[ntp:questions] Peridoc anomalies in loopstats file ...

Heiko Gerstung heiko.removethistext.gerstung at meinberg.de
Wed Jan 12 10:05:07 UTC 2011


Just an addition:

The peerstats file shows the nearly the same time jumps at exactly the same time. I am still wondering if this is NTP or the
Kernel ...

Best Regards,
  Heiko


Am 10.01.2011 11:15, schrieb Heiko Gerstung:
> Hi Everybody!
> 
> Did anybody ever see this kind of anomaly:
> 
> I see a periodic "jump" of time on my Geode LX800 based embedded CPU
> board running Linux. This looks like an overflow or something, but the
> time jumps recorded in loopstats are up to -400 microseconds and appear
> to be happening exactly every 12264 seconds (3 hours, 24 minutes, 24
> seconds). In between those jumps, the loopstats file records a maxmimum
> offset of +/- 2 microseconds to the refclock.
> 
> Here are the three occurrences from my latest loopstats file:
> 
> [... lots of records with a max. of +/-2 microseconds offset]
> 55571 1278.037 -0.000001000 -85.118 0.000001924 0.000352 3
> 55571 1286.037 0.000000000 -85.118 0.000001922 0.000329 3
> 55571 1294.037 -0.000228000 -85.230 0.000080528 0.039362 3
> 55571 1302.037 0.000035000 -85.213 0.000119531 0.037312 3
> 55571 1310.037 0.000047000 -85.190 0.000111893 0.035833 3
> 55571 1318.037 0.000040000 -85.170 0.000104692 0.034222 3
> 55571 1326.037 0.000032000 -85.154 0.000097979 0.032485 3
> 55571 1334.037 0.000021000 -85.144 0.000091723 0.030603 3
> 55571 1342.037 0.000016000 -85.136 0.000085819 0.028759 3
> 55571 1350.037 0.000012000 -85.131 0.000080291 0.026981 3
> 55571 1358.037 0.000009000 -85.126 0.000075111 0.025287 3
> 55571 1366.037 0.000008000 -85.122 0.000070263 0.023694 3
> 55571 1374.037 0.000007000 -85.119 0.000065729 0.022196 3
> 55571 1382.037 0.000004000 -85.117 0.000061491 0.020774 3
> 55571 1390.037 0.000001000 -85.116 0.000057527 0.019433 3
> 55571 1398.037 0.000002000 -85.115 0.000053816 0.018181 3
> 55571 1406.037 0.000001000 -85.115 0.000050344 0.017008 3
> 55571 1414.037 0.000001000 -85.114 0.000047098 0.015911 3
> 55571 1422.037 0.000002000 -85.113 0.000044061 0.014887 3
> [... lots of records with a max. of +/-2 microseconds offset]
> 55571 13526.037 -0.000001000 -85.112 0.000001907 0.000348 3
> 55571 13534.037 0.000000000 -85.112 0.000001907 0.000325 3
> 55571 13542.037 0.000000000 -85.112 0.000001907 0.000304 3
> 55571 13550.037 0.000000000 -85.112 0.000001907 0.000285 3
> 55571 13558.037 -0.000400000 -85.307 0.000141482 0.069054 3
> 55571 13566.037 0.000063000 -85.276 0.000210342 0.065503 3
> 55571 13574.037 0.000087000 -85.234 0.000196946 0.063087 3
> 55571 13582.037 0.000074000 -85.197 0.000184281 0.060379 3
> 55571 13590.037 0.000056000 -85.170 0.000172496 0.057301 3
> 55571 13598.037 0.000040000 -85.151 0.000161456 0.054043 3
> 55571 13606.037 0.000028000 -85.137 0.000151090 0.050783 3
> 55571 13614.037 0.000022000 -85.126 0.000141345 0.047655 3
> 55571 13622.037 0.000016000 -85.118 0.000132238 0.044663 3
> 55571 13630.037 0.000012000 -85.112 0.000123703 0.041829 3
> 55571 13638.037 0.000010000 -85.108 0.000115716 0.039166 3
> 55571 13646.037 0.000007000 -85.104 0.000108248 0.036656 3
> 55571 13654.037 0.000004000 -85.102 0.000101261 0.034296 3
> 55571 13662.037 0.000003000 -85.101 0.000094723 0.032085 3
> 55571 13670.037 0.000003000 -85.099 0.000088608 0.030017 3
> 55571 13678.037 0.000001000 -85.099 0.000082888 0.028079 3
> 55571 13686.037 0.000002000 -85.098 0.000077537 0.026268 3
> 55571 13694.037 0.000001000 -85.097 0.000072533 0.024572 3
> 55571 13702.037 0.000001000 -85.097 0.000067851 0.022985 3
> 55571 13710.037 -0.000001000 -85.097 0.000063474 0.021502 3
> 55571 13718.037 0.000000000 -85.097 0.000059378 0.020113 3
> [... lots of records with a max. of +/-2 microseconds offset]
> 55571 25806.037 -0.000001000 -85.065 0.000001931 0.000281 3
> 55571 25814.037 -0.000152000 -85.139 0.000053561 0.026242 3
> 55571 25822.037 0.000024000 -85.127 0.000079866 0.024894 3
> 55571 25830.037 0.000032000 -85.112 0.000074760 0.023932 3
> 55571 25838.037 0.000027000 -85.098 0.000069950 0.022867 3
> 55571 25846.037 0.000020000 -85.089 0.000065476 0.021667 3
> 55571 25854.037 0.000014000 -85.082 0.000061292 0.020411 3
> 55571 25862.037 0.000011000 -85.076 0.000057339 0.019187 3
> 55571 25870.037 0.000009000 -85.072 0.000053645 0.018015 3
> 55571 25878.037 0.000008000 -85.068 0.000050185 0.016908 3
> 55571 25886.037 0.000006000 -85.065 0.000046951 0.015850 3
> 55571 25894.037 0.000004000 -85.063 0.000043925 0.014842 3
> 55571 25902.037 0.000002000 -85.062 0.000041093 0.013888 3
> 55571 25910.037 0.000002000 -85.061 0.000038445 0.012996 3
> 55571 25918.037 0.000001000 -85.061 0.000035968 0.012157 3
> 55571 25926.037 0.000000000 -85.061 0.000033652 0.011372 3
> 55571 25934.037 0.000001000 -85.060 0.000031486 0.010639 3
> 55571 25942.037 0.000001000 -85.060 0.000029460 0.009954 3
> 55571 25950.037 0.000000000 -85.060 0.000027566 0.009311 3
> [... lots of records with a max. of +/-2 microseconds offset]
> 
> I would be grateful for *any* suggestions/explanations. I already tried
> using a different clocksource, to no avail. The same hardware did not
> show this behavior with an older kernel/ntp combination (2.6.15.1 and
> ntp 4.2.0b), unfortunately it is not easily possible to replace only the
> kernel OR ntp.
> 
> Some information: ntp4.2.6p3 on Linux 32bit using tsc clocksource,
> Embedded device, synchronized to GPS receiver with PPS support, refclock
> driver 8, PPSAPI patches for kernel installed and working
> 
> Best Regards,
>   Heiko




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