1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_RUNTIME_INTERN_TABLE_H_ 18 #define ART_RUNTIME_INTERN_TABLE_H_ 19 20 #include <unordered_set> 21 22 #include "base/allocator.h" 23 #include "base/hash_set.h" 24 #include "base/mutex.h" 25 #include "gc_root.h" 26 #include "object_callbacks.h" 27 28 namespace art { 29 30 namespace gc { 31 namespace space { 32 class ImageSpace; 33 } // namespace space 34 } // namespace gc 35 36 enum VisitRootFlags : uint8_t; 37 38 namespace mirror { 39 class String; 40 } // namespace mirror 41 class Transaction; 42 43 /** 44 * Used to intern strings. 45 * 46 * There are actually two tables: one that holds strong references to its strings, and one that 47 * holds weak references. The former is used for string literals, for which there is an effective 48 * reference from the constant pool. The latter is used for strings interned at runtime via 49 * String.intern. Some code (XML parsers being a prime example) relies on being able to intern 50 * arbitrarily many strings for the duration of a parse without permanently increasing the memory 51 * footprint. 52 */ 53 class InternTable { 54 public: 55 InternTable(); 56 57 // Interns a potentially new string in the 'strong' table. (See above.) 58 mirror::String* InternStrong(int32_t utf16_length, const char* utf8_data) 59 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 60 61 // Interns a potentially new string in the 'strong' table. (See above.) 62 mirror::String* InternStrong(const char* utf8_data) 63 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 64 65 // Interns a potentially new string in the 'strong' table. (See above.) 66 mirror::String* InternStrong(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 67 68 // Interns a potentially new string in the 'weak' table. (See above.) 69 mirror::String* InternWeak(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 70 71 void SweepInternTableWeaks(IsMarkedCallback* callback, void* arg) 72 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 73 74 bool ContainsWeak(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 75 76 // Total number of interned strings. 77 size_t Size() const LOCKS_EXCLUDED(Locks::intern_table_lock_); 78 // Total number of weakly live interned strings. 79 size_t StrongSize() const LOCKS_EXCLUDED(Locks::intern_table_lock_); 80 // Total number of strongly live interned strings. 81 size_t WeakSize() const LOCKS_EXCLUDED(Locks::intern_table_lock_); 82 83 void VisitRoots(RootCallback* callback, void* arg, VisitRootFlags flags) 84 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 85 86 void DumpForSigQuit(std::ostream& os) const; 87 88 void DisallowNewInterns() EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_); 89 void AllowNewInterns() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 90 91 // Adds all of the resolved image strings from the image space into the intern table. The 92 // advantage of doing this is preventing expensive DexFile::FindStringId calls. 93 void AddImageStringsToTable(gc::space::ImageSpace* image_space) 94 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) LOCKS_EXCLUDED(Locks::intern_table_lock_); 95 // Copy the post zygote tables to pre zygote to save memory by preventing dirty pages. 96 void SwapPostZygoteWithPreZygote() 97 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) LOCKS_EXCLUDED(Locks::intern_table_lock_); 98 99 private: 100 class StringHashEquals { 101 public: 102 std::size_t operator()(const GcRoot<mirror::String>& root) const NO_THREAD_SAFETY_ANALYSIS; 103 bool operator()(const GcRoot<mirror::String>& a, const GcRoot<mirror::String>& b) const 104 NO_THREAD_SAFETY_ANALYSIS; 105 }; 106 class GcRootEmptyFn { 107 public: 108 void MakeEmpty(GcRoot<mirror::String>& item) const { 109 item = GcRoot<mirror::String>(); 110 } 111 bool IsEmpty(const GcRoot<mirror::String>& item) const { 112 return item.IsNull(); 113 } 114 }; 115 116 // Table which holds pre zygote and post zygote interned strings. There is one instance for 117 // weak interns and strong interns. 118 class Table { 119 public: 120 mirror::String* Find(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 121 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 122 void Insert(mirror::String* s) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 123 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 124 void Remove(mirror::String* s) 125 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 126 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 127 void VisitRoots(RootCallback* callback, void* arg) 128 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 129 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 130 void SweepWeaks(IsMarkedCallback* callback, void* arg) 131 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 132 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 133 void SwapPostZygoteWithPreZygote() EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 134 size_t Size() const EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 135 136 private: 137 typedef HashSet<GcRoot<mirror::String>, GcRootEmptyFn, StringHashEquals, StringHashEquals, 138 TrackingAllocator<GcRoot<mirror::String>, kAllocatorTagInternTable>> UnorderedSet; 139 140 void SweepWeaks(UnorderedSet* set, IsMarkedCallback* callback, void* arg) 141 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 142 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 143 144 // We call SwapPostZygoteWithPreZygote when we create the zygote to reduce private dirty pages 145 // caused by modifying the zygote intern table hash table. The pre zygote table are the 146 // interned strings which were interned before we created the zygote space. Post zygote is self 147 // explanatory. 148 UnorderedSet pre_zygote_table_; 149 UnorderedSet post_zygote_table_; 150 }; 151 152 // Insert if non null, otherwise return nullptr. 153 mirror::String* Insert(mirror::String* s, bool is_strong) 154 LOCKS_EXCLUDED(Locks::intern_table_lock_) 155 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_); 156 157 mirror::String* LookupStrong(mirror::String* s) 158 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 159 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 160 mirror::String* LookupWeak(mirror::String* s) 161 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 162 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 163 mirror::String* InsertStrong(mirror::String* s) 164 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 165 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 166 mirror::String* InsertWeak(mirror::String* s) 167 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 168 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 169 void RemoveStrong(mirror::String* s) 170 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 171 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 172 void RemoveWeak(mirror::String* s) 173 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 174 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 175 176 // Transaction rollback access. 177 mirror::String* LookupStringFromImage(mirror::String* s) 178 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 179 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 180 mirror::String* InsertStrongFromTransaction(mirror::String* s) 181 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 182 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 183 mirror::String* InsertWeakFromTransaction(mirror::String* s) 184 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 185 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 186 void RemoveStrongFromTransaction(mirror::String* s) 187 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 188 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 189 void RemoveWeakFromTransaction(mirror::String* s) 190 SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) 191 EXCLUSIVE_LOCKS_REQUIRED(Locks::intern_table_lock_); 192 friend class Transaction; 193 194 bool image_added_to_intern_table_ GUARDED_BY(Locks::intern_table_lock_); 195 bool log_new_roots_ GUARDED_BY(Locks::intern_table_lock_); 196 bool allow_new_interns_ GUARDED_BY(Locks::intern_table_lock_); 197 ConditionVariable new_intern_condition_ GUARDED_BY(Locks::intern_table_lock_); 198 // Since this contains (strong) roots, they need a read barrier to 199 // enable concurrent intern table (strong) root scan. Do not 200 // directly access the strings in it. Use functions that contain 201 // read barriers. 202 Table strong_interns_ GUARDED_BY(Locks::intern_table_lock_); 203 std::vector<GcRoot<mirror::String>> new_strong_intern_roots_ 204 GUARDED_BY(Locks::intern_table_lock_); 205 // Since this contains (weak) roots, they need a read barrier. Do 206 // not directly access the strings in it. Use functions that contain 207 // read barriers. 208 Table weak_interns_ GUARDED_BY(Locks::intern_table_lock_); 209 }; 210 211 } // namespace art 212 213 #endif // ART_RUNTIME_INTERN_TABLE_H_ 214
