Bring back high promotion mode to shrink young generation size when scavenging latency is high.

src/heap/heap.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_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 2094 matching lines @@
 
   // Initializes the allocation sites scratchpad with undefined values.
   void InitializeAllocationSitesScratchpad();
 
   // Adds an allocation site to the scratchpad if there is space left.
   void AddAllocationSiteToScratchpad(AllocationSite* site,
                                      ScratchpadSlotMode mode);
 
   void UpdateSurvivalStatistics(int start_new_space_size);
 
+  enum SurvivalRateTrend { INCREASING, STABLE, DECREASING, FLUCTUATING };
+
   static const int kYoungSurvivalRateHighThreshold = 90;
+  static const int kYoungSurvivalRateLowThreshold = 10;
   static const int kYoungSurvivalRateAllowedDeviation = 15;
 
   static const int kOldSurvivalRateLowThreshold = 10;
 
+  bool new_space_high_promotion_mode_active_;
   int high_survival_rate_period_length_;
   intptr_t promoted_objects_size_;
+  int low_survival_rate_period_length_;
+  double survival_rate_;
   double promotion_ratio_;
   double promotion_rate_;
   intptr_t semi_space_copied_object_size_;
   intptr_t previous_semi_space_copied_object_size_;
   double semi_space_copied_rate_;
   int nodes_died_in_new_space_;
   int nodes_copied_in_new_space_;
   int nodes_promoted_;
 
   // This is the pretenuring trigger for allocation sites that are in maybe
   // tenure state. When we switched to the maximum new space size we deoptimize
   // the code that belongs to the allocation site and derive the lifetime
   // of the allocation site.
   unsigned int maximum_size_scavenges_;
 
+  SurvivalRateTrend previous_survival_rate_trend_;
+  SurvivalRateTrend survival_rate_trend_;
+
+  void set_survival_rate_trend(SurvivalRateTrend survival_rate_trend) {
+    DCHECK(survival_rate_trend != FLUCTUATING);
+    previous_survival_rate_trend_ = survival_rate_trend_;
+    survival_rate_trend_ = survival_rate_trend;
+  }
+
+  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_;
+    }
+  }
+
+  bool IsStableOrIncreasingSurvivalTrend() {
+    switch (survival_rate_trend()) {
+      case STABLE:
+      case INCREASING:
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  bool IsStableOrDecreasingSurvivalTrend() {
+    switch (survival_rate_trend()) {
+      case STABLE:
+      case DECREASING:
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  bool IsIncreasingSurvivalTrend() {
+    return survival_rate_trend() == INCREASING;
+  }
+
+  bool IsLowSurvivalRate() { return low_survival_rate_period_length_ > 0; }
+
   // TODO(hpayer): Allocation site pretenuring may make this method obsolete.
   // Re-visit incremental marking heuristics.
   bool IsHighSurvivalRate() { return high_survival_rate_period_length_ > 0; }
 
   void ConfigureInitialOldGenerationSize();
 
+  void ConfigureNewGenerationSize();
+
   void SelectScavengingVisitorsTable();
 
   bool HasLowAllocationRate(size_t allocaion_rate);
 
   void ReduceNewSpaceSize(size_t allocaion_rate);
 
   bool TryFinalizeIdleIncrementalMarking(
       double idle_time_in_ms, size_t size_of_objects,
       size_t mark_compact_speed_in_bytes_per_ms);
 
@@ skipping 574 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_