view src/hotspot/share/gc/shared/markBitMap.hpp @ 52600:5b87d3fc1093

8213373: Bulk MarkBitMap clearing methods Reviewed-by: rkennke, zgu
author shade
date Thu, 15 Nov 2018 21:05:47 +0100
parents 31b159f30fb2
children 9807daeb47c4
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 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit if you need additional information or have any
 * questions.


#include "memory/memRegion.hpp"
#include "oops/oopsHierarchy.hpp"
#include "utilities/bitMap.hpp"

// A generic mark bitmap for concurrent marking.  This is essentially a wrapper
// around the BitMap class that is based on HeapWords, with one bit per (1 << _shifter) HeapWords.
class MarkBitMap {
  MemRegion _covered;    // The heap area covered by this bitmap.

  const int _shifter;    // Shift amount from heap index to bit index in the bitmap.

  BitMapView _bm;        // The actual bitmap.

  virtual void check_mark(HeapWord* addr) NOT_DEBUG_RETURN;

  // Convert from bit offset to address.
  HeapWord* offset_to_addr(size_t offset) const {
    return _covered.start() + (offset << _shifter);
  // Convert from address to bit offset.
  size_t addr_to_offset(const HeapWord* addr) const {
    return pointer_delta(addr, _covered.start()) >> _shifter;

  // Clear bitmap range
  void do_clear(MemRegion mr, bool large);

  static size_t compute_size(size_t heap_size);
  // Returns the amount of bytes on the heap between two marks in the bitmap.
  static size_t mark_distance();
  // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
  // mark bitmap corresponds to. This is the same as the mark distance above.
  static size_t heap_map_factor() {
    return mark_distance();

  MarkBitMap() : _covered(), _shifter(LogMinObjAlignment), _bm() {}

  // Initializes the underlying BitMap to cover the given area.
  void initialize(MemRegion heap, MemRegion storage);

  // Read marks
  bool is_marked(oop obj) const;
  bool is_marked(HeapWord* addr) const {
           "Address " PTR_FORMAT " is outside underlying space from " PTR_FORMAT " to " PTR_FORMAT,
           p2i(addr), p2i(_covered.start()), p2i(_covered.end()));

  // Return the address corresponding to the next marked bit at or after
  // "addr", and before "limit", if "limit" is non-NULL.  If there is no
  // such bit, returns "limit" if that is non-NULL, or else "endWord()".
  inline HeapWord* get_next_marked_addr(const HeapWord* addr,
                                        const HeapWord* limit) const;

  void print_on_error(outputStream* st, const char* prefix) const;

  // Write marks.
  inline void mark(HeapWord* addr);
  inline void clear(HeapWord* addr);
  inline void clear(oop obj);
  inline bool par_mark(HeapWord* addr);
  inline bool par_mark(oop obj);

  // Clear bitmap.
  void clear()                         { do_clear(_covered, true); }
  void clear_range(MemRegion mr)       { do_clear(mr, false);      }
  void clear_range_large(MemRegion mr) { do_clear(mr, true);       }