1/*
2 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25#ifndef SHARE_VM_GC_G1_G1CARDLIVEDATA_HPP
26#define SHARE_VM_GC_G1_G1CARDLIVEDATA_HPP
27
28#include "gc/g1/g1CollectedHeap.hpp"
29#include "utilities/bitMap.hpp"
30#include "utilities/globalDefinitions.hpp"
31
32class G1CollectedHeap;
33class G1CMBitMap;
34class WorkGang;
35
36// Information about object liveness on the Java heap on a "card" basis.
37// Can be used for various purposes, like as remembered set for completely
38// coarsened remembered sets, scrubbing remembered sets or estimating liveness.
39// This information is created as part of the concurrent marking cycle.
40class G1CardLiveData VALUE_OBJ_CLASS_SPEC {
41  friend class G1CardLiveDataHelper;
42  friend class G1VerifyCardLiveDataTask;
43private:
44  typedef BitMap::bm_word_t bm_word_t;
45  // Store some additional information about the covered area to be able to test.
46  size_t _max_capacity;
47  size_t _cards_per_region;
48
49  // Regions may be reclaimed while concurrently creating live data (e.g. due to humongous
50  // eager reclaim). This results in wrong live data for these regions at the end.
51  // So we need to somehow detect these regions, and during live data finalization completely
52  // recreate their information.
53  // This _gc_timestamp_at_create tracks the global timestamp when live data creation
54  // has started. Any regions with a higher time stamp have been cleared after that
55  // point in time, and need re-finalization.
56  // Unsynchronized access to this variable is okay, since this value is only set during a
57  // concurrent phase, and read only at the Cleanup safepoint. I.e. there is always
58  // full memory synchronization inbetween.
59  uint _gc_timestamp_at_create;
60  // The per-card liveness bitmap.
61  bm_word_t* _live_cards;
62  size_t _live_cards_size_in_bits;
63  // The per-region liveness bitmap.
64  bm_word_t* _live_regions;
65  size_t _live_regions_size_in_bits;
66  // The bits in this bitmap contain for every card whether it contains
67  // at least part of at least one live object.
68  BitMapView live_cards_bm() const { return BitMapView(_live_cards, _live_cards_size_in_bits); }
69  // The bits in this bitmap indicate that a given region contains some live objects.
70  BitMapView live_regions_bm() const { return BitMapView(_live_regions, _live_regions_size_in_bits); }
71
72  // Allocate a "large" bitmap from virtual memory with the given size in bits.
73  bm_word_t* allocate_large_bitmap(size_t size_in_bits);
74  void free_large_bitmap(bm_word_t* map, size_t size_in_bits);
75
76  inline BitMapView live_card_bitmap(uint region);
77
78  inline bool is_card_live_at(BitMap::idx_t idx) const;
79
80  size_t live_region_bitmap_size_in_bits() const;
81  size_t live_card_bitmap_size_in_bits() const;
82public:
83  uint gc_timestamp_at_create() const { return _gc_timestamp_at_create; }
84
85  inline bool is_region_live(uint region) const;
86
87  inline void remove_nonlive_cards(uint region, BitMap* bm);
88  inline void remove_nonlive_regions(BitMap* bm);
89
90  G1CardLiveData();
91  ~G1CardLiveData();
92
93  void initialize(size_t max_capacity, uint num_max_regions);
94  void pretouch();
95
96  // Create the initial liveness data based on the marking result from the bottom
97  // to the ntams of every region in the heap and the marks in the given bitmap.
98  void create(WorkGang* workers, G1CMBitMap* mark_bitmap);
99  // Finalize the liveness data.
100  void finalize(WorkGang* workers, G1CMBitMap* mark_bitmap);
101
102  // Verify that the liveness count data created concurrently matches one created
103  // during this safepoint.
104  void verify(WorkGang* workers, G1CMBitMap* actual_bitmap);
105  // Clear all data structures, prepare for next processing.
106  void clear(WorkGang* workers);
107
108  void verify_is_clear() PRODUCT_RETURN;
109};
110
111#endif /* SHARE_VM_GC_G1_G1CARDLIVEDATA_HPP */
112
113