Gary E. Miller gem at rellim.com
Sun Mar 10 03:11:09 UTC 2019

Yo NTPfiend!

On Sat, 9 Mar 2019 09:48:36 +0000
NTPfiend <ntpsec at goldhill.co.uk> wrote:

> Since then, running a cronjob at 0000z with
> ntpviz, produces a nasty spike of local clock jitter, offset and
> clock wobble.

I just ran a quick cProfile of an ntpviz run on an Intel host:

The entire process took 10.214 seconds.
gnuplot took 7.560 seconds.
Just reading the ntpd stats files took 0.923 seconds
Nothing else jumps out as taking much time at all.

So not much can be done to make things faster, beyond replacing
gnuplot with something faster...

A bit worse on a RasPi:

Total time  71.014 
gnuplot  26.467
file reading 14.840

Nothing else jumps out, except that the floating point functions,
like pow(), are a bigger percentage of the runtim on the RasPi.

So maybe I can find some ways to improve running on the RasPi, but
I don't expect anything big.

> I now run the graph production nice'd to n -19 but there is no 
> discernible difference.   No other cronjobs run at 0000z.

I assume you meant nice to n +20.  You said n -19 which would make it
the highest, not lowest, priority.

As the man page says:

    "Niceness values range from -20 (most favorable to the process) to
    19 (least favorable to the process). "

I tried nice +10, no improvement...

The suggestion Paul Theodoropoulos made to check your CPU governor seems
the besst thing to check.  Beyond that, ideas welcome...

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
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