At the end of 2020, Intel’s programming manuals detailed the enhanced hardware feedback interface for the processor to provide guidance to the kernel planner on the optimal placement of workload tasks. Although it is marketed as Thread Director with the new 12th generation Alder Lake processors, this hardware return interface support is becoming square for the Linux kernel to improve support. load of these newer processors.

Microsoft Windows 11 already supports Intel’s hardware feedback interface as part of its Alder Lake / Thread Director optimizations, while support for the Linux kernel is only recently underway. In November, a few first “intel_hfi” fixes were released while just before Christmas Intel dropped a second version of the fixes with many changes and improvements resulting from the first code review.

The Intel Hardware Feedback interface is used to communicate performance and power efficiency details of each processor core to the kernel / operating system. The patch series sums it up as follows:

Currently, the Linux kernel relies on the ITMT / Turbo Boost Max 3.0 driver code with information exposed by the firmware to decide on the proper handling of P and E cores, while support for Intel HFI ultimately seems be more robust and exhibit performance. basic details in the user area.

The v2 patch bundle of this “intel_hfi” driver is now available for review. Although given the schedule and has not yet been picked up by the “-next” branch of power management, it is not clear if it will be ready in time for the next Linux cycle. 5.17 or whether it will be postponed until later in 2022.