size_t CollectorPolicy::compute_heap_alignment() {

  // The card marking array and the offset arrays for old generations are

  // committed in os pages as well. Make sure they are entirely full (to

  // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1

  // byte entry and the os page size is 4096, the maximum heap size should

  // be 512*4096 = 2MB aligned.

  // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable

  // is supported.

  // Requirements of any new remembered set implementations must be added here.

  size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);

  // Parallel GC does its own alignment of the generations to avoid requiring a

  // large page (256M on some platforms) for the permanent generation.  The

  // other collectors should also be updated to do their own alignment and then

  // this use of lcm() should be removed.

  if (UseLargePages && !UseParallelGC) {

      // in presence of large pages we have to make sure that our

      // alignment is large page aware

      alignment = lcm(os::large_page_size(), alignment);

  }

  return alignment;

}