1 /*
2 * Copyright (c) 2015, 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
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23 */
24
25 #ifndef SHARE_VM_GC_SHARED_CMBITMAP_HPP
26 #define SHARE_VM_GC_SHARED_CMBITMAP_HPP
27
28 #include "memory/memRegion.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "utilities/bitMap.hpp"
31 #include "utilities/globalDefinitions.hpp"
32
33 // A generic CM bit map. This is essentially a wrapper around the BitMap
34 // class, with one bit per (1<<_shifter) HeapWords.
35
36 class MarkBitMapRO VALUE_OBJ_CLASS_SPEC {
37 protected:
38 MemRegion _covered; // The heap area covered by this bitmap.
39 HeapWord* _bmStartWord; // base address of range covered by map
40 size_t _bmWordSize; // map size (in #HeapWords covered)
41 const int _shifter; // map to char or bit
42 BitMap _bm; // the bit map itself
43
44 public:
45 // constructor
46 MarkBitMapRO(int shifter);
47
48 // inquiries
49 HeapWord* startWord() const { return _bmStartWord; }
50 // the following is one past the last word in space
51 HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
52
53 // read marks
54
55 bool isMarked(HeapWord* addr) const {
56 assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
57 "outside underlying space?");
58 return _bm.at(heapWordToOffset(addr));
59 }
60
61 // iteration
62 inline bool iterate(BitMapClosure* cl, MemRegion mr);
63
64 // Return the address corresponding to the next marked bit at or after
65 // "addr", and before "limit", if "limit" is non-NULL. If there is no
66 // such bit, returns "limit" if that is non-NULL, or else "endWord()".
67 inline HeapWord* getNextMarkedWordAddress(const HeapWord* addr,
68 const HeapWord* limit = NULL) const;
69
70 // conversion utilities
71 HeapWord* offsetToHeapWord(size_t offset) const {
72 return _bmStartWord + (offset << _shifter);
73 }
74 size_t heapWordToOffset(const HeapWord* addr) const {
75 return pointer_delta(addr, _bmStartWord) >> _shifter;
76 }
77
78 // The argument addr should be the start address of a valid object
79 inline HeapWord* nextObject(HeapWord* addr);
80
81 void print_on_error(outputStream* st, const char* prefix) const;
82
83 // debugging
84 NOT_PRODUCT(bool covers(MemRegion rs) const;)
85 };
86
87 class MarkBitMap : public MarkBitMapRO {
88 private:
89 // Clear bitmap range
90 void do_clear(MemRegion mr, bool large);
91
92 public:
93 static size_t compute_size(size_t heap_size);
94 // Returns the amount of bytes on the heap between two marks in the bitmap.
95 static size_t mark_distance();
96 // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
97 // mark bitmap corresponds to. This is the same as the mark distance above. static size_t heap_map_factor() {
98 static size_t heap_map_factor() {
99 return mark_distance();
100 }
101
102 MarkBitMap() : MarkBitMapRO(LogMinObjAlignment) {}
103
104 // Initializes the underlying BitMap to cover the given area.
105 void initialize(MemRegion heap, MemRegion bitmap);
106
107 // Write marks.
108 inline void mark(HeapWord* addr);
109 inline void clear(HeapWord* addr);
110 inline bool parMark(HeapWord* addr);
111
112 // Clear range. For larger regions, use *_large.
113 void clear() { do_clear(_covered, true); }
114 void clear_range(MemRegion mr) { do_clear(mr, false); }
115 void clear_range_large(MemRegion mr) { do_clear(mr, true); }
116 };
117
118 #endif // SHARE_VM_GC_SHARED_CMBITMAP_HPP