Re: [PATCH 8/11] Add a CPU KHZ calibration function to paravirt-ops

From: Zachary Amsden
Date: Tue Feb 06 2007 - 16:55:41 EST


Andi Kleen wrote:
On Mon, Feb 05, 2007 at 07:53:23PM -0800, Zachary Amsden wrote:
Provide a paravirtualized way to get the CPU clock frequency; this allows much
of the code in tsc.c to be shared between all paravirt implementations.

Is this really needed?

Honestly, no. But it is better and more accurate to do it.

What worries me somewhat of your patches is that you seem
to be quick at adding new hooks. But I would like to keep
paravirtops as minimal as possible with new hooks only
added when there is a very good justification.

I don't see it here.

We can calibrate CPU frequency pretty accurately, despite being in a VM where time does not operate in the normal way. Many other hypervisors won't be able to do such a good job, or might not implement the required hardware.

Adding this hook allows everyone to just re-use all the frequency scaling / recalibration code in tsc.c.

The primary justification is allowing code re-use, which is why I allowed myself to add a hook. I also want paravirt-ops to be as minimal as possible.

Zach
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