1 /* 2 * Copyright (c) 2001, 2018, 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 #ifndef SHARE_VM_GC_SHARED_REFERENCEPROCESSOR_HPP 26 #define SHARE_VM_GC_SHARED_REFERENCEPROCESSOR_HPP 27 28 #include "gc/shared/referenceDiscoverer.hpp" 29 #include "gc/shared/referencePolicy.hpp" 30 #include "gc/shared/referenceProcessorStats.hpp" 31 #include "memory/referenceType.hpp" 32 #include "oops/instanceRefKlass.hpp" 33 34 class AbstractRefProcTaskExecutor; 35 class GCTimer; 36 class ReferencePolicy; 37 class ReferenceProcessorPhaseTimes; 38 39 // List of discovered references. 40 class DiscoveredList { 41 public: 42 DiscoveredList() : _oop_head(NULL), _compressed_head(0), _len(0) { } 43 inline oop head() const; 44 HeapWord* adr_head() { 45 return UseCompressedOops ? (HeapWord*)&_compressed_head : 46 (HeapWord*)&_oop_head; 47 } 48 inline void set_head(oop o); 49 inline bool is_empty() const; 50 size_t length() { return _len; } 51 void set_length(size_t len) { _len = len; } 52 void inc_length(size_t inc) { _len += inc; assert(_len > 0, "Error"); } 53 void dec_length(size_t dec) { _len -= dec; } 54 55 inline void clear(); 56 private: 57 // Set value depending on UseCompressedOops. This could be a template class 58 // but then we have to fix all the instantiations and declarations that use this class. 59 oop _oop_head; 60 narrowOop _compressed_head; 61 size_t _len; 62 }; 63 64 // Iterator for the list of discovered references. 65 class DiscoveredListIterator { 66 private: 67 DiscoveredList& _refs_list; 68 HeapWord* _prev_discovered_addr; 69 oop _prev_discovered; 70 oop _current_discovered; 71 HeapWord* _current_discovered_addr; 72 oop _next_discovered; 73 74 HeapWord* _referent_addr; 75 oop _referent; 76 77 OopClosure* _keep_alive; 78 BoolObjectClosure* _is_alive; 79 80 DEBUG_ONLY( 81 oop _first_seen; // cyclic linked list check 82 ) 83 84 size_t _processed; 85 size_t _removed; 86 87 public: 88 inline DiscoveredListIterator(DiscoveredList& refs_list, 89 OopClosure* keep_alive, 90 BoolObjectClosure* is_alive); 91 92 // End Of List. 93 inline bool has_next() const { return _current_discovered != NULL; } 94 95 // Get oop to the Reference object. 96 inline oop obj() const { return _current_discovered; } 97 98 // Get oop to the referent object. 99 inline oop referent() const { return _referent; } 100 101 // Returns true if referent is alive. 102 inline bool is_referent_alive() const { 103 return _is_alive->do_object_b(_referent); 104 } 105 106 // Loads data for the current reference. 107 // The "allow_null_referent" argument tells us to allow for the possibility 108 // of a NULL referent in the discovered Reference object. This typically 109 // happens in the case of concurrent collectors that may have done the 110 // discovery concurrently, or interleaved, with mutator execution. 111 void load_ptrs(DEBUG_ONLY(bool allow_null_referent)); 112 113 // Move to the next discovered reference. 114 inline void next() { 115 _prev_discovered_addr = _current_discovered_addr; 116 _prev_discovered = _current_discovered; 117 move_to_next(); 118 } 119 120 // Remove the current reference from the list 121 void remove(); 122 123 // Make the referent alive. 124 inline void make_referent_alive() { 125 if (UseCompressedOops) { 126 _keep_alive->do_oop((narrowOop*)_referent_addr); 127 } else { 128 _keep_alive->do_oop((oop*)_referent_addr); 129 } 130 } 131 132 // Do enqueuing work, i.e. notifying the GC about the changed discovered pointers. 133 void enqueue(); 134 135 // Move enqueued references to the reference pending list. 136 void complete_enqueue(); 137 138 // NULL out referent pointer. 139 void clear_referent(); 140 141 // Statistics 142 inline size_t processed() const { return _processed; } 143 inline size_t removed() const { return _removed; } 144 145 inline void move_to_next() { 146 if (_current_discovered == _next_discovered) { 147 // End of the list. 148 _current_discovered = NULL; 149 } else { 150 _current_discovered = _next_discovered; 151 } 152 assert(_current_discovered != _first_seen, "cyclic ref_list found"); 153 _processed++; 154 } 155 }; 156 157 // The ReferenceProcessor class encapsulates the per-"collector" processing 158 // of java.lang.Reference objects for GC. The interface is useful for supporting 159 // a generational abstraction, in particular when there are multiple 160 // generations that are being independently collected -- possibly 161 // concurrently and/or incrementally. 162 // ReferenceProcessor class abstracts away from a generational setting 163 // by using a closure that determines whether a given reference or referent are 164 // subject to this ReferenceProcessor's discovery, thus allowing its use in a 165 // straightforward manner in a general, non-generational, non-contiguous generation 166 // (or heap) setting. 167 class ReferenceProcessor : public ReferenceDiscoverer { 168 friend class RefProcPhase1Task; 169 friend class RefProcPhase2Task; 170 friend class RefProcPhase3Task; 171 friend class RefProcPhase4Task; 172 public: 173 // Names of sub-phases of reference processing. Indicates the type of the reference 174 // processed and the associated phase number at the end. 175 enum RefProcSubPhases { 176 SoftRefSubPhase1, 177 SoftRefSubPhase2, 178 WeakRefSubPhase2, 179 FinalRefSubPhase2, 180 FinalRefSubPhase3, 181 PhantomRefSubPhase4, 182 RefSubPhaseMax 183 }; 184 185 // Main phases of reference processing. 186 enum RefProcPhases { 187 RefPhase1, 188 RefPhase2, 189 RefPhase3, 190 RefPhase4, 191 RefPhaseMax 192 }; 193 194 private: 195 size_t total_count(DiscoveredList lists[]) const; 196 void verify_total_count_zero(DiscoveredList lists[], const char* type) NOT_DEBUG_RETURN; 197 198 // The SoftReference master timestamp clock 199 static jlong _soft_ref_timestamp_clock; 200 201 BoolObjectClosure* _is_subject_to_discovery; // determines whether a given oop is subject 202 // to this ReferenceProcessor's discovery 203 // (and further processing). 204 205 bool _discovering_refs; // true when discovery enabled 206 bool _discovery_is_atomic; // if discovery is atomic wrt 207 // other collectors in configuration 208 bool _discovery_is_mt; // true if reference discovery is MT. 209 210 bool _enqueuing_is_done; // true if all weak references enqueued 211 bool _processing_is_mt; // true during phases when 212 // reference processing is MT. 213 uint _next_id; // round-robin mod _num_queues counter in 214 // support of work distribution 215 216 bool _adjust_no_of_processing_threads; // allow dynamic adjustment of processing threads 217 // For collectors that do not keep GC liveness information 218 // in the object header, this field holds a closure that 219 // helps the reference processor determine the reachability 220 // of an oop. It is currently initialized to NULL for all 221 // collectors except for CMS and G1. 222 BoolObjectClosure* _is_alive_non_header; 223 224 // Soft ref clearing policies 225 // . the default policy 226 static ReferencePolicy* _default_soft_ref_policy; 227 // . the "clear all" policy 228 static ReferencePolicy* _always_clear_soft_ref_policy; 229 // . the current policy below is either one of the above 230 ReferencePolicy* _current_soft_ref_policy; 231 232 // The discovered ref lists themselves 233 234 // The active MT'ness degree of the queues below 235 uint _num_queues; 236 // The maximum MT'ness degree of the queues below 237 uint _max_num_queues; 238 239 // Master array of discovered oops 240 DiscoveredList* _discovered_refs; 241 242 // Arrays of lists of oops, one per thread (pointers into master array above) 243 DiscoveredList* _discoveredSoftRefs; 244 DiscoveredList* _discoveredWeakRefs; 245 DiscoveredList* _discoveredFinalRefs; 246 DiscoveredList* _discoveredPhantomRefs; 247 248 // Phase 1: Re-evaluate soft ref policy. 249 void process_soft_ref_reconsider(BoolObjectClosure* is_alive, 250 OopClosure* keep_alive, 251 VoidClosure* complete_gc, 252 AbstractRefProcTaskExecutor* task_executor, 253 ReferenceProcessorPhaseTimes* phase_times); 254 255 // Phase 2: Drop Soft/Weak/Final references with a NULL or live referent, and clear 256 // and enqueue non-Final references. 257 void process_soft_weak_final_refs(BoolObjectClosure* is_alive, 258 OopClosure* keep_alive, 259 VoidClosure* complete_gc, 260 AbstractRefProcTaskExecutor* task_executor, 261 ReferenceProcessorPhaseTimes* phase_times); 262 263 // Phase 3: Keep alive followers of Final references, and enqueue. 264 void process_final_keep_alive(OopClosure* keep_alive, 265 VoidClosure* complete_gc, 266 AbstractRefProcTaskExecutor* task_executor, 267 ReferenceProcessorPhaseTimes* phase_times); 268 269 // Phase 4: Drop and keep alive live Phantom references, or clear and enqueue if dead. 270 void process_phantom_refs(BoolObjectClosure* is_alive, 271 OopClosure* keep_alive, 272 VoidClosure* complete_gc, 273 AbstractRefProcTaskExecutor* task_executor, 274 ReferenceProcessorPhaseTimes* phase_times); 275 276 // Work methods used by the process_* methods. All methods return the number of 277 // removed elements. 278 279 // (SoftReferences only) Traverse the list and remove any SoftReferences whose 280 // referents are not alive, but that should be kept alive for policy reasons. 281 // Keep alive the transitive closure of all such referents. 282 size_t process_soft_ref_reconsider_work(DiscoveredList& refs_list, 283 ReferencePolicy* policy, 284 BoolObjectClosure* is_alive, 285 OopClosure* keep_alive, 286 VoidClosure* complete_gc); 287 288 // Traverse the list and remove any Refs whose referents are alive, 289 // or NULL if discovery is not atomic. Enqueue and clear the reference for 290 // others if do_enqueue_and_clear is set. 291 size_t process_soft_weak_final_refs_work(DiscoveredList& refs_list, 292 BoolObjectClosure* is_alive, 293 OopClosure* keep_alive, 294 bool do_enqueue_and_clear); 295 296 // Keep alive followers of referents for FinalReferences. Must only be called for 297 // those. 298 size_t process_final_keep_alive_work(DiscoveredList& refs_list, 299 OopClosure* keep_alive, 300 VoidClosure* complete_gc); 301 302 size_t process_phantom_refs_work(DiscoveredList& refs_list, 303 BoolObjectClosure* is_alive, 304 OopClosure* keep_alive, 305 VoidClosure* complete_gc); 306 307 public: 308 static int number_of_subclasses_of_ref() { return (REF_PHANTOM - REF_OTHER); } 309 310 uint num_queues() const { return _num_queues; } 311 uint max_num_queues() const { return _max_num_queues; } 312 void set_active_mt_degree(uint v); 313 314 ReferencePolicy* setup_policy(bool always_clear) { 315 _current_soft_ref_policy = always_clear ? 316 _always_clear_soft_ref_policy : _default_soft_ref_policy; 317 _current_soft_ref_policy->setup(); // snapshot the policy threshold 318 return _current_soft_ref_policy; 319 } 320 321 // "Preclean" all the discovered reference lists by removing references that 322 // are active (e.g. due to the mutator calling enqueue()) or with NULL or 323 // strongly reachable referents. 324 // The first argument is a predicate on an oop that indicates 325 // its (strong) reachability and the fourth is a closure that 326 // may be used to incrementalize or abort the precleaning process. 327 // The caller is responsible for taking care of potential 328 // interference with concurrent operations on these lists 329 // (or predicates involved) by other threads. 330 void preclean_discovered_references(BoolObjectClosure* is_alive, 331 OopClosure* keep_alive, 332 VoidClosure* complete_gc, 333 YieldClosure* yield, 334 GCTimer* gc_timer); 335 336 private: 337 // Returns the name of the discovered reference list 338 // occupying the i / _num_queues slot. 339 const char* list_name(uint i); 340 341 // "Preclean" the given discovered reference list by removing references with 342 // the attributes mentioned in preclean_discovered_references(). 343 // Supports both normal and fine grain yielding. 344 // Returns whether the operation should be aborted. 345 bool preclean_discovered_reflist(DiscoveredList& refs_list, 346 BoolObjectClosure* is_alive, 347 OopClosure* keep_alive, 348 VoidClosure* complete_gc, 349 YieldClosure* yield); 350 351 // round-robin mod _num_queues (not: _not_ mod _max_num_queues) 352 uint next_id() { 353 uint id = _next_id; 354 assert(!_discovery_is_mt, "Round robin should only be used in serial discovery"); 355 if (++_next_id == _num_queues) { 356 _next_id = 0; 357 } 358 assert(_next_id < _num_queues, "_next_id %u _num_queues %u _max_num_queues %u", _next_id, _num_queues, _max_num_queues); 359 return id; 360 } 361 DiscoveredList* get_discovered_list(ReferenceType rt); 362 inline void add_to_discovered_list_mt(DiscoveredList& refs_list, oop obj, 363 HeapWord* discovered_addr); 364 365 void clear_discovered_references(DiscoveredList& refs_list); 366 367 void log_reflist(const char* prefix, DiscoveredList list[], uint num_active_queues); 368 void log_reflist_counts(DiscoveredList ref_lists[], uint num_active_queues) PRODUCT_RETURN; 369 370 // Balances reference queues. 371 void balance_queues(DiscoveredList refs_lists[]); 372 bool need_balance_queues(DiscoveredList refs_lists[]); 373 374 // If there is need to balance the given queue, do it. 375 void maybe_balance_queues(DiscoveredList refs_lists[]); 376 377 // Update (advance) the soft ref master clock field. 378 void update_soft_ref_master_clock(); 379 380 bool is_subject_to_discovery(oop const obj) const; 381 382 bool is_mt_processing_set_up(AbstractRefProcTaskExecutor* task_executor) const; 383 384 public: 385 // Default parameters give you a vanilla reference processor. 386 ReferenceProcessor(BoolObjectClosure* is_subject_to_discovery, 387 bool mt_processing = false, uint mt_processing_degree = 1, 388 bool mt_discovery = false, uint mt_discovery_degree = 1, 389 bool atomic_discovery = true, 390 BoolObjectClosure* is_alive_non_header = NULL, 391 bool adjust_no_of_processing_threads = false); 392 393 // RefDiscoveryPolicy values 394 enum DiscoveryPolicy { 395 ReferenceBasedDiscovery = 0, 396 ReferentBasedDiscovery = 1, 397 DiscoveryPolicyMin = ReferenceBasedDiscovery, 398 DiscoveryPolicyMax = ReferentBasedDiscovery 399 }; 400 401 static void init_statics(); 402 403 // get and set "is_alive_non_header" field 404 BoolObjectClosure* is_alive_non_header() { 405 return _is_alive_non_header; 406 } 407 void set_is_alive_non_header(BoolObjectClosure* is_alive_non_header) { 408 _is_alive_non_header = is_alive_non_header; 409 } 410 411 BoolObjectClosure* is_subject_to_discovery_closure() const { return _is_subject_to_discovery; } 412 void set_is_subject_to_discovery_closure(BoolObjectClosure* cl) { _is_subject_to_discovery = cl; } 413 414 // start and stop weak ref discovery 415 void enable_discovery(bool check_no_refs = true); 416 void disable_discovery() { _discovering_refs = false; } 417 bool discovery_enabled() { return _discovering_refs; } 418 419 // whether discovery is atomic wrt other collectors 420 bool discovery_is_atomic() const { return _discovery_is_atomic; } 421 void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; } 422 423 // whether discovery is done by multiple threads same-old-timeously 424 bool discovery_is_mt() const { return _discovery_is_mt; } 425 void set_mt_discovery(bool mt) { _discovery_is_mt = mt; } 426 427 // Whether we are in a phase when _processing_ is MT. 428 bool processing_is_mt() const { return _processing_is_mt; } 429 void set_mt_processing(bool mt) { _processing_is_mt = mt; } 430 431 // whether all enqueueing of weak references is complete 432 bool enqueuing_is_done() { return _enqueuing_is_done; } 433 void set_enqueuing_is_done(bool v) { _enqueuing_is_done = v; } 434 435 // iterate over oops 436 void weak_oops_do(OopClosure* f); // weak roots 437 438 void verify_list(DiscoveredList& ref_list); 439 440 // Discover a Reference object, using appropriate discovery criteria 441 virtual bool discover_reference(oop obj, ReferenceType rt); 442 443 // Has discovered references that need handling 444 bool has_discovered_references(); 445 446 // Process references found during GC (called by the garbage collector) 447 ReferenceProcessorStats 448 process_discovered_references(BoolObjectClosure* is_alive, 449 OopClosure* keep_alive, 450 VoidClosure* complete_gc, 451 AbstractRefProcTaskExecutor* task_executor, 452 ReferenceProcessorPhaseTimes* phase_times); 453 454 // If a discovery is in process that is being superceded, abandon it: all 455 // the discovered lists will be empty, and all the objects on them will 456 // have NULL discovered fields. Must be called only at a safepoint. 457 void abandon_partial_discovery(); 458 459 size_t total_reference_count(ReferenceType rt) const; 460 461 // debugging 462 void verify_no_references_recorded() PRODUCT_RETURN; 463 void verify_referent(oop obj) PRODUCT_RETURN; 464 465 bool adjust_no_of_processing_threads() const { return _adjust_no_of_processing_threads; } 466 }; 467 468 // A subject-to-discovery closure that uses a single memory span to determine the area that 469 // is subject to discovery. Useful for collectors which have contiguous generations. 470 class SpanSubjectToDiscoveryClosure : public BoolObjectClosure { 471 MemRegion _span; 472 473 public: 474 SpanSubjectToDiscoveryClosure() : BoolObjectClosure(), _span() { } 475 SpanSubjectToDiscoveryClosure(MemRegion span) : BoolObjectClosure(), _span(span) { } 476 477 MemRegion span() const { return _span; } 478 479 void set_span(MemRegion mr) { 480 _span = mr; 481 } 482 483 virtual bool do_object_b(oop obj) { 484 return _span.contains(obj); 485 } 486 }; 487 488 // A utility class to disable reference discovery in 489 // the scope which contains it, for given ReferenceProcessor. 490 class NoRefDiscovery: StackObj { 491 private: 492 ReferenceProcessor* _rp; 493 bool _was_discovering_refs; 494 public: 495 NoRefDiscovery(ReferenceProcessor* rp) : _rp(rp) { 496 _was_discovering_refs = _rp->discovery_enabled(); 497 if (_was_discovering_refs) { 498 _rp->disable_discovery(); 499 } 500 } 501 502 ~NoRefDiscovery() { 503 if (_was_discovering_refs) { 504 _rp->enable_discovery(false /*check_no_refs*/); 505 } 506 } 507 }; 508 509 // A utility class to temporarily mutate the subject discovery closure of the 510 // given ReferenceProcessor in the scope that contains it. 511 class ReferenceProcessorSubjectToDiscoveryMutator : StackObj { 512 ReferenceProcessor* _rp; 513 BoolObjectClosure* _saved_cl; 514 515 public: 516 ReferenceProcessorSubjectToDiscoveryMutator(ReferenceProcessor* rp, BoolObjectClosure* cl): 517 _rp(rp) { 518 _saved_cl = _rp->is_subject_to_discovery_closure(); 519 _rp->set_is_subject_to_discovery_closure(cl); 520 } 521 522 ~ReferenceProcessorSubjectToDiscoveryMutator() { 523 _rp->set_is_subject_to_discovery_closure(_saved_cl); 524 } 525 }; 526 527 // A utility class to temporarily mutate the span of the 528 // given ReferenceProcessor in the scope that contains it. 529 class ReferenceProcessorSpanMutator : StackObj { 530 ReferenceProcessor* _rp; 531 SpanSubjectToDiscoveryClosure _discoverer; 532 BoolObjectClosure* _old_discoverer; 533 534 public: 535 ReferenceProcessorSpanMutator(ReferenceProcessor* rp, 536 MemRegion span): 537 _rp(rp), 538 _discoverer(span), 539 _old_discoverer(rp->is_subject_to_discovery_closure()) { 540 541 rp->set_is_subject_to_discovery_closure(&_discoverer); 542 } 543 544 ~ReferenceProcessorSpanMutator() { 545 _rp->set_is_subject_to_discovery_closure(_old_discoverer); 546 } 547 }; 548 549 // A utility class to temporarily change the MT'ness of 550 // reference discovery for the given ReferenceProcessor 551 // in the scope that contains it. 552 class ReferenceProcessorMTDiscoveryMutator: StackObj { 553 private: 554 ReferenceProcessor* _rp; 555 bool _saved_mt; 556 557 public: 558 ReferenceProcessorMTDiscoveryMutator(ReferenceProcessor* rp, 559 bool mt): 560 _rp(rp) { 561 _saved_mt = _rp->discovery_is_mt(); 562 _rp->set_mt_discovery(mt); 563 } 564 565 ~ReferenceProcessorMTDiscoveryMutator() { 566 _rp->set_mt_discovery(_saved_mt); 567 } 568 }; 569 570 // A utility class to temporarily change the disposition 571 // of the "is_alive_non_header" closure field of the 572 // given ReferenceProcessor in the scope that contains it. 573 class ReferenceProcessorIsAliveMutator: StackObj { 574 private: 575 ReferenceProcessor* _rp; 576 BoolObjectClosure* _saved_cl; 577 578 public: 579 ReferenceProcessorIsAliveMutator(ReferenceProcessor* rp, 580 BoolObjectClosure* cl): 581 _rp(rp) { 582 _saved_cl = _rp->is_alive_non_header(); 583 _rp->set_is_alive_non_header(cl); 584 } 585 586 ~ReferenceProcessorIsAliveMutator() { 587 _rp->set_is_alive_non_header(_saved_cl); 588 } 589 }; 590 591 // A utility class to temporarily change the disposition 592 // of the "discovery_is_atomic" field of the 593 // given ReferenceProcessor in the scope that contains it. 594 class ReferenceProcessorAtomicMutator: StackObj { 595 private: 596 ReferenceProcessor* _rp; 597 bool _saved_atomic_discovery; 598 599 public: 600 ReferenceProcessorAtomicMutator(ReferenceProcessor* rp, 601 bool atomic): 602 _rp(rp) { 603 _saved_atomic_discovery = _rp->discovery_is_atomic(); 604 _rp->set_atomic_discovery(atomic); 605 } 606 607 ~ReferenceProcessorAtomicMutator() { 608 _rp->set_atomic_discovery(_saved_atomic_discovery); 609 } 610 }; 611 612 613 // A utility class to temporarily change the MT processing 614 // disposition of the given ReferenceProcessor instance 615 // in the scope that contains it. 616 class ReferenceProcessorMTProcMutator: StackObj { 617 private: 618 ReferenceProcessor* _rp; 619 bool _saved_mt; 620 621 public: 622 ReferenceProcessorMTProcMutator(ReferenceProcessor* rp, 623 bool mt): 624 _rp(rp) { 625 _saved_mt = _rp->processing_is_mt(); 626 _rp->set_mt_processing(mt); 627 } 628 629 ~ReferenceProcessorMTProcMutator() { 630 _rp->set_mt_processing(_saved_mt); 631 } 632 }; 633 634 // This class is an interface used to implement task execution for the 635 // reference processing. 636 class AbstractRefProcTaskExecutor { 637 public: 638 639 // Abstract tasks to execute. 640 class ProcessTask; 641 642 // Executes a task using worker threads. 643 virtual void execute(ProcessTask& task, uint ergo_workers) = 0; 644 645 // Switch to single threaded mode. 646 virtual void set_single_threaded_mode() { }; 647 }; 648 649 // Abstract reference processing task to execute. 650 class AbstractRefProcTaskExecutor::ProcessTask { 651 protected: 652 ReferenceProcessor& _ref_processor; 653 // Indicates whether the phase could generate work that should be balanced across 654 // threads after execution. 655 bool _marks_oops_alive; 656 ReferenceProcessorPhaseTimes* _phase_times; 657 658 ProcessTask(ReferenceProcessor& ref_processor, 659 bool marks_oops_alive, 660 ReferenceProcessorPhaseTimes* phase_times) 661 : _ref_processor(ref_processor), 662 _marks_oops_alive(marks_oops_alive), 663 _phase_times(phase_times) 664 { } 665 666 public: 667 virtual void work(uint worker_id, 668 BoolObjectClosure& is_alive, 669 OopClosure& keep_alive, 670 VoidClosure& complete_gc) = 0; 671 672 bool marks_oops_alive() const { return _marks_oops_alive; } 673 }; 674 675 // Temporarily change the number of workers based on given reference count. 676 // This ergonomically decided worker count will be used to activate worker threads. 677 class RefProcMTDegreeAdjuster : public StackObj { 678 typedef ReferenceProcessor::RefProcPhases RefProcPhases; 679 680 ReferenceProcessor* _rp; 681 bool _saved_mt_processing; 682 uint _saved_num_queues; 683 684 // Calculate based on total of references. 685 uint ergo_proc_thread_count(size_t ref_count, 686 uint max_threads, 687 RefProcPhases phase) const; 688 689 bool use_max_threads(RefProcPhases phase) const; 690 691 public: 692 RefProcMTDegreeAdjuster(ReferenceProcessor* rp, 693 RefProcPhases phase, 694 size_t ref_count); 695 ~RefProcMTDegreeAdjuster(); 696 }; 697 698 #endif // SHARE_VM_GC_SHARED_REFERENCEPROCESSOR_HPP