[ntp:questions] clockstats pausing during ntpq poll

Dave Hart hart at ntp.org
Fri Feb 17 17:23:15 UTC 2012


On Fri, Feb 17, 2012 at 16:44, unruh <unruh at invalid.ca> wrote:
> On 2012-02-17, Dave Hart <hart at ntp.org> wrote:
>> On Fri, Feb 17, 2012 at 06:06, A C <agcarver+ntp at acarver.net> wrote:
>>> As part of my testing I'm observing the main log, peers, loops, and
>>> clockstats in one window while I observe ntpq (running on a different
>>> machine) polling the server every five seconds. ?The PPS refclock has flag4
>>> set so that clockstats are recorded.
>>>
>>> What I've noticed is that normally the clockstats is updated once per second
>>> as the PPS ticks. ?However, during a query by the remote ntpq instance, the
>>> clockstats file pauses for about one second and then resumes. ?You can see
>>> it below in a direct copy from the clockstats file. ?There's a missing
>>> 'tick' at 21828 seconds and one at 21832. ?PPS is most certainly ticking at
>>> these times. ?It is extremely obvious, when the two terminal windows are
>>> side by side, that the ntpq poll freezes ntpd.
>>>
>>>> 55974 21822.994 127.127.22.0 -0.000033126
>>>> 55974 21824.099 127.127.22.0 -0.000026711
>>>> 55974 21825.994 127.127.22.0 -0.000010522
>>>> 55974 21826.993 127.127.22.0 -0.000039330
>>>> 55974 21827.994 127.127.22.0 -0.000019143
>>>> 55974 21829.099 127.127.22.0 -0.000006765
>>>> 55974 21830.993 127.127.22.0 -0.000023575
>>>> 55974 21831.993 127.127.22.0 -0.000033386
>>>> 55974 21833.102 127.127.22.0 -0.000004012
>>
>> Round those figures in the 2nd column to whole seconds and you'll note
>> there are no missing PPS events.  You don't say which ntpq query, so
>
> Uh. Yes, there are!. Maybe no the ones he mentions, but there are
> missing seconds.
>
> The rounded figures are
> 23 24 26 27 28 29 31 32 33
>     ^           ^

Good catch, I obviously need to get more sleep.

Cheers,
Dave Hart


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