1 /* 2 * Copyright (c) 2001, 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/javaClasses.inline.hpp" 27 #include "classfile/systemDictionary.hpp" 28 #include "gc/shared/collectedHeap.hpp" 29 #include "gc/shared/collectedHeap.inline.hpp" 30 #include "gc/shared/gcTimer.hpp" 31 #include "gc/shared/gcTraceTime.inline.hpp" 32 #include "gc/shared/referencePolicy.hpp" 33 #include "gc/shared/referenceProcessor.inline.hpp" 34 #include "logging/log.hpp" 35 #include "memory/allocation.hpp" 36 #include "memory/resourceArea.hpp" 37 #include "oops/oop.inline.hpp" 38 #include "runtime/java.hpp" 39 #include "runtime/jniHandles.hpp" 40 41 ReferencePolicy* ReferenceProcessor::_always_clear_soft_ref_policy = NULL; 42 ReferencePolicy* ReferenceProcessor::_default_soft_ref_policy = NULL; 43 jlong ReferenceProcessor::_soft_ref_timestamp_clock = 0; 44 45 void referenceProcessor_init() { 46 ReferenceProcessor::init_statics(); 47 } 48 49 void ReferenceProcessor::init_statics() { 50 // We need a monotonically non-decreasing time in ms but 51 // os::javaTimeMillis() does not guarantee monotonicity. 52 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 53 54 // Initialize the soft ref timestamp clock. 55 _soft_ref_timestamp_clock = now; 56 // Also update the soft ref clock in j.l.r.SoftReference 57 java_lang_ref_SoftReference::set_clock(_soft_ref_timestamp_clock); 58 59 _always_clear_soft_ref_policy = new AlwaysClearPolicy(); 60 if (is_server_compilation_mode_vm()) { 61 _default_soft_ref_policy = new LRUMaxHeapPolicy(); 62 } else { 63 _default_soft_ref_policy = new LRUCurrentHeapPolicy(); 64 } 65 if (_always_clear_soft_ref_policy == NULL || _default_soft_ref_policy == NULL) { 66 vm_exit_during_initialization("Could not allocate reference policy object"); 67 } 68 guarantee(RefDiscoveryPolicy == ReferenceBasedDiscovery || 69 RefDiscoveryPolicy == ReferentBasedDiscovery, 70 "Unrecognized RefDiscoveryPolicy"); 71 } 72 73 void ReferenceProcessor::enable_discovery(bool check_no_refs) { 74 #ifdef ASSERT 75 // Verify that we're not currently discovering refs 76 assert(!_discovering_refs, "nested call?"); 77 78 if (check_no_refs) { 79 // Verify that the discovered lists are empty 80 verify_no_references_recorded(); 81 } 82 #endif // ASSERT 83 84 // Someone could have modified the value of the static 85 // field in the j.l.r.SoftReference class that holds the 86 // soft reference timestamp clock using reflection or 87 // Unsafe between GCs. Unconditionally update the static 88 // field in ReferenceProcessor here so that we use the new 89 // value during reference discovery. 90 91 _soft_ref_timestamp_clock = java_lang_ref_SoftReference::clock(); 92 _discovering_refs = true; 93 } 94 95 ReferenceProcessor::ReferenceProcessor(MemRegion span, 96 bool mt_processing, 97 uint mt_processing_degree, 98 bool mt_discovery, 99 uint mt_discovery_degree, 100 bool atomic_discovery, 101 BoolObjectClosure* is_alive_non_header) : 102 _discovering_refs(false), 103 _enqueuing_is_done(false), 104 _is_alive_non_header(is_alive_non_header), 105 _processing_is_mt(mt_processing), 106 _next_id(0) 107 { 108 _span = span; 109 _discovery_is_atomic = atomic_discovery; 110 _discovery_is_mt = mt_discovery; 111 _num_q = MAX2(1U, mt_processing_degree); 112 _max_num_q = MAX2(_num_q, mt_discovery_degree); 113 _discovered_refs = NEW_C_HEAP_ARRAY(DiscoveredList, 114 _max_num_q * number_of_subclasses_of_ref(), mtGC); 115 116 if (_discovered_refs == NULL) { 117 vm_exit_during_initialization("Could not allocated RefProc Array"); 118 } 119 _discoveredSoftRefs = &_discovered_refs[0]; 120 _discoveredWeakRefs = &_discoveredSoftRefs[_max_num_q]; 121 _discoveredFinalRefs = &_discoveredWeakRefs[_max_num_q]; 122 _discoveredPhantomRefs = &_discoveredFinalRefs[_max_num_q]; 123 124 // Initialize all entries to NULL 125 for (uint i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { 126 _discovered_refs[i].set_head(NULL); 127 _discovered_refs[i].set_length(0); 128 } 129 130 setup_policy(false /* default soft ref policy */); 131 } 132 133 #ifndef PRODUCT 134 void ReferenceProcessor::verify_no_references_recorded() { 135 guarantee(!_discovering_refs, "Discovering refs?"); 136 for (uint i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { 137 guarantee(_discovered_refs[i].is_empty(), 138 "Found non-empty discovered list at %u", i); 139 } 140 } 141 #endif 142 143 void ReferenceProcessor::weak_oops_do(OopClosure* f) { 144 for (uint i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { 145 if (UseCompressedOops) { 146 f->do_oop((narrowOop*)_discovered_refs[i].adr_head()); 147 } else { 148 f->do_oop((oop*)_discovered_refs[i].adr_head()); 149 } 150 } 151 } 152 153 void ReferenceProcessor::update_soft_ref_master_clock() { 154 // Update (advance) the soft ref master clock field. This must be done 155 // after processing the soft ref list. 156 157 // We need a monotonically non-decreasing time in ms but 158 // os::javaTimeMillis() does not guarantee monotonicity. 159 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 160 jlong soft_ref_clock = java_lang_ref_SoftReference::clock(); 161 assert(soft_ref_clock == _soft_ref_timestamp_clock, "soft ref clocks out of sync"); 162 163 NOT_PRODUCT( 164 if (now < _soft_ref_timestamp_clock) { 165 log_warning(gc)("time warp: " JLONG_FORMAT " to " JLONG_FORMAT, 166 _soft_ref_timestamp_clock, now); 167 } 168 ) 169 // The values of now and _soft_ref_timestamp_clock are set using 170 // javaTimeNanos(), which is guaranteed to be monotonically 171 // non-decreasing provided the underlying platform provides such 172 // a time source (and it is bug free). 173 // In product mode, however, protect ourselves from non-monotonicity. 174 if (now > _soft_ref_timestamp_clock) { 175 _soft_ref_timestamp_clock = now; 176 java_lang_ref_SoftReference::set_clock(now); 177 } 178 // Else leave clock stalled at its old value until time progresses 179 // past clock value. 180 } 181 182 size_t ReferenceProcessor::total_count(DiscoveredList lists[]) { 183 size_t total = 0; 184 for (uint i = 0; i < _max_num_q; ++i) { 185 total += lists[i].length(); 186 } 187 return total; 188 } 189 190 ReferenceProcessorStats ReferenceProcessor::process_discovered_references( 191 BoolObjectClosure* is_alive, 192 OopClosure* keep_alive, 193 VoidClosure* complete_gc, 194 AbstractRefProcTaskExecutor* task_executor, 195 GCTimer* gc_timer) { 196 197 assert(!enqueuing_is_done(), "If here enqueuing should not be complete"); 198 // Stop treating discovered references specially. 199 disable_discovery(); 200 201 // If discovery was concurrent, someone could have modified 202 // the value of the static field in the j.l.r.SoftReference 203 // class that holds the soft reference timestamp clock using 204 // reflection or Unsafe between when discovery was enabled and 205 // now. Unconditionally update the static field in ReferenceProcessor 206 // here so that we use the new value during processing of the 207 // discovered soft refs. 208 209 _soft_ref_timestamp_clock = java_lang_ref_SoftReference::clock(); 210 211 ReferenceProcessorStats stats( 212 total_count(_discoveredSoftRefs), 213 total_count(_discoveredWeakRefs), 214 total_count(_discoveredFinalRefs), 215 total_count(_discoveredPhantomRefs)); 216 217 // Soft references 218 { 219 GCTraceTime(Debug, gc, ref) tt("SoftReference", gc_timer); 220 process_discovered_reflist(_discoveredSoftRefs, _current_soft_ref_policy, true, 221 is_alive, keep_alive, complete_gc, task_executor); 222 } 223 224 update_soft_ref_master_clock(); 225 226 // Weak references 227 { 228 GCTraceTime(Debug, gc, ref) tt("WeakReference", gc_timer); 229 process_discovered_reflist(_discoveredWeakRefs, NULL, true, 230 is_alive, keep_alive, complete_gc, task_executor); 231 } 232 233 // Final references 234 { 235 GCTraceTime(Debug, gc, ref) tt("FinalReference", gc_timer); 236 process_discovered_reflist(_discoveredFinalRefs, NULL, false, 237 is_alive, keep_alive, complete_gc, task_executor); 238 } 239 240 // Phantom references 241 { 242 GCTraceTime(Debug, gc, ref) tt("PhantomReference", gc_timer); 243 process_discovered_reflist(_discoveredPhantomRefs, NULL, true, 244 is_alive, keep_alive, complete_gc, task_executor); 245 } 246 247 // Weak global JNI references. It would make more sense (semantically) to 248 // traverse these simultaneously with the regular weak references above, but 249 // that is not how the JDK1.2 specification is. See #4126360. Native code can 250 // thus use JNI weak references to circumvent the phantom references and 251 // resurrect a "post-mortem" object. 252 { 253 GCTraceTime(Debug, gc, ref) tt("JNI Weak Reference", gc_timer); 254 if (task_executor != NULL) { 255 task_executor->set_single_threaded_mode(); 256 } 257 process_phaseJNI(is_alive, keep_alive, complete_gc); 258 } 259 260 log_debug(gc, ref)("Ref Counts: Soft: " SIZE_FORMAT " Weak: " SIZE_FORMAT " Final: " SIZE_FORMAT " Phantom: " SIZE_FORMAT, 261 stats.soft_count(), stats.weak_count(), stats.final_count(), stats.phantom_count()); 262 log_develop_trace(gc, ref)("JNI Weak Reference count: " SIZE_FORMAT, count_jni_refs()); 263 264 return stats; 265 } 266 267 #ifndef PRODUCT 268 // Calculate the number of jni handles. 269 size_t ReferenceProcessor::count_jni_refs() { 270 class CountHandleClosure: public OopClosure { 271 private: 272 size_t _count; 273 public: 274 CountHandleClosure(): _count(0) {} 275 void do_oop(oop* unused) { _count++; } 276 void do_oop(narrowOop* unused) { ShouldNotReachHere(); } 277 size_t count() { return _count; } 278 }; 279 CountHandleClosure global_handle_count; 280 JNIHandles::weak_oops_do(&global_handle_count); 281 return global_handle_count.count(); 282 } 283 #endif 284 285 void ReferenceProcessor::process_phaseJNI(BoolObjectClosure* is_alive, 286 OopClosure* keep_alive, 287 VoidClosure* complete_gc) { 288 JNIHandles::weak_oops_do(is_alive, keep_alive); 289 complete_gc->do_void(); 290 } 291 292 void ReferenceProcessor::enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor) { 293 // Enqueue references that are not made active again, and 294 // clear the decks for the next collection (cycle). 295 enqueue_discovered_reflists(task_executor); 296 297 // Stop treating discovered references specially. 298 disable_discovery(); 299 } 300 301 void ReferenceProcessor::enqueue_discovered_reflist(DiscoveredList& refs_list) { 302 // Given a list of refs linked through the "discovered" field 303 // (java.lang.ref.Reference.discovered), self-loop their "next" field 304 // thus distinguishing them from active References, then 305 // prepend them to the pending list. 306 // 307 // The Java threads will see the Reference objects linked together through 308 // the discovered field. Instead of trying to do the write barrier updates 309 // in all places in the reference processor where we manipulate the discovered 310 // field we make sure to do the barrier here where we anyway iterate through 311 // all linked Reference objects. Note that it is important to not dirty any 312 // cards during reference processing since this will cause card table 313 // verification to fail for G1. 314 log_develop_trace(gc, ref)("ReferenceProcessor::enqueue_discovered_reflist list " INTPTR_FORMAT, p2i(&refs_list)); 315 316 oop obj = NULL; 317 oop next_d = refs_list.head(); 318 // Walk down the list, self-looping the next field 319 // so that the References are not considered active. 320 while (obj != next_d) { 321 obj = next_d; 322 assert(obj->is_instance(), "should be an instance object"); 323 assert(InstanceKlass::cast(obj->klass())->is_reference_instance_klass(), "should be reference object"); 324 next_d = java_lang_ref_Reference::discovered(obj); 325 log_develop_trace(gc, ref)(" obj " INTPTR_FORMAT "/next_d " INTPTR_FORMAT, p2i(obj), p2i(next_d)); 326 assert(java_lang_ref_Reference::next(obj) == NULL, 327 "Reference not active; should not be discovered"); 328 // Self-loop next, so as to make Ref not active. 329 java_lang_ref_Reference::set_next_raw(obj, obj); 330 if (next_d != obj) { 331 oopDesc::bs()->write_ref_field(java_lang_ref_Reference::discovered_addr(obj), next_d); 332 } else { 333 // This is the last object. 334 // Swap refs_list into pending list and set obj's 335 // discovered to what we read from the pending list. 336 oop old = Universe::swap_reference_pending_list(refs_list.head()); 337 java_lang_ref_Reference::set_discovered_raw(obj, old); // old may be NULL 338 oopDesc::bs()->write_ref_field(java_lang_ref_Reference::discovered_addr(obj), old); 339 } 340 } 341 } 342 343 // Parallel enqueue task 344 class RefProcEnqueueTask: public AbstractRefProcTaskExecutor::EnqueueTask { 345 public: 346 RefProcEnqueueTask(ReferenceProcessor& ref_processor, 347 DiscoveredList discovered_refs[], 348 int n_queues) 349 : EnqueueTask(ref_processor, discovered_refs, n_queues) 350 { } 351 352 virtual void work(unsigned int work_id) { 353 assert(work_id < (unsigned int)_ref_processor.max_num_q(), "Index out-of-bounds"); 354 // Simplest first cut: static partitioning. 355 int index = work_id; 356 // The increment on "index" must correspond to the maximum number of queues 357 // (n_queues) with which that ReferenceProcessor was created. That 358 // is because of the "clever" way the discovered references lists were 359 // allocated and are indexed into. 360 assert(_n_queues == (int) _ref_processor.max_num_q(), "Different number not expected"); 361 for (int j = 0; 362 j < ReferenceProcessor::number_of_subclasses_of_ref(); 363 j++, index += _n_queues) { 364 _ref_processor.enqueue_discovered_reflist(_refs_lists[index]); 365 _refs_lists[index].set_head(NULL); 366 _refs_lists[index].set_length(0); 367 } 368 } 369 }; 370 371 // Enqueue references that are not made active again 372 void ReferenceProcessor::enqueue_discovered_reflists(AbstractRefProcTaskExecutor* task_executor) { 373 if (_processing_is_mt && task_executor != NULL) { 374 // Parallel code 375 RefProcEnqueueTask tsk(*this, _discovered_refs, _max_num_q); 376 task_executor->execute(tsk); 377 } else { 378 // Serial code: call the parent class's implementation 379 for (uint i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { 380 enqueue_discovered_reflist(_discovered_refs[i]); 381 _discovered_refs[i].set_head(NULL); 382 _discovered_refs[i].set_length(0); 383 } 384 } 385 } 386 387 void DiscoveredListIterator::load_ptrs(DEBUG_ONLY(bool allow_null_referent)) { 388 _discovered_addr = java_lang_ref_Reference::discovered_addr(_ref); 389 oop discovered = java_lang_ref_Reference::discovered(_ref); 390 assert(_discovered_addr && discovered->is_oop_or_null(), 391 "Expected an oop or NULL for discovered field at " PTR_FORMAT, p2i(discovered)); 392 _next = discovered; 393 _referent_addr = java_lang_ref_Reference::referent_addr(_ref); 394 _referent = java_lang_ref_Reference::referent(_ref); 395 assert(Universe::heap()->is_in_reserved_or_null(_referent), 396 "Wrong oop found in java.lang.Reference object"); 397 assert(allow_null_referent ? 398 _referent->is_oop_or_null() 399 : _referent->is_oop(), 400 "Expected an oop%s for referent field at " PTR_FORMAT, 401 (allow_null_referent ? " or NULL" : ""), 402 p2i(_referent)); 403 } 404 405 void DiscoveredListIterator::remove() { 406 assert(_ref->is_oop(), "Dropping a bad reference"); 407 oop_store_raw(_discovered_addr, NULL); 408 409 // First _prev_next ref actually points into DiscoveredList (gross). 410 oop new_next; 411 if (_next == _ref) { 412 // At the end of the list, we should make _prev point to itself. 413 // If _ref is the first ref, then _prev_next will be in the DiscoveredList, 414 // and _prev will be NULL. 415 new_next = _prev; 416 } else { 417 new_next = _next; 418 } 419 // Remove Reference object from discovered list. Note that G1 does not need a 420 // pre-barrier here because we know the Reference has already been found/marked, 421 // that's how it ended up in the discovered list in the first place. 422 oop_store_raw(_prev_next, new_next); 423 NOT_PRODUCT(_removed++); 424 _refs_list.dec_length(1); 425 } 426 427 void DiscoveredListIterator::clear_referent() { 428 oop_store_raw(_referent_addr, NULL); 429 } 430 431 // NOTE: process_phase*() are largely similar, and at a high level 432 // merely iterate over the extant list applying a predicate to 433 // each of its elements and possibly removing that element from the 434 // list and applying some further closures to that element. 435 // We should consider the possibility of replacing these 436 // process_phase*() methods by abstracting them into 437 // a single general iterator invocation that receives appropriate 438 // closures that accomplish this work. 439 440 // (SoftReferences only) Traverse the list and remove any SoftReferences whose 441 // referents are not alive, but that should be kept alive for policy reasons. 442 // Keep alive the transitive closure of all such referents. 443 void 444 ReferenceProcessor::process_phase1(DiscoveredList& refs_list, 445 ReferencePolicy* policy, 446 BoolObjectClosure* is_alive, 447 OopClosure* keep_alive, 448 VoidClosure* complete_gc) { 449 assert(policy != NULL, "Must have a non-NULL policy"); 450 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); 451 // Decide which softly reachable refs should be kept alive. 452 while (iter.has_next()) { 453 iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */)); 454 bool referent_is_dead = (iter.referent() != NULL) && !iter.is_referent_alive(); 455 if (referent_is_dead && 456 !policy->should_clear_reference(iter.obj(), _soft_ref_timestamp_clock)) { 457 log_develop_trace(gc, ref)("Dropping reference (" INTPTR_FORMAT ": %s" ") by policy", 458 p2i(iter.obj()), iter.obj()->klass()->internal_name()); 459 // Remove Reference object from list 460 iter.remove(); 461 // keep the referent around 462 iter.make_referent_alive(); 463 iter.move_to_next(); 464 } else { 465 iter.next(); 466 } 467 } 468 // Close the reachable set 469 complete_gc->do_void(); 470 log_develop_trace(gc, ref)(" Dropped " SIZE_FORMAT " dead Refs out of " SIZE_FORMAT " discovered Refs by policy, from list " INTPTR_FORMAT, 471 iter.removed(), iter.processed(), p2i(&refs_list)); 472 } 473 474 // Traverse the list and remove any Refs that are not active, or 475 // whose referents are either alive or NULL. 476 void 477 ReferenceProcessor::pp2_work(DiscoveredList& refs_list, 478 BoolObjectClosure* is_alive, 479 OopClosure* keep_alive) { 480 assert(discovery_is_atomic(), "Error"); 481 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); 482 while (iter.has_next()) { 483 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); 484 DEBUG_ONLY(oop next = java_lang_ref_Reference::next(iter.obj());) 485 assert(next == NULL, "Should not discover inactive Reference"); 486 if (iter.is_referent_alive()) { 487 log_develop_trace(gc, ref)("Dropping strongly reachable reference (" INTPTR_FORMAT ": %s)", 488 p2i(iter.obj()), iter.obj()->klass()->internal_name()); 489 // The referent is reachable after all. 490 // Remove Reference object from list. 491 iter.remove(); 492 // Update the referent pointer as necessary: Note that this 493 // should not entail any recursive marking because the 494 // referent must already have been traversed. 495 iter.make_referent_alive(); 496 iter.move_to_next(); 497 } else { 498 iter.next(); 499 } 500 } 501 NOT_PRODUCT( 502 if (iter.processed() > 0) { 503 log_develop_trace(gc, ref)(" Dropped " SIZE_FORMAT " active Refs out of " SIZE_FORMAT 504 " Refs in discovered list " INTPTR_FORMAT, 505 iter.removed(), iter.processed(), p2i(&refs_list)); 506 } 507 ) 508 } 509 510 void 511 ReferenceProcessor::pp2_work_concurrent_discovery(DiscoveredList& refs_list, 512 BoolObjectClosure* is_alive, 513 OopClosure* keep_alive, 514 VoidClosure* complete_gc) { 515 assert(!discovery_is_atomic(), "Error"); 516 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); 517 while (iter.has_next()) { 518 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); 519 HeapWord* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); 520 oop next = java_lang_ref_Reference::next(iter.obj()); 521 if ((iter.referent() == NULL || iter.is_referent_alive() || 522 next != NULL)) { 523 assert(next->is_oop_or_null(), "Expected an oop or NULL for next field at " PTR_FORMAT, p2i(next)); 524 // Remove Reference object from list 525 iter.remove(); 526 // Trace the cohorts 527 iter.make_referent_alive(); 528 if (UseCompressedOops) { 529 keep_alive->do_oop((narrowOop*)next_addr); 530 } else { 531 keep_alive->do_oop((oop*)next_addr); 532 } 533 iter.move_to_next(); 534 } else { 535 iter.next(); 536 } 537 } 538 // Now close the newly reachable set 539 complete_gc->do_void(); 540 NOT_PRODUCT( 541 if (iter.processed() > 0) { 542 log_develop_trace(gc, ref)(" Dropped " SIZE_FORMAT " active Refs out of " SIZE_FORMAT 543 " Refs in discovered list " INTPTR_FORMAT, 544 iter.removed(), iter.processed(), p2i(&refs_list)); 545 } 546 ) 547 } 548 549 // Traverse the list and process the referents, by either 550 // clearing them or keeping them (and their reachable 551 // closure) alive. 552 void 553 ReferenceProcessor::process_phase3(DiscoveredList& refs_list, 554 bool clear_referent, 555 BoolObjectClosure* is_alive, 556 OopClosure* keep_alive, 557 VoidClosure* complete_gc) { 558 ResourceMark rm; 559 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); 560 while (iter.has_next()) { 561 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); 562 if (clear_referent) { 563 // NULL out referent pointer 564 iter.clear_referent(); 565 } else { 566 // keep the referent around 567 iter.make_referent_alive(); 568 } 569 log_develop_trace(gc, ref)("Adding %sreference (" INTPTR_FORMAT ": %s) as pending", 570 clear_referent ? "cleared " : "", p2i(iter.obj()), iter.obj()->klass()->internal_name()); 571 assert(iter.obj()->is_oop(UseConcMarkSweepGC), "Adding a bad reference"); 572 iter.next(); 573 } 574 // Close the reachable set 575 complete_gc->do_void(); 576 } 577 578 void 579 ReferenceProcessor::clear_discovered_references(DiscoveredList& refs_list) { 580 oop obj = NULL; 581 oop next = refs_list.head(); 582 while (next != obj) { 583 obj = next; 584 next = java_lang_ref_Reference::discovered(obj); 585 java_lang_ref_Reference::set_discovered_raw(obj, NULL); 586 } 587 refs_list.set_head(NULL); 588 refs_list.set_length(0); 589 } 590 591 void ReferenceProcessor::abandon_partial_discovery() { 592 // loop over the lists 593 for (uint i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { 594 if ((i % _max_num_q) == 0) { 595 log_develop_trace(gc, ref)("Abandoning %s discovered list", list_name(i)); 596 } 597 clear_discovered_references(_discovered_refs[i]); 598 } 599 } 600 601 class RefProcPhase1Task: public AbstractRefProcTaskExecutor::ProcessTask { 602 public: 603 RefProcPhase1Task(ReferenceProcessor& ref_processor, 604 DiscoveredList refs_lists[], 605 ReferencePolicy* policy, 606 bool marks_oops_alive) 607 : ProcessTask(ref_processor, refs_lists, marks_oops_alive), 608 _policy(policy) 609 { } 610 virtual void work(unsigned int i, BoolObjectClosure& is_alive, 611 OopClosure& keep_alive, 612 VoidClosure& complete_gc) 613 { 614 _ref_processor.process_phase1(_refs_lists[i], _policy, 615 &is_alive, &keep_alive, &complete_gc); 616 } 617 private: 618 ReferencePolicy* _policy; 619 }; 620 621 class RefProcPhase2Task: public AbstractRefProcTaskExecutor::ProcessTask { 622 public: 623 RefProcPhase2Task(ReferenceProcessor& ref_processor, 624 DiscoveredList refs_lists[], 625 bool marks_oops_alive) 626 : ProcessTask(ref_processor, refs_lists, marks_oops_alive) 627 { } 628 virtual void work(unsigned int i, BoolObjectClosure& is_alive, 629 OopClosure& keep_alive, 630 VoidClosure& complete_gc) 631 { 632 _ref_processor.process_phase2(_refs_lists[i], 633 &is_alive, &keep_alive, &complete_gc); 634 } 635 }; 636 637 class RefProcPhase3Task: public AbstractRefProcTaskExecutor::ProcessTask { 638 public: 639 RefProcPhase3Task(ReferenceProcessor& ref_processor, 640 DiscoveredList refs_lists[], 641 bool clear_referent, 642 bool marks_oops_alive) 643 : ProcessTask(ref_processor, refs_lists, marks_oops_alive), 644 _clear_referent(clear_referent) 645 { } 646 virtual void work(unsigned int i, BoolObjectClosure& is_alive, 647 OopClosure& keep_alive, 648 VoidClosure& complete_gc) 649 { 650 _ref_processor.process_phase3(_refs_lists[i], _clear_referent, 651 &is_alive, &keep_alive, &complete_gc); 652 } 653 private: 654 bool _clear_referent; 655 }; 656 657 #ifndef PRODUCT 658 void ReferenceProcessor::log_reflist_counts(DiscoveredList ref_lists[], uint active_length, size_t total_refs) { 659 if (!log_is_enabled(Trace, gc, ref)) { 660 return; 661 } 662 663 stringStream st; 664 for (uint i = 0; i < active_length; ++i) { 665 st.print(SIZE_FORMAT " ", ref_lists[i].length()); 666 } 667 log_develop_trace(gc, ref)("%s= " SIZE_FORMAT, st.as_string(), total_refs); 668 #ifdef ASSERT 669 for (uint i = active_length; i < _max_num_q; i++) { 670 assert(ref_lists[i].length() == 0, SIZE_FORMAT " unexpected References in %u", 671 ref_lists[i].length(), i); 672 } 673 #endif 674 } 675 #endif 676 677 void ReferenceProcessor::set_active_mt_degree(uint v) { 678 _num_q = v; 679 _next_id = 0; 680 } 681 682 // Balances reference queues. 683 // Move entries from all queues[0, 1, ..., _max_num_q-1] to 684 // queues[0, 1, ..., _num_q-1] because only the first _num_q 685 // corresponding to the active workers will be processed. 686 void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[]) 687 { 688 // calculate total length 689 size_t total_refs = 0; 690 log_develop_trace(gc, ref)("Balance ref_lists "); 691 692 for (uint i = 0; i < _max_num_q; ++i) { 693 total_refs += ref_lists[i].length(); 694 } 695 log_reflist_counts(ref_lists, _max_num_q, total_refs); 696 size_t avg_refs = total_refs / _num_q + 1; 697 uint to_idx = 0; 698 for (uint from_idx = 0; from_idx < _max_num_q; from_idx++) { 699 bool move_all = false; 700 if (from_idx >= _num_q) { 701 move_all = ref_lists[from_idx].length() > 0; 702 } 703 while ((ref_lists[from_idx].length() > avg_refs) || 704 move_all) { 705 assert(to_idx < _num_q, "Sanity Check!"); 706 if (ref_lists[to_idx].length() < avg_refs) { 707 // move superfluous refs 708 size_t refs_to_move; 709 // Move all the Ref's if the from queue will not be processed. 710 if (move_all) { 711 refs_to_move = MIN2(ref_lists[from_idx].length(), 712 avg_refs - ref_lists[to_idx].length()); 713 } else { 714 refs_to_move = MIN2(ref_lists[from_idx].length() - avg_refs, 715 avg_refs - ref_lists[to_idx].length()); 716 } 717 718 assert(refs_to_move > 0, "otherwise the code below will fail"); 719 720 oop move_head = ref_lists[from_idx].head(); 721 oop move_tail = move_head; 722 oop new_head = move_head; 723 // find an element to split the list on 724 for (size_t j = 0; j < refs_to_move; ++j) { 725 move_tail = new_head; 726 new_head = java_lang_ref_Reference::discovered(new_head); 727 } 728 729 // Add the chain to the to list. 730 if (ref_lists[to_idx].head() == NULL) { 731 // to list is empty. Make a loop at the end. 732 java_lang_ref_Reference::set_discovered_raw(move_tail, move_tail); 733 } else { 734 java_lang_ref_Reference::set_discovered_raw(move_tail, ref_lists[to_idx].head()); 735 } 736 ref_lists[to_idx].set_head(move_head); 737 ref_lists[to_idx].inc_length(refs_to_move); 738 739 // Remove the chain from the from list. 740 if (move_tail == new_head) { 741 // We found the end of the from list. 742 ref_lists[from_idx].set_head(NULL); 743 } else { 744 ref_lists[from_idx].set_head(new_head); 745 } 746 ref_lists[from_idx].dec_length(refs_to_move); 747 if (ref_lists[from_idx].length() == 0) { 748 break; 749 } 750 } else { 751 to_idx = (to_idx + 1) % _num_q; 752 } 753 } 754 } 755 #ifdef ASSERT 756 size_t balanced_total_refs = 0; 757 for (uint i = 0; i < _num_q; ++i) { 758 balanced_total_refs += ref_lists[i].length(); 759 } 760 log_reflist_counts(ref_lists, _num_q, balanced_total_refs); 761 assert(total_refs == balanced_total_refs, "Balancing was incomplete"); 762 #endif 763 } 764 765 void ReferenceProcessor::balance_all_queues() { 766 balance_queues(_discoveredSoftRefs); 767 balance_queues(_discoveredWeakRefs); 768 balance_queues(_discoveredFinalRefs); 769 balance_queues(_discoveredPhantomRefs); 770 } 771 772 void ReferenceProcessor::process_discovered_reflist( 773 DiscoveredList refs_lists[], 774 ReferencePolicy* policy, 775 bool clear_referent, 776 BoolObjectClosure* is_alive, 777 OopClosure* keep_alive, 778 VoidClosure* complete_gc, 779 AbstractRefProcTaskExecutor* task_executor) 780 { 781 bool mt_processing = task_executor != NULL && _processing_is_mt; 782 // If discovery used MT and a dynamic number of GC threads, then 783 // the queues must be balanced for correctness if fewer than the 784 // maximum number of queues were used. The number of queue used 785 // during discovery may be different than the number to be used 786 // for processing so don't depend of _num_q < _max_num_q as part 787 // of the test. 788 bool must_balance = _discovery_is_mt; 789 790 if ((mt_processing && ParallelRefProcBalancingEnabled) || 791 must_balance) { 792 balance_queues(refs_lists); 793 } 794 795 // Phase 1 (soft refs only): 796 // . Traverse the list and remove any SoftReferences whose 797 // referents are not alive, but that should be kept alive for 798 // policy reasons. Keep alive the transitive closure of all 799 // such referents. 800 if (policy != NULL) { 801 if (mt_processing) { 802 RefProcPhase1Task phase1(*this, refs_lists, policy, true /*marks_oops_alive*/); 803 task_executor->execute(phase1); 804 } else { 805 for (uint i = 0; i < _max_num_q; i++) { 806 process_phase1(refs_lists[i], policy, 807 is_alive, keep_alive, complete_gc); 808 } 809 } 810 } else { // policy == NULL 811 assert(refs_lists != _discoveredSoftRefs, 812 "Policy must be specified for soft references."); 813 } 814 815 // Phase 2: 816 // . Traverse the list and remove any refs whose referents are alive. 817 if (mt_processing) { 818 RefProcPhase2Task phase2(*this, refs_lists, !discovery_is_atomic() /*marks_oops_alive*/); 819 task_executor->execute(phase2); 820 } else { 821 for (uint i = 0; i < _max_num_q; i++) { 822 process_phase2(refs_lists[i], is_alive, keep_alive, complete_gc); 823 } 824 } 825 826 // Phase 3: 827 // . Traverse the list and process referents as appropriate. 828 if (mt_processing) { 829 RefProcPhase3Task phase3(*this, refs_lists, clear_referent, true /*marks_oops_alive*/); 830 task_executor->execute(phase3); 831 } else { 832 for (uint i = 0; i < _max_num_q; i++) { 833 process_phase3(refs_lists[i], clear_referent, 834 is_alive, keep_alive, complete_gc); 835 } 836 } 837 } 838 839 inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt) { 840 uint id = 0; 841 // Determine the queue index to use for this object. 842 if (_discovery_is_mt) { 843 // During a multi-threaded discovery phase, 844 // each thread saves to its "own" list. 845 Thread* thr = Thread::current(); 846 id = thr->as_Worker_thread()->id(); 847 } else { 848 // single-threaded discovery, we save in round-robin 849 // fashion to each of the lists. 850 if (_processing_is_mt) { 851 id = next_id(); 852 } 853 } 854 assert(id < _max_num_q, "Id is out-of-bounds id %u and max id %u)", id, _max_num_q); 855 856 // Get the discovered queue to which we will add 857 DiscoveredList* list = NULL; 858 switch (rt) { 859 case REF_OTHER: 860 // Unknown reference type, no special treatment 861 break; 862 case REF_SOFT: 863 list = &_discoveredSoftRefs[id]; 864 break; 865 case REF_WEAK: 866 list = &_discoveredWeakRefs[id]; 867 break; 868 case REF_FINAL: 869 list = &_discoveredFinalRefs[id]; 870 break; 871 case REF_PHANTOM: 872 list = &_discoveredPhantomRefs[id]; 873 break; 874 case REF_NONE: 875 // we should not reach here if we are an InstanceRefKlass 876 default: 877 ShouldNotReachHere(); 878 } 879 log_develop_trace(gc, ref)("Thread %d gets list " INTPTR_FORMAT, id, p2i(list)); 880 return list; 881 } 882 883 inline void 884 ReferenceProcessor::add_to_discovered_list_mt(DiscoveredList& refs_list, 885 oop obj, 886 HeapWord* discovered_addr) { 887 assert(_discovery_is_mt, "!_discovery_is_mt should have been handled by caller"); 888 // First we must make sure this object is only enqueued once. CAS in a non null 889 // discovered_addr. 890 oop current_head = refs_list.head(); 891 // The last ref must have its discovered field pointing to itself. 892 oop next_discovered = (current_head != NULL) ? current_head : obj; 893 894 oop retest = oopDesc::atomic_compare_exchange_oop(next_discovered, discovered_addr, 895 NULL); 896 if (retest == NULL) { 897 // This thread just won the right to enqueue the object. 898 // We have separate lists for enqueueing, so no synchronization 899 // is necessary. 900 refs_list.set_head(obj); 901 refs_list.inc_length(1); 902 903 log_develop_trace(gc, ref)("Discovered reference (mt) (" INTPTR_FORMAT ": %s)", 904 p2i(obj), obj->klass()->internal_name()); 905 } else { 906 // If retest was non NULL, another thread beat us to it: 907 // The reference has already been discovered... 908 log_develop_trace(gc, ref)("Already discovered reference (" INTPTR_FORMAT ": %s)", 909 p2i(obj), obj->klass()->internal_name()); 910 } 911 } 912 913 #ifndef PRODUCT 914 // Non-atomic (i.e. concurrent) discovery might allow us 915 // to observe j.l.References with NULL referents, being those 916 // cleared concurrently by mutators during (or after) discovery. 917 void ReferenceProcessor::verify_referent(oop obj) { 918 bool da = discovery_is_atomic(); 919 oop referent = java_lang_ref_Reference::referent(obj); 920 assert(da ? referent->is_oop() : referent->is_oop_or_null(), 921 "Bad referent " INTPTR_FORMAT " found in Reference " 922 INTPTR_FORMAT " during %satomic discovery ", 923 p2i(referent), p2i(obj), da ? "" : "non-"); 924 } 925 #endif 926 927 // We mention two of several possible choices here: 928 // #0: if the reference object is not in the "originating generation" 929 // (or part of the heap being collected, indicated by our "span" 930 // we don't treat it specially (i.e. we scan it as we would 931 // a normal oop, treating its references as strong references). 932 // This means that references can't be discovered unless their 933 // referent is also in the same span. This is the simplest, 934 // most "local" and most conservative approach, albeit one 935 // that may cause weak references to be enqueued least promptly. 936 // We call this choice the "ReferenceBasedDiscovery" policy. 937 // #1: the reference object may be in any generation (span), but if 938 // the referent is in the generation (span) being currently collected 939 // then we can discover the reference object, provided 940 // the object has not already been discovered by 941 // a different concurrently running collector (as may be the 942 // case, for instance, if the reference object is in CMS and 943 // the referent in DefNewGeneration), and provided the processing 944 // of this reference object by the current collector will 945 // appear atomic to every other collector in the system. 946 // (Thus, for instance, a concurrent collector may not 947 // discover references in other generations even if the 948 // referent is in its own generation). This policy may, 949 // in certain cases, enqueue references somewhat sooner than 950 // might Policy #0 above, but at marginally increased cost 951 // and complexity in processing these references. 952 // We call this choice the "RefeferentBasedDiscovery" policy. 953 bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) { 954 // Make sure we are discovering refs (rather than processing discovered refs). 955 if (!_discovering_refs || !RegisterReferences) { 956 return false; 957 } 958 // We only discover active references. 959 oop next = java_lang_ref_Reference::next(obj); 960 if (next != NULL) { // Ref is no longer active 961 return false; 962 } 963 964 HeapWord* obj_addr = (HeapWord*)obj; 965 if (RefDiscoveryPolicy == ReferenceBasedDiscovery && 966 !_span.contains(obj_addr)) { 967 // Reference is not in the originating generation; 968 // don't treat it specially (i.e. we want to scan it as a normal 969 // object with strong references). 970 return false; 971 } 972 973 // We only discover references whose referents are not (yet) 974 // known to be strongly reachable. 975 if (is_alive_non_header() != NULL) { 976 verify_referent(obj); 977 if (is_alive_non_header()->do_object_b(java_lang_ref_Reference::referent(obj))) { 978 return false; // referent is reachable 979 } 980 } 981 if (rt == REF_SOFT) { 982 // For soft refs we can decide now if these are not 983 // current candidates for clearing, in which case we 984 // can mark through them now, rather than delaying that 985 // to the reference-processing phase. Since all current 986 // time-stamp policies advance the soft-ref clock only 987 // at a full collection cycle, this is always currently 988 // accurate. 989 if (!_current_soft_ref_policy->should_clear_reference(obj, _soft_ref_timestamp_clock)) { 990 return false; 991 } 992 } 993 994 ResourceMark rm; // Needed for tracing. 995 996 HeapWord* const discovered_addr = java_lang_ref_Reference::discovered_addr(obj); 997 const oop discovered = java_lang_ref_Reference::discovered(obj); 998 assert(discovered->is_oop_or_null(), "Expected an oop or NULL for discovered field at " PTR_FORMAT, p2i(discovered)); 999 if (discovered != NULL) { 1000 // The reference has already been discovered... 1001 log_develop_trace(gc, ref)("Already discovered reference (" INTPTR_FORMAT ": %s)", 1002 p2i(obj), obj->klass()->internal_name()); 1003 if (RefDiscoveryPolicy == ReferentBasedDiscovery) { 1004 // assumes that an object is not processed twice; 1005 // if it's been already discovered it must be on another 1006 // generation's discovered list; so we won't discover it. 1007 return false; 1008 } else { 1009 assert(RefDiscoveryPolicy == ReferenceBasedDiscovery, 1010 "Unrecognized policy"); 1011 // Check assumption that an object is not potentially 1012 // discovered twice except by concurrent collectors that potentially 1013 // trace the same Reference object twice. 1014 assert(UseConcMarkSweepGC || UseG1GC, 1015 "Only possible with a concurrent marking collector"); 1016 return true; 1017 } 1018 } 1019 1020 if (RefDiscoveryPolicy == ReferentBasedDiscovery) { 1021 verify_referent(obj); 1022 // Discover if and only if EITHER: 1023 // .. reference is in our span, OR 1024 // .. we are an atomic collector and referent is in our span 1025 if (_span.contains(obj_addr) || 1026 (discovery_is_atomic() && 1027 _span.contains(java_lang_ref_Reference::referent(obj)))) { 1028 // should_enqueue = true; 1029 } else { 1030 return false; 1031 } 1032 } else { 1033 assert(RefDiscoveryPolicy == ReferenceBasedDiscovery && 1034 _span.contains(obj_addr), "code inconsistency"); 1035 } 1036 1037 // Get the right type of discovered queue head. 1038 DiscoveredList* list = get_discovered_list(rt); 1039 if (list == NULL) { 1040 return false; // nothing special needs to be done 1041 } 1042 1043 if (_discovery_is_mt) { 1044 add_to_discovered_list_mt(*list, obj, discovered_addr); 1045 } else { 1046 // We do a raw store here: the field will be visited later when processing 1047 // the discovered references. 1048 oop current_head = list->head(); 1049 // The last ref must have its discovered field pointing to itself. 1050 oop next_discovered = (current_head != NULL) ? current_head : obj; 1051 1052 assert(discovered == NULL, "control point invariant"); 1053 oop_store_raw(discovered_addr, next_discovered); 1054 list->set_head(obj); 1055 list->inc_length(1); 1056 1057 log_develop_trace(gc, ref)("Discovered reference (" INTPTR_FORMAT ": %s)", p2i(obj), obj->klass()->internal_name()); 1058 } 1059 assert(obj->is_oop(), "Discovered a bad reference"); 1060 verify_referent(obj); 1061 return true; 1062 } 1063 1064 bool ReferenceProcessor::has_discovered_references() { 1065 for (uint i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) { 1066 if (!_discovered_refs[i].is_empty()) { 1067 return true; 1068 } 1069 } 1070 return false; 1071 } 1072 1073 // Preclean the discovered references by removing those 1074 // whose referents are alive, and by marking from those that 1075 // are not active. These lists can be handled here 1076 // in any order and, indeed, concurrently. 1077 void ReferenceProcessor::preclean_discovered_references( 1078 BoolObjectClosure* is_alive, 1079 OopClosure* keep_alive, 1080 VoidClosure* complete_gc, 1081 YieldClosure* yield, 1082 GCTimer* gc_timer) { 1083 1084 // Soft references 1085 { 1086 GCTraceTime(Debug, gc, ref) tm("Preclean SoftReferences", gc_timer); 1087 for (uint i = 0; i < _max_num_q; i++) { 1088 if (yield->should_return()) { 1089 return; 1090 } 1091 preclean_discovered_reflist(_discoveredSoftRefs[i], is_alive, 1092 keep_alive, complete_gc, yield); 1093 } 1094 } 1095 1096 // Weak references 1097 { 1098 GCTraceTime(Debug, gc, ref) tm("Preclean WeakReferences", gc_timer); 1099 for (uint i = 0; i < _max_num_q; i++) { 1100 if (yield->should_return()) { 1101 return; 1102 } 1103 preclean_discovered_reflist(_discoveredWeakRefs[i], is_alive, 1104 keep_alive, complete_gc, yield); 1105 } 1106 } 1107 1108 // Final references 1109 { 1110 GCTraceTime(Debug, gc, ref) tm("Preclean FinalReferences", gc_timer); 1111 for (uint i = 0; i < _max_num_q; i++) { 1112 if (yield->should_return()) { 1113 return; 1114 } 1115 preclean_discovered_reflist(_discoveredFinalRefs[i], is_alive, 1116 keep_alive, complete_gc, yield); 1117 } 1118 } 1119 1120 // Phantom references 1121 { 1122 GCTraceTime(Debug, gc, ref) tm("Preclean PhantomReferences", gc_timer); 1123 for (uint i = 0; i < _max_num_q; i++) { 1124 if (yield->should_return()) { 1125 return; 1126 } 1127 preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive, 1128 keep_alive, complete_gc, yield); 1129 } 1130 } 1131 } 1132 1133 // Walk the given discovered ref list, and remove all reference objects 1134 // whose referents are still alive, whose referents are NULL or which 1135 // are not active (have a non-NULL next field). NOTE: When we are 1136 // thus precleaning the ref lists (which happens single-threaded today), 1137 // we do not disable refs discovery to honor the correct semantics of 1138 // java.lang.Reference. As a result, we need to be careful below 1139 // that ref removal steps interleave safely with ref discovery steps 1140 // (in this thread). 1141 void 1142 ReferenceProcessor::preclean_discovered_reflist(DiscoveredList& refs_list, 1143 BoolObjectClosure* is_alive, 1144 OopClosure* keep_alive, 1145 VoidClosure* complete_gc, 1146 YieldClosure* yield) { 1147 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); 1148 while (iter.has_next()) { 1149 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); 1150 oop obj = iter.obj(); 1151 oop next = java_lang_ref_Reference::next(obj); 1152 if (iter.referent() == NULL || iter.is_referent_alive() || 1153 next != NULL) { 1154 // The referent has been cleared, or is alive, or the Reference is not 1155 // active; we need to trace and mark its cohort. 1156 log_develop_trace(gc, ref)("Precleaning Reference (" INTPTR_FORMAT ": %s)", 1157 p2i(iter.obj()), iter.obj()->klass()->internal_name()); 1158 // Remove Reference object from list 1159 iter.remove(); 1160 // Keep alive its cohort. 1161 iter.make_referent_alive(); 1162 if (UseCompressedOops) { 1163 narrowOop* next_addr = (narrowOop*)java_lang_ref_Reference::next_addr(obj); 1164 keep_alive->do_oop(next_addr); 1165 } else { 1166 oop* next_addr = (oop*)java_lang_ref_Reference::next_addr(obj); 1167 keep_alive->do_oop(next_addr); 1168 } 1169 iter.move_to_next(); 1170 } else { 1171 iter.next(); 1172 } 1173 } 1174 // Close the reachable set 1175 complete_gc->do_void(); 1176 1177 NOT_PRODUCT( 1178 if (iter.processed() > 0) { 1179 log_develop_trace(gc, ref)(" Dropped " SIZE_FORMAT " Refs out of " SIZE_FORMAT " Refs in discovered list " INTPTR_FORMAT, 1180 iter.removed(), iter.processed(), p2i(&refs_list)); 1181 } 1182 ) 1183 } 1184 1185 const char* ReferenceProcessor::list_name(uint i) { 1186 assert(i <= _max_num_q * number_of_subclasses_of_ref(), 1187 "Out of bounds index"); 1188 1189 int j = i / _max_num_q; 1190 switch (j) { 1191 case 0: return "SoftRef"; 1192 case 1: return "WeakRef"; 1193 case 2: return "FinalRef"; 1194 case 3: return "PhantomRef"; 1195 } 1196 ShouldNotReachHere(); 1197 return NULL; 1198 } 1199