1 /* 2 * Copyright (c) 1997, 2016, 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() ? AltHashing::murmur3_32(seed(), s, len) : 100 java_lang_String::hash_code(s, len); 101 } 102 103 unsigned int StringTable::hash_string(oop string) { 104 EXCEPTION_MARK; 105 if (string == NULL) { 106 return hash_string((jchar*)NULL, 0); 107 } 108 ResourceMark rm(THREAD); 109 // All String oops are hashed as unicode 110 int length; 111 jchar* chars = java_lang_String::as_unicode_string(string, length, THREAD); 112 if (chars != NULL) { 113 return hash_string(chars, length); 114 } else { 115 vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "unable to create Unicode string for verification"); 116 return 0; 117 } 118 } 119 120 oop StringTable::lookup_shared(jchar* name, int len) { 121 // java_lang_String::hash_code() was used to compute hash values in the shared table. Don't 122 // use the hash value from StringTable::hash_string() as it might use alternate hashcode. 123 return _shared_table.lookup((const char*)name, 124 java_lang_String::hash_code(name, len), len); 125 } 126 127 oop StringTable::lookup_in_main_table(int index, jchar* name, 128 int len, unsigned int hash) { 129 int count = 0; 130 for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) { 131 count++; 132 if (l->hash() == hash) { 133 if (java_lang_String::equals(l->literal(), name, len)) { 134 return l->literal(); 135 } 136 } 137 } 138 // If the bucket size is too deep check if this hash code is insufficient. 139 if (count >= rehash_count && !needs_rehashing()) { 140 _needs_rehashing = check_rehash_table(count); 141 } 142 return NULL; 143 } 144 145 146 oop StringTable::basic_add(int index_arg, Handle string, jchar* name, 147 int len, unsigned int hashValue_arg, TRAPS) { 148 149 assert(java_lang_String::equals(string(), name, len), 150 "string must be properly initialized"); 151 // Cannot hit a safepoint in this function because the "this" pointer can move. 152 NoSafepointVerifier nsv; 153 154 // Check if the symbol table has been rehashed, if so, need to recalculate 155 // the hash value and index before second lookup. 156 unsigned int hashValue; 157 int index; 158 if (use_alternate_hashcode()) { 159 hashValue = hash_string(name, len); 160 index = hash_to_index(hashValue); 161 } else { 162 hashValue = hashValue_arg; 163 index = index_arg; 164 } 165 166 // Since look-up was done lock-free, we need to check if another 167 // thread beat us in the race to insert the symbol. 168 169 // No need to lookup the shared table from here since the caller (intern()) already did 170 oop test = lookup_in_main_table(index, name, len, hashValue); // calls lookup(u1*, int) 171 if (test != NULL) { 172 // Entry already added 173 return test; 174 } 175 176 HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string()); 177 add_entry(index, entry); 178 return string(); 179 } 180 181 182 oop StringTable::lookup(Symbol* symbol) { 183 ResourceMark rm; 184 int length; 185 jchar* chars = symbol->as_unicode(length); 186 return lookup(chars, length); 187 } 188 189 // Tell the GC that this string was looked up in the StringTable. 190 static void ensure_string_alive(oop string) { 191 // A lookup in the StringTable could return an object that was previously 192 // considered dead. The SATB part of G1 needs to get notified about this 193 // potential resurrection, otherwise the marking might not find the object. 194 #if INCLUDE_ALL_GCS 195 if (UseG1GC && string != NULL) { 196 G1SATBCardTableModRefBS::enqueue(string); 197 } 198 #endif 199 } 200 201 oop StringTable::lookup(jchar* name, int len) { 202 oop string = lookup_shared(name, len); 203 if (string != NULL) { 204 return string; 205 } 206 207 unsigned int hash = hash_string(name, len); 208 int index = the_table()->hash_to_index(hash); 209 string = the_table()->lookup_in_main_table(index, name, len, hash); 210 211 ensure_string_alive(string); 212 213 return string; 214 } 215 216 oop StringTable::intern(Handle string_or_null, jchar* name, 217 int len, TRAPS) { 218 oop found_string = lookup_shared(name, len); 219 if (found_string != NULL) { 220 return found_string; 221 } 222 223 unsigned int hashValue = hash_string(name, len); 224 int index = the_table()->hash_to_index(hashValue); 225 found_string = the_table()->lookup_in_main_table(index, name, len, hashValue); 226 227 // Found 228 if (found_string != NULL) { 229 if (found_string != string_or_null()) { 230 ensure_string_alive(found_string); 231 } 232 return found_string; 233 } 234 235 debug_only(StableMemoryChecker smc(name, len * sizeof(name[0]))); 236 assert(!Universe::heap()->is_in_reserved(name), 237 "proposed name of symbol must be stable"); 238 239 Handle string; 240 // try to reuse the string if possible 241 if (!string_or_null.is_null()) { 242 string = string_or_null; 243 } else { 244 string = java_lang_String::create_from_unicode(name, len, CHECK_NULL); 245 } 246 247 #if INCLUDE_ALL_GCS 248 if (G1StringDedup::is_enabled()) { 249 // Deduplicate the string before it is interned. Note that we should never 250 // deduplicate a string after it has been interned. Doing so will counteract 251 // compiler optimizations done on e.g. interned string literals. 252 G1StringDedup::deduplicate(string()); 253 } 254 #endif 255 256 // Grab the StringTable_lock before getting the_table() because it could 257 // change at safepoint. 258 oop added_or_found; 259 { 260 MutexLocker ml(StringTable_lock, THREAD); 261 // Otherwise, add to symbol to table 262 added_or_found = the_table()->basic_add(index, string, name, len, 263 hashValue, CHECK_NULL); 264 } 265 266 if (added_or_found != string()) { 267 ensure_string_alive(added_or_found); 268 } 269 270 return added_or_found; 271 } 272 273 oop StringTable::intern(Symbol* symbol, TRAPS) { 274 if (symbol == NULL) return NULL; 275 ResourceMark rm(THREAD); 276 int length; 277 jchar* chars = symbol->as_unicode(length); 278 Handle string; 279 oop result = intern(string, chars, length, CHECK_NULL); 280 return result; 281 } 282 283 284 oop StringTable::intern(oop string, TRAPS) 285 { 286 if (string == NULL) return NULL; 287 ResourceMark rm(THREAD); 288 int length; 289 Handle h_string (THREAD, string); 290 jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL); 291 oop result = intern(h_string, chars, length, CHECK_NULL); 292 return result; 293 } 294 295 296 oop StringTable::intern(const char* utf8_string, TRAPS) { 297 if (utf8_string == NULL) return NULL; 298 ResourceMark rm(THREAD); 299 int length = UTF8::unicode_length(utf8_string); 300 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length); 301 UTF8::convert_to_unicode(utf8_string, chars, length); 302 Handle string; 303 oop result = intern(string, chars, length, CHECK_NULL); 304 return result; 305 } 306 307 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) { 308 buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), processed, removed); 309 } 310 311 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) { 312 // Readers of the table are unlocked, so we should only be removing 313 // entries at a safepoint. 314 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 315 const int limit = the_table()->table_size(); 316 317 for (;;) { 318 // Grab next set of buckets to scan 319 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize; 320 if (start_idx >= limit) { 321 // End of table 322 break; 323 } 324 325 int end_idx = MIN2(limit, start_idx + ClaimChunkSize); 326 buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, processed, removed); 327 } 328 } 329 330 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) { 331 const int limit = the_table()->table_size(); 332 333 assert(0 <= start_idx && start_idx <= limit, 334 "start_idx (%d) is out of bounds", start_idx); 335 assert(0 <= end_idx && end_idx <= limit, 336 "end_idx (%d) is out of bounds", end_idx); 337 assert(start_idx <= end_idx, 338 "Index ordering: start_idx=%d, end_idx=%d", 339 start_idx, end_idx); 340 341 for (int i = start_idx; i < end_idx; i += 1) { 342 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i); 343 while (entry != NULL) { 344 assert(!entry->is_shared(), "CDS not used for the StringTable"); 345 346 f->do_oop((oop*)entry->literal_addr()); 347 348 entry = entry->next(); 349 } 350 } 351 } 352 353 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed) { 354 const int limit = the_table()->table_size(); 355 356 assert(0 <= start_idx && start_idx <= limit, 357 "start_idx (%d) is out of bounds", start_idx); 358 assert(0 <= end_idx && end_idx <= limit, 359 "end_idx (%d) is out of bounds", end_idx); 360 assert(start_idx <= end_idx, 361 "Index ordering: start_idx=%d, end_idx=%d", 362 start_idx, end_idx); 363 364 for (int i = start_idx; i < end_idx; ++i) { 365 HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i); 366 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i); 367 while (entry != NULL) { 368 assert(!entry->is_shared(), "CDS not used for the StringTable"); 369 370 if (is_alive->do_object_b(entry->literal())) { 371 if (f != NULL) { 372 f->do_oop((oop*)entry->literal_addr()); 373 } 374 p = entry->next_addr(); 375 } else { 376 *p = entry->next(); 377 the_table()->free_entry(entry); 378 (*removed)++; 379 } 380 (*processed)++; 381 entry = *p; 382 } 383 } 384 } 385 386 void StringTable::oops_do(OopClosure* f) { 387 buckets_oops_do(f, 0, the_table()->table_size()); 388 } 389 390 void StringTable::possibly_parallel_oops_do(OopClosure* f) { 391 const int limit = the_table()->table_size(); 392 393 for (;;) { 394 // Grab next set of buckets to scan 395 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize; 396 if (start_idx >= limit) { 397 // End of table 398 break; 399 } 400 401 int end_idx = MIN2(limit, start_idx + ClaimChunkSize); 402 buckets_oops_do(f, start_idx, end_idx); 403 } 404 } 405 406 // This verification is part of Universe::verify() and needs to be quick. 407 // See StringTable::verify_and_compare() below for exhaustive verification. 408 void StringTable::verify() { 409 for (int i = 0; i < the_table()->table_size(); ++i) { 410 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i); 411 for ( ; p != NULL; p = p->next()) { 412 oop s = p->literal(); 413 guarantee(s != NULL, "interned string is NULL"); 414 unsigned int h = hash_string(s); 415 guarantee(p->hash() == h, "broken hash in string table entry"); 416 guarantee(the_table()->hash_to_index(h) == i, 417 "wrong index in string table"); 418 } 419 } 420 } 421 422 void StringTable::dump(outputStream* st, bool verbose) { 423 if (!verbose) { 424 the_table()->dump_table(st, "StringTable"); 425 } else { 426 Thread* THREAD = Thread::current(); 427 st->print_cr("VERSION: 1.1"); 428 for (int i = 0; i < the_table()->table_size(); ++i) { 429 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i); 430 for ( ; p != NULL; p = p->next()) { 431 oop s = p->literal(); 432 typeArrayOop value = java_lang_String::value(s); 433 int length = java_lang_String::length(s); 434 bool is_latin1 = java_lang_String::is_latin1(s); 435 436 if (length <= 0) { 437 st->print("%d: ", length); 438 } else { 439 ResourceMark rm(THREAD); 440 int utf8_length = length; 441 char* utf8_string; 442 443 if (!is_latin1) { 444 jchar* chars = value->char_at_addr(0); 445 utf8_string = UNICODE::as_utf8(chars, utf8_length); 446 } else { 447 jbyte* bytes = value->byte_at_addr(0); 448 utf8_string = UNICODE::as_utf8(bytes, utf8_length); 449 } 450 451 st->print("%d: ", utf8_length); 452 HashtableTextDump::put_utf8(st, utf8_string, utf8_length); 453 } 454 st->cr(); 455 } 456 } 457 } 458 } 459 460 StringTable::VerifyRetTypes StringTable::compare_entries( 461 int bkt1, int e_cnt1, 462 HashtableEntry<oop, mtSymbol>* e_ptr1, 463 int bkt2, int e_cnt2, 464 HashtableEntry<oop, mtSymbol>* e_ptr2) { 465 // These entries are sanity checked by verify_and_compare_entries() 466 // before this function is called. 467 oop str1 = e_ptr1->literal(); 468 oop str2 = e_ptr2->literal(); 469 470 if (str1 == str2) { 471 tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") " 472 "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]", 473 p2i(str1), bkt1, e_cnt1, bkt2, e_cnt2); 474 return _verify_fail_continue; 475 } 476 477 if (java_lang_String::equals(str1, str2)) { 478 tty->print_cr("ERROR: identical String values in entry @ " 479 "bucket[%d][%d] and entry @ bucket[%d][%d]", 480 bkt1, e_cnt1, bkt2, e_cnt2); 481 return _verify_fail_continue; 482 } 483 484 return _verify_pass; 485 } 486 487 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt, 488 HashtableEntry<oop, mtSymbol>* e_ptr, 489 StringTable::VerifyMesgModes mesg_mode) { 490 491 VerifyRetTypes ret = _verify_pass; // be optimistic 492 493 oop str = e_ptr->literal(); 494 if (str == NULL) { 495 if (mesg_mode == _verify_with_mesgs) { 496 tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt, 497 e_cnt); 498 } 499 // NULL oop means no more verifications are possible 500 return _verify_fail_done; 501 } 502 503 if (str->klass() != SystemDictionary::String_klass()) { 504 if (mesg_mode == _verify_with_mesgs) { 505 tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]", 506 bkt, e_cnt); 507 } 508 // not a String means no more verifications are possible 509 return _verify_fail_done; 510 } 511 512 unsigned int h = hash_string(str); 513 if (e_ptr->hash() != h) { 514 if (mesg_mode == _verify_with_mesgs) { 515 tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], " 516 "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h); 517 } 518 ret = _verify_fail_continue; 519 } 520 521 if (the_table()->hash_to_index(h) != bkt) { 522 if (mesg_mode == _verify_with_mesgs) { 523 tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], " 524 "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h, 525 the_table()->hash_to_index(h)); 526 } 527 ret = _verify_fail_continue; 528 } 529 530 return ret; 531 } 532 533 // See StringTable::verify() above for the quick verification that is 534 // part of Universe::verify(). This verification is exhaustive and 535 // reports on every issue that is found. StringTable::verify() only 536 // reports on the first issue that is found. 537 // 538 // StringTable::verify_entry() checks: 539 // - oop value != NULL (same as verify()) 540 // - oop value is a String 541 // - hash(String) == hash in entry (same as verify()) 542 // - index for hash == index of entry (same as verify()) 543 // 544 // StringTable::compare_entries() checks: 545 // - oops are unique across all entries 546 // - String values are unique across all entries 547 // 548 int StringTable::verify_and_compare_entries() { 549 assert(StringTable_lock->is_locked(), "sanity check"); 550 551 int fail_cnt = 0; 552 553 // first, verify all the entries individually: 554 for (int bkt = 0; bkt < the_table()->table_size(); bkt++) { 555 HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt); 556 for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) { 557 VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs); 558 if (ret != _verify_pass) { 559 fail_cnt++; 560 } 561 } 562 } 563 564 // Optimization: if the above check did not find any failures, then 565 // the comparison loop below does not need to call verify_entry() 566 // before calling compare_entries(). If there were failures, then we 567 // have to call verify_entry() to see if the entry can be passed to 568 // compare_entries() safely. When we call verify_entry() in the loop 569 // below, we do so quietly to void duplicate messages and we don't 570 // increment fail_cnt because the failures have already been counted. 571 bool need_entry_verify = (fail_cnt != 0); 572 573 // second, verify all entries relative to each other: 574 for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) { 575 HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1); 576 for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) { 577 if (need_entry_verify) { 578 VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1, 579 _verify_quietly); 580 if (ret == _verify_fail_done) { 581 // cannot use the current entry to compare against other entries 582 continue; 583 } 584 } 585 586 for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) { 587 HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2); 588 int e_cnt2; 589 for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) { 590 if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) { 591 // skip the entries up to and including the one that 592 // we're comparing against 593 continue; 594 } 595 596 if (need_entry_verify) { 597 VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2, 598 _verify_quietly); 599 if (ret == _verify_fail_done) { 600 // cannot compare against this entry 601 continue; 602 } 603 } 604 605 // compare two entries, report and count any failures: 606 if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2) 607 != _verify_pass) { 608 fail_cnt++; 609 } 610 } 611 } 612 } 613 } 614 return fail_cnt; 615 } 616 617 // Create a new table and using alternate hash code, populate the new table 618 // with the existing strings. Set flag to use the alternate hash code afterwards. 619 void StringTable::rehash_table() { 620 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); 621 // This should never happen with -Xshare:dump but it might in testing mode. 622 if (DumpSharedSpaces) return; 623 StringTable* new_table = new StringTable(); 624 625 // Rehash the table 626 the_table()->move_to(new_table); 627 628 // Delete the table and buckets (entries are reused in new table). 629 delete _the_table; 630 // Don't check if we need rehashing until the table gets unbalanced again. 631 // Then rehash with a new global seed. 632 _needs_rehashing = false; 633 _the_table = new_table; 634 } 635 636 // Utility for dumping strings 637 StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) : 638 DCmdWithParser(output, heap), 639 _verbose("-verbose", "Dump the content of each string in the table", 640 "BOOLEAN", false, "false") { 641 _dcmdparser.add_dcmd_option(&_verbose); 642 } 643 644 void StringtableDCmd::execute(DCmdSource source, TRAPS) { 645 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings, 646 _verbose.value()); 647 VMThread::execute(&dumper); 648 } 649 650 int StringtableDCmd::num_arguments() { 651 ResourceMark rm; 652 StringtableDCmd* dcmd = new StringtableDCmd(NULL, false); 653 if (dcmd != NULL) { 654 DCmdMark mark(dcmd); 655 return dcmd->_dcmdparser.num_arguments(); 656 } else { 657 return 0; 658 } 659 } 660 661 // Sharing 662 bool StringTable::copy_shared_string(GrowableArray<MemRegion> *string_space, 663 CompactStringTableWriter* writer) { 664 #if INCLUDE_CDS && INCLUDE_ALL_GCS && defined(_LP64) && !defined(_WINDOWS) 665 assert(UseG1GC, "Only support G1 GC"); 666 assert(UseCompressedOops && UseCompressedClassPointers, 667 "Only support UseCompressedOops and UseCompressedClassPointers enabled"); 668 669 Thread* THREAD = Thread::current(); 670 G1CollectedHeap::heap()->begin_archive_alloc_range(); 671 for (int i = 0; i < the_table()->table_size(); ++i) { 672 HashtableEntry<oop, mtSymbol>* bucket = the_table()->bucket(i); 673 for ( ; bucket != NULL; bucket = bucket->next()) { 674 oop s = bucket->literal(); 675 unsigned int hash = java_lang_String::hash_code(s); 676 if (hash == 0) { 677 continue; 678 } 679 680 // allocate the new 'value' array first 681 typeArrayOop v = java_lang_String::value(s); 682 int v_len = v->size(); 683 typeArrayOop new_v; 684 if (G1CollectedHeap::heap()->is_archive_alloc_too_large(v_len)) { 685 continue; // skip the current String. The 'value' array is too large to handle 686 } else { 687 new_v = (typeArrayOop)G1CollectedHeap::heap()->archive_mem_allocate(v_len); 688 if (new_v == NULL) { 689 return false; // allocation failed 690 } 691 } 692 // now allocate the new String object 693 int s_len = s->size(); 694 oop new_s = (oop)G1CollectedHeap::heap()->archive_mem_allocate(s_len); 695 if (new_s == NULL) { 696 return false; 697 } 698 699 s->identity_hash(); 700 v->identity_hash(); 701 702 // copy the objects' data 703 Copy::aligned_disjoint_words((HeapWord*)s, (HeapWord*)new_s, s_len); 704 Copy::aligned_disjoint_words((HeapWord*)v, (HeapWord*)new_v, v_len); 705 706 // adjust the pointer to the 'value' field in the new String oop. Also pre-compute and set the 707 // 'hash' field. That avoids "write" to the shared strings at runtime by the deduplication process. 708 java_lang_String::set_value_raw(new_s, new_v); 709 if (java_lang_String::hash(new_s) == 0) { 710 java_lang_String::set_hash(new_s, hash); 711 } 712 713 // add to the compact table 714 writer->add(hash, new_s); 715 } 716 } 717 718 G1CollectedHeap::heap()->end_archive_alloc_range(string_space, os::vm_allocation_granularity()); 719 assert(string_space->length() <= 2, "sanity"); 720 #endif 721 return true; 722 } 723 724 void StringTable::serialize(SerializeClosure* soc, GrowableArray<MemRegion> *string_space, 725 size_t* space_size) { 726 #if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS) 727 _shared_table.reset(); 728 if (soc->writing()) { 729 if (!(UseG1GC && UseCompressedOops && UseCompressedClassPointers)) { 730 if (PrintSharedSpaces) { 731 tty->print_cr( 732 "Shared strings are excluded from the archive as UseG1GC, " 733 "UseCompressedOops and UseCompressedClassPointers are required." 734 "Current settings: UseG1GC=%s, UseCompressedOops=%s, UseCompressedClassPointers=%s.", 735 BOOL_TO_STR(UseG1GC), BOOL_TO_STR(UseCompressedOops), 736 BOOL_TO_STR(UseCompressedClassPointers)); 737 } 738 } else { 739 int num_buckets = the_table()->number_of_entries() / 740 SharedSymbolTableBucketSize; 741 // calculation of num_buckets can result in zero buckets, we need at least one 742 CompactStringTableWriter writer(num_buckets > 1 ? num_buckets : 1, 743 &MetaspaceShared::stats()->string); 744 745 // Copy the interned strings into the "string space" within the java heap 746 if (copy_shared_string(string_space, &writer)) { 747 for (int i = 0; i < string_space->length(); i++) { 748 *space_size += string_space->at(i).byte_size(); 749 } 750 writer.dump(&_shared_table); 751 } 752 } 753 } 754 755 _shared_table.set_type(CompactHashtable<oop, char>::_string_table); 756 _shared_table.serialize(soc); 757 758 if (soc->writing()) { 759 _shared_table.reset(); // Sanity. Make sure we don't use the shared table at dump time 760 } else if (_ignore_shared_strings) { 761 _shared_table.reset(); 762 } 763 #endif 764 } 765 766 void StringTable::shared_oops_do(OopClosure* f) { 767 #if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS) 768 _shared_table.oops_do(f); 769 #endif 770 } 771