bug#37904: CPU overheating on recent laptops

["Ludovic Courtès" <ludovic.courtes@inria.fr>]

Hello,

I’ve had reports that Guix System on recent Dell laptops tends to lead
to overheating (with GNOME and all).

According to /sys/devices/system/cpu/cpu?/cpufreq/scaling_governor, all
the CPUs are running on the ‘performance’ governor by default, with
frequencies around 4 GHz (CPUs on these machines range from 400 MHz to
4.7 GHz).  So with just a load of 0.3 or so, the CPUs would be at ~65°C
(as reported by ‘sensors’) and the fans would start making noise.

If we explicitly change to the ‘powersave’ governor by writing to /sys,
frequencies go down and the machine behaves better.

However, I would expect UPower to do the right thing in the first
place.  Do you know what the story is here?  Are we missing some config
bits?

Also, there used to be an “ondemand” governor, which is no longer listed
in /sys/devices/system/cpu/cpu?/cpufreq/scaling_available_governors.
Was it removed or are we just missing a kconfig option?

Thanks,
Ludo’.