The article examines Linux’s CFS scheduler, explaining why its 4 ms tick (250 Hz) defines task switching intervals, how event‑driven mechanisms like task wake and IRQ updates shape scheduling, and compares PELT and WALT load‑tracking methods, especially under heterogeneous big‑little CPU architectures.
This article explains Linux's CFS scheduler mechanics, including the impact of priority, virtual runtime, event‑driven scheduling, the differences between PELT and WALT load‑tracking algorithms, and the complexities introduced by big‑LITTLE architectures on task placement, throughput, and latency.
The article explains how Linux’s multicore scheduler distributes tasks across CPU cores, describes the core CFS and real‑time algorithms, details load‑balancing mechanisms such as pull/push and active/passive strategies, and discusses power, thermal, and algorithmic optimizations for servers and embedded devices.
PELT (Per‑Entity Load Tracking) replaces the coarse per‑run‑queue load model in Linux’s CFS scheduler with fine‑grained, decay‑based load and utility measurements for each scheduling entity, enabling more accurate load‑balancing, CPU‑frequency decisions, and hierarchical group scheduling across heterogeneous cores.
