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