The problem arises in Arguments::set_heap_size when ergonomically calculating the value for InitialHeapSize. A user might have specified a certain value for -XX:MaxHeapSize, for example 512m. If the machine has a lot of RAM, and InitialRAMFraction is unchanged, then:

  julong reasonable_initial = phys_mem / InitialRAMFraction;

might become larger than MaxHeapSize. This will cause:

  reasonable_initial = MIN2(reasonable_initial, (julong)MaxHeapSize);

to equal MaxHeapSize. This is not a huge problem until GenCollectorPolicy::initialize_size_info:

  if (_max_heap_byte_size == _initial_heap_byte_size) {
    // The maximum and initial heap sizes are the same so the generation's
    // initial size must be the same as it maximum size. Use NewSize as the
    // size if set on command line.
    _max_young_size = FLAG_IS_CMDLINE(NewSize) ? NewSize : _max_young_size;
    _initial_young_size = _max_young_size;

    // Also update the minimum size if min == initial == max.
    if (_max_heap_byte_size == _min_heap_byte_size) {
      _min_young_size = _max_young_size;
    }
  }

This might cause an unexpected value for MaxNewSize.