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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/_genMarkSweep.cpp.incl"
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27
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28 void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,
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29 bool clear_all_softrefs) {
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30 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
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31
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32 // hook up weak ref data so it can be used during Mark-Sweep
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33 assert(ref_processor() == NULL, "no stomping");
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34 _ref_processor = rp;
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35 assert(rp != NULL, "should be non-NULL");
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36
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37 TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
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38
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39 // When collecting the permanent generation methodOops may be moving,
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40 // so we either have to flush all bcp data or convert it into bci.
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41 CodeCache::gc_prologue();
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42 Threads::gc_prologue();
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43
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44 // Increment the invocation count for the permanent generation, since it is
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45 // implicitly collected whenever we do a full mark sweep collection.
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46 GenCollectedHeap* gch = GenCollectedHeap::heap();
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47 gch->perm_gen()->stat_record()->invocations++;
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48
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49 // Capture heap size before collection for printing.
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50 size_t gch_prev_used = gch->used();
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51
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52 // Some of the card table updates below assume that the perm gen is
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53 // also being collected.
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54 assert(level == gch->n_gens() - 1,
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55 "All generations are being collected, ergo perm gen too.");
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56
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57 // Capture used regions for each generation that will be
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58 // subject to collection, so that card table adjustments can
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59 // be made intelligently (see clear / invalidate further below).
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60 gch->save_used_regions(level, true /* perm */);
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61
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62 allocate_stacks();
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63
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64 mark_sweep_phase1(level, clear_all_softrefs);
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65
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66 mark_sweep_phase2();
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67
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68 // Don't add any more derived pointers during phase3
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69 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
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70 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
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71
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72 mark_sweep_phase3(level);
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73
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74 VALIDATE_MARK_SWEEP_ONLY(
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75 if (ValidateMarkSweep) {
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76 guarantee(_root_refs_stack->length() == 0,
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77 "should be empty by now");
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78 }
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79 )
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80
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81 mark_sweep_phase4();
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82
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83 VALIDATE_MARK_SWEEP_ONLY(
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84 if (ValidateMarkSweep) {
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85 guarantee(_live_oops->length() == _live_oops_moved_to->length(),
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86 "should be the same size");
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87 }
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88 )
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89
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90 restore_marks();
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91
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92 // Set saved marks for allocation profiler (and other things? -- dld)
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93 // (Should this be in general part?)
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94 gch->save_marks();
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95
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96 deallocate_stacks();
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97
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98 // If compaction completely evacuated all generations younger than this
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99 // one, then we can clear the card table. Otherwise, we must invalidate
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100 // it (consider all cards dirty). In the future, we might consider doing
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101 // compaction within generations only, and doing card-table sliding.
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102 bool all_empty = true;
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103 for (int i = 0; all_empty && i < level; i++) {
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104 Generation* g = gch->get_gen(i);
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105 all_empty = all_empty && gch->get_gen(i)->used() == 0;
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106 }
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107 GenRemSet* rs = gch->rem_set();
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108 // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
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109 if (all_empty) {
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110 // We've evacuated all generations below us.
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111 Generation* g = gch->get_gen(level);
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112 rs->clear_into_younger(g, true /* perm */);
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113 } else {
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114 // Invalidate the cards corresponding to the currently used
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115 // region and clear those corresponding to the evacuated region
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116 // of all generations just collected (i.e. level and younger).
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117 rs->invalidate_or_clear(gch->get_gen(level),
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118 true /* younger */,
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119 true /* perm */);
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120 }
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121
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122 Threads::gc_epilogue();
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123 CodeCache::gc_epilogue();
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124
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125 if (PrintGC && !PrintGCDetails) {
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126 gch->print_heap_change(gch_prev_used);
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127 }
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128
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129 // refs processing: clean slate
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130 _ref_processor = NULL;
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131
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132 // Update heap occupancy information which is used as
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133 // input to soft ref clearing policy at the next gc.
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134 Universe::update_heap_info_at_gc();
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135
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136 // Update time of last gc for all generations we collected
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137 // (which curently is all the generations in the heap).
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138 gch->update_time_of_last_gc(os::javaTimeMillis());
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139 }
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140
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141 void GenMarkSweep::allocate_stacks() {
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142 GenCollectedHeap* gch = GenCollectedHeap::heap();
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143 // Scratch request on behalf of oldest generation; will do no
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144 // allocation.
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145 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
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146
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147 // $$$ To cut a corner, we'll only use the first scratch block, and then
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148 // revert to malloc.
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149 if (scratch != NULL) {
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150 _preserved_count_max =
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151 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
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152 } else {
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153 _preserved_count_max = 0;
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154 }
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155
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156 _preserved_marks = (PreservedMark*)scratch;
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157 _preserved_count = 0;
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158 _preserved_mark_stack = NULL;
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159 _preserved_oop_stack = NULL;
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160
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161 _marking_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
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162
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163 int size = SystemDictionary::number_of_classes() * 2;
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164 _revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
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165
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166 #ifdef VALIDATE_MARK_SWEEP
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167 if (ValidateMarkSweep) {
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168 _root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<oop*>(100, true);
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169 _other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<oop*>(100, true);
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170 _adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray<oop*>(100, true);
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171 _live_oops = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
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172 _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
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173 _live_oops_size = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
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174 }
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175 if (RecordMarkSweepCompaction) {
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176 if (_cur_gc_live_oops == NULL) {
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177 _cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
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178 _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
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179 _cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
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180 _last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
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181 _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
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182 _last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
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183 } else {
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184 _cur_gc_live_oops->clear();
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185 _cur_gc_live_oops_moved_to->clear();
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186 _cur_gc_live_oops_size->clear();
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187 }
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188 }
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189 #endif
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190 }
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191
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192
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193 void GenMarkSweep::deallocate_stacks() {
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194 if (_preserved_oop_stack) {
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195 delete _preserved_mark_stack;
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196 _preserved_mark_stack = NULL;
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197 delete _preserved_oop_stack;
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198 _preserved_oop_stack = NULL;
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199 }
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200
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201 delete _marking_stack;
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202 delete _revisit_klass_stack;
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203
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204 #ifdef VALIDATE_MARK_SWEEP
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205 if (ValidateMarkSweep) {
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206 delete _root_refs_stack;
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207 delete _other_refs_stack;
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208 delete _adjusted_pointers;
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209 delete _live_oops;
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210 delete _live_oops_size;
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211 delete _live_oops_moved_to;
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212 _live_oops_index = 0;
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213 _live_oops_index_at_perm = 0;
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214 }
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215 #endif
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216 }
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217
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218 void GenMarkSweep::mark_sweep_phase1(int level,
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219 bool clear_all_softrefs) {
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220 // Recursively traverse all live objects and mark them
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221 EventMark m("1 mark object");
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222 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
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223 trace(" 1");
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224
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225 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
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226
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227 GenCollectedHeap* gch = GenCollectedHeap::heap();
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228
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229 // Because follow_root_closure is created statically, cannot
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230 // use OopsInGenClosure constructor which takes a generation,
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231 // as the Universe has not been created when the static constructors
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232 // are run.
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233 follow_root_closure.set_orig_generation(gch->get_gen(level));
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234
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235 gch->gen_process_strong_roots(level,
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236 false, // Younger gens are not roots.
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237 true, // Collecting permanent generation.
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238 SharedHeap::SO_SystemClasses,
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239 &follow_root_closure, &follow_root_closure);
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240
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241 // Process reference objects found during marking
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242 {
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243 ReferencePolicy *soft_ref_policy;
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244 if (clear_all_softrefs) {
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245 soft_ref_policy = new AlwaysClearPolicy();
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246 } else {
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247 #ifdef COMPILER2
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248 soft_ref_policy = new LRUMaxHeapPolicy();
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249 #else
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250 soft_ref_policy = new LRUCurrentHeapPolicy();
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251 #endif // COMPILER2
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252 }
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253 assert(soft_ref_policy != NULL,"No soft reference policy");
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254 ref_processor()->process_discovered_references(
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255 soft_ref_policy, &is_alive, &keep_alive,
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256 &follow_stack_closure, NULL);
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257 }
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258
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259 // Follow system dictionary roots and unload classes
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260 bool purged_class = SystemDictionary::do_unloading(&is_alive);
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261
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262 // Follow code cache roots
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263 CodeCache::do_unloading(&is_alive, &keep_alive, purged_class);
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264 follow_stack(); // Flush marking stack
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265
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266 // Update subklass/sibling/implementor links of live klasses
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267 follow_weak_klass_links();
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268 assert(_marking_stack->is_empty(), "just drained");
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269
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270 // Visit symbol and interned string tables and delete unmarked oops
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271 SymbolTable::unlink(&is_alive);
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272 StringTable::unlink(&is_alive);
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273
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274 assert(_marking_stack->is_empty(), "stack should be empty by now");
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275 }
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276
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277
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278 void GenMarkSweep::mark_sweep_phase2() {
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279 // Now all live objects are marked, compute the new object addresses.
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280
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281 // It is imperative that we traverse perm_gen LAST. If dead space is
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282 // allowed a range of dead object may get overwritten by a dead int
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283 // array. If perm_gen is not traversed last a klassOop may get
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284 // overwritten. This is fine since it is dead, but if the class has dead
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285 // instances we have to skip them, and in order to find their size we
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286 // need the klassOop!
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287 //
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288 // It is not required that we traverse spaces in the same order in
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289 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
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290 // tracking expects us to do so. See comment under phase4.
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291
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292 GenCollectedHeap* gch = GenCollectedHeap::heap();
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293 Generation* pg = gch->perm_gen();
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294
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295 EventMark m("2 compute new addresses");
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296 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
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297 trace("2");
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298
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299 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
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300
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301 gch->prepare_for_compaction();
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302
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303 VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index);
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304 CompactPoint perm_cp(pg, NULL, NULL);
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305 pg->prepare_for_compaction(&perm_cp);
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306 }
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307
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308 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
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309 public:
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310 void do_generation(Generation* gen) {
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311 gen->adjust_pointers();
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312 }
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313 };
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314
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315 void GenMarkSweep::mark_sweep_phase3(int level) {
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316 GenCollectedHeap* gch = GenCollectedHeap::heap();
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317 Generation* pg = gch->perm_gen();
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318
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319 // Adjust the pointers to reflect the new locations
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320 EventMark m("3 adjust pointers");
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321 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
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322 trace("3");
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323
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324 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
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325
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326 // Needs to be done before the system dictionary is adjusted.
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327 pg->pre_adjust_pointers();
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328
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329 // Because the two closures below are created statically, cannot
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330 // use OopsInGenClosure constructor which takes a generation,
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331 // as the Universe has not been created when the static constructors
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332 // are run.
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333 adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
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334 adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
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335
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336 gch->gen_process_strong_roots(level,
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337 false, // Younger gens are not roots.
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338 true, // Collecting permanent generation.
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339 SharedHeap::SO_AllClasses,
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340 &adjust_root_pointer_closure,
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341 &adjust_root_pointer_closure);
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342
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343 // Now adjust pointers in remaining weak roots. (All of which should
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344 // have been cleared if they pointed to non-surviving objects.)
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345 gch->gen_process_weak_roots(&adjust_root_pointer_closure,
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346 &adjust_pointer_closure);
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347
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348 adjust_marks();
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349 GenAdjustPointersClosure blk;
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350 gch->generation_iterate(&blk, true);
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351 pg->adjust_pointers();
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352 }
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353
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354 class GenCompactClosure: public GenCollectedHeap::GenClosure {
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355 public:
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356 void do_generation(Generation* gen) {
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357 gen->compact();
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358 }
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359 };
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360
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361 void GenMarkSweep::mark_sweep_phase4() {
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362 // All pointers are now adjusted, move objects accordingly
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363
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364 // It is imperative that we traverse perm_gen first in phase4. All
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365 // classes must be allocated earlier than their instances, and traversing
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366 // perm_gen first makes sure that all klassOops have moved to their new
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367 // location before any instance does a dispatch through it's klass!
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368
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369 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
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370 // in the same order in phase2, phase3 and phase4. We don't quite do that
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371 // here (perm_gen first rather than last), so we tell the validate code
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372 // to use a higher index (saved from phase2) when verifying perm_gen.
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373 GenCollectedHeap* gch = GenCollectedHeap::heap();
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374 Generation* pg = gch->perm_gen();
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375
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376 EventMark m("4 compact heap");
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377 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
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378 trace("4");
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379
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380 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true));
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381
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382 pg->compact();
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383
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384 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
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385
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386 GenCompactClosure blk;
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387 gch->generation_iterate(&blk, true);
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388
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389 VALIDATE_MARK_SWEEP_ONLY(compaction_complete());
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390
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391 pg->post_compact(); // Shared spaces verification.
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392 }
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