PGO and Production Build Flags

PGO and Production Build Flags

Overview

Profile-guided optimization (PGO) feeds CPU profiles into the compiler for better inlining/layout on hot paths. Combine with production build flags for smaller, clearer binaries.

Production build baseline

CGO_ENABLED=0 go build -trimpath \
  -ldflags="-s -w -X main.version=${VERSION}" \
  -o bin/app ./cmd/app

Flag	Effect
CGO_ENABLED=0	Static-ish pure Go, portable
-trimpath	Reproducible paths
-s -w	Strip symbol/DWARF (harder debug)
-X	Inject version

Keep a debug build variant for crash analysis when needed.

PGO workflow (Go 1.20+)

# 1) collect profile from realistic load (30s+)
curl -o cpu.pprof "http://localhost:6060/debug/pprof/cpu?seconds=30"

# 2) rebuild with profile
go build -pgo=cpu.pprof -o bin/app ./cmd/app

# 3) compare benchmarks / load test

Or default auto PGO if default.pgo is in the main package directory (per Go release docs).

When PGO helps

Helps	Less impact
Large codebases, hot call chains	Tiny programs already inlined
After stable production shape	Random microbench only

Rules of thumb

Do	Don’t
Profile production-like traffic	Use toy profiles for PGO
A/B load test before/after	Assume free wins always
Document Go version + flags	Mystery binaries in prod

Try next

1. Capture 30s CPU pprof under hey.
   
2. Build with -pgo and remeasure p99.
   
3. Add version ldflags; verify app version.