5 Replies Latest reply on Sep 26, 2011 8:18 PM by Peter Johnson

    JBoss OutOfMemoryError - Help needed regarding Heap Size!

    Kumar Jaya Newbie

      I am using Jboss 4.2.2. I am using EJBs and hibernate for the project. I got OOME after running a load test and checked the wikis and increased my heap size to -Xms512m -Xmx1024m.

      This still didnot help me a I just added the tag

      -XX:MaxPermSize=512m to the above Option. I still didnot fix my problem and I guessed of increasing my memory size to


      -Xms1024m -Xmx2048m. But this is giving me a error in my console..

      Error occurred during initialization of VM
      Could not reserve enough space for object heap
      Could not create the Java virtual machine.
      Press any key to continue . . .

      Am I missing something or its a wrong configuration altogether.

      Any help is greatly appreciated..

        • 1. Re: JBoss OutOfMemoryError - Help needed regarding Heap Size
          Peter Johnson Master

          What operating system, are you using? I will assume Windows, and that it is 32-bit. In that case, you can only allocate around a 1.5GB heap.

          Also, what kind of OOME are you getting? See http://wiki.jboss.org/wiki/OutOfMemoryExceptions for suggested fixes.

          Based on your description, I am guessing that it is not a permgen space problem (those usually happen when you redeploy an app). In which case you probably have a memory leak somewhere in your application. You might want to monitor heap usage. See my presentation at http://www.cecmg.de/doc/tagung_2007/agenda07/24-mai/2b3-peter-johnson/index.html for some suggestions.

          • 2. Re: JBoss OutOfMemoryError - Help needed regarding Heap Size
            Kumar Jaya Newbie

            Thanks Peter. That was a great post! I am looking on to your presentation and checking to see if I can optimize my GC. BTW I am using Window XP as my platform, and is there a relation between the operating system word length and the maximum heap size that can be allocated?? Do we have any statistical relation for it?

            If I consider my OS to be 32 bit then I should be allowed to set a Maximum heap size 1.5GB which is 1536m (to be in multiples of 512m). If thats the case I am getting error for this statement

            Xms1536m -Xmx1536m.
            Error occurred during initialization of VM
            Could not reserve enough space for object heap
            Could not create the Java virtual machine.
            Press any key to continue . . .

            • 3. Re: JBoss OutOfMemoryError - Help needed regarding Heap Size
              Peter Johnson Master

              The maximum heap you allocate depends on the operating system, even the patches to the operating system, the amount of RAM and swap space available, and the other DLLs that are loaded into the JVMs address space.

              For example, on a machine with 1GB RAM and 1GB swap space, you probably will not have enough free memory available to allocate 1.5GB.

              Another example: I recall that a certain software registered a lot of performance statistics, so when I ran the JVM I saw a lot of that software's DLLs in the JVM address space. One way you can check what DLLs are loaded with your JVM is with the listdlls or Process Explorer tools from SysInternals. Look at where the DLLs are loaded into memory - the JVM always allocates the heap in one contiguous block so you can only allocate as much heap as the largest free memory block.

              • 4. Re: JBoss OutOfMemoryError - Help needed regarding Heap Size
                harkconnen Newbie

                Hi Petter,

                 

                According to your comments, using Windows Server 2003 32bits there is a top limit of 1.5gb for HEAP.

                 

                I'm having these message after executing run.bat

                 

                Error occurred during initialization of  VM

                  Could not reserve enough space for object heap

                  Could not create the Java virtual machine.

                 

                When using this set line on RUN.BAT it works OK

                set JAVA_OPTS=%JAVA_OPTS% -Xms512m -Xmx1600m

                 

                But when using this set line on RUN.BAT it fails

                set JAVA_OPTS=%JAVA_OPTS% -Xms512m -Xmx1700m

                 

                I need to increase JVM memory up to 2GB, is there a way to ? using Windows Server 32bits?

                Thanks!

                Kind regards

                 

                Juan Chicchón

                From Lima, PERÚ

                • 5. Re: JBoss OutOfMemoryError - Help needed regarding Heap Size
                  Peter Johnson Master

                  No, you cannot do that, not with the 32-bit Hotspot JVM. That JVM requires a large contiguous memory area to hold the heap. The way Windows lays out the memory, the top 2GB is address space is reservered for the OS. Immediatly underneath is where the various Win32 DLLs get loaded. The JVM DLL gets loaded just under that. The lower portion of memory is used by some legacy stuff and by java.exe itself. And then you need to provide some space for the permgen and also space for the thread stack. Thus you are left with 1.6GB. Even if you boot Windows with the /3G option, you will not get a much larger heap because the extra space is above the DLLs and is not contiguous with the lower memory where the heap is allocated. My company once created a JVM that did not need a contiguous heap space; it could allocate around 2.6GB of heap on 32-bit Windows. But then we usually ran out of room for in the OS space (where file handles, thread handles, and other things are kept).

                   

                  If you really want 2GB heaps, you will need to run a 64-bit OS and a 64-bit JVM. (Though I recall some Linux users claiming 2GB heaps with a 32-bit JVM.)