1 /*
2 * Copyright (c) 1997, 2017, 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_SYMBOLTABLE_HPP
26 #define SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
27
28 #include "memory/allocation.hpp"
29 #include "oops/symbol.hpp"
30 #include "utilities/hashtable.hpp"
31
32 // The symbol table holds all Symbol*s and corresponding interned strings.
33 // Symbol*s and literal strings should be canonicalized.
34 //
35 // The interned strings are created lazily.
36 //
37 // It is implemented as an open hash table with a fixed number of buckets.
38 //
39 // %note:
40 // - symbolTableEntrys are allocated in blocks to reduce the space overhead.
41
42 class BoolObjectClosure;
43 class outputStream;
44 class SerializeClosure;
45
46 // TempNewSymbol acts as a handle class in a handle/body idiom and is
47 // responsible for proper resource management of the body (which is a Symbol*).
48 // The body is resource managed by a reference counting scheme.
49 // TempNewSymbol can therefore be used to properly hold a newly created or referenced
50 // Symbol* temporarily in scope.
51 //
52 // Routines in SymbolTable will initialize the reference count of a Symbol* before
53 // it becomes "managed" by TempNewSymbol instances. As a handle class, TempNewSymbol
54 // needs to maintain proper reference counting in context of copy semantics.
55 //
56 // In SymbolTable, new_symbol() and lookup() will create a Symbol* if not already in the
57 // symbol table and add to the symbol's reference count.
58 // probe() and lookup_only() will increment the refcount if symbol is found.
59 class TempNewSymbol : public StackObj {
60 Symbol* _temp;
61
62 public:
63 TempNewSymbol() : _temp(NULL) {}
64
79 // decrement upon destruction.
80 void operator=(TempNewSymbol rhs) {
81 Symbol* tmp = rhs._temp;
82 rhs._temp = _temp;
83 _temp = tmp;
84 }
85
86 // Decrement reference counter so it can go away if it's unused
87 ~TempNewSymbol() {
88 if (_temp != NULL) {
89 _temp->decrement_refcount();
90 }
91 }
92
93 // Symbol* conversion operators
94 Symbol* operator -> () const { return _temp; }
95 bool operator == (Symbol* o) const { return _temp == o; }
96 operator Symbol*() { return _temp; }
97 };
98
99 template <class T, class N> class CompactHashtable;
100
101 class SymbolTable : public RehashableHashtable<Symbol*, mtSymbol> {
102 friend class VMStructs;
103 friend class ClassFileParser;
104
105 private:
106 // The symbol table
107 static SymbolTable* _the_table;
108
109 // Set if one bucket is out of balance due to hash algorithm deficiency
110 static bool _needs_rehashing;
111 static bool _lookup_shared_first;
112
113 // For statistics
114 static int _symbols_removed;
115 static int _symbols_counted;
116
117 // shared symbol table.
118 static CompactHashtable<Symbol*, char> _shared_table;
119
120 Symbol* allocate_symbol(const u1* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F
121
122 // Adding elements
123 Symbol* basic_add(int index, u1* name, int len, unsigned int hashValue,
124 bool c_heap, TRAPS);
125 bool basic_add(ClassLoaderData* loader_data,
126 const constantPoolHandle& cp, int names_count,
127 const char** names, int* lengths, int* cp_indices,
128 unsigned int* hashValues, TRAPS);
129
130 static void new_symbols(ClassLoaderData* loader_data,
131 const constantPoolHandle& cp, int names_count,
132 const char** name, int* lengths,
133 int* cp_indices, unsigned int* hashValues,
134 TRAPS) {
135 add(loader_data, cp, names_count, name, lengths, cp_indices, hashValues, THREAD);
136 }
137
138 static Symbol* lookup_shared(const char* name, int len, unsigned int hash);
139 Symbol* lookup_dynamic(int index, const char* name, int len, unsigned int hash);
140 Symbol* lookup(int index, const char* name, int len, unsigned int hash);
141
142 SymbolTable()
143 : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>)) {}
144
145 SymbolTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
146 : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>), t,
147 number_of_entries) {}
148
149 // Arena for permanent symbols (null class loader) that are never unloaded
150 static Arena* _arena;
151 static Arena* arena() { return _arena; } // called for statistics
152
153 static void initialize_symbols(int arena_alloc_size = 0);
154
155 static volatile int _parallel_claimed_idx;
156
157 typedef SymbolTable::BucketUnlinkContext BucketUnlinkContext;
158 // Release any dead symbols. Unlinked bucket entries are collected in the given
159 // context to be freed later.
160 // This allows multiple threads to work on the table at once.
161 static void buckets_unlink(int start_idx, int end_idx, BucketUnlinkContext* context);
162 public:
163 enum {
164 symbol_alloc_batch_size = 8,
165 // Pick initial size based on java -version size measurements
166 symbol_alloc_arena_size = 360*K
167 };
168
169 // The symbol table
170 static SymbolTable* the_table() { return _the_table; }
171
172 // Size of one bucket in the string table. Used when checking for rollover.
173 static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
174
175 static void create_table() {
176 assert(_the_table == NULL, "One symbol table allowed.");
177 _the_table = new SymbolTable();
178 initialize_symbols(symbol_alloc_arena_size);
179 }
180
181 static unsigned int hash_symbol(const char* s, int len);
182 static unsigned int hash_shared_symbol(const char* s, int len);
183
184 static Symbol* lookup(const char* name, int len, TRAPS);
185 // lookup only, won't add. Also calculate hash.
186 static Symbol* lookup_only(const char* name, int len, unsigned int& hash);
187 // Only copy to C string to be added if lookup failed.
188 static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS);
189
190 static void release(Symbol* sym);
191
192 // Look up the address of the literal in the SymbolTable for this Symbol*
193 static Symbol** lookup_symbol_addr(Symbol* sym);
194
195 // jchar (UTF16) version of lookups
196 static Symbol* lookup_unicode(const jchar* name, int len, TRAPS);
197 static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash);
198
199 static void add(ClassLoaderData* loader_data,
200 const constantPoolHandle& cp, int names_count,
201 const char** names, int* lengths, int* cp_indices,
202 unsigned int* hashValues, TRAPS);
203
204 // Release any dead symbols
205 static void unlink() {
206 int processed = 0;
207 int removed = 0;
208 unlink(&processed, &removed);
209 }
210 static void unlink(int* processed, int* removed);
211 // Release any dead symbols, possibly parallel version
212 static void possibly_parallel_unlink(int* processed, int* removed);
213
214 // iterate over symbols
215 static void symbols_do(SymbolClosure *cl);
216 static void metaspace_pointers_do(MetaspaceClosure* it);
217
218 // Symbol creation
219 static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) {
220 assert(utf8_buffer != NULL, "just checking");
221 return lookup(utf8_buffer, length, THREAD);
222 }
223 static Symbol* new_symbol(const char* name, TRAPS) {
224 return new_symbol(name, (int)strlen(name), THREAD);
225 }
226 static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) {
227 assert(begin <= end && end <= sym->utf8_length(), "just checking");
228 return lookup(sym, begin, end, THREAD);
229 }
230
231 // Create a symbol in the arena for symbols that are not deleted
232 static Symbol* new_permanent_symbol(const char* name, TRAPS);
233
234 // Symbol lookup
235 static Symbol* lookup(int index, const char* name, int len, TRAPS);
236
237 // Needed for preloading classes in signatures when compiling.
238 // Returns the symbol is already present in symbol table, otherwise
239 // NULL. NO ALLOCATION IS GUARANTEED!
240 static Symbol* probe(const char* name, int len) {
241 unsigned int ignore_hash;
242 return lookup_only(name, len, ignore_hash);
243 }
244 static Symbol* probe_unicode(const jchar* name, int len) {
245 unsigned int ignore_hash;
246 return lookup_only_unicode(name, len, ignore_hash);
247 }
248
249 // Histogram
250 static void print_histogram() PRODUCT_RETURN;
251 static void print() PRODUCT_RETURN;
252
253 // Debugging
254 static void verify();
255 static void dump(outputStream* st, bool verbose=false);
256 static void read(const char* filename, TRAPS);
257
258 // Sharing
259 static void write_to_archive();
260 static void serialize(SerializeClosure* soc);
261 static u4 encode_shared(Symbol* sym);
262 static Symbol* decode_shared(u4 offset);
263
264 // Rehash the symbol table if it gets out of balance
265 static void rehash_table();
266 static bool needs_rehashing() { return _needs_rehashing; }
267 // Parallel chunked scanning
268 static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
269 static int parallel_claimed_index() { return _parallel_claimed_idx; }
270 };
271
272 #endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
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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_SYMBOLTABLE_HPP
26 #define SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
27
28 #include "memory/allocation.hpp"
29 #include "memory/padded.hpp"
30 #include "oops/symbol.hpp"
31 #include "utilities/hashtable.hpp"
32 #include "utilities/concurrentHashTable.hpp"
33
34 // TempNewSymbol acts as a handle class in a handle/body idiom and is
35 // responsible for proper resource management of the body (which is a Symbol*).
36 // The body is resource managed by a reference counting scheme.
37 // TempNewSymbol can therefore be used to properly hold a newly created or referenced
38 // Symbol* temporarily in scope.
39 //
40 // Routines in SymbolTable will initialize the reference count of a Symbol* before
41 // it becomes "managed" by TempNewSymbol instances. As a handle class, TempNewSymbol
42 // needs to maintain proper reference counting in context of copy semantics.
43 //
44 // In SymbolTable, new_symbol() and lookup() will create a Symbol* if not already in the
45 // symbol table and add to the symbol's reference count.
46 // probe() and lookup_only() will increment the refcount if symbol is found.
47 class TempNewSymbol : public StackObj {
48 Symbol* _temp;
49
50 public:
51 TempNewSymbol() : _temp(NULL) {}
52
67 // decrement upon destruction.
68 void operator=(TempNewSymbol rhs) {
69 Symbol* tmp = rhs._temp;
70 rhs._temp = _temp;
71 _temp = tmp;
72 }
73
74 // Decrement reference counter so it can go away if it's unused
75 ~TempNewSymbol() {
76 if (_temp != NULL) {
77 _temp->decrement_refcount();
78 }
79 }
80
81 // Symbol* conversion operators
82 Symbol* operator -> () const { return _temp; }
83 bool operator == (Symbol* o) const { return _temp == o; }
84 operator Symbol*() { return _temp; }
85 };
86
87 // The symbol table holds all Symbol*s and corresponding interned strings.
88 // Symbol*s and literal strings should be canonicalized.
89 //
90 // The interned strings are created lazily.
91 //
92 // %note:
93 // - symbolTableEntrys are allocated in blocks to reduce the space overhead.
94 template <class T, class N> class CompactHashtable;
95 class CompactSymbolTableWriter;
96 class SerializeClosure;
97
98 class SymbolTable;
99 class SymbolTableConfig;
100 typedef ConcurrentHashTable<Symbol*,
101 SymbolTableConfig, mtSymbol> SymbolTableHash;
102
103 class SymbolTableCreateEntry;
104
105 class SymbolTable : public CHeapObj<mtSymbol> {
106 friend class VMStructs;
107 friend class Symbol;
108 friend class ClassFileParser;
109 friend class SymbolTableConfig;
110 friend class SymbolTableCreateEntry;
111
112 private:
113 static void delete_symbol(Symbol* sym);
114 void grow(JavaThread* jt);
115 void clean_dead_entries(JavaThread* jt);
116
117 // The symbol table
118 static SymbolTable* _the_table;
119 // Shared symbol table.
120 static CompactHashtable<Symbol*, char> _shared_table;
121 static bool _lookup_shared_first;
122 static bool _alt_hash;
123
124 // For statistics
125 static int _symbols_removed;
126 static int _symbols_counted;
127
128 private:
129
130 // Set if one bucket is out of balance due to hash algorithm deficiency
131 SymbolTableHash* _local_table;
132 size_t _current_size;
133 volatile bool _has_work;
134 volatile bool _needs_rehashing;
135
136 volatile size_t _items;
137 DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
138 volatile int _uncleaned_items;
139 DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile int));
140
141 double get_load_factor();
142 double get_dead_factor();
143
144 void check_concurrent_work();
145 void trigger_concurrent_work();
146
147 static uintx item_added();
148 static void item_removed();
149 static void set_item_clean_count(size_t ncl);
150 static void mark_item_clean_count();
151
152 SymbolTable();
153
154 Symbol* allocate_symbol(const u1* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F
155 Symbol* do_lookup(char* name, int len, uintx hash);
156 Symbol* do_add_if_needed(char* name, int len, uintx hash, bool heap, TRAPS);
157
158 // Adding elements
159 static void add(ClassLoaderData* loader_data,
160 const constantPoolHandle& cp, int names_count,
161 const char** names, int* lengths, int* cp_indices,
162 unsigned int* hashValues, TRAPS);
163
164 static void new_symbols(ClassLoaderData* loader_data,
165 const constantPoolHandle& cp, int names_count,
166 const char** name, int* lengths,
167 int* cp_indices, unsigned int* hashValues,
168 TRAPS) {
169 add(loader_data, cp, names_count, name, lengths, cp_indices, hashValues, THREAD);
170 }
171
172 static Symbol* lookup_shared(const char* name, int len, unsigned int hash);
173 Symbol* lookup_dynamic(const char* name, int len, unsigned int hash);
174 Symbol* lookup_common(const char* name, int len, unsigned int hash);
175
176 // Arena for permanent symbols (null class loader) that are never unloaded
177 static Arena* _arena;
178 static Arena* arena() { return _arena; } // called for statistics
179
180 static void initialize_symbols(int arena_alloc_size = 0);
181
182 void concurrent_work(JavaThread* jt);
183 void print_table_statistics(outputStream* st, const char* table_name);
184
185 void try_rehash_table();
186 bool do_rehash();
187
188 public:
189 // The symbol table
190 static SymbolTable* the_table() { return _the_table; }
191 size_t table_size(Thread* thread = NULL);
192
193 enum {
194 symbol_alloc_batch_size = 8,
195 // Pick initial size based on java -version size measurements
196 symbol_alloc_arena_size = 360*K // TODO (revisit)
197 };
198
199 static void create_table() {
200 assert(_the_table == NULL, "One symbol table allowed.");
201 _the_table = new SymbolTable();
202 initialize_symbols(symbol_alloc_arena_size);
203 }
204
205 static void unlink() {
206 do_check_concurrent_work();
207 }
208 static void do_check_concurrent_work();
209 static void do_concurrent_work(JavaThread* jt);
210 static bool has_work() { return the_table()->_has_work; }
211
212 // Probing
213 static Symbol* lookup(const char* name, int len, TRAPS);
214 // lookup only, won't add. Also calculate hash.
215 static Symbol* lookup_only(const char* name, int len, unsigned int& hash);
216 // Only copy to C string to be added if lookup failed.
217 static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS);
218 // jchar (UTF16) version of lookups
219 static Symbol* lookup_unicode(const jchar* name, int len, TRAPS);
220 static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash);
221 // Needed for preloading classes in signatures when compiling.
222 // Returns the symbol is already present in symbol table, otherwise
223 // NULL. NO ALLOCATION IS GUARANTEED!
224 static Symbol* probe(const char* name, int len) {
225 unsigned int ignore_hash;
226 return lookup_only(name, len, ignore_hash);
227 }
228 static Symbol* probe_unicode(const jchar* name, int len) {
229 unsigned int ignore_hash;
230 return lookup_only_unicode(name, len, ignore_hash);
231 }
232
233 // Symbol creation
234 static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) {
235 assert(utf8_buffer != NULL, "just checking");
236 return lookup(utf8_buffer, length, THREAD);
237 }
238 static Symbol* new_symbol(const char* name, TRAPS) {
239 return new_symbol(name, (int)strlen(name), THREAD);
240 }
241 static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) {
242 assert(begin <= end && end <= sym->utf8_length(), "just checking");
243 return lookup(sym, begin, end, THREAD);
244 }
245 // Create a symbol in the arena for symbols that are not deleted
246 static Symbol* new_permanent_symbol(const char* name, TRAPS);
247
248 // Rehash the string table if it gets out of balance
249 static void rehash_table();
250 static bool needs_rehashing()
251 { return SymbolTable::the_table()->_needs_rehashing; }
252
253 // Heap dumper and CDS
254 static void symbols_do(SymbolClosure *cl);
255
256 // Sharing
257 private:
258 static void copy_shared_symbol_table(CompactSymbolTableWriter* ch_table);
259 public:
260 static void write_to_archive() NOT_CDS_RETURN;
261 static void serialize(SerializeClosure* soc) NOT_CDS_RETURN;
262 static void metaspace_pointers_do(MetaspaceClosure* it);
263
264 // Jcmd
265 static void dump(outputStream* st, bool verbose=false);
266 // Debugging
267 static void verify();
268 static void read(const char* filename, TRAPS);
269
270 // Histogram
271 static void print_histogram() PRODUCT_RETURN;
272 };
273
274 #endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
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