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RE: [Xen-devel] cpufreq status information

>>> "Tian, Kevin" <kevin.tian@xxxxxxxxx> 08.09.08 15:22 >>>
>>From: Jan Beulich
>>Sent: 2008年9月8日 21:12
>>Trying to understand whether CPU frequency scaling is actually 
>>working on
>>a system currently requires (afaics) source patches, as there 
>>is no way to
>>get the current state of a CPU. Even if this is intentional, 
>What do you mean by current state of CPU? If cpufreq is enabled,
>user should be able to retrieve statistics information by sysctl

How? I can't see where the current frequency a CPU is running at
is being exposed.

>>this doesn't seem
>>very helpful when considering to make this functionality available to
>>customers: I'm certain quite a few will ask how they can tell 
>>whether this
>>is actually working.
>>Now, apart from the simple job of adding a sub-hypercall to 
>>retrieve the
>>necessary bits, I'm wondering whether this wouldn't be just one more
>>element that would much better be surfaced to the guest via the vCPU
>>info structure (or, as that's size constrained, a new construct to make
>>guest-read-only information available via a shared page). Other
>>(potential) items to make available this same way would e.g. be guest-
>>accessible last-exception-from/-to MSR values (as the values read would
>>be meaningless if read through rdmsr).
>Not quite understand. Cpufreq is physical cpu stuff, and do you aim
>to expose physical information through vcpu specific shared page?
>Then that would add fixed requirement on dom0 vcpu number to
>physical cpus, which is intentially avoided in current design.

The intent is to expose the frequency of the pCPU the particular vCPU
is currently running on, perhaps only in Dom0.


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