Thu, 24 Mar 2016 21:38:15 -0700
8150752: Share Class Data
Reviewed-by: acorn, hseigel, mschoene
1 /*
2 * Copyright (c) 1997, 2013, 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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
25 #ifndef SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
26 #define SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
28 #include "memory/allocation.inline.hpp"
29 #include "oops/symbol.hpp"
30 #include "utilities/hashtable.hpp"
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.
42 class BoolObjectClosure;
43 class outputStream;
46 // Class to hold a newly created or referenced Symbol* temporarily in scope.
47 // new_symbol() and lookup() will create a Symbol* if not already in the
48 // symbol table and add to the symbol's reference count.
49 // probe() and lookup_only() will increment the refcount if symbol is found.
50 class TempNewSymbol : public StackObj {
51 Symbol* _temp;
53 public:
54 TempNewSymbol() : _temp(NULL) {}
55 // Creating or looking up a symbol increments the symbol's reference count
56 TempNewSymbol(Symbol *s) : _temp(s) {}
58 // Operator= increments reference count.
59 void operator=(const TempNewSymbol &s) {
60 //clear(); //FIXME
61 _temp = s._temp;
62 if (_temp !=NULL) _temp->increment_refcount();
63 }
65 // Decrement reference counter so it can go away if it's unique
66 void clear() { if (_temp != NULL) _temp->decrement_refcount(); _temp = NULL; }
68 ~TempNewSymbol() { clear(); }
70 // Operators so they can be used like Symbols
71 Symbol* operator -> () const { return _temp; }
72 bool operator == (Symbol* o) const { return _temp == o; }
73 // Sneaky conversion function
74 operator Symbol*() { return _temp; }
75 };
77 class SymbolTable : public RehashableHashtable<Symbol*, mtSymbol> {
78 friend class VMStructs;
79 friend class ClassFileParser;
81 private:
82 // The symbol table
83 static SymbolTable* _the_table;
85 // Set if one bucket is out of balance due to hash algorithm deficiency
86 static bool _needs_rehashing;
88 // For statistics
89 static int _symbols_removed;
90 static int _symbols_counted;
92 Symbol* allocate_symbol(const u1* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F
94 // Adding elements
95 Symbol* basic_add(int index, u1* name, int len, unsigned int hashValue,
96 bool c_heap, TRAPS);
97 bool basic_add(ClassLoaderData* loader_data,
98 constantPoolHandle cp, int names_count,
99 const char** names, int* lengths, int* cp_indices,
100 unsigned int* hashValues, TRAPS);
102 static void new_symbols(ClassLoaderData* loader_data,
103 constantPoolHandle cp, int names_count,
104 const char** name, int* lengths,
105 int* cp_indices, unsigned int* hashValues,
106 TRAPS) {
107 add(loader_data, cp, names_count, name, lengths, cp_indices, hashValues, THREAD);
108 }
110 Symbol* lookup(int index, const char* name, int len, unsigned int hash);
112 SymbolTable()
113 : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>)) {}
115 SymbolTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
116 : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>), t,
117 number_of_entries) {}
119 // Arena for permanent symbols (null class loader) that are never unloaded
120 static Arena* _arena;
121 static Arena* arena() { return _arena; } // called for statistics
123 static void initialize_symbols(int arena_alloc_size = 0);
125 static volatile int _parallel_claimed_idx;
127 // Release any dead symbols
128 static void buckets_unlink(int start_idx, int end_idx, int* processed, int* removed, size_t* memory_total);
129 public:
130 enum {
131 symbol_alloc_batch_size = 8,
132 // Pick initial size based on java -version size measurements
133 symbol_alloc_arena_size = 360*K
134 };
136 // The symbol table
137 static SymbolTable* the_table() { return _the_table; }
139 // Size of one bucket in the string table. Used when checking for rollover.
140 static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
142 static void create_table() {
143 assert(_the_table == NULL, "One symbol table allowed.");
144 _the_table = new SymbolTable();
145 initialize_symbols(symbol_alloc_arena_size);
146 }
148 static void create_table(HashtableBucket<mtSymbol>* t, int length,
149 int number_of_entries) {
150 assert(_the_table == NULL, "One symbol table allowed.");
152 // If CDS archive used a different symbol table size, use that size instead
153 // which is better than giving an error.
154 SymbolTableSize = length/bucket_size();
156 _the_table = new SymbolTable(t, number_of_entries);
157 // if CDS give symbol table a default arena size since most symbols
158 // are already allocated in the shared misc section.
159 initialize_symbols();
160 }
162 static unsigned int hash_symbol(const char* s, int len);
164 static Symbol* lookup(const char* name, int len, TRAPS);
165 // lookup only, won't add. Also calculate hash.
166 static Symbol* lookup_only(const char* name, int len, unsigned int& hash);
167 // Only copy to C string to be added if lookup failed.
168 static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS);
170 static void release(Symbol* sym);
172 // Look up the address of the literal in the SymbolTable for this Symbol*
173 static Symbol** lookup_symbol_addr(Symbol* sym);
175 // jchar (utf16) version of lookups
176 static Symbol* lookup_unicode(const jchar* name, int len, TRAPS);
177 static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash);
179 static void add(ClassLoaderData* loader_data,
180 constantPoolHandle cp, int names_count,
181 const char** names, int* lengths, int* cp_indices,
182 unsigned int* hashValues, TRAPS);
184 // Release any dead symbols
185 static void unlink() {
186 int processed = 0;
187 int removed = 0;
188 unlink(&processed, &removed);
189 }
190 static void unlink(int* processed, int* removed);
191 // Release any dead symbols, possibly parallel version
192 static void possibly_parallel_unlink(int* processed, int* removed);
194 // iterate over symbols
195 static void symbols_do(SymbolClosure *cl);
197 // Symbol creation
198 static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) {
199 assert(utf8_buffer != NULL, "just checking");
200 return lookup(utf8_buffer, length, THREAD);
201 }
202 static Symbol* new_symbol(const char* name, TRAPS) {
203 return new_symbol(name, (int)strlen(name), THREAD);
204 }
205 static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) {
206 assert(begin <= end && end <= sym->utf8_length(), "just checking");
207 return lookup(sym, begin, end, THREAD);
208 }
210 // Create a symbol in the arena for symbols that are not deleted
211 static Symbol* new_permanent_symbol(const char* name, TRAPS);
213 // Symbol lookup
214 static Symbol* lookup(int index, const char* name, int len, TRAPS);
216 // Needed for preloading classes in signatures when compiling.
217 // Returns the symbol is already present in symbol table, otherwise
218 // NULL. NO ALLOCATION IS GUARANTEED!
219 static Symbol* probe(const char* name, int len) {
220 unsigned int ignore_hash;
221 return lookup_only(name, len, ignore_hash);
222 }
223 static Symbol* probe_unicode(const jchar* name, int len) {
224 unsigned int ignore_hash;
225 return lookup_only_unicode(name, len, ignore_hash);
226 }
228 // Histogram
229 static void print_histogram() PRODUCT_RETURN;
230 static void print() PRODUCT_RETURN;
232 // Debugging
233 static void verify();
234 static void dump(outputStream* st);
236 // Sharing
237 static void copy_buckets(char** top, char*end) {
238 the_table()->Hashtable<Symbol*, mtSymbol>::copy_buckets(top, end);
239 }
240 static void copy_table(char** top, char*end) {
241 the_table()->Hashtable<Symbol*, mtSymbol>::copy_table(top, end);
242 }
243 static void reverse(void* boundary = NULL) {
244 the_table()->Hashtable<Symbol*, mtSymbol>::reverse(boundary);
245 }
247 // Rehash the symbol table if it gets out of balance
248 static void rehash_table();
249 static bool needs_rehashing() { return _needs_rehashing; }
250 // Parallel chunked scanning
251 static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
252 static int parallel_claimed_index() { return _parallel_claimed_idx; }
253 };
255 class StringTable : public RehashableHashtable<oop, mtSymbol> {
256 friend class VMStructs;
258 private:
259 // The string table
260 static StringTable* _the_table;
262 // Set if one bucket is out of balance due to hash algorithm deficiency
263 static bool _needs_rehashing;
265 // Claimed high water mark for parallel chunked scanning
266 static volatile int _parallel_claimed_idx;
268 static oop intern(Handle string_or_null, jchar* chars, int length, TRAPS);
269 oop basic_add(int index, Handle string_or_null, jchar* name, int len,
270 unsigned int hashValue, TRAPS);
272 oop lookup(int index, jchar* chars, int length, unsigned int hashValue);
274 // Apply the give oop closure to the entries to the buckets
275 // in the range [start_idx, end_idx).
276 static void buckets_oops_do(OopClosure* f, int start_idx, int end_idx);
277 // Unlink or apply the give oop closure to the entries to the buckets
278 // in the range [start_idx, end_idx).
279 static void buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed);
281 StringTable() : RehashableHashtable<oop, mtSymbol>((int)StringTableSize,
282 sizeof (HashtableEntry<oop, mtSymbol>)) {}
284 StringTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
285 : RehashableHashtable<oop, mtSymbol>((int)StringTableSize, sizeof (HashtableEntry<oop, mtSymbol>), t,
286 number_of_entries) {}
287 public:
288 // The string table
289 static StringTable* the_table() { return _the_table; }
291 // Size of one bucket in the string table. Used when checking for rollover.
292 static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
294 static void create_table() {
295 assert(_the_table == NULL, "One string table allowed.");
296 _the_table = new StringTable();
297 }
299 // GC support
300 // Delete pointers to otherwise-unreachable objects.
301 static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f) {
302 int processed = 0;
303 int removed = 0;
304 unlink_or_oops_do(cl, f, &processed, &removed);
305 }
306 static void unlink(BoolObjectClosure* cl) {
307 int processed = 0;
308 int removed = 0;
309 unlink_or_oops_do(cl, NULL, &processed, &removed);
310 }
311 static void unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
312 static void unlink(BoolObjectClosure* cl, int* processed, int* removed) {
313 unlink_or_oops_do(cl, NULL, processed, removed);
314 }
315 // Serially invoke "f->do_oop" on the locations of all oops in the table.
316 static void oops_do(OopClosure* f);
318 // Possibly parallel versions of the above
319 static void possibly_parallel_unlink_or_oops_do(BoolObjectClosure* cl, OopClosure* f, int* processed, int* removed);
320 static void possibly_parallel_unlink(BoolObjectClosure* cl, int* processed, int* removed) {
321 possibly_parallel_unlink_or_oops_do(cl, NULL, processed, removed);
322 }
323 static void possibly_parallel_oops_do(OopClosure* f);
325 // Hashing algorithm, used as the hash value used by the
326 // StringTable for bucket selection and comparison (stored in the
327 // HashtableEntry structures). This is used in the String.intern() method.
328 static unsigned int hash_string(const jchar* s, int len);
330 // Internal test.
331 static void test_alt_hash() PRODUCT_RETURN;
333 // Probing
334 static oop lookup(Symbol* symbol);
335 static oop lookup(jchar* chars, int length);
337 // Interning
338 static oop intern(Symbol* symbol, TRAPS);
339 static oop intern(oop string, TRAPS);
340 static oop intern(const char *utf8_string, TRAPS);
342 // Debugging
343 static void verify();
344 static void dump(outputStream* st);
346 enum VerifyMesgModes {
347 _verify_quietly = 0,
348 _verify_with_mesgs = 1
349 };
351 enum VerifyRetTypes {
352 _verify_pass = 0,
353 _verify_fail_continue = 1,
354 _verify_fail_done = 2
355 };
357 static VerifyRetTypes compare_entries(int bkt1, int e_cnt1,
358 HashtableEntry<oop, mtSymbol>* e_ptr1,
359 int bkt2, int e_cnt2,
360 HashtableEntry<oop, mtSymbol>* e_ptr2);
361 static VerifyRetTypes verify_entry(int bkt, int e_cnt,
362 HashtableEntry<oop, mtSymbol>* e_ptr,
363 VerifyMesgModes mesg_mode);
364 static int verify_and_compare_entries();
366 // Sharing
367 static void copy_buckets(char** top, char*end) {
368 the_table()->Hashtable<oop, mtSymbol>::copy_buckets(top, end);
369 }
370 static void copy_table(char** top, char*end) {
371 the_table()->Hashtable<oop, mtSymbol>::copy_table(top, end);
372 }
373 static void reverse() {
374 the_table()->Hashtable<oop, mtSymbol>::reverse();
375 }
377 // Rehash the symbol table if it gets out of balance
378 static void rehash_table();
379 static bool needs_rehashing() { return _needs_rehashing; }
381 // Parallel chunked scanning
382 static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
383 static int parallel_claimed_index() { return _parallel_claimed_idx; }
384 };
385 #endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP