1 /*
2 * Copyright (c) 1997, 2019, 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.hpp"
28 #include "classfile/javaClasses.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "memory/allocation.inline.hpp"
31 #include "memory/dynamicArchive.hpp"
32 #include "memory/metaspaceClosure.hpp"
33 #include "memory/metaspaceShared.hpp"
34 #include "memory/resourceArea.hpp"
35 #include "oops/oop.inline.hpp"
36 #include "runtime/atomic.hpp"
37 #include "runtime/interfaceSupport.inline.hpp"
38 #include "runtime/timerTrace.hpp"
39 #include "services/diagnosticCommand.hpp"
40 #include "utilities/concurrentHashTable.inline.hpp"
41 #include "utilities/concurrentHashTableTasks.inline.hpp"
42 #include "utilities/utf8.hpp"
43
44 // We used to not resize at all, so let's be conservative
45 // and not set it too short before we decide to resize,
46 // to match previous startup behavior
47 const double PREF_AVG_LIST_LEN = 8.0;
48 // 2^24 is max size, like StringTable.
49 const size_t END_SIZE = 24;
50 // If a chain gets to 100 something might be wrong
51 const size_t REHASH_LEN = 100;
52
53 const size_t ON_STACK_BUFFER_LENGTH = 128;
54
55 // --------------------------------------------------------------------------
56
symbol_equals_compact_hashtable_entry(Symbol * value,const char * key,int len)57 inline bool symbol_equals_compact_hashtable_entry(Symbol* value, const char* key, int len) {
58 if (value->equals(key, len)) {
59 assert(value->refcount() == PERM_REFCOUNT, "must be shared");
60 return true;
61 } else {
62 return false;
63 }
64 }
65
66 static OffsetCompactHashtable<
67 const char*, Symbol*,
68 symbol_equals_compact_hashtable_entry
69 > _shared_table;
70
71 static OffsetCompactHashtable<
72 const char*, Symbol*,
73 symbol_equals_compact_hashtable_entry
74 > _dynamic_shared_table;
75
76 // --------------------------------------------------------------------------
77
78 typedef ConcurrentHashTable<SymbolTableConfig, mtSymbol> SymbolTableHash;
79 static SymbolTableHash* _local_table = NULL;
80
81 volatile bool SymbolTable::_has_work = 0;
82 volatile bool SymbolTable::_needs_rehashing = false;
83
84 // For statistics
85 static size_t _symbols_removed = 0;
86 static size_t _symbols_counted = 0;
87 static size_t _current_size = 0;
88
89 static volatile size_t _items_count = 0;
90 static volatile bool _has_items_to_clean = false;
91
92
93 static volatile bool _alt_hash = false;
94 static volatile bool _lookup_shared_first = false;
95
96 // Static arena for symbols that are not deallocated
97 Arena* SymbolTable::_arena = NULL;
98
99 static juint murmur_seed = 0;
100
log_trace_symboltable_helper(Symbol * sym,const char * msg)101 static inline void log_trace_symboltable_helper(Symbol* sym, const char* msg) {
102 #ifndef PRODUCT
103 ResourceMark rm;
104 log_trace(symboltable)("%s [%s]", msg, sym->as_quoted_ascii());
105 #endif // PRODUCT
106 }
107
108 // Pick hashing algorithm.
hash_symbol(const char * s,int len,bool useAlt)109 static uintx hash_symbol(const char* s, int len, bool useAlt) {
110 return useAlt ?
111 AltHashing::murmur3_32(murmur_seed, (const jbyte*)s, len) :
112 java_lang_String::hash_code((const jbyte*)s, len);
113 }
114
115 #if INCLUDE_CDS
hash_shared_symbol(const char * s,int len)116 static uintx hash_shared_symbol(const char* s, int len) {
117 return java_lang_String::hash_code((const jbyte*)s, len);
118 }
119 #endif
120
121 class SymbolTableConfig : public AllStatic {
122 private:
123 public:
124 typedef Symbol* Value; // value of the Node in the hashtable
125
get_hash(Value const & value,bool * is_dead)126 static uintx get_hash(Value const& value, bool* is_dead) {
127 *is_dead = (value->refcount() == 0);
128 if (*is_dead) {
129 return 0;
130 } else {
131 return hash_symbol((const char*)value->bytes(), value->utf8_length(), _alt_hash);
132 }
133 }
134 // We use default allocation/deallocation but counted
allocate_node(size_t size,Value const & value)135 static void* allocate_node(size_t size, Value const& value) {
136 SymbolTable::item_added();
137 return AllocateHeap(size, mtSymbol);
138 }
free_node(void * memory,Value const & value)139 static void free_node(void* memory, Value const& value) {
140 // We get here because #1 some threads lost a race to insert a newly created Symbol
141 // or #2 we're cleaning up unused symbol.
142 // If #1, then the symbol can be either permanent (refcount==PERM_REFCOUNT),
143 // or regular newly created one (refcount==1)
144 // If #2, then the symbol is dead (refcount==0)
145 assert((value->refcount() == PERM_REFCOUNT) || (value->refcount() == 1) || (value->refcount() == 0),
146 "refcount %d", value->refcount());
147 if (value->refcount() == 1) {
148 value->decrement_refcount();
149 assert(value->refcount() == 0, "expected dead symbol");
150 }
151 SymbolTable::delete_symbol(value);
152 FreeHeap(memory);
153 SymbolTable::item_removed();
154 }
155 };
156
ceil_log2(size_t value)157 static size_t ceil_log2(size_t value) {
158 size_t ret;
159 for (ret = 1; ((size_t)1 << ret) < value; ++ret);
160 return ret;
161 }
162
create_table()163 void SymbolTable::create_table () {
164 size_t start_size_log_2 = ceil_log2(SymbolTableSize);
165 _current_size = ((size_t)1) << start_size_log_2;
166 log_trace(symboltable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")",
167 _current_size, start_size_log_2);
168 _local_table = new SymbolTableHash(start_size_log_2, END_SIZE, REHASH_LEN);
169
170 // Initialize the arena for global symbols, size passed in depends on CDS.
171 if (symbol_alloc_arena_size == 0) {
172 _arena = new (mtSymbol) Arena(mtSymbol);
173 } else {
174 _arena = new (mtSymbol) Arena(mtSymbol, symbol_alloc_arena_size);
175 }
176 }
177
delete_symbol(Symbol * sym)178 void SymbolTable::delete_symbol(Symbol* sym) {
179 if (sym->refcount() == PERM_REFCOUNT) {
180 MutexLocker ml(SymbolArena_lock, Mutex::_no_safepoint_check_flag); // Protect arena
181 // Deleting permanent symbol should not occur very often (insert race condition),
182 // so log it.
183 log_trace_symboltable_helper(sym, "Freeing permanent symbol");
184 if (!arena()->Afree(sym, sym->size())) {
185 log_trace_symboltable_helper(sym, "Leaked permanent symbol");
186 }
187 } else {
188 delete sym;
189 }
190 }
191
reset_has_items_to_clean()192 void SymbolTable::reset_has_items_to_clean() { Atomic::store(&_has_items_to_clean, false); }
mark_has_items_to_clean()193 void SymbolTable::mark_has_items_to_clean() { Atomic::store(&_has_items_to_clean, true); }
has_items_to_clean()194 bool SymbolTable::has_items_to_clean() { return Atomic::load(&_has_items_to_clean); }
195
item_added()196 void SymbolTable::item_added() {
197 Atomic::inc(&_items_count);
198 }
199
item_removed()200 void SymbolTable::item_removed() {
201 Atomic::inc(&(_symbols_removed));
202 Atomic::dec(&_items_count);
203 }
204
get_load_factor()205 double SymbolTable::get_load_factor() {
206 return (double)_items_count/_current_size;
207 }
208
table_size()209 size_t SymbolTable::table_size() {
210 return ((size_t)1) << _local_table->get_size_log2(Thread::current());
211 }
212
trigger_cleanup()213 void SymbolTable::trigger_cleanup() {
214 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
215 _has_work = true;
216 Service_lock->notify_all();
217 }
218
allocate_symbol(const char * name,int len,bool c_heap)219 Symbol* SymbolTable::allocate_symbol(const char* name, int len, bool c_heap) {
220 assert (len <= Symbol::max_length(), "should be checked by caller");
221
222 Symbol* sym;
223 if (Arguments::is_dumping_archive()) {
224 c_heap = false;
225 }
226 if (c_heap) {
227 // refcount starts as 1
228 sym = new (len) Symbol((const u1*)name, len, 1);
229 assert(sym != NULL, "new should call vm_exit_out_of_memory if C_HEAP is exhausted");
230 } else {
231 // Allocate to global arena
232 MutexLocker ml(SymbolArena_lock, Mutex::_no_safepoint_check_flag); // Protect arena
233 sym = new (len, arena()) Symbol((const u1*)name, len, PERM_REFCOUNT);
234 }
235 return sym;
236 }
237
238 class SymbolsDo : StackObj {
239 SymbolClosure *_cl;
240 public:
SymbolsDo(SymbolClosure * cl)241 SymbolsDo(SymbolClosure *cl) : _cl(cl) {}
operator ()(Symbol ** value)242 bool operator()(Symbol** value) {
243 assert(value != NULL, "expected valid value");
244 assert(*value != NULL, "value should point to a symbol");
245 _cl->do_symbol(value);
246 return true;
247 };
248 };
249
250 class SharedSymbolIterator {
251 SymbolClosure* _symbol_closure;
252 public:
SharedSymbolIterator(SymbolClosure * f)253 SharedSymbolIterator(SymbolClosure* f) : _symbol_closure(f) {}
do_value(Symbol * symbol)254 void do_value(Symbol* symbol) {
255 _symbol_closure->do_symbol(&symbol);
256 }
257 };
258
259 // Call function for all symbols in the symbol table.
symbols_do(SymbolClosure * cl)260 void SymbolTable::symbols_do(SymbolClosure *cl) {
261 // all symbols from shared table
262 SharedSymbolIterator iter(cl);
263 _shared_table.iterate(&iter);
264 _dynamic_shared_table.iterate(&iter);
265
266 // all symbols from the dynamic table
267 SymbolsDo sd(cl);
268 if (!_local_table->try_scan(Thread::current(), sd)) {
269 log_info(symboltable)("symbols_do unavailable at this moment");
270 }
271 }
272
273 class MetaspacePointersDo : StackObj {
274 MetaspaceClosure *_it;
275 public:
MetaspacePointersDo(MetaspaceClosure * it)276 MetaspacePointersDo(MetaspaceClosure *it) : _it(it) {}
operator ()(Symbol ** value)277 bool operator()(Symbol** value) {
278 assert(value != NULL, "expected valid value");
279 assert(*value != NULL, "value should point to a symbol");
280 _it->push(value);
281 return true;
282 };
283 };
284
metaspace_pointers_do(MetaspaceClosure * it)285 void SymbolTable::metaspace_pointers_do(MetaspaceClosure* it) {
286 Arguments::assert_is_dumping_archive();
287 MetaspacePointersDo mpd(it);
288 _local_table->do_safepoint_scan(mpd);
289 }
290
lookup_dynamic(const char * name,int len,unsigned int hash)291 Symbol* SymbolTable::lookup_dynamic(const char* name,
292 int len, unsigned int hash) {
293 Symbol* sym = do_lookup(name, len, hash);
294 assert((sym == NULL) || sym->refcount() != 0, "refcount must not be zero");
295 return sym;
296 }
297
298 #if INCLUDE_CDS
lookup_shared(const char * name,int len,unsigned int hash)299 Symbol* SymbolTable::lookup_shared(const char* name,
300 int len, unsigned int hash) {
301 Symbol* sym = NULL;
302 if (!_shared_table.empty()) {
303 if (_alt_hash) {
304 // hash_code parameter may use alternate hashing algorithm but the shared table
305 // always uses the same original hash code.
306 hash = hash_shared_symbol(name, len);
307 }
308 sym = _shared_table.lookup(name, hash, len);
309 if (sym == NULL && DynamicArchive::is_mapped()) {
310 sym = _dynamic_shared_table.lookup(name, hash, len);
311 }
312 }
313 return sym;
314 }
315 #endif
316
lookup_common(const char * name,int len,unsigned int hash)317 Symbol* SymbolTable::lookup_common(const char* name,
318 int len, unsigned int hash) {
319 Symbol* sym;
320 if (_lookup_shared_first) {
321 sym = lookup_shared(name, len, hash);
322 if (sym == NULL) {
323 _lookup_shared_first = false;
324 sym = lookup_dynamic(name, len, hash);
325 }
326 } else {
327 sym = lookup_dynamic(name, len, hash);
328 if (sym == NULL) {
329 sym = lookup_shared(name, len, hash);
330 if (sym != NULL) {
331 _lookup_shared_first = true;
332 }
333 }
334 }
335 return sym;
336 }
337
new_symbol(const char * name,int len)338 Symbol* SymbolTable::new_symbol(const char* name, int len) {
339 unsigned int hash = hash_symbol(name, len, _alt_hash);
340 Symbol* sym = lookup_common(name, len, hash);
341 if (sym == NULL) {
342 sym = do_add_if_needed(name, len, hash, true);
343 }
344 assert(sym->refcount() != 0, "lookup should have incremented the count");
345 assert(sym->equals(name, len), "symbol must be properly initialized");
346 return sym;
347 }
348
new_symbol(const Symbol * sym,int begin,int end)349 Symbol* SymbolTable::new_symbol(const Symbol* sym, int begin, int end) {
350 assert(begin <= end && end <= sym->utf8_length(), "just checking");
351 assert(sym->refcount() != 0, "require a valid symbol");
352 const char* name = (const char*)sym->base() + begin;
353 int len = end - begin;
354 unsigned int hash = hash_symbol(name, len, _alt_hash);
355 Symbol* found = lookup_common(name, len, hash);
356 if (found == NULL) {
357 found = do_add_if_needed(name, len, hash, true);
358 }
359 return found;
360 }
361
362 class SymbolTableLookup : StackObj {
363 private:
364 Thread* _thread;
365 uintx _hash;
366 int _len;
367 const char* _str;
368 public:
SymbolTableLookup(const char * key,int len,uintx hash)369 SymbolTableLookup(const char* key, int len, uintx hash)
370 : _hash(hash), _len(len), _str(key) {}
get_hash() const371 uintx get_hash() const {
372 return _hash;
373 }
equals(Symbol ** value,bool * is_dead)374 bool equals(Symbol** value, bool* is_dead) {
375 assert(value != NULL, "expected valid value");
376 assert(*value != NULL, "value should point to a symbol");
377 Symbol *sym = *value;
378 if (sym->equals(_str, _len)) {
379 if (sym->try_increment_refcount()) {
380 // something is referencing this symbol now.
381 return true;
382 } else {
383 assert(sym->refcount() == 0, "expected dead symbol");
384 *is_dead = true;
385 return false;
386 }
387 } else {
388 *is_dead = (sym->refcount() == 0);
389 return false;
390 }
391 }
392 };
393
394 class SymbolTableGet : public StackObj {
395 Symbol* _return;
396 public:
SymbolTableGet()397 SymbolTableGet() : _return(NULL) {}
operator ()(Symbol ** value)398 void operator()(Symbol** value) {
399 assert(value != NULL, "expected valid value");
400 assert(*value != NULL, "value should point to a symbol");
401 _return = *value;
402 }
get_res_sym() const403 Symbol* get_res_sym() const {
404 return _return;
405 }
406 };
407
do_lookup(const char * name,int len,uintx hash)408 Symbol* SymbolTable::do_lookup(const char* name, int len, uintx hash) {
409 Thread* thread = Thread::current();
410 SymbolTableLookup lookup(name, len, hash);
411 SymbolTableGet stg;
412 bool rehash_warning = false;
413 _local_table->get(thread, lookup, stg, &rehash_warning);
414 update_needs_rehash(rehash_warning);
415 Symbol* sym = stg.get_res_sym();
416 assert((sym == NULL) || sym->refcount() != 0, "found dead symbol");
417 return sym;
418 }
419
lookup_only(const char * name,int len,unsigned int & hash)420 Symbol* SymbolTable::lookup_only(const char* name, int len, unsigned int& hash) {
421 hash = hash_symbol(name, len, _alt_hash);
422 return lookup_common(name, len, hash);
423 }
424
425 // Suggestion: Push unicode-based lookup all the way into the hashing
426 // and probing logic, so there is no need for convert_to_utf8 until
427 // an actual new Symbol* is created.
new_symbol(const jchar * name,int utf16_length)428 Symbol* SymbolTable::new_symbol(const jchar* name, int utf16_length) {
429 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
430 char stack_buf[ON_STACK_BUFFER_LENGTH];
431 if (utf8_length < (int) sizeof(stack_buf)) {
432 char* chars = stack_buf;
433 UNICODE::convert_to_utf8(name, utf16_length, chars);
434 return new_symbol(chars, utf8_length);
435 } else {
436 ResourceMark rm;
437 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
438 UNICODE::convert_to_utf8(name, utf16_length, chars);
439 return new_symbol(chars, utf8_length);
440 }
441 }
442
lookup_only_unicode(const jchar * name,int utf16_length,unsigned int & hash)443 Symbol* SymbolTable::lookup_only_unicode(const jchar* name, int utf16_length,
444 unsigned int& hash) {
445 int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
446 char stack_buf[ON_STACK_BUFFER_LENGTH];
447 if (utf8_length < (int) sizeof(stack_buf)) {
448 char* chars = stack_buf;
449 UNICODE::convert_to_utf8(name, utf16_length, chars);
450 return lookup_only(chars, utf8_length, hash);
451 } else {
452 ResourceMark rm;
453 char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
454 UNICODE::convert_to_utf8(name, utf16_length, chars);
455 return lookup_only(chars, utf8_length, hash);
456 }
457 }
458
new_symbols(ClassLoaderData * loader_data,const constantPoolHandle & cp,int names_count,const char ** names,int * lengths,int * cp_indices,unsigned int * hashValues)459 void SymbolTable::new_symbols(ClassLoaderData* loader_data, const constantPoolHandle& cp,
460 int names_count, const char** names, int* lengths,
461 int* cp_indices, unsigned int* hashValues) {
462 bool c_heap = !loader_data->is_the_null_class_loader_data();
463 for (int i = 0; i < names_count; i++) {
464 const char *name = names[i];
465 int len = lengths[i];
466 unsigned int hash = hashValues[i];
467 assert(lookup_shared(name, len, hash) == NULL, "must have checked already");
468 Symbol* sym = do_add_if_needed(name, len, hash, c_heap);
469 assert(sym->refcount() != 0, "lookup should have incremented the count");
470 cp->symbol_at_put(cp_indices[i], sym);
471 }
472 }
473
do_add_if_needed(const char * name,int len,uintx hash,bool heap)474 Symbol* SymbolTable::do_add_if_needed(const char* name, int len, uintx hash, bool heap) {
475 SymbolTableLookup lookup(name, len, hash);
476 SymbolTableGet stg;
477 bool clean_hint = false;
478 bool rehash_warning = false;
479 Symbol* sym = NULL;
480 Thread* THREAD = Thread::current();
481
482 do {
483 // Callers have looked up the symbol once, insert the symbol.
484 sym = allocate_symbol(name, len, heap);
485 if (_local_table->insert(THREAD, lookup, sym, &rehash_warning, &clean_hint)) {
486 break;
487 }
488 // In case another thread did a concurrent add, return value already in the table.
489 // This could fail if the symbol got deleted concurrently, so loop back until success.
490 if (_local_table->get(THREAD, lookup, stg, &rehash_warning)) {
491 sym = stg.get_res_sym();
492 break;
493 }
494 } while(true);
495
496 update_needs_rehash(rehash_warning);
497
498 if (clean_hint) {
499 mark_has_items_to_clean();
500 check_concurrent_work();
501 }
502
503 assert((sym == NULL) || sym->refcount() != 0, "found dead symbol");
504 return sym;
505 }
506
new_permanent_symbol(const char * name)507 Symbol* SymbolTable::new_permanent_symbol(const char* name) {
508 unsigned int hash = 0;
509 int len = (int)strlen(name);
510 Symbol* sym = SymbolTable::lookup_only(name, len, hash);
511 if (sym == NULL) {
512 sym = do_add_if_needed(name, len, hash, false);
513 }
514 if (!sym->is_permanent()) {
515 sym->make_permanent();
516 log_trace_symboltable_helper(sym, "Asked for a permanent symbol, but got a regular one");
517 }
518 return sym;
519 }
520
521 struct SizeFunc : StackObj {
operator ()SizeFunc522 size_t operator()(Symbol** value) {
523 assert(value != NULL, "expected valid value");
524 assert(*value != NULL, "value should point to a symbol");
525 return (*value)->size() * HeapWordSize;
526 };
527 };
528
get_table_statistics()529 TableStatistics SymbolTable::get_table_statistics() {
530 static TableStatistics ts;
531 SizeFunc sz;
532 ts = _local_table->statistics_get(Thread::current(), sz, ts);
533 return ts;
534 }
535
print_table_statistics(outputStream * st,const char * table_name)536 void SymbolTable::print_table_statistics(outputStream* st,
537 const char* table_name) {
538 SizeFunc sz;
539 _local_table->statistics_to(Thread::current(), sz, st, table_name);
540 }
541
542 // Verification
543 class VerifySymbols : StackObj {
544 public:
operator ()(Symbol ** value)545 bool operator()(Symbol** value) {
546 guarantee(value != NULL, "expected valid value");
547 guarantee(*value != NULL, "value should point to a symbol");
548 Symbol* sym = *value;
549 guarantee(sym->equals((const char*)sym->bytes(), sym->utf8_length()),
550 "symbol must be internally consistent");
551 return true;
552 };
553 };
554
verify()555 void SymbolTable::verify() {
556 Thread* thr = Thread::current();
557 VerifySymbols vs;
558 if (!_local_table->try_scan(thr, vs)) {
559 log_info(symboltable)("verify unavailable at this moment");
560 }
561 }
562
563 // Dumping
564 class DumpSymbol : StackObj {
565 Thread* _thr;
566 outputStream* _st;
567 public:
DumpSymbol(Thread * thr,outputStream * st)568 DumpSymbol(Thread* thr, outputStream* st) : _thr(thr), _st(st) {}
operator ()(Symbol ** value)569 bool operator()(Symbol** value) {
570 assert(value != NULL, "expected valid value");
571 assert(*value != NULL, "value should point to a symbol");
572 Symbol* sym = *value;
573 const char* utf8_string = (const char*)sym->bytes();
574 int utf8_length = sym->utf8_length();
575 _st->print("%d %d: ", utf8_length, sym->refcount());
576 HashtableTextDump::put_utf8(_st, utf8_string, utf8_length);
577 _st->cr();
578 return true;
579 };
580 };
581
dump(outputStream * st,bool verbose)582 void SymbolTable::dump(outputStream* st, bool verbose) {
583 if (!verbose) {
584 print_table_statistics(st, "SymbolTable");
585 } else {
586 Thread* thr = Thread::current();
587 ResourceMark rm(thr);
588 st->print_cr("VERSION: 1.1");
589 DumpSymbol ds(thr, st);
590 if (!_local_table->try_scan(thr, ds)) {
591 log_info(symboltable)("dump unavailable at this moment");
592 }
593 }
594 }
595
596 #if INCLUDE_CDS
597 struct CopyToArchive : StackObj {
598 CompactHashtableWriter* _writer;
CopyToArchiveCopyToArchive599 CopyToArchive(CompactHashtableWriter* writer) : _writer(writer) {}
operator ()CopyToArchive600 bool operator()(Symbol** value) {
601 assert(value != NULL, "expected valid value");
602 assert(*value != NULL, "value should point to a symbol");
603 Symbol* sym = *value;
604 unsigned int fixed_hash = hash_shared_symbol((const char*)sym->bytes(), sym->utf8_length());
605 assert(fixed_hash == hash_symbol((const char*)sym->bytes(), sym->utf8_length(), false),
606 "must not rehash during dumping");
607 if (DynamicDumpSharedSpaces) {
608 sym = DynamicArchive::original_to_target(sym);
609 }
610 _writer->add(fixed_hash, MetaspaceShared::object_delta_u4(sym));
611 return true;
612 }
613 };
614
copy_shared_symbol_table(CompactHashtableWriter * writer)615 void SymbolTable::copy_shared_symbol_table(CompactHashtableWriter* writer) {
616 CopyToArchive copy(writer);
617 _local_table->do_safepoint_scan(copy);
618 }
619
estimate_size_for_archive()620 size_t SymbolTable::estimate_size_for_archive() {
621 return CompactHashtableWriter::estimate_size(int(_items_count));
622 }
623
write_to_archive(bool is_static_archive)624 void SymbolTable::write_to_archive(bool is_static_archive) {
625 CompactHashtableWriter writer(int(_items_count),
626 &MetaspaceShared::stats()->symbol);
627 copy_shared_symbol_table(&writer);
628 if (is_static_archive) {
629 _shared_table.reset();
630 writer.dump(&_shared_table, "symbol");
631
632 // Verify table is correct
633 Symbol* sym = vmSymbols::java_lang_Object();
634 const char* name = (const char*)sym->bytes();
635 int len = sym->utf8_length();
636 unsigned int hash = hash_symbol(name, len, _alt_hash);
637 assert(sym == _shared_table.lookup(name, hash, len), "sanity");
638 } else {
639 _dynamic_shared_table.reset();
640 writer.dump(&_dynamic_shared_table, "symbol");
641 }
642 }
643
serialize_shared_table_header(SerializeClosure * soc,bool is_static_archive)644 void SymbolTable::serialize_shared_table_header(SerializeClosure* soc,
645 bool is_static_archive) {
646 OffsetCompactHashtable<const char*, Symbol*, symbol_equals_compact_hashtable_entry> * table;
647 if (is_static_archive) {
648 table = &_shared_table;
649 } else {
650 table = &_dynamic_shared_table;
651 }
652 table->serialize_header(soc);
653 if (soc->writing()) {
654 // Sanity. Make sure we don't use the shared table at dump time
655 table->reset();
656 }
657 }
658 #endif //INCLUDE_CDS
659
660 // Concurrent work
grow(JavaThread * jt)661 void SymbolTable::grow(JavaThread* jt) {
662 SymbolTableHash::GrowTask gt(_local_table);
663 if (!gt.prepare(jt)) {
664 return;
665 }
666 log_trace(symboltable)("Started to grow");
667 {
668 TraceTime timer("Grow", TRACETIME_LOG(Debug, symboltable, perf));
669 while (gt.do_task(jt)) {
670 gt.pause(jt);
671 {
672 ThreadBlockInVM tbivm(jt);
673 }
674 gt.cont(jt);
675 }
676 }
677 gt.done(jt);
678 _current_size = table_size();
679 log_debug(symboltable)("Grown to size:" SIZE_FORMAT, _current_size);
680 }
681
682 struct SymbolTableDoDelete : StackObj {
683 size_t _deleted;
SymbolTableDoDeleteSymbolTableDoDelete684 SymbolTableDoDelete() : _deleted(0) {}
operator ()SymbolTableDoDelete685 void operator()(Symbol** value) {
686 assert(value != NULL, "expected valid value");
687 assert(*value != NULL, "value should point to a symbol");
688 Symbol *sym = *value;
689 assert(sym->refcount() == 0, "refcount");
690 _deleted++;
691 }
692 };
693
694 struct SymbolTableDeleteCheck : StackObj {
695 size_t _processed;
SymbolTableDeleteCheckSymbolTableDeleteCheck696 SymbolTableDeleteCheck() : _processed(0) {}
operator ()SymbolTableDeleteCheck697 bool operator()(Symbol** value) {
698 assert(value != NULL, "expected valid value");
699 assert(*value != NULL, "value should point to a symbol");
700 _processed++;
701 Symbol *sym = *value;
702 return (sym->refcount() == 0);
703 }
704 };
705
clean_dead_entries(JavaThread * jt)706 void SymbolTable::clean_dead_entries(JavaThread* jt) {
707 SymbolTableHash::BulkDeleteTask bdt(_local_table);
708 if (!bdt.prepare(jt)) {
709 return;
710 }
711
712 SymbolTableDeleteCheck stdc;
713 SymbolTableDoDelete stdd;
714 {
715 TraceTime timer("Clean", TRACETIME_LOG(Debug, symboltable, perf));
716 while (bdt.do_task(jt, stdc, stdd)) {
717 bdt.pause(jt);
718 {
719 ThreadBlockInVM tbivm(jt);
720 }
721 bdt.cont(jt);
722 }
723 reset_has_items_to_clean();
724 bdt.done(jt);
725 }
726
727 Atomic::add(&_symbols_counted, stdc._processed);
728
729 log_debug(symboltable)("Cleaned " SIZE_FORMAT " of " SIZE_FORMAT,
730 stdd._deleted, stdc._processed);
731 }
732
check_concurrent_work()733 void SymbolTable::check_concurrent_work() {
734 if (_has_work) {
735 return;
736 }
737 // We should clean/resize if we have
738 // more items than preferred load factor or
739 // more dead items than water mark.
740 if (has_items_to_clean() || (get_load_factor() > PREF_AVG_LIST_LEN)) {
741 log_debug(symboltable)("Concurrent work triggered, load factor: %f, items to clean: %s",
742 get_load_factor(), has_items_to_clean() ? "true" : "false");
743 trigger_cleanup();
744 }
745 }
746
do_concurrent_work(JavaThread * jt)747 void SymbolTable::do_concurrent_work(JavaThread* jt) {
748 double load_factor = get_load_factor();
749 log_debug(symboltable, perf)("Concurrent work, live factor: %g", load_factor);
750 // We prefer growing, since that also removes dead items
751 if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {
752 grow(jt);
753 } else {
754 clean_dead_entries(jt);
755 }
756 _has_work = false;
757 }
758
759 // Rehash
do_rehash()760 bool SymbolTable::do_rehash() {
761 if (!_local_table->is_safepoint_safe()) {
762 return false;
763 }
764
765 // We use current size
766 size_t new_size = _local_table->get_size_log2(Thread::current());
767 SymbolTableHash* new_table = new SymbolTableHash(new_size, END_SIZE, REHASH_LEN);
768 // Use alt hash from now on
769 _alt_hash = true;
770 if (!_local_table->try_move_nodes_to(Thread::current(), new_table)) {
771 _alt_hash = false;
772 delete new_table;
773 return false;
774 }
775
776 // free old table
777 delete _local_table;
778 _local_table = new_table;
779
780 return true;
781 }
782
rehash_table()783 void SymbolTable::rehash_table() {
784 static bool rehashed = false;
785 log_debug(symboltable)("Table imbalanced, rehashing called.");
786
787 // Grow instead of rehash.
788 if (get_load_factor() > PREF_AVG_LIST_LEN &&
789 !_local_table->is_max_size_reached()) {
790 log_debug(symboltable)("Choosing growing over rehashing.");
791 trigger_cleanup();
792 _needs_rehashing = false;
793 return;
794 }
795
796 // Already rehashed.
797 if (rehashed) {
798 log_warning(symboltable)("Rehashing already done, still long lists.");
799 trigger_cleanup();
800 _needs_rehashing = false;
801 return;
802 }
803
804 murmur_seed = AltHashing::compute_seed();
805
806 if (do_rehash()) {
807 rehashed = true;
808 } else {
809 log_info(symboltable)("Resizes in progress rehashing skipped.");
810 }
811
812 _needs_rehashing = false;
813 }
814
815 //---------------------------------------------------------------------------
816 // Non-product code
817
818 #ifndef PRODUCT
819
820 class HistogramIterator : StackObj {
821 public:
822 static const size_t results_length = 100;
823 size_t counts[results_length];
824 size_t sizes[results_length];
825 size_t total_size;
826 size_t total_count;
827 size_t total_length;
828 size_t max_length;
829 size_t out_of_range_count;
830 size_t out_of_range_size;
HistogramIterator()831 HistogramIterator() : total_size(0), total_count(0), total_length(0),
832 max_length(0), out_of_range_count(0), out_of_range_size(0) {
833 // initialize results to zero
834 for (size_t i = 0; i < results_length; i++) {
835 counts[i] = 0;
836 sizes[i] = 0;
837 }
838 }
operator ()(Symbol ** value)839 bool operator()(Symbol** value) {
840 assert(value != NULL, "expected valid value");
841 assert(*value != NULL, "value should point to a symbol");
842 Symbol* sym = *value;
843 size_t size = sym->size();
844 size_t len = sym->utf8_length();
845 if (len < results_length) {
846 counts[len]++;
847 sizes[len] += size;
848 } else {
849 out_of_range_count++;
850 out_of_range_size += size;
851 }
852 total_count++;
853 total_size += size;
854 total_length += len;
855 max_length = MAX2(max_length, len);
856
857 return true;
858 };
859 };
860
print_histogram()861 void SymbolTable::print_histogram() {
862 HistogramIterator hi;
863 _local_table->do_scan(Thread::current(), hi);
864 tty->print_cr("Symbol Table Histogram:");
865 tty->print_cr(" Total number of symbols " SIZE_FORMAT_W(7), hi.total_count);
866 tty->print_cr(" Total size in memory " SIZE_FORMAT_W(7) "K",
867 (hi.total_size * wordSize) / 1024);
868 tty->print_cr(" Total counted " SIZE_FORMAT_W(7), _symbols_counted);
869 tty->print_cr(" Total removed " SIZE_FORMAT_W(7), _symbols_removed);
870 if (_symbols_counted > 0) {
871 tty->print_cr(" Percent removed %3.2f",
872 ((float)_symbols_removed / _symbols_counted) * 100);
873 }
874 tty->print_cr(" Reference counts " SIZE_FORMAT_W(7), Symbol::_total_count);
875 tty->print_cr(" Symbol arena used " SIZE_FORMAT_W(7) "K", arena()->used() / 1024);
876 tty->print_cr(" Symbol arena size " SIZE_FORMAT_W(7) "K", arena()->size_in_bytes() / 1024);
877 tty->print_cr(" Total symbol length " SIZE_FORMAT_W(7), hi.total_length);
878 tty->print_cr(" Maximum symbol length " SIZE_FORMAT_W(7), hi.max_length);
879 tty->print_cr(" Average symbol length %7.2f", ((float)hi.total_length / hi.total_count));
880 tty->print_cr(" Symbol length histogram:");
881 tty->print_cr(" %6s %10s %10s", "Length", "#Symbols", "Size");
882 for (size_t i = 0; i < hi.results_length; i++) {
883 if (hi.counts[i] > 0) {
884 tty->print_cr(" " SIZE_FORMAT_W(6) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) "K",
885 i, hi.counts[i], (hi.sizes[i] * wordSize) / 1024);
886 }
887 }
888 tty->print_cr(" >=" SIZE_FORMAT_W(6) " " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) "K\n",
889 hi.results_length, hi.out_of_range_count, (hi.out_of_range_size*wordSize) / 1024);
890 }
891 #endif // PRODUCT
892
893 // Utility for dumping symbols
SymboltableDCmd(outputStream * output,bool heap)894 SymboltableDCmd::SymboltableDCmd(outputStream* output, bool heap) :
895 DCmdWithParser(output, heap),
896 _verbose("-verbose", "Dump the content of each symbol in the table",
897 "BOOLEAN", false, "false") {
898 _dcmdparser.add_dcmd_option(&_verbose);
899 }
900
execute(DCmdSource source,TRAPS)901 void SymboltableDCmd::execute(DCmdSource source, TRAPS) {
902 VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpSymbols,
903 _verbose.value());
904 VMThread::execute(&dumper);
905 }
906
num_arguments()907 int SymboltableDCmd::num_arguments() {
908 ResourceMark rm;
909 SymboltableDCmd* dcmd = new SymboltableDCmd(NULL, false);
910 if (dcmd != NULL) {
911 DCmdMark mark(dcmd);
912 return dcmd->_dcmdparser.num_arguments();
913 } else {
914 return 0;
915 }
916 }
917