1 /*
2 * Copyright (c) 1997, 2020, 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.hpp"
28 #include "classfile/javaClasses.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "memory/allocation.inline.hpp"
31 #include "memory/dynamicArchive.hpp"
32 #include "memory/metaspaceClosure.hpp"
33 #include "memory/metaspaceShared.hpp"
34 #include "memory/resourceArea.hpp"
35 #include "oops/oop.inline.hpp"
36 #include "runtime/atomic.hpp"
37 #include "runtime/interfaceSupport.inline.hpp"
38 #include "runtime/timerTrace.hpp"
39 #include "services/diagnosticCommand.hpp"
40 #include "utilities/concurrentHashTable.inline.hpp"
41 #include "utilities/concurrentHashTableTasks.inline.hpp"
42 #include "utilities/utf8.hpp"
43
44 // We used to not resize at all, so let's be conservative
45 // and not set it too short before we decide to resize,
46 // to match previous startup behavior
47 const double PREF_AVG_LIST_LEN = 8.0;
48 // 2^24 is max size, like StringTable.
49 const size_t END_SIZE = 24;
50 // If a chain gets to 100 something might be wrong
51 const size_t REHASH_LEN = 100;
52
53 const size_t ON_STACK_BUFFER_LENGTH = 128;
54
55 // --------------------------------------------------------------------------
56
57 inline bool symbol_equals_compact_hashtable_entry(Symbol* value, const char* key, int len) {
58 if (value->equals(key, len)) {
59 assert(value->is_permanent(), "must be shared");
60 return true;
61 } else {
62 return false;
63 }
64 }
65
66 static OffsetCompactHashtable<
67 const char*, Symbol*,
68 symbol_equals_compact_hashtable_entry
69 > _shared_table;
70
71 static OffsetCompactHashtable<
72 const char*, Symbol*,
73 symbol_equals_compact_hashtable_entry
74 > _dynamic_shared_table;
75
76 // --------------------------------------------------------------------------
77
78 typedef ConcurrentHashTable<SymbolTableConfig, mtSymbol> SymbolTableHash;
79 static SymbolTableHash* _local_table = NULL;
80
81 volatile bool SymbolTable::_has_work = 0;
82 volatile bool SymbolTable::_needs_rehashing = false;
83
84 // For statistics
85 static size_t _symbols_removed = 0;
86 static size_t _symbols_counted = 0;
87 static size_t _current_size = 0;
88
89 static volatile size_t _items_count = 0;
90 static volatile bool _has_items_to_clean = false;
91
92
93 static volatile bool _alt_hash = false;
94 static volatile bool _lookup_shared_first = false;
95
96 // Static arena for symbols that are not deallocated
97 Arena* SymbolTable::_arena = NULL;
98
99 static juint murmur_seed = 0;
100
101 static inline void log_trace_symboltable_helper(Symbol* sym, const char* msg) {
102 #ifndef PRODUCT
103 ResourceMark rm;
104 log_trace(symboltable)("%s [%s]", msg, sym->as_quoted_ascii());
105 #endif // PRODUCT
106 }
107
108 // Pick hashing algorithm.
109 static uintx hash_symbol(const char* s, int len, bool useAlt) {
110 return useAlt ?
111 AltHashing::murmur3_32(murmur_seed, (const jbyte*)s, len) :
112 java_lang_String::hash_code((const jbyte*)s, len);
113 }
114
115 #if INCLUDE_CDS
116 static uintx hash_shared_symbol(const char* s, int len) {
117 return java_lang_String::hash_code((const jbyte*)s, len);
118 }
119 #endif
120
121 class SymbolTableConfig : public AllStatic {
122 private:
123 public:
124 typedef Symbol* Value; // value of the Node in the hashtable
125
126 static uintx get_hash(Value const& value, bool* is_dead) {
127 *is_dead = (value->refcount() == 0);
128 if (*is_dead) {
129 return 0;
130 } else {
131 return hash_symbol((const char*)value->bytes(), value->utf8_length(), _alt_hash);
132 }
133 }
134 // We use default allocation/deallocation but counted
135 static void* allocate_node(size_t size, Value const& value) {
136 SymbolTable::item_added();
137 return AllocateHeap(size, mtSymbol);
138 }
139 static void free_node(void* memory, Value const& value) {
140 // We get here because #1 some threads lost a race to insert a newly created Symbol
141 // or #2 we're cleaning up unused symbol.
142 // If #1, then the symbol can be either permanent,
143 // or regular newly created one (refcount==1)
144 // If #2, then the symbol is dead (refcount==0)
145 assert(value->is_permanent() || (value->refcount() == 1) || (value->refcount() == 0),
146 "refcount %d", value->refcount());
147 if (value->refcount() == 1) {
148 value->decrement_refcount();
149 assert(value->refcount() == 0, "expected dead symbol");
150 }
151 SymbolTable::delete_symbol(value);
152 FreeHeap(memory);
153 SymbolTable::item_removed();
154 }
155 };
156
157 static size_t ceil_log2(size_t value) {
158 size_t ret;
159 for (ret = 1; ((size_t)1 << ret) < value; ++ret);
160 return ret;
161 }
162
163 void SymbolTable::create_table () {
164 size_t start_size_log_2 = ceil_log2(SymbolTableSize);
165 _current_size = ((size_t)1) << start_size_log_2;
166 log_trace(symboltable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")",
167 _current_size, start_size_log_2);
168 _local_table = new SymbolTableHash(start_size_log_2, END_SIZE, REHASH_LEN);
169
170 // Initialize the arena for global symbols, size passed in depends on CDS.
171 if (symbol_alloc_arena_size == 0) {
172 _arena = new (mtSymbol) Arena(mtSymbol);
173 } else {
174 _arena = new (mtSymbol) Arena(mtSymbol, symbol_alloc_arena_size);
175 }
176 }
177
178 void SymbolTable::delete_symbol(Symbol* sym) {
179 if (sym->is_permanent()) {
180 MutexLocker ml(SymbolArena_lock, Mutex::_no_safepoint_check_flag); // Protect arena
181 // Deleting permanent symbol should not occur very often (insert race condition),
182 // so log it.
183 log_trace_symboltable_helper(sym, "Freeing permanent symbol");
184 if (!arena()->Afree(sym, sym->size())) {
185 log_trace_symboltable_helper(sym, "Leaked permanent symbol");
186 }
187 } else {
188 delete sym;
189 }
190 }
191
192 void SymbolTable::reset_has_items_to_clean() { Atomic::store(&_has_items_to_clean, false); }
193 void SymbolTable::mark_has_items_to_clean() { Atomic::store(&_has_items_to_clean, true); }
194 bool SymbolTable::has_items_to_clean() { return Atomic::load(&_has_items_to_clean); }
195
196 void SymbolTable::item_added() {
197 Atomic::inc(&_items_count);
198 }
199
200 void SymbolTable::item_removed() {
201 Atomic::inc(&(_symbols_removed));
202 Atomic::dec(&_items_count);
203 }
204
205 double SymbolTable::get_load_factor() {
206 return (double)_items_count/_current_size;
207 }
208
209 size_t SymbolTable::table_size() {
210 return ((size_t)1) << _local_table->get_size_log2(Thread::current());
211 }
212
213 void SymbolTable::trigger_cleanup() {
214 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
215 _has_work = true;
216 Service_lock->notify_all();
217 }
218
219 Symbol* SymbolTable::allocate_symbol(const char* name, int len, bool c_heap) {
220 assert (len <= Symbol::max_length(), "should be checked by caller");
221
222 Symbol* sym;
223 if (Arguments::is_dumping_archive()) {
224 c_heap = false;
225 }
226 if (c_heap) {
227 // refcount starts as 1
228 sym = new (len) Symbol((const u1*)name, len, 1);
229 assert(sym != NULL, "new should call vm_exit_out_of_memory if C_HEAP is exhausted");
230 } else {
231 // Allocate to global arena
232 MutexLocker ml(SymbolArena_lock, Mutex::_no_safepoint_check_flag); // Protect arena
233 sym = new (len, arena()) Symbol((const u1*)name, len, PERM_REFCOUNT);
234 }
235 return sym;
236 }
237
238 class SymbolsDo : StackObj {
239 SymbolClosure *_cl;
240 public:
241 SymbolsDo(SymbolClosure *cl) : _cl(cl) {}
242 bool operator()(Symbol** value) {
243 assert(value != NULL, "expected valid value");
244 assert(*value != NULL, "value should point to a symbol");
245 _cl->do_symbol(value);
246 return true;
247 };
248 };
249
250 class SharedSymbolIterator {
251 SymbolClosure* _symbol_closure;
252 public:
253 SharedSymbolIterator(SymbolClosure* f) : _symbol_closure(f) {}
254 void do_value(Symbol* symbol) {
255 _symbol_closure->do_symbol(&symbol);
256 }
257 };
258
259 // Call function for all symbols in the symbol table.
260 void SymbolTable::symbols_do(SymbolClosure *cl) {
261 // all symbols from shared table
262 SharedSymbolIterator iter(cl);
263 _shared_table.iterate(&iter);
264 _dynamic_shared_table.iterate(&iter);
265
266 // all symbols from the dynamic table
267 SymbolsDo sd(cl);
268 if (!_local_table->try_scan(Thread::current(), sd)) {
269 log_info(symboltable)("symbols_do unavailable at this moment");
270 }
271 }
272
273 class MetaspacePointersDo : StackObj {
274 MetaspaceClosure *_it;
275 public:
276 MetaspacePointersDo(MetaspaceClosure *it) : _it(it) {}
277 bool operator()(Symbol** value) {
278 assert(value != NULL, "expected valid value");
279 assert(*value != NULL, "value should point to a symbol");
280 _it->push(value);
281 return true;
282 };
283 };
284
285 void SymbolTable::metaspace_pointers_do(MetaspaceClosure* it) {
286 Arguments::assert_is_dumping_archive();
287 MetaspacePointersDo mpd(it);
288 _local_table->do_safepoint_scan(mpd);
289 }
290
291 Symbol* SymbolTable::lookup_dynamic(const char* name,
292 int len, unsigned int hash) {
293 Symbol* sym = do_lookup(name, len, hash);
294 assert((sym == NULL) || sym->refcount() != 0, "refcount must not be zero");
295 return sym;
296 }
297
298 #if INCLUDE_CDS
299 Symbol* SymbolTable::lookup_shared(const char* name,
300 int len, unsigned int hash) {
301 Symbol* sym = NULL;
302 if (!_shared_table.empty()) {
303 if (_alt_hash) {
304 // hash_code parameter may use alternate hashing algorithm but the shared table
305 // always uses the same original hash code.
306 hash = hash_shared_symbol(name, len);
307 }
308 sym = _shared_table.lookup(name, hash, len);
309 if (sym == NULL && DynamicArchive::is_mapped()) {
310 sym = _dynamic_shared_table.lookup(name, hash, len);
311 }
312 }
313 return sym;
314 }
315 #endif
316
317 Symbol* SymbolTable::lookup_common(const char* name,
318 int len, unsigned int hash) {
319 Symbol* sym;
320 if (_lookup_shared_first) {
321 sym = lookup_shared(name, len, hash);
322 if (sym == NULL) {
323 _lookup_shared_first = false;
324 sym = lookup_dynamic(name, len, hash);
325 }
326 } else {
327 sym = lookup_dynamic(name, len, hash);
328 if (sym == NULL) {
329 sym = lookup_shared(name, len, hash);
330 if (sym != NULL) {
331 _lookup_shared_first = true;
332 }
333 }
334 }
335 return sym;
336 }
337
338 Symbol* SymbolTable::new_symbol(const char* name, int len) {
339 unsigned int hash = hash_symbol(name, len, _alt_hash);
340 Symbol* sym = lookup_common(name, len, hash);
341 if (sym == NULL) {
342 sym = do_add_if_needed(name, len, hash, true);
343 }
344 assert(sym->refcount() != 0, "lookup should have incremented the count");
345 assert(sym->equals(name, len), "symbol must be properly initialized");
346 return sym;
347 }
348
349 Symbol* SymbolTable::new_symbol(const Symbol* sym, int begin, int end) {
350 assert(begin <= end && end <= sym->utf8_length(), "just checking");
351 assert(sym->refcount() != 0, "require a valid symbol");
352 const char* name = (const char*)sym->base() + begin;
353 int len = end - begin;
354 unsigned int hash = hash_symbol(name, len, _alt_hash);
355 Symbol* found = lookup_common(name, len, hash);
356 if (found == NULL) {
357 found = do_add_if_needed(name, len, hash, true);
358 }
359 return found;
360 }
361
362 class SymbolTableLookup : StackObj {
363 private:
364 Thread* _thread;
365 uintx _hash;
366 int _len;
367 const char* _str;
368 public:
369 SymbolTableLookup(const char* key, int len, uintx hash)
370 : _hash(hash), _len(len), _str(key) {}
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 return true;
382 } else {
383 assert(sym->refcount() == 0, "expected dead symbol");
384 *is_dead = true;
385 return false;
386 }
387 } else {
388 *is_dead = (sym->refcount() == 0);
389 return false;
390 }
391 }
392 };
393
394 class SymbolTableGet : public StackObj {
395 Symbol* _return;
396 public:
397 SymbolTableGet() : _return(NULL) {}
398 void operator()(Symbol** value) {
399 assert(value != NULL, "expected valid value");
400 assert(*value != NULL, "value should point to a symbol");
401 _return = *value;
402 }
403 Symbol* get_res_sym() const {
404 return _return;
405 }
406 };
407
408 Symbol* SymbolTable::do_lookup(const char* name, int len, uintx hash) {
409 Thread* thread = Thread::current();
410 SymbolTableLookup lookup(name, len, hash);
411 SymbolTableGet stg;
412 bool rehash_warning = false;
413 _local_table->get(thread, lookup, stg, &rehash_warning);
414 update_needs_rehash(rehash_warning);
415 Symbol* sym = stg.get_res_sym();
416 assert((sym == NULL) || sym->refcount() != 0, "found dead symbol");
417 return sym;
418 }
419
420 Symbol* SymbolTable::lookup_only(const char* name, int len, unsigned int& hash) {
421 hash = hash_symbol(name, len, _alt_hash);
422 return lookup_common(name, len, hash);
423 }
424
425 // Suggestion: Push unicode-based lookup all the way into the hashing
426 // and probing logic, so there is no need for convert_to_utf8 until
427 // an actual new Symbol* is created.
428 Symbol* SymbolTable::new_symbol(const jchar* name, int utf16_length) {
429 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
430 char stack_buf[ON_STACK_BUFFER_LENGTH];
431 if (utf8_length < (int) sizeof(stack_buf)) {
432 char* chars = stack_buf;
433 UNICODE::convert_to_utf8(name, utf16_length, chars);
434 return new_symbol(chars, utf8_length);
435 } else {
436 ResourceMark rm;
437 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
438 UNICODE::convert_to_utf8(name, utf16_length, chars);
439 return new_symbol(chars, utf8_length);
440 }
441 }
442
443 Symbol* SymbolTable::lookup_only_unicode(const jchar* name, int utf16_length,
444 unsigned int& hash) {
445 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
446 char stack_buf[ON_STACK_BUFFER_LENGTH];
447 if (utf8_length < (int) sizeof(stack_buf)) {
448 char* chars = stack_buf;
449 UNICODE::convert_to_utf8(name, utf16_length, chars);
450 return lookup_only(chars, utf8_length, hash);
451 } else {
452 ResourceMark rm;
453 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
454 UNICODE::convert_to_utf8(name, utf16_length, chars);
455 return lookup_only(chars, utf8_length, hash);
456 }
457 }
458
459 void SymbolTable::new_symbols(ClassLoaderData* loader_data, const constantPoolHandle& cp,
460 int names_count, const char** names, int* lengths,
461 int* cp_indices, unsigned int* hashValues) {
462 // Note that c_heap will be true for non-strong hidden classes and unsafe anonymous classes
463 // even if their loader is the boot loader because they will have a different cld.
464 bool c_heap = !loader_data->is_the_null_class_loader_data();
465 for (int i = 0; i < names_count; i++) {
466 const char *name = names[i];
467 int len = lengths[i];
468 unsigned int hash = hashValues[i];
469 assert(lookup_shared(name, len, hash) == NULL, "must have checked already");
470 Symbol* sym = do_add_if_needed(name, len, hash, c_heap);
471 assert(sym->refcount() != 0, "lookup should have incremented the count");
472 cp->symbol_at_put(cp_indices[i], sym);
473 }
474 }
475
476 Symbol* SymbolTable::do_add_if_needed(const char* name, int len, uintx hash, bool heap) {
477 SymbolTableLookup lookup(name, len, hash);
478 SymbolTableGet stg;
479 bool clean_hint = false;
480 bool rehash_warning = false;
481 Symbol* sym = NULL;
482 Thread* THREAD = Thread::current();
483
484 do {
485 // Callers have looked up the symbol once, insert the symbol.
486 sym = allocate_symbol(name, len, heap);
487 if (_local_table->insert(THREAD, lookup, sym, &rehash_warning, &clean_hint)) {
488 break;
489 }
490 // In case another thread did a concurrent add, return value already in the table.
491 // This could fail if the symbol got deleted concurrently, so loop back until success.
492 if (_local_table->get(THREAD, lookup, stg, &rehash_warning)) {
493 sym = stg.get_res_sym();
494 break;
495 }
496 } while(true);
497
498 update_needs_rehash(rehash_warning);
499
500 if (clean_hint) {
501 mark_has_items_to_clean();
502 check_concurrent_work();
503 }
504
505 assert((sym == NULL) || sym->refcount() != 0, "found dead symbol");
506 return sym;
507 }
508
509 Symbol* SymbolTable::new_permanent_symbol(const char* name) {
510 unsigned int hash = 0;
511 int len = (int)strlen(name);
512 Symbol* sym = SymbolTable::lookup_only(name, len, hash);
513 if (sym == NULL) {
514 sym = do_add_if_needed(name, len, hash, false);
515 }
516 if (!sym->is_permanent()) {
517 sym->make_permanent();
518 log_trace_symboltable_helper(sym, "Asked for a permanent symbol, but got a regular one");
519 }
520 return sym;
521 }
522
523 struct SizeFunc : StackObj {
524 size_t operator()(Symbol** value) {
525 assert(value != NULL, "expected valid value");
526 assert(*value != NULL, "value should point to a symbol");
527 return (*value)->size() * HeapWordSize;
528 };
529 };
530
531 TableStatistics SymbolTable::get_table_statistics() {
532 static TableStatistics ts;
533 SizeFunc sz;
534 ts = _local_table->statistics_get(Thread::current(), sz, ts);
535 return ts;
536 }
537
538 void SymbolTable::print_table_statistics(outputStream* st,
539 const char* table_name) {
540 SizeFunc sz;
541 _local_table->statistics_to(Thread::current(), sz, st, table_name);
542 }
543
544 // Verification
545 class VerifySymbols : StackObj {
546 public:
547 bool operator()(Symbol** value) {
548 guarantee(value != NULL, "expected valid value");
549 guarantee(*value != NULL, "value should point to a symbol");
550 Symbol* sym = *value;
551 guarantee(sym->equals((const char*)sym->bytes(), sym->utf8_length()),
552 "symbol must be internally consistent");
553 return true;
554 };
555 };
556
557 void SymbolTable::verify() {
558 Thread* thr = Thread::current();
559 VerifySymbols vs;
560 if (!_local_table->try_scan(thr, vs)) {
561 log_info(symboltable)("verify unavailable at this moment");
562 }
563 }
564
565 // Dumping
566 class DumpSymbol : StackObj {
567 Thread* _thr;
568 outputStream* _st;
569 public:
570 DumpSymbol(Thread* thr, outputStream* st) : _thr(thr), _st(st) {}
571 bool operator()(Symbol** value) {
572 assert(value != NULL, "expected valid value");
573 assert(*value != NULL, "value should point to a symbol");
574 Symbol* sym = *value;
575 const char* utf8_string = (const char*)sym->bytes();
576 int utf8_length = sym->utf8_length();
577 _st->print("%d %d: ", utf8_length, sym->refcount());
578 HashtableTextDump::put_utf8(_st, utf8_string, utf8_length);
579 _st->cr();
580 return true;
581 };
582 };
583
584 void SymbolTable::dump(outputStream* st, bool verbose) {
585 if (!verbose) {
586 print_table_statistics(st, "SymbolTable");
587 } else {
588 Thread* thr = Thread::current();
589 ResourceMark rm(thr);
590 st->print_cr("VERSION: 1.1");
591 DumpSymbol ds(thr, st);
592 if (!_local_table->try_scan(thr, ds)) {
593 log_info(symboltable)("dump unavailable at this moment");
594 }
595 }
596 }
597
598 #if INCLUDE_CDS
599 struct CopyToArchive : StackObj {
600 CompactHashtableWriter* _writer;
601 CopyToArchive(CompactHashtableWriter* writer) : _writer(writer) {}
602 bool operator()(Symbol** value) {
603 assert(value != NULL, "expected valid value");
604 assert(*value != NULL, "value should point to a symbol");
605 Symbol* sym = *value;
606 unsigned int fixed_hash = hash_shared_symbol((const char*)sym->bytes(), sym->utf8_length());
607 assert(fixed_hash == hash_symbol((const char*)sym->bytes(), sym->utf8_length(), false),
608 "must not rehash during dumping");
609 if (DynamicDumpSharedSpaces) {
610 sym = DynamicArchive::original_to_target(sym);
611 }
612 _writer->add(fixed_hash, MetaspaceShared::object_delta_u4(sym));
613 return true;
614 }
615 };
616
617 void SymbolTable::copy_shared_symbol_table(CompactHashtableWriter* writer) {
618 CopyToArchive copy(writer);
619 _local_table->do_safepoint_scan(copy);
620 }
621
622 size_t SymbolTable::estimate_size_for_archive() {
623 return CompactHashtableWriter::estimate_size(int(_items_count));
624 }
625
626 void SymbolTable::write_to_archive(bool is_static_archive) {
627 CompactHashtableWriter writer(int(_items_count),
628 &MetaspaceShared::stats()->symbol);
629 copy_shared_symbol_table(&writer);
630 if (is_static_archive) {
631 _shared_table.reset();
632 writer.dump(&_shared_table, "symbol");
633
634 // Verify table is correct
635 Symbol* sym = vmSymbols::java_lang_Object();
636 const char* name = (const char*)sym->bytes();
637 int len = sym->utf8_length();
638 unsigned int hash = hash_symbol(name, len, _alt_hash);
639 assert(sym == _shared_table.lookup(name, hash, len), "sanity");
640 } else {
641 _dynamic_shared_table.reset();
642 writer.dump(&_dynamic_shared_table, "symbol");
643 }
644 }
645
646 void SymbolTable::serialize_shared_table_header(SerializeClosure* soc,
647 bool is_static_archive) {
648 OffsetCompactHashtable<const char*, Symbol*, symbol_equals_compact_hashtable_entry> * table;
649 if (is_static_archive) {
650 table = &_shared_table;
651 } else {
652 table = &_dynamic_shared_table;
653 }
654 table->serialize_header(soc);
655 if (soc->writing()) {
656 // Sanity. Make sure we don't use the shared table at dump time
657 table->reset();
658 }
659 }
660 #endif //INCLUDE_CDS
661
662 // Concurrent work
663 void SymbolTable::grow(JavaThread* jt) {
664 SymbolTableHash::GrowTask gt(_local_table);
665 if (!gt.prepare(jt)) {
666 return;
667 }
668 log_trace(symboltable)("Started to grow");
669 {
670 TraceTime timer("Grow", TRACETIME_LOG(Debug, symboltable, perf));
671 while (gt.do_task(jt)) {
672 gt.pause(jt);
673 {
674 ThreadBlockInVM tbivm(jt);
675 }
676 gt.cont(jt);
677 }
678 }
679 gt.done(jt);
680 _current_size = table_size();
681 log_debug(symboltable)("Grown to size:" SIZE_FORMAT, _current_size);
682 }
683
684 struct SymbolTableDoDelete : StackObj {
685 size_t _deleted;
686 SymbolTableDoDelete() : _deleted(0) {}
687 void operator()(Symbol** value) {
688 assert(value != NULL, "expected valid value");
689 assert(*value != NULL, "value should point to a symbol");
690 Symbol *sym = *value;
691 assert(sym->refcount() == 0, "refcount");
692 _deleted++;
693 }
694 };
695
696 struct SymbolTableDeleteCheck : StackObj {
697 size_t _processed;
698 SymbolTableDeleteCheck() : _processed(0) {}
699 bool operator()(Symbol** value) {
700 assert(value != NULL, "expected valid value");
701 assert(*value != NULL, "value should point to a symbol");
702 _processed++;
703 Symbol *sym = *value;
704 return (sym->refcount() == 0);
705 }
706 };
707
708 void SymbolTable::clean_dead_entries(JavaThread* jt) {
709 SymbolTableHash::BulkDeleteTask bdt(_local_table);
710 if (!bdt.prepare(jt)) {
711 return;
712 }
713
714 SymbolTableDeleteCheck stdc;
715 SymbolTableDoDelete stdd;
716 {
717 TraceTime timer("Clean", TRACETIME_LOG(Debug, symboltable, perf));
718 while (bdt.do_task(jt, stdc, stdd)) {
719 bdt.pause(jt);
720 {
721 ThreadBlockInVM tbivm(jt);
722 }
723 bdt.cont(jt);
724 }
725 reset_has_items_to_clean();
726 bdt.done(jt);
727 }
728
729 Atomic::add(&_symbols_counted, stdc._processed);
730
731 log_debug(symboltable)("Cleaned " SIZE_FORMAT " of " SIZE_FORMAT,
732 stdd._deleted, stdc._processed);
733 }
734
735 void SymbolTable::check_concurrent_work() {
736 if (_has_work) {
737 return;
738 }
739 // We should clean/resize if we have
740 // more items than preferred load factor or
741 // more dead items than water mark.
742 if (has_items_to_clean() || (get_load_factor() > PREF_AVG_LIST_LEN)) {
743 log_debug(symboltable)("Concurrent work triggered, load factor: %f, items to clean: %s",
744 get_load_factor(), has_items_to_clean() ? "true" : "false");
745 trigger_cleanup();
746 }
747 }
748
749 void SymbolTable::do_concurrent_work(JavaThread* jt) {
750 double load_factor = get_load_factor();
751 log_debug(symboltable, perf)("Concurrent work, live factor: %g", load_factor);
752 // We prefer growing, since that also removes dead items
753 if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {
754 grow(jt);
755 } else {
756 clean_dead_entries(jt);
757 }
758 _has_work = false;
759 }
760
761 // Rehash
762 bool SymbolTable::do_rehash() {
763 if (!_local_table->is_safepoint_safe()) {
764 return false;
765 }
766
767 // We use current size
768 size_t new_size = _local_table->get_size_log2(Thread::current());
769 SymbolTableHash* new_table = new SymbolTableHash(new_size, END_SIZE, REHASH_LEN);
770 // Use alt hash from now on
771 _alt_hash = true;
772 if (!_local_table->try_move_nodes_to(Thread::current(), new_table)) {
773 _alt_hash = false;
774 delete new_table;
775 return false;
776 }
777
778 // free old table
779 delete _local_table;
780 _local_table = new_table;
781
782 return true;
783 }
784
785 void SymbolTable::rehash_table() {
786 static bool rehashed = false;
787 log_debug(symboltable)("Table imbalanced, rehashing called.");
788
789 // Grow instead of rehash.
790 if (get_load_factor() > PREF_AVG_LIST_LEN &&
791 !_local_table->is_max_size_reached()) {
792 log_debug(symboltable)("Choosing growing over rehashing.");
793 trigger_cleanup();
794 _needs_rehashing = false;
795 return;
796 }
797
798 // Already rehashed.
799 if (rehashed) {
800 log_warning(symboltable)("Rehashing already done, still long lists.");
801 trigger_cleanup();
802 _needs_rehashing = false;
803 return;
804 }
805
806 murmur_seed = AltHashing::compute_seed();
807
808 if (do_rehash()) {
809 rehashed = true;
810 } else {
811 log_info(symboltable)("Resizes in progress rehashing skipped.");
812 }
813
814 _needs_rehashing = false;
815 }
816
817 //---------------------------------------------------------------------------
818 // Non-product code
819
820 #ifndef PRODUCT
821
822 class HistogramIterator : StackObj {
823 public:
824 static const size_t results_length = 100;
825 size_t counts[results_length];
826 size_t sizes[results_length];
827 size_t total_size;
828 size_t total_count;
829 size_t total_length;
830 size_t max_length;
831 size_t out_of_range_count;
832 size_t out_of_range_size;
833 HistogramIterator() : total_size(0), total_count(0), total_length(0),
834 max_length(0), out_of_range_count(0), out_of_range_size(0) {
835 // initialize results to zero
836 for (size_t i = 0; i < results_length; i++) {
837 counts[i] = 0;
838 sizes[i] = 0;
839 }
840 }
841 bool operator()(Symbol** value) {
842 assert(value != NULL, "expected valid value");
843 assert(*value != NULL, "value should point to a symbol");
844 Symbol* sym = *value;
845 size_t size = sym->size();
846 size_t len = sym->utf8_length();
847 if (len < results_length) {
848 counts[len]++;
849 sizes[len] += size;
850 } else {
851 out_of_range_count++;
852 out_of_range_size += size;
853 }
854 total_count++;
855 total_size += size;
856 total_length += len;
857 max_length = MAX2(max_length, len);
858
859 return true;
860 };
861 };
862
863 void SymbolTable::print_histogram() {
864 HistogramIterator hi;
865 _local_table->do_scan(Thread::current(), hi);
866 tty->print_cr("Symbol Table Histogram:");
867 tty->print_cr(" Total number of symbols " SIZE_FORMAT_W(7), hi.total_count);
868 tty->print_cr(" Total size in memory " SIZE_FORMAT_W(7) "K",
869 (hi.total_size * wordSize) / 1024);
870 tty->print_cr(" Total counted " SIZE_FORMAT_W(7), _symbols_counted);
871 tty->print_cr(" Total removed " SIZE_FORMAT_W(7), _symbols_removed);
872 if (_symbols_counted > 0) {
873 tty->print_cr(" Percent removed %3.2f",
874 ((float)_symbols_removed / _symbols_counted) * 100);
875 }
876 tty->print_cr(" Reference counts " SIZE_FORMAT_W(7), Symbol::_total_count);
877 tty->print_cr(" Symbol arena used " SIZE_FORMAT_W(7) "K", arena()->used() / 1024);
878 tty->print_cr(" Symbol arena size " SIZE_FORMAT_W(7) "K", arena()->size_in_bytes() / 1024);
879 tty->print_cr(" Total symbol length " SIZE_FORMAT_W(7), hi.total_length);
880 tty->print_cr(" Maximum symbol length " SIZE_FORMAT_W(7), hi.max_length);
881 tty->print_cr(" Average symbol length %7.2f", ((float)hi.total_length / hi.total_count));
882 tty->print_cr(" Symbol length histogram:");
883 tty->print_cr(" %6s %10s %10s", "Length", "#Symbols", "Size");
884 for (size_t i = 0; i < hi.results_length; i++) {
885 if (hi.counts[i] > 0) {
886 tty->print_cr(" " SIZE_FORMAT_W(6) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) "K",
887 i, hi.counts[i], (hi.sizes[i] * wordSize) / 1024);
888 }
889 }
890 tty->print_cr(" >=" SIZE_FORMAT_W(6) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) "K\n",
891 hi.results_length, hi.out_of_range_count, (hi.out_of_range_size*wordSize) / 1024);
892 }
893 #endif // PRODUCT
894
895 // Utility for dumping symbols
896 SymboltableDCmd::SymboltableDCmd(outputStream* output, bool heap) :
897 DCmdWithParser(output, heap),
898 _verbose("-verbose", "Dump the content of each symbol in the table",
899 "BOOLEAN", false, "false") {
900 _dcmdparser.add_dcmd_option(&_verbose);
901 }
902
903 void SymboltableDCmd::execute(DCmdSource source, TRAPS) {
904 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSymbols,
905 _verbose.value());
906 VMThread::execute(&dumper);
907 }
908
909 int SymboltableDCmd::num_arguments() {
910 ResourceMark rm;
911 SymboltableDCmd* dcmd = new SymboltableDCmd(NULL, false);
912 if (dcmd != NULL) {
913 DCmdMark mark(dcmd);
914 return dcmd->_dcmdparser.num_arguments();
915 } else {
916 return 0;
917 }
918 }
--- EOF ---