So ntpd has been behaving reasonably well with the snprintf fix. I had
good results with only internet servers. My PPS and SHM refclocks were
set to noselect.
I removed the noselect on the PPS refclock and left flag3 set to zero
(no kernel discipline).
Everything seemed fine and then:
Sat Feb 11 01:12:10 PST 2012
remote refid st t when poll reach delay offset jitter
==============================================================================
x127.127.22.0 .PPS. 0 l - 16 377 0.000 -111.40 351.464
127.127.28.0 .GPSD. 4 l 49 128 377 0.000 -14655. 2814.64
169.229.70.201 169.229.128.214 3 u 103 512 377 39.347 -9274.2 6597.61
72.14.179.211 127.67.113.92 2 u 79 512 377 57.746 -14699. 10685.0
24.124.0.251 132.236.56.250 3 u 521 512 377 77.930 -9835.0 7451.10
130.207.165.28 130.207.244.240 2 u 153 512 377 79.131 -9155.6 6554.15
131.144.4.10 130.207.244.240 2 u 142 512 377 86.537 -9102.3 6526.3
This occurred very suddenly (over the course of only 30 seconds). The
clockstats show the offset wandering in cycles going up to 1 second and
down to -1 second. This happened within a few hours of starting ntpd
with the PPS enabled.
I'm not sure what happened. But when I restart ntpd:
11 Feb 09:17:17 ntpd[6823]: 0.0.0.0 c61c 0c clock_step -16.611482 s
11 Feb 09:17:01 ntpd[6823]: 0.0.0.0 c615 05 clock_sync
and the offsets calm down (this is just moments after restarting the
jitter and offsets are continuing to drop down to their former values of
about 1-2ms or better):
remote refid st t when poll reach delay offset jitter
==============================================================================
x127.127.22.0 .PPS. 0 l 12 16 17 0.000 -27.265 16.503
127.127.28.0 .GPSD. 4 l 75 128 1 0.000 -16595. 0.122
69.65.40.29 209.51.161.238 2 u 2 64 1 74.261 -16.396 2.797
+169.229.70.201 169.229.128.214 3 u 37 64 1 37.577 -33.420 12.747
*198.137.202.16 69.36.224.15 2 u 35 64 1 36.607 -32.686 12.116
130.207.165.28 130.207.244.240 2 u 9 64 3 77.754 -20.400 11.968
131.144.4.10 130.207.244.240 2 u 9 64 3 85.509 -17.853 7.143
The actual PPS signal coming into the system is extremely stable. The
jitter remained below 100us for several days straight (reported by
clockstats while PPS was in noselect).
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