How to use AMD P-State in Linux

mcury · May 6, 2023, 2:38pm

I set amd-pstate=active to test. Using zen3 CPU here.
I’m using all the defaults and it seems to be ok.

cpupower.service shows amd_pstate_epp driver with powersave governor.
/sys/devices/system/cpu/cpufreq/policy0/energy_performance_preference shows balance_performance.

cpu frequency

cpu MHz         : 550.000
cpu MHz         : 3966.583
cpu MHz         : 3709.286
cpu MHz         : 550.000
cpu MHz         : 550.000
cpu MHz         : 550.000
cpu MHz         : 550.000
cpu MHz         : 550.000
cpu MHz         : 550.000
cpu MHz         : 550.000
cpu MHz         : 550.000
cpu MHz         : 550.000
cpu MHz         : 3578.267
cpu MHz         : 550.000
cpu MHz         : 550.000
cpu MHz         : 550.000

BS86 · May 6, 2023, 3:08pm

yes, for some reason, they changed the default to the more sane balance_performance - I still use balance_power though

ricklinux · May 6, 2023, 3:26pm

I just set mine to amd-pstate=active but cpu power service won’t start. Not sure why as i had this working before.

Edit:

[ricklinux@eos-plasma ~]$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
amd_pstate_epp

[ricklinux@eos-plasma ~]$ cpupower frequency-info   
analyzing CPU 3:
  driver: amd_pstate_epp
  CPUs which run at the same hardware frequency: 3
  CPUs which need to have their frequency coordinated by software: 3
  maximum transition latency:  Cannot determine or is not supported.
  hardware limits: 550 MHz - 4.56 GHz
  available cpufreq governors: performance powersave
  current policy: frequency should be within 550 MHz and 4.56 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency: Unable to call hardware
  current CPU frequency: 550 MHz (asserted by call to kernel)
  boost state support:
    Supported: yes
    Active: no
[ricklinux@eos-plasma ~]$

[ricklinux@eos-plasma ~]$ systemctl status cpupower.service
× cpupower.service - Apply cpupower configuration
     Loaded: loaded (/usr/lib/systemd/system/cpupower.service; enabled; preset: disabled)
     Active: failed (Result: exit-code) since Sat 2023-05-06 11:19:36 EDT; 8min ago
    Process: 3564 ExecStart=/usr/lib/systemd/scripts/cpupower (code=exited, status=1/FAILURE)
   Main PID: 3564 (code=exited, status=1/FAILURE)
        CPU: 3ms

May 06 11:19:36 eos-plasma systemd[1]: Starting Apply cpupower configuration...
May 06 11:19:36 eos-plasma systemd[1]: cpupower.service: Main process exited, code=exited, status=1/FAILURE
May 06 11:19:36 eos-plasma systemd[1]: cpupower.service: Failed with result 'exit-code'.
May 06 11:19:36 eos-plasma systemd[1]: Failed to start Apply cpupower configuration.
[ricklinux@eos-plasma ~]$

BS86 · May 6, 2023, 3:31pm

what do you want to set with cpu-power?

That tool lost its value when using epp for me as we shouldn’t change governor anyway and frequencies are mostly non-relevant numbers anyway (the power level that the CPU uses doesn’t depend on frequencies for some generations now)

ricklinux · May 6, 2023, 3:31pm

So we shouldn’t be using cpu power anymore?

BS86 · May 6, 2023, 3:35pm

depends on what you want to achieve - but most options it offers are non-relevant now.

It can’t change the energy_performance_preference which is the only value that makes sense to modify now. I use a self-written systemd-service with a self-written bash script for that:

cat /etc/systemd/system/set_pstate_epp_preference.service             
[Unit]
Description=Set AMD P-State-EPP preference

[Service]
ExecStart=/usr/bin/set_balance_power.sh

[Install]
WantedBy=multi-user.target

cat /usr/bin/set_balance_power.sh                        
#!/usr/bin/env bash

sleep 5
echo balance_power > /sys/devices/system/cpu/cpufreq/policy0/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy1/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy2/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy3/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy4/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy5/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy6/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy7/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy8/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy9/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy10/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy11/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy12/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy13/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy14/energy_performance_preference
echo balance_power > /sys/devices/system/cpu/cpufreq/policy15/energy_performance_preference

I know that there are better ways to set those values, but I didn’t have time to write them.

that said - it does not make that much of a difference so using the default is ok, too.

ricklinux · May 6, 2023, 3:39pm

Mine shows the same as @mcury balance_performance

[ricklinux@eos-plasma ~]$ cat /sys/devices/system/cpu/cpufreq/policy0/energy_performance_preference 
balance_performance

So i can just uninstall cpupower?

ricklinux · May 6, 2023, 3:41pm

How are you getting it to show the cpu frequency? I set mine and cpupower service doesn’t seem to work.

mcury · May 6, 2023, 3:45pm

I’m using cpupower to check the driver and the governor being used.
You can leave it installed and disabled just to check these values in case you need.

To check it, issue the following command: cpupower frequency-info

As you can see below, cpupower doesn’t provide the options such as, balance_power balance_performance…

$ cat /etc/default/cpupower

# Define CPUs governor
# valid governors: ondemand, performance, powersave, conservative, userspace.
#governor='ondemand'

Based on @BS686 posts, you would need to use another method to change the values, such as the script he provided.

To check the CPU frequency, I used:

watch -n1 "grep \"^[c]pu MHz\" /proc/cpuinfo"

ricklinux · May 6, 2023, 3:50pm

So i should leave this commented then because it’s now controlled by the kernel?

Edit: I get this when run.

[ricklinux@eos-plasma ~]$ cpupower frequency-info
analyzing CPU 12:
  driver: amd_pstate_epp
  CPUs which run at the same hardware frequency: 12
  CPUs which need to have their frequency coordinated by software: 12
  maximum transition latency:  Cannot determine or is not supported.
  hardware limits: 550 MHz - 4.56 GHz
  available cpufreq governors: performance powersave
  current policy: frequency should be within 550 MHz and 4.56 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency: Unable to call hardware
  current CPU frequency: 3.46 GHz (asserted by call to kernel)
  boost state support:
    Supported: yes
    Active: no
[ricklinux@eos-plasma ~]$

pebcak · May 6, 2023, 3:52pm

Does power-profiles-daemon show those options? Just being curios

powerprofilesctl list

My CPU or firmware on this laptop doesn’t support amd_pstate so I couldn’t check.

mcury · May 6, 2023, 3:53pm

I’m not using it… I would leave it commented since governor “ondemand” is not available anymore for amd_pstate_epp, Actually, cpupower does not even show the options we are using now as available in that config file…

I suppose that cpupower.service is failing to launch because of that… You probably set a governor that amd_pstate_epp doesn’t support.

ricklinux · May 6, 2023, 3:54pm

I had it set to ondemand before. But i commented it out now.

mcury · May 6, 2023, 3:55pm

Not sure if this is what you asked

$ powerprofilesctl list

  performance:
    Driver:     amd_pstate
    Degraded:   no

* balanced:
    Driver:     amd_pstate

  power-saver:
    Driver:     amd_pstate

ricklinux · May 6, 2023, 3:57pm

Why does it show amd_pstate here when we have set?

amd_pstate_epp

mcury · May 6, 2023, 3:58pm

hmm, did you set it in your kernel cmdline and run reinstall_kernels?

ricklinux · May 6, 2023, 3:58pm

I’m on grub so i ran update grub command.

Edit: Is it supposed to be amd-pstate=active or amd_pstate=active

mcury · May 6, 2023, 4:01pm

It should be working… At least this is all I have done here, updated my kernel cmdline, reinstalled kernels and next boot it was already set.
Are you using zen3?

amd_pstate=active

pebcak · May 6, 2023, 4:01pm

Yes.
Since those options (balance_power balance_performance…) are not available for cpupower, I thought maybe one could switch between them using powerprofilesctl. But it doesn’t seem so …

powerprofilesctl --help
Usage:
  powerprofilesctl COMMAND [ARGS…]

Commands:
  help       Print help
  version    Print version
  get        Print the currently active power profile
  set        Set the currently active power profile
  list       List available power profiles
  list-holds List current power profile holds
  launch     Launch a command while holding a power profile

mcury · May 6, 2023, 4:03pm

I didn’t even know that powerprofilectl existed… I’ll check it… is this available in arch’s wiki?