golang json unmarshal benchmarks

main_test.go

package main

import (
	"encoding/json"
	"fmt"
	"testing"
)

type elements map[string]int

var unmarshalled elements

func genJSON(size int) []byte {
	data := make([]byte, 0, size+20) // we'll go over just a small bit
	data = append(data, '{')
	i := 0
	for len(data) <= size {
		data = append(data, []byte(fmt.Sprintf(`"%d": %d,`, i, i))...)
		i++
	}
	data[len(data)-1] = '}'

	return data
}

func benchmark(b *testing.B, size int) {
	b.StopTimer()
	data := genJSON(size)
	b.StartTimer()

	for i := 0; i < b.N; i++ {
		unmarshalled = elements{}
		err := json.Unmarshal(data, &unmarshalled)
		if err != nil {
			b.Fatal(err)
		}
	}
}

func Benchmark16k(b *testing.B) {
	benchmark(b, 16*1024)
}
func Benchmark32k(b *testing.B) {
	benchmark(b, 32*1024)
}
func Benchmark64k(b *testing.B) {
	benchmark(b, 64*1024)
}
func Benchmark128k(b *testing.B) {
	benchmark(b, 128*1024)
}

output

# go test -bench=. -v ./...
testing: warning: no tests to run
PASS
Benchmark16k	    1000	   1911398 ns/op
Benchmark32k	     500	   3439059 ns/op
Benchmark64k	     200	   6448114 ns/op
Benchmark128k	     100	  13139580 ns/op
ok  	tmp/8pg	7.482s