Currently, some of the Zen2 and Zen3 processors support amd-pstate and the new amd_pstate_epp scaling driver. You also have to have CPPC support enabled in your UEFI. In the future, it will be supported on more and more AMD processors.
There are two methods for adjusting CPU performance on AMD CPU/APUs:
amd-pstateacpi-cpufreq
acpi-cpufreq is currently default for most distros, regardless of the CPU in use. on most AMD CPUs this is a limiting factor, as it offers limited performance options with only a few fixed levels for CPU speed.
On newer AMD CPUs and APUs (aka Zen2 and above), there is a more advanced method called Collaborative Processor Performance Control (CPPC mentioned in the requirements), which allows for fine-tuned and continuous adjustments of the CPU frequency, with the potential to provide better performance and energy efficiency compared to the older fixed levels.
And that's where amd-pstate comes in, as it is a new kernel module that supports the newer and more efficient AMD P-States mechanism.
There are 3 options available, listed below, in order of release:
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amd_pstate=passive(Kernel 6.1+) -
amd_pstate=active(Kernel 6.3+) -
amd_pstate=guided(kernel 6.4+)
amd_pstate=passive
When you set amd_pstate=passive, the processor aims for a certain performance level relative to its maximum capacity. Below a specific point, the performance is average, while above it, the performance remains at its best.
amd_pstate=active
Setting amd_pstate=active gives low-level control to the processor's firmware. It can prioritize either performance or energy efficiency based on software hints AND the amd_pstate_epp driver.
The amd_pstate_epp (Energy Performance Preference) driver provides the firmware with a hint.
On most AMD CPUs, these hints are:
defaultperformancebalance_performancebalance_powerpower
amd_pstate=guided
Choosing amd_pstate=guided lets the platform automatically select a suitable performance level within a given range based on the workload.
To enable the amd_pstate_epp scaling driver, which also includes instructions for the original amd_pstate scaling driver, you will need to add a kernel parameter. If you are using PopOS (like me) or any other distribution utilising kernelstub, this process can be easily accomplished with the following steps:
IMPORTANT: The option 'amd_pstate=guided' is only available on Kernel 6.4 or later versions.
- Add the desired kernel parameter by running the following command:
# Add the desired Kernel Parameter
sudo kernelstub -a "amd_pstate=guided" # Change this to passive if preferred
- To confirm that the kernel parameter has been successfully added, use the following command:
# Verify that the kernel parameter has been added
sudo kernelstub -p
To verify that this is functioning correctly, reboot your machine, and run
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
If amd_pstate was set to either passive or guided, this should now show:
amd-pstate
To enable the amd_pstate_epp scaling driver, which also includes instructions for the original amd_pstate scaling driver, you will need to add a kernel parameter. If you are using PopOS (like me) or any other distribution utilising kernelstub, this process can be easily accomplished with the following steps:
IMPORTANT: The option 'amd_pstate=active' is only available on Kernel 6.3 or later versions.
- Add the desired kernel parameter by running the following command:
# Add the desired Kernel Parameter
sudo kernelstub -a "amd_pstate=active"
- To confirm that the kernel parameter has been successfully added, use the following command:
# Verify that the kernel parameter has been added
sudo kernelstub -p
To verify that this is functioning correctly, reboot your machine, and run
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
If amd_pstate was set to active, this should now show:
amd-pstate-epp
The amd_pstate_epp scaling driver introduces a new parameter known as "Energy Performance Preference" (EPP) hint. This setting can be adjusted through sysfs, with two main files controlling it:
-
/sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference: This file displays the current EPP hint for the respective CPU core. -
/sys/devices/system/cpu/cpu*/cpufreq/energy_performance_available_preferences: This file provides the available EPP hints for the respective CPU core.
To see your current EPP hints (note * = all CPU cores), use the following command:
cat /sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference
To view the available EPP hints (which should be the same for all cores), use this command:
cat /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_available_preferences
# What you see below, is my results on my Ryzen 7 7735HS
default performance balance_performance balance_power power
If you'd like to set the same EPP hint across all cores, for instance, setting EPP to "power" (like in my case), you can use this command:
echo "power" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference
power
NOTE: This is not permanent, and will be reverted upon reboot. To make this permanent, you can use multiple tools, or, create a cron job
The Scaling Driver is different than the CPU governor (e.g. powersave, performance, ondemand, schedulutil, etc.), and the two can be mixed and matched to create your perfect combo.
To check what's the current cpu governor, use the command below:
cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
In my case, that's what I'm seeing:
user@machine ~> cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
powersave
If you've configured amd_pstate=active, you can mix and match governors with EPP hints. Phoronix has an excellent breakdown of all the combinations of governors + EPP hints (referenced in the resources section at the end of this post).
Personally, for my laptop usage, I still find amd_pstate=passive to be the best for my use case, but YMMV depending on the devices you're configuring this on, and your use case :)
Thanks to the amazing work of /jothiprasath, we've can now switch EPP Hints automatically when going from Battery to AC, and viceversa.
Here's the link to his amazing work Auto-EPP
NOTE: This hasn't been written by me and I've yet to test it, please make sure you have reviewed the code before deploying it to your machines
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an amazing Redditor (whose post I cannot find anymore) that served as a basis for this very post (if anyone finds it, please do let me know, and I'll reference them right away)
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ChatGPT who helped me phrase some sentences a bit better
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Benchmarks for server using AMD P-State EPP: https://www.phoronix.com/review/linux-63-amd-epyc-epp
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Benchmarks for Ryzen mobile system using AMD P-State EPP: https://www.phoronix.com/review/amd-pstate-epp-ryzen-mobile
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Kernel.org documentation on new AMD P-State driver: https://www.kernel.org/doc/html/latest/admin-guide/pm/amd-pstate.html
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Arch Wiki page on CPU Scaling: https://wiki.archlinux.org/title/CPU_frequency_scaling