Volker Jahns wrote:
Bruce Cran wrote:
Volker Jahns wrote:
On Thu, May 15, 2008 at 09:53:02PM +0200, Volker Jahns wrote:
On Thu, May 15, 2008 at 12:18:57PM -0700, Chuck Swiger wrote:
On May 15, 2008, at 11:57 AM, Volker Jahns wrote:
FreeBSD 6.2 running on X86 hardware (FSC) shows a remarkable
time drift
running ntpdate every half hour shows that the system looses
about 10-14 sec each time.
15 May 10:06:48 ntpdate[7200]: step time server 192.53.103.108
offset -13.799602 sec
15 May 10:36:48 ntpdate[7515]: step time server 192.53.103.108
offset -12.813941 sec
15 May 11:06:48 ntpdate[7879]: step time server 192.53.103.108
offset -13.651921 sec
15 May 11:36:50 ntpdate[8079]: step time server 192.53.103.108
offset -11.109298 sec
15 May 12:06:50 ntpdate[8289]: step time server 192.53.103.108
offset -11.836499 sec
You should also take a look at the output of "sysctl
kern.timecounter", and possibly switch to a different mechanism,
if the existing choice doesn't work out well for your machine...
Thanks for the hint.
A few years ago a time drift problem had been observed by a German
freebsd
user (http://www.freebsd.de/rachive/de-bsd-questions.200304/0643.html).
Time drift 15 sec every half hour, ntpd dies away running on his
machine.
Setting kern.timecounter.hardware to TSC had been recommended as
a solution.
There's also a FreeBSD PR open about this problem:
http://www.freebsd.org/cgi/query-pr.cgi?pr=i386/123462
sysctl -w kern.timecounter.hardware=TSC and then this:
16 May 08:37:01 ntpdate[28819]: adjust time server 192.53.103.108
offset -0.347027 sec
16 May 09:07:00 ntpdate[29258]: adjust time server 192.53.103.108
offset -0.313608 sec
16 May 09:37:00 ntpdate[29492]: adjust time server 192.53.103.108
offset -0.314357 sec
16 May 10:07:00 ntpdate[29826]: adjust time server 192.53.103.108
offset -0.313694 sec
(Please note the use of ntpdate is for debugging purposes only, this
is _not_ an ntp issue)
Finally I want to come back to the time drift issue and howto improve
it. Setting
kern.timecounter.hardware: i8254
machdep.i8254_freq: 1193182
16 May 12:07:01 ntpdate[31752]: adjust time server 192.53.103.108 offset
-0.404453 sec
16 May 12:37:00 ntpdate[32425]: adjust time server 192.53.103.108 offset
-0.396156 sec
16 May 13:07:01 ntpdate[32787]: adjust time server 192.53.103.108 offset
-0.383712 sec
16 May 13:37:01 ntpdate[33126]: adjust time server 192.53.103.108 offset
-0.387233 sec
Clock is too slow, frequency must be increased.
Corrected machdep.i8254_freq from 1193182 to 1193448
16 May 17:37:00 ntpdate[36310]: adjust time server 192.53.103.108 offset
-0.033320 sec
16 May 18:07:01 ntpdate[36632]: adjust time server 192.53.103.108 offset
-0.053532 sec
16 May 18:37:00 ntpdate[37011]: adjust time server 192.53.103.108 offset
-0.043264 sec
16 May 19:07:01 ntpdate[37361]: adjust time server 192.53.103.108 offset
-0.055725 sec
Time drift is now only about 50 millisecs per half an hour.
--
Volker Jahns, [EMAIL PROTECTED]
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