[heap] Move to LAB-based allocation for newspace evacuation.

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index 40604d424cc425b43871446b53d41599fd395a6c..ce1c79c6ed90a032b9c384082c5127579c6def37 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -1465,7 +1465,13 @@ class PageIterator BASE_EMBEDDED {
 // space.
 class AllocationInfo {
  public:
-  AllocationInfo() : top_(NULL), limit_(NULL) {}
+  AllocationInfo() : top_(nullptr), limit_(nullptr) {}
+  AllocationInfo(Address top, Address limit) : top_(top), limit_(limit) {}
+
+  void Reset(Address top, Address limit) {
+    set_top(top);
+    set_limit(limit);
+  }
 
   INLINE(void set_top(Address top)) {
     SLOW_DCHECK(top == NULL ||
@@ -1862,6 +1868,37 @@ class AllocationResult {
 STATIC_ASSERT(sizeof(AllocationResult) == kPointerSize);
 
 
+class LocalAllocationBuffer {

[Hannes Payer (out of office), 2015/12/18 10:29:06]

This class needs a bunch of comments, explaining what is going on.

[Michael Lippautz, 2015/12/18 10:53:05]

Done.

+ public:
+  static inline LocalAllocationBuffer InvalidBuffer();
+  static inline LocalAllocationBuffer FromResult(Heap* heap,
+                                                 AllocationResult result,
+                                                 intptr_t size);
+
+  ~LocalAllocationBuffer() { Close(); }
+
+  // Convert to C++11 move-semantics once allowed by the style guide.
+  LocalAllocationBuffer(const LocalAllocationBuffer& other);
+  LocalAllocationBuffer& operator=(const LocalAllocationBuffer& other);
+
+  MUST_USE_RESULT inline AllocationResult AllocateRawAligned(
+      int size_in_bytes, AllocationAlignment alignment);
+
+  inline bool IsValid() { return allocation_info_.top() != nullptr; }
+
+  // Try to merge LABs, which is only possible when they are adjacent in memory.
+  inline bool TryMerge(LocalAllocationBuffer* other);
+
+ private:
+  LocalAllocationBuffer(Heap* heap, AllocationInfo allocation_info);
+
+  void Close();
+
+  Heap* heap_;
+  AllocationInfo allocation_info_;
+};
+
+
 class PagedSpace : public Space {
  public:
   static const intptr_t kCompactionMemoryWanted = 500 * KB;
@@ -1992,8 +2029,7 @@ class PagedSpace : public Space {
     DCHECK(top == limit ||
            Page::FromAddress(top) == Page::FromAddress(limit - 1));
     MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
-    allocation_info_.set_top(top);
-    allocation_info_.set_limit(limit);
+    allocation_info_.Reset(top, limit);
   }
 
   // Empty space allocation info, returning unused area to free list.
@@ -2734,6 +2770,9 @@ class NewSpace : public Space {
   MUST_USE_RESULT INLINE(AllocationResult AllocateRaw(
       int size_in_bytes, AllocationAlignment alignment));
 
+  MUST_USE_RESULT inline AllocationResult AllocateRawSynchronized(
+      int size_in_bytes, AllocationAlignment alignment);
+
   // Reset the allocation pointer to the beginning of the active semispace.
   void ResetAllocationInfo();
 
@@ -2783,6 +2822,7 @@ class NewSpace : public Space {
   // are no pages, or the current page is already empty), or true
   // if successful.
   bool AddFreshPage();
+  bool AddFreshPageSynchronized();
 
 #ifdef VERIFY_HEAP
   // Verify the active semispace.
@@ -2826,6 +2866,8 @@ class NewSpace : public Space {
   // Update allocation info to match the current to-space page.
   void UpdateAllocationInfo();
 
+  base::Mutex mutex_;
+
   Address chunk_base_;
   uintptr_t chunk_size_;