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_METABLOCK_HPP |
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25 #define SHARE_VM_MEMORY_METABLOCK_HPP |
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26 |
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27 // Metablock are the unit of allocation from a Chunk. It is initialized |
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28 // with the size of the requested allocation. That size is overwritten |
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29 // once the allocation returns. |
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30 // |
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31 // A Metablock may be reused by its SpaceManager but are never moved between |
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32 // SpaceManagers. There is no explicit link to the Metachunk |
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33 // from which it was allocated. Metablock may be deallocated and |
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34 // put on a freelist but the space is never freed, rather |
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35 // the Metachunk it is a part of will be deallocated when it's |
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36 // associated class loader is collected. |
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37 |
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38 class Metablock VALUE_OBJ_CLASS_SPEC { |
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39 friend class VMStructs; |
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40 private: |
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41 // Used to align the allocation (see below). |
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42 union block_t { |
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43 void* _data[3]; |
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44 struct header_t { |
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45 size_t _word_size; |
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46 Metablock* _next; |
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47 Metablock* _prev; |
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48 } _header; |
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49 } _block; |
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50 static size_t _min_block_byte_size; |
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51 |
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52 typedef union block_t Block; |
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53 typedef struct header_t Header; |
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54 const Block* block() const { return &_block; } |
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55 const Block::header_t* header() const { return &(block()->_header); } |
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56 public: |
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57 |
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58 static Metablock* initialize(MetaWord* p, size_t word_size); |
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59 |
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60 // This places the body of the block at a 2 word boundary |
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61 // because every block starts on a 2 word boundary. Work out |
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62 // how to make the body on a 2 word boundary if the block |
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63 // starts on a arbitrary boundary. JJJ |
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64 |
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65 size_t word_size() const { return header()->_word_size; } |
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66 void set_word_size(size_t v) { _block._header._word_size = v; } |
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67 size_t size() const volatile { return _block._header._word_size; } |
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68 void set_size(size_t v) { _block._header._word_size = v; } |
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69 Metablock* next() const { return header()->_next; } |
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70 void set_next(Metablock* v) { _block._header._next = v; } |
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71 Metablock* prev() const { return header()->_prev; } |
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72 void set_prev(Metablock* v) { _block._header._prev = v; } |
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73 |
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74 static size_t min_block_byte_size() { return _min_block_byte_size; } |
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75 |
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76 bool is_free() { return header()->_word_size != 0; } |
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77 void clear_next() { set_next(NULL); } |
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78 void link_prev(Metablock* ptr) { set_prev(ptr); } |
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79 uintptr_t* end() { return ((uintptr_t*) this) + size(); } |
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80 bool cantCoalesce() const { return false; } |
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81 void link_next(Metablock* ptr) { set_next(ptr); } |
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82 void link_after(Metablock* ptr){ |
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83 link_next(ptr); |
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84 if (ptr != NULL) ptr->link_prev(this); |
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85 } |
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86 |
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87 // Should not be needed in a free list of Metablocks |
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88 void markNotFree() { ShouldNotReachHere(); } |
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89 |
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90 // Debug support |
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91 #ifdef ASSERT |
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92 void* prev_addr() const { return (void*)&_block._header._prev; } |
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93 void* next_addr() const { return (void*)&_block._header._next; } |
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94 void* size_addr() const { return (void*)&_block._header._word_size; } |
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95 #endif |
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96 bool verify_chunk_in_free_list(Metablock* tc) const { return true; } |
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97 bool verify_par_locked() { return true; } |
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98 |
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99 void assert_is_mangled() const {/* Don't check "\*/} |
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100 }; |
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101 #endif // SHARE_VM_MEMORY_METABLOCK_HPP |
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