我写了一个小程序来比较 Windows 中 Critical Section 与 Mutex 的性能。
在我运行的测试中,获取关键部分似乎更慢:O 谁能解释为什么这两件事花费几乎相同的时间,以及内部发生了什么。
这是我使用的计时器 - http://cplus.about.com/od/howtodothingsi2/a/timing.htm
#include "stdafx.h"
#include<iostream>
#include<vector>
#include "h_timer.h"
#include<WinBase.h>
#include<Windows.h>
#include<stdio.h>
#define MAX_THREADS 2000
//Comment and Uncomment this to enable/disable critialSection / Mutex
#define CRIT 1
using namespace std;
HANDLE Mutex;
CRITICAL_SECTION critSection;
DWORD WINAPI Contention( LPVOID );
int main( void )
{
HANDLE Thread[MAX_THREADS];
DWORD ThreadID;
int i;
#ifdef CRIT
//create a critical section
InitializeCriticalSection(&critSection);
#else
// Create a mutex with no initial owner
Mutex = CreateMutex( NULL, FALSE,NULL);
#endif
// Create worker threads
CStopWatch timer, tempTimer;
timer.startTimer();
for( i=0; i < MAX_THREADS; i++ )
{
Thread[i] = CreateThread( NULL,
0,(LPTHREAD_START_ROUTINE)Contention,NULL,0,&ThreadID);
}
WaitForMultipleObjects(MAX_THREADS, Thread, TRUE, INFINITE);
timer.stopTimer();
cout<<endl<<"Elapsed Time:"<<timer.getElapsedTime();
cin.get();
// Close thread and mutex handles
for( i=0; i < MAX_THREADS; i++ )
CloseHandle(Thread[i]);
CloseHandle(Mutex);
return 0;
}
DWORD WINAPI Contention( LPVOID lpParam )
{
#ifdef CRIT
EnterCriticalSection(&critSection);
//printf("ThreadId: %d\n",GetCurrentThreadId());
//printf("Let's try Again. %d\n\n", GetCurrentThreadId());
LeaveCriticalSection(&critSection);
#else
// lpParam not used in this example
UNREFERENCED_PARAMETER(lpParam);
DWORD dwCount=0, dwWaitResult;
// Request ownership of mutex.
dwWaitResult = WaitForSingleObject(
ghMutex, // handle to mutex
INFINITE); // no time-out interval
dwCount++;
ReleaseMutex(ghMutex);
#endif
return TRUE;
}
对于 2000 个线程,在四核 HPZ210 上,两者都需要大约 1.5 秒。