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 *
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,
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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_allocated_length() {
96 assert(_allocated_length < _max_length, "pre-condition");
97 _allocated_length++;
98 }
99
100 void increment_length() {
101 assert(_length < _max_length, "pre-condition");
102 _length++;
103 }
104
105 void decrement_length() {
106 assert(_length > 0, "pre-condition");
107 _length--;
108 }
109
110 public:
111 // Empty contructor, we'll initialize it with the initialize() method.
112 HeapRegionSeq() { }
113
114 void initialize(HeapWord* bottom, HeapWord* end, uint max_length);
115
116 // Return the HeapRegion at the given index. Assume that the index
117 // is valid.
118 inline HeapRegion* at(uint index) const;
119
120 // If addr is within the committed space return its corresponding
121 // HeapRegion, otherwise return NULL.
122 inline HeapRegion* addr_to_region(HeapWord* addr) const;
123
124 // Return the HeapRegion that corresponds to the given
125 // address. Assume the address is valid.
126 inline HeapRegion* addr_to_region_unsafe(HeapWord* addr) const;
127
128 // Return the number of regions that have been committed in the heap.
129 uint length() const { return _length; }
130
131 // Return the maximum number of regions in the heap.
132 uint max_length() const { return _max_length; }
133
134 // Expand the sequence to reflect that the heap has grown from
135 // old_end to new_end. Either create new HeapRegions, or re-use
136 // existing ones, and return them in the given list. Returns the
137 // memory region that covers the newly-created regions. If a
138 // HeapRegion allocation fails, the result memory region might be
139 // smaller than the desired one.
140 MemRegion expand_by(HeapWord* old_end, HeapWord* new_end,
141 FreeRegionList* list);
142
143 // Return the number of contiguous regions at the end of the sequence
144 // that are available for allocation.
145 uint free_suffix();
146
147 // Find a contiguous set of empty regions of length num and return
148 // the index of the first region or G1_NULL_HRS_INDEX if the
149 // search was unsuccessful.
150 uint find_contiguous(uint num);
151
152 // Apply blk->doHeapRegion() on all committed regions in address order,
153 // terminating the iteration early if doHeapRegion() returns true.
154 void iterate(HeapRegionClosure* blk) const;
155
156 // As above, but start the iteration from hr and loop around. If hr
157 // is NULL, we start from the first region in the heap.
158 void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const;
159
160 // Tag as uncommitted as many regions that are completely free as
161 // possible, up to num_regions_to_remove, from the suffix of the committed
162 // sequence. Return the actual number of removed regions.
163 uint shrink_by(uint num_regions_to_remove);
164
165 // Do some sanity checking.
166 void verify_optional() PRODUCT_RETURN;
167 };
168
169 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP