golang之包和鎖的機制

互斥鎖

同一時刻只有一個攜程在操作

package main

import (
    "fmt"
    "math/rand"
    "sync"
    "time"
)
//互斥鎖
var lock sync.Mutex

func testMap() {
    var a map[int]int
    a = make(map[int]int, 5)
    a[8] = 10
    a[3] = 10
    a[2] = 10
    a[1] = 10
    for i := 0; i < 2; i++ {
        func(b map[int]int) {
            lock.Lock()
            b[8] = rand.Intn(100)
            lock.Unlock()
        }(a)
    }
    lock.Lock()
    fmt.Println(a)
    lock.Unlock()
    time.Sleep(time.Second)
}
func main() {
    //互斥鎖
    testMap()
}

讀寫鎖

讀多寫少的情況，用讀寫鎖， 攜程同時在操作讀。

package main

import (
    "fmt"
    "math/rand"
    "sync"
    "time"
)

//讀寫鎖
var rwLock sync.RWMutex

func testRWLock() {
    var a map[int]int
    a = make(map[int]int, 5)
    a[8] = 10
    a[3] = 10
    a[2] = 10
    a[1] = 10
    a[18] = 10
    for i := 0; i < 2; i++ {
        go func(b map[int]int) {
            rwLock.Lock()
            b[8] = rand.Intn(100)
            rwLock.Unlock()
        }(a)
    }
    for i := 0; i < 100; i++ {
        go func(b map[int]int) {
            rwLock.RLock() //讀鎖
            fmt.Println(a)
            rwLock.RUnlock()
        }(a)
    }
    time.Sleep(time.Second * 20)

}
func main() {
    
    testRWLock()
    //讀多寫少的時候，用讀寫鎖
}

讀寫鎖，互斥鎖，性能比較

package main

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

//讀寫鎖
var rwLock sync.RWMutex
var lock sync.Mutex

func testRWLock() {
    var a map[int]int
    a = make(map[int]int, 5)
    var count int32
    a[8] = 10
    a[3] = 10
    a[2] = 10
    a[1] = 10
    a[18] = 10
    for i := 0; i < 2; i++ {
        go func(b map[int]int) {
            //rwLock.Lock() //讀寫鎖的代碼
            lock.Lock() //互斥鎖的代碼
            b[8] = rand.Intn(100)
            time.Sleep(10 * time.Microsecond) //微妙
            //rwLock.Unlock()
            lock.Unlock()

        }(a)
    }
    for i := 0; i < 100; i++ {
        go func(b map[int]int) {
            for {
                //rwLock.RLock() //讀寫鎖的代碼
                lock.Lock()
                time.Sleep(time.Millisecond)
                //rwLock.RUnlock()
                lock.Unlock()
                atomic.AddInt32(&count, 1)
            }
        }(a)
    }
    time.Sleep(time.Second * 20)
    fmt.Println(atomic.LoadInt32(&count))
}
func main() {
    //互斥鎖
    testRWLock()
    //讀多寫少的時候，用讀寫鎖
}