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342
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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/_g1MarkSweep.cpp.incl"
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27
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28 class HeapRegion;
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29
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30 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
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31 bool clear_all_softrefs) {
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32 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
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33
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34 // hook up weak ref data so it can be used during Mark-Sweep
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35 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
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36 GenMarkSweep::_ref_processor = rp;
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37 assert(rp != NULL, "should be non-NULL");
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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 SharedHeap* sh = SharedHeap::heap();
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47 sh->perm_gen()->stat_record()->invocations++;
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48
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49 bool marked_for_unloading = false;
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50
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51 allocate_stacks();
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52
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53 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
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54
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55 if (G1VerifyConcMark) {
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56 G1CollectedHeap* g1h = G1CollectedHeap::heap();
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57 g1h->checkConcurrentMark();
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58 }
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59
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60 mark_sweep_phase2();
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61
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62 // Don't add any more derived pointers during phase3
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63 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
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64
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65 mark_sweep_phase3();
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66
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67 mark_sweep_phase4();
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68
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69 GenMarkSweep::restore_marks();
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70
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71 GenMarkSweep::deallocate_stacks();
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72
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73 // We must invalidate the perm-gen rs, so that it gets rebuilt.
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74 GenRemSet* rs = sh->rem_set();
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75 rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);
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76
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77 // "free at last gc" is calculated from these.
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78 // CHF: cheating for now!!!
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79 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
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80 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
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81
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82 Threads::gc_epilogue();
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83 CodeCache::gc_epilogue();
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84
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85 // refs processing: clean slate
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86 GenMarkSweep::_ref_processor = NULL;
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87 }
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88
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89
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90 void G1MarkSweep::allocate_stacks() {
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91 GenMarkSweep::_preserved_count_max = 0;
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92 GenMarkSweep::_preserved_marks = NULL;
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93 GenMarkSweep::_preserved_count = 0;
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94 GenMarkSweep::_preserved_mark_stack = NULL;
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95 GenMarkSweep::_preserved_oop_stack = NULL;
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96
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97 GenMarkSweep::_marking_stack =
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98 new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
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99
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100 size_t size = SystemDictionary::number_of_classes() * 2;
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101 GenMarkSweep::_revisit_klass_stack =
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102 new (ResourceObj::C_HEAP) GrowableArray<Klass*>((int)size, true);
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103 }
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104
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105 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
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106 bool clear_all_softrefs) {
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107 // Recursively traverse all live objects and mark them
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108 EventMark m("1 mark object");
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109 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
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110 GenMarkSweep::trace(" 1");
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111
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112 SharedHeap* sh = SharedHeap::heap();
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113
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114 sh->process_strong_roots(true, // Collecting permanent generation.
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115 SharedHeap::SO_SystemClasses,
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116 &GenMarkSweep::follow_root_closure,
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117 &GenMarkSweep::follow_root_closure);
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118
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119 // Process reference objects found during marking
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120 ReferencePolicy *soft_ref_policy;
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121 if (clear_all_softrefs) {
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122 soft_ref_policy = new AlwaysClearPolicy();
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123 } else {
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124 #ifdef COMPILER2
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125 soft_ref_policy = new LRUMaxHeapPolicy();
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126 #else
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127 soft_ref_policy = new LRUCurrentHeapPolicy();
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128 #endif
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129 }
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130 assert(soft_ref_policy != NULL,"No soft reference policy");
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131 GenMarkSweep::ref_processor()->process_discovered_references(
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132 soft_ref_policy,
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133 &GenMarkSweep::is_alive,
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134 &GenMarkSweep::keep_alive,
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135 &GenMarkSweep::follow_stack_closure,
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136 NULL);
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137
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138 // Follow system dictionary roots and unload classes
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139 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
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140 assert(GenMarkSweep::_marking_stack->is_empty(),
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141 "stack should be empty by now");
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142
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143 // Follow code cache roots (has to be done after system dictionary,
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144 // assumes all live klasses are marked)
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145 CodeCache::do_unloading(&GenMarkSweep::is_alive,
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146 &GenMarkSweep::keep_alive,
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147 purged_class);
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148 GenMarkSweep::follow_stack();
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149
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150 // Update subklass/sibling/implementor links of live klasses
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151 GenMarkSweep::follow_weak_klass_links();
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152 assert(GenMarkSweep::_marking_stack->is_empty(),
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153 "stack should be empty by now");
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154
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155 // Visit symbol and interned string tables and delete unmarked oops
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156 SymbolTable::unlink(&GenMarkSweep::is_alive);
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157 StringTable::unlink(&GenMarkSweep::is_alive);
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158
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159 assert(GenMarkSweep::_marking_stack->is_empty(),
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160 "stack should be empty by now");
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161 }
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162
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163 class G1PrepareCompactClosure: public HeapRegionClosure {
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164 ModRefBarrierSet* _mrbs;
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165 CompactPoint _cp;
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166 bool _popular_only;
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167
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168 void free_humongous_region(HeapRegion* hr) {
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169 HeapWord* bot = hr->bottom();
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170 HeapWord* end = hr->end();
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171 assert(hr->startsHumongous(),
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172 "Only the start of a humongous region should be freed.");
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173 G1CollectedHeap::heap()->free_region(hr);
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174 hr->prepare_for_compaction(&_cp);
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175 // Also clear the part of the card table that will be unused after
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176 // compaction.
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177 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
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178 }
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179
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180 public:
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181 G1PrepareCompactClosure(CompactibleSpace* cs, bool popular_only) :
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182 _cp(NULL, cs, cs->initialize_threshold()),
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183 _mrbs(G1CollectedHeap::heap()->mr_bs()),
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184 _popular_only(popular_only)
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185 {}
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186 bool doHeapRegion(HeapRegion* hr) {
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187 if (_popular_only && !hr->popular())
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188 return true; // terminate early
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189 else if (!_popular_only && hr->popular())
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190 return false; // skip this one.
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191
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192 if (hr->isHumongous()) {
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193 if (hr->startsHumongous()) {
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194 oop obj = oop(hr->bottom());
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195 if (obj->is_gc_marked()) {
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196 obj->forward_to(obj);
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197 } else {
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198 free_humongous_region(hr);
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199 }
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200 } else {
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201 assert(hr->continuesHumongous(), "Invalid humongous.");
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202 }
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203 } else {
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204 hr->prepare_for_compaction(&_cp);
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205 // Also clear the part of the card table that will be unused after
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206 // compaction.
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207 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
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208 }
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209 return false;
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210 }
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211 };
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212 // Stolen verbatim from g1CollectedHeap.cpp
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213 class FindFirstRegionClosure: public HeapRegionClosure {
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214 HeapRegion* _a_region;
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215 bool _find_popular;
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216 public:
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217 FindFirstRegionClosure(bool find_popular) :
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218 _a_region(NULL), _find_popular(find_popular) {}
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219 bool doHeapRegion(HeapRegion* r) {
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220 if (r->popular() == _find_popular) {
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221 _a_region = r;
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222 return true;
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223 } else {
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224 return false;
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225 }
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226 }
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227 HeapRegion* result() { return _a_region; }
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228 };
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229
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230 void G1MarkSweep::mark_sweep_phase2() {
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231 // Now all live objects are marked, compute the new object addresses.
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232
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233 // It is imperative that we traverse perm_gen LAST. If dead space is
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234 // allowed a range of dead object may get overwritten by a dead int
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235 // array. If perm_gen is not traversed last a klassOop may get
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236 // overwritten. This is fine since it is dead, but if the class has dead
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237 // instances we have to skip them, and in order to find their size we
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238 // need the klassOop!
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239 //
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240 // It is not required that we traverse spaces in the same order in
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241 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
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242 // tracking expects us to do so. See comment under phase4.
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243
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244 G1CollectedHeap* g1h = G1CollectedHeap::heap();
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245 Generation* pg = g1h->perm_gen();
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246
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247 EventMark m("2 compute new addresses");
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248 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
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249 GenMarkSweep::trace("2");
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250
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251 // First we compact the popular regions.
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252 if (G1NumPopularRegions > 0) {
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253 CompactibleSpace* sp = g1h->first_compactible_space();
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254 FindFirstRegionClosure cl(true /*find_popular*/);
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255 g1h->heap_region_iterate(&cl);
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256 HeapRegion *r = cl.result();
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257 assert(r->popular(), "should have found a popular region.");
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258 assert(r == sp, "first popular heap region should "
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259 "== first compactible space");
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260 G1PrepareCompactClosure blk(sp, true/*popular_only*/);
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261 g1h->heap_region_iterate(&blk);
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262 }
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263
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264 // Now we do the regular regions.
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265 FindFirstRegionClosure cl(false /*find_popular*/);
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266 g1h->heap_region_iterate(&cl);
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267 HeapRegion *r = cl.result();
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268 assert(!r->popular(), "should have founda non-popular region.");
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269 CompactibleSpace* sp = r;
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270 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
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271 sp = r->next_compaction_space();
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272 }
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273
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274 G1PrepareCompactClosure blk(sp, false/*popular_only*/);
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275 g1h->heap_region_iterate(&blk);
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276
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277 CompactPoint perm_cp(pg, NULL, NULL);
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278 pg->prepare_for_compaction(&perm_cp);
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279 }
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280
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281 class G1AdjustPointersClosure: public HeapRegionClosure {
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282 public:
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283 bool doHeapRegion(HeapRegion* r) {
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284 if (r->isHumongous()) {
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285 if (r->startsHumongous()) {
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286 // We must adjust the pointers on the single H object.
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287 oop obj = oop(r->bottom());
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288 debug_only(GenMarkSweep::track_interior_pointers(obj));
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289 // point all the oops to the new location
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290 obj->adjust_pointers();
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291 debug_only(GenMarkSweep::check_interior_pointers());
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292 }
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293 } else {
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294 // This really ought to be "as_CompactibleSpace"...
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295 r->adjust_pointers();
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296 }
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297 return false;
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298 }
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299 };
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300
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301 void G1MarkSweep::mark_sweep_phase3() {
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302 G1CollectedHeap* g1h = G1CollectedHeap::heap();
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303 Generation* pg = g1h->perm_gen();
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304
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305 // Adjust the pointers to reflect the new locations
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306 EventMark m("3 adjust pointers");
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307 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
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308 GenMarkSweep::trace("3");
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309
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310 SharedHeap* sh = SharedHeap::heap();
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311
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312 sh->process_strong_roots(true, // Collecting permanent generation.
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313 SharedHeap::SO_AllClasses,
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314 &GenMarkSweep::adjust_root_pointer_closure,
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315 &GenMarkSweep::adjust_pointer_closure);
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316
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317 g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
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318
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319 // Now adjust pointers in remaining weak roots. (All of which should
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320 // have been cleared if they pointed to non-surviving objects.)
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321 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
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322 &GenMarkSweep::adjust_pointer_closure);
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323
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324 GenMarkSweep::adjust_marks();
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325
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326 G1AdjustPointersClosure blk;
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327 g1h->heap_region_iterate(&blk);
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328 pg->adjust_pointers();
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329 }
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330
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331 class G1SpaceCompactClosure: public HeapRegionClosure {
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332 public:
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333 G1SpaceCompactClosure() {}
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334
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335 bool doHeapRegion(HeapRegion* hr) {
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336 if (hr->isHumongous()) {
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337 if (hr->startsHumongous()) {
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338 oop obj = oop(hr->bottom());
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339 if (obj->is_gc_marked()) {
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340 obj->init_mark();
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341 } else {
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342 assert(hr->is_empty(), "Should have been cleared in phase 2.");
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343 }
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344 hr->reset_during_compaction();
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345 }
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346 } else {
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347 hr->compact();
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348 }
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349 return false;
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350 }
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351 };
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352
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353 void G1MarkSweep::mark_sweep_phase4() {
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354 // All pointers are now adjusted, move objects accordingly
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355
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356 // It is imperative that we traverse perm_gen first in phase4. All
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357 // classes must be allocated earlier than their instances, and traversing
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358 // perm_gen first makes sure that all klassOops have moved to their new
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359 // location before any instance does a dispatch through it's klass!
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360
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361 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
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362 // in the same order in phase2, phase3 and phase4. We don't quite do that
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363 // here (perm_gen first rather than last), so we tell the validate code
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364 // to use a higher index (saved from phase2) when verifying perm_gen.
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365 G1CollectedHeap* g1h = G1CollectedHeap::heap();
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366 Generation* pg = g1h->perm_gen();
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367
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368 EventMark m("4 compact heap");
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369 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
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370 GenMarkSweep::trace("4");
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371
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372 pg->compact();
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373
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374 G1SpaceCompactClosure blk;
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375 g1h->heap_region_iterate(&blk);
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376
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377 }
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378
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379 // Local Variables: ***
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380 // c-indentation-style: gnu ***
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381 // End: ***
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