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 <p...@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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