Basic implementation of incremental marking.

src/heap.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1101 matching lines @@
   static inline void MoveBlock(Address dst, Address src, int byte_size);
 
   // Check new space expansion criteria and expand semispaces if it was hit.
   static void CheckNewSpaceExpansionCriteria();
 
   static inline void IncrementYoungSurvivorsCounter(int survived) {
     young_survivors_after_last_gc_ = survived;
     survived_since_last_expansion_ += survived;
   }
 
+  static inline bool NextGCIsLikelyToBeFull() {
+    intptr_t total_promoted =
+        PromotedSpaceSize() + PromotedExternalMemorySize();
+
+    intptr_t adjusted_promotion_limit =
+        old_gen_promotion_limit_ - new_space_.Capacity();
+
+    if (total_promoted >= adjusted_promotion_limit) return true;
+
+    intptr_t adjusted_allocation_limit =
+        old_gen_allocation_limit_ - new_space_.Capacity() / 5;
+
+    if (PromotedSpaceSize() >= adjusted_allocation_limit) return true;
+
+    return false;
+  }
+
+
   static void UpdateNewSpaceReferencesInExternalStringTable(
       ExternalStringTableUpdaterCallback updater_func);
 
   static void ProcessWeakReferences(WeakObjectRetainer* retainer);
 
   // Helper function that governs the promotion policy from new space to
   // old.  If the object's old address lies below the new space's age
   // mark or if we've already filled the bottom 1/16th of the to space,
   // we try to promote this object.
   static inline bool ShouldBePromoted(Address old_address, int object_size);
@@ skipping 1023 matching lines @@
 
  private:
   static const uintptr_t kNotMarkedBit = 0x1;
   STATIC_ASSERT((kHeapObjectTag & kNotMarkedBit) != 0);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_