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