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Windbg commands

Occasionally I need to use Windbg to analyze issue in production environment but I can never remember its commands and google for them can be annoying because the commands may change between different .Net versions. Perhaps writing a blog post so that I can find them later using Google is a good idea!

Common commands

Load SOS:

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.loadby sos clr

Memory commands

Dump all objects of a specific type:

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!dumpheap -type [Type]

Get memory statistics:

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!dumpheap -stat

View all heaps summary:

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!EEHeap

View managed heap summary:

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!EEHeap -gc

View loader heap summary:

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!EEHeap -loader

View loaded modules which are loaded by using LoadLibrary:

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lm

From CLR 4.0, custom .Net DLLs are no longer loaded using LoadLibrary. An alternative is:

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!sos.dumpdomain

Check how much memory dlls/stack/heap takes:

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!address -summary

which gives:

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--- Usage Summary ---------------- RgnCount ----------- Total Size -------- %ofBusy %ofTotal
Free                                    451     7dfc`aa5e4000 ( 125.987 TB)           98.43%
<unknown>                              2745      203`40a8f000 (   2.013 TB)  99.98%    1.57%
Image                                  1340        0`11c92000 ( 284.570 MB)   0.01%    0.00%
Heap                                     45        0`01b0b000 (  27.043 MB)   0.00%    0.00%
Stack                                   136        0`015c0000 (  21.750 MB)   0.00%    0.00%
Other                                     7        0`001c5000 (   1.770 MB)   0.00%    0.00%
TEB                                      45        0`0005a000 ( 360.000 kB)   0.00%    0.00%
PEB                                       1        0`00001000 (   4.000 kB)   0.00%    0.00%

Native heaps:

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!heap -s

Exception commands

Dump all exceptions of a specific type:

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!dumpheap -type [Exception type]

For example:

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!dumpheap -type System.Reflection.ReflectionTypeLoadException

The fun thing is thanks to GC, exception objects are usually still in memory somewhere after they happened but before GC do its job.

Dump content of an exception:

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!DumpObj /d [Address]

This step is in fact simple because you can click on the address shown in Windbg.

Threading commands

[Will update when I need them again :)]

Other memory tools

Debug Diagnostic Tool is another useful tool with some predefined analysis rules. Its biggest advantage is that it can give a bunch of useful analysis details for us without the cumbersome of Windbg commands.

VMMAP is another great tool.

Credits

  • http://kate-butenko.blogspot.com/2012/07/investigating-issues-with-unmanaged.html

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