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