1 /*
  2  * Copyright (c) 2014, 2018, 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/arrayOop.inline.hpp"
 36 #include "oops/oop.inline.hpp"
 37 #include "oops/typeArrayOop.hpp"
 38 #include "runtime/mutexLocker.hpp"
 39 
 40 //
 41 // List of deduplication table entries. Links table
 42 // entries together using their _next fields.
 43 //
 44 class G1StringDedupEntryList : public CHeapObj<mtGC> {
 45 private:
 46   G1StringDedupEntry* _list;
 47   size_t              _length;
 48 
 49 public:
 50   G1StringDedupEntryList() :
 51     _list(NULL),
 52     _length(0) {
 53   }
 54 
 55   void add(G1StringDedupEntry* entry) {
 56     entry->set_next(_list);
 57     _list = entry;
 58     _length++;
 59   }
 60 
 61   G1StringDedupEntry* remove() {
 62     G1StringDedupEntry* entry = _list;
 63     if (entry != NULL) {
 64       _list = entry->next();
 65       _length--;
 66     }
 67     return entry;
 68   }
 69 
 70   G1StringDedupEntry* remove_all() {
 71     G1StringDedupEntry* list = _list;
 72     _list = NULL;
 73     return list;
 74   }
 75 
 76   size_t length() {
 77     return _length;
 78   }
 79 };
 80 
 81 //
 82 // Cache of deduplication table entries. This cache provides fast allocation and
 83 // reuse of table entries to lower the pressure on the underlying allocator.
 84 // But more importantly, it provides fast/deferred freeing of table entries. This
 85 // is important because freeing of table entries is done during stop-the-world
 86 // phases and it is not uncommon for large number of entries to be freed at once.
 87 // Tables entries that are freed during these phases are placed onto a freelist in
 88 // the cache. The deduplication thread, which executes in a concurrent phase, will
 89 // later reuse or free the underlying memory for these entries.
 90 //
 91 // The cache allows for single-threaded allocations and multi-threaded frees.
 92 // Allocations are synchronized by StringDedupTable_lock as part of a table
 93 // modification.
 94 //
 95 class G1StringDedupEntryCache : public CHeapObj<mtGC> {
 96 private:
 97   // One cache/overflow list per GC worker to allow lock less freeing of
 98   // entries while doing a parallel scan of the table. Using PaddedEnd to
 99   // avoid false sharing.
100   size_t                             _nlists;
101   size_t                             _max_list_length;
102   PaddedEnd<G1StringDedupEntryList>* _cached;
103   PaddedEnd<G1StringDedupEntryList>* _overflowed;
104 
105 public:
106   G1StringDedupEntryCache(size_t max_size);
107   ~G1StringDedupEntryCache();
108 
109   // Set max number of table entries to cache.
110   void set_max_size(size_t max_size);
111 
112   // Get a table entry from the cache, or allocate a new entry if the cache is empty.
113   G1StringDedupEntry* alloc();
114 
115   // Insert a table entry into the cache.
116   void free(G1StringDedupEntry* entry, uint worker_id);
117 
118   // Returns current number of entries in the cache.
119   size_t size();
120 
121   // Deletes overflowed entries.
122   void delete_overflowed();
123 };
124 
125 G1StringDedupEntryCache::G1StringDedupEntryCache(size_t max_size) :
126   _nlists(ParallelGCThreads),
127   _max_list_length(0),
128   _cached(PaddedArray<G1StringDedupEntryList, mtGC>::create_unfreeable((uint)_nlists)),
129   _overflowed(PaddedArray<G1StringDedupEntryList, mtGC>::create_unfreeable((uint)_nlists)) {
130   set_max_size(max_size);
131 }
132 
133 G1StringDedupEntryCache::~G1StringDedupEntryCache() {
134   ShouldNotReachHere();
135 }
136 
137 void G1StringDedupEntryCache::set_max_size(size_t size) {
138   _max_list_length = size / _nlists;
139 }
140 
141 G1StringDedupEntry* G1StringDedupEntryCache::alloc() {
142   for (size_t i = 0; i < _nlists; i++) {
143     G1StringDedupEntry* entry = _cached[i].remove();
144     if (entry != NULL) {
145       return entry;
146     }
147   }
148   return new G1StringDedupEntry();
149 }
150 
151 void G1StringDedupEntryCache::free(G1StringDedupEntry* entry, uint worker_id) {
152   assert(entry->obj() != NULL, "Double free");
153   assert(worker_id < _nlists, "Invalid worker id");
154 
155   entry->set_obj(NULL);
156   entry->set_hash(0);
157 
158   if (_cached[worker_id].length() < _max_list_length) {
159     // Cache is not full
160     _cached[worker_id].add(entry);
161   } else {
162     // Cache is full, add to overflow list for later deletion
163     _overflowed[worker_id].add(entry);
164   }
165 }
166 
167 size_t G1StringDedupEntryCache::size() {
168   size_t size = 0;
169   for (size_t i = 0; i < _nlists; i++) {
170     size += _cached[i].length();
171   }
172   return size;
173 }
174 
175 void G1StringDedupEntryCache::delete_overflowed() {
176   double start = os::elapsedTime();
177   uintx count = 0;
178 
179   for (size_t i = 0; i < _nlists; i++) {
180     G1StringDedupEntry* entry;
181 
182     {
183       // The overflow list can be modified during safepoints, therefore
184       // we temporarily join the suspendible thread set while removing
185       // all entries from the list.
186       SuspendibleThreadSetJoiner sts_join;
187       entry = _overflowed[i].remove_all();
188     }
189 
190     // Delete all entries
191     while (entry != NULL) {
192       G1StringDedupEntry* next = entry->next();
193       delete entry;
194       entry = next;
195       count++;
196     }
197   }
198 
199   double end = os::elapsedTime();
200   log_trace(gc, stringdedup)("Deleted " UINTX_FORMAT " entries, " G1_STRDEDUP_TIME_FORMAT_MS,
201                              count, G1_STRDEDUP_TIME_PARAM_MS(end - start));
202 }
203 
204 G1StringDedupTable*      G1StringDedupTable::_table = NULL;
205 G1StringDedupEntryCache* G1StringDedupTable::_entry_cache = NULL;
206 
207 const size_t             G1StringDedupTable::_min_size = (1 << 10);   // 1024
208 const size_t             G1StringDedupTable::_max_size = (1 << 24);   // 16777216
209 const double             G1StringDedupTable::_grow_load_factor = 2.0; // Grow table at 200% load
210 const double             G1StringDedupTable::_shrink_load_factor = _grow_load_factor / 3.0; // Shrink table at 67% load
211 const double             G1StringDedupTable::_max_cache_factor = 0.1; // Cache a maximum of 10% of the table size
212 const uintx              G1StringDedupTable::_rehash_multiple = 60;   // Hash bucket has 60 times more collisions than expected
213 const uintx              G1StringDedupTable::_rehash_threshold = (uintx)(_rehash_multiple * _grow_load_factor);
214 
215 uintx                    G1StringDedupTable::_entries_added = 0;
216 uintx                    G1StringDedupTable::_entries_removed = 0;
217 uintx                    G1StringDedupTable::_resize_count = 0;
218 uintx                    G1StringDedupTable::_rehash_count = 0;
219 
220 G1StringDedupTable::G1StringDedupTable(size_t size, jint hash_seed) :
221   _size(size),
222   _entries(0),
223   _grow_threshold((uintx)(size * _grow_load_factor)),
224   _shrink_threshold((uintx)(size * _shrink_load_factor)),
225   _rehash_needed(false),
226   _hash_seed(hash_seed) {
227   assert(is_power_of_2(size), "Table size must be a power of 2");
228   _buckets = NEW_C_HEAP_ARRAY(G1StringDedupEntry*, _size, mtGC);
229   memset(_buckets, 0, _size * sizeof(G1StringDedupEntry*));
230 }
231 
232 G1StringDedupTable::~G1StringDedupTable() {
233   FREE_C_HEAP_ARRAY(G1StringDedupEntry*, _buckets);
234 }
235 
236 void G1StringDedupTable::create() {
237   assert(_table == NULL, "One string deduplication table allowed");
238   _entry_cache = new G1StringDedupEntryCache(_min_size * _max_cache_factor);
239   _table = new G1StringDedupTable(_min_size);
240 }
241 
242 void G1StringDedupTable::add(typeArrayOop value, bool latin1, unsigned int hash, G1StringDedupEntry** list) {
243   G1StringDedupEntry* entry = _entry_cache->alloc();
244   entry->set_obj(value);
245   entry->set_hash(hash);
246   entry->set_latin1(latin1);
247   entry->set_next(*list);
248   *list = entry;
249   _entries++;
250 }
251 
252 void G1StringDedupTable::remove(G1StringDedupEntry** pentry, uint worker_id) {
253   G1StringDedupEntry* entry = *pentry;
254   *pentry = entry->next();
255   _entry_cache->free(entry, worker_id);
256 }
257 
258 void G1StringDedupTable::transfer(G1StringDedupEntry** pentry, G1StringDedupTable* dest) {
259   G1StringDedupEntry* entry = *pentry;
260   *pentry = entry->next();
261   unsigned int hash = entry->hash();
262   size_t index = dest->hash_to_index(hash);
263   G1StringDedupEntry** list = dest->bucket(index);
264   entry->set_next(*list);
265   *list = entry;
266 }
267 
268 bool G1StringDedupTable::equals(typeArrayOop value1, typeArrayOop value2) {
269   return (value1 == value2 ||
270           (value1->length() == value2->length() &&
271            (!memcmp(value1->base(T_BYTE),
272                     value2->base(T_BYTE),
273                     value1->length() * sizeof(jbyte)))));
274 }
275 
276 typeArrayOop G1StringDedupTable::lookup(typeArrayOop value, bool latin1, unsigned int hash,
277                                         G1StringDedupEntry** list, uintx &count) {
278   for (G1StringDedupEntry* entry = *list; entry != NULL; entry = entry->next()) {
279     if (entry->hash() == hash && entry->latin1() == latin1) {
280       typeArrayOop existing_value = entry->obj();
281       if (equals(value, existing_value)) {
282         // Match found
283         return existing_value;
284       }
285     }
286     count++;
287   }
288 
289   // Not found
290   return NULL;
291 }
292 
293 typeArrayOop G1StringDedupTable::lookup_or_add_inner(typeArrayOop value, bool latin1, unsigned int hash) {
294   size_t index = hash_to_index(hash);
295   G1StringDedupEntry** list = bucket(index);
296   uintx count = 0;
297 
298   // Lookup in list
299   typeArrayOop existing_value = lookup(value, latin1, hash, list, count);
300 
301   // Check if rehash is needed
302   if (count > _rehash_threshold) {
303     _rehash_needed = true;
304   }
305 
306   if (existing_value == NULL) {
307     // Not found, add new entry
308     add(value, latin1, hash, list);
309 
310     // Update statistics
311     _entries_added++;
312   }
313 
314   return existing_value;
315 }
316 
317 unsigned int G1StringDedupTable::hash_code(typeArrayOop value, bool latin1) {
318   unsigned int hash;
319   int length = value->length();
320   if (latin1) {
321     const jbyte* data = (jbyte*)value->base(T_BYTE);
322     if (use_java_hash()) {
323       hash = java_lang_String::hash_code(data, length);
324     } else {
325       hash = AltHashing::murmur3_32(_table->_hash_seed, data, length);
326     }
327   } else {
328     length /= sizeof(jchar) / sizeof(jbyte); // Convert number of bytes to number of chars
329     const jchar* data = (jchar*)value->base(T_CHAR);
330     if (use_java_hash()) {
331       hash = java_lang_String::hash_code(data, length);
332     } else {
333       hash = AltHashing::murmur3_32(_table->_hash_seed, data, length);
334     }
335   }
336 
337   return hash;
338 }
339 
340 void G1StringDedupTable::deduplicate(oop java_string, G1StringDedupStat& stat) {
341   assert(java_lang_String::is_instance(java_string), "Must be a string");
342   NoSafepointVerifier nsv;
343 
344   stat.inc_inspected();
345 
346   typeArrayOop value = java_lang_String::value(java_string);
347   if (value == NULL) {
348     // String has no value
349     stat.inc_skipped();
350     return;
351   }
352 
353   bool latin1 = java_lang_String::is_latin1(java_string);
354   unsigned int hash = 0;
355 
356   if (use_java_hash()) {
357     // Get hash code from cache
358     hash = java_lang_String::hash(java_string);
359   }
360 
361   if (hash == 0) {
362     // Compute hash
363     hash = hash_code(value, latin1);
364     stat.inc_hashed();
365 
366     if (use_java_hash() && hash != 0) {
367       // Store hash code in cache
368       java_lang_String::set_hash(java_string, hash);
369     }
370   }
371 
372   typeArrayOop existing_value = lookup_or_add(value, latin1, hash);
373   if (existing_value == value) {
374     // Same value, already known
375     stat.inc_known();
376     return;
377   }
378 
379   // Get size of value array
380   uintx size_in_bytes = value->size() * HeapWordSize;
381   stat.inc_new(size_in_bytes);
382 
383   if (existing_value != NULL) {
384     // Enqueue the reference to make sure it is kept alive. Concurrent mark might
385     // otherwise declare it dead if there are no other strong references to this object.
386     G1SATBCardTableModRefBS::enqueue(existing_value);
387 
388     // Existing value found, deduplicate string
389     java_lang_String::set_value(java_string, existing_value);
390 
391     if (G1CollectedHeap::heap()->is_in_young(value)) {
392       stat.inc_deduped_young(size_in_bytes);
393     } else {
394       stat.inc_deduped_old(size_in_bytes);
395     }
396   }
397 }
398 
399 G1StringDedupTable* G1StringDedupTable::prepare_resize() {
400   size_t size = _table->_size;
401 
402   // Check if the hashtable needs to be resized
403   if (_table->_entries > _table->_grow_threshold) {
404     // Grow table, double the size
405     size *= 2;
406     if (size > _max_size) {
407       // Too big, don't resize
408       return NULL;
409     }
410   } else if (_table->_entries < _table->_shrink_threshold) {
411     // Shrink table, half the size
412     size /= 2;
413     if (size < _min_size) {
414       // Too small, don't resize
415       return NULL;
416     }
417   } else if (StringDeduplicationResizeALot) {
418     // Force grow
419     size *= 2;
420     if (size > _max_size) {
421       // Too big, force shrink instead
422       size /= 4;
423     }
424   } else {
425     // Resize not needed
426     return NULL;
427   }
428 
429   // Update statistics
430   _resize_count++;
431 
432   // Update max cache size
433   _entry_cache->set_max_size(size * _max_cache_factor);
434 
435   // Allocate the new table. The new table will be populated by workers
436   // calling unlink_or_oops_do() and finally installed by finish_resize().
437   return new G1StringDedupTable(size, _table->_hash_seed);
438 }
439 
440 void G1StringDedupTable::finish_resize(G1StringDedupTable* resized_table) {
441   assert(resized_table != NULL, "Invalid table");
442 
443   resized_table->_entries = _table->_entries;
444 
445   // Free old table
446   delete _table;
447 
448   // Install new table
449   _table = resized_table;
450 }
451 
452 void G1StringDedupTable::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, uint worker_id) {
453   // The table is divided into partitions to allow lock-less parallel processing by
454   // multiple worker threads. A worker thread first claims a partition, which ensures
455   // exclusive access to that part of the table, then continues to process it. To allow
456   // shrinking of the table in parallel we also need to make sure that the same worker
457   // thread processes all partitions where entries will hash to the same destination
458   // partition. Since the table size is always a power of two and we always shrink by
459   // dividing the table in half, we know that for a given partition there is only one
460   // other partition whoes entries will hash to the same destination partition. That
461   // other partition is always the sibling partition in the second half of the table.
462   // For example, if the table is divided into 8 partitions, the sibling of partition 0
463   // is partition 4, the sibling of partition 1 is partition 5, etc.
464   size_t table_half = _table->_size / 2;
465 
466   // Let each partition be one page worth of buckets
467   size_t partition_size = MIN2(table_half, os::vm_page_size() / sizeof(G1StringDedupEntry*));
468   assert(table_half % partition_size == 0, "Invalid partition size");
469 
470   // Number of entries removed during the scan
471   uintx removed = 0;
472 
473   for (;;) {
474     // Grab next partition to scan
475     size_t partition_begin = cl->claim_table_partition(partition_size);
476     size_t partition_end = partition_begin + partition_size;
477     if (partition_begin >= table_half) {
478       // End of table
479       break;
480     }
481 
482     // Scan the partition followed by the sibling partition in the second half of the table
483     removed += unlink_or_oops_do(cl, partition_begin, partition_end, worker_id);
484     removed += unlink_or_oops_do(cl, table_half + partition_begin, table_half + partition_end, worker_id);
485   }
486 
487   // Delayed update to avoid contention on the table lock
488   if (removed > 0) {
489     MutexLockerEx ml(StringDedupTable_lock, Mutex::_no_safepoint_check_flag);
490     _table->_entries -= removed;
491     _entries_removed += removed;
492   }
493 }
494 
495 uintx G1StringDedupTable::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl,
496                                             size_t partition_begin,
497                                             size_t partition_end,
498                                             uint worker_id) {
499   uintx removed = 0;
500   for (size_t bucket = partition_begin; bucket < partition_end; bucket++) {
501     G1StringDedupEntry** entry = _table->bucket(bucket);
502     while (*entry != NULL) {
503       oop* p = (oop*)(*entry)->obj_addr();
504       if (cl->is_alive(*p)) {
505         cl->keep_alive(p);
506         if (cl->is_resizing()) {
507           // We are resizing the table, transfer entry to the new table
508           _table->transfer(entry, cl->resized_table());
509         } else {
510           if (cl->is_rehashing()) {
511             // We are rehashing the table, rehash the entry but keep it
512             // in the table. We can't transfer entries into the new table
513             // at this point since we don't have exclusive access to all
514             // destination partitions. finish_rehash() will do a single
515             // threaded transfer of all entries.
516             typeArrayOop value = (typeArrayOop)*p;
517             bool latin1 = (*entry)->latin1();
518             unsigned int hash = hash_code(value, latin1);
519             (*entry)->set_hash(hash);
520           }
521 
522           // Move to next entry
523           entry = (*entry)->next_addr();
524         }
525       } else {
526         // Not alive, remove entry from table
527         _table->remove(entry, worker_id);
528         removed++;
529       }
530     }
531   }
532 
533   return removed;
534 }
535 
536 G1StringDedupTable* G1StringDedupTable::prepare_rehash() {
537   if (!_table->_rehash_needed && !StringDeduplicationRehashALot) {
538     // Rehash not needed
539     return NULL;
540   }
541 
542   // Update statistics
543   _rehash_count++;
544 
545   // Compute new hash seed
546   _table->_hash_seed = AltHashing::compute_seed();
547 
548   // Allocate the new table, same size and hash seed
549   return new G1StringDedupTable(_table->_size, _table->_hash_seed);
550 }
551 
552 void G1StringDedupTable::finish_rehash(G1StringDedupTable* rehashed_table) {
553   assert(rehashed_table != NULL, "Invalid table");
554 
555   // Move all newly rehashed entries into the correct buckets in the new table
556   for (size_t bucket = 0; bucket < _table->_size; bucket++) {
557     G1StringDedupEntry** entry = _table->bucket(bucket);
558     while (*entry != NULL) {
559       _table->transfer(entry, rehashed_table);
560     }
561   }
562 
563   rehashed_table->_entries = _table->_entries;
564 
565   // Free old table
566   delete _table;
567 
568   // Install new table
569   _table = rehashed_table;
570 }
571 
572 void G1StringDedupTable::verify() {
573   for (size_t bucket = 0; bucket < _table->_size; bucket++) {
574     // Verify entries
575     G1StringDedupEntry** entry = _table->bucket(bucket);
576     while (*entry != NULL) {
577       typeArrayOop value = (*entry)->obj();
578       guarantee(value != NULL, "Object must not be NULL");
579       guarantee(G1CollectedHeap::heap()->is_in_reserved(value), "Object must be on the heap");
580       guarantee(!value->is_forwarded(), "Object must not be forwarded");
581       guarantee(value->is_typeArray(), "Object must be a typeArrayOop");
582       bool latin1 = (*entry)->latin1();
583       unsigned int hash = hash_code(value, latin1);
584       guarantee((*entry)->hash() == hash, "Table entry has inorrect hash");
585       guarantee(_table->hash_to_index(hash) == bucket, "Table entry has incorrect index");
586       entry = (*entry)->next_addr();
587     }
588 
589     // Verify that we do not have entries with identical oops or identical arrays.
590     // We only need to compare entries in the same bucket. If the same oop or an
591     // identical array has been inserted more than once into different/incorrect
592     // buckets the verification step above will catch that.
593     G1StringDedupEntry** entry1 = _table->bucket(bucket);
594     while (*entry1 != NULL) {
595       typeArrayOop value1 = (*entry1)->obj();
596       bool latin1_1 = (*entry1)->latin1();
597       G1StringDedupEntry** entry2 = (*entry1)->next_addr();
598       while (*entry2 != NULL) {
599         typeArrayOop value2 = (*entry2)->obj();
600         bool latin1_2 = (*entry2)->latin1();
601         guarantee(latin1_1 != latin1_2 || !equals(value1, value2), "Table entries must not have identical arrays");
602         entry2 = (*entry2)->next_addr();
603       }
604       entry1 = (*entry1)->next_addr();
605     }
606   }
607 }
608 
609 void G1StringDedupTable::clean_entry_cache() {
610   _entry_cache->delete_overflowed();
611 }
612 
613 void G1StringDedupTable::print_statistics() {
614   Log(gc, stringdedup) log;
615   log.debug("  Table");
616   log.debug("    Memory Usage: " G1_STRDEDUP_BYTES_FORMAT_NS,
617             G1_STRDEDUP_BYTES_PARAM(_table->_size * sizeof(G1StringDedupEntry*) + (_table->_entries + _entry_cache->size()) * sizeof(G1StringDedupEntry)));
618   log.debug("    Size: " SIZE_FORMAT ", Min: " SIZE_FORMAT ", Max: " SIZE_FORMAT, _table->_size, _min_size, _max_size);
619   log.debug("    Entries: " UINTX_FORMAT ", Load: " G1_STRDEDUP_PERCENT_FORMAT_NS ", Cached: " UINTX_FORMAT ", Added: " UINTX_FORMAT ", Removed: " UINTX_FORMAT,
620             _table->_entries, percent_of(_table->_entries, _table->_size), _entry_cache->size(), _entries_added, _entries_removed);
621   log.debug("    Resize Count: " UINTX_FORMAT ", Shrink Threshold: " UINTX_FORMAT "(" G1_STRDEDUP_PERCENT_FORMAT_NS "), Grow Threshold: " UINTX_FORMAT "(" G1_STRDEDUP_PERCENT_FORMAT_NS ")",
622             _resize_count, _table->_shrink_threshold, _shrink_load_factor * 100.0, _table->_grow_threshold, _grow_load_factor * 100.0);
623   log.debug("    Rehash Count: " UINTX_FORMAT ", Rehash Threshold: " UINTX_FORMAT ", Hash Seed: 0x%x", _rehash_count, _rehash_threshold, _table->_hash_seed);
624   log.debug("    Age Threshold: " UINTX_FORMAT, StringDeduplicationAgeThreshold);
625 }