Paul Theodoropoulos paul at anastrophe.com
Sat Mar 9 22:12:32 UTC 2019

What CPU governor are you running? If it's not a fixed speed governor, 
that can cause significant additional 'noise' as the the clock speed pegs 
the needle while processing the graphs.  You should use either 'powersave' 
or 'performance'. Those lock the speed at minimum or maximum, 
respectively. Lots of people confuse the 'conservative' governor with 
minspeed lock, but conservatively simply ramps up the clock speed slower 
than the other governors.

Some spikes are to be expected if you run intermittent loads on the ntpsec 
server, regardless of the governor. The clock crystal on Raspi's are _not_ 
TXCO - Temperature compensated crystal oscillators. Which is to be 
expected on a super-low cost device.

I run all ntpviz processing on my older rev 1.2 B+, and ntpsec only on the 
newer 1.3 B+.

On 3/9/2019 1:48 AM, NTPfiend wrote:
> Just under a week ago, I updated ntpsec to the latest (ntpsec-1.1.3+) 
> from ISTR 1.1.1.   Since then, running a cronjob at 0000z with ntpviz, 
> produces a nasty spike of local clock jitter, offset and clock wobble.   
> The system rapidly recovers.
> http://www.goldhill.uk/ntpvizplots/index.html
> I now run the graph production nice'd to n -19 but there is no 
> discernible difference.   No other cronjobs run at 0000z.
> I would be inclined to think my Raspberry Pi:
>    Hardware revision 0010, Model B+
>    Uputronics GPS board
> was inadequate but I don't recall such a performance hit with the 
> earlier 1.1.1
> I'm not sure what to try next; it seems inadequate to have to run ntpviz 
> away from the ntpsec R Pi.   What have I missed ?
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Paul Theodoropoulos

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