Parallelize marking phase of mark-sweep/compact collection cycle.

src/mark-compact.h

 // Copyright 2006-2008 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:
 //
 //     * 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 21 matching lines @@
 namespace internal {
 
 // Callback function, returns whether an object is alive. The heap size
 // of the object is returned in size. It optionally updates the offset
 // to the first live object in the page (only used for old and map objects).
 typedef bool (*IsAliveFunction)(HeapObject* obj, int* size, int* offset);
 
 // Forward declarations.
 class RootMarkingVisitor;
 class MarkingVisitor;
+class Marker;
 
-
+// ----------------------------------------------------------------------------
+// Marking stack for tracing live objects.
 // -------------------------------------------------------------------------
 // Mark-Compact collector
 //
 // All methods are static.
 
 class MarkCompactCollector: public AllStatic {
  public:
   // Type of functions to compute forwarding addresses of objects in
   // compacted spaces.  Given an object and its size, return a (non-failure)
   // Object* that will be the object after forwarding.  There is a separate
@@ skipping 40 matching lines @@
   static bool IsCompacting() {
 #ifdef DEBUG
     // For the purposes of asserts we don't want this to keep returning true
     // after the collection is completed.
     return state_ != IDLE && compacting_collection_;
 #else
     return compacting_collection_;
 #endif
   }
 
-  // The count of the number of objects left marked at the end of the last
-  // completed full GC (expected to be zero).
-  static int previous_marked_count() { return previous_marked_count_; }
-
   // During a full GC, there is a stack-allocated GCTracer that is used for
   // bookkeeping information.  Return a pointer to that tracer.
   static GCTracer* tracer() { return tracer_; }
 
 #ifdef DEBUG
   // Checks whether performing mark-compact collection.
   static bool in_use() { return state_ > PREPARE_GC; }
   static bool are_map_pointers_encoded() { return state_ == UPDATE_POINTERS; }
 #endif
 
@@ skipping 23 matching lines @@
 
   // Global flag that forces a compaction.
   static bool force_compaction_;
 
   // Global flag indicating whether spaces were compacted on the last GC.
   static bool compacting_collection_;
 
   // Global flag indicating whether spaces will be compacted on the next GC.
   static bool compact_on_next_gc_;
 
-  // The number of objects left marked at the end of the last completed full
-  // GC (expected to be zero).
-  static int previous_marked_count_;
-
   // A pointer to the current stack-allocated GC tracer object during a full
   // collection (NULL before and after).
   static GCTracer* tracer_;
 
   // Finishes GC, performs heap verification if enabled.
   static void Finish();
 
   // -----------------------------------------------------------------------
   // Phase 1: Marking live objects.
   //
   //  Before: The heap has been prepared for garbage collection by
   //          MarkCompactCollector::Prepare() and is otherwise in its
   //          normal state.
   //
   //   After: Live objects are marked and non-live objects are unmarked.
 
 
   friend class RootMarkingVisitor;
   friend class MarkingVisitor;
   friend class StaticMarkingVisitor;
   friend class CodeMarkingVisitor;
   friend class SharedFunctionInfoMarkingVisitor;
+  friend class Marker;
 
   static void PrepareForCodeFlushing();
 
+  // Return total number of markers that will be used during
+  // marking phase.
+  static int NumberOfMarkers() {
+    // If parallel marking is enabled and atomic operations is supported
+    // on this platform use FLAG_number_of_markers otherwise use only
+    // main marker.
+#if ATOMIC_SUPPORTED
+    if (FLAG_parallel_marking) {
+      return 1 + FLAG_number_of_markers;
+    }
+#endif
+
+    return 1;
+  }
+
+
   // Marking operations for objects reachable from roots.
   static void MarkLiveObjects();
 
-  static void MarkUnmarkedObject(HeapObject* obj);
-
-  static inline void MarkObject(HeapObject* obj) {
-    if (!obj->IsMarked()) MarkUnmarkedObject(obj);
-  }
-
-  static inline void SetMark(HeapObject* obj) {
-    tracer_->increment_marked_count();
-#ifdef DEBUG
-    UpdateLiveObjectCount(obj);
-#endif
-    obj->SetMark();
-  }
-
   // Creates back pointers for all map transitions, stores them in
   // the prototype field.  The original prototype pointers are restored
   // in ClearNonLiveTransitions().  All JSObject maps
   // connected by map transitions have the same prototype object, which
   // is why we can use this field temporarily for back pointers.
   static void CreateBackPointers();
 
   // Mark a Map and its DescriptorArray together, skipping transitions.
-  static void MarkMapContents(Map* map);
-  static void MarkDescriptorArray(DescriptorArray* descriptors);
+  static void MarkMapContents(Map* map, Marker* marker);
+
+  static void MarkDescriptorArray(DescriptorArray* descriptors, Marker* marker);
 
   // Mark the heap roots and all objects reachable from them.
-  static void MarkRoots(RootMarkingVisitor* visitor);
+  static void MarkRoots();
 
   // Mark the symbol table specially.  References to symbols from the
   // symbol table are weak.
-  static void MarkSymbolTable();
+  static void MarkSymbolTable(Marker* marker);
 
   // Mark objects in object groups that have at least one object in the
   // group marked.
   static void MarkObjectGroups();
 
   // Mark all objects in an object group with at least one marked
   // object, then all objects reachable from marked objects in object
   // groups, and repeat.
   static void ProcessObjectGroups();
 
-  // Mark objects reachable (transitively) from objects in the marking stack
-  // or overflowed in the heap.
-  static void ProcessMarkingStack();
-
-  // Mark objects reachable (transitively) from objects in the marking
-  // stack.  This function empties the marking stack, but may leave
-  // overflowed objects in the heap, in which case the marking stack's
-  // overflow flag will be set.
-  static void EmptyMarkingStack();
-
-  // Refill the marking stack with overflowed objects from the heap.  This
-  // function either leaves the marking stack full or clears the overflow
-  // flag on the marking stack.
-  static void RefillMarkingStack();
-
   // Callback function for telling whether the object *p is an unmarked
   // heap object.
   static bool IsUnmarkedHeapObject(Object** p);
 
 #ifdef DEBUG
   static void UpdateLiveObjectCount(HeapObject* obj);
 #endif
 
   // We sweep the large object space in the same way whether we are
   // compacting or not, because the large object space is never compacted.
@@ skipping 171 matching lines @@
 
   friend class UnmarkObjectVisitor;
   static void UnmarkObject(HeapObject* obj);
 #endif
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_MARK_COMPACT_H_