Re: [Xen-devel] [patch 14/33] xen: xen time implementation

Keir Fraser
2007-06-06T11:53:17Z

On 6/6/07 12:00, "Jan Beulich" <jbeulich@novell.com> wrote:

>> If the error across CPUS is +/- just a few microseconds at worst then having
>> the clocksource clamp to no less than the last timestamp returned seems a
>> reasonable fix. Time won't 'stop' for longer than the cross-CPU error, and
>> that should always be a tiny value.
>
> Are you sure this is also true when e.g. a CPU gets throttled due to thermal
> conditions? It is my understanding that both the duty cycle adjustment and
> the frequency reduction would yield a reduced rate TSC, which would be
> accounted for only the next time the local clock gets calibrated. Otherwise,
> immediate calibration (and vcpu update) would need to be forced out of the
> thermal interrupt.

Yes, this could be an issue. Is there any way to get an interrupt or MCE
when thermal throttling occurs?

-- Keir