Re: [Xen-devel] [PATCH v11] tolerate jitter in cpu_khz calculation to avoid TSC emulation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.12.18 at 14:25, <olaf@xxxxxxxxx> wrote:
> The question is, how much drift can be tolerated even without my patch.

This depends on what a system is used for. A few seconds off may
be fine for one purpose, but a significant problem for another.
Similarly a sudden (however small) change to the TSC tick rate
may be a problem for one purpose, but not for another.

If otoh (and just to give an example) it was determined that the
TSC tick rate on a physical system varies over time within
certain boundaries, then leveraging this to change (slowly, i.e.
with no steeper a gradient than might be observable on bare
hardware) the rate to match the new host's might be an option.
Emulation then could be turned off after a certain period of time.

Jan



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