ntpd struggling to keep up - how to fix?

[Jeremy Chadwick]

On Fri, Feb 12, 2010 at 05:44:52PM +0100, Torfinn Ingolfsen wrote:
> On Fri, 12 Feb 2010 05:11:17 -0800
> Jeremy Chadwick <freebsd at jdc.parodius.com> wrote:
> 
> > Please try doing this:
> > 
> > - stop ntpd
> > - rm /var/db/ntpd.drift
> > - sysctl kern.timecounter.hardware=ACPI-safe
> > - start ntpd
> 
> Thanks, I'm currently testing that. Results in 72 hours (or less) :-)

Something else came to mind: some BIOSes let you disable/enable HPET.
Often labelled as "High Performance Event Timer" or "Multimedia Timer",
you could disable this option then check kern.timecounter.choice to see
if HPET is gone from the list.

If it is, FreeBSD will very likely choose ACPI-safe as the default
timecounter (again, check kern.timecounter.hardware to see what the
kernel chose itself.  Remember that your sysctl.conf entry will
override this though!  :-) ), which -- assuming it works -- should
solve your problem.

Technical footnote: I wish I understood 1) the difference between
ACPI-safe and ACPI-fast, and 2) how the system or OS "ranks" the
timecounters (the higher the value in parenthesis, supposedly the more
accurate/preferred it is).  Xin, do you happen to know how this works?

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |