Never uncommit the whole marking deque in case we can't get it back

src/heap/mark-compact.h

 // Copyright 2012 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_MARK_COMPACT_H_
 #define V8_HEAP_MARK_COMPACT_H_
 
 #include "src/base/bits.h"
 #include "src/heap/spaces.h"
 
@@ skipping 164 matching lines @@
 
  private:
   Heap* heap_;
 };
 
 // ----------------------------------------------------------------------------
 // Marking deque for tracing live objects.
 class MarkingDeque {
  public:
   MarkingDeque()
-      : array_(NULL), top_(0), bottom_(0), mask_(0), overflowed_(false) {}
+      : array_(NULL),
+        top_(0),
+        bottom_(0),
+        mask_(0),
+        overflowed_(false),
+        in_use_(false) {}
 
-  void Initialize(Address low, Address high) {
-    HeapObject** obj_low = reinterpret_cast<HeapObject**>(low);
-    HeapObject** obj_high = reinterpret_cast<HeapObject**>(high);
-    array_ = obj_low;
-    mask_ = base::bits::RoundDownToPowerOfTwo32(
-                static_cast<uint32_t>(obj_high - obj_low)) -
-            1;
-    top_ = bottom_ = 0;
-    overflowed_ = false;
-  }
+  void Initialize(Address low, Address high);
+  void Uninitialize(bool aborting = false);
 
   inline bool IsFull() { return ((top_ + 1) & mask_) == bottom_; }
 
   inline bool IsEmpty() { return top_ == bottom_; }
 
   bool overflowed() const { return overflowed_; }
 
+  bool in_use() const { return in_use_; }
+
   void ClearOverflowed() { overflowed_ = false; }
 
   void SetOverflowed() { overflowed_ = true; }
 
   // Push the (marked) object on the marking stack if there is room,
   // otherwise mark the object as overflowed and wait for a rescan of the
   // heap.
   INLINE(void PushBlack(HeapObject* object)) {
     DCHECK(object->IsHeapObject());
     DCHECK(object->map()->IsMap());
@@ skipping 21 matching lines @@
   INLINE(HeapObject* Pop()) {
     DCHECK(!IsEmpty());
     top_ = ((top_ - 1) & mask_);
     HeapObject* object = array_[top_];
     DCHECK(object->IsHeapObject());
     return object;
   }
 
   INLINE(void UnshiftGrey(HeapObject* object)) {
     DCHECK(object->IsHeapObject());
-    DCHECK(Marking::IsGrey(Marking::MarkBitFrom(object)));
     if (IsFull()) {
       SetOverflowed();
     } else {
       bottom_ = ((bottom_ - 1) & mask_);
       array_[bottom_] = object;
     }
   }
 
   INLINE(void UnshiftBlack(HeapObject* object)) {
     DCHECK(object->IsHeapObject());
@@ skipping 16 matching lines @@
 
  private:
   HeapObject** array_;
   // array_[(top - 1) & mask_] is the top element in the deque.  The Deque is
   // empty when top_ == bottom_.  It is full when top_ + 1 == bottom
   // (mod mask + 1).
   int top_;
   int bottom_;
   int mask_;
   bool overflowed_;
+  bool in_use_;
 
   DISALLOW_COPY_AND_ASSIGN(MarkingDeque);
 };
 
 
 class SlotsBufferAllocator {
  public:
   SlotsBuffer* AllocateBuffer(SlotsBuffer* next_buffer);
   void DeallocateBuffer(SlotsBuffer* buffer);
 
@@ skipping 421 matching lines @@
   // Special case for processing weak references in a full collection. We need
   // to artificially keep AllocationSites alive for a time.
   void MarkAllocationSite(AllocationSite* site);
 
   // Mark objects in implicit references groups if their parent object
   // is marked.
   void MarkImplicitRefGroups(MarkObjectFunction mark_object);
 
   MarkingDeque* marking_deque() { return &marking_deque_; }
 
-  void EnsureMarkingDequeIsCommittedAndInitialize(size_t max_size = 4 * MB);
+  static const size_t kMaxMarkingDequeSize = 4 * MB;
+  static const size_t kMinMarkingDequeSize = 256 * KB;
+
+  void EnsureMarkingDequeIsCommittedAndInitialize(size_t max_size) {
+    if (!marking_deque_.in_use()) {
+      EnsureMarkingDequeIsCommitted(max_size);
+      InitializeMarkingDeque();
+    }
+  }
+
+  void EnsureMarkingDequeIsCommitted(size_t max_size);
+  void EnsureMarkingDequeIsReserved();
 
   void InitializeMarkingDeque();
 
-  void UncommitMarkingDeque();
-
   // The following four methods can just be called after marking, when the
   // whole transitive closure is known. They must be called before sweeping
   // when mark bits are still intact.
   bool IsSlotInBlackObject(Page* p, Address slot, HeapObject** out_object);
   bool IsSlotInBlackObjectSlow(Page* p, Address slot);
   bool IsSlotInLiveObject(Address slot);
   void VerifyIsSlotInLiveObject(Address slot, HeapObject* object);
 
  private:
   class SweeperTask;
@@ skipping 208 matching lines @@
 #ifdef DEBUG
   friend class MarkObjectVisitor;
   static void VisitObject(HeapObject* obj);
 
   friend class UnmarkObjectVisitor;
   static void UnmarkObject(HeapObject* obj);
 #endif
 
   Heap* heap_;
   base::VirtualMemory* marking_deque_memory_;
-  bool marking_deque_memory_committed_;
+  size_t marking_deque_memory_committed_;
   MarkingDeque marking_deque_;
   CodeFlusher* code_flusher_;
   bool have_code_to_deoptimize_;
 
   List<Page*> evacuation_candidates_;
   List<Code*> invalidated_code_;
 
   SmartPointer<FreeList> free_list_old_space_;
 
   friend class Heap;
@@ skipping 53 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_MARK_COMPACT_H_