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Vamsi Tokala's blog: Identifying Memory leaks in .Net using winDBG

Wednesday, February 1, 2012

Identifying Memory leaks in .Net using winDBG

Identifying Memory Leaks due to object references in Finalize queue


Load the SOS debugger extension for a CLR 4.0 application

.loadby sos clr

1) Identify the objects in finalizeQueue which survived Garbage collection

!fq

SyncBlocks to be cleaned up: 0

MTA Interfaces to be released: 0

STA Interfaces to be released: 0

----------------------------------

generation 0 has 1 finalizable objects (000000008ba63058->000000008ba63060)

generation 1 has 15 finalizable objects (000000008ba62fe0->000000008ba63058)

generation 2 has 14884 finalizable objects (000000008ba45ec0->000000008ba62fe0)

Ready for finalization 0 objects (000000008ba63060->000000008ba63060)



000007ff01d58610 2 1024 System.Data.DataTable

000007ff0164e298 4 1120 System.Diagnostics.Process

000007ff01d82738 8 1728 System.Data.DataColumn

000007ff017235a0 16 1920 System.Threading.OverlappedData

000007ff001f1780 28 2464 System.Threading.Thread

000007ff006764b8 52 3744 System.Reflection.Emit.DynamicResolver

000007ff0026fba8 66 4224 System.Threading.ReaderWriterLock

000007ff01e7bb00 314 10048 System.Data.SqlClient.SNIPacket

000007ff01e717e0 546 21840 System.Data.SqlClient.SNIHandle

000007ff01e49f30 314 32656 System.Data.SqlClient.SqlConnection

000007ff02933bf0 302 45904 System.Data.SqlClient.SqlDataAdapter

000007ff0166d240 398 70048 System.Diagnostics.PerformanceCounter

000007ff01e0d0e8 1510 338240 System.Data.SqlClient.SqlCommand

000007ff0057d8f8 11209 358688 System.WeakReference



2) You can also print the details of the finalizable objects for Gen2 using the above details

dd 000000008ba45ec0 000000008ba62fe0


3) Identify the suspected object having leaks

!dumpheap -type System.Data.SqlClient.SqlCommand

Address MT Size

0000000010c43f40 000007ff01e0d0e8 224

0000000010c44020 000007ff01e0d0e8 224

0000000010c44198 000007ff01e0d0e8 224

0000000010c44278 000007ff01e0d0e8 224

0000000010c444e8 000007ff01e0d0e8 224


4) Identify the GC roots for the objects. It contains the call stack

!gcroot 0000000010c43f40

Scan Thread 15 OSTHread 1bc0

Scan Thread 16 OSTHread 1d74

Scan Thread 19 OSTHread 3200

Scan Thread 17 OSTHread 21f0

Scan Thread 18 OSTHread 3564

Scan Thread 20 OSTHread 322c

Scan Thread 21 OSTHread 2b80

Scan Thread 28 OSTHread 2e5c

Scan Thread 29 OSTHread 35d0

Scan Thread 30 OSTHread 3bc

Scan Thread 31 OSTHread 2770

Scan Thread 33 OSTHread 19b4

Scan Thread 34 OSTHread 534

Scan Thread 35 OSTHread 3280

Scan Thread 36 OSTHread 1908

Scan Thread 37 OSTHread 344c

Scan Thread 38 OSTHread 13d4

Scan Thread 39 OSTHread 21d4

Scan Thread 40 OSTHread 31a4

DOMAIN(0000000001AB88B0):HANDLE(Pinned):1217c0:Root: 000000002070f040(System.Object[])->

00000000108c9ac0(System.Collections.Hashtable+SyncHashtable)->

00000000108c91e8(System.Collections.Hashtable)->

000000001171efc0(System.Collections.Hashtable+bucket[])->

00000000120a3768(System.Collections.Hashtable)->

00000000120a37c0(System.Collections.Hashtable+bucket[])->

00000000120a3820(System.Collections.Hashtable)->

00000000120fa180(System.Collections.Hashtable+bucket[])->

00000000120b7200(System.Collections.Generic.Dictionary`2[[ATOM.AS.CobolBase.CobolProgramName, ATOM.AS.CobolBase],[ATOM.AS.CobolBase.CobolProgram, ATOM.AS.CobolBase]])->

00000000120b7360(System.Collections.Generic.Dictionary`2+Entry[[ATOM.AS.CobolBase.CobolProgramName, ATOM.AS.CobolBase],[ATOM.AS.CobolBase.CobolProgram, ATOM.AS.CobolBase]][])->

00000000120b7258(ATOM.AS.CobolBase.CobolProgram)->

00000000120b7310(System.Collections.Generic.List`1[[ATOM.AS.CobolBase.IProgramEvents, ATOM.AS.CobolBase]])->

0000000019b0f918(System.Object[])->

0000000019b0f590(ATOM.AS.DataAccess.DataAccess)->

0000000019b13c40(ATOM.AS.DataAccess.ProviderSQL)->

0000000019b13d70(System.Data.SqlClient.SqlCommand)->

0000000019b15978(System.Data.SqlClient.SqlCommand+CachedAsyncState)




@2011, copyright Vamsidhar Tokala

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