Slides for .NET Debugging Presentation

1. .NET
DEBUGGING
@TessFerrandez
Microsoft

2. Crashes
Performance Issues
Memory Leaks
Issues that we can’t step by step debug
@TessFerrandez

3. MEMORY
DUMPS

4. User-mode dump
Snapshot of a process and the memory
it addresses
@TessFerrandez

5. Threads call stacks, stack objects
Modules dlls, exes
.NET Heap .net objects, sizes, info
@TessFerrandez

6. GATHERING
MEMORY DUMPS

7. TASK MANAGER
@TessFerrandez

8. PROCDUMP
Light-weight, no-install utility for generating
dumps
Procdump –ma app.exe app.dmp
Procdump –ma –h app.exe hang.dmp
Procdump –ma –e app.exe crash.dmp
Procdump –ma –c 90 app.exe cpu.dmp
@TessFerrandez

9. DEBUG DIAG
GUI tool to generate dumps based on rules
and analyze dumps for common .net issues
@TessFerrandez

10. ANALYZING
MEMORY DUMPS

11. WINDBG
Native debugger
Installed with WDK and Debugging tools for
Windows
@TessFerrandez

12. @TessFerrandez
DEBUG DIAG

13. VISUAL STUDIO
@TessFerrandez

14. CRASHES

15. When I open an email with a pdf attachement that is
larger than 2 MB, a message box saying Unknown Error
shows up and then the process exits
Tess!!! the internet e-thingy is not working anymore

16. WHO
DUNNIT?
Unhandled Exception – 2nd chance
StackOverflowException
OutOfMemoryException
ExecutionEngineException
Kill or recycle

17. 1 Check the event viewer
2 Capture dump on crash
3 Look at the faulting stack
@TessFerrandez

18. PERFORMANCE
ISSUES

19. App is not responding
Requests take too long
How long should they take?
CPU is going hey-wire

20. WHO
DUNNIT?
LOW CPU
Waiting for an external resource
Deadlock
HIGH CPU
Busy, Tight loop
High CPU in GC

21. 1 Determine if it is high or low CPU
2 Capture one or more dumps
3 Look at all stacks
If you can repro in test, consider profiling
@TessFerrandez

22. MEMORY
LEAKS

23. OutOfMemoryExceptions
Slow response times
Due to GC activities
Memory increase in perfmon or task manager

24. WHO
DUNNIT?
Cache or Session State
Static / Pinned
Blocked Finalizer
Assembly Leak
Native Leak

25. 1 Capture multiple dumps
2 Compare to see what objects are leaking
3 Find out why they are still around
For native leaks, use leaktracking in debug diag
@TessFerrandez

26. AUTOMATION

27. CLRMD
@TessFerrandez

28. DataTarget target = DataTarget.LoadCrashDump(@"TheApp.dmp");
target.SymbolLocator.SymbolCache = @"c:symbols";
target.SymbolLocator.SymbolPath = "http://msdl.microsoft.com/download/symbols";
var runtime = target.ClrVersions[0].CreateRuntime();
Console.WriteLine("Is Server GC: {0}", runtime.ServerGC);
Console.WriteLine("Number of heaps: {0}", runtime.HeapCount);
Console.WriteLine("Number of threads: {0}", runtime.Threads.Count);
@TessFerrandez

29. foreach (var thread in runtime.Threads) {
var e = thread.CurrentException;
if (e != null) {
Console.WriteLine("Thread {0}", thread.ManagedThreadId);
Console.WriteLine("t{0} - {1}", e.Type.Name, e.Message);
foreach (var frame in e.StackTrace) {
Console.WriteLine("t" + frame.DisplayString);
}
}
}
@TessFerrandez

30. .NET
DEBUGGING
@TessFerrandez
Microsoft