0
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1 /*
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2 * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 # include "incls/_precompiled.incl"
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26 # include "incls/_psMarkSweepDecorator.cpp.incl"
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27
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28 PSMarkSweepDecorator* PSMarkSweepDecorator::_destination_decorator = NULL;
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29
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30
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31 void PSMarkSweepDecorator::set_destination_decorator_tenured() {
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32 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
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33 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
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34
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35 _destination_decorator = heap->old_gen()->object_mark_sweep();
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36 }
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37
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38 void PSMarkSweepDecorator::set_destination_decorator_perm_gen() {
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39 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
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40 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
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41
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42 _destination_decorator = heap->perm_gen()->object_mark_sweep();
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43 }
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44
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45 void PSMarkSweepDecorator::advance_destination_decorator() {
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46 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
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47 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
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48
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49 assert(_destination_decorator != NULL, "Sanity");
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50 guarantee(_destination_decorator != heap->perm_gen()->object_mark_sweep(), "Cannot advance perm gen decorator");
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51
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52 PSMarkSweepDecorator* first = heap->old_gen()->object_mark_sweep();
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53 PSMarkSweepDecorator* second = heap->young_gen()->eden_mark_sweep();
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54 PSMarkSweepDecorator* third = heap->young_gen()->from_mark_sweep();
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55 PSMarkSweepDecorator* fourth = heap->young_gen()->to_mark_sweep();
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56
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57 if ( _destination_decorator == first ) {
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58 _destination_decorator = second;
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59 } else if ( _destination_decorator == second ) {
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60 _destination_decorator = third;
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61 } else if ( _destination_decorator == third ) {
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62 _destination_decorator = fourth;
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63 } else {
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64 fatal("PSMarkSweep attempting to advance past last compaction area");
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65 }
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66 }
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67
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68 PSMarkSweepDecorator* PSMarkSweepDecorator::destination_decorator() {
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69 assert(_destination_decorator != NULL, "Sanity");
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70
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71 return _destination_decorator;
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72 }
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73
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74 // FIX ME FIX ME FIX ME FIX ME!!!!!!!!!
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75 // The object forwarding code is duplicated. Factor this out!!!!!
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76 //
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77 // This method "precompacts" objects inside its space to dest. It places forwarding
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78 // pointers into markOops for use by adjust_pointers. If "dest" should overflow, we
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79 // finish by compacting into our own space.
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80
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81 void PSMarkSweepDecorator::precompact() {
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82 // Reset our own compact top.
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83 set_compaction_top(space()->bottom());
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84
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85 /* We allow some amount of garbage towards the bottom of the space, so
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86 * we don't start compacting before there is a significant gain to be made.
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87 * Occasionally, we want to ensure a full compaction, which is determined
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88 * by the MarkSweepAlwaysCompactCount parameter. This is a significant
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89 * performance improvement!
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90 */
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91 bool skip_dead = ((PSMarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0);
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92
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93 ssize_t allowed_deadspace = 0;
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94 if (skip_dead) {
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95 int ratio = allowed_dead_ratio();
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96 allowed_deadspace = (space()->capacity_in_bytes() * ratio / 100) / HeapWordSize;
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97 }
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98
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99 // Fetch the current destination decorator
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100 PSMarkSweepDecorator* dest = destination_decorator();
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101 ObjectStartArray* start_array = dest->start_array();
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102
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103 HeapWord* compact_top = dest->compaction_top();
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104 HeapWord* compact_end = dest->space()->end();
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105
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106 HeapWord* q = space()->bottom();
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107 HeapWord* t = space()->top();
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108
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109 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last
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110 live object. */
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111 HeapWord* first_dead = space()->end(); /* The first dead object. */
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112 LiveRange* liveRange = NULL; /* The current live range, recorded in the
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113 first header of preceding free area. */
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114 _first_dead = first_dead;
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115
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116 const intx interval = PrefetchScanIntervalInBytes;
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117
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118 while (q < t) {
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119 assert(oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() ||
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120 oop(q)->mark()->has_bias_pattern(),
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121 "these are the only valid states during a mark sweep");
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122 if (oop(q)->is_gc_marked()) {
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123 /* prefetch beyond q */
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124 Prefetch::write(q, interval);
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125 size_t size = oop(q)->size();
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126
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127 size_t compaction_max_size = pointer_delta(compact_end, compact_top);
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128
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129 // This should only happen if a space in the young gen overflows the
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130 // old gen. If that should happen, we null out the start_array, because
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131 // the young spaces are not covered by one.
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132 while(size > compaction_max_size) {
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133 // First record the last compact_top
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134 dest->set_compaction_top(compact_top);
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135
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136 // Advance to the next compaction decorator
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137 advance_destination_decorator();
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138 dest = destination_decorator();
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139
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140 // Update compaction info
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141 start_array = dest->start_array();
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142 compact_top = dest->compaction_top();
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143 compact_end = dest->space()->end();
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144 assert(compact_top == dest->space()->bottom(), "Advanced to space already in use");
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145 assert(compact_end > compact_top, "Must always be space remaining");
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146 compaction_max_size =
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147 pointer_delta(compact_end, compact_top);
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148 }
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149
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150 // store the forwarding pointer into the mark word
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151 if (q != compact_top) {
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152 oop(q)->forward_to(oop(compact_top));
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153 assert(oop(q)->is_gc_marked(), "encoding the pointer should preserve the mark");
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154 } else {
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155 // Don't clear the mark since it's confuses parallel old
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156 // verification.
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157 if (!UseParallelOldGC || !VerifyParallelOldWithMarkSweep) {
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158 // if the object isn't moving we can just set the mark to the default
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159 // mark and handle it specially later on.
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160 oop(q)->init_mark();
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161 }
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162 assert(oop(q)->forwardee() == NULL, "should be forwarded to NULL");
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163 }
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164
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165 // Update object start array
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166 if (!UseParallelOldGC || !VerifyParallelOldWithMarkSweep) {
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167 if (start_array)
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168 start_array->allocate_block(compact_top);
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169 }
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170
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171 debug_only(MarkSweep::register_live_oop(oop(q), size));
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172 compact_top += size;
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173 assert(compact_top <= dest->space()->end(),
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174 "Exceeding space in destination");
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175
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176 q += size;
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177 end_of_live = q;
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178 } else {
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179 /* run over all the contiguous dead objects */
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180 HeapWord* end = q;
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181 do {
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182 /* prefetch beyond end */
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183 Prefetch::write(end, interval);
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184 end += oop(end)->size();
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185 } while (end < t && (!oop(end)->is_gc_marked()));
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186
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187 /* see if we might want to pretend this object is alive so that
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188 * we don't have to compact quite as often.
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189 */
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190 if (allowed_deadspace > 0 && q == compact_top) {
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191 size_t sz = pointer_delta(end, q);
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192 if (insert_deadspace(allowed_deadspace, q, sz)) {
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193 size_t compaction_max_size = pointer_delta(compact_end, compact_top);
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194
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195 // This should only happen if a space in the young gen overflows the
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196 // old gen. If that should happen, we null out the start_array, because
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197 // the young spaces are not covered by one.
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198 while (sz > compaction_max_size) {
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199 // First record the last compact_top
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200 dest->set_compaction_top(compact_top);
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201
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202 // Advance to the next compaction decorator
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203 advance_destination_decorator();
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204 dest = destination_decorator();
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205
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206 // Update compaction info
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207 start_array = dest->start_array();
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208 compact_top = dest->compaction_top();
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209 compact_end = dest->space()->end();
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210 assert(compact_top == dest->space()->bottom(), "Advanced to space already in use");
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211 assert(compact_end > compact_top, "Must always be space remaining");
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212 compaction_max_size =
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213 pointer_delta(compact_end, compact_top);
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214 }
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215
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216 // store the forwarding pointer into the mark word
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217 if (q != compact_top) {
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218 oop(q)->forward_to(oop(compact_top));
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219 assert(oop(q)->is_gc_marked(), "encoding the pointer should preserve the mark");
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220 } else {
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221 // if the object isn't moving we can just set the mark to the default
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222 // Don't clear the mark since it's confuses parallel old
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223 // verification.
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224 if (!UseParallelOldGC || !VerifyParallelOldWithMarkSweep) {
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225 // mark and handle it specially later on.
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226 oop(q)->init_mark();
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227 }
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228 assert(oop(q)->forwardee() == NULL, "should be forwarded to NULL");
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229 }
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230
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231 if (!UseParallelOldGC || !VerifyParallelOldWithMarkSweep) {
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232 // Update object start array
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233 if (start_array)
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234 start_array->allocate_block(compact_top);
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235 }
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236
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237 debug_only(MarkSweep::register_live_oop(oop(q), sz));
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238 compact_top += sz;
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239 assert(compact_top <= dest->space()->end(),
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240 "Exceeding space in destination");
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241
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242 q = end;
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243 end_of_live = end;
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244 continue;
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245 }
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246 }
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247
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248 /* for the previous LiveRange, record the end of the live objects. */
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249 if (liveRange) {
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250 liveRange->set_end(q);
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251 }
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252
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253 /* record the current LiveRange object.
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254 * liveRange->start() is overlaid on the mark word.
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255 */
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256 liveRange = (LiveRange*)q;
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257 liveRange->set_start(end);
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258 liveRange->set_end(end);
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259
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260 /* see if this is the first dead region. */
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261 if (q < first_dead) {
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262 first_dead = q;
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263 }
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264
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265 /* move on to the next object */
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266 q = end;
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267 }
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268 }
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269
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270 assert(q == t, "just checking");
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271 if (liveRange != NULL) {
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272 liveRange->set_end(q);
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273 }
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274 _end_of_live = end_of_live;
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275 if (end_of_live < first_dead) {
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276 first_dead = end_of_live;
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277 }
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278 _first_dead = first_dead;
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279
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280 // Update compaction top
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281 dest->set_compaction_top(compact_top);
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282 }
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283
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284 bool PSMarkSweepDecorator::insert_deadspace(ssize_t& allowed_deadspace_words,
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285 HeapWord* q, size_t deadlength) {
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286 allowed_deadspace_words -= deadlength;
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287 if (allowed_deadspace_words >= 0) {
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288 oop(q)->set_mark(markOopDesc::prototype()->set_marked());
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289 const size_t aligned_min_int_array_size =
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290 align_object_size(typeArrayOopDesc::header_size(T_INT));
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291 if (deadlength >= aligned_min_int_array_size) {
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292 oop(q)->set_klass(Universe::intArrayKlassObj());
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293 assert(((deadlength - aligned_min_int_array_size) * (HeapWordSize/sizeof(jint))) < (size_t)max_jint,
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294 "deadspace too big for Arrayoop");
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295 typeArrayOop(q)->set_length((int)((deadlength - aligned_min_int_array_size)
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296 * (HeapWordSize/sizeof(jint))));
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297 } else {
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298 assert((int) deadlength == instanceOopDesc::header_size(),
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299 "size for smallest fake dead object doesn't match");
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300 oop(q)->set_klass(SystemDictionary::object_klass());
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301 }
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302 assert((int) deadlength == oop(q)->size(),
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303 "make sure size for fake dead object match");
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304 // Recall that we required "q == compaction_top".
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305 return true;
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306 } else {
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307 allowed_deadspace_words = 0;
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308 return false;
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309 }
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310 }
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311
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312 void PSMarkSweepDecorator::adjust_pointers() {
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313 // adjust all the interior pointers to point at the new locations of objects
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314 // Used by MarkSweep::mark_sweep_phase3()
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315
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316 HeapWord* q = space()->bottom();
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317 HeapWord* t = _end_of_live; // Established by "prepare_for_compaction".
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318
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319 assert(_first_dead <= _end_of_live, "Stands to reason, no?");
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320
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321 if (q < t && _first_dead > q &&
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322 !oop(q)->is_gc_marked()) {
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323 // we have a chunk of the space which hasn't moved and we've
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324 // reinitialized the mark word during the previous pass, so we can't
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325 // use is_gc_marked for the traversal.
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326 HeapWord* end = _first_dead;
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327
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328 while (q < end) {
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329 debug_only(MarkSweep::track_interior_pointers(oop(q)));
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330
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331 // point all the oops to the new location
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332 size_t size = oop(q)->adjust_pointers();
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333
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334 debug_only(MarkSweep::check_interior_pointers());
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335
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336 debug_only(MarkSweep::validate_live_oop(oop(q), size));
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337
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338 q += size;
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339 }
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340
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341 if (_first_dead == t) {
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342 q = t;
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343 } else {
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344 // $$$ This is funky. Using this to read the previously written
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345 // LiveRange. See also use below.
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346 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer();
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347 }
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348 }
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349 const intx interval = PrefetchScanIntervalInBytes;
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350
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351 debug_only(HeapWord* prev_q = NULL);
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352 while (q < t) {
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353 // prefetch beyond q
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354 Prefetch::write(q, interval);
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355 if (oop(q)->is_gc_marked()) {
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356 // q is alive
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357 debug_only(MarkSweep::track_interior_pointers(oop(q)));
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358 // point all the oops to the new location
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359 size_t size = oop(q)->adjust_pointers();
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360 debug_only(MarkSweep::check_interior_pointers());
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361 debug_only(MarkSweep::validate_live_oop(oop(q), size));
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362 debug_only(prev_q = q);
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363 q += size;
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364 } else {
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365 // q is not a live object, so its mark should point at the next
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366 // live object
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367 debug_only(prev_q = q);
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368 q = (HeapWord*) oop(q)->mark()->decode_pointer();
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369 assert(q > prev_q, "we should be moving forward through memory");
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370 }
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371 }
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372
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373 assert(q == t, "just checking");
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374 }
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375
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376 void PSMarkSweepDecorator::compact(bool mangle_free_space ) {
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377 // Copy all live objects to their new location
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378 // Used by MarkSweep::mark_sweep_phase4()
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379
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380 HeapWord* q = space()->bottom();
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381 HeapWord* const t = _end_of_live;
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382 debug_only(HeapWord* prev_q = NULL);
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383
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384 if (q < t && _first_dead > q &&
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385 !oop(q)->is_gc_marked()) {
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386 #ifdef ASSERT
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387 // we have a chunk of the space which hasn't moved and we've reinitialized the
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388 // mark word during the previous pass, so we can't use is_gc_marked for the
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389 // traversal.
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390 HeapWord* const end = _first_dead;
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391
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392 while (q < end) {
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393 size_t size = oop(q)->size();
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394 assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)");
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395 debug_only(MarkSweep::live_oop_moved_to(q, size, q));
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396 debug_only(prev_q = q);
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397 q += size;
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398 }
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399 #endif
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400
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401 if (_first_dead == t) {
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402 q = t;
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403 } else {
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404 // $$$ Funky
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405 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer();
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406 }
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407 }
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408
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409 const intx scan_interval = PrefetchScanIntervalInBytes;
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410 const intx copy_interval = PrefetchCopyIntervalInBytes;
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411
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412 while (q < t) {
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413 if (!oop(q)->is_gc_marked()) {
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414 // mark is pointer to next marked oop
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415 debug_only(prev_q = q);
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416 q = (HeapWord*) oop(q)->mark()->decode_pointer();
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417 assert(q > prev_q, "we should be moving forward through memory");
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418 } else {
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419 // prefetch beyond q
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420 Prefetch::read(q, scan_interval);
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421
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422 // size and destination
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423 size_t size = oop(q)->size();
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424 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee();
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425
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426 // prefetch beyond compaction_top
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427 Prefetch::write(compaction_top, copy_interval);
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428
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429 // copy object and reinit its mark
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430 debug_only(MarkSweep::live_oop_moved_to(q, size, compaction_top));
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431 assert(q != compaction_top, "everything in this pass should be moving");
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432 Copy::aligned_conjoint_words(q, compaction_top, size);
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433 oop(compaction_top)->init_mark();
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434 assert(oop(compaction_top)->klass() != NULL, "should have a class");
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435
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436 debug_only(prev_q = q);
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437 q += size;
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438 }
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439 }
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440
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441 assert(compaction_top() >= space()->bottom() && compaction_top() <= space()->end(),
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442 "should point inside space");
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443 space()->set_top(compaction_top());
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444
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445 if (mangle_free_space) space()->mangle_unused_area();
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446 }
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