CPU dip when using collectd


I’m running a Pi for testing different antennas so loaded the Joe Prochazka web portal. I noticed the dips in CPU every 10 minutes so thought I’d forgotten something as I’ve never seen the dips before. I formatted the SD card and loaded 3.5.1 Piaware but the dips are still there.

The dip are genuine as I can see them on the message count on the map view.

Any ideas what is causing them?

CPU utilisation



I note that the message rate drops at the same time so it would be reasonable to expect the CPU use to drop too. I think it is message rate / number of aircraft related, and CPU use drop is the result.

I have noticed something similar here (south coast of England) and wondered if it is the air traffic control regulating aircraft with a gap every 10 minutes for “contingency” space for e.g. late aircraft?

Maybe somebody knows if this is true?



A more likely explanation is that something’s restarting every 10 mins; does dump1090 looks healthy?


dump1090 looks OK to me. Usually you get a message on the map letting you know dump1090 has stopped. I don’t see any such messages.

At each dip, “top” shows dump1090 continues to run at about 45% then gradually drops to 25%. 2 instances of rrdtool appear 1 running at 25% and the other at 10%.

I’ll do another fresh install.