From: Andi Kleen <ak@suse.de>
To: Ulrich Drepper <drepper@redhat.com>
Cc: Andi Kleen <ak@suse.de>, Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: getcpu after sched_setaffinity
Date: Fri, 11 May 2007 09:08:53 +0200 [thread overview]
Message-ID: <20070511070853.GD2012@bingen.suse.de> (raw)
In-Reply-To: <4643A616.3090202@redhat.com>
On Thu, May 10, 2007 at 04:09:10PM -0700, Ulrich Drepper wrote:
> >is only designed for the case where you don't set the affinity explicitely;
> >otherwise you should already know where you are and don't need it.
>
> That's not true in general. Yes, because I want to test vgetcpu() I
> restrict the set to just one CPU.
>
> But if I have more than 2 "CPUs" and I set the affinity to two CPUs
> which currently are not used you cannot make this argument.
All the users I talked to never mentioned this as a use case.
They were only interested in fully unrestricted programs.
Anyways you can handle it too, just invalidate or do getcpu with
a new cache afterwards.
Or just wait the jiffie for the cache to expire.
>
> getcpu should always work correctly not only if you cannot determine it
> in another way.
getcpu by design is approximate. If you don't understand this
don't bother using it.
-Andi
next prev parent reply other threads:[~2007-05-11 6:11 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-10 22:24 getcpu after sched_setaffinity Ulrich Drepper
2007-05-10 23:44 ` Andi Kleen
2007-05-10 23:09 ` Ulrich Drepper
2007-05-11 7:08 ` Andi Kleen [this message]
2007-05-12 10:16 ` Bert Wesarg
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