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

src/heap/spaces.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include "src/allocation.h"
 #include "src/atomic-utils.h"
 #include "src/base/atomicops.h"
@@ skipping 1454 matching lines @@
 
 
 // -----------------------------------------------------------------------------
 // A space has a circular list of pages. The next page can be accessed via
 // Page::next_page() call.
 
 // An abstraction of allocation and relocation pointers in a page-structured
 // 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 ||
                 (reinterpret_cast<intptr_t>(top) & kHeapObjectTagMask) == 0);
     top_ = top;
   }
 
   INLINE(Address top()) const {
     SLOW_DCHECK(top_ == NULL ||
                 (reinterpret_cast<intptr_t>(top_) & kHeapObjectTagMask) == 0);
@@ skipping 376 matching lines @@
   explicit AllocationResult(AllocationSpace space)
       : object_(Smi::FromInt(static_cast<int>(space))) {}
 
   Object* object_;
 };
 
 
 STATIC_ASSERT(sizeof(AllocationResult) == kPointerSize);
 
 
+// LocalAllocationBuffer represents a linear allocation area that is created
+// from a given {AllocationResult} and can be used to allocate memory without
+// synchronization.
+//
+// The buffer is properly closed upon destruction and reassignment.
+// Example:
+//   {
+//     AllocationResult result = ...;
+//     LocalAllocationBuffer a(heap, result, size);
+//     LocalAllocationBuffer b = a;
+//     CHECK(!a.IsValid());
+//     CHECK(b.IsValid());
+//     // {a} is invalid now and cannot be used for further allocations.
+//   }
+//   // Since {b} went out of scope, the LAB is closed, resulting in creating a
+//   // filler object for the remaining area.
+class LocalAllocationBuffer {
+ public:
+  // Indicates that a buffer cannot be used for allocations anymore. Can result
+  // from either reassigning a buffer, or trying to construct it from an
+  // invalid {AllocationResult}.
+  static inline LocalAllocationBuffer InvalidBuffer();
+
+  // Creates a new LAB from a given {AllocationResult}. Results in
+  // InvalidBuffer if the result indicates a retry.
+  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.
+  // Returns true if the merge was successful, false otherwise.
+  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;
 
   // Creates a space with an id.
   PagedSpace(Heap* heap, AllocationSpace id, Executability executable);
 
   ~PagedSpace() override { TearDown(); }
 
   // Set up the space using the given address range of virtual memory (from
@@ skipping 110 matching lines @@
     return size_in_bytes - wasted;
   }
 
   void ResetFreeList() { free_list_.Reset(); }
 
   // Set space allocation info.
   void SetTopAndLimit(Address top, Address limit) {
     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.
   void EmptyAllocationInfo() {
     // Mark the old linear allocation area with a free space map so it can be
     // skipped when scanning the heap.
     int old_linear_size = static_cast<int>(limit() - top());
     Free(top(), old_linear_size);
     SetTopAndLimit(NULL, NULL);
   }
@@ skipping 720 matching lines @@
 
   MUST_USE_RESULT INLINE(AllocationResult AllocateRawAligned(
       int size_in_bytes, AllocationAlignment alignment));
 
   MUST_USE_RESULT INLINE(
       AllocationResult AllocateRawUnaligned(int size_in_bytes));
 
   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();
 
   void UpdateInlineAllocationLimit(int size_in_bytes);
 
   // Allows observation of inline allocation. The observer->Step() method gets
   // called after every step_size bytes have been allocated (approximately).
   // This works by adjusting the allocation limit to a lower value and adjusting
   // it after each step.
   void AddInlineAllocationObserver(InlineAllocationObserver* observer);
@@ skipping 29 matching lines @@
   // 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); }
 
   // 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 AddFreshPageSynchronized();
 
 #ifdef VERIFY_HEAP
   // Verify the active semispace.
   virtual void Verify();
 #endif
 
 #ifdef DEBUG
   // Print the active semispace.
   void Print() override { to_space_.Print(); }
 #endif
@@ skipping 23 matching lines @@
   }
 
   bool IsFromSpaceCommitted() { return from_space_.is_committed(); }
 
   SemiSpace* active_space() { return &to_space_; }
 
  private:
   // Update allocation info to match the current to-space page.
   void UpdateAllocationInfo();
 
+  base::Mutex mutex_;
+
   Address chunk_base_;
   uintptr_t chunk_size_;
 
   // The semispaces.
   SemiSpace to_space_;
   SemiSpace from_space_;
   base::VirtualMemory reservation_;
   int pages_used_;
 
   // Start address and bit mask for containment testing.
@@ skipping 309 matching lines @@
     count = 0;
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_