[ntp:questions] ntpd goes into oscillation

unruh unruh at wormhole.physics.ubc.ca
Tue Dec 29 21:31:50 UTC 2009

ntpd has suddenly broken out into oscillations. it is fed by a Garmin
18 LVC PPS via shm. The oscillation has a period of just under an hour (
about 50 min) and an amplitude of about 10usec. in the offsets (
amplitude of about .005PPM in the rate). Since this is acting as the
clock for a number of other machines, they are also showing the
oscillation especially in the rate.
While I suppose this could be something in the GPS itself, it looks more
like an oscillation in ntpd. 
Nothing changed when the oscillations started. Ntpd had been started
on Dec 14, and this change began on Dec24. 
You can see the graph on www.theory.physics.ubc.ca/chrony/chrony.html ,
the graph for the machine called string. 

Has anyone else ever seen this kind of thing?

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