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 }