[heap] Use RAIL mode for initial heap sizing

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index babe107f2fe37f84facbfdacfd38d5d0f3d7c22f..d3af0ea7c20228ce4021e41d8938a5971d4aef38 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -586,8 +586,6 @@ class Heap {
   };
   typedef List<Chunk> Reservation;
 
-  static const int kInitalOldGenerationLimitFactor = 2;
-
 #if V8_OS_ANDROID
   // Don't apply pointer multiplier on Android since it has no swap space and
   // should instead adapt it's heap size based on available physical memory.
@@ -1708,8 +1706,6 @@ class Heap {
   // Flush the number to string cache.
   void FlushNumberStringCache();
 
-  void ConfigureInitialOldGenerationSize();
-
   bool HasLowYoungGenerationAllocationRate();
   bool HasLowOldGenerationAllocationRate();
   double YoungGenerationMutatorUtilization();
@@ -1798,9 +1794,7 @@ class Heap {
   // GC statistics. ============================================================
   // ===========================================================================
 
-  inline intptr_t OldGenerationSpaceAvailable() {
-    return old_generation_allocation_limit_ - PromotedTotalSize();
-  }
+  intptr_t OldGenerationSpaceAvailable();
 
   void UpdateTotalGCTime(double duration);
 
@@ -1810,6 +1804,16 @@ class Heap {
   // Growing strategy. =========================================================
   // ===========================================================================
 
+  static const int kInitalOldGenerationLimitFactor = 2;
+
+  // For some webpages RAIL mode does not switch from PERFORMANCE_LOAD.
+  // This constant limits the effect of load RAIL mode on GC.
+  // The value is arbitrary and chosen as the largest load time observed in
+  // v8 browsing benchmarks.
+  static const int kMaxLoadTimeMs = 3000;

[Hannes Payer (out of office), 2016/10/11 09:02:09]

Why 3 seconds? Load was originally aiming for 1 second.

[ulan, 2016/12/02 11:42:28]

The value is chosen as the largest load time observed in v8 browsing benchmarks.

+
+  bool ShouldOptimizeForLoadTime();
+
   // Decrease the allocation limit if the new limit based on the given
   // parameters is lower than the current limit.
   void DampenOldGenerationAllocationLimit(intptr_t old_gen_size,
@@ -2096,8 +2100,6 @@ class Heap {
   int max_semi_space_size_;
   int initial_semispace_size_;
   intptr_t max_old_generation_size_;
-  intptr_t initial_old_generation_size_;
-  bool old_generation_size_configured_;
   intptr_t max_executable_size_;
   size_t maximum_committed_;