go value vs pointer benchmark

bench_test.go

package main

import "testing"

var blackholeStr = ""
var blackholeValue student
var blackholePointer *student

func BenchmarkPointerVSStruct(b *testing.B) {

	b.Run("return pointer", func(b *testing.B) {
		b.ReportAllocs()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			blackholePointer = returnByPointer()
		}
	})

	b.Run("return  value", func(b *testing.B) {
		b.ReportAllocs()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			blackholeValue = returnByValue()
		}
	})

	b.Run("value receiver", func(b *testing.B) {
		b.ReportAllocs()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			r := student{
				name: randStr,
			}
			blackholeStr = r.getNameByValue()
		}
	})
	b.Run("pointer receiver", func(b *testing.B) {
		b.ReportAllocs()
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			r := &student{
				name: randStr,
			}
			blackholeStr = r.getNameByPointer()
		}
	})

}

result.txt

go test -run ^NOTHING -bench Struct bench_test.go  snippet.go
goos: darwin
goarch: amd64
BenchmarkPointerVSStruct/return_pointer-8               34476903                32.4 ns/op            16 B/op          1 allocs/op
BenchmarkPointerVSStruct/return__value-8                530538498                2.27 ns/op            0 B/op          0 allocs/op
BenchmarkPointerVSStruct/value_receiver-8               415309486                2.86 ns/op            0 B/op          0 allocs/op
BenchmarkPointerVSStruct/pointer_receiver-8             348904872                3.23 ns/op            0 B/op          0 allocs/op
PASS
ok      command-line-arguments  5.699s

snippet.go

// -*- mode:go;mode:go-playground -*-
// snippet of code @ 2020-03-15 11:33:13

// === Go Playground ===
// Execute the snippet with Ctl-Return
// Provide custom arguments to compile with Alt-Return
// Remove the snippet completely with its dir and all files M-x `go-playground-rm`

package main

import (
	"fmt"
)

type student struct {
	name string
}

//go:noinline
func (s student) getNameByValue() string {
	return s.name
}

//go:noinline
func (s *student) getNameByPointer() string {
	return s.name
}

const randStr = "a very long string,a very long string,a very long string,a very long string"

//go:noinline
func returnByValue() student {
	return student{randStr}
}

//go:noinline
func returnByPointer() *student {
	return &student{randStr}
}

func main() {

	foo := student{name: "foo"}
	bar := foo
	bar.name = "bar"
	fmt.Println(foo.name)

	bar2 := &foo
	bar2.name = "bar"
	fmt.Println(foo.name)

}