In article <[EMAIL PROTECTED]>, David Woolley <[EMAIL PROTECTED]> writes: >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.
Interesting suggestion. Thanks. Something changes when I turn off the tickless stuff in the kernel. I haven't sorted out what's going on yet. >Note that tickless clock processing also led to some unofficial changes >in ntpd, in Linux, which again are the responsibility of the Linux >developers. I'm using a recent ntp-dev with no changes from any distribution channels. >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. Yes. It's a simple/dumb user program. It pokes a serial port a lot and occasionally writes a line to a log file. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
