Introduction
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:
CoInitializeEx(0, COINIT_MULTITHREADED);
Step 2: Set COM security levels:
CoInitializeSecurity(
NULL,
-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(
CLSID_WbemLocator,
0,
CLSCTX_INPROC_SERVER,
IID_IWbemLocator, (LPVOID *) &pLoc);
Step 4: Connect to WMI through the IWbemLocator::ConnectServer
method:
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:
CoSetProxyBlanket(
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("WQL"),
bstr_t("SELECT * FROM Win32_PerfRawData_PerfOS_Processor"),
WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
NULL,
&pEnumerator);
Step 7: Get data from the query in step 6.
IWbemClassObject *pclsObj;
while (1)
{
HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1, &pclsObj, &uReturn);
if(0 == uReturn)
{
break;
}
VARIANT vtProp;
VariantInit(&vtProp);
hr = pclsObj->Get(L"PercentProcessorTime", 0, &vtProp, 0, 0);
hr = pclsObj->Get(L"TimeStamp_Sys100NS", 0, &vtProp, 0, 0);
}
Note
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.