On 4/5/2012 2:51 AM, David J Taylor wrote:
Mike, have you tried FreeBSD instead? Does it show the same problems?
I have a couple of Soekris Net 4501s running FreeBSD and NTP. They don't have much jitter, but they're a very different architecture. The machine with the jitter is my home "do all" machine - router, firewall, file/email/print/web/ntp server, etc.
It's certainly not critical to get rid of the jitter, it's a time-nuts thing. It bothers me. I noticed that when my backup process ran, NTP jitter dropped very significantly. I'm sure it's related in some way to interrupt latency - the first thing the PPS driver does when a PPS interrupt comes in is to save a nanotimestamp.
Dennis Ferguson mentioned the OS idle loop. So, I added "no-hlt" to the kernel boot line. This did improve things quite a bit. All else the same, it reduces jitter to the 3-4 us range - better than the 20 us without, but not as good as the 1-2 when I simply load up the processor.
_______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
