AMD P-State Driver Introducing New Features With Linux 7.1
A few Linux kernel releases have passed since there have been any new features to talk about for the AMD P-State driver for CPU frequency scaling / power management with modern AMD Ryzen and EPYC processors. But for the upcoming Linux 7.1 kernel there are some new features now ready for mainline.
There are a few new features for the "amd_pstate" driver with Linux 7.1 plus a couple of fixes too. Mario Limonciello of AMD, who has now taken over as the formal AMD P-State driver maintainer, sent out the pull request today for queuing in the power management subsystem's "-next" branch until the Linux 7.1 merge window opens up later in April.
First up is the AMD CPPC Performance Priority feature set for inclusion in Linux 7.1. The CPPC Performance Priority lets user-space assign different floor performance levels to different CPU cores. The platform firmware will interpret these floor performance levels for consideration when throttling CPU cores under power and/or thermal constraints. With the AMD P-State driver new "floor_freq" and "floor_count" sysfs attributes are exposed for letting administrators or user-space configuration daemons adapt the power management.
Another new feature for AMD P-State control in Linux 7.1 is Dynamic Energy Performance Preference (EPP). Dynamic Energy Performance Preference allows changing the EPP profile depending upon whether the Ryzen laptop is running on AC or DC power. The EPP values can be dynamically adjusted based on power supply plug-in / plug-out events. Dynamic EPP can be enabled/disabled via the Linux kernel Kconfig or via new boot time options if so desired.
Lastly is a new Raw EPP feature. This overcomes the limitation of the EPP value being an integer between 0 and 255 but the user-configurable options tend to just be one of four preset values. For further tuning of workloads/performance, Raw EPP allows specifying a 0 to 255 value in the sysfs file for the EPP rather than relying on the static options.
AMD P-State for Linux 7.1 also has fixes for real-time "PREEMPT_RT" kernel builds and other bugs being addressed.
This is a nice update for the AMD P-State driver coming in Linux 7.1, especially with the upcoming AMD Zen 6 processors around the corner. The full list of AMD P-State feature patches for Linux 7.1 can be found via today's pull request.
There are a few new features for the "amd_pstate" driver with Linux 7.1 plus a couple of fixes too. Mario Limonciello of AMD, who has now taken over as the formal AMD P-State driver maintainer, sent out the pull request today for queuing in the power management subsystem's "-next" branch until the Linux 7.1 merge window opens up later in April.
First up is the AMD CPPC Performance Priority feature set for inclusion in Linux 7.1. The CPPC Performance Priority lets user-space assign different floor performance levels to different CPU cores. The platform firmware will interpret these floor performance levels for consideration when throttling CPU cores under power and/or thermal constraints. With the AMD P-State driver new "floor_freq" and "floor_count" sysfs attributes are exposed for letting administrators or user-space configuration daemons adapt the power management.
👁 AMD Performance Priority feature documentation
Another new feature for AMD P-State control in Linux 7.1 is Dynamic Energy Performance Preference (EPP). Dynamic Energy Performance Preference allows changing the EPP profile depending upon whether the Ryzen laptop is running on AC or DC power. The EPP values can be dynamically adjusted based on power supply plug-in / plug-out events. Dynamic EPP can be enabled/disabled via the Linux kernel Kconfig or via new boot time options if so desired.
Lastly is a new Raw EPP feature. This overcomes the limitation of the EPP value being an integer between 0 and 255 but the user-configurable options tend to just be one of four preset values. For further tuning of workloads/performance, Raw EPP allows specifying a 0 to 255 value in the sysfs file for the EPP rather than relying on the static options.
AMD P-State for Linux 7.1 also has fixes for real-time "PREEMPT_RT" kernel builds and other bugs being addressed.
This is a nice update for the AMD P-State driver coming in Linux 7.1, especially with the upcoming AMD Zen 6 processors around the corner. The full list of AMD P-State feature patches for Linux 7.1 can be found via today's pull request.