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Getting CPU Usage in a Multiprocessor Machine

, 30 May 2005
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Getting CPU usage in a multiprocessor machine.

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,                          // COM authentication
        NULL,                        // Authentication services
        NULL,                        // Reserved
        RPC_C_AUTHN_LEVEL_DEFAULT,   // Default authentication 
        RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation  
        NULL,                        // Authentication info
        EOAC_NONE,                   // Additional capabilities 
        NULL                         // Reserved
        );

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;
 
    // Connect to the root\cimv2 namespace with
    // the current user and obtain pointer pSvc
    // to make IWbemServices calls.
    hres = pLoc->ConnectServer(
         _bstr_t(L"ROOT\\CIMV2"), // Object path of WMI namespace
         NULL,                    // User name. NULL = current user
         NULL,                    // User password. NULL = current
         0,                       // Locale. NULL indicates current
         NULL,                    // Security flags.
         0,                       // Authority (e.g. Kerberos)
         0,                       // Context object 
         &pSvc                    // pointer to IWbemServices proxy
         );

Step 5: Set security levels on the proxy:

CoSetProxyBlanket(
       pSvc,                        // Indicates the proxy to set
       RPC_C_AUTHN_WINNT,           // RPC_C_AUTHN_xxx
       RPC_C_AUTHZ_NONE,            // RPC_C_AUTHZ_xxx
       NULL,                        // Server principal name 
       RPC_C_AUTHN_LEVEL_CALL,      // RPC_C_AUTHN_LEVEL_xxx 
       RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
       NULL,                        // client identity
       EOAC_NONE                    // proxy capabilities 
    );

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);

          // Use it

           hr = pclsObj->Get(L"TimeStamp_Sys100NS", 0, &vtProp, 0, 0);

          // Use it
    }

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.

License

This article, along with any associated source code and files, is licensed under The Microsoft Public License (Ms-PL)

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About the Author

BimalV

India India
No Biography provided

Comments and Discussions

 
GeneralNot Practical PinmemberVitalyTomilov6-Jun-08 7:38 
This implementation doesn't allow to retrieve the current CPU usage, because you are using such things as Sleep(2000) in your code, which not only lags the result, but if the result is needed immediately, the code isn't usable.
 
For instance, say you have a worker thread that needs to know the CPU usage right now to decide what priority it should use for execution. It cannot wait for 2 seconds to get the results about the CPU usage, it needs the results under 1ms.
Questionerror C2061:syntax error : identifier 'DWORD_PTR' Pinmemberthaithiensu12-Feb-08 20:53 
GeneralC# Code Available PinmemberAdam L. Stevenson30-Dec-07 5:25 
GeneralRe: C# Code Available PinmemberMember 296291322-Jul-08 6:12 
GeneralRe: C# Code Available PinmemberManish K. Agarwal29-Mar-10 21:01 
GeneralRe: C# Code Available Pinmemberlalit.k.bhatia21-Sep-14 17:31 
GeneralDevision By Zero Pinmember_pmneo_18-Nov-06 7:48 
GeneralRe: Devision By Zero Pinmember_pmneo_18-Nov-06 13:17 
GeneralRe: Devision By Zero PinmemberFinix21-Mar-07 18:16 
GeneralRe: Devision By Zero PinmemberBimalV11-Jul-07 0:44 
GeneralRe: Devision By Zero Pinmemberbren1239-Aug-07 7:43 
GeneralRe: Devision By Zero Pinmemberhorse199721-Nov-07 16:17 
GeneralRe: Devision By Zero PinmemberMember 768255519-Feb-11 5:27 
QuestionAccess PoolNonPagedBytes Pinmembersuresh_suryavanshi2-Nov-06 3:14 
QuestionPoolNonPagedBytes Pinmembersuresh_suryavanshi2-Nov-06 3:12 
QuestionRegarding accessing the PoolNonPagedBytes Pinmembersuresh_suryavanshi2-Nov-06 3:12 
QuestionPoolNonPagedBytes for only one process Pinmembersuresh_suryavanshi2-Nov-06 3:11 
QuestionAccess PoolNonPagedBytes for only one process Pinmembersuresh_suryavanshi2-Nov-06 3:11 
QuestionPoolNonPagedBytes for only one process from Win32_PerfFormattedData_PerfProc_Process Pinmembersuresh_suryavanshi2-Nov-06 3:10 
QuestionAccess the PoolNonPagedBytes for only one process from Win32_PerfFormattedData_PerfProc_Process Pinmembersuresh_suryavanshi2-Nov-06 3:10 
QuestionGetting the PoolNonPagedBytes for only one process from Win32_PerfFormattedData_PerfProc_Process Pinmembersuresh_suryavanshi2-Nov-06 3:09 
QuestionHow to access the PoolNonPagedBytes for only one process from Win32_PerfFormattedData_PerfProc_Process Pinmembersuresh_suryavanshi2-Nov-06 3:09 
GeneralWin2K3 Pinmemberisdi10-Mar-06 12:58 
Generalgetting CPU Usage of each CPU for a process running on multi CPUs system. Pinmemberlvantin9-Feb-06 20:57 
GeneralRe: getting CPU Usage of each CPU for a process running on multi CPUs system. PinmemberBimalV11-Jul-07 0:38 

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