6885
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1 /*
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2 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * questions.
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22 *
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23 */
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24 #ifndef SHARE_VM_MEMORY_METACHUNK_HPP
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25 #define SHARE_VM_MEMORY_METACHUNK_HPP
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26
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27 // Metachunk - Quantum of allocation from a Virtualspace
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28 // Metachunks are reused (when freed are put on a global freelist) and
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29 // have no permanent association to a SpaceManager.
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30
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31 // +--------------+ <- end
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32 // | | --+ ---+
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33 // | | | free |
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34 // | | | |
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35 // | | | | capacity
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36 // | | | |
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37 // | | <- top --+ |
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38 // | | ---+ |
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39 // | | | used |
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40 // | | | |
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41 // | | | |
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42 // +--------------+ <- bottom ---+ ---+
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43
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44 class Metachunk VALUE_OBJ_CLASS_SPEC {
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45 // link to support lists of chunks
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46 Metachunk* _next;
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47 Metachunk* _prev;
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48
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49 MetaWord* _bottom;
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50 MetaWord* _end;
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51 MetaWord* _top;
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52 size_t _word_size;
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53 // Used in a guarantee() so included in the Product builds
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54 // even through it is only for debugging.
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55 bool _is_free;
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56
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57 // Metachunks are allocated out of a MetadataVirtualSpace and
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58 // and use some of its space to describe itself (plus alignment
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59 // considerations). Metadata is allocated in the rest of the chunk.
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60 // This size is the overhead of maintaining the Metachunk within
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61 // the space.
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62 static size_t _overhead;
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63
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64 void set_bottom(MetaWord* v) { _bottom = v; }
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65 void set_end(MetaWord* v) { _end = v; }
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66 void set_top(MetaWord* v) { _top = v; }
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67 void set_word_size(size_t v) { _word_size = v; }
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68 public:
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69 #ifdef ASSERT
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70 Metachunk() : _bottom(NULL), _end(NULL), _top(NULL), _is_free(false) {}
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71 #else
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72 Metachunk() : _bottom(NULL), _end(NULL), _top(NULL) {}
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73 #endif
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74
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75 // Used to add a Metachunk to a list of Metachunks
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76 void set_next(Metachunk* v) { _next = v; assert(v != this, "Boom");}
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77 void set_prev(Metachunk* v) { _prev = v; assert(v != this, "Boom");}
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78
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79 MetaWord* allocate(size_t word_size);
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80 static Metachunk* initialize(MetaWord* ptr, size_t word_size);
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81
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82 // Accessors
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83 Metachunk* next() const { return _next; }
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84 Metachunk* prev() const { return _prev; }
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85 MetaWord* bottom() const { return _bottom; }
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86 MetaWord* end() const { return _end; }
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87 MetaWord* top() const { return _top; }
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88 size_t word_size() const { return _word_size; }
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89 size_t size() const volatile { return _word_size; }
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90 void set_size(size_t v) { _word_size = v; }
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91 bool is_free() { return _is_free; }
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92 void set_is_free(bool v) { _is_free = v; }
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93 static size_t overhead() { return _overhead; }
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94 void clear_next() { set_next(NULL); }
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95 void link_prev(Metachunk* ptr) { set_prev(ptr); }
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96 uintptr_t* end() { return ((uintptr_t*) this) + size(); }
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97 bool cantCoalesce() const { return false; }
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98 void link_next(Metachunk* ptr) { set_next(ptr); }
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99 void link_after(Metachunk* ptr){
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100 link_next(ptr);
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101 if (ptr != NULL) ptr->link_prev(this);
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102 }
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103
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104 // Reset top to bottom so chunk can be reused.
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105 void reset_empty() { _top = (_bottom + _overhead); }
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106 bool is_empty() { return _top == (_bottom + _overhead); }
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107
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108 // used (has been allocated)
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109 // free (available for future allocations)
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110 // capacity (total size of chunk)
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111 size_t used_word_size();
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112 size_t free_word_size();
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113 size_t capacity_word_size();
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114
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115 // Debug support
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116 #ifdef ASSERT
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117 void* prev_addr() const { return (void*)&_prev; }
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118 void* next_addr() const { return (void*)&_next; }
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119 void* size_addr() const { return (void*)&_word_size; }
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120 #endif
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121 bool verify_chunk_in_free_list(Metachunk* tc) const { return true; }
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122 bool verify_par_locked() { return true; }
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123
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124 void assert_is_mangled() const {/* Don't check "\*/}
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125
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126 #ifdef ASSERT
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127 void mangle();
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128 #endif // ASSERT
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129
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130 void print_on(outputStream* st) const;
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131 void verify();
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132 };
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133 #endif // SHARE_VM_MEMORY_METACHUNK_HPP
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