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 CompactStringTableWriter;
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(CompactStringTableWriter* 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