1 /*
2 * Copyright (c) 1997, 2006, 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
21 * questions.
22 *
23 */
24
25 // Blocks
26
27 class HeapBlock VALUE_OBJ_CLASS_SPEC {
28 friend class VMStructs;
29
30 public:
31 struct Header {
32 size_t _length; // the length in segments
33 bool _used; // Used bit
34 };
35
36 protected:
37 union {
38 Header _header;
39 int64_t _padding[ (sizeof(Header) + sizeof(int64_t)-1) / sizeof(int64_t) ];
40 // pad to 0 mod 8
41 };
42
43 public:
44 // Initialization
45 void initialize(size_t length) { _header._length = length; set_used(); }
46
47 // Accessors
48 void* allocated_space() const { return (void*)(this + 1); }
49 size_t length() const { return _header._length; }
50
51 // Used/free
52 void set_used() { _header._used = true; }
53 void set_free() { _header._used = false; }
54 bool free() { return !_header._used; }
55 };
56
57 class FreeBlock: public HeapBlock {
58 friend class VMStructs;
59 protected:
60 FreeBlock* _link;
61
62 public:
63 // Initialization
64 void initialize(size_t length) { HeapBlock::initialize(length); _link= NULL; }
65
66 // Merging
67 void set_length(size_t l) { _header._length = l; }
68
69 // Accessors
70 FreeBlock* link() const { return _link; }
71 void set_link(FreeBlock* link) { _link = link; }
72 };
73
74 class CodeHeap : public CHeapObj {
75 friend class VMStructs;
76 private:
77 VirtualSpace _memory; // the memory holding the blocks
78 VirtualSpace _segmap; // the memory holding the segment map
79
80 size_t _number_of_committed_segments;
81 size_t _number_of_reserved_segments;
82 size_t _segment_size;
83 int _log2_segment_size;
84
85 size_t _next_segment;
86
87 FreeBlock* _freelist;
88 size_t _free_segments; // No. of segments in freelist
89
90 // Helper functions
91 size_t number_of_segments(size_t size) const { return (size + _segment_size - 1) >> _log2_segment_size; }
92 size_t size(size_t number_of_segments) const { return number_of_segments << _log2_segment_size; }
93
94 size_t segment_for(void* p) const { return ((char*)p - _memory.low()) >> _log2_segment_size; }
95 HeapBlock* block_at(size_t i) const { return (HeapBlock*)(_memory.low() + (i << _log2_segment_size)); }
96
97 void mark_segmap_as_free(size_t beg, size_t end);
98 void mark_segmap_as_used(size_t beg, size_t end);
99
100 // Freelist management helpers
101 FreeBlock* following_block(FreeBlock *b);
102 void insert_after(FreeBlock* a, FreeBlock* b);
103 void merge_right (FreeBlock* a);
104
105 // Toplevel freelist management
106 void add_to_freelist(HeapBlock *b);
107 FreeBlock* search_freelist(size_t length);
108
109 // Iteration helpers
110 void* next_free(HeapBlock* b) const;
111 HeapBlock* first_block() const;
112 HeapBlock* next_block(HeapBlock* b) const;
113 HeapBlock* block_start(void* p) const;
114
115 // to perform additional actions on creation of executable code
116 void on_code_mapping(char* base, size_t size);
117
118 public:
119 CodeHeap();
120
121 // Heap extents
122 bool reserve(size_t reserved_size, size_t committed_size, size_t segment_size);
123 void release(); // releases all allocated memory
124 bool expand_by(size_t size); // expands commited memory by size
125 void shrink_by(size_t size); // shrinks commited memory by size
126 void clear(); // clears all heap contents
127
128 // Memory allocation
129 void* allocate (size_t size); // allocates a block of size or returns NULL
130 void deallocate(void* p); // deallocates a block
131
132 // Attributes
133 void* begin() const { return _memory.low (); }
134 void* end() const { return _memory.high(); }
135 bool contains(void* p) const { return begin() <= p && p < end(); }
136 void* find_start(void* p) const; // returns the block containing p or NULL
137 size_t alignment_unit() const; // alignment of any block
138 size_t alignment_offset() const; // offset of first byte of any block, within the enclosing alignment unit
139 static size_t header_size(); // returns the header size for each heap block
140
141 // Returns reserved area high and low addresses
142 char *low_boundary() const { return _memory.low_boundary (); }
143 char *high_boundary() const { return _memory.high_boundary(); }
144
145 // Iteration
146
147 // returns the first block or NULL
148 void* first() const { return next_free(first_block()); }
149 // returns the next block given a block p or NULL
150 void* next(void* p) const { return next_free(next_block(block_start(p))); }
151
152 // Statistics
153 size_t capacity() const;
154 size_t max_capacity() const;
155 size_t allocated_capacity() const;
156 size_t unallocated_capacity() const { return max_capacity() - allocated_capacity(); }
157
158 // Debugging
159 void verify();
160 void print() PRODUCT_RETURN;
161 };