1 /* 2 * Copyright (c) 1997, 2019, 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.inline.hpp" 29 #include "classfile/stringTable.hpp" 30 #include "classfile/systemDictionary.hpp" 31 #include "gc/shared/collectedHeap.hpp" 32 #include "gc/shared/oopStorage.inline.hpp" 33 #include "gc/shared/oopStorageSet.hpp" 34 #include "logging/log.hpp" 35 #include "logging/logStream.hpp" 36 #include "memory/allocation.inline.hpp" 37 #include "memory/filemap.hpp" 38 #include "memory/heapShared.inline.hpp" 39 #include "memory/resourceArea.hpp" 40 #include "memory/universe.hpp" 41 #include "oops/access.inline.hpp" 42 #include "oops/compressedOops.hpp" 43 #include "oops/oop.inline.hpp" 44 #include "oops/typeArrayOop.inline.hpp" 45 #include "oops/weakHandle.inline.hpp" 46 #include "runtime/atomic.hpp" 47 #include "runtime/handles.inline.hpp" 48 #include "runtime/mutexLocker.hpp" 49 #include "runtime/safepointVerifiers.hpp" 50 #include "runtime/timerTrace.hpp" 51 #include "runtime/interfaceSupport.inline.hpp" 52 #include "services/diagnosticCommand.hpp" 53 #include "utilities/concurrentHashTable.inline.hpp" 54 #include "utilities/concurrentHashTableTasks.inline.hpp" 55 #include "utilities/macros.hpp" 56 #include "utilities/utf8.hpp" 57 58 // We prefer short chains of avg 2 59 const double PREF_AVG_LIST_LEN = 2.0; 60 // 2^24 is max size 61 const size_t END_SIZE = 24; 62 // If a chain gets to 100 something might be wrong 63 const size_t REHASH_LEN = 100; 64 // If we have as many dead items as 50% of the number of bucket 65 const double CLEAN_DEAD_HIGH_WATER_MARK = 0.5; 66 67 #if INCLUDE_CDS_JAVA_HEAP 68 inline oop read_string_from_compact_hashtable(address base_address, u4 offset) { 69 assert(sizeof(narrowOop) == sizeof(offset), "must be"); 70 narrowOop v = (narrowOop)offset; 71 return HeapShared::decode_from_archive(v); 72 } 73 74 static CompactHashtable< 75 const jchar*, oop, 76 read_string_from_compact_hashtable, 77 java_lang_String::equals 78 > _shared_table; 79 #endif 80 81 // -------------------------------------------------------------------------- 82 83 typedef ConcurrentHashTable<StringTableConfig, mtSymbol> StringTableHash; 84 static StringTableHash* _local_table = NULL; 85 86 volatile bool StringTable::_has_work = false; 87 volatile bool StringTable::_needs_rehashing = false; 88 89 volatile size_t StringTable::_uncleaned_items_count = 0; 90 91 static size_t _current_size = 0; 92 static volatile size_t _items_count = 0; 93 94 volatile bool _alt_hash = false; 95 static juint murmur_seed = 0; 96 97 uintx hash_string(const jchar* s, int len, bool useAlt) { 98 return useAlt ? 99 AltHashing::murmur3_32(murmur_seed, s, len) : 100 java_lang_String::hash_code(s, len); 101 } 102 103 class StringTableConfig : public StackObj { 104 private: 105 public: 106 typedef WeakHandle<vm_string_table_data> Value; 107 108 static uintx get_hash(Value const& value, bool* is_dead) { 109 EXCEPTION_MARK; 110 oop val_oop = value.peek(); 111 if (val_oop == NULL) { 112 *is_dead = true; 113 return 0; 114 } 115 *is_dead = false; 116 ResourceMark rm(THREAD); 117 // All String oops are hashed as unicode 118 int length; 119 jchar* chars = java_lang_String::as_unicode_string(val_oop, length, THREAD); 120 if (chars != NULL) { 121 return hash_string(chars, length, _alt_hash); 122 } 123 vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "get hash from oop"); 124 return 0; 125 } 126 // We use default allocation/deallocation but counted 127 static void* allocate_node(size_t size, Value const& value) { 128 StringTable::item_added(); 129 return AllocateHeap(size, mtSymbol); 130 } 131 static void free_node(void* memory, Value const& value) { 132 value.release(); 133 FreeHeap(memory); 134 StringTable::item_removed(); 135 } 136 }; 137 138 class StringTableLookupJchar : StackObj { 139 private: 140 Thread* _thread; 141 uintx _hash; 142 int _len; 143 const jchar* _str; 144 Handle _found; 145 146 public: 147 StringTableLookupJchar(Thread* thread, uintx hash, const jchar* key, int len) 148 : _thread(thread), _hash(hash), _len(len), _str(key) { 149 } 150 uintx get_hash() const { 151 return _hash; 152 } 153 bool equals(WeakHandle<vm_string_table_data>* value, bool* is_dead) { 154 oop val_oop = value->peek(); 155 if (val_oop == NULL) { 156 // dead oop, mark this hash dead for cleaning 157 *is_dead = true; 158 return false; 159 } 160 bool equals = java_lang_String::equals(val_oop, _str, _len); 161 if (!equals) { 162 return false; 163 } 164 // Need to resolve weak handle and Handleize through possible safepoint. 165 _found = Handle(_thread, value->resolve()); 166 return true; 167 } 168 }; 169 170 class StringTableLookupOop : public StackObj { 171 private: 172 Thread* _thread; 173 uintx _hash; 174 Handle _find; 175 Handle _found; // Might be a different oop with the same value that's already 176 // in the table, which is the point. 177 public: 178 StringTableLookupOop(Thread* thread, uintx hash, Handle handle) 179 : _thread(thread), _hash(hash), _find(handle) { } 180 181 uintx get_hash() const { 182 return _hash; 183 } 184 185 bool equals(WeakHandle<vm_string_table_data>* value, bool* is_dead) { 186 oop val_oop = value->peek(); 187 if (val_oop == NULL) { 188 // dead oop, mark this hash dead for cleaning 189 *is_dead = true; 190 return false; 191 } 192 bool equals = java_lang_String::equals(_find(), val_oop); 193 if (!equals) { 194 return false; 195 } 196 // Need to resolve weak handle and Handleize through possible safepoint. 197 _found = Handle(_thread, value->resolve()); 198 return true; 199 } 200 }; 201 202 static size_t ceil_log2(size_t val) { 203 size_t ret; 204 for (ret = 1; ((size_t)1 << ret) < val; ++ret); 205 return ret; 206 } 207 208 void StringTable::create_table() { 209 size_t start_size_log_2 = ceil_log2(StringTableSize); 210 _current_size = ((size_t)1) << start_size_log_2; 211 log_trace(stringtable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")", 212 _current_size, start_size_log_2); 213 _local_table = new StringTableHash(start_size_log_2, END_SIZE, REHASH_LEN); 214 } 215 216 size_t StringTable::item_added() { 217 return Atomic::add(&_items_count, (size_t)1); 218 } 219 220 size_t StringTable::add_items_to_clean(size_t ndead) { 221 size_t total = Atomic::add(&_uncleaned_items_count, (size_t)ndead); 222 log_trace(stringtable)( 223 "Uncleaned items:" SIZE_FORMAT " added: " SIZE_FORMAT " total:" SIZE_FORMAT, 224 _uncleaned_items_count, ndead, total); 225 return total; 226 } 227 228 void StringTable::item_removed() { 229 Atomic::add(&_items_count, (size_t)-1); 230 } 231 232 double StringTable::get_load_factor() { 233 return (double)_items_count/_current_size; 234 } 235 236 double StringTable::get_dead_factor() { 237 return (double)_uncleaned_items_count/_current_size; 238 } 239 240 size_t StringTable::table_size() { 241 return ((size_t)1) << _local_table->get_size_log2(Thread::current()); 242 } 243 244 void StringTable::trigger_concurrent_work() { 245 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag); 246 _has_work = true; 247 Service_lock->notify_all(); 248 } 249 250 // Probing 251 oop StringTable::lookup(Symbol* symbol) { 252 ResourceMark rm; 253 int length; 254 jchar* chars = symbol->as_unicode(length); 255 return lookup(chars, length); 256 } 257 258 oop StringTable::lookup(const jchar* name, int len) { 259 unsigned int hash = java_lang_String::hash_code(name, len); 260 oop string = lookup_shared(name, len, hash); 261 if (string != NULL) { 262 return string; 263 } 264 if (_alt_hash) { 265 hash = hash_string(name, len, true); 266 } 267 return do_lookup(name, len, hash); 268 } 269 270 class StringTableGet : public StackObj { 271 Thread* _thread; 272 Handle _return; 273 public: 274 StringTableGet(Thread* thread) : _thread(thread) {} 275 void operator()(WeakHandle<vm_string_table_data>* val) { 276 oop result = val->resolve(); 277 assert(result != NULL, "Result should be reachable"); 278 _return = Handle(_thread, result); 279 } 280 oop get_res_oop() { 281 return _return(); 282 } 283 }; 284 285 oop StringTable::do_lookup(const jchar* name, int len, uintx hash) { 286 Thread* thread = Thread::current(); 287 StringTableLookupJchar lookup(thread, hash, name, len); 288 StringTableGet stg(thread); 289 bool rehash_warning; 290 _local_table->get(thread, lookup, stg, &rehash_warning); 291 update_needs_rehash(rehash_warning); 292 return stg.get_res_oop(); 293 } 294 295 // Interning 296 oop StringTable::intern(Symbol* symbol, TRAPS) { 297 if (symbol == NULL) return NULL; 298 ResourceMark rm(THREAD); 299 int length; 300 jchar* chars = symbol->as_unicode(length); 301 Handle string; 302 oop result = intern(string, chars, length, CHECK_NULL); 303 return result; 304 } 305 306 oop StringTable::intern(oop string, TRAPS) { 307 if (string == NULL) return NULL; 308 ResourceMark rm(THREAD); 309 int length; 310 Handle h_string (THREAD, string); 311 jchar* chars = java_lang_String::as_unicode_string(string, length, 312 CHECK_NULL); 313 oop result = intern(h_string, chars, length, CHECK_NULL); 314 return result; 315 } 316 317 oop StringTable::intern(const char* utf8_string, TRAPS) { 318 if (utf8_string == NULL) return NULL; 319 ResourceMark rm(THREAD); 320 int length = UTF8::unicode_length(utf8_string); 321 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length); 322 UTF8::convert_to_unicode(utf8_string, chars, length); 323 Handle string; 324 oop result = intern(string, chars, length, CHECK_NULL); 325 return result; 326 } 327 328 oop StringTable::intern(Handle string_or_null_h, const jchar* name, int len, TRAPS) { 329 // shared table always uses java_lang_String::hash_code 330 unsigned int hash = java_lang_String::hash_code(name, len); 331 oop found_string = lookup_shared(name, len, hash); 332 if (found_string != NULL) { 333 return found_string; 334 } 335 if (_alt_hash) { 336 hash = hash_string(name, len, true); 337 } 338 found_string = do_lookup(name, len, hash); 339 if (found_string != NULL) { 340 return found_string; 341 } 342 return do_intern(string_or_null_h, name, len, hash, THREAD); 343 } 344 345 oop StringTable::do_intern(Handle string_or_null_h, const jchar* name, 346 int len, uintx hash, TRAPS) { 347 HandleMark hm(THREAD); // cleanup strings created 348 Handle string_h; 349 350 if (!string_or_null_h.is_null()) { 351 string_h = string_or_null_h; 352 } else { 353 string_h = java_lang_String::create_from_unicode(name, len, CHECK_NULL); 354 } 355 356 // Deduplicate the string before it is interned. Note that we should never 357 // deduplicate a string after it has been interned. Doing so will counteract 358 // compiler optimizations done on e.g. interned string literals. 359 Universe::heap()->deduplicate_string(string_h()); 360 361 assert(java_lang_String::equals(string_h(), name, len), 362 "string must be properly initialized"); 363 assert(len == java_lang_String::length(string_h()), "Must be same length"); 364 365 StringTableLookupOop lookup(THREAD, hash, string_h); 366 StringTableGet stg(THREAD); 367 368 bool rehash_warning; 369 do { 370 // Callers have already looked up the String using the jchar* name, so just go to add. 371 WeakHandle<vm_string_table_data> wh = WeakHandle<vm_string_table_data>::create(string_h); 372 // The hash table takes ownership of the WeakHandle, even if it's not inserted. 373 if (_local_table->insert(THREAD, lookup, wh, &rehash_warning)) { 374 update_needs_rehash(rehash_warning); 375 return wh.resolve(); 376 } 377 // In case another thread did a concurrent add, return value already in the table. 378 // This could fail if the String got gc'ed concurrently, so loop back until success. 379 if (_local_table->get(THREAD, lookup, stg, &rehash_warning)) { 380 update_needs_rehash(rehash_warning); 381 return stg.get_res_oop(); 382 } 383 } while(true); 384 } 385 386 void StringTable::oops_do(OopClosure* f) { 387 assert(f != NULL, "No closure"); 388 OopStorageSet::string_table_weak()->oops_do(f); 389 } 390 391 // Concurrent work 392 void StringTable::grow(JavaThread* jt) { 393 StringTableHash::GrowTask gt(_local_table); 394 if (!gt.prepare(jt)) { 395 return; 396 } 397 log_trace(stringtable)("Started to grow"); 398 { 399 TraceTime timer("Grow", TRACETIME_LOG(Debug, stringtable, perf)); 400 while (gt.do_task(jt)) { 401 gt.pause(jt); 402 { 403 ThreadBlockInVM tbivm(jt); 404 } 405 gt.cont(jt); 406 } 407 } 408 gt.done(jt); 409 _current_size = table_size(); 410 log_debug(stringtable)("Grown to size:" SIZE_FORMAT, _current_size); 411 } 412 413 struct StringTableDoDelete : StackObj { 414 void operator()(WeakHandle<vm_string_table_data>* val) { 415 /* do nothing */ 416 } 417 }; 418 419 struct StringTableDeleteCheck : StackObj { 420 long _count; 421 long _item; 422 StringTableDeleteCheck() : _count(0), _item(0) {} 423 bool operator()(WeakHandle<vm_string_table_data>* val) { 424 ++_item; 425 oop tmp = val->peek(); 426 if (tmp == NULL) { 427 ++_count; 428 return true; 429 } else { 430 return false; 431 } 432 } 433 }; 434 435 void StringTable::clean_dead_entries(JavaThread* jt) { 436 StringTableHash::BulkDeleteTask bdt(_local_table); 437 if (!bdt.prepare(jt)) { 438 return; 439 } 440 441 StringTableDeleteCheck stdc; 442 StringTableDoDelete stdd; 443 { 444 TraceTime timer("Clean", TRACETIME_LOG(Debug, stringtable, perf)); 445 while(bdt.do_task(jt, stdc, stdd)) { 446 bdt.pause(jt); 447 { 448 ThreadBlockInVM tbivm(jt); 449 } 450 bdt.cont(jt); 451 } 452 bdt.done(jt); 453 } 454 log_debug(stringtable)("Cleaned %ld of %ld", stdc._count, stdc._item); 455 } 456 457 void StringTable::check_concurrent_work() { 458 if (_has_work) { 459 return; 460 } 461 462 double load_factor = StringTable::get_load_factor(); 463 double dead_factor = StringTable::get_dead_factor(); 464 // We should clean/resize if we have more dead than alive, 465 // more items than preferred load factor or 466 // more dead items than water mark. 467 if ((dead_factor > load_factor) || 468 (load_factor > PREF_AVG_LIST_LEN) || 469 (dead_factor > CLEAN_DEAD_HIGH_WATER_MARK)) { 470 log_debug(stringtable)("Concurrent work triggered, live factor: %g dead factor: %g", 471 load_factor, dead_factor); 472 trigger_concurrent_work(); 473 } 474 } 475 476 void StringTable::do_concurrent_work(JavaThread* jt) { 477 _has_work = false; 478 double load_factor = get_load_factor(); 479 log_debug(stringtable, perf)("Concurrent work, live factor: %g", load_factor); 480 // We prefer growing, since that also removes dead items 481 if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) { 482 grow(jt); 483 } else { 484 clean_dead_entries(jt); 485 } 486 } 487 488 // Rehash 489 bool StringTable::do_rehash() { 490 if (!_local_table->is_safepoint_safe()) { 491 return false; 492 } 493 494 // We use current size, not max size. 495 size_t new_size = _local_table->get_size_log2(Thread::current()); 496 StringTableHash* new_table = new StringTableHash(new_size, END_SIZE, REHASH_LEN); 497 // Use alt hash from now on 498 _alt_hash = true; 499 if (!_local_table->try_move_nodes_to(Thread::current(), new_table)) { 500 _alt_hash = false; 501 delete new_table; 502 return false; 503 } 504 505 // free old table 506 delete _local_table; 507 _local_table = new_table; 508 509 return true; 510 } 511 512 void StringTable::rehash_table() { 513 static bool rehashed = false; 514 log_debug(stringtable)("Table imbalanced, rehashing called."); 515 516 // Grow instead of rehash. 517 if (get_load_factor() > PREF_AVG_LIST_LEN && 518 !_local_table->is_max_size_reached()) { 519 log_debug(stringtable)("Choosing growing over rehashing."); 520 trigger_concurrent_work(); 521 _needs_rehashing = false; 522 return; 523 } 524 // Already rehashed. 525 if (rehashed) { 526 log_warning(stringtable)("Rehashing already done, still long lists."); 527 trigger_concurrent_work(); 528 _needs_rehashing = false; 529 return; 530 } 531 532 murmur_seed = AltHashing::compute_seed(); 533 { 534 if (do_rehash()) { 535 rehashed = true; 536 } else { 537 log_info(stringtable)("Resizes in progress rehashing skipped."); 538 } 539 } 540 _needs_rehashing = false; 541 } 542 543 // Statistics 544 static int literal_size(oop obj) { 545 // NOTE: this would over-count if (pre-JDK8) 546 // java_lang_Class::has_offset_field() is true and the String.value array is 547 // shared by several Strings. However, starting from JDK8, the String.value 548 // array is not shared anymore. 549 if (obj == NULL) { 550 return 0; 551 } else if (obj->klass() == SystemDictionary::String_klass()) { 552 return (obj->size() + java_lang_String::value(obj)->size()) * HeapWordSize; 553 } else { 554 return obj->size(); 555 } 556 } 557 558 struct SizeFunc : StackObj { 559 size_t operator()(WeakHandle<vm_string_table_data>* val) { 560 oop s = val->peek(); 561 if (s == NULL) { 562 // Dead 563 return 0; 564 } 565 return literal_size(s); 566 }; 567 }; 568 569 TableStatistics StringTable::get_table_statistics() { 570 static TableStatistics ts; 571 SizeFunc sz; 572 ts = _local_table->statistics_get(Thread::current(), sz, ts); 573 return ts; 574 } 575 576 void StringTable::print_table_statistics(outputStream* st, 577 const char* table_name) { 578 SizeFunc sz; 579 _local_table->statistics_to(Thread::current(), sz, st, table_name); 580 } 581 582 // Verification 583 class VerifyStrings : StackObj { 584 public: 585 bool operator()(WeakHandle<vm_string_table_data>* val) { 586 oop s = val->peek(); 587 if (s != NULL) { 588 assert(java_lang_String::length(s) >= 0, "Length on string must work."); 589 } 590 return true; 591 }; 592 }; 593 594 // This verification is part of Universe::verify() and needs to be quick. 595 void StringTable::verify() { 596 Thread* thr = Thread::current(); 597 VerifyStrings vs; 598 if (!_local_table->try_scan(thr, vs)) { 599 log_info(stringtable)("verify unavailable at this moment"); 600 } 601 } 602 603 // Verification and comp 604 class VerifyCompStrings : StackObj { 605 GrowableArray<oop>* _oops; 606 public: 607 size_t _errors; 608 VerifyCompStrings(GrowableArray<oop>* oops) : _oops(oops), _errors(0) {} 609 bool operator()(WeakHandle<vm_string_table_data>* val) { 610 oop s = val->resolve(); 611 if (s == NULL) { 612 return true; 613 } 614 int len = _oops->length(); 615 for (int i = 0; i < len; i++) { 616 bool eq = java_lang_String::equals(s, _oops->at(i)); 617 assert(!eq, "Duplicate strings"); 618 if (eq) { 619 _errors++; 620 } 621 } 622 _oops->push(s); 623 return true; 624 }; 625 }; 626 627 size_t StringTable::verify_and_compare_entries() { 628 Thread* thr = Thread::current(); 629 GrowableArray<oop>* oops = 630 new (ResourceObj::C_HEAP, mtInternal) 631 GrowableArray<oop>((int)_current_size, true); 632 633 VerifyCompStrings vcs(oops); 634 if (!_local_table->try_scan(thr, vcs)) { 635 log_info(stringtable)("verify unavailable at this moment"); 636 } 637 delete oops; 638 return vcs._errors; 639 } 640 641 // Dumping 642 class PrintString : StackObj { 643 Thread* _thr; 644 outputStream* _st; 645 public: 646 PrintString(Thread* thr, outputStream* st) : _thr(thr), _st(st) {} 647 bool operator()(WeakHandle<vm_string_table_data>* val) { 648 oop s = val->peek(); 649 if (s == NULL) { 650 return true; 651 } 652 typeArrayOop value = java_lang_String::value_no_keepalive(s); 653 int length = java_lang_String::length(s); 654 bool is_latin1 = java_lang_String::is_latin1(s); 655 656 if (length <= 0) { 657 _st->print("%d: ", length); 658 } else { 659 ResourceMark rm(_thr); 660 int utf8_length = length; 661 char* utf8_string; 662 663 if (!is_latin1) { 664 jchar* chars = value->char_at_addr(0); 665 utf8_string = UNICODE::as_utf8(chars, utf8_length); 666 } else { 667 jbyte* bytes = value->byte_at_addr(0); 668 utf8_string = UNICODE::as_utf8(bytes, utf8_length); 669 } 670 671 _st->print("%d: ", utf8_length); 672 HashtableTextDump::put_utf8(_st, utf8_string, utf8_length); 673 } 674 _st->cr(); 675 return true; 676 }; 677 }; 678 679 void StringTable::dump(outputStream* st, bool verbose) { 680 if (!verbose) { 681 print_table_statistics(st, "StringTable"); 682 } else { 683 Thread* thr = Thread::current(); 684 ResourceMark rm(thr); 685 st->print_cr("VERSION: 1.1"); 686 PrintString ps(thr, st); 687 if (!_local_table->try_scan(thr, ps)) { 688 st->print_cr("dump unavailable at this moment"); 689 } 690 } 691 } 692 693 // Utility for dumping strings 694 StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) : 695 DCmdWithParser(output, heap), 696 _verbose("-verbose", "Dump the content of each string in the table", 697 "BOOLEAN", false, "false") { 698 _dcmdparser.add_dcmd_option(&_verbose); 699 } 700 701 void StringtableDCmd::execute(DCmdSource source, TRAPS) { 702 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings, 703 _verbose.value()); 704 VMThread::execute(&dumper); 705 } 706 707 int StringtableDCmd::num_arguments() { 708 ResourceMark rm; 709 StringtableDCmd* dcmd = new StringtableDCmd(NULL, false); 710 if (dcmd != NULL) { 711 DCmdMark mark(dcmd); 712 return dcmd->_dcmdparser.num_arguments(); 713 } else { 714 return 0; 715 } 716 } 717 718 // Sharing 719 #if INCLUDE_CDS_JAVA_HEAP 720 oop StringTable::lookup_shared(const jchar* name, int len, unsigned int hash) { 721 assert(hash == java_lang_String::hash_code(name, len), 722 "hash must be computed using java_lang_String::hash_code"); 723 return _shared_table.lookup(name, hash, len); 724 } 725 726 oop StringTable::create_archived_string(oop s, Thread* THREAD) { 727 assert(DumpSharedSpaces, "this function is only used with -Xshare:dump"); 728 729 if (HeapShared::is_archived_object(s)) { 730 return s; 731 } 732 733 oop new_s = NULL; 734 typeArrayOop v = java_lang_String::value_no_keepalive(s); 735 typeArrayOop new_v = (typeArrayOop)HeapShared::archive_heap_object(v, THREAD); 736 if (new_v == NULL) { 737 return NULL; 738 } 739 new_s = HeapShared::archive_heap_object(s, THREAD); 740 if (new_s == NULL) { 741 return NULL; 742 } 743 744 // adjust the pointer to the 'value' field in the new String oop 745 java_lang_String::set_value_raw(new_s, new_v); 746 return new_s; 747 } 748 749 struct CopyToArchive : StackObj { 750 CompactHashtableWriter* _writer; 751 CopyToArchive(CompactHashtableWriter* writer) : _writer(writer) {} 752 bool operator()(WeakHandle<vm_string_table_data>* val) { 753 oop s = val->peek(); 754 if (s == NULL) { 755 return true; 756 } 757 unsigned int hash = java_lang_String::hash_code(s); 758 oop new_s = StringTable::create_archived_string(s, Thread::current()); 759 if (new_s == NULL) { 760 return true; 761 } 762 763 val->replace(new_s); 764 // add to the compact table 765 _writer->add(hash, CompressedOops::encode(new_s)); 766 return true; 767 } 768 }; 769 770 void StringTable::copy_shared_string_table(CompactHashtableWriter* writer) { 771 assert(HeapShared::is_heap_object_archiving_allowed(), "must be"); 772 773 CopyToArchive copy(writer); 774 _local_table->do_safepoint_scan(copy); 775 } 776 777 void StringTable::write_to_archive() { 778 assert(HeapShared::is_heap_object_archiving_allowed(), "must be"); 779 780 _shared_table.reset(); 781 CompactHashtableWriter writer(_items_count, &MetaspaceShared::stats()->string); 782 783 // Copy the interned strings into the "string space" within the java heap 784 copy_shared_string_table(&writer); 785 writer.dump(&_shared_table, "string"); 786 } 787 788 void StringTable::serialize_shared_table_header(SerializeClosure* soc) { 789 _shared_table.serialize_header(soc); 790 791 if (soc->writing()) { 792 // Sanity. Make sure we don't use the shared table at dump time 793 _shared_table.reset(); 794 } else if (!HeapShared::closed_archive_heap_region_mapped()) { 795 _shared_table.reset(); 796 } 797 } 798 799 class SharedStringIterator { 800 OopClosure* _oop_closure; 801 public: 802 SharedStringIterator(OopClosure* f) : _oop_closure(f) {} 803 void do_value(oop string) { 804 _oop_closure->do_oop(&string); 805 } 806 }; 807 808 void StringTable::shared_oops_do(OopClosure* f) { 809 SharedStringIterator iter(f); 810 _shared_table.iterate(&iter); 811 } 812 #endif //INCLUDE_CDS_JAVA_HEAP