1 /*
2 * Copyright (c) 2001, 2019, 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_GC_G1_G1CARDTABLE_HPP
26 #define SHARE_GC_G1_G1CARDTABLE_HPP
27
28 #include "gc/g1/g1RegionToSpaceMapper.hpp"
29 #include "gc/shared/cardTable.hpp"
30 #include "oops/oopsHierarchy.hpp"
31 #include "utilities/macros.hpp"
32
33 class G1CardTable;
34 class G1RegionToSpaceMapper;
35
36 class G1CardTableChangedListener : public G1MappingChangedListener {
37 private:
38 G1CardTable* _card_table;
39 public:
40 G1CardTableChangedListener() : _card_table(NULL) { }
41
42 void set_card_table(G1CardTable* card_table) { _card_table = card_table; }
43
44 virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
45 };
46
47 class G1CardTable : public CardTable {
48 friend class VMStructs;
49 friend class G1CardTableChangedListener;
50
51 G1CardTableChangedListener _listener;
52
53 public:
54 enum G1CardValues {
55 g1_young_gen = CT_MR_BS_last_reserved << 1,
56
57 // During evacuation we use the card table to consolidate the cards we need to
58 // scan for roots onto the card table from the various sources. Further it is
59 // used to record already completely scanned cards to avoid re-scanning them
60 // when incrementally evacuating the old gen regions of a collection set.
61 // This means that already scanned cards should be preserved.
62 //
63 // The merge at the start of each evacuation round simply sets cards to dirty
64 // that are clean; scanned cards are set to 0x1.
65 //
66 // This means that the LSB determines what to do with the card during evacuation
67 // given the following possible values:
68 //
69 // 11111111 - clean, do not scan
70 // 00000001 - already scanned, do not scan
71 // 00000000 - dirty, needs to be scanned.
72 //
73 g1_card_already_scanned = 0x1
74 };
75
76 static const size_t WordAllClean = SIZE_MAX;
77 static const size_t WordAllDirty = 0;
78
79 STATIC_ASSERT(BitsPerByte == 8);
80 static const size_t WordAlreadyScanned = (SIZE_MAX / 255) * g1_card_already_scanned;
81
82 G1CardTable(MemRegion whole_heap): CardTable(whole_heap, /* scanned concurrently */ true), _listener() {
83 _listener.set_card_table(this);
84 }
85
86 static CardValue g1_young_card_val() { return g1_young_gen; }
87
88 void verify_g1_young_region(MemRegion mr) PRODUCT_RETURN;
89 void g1_mark_as_young(const MemRegion& mr);
90
91 size_t index_for_cardvalue(CardValue const* p) const {
92 return pointer_delta(p, _byte_map, sizeof(CardValue));
93 }
94
95 // Mark the given card as Dirty if it is Clean.
96 inline void mark_clean_as_dirty(size_t card_index);
97
98 // Change Clean cards in a (large) area on the card table as Dirty, preserving
99 // already scanned cards. Assumes that most cards in that area are Clean.
100 inline void mark_region_dirty(size_t start_card_index, size_t num_cards);
101
102 // Mark the given range of cards as Scanned. All of these cards must be Dirty.
103 inline void mark_as_scanned(size_t start_card_index, size_t num_cards);
104
105 inline uint region_idx_for(CardValue* p);
106
107 static size_t compute_size(size_t mem_region_size_in_words) {
108 size_t number_of_slots = (mem_region_size_in_words / card_size_in_words);
109 return ReservedSpace::allocation_align_size_up(number_of_slots);
110 }
111
112 // Returns how many bytes of the heap a single byte of the Card Table corresponds to.
113 static size_t heap_map_factor() { return card_size; }
114
115 void initialize() {}
116 void initialize(G1RegionToSpaceMapper* mapper);
117
118 virtual void resize_covered_region(MemRegion new_region) { ShouldNotReachHere(); }
119
120 virtual bool is_in_young(oop obj) const;
121 };
122
123 #endif // SHARE_GC_G1_G1CARDTABLE_HPP