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8 replies Latest Post - ‏2013-02-25T14:27:37Z by Sunit
SystemAdmin
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Pinned topic Can Java processes take more memory then spedified Max heap and max perm s

‏2013-02-23T13:53:27Z |
Hello All,

Can Java processes take memory more then specified for Max heap + Max perm size ?

Consider I have min heap 2 GB , Max is of 5 GB and Max Perm Size of 1 GB on 64 bit OS

So can Java processes can take 5 + 1 = 6 GB + ? if yes , can we say Garbage collection is not working ? Is there any command to invoke the Garbage collection on App server of windows OS.

Best Regards,
Mitesh Kothari
Updated on 2013-02-25T14:27:37Z at 2013-02-25T14:27:37Z by Sunit
  • SystemAdmin
    SystemAdmin
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    Re: Can Java processes take more memory then spedified Max heap and max perm s

    ‏2013-02-23T16:18:41Z  in response to SystemAdmin
    > dctmmit wrote:
    > Hello All,
    >
    > Can Java processes take memory more then specified for Max heap + Max perm size ?
    >
    > Consider I have min heap 2 GB , Max is of 5 GB and Max Perm Size of 1 GB on 64 bit OS
    >
    > So can Java processes can take 5 + 1 = 6 GB + ? if yes , can we say Garbage collection is not working ? Is there any command to invoke the Garbage collection on App server of windows OS.

    The JVM process can allocate memory outside of the java heap. See for example http://docs.oracle.com/javase/1.5.0/docs/api/java/nio/ByteBuffer.html or any JNI code using native memory.
    • SystemAdmin
      SystemAdmin
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      Re: Can Java processes take more memory then spedified Max heap and max perm s

      ‏2013-02-24T06:35:18Z  in response to SystemAdmin
      not using both.
      • SystemAdmin
        SystemAdmin
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        Re: Can Java processes take more memory then spedified Max heap and max perm s

        ‏2013-02-24T15:08:50Z  in response to SystemAdmin
        > dctmmit wrote:
        > not using both.

        Confused. The application server uses JNI and ByteBuffers.
      • SystemAdmin
        SystemAdmin
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        Re: Can Java processes take more memory then spedified Max heap and max perm s

        ‏2013-02-24T16:20:07Z  in response to SystemAdmin
        > dctmmit wrote:
        > not using both.

        I'm pretty sure the application server uses both.
        • SystemAdmin
          SystemAdmin
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          Re: Can Java processes take more memory then spedified Max heap and max perm s

          ‏2013-02-25T05:10:16Z  in response to SystemAdmin
          OK as per your exepriance WebSphere application server uses both , do we have any documentations on the same for WebSphere 7.0.0.7 or any support note from WebPhere , So I need to provide these details to client with proven documentations.

          To overcome, IBM have suggestes any thing ?
          • SystemAdmin
            SystemAdmin
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            Re: Can Java processes take more memory then spedified Max heap and max perm s

            ‏2013-02-25T12:35:10Z  in response to SystemAdmin
            If you think the memory usage is unreasonable, open a PMR and have it analyzed. Just by virtue of memory usage > max heap + permgen is not basis for saying it's unreasonable, though.
            • SystemAdmin
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              Re: Can Java processes take more memory then spedified Max heap and max perm s

              ‏2013-02-25T13:32:39Z  in response to SystemAdmin
              Yes, I have just reaised PMR. Any idea how much time they take to provide clarifications / resolve. Reaised First time.
              • Sunit
                Sunit
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                Re: Can Java processes take more memory then spedified Max heap and max perm s

                ‏2013-02-25T14:27:37Z  in response to SystemAdmin
                There is more to what OS reports as memory used by a Java process than simply adding those two numbers.

                See http://www.ibm.com/developerworks/java/library/j-codetoheap/index.html

                --Sunit