On Thu, Aug 10, 2017 at 4:49 PM, Miroslav Lichvar <mlich...@redhat.com> wrote: > On Thu, Aug 10, 2017 at 01:22:25PM +0300, Horia Muntean wrote: >> The root dispersion just after a clock update contains what the server >> reports right ? > > It includes dispersion that accumulated since the best measurement was > made (it doesn't have to be the last one) and also peer dispersion of > the measurement. > >> In my opinion the values (root delay end dispersion) taken just after >> the clock update >> along with a short update interval (less than few seconds) would give >> a good max. error estimate. >> In a short amount of time between the updates the root dispersion >> should not increase too much. > > If the network is heavily loaded, chronyd may drop a large number of > consecutive measurements. > > I think what people are interested in is the maximum possible error of > the clock at any time, not just the points when the clock was updated.
I agree. Maybe a whole different log with this info would be more appropriate or one should should just put 'chronyc -n tracking' in a loop and compute system_time + root_delay / 2 + root_dispersion ? > If we know at time t the error was 10 +/- 50 microseconds and at time > t+100 (seconds) it was -20 +/- 70 microseconds, what can we say about > t+1, t+50 and t+99, if we assume the frequency of clock is accurate to > 1 ppm? In 100 seconds you would have a maximum drift of 100 ppm = 100 us and so in 100 seconds your error could grow to 60 + 100 = 160 us. But because at the second measurement you have only a 90 us error it means that during 100 seconds period the error was not higher then 90 us ? Or that was a rhetorical question ? -- To unsubscribe email chrony-users-requ...@chrony.tuxfamily.org with "unsubscribe" in the subject. For help email chrony-users-requ...@chrony.tuxfamily.org with "help" in the subject. Trouble? Email listmas...@chrony.tuxfamily.org.