76   _guard_index = cards_required(_whole_heap.word_size()) - 1;
  77   _last_valid_index = _guard_index - 1;
  78 
  79   _byte_map_size = compute_byte_map_size();
  80 
  81   HeapWord* low_bound  = _whole_heap.start();
  82   HeapWord* high_bound = _whole_heap.end();
  83 
  84   _cur_covered_regions = 0;
  85   _committed = new MemRegion[_max_covered_regions];
  86   if (_committed == NULL) {
  87     vm_exit_during_initialization("Could not allocate card table committed region set.");
  88   }
  89 
  90   const size_t rs_align = _page_size == (size_t) os::vm_page_size() ? 0 :
  91     MAX2(_page_size, (size_t) os::vm_allocation_granularity());
  92   ReservedSpace heap_rs(_byte_map_size, rs_align, false);
  93 
  94   MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC);
  95 
  96   os::trace_page_sizes("card table", _guard_index + 1, _guard_index + 1,
  97                        _page_size, heap_rs.base(), heap_rs.size());
  98   if (!heap_rs.is_reserved()) {
  99     vm_exit_during_initialization("Could not reserve enough space for the "
 100                                   "card marking array");
 101   }
 102 
 103   // The assembler store_check code will do an unsigned shift of the oop,
 104   // then add it to byte_map_base, i.e.
 105   //
 106   //   _byte_map = byte_map_base + (uintptr_t(low_bound) >> card_shift)
 107   _byte_map = (jbyte*) heap_rs.base();
 108   byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
 109   assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
 110   assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
 111 
 112   jbyte* guard_card = &_byte_map[_guard_index];
 113   uintptr_t guard_page = align_size_down((uintptr_t)guard_card, _page_size);
 114   _guard_region = MemRegion((HeapWord*)guard_page, _page_size);
 115   os::commit_memory_or_exit((char*)guard_page, _page_size, _page_size,
 116                             !ExecMem, "card table last card");

  76   _guard_index = cards_required(_whole_heap.word_size()) - 1;
  77   _last_valid_index = _guard_index - 1;
  78 
  79   _byte_map_size = compute_byte_map_size();
  80 
  81   HeapWord* low_bound  = _whole_heap.start();
  82   HeapWord* high_bound = _whole_heap.end();
  83 
  84   _cur_covered_regions = 0;
  85   _committed = new MemRegion[_max_covered_regions];
  86   if (_committed == NULL) {
  87     vm_exit_during_initialization("Could not allocate card table committed region set.");
  88   }
  89 
  90   const size_t rs_align = _page_size == (size_t) os::vm_page_size() ? 0 :
  91     MAX2(_page_size, (size_t) os::vm_allocation_granularity());
  92   ReservedSpace heap_rs(_byte_map_size, rs_align, false);
  93 
  94   MemTracker::record_virtual_memory_type((address)heap_rs.base(), mtGC);
  95 
  96   os::trace_page_sizes("Card Table", _guard_index + 1, _guard_index + 1,
  97                        _page_size, heap_rs.base(), heap_rs.size());
  98   if (!heap_rs.is_reserved()) {
  99     vm_exit_during_initialization("Could not reserve enough space for the "
 100                                   "card marking array");
 101   }
 102 
 103   // The assembler store_check code will do an unsigned shift of the oop,
 104   // then add it to byte_map_base, i.e.
 105   //
 106   //   _byte_map = byte_map_base + (uintptr_t(low_bound) >> card_shift)
 107   _byte_map = (jbyte*) heap_rs.base();
 108   byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
 109   assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
 110   assert(byte_for(high_bound-1) <= &_byte_map[_last_valid_index], "Checking end of map");
 111 
 112   jbyte* guard_card = &_byte_map[_guard_index];
 113   uintptr_t guard_page = align_size_down((uintptr_t)guard_card, _page_size);
 114   _guard_region = MemRegion((HeapWord*)guard_page, _page_size);
 115   os::commit_memory_or_exit((char*)guard_page, _page_size, _page_size,
 116                             !ExecMem, "card table last card");