INFO: Collecting Performance Data Using PDH APIs from Visual Basic |
Q296526
The information in this article applies to:
- Microsoft Win32 Application Programming Interface (API), used with:
- the operating system: Microsoft Windows 2000
- the operating system: Microsoft Windows NT 4.0
SUMMARY
Performance Data Helper (PDH) APIs can be used to collect performance data from various performance counters or instances that are available on the system. This article demonstrates the PDH API calls needed to collect performance data of a given performance object, counter, and instance name from Microsoft Visual Basic.
MORE INFORMATION
The following sample code has a function called ConstructCounterPath() which constructs the counter path as required by the PdhAddCounter() API for the specified performance object, counter, and instance names. Command1_Click below constructs an array of counter paths that an application is interested in collecting the performance data from and then calls the CollectAndDisplayPerformanceData Visual Basic helper procedure.
CollectAndDisplayPerformanceData interfaces with PDH APIs to collect/display performance data values.
The hex error codes returned by PDH APIs are defined in the Pdhmsg.h header file.
Option Explicit
' PDH API Success Status
Private Const ERROR_SUCCESS = 0
Const PERF_SIZE_LARGE = &H100
Const PDH_FMT_LONG = &H100
Private Type PDH_COUNTER_INFO
dwLength As Long
dwType As Long
CVersion As Long
CStatus As Long
lScale As Long
lDefaultScale As Long
dwUserData As Long
dwQueryUserData As Long
szFullPath As Long
szMachineName As Long
szObjectName As Long
szInstanceName As Long
szParentInstance As Long
dwInstanceIndex As Long
szCounterName As Long
szExplainText As Long
DataBuffer As Long
End Type
Private Type PDH_FMT_COUNTERVALUE
CStatus As Long
unionPadding As Long
longValue As Long
extraBytes As Long
End Type
Private Declare Function PdhOpenQuery Lib "pdh" Alias "PdhVbOpenQuery" _
(ByRef hQuery As Long) As Long
Private Declare Function PdhCloseQuery Lib "pdh" _
(ByVal hQuery As Long) As Long
Private Declare Function PdhCollectQueryData Lib "pdh" _
(ByVal hQuery As Long) As Long
Private Declare Function PdhAddCounter Lib "pdh" Alias "PdhVbAddCounter" _
(ByVal hQuery As Long, _
ByVal counterPath As String, _
ByRef hCounter As Long) As Long
Private Declare Function PdhRemoveCounter Lib "pdh" _
(ByVal hCounter As Long) As Long
Private Declare Function PdhVbGetDoubleCounterValue Lib "pdh" _
(ByVal hCounter As Long, _
ByRef CounterStatus As Long) As Double
Private Declare Function PdhVbIsGoodStatus Lib "pdh" _
(ByVal StatusValue As Long) As Long
Private Declare Function PdhGetFormattedCounterValue Lib "pdh" _
(ByVal hCounter As Long, _
ByVal dwFormat As Long, _
lpdwType As Long, _
pValue As PDH_FMT_COUNTERVALUE) As Long
Private Declare Function PdhGetCounterInfo Lib "pdh" Alias "PdhGetCounterInfoA" _
(ByVal hCounter As Long, _
ByVal bRetrieveExplainText As Long, _
pdwBufferSize As Long, _
lpBuffer As Any) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
(hpvDest As Any, hpvSource As Any, ByVal cbCopy As Long)
Private Declare Sub Sleep Lib "kernel32" (ByVal dwMillseconds As Long)
Private Sub CollectAndDisplayPerformanceData(ByRef counterPath() As String)
Dim ret As Long
Dim hQuery As Long
Dim index As Long
Dim maxIndex As Long
Dim value As Double
Dim counterValue As PDH_FMT_COUNTERVALUE
Dim bufferSize As Long
Dim counterInfo As PDH_COUNTER_INFO
Dim dwType As Long
hQuery = 0
maxIndex = UBound(counterPath)
ReDim hCounters(0 To maxIndex)
ReDim counterTypes(0 To maxIndex)
' Create a PDH Query
ret = PdhOpenQuery(hQuery)
If ret <> ERROR_SUCCESS Then
Debug.Print "PdhOpenQuery failed with error code : " & Hex(ret)
Exit Sub
End If
' Add a counter to the query for the counterPath specified.
' If there are multiple counters to be monitored add them to
' created PDH query
For index = 0 To maxIndex
ret = PdhAddCounter(hQuery, counterPath(index), hCounters(index))
If ret <> ERROR_SUCCESS Then
Debug.Print "PdhAddCounter failed with error code : " & Hex(ret)
GoTo Cleanup
End If
'Get the counter type information for the counter created
bufferSize = 0
ret = PdhGetCounterInfo(hCounters(index), 0, bufferSize, ByVal 0)
ReDim lpBuffer(bufferSize)
ret = PdhGetCounterInfo(hCounters(index), 0, bufferSize, lpBuffer(0))
If ret <> ERROR_SUCCESS Then
Debug.Print "PdhGetCounterInfo failed with error code : " & Hex(ret)
GoTo Cleanup
End If
CopyMemory counterInfo, lpBuffer(0), Len(counterInfo)
counterTypes(index) = counterInfo.dwType
Next
' Collect the first snapshot of performance data for all counters.
' We ignore the first snapshot as most performance counters require two
' snapshots to get a calculated value
ret = PdhCollectQueryData(hQuery)
If ret <> ERROR_SUCCESS Then
Debug.Print "PdhCollectQueryData failed with error code : " & Hex(ret)
GoTo Cleanup
End If
Dim nMaxCollections As Long
Dim nCollection As Long
nCollection = 0
nMaxCollections = 10
For nCollection = 1 To nMaxCollections
'Sleep for a while between each collection
Sleep (1000)
' Collect the next snapshot of performance data.
ret = PdhCollectQueryData(hQuery)
If ret <> ERROR_SUCCESS Then
Debug.Print "PdhCollectQueryData failed with error code : " & Hex(ret)
GoTo Cleanup
End If
' Get Calculated performance data values for each counter and display them
For index = 0 To maxIndex
' Check if it is a LARGE counter type.
If counterTypes(index) And PERF_SIZE_LARGE Then
value = PdhVbGetDoubleCounterValue(hCounters(index), ret)
If PdhVbIsGoodStatus(ret) = 0 Then
Debug.Print "PdhVbGetDoubleCounterValue " & counterPath(index) & " failed with error code : " & Hex(ret)
Else
Debug.Print counterPath(index) & " [" & value & "]"
End If
Else
ret = PdhGetFormattedCounterValue(hCounters(index), _
PDH_FMT_LONG, dwType, counterValue)
If ret <> ERROR_SUCCESS Then
Debug.Print "PdhGetFormattedCounterValue " & counterPath(index) & " failed with error code : " & Hex(ret)
Else
Debug.Print counterPath(index) & " [" & counterValue.longValue & "]"
End If
End If
Next
Next
Cleanup:
' If hQuery has been created
If hQuery <> 0 Then
For index = 0 To maxIndex
' Remove all the counters that have been added successfully, from the query
If (hCounters(index) <> 0) Then
ret = PdhRemoveCounter(hCounters(index))
If ret <> ERROR_SUCCESS Then
Debug.Print "PdhRemoveCounter failed with error code : " & Hex(ret)
End If
End If
Next
ret = PdhCloseQuery(hQuery)
If (ret <> ERROR_SUCCESS) Then
Debug.Print "PdhCloseQuery failed with error code : " & Hex(ret)
End If
End If
End Sub
Private Function ConstructCounterPath(ByVal szMachineName As String, _
ByVal szObjectName As String, ByVal szCounterName As String, ByVal szInstanceName As String) As String
Dim counterPath As String
counterPath = ""
' If szMachineName is specified
If Len(szMachineName) Then
counterPath = "\\" + szMachineName
End If
counterPath = counterPath + "\" + szObjectName
' If szInstanceName is specified
If Len(szInstanceName) Then
counterPath = counterPath + "(" + szInstanceName + ")"
End If
counterPath = counterPath + "\" + szCounterName
ConstructCounterPath = counterPath
End Function
Private Sub Command1_Click()
Dim counterPath(0 To 5) As String
'Performance Counters that have instance names
counterPath(0) = ConstructCounterPath("PRABAGAR4", "Processor", "% Processor Time", "0")
counterPath(1) = ConstructCounterPath("PRABAGAR4", "Process", "% Processor Time", "csrss")
'Performance Counters that DOES NOT have instance names
counterPath(2) = ConstructCounterPath("SERVERNAME", "System", "Processes", vbNullString)
counterPath(3) = ConstructCounterPath("SERVERNAME", "System", "Threads", vbNullString)
counterPath(4) = ConstructCounterPath("SERVERNAME", "Objects", "Events", vbNullString)
counterPath(5) = ConstructCounterPath("SERVERNAME", "Objects", "Mutexes", vbNullString)
CollectAndDisplayPerformanceData counterPath
End Sub
REFERENCES
PDH APIs are implemented in PDH.dll, and this DLL comes with the Windows 2000 operating system.
For additional information on the PDH APIs, refer to the Performance Monitoring topics in the Base Services section of the MSDN Library (http://msdn.microsoft.com/library/default.asp?URL=/library/psdk/pdh/perfdata_0pgn.htm) or Microsoft Platform SDK.
Additional query words:
Keywords : kbAPI kbKernBase kbPerfMon kbSDKWin32 kbDSupport kbGrpDSKernBase
Issue type : kbinfo
Technology : kbAudDeveloper kbWin32sSearch kbWin32API
Last Reviewed: June 28, 2001 |
