diff --git a/src/spaces.h b/src/spaces.h
index b614c3b..f156496 100644
--- a/src/spaces.h
+++ b/src/spaces.h
@@ -29,7 +29,6 @@
 #define V8_SPACES_H_
 
 #include "allocation.h"
-#include "hashmap.h"
 #include "list.h"
 #include "log.h"
 
@@ -50,47 +49,45 @@
 //
 // The semispaces of the young generation are contiguous.  The old and map
 // spaces consists of a list of pages. A page has a page header and an object
-// area.
+// area. A page size is deliberately chosen as 8K bytes.
+// The first word of a page is an opaque page header that has the
+// address of the next page and its ownership information. The second word may
+// have the allocation top address of this page. Heap objects are aligned to the
+// pointer size.
 //
 // There is a separate large object space for objects larger than
 // Page::kMaxHeapObjectSize, so that they do not have to move during
 // collection. The large object space is paged. Pages in large object space
-// may be larger than the page size.
+// may be larger than 8K.
 //
-// A store-buffer based write barrier is used to keep track of intergenerational
-// references.  See store-buffer.h.
+// A card marking write barrier is used to keep track of intergenerational
+// references. Old space pages are divided into regions of Page::kRegionSize
+// size. Each region has a corresponding dirty bit in the page header which is
+// set if the region might contain pointers to new space. For details about
+// dirty bits encoding see comments in the Page::GetRegionNumberForAddress()
+// method body.
 //
-// During scavenges and mark-sweep collections we sometimes (after a store
-// buffer overflow) iterate intergenerational pointers without decoding heap
-// object maps so if the page belongs to old pointer space or large object
-// space it is essential to guarantee that the page does not contain any
-// garbage pointers to new space: every pointer aligned word which satisfies
-// the Heap::InNewSpace() predicate must be a pointer to a live heap object in
-// new space. Thus objects in old pointer and large object spaces should have a
-// special layout (e.g. no bare integer fields). This requirement does not
-// apply to map space which is iterated in a special fashion. However we still
-// require pointer fields of dead maps to be cleaned.
+// During scavenges and mark-sweep collections we iterate intergenerational
+// pointers without decoding heap object maps so if the page belongs to old
+// pointer space or large object space it is essential to guarantee that
+// the page does not contain any garbage pointers to new space: every pointer
+// aligned word which satisfies the Heap::InNewSpace() predicate must be a
+// pointer to a live heap object in new space. Thus objects in old pointer
+// and large object spaces should have a special layout (e.g. no bare integer
+// fields). This requirement does not apply to map space which is iterated in
+// a special fashion. However we still require pointer fields of dead maps to
+// be cleaned.
 //
-// To enable lazy cleaning of old space pages we can mark chunks of the page
-// as being garbage.  Garbage sections are marked with a special map.  These
-// sections are skipped when scanning the page, even if we are otherwise
-// scanning without regard for object boundaries.  Garbage sections are chained
-// together to form a free list after a GC.  Garbage sections created outside
-// of GCs by object trunctation etc. may not be in the free list chain.  Very
-// small free spaces are ignored, they need only be cleaned of bogus pointers
-// into new space.
+// To enable lazy cleaning of old space pages we use a notion of allocation
+// watermark. Every pointer under watermark is considered to be well formed.
+// Page allocation watermark is not necessarily equal to page allocation top but
+// all alive objects on page should reside under allocation watermark.
+// During scavenge allocation watermark might be bumped and invalid pointers
+// might appear below it. To avoid following them we store a valid watermark
+// into special field in the page header and set a page WATERMARK_INVALIDATED
+// flag. For details see comments in the Page::SetAllocationWatermark() method
+// body.
 //
-// Each page may have up to one special garbage section.  The start of this
-// section is denoted by the top field in the space.  The end of the section
-// is denoted by the limit field in the space.  This special garbage section
-// is not marked with a free space map in the data.  The point of this section
-// is to enable linear allocation without having to constantly update the byte
-// array every time the top field is updated and a new object is created.  The
-// special garbage section is not in the chain of garbage sections.
-//
-// Since the top and limit fields are in the space, not the page, only one page
-// has a special garbage section, and if the top and limit are equal then there
-// is no special garbage section.
 
 // Some assertion macros used in the debugging mode.
 
@@ -104,7 +101,7 @@
   ASSERT((OffsetFrom(address) & kMapAlignmentMask) == 0)
 
 #define ASSERT_OBJECT_SIZE(size)                                               \
-  ASSERT((0 < size) && (size <= Page::kMaxNonCodeHeapObjectSize))
+  ASSERT((0 < size) && (size <= Page::kMaxHeapObjectSize))
 
 #define ASSERT_PAGE_OFFSET(offset)                                             \
   ASSERT((Page::kObjectStartOffset <= offset)                                  \
@@ -117,540 +114,30 @@
 class PagedSpace;
 class MemoryAllocator;
 class AllocationInfo;
-class Space;
-class FreeList;
-class MemoryChunk;
-
-class MarkBit {
- public:
-  typedef uint32_t CellType;
-
-  inline MarkBit(CellType* cell, CellType mask, bool data_only)
-      : cell_(cell), mask_(mask), data_only_(data_only) { }
-
-  inline CellType* cell() { return cell_; }
-  inline CellType mask() { return mask_; }
-
-#ifdef DEBUG
-  bool operator==(const MarkBit& other) {
-    return cell_ == other.cell_ && mask_ == other.mask_;
-  }
-#endif
-
-  inline void Set() { *cell_ |= mask_; }
-  inline bool Get() { return (*cell_ & mask_) != 0; }
-  inline void Clear() { *cell_ &= ~mask_; }
-
-  inline bool data_only() { return data_only_; }
-
-  inline MarkBit Next() {
-    CellType new_mask = mask_ << 1;
-    if (new_mask == 0) {
-      return MarkBit(cell_ + 1, 1, data_only_);
-    } else {
-      return MarkBit(cell_, new_mask, data_only_);
-    }
-  }
-
- private:
-  CellType* cell_;
-  CellType mask_;
-  // This boolean indicates that the object is in a data-only space with no
-  // pointers.  This enables some optimizations when marking.
-  // It is expected that this field is inlined and turned into control flow
-  // at the place where the MarkBit object is created.
-  bool data_only_;
-};
-
-
-// Bitmap is a sequence of cells each containing fixed number of bits.
-class Bitmap {
- public:
-  static const uint32_t kBitsPerCell = 32;
-  static const uint32_t kBitsPerCellLog2 = 5;
-  static const uint32_t kBitIndexMask = kBitsPerCell - 1;
-  static const uint32_t kBytesPerCell = kBitsPerCell / kBitsPerByte;
-  static const uint32_t kBytesPerCellLog2 = kBitsPerCellLog2 - kBitsPerByteLog2;
-
-  static const size_t kLength =
-    (1 << kPageSizeBits) >> (kPointerSizeLog2);
-
-  static const size_t kSize =
-    (1 << kPageSizeBits) >> (kPointerSizeLog2 + kBitsPerByteLog2);
-
-
-  static int CellsForLength(int length) {
-    return (length + kBitsPerCell - 1) >> kBitsPerCellLog2;
-  }
-
-  int CellsCount() {
-    return CellsForLength(kLength);
-  }
-
-  static int SizeFor(int cells_count) {
-    return sizeof(MarkBit::CellType) * cells_count;
-  }
-
-  INLINE(static uint32_t IndexToCell(uint32_t index)) {
-    return index >> kBitsPerCellLog2;
-  }
-
-  INLINE(static uint32_t CellToIndex(uint32_t index)) {
-    return index << kBitsPerCellLog2;
-  }
-
-  INLINE(static uint32_t CellAlignIndex(uint32_t index)) {
-    return (index + kBitIndexMask) & ~kBitIndexMask;
-  }
-
-  INLINE(MarkBit::CellType* cells()) {
-    return reinterpret_cast<MarkBit::CellType*>(this);
-  }
-
-  INLINE(Address address()) {
-    return reinterpret_cast<Address>(this);
-  }
-
-  INLINE(static Bitmap* FromAddress(Address addr)) {
-    return reinterpret_cast<Bitmap*>(addr);
-  }
-
-  inline MarkBit MarkBitFromIndex(uint32_t index, bool data_only = false) {
-    MarkBit::CellType mask = 1 << (index & kBitIndexMask);
-    MarkBit::CellType* cell = this->cells() + (index >> kBitsPerCellLog2);
-    return MarkBit(cell, mask, data_only);
-  }
-
-  static inline void Clear(MemoryChunk* chunk);
-
-  static void PrintWord(uint32_t word, uint32_t himask = 0) {
-    for (uint32_t mask = 1; mask != 0; mask <<= 1) {
-      if ((mask & himask) != 0) PrintF("[");
-      PrintF((mask & word) ? "1" : "0");
-      if ((mask & himask) != 0) PrintF("]");
-    }
-  }
-
-  class CellPrinter {
-   public:
-    CellPrinter() : seq_start(0), seq_type(0), seq_length(0) { }
-
-    void Print(uint32_t pos, uint32_t cell) {
-      if (cell == seq_type) {
-        seq_length++;
-        return;
-      }
-
-      Flush();
-
-      if (IsSeq(cell)) {
-        seq_start = pos;
-        seq_length = 0;
-        seq_type = cell;
-        return;
-      }
-
-      PrintF("%d: ", pos);
-      PrintWord(cell);
-      PrintF("\n");
-    }
-
-    void Flush() {
-      if (seq_length > 0) {
-        PrintF("%d: %dx%d\n",
-               seq_start,
-               seq_type == 0 ? 0 : 1,
-               seq_length * kBitsPerCell);
-        seq_length = 0;
-      }
-    }
-
-    static bool IsSeq(uint32_t cell) { return cell == 0 || cell == 0xFFFFFFFF; }
-
-   private:
-    uint32_t seq_start;
-    uint32_t seq_type;
-    uint32_t seq_length;
-  };
-
-  void Print() {
-    CellPrinter printer;
-    for (int i = 0; i < CellsCount(); i++) {
-      printer.Print(i, cells()[i]);
-    }
-    printer.Flush();
-    PrintF("\n");
-  }
-
-  bool IsClean() {
-    for (int i = 0; i < CellsCount(); i++) {
-      if (cells()[i] != 0) return false;
-    }
-    return true;
-  }
-};
-
-
-class SkipList;
-class SlotsBuffer;
-
-// MemoryChunk represents a memory region owned by a specific space.
-// It is divided into the header and the body. Chunk start is always
-// 1MB aligned. Start of the body is aligned so it can accommodate
-// any heap object.
-class MemoryChunk {
- public:
-  // Only works if the pointer is in the first kPageSize of the MemoryChunk.
-  static MemoryChunk* FromAddress(Address a) {
-    return reinterpret_cast<MemoryChunk*>(OffsetFrom(a) & ~kAlignmentMask);
-  }
-
-  // Only works for addresses in pointer spaces, not data or code spaces.
-  static inline MemoryChunk* FromAnyPointerAddress(Address addr);
-
-  Address address() { return reinterpret_cast<Address>(this); }
-
-  bool is_valid() { return address() != NULL; }
-
-  MemoryChunk* next_chunk() const { return next_chunk_; }
-  MemoryChunk* prev_chunk() const { return prev_chunk_; }
-
-  void set_next_chunk(MemoryChunk* next) { next_chunk_ = next; }
-  void set_prev_chunk(MemoryChunk* prev) { prev_chunk_ = prev; }
-
-  Space* owner() const {
-    if ((reinterpret_cast<intptr_t>(owner_) & kFailureTagMask) ==
-        kFailureTag) {
-      return reinterpret_cast<Space*>(owner_ - kFailureTag);
-    } else {
-      return NULL;
-    }
-  }
-
-  void set_owner(Space* space) {
-    ASSERT((reinterpret_cast<intptr_t>(space) & kFailureTagMask) == 0);
-    owner_ = reinterpret_cast<Address>(space) + kFailureTag;
-    ASSERT((reinterpret_cast<intptr_t>(owner_) & kFailureTagMask) ==
-           kFailureTag);
-  }
-
-  VirtualMemory* reserved_memory() {
-    return &reservation_;
-  }
-
-  void InitializeReservedMemory() {
-    reservation_.Reset();
-  }
-
-  void set_reserved_memory(VirtualMemory* reservation) {
-    ASSERT_NOT_NULL(reservation);
-    reservation_.TakeControl(reservation);
-  }
-
-  bool scan_on_scavenge() { return IsFlagSet(SCAN_ON_SCAVENGE); }
-  void initialize_scan_on_scavenge(bool scan) {
-    if (scan) {
-      SetFlag(SCAN_ON_SCAVENGE);
-    } else {
-      ClearFlag(SCAN_ON_SCAVENGE);
-    }
-  }
-  inline void set_scan_on_scavenge(bool scan);
-
-  int store_buffer_counter() { return store_buffer_counter_; }
-  void set_store_buffer_counter(int counter) {
-    store_buffer_counter_ = counter;
-  }
-
-  bool Contains(Address addr) {
-    return addr >= area_start() && addr < area_end();
-  }
-
-  // Checks whether addr can be a limit of addresses in this page.
-  // It's a limit if it's in the page, or if it's just after the
-  // last byte of the page.
-  bool ContainsLimit(Address addr) {
-    return addr >= area_start() && addr <= area_end();
-  }
-
-  enum MemoryChunkFlags {
-    IS_EXECUTABLE,
-    ABOUT_TO_BE_FREED,
-    POINTERS_TO_HERE_ARE_INTERESTING,
-    POINTERS_FROM_HERE_ARE_INTERESTING,
-    SCAN_ON_SCAVENGE,
-    IN_FROM_SPACE,  // Mutually exclusive with IN_TO_SPACE.
-    IN_TO_SPACE,    // All pages in new space has one of these two set.
-    NEW_SPACE_BELOW_AGE_MARK,
-    CONTAINS_ONLY_DATA,
-    EVACUATION_CANDIDATE,
-    RESCAN_ON_EVACUATION,
-
-    // Pages swept precisely can be iterated, hitting only the live objects.
-    // Whereas those swept conservatively cannot be iterated over. Both flags
-    // indicate that marking bits have been cleared by the sweeper, otherwise
-    // marking bits are still intact.
-    WAS_SWEPT_PRECISELY,
-    WAS_SWEPT_CONSERVATIVELY,
-
-    // Last flag, keep at bottom.
-    NUM_MEMORY_CHUNK_FLAGS
-  };
-
-
-  static const int kPointersToHereAreInterestingMask =
-      1 << POINTERS_TO_HERE_ARE_INTERESTING;
-
-  static const int kPointersFromHereAreInterestingMask =
-      1 << POINTERS_FROM_HERE_ARE_INTERESTING;
-
-  static const int kEvacuationCandidateMask =
-      1 << EVACUATION_CANDIDATE;
-
-  static const int kSkipEvacuationSlotsRecordingMask =
-      (1 << EVACUATION_CANDIDATE) |
-      (1 << RESCAN_ON_EVACUATION) |
-      (1 << IN_FROM_SPACE) |
-      (1 << IN_TO_SPACE);
-
-
-  void SetFlag(int flag) {
-    flags_ |= static_cast<uintptr_t>(1) << flag;
-  }
-
-  void ClearFlag(int flag) {
-    flags_ &= ~(static_cast<uintptr_t>(1) << flag);
-  }
-
-  void SetFlagTo(int flag, bool value) {
-    if (value) {
-      SetFlag(flag);
-    } else {
-      ClearFlag(flag);
-    }
-  }
-
-  bool IsFlagSet(int flag) {
-    return (flags_ & (static_cast<uintptr_t>(1) << flag)) != 0;
-  }
-
-  // Set or clear multiple flags at a time. The flags in the mask
-  // are set to the value in "flags", the rest retain the current value
-  // in flags_.
-  void SetFlags(intptr_t flags, intptr_t mask) {
-    flags_ = (flags_ & ~mask) | (flags & mask);
-  }
-
-  // Return all current flags.
-  intptr_t GetFlags() { return flags_; }
-
-  // Manage live byte count (count of bytes known to be live,
-  // because they are marked black).
-  void ResetLiveBytes() {
-    if (FLAG_gc_verbose) {
-      PrintF("ResetLiveBytes:%p:%x->0\n",
-             static_cast<void*>(this), live_byte_count_);
-    }
-    live_byte_count_ = 0;
-  }
-  void IncrementLiveBytes(int by) {
-    if (FLAG_gc_verbose) {
-      printf("UpdateLiveBytes:%p:%x%c=%x->%x\n",
-             static_cast<void*>(this), live_byte_count_,
-             ((by < 0) ? '-' : '+'), ((by < 0) ? -by : by),
-             live_byte_count_ + by);
-    }
-    live_byte_count_ += by;
-    ASSERT_LE(static_cast<unsigned>(live_byte_count_), size_);
-  }
-  int LiveBytes() {
-    ASSERT(static_cast<unsigned>(live_byte_count_) <= size_);
-    return live_byte_count_;
-  }
-
-  static void IncrementLiveBytesFromGC(Address address, int by) {
-    MemoryChunk::FromAddress(address)->IncrementLiveBytes(by);
-  }
-
-  static void IncrementLiveBytesFromMutator(Address address, int by);
-
-  static const intptr_t kAlignment =
-      (static_cast<uintptr_t>(1) << kPageSizeBits);
-
-  static const intptr_t kAlignmentMask = kAlignment - 1;
-
-  static const intptr_t kSizeOffset = kPointerSize + kPointerSize;
-
-  static const intptr_t kLiveBytesOffset =
-     kSizeOffset + kPointerSize + kPointerSize + kPointerSize +
-     kPointerSize + kPointerSize +
-     kPointerSize + kPointerSize + kPointerSize + kIntSize;
-
-  static const size_t kSlotsBufferOffset = kLiveBytesOffset + kIntSize;
-
-  static const size_t kHeaderSize =
-      kSlotsBufferOffset + kPointerSize + kPointerSize;
-
-  static const int kBodyOffset =
-    CODE_POINTER_ALIGN(MAP_POINTER_ALIGN(kHeaderSize + Bitmap::kSize));
-
-  // The start offset of the object area in a page. Aligned to both maps and
-  // code alignment to be suitable for both.  Also aligned to 32 words because
-  // the marking bitmap is arranged in 32 bit chunks.
-  static const int kObjectStartAlignment = 32 * kPointerSize;
-  static const int kObjectStartOffset = kBodyOffset - 1 +
-      (kObjectStartAlignment - (kBodyOffset - 1) % kObjectStartAlignment);
-
-  size_t size() const { return size_; }
-
-  void set_size(size_t size) {
-    size_ = size;
-  }
-
-  void SetArea(Address area_start, Address area_end) {
-    area_start_ = area_start;
-    area_end_ = area_end;
-  }
-
-  Executability executable() {
-    return IsFlagSet(IS_EXECUTABLE) ? EXECUTABLE : NOT_EXECUTABLE;
-  }
-
-  bool ContainsOnlyData() {
-    return IsFlagSet(CONTAINS_ONLY_DATA);
-  }
-
-  bool InNewSpace() {
-    return (flags_ & ((1 << IN_FROM_SPACE) | (1 << IN_TO_SPACE))) != 0;
-  }
-
-  bool InToSpace() {
-    return IsFlagSet(IN_TO_SPACE);
-  }
-
-  bool InFromSpace() {
-    return IsFlagSet(IN_FROM_SPACE);
-  }
-
-  // ---------------------------------------------------------------------
-  // Markbits support
-
-  inline Bitmap* markbits() {
-    return Bitmap::FromAddress(address() + kHeaderSize);
-  }
-
-  void PrintMarkbits() { markbits()->Print(); }
-
-  inline uint32_t AddressToMarkbitIndex(Address addr) {
-    return static_cast<uint32_t>(addr - this->address()) >> kPointerSizeLog2;
-  }
-
-  inline static uint32_t FastAddressToMarkbitIndex(Address addr) {
-    const intptr_t offset =
-        reinterpret_cast<intptr_t>(addr) & kAlignmentMask;
-
-    return static_cast<uint32_t>(offset) >> kPointerSizeLog2;
-  }
-
-  inline Address MarkbitIndexToAddress(uint32_t index) {
-    return this->address() + (index << kPointerSizeLog2);
-  }
-
-  void InsertAfter(MemoryChunk* other);
-  void Unlink();
-
-  inline Heap* heap() { return heap_; }
-
-  static const int kFlagsOffset = kPointerSize * 3;
-
-  bool IsEvacuationCandidate() { return IsFlagSet(EVACUATION_CANDIDATE); }
-
-  bool ShouldSkipEvacuationSlotRecording() {
-    return (flags_ & kSkipEvacuationSlotsRecordingMask) != 0;
-  }
-
-  inline SkipList* skip_list() {
-    return skip_list_;
-  }
-
-  inline void set_skip_list(SkipList* skip_list) {
-    skip_list_ = skip_list;
-  }
-
-  inline SlotsBuffer* slots_buffer() {
-    return slots_buffer_;
-  }
-
-  inline SlotsBuffer** slots_buffer_address() {
-    return &slots_buffer_;
-  }
-
-  void MarkEvacuationCandidate() {
-    ASSERT(slots_buffer_ == NULL);
-    SetFlag(EVACUATION_CANDIDATE);
-  }
-
-  void ClearEvacuationCandidate() {
-    ASSERT(slots_buffer_ == NULL);
-    ClearFlag(EVACUATION_CANDIDATE);
-  }
-
-  Address area_start() { return area_start_; }
-  Address area_end() { return area_end_; }
-  int area_size() {
-    return static_cast<int>(area_end() - area_start());
-  }
-
- protected:
-  MemoryChunk* next_chunk_;
-  MemoryChunk* prev_chunk_;
-  size_t size_;
-  intptr_t flags_;
-
-  // Start and end of allocatable memory on this chunk.
-  Address area_start_;
-  Address area_end_;
-
-  // If the chunk needs to remember its memory reservation, it is stored here.
-  VirtualMemory reservation_;
-  // The identity of the owning space.  This is tagged as a failure pointer, but
-  // no failure can be in an object, so this can be distinguished from any entry
-  // in a fixed array.
-  Address owner_;
-  Heap* heap_;
-  // Used by the store buffer to keep track of which pages to mark scan-on-
-  // scavenge.
-  int store_buffer_counter_;
-  // Count of bytes marked black on page.
-  int live_byte_count_;
-  SlotsBuffer* slots_buffer_;
-  SkipList* skip_list_;
-
-  static MemoryChunk* Initialize(Heap* heap,
-                                 Address base,
-                                 size_t size,
-                                 Address area_start,
-                                 Address area_end,
-                                 Executability executable,
-                                 Space* owner);
-
-  friend class MemoryAllocator;
-};
-
-STATIC_CHECK(sizeof(MemoryChunk) <= MemoryChunk::kHeaderSize);
 
 // -----------------------------------------------------------------------------
-// A page is a memory chunk of a size 1MB. Large object pages may be larger.
+// A page normally has 8K bytes. Large object pages may be larger.  A page
+// address is always aligned to the 8K page size.
+//
+// Each page starts with a header of Page::kPageHeaderSize size which contains
+// bookkeeping data.
+//
+// The mark-compact collector transforms a map pointer into a page index and a
+// page offset. The exact encoding is described in the comments for
+// class MapWord in objects.h.
 //
 // The only way to get a page pointer is by calling factory methods:
 //   Page* p = Page::FromAddress(addr); or
 //   Page* p = Page::FromAllocationTop(top);
-class Page : public MemoryChunk {
+class Page {
  public:
   // Returns the page containing a given address. The address ranges
   // from [page_addr .. page_addr + kPageSize[
-  // This only works if the object is in fact in a page.  See also MemoryChunk::
-  // FromAddress() and FromAnyAddress().
+  //
+  // Note that this function only works for addresses in normal paged
+  // spaces and addresses in the first 8K of large object pages (i.e.,
+  // the start of large objects but not necessarily derived pointers
+  // within them).
   INLINE(static Page* FromAddress(Address a)) {
     return reinterpret_cast<Page*>(OffsetFrom(a) & ~kPageAlignmentMask);
   }
@@ -661,23 +148,66 @@
   // [page_addr + kObjectStartOffset .. page_addr + kPageSize].
   INLINE(static Page* FromAllocationTop(Address top)) {
     Page* p = FromAddress(top - kPointerSize);
+    ASSERT_PAGE_OFFSET(p->Offset(top));
     return p;
   }
 
-  // Returns the next page in the chain of pages owned by a space.
+  // Returns the start address of this page.
+  Address address() { return reinterpret_cast<Address>(this); }
+
+  // Checks whether this is a valid page address.
+  bool is_valid() { return address() != NULL; }
+
+  // Returns the next page of this page.
   inline Page* next_page();
-  inline Page* prev_page();
-  inline void set_next_page(Page* page);
-  inline void set_prev_page(Page* page);
+
+  // Return the end of allocation in this page. Undefined for unused pages.
+  inline Address AllocationTop();
+
+  // Return the allocation watermark for the page.
+  // For old space pages it is guaranteed that the area under the watermark
+  // does not contain any garbage pointers to new space.
+  inline Address AllocationWatermark();
+
+  // Return the allocation watermark offset from the beginning of the page.
+  inline uint32_t AllocationWatermarkOffset();
+
+  inline void SetAllocationWatermark(Address allocation_watermark);
+
+  inline void SetCachedAllocationWatermark(Address allocation_watermark);
+  inline Address CachedAllocationWatermark();
+
+  // Returns the start address of the object area in this page.
+  Address ObjectAreaStart() { return address() + kObjectStartOffset; }
+
+  // Returns the end address (exclusive) of the object area in this page.
+  Address ObjectAreaEnd() { return address() + Page::kPageSize; }
 
   // Checks whether an address is page aligned.
   static bool IsAlignedToPageSize(Address a) {
     return 0 == (OffsetFrom(a) & kPageAlignmentMask);
   }
 
+  // True if this page was in use before current compaction started.
+  // Result is valid only for pages owned by paged spaces and
+  // only after PagedSpace::PrepareForMarkCompact was called.
+  inline bool WasInUseBeforeMC();
+
+  inline void SetWasInUseBeforeMC(bool was_in_use);
+
+  // True if this page is a large object page.
+  inline bool IsLargeObjectPage();
+
+  inline void SetIsLargeObjectPage(bool is_large_object_page);
+
+  inline Executability PageExecutability();
+
+  inline void SetPageExecutability(Executability executable);
+
   // Returns the offset of a given address to this page.
   INLINE(int Offset(Address a)) {
     int offset = static_cast<int>(a - address());
+    ASSERT_PAGE_OFFSET(offset);
     return offset;
   }
 
@@ -688,70 +218,144 @@
   }
 
   // ---------------------------------------------------------------------
+  // Card marking support
+
+  static const uint32_t kAllRegionsCleanMarks = 0x0;
+  static const uint32_t kAllRegionsDirtyMarks = 0xFFFFFFFF;
+
+  inline uint32_t GetRegionMarks();
+  inline void SetRegionMarks(uint32_t dirty);
+
+  inline uint32_t GetRegionMaskForAddress(Address addr);
+  inline uint32_t GetRegionMaskForSpan(Address start, int length_in_bytes);
+  inline int GetRegionNumberForAddress(Address addr);
+
+  inline void MarkRegionDirty(Address addr);
+  inline bool IsRegionDirty(Address addr);
+
+  inline void ClearRegionMarks(Address start,
+                               Address end,
+                               bool reaches_limit);
 
   // Page size in bytes.  This must be a multiple of the OS page size.
   static const int kPageSize = 1 << kPageSizeBits;
 
-  // Object area size in bytes.
-  static const int kNonCodeObjectAreaSize = kPageSize - kObjectStartOffset;
-
-  // Maximum object size that fits in a page.
-  static const int kMaxNonCodeHeapObjectSize = kNonCodeObjectAreaSize;
-
   // Page size mask.
   static const intptr_t kPageAlignmentMask = (1 << kPageSizeBits) - 1;
 
+  static const int kPageHeaderSize = kPointerSize + kPointerSize + kIntSize +
+    kIntSize + kPointerSize + kPointerSize;
+
+  // The start offset of the object area in a page. Aligned to both maps and
+  // code alignment to be suitable for both.
+  static const int kObjectStartOffset =
+      CODE_POINTER_ALIGN(MAP_POINTER_ALIGN(kPageHeaderSize));
+
+  // Object area size in bytes.
+  static const int kObjectAreaSize = kPageSize - kObjectStartOffset;
+
+  // Maximum object size that fits in a page.
+  static const int kMaxHeapObjectSize = kObjectAreaSize;
+
+  static const int kDirtyFlagOffset = 2 * kPointerSize;
+  static const int kRegionSizeLog2 = 8;
+  static const int kRegionSize = 1 << kRegionSizeLog2;
+  static const intptr_t kRegionAlignmentMask = (kRegionSize - 1);
+
+  STATIC_CHECK(kRegionSize == kPageSize / kBitsPerInt);
+
+  enum PageFlag {
+    IS_NORMAL_PAGE = 0,
+    WAS_IN_USE_BEFORE_MC,
+
+    // Page allocation watermark was bumped by preallocation during scavenge.
+    // Correct watermark can be retrieved by CachedAllocationWatermark() method
+    WATERMARK_INVALIDATED,
+    IS_EXECUTABLE,
+    NUM_PAGE_FLAGS  // Must be last
+  };
+  static const int kPageFlagMask = (1 << NUM_PAGE_FLAGS) - 1;
+
+  // To avoid an additional WATERMARK_INVALIDATED flag clearing pass during
+  // scavenge we just invalidate the watermark on each old space page after
+  // processing it. And then we flip the meaning of the WATERMARK_INVALIDATED
+  // flag at the beginning of the next scavenge and each page becomes marked as
+  // having a valid watermark.
+  //
+  // The following invariant must hold for pages in old pointer and map spaces:
+  //     If page is in use then page is marked as having invalid watermark at
+  //     the beginning and at the end of any GC.
+  //
+  // This invariant guarantees that after flipping flag meaning at the
+  // beginning of scavenge all pages in use will be marked as having valid
+  // watermark.
+  static inline void FlipMeaningOfInvalidatedWatermarkFlag(Heap* heap);
+
+  // Returns true if the page allocation watermark was not altered during
+  // scavenge.
+  inline bool IsWatermarkValid();
+
+  inline void InvalidateWatermark(bool value);
+
+  inline bool GetPageFlag(PageFlag flag);
+  inline void SetPageFlag(PageFlag flag, bool value);
+  inline void ClearPageFlags();
+
   inline void ClearGCFields();
 
-  static inline Page* Initialize(Heap* heap,
-                                 MemoryChunk* chunk,
-                                 Executability executable,
-                                 PagedSpace* owner);
+  static const int kAllocationWatermarkOffsetShift = WATERMARK_INVALIDATED + 1;
+  static const int kAllocationWatermarkOffsetBits  = kPageSizeBits + 1;
+  static const uint32_t kAllocationWatermarkOffsetMask =
+      ((1 << kAllocationWatermarkOffsetBits) - 1) <<
+      kAllocationWatermarkOffsetShift;
 
-  void InitializeAsAnchor(PagedSpace* owner);
+  static const uint32_t kFlagsMask =
+    ((1 << kAllocationWatermarkOffsetShift) - 1);
 
-  bool WasSweptPrecisely() { return IsFlagSet(WAS_SWEPT_PRECISELY); }
-  bool WasSweptConservatively() { return IsFlagSet(WAS_SWEPT_CONSERVATIVELY); }
-  bool WasSwept() { return WasSweptPrecisely() || WasSweptConservatively(); }
+  STATIC_CHECK(kBitsPerInt - kAllocationWatermarkOffsetShift >=
+               kAllocationWatermarkOffsetBits);
 
-  void MarkSweptPrecisely() { SetFlag(WAS_SWEPT_PRECISELY); }
-  void MarkSweptConservatively() { SetFlag(WAS_SWEPT_CONSERVATIVELY); }
+  //---------------------------------------------------------------------------
+  // Page header description.
+  //
+  // If a page is not in the large object space, the first word,
+  // opaque_header, encodes the next page address (aligned to kPageSize 8K)
+  // and the chunk number (0 ~ 8K-1).  Only MemoryAllocator should use
+  // opaque_header. The value range of the opaque_header is [0..kPageSize[,
+  // or [next_page_start, next_page_end[. It cannot point to a valid address
+  // in the current page.  If a page is in the large object space, the first
+  // word *may* (if the page start and large object chunk start are the
+  // same) contain the address of the next large object chunk.
+  intptr_t opaque_header;
 
-  void ClearSweptPrecisely() { ClearFlag(WAS_SWEPT_PRECISELY); }
-  void ClearSweptConservatively() { ClearFlag(WAS_SWEPT_CONSERVATIVELY); }
+  // If the page is not in the large object space, the low-order bit of the
+  // second word is set. If the page is in the large object space, the
+  // second word *may* (if the page start and large object chunk start are
+  // the same) contain the large object chunk size.  In either case, the
+  // low-order bit for large object pages will be cleared.
+  // For normal pages this word is used to store page flags and
+  // offset of allocation top.
+  intptr_t flags_;
 
-#ifdef DEBUG
-  void Print();
-#endif  // DEBUG
+  // This field contains dirty marks for regions covering the page. Only dirty
+  // regions might contain intergenerational references.
+  // Only 32 dirty marks are supported so for large object pages several regions
+  // might be mapped to a single dirty mark.
+  uint32_t dirty_regions_;
 
-  friend class MemoryAllocator;
+  // The index of the page in its owner space.
+  int mc_page_index;
+
+  // During mark-compact collections this field contains the forwarding address
+  // of the first live object in this page.
+  // During scavenge collection this field is used to store allocation watermark
+  // if it is altered during scavenge.
+  Address mc_first_forwarded;
+
+  Heap* heap_;
 };
 
 
-STATIC_CHECK(sizeof(Page) <= MemoryChunk::kHeaderSize);
-
-
-class LargePage : public MemoryChunk {
- public:
-  HeapObject* GetObject() {
-    return HeapObject::FromAddress(area_start());
-  }
-
-  inline LargePage* next_page() const {
-    return static_cast<LargePage*>(next_chunk());
-  }
-
-  inline void set_next_page(LargePage* page) {
-    set_next_chunk(page);
-  }
- private:
-  static inline LargePage* Initialize(Heap* heap, MemoryChunk* chunk);
-
-  friend class MemoryAllocator;
-};
-
-STATIC_CHECK(sizeof(LargePage) <= MemoryChunk::kHeaderSize);
-
 // ----------------------------------------------------------------------------
 // Space is the abstract superclass for all allocation spaces.
 class Space : public Malloced {
@@ -776,14 +380,6 @@
   // (e.g. see LargeObjectSpace).
   virtual intptr_t SizeOfObjects() { return Size(); }
 
-  virtual int RoundSizeDownToObjectAlignment(int size) {
-    if (id_ == CODE_SPACE) {
-      return RoundDown(size, kCodeAlignment);
-    } else {
-      return RoundDown(size, kPointerSize);
-    }
-  }
-
 #ifdef DEBUG
   virtual void Print() = 0;
 #endif
@@ -818,7 +414,7 @@
   // Reserves a range of virtual memory, but does not commit any of it.
   // Can only be called once, at heap initialization time.
   // Returns false on failure.
-  bool SetUp(const size_t requested_size);
+  bool Setup(const size_t requested_size);
 
   // Frees the range of virtual memory, and frees the data structures used to
   // manage it.
@@ -834,9 +430,9 @@
   // Allocates a chunk of memory from the large-object portion of
   // the code range.  On platforms with no separate code range, should
   // not be called.
-  MUST_USE_RESULT Address AllocateRawMemory(const size_t requested,
-                                            size_t* allocated);
-  void FreeRawMemory(Address buf, size_t length);
+  MUST_USE_RESULT void* AllocateRawMemory(const size_t requested,
+                                          size_t* allocated);
+  void FreeRawMemory(void* buf, size_t length);
 
  private:
   Isolate* isolate_;
@@ -847,15 +443,9 @@
   class FreeBlock {
    public:
     FreeBlock(Address start_arg, size_t size_arg)
-        : start(start_arg), size(size_arg) {
-      ASSERT(IsAddressAligned(start, MemoryChunk::kAlignment));
-      ASSERT(size >= static_cast<size_t>(Page::kPageSize));
-    }
+        : start(start_arg), size(size_arg) {}
     FreeBlock(void* start_arg, size_t size_arg)
-        : start(static_cast<Address>(start_arg)), size(size_arg) {
-      ASSERT(IsAddressAligned(start, MemoryChunk::kAlignment));
-      ASSERT(size >= static_cast<size_t>(Page::kPageSize));
-    }
+        : start(static_cast<Address>(start_arg)), size(size_arg) {}
 
     Address start;
     size_t size;
@@ -883,80 +473,123 @@
 };
 
 
-class SkipList {
- public:
-  SkipList() {
-    Clear();
-  }
-
-  void Clear() {
-    for (int idx = 0; idx < kSize; idx++) {
-      starts_[idx] = reinterpret_cast<Address>(-1);
-    }
-  }
-
-  Address StartFor(Address addr) {
-    return starts_[RegionNumber(addr)];
-  }
-
-  void AddObject(Address addr, int size) {
-    int start_region = RegionNumber(addr);
-    int end_region = RegionNumber(addr + size - kPointerSize);
-    for (int idx = start_region; idx <= end_region; idx++) {
-      if (starts_[idx] > addr) starts_[idx] = addr;
-    }
-  }
-
-  static inline int RegionNumber(Address addr) {
-    return (OffsetFrom(addr) & Page::kPageAlignmentMask) >> kRegionSizeLog2;
-  }
-
-  static void Update(Address addr, int size) {
-    Page* page = Page::FromAddress(addr);
-    SkipList* list = page->skip_list();
-    if (list == NULL) {
-      list = new SkipList();
-      page->set_skip_list(list);
-    }
-
-    list->AddObject(addr, size);
-  }
-
- private:
-  static const int kRegionSizeLog2 = 13;
-  static const int kRegionSize = 1 << kRegionSizeLog2;
-  static const int kSize = Page::kPageSize / kRegionSize;
-
-  STATIC_ASSERT(Page::kPageSize % kRegionSize == 0);
-
-  Address starts_[kSize];
-};
-
-
 // ----------------------------------------------------------------------------
 // A space acquires chunks of memory from the operating system. The memory
-// allocator allocated and deallocates pages for the paged heap spaces and large
-// pages for large object space.
+// allocator manages chunks for the paged heap spaces (old space and map
+// space).  A paged chunk consists of pages. Pages in a chunk have contiguous
+// addresses and are linked as a list.
 //
-// Each space has to manage it's own pages.
+// The allocator keeps an initial chunk which is used for the new space.  The
+// leftover regions of the initial chunk are used for the initial chunks of
+// old space and map space if they are big enough to hold at least one page.
+// The allocator assumes that there is one old space and one map space, each
+// expands the space by allocating kPagesPerChunk pages except the last
+// expansion (before running out of space).  The first chunk may contain fewer
+// than kPagesPerChunk pages as well.
 //
+// The memory allocator also allocates chunks for the large object space, but
+// they are managed by the space itself.  The new space does not expand.
+//
+// The fact that pages for paged spaces are allocated and deallocated in chunks
+// induces a constraint on the order of pages in a linked lists. We say that
+// pages are linked in the chunk-order if and only if every two consecutive
+// pages from the same chunk are consecutive in the linked list.
+//
+
+
 class MemoryAllocator {
  public:
   explicit MemoryAllocator(Isolate* isolate);
 
   // Initializes its internal bookkeeping structures.
   // Max capacity of the total space and executable memory limit.
-  bool SetUp(intptr_t max_capacity, intptr_t capacity_executable);
+  bool Setup(intptr_t max_capacity, intptr_t capacity_executable);
 
+  // Deletes valid chunks.
   void TearDown();
 
-  Page* AllocatePage(PagedSpace* owner, Executability executable);
+  // Reserves an initial address range of virtual memory to be split between
+  // the two new space semispaces, the old space, and the map space.  The
+  // memory is not yet committed or assigned to spaces and split into pages.
+  // The initial chunk is unmapped when the memory allocator is torn down.
+  // This function should only be called when there is not already a reserved
+  // initial chunk (initial_chunk_ should be NULL).  It returns the start
+  // address of the initial chunk if successful, with the side effect of
+  // setting the initial chunk, or else NULL if unsuccessful and leaves the
+  // initial chunk NULL.
+  void* ReserveInitialChunk(const size_t requested);
 
-  LargePage* AllocateLargePage(intptr_t object_size,
-                                      Executability executable,
-                                      Space* owner);
+  // Commits pages from an as-yet-unmanaged block of virtual memory into a
+  // paged space.  The block should be part of the initial chunk reserved via
+  // a call to ReserveInitialChunk.  The number of pages is always returned in
+  // the output parameter num_pages.  This function assumes that the start
+  // address is non-null and that it is big enough to hold at least one
+  // page-aligned page.  The call always succeeds, and num_pages is always
+  // greater than zero.
+  Page* CommitPages(Address start, size_t size, PagedSpace* owner,
+                    int* num_pages);
 
-  void Free(MemoryChunk* chunk);
+  // Commit a contiguous block of memory from the initial chunk.  Assumes that
+  // the address is not NULL, the size is greater than zero, and that the
+  // block is contained in the initial chunk.  Returns true if it succeeded
+  // and false otherwise.
+  bool CommitBlock(Address start, size_t size, Executability executable);
+
+  // Uncommit a contiguous block of memory [start..(start+size)[.
+  // start is not NULL, the size is greater than zero, and the
+  // block is contained in the initial chunk.  Returns true if it succeeded
+  // and false otherwise.
+  bool UncommitBlock(Address start, size_t size);
+
+  // Zaps a contiguous block of memory [start..(start+size)[ thus
+  // filling it up with a recognizable non-NULL bit pattern.
+  void ZapBlock(Address start, size_t size);
+
+  // Attempts to allocate the requested (non-zero) number of pages from the
+  // OS.  Fewer pages might be allocated than requested. If it fails to
+  // allocate memory for the OS or cannot allocate a single page, this
+  // function returns an invalid page pointer (NULL). The caller must check
+  // whether the returned page is valid (by calling Page::is_valid()).  It is
+  // guaranteed that allocated pages have contiguous addresses.  The actual
+  // number of allocated pages is returned in the output parameter
+  // allocated_pages.  If the PagedSpace owner is executable and there is
+  // a code range, the pages are allocated from the code range.
+  Page* AllocatePages(int requested_pages, int* allocated_pages,
+                      PagedSpace* owner);
+
+  // Frees pages from a given page and after. Requires pages to be
+  // linked in chunk-order (see comment for class).
+  // If 'p' is the first page of a chunk, pages from 'p' are freed
+  // and this function returns an invalid page pointer.
+  // Otherwise, the function searches a page after 'p' that is
+  // the first page of a chunk. Pages after the found page
+  // are freed and the function returns 'p'.
+  Page* FreePages(Page* p);
+
+  // Frees all pages owned by given space.
+  void FreeAllPages(PagedSpace* space);
+
+  // Allocates and frees raw memory of certain size.
+  // These are just thin wrappers around OS::Allocate and OS::Free,
+  // but keep track of allocated bytes as part of heap.
+  // If the flag is EXECUTABLE and a code range exists, the requested
+  // memory is allocated from the code range.  If a code range exists
+  // and the freed memory is in it, the code range manages the freed memory.
+  MUST_USE_RESULT void* AllocateRawMemory(const size_t requested,
+                                          size_t* allocated,
+                                          Executability executable);
+  void FreeRawMemory(void* buf,
+                     size_t length,
+                     Executability executable);
+  void PerformAllocationCallback(ObjectSpace space,
+                                 AllocationAction action,
+                                 size_t size);
+
+  void AddMemoryAllocationCallback(MemoryAllocationCallback callback,
+                                   ObjectSpace space,
+                                   AllocationAction action);
+  void RemoveMemoryAllocationCallback(MemoryAllocationCallback callback);
+  bool MemoryAllocationCallbackRegistered(MemoryAllocationCallback callback);
 
   // Returns the maximum available bytes of heaps.
   intptr_t Available() { return capacity_ < size_ ? 0 : capacity_ - size_; }
@@ -975,85 +608,70 @@
 
   // Returns maximum available bytes that the old space can have.
   intptr_t MaxAvailable() {
-    return (Available() / Page::kPageSize) * Page::kMaxNonCodeHeapObjectSize;
+    return (Available() / Page::kPageSize) * Page::kObjectAreaSize;
   }
 
+  // Links two pages.
+  inline void SetNextPage(Page* prev, Page* next);
+
+  // Returns the next page of a given page.
+  inline Page* GetNextPage(Page* p);
+
+  // Checks whether a page belongs to a space.
+  inline bool IsPageInSpace(Page* p, PagedSpace* space);
+
+  // Returns the space that owns the given page.
+  inline PagedSpace* PageOwner(Page* page);
+
+  // Finds the first/last page in the same chunk as a given page.
+  Page* FindFirstPageInSameChunk(Page* p);
+  Page* FindLastPageInSameChunk(Page* p);
+
+  // Relinks list of pages owned by space to make it chunk-ordered.
+  // Returns new first and last pages of space.
+  // Also returns last page in relinked list which has WasInUsedBeforeMC
+  // flag set.
+  void RelinkPageListInChunkOrder(PagedSpace* space,
+                                  Page** first_page,
+                                  Page** last_page,
+                                  Page** last_page_in_use);
+
 #ifdef DEBUG
   // Reports statistic info of the space.
   void ReportStatistics();
 #endif
 
-  MemoryChunk* AllocateChunk(intptr_t body_size,
-                             Executability executable,
-                             Space* space);
-
-  Address ReserveAlignedMemory(size_t requested,
-                               size_t alignment,
-                               VirtualMemory* controller);
-  Address AllocateAlignedMemory(size_t requested,
-                                size_t alignment,
-                                Executability executable,
-                                VirtualMemory* controller);
-
-  void FreeMemory(VirtualMemory* reservation, Executability executable);
-  void FreeMemory(Address addr, size_t size, Executability executable);
-
-  // Commit a contiguous block of memory from the initial chunk.  Assumes that
-  // the address is not NULL, the size is greater than zero, and that the
-  // block is contained in the initial chunk.  Returns true if it succeeded
-  // and false otherwise.
-  bool CommitBlock(Address start, size_t size, Executability executable);
-
-  // Uncommit a contiguous block of memory [start..(start+size)[.
-  // start is not NULL, the size is greater than zero, and the
-  // block is contained in the initial chunk.  Returns true if it succeeded
-  // and false otherwise.
-  bool UncommitBlock(Address start, size_t size);
-
-  // Zaps a contiguous block of memory [start..(start+size)[ thus
-  // filling it up with a recognizable non-NULL bit pattern.
-  void ZapBlock(Address start, size_t size);
-
-  void PerformAllocationCallback(ObjectSpace space,
-                                 AllocationAction action,
-                                 size_t size);
-
-  void AddMemoryAllocationCallback(MemoryAllocationCallback callback,
-                                          ObjectSpace space,
-                                          AllocationAction action);
-
-  void RemoveMemoryAllocationCallback(
-      MemoryAllocationCallback callback);
-
-  bool MemoryAllocationCallbackRegistered(
-      MemoryAllocationCallback callback);
-
-  static int CodePageGuardStartOffset();
-
-  static int CodePageGuardSize();
-
-  static int CodePageAreaStartOffset();
-
-  static int CodePageAreaEndOffset();
-
-  static int CodePageAreaSize() {
-    return CodePageAreaEndOffset() - CodePageAreaStartOffset();
-  }
-
-  static bool CommitCodePage(VirtualMemory* vm, Address start, size_t size);
+  // Due to encoding limitation, we can only have 8K chunks.
+  static const int kMaxNofChunks = 1 << kPageSizeBits;
+  // If a chunk has at least 16 pages, the maximum heap size is about
+  // 8K * 8K * 16 = 1G bytes.
+#ifdef V8_TARGET_ARCH_X64
+  static const int kPagesPerChunk = 32;
+  // On 64 bit the chunk table consists of 4 levels of 4096-entry tables.
+  static const int kChunkTableLevels = 4;
+  static const int kChunkTableBitsPerLevel = 12;
+#else
+  static const int kPagesPerChunk = 16;
+  // On 32 bit the chunk table consists of 2 levels of 256-entry tables.
+  static const int kChunkTableLevels = 2;
+  static const int kChunkTableBitsPerLevel = 8;
+#endif
 
  private:
+  static const int kChunkSize = kPagesPerChunk * Page::kPageSize;
+
   Isolate* isolate_;
 
   // Maximum space size in bytes.
-  size_t capacity_;
+  intptr_t capacity_;
   // Maximum subset of capacity_ that can be executable
-  size_t capacity_executable_;
+  intptr_t capacity_executable_;
 
   // Allocated space size in bytes.
-  size_t size_;
+  intptr_t size_;
+
   // Allocated executable space size in bytes.
-  size_t size_executable_;
+  intptr_t size_executable_;
 
   struct MemoryAllocationCallbackRegistration {
     MemoryAllocationCallbackRegistration(MemoryAllocationCallback callback,
@@ -1065,11 +683,64 @@
     ObjectSpace space;
     AllocationAction action;
   };
-
   // A List of callback that are triggered when memory is allocated or free'd
   List<MemoryAllocationCallbackRegistration>
       memory_allocation_callbacks_;
 
+  // The initial chunk of virtual memory.
+  VirtualMemory* initial_chunk_;
+
+  // Allocated chunk info: chunk start address, chunk size, and owning space.
+  class ChunkInfo BASE_EMBEDDED {
+   public:
+    ChunkInfo() : address_(NULL),
+                  size_(0),
+                  owner_(NULL),
+                  executable_(NOT_EXECUTABLE),
+                  owner_identity_(FIRST_SPACE) {}
+    inline void init(Address a, size_t s, PagedSpace* o);
+    Address address() { return address_; }
+    size_t size() { return size_; }
+    PagedSpace* owner() { return owner_; }
+    // We save executability of the owner to allow using it
+    // when collecting stats after the owner has been destroyed.
+    Executability executable() const { return executable_; }
+    AllocationSpace owner_identity() const { return owner_identity_; }
+
+   private:
+    Address address_;
+    size_t size_;
+    PagedSpace* owner_;
+    Executability executable_;
+    AllocationSpace owner_identity_;
+  };
+
+  // Chunks_, free_chunk_ids_ and top_ act as a stack of free chunk ids.
+  List<ChunkInfo> chunks_;
+  List<int> free_chunk_ids_;
+  int max_nof_chunks_;
+  int top_;
+
+  // Push/pop a free chunk id onto/from the stack.
+  void Push(int free_chunk_id);
+  int Pop();
+  bool OutOfChunkIds() { return top_ == 0; }
+
+  // Frees a chunk.
+  void DeleteChunk(int chunk_id);
+
+  // Basic check whether a chunk id is in the valid range.
+  inline bool IsValidChunkId(int chunk_id);
+
+  // Checks whether a chunk id identifies an allocated chunk.
+  inline bool IsValidChunk(int chunk_id);
+
+  // Returns the chunk id that a page belongs to.
+  inline int GetChunkId(Page* p);
+
+  // True if the address lies in the initial chunk.
+  inline bool InInitialChunk(Address address);
+
   // Initializes pages in a chunk. Returns the first page address.
   // This function and GetChunkId() are provided for the mark-compact
   // collector to rebuild page headers in the from space, which is
@@ -1077,7 +748,13 @@
   Page* InitializePagesInChunk(int chunk_id, int pages_in_chunk,
                                PagedSpace* owner);
 
-  DISALLOW_IMPLICIT_CONSTRUCTORS(MemoryAllocator);
+  Page* RelinkPagesInChunk(int chunk_id,
+                           Address chunk_start,
+                           size_t chunk_size,
+                           Page* prev,
+                           Page** last_page_in_use);
+
+  DISALLOW_COPY_AND_ASSIGN(MemoryAllocator);
 };
 
 
@@ -1100,67 +777,111 @@
 // -----------------------------------------------------------------------------
 // Heap object iterator in new/old/map spaces.
 //
-// A HeapObjectIterator iterates objects from the bottom of the given space
-// to its top or from the bottom of the given page to its top.
+// A HeapObjectIterator iterates objects from a given address to the
+// top of a space. The given address must be below the current
+// allocation pointer (space top). There are some caveats.
 //
-// If objects are allocated in the page during iteration the iterator may
-// or may not iterate over those objects.  The caller must create a new
-// iterator in order to be sure to visit these new objects.
+// (1) If the space top changes upward during iteration (because of
+//     allocating new objects), the iterator does not iterate objects
+//     above the original space top. The caller must create a new
+//     iterator starting from the old top in order to visit these new
+//     objects.
+//
+// (2) If new objects are allocated below the original allocation top
+//     (e.g., free-list allocation in paged spaces), the new objects
+//     may or may not be iterated depending on their position with
+//     respect to the current point of iteration.
+//
+// (3) The space top should not change downward during iteration,
+//     otherwise the iterator will return not-necessarily-valid
+//     objects.
+
 class HeapObjectIterator: public ObjectIterator {
  public:
-  // Creates a new object iterator in a given space.
+  // Creates a new object iterator in a given space. If a start
+  // address is not given, the iterator starts from the space bottom.
   // If the size function is not given, the iterator calls the default
   // Object::Size().
   explicit HeapObjectIterator(PagedSpace* space);
   HeapObjectIterator(PagedSpace* space, HeapObjectCallback size_func);
+  HeapObjectIterator(PagedSpace* space, Address start);
+  HeapObjectIterator(PagedSpace* space,
+                     Address start,
+                     HeapObjectCallback size_func);
   HeapObjectIterator(Page* page, HeapObjectCallback size_func);
 
-  // Advance to the next object, skipping free spaces and other fillers and
-  // skipping the special garbage section of which there is one per space.
-  // Returns NULL when the iteration has ended.
-  inline HeapObject* Next() {
-    do {
-      HeapObject* next_obj = FromCurrentPage();
-      if (next_obj != NULL) return next_obj;
-    } while (AdvanceToNextPage());
-    return NULL;
+  inline HeapObject* next() {
+    return (cur_addr_ < cur_limit_) ? FromCurrentPage() : FromNextPage();
   }
 
-  virtual HeapObject* next_object() {
-    return Next();
-  }
+  // implementation of ObjectIterator.
+  virtual HeapObject* next_object() { return next(); }
 
  private:
-  enum PageMode { kOnePageOnly, kAllPagesInSpace };
+  Address cur_addr_;  // current iteration point
+  Address end_addr_;  // end iteration point
+  Address cur_limit_;  // current page limit
+  HeapObjectCallback size_func_;  // size function
+  Page* end_page_;  // caches the page of the end address
 
-  Address cur_addr_;  // Current iteration point.
-  Address cur_end_;   // End iteration point.
-  HeapObjectCallback size_func_;  // Size function or NULL.
-  PagedSpace* space_;
-  PageMode page_mode_;
+  HeapObject* FromCurrentPage() {
+    ASSERT(cur_addr_ < cur_limit_);
 
-  // Fast (inlined) path of next().
-  inline HeapObject* FromCurrentPage();
+    HeapObject* obj = HeapObject::FromAddress(cur_addr_);
+    int obj_size = (size_func_ == NULL) ? obj->Size() : size_func_(obj);
+    ASSERT_OBJECT_SIZE(obj_size);
 
-  // Slow path of next(), goes into the next page.  Returns false if the
-  // iteration has ended.
-  bool AdvanceToNextPage();
+    cur_addr_ += obj_size;
+    ASSERT(cur_addr_ <= cur_limit_);
+
+    return obj;
+  }
+
+  // Slow path of next, goes into the next page.
+  HeapObject* FromNextPage();
 
   // Initializes fields.
-  inline void Initialize(PagedSpace* owner,
-                         Address start,
-                         Address end,
-                         PageMode mode,
-                         HeapObjectCallback size_func);
+  void Initialize(Address start, Address end, HeapObjectCallback size_func);
+
+#ifdef DEBUG
+  // Verifies whether fields have valid values.
+  void Verify();
+#endif
 };
 
 
 // -----------------------------------------------------------------------------
 // A PageIterator iterates the pages in a paged space.
+//
+// The PageIterator class provides three modes for iterating pages in a space:
+//   PAGES_IN_USE iterates pages containing allocated objects.
+//   PAGES_USED_BY_MC iterates pages that hold relocated objects during a
+//                    mark-compact collection.
+//   ALL_PAGES iterates all pages in the space.
+//
+// There are some caveats.
+//
+// (1) If the space expands during iteration, new pages will not be
+//     returned by the iterator in any mode.
+//
+// (2) If new objects are allocated during iteration, they will appear
+//     in pages returned by the iterator.  Allocation may cause the
+//     allocation pointer or MC allocation pointer in the last page to
+//     change between constructing the iterator and iterating the last
+//     page.
+//
+// (3) The space should not shrink during iteration, otherwise the
+//     iterator will return deallocated pages.
 
 class PageIterator BASE_EMBEDDED {
  public:
-  explicit inline PageIterator(PagedSpace* space);
+  enum Mode {
+    PAGES_IN_USE,
+    PAGES_USED_BY_MC,
+    ALL_PAGES
+  };
+
+  PageIterator(PagedSpace* space, Mode mode);
 
   inline bool has_next();
   inline Page* next();
@@ -1168,25 +889,21 @@
  private:
   PagedSpace* space_;
   Page* prev_page_;  // Previous page returned.
-  // Next page that will be returned.  Cached here so that we can use this
-  // iterator for operations that deallocate pages.
-  Page* next_page_;
+  Page* stop_page_;  // Page to stop at (last page returned by the iterator).
 };
 
 
 // -----------------------------------------------------------------------------
-// A space has a circular list of pages. The next page can be accessed via
-// Page::next_page() call.
+// A space has a list of pages. The next page can be accessed via
+// Page::next_page() call. The next page of the last page is an
+// invalid page pointer. A space can expand and shrink dynamically.
 
 // An abstraction of allocation and relocation pointers in a page-structured
 // space.
 class AllocationInfo {
  public:
-  AllocationInfo() : top(NULL), limit(NULL) {
-  }
-
-  Address top;  // Current allocation top.
-  Address limit;  // Current allocation limit.
+  Address top;  // current allocation top
+  Address limit;  // current allocation limit
 
 #ifdef DEBUG
   bool VerifyPagedAllocation() {
@@ -1198,11 +915,11 @@
 
 
 // An abstraction of the accounting statistics of a page-structured space.
-// The 'capacity' of a space is the number of object-area bytes (i.e., not
+// The 'capacity' of a space is the number of object-area bytes (ie, not
 // including page bookkeeping structures) currently in the space. The 'size'
 // of a space is the number of allocated bytes, the 'waste' in the space is
 // the number of bytes that are not allocated and not available to
-// allocation without reorganizing the space via a GC (e.g. small blocks due
+// allocation without reorganizing the space via a GC (eg, small blocks due
 // to internal fragmentation, top of page areas in map space), and the bytes
 // 'available' is the number of unallocated bytes that are not waste.  The
 // capacity is the sum of size, waste, and available.
@@ -1215,213 +932,73 @@
  public:
   AllocationStats() { Clear(); }
 
-  // Zero out all the allocation statistics (i.e., no capacity).
+  // Zero out all the allocation statistics (ie, no capacity).
   void Clear() {
     capacity_ = 0;
+    available_ = 0;
     size_ = 0;
     waste_ = 0;
   }
 
-  void ClearSizeWaste() {
-    size_ = capacity_;
-    waste_ = 0;
-  }
-
-  // Reset the allocation statistics (i.e., available = capacity with no
+  // Reset the allocation statistics (ie, available = capacity with no
   // wasted or allocated bytes).
   void Reset() {
+    available_ = capacity_;
     size_ = 0;
     waste_ = 0;
   }
 
   // Accessors for the allocation statistics.
   intptr_t Capacity() { return capacity_; }
+  intptr_t Available() { return available_; }
   intptr_t Size() { return size_; }
   intptr_t Waste() { return waste_; }
 
-  // Grow the space by adding available bytes.  They are initially marked as
-  // being in use (part of the size), but will normally be immediately freed,
-  // putting them on the free list and removing them from size_.
+  // Grow the space by adding available bytes.
   void ExpandSpace(int size_in_bytes) {
     capacity_ += size_in_bytes;
-    size_ += size_in_bytes;
-    ASSERT(size_ >= 0);
+    available_ += size_in_bytes;
   }
 
-  // Shrink the space by removing available bytes.  Since shrinking is done
-  // during sweeping, bytes have been marked as being in use (part of the size)
-  // and are hereby freed.
+  // Shrink the space by removing available bytes.
   void ShrinkSpace(int size_in_bytes) {
     capacity_ -= size_in_bytes;
-    size_ -= size_in_bytes;
-    ASSERT(size_ >= 0);
+    available_ -= size_in_bytes;
   }
 
   // Allocate from available bytes (available -> size).
   void AllocateBytes(intptr_t size_in_bytes) {
+    available_ -= size_in_bytes;
     size_ += size_in_bytes;
-    ASSERT(size_ >= 0);
   }
 
   // Free allocated bytes, making them available (size -> available).
   void DeallocateBytes(intptr_t size_in_bytes) {
     size_ -= size_in_bytes;
-    ASSERT(size_ >= 0);
+    available_ += size_in_bytes;
   }
 
   // Waste free bytes (available -> waste).
   void WasteBytes(int size_in_bytes) {
-    size_ -= size_in_bytes;
+    available_ -= size_in_bytes;
     waste_ += size_in_bytes;
-    ASSERT(size_ >= 0);
+  }
+
+  // Consider the wasted bytes to be allocated, as they contain filler
+  // objects (waste -> size).
+  void FillWastedBytes(intptr_t size_in_bytes) {
+    waste_ -= size_in_bytes;
+    size_ += size_in_bytes;
   }
 
  private:
   intptr_t capacity_;
+  intptr_t available_;
   intptr_t size_;
   intptr_t waste_;
 };
 
 
-// -----------------------------------------------------------------------------
-// Free lists for old object spaces
-//
-// Free-list nodes are free blocks in the heap.  They look like heap objects
-// (free-list node pointers have the heap object tag, and they have a map like
-// a heap object).  They have a size and a next pointer.  The next pointer is
-// the raw address of the next free list node (or NULL).
-class FreeListNode: public HeapObject {
- public:
-  // Obtain a free-list node from a raw address.  This is not a cast because
-  // it does not check nor require that the first word at the address is a map
-  // pointer.
-  static FreeListNode* FromAddress(Address address) {
-    return reinterpret_cast<FreeListNode*>(HeapObject::FromAddress(address));
-  }
-
-  static inline bool IsFreeListNode(HeapObject* object);
-
-  // Set the size in bytes, which can be read with HeapObject::Size().  This
-  // function also writes a map to the first word of the block so that it
-  // looks like a heap object to the garbage collector and heap iteration
-  // functions.
-  void set_size(Heap* heap, int size_in_bytes);
-
-  // Accessors for the next field.
-  inline FreeListNode* next();
-  inline FreeListNode** next_address();
-  inline void set_next(FreeListNode* next);
-
-  inline void Zap();
-
- private:
-  static const int kNextOffset = POINTER_SIZE_ALIGN(FreeSpace::kHeaderSize);
-
-  DISALLOW_IMPLICIT_CONSTRUCTORS(FreeListNode);
-};
-
-
-// The free list for the old space.  The free list is organized in such a way
-// as to encourage objects allocated around the same time to be near each
-// other.  The normal way to allocate is intended to be by bumping a 'top'
-// pointer until it hits a 'limit' pointer.  When the limit is hit we need to
-// find a new space to allocate from.  This is done with the free list, which
-// is divided up into rough categories to cut down on waste.  Having finer
-// categories would scatter allocation more.
-
-// The old space free list is organized in categories.
-// 1-31 words:  Such small free areas are discarded for efficiency reasons.
-//     They can be reclaimed by the compactor.  However the distance between top
-//     and limit may be this small.
-// 32-255 words: There is a list of spaces this large.  It is used for top and
-//     limit when the object we need to allocate is 1-31 words in size.  These
-//     spaces are called small.
-// 256-2047 words: There is a list of spaces this large.  It is used for top and
-//     limit when the object we need to allocate is 32-255 words in size.  These
-//     spaces are called medium.
-// 1048-16383 words: There is a list of spaces this large.  It is used for top
-//     and limit when the object we need to allocate is 256-2047 words in size.
-//     These spaces are call large.
-// At least 16384 words.  This list is for objects of 2048 words or larger.
-//     Empty pages are added to this list.  These spaces are called huge.
-class FreeList BASE_EMBEDDED {
- public:
-  explicit FreeList(PagedSpace* owner);
-
-  // Clear the free list.
-  void Reset();
-
-  // Return the number of bytes available on the free list.
-  intptr_t available() { return available_; }
-
-  // Place a node on the free list.  The block of size 'size_in_bytes'
-  // starting at 'start' is placed on the free list.  The return value is the
-  // number of bytes that have been lost due to internal fragmentation by
-  // freeing the block.  Bookkeeping information will be written to the block,
-  // i.e., its contents will be destroyed.  The start address should be word
-  // aligned, and the size should be a non-zero multiple of the word size.
-  int Free(Address start, int size_in_bytes);
-
-  // Allocate a block of size 'size_in_bytes' from the free list.  The block
-  // is unitialized.  A failure is returned if no block is available.  The
-  // number of bytes lost to fragmentation is returned in the output parameter
-  // 'wasted_bytes'.  The size should be a non-zero multiple of the word size.
-  MUST_USE_RESULT HeapObject* Allocate(int size_in_bytes);
-
-#ifdef DEBUG
-  void Zap();
-  static intptr_t SumFreeList(FreeListNode* node);
-  static int FreeListLength(FreeListNode* cur);
-  intptr_t SumFreeLists();
-  bool IsVeryLong();
-#endif
-
-  struct SizeStats {
-    intptr_t Total() {
-      return small_size_ + medium_size_ + large_size_ + huge_size_;
-    }
-
-    intptr_t small_size_;
-    intptr_t medium_size_;
-    intptr_t large_size_;
-    intptr_t huge_size_;
-  };
-
-  void CountFreeListItems(Page* p, SizeStats* sizes);
-
-  intptr_t EvictFreeListItems(Page* p);
-
- private:
-  // The size range of blocks, in bytes.
-  static const int kMinBlockSize = 3 * kPointerSize;
-  static const int kMaxBlockSize = Page::kMaxNonCodeHeapObjectSize;
-
-  FreeListNode* PickNodeFromList(FreeListNode** list, int* node_size);
-
-  FreeListNode* FindNodeFor(int size_in_bytes, int* node_size);
-
-  PagedSpace* owner_;
-  Heap* heap_;
-
-  // Total available bytes in all blocks on this free list.
-  int available_;
-
-  static const int kSmallListMin = 0x20 * kPointerSize;
-  static const int kSmallListMax = 0xff * kPointerSize;
-  static const int kMediumListMax = 0x7ff * kPointerSize;
-  static const int kLargeListMax = 0x3fff * kPointerSize;
-  static const int kSmallAllocationMax = kSmallListMin - kPointerSize;
-  static const int kMediumAllocationMax = kSmallListMax;
-  static const int kLargeAllocationMax = kMediumListMax;
-  FreeListNode* small_list_;
-  FreeListNode* medium_list_;
-  FreeListNode* large_list_;
-  FreeListNode* huge_list_;
-
-  DISALLOW_IMPLICIT_CONSTRUCTORS(FreeList);
-};
-
-
 class PagedSpace : public Space {
  public:
   // Creates a space with a maximum capacity, and an id.
@@ -1436,11 +1013,11 @@
   // the memory allocator's initial chunk) if possible.  If the block of
   // addresses is not big enough to contain a single page-aligned page, a
   // fresh chunk will be allocated.
-  bool SetUp();
+  bool Setup(Address start, size_t size);
 
   // Returns true if the space has been successfully set up and not
   // subsequently torn down.
-  bool HasBeenSetUp();
+  bool HasBeenSetup();
 
   // Cleans up the space, frees all pages in this space except those belonging
   // to the initial chunk, uncommits addresses in the initial chunk.
@@ -1449,6 +1026,8 @@
   // Checks whether an object/address is in this space.
   inline bool Contains(Address a);
   bool Contains(HeapObject* o) { return Contains(o->address()); }
+  // Never crashes even if a is not a valid pointer.
+  inline bool SafeContains(Address a);
 
   // Given an address occupied by a live object, return that object if it is
   // in this space, or Failure::Exception() if it is not. The implementation
@@ -1456,92 +1035,104 @@
   // linear in the number of objects in the page. It may be slow.
   MUST_USE_RESULT MaybeObject* FindObject(Address addr);
 
-  // Prepares for a mark-compact GC.
-  virtual void PrepareForMarkCompact();
+  // Checks whether page is currently in use by this space.
+  bool IsUsed(Page* page);
 
-  // Current capacity without growing (Size() + Available()).
+  void MarkAllPagesClean();
+
+  // Prepares for a mark-compact GC.
+  virtual void PrepareForMarkCompact(bool will_compact);
+
+  // The top of allocation in a page in this space. Undefined if page is unused.
+  Address PageAllocationTop(Page* page) {
+    return page == TopPageOf(allocation_info_) ? top()
+        : PageAllocationLimit(page);
+  }
+
+  // The limit of allocation for a page in this space.
+  virtual Address PageAllocationLimit(Page* page) = 0;
+
+  void FlushTopPageWatermark() {
+    AllocationTopPage()->SetCachedAllocationWatermark(top());
+    AllocationTopPage()->InvalidateWatermark(true);
+  }
+
+  // Current capacity without growing (Size() + Available() + Waste()).
   intptr_t Capacity() { return accounting_stats_.Capacity(); }
 
   // Total amount of memory committed for this space.  For paged
   // spaces this equals the capacity.
   intptr_t CommittedMemory() { return Capacity(); }
 
-  // Sets the capacity, the available space and the wasted space to zero.
-  // The stats are rebuilt during sweeping by adding each page to the
-  // capacity and the size when it is encountered.  As free spaces are
-  // discovered during the sweeping they are subtracted from the size and added
-  // to the available and wasted totals.
-  void ClearStats() {
-    accounting_stats_.ClearSizeWaste();
-  }
+  // Available bytes without growing.
+  intptr_t Available() { return accounting_stats_.Available(); }
 
-  // Available bytes without growing.  These are the bytes on the free list.
-  // The bytes in the linear allocation area are not included in this total
-  // because updating the stats would slow down allocation.  New pages are
-  // immediately added to the free list so they show up here.
-  intptr_t Available() { return free_list_.available(); }
-
-  // Allocated bytes in this space.  Garbage bytes that were not found due to
-  // lazy sweeping are counted as being allocated!  The bytes in the current
-  // linear allocation area (between top and limit) are also counted here.
+  // Allocated bytes in this space.
   virtual intptr_t Size() { return accounting_stats_.Size(); }
 
-  // As size, but the bytes in lazily swept pages are estimated and the bytes
-  // in the current linear allocation area are not included.
-  virtual intptr_t SizeOfObjects() {
-    ASSERT(!IsSweepingComplete() || (unswept_free_bytes_ == 0));
-    return Size() - unswept_free_bytes_ - (limit() - top());
-  }
+  // Wasted bytes due to fragmentation and not recoverable until the
+  // next GC of this space.
+  intptr_t Waste() { return accounting_stats_.Waste(); }
 
-  // Wasted bytes in this space.  These are just the bytes that were thrown away
-  // due to being too small to use for allocation.  They do not include the
-  // free bytes that were not found at all due to lazy sweeping.
-  virtual intptr_t Waste() { return accounting_stats_.Waste(); }
+  // Returns the address of the first object in this space.
+  Address bottom() { return first_page_->ObjectAreaStart(); }
 
   // Returns the allocation pointer in this space.
   Address top() { return allocation_info_.top; }
-  Address limit() { return allocation_info_.limit; }
 
   // Allocate the requested number of bytes in the space if possible, return a
   // failure object if not.
   MUST_USE_RESULT inline MaybeObject* AllocateRaw(int size_in_bytes);
 
+  // Allocate the requested number of bytes for relocation during mark-compact
+  // collection.
+  MUST_USE_RESULT inline MaybeObject* MCAllocateRaw(int size_in_bytes);
+
   virtual bool ReserveSpace(int bytes);
 
-  // Give a block of memory to the space's free list.  It might be added to
-  // the free list or accounted as waste.
-  // If add_to_freelist is false then just accounting stats are updated and
-  // no attempt to add area to free list is made.
-  int Free(Address start, int size_in_bytes) {
-    int wasted = free_list_.Free(start, size_in_bytes);
-    accounting_stats_.DeallocateBytes(size_in_bytes - wasted);
-    return size_in_bytes - wasted;
-  }
+  // Used by ReserveSpace.
+  virtual void PutRestOfCurrentPageOnFreeList(Page* current_page) = 0;
+
+  // Free all pages in range from prev (exclusive) to last (inclusive).
+  // Freed pages are moved to the end of page list.
+  void FreePages(Page* prev, Page* last);
+
+  // Deallocates a block.
+  virtual void DeallocateBlock(Address start,
+                               int size_in_bytes,
+                               bool add_to_freelist) = 0;
 
   // Set space allocation info.
-  void SetTop(Address top, Address limit) {
-    ASSERT(top == limit ||
-           Page::FromAddress(top) == Page::FromAddress(limit - 1));
+  void SetTop(Address top) {
     allocation_info_.top = top;
-    allocation_info_.limit = limit;
+    allocation_info_.limit = PageAllocationLimit(Page::FromAllocationTop(top));
   }
 
-  void Allocate(int bytes) {
-    accounting_stats_.AllocateBytes(bytes);
+  // ---------------------------------------------------------------------------
+  // Mark-compact collection support functions
+
+  // Set the relocation point to the beginning of the space.
+  void MCResetRelocationInfo();
+
+  // Writes relocation info to the top page.
+  void MCWriteRelocationInfoToPage() {
+    TopPageOf(mc_forwarding_info_)->
+        SetAllocationWatermark(mc_forwarding_info_.top);
   }
 
-  void IncreaseCapacity(int size) {
-    accounting_stats_.ExpandSpace(size);
-  }
+  // Computes the offset of a given address in this space to the beginning
+  // of the space.
+  int MCSpaceOffsetForAddress(Address addr);
 
-  // Releases an unused page and shrinks the space.
-  void ReleasePage(Page* page);
+  // Updates the allocation pointer to the relocation top after a mark-compact
+  // collection.
+  virtual void MCCommitRelocationInfo() = 0;
 
-  // Releases all of the unused pages.
-  void ReleaseAllUnusedPages();
+  // Releases half of unused pages.
+  void Shrink();
 
-  // The dummy page that anchors the linked list of pages.
-  Page* anchor() { return &anchor_; }
+  // Ensures that the capacity is at least 'capacity'. Returns false on failure.
+  bool EnsureCapacity(int capacity);
 
 #ifdef DEBUG
   // Print meta info and objects in this space.
@@ -1550,9 +1141,6 @@
   // Verify integrity of this space.
   virtual void Verify(ObjectVisitor* visitor);
 
-  // Reports statistics for the space
-  void ReportStatistics();
-
   // Overridden by subclasses to verify space-specific object
   // properties (e.g., only maps or free-list nodes are in map space).
   virtual void VerifyObject(HeapObject* obj) {}
@@ -1563,108 +1151,91 @@
   static void ResetCodeStatistics();
 #endif
 
-  bool was_swept_conservatively() { return was_swept_conservatively_; }
-  void set_was_swept_conservatively(bool b) { was_swept_conservatively_ = b; }
+  // Returns the page of the allocation pointer.
+  Page* AllocationTopPage() { return TopPageOf(allocation_info_); }
 
-  // Evacuation candidates are swept by evacuator.  Needs to return a valid
-  // result before _and_ after evacuation has finished.
-  static bool ShouldBeSweptLazily(Page* p) {
-    return !p->IsEvacuationCandidate() &&
-           !p->IsFlagSet(Page::RESCAN_ON_EVACUATION) &&
-           !p->WasSweptPrecisely();
-  }
-
-  void SetPagesToSweep(Page* first) {
-    ASSERT(unswept_free_bytes_ == 0);
-    if (first == &anchor_) first = NULL;
-    first_unswept_page_ = first;
-  }
-
-  void IncrementUnsweptFreeBytes(int by) {
-    unswept_free_bytes_ += by;
-  }
-
-  void IncreaseUnsweptFreeBytes(Page* p) {
-    ASSERT(ShouldBeSweptLazily(p));
-    unswept_free_bytes_ += (p->area_size() - p->LiveBytes());
-  }
-
-  void DecreaseUnsweptFreeBytes(Page* p) {
-    ASSERT(ShouldBeSweptLazily(p));
-    unswept_free_bytes_ -= (p->area_size() - p->LiveBytes());
-  }
-
-  bool AdvanceSweeper(intptr_t bytes_to_sweep);
-
-  bool IsSweepingComplete() {
-    return !first_unswept_page_->is_valid();
-  }
-
-  Page* FirstPage() { return anchor_.next_page(); }
-  Page* LastPage() { return anchor_.prev_page(); }
-
-  void CountFreeListItems(Page* p, FreeList::SizeStats* sizes) {
-    free_list_.CountFreeListItems(p, sizes);
-  }
-
-  void EvictEvacuationCandidatesFromFreeLists();
-
-  bool CanExpand();
-
-  // Returns the number of total pages in this space.
-  int CountTotalPages();
-
-  // Return size of allocatable area on a page in this space.
-  inline int AreaSize() {
-    return area_size_;
-  }
+  void RelinkPageListInChunkOrder(bool deallocate_blocks);
 
  protected:
-  int area_size_;
-
   // Maximum capacity of this space.
   intptr_t max_capacity_;
 
   // Accounting information for this space.
   AllocationStats accounting_stats_;
 
-  // The dummy page that anchors the double linked list of pages.
-  Page anchor_;
+  // The first page in this space.
+  Page* first_page_;
 
-  // The space's free list.
-  FreeList free_list_;
+  // The last page in this space.  Initially set in Setup, updated in
+  // Expand and Shrink.
+  Page* last_page_;
+
+  // True if pages owned by this space are linked in chunk-order.
+  // See comment for class MemoryAllocator for definition of chunk-order.
+  bool page_list_is_chunk_ordered_;
 
   // Normal allocation information.
   AllocationInfo allocation_info_;
 
+  // Relocation information during mark-compact collections.
+  AllocationInfo mc_forwarding_info_;
+
   // Bytes of each page that cannot be allocated.  Possibly non-zero
   // for pages in spaces with only fixed-size objects.  Always zero
   // for pages in spaces with variable sized objects (those pages are
   // padded with free-list nodes).
   int page_extra_;
 
-  bool was_swept_conservatively_;
+  // Sets allocation pointer to a page bottom.
+  static void SetAllocationInfo(AllocationInfo* alloc_info, Page* p);
 
-  // The first page to be swept when the lazy sweeper advances. Is set
-  // to NULL when all pages have been swept.
-  Page* first_unswept_page_;
+  // Returns the top page specified by an allocation info structure.
+  static Page* TopPageOf(AllocationInfo alloc_info) {
+    return Page::FromAllocationTop(alloc_info.limit);
+  }
 
-  // The number of free bytes which could be reclaimed by advancing the
-  // lazy sweeper.  This is only an estimation because lazy sweeping is
-  // done conservatively.
-  intptr_t unswept_free_bytes_;
+  int CountPagesToTop() {
+    Page* p = Page::FromAllocationTop(allocation_info_.top);
+    PageIterator it(this, PageIterator::ALL_PAGES);
+    int counter = 1;
+    while (it.has_next()) {
+      if (it.next() == p) return counter;
+      counter++;
+    }
+    UNREACHABLE();
+    return -1;
+  }
 
   // Expands the space by allocating a fixed number of pages. Returns false if
-  // it cannot allocate requested number of pages from OS, or if the hard heap
-  // size limit has been hit.
-  bool Expand();
+  // it cannot allocate requested number of pages from OS. Newly allocated
+  // pages are append to the last_page;
+  bool Expand(Page* last_page);
 
-  // Generic fast case allocation function that tries linear allocation at the
-  // address denoted by top in allocation_info_.
-  inline HeapObject* AllocateLinearly(int size_in_bytes);
+  // Generic fast case allocation function that tries linear allocation in
+  // the top page of 'alloc_info'.  Returns NULL on failure.
+  inline HeapObject* AllocateLinearly(AllocationInfo* alloc_info,
+                                      int size_in_bytes);
+
+  // During normal allocation or deserialization, roll to the next page in
+  // the space (there is assumed to be one) and allocate there.  This
+  // function is space-dependent.
+  virtual HeapObject* AllocateInNextPage(Page* current_page,
+                                         int size_in_bytes) = 0;
 
   // Slow path of AllocateRaw.  This function is space-dependent.
-  MUST_USE_RESULT virtual HeapObject* SlowAllocateRaw(int size_in_bytes);
+  MUST_USE_RESULT virtual HeapObject* SlowAllocateRaw(int size_in_bytes) = 0;
+
+  // Slow path of MCAllocateRaw.
+  MUST_USE_RESULT HeapObject* SlowMCAllocateRaw(int size_in_bytes);
+
+#ifdef DEBUG
+  // Returns the number of total pages in this space.
+  int CountTotalPages();
+#endif
+
+ private:
+  // Returns a pointer to the page of the relocation pointer.
+  Page* MCRelocationTopPage() { return TopPageOf(mc_forwarding_info_); }
 
   friend class PageIterator;
 };
@@ -1705,128 +1276,39 @@
 };
 
 
-enum SemiSpaceId {
-  kFromSpace = 0,
-  kToSpace = 1
-};
-
-
-class SemiSpace;
-
-
-class NewSpacePage : public MemoryChunk {
- public:
-  // GC related flags copied from from-space to to-space when
-  // flipping semispaces.
-  static const intptr_t kCopyOnFlipFlagsMask =
-    (1 << MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING) |
-    (1 << MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING) |
-    (1 << MemoryChunk::SCAN_ON_SCAVENGE);
-
-  static const int kAreaSize = Page::kNonCodeObjectAreaSize;
-
-  inline NewSpacePage* next_page() const {
-    return static_cast<NewSpacePage*>(next_chunk());
-  }
-
-  inline void set_next_page(NewSpacePage* page) {
-    set_next_chunk(page);
-  }
-
-  inline NewSpacePage* prev_page() const {
-    return static_cast<NewSpacePage*>(prev_chunk());
-  }
-
-  inline void set_prev_page(NewSpacePage* page) {
-    set_prev_chunk(page);
-  }
-
-  SemiSpace* semi_space() {
-    return reinterpret_cast<SemiSpace*>(owner());
-  }
-
-  bool is_anchor() { return !this->InNewSpace(); }
-
-  static bool IsAtStart(Address addr) {
-    return (reinterpret_cast<intptr_t>(addr) & Page::kPageAlignmentMask)
-        == kObjectStartOffset;
-  }
-
-  static bool IsAtEnd(Address addr) {
-    return (reinterpret_cast<intptr_t>(addr) & Page::kPageAlignmentMask) == 0;
-  }
-
-  Address address() {
-    return reinterpret_cast<Address>(this);
-  }
-
-  // Finds the NewSpacePage containg the given address.
-  static inline NewSpacePage* FromAddress(Address address_in_page) {
-    Address page_start =
-        reinterpret_cast<Address>(reinterpret_cast<uintptr_t>(address_in_page) &
-                                  ~Page::kPageAlignmentMask);
-    NewSpacePage* page = reinterpret_cast<NewSpacePage*>(page_start);
-    return page;
-  }
-
-  // Find the page for a limit address. A limit address is either an address
-  // inside a page, or the address right after the last byte of a page.
-  static inline NewSpacePage* FromLimit(Address address_limit) {
-    return NewSpacePage::FromAddress(address_limit - 1);
-  }
-
- private:
-  // Create a NewSpacePage object that is only used as anchor
-  // for the doubly-linked list of real pages.
-  explicit NewSpacePage(SemiSpace* owner) {
-    InitializeAsAnchor(owner);
-  }
-
-  static NewSpacePage* Initialize(Heap* heap,
-                                  Address start,
-                                  SemiSpace* semi_space);
-
-  // Intialize a fake NewSpacePage used as sentinel at the ends
-  // of a doubly-linked list of real NewSpacePages.
-  // Only uses the prev/next links, and sets flags to not be in new-space.
-  void InitializeAsAnchor(SemiSpace* owner);
-
-  friend class SemiSpace;
-  friend class SemiSpaceIterator;
-};
-
-
 // -----------------------------------------------------------------------------
 // SemiSpace in young generation
 //
-// A semispace is a contiguous chunk of memory holding page-like memory
-// chunks. The mark-compact collector  uses the memory of the first page in
-// the from space as a marking stack when tracing live objects.
+// A semispace is a contiguous chunk of memory. The mark-compact collector
+// uses the memory in the from space as a marking stack when tracing live
+// objects.
 
 class SemiSpace : public Space {
  public:
   // Constructor.
-  SemiSpace(Heap* heap, SemiSpaceId semispace)
-    : Space(heap, NEW_SPACE, NOT_EXECUTABLE),
-      start_(NULL),
-      age_mark_(NULL),
-      id_(semispace),
-      anchor_(this),
-      current_page_(NULL) { }
+  explicit SemiSpace(Heap* heap) : Space(heap, NEW_SPACE, NOT_EXECUTABLE) {
+    start_ = NULL;
+    age_mark_ = NULL;
+  }
 
   // Sets up the semispace using the given chunk.
-  void SetUp(Address start, int initial_capacity, int maximum_capacity);
+  bool Setup(Address start, int initial_capacity, int maximum_capacity);
 
   // Tear down the space.  Heap memory was not allocated by the space, so it
   // is not deallocated here.
   void TearDown();
 
   // True if the space has been set up but not torn down.
-  bool HasBeenSetUp() { return start_ != NULL; }
+  bool HasBeenSetup() { return start_ != NULL; }
+
+  // Grow the size of the semispace by committing extra virtual memory.
+  // Assumes that the caller has checked that the semispace has not reached
+  // its maximum capacity (and thus there is space available in the reserved
+  // address range to grow).
+  bool Grow();
 
   // Grow the semispace to the new capacity.  The new capacity
-  // requested must be larger than the current capacity and less than
-  // the maximum capacity.
+  // requested must be larger than the current capacity.
   bool GrowTo(int new_capacity);
 
   // Shrinks the semispace to the new capacity.  The new capacity
@@ -1834,40 +1316,14 @@
   // semispace and less than the current capacity.
   bool ShrinkTo(int new_capacity);
 
-  // Returns the start address of the first page of the space.
-  Address space_start() {
-    ASSERT(anchor_.next_page() != &anchor_);
-    return anchor_.next_page()->area_start();
-  }
-
-  // Returns the start address of the current page of the space.
-  Address page_low() {
-    return current_page_->area_start();
-  }
-
+  // Returns the start address of the space.
+  Address low() { return start_; }
   // Returns one past the end address of the space.
-  Address space_end() {
-    return anchor_.prev_page()->area_end();
-  }
-
-  // Returns one past the end address of the current page of the space.
-  Address page_high() {
-    return current_page_->area_end();
-  }
-
-  bool AdvancePage() {
-    NewSpacePage* next_page = current_page_->next_page();
-    if (next_page == anchor()) return false;
-    current_page_ = next_page;
-    return true;
-  }
-
-  // Resets the space to using the first page.
-  void Reset();
+  Address high() { return low() + capacity_; }
 
   // Age mark accessors.
   Address age_mark() { return age_mark_; }
-  void set_age_mark(Address mark);
+  void set_age_mark(Address mark) { age_mark_ = mark; }
 
   // True if the address is in the address range of this semispace (not
   // necessarily below the allocation pointer).
@@ -1882,6 +1338,11 @@
     return (reinterpret_cast<uintptr_t>(o) & object_mask_) == object_expected_;
   }
 
+  // The offset of an address from the beginning of the space.
+  int SpaceOffsetForAddress(Address addr) {
+    return static_cast<int>(addr - low());
+  }
+
   // If we don't have these here then SemiSpace will be abstract.  However
   // they should never be called.
   virtual intptr_t Size() {
@@ -1898,19 +1359,9 @@
   bool Commit();
   bool Uncommit();
 
-  NewSpacePage* first_page() { return anchor_.next_page(); }
-  NewSpacePage* current_page() { return current_page_; }
-
 #ifdef DEBUG
   virtual void Print();
   virtual void Verify();
-  // Validate a range of of addresses in a SemiSpace.
-  // The "from" address must be on a page prior to the "to" address,
-  // in the linked page order, or it must be earlier on the same page.
-  static void AssertValidRange(Address from, Address to);
-#else
-  // Do nothing.
-  inline static void AssertValidRange(Address from, Address to) {}
 #endif
 
   // Returns the current capacity of the semi space.
@@ -1922,17 +1373,7 @@
   // Returns the initial capacity of the semi space.
   int InitialCapacity() { return initial_capacity_; }
 
-  SemiSpaceId id() { return id_; }
-
-  static void Swap(SemiSpace* from, SemiSpace* to);
-
  private:
-  // Flips the semispace between being from-space and to-space.
-  // Copies the flags into the masked positions on all pages in the space.
-  void FlipPages(intptr_t flags, intptr_t flag_mask);
-
-  NewSpacePage* anchor() { return &anchor_; }
-
   // The current and maximum capacity of the space.
   int capacity_;
   int maximum_capacity_;
@@ -1949,13 +1390,7 @@
   uintptr_t object_expected_;
 
   bool committed_;
-  SemiSpaceId id_;
 
-  NewSpacePage anchor_;
-  NewSpacePage* current_page_;
-
-  friend class SemiSpaceIterator;
-  friend class NewSpacePageIterator;
  public:
   TRACK_MEMORY("SemiSpace")
 };
@@ -1971,26 +1406,12 @@
   // Create an iterator over the objects in the given space.  If no start
   // address is given, the iterator starts from the bottom of the space.  If
   // no size function is given, the iterator calls Object::Size().
-
-  // Iterate over all of allocated to-space.
   explicit SemiSpaceIterator(NewSpace* space);
-  // Iterate over all of allocated to-space, with a custome size function.
   SemiSpaceIterator(NewSpace* space, HeapObjectCallback size_func);
-  // Iterate over part of allocated to-space, from start to the end
-  // of allocation.
   SemiSpaceIterator(NewSpace* space, Address start);
-  // Iterate from one address to another in the same semi-space.
-  SemiSpaceIterator(Address from, Address to);
 
-  HeapObject* Next() {
+  HeapObject* next() {
     if (current_ == limit_) return NULL;
-    if (NewSpacePage::IsAtEnd(current_)) {
-      NewSpacePage* page = NewSpacePage::FromLimit(current_);
-      page = page->next_page();
-      ASSERT(!page->is_anchor());
-      current_ = page->area_start();
-      if (current_ == limit_) return NULL;
-    }
 
     HeapObject* object = HeapObject::FromAddress(current_);
     int size = (size_func_ == NULL) ? object->Size() : size_func_(object);
@@ -2000,13 +1421,14 @@
   }
 
   // Implementation of the ObjectIterator functions.
-  virtual HeapObject* next_object() { return Next(); }
+  virtual HeapObject* next_object() { return next(); }
 
  private:
-  void Initialize(Address start,
-                  Address end,
+  void Initialize(NewSpace* space, Address start, Address end,
                   HeapObjectCallback size_func);
 
+  // The semispace.
+  SemiSpace* space_;
   // The current iteration point.
   Address current_;
   // The end of iteration.
@@ -2017,34 +1439,6 @@
 
 
 // -----------------------------------------------------------------------------
-// A PageIterator iterates the pages in a semi-space.
-class NewSpacePageIterator BASE_EMBEDDED {
- public:
-  // Make an iterator that runs over all pages in to-space.
-  explicit inline NewSpacePageIterator(NewSpace* space);
-
-  // Make an iterator that runs over all pages in the given semispace,
-  // even those not used in allocation.
-  explicit inline NewSpacePageIterator(SemiSpace* space);
-
-  // Make iterator that iterates from the page containing start
-  // to the page that contains limit in the same semispace.
-  inline NewSpacePageIterator(Address start, Address limit);
-
-  inline bool has_next();
-  inline NewSpacePage* next();
-
- private:
-  NewSpacePage* prev_page_;  // Previous page returned.
-  // Next page that will be returned.  Cached here so that we can use this
-  // iterator for operations that deallocate pages.
-  NewSpacePage* next_page_;
-  // Last page returned.
-  NewSpacePage* last_page_;
-};
-
-
-// -----------------------------------------------------------------------------
 // The young generation space.
 //
 // The new space consists of a contiguous pair of semispaces.  It simply
@@ -2055,21 +1449,19 @@
   // Constructor.
   explicit NewSpace(Heap* heap)
     : Space(heap, NEW_SPACE, NOT_EXECUTABLE),
-      to_space_(heap, kToSpace),
-      from_space_(heap, kFromSpace),
-      reservation_(),
-      inline_allocation_limit_step_(0) {}
+      to_space_(heap),
+      from_space_(heap) {}
 
   // Sets up the new space using the given chunk.
-  bool SetUp(int reserved_semispace_size_, int max_semispace_size);
+  bool Setup(Address start, int size);
 
   // Tears down the space.  Heap memory was not allocated by the space, so it
   // is not deallocated here.
   void TearDown();
 
   // True if the space has been set up but not torn down.
-  bool HasBeenSetUp() {
-    return to_space_.HasBeenSetUp() && from_space_.HasBeenSetUp();
+  bool HasBeenSetup() {
+    return to_space_.HasBeenSetup() && from_space_.HasBeenSetup();
   }
 
   // Flip the pair of spaces.
@@ -2088,30 +1480,18 @@
     return (reinterpret_cast<uintptr_t>(a) & address_mask_)
         == reinterpret_cast<uintptr_t>(start_);
   }
-
   bool Contains(Object* o) {
-    Address a = reinterpret_cast<Address>(o);
-    return (reinterpret_cast<uintptr_t>(a) & object_mask_) == object_expected_;
+    return (reinterpret_cast<uintptr_t>(o) & object_mask_) == object_expected_;
   }
 
   // Return the allocated bytes in the active semispace.
-  virtual intptr_t Size() {
-    return pages_used_ * NewSpacePage::kAreaSize +
-        static_cast<int>(top() - to_space_.page_low());
-  }
-
+  virtual intptr_t Size() { return static_cast<int>(top() - bottom()); }
   // The same, but returning an int.  We have to have the one that returns
   // intptr_t because it is inherited, but if we know we are dealing with the
   // new space, which can't get as big as the other spaces then this is useful:
   int SizeAsInt() { return static_cast<int>(Size()); }
 
   // Return the current capacity of a semispace.
-  intptr_t EffectiveCapacity() {
-    SLOW_ASSERT(to_space_.Capacity() == from_space_.Capacity());
-    return (to_space_.Capacity() / Page::kPageSize) * NewSpacePage::kAreaSize;
-  }
-
-  // Return the current capacity of a semispace.
   intptr_t Capacity() {
     ASSERT(to_space_.Capacity() == from_space_.Capacity());
     return to_space_.Capacity();
@@ -2123,10 +1503,8 @@
     return Capacity();
   }
 
-  // Return the available bytes without growing.
-  intptr_t Available() {
-    return Capacity() - Size();
-  }
+  // Return the available bytes without growing in the active semispace.
+  intptr_t Available() { return Capacity() - Size(); }
 
   // Return the maximum capacity of a semispace.
   int MaximumCapacity() {
@@ -2141,12 +1519,9 @@
   }
 
   // Return the address of the allocation pointer in the active semispace.
-  Address top() {
-    ASSERT(to_space_.current_page()->ContainsLimit(allocation_info_.top));
-    return allocation_info_.top;
-  }
+  Address top() { return allocation_info_.top; }
   // Return the address of the first object in the active semispace.
-  Address bottom() { return to_space_.space_start(); }
+  Address bottom() { return to_space_.low(); }
 
   // Get the age mark of the inactive semispace.
   Address age_mark() { return from_space_.age_mark(); }
@@ -2158,68 +1533,54 @@
   Address start() { return start_; }
   uintptr_t mask() { return address_mask_; }
 
-  INLINE(uint32_t AddressToMarkbitIndex(Address addr)) {
-    ASSERT(Contains(addr));
-    ASSERT(IsAligned(OffsetFrom(addr), kPointerSize) ||
-           IsAligned(OffsetFrom(addr) - 1, kPointerSize));
-    return static_cast<uint32_t>(addr - start_) >> kPointerSizeLog2;
-  }
-
-  INLINE(Address MarkbitIndexToAddress(uint32_t index)) {
-    return reinterpret_cast<Address>(index << kPointerSizeLog2);
-  }
-
   // The allocation top and limit addresses.
   Address* allocation_top_address() { return &allocation_info_.top; }
   Address* allocation_limit_address() { return &allocation_info_.limit; }
 
-  MUST_USE_RESULT INLINE(MaybeObject* AllocateRaw(int size_in_bytes));
+  MUST_USE_RESULT MaybeObject* AllocateRaw(int size_in_bytes) {
+    return AllocateRawInternal(size_in_bytes, &allocation_info_);
+  }
+
+  // Allocate the requested number of bytes for relocation during mark-compact
+  // collection.
+  MUST_USE_RESULT MaybeObject* MCAllocateRaw(int size_in_bytes) {
+    return AllocateRawInternal(size_in_bytes, &mc_forwarding_info_);
+  }
 
   // Reset the allocation pointer to the beginning of the active semispace.
   void ResetAllocationInfo();
+  // Reset the reloction pointer to the bottom of the inactive semispace in
+  // preparation for mark-compact collection.
+  void MCResetRelocationInfo();
+  // Update the allocation pointer in the active semispace after a
+  // mark-compact collection.
+  void MCCommitRelocationInfo();
 
-  void LowerInlineAllocationLimit(intptr_t step) {
-    inline_allocation_limit_step_ = step;
-    if (step == 0) {
-      allocation_info_.limit = to_space_.page_high();
-    } else {
-      allocation_info_.limit = Min(
-          allocation_info_.top + inline_allocation_limit_step_,
-          allocation_info_.limit);
-    }
-    top_on_previous_step_ = allocation_info_.top;
+  // Get the extent of the inactive semispace (for use as a marking stack).
+  Address FromSpaceLow() { return from_space_.low(); }
+  Address FromSpaceHigh() { return from_space_.high(); }
+
+  // Get the extent of the active semispace (to sweep newly copied objects
+  // during a scavenge collection).
+  Address ToSpaceLow() { return to_space_.low(); }
+  Address ToSpaceHigh() { return to_space_.high(); }
+
+  // Offsets from the beginning of the semispaces.
+  int ToSpaceOffsetForAddress(Address a) {
+    return to_space_.SpaceOffsetForAddress(a);
   }
-
-  // Get the extent of the inactive semispace (for use as a marking stack,
-  // or to zap it). Notice: space-addresses are not necessarily on the
-  // same page, so FromSpaceStart() might be above FromSpaceEnd().
-  Address FromSpacePageLow() { return from_space_.page_low(); }
-  Address FromSpacePageHigh() { return from_space_.page_high(); }
-  Address FromSpaceStart() { return from_space_.space_start(); }
-  Address FromSpaceEnd() { return from_space_.space_end(); }
-
-  // Get the extent of the active semispace's pages' memory.
-  Address ToSpaceStart() { return to_space_.space_start(); }
-  Address ToSpaceEnd() { return to_space_.space_end(); }
-
-  inline bool ToSpaceContains(Address address) {
-    return to_space_.Contains(address);
-  }
-  inline bool FromSpaceContains(Address address) {
-    return from_space_.Contains(address);
+  int FromSpaceOffsetForAddress(Address a) {
+    return from_space_.SpaceOffsetForAddress(a);
   }
 
   // True if the object is a heap object in the address range of the
   // respective semispace (not necessarily below the allocation pointer of the
   // semispace).
-  inline bool ToSpaceContains(Object* o) { return to_space_.Contains(o); }
-  inline bool FromSpaceContains(Object* o) { return from_space_.Contains(o); }
+  bool ToSpaceContains(Object* o) { return to_space_.Contains(o); }
+  bool FromSpaceContains(Object* o) { return from_space_.Contains(o); }
 
-  // Try to switch the active semispace to a new, empty, page.
-  // Returns false if this isn't possible or reasonable (i.e., there
-  // are no pages, or the current page is already empty), or true
-  // if successful.
-  bool AddFreshPage();
+  bool ToSpaceContains(Address a) { return to_space_.Contains(a); }
+  bool FromSpaceContains(Address a) { return from_space_.Contains(a); }
 
   virtual bool ReserveSpace(int bytes);
 
@@ -2259,24 +1620,10 @@
     return from_space_.Uncommit();
   }
 
-  inline intptr_t inline_allocation_limit_step() {
-    return inline_allocation_limit_step_;
-  }
-
-  SemiSpace* active_space() { return &to_space_; }
-
  private:
-  // Update allocation info to match the current to-space page.
-  void UpdateAllocationInfo();
-
-  Address chunk_base_;
-  uintptr_t chunk_size_;
-
   // The semispaces.
   SemiSpace to_space_;
   SemiSpace from_space_;
-  VirtualMemory reservation_;
-  int pages_used_;
 
   // Start address and bit mask for containment testing.
   Address start_;
@@ -2287,19 +1634,15 @@
   // Allocation pointer and limit for normal allocation and allocation during
   // mark-compact collection.
   AllocationInfo allocation_info_;
-
-  // When incremental marking is active we will set allocation_info_.limit
-  // to be lower than actual limit and then will gradually increase it
-  // in steps to guarantee that we do incremental marking steps even
-  // when all allocation is performed from inlined generated code.
-  intptr_t inline_allocation_limit_step_;
-
-  Address top_on_previous_step_;
+  AllocationInfo mc_forwarding_info_;
 
   HistogramInfo* allocated_histogram_;
   HistogramInfo* promoted_histogram_;
 
-  MUST_USE_RESULT MaybeObject* SlowAllocateRaw(int size_in_bytes);
+  // Implementation of AllocateRaw and MCAllocateRaw.
+  MUST_USE_RESULT inline MaybeObject* AllocateRawInternal(
+      int size_in_bytes,
+      AllocationInfo* alloc_info);
 
   friend class SemiSpaceIterator;
 
@@ -2309,6 +1652,193 @@
 
 
 // -----------------------------------------------------------------------------
+// Free lists for old object spaces
+//
+// Free-list nodes are free blocks in the heap.  They look like heap objects
+// (free-list node pointers have the heap object tag, and they have a map like
+// a heap object).  They have a size and a next pointer.  The next pointer is
+// the raw address of the next free list node (or NULL).
+class FreeListNode: public HeapObject {
+ public:
+  // Obtain a free-list node from a raw address.  This is not a cast because
+  // it does not check nor require that the first word at the address is a map
+  // pointer.
+  static FreeListNode* FromAddress(Address address) {
+    return reinterpret_cast<FreeListNode*>(HeapObject::FromAddress(address));
+  }
+
+  static inline bool IsFreeListNode(HeapObject* object);
+
+  // Set the size in bytes, which can be read with HeapObject::Size().  This
+  // function also writes a map to the first word of the block so that it
+  // looks like a heap object to the garbage collector and heap iteration
+  // functions.
+  void set_size(Heap* heap, int size_in_bytes);
+
+  // Accessors for the next field.
+  inline Address next(Heap* heap);
+  inline void set_next(Heap* heap, Address next);
+
+ private:
+  static const int kNextOffset = POINTER_SIZE_ALIGN(ByteArray::kHeaderSize);
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(FreeListNode);
+};
+
+
+// The free list for the old space.
+class OldSpaceFreeList BASE_EMBEDDED {
+ public:
+  OldSpaceFreeList(Heap* heap, AllocationSpace owner);
+
+  // Clear the free list.
+  void Reset();
+
+  // Return the number of bytes available on the free list.
+  intptr_t available() { return available_; }
+
+  // Place a node on the free list.  The block of size 'size_in_bytes'
+  // starting at 'start' is placed on the free list.  The return value is the
+  // number of bytes that have been lost due to internal fragmentation by
+  // freeing the block.  Bookkeeping information will be written to the block,
+  // ie, its contents will be destroyed.  The start address should be word
+  // aligned, and the size should be a non-zero multiple of the word size.
+  int Free(Address start, int size_in_bytes);
+
+  // Allocate a block of size 'size_in_bytes' from the free list.  The block
+  // is unitialized.  A failure is returned if no block is available.  The
+  // number of bytes lost to fragmentation is returned in the output parameter
+  // 'wasted_bytes'.  The size should be a non-zero multiple of the word size.
+  MUST_USE_RESULT MaybeObject* Allocate(int size_in_bytes, int* wasted_bytes);
+
+  void MarkNodes();
+
+ private:
+  // The size range of blocks, in bytes. (Smaller allocations are allowed, but
+  // will always result in waste.)
+  static const int kMinBlockSize = 2 * kPointerSize;
+  static const int kMaxBlockSize = Page::kMaxHeapObjectSize;
+
+  Heap* heap_;
+
+  // The identity of the owning space, for building allocation Failure
+  // objects.
+  AllocationSpace owner_;
+
+  // Total available bytes in all blocks on this free list.
+  int available_;
+
+  // Blocks are put on exact free lists in an array, indexed by size in words.
+  // The available sizes are kept in an increasingly ordered list. Entries
+  // corresponding to sizes < kMinBlockSize always have an empty free list
+  // (but index kHead is used for the head of the size list).
+  struct SizeNode {
+    // Address of the head FreeListNode of the implied block size or NULL.
+    Address head_node_;
+    // Size (words) of the next larger available size if head_node_ != NULL.
+    int next_size_;
+  };
+  static const int kFreeListsLength = kMaxBlockSize / kPointerSize + 1;
+  SizeNode free_[kFreeListsLength];
+
+  // Sentinel elements for the size list. Real elements are in ]kHead..kEnd[.
+  static const int kHead = kMinBlockSize / kPointerSize - 1;
+  static const int kEnd = kMaxInt;
+
+  // We keep a "finger" in the size list to speed up a common pattern:
+  // repeated requests for the same or increasing sizes.
+  int finger_;
+
+  // Starting from *prev, find and return the smallest size >= index (words),
+  // or kEnd. Update *prev to be the largest size < index, or kHead.
+  int FindSize(int index, int* prev) {
+    int cur = free_[*prev].next_size_;
+    while (cur < index) {
+      *prev = cur;
+      cur = free_[cur].next_size_;
+    }
+    return cur;
+  }
+
+  // Remove an existing element from the size list.
+  void RemoveSize(int index) {
+    int prev = kHead;
+    int cur = FindSize(index, &prev);
+    ASSERT(cur == index);
+    free_[prev].next_size_ = free_[cur].next_size_;
+    finger_ = prev;
+  }
+
+  // Insert a new element into the size list.
+  void InsertSize(int index) {
+    int prev = kHead;
+    int cur = FindSize(index, &prev);
+    ASSERT(cur != index);
+    free_[prev].next_size_ = index;
+    free_[index].next_size_ = cur;
+  }
+
+  // The size list is not updated during a sequence of calls to Free, but is
+  // rebuilt before the next allocation.
+  void RebuildSizeList();
+  bool needs_rebuild_;
+
+#ifdef DEBUG
+  // Does this free list contain a free block located at the address of 'node'?
+  bool Contains(FreeListNode* node);
+#endif
+
+  DISALLOW_COPY_AND_ASSIGN(OldSpaceFreeList);
+};
+
+
+// The free list for the map space.
+class FixedSizeFreeList BASE_EMBEDDED {
+ public:
+  FixedSizeFreeList(Heap* heap, AllocationSpace owner, int object_size);
+
+  // Clear the free list.
+  void Reset();
+
+  // Return the number of bytes available on the free list.
+  intptr_t available() { return available_; }
+
+  // Place a node on the free list.  The block starting at 'start' (assumed to
+  // have size object_size_) is placed on the free list.  Bookkeeping
+  // information will be written to the block, ie, its contents will be
+  // destroyed.  The start address should be word aligned.
+  void Free(Address start);
+
+  // Allocate a fixed sized block from the free list.  The block is unitialized.
+  // A failure is returned if no block is available.
+  MUST_USE_RESULT MaybeObject* Allocate();
+
+  void MarkNodes();
+
+ private:
+  Heap* heap_;
+
+  // Available bytes on the free list.
+  intptr_t available_;
+
+  // The head of the free list.
+  Address head_;
+
+  // The tail of the free list.
+  Address tail_;
+
+  // The identity of the owning space, for building allocation Failure
+  // objects.
+  AllocationSpace owner_;
+
+  // The size of the objects in this space.
+  int object_size_;
+
+  DISALLOW_COPY_AND_ASSIGN(FixedSizeFreeList);
+};
+
+
+// -----------------------------------------------------------------------------
 // Old object space (excluding map objects)
 
 class OldSpace : public PagedSpace {
@@ -2319,28 +1849,71 @@
            intptr_t max_capacity,
            AllocationSpace id,
            Executability executable)
-      : PagedSpace(heap, max_capacity, id, executable) {
+      : PagedSpace(heap, max_capacity, id, executable),
+        free_list_(heap, id) {
     page_extra_ = 0;
   }
 
+  // The bytes available on the free list (ie, not above the linear allocation
+  // pointer).
+  intptr_t AvailableFree() { return free_list_.available(); }
+
   // The limit of allocation for a page in this space.
   virtual Address PageAllocationLimit(Page* page) {
-    return page->area_end();
+    return page->ObjectAreaEnd();
   }
 
+  // Give a block of memory to the space's free list.  It might be added to
+  // the free list or accounted as waste.
+  // If add_to_freelist is false then just accounting stats are updated and
+  // no attempt to add area to free list is made.
+  void Free(Address start, int size_in_bytes, bool add_to_freelist) {
+    accounting_stats_.DeallocateBytes(size_in_bytes);
+
+    if (add_to_freelist) {
+      int wasted_bytes = free_list_.Free(start, size_in_bytes);
+      accounting_stats_.WasteBytes(wasted_bytes);
+    }
+  }
+
+  virtual void DeallocateBlock(Address start,
+                               int size_in_bytes,
+                               bool add_to_freelist);
+
+  // Prepare for full garbage collection.  Resets the relocation pointer and
+  // clears the free list.
+  virtual void PrepareForMarkCompact(bool will_compact);
+
+  // Updates the allocation pointer to the relocation top after a mark-compact
+  // collection.
+  virtual void MCCommitRelocationInfo();
+
+  virtual void PutRestOfCurrentPageOnFreeList(Page* current_page);
+
+  void MarkFreeListNodes() { free_list_.MarkNodes(); }
+
+#ifdef DEBUG
+  // Reports statistics for the space
+  void ReportStatistics();
+#endif
+
+ protected:
+  // Virtual function in the superclass.  Slow path of AllocateRaw.
+  MUST_USE_RESULT HeapObject* SlowAllocateRaw(int size_in_bytes);
+
+  // Virtual function in the superclass.  Allocate linearly at the start of
+  // the page after current_page (there is assumed to be one).
+  HeapObject* AllocateInNextPage(Page* current_page, int size_in_bytes);
+
+ private:
+  // The space's free list.
+  OldSpaceFreeList free_list_;
+
  public:
   TRACK_MEMORY("OldSpace")
 };
 
 
-// For contiguous spaces, top should be in the space (or at the end) and limit
-// should be the end of the space.
-#define ASSERT_SEMISPACE_ALLOCATION_INFO(info, space) \
-  SLOW_ASSERT((space).page_low() <= (info).top             \
-              && (info).top <= (space).page_high()         \
-              && (info).limit <= (space).page_high())
-
-
 // -----------------------------------------------------------------------------
 // Old space for objects of a fixed size
 
@@ -2353,21 +1926,56 @@
              const char* name)
       : PagedSpace(heap, max_capacity, id, NOT_EXECUTABLE),
         object_size_in_bytes_(object_size_in_bytes),
-        name_(name) {
-    page_extra_ = Page::kNonCodeObjectAreaSize % object_size_in_bytes;
+        name_(name),
+        free_list_(heap, id, object_size_in_bytes) {
+    page_extra_ = Page::kObjectAreaSize % object_size_in_bytes;
   }
 
   // The limit of allocation for a page in this space.
   virtual Address PageAllocationLimit(Page* page) {
-    return page->area_end() - page_extra_;
+    return page->ObjectAreaEnd() - page_extra_;
   }
 
   int object_size_in_bytes() { return object_size_in_bytes_; }
 
+  // Give a fixed sized block of memory to the space's free list.
+  // If add_to_freelist is false then just accounting stats are updated and
+  // no attempt to add area to free list is made.
+  void Free(Address start, bool add_to_freelist) {
+    if (add_to_freelist) {
+      free_list_.Free(start);
+    }
+    accounting_stats_.DeallocateBytes(object_size_in_bytes_);
+  }
+
   // Prepares for a mark-compact GC.
-  virtual void PrepareForMarkCompact();
+  virtual void PrepareForMarkCompact(bool will_compact);
+
+  // Updates the allocation pointer to the relocation top after a mark-compact
+  // collection.
+  virtual void MCCommitRelocationInfo();
+
+  virtual void PutRestOfCurrentPageOnFreeList(Page* current_page);
+
+  virtual void DeallocateBlock(Address start,
+                               int size_in_bytes,
+                               bool add_to_freelist);
+
+  void MarkFreeListNodes() { free_list_.MarkNodes(); }
+
+#ifdef DEBUG
+  // Reports statistic info of the space
+  void ReportStatistics();
+#endif
 
  protected:
+  // Virtual function in the superclass.  Slow path of AllocateRaw.
+  MUST_USE_RESULT HeapObject* SlowAllocateRaw(int size_in_bytes);
+
+  // Virtual function in the superclass.  Allocate linearly at the start of
+  // the page after current_page (there is assumed to be one).
+  HeapObject* AllocateInNextPage(Page* current_page, int size_in_bytes);
+
   void ResetFreeList() {
     free_list_.Reset();
   }
@@ -2378,6 +1986,9 @@
 
   // The name of this space.
   const char* name_;
+
+  // The space's free list.
+  FixedSizeFreeList free_list_;
 };
 
 
@@ -2387,21 +1998,89 @@
 class MapSpace : public FixedSpace {
  public:
   // Creates a map space object with a maximum capacity.
-  MapSpace(Heap* heap, intptr_t max_capacity, AllocationSpace id)
+  MapSpace(Heap* heap,
+           intptr_t max_capacity,
+           int max_map_space_pages,
+           AllocationSpace id)
       : FixedSpace(heap, max_capacity, id, Map::kSize, "map"),
-        max_map_space_pages_(kMaxMapPageIndex - 1) {
+        max_map_space_pages_(max_map_space_pages) {
+    ASSERT(max_map_space_pages < kMaxMapPageIndex);
   }
 
-  // Given an index, returns the page address.
-  // TODO(1600): this limit is artifical just to keep code compilable
-  static const int kMaxMapPageIndex = 1 << 16;
+  // Prepares for a mark-compact GC.
+  virtual void PrepareForMarkCompact(bool will_compact);
 
-  virtual int RoundSizeDownToObjectAlignment(int size) {
-    if (IsPowerOf2(Map::kSize)) {
-      return RoundDown(size, Map::kSize);
-    } else {
-      return (size / Map::kSize) * Map::kSize;
+  // Given an index, returns the page address.
+  Address PageAddress(int page_index) { return page_addresses_[page_index]; }
+
+  static const int kMaxMapPageIndex = 1 << MapWord::kMapPageIndexBits;
+
+  // Are map pointers encodable into map word?
+  bool MapPointersEncodable() {
+    if (!FLAG_use_big_map_space) {
+      ASSERT(CountPagesToTop() <= kMaxMapPageIndex);
+      return true;
     }
+    return CountPagesToTop() <= max_map_space_pages_;
+  }
+
+  // Should be called after forced sweep to find out if map space needs
+  // compaction.
+  bool NeedsCompaction(int live_maps) {
+    return !MapPointersEncodable() && live_maps <= CompactionThreshold();
+  }
+
+  Address TopAfterCompaction(int live_maps) {
+    ASSERT(NeedsCompaction(live_maps));
+
+    int pages_left = live_maps / kMapsPerPage;
+    PageIterator it(this, PageIterator::ALL_PAGES);
+    while (pages_left-- > 0) {
+      ASSERT(it.has_next());
+      it.next()->SetRegionMarks(Page::kAllRegionsCleanMarks);
+    }
+    ASSERT(it.has_next());
+    Page* top_page = it.next();
+    top_page->SetRegionMarks(Page::kAllRegionsCleanMarks);
+    ASSERT(top_page->is_valid());
+
+    int offset = live_maps % kMapsPerPage * Map::kSize;
+    Address top = top_page->ObjectAreaStart() + offset;
+    ASSERT(top < top_page->ObjectAreaEnd());
+    ASSERT(Contains(top));
+
+    return top;
+  }
+
+  void FinishCompaction(Address new_top, int live_maps) {
+    Page* top_page = Page::FromAddress(new_top);
+    ASSERT(top_page->is_valid());
+
+    SetAllocationInfo(&allocation_info_, top_page);
+    allocation_info_.top = new_top;
+
+    int new_size = live_maps * Map::kSize;
+    accounting_stats_.DeallocateBytes(accounting_stats_.Size());
+    accounting_stats_.AllocateBytes(new_size);
+
+    // Flush allocation watermarks.
+    for (Page* p = first_page_; p != top_page; p = p->next_page()) {
+      p->SetAllocationWatermark(p->AllocationTop());
+    }
+    top_page->SetAllocationWatermark(new_top);
+
+#ifdef DEBUG
+    if (FLAG_enable_slow_asserts) {
+      intptr_t actual_size = 0;
+      for (Page* p = first_page_; p != top_page; p = p->next_page())
+        actual_size += kMapsPerPage * Map::kSize;
+      actual_size += (new_top - top_page->ObjectAreaStart());
+      ASSERT(accounting_stats_.Size() == actual_size);
+    }
+#endif
+
+    Shrink();
+    ResetFreeList();
   }
 
  protected:
@@ -2410,7 +2089,7 @@
 #endif
 
  private:
-  static const int kMapsPerPage = Page::kNonCodeObjectAreaSize / Map::kSize;
+  static const int kMapsPerPage = Page::kObjectAreaSize / Map::kSize;
 
   // Do map space compaction if there is a page gap.
   int CompactionThreshold() {
@@ -2419,6 +2098,9 @@
 
   const int max_map_space_pages_;
 
+  // An array of page start address in a map space.
+  Address page_addresses_[kMaxMapPageIndex];
+
  public:
   TRACK_MEMORY("MapSpace")
 };
@@ -2434,14 +2116,6 @@
       : FixedSpace(heap, max_capacity, id, JSGlobalPropertyCell::kSize, "cell")
   {}
 
-  virtual int RoundSizeDownToObjectAlignment(int size) {
-    if (IsPowerOf2(JSGlobalPropertyCell::kSize)) {
-      return RoundDown(size, JSGlobalPropertyCell::kSize);
-    } else {
-      return (size / JSGlobalPropertyCell::kSize) * JSGlobalPropertyCell::kSize;
-    }
-  }
-
  protected:
 #ifdef DEBUG
   virtual void VerifyObject(HeapObject* obj);
@@ -2459,26 +2133,81 @@
 // A large object always starts at Page::kObjectStartOffset to a page.
 // Large objects do not move during garbage collections.
 
-class LargeObjectSpace : public Space {
+// A LargeObjectChunk holds exactly one large object page with exactly one
+// large object.
+class LargeObjectChunk {
  public:
-  LargeObjectSpace(Heap* heap, intptr_t max_capacity, AllocationSpace id);
-  virtual ~LargeObjectSpace() {}
+  // Allocates a new LargeObjectChunk that contains a large object page
+  // (Page::kPageSize aligned) that has at least size_in_bytes (for a large
+  // object) bytes after the object area start of that page.
+  static LargeObjectChunk* New(int size_in_bytes, Executability executable);
 
-  // Initializes internal data structures.
-  bool SetUp();
+  // Free the memory associated with the chunk.
+  void Free(Executability executable);
 
-  // Releases internal resources, frees objects in this space.
-  void TearDown();
+  // Interpret a raw address as a large object chunk.
+  static LargeObjectChunk* FromAddress(Address address) {
+    return reinterpret_cast<LargeObjectChunk*>(address);
+  }
 
+  // Returns the address of this chunk.
+  Address address() { return reinterpret_cast<Address>(this); }
+
+  Page* GetPage() {
+    return Page::FromAddress(RoundUp(address(), Page::kPageSize));
+  }
+
+  // Accessors for the fields of the chunk.
+  LargeObjectChunk* next() { return next_; }
+  void set_next(LargeObjectChunk* chunk) { next_ = chunk; }
+  size_t size() { return size_ & ~Page::kPageFlagMask; }
+
+  // Compute the start address in the chunk.
+  Address GetStartAddress() { return GetPage()->ObjectAreaStart(); }
+
+  // Returns the object in this chunk.
+  HeapObject* GetObject() { return HeapObject::FromAddress(GetStartAddress()); }
+
+  // Given a requested size returns the physical size of a chunk to be
+  // allocated.
+  static int ChunkSizeFor(int size_in_bytes);
+
+  // Given a chunk size, returns the object size it can accommodate.  Used by
+  // LargeObjectSpace::Available.
   static intptr_t ObjectSizeFor(intptr_t chunk_size) {
     if (chunk_size <= (Page::kPageSize + Page::kObjectStartOffset)) return 0;
     return chunk_size - Page::kPageSize - Page::kObjectStartOffset;
   }
 
-  // Shared implementation of AllocateRaw, AllocateRawCode and
-  // AllocateRawFixedArray.
-  MUST_USE_RESULT MaybeObject* AllocateRaw(int object_size,
-                                           Executability executable);
+ private:
+  // A pointer to the next large object chunk in the space or NULL.
+  LargeObjectChunk* next_;
+
+  // The total size of this chunk.
+  size_t size_;
+
+ public:
+  TRACK_MEMORY("LargeObjectChunk")
+};
+
+
+class LargeObjectSpace : public Space {
+ public:
+  LargeObjectSpace(Heap* heap, AllocationSpace id);
+  virtual ~LargeObjectSpace() {}
+
+  // Initializes internal data structures.
+  bool Setup();
+
+  // Releases internal resources, frees objects in this space.
+  void TearDown();
+
+  // Allocates a (non-FixedArray, non-Code) large object.
+  MUST_USE_RESULT MaybeObject* AllocateRaw(int size_in_bytes);
+  // Allocates a large Code object.
+  MUST_USE_RESULT MaybeObject* AllocateRawCode(int size_in_bytes);
+  // Allocates a large FixedArray.
+  MUST_USE_RESULT MaybeObject* AllocateRawFixedArray(int size_in_bytes);
 
   // Available bytes for objects in this space.
   inline intptr_t Available();
@@ -2500,9 +2229,12 @@
   // space, may be slow.
   MaybeObject* FindObject(Address a);
 
-  // Finds a large object page containing the given address, returns NULL
+  // Finds a large object page containing the given pc, returns NULL
   // if such a page doesn't exist.
-  LargePage* FindPage(Address a);
+  LargeObjectChunk* FindChunkContainingPc(Address pc);
+
+  // Iterates objects covered by dirty regions.
+  void IterateDirtyRegions(ObjectSlotCallback func);
 
   // Frees unmarked objects.
   void FreeUnmarkedObjects();
@@ -2511,15 +2243,13 @@
   bool Contains(HeapObject* obj);
 
   // Checks whether the space is empty.
-  bool IsEmpty() { return first_page_ == NULL; }
+  bool IsEmpty() { return first_chunk_ == NULL; }
 
   // See the comments for ReserveSpace in the Space class.  This has to be
   // called after ReserveSpace has been called on the paged spaces, since they
   // may use some memory, leaving less for large objects.
   virtual bool ReserveSpace(int bytes);
 
-  LargePage* first_page() { return first_page_; }
-
 #ifdef DEBUG
   virtual void Verify();
   virtual void Print();
@@ -2531,14 +2261,17 @@
   bool SlowContains(Address addr) { return !FindObject(addr)->IsFailure(); }
 
  private:
-  intptr_t max_capacity_;
   // The head of the linked list of large object chunks.
-  LargePage* first_page_;
+  LargeObjectChunk* first_chunk_;
   intptr_t size_;  // allocated bytes
   int page_count_;  // number of chunks
   intptr_t objects_size_;  // size of objects
-  // Map MemoryChunk::kAlignment-aligned chunks to large pages covering them
-  HashMap chunk_map_;
+
+  // Shared implementation of AllocateRaw, AllocateRawCode and
+  // AllocateRawFixedArray.
+  MUST_USE_RESULT MaybeObject* AllocateRawInternal(int requested_size,
+                                                   int object_size,
+                                                   Executability executable);
 
   friend class LargeObjectIterator;
 
@@ -2552,78 +2285,17 @@
   explicit LargeObjectIterator(LargeObjectSpace* space);
   LargeObjectIterator(LargeObjectSpace* space, HeapObjectCallback size_func);
 
-  HeapObject* Next();
+  HeapObject* next();
 
   // implementation of ObjectIterator.
-  virtual HeapObject* next_object() { return Next(); }
+  virtual HeapObject* next_object() { return next(); }
 
  private:
-  LargePage* current_;
+  LargeObjectChunk* current_;
   HeapObjectCallback size_func_;
 };
 
 
-// Iterates over the chunks (pages and large object pages) that can contain
-// pointers to new space.
-class PointerChunkIterator BASE_EMBEDDED {
- public:
-  inline explicit PointerChunkIterator(Heap* heap);
-
-  // Return NULL when the iterator is done.
-  MemoryChunk* next() {
-    switch (state_) {
-      case kOldPointerState: {
-        if (old_pointer_iterator_.has_next()) {
-          return old_pointer_iterator_.next();
-        }
-        state_ = kMapState;
-        // Fall through.
-      }
-      case kMapState: {
-        if (map_iterator_.has_next()) {
-          return map_iterator_.next();
-        }
-        state_ = kLargeObjectState;
-        // Fall through.
-      }
-      case kLargeObjectState: {
-        HeapObject* heap_object;
-        do {
-          heap_object = lo_iterator_.Next();
-          if (heap_object == NULL) {
-            state_ = kFinishedState;
-            return NULL;
-          }
-          // Fixed arrays are the only pointer-containing objects in large
-          // object space.
-        } while (!heap_object->IsFixedArray());
-        MemoryChunk* answer = MemoryChunk::FromAddress(heap_object->address());
-        return answer;
-      }
-      case kFinishedState:
-        return NULL;
-      default:
-        break;
-    }
-    UNREACHABLE();
-    return NULL;
-  }
-
-
- private:
-  enum State {
-    kOldPointerState,
-    kMapState,
-    kLargeObjectState,
-    kFinishedState
-  };
-  State state_;
-  PageIterator old_pointer_iterator_;
-  PageIterator map_iterator_;
-  LargeObjectIterator lo_iterator_;
-};
-
-
 #ifdef DEBUG
 struct CommentStatistic {
   const char* comment;