Re: PPS in GPSD vs Chrony

[Gary E. Miller]

Yo Miroslav!

On Wed, 1 Jul 2020 15:49:37 +0200
Miroslav Lichvar <mlichvar@redhat.com> wrote:

> > Interesting.  Do you have data on this configuration compared to
> > plain PPS?  
> 
> Here is a quick test comparing the PPS rate of 32 and 1 Hz. The
> polling interval didn't change (1 second) and it was running on an
> idle system (an Orange Pi PC). The RMS offset value is about 4.7 ns vs
> 13.5 ns, so the improvement is not as good as the square root of the
> rate ratio, but still significant.
> 
> https://i.imgur.com/9E7zUai.png

If the poll rate stays at 1Hz then why does a higher "PPS" help?  Maybe
it keeps chronyd (I assume you are using chronyd) fresh in the CPU
cache and running on its own core.  This is an odd one.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@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

pgp9mWfXOqCyP.pgp
Description: OpenPGP digital signature