Re: [ntp:questions] ntpd goes into oscillation
unruh wrote: The temp should be relatively stable ( certainly no air conditioner, although possibly cooler than usual because the heating has been turned down for the Christmas break-- After all nothing happens in the University during Christmas. Research-- what's that?. I don't know about UBC but we always got a lot of research done exactly at times like that during the holidays. After all there weren't any students around to teach. Danny -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] ntpd goes into oscillation
unruh un...@wormhole.physics.ubc.ca wrote in message news:slrnhjkta6.4e4.un...@wormhole.physics.ubc.ca... 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? Something similar, perhaps, yes, and I reported it here before. It seems that NTP hits the +/- 500 ppm drift limit and can't recover - check the drift file contents. You might try deleting (or renaming) the drift file. I haven't seen this for some time, though. What version are you running? Cheers, David ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] ntpd goes into oscillation
In article slrnhjkta6.4e4.un...@wormhole.physics.ubc.ca, unruh un...@wormhole.physics.ubc.ca writes: 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? What OS? (version?) What is the temperature like? If you feed a sawtooth into a PLL, the offset will be the derivative, a square wave. The amplitude of the square wave is smaller with higher gain. A sawtooth with a 1 hour period is possible from air conditioners. I've seen oscillations on boxes using the pool, or at least stuff that looks like oscillations to my eyeball. That's on Linux. (They have been fixing the timekeeping code. I wouldn't be surprised by anything.) -- These are my opinions, not necessarily my employer's. I hate spam. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] ntpd goes into oscillation
On 2009-12-30, David J Taylor david-tay...@blueyonder.delete-this-bit.and-this-part.co.uk.invalid wrote: unruh un...@wormhole.physics.ubc.ca wrote in message news:slrnhjkta6.4e4.un...@wormhole.physics.ubc.ca... 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? Something similar, perhaps, yes, and I reported it here before. It seems that NTP hits the +/- 500 ppm drift limit and can't recover - check the drift file contents. You might try deleting (or renaming) the drift file. I haven't seen this for some time, though. What version are you running? Nope, the drift is NOT at the limit ( it is at about 200) ntp 2.4.2p4 Cheers, David ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] ntpd goes into oscillation
On 2009-12-30, Hal Murray hal-use...@ip-64-139-1-69.sjc.megapath.net wrote: In article slrnhjkta6.4e4.un...@wormhole.physics.ubc.ca, unruh un...@wormhole.physics.ubc.ca writes: 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? What OS? (version?) Linux-- Mandriva 2008.1 ( kernel 2.6.24.7-desktop-3mnb) This oscillation has just started. What is the temperature like? The temp should be relatively stable ( certainly no air conditioner, although possibly cooler than usual because the heating has been turned down for the Christmas break-- After all nothing happens in the University during Christmas. Research-- what's that?. HOwever it so happens that I have the internal temp recorded via lmsensors for the past 5 days, and there is some evidence of a one degree flucutation (the resolution of the onboard thermometers) with about the same period. No idea what that is, since there is no airconditioning/heating. But I suppose it could be causing that fluctuation in the rate and thus the offset. Which somehow started on Dec 24. Lets see what happens when classes begin again next week. If you feed a sawtooth into a PLL, the offset will be the derivative, a square wave. The amplitude of the square wave is smaller with higher gain. A sawtooth with a 1 hour period is possible from air conditioners. Actually, no, the offset is the integral, not the derivative, of the drift, so the offset will be a bunch of peaks. I've seen oscillations on boxes using the pool, or at least stuff that looks like oscillations to my eyeball. That's on Linux. (They have been fixing the timekeeping code. I wouldn't be surprised by anything.) Yes, but then this fix whatever it is, has been the same for months now. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] ntpd goes into oscillation
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? ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
