[ntp:hackers] Of Linux and jitter

David L. Mills mills at udel.edu
Tue Oct 19 10:57:49 PDT 2004


1. All the backroom and campus machines are now running ntp-dev and all 
seem to work except Linux albert on the campus wire. It segfaults after 
a few minutes. I am dumb with Linux debugging tools, so I'll leave the 
carcass on the hope some Linux jockey can look at it.

2. I'm very suspicious about the Solaris jitter using a serial port and 
any of several radios. The jitter can be over one second(!) and varies 
in intensity with time. I can't believe the port interrupt routine can 
have jitter that high. The jitter does not occur with a SunOS SPARC IPC 
running ntp-dev, which is now the best timekeeper we have. The jitter 
first showed up on Ultra-1 pogo running Solaris 8/9 and Blade 1500 
running Solaris 9. Could there be something in the ntpd I/O code causing 
this? It's only in the serial port code; there is no such jitter in the 
packet I/O code.


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