rev 48017 : [mq]: Access_strings

   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/access.inline.hpp"
  39 #include "oops/oop.inline.hpp"
  40 #include "runtime/atomic.hpp"
  41 #include "runtime/mutexLocker.hpp"
  42 #include "services/diagnosticCommand.hpp"
  43 #include "utilities/hashtable.inline.hpp"
  44 #include "utilities/macros.hpp"
  45 #if INCLUDE_ALL_GCS
  46 #include "gc/g1/g1CollectedHeap.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::string_object(HashtableEntry<oop, mtSymbol>* entry) {
 128   return RootAccess<ON_PHANTOM_OOP_REF>::oop_load(entry->literal_addr());
 129 }
 130 
 131 oop StringTable::string_object_no_keepalive(HashtableEntry<oop, mtSymbol>* entry) {
 132   // The AS_NO_KEEPALIVE peeks at the oop without keeping it alive.
 133   // This is *very dangerous* in general but is okay in this specific
 134   // case. The subsequent oop_load keeps the oop alive if it it matched
 135   // the jchar* string.
 136   return RootAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(entry->literal_addr());
 137 }
 138 
 139 void StringTable::set_string_object(HashtableEntry<oop, mtSymbol>* entry, oop string) {
 140   RootAccess<ON_PHANTOM_OOP_REF>::oop_store(entry->literal_addr(), string);
 141 }
 142 
 143 oop StringTable::lookup_shared(jchar* name, int len, unsigned int hash) {
 144   assert(hash == java_lang_String::hash_code(name, len),
 145          "hash must be computed using java_lang_String::hash_code");
 146   return _shared_table.lookup((const char*)name, hash, len);
 147 }
 148 
 149 oop StringTable::lookup_in_main_table(int index, jchar* name,
 150                                       int len, unsigned int hash) {
 151   int count = 0;
 152   for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {
 153     count++;
 154     if (l->hash() == hash) {
 155       oop string = string_object_no_keepalive(l);
 156       if (java_lang_String::equals(string, name, len)) {
 157         return string_object(l);
 158       }
 159     }
 160   }
 161   // If the bucket size is too deep check if this hash code is insufficient.
 162   if (count >= rehash_count && !needs_rehashing()) {
 163     _needs_rehashing = check_rehash_table(count);
 164   }
 165   return NULL;
 166 }
 167 
 168 
 169 oop StringTable::basic_add(int index_arg, Handle string, jchar* name,
 170                            int len, unsigned int hashValue_arg, TRAPS) {
 171 
 172   assert(java_lang_String::equals(string(), name, len),
 173          "string must be properly initialized");
 174   // Cannot hit a safepoint in this function because the "this" pointer can move.
 175   NoSafepointVerifier nsv;
 176 
 177   // Check if the symbol table has been rehashed, if so, need to recalculate
 178   // the hash value and index before second lookup.
 179   unsigned int hashValue;
 180   int index;
 181   if (use_alternate_hashcode()) {
 182     hashValue = alt_hash_string(name, len);
 183     index = hash_to_index(hashValue);
 184   } else {
 185     hashValue = hashValue_arg;
 186     index = index_arg;
 187   }
 188 
 189   // Since look-up was done lock-free, we need to check if another
 190   // thread beat us in the race to insert the symbol.
 191 
 192   // No need to lookup the shared table from here since the caller (intern()) already did
 193   oop test = lookup_in_main_table(index, name, len, hashValue); // calls lookup(u1*, int)
 194   if (test != NULL) {
 195     // Entry already added
 196     return test;
 197   }
 198 
 199   HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());
 200   add_entry(index, entry);
 201   return string();
 202 }
 203 
 204 
 205 oop StringTable::lookup(Symbol* symbol) {
 206   ResourceMark rm;
 207   int length;
 208   jchar* chars = symbol->as_unicode(length);
 209   return lookup(chars, length);
 210 }
 211 












 212 oop StringTable::lookup(jchar* name, int len) {
 213   // shared table always uses java_lang_String::hash_code
 214   unsigned int hash = java_lang_String::hash_code(name, len);
 215   oop string = lookup_shared(name, len, hash);
 216   if (string != NULL) {
 217     return string;
 218   }
 219   if (use_alternate_hashcode()) {
 220     hash = alt_hash_string(name, len);
 221   }
 222   int index = the_table()->hash_to_index(hash);
 223   string = the_table()->lookup_in_main_table(index, name, len, hash);
 224 


 225   return string;
 226 }
 227 
 228 oop StringTable::intern(Handle string_or_null, jchar* name,
 229                         int len, TRAPS) {
 230   // shared table always uses java_lang_String::hash_code
 231   unsigned int hashValue = java_lang_String::hash_code(name, len);
 232   oop found_string = lookup_shared(name, len, hashValue);
 233   if (found_string != NULL) {
 234     return found_string;
 235   }
 236   if (use_alternate_hashcode()) {
 237     hashValue = alt_hash_string(name, len);
 238   }
 239   int index = the_table()->hash_to_index(hashValue);
 240   found_string = the_table()->lookup_in_main_table(index, name, len, hashValue);
 241 
 242   // Found
 243   if (found_string != NULL) {



 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   return added_or_found;
 280 }
 281 
 282 oop StringTable::intern(Symbol* symbol, TRAPS) {
 283   if (symbol == NULL) return NULL;
 284   ResourceMark rm(THREAD);
 285   int length;
 286   jchar* chars = symbol->as_unicode(length);
 287   Handle string;
 288   oop result = intern(string, chars, length, CHECK_NULL);
 289   return result;
 290 }
 291 
 292 
 293 oop StringTable::intern(oop string, TRAPS)
 294 {
 295   if (string == NULL) return NULL;
 296   ResourceMark rm(THREAD);
 297   int length;
 298   Handle h_string (THREAD, string);
 299   jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL);
 300   oop result = intern(h_string, chars, length, CHECK_NULL);
 301   return result;
 302 }
 303 
 304 
 305 oop StringTable::intern(const char* utf8_string, TRAPS) {
 306   if (utf8_string == NULL) return NULL;
 307   ResourceMark rm(THREAD);
 308   int length = UTF8::unicode_length(utf8_string);
 309   jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
 310   UTF8::convert_to_unicode(utf8_string, chars, length);
 311   Handle string;
 312   oop result = intern(string, chars, length, CHECK_NULL);
 313   return result;
 314 }
 315 
 316 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
 317   BucketUnlinkContext context;
 318   buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), &context);
 319   _the_table->bulk_free_entries(&context);
 320   *processed = context._num_processed;
 321   *removed = context._num_removed;
 322 }
 323 
 324 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
 325   // Readers of the table are unlocked, so we should only be removing
 326   // entries at a safepoint.
 327   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
 328   const int limit = the_table()->table_size();
 329 
 330   BucketUnlinkContext context;
 331   for (;;) {
 332     // Grab next set of buckets to scan
 333     int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
 334     if (start_idx >= limit) {
 335       // End of table
 336       break;
 337     }
 338 
 339     int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
 340     buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, &context);
 341   }
 342   _the_table->bulk_free_entries(&context);
 343   *processed = context._num_processed;
 344   *removed = context._num_removed;
 345 }
 346 
 347 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {
 348   const int limit = the_table()->table_size();
 349 
 350   assert(0 <= start_idx && start_idx <= limit,
 351          "start_idx (%d) is out of bounds", start_idx);
 352   assert(0 <= end_idx && end_idx <= limit,
 353          "end_idx (%d) is out of bounds", end_idx);
 354   assert(start_idx <= end_idx,
 355          "Index ordering: start_idx=%d, end_idx=%d",
 356          start_idx, end_idx);
 357 
 358   for (int i = start_idx; i < end_idx; i += 1) {
 359     HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
 360     while (entry != NULL) {
 361       assert(!entry->is_shared(), "CDS not used for the StringTable");
 362 
 363       f->do_oop((oop*)entry->literal_addr());
 364 
 365       entry = entry->next();
 366     }
 367   }
 368 }
 369 
 370 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, BucketUnlinkContext* context) {
 371   const int limit = the_table()->table_size();
 372 
 373   assert(0 <= start_idx && start_idx <= limit,
 374          "start_idx (%d) is out of bounds", start_idx);
 375   assert(0 <= end_idx && end_idx <= limit,
 376          "end_idx (%d) is out of bounds", end_idx);
 377   assert(start_idx <= end_idx,
 378          "Index ordering: start_idx=%d, end_idx=%d",
 379          start_idx, end_idx);
 380 
 381   for (int i = start_idx; i < end_idx; ++i) {
 382     HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i);
 383     HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
 384     while (entry != NULL) {
 385       assert(!entry->is_shared(), "CDS not used for the StringTable");
 386 
 387       if (is_alive->do_object_b(string_object_no_keepalive(entry))) {
 388         if (f != NULL) {
 389           f->do_oop(entry->literal_addr());
 390         }
 391         p = entry->next_addr();
 392       } else {
 393         *p = entry->next();
 394         context->free_entry(entry);
 395       }
 396       context->_num_processed++;
 397       entry = *p;
 398     }
 399   }
 400 }
 401 
 402 void StringTable::oops_do(OopClosure* f) {
 403   buckets_oops_do(f, 0, the_table()->table_size());
 404 }
 405 
 406 void StringTable::possibly_parallel_oops_do(OopClosure* f) {
 407   const int limit = the_table()->table_size();
 408 
 409   for (;;) {
 410     // Grab next set of buckets to scan
 411     int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
 412     if (start_idx >= limit) {
 413       // End of table
 414       break;
 415     }
 416 
 417     int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
 418     buckets_oops_do(f, start_idx, end_idx);
 419   }
 420 }
 421 
 422 // This verification is part of Universe::verify() and needs to be quick.
 423 // See StringTable::verify_and_compare() below for exhaustive verification.
 424 void StringTable::verify() {
 425   for (int i = 0; i < the_table()->table_size(); ++i) {
 426     HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
 427     for ( ; p != NULL; p = p->next()) {
 428       oop s = string_object_no_keepalive(p);
 429       guarantee(s != NULL, "interned string is NULL");
 430       unsigned int h = hash_string(s);
 431       guarantee(p->hash() == h, "broken hash in string table entry");
 432       guarantee(the_table()->hash_to_index(h) == i,
 433                 "wrong index in string table");
 434     }
 435   }
 436 }
 437 
 438 void StringTable::dump(outputStream* st, bool verbose) {
 439   if (!verbose) {
 440     the_table()->print_table_statistics(st, "StringTable");
 441   } else {
 442     Thread* THREAD = Thread::current();
 443     st->print_cr("VERSION: 1.1");
 444     for (int i = 0; i < the_table()->table_size(); ++i) {
 445       HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
 446       for ( ; p != NULL; p = p->next()) {
 447         oop s = string_object_no_keepalive(p);
 448         typeArrayOop value     = java_lang_String::value_no_keepalive(s);
 449         int          length    = java_lang_String::length(s);
 450         bool         is_latin1 = java_lang_String::is_latin1(s);
 451 
 452         if (length <= 0) {
 453           st->print("%d: ", length);
 454         } else {
 455           ResourceMark rm(THREAD);
 456           int utf8_length = length;
 457           char* utf8_string;
 458 
 459           if (!is_latin1) {
 460             jchar* chars = value->char_at_addr(0);
 461             utf8_string = UNICODE::as_utf8(chars, utf8_length);
 462           } else {
 463             jbyte* bytes = value->byte_at_addr(0);
 464             utf8_string = UNICODE::as_utf8(bytes, utf8_length);
 465           }
 466 
 467           st->print("%d: ", utf8_length);
 468           HashtableTextDump::put_utf8(st, utf8_string, utf8_length);
 469         }
 470         st->cr();
 471       }
 472     }
 473   }
 474 }
 475 
 476 StringTable::VerifyRetTypes StringTable::compare_entries(
 477                                       int bkt1, int e_cnt1,
 478                                       HashtableEntry<oop, mtSymbol>* e_ptr1,
 479                                       int bkt2, int e_cnt2,
 480                                       HashtableEntry<oop, mtSymbol>* e_ptr2) {
 481   // These entries are sanity checked by verify_and_compare_entries()
 482   // before this function is called.
 483   oop str1 = string_object_no_keepalive(e_ptr1);
 484   oop str2 = string_object_no_keepalive(e_ptr2);
 485 
 486   if (str1 == str2) {
 487     tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "
 488                   "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",
 489                   p2i(str1), bkt1, e_cnt1, bkt2, e_cnt2);
 490     return _verify_fail_continue;
 491   }
 492 
 493   if (java_lang_String::equals(str1, str2)) {
 494     tty->print_cr("ERROR: identical String values in entry @ "
 495                   "bucket[%d][%d] and entry @ bucket[%d][%d]",
 496                   bkt1, e_cnt1, bkt2, e_cnt2);
 497     return _verify_fail_continue;
 498   }
 499 
 500   return _verify_pass;
 501 }
 502 
 503 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,
 504                                                       HashtableEntry<oop, mtSymbol>* e_ptr,
 505                                                       StringTable::VerifyMesgModes mesg_mode) {
 506 
 507   VerifyRetTypes ret = _verify_pass;  // be optimistic
 508 
 509   oop str = string_object_no_keepalive(e_ptr);
 510   if (str == NULL) {
 511     if (mesg_mode == _verify_with_mesgs) {
 512       tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,
 513                     e_cnt);
 514     }
 515     // NULL oop means no more verifications are possible
 516     return _verify_fail_done;
 517   }
 518 
 519   if (str->klass() != SystemDictionary::String_klass()) {
 520     if (mesg_mode == _verify_with_mesgs) {
 521       tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",
 522                     bkt, e_cnt);
 523     }
 524     // not a String means no more verifications are possible
 525     return _verify_fail_done;
 526   }
 527 
 528   unsigned int h = hash_string(str);
 529   if (e_ptr->hash() != h) {
 530     if (mesg_mode == _verify_with_mesgs) {
 531       tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "
 532                     "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);
 533     }
 534     ret = _verify_fail_continue;
 535   }
 536 
 537   if (the_table()->hash_to_index(h) != bkt) {
 538     if (mesg_mode == _verify_with_mesgs) {
 539       tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "
 540                     "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,
 541                     the_table()->hash_to_index(h));
 542     }
 543     ret = _verify_fail_continue;
 544   }
 545 
 546   return ret;
 547 }
 548 
 549 // See StringTable::verify() above for the quick verification that is
 550 // part of Universe::verify(). This verification is exhaustive and
 551 // reports on every issue that is found. StringTable::verify() only
 552 // reports on the first issue that is found.
 553 //
 554 // StringTable::verify_entry() checks:
 555 // - oop value != NULL (same as verify())
 556 // - oop value is a String
 557 // - hash(String) == hash in entry (same as verify())
 558 // - index for hash == index of entry (same as verify())
 559 //
 560 // StringTable::compare_entries() checks:
 561 // - oops are unique across all entries
 562 // - String values are unique across all entries
 563 //
 564 int StringTable::verify_and_compare_entries() {
 565   assert(StringTable_lock->is_locked(), "sanity check");
 566 
 567   int  fail_cnt = 0;
 568 
 569   // first, verify all the entries individually:
 570   for (int bkt = 0; bkt < the_table()->table_size(); bkt++) {
 571     HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);
 572     for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {
 573       VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);
 574       if (ret != _verify_pass) {
 575         fail_cnt++;
 576       }
 577     }
 578   }
 579 
 580   // Optimization: if the above check did not find any failures, then
 581   // the comparison loop below does not need to call verify_entry()
 582   // before calling compare_entries(). If there were failures, then we
 583   // have to call verify_entry() to see if the entry can be passed to
 584   // compare_entries() safely. When we call verify_entry() in the loop
 585   // below, we do so quietly to void duplicate messages and we don't
 586   // increment fail_cnt because the failures have already been counted.
 587   bool need_entry_verify = (fail_cnt != 0);
 588 
 589   // second, verify all entries relative to each other:
 590   for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {
 591     HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);
 592     for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {
 593       if (need_entry_verify) {
 594         VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,
 595                                           _verify_quietly);
 596         if (ret == _verify_fail_done) {
 597           // cannot use the current entry to compare against other entries
 598           continue;
 599         }
 600       }
 601 
 602       for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {
 603         HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);
 604         int e_cnt2;
 605         for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {
 606           if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {
 607             // skip the entries up to and including the one that
 608             // we're comparing against
 609             continue;
 610           }
 611 
 612           if (need_entry_verify) {
 613             VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,
 614                                               _verify_quietly);
 615             if (ret == _verify_fail_done) {
 616               // cannot compare against this entry
 617               continue;
 618             }
 619           }
 620 
 621           // compare two entries, report and count any failures:
 622           if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)
 623               != _verify_pass) {
 624             fail_cnt++;
 625           }
 626         }
 627       }
 628     }
 629   }
 630   return fail_cnt;
 631 }
 632 
 633 // Create a new table and using alternate hash code, populate the new table
 634 // with the existing strings.   Set flag to use the alternate hash code afterwards.
 635 void StringTable::rehash_table() {
 636   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
 637   // This should never happen with -Xshare:dump but it might in testing mode.
 638   if (DumpSharedSpaces) return;
 639   StringTable* new_table = new StringTable();
 640 
 641   // Rehash the table
 642   the_table()->move_to(new_table);
 643 
 644   // Delete the table and buckets (entries are reused in new table).
 645   delete _the_table;
 646   // Don't check if we need rehashing until the table gets unbalanced again.
 647   // Then rehash with a new global seed.
 648   _needs_rehashing = false;
 649   _the_table = new_table;
 650 }
 651 
 652 // Utility for dumping strings
 653 StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) :
 654                                  DCmdWithParser(output, heap),
 655   _verbose("-verbose", "Dump the content of each string in the table",
 656            "BOOLEAN", false, "false") {
 657   _dcmdparser.add_dcmd_option(&_verbose);
 658 }
 659 
 660 void StringtableDCmd::execute(DCmdSource source, TRAPS) {
 661   VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings,
 662                          _verbose.value());
 663   VMThread::execute(&dumper);
 664 }
 665 
 666 int StringtableDCmd::num_arguments() {
 667   ResourceMark rm;
 668   StringtableDCmd* dcmd = new StringtableDCmd(NULL, false);
 669   if (dcmd != NULL) {
 670     DCmdMark mark(dcmd);
 671     return dcmd->_dcmdparser.num_arguments();
 672   } else {
 673     return 0;
 674   }
 675 }
 676 
 677 #if INCLUDE_CDS_JAVA_HEAP
 678 // Sharing
 679 oop StringTable::create_archived_string(oop s, Thread* THREAD) {
 680   assert(DumpSharedSpaces, "this function is only used with -Xshare:dump");
 681 
 682   oop new_s = NULL;
 683   typeArrayOop v = java_lang_String::value_no_keepalive(s);
 684   typeArrayOop new_v = (typeArrayOop)MetaspaceShared::archive_heap_object(v, THREAD);
 685   if (new_v == NULL) {
 686     return NULL;
 687   }
 688   new_s = MetaspaceShared::archive_heap_object(s, THREAD);
 689   if (new_s == NULL) {
 690     return NULL;
 691   }
 692 
 693   // adjust the pointer to the 'value' field in the new String oop
 694   java_lang_String::set_value_raw(new_s, new_v);
 695   return new_s;
 696 }
 697 
 698 bool StringTable::copy_shared_string(GrowableArray<MemRegion> *string_space,
 699                                      CompactStringTableWriter* writer) {
 700   assert(MetaspaceShared::is_heap_object_archiving_allowed(), "must be");
 701 
 702   Thread* THREAD = Thread::current();
 703   G1CollectedHeap::heap()->begin_archive_alloc_range();
 704   for (int i = 0; i < the_table()->table_size(); ++i) {
 705     HashtableEntry<oop, mtSymbol>* bucket = the_table()->bucket(i);
 706     for ( ; bucket != NULL; bucket = bucket->next()) {
 707       oop s = string_object_no_keepalive(bucket);
 708       unsigned int hash = java_lang_String::hash_code(s);
 709       if (hash == 0) {
 710         continue;
 711       }
 712 
 713       java_lang_String::set_hash(s, hash);
 714       oop new_s = create_archived_string(s, THREAD);
 715       if (new_s == NULL) {
 716         continue;
 717       }
 718 
 719       // set the archived string in bucket
 720       set_string_object(bucket, new_s);
 721 
 722       // add to the compact table
 723       writer->add(hash, new_s);
 724     }
 725   }
 726 
 727   G1CollectedHeap::heap()->end_archive_alloc_range(string_space, os::vm_allocation_granularity());
 728   return true;
 729 }
 730 
 731 void StringTable::write_to_archive(GrowableArray<MemRegion> *string_space) {
 732   assert(MetaspaceShared::is_heap_object_archiving_allowed(), "must be");
 733 
 734   _shared_table.reset();
 735   int num_buckets = the_table()->number_of_entries() /
 736                          SharedSymbolTableBucketSize;
 737   // calculation of num_buckets can result in zero buckets, we need at least one
 738   CompactStringTableWriter writer(num_buckets > 1 ? num_buckets : 1,
 739                                   &MetaspaceShared::stats()->string);
 740 
 741   // Copy the interned strings into the "string space" within the java heap
 742   if (copy_shared_string(string_space, &writer)) {
 743     writer.dump(&_shared_table);
 744   }
 745 }
 746 
 747 void StringTable::serialize(SerializeClosure* soc) {
 748   _shared_table.set_type(CompactHashtable<oop, char>::_string_table);
 749   _shared_table.serialize(soc);
 750 
 751   if (soc->writing()) {
 752     _shared_table.reset(); // Sanity. Make sure we don't use the shared table at dump time
 753   } else if (!_shared_string_mapped) {
 754     _shared_table.reset();
 755   }
 756 }
 757 
 758 void StringTable::shared_oops_do(OopClosure* f) {
 759   _shared_table.oops_do(f);
 760 }
 761 #endif //INCLUDE_CDS_JAVA_HEAP

--- EOF ---