1 /*
2 * Copyright (c) 2001, 2013, 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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23 */
24
25 #ifndef SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP
26 #define SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP
27
28 #include "memory/referencePolicy.hpp"
29 #include "memory/referenceProcessorStats.hpp"
30 #include "memory/referenceType.hpp"
31 #include "oops/instanceRefKlass.hpp"
32
33 class GCTimer;
34
35 // ReferenceProcessor class encapsulates the per-"collector" processing
36 // of java.lang.Reference objects for GC. The interface is useful for supporting
37 // a generational abstraction, in particular when there are multiple
38 // generations that are being independently collected -- possibly
39 // concurrently and/or incrementally. Note, however, that the
40 // ReferenceProcessor class abstracts away from a generational setting
41 // by using only a heap interval (called "span" below), thus allowing
42 // its use in a straightforward manner in a general, non-generational
43 // setting.
44 //
45 // The basic idea is that each ReferenceProcessor object concerns
46 // itself with ("weak") reference processing in a specific "span"
47 // of the heap of interest to a specific collector. Currently,
48 // the span is a convex interval of the heap, but, efficiency
49 // apart, there seems to be no reason it couldn't be extended
50 // (with appropriate modifications) to any "non-convex interval".
51
52 // forward references
53 class ReferencePolicy;
54 class AbstractRefProcTaskExecutor;
55
56 // List of discovered references.
57 class DiscoveredList {
58 public:
59 DiscoveredList() : _len(0), _compressed_head(0), _oop_head(NULL) { }
60 oop head() const {
61 return UseCompressedOops ? oopDesc::decode_heap_oop(_compressed_head) :
62 _oop_head;
63 }
64 HeapWord* adr_head() {
65 return UseCompressedOops ? (HeapWord*)&_compressed_head :
66 (HeapWord*)&_oop_head;
67 }
68 void set_head(oop o) {
69 if (UseCompressedOops) {
70 // Must compress the head ptr.
71 _compressed_head = oopDesc::encode_heap_oop(o);
72 } else {
73 _oop_head = o;
74 }
75 }
76 bool is_empty() const { return head() == NULL; }
77 size_t length() { return _len; }
78 void set_length(size_t len) { _len = len; }
79 void inc_length(size_t inc) { _len += inc; assert(_len > 0, "Error"); }
80 void dec_length(size_t dec) { _len -= dec; }
81 private:
82 // Set value depending on UseCompressedOops. This could be a template class
83 // but then we have to fix all the instantiations and declarations that use this class.
84 oop _oop_head;
85 narrowOop _compressed_head;
86 size_t _len;
87 };
88
89 // Iterator for the list of discovered references.
90 class DiscoveredListIterator {
91 private:
92 DiscoveredList& _refs_list;
93 HeapWord* _prev_next;
94 oop _prev;
95 oop _ref;
96 HeapWord* _discovered_addr;
97 oop _next;
98 HeapWord* _referent_addr;
99 oop _referent;
100 OopClosure* _keep_alive;
101 BoolObjectClosure* _is_alive;
102
103 DEBUG_ONLY(
104 oop _first_seen; // cyclic linked list check
105 )
106
107 NOT_PRODUCT(
108 size_t _processed;
109 size_t _removed;
110 )
111
112 public:
113 inline DiscoveredListIterator(DiscoveredList& refs_list,
114 OopClosure* keep_alive,
115 BoolObjectClosure* is_alive):
116 _refs_list(refs_list),
117 _prev_next(refs_list.adr_head()),
118 _prev(NULL),
119 _ref(refs_list.head()),
120 #ifdef ASSERT
121 _first_seen(refs_list.head()),
122 #endif
123 #ifndef PRODUCT
124 _processed(0),
125 _removed(0),
126 #endif
127 _next(NULL),
128 _keep_alive(keep_alive),
129 _is_alive(is_alive)
130 { }
131
132 // End Of List.
133 inline bool has_next() const { return _ref != NULL; }
134
135 // Get oop to the Reference object.
136 inline oop obj() const { return _ref; }
137
138 // Get oop to the referent object.
139 inline oop referent() const { return _referent; }
140
141 // Returns true if referent is alive.
142 inline bool is_referent_alive() const {
143 return _is_alive->do_object_b(_referent);
144 }
145
146 // Loads data for the current reference.
147 // The "allow_null_referent" argument tells us to allow for the possibility
148 // of a NULL referent in the discovered Reference object. This typically
149 // happens in the case of concurrent collectors that may have done the
150 // discovery concurrently, or interleaved, with mutator execution.
151 void load_ptrs(DEBUG_ONLY(bool allow_null_referent));
152
153 // Move to the next discovered reference.
154 inline void next() {
155 _prev_next = _discovered_addr;
156 _prev = _ref;
157 move_to_next();
158 }
159
160 // Remove the current reference from the list
161 void remove();
162
163 // Make the Reference object active again.
164 void make_active();
165
166 // Make the referent alive.
167 inline void make_referent_alive() {
168 if (UseCompressedOops) {
169 _keep_alive->do_oop((narrowOop*)_referent_addr);
170 } else {
171 _keep_alive->do_oop((oop*)_referent_addr);
172 }
173 }
174
175 // Update the discovered field.
176 inline void update_discovered() {
177 // First _prev_next ref actually points into DiscoveredList (gross).
178 if (UseCompressedOops) {
179 if (!oopDesc::is_null(*(narrowOop*)_prev_next)) {
180 _keep_alive->do_oop((narrowOop*)_prev_next);
181 }
182 } else {
183 if (!oopDesc::is_null(*(oop*)_prev_next)) {
184 _keep_alive->do_oop((oop*)_prev_next);
185 }
186 }
187 }
188
189 // NULL out referent pointer.
190 void clear_referent();
191
192 // Statistics
193 NOT_PRODUCT(
194 inline size_t processed() const { return _processed; }
195 inline size_t removed() const { return _removed; }
196 )
197
198 inline void move_to_next() {
199 if (_ref == _next) {
200 // End of the list.
201 _ref = NULL;
202 } else {
203 _ref = _next;
204 }
205 assert(_ref != _first_seen, "cyclic ref_list found");
206 NOT_PRODUCT(_processed++);
207 }
208 };
209
210 class ReferenceProcessor : public CHeapObj<mtGC> {
211
212 private:
213 size_t total_count(DiscoveredList lists[]);
214
215 protected:
216 // Compatibility with pre-4965777 JDK's
217 static bool _pending_list_uses_discovered_field;
218
219 // The SoftReference master timestamp clock
220 static jlong _soft_ref_timestamp_clock;
221
222 MemRegion _span; // (right-open) interval of heap
223 // subject to wkref discovery
224
225 bool _discovering_refs; // true when discovery enabled
226 bool _discovery_is_atomic; // if discovery is atomic wrt
227 // other collectors in configuration
228 bool _discovery_is_mt; // true if reference discovery is MT.
229
230 // If true, setting "next" field of a discovered refs list requires
231 // write barrier(s). (Must be true if used in a collector in which
232 // elements of a discovered list may be moved during discovery: for
233 // example, a collector like Garbage-First that moves objects during a
234 // long-term concurrent marking phase that does weak reference
235 // discovery.)
236 bool _discovered_list_needs_barrier;
237
238 bool _enqueuing_is_done; // true if all weak references enqueued
239 bool _processing_is_mt; // true during phases when
240 // reference processing is MT.
241 uint _next_id; // round-robin mod _num_q counter in
242 // support of work distribution
243
244 // For collectors that do not keep GC liveness information
245 // in the object header, this field holds a closure that
246 // helps the reference processor determine the reachability
247 // of an oop. It is currently initialized to NULL for all
248 // collectors except for CMS and G1.
249 BoolObjectClosure* _is_alive_non_header;
250
251 // Soft ref clearing policies
252 // . the default policy
253 static ReferencePolicy* _default_soft_ref_policy;
254 // . the "clear all" policy
255 static ReferencePolicy* _always_clear_soft_ref_policy;
256 // . the current policy below is either one of the above
257 ReferencePolicy* _current_soft_ref_policy;
258
259 // The discovered ref lists themselves
260
261 // The active MT'ness degree of the queues below
262 uint _num_q;
263 // The maximum MT'ness degree of the queues below
264 uint _max_num_q;
265
266 // Master array of discovered oops
267 DiscoveredList* _discovered_refs;
268
269 // Arrays of lists of oops, one per thread (pointers into master array above)
270 DiscoveredList* _discoveredSoftRefs;
271 DiscoveredList* _discoveredWeakRefs;
272 DiscoveredList* _discoveredFinalRefs;
273 DiscoveredList* _discoveredPhantomRefs;
274
275 public:
276 static int number_of_subclasses_of_ref() { return (REF_PHANTOM - REF_OTHER); }
277
278 uint num_q() { return _num_q; }
279 uint max_num_q() { return _max_num_q; }
280 void set_active_mt_degree(uint v) { _num_q = v; }
281
282 DiscoveredList* discovered_refs() { return _discovered_refs; }
283
284 ReferencePolicy* setup_policy(bool always_clear) {
285 _current_soft_ref_policy = always_clear ?
286 _always_clear_soft_ref_policy : _default_soft_ref_policy;
287 _current_soft_ref_policy->setup(); // snapshot the policy threshold
288 return _current_soft_ref_policy;
289 }
290
291 // Process references with a certain reachability level.
292 size_t process_discovered_reflist(DiscoveredList refs_lists[],
293 ReferencePolicy* policy,
294 bool clear_referent,
295 BoolObjectClosure* is_alive,
296 OopClosure* keep_alive,
297 VoidClosure* complete_gc,
298 AbstractRefProcTaskExecutor* task_executor);
299
300 void process_phaseJNI(BoolObjectClosure* is_alive,
301 OopClosure* keep_alive,
302 VoidClosure* complete_gc);
303
304 // Work methods used by the method process_discovered_reflist
305 // Phase1: keep alive all those referents that are otherwise
306 // dead but which must be kept alive by policy (and their closure).
307 void process_phase1(DiscoveredList& refs_list,
308 ReferencePolicy* policy,
309 BoolObjectClosure* is_alive,
310 OopClosure* keep_alive,
311 VoidClosure* complete_gc);
312 // Phase2: remove all those references whose referents are
313 // reachable.
314 inline void process_phase2(DiscoveredList& refs_list,
315 BoolObjectClosure* is_alive,
316 OopClosure* keep_alive,
317 VoidClosure* complete_gc) {
318 if (discovery_is_atomic()) {
319 // complete_gc is ignored in this case for this phase
320 pp2_work(refs_list, is_alive, keep_alive);
321 } else {
322 assert(complete_gc != NULL, "Error");
323 pp2_work_concurrent_discovery(refs_list, is_alive,
324 keep_alive, complete_gc);
325 }
326 }
327 // Work methods in support of process_phase2
328 void pp2_work(DiscoveredList& refs_list,
329 BoolObjectClosure* is_alive,
330 OopClosure* keep_alive);
331 void pp2_work_concurrent_discovery(
332 DiscoveredList& refs_list,
333 BoolObjectClosure* is_alive,
334 OopClosure* keep_alive,
335 VoidClosure* complete_gc);
336 // Phase3: process the referents by either clearing them
337 // or keeping them alive (and their closure)
338 void process_phase3(DiscoveredList& refs_list,
339 bool clear_referent,
340 BoolObjectClosure* is_alive,
341 OopClosure* keep_alive,
342 VoidClosure* complete_gc);
343
344 // Enqueue references with a certain reachability level
345 void enqueue_discovered_reflist(DiscoveredList& refs_list, HeapWord* pending_list_addr);
346
347 // "Preclean" all the discovered reference lists
348 // by removing references with strongly reachable referents.
349 // The first argument is a predicate on an oop that indicates
350 // its (strong) reachability and the second is a closure that
351 // may be used to incrementalize or abort the precleaning process.
352 // The caller is responsible for taking care of potential
353 // interference with concurrent operations on these lists
354 // (or predicates involved) by other threads. Currently
355 // only used by the CMS collector.
356 void preclean_discovered_references(BoolObjectClosure* is_alive,
357 OopClosure* keep_alive,
358 VoidClosure* complete_gc,
359 YieldClosure* yield,
360 GCTimer* gc_timer);
361
362 // Delete entries in the discovered lists that have
363 // either a null referent or are not active. Such
364 // Reference objects can result from the clearing
365 // or enqueueing of Reference objects concurrent
366 // with their discovery by a (concurrent) collector.
367 // For a definition of "active" see java.lang.ref.Reference;
368 // Refs are born active, become inactive when enqueued,
369 // and never become active again. The state of being
370 // active is encoded as follows: A Ref is active
371 // if and only if its "next" field is NULL.
372 void clean_up_discovered_references();
373 void clean_up_discovered_reflist(DiscoveredList& refs_list);
374
375 // Returns the name of the discovered reference list
376 // occupying the i / _num_q slot.
377 const char* list_name(uint i);
378
379 void enqueue_discovered_reflists(HeapWord* pending_list_addr, AbstractRefProcTaskExecutor* task_executor);
380
381 protected:
382 // Set the 'discovered' field of the given reference to
383 // the given value - emitting barriers depending upon
384 // the value of _discovered_list_needs_barrier.
385 void set_discovered(oop ref, oop value);
386
387 // "Preclean" the given discovered reference list
388 // by removing references with strongly reachable referents.
389 // Currently used in support of CMS only.
390 void preclean_discovered_reflist(DiscoveredList& refs_list,
391 BoolObjectClosure* is_alive,
392 OopClosure* keep_alive,
393 VoidClosure* complete_gc,
394 YieldClosure* yield);
395
396 // round-robin mod _num_q (not: _not_ mode _max_num_q)
397 uint next_id() {
398 uint id = _next_id;
399 if (++_next_id == _num_q) {
400 _next_id = 0;
401 }
402 return id;
403 }
404 DiscoveredList* get_discovered_list(ReferenceType rt);
405 inline void add_to_discovered_list_mt(DiscoveredList& refs_list, oop obj,
406 HeapWord* discovered_addr);
407 void verify_ok_to_handle_reflists() PRODUCT_RETURN;
408
409 void clear_discovered_references(DiscoveredList& refs_list);
410 void abandon_partial_discovered_list(DiscoveredList& refs_list);
411
412 // Calculate the number of jni handles.
413 unsigned int count_jni_refs();
414
415 // Balances reference queues.
416 void balance_queues(DiscoveredList ref_lists[]);
417
418 // Update (advance) the soft ref master clock field.
419 void update_soft_ref_master_clock();
420
421 public:
422 // Default parameters give you a vanilla reference processor.
423 ReferenceProcessor(MemRegion span,
424 bool mt_processing = false, uint mt_processing_degree = 1,
425 bool mt_discovery = false, uint mt_discovery_degree = 1,
426 bool atomic_discovery = true,
427 BoolObjectClosure* is_alive_non_header = NULL,
428 bool discovered_list_needs_barrier = false);
429
430 // RefDiscoveryPolicy values
431 enum DiscoveryPolicy {
432 ReferenceBasedDiscovery = 0,
433 ReferentBasedDiscovery = 1,
434 DiscoveryPolicyMin = ReferenceBasedDiscovery,
435 DiscoveryPolicyMax = ReferentBasedDiscovery
436 };
437
438 static void init_statics();
439
440 public:
441 // get and set "is_alive_non_header" field
442 BoolObjectClosure* is_alive_non_header() {
443 return _is_alive_non_header;
444 }
445 void set_is_alive_non_header(BoolObjectClosure* is_alive_non_header) {
446 _is_alive_non_header = is_alive_non_header;
447 }
448
449 // get and set span
450 MemRegion span() { return _span; }
451 void set_span(MemRegion span) { _span = span; }
452
453 // start and stop weak ref discovery
454 void enable_discovery(bool verify_disabled, bool check_no_refs);
455 void disable_discovery() { _discovering_refs = false; }
456 bool discovery_enabled() { return _discovering_refs; }
457
458 // whether discovery is atomic wrt other collectors
459 bool discovery_is_atomic() const { return _discovery_is_atomic; }
460 void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; }
461
462 // whether the JDK in which we are embedded is a pre-4965777 JDK,
463 // and thus whether or not it uses the discovered field to chain
464 // the entries in the pending list.
465 static bool pending_list_uses_discovered_field() {
466 return _pending_list_uses_discovered_field;
467 }
468
469 // whether discovery is done by multiple threads same-old-timeously
470 bool discovery_is_mt() const { return _discovery_is_mt; }
471 void set_mt_discovery(bool mt) { _discovery_is_mt = mt; }
472
473 // Whether we are in a phase when _processing_ is MT.
474 bool processing_is_mt() const { return _processing_is_mt; }
475 void set_mt_processing(bool mt) { _processing_is_mt = mt; }
476
477 // whether all enqueueing of weak references is complete
478 bool enqueuing_is_done() { return _enqueuing_is_done; }
479 void set_enqueuing_is_done(bool v) { _enqueuing_is_done = v; }
480
481 // iterate over oops
482 void weak_oops_do(OopClosure* f); // weak roots
483
484 // Balance each of the discovered lists.
485 void balance_all_queues();
486 void verify_list(DiscoveredList& ref_list);
487
488 // Discover a Reference object, using appropriate discovery criteria
489 bool discover_reference(oop obj, ReferenceType rt);
490
491 // Process references found during GC (called by the garbage collector)
492 ReferenceProcessorStats
493 process_discovered_references(BoolObjectClosure* is_alive,
494 OopClosure* keep_alive,
495 VoidClosure* complete_gc,
496 AbstractRefProcTaskExecutor* task_executor,
497 GCTimer *gc_timer);
498
499 // Enqueue references at end of GC (called by the garbage collector)
500 bool enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor = NULL);
501
502 // If a discovery is in process that is being superceded, abandon it: all
503 // the discovered lists will be empty, and all the objects on them will
504 // have NULL discovered fields. Must be called only at a safepoint.
505 void abandon_partial_discovery();
506
507 // debugging
508 void verify_no_references_recorded() PRODUCT_RETURN;
509 void verify_referent(oop obj) PRODUCT_RETURN;
510
511 // clear the discovered lists (unlinking each entry).
512 void clear_discovered_references() PRODUCT_RETURN;
513 };
514
515 // A utility class to disable reference discovery in
516 // the scope which contains it, for given ReferenceProcessor.
517 class NoRefDiscovery: StackObj {
518 private:
519 ReferenceProcessor* _rp;
520 bool _was_discovering_refs;
521 public:
522 NoRefDiscovery(ReferenceProcessor* rp) : _rp(rp) {
523 _was_discovering_refs = _rp->discovery_enabled();
524 if (_was_discovering_refs) {
525 _rp->disable_discovery();
526 }
527 }
528
529 ~NoRefDiscovery() {
530 if (_was_discovering_refs) {
531 _rp->enable_discovery(true /*verify_disabled*/, false /*check_no_refs*/);
532 }
533 }
534 };
535
536
537 // A utility class to temporarily mutate the span of the
538 // given ReferenceProcessor in the scope that contains it.
539 class ReferenceProcessorSpanMutator: StackObj {
540 private:
541 ReferenceProcessor* _rp;
542 MemRegion _saved_span;
543
544 public:
545 ReferenceProcessorSpanMutator(ReferenceProcessor* rp,
546 MemRegion span):
547 _rp(rp) {
548 _saved_span = _rp->span();
549 _rp->set_span(span);
550 }
551
552 ~ReferenceProcessorSpanMutator() {
553 _rp->set_span(_saved_span);
554 }
555 };
556
557 // A utility class to temporarily change the MT'ness of
558 // reference discovery for the given ReferenceProcessor
559 // in the scope that contains it.
560 class ReferenceProcessorMTDiscoveryMutator: StackObj {
561 private:
562 ReferenceProcessor* _rp;
563 bool _saved_mt;
564
565 public:
566 ReferenceProcessorMTDiscoveryMutator(ReferenceProcessor* rp,
567 bool mt):
568 _rp(rp) {
569 _saved_mt = _rp->discovery_is_mt();
570 _rp->set_mt_discovery(mt);
571 }
572
573 ~ReferenceProcessorMTDiscoveryMutator() {
574 _rp->set_mt_discovery(_saved_mt);
575 }
576 };
577
578
579 // A utility class to temporarily change the disposition
580 // of the "is_alive_non_header" closure field of the
581 // given ReferenceProcessor in the scope that contains it.
582 class ReferenceProcessorIsAliveMutator: StackObj {
583 private:
584 ReferenceProcessor* _rp;
585 BoolObjectClosure* _saved_cl;
586
587 public:
588 ReferenceProcessorIsAliveMutator(ReferenceProcessor* rp,
589 BoolObjectClosure* cl):
590 _rp(rp) {
591 _saved_cl = _rp->is_alive_non_header();
592 _rp->set_is_alive_non_header(cl);
593 }
594
595 ~ReferenceProcessorIsAliveMutator() {
596 _rp->set_is_alive_non_header(_saved_cl);
597 }
598 };
599
600 // A utility class to temporarily change the disposition
601 // of the "discovery_is_atomic" field of the
602 // given ReferenceProcessor in the scope that contains it.
603 class ReferenceProcessorAtomicMutator: StackObj {
604 private:
605 ReferenceProcessor* _rp;
606 bool _saved_atomic_discovery;
607
608 public:
609 ReferenceProcessorAtomicMutator(ReferenceProcessor* rp,
610 bool atomic):
611 _rp(rp) {
612 _saved_atomic_discovery = _rp->discovery_is_atomic();
613 _rp->set_atomic_discovery(atomic);
614 }
615
616 ~ReferenceProcessorAtomicMutator() {
617 _rp->set_atomic_discovery(_saved_atomic_discovery);
618 }
619 };
620
621
622 // A utility class to temporarily change the MT processing
623 // disposition of the given ReferenceProcessor instance
624 // in the scope that contains it.
625 class ReferenceProcessorMTProcMutator: StackObj {
626 private:
627 ReferenceProcessor* _rp;
628 bool _saved_mt;
629
630 public:
631 ReferenceProcessorMTProcMutator(ReferenceProcessor* rp,
632 bool mt):
633 _rp(rp) {
634 _saved_mt = _rp->processing_is_mt();
635 _rp->set_mt_processing(mt);
636 }
637
638 ~ReferenceProcessorMTProcMutator() {
639 _rp->set_mt_processing(_saved_mt);
640 }
641 };
642
643
644 // This class is an interface used to implement task execution for the
645 // reference processing.
646 class AbstractRefProcTaskExecutor {
647 public:
648
649 // Abstract tasks to execute.
650 class ProcessTask;
651 class EnqueueTask;
652
653 // Executes a task using worker threads.
654 virtual void execute(ProcessTask& task) = 0;
655 virtual void execute(EnqueueTask& task) = 0;
656
657 // Switch to single threaded mode.
658 virtual void set_single_threaded_mode() { };
659 };
660
661 // Abstract reference processing task to execute.
662 class AbstractRefProcTaskExecutor::ProcessTask {
663 protected:
664 ProcessTask(ReferenceProcessor& ref_processor,
665 DiscoveredList refs_lists[],
666 bool marks_oops_alive)
667 : _ref_processor(ref_processor),
668 _refs_lists(refs_lists),
669 _marks_oops_alive(marks_oops_alive)
670 { }
671
672 public:
673 virtual void work(unsigned int work_id, BoolObjectClosure& is_alive,
674 OopClosure& keep_alive,
675 VoidClosure& complete_gc) = 0;
676
677 // Returns true if a task marks some oops as alive.
678 bool marks_oops_alive() const
679 { return _marks_oops_alive; }
680
681 protected:
682 ReferenceProcessor& _ref_processor;
683 DiscoveredList* _refs_lists;
684 const bool _marks_oops_alive;
685 };
686
687 // Abstract reference processing task to execute.
688 class AbstractRefProcTaskExecutor::EnqueueTask {
689 protected:
690 EnqueueTask(ReferenceProcessor& ref_processor,
691 DiscoveredList refs_lists[],
692 HeapWord* pending_list_addr,
693 int n_queues)
694 : _ref_processor(ref_processor),
695 _refs_lists(refs_lists),
696 _pending_list_addr(pending_list_addr),
697 _n_queues(n_queues)
698 { }
699
700 public:
701 virtual void work(unsigned int work_id) = 0;
702
703 protected:
704 ReferenceProcessor& _ref_processor;
705 DiscoveredList* _refs_lists;
706 HeapWord* _pending_list_addr;
707 int _n_queues;
708 };
709
710 #endif // SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP