Re: [Xen-devel] [PATCH v12] tolerate jitter in cpu_khz calculation to avoid TSC emulation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.03.19 at 20:29, <olaf@xxxxxxxxx> wrote:
> Am Fri,  8 Mar 2019 20:20:59 +0100
> schrieb Olaf Hering <olaf@xxxxxxxxx>:
> 
>> To reiterate the second paragraph: if a domU uses TSC as primary clock
>> source, it is expected that it runs NTP to cover for the resulting
>> drift. Therefore this change does no need a knob to turn it on or off.
> 
> One interesting aspect is: the xenlinux based kernels report clocksource=tsc,

I don't think they do - iirc they are hardcoded to clocksource=xen.

> but I think there was no explicit requirement to run NTP in domU.

Correct, unless "independent wall clock" mode was used.

> There was even that 'independent_wallclock' knob. Why is that?

Why is what? Are you questioning the presence of the setting in
the XenoLinux kernels, or its absence in the pv-ops ones?

Jan



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