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