1 /*
2 * Copyright (c) 1997, 2016, 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 "memory/allocation.inline.hpp"
34 #include "memory/filemap.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "oops/oop.inline.hpp"
37 #include "runtime/atomic.inline.hpp"
38 #include "runtime/mutexLocker.hpp"
39 #include "utilities/hashtable.inline.hpp"
40 #include "utilities/macros.hpp"
41 #if INCLUDE_ALL_GCS
42 #include "gc/g1/g1CollectedHeap.hpp"
43 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
44 #include "gc/g1/g1StringDedup.hpp"
45 #endif
46
47 // the number of buckets a thread claims
48 const int ClaimChunkSize = 32;
49
50 #ifdef ASSERT
51 class StableMemoryChecker : public StackObj {
52 enum { _bufsize = wordSize*4 };
53
54 address _region;
55 jint _size;
56 u1 _save_buf[_bufsize];
57
58 int sample(u1* save_buf) {
59 if (_size <= _bufsize) {
60 memcpy(save_buf, _region, _size);
61 return _size;
62 } else {
63 // copy head and tail
64 memcpy(&save_buf[0], _region, _bufsize/2);
65 memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);
66 return (_bufsize/2)*2;
67 }
68 }
69
70 public:
71 StableMemoryChecker(const void* region, jint size) {
72 _region = (address) region;
73 _size = size;
74 sample(_save_buf);
75 }
76
77 bool verify() {
78 u1 check_buf[sizeof(_save_buf)];
79 int check_size = sample(check_buf);
80 return (0 == memcmp(_save_buf, check_buf, check_size));
81 }
82
83 void set_region(const void* region) { _region = (address) region; }
84 };
85 #endif
86
87
88 // --------------------------------------------------------------------------
89 StringTable* StringTable::_the_table = NULL;
90 bool StringTable::_ignore_shared_strings = false;
91 bool StringTable::_needs_rehashing = false;
92
93 volatile int StringTable::_parallel_claimed_idx = 0;
94
95 CompactHashtable<oop, char> StringTable::_shared_table;
96
97 // Pick hashing algorithm
98 unsigned int StringTable::hash_string(const jchar* s, int len) {
99 return use_alternate_hashcode() ? AltHashing::murmur3_32(seed(), s, len) :
100 java_lang_String::hash_code(s, len);
101 }
102
103 unsigned int StringTable::hash_string(oop string) {
104 EXCEPTION_MARK;
105 if (string == NULL) {
106 return hash_string((jchar*)NULL, 0);
107 }
108 ResourceMark rm(THREAD);
109 // All String oops are hashed as unicode
110 int length;
111 jchar* chars = java_lang_String::as_unicode_string(string, length, THREAD);
112 if (chars != NULL) {
113 return hash_string(chars, length);
114 } else {
115 vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "unable to create Unicode string for verification");
116 return 0;
117 }
118 }
119
120 oop StringTable::lookup_shared(jchar* name, int len) {
121 // java_lang_String::hash_code() was used to compute hash values in the shared table. Don't
122 // use the hash value from StringTable::hash_string() as it might use alternate hashcode.
123 return _shared_table.lookup((const char*)name,
124 java_lang_String::hash_code(name, len), len);
125 }
126
127 oop StringTable::lookup_in_main_table(int index, jchar* name,
128 int len, unsigned int hash) {
129 int count = 0;
130 for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {
131 count++;
132 if (l->hash() == hash) {
133 if (java_lang_String::equals(l->literal(), name, len)) {
134 return l->literal();
135 }
136 }
137 }
138 // If the bucket size is too deep check if this hash code is insufficient.
139 if (count >= rehash_count && !needs_rehashing()) {
140 _needs_rehashing = check_rehash_table(count);
141 }
142 return NULL;
143 }
144
145
146 oop StringTable::basic_add(int index_arg, Handle string, jchar* name,
147 int len, unsigned int hashValue_arg, TRAPS) {
148
149 assert(java_lang_String::equals(string(), name, len),
150 "string must be properly initialized");
151 // Cannot hit a safepoint in this function because the "this" pointer can move.
152 NoSafepointVerifier nsv;
153
154 // Check if the symbol table has been rehashed, if so, need to recalculate
155 // the hash value and index before second lookup.
156 unsigned int hashValue;
157 int index;
158 if (use_alternate_hashcode()) {
159 hashValue = hash_string(name, len);
160 index = hash_to_index(hashValue);
161 } else {
162 hashValue = hashValue_arg;
163 index = index_arg;
164 }
165
166 // Since look-up was done lock-free, we need to check if another
167 // thread beat us in the race to insert the symbol.
168
169 // No need to lookup the shared table from here since the caller (intern()) already did
170 oop test = lookup_in_main_table(index, name, len, hashValue); // calls lookup(u1*, int)
171 if (test != NULL) {
172 // Entry already added
173 return test;
174 }
175
176 HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());
177 add_entry(index, entry);
178 return string();
179 }
180
181
182 oop StringTable::lookup(Symbol* symbol) {
183 ResourceMark rm;
184 int length;
185 jchar* chars = symbol->as_unicode(length);
186 return lookup(chars, length);
187 }
188
189 // Tell the GC that this string was looked up in the StringTable.
190 static void ensure_string_alive(oop string) {
191 // A lookup in the StringTable could return an object that was previously
192 // considered dead. The SATB part of G1 needs to get notified about this
193 // potential resurrection, otherwise the marking might not find the object.
194 #if INCLUDE_ALL_GCS
195 if (UseG1GC && string != NULL) {
196 G1SATBCardTableModRefBS::enqueue(string);
197 }
198 #endif
199 }
200
201 oop StringTable::lookup(jchar* name, int len) {
202 oop string = lookup_shared(name, len);
203 if (string != NULL) {
204 return string;
205 }
206
207 unsigned int hash = hash_string(name, len);
208 int index = the_table()->hash_to_index(hash);
209 string = the_table()->lookup_in_main_table(index, name, len, hash);
210
211 ensure_string_alive(string);
212
213 return string;
214 }
215
216 oop StringTable::intern(Handle string_or_null, jchar* name,
217 int len, TRAPS) {
218 oop found_string = lookup_shared(name, len);
219 if (found_string != NULL) {
220 return found_string;
221 }
222
223 unsigned int hashValue = hash_string(name, len);
224 int index = the_table()->hash_to_index(hashValue);
225 found_string = the_table()->lookup_in_main_table(index, name, len, hashValue);
226
227 // Found
228 if (found_string != NULL) {
229 if (found_string != string_or_null()) {
230 ensure_string_alive(found_string);
231 }
232 return found_string;
233 }
234
235 debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
236 assert(!Universe::heap()->is_in_reserved(name),
237 "proposed name of symbol must be stable");
238
239 Handle string;
240 // try to reuse the string if possible
241 if (!string_or_null.is_null()) {
242 string = string_or_null;
243 } else {
244 string = java_lang_String::create_from_unicode(name, len, CHECK_NULL);
245 }
246
247 #if INCLUDE_ALL_GCS
248 if (G1StringDedup::is_enabled()) {
249 // Deduplicate the string before it is interned. Note that we should never
250 // deduplicate a string after it has been interned. Doing so will counteract
251 // compiler optimizations done on e.g. interned string literals.
252 G1StringDedup::deduplicate(string());
253 }
254 #endif
255
256 // Grab the StringTable_lock before getting the_table() because it could
257 // change at safepoint.
258 oop added_or_found;
259 {
260 MutexLocker ml(StringTable_lock, THREAD);
261 // Otherwise, add to symbol to table
262 added_or_found = the_table()->basic_add(index, string, name, len,
263 hashValue, CHECK_NULL);
264 }
265
266 if (added_or_found != string()) {
267 ensure_string_alive(added_or_found);
268 }
269
270 return added_or_found;
271 }
272
273 oop StringTable::intern(Symbol* symbol, TRAPS) {
274 if (symbol == NULL) return NULL;
275 ResourceMark rm(THREAD);
276 int length;
277 jchar* chars = symbol->as_unicode(length);
278 Handle string;
279 oop result = intern(string, chars, length, CHECK_NULL);
280 return result;
281 }
282
283
284 oop StringTable::intern(oop string, TRAPS)
285 {
286 if (string == NULL) return NULL;
287 ResourceMark rm(THREAD);
288 int length;
289 Handle h_string (THREAD, string);
290 jchar* chars = java_lang_String::as_unicode_string(string, length, CHECK_NULL);
291 oop result = intern(h_string, chars, length, CHECK_NULL);
292 return result;
293 }
294
295
296 oop StringTable::intern(const char* utf8_string, TRAPS) {
297 if (utf8_string == NULL) return NULL;
298 ResourceMark rm(THREAD);
299 int length = UTF8::unicode_length(utf8_string);
300 jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
301 UTF8::convert_to_unicode(utf8_string, chars, length);
302 Handle string;
303 oop result = intern(string, chars, length, CHECK_NULL);
304 return result;
305 }
306
307 void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
308 buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), processed, removed);
309 }
310
311 void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
312 // Readers of the table are unlocked, so we should only be removing
313 // entries at a safepoint.
314 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
315 const int limit = the_table()->table_size();
316
317 for (;;) {
318 // Grab next set of buckets to scan
319 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
320 if (start_idx >= limit) {
321 // End of table
322 break;
323 }
324
325 int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
326 buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, processed, removed);
327 }
328 }
329
330 void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {
331 const int limit = the_table()->table_size();
332
333 assert(0 <= start_idx && start_idx <= limit,
334 "start_idx (%d) is out of bounds", start_idx);
335 assert(0 <= end_idx && end_idx <= limit,
336 "end_idx (%d) is out of bounds", end_idx);
337 assert(start_idx <= end_idx,
338 "Index ordering: start_idx=%d, end_idx=%d",
339 start_idx, end_idx);
340
341 for (int i = start_idx; i < end_idx; i += 1) {
342 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
343 while (entry != NULL) {
344 assert(!entry->is_shared(), "CDS not used for the StringTable");
345
346 f->do_oop((oop*)entry->literal_addr());
347
348 entry = entry->next();
349 }
350 }
351 }
352
353 void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, int* processed, int* removed) {
354 const int limit = the_table()->table_size();
355
356 assert(0 <= start_idx && start_idx <= limit,
357 "start_idx (%d) is out of bounds", start_idx);
358 assert(0 <= end_idx && end_idx <= limit,
359 "end_idx (%d) is out of bounds", end_idx);
360 assert(start_idx <= end_idx,
361 "Index ordering: start_idx=%d, end_idx=%d",
362 start_idx, end_idx);
363
364 for (int i = start_idx; i < end_idx; ++i) {
365 HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i);
366 HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
367 while (entry != NULL) {
368 assert(!entry->is_shared(), "CDS not used for the StringTable");
369
370 if (is_alive->do_object_b(entry->literal())) {
371 if (f != NULL) {
372 f->do_oop((oop*)entry->literal_addr());
373 }
374 p = entry->next_addr();
375 } else {
376 *p = entry->next();
377 the_table()->free_entry(entry);
378 (*removed)++;
379 }
380 (*processed)++;
381 entry = *p;
382 }
383 }
384 }
385
386 void StringTable::oops_do(OopClosure* f) {
387 buckets_oops_do(f, 0, the_table()->table_size());
388 }
389
390 void StringTable::possibly_parallel_oops_do(OopClosure* f) {
391 const int limit = the_table()->table_size();
392
393 for (;;) {
394 // Grab next set of buckets to scan
395 int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
396 if (start_idx >= limit) {
397 // End of table
398 break;
399 }
400
401 int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
402 buckets_oops_do(f, start_idx, end_idx);
403 }
404 }
405
406 // This verification is part of Universe::verify() and needs to be quick.
407 // See StringTable::verify_and_compare() below for exhaustive verification.
408 void StringTable::verify() {
409 for (int i = 0; i < the_table()->table_size(); ++i) {
410 HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
411 for ( ; p != NULL; p = p->next()) {
412 oop s = p->literal();
413 guarantee(s != NULL, "interned string is NULL");
414 unsigned int h = hash_string(s);
415 guarantee(p->hash() == h, "broken hash in string table entry");
416 guarantee(the_table()->hash_to_index(h) == i,
417 "wrong index in string table");
418 }
419 }
420 }
421
422 void StringTable::dump(outputStream* st, bool verbose) {
423 if (!verbose) {
424 the_table()->dump_table(st, "StringTable");
425 } else {
426 Thread* THREAD = Thread::current();
427 st->print_cr("VERSION: 1.1");
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 typeArrayOop value = java_lang_String::value(s);
433 int length = java_lang_String::length(s);
434 bool is_latin1 = java_lang_String::is_latin1(s);
435
436 if (length <= 0) {
437 st->print("%d: ", length);
438 } else {
439 ResourceMark rm(THREAD);
440 int utf8_length;
441 char* utf8_string;
442
443 if (!is_latin1) {
444 jchar* chars = value->char_at_addr(0);
445 utf8_length = UNICODE::utf8_length(chars, length);
446 utf8_string = UNICODE::as_utf8(chars, length);
447 } else {
448 jbyte* bytes = value->byte_at_addr(0);
449 utf8_length = UNICODE::utf8_length(bytes, length);
450 utf8_string = UNICODE::as_utf8(bytes, length);
451 }
452
453 st->print("%d: ", utf8_length);
454 HashtableTextDump::put_utf8(st, utf8_string, utf8_length);
455 }
456 st->cr();
457 }
458 }
459 }
460 }
461
462 StringTable::VerifyRetTypes StringTable::compare_entries(
463 int bkt1, int e_cnt1,
464 HashtableEntry<oop, mtSymbol>* e_ptr1,
465 int bkt2, int e_cnt2,
466 HashtableEntry<oop, mtSymbol>* e_ptr2) {
467 // These entries are sanity checked by verify_and_compare_entries()
468 // before this function is called.
469 oop str1 = e_ptr1->literal();
470 oop str2 = e_ptr2->literal();
471
472 if (str1 == str2) {
473 tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "
474 "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",
475 p2i(str1), bkt1, e_cnt1, bkt2, e_cnt2);
476 return _verify_fail_continue;
477 }
478
479 if (java_lang_String::equals(str1, str2)) {
480 tty->print_cr("ERROR: identical String values in entry @ "
481 "bucket[%d][%d] and entry @ bucket[%d][%d]",
482 bkt1, e_cnt1, bkt2, e_cnt2);
483 return _verify_fail_continue;
484 }
485
486 return _verify_pass;
487 }
488
489 StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,
490 HashtableEntry<oop, mtSymbol>* e_ptr,
491 StringTable::VerifyMesgModes mesg_mode) {
492
493 VerifyRetTypes ret = _verify_pass; // be optimistic
494
495 oop str = e_ptr->literal();
496 if (str == NULL) {
497 if (mesg_mode == _verify_with_mesgs) {
498 tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,
499 e_cnt);
500 }
501 // NULL oop means no more verifications are possible
502 return _verify_fail_done;
503 }
504
505 if (str->klass() != SystemDictionary::String_klass()) {
506 if (mesg_mode == _verify_with_mesgs) {
507 tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",
508 bkt, e_cnt);
509 }
510 // not a String means no more verifications are possible
511 return _verify_fail_done;
512 }
513
514 unsigned int h = hash_string(str);
515 if (e_ptr->hash() != h) {
516 if (mesg_mode == _verify_with_mesgs) {
517 tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "
518 "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);
519 }
520 ret = _verify_fail_continue;
521 }
522
523 if (the_table()->hash_to_index(h) != bkt) {
524 if (mesg_mode == _verify_with_mesgs) {
525 tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "
526 "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,
527 the_table()->hash_to_index(h));
528 }
529 ret = _verify_fail_continue;
530 }
531
532 return ret;
533 }
534
535 // See StringTable::verify() above for the quick verification that is
536 // part of Universe::verify(). This verification is exhaustive and
537 // reports on every issue that is found. StringTable::verify() only
538 // reports on the first issue that is found.
539 //
540 // StringTable::verify_entry() checks:
541 // - oop value != NULL (same as verify())
542 // - oop value is a String
543 // - hash(String) == hash in entry (same as verify())
544 // - index for hash == index of entry (same as verify())
545 //
546 // StringTable::compare_entries() checks:
547 // - oops are unique across all entries
548 // - String values are unique across all entries
549 //
550 int StringTable::verify_and_compare_entries() {
551 assert(StringTable_lock->is_locked(), "sanity check");
552
553 int fail_cnt = 0;
554
555 // first, verify all the entries individually:
556 for (int bkt = 0; bkt < the_table()->table_size(); bkt++) {
557 HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);
558 for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {
559 VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);
560 if (ret != _verify_pass) {
561 fail_cnt++;
562 }
563 }
564 }
565
566 // Optimization: if the above check did not find any failures, then
567 // the comparison loop below does not need to call verify_entry()
568 // before calling compare_entries(). If there were failures, then we
569 // have to call verify_entry() to see if the entry can be passed to
570 // compare_entries() safely. When we call verify_entry() in the loop
571 // below, we do so quietly to void duplicate messages and we don't
572 // increment fail_cnt because the failures have already been counted.
573 bool need_entry_verify = (fail_cnt != 0);
574
575 // second, verify all entries relative to each other:
576 for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {
577 HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);
578 for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {
579 if (need_entry_verify) {
580 VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,
581 _verify_quietly);
582 if (ret == _verify_fail_done) {
583 // cannot use the current entry to compare against other entries
584 continue;
585 }
586 }
587
588 for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {
589 HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);
590 int e_cnt2;
591 for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {
592 if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {
593 // skip the entries up to and including the one that
594 // we're comparing against
595 continue;
596 }
597
598 if (need_entry_verify) {
599 VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,
600 _verify_quietly);
601 if (ret == _verify_fail_done) {
602 // cannot compare against this entry
603 continue;
604 }
605 }
606
607 // compare two entries, report and count any failures:
608 if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)
609 != _verify_pass) {
610 fail_cnt++;
611 }
612 }
613 }
614 }
615 }
616 return fail_cnt;
617 }
618
619 // Create a new table and using alternate hash code, populate the new table
620 // with the existing strings. Set flag to use the alternate hash code afterwards.
621 void StringTable::rehash_table() {
622 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
623 // This should never happen with -Xshare:dump but it might in testing mode.
624 if (DumpSharedSpaces) return;
625 StringTable* new_table = new StringTable();
626
627 // Rehash the table
628 the_table()->move_to(new_table);
629
630 // Delete the table and buckets (entries are reused in new table).
631 delete _the_table;
632 // Don't check if we need rehashing until the table gets unbalanced again.
633 // Then rehash with a new global seed.
634 _needs_rehashing = false;
635 _the_table = new_table;
636 }
637
638 // Utility for dumping strings
639 StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) :
640 DCmdWithParser(output, heap),
641 _verbose("-verbose", "Dump the content of each string in the table",
642 "BOOLEAN", false, "false") {
643 _dcmdparser.add_dcmd_option(&_verbose);
644 }
645
646 void StringtableDCmd::execute(DCmdSource source, TRAPS) {
647 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings,
648 _verbose.value());
649 VMThread::execute(&dumper);
650 }
651
652 int StringtableDCmd::num_arguments() {
653 ResourceMark rm;
654 StringtableDCmd* dcmd = new StringtableDCmd(NULL, false);
655 if (dcmd != NULL) {
656 DCmdMark mark(dcmd);
657 return dcmd->_dcmdparser.num_arguments();
658 } else {
659 return 0;
660 }
661 }
662
663 // Sharing
664 bool StringTable::copy_shared_string(GrowableArray<MemRegion> *string_space,
665 CompactHashtableWriter* ch_table) {
666 #if INCLUDE_CDS && INCLUDE_ALL_GCS && defined(_LP64) && !defined(_WINDOWS)
667 assert(UseG1GC, "Only support G1 GC");
668 assert(UseCompressedOops && UseCompressedClassPointers,
669 "Only support UseCompressedOops and UseCompressedClassPointers enabled");
670
671 Thread* THREAD = Thread::current();
672 G1CollectedHeap::heap()->begin_archive_alloc_range();
673 for (int i = 0; i < the_table()->table_size(); ++i) {
674 HashtableEntry<oop, mtSymbol>* bucket = the_table()->bucket(i);
675 for ( ; bucket != NULL; bucket = bucket->next()) {
676 oop s = bucket->literal();
677 unsigned int hash = java_lang_String::hash_code(s);
678 if (hash == 0) {
679 continue;
680 }
681
682 // allocate the new 'value' array first
683 typeArrayOop v = java_lang_String::value(s);
684 int v_len = v->size();
685 typeArrayOop new_v;
686 if (G1CollectedHeap::heap()->is_archive_alloc_too_large(v_len)) {
687 continue; // skip the current String. The 'value' array is too large to handle
688 } else {
689 new_v = (typeArrayOop)G1CollectedHeap::heap()->archive_mem_allocate(v_len);
690 if (new_v == NULL) {
691 return false; // allocation failed
692 }
693 }
694 // now allocate the new String object
695 int s_len = s->size();
696 oop new_s = (oop)G1CollectedHeap::heap()->archive_mem_allocate(s_len);
697 if (new_s == NULL) {
698 return false;
699 }
700
701 s->identity_hash();
702 v->identity_hash();
703
704 // copy the objects' data
705 Copy::aligned_disjoint_words((HeapWord*)s, (HeapWord*)new_s, s_len);
706 Copy::aligned_disjoint_words((HeapWord*)v, (HeapWord*)new_v, v_len);
707
708 // adjust the pointer to the 'value' field in the new String oop. Also pre-compute and set the
709 // 'hash' field. That avoids "write" to the shared strings at runtime by the deduplication process.
710 java_lang_String::set_value_raw(new_s, new_v);
711 if (java_lang_String::hash(new_s) == 0) {
712 java_lang_String::set_hash(new_s, hash);
713 }
714
715 // add to the compact table
716 ch_table->add(hash, new_s);
717 }
718 }
719
720 G1CollectedHeap::heap()->end_archive_alloc_range(string_space, os::vm_allocation_granularity());
721 assert(string_space->length() <= 2, "sanity");
722 #endif
723 return true;
724 }
725
726 bool StringTable::copy_compact_table(char** top, char *end, GrowableArray<MemRegion> *string_space,
727 size_t* space_size) {
728 #if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS)
729 if (!(UseG1GC && UseCompressedOops && UseCompressedClassPointers)) {
730 if (PrintSharedSpaces) {
731 tty->print_cr("Shared strings are excluded from the archive as UseG1GC, "
732 "UseCompressedOops and UseCompressedClassPointers are required.");
733 }
734 return true;
735 }
736
737 CompactHashtableWriter ch_table(CompactHashtable<oop, char>::_string_table,
738 the_table()->number_of_entries(),
739 &MetaspaceShared::stats()->string);
740
741 // Copy the interned strings into the "string space" within the java heap
742 if (!copy_shared_string(string_space, &ch_table)) {
743 return false;
744 }
745
746 for (int i = 0; i < string_space->length(); i++) {
747 *space_size += string_space->at(i).byte_size();
748 }
749
750 // Now dump the compact table
751 if (*top + ch_table.get_required_bytes() > end) {
752 // not enough space left
753 return false;
754 }
755 ch_table.dump(top, end);
756 *top = (char*)align_ptr_up(*top, sizeof(void*));
757
758 #endif
759 return true;
760 }
761
762 void StringTable::shared_oops_do(OopClosure* f) {
763 #if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS)
764 _shared_table.oops_do(f);
765 #endif
766 }
767
768 const char* StringTable::init_shared_table(FileMapInfo *mapinfo, char *buffer) {
769 #if INCLUDE_CDS && defined(_LP64) && !defined(_WINDOWS)
770 if (mapinfo->space_capacity(MetaspaceShared::first_string) == 0) {
771 // no shared string data
772 return buffer;
773 }
774
775 // initialize the shared table
776 juint *p = (juint*)buffer;
777 const char* end = _shared_table.init(
778 CompactHashtable<oop, char>::_string_table, (char*)p);
779 const char* aligned_end = (const char*)align_ptr_up(end, sizeof(void*));
780
781 if (_ignore_shared_strings) {
782 _shared_table.reset();
783 }
784
785 return aligned_end;
786 #endif
787
788 return buffer;
789 }