linux-kernel - Re: Large increase in context switch rate

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Date:	Thu, 17 Jul 2008 23:43:24 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	"Alex Nixon (Intern)" <Alex.Nixon@...citrix.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ian Campbell <Ian.Campbell@...citrix.com>
Subject: Re: Large increase in context switch rate

Jeremy Fitzhardinge <jeremy@...p.org> writes:
>
> 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.

If it's that easily reproducible you could just bisect it?

-Andi
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