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