1 /*
2 * Copyright (c) 2018, 2023, 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_GC_SHARED_MARKBITMAP_HPP
26 #define SHARE_GC_SHARED_MARKBITMAP_HPP
27
28 #include "memory/memRegion.hpp"
29 #include "oops/oopsHierarchy.hpp"
30 #include "utilities/bitMap.hpp"
31
32 // A generic mark bitmap for concurrent marking. This is essentially a wrapper
33 // around the BitMap class that is based on HeapWords, with one bit per (1 << _shifter) HeapWords.
34 class MarkBitMap {
35 protected:
36 MemRegion _covered; // The heap area covered by this bitmap.
37
38 const int _shifter; // Shift amount from heap index to bit index in the bitmap.
39
40 BitMapView _bm; // The actual bitmap.
41
42 virtual void check_mark(HeapWord* addr) NOT_DEBUG_RETURN;
43
44 // Convert from bit offset to address.
45 HeapWord* offset_to_addr(size_t offset) const {
46 return _covered.start() + (offset << _shifter);
47 }
48 // Convert from address to bit offset.
49 size_t addr_to_offset(const HeapWord* addr) const {
50 return pointer_delta(addr, _covered.start()) >> _shifter;
51 }
52
53 // Clear bitmap range
54 void do_clear(MemRegion mr, bool large);
55
56 // Returns the amount of bytes on the heap between two marks in the bitmap.
57 static size_t mark_distance();
58
59 public:
60 static size_t compute_size(size_t heap_size);
61 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
62 // mark bitmap corresponds to. This is the same as the mark distance above.
63 static size_t heap_map_factor() {
64 return mark_distance();
65 }
66
67 MarkBitMap() : _covered(), _shifter(LogMinObjAlignment), _bm() {}
68
69 // Initializes the underlying BitMap to cover the given area.
70 void initialize(MemRegion heap, MemRegion storage);
71
72 // Read marks
73 bool is_marked(oop obj) const;
74 bool is_marked(HeapWord* addr) const {
75 assert(_covered.contains(addr),
76 "Address " PTR_FORMAT " is outside underlying space from " PTR_FORMAT " to " PTR_FORMAT,
77 p2i(addr), p2i(_covered.start()), p2i(_covered.end()));
78 return _bm.at(addr_to_offset(addr));
79 }
80
81 // Return the address corresponding to the next marked bit at or after
82 // "addr", and before "limit", if "limit" is non-null. If there is no
83 // such bit, returns "limit" if that is non-null, or else "endWord()".
84 inline HeapWord* get_next_marked_addr(const HeapWord* addr,
85 HeapWord* limit) const;
86
87 void print_on_error(outputStream* st, const char* prefix) const;
88
89 // Write marks.
90 inline void mark(HeapWord* addr);
91 inline void mark(oop obj);
92 inline void clear(HeapWord* addr);
93 inline void clear(oop obj);
94 inline bool par_mark(HeapWord* addr);
95 inline bool par_mark(oop obj);
96
97 // Clear bitmap.
98 void clear() { do_clear(_covered, true); }
99 void clear_range(MemRegion mr) { do_clear(mr, false); }
100 void clear_range_large(MemRegion mr) { do_clear(mr, true); }
101
102 size_t count_marked(MemRegion mr);
103 };
104
105 #endif // SHARE_GC_SHARED_MARKBITMAP_HPP