[ntp:questions] Sure GPS - Very High Jitter and Offset

Ken Link klink at numberzero.org
Thu Aug 18 18:16:22 UTC 2011


That was the missing piece! Now ntpd is synced with an 'o' to the GPS
clock, with -0.005ms offset and 0.003 jitter.

Question (hopefully last) about the behavior in this state. While
there is an 'o' next to the GPS clock, meaning it's the PPS peer, ntpd
also selects another peer with a '*' (the other peers are from the NTP
pool). Why does it select an additional peer? The only preferred peer
in ntp.conf is the GPS device. Shouldn't ntpd get the time AND pps
from the GPS clock?

Running "ntpq -c assoc" shows the GPS clock as the pps.peer and the
pool source as sys.peer.

Thanks,
Ken

On Tue, Aug 16, 2011 at 1:42 PM, Miroslav Lichvar <mlichvar at redhat.com> wrote:
> On Tue, Aug 16, 2011 at 12:49:16PM -0500, Ken Link wrote:
>
>> I tried copying the header from ntpsrc/ports/winnt/include/timepps.h
>> to /usr/include/timepps.h, but no dice. Do I just need to copy some
>> more headers somewhere or does this mean I have to recompile the
>> kernel?
>
> I think you just need the timepps.h header, try this one
> https://raw.github.com/ago/pps-tools/HEAD/timepps.h
>
> --
> Miroslav Lichvar
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