1 /* 2 * Copyright (c) 1997, 2024, 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 "cds/archiveBuilder.hpp" 27 #include "cds/cdsConfig.hpp" 28 #include "cds/dynamicArchive.hpp" 29 #include "classfile/altHashing.hpp" 30 #include "classfile/classLoaderData.hpp" 31 #include "classfile/compactHashtable.hpp" 32 #include "classfile/javaClasses.hpp" 33 #include "classfile/symbolTable.hpp" 34 #include "memory/allocation.inline.hpp" 35 #include "memory/metaspaceClosure.hpp" 36 #include "memory/resourceArea.hpp" 37 #include "oops/oop.inline.hpp" 38 #include "runtime/atomic.hpp" 39 #include "runtime/interfaceSupport.inline.hpp" 40 #include "runtime/timerTrace.hpp" 41 #include "runtime/trimNativeHeap.hpp" 42 #include "services/diagnosticCommand.hpp" 43 #include "utilities/concurrentHashTable.inline.hpp" 44 #include "utilities/concurrentHashTableTasks.inline.hpp" 45 #include "utilities/utf8.hpp" 46 47 // We used to not resize at all, so let's be conservative 48 // and not set it too short before we decide to resize, 49 // to match previous startup behavior 50 const double PREF_AVG_LIST_LEN = 8.0; 51 // 2^24 is max size, like StringTable. 52 const size_t END_SIZE = 24; 53 // If a chain gets to 100 something might be wrong 54 const size_t REHASH_LEN = 100; 55 56 const size_t ON_STACK_BUFFER_LENGTH = 128; 57 58 // -------------------------------------------------------------------------- 59 60 inline bool symbol_equals_compact_hashtable_entry(Symbol* value, const char* key, int len) { 61 if (value->equals(key, len)) { 62 return true; 63 } else { 64 return false; 65 } 66 } 67 68 static OffsetCompactHashtable< 69 const char*, Symbol*, 70 symbol_equals_compact_hashtable_entry 71 > _shared_table, _dynamic_shared_table, _shared_table_for_dumping; 72 73 // -------------------------------------------------------------------------- 74 75 typedef ConcurrentHashTable<SymbolTableConfig, mtSymbol> SymbolTableHash; 76 static SymbolTableHash* _local_table = nullptr; 77 78 volatile bool SymbolTable::_has_work = 0; 79 volatile bool SymbolTable::_needs_rehashing = false; 80 81 // For statistics 82 static size_t _symbols_removed = 0; 83 static size_t _symbols_counted = 0; 84 static size_t _current_size = 0; 85 86 static volatile size_t _items_count = 0; 87 static volatile bool _has_items_to_clean = false; 88 89 90 static volatile bool _alt_hash = false; 91 92 #ifdef USE_LIBRARY_BASED_TLS_ONLY 93 static volatile bool _lookup_shared_first = false; 94 #else 95 // "_lookup_shared_first" can get highly contended with many cores if multiple threads 96 // are updating "lookup success history" in a global shared variable. If built-in TLS is available, use it. 97 static THREAD_LOCAL bool _lookup_shared_first = false; 98 #endif 99 100 // Static arena for symbols that are not deallocated 101 Arena* SymbolTable::_arena = nullptr; 102 103 static bool _rehashed = false; 104 static uint64_t _alt_hash_seed = 0; 105 106 static inline void log_trace_symboltable_helper(Symbol* sym, const char* msg) { 107 #ifndef PRODUCT 108 ResourceMark rm; 109 log_trace(symboltable)("%s [%s]", msg, sym->as_quoted_ascii()); 110 #endif // PRODUCT 111 } 112 113 // Pick hashing algorithm. 114 static unsigned int hash_symbol(const char* s, int len, bool useAlt) { 115 return useAlt ? 116 AltHashing::halfsiphash_32(_alt_hash_seed, (const uint8_t*)s, len) : 117 java_lang_String::hash_code((const jbyte*)s, len); 118 } 119 120 #if INCLUDE_CDS 121 static unsigned int hash_shared_symbol(const char* s, int len) { 122 return java_lang_String::hash_code((const jbyte*)s, len); 123 } 124 #endif 125 126 class SymbolTableConfig : public AllStatic { 127 128 public: 129 typedef Symbol Value; // value of the Node in the hashtable 130 131 static uintx get_hash(Value const& value, bool* is_dead) { 132 *is_dead = (value.refcount() == 0); 133 if (*is_dead) { 134 return 0; 135 } else { 136 return hash_symbol((const char*)value.bytes(), value.utf8_length(), _alt_hash); 137 } 138 } 139 // We use default allocation/deallocation but counted 140 static void* allocate_node(void* context, size_t size, Value const& value) { 141 SymbolTable::item_added(); 142 return allocate_node_impl(size, value); 143 } 144 static void free_node(void* context, void* memory, Value & value) { 145 // We get here because #1 some threads lost a race to insert a newly created Symbol 146 // or #2 we're cleaning up unused symbol. 147 // If #1, then the symbol can be either permanent, 148 // or regular newly created one (refcount==1) 149 // If #2, then the symbol is dead (refcount==0) 150 assert(value.is_permanent() || (value.refcount() == 1) || (value.refcount() == 0), 151 "refcount %d", value.refcount()); 152 #if INCLUDE_CDS 153 if (CDSConfig::is_dumping_static_archive()) { 154 // We have allocated with MetaspaceShared::symbol_space_alloc(). No deallocation is needed. 155 // Unreferenced Symbols will not be copied into the archive. 156 return; 157 } 158 #endif 159 if (value.refcount() == 1) { 160 value.decrement_refcount(); 161 assert(value.refcount() == 0, "expected dead symbol"); 162 } 163 if (value.refcount() != PERM_REFCOUNT) { 164 FreeHeap(memory); 165 } else { 166 MutexLocker ml(SymbolArena_lock, Mutex::_no_safepoint_check_flag); // Protect arena 167 // Deleting permanent symbol should not occur very often (insert race condition), 168 // so log it. 169 log_trace_symboltable_helper(&value, "Freeing permanent symbol"); 170 size_t alloc_size = SymbolTableHash::get_dynamic_node_size(value.byte_size()); 171 if (!SymbolTable::arena()->Afree(memory, alloc_size)) { 172 log_trace_symboltable_helper(&value, "Leaked permanent symbol"); 173 } 174 } 175 SymbolTable::item_removed(); 176 } 177 178 private: 179 static void* allocate_node_impl(size_t size, Value const& value) { 180 size_t alloc_size = SymbolTableHash::get_dynamic_node_size(value.byte_size()); 181 #if INCLUDE_CDS 182 if (CDSConfig::is_dumping_static_archive()) { 183 MutexLocker ml(DumpRegion_lock, Mutex::_no_safepoint_check_flag); 184 // To get deterministic output from -Xshare:dump, we ensure that Symbols are allocated in 185 // increasing addresses. When the symbols are copied into the archive, we preserve their 186 // relative address order (sorted, see ArchiveBuilder::gather_klasses_and_symbols). 187 // 188 // We cannot use arena because arena chunks are allocated by the OS. As a result, for example, 189 // the archived symbol of "java/lang/Object" may sometimes be lower than "java/lang/String", and 190 // sometimes be higher. This would cause non-deterministic contents in the archive. 191 DEBUG_ONLY(static void* last = 0); 192 void* p = (void*)MetaspaceShared::symbol_space_alloc(alloc_size); 193 assert(p > last, "must increase monotonically"); 194 DEBUG_ONLY(last = p); 195 return p; 196 } 197 #endif 198 if (value.refcount() != PERM_REFCOUNT) { 199 return AllocateHeap(alloc_size, mtSymbol); 200 } else { 201 // Allocate to global arena 202 MutexLocker ml(SymbolArena_lock, Mutex::_no_safepoint_check_flag); // Protect arena 203 return SymbolTable::arena()->Amalloc(alloc_size); 204 } 205 } 206 }; 207 208 void SymbolTable::create_table () { 209 size_t start_size_log_2 = ceil_log2(SymbolTableSize); 210 _current_size = ((size_t)1) << start_size_log_2; 211 log_trace(symboltable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")", 212 _current_size, start_size_log_2); 213 _local_table = new SymbolTableHash(start_size_log_2, END_SIZE, REHASH_LEN, true); 214 215 // Initialize the arena for global symbols, size passed in depends on CDS. 216 if (symbol_alloc_arena_size == 0) { 217 _arena = new (mtSymbol) Arena(mtSymbol); 218 } else { 219 _arena = new (mtSymbol) Arena(mtSymbol, Arena::Tag::tag_other, symbol_alloc_arena_size); 220 } 221 } 222 223 void SymbolTable::reset_has_items_to_clean() { Atomic::store(&_has_items_to_clean, false); } 224 void SymbolTable::mark_has_items_to_clean() { Atomic::store(&_has_items_to_clean, true); } 225 bool SymbolTable::has_items_to_clean() { return Atomic::load(&_has_items_to_clean); } 226 227 void SymbolTable::item_added() { 228 Atomic::inc(&_items_count); 229 } 230 231 void SymbolTable::item_removed() { 232 Atomic::inc(&(_symbols_removed)); 233 Atomic::dec(&_items_count); 234 } 235 236 double SymbolTable::get_load_factor() { 237 return (double)_items_count/(double)_current_size; 238 } 239 240 size_t SymbolTable::table_size() { 241 return ((size_t)1) << _local_table->get_size_log2(Thread::current()); 242 } 243 244 bool SymbolTable::has_work() { return Atomic::load_acquire(&_has_work); } 245 246 void SymbolTable::trigger_cleanup() { 247 // Avoid churn on ServiceThread 248 if (!has_work()) { 249 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag); 250 _has_work = true; 251 Service_lock->notify_all(); 252 } 253 } 254 255 class SymbolsDo : StackObj { 256 SymbolClosure *_cl; 257 public: 258 SymbolsDo(SymbolClosure *cl) : _cl(cl) {} 259 bool operator()(Symbol* value) { 260 assert(value != nullptr, "expected valid value"); 261 _cl->do_symbol(&value); 262 return true; 263 }; 264 }; 265 266 class SharedSymbolIterator { 267 SymbolClosure* _symbol_closure; 268 public: 269 SharedSymbolIterator(SymbolClosure* f) : _symbol_closure(f) {} 270 void do_value(Symbol* symbol) { 271 _symbol_closure->do_symbol(&symbol); 272 } 273 }; 274 275 // Call function for all symbols in the symbol table. 276 void SymbolTable::symbols_do(SymbolClosure *cl) { 277 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint"); 278 // all symbols from shared table 279 SharedSymbolIterator iter(cl); 280 _shared_table.iterate(&iter); 281 _dynamic_shared_table.iterate(&iter); 282 283 // all symbols from the dynamic table 284 SymbolsDo sd(cl); 285 _local_table->do_safepoint_scan(sd); 286 } 287 288 // Call function for all symbols in shared table. Used by -XX:+PrintSharedArchiveAndExit 289 void SymbolTable::shared_symbols_do(SymbolClosure *cl) { 290 SharedSymbolIterator iter(cl); 291 _shared_table.iterate(&iter); 292 _dynamic_shared_table.iterate(&iter); 293 } 294 295 Symbol* SymbolTable::lookup_dynamic(const char* name, 296 int len, unsigned int hash) { 297 Symbol* sym = do_lookup(name, len, hash); 298 assert((sym == nullptr) || sym->refcount() != 0, "refcount must not be zero"); 299 return sym; 300 } 301 302 #if INCLUDE_CDS 303 Symbol* SymbolTable::lookup_shared(const char* name, 304 int len, unsigned int hash) { 305 Symbol* sym = nullptr; 306 if (!_shared_table.empty()) { 307 if (_alt_hash) { 308 // hash_code parameter may use alternate hashing algorithm but the shared table 309 // always uses the same original hash code. 310 hash = hash_shared_symbol(name, len); 311 } 312 sym = _shared_table.lookup(name, hash, len); 313 if (sym == nullptr && DynamicArchive::is_mapped()) { 314 sym = _dynamic_shared_table.lookup(name, hash, len); 315 } 316 } 317 return sym; 318 } 319 #endif 320 321 Symbol* SymbolTable::lookup_common(const char* name, 322 int len, unsigned int hash) { 323 Symbol* sym; 324 if (_lookup_shared_first) { 325 sym = lookup_shared(name, len, hash); 326 if (sym == nullptr) { 327 _lookup_shared_first = false; 328 sym = lookup_dynamic(name, len, hash); 329 } 330 } else { 331 sym = lookup_dynamic(name, len, hash); 332 if (sym == nullptr) { 333 sym = lookup_shared(name, len, hash); 334 if (sym != nullptr) { 335 _lookup_shared_first = true; 336 } 337 } 338 } 339 return sym; 340 } 341 342 // Symbols should represent entities from the constant pool that are 343 // limited to <64K in length, but usage errors creep in allowing Symbols 344 // to be used for arbitrary strings. For debug builds we will assert if 345 // a string is too long, whereas product builds will truncate it. 346 static int check_length(const char* name, int len) { 347 assert(len <= Symbol::max_length(), 348 "String length %d exceeds the maximum Symbol length of %d", len, Symbol::max_length()); 349 if (len > Symbol::max_length()) { 350 warning("A string \"%.80s ... %.80s\" exceeds the maximum Symbol " 351 "length of %d and has been truncated", name, (name + len - 80), Symbol::max_length()); 352 len = Symbol::max_length(); 353 } 354 return len; 355 } 356 357 Symbol* SymbolTable::new_symbol(const char* name, int len) { 358 len = check_length(name, len); 359 unsigned int hash = hash_symbol(name, len, _alt_hash); 360 Symbol* sym = lookup_common(name, len, hash); 361 if (sym == nullptr) { 362 sym = do_add_if_needed(name, len, hash, /* is_permanent */ false); 363 } 364 assert(sym->refcount() != 0, "lookup should have incremented the count"); 365 assert(sym->equals(name, len), "symbol must be properly initialized"); 366 return sym; 367 } 368 369 Symbol* SymbolTable::new_symbol(const Symbol* sym, int begin, int end) { 370 assert(begin <= end && end <= sym->utf8_length(), "just checking"); 371 assert(sym->refcount() != 0, "require a valid symbol"); 372 const char* name = (const char*)sym->base() + begin; 373 int len = end - begin; 374 assert(len <= Symbol::max_length(), "sanity"); 375 unsigned int hash = hash_symbol(name, len, _alt_hash); 376 Symbol* found = lookup_common(name, len, hash); 377 if (found == nullptr) { 378 found = do_add_if_needed(name, len, hash, /* is_permanent */ false); 379 } 380 return found; 381 } 382 383 class SymbolTableLookup : StackObj { 384 private: 385 uintx _hash; 386 int _len; 387 const char* _str; 388 public: 389 SymbolTableLookup(const char* key, int len, uintx hash) 390 : _hash(hash), _len(len), _str(key) {} 391 uintx get_hash() const { 392 return _hash; 393 } 394 // Note: When equals() returns "true", the symbol's refcount is incremented. This is 395 // needed to ensure that the symbol is kept alive before equals() returns to the caller, 396 // so that another thread cannot clean the symbol up concurrently. The caller is 397 // responsible for decrementing the refcount, when the symbol is no longer needed. 398 bool equals(Symbol* value) { 399 assert(value != nullptr, "expected valid value"); 400 Symbol *sym = value; 401 if (sym->equals(_str, _len)) { 402 if (sym->try_increment_refcount()) { 403 // something is referencing this symbol now. 404 return true; 405 } else { 406 assert(sym->refcount() == 0, "expected dead symbol"); 407 return false; 408 } 409 } else { 410 return false; 411 } 412 } 413 bool is_dead(Symbol* value) { 414 return value->refcount() == 0; 415 } 416 }; 417 418 class SymbolTableGet : public StackObj { 419 Symbol* _return; 420 public: 421 SymbolTableGet() : _return(nullptr) {} 422 void operator()(Symbol* value) { 423 assert(value != nullptr, "expected valid value"); 424 _return = value; 425 } 426 Symbol* get_res_sym() const { 427 return _return; 428 } 429 }; 430 431 void SymbolTable::update_needs_rehash(bool rehash) { 432 if (rehash) { 433 _needs_rehashing = true; 434 trigger_cleanup(); 435 } 436 } 437 438 Symbol* SymbolTable::do_lookup(const char* name, int len, uintx hash) { 439 Thread* thread = Thread::current(); 440 SymbolTableLookup lookup(name, len, hash); 441 SymbolTableGet stg; 442 bool rehash_warning = false; 443 _local_table->get(thread, lookup, stg, &rehash_warning); 444 update_needs_rehash(rehash_warning); 445 Symbol* sym = stg.get_res_sym(); 446 assert((sym == nullptr) || sym->refcount() != 0, "found dead symbol"); 447 return sym; 448 } 449 450 Symbol* SymbolTable::lookup_only(const char* name, int len, unsigned int& hash) { 451 hash = hash_symbol(name, len, _alt_hash); 452 return lookup_common(name, len, hash); 453 } 454 455 // Suggestion: Push unicode-based lookup all the way into the hashing 456 // and probing logic, so there is no need for convert_to_utf8 until 457 // an actual new Symbol* is created. 458 Symbol* SymbolTable::new_symbol(const jchar* name, int utf16_length) { 459 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length); 460 char stack_buf[ON_STACK_BUFFER_LENGTH]; 461 if (utf8_length < (int) sizeof(stack_buf)) { 462 char* chars = stack_buf; 463 UNICODE::convert_to_utf8(name, utf16_length, chars); 464 return new_symbol(chars, utf8_length); 465 } else { 466 ResourceMark rm; 467 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1); 468 UNICODE::convert_to_utf8(name, utf16_length, chars); 469 return new_symbol(chars, utf8_length); 470 } 471 } 472 473 Symbol* SymbolTable::lookup_only_unicode(const jchar* name, int utf16_length, 474 unsigned int& hash) { 475 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length); 476 char stack_buf[ON_STACK_BUFFER_LENGTH]; 477 if (utf8_length < (int) sizeof(stack_buf)) { 478 char* chars = stack_buf; 479 UNICODE::convert_to_utf8(name, utf16_length, chars); 480 return lookup_only(chars, utf8_length, hash); 481 } else { 482 ResourceMark rm; 483 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1); 484 UNICODE::convert_to_utf8(name, utf16_length, chars); 485 return lookup_only(chars, utf8_length, hash); 486 } 487 } 488 489 void SymbolTable::new_symbols(ClassLoaderData* loader_data, const constantPoolHandle& cp, 490 int names_count, const char** names, int* lengths, 491 int* cp_indices, unsigned int* hashValues) { 492 // Note that is_permanent will be false for non-strong hidden classes. 493 // even if their loader is the boot loader because they will have a different cld. 494 bool is_permanent = loader_data->is_the_null_class_loader_data(); 495 for (int i = 0; i < names_count; i++) { 496 const char *name = names[i]; 497 int len = lengths[i]; 498 assert(len <= Symbol::max_length(), "must be - these come from the constant pool"); 499 unsigned int hash = hashValues[i]; 500 assert(lookup_shared(name, len, hash) == nullptr, "must have checked already"); 501 Symbol* sym = do_add_if_needed(name, len, hash, is_permanent); 502 assert(sym->refcount() != 0, "lookup should have incremented the count"); 503 cp->symbol_at_put(cp_indices[i], sym); 504 } 505 } 506 507 Symbol* SymbolTable::do_add_if_needed(const char* name, int len, uintx hash, bool is_permanent) { 508 assert(len <= Symbol::max_length(), "caller should have ensured this"); 509 SymbolTableLookup lookup(name, len, hash); 510 SymbolTableGet stg; 511 bool clean_hint = false; 512 bool rehash_warning = false; 513 Thread* current = Thread::current(); 514 Symbol* sym; 515 516 ResourceMark rm(current); 517 const int alloc_size = Symbol::byte_size(len); 518 u1* u1_buf = NEW_RESOURCE_ARRAY_IN_THREAD(current, u1, alloc_size); 519 Symbol* tmp = ::new ((void*)u1_buf) Symbol((const u1*)name, len, 520 (is_permanent || CDSConfig::is_dumping_static_archive()) ? PERM_REFCOUNT : 1); 521 522 do { 523 if (_local_table->insert(current, lookup, *tmp, &rehash_warning, &clean_hint)) { 524 if (_local_table->get(current, lookup, stg, &rehash_warning)) { 525 sym = stg.get_res_sym(); 526 // The get adds one to ref count, but we inserted with our ref already included. 527 // Therefore decrement with one. 528 if (sym->refcount() != PERM_REFCOUNT) { 529 sym->decrement_refcount(); 530 } 531 break; 532 } 533 } 534 535 // In case another thread did a concurrent add, return value already in the table. 536 // This could fail if the symbol got deleted concurrently, so loop back until success. 537 if (_local_table->get(current, lookup, stg, &rehash_warning)) { 538 // The lookup added a refcount, which is ours. 539 sym = stg.get_res_sym(); 540 break; 541 } 542 } while(true); 543 544 update_needs_rehash(rehash_warning); 545 546 if (clean_hint) { 547 mark_has_items_to_clean(); 548 check_concurrent_work(); 549 } 550 551 assert((sym == nullptr) || sym->refcount() != 0, "found dead symbol"); 552 return sym; 553 } 554 555 Symbol* SymbolTable::new_permanent_symbol(const char* name) { 556 unsigned int hash = 0; 557 int len = check_length(name, (int)strlen(name)); 558 Symbol* sym = SymbolTable::lookup_only(name, len, hash); 559 if (sym == nullptr) { 560 sym = do_add_if_needed(name, len, hash, /* is_permanent */ true); 561 } 562 if (!sym->is_permanent()) { 563 sym->make_permanent(); 564 log_trace_symboltable_helper(sym, "Asked for a permanent symbol, but got a regular one"); 565 } 566 return sym; 567 } 568 569 struct SizeFunc : StackObj { 570 size_t operator()(Symbol* value) { 571 assert(value != nullptr, "expected valid value"); 572 return (value)->size() * HeapWordSize; 573 }; 574 }; 575 576 TableStatistics SymbolTable::get_table_statistics() { 577 static TableStatistics ts; 578 SizeFunc sz; 579 ts = _local_table->statistics_get(Thread::current(), sz, ts); 580 return ts; 581 } 582 583 void SymbolTable::print_table_statistics(outputStream* st) { 584 SizeFunc sz; 585 _local_table->statistics_to(Thread::current(), sz, st, "SymbolTable"); 586 587 if (!_shared_table.empty()) { 588 _shared_table.print_table_statistics(st, "Shared Symbol Table"); 589 } 590 591 if (!_dynamic_shared_table.empty()) { 592 _dynamic_shared_table.print_table_statistics(st, "Dynamic Shared Symbol Table"); 593 } 594 } 595 596 // Verification 597 class VerifySymbols : StackObj { 598 public: 599 bool operator()(Symbol* value) { 600 guarantee(value != nullptr, "expected valid value"); 601 Symbol* sym = value; 602 guarantee(sym->equals((const char*)sym->bytes(), sym->utf8_length()), 603 "symbol must be internally consistent"); 604 return true; 605 }; 606 }; 607 608 void SymbolTable::verify() { 609 Thread* thr = Thread::current(); 610 VerifySymbols vs; 611 if (!_local_table->try_scan(thr, vs)) { 612 log_info(symboltable)("verify unavailable at this moment"); 613 } 614 } 615 616 static void print_symbol(outputStream* st, Symbol* sym) { 617 const char* utf8_string = (const char*)sym->bytes(); 618 int utf8_length = sym->utf8_length(); 619 st->print("%d %d: ", utf8_length, sym->refcount()); 620 HashtableTextDump::put_utf8(st, utf8_string, utf8_length); 621 st->cr(); 622 } 623 624 // Dumping 625 class DumpSymbol : StackObj { 626 Thread* _thr; 627 outputStream* _st; 628 public: 629 DumpSymbol(Thread* thr, outputStream* st) : _thr(thr), _st(st) {} 630 bool operator()(Symbol* value) { 631 assert(value != nullptr, "expected valid value"); 632 print_symbol(_st, value); 633 return true; 634 }; 635 }; 636 637 class DumpSharedSymbol : StackObj { 638 outputStream* _st; 639 public: 640 DumpSharedSymbol(outputStream* st) : _st(st) {} 641 void do_value(Symbol* value) { 642 assert(value != nullptr, "value should point to a symbol"); 643 print_symbol(_st, value); 644 }; 645 }; 646 647 void SymbolTable::dump(outputStream* st, bool verbose) { 648 if (!verbose) { 649 print_table_statistics(st); 650 } else { 651 Thread* thr = Thread::current(); 652 ResourceMark rm(thr); 653 st->print_cr("VERSION: 1.1"); 654 DumpSymbol ds(thr, st); 655 if (!_local_table->try_scan(thr, ds)) { 656 log_info(symboltable)("dump unavailable at this moment"); 657 } 658 if (!_shared_table.empty()) { 659 st->print_cr("#----------------"); 660 st->print_cr("# Shared symbols:"); 661 st->print_cr("#----------------"); 662 DumpSharedSymbol dss(st); 663 _shared_table.iterate(&dss); 664 } 665 if (!_dynamic_shared_table.empty()) { 666 st->print_cr("#------------------------"); 667 st->print_cr("# Dynamic shared symbols:"); 668 st->print_cr("#------------------------"); 669 DumpSharedSymbol dss(st); 670 _dynamic_shared_table.iterate(&dss); 671 } 672 } 673 } 674 675 #if INCLUDE_CDS 676 void SymbolTable::copy_shared_symbol_table(GrowableArray<Symbol*>* symbols, 677 CompactHashtableWriter* writer) { 678 ArchiveBuilder* builder = ArchiveBuilder::current(); 679 int len = symbols->length(); 680 for (int i = 0; i < len; i++) { 681 Symbol* sym = ArchiveBuilder::get_buffered_symbol(symbols->at(i)); 682 unsigned int fixed_hash = hash_shared_symbol((const char*)sym->bytes(), sym->utf8_length()); 683 assert(fixed_hash == hash_symbol((const char*)sym->bytes(), sym->utf8_length(), false), 684 "must not rehash during dumping"); 685 sym->set_permanent(); 686 writer->add(fixed_hash, builder->buffer_to_offset_u4((address)sym)); 687 } 688 } 689 690 size_t SymbolTable::estimate_size_for_archive() { 691 if (_items_count > (size_t)max_jint) { 692 fatal("Too many symbols to be archived: %zu", _items_count); 693 } 694 return CompactHashtableWriter::estimate_size(int(_items_count)); 695 } 696 697 void SymbolTable::write_to_archive(GrowableArray<Symbol*>* symbols) { 698 CompactHashtableWriter writer(int(_items_count), ArchiveBuilder::symbol_stats()); 699 copy_shared_symbol_table(symbols, &writer); 700 _shared_table_for_dumping.reset(); 701 writer.dump(&_shared_table_for_dumping, "symbol"); 702 } 703 704 void SymbolTable::serialize_shared_table_header(SerializeClosure* soc, 705 bool is_static_archive) { 706 OffsetCompactHashtable<const char*, Symbol*, symbol_equals_compact_hashtable_entry> * table; 707 if (soc->reading()) { 708 if (is_static_archive) { 709 table = &_shared_table; 710 } else { 711 table = &_dynamic_shared_table; 712 } 713 } else { 714 table = &_shared_table_for_dumping; 715 } 716 717 table->serialize_header(soc); 718 } 719 #endif //INCLUDE_CDS 720 721 // Concurrent work 722 void SymbolTable::grow(JavaThread* jt) { 723 SymbolTableHash::GrowTask gt(_local_table); 724 if (!gt.prepare(jt)) { 725 return; 726 } 727 log_trace(symboltable)("Started to grow"); 728 { 729 TraceTime timer("Grow", TRACETIME_LOG(Debug, symboltable, perf)); 730 while (gt.do_task(jt)) { 731 gt.pause(jt); 732 { 733 ThreadBlockInVM tbivm(jt); 734 } 735 gt.cont(jt); 736 } 737 } 738 gt.done(jt); 739 _current_size = table_size(); 740 log_debug(symboltable)("Grown to size:" SIZE_FORMAT, _current_size); 741 } 742 743 struct SymbolTableDoDelete : StackObj { 744 size_t _deleted; 745 SymbolTableDoDelete() : _deleted(0) {} 746 void operator()(Symbol* value) { 747 assert(value != nullptr, "expected valid value"); 748 Symbol *sym = value; 749 assert(sym->refcount() == 0, "refcount"); 750 _deleted++; 751 } 752 }; 753 754 struct SymbolTableDeleteCheck : StackObj { 755 size_t _processed; 756 SymbolTableDeleteCheck() : _processed(0) {} 757 bool operator()(Symbol* value) { 758 assert(value != nullptr, "expected valid value"); 759 _processed++; 760 Symbol *sym = value; 761 return (sym->refcount() == 0); 762 } 763 }; 764 765 void SymbolTable::clean_dead_entries(JavaThread* jt) { 766 SymbolTableHash::BulkDeleteTask bdt(_local_table); 767 if (!bdt.prepare(jt)) { 768 return; 769 } 770 771 SymbolTableDeleteCheck stdc; 772 SymbolTableDoDelete stdd; 773 NativeHeapTrimmer::SuspendMark sm("symboltable"); 774 { 775 TraceTime timer("Clean", TRACETIME_LOG(Debug, symboltable, perf)); 776 while (bdt.do_task(jt, stdc, stdd)) { 777 bdt.pause(jt); 778 { 779 ThreadBlockInVM tbivm(jt); 780 } 781 bdt.cont(jt); 782 } 783 reset_has_items_to_clean(); 784 bdt.done(jt); 785 } 786 787 Atomic::add(&_symbols_counted, stdc._processed); 788 789 log_debug(symboltable)("Cleaned " SIZE_FORMAT " of " SIZE_FORMAT, 790 stdd._deleted, stdc._processed); 791 } 792 793 void SymbolTable::check_concurrent_work() { 794 if (has_work()) { 795 return; 796 } 797 // We should clean/resize if we have 798 // more items than preferred load factor or 799 // more dead items than water mark. 800 if (has_items_to_clean() || (get_load_factor() > PREF_AVG_LIST_LEN)) { 801 log_debug(symboltable)("Concurrent work triggered, load factor: %f, items to clean: %s", 802 get_load_factor(), has_items_to_clean() ? "true" : "false"); 803 trigger_cleanup(); 804 } 805 } 806 807 bool SymbolTable::should_grow() { 808 return get_load_factor() > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached(); 809 } 810 811 void SymbolTable::do_concurrent_work(JavaThread* jt) { 812 // Rehash if needed. Rehashing goes to a safepoint but the rest of this 813 // work is concurrent. 814 if (needs_rehashing() && maybe_rehash_table()) { 815 Atomic::release_store(&_has_work, false); 816 return; // done, else grow 817 } 818 log_debug(symboltable, perf)("Concurrent work, live factor: %g", get_load_factor()); 819 // We prefer growing, since that also removes dead items 820 if (should_grow()) { 821 grow(jt); 822 } else { 823 clean_dead_entries(jt); 824 } 825 Atomic::release_store(&_has_work, false); 826 } 827 828 // Called at VM_Operation safepoint 829 void SymbolTable::rehash_table() { 830 assert(SafepointSynchronize::is_at_safepoint(), "must be called at safepoint"); 831 // The ServiceThread initiates the rehashing so it is not resizing. 832 assert (_local_table->is_safepoint_safe(), "Should not be resizing now"); 833 834 _alt_hash_seed = AltHashing::compute_seed(); 835 836 // We use current size 837 size_t new_size = _local_table->get_size_log2(Thread::current()); 838 SymbolTableHash* new_table = new SymbolTableHash(new_size, END_SIZE, REHASH_LEN, true); 839 // Use alt hash from now on 840 _alt_hash = true; 841 _local_table->rehash_nodes_to(Thread::current(), new_table); 842 843 // free old table 844 delete _local_table; 845 _local_table = new_table; 846 847 _rehashed = true; 848 _needs_rehashing = false; 849 } 850 851 bool SymbolTable::maybe_rehash_table() { 852 log_debug(symboltable)("Table imbalanced, rehashing called."); 853 854 // Grow instead of rehash. 855 if (should_grow()) { 856 log_debug(symboltable)("Choosing growing over rehashing."); 857 _needs_rehashing = false; 858 return false; 859 } 860 861 // Already rehashed. 862 if (_rehashed) { 863 log_warning(symboltable)("Rehashing already done, still long lists."); 864 _needs_rehashing = false; 865 return false; 866 } 867 868 VM_RehashSymbolTable op; 869 VMThread::execute(&op); 870 return true; 871 } 872 873 //--------------------------------------------------------------------------- 874 // Non-product code 875 876 #ifndef PRODUCT 877 878 class HistogramIterator : StackObj { 879 public: 880 static const size_t results_length = 100; 881 size_t counts[results_length]; 882 size_t sizes[results_length]; 883 size_t total_size; 884 size_t total_count; 885 size_t total_length; 886 size_t max_length; 887 size_t out_of_range_count; 888 size_t out_of_range_size; 889 HistogramIterator() : total_size(0), total_count(0), total_length(0), 890 max_length(0), out_of_range_count(0), out_of_range_size(0) { 891 // initialize results to zero 892 for (size_t i = 0; i < results_length; i++) { 893 counts[i] = 0; 894 sizes[i] = 0; 895 } 896 } 897 bool operator()(Symbol* value) { 898 assert(value != nullptr, "expected valid value"); 899 Symbol* sym = value; 900 size_t size = sym->size(); 901 size_t len = sym->utf8_length(); 902 if (len < results_length) { 903 counts[len]++; 904 sizes[len] += size; 905 } else { 906 out_of_range_count++; 907 out_of_range_size += size; 908 } 909 total_count++; 910 total_size += size; 911 total_length += len; 912 max_length = MAX2(max_length, len); 913 914 return true; 915 }; 916 }; 917 918 void SymbolTable::print_histogram() { 919 HistogramIterator hi; 920 _local_table->do_scan(Thread::current(), hi); 921 tty->print_cr("Symbol Table Histogram:"); 922 tty->print_cr(" Total number of symbols " SIZE_FORMAT_W(7), hi.total_count); 923 tty->print_cr(" Total size in memory " SIZE_FORMAT_W(7) "K", (hi.total_size * wordSize) / K); 924 tty->print_cr(" Total counted " SIZE_FORMAT_W(7), _symbols_counted); 925 tty->print_cr(" Total removed " SIZE_FORMAT_W(7), _symbols_removed); 926 if (_symbols_counted > 0) { 927 tty->print_cr(" Percent removed %3.2f", 928 ((double)_symbols_removed / (double)_symbols_counted) * 100); 929 } 930 tty->print_cr(" Reference counts " SIZE_FORMAT_W(7), Symbol::_total_count); 931 tty->print_cr(" Symbol arena used " SIZE_FORMAT_W(7) "K", arena()->used() / K); 932 tty->print_cr(" Symbol arena size " SIZE_FORMAT_W(7) "K", arena()->size_in_bytes() / K); 933 tty->print_cr(" Total symbol length " SIZE_FORMAT_W(7), hi.total_length); 934 tty->print_cr(" Maximum symbol length " SIZE_FORMAT_W(7), hi.max_length); 935 tty->print_cr(" Average symbol length %7.2f", ((double)hi.total_length / (double)hi.total_count)); 936 tty->print_cr(" Symbol length histogram:"); 937 tty->print_cr(" %6s %10s %10s", "Length", "#Symbols", "Size"); 938 for (size_t i = 0; i < hi.results_length; i++) { 939 if (hi.counts[i] > 0) { 940 tty->print_cr(" " SIZE_FORMAT_W(6) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) "K", 941 i, hi.counts[i], (hi.sizes[i] * wordSize) / K); 942 } 943 } 944 tty->print_cr(" >=" SIZE_FORMAT_W(6) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) "K\n", 945 hi.results_length, hi.out_of_range_count, (hi.out_of_range_size*wordSize) / K); 946 } 947 #endif // PRODUCT 948 949 // Utility for dumping symbols 950 SymboltableDCmd::SymboltableDCmd(outputStream* output, bool heap) : 951 DCmdWithParser(output, heap), 952 _verbose("-verbose", "Dump the content of each symbol in the table", 953 "BOOLEAN", false, "false") { 954 _dcmdparser.add_dcmd_option(&_verbose); 955 } 956 957 void SymboltableDCmd::execute(DCmdSource source, TRAPS) { 958 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSymbols, 959 _verbose.value()); 960 VMThread::execute(&dumper); 961 }