bhyve clock problem, solved by kern.timecounter.hardware="TSC-low" in /etc/sysctl.conf

[Matthew Grooms]

Perhaps applying this commit would have some positive effect ( HPET vs 
LAPIC )?

https://docs.freebsd.org/cgi/getmsg.cgi?fetch=885358+0+archive/2015/svn-src-head/20150322.svn-src-head

-Matthew

On 4/10/2015 12:51 PM, Stephen Stuart wrote:
> I think the right thing is to set (in /boot/loader.conf)
> kern.timecounter.tc.TSC-low.quality to a value higher than that for HPET,
> to force the clock choice over what the kernel decides for the hardware
> that you're running on. See timecounters(4).
>
> Stephen
>
> On Fri, Apr 10, 2015 at 10:35 AM, Paul Vixie <paul at redbarn.org> wrote:
>
>> here is a representative one-hour sample of ntp messages from
>> /var/log/messages on a freebsd 10.1 bhyve guest:
>>
>>> Apr 10 12:00:46 family ntpd[634]: time reset -0.613057 s
>>> Apr 10 12:17:02 family ntpd[634]: time reset -0.604933 s
>>> Apr 10 12:33:51 family ntpd[634]: time reset -0.650622 s
>>> Apr 10 12:55:06 family ntpd[634]: time reset -0.743930 s
>>
>> that's with kern.timecounter.hardware: HPET, which is the default.
>>
>> a "time reset" from ntpd means the clock either won't slew at all or
>> can't slew fast enough. in other words a normal freebsd 10.1 server can
>> run for months or even years without ever outputting one of these messages.
>>
>> google reports that some folks have had good luck with
>> kern.timecounter.hardware: TSC-low. so i tried that on another freebsd
>> 10.1 bhyve guest on the same bhyve server, with dramatic results -- no
>> more ntpd messages.
>>
>> can we make TSC-low the default?
>>
>> vixie
>>
>>
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