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Use Debug Diagnostic Tool to troubleshoot memory leaks

Translated from: https://mssqlwiki.com/2012/12/06/debugging-memory-leaks-using-debug-diagnostic-tool/

In my previous blog post (SQL Server memory leak), I explained how to use the "! heap" command to identify which module leaked memory. Sometimes we use the "! d" command to find the model or the search memory command (s) to find the reason not by displaying memory.

In this case, we can use Debug Diagnostic Tools or UMDH to track memory leaks. This blog post explains how to use Debug Diagnostics Tools to identify memory leaks.

Download and install Debug Diagnostic Tools from http://www.microsoft.com/en-us/download/details.aspx?id=26798

1. Navigate to Tools, "Options"-> "Preferences" and select "Record call stacks immediately when monitoring the leaks".

two。 Navigate to the "rules" tab and select "add rule".

3. Select Naive (non .net) memory leak and handle leak.

4. Select SQL Server or trace any processes used for memory leaks.

5. Click "Next" and leave the default option (you can select "auto-unload Leak track" when the rule is complete or invalid).

6. Click "Next" and activate the rule now.

7.Leaktrack.dll has been added to the process used to track allocations.

8. Now you can wait for the leak to happen again.

-- If you are learning how to troubleshoot SQL Server memory leak follow the steps which we followed in previous post (https://mssqlwiki.com/2012/12/04/sql-server-memory-leak/)to leak the memory.-- Download HeapLeak.dll from this link.-- Create an extended stored procedure in SQL Serversp_addextendedproc 'HeapLeak','C:\ HeapLeakdll\ HeapLeak.dll'-- Let us execute this Extended SP 30 times and leak memory.exec HeapLeakgo 30

9. When you guess a memory leak, navigate to "rules" and execute a full user dump by right-clicking "Leak rule".

10. After the dump is captured, navigate to the advanced analysis tab, add the data file, and select the dump we generated.

11. Locate Tools, "Options"-> "set the symbol path for analysis". The default Microsoft symbol path is below.

Srv*c:\ Websymbols* http://msdl.microsoft.com/download/symbols;c:\Release

Important: replace c:\ Release with the symbolic path of the DLL loaded into SQL Server (optional)

twelve。 In the available analysis script, select memory pressure Analyzer (memory analysis.asp).

13. Click "Start Analysis".

14. Depending on the time it takes to load symbols, the analysis may take some time. When the analysis is complete, a HTML report is generated and opened. This HTML report is stored in C:\ Program Files\ DebugDiag\ Reports\ by default and can be used for subsequent reference.

I attached a sample report that was collected when using heapleak.dll memory leaks, here http://sdrv.ms/TH1qfR. You can use it as a reference.

Debug Diagnostic Tool's memory pressure analyzer generates reports with analysis summaries and the following table memory.

Sqlservr.exe__. Dmp Virtual Memory Analysis Report Heap Analysis Report Leak Analysis Report Outstanding allocation summary Detailed module report (Memory) Detailed module report (Handles)

15. The summary of the analysis is that a good part of the report locates which module leaks memory. View the following report.

16. The report clearly shows that HeapLeak.dll has a significant allocation of 255MB. In heapleak.dll, the "Sub" function is used to allocate the memory at offset 23.

17. View the virtual memory summary. It gives a complete picture of the memory distribution at the virtual address Kong Jia. Keep 1.57GB in the following summary, which is normal in 32-bit SQL Server, but it is not normal to have 272.94MB in the local heap memory.

Check the heap summary, there are 50 heaps.

18. Now look at the significant allocation summary. It gives the first 10 modules of the total number and size of allocation. In the following summary, HeapLeak occupies 26182 of the 255.6MB size.

Note: in this report it is HeapLeak, but in practice it could be any module that leaks memory.

19. You can also view the detailed module report (Memory). It gives the memory allocation from each module as well as the function and the source line of the allocated memory (if you set symbols for all loaded modules).

Now we confirm that the Sub function in HeapLeak.dll has assigned 255MB at line number 14 and has not been released. This report also gives you a callstack example, showing the code path when the function allocates memory. Refer to the sample HTML report file http://sdrv.ms/TH1qfR.

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