marker.h

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// 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/gc_shared.h"
#include "vm/heap/pointer_block.h"
#include "vm/os_thread.h"  // Mutex.
 
namespace dart {
 
// Forward declarations.
class HandleVisitor;
class Heap;
class IsolateGroup;
class ObjectPointerVisitor;
class PageSpace;
template <bool sync>
class MarkingVisitorBase;
class Page;
class Thread;
 
// 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
// UntaggedObject. Instances have a lifetime that spans from the beginning 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(IsolateGroup* isolate_group, 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);
 
  // Contribute to marking.
  void IncrementalMarkWithUnlimitedBudget(PageSpace* page_space);
  void IncrementalMarkWithSizeBudget(PageSpace* page_space, intptr_t size);
  void IncrementalMarkWithTimeBudget(PageSpace* page_space, int64_t deadline);
 
  // (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);
 
  intptr_t marked_words() const { return marked_bytes_ >> kWordSizeLog2; }
  intptr_t MarkedWordsPerMicro() const;
 
  void PruneWeak(Scavenger* scavenger);
 
 private:
  void Prologue();
  void Epilogue();
  void ResetSlices();
  void IterateRoots(ObjectPointerVisitor* visitor);
  void IterateWeakRoots(Thread* thread);
  void ProcessWeakHandles(Thread* thread);
  void ProcessWeakTables(Thread* thread);
  void ProcessRememberedSet(Thread* thread);
 
  // Called by anyone: finalize and accumulate stats from 'visitor'.
  template <class MarkingVisitorType>
  void FinalizeResultsFrom(MarkingVisitorType* visitor);
 
  IsolateGroup* const isolate_group_;
  Heap* const heap_;
  // The regular marking worklists, divided by generation. The marker and the
  // write-barrier push here. Dividing by generation allows faster filtering at
  // the end of a scavenge.
  MarkingStack old_marking_stack_;
  MarkingStack new_marking_stack_;
  // New-space objects whose scanning is being delayed because they are still in
  // a TLAB and subject to write barrier eliminiation. Unlike
  // [deferred_marking_stack_], the objects are always marked and never
  // repeated. Tney can be folded back into the regular mark list after a
  // scavenge, preventing accumulation of STW work.
  MarkingStack tlab_deferred_marking_stack_;
  // Objects that need to be marked (non-writable instructions) or scanned
  // (object used in a barrier-skipping context) during the final STW phase.
  // Unlike the other mark lists, objects might be repeated in this list, and
  // need to be scanned even if they are already marked.
  MarkingStack deferred_marking_stack_;
  GCLinkedLists global_list_;
  MarkingVisitorBase<true>** visitors_;
 
  Monitor root_slices_monitor_;
  RelaxedAtomic<intptr_t> root_slices_started_;
  intptr_t root_slices_finished_;
  intptr_t root_slices_count_;
  RelaxedAtomic<intptr_t> weak_slices_started_;
 
  uintptr_t marked_bytes_;
  int64_t marked_micros_;
 
  friend class ConcurrentMarkTask;
  friend class ParallelMarkTask;
  friend class Scavenger;
  template <bool sync>
  friend class MarkingVisitorBase;
  DISALLOW_IMPLICIT_CONSTRUCTORS(GCMarker);
};
 
}  // namespace dart
 
#endif  // RUNTIME_VM_HEAP_MARKER_H_