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. NET Debugging for the Production Environment

. NET Debugging for the Production Environment. Part 4: Common Debugging C ommands. Brad Linscott. Premier Field Engineeringing. Agenda. Symbols Commands Common debugging commands: miscellaneous Common debugging commands for hangs Common debugging commands for exceptions

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. NET Debugging for the Production Environment

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  1. .NET Debugging for the Production Environment Part 4: Common Debugging Commands Brad Linscott Premier Field Engineeringing

  2. Agenda • Symbols • Commands • Common debugging commands: miscellaneous • Common debugging commands for hangs • Common debugging commands for exceptions • Common debugging commands for memory pressure

  3. Symbols • Not needed to resolve managed call stacks • Needed to resolve native call stacks • Translation: Not always mandatory, but in general, a good idea to ensure symbols are lined up for managed issues • File, Symbol File Path; .sympath; .symfix • http://msdl.microsoft.com/download/symbols

  4. Breakdown of Debugger Commands • Commands • Meta commands (.) • Extension commands(!)

  5. Common Miscellaneous commands • | - pipe command displays command line of process 0:029> | . 0 id: 5ec examine name: c:\WINDOWS\system32\inetsrv\w3wp.exe • vertarget shows dump time, OS version, process’ lifetime, and more 0:029> vertarget Windows Server 2003 Version 3790 (Service Pack 2) MP (2 procs) Free x86 compatible Product: Server, suite: TerminalServerSingleUserTS kernel32.dll version: 5.2.3790.4062 (srv03_sp2_gdr.070417-0203) Machine Name: Debug session time: Tue Jul 29 10:51:49.000 2008 (GMT-5) System Uptime: 0 days 6:19:45.750 Process Uptime: 0 days 4:34:57.000 Kernel time: 0 days 0:24:43.000 User time: 0 days 0:05:48.000

  6. Common Miscellaneous commands (cont’d) • .load <extension> loads a debugging extension • .unload <extension> unloads a debugging extension • .chain shows loaded extensions, most recently-loaded is listed first. 0:000> .chain Extension DLL search Path: C:\debuggersx86\WINXP;C:\debuggersx86\winext;C:\debuggersx86\winext\arcade psscor2.dll: image 2.0.50826.0, API 1.0.0, built Wed Oct 29 12:48:12 2008 [path: C:\debuggersx86\psscor2.dll] dbghelp: image 6.13.0009.1140, API 6.2.6, built Tue May 17 18:15:43 2011 [path: C:\debuggersx86\dbghelp.dll] ext: image 6.13.0009.1140, API 1.0.0, built Tue May 17 18:16:08 2011 [path: C:\debuggersx86\winext\ext.dll] exts: image 6.13.0009.1140, API 1.0.0, built Tue May 17 18:16:36 2011 [path: C:\debuggersx86\WINXP\exts.dll] uext: image 6.13.0009.1140, API 1.0.0, built Tue May 17 18:16:03 2011 [path: C:\debuggersx86\winext\uext.dll]

  7. Common Miscellaneous commands (cont’d) • !help displays help for top-most extension • !psscorX.help <command> displays detailed help for <command> • .hh <command> opens debugger.chm to the <command> topic. <command> can’t be from an extension outside the Debugging Windows for Tools package • !peb shows loaded modules, environment variables, command line arg, and more

  8. Common Miscellaneous commands (cont’d) • !runaway shows quanta of each thread 0:029> !runaway User Mode Time Thread Time 17:828 0 days 0:04:40.578 11:380 0 days 0:04:24.046 14:288 0 days 0:04:14.296 13:4a0 0 days 0:03:58.984 29:13e4 0 days 0:01:13.078 • ~ displays PID and TID; ~#s switches the active thread to thread # 0:000> ~ . 0 Id: 2c14.2048 Suspend: 0 Teb: 7ffde000 Unfrozen 1 Id: 2c14.35b8 Suspend: 0 Teb: 7ffdd000 Unfrozen 2 Id: 2c14.32f8 Suspend: 0 Teb: 7ffdc000 Unfrozen 3 Id: 2c14.3754 Suspend: 0 Teb: 7ffd9000 Unfrozen Red– logical Thread ID Blue – Hex Thread ID Purple– Process ID Green – beginning address of Thread Environment Block

  9. Common Miscellaneous commands (cont’d) • k, kn, kb, kP, etc displays the native stack in various ways 0:006> kbnL # ChildEBPRetAddrArgs to Child 00 0114fcec 7c827b89 7c83c5fe 0000001c 0114fd34 ntdll!KiFastSystemCallRet 01 0114fcf0 7c83c5fe 0000001c 0114fd34 00000001 ntdll!ZwWaitForMultipleObjects+0xc 02 0114ffb8 77e6482f 00000000 00000000 00000000 ntdll!RtlpWaitThread+0x161 03 0114ffec 00000000 7c83c4b3 00000000 00000000 kernel32!BaseThreadStart+0x34 • !clrstack is from psscorX; displays managed call stack 0:055> !clrstack OS Thread Id: 0x1ea0 (55) ESP EIP 386fe4a4 7c82847c [HelperMethodFrame_1OBJ: 386fe4a4] System.Threading.WaitHandle.WaitMultiple(System.Threading.WaitHandle[], Int32, Boolean, Boolean) 386fe570 7928b3ff System.Threading.WaitHandle.WaitAny(System.Threading.WaitHandle[], Int32, Boolean) 386fe590 129dd8cb System.Net.TimerThread.ThreadProc() 386fe5dc 792d6e46 System.Threading.ThreadHelper.ThreadStart_Context(System.Object) 386fe5e8 792f5781 System.Threading.ExecutionContext.runTryCode(System.Object) <clip>

  10. Common commands for hangs • ~*k; ~*e!clrstack displays all the stacks • !syncblkfinds outstanding syncblocks on which other threads are waiting ||0:0:000> !syncblk Index SyncBlockMonitorHeld Recursion Thread ThreadID Object Waiting 3724 0x06c7b13c 59 1 0x101dc0 0x120c 14 0x1c2643f8 System.String Waiting threads: 22 23 24 25 27 30 31 39 40 45 50 51 52 53 54 55 56 57 59 60 61 62 63 64 65 66 67 68 70 3752 0x02b382a0 9 1 0x6d5a4b8 0x1390 70 0x140159ec System.String Waiting threads: 69 74 78 79 ----------------------------- Total 3942 ComCallWrapper 7 ComPlusWrapper 3 ComClassFactory 0 Free 234

  11. Common commands for hangs, cont’d • !finalizequeue from psscorX lists objects registered for finalization. • 0:000> !finalizequeueSyncBlocks to be cleaned up: 524MTA Interfaces to be released: 0STA Interfaces to be released: 0----------------------------------generation 0 has 577 finalizable objects (0e480940->0e481244)generation 1 has 41 finalizable objects (0e48089c->0e480940)generation 2 has 543 finalizable objects (0e480020->0e48089c)Ready for finalization 151459 objects (0e481244->0e5150d0) A number > 0 indicates possible problems. A number this big indicates a definite problem.Statistics:<clip> • If this is the case, investigate the Finalizer thread (!threadsis one way to find it) to determine cause of blockage.

  12. Common commands for exceptions • !dae from psscorX displays all managed exceptions in the GC heaps • Double-check single OutOfMemoryException, StackOverflowException, and ExecutionEngineException instances • !pe <exception addr> from psscorX provides more detailed information on a specific managed exception.

  13. Common commands for exceptions, cont’d • To a large extent, debugging crash dumps of a managed & native app don’t differ by much • Upon opening dump, active thread is faulting thread. . • !u for deeper analysis of the disassembly • Native debugging skills as well commonly needed to determine root cause

  14. Common commands for memory pressure • !address shows information about a particular address (type, protection, state, usage) 0:000> !address -summary -------------------- Usage SUMMARY -------------------------- TotSize ( KB) Pct(Tots) Pct(Busy) Usage 2ec53000 ( 766284) : 36.54% 72.26% : RegionUsageIsVAD 3f451000 ( 1036612) : 49.43% 00.00% : RegionUsageFree 83fb000 ( 135148) : 06.44% 12.74% : RegionUsageImage <clip> Tot: 7fff0000 (2097088 KB) Busy: 40b9f000 (1060476 KB) -------------------- Type SUMMARY -------------------------- TotSize ( KB) Pct(Tots) Usage 3f451000 ( 1036612) : 49.43% : <free> 8cb5000 ( 144084) : 06.87% : MEM_IMAGE 1aa64000 ( 436624) : 20.82% : MEM_MAPPED 1d486000 ( 479768) : 22.88% : MEM_PRIVATE -------------------- State SUMMARY -------------------------- TotSize ( KB) Pct(Tots) Usage 32628000 ( 825504) : 39.36% : MEM_COMMIT 3f451000 ( 1036612) : 49.43% : MEM_FREE e577000 ( 234972) : 11.20% : MEM_RESERVE Largest free region: Base 6e0e0000 - Size 03970000 (58816KB) • 1GBfree and your largest contiguous FREE is 58MB is a good sign of VA fragmentation

  15. Common commands for memory pressure • A managed leak/bloat is usually in one of 2 places: • GC Heaps (!eeheap –gc) • Loader heaps (!eeheap –loader)

  16. Common commands for memory pressure, cont’d • Loader heaps: • Contain type definitions and other internal structures • ~20MB is usually considered high for a busy w3wp • If !ddaresults in too many assemblies (generally, more than a few hundred means this is contributor to high mem), find why they’re being created • !dumpdomainlists assemblies loaded in each appdomain • In w3wp, !finddebugtruetells you if <compilation debug=“true”/>, which is a root cause of high memory • Q886385, Q316775 are common root causes

  17. Common commands for memory pressure, cont’d • !eeheap –gc • Breaks down mem usage among Gens within GC heaps. Helps you to see if memory issue is concentrated in a specific generation or the LOH. • !dumpheap –stat may help. Focus on objects with high Count and/or high Total Memory. !gcroot <mt address> may help find root cause • !clrusage may also give helpful insight ||0:0:000> !help clrusage ------------------------------------------------------------------------------- !CLRUsage [-v] !CLRUsage dumps out the memory that .NET is using. This is different from !EEHeap -gc in that it gives how much memory is committed and reserved and also gives the initial allocation that we made.

  18. Conclusion • Many commands are used regularly, this session has covered just a few • Be curious – use !help frequently • Practice, Practice, Practice

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