What is CPU scheduling in Linux?

CPU scheduling decides which process gets execution time on a CPU core. Modern Linux uses the Completely Fair Scheduler (CFS):

• CFS models a "perfect multi-tasking CPU" on real hardware.
• It tracks execution time for each process using a metric called Virtual Runtime (vruntime).
• The scheduler always selects the process with the smallest vruntime to run next, utilizing a Red-Black tree structure to retrieve processes in $O(\log N)$ time.