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.
22 *
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
32 class G1CollectedHeap;
33 class G1CMBitMap;
34 class 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.
40 class G1CardLiveData VALUE_OBJ_CLASS_SPEC {
41 friend class G1CardLiveDataHelper;
42 friend class G1VerifyCardLiveDataTask;
43 private:
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 // While concurrently creating live data regions may be reclaimed (e.g. 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 BitMap live_cards_bm() const { return BitMap(_live_cards, _live_cards_size_in_bits); }
69 // The bits in this bitmap indicate that a given region contains some live objects.
70 BitMap live_regions_bm() const { return BitMap(_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 BitMap 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;
82 public:
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