Linux power management and ACPI subsystems maintainer Rafael Wysocki last week sent out the assortment of ACPI/PM material for the new Linux 6.15 kernel cycle. The AMD P-State driver continues to be heavy with its code churn and there have been various other optimizations and code clean-ups. The CPUIdle Menu governor also received some performance tuning worth mentioning.
The AMD P-State driver continues seeing a variety of optimizations so it functions more efficiently and ultimately more well-runded. There is work in Linux 6.15 to avoid carrying out the same writes multiple times and needlessly caching some variables. The AMD P-State driver also went through a locking overhaul and other low-level code improvements.
The menu governor as the default CPUIdle governor on tickless Linux systems has seen some improvements too for Linux 6.15. In some cases this menu governor work can lead to “significant improvements in some performance benchmarks” due to better prediction by this governor around idle intervals. Intel engineer Rafael Wysocki who pursued the menu governor improvements had commented with the patch series on the motivation and impact:
“This work had been triggered by a report that commit 0611a640e60a (“eventpoll: prefer kfree_rcu() in __ep_remove()”) had caused the critical-jOPS metric of the SPECjbb 2015 benchmark to drop by around 50% even though it generally reduced kernel overhead. Indeed, it was found during further investigation that the total interrupt rate while running the SPECjbb workload had fallen as a result of that commit by 55% and the local timer interrupt rate had fallen by almost 80%.
…
This series turns out to restore the SPECjbb critical-jOPS metric on affected systems to the level from before commit 0611a640e60a and it also happens to increase its max-jOPS metric by around 3%.”
So with Linux 6.15 that particular SPECjbb Java regression should be resolved. There weren’t performance numbers provided on any other workloads/benchmarks for where else this menu governor optimizing may benefit.
There have also been clean-ups for the Intel P-State driver, Energy Model code, cpupower utility improvements, and other code enhancements throughout the power management subsystem. See the PM pull for this since-merged code to Linux 6.15.
Meanwhile the merged ACPI updates add fan speed reporting for ACPI fans with “_FST” but lacking the entire ACPIv4 fan interface, reworking the sysfs attribute handling in the ACPI platform profile driver, and other code clean-ups.
