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
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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13 * accompanied this code).
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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 (oopDesc::unsafe_equals(_current_discovered, _next_discovered)) {
147 // End of the list.
148 _current_discovered = NULL;
149 } else {
150 _current_discovered = _next_discovered;
151 }
152 assert(! oopDesc::unsafe_equals(_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