User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:86.0) Gecko/20100101 Firefox/86.0
Steps to reproduce:
- Start Firefox (my machine is a Debian/unstable laptop).
- Use it.
But this may be hard to reproduce.
According to htop, Firefox suddenly started to take up to 100% CPU time (80% in average), and has been like that for several dozens of minutes. According to atop, from 15:30 to 16:30,
PID SYSCPU USRCPU RDELAY VGROW RGROW RDDSK WRDSK CPU CMD
29571 0.89s 77.94s 0.09s 0K 6580K 0K 0K 13% Web Content
29571 0.89s 2m08s 0.13s -1024K 5304K 0K 0K 22% Web Content
29571 1.18s 4m48s 0.21s 1024K 668K 0K 0K 48% Web Content
29571 1.80s 8m05s 0.40s -13.4M -5704K 0K 0K 81% Web Content
29571 1.90s 8m06s 0.47s 11340K -6656K 0K 0K 82% Web Content
29571 1.78s 7m56s 0.36s -1024K 9556K 0K 0K 80% Web Content
29571 1.98s 8m04s 0.35s -18.6M -12.2M 0K 0K 81% Web Content
I don't know whether I was using Firefox when this started to occur. I noticed the issue because the fan of my laptop started to make a lot of noise around 16:00.
I've looked at about:performance, but every tab (from the 12 listed ones) and the only add-on are low (Energy Impact), while the CPU usage issue remains.
Firefox should not take CPU time (or very little).