From: Davide Libenzi <davidel@xmailserver.org>
To: David Schwartz <davids@webmaster.com>
Cc: linux-kernel@vger.kernel.org
Subject: RE: Why use threads ( was: Alan Cox quote?)
Date: Thu, 21 Jun 2001 09:10:50 -0700 (PDT) [thread overview]
Message-ID: <XFMail.20010621091050.davidel@xmailserver.org> (raw)
In-Reply-To: <NCBBLIEPOCNJOAEKBEAKCEPBPPAA.davids@webmaster.com>
On 21-Jun-2001 David Schwartz wrote:
> Okay, let's compare two servers.
>
> Server one is handling 10 file descriptors. The cost of a single call to
> poll is 3 microseconds. Assume that the server is coded to get back to
> 'poll' as quickly as it can, but due to load the code manages to call 'poll'
> every 100 microseconds, so the overhead of poll is 3% of the available CPU.
Maybe You read a paper by Richard Gooch but I think You read it wrong :
http://www.atnf.csiro.au/~rgooch/linux/docs/io-events.html
<quote>
The kernel has to scan your array of FDs and check which ones are active. This
takes approximately 3 microseconds (3 us) per FD on a Pentium 100 running Linux
2.1.x. Now you might think that 3 us is quite fast, but consider if you have an
array of 1000 FDs. This is now 3 milliseconds (3 ms), which is 30% of your
timeslice (each timeslice is 10 ms). If it happens that there is initially no
activity and you specified a timeout, the kernel will have to perform a second
scan after some activity occurs or the syscall times out. Ouch! If you have an
even bigger application (like a large http server), you can easily have 10000
FDs. Scanning times will then take 30 ms, which is three timeslices! This is
just way too much.
</quote>
Anyway there's no need to continue this ( quite long ) thread.
- Davide
next prev parent reply other threads:[~2001-06-21 16:08 UTC|newest]
Thread overview: 149+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-06-19 14:53 accounting for threads Dan Kegel
2001-06-19 14:57 ` J . A . Magallon
2001-06-19 15:44 ` ognen
2001-06-19 15:58 ` Alan Cox quote? (was: Re: accounting for threads) Dan Kegel
2001-06-19 16:02 ` Ben Pfaff
2001-06-19 16:09 ` Larry McVoy
2001-06-19 16:26 ` Matthew Kirkwood
2001-06-19 16:52 ` Larry McVoy
2001-06-19 18:18 ` Rob Landley
2001-06-19 23:31 ` Timur Tabi
2001-06-20 11:52 ` Rob Landley
2001-06-20 21:20 ` Albert D. Cahalan
2001-06-20 18:12 ` Rob Landley
2001-06-20 23:28 ` Dan Podeanu
2001-06-21 0:42 ` D. Stimits
2001-06-20 20:18 ` Rob Landley
2001-06-21 1:57 ` D. Stimits
2001-06-21 14:46 ` Idea: Patches-from-linus mailing list? (Was Re: Alan Cox quote? (was: Re: accounting for threads)) Rob Landley
2001-06-21 14:02 ` Alan Cox quote? (was: Re: accounting for threads) Jesse Pollard
2001-06-21 14:18 ` Rob Landley
2001-06-22 14:46 ` Mikulas Patocka
2001-06-22 13:29 ` Rob Landley
2001-06-24 21:41 ` J . A . Magallon
2001-06-24 16:55 ` Rob Landley
2001-06-24 22:30 ` J . A . Magallon
2001-06-24 18:21 ` Rob Landley
2001-06-25 13:48 ` J . A . Magallon
2001-06-24 22:39 ` Steven Walter
2001-06-24 23:50 ` Larry McVoy
2001-06-24 20:24 ` Rob Landley
2001-06-25 0:05 ` J . A . Magallon
2001-06-25 0:32 ` Gerhard Mack
2001-06-25 0:59 ` Davide Libenzi
2001-06-25 2:18 ` Galen Hancock
2001-06-20 14:59 ` Matthias Urlichs
2001-06-20 19:14 ` Victor Yodaiken
2001-06-20 21:01 ` RE:Why use threads ( was: Alan Cox quote?) David Schwartz
2001-06-20 21:26 ` Why " Victor Yodaiken
2001-06-20 22:18 ` David Schwartz
2001-06-20 22:41 ` Davide Libenzi
2001-06-20 22:47 ` [OT] " Jeff Garzik
2001-06-21 0:21 ` David Schwartz
2001-06-21 0:56 ` Davide Libenzi
2001-06-21 1:32 ` David Schwartz
2001-06-21 2:22 ` Davide Libenzi
2001-06-21 2:43 ` David Schwartz
2001-06-21 16:10 ` Davide Libenzi [this message]
2001-06-21 19:55 ` Marco Colombo
2001-06-20 22:43 ` Mike Castle
2001-06-21 1:43 ` David Schwartz
2001-06-19 17:10 ` Alan Cox quote? (was: Re: accounting for threads) Matti Aarnio
2001-06-19 17:20 ` Mike Castle
2001-06-19 17:37 ` Larry McVoy
2001-06-19 17:45 ` Mike Castle
2001-06-19 19:38 ` Georg Nikodym
2001-06-19 19:56 ` Michael Meissner
2001-06-19 17:53 ` Steve Underwood
2001-06-19 19:01 ` Alan Cox
2001-06-20 2:57 ` Michael Rothwell
2001-06-20 3:04 ` Larry McVoy
2001-06-20 3:38 ` John R Lenton
2001-06-20 10:21 ` john slee
2001-06-20 18:08 ` Larry McVoy
2001-06-20 16:21 ` Davide Libenzi
2001-06-20 9:14 ` Alan Cox
2001-06-22 2:36 ` Michael Rothwell
2001-06-19 18:08 ` Georg Nikodym
2001-06-19 20:57 ` David S. Miller
2001-06-19 21:15 ` David S. Miller
2001-06-20 0:04 ` Chris Ricker
2001-06-20 0:59 ` Robert Love
2001-06-19 17:36 ` Jonathan Lundell
2001-06-19 17:41 ` Larry McVoy
2001-06-19 21:11 ` Jonathan Lundell
2001-06-19 23:56 ` Jonathan Lundell
2001-06-20 0:19 ` Mike Castle
2001-06-20 0:28 ` Larry McVoy
2001-06-20 1:30 ` Ben Greear
2001-06-20 2:14 ` Mike Castle
2001-06-20 9:00 ` Henning P. Schmiedehausen
2001-06-20 11:25 ` [OT] Threads, inelegance, and Java Aaron Lehmann
2001-06-20 11:25 ` Rob Landley
2001-06-20 17:36 ` Martin Dalecki
2001-06-20 19:27 ` Mike Harrold
2001-06-20 17:46 ` Rob Landley
2001-06-20 19:53 ` Martin Dalecki
2001-06-20 17:53 ` Rob Landley
2001-06-21 7:45 ` Albert D. Cahalan
2001-06-20 20:16 ` Pete Zaitcev
2001-06-20 22:05 ` Alan Cox
[not found] ` <20010621000725.A24672@werewolf.able.es>
2001-06-20 19:15 ` Rob Landley
2001-06-21 3:13 ` Pete Zaitcev
2001-06-21 13:59 ` Rob Landley
2001-06-21 9:40 ` Jonathan Morton
2001-06-21 16:48 ` Adam Sampson
2001-06-20 15:12 ` Ben Greear
2001-06-20 15:44 ` Russell Leighton
2001-06-20 16:32 ` Davide Libenzi
2001-06-20 16:54 ` Russell Leighton
2001-06-20 17:03 ` Tony Hoyle
2001-06-20 15:10 ` Rob Landley
2001-06-20 20:23 ` Tony Hoyle
2001-06-21 8:12 ` Henning P. Schmiedehausen
2001-06-20 20:40 ` Richard B. Johnson
2001-06-20 20:48 ` Tony Hoyle
2001-06-20 21:00 ` Daniel Phillips
2001-06-20 21:06 ` Richard B. Johnson
2001-06-20 18:14 ` Henning P. Schmiedehausen
2001-06-20 16:53 ` Larry McVoy
2001-06-20 12:36 ` Rob Landley
2001-06-20 21:14 ` Aaron Lehmann
2001-06-20 18:09 ` Henning P. Schmiedehausen
2001-06-20 19:05 ` William T Wilson
2001-06-19 16:02 ` Alan Cox quote? (was: Re: accounting for threads) David S. Miller
2001-06-19 16:12 ` Padraig Brady
2001-06-19 19:10 ` bert hubert
2001-06-19 19:18 ` Alan Cox
2001-06-19 19:32 ` bert hubert
2001-06-19 19:43 ` Alexander Viro
2001-06-20 15:22 ` Jes Sorensen
2001-06-20 15:33 ` Alexander Viro
2001-06-20 15:59 ` Threads are processes that share more bert hubert
2001-06-20 16:15 ` Alexander Viro
2001-06-20 18:48 ` Martin Devera
2001-06-20 19:19 ` Unknown PCI Net Device Greg Ingram
2001-06-20 22:53 ` Andreas Dilger
2001-06-20 22:56 ` Jeff Garzik
2001-06-20 23:00 ` Alan Cox
2001-06-20 22:08 ` Threads are processes that share more Stephen Satchell
2001-06-20 22:14 ` ognen
2001-06-20 23:10 ` J . A . Magallon
2001-06-24 23:47 ` Larry McVoy
2001-06-25 2:23 ` David S. Miller
2001-06-20 16:39 ` Alan Cox quote? (was: Re: accounting for threads) george anzinger
2001-06-20 18:35 ` Alexander Viro
2001-06-21 4:11 ` Rusty Russell
2001-06-21 23:37 ` Alexander Viro
2001-06-21 23:55 ` Alexander Viro
2001-06-22 14:53 ` Richard Gooch
2001-06-20 16:40 ` Jes Sorensen
2001-06-20 20:09 ` Rob Landley
2001-06-20 19:05 ` Victor Yodaiken
2001-06-20 14:35 ` Mike Porter
2001-06-20 11:56 ` Rob Landley
2001-06-19 18:01 ` Alan Cox quote? Kai Henningsen
2001-06-19 18:49 ` Larry McVoy
2001-06-19 20:12 ` Henning P. Schmiedehausen
2001-06-19 21:12 ` Richard Gooch
2001-06-19 22:50 ` Henning P. Schmiedehausen
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