Ever since I saw 'Performance' application on Windows 2000, I wondered if there is a way / Windows API to programmatically determine CPU usage for each of the individual CPUs in a multi-processor machine. Though there are many articles for getting the CPU usage, none helped when it came to multi-processor machines.
After some digging in MSDN, I could find WMI (Windows Management and Instrumentation) has a few performance counter classes. I chose to use the
Win32_PerfRawData_PerfOS_Processor class in this case as it is supported on Windows 2000 onwards.
How to use it?
Follow these seven steps:
Step 1: Initialize COM:
Step 2: Set COM security levels:
-1, NULL, NULL, RPC_C_AUTHN_LEVEL_DEFAULT, RPC_C_IMP_LEVEL_IMPERSONATE, NULL, EOAC_NONE, NULL );
Step 3: Obtain the initial locator to WMI:
IWbemLocator *pLoc = NULL;
hres = CoCreateInstance(
IID_IWbemLocator, (LPVOID *) &pLoc);
Step 4: Connect to WMI through the
IWbemServices *pSvc = NULL;
hres = pLoc->ConnectServer(
_bstr_t(L"ROOT\\CIMV2"), NULL, NULL, 0, NULL, 0, 0, &pSvc );
Step 5: Set security levels on the proxy:
pSvc, RPC_C_AUTHN_WINNT, RPC_C_AUTHZ_NONE, NULL, RPC_C_AUTHN_LEVEL_CALL, RPC_C_IMP_LEVEL_IMPERSONATE, NULL, EOAC_NONE );
Step 6: Use the
IWbemServices pointer to make requests of WMI:
IEnumWbemClassObject* pEnumerator = NULL;
HRESULT hres = pSvc->ExecQuery(
bstr_t("SELECT * FROM Win32_PerfRawData_PerfOS_Processor"),
WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
Step 7: Get data from the query in step 6.
HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1, &pclsObj, &uReturn);
if(0 == uReturn)
hr = pclsObj->Get(L"PercentProcessorTime", 0, &vtProp, 0, 0);
hr = pclsObj->Get(L"TimeStamp_Sys100NS", 0, &vtProp, 0, 0);
I have tried to keep the source code in the attached project simple. So I have taken the number of processors as the input though you may like to programmatically get the number of processors using
GetSystemInfo Win32 API.
I have tested it on Microsoft Windows 2000 Professional OS running on a dual processor machine. It should work on Windows XP/ Windows 2003 Server as well.