optimizing-go-performance

name	optimizing-go-performance
description	Audits measured Go performance.
metadata	{"internal":true}

Optimizing Go Performance

Use -benchmem and the relevant pprof/trace evidence before changing allocations, concurrency, pooling, or an API for escape behavior.

1. Read Go performance audit.
2. Scan for conversion loops, fmt, append/map growth, interface/reflection paths, goroutine-per-item work, channel contention, and default-use sync.Pool.
3. Use PGO only from representative whole-program CPU profiles. Go has NO ergonomic portable SIMD: for a genuine hot loop — a lexer scanning identifiers, strings, template bodies, or whitespace qualifies, ordinary code does not — hand-write per-arch Plan 9 assembly, amd64 SSE2/AVX2 and arm64 NEON, behind golang.org/x/sys/cpu runtime feature dispatch with a //go:build !amd64 && !arm64 scalar fallback; no cgo, no GOEXPERIMENT. Do NOT raise GOAMD64 to v2/v3/v4 for a binary distributed to CPUs you do not control — it raises the ISA floor and crashes on older CPUs; a single default v1 binary plus x/sys/cpu dispatch still uses AVX2 when present and runs everywhere. Pin GOAMD64 only to a floor a controlled target guarantees — a homogeneous fleet or a per-ISA build matrix — and record why. Enforced by scripts/fleet/check/build-microarch-is-portable.mts.
4. Test cancellation, backpressure, and races after concurrency changes.
5. Keep the change only when CPU, allocations, GC work, peak heap, and tail latency improve on the same workload.