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 bool SymbolTable::_alt_hash = false;
62 // Static arena for symbols that are not deallocated
63 Arena* SymbolTable::_arena = NULL;
64 bool SymbolTable::_lookup_shared_first = false;
65 int SymbolTable::_symbols_removed = 0;
66 int SymbolTable::_symbols_counted = 0;
67
68 static juint murmur_seed = 0;
69
70 static inline void _log_trace_symboltable_helper(Symbol* sym, const char* msg) {
71 #ifndef PRODUCT
72 if (log_is_enabled(Trace, symboltable)) {
73 char *s;
74 {
75 ResourceMark rm;
76 s = sym->as_quoted_ascii();
77 s = os::strdup(s);
78 }
79 if (s == NULL) {
80 log_trace(symboltable)("%s [%s]", msg, "NULL");
81 } else {
82 log_trace(symboltable)("%s [%s]", msg, s);
83 os::free(s);
84 }
85 }
86 #endif // PRODUCT
87 }
88
89 // Pick hashing algorithm.
90 static uintx hash_symbol(const char* s, int len, bool useAlt) {
91 return useAlt ?
92 AltHashing::murmur3_32(murmur_seed, (const jbyte*)s, len) :
93 java_lang_String::hash_code((const jbyte*)s, len);
94 }
95
96 static uintx hash_shared_symbol(const char* s, int len) {
97 return java_lang_String::hash_code((const jbyte*)s, len);
98 }
99
100 class SymbolTableConfig : public SymbolTableHash::BaseConfig {
101 private:
102 public:
103 static uintx get_hash(Symbol* const& value, bool* is_dead) {
104 *is_dead = (value->refcount() == 0);
105 if (*is_dead) {
106 return 0;
107 } else {
108 return hash_symbol((char*)value->bytes(), value->utf8_length(), SymbolTable::_alt_hash);
109 }
110 }
111 // We use default allocation/deallocation but counted
112 static void* allocate_node(size_t size, Symbol* const& value) {
113 SymbolTable::item_added();
114 return SymbolTableHash::BaseConfig::allocate_node(size, value);
115 }
116 static void free_node(void* memory, Symbol* const& value) {
117 // We get here either because #1 some threads lost a race
118 // to insert a newly created Symbol, or #2 we are freeing
119 // a symbol during normal cleanup deletion.
120 // If #1, then the symbol can be a permanent (refcount==PERM_REFCOUNT),
121 // or regular newly created one but with refcount==0 (see SymbolTableCreateEntry)
122 // If #2, then the symbol must have refcount==0
123 assert((value->refcount() == PERM_REFCOUNT) || (value->refcount() == 0),
124 "refcount %d", value->refcount());
125 SymbolTable::delete_symbol(value);
126 SymbolTableHash::BaseConfig::free_node(memory, value);
127 SymbolTable::item_removed();
128 }
129 };
130
131 static size_t ceil_pow_2(uintx value) {
132 size_t ret;
133 for (ret = 1; ((size_t)1 << ret) < value; ++ret);
134 return ret;
135 }
136
137 SymbolTable::SymbolTable() : _local_table(NULL), _current_size(0), _has_work(0),
138 _needs_rehashing(false), _items(0), _uncleaned_items(0) {
139
140 size_t start_size_log_2 = ceil_pow_2(SymbolTableSize);
141 _current_size = ((size_t)1) << start_size_log_2;
142 log_trace(symboltable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")",
143 _current_size, start_size_log_2);
144 _local_table = new SymbolTableHash(start_size_log_2, END_SIZE, REHASH_LEN);
145 }
146
147 void SymbolTable::delete_symbol(Symbol* sym) {
148 if (sym->refcount() == PERM_REFCOUNT) {
149 MutexLocker ml(SymbolTable_lock); // Protect arena
150 // Deleting permanent symbol should not occur very often (insert race condition),
151 // so log it.
152 _log_trace_symboltable_helper(sym, "Freeing permanent symbol");
153 if (!arena()->Afree(sym, sym->size())) {
154 _log_trace_symboltable_helper(sym, "Leaked permanent symbol");
155 }
156 } else {
157 delete sym;
158 }
159 }
160
161 size_t SymbolTable::item_added() {
162 return Atomic::add(1, &(SymbolTable::the_table()->_items));
163 }
164
165 void SymbolTable::set_item_clean_count(size_t ncl) {
166 Atomic::store((int)ncl, &(SymbolTable::the_table()->_uncleaned_items));
167 log_trace(symboltable)("Set uncleaned items:" INT32_FORMAT, SymbolTable::the_table()->_uncleaned_items);
168 }
169
170 void SymbolTable::mark_item_clean_count() {
171 if (Atomic::cmpxchg(1, &(SymbolTable::the_table()->_uncleaned_items), 0) == 0) { // only mark if unset
172 log_trace(symboltable)("Marked uncleaned items:" INT32_FORMAT, SymbolTable::the_table()->_uncleaned_items);
173 }
174 }
175
176 void SymbolTable::item_removed() {
177 Atomic::add(1, &(SymbolTable::the_table()->_symbols_removed));
178 Atomic::sub(1, &(SymbolTable::the_table()->_items));
179 }
180
181 double SymbolTable::get_load_factor() {
182 return (_items*1.0)/_current_size;
183 }
184
185 double SymbolTable::get_dead_factor() {
186 return (_uncleaned_items*1.0)/_current_size;
187 }
188
189 size_t SymbolTable::table_size(Thread* thread) {
190 return ((size_t)(1)) << _local_table->get_size_log2(thread != NULL ? thread
191 : Thread::current());
192 }
193
194 void SymbolTable::trigger_concurrent_work() {
195 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
196 SymbolTable::the_table()->_has_work = true;
197 Service_lock->notify_all();
198 }
199
200 Symbol* SymbolTable::allocate_symbol(const u1* name, int len, bool c_heap, TRAPS) {
201 assert (len <= Symbol::max_length(), "should be checked by caller");
202
203 Symbol* sym;
204 if (DumpSharedSpaces) {
205 c_heap = false;
206 }
207 if (c_heap) {
208 // refcount starts as 1
209 sym = new (len, THREAD) Symbol(name, len, 1);
210 assert(sym != NULL, "new should call vm_exit_out_of_memory if C_HEAP is exhausted");
211 } else {
212 // Allocate to global arena
213 MutexLocker ml(SymbolTable_lock); // Protect arena
214 sym = new (len, arena(), THREAD) Symbol(name, len, PERM_REFCOUNT);
215 }
216 return sym;
217 }
218
219 void SymbolTable::initialize_symbols(int arena_alloc_size) {
220 // Initialize the arena for global symbols, size passed in depends on CDS.
221 if (arena_alloc_size == 0) {
222 _arena = new (mtSymbol) Arena(mtSymbol);
223 } else {
224 _arena = new (mtSymbol) Arena(mtSymbol, arena_alloc_size);
225 }
226 }
227
228 class SymbolsDo : StackObj {
229 SymbolClosure *_cl;
230 public:
231 SymbolsDo(SymbolClosure *cl) : _cl(cl) {}
232 bool operator()(Symbol** value) {
233 assert(value != NULL, "expected valid value");
234 assert(*value != NULL, "value should point to a symbol");
235 _cl->do_symbol(value);
236 return true;
237 };
238 };
239
240 // Call function for all symbols in the symbol table.
241 void SymbolTable::symbols_do(SymbolClosure *cl) {
242 // all symbols from shared table
243 _shared_table.symbols_do(cl);
244
245 // all symbols from the dynamic table
246 SymbolsDo sd(cl);
247 if (!SymbolTable::the_table()->_local_table->try_scan(Thread::current(), sd)) {
248 log_info(stringtable)("symbols_do unavailable at this moment");
249 }
250 }
251
252 class MetaspacePointersDo : StackObj {
253 MetaspaceClosure *_it;
254 public:
255 MetaspacePointersDo(MetaspaceClosure *it) : _it(it) {}
256 bool operator()(Symbol** value) {
257 assert(value != NULL, "expected valid value");
258 assert(*value != NULL, "value should point to a symbol");
259 _it->push(value);
260 return true;
261 };
262 };
263
264 void SymbolTable::metaspace_pointers_do(MetaspaceClosure* it) {
265 assert(DumpSharedSpaces, "called only during dump time");
266 MetaspacePointersDo mpd(it);
267 SymbolTable::the_table()->_local_table->do_scan(Thread::current(), mpd);
268 }
269
270 Symbol* SymbolTable::lookup_dynamic(const char* name,
271 int len, unsigned int hash) {
272 Symbol* sym = SymbolTable::the_table()->do_lookup((char*)name, len, hash);
273 assert((sym == NULL) || sym->refcount() != 0, "refcount must not be zero");
274 return sym;
275 }
276
277 Symbol* SymbolTable::lookup_shared(const char* name,
278 int len, unsigned int hash) {
279 if (!_shared_table.empty()) {
280 if (SymbolTable::_alt_hash) {
281 // hash_code parameter may use alternate hashing algorithm but the shared table
282 // always uses the same original hash code.
283 hash = hash_shared_symbol(name, len);
284 }
285 return _shared_table.lookup(name, hash, len);
286 } else {
287 return NULL;
288 }
289 }
290
291 Symbol* SymbolTable::lookup_common(const char* name,
292 int len, unsigned int hash) {
293 Symbol* sym;
294 if (_lookup_shared_first) {
295 sym = lookup_shared(name, len, hash);
296 if (sym == NULL) {
297 _lookup_shared_first = false;
298 sym = lookup_dynamic(name, len, hash);
299 }
300 } else {
301 sym = lookup_dynamic(name, len, hash);
302 if (sym == NULL) {
303 sym = lookup_shared(name, len, hash);
304 if (sym != NULL) {
305 _lookup_shared_first = true;
306 }
307 }
308 }
309 return sym;
310 }
311
312 Symbol* SymbolTable::lookup(const char* name, int len, TRAPS) {
313 unsigned int hash = hash_symbol(name, len, SymbolTable::_alt_hash);
314 Symbol* sym = SymbolTable::the_table()->lookup_common(name, len, hash);
315 if (sym == NULL) {
316 sym = SymbolTable::the_table()->do_add_if_needed((char*)name, len, hash, true, CHECK_NULL);
317 }
318 assert(sym->refcount() != 0, "lookup should have incremented the count");
319 assert(sym->equals((char*)name, len), "symbol must be properly initialized");
320 return sym;
321 }
322
323 Symbol* SymbolTable::lookup(const Symbol* sym, int begin, int end, TRAPS) {
324 char* buffer;
325 int len;
326 unsigned int hash;
327 char* name;
328 {
329 debug_only(NoSafepointVerifier nsv;)
330
331 name = (char*)sym->base() + begin;
332 len = end - begin;
333 hash = hash_symbol(name, len, SymbolTable::_alt_hash);
334 Symbol* sym = SymbolTable::the_table()->lookup_common(name, len, hash);
335
336 // Found
337 if (sym != NULL) {
338 assert(sym->refcount() != 0, "lookup should have incremented the count");
339 return sym;
340 }
341 }
342
343 // Otherwise, add the symbol to table. Copy to a C string first.
344 char stack_buf[ON_STACK_BUFFER_LENGTH];
345 ResourceMark rm(THREAD);
346 if (len <= ON_STACK_BUFFER_LENGTH) {
347 buffer = stack_buf;
348 } else {
349 buffer = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, len);
350 }
351 for (int i=0; i<len; i++) {
352 buffer[i] = name[i];
353 }
354 // Make sure there is no safepoint in the code above since name can't move.
355 // We can't include the code in NoSafepointVerifier because of the
356 // ResourceMark.
357 return SymbolTable::the_table()->do_add_if_needed((char*)name, len, hash, true, THREAD);
358 }
359
360 class SymbolTableLookupChar : StackObj {
361 private:
362 Thread* _thread;
363 uintx _hash;
364 int _len;
365 const char* _str;
366 Symbol* _found;
367 public:
368 SymbolTableLookupChar(Thread* thread, const char* key, int len, uintx hash)
369 : _thread(thread), _hash(hash), _str(key), _len(len) , _found(NULL) {
370 }
371 uintx get_hash() const {
372 return _hash;
373 }
374 bool equals(Symbol** value, bool* is_dead) {
375 assert(value != NULL, "expected valid value");
376 assert(*value != NULL, "value should point to a symbol");
377 Symbol *sym = *value;
378 if (sym->equals(_str, _len)) {
379 if (sym->try_increment_refcount()) {
380 // something is referencing this symbol now.
381 _found = sym;
382 return true;
383 } else {
384 *is_dead = (sym->refcount() == 0);
385 return false;
386 }
387 } else {
388 return false;
389 }
390 }
391 };
392
393 class SymbolTableGet : public StackObj {
394 Symbol* _return;
395 public:
396 SymbolTableGet() : _return(NULL) { }
397 void operator()(Symbol** value) {
398 assert(value != NULL, "expected valid value");
399 assert(*value != NULL, "value should point to a symbol");
400 _return = *value;
401 }
402 Symbol* get_res_sym() {
403 return _return;
404 }
405 };
406
407 Symbol* SymbolTable::do_lookup(char* name, int len, uintx hash) {
408 Thread* thread = Thread::current();
409 SymbolTableLookupChar lookup(thread, name, len, hash);
410 SymbolTableGet stg;
411 bool rehash_warning;
412 _local_table->get(thread, lookup, stg, &rehash_warning);
413 if (rehash_warning) {
414 _needs_rehashing = true;
415 }
416 Symbol* sym = stg.get_res_sym();
417 assert((sym == NULL) || sym->refcount() != 0, "found dead symbol");
418 return sym;
419 }
420
421 Symbol* SymbolTable::lookup_only(const char* name, int len, unsigned int& hash) {
422 hash = hash_symbol(name, len, SymbolTable::_alt_hash);
423 return SymbolTable::the_table()->lookup_common(name, len, hash);
424 }
425
426 // Suggestion: Push unicode-based lookup all the way into the hashing
427 // and probing logic, so there is no need for convert_to_utf8 until
428 // an actual new Symbol* is created.
429 Symbol* SymbolTable::lookup_unicode(const jchar* name, int utf16_length, TRAPS) {
430 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
431 char stack_buf[ON_STACK_BUFFER_LENGTH];
432 if (utf8_length < (int) sizeof(stack_buf)) {
433 char* chars = stack_buf;
434 UNICODE::convert_to_utf8(name, utf16_length, chars);
435 return lookup(chars, utf8_length, THREAD);
436 } else {
437 ResourceMark rm(THREAD);
438 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
439 UNICODE::convert_to_utf8(name, utf16_length, chars);
440 return lookup(chars, utf8_length, THREAD);
441 }
442 }
443
444 Symbol* SymbolTable::lookup_only_unicode(const jchar* name, int utf16_length,
445 unsigned int& hash) {
446 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
447 char stack_buf[ON_STACK_BUFFER_LENGTH];
448 if (utf8_length < (int) sizeof(stack_buf)) {
449 char* chars = stack_buf;
450 UNICODE::convert_to_utf8(name, utf16_length, chars);
451 return lookup_only(chars, utf8_length, hash);
452 } else {
453 ResourceMark rm;
454 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
455 UNICODE::convert_to_utf8(name, utf16_length, chars);
456 return lookup_only(chars, utf8_length, hash);
457 }
458 }
459
460 void SymbolTable::add(ClassLoaderData* loader_data, const constantPoolHandle& cp,
461 int names_count, const char** names, int* lengths,
462 int* cp_indices, unsigned int* hashValues, TRAPS) {
463 bool c_heap = !loader_data->is_the_null_class_loader_data();
464 for (int i=0; i<names_count; i++) {
465 char *name = (char*)names[i];
466 int len = lengths[i];
467 unsigned int hash = hashValues[i];
468 Symbol* sym = SymbolTable::the_table()->lookup_common(name, len, hash);
469 if (sym == NULL) {
470 sym = SymbolTable::the_table()->do_add_if_needed(name, len, hash, c_heap, CHECK);
471 }
472 assert(sym->refcount()!=0, "lookup should have incremented the count");
473 cp->symbol_at_put(cp_indices[i], sym);
474 }
475 }
476
477 class SymbolTableCreateEntry : public StackObj {
478 private:
479 Thread* _thread;
480 const char* _name;
481 int _len;
482 bool _heap;
483 Symbol* _return;
484 Symbol* _created;
485
486 #ifdef ASSERT
487 void _assert_for_name(Symbol* sym, const char* where) const {
488 assert(sym->utf8_length() == _len, "%s [%d,%d]", where, sym->utf8_length(), _len);
489 for (int i=0; i<_len; i++) {
490 assert(sym->byte_at(i) == _name[i],
491 "%s [%d,%d,%d]", where, i, sym->byte_at(i), _name[i]);
492 }
493 }
494 #endif
495
496 public:
497 SymbolTableCreateEntry(Thread* thread, const char* name, int len, bool heap)
498 : _thread(thread), _name(name) , _len(len), _heap(heap), _return(NULL) , _created(NULL) {
499 assert(_name != NULL, "expected valid name");
500 }
501 Symbol* operator()() {
502 _created = SymbolTable::the_table()->allocate_symbol((const u1*)_name, _len, _heap, _thread);
503 assert(_created != NULL, "expected created symbol");
504 #ifdef ASSERT
505 _assert_for_name(_created, "operator()()");
506 #endif
507 assert(_created->equals((char*)_name, _len),
508 "symbol must be properly initialized [%p,%d,%d]", _name, _len, (int)_heap);
509 return _created;
510 }
511 void operator()(bool inserted, Symbol** value) {
512 assert(value != NULL, "expected valid value");
513 assert(*value != NULL, "value should point to a symbol");
514 if (!inserted && (_created != NULL)) {
515 // We created our symbol, but someone else inserted
516 // theirs first, so ours will be destroyed.
517 // Since symbols are created with refcount of 1,
518 // we must decrement it here to 0 to delete,
519 // unless it's a permanent one.
520 if (_created->refcount() != PERM_REFCOUNT) {
521 assert(_created->refcount() == 1, "expected newly created symbol");
522 _created->decrement_refcount();
523 assert(_created->refcount() == 0, "expected dead symbol");
524 }
525 }
526 _return = *value;
527 #ifdef ASSERT
528 _assert_for_name(_return, "operator()");
529 #endif
530 }
531 Symbol* get_new_sym() const {
532 #ifdef ASSERT
533 _assert_for_name(_return, "get_new_sym");
534 #endif
535 return _return;
536 }
537 };
538
539 Symbol* SymbolTable::do_add_if_needed(char* name, int len, uintx hash, bool heap, TRAPS) {
540 SymbolTableLookupChar lookup(THREAD, name, len, hash);
541 SymbolTableCreateEntry stce(THREAD, name, len, heap);
542 bool rehash_warning;
543 bool clean_hint;
544 _local_table->get_insert_lazy(THREAD, lookup, stce, stce, &rehash_warning, &clean_hint);
545 if (rehash_warning) {
546 _needs_rehashing = true;
547 }
548 if (clean_hint) {
549 // we just found out that there is a dead item,
550 // which we were unable to clean right now,
551 // but we have no way of telling whether it's
552 // been previously counted or not, so mark
553 // it only if no other items were found yet
554 mark_item_clean_count();
555 check_concurrent_work();
556 }
557 Symbol* sym = stce.get_new_sym();
558 assert(sym->refcount() != 0, "zero is invalid");
559 return sym;
560 }
561
562 Symbol* SymbolTable::new_permanent_symbol(const char* name, TRAPS) {
563 unsigned int hash = 0;
564 int len = (int)strlen(name);
565 Symbol* sym = SymbolTable::lookup_only(name, len, hash);
566 if (sym == NULL) {
567 sym = SymbolTable::the_table()->do_add_if_needed((char*)name, len, hash, false, CHECK_NULL);
568 }
569 if (sym->refcount() != PERM_REFCOUNT) {
570 sym->increment_refcount();
571 _log_trace_symboltable_helper(sym, "Asked for a permanent symbol, but got a regular one");
572 }
573 return sym;
574 }
575
576 struct SizeFunc : StackObj {
577 size_t operator()(Symbol** value) {
578 assert(value != NULL, "expected valid value");
579 assert(*value != NULL, "value should point to a symbol");
580 return (*value)->size() * HeapWordSize;
581 };
582 };
583
584 void SymbolTable::print_table_statistics(outputStream* st,
585 const char* table_name) {
586 SizeFunc sz;
587 _local_table->statistics_to(Thread::current(), sz, st, table_name);
588 }
589
590 // Verification
591 class VerifySymbols : StackObj {
592 public:
593 bool operator()(Symbol** value) {
594 guarantee(value != NULL, "expected valid value");
595 guarantee(*value != NULL, "value should point to a symbol");
596 Symbol* sym = *value;
597 guarantee(sym->equals((char*)sym->bytes(), sym->utf8_length()),
598 "symbol must be internally consistent");
599 return true;
600 };
601 };
602
603 void SymbolTable::verify() {
604 Thread* thr = Thread::current();
605 VerifySymbols vs;
606 if (!SymbolTable::the_table()->_local_table->try_scan(thr, vs)) {
607 log_info(stringtable)("verify unavailable at this moment");
608 }
609 }
610
611 // Dumping
612 class DumpSymbol : StackObj {
613 Thread* _thr;
614 outputStream* _st;
615 public:
616 DumpSymbol(Thread* thr, outputStream* st) : _thr(thr), _st(st) {}
617 bool operator()(Symbol** value) {
618 assert(value != NULL, "expected valid value");
619 assert(*value != NULL, "value should point to a symbol");
620 Symbol* sym = *value;
621 const char* utf8_string = (const char*)sym->bytes();
622 int utf8_length = sym->utf8_length();
623 _st->print("%d %d: ", utf8_length, sym->refcount());
624 HashtableTextDump::put_utf8(_st, utf8_string, utf8_length);
625 _st->cr();
626 return true;
627 };
628 };
629
630 void SymbolTable::dump(outputStream* st, bool verbose) {
631 if (!verbose) {
632 SymbolTable::the_table()->print_table_statistics(st, "SymbolTable");
633 } else {
634 Thread* thr = Thread::current();
635 ResourceMark rm(thr);
636 st->print_cr("VERSION: 1.1");
637 DumpSymbol ds(thr, st);
638 if (!SymbolTable::the_table()->_local_table->try_scan(thr, ds)) {
639 log_info(symboltable)("dump unavailable at this moment");
640 }
641 }
642 }
643
644 #if INCLUDE_CDS
645 struct CopyToArchive : StackObj {
646 CompactSymbolTableWriter* _writer;
647 CopyToArchive(CompactSymbolTableWriter* writer) : _writer(writer) {}
648 bool operator()(Symbol** value) {
649 assert(value != NULL, "expected valid value");
650 assert(*value != NULL, "value should point to a symbol");
651 Symbol* sym = *value;
652 unsigned int fixed_hash = hash_shared_symbol((char*)sym->bytes(), sym->utf8_length());
653 if (fixed_hash == 0) {
654 return true;
655 }
656 assert(fixed_hash == hash_symbol((char*)sym->bytes(), sym->utf8_length(), false),
657 "must not rehash during dumping");
658
659 // add to the compact table
660 _writer->add(fixed_hash, sym);
661
662 return true;
663 }
664 };
665
666 void SymbolTable::copy_shared_symbol_table(CompactSymbolTableWriter* writer) {
667 CopyToArchive copy(writer);
668 SymbolTable::the_table()->_local_table->do_scan(Thread::current(), copy);
669 }
670
671 void SymbolTable::write_to_archive() {
672 _shared_table.reset();
673
674 int num_buckets = (SymbolTable::the_table()->_items / SharedSymbolTableBucketSize);
675 // calculation of num_buckets can result in zero buckets, we need at least one
676 CompactSymbolTableWriter writer(num_buckets > 1 ? num_buckets : 1,
677 &MetaspaceShared::stats()->symbol);
678 copy_shared_symbol_table(&writer);
679 writer.dump(&_shared_table);
680
681 // Verify table is correct
682 Symbol* sym = vmSymbols::java_lang_Object();
683 const char* name = (const char*)sym->bytes();
684 int len = sym->utf8_length();
685 unsigned int hash = hash_symbol(name, len, SymbolTable::_alt_hash);
686 assert(sym == _shared_table.lookup(name, hash, len), "sanity");
687 }
688
689 void SymbolTable::serialize(SerializeClosure* soc) {
690 _shared_table.set_type(CompactHashtable<Symbol*, char>::_symbol_table);
691 _shared_table.serialize(soc);
692
693 if (soc->writing()) {
694 // Sanity. Make sure we don't use the shared table at dump time
695 _shared_table.reset();
696 }
697 }
698 #endif //INCLUDE_CDS
699
700 // Concurrent work
701 void SymbolTable::grow(JavaThread* jt) {
702 SymbolTableHash::GrowTask gt(_local_table);
703 if (!gt.prepare(jt)) {
704 return;
705 }
706 log_trace(symboltable)("Started to grow");
707 {
708 TraceTime timer("Grow", TRACETIME_LOG(Debug, symboltable, perf));
709 while (gt.do_task(jt)) {
710 gt.pause(jt);
711 {
712 ThreadBlockInVM tbivm(jt);
713 }
714 gt.cont(jt);
715 }
716 }
717 gt.done(jt);
718 _current_size = table_size(jt);
719 log_debug(symboltable)("Grown to size:" SIZE_FORMAT, _current_size);
720 }
721
722 struct SymbolTableDoDelete : StackObj {
723 int _deleted;
724 SymbolTableDoDelete() : _deleted(0) {}
725 void operator()(Symbol** value) {
726 assert(value != NULL, "expected valid value");
727 assert(*value != NULL, "value should point to a symbol");
728 Symbol *sym = *value;
729 assert(sym->refcount() == 0, "refcount");
730 _deleted++;
731 }
732 };
733
734 struct SymbolTableDeleteCheck : StackObj {
735 int _processed;
736 SymbolTableDeleteCheck() : _processed(0) {}
737 bool operator()(Symbol** value) {
738 assert(value != NULL, "expected valid value");
739 assert(*value != NULL, "value should point to a symbol");
740 _processed++;
741 Symbol *sym = *value;
742 if (sym->refcount() == 0) {
743 return true;
744 } else {
745 return false;
746 }
747 }
748 };
749
750 void SymbolTable::clean_dead_entries(JavaThread* jt) {
751 SymbolTableHash::BulkDeleteTask bdt(_local_table);
752 if (!bdt.prepare(jt)) {
753 return;
754 }
755
756 SymbolTableDeleteCheck stdc;
757 SymbolTableDoDelete stdd;
758 {
759 TraceTime timer("Clean", TRACETIME_LOG(Debug, symboltable, perf));
760 while (bdt.do_task(jt, stdc, stdd)) {
761 bdt.pause(jt);
762 {
763 ThreadBlockInVM tbivm(jt);
764 }
765 bdt.cont(jt);
766 }
767 SymbolTable::the_table()->set_item_clean_count(0);
768 bdt.done(jt);
769 }
770
771 Atomic::add(stdc._processed, &_symbols_counted);
772
773 log_debug(symboltable)("Cleaned " INT32_FORMAT " of " INT32_FORMAT,
774 stdd._deleted, stdc._processed);
775 }
776
777 void SymbolTable::check_concurrent_work() {
778 if (_has_work) {
779 return;
780 }
781 double load_factor = SymbolTable::get_load_factor();
782 double dead_factor = SymbolTable::get_dead_factor();
783 // We should clean/resize if we have more dead than alive,
784 // more items than preferred load factor or
785 // more dead items than water mark.
786 if ((dead_factor > load_factor) ||
787 (load_factor > PREF_AVG_LIST_LEN) ||
788 (dead_factor > CLEAN_DEAD_HIGH_WATER_MARK)) {
789 log_debug(symboltable)("Concurrent work triggered, live factor:%f dead factor:%f",
790 load_factor, dead_factor);
791 trigger_concurrent_work();
792 }
793 }
794
795 void SymbolTable::concurrent_work(JavaThread* jt) {
796 double load_factor = get_load_factor();
797 log_debug(symboltable, perf)("Concurrent work, live factor: %g", load_factor);
798 // We prefer growing, since that also removes dead items
799 if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {
800 grow(jt);
801 } else {
802 clean_dead_entries(jt);
803 }
804 _has_work = false;
805 }
806
807 class CountDead : StackObj {
808 int _count;
809 public:
810 CountDead() : _count(0) {}
811 bool operator()(Symbol** value) {
812 assert(value != NULL, "expected valid value");
813 assert(*value != NULL, "value should point to a symbol");
814 Symbol* sym = *value;
815 if (sym->refcount() == 0) {
816 _count++;
817 }
818 return true;
819 };
820 int get_dead_count() {
821 return _count;
822 }
823 };
824
825 void SymbolTable::do_check_concurrent_work() {
826 CountDead counter;
827 if (!SymbolTable::the_table()->_local_table->try_scan(Thread::current(), counter)) {
828 log_info(symboltable)("count dead unavailable at this moment");
829 } else {
830 SymbolTable::the_table()->set_item_clean_count(counter.get_dead_count());
831 SymbolTable::the_table()->check_concurrent_work();
832 }
833 }
834
835 void SymbolTable::do_concurrent_work(JavaThread* jt) {
836 SymbolTable::the_table()->concurrent_work(jt);
837 }
838
839 // Rehash
840 bool SymbolTable::do_rehash() {
841 if (!_local_table->is_safepoint_safe()) {
842 return false;
843 }
844
845 // We use max size
846 SymbolTableHash* new_table = new SymbolTableHash(END_SIZE, END_SIZE, REHASH_LEN);
847 // Use alt hash from now on
848 _alt_hash = true;
849 if (!_local_table->try_move_nodes_to(Thread::current(), new_table)) {
850 _alt_hash = false;
851 delete new_table;
852 return false;
853 }
854
855 // free old table
856 delete _local_table;
857 _local_table = new_table;
858
859 return true;
860 }
861
862 void SymbolTable::try_rehash_table() {
863 static bool rehashed = false;
864 log_debug(symboltable)("Table imbalanced, rehashing called.");
865
866 // Grow instead of rehash.
867 if (get_load_factor() > PREF_AVG_LIST_LEN &&
868 !_local_table->is_max_size_reached()) {
869 log_debug(symboltable)("Choosing growing over rehashing.");
870 trigger_concurrent_work();
871 _needs_rehashing = false;
872 return;
873 }
874
875 // Already rehashed.
876 if (rehashed) {
877 log_warning(symboltable)("Rehashing already done, still long lists.");
878 trigger_concurrent_work();
879 _needs_rehashing = false;
880 return;
881 }
882
883 murmur_seed = AltHashing::compute_seed();
884
885 if (do_rehash()) {
886 rehashed = true;
887 } else {
888 log_info(symboltable)("Resizes in progress rehashing skipped.");
889 }
890
891 _needs_rehashing = false;
892 }
893
894 void SymbolTable::rehash_table() {
895 SymbolTable::the_table()->try_rehash_table();
896 }
897
898 //---------------------------------------------------------------------------
899 // Non-product code
900
901 #ifndef PRODUCT
902
903 class HistogramIterator : StackObj {
904 public:
905 static const int results_length = 100;
906 int counts[results_length];
907 int sizes[results_length];
908 int total_size;
909 int total_count;
910 int total_length;
911 int max_length;
912 int out_of_range_count;
913 int out_of_range_size;
914 HistogramIterator() : total_size(0), total_count(0), total_length(0),
915 max_length(0), out_of_range_count(0), out_of_range_size(0) {
916 // initialize results to zero
917 for (int i = 0; i < results_length; i++) {
918 counts[i] = 0;
919 sizes[i] = 0;
920 }
921 }
922 bool operator()(Symbol** value) {
923 assert(value != NULL, "expected valid value");
924 assert(*value != NULL, "value should point to a symbol");
925 Symbol* sym = *value;
926 int size = sym->size();
927 int len = sym->utf8_length();
928 if (len < results_length) {
929 counts[len]++;
930 sizes[len] += size;
931 } else {
932 out_of_range_count++;
933 out_of_range_size += size;
934 }
935 total_count++;
936 total_size += size;
937 total_length += len;
938 max_length = MAX2(max_length, len);
939
940 return true;
941 };
942 };
943
944 void SymbolTable::print_histogram() {
945 HistogramIterator hi;
946 SymbolTable::the_table()->_local_table->do_scan(Thread::current(), hi);
947 tty->print_cr("Symbol Table Histogram:");
948 tty->print_cr(" Total number of symbols %7d", hi.total_count);
949 tty->print_cr(" Total size in memory %7dK",
950 (hi.total_size*wordSize)/1024);
951 tty->print_cr(" Total counted %7d", _symbols_counted);
952 tty->print_cr(" Total removed %7d", _symbols_removed);
953 if (_symbols_counted > 0) {
954 tty->print_cr(" Percent removed %3.2f",
955 ((float)_symbols_removed/(float)_symbols_counted)* 100);
956 }
957 tty->print_cr(" Reference counts %7d", Symbol::_total_count);
958 tty->print_cr(" Symbol arena used " SIZE_FORMAT_W(7) "K", arena()->used()/1024);
959 tty->print_cr(" Symbol arena size " SIZE_FORMAT_W(7) "K", arena()->size_in_bytes()/1024);
960 tty->print_cr(" Total symbol length %7d", hi.total_length);
961 tty->print_cr(" Maximum symbol length %7d", hi.max_length);
962 tty->print_cr(" Average symbol length %7.2f", ((float) hi.total_length / (float) hi.total_count));
963 tty->print_cr(" Symbol length histogram:");
964 tty->print_cr(" %6s %10s %10s", "Length", "#Symbols", "Size");
965 for (int i = 0; i < hi.results_length; i++) {
966 if (hi.counts[i] > 0) {
967 tty->print_cr(" %6d %10d %10dK", i, hi.counts[i], (hi.sizes[i]*wordSize)/1024);
968 }
969 }
970 tty->print_cr(" >=%6d %10d %10dK\n", hi.results_length,
971 hi.out_of_range_count, (hi.out_of_range_size*wordSize)/1024);
972 }
973 #endif // PRODUCT
974
975 // Utility for dumping symbols
976 SymboltableDCmd::SymboltableDCmd(outputStream* output, bool heap) :
977 DCmdWithParser(output, heap),
978 _verbose("-verbose", "Dump the content of each symbol in the table",
979 "BOOLEAN", false, "false") {
980 _dcmdparser.add_dcmd_option(&_verbose);
981 }
982
983 void SymboltableDCmd::execute(DCmdSource source, TRAPS) {
984 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSymbols,
985 _verbose.value());
986 VMThread::execute(&dumper);
987 }
988
989 int SymboltableDCmd::num_arguments() {
990 ResourceMark rm;
991 SymboltableDCmd* dcmd = new SymboltableDCmd(NULL, false);
992 if (dcmd != NULL) {
993 DCmdMark mark(dcmd);
994 return dcmd->_dcmdparser.num_arguments();
995 } else {
996 return 0;
997 }
998 }