Udo van den Heuvel via devel writes: > When then is the jitter so low? > If solely using NMEA the jitter and offset would be worse.
Well, run ntpq with the -u switch to see what those really are. If you've set the serial to low latency and a fairly high speed, you can expect jitter in the single-to-double digit µs range, so it would show up as all zero in ntpq in standard display mode. > But: should ttyS0 show up in /proc/interrups? (ttyS1 does) Don't know… >> although from your boot log it's clear you were apparently expecting to >> use that. Have you set the flag to use the PPS and does the device >> deliver (stable) PPS signal? > > # ppswatch /dev/pps0 > trying PPS source "/dev/pps0" > found PPS source "/dev/pps0" > timestamp: 1586697390, sequence: 139, offset: 199075943 > timestamp: 1586698062, sequence: 140, offset: 196910388 > timestamp: 1586698062, sequence: 140, offset: 196910388 > timestamp: 1586698063, sequence: 141, offset: 196889843 > timestamp: 1586698063, sequence: 141, offset: 196889843 > timestamp: 1586698064, sequence: 142, offset: 196873213 > timestamp: 1586698064, sequence: 142, offset: 196873213 > timestamp: 1586698065, sequence: 143, offset: 196852628 > timestamp: 1586698065, sequence: 143, offset: 196852628 > timestamp: 1586698066, sequence: 144, offset: 196834846 > timestamp: 1586698066, sequence: 144, offset: 196834846 > timestamp: 1586698067, sequence: 145, offset: 196818850 > timestamp: 1586698067, sequence: 145, offset: 196818850 > timestamp: 1586698068, sequence: 146, offset: 196800678 > timestamp: 1586698068, sequence: 146, offset: 196800678 > timestamp: 1586698069, sequence: 147, offset: 196782262 > timestamp: 1586698069, sequence: 147, offset: 196782262 > timestamp: 1586698070, sequence: 148, offset: 196762613 That could become about 20µs jitter from eyeballing the data. The sequence numbers look awfully low though for a system that is up for a while already? > # ppswatch /chroot/ntpd/dev/pps0 > (shows similar output) Good, but does ntpd see the same? > Something is coming out of it. > >> If so, does the device file expected by >> ntpd exist in your chroot environment (generally a symlink to the real >> /dev/pps* device) and is it readable by ntpd? > > # ls -l /dev/*ps* > lrwxrwxrwx 1 root root 5 Apr 12 11:58 /dev/gps0 -> ttyS0 > lrwxrwxrwx 1 root root 4 Apr 12 11:58 /dev/gpspps0 -> pps0 > crw-rw---- 1 root ntp 253, 0 Apr 12 11:58 /dev/pps0 > # ls -l /chroot/ntpd/dev/*ps* > lrwxrwxrwx 1 root root 5 Mar 9 2018 /chroot/ntpd/dev/gps0 -> ttyS0 > lrwxrwxrwx 1 root root 4 Mar 9 2018 /chroot/ntpd/dev/gpspps0 -> pps0 > crw-r--r-- 1 ntp ntp 253, 0 Nov 3 17:15 /chroot/ntpd/dev/pps0 The files used by ntpd should be gps0 / gpspps0. >> Also, if there's an >> apparmor profile for ntpd, check in /var/log/audit/audit.log (or >> wherever that is under Fedora, also in the chroot maybe) that apparmor >> allows the access as well. > > selinux is disabled. > never used apparmor. Fedora / RHEL traditionally wasn't using it, I have no idea what the current state on these platforms is. I just mentioned it because it can cause an otherwise perfectly fine configuration to fail rather obscurely. Regards, Achim. -- +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+ Wavetables for the Waldorf Blofeld: http://Synth.Stromeko.net/Downloads.html#BlofeldUserWavetables _______________________________________________ devel mailing list devel@ntpsec.org http://lists.ntpsec.org/mailman/listinfo/devel
