go copy bench

copy_test.go

package main

import (
	"testing"
	"unsafe"
)

const N = 32 << 20 // 32 MiB

type struct32 struct {
	b bool
	d [12]int8
	i byte
	j int16
	f float32
	k int32
	g float64
}

func TestSize_struct32(t *testing.T) {
	size := unsafe.Sizeof(struct32{})
	if size != 32 {
		t.Errorf("expected struct32 size of 32 bytes (%d actual)", size)
	}
}

func BenchmarkCopy_byte(b *testing.B) {
	var dst, src [N]byte
	b.SetBytes(N)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		copy(dst[:], src[:])
	}
}

func BenchmarkCopy_int64(b *testing.B) {
	var dst, src [N / 8]int64
	b.SetBytes(N)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		copy(dst[:], src[:])
	}
}

func BenchmarkCopy_4byte(b *testing.B) {
	var dst, src [N / 4][4]byte
	b.SetBytes(N)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		copy(dst[:], src[:])
	}
}

func BenchmarkCopy_16byte(b *testing.B) {
	var dst, src [N / 16][16]byte
	b.SetBytes(N)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		copy(dst[:], src[:])
	}
}

func BenchmarkCopy_struct32(b *testing.B) {
	var dst, src [N / 32]struct32
	b.SetBytes(N)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		copy(dst[:], src[:])
	}
}

results.txt

# Intel Atom N450 1.66GHz

GOARCH=amd64 go test -bench .
PASS
BenchmarkCopy_byte            50          29592577 ns/op        1133.88 MB/s
BenchmarkCopy_int64           50          29635021 ns/op        1132.26 MB/s
BenchmarkCopy_4byte           50          29905231 ns/op        1122.03 MB/s
BenchmarkCopy_16byte          50          29697470 ns/op        1129.88 MB/s
BenchmarkCopy_struct32        50          29572247 ns/op        1134.66 MB/s

GOARCH=386 go test -bench .
PASS
BenchmarkCopy_byte            50          29507551 ns/op        1137.15 MB/s
BenchmarkCopy_int64           50          29393642 ns/op        1141.55 MB/s
BenchmarkCopy_4byte           50          29930332 ns/op        1121.08 MB/s
BenchmarkCopy_16byte          50          30106251 ns/op        1114.53 MB/s
BenchmarkCopy_struct32        50          29465431 ns/op        1138.77 MB/s

GOARCH=386 GO386=387 go test -bench .
PASS
BenchmarkCopy_byte            50          29960040 ns/op        1119.97 MB/s
BenchmarkCopy_int64          100          29958192 ns/op        1120.04 MB/s
BenchmarkCopy_4byte           50          30005881 ns/op        1118.26 MB/s
BenchmarkCopy_16byte          50          29578779 ns/op        1134.41 MB/s
BenchmarkCopy_struct32        50          29460366 ns/op        1138.97 MB/s