Re: [Xen-devel] RFC: cpu frequency scaling

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 26/10/06 1:35 pm, "Petersson, Mats" <Mats.Petersson@xxxxxxx> wrote:

> So you need to get the actual load of each physical CPU, then sort them
> "per socket" and do any changes based on the highest (or lowest) load of
> the actual socket. I'm not sure if all the necessary information is
> available in Dom0 unless it's also running on all available cores -
> however, neither am I sure if there's much point in pursuing the case
> where all CPU's are NOT in Dom0... Allowing those cores that are not
> Dom0-cores to have a driver-domain to control the speed would be
> sensible solution - interesting things happen, however, if someone puts
> core0 of a socket to Dom0, and Core1 of the same socket as DomU - you
> can't really control that one even with a driver domain...

We should state that as an assumption of the cpufreq domain (that it has a
one-to-one correspondence between VCPUs and PCPUs). We liekly also need an
interface to allow a domain to find out the 'topology' of its VCPUs, so that
the cpufreq drivers know which VCPUs share a socket, etc. They could also
work this out from cpuid in most cases I expect, but it's probably a better
fit with the Linux code to provide a generic 'topology info' interface and
people experimenting with NUMA will appreciate it too.

 -- Keir



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