questions about DVFS in saving energy

Tomas L. Byrnes tomb at
Thu May 14 16:19:59 UTC 2009

Apologies for skirting close, but I think power consumption and heat
dissipation are pretty big operator costs, and anything we can do to
reduce those are beneficial to the bottom line; never mind the
environment. More below:

>-----Original Message-----
>From: Karl Southern [mailto:karl at]
>Sent: Thursday, May 14, 2009 1:10 AM
>To: Tomas L. Byrnes
>Cc: nanog at
>Subject: Re: questions about DVFS in saving energy
>Tomas L. Byrnes wrote:
>> Basically the CPU scaling on the host makes the guest OS fall apart.
>Apologies for the general noise (and even more apologies for stepping
>outside of the nanog scope), but if it's timing related issues does
>/usepmtimer not resolve this issue for the VMs? It certainly does on
>other virtualisation solutions.

[TLB:] We tried all the solutions we could Google, including
/usepmtimer. A potential 50% reduction in power per system (which is
what we were measuring in the tests) would be significant.
Unfortunately, it was not stable. It appears to be a Win2K3 issue,
although Red Hat Enterprise ran at the declock speed all the time, even
under heavy loads (it didn't crash and corrupt volumes like Win2K3,

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