Spoon wrote: > Hans Jørgen Jakobsen wrote: > >> Dmitry Ivanov wrote: >> >>> Spoon wrote: >>> >>>> I've noticed something I find very strange on the systems I have to >>>> work with. Every time I reboot the computer, the clock skew of the >>>> local clock changes, sometimes by what seems to be a huge amount. >>>> >>>> For example, I boot the computer, let ntpd run for 12 hours, and the >>>> value recorded in the drift file is 35 ppm. I reboot the computer, let >>>> ntpd run for 12 hours, and I get 5 ppm... >>> >>> I see the same behaviour on many systems. Looks like common problem. >> >> Could it be that some systems at reboot try to calibrate the clock >> (whatever that might be) relative to the TOD chip? >> On some systems the TOD chip has the lowest frequency offset >> and this would on systems not runing NTP lead to a system drifting less. >> But it's poison for the value in the driftfile. > > # dmesg | grep -i calib > Calibrating delay using timer specific routine.. > 2535.15 BogoMIPS (lpj=12675781) > > Are you referring to this calibration? > > I'll check the source code to find where this message comes from.
It's coming from init/calibrate.c /* This routine uses the read_current_timer() routine and gets the * loops per jiffy directly, instead of guessing it using delay(). * Also, this code tries to handle non-maskable asynchronous events * (like SMIs) */ http://lxr.linux.no/source/init/calibrate.c I see it's possible to skip the calibration code by providing a boot time parameter. I'll test this and report back here. Regards. _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
