heap.hpp revision 1827:1e9a9d2e6509 
1/*
2 * Copyright (c) 1997, 2010, 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
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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,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
24
25// Blocks
26
27class 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
57class 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
74class 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() const                             { return _memory.high(); }
144  char *high_boundary() const                    { return _memory.high_boundary(); }
145
146  // Iteration
147
148  // returns the first block or NULL
149  void* first() const       { return next_free(first_block()); }
150  // returns the next block given a block p or NULL
151  void* next(void* p) const { return next_free(next_block(block_start(p))); }
152
153  // Statistics
154  size_t capacity() const;
155  size_t max_capacity() const;
156  size_t allocated_capacity() const;
157  size_t unallocated_capacity() const            { return max_capacity() - allocated_capacity(); }
158
159  // Debugging
160  void verify();
161  void print()  PRODUCT_RETURN;
162};
163