1 /*
2 * Copyright (c) 2001, 2012, 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.
8 *
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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
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23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
27
28 class HeapRegion;
29 class HeapRegionClosure;
30 class FreeRegionList;
31
32 // This class keeps track of the region metadata (i.e., HeapRegion
33 // instances). They are kept in the _regions array in address
34 // order. A region's index in the array corresponds to its index in
35 // the heap (i.e., 0 is the region at the bottom of the heap, 1 is
36 // the one after it, etc.). Two regions that are consecutive in the
37 // array should also be adjacent in the address space (i.e.,
38 // region(i).end() == region(i+1).bottom().
39 //
40 // We create a HeapRegion when we commit the region's address space
41 // for the first time. When we uncommit the address space of a
42 // region we retain the HeapRegion to be able to re-use it in the
43 // future (in case we recommit it).
44 //
45 // We keep track of three lengths:
46 //
47 // * _length (returned by length()) is the number of currently
48 // committed regions.
49 // * _allocated_length (not exposed outside this class) is the
50 // number of regions for which we have HeapRegions.
51 // * _max_length (returned by max_length()) is the maximum number of
52 // regions the heap can have.
53 //
54 // and maintain that: _length <= _allocated_length <= _max_length
55
56 class HeapRegionSeq: public CHeapObj<mtGC> {
57 friend class VMStructs;
58
59 // The array that holds the HeapRegions.
60 HeapRegion** _regions;
61
62 // Version of _regions biased to address 0
63 HeapRegion** _regions_biased;
64
65 // The number of regions committed in the heap.
66 uint _length;
67
68 // The address of the first reserved word in the heap.
69 HeapWord* _heap_bottom;
70
71 // The address of the last reserved word in the heap - 1.
72 HeapWord* _heap_end;
73
74 // The log of the region byte size.
75 uint _region_shift;
76
77 // A hint for which index to start searching from for humongous
78 // allocations.
79 uint _next_search_index;
80
81 // The number of regions for which we have allocated HeapRegions for.
82 uint _allocated_length;
83
84 // The maximum number of regions in the heap.
85 uint _max_length;
86
87 // Find a contiguous set of empty regions of length num, starting
88 // from the given index.
89 uint find_contiguous_from(uint from, uint num);
90
91 // Map a heap address to a biased region index. Assume that the
92 // address is valid.
93 inline uintx addr_to_index_biased(HeapWord* addr) const;
94
95 void increment_length(uint* length) {
96 assert(*length < _max_length, "pre-condition");
97 *length += 1;
98 }
99
100 void decrement_length(uint* length) {
101 assert(*length > 0, "pre-condition");
102 *length -= 1;
103 }
104
105 public:
106 // Empty contructor, we'll initialize it with the initialize() method.
107 HeapRegionSeq() { }
108
109 void initialize(HeapWord* bottom, HeapWord* end, uint max_length);
110
111 // Return the HeapRegion at the given index. Assume that the index
112 // is valid.
113 inline HeapRegion* at(uint index) const;
114
115 // If addr is within the committed space return its corresponding
116 // HeapRegion, otherwise return NULL.
117 inline HeapRegion* addr_to_region(HeapWord* addr) const;
118
119 // Return the HeapRegion that corresponds to the given
120 // address. Assume the address is valid.
121 inline HeapRegion* addr_to_region_unsafe(HeapWord* addr) const;
122
123 // Return the number of regions that have been committed in the heap.
124 uint length() const { return _length; }
125
126 // Return the maximum number of regions in the heap.
127 uint max_length() const { return _max_length; }
128
129 // Expand the sequence to reflect that the heap has grown from
130 // old_end to new_end. Either create new HeapRegions, or re-use
131 // existing ones, and return them in the given list. Returns the
132 // memory region that covers the newly-created regions. If a
133 // HeapRegion allocation fails, the result memory region might be
134 // smaller than the desired one.
135 MemRegion expand_by(HeapWord* old_end, HeapWord* new_end,
136 FreeRegionList* list);
137
138 // Return the number of contiguous regions at the end of the sequence
139 // that are available for allocation.
140 uint free_suffix();
141
142 // Find a contiguous set of empty regions of length num and return
143 // the index of the first region or G1_NULL_HRS_INDEX if the
144 // search was unsuccessful.
145 uint find_contiguous(uint num);
146
147 // Apply blk->doHeapRegion() on all committed regions in address order,
148 // terminating the iteration early if doHeapRegion() returns true.
149 void iterate(HeapRegionClosure* blk) const;
150
151 // As above, but start the iteration from hr and loop around. If hr
152 // is NULL, we start from the first region in the heap.
153 void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const;
154
155 // Tag as uncommitted as many regions that are completely free as
156 // possible, up to shrink_bytes, from the suffix of the committed
157 // sequence. Return a MemRegion that corresponds to the address
158 // range of the uncommitted regions. Assume shrink_bytes is page and
159 // heap region aligned.
160 MemRegion shrink_by(size_t shrink_bytes, uint* num_regions_deleted);
161
162 // Do some sanity checking.
163 void verify_optional() PRODUCT_RETURN;
164 };
165
166 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP