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From: Linus Torvalds <torvalds@transmeta.com>
To: Marcelo Tosatti <marcelo@conectiva.com.br>
Cc: Jens Axboe <axboe@suse.de>,
	Manfred Spraul <manfred@colorfullife.com>,
	Ben LaHaise <bcrl@redhat.com>, Ingo Molnar <mingo@elte.hu>,
	"Stephen C. Tweedie" <sct@redhat.com>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>, Steve Lord <lord@sgi.com>,
	Linux Kernel List <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 15:26:44 -0800 (PST)	[thread overview]
Message-ID: <Pine.LNX.4.10.10102061516570.1972-100000@penguin.transmeta.com> (raw)
In-Reply-To: <Pine.LNX.4.21.0102061900060.23574-100000@freak.distro.conectiva>



On Tue, 6 Feb 2001, Marcelo Tosatti wrote:
> 
> Its arguing against making a smart application block on the disk while its
> able to use the CPU for other work.

There are currently no other alternatives in user space. You'd have to
create whole new interfaces for aio_read/write, and ways for the kernel to
inform user space that "now you can re-try submitting your IO".

Could be done. But that's a big thing.

> An application which sets non blocking behavior and busy waits for a
> request (which seems to be your argument) is just stupid, of course.

Tell me what else it could do at some point? You need something like
select() to wait on it. There are no such interfaces right now...

(besides, latency would suck. I bet you're better off waiting for the
requests if they are all used up. It takes too long to get deep into the
kernel from user space, and you cannot use the exclusive waiters with its
anti-herd behaviour etc).

Simple rule: if you want to optimize concurrency and avoid waiting - use
several processes or threads instead. At which point you can get real work
done on multiple CPU's, instead of worrying about what happens when you
have to wait on the disk.

		Linus

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  reply	other threads:[~2001-02-06 23:27 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
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 [this message]
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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