定时器精度测试

#include <stdio.h>#include <winsock2.h>#pragma comment(lib, "ws2_32.lib")#include "mmsystem.h"#pragma comment(lib, "Winmm.lib")/* 函数功能: 测试select,WaitForSingleObject, Sleep函数的时间精度, 以及对CPU的占用率情况, 多媒体计时函数timeBeginPeriod对上述函数的影响; 测试时间: 2011年01月13日 测试结果: 1.定时器精度必须设置, 否则使用的是系统默认精度15ms左右; 也就是说必须调用timeBeginPeriod并指定为1ms; 2.无论定时器精度是否设置, 调用两次GetTickCount函数获取的差值都不准确; 3.定时器精度设置为1ms后, select, sleep, timeGetTime, WaitForSingleObject这些依赖于定时器的函数都将变得精确; 4.死循环调用 sleep(1ms超时) 或 select(1ms超时) 不造成明显的CPU占用, 测试前提,已经设置了定时器精度为1ms;*/// Test "select" 1msvoid TestTime1(){SOCKET sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);struct sockaddr_in serv;memset(&serv, 0, sizeof(struct sockaddr_in));serv.sin_family = AF_INET;serv.sin_addr.s_addr = inet_addr("192.168.3.103");serv.sin_port = htons(554);timeBeginPeriod(1);if( 0 == connect(sListen, (struct sockaddr*)&serv, sizeof(struct sockaddr_in))){while(1){TIMEVAL tv;tv.tv_sec = 0;tv.tv_usec = 1*1000;fd_set fdRead;FD_ZERO(&fdRead);FD_SET(sListen, &fdRead);DWORD dwStart = timeGetTime();int ret = select( sListen +1 , &fdRead, NULL, NULL, &tv );if( ret > 0){char szTmp[512] = {0};recv( sListen, szTmp, 512, 0);}else if ( ret ==0){int i = 0;}else if( ret <0){int dwErr = WSAGetLastError();int i = 0;}DWORD dwEnd = timeGetTime(); DWORD dwUsed = dwEnd - dwStart;printf("%d/n", dwUsed);}}timeEndPeriod(1);}// Test "Sleep", "WaitForSingleObject", 1msvoid TestTime2(){HANDLE hEvent = ::CreateEvent(NULL, FALSE, FALSE, NULL);timeBeginPeriod(1);while(1){DWORD dwStart = timeGetTime();Sleep(1);::WaitForSingleObject( hEvent, 1);DWORD dwEnd = timeGetTime(); DWORD dwUsed = dwEnd - dwStart;printf("%d/n", dwUsed);}timeEndPeriod(1);CloseHandle( hEvent);}