Date: Fri, 16 May 2008 11:32:15 +0200 From: Volker Jahns <volker@thalreit.de> To: Bruce Cran <bruce@cran.org.uk> Cc: freebsd-questions@freebsd.org Subject: Re: time drift Message-ID: <482D549F.9050300@thalreit.de> In-Reply-To: <482CA8EE.7040906@cran.org.uk> References: <20080515185758.GA12709@ikarus.thalreit> <597571FB-C72D-4603-B379-A59A435843BE@mac.com> <20080515195302.GA13531@ikarus.thalreit> <20080515203728.GA14284@ikarus.thalreit> <482CA8EE.7040906@cran.org.uk>
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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@thalreit.de
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