linux-kernel - Re: How does Linux measure CPU frequency?

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Message-ID: <alpine.DEB.1.10.0804060935520.7751@twinlark.arctic.org>
Date:	Sun, 6 Apr 2008 09:37:31 -0700 (PDT)
From:	dean gaudet <dean@...tic.org>
To:	Jack Harvard <jack.harvard@...glemail.com>
cc:	linux-kernel@...r.kernel.org
Subject: Re: How does Linux measure CPU frequency?

linux knows what style of cpu it is running on and uses non-portable 
techniques to read the time-stamp counter.

lmbench uses some really nice tricks to estimate the cpu frequency in a 
portable manner... all it requires is that at least two of the N code 
sequences it times take a co-prime number of cycles.

-dean

On Sun, 6 Apr 2008, Jack Harvard wrote:

> Hi,
> 
> I want to find out how Linux calibrates the frequency of CPUs, and
> want to compare with the way how lmbench measures processor frequency.
> I had a thorough google search of this topic but didn't get too much
> useful results.
> 
> Thanks a lot,
> Jack
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