原子操作

针对整数数据类型（int32、uint32、int64、uint64）我们还可以使用原子操作来保证并发安全，通常直接使用原子操作比使用锁操作效率更高。Go语言中原子操作由内置的标准库sync/atomic提供。

atomic包

 

方法	解释
func LoadInt32(addr *int32) (val int32) func LoadInt64(addr *int64) (val int64) func LoadUint32(addr *uint32) (val uint32) func LoadUint64(addr *uint64) (val uint64) func LoadUintptr(addr *uintptr) (val uintptr) func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer)	读取操作
func StoreInt32(addr *int32, val int32) func StoreInt64(addr *int64, val int64) func StoreUint32(addr *uint32, val uint32) func StoreUint64(addr *uint64, val uint64) func StoreUintptr(addr *uintptr, val uintptr) func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer)	写入操作
func AddInt32(addr *int32, delta int32) (new int32) func AddInt64(addr *int64, delta int64) (new int64) func AddUint32(addr *uint32, delta uint32) (new uint32) func AddUint64(addr *uint64, delta uint64) (new uint64) func AddUintptr(addr *uintptr, delta uintptr) (new uintptr)	修改操作
func SwapInt32(addr *int32, new int32) (old int32) func SwapInt64(addr *int64, new int64) (old int64) func SwapUint32(addr *uint32, new uint32) (old uint32) func SwapUint64(addr *uint64, new uint64) (old uint64) func SwapUintptr(addr *uintptr, new uintptr) (old uintptr) func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer)	交换操作
func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool) func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool) func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool) func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool) func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool) func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool)	比较并交换操作

package main

import (
	"fmt"
	"sync"
	"sync/atomic"
	"time"
)

type Counter interface {
	Inc()
	Load() int64
}

// 普通版
type CommonCounter struct {
	counter int64
}

func (c CommonCounter) Inc() {
	c.counter++
}

func (c CommonCounter) Load() int64 {
	return c.counter
}

// 互斥锁版
type MutexCounter struct {
	counter int64
	lock    sync.Mutex
}

func (m *MutexCounter) Inc() {
	m.lock.Lock()
	defer m.lock.Unlock()
	m.counter++
}

func (m *MutexCounter) Load() int64 {
	m.lock.Lock()
	defer m.lock.Unlock()
	return m.counter
}

// 原子操作版
type AtomicCounter struct {
	counter int64
}

func (a *AtomicCounter) Inc() {
	atomic.AddInt64(&a.counter, 1)
}

func (a *AtomicCounter) Load() int64 {
	return atomic.LoadInt64(&a.counter)
}

func test(c Counter) {
	var wg sync.WaitGroup
	start := time.Now()
	for i := 0; i < 1000; i++ {
		wg.Add(1)
		go func() {
			c.Inc()
			wg.Done()
		}()
	}
	wg.Wait()
	end := time.Now()
	fmt.Println(c.Load(), end.Sub(start))
}

func main() {
	c1 := CommonCounter{} // 非并发安全
	test(c1)
	c2 := MutexCounter{} // 使用互斥锁实现并发安全
	test(&c2)
	c3 := AtomicCounter{} // 并发安全且比互斥锁效率更高
	test(&c3)
}

　　atomic包提供了底层的原子级内存操作，对于同步算法的实现很有用。这些函数必须谨慎地保证正确使用。除了某些特殊的底层应用，使用通道或者 sync 包的函数/类型实现同步更好。

参考：Go语言基础之并发 | 李文周的博客 (liwenzhou.com)