1 /* 2 * Copyright (c) 2012, 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 #include "precompiled.hpp" 26 #include "memory/allocation.hpp" 27 #include "memory/metachunk.hpp" 28 #include "utilities/copy.hpp" 29 #include "utilities/debug.hpp" 30 31 class VirtualSpaceNode; 32 // 33 // Future modification 34 // 35 // The Metachunk can conceivable be replaced by the Chunk in 36 // allocation.hpp. Note that the latter Chunk is the space for 37 // allocation (allocations from the chunk are out of the space in 38 // the Chunk after the header for the Chunk) where as Metachunks 39 // point to space in a VirtualSpace. To replace Metachunks with 40 // Chunks, change Chunks so that they can be allocated out of a VirtualSpace. 41 42 const size_t metadata_chunk_initialize = 0xf7f7f7f7; 43 44 size_t Metachunk::_overhead = 45 Chunk::aligned_overhead_size(sizeof(Metachunk)) / BytesPerWord; 46 47 // Metachunk methods 48 49 Metachunk::Metachunk(size_t word_size, 50 VirtualSpaceNode* container) : 51 _word_size(word_size), 52 _bottom(NULL), 53 _end(NULL), 54 _top(NULL), 55 _next(NULL), 56 _prev(NULL), 57 _container(container) 58 { 59 _bottom = (MetaWord*)this; 60 _top = (MetaWord*)this + _overhead; 61 _end = (MetaWord*)this + word_size; 62 #ifdef ASSERT 63 set_is_free(false); 64 size_t data_word_size = pointer_delta(end(), 65 top(), 66 sizeof(MetaWord)); 67 Copy::fill_to_words((HeapWord*) top(), 68 data_word_size, 69 metadata_chunk_initialize); 70 #endif 71 } 72 73 MetaWord* Metachunk::allocate(size_t word_size) { 74 MetaWord* result = NULL; 75 // If available, bump the pointer to allocate. 76 if (free_word_size() >= word_size) { 77 result = _top; 78 _top = _top + word_size; 79 } 80 return result; 81 } 82 83 // _bottom points to the start of the chunk including the overhead. 84 size_t Metachunk::used_word_size() const { 85 return pointer_delta(_top, _bottom, sizeof(MetaWord)); 86 } 87 88 size_t Metachunk::free_word_size() const { 89 return pointer_delta(_end, _top, sizeof(MetaWord)); 90 } 91 92 size_t Metachunk::capacity_word_size() const { 93 return pointer_delta(_end, _bottom, sizeof(MetaWord)); 94 } 95 96 void Metachunk::print_on(outputStream* st) const { 97 st->print_cr("Metachunk:" 98 " bottom " PTR_FORMAT " top " PTR_FORMAT 99 " end " PTR_FORMAT " size " SIZE_FORMAT, 100 bottom(), top(), end(), word_size()); 101 if (Verbose) { 102 st->print_cr(" used " SIZE_FORMAT " free " SIZE_FORMAT, 103 used_word_size(), free_word_size()); 104 } 105 } 106 107 #ifndef PRODUCT 108 void Metachunk::mangle() { 109 // Mangle the payload of the chunk and not the links that 110 // maintain list of chunks. 111 HeapWord* start = (HeapWord*)(bottom() + overhead()); 112 size_t word_size = capacity_word_size() - overhead(); 113 Copy::fill_to_words(start, word_size, metadata_chunk_initialize); 114 } 115 #endif // PRODUCT 116 117 void Metachunk::verify() { 118 #ifdef ASSERT 119 // Cannot walk through the blocks unless the blocks have 120 // headers with sizes. 121 assert(_bottom <= _top && 122 _top <= _end, 123 "Chunk has been smashed"); 124 #endif 125 return; 126 }