Making Facebook’s software infrastructure more energy efficient with Autoscale

This post introduces Autoscale, a power-efficient load balancing system for Facebook's web clusters. Autoscale dynamically adjusts the active server pool to ensure each active server maintains at least medium-level CPU utilization, thereby avoiding inefficient low-utilization states. It uses a feedback loop control system with a PI controller and models the relationship between CPU utilization and RPS based on experimental data. Deployed to production, Autoscale achieved an average of 10-15% power savings over a 24-hour cycle, with up to 27% savings during low-workload periods.