[]byte と string の slice パフォーマンスの違い

コード

package main

import (
 "fmt"
 "time"
)

var tests = []string{
 "Lorem ipsum dolor sit amet",
 "consectetur adipisicing elit",
 "sed do eiusmod tempor incididunt ut labore et dolore magna aliqua",
 "Ut enim ad minim veniam",
 "quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat",
}

func foo(s string) {
}

func stringSlice() {
 for n := 0; n < len(tests); n ++ {
  text := tests[n]
  for len(text) > 0 {
   foo(text[:1])
   text = text[1:]
  }
 }
}

func boo(s []byte) {
}

func byteSlice() {
 for n := 0; n < len(tests); n ++ {
  text := []byte(tests[n])
  for len(text) > 0 {
   boo(text[:1])
   text = text[1:]
  }
 }
}

func measure(loop, times int) {
 fmt.Println("--- loop:", loop, "---")

 var (
  start time.Time
  end   time.Time
 )
 durations := make([]int64, 2)

 for n := 0; n < times; n++ {
  start = time.Now()
  for n := 0; n < loop; n++ {
   stringSlice()
  }
  end = time.Now()
  durations[0] += end.Sub(start).Nanoseconds()

  start = time.Now()
  for n := 0; n < loop; n++ {
   byteSlice()
  }
  end = time.Now()
  durations[1] += end.Sub(start).Nanoseconds()
 }

 divied := int64(times*1000)
 fmt.Println("stringSlice()", durations[0]/divied, "us/times")
 fmt.Println("byteSlice()", durations[1]/divied, "us/times")
}

func main() {
 measure(100000, 10)
}

結果

loop: 100000

stringSlice()

170,985 us/times

byteSlice()

96,531 us/times

string の slice の方が 1.77 倍時間が掛かってる。