[ntp:questions] Precision changed after upgrade from ntp 4.2.4p4 to 4.2.6p2

Miroslav Lichvar mlichvar at redhat.com
Mon May 5 09:13:03 UTC 2014


On Sun, May 04, 2014 at 08:29:26PM +0100, Caecilius wrote:
> After upgrading ntp from 4.2.4p4 to 4.2.6p2 as part of a Linux upgrade
> from Debian Lenny to Squueze, I've noticed that the precision variable
> has changed from -20 to -22. So it appears that my clock has now got a
> better precision. But the hardware is unchanged, and I'm running the
> same kernel.
> 
> I thought the precision was dependent on the "granularity" of the
> system clock, which I would have expected to be independent of the ntp
> version and any other userland code.  Am I misunderstanding something
> perhaps?

The older ntpd is probably using gettimeofday() which has microsecond
resolution (-20 in the log scale) and not the nanosecond
clock_gettime().

-- 
Miroslav Lichvar


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