在函數(shù)?GetIdleTime 的用法中，MSDN 推薦的 CPU 使用率的計算方法，在部分平臺下使用時得到的使用率異常：非 0-100% 的數(shù)值。

先看看 MSDN 推薦的算法的大概實現(xiàn)：

static?void?CallCountCpuIdleThread(CCountCpuDlg?*pCCountCpuDlg)
{
?DWORD?dwStartTick;
?DWORD?dwIdleStart;
?DWORD?dwStopTick;
?DWORD?dwIdleEnd;
?int???nPresentIdle;
?int???nCpuUage[10]={0};
?int???nCount=0;
?int???ave=0;
?DWORD?sum=0;?
?int?i;

?while(1)
?{
??dwStartTick=GetTickCount();????//?此處為關鍵代碼?Leo.Zheng
??dwIdleStart=GetIdleTime();
??Sleep(100);
??dwStopTick=GetTickCount();
??dwIdleEnd=GetIdleTime();

??nPresentIdle=(100*(dwIdleEnd-dwIdleStart))/((dwStopTick-dwStartTick));
??//?算法多次的一個平均值?Leo.Zheng
??if(nCount<10)
??{
???nCpuUage[nCount]=nPresentIdle;
???nCount++;
???if(nCount==10)
???{
????for(i=0;i<10;i++)
?????sum+=nCpuUage[i];
????ave=sum/10;
????//?g_nCpuIdle?only?read?in?the?main?thread
????g_nCpuIdle=ave;
????nCount=0;
????sum=0;
????//RETAILMSG(1,(TEXT("CPU?laoding?is?%d?/r/n"),ave));
????}??
??}
?}
}

不使用 ?GetIdleTime??的計算 CPU 使用率的方法及調(diào)用示例如下：

/*
//?調(diào)用示例
DWORD?dwThreadID?=?0;
HANDLE?hThread?=?NULL;
hThread?=?CreateThread(NULL,0,ThreadPrintCpuLoad,this,0,&dwThreadID);
if(NULL?!=?hThread)
{
	CloseHandle(hThread);
}
*/
static?DWORD?GetThreadTick(FILETIME?*pFtKernel,?FILETIME?*pFtUser)
{
	__int64?iKernel64?=?0;
	__int64?iUser64?=?0;

	iKernel64?=?pFtKernel->dwHighDateTime;
	iKernel64?<dwLowDateTime;

	iUser64?=?pFtUser->dwHighDateTime;
	iUser64?<dwLowDateTime;

	iKernel64?+=?iUser64;

	//?nano?sec?to?milli?sec
	iKernel64?/=?10000;

	return?(DWORD)iKernel64;
}

static?void?IdleThread(LPVOID?pvParams)
{
	while(1)
	{
	}
}

static?DWORD?ThreadPrintCpuLoad(LPVOID?lpParameter)
{
	DWORD?dwThreadID?=?0;
	HANDLE?hIdleThread?=?NULL;

	SetThreadPriority(GetCurrentThread(),THREAD_PRIORITY_HIGHEST);	//?設置高的優(yōu)先級，保證?CPU?忙的時候也能打印?Leo

	hIdleThread?=?CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)IdleThread,NULL,CREATE_SUSPENDED,&dwThreadID);	//?創(chuàng)建低優(yōu)先級空閑線程?Leo.Zheng
	SetThreadPriority(hIdleThread,THREAD_PRIORITY_IDLE);
	ResumeThread(hIdleThread);

	while(1)
	{
		Sleep(1000);	//?1S打印一次?Leo.Zheng

		static?DWORD?dwLastThreadTime?=?0;
		static?DWORD?dwLastTickTime?=?0;
		DWORD?dwCurrentThreadTime?=?0;
		DWORD?dwCurrentTickTime?=?0;
		DWORD?dwCpuPower?=?0;

		FILETIME?ftCreationTime;
		FILETIME?ftExitTime;
		FILETIME?ftKernelTime;
		FILETIME?ftUserTime;

		SuspendThread(hIdleThread);

		dwCurrentTickTime?=?GetTickCount();
		GetThreadTimes(hIdleThread,&ftCreationTime,&ftExitTime,&ftKernelTime,&ftUserTime);
		dwCurrentThreadTime?=?GetThreadTick(&ftKernelTime,&ftUserTime);

		//?計算?CPU?占用率
		if(dwCurrentTickTime?!=?dwLastTickTime?||?0?!=?dwLastThreadTime?||?0?!=?dwLastTickTime)
		{
			dwCpuPower?=?100?-?(((dwCurrentThreadTime?-?dwLastThreadTime)?*?100)?/?(dwCurrentTickTime?-?dwLastTickTime));
		}
		else
		{
			dwCpuPower?=?0;
		}

		//?save?status
		dwLastTickTime?=?GetTickCount();
		dwLastThreadTime?=?dwCurrentThreadTime;

		printf("CPU?loaded:?%d%%rn",dwCpuPower);
		
		ResumeThread(hIdleThread);
	}
}