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 "memory/allocation.inline.hpp" 34 #include "memory/filemap.hpp" 35 #include "memory/resourceArea.hpp" 36 #include "oops/oop.inline.hpp" 37 #include "runtime/atomic.hpp" 38 #include "runtime/mutexLocker.hpp" 39 #include "utilities/hashtable.inline.hpp" 40 #include "utilities/macros.hpp" 41 #if INCLUDE_ALL_GCS 42 #include "gc/g1/g1CollectedHeap.hpp" 43 #include "gc/g1/g1SATBCardTableModRefBS.hpp" 44 #include "gc/g1/g1StringDedup.hpp" 45 #endif 46 47 // the number of buckets a thread claims 48 const int ClaimChunkSize = 32; 49 50 #ifdef ASSERT 51 class StableMemoryChecker : public StackObj { 52 enum { _bufsize = wordSize*4 }; 53 54 address _region; 55 jint _size; 56 u1 _save_buf[_bufsize]; 57 58 int sample(u1* save_buf) { 59 if (_size <= _bufsize) { 60 memcpy(save_buf, _region, _size); 61 return _size; 62 } else { 63 // copy head and tail 64 memcpy(&save_buf[0], _region, _bufsize/2); 65 memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2); 66 return (_bufsize/2)*2; 67 } 68 } 69 70 public: 71 StableMemoryChecker(const void* region, jint size) { 72 _region = (address) region; 73 _size = size; 74 sample(_save_buf); 75 } 76 77 bool verify() { 78 u1 check_buf[sizeof(_save_buf)]; 79 int check_size = sample(check_buf); 80 return (0 == memcmp(_save_buf, check_buf, check_size)); 81 } 82 83 void set_region(const void* region) { _region = (address) region; } 84 }; 85 #endif 86 87 88 // -------------------------------------------------------------------------- 89 StringTable* StringTable::_the_table = NULL; 90 bool StringTable::_ignore_shared_strings = false; 91 bool StringTable::_needs_rehashing = false; 92 93 volatile int StringTable::_parallel_claimed_idx = 0; 94 95 CompactHashtable<oop, char> StringTable::_shared_table; 96 97 // Pick hashing algorithm 98 unsigned int StringTable::hash_string(const jchar* s, int len) { 99 return use_alternate_hashcode() ? alt_hash_string(s, len) : 100 java_lang_String::hash_code(s, len); 101 } 102 103 unsigned int StringTable::alt_hash_string(const jchar* s, int len) { 104 return AltHashing::murmur3_32(seed(), s, len); 105 } 106 107 unsigned int StringTable::hash_string(oop string) { 108 EXCEPTION_MARK; 109 if (string == NULL) { 110 return hash_string((jchar*)NULL, 0); 111 } 112 ResourceMark rm(THREAD); 113 // All String oops are hashed as unicode 114 int length; 115 jchar* chars = java_lang_String::as_unicode_string(string, length, THREAD); 116 if (chars != NULL) { 117 return hash_string(chars, length); 118 } else { 119 vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "unable to create Unicode string for verification"); 120 return 0; 121 } 122 } 123 124 oop StringTable::lookup_shared(jchar* name, int len, unsigned int hash) { 125 assert(hash == java_lang_String::hash_code(name, len), 126 "hash must be computed using java_lang_String::hash_code"); 127 return _shared_table.lookup((const char*)name, hash, len); 128 } 129 130 oop StringTable::lookup_in_main_table(int index, jchar* name, 131 int len, unsigned int hash) { 132 int count = 0; 133 for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) { 134 count++; 135 if (l->hash() == hash) { 136 if (java_lang_String::equals(l->literal(), name, len)) { 137 return l->literal(); 138 } 139 } 140 } 141 // If the bucket size is too deep check if this hash code is insufficient. 142 if (count >= rehash_count && !needs_rehashing()) { 143 _needs_rehashing = check_rehash_table(count); 144 } 145 return NULL; 146 } 147 148 149 oop StringTable::basic_add(int index_arg, Handle string, jchar* name, 150 int len, unsigned int hashValue_arg, TRAPS) { 151 152 assert(java_lang_String::equals(string(), name, len), 153 "string must be properly initialized"); 154 // Cannot hit a safepoint in this function because the "this" pointer can move. 155 NoSafepointVerifier nsv; 156 157 // Check if the symbol table has been rehashed, if so, need to recalculate 158 // the hash value and index before second lookup. 159 unsigned int hashValue; 160 int index; 161 if (use_alternate_hashcode()) { 162 hashValue = alt_hash_string(name, len); 163 index = hash_to_index(hashValue); 164 } else { 165 hashValue = hashValue_arg; 166 index = index_arg; 167 } 168 169 // Since look-up was done lock-free, we need to check if another 170 // thread beat us in the race to insert the symbol. 171 172 // No need to lookup the shared table from here since the caller (intern()) already did 173 oop test = lookup_in_main_table(index, name, len, hashValue); // calls lookup(u1*, int) 174 if (test != NULL) { 175 // Entry already added 176 return test; 177 } 178 179 HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string()); 180 add_entry(index, entry); 181 return string(); 182 } 183 184 185 oop StringTable::lookup(Symbol* symbol) { 186 ResourceMark rm; 187 int length; 188 jchar* chars = symbol->as_unicode(length); 189 return lookup(chars, length); 190 } 191 192 // Tell the GC that this string was looked up in the StringTable. 193 static void ensure_string_alive(oop string) { 194 // A lookup in the StringTable could return an object that was previously 195 // considered dead. The SATB part of G1 needs to get notified about this 196 // potential resurrection, otherwise the marking might not find the object. 197 #if INCLUDE_ALL_GCS 198 if (UseG1GC && string != NULL) { 199 G1SATBCardTableModRefBS::enqueue(string); 200 } 201 #endif 202 } 203 204 oop StringTable::lookup(jchar* name, int len) { 205 // shared table always uses java_lang_String::hash_code 206 unsigned int hash = java_lang_String::hash_code(name, len); 207 oop string = lookup_shared(name, len, hash); 208 if (string != NULL) { 209 return string; 210 } 211 if (use_alternate_hashcode()) { 212 hash = alt_hash_string(name, len); 213 } 214 int index = the_table()->hash_to_index(hash); 215 string = the_table()->lookup_in_main_table(index, name, len, hash); 216 217 ensure_string_alive(string); 218 219 return string; 220 } 221 222 oop StringTable::intern(Handle string_or_null, jchar* name, 223 int len, TRAPS) { 224 // shared table always uses java_lang_String::hash_code 225 unsigned int hashValue = java_lang_String::hash_code(name, len); 226 oop found_string = lookup_shared(name, len, hashValue); 227 if (found_string != NULL) { 228 return found_string; 229 } 230 if (use_alternate_hashcode()) { 231 hashValue = alt_hash_string(name, len); 232 } 233 int index = the_table()->hash_to_index(hashValue); 234 found_string = the_table()->lookup_in_main_table(index, name, len, hashValue); 235 236 // Found 237 if (found_string != NULL) { 238 if (found_string != string_or_null()) { 239 ensure_string_alive(found_string); 240 } 241 return found_string; 242 } 243 244 debug_only(StableMemoryChecker smc(name, len * sizeof(name[0]))); 245 assert(!Universe::heap()->is_in_reserved(name), 246 "proposed name of symbol must be stable"); 247 248 HandleMark hm(THREAD); // cleanup strings created 249 Handle string; 250 // try to reuse the string if possible 251 if (!string_or_null.is_null()) { 252 string = string_or_null; 253 } else { 254 string = java_lang_String::create_from_unicode(name, len, CHECK_NULL); 255 } 256 257 #if INCLUDE_ALL_GCS 258 if (G1StringDedup::is_enabled()) { 259 // Deduplicate the string before it is interned. Note that we should never 260 // deduplicate a string after it has been interned. Doing so will counteract 261 // compiler optimizations done on e.g. interned string literals. 262 G1StringDedup::deduplicate(string()); 263 } 264 #endif 265 266 // Grab the StringTable_lock before getting the_table() because it could 267 // change at safepoint. 268 oop added_or_found; 269 { 270 MutexLocker ml(StringTable_lock, THREAD); 271 // Otherwise, add to symbol to table 272 added_or_found = the_table()->basic_add(index, string, name, len, 273 hashValue, CHECK_NULL); 274 } 275 276 if (added_or_found != string()) { 277 ensure_string_alive(added_or_found); 278 } 279 280 return added_or_found; 281 } 282 283 oop StringTable::intern(Symbol* symbol, TRAPS) { 284 if (symbol == NULL) return NULL; 285 ResourceMark rm(THREAD); 286 int length; 287 jchar* chars = symbol->as_unicode(length); 288 Handle string; 289 oop result = intern(string, chars, length, CHECK_NULL); 290 return result; 291 } 292 293 294 oop StringTable::intern(oop string, TRAPS) 295 { 296 if (string == NULL) return NULL; 297 ResourceMark rm(THREAD); 298 int length; 299 Handle h_string (THREAD, string); 300 jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL); 301 oop result = intern(h_string, chars, length, CHECK_NULL); 302 return result; 303 } 304 305 306 oop StringTable::intern(const char* utf8_string, TRAPS) { 307 if (utf8_string == NULL) return NULL; 308 ResourceMark rm(THREAD); 309 int length = UTF8::unicode_length(utf8_string); 310 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length); 311 UTF8::convert_to_unicode(utf8_string, chars, length); 312 Handle string; 313 oop result = intern(string, chars, length, CHECK_NULL); 314 return result; 315 } 316 317 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) { 318 buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), processed, removed); 319 } 320 321 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) { 322 // Readers of the table are unlocked, so we should only be removing 323 // entries at a safepoint. 324 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 325 const int limit = the_table()->table_size(); 326 327 for (;;) { 328 // Grab next set of buckets to scan 329 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize; 330 if (start_idx >= limit) { 331 // End of table 332 break; 333 } 334 335 int end_idx = MIN2(limit, start_idx + ClaimChunkSize); 336 buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, processed, removed); 337 } 338 } 339 340 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) { 341 const int limit = the_table()->table_size(); 342 343 assert(0 <= start_idx && start_idx <= limit, 344 "start_idx (%d) is out of bounds", start_idx); 345 assert(0 <= end_idx && end_idx <= limit, 346 "end_idx (%d) is out of bounds", end_idx); 347 assert(start_idx <= end_idx, 348 "Index ordering: start_idx=%d, end_idx=%d", 349 start_idx, end_idx); 350 351 for (int i = start_idx; i < end_idx; i += 1) { 352 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i); 353 while (entry != NULL) { 354 assert(!entry->is_shared(), "CDS not used for the StringTable"); 355 356 f->do_oop((oop*)entry->literal_addr()); 357 358 entry = entry->next(); 359 } 360 } 361 } 362 363 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed) { 364 const int limit = the_table()->table_size(); 365 366 assert(0 <= start_idx && start_idx <= limit, 367 "start_idx (%d) is out of bounds", start_idx); 368 assert(0 <= end_idx && end_idx <= limit, 369 "end_idx (%d) is out of bounds", end_idx); 370 assert(start_idx <= end_idx, 371 "Index ordering: start_idx=%d, end_idx=%d", 372 start_idx, end_idx); 373 374 for (int i = start_idx; i < end_idx; ++i) { 375 HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i); 376 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i); 377 while (entry != NULL) { 378 assert(!entry->is_shared(), "CDS not used for the StringTable"); 379 380 if (is_alive->do_object_b(entry->literal())) { 381 if (f != NULL) { 382 f->do_oop((oop*)entry->literal_addr()); 383 } 384 p = entry->next_addr(); 385 } else { 386 *p = entry->next(); 387 the_table()->free_entry(entry); 388 (*removed)++; 389 } 390 (*processed)++; 391 entry = *p; 392 } 393 } 394 } 395 396 void StringTable::oops_do(OopClosure* f) { 397 buckets_oops_do(f, 0, the_table()->table_size()); 398 } 399 400 void StringTable::possibly_parallel_oops_do(OopClosure* f) { 401 const int limit = the_table()->table_size(); 402 403 for (;;) { 404 // Grab next set of buckets to scan 405 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize; 406 if (start_idx >= limit) { 407 // End of table 408 break; 409 } 410 411 int end_idx = MIN2(limit, start_idx + ClaimChunkSize); 412 buckets_oops_do(f, start_idx, end_idx); 413 } 414 } 415 416 // This verification is part of Universe::verify() and needs to be quick. 417 // See StringTable::verify_and_compare() below for exhaustive verification. 418 void StringTable::verify() { 419 for (int i = 0; i < the_table()->table_size(); ++i) { 420 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i); 421 for ( ; p != NULL; p = p->next()) { 422 oop s = p->literal(); 423 guarantee(s != NULL, "interned string is NULL"); 424 unsigned int h = hash_string(s); 425 guarantee(p->hash() == h, "broken hash in string table entry"); 426 guarantee(the_table()->hash_to_index(h) == i, 427 "wrong index in string table"); 428 } 429 } 430 } 431 432 void StringTable::dump(outputStream* st, bool verbose) { 433 if (!verbose) { 434 the_table()->dump_table(st, "StringTable"); 435 } else { 436 Thread* THREAD = Thread::current(); 437 st->print_cr("VERSION: 1.1"); 438 for (int i = 0; i < the_table()->table_size(); ++i) { 439 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i); 440 for ( ; p != NULL; p = p->next()) { 441 oop s = p->literal(); 442 typeArrayOop value = java_lang_String::value(s); 443 int length = java_lang_String::length(s); 444 bool is_latin1 = java_lang_String::is_latin1(s); 445 446 if (length <= 0) { 447 st->print("%d: ", length); 448 } else { 449 ResourceMark rm(THREAD); 450 int utf8_length = length; 451 char* utf8_string; 452 453 if (!is_latin1) { 454 jchar* chars = value->char_at_addr(0); 455 utf8_string = UNICODE::as_utf8(chars, utf8_length); 456 } else { 457 jbyte* bytes = value->byte_at_addr(0); 458 utf8_string = UNICODE::as_utf8(bytes, utf8_length); 459 } 460 461 st->print("%d: ", utf8_length); 462 HashtableTextDump::put_utf8(st, utf8_string, utf8_length); 463 } 464 st->cr(); 465 } 466 } 467 } 468 } 469 470 StringTable::VerifyRetTypes StringTable::compare_entries( 471 int bkt1, int e_cnt1, 472 HashtableEntry<oop, mtSymbol>* e_ptr1, 473 int bkt2, int e_cnt2, 474 HashtableEntry<oop, mtSymbol>* e_ptr2) { 475 // These entries are sanity checked by verify_and_compare_entries() 476 // before this function is called. 477 oop str1 = e_ptr1->literal(); 478 oop str2 = e_ptr2->literal(); 479 480 if (str1 == str2) { 481 tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") " 482 "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]", 483 p2i(str1), bkt1, e_cnt1, bkt2, e_cnt2); 484 return _verify_fail_continue; 485 } 486 487 if (java_lang_String::equals(str1, str2)) { 488 tty->print_cr("ERROR: identical String values in entry @ " 489 "bucket[%d][%d] and entry @ bucket[%d][%d]", 490 bkt1, e_cnt1, bkt2, e_cnt2); 491 return _verify_fail_continue; 492 } 493 494 return _verify_pass; 495 } 496 497 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt, 498 HashtableEntry<oop, mtSymbol>* e_ptr, 499 StringTable::VerifyMesgModes mesg_mode) { 500 501 VerifyRetTypes ret = _verify_pass; // be optimistic 502 503 oop str = e_ptr->literal(); 504 if (str == NULL) { 505 if (mesg_mode == _verify_with_mesgs) { 506 tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt, 507 e_cnt); 508 } 509 // NULL oop means no more verifications are possible 510 return _verify_fail_done; 511 } 512 513 if (str->klass() != SystemDictionary::String_klass()) { 514 if (mesg_mode == _verify_with_mesgs) { 515 tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]", 516 bkt, e_cnt); 517 } 518 // not a String means no more verifications are possible 519 return _verify_fail_done; 520 } 521 522 unsigned int h = hash_string(str); 523 if (e_ptr->hash() != h) { 524 if (mesg_mode == _verify_with_mesgs) { 525 tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], " 526 "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h); 527 } 528 ret = _verify_fail_continue; 529 } 530 531 if (the_table()->hash_to_index(h) != bkt) { 532 if (mesg_mode == _verify_with_mesgs) { 533 tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], " 534 "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h, 535 the_table()->hash_to_index(h)); 536 } 537 ret = _verify_fail_continue; 538 } 539 540 return ret; 541 } 542 543 // See StringTable::verify() above for the quick verification that is 544 // part of Universe::verify(). This verification is exhaustive and 545 // reports on every issue that is found. StringTable::verify() only 546 // reports on the first issue that is found. 547 // 548 // StringTable::verify_entry() checks: 549 // - oop value != NULL (same as verify()) 550 // - oop value is a String 551 // - hash(String) == hash in entry (same as verify()) 552 // - index for hash == index of entry (same as verify()) 553 // 554 // StringTable::compare_entries() checks: 555 // - oops are unique across all entries 556 // - String values are unique across all entries 557 // 558 int StringTable::verify_and_compare_entries() { 559 assert(StringTable_lock->is_locked(), "sanity check"); 560 561 int fail_cnt = 0; 562 563 // first, verify all the entries individually: 564 for (int bkt = 0; bkt < the_table()->table_size(); bkt++) { 565 HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt); 566 for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) { 567 VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs); 568 if (ret != _verify_pass) { 569 fail_cnt++; 570 } 571 } 572 } 573 574 // Optimization: if the above check did not find any failures, then 575 // the comparison loop below does not need to call verify_entry() 576 // before calling compare_entries(). If there were failures, then we 577 // have to call verify_entry() to see if the entry can be passed to 578 // compare_entries() safely. When we call verify_entry() in the loop 579 // below, we do so quietly to void duplicate messages and we don't 580 // increment fail_cnt because the failures have already been counted. 581 bool need_entry_verify = (fail_cnt != 0); 582 583 // second, verify all entries relative to each other: 584 for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) { 585 HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1); 586 for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) { 587 if (need_entry_verify) { 588 VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1, 589 _verify_quietly); 590 if (ret == _verify_fail_done) { 591 // cannot use the current entry to compare against other entries 592 continue; 593 } 594 } 595 596 for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) { 597 HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2); 598 int e_cnt2; 599 for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) { 600 if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) { 601 // skip the entries up to and including the one that 602 // we're comparing against 603 continue; 604 } 605 606 if (need_entry_verify) { 607 VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2, 608 _verify_quietly); 609 if (ret == _verify_fail_done) { 610 // cannot compare against this entry 611 continue; 612 } 613 } 614 615 // compare two entries, report and count any failures: 616 if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2) 617 != _verify_pass) { 618 fail_cnt++; 619 } 620 } 621 } 622 } 623 } 624 return fail_cnt; 625 } 626 627 // Create a new table and using alternate hash code, populate the new table 628 // with the existing strings. Set flag to use the alternate hash code afterwards. 629 void StringTable::rehash_table() { 630 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 631 // This should never happen with -Xshare:dump but it might in testing mode. 632 if (DumpSharedSpaces) return; 633 StringTable* new_table = new StringTable(); 634 635 // Rehash the table 636 the_table()->move_to(new_table); 637 638 // Delete the table and buckets (entries are reused in new table). 639 delete _the_table; 640 // Don't check if we need rehashing until the table gets unbalanced again. 641 // Then rehash with a new global seed. 642 _needs_rehashing = false; 643 _the_table = new_table; 644 } 645 646 // Utility for dumping strings 647 StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) : 648 DCmdWithParser(output, heap), 649 _verbose("-verbose", "Dump the content of each string in the table", 650 "BOOLEAN", false, "false") { 651 _dcmdparser.add_dcmd_option(&_verbose); 652 } 653 654 void StringtableDCmd::execute(DCmdSource source, TRAPS) { 655 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings, 656 _verbose.value()); 657 VMThread::execute(&dumper); 658 } 659 660 int StringtableDCmd::num_arguments() { 661 ResourceMark rm; 662 StringtableDCmd* dcmd = new StringtableDCmd(NULL, false); 663 if (dcmd != NULL) { 664 DCmdMark mark(dcmd); 665 return dcmd->_dcmdparser.num_arguments(); 666 } else { 667 return 0; 668 } 669 } 670 671 // Sharing 672 bool StringTable::copy_shared_string(GrowableArray<MemRegion> *string_space, 673 CompactStringTableWriter* writer) { 674 #if INCLUDE_CDS && INCLUDE_ALL_GCS && defined(_LP64) && !defined(_WINDOWS) 675 assert(UseG1GC, "Only support G1 GC"); 676 assert(UseCompressedOops && UseCompressedClassPointers, 677 "Only support UseCompressedOops and UseCompressedClassPointers enabled"); 678 679 Thread* THREAD = Thread::current(); 680 G1CollectedHeap::heap()->begin_archive_alloc_range(); 681 for (int i = 0; i < the_table()->table_size(); ++i) { 682 HashtableEntry<oop, mtSymbol>* bucket = the_table()->bucket(i); 683 for ( ; bucket != NULL; bucket = bucket->next()) { 684 oop s = bucket->literal(); 685 unsigned int hash = java_lang_String::hash_code(s); 686 if (hash == 0) { 687 continue; 688 } 689 690 // allocate the new 'value' array first 691 typeArrayOop v = java_lang_String::value(s); 692 int v_len = v->size(); 693 typeArrayOop new_v; 694 if (G1CollectedHeap::heap()->is_archive_alloc_too_large(v_len)) { 695 continue; // skip the current String. The 'value' array is too large to handle 696 } else { 697 new_v = (typeArrayOop)G1CollectedHeap::heap()->archive_mem_allocate(v_len); 698 if (new_v == NULL) { 699 return false; // allocation failed 700 } 701 } 702 // now allocate the new String object 703 int s_len = s->size(); 704 oop new_s = (oop)G1CollectedHeap::heap()->archive_mem_allocate(s_len); 705 if (new_s == NULL) { 706 return false; 707 } 708 709 s->identity_hash(); 710 v->identity_hash(); 711 712 // copy the objects' data 713 Copy::aligned_disjoint_words((HeapWord*)s, (HeapWord*)new_s, s_len); 714 Copy::aligned_disjoint_words((HeapWord*)v, (HeapWord*)new_v, v_len); 715 716 // adjust the pointer to the 'value' field in the new String oop. Also pre-compute and set the 717 // 'hash' field. That avoids "write" to the shared strings at runtime by the deduplication process. 718 java_lang_String::set_value_raw(new_s, new_v); 719 if (java_lang_String::hash(new_s) == 0) { 720 java_lang_String::set_hash(new_s, hash); 721 } 722 723 // add to the compact table 724 writer->add(hash, new_s); 725 } 726 } 727 728 G1CollectedHeap::heap()->end_archive_alloc_range(string_space, os::vm_allocation_granularity()); 729 assert(string_space->length() <= 2, "sanity"); 730 #endif 731 return true; 732 } 733 734 void StringTable::serialize(SerializeClosure* soc, GrowableArray<MemRegion> *string_space, 735 size_t* space_size) { 736 #if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS) 737 _shared_table.reset(); 738 if (soc->writing()) { 739 if (!(UseG1GC && UseCompressedOops && UseCompressedClassPointers)) { 740 if (PrintSharedSpaces) { 741 tty->print_cr( 742 "Shared strings are excluded from the archive as UseG1GC, " 743 "UseCompressedOops and UseCompressedClassPointers are required." 744 "Current settings: UseG1GC=%s, UseCompressedOops=%s, UseCompressedClassPointers=%s.", 745 BOOL_TO_STR(UseG1GC), BOOL_TO_STR(UseCompressedOops), 746 BOOL_TO_STR(UseCompressedClassPointers)); 747 } 748 } else { 749 int num_buckets = the_table()->number_of_entries() / 750 SharedSymbolTableBucketSize; 751 // calculation of num_buckets can result in zero buckets, we need at least one 752 CompactStringTableWriter writer(num_buckets > 1 ? num_buckets : 1, 753 &MetaspaceShared::stats()->string); 754 755 // Copy the interned strings into the "string space" within the java heap 756 if (copy_shared_string(string_space, &writer)) { 757 for (int i = 0; i < string_space->length(); i++) { 758 *space_size += string_space->at(i).byte_size(); 759 } 760 writer.dump(&_shared_table); 761 } 762 } 763 } 764 765 _shared_table.set_type(CompactHashtable<oop, char>::_string_table); 766 _shared_table.serialize(soc); 767 768 if (soc->writing()) { 769 _shared_table.reset(); // Sanity. Make sure we don't use the shared table at dump time 770 } else if (_ignore_shared_strings) { 771 _shared_table.reset(); 772 } 773 #endif 774 } 775 776 void StringTable::shared_oops_do(OopClosure* f) { 777 #if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS) 778 _shared_table.oops_do(f); 779 #endif 780 } 781