RE: Memory increasing even when in debug-break
- From: jetan@xxxxxxxxxxxxxxxxxxxx ("Jeffrey Tan[MSFT]")
- Date: Fri, 16 Mar 2007 07:06:42 GMT
Hi John ,
Based on my understanding, your complex pure managed C# application is
experiencing memory leak which is indicated by "Private Bytes" counter from
PerfMon. Even strange, your application event leaks while the debugger
breaks your application. If I have misunderstood you, please feel free to
tell me, thanks.
Actually, there are 2 types of memory leak in .Net: native leak and managed
leak. The "Private Bytes" increases without reduce indicates that there is
memory leak in your application. Then you should check if ".NET # of Bytes
in all Heaps" counter also increases during the leak. If it also increases
without reduce, it means a managed memory leak. Otherwise, there is a
native leak(for example, in the FCL or even CLR native code). Please refer
to the links below for more details:
"I have a memory leak!!! What do i do? (defining the "where")"
http://blogs.msdn.com/tess/archive/2005/11/25/496899.aspx
"Debugging Memory Problems"
http://msdn2.microsoft.com/en-us/library/ms954591.aspx
I recommend you to give it a check.
More interesting is the debugger breaks while memory still increasing
issue. Can you tell me what debugger you are using to break your
application, VS debugger or Windbg? If you are using VS debugger, the only
possibility is caused by the activity of the debugger help thread. VS
debugger leverages a special debugger help thread in debuggee process to
get information of the managed process and to execute certain debugging
operations. I suspect while the debugger breaks the debugger help thread is
still allocating memory, which causes the memory increase. Anyway, this is
merely a guess. Please refer to the link below for more details:
"Special threads in CLR "
http://blogs.msdn.com/yunjin/archive/2005/07/05/435726.aspx
"Implications of using a helper thread for debugging"
http://blogs.msdn.com/jmstall/archive/2004/10/13/241828.aspx
To prove my thought, I would recommend you to use windbg to attach and
break your application, will the memory still increase? Windbg uses native
Win32 debugging service. It normally issues a "int 3" software
interrupt(software breakpoint) in the debuggee, which causes the CPU to
stop all the threads(including the thread that performs GC, finalizer) in
your application. Since there are no running threads in your process, the
memory should not be touched by anybody(threads). You may give it a try.
Additionally, you may use Process Explorer to monitor if any threads are
still activating while your debugger breaks the application. This will help
to reveal which thread is responsible for the memory increasing problem.
I will wait for your further test result, thanks.
Best regards,
Jeffrey Tan
Microsoft Online Community Support
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