Debugging Microsoft ASP.NET and other .NET issues using WinDbg and Microsoft Visual Studio .NET 2010

Tess FerrandezASP.NET Escalation EngineerMicrosoftSession Code: WIA402

Problem types

Hangs and performance issuesMemory leaks and high memory usageCrashesExceptions

Tools and Resources

WinDbg.exe and adplus.vbs (Included with Debugging Tools for Windows)SOS.dll (Included with .NET framework)Debug Diagnostics 1.1Tinyget.exe(Included in the IIS Resource kit)Microsoft Visual Studio .NET 2010Blog: If broken it is, fix it you shouldhttp://blogs.msdn.com/Tess

Hangs and performance issues

Idle hangs Waiting for external resourcesWaiting for locks/sync objects

Busy hangsCPU Intensive operationsHigh CPU in GCApplication restarts

Step-By-Step

1. Reproduce problem2. Look at perf data (CPU Usage etc.)3. Get a memory dump (or two)4. Examine threads

a) (Idle) Find blocking calls or calls to external resources

b) (Busy) Look for active threads

Memory leaks and high mem. usage

Managed (.NET)Cache / SessionHeavy Large Object Heap (LOH) usageBlocked finalizerGC heap fragmentation (pinning)

Loader heap issuesDynamic assembliesLots of apps in one app pool

Step-By-Step

1. Look at perf data (.NET / Native or Loader heap issue)

2. Get a memory dump (or two)3. Check if the finalizer is blocked4. Dump the .NET GC Heap and determine where

the memory is going 5. Dump objects, or !gcroot them to see why they

are not being collected

Crashes

OutOfMemoryExceptionStackOverflowExceptionExecutionEngineException.NET and Native Heap corruptionUnhandled exceptionsRecycling

Exceptions

Tracing exceptionsDumping on exceptions

Step-By-Step

1. Check Event logs2. Disable Recycling3. Set up a Debug Diag rule to capture dumps on

exceptions or crash4. Reproduce5. Look at stacks/exceptions in the dump (and/or

in log files)

question & answer

www.microsoft.com/teched

Sessions On-Demand & Community

http://microsoft.com/technet

Resources for IT Professionals

http://microsoft.com/msdn

Resources for Developers

www.microsoft.com/learning

Microsoft Certification & Training Resources

Resources

Track Resources

Blogs:http://blogs.msdn.com/tesshttp://blogs.msdn.com/johanhttp://blogs.msdn.com/carlochttp://blogs.msdn.com/debuggingtoolbox/http://www.wintellect.com/cs/blogs/jrobbins/default.aspxhttp://blogs.msdn.com/profiler/

Tools:Debugging tools for windowsTinyget – IIS Resource KitDebug Diag 1.1Microsoft Visual Studio .NET 2010Red Gate .NET Reflector

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