[EMAIL PROTECTED] wrote: > Michael L. Semon wrote: >> 1) Use my current Linux 2.6.18.1 + LinuxPPS and sit and watch as ntpd >> darts +/- 120 us over the course of a few hours, even when idle. >> >> 2) Reboot to FreeBSD and let the kernel, hardpps, and the NTP kernel >> code make more radical short-term adjustments, and ntpd will dart +/- 10 >> us over a few hours. >> >> 3) Recompile glibc with support with older kernels without breaking my >> system, then fetch Linux 2.6.17.8, fetch Ulrich's last PPSkit alpha, and >> hope it all works. > > If you do try a 2.6.17.X kernel maybe try with linuxpps. It seems > there were changes to the linux clock in 2.6.18 that make convergence > a lot slower. With 2.6.17 or 2.6.16 + linuxpps and default minpoll > maxpoll my time usually stays within +/- 10us. Minpoll 4 maxpoll 4 and > it is down to +/- 3us. For me 2.6.18 and later with default minpoll > maxpoll means +/- 250us. Minpoll 4 maxpoll 4 and I am still looking at > +/- 40us. > > My drift changes by less than 0.6ppm during the temperature cycle of a > day. Freebsd or 2.6.17 (and lower) + linuxpps have no trouble > following that change. 2.6.18 and later react too slowly. > > James
I might try that, one day in the near future. Thank you for motivating me to go back to kernel 2.6.17.8 kernel. I tried the PPSkit patch that is meant for that kernel, and it's a definite improvement over my old setup. [BTW, there was a typo in my previous post. I was using 2.6.19.1, not 2.6.18.1.] The PPSkit patch is marked as alpha for a reason--it burps a little bit, and it does not like the 1000-Hz kernel timer frequency at all--but overall, it does a decent job at the 100-Hz and 250-Hz timer frequencies. Michael _______________________________________________ questions mailing list [EMAIL PROTECTED] https://lists.ntp.isc.org/mailman/listinfo/questions
