Take survival rates of young objects into account when choosing old generation limits.

src/heap.h

 // Copyright 2006-2008 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 987 matching lines @@
   static inline void MoveBlock(Address dst, Address src, int byte_size);
 
   static inline void MoveBlockToOldSpaceAndUpdateRegionMarks(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 void UpdateNewSpaceReferencesInExternalStringTable(
       ExternalStringTableUpdaterCallback updater_func);
 
   // 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.
@@ skipping 247 matching lines @@
 
   // Initializes the number to string cache based on the max semispace size.
   static Object* InitializeNumberStringCache();
   // Flush the number to string cache.
   static void FlushNumberStringCache();
 
   // Flush code from functions we do not expect to use again. The code will
   // be replaced with a lazy compilable version.
   static void FlushCode();
 
+  static void UpdateSurvivalRateTrend(int start_new_space_size);
+
+  enum SurvivalRateTrend { INCREASING, STABLE, DECREASING, FLUCTUATING };
+
+  static const int kYoungSurvivalRateThreshold = 90;
+  static const int kYoungSurvivalRateAllowedDeviation = 15;
+
+  static int young_survivors_after_last_gc_;
+  static int high_survival_rate_period_length_;
+  static int survival_rate_;
+  static SurvivalRateTrend previous_survival_rate_trend_;
+  static SurvivalRateTrend survival_rate_trend_;
+  static bool bumped_old_gen_limits_;
+
+  static void set_survival_rate_trend(SurvivalRateTrend survival_rate_trend) {
+    ASSERT(survival_rate_trend != FLUCTUATING);
+    previous_survival_rate_trend_ = survival_rate_trend_;
+    survival_rate_trend_ = survival_rate_trend;
+  }
+
+  static SurvivalRateTrend survival_rate_trend() {
+    if (survival_rate_trend_ == STABLE) {
+      return STABLE;
+    } else if (previous_survival_rate_trend_ == STABLE) {
+      return survival_rate_trend_;
+    } else if (survival_rate_trend_ != previous_survival_rate_trend_) {
+      return FLUCTUATING;
+    } else {
+      return survival_rate_trend_;
+    }
+  }
+
+  static bool IsStableOrIncreasingSurvivalTrend() {
+    switch (survival_rate_trend()) {
+      case STABLE:
+      case INCREASING:
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  static bool IsIncreasingSurvivalTrend() {
+    return survival_rate_trend() == INCREASING;
+  }
+
+  static bool IsHighSurvivalRate() {
+    return high_survival_rate_period_length_ > 0;
+  }
+
   static const int kInitialSymbolTableSize = 2048;
   static const int kInitialEvalCacheSize = 64;
 
   friend class Factory;
   friend class DisallowAllocationFailure;
   friend class AlwaysAllocateScope;
   friend class LinearAllocationScope;
 };
 
 
@@ skipping 649 matching lines @@
 
   // To speed up scavenge collections new space string are kept
   // separate from old space strings.
   static List<Object*> new_space_strings_;
   static List<Object*> old_space_strings_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_