static int computeMaxMem() {
    final long maxMemInMegabytes = Runtime.getRuntime().maxMemory() / (1024 * 1024);
    final long maxMemoryToUse = (long) (maxMemInMegabytes * 0.90);
    int ret;
    if (maxMemoryToUse < Integer.MAX_VALUE) {
      ret = (int) maxMemoryToUse;
      if (ret < 1) {
        ret = 1;
      }
    } else {
      ret = Integer.MAX_VALUE;
    }
    return ret;
  }
Default local max memory value in megabytes. By default each partitioned Region can contribute
90% of the maximum memory allocated to a VM.
geode-core/src/main/java/org/apache/geode/cache/PartitionAttributesFactory.java