Use worst-fit allocation in old space for prentured objects.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 3b8a9eadb385bd92b9c0d29659bd01fccdd2fe3b..f3bcf33fbb542cf85bfb327a5bf53b3b45e4493b 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1524,10 +1524,22 @@ class Heap {
     return PromotedSpaceSizeOfObjects() + PromotedExternalMemorySize();
   }
 
+  // TODO(hpayer): When we provide pretenuring support for all kinds of
+  // objects we can change this heuristic and make it depend on the high
+  // promotion mode.
+  inline bool AggressivePromotionMode() {
+    return PretenuredSizeOfObjects() > 0;
+  }
+
+  inline int OldGenerationHighPromotionFactor() {
+    return AggressivePromotionMode() ? 2 : 1;
+  }
+
   // True if we have reached the allocation limit in the old generation that
   // should force the next GC (caused normally) to be a full one.
   inline bool OldGenerationPromotionLimitReached() {
-    return PromotedTotalSize() > old_gen_promotion_limit_;
+    return PromotedTotalSize() >
+        old_gen_promotion_limit_ * OldGenerationHighPromotionFactor();
   }
 
   inline intptr_t OldGenerationSpaceAvailable() {
@@ -1631,12 +1643,14 @@ class Heap {
     intptr_t total_promoted = PromotedTotalSize();
 
     intptr_t adjusted_promotion_limit =
-        old_gen_promotion_limit_ - new_space_.Capacity();
+        old_gen_promotion_limit_ * OldGenerationHighPromotionFactor() -
+            new_space_.Capacity();
 
     if (total_promoted >= adjusted_promotion_limit) return true;
 
     intptr_t adjusted_allocation_limit =
-        old_gen_allocation_limit_ - new_space_.Capacity() / 5;
+        old_gen_allocation_limit_ * OldGenerationHighPromotionFactor() -
+            new_space_.Capacity() / 5;
 
     if (PromotedSpaceSizeOfObjects() >= adjusted_allocation_limit) return true;
 
@@ -1671,6 +1685,10 @@ class Heap {
   // Returns the size of objects residing in non new spaces.
   intptr_t PromotedSpaceSizeOfObjects();
 
+  // TODO(hpayer): We can remove PretenuredSizeOfObjects() when
+  // we provide pretenuring support for all kinds of objects.
+  intptr_t PretenuredSizeOfObjects();
+
   double total_regexp_code_generated() { return total_regexp_code_generated_; }
   void IncreaseTotalRegexpCodeGenerated(int size) {
     total_regexp_code_generated_ += size;