1 /*
   2  * Copyright (c) 2014, 2015, 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/g1/g1CollectedHeap.inline.hpp"
  29 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
  30 #include "gc/g1/g1StringDedup.hpp"
  31 #include "gc/g1/g1StringDedupTable.hpp"
  32 #include "gc/shared/gcLocker.hpp"
  33 #include "logging/log.hpp"
  34 #include "memory/padded.inline.hpp"
  35 #include "oops/oop.inline.hpp"
  36 #include "oops/typeArrayOop.hpp"
  37 #include "runtime/mutexLocker.hpp"
  38 
  39 //
  40 // Freelist in the deduplication table entry cache. Links table
  41 // entries together using their _next fields.
  42 //
  43 class G1StringDedupEntryFreeList : public CHeapObj<mtGC> {
  44 private:
  45   G1StringDedupEntry* _list;
  46   size_t              _length;
  47 
  48 public:
  49   G1StringDedupEntryFreeList() :
  50     _list(NULL),
  51     _length(0) {
  52   }
  53 
  54   void add(G1StringDedupEntry* entry) {
  55     entry->set_next(_list);
  56     _list = entry;
  57     _length++;
  58   }
  59 
  60   G1StringDedupEntry* remove() {
  61     G1StringDedupEntry* entry = _list;
  62     if (entry != NULL) {
  63       _list = entry->next();
  64       _length--;
  65     }
  66     return entry;
  67   }
  68 
  69   size_t length() {
  70     return _length;
  71   }
  72 };
  73 
  74 //
  75 // Cache of deduplication table entries. This cache provides fast allocation and
  76 // reuse of table entries to lower the pressure on the underlying allocator.
  77 // But more importantly, it provides fast/deferred freeing of table entries. This
  78 // is important because freeing of table entries is done during stop-the-world
  79 // phases and it is not uncommon for large number of entries to be freed at once.
  80 // Tables entries that are freed during these phases are placed onto a freelist in
  81 // the cache. The deduplication thread, which executes in a concurrent phase, will
  82 // later reuse or free the underlying memory for these entries.
  83 //
  84 // The cache allows for single-threaded allocations and multi-threaded frees.
  85 // Allocations are synchronized by StringDedupTable_lock as part of a table
  86 // modification.
  87 //
  88 class G1StringDedupEntryCache : public CHeapObj<mtGC> {
  89 private:
  90   // One freelist per GC worker to allow lock less freeing of
  91   // entries while doing a parallel scan of the table. Using
  92   // PaddedEnd to avoid false sharing.
  93   PaddedEnd<G1StringDedupEntryFreeList>* _lists;
  94   size_t                                 _nlists;
  95 
  96 public:
  97   G1StringDedupEntryCache();
  98   ~G1StringDedupEntryCache();
  99 
 100   // Get a table entry from the cache freelist, or allocate a new
 101   // entry if the cache is empty.
 102   G1StringDedupEntry* alloc();
 103 
 104   // Insert a table entry into the cache freelist.
 105   void free(G1StringDedupEntry* entry, uint worker_id);
 106 
 107   // Returns current number of entries in the cache.
 108   size_t size();
 109 
 110   // If the cache has grown above the given max size, trim it down
 111   // and deallocate the memory occupied by trimmed of entries.
 112   void trim(size_t max_size);
 113 };
 114 
 115 G1StringDedupEntryCache::G1StringDedupEntryCache() {
 116   _nlists = ParallelGCThreads;
 117   _lists = PaddedArray<G1StringDedupEntryFreeList, mtGC>::create_unfreeable((uint)_nlists);
 118 }
 119 
 120 G1StringDedupEntryCache::~G1StringDedupEntryCache() {
 121   ShouldNotReachHere();
 122 }
 123 
 124 G1StringDedupEntry* G1StringDedupEntryCache::alloc() {
 125   for (size_t i = 0; i < _nlists; i++) {
 126     G1StringDedupEntry* entry = _lists[i].remove();
 127     if (entry != NULL) {
 128       return entry;
 129     }
 130   }
 131   return new G1StringDedupEntry();
 132 }
 133 
 134 void G1StringDedupEntryCache::free(G1StringDedupEntry* entry, uint worker_id) {
 135   assert(entry->obj() != NULL, "Double free");
 136   assert(worker_id < _nlists, "Invalid worker id");
 137   entry->set_obj(NULL);
 138   entry->set_hash(0);
 139   _lists[worker_id].add(entry);
 140 }
 141 
 142 size_t G1StringDedupEntryCache::size() {
 143   size_t size = 0;
 144   for (size_t i = 0; i < _nlists; i++) {
 145     size += _lists[i].length();
 146   }
 147   return size;
 148 }
 149 
 150 void G1StringDedupEntryCache::trim(size_t max_size) {
 151   size_t cache_size = 0;
 152   for (size_t i = 0; i < _nlists; i++) {
 153     G1StringDedupEntryFreeList* list = &_lists[i];
 154     cache_size += list->length();
 155     while (cache_size > max_size) {
 156       G1StringDedupEntry* entry = list->remove();
 157       assert(entry != NULL, "Should not be null");
 158       cache_size--;
 159       delete entry;
 160     }
 161   }
 162 }
 163 
 164 G1StringDedupTable*      G1StringDedupTable::_table = NULL;
 165 G1StringDedupEntryCache* G1StringDedupTable::_entry_cache = NULL;
 166 
 167 const size_t             G1StringDedupTable::_min_size = (1 << 10);   // 1024
 168 const size_t             G1StringDedupTable::_max_size = (1 << 24);   // 16777216
 169 const double             G1StringDedupTable::_grow_load_factor = 2.0; // Grow table at 200% load
 170 const double             G1StringDedupTable::_shrink_load_factor = _grow_load_factor / 3.0; // Shrink table at 67% load
 171 const double             G1StringDedupTable::_max_cache_factor = 0.1; // Cache a maximum of 10% of the table size
 172 const uintx              G1StringDedupTable::_rehash_multiple = 60;   // Hash bucket has 60 times more collisions than expected
 173 const uintx              G1StringDedupTable::_rehash_threshold = (uintx)(_rehash_multiple * _grow_load_factor);
 174 
 175 uintx                    G1StringDedupTable::_entries_added = 0;
 176 uintx                    G1StringDedupTable::_entries_removed = 0;
 177 uintx                    G1StringDedupTable::_resize_count = 0;
 178 uintx                    G1StringDedupTable::_rehash_count = 0;
 179 
 180 G1StringDedupTable::G1StringDedupTable(size_t size, jint hash_seed) :
 181   _size(size),
 182   _entries(0),
 183   _grow_threshold((uintx)(size * _grow_load_factor)),
 184   _shrink_threshold((uintx)(size * _shrink_load_factor)),
 185   _rehash_needed(false),
 186   _hash_seed(hash_seed) {
 187   assert(is_power_of_2(size), "Table size must be a power of 2");
 188   _buckets = NEW_C_HEAP_ARRAY(G1StringDedupEntry*, _size, mtGC);
 189   memset(_buckets, 0, _size * sizeof(G1StringDedupEntry*));
 190 }
 191 
 192 G1StringDedupTable::~G1StringDedupTable() {
 193   FREE_C_HEAP_ARRAY(G1StringDedupEntry*, _buckets);
 194 }
 195 
 196 void G1StringDedupTable::create() {
 197   assert(_table == NULL, "One string deduplication table allowed");
 198   _entry_cache = new G1StringDedupEntryCache();
 199   _table = new G1StringDedupTable(_min_size);
 200 }
 201 
 202 void G1StringDedupTable::add(typeArrayOop value, bool latin1, unsigned int hash, G1StringDedupEntry** list) {
 203   G1StringDedupEntry* entry = _entry_cache->alloc();
 204   entry->set_obj(value);
 205   entry->set_hash(hash);
 206   entry->set_latin1(latin1);
 207   entry->set_next(*list);
 208   *list = entry;
 209   _entries++;
 210 }
 211 
 212 void G1StringDedupTable::remove(G1StringDedupEntry** pentry, uint worker_id) {
 213   G1StringDedupEntry* entry = *pentry;
 214   *pentry = entry->next();
 215   _entry_cache->free(entry, worker_id);
 216 }
 217 
 218 void G1StringDedupTable::transfer(G1StringDedupEntry** pentry, G1StringDedupTable* dest) {
 219   G1StringDedupEntry* entry = *pentry;
 220   *pentry = entry->next();
 221   unsigned int hash = entry->hash();
 222   size_t index = dest->hash_to_index(hash);
 223   G1StringDedupEntry** list = dest->bucket(index);
 224   entry->set_next(*list);
 225   *list = entry;
 226 }
 227 
 228 bool G1StringDedupTable::equals(typeArrayOop value1, typeArrayOop value2) {
 229   return (value1 == value2 ||
 230           (value1->length() == value2->length() &&
 231            (!memcmp(value1->base(T_BYTE),
 232                     value2->base(T_BYTE),
 233                     value1->length() * sizeof(jbyte)))));
 234 }
 235 
 236 typeArrayOop G1StringDedupTable::lookup(typeArrayOop value, bool latin1, unsigned int hash,
 237                                         G1StringDedupEntry** list, uintx &count) {
 238   for (G1StringDedupEntry* entry = *list; entry != NULL; entry = entry->next()) {
 239     if (entry->hash() == hash && entry->latin1() == latin1) {
 240       typeArrayOop existing_value = entry->obj();
 241       if (equals(value, existing_value)) {
 242         // Match found
 243         return existing_value;
 244       }
 245     }
 246     count++;
 247   }
 248 
 249   // Not found
 250   return NULL;
 251 }
 252 
 253 typeArrayOop G1StringDedupTable::lookup_or_add_inner(typeArrayOop value, bool latin1, unsigned int hash) {
 254   size_t index = hash_to_index(hash);
 255   G1StringDedupEntry** list = bucket(index);
 256   uintx count = 0;
 257 
 258   // Lookup in list
 259   typeArrayOop existing_value = lookup(value, latin1, hash, list, count);
 260 
 261   // Check if rehash is needed
 262   if (count > _rehash_threshold) {
 263     _rehash_needed = true;
 264   }
 265 
 266   if (existing_value == NULL) {
 267     // Not found, add new entry
 268     add(value, latin1, hash, list);
 269 
 270     // Update statistics
 271     _entries_added++;
 272   }
 273 
 274   return existing_value;
 275 }
 276 
 277 unsigned int G1StringDedupTable::hash_code(typeArrayOop value, bool latin1) {
 278   unsigned int hash;
 279   int length = value->length();
 280   if (latin1) {
 281     const jbyte* data = (jbyte*)value->base(T_BYTE);
 282     if (use_java_hash()) {
 283       hash = java_lang_String::hash_code(data, length);
 284     } else {
 285       hash = AltHashing::murmur3_32(_table->_hash_seed, data, length);
 286     }
 287   } else {
 288     length /= sizeof(jchar) / sizeof(jbyte); // Convert number of bytes to number of chars
 289     const jchar* data = (jchar*)value->base(T_CHAR);
 290     if (use_java_hash()) {
 291       hash = java_lang_String::hash_code(data, length);
 292     } else {
 293       hash = AltHashing::murmur3_32(_table->_hash_seed, data, length);
 294     }
 295   }
 296 
 297   return hash;
 298 }
 299 
 300 void G1StringDedupTable::deduplicate(oop java_string, G1StringDedupStat& stat) {
 301   assert(java_lang_String::is_instance(java_string), "Must be a string");
 302   No_Safepoint_Verifier nsv;
 303 
 304   stat.inc_inspected();
 305 
 306   typeArrayOop value = java_lang_String::value(java_string);
 307   if (value == NULL) {
 308     // String has no value
 309     stat.inc_skipped();
 310     return;
 311   }
 312 
 313   bool latin1 = java_lang_String::is_latin1(java_string);
 314   unsigned int hash = 0;
 315 
 316   if (use_java_hash()) {
 317     // Get hash code from cache
 318     hash = java_lang_String::hash(java_string);
 319   }
 320 
 321   if (hash == 0) {
 322     // Compute hash
 323     hash = hash_code(value, latin1);
 324     stat.inc_hashed();
 325 
 326     if (use_java_hash() && hash != 0) {
 327       // Store hash code in cache
 328       java_lang_String::set_hash(java_string, hash);
 329     }
 330   }
 331 
 332   typeArrayOop existing_value = lookup_or_add(value, latin1, hash);
 333   if (existing_value == value) {
 334     // Same value, already known
 335     stat.inc_known();
 336     return;
 337   }
 338 
 339   // Get size of value array
 340   uintx size_in_bytes = value->size() * HeapWordSize;
 341   stat.inc_new(size_in_bytes);
 342 
 343   if (existing_value != NULL) {
 344     // Enqueue the reference to make sure it is kept alive. Concurrent mark might
 345     // otherwise declare it dead if there are no other strong references to this object.
 346     G1SATBCardTableModRefBS::enqueue(existing_value);
 347 
 348     // Existing value found, deduplicate string
 349     java_lang_String::set_value(java_string, existing_value);
 350 
 351     if (G1CollectedHeap::heap()->is_in_young(value)) {
 352       stat.inc_deduped_young(size_in_bytes);
 353     } else {
 354       stat.inc_deduped_old(size_in_bytes);
 355     }
 356   }
 357 }
 358 
 359 G1StringDedupTable* G1StringDedupTable::prepare_resize() {
 360   size_t size = _table->_size;
 361 
 362   // Check if the hashtable needs to be resized
 363   if (_table->_entries > _table->_grow_threshold) {
 364     // Grow table, double the size
 365     size *= 2;
 366     if (size > _max_size) {
 367       // Too big, don't resize
 368       return NULL;
 369     }
 370   } else if (_table->_entries < _table->_shrink_threshold) {
 371     // Shrink table, half the size
 372     size /= 2;
 373     if (size < _min_size) {
 374       // Too small, don't resize
 375       return NULL;
 376     }
 377   } else if (StringDeduplicationResizeALot) {
 378     // Force grow
 379     size *= 2;
 380     if (size > _max_size) {
 381       // Too big, force shrink instead
 382       size /= 4;
 383     }
 384   } else {
 385     // Resize not needed
 386     return NULL;
 387   }
 388 
 389   // Update statistics
 390   _resize_count++;
 391 
 392   // Allocate the new table. The new table will be populated by workers
 393   // calling unlink_or_oops_do() and finally installed by finish_resize().
 394   return new G1StringDedupTable(size, _table->_hash_seed);
 395 }
 396 
 397 void G1StringDedupTable::finish_resize(G1StringDedupTable* resized_table) {
 398   assert(resized_table != NULL, "Invalid table");
 399 
 400   resized_table->_entries = _table->_entries;
 401 
 402   // Free old table
 403   delete _table;
 404 
 405   // Install new table
 406   _table = resized_table;
 407 }
 408 
 409 void G1StringDedupTable::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, uint worker_id) {
 410   // The table is divided into partitions to allow lock-less parallel processing by
 411   // multiple worker threads. A worker thread first claims a partition, which ensures
 412   // exclusive access to that part of the table, then continues to process it. To allow
 413   // shrinking of the table in parallel we also need to make sure that the same worker
 414   // thread processes all partitions where entries will hash to the same destination
 415   // partition. Since the table size is always a power of two and we always shrink by
 416   // dividing the table in half, we know that for a given partition there is only one
 417   // other partition whoes entries will hash to the same destination partition. That
 418   // other partition is always the sibling partition in the second half of the table.
 419   // For example, if the table is divided into 8 partitions, the sibling of partition 0
 420   // is partition 4, the sibling of partition 1 is partition 5, etc.
 421   size_t table_half = _table->_size / 2;
 422 
 423   // Let each partition be one page worth of buckets
 424   size_t partition_size = MIN2(table_half, os::vm_page_size() / sizeof(G1StringDedupEntry*));
 425   assert(table_half % partition_size == 0, "Invalid partition size");
 426 
 427   // Number of entries removed during the scan
 428   uintx removed = 0;
 429 
 430   for (;;) {
 431     // Grab next partition to scan
 432     size_t partition_begin = cl->claim_table_partition(partition_size);
 433     size_t partition_end = partition_begin + partition_size;
 434     if (partition_begin >= table_half) {
 435       // End of table
 436       break;
 437     }
 438 
 439     // Scan the partition followed by the sibling partition in the second half of the table
 440     removed += unlink_or_oops_do(cl, partition_begin, partition_end, worker_id);
 441     removed += unlink_or_oops_do(cl, table_half + partition_begin, table_half + partition_end, worker_id);
 442   }
 443 
 444   // Delayed update avoid contention on the table lock
 445   if (removed > 0) {
 446     MutexLockerEx ml(StringDedupTable_lock, Mutex::_no_safepoint_check_flag);
 447     _table->_entries -= removed;
 448     _entries_removed += removed;
 449   }
 450 }
 451 
 452 uintx G1StringDedupTable::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl,
 453                                             size_t partition_begin,
 454                                             size_t partition_end,
 455                                             uint worker_id) {
 456   uintx removed = 0;
 457   for (size_t bucket = partition_begin; bucket < partition_end; bucket++) {
 458     G1StringDedupEntry** entry = _table->bucket(bucket);
 459     while (*entry != NULL) {
 460       oop* p = (oop*)(*entry)->obj_addr();
 461       if (cl->is_alive(*p)) {
 462         cl->keep_alive(p);
 463         if (cl->is_resizing()) {
 464           // We are resizing the table, transfer entry to the new table
 465           _table->transfer(entry, cl->resized_table());
 466         } else {
 467           if (cl->is_rehashing()) {
 468             // We are rehashing the table, rehash the entry but keep it
 469             // in the table. We can't transfer entries into the new table
 470             // at this point since we don't have exclusive access to all
 471             // destination partitions. finish_rehash() will do a single
 472             // threaded transfer of all entries.
 473             typeArrayOop value = (typeArrayOop)*p;
 474             bool latin1 = (*entry)->latin1();
 475             unsigned int hash = hash_code(value, latin1);
 476             (*entry)->set_hash(hash);
 477           }
 478 
 479           // Move to next entry
 480           entry = (*entry)->next_addr();
 481         }
 482       } else {
 483         // Not alive, remove entry from table
 484         _table->remove(entry, worker_id);
 485         removed++;
 486       }
 487     }
 488   }
 489 
 490   return removed;
 491 }
 492 
 493 G1StringDedupTable* G1StringDedupTable::prepare_rehash() {
 494   if (!_table->_rehash_needed && !StringDeduplicationRehashALot) {
 495     // Rehash not needed
 496     return NULL;
 497   }
 498 
 499   // Update statistics
 500   _rehash_count++;
 501 
 502   // Compute new hash seed
 503   _table->_hash_seed = AltHashing::compute_seed();
 504 
 505   // Allocate the new table, same size and hash seed
 506   return new G1StringDedupTable(_table->_size, _table->_hash_seed);
 507 }
 508 
 509 void G1StringDedupTable::finish_rehash(G1StringDedupTable* rehashed_table) {
 510   assert(rehashed_table != NULL, "Invalid table");
 511 
 512   // Move all newly rehashed entries into the correct buckets in the new table
 513   for (size_t bucket = 0; bucket < _table->_size; bucket++) {
 514     G1StringDedupEntry** entry = _table->bucket(bucket);
 515     while (*entry != NULL) {
 516       _table->transfer(entry, rehashed_table);
 517     }
 518   }
 519 
 520   rehashed_table->_entries = _table->_entries;
 521 
 522   // Free old table
 523   delete _table;
 524 
 525   // Install new table
 526   _table = rehashed_table;
 527 }
 528 
 529 void G1StringDedupTable::verify() {
 530   for (size_t bucket = 0; bucket < _table->_size; bucket++) {
 531     // Verify entries
 532     G1StringDedupEntry** entry = _table->bucket(bucket);
 533     while (*entry != NULL) {
 534       typeArrayOop value = (*entry)->obj();
 535       guarantee(value != NULL, "Object must not be NULL");
 536       guarantee(G1CollectedHeap::heap()->is_in_reserved(value), "Object must be on the heap");
 537       guarantee(!value->is_forwarded(), "Object must not be forwarded");
 538       guarantee(value->is_typeArray(), "Object must be a typeArrayOop");
 539       bool latin1 = (*entry)->latin1();
 540       unsigned int hash = hash_code(value, latin1);
 541       guarantee((*entry)->hash() == hash, "Table entry has inorrect hash");
 542       guarantee(_table->hash_to_index(hash) == bucket, "Table entry has incorrect index");
 543       entry = (*entry)->next_addr();
 544     }
 545 
 546     // Verify that we do not have entries with identical oops or identical arrays.
 547     // We only need to compare entries in the same bucket. If the same oop or an
 548     // identical array has been inserted more than once into different/incorrect
 549     // buckets the verification step above will catch that.
 550     G1StringDedupEntry** entry1 = _table->bucket(bucket);
 551     while (*entry1 != NULL) {
 552       typeArrayOop value1 = (*entry1)->obj();
 553       bool latin1_1 = (*entry1)->latin1();
 554       G1StringDedupEntry** entry2 = (*entry1)->next_addr();
 555       while (*entry2 != NULL) {
 556         typeArrayOop value2 = (*entry2)->obj();
 557         bool latin1_2 = (*entry2)->latin1();
 558         guarantee(latin1_1 != latin1_2 || !equals(value1, value2), "Table entries must not have identical arrays");
 559         entry2 = (*entry2)->next_addr();
 560       }
 561       entry1 = (*entry1)->next_addr();
 562     }
 563   }
 564 }
 565 
 566 void G1StringDedupTable::trim_entry_cache() {
 567   MutexLockerEx ml(StringDedupTable_lock, Mutex::_no_safepoint_check_flag);
 568   size_t max_cache_size = (size_t)(_table->_size * _max_cache_factor);
 569   _entry_cache->trim(max_cache_size);
 570 }
 571 
 572 void G1StringDedupTable::print_statistics() {
 573   log_trace(gc, stringdedup)(
 574     "   [Table]\n"
 575     "      [Memory Usage: " G1_STRDEDUP_BYTES_FORMAT_NS "]\n"
 576     "      [Size: " SIZE_FORMAT ", Min: " SIZE_FORMAT ", Max: " SIZE_FORMAT "]\n"
 577     "      [Entries: " UINTX_FORMAT ", Load: " G1_STRDEDUP_PERCENT_FORMAT_NS ", Cached: " UINTX_FORMAT ", Added: " UINTX_FORMAT ", Removed: " UINTX_FORMAT "]\n"
 578     "      [Resize Count: " UINTX_FORMAT ", Shrink Threshold: " UINTX_FORMAT "(" G1_STRDEDUP_PERCENT_FORMAT_NS "), Grow Threshold: " UINTX_FORMAT "(" G1_STRDEDUP_PERCENT_FORMAT_NS ")]\n"
 579     "      [Rehash Count: " UINTX_FORMAT ", Rehash Threshold: " UINTX_FORMAT ", Hash Seed: 0x%x]\n"
 580     "      [Age Threshold: " UINTX_FORMAT "]",
 581     G1_STRDEDUP_BYTES_PARAM(_table->_size * sizeof(G1StringDedupEntry*) + (_table->_entries + _entry_cache->size()) * sizeof(G1StringDedupEntry)),
 582     _table->_size, _min_size, _max_size,
 583     _table->_entries, (double)_table->_entries / (double)_table->_size * 100.0, _entry_cache->size(), _entries_added, _entries_removed,
 584     _resize_count, _table->_shrink_threshold, _shrink_load_factor * 100.0, _table->_grow_threshold, _grow_load_factor * 100.0,
 585     _rehash_count, _rehash_threshold, _table->_hash_seed,
 586     StringDeduplicationAgeThreshold);
 587 }