1 /* 2 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_CLASSFILE_STRINGTABLE_HPP 26 #define SHARE_VM_CLASSFILE_STRINGTABLE_HPP 27 28 #include "gc/shared/oopStorage.hpp" 29 #include "gc/shared/oopStorageParState.hpp" 30 #include "memory/allocation.hpp" 31 #include "memory/padded.hpp" 32 #include "oops/oop.hpp" 33 #include "oops/weakHandle.hpp" 34 #include "utilities/concurrentHashTable.hpp" 35 36 class CompactHashtableWriter; 37 class SerializeClosure; 38 39 class StringTable; 40 class StringTableConfig; 41 typedef ConcurrentHashTable<WeakHandle<vm_string_table_data>, 42 StringTableConfig, mtSymbol> StringTableHash; 43 44 class StringTableCreateEntry; 45 46 class StringTable : public CHeapObj<mtSymbol>{ 47 friend class VMStructs; 48 friend class Symbol; 49 friend class StringTableConfig; 50 friend class StringTableCreateEntry; 51 52 private: 53 void grow(JavaThread* jt); 54 void clean_dead_entries(JavaThread* jt); 55 56 // The string table 57 static StringTable* _the_table; 58 static volatile bool _shared_string_mapped; 59 static volatile bool _alt_hash; 60 61 private: 62 63 StringTableHash* _local_table; 64 size_t _current_size; 65 volatile bool _has_work; 66 // Set if one bucket is out of balance due to hash algorithm deficiency 67 volatile bool _needs_rehashing; 68 69 OopStorage* _weak_handles; 70 71 volatile size_t _items_count; 72 DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t)); 73 volatile size_t _uncleaned_items_count; 74 DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t)); 75 76 double get_load_factor(); 77 double get_dead_factor(); 78 79 void check_concurrent_work(); 80 void trigger_concurrent_work(); 81 82 static size_t item_added(); 83 static void item_removed(); 84 size_t add_items_count_to_clean(size_t ndead); 85 86 StringTable(); 87 88 static oop intern(Handle string_or_null_h, const jchar* name, int len, TRAPS); 89 oop do_intern(Handle string_or_null, const jchar* name, int len, uintx hash, TRAPS); 90 oop do_lookup(const jchar* name, int len, uintx hash); 91 92 void concurrent_work(JavaThread* jt); 93 void print_table_statistics(outputStream* st, const char* table_name); 94 95 void try_rehash_table(); 96 bool do_rehash(); 97 98 public: 99 // The string table 100 static StringTable* the_table() { return _the_table; } 101 size_t table_size(); 102 103 static OopStorage* weak_storage() { return the_table()->_weak_handles; } 104 105 static void create_table() { 106 assert(_the_table == NULL, "One string table allowed."); 107 _the_table = new StringTable(); 108 } 109 110 static void do_concurrent_work(JavaThread* jt); 111 static bool has_work() { return the_table()->_has_work; } 112 113 // GC support 114 115 // Must be called before a parallel walk where strings might die. 116 static void reset_dead_counter() { 117 the_table()->_uncleaned_items_count = 0; 118 } 119 // After the parallel walk this method must be called to trigger 120 // cleaning. Note it might trigger a resize instead. 121 static void finish_dead_counter() { 122 the_table()->check_concurrent_work(); 123 } 124 125 // If GC uses ParState directly it should add the number of cleared 126 // strings to this method. 127 static void inc_dead_counter(size_t ndead) { 128 the_table()->add_items_count_to_clean(ndead); 129 } 130 131 // Delete pointers to otherwise-unreachable objects. 132 static void unlink(BoolObjectClosure* cl) { 133 unlink_or_oops_do(cl); 134 } 135 static void unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f = NULL, 136 size_t* processed = NULL, size_t* removed = NULL); 137 138 // Serially invoke "f->do_oop" on the locations of all oops in the table. 139 static void oops_do(OopClosure* f); 140 141 // Possibly parallel versions of the above 142 static void possibly_parallel_unlink( 143 OopStorage::ParState<false /* concurrent */, false /* const*/>* par_state_string, 144 BoolObjectClosure* cl, size_t* processed, size_t* removed); 145 static void possibly_parallel_oops_do( 146 OopStorage::ParState<false /* concurrent */, false /* const*/>* par_state_string, 147 OopClosure* f); 148 149 // Probing 150 static oop lookup(Symbol* symbol); 151 static oop lookup(const jchar* chars, int length); 152 153 // Interning 154 static oop intern(Symbol* symbol, TRAPS); 155 static oop intern(oop string, TRAPS); 156 static oop intern(const char *utf8_string, TRAPS); 157 158 // Rehash the string table if it gets out of balance 159 static void rehash_table(); 160 static bool needs_rehashing() 161 { return StringTable::the_table()->_needs_rehashing; } 162 163 // Sharing 164 private: 165 oop lookup_shared(const jchar* name, int len, unsigned int hash) NOT_CDS_JAVA_HEAP_RETURN_(NULL); 166 static void copy_shared_string_table(CompactHashtableWriter* ch_table) NOT_CDS_JAVA_HEAP_RETURN; 167 public: 168 static oop create_archived_string(oop s, Thread* THREAD) NOT_CDS_JAVA_HEAP_RETURN_(NULL); 169 static void set_shared_string_mapped() { _shared_string_mapped = true; } 170 static bool shared_string_mapped() { return _shared_string_mapped; } 171 static void shared_oops_do(OopClosure* f) NOT_CDS_JAVA_HEAP_RETURN; 172 static void write_to_archive() NOT_CDS_JAVA_HEAP_RETURN; 173 static void serialize(SerializeClosure* soc) NOT_CDS_JAVA_HEAP_RETURN; 174 175 // Jcmd 176 static void dump(outputStream* st, bool verbose=false); 177 // Debugging 178 static size_t verify_and_compare_entries(); 179 static void verify(); 180 }; 181 182 #endif // SHARE_VM_CLASSFILE_STRINGTABLE_HPP