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