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Chapter 16. Kernel

The following chapters contain the most notable changes to kernel between RHEL 9 and RHEL 10.

16.1. Notable changes to kernel
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sched_ext scheduler for creating a custom scheduler

In RHEL 10, with sched_ext you can create custom process scheduling code in extended Berkeley Packet Filter (eBPF) at runtime. The sched_ext scheduler allows you to replace the standard kernel scheduler with your own scheduling logic to control process prioritization, resource allocation, and execution behavior.

Please note that Red Hat does not provide support for a custom scheduler.

CFS is replaced with the EEVDF scheduler

The Completely Fair Scheduler (CFS) is replaced with a new scheduler, Enhanced Earliest Deadline First (EEVDF). This includes the following changes:

  • sched_min_granularity is now sched_base_slice, and it uses the same unit.

  • sched_wakeup_granularity is unused in EEVDF and therefore, it is removed.

    sched_base_slice
    defines the minimum time that a task can be deferred from running.
    sched_wakeup_granularity
    sets the baseline priority (as a fraction of a CPU) for all tasks on the CPU.

CFS and EEVDF deliver similar workload results in most cases. However, minor variations in performance might be observed because the logic of each task selection is different.

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