linux-kernel - Re: Perfomance governor is still changing frequency

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Message-ID: <20081223175600.GB17426@srcf.ucam.org>
Date:	Tue, 23 Dec 2008 17:56:00 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Len Brown <lenb@...nel.org>
Cc:	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	cpufreq@...r.kernel.org
Subject: Re: Perfomance governor is still changing frequency

On Mon, Dec 15, 2008 at 12:59:15PM -0500, Len Brown wrote:

> and that will tell us if turbo is related to your
> occasional obervance of low-frequency-mode.

We've observed this on certain other pieces of modern Intel hardware - 
the best hypothesis we've been able to come up with is that if the msr 
read is the first instruction run on the core when it's previously been 
in a deep C state, the low-clock speed is reported. However, some 
Thinkpads will also automatically limit their speed for thermal reasons.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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