[ntp:questions] what happens with overload on system for NTP

Richard B. Gilbert rgilbert88 at comcast.net
Tue Feb 9 16:45:43 UTC 2010


Ananth Shenoy wrote:
> NTP version 4.2.0
> 
> I'am currently working on a problem on NTP. NTP log files show lot of drift.. The offset and frequency keep increasing and once the frequency rises above 500ppm the NTP displays error message.
> 
> frequency error 513 PPM exceeds tolerance 500 PPM
> 
> we see the offset bouncing around in +ve and -ve values sometimes high and low.
> 
> what could be the cause of this ?
> 
> Also, what are the effects of heavy load on the system ?
> If suppose NTP is running on low priority and some high priority processes continously preempt NTP from getting the CPU what will happen.  Will then calculations of offset go wrong ?
> If it was calculating the offset in process_packet function, and it got pre-empted and got the CPU after a while, what will happen to the calculations ?
> 

NTPD needs to run at high priority.  It needs less than 1% of most CPUs 
and the effects of running it at high priority should not be noticeable.




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