互斥 临界区 自旋锁 排队自旋锁 MCSLOCK 性能简单测试

VS2013

#include <windows.h>#include <process.h>#include <iostream>using namespace std;DWORD dwTest;const DWORD dwMax = 20000000;//#define MY_CRITICAL//#define MY_MUTEX#define MY_SPINLOCK#ifdef MY_CRITICAL    CRITICAL_SECTION g_cs;#elif defined MY_MUTEX    HANDLE  g_mutex;#else     SHORT   g_count;#endifint Init(){#ifdef MY_CRITICALInitializeCriticalSection(&g_cs);#elif defined MY_MUTEXg_mutex = CreateMutex(NULL,FALSE,NULL);if (g_mutex){if (ERROR_ALREADY_EXISTS == GetLastError()){cout << "only one instance can run!" << endl;return 0;}}else{cout <<"mutex is null."<<endl;return 0; }#else g_count = 0;#endifreturn 1;}void Lock(){#ifdef MY_CRITICALEnterCriticalSection(&g_cs);#elif defined MY_MUTEXWaitForSingleObject(g_mutex,INFINITE);#else while(InterlockedExchange16(&g_count,1) == 1)Sleep(1);#endif}void UnLock(){#ifdef MY_CRITICALLeaveCriticalSection(&g_cs);#elif defined MY_MUTEXReleaseMutex(g_mutex);#else InterlockedExchange16(&g_count, 0);#endif}UINT WINAPI ThreadProc(void *){while (true){Lock();dwTest++;if (dwTest >= dwMax){UnLock();return 1;}UnLock();}return 0;}int main(){if(!Init())return 0;dwTest = 0;#define num 2HANDLE hThread[num]; int i = 0;DWORD begin = GetTickCount();hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, NULL, 0, NULL);hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, NULL, 0, NULL);WaitForMultipleObjects(num, hThread,0,INFINITE);DWORD end = GetTickCount();cout << "花费的时间为: "<<end-begin<<" 毫秒"<< endl;system("pause");return 0;}

根据我的测试结果得出简单结论(不一定很准确):

耗时    互斥 > 临界 > 自旋锁

自旋锁采用Sleep(0)时

CPU  自旋锁  > 临界 > 互斥

采用Sleep(1) 自旋锁较低，后面考虑其它方法优化自旋锁，使之空转和Sleep浪费的时间充分利用起来!!!

优化后代码如下：

<pre name="code" class="cpp">#include <windows.h>#include <process.h>#include <iostream>using namespace std;DWORD dwTest;const DWORD dwMax = 200000000;#define MY_CRITICAL//#define MY_MUTEX//#define MY_SPINLOCK#ifdef MY_CRITICALCRITICAL_SECTION g_cs;#elif defined MY_MUTEXHANDLE  g_mutex;#else DWORD   g_count;#endifint Init(){#ifdef MY_CRITICALInitializeCriticalSection(&g_cs);#elif defined MY_MUTEXg_mutex = CreateMutex(NULL, FALSE, NULL);if (g_mutex){if (ERROR_ALREADY_EXISTS == GetLastError()){cout << "only one instance can run!" << endl;return 0;}}else{ cout << "mutex is null." << endl; return 0; }#else g_count = 0;#endifreturn 1;}#ifdef MY_CRITICAL#elif defined MY_MUTEX#else void spin_lock(){// 1 优点：比2指令更少//while (InterlockedExchange(&g_count, 1) == 1)//Sleep(1);// 2 优点：资源被锁时，占用总线比1机会更少//while (InterlockedCompareExchange(&g_count, 1, 0) == 1)//Sleep(1);// 3 结合1和2的优点(测试发现并不比1、2快。。)DWORD loop_count, yield_cnt, spin_count, pause_cnt;DWORD hold_cnt = 2;if (InterlockedExchange(&g_count, 1U) == 1U){loop_count = 0;spin_count = 1;do {if (loop_count < hold_cnt) {for (pause_cnt = spin_count; pause_cnt > 0; --pause_cnt) {_mm_pause();        // 这是为支持超线程的 CPU 准备的切换提示}spin_count *= hold_cnt;}else {yield_cnt = loop_count - 1;if ((yield_cnt & 63) == 63) {Sleep(1);          // 真正的休眠, 转入内核态}else if ((yield_cnt & 3) == 3) {Sleep(0);          // 切换到优先级跟自己一样或更高的线程, 可以换到别的CPU核心上}else {if (!SwitchToThread()) {    // 让步给该线程所在的CPU核心上的别的线程,// 不能切换到别的CPU核心上等待的线程Sleep(0);      // 如果同核心上没有可切换的线程,// 则切到别的核心试试(只能切优先级跟自己相同或更好的)}}}loop_count++;} while (InterlockedCompareExchange(&g_count, 1U, 0U) == 1U);}}void spin_unlock(){InterlockedExchange(&g_count, 0);//InterlockedCompareExchange(&g_count, 0, 1);}#endifvoid Lock(){#ifdef MY_CRITICALEnterCriticalSection(&g_cs);#elif defined MY_MUTEXWaitForSingleObject(g_mutex, INFINITE);#else spin_lock();#endif}void UnLock(){#ifdef MY_CRITICALLeaveCriticalSection(&g_cs);#elif defined MY_MUTEXReleaseMutex(g_mutex);#else spin_unlock();#endif}UINT WINAPI ThreadProc(void *){while (true){Lock();dwTest++;if ((dwTest < 1000000 && dwTest % 10000 == 0) || (dwTest < 100000000 && dwTest % 1000000 == 0) || (dwTest % 10000000 == 0))cout << dwTest << endl;if (dwTest >= dwMax){UnLock();return 1;}UnLock();}return 0;}int main(){if (!Init())return 0;dwTest = 0;#define num 4HANDLE hThread[num]; int i = 0;DWORD begin = GetTickCount();hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, NULL, 0, NULL);//SetThreadAffinityMask(hThread[i-1],i);hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, NULL, 0, NULL);//SetThreadAffinityMask(hThread[i - 1], i);hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, NULL, 0, NULL);//SetThreadAffinityMask(hThread[i - 1], i);hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, NULL, 0, NULL);//SetThreadAffinityMask(hThread[i - 1], i);WaitForMultipleObjects(num, hThread, 0, INFINITE);DWORD end = GetTickCount();cout << "花费的时间为: " << end - begin << " 毫秒" << endl;system("pause");return 0;}

以上是不公平锁，即锁A锁住资源，此时B等待，然后C等待，A释放资源后，B、C都有可能获得锁资源，而不是B获得，下面介绍一种公平锁MCSLOCK：

运行后发现效率很低。当然还是比互斥锁好些

<pre name="code" class="cpp">#include <windows.h>#include <process.h>#include <iostream>using namespace std;#define CAS(a,b,c) (InterlockedCompareExchangePointer((volatile PVOID*)a,(PVOID)c,(PVOID)b) == b)DWORD dwTest;const DWORD dwMax = 200000000;int   nTest = dwMax;//使用公平锁 MSCLOCK//线程节点struct ThreadNode{ThreadNode *next;bool       islock;};//线程队列struct ThreadQueue{ThreadNode *head;};int Init(ThreadQueue *&queue){queue = nullptr;queue = new ThreadQueue;if (!queue) return 0;queue->head = nullptr;return 1;}void NodeIsLock(ThreadNode *node){DWORD count = 0, loop = 10, forloop = 1, elsecount = 0, else1 = 12, else2 = 64;while (node->islock){if (count < loop){for (int i = 0; i < forloop; i++)_mm_pause();forloop *= 2;}else{elsecount++;if (elsecount < else1)Sleep(0);else if (elsecount < else2){if (!SwitchToThread())Sleep(0);}elseSleep(1);}count++;}}void NodeNextIsNull(ThreadNode *node){DWORD count = 0, loop = 10, forloop = 1, elsecount = 0, else1 = 12, else2 = 64;while (node->next == nullptr){if (count < loop){for (int i = 0; i < forloop; i++)_mm_pause();forloop *= 2;}else{elsecount++;if (elsecount < else1)Sleep(0);else if (elsecount < else2){if (!SwitchToThread())Sleep(0);}elseSleep(1);}count++;}}void Lock(ThreadQueue *queue, ThreadNode *node){node->next = nullptr;ThreadNode *tmp = node;ThreadNode *pre = (ThreadNode *)InterlockedExchangePointer((PVOID volatile *)&queue->head, (PVOID)tmp);if (pre == nullptr)  //空闲return;node->islock = true; //a__asm{sfence}        //写屏障 //_WriteBarrier();pre->next = node;    //b//NodeIsLock(node);while (node->islock)Sleep(0);//_mm_pause();}void UnLock(ThreadQueue *queue, ThreadNode *node){if (node->next == nullptr){if (CAS(&queue->head, node, nullptr))return;//NodeNextIsNull(node);while (node->next == nullptr)Sleep(0);}node->next->islock = false;}UINT WINAPI ThreadProc(void *ptr){ThreadQueue *queue = (ThreadQueue *)ptr;ThreadNode *node = new ThreadNode;while (true){Lock(queue, node);if (dwTest >= dwMax){UnLock(queue, node);delete node;return 1;}dwTest++;if ((dwTest < 1000000 && dwTest % 10000 == 0) || (dwTest < 100000000 && dwTest % 1000000 == 0) || (dwTest % 10000000 == 0))cout << dwTest << endl;nTest--;UnLock(queue, node);}//delete node; //应该所有线程结束后释放return 0;}int main(){ThreadQueue *queue = nullptr;if (!Init(queue))return 0;dwTest = 0;#define num 4HANDLE hThread[num]; int i = 0;DWORD begin = GetTickCount();hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, queue, 0, NULL);//SetThreadAffinityMask(hThread[i-1],i);hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, queue, 0, NULL);//SetThreadAffinityMask(hThread[i - 1], i);hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, queue, 0, NULL);//SetThreadAffinityMask(hThread[i - 1], i);hThread[i++] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, queue, 0, NULL);//SetThreadAffinityMask(hThread[i - 1], i);WaitForMultipleObjects(num, hThread, 0, INFINITE);DWORD end = GetTickCount();cout << "nTest=0则锁操作是正确的.nTest=" << nTest << endl;cout << "花费的时间为: " << end - begin << " 毫秒" << endl;system("pause");return 0;}

使用此锁，发现CPU超高！！！而在while处改成NodeIsLock和NodeNextIsNull后CPU虽然降下来了，但是运行速度很慢!!!

CLH LOCK也是排队自旋锁，有空可以实现一下C++般般

数组自旋锁:

#include <windows.h>#include <process.h>#include <iostream>using namespace std;#define CAS(a,b,c) (InterlockedCompareExchangePointer((volatile PVOID*)a,(PVOID)c,(PVOID)b) == b)#define num 4//使用数组锁DWORD dwTest;const DWORD dwMax = 2000000;// 200000000;int   nTest = dwMax;DWORD _count = 0XFFFFFFFF;bool  _lockarr[num] = {false};void Lock(DWORD *ptr){//DWORD ret = InterlockedIncrement(&_count);//DWORD index = ret % num;//*ptr = index;//__asm{sfence}while (!_lockarr[*ptr])Sleep(0);}void UnLock(DWORD *ptr){_lockarr[*ptr] = false;__asm{sfence}_lockarr[(*ptr + 1) % num] = true;}UINT WINAPI ThreadProc(void *ptr){DWORD *Ptr = (DWORD *)ptr;while (true){Lock(Ptr);if (dwTest >= dwMax){UnLock(Ptr);return 1;}dwTest++;if ((dwTest < 1000000 && dwTest % 10000 == 0) || (dwTest < 100000000 && dwTest % 1000000 == 0) || (dwTest % 10000000 == 0))cout << dwTest << endl;nTest--;UnLock(Ptr);}return 0;}int main(){dwTest = 0;DWORD index[num];for (int i = 0; i < num; i++)index[i] = i;HANDLE hThread[num]; int i = 0;DWORD begin = GetTickCount();_lockarr[0] = true;hThread[i] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, &index[i], 0, NULL); i++;//SetThreadAffinityMask(hThread[i-1],i);hThread[i] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, &index[i], 0, NULL); i++;//SetThreadAffinityMask(hThread[i - 1], i);hThread[i] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, &index[i], 0, NULL); i++;//SetThreadAffinityMask(hThread[i - 1], i);hThread[i] = (HANDLE)_beginthreadex(NULL, 0, ThreadProc, &index[i], 0, NULL); i++;//SetThreadAffinityMask(hThread[i - 1], i);WaitForMultipleObjects(num, hThread, 0, INFINITE);DWORD end = GetTickCount();cout << "nTest=0则锁操作是正确的.nTest=" << nTest << endl;cout << "花费的时间为: " << end - begin << " 毫秒" << endl;system("pause");return 0;}