Question

Debug Diagnostic analysis

Asked by: brij_rauthan

Hi

We have a website and over a period of time, CPU utilization goes 100% and almost everything is being eaten by DLlhost.exe. I used DebugDiagnostic to anlyse the problem, and found that some objects are not being cleared. I disposed explicitly in the code, still having problems.

Can someone help:

Following is excerpt from Debug Diag:

The COM+ STA ThreadPool may have been depleted prior to the time of the dump in dllhost.exe__P41__PID__3736__Date__07_31_2009__Time_05_02_13PM__828__Manual Dump.dmp. The pool has grown to its maximum allowable size, but some threads do not currently have any activity bound to it.

Thread taking high CPU:

Thread 57 - System ID 6968
Entry point   rpcrt4!ThreadStartRoutine
Create time   7/31/2009 4:23:26 PM
Time spent in user mode   0 Days 00:04:53.796
Time spent in kernel mode   0 Days 00:00:40.828




Function   Source
ntdll!KiFastSystemCallRet    
ntdll!NtWaitForSingleObject+c    
kernel32!WaitForSingleObjectEx+ac    
mscorwks!PEImage::LoadImage+1af    
mscorwks!CLREvent::WaitEx+117    
mscorwks!CLREvent::Wait+17    
mscorwks!SVR::gc_heap::wait_for_gc_done+62    
mscorwks!SVR::GCHeap::GarbageCollectGeneration+1b5    
mscorwks!SVR::gc_heap::try_allocate_more_space+136    
mscorwks!SVR::gc_heap::allocate_more_space+2e    
mscorwks!SVR::GCHeap::Alloc+54    
mscorwks!Alloc+60    
mscorwks!SlowAllocateString+29    
mscorwks!FramedAllocateString+a0    
mscorlib_ni+2a25ca

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Asked On
2009-07-31 at 22:52:40ID24618478
Tags

COM+ Dllhost.exe high CPU utilization

Topics

Debugging Software for Development

,

Computer CPU Processors

Participating Experts
1
Points
500
Comments
13

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Answers

 

by: roman2Posted on 2009-08-01 at 05:43:56ID: 24995073

Hello,
I think one of the reason of high CPU utilization is a frequent garbage collections (GC). Unfortunately, there are not enough information from dump in your question (for example, dumping stack for all threads in the process).
I recommend you to run perfmon and add counters: change the perfomance object to ".NET CLR Memory", then, select the "# Bytes in all heaps", "Gen 0 Collections", "Gen 1 Collections", "Gen 2 Collections", "% Time in GC" counters, then, select your process (dllhost.exe) in the instance box and click Add. While process is running, you'll keep track of counters and pay attention to "% Time in GC" and "# Bytes in all heaps" (what values come out?). If "% Time in GC" is zero and "# Bytes in all heaps" is increasing on and on, GC thread(s) is locked.

 

by: brij_rauthanPosted on 2009-08-05 at 10:51:00ID: 25026119

Hi

I am attaching latest analysis.

Please help as I am not able to think further...

I have attached file in .txt, please rename to .mht before viewing

 

by: roman2Posted on 2009-08-06 at 05:19:33ID: 25032367

Hello,
Can you execute some commands in windbg? WinDbg is a part of "Debugging Tools for Windows" (http://www.microsoft.com/whdc/devtools/debugging/default.mspx).
Run WinDbg.exe, File -> Open Crash Dump (select dllhost.exe__P41__PID__2620__Date__08_05_2009__Time_04_02_43PM__525__Manual Dump.dmp), in command window enter following commands:
lm vm mscorwks
.loadby sos mscorwks
!threads
~9s
kb250
after that, Edit -> Write window text to file. And post saved file here.
I repeat that information from perfomance counters would be useful

 

by: brij_rauthanPosted on 2009-08-08 at 09:44:41ID: 25050828

Hi roman2

I did as you described. Posting the file here.

 

by: roman2Posted on 2009-08-08 at 20:38:17ID: 25052702

Hello,
sorry, I forgot about symbols. If the system in question does not have an Internet connection, you have to copy the dump file on system which does. After that, you have to install "Debugging Tools for Windows" and create directory c:\symbols there. Presumably, debug symbols are present in your system, but I don't know where Debug Diagnostics tool found them. Run WinDbg.exe, File -> Open Crash Dump (select dllhost.exe__P41__PID__2620__Date__08_05_2009__Time_04_02_43PM__525__Manual Dump.dmp), in command window enter following commands:
.sympath srv*c:\symbols*http://msdl.microsoft.com/download/symbols
.reload
.loadby sos mscorwks
!threads

 

by: brij_rauthanPosted on 2009-08-08 at 23:28:13ID: 25053064

Hi
Attaching file after loading symbol info

 

by: roman2Posted on 2009-08-09 at 08:16:14ID: 25054465

Hello,
I think one of the web-requests was slowly handled. Let us check this:
.sympath srv*c:\symbols*http://msdl.microsoft.com/download/symbols (if necessary)
.loadby sos mscorwks
~55s
kb250
!clrstack
!dso

 

by: brij_rauthanPosted on 2009-08-09 at 12:15:06ID: 25055484

Done this.

File attached.

 

by: roman2Posted on 2009-08-09 at 22:55:06ID: 25057419

Hello,
it's hard case, but, let's continue ;-)
.loadby sos mscorwks
!vmstat
!eeheap -gc
!threadpool
!SyncBlk
~*kb250

 

by: brij_rauthanPosted on 2009-08-10 at 01:15:30ID: 25057932

Hi Roman2

I see that this command listed 0ee0eac0 055b4ea8 System.Web.HttpUtility+UrlDecoder

Can this be culprit. I looked at the code and there is a loop around this method:

while(signature.Contains("%"))
{
    signature = System.Web.HttpUtility.UrlDecode(signature);
}

while (parts[0].Contains("%"))
{
    parts[0] = System.Web.HttpUtility.UrlDecode(parts[0]);
}

Might be this is going into infinite loop.

 

by: brij_rauthanPosted on 2009-08-10 at 02:03:23ID: 25058140

attached file

 

by: roman2Posted on 2009-08-10 at 06:13:21ID: 25059589

Hello,
you absolutely right. I wrote test project and his execution infinitely loops:
using System;
using System.Collections.Generic;
using System.Text;
using System.Web;

namespace UrlDecode
{
    class Program
    {
        static void Main(string[] args)
        {
            string signature = @"a_osch%~"; // was took from dump
            while (signature.Contains("%"))
            {
                signature = System.Web.HttpUtility.UrlDecode(signature);
            }
        }
    }
}

 

by: brij_rauthanPosted on 2009-08-10 at 07:30:08ID: 25060203

Hi Roman2

Thanks for your help and sorting this out.

Regards
Brij

20120131-EE-VQP-002

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