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 template <class T, class N> class CompactHashtable;
37 class CompactStringTableWriter;
38 class SerializeClosure;
39
40 class StringTable;
41 class StringTableConfig;
42 typedef ConcurrentHashTable<WeakHandle<vm_string_table_data>,
43 StringTableConfig, mtSymbol> StringTableHash;
44
45 class StringTableCreateEntry;
46
47 class StringTable : public CHeapObj<mtSymbol>{
48 friend class VMStructs;
49 friend class Symbol;
50 friend class StringTableConfig;
51 friend class StringTableCreateEntry;
52
53 private:
54 void grow(JavaThread* jt);
55 void clean_dead_entries(JavaThread* jt);
56
57 // The string table
58 static StringTable* _the_table;
59 // Shared string table
60 static CompactHashtable<oop, char> _shared_table;
61 static volatile bool _shared_string_mapped;
62 static volatile bool _alt_hash;
63
64 private:
65
66 StringTableHash* _local_table;
67 size_t _current_size;
68 volatile bool _has_work;
69 // Set if one bucket is out of balance due to hash algorithm deficiency
70 volatile bool _needs_rehashing;
71
72 OopStorage* _weak_handles;
73
74 volatile size_t _items_count;
75 DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
76 volatile size_t _uncleaned_items_count;
77 DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
78
79 double get_load_factor();
80 double get_dead_factor();
81
82 void check_concurrent_work();
83 void trigger_concurrent_work();
84
85 static size_t item_added();
86 static void item_removed();
87 size_t add_items_count_to_clean(size_t ndead);
88
89 StringTable();
90
91 static oop intern(Handle string_or_null_h, jchar* name, int len, TRAPS);
92 oop do_intern(Handle string_or_null, jchar* name, int len, uintx hash, TRAPS);
93 oop do_lookup(jchar* name, int len, uintx hash);
94
95 void concurrent_work(JavaThread* jt);
96 void print_table_statistics(outputStream* st, const char* table_name);
97
98 void try_rehash_table();
99 bool do_rehash();
100
101 public:
102 // The string table
103 static StringTable* the_table() { return _the_table; }
104 size_t table_size();
105
106 static OopStorage* weak_storage() { return the_table()->_weak_handles; }
107
108 static void create_table() {
109 assert(_the_table == NULL, "One string table allowed.");
110 _the_table = new StringTable();
111 }
112
113 static void do_concurrent_work(JavaThread* jt);
114 static bool has_work() { return the_table()->_has_work; }
115
116 // GC support
117
118 // Must be called before a parallel walk where strings might die.
119 static void reset_dead_counter() {
120 the_table()->_uncleaned_items_count = 0;
121 }
122 // After the parallel walk this method must be called to trigger
123 // cleaning. Note it might trigger a resize instead.
124 static void finish_dead_counter() {
125 the_table()->check_concurrent_work();
126 }
127
128 // If GC uses ParState directly it should add the number of cleared
129 // strings to this method.
130 static void inc_dead_counter(size_t ndead) {
131 the_table()->add_items_count_to_clean(ndead);
132 }
133
134 // Delete pointers to otherwise-unreachable objects.
135 static void unlink(BoolObjectClosure* cl) {
136 unlink_or_oops_do(cl);
137 }
138 static void unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f = NULL,
139 int* processed = NULL, int* removed = NULL);
140
141 // Serially invoke "f->do_oop" on the locations of all oops in the table.
142 static void oops_do(OopClosure* f);
143
144 // Possibly parallel versions of the above
145 static void possibly_parallel_unlink(
146 OopStorage::ParState<false /* concurrent */, false /* const*/>* par_state_string,
147 BoolObjectClosure* cl, int* processed, int* removed);
148 static void possibly_parallel_oops_do(
149 OopStorage::ParState<false /* concurrent */, false /* const*/>* par_state_string,
150 OopClosure* f);
151
152 // Probing
153 static oop lookup(Symbol* symbol);
154 static oop lookup(jchar* chars, int length);
155
156 // Interning
157 static oop intern(Symbol* symbol, TRAPS);
158 static oop intern(oop string, TRAPS);
159 static oop intern(const char *utf8_string, TRAPS);
160
161 // Rehash the string table if it gets out of balance
162 static void rehash_table();
163 static bool needs_rehashing()
164 { return StringTable::the_table()->_needs_rehashing; }
165
166 // Sharing
167 private:
168 oop lookup_shared(jchar* name, int len, unsigned int hash) NOT_CDS_JAVA_HEAP_RETURN_(NULL);
169 static void copy_shared_string_table(CompactStringTableWriter* ch_table) NOT_CDS_JAVA_HEAP_RETURN;
170 public:
171 static oop create_archived_string(oop s, Thread* THREAD) NOT_CDS_JAVA_HEAP_RETURN_(NULL);
172 static void set_shared_string_mapped() { _shared_string_mapped = true; }
173 static bool shared_string_mapped() { return _shared_string_mapped; }
174 static void shared_oops_do(OopClosure* f) NOT_CDS_JAVA_HEAP_RETURN;
175 static void write_to_archive() NOT_CDS_JAVA_HEAP_RETURN;
176 static void serialize(SerializeClosure* soc) NOT_CDS_JAVA_HEAP_RETURN;
177
178 // Jcmd
179 static void dump(outputStream* st, bool verbose=false);
180 // Debugging
181 static size_t verify_and_compare_entries();
182 static void verify();
183 };
184
185 #endif // SHARE_VM_CLASSFILE_STRINGTABLE_HPP