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 #include "precompiled.hpp"
26 #include "classfile/altHashing.hpp"
27 #include "classfile/compactHashtable.inline.hpp"
28 #include "classfile/javaClasses.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "memory/allocation.inline.hpp"
31 #include "memory/metaspaceClosure.hpp"
32 #include "memory/resourceArea.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/atomic.hpp"
35 #include "runtime/interfaceSupport.inline.hpp"
36 #include "runtime/timerTrace.hpp"
37 #include "services/diagnosticCommand.hpp"
38 #include "utilities/concurrentHashTable.inline.hpp"
39 #include "utilities/concurrentHashTableTasks.inline.hpp"
40
41 // We used to not resize at all, so let's be conservative
42 // and not set it too short before we decide to resize,
43 // to match previous startup behavior
44 #define PREF_AVG_LIST_LEN 8
45 // 2^17 (131,072) is max size, which is about 6.5 times as large
46 // as the previous table size (used to be 20,011),
47 // which never resized
48 #define END_SIZE 17
49 // If a chain gets to 100 something might be wrong
50 #define REHASH_LEN 100
51 // We only get a chance to check whether we need
52 // to clean infrequently (on class unloading),
53 // so if we have even one dead entry then mark table for cleaning
54 #define CLEAN_DEAD_HIGH_WATER_MARK 0.0
55
56 #define ON_STACK_BUFFER_LENGTH 128
57
58 // --------------------------------------------------------------------------
59 SymbolTable* SymbolTable::_the_table = NULL;
60 CompactHashtable<Symbol*, char> SymbolTable::_shared_table;
61 volatile bool SymbolTable::_alt_hash = false;
62 volatile bool SymbolTable::_lookup_shared_first = false;
63 // Static arena for symbols that are not deallocated
64 Arena* SymbolTable::_arena = NULL;
65
66 static juint murmur_seed = 0;
67
68 static inline void _log_trace_symboltable_helper(Symbol* sym, const char* msg) {
69 #ifndef PRODUCT
70 if (log_is_enabled(Trace, symboltable)) {
71 if (sym->as_quoted_ascii() == NULL) {
72 log_trace(symboltable)("%s [%s]", msg, "NULL");
73 } else {
74 log_trace(symboltable)("%s [%s]", msg, sym->as_quoted_ascii());
75 }
76 }
77 #endif // PRODUCT
78 }
79
80 // Pick hashing algorithm.
81 static uintx hash_symbol(const char* s, int len, bool useAlt) {
82 return useAlt ?
83 AltHashing::murmur3_32(murmur_seed, (const jbyte*)s, len) :
84 java_lang_String::hash_code((const jbyte*)s, len);
85 }
86
87 static uintx hash_shared_symbol(const char* s, int len) {
88 return java_lang_String::hash_code((const jbyte*)s, len);
89 }
90
91 class SymbolTableConfig : public SymbolTableHash::BaseConfig {
92 private:
93 public:
94 static uintx get_hash(Symbol* const& value, bool* is_dead) {
95 *is_dead = (value->refcount() == 0);
96 if (*is_dead) {
97 return 0;
98 } else {
99 return hash_symbol((const char*)value->bytes(), value->utf8_length(), SymbolTable::_alt_hash);
100 }
101 }
102 // We use default allocation/deallocation but counted
103 static void* allocate_node(size_t size, Symbol* const& value) {
104 SymbolTable::item_added();
105 return SymbolTableHash::BaseConfig::allocate_node(size, value);
106 }
107 static void free_node(void* memory, Symbol* const& value) {
108 // We get here either because #1 some threads lost a race
109 // to insert a newly created Symbol, or #2 we are freeing
110 // a symbol during normal cleanup deletion.
111 // If #1, then the symbol can be a permanent (refcount==PERM_REFCOUNT),
112 // or regular newly created one but with refcount==0 (see SymbolTableCreateEntry)
113 // If #2, then the symbol must have refcount==0
114 assert((value->refcount() == PERM_REFCOUNT) || (value->refcount() == 0),
115 "refcount %d", value->refcount());
116 SymbolTable::delete_symbol(value);
117 SymbolTableHash::BaseConfig::free_node(memory, value);
118 SymbolTable::item_removed();
119 }
120 };
121
122 static size_t log2_ceil(uintx value) {
123 size_t ret;
124 for (ret = 1; ((size_t)1 << ret) < value; ++ret);
125 return ret;
126 }
127
128 SymbolTable::SymbolTable() : _local_table(NULL), _current_size(0), _has_work(0),
129 _needs_rehashing(false), _items_count(0), _uncleaned_items_count(0),
130 _symbols_removed(0), _symbols_counted(0) {
131
132 size_t start_size_log_2 = log2_ceil(SymbolTableSize);
133 _current_size = ((size_t)1) << start_size_log_2;
134 log_trace(symboltable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")",
135 _current_size, start_size_log_2);
136 _local_table = new SymbolTableHash(start_size_log_2, END_SIZE, REHASH_LEN);
137 }
138
139 void SymbolTable::delete_symbol(Symbol* sym) {
140 if (sym->refcount() == PERM_REFCOUNT) {
141 MutexLocker ml(SymbolTable_lock); // Protect arena
142 // Deleting permanent symbol should not occur very often (insert race condition),
143 // so log it.
144 _log_trace_symboltable_helper(sym, "Freeing permanent symbol");
145 if (!arena()->Afree(sym, sym->size())) {
146 _log_trace_symboltable_helper(sym, "Leaked permanent symbol");
147 }
148 } else {
149 delete sym;
150 }
151 }
152
153 void SymbolTable::item_added() {
154 Atomic::inc(&(SymbolTable::the_table()->_items_count));
155 }
156
157 void SymbolTable::set_item_clean_count(size_t ncl) {
158 Atomic::store(ncl, &(SymbolTable::the_table()->_uncleaned_items_count));
159 log_trace(symboltable)("Set uncleaned items:" SIZE_FORMAT, SymbolTable::the_table()->_uncleaned_items_count);
160 }
161
162 void SymbolTable::mark_item_clean_count() {
163 if (Atomic::cmpxchg((size_t)1, &(SymbolTable::the_table()->_uncleaned_items_count), (size_t)0) == 0) { // only mark if unset
164 log_trace(symboltable)("Marked uncleaned items:" SIZE_FORMAT, SymbolTable::the_table()->_uncleaned_items_count);
165 }
166 }
167
168 void SymbolTable::item_removed() {
169 Atomic::inc(&(SymbolTable::the_table()->_symbols_removed));
170 Atomic::dec(&(SymbolTable::the_table()->_items_count));
171 }
172
173 double SymbolTable::get_load_factor() {
174 return (double)_items_count/_current_size;
175 }
176
177 double SymbolTable::get_dead_factor() {
178 return (double)_uncleaned_items_count/_current_size;
179 }
180
181 size_t SymbolTable::table_size(Thread* thread) {
182 return ((size_t)(1)) << _local_table->get_size_log2(thread != NULL ? thread
183 : Thread::current());
184 }
185
186 void SymbolTable::trigger_concurrent_work() {
187 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
188 SymbolTable::the_table()->_has_work = true;
189 Service_lock->notify_all();
190 }
191
192 Symbol* SymbolTable::allocate_symbol(const char* name, int len, bool c_heap, TRAPS) {
193 assert (len <= Symbol::max_length(), "should be checked by caller");
194
195 Symbol* sym;
196 if (DumpSharedSpaces) {
197 c_heap = false;
198 }
199 if (c_heap) {
200 // refcount starts as 1
201 sym = new (len, THREAD) Symbol((const u1*)name, len, 1);
202 assert(sym != NULL, "new should call vm_exit_out_of_memory if C_HEAP is exhausted");
203 } else {
204 // Allocate to global arena
205 MutexLocker ml(SymbolTable_lock); // Protect arena
206 sym = new (len, arena(), THREAD) Symbol((const u1*)name, len, PERM_REFCOUNT);
207 }
208 return sym;
209 }
210
211 void SymbolTable::initialize_symbols(int arena_alloc_size) {
212 // Initialize the arena for global symbols, size passed in depends on CDS.
213 if (arena_alloc_size == 0) {
214 _arena = new (mtSymbol) Arena(mtSymbol);
215 } else {
216 _arena = new (mtSymbol) Arena(mtSymbol, arena_alloc_size);
217 }
218 }
219
220 class SymbolsDo : StackObj {
221 SymbolClosure *_cl;
222 public:
223 SymbolsDo(SymbolClosure *cl) : _cl(cl) {}
224 bool operator()(Symbol** value) {
225 assert(value != NULL, "expected valid value");
226 assert(*value != NULL, "value should point to a symbol");
227 _cl->do_symbol(value);
228 return true;
229 };
230 };
231
232 // Call function for all symbols in the symbol table.
233 void SymbolTable::symbols_do(SymbolClosure *cl) {
234 // all symbols from shared table
235 _shared_table.symbols_do(cl);
236
237 // all symbols from the dynamic table
238 SymbolsDo sd(cl);
239 if (!SymbolTable::the_table()->_local_table->try_scan(Thread::current(), sd)) {
240 log_info(stringtable)("symbols_do unavailable at this moment");
241 }
242 }
243
244 class MetaspacePointersDo : StackObj {
245 MetaspaceClosure *_it;
246 public:
247 MetaspacePointersDo(MetaspaceClosure *it) : _it(it) {}
248 bool operator()(Symbol** value) {
249 assert(value != NULL, "expected valid value");
250 assert(*value != NULL, "value should point to a symbol");
251 _it->push(value);
252 return true;
253 };
254 };
255
256 void SymbolTable::metaspace_pointers_do(MetaspaceClosure* it) {
257 assert(DumpSharedSpaces, "called only during dump time");
258 MetaspacePointersDo mpd(it);
259 SymbolTable::the_table()->_local_table->do_scan(Thread::current(), mpd);
260 }
261
262 Symbol* SymbolTable::lookup_dynamic(const char* name,
263 int len, unsigned int hash) {
264 Symbol* sym = SymbolTable::the_table()->do_lookup(name, len, hash);
265 assert((sym == NULL) || sym->refcount() != 0, "refcount must not be zero");
266 return sym;
267 }
268
269 Symbol* SymbolTable::lookup_shared(const char* name,
270 int len, unsigned int hash) {
271 if (!_shared_table.empty()) {
272 if (SymbolTable::_alt_hash) {
273 // hash_code parameter may use alternate hashing algorithm but the shared table
274 // always uses the same original hash code.
275 hash = hash_shared_symbol(name, len);
276 }
277 return _shared_table.lookup(name, hash, len);
278 } else {
279 return NULL;
280 }
281 }
282
283 Symbol* SymbolTable::lookup_common(const char* name,
284 int len, unsigned int hash) {
285 Symbol* sym;
286 if (_lookup_shared_first) {
287 sym = lookup_shared(name, len, hash);
288 if (sym == NULL) {
289 _lookup_shared_first = false;
290 sym = lookup_dynamic(name, len, hash);
291 }
292 } else {
293 sym = lookup_dynamic(name, len, hash);
294 if (sym == NULL) {
295 sym = lookup_shared(name, len, hash);
296 if (sym != NULL) {
297 _lookup_shared_first = true;
298 }
299 }
300 }
301 return sym;
302 }
303
304 Symbol* SymbolTable::lookup(const char* name, int len, TRAPS) {
305 unsigned int hash = hash_symbol(name, len, SymbolTable::_alt_hash);
306 Symbol* sym = SymbolTable::the_table()->lookup_common(name, len, hash);
307 if (sym == NULL) {
308 sym = SymbolTable::the_table()->do_add_if_needed(name, len, hash, true, CHECK_NULL);
309 }
310 assert(sym->refcount() != 0, "lookup should have incremented the count");
311 assert(sym->equals(name, len), "symbol must be properly initialized");
312 return sym;
313 }
314
315 Symbol* SymbolTable::lookup(const Symbol* sym, int begin, int end, TRAPS) {
316 assert(sym->refcount() != 0, "require a valid symbol");
317 const char* name = (const char*)sym->base() + begin;
318 int len = end - begin;
319 unsigned int hash = hash_symbol(name, len, SymbolTable::_alt_hash);
320 Symbol* found = SymbolTable::the_table()->lookup_common(name, len, hash);
321 if (found == NULL) {
322 found = SymbolTable::the_table()->do_add_if_needed(name, len, hash, true, THREAD);
323 }
324 return found;
325 }
326
327 class SymbolTableLookup : StackObj {
328 private:
329 Thread* _thread;
330 uintx _hash;
331 int _len;
332 const char* _str;
333 public:
334 SymbolTableLookup(Thread* thread, const char* key, int len, uintx hash)
335 : _thread(thread), _hash(hash), _str(key), _len(len) {}
336 uintx get_hash() const {
337 return _hash;
338 }
339 bool equals(Symbol** value, bool* is_dead) {
340 assert(value != NULL, "expected valid value");
341 assert(*value != NULL, "value should point to a symbol");
342 Symbol *sym = *value;
343 if (sym->equals(_str, _len)) {
344 if (sym->try_increment_refcount()) {
345 // something is referencing this symbol now.
346 return true;
347 } else {
348 assert(sym->refcount() == 0, "expected dead symbol");
349 *is_dead = true;
350 return false;
351 }
352 } else {
353 *is_dead = (sym->refcount() == 0);
354 return false;
355 }
356 }
357 };
358
359 class SymbolTableGet : public StackObj {
360 Symbol* _return;
361 public:
362 SymbolTableGet() : _return(NULL) { }
363 void operator()(Symbol** value) {
364 assert(value != NULL, "expected valid value");
365 assert(*value != NULL, "value should point to a symbol");
366 _return = *value;
367 }
368 Symbol* get_res_sym() {
369 return _return;
370 }
371 };
372
373 Symbol* SymbolTable::do_lookup(const char* name, int len, uintx hash) {
374 Thread* thread = Thread::current();
375 SymbolTableLookup lookup(thread, name, len, hash);
376 SymbolTableGet stg;
377 bool rehash_warning = false;
378 _local_table->get(thread, lookup, stg, &rehash_warning);
379 if (rehash_warning) {
380 _needs_rehashing = true;
381 }
382 Symbol* sym = stg.get_res_sym();
383 assert((sym == NULL) || sym->refcount() != 0, "found dead symbol");
384 return sym;
385 }
386
387 Symbol* SymbolTable::lookup_only(const char* name, int len, unsigned int& hash) {
388 hash = hash_symbol(name, len, SymbolTable::_alt_hash);
389 return SymbolTable::the_table()->lookup_common(name, len, hash);
390 }
391
392 // Suggestion: Push unicode-based lookup all the way into the hashing
393 // and probing logic, so there is no need for convert_to_utf8 until
394 // an actual new Symbol* is created.
395 Symbol* SymbolTable::lookup_unicode(const jchar* name, int utf16_length, TRAPS) {
396 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
397 char stack_buf[ON_STACK_BUFFER_LENGTH];
398 if (utf8_length < (int) sizeof(stack_buf)) {
399 char* chars = stack_buf;
400 UNICODE::convert_to_utf8(name, utf16_length, chars);
401 return lookup(chars, utf8_length, THREAD);
402 } else {
403 ResourceMark rm(THREAD);
404 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
405 UNICODE::convert_to_utf8(name, utf16_length, chars);
406 return lookup(chars, utf8_length, THREAD);
407 }
408 }
409
410 Symbol* SymbolTable::lookup_only_unicode(const jchar* name, int utf16_length,
411 unsigned int& hash) {
412 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
413 char stack_buf[ON_STACK_BUFFER_LENGTH];
414 if (utf8_length < (int) sizeof(stack_buf)) {
415 char* chars = stack_buf;
416 UNICODE::convert_to_utf8(name, utf16_length, chars);
417 return lookup_only(chars, utf8_length, hash);
418 } else {
419 ResourceMark rm;
420 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
421 UNICODE::convert_to_utf8(name, utf16_length, chars);
422 return lookup_only(chars, utf8_length, hash);
423 }
424 }
425
426 void SymbolTable::add(ClassLoaderData* loader_data, const constantPoolHandle& cp,
427 int names_count, const char** names, int* lengths,
428 int* cp_indices, unsigned int* hashValues, TRAPS) {
429 bool c_heap = !loader_data->is_the_null_class_loader_data();
430 for (int i = 0; i < names_count; i++) {
431 const char *name = names[i];
432 int len = lengths[i];
433 unsigned int hash = hashValues[i];
434 Symbol* sym = SymbolTable::the_table()->lookup_common(name, len, hash);
435 if (sym == NULL) {
436 sym = SymbolTable::the_table()->do_add_if_needed(name, len, hash, c_heap, CHECK);
437 }
438 assert(sym->refcount() != 0, "lookup should have incremented the count");
439 cp->symbol_at_put(cp_indices[i], sym);
440 }
441 }
442
443 class SymbolTableCreateEntry : public StackObj {
444 private:
445 Thread* _thread;
446 const char* _name;
447 int _len;
448 bool _heap;
449 Symbol* _return;
450 Symbol* _created;
451
452 void assert_for_name(Symbol* sym, const char* where) const {
453 #ifdef ASSERT
454 assert(sym->utf8_length() == _len, "%s [%d,%d]", where, sym->utf8_length(), _len);
455 for (int i = 0; i < _len; i++) {
456 assert(sym->byte_at(i) == _name[i],
457 "%s [%d,%d,%d]", where, i, sym->byte_at(i), _name[i]);
458 }
459 #endif
460 }
461
462 public:
463 SymbolTableCreateEntry(Thread* thread, const char* name, int len, bool heap)
464 : _thread(thread), _name(name) , _len(len), _heap(heap), _return(NULL) , _created(NULL) {
465 assert(_name != NULL, "expected valid name");
466 }
467 Symbol* operator()() {
468 _created = SymbolTable::the_table()->allocate_symbol(_name, _len, _heap, _thread);
469 assert(_created != NULL, "expected created symbol");
470 assert_for_name(_created, "operator()()");
471 assert(_created->equals(_name, _len),
472 "symbol must be properly initialized [%p,%d,%d]", _name, _len, (int)_heap);
473 return _created;
474 }
475 void operator()(bool inserted, Symbol** value) {
476 assert(value != NULL, "expected valid value");
477 assert(*value != NULL, "value should point to a symbol");
478 if (!inserted && (_created != NULL)) {
479 // We created our symbol, but someone else inserted
480 // theirs first, so ours will be destroyed.
481 // Since symbols are created with refcount of 1,
482 // we must decrement it here to 0 to delete,
483 // unless it's a permanent one.
484 if (_created->refcount() != PERM_REFCOUNT) {
485 assert(_created->refcount() == 1, "expected newly created symbol");
486 _created->decrement_refcount();
487 assert(_created->refcount() == 0, "expected dead symbol");
488 }
489 }
490 _return = *value;
491 assert_for_name(_return, "operator()");
492 }
493 Symbol* get_new_sym() const {
494 assert_for_name(_return, "get_new_sym");
495 return _return;
496 }
497 };
498
499 Symbol* SymbolTable::do_add_if_needed(const char* name, int len, uintx hash, bool heap, TRAPS) {
500 SymbolTableLookup lookup(THREAD, name, len, hash);
501 SymbolTableCreateEntry stce(THREAD, name, len, heap);
502 bool rehash_warning = false;
503 bool clean_hint = false;
504 _local_table->get_insert_lazy(THREAD, lookup, stce, stce, &rehash_warning, &clean_hint);
505 if (rehash_warning) {
506 _needs_rehashing = true;
507 }
508 if (clean_hint) {
509 // we just found out that there is a dead item,
510 // which we were unable to clean right now,
511 // but we have no way of telling whether it's
512 // been previously counted or not, so mark
513 // it only if no other items were found yet
514 mark_item_clean_count();
515 check_concurrent_work();
516 }
517 Symbol* sym = stce.get_new_sym();
518 assert(sym->refcount() != 0, "zero is invalid");
519 return sym;
520 }
521
522 Symbol* SymbolTable::new_permanent_symbol(const char* name, TRAPS) {
523 unsigned int hash = 0;
524 int len = (int)strlen(name);
525 Symbol* sym = SymbolTable::lookup_only(name, len, hash);
526 if (sym == NULL) {
527 sym = SymbolTable::the_table()->do_add_if_needed(name, len, hash, false, CHECK_NULL);
528 }
529 if (sym->refcount() != PERM_REFCOUNT) {
530 sym->increment_refcount();
531 _log_trace_symboltable_helper(sym, "Asked for a permanent symbol, but got a regular one");
532 }
533 return sym;
534 }
535
536 struct SizeFunc : StackObj {
537 size_t operator()(Symbol** value) {
538 assert(value != NULL, "expected valid value");
539 assert(*value != NULL, "value should point to a symbol");
540 return (*value)->size() * HeapWordSize;
541 };
542 };
543
544 void SymbolTable::print_table_statistics(outputStream* st,
545 const char* table_name) {
546 SizeFunc sz;
547 _local_table->statistics_to(Thread::current(), sz, st, table_name);
548 }
549
550 // Verification
551 class VerifySymbols : StackObj {
552 public:
553 bool operator()(Symbol** value) {
554 guarantee(value != NULL, "expected valid value");
555 guarantee(*value != NULL, "value should point to a symbol");
556 Symbol* sym = *value;
557 guarantee(sym->equals((const char*)sym->bytes(), sym->utf8_length()),
558 "symbol must be internally consistent");
559 return true;
560 };
561 };
562
563 void SymbolTable::verify() {
564 Thread* thr = Thread::current();
565 VerifySymbols vs;
566 if (!SymbolTable::the_table()->_local_table->try_scan(thr, vs)) {
567 log_info(stringtable)("verify unavailable at this moment");
568 }
569 }
570
571 // Dumping
572 class DumpSymbol : StackObj {
573 Thread* _thr;
574 outputStream* _st;
575 public:
576 DumpSymbol(Thread* thr, outputStream* st) : _thr(thr), _st(st) {}
577 bool operator()(Symbol** value) {
578 assert(value != NULL, "expected valid value");
579 assert(*value != NULL, "value should point to a symbol");
580 Symbol* sym = *value;
581 const char* utf8_string = (const char*)sym->bytes();
582 int utf8_length = sym->utf8_length();
583 _st->print("%d %d: ", utf8_length, sym->refcount());
584 HashtableTextDump::put_utf8(_st, utf8_string, utf8_length);
585 _st->cr();
586 return true;
587 };
588 };
589
590 void SymbolTable::dump(outputStream* st, bool verbose) {
591 if (!verbose) {
592 SymbolTable::the_table()->print_table_statistics(st, "SymbolTable");
593 } else {
594 Thread* thr = Thread::current();
595 ResourceMark rm(thr);
596 st->print_cr("VERSION: 1.1");
597 DumpSymbol ds(thr, st);
598 if (!SymbolTable::the_table()->_local_table->try_scan(thr, ds)) {
599 log_info(symboltable)("dump unavailable at this moment");
600 }
601 }
602 }
603
604 #if INCLUDE_CDS
605 struct CopyToArchive : StackObj {
606 CompactSymbolTableWriter* _writer;
607 CopyToArchive(CompactSymbolTableWriter* writer) : _writer(writer) {}
608 bool operator()(Symbol** value) {
609 assert(value != NULL, "expected valid value");
610 assert(*value != NULL, "value should point to a symbol");
611 Symbol* sym = *value;
612 unsigned int fixed_hash = hash_shared_symbol((const char*)sym->bytes(), sym->utf8_length());
613 if (fixed_hash == 0) {
614 return true;
615 }
616 assert(fixed_hash == hash_symbol((const char*)sym->bytes(), sym->utf8_length(), false),
617 "must not rehash during dumping");
618
619 // add to the compact table
620 _writer->add(fixed_hash, sym);
621
622 return true;
623 }
624 };
625
626 void SymbolTable::copy_shared_symbol_table(CompactSymbolTableWriter* writer) {
627 CopyToArchive copy(writer);
628 SymbolTable::the_table()->_local_table->do_scan(Thread::current(), copy);
629 }
630
631 void SymbolTable::write_to_archive() {
632 _shared_table.reset();
633
634 int num_buckets = (SymbolTable::the_table()->_items_count / SharedSymbolTableBucketSize);
635 // calculation of num_buckets can result in zero buckets, we need at least one
636 CompactSymbolTableWriter writer(num_buckets > 1 ? num_buckets : 1,
637 &MetaspaceShared::stats()->symbol);
638 copy_shared_symbol_table(&writer);
639 writer.dump(&_shared_table);
640
641 // Verify table is correct
642 Symbol* sym = vmSymbols::java_lang_Object();
643 const char* name = (const char*)sym->bytes();
644 int len = sym->utf8_length();
645 unsigned int hash = hash_symbol(name, len, SymbolTable::_alt_hash);
646 assert(sym == _shared_table.lookup(name, hash, len), "sanity");
647 }
648
649 void SymbolTable::serialize(SerializeClosure* soc) {
650 _shared_table.set_type(CompactHashtable<Symbol*, char>::_symbol_table);
651 _shared_table.serialize(soc);
652
653 if (soc->writing()) {
654 // Sanity. Make sure we don't use the shared table at dump time
655 _shared_table.reset();
656 }
657 }
658 #endif //INCLUDE_CDS
659
660 // Concurrent work
661 void SymbolTable::grow(JavaThread* jt) {
662 SymbolTableHash::GrowTask gt(_local_table);
663 if (!gt.prepare(jt)) {
664 return;
665 }
666 log_trace(symboltable)("Started to grow");
667 {
668 TraceTime timer("Grow", TRACETIME_LOG(Debug, symboltable, perf));
669 while (gt.do_task(jt)) {
670 gt.pause(jt);
671 {
672 ThreadBlockInVM tbivm(jt);
673 }
674 gt.cont(jt);
675 }
676 }
677 gt.done(jt);
678 _current_size = table_size(jt);
679 log_debug(symboltable)("Grown to size:" SIZE_FORMAT, _current_size);
680 }
681
682 struct SymbolTableDoDelete : StackObj {
683 int _deleted;
684 SymbolTableDoDelete() : _deleted(0) {}
685 void operator()(Symbol** value) {
686 assert(value != NULL, "expected valid value");
687 assert(*value != NULL, "value should point to a symbol");
688 Symbol *sym = *value;
689 assert(sym->refcount() == 0, "refcount");
690 _deleted++;
691 }
692 };
693
694 struct SymbolTableDeleteCheck : StackObj {
695 int _processed;
696 SymbolTableDeleteCheck() : _processed(0) {}
697 bool operator()(Symbol** value) {
698 assert(value != NULL, "expected valid value");
699 assert(*value != NULL, "value should point to a symbol");
700 _processed++;
701 Symbol *sym = *value;
702 return (sym->refcount() == 0);
703 }
704 };
705
706 void SymbolTable::clean_dead_entries(JavaThread* jt) {
707 SymbolTableHash::BulkDeleteTask bdt(_local_table);
708 if (!bdt.prepare(jt)) {
709 return;
710 }
711
712 SymbolTableDeleteCheck stdc;
713 SymbolTableDoDelete stdd;
714 {
715 TraceTime timer("Clean", TRACETIME_LOG(Debug, symboltable, perf));
716 while (bdt.do_task(jt, stdc, stdd)) {
717 bdt.pause(jt);
718 {
719 ThreadBlockInVM tbivm(jt);
720 }
721 bdt.cont(jt);
722 }
723 SymbolTable::the_table()->set_item_clean_count(0);
724 bdt.done(jt);
725 }
726
727 Atomic::add((size_t)stdc._processed, &_symbols_counted);
728
729 log_debug(symboltable)("Cleaned " INT32_FORMAT " of " INT32_FORMAT,
730 stdd._deleted, stdc._processed);
731 }
732
733 void SymbolTable::check_concurrent_work() {
734 if (_has_work) {
735 return;
736 }
737 double load_factor = SymbolTable::get_load_factor();
738 double dead_factor = SymbolTable::get_dead_factor();
739 // We should clean/resize if we have more dead than alive,
740 // more items than preferred load factor or
741 // more dead items than water mark.
742 if ((dead_factor > load_factor) ||
743 (load_factor > PREF_AVG_LIST_LEN) ||
744 (dead_factor > CLEAN_DEAD_HIGH_WATER_MARK)) {
745 log_debug(symboltable)("Concurrent work triggered, live factor:%f dead factor:%f",
746 load_factor, dead_factor);
747 trigger_concurrent_work();
748 }
749 }
750
751 void SymbolTable::concurrent_work(JavaThread* jt) {
752 double load_factor = get_load_factor();
753 log_debug(symboltable, perf)("Concurrent work, live factor: %g", load_factor);
754 // We prefer growing, since that also removes dead items
755 if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {
756 grow(jt);
757 } else {
758 clean_dead_entries(jt);
759 }
760 _has_work = false;
761 }
762
763 class CountDead : StackObj {
764 int _count;
765 public:
766 CountDead() : _count(0) {}
767 bool operator()(Symbol** value) {
768 assert(value != NULL, "expected valid value");
769 assert(*value != NULL, "value should point to a symbol");
770 Symbol* sym = *value;
771 if (sym->refcount() == 0) {
772 _count++;
773 }
774 return true;
775 };
776 int get_dead_count() {
777 return _count;
778 }
779 };
780
781 void SymbolTable::do_check_concurrent_work() {
782 CountDead counter;
783 if (!SymbolTable::the_table()->_local_table->try_scan(Thread::current(), counter)) {
784 log_info(symboltable)("count dead unavailable at this moment");
785 } else {
786 SymbolTable::the_table()->set_item_clean_count(counter.get_dead_count());
787 SymbolTable::the_table()->check_concurrent_work();
788 }
789 }
790
791 void SymbolTable::do_concurrent_work(JavaThread* jt) {
792 SymbolTable::the_table()->concurrent_work(jt);
793 }
794
795 // Rehash
796 bool SymbolTable::do_rehash() {
797 if (!_local_table->is_safepoint_safe()) {
798 return false;
799 }
800
801 // We use max size
802 SymbolTableHash* new_table = new SymbolTableHash(END_SIZE, END_SIZE, REHASH_LEN);
803 // Use alt hash from now on
804 _alt_hash = true;
805 if (!_local_table->try_move_nodes_to(Thread::current(), new_table)) {
806 _alt_hash = false;
807 delete new_table;
808 return false;
809 }
810
811 // free old table
812 delete _local_table;
813 _local_table = new_table;
814
815 return true;
816 }
817
818 void SymbolTable::try_rehash_table() {
819 static bool rehashed = false;
820 log_debug(symboltable)("Table imbalanced, rehashing called.");
821
822 // Grow instead of rehash.
823 if (get_load_factor() > PREF_AVG_LIST_LEN &&
824 !_local_table->is_max_size_reached()) {
825 log_debug(symboltable)("Choosing growing over rehashing.");
826 trigger_concurrent_work();
827 _needs_rehashing = false;
828 return;
829 }
830
831 // Already rehashed.
832 if (rehashed) {
833 log_warning(symboltable)("Rehashing already done, still long lists.");
834 trigger_concurrent_work();
835 _needs_rehashing = false;
836 return;
837 }
838
839 murmur_seed = AltHashing::compute_seed();
840
841 if (do_rehash()) {
842 rehashed = true;
843 } else {
844 log_info(symboltable)("Resizes in progress rehashing skipped.");
845 }
846
847 _needs_rehashing = false;
848 }
849
850 void SymbolTable::rehash_table() {
851 SymbolTable::the_table()->try_rehash_table();
852 }
853
854 //---------------------------------------------------------------------------
855 // Non-product code
856
857 #ifndef PRODUCT
858
859 class HistogramIterator : StackObj {
860 public:
861 static const size_t results_length = 100;
862 size_t counts[results_length];
863 size_t sizes[results_length];
864 size_t total_size;
865 size_t total_count;
866 size_t total_length;
867 size_t max_length;
868 size_t out_of_range_count;
869 size_t out_of_range_size;
870 HistogramIterator() : total_size(0), total_count(0), total_length(0),
871 max_length(0), out_of_range_count(0), out_of_range_size(0) {
872 // initialize results to zero
873 for (size_t i = 0; i < results_length; i++) {
874 counts[i] = 0;
875 sizes[i] = 0;
876 }
877 }
878 bool operator()(Symbol** value) {
879 assert(value != NULL, "expected valid value");
880 assert(*value != NULL, "value should point to a symbol");
881 Symbol* sym = *value;
882 size_t size = sym->size();
883 size_t len = sym->utf8_length();
884 if (len < results_length) {
885 counts[len]++;
886 sizes[len] += size;
887 } else {
888 out_of_range_count++;
889 out_of_range_size += size;
890 }
891 total_count++;
892 total_size += size;
893 total_length += len;
894 max_length = MAX2(max_length, len);
895
896 return true;
897 };
898 };
899
900 void SymbolTable::print_histogram() {
901 SymbolTable* st = SymbolTable::the_table();
902 HistogramIterator hi;
903 st->_local_table->do_scan(Thread::current(), hi);
904 tty->print_cr("Symbol Table Histogram:");
905 tty->print_cr(" Total number of symbols " SIZE_FORMAT_W(7), hi.total_count);
906 tty->print_cr(" Total size in memory " SIZE_FORMAT_W(7) "K",
907 (hi.total_size * wordSize) / 1024);
908 tty->print_cr(" Total counted " SIZE_FORMAT_W(7), st->_symbols_counted);
909 tty->print_cr(" Total removed " SIZE_FORMAT_W(7), st->_symbols_removed);
910 if (SymbolTable::the_table()->_symbols_counted > 0) {
911 tty->print_cr(" Percent removed %3.2f",
912 ((float)st->_symbols_removed / st->_symbols_counted) * 100);
913 }
914 tty->print_cr(" Reference counts " SIZE_FORMAT_W(7), Symbol::_total_count);
915 tty->print_cr(" Symbol arena used " SIZE_FORMAT_W(7) "K", arena()->used() / 1024);
916 tty->print_cr(" Symbol arena size " SIZE_FORMAT_W(7) "K", arena()->size_in_bytes() / 1024);
917 tty->print_cr(" Total symbol length " SIZE_FORMAT_W(7), hi.total_length);
918 tty->print_cr(" Maximum symbol length " SIZE_FORMAT_W(7), hi.max_length);
919 tty->print_cr(" Average symbol length %7.2f", ((float)hi.total_length / hi.total_count));
920 tty->print_cr(" Symbol length histogram:");
921 tty->print_cr(" %6s %10s %10s", "Length", "#Symbols", "Size");
922 for (size_t i = 0; i < hi.results_length; i++) {
923 if (hi.counts[i] > 0) {
924 tty->print_cr(" " SIZE_FORMAT_W(6) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) "K",
925 i, hi.counts[i], (hi.sizes[i] * wordSize) / 1024);
926 }
927 }
928 tty->print_cr(" >=" SIZE_FORMAT_W(6) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) "K\n",
929 hi.results_length, hi.out_of_range_count, (hi.out_of_range_size*wordSize) / 1024);
930 }
931 #endif // PRODUCT
932
933 // Utility for dumping symbols
934 SymboltableDCmd::SymboltableDCmd(outputStream* output, bool heap) :
935 DCmdWithParser(output, heap),
936 _verbose("-verbose", "Dump the content of each symbol in the table",
937 "BOOLEAN", false, "false") {
938 _dcmdparser.add_dcmd_option(&_verbose);
939 }
940
941 void SymboltableDCmd::execute(DCmdSource source, TRAPS) {
942 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSymbols,
943 _verbose.value());
944 VMThread::execute(&dumper);
945 }
946
947 int SymboltableDCmd::num_arguments() {
948 ResourceMark rm;
949 SymboltableDCmd* dcmd = new SymboltableDCmd(NULL, false);
950 if (dcmd != NULL) {
951 DCmdMark mark(dcmd);
952 return dcmd->_dcmdparser.num_arguments();
953 } else {
954 return 0;
955 }
956 }