From: Andrew Morton <akpm@linux-foundation.org>
To: Ulrich Drepper <drepper@redhat.com>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: getting processor numbers
Date: Tue, 3 Apr 2007 13:16:23 -0700 [thread overview]
Message-ID: <20070403131623.c6831607.akpm@linux-foundation.org> (raw)
In-Reply-To: <461286D6.2040407@redhat.com>
On Tue, 03 Apr 2007 09:54:46 -0700
Ulrich Drepper <drepper@redhat.com> wrote:
> More and more code depends on knowing the number of processors in the
> system to efficiently scale the code. E.g., in OpenMP it is used by
> default to determine how many threads to create. Creating more threads
> than there are processors/cores doesn't make sense.
but... It would be a mistake for an application to assume that it is
allowed to _use_ all the present CPUs. People can and do run applications
within cpusets, and under sched_setaffinity().
So I'd have thought that in general an application should be querying its
present affinity mask - something like sched_getaffinity()? That fixes the
CPU hotplug issues too, of course.
But we discussed this all a couple years back and it was decided that
sched_getaffinity() was unsuitable. I remember at the time not really
understanding why?
next prev parent reply other threads:[~2007-04-03 20:16 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-03 16:54 getting processor numbers Ulrich Drepper
2007-04-03 17:30 ` linux-os (Dick Johnson)
2007-04-03 17:37 ` Ulrich Drepper
2007-04-03 17:56 ` Dr. David Alan Gilbert
2007-04-03 18:11 ` Andi Kleen
2007-04-03 17:17 ` Ulrich Drepper
2007-04-03 17:22 ` Alan Cox
2007-04-03 17:30 ` Andi Kleen
2007-04-03 20:24 ` Jeremy Fitzhardinge
2007-04-03 17:27 ` Andi Kleen
2007-04-03 17:30 ` Ulrich Drepper
2007-04-03 17:35 ` Andi Kleen
2007-04-03 17:45 ` Ulrich Drepper
2007-04-03 17:58 ` Andi Kleen
2007-04-03 18:05 ` Ulrich Drepper
2007-04-03 18:11 ` Andi Kleen
2007-04-03 18:21 ` Ulrich Drepper
2007-04-03 17:44 ` Siddha, Suresh B
2007-04-03 17:59 ` Ulrich Drepper
2007-04-03 19:40 ` Jakub Jelinek
2007-04-03 20:13 ` Ingo Oeser
2007-04-03 23:38 ` J.A. Magallón
2007-04-03 19:55 ` Ulrich Drepper
2007-04-03 20:13 ` Siddha, Suresh B
2007-04-03 20:19 ` Ulrich Drepper
2007-04-03 20:32 ` Eric Dumazet
2007-04-03 20:20 ` Nathan Lynch
2007-04-03 19:15 ` Davide Libenzi
2007-04-03 19:32 ` Ulrich Drepper
2007-04-04 0:31 ` H. Peter Anvin
2007-04-04 0:35 ` Jeremy Fitzhardinge
2007-04-04 0:38 ` H. Peter Anvin
2007-04-04 5:09 ` Eric Dumazet
2007-04-04 5:16 ` H. Peter Anvin
2007-04-04 5:22 ` Jeremy Fitzhardinge
2007-04-04 5:40 ` H. Peter Anvin
2007-04-04 5:46 ` Eric Dumazet
2007-04-04 5:29 ` Eric Dumazet
2007-04-03 20:16 ` Andrew Morton [this message]
[not found] ` <4612BB89.8040102@redhat.com>
[not found] ` <20070403141348.9bcdb13e.akpm@linux-foundation.org>
2007-04-03 22:13 ` Ulrich Drepper
2007-04-03 22:48 ` Andrew Morton
2007-04-03 23:00 ` Ulrich Drepper
2007-04-03 23:23 ` Andrew Morton
2007-04-03 23:54 ` Ulrich Drepper
2007-04-04 2:55 ` Paul Jackson
2007-04-04 8:39 ` Oleg Nesterov
2007-04-04 9:39 ` Ingo Molnar
2007-04-04 8:57 ` Oleg Nesterov
2007-04-04 10:01 ` Ingo Molnar
2007-04-04 2:58 ` Paul Jackson
2007-04-04 3:04 ` Paul Jackson
2007-04-04 2:52 ` Paul Jackson
2007-04-04 2:04 ` Paul Jackson
2007-04-04 6:47 ` Jakub Jelinek
2007-04-04 7:02 ` Paul Jackson
2007-04-04 14:51 ` Cliff Wickman
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