[ntp:questions] ntpd and High resolution timer
hal-usenet at ip-64-139-1-69.sjc.megapath.net
Tue Apr 29 17:49:10 UTC 2008
>I am using NTPd and I have guessed that it uses the High Resolution Timer,
>brought to the linux kernel since the 2.6.16 release.
>Does anyone know if it said somewhere in the documentation or any other
>"official" source, a trusty one.
ntpd "just" calls the kernel.
Recent Linux kernels have several modules for timekeeping.
Look in .../Documentation/kernel-parameters.txt
I think the normal one is TSC. (At least on the machines I've
worked with.) The TSC calibration code is buggy. It doesn't
quite get the same answer each time. (If you patch the kernel
to call it several times, you will get several different answers.)
It's very close, but it's off by enough to confuse ntpd. In
particular, it will introuduce a startup transient after each
roboot until ntpd figures out the new drift value. It took my
system several/many hours to do that.
I haven't seen that problem since I added
on the boot time parameters.
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