Ubuntu – CPU overheating in Ubuntu 18.04

There is a bug report filed against thermald:

Erratic behavior of CPU frequency control under load

People get the same errors you report:

Oct 14 22:30:59 p5520 kernel: [ 9481.033687] CPU3: Package temperature above threshold, cpu clock throttled (total events = 5845)
Oct 14 22:30:59 p5520 kernel: [ 9481.033688] CPU7: Package temperature above threshold, cpu clock throttled (total events = 5845)
Oct 14 22:30:59 p5520 kernel: [ 9481.033718] CPU1: Package temperature above threshold, cpu clock throttled (total events = 5845)
Oct 14 22:30:59 p5520 kernel: [ 9481.033719] CPU5: Package temperature above threshold, cpu clock throttled (total events = 5845)
Oct 14 22:30:59 p5520 kernel: [ 9481.033720] CPU0: Package temperature above threshold, cpu clock throttled (total events = 5845)
Oct 14 22:30:59 p5520 kernel: [ 9481.033720] CPU4: Package temperature above threshold, cpu clock throttled (total events = 5845)
Oct 14 22:30:59 p5520 kernel: [ 9481.033722] CPU6: Package temperature above threshold, cpu clock throttled (total events = 5845)
Oct 14 22:30:59 p5520 kernel: [ 9481.033722] CPU2: Package temperature above threshold, cpu clock throttled (total events = 5845)
Oct 14 22:30:59 p5520 kernel: [ 9481.034709] CPU3: Package temperature/speed normal
Oct 14 22:30:59 p5520 kernel: [ 9481.034710] CPU0: Package temperature/speed normal
Oct 14 22:30:59 p5520 kernel: [ 9481.034711] CPU4: Package temperature/speed normal
Oct 14 22:30:59 p5520 kernel: [ 9481.034711] CPU7: Package temperature/speed normal
Oct 14 22:30:59 p5520 kernel: [ 9481.034738] CPU2: Package temperature/speed normal
Oct 14 22:30:59 p5520 kernel: [ 9481.034738] CPU6: Package temperature/speed normal
Oct 14 22:30:59 p5520 kernel: [ 9481.034739] CPU1: Package temperature/speed normal
Oct 14 22:30:59 p5520 kernel: [ 9481.034740] CPU5: Package temperature/speed normal

Comment #18 says to:

try running thermald in a window from command line.

systemctl stop thermald
#thermald --no-daemon --loglevel=info

Then do what triggers this, and attach the output of the above command.

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On my machine I can't duplicate the problem with thermald and tlp loaded. I opened five terminals and typed into each one:

while true ; do : ; done

All that happened is five cores are running at 100% and 3100 MHz. No throttling has occurred but it did make the two laptop fans run on low speed. Normally in Linux they are off (or at least I can't hear them). System temperature is 88 Celsius and keyboard is still responsive to type this answer. The living room does feel a bit warmer though...

Disable intel_pstate at boot by editing your grub configuration.

Open /etc/default/grub with your preferred text editor and locate the line that begins with:

GRUB_CMDLINE_LINUX_DEFAULT

And add intel_pstate=disable at the end of that string. Here's how mine looks after that:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_pstate=disable"

Now, execute:

sudo update-grub

And reboot your laptop. That's it. It should work as smooth and cool as with 16.04.

Some additional information: intel_pstate governor seems to be buggy, or just plain stupid and unable to detect quick temperature raises and reduce the processor speed in consequence. It seems it'd just pray to Saint Cooling Device for it to keep the CPU below the shutdown threshold. In a desktop computer with a DC9 turbine like fan such leap of faith maybe justified, but in laptops with one small fan like my XPS13 it's better to be skeptic and leave those things to the good old ACPI (Atheist Configuration and Power Interface). At least until the intel_pstate governor grow some brains.

And the turbo boost is mostly useless. Chances are that you won't lose anything for having it disabled. That feature was useful in the days of monocore 32 bit processor, but not in the 64 bit multicore world we're living on right now.