package main

import (
	"fmt"
	"sync"
	"time"
)

// 读写互斥锁，读的时候远远大于写的场景
// rwlock
// 当读的时候加读锁，写的时候加写锁。和互斥锁相比性能差很多
// 当持有写锁，所有的goroutine都需要等待写锁解锁不能读也不能写，当持有读锁，所有goroutine仍然能够读访问共享资源，但不允许写
var (
	v        = 0
	locker   sync.Mutex
	w        sync.WaitGroup
	rwlocker sync.RWMutex
)

func read() {
	defer w.Done()
	locker.Lock()
	//rwlocker.RLock()
	fmt.Println(v)
	time.Sleep(time.Millisecond * 1)
	locker.Unlock()
	//rwlocker.RUnlock()
}

func write() {
	defer w.Done()
	locker.Lock()
	//rwlocker.Lock()
	v += 1
	time.Sleep(time.Millisecond * 5)
	locker.Unlock()
	//rwlocker.Unlock()
}

func main() {
	start := time.Now()
	for i := 0; i < 10; i++ {
		w.Add(1)
		go write()
	}
	time.Sleep(time.Second)
	for i := 0; i < 1000; i++ {
		w.Add(1)
		go read()
	}
	w.Wait()
	fmt.Println(time.Now().Sub(start))
}