Start incremental marking on idle notification.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index f488b8cda276316df11e6df8b3e645a533c8b111..f100329daea252846d7231107e69a5ed0e6a887c 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1268,8 +1268,8 @@ class Heap {
     return Min(limit, halfway_to_the_max);
   }
 
-  // Can be called when the embedding application is idle.
-  bool IdleNotification();
+  // Implements the corresponding V8 API function.
+  bool IdleNotification(int hint);
 
   // Declare all the root indices.
   enum RootListIndex {
@@ -1392,6 +1392,17 @@ class Heap {
     return &incremental_marking_;
   }
 
+  bool IsSweepingComplete() {
+    return old_data_space()->IsSweepingComplete() &&
+           old_pointer_space()->IsSweepingComplete();
+  }
+
+  bool AdvanceSweepers(int step_size) {
+    bool sweeping_complete = old_data_space()->AdvanceSweeper(step_size);
+    sweeping_complete &= old_pointer_space()->AdvanceSweeper(step_size);
+    return sweeping_complete;
+  }
+
   ExternalStringTable* external_string_table() {
     return &external_string_table_;
   }
@@ -1427,6 +1438,10 @@ class Heap {
   // The roots that have an index less than this are always in old space.
   static const int kOldSpaceRoots = 0x20;
 
+  bool idle_notification_will_schedule_next_gc() {
+    return idle_notification_will_schedule_next_gc_;
+  }
+
  private:
   Heap();
 
@@ -1477,6 +1492,7 @@ class Heap {
 
   int ms_count_;  // how many mark-sweep collections happened
   unsigned int gc_count_;  // how many gc happened
+  int scavenges_since_last_full_gc_;
 
   // Total length of the strings we failed to flatten since the last GC.
   int unflattened_strings_length_;
@@ -1752,6 +1768,36 @@ class Heap {
 
   void SelectScavengingVisitorsTable();
 
+  void StartIdleRound() {
+    mark_sweeps_since_idle_round_started_ = 0;
+    ms_count_at_last_idle_notification_ = ms_count_;
+  }
+
+  void FinishIdleRound() {
+    mark_sweeps_since_idle_round_started_ = kMaxMarkSweepsInIdleRound;
+  }
+
+  bool EnoughGarbageSinceLastIdleRound() {
+    return (scavenges_since_last_full_gc_ > 4);
+  }
+
+  bool WorthStartingGCWhenIdle() {
+    if (contexts_disposed_ > 0) {
+      return true;
+    }
+    if (mark_sweeps_since_idle_round_started_ < kMaxMarkSweepsInIdleRound) {
+      return incremental_marking()->WorthActivating();
+    }
+    if (EnoughGarbageSinceLastIdleRound()) {
+      return incremental_marking()->WorthActivating() &&
+             NextGCIsLikelyToBeFull();
+    }
+    return false;
+  }
+
+  // Returns true if no more GC work is left.
+  bool IdleGlobalGC();
+
   static const int kInitialSymbolTableSize = 2048;
   static const int kInitialEvalCacheSize = 64;
 
@@ -1781,6 +1827,13 @@ class Heap {
   unsigned int last_idle_notification_gc_count_;
   bool last_idle_notification_gc_count_init_;
 
+  bool idle_notification_will_schedule_next_gc_;
+  int mark_sweeps_since_idle_round_started_;
+  int ms_count_at_last_idle_notification_;
+  unsigned int gc_count_at_last_idle_gc_;
+
+  static const int kMaxMarkSweepsInIdleRound = 7;
+
   // Shared state read by the scavenge collector and set by ScavengeObject.
   PromotionQueue promotion_queue_;