Adjust heuristics for idle notifications after context disposal.

src/heap.h

 // Copyright 2012 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:
 //
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@@ skipping 1942 matching lines @@
     return (scavenges_since_last_idle_round_ >= kIdleScavengeThreshold);
   }
 
   bool WorthStartingGCWhenIdle() {
     if (contexts_disposed_ > 0) {
       return true;
     }
     return incremental_marking()->WorthActivating();
   }
 
+  // Estimates how many milliseconds a Mark-Sweep would take to complete.
+  // In idle notification handler we assume that this function will return:
+  // - a number less than 1000 for any heap size.

[Erik Corry, 2012/03/20 08:16:00]

We should either make sure that this is true, or make sure that we do not assume
it.  I would prefer the latter.

+  // - a number less than 10 for small heaps, which are less than 8Mb.
+  // - a number greater than 10 for large heaps, which are greater than 32Mb.
+  int TimeMarkSweepWouldTakeInMs() {
+    // Rough estimate of how many megabytes of heap can be processed in 1 ms.
+    static const int kMbPerMs = 2;
+
+    int heap_size_mb = static_cast<int>(SizeOfObjects() / MB);
+    return heap_size_mb / kMbPerMs;
+  }
+
   // Returns true if no more GC work is left.
   bool IdleGlobalGC();
 
+  void AdvanceIdleIncrementalMarking(intptr_t step_size);
+
+
   static const int kInitialSymbolTableSize = 2048;
   static const int kInitialEvalCacheSize = 64;
   static const int kInitialNumberStringCacheSize = 256;
 
   // Maximum GC pause.
   int max_gc_pause_;
 
   // Maximum size of objects alive after GC.
   intptr_t max_alive_after_gc_;
 
@@ skipping 695 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_