Power Management Improvements Could Benefit Intel Server Performance In Linux 5.6

Some Intel server platforms could see better performance with the Linux 5.6 kernel cycle.

Intel's Rafael Wysocki who also serves as the Linux kernel's power management subsystem maintainer has been queuing some patches recently in working on ACPI _CST support around the Intel-Idle driver. With the final patch for using ACPI _CST on server systems with the Intel-Idle driver, Rafael explained:

In many cases, especially on server systems, it is desirable to avoid enabling C-states that have been disabled in the platform firmware (BIOS) setup, except for C1E.

As a rule, the C-states disabled this way are not listed by ACPI _CST, so if that is used by intel_idle along with the specific table of C-states that it has for the given processor, the C-states disabled through the platform firmware will not be enabled by default by intel_idle.

This updated behavior applies for server platforms back to Nehalem and each generation there after as part of the server or X-Series.

With this updated intel_idle driver behavior, Intel's own monitoring is showing around a 12.6% improvement for FS-Mark that is a file-system benchmark but the CPU performance plays an important role too. It will be interesting to see how this Intel server power management behavioral change affects other workloads as well, which we'll begin benchmarking shortly.

The Linux 5.6 merge window should be open around the end of January or early February. Until then the Linux power management work for Intel and other hardware will continue queuing as usual within linux-pm.git's linux-next.