fallenpega...@gmail.com said: > At the F2F this weekend, ESR brought up that you think we may be able to > excise the PLL code from NTPsec.
> Can you expand on that, please? It's more complicated that a simple excise. My knowledge may be buggy. It's not clear that any of this makes Eric's job easier. There are two RFCs describing PPS stuff. RFC 1589, 37 pages A Kernel Model for Precision Timekeeping https://tools.ietf.org/html/rfc1589 RFC 2783, 31 pages Pulse-Per-Second API for UNIX-like Operating Systems, Version 1.0 https://tools.ietf.org/html/rfc2783 The second is the API to read the info the kernel captures when a PPS type pulse happens and all the stuff to turn it on/off and such. The first describes a PLL that lives in the kernel. I thought the RFC included large code fragments, but I didn't see them. The idea is that ntpd hands off timekeeping duties to the kernel and the kernel does all the work. ntpd just monitors things and tells the kernel to stop if things get out of whack. Why is there that much code in the kernel? I think that's leftover from when machines were slow and busy and schedulers were dumb. I think it should be possible to wake up user code on the PPS, read the time stamp, do the calculations in user land, and tell the kernel what to do all within a reasonable amount of time. That's basically moving the inner loop of the kernel PLL out to user land. One complication in this area is that most kernels don't implement the wake-on-PPS option. ntpd polls. The part of this area that I don't understand is the PLL parameters. ntpd already adjusts the polling rate and along with that various parameters. Will the pseudo-kernel mode work at the extreme end of the normal parameters or is the kernel PLL totally different? ------ Linux has rewritten that area. Several years ago, there was a time when there was no kernel PLL. ntpd kept on working. We should be able to comment out a few lines of code and just try it to see how well/poorly it works. It would be interesting to compare various OSes running on the same hardware. -- These are my opinions. I hate spam. _______________________________________________ devel mailing list devel@ntpsec.org http://lists.ntpsec.org/mailman/listinfo/devel
