linux-kernel - Re: exposing FSB clock speed in /sys

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Date:	Fri, 30 Mar 2007 08:49:52 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	eranian@....hp.com
Cc:	linux-kernel@...r.kernel.org, perfmon@...ali.hpl.hp.com
Subject: Re: exposing FSB clock speed in /sys

On Fri, 2007-03-30 at 07:39 -0800, Stephane Eranian wrote:
> Hello,
> 
> It seems that the kernel does not expose the Front-Side Bus (FSN) Clock
> speed to user applications

and that is a good thing ;)



> Knowledge the the FSB speed is very useful to monitoring tools. It is used
> to compute certain bus-related metrics.

perhaps. 
> 
> Looking at the code, it seems that there is no standard way of extracting
> the FSB speed. For each processor model, you have different MSRs. I would
> think that the routines in the cpufreq code could be moved out and used
> as the basis to expose the information somewhere in /sys.

... yet not all CPU's *have* an FSB. Notably AMD ones do not, and I'm
sure you've read on a lot of online tech magazines that other vendors
may also not have one in the future  :-)

Exposing a concept that we KNOW does not make sense via a kernel
interface (which means we need to keep it around forever) is in my
opinion quite a bad mistake to make.... Please lets not do this.



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