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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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 *
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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
27
28 #include "gc_implementation/g1/g1HeapSpanningTable.hpp"
29
30 class HeapRegion;
31 class HeapRegionClosure;
32 class FreeRegionList;
33
34 // This class keeps track of the region metadata (i.e., HeapRegion
35 // instances). They are kept in the _regions array in address
36 // order. A region's index in the array corresponds to its index in
37 // the heap (i.e., 0 is the region at the bottom of the heap, 1 is
38 // the one after it, etc.). Two regions that are consecutive in the
39 // array should also be adjacent in the address space (i.e.,
40 // region(i).end() == region(i+1).bottom().
41 //
42 // We create a HeapRegion when we commit the region's address space
43 // for the first time. When we uncommit the address space of a
44 // region we retain the HeapRegion to be able to re-use it in the
45 // future (in case we recommit it).
46 //
47 // We keep track of three lengths (all three are maintained by the
48 // G1HeapSpanningTable superclass):
49 //
50 // * _length (returned by length()) is the number of currently
51 // committed regions.
52 // * _length_high_watermark is the number of regions for which we have
53 // already allocated HeapRegions.
54 // * _max_length (returned by max_length()) is the maximum number of
55 // regions the heap can have.
56 //
57 // and maintain that: _length <= _length_high_watermark <= _max_length
58
59 class HeapRegionSeq: public G1HeapSpanningTable<HeapRegion*> {
60 friend class VMStructs;
61
62 // The array that holds the HeapRegion instances.
63 HeapRegion** _regions;
64
65 // As above, but biased to address 0.
66 HeapRegion** _regions_biased;
67
68 // A hint for which index to start searching from for humongous
69 // allocations.
70 uint _next_search_index;
71
72 // Find a contiguous set of empty regions of length num, starting
73 // from the given index.
74 uint find_contiguous_from(uint from, uint num);
75
76 public:
77
78 // Return the HeapRegion at the given index. Assume that the index
79 // is valid.
80 inline HeapRegion* at(uint index) const;
81
82 // If addr is within the committed space return its corresponding
83 // HeapRegion, otherwise return NULL.
84 inline HeapRegion* at(HeapWord* addr) const;
85
86 // Return the HeapRegion that corresponds to the given address.
87 // Assume the address is valid.
88 inline HeapRegion* at_unsafe(HeapWord* addr) const;
89
90 // Return the number of contiguous regions at the end of the sequence
91 // that are available for allocation.
92 uint free_suffix();
93
94 // Find a contiguous set of empty regions of length num and return
95 // the index of the first region or G1_NULL_HRS_INDEX if the
96 // search was unsuccessful.
97 uint find_contiguous(uint num);
98
99 // Apply blk->doHeapRegion() on all committed regions in address order,
100 // terminating the iteration early if doHeapRegion() returns true.
101 void iterate(HeapRegionClosure* blk) const;
102
103 // As above, but start the iteration from hr and loop around. If hr
104 // is NULL, we start from the first region in the heap.
105 void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const;
106
107 // Expand the sequence to reflect that the heap has grown from
108 // old_end to new_end. Either create new HeapRegions, or re-use
109 // existing ones, and return them in the given list. Returns the
110 // memory region that covers the newly-created regions. If a
111 // HeapRegion allocation fails, the returned memory region might be
112 // smaller than the desired one.
113 MemRegion expand_to(HeapWord* new_end, FreeRegionList* list);
114
115 // Tag as uncommitted as many regions that are completely free as
116 // possible, up to new_end, from the suffix of the committed
117 // sequence. Return a MemRegion that corresponds to the address
118 // range of the uncommitted regions.
119 MemRegion shrink_to(HeapWord* new_end, uint* num_regions_deleted);
120
121 // Do sanity checking.
122 void verify_optional() PRODUCT_RETURN;
123
124 // Empty constructor, we'll do all initialization in the initialize() method.
125 HeapRegionSeq() { }
126
127 void initialize(HeapWord* bottom, HeapWord* max_end);
128 };
129
130 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP