Windows Embedded Compact 7(WEC7)一個最重要的特性就是對多核處理器的支持(Symmetric Multi-Processing(SMP))，ESM6802是英創(chuàng)公司推出的基于Freescale i.MX6DL雙核處理器的高性能工控主板，預裝正版WEC7嵌入式操作系統(tǒng)，并且內(nèi)核啟用了對SMP的支持。在多個程序同時執(zhí)行的情況下，支持SMP的多核系統(tǒng)具有比單處理器更好的性能，因為不同的程序可以在不同的處理器上同時運行，支持SMP還可以實現(xiàn)在一個核心上執(zhí)行硬實時應用程序，而用戶界面(UI)或其它應用程序可在另一個核心上運行，以提高系統(tǒng)的效率。

WEC7提供了一組處理多核系統(tǒng)上線程和處理器調(diào)度的SMP API接口函數(shù)：

https://msdn.microsoft.com/en-us/library/gg154433(v=winembedded.70).aspx

其中應用程序常用的SMP API如下所示：

默認情況下，WEC7系統(tǒng)會自動的將系統(tǒng)負載分配到CPU的所有核心上運行，應用程序不需要做任何設置。但根據(jù)不同的應用場景，應用程序也可以利用SMP API手動的設置每個進程、每個線程在指定的CPU核心上運行，這里以計算ESM6802 i.MX6DL CPU每個核心的負載為例，介紹WEC7 SMP API的使用方法。

應用程序首先通過CeGetTotalProcessors函數(shù)獲取當前系統(tǒng)總的處理器(核心)個數(shù)，然后根據(jù)CPU核心個數(shù)創(chuàng)建相同數(shù)量的CPUIdleMonitorThread應用線程用于計算CPU負載，在創(chuàng)建線程后通過CeSetThreadAffinity函數(shù)將所創(chuàng)建的線程固定在指定的CPU核心上運行。CPUIdleMonitorThread線程函數(shù)在執(zhí)行時先調(diào)用GetCurrentProcessorNumber函數(shù)取得執(zhí)行當前線程的CPU核，而后再利用CeGetIdleTimeEx函數(shù)最終計算出每個CPU核心的負載率。完整的例子代碼如下：

#include"stdafx.h"

// time in seconds to run the monitor thread

#defineIDLE_MONITOR_TIME 100

HANDLE g_hMonitorThreads[4];

UINT32CPUIdleMonitorThread(PVOID pContext)

{

UINT32 nCPUId = ((UINT32*)pContext)[0];

UINT32 nRunTime = ((UINT32*)pContext)[1];

UINT32 nIdleBefore, nIdleAfter, nIdleDiff, nIdlePercent;

UINT32 nReturn = ERROR_SUCCESS;

LARGE_INTEGER pcBefore = { 0, 0 };

LARGE_INTEGER pcAfter = { 0, 0 };

LARGE_INTEGER diff;

LARGE_INTEGER freq;

RETAILMSG(1, (L"[CPU%d] Run monitor thread for %d seconds\r\n", nCPUId, nRunTime));

// The processor number is a 1-based index.

QueryPerformanceFrequency(&freq);

while(nRunTime > 0)

{

nCPUId = GetCurrentProcessorNumber();

CeGetIdleTimeEx(nCPUId, (LPDWORD)&nIdleBefore);

QueryPerformanceCounter(&pcBefore);

Sleep(2000);

QueryPerformanceCounter(&pcAfter);

CeGetIdleTimeEx(nCPUId, (LPDWORD)&nIdleAfter);

diff.QuadPart = (pcAfter.QuadPart - pcBefore.QuadPart) * 1000 / freq.QuadPart;

nIdleDiff = nIdleAfter - nIdleBefore;

nIdlePercent = nIdleDiff / 20;

RETAILMSG(1, (L"[CPU%d] Sleep: 2000 ms (actual:%d ms) Idle: %03d ms (CPU%d = %d%%)\r\n",

nCPUId, diff.LowPart, nIdleDiff, nCPUId, 100 - nIdlePercent));

nRunTime--;

}

SetEvent(g_hMonitorThreads[nCPUId - 1]);

returnnReturn;

}

intWINAPI WinMain(HINSTANCE hInstance,

HINSTANCE hPrevInstance,

LPTSTR lpCmdLine,

int nCmdShow)

{

UINT32 nCPUCount;

UINT32 nTemp = 0;

UINT32 i;

UINT32 nParam[8] = { 1, IDLE_MONITOR_TIME, 2, IDLE_MONITOR_TIME, 3, IDLE_MONITOR_TIME, 4,IDLE_MONITOR_TIME };

nCPUCount = CeGetTotalProcessors();

for(i = 0; i < nCPUCount; i++)

g_hMonitorThreads[i] = CreateEvent(NULL, TRUE, FALSE, NULL);

nTemp = 1;

CeSetThreadAffinity(GetCurrentThread(), 1);

for(i = 1; i < nCPUCount; i++)

{

HANDLE hThread = CreateThread(

NULL,

0,

(LPTHREAD_START_ROUTINE)CPUIdleMonitorThread,

&nParam[i * 2],

CREATE_SUSPENDED,

NULL);

if(NULL != hThread)

{

CeSetThreadAffinity(hThread, i + 1);

ResumeThread(hThread);

Sleep(0);

CloseHandle(hThread);

nTemp++;

}

else

{

SetEvent(g_hMonitorThreads[i]);

}

}

CPUIdleMonitorThread(&nParam[0]);

Sleep(2000);

for(i = 0; i < nCPUCount; i++)

WaitForSingleObject(g_hMonitorThreads[i], (IDLE_MONITOR_TIME + 5) * 1000);

RETAILMSG(1, (L"[CPULOAD] Number of CPUs monitored: %d\r\n", nTemp));

return0;

}