Subject: Re: [patch] prefer TSC over PM Timer
From: john stultz <johnstul@us.ibm.com>
To: Arjan van de Ven <arjan@infradead.org>
Cc: dean gaudet <dean-list-linux-kernel@arctic.org>,
       lkml <linux-kernel@vger.kernel.org>
In-Reply-To: <1100592718.2811.8.camel@laptop.fenrus.org>
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	 <1100569104.21267.58.camel@cog.beaverton.ibm.com>
	 <1100592718.2811.8.camel@laptop.fenrus.org>
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Date: Tue, 16 Nov 2004 01:36:32 -0800
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On Tue, 2004-11-16 at 09:11 +0100, Arjan van de Ven wrote:
> > While there are a great number of systems that can use the TSC, cpufreq
> > scaling laptops, and a number of SMP and NUMA systems cannot use it as a
> > time source. 
> 
> please don't drag cpufreq into this; cpufreq adjusts this timer on
> frequency changes just fine.

Fair enough. Dominik and others have done some great work there and I
shouldn't cast doubt on it.  I just haven't played with it enough to
really get confident that there really aren't any holes with it. 

That said, not all laptops properly notify the kernel when they change
frequency. The BIOS just changes it on its own. My old one had this
problem and the pmtmr helped quite a bit there. But maybe these cases
are just rare enough that its not an issue.

thanks
-john

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