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From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Robert Hancock <hancockr@shaw.ca>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: sched_yield() makes OpenLDAP slow
Date: Sat, 20 Aug 2005 14:18:46 +1000	[thread overview]
Message-ID: <4306AF26.3030106@yahoo.com.au> (raw)
In-Reply-To: <4306A176.3090907@shaw.ca>

Robert Hancock wrote:

> 
> I fail to see how sched_yield is going to be very helpful in this 
> situation. Since that call can sleep from a range of time ranging from 
> zero to a long time, it's going to give unpredictable results.
> 

Well, not sleep technically, but yield the CPU for some undefined
amount of time.

> It seems to me that this sort of thing is why we have POSIX pthread 
> synchronization primitives.. sched_yield is basically there for a 
> process to indicate that "what I'm doing doesn't matter much, let other 
> stuff run". Any other use of it generally constitutes some kind of hack.
> 

In SCHED_OTHER mode, you're right, sched_yield is basically meaningless.

In a realtime system, there is a very well defined and probably useful
behaviour.

Eg. If 2 SCHED_FIFO processes are running at the same priority, One can
call sched_yield to deterministically give the CPU to the other guy.

-- 
SUSE Labs, Novell Inc.

Send instant messages to your online friends http://au.messenger.yahoo.com 

  reply	other threads:[~2005-08-20  4:18 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <4D8eT-4rg-31@gated-at.bofh.it>
2005-08-20  3:20 ` sched_yield() makes OpenLDAP slow Robert Hancock
2005-08-20  4:18   ` Nick Piggin [this message]
2005-08-20 18:38     ` Howard Chu
2005-08-20 20:57       ` Lee Revell
2005-08-20 21:24         ` Howard Chu
2005-08-21  0:36           ` Nick Piggin
2005-08-21 11:33           ` Nikita Danilov
2005-08-22  8:06             ` Howard Chu
2005-08-20 21:50       ` Lee Revell
2005-08-21  1:04       ` Robert Hancock
2005-08-22 11:44         ` linux-os (Dick Johnson)
2005-08-22 14:26           ` Robert Hancock
2005-08-23 11:17             ` linux-os (Dick Johnson)
2005-08-23 12:07               ` Denis Vlasenko
2005-08-24  3:37                 ` Lincoln Dale
2006-01-24 22:59 e100 oops on resume Stefan Seyfried
2006-01-24 23:21 ` Mattia Dongili
2006-01-25  9:02   ` Olaf Kirch
2006-01-25 12:11     ` Olaf Kirch
2006-01-25 13:51       ` sched_yield() makes OpenLDAP slow Howard Chu
2006-01-25 14:38         ` Robert Hancock
2006-01-25 17:49         ` Christopher Friesen
2006-01-26  1:07         ` David Schwartz
2006-01-26  8:30           ` Helge Hafting
2006-01-26  9:01             ` Nick Piggin
2006-01-26 10:50             ` Nikita Danilov
     [not found] <5uZqb-4fo-15@gated-at.bofh.it>
2006-01-14 22:47 ` Robert Hancock
  -- strict thread matches above, loose matches on Subject: below --
2006-01-14 19:29 Howard Chu
     [not found] <43057641.70700@symas.com.suse.lists.linux.kernel>
     [not found] ` <17157.45712.877795.437505@gargle.gargle.HOWL.suse.lists.linux.kernel>
     [not found]   ` <430666DB.70802@symas.com.suse.lists.linux.kernel>
2005-08-20 13:48     ` Andi Kleen
2005-08-21 19:47       ` Florian Weimer
2005-08-22  5:09         ` Howard Chu
2005-08-22 13:06           ` Andi Kleen
2005-08-22 18:47             ` Howard Chu
2005-08-22 13:20           ` Florian Weimer
2005-08-22 23:19             ` Howard Chu
2005-08-19  6:03 Howard Chu
2005-08-19  6:34 ` Nick Piggin
2005-08-19  6:59 ` Chris Wedgwood
2005-08-19 22:45   ` Howard Chu
2005-08-19 10:21 ` Nikita Danilov
2005-08-19 23:10   ` Howard Chu
2005-08-20 13:23     ` Nikita Danilov
2005-08-20 19:49       ` Howard Chu
2005-08-20 22:08         ` Nikita Danilov
     [not found] <4303DB48.8010902@develer.com.suse.lists.linux.kernel>
     [not found] ` <20050818010703.GA13127@nineveh.rivenstone.net.suse.lists.linux.kernel>
     [not found]   ` <4303F967.6000404@yahoo.com.au.suse.lists.linux.kernel>
     [not found]     ` <43054D9A.7090509@develer.com.suse.lists.linux.kernel>
2005-08-19  3:19       ` Andi Kleen
2005-08-19  3:30         ` Bernardo Innocenti
2005-08-18  0:50 Bernardo Innocenti
2005-08-18  0:47 ` Con Kolivas
2005-08-18 10:48   ` Maciej Soltysiak
2005-08-18  1:07 ` Joseph Fannin
2005-08-18  2:25   ` Bernardo Innocenti
2005-08-18  2:58   ` Nick Piggin
2005-08-19  3:10     ` Bernardo Innocenti

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