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.NET Forum / .NET Framework / CLR / November 2003Memory leak recommendations
Hello, We're currently trying to identify the source of a memory leak in a web application. We notice that the privates bytes increases constantly as the gc bytes continuously raise and fall at normal intervals (collections), as a result we feel that this is more than likely a native issue. The web application as a whole has many assemblies in it and some of these assemblies do reference and handle unmanaged memory. I was wondering if anyone had some advice on how to narrow down the culprit assemblies. I'm currently learning how to use the debugging tools for windows to inspect this; how to inspect the managed heap and so forth. But if the problem is unmanaged memory not being cleaned up, how can I discover which assembly is holding onto the references, or what objects are holding onto the references? My knowledge of the debugging utilities are unfortunately limited at this point; something which I am working to fix. My starting point for all of this is http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnbda/html/DBGc h02.asp. All of the GC knowledge I have already, but knowledge of using the tools discussed in this article I didn't have until reading it (windbg, sos, etc.) just this morning :-( Thanks, Ben To be sure as to where the memory leaks come from, you can use the CLR Profiler (version2 just came out). http://www.microsoft.com/downloads/details.aspx?FamilyID=86ce6052-d7f4-4aeb-9b7a -94635beebdda&DisplayLang=en Allocation profiler here: http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=36A3E666- 6877-4C26-B62D-BFD7CB3154AC If you interop with COM object, you should take a look at the Debug Probes of the CLR Spy tool http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=c7b955c7- 231a-406c-9fa5-ad09ef3bb37f The CLR Profiler will give you all the objects allocated and where/why, the large object heap, everything you need. Pay attention to string allocations, when interned i don't know if a string is ever cleaned up completely...  SignatureSebastien Lambla http://thetechnologist.is-a-geek.com/blog/ > Hello, > [quoted text clipped - 15 lines] > > My starting point for all of this is http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnbda/html/DBGc h02.asp. > All of the GC knowledge I have already, but knowledge of using the tools > discussed in this article I didn't have until reading it (windbg, sos, etc.) > just this morning :-( > > Thanks, > Ben Sebastien, Thanks for the response first off. The problem is that it appears to be an unmanaged issue; not a managed issue, so I don't see how inspecting the managed heap with things like the CLR profiler will help. I guess that's a more refined question I would like to ask, if a managed executable is requesting unmanaged resources and never disposing of the them, is it possible to detect this and to detect who the managed culprit is? The unmanaged blob of memory that was requested by the process doesn't exist on the managed heap, but the reference to that does (if requested from a managed resource), can I detect these references and find out who requested them and never diposed of them? Thanks again, Ben > To be sure as to where the memory leaks come from, you can use the CLR > Profiler (version2 just came out). http://www.microsoft.com/downloads/details.aspx?FamilyID=86ce6052-d7f4-4aeb-9b7a -94635beebdda&DisplayLang=en > Allocation profiler here: http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=36A3E666- 6877-4C26-B62D-BFD7CB3154AC > If you interop with COM object, you should take a look at the Debug Probes > of the CLR Spy tool http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=c7b955c7- 231a-406c-9fa5-ad09ef3bb37f > The CLR Profiler will give you all the objects allocated and where/why, the > large object heap, everything you need. Pay attention to string allocations, [quoted text clipped - 22 lines] > > > > My starting point for all of this is http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnbda/html/DBGc h02.asp. > > All of the GC knowledge I have already, but knowledge of using the tools > > discussed in this article I didn't have until reading it (windbg, sos, [quoted text clipped - 3 lines] > > Thanks, > > Ben Are you on 1.0? Be sure that you are calling Dispose on everything that exposes it. Use these sites as references. Read the scitech PDF closely. http://www.automatedqa.com/techpapers/net_allocation_profiler.asp http://www.scitech.se/memprofiler/ http://support.microsoft.com/support/misc/kblookup.asp?id=817723 There are leaks in the framework libraries. You should contact Microsoft after cleaning up your own code (I had created a few of my own leaks through event registrations to a static object). They have a hotfix available for 1.0 and 1.1. HTH; Eric Cadwell http://www.origincontrols.com >Be sure that you are calling Dispose on everything that exposes it. Is there a list anywhere that gives a rough idea of what objects expose IDisposable? In the help index type Dispose method and it will show a list of all classes that support IDisposable. I'm showing 161 for 1.0 Framework. For your own classes, if they contain any objects that support IDisposable make sure that you implement IDisposable. Call this method from inside the Dispose() method and it will check all the private instance variables for IDisposable. It saves you from having to write a bunch of clean up code. public void Disposer() { Type type = this.GetType(); if (type != null) { foreach(FieldInfo fi in type.GetFields(BindingFlags.NonPublic | BindingFlags.Instance)) { object field = fi.GetValue(this); if (field is IDisposable) { ((IDisposable)field).Dispose(); Console.WriteLine("disposed field:" + fi.Name); } } } } HTH; Eric Cadwell http://www.origincontrols.com >In the help index type Dispose method and it will show a list of all classes >that support IDisposable. I'm showing 161 for 1.0 Framework. Thanks for the response. I found that last night in the MSDN help after posting. I should have RTFM first. :) The code tip is cool. I'll make a note of that one. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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