1/*
2 * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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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).
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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.
34class MarkBitMap {
35protected:
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
56public:
57 static size_t compute_size(size_t heap_size);
58 // Returns the amount of bytes on the heap between two marks in the bitmap.
59 static size_t mark_distance();
60 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
61 // mark bitmap corresponds to. This is the same as the mark distance above.
62 static size_t heap_map_factor() {
63 return mark_distance();
64 }
65
66 MarkBitMap() : _covered(), _shifter(LogMinObjAlignment), _bm() {}
67
68 // Initializes the underlying BitMap to cover the given area.
69 void initialize(MemRegion heap, MemRegion storage);
70
71 // Read marks
72 bool is_marked(oop obj) const;
73 bool is_marked(HeapWord* addr) const {
74 assert(_covered.contains(addr),
75 "Address " PTR_FORMAT " is outside underlying space from " PTR_FORMAT " to " PTR_FORMAT,
76 p2i(addr), p2i(_covered.start()), p2i(_covered.end()));
77 return _bm.at(addr_to_offset(addr));
78 }
79
80 // Return the address corresponding to the next marked bit at or after
81 // "addr", and before "limit", if "limit" is non-NULL. If there is no
82 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
83 inline HeapWord* get_next_marked_addr(const HeapWord* addr,
84 const HeapWord* limit) const;
85
86 void print_on_error(outputStream* st, const char* prefix) const;
87
88 // Write marks.
89 inline void mark(HeapWord* addr);
90 inline void clear(HeapWord* addr);
91 inline void clear(oop obj);
92 inline bool par_mark(HeapWord* addr);
93 inline bool par_mark(oop obj);
94
95 // Clear bitmap.
96 void clear() { do_clear(_covered, true); }
97 void clear_range(MemRegion mr) { do_clear(mr, false); }
98 void clear_range_large(MemRegion mr) { do_clear(mr, true); }
99};
100
101#endif // SHARE_GC_SHARED_MARKBITMAP_HPP
102