Re: [Xen-devel] Clocksources and other mysteries

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 12/01/2009 09:43, "Carsten Schiers" <carsten@xxxxxxxxxx> wrote:

> First mystery: when jiffies is used as clocksource, why is the system checking
> and complaining about deltas in TSC? Can I thus ignore them?
> 
> Second mystery: when Xen reports:(XEN) Platform timer is 25.000MHz HPET, why
> isn't Xen using it? Shouldn't it? Wouldn't be the HPET the best choice for my
> non-TSC-invariant CPU?

Fine-grained system time is computed from TSC, calibrated periodically to
the platform timesource (HPET). Xen kernels compute jiffies from Xen system
time, hence computed from TSC.

If the time went backwards messages are occasional you can ignore them, or
even disable them.

 -- Keir



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