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：

 1 static void CallCountCpuIdleThread(CCountCpuDlg *pCCountCpuDlg)  
 2 {  
 3  DWORD dwStartTick;  
 4  DWORD dwIdleStart;  
 5  DWORD dwStopTick;  
 6  DWORD dwIdleEnd;  
 7  int   nPresentIdle;  
 8  int   nCpuUage[10]={0};  
 9  int   nCount=0;  
10  int   ave=0;  
11  DWORD sum=0;   
12  int i;  
13   
14  while(1)  
15  {  
16   dwStartTick=GetTickCount();    // 此处为关键代码 Leo.Zheng  
17   dwIdleStart=GetIdleTime();  
18   Sleep(100);  
19   dwStopTick=GetTickCount();  
20   dwIdleEnd=GetIdleTime();  
21   
22   nPresentIdle=(100*(dwIdleEnd-dwIdleStart))/((dwStopTick-dwStartTick));  
23   // 算法多次的一个平均值 Leo.Zheng  
24   if(nCount<10)  
25   {  
26    nCpuUage[nCount]=nPresentIdle;  
27    nCount++;  
28    if(nCount==10)  
29    {  
30     for(i=0;i<10;i++)  
31      sum+=nCpuUage[i];  
32     ave=sum/10;  
33     // g_nCpuIdle only read in the main thread  
34     g_nCpuIdle=ave;  
35     nCount=0;  
36     sum=0;  
37     //RETAILMSG(1,(TEXT("CPU laoding is %d /r/n"),ave));  
38     }    
39   }  
40  }  
41 }  

不使用  GetIdleTime  的计算 CPU 使用率的方法及调用示例如下：

 1 /* 
 2 // 调用示例 
 3 DWORD dwThreadID = 0; 
 4 HANDLE hThread = NULL; 
 5 hThread = CreateThread(NULL,0,ThreadPrintCpuLoad,this,0,&dwThreadID); 
 6 if(NULL != hThread) 
 7 { 
 8     CloseHandle(hThread); 
 9 } 
10 */  
11 static DWORD GetThreadTick(FILETIME *pFtKernel, FILETIME *pFtUser)  
12 {  
13     __int64 iKernel64 = 0;  
14     __int64 iUser64 = 0;  
15   
16     iKernel64 = pFtKernel->dwHighDateTime;  
17     iKernel64 <<= 32;  
18     iKernel64 += pFtKernel->dwLowDateTime;  
19   
20     iUser64 = pFtUser->dwHighDateTime;  
21     iUser64 <<= 32;  
22     iKernel64 += pFtUser->dwLowDateTime;  
23   
24     iKernel64 += iUser64;  
25   
26     // nano sec to milli sec  
27     iKernel64 /= 10000;  
28   
29     return (DWORD)iKernel64;  
30 }  
31   
32 static void IdleThread(LPVOID pvParams)  
33 {  
34     while(1)  
35     {  
36     }  
37 }  
38   
39 static DWORD ThreadPrintCpuLoad(LPVOID lpParameter)  
40 {  
41     DWORD dwThreadID = 0;  
42     HANDLE hIdleThread = NULL;  
43   
44     SetThreadPriority(GetCurrentThread(),THREAD_PRIORITY_HIGHEST);  // 设置高的优先级，保证 CPU 忙的时候也能打印 Leo  
45   
46     hIdleThread = CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)IdleThread,NULL,CREATE_SUSPENDED,&dwThreadID);    // 创建低优先级空闲线程 Leo.Zheng  
47     SetThreadPriority(hIdleThread,THREAD_PRIORITY_IDLE);  
48     ResumeThread(hIdleThread);  
49   
50     while(1)  
51     {  
52         Sleep(1000);    // 1S打印一次 Leo.Zheng  
53   
54         static DWORD dwLastThreadTime = 0;  
55         static DWORD dwLastTickTime = 0;  
56         DWORD dwCurrentThreadTime = 0;  
57         DWORD dwCurrentTickTime = 0;  
58         DWORD dwCpuPower = 0;  
59   
60         FILETIME ftCreationTime;  
61         FILETIME ftExitTime;  
62         FILETIME ftKernelTime;  
63         FILETIME ftUserTime;  
64   
65         SuspendThread(hIdleThread);  
66   
67         dwCurrentTickTime = GetTickCount();  
68         GetThreadTimes(hIdleThread,&ftCreationTime,&ftExitTime,&ftKernelTime,&ftUserTime);  
69         dwCurrentThreadTime = GetThreadTick(&ftKernelTime,&ftUserTime);  
70   
71         // 计算 CPU 占用率  
72         if(dwCurrentTickTime != dwLastTickTime || 0 != dwLastThreadTime || 0 != dwLastTickTime)  
73         {  
74             dwCpuPower = 100 - (((dwCurrentThreadTime - dwLastThreadTime) * 100) / (dwCurrentTickTime - dwLastTickTime));  
75         }  
76         else  
77         {  
78             dwCpuPower = 0;  
79         }  
80   
81         // save status  
82         dwLastTickTime = GetTickCount();  
83         dwLastThreadTime = dwCurrentThreadTime;  
84   
85         printf("CPU loaded: %d%%\r\n",dwCpuPower);  
86           
87         ResumeThread(hIdleThread);  
88     }  
89 }