Introduction to Common Language Runtime Profiling

1
Introduction to Common Language Runtime Profiling

• Brian Dowds
• Microsoft Visual C .NET
• Support Team

2
The Dilemma

• Win32 and COM programming benefits came with
  support costs
• Limited ability to peek inside a process to
  investigate runtime problems
• Crashes, hangs, heap corruption
• Memory leaks, mismatched reference counts
• Build-your-own instrumentation
• Detours technology, many, many printf calls,
  custom crash handlers

3
The Remedy

• Microsoft .NET Common Language Runtime Profiling
  Interfaces
• Create one COM object to profile any .NET managed
  application
• Common language runtime provides dozens of
  built-in metrics about runtime behavior

4
Agenda

• Brief discussion of the common language runtime
• Details about the profiling interfaces
• Inside a profiler object
• Details of profiling managed code
• Examples using .NET SDK samples
• Summary
• QA

5
Common Language Runtime in Brief

• Provides many services to managed applications
• Automatic memory management
• Security, interoperability with unmanaged code
• Cross-language debugging support
• Garbage collection for managed resources
• Common type system
• Interoperation with classic COM

6
Common Language Runtime

• Offers easy access to runtime information through
  two new interfaces
• Use them with a profiling object that implements
  one interface, and calls methods on the other
• Collect runtime information about your
  application from up to 58 new runtime events

7
Common Language Runtime Profiling Diagram
Common Language Runtime
Managed Code Application
ICorProfilerInfo
Profiling Object
ICorProfilerCallBack
Log File
8
The Profiling Interfaces

• ICorProfilerInfo
• Instantiated by the common language runtime
• Available from IUnknown pointer returned through
  your profilers Initialize method
• 33 methods provide detailed information about the
  target process
• ICorProfilerCallback
• You implement it in your profiler
• Common language runtime calls methods and passes
  in data about particular runtime events

9
The Profiling Interfaces (2)

• Defined in Corprof.IDL
• See Profiling.doc in the .NET Tool Developers
  Guide for full details(Program Files\Microsoft
  Visual Studio .NET\FrameworkSDK\Tool Developers
  Guide\docs)

10
Inside a Profiler Object

• Served up by a classic COM in-proc server
• Yes, its un-managed code.
• Profiler object inherits from and implements all
  58 methods of ICorProfilerCallback.
• Common language runtime calls obtain an IUnknown
  pointer to ICorProfilerInfo through the
  Initialize method.

11
Inside a Profiler Object (2)

• Profiler calls QueryInterface to obtain an
  ICorProfilerInfo pointer, and stores it for use.
• Profiler then calls methods on ICorProfilerInfo
  pointer to learn details about common language
  runtime events.
• Great example profilers available
• Matt Pietreks DNProfiler from MSDN December,
  2001 Under The Hood
• HST_Profiler and GCP_Profiler from the .NET Tool
  Developers Guide samples

12
DNProfiler Code Snippet

• HRESULT CProfilerCallbackClassLoadFinished(UINT
  classId, HRESULT hrStatus)
• ChangeNestingLevel( -1 )
• ProfilerPrintf( "ClassLoadFinished\n" )
• return E_NOTIMPL

13
SDK HSTProfiler Code Snippet

• void ProfilerCallbackEnter( FunctionID
  functionID )
• TimeTracker timer( static_castltPrfInfo gt(
  g_pCallbackObject ) )
• try
• g_pCallbackObject-gtUpdateCallStack(
  functionID, PUSH )
• catch ( BaseException exception )
• exception-gtReportFailure()
• delete exception
• g_pCallbackObject-gtFailure()
• // ProfilerCallbackEnter

14
ICorProfilerCallback

• At run time, common language runtime calls
  methods on your implementation of
  ICorProfilerCallback.
• Implementation complexity varies, depending on
  requirements
• Can be as basic as returning E_NOTIMPL
• Bulk up a method with code to call every
  appropriate method of ICorProfileInfo

15
ICorProfilerInfo

• Obtain details about classes, threads, functions,
  stack frames, and so on.
• Currently, there are 33 methods available to a
  profiler. See Profiling.doc in the tool
  developers guide for full documentation.
• Return values are either S_OK or CORPROF_E_ as
  defined in CorError.h

16
Often-Called ICorProfilerInfo Methods

• GetModuleInfo returns moduleID, module name,
  ModuleToken, and AssemblyID, among other data.
• GetThreadInfo returns a pointer to the Win32
  thread ID for a specific thread.
• SetEventMask indicates the event categories that
  are interesting to the Profiler. Use this to
  limit callbacks from the common language runtime
  to selected categories.

17
Visual Basic .NET and Visual C Profiler Objects

• Not possible to create a profiler in these
  languages
• Managed code cant profile managed code
• Why?

18
Details of Profiling Managed Code

• Environment variables control profiling
• set Cor_Enable_Profiling0x1 for ON
• set Cor_Enable_Profiling0x0 for OFF
• Specify which profiler to use
• set COR_PROFILER
• GUID_OF_MY_PROFILER
• set COR_PROFILERMyProfilerProgID

19
Remote Profiling

• Remote profiling is currently not supported
• Profiler object must be located on the target
  machine
• Must register at least ICorProfilerCallback
  interface with the common language runtime on the
  local machine
• Tool developers can create collector agents
  that run on remote systems to batch profiling data

20
Is it Possible to Profile Unmanaged Code?

• Minimal support provided
• Enumerate callstack chains with ICorDebugChain
  methods
• Discover whether callstack belongs to managed or
  unmanaged code with ICorDebugChainIsManaged

21
Profiling Examples

• Output generated by two sample Profilers
• Matt Pietreks DNProfiler object
• SDK Sample HSTProfiler
• .NET Platform SDK samples used
• MDI
• HelloWorldControl

22
MDI Profile Output

• JITCompilationStarted
• System.Runtime.Remoting.Proxies.ProxyAttribute.
  ctor
• JITCompilationFinished
• ObjectAllocated ArrayListEnumeratorSimple
• ObjectAllocated System.String
• ManagedToUnmanagedTransition WndProcInvoke
• UnmanagedToManagedTransition System.Windows.Forms
  .UnsafeNativeMethods
• SendMessage

23
HelloWorldControl Profile Output

• Thread ID 0x000007ec
• Functions Type and Name
• bool System.Windows.Forms.ControlContains(
  System.Windows.Forms.Control )
• Times Called 5
• Exclusive Time 0.000017
• Inclusive Time 0.000311
• Callee Time 0.000099
• Suspended Time 0.000000
• Profiler Time 0.000195

24
Summary

• Brief discussion of the common language runtime
• Details about the profiling interfaces
• Inside a profiler object
• Details of profiling managed code
• Examples using .NET SDK samples

25
Where to Get More Information

• Two great documents from the Tool Developers
  Guide that ships with the .NET Framework SDK
• Profile.doc
• Debugref.doc

26

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