FreeBSD-11.0 BHyve ntpd issues

[James B. Byrne]

I see this in /var/log/messages:

> Dec 28 03:57:47 SAMBA-01 ntpd[560]:
>   frequency error -500 PPM exceeds tolerance 500 PPM
> Dec 28 06:05:04 SAMBA-01 ntpd[560]:
>   frequency error -500 PPM exceeds tolerance 500 PPM

Reading up on ntpd issues wrt vm's I ran these diagnostics on the vm:


[root at SAMBA-01 ~]#  dmesg | grep Timecounter
Timecounter "i8254" frequency 1193182 Hz quality 0
Timecounter "HPET" frequency 10000000 Hz quality 950
Timecounter "ACPI-fast" frequency 3579545 Hz quality 900
Timecounters tick every 1.000 msec
[root at SAMBA-01 ~]# sysctl kern.timecounter.hardware
kern.timecounter.hardware: HPET


I also found this thread,
https://lists.freebsd.org/pipermail/freebsd-virtualization/2016-April/004382.html,
on the FreeBSd list which suggested the following fix:

> I found errors in /var/log/messages and fix adding:
>
> kern.timecounter.hardware=TSC-low
> into /etc/sysctl.conf file

I can add this as suggested but before I do can someone enlighten as
to what is happening, why it happens, what the consequences are of not
dealing with the problem, and what the recommended fix accomplishes. 
Should this suggestion be implemented or is there a better solution?

The vm in question is, as its name suggests, a samba based AD-DC. Time
synchronisation with the desktop units is critical for authentication.

Thanks,

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James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
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