Re: a question about p4_clockmod module on Xeon quad core processors

[Xiaoning Ding <dingxn@ymail.com>]

Thanks for the correction. 
My experiments need to reduce CPU speed. However, I can only reduce the speed by about 30% (from 2.67GHz to 2GHz) with ACPI. That is not enough for the experiments. 

p4-clockmod has not been removed from 2.6.29. It is under the same directory as acpi-cpufreq (arch/x86/kernel/cpu/cpufreq). So I thought it was an alternative approach. But I could not get it loaded.

Xiaoning


--- On Wed, 1/28/09, Dave Jones <davej@redhat.com> wrote:

> From: Dave Jones <davej@redhat.com>
> Subject: Re: a question about p4_clockmod module on Xeon quad core processors
> To: "Xiaoning Ding" <dingxn@ymail.com>
> Cc: linux-kernel@vger.kernel.org
> Date: Wednesday, January 28, 2009, 9:02 PM
> On Tue, Jan 27, 2009 at 12:17:25PM -0800, Xiaoning Ding
> wrote:
>  > Hi list,
>  > 
>  > I have tried the p4-clockmod module in Linux kernel
> 2.6.29 on Xeon 5355 quad-core CPUs with no luck. It seems
> current p4-clockmod driver still cannot support Intel Quad
> core processors, right? 
>  > 
>  > I know I can also use acpi-cpufreq. It can only scale
> down the frequence from 2.67GHz to 2GHz. But I need some
> lower frequencies for some experiments.
> 
> p4-clockmod doesn't change the processor frequency.
> Because of common misconceptions like this, the user
> interface has been removed.
> 
> In 2.6.29, the clock modulation code is called directly
> from ACPI
> whenever thermal events indicate that throttling is
> necessary.
> 
> 	Dave
> 
> -- 
> http://www.codemonkey.org.uk