AMD Shifts to P-State Driver for EPYC CPUs, Including Zen 5 Chips, to Boost Performance and Efficiency

AMD’s EPYC 9005 “Zen 5” CPUs are adopting the Linux P-State driver to enhance performance per watt compared to previous generations. AMD has just released two updates for the Linux kernel that could mean changing how you manage EPYC settings on your AMD-based servers running a distribution of GNU/Linux like Ubuntu. In the past, nearly all EPYC families used the ACPI CPUFreq Linux driver, which provided scarce access to controlling the amount of power and performance that CPUs use.

More About the AMD P-State Driver

These updates will provide a substantial uplift for the newest EPYC CPU families enabling application and data center businesses with improved performance per watt in these high-performance chips. The AMD P-State driver provides patches in order for the EPYC 9005 series to use ACPI CPPC (Collaborative Performance Processor Control), as Phoronix reports. This enhancement is going to better power and performance management of the CPU cores.

Previously, EPYC processors were based on the generic ACPI CPUFreq driver that works across multiple architectures for scaling frequencies of CPUs with lower maturity compared to P-State but without its advanced load-based features already implemented in a number of mainline Zen generations. It uses the P-State driver for better control over CPU cores, which is what also happened to Zen 2, Zen 3, Zen 4, and Zen 5.

The P-State driver is going to feature in the Linux Kernel that has plans for the new Family 1Ah, or EPYC 9005 processors. The resolution to this might come from the fact that EPYC 4004 processors have an in-the-box P-State driver already because their structure is quite similar to mainstream Ryzen chips. Tests have shown that using the P-State driver in active mode with a performance governor can achieve equivalent or superior performance per watt compared to the ACPI CPUFreq driver. The latest patches will also prevent frequency throttling in power-limited systems when using the P-State driver.

In addition, AMD is enabling users to switch back to the ACPI CPUFreq driver using “amd_pstate=disable” on their kernel command line for even more flexibility. These patches should end up in the next Linux Kernel 6.13, and into future EPYC processors as well.

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