WinCE 下 CPU 使用率的计算方法

在函数 GetIdleTime 的用法中，MSDN 推荐的 CPU 使用率的计算方法，在部分平台下使用时得到的使用率异常：非 0-100% 的数值。

先看看 MSDN 推荐的算法的大概实现：

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();    // 此处为关键代码 Leo.Zheng  
  dwIdleStart=GetIdleTime();  
  Sleep(100);  
  dwStopTick=GetTickCount();  
  dwIdleEnd=GetIdleTime();  
  
  nPresentIdle=(100*(dwIdleEnd-dwIdleStart))/((dwStopTick-dwStartTick));  
  // 算法多次的一个平均值 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  的计算 CPU 使用率的方法及调用示例如下：

/* 
// 调用示例 
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 <<= 32;  
    iKernel64 += pFtKernel->dwLowDateTime;  
  
    iUser64 = pFtUser->dwHighDateTime;  
    iUser64 <<= 32;  
    iKernel64 += pFtUser->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);  // 设置高的优先级，保证 CPU 忙的时候也能打印 Leo  
  
    hIdleThread = CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)IdleThread,NULL,CREATE_SUSPENDED,&dwThreadID);    // 创建低优先级空闲线程 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);  
  
        // 计算 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%%
",dwCpuPower);  
          
        ResumeThread(hIdleThread);  
    }  
}