I wrote a small program to compare the performance of Critical Section vs Mutex in Windows.
On the tests I ran, acquiring Critical Section seems to be Slower :O Can anybody explain why both things take almost the same amount of time, and what is happening internally.
This is the timer I used - 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 1using 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 sectionInitializeCriticalSection(&critSection);#else // Create a mutex with no initial owner Mutex = CreateMutex( NULL, FALSE,NULL);#endif // Create worker threadsCStopWatch 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 CRITEnterCriticalSection(&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);#endifreturn TRUE;}For 2000 threads, on a Quad Core HPZ210, both take roughly 1.5 secs.
