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1 /* |
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2 * Copyright (c) 2017, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
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22 * |
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23 */ |
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24 |
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25 #ifndef SHARE_VM_MEMORY_METASPACE_ITERATOR_HPP |
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26 #define SHARE_VM_MEMORY_METASPACE_ITERATOR_HPP |
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27 |
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28 #include "logging/log.hpp" |
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29 #include "memory/allocation.hpp" |
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30 #include "oops/array.hpp" |
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31 #include "utilities/growableArray.hpp" |
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32 #include "utilities/resourceHash.hpp" |
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33 |
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34 // The metadata hierarchy is separate from the oop hierarchy |
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35 class MetaspaceObj; // no C++ vtable |
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36 //class Array; // no C++ vtable |
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37 class Annotations; // no C++ vtable |
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38 class ConstantPoolCache; // no C++ vtable |
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39 class ConstMethod; // no C++ vtable |
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40 class MethodCounters; // no C++ vtable |
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41 class Symbol; // no C++ vtable |
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42 class Metadata; // has C++ vtable (so do all subclasses) |
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43 class ConstantPool; |
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44 class MethodData; |
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45 class Method; |
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46 class Klass; |
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47 class InstanceKlass; |
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48 class InstanceMirrorKlass; |
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49 class InstanceClassLoaderKlass; |
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50 class InstanceRefKlass; |
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51 class ArrayKlass; |
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52 class ObjArrayKlass; |
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53 class TypeArrayKlass; |
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54 |
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55 // class MetaspaceClosure -- |
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56 // |
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57 // This class is used for iterating the objects in the HotSpot Metaspaces. It |
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58 // provides an API to walk all the reachable objects starting from a set of |
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59 // root references (such as all Klass'es in the SystemDictionary). |
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60 // |
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61 // Currently it is used for compacting the CDS archive by eliminate temporary |
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62 // objects allocated during archive creation time. See ArchiveCompactor in |
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63 // metaspaceShared.cpp for an example. |
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64 // |
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65 // To support MetaspaceClosure, each subclass of MetaspaceObj must provide |
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66 // a method of the type void metaspace_pointers_do(MetaspaceClosure*). This method |
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67 // should call MetaspaceClosure::push() on every pointer fields of this |
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68 // class that points to a MetaspaceObj. See Annotations::metaspace_pointers_do() |
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69 // for an example. |
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70 class MetaspaceClosure { |
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71 public: |
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72 enum Writability { |
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73 _writable, |
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74 _not_writable, |
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75 _default |
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76 }; |
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77 |
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78 // class MetaspaceClosure::Ref -- |
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79 // |
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80 // MetaspaceClosure can be viewed as a very simple type of copying garbage |
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81 // collector. For it to function properly, it requires each subclass of |
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82 // MetaspaceObj to provide two methods: |
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83 // |
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84 // size_t size(); -- to determine how much data to copy |
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85 // void metaspace_pointers_do(MetaspaceClosure*); -- to locate all the embedded pointers |
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86 // |
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87 // Calling these methods would be trivial if these two were virtual methods. |
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88 // However, to save space, MetaspaceObj has NO vtable. The vtable is introduced |
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89 // only in the Metadata class. |
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90 // |
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91 // To work around the lack of a vtable, we use Ref class with templates |
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92 // (see ObjectRef, PrimitiveArrayRef and PointerArrayRef) |
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93 // so that we can statically discover the type of a object. The use of Ref |
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94 // depends on the fact that: |
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95 // |
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96 // [1] We don't use polymorphic pointers for MetaspaceObj's that are not subclasses |
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97 // of Metadata. I.e., we don't do this: |
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98 // class Klass { |
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99 // MetaspaceObj *_obj; |
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100 // Array<int>* foo() { return (Array<int>*)_obj; } |
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101 // Symbol* bar() { return (Symbol*) _obj; } |
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102 // |
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103 // [2] All Array<T> dimensions are statically declared. |
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104 class Ref { |
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105 protected: |
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106 virtual void** mpp() const = 0; |
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107 public: |
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108 virtual bool not_null() const = 0; |
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109 virtual int size() const = 0; |
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110 virtual void metaspace_pointers_do(MetaspaceClosure *it) const = 0; |
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111 virtual void metaspace_pointers_do_at(MetaspaceClosure *it, address new_loc) const = 0; |
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112 virtual MetaspaceObj::Type msotype() const = 0; |
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113 virtual bool is_read_only_by_default() const = 0; |
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114 |
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115 address obj() const { |
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116 // In some rare cases (see CPSlot in constantPool.hpp) we store some flags in the lowest |
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117 // 2 bits of a MetaspaceObj pointer. Unmask these when manipulating the pointer. |
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118 uintx p = (uintx)*mpp(); |
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119 return (address)(p & (~FLAG_MASK)); |
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120 } |
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121 |
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122 void update(address new_loc) const; |
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123 |
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124 private: |
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125 static const uintx FLAG_MASK = 0x03; |
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126 |
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127 int flag_bits() const { |
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128 uintx p = (uintx)*mpp(); |
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129 return (int)(p & FLAG_MASK); |
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130 } |
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131 }; |
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132 |
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133 private: |
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134 // -------------------------------------------------- ObjectRef |
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135 template <class T> class ObjectRef : public Ref { |
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136 T** _mpp; |
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137 T* dereference() const { |
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138 return *_mpp; |
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139 } |
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140 protected: |
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141 virtual void** mpp() const { |
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142 return (void**)_mpp; |
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143 } |
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144 |
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145 public: |
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146 ObjectRef(T** mpp) : _mpp(mpp) {} |
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147 |
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148 virtual bool is_read_only_by_default() const { return T::is_read_only_by_default(); } |
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149 virtual bool not_null() const { return dereference() != NULL; } |
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150 virtual int size() const { return dereference()->size(); } |
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151 virtual MetaspaceObj::Type msotype() const { return dereference()->type(); } |
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152 |
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153 virtual void metaspace_pointers_do(MetaspaceClosure *it) const { |
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154 dereference()->metaspace_pointers_do(it); |
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155 } |
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156 virtual void metaspace_pointers_do_at(MetaspaceClosure *it, address new_loc) const { |
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157 ((T*)new_loc)->metaspace_pointers_do(it); |
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158 } |
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159 }; |
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160 |
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161 // -------------------------------------------------- PrimitiveArrayRef |
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162 template <class T> class PrimitiveArrayRef : public Ref { |
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163 Array<T>** _mpp; |
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164 Array<T>* dereference() const { |
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165 return *_mpp; |
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166 } |
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167 protected: |
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168 virtual void** mpp() const { |
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169 return (void**)_mpp; |
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170 } |
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171 |
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172 public: |
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173 PrimitiveArrayRef(Array<T>** mpp) : _mpp(mpp) {} |
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174 |
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175 // all Arrays are read-only by default |
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176 virtual bool is_read_only_by_default() const { return true; } |
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177 virtual bool not_null() const { return dereference() != NULL; } |
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178 virtual int size() const { return dereference()->size(); } |
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179 virtual MetaspaceObj::Type msotype() const { return MetaspaceObj::array_type(sizeof(T)); } |
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180 |
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181 virtual void metaspace_pointers_do(MetaspaceClosure *it) const { |
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182 Array<T>* array = dereference(); |
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183 log_trace(cds)("Iter(PrimitiveArray): %p [%d]", array, array->length()); |
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184 } |
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185 virtual void metaspace_pointers_do_at(MetaspaceClosure *it, address new_loc) const { |
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186 Array<T>* array = (Array<T>*)new_loc; |
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187 log_trace(cds)("Iter(PrimitiveArray): %p [%d]", array, array->length()); |
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188 } |
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189 }; |
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190 |
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191 // -------------------------------------------------- PointerArrayRef |
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192 template <class T> class PointerArrayRef : public Ref { |
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193 Array<T*>** _mpp; |
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194 Array<T*>* dereference() const { |
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195 return *_mpp; |
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196 } |
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197 protected: |
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198 virtual void** mpp() const { |
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199 return (void**)_mpp; |
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200 } |
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201 |
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202 public: |
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203 PointerArrayRef(Array<T*>** mpp) : _mpp(mpp) {} |
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204 |
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205 // all Arrays are read-only by default |
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206 virtual bool is_read_only_by_default() const { return true; } |
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207 virtual bool not_null() const { return dereference() != NULL; } |
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208 virtual int size() const { return dereference()->size(); } |
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209 virtual MetaspaceObj::Type msotype() const { return MetaspaceObj::array_type(sizeof(T*)); } |
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210 |
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211 virtual void metaspace_pointers_do(MetaspaceClosure *it) const { |
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212 metaspace_pointers_do_at_impl(it, dereference()); |
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213 } |
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214 virtual void metaspace_pointers_do_at(MetaspaceClosure *it, address new_loc) const { |
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215 metaspace_pointers_do_at_impl(it, (Array<T*>*)new_loc); |
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216 } |
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217 private: |
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218 void metaspace_pointers_do_at_impl(MetaspaceClosure *it, Array<T*>* array) const { |
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219 log_trace(cds)("Iter(ObjectArray): %p [%d]", array, array->length()); |
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220 for (int i = 0; i < array->length(); i++) { |
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221 T** mpp = array->adr_at(i); |
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222 it->push(mpp); |
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223 } |
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224 } |
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225 }; |
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226 |
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227 void push_impl(Ref* ref, Writability w); |
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228 |
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229 public: |
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230 // returns true if we want to keep iterating the pointers embedded inside <ref> |
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231 virtual bool do_ref(Ref* ref, bool read_only) = 0; |
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232 |
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233 // When you do: |
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234 // void MyType::metaspace_pointers_do(MetaspaceClosure* it) { |
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235 // it->push(_my_field) |
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236 // |
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237 // C++ will try to match the "most specific" template function. This one will |
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238 // will be matched if possible (if mpp is an Array<> of any pointer type). |
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239 template <typename T> void push(Array<T*>** mpp, Writability w = _default) { |
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240 PointerArrayRef<T> ref(mpp); |
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241 push_impl(&ref, w); |
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242 } |
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243 |
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244 // If the above function doesn't match (mpp is an Array<>, but T is not a pointer type), then |
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245 // this is the second choice. |
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246 template <typename T> void push(Array<T>** mpp, Writability w = _default) { |
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247 PrimitiveArrayRef<T> ref(mpp); |
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248 push_impl(&ref, w); |
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249 } |
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250 |
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251 // If the above function doesn't match (mpp is not an Array<> type), then |
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252 // this will be matched by default. |
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253 template <class T> void push(T** mpp, Writability w = _default) { |
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254 ObjectRef<T> ref(mpp); |
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255 push_impl(&ref, w); |
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256 } |
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257 }; |
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258 |
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259 // This is a special MetaspaceClosure that visits each unique MetaspaceObj once. |
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260 class UniqueMetaspaceClosure : public MetaspaceClosure { |
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261 // Do not override. Returns true if we are discovering ref->obj() for the first time. |
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262 virtual bool do_ref(Ref* ref, bool read_only); |
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263 |
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264 public: |
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265 // Gets called the first time we discover an object. |
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266 virtual void do_unique_ref(Ref* ref, bool read_only) = 0; |
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267 private: |
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268 static unsigned my_hash(const address& a) { |
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269 return primitive_hash<address>(a); |
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270 } |
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271 static bool my_equals(const address& a0, const address& a1) { |
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272 return primitive_equals<address>(a0, a1); |
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273 } |
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274 ResourceHashtable< |
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275 address, bool, |
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276 UniqueMetaspaceClosure::my_hash, // solaris compiler doesn't like: primitive_hash<address> |
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277 UniqueMetaspaceClosure::my_equals, // solaris compiler doesn't like: primitive_equals<address> |
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278 15889, // prime number |
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279 ResourceObj::C_HEAP> _has_been_visited; |
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280 }; |
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281 |
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282 #endif // SHARE_VM_MEMORY_METASPACE_ITERATOR_HPP |