Golang Defer Benchmark (1.22)

golang-defer-benchmark.go

package bench

import (
	"testing"
)
func doNoDefer(t *int) {
	*t++
	func() {
		*t++
	}()
}

func doDefer(t *int) {
	defer func() {
		*t++
	}()
	*t++
}

func BenchmarkDeferYes(b *testing.B) {
	t := 0
	for i := 0; i < b.N; i++ {
		doDefer(&t)
	}
}

func BenchmarkDeferNo(b *testing.B) {
	t := 0
	for i := 0; i < b.N; i++ {
		doNoDefer(&t)
	}
}

// Benchmark taken from https://medium.com/i0exception/runtime-overhead-of-using-defer-in-go-7140d5c40e32 which used an older Go version.
// I added one operation after the defer, to avoid compiler optimizations that wouldn't appear in typical code.
// On Go 1.22 in this modified benchmark, defer costs about 100% or 2ns.
//
// % go version
// go version go1.22.4 darwin/arm64
//
// % go test -bench=.
// goos: darwin
// goarch: arm64
// pkg: local/scratch/bench
// BenchmarkDeferYes-10    	279516777	         4.237 ns/op
// BenchmarkDeferNo-10     	532519959	         2.246 ns/op
// PASS
// ok  	local/scratch/bench	3.505s