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

[Olaf Hering <olaf@xxxxxxxxx>]

Am Thu, 13 Dec 2018 01:45:39 -0700
schrieb "Jan Beulich" <JBeulich@xxxxxxxx>:

> >>> On 13.12.18 at 09:18, <olaf@xxxxxxxxx> wrote:  
> > Am Wed, 12 Dec 2018 09:39:25 -0700
> > schrieb "Jan Beulich" <JBeulich@xxxxxxxx>:
> >   
> >> >>> On 12.12.18 at 16:20, <olaf@xxxxxxxxx> wrote:    
> >> > If a domU uses TSC as clocksoure it also must run NTP in some way to
> >> > avoid the potential drift what will most likely happen, independent of
> >> > any migration.    
> >> Which drift? While anyone's well advised to run NTP, a completely
> >> isolated set of systems may have no need to, if their interactions don't
> >> depend on exactly matching time.  
> > 
> > If these hosts do not sync time to some reference host, the advancing of 
> > time
> > is undefined before and after my change.  
> 
> I'm lost. I simply don't understand what you're trying to tell me,
> or how your answer relates to my question.

Then please rephrase the question? I do not see how my path affects the
advancing of time in domUs running on isolated systems. If their hardware
clocks advance at the same speed, my patch will not affect it. And if they
do advance at a different speed, what can emulation do to help with 
"correctness"?

Olaf

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