Linux Kernel Journey

Dec 27, 2024 · Fundamentals

Understanding Fair CFS Scheduling Classes: SCHED_NORMAL, SCHED_BATCH, and SCHED_IDLE

The article explains how Linux's Completely Fair Scheduler (CFS) uses nice values and weight tables to compute virtual runtime, organizes tasks in a red‑black tree, and demonstrates through experiments how SCHED_NORMAL, SCHED_BATCH, and SCHED_IDLE differ in priority, preemption rules, and CPU share.