweedie
2001-02-07 1:51 ` Jeff V. Merkey
2001-02-07 1:01 ` Ingo Molnar
2001-02-07 1:59 ` Jeff V. Merkey
2001-02-07 1:02 ` Jens Axboe
2001-02-07 1:19 ` Linus Torvalds
2001-02-07 1:39 ` Jens Axboe
2001-02-07 1:45 ` Linus Torvalds
2001-02-07 1:55 ` Jens Axboe
2001-02-07 9:10 ` David Howells
2001-02-07 12:16 ` Stephen C. Tweedie
2001-02-07 2:00 ` Jeff V. Merkey
2001-02-07 1:06 ` Ingo Molnar
2001-02-07 1:09 ` Jens Axboe
2001-02-07 1:11 ` Ingo Molnar
2001-02-07 1:26 ` Linus Torvalds
2001-02-07 2:07 ` Jeff V. Merkey
2001-02-07 1:08 ` Jens Axboe
2001-02-07 2:08 ` Jeff V. Merkey
2001-02-07 1:42 ` Jeff V. Merkey
2001-02-07 0:42 ` Linus Torvalds
2001-02-07 0:35 ` Jens Axboe
2001-02-07 0:41 ` Linus Torvalds
2001-02-07 1:27 ` Stephen C. Tweedie
2001-02-07 1:40 ` Linus Torvalds
2001-02-12 10:07 ` Jamie Lokier
2001-02-06 20:26 ` Linus Torvalds
2001-02-06 20:25 ` Christoph Hellwig
2001-02-06 20:35 ` Ingo Molnar
2001-02-06 19:05 ` Marcelo Tosatti
2001-02-06 20:59 ` Ingo Molnar
2001-02-06 21:20 ` Steve Lord
2001-02-07 18:27 ` Christoph Hellwig
2001-02-06 20:59 ` Linus Torvalds
2001-02-07 18:26 ` Christoph Hellwig
2001-02-07 18:36 ` Linus Torvalds
2001-02-07 18:44 ` Christoph Hellwig
2001-02-08 0:34 ` Neil Brown
2001-02-06 19:46 ` Ingo Molnar
2001-02-06 20:16 ` Ben LaHaise
2001-02-06 20:22 ` Ingo Molnar
2001-02-06 19:20 ` Linus Torvalds
2001-02-06 0:31 ` Roman Zippel
2001-02-06 1:01 ` Linus Torvalds
2001-02-06 9:22 ` Roman Zippel
2001-02-06 9:30 ` Ingo Molnar
2001-02-06 1:08 ` David S. Miller
2001-02-05 22:09 ` [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait /notify + callback chains Ingo Molnar
2001-02-05 16:56 ` Linus Torvalds
2001-02-05 17:27 ` [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait Alan Cox
2001-02-05 16:36 ` [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait /notify + callback chains Linus Torvalds
2001-02-05 19:08 ` Stephen C. Tweedie
2001-02-01 17:49 ` Christoph Hellwig
2001-02-01 17:58 ` Alan Cox
2001-02-01 18:32 ` Rik van Riel
2001-02-01 18:59 ` yodaiken
2001-02-01 19:33 ` Stephen C. Tweedie
2001-02-01 18:51 ` bcrl
2001-02-01 16:16 ` Stephen C. Tweedie
2001-02-01 17:05 ` Christoph Hellwig
2001-02-01 17:09 ` Christoph Hellwig
2001-02-01 17:41 ` Stephen C. Tweedie
2001-02-01 18:14 ` Christoph Hellwig
2001-02-01 18:25 ` Alan Cox
2001-02-01 18:39 ` Rik van Riel
2001-02-01 18:46 ` [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait Alan Cox
2001-02-01 18:48 ` [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait /notify + callback chains Christoph Hellwig
2001-02-01 18:57 ` Alan Cox
2001-02-01 19:00 ` Christoph Hellwig
2001-02-01 19:32 ` Stephen C. Tweedie
2001-02-01 20:46 ` Christoph Hellwig
2001-02-01 21:25 ` Stephen C. Tweedie
2001-02-02 11:51 ` Christoph Hellwig
2001-02-02 14:04 ` Stephen C. Tweedie
2001-02-02 4:18 ` bcrl
2001-02-02 12:12 ` Christoph Hellwig
2001-02-01 20:04 ` Chaitanya Tumuluri
[not found] <CA2569E9.004A4E23.00@d73mta05.au.ibm.com>
2001-02-04 16:46 ` [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait Alan Cox
2001-02-12 14:56 bsuparna
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