A small patch increases Intel CPU performance by 32%

Intel's fifth-generation Xeon Emerald Rapids series CPU will be launched in December 2023. Recently, a small patch has pushed its performance to new heights.Canonical engineer Pedro Henrique Kopper submitted a patch to the Linux Kernel Mailing List (LKML) with the title "UpdateBalanceperformanceEPPforEmeraldRapids."

This seemingly minor adjustment is an optimization of the EPP (Energy Performance Preference) value, which has significantly improved the performance and energy efficiency of Intel's data center CPUs.

By default, the EPP value in balanced performance mode is 128, however, during a joint internal investigation with Intel, the team found that setting the EPP value to 32 is more appropriate.

This change not only improves performance, but also maintains better energy efficiency. Specifically, this adjustment brings significant improvements in the following aspects:

POV-Ray rendering speed is increased by 32% and energy consumption is reduced by 12%.

OpenSSL encryption speed increased by 12%, and energy consumption changed within 1%.

Building the Linux kernel is 29% faster and consumes 18% less energy.

Pedro recommended changing the default EPP value in Balanced Performance Mode to 32, which is consistent with the adjustments made to SapphireRapids last year, when a simple one-line code patch brought significant performance improvements.

It is worth noting that this performance increase and energy consumption reduction only affects the default balanced performance mode in Ubuntu Linux and other Linux-based operating systems.

Users who switch to "Performance" and other modes will not have these optimization improvements, but even so, an EPP value of 32 can still save more power than 128.

LinuxPM maintainer Rafael Wysocki expects to implement this patch for the Linux 6.11 kernel within a week or two.