Golang mutex and RWMutex 测试比较

diff.diff

 ~ ✗ diff -ruN mutex.go mutexv2.go
--- mutex.go	2012-10-25 11:30:04.170656858 +0800
+++ mutexv2.go	2012-10-25 11:30:04.174656858 +0800
@@ -9,8 +9,9 @@
 )
 
 type Msg struct {
-	mutex sync.Mutex
-	count map[int64]string
+	rmutex sync.RWMutex
+	mutex  sync.Mutex
+	count  map[int64]string
 }
 
 func (m *Msg) InitMsg(key int64, value string) {
@@ -21,15 +22,15 @@
 
 func (m *Msg) Get(key int64, c chan bool) (str string) {
 	defer func() { <-c }()
-	m.mutex.Lock()
+	m.rmutex.RLock()
 	if _, ok := m.count[key]; !ok {
-		m.mutex.Unlock()
+		m.rmutex.RUnlock()
 		m.InitMsg(key, strconv.Itoa(int(key)))
 	} else {
-		m.mutex.Unlock()
+		m.rmutex.RUnlock()
 	}
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
+	m.rmutex.RLock()
+	defer m.rmutex.RUnlock()
 	if str, ok := m.count[key]; ok {
 		return str
 	}

mutex.go

package main

import (
	"fmt"
	"runtime"
	"strconv"
	"sync"
	"time"
)

type Msg struct {
	mutex sync.Mutex
	count map[int64]string
}

func (m *Msg) InitMsg(key int64, value string) {
	m.mutex.Lock()
	defer m.mutex.Unlock()
	m.count[key] = value
}

func (m *Msg) Get(key int64, c chan bool) (str string) {
	defer func() { <-c }()
	m.mutex.Lock()
	if _, ok := m.count[key]; !ok {
		m.mutex.Unlock()
		m.InitMsg(key, strconv.Itoa(int(key)))
	} else {
		m.mutex.Unlock()
	}
	m.mutex.Lock()
	defer m.mutex.Unlock()
	if str, ok := m.count[key]; ok {
		return str
	}
	return
}

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU() * 2)
	msg := &Msg{count: map[int64]string{}}
	var i int64
	c := make(chan bool, 2000)
	t1 := time.Now().UnixNano()
	for i = 0; i <= 1024000; i++ {
		msg.InitMsg(i, strconv.Itoa(int(i)))
	}
	for i = 0; i <= 2048000; i++ {
		c <- true
		go msg.Get(i, c)
	}
	t2 := time.Now().UnixNano()
	fmt.Println(t2 - t1)
}

mutexv2.go

package main

import (
	"fmt"
	"runtime"
	"strconv"
	"sync"
	"time"
)

type Msg struct {
	rmutex sync.RWMutex
	mutex  sync.Mutex
	count  map[int64]string
}

func (m *Msg) InitMsg(key int64, value string) {
	m.mutex.Lock()
	defer m.mutex.Unlock()
	m.count[key] = value
}

func (m *Msg) Get(key int64, c chan bool) (str string) {
	defer func() { <-c }()
	m.rmutex.RLock()
	if _, ok := m.count[key]; !ok {
		m.rmutex.RUnlock()
		m.InitMsg(key, strconv.Itoa(int(key)))
	} else {
		m.rmutex.RUnlock()
	}
	m.rmutex.RLock()
	defer m.rmutex.RUnlock()
	if str, ok := m.count[key]; ok {
		return str
	}
	return
}

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU() * 2)
	msg := &Msg{count: map[int64]string{}}
	var i int64
	c := make(chan bool, 2000)
	t1 := time.Now().UnixNano()
	for i = 0; i <= 1024000; i++ {
		msg.InitMsg(i, strconv.Itoa(int(i)))
	}
	for i = 0; i <= 2048000; i++ {
		c <- true
		go msg.Get(i, c)
	}
	t2 := time.Now().UnixNano()
	fmt.Println(t2 - t1)
}

测试结果

 ~ ✗ go run mutex.go         
7566709000
 ~ ✗ go run mutexv2.go       
3387533000

go run mutexv2.go

will throw

fatal error: concurrent map read and map write

goroutine 1024111 [running]:
runtime.throw(0x10b6140, 0x21)
	/usr/local/Cellar/go/1.8/libexec/src/runtime/panic.go:596 +0x95 fp=0xc420fd9758 sp=0xc420fd9738
runtime.mapaccess2_fast64(0x109af60, 0xc4200720c0, 0xfa029, 0x102d388, 0x10b8560)
	/usr/local/Cellar/go/1.8/libexec/src/runtime/hashmap_fast.go:168 +0x1b2 fp=0xc420fd9780 sp=0xc420fd9758
main.(*Msg).Get(0xc420072090, 0xfa029, 0xc420086000, 0x0, 0x0)
	/Users/bamboo/Downloads/mutexv2.go:26 +0x9e fp=0xc420fd97b8 sp=0xc420fd9780
runtime.goexit()
	/usr/local/Cellar/go/1.8/libexec/src/runtime/asm_amd64.s:2197 +0x1 fp=0xc420fd97c0 sp=0xc420fd97b8
created by main.main
	/Users/bamboo/Downloads/mutexv2.go:51 +0x1e1

goroutine 1 [runnable]:
main.main()
	/Users/bamboo/Downloads/mutexv2.go:50 +0x1ab

goroutine 1024224 [runnable]:
main.(*Msg).Get(0xc420072090, 0xfa09a, 0xc420086000, 0x0, 0x0)
	/Users/bamboo/Downloads/mutexv2.go:23
created by main.main
	/Users/bamboo/Downloads/mutexv2.go:51 +0x1e1

goroutine 1024314 [runnable]:
main.(*Msg).Get(0xc420072090, 0xfa0f4, 0xc420086000, 0x0, 0x0)
	/Users/bamboo/Downloads/mutexv2.go:23
created by main.main
	/Users/bamboo/Downloads/mutexv2.go:51 +0x1e1

goroutine 1024266 [runnable]:
main.(*Msg).Get(0xc420072090, 0xfa0c4, 0xc420086000, 0x0, 0x0)
	/Users/bamboo/Downloads/mutexv2.go:23
created by main.main
	/Users/bamboo/Downloads/mutexv2.go:51 +0x1e1

...

in the go version go1.8 darwin/amd64