Benchmark for a Go proposal where a nil *log.Logger is a valid logger. This file works in the directory src/log/ .

log_nil_test.go

package log

import (
	"io"
	"testing"
)

// New(io.Discard, "", 0) is the standard way of creating a
// disabled logger.
//
// l.SetOuput(io.Discard) is the standard way of disabling a
// logger l.
//
// They are expensive, as they actually compute the logs, holding
// a mutex locked, before discarding the logs.

func BenchmarkPrintfNumberDiscard(b *testing.B) {
	logger := New(io.Discard, "", 0)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		n := i % 100
		logger.Printf("n=%d", n)
	}
}

func BenchmarkPrintfMapDiscard(b *testing.B) {
	m := map[string]int{
		"one": 1,
		"two": 2,
	}
	logger := New(io.Discard, "", 0)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		logger.Printf("x=%v", m)
	}
}

// This is the proposed way of creating a disabled logger:
// use nil.
//
// These benchmarks are intended for a Go stdlib with
// log/log.go already patched (otherwise they will panic).

func BenchmarkPrintfNumberNil(b *testing.B) {
	var logger *Logger = nil
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		n := i % 100
		logger.Printf("n=%d", n)
	}
}

func BenchmarkPrintfMapNil(b *testing.B) {
	m := map[string]int{
		"one": 1,
		"two": 2,
	}
	var logger *Logger = nil
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		logger.Printf("x=%v", m)
	}
}

The proposal: golang/go#47164