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