5 Replies Latest reply on Feb 12, 2002 7:03 AM by adrian.brock

    Memory leak by too many classes loaded

    frebe73
    frebe73 Feb 8, 2002 5:38 AM

      When I am running JBoss the JVM loads thousands of classes with the name sun.reflect.GeneratedSerializationConstructorAccessorXXXX.

      The classes get instanciated once and are never more used, but remains loaded, and occupies memory (I think).

      Does anyone recognize this problem??

      /Fredrik

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        • 1. Re: Memory leak by too many classes loaded
          adrian.brock Feb 8, 2002 2:53 PM (in response to frebe73)

          I don't recognise this exact class.

          There was a problem before 2.4.4 with proxy classes
          not getting garbage collected due to their methods
          being cached and not released.

          You don't mention any version numbers, OS/JBoss/VM

          How many is thousands? The garbage collector can
          be unpredictable at times. Sometimes you get
          stuff lying around the heap, but the garbage doesn't
          seem to be interested. Using System.gc() reveals
          there really is no problem.

          Did you get this information from hprof?
          What is the stacktrace for the site (the number in
          the last column before the class name)?

          Regards,
          Adrain

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          • 2. Re: Memory leak by too many classes loaded
            frebe73
            frebe73 Feb 11, 2002 1:54 AM (in response to frebe73)

            I am using JBoss 2.4.4, Windows 2000 Server (and Professional) and JDK 1.4 RC. I am using OptimizeIT so I have not got any information from hprof.

            I don't think this is a garbage collection problem, because the number of instances is zero. The problem is that the class is loaded. After about 15 minutes of running I have 2000 classes of this sort loaded, and it increases fast.

            /Fredrik

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            • 3. Re: Memory leak by too many classes loaded
              adrian.brock Feb 11, 2002 4:51 AM (in response to frebe73)

              Ok,

              Perhaps you can explain what you're app is doing?

              Maybe you could post a simple version that has the same
              problem. I'll have a look to see whether it is a leak
              within JBoss or just a lazy garbage collector :-)

              But, I don't have JDK 1.4

              Regards,
              Adrian

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              • 4. Re: Memory leak by too many classes loaded
                frebe73
                frebe73 Feb 12, 2002 2:37 AM (in response to frebe73)

                I have done a very simple bean and client (attacted to this message). Even with this simple example I see that there are loaded hundreds of classes named sun.reflect.GeneratedSerializationConstructorAccessorXXXX,there XXXX is a running number. I also se a small memory leak.

                I would be very thankful if you could run this example in OptimizeIt and give me some help. (The problem is the same with JDK1.3).

                Regard Fredrik

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                • 5. Re: Memory leak by too many classes loaded
                  adrian.brock Feb 12, 2002 7:03 AM (in response to frebe73)

                  I haven't got optimizeIt, but I have used hprof.

                  Interestingly, that class does not appear.
                  I have got a class called that has 1575
                  live references out of a total of 1577 allocated,
                  this is probably the class you are referring to.

                  Anyway, using hprof, there is only one jboss reference
                  left over from the test.
                  This is the SecurityAssociation that gets attached
                  the thread. This won't get garbage collected until
                  the thread ends.

                  The other objects not garbage collected are all
                  as I would expect.
                  Caching of Jar entries for the classes loaded
                  Caching of security
                  Caching of RMI worker objects

                  Once you start using RMI it creates some helpers that are
                  kept for future use. I think the class you are referring
                  to is one of these. The number of live objects doesn't
                  change, regardless of the number of iterations.

                  P.S. I wouldn't recommend creating an InitialContext in
                  a loop. I think you know this, and you are only testing :-)

                  Regards,
                  Adrian

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