From: Jeremy Fitzhardinge <jeremy@goop.org>
To: "Alex Nixon (Intern)" <Alex.Nixon@eu.citrix.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@elte.hu>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ian Campbell <Ian.Campbell@eu.citrix.com>
Subject: Re: Large increase in context switch rate
Date: Thu, 17 Jul 2008 09:11:11 -0700 [thread overview]
Message-ID: <487F6F1F.2030808@goop.org> (raw)
In-Reply-To: <0E902970173AF84089673FA54B7FE78A32906C@lonpexch01.citrite.net>
(Don't top-post.)
Alex Nixon (Intern) wrote:
> I'm talking about total number of context switches - kernbench gets it
> from
>
> time -f "%c" make -j 4
>
> Dividing through it gives me a rate of around 250/sec (vs Peters 3000),
> but I've set CONFIG_HZ=100 (vs Peters 1000), so they don't wildly
> conflict.
>
> Well spotted :-)
>
OK, but that still doesn't account for the relatively large increase
from 2.6.18 -> 2.6.26. You're using HZ=100 in both cases, I presume.
The other variable is NOHZ and highres timers. You could try turning
those off in 2.6.26. Also, CONFIG_PREEMPT could well make a
difference. 2.6.18-xen doesn't support CONFIG_PREEMPT at all, but
pvops(-xen) does.
J
next prev parent reply other threads:[~2008-07-17 16:11 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-16 18:54 Large increase in context switch rate Jeremy Fitzhardinge
2008-07-17 9:17 ` Peter Zijlstra
2008-07-17 15:02 ` Jeremy Fitzhardinge
2008-07-17 15:14 ` Alex Nixon (Intern)
2008-07-17 15:21 ` Peter Zijlstra
2008-07-17 15:45 ` Jeremy Fitzhardinge
2008-07-17 16:04 ` Alex Nixon (Intern)
2008-07-17 16:11 ` Jeremy Fitzhardinge [this message]
2008-07-17 21:43 ` Andi Kleen
2008-07-18 17:00 ` Alex Nixon (Intern)
2008-07-23 9:34 ` Alex Nixon (Intern)
2008-07-23 13:54 ` Andi Kleen
2008-07-24 1:26 ` Nick Piggin
2008-07-25 11:31 ` Alex Nixon
2008-07-25 11:39 ` Peter Zijlstra
2008-07-25 14:54 ` Jeremy Fitzhardinge
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