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Obtaining Statistical Performance Data

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In WMI, you can define statistical performance data based on data in formatted performance classes derived from Win32_PerfFormattedData. The available statistics are average, minimum, maximum, range, and variance, as defined in Statistical Counter Types.

The following list includes the special statistical counter types:

The following examples show how to:

  • Create a MOF file that defines a class of calculated data.
  • Write a script that creates an instance of the class, and periodically refreshes the data in the instance with the recalculated statistical values.

MOF File

The following MOF code example creates a new calculated data class named Win32_PerfFormattedData_AvailableMBytes. This class contains data from the AvailableMBytes property of the raw class Win32_PerfRawData_PerfOS_Memory. The Win32_PerfFormattedData_AvailableBytes class defines the properties Average, Min, Max, Range, and Variance.

The MOF file uses the Property Qualifiers for Formatted Performance Counter Classes to define the property data source and the calculation formula.

  • The Average property obtains raw data from the Win32_PerfRawData_PerfOS_Memory.AvailableMBytes property.
  • The Counter qualifier for the Average property specifies the raw data source.
  • The CookingType qualifier specifies the formula COOKER_MIN for calculating the data.
  • The SampleWindow qualifier specifies how many samples to take before performing the calculation.
// Store the new Win32_PerfFormattedData_MemoryStatistics
//     class in the Root\Cimv2 namespace
#pragma autorecover
#pragma namespace("\\\\.\\Root\\CimV2")

qualifier vendor:ToInstance;
qualifier guid:ToInstance;
qualifier displayname:ToInstance;
qualifier perfindex:ToInstance;
qualifier helpindex:ToInstance;
qualifier perfdetail:ToInstance;
qualifier countertype:ToInstance;
qualifier perfdefault:ToInstance;
qualifier defaultscale:ToInstance;

qualifier dynamic:ToInstance;
qualifier hiperf:ToInstance;
qualifier AutoCook:ToInstance;
qualifier AutoCook_RawClass:ToInstance;
qualifier CookingType:ToInstance;
qualifier Counter:ToInstance;


// Define the Win32_PerFormattedData_MemoryStatistics
//     class, derived from Win32_PerfFormattedData
[
  dynamic,
  // Name of formatted data provider: "WMIPerfInst" for Vista 
  //   and later
  provider("HiPerfCooker_v1"), 
  // Text that will identify new counter in Perfmon
  displayname("My Calculated Counter"),                            
  // A high performance class     
  Hiperf,
  // Contains calculated data 
  Cooked, 
  // Value must be 1 
  AutoCook(1), 
  // Raw performance class to get data for calculations
  AutoCook_RawClass("Win32_PerfRawData_PerfOS_Memory"),
  // Value must be 1        
  AutoCook_RawDefault(1),
  // Name of raw class property to use for timestamp in formulas 
  PerfSysTimeStamp("Timestamp_PerfTime"), 
  // Name of raw class property to use for frequency in formulas
  PerfSysTimeFreq("Frequency_PerfTime"), 
  // Name of raw class property to use for timestamp in formulas
  Perf100NSTimeStamp("Timestamp_Sys100NS"),
  // Name of raw class property to use for frequency in formulas
  Perf100NSTimeFreq("Frequency_Sys100NS"),
  // Name of raw class property to use for timestamp in formulas
  PerfObjTimeStamp("Timestamp_Object"),
  // Name of raw class property to use for frequency in formulas 
  PerfObjTimeFreq("Frequency_Object"),
  // Only one instance of class allowed in namespace
  singleton                                                   
]

class Win32_PerfFormattedData_MemoryStatistics
          : Win32_PerfFormattedData
{

// Define the properties for the class. 
// All the properties perform different
//     statistical operations on the same
//     property, AvailableMBytes, in the raw class

// Define the Average property,
//     which uses the "COOKER_AVERAGE" counter type and 
//     gets its data from the AvailableMBytes 
//     property in the raw class

    [
     CookingType("COOKER_AVERAGE"),
     Counter("AvailableMBytes"),
     SampleWindow(10)
    ]
    uint64 Average = 0;

// Define the Min property, which uses
//     the "COOKER_MIN" counter type and 
//     gets its data from the AvailableMBytes
//     property in the raw class

    [
     CookingType("COOKER_MIN"),
     Counter("AvailableMBytes"),
     SampleWindow(10)
    ]
    uint64 Min = 0;

// Define the Max property, which uses
//     the "COOKER_MAX" counter type and 
//     gets its data from the
//     AvailableMBytes property in the raw class

    [
     CookingType("COOKER_MAX"),
     Counter("AvailableMBytes"),
     SampleWindow(10)
    ]
    uint64 Max = 0;

// Define the Range property, which uses
//     the "COOKER_RANGE" counter type and 
//     gets its data from the AvailableMBytes
//     property in the raw class

    [
     CookingType("COOKER_RANGE"),
     Counter("AvailableMBytes"),
     SampleWindow(10)
    ]
    uint64 Range = 0;

// Define the Variance property, which uses
//     the "COOKER_VARIANCE" counter type and 
//     gets its data from the AvailableMBytes
//     property in the raw class

    [
     CookingType("COOKER_VARIANCE"),
     Counter("AvailableMBytes"),
     SampleWindow(10)
    ]
    uint64 Variance = 0;
};

Script

The following script code example obtains statistics about available memory, in megabytes, using the MOF created previously. The script uses the SWbemRefresher scripting object to create a refresher that contains one instance of the statistics class that the MOF file creates, which is Win32_PerfFormattedData_MemoryStatistics. For more information about using scripts, see Refreshing WMI Data in Scripts. If working in C++, see Accessing Performance Data in C++.

Note

SWbemRefreshableItem.Object must be called after obtaining the item from the call to SWbemRefresher.Add or the script will fail. SWbemRefresher.Refresh must be called before entering the loop to obtain baseline values, or the statistical properties is zero (0) on the first pass.

 

' Connect to the Root\Cimv2 namespace
strComputer = "."
Set objService = GetObject("winmgmts:" _
    & "{impersonationLevel=impersonate}!\\" _
    & strComputer & "\root\cimv2")

' Create a refresher
Set Refresher = CreateObject("WbemScripting.SWbemRefresher")
If Err <> 0 Then
WScript.Echo Err
WScript.Quit
End If

' Add the single instance of the statistics
'    class to the refresher
Set obMemoryStatistics = Refresher.Add(objService, _
    "Win32_PerfFormattedData_MemoryStatistics=@").Object

' Refresh once to obtain base values for cooking calculations
Refresher.Refresh

Const REFRESH_INTERVAL = 10

' Refresh every REFRESH_INTERVAL seconds 
For I=1 to 3
  WScript.Sleep REFRESH_INTERVAL * 1000
  Refresher.Refresh

  WScript.Echo "System memory statistics" _
      & "(Available Megabytes) " _
      & "for the past 100 seconds - pass " & i 
  WScript.Echo "Average = " _
     & obMemoryStatistics.Average & VBNewLine & "Max = " _
     & obMemoryStatistics.Max & VBNewLine & "Min = " _
     & obMemoryStatistics.Min & VBNewLine & "Range = " _ 
     & obMemoryStatistics.Range & VBNewLine & "Variance = " _
     & obMemoryStatistics.Variance 
Next

Running the Script

The following procedure describes how to run the example.

To run the example script

  1. Copy both the MOF code and script to files on your computer.
  2. Give the MOF file a .mof extension and the script file a .vbs description.
  3. On the command line, change to the directory where the files are stored, and run Mofcomp on the MOF file. For example, if you name the file CalculatedData.mof, then the command is Mofcomp CalculatedData.mof
  4. Run the script.

Monitoring Performance Data

Accessing WMI Preinstalled Performance Classes

Property Qualifiers for Formatted Performance Counter Classes

Statistical Counter Types