<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body text="#009900" bgcolor="#FFFFFF">
OK, replies noted carefully.<br>
<br>
From 1200gmt on 10 March, I started running the ntpviz graph
production (and uploading to the web site) hourly. It appears that
the nasty spikes are related to this task. Yes, typo; the results
are nice -n 19 (user script so lower priority).<br>
<br>
CPU governor, new territory for me. R Pi documentation says the
default is "ondemand":<br>
<a class="moz-txt-link-freetext" href="https://www.raspberrypi.org/documentation/configuration/config-txt/overclocking.md">https://www.raspberrypi.org/documentation/configuration/config-txt/overclocking.md</a><br>
which at first sight is a problem. But, my R Pi has the upper and
lower limits both at 700 MHz, so unless the mere task of ramping
nowhere takes cpu oomph, there should be no difference from
"powersave" or "performance". I could edit
/etc/init.d/cpufrequtils or possibly /etc/init.d/raspi-config (not
the usual raspi-config) perhaps.<br>
<br>
$ cpufreq-info<br>
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009<br>
Report errors and bugs to <a class="moz-txt-link-abbreviated" href="mailto:cpufreq@vger.kernel.org">cpufreq@vger.kernel.org</a>, please.<br>
analyzing CPU 0:<br>
driver: BCM2835 CPUFreq<br>
CPUs which run at the same hardware frequency: 0<br>
CPUs which need to have their frequency coordinated by software: 0<br>
maximum transition latency: 355 us.<br>
hardware limits: 700 MHz - 700 MHz<br>
available frequency steps: 700 MHz<br>
available cpufreq governors: conservative, ondemand, userspace,
powersave, performance<br>
current policy: frequency should be within 700 MHz and 700 MHz.<br>
The governor "performance" may decide which speed
to use<br>
within this range.<br>
current CPU frequency is 700 MHz.<br>
cpufreq stats: 700 MHz:100.00%<br>
<br>
To use ntpviz on a remote machine, I'd have to transfer the files.
It appears simple (to me) to rsync from the ntpsec R Pi to somewhere
else, with rsync being nice'd, maybe ionice'd and well throttled
back with the --bwlimit option.<br>
<br>
I'd like to experiment with the gps plots as well, which ISTR can
impact heavily on the ntpsec R Pi significantly. Maybe I could
test overclocking. although that seems inherently unreliable to me
and therefore a "bad thing" for timekeeping.<br>
</body>
</html>