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1 /*
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2 * Copyright 1997-2007 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 class ReferenceProcessor;
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26
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27 // MarkSweep takes care of global mark-compact garbage collection for a
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28 // GenCollectedHeap using a four-phase pointer forwarding algorithm. All
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29 // generations are assumed to support marking; those that can also support
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30 // compaction.
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31 //
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32 // Class unloading will only occur when a full gc is invoked.
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33
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34 // If VALIDATE_MARK_SWEEP is defined, the -XX:+ValidateMarkSweep flag will
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35 // be operational, and will provide slow but comprehensive self-checks within
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36 // the GC. This is not enabled by default in product or release builds,
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37 // since the extra call to track_adjusted_pointer() in _adjust_pointer()
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38 // would be too much overhead, and would disturb performance measurement.
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39 // However, debug builds are sometimes way too slow to run GC tests!
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40 #ifdef ASSERT
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41 #define VALIDATE_MARK_SWEEP 1
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42 #endif
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43 #ifdef VALIDATE_MARK_SWEEP
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44 #define VALIDATE_MARK_SWEEP_ONLY(code) code
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45 #else
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46 #define VALIDATE_MARK_SWEEP_ONLY(code)
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47 #endif
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48
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49
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50 // declared at end
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51 class PreservedMark;
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52
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53 class MarkSweep : AllStatic {
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54 //
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55 // In line closure decls
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56 //
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57
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58 class FollowRootClosure: public OopsInGenClosure{
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59 public:
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60 void do_oop(oop* p) { follow_root(p); }
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61 virtual const bool do_nmethods() const { return true; }
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62 };
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63
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64 class MarkAndPushClosure: public OopClosure {
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65 public:
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66 void do_oop(oop* p) { mark_and_push(p); }
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67 virtual const bool do_nmethods() const { return true; }
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68 };
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69
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70 class FollowStackClosure: public VoidClosure {
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71 public:
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72 void do_void() { follow_stack(); }
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73 };
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74
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75 class AdjustPointerClosure: public OopsInGenClosure {
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76 bool _is_root;
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77 public:
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78 AdjustPointerClosure(bool is_root) : _is_root(is_root) {}
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79 void do_oop(oop* p) { _adjust_pointer(p, _is_root); }
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80 };
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81
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82 // Used for java/lang/ref handling
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83 class IsAliveClosure: public BoolObjectClosure {
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84 public:
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85 void do_object(oop p) { assert(false, "don't call"); }
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86 bool do_object_b(oop p) { return p->is_gc_marked(); }
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87 };
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88
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89 class KeepAliveClosure: public OopClosure {
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90 public:
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91 void do_oop(oop* p);
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92 };
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93
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94 //
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95 // Friend decls
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96 //
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97
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98 friend class AdjustPointerClosure;
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99 friend class KeepAliveClosure;
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100 friend class VM_MarkSweep;
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101 friend void marksweep_init();
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102
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103 //
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104 // Vars
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105 //
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106 protected:
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107 // Traversal stack used during phase1
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108 static GrowableArray<oop>* _marking_stack;
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109 // Stack for live klasses to revisit at end of marking phase
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110 static GrowableArray<Klass*>* _revisit_klass_stack;
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111
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112 // Space for storing/restoring mark word
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113 static GrowableArray<markOop>* _preserved_mark_stack;
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114 static GrowableArray<oop>* _preserved_oop_stack;
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115 static size_t _preserved_count;
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116 static size_t _preserved_count_max;
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117 static PreservedMark* _preserved_marks;
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118
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119 // Reference processing (used in ...follow_contents)
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120 static ReferenceProcessor* _ref_processor;
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121
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122 #ifdef VALIDATE_MARK_SWEEP
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123 static GrowableArray<oop*>* _root_refs_stack;
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124 static GrowableArray<oop> * _live_oops;
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125 static GrowableArray<oop> * _live_oops_moved_to;
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126 static GrowableArray<size_t>* _live_oops_size;
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127 static size_t _live_oops_index;
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128 static size_t _live_oops_index_at_perm;
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129 static GrowableArray<oop*>* _other_refs_stack;
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130 static GrowableArray<oop*>* _adjusted_pointers;
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131 static bool _pointer_tracking;
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132 static bool _root_tracking;
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133
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134 // The following arrays are saved since the time of the last GC and
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135 // assist in tracking down problems where someone has done an errant
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136 // store into the heap, usually to an oop that wasn't properly
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137 // handleized across a GC. If we crash or otherwise fail before the
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138 // next GC, we can query these arrays to find out the object we had
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139 // intended to do the store to (assuming it is still alive) and the
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140 // offset within that object. Covered under RecordMarkSweepCompaction.
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141 static GrowableArray<HeapWord*> * _cur_gc_live_oops;
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142 static GrowableArray<HeapWord*> * _cur_gc_live_oops_moved_to;
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143 static GrowableArray<size_t>* _cur_gc_live_oops_size;
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144 static GrowableArray<HeapWord*> * _last_gc_live_oops;
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145 static GrowableArray<HeapWord*> * _last_gc_live_oops_moved_to;
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146 static GrowableArray<size_t>* _last_gc_live_oops_size;
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147 #endif
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148
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149
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150 // Non public closures
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151 static IsAliveClosure is_alive;
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152 static KeepAliveClosure keep_alive;
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153
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154 // Class unloading. Update subklass/sibling/implementor links at end of marking phase.
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155 static void follow_weak_klass_links();
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156
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157 // Debugging
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158 static void trace(const char* msg) PRODUCT_RETURN;
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159
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160 public:
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161 // Public closures
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162 static FollowRootClosure follow_root_closure;
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163 static MarkAndPushClosure mark_and_push_closure;
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164 static FollowStackClosure follow_stack_closure;
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165 static AdjustPointerClosure adjust_root_pointer_closure;
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166 static AdjustPointerClosure adjust_pointer_closure;
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167
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168 // Reference Processing
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169 static ReferenceProcessor* const ref_processor() { return _ref_processor; }
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170
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171 // Call backs for marking
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172 static void mark_object(oop obj);
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173 static void follow_root(oop* p); // Mark pointer and follow contents. Empty marking
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174
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175 // stack afterwards.
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176
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177 static void mark_and_follow(oop* p); // Mark pointer and follow contents.
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178 static void _mark_and_push(oop* p); // Mark pointer and push obj on
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179 // marking stack.
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180
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181
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182 static void mark_and_push(oop* p) { // Check mark and maybe push on
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183 // marking stack
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184 // assert(Universe::is_reserved_heap((oop)p), "we should only be traversing objects here");
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185 oop m = *p;
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186 if (m != NULL && !m->mark()->is_marked()) {
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187 _mark_and_push(p);
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188 }
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189 }
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190
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191 static void follow_stack(); // Empty marking stack.
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192
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193
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194 static void preserve_mark(oop p, markOop mark); // Save the mark word so it can be restored later
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195 static void adjust_marks(); // Adjust the pointers in the preserved marks table
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196 static void restore_marks(); // Restore the marks that we saved in preserve_mark
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197
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198 static void _adjust_pointer(oop* p, bool isroot);
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199
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200 static void adjust_root_pointer(oop* p) { _adjust_pointer(p, true); }
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201 static void adjust_pointer(oop* p) { _adjust_pointer(p, false); }
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202
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203 #ifdef VALIDATE_MARK_SWEEP
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204 static void track_adjusted_pointer(oop* p, oop newobj, bool isroot);
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205 static void check_adjust_pointer(oop* p); // Adjust this pointer
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206 static void track_interior_pointers(oop obj);
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207 static void check_interior_pointers();
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208
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209 static void reset_live_oop_tracking(bool at_perm);
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210 static void register_live_oop(oop p, size_t size);
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211 static void validate_live_oop(oop p, size_t size);
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212 static void live_oop_moved_to(HeapWord* q, size_t size, HeapWord* compaction_top);
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213 static void compaction_complete();
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214
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215 // Querying operation of RecordMarkSweepCompaction results.
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216 // Finds and prints the current base oop and offset for a word
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217 // within an oop that was live during the last GC. Helpful for
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218 // tracking down heap stomps.
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219 static void print_new_location_of_heap_address(HeapWord* q);
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220 #endif
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221
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222 // Call backs for class unloading
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223 static void revisit_weak_klass_link(Klass* k); // Update subklass/sibling/implementor links at end of marking.
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224 };
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225
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226
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227 class PreservedMark VALUE_OBJ_CLASS_SPEC {
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228 private:
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229 oop _obj;
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230 markOop _mark;
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231
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232 public:
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233 void init(oop obj, markOop mark) {
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234 _obj = obj;
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235 _mark = mark;
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236 }
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237
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238 void adjust_pointer() {
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239 MarkSweep::adjust_pointer(&_obj);
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240 }
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241
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242 void restore() {
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243 _obj->set_mark(_mark);
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244 }
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245 };
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