[ntp:questions] Sudden change in precision and jitter

David Woolley david at ex.djwhome.demon.invalid
Sun Jun 2 20:33:11 UTC 2013

Harlan Stenn wrote:
> A C writes:
>> On 6/2/2013 02:24, David Woolley wrote:
>>>> That would be interesting since I have a cron job restarting it at an
>>>> odd hour away from any other cron jobs left.  I'll check and see if
>>> Why are you restarting it?  ntpd works  best if left to run continuously.
>> I know it does...unless there is a bug (a compound bug between ntpd and 
>> the kernel) that causes ntpd to spin out of control every few weeks and 
>> forces me to restart it anyway.  By spin out of control I do mean that 
>> CPU usage goes to near 100% and ntpd stops disciplining the clock after 
>> it managed to force the clock to run at some insane rate (e.g. nominal 
>> PPM tick adjustment might be -78 and it ramps the tick to +350 PPM over 
>> a few minutes).  The end result is that the clock is very wrong, ntpd 
>> has totally stopped doing anything, but somehow it's caught in an 
>> infinite loop with maximum CPU usage meaning almost nothing else on the 
>> system is working right.
> It would be really great to run truss or something in this case, and
> I would also hope that the GSoC project to upgrade NTP's loggingd and
> debugging interface will help with this too.
> If you want to open a bug report on this that's fine too - we won't be
> able to do much about it until we can repeat it or debug it, but it
> might be useful information for the aforementioned GSoC project.

I think this could be an already known NetBSD bug, see 

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