On my laptop (ThinkPad X1C5 / i7-7500U / 16GB RAM), I am running latest firefox (currently
67.0+build2-0ubuntu0.18.04.1) with 6-8 windows and around 70-100 tabs at any given time. I have uBlock Origin and I use NoScript aggressivelly.
Recently I've been noticing that when the machine is supposedly idle, the cpu usage is going high enough for long enough that the fan goes on for a few seconds every few seconds/minutes (normally the fan never runs whatever I'm doing).
top shows that one or two
Web Content processes are periodically jumping up to 100% CPU at times that correlate with the fan coming on.
Quitting firefox and reloading the session makes the symptoms go away, so presumably something is going wonky when firefox runs too long.
Yesterday I discovered
about:performance. However, if I open a firefox window on it, I see nothing using enough to seem to warrant the cpu load or fan: There are perhaps 5-10 lines of energy impact "Low" and one, sometimes two, lines of "Medium", all I believe of type "Tab", and none for very long. Activity shown is not obviously different when the fan runs.
I'm now starting firefox from the terminal to see if any relevant diagnostic messages appear. So far none has.
I don't see any obviously relevant bugs in launchpad.
What other methods can I use to pinpoint the cause of the issue?