Go sync.Pool Slice Benchmark

发表于 2017-07-02

| 0 Comments

纠结于[]struct还是[]*struct
直接make([]struct,0) 后append 还是 用sync.Pool make([]struct,100)

写段代码跑个分, 结论是

1. []*struct的要比[]struct多n次取指针的内存分配, 所有更慢, 如果不用修改结构体元素内的值, 没有必要用指针切片
2. append[]*struct要比[]struct慢
3. sync.Pool效果明显

benchmark结果

BenchmarkStructSliceWithoutPool-8                 200000              5458 ns/op           16320 B/op          8 allocs/op
BenchmarkStructPointerSliceWithoutPool-8          200000              6045 ns/op            8504 B/op        109 allocs/op
BenchmarkStructSliceWithPool-8                   1000000              1287 ns/op              32 B/op          1 allocs/op
BenchmarkStructPointerSliceWithPool-8             300000              4910 ns/op            6498 B/op        102 allocs/op

benchmark代码

package main

import (
	"sync"
	"testing"
)

var structSlicePool = sync.Pool{
	New: func() interface{} {
		return make([]Basic, 100)
	},
}

var structPointerSlicePool = sync.Pool{
	New: func() interface{} {
		return make([]*Basic, 100)
	},
}

type Basic struct {
	Id, N1, N2, N3, N4, N5 int
	Name                   string
}

func BenchmarkStructSliceWithoutPool(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var list []Basic
		for j := 0; j < 101; j++ {
			var data = Basic{Id: j, Name: "Name"}
			list = append(list, data)
		}
	}
}

func BenchmarkStructPointerSliceWithoutPool(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var list []*Basic
		for j := 0; j < 101; j++ {
			var data = Basic{Id: j, Name: "Name"}
			list = append(list, &data)
		}
	}
}

func BenchmarkStructSliceWithPool(b *testing.B) {
	for i := 0; i < b.N; i++ {
		list := structSlicePool.Get().([]Basic)
		initLen := len(list)
		for j := 0; j < 101; j++ {
			var data = Basic{Id: j, Name: "Name"}
			if j < initLen {
				list[j] = data
			} else {
				list = append(list, data)
			}
		}
		structSlicePool.Put(list)
	}
}

func BenchmarkStructPointerSliceWithPool(b *testing.B) {
	for i := 0; i < b.N; i++ {
		list := structPointerSlicePool.Get().([]*Basic)
		initLen := len(list)
		for j := 0; j < 101; j++ {
			var data = Basic{Id: j, Name: "Name"}
			if j < initLen {
				list[j] = &data
			} else {
				list = append(list, &data)
			}
		}
		structPointerSlicePool.Put(list)
	}

}