Speaker
Description
During OSPM 2026, there was an agreement to stop requiring schedutil to enable EAS on x86 platforms, which implies EAS may soon be active by default on these systems.
Energy-Aware Scheduling (EAS) places tasks by comparing estimated energy costs across performance domains, directing light tasks to power-efficient cores on asymmetric systems. The known trade-off is that EAS packing introduces runqueue contention when idle CPUs are available: tasks are packed onto fewer CPUs, and wakeups that land on already-busy CPUs incur queuing delay even when other CPUs sit idle.
This talk uses quantitative wakeup latency decomposition on x86 hybrid platforms as a starting point to motivate making EAS more aggressive in selecting idle CPUs. I examine where in find_energy_efficient_cpu() idle-CPU preference can be strengthened without abandoning the energy-efficiency objective, measure the resulting impact on tail latency (p99+) and energy consumption via platform power counters, and discuss how the latency–power trade-off compares to the packing baseline.