1 /*
   2  * Copyright (c) 2014, 2019, 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/javaClasses.inline.hpp"
  28 #include "gc/shared/stringdedup/stringDedup.hpp"
  29 #include "gc/shared/stringdedup/stringDedupTable.hpp"
  30 #include "gc/shared/suspendibleThreadSet.hpp"
  31 #include "logging/log.hpp"
  32 #include "memory/padded.inline.hpp"
  33 #include "memory/universe.hpp"
  34 #include "oops/access.inline.hpp"
  35 #include "oops/arrayOop.inline.hpp"
  36 #include "oops/oop.inline.hpp"
  37 #include "oops/typeArrayOop.hpp"
  38 #include "runtime/mutexLocker.hpp"
  39 #include "runtime/safepointVerifiers.hpp"
  40 
  41 //
  42 // List of deduplication table entries. Links table
  43 // entries together using their _next fields.
  44 //
  45 class StringDedupEntryList : public CHeapObj<mtGC> {
  46 private:
  47   StringDedupEntry*   _list;
  48   size_t              _length;
  49 
  50 public:
  51   StringDedupEntryList() :
  52     _list(NULL),
  53     _length(0) {
  54   }
  55 
  56   void add(StringDedupEntry* entry) {
  57     entry->set_next(_list);
  58     _list = entry;
  59     _length++;
  60   }
  61 
  62   StringDedupEntry* remove() {
  63     StringDedupEntry* entry = _list;
  64     if (entry != NULL) {
  65       _list = entry->next();
  66       _length--;
  67     }
  68     return entry;
  69   }
  70 
  71   StringDedupEntry* remove_all() {
  72     StringDedupEntry* list = _list;
  73     _list = NULL;
  74     return list;
  75   }
  76 
  77   size_t length() {
  78     return _length;
  79   }
  80 };
  81 
  82 //
  83 // Cache of deduplication table entries. This cache provides fast allocation and
  84 // reuse of table entries to lower the pressure on the underlying allocator.
  85 // But more importantly, it provides fast/deferred freeing of table entries. This
  86 // is important because freeing of table entries is done during stop-the-world
  87 // phases and it is not uncommon for large number of entries to be freed at once.
  88 // Tables entries that are freed during these phases are placed onto a freelist in
  89 // the cache. The deduplication thread, which executes in a concurrent phase, will
  90 // later reuse or free the underlying memory for these entries.
  91 //
  92 // The cache allows for single-threaded allocations and multi-threaded frees.
  93 // Allocations are synchronized by StringDedupTable_lock as part of a table
  94 // modification.
  95 //
  96 class StringDedupEntryCache : public CHeapObj<mtGC> {
  97 private:
  98   // One cache/overflow list per GC worker to allow lock less freeing of
  99   // entries while doing a parallel scan of the table. Using PaddedEnd to
 100   // avoid false sharing.
 101   size_t                             _nlists;
 102   size_t                             _max_list_length;
 103   PaddedEnd<StringDedupEntryList>*   _cached;
 104   PaddedEnd<StringDedupEntryList>*   _overflowed;
 105 
 106 public:
 107   StringDedupEntryCache(size_t max_size);
 108   ~StringDedupEntryCache();
 109 
 110   // Set max number of table entries to cache.
 111   void set_max_size(size_t max_size);
 112 
 113   // Get a table entry from the cache, or allocate a new entry if the cache is empty.
 114   StringDedupEntry* alloc();
 115 
 116   // Insert a table entry into the cache.
 117   void free(StringDedupEntry* entry, uint worker_id);
 118 
 119   // Returns current number of entries in the cache.
 120   size_t size();
 121 
 122   // Deletes overflowed entries.
 123   void delete_overflowed();
 124 };
 125 
 126 StringDedupEntryCache::StringDedupEntryCache(size_t max_size) :
 127   _nlists(ParallelGCThreads),
 128   _max_list_length(0),
 129   _cached(PaddedArray<StringDedupEntryList, mtGC>::create_unfreeable((uint)_nlists)),
 130   _overflowed(PaddedArray<StringDedupEntryList, mtGC>::create_unfreeable((uint)_nlists)) {
 131   set_max_size(max_size);
 132 }
 133 
 134 StringDedupEntryCache::~StringDedupEntryCache() {
 135   ShouldNotReachHere();
 136 }
 137 
 138 void StringDedupEntryCache::set_max_size(size_t size) {
 139   _max_list_length = size / _nlists;
 140 }
 141 
 142 StringDedupEntry* StringDedupEntryCache::alloc() {
 143   for (size_t i = 0; i < _nlists; i++) {
 144     StringDedupEntry* entry = _cached[i].remove();
 145     if (entry != NULL) {
 146       return entry;
 147     }
 148   }
 149   return new StringDedupEntry();
 150 }
 151 
 152 void StringDedupEntryCache::free(StringDedupEntry* entry, uint worker_id) {
 153   assert(entry->obj() != NULL, "Double free");
 154   assert(worker_id < _nlists, "Invalid worker id");
 155 
 156   entry->set_obj(NULL);
 157   entry->set_hash(0);
 158 
 159   if (_cached[worker_id].length() < _max_list_length) {
 160     // Cache is not full
 161     _cached[worker_id].add(entry);
 162   } else {
 163     // Cache is full, add to overflow list for later deletion
 164     _overflowed[worker_id].add(entry);
 165   }
 166 }
 167 
 168 size_t StringDedupEntryCache::size() {
 169   size_t size = 0;
 170   for (size_t i = 0; i < _nlists; i++) {
 171     size += _cached[i].length();
 172   }
 173   return size;
 174 }
 175 
 176 void StringDedupEntryCache::delete_overflowed() {
 177   double start = os::elapsedTime();
 178   uintx count = 0;
 179 
 180   for (size_t i = 0; i < _nlists; i++) {
 181     StringDedupEntry* entry;
 182 
 183     {
 184       // The overflow list can be modified during safepoints, therefore
 185       // we temporarily join the suspendible thread set while removing
 186       // all entries from the list.
 187       SuspendibleThreadSetJoiner sts_join;
 188       entry = _overflowed[i].remove_all();
 189     }
 190 
 191     // Delete all entries
 192     while (entry != NULL) {
 193       StringDedupEntry* next = entry->next();
 194       delete entry;
 195       entry = next;
 196       count++;
 197     }
 198   }
 199 
 200   double end = os::elapsedTime();
 201   log_trace(gc, stringdedup)("Deleted " UINTX_FORMAT " entries, " STRDEDUP_TIME_FORMAT_MS,
 202                              count, STRDEDUP_TIME_PARAM_MS(end - start));
 203 }
 204 
 205 StringDedupTable*        StringDedupTable::_table = NULL;
 206 StringDedupEntryCache*   StringDedupTable::_entry_cache = NULL;
 207 
 208 const size_t             StringDedupTable::_min_size = (1 << 10);   // 1024
 209 const size_t             StringDedupTable::_max_size = (1 << 24);   // 16777216
 210 const double             StringDedupTable::_grow_load_factor = 2.0; // Grow table at 200% load
 211 const double             StringDedupTable::_shrink_load_factor = _grow_load_factor / 3.0; // Shrink table at 67% load
 212 const double             StringDedupTable::_max_cache_factor = 0.1; // Cache a maximum of 10% of the table size
 213 const uintx              StringDedupTable::_rehash_multiple = 60;   // Hash bucket has 60 times more collisions than expected
 214 const uintx              StringDedupTable::_rehash_threshold = (uintx)(_rehash_multiple * _grow_load_factor);
 215 
 216 uintx                    StringDedupTable::_entries_added = 0;
 217 uintx                    StringDedupTable::_entries_removed = 0;
 218 uintx                    StringDedupTable::_resize_count = 0;
 219 uintx                    StringDedupTable::_rehash_count = 0;
 220 
 221 StringDedupTable*        StringDedupTable::_resized_table = NULL;
 222 StringDedupTable*        StringDedupTable::_rehashed_table = NULL;
 223 volatile size_t          StringDedupTable::_claimed_index = 0;
 224 
 225 StringDedupTable::StringDedupTable(size_t size, jint hash_seed) :
 226   _size(size),
 227   _entries(0),
 228   _shrink_threshold((uintx)(size * _shrink_load_factor)),
 229   _grow_threshold((uintx)(size * _grow_load_factor)),
 230   _rehash_needed(false),
 231   _hash_seed(hash_seed) {
 232   assert(is_power_of_2(size), "Table size must be a power of 2");
 233   _buckets = NEW_C_HEAP_ARRAY(StringDedupEntry*, _size, mtGC);
 234   memset(_buckets, 0, _size * sizeof(StringDedupEntry*));
 235 }
 236 
 237 StringDedupTable::~StringDedupTable() {
 238   FREE_C_HEAP_ARRAY(G1StringDedupEntry*, _buckets);
 239 }
 240 
 241 void StringDedupTable::create() {
 242   assert(_table == NULL, "One string deduplication table allowed");
 243   _entry_cache = new StringDedupEntryCache(_min_size * _max_cache_factor);
 244   _table = new StringDedupTable(_min_size);
 245 }
 246 
 247 void StringDedupTable::add(typeArrayOop value, bool latin1, unsigned int hash, StringDedupEntry** list) {
 248   StringDedupEntry* entry = _entry_cache->alloc();
 249   entry->set_obj(value);
 250   entry->set_hash(hash);
 251   entry->set_latin1(latin1);
 252   entry->set_next(*list);
 253   *list = entry;
 254   _entries++;
 255 }
 256 
 257 void StringDedupTable::remove(StringDedupEntry** pentry, uint worker_id) {
 258   StringDedupEntry* entry = *pentry;
 259   *pentry = entry->next();
 260   _entry_cache->free(entry, worker_id);
 261 }
 262 
 263 void StringDedupTable::transfer(StringDedupEntry** pentry, StringDedupTable* dest) {
 264   StringDedupEntry* entry = *pentry;
 265   *pentry = entry->next();
 266   unsigned int hash = entry->hash();
 267   size_t index = dest->hash_to_index(hash);
 268   StringDedupEntry** list = dest->bucket(index);
 269   entry->set_next(*list);
 270   *list = entry;
 271 }
 272 
 273 typeArrayOop StringDedupTable::lookup(typeArrayOop value, bool latin1, unsigned int hash,
 274                                       StringDedupEntry** list, uintx &count) {
 275   for (StringDedupEntry* entry = *list; entry != NULL; entry = entry->next()) {
 276     if (entry->hash() == hash && entry->latin1() == latin1) {
 277       oop* obj_addr = (oop*)entry->obj_addr();
 278       oop obj = NativeAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(obj_addr);
 279       if (java_lang_String::value_equals(value, static_cast<typeArrayOop>(obj))) {
 280         obj = NativeAccess<ON_PHANTOM_OOP_REF>::oop_load(obj_addr);
 281         return static_cast<typeArrayOop>(obj);
 282       }
 283     }
 284     count++;
 285   }
 286 
 287   // Not found
 288   return NULL;
 289 }
 290 
 291 typeArrayOop StringDedupTable::lookup_or_add_inner(typeArrayOop value, bool latin1, unsigned int hash) {
 292   size_t index = hash_to_index(hash);
 293   StringDedupEntry** list = bucket(index);
 294   uintx count = 0;
 295 
 296   // Lookup in list
 297   typeArrayOop existing_value = lookup(value, latin1, hash, list, count);
 298 
 299   // Check if rehash is needed
 300   if (count > _rehash_threshold) {
 301     _rehash_needed = true;
 302   }
 303 
 304   if (existing_value == NULL) {
 305     // Not found, add new entry
 306     add(value, latin1, hash, list);
 307 
 308     // Update statistics
 309     _entries_added++;
 310   }
 311 
 312   return existing_value;
 313 }
 314 
 315 unsigned int StringDedupTable::hash_code(typeArrayOop value, bool latin1) {
 316   unsigned int hash;
 317   int length = value->length();
 318   if (latin1) {
 319     const jbyte* data = (jbyte*)value->base(T_BYTE);
 320     if (use_java_hash()) {
 321       hash = java_lang_String::hash_code(data, length);
 322     } else {
 323       hash = AltHashing::murmur3_32(_table->_hash_seed, data, length);
 324     }
 325   } else {
 326     length /= sizeof(jchar) / sizeof(jbyte); // Convert number of bytes to number of chars
 327     const jchar* data = (jchar*)value->base(T_CHAR);
 328     if (use_java_hash()) {
 329       hash = java_lang_String::hash_code(data, length);
 330     } else {
 331       hash = AltHashing::murmur3_32(_table->_hash_seed, data, length);
 332     }
 333   }
 334 
 335   return hash;
 336 }
 337 
 338 void StringDedupTable::deduplicate(oop java_string, StringDedupStat* stat) {
 339   assert(java_lang_String::is_instance(java_string), "Must be a string");
 340   NoSafepointVerifier nsv;
 341 
 342   stat->inc_inspected();
 343 
 344   typeArrayOop value = java_lang_String::value(java_string);
 345   if (value == NULL) {
 346     // String has no value
 347     stat->inc_skipped();
 348     return;
 349   }
 350 
 351   bool latin1 = java_lang_String::is_latin1(java_string);
 352   unsigned int hash = 0;
 353 
 354   if (use_java_hash()) {
 355     if (!java_lang_String::hash_is_set(java_string)) {
 356       stat->inc_hashed();
 357     }
 358     hash = java_lang_String::hash_code(java_string);
 359   } else {
 360     // Compute hash
 361     hash = hash_code(value, latin1);
 362     stat->inc_hashed();
 363   }
 364 
 365   typeArrayOop existing_value = lookup_or_add(value, latin1, hash);
 366   if (existing_value == value) {
 367     // Same value, already known
 368     stat->inc_known();
 369     return;
 370   }
 371 
 372   // Get size of value array
 373   uintx size_in_bytes = value->size() * HeapWordSize;
 374   stat->inc_new(size_in_bytes);
 375 
 376   if (existing_value != NULL) {
 377     // Existing value found, deduplicate string
 378     java_lang_String::set_value(java_string, existing_value);
 379     stat->deduped(value, size_in_bytes);
 380   }
 381 }
 382 
 383 bool StringDedupTable::is_resizing() {
 384   return _resized_table != NULL;
 385 }
 386 
 387 bool StringDedupTable::is_rehashing() {
 388   return _rehashed_table != NULL;
 389 }
 390 
 391 StringDedupTable* StringDedupTable::prepare_resize() {
 392   size_t size = _table->_size;
 393 
 394   // Check if the hashtable needs to be resized
 395   if (_table->_entries > _table->_grow_threshold) {
 396     // Grow table, double the size
 397     size *= 2;
 398     if (size > _max_size) {
 399       // Too big, don't resize
 400       return NULL;
 401     }
 402   } else if (_table->_entries < _table->_shrink_threshold) {
 403     // Shrink table, half the size
 404     size /= 2;
 405     if (size < _min_size) {
 406       // Too small, don't resize
 407       return NULL;
 408     }
 409   } else if (StringDeduplicationResizeALot) {
 410     // Force grow
 411     size *= 2;
 412     if (size > _max_size) {
 413       // Too big, force shrink instead
 414       size /= 4;
 415     }
 416   } else {
 417     // Resize not needed
 418     return NULL;
 419   }
 420 
 421   // Update statistics
 422   _resize_count++;
 423 
 424   // Update max cache size
 425   _entry_cache->set_max_size(size * _max_cache_factor);
 426 
 427   // Allocate the new table. The new table will be populated by workers
 428   // calling unlink_or_oops_do() and finally installed by finish_resize().
 429   return new StringDedupTable(size, _table->_hash_seed);
 430 }
 431 
 432 void StringDedupTable::finish_resize(StringDedupTable* resized_table) {
 433   assert(resized_table != NULL, "Invalid table");
 434 
 435   resized_table->_entries = _table->_entries;
 436 
 437   // Free old table
 438   delete _table;
 439 
 440   // Install new table
 441   _table = resized_table;
 442 }
 443 
 444 void StringDedupTable::unlink_or_oops_do(StringDedupUnlinkOrOopsDoClosure* cl, uint worker_id) {
 445   // The table is divided into partitions to allow lock-less parallel processing by
 446   // multiple worker threads. A worker thread first claims a partition, which ensures
 447   // exclusive access to that part of the table, then continues to process it. To allow
 448   // shrinking of the table in parallel we also need to make sure that the same worker
 449   // thread processes all partitions where entries will hash to the same destination
 450   // partition. Since the table size is always a power of two and we always shrink by
 451   // dividing the table in half, we know that for a given partition there is only one
 452   // other partition whoes entries will hash to the same destination partition. That
 453   // other partition is always the sibling partition in the second half of the table.
 454   // For example, if the table is divided into 8 partitions, the sibling of partition 0
 455   // is partition 4, the sibling of partition 1 is partition 5, etc.
 456   size_t table_half = _table->_size / 2;
 457 
 458   // Let each partition be one page worth of buckets
 459   size_t partition_size = MIN2(table_half, os::vm_page_size() / sizeof(StringDedupEntry*));
 460   assert(table_half % partition_size == 0, "Invalid partition size");
 461 
 462   // Number of entries removed during the scan
 463   uintx removed = 0;
 464 
 465   for (;;) {
 466     // Grab next partition to scan
 467     size_t partition_begin = claim_table_partition(partition_size);
 468     size_t partition_end = partition_begin + partition_size;
 469     if (partition_begin >= table_half) {
 470       // End of table
 471       break;
 472     }
 473 
 474     // Scan the partition followed by the sibling partition in the second half of the table
 475     removed += unlink_or_oops_do(cl, partition_begin, partition_end, worker_id);
 476     removed += unlink_or_oops_do(cl, table_half + partition_begin, table_half + partition_end, worker_id);
 477   }
 478 
 479   // Delayed update to avoid contention on the table lock
 480   if (removed > 0) {
 481     MutexLocker ml(StringDedupTable_lock, Mutex::_no_safepoint_check_flag);
 482     _table->_entries -= removed;
 483     _entries_removed += removed;
 484   }
 485 }
 486 
 487 uintx StringDedupTable::unlink_or_oops_do(StringDedupUnlinkOrOopsDoClosure* cl,
 488                                           size_t partition_begin,
 489                                           size_t partition_end,
 490                                           uint worker_id) {
 491   uintx removed = 0;
 492   for (size_t bucket = partition_begin; bucket < partition_end; bucket++) {
 493     StringDedupEntry** entry = _table->bucket(bucket);
 494     while (*entry != NULL) {
 495       oop* p = (oop*)(*entry)->obj_addr();
 496       if (cl->is_alive(*p)) {
 497         cl->keep_alive(p);
 498         if (is_resizing()) {
 499           // We are resizing the table, transfer entry to the new table
 500           _table->transfer(entry, _resized_table);
 501         } else {
 502           if (is_rehashing()) {
 503             // We are rehashing the table, rehash the entry but keep it
 504             // in the table. We can't transfer entries into the new table
 505             // at this point since we don't have exclusive access to all
 506             // destination partitions. finish_rehash() will do a single
 507             // threaded transfer of all entries.
 508             typeArrayOop value = (typeArrayOop)*p;
 509             bool latin1 = (*entry)->latin1();
 510             unsigned int hash = hash_code(value, latin1);
 511             (*entry)->set_hash(hash);
 512           }
 513 
 514           // Move to next entry
 515           entry = (*entry)->next_addr();
 516         }
 517       } else {
 518         // Not alive, remove entry from table
 519         _table->remove(entry, worker_id);
 520         removed++;
 521       }
 522     }
 523   }
 524 
 525   return removed;
 526 }
 527 
 528 void StringDedupTable::gc_prologue(bool resize_and_rehash_table) {
 529   assert(!is_resizing() && !is_rehashing(), "Already in progress?");
 530 
 531   _claimed_index = 0;
 532   if (resize_and_rehash_table) {
 533     // If both resize and rehash is needed, only do resize. Rehash of
 534     // the table will eventually happen if the situation persists.
 535     _resized_table = StringDedupTable::prepare_resize();
 536     if (!is_resizing()) {
 537       _rehashed_table = StringDedupTable::prepare_rehash();
 538     }
 539   }
 540 }
 541 
 542 void StringDedupTable::gc_epilogue() {
 543   assert(!is_resizing() || !is_rehashing(), "Can not both resize and rehash");
 544   assert(_claimed_index >= _table->_size / 2 || _claimed_index == 0, "All or nothing");
 545 
 546   if (is_resizing()) {
 547     StringDedupTable::finish_resize(_resized_table);
 548     _resized_table = NULL;
 549   } else if (is_rehashing()) {
 550     StringDedupTable::finish_rehash(_rehashed_table);
 551     _rehashed_table = NULL;
 552   }
 553 }
 554 
 555 StringDedupTable* StringDedupTable::prepare_rehash() {
 556   if (!_table->_rehash_needed && !StringDeduplicationRehashALot) {
 557     // Rehash not needed
 558     return NULL;
 559   }
 560 
 561   // Update statistics
 562   _rehash_count++;
 563 
 564   // Compute new hash seed
 565   _table->_hash_seed = AltHashing::compute_seed();
 566 
 567   // Allocate the new table, same size and hash seed
 568   return new StringDedupTable(_table->_size, _table->_hash_seed);
 569 }
 570 
 571 void StringDedupTable::finish_rehash(StringDedupTable* rehashed_table) {
 572   assert(rehashed_table != NULL, "Invalid table");
 573 
 574   // Move all newly rehashed entries into the correct buckets in the new table
 575   for (size_t bucket = 0; bucket < _table->_size; bucket++) {
 576     StringDedupEntry** entry = _table->bucket(bucket);
 577     while (*entry != NULL) {
 578       _table->transfer(entry, rehashed_table);
 579     }
 580   }
 581 
 582   rehashed_table->_entries = _table->_entries;
 583 
 584   // Free old table
 585   delete _table;
 586 
 587   // Install new table
 588   _table = rehashed_table;
 589 }
 590 
 591 size_t StringDedupTable::claim_table_partition(size_t partition_size) {
 592   return Atomic::add(partition_size, &_claimed_index) - partition_size;
 593 }
 594 
 595 void StringDedupTable::verify() {
 596   for (size_t bucket = 0; bucket < _table->_size; bucket++) {
 597     // Verify entries
 598     StringDedupEntry** entry = _table->bucket(bucket);
 599     while (*entry != NULL) {
 600       typeArrayOop value = (*entry)->obj();
 601       guarantee(value != NULL, "Object must not be NULL");
 602       guarantee(Universe::heap()->is_in(value), "Object must be on the heap");
 603       guarantee(!value->is_forwarded(), "Object must not be forwarded");
 604       guarantee(value->is_typeArray(), "Object must be a typeArrayOop");
 605       bool latin1 = (*entry)->latin1();
 606       unsigned int hash = hash_code(value, latin1);
 607       guarantee((*entry)->hash() == hash, "Table entry has inorrect hash");
 608       guarantee(_table->hash_to_index(hash) == bucket, "Table entry has incorrect index");
 609       entry = (*entry)->next_addr();
 610     }
 611 
 612     // Verify that we do not have entries with identical oops or identical arrays.
 613     // We only need to compare entries in the same bucket. If the same oop or an
 614     // identical array has been inserted more than once into different/incorrect
 615     // buckets the verification step above will catch that.
 616     StringDedupEntry** entry1 = _table->bucket(bucket);
 617     while (*entry1 != NULL) {
 618       typeArrayOop value1 = (*entry1)->obj();
 619       bool latin1_1 = (*entry1)->latin1();
 620       StringDedupEntry** entry2 = (*entry1)->next_addr();
 621       while (*entry2 != NULL) {
 622         typeArrayOop value2 = (*entry2)->obj();
 623         bool latin1_2 = (*entry2)->latin1();
 624         guarantee(latin1_1 != latin1_2 || !java_lang_String::value_equals(value1, value2), "Table entries must not have identical arrays");
 625         entry2 = (*entry2)->next_addr();
 626       }
 627       entry1 = (*entry1)->next_addr();
 628     }
 629   }
 630 }
 631 
 632 void StringDedupTable::clean_entry_cache() {
 633   _entry_cache->delete_overflowed();
 634 }
 635 
 636 void StringDedupTable::print_statistics() {
 637   Log(gc, stringdedup) log;
 638   log.debug("  Table");
 639   log.debug("    Memory Usage: " STRDEDUP_BYTES_FORMAT_NS,
 640             STRDEDUP_BYTES_PARAM(_table->_size * sizeof(StringDedupEntry*) + (_table->_entries + _entry_cache->size()) * sizeof(StringDedupEntry)));
 641   log.debug("    Size: " SIZE_FORMAT ", Min: " SIZE_FORMAT ", Max: " SIZE_FORMAT, _table->_size, _min_size, _max_size);
 642   log.debug("    Entries: " UINTX_FORMAT ", Load: " STRDEDUP_PERCENT_FORMAT_NS ", Cached: " UINTX_FORMAT ", Added: " UINTX_FORMAT ", Removed: " UINTX_FORMAT,
 643             _table->_entries, percent_of((size_t)_table->_entries, _table->_size), _entry_cache->size(), _entries_added, _entries_removed);
 644   log.debug("    Resize Count: " UINTX_FORMAT ", Shrink Threshold: " UINTX_FORMAT "(" STRDEDUP_PERCENT_FORMAT_NS "), Grow Threshold: " UINTX_FORMAT "(" STRDEDUP_PERCENT_FORMAT_NS ")",
 645             _resize_count, _table->_shrink_threshold, _shrink_load_factor * 100.0, _table->_grow_threshold, _grow_load_factor * 100.0);
 646   log.debug("    Rehash Count: " UINTX_FORMAT ", Rehash Threshold: " UINTX_FORMAT ", Hash Seed: 0x%x", _rehash_count, _rehash_threshold, _table->_hash_seed);
 647   log.debug("    Age Threshold: " UINTX_FORMAT, StringDeduplicationAgeThreshold);
 648 }
--- EOF ---