[ntp:questions] Very large offset and jitter values after reboot
Unruh
unruh-spam at physics.ubc.ca
Mon Aug 25 17:55:28 UTC 2008
nb at komeda-berlin.de (Nicola Berndt) writes:
>Unruh schrieb:
>> nb at komeda-berlin.de (Nicola Berndt) writes:
>>
>>>>> remote refid st t when poll reach delay offset
>>>>> jitter
>>>>> ==============================================================================
>>>>> GPS_NMEA(0) .GPS. 0 l 9 64 37 0.000 -580.75
>>>>> 3965.19
>>>> You've not had your first 8 samples yet. You haven't actually had
>>>> enough for ntpd to act on the data. You can speed that up with iburst,
>>>> but ntpd will still take a long time to get a very tight lock. jitter
>>>> will reduce as you get to the eight samples. The good? think, is that
>>>> you are more than 128ms out, so that ntpd will step the time, to zero
>>>> the offset, once it gets enough samples.
>>
>>
>>> Just tried the iburst option, but I had to figure it only works with the
>>> server command, not on refclocks.
>>
>> Oops forgot you have a gps clock. chrony does not work with refclocks.
>>
>>
>>> What really puzzles me, is the stoical 600 ms offset after rebooting.
>>> Since it is always returning having more or less the same amount, I
>>> should really be able to get rid of it, no?
>>
>> It sounds like your rtc has problems. You can use hwclock to compensate for
>> rtc problems.
>Well, I tried 'hwclock --systohc' with no different result. More
>suggestions?
Try using the --directisa option both when you write the rtc on
shutdown and when you read it on bootup. If you have a very modermn machine
with HPET the rtc driver is badly munged. It should only be out by about
13ms, not 600 however.
Also look at the /etc/adjtime file
>nb at komeda-berlin.de
>tel: +49 30 / 6730 1395
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