runtime/vm/heap/marker.h

// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#ifndef RUNTIME_VM_HEAP_MARKER_H_
#define RUNTIME_VM_HEAP_MARKER_H_

#include "vm/allocation.h"
#include "vm/heap/pointer_block.h"
#include "vm/os_thread.h"  // Mutex.

namespace dart {

// Forward declarations.
class HandleVisitor;
class Heap;
class Isolate;
class ObjectPointerVisitor;
class PageSpace;
class RawWeakProperty;
template <bool sync>
class MarkingVisitorBase;

// The class GCMarker is used to mark reachable old generation objects as part
// of the mark-sweep collection. The marking bit used is defined in RawObject.
// Instances have a lifetime that spans from the beginining of concurrent
// marking (or stop-the-world marking) until marking is complete. In particular,
// an instance may be created and destroyed on different threads if the isolate
// is exited during concurrent marking.
class GCMarker {
 public:
  GCMarker(Isolate* isolate, Heap* heap);
  ~GCMarker();

  // Mark roots synchronously, then spawn tasks to concurrently drain the
  // marking queue. Only called when no marking or sweeping is in progress.
  // Marking must later be finalized by calling MarkObjects.
  void StartConcurrentMark(PageSpace* page_space, bool collect_code);

  // (Re)mark roots, drain the marking queue and finalize weak references.
  // Does not required StartConcurrentMark to have been previously called.
  void MarkObjects(PageSpace* page_space, bool collect_code);

  intptr_t marked_words() const { return marked_bytes_ >> kWordSizeLog2; }
  intptr_t MarkedWordsPerMicro() const;

 private:
  void Prologue();
  void Epilogue();
  void IterateRoots(ObjectPointerVisitor* visitor,
                    intptr_t slice_index,
                    intptr_t num_slices);
  void IterateWeakRoots(HandleVisitor* visitor);
  template <class MarkingVisitorType>
  void IterateWeakReferences(MarkingVisitorType* visitor);
  void ProcessWeakTables(PageSpace* page_space);
  void ProcessObjectIdTable();

  // Called by anyone: finalize and accumulate stats from 'visitor'.
  template <class MarkingVisitorType>
  void FinalizeResultsFrom(MarkingVisitorType* visitor);

  Isolate* const isolate_;
  Heap* const heap_;
  MarkingStack marking_stack_;
  MarkingVisitorBase<true>** visitors_;

  Mutex stats_mutex_;
  uintptr_t marked_bytes_;
  int64_t marked_micros_;

  friend class ConcurrentMarkTask;
  friend class MarkTask;
  DISALLOW_IMPLICIT_CONSTRUCTORS(GCMarker);
};

}  // namespace dart

#endif  // RUNTIME_VM_HEAP_MARKER_H_