Reclaiming CPU for free with Go's Profile Guided Optimization

This post details the process of applying Profile Guided Optimization (PGO) to a Go-based service (wshim) within Cloudflare's Observability team. It covers collecting representative CPU profiles from production infrastructure using Thanos and pprof, merging these profiles, and recompiling the service with the `-pgo` flag. The results show a ~3.5% reduction in CPU usage, translating to approximately 97 fewer cores, demonstrating the effectiveness of PGO for optimizing existing code without modification.