Intel HFI Driver Will Quit Wasting CPU Cycles With Linux 6.10

Intel's Hardware Feedback Interface (HFI) driver will act more efficiently come the Linux 6.10 kernel this summer.

You may recall the Linux kernel patches for the Intel HFI driver talked about back in February for only enabling the HFI driver when it's actually being used with a user-space software component like Intel Speed Select or the Intel Low Power Daemon actually wanting to make use of HFI events. By skipping out on Intel HFI driver activity when no user-space components are actively leveraging it, "tons of CPU cycles" can be saved according to Intel Linux engineers.

Intel's Hardware Feedback Interface is used for communicating performance / energy efficiency capability information on each CPU core to the operating system. Linux can make use of Intel HFI for better task placement that is particularly important for recent Intel Core processors employing a hybrid design.

Intel engineers didn't quantify the impact of the CPU cycle savings, but the news now is that these patches are slated for premiering in Linux 6.10. This past week the patches to only enable Intel HFI when required have been queued into the power management subsystem's "linux-next" branch. With the code hitting this milestone, it's destined for the next merge window (v6.10) barring any last minute issues from appearing.

"Enable and disable hardware feedback interface (HFI) when user space handler is present. For example, enable HFI, when intel-speed-select or Intel Low Power daemon is running and subscribing to thermal netlink events. When user space handlers exit or remove subscription for thermal netlink events, disable HFI."

So for now it's in Linux-pm.git's linux-next branch ahead of the 6.10 merge window opening in May.