Oilpan: Scale up the number of marking threads according to available processors

Source/platform/heap/Heap.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 76 matching lines @@
 const size_t sizeMask = ~heapObjectAgeMask & ~static_cast<size_t>(7);
 #else
 const size_t sizeMask = ~static_cast<size_t>(7);
 #endif
 const uint8_t freelistZapValue = 42;
 const uint8_t finalizedZapValue = 24;
 // The orphaned zap value must be zero in the lowest bits to allow for using
 // the mark bit when tracing.
 const uint8_t orphanedZapValue = 240;
 
-const int numberOfMarkingThreads = 2;
+const int maxNumberOfMarkingThreads = 4;
 
 const int numberOfPagesToConsiderForCoalescing = 100;
 
 enum CallbackInvocationMode {
     GlobalMarking,
     ThreadLocalMarking,
 };
 
 class CallbackStack;
 class HeapStats;
@@ skipping 844 matching lines @@
 
     template<typename T, typename HeapTraits> static Address allocate(size_t);
     // FIXME: remove this once c++11 is allowed everywhere:
     template<typename T> static Address allocate(size_t);
 
     template<typename T> static Address reallocate(void* previous, size_t);
 
     static void collectGarbage(ThreadState::StackState, ThreadState::CauseOfGC = ThreadState::NormalGC);
     static void collectGarbageForTerminatingThread(ThreadState*);
     static void collectAllGarbage();
-    static void processMarkingStackEntries(int* numberOfMarkingThreads);
+    static void processMarkingStackEntries(int*);
     static void processMarkingStackOnMultipleThreads();
     static void processMarkingStackInParallel();
     template<CallbackInvocationMode Mode> static void processMarkingStack();
     static void postMarkingProcessing();
     static void globalWeakProcessing();
     static void setForcePreciseGCForTesting();
 
     static void prepareForGC();
 
     // Conservatively checks whether an address is a pointer in any of the thread
@@ skipping 1477 matching lines @@
 };
 
 template<typename T>
 struct IfWeakMember<WeakMember<T> > {
     static bool isDead(Visitor* visitor, const WeakMember<T>& t) { return !visitor->isAlive(t.get()); }
 };
 
 }
 
 #endif // Heap_h