README:
  This file explains how to compile and run the BDA hotspot VM on a Linux x86_x64 system.

Build Instructions:
  In the hotspot directory there exists a "run" directory.
  Run the build.script file, with execution permissions in order to build the VM. Some arguments are, however, needed:
      -buildir <directory where to output the build files>
      -bootdir <direcotry where a prior instalation of a JVM exists> (for example: /usr/lib/jvm/java-7-openjdk)
      -mode <product,debug,optimized or clean> (product is a version without assert calls on the code; debug asserts every value --- considerably slower ---, and clean cleans the output directory --- buildir argument. optimized is being deprecated since product already provides everything that optimized did).
      -debugbin (if debug binaries are wanted)
      -header (use an additional header word to identify the BDA-region segment of the BDA-heap for an object. -header and -hash cannot be used simultaneously)
      -hash (use the hashing of the klass pointer to identify the BDA-region segment of the BDA-heap for an object)

      If no -header or -hash is called, it produces a normal JVM.

Run instructions:
  The build process produces a libjvm.so file. This file should be included (by copying) in another jdk installation or called by the XXaltjvm argument.
  When the BDA-heap is to be created, such as when built with -header or -hash, the -XX:+UseBDA argument must be passed to the launcher.

  Note well: A limitation exists when the old generation is shrunk after a full collection (the parallel scavenge collector tries to erase a BDA-region by shrinking below its address). Always use (disable) the -XX:-UseAdaptiveGenerationSizePolicyAtMajorCollection.

  Examples:
        When the libjvm.so was not installed on the jdk directory:
        java -Dsun.java.launcher=gamma -XXaltjvm=`cd /home/xpto/bdahotspot/linux/product/ && pwd` -XX:+UseBDA -XX:-UseAdaptiveGenerationSizePolicyAtMajorCollection <java arguments>

        When it was installed on the jdk directory:
        java -XX:+UseBDA -XX:-UseAdaptiveGenerationSizePolicyAtMajorCollection <java arguments)

     Run-down of the available arguments:
       -XX:BDAThreshold=<1-100> Set the threshold of the ratio between the highest count of a special object and the lowest count of a special object within a compacting region (used only on the full collection)
       -XX:BDAKlassHashArray=<integer> Set the size of the array where the hashed klass pointer indexes BDA-region identifiers. Only useful in the -hash configuration.