Higher performance UnsafeStringToSlice

[dxasu]

netpoll/nocopy.go

Line 279 in 44a7f98

func unsafeStringToSlice(s string) (b []byte) {

建议用如下函数替换UnsafeStringToSlice，经过benchmark测试，性能提高约30%左右，代码也更优雅

func UnsafeStringToSlice2(s string) []byte {
	return *(*[]byte)(unsafe.Pointer(
		&struct {
			string
			int
		}{s, len(s)},
	))
}

### 测试详情

go test -bench . -benchmem
goos: darwin
goarch: arm64
pkg: gitlab-vywrajy.zd100.net/slice/service
BenchmarkToSlice/UnsafeStringToSlice-8 737677520 1.542 ns/op 0 B/op 0 allocs/op
BenchmarkToSlice/UnsafeStringToSlice2-8 1000000000 1.188 ns/op 0 B/op 0 allocs/op
PASS
ok gitlab-vywrajy.zd100.net/slice/service 2.928s

### 相关测试代码

package service

import (
	"reflect"
	"testing"
	"unsafe"
)

func BenchmarkToSlice(b *testing.B) {
	a := "hello world"
	var bs []byte
	b.Run("UnsafeStringToSlice", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			bs = UnsafeStringToSlice(a)
		}
	})
	b.Run("UnsafeStringToSlice2", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			bs = UnsafeStringToSlice2(a)
		}
	})

	_ = bs
}



func UnsafeStringToSlice(s string) (b []byte) {
	p := unsafe.Pointer((*reflect.StringHeader)(unsafe.Pointer(&s)).Data)
	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&b))
	hdr.Data = uintptr(p)
	hdr.Cap = len(s)
	hdr.Len = len(s)
	return b
}

func UnsafeStringToSlice2(s string) []byte {
	return *(*[]byte)(unsafe.Pointer(
		&struct {
			string
			int
		}{s, len(s)},
	))
}

[joway]

@dxasu 可以提个 PR 优化下这块，看了下，就是少了几个 MOVQ 指令

[someview]

这比官方最新提供的解决方案还好吗?

func strToBytes(str string) []byte {
	return unsafe.Slice(unsafe.StringData(str), len(str))
}

func btsToString(bts []byte) (str string) {
	return unsafe.String(unsafe.SliceData(bts), len(bts))
}

[jayantxie]

官方的api暂时有版本限制，在最低go版本提升至1.20之前，暂时仍使用替代方案

[someview]

我c,这都 2年了，还有没跟进版本的，滴滴k8s 版本过旧前车之鉴