On 2106.02.20 00:50 Arto Jantunen wrote:

When using kernel 4.5-rc4 my Skylake machine runs very warm since all
cpu cores are always kept at 3.10Ghz (with maximum without turboboost
being 2.6Ghz), completely regardless of load. Swapping between the
governors (performance and powersave) doesn't change the result in any
way, frequency remains at a constant 3.10Ghz.

The machine is using the intel_pstate driver, I don't know if it's
possible to choose to use the acpi driver instead (without recompiling
the kernel so that intel_pstate is not supported).

If you use grub then you can disable the intel_pstate driver by modifying
the grub command line. Here is an example, where I have left other stuff
that I use:

GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 intel_pstate=disable net.ifnames=1 biosdevname=0"

Here is an example, with the intel_pstate directive by itself:

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

If the intel_pstate driver is disabled, then the acpi-cpufreq CPU
frequency scaling driver will be used. 
Remember to update grub after the above edit.

If you do not use grub, then I don't know.

Please, and as a test, also try this and report back:

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=no_hwp"

I can force the frequency down manually with cpufreq-set, so the problem
doesn't seem to be with the actual frequency changing.

Cpuinfo (taken from 4.4 which doesn't have the problem):

Is kernel 4.5-rc4 the first one you have tried in the 4.5 series?
What I am asking is if you know if the issue was introduced between
kernels 4.4 and 4.5-rc1 (most likely) or between 4.5-rc3 and 4.5-rc4 or?

What distribution, if any, of Linux do you use?

It might make sense to take this off-list and into a bugzilla bug report.

... Doug