Windows Embedded Compact 7(WEC7)一個(gè)最重要的特性就是對(duì)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(yù)裝正版WEC7嵌入式操作系統(tǒng)，并且內(nèi)核啟用了對(duì)SMP的支持。在多個(gè)程序同時(shí)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?yàn)椴煌某绦蚩梢栽诓煌奶幚砥魃贤瑫r(shí)運(yùn)行，支持SMP還可以實(shí)現(xiàn)在一個(gè)核心上執(zhí)行硬實(shí)時(shí)應(yīng)用程序，而用戶界面(UI)或其它應(yīng)用程序可在另一個(gè)核心上運(yùn)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(yīng)用程序常用的SMP API如下所示：
GetCurrentProcessorNumber 獲取在調(diào)用此函數(shù)期間當(dāng)前線程正在運(yùn)行的處理器
CeGetIdleTimeEx 獲取指定處理器的空閑時(shí)間
CeGetProcessAffinity 獲取指定進(jìn)程的進(jìn)程關(guān)聯(lián)
CeGetThreadAffinity 獲取指定線程的線程關(guān)聯(lián)
CeGetTotalProcessors 獲取系統(tǒng)中的處理器核心總數(shù)
CeSetProcessAffinity 為指定的進(jìn)程設(shè)置處理器關(guān)聯(lián)
CeSetThreadAffinity 為指定的線程設(shè)置處理器關(guān)聯(lián)
默認(rèn)情況下，WEC7系統(tǒng)會(huì)自動(dòng)的將系統(tǒng)負(fù)載分配到CPU的所有核心上運(yùn)行，應(yīng)用程序不需要做任何設(shè)置。但根據(jù)不同的應(yīng)用場(chǎng)景，應(yīng)用程序也可以利用SMP API手動(dòng)的設(shè)置每個(gè)進(jìn)程、每個(gè)線程在指定的CPU核心上運(yùn)行，這里以計(jì)算ESM6802 i.MX6DL CPU每個(gè)核心的負(fù)載為例，介紹WEC7 SMP API的使用方法。
應(yīng)用程序首先通過CeGetTotalProcessors函數(shù)獲取當(dāng)前系統(tǒng)總的處理器(核心)個(gè)數(shù)，然后根據(jù)CPU核心個(gè)數(shù)創(chuàng)建相同數(shù)量的CPUIdleMonitorThread應(yīng)用線程用于計(jì)算CPU負(fù)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(yùn)行。CPUIdleMonitorThread線程函數(shù)在執(zhí)行時(shí)先調(diào)用GetCurrentProcessorNumber函數(shù)取得執(zhí)行當(dāng)前線程的CPU核，而后再利用CeGetIdleTimeEx函數(shù)最終計(jì)算出每個(gè)CPU核心的負(fù)載率。完整的例子代碼如下：
#include "stdafx.h"
// time in seconds to run the monitor thread
#define IDLE_MONITOR_TIME 100
HANDLE g_hMonitorThreads[4];
UINT32 CPUIdleMonitorThread(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
", 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%%)
",
nCPUId, diff.LowPart, nIdleDiff, nCPUId, 100 - nIdlePercent));
nRunTime--;
}
SetEvent(g_hMonitorThreads[nCPUId - 1]);
return nReturn;
}
int WINAPI 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
", nTemp));
return 0;
}
