1 /*
2 * Copyright (c) 1997, 2019, 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_CLASSFILE_STRINGTABLE_HPP
26 #define SHARE_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 _alt_hash;
59
60 private:
61
62 StringTableHash* _local_table;
63 size_t _current_size;
64 volatile bool _has_work;
65 // Set if one bucket is out of balance due to hash algorithm deficiency
66 volatile bool _needs_rehashing;
67
68 OopStorage* _weak_handles;
69
70 volatile size_t _items_count;
71 DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
72 volatile size_t _uncleaned_items_count;
73 DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
74
75 double get_load_factor() const;
76 double get_dead_factor() const;
77
78 void check_concurrent_work();
79 void trigger_concurrent_work();
80
81 static size_t item_added();
82 static void item_removed();
83 size_t add_items_to_clean(size_t ndead);
84
85 StringTable();
86
87 static oop intern(Handle string_or_null_h, const jchar* name, int len, TRAPS);
88 oop do_intern(Handle string_or_null, const jchar* name, int len, uintx hash, TRAPS);
89 oop do_lookup(const jchar* name, int len, uintx hash);
90
91 void concurrent_work(JavaThread* jt);
92 void print_table_statistics(outputStream* st, const char* table_name);
93
94 void try_rehash_table();
95 bool do_rehash();
96 inline void update_needs_rehash(bool rehash);
97
98 public:
99 // The string table
100 static StringTable* the_table() { return _the_table; }
101 size_t table_size();
102 TableStatistics get_table_statistics();
103
104 static OopStorage* weak_storage() { return the_table()->_weak_handles; }
105
106 static void create_table() {
107 assert(_the_table == NULL, "One string table allowed.");
108 _the_table = new StringTable();
109 }
110
111 static void do_concurrent_work(JavaThread* jt);
112 static bool has_work() { return the_table()->_has_work; }
113
114 // GC support
115
116 // Must be called before a parallel walk where strings might die.
117 static void reset_dead_counter() {
118 the_table()->_uncleaned_items_count = 0;
119 }
120 // After the parallel walk this method must be called to trigger
121 // cleaning. Note it might trigger a resize instead.
122 static void finish_dead_counter() {
123 the_table()->check_concurrent_work();
124 }
125
126 // If GC uses ParState directly it should add the number of cleared
127 // strings to this method.
128 static void inc_dead_counter(size_t ndead) {
129 the_table()->add_items_to_clean(ndead);
130 }
131
132 // Serially invoke "f->do_oop" on the locations of all oops in the table.
133 static void oops_do(OopClosure* f);
134
135 // Possibly parallel versions of the above
136 static void possibly_parallel_oops_do(
137 OopStorage::ParState<false /* concurrent */, false /* const*/>* par_state_string,
138 OopClosure* f);
139
140 // Probing
141 static oop lookup(Symbol* symbol);
142 static oop lookup(const jchar* chars, int length);
143
144 // Interning
145 static oop intern(Symbol* symbol, TRAPS);
146 static oop intern(oop string, TRAPS);
147 static oop intern(const char *utf8_string, TRAPS);
148
149 // Rehash the string table if it gets out of balance
150 static void rehash_table();
151 static bool needs_rehashing()
152 { return StringTable::the_table()->_needs_rehashing; }
153
154 // Sharing
155 private:
156 oop lookup_shared(const jchar* name, int len, unsigned int hash) NOT_CDS_JAVA_HEAP_RETURN_(NULL);
157 static void copy_shared_string_table(CompactHashtableWriter* ch_table) NOT_CDS_JAVA_HEAP_RETURN;
158 public:
159 static oop create_archived_string(oop s, Thread* THREAD) NOT_CDS_JAVA_HEAP_RETURN_(NULL);
160 static void shared_oops_do(OopClosure* f) NOT_CDS_JAVA_HEAP_RETURN;
161 static void write_to_archive() NOT_CDS_JAVA_HEAP_RETURN;
162 static void serialize_shared_table_header(SerializeClosure* soc) NOT_CDS_JAVA_HEAP_RETURN;
163
164 // Jcmd
165 static void dump(outputStream* st, bool verbose=false);
166 // Debugging
167 static size_t verify_and_compare_entries();
168 static void verify();
169 };
170
171 #endif // SHARE_CLASSFILE_STRINGTABLE_HPP