[heap] Introduce parallel compaction algorithm.

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index 9a91abb537145b31a128c2a89c703244f1eca360..3c3157ec432241a3cb9c1b92dfa0f35db9d63c63 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -268,6 +268,19 @@ class SlotsBuffer;
 // any heap object.
 class MemoryChunk {
  public:
+  // |kCompactionDone|: Initial compaction state of a |MemoryChunk|.
+  // |kCompactingInProgress|:  Parallel compaction is currently in progress.
+  // |kCompactingFinalize|: Parallel compaction is done but the chunk needs to
+  //   be finalized.
+  // |kCompactingAborted|: Parallel compaction has been aborted, which should
+  //   for now only happen in OOM scenarios.
+  enum ParallelCompactingState {
+    kCompactingDone,
+    kCompactingInProgress,
+    kCompactingFinalize,
+    kCompactingAborted,
+  };
+
   // 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);
@@ -458,6 +471,10 @@ class MemoryChunk {
     base::Release_Store(&parallel_sweeping_, state);
   }
 
+  AtomicValue<ParallelCompactingState>& parallel_compaction_state() {
+    return parallel_compaction_;
+  }
+
   bool TryLock() { return mutex_->TryLock(); }
 
   base::Mutex* mutex() { return mutex_; }
@@ -566,6 +583,7 @@ class MemoryChunk {
       + kPointerSize      // AtomicValue high_water_mark_
       + kPointerSize      // base::Mutex* mutex_
       + kPointerSize      // base::AtomicWord parallel_sweeping_
+      + kPointerSize      // AtomicValue parallel_compaction_
       + 5 * kPointerSize  // AtomicNumber free-list statistics
       + kPointerSize      // base::AtomicWord next_chunk_
       + kPointerSize;     // base::AtomicWord prev_chunk_
@@ -726,6 +744,7 @@ class MemoryChunk {
 
   base::Mutex* mutex_;
   base::AtomicWord parallel_sweeping_;
+  AtomicValue<ParallelCompactingState> parallel_compaction_;
 
   // PagedSpace free-list statistics.
   AtomicNumber<intptr_t> available_in_small_free_list_;
@@ -986,9 +1005,6 @@ class CodeRange {
   bool UncommitRawMemory(Address start, size_t length);
   void FreeRawMemory(Address buf, size_t length);
 
-  void ReserveEmergencyBlock();
-  void ReleaseEmergencyBlock();
-
  private:
   // Frees the range of virtual memory, and frees the data structures used to
   // manage it.
@@ -1031,12 +1047,6 @@ class CodeRange {
   List<FreeBlock> allocation_list_;
   int current_allocation_block_index_;
 
-  // Emergency block guarantees that we can always allocate a page for
-  // evacuation candidates when code space is compacted. Emergency block is
-  // reserved immediately after GC and is released immedietely before
-  // allocating a page for evacuation.
-  FreeBlock emergency_block_;
-
   // Finds a block on the allocation list that contains at least the
   // requested amount of memory.  If none is found, sorts and merges
   // the existing free memory blocks, and searches again.
@@ -1969,17 +1979,12 @@ class PagedSpace : public Space {
   // Return size of allocatable area on a page in this space.
   inline int AreaSize() { return area_size_; }
 
-  void CreateEmergencyMemory();
-  void FreeEmergencyMemory();
-  void UseEmergencyMemory();
-  intptr_t MaxEmergencyMemoryAllocated();
-
-  bool HasEmergencyMemory() { return emergency_memory_ != NULL; }
-
   // Merges {other} into the current space. Note that this modifies {other},
   // e.g., removes its bump pointer area and resets statistics.
   void MergeCompactionSpace(CompactionSpace* other);
 
+  void MoveOverFreeMemory(PagedSpace* other);
+
  protected:
   // PagedSpaces that should be included in snapshots have different, i.e.,
   // smaller, initial pages.
@@ -2040,12 +2045,6 @@ class PagedSpace : public Space {
   // end_of_unswept_pages_ page.
   Page* end_of_unswept_pages_;
 
-  // Emergency memory is the memory of a full page for a given space, allocated
-  // conservatively before evacuating a page. If compaction fails due to out
-  // of memory error the emergency memory can be used to complete compaction.
-  // If not used, the emergency memory is released after compaction.
-  MemoryChunk* emergency_memory_;
-
   // Mutex guarding any concurrent access to the space.
   base::Mutex space_mutex_;
 
@@ -2744,6 +2743,32 @@ class CompactionSpace : public PagedSpace {
 };
 
 
+// A collection of |CompactionSpace|s used by a single compaction task.
+class CompactionSpaceCollection : public Malloced {
+ public:
+  explicit CompactionSpaceCollection(Heap* heap)
+      : old_space_(heap, OLD_SPACE, Executability::NOT_EXECUTABLE),
+        code_space_(heap, CODE_SPACE, Executability::EXECUTABLE) {}
+
+  CompactionSpace* Get(AllocationSpace space) {
+    switch (space) {
+      case OLD_SPACE:
+        return &old_space_;
+      case CODE_SPACE:
+        return &code_space_;
+      default:
+        UNREACHABLE();
+    }
+    UNREACHABLE();
+    return nullptr;
+  }
+
+ private:
+  CompactionSpace old_space_;
+  CompactionSpace code_space_;
+};
+
+
 // -----------------------------------------------------------------------------
 // Old object space (includes the old space of objects and code space)