Accelerate old-space growth

runtime/vm/pages.h

Index: runtime/vm/pages.h
===================================================================
--- runtime/vm/pages.h	(revision 35208)
+++ runtime/vm/pages.h	(working copy)
@@ -95,6 +95,8 @@
 
   int GarbageCollectionTimeFraction();
 
+  bool IsEmpty() const { return index_ == 0; }
+
  private:
   static const intptr_t kHistoryLength = 4;
   int64_t start_[kHistoryLength];
@@ -106,14 +108,11 @@
 };
 
 
-// If GC is able to reclaim more than heap_growth_ratio (in percent) memory
-// and if the relative GC time is below a given threshold,
-// then the heap is not grown when the next GC decision is made.
 // PageSpaceController controls the heap size.
 class PageSpaceController {
  public:
   PageSpaceController(int heap_growth_ratio,
-                      int heap_growth_rate,
+                      int heap_growth_max,
                       int garbage_collection_time_ratio);
   ~PageSpaceController();
 
@@ -123,10 +122,6 @@
   bool NeedsGarbageCollection(SpaceUsage after) const;
 
   // Should be called after each collection to update the controller state.
-  // A garbage collection is considered as successful if more than
-  // heap_growth_ratio % of memory got deallocated by the garbage collector.
-  // In this case garbage collection will be performed next time. Otherwise
-  // the heap will grow.
   void EvaluateGarbageCollection(SpaceUsage before,
                                  SpaceUsage after,
                                  int64_t start, int64_t end);
@@ -164,11 +159,11 @@
   // Equivalent to \frac{100-heap_growth_ratio_}{100}.
   double desired_utilization_;
 
-  // Number of pages we grow.
-  int heap_growth_rate_;
+  // Max number of pages we grow.
+  int heap_growth_max_;
 
-  // If the relative GC time stays below garbage_collection_time_ratio_
-  // garbage collection can be performed.
+  // If the relative GC time goes above garbage_collection_time_ratio_ %,
+  // we grow the heap more aggressively.
   int garbage_collection_time_ratio_;
 
   // The time in microseconds of the last time we tried to collect unused