AMD Ryzen & EPYC CPUs Even Enhanced Power & Performance Control Through Latest P-State EPP Drivers

Jason R. Wilson
AMD Ryzen & EPYC CPUs Even Enhanced Power & Performance Control Through Latest P-State EPP Drivers 1
Image source: J. Wilson, Wccftech.

The newest update to AMD's P-State EPP Linux driver hit today, offering better Ryzen & EPYC CPU performance & better control of processing power. Today launches the fourth version of the P-State EPP driver. The update affects both AMD Ryzen and EPYC CPUs.

AMD P-State EPP Linux driver will allow users better performance and control power consumption with Ryzen & EPYC CPUs

A portion of the message from Perry Yuan, one of the AMD open-source engineers working on the P-State EPP driver, is shown below.

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Hi all,

This patchset implements one new AMD CPU frequency driver
"amd-pstate-epp” instance for better performance and power control.
CPPC has a parameter called energy preference performance (EPP).
The EPP is used in the CCLK DPM controller to drive the frequency that a core
is going to operate during short periods of activity.
EPP values will be utilized for different OS profiles (balanced, performance, power savings).

AMD Energy Performance Preference (EPP) provides a hint to the hardware
if software wants to bias toward performance (0x0) or energy efficiency (0xff)
The lowlevel power firmware will calculate the runtime frequency according to the EPP preference
value. So the EPP hint will impact the CPU cores frequency responsiveness.

We use the RAPL interface with "perf" tool to get the energy data of the package power.

— Perry Yuan, AMD developer

Further, into the documentation, the team listed the change of events from the last version to the fourth version of the P-State EPP driver.

Changes from v3:

  • add one more document update patch for the active and passive mode
  • drive most of the feedback from Mario
  • drive feedback from Rafael for the cppc_acpi driver.
  • remove the epp raw data set/get function
  • set the amd-pstate drive by passing the kernel parameter
  • set amd-pstate driver disabled by default if no kernel parameter
    input from booting
  • get cppc_set_auto_epp and cppc_set_epp_perf combined
  • pick up reviewed by a flag from Mario

AMD's P-State EPP driver was to offer an alternative to the Advanced Configuration and Power Interface (ACPI) CPUFreq driver. The ACPI CPUFreq driver controls the frequency of a specified processor through ACPI, enabling communication between the hardware and the kernel. ACPI's specification is an industry standard for better power consumption management in PCs and laptops. ACPI defines the system's common I/O, peripherals, and operating system compared to power consumption.

You can check out more information about the new AMD P-State EPP driver on the kernel page.

News Sources: Phoronix, Linux kernel

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