time drift

[Volker Jahns]

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
16 May 10:37:00 ntpdate[30203]: adjust time server 192.53.103.108 offset 
-0.313976 sec
16 May 11:07:00 ntpdate[30886]: adjust time server 192.53.103.108 offset 
-0.314679 sec


(Please note the use of ntpdate is for debugging purposes only, this is 
_not_ an ntp issue)

-- 
Volker Jahns, volker at thalreit.de