Engineers at AMD have continued work on the P-State CPU frequency scaling driver to offer another option in place of the ACPI CPUFreq driver used for the server over the last week. AMD introduced the P-State Energy Preference Performance (EPP) to assist with enhanced performance per Watt for years. The company hopes to supply better performance and efficiency of power within the Zen 2 architecture and those that followed, including the EPYC server p per Watt.
AMD's New P-State Driver To Deliver Significant CPU Performance Per Watt Improvements On Linux
The original P-State driver was never capable of working as efficiently as the ACPI CPUFreq. It did produce increased performance per Watt, but it never hit as well as it should. The driver would be broken, even at a minor degree, or would not offer the same performance as the ACPI CPUFreq. AMD hopes the new P-State EPP will improve Watt's performance with no shortcomings as in its prior stage.
The new P-State EPP driver concentrates on integrating energy preference performance and is slated to be compatible with the older Zen 2 architecture up to the latest processors for ACPI Collaborative Processor Performance Control capability, or CPPC.
Via Phoronix: 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).
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.
AMD showed amd-pstate-epp delivers better performance-per-Watt on a Zen 2 EPYC server compared to acpi-cpufreq or amd-pstate using assorted governors in recent benchmarks provided by the company.
The amd-pstate-epp in "power" mode potentially offers up to fourteen percent increased performance per Watt, which is the same provided by cpu-freq schedutil while utilizing the EPP "performance" mode.
Readers and users will need to wait to utilize the new amd-pstate-epp driver patchwork after it is reviewed in the official kernel mailing list.
News Source: Phoronix