changeset 27270:44d8e9fd8244

8146399: Refactor the BlockOffsetTable classes. Reviewed-by: mgerdin, jwilhelm, tschatzl
author david
date Thu, 07 Jan 2016 16:25:53 +0100
parents e80bca696e3b
children bd73f2212479 50dd5b051754
files src/share/vm/gc/g1/g1AllocRegion.cpp src/share/vm/gc/g1/g1BlockOffsetTable.cpp src/share/vm/gc/g1/g1BlockOffsetTable.hpp src/share/vm/gc/g1/g1BlockOffsetTable.inline.hpp src/share/vm/gc/g1/g1CollectedHeap.cpp src/share/vm/gc/g1/g1CollectedHeap.hpp src/share/vm/gc/g1/g1CollectedHeap_ext.cpp src/share/vm/gc/g1/g1RemSet.cpp src/share/vm/gc/g1/g1RemSet.hpp src/share/vm/gc/g1/heapRegion.cpp src/share/vm/gc/g1/heapRegion.hpp src/share/vm/gc/g1/heapRegion.inline.hpp src/share/vm/gc/g1/heapRegionRemSet.cpp src/share/vm/gc/g1/heapRegionRemSet.hpp src/share/vm/gc/g1/heapRegionSet.cpp src/share/vm/gc/g1/vmStructs_g1.hpp src/share/vm/gc/shared/blockOffsetTable.hpp
diffstat 17 files changed, 267 insertions(+), 519 deletions(-) [+]
line wrap: on
line diff
--- a/src/share/vm/gc/g1/g1AllocRegion.cpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/g1AllocRegion.cpp	Thu Jan 07 16:25:53 2016 +0100
@@ -277,7 +277,7 @@
     // Determine how far we are from the next card boundary. If it is smaller than
     // the minimum object size we can allocate into, expand into the next card.
     HeapWord* top = cur->top();
-    HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);
+    HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetTable::N_bytes);
 
     size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
 
--- a/src/share/vm/gc/g1/g1BlockOffsetTable.cpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/g1BlockOffsetTable.cpp	Thu Jan 07 16:25:53 2016 +0100
@@ -35,35 +35,29 @@
 
 
 //////////////////////////////////////////////////////////////////////
-// G1BlockOffsetSharedArray
+// G1BlockOffsetTable
 //////////////////////////////////////////////////////////////////////
 
-G1BlockOffsetSharedArray::G1BlockOffsetSharedArray(MemRegion heap, G1RegionToSpaceMapper* storage) :
-  _reserved(), _end(NULL), _listener(), _offset_array(NULL) {
-
-  _reserved = heap;
-  _end = NULL;
+G1BlockOffsetTable::G1BlockOffsetTable(MemRegion heap, G1RegionToSpaceMapper* storage) :
+  _reserved(heap), _offset_array(NULL) {
 
   MemRegion bot_reserved = storage->reserved();
 
   _offset_array = (u_char*)bot_reserved.start();
-  _end = _reserved.end();
 
-  storage->set_mapping_changed_listener(&_listener);
-
-  log_trace(gc, bot)("G1BlockOffsetSharedArray::G1BlockOffsetSharedArray: ");
+  log_trace(gc, bot)("G1BlockOffsetTable::G1BlockOffsetTable: ");
   log_trace(gc, bot)("    rs.base(): " PTR_FORMAT "  rs.size(): " SIZE_FORMAT "  rs end(): " PTR_FORMAT,
                      p2i(bot_reserved.start()), bot_reserved.byte_size(), p2i(bot_reserved.end()));
 }
 
-bool G1BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
+bool G1BlockOffsetTable::is_card_boundary(HeapWord* p) const {
   assert(p >= _reserved.start(), "just checking");
   size_t delta = pointer_delta(p, _reserved.start());
   return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
 }
 
 #ifdef ASSERT
-void G1BlockOffsetSharedArray::check_index(size_t index, const char* msg) const {
+void G1BlockOffsetTable::check_index(size_t index, const char* msg) const {
   assert((index) < (_reserved.word_size() >> LogN_words),
          "%s - index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT,
          msg, (index), (_reserved.word_size() >> LogN_words));
@@ -77,25 +71,19 @@
 #endif // ASSERT
 
 //////////////////////////////////////////////////////////////////////
-// G1BlockOffsetArray
+// G1BlockOffsetTablePart
 //////////////////////////////////////////////////////////////////////
 
-G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array,
-                                       MemRegion mr) :
-  G1BlockOffsetTable(mr.start(), mr.end()),
-  _unallocated_block(_bottom),
-  _array(array), _gsp(NULL) {
-  assert(_bottom <= _end, "arguments out of order");
-}
-
-void G1BlockOffsetArray::set_space(G1OffsetTableContigSpace* sp) {
-  _gsp = sp;
-}
+G1BlockOffsetTablePart::G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp) :
+  _bot(array),
+  _space(gsp),
+  _next_offset_threshold(NULL),
+  _next_offset_index(0)
+{ }
 
 // The arguments follow the normal convention of denoting
 // a right-open interval: [start, end)
-void
-G1BlockOffsetArray:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) {
+void G1BlockOffsetTablePart:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) {
 
   if (start >= end) {
     // The start address is equal to the end address (or to
@@ -137,23 +125,22 @@
   //      Move back N (e.g., 8) entries and repeat with the
   //        value of the new entry
   //
-  size_t start_card = _array->index_for(start);
-  size_t end_card = _array->index_for(end-1);
-  assert(start ==_array->address_for_index(start_card), "Precondition");
-  assert(end ==_array->address_for_index(end_card)+N_words, "Precondition");
+  size_t start_card = _bot->index_for(start);
+  size_t end_card = _bot->index_for(end-1);
+  assert(start ==_bot->address_for_index(start_card), "Precondition");
+  assert(end ==_bot->address_for_index(end_card)+N_words, "Precondition");
   set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval
 }
 
 // Unlike the normal convention in this code, the argument here denotes
 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
 // above.
-void
-G1BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) {
+void G1BlockOffsetTablePart::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) {
   if (start_card > end_card) {
     return;
   }
-  assert(start_card > _array->index_for(_bottom), "Cannot be first card");
-  assert(_array->offset_array(start_card-1) <= N_words,
+  assert(start_card > _bot->index_for(_space->bottom()), "Cannot be first card");
+  assert(_bot->offset_array(start_card-1) <= N_words,
          "Offset card has an unexpected value");
   size_t start_card_for_region = start_card;
   u_char offset = max_jubyte;
@@ -164,11 +151,11 @@
     size_t reach = start_card - 1 + (BlockOffsetArray::power_to_cards_back(i+1) - 1);
     offset = N_words + i;
     if (reach >= end_card) {
-      _array->set_offset_array(start_card_for_region, end_card, offset);
+      _bot->set_offset_array(start_card_for_region, end_card, offset);
       start_card_for_region = reach + 1;
       break;
     }
-    _array->set_offset_array(start_card_for_region, reach, offset);
+    _bot->set_offset_array(start_card_for_region, reach, offset);
     start_card_for_region = reach + 1;
   }
   assert(start_card_for_region > end_card, "Sanity check");
@@ -178,79 +165,44 @@
 // The card-interval [start_card, end_card] is a closed interval; this
 // is an expensive check -- use with care and only under protection of
 // suitable flag.
-void G1BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const {
+void G1BlockOffsetTablePart::check_all_cards(size_t start_card, size_t end_card) const {
 
   if (end_card < start_card) {
     return;
   }
-  guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card");
+  guarantee(_bot->offset_array(start_card) == N_words, "Wrong value in second card");
   for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
-    u_char entry = _array->offset_array(c);
+    u_char entry = _bot->offset_array(c);
     if (c - start_card > BlockOffsetArray::power_to_cards_back(1)) {
       guarantee(entry > N_words,
                 "Should be in logarithmic region - "
                 "entry: %u, "
                 "_array->offset_array(c): %u, "
                 "N_words: %u",
-                (uint)entry, (uint)_array->offset_array(c), (uint)N_words);
+                (uint)entry, (uint)_bot->offset_array(c), (uint)N_words);
     }
     size_t backskip = BlockOffsetArray::entry_to_cards_back(entry);
     size_t landing_card = c - backskip;
     guarantee(landing_card >= (start_card - 1), "Inv");
     if (landing_card >= start_card) {
-      guarantee(_array->offset_array(landing_card) <= entry,
+      guarantee(_bot->offset_array(landing_card) <= entry,
                 "Monotonicity - landing_card offset: %u, "
                 "entry: %u",
-                (uint)_array->offset_array(landing_card), (uint)entry);
+                (uint)_bot->offset_array(landing_card), (uint)entry);
     } else {
       guarantee(landing_card == start_card - 1, "Tautology");
       // Note that N_words is the maximum offset value
-      guarantee(_array->offset_array(landing_card) <= N_words,
+      guarantee(_bot->offset_array(landing_card) <= N_words,
                 "landing card offset: %u, "
                 "N_words: %u",
-                (uint)_array->offset_array(landing_card), (uint)N_words);
+                (uint)_bot->offset_array(landing_card), (uint)N_words);
     }
   }
 }
 
-HeapWord* G1BlockOffsetArray::block_start_unsafe(const void* addr) {
-  assert(_bottom <= addr && addr < _end,
-         "addr must be covered by this Array");
-  // Must read this exactly once because it can be modified by parallel
-  // allocation.
-  HeapWord* ub = _unallocated_block;
-  if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
-    assert(ub < _end, "tautology (see above)");
-    return ub;
-  }
-  // Otherwise, find the block start using the table.
-  HeapWord* q = block_at_or_preceding(addr, false, 0);
-  return forward_to_block_containing_addr(q, addr);
-}
-
-// This duplicates a little code from the above: unavoidable.
-HeapWord*
-G1BlockOffsetArray::block_start_unsafe_const(const void* addr) const {
-  assert(_bottom <= addr && addr < _end,
-         "addr must be covered by this Array");
-  // Must read this exactly once because it can be modified by parallel
-  // allocation.
-  HeapWord* ub = _unallocated_block;
-  if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
-    assert(ub < _end, "tautology (see above)");
-    return ub;
-  }
-  // Otherwise, find the block start using the table.
-  HeapWord* q = block_at_or_preceding(addr, false, 0);
-  HeapWord* n = q + block_size(q);
-  return forward_to_block_containing_addr_const(q, n, addr);
-}
-
-
-HeapWord*
-G1BlockOffsetArray::forward_to_block_containing_addr_slow(HeapWord* q,
-                                                          HeapWord* n,
-                                                          const void* addr) {
+HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr_slow(HeapWord* q,
+                                                                        HeapWord* n,
+                                                                        const void* addr) {
   // We're not in the normal case.  We need to handle an important subcase
   // here: LAB allocation.  An allocation previously recorded in the
   // offset table was actually a lab allocation, and was divided into
@@ -260,17 +212,17 @@
   // If the fist object's end q is at the card boundary. Start refining
   // with the corresponding card (the value of the entry will be basically
   // set to 0). If the object crosses the boundary -- start from the next card.
-  size_t n_index = _array->index_for(n);
-  size_t next_index = _array->index_for(n) + !_array->is_card_boundary(n);
+  size_t n_index = _bot->index_for(n);
+  size_t next_index = _bot->index_for(n) + !_bot->is_card_boundary(n);
   // Calculate a consistent next boundary.  If "n" is not at the boundary
   // already, step to the boundary.
-  HeapWord* next_boundary = _array->address_for_index(n_index) +
+  HeapWord* next_boundary = _bot->address_for_index(n_index) +
                             (n_index == next_index ? 0 : N_words);
-  assert(next_boundary <= _array->_end,
+  assert(next_boundary <= _bot->_reserved.end(),
          "next_boundary is beyond the end of the covered region "
          " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT,
-         p2i(next_boundary), p2i(_array->_end));
-  if (addr >= gsp()->top()) return gsp()->top();
+         p2i(next_boundary), p2i(_bot->_reserved.end()));
+  if (addr >= _space->top()) return _space->top();
   while (next_boundary < addr) {
     while (n <= next_boundary) {
       q = n;
@@ -280,18 +232,11 @@
     }
     assert(q <= next_boundary && n > next_boundary, "Consequence of loop");
     // [q, n) is the block that crosses the boundary.
-    alloc_block_work2(&next_boundary, &next_index, q, n);
+    alloc_block_work(&next_boundary, &next_index, q, n);
   }
   return forward_to_block_containing_addr_const(q, n, addr);
 }
 
-// Note that the committed size of the covered space may have changed,
-// so the table size might also wish to change.
-void G1BlockOffsetArray::resize(size_t new_word_size) {
-  HeapWord* new_end = _bottom + new_word_size;
-  _end = new_end;  // update _end
-}
-
 //
 //              threshold_
 //              |   _index_
@@ -302,8 +247,8 @@
 //       ( ^    ]
 //         block-start
 //
-void G1BlockOffsetArray::alloc_block_work2(HeapWord** threshold_, size_t* index_,
-                                           HeapWord* blk_start, HeapWord* blk_end) {
+void G1BlockOffsetTablePart::alloc_block_work(HeapWord** threshold_, size_t* index_,
+                                              HeapWord* blk_start, HeapWord* blk_end) {
   // For efficiency, do copy-in/copy-out.
   HeapWord* threshold = *threshold_;
   size_t    index = *index_;
@@ -318,7 +263,7 @@
          "reference must be into the heap");
   assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1),
          "limit must be within the heap");
-  assert(threshold == _array->_reserved.start() + index*N_words,
+  assert(threshold == _bot->_reserved.start() + index*N_words,
          "index must agree with threshold");
 
   DEBUG_ONLY(size_t orig_index = index;)
@@ -326,26 +271,26 @@
   // Mark the card that holds the offset into the block.  Note
   // that _next_offset_index and _next_offset_threshold are not
   // updated until the end of this method.
-  _array->set_offset_array(index, threshold, blk_start);
+  _bot->set_offset_array(index, threshold, blk_start);
 
   // We need to now mark the subsequent cards that this blk spans.
 
   // Index of card on which blk ends.
-  size_t end_index   = _array->index_for(blk_end - 1);
+  size_t end_index   = _bot->index_for(blk_end - 1);
 
   // Are there more cards left to be updated?
   if (index + 1 <= end_index) {
-    HeapWord* rem_st  = _array->address_for_index(index + 1);
+    HeapWord* rem_st  = _bot->address_for_index(index + 1);
     // Calculate rem_end this way because end_index
     // may be the last valid index in the covered region.
-    HeapWord* rem_end = _array->address_for_index(end_index) +  N_words;
+    HeapWord* rem_end = _bot->address_for_index(end_index) +  N_words;
     set_remainder_to_point_to_start(rem_st, rem_end);
   }
 
   index = end_index + 1;
   // Calculate threshold_ this way because end_index
   // may be the last valid index in the covered region.
-  threshold = _array->address_for_index(end_index) + N_words;
+  threshold = _bot->address_for_index(end_index) + N_words;
   assert(threshold >= blk_end, "Incorrect offset threshold");
 
   // index_ and threshold_ updated here.
@@ -355,49 +300,49 @@
 #ifdef ASSERT
   // The offset can be 0 if the block starts on a boundary.  That
   // is checked by an assertion above.
-  size_t start_index = _array->index_for(blk_start);
-  HeapWord* boundary = _array->address_for_index(start_index);
-  assert((_array->offset_array(orig_index) == 0 && blk_start == boundary) ||
-         (_array->offset_array(orig_index) > 0 && _array->offset_array(orig_index) <= N_words),
+  size_t start_index = _bot->index_for(blk_start);
+  HeapWord* boundary = _bot->address_for_index(start_index);
+  assert((_bot->offset_array(orig_index) == 0 && blk_start == boundary) ||
+         (_bot->offset_array(orig_index) > 0 && _bot->offset_array(orig_index) <= N_words),
          "offset array should have been set - "
          "orig_index offset: %u, "
          "blk_start: " PTR_FORMAT ", "
          "boundary: " PTR_FORMAT,
-         (uint)_array->offset_array(orig_index),
+         (uint)_bot->offset_array(orig_index),
          p2i(blk_start), p2i(boundary));
   for (size_t j = orig_index + 1; j <= end_index; j++) {
-    assert(_array->offset_array(j) > 0 &&
-           _array->offset_array(j) <=
+    assert(_bot->offset_array(j) > 0 &&
+           _bot->offset_array(j) <=
              (u_char) (N_words+BlockOffsetArray::N_powers-1),
            "offset array should have been set - "
            "%u not > 0 OR %u not <= %u",
-           (uint) _array->offset_array(j),
-           (uint) _array->offset_array(j),
+           (uint) _bot->offset_array(j),
+           (uint) _bot->offset_array(j),
            (uint) (N_words+BlockOffsetArray::N_powers-1));
   }
 #endif
 }
 
-void G1BlockOffsetArray::verify() const {
-  assert(gsp()->bottom() < gsp()->top(), "Only non-empty regions should be verified.");
-  size_t start_card = _array->index_for(gsp()->bottom());
-  size_t end_card = _array->index_for(gsp()->top() - 1);
+void G1BlockOffsetTablePart::verify() const {
+  assert(_space->bottom() < _space->top(), "Only non-empty regions should be verified.");
+  size_t start_card = _bot->index_for(_space->bottom());
+  size_t end_card = _bot->index_for(_space->top() - 1);
 
   for (size_t current_card = start_card; current_card < end_card; current_card++) {
-    u_char entry = _array->offset_array(current_card);
+    u_char entry = _bot->offset_array(current_card);
     if (entry < N_words) {
       // The entry should point to an object before the current card. Verify that
       // it is possible to walk from that object in to the current card by just
       // iterating over the objects following it.
-      HeapWord* card_address = _array->address_for_index(current_card);
+      HeapWord* card_address = _bot->address_for_index(current_card);
       HeapWord* obj_end = card_address - entry;
       while (obj_end < card_address) {
         HeapWord* obj = obj_end;
         size_t obj_size = block_size(obj);
         obj_end = obj + obj_size;
-        guarantee(obj_end > obj && obj_end <= gsp()->top(),
+        guarantee(obj_end > obj && obj_end <= _space->top(),
                   "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT,
-                  p2i(obj), obj_size, p2i(obj_end), p2i(gsp()->top()));
+                  p2i(obj), obj_size, p2i(obj_end), p2i(_space->top()));
       }
     } else {
       // Because we refine the BOT based on which cards are dirty there is not much we can verify here.
@@ -411,103 +356,66 @@
                 "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT,
                 start_card, current_card, backskip);
 
-      HeapWord* backskip_address = _array->address_for_index(current_card - backskip);
-      guarantee(backskip_address >= gsp()->bottom(),
+      HeapWord* backskip_address = _bot->address_for_index(current_card - backskip);
+      guarantee(backskip_address >= _space->bottom(),
                 "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT,
-                p2i(gsp()->bottom()), p2i(backskip_address));
+                p2i(_space->bottom()), p2i(backskip_address));
     }
   }
 }
 
 #ifndef PRODUCT
 void
-G1BlockOffsetArray::print_on(outputStream* out) {
-  size_t from_index = _array->index_for(_bottom);
-  size_t to_index = _array->index_for(_end);
+G1BlockOffsetTablePart::print_on(outputStream* out) {
+  size_t from_index = _bot->index_for(_space->bottom());
+  size_t to_index = _bot->index_for(_space->end());
   out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") "
                 "cards [" SIZE_FORMAT "," SIZE_FORMAT ")",
-                p2i(_bottom), p2i(_end), from_index, to_index);
+                p2i(_space->bottom()), p2i(_space->end()), from_index, to_index);
   for (size_t i = from_index; i < to_index; ++i) {
     out->print_cr("  entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u",
-                  i, p2i(_array->address_for_index(i)),
-                  (uint) _array->offset_array(i));
+                  i, p2i(_bot->address_for_index(i)),
+                  (uint) _bot->offset_array(i));
   }
+  out->print_cr("  next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold));
+  out->print_cr("  next offset index:     " SIZE_FORMAT, _next_offset_index);
 }
 #endif // !PRODUCT
 
-//////////////////////////////////////////////////////////////////////
-// G1BlockOffsetArrayContigSpace
-//////////////////////////////////////////////////////////////////////
-
-HeapWord*
-G1BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) {
-  assert(_bottom <= addr && addr < _end,
-         "addr must be covered by this Array");
-  HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
-  return forward_to_block_containing_addr(q, addr);
-}
-
-HeapWord*
-G1BlockOffsetArrayContigSpace::
-block_start_unsafe_const(const void* addr) const {
-  assert(_bottom <= addr && addr < _end,
-         "addr must be covered by this Array");
-  HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
-  HeapWord* n = q + block_size(q);
-  return forward_to_block_containing_addr_const(q, n, addr);
-}
-
-G1BlockOffsetArrayContigSpace::
-G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array,
-                              MemRegion mr) :
-  G1BlockOffsetArray(array, mr)
-{
-  _next_offset_threshold = NULL;
-  _next_offset_index = 0;
-}
-
-HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold_raw() {
-  assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array),
+HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() {
+  assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
          "just checking");
-  _next_offset_index = _array->index_for_raw(_bottom);
+  _next_offset_index = _bot->index_for_raw(_space->bottom());
   _next_offset_index++;
   _next_offset_threshold =
-    _array->address_for_index_raw(_next_offset_index);
+    _bot->address_for_index_raw(_next_offset_index);
   return _next_offset_threshold;
 }
 
-void G1BlockOffsetArrayContigSpace::zero_bottom_entry_raw() {
-  assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array),
+void G1BlockOffsetTablePart::zero_bottom_entry_raw() {
+  assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
          "just checking");
-  size_t bottom_index = _array->index_for_raw(_bottom);
-  assert(_array->address_for_index_raw(bottom_index) == _bottom,
+  size_t bottom_index = _bot->index_for_raw(_space->bottom());
+  assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(),
          "Precondition of call");
-  _array->set_offset_array_raw(bottom_index, 0);
+  _bot->set_offset_array_raw(bottom_index, 0);
 }
 
-HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold() {
-  assert(!G1CollectedHeap::heap()->is_in_reserved(_array->_offset_array),
+HeapWord* G1BlockOffsetTablePart::initialize_threshold() {
+  assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
          "just checking");
-  _next_offset_index = _array->index_for(_bottom);
+  _next_offset_index = _bot->index_for(_space->bottom());
   _next_offset_index++;
   _next_offset_threshold =
-    _array->address_for_index(_next_offset_index);
+    _bot->address_for_index(_next_offset_index);
   return _next_offset_threshold;
 }
 
-void G1BlockOffsetArrayContigSpace::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) {
+void G1BlockOffsetTablePart::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) {
   // The first BOT entry should have offset 0.
   reset_bot();
-  alloc_block(_bottom, obj_top);
+  alloc_block(_space->bottom(), obj_top);
   if (fill_size > 0) {
     alloc_block(obj_top, fill_size);
   }
 }
-
-#ifndef PRODUCT
-void G1BlockOffsetArrayContigSpace::print_on(outputStream* out) {
-  G1BlockOffsetArray::print_on(out);
-  out->print_cr("  next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold));
-  out->print_cr("  next offset index:     " SIZE_FORMAT, _next_offset_index);
-}
-#endif // !PRODUCT
--- a/src/share/vm/gc/g1/g1BlockOffsetTable.hpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/g1BlockOffsetTable.hpp	Thu Jan 07 16:25:53 2016 +0100
@@ -30,119 +30,25 @@
 #include "memory/virtualspace.hpp"
 #include "utilities/globalDefinitions.hpp"
 
-// The CollectedHeap type requires subtypes to implement a method
-// "block_start".  For some subtypes, notably generational
-// systems using card-table-based write barriers, the efficiency of this
-// operation may be important.  Implementations of the "BlockOffsetArray"
-// class may be useful in providing such efficient implementations.
-//
-// While generally mirroring the structure of the BOT for GenCollectedHeap,
-// the following types are tailored more towards G1's uses; these should,
-// however, be merged back into a common BOT to avoid code duplication
-// and reduce maintenance overhead.
-//
-//    G1BlockOffsetTable (abstract)
-//    -- G1BlockOffsetArray                (uses G1BlockOffsetSharedArray)
-//       -- G1BlockOffsetArrayContigSpace
-//
-// A main impediment to the consolidation of this code might be the
-// effect of making some of the block_start*() calls non-const as
-// below. Whether that might adversely affect performance optimizations
-// that compilers might normally perform in the case of non-G1
-// collectors needs to be carefully investigated prior to any such
-// consolidation.
-
 // Forward declarations
-class G1BlockOffsetSharedArray;
-class G1OffsetTableContigSpace;
-
-class G1BlockOffsetTable VALUE_OBJ_CLASS_SPEC {
-  friend class VMStructs;
-protected:
-  // These members describe the region covered by the table.
-
-  // The space this table is covering.
-  HeapWord* _bottom;    // == reserved.start
-  HeapWord* _end;       // End of currently allocated region.
-
-public:
-  // Initialize the table to cover the given space.
-  // The contents of the initial table are undefined.
-  G1BlockOffsetTable(HeapWord* bottom, HeapWord* end) :
-    _bottom(bottom), _end(end)
-    {
-      assert(_bottom <= _end, "arguments out of order");
-    }
-
-  // Note that the committed size of the covered space may have changed,
-  // so the table size might also wish to change.
-  virtual void resize(size_t new_word_size) = 0;
-
-  virtual void set_bottom(HeapWord* new_bottom) {
-    assert(new_bottom <= _end,
-           "new_bottom (" PTR_FORMAT ") > _end (" PTR_FORMAT ")",
-           p2i(new_bottom), p2i(_end));
-    _bottom = new_bottom;
-    resize(pointer_delta(_end, _bottom));
-  }
-
-  // Requires "addr" to be contained by a block, and returns the address of
-  // the start of that block.  (May have side effects, namely updating of
-  // shared array entries that "point" too far backwards.  This can occur,
-  // for example, when LAB allocation is used in a space covered by the
-  // table.)
-  virtual HeapWord* block_start_unsafe(const void* addr) = 0;
-  // Same as above, but does not have any of the possible side effects
-  // discussed above.
-  virtual HeapWord* block_start_unsafe_const(const void* addr) const = 0;
-
-  // Returns the address of the start of the block containing "addr", or
-  // else "null" if it is covered by no block.  (May have side effects,
-  // namely updating of shared array entries that "point" too far
-  // backwards.  This can occur, for example, when lab allocation is used
-  // in a space covered by the table.)
-  inline HeapWord* block_start(const void* addr);
-  // Same as above, but does not have any of the possible side effects
-  // discussed above.
-  inline HeapWord* block_start_const(const void* addr) const;
-};
-
-class G1BlockOffsetSharedArrayMappingChangedListener : public G1MappingChangedListener {
- public:
-  virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
-    // Nothing to do. The BOT is hard-wired to be part of the HeapRegion, and we cannot
-    // retrieve it here since this would cause firing of several asserts. The code
-    // executed after commit of a region already needs to do some re-initialization of
-    // the HeapRegion, so we combine that.
-  }
-};
+class G1BlockOffsetTable;
+class G1ContiguousSpace;
 
 // This implementation of "G1BlockOffsetTable" divides the covered region
 // into "N"-word subregions (where "N" = 2^"LogN".  An array with an entry
 // for each such subregion indicates how far back one must go to find the
 // start of the chunk that includes the first word of the subregion.
 //
-// Each BlockOffsetArray is owned by a Space.  However, the actual array
-// may be shared by several BlockOffsetArrays; this is useful
-// when a single resizable area (such as a generation) is divided up into
-// several spaces in which contiguous allocation takes place,
-// such as, for example, in G1 or in the train generation.)
+// Each G1BlockOffsetTablePart is owned by a G1ContiguousSpace.
 
-// Here is the shared array type.
-
-class G1BlockOffsetSharedArray: public CHeapObj<mtGC> {
-  friend class G1BlockOffsetArray;
-  friend class G1BlockOffsetArrayContigSpace;
+class G1BlockOffsetTable: public CHeapObj<mtGC> {
+  friend class G1BlockOffsetTablePart;
   friend class VMStructs;
 
 private:
-  G1BlockOffsetSharedArrayMappingChangedListener _listener;
-  // The reserved region covered by the shared array.
+  // The reserved region covered by the table.
   MemRegion _reserved;
 
-  // End of the current committed region.
-  HeapWord* _end;
-
   // Array for keeping offsets for retrieving object start fast given an
   // address.
   u_char* _offset_array;          // byte array keeping backwards offsets
@@ -192,13 +98,9 @@
     N_words = 1 << LogN_words
   };
 
-  // Initialize the table to cover from "base" to (at least)
-  // "base + init_word_size".  In the future, the table may be expanded
-  // (see "resize" below) up to the size of "_reserved" (which must be at
-  // least "init_word_size".) The contents of the initial table are
-  // undefined; it is the responsibility of the constituent
-  // G1BlockOffsetTable(s) to initialize cards.
-  G1BlockOffsetSharedArray(MemRegion heap, G1RegionToSpaceMapper* storage);
+  // Initialize the Block Offset Table to cover the memory region passed
+  // in the heap parameter.
+  G1BlockOffsetTable(MemRegion heap, G1RegionToSpaceMapper* storage);
 
   // Return the appropriate index into "_offset_array" for "p".
   inline size_t index_for(const void* p) const;
@@ -213,29 +115,24 @@
   }
 };
 
-// And here is the G1BlockOffsetTable subtype that uses the array.
-
-class G1BlockOffsetArray: public G1BlockOffsetTable {
-  friend class G1BlockOffsetSharedArray;
-  friend class G1BlockOffsetArrayContigSpace;
+class G1BlockOffsetTablePart VALUE_OBJ_CLASS_SPEC {
+  friend class G1BlockOffsetTable;
   friend class VMStructs;
 private:
   enum SomePrivateConstants {
-    N_words = G1BlockOffsetSharedArray::N_words,
-    LogN    = G1BlockOffsetSharedArray::LogN
+    N_words = G1BlockOffsetTable::N_words,
+    LogN    = G1BlockOffsetTable::LogN
   };
 
-  // This is the array, which can be shared by several BlockOffsetArray's
-  // servicing different
-  G1BlockOffsetSharedArray* _array;
+  // allocation boundary at which offset array must be updated
+  HeapWord* _next_offset_threshold;
+  size_t    _next_offset_index;      // index corresponding to that boundary
+
+  // This is the global BlockOffsetTable.
+  G1BlockOffsetTable* _bot;
 
   // The space that owns this subregion.
-  G1OffsetTableContigSpace* _gsp;
-
-  // The portion [_unallocated_block, _sp.end()) of the space that
-  // is a single block known not to contain any objects.
-  // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag.
-  HeapWord* _unallocated_block;
+  G1ContiguousSpace* _space;
 
   // Sets the entries
   // corresponding to the cards starting at "start" and ending at "end"
@@ -246,9 +143,12 @@
   // that is closed: [start_index, end_index]
   void set_remainder_to_point_to_start_incl(size_t start, size_t end);
 
-protected:
-
-  G1OffsetTableContigSpace* gsp() const { return _gsp; }
+  // Zero out the entry for _bottom (offset will be zero). Does not check for availability of the
+  // memory first.
+  void zero_bottom_entry_raw();
+  // Variant of initialize_threshold that does not check for availability of the
+  // memory first.
+  HeapWord* initialize_threshold_raw();
 
   inline size_t block_size(const HeapWord* p) const;
 
@@ -263,9 +163,8 @@
   // next block (or the end of the space.)  Return the address of the
   // beginning of the block that contains "addr".  Does so without side
   // effects (see, e.g., spec of  block_start.)
-  inline HeapWord*
-  forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,
-                                         const void* addr) const;
+  inline HeapWord* forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,
+                                                          const void* addr) const;
 
   // "q" is a block boundary that is <= "addr"; return the address of the
   // beginning of the block that contains "addr".  May have side effects
@@ -288,60 +187,26 @@
   // starting at "*threshold_", and for any other indices crossed by the
   // block.  Updates "*threshold_" and "*index_" to correspond to the first
   // index after the block end.
-  void alloc_block_work2(HeapWord** threshold_, size_t* index_,
-                         HeapWord* blk_start, HeapWord* blk_end);
-
-public:
-  // The space may not have it's bottom and top set yet, which is why the
-  // region is passed as a parameter. The elements of the array are
-  // initialized to zero.
-  G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr);
-
-  // Note: this ought to be part of the constructor, but that would require
-  // "this" to be passed as a parameter to a member constructor for
-  // the containing concrete subtype of Space.
-  // This would be legal C++, but MS VC++ doesn't allow it.
-  void set_space(G1OffsetTableContigSpace* sp);
-
-  // Resets the covered region to one with the same _bottom as before but
-  // the "new_word_size".
-  void resize(size_t new_word_size);
-
-  virtual HeapWord* block_start_unsafe(const void* addr);
-  virtual HeapWord* block_start_unsafe_const(const void* addr) const;
+  void alloc_block_work(HeapWord** threshold_, size_t* index_,
+                        HeapWord* blk_start, HeapWord* blk_end);
 
   void check_all_cards(size_t left_card, size_t right_card) const;
 
+public:
+  //  The elements of the array are initialized to zero.
+  G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp);
+
   void verify() const;
 
-  virtual void print_on(outputStream* out) PRODUCT_RETURN;
-};
-
-// A subtype of BlockOffsetArray that takes advantage of the fact
-// that its underlying space is a ContiguousSpace, so that its "active"
-// region can be more efficiently tracked (than for a non-contiguous space).
-class G1BlockOffsetArrayContigSpace: public G1BlockOffsetArray {
-  friend class VMStructs;
-
-  // allocation boundary at which offset array must be updated
-  HeapWord* _next_offset_threshold;
-  size_t    _next_offset_index;      // index corresponding to that boundary
-
-  // Work function to be called when allocation start crosses the next
-  // threshold in the contig space.
-  void alloc_block_work1(HeapWord* blk_start, HeapWord* blk_end) {
-    alloc_block_work2(&_next_offset_threshold, &_next_offset_index,
-                      blk_start, blk_end);
-  }
-
-  // Zero out the entry for _bottom (offset will be zero). Does not check for availability of the
-  // memory first.
-  void zero_bottom_entry_raw();
-  // Variant of initialize_threshold that does not check for availability of the
-  // memory first.
-  HeapWord* initialize_threshold_raw();
- public:
-  G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr);
+  // Returns the address of the start of the block containing "addr", or
+  // else "null" if it is covered by no block.  (May have side effects,
+  // namely updating of shared array entries that "point" too far
+  // backwards.  This can occur, for example, when lab allocation is used
+  // in a space covered by the table.)
+  inline HeapWord* block_start(const void* addr);
+  // Same as above, but does not have any of the possible side effects
+  // discussed above.
+  inline HeapWord* block_start_const(const void* addr) const;
 
   // Initialize the threshold to reflect the first boundary after the
   // bottom of the covered region.
@@ -362,19 +227,16 @@
   // never exceeds the "_next_offset_threshold".
   void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
     if (blk_end > _next_offset_threshold) {
-      alloc_block_work1(blk_start, blk_end);
+      alloc_block_work(&_next_offset_threshold, &_next_offset_index, blk_start, blk_end);
     }
   }
   void alloc_block(HeapWord* blk, size_t size) {
     alloc_block(blk, blk+size);
   }
 
-  HeapWord* block_start_unsafe(const void* addr);
-  HeapWord* block_start_unsafe_const(const void* addr) const;
-
   void set_for_starts_humongous(HeapWord* obj_top, size_t fill_size);
 
-  virtual void print_on(outputStream* out) PRODUCT_RETURN;
+  void print_on(outputStream* out) PRODUCT_RETURN;
 };
 
 #endif // SHARE_VM_GC_G1_G1BLOCKOFFSETTABLE_HPP
--- a/src/share/vm/gc/g1/g1BlockOffsetTable.inline.hpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/g1BlockOffsetTable.inline.hpp	Thu Jan 07 16:25:53 2016 +0100
@@ -30,34 +30,36 @@
 #include "gc/shared/memset_with_concurrent_readers.hpp"
 #include "gc/shared/space.hpp"
 
-inline HeapWord* G1BlockOffsetTable::block_start(const void* addr) {
-  if (addr >= _bottom && addr < _end) {
-    return block_start_unsafe(addr);
+inline HeapWord* G1BlockOffsetTablePart::block_start(const void* addr) {
+  if (addr >= _space->bottom() && addr < _space->end()) {
+    HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
+    return forward_to_block_containing_addr(q, addr);
   } else {
     return NULL;
   }
 }
 
-inline HeapWord*
-G1BlockOffsetTable::block_start_const(const void* addr) const {
-  if (addr >= _bottom && addr < _end) {
-    return block_start_unsafe_const(addr);
+inline HeapWord* G1BlockOffsetTablePart::block_start_const(const void* addr) const {
+  if (addr >= _space->bottom() && addr < _space->end()) {
+    HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1);
+    HeapWord* n = q + block_size(q);
+    return forward_to_block_containing_addr_const(q, n, addr);
   } else {
     return NULL;
   }
 }
 
-u_char G1BlockOffsetSharedArray::offset_array(size_t index) const {
+u_char G1BlockOffsetTable::offset_array(size_t index) const {
   check_index(index, "index out of range");
   return _offset_array[index];
 }
 
-void G1BlockOffsetSharedArray::set_offset_array(size_t index, u_char offset) {
+void G1BlockOffsetTable::set_offset_array(size_t index, u_char offset) {
   check_index(index, "index out of range");
   set_offset_array_raw(index, offset);
 }
 
-void G1BlockOffsetSharedArray::set_offset_array(size_t index, HeapWord* high, HeapWord* low) {
+void G1BlockOffsetTable::set_offset_array(size_t index, HeapWord* high, HeapWord* low) {
   check_index(index, "index out of range");
   assert(high >= low, "addresses out of order");
   size_t offset = pointer_delta(high, low);
@@ -65,7 +67,7 @@
   set_offset_array(index, (u_char)offset);
 }
 
-void G1BlockOffsetSharedArray::set_offset_array(size_t left, size_t right, u_char offset) {
+void G1BlockOffsetTable::set_offset_array(size_t left, size_t right, u_char offset) {
   check_index(right, "right index out of range");
   assert(left <= right, "indexes out of order");
   size_t num_cards = right - left + 1;
@@ -73,11 +75,11 @@
 }
 
 // Variant of index_for that does not check the index for validity.
-inline size_t G1BlockOffsetSharedArray::index_for_raw(const void* p) const {
+inline size_t G1BlockOffsetTable::index_for_raw(const void* p) const {
   return pointer_delta((char*)p, _reserved.start(), sizeof(char)) >> LogN;
 }
 
-inline size_t G1BlockOffsetSharedArray::index_for(const void* p) const {
+inline size_t G1BlockOffsetTable::index_for(const void* p) const {
   char* pc = (char*)p;
   assert(pc >= (char*)_reserved.start() &&
          pc <  (char*)_reserved.end(),
@@ -88,8 +90,7 @@
   return result;
 }
 
-inline HeapWord*
-G1BlockOffsetSharedArray::address_for_index(size_t index) const {
+inline HeapWord* G1BlockOffsetTable::address_for_index(size_t index) const {
   check_index(index, "index out of range");
   HeapWord* result = address_for_index_raw(index);
   assert(result >= _reserved.start() && result < _reserved.end(),
@@ -99,47 +100,45 @@
   return result;
 }
 
-inline size_t
-G1BlockOffsetArray::block_size(const HeapWord* p) const {
-  return gsp()->block_size(p);
+inline size_t G1BlockOffsetTablePart::block_size(const HeapWord* p) const {
+  return _space->block_size(p);
 }
 
-inline HeapWord*
-G1BlockOffsetArray::block_at_or_preceding(const void* addr,
-                                          bool has_max_index,
-                                          size_t max_index) const {
-  assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
-  size_t index = _array->index_for(addr);
+inline HeapWord* G1BlockOffsetTablePart::block_at_or_preceding(const void* addr,
+                                                               bool has_max_index,
+                                                               size_t max_index) const {
+  assert(_bot->offset_array(0) == 0, "objects can't cross covered areas");
+  size_t index = _bot->index_for(addr);
   // We must make sure that the offset table entry we use is valid.  If
   // "addr" is past the end, start at the last known one and go forward.
   if (has_max_index) {
     index = MIN2(index, max_index);
   }
-  HeapWord* q = _array->address_for_index(index);
+  HeapWord* q = _bot->address_for_index(index);
 
-  uint offset = _array->offset_array(index);  // Extend u_char to uint.
+  uint offset = _bot->offset_array(index);  // Extend u_char to uint.
   while (offset >= N_words) {
     // The excess of the offset from N_words indicates a power of Base
     // to go back by.
     size_t n_cards_back = BlockOffsetArray::entry_to_cards_back(offset);
     q -= (N_words * n_cards_back);
     index -= n_cards_back;
-    offset = _array->offset_array(index);
+    offset = _bot->offset_array(index);
   }
   assert(offset < N_words, "offset too large");
   q -= offset;
   return q;
 }
 
-inline HeapWord*
-G1BlockOffsetArray::
-forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,
-                                       const void* addr) const {
-  if (addr >= gsp()->top()) return gsp()->top();
+inline HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,
+                                                                                const void* addr) const {
+  if (addr >= _space->top()) return _space->top();
   while (n <= addr) {
     q = n;
     oop obj = oop(q);
-    if (obj->klass_or_null() == NULL) return q;
+    if (obj->klass_or_null() == NULL) {
+      return q;
+    }
     n += block_size(q);
   }
   assert(q <= n, "wrong order for q and addr");
@@ -147,10 +146,11 @@
   return q;
 }
 
-inline HeapWord*
-G1BlockOffsetArray::forward_to_block_containing_addr(HeapWord* q,
-                                                     const void* addr) {
-  if (oop(q)->klass_or_null() == NULL) return q;
+inline HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr(HeapWord* q,
+                                                                          const void* addr) {
+  if (oop(q)->klass_or_null() == NULL) {
+    return q;
+  }
   HeapWord* n = q + block_size(q);
   // In the normal case, where the query "addr" is a card boundary, and the
   // offset table chunks are the same size as cards, the block starting at
--- a/src/share/vm/gc/g1/g1CollectedHeap.cpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/g1CollectedHeap.cpp	Thu Jan 07 16:25:53 2016 +0100
@@ -1745,7 +1745,7 @@
   _is_alive_closure_stw(this),
   _ref_processor_cm(NULL),
   _ref_processor_stw(NULL),
-  _bot_shared(NULL),
+  _bot(NULL),
   _cg1r(NULL),
   _g1mm(NULL),
   _refine_cte_cl(NULL),
@@ -1906,8 +1906,8 @@
   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
   G1RegionToSpaceMapper* bot_storage =
     create_aux_memory_mapper("Block offset table",
-                             G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
-                             G1BlockOffsetSharedArray::heap_map_factor());
+                             G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
+                             G1BlockOffsetTable::heap_map_factor());
 
   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
   G1RegionToSpaceMapper* cardtable_storage =
@@ -1945,7 +1945,7 @@
 
   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
 
-  _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
+  _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
 
   {
     HeapWord* start = _hrm.reserved().start();
--- a/src/share/vm/gc/g1/g1CollectedHeap.hpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/g1CollectedHeap.hpp	Thu Jan 07 16:25:53 2016 +0100
@@ -154,7 +154,7 @@
   uint _expansion_regions;
 
   // The block offset table for the G1 heap.
-  G1BlockOffsetSharedArray* _bot_shared;
+  G1BlockOffsetTable* _bot;
 
   // Tears down the region sets / lists so that they are empty and the
   // regions on the heap do not belong to a region set / list. The
@@ -1008,7 +1008,7 @@
   void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
 
   // The shared block offset table array.
-  G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
+  G1BlockOffsetTable* bot() const { return _bot; }
 
   // Reference Processing accessors
 
--- a/src/share/vm/gc/g1/g1CollectedHeap_ext.cpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/g1CollectedHeap_ext.cpp	Thu Jan 07 16:25:53 2016 +0100
@@ -36,5 +36,5 @@
 
 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
                                              MemRegion mr) {
-  return new HeapRegion(hrs_index, bot_shared(), mr);
+  return new HeapRegion(hrs_index, bot(), mr);
 }
--- a/src/share/vm/gc/g1/g1RemSet.cpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/g1RemSet.cpp	Thu Jan 07 16:25:53 2016 +0100
@@ -97,7 +97,7 @@
   _worker_i(worker_i),
   _try_claimed(false) {
   _g1h = G1CollectedHeap::heap();
-  _bot_shared = _g1h->bot_shared();
+  _bot = _g1h->bot();
   _ct_bs = _g1h->g1_barrier_set();
   _block_size = MAX2<size_t>(G1RSetScanBlockSize, 1);
 }
@@ -109,7 +109,7 @@
 
   // Set the "from" region in the closure.
   _oc->set_region(r);
-  MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words);
+  MemRegion card_region(_bot->address_for_index(index), G1BlockOffsetTable::N_words);
   MemRegion pre_gc_allocated(r->bottom(), r->scan_top());
   MemRegion mr = pre_gc_allocated.intersection(card_region);
   if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
@@ -153,7 +153,7 @@
       jump_to_card = hrrs->iter_claimed_next(_block_size);
     }
     if (current_card < jump_to_card) continue;
-    HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
+    HeapWord* card_start = _g1h->bot()->address_for_index(card_index);
 
     HeapRegion* card_region = _g1h->heap_region_containing(card_start);
     _cards++;
--- a/src/share/vm/gc/g1/g1RemSet.hpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/g1RemSet.hpp	Thu Jan 07 16:25:53 2016 +0100
@@ -36,7 +36,7 @@
 
 class BitMap;
 class CardTableModRefBS;
-class G1BlockOffsetSharedArray;
+class G1BlockOffsetTable;
 class ConcurrentG1Refine;
 class CodeBlobClosure;
 class G1CollectedHeap;
@@ -171,7 +171,7 @@
   G1ParPushHeapRSClosure* _oc;
   CodeBlobClosure* _code_root_cl;
 
-  G1BlockOffsetSharedArray* _bot_shared;
+  G1BlockOffsetTable* _bot;
   G1SATBCardTableModRefBS *_ct_bs;
 
   double _strong_code_root_scan_time_sec;
--- a/src/share/vm/gc/g1/heapRegion.cpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/heapRegion.cpp	Thu Jan 07 16:25:53 2016 +0100
@@ -153,7 +153,7 @@
 }
 
 void HeapRegion::reset_after_compaction() {
-  G1OffsetTableContigSpace::reset_after_compaction();
+  G1ContiguousSpace::reset_after_compaction();
   // After a compaction the mark bitmap is invalid, so we must
   // treat all objects as being inside the unmarked area.
   zero_marked_bytes();
@@ -183,7 +183,6 @@
   }
   zero_marked_bytes();
 
-  _offsets.resize(HeapRegion::GrainWords);
   init_top_at_mark_start();
   if (clear_space) clear(SpaceDecorator::Mangle);
 }
@@ -219,7 +218,7 @@
   _type.set_starts_humongous();
   _humongous_start_region = this;
 
-  _offsets.set_for_starts_humongous(obj_top, fill_size);
+  _bot_part.set_for_starts_humongous(obj_top, fill_size);
 }
 
 void HeapRegion::set_continues_humongous(HeapRegion* first_hr) {
@@ -239,9 +238,9 @@
 }
 
 HeapRegion::HeapRegion(uint hrm_index,
-                       G1BlockOffsetSharedArray* sharedOffsetArray,
+                       G1BlockOffsetTable* bot,
                        MemRegion mr) :
-    G1OffsetTableContigSpace(sharedOffsetArray, mr),
+    G1ContiguousSpace(bot),
     _hrm_index(hrm_index),
     _allocation_context(AllocationContext::system()),
     _humongous_start_region(NULL),
@@ -257,7 +256,7 @@
     _rem_set(NULL), _recorded_rs_length(0), _predicted_elapsed_time_ms(0),
     _predicted_bytes_to_copy(0)
 {
-  _rem_set = new HeapRegionRemSet(sharedOffsetArray, this);
+  _rem_set = new HeapRegionRemSet(bot, this);
 
   initialize(mr);
 }
@@ -265,7 +264,7 @@
 void HeapRegion::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
   assert(_rem_set->is_empty(), "Remembered set must be empty");
 
-  G1OffsetTableContigSpace::initialize(mr, clear_space, mangle_space);
+  G1ContiguousSpace::initialize(mr, clear_space, mangle_space);
 
   hr_clear(false /*par*/, false /*clear_space*/);
   set_top(bottom());
@@ -773,7 +772,7 @@
   }
 
   if (!is_young() && !is_empty()) {
-    _offsets.verify();
+    _bot_part.verify();
   }
 
   if (is_region_humongous) {
@@ -797,7 +796,7 @@
   if (p < the_end) {
     // Look up top
     HeapWord* addr_1 = p;
-    HeapWord* b_start_1 = _offsets.block_start_const(addr_1);
+    HeapWord* b_start_1 = _bot_part.block_start_const(addr_1);
     if (b_start_1 != p) {
       log_info(gc, verify)("BOT look up for top: " PTR_FORMAT " "
                            " yielded " PTR_FORMAT ", expecting " PTR_FORMAT,
@@ -809,7 +808,7 @@
     // Look up top + 1
     HeapWord* addr_2 = p + 1;
     if (addr_2 < the_end) {
-      HeapWord* b_start_2 = _offsets.block_start_const(addr_2);
+      HeapWord* b_start_2 = _bot_part.block_start_const(addr_2);
       if (b_start_2 != p) {
         log_info(gc, verify)("BOT look up for top + 1: " PTR_FORMAT " "
                              " yielded " PTR_FORMAT ", expecting " PTR_FORMAT,
@@ -823,7 +822,7 @@
     size_t diff = pointer_delta(the_end, p) / 2;
     HeapWord* addr_3 = p + diff;
     if (addr_3 < the_end) {
-      HeapWord* b_start_3 = _offsets.block_start_const(addr_3);
+      HeapWord* b_start_3 = _bot_part.block_start_const(addr_3);
       if (b_start_3 != p) {
         log_info(gc, verify)("BOT look up for top + diff: " PTR_FORMAT " "
                              " yielded " PTR_FORMAT ", expecting " PTR_FORMAT,
@@ -835,7 +834,7 @@
 
     // Look up end - 1
     HeapWord* addr_4 = the_end - 1;
-    HeapWord* b_start_4 = _offsets.block_start_const(addr_4);
+    HeapWord* b_start_4 = _bot_part.block_start_const(addr_4);
     if (b_start_4 != p) {
       log_info(gc, verify)("BOT look up for end - 1: " PTR_FORMAT " "
                            " yielded " PTR_FORMAT ", expecting " PTR_FORMAT,
@@ -860,52 +859,41 @@
 // G1OffsetTableContigSpace code; copied from space.cpp.  Hope this can go
 // away eventually.
 
-void G1OffsetTableContigSpace::clear(bool mangle_space) {
+void G1ContiguousSpace::clear(bool mangle_space) {
   set_top(bottom());
   _scan_top = bottom();
   CompactibleSpace::clear(mangle_space);
   reset_bot();
 }
 
-void G1OffsetTableContigSpace::set_bottom(HeapWord* new_bottom) {
-  Space::set_bottom(new_bottom);
-  _offsets.set_bottom(new_bottom);
-}
-
-void G1OffsetTableContigSpace::set_end(HeapWord* new_end) {
-  assert(new_end == _bottom + HeapRegion::GrainWords, "set_end should only ever be set to _bottom + HeapRegion::GrainWords");
-  Space::set_end(new_end);
-  _offsets.resize(new_end - bottom());
-}
-
 #ifndef PRODUCT
-void G1OffsetTableContigSpace::mangle_unused_area() {
+void G1ContiguousSpace::mangle_unused_area() {
   mangle_unused_area_complete();
 }
 
-void G1OffsetTableContigSpace::mangle_unused_area_complete() {
+void G1ContiguousSpace::mangle_unused_area_complete() {
   SpaceMangler::mangle_region(MemRegion(top(), end()));
 }
 #endif
 
-void G1OffsetTableContigSpace::print() const {
+void G1ContiguousSpace::print() const {
   print_short();
   tty->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", "
                 INTPTR_FORMAT ", " INTPTR_FORMAT ")",
-                p2i(bottom()), p2i(top()), p2i(_offsets.threshold()), p2i(end()));
+                p2i(bottom()), p2i(top()), p2i(_bot_part.threshold()), p2i(end()));
 }
 
-HeapWord* G1OffsetTableContigSpace::initialize_threshold() {
-  return _offsets.initialize_threshold();
+HeapWord* G1ContiguousSpace::initialize_threshold() {
+  return _bot_part.initialize_threshold();
 }
 
-HeapWord* G1OffsetTableContigSpace::cross_threshold(HeapWord* start,
+HeapWord* G1ContiguousSpace::cross_threshold(HeapWord* start,
                                                     HeapWord* end) {
-  _offsets.alloc_block(start, end);
-  return _offsets.threshold();
+  _bot_part.alloc_block(start, end);
+  return _bot_part.threshold();
 }
 
-HeapWord* G1OffsetTableContigSpace::scan_top() const {
+HeapWord* G1ContiguousSpace::scan_top() const {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   HeapWord* local_top = top();
   OrderAccess::loadload();
@@ -918,7 +906,7 @@
   }
 }
 
-void G1OffsetTableContigSpace::record_timestamp() {
+void G1ContiguousSpace::record_timestamp() {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   unsigned curr_gc_time_stamp = g1h->get_gc_time_stamp();
 
@@ -935,17 +923,17 @@
   }
 }
 
-void G1OffsetTableContigSpace::record_retained_region() {
+void G1ContiguousSpace::record_retained_region() {
   // scan_top is the maximum address where it's safe for the next gc to
   // scan this region.
   _scan_top = top();
 }
 
-void G1OffsetTableContigSpace::safe_object_iterate(ObjectClosure* blk) {
+void G1ContiguousSpace::safe_object_iterate(ObjectClosure* blk) {
   object_iterate(blk);
 }
 
-void G1OffsetTableContigSpace::object_iterate(ObjectClosure* blk) {
+void G1ContiguousSpace::object_iterate(ObjectClosure* blk) {
   HeapWord* p = bottom();
   while (p < top()) {
     if (block_is_obj(p)) {
@@ -955,17 +943,14 @@
   }
 }
 
-G1OffsetTableContigSpace::
-G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
-                         MemRegion mr) :
-  _offsets(sharedOffsetArray, mr),
+G1ContiguousSpace::G1ContiguousSpace(G1BlockOffsetTable* bot) :
+  _bot_part(bot, this),
   _par_alloc_lock(Mutex::leaf, "OffsetTableContigSpace par alloc lock", true),
   _gc_time_stamp(0)
 {
-  _offsets.set_space(this);
 }
 
-void G1OffsetTableContigSpace::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
+void G1ContiguousSpace::initialize(MemRegion mr, bool clear_space, bool mangle_space) {
   CompactibleSpace::initialize(mr, clear_space, mangle_space);
   _top = bottom();
   _scan_top = bottom();
--- a/src/share/vm/gc/g1/heapRegion.hpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/heapRegion.hpp	Thu Jan 07 16:25:53 2016 +0100
@@ -115,12 +115,12 @@
 // The time stamps are re-initialized to zero at cleanup and at Full GCs.
 // The current scheme that uses sequential unsigned ints will fail only if we have 4b
 // evacuation pauses between two cleanups, which is _highly_ unlikely.
-class G1OffsetTableContigSpace: public CompactibleSpace {
+class G1ContiguousSpace: public CompactibleSpace {
   friend class VMStructs;
   HeapWord* volatile _top;
   HeapWord* volatile _scan_top;
  protected:
-  G1BlockOffsetArrayContigSpace _offsets;
+  G1BlockOffsetTablePart _bot_part;
   Mutex _par_alloc_lock;
   volatile unsigned _gc_time_stamp;
   // When we need to retire an allocation region, while other threads
@@ -132,14 +132,13 @@
   HeapWord* _pre_dummy_top;
 
  public:
-  G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
-                           MemRegion mr);
+  G1ContiguousSpace(G1BlockOffsetTable* bot);
 
   void set_top(HeapWord* value) { _top = value; }
   HeapWord* top() const { return _top; }
 
  protected:
-  // Reset the G1OffsetTableContigSpace.
+  // Reset the G1ContiguousSpace.
   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 
   HeapWord* volatile* top_addr() { return &_top; }
@@ -167,9 +166,6 @@
   void object_iterate(ObjectClosure* blk);
   void safe_object_iterate(ObjectClosure* blk);
 
-  void set_bottom(HeapWord* value);
-  void set_end(HeapWord* value);
-
   void mangle_unused_area() PRODUCT_RETURN;
   void mangle_unused_area_complete() PRODUCT_RETURN;
 
@@ -213,15 +209,15 @@
   virtual void print() const;
 
   void reset_bot() {
-    _offsets.reset_bot();
+    _bot_part.reset_bot();
   }
 
   void print_bot_on(outputStream* out) {
-    _offsets.print_on(out);
+    _bot_part.print_on(out);
   }
 };
 
-class HeapRegion: public G1OffsetTableContigSpace {
+class HeapRegion: public G1ContiguousSpace {
   friend class VMStructs;
   // Allow scan_and_forward to call (private) overrides for auxiliary functions on this class
   template <typename SpaceType>
@@ -233,8 +229,6 @@
   // issues.)
   HeapRegionRemSet* _rem_set;
 
-  G1BlockOffsetArrayContigSpace* offsets() { return &_offsets; }
-
   // Auxiliary functions for scan_and_forward support.
   // See comments for CompactibleSpace for more information.
   inline HeapWord* scan_limit() const {
@@ -330,7 +324,7 @@
 
  public:
   HeapRegion(uint hrm_index,
-             G1BlockOffsetSharedArray* sharedOffsetArray,
+             G1BlockOffsetTable* bot,
              MemRegion mr);
 
   // Initializing the HeapRegion not only resets the data structure, but also
--- a/src/share/vm/gc/g1/heapRegion.inline.hpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/heapRegion.inline.hpp	Thu Jan 07 16:25:53 2016 +0100
@@ -32,9 +32,9 @@
 #include "oops/oop.inline.hpp"
 #include "runtime/atomic.inline.hpp"
 
-inline HeapWord* G1OffsetTableContigSpace::allocate_impl(size_t min_word_size,
-                                                         size_t desired_word_size,
-                                                         size_t* actual_size) {
+inline HeapWord* G1ContiguousSpace::allocate_impl(size_t min_word_size,
+                                                  size_t desired_word_size,
+                                                  size_t* actual_size) {
   HeapWord* obj = top();
   size_t available = pointer_delta(end(), obj);
   size_t want_to_allocate = MIN2(available, desired_word_size);
@@ -49,9 +49,9 @@
   }
 }
 
-inline HeapWord* G1OffsetTableContigSpace::par_allocate_impl(size_t min_word_size,
-                                                             size_t desired_word_size,
-                                                             size_t* actual_size) {
+inline HeapWord* G1ContiguousSpace::par_allocate_impl(size_t min_word_size,
+                                                      size_t desired_word_size,
+                                                      size_t* actual_size) {
   do {
     HeapWord* obj = top();
     size_t available = pointer_delta(end(), obj);
@@ -73,22 +73,22 @@
   } while (true);
 }
 
-inline HeapWord* G1OffsetTableContigSpace::allocate(size_t min_word_size,
-                                                    size_t desired_word_size,
-                                                    size_t* actual_size) {
+inline HeapWord* G1ContiguousSpace::allocate(size_t min_word_size,
+                                             size_t desired_word_size,
+                                             size_t* actual_size) {
   HeapWord* res = allocate_impl(min_word_size, desired_word_size, actual_size);
   if (res != NULL) {
-    _offsets.alloc_block(res, *actual_size);
+    _bot_part.alloc_block(res, *actual_size);
   }
   return res;
 }
 
-inline HeapWord* G1OffsetTableContigSpace::allocate(size_t word_size) {
+inline HeapWord* G1ContiguousSpace::allocate(size_t word_size) {
   size_t temp;
   return allocate(word_size, word_size, &temp);
 }
 
-inline HeapWord* G1OffsetTableContigSpace::par_allocate(size_t word_size) {
+inline HeapWord* G1ContiguousSpace::par_allocate(size_t word_size) {
   size_t temp;
   return par_allocate(word_size, word_size, &temp);
 }
@@ -96,20 +96,20 @@
 // Because of the requirement of keeping "_offsets" up to date with the
 // allocations, we sequentialize these with a lock.  Therefore, best if
 // this is used for larger LAB allocations only.
-inline HeapWord* G1OffsetTableContigSpace::par_allocate(size_t min_word_size,
-                                                        size_t desired_word_size,
-                                                        size_t* actual_size) {
+inline HeapWord* G1ContiguousSpace::par_allocate(size_t min_word_size,
+                                                 size_t desired_word_size,
+                                                 size_t* actual_size) {
   MutexLocker x(&_par_alloc_lock);
   return allocate(min_word_size, desired_word_size, actual_size);
 }
 
-inline HeapWord* G1OffsetTableContigSpace::block_start(const void* p) {
-  return _offsets.block_start(p);
+inline HeapWord* G1ContiguousSpace::block_start(const void* p) {
+  return _bot_part.block_start(p);
 }
 
 inline HeapWord*
-G1OffsetTableContigSpace::block_start_const(const void* p) const {
-  return _offsets.block_start_const(p);
+G1ContiguousSpace::block_start_const(const void* p) const {
+  return _bot_part.block_start_const(p);
 }
 
 inline bool
--- a/src/share/vm/gc/g1/heapRegionRemSet.cpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/heapRegionRemSet.cpp	Thu Jan 07 16:25:53 2016 +0100
@@ -687,9 +687,9 @@
   _sparse_table.do_cleanup_work(hrrs_cleanup_task);
 }
 
-HeapRegionRemSet::HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
+HeapRegionRemSet::HeapRegionRemSet(G1BlockOffsetTable* bot,
                                    HeapRegion* hr)
-  : _bosa(bosa),
+  : _bot(bot),
     _m(Mutex::leaf, FormatBuffer<128>("HeapRegionRemSet lock #%u", hr->hrm_index()), true, Monitor::_safepoint_check_never),
     _code_roots(), _other_regions(hr, &_m), _iter_state(Unclaimed), _iter_claimed(0) {
   reset_for_par_iteration();
@@ -728,8 +728,7 @@
   HeapRegionRemSetIterator iter(this);
   size_t card_index;
   while (iter.has_next(card_index)) {
-    HeapWord* card_start =
-      G1CollectedHeap::heap()->bot_shared()->address_for_index(card_index);
+    HeapWord* card_start = _bot->address_for_index(card_index);
     tty->print_cr("  Card " PTR_FORMAT, p2i(card_start));
   }
   if (iter.n_yielded() != occupied()) {
@@ -825,7 +824,7 @@
   _hrrs(hrrs),
   _g1h(G1CollectedHeap::heap()),
   _coarse_map(&hrrs->_other_regions._coarse_map),
-  _bosa(hrrs->_bosa),
+  _bot(hrrs->_bot),
   _is(Sparse),
   // Set these values so that we increment to the first region.
   _coarse_cur_region_index(-1),
@@ -852,7 +851,7 @@
       _coarse_cur_region_cur_card = 0;
       HeapWord* r_bot =
         _g1h->region_at((uint) _coarse_cur_region_index)->bottom();
-      _cur_region_card_offset = _bosa->index_for(r_bot);
+      _cur_region_card_offset = _bot->index_for(r_bot);
     } else {
       return false;
     }
@@ -893,7 +892,7 @@
   _fine_cur_prt = prt;
 
   HeapWord* r_bot = _fine_cur_prt->hr()->bottom();
-  _cur_region_card_offset = _bosa->index_for(r_bot);
+  _cur_region_card_offset = _bot->index_for(r_bot);
 
   // The bitmap scan for the PRT always scans from _cur_region_cur_card + 1.
   // To avoid special-casing this start case, and not miss the first bitmap
@@ -1001,7 +1000,7 @@
   size_t card_index;
   while (iter.has_next(card_index)) {
     HeapWord* card_start =
-      G1CollectedHeap::heap()->bot_shared()->address_for_index(card_index);
+      G1CollectedHeap::heap()->bot()->address_for_index(card_index);
     tty->print_cr("  Card " PTR_FORMAT ".", p2i(card_start));
     sum++;
   }
--- a/src/share/vm/gc/g1/heapRegionRemSet.hpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/heapRegionRemSet.hpp	Thu Jan 07 16:25:53 2016 +0100
@@ -34,7 +34,7 @@
 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
 
 class G1CollectedHeap;
-class G1BlockOffsetSharedArray;
+class G1BlockOffsetTable;
 class HeapRegion;
 class HeapRegionRemSetIterator;
 class PerRegionTable;
@@ -174,7 +174,7 @@
   friend class HeapRegionRemSetIterator;
 
 private:
-  G1BlockOffsetSharedArray* _bosa;
+  G1BlockOffsetTable* _bot;
 
   // A set of code blobs (nmethods) whose code contains pointers into
   // the region that owns this RSet.
@@ -189,7 +189,7 @@
   volatile size_t _iter_claimed;
 
 public:
-  HeapRegionRemSet(G1BlockOffsetSharedArray* bosa, HeapRegion* hr);
+  HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
 
   static void setup_remset_size();
 
@@ -350,7 +350,7 @@
   // Local caching of HRRS fields.
   const BitMap*             _coarse_map;
 
-  G1BlockOffsetSharedArray* _bosa;
+  G1BlockOffsetTable*       _bot;
   G1CollectedHeap*          _g1h;
 
   // The number of cards yielded since initialization.
--- a/src/share/vm/gc/g1/heapRegionSet.cpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/heapRegionSet.cpp	Thu Jan 07 16:25:53 2016 +0100
@@ -381,17 +381,17 @@
   MemRegion heap(NULL, num_regions_in_test * HeapRegion::GrainWords);
   // Allocate a fake BOT because the HeapRegion constructor initializes
   // the BOT.
-  size_t bot_size = G1BlockOffsetSharedArray::compute_size(heap.word_size());
+  size_t bot_size = G1BlockOffsetTable::compute_size(heap.word_size());
   HeapWord* bot_data = NEW_C_HEAP_ARRAY(HeapWord, bot_size, mtGC);
-  ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(heap.word_size()));
+  ReservedSpace bot_rs(G1BlockOffsetTable::compute_size(heap.word_size()));
   G1RegionToSpaceMapper* bot_storage =
     G1RegionToSpaceMapper::create_mapper(bot_rs,
                                          bot_rs.size(),
                                          os::vm_page_size(),
                                          HeapRegion::GrainBytes,
-                                         G1BlockOffsetSharedArray::N_bytes,
+                                         G1BlockOffsetTable::N_bytes,
                                          mtGC);
-  G1BlockOffsetSharedArray oa(heap, bot_storage);
+  G1BlockOffsetTable bot(heap, bot_storage);
   bot_storage->commit_regions(0, num_regions_in_test);
 
   // Set up memory regions for the heap regions.
@@ -401,11 +401,11 @@
   MemRegion mr3(mr2.end(), HeapRegion::GrainWords);
   MemRegion mr4(mr3.end(), HeapRegion::GrainWords);
 
-  HeapRegion hr0(0, &oa, mr0);
-  HeapRegion hr1(1, &oa, mr1);
-  HeapRegion hr2(2, &oa, mr2);
-  HeapRegion hr3(3, &oa, mr3);
-  HeapRegion hr4(4, &oa, mr4);
+  HeapRegion hr0(0, &bot, mr0);
+  HeapRegion hr1(1, &bot, mr1);
+  HeapRegion hr2(2, &bot, mr2);
+  HeapRegion hr3(3, &bot, mr3);
+  HeapRegion hr4(4, &bot, mr4);
   l.add_ordered(&hr1);
   l.add_ordered(&hr0);
   l.add_ordered(&hr3);
--- a/src/share/vm/gc/g1/vmStructs_g1.hpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/g1/vmStructs_g1.hpp	Thu Jan 07 16:25:53 2016 +0100
@@ -35,7 +35,7 @@
   static_field(HeapRegion, GrainBytes,        size_t)                         \
   static_field(HeapRegion, LogOfHRGrainBytes, int)                            \
                                                                               \
-  nonstatic_field(G1OffsetTableContigSpace, _top,       HeapWord* volatile)   \
+  nonstatic_field(G1ContiguousSpace, _top,              HeapWord* volatile)   \
                                                                               \
   nonstatic_field(G1HeapRegionTable, _base,             address)              \
   nonstatic_field(G1HeapRegionTable, _length,           size_t)               \
@@ -96,8 +96,8 @@
                                                                               \
   declare_type(G1CollectedHeap, CollectedHeap)                                \
                                                                               \
-  declare_type(G1OffsetTableContigSpace, CompactibleSpace)                    \
-  declare_type(HeapRegion, G1OffsetTableContigSpace)                          \
+  declare_type(G1ContiguousSpace, CompactibleSpace)                           \
+  declare_type(HeapRegion, G1ContiguousSpace)                                 \
   declare_toplevel_type(HeapRegionManager)                                    \
   declare_toplevel_type(HeapRegionSetBase)                                    \
   declare_toplevel_type(G1MonitoringSupport)                                  \
--- a/src/share/vm/gc/shared/blockOffsetTable.hpp	Thu Jan 07 14:55:12 2016 +0100
+++ b/src/share/vm/gc/shared/blockOffsetTable.hpp	Thu Jan 07 16:25:53 2016 +0100
@@ -248,7 +248,7 @@
 //////////////////////////////////////////////////////////////////////////
 class BlockOffsetArray: public BlockOffsetTable {
   friend class VMStructs;
-  friend class G1BlockOffsetArray; // temp. until we restructure and cleanup
+  friend class G1BlockOffsetTablePart; // temp. until we restructure and cleanup
  protected:
   // The following enums are used by do_block_internal() below
   enum Action {