NTP Performance

Gary E. Miller gem at rellim.com
Thu Nov 21 00:33:45 UTC 2019

Yo Richard!

On Wed, 20 Nov 2019 16:02:32 -0600
Richard Laager via devel <devel at ntpsec.org> wrote:

> I now have a second stratum 1 server, with an independent setup. This
> allows me to compare the two.


> Why does ntp1 have this very specific
> repeating pattern of local clock offset? It's roughly +7 us, -5 us, +2
> us, -4 us and then repeats again, over and over.

Check your crontab, and other recurrent jobs.  Those are way too large
for an idle server.  Could be a remote cronjob doing something like a 
log pull or other test.

> I could try fiddling around with the polling interval.

Nah, your jumps are too large for poll to have a noticeable effect on them.

> Another idea might be to switch to the PPS refclock on ntp2 to see if
> it behaves similarly with the ublox PPS.

My bet is that it does.

> As a second question, if you look at the ntp2 weekly graphs, there is
> a single huge transient. Any idea what that might be? I've seen these
> about once or twice a week since I put this in a couple weeks ago:
> https://ntp2.wiktel.com/week/

Usually some sort of kernel stall.  Likely some big job, or a backup,
happened during those events.  Less likely, but very possible, a disk
drive or NFS mount hung the entire system for 50 ms.

Also check the ntpd is locked to your PPS during the events.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 851 bytes
Desc: OpenPGP digital signature
URL: <https://lists.ntpsec.org/pipermail/devel/attachments/20191120/30c20f57/attachment.bin>

More information about the devel mailing list