1 /*
2 * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/altHashing.hpp"
27 #include "classfile/compactHashtable.inline.hpp"
28 #include "classfile/javaClasses.inline.hpp"
29 #include "classfile/stringTable.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "gc/shared/collectedHeap.inline.hpp"
32 #include "gc/shared/gcLocker.inline.hpp"
33 #include "logging/log.hpp"
34 #include "memory/allocation.inline.hpp"
35 #include "memory/filemap.hpp"
36 #include "memory/metaspaceShared.hpp"
37 #include "memory/resourceArea.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "runtime/atomic.hpp"
40 #include "runtime/mutexLocker.hpp"
41 #include "services/diagnosticCommand.hpp"
42 #include "utilities/hashtable.inline.hpp"
43 #include "utilities/macros.hpp"
44 #if INCLUDE_ALL_GCS
45 #include "gc/g1/g1CollectedHeap.hpp"
46 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
47 #include "gc/g1/g1StringDedup.hpp"
48 #endif
49
50 // the number of buckets a thread claims
51 const int ClaimChunkSize = 32;
52
53 #ifdef ASSERT
54 class StableMemoryChecker : public StackObj {
55 enum { _bufsize = wordSize*4 };
56
57 address _region;
58 jint _size;
59 u1 _save_buf[_bufsize];
60
61 int sample(u1* save_buf) {
62 if (_size <= _bufsize) {
63 memcpy(save_buf, _region, _size);
64 return _size;
65 } else {
66 // copy head and tail
67 memcpy(&save_buf[0], _region, _bufsize/2);
68 memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);
69 return (_bufsize/2)*2;
70 }
71 }
72
73 public:
74 StableMemoryChecker(const void* region, jint size) {
75 _region = (address) region;
76 _size = size;
77 sample(_save_buf);
78 }
79
80 bool verify() {
81 u1 check_buf[sizeof(_save_buf)];
82 int check_size = sample(check_buf);
83 return (0 == memcmp(_save_buf, check_buf, check_size));
84 }
85
86 void set_region(const void* region) { _region = (address) region; }
87 };
88 #endif
89
90
91 // --------------------------------------------------------------------------
92 StringTable* StringTable::_the_table = NULL;
93 bool StringTable::_ignore_shared_strings = false;
94 bool StringTable::_needs_rehashing = false;
95
96 volatile int StringTable::_parallel_claimed_idx = 0;
97
98 CompactHashtable<oop, char> StringTable::_shared_table;
99
100 // Pick hashing algorithm
101 unsigned int StringTable::hash_string(const jchar* s, int len) {
102 return use_alternate_hashcode() ? alt_hash_string(s, len) :
103 java_lang_String::hash_code(s, len);
104 }
105
106 unsigned int StringTable::alt_hash_string(const jchar* s, int len) {
107 return AltHashing::murmur3_32(seed(), s, len);
108 }
109
110 unsigned int StringTable::hash_string(oop string) {
111 EXCEPTION_MARK;
112 if (string == NULL) {
113 return hash_string((jchar*)NULL, 0);
114 }
115 ResourceMark rm(THREAD);
116 // All String oops are hashed as unicode
117 int length;
118 jchar* chars = java_lang_String::as_unicode_string(string, length, THREAD);
119 if (chars != NULL) {
120 return hash_string(chars, length);
121 } else {
122 vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "unable to create Unicode string for verification");
123 return 0;
124 }
125 }
126
127 oop StringTable::lookup_shared(jchar* name, int len, unsigned int hash) {
128 assert(hash == java_lang_String::hash_code(name, len),
129 "hash must be computed using java_lang_String::hash_code");
130 return _shared_table.lookup((const char*)name, hash, len);
131 }
132
133 oop StringTable::lookup_in_main_table(int index, jchar* name,
134 int len, unsigned int hash) {
135 int count = 0;
136 for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {
137 count++;
138 if (l->hash() == hash) {
139 if (java_lang_String::equals(l->literal(), name, len)) {
140 return l->literal();
141 }
142 }
143 }
144 // If the bucket size is too deep check if this hash code is insufficient.
145 if (count >= rehash_count && !needs_rehashing()) {
146 _needs_rehashing = check_rehash_table(count);
147 }
148 return NULL;
149 }
150
151
152 oop StringTable::basic_add(int index_arg, Handle string, jchar* name,
153 int len, unsigned int hashValue_arg, TRAPS) {
154
155 assert(java_lang_String::equals(string(), name, len),
156 "string must be properly initialized");
157 // Cannot hit a safepoint in this function because the "this" pointer can move.
158 NoSafepointVerifier nsv;
159
160 // Check if the symbol table has been rehashed, if so, need to recalculate
161 // the hash value and index before second lookup.
162 unsigned int hashValue;
163 int index;
164 if (use_alternate_hashcode()) {
165 hashValue = alt_hash_string(name, len);
166 index = hash_to_index(hashValue);
167 } else {
168 hashValue = hashValue_arg;
169 index = index_arg;
170 }
171
172 // Since look-up was done lock-free, we need to check if another
173 // thread beat us in the race to insert the symbol.
174
175 // No need to lookup the shared table from here since the caller (intern()) already did
176 oop test = lookup_in_main_table(index, name, len, hashValue); // calls lookup(u1*, int)
177 if (test != NULL) {
178 // Entry already added
179 return test;
180 }
181
182 HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());
183 add_entry(index, entry);
184 return string();
185 }
186
187
188 oop StringTable::lookup(Symbol* symbol) {
189 ResourceMark rm;
190 int length;
191 jchar* chars = symbol->as_unicode(length);
192 return lookup(chars, length);
193 }
194
195 // Tell the GC that this string was looked up in the StringTable.
196 static void ensure_string_alive(oop string) {
197 // A lookup in the StringTable could return an object that was previously
198 // considered dead. The SATB part of G1 needs to get notified about this
199 // potential resurrection, otherwise the marking might not find the object.
200 #if INCLUDE_ALL_GCS
201 if (UseG1GC && string != NULL) {
202 G1SATBCardTableModRefBS::enqueue(string);
203 }
204 #endif
205 }
206
207 oop StringTable::lookup(jchar* name, int len) {
208 // shared table always uses java_lang_String::hash_code
209 unsigned int hash = java_lang_String::hash_code(name, len);
210 oop string = lookup_shared(name, len, hash);
211 if (string != NULL) {
212 return string;
213 }
214 if (use_alternate_hashcode()) {
215 hash = alt_hash_string(name, len);
216 }
217 int index = the_table()->hash_to_index(hash);
218 string = the_table()->lookup_in_main_table(index, name, len, hash);
219
220 ensure_string_alive(string);
221
222 return string;
223 }
224
225 oop StringTable::intern(Handle string_or_null, jchar* name,
226 int len, TRAPS) {
227 // shared table always uses java_lang_String::hash_code
228 unsigned int hashValue = java_lang_String::hash_code(name, len);
229 oop found_string = lookup_shared(name, len, hashValue);
230 if (found_string != NULL) {
231 return found_string;
232 }
233 if (use_alternate_hashcode()) {
234 hashValue = alt_hash_string(name, len);
235 }
236 int index = the_table()->hash_to_index(hashValue);
237 found_string = the_table()->lookup_in_main_table(index, name, len, hashValue);
238
239 // Found
240 if (found_string != NULL) {
241 if (found_string != string_or_null()) {
242 ensure_string_alive(found_string);
243 }
244 return found_string;
245 }
246
247 debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
248 assert(!Universe::heap()->is_in_reserved(name),
249 "proposed name of symbol must be stable");
250
251 HandleMark hm(THREAD); // cleanup strings created
252 Handle string;
253 // try to reuse the string if possible
254 if (!string_or_null.is_null()) {
255 string = string_or_null;
256 } else {
257 string = java_lang_String::create_from_unicode(name, len, CHECK_NULL);
258 }
259
260 #if INCLUDE_ALL_GCS
261 if (G1StringDedup::is_enabled()) {
262 // Deduplicate the string before it is interned. Note that we should never
263 // deduplicate a string after it has been interned. Doing so will counteract
264 // compiler optimizations done on e.g. interned string literals.
265 G1StringDedup::deduplicate(string());
266 }
267 #endif
268
269 // Grab the StringTable_lock before getting the_table() because it could
270 // change at safepoint.
271 oop added_or_found;
272 {
273 MutexLocker ml(StringTable_lock, THREAD);
274 // Otherwise, add to symbol to table
275 added_or_found = the_table()->basic_add(index, string, name, len,
276 hashValue, CHECK_NULL);
277 }
278
279 if (added_or_found != string()) {
280 ensure_string_alive(added_or_found);
281 }
282
283 return added_or_found;
284 }
285
286 oop StringTable::intern(Symbol* symbol, TRAPS) {
287 if (symbol == NULL) return NULL;
288 ResourceMark rm(THREAD);
289 int length;
290 jchar* chars = symbol->as_unicode(length);
291 Handle string;
292 oop result = intern(string, chars, length, CHECK_NULL);
293 return result;
294 }
295
296
297 oop StringTable::intern(oop string, TRAPS)
298 {
299 if (string == NULL) return NULL;
300 ResourceMark rm(THREAD);
301 int length;
302 Handle h_string (THREAD, string);
303 jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL);
304 oop result = intern(h_string, chars, length, CHECK_NULL);
305 return result;
306 }
307
308
309 oop StringTable::intern(const char* utf8_string, TRAPS) {
310 if (utf8_string == NULL) return NULL;
311 ResourceMark rm(THREAD);
312 int length = UTF8::unicode_length(utf8_string);
313 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
314 UTF8::convert_to_unicode(utf8_string, chars, length);
315 Handle string;
316 oop result = intern(string, chars, length, CHECK_NULL);
317 return result;
318 }
319
320 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
321 BucketUnlinkContext context;
322 buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), &context);
323 _the_table->bulk_free_entries(&context);
324 *processed = context._num_processed;
325 *removed = context._num_removed;
326 }
327
328 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
329 // Readers of the table are unlocked, so we should only be removing
330 // entries at a safepoint.
331 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
332 const int limit = the_table()->table_size();
333
334 BucketUnlinkContext context;
335 for (;;) {
336 // Grab next set of buckets to scan
337 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
338 if (start_idx >= limit) {
339 // End of table
340 break;
341 }
342
343 int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
344 buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, &context);
345 }
346 _the_table->bulk_free_entries(&context);
347 *processed = context._num_processed;
348 *removed = context._num_removed;
349 }
350
351 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {
352 const int limit = the_table()->table_size();
353
354 assert(0 <= start_idx && start_idx <= limit,
355 "start_idx (%d) is out of bounds", start_idx);
356 assert(0 <= end_idx && end_idx <= limit,
357 "end_idx (%d) is out of bounds", end_idx);
358 assert(start_idx <= end_idx,
359 "Index ordering: start_idx=%d, end_idx=%d",
360 start_idx, end_idx);
361
362 for (int i = start_idx; i < end_idx; i += 1) {
363 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
364 while (entry != NULL) {
365 assert(!entry->is_shared(), "CDS not used for the StringTable");
366
367 f->do_oop((oop*)entry->literal_addr());
368
369 entry = entry->next();
370 }
371 }
372 }
373
374 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, BucketUnlinkContext* context) {
375 const int limit = the_table()->table_size();
376
377 assert(0 <= start_idx && start_idx <= limit,
378 "start_idx (%d) is out of bounds", start_idx);
379 assert(0 <= end_idx && end_idx <= limit,
380 "end_idx (%d) is out of bounds", end_idx);
381 assert(start_idx <= end_idx,
382 "Index ordering: start_idx=%d, end_idx=%d",
383 start_idx, end_idx);
384
385 for (int i = start_idx; i < end_idx; ++i) {
386 HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i);
387 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
388 while (entry != NULL) {
389 assert(!entry->is_shared(), "CDS not used for the StringTable");
390
391 if (is_alive->do_object_b(entry->literal())) {
392 if (f != NULL) {
393 f->do_oop((oop*)entry->literal_addr());
394 }
395 p = entry->next_addr();
396 } else {
397 *p = entry->next();
398 context->free_entry(entry);
399 }
400 context->_num_processed++;
401 entry = *p;
402 }
403 }
404 }
405
406 void StringTable::oops_do(OopClosure* f) {
407 buckets_oops_do(f, 0, the_table()->table_size());
408 }
409
410 void StringTable::possibly_parallel_oops_do(OopClosure* f) {
411 const int limit = the_table()->table_size();
412
413 for (;;) {
414 // Grab next set of buckets to scan
415 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
416 if (start_idx >= limit) {
417 // End of table
418 break;
419 }
420
421 int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
422 buckets_oops_do(f, start_idx, end_idx);
423 }
424 }
425
426 // This verification is part of Universe::verify() and needs to be quick.
427 // See StringTable::verify_and_compare() below for exhaustive verification.
428 void StringTable::verify() {
429 for (int i = 0; i < the_table()->table_size(); ++i) {
430 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
431 for ( ; p != NULL; p = p->next()) {
432 oop s = p->literal();
433 guarantee(s != NULL, "interned string is NULL");
434 unsigned int h = hash_string(s);
435 guarantee(p->hash() == h, "broken hash in string table entry");
436 guarantee(the_table()->hash_to_index(h) == i,
437 "wrong index in string table");
438 }
439 }
440 }
441
442 void StringTable::dump(outputStream* st, bool verbose) {
443 if (!verbose) {
444 the_table()->print_table_statistics(st, "StringTable");
445 } else {
446 Thread* THREAD = Thread::current();
447 st->print_cr("VERSION: 1.1");
448 for (int i = 0; i < the_table()->table_size(); ++i) {
449 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
450 for ( ; p != NULL; p = p->next()) {
451 oop s = p->literal();
452 typeArrayOop value = java_lang_String::value(s);
453 int length = java_lang_String::length(s);
454 bool is_latin1 = java_lang_String::is_latin1(s);
455
456 if (length <= 0) {
457 st->print("%d: ", length);
458 } else {
459 ResourceMark rm(THREAD);
460 int utf8_length = length;
461 char* utf8_string;
462
463 if (!is_latin1) {
464 jchar* chars = value->char_at_addr(0);
465 utf8_string = UNICODE::as_utf8(chars, utf8_length);
466 } else {
467 jbyte* bytes = value->byte_at_addr(0);
468 utf8_string = UNICODE::as_utf8(bytes, utf8_length);
469 }
470
471 st->print("%d: ", utf8_length);
472 HashtableTextDump::put_utf8(st, utf8_string, utf8_length);
473 }
474 st->cr();
475 }
476 }
477 }
478 }
479
480 StringTable::VerifyRetTypes StringTable::compare_entries(
481 int bkt1, int e_cnt1,
482 HashtableEntry<oop, mtSymbol>* e_ptr1,
483 int bkt2, int e_cnt2,
484 HashtableEntry<oop, mtSymbol>* e_ptr2) {
485 // These entries are sanity checked by verify_and_compare_entries()
486 // before this function is called.
487 oop str1 = e_ptr1->literal();
488 oop str2 = e_ptr2->literal();
489
490 if (str1 == str2) {
491 tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "
492 "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",
493 p2i(str1), bkt1, e_cnt1, bkt2, e_cnt2);
494 return _verify_fail_continue;
495 }
496
497 if (java_lang_String::equals(str1, str2)) {
498 tty->print_cr("ERROR: identical String values in entry @ "
499 "bucket[%d][%d] and entry @ bucket[%d][%d]",
500 bkt1, e_cnt1, bkt2, e_cnt2);
501 return _verify_fail_continue;
502 }
503
504 return _verify_pass;
505 }
506
507 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,
508 HashtableEntry<oop, mtSymbol>* e_ptr,
509 StringTable::VerifyMesgModes mesg_mode) {
510
511 VerifyRetTypes ret = _verify_pass; // be optimistic
512
513 oop str = e_ptr->literal();
514 if (str == NULL) {
515 if (mesg_mode == _verify_with_mesgs) {
516 tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,
517 e_cnt);
518 }
519 // NULL oop means no more verifications are possible
520 return _verify_fail_done;
521 }
522
523 if (str->klass() != SystemDictionary::String_klass()) {
524 if (mesg_mode == _verify_with_mesgs) {
525 tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",
526 bkt, e_cnt);
527 }
528 // not a String means no more verifications are possible
529 return _verify_fail_done;
530 }
531
532 unsigned int h = hash_string(str);
533 if (e_ptr->hash() != h) {
534 if (mesg_mode == _verify_with_mesgs) {
535 tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "
536 "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);
537 }
538 ret = _verify_fail_continue;
539 }
540
541 if (the_table()->hash_to_index(h) != bkt) {
542 if (mesg_mode == _verify_with_mesgs) {
543 tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "
544 "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,
545 the_table()->hash_to_index(h));
546 }
547 ret = _verify_fail_continue;
548 }
549
550 return ret;
551 }
552
553 // See StringTable::verify() above for the quick verification that is
554 // part of Universe::verify(). This verification is exhaustive and
555 // reports on every issue that is found. StringTable::verify() only
556 // reports on the first issue that is found.
557 //
558 // StringTable::verify_entry() checks:
559 // - oop value != NULL (same as verify())
560 // - oop value is a String
561 // - hash(String) == hash in entry (same as verify())
562 // - index for hash == index of entry (same as verify())
563 //
564 // StringTable::compare_entries() checks:
565 // - oops are unique across all entries
566 // - String values are unique across all entries
567 //
568 int StringTable::verify_and_compare_entries() {
569 assert(StringTable_lock->is_locked(), "sanity check");
570
571 int fail_cnt = 0;
572
573 // first, verify all the entries individually:
574 for (int bkt = 0; bkt < the_table()->table_size(); bkt++) {
575 HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);
576 for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {
577 VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);
578 if (ret != _verify_pass) {
579 fail_cnt++;
580 }
581 }
582 }
583
584 // Optimization: if the above check did not find any failures, then
585 // the comparison loop below does not need to call verify_entry()
586 // before calling compare_entries(). If there were failures, then we
587 // have to call verify_entry() to see if the entry can be passed to
588 // compare_entries() safely. When we call verify_entry() in the loop
589 // below, we do so quietly to void duplicate messages and we don't
590 // increment fail_cnt because the failures have already been counted.
591 bool need_entry_verify = (fail_cnt != 0);
592
593 // second, verify all entries relative to each other:
594 for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {
595 HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);
596 for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {
597 if (need_entry_verify) {
598 VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,
599 _verify_quietly);
600 if (ret == _verify_fail_done) {
601 // cannot use the current entry to compare against other entries
602 continue;
603 }
604 }
605
606 for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {
607 HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);
608 int e_cnt2;
609 for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {
610 if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {
611 // skip the entries up to and including the one that
612 // we're comparing against
613 continue;
614 }
615
616 if (need_entry_verify) {
617 VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,
618 _verify_quietly);
619 if (ret == _verify_fail_done) {
620 // cannot compare against this entry
621 continue;
622 }
623 }
624
625 // compare two entries, report and count any failures:
626 if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)
627 != _verify_pass) {
628 fail_cnt++;
629 }
630 }
631 }
632 }
633 }
634 return fail_cnt;
635 }
636
637 // Create a new table and using alternate hash code, populate the new table
638 // with the existing strings. Set flag to use the alternate hash code afterwards.
639 void StringTable::rehash_table() {
640 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
641 // This should never happen with -Xshare:dump but it might in testing mode.
642 if (DumpSharedSpaces) return;
643 StringTable* new_table = new StringTable();
644
645 // Rehash the table
646 the_table()->move_to(new_table);
647
648 // Delete the table and buckets (entries are reused in new table).
649 delete _the_table;
650 // Don't check if we need rehashing until the table gets unbalanced again.
651 // Then rehash with a new global seed.
652 _needs_rehashing = false;
653 _the_table = new_table;
654 }
655
656 // Utility for dumping strings
657 StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) :
658 DCmdWithParser(output, heap),
659 _verbose("-verbose", "Dump the content of each string in the table",
660 "BOOLEAN", false, "false") {
661 _dcmdparser.add_dcmd_option(&_verbose);
662 }
663
664 void StringtableDCmd::execute(DCmdSource source, TRAPS) {
665 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings,
666 _verbose.value());
667 VMThread::execute(&dumper);
668 }
669
670 int StringtableDCmd::num_arguments() {
671 ResourceMark rm;
672 StringtableDCmd* dcmd = new StringtableDCmd(NULL, false);
673 if (dcmd != NULL) {
674 DCmdMark mark(dcmd);
675 return dcmd->_dcmdparser.num_arguments();
676 } else {
677 return 0;
678 }
679 }
680
681 // Sharing
682 bool StringTable::copy_shared_string(GrowableArray<MemRegion> *string_space,
683 CompactStringTableWriter* writer) {
684 #if INCLUDE_CDS && INCLUDE_ALL_GCS && defined(_LP64) && !defined(_WINDOWS)
685 assert(UseG1GC, "Only support G1 GC");
686 assert(UseCompressedOops && UseCompressedClassPointers,
687 "Only support UseCompressedOops and UseCompressedClassPointers enabled");
688
689 Thread* THREAD = Thread::current();
690 G1CollectedHeap::heap()->begin_archive_alloc_range();
691 for (int i = 0; i < the_table()->table_size(); ++i) {
692 HashtableEntry<oop, mtSymbol>* bucket = the_table()->bucket(i);
693 for ( ; bucket != NULL; bucket = bucket->next()) {
694 oop s = bucket->literal();
695 unsigned int hash = java_lang_String::hash_code(s);
696 if (hash == 0) {
697 continue;
698 }
699
700 // allocate the new 'value' array first
701 typeArrayOop v = java_lang_String::value(s);
702 int v_len = v->size();
703 typeArrayOop new_v;
704 if (G1CollectedHeap::heap()->is_archive_alloc_too_large(v_len)) {
705 continue; // skip the current String. The 'value' array is too large to handle
706 } else {
707 new_v = (typeArrayOop)G1CollectedHeap::heap()->archive_mem_allocate(v_len);
708 if (new_v == NULL) {
709 return false; // allocation failed
710 }
711 }
712 // now allocate the new String object
713 int s_len = s->size();
714 oop new_s = (oop)G1CollectedHeap::heap()->archive_mem_allocate(s_len);
715 if (new_s == NULL) {
716 return false;
717 }
718
719 s->identity_hash();
720 v->identity_hash();
721
722 // copy the objects' data
723 Copy::aligned_disjoint_words((HeapWord*)s, (HeapWord*)new_s, s_len);
724 Copy::aligned_disjoint_words((HeapWord*)v, (HeapWord*)new_v, v_len);
725
726 // adjust the pointer to the 'value' field in the new String oop. Also pre-compute and set the
727 // 'hash' field. That avoids "write" to the shared strings at runtime by the deduplication process.
728 java_lang_String::set_value_raw(new_s, new_v);
729 if (java_lang_String::hash(new_s) == 0) {
730 java_lang_String::set_hash(new_s, hash);
731 }
732
733 // add to the compact table
734 writer->add(hash, new_s);
735
736 MetaspaceShared::relocate_klass_ptr(new_s);
737 MetaspaceShared::relocate_klass_ptr(new_v);
738 }
739 }
740
741 G1CollectedHeap::heap()->end_archive_alloc_range(string_space, os::vm_allocation_granularity());
742 assert(string_space->length() <= 2, "sanity");
743 #endif
744 return true;
745 }
746
747 void StringTable::write_to_archive(GrowableArray<MemRegion> *string_space) {
748 #if INCLUDE_CDS
749 _shared_table.reset();
750 if (!(UseG1GC && UseCompressedOops && UseCompressedClassPointers)) {
751 log_info(cds)(
752 "Shared strings are excluded from the archive as UseG1GC, "
753 "UseCompressedOops and UseCompressedClassPointers are required."
754 "Current settings: UseG1GC=%s, UseCompressedOops=%s, UseCompressedClassPointers=%s.",
755 BOOL_TO_STR(UseG1GC), BOOL_TO_STR(UseCompressedOops),
756 BOOL_TO_STR(UseCompressedClassPointers));
757 } else {
758 int num_buckets = the_table()->number_of_entries() /
759 SharedSymbolTableBucketSize;
760 // calculation of num_buckets can result in zero buckets, we need at least one
761 CompactStringTableWriter writer(num_buckets > 1 ? num_buckets : 1,
762 &MetaspaceShared::stats()->string);
763
764 // Copy the interned strings into the "string space" within the java heap
765 if (copy_shared_string(string_space, &writer)) {
766 writer.dump(&_shared_table);
767 }
768 }
769 #endif
770 }
771
772 void StringTable::serialize(SerializeClosure* soc) {
773 #if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS)
774 _shared_table.set_type(CompactHashtable<oop, char>::_string_table);
775 _shared_table.serialize(soc);
776
777 if (soc->writing()) {
778 _shared_table.reset(); // Sanity. Make sure we don't use the shared table at dump time
779 } else if (_ignore_shared_strings) {
780 _shared_table.reset();
781 }
782 #endif
783 }
784
785 void StringTable::shared_oops_do(OopClosure* f) {
786 #if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS)
787 _shared_table.oops_do(f);
788 #endif
789 }
790