Linux 6.7 Boasts Some Scheduler Improvements & Intel IBRS Mitigation Change

Linux 6.6 saw EEVDF merged and Intel hybrid cluster scheduling re-introduced. The core scheduler improvements merged this past week for the in-development Linux 6.7 isn't quite as exciting but still there are some healthy scheduler improvements this round.

The pull request submitted by Ingo Molnar at the start of the Linux 6.7 merge window brings fair scheduler improvements, NUMA scheduling improvements, energy scheduling improvements, real-time (RT) scheduling improvements, scheduler scalability improvements, and core scheduler infrastructure work. This round isn't quite as exciting as the major items introduced with Linux 6.6 but overall there are a lot of low-level scheduling enhancements that were merged this week.

Among the particulars are scanning cluster before scanning the last-level cache in the wake-up path as part of the cluster scheduler (should benefit some ARM64 platforms), several NUMA scheduler fixes from Linutronix, on x86 disabling Intel IBRS when a CPU is offline to improve the single-threaded performance, micro-optimizing the PSI code, and various debugging enhancements.

The change to disable Indirect Branch Restricted Speculation (IBRS) when CPU is offline is yielding some nice performance improvements and there is also a new "ibrs_off" module parameter to force-disable IBRS.

More details on the main set of scheduler enhancements for Linux 6.7 via the pull.