Ubuntu – One core goes to 100% usage and activate fan on Ubuntu 18.10,

18.10cpufan

I recently switched from Windows to Ubuntu 18.10 with this Notebook, and despite is not a serious problem I noticed that often the fan turn on for ~3 sec. then turn off for ~5 sec. and then turn on again following this pattern.

I've taken a look to system monitor and I noticed that every time it happens, is because one of the cores of the CPU has gone to 100% of usage for few seconds (while the others are almost idle), like it shows the pic below:enter image description here

I don't get why sometimes one core goes to 100% (for example it happens when I'm just running Firefox with few tabs on the process Web Content) and if I can do sometimes to avoid it (at least to the fan, beacuse the continuosly turn on/off it's a bit annoying).

Thanks!

UPDATE
It's a little bit difficult to reproduce the problem when I try. Anyway, testing again showed me that sometimes fans activate in the same way also when no CPU reaches 100% of utilization (just lower peaks). Running ps aux --sort=-pcpu | head as @Fabby in the comment said, gave me the following :

  1. ollaw 2053 15.1 0.7 443272 126220 tty2 Sl+ nov28 17:00 /usr/lib/xorg/Xorg vt2 -displayfd 3 -auth /run/user/1000/gdm/Xauthority -background none -noreset -keeptty -verbose 3
  2. ollaw 7543 12.0 2.4 2532128 402472 tty2 Sl+ 01:03 1:22 /usr/lib/firefox/firefox -new-window
  3. ollaw 7612 10.8 2.5 1978608 413444 tty2 Sl+ 01:03 1:13 /usr/lib/firefox/firefox -contentproc -childID 1 -isForBrowser [etc....]
  4. Almost the same as 3
  5. ollaw 2234 5.3 1.4 3300616 244520 tty2 Rl+ nov28 5:58 /usr/bin/gnome-shell

Other informations:

  • No error in dmesg since someone in the answer asked.
  • Currently using nvidia-driver-390 drivers.
  • Nvidia is in intel-mode (but pretty sure it happens also in nvidia-mode).

Best Answer

Use a tool like top during the spikes to see which processes are using up your CPU and then kill them (by closing the app or with the kill CLI tool).

Or if it's a kernel issue, you would see some errors in dmesg, so at least run the command. If there's some text that's red colored or looks like an error that could be the problem.

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