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