1. CLR MD A New Swiss Army Knife tool for Advanced Debugging
Kamran Bilgrami

2. Agenda Lots of Demos Production Debugging Methodology & Challenges
CLR Memory Diagnostics (CLR MD)
What, Why, Where, How
Lots of Demos

3. What is Production Debugging

4. Bugs Lifecycle

5. Production Debugging - Goals
Find Actionable information Fast
Constrained Environment
Limited Access to Client DCs
Can’t run intrusive tools

6. Dump file based approach
Free Dump Analysis Tools from Microsoft
DebugDiag
PerfView
Windbg
These are extremely useful tools, not always provide root cause.
Without additional help (extensibility points)

7. Real Life Example Extremely slow Web Portal IIS consuming High Memory
Dump file collected
Dump file Analysis
DebugDiag
PerfView
Windbg

8. Where CLR MD fits in puzzle
Extending existing tools
Custom Analysis Rules for DebugDiag
Extension Dlls for Windbg
Beyond Production Debugging
Write your own tools for analysis

9. What is CLR Memory Diagnostics (CLR MD)
APIs for programmatically inspecting a .NET live process or crash dump
A.K.A CLR Managed Debugger
Microsoft.Diagnostics.Runtime.dll
Open Source
Still in Beta (0.8.31)
Microsoft does not recommend for production use

10. CLR MD Features Be Mindful of these features during live debugging
Memory Diagnostics
Walk the GC Heaps
Walk Roots in the Process
Walk threads in the process to get call stacks
Walk AppDomain
Lot more
Be Mindful of these features during live debugging

11. CLR MD Object Model DataTarget ClrModule ClrRuntime ClrType ClrHandle
ClrStackFrame
ClrHeap
ClrInterface

12. DataTarget DataTarget for Extension Dll
Represents a crash dump file or a live process that you want to debug.
DataTarget for a Crash dump
DataTarget target =
DataTarget for Live Process
DataTarget target = DataTarget. AttachToProcess(processId, timeout);
DataTarget for Extension Dll
DataTarget target = DataTarget.CreateFromDebuggerInterface(IDebugClient);

13. ClrRuntime Represents data for a CLR version present in a process.
Few key properties
ServerGC (true/false)
HeapCount
Threads
AppDomains

14. Writing an Extension Dll – 1/2
Create a Class Library Project
Dependencies
CLR MD ( Install-Package Microsoft.Diagnostics.Runtime –Pre )
Unmanaged Export (Install-Package UnmanagedExports )

15. Writing an Extension Dll – 2/2
One-time setup code
Function Exports
Stream for output
IDebugClient
DataTarget
ClrRuntime

16. Creating Extension dll

17. Extending DebugDiag
DebugDiag offers extensibility mechanism using .NET
Requires to implement one or more DebugDiag API Interfaces

18. DebugDiag API Interfaces
Description
IAnalysisRuleMetadata
Used for providing classifications for Analysis Rules
IMultiDumpRule
Executed once per each memory dump when a series of dumps are selected. Could be used for analyzing the increase in memory usage between multiple dump files.
IHangDumpRule
Executed once per memory dump being analyzed. Used for items on the heap, or deadlocks/blocking involving multiple threads.
IHangThreadRule
Executed once per thread in each dump being analyzed. Could be used for checking anything thread-specific, such as call stacks or stack objects
IExceptionThreadRule
Executed on dumps where the context is set to a thread with an Exception. Could be used for Checking a faulting thread for a specific call stack and exception type.

19. Writing Custom DebugDiag Rule
Create a Class Library Project
Dependencies
CLR MD (DebugDiag Installation Folder )
DebugDiag.DotNet.dll (DebugDiag Installation Folder)
Implement one or more interfaces

20. Custom DebugDiag Rule

21. Beyond Production Debugging

23. Useful Links Defrag Tools – DebugDiags Series
Defrag Tools – Writing CLR Debugger Extension
Debugger-Extension-Part-1
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