On 20 August 2013 17:16, Mike S <[email protected]> wrote: > > By default, the tsc is calibrated at each boot, which means that timing > will likely change (and ntp drift values will be off) each time you boot. > > There's a linux kernel command line option which will fix that and provide > consistency between boots, something like "clocksource=tsc > tsc_khz=2410988". The exact value depends on how fast the processor is > clocked.
True, this will help, and needless to say, dynamic CPU frequency etc. is a no-no, and it's best to bind the (ntp) process to a single CPU core. However I find it that the drift differences will be sub-1ppm across reboots. In my case (data center) they are in fact sub-500ppb - calculated with ptpd. You always need some stabilisation time after reboot, especially that your wall clock will likely get re-initialised from RTC. I think overcoming that may sometimes take longer than re-calculating drift. I pointed to TSC mostly because of the PTP GM side of the original poster's query. Regards Wojciech - Wojciech Owczarek _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
