1 /* 2 * Copyright (c) 1997, 2017, 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.inline.hpp" 29 #include "classfile/stringTable.hpp" 30 #include "classfile/systemDictionary.hpp" 31 #include "gc/shared/collectedHeap.inline.hpp" 32 #include "gc/shared/gcLocker.inline.hpp" 33 #include "logging/log.hpp" 34 #include "memory/allocation.inline.hpp" 35 #include "memory/filemap.hpp" 36 #include "memory/metaspaceShared.hpp" 37 #include "memory/resourceArea.hpp" 38 #include "oops/oop.inline.hpp" 39 #include "runtime/atomic.hpp" 40 #include "runtime/mutexLocker.hpp" 41 #include "services/diagnosticCommand.hpp" 42 #include "utilities/hashtable.inline.hpp" 43 #include "utilities/macros.hpp" 44 #if INCLUDE_ALL_GCS 45 #include "gc/g1/g1CollectedHeap.hpp" 46 #include "gc/g1/g1SATBCardTableModRefBS.hpp" 47 #include "gc/g1/g1StringDedup.hpp" 48 #endif 49 50 // the number of buckets a thread claims 51 const int ClaimChunkSize = 32; 52 53 #ifdef ASSERT 54 class StableMemoryChecker : public StackObj { 55 enum { _bufsize = wordSize*4 }; 56 57 address _region; 58 jint _size; 59 u1 _save_buf[_bufsize]; 60 61 int sample(u1* save_buf) { 62 if (_size <= _bufsize) { 63 memcpy(save_buf, _region, _size); 64 return _size; 65 } else { 66 // copy head and tail 67 memcpy(&save_buf[0], _region, _bufsize/2); 68 memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2); 69 return (_bufsize/2)*2; 70 } 71 } 72 73 public: 74 StableMemoryChecker(const void* region, jint size) { 75 _region = (address) region; 76 _size = size; 77 sample(_save_buf); 78 } 79 80 bool verify() { 81 u1 check_buf[sizeof(_save_buf)]; 82 int check_size = sample(check_buf); 83 return (0 == memcmp(_save_buf, check_buf, check_size)); 84 } 85 86 void set_region(const void* region) { _region = (address) region; } 87 }; 88 #endif 89 90 91 // -------------------------------------------------------------------------- 92 StringTable* StringTable::_the_table = NULL; 93 bool StringTable::_shared_string_mapped = false; 94 bool StringTable::_needs_rehashing = false; 95 96 volatile int StringTable::_parallel_claimed_idx = 0; 97 98 CompactHashtable<oop, char> StringTable::_shared_table; 99 100 // Pick hashing algorithm 101 unsigned int StringTable::hash_string(const jchar* s, int len) { 102 return use_alternate_hashcode() ? alt_hash_string(s, len) : 103 java_lang_String::hash_code(s, len); 104 } 105 106 unsigned int StringTable::alt_hash_string(const jchar* s, int len) { 107 return AltHashing::murmur3_32(seed(), s, len); 108 } 109 110 unsigned int StringTable::hash_string(oop string) { 111 EXCEPTION_MARK; 112 if (string == NULL) { 113 return hash_string((jchar*)NULL, 0); 114 } 115 ResourceMark rm(THREAD); 116 // All String oops are hashed as unicode 117 int length; 118 jchar* chars = java_lang_String::as_unicode_string(string, length, THREAD); 119 if (chars != NULL) { 120 return hash_string(chars, length); 121 } else { 122 vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "unable to create Unicode string for verification"); 123 return 0; 124 } 125 } 126 127 oop StringTable::lookup_shared(jchar* name, int len, unsigned int hash) { 128 assert(hash == java_lang_String::hash_code(name, len), 129 "hash must be computed using java_lang_String::hash_code"); 130 return _shared_table.lookup((const char*)name, hash, len); 131 } 132 133 oop StringTable::lookup_in_main_table(int index, jchar* name, 134 int len, unsigned int hash) { 135 int count = 0; 136 for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) { 137 count++; 138 if (l->hash() == hash) { 139 if (java_lang_String::equals(l->literal(), name, len)) { 140 return l->literal(); 141 } 142 } 143 } 144 // If the bucket size is too deep check if this hash code is insufficient. 145 if (count >= rehash_count && !needs_rehashing()) { 146 _needs_rehashing = check_rehash_table(count); 147 } 148 return NULL; 149 } 150 151 152 oop StringTable::basic_add(int index_arg, Handle string, jchar* name, 153 int len, unsigned int hashValue_arg, TRAPS) { 154 155 assert(java_lang_String::equals(string(), name, len), 156 "string must be properly initialized"); 157 // Cannot hit a safepoint in this function because the "this" pointer can move. 158 NoSafepointVerifier nsv; 159 160 // Check if the symbol table has been rehashed, if so, need to recalculate 161 // the hash value and index before second lookup. 162 unsigned int hashValue; 163 int index; 164 if (use_alternate_hashcode()) { 165 hashValue = alt_hash_string(name, len); 166 index = hash_to_index(hashValue); 167 } else { 168 hashValue = hashValue_arg; 169 index = index_arg; 170 } 171 172 // Since look-up was done lock-free, we need to check if another 173 // thread beat us in the race to insert the symbol. 174 175 // No need to lookup the shared table from here since the caller (intern()) already did 176 oop test = lookup_in_main_table(index, name, len, hashValue); // calls lookup(u1*, int) 177 if (test != NULL) { 178 // Entry already added 179 return test; 180 } 181 182 HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string()); 183 add_entry(index, entry); 184 return string(); 185 } 186 187 188 oop StringTable::lookup(Symbol* symbol) { 189 ResourceMark rm; 190 int length; 191 jchar* chars = symbol->as_unicode(length); 192 return lookup(chars, length); 193 } 194 195 // Tell the GC that this string was looked up in the StringTable. 196 static void ensure_string_alive(oop string) { 197 // A lookup in the StringTable could return an object that was previously 198 // considered dead. The SATB part of G1 needs to get notified about this 199 // potential resurrection, otherwise the marking might not find the object. 200 #if INCLUDE_ALL_GCS 201 if (UseG1GC && string != NULL) { 202 G1SATBCardTableModRefBS::enqueue(string); 203 } 204 #endif 205 } 206 207 oop StringTable::lookup(jchar* name, int len) { 208 // shared table always uses java_lang_String::hash_code 209 unsigned int hash = java_lang_String::hash_code(name, len); 210 oop string = lookup_shared(name, len, hash); 211 if (string != NULL) { 212 return string; 213 } 214 if (use_alternate_hashcode()) { 215 hash = alt_hash_string(name, len); 216 } 217 int index = the_table()->hash_to_index(hash); 218 string = the_table()->lookup_in_main_table(index, name, len, hash); 219 220 ensure_string_alive(string); 221 222 return string; 223 } 224 225 oop StringTable::intern(Handle string_or_null, jchar* name, 226 int len, TRAPS) { 227 // shared table always uses java_lang_String::hash_code 228 unsigned int hashValue = java_lang_String::hash_code(name, len); 229 oop found_string = lookup_shared(name, len, hashValue); 230 if (found_string != NULL) { 231 return found_string; 232 } 233 if (use_alternate_hashcode()) { 234 hashValue = alt_hash_string(name, len); 235 } 236 int index = the_table()->hash_to_index(hashValue); 237 found_string = the_table()->lookup_in_main_table(index, name, len, hashValue); 238 239 // Found 240 if (found_string != NULL) { 241 if (found_string != string_or_null()) { 242 ensure_string_alive(found_string); 243 } 244 return found_string; 245 } 246 247 debug_only(StableMemoryChecker smc(name, len * sizeof(name[0]))); 248 assert(!Universe::heap()->is_in_reserved(name), 249 "proposed name of symbol must be stable"); 250 251 HandleMark hm(THREAD); // cleanup strings created 252 Handle string; 253 // try to reuse the string if possible 254 if (!string_or_null.is_null()) { 255 string = string_or_null; 256 } else { 257 string = java_lang_String::create_from_unicode(name, len, CHECK_NULL); 258 } 259 260 #if INCLUDE_ALL_GCS 261 if (G1StringDedup::is_enabled()) { 262 // Deduplicate the string before it is interned. Note that we should never 263 // deduplicate a string after it has been interned. Doing so will counteract 264 // compiler optimizations done on e.g. interned string literals. 265 G1StringDedup::deduplicate(string()); 266 } 267 #endif 268 269 // Grab the StringTable_lock before getting the_table() because it could 270 // change at safepoint. 271 oop added_or_found; 272 { 273 MutexLocker ml(StringTable_lock, THREAD); 274 // Otherwise, add to symbol to table 275 added_or_found = the_table()->basic_add(index, string, name, len, 276 hashValue, CHECK_NULL); 277 } 278 279 if (added_or_found != string()) { 280 ensure_string_alive(added_or_found); 281 } 282 283 return added_or_found; 284 } 285 286 oop StringTable::intern(Symbol* symbol, TRAPS) { 287 if (symbol == NULL) return NULL; 288 ResourceMark rm(THREAD); 289 int length; 290 jchar* chars = symbol->as_unicode(length); 291 Handle string; 292 oop result = intern(string, chars, length, CHECK_NULL); 293 return result; 294 } 295 296 297 oop StringTable::intern(oop string, TRAPS) 298 { 299 if (string == NULL) return NULL; 300 ResourceMark rm(THREAD); 301 int length; 302 Handle h_string (THREAD, string); 303 jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL); 304 oop result = intern(h_string, chars, length, CHECK_NULL); 305 return result; 306 } 307 308 309 oop StringTable::intern(const char* utf8_string, TRAPS) { 310 if (utf8_string == NULL) return NULL; 311 ResourceMark rm(THREAD); 312 int length = UTF8::unicode_length(utf8_string); 313 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length); 314 UTF8::convert_to_unicode(utf8_string, chars, length); 315 Handle string; 316 oop result = intern(string, chars, length, CHECK_NULL); 317 return result; 318 } 319 320 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) { 321 BucketUnlinkContext context; 322 buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), &context); 323 _the_table->bulk_free_entries(&context); 324 *processed = context._num_processed; 325 *removed = context._num_removed; 326 } 327 328 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) { 329 // Readers of the table are unlocked, so we should only be removing 330 // entries at a safepoint. 331 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 332 const int limit = the_table()->table_size(); 333 334 BucketUnlinkContext context; 335 for (;;) { 336 // Grab next set of buckets to scan 337 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize; 338 if (start_idx >= limit) { 339 // End of table 340 break; 341 } 342 343 int end_idx = MIN2(limit, start_idx + ClaimChunkSize); 344 buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, &context); 345 } 346 _the_table->bulk_free_entries(&context); 347 *processed = context._num_processed; 348 *removed = context._num_removed; 349 } 350 351 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) { 352 const int limit = the_table()->table_size(); 353 354 assert(0 <= start_idx && start_idx <= limit, 355 "start_idx (%d) is out of bounds", start_idx); 356 assert(0 <= end_idx && end_idx <= limit, 357 "end_idx (%d) is out of bounds", end_idx); 358 assert(start_idx <= end_idx, 359 "Index ordering: start_idx=%d, end_idx=%d", 360 start_idx, end_idx); 361 362 for (int i = start_idx; i < end_idx; i += 1) { 363 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i); 364 while (entry != NULL) { 365 assert(!entry->is_shared(), "CDS not used for the StringTable"); 366 367 f->do_oop((oop*)entry->literal_addr()); 368 369 entry = entry->next(); 370 } 371 } 372 } 373 374 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, BucketUnlinkContext* context) { 375 const int limit = the_table()->table_size(); 376 377 assert(0 <= start_idx && start_idx <= limit, 378 "start_idx (%d) is out of bounds", start_idx); 379 assert(0 <= end_idx && end_idx <= limit, 380 "end_idx (%d) is out of bounds", end_idx); 381 assert(start_idx <= end_idx, 382 "Index ordering: start_idx=%d, end_idx=%d", 383 start_idx, end_idx); 384 385 for (int i = start_idx; i < end_idx; ++i) { 386 HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i); 387 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i); 388 while (entry != NULL) { 389 assert(!entry->is_shared(), "CDS not used for the StringTable"); 390 391 if (is_alive->do_object_b(entry->literal())) { 392 if (f != NULL) { 393 f->do_oop((oop*)entry->literal_addr()); 394 } 395 p = entry->next_addr(); 396 } else { 397 *p = entry->next(); 398 context->free_entry(entry); 399 } 400 context->_num_processed++; 401 entry = *p; 402 } 403 } 404 } 405 406 void StringTable::oops_do(OopClosure* f) { 407 buckets_oops_do(f, 0, the_table()->table_size()); 408 } 409 410 void StringTable::possibly_parallel_oops_do(OopClosure* f) { 411 const int limit = the_table()->table_size(); 412 413 for (;;) { 414 // Grab next set of buckets to scan 415 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize; 416 if (start_idx >= limit) { 417 // End of table 418 break; 419 } 420 421 int end_idx = MIN2(limit, start_idx + ClaimChunkSize); 422 buckets_oops_do(f, start_idx, end_idx); 423 } 424 } 425 426 // This verification is part of Universe::verify() and needs to be quick. 427 // See StringTable::verify_and_compare() below for exhaustive verification. 428 void StringTable::verify() { 429 for (int i = 0; i < the_table()->table_size(); ++i) { 430 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i); 431 for ( ; p != NULL; p = p->next()) { 432 oop s = p->literal(); 433 guarantee(s != NULL, "interned string is NULL"); 434 unsigned int h = hash_string(s); 435 guarantee(p->hash() == h, "broken hash in string table entry"); 436 guarantee(the_table()->hash_to_index(h) == i, 437 "wrong index in string table"); 438 } 439 } 440 } 441 442 void StringTable::dump(outputStream* st, bool verbose) { 443 if (!verbose) { 444 the_table()->print_table_statistics(st, "StringTable"); 445 } else { 446 Thread* THREAD = Thread::current(); 447 st->print_cr("VERSION: 1.1"); 448 for (int i = 0; i < the_table()->table_size(); ++i) { 449 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i); 450 for ( ; p != NULL; p = p->next()) { 451 oop s = p->literal(); 452 typeArrayOop value = java_lang_String::value(s); 453 int length = java_lang_String::length(s); 454 bool is_latin1 = java_lang_String::is_latin1(s); 455 456 if (length <= 0) { 457 st->print("%d: ", length); 458 } else { 459 ResourceMark rm(THREAD); 460 int utf8_length = length; 461 char* utf8_string; 462 463 if (!is_latin1) { 464 jchar* chars = value->char_at_addr(0); 465 utf8_string = UNICODE::as_utf8(chars, utf8_length); 466 } else { 467 jbyte* bytes = value->byte_at_addr(0); 468 utf8_string = UNICODE::as_utf8(bytes, utf8_length); 469 } 470 471 st->print("%d: ", utf8_length); 472 HashtableTextDump::put_utf8(st, utf8_string, utf8_length); 473 } 474 st->cr(); 475 } 476 } 477 } 478 } 479 480 StringTable::VerifyRetTypes StringTable::compare_entries( 481 int bkt1, int e_cnt1, 482 HashtableEntry<oop, mtSymbol>* e_ptr1, 483 int bkt2, int e_cnt2, 484 HashtableEntry<oop, mtSymbol>* e_ptr2) { 485 // These entries are sanity checked by verify_and_compare_entries() 486 // before this function is called. 487 oop str1 = e_ptr1->literal(); 488 oop str2 = e_ptr2->literal(); 489 490 if (str1 == str2) { 491 tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") " 492 "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]", 493 p2i(str1), bkt1, e_cnt1, bkt2, e_cnt2); 494 return _verify_fail_continue; 495 } 496 497 if (java_lang_String::equals(str1, str2)) { 498 tty->print_cr("ERROR: identical String values in entry @ " 499 "bucket[%d][%d] and entry @ bucket[%d][%d]", 500 bkt1, e_cnt1, bkt2, e_cnt2); 501 return _verify_fail_continue; 502 } 503 504 return _verify_pass; 505 } 506 507 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt, 508 HashtableEntry<oop, mtSymbol>* e_ptr, 509 StringTable::VerifyMesgModes mesg_mode) { 510 511 VerifyRetTypes ret = _verify_pass; // be optimistic 512 513 oop str = e_ptr->literal(); 514 if (str == NULL) { 515 if (mesg_mode == _verify_with_mesgs) { 516 tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt, 517 e_cnt); 518 } 519 // NULL oop means no more verifications are possible 520 return _verify_fail_done; 521 } 522 523 if (str->klass() != SystemDictionary::String_klass()) { 524 if (mesg_mode == _verify_with_mesgs) { 525 tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]", 526 bkt, e_cnt); 527 } 528 // not a String means no more verifications are possible 529 return _verify_fail_done; 530 } 531 532 unsigned int h = hash_string(str); 533 if (e_ptr->hash() != h) { 534 if (mesg_mode == _verify_with_mesgs) { 535 tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], " 536 "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h); 537 } 538 ret = _verify_fail_continue; 539 } 540 541 if (the_table()->hash_to_index(h) != bkt) { 542 if (mesg_mode == _verify_with_mesgs) { 543 tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], " 544 "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h, 545 the_table()->hash_to_index(h)); 546 } 547 ret = _verify_fail_continue; 548 } 549 550 return ret; 551 } 552 553 // See StringTable::verify() above for the quick verification that is 554 // part of Universe::verify(). This verification is exhaustive and 555 // reports on every issue that is found. StringTable::verify() only 556 // reports on the first issue that is found. 557 // 558 // StringTable::verify_entry() checks: 559 // - oop value != NULL (same as verify()) 560 // - oop value is a String 561 // - hash(String) == hash in entry (same as verify()) 562 // - index for hash == index of entry (same as verify()) 563 // 564 // StringTable::compare_entries() checks: 565 // - oops are unique across all entries 566 // - String values are unique across all entries 567 // 568 int StringTable::verify_and_compare_entries() { 569 assert(StringTable_lock->is_locked(), "sanity check"); 570 571 int fail_cnt = 0; 572 573 // first, verify all the entries individually: 574 for (int bkt = 0; bkt < the_table()->table_size(); bkt++) { 575 HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt); 576 for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) { 577 VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs); 578 if (ret != _verify_pass) { 579 fail_cnt++; 580 } 581 } 582 } 583 584 // Optimization: if the above check did not find any failures, then 585 // the comparison loop below does not need to call verify_entry() 586 // before calling compare_entries(). If there were failures, then we 587 // have to call verify_entry() to see if the entry can be passed to 588 // compare_entries() safely. When we call verify_entry() in the loop 589 // below, we do so quietly to void duplicate messages and we don't 590 // increment fail_cnt because the failures have already been counted. 591 bool need_entry_verify = (fail_cnt != 0); 592 593 // second, verify all entries relative to each other: 594 for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) { 595 HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1); 596 for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) { 597 if (need_entry_verify) { 598 VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1, 599 _verify_quietly); 600 if (ret == _verify_fail_done) { 601 // cannot use the current entry to compare against other entries 602 continue; 603 } 604 } 605 606 for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) { 607 HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2); 608 int e_cnt2; 609 for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) { 610 if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) { 611 // skip the entries up to and including the one that 612 // we're comparing against 613 continue; 614 } 615 616 if (need_entry_verify) { 617 VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2, 618 _verify_quietly); 619 if (ret == _verify_fail_done) { 620 // cannot compare against this entry 621 continue; 622 } 623 } 624 625 // compare two entries, report and count any failures: 626 if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2) 627 != _verify_pass) { 628 fail_cnt++; 629 } 630 } 631 } 632 } 633 } 634 return fail_cnt; 635 } 636 637 // Create a new table and using alternate hash code, populate the new table 638 // with the existing strings. Set flag to use the alternate hash code afterwards. 639 void StringTable::rehash_table() { 640 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 641 // This should never happen with -Xshare:dump but it might in testing mode. 642 if (DumpSharedSpaces) return; 643 StringTable* new_table = new StringTable(); 644 645 // Rehash the table 646 the_table()->move_to(new_table); 647 648 // Delete the table and buckets (entries are reused in new table). 649 delete _the_table; 650 // Don't check if we need rehashing until the table gets unbalanced again. 651 // Then rehash with a new global seed. 652 _needs_rehashing = false; 653 _the_table = new_table; 654 } 655 656 // Utility for dumping strings 657 StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) : 658 DCmdWithParser(output, heap), 659 _verbose("-verbose", "Dump the content of each string in the table", 660 "BOOLEAN", false, "false") { 661 _dcmdparser.add_dcmd_option(&_verbose); 662 } 663 664 void StringtableDCmd::execute(DCmdSource source, TRAPS) { 665 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings, 666 _verbose.value()); 667 VMThread::execute(&dumper); 668 } 669 670 int StringtableDCmd::num_arguments() { 671 ResourceMark rm; 672 StringtableDCmd* dcmd = new StringtableDCmd(NULL, false); 673 if (dcmd != NULL) { 674 DCmdMark mark(dcmd); 675 return dcmd->_dcmdparser.num_arguments(); 676 } else { 677 return 0; 678 } 679 } 680 681 #if INCLUDE_CDS_JAVA_HEAP 682 // Sharing 683 oop StringTable::archive_string(oop s, Thread* THREAD) { 684 assert(DumpSharedSpaces, "this function is only used with -Xshare:dump"); 685 686 oop new_s = NULL; 687 typeArrayOop v = java_lang_String::value(s); 688 typeArrayOop new_v = (typeArrayOop)MetaspaceShared::archive_heap_object(v, THREAD); 689 if (new_v == NULL) { 690 return NULL; 691 } 692 new_s = MetaspaceShared::archive_heap_object(s, THREAD); 693 if (new_s == NULL) { 694 return NULL; 695 } 696 697 // adjust the pointer to the 'value' field in the new String oop 698 java_lang_String::set_value_raw(new_s, new_v); 699 return new_s; 700 } 701 702 bool StringTable::copy_shared_string(GrowableArray<MemRegion> *string_space, 703 CompactStringTableWriter* writer) { 704 assert(UseG1GC, "Only support G1 GC"); 705 assert(UseCompressedOops && UseCompressedClassPointers, 706 "Only support UseCompressedOops and UseCompressedClassPointers enabled"); 707 708 Thread* THREAD = Thread::current(); 709 G1CollectedHeap::heap()->begin_archive_alloc_range(); 710 for (int i = 0; i < the_table()->table_size(); ++i) { 711 HashtableEntry<oop, mtSymbol>* bucket = the_table()->bucket(i); 712 for ( ; bucket != NULL; bucket = bucket->next()) { 713 oop s = bucket->literal(); 714 unsigned int hash = java_lang_String::hash_code(s); 715 if (hash == 0) { 716 continue; 717 } 718 719 java_lang_String::set_hash(s, hash); 720 oop new_s = archive_string(s, THREAD); 721 if (new_s == NULL) { 722 continue; 723 } 724 725 // set the archived string in bucket 726 bucket->set_literal(new_s); 727 728 // add to the compact table 729 writer->add(hash, new_s); 730 } 731 } 732 733 G1CollectedHeap::heap()->end_archive_alloc_range(string_space, os::vm_allocation_granularity()); 734 assert(string_space->length() <= 2, "sanity"); 735 return true; 736 } 737 738 void StringTable::write_to_archive(GrowableArray<MemRegion> *string_space) { 739 assert(UseG1GC, "Only support G1 GC"); 740 assert(UseCompressedOops && UseCompressedClassPointers, 741 "Only support UseCompressedOops and UseCompressedClassPointers enabled"); 742 743 _shared_table.reset(); 744 int num_buckets = the_table()->number_of_entries() / 745 SharedSymbolTableBucketSize; 746 // calculation of num_buckets can result in zero buckets, we need at least one 747 CompactStringTableWriter writer(num_buckets > 1 ? num_buckets : 1, 748 &MetaspaceShared::stats()->string); 749 750 // Copy the interned strings into the "string space" within the java heap 751 if (copy_shared_string(string_space, &writer)) { 752 writer.dump(&_shared_table); 753 } 754 } 755 756 void StringTable::serialize(SerializeClosure* soc) { 757 _shared_table.set_type(CompactHashtable<oop, char>::_string_table); 758 _shared_table.serialize(soc); 759 760 if (soc->writing()) { 761 _shared_table.reset(); // Sanity. Make sure we don't use the shared table at dump time 762 } else if (!_shared_string_mapped) { 763 _shared_table.reset(); 764 } 765 } 766 767 void StringTable::shared_oops_do(OopClosure* f) { 768 _shared_table.oops_do(f); 769 } 770 #endif //INCLUDE_CDS_JAVA_HEAP 771