.NET

DEBUGGING

@TessFerrandez

Microsoft

Crashes

Performance Issues

Memory LeaksIssues that we can’t step by step debug

@TessFerrandez

MEMORY

DUMPS

User-mode dump

Snapshot of a process and the memory

it addresses

@TessFerrandez

Threads call stacks, stack objects

Modules dlls, exes

.NET Heap .net objects, sizes, info

@TessFerrandez

GATHERING

MEMORY DUMPS

TASK MANAGER

@TessFerrandez

PROCDUMP

Light-weight, no-install utility for generating dumps

Procdump –ma app.exe app.dmpProcdump –ma –h app.exe hang.dmpProcdump –ma –e app.exe crash.dmp Procdump –ma –c 90 app.exe cpu.dmp

@TessFerrandez

DEBUG DIAG

GUI tool to generate dumps based on rules and analyze dumps for common .net issues

@TessFerrandez

ANALYZING

MEMORY DUMPS

WINDBG

Native debugger

Installed with WDK and Debugging tools for Windows

@TessFerrandez

@TessFerrandez

DEBUG DIAG

VISUAL STUDIO

@TessFerrandez

CRASHES

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

WHO

DUNNIT?

Unhandled Exception – 2nd chance

StackOverflowException

OutOfMemoryException

ExecutionEngineException

Kill or recycle

1 Check the event viewer

2 Capture dump on crash

3 Look at the faulting stack

@TessFerrandez

PERFORMANCE

ISSUES

App is not responding

Requests take too longHow long should they take?

CPU is going hey-wire

WHO

DUNNIT?

LOW CPU

Waiting for an external resource

Deadlock

HIGH CPU

Busy, Tight loop

High CPU in GC

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

MEMORY

LEAKS

OutOfMemoryExceptions

Slow response timesDue to GC activities

Memory increase in perfmon or task manager

WHO

DUNNIT?

Cache or Session State

Static / Pinned

Blocked Finalizer

Assembly Leak

Native Leak

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

AUTOMATION

CLRMD

@TessFerrandez

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

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

.NET

DEBUGGING

@TessFerrandez

Microsoft