ntpd struggling to keep up - how to fix?

[David Magda]

On Feb 21, 2010, at 11:36, Torfinn Ingolfsen wrote:

> On Sun, 21 Feb 2010 16:08:23 +1100 Peter Jeremy  
> <peterjeremy at acm.org> wrote:
>
>> Having re-checked my maths, using both your "time reset" results, can
>> you please try:
>>  sysctl machdep.acpi_timer_freq=3570847
>> That should result in a drift of close to zero (well within NTP's
>> lock range of +/- 300ppm).
>
> And a few hours later: from /var/log/messages:
> Feb 21 09:54:50 kg-f2 ntpd[55452]: ntpd 4.2.4p5-a (1)
> Feb 21 09:59:10 kg-f2 ntpd[55453]: kernel time sync status change 2001
>
> More info:
> root at kg-f2# ntpq -p
>     remote           refid      st t when poll reach   delay    
> offset  jitter
> ==========================================================
> *kg-omni1.kg4.no 78.157.115.4     3 u   31   64  377    0.174   
> -10.253   0.160
> root at kg-f2# ntpdc -c loopi -c sysi
> offset:               -0.010253 s
> frequency:            6.744 ppm
> poll adjust:          -30
> watchdog timer:       47 s
[...]

For future reference, how does the math work? How do you go from  
taking a timer number:

	$ sysctl machdep.acpi_timer_freq
	machdep.acpi_timer_freq: 3577045

And the ntpd(8) time reset log entries to adjust the frequency? Or do  
you use the PPM output of the ntpdc(8) command?

I'm not quite sure I understand what happened here. :)