Use UMDH to identify memory leak problem

We sometimes got memory leak problem, and we need to find the leaked memory, Here is a usful tool from MS, UMDH, it is included in WinDBG install package.

• It need the PDB files to analyse access the symbol table, then a human readable stack can be generated.
• You need to generated two set of current used memory, and compare the two to have a result.
• It compares the current used memory, so you can identify the still-in-use memory, That is the memory you stored somewhere, but they will actually never be used again, and should be released.
• And of cause, it can identify the memory with out a ptr pointing to when comparing.

You should let memory leak a little more to get a clear view of the result.

Here is the steps to use UMDH:
1. Install Windbg, you can get WinDBG from MS site:http://msdn.microsoft.com/en-us/windows/hardware/hh852365
2. Open a Dos Prompt as Administrator and navigate to the installation folder of WinDbg
3. Set Symbol Path as a System Variable

set _NT_SYMBOL_PATH= SRV*C:\websymbols*http://msdl.microsoft.com/download/symbols; c:\xosymbol

4. Download PDB file and copy to the “C:\xosymbol” which is set part of above environment variable “_NT_SYMBOL_PATH”
5. Start collecting stack traces for user-mode allocations, run command:

gflags /i <Your_process_name.exe> +ust

6. Restart your process.
7. Keep it running, wait until it become steady..
8. Collect a baseline snapshot, run command:

umdh -pn:<Your_process_name.exe> -f:c:\1.log

9. Wait until the memory usage of your process exceeds 1GB or more.
10. Generate a new snapshot, run command:

umdh -pn:<Your_process_name.exe> -f:c:\2.log

11. Compare the two snapshots and get the final report from UMDH

umdh -d c:\1.log c:\2.log > c:\result12.log

12. In the result, we can see the stack where the leaked memory is allocated, You got a direct hint to resolve the leak problem.