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

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Date:	Wed, 28 Jan 2009 18:06:37 -0800 (PST)
From:	Xiaoning Ding <dingxn@...il.com>
To:	Dave Jones <davej@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: a question about p4_clockmod module on Xeon quad core processors

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@...hat.com> wrote:

> From: Dave Jones <davej@...hat.com>
> Subject: Re: a question about p4_clockmod module on Xeon quad core processors
> To: "Xiaoning Ding" <dingxn@...il.com>
> Cc: linux-kernel@...r.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


      

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