Questions[intel](ubuntu)

I've just finished building a new machine with a i9 9900k CPU, a CPU with 1 socket, 8 cores and 16 threads. I installed Ubuntu Bionic on it, and I am just about to add checks to the CPU temperatures.

However, when I run cat /sys/class/thermal/thermal_zone*/temp (as recommended by https://askubuntu.com/a/15834/822289) I get 3 results:

27800
40000
28000

Edit 1: The "correct" CPU-temperature is the one shown at thermal_zone2.

I thought maybe a 3rd-party program like acpi might help:

# acpi -t
Thermal 0: ok, 27.8 degrees C

But that one only gives me what's on thermal_zone0. What do the other ones represent, especially thermal_zone1, and how can I find more information about that?

Edit 2: The answer to what do the other ones represent can be found by running the following command:

cat /sys/class/thermal/thermal_zone*/type

Which gives me, in this case, the following output:

acpitz
pch_cannonlake
x86_pkg_temp

I had this same issue in my last attempt to upgrade (with a clean install) from 16.04 LTS to 18.04 LTS. When I am browsing internet and specially when I am playing videos my CPU+GPU raises to fast to high levels causing throttling to fire and producing intolerable lags, leaving the system unusable for about 60 seconds or more.

With Ubuntu 16.04 LTS I never experienced this problem. Of course temperatures raised and throttling fired frequently (after all this is a laptop), but system was never unusable and video playback was smooth.

My previous solution was to downgrade to 16.04 LTS again, but now I need the newer version so I want to find a solution.

System specs:

• CPU: Intel Core i7-6500U
• GPU: Intel HD Graphics 520
• Ubuntu: 18.04 LTS
• Linux: 4.15.0-30
• Mesa: 18.0.5
• Hardware acceleration: on

UPDATE 1

Definitively it is a problem with frequency throttling. Instead of throttling CPU frequency to avoid overheating the procesor, the system is waiting until temperature reaches a limit (default of 85ºC) and then intel_powerclamp module fires, turning the system unusable for 60 seconds or more.

I would expect a progressive performance degradation from intel_powerclamp, but no, it is all or nothing. ¿Can this be configured?

My current solution is a modification of the script of this answer. It seems to work, but it is a big hack. There must be a conventional way to tweak system configuration to accomplish the same result.

UPDATE 2

If I turn off frequency turbo boost (echo "1" | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo) the problem completely disappears. Temperature never reaches the limit and the script introduced on update 1 nor intel_powerclamp fires and the laptop is smooth and usable.

Problem now is that turbo boost is disabled. With Ubuntu 16.04 LTS I never had this issue.

This is clearly a bad configuration of the thermal management subsystem of Ubuntu 18.04 LTS. Is there a way to fix it?

UPDATE 3

System is still unusable. Installing Ubuntu 18.04 LTS server and anything else than Gnome3 works. Well, it's not a novelty that Gnome sucks, but it was usable with 16.04...

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I tried this but it seems to only detect Nehalem CPUs.