Hal Murray wrote: > The quirk is that the drift changes when I run the monitoring > program. It changes more if I poll faster. It changed by > 20 ppm when I was polling with a 10 ms delay and it's more > than 80 ppm and still climbing when I reduced the delay to 1 ms.
My first guess would be a bug in the tickless clock in some recent Linuxes. If possible, disable this and see if it improves things. If it does take it up with the Linux kernel developers (I think this one came from Red Hat), but let us know as well, as this is something that was introduced without consulting the NTP community. Note that tickless clock processing also led to some unofficial changes in ntpd, in Linux, which again are the responsibility of the Linux developers. Note, to operate with 1ms delays in a non-tickless system, you need a 1000Hz clock and that is vulnerable to lost interrupts from slow device drivers. I'm assuming that the UPS monitoring program runs in user space, otherwise it could be causing lost interrupts, itself. _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
