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