On Thursday, 5 March 2020 00:28:21 GMT Walter Dnes wrote: > I've cobbled together a script to select cpu governors and speeds. > One weird thing I've noticed is that reported cpu speed doesn't quite > match the selected speed. E.g. on my machine (yours will vary)... > > cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies > > ...shows avalable speeds... > > 3001000 3000000 2900000 2800000 2700000 2600000 2500000 2400000 2300000 > 2200000 2100000 2000000 1900000 1800000 1700000 1600000 > > ***IMPORTANT*** "userspace" governor must be present. > > /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq reports speeds > very close to, but slightly lower than the selected values, and they also > seem to jump around a bit. What gives?
My reported CPU frequency is also slightly lower than the values reported in
'scaling_available_frequencies' and it fluctuates as the load on the CPU
varies. I take these values to be rounded upper limits, rather than what the
CPU will be pegged at.
MoBo firmware plus kernel options seem to control (limit) the CPU frequency.
I was installing Gentoo on a laptop, using a minimal CD and the CPU thermal
cut out would kick in every time I tried to install packages shutting down the
PC. The frequency at the time reached 3600-3900MHz. After I completed the
install by limiting jobs and using an external cooling fan, I booted with my
own newly configured kernel. I felt disappointed to notice the frequency
would never go above 2500, no matter what scaling_governor I used and what max
frequency I selected. I also tried using sys-power/cpupower to manipulate
governors and frequencies, but nothing would change this hard limit of
2500MHz.
I can't recall what the LiveCD was missing in the kernel/packages - it might
have been acpi-freq. This is the current state of affairs:
$ cpupower frequency-info
analyzing CPU 0:
driver: acpi-cpufreq
CPUs which run at the same hardware frequency: 0
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: 4.0 us
hardware limits: 1.40 GHz - 2.50 GHz
available frequency steps: 2.50 GHz, 2.10 GHz, 1.80 GHz, 1.40 GHz
available cpufreq governors: ondemand userspace performance schedutil
current policy: frequency should be within 1.40 GHz and 2.50 GHz.
The governor "schedutil" may decide which speed to use
within this range.
current CPU frequency: Unable to call hardware
current CPU frequency: 1.31 GHz (asserted by call to kernel)
boost state support:
Supported: yes
Active: yes
Anyway, since I couldn't push it above 2500MHz, I've left it alone running on
schedutil and it never overheats or cuts out.
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