1 /*
  2  * Copyright (c) 2015, 2021, Oracle and/or its affiliates. All rights reserved.
  3  * Copyright (c) 2020, 2021, Red Hat, Inc. and/or its affiliates.
  4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  5  *
  6  * This code is free software; you can redistribute it and/or modify it
  7  * under the terms of the GNU General Public License version 2 only, as
  8  * published by the Free Software Foundation.
  9  *
 10  * This code is distributed in the hope that it will be useful, but WITHOUT
 11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 13  * version 2 for more details (a copy is included in the LICENSE file that
 14  * accompanied this code).
 15  *
 16  * You should have received a copy of the GNU General Public License version
 17  * 2 along with this work; if not, write to the Free Software Foundation,
 18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 19  *
 20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 21  * or visit www.oracle.com if you need additional information or have any
 22  * questions.
 23  *
 24  */
 25 
 26 #include "precompiled.hpp"
 27 #include "classfile/javaClasses.hpp"
 28 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
 29 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
 30 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
 31 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
 32 #include "gc/shenandoah/shenandoahUtils.hpp"
 33 #include "runtime/atomic.hpp"
 34 #include "logging/log.hpp"
 35 
 36 static ReferenceType reference_type(oop reference) {
 37   return InstanceKlass::cast(reference->klass())->reference_type();
 38 }
 39 
 40 static const char* reference_type_name(ReferenceType type) {
 41   switch (type) {
 42     case REF_SOFT:
 43       return "Soft";
 44 
 45     case REF_WEAK:
 46       return "Weak";
 47 
 48     case REF_FINAL:
 49       return "Final";
 50 
 51     case REF_PHANTOM:
 52       return "Phantom";
 53 
 54     default:
 55       ShouldNotReachHere();
 56       return NULL;
 57   }
 58 }
 59 
 60 template <typename T>
 61 static void set_oop_field(T* field, oop value);
 62 
 63 template <>
 64 void set_oop_field<oop>(oop* field, oop value) {
 65   *field = value;
 66 }
 67 
 68 template <>
 69 void set_oop_field<narrowOop>(narrowOop* field, oop value) {
 70   *field = CompressedOops::encode(value);
 71 }
 72 
 73 static oop lrb(oop obj) {
 74   if (obj != NULL && ShenandoahHeap::heap()->marking_context()->is_marked(obj)) {
 75     return ShenandoahBarrierSet::barrier_set()->load_reference_barrier(obj);
 76   } else {
 77     return obj;
 78   }
 79 }
 80 
 81 template <typename T>
 82 static volatile T* reference_referent_addr(oop reference) {
 83   return (volatile T*)java_lang_ref_Reference::referent_addr_raw(reference);
 84 }
 85 
 86 template <typename T>
 87 static oop reference_referent(oop reference) {
 88   T heap_oop = Atomic::load(reference_referent_addr<T>(reference));
 89   return CompressedOops::decode(heap_oop);
 90 }
 91 
 92 static void reference_clear_referent(oop reference) {
 93   java_lang_ref_Reference::clear_referent(reference);
 94 }
 95 
 96 template <typename T>
 97 static T* reference_discovered_addr(oop reference) {
 98   return reinterpret_cast<T*>(java_lang_ref_Reference::discovered_addr_raw(reference));
 99 }
100 
101 template <typename T>
102 static oop reference_discovered(oop reference) {
103   T heap_oop = *reference_discovered_addr<T>(reference);
104   return lrb(CompressedOops::decode(heap_oop));
105 }
106 
107 template <typename T>
108 static void reference_set_discovered(oop reference, oop discovered);
109 
110 template <>
111 void reference_set_discovered<oop>(oop reference, oop discovered) {
112   *reference_discovered_addr<oop>(reference) = discovered;
113 }
114 
115 template <>
116 void reference_set_discovered<narrowOop>(oop reference, oop discovered) {
117   *reference_discovered_addr<narrowOop>(reference) = CompressedOops::encode(discovered);
118 }
119 
120 template<typename T>
121 static bool reference_cas_discovered(oop reference, oop discovered) {
122   T* addr = reinterpret_cast<T *>(java_lang_ref_Reference::discovered_addr_raw(reference));
123   return ShenandoahHeap::atomic_update_oop_check(discovered, addr, NULL);
124 }
125 
126 template <typename T>
127 static T* reference_next_addr(oop reference) {
128   return reinterpret_cast<T*>(java_lang_ref_Reference::next_addr_raw(reference));
129 }
130 
131 template <typename T>
132 static oop reference_next(oop reference) {
133   T heap_oop = RawAccess<>::oop_load(reference_next_addr<T>(reference));
134   return lrb(CompressedOops::decode(heap_oop));
135 }
136 
137 static void reference_set_next(oop reference, oop next) {
138   java_lang_ref_Reference::set_next_raw(reference, next);
139 }
140 
141 static void soft_reference_update_clock() {
142   const jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
143   java_lang_ref_SoftReference::set_clock(now);
144 }
145 
146 ShenandoahRefProcThreadLocal::ShenandoahRefProcThreadLocal() :
147   _discovered_list(NULL),
148   _encountered_count(),
149   _discovered_count(),
150   _enqueued_count() {
151 }
152 
153 void ShenandoahRefProcThreadLocal::reset() {
154   _discovered_list = NULL;
155   _mark_closure = NULL;
156   for (uint i = 0; i < reference_type_count; i++) {
157     _encountered_count[i] = 0;
158     _discovered_count[i] = 0;
159     _enqueued_count[i] = 0;
160   }
161 }
162 
163 template <typename T>
164 T* ShenandoahRefProcThreadLocal::discovered_list_addr() {
165   return reinterpret_cast<T*>(&_discovered_list);
166 }
167 
168 template <>
169 oop ShenandoahRefProcThreadLocal::discovered_list_head<oop>() const {
170   return *reinterpret_cast<const oop*>(&_discovered_list);
171 }
172 
173 template <>
174 oop ShenandoahRefProcThreadLocal::discovered_list_head<narrowOop>() const {
175   return CompressedOops::decode(*reinterpret_cast<const narrowOop*>(&_discovered_list));
176 }
177 
178 template <>
179 void ShenandoahRefProcThreadLocal::set_discovered_list_head<narrowOop>(oop head) {
180   *discovered_list_addr<narrowOop>() = CompressedOops::encode(head);
181 }
182 
183 template <>
184 void ShenandoahRefProcThreadLocal::set_discovered_list_head<oop>(oop head) {
185   *discovered_list_addr<oop>() = head;
186 }
187 
188 ShenandoahReferenceProcessor::ShenandoahReferenceProcessor(uint max_workers) :
189   _soft_reference_policy(NULL),
190   _ref_proc_thread_locals(NEW_C_HEAP_ARRAY(ShenandoahRefProcThreadLocal, max_workers, mtGC)),
191   _pending_list(NULL),
192   _pending_list_tail(&_pending_list),
193   _iterate_discovered_list_id(0U),
194   _stats() {
195   for (size_t i = 0; i < max_workers; i++) {
196     _ref_proc_thread_locals[i].reset();
197   }
198 }
199 
200 void ShenandoahReferenceProcessor::reset_thread_locals() {
201   uint max_workers = ShenandoahHeap::heap()->max_workers();
202   for (uint i = 0; i < max_workers; i++) {
203     _ref_proc_thread_locals[i].reset();
204   }
205 }
206 
207 void ShenandoahReferenceProcessor::set_mark_closure(uint worker_id, ShenandoahMarkRefsSuperClosure* mark_closure) {
208   _ref_proc_thread_locals[worker_id].set_mark_closure(mark_closure);
209 }
210 
211 void ShenandoahReferenceProcessor::set_soft_reference_policy(bool clear) {
212   static AlwaysClearPolicy always_clear_policy;
213   static LRUMaxHeapPolicy lru_max_heap_policy;
214 
215   if (clear) {
216     log_info(gc, ref)("Clearing All SoftReferences");
217     _soft_reference_policy = &always_clear_policy;
218   } else {
219     _soft_reference_policy = &lru_max_heap_policy;
220   }
221 
222   _soft_reference_policy->setup();
223 }
224 
225 template <typename T>
226 bool ShenandoahReferenceProcessor::is_inactive(oop reference, oop referent, ReferenceType type) const {
227   if (type == REF_FINAL) {
228     // A FinalReference is inactive if its next field is non-null. An application can't
229     // call enqueue() or clear() on a FinalReference.
230     return reference_next<T>(reference) != NULL;
231   } else {
232     // A non-FinalReference is inactive if the referent is null. The referent can only
233     // be null if the application called Reference.enqueue() or Reference.clear().
234     return referent == NULL;
235   }
236 }
237 
238 bool ShenandoahReferenceProcessor::is_strongly_live(oop referent) const {
239   return ShenandoahHeap::heap()->marking_context()->is_marked_strong(referent);
240 }
241 
242 bool ShenandoahReferenceProcessor::is_softly_live(oop reference, ReferenceType type) const {
243   if (type != REF_SOFT) {
244     // Not a SoftReference
245     return false;
246   }
247 
248   // Ask SoftReference policy
249   const jlong clock = java_lang_ref_SoftReference::clock();
250   assert(clock != 0, "Clock not initialized");
251   assert(_soft_reference_policy != NULL, "Policy not initialized");
252   return !_soft_reference_policy->should_clear_reference(reference, clock);
253 }
254 
255 template <typename T>
256 bool ShenandoahReferenceProcessor::should_discover(oop reference, ReferenceType type) const {
257   T* referent_addr = (T*) java_lang_ref_Reference::referent_addr_raw(reference);
258   T heap_oop = RawAccess<>::oop_load(referent_addr);
259   oop referent = CompressedOops::decode(heap_oop);
260   ShenandoahHeap* heap = ShenandoahHeap::heap();
261 
262   if (is_inactive<T>(reference, referent, type)) {
263     log_trace(gc,ref)("Reference inactive: " PTR_FORMAT, p2i(reference));
264     return false;
265   }
266 
267   if (is_strongly_live(referent)) {
268     log_trace(gc,ref)("Reference strongly live: " PTR_FORMAT, p2i(reference));
269     return false;
270   }
271 
272   if (is_softly_live(reference, type)) {
273     log_trace(gc,ref)("Reference softly live: " PTR_FORMAT, p2i(reference));
274     return false;
275   }
276 
277   if (!heap->is_in_active_generation(referent)) {
278     log_trace(gc,ref)("Referent outside of active generation: " PTR_FORMAT, p2i(referent));
279     return false;
280   }
281 
282   return true;
283 }
284 
285 template <typename T>
286 bool ShenandoahReferenceProcessor::should_drop(oop reference, ReferenceType type) const {
287   const oop referent = reference_referent<T>(reference);
288   if (referent == NULL) {
289     // Reference has been cleared, by a call to Reference.enqueue()
290     // or Reference.clear() from the application, which means we
291     // should drop the reference.
292     return true;
293   }
294 
295   // Check if the referent is still alive, in which case we should
296   // drop the reference.
297   if (type == REF_PHANTOM) {
298     return ShenandoahHeap::heap()->complete_marking_context()->is_marked(referent);
299   } else {
300     return ShenandoahHeap::heap()->complete_marking_context()->is_marked_strong(referent);
301   }
302 }
303 
304 template <typename T>
305 void ShenandoahReferenceProcessor::make_inactive(oop reference, ReferenceType type) const {
306   if (type == REF_FINAL) {
307     // Don't clear referent. It is needed by the Finalizer thread to make the call
308     // to finalize(). A FinalReference is instead made inactive by self-looping the
309     // next field. An application can't call FinalReference.enqueue(), so there is
310     // no race to worry about when setting the next field.
311     assert(reference_next<T>(reference) == NULL, "Already inactive");
312     assert(ShenandoahHeap::heap()->marking_context()->is_marked(reference_referent<T>(reference)), "only make inactive final refs with alive referents");
313     reference_set_next(reference, reference);
314   } else {
315     // Clear referent
316     reference_clear_referent(reference);
317   }
318 }
319 
320 template <typename T>
321 bool ShenandoahReferenceProcessor::discover(oop reference, ReferenceType type, uint worker_id) {
322   if (!should_discover<T>(reference, type)) {
323     // Not discovered
324     return false;
325   }
326 
327   if (reference_discovered<T>(reference) != NULL) {
328     // Already discovered. This can happen if the reference is marked finalizable first, and then strong,
329     // in which case it will be seen 2x by marking.
330     log_trace(gc,ref)("Reference already discovered: " PTR_FORMAT, p2i(reference));
331     return true;
332   }
333 
334   if (type == REF_FINAL) {
335     ShenandoahMarkRefsSuperClosure* cl = _ref_proc_thread_locals[worker_id].mark_closure();
336     bool weak = cl->is_weak();
337     cl->set_weak(true);
338     if (UseCompressedOops) {
339       cl->do_oop(reinterpret_cast<narrowOop*>(java_lang_ref_Reference::referent_addr_raw(reference)));
340     } else {
341       cl->do_oop(reinterpret_cast<oop*>(java_lang_ref_Reference::referent_addr_raw(reference)));
342     }
343     cl->set_weak(weak);
344   }
345 
346   // Add reference to discovered list
347   assert(worker_id != ShenandoahThreadLocalData::INVALID_WORKER_ID, "need valid worker ID");
348   ShenandoahRefProcThreadLocal& refproc_data = _ref_proc_thread_locals[worker_id];
349   oop discovered_head = refproc_data.discovered_list_head<T>();
350   if (discovered_head == NULL) {
351     // Self-loop tail of list. We distinguish discovered from not-discovered references by looking at their
352     // discovered field: if it is NULL, then it is not-yet discovered, otherwise it is discovered
353     discovered_head = reference;
354   }
355   if (reference_cas_discovered<T>(reference, discovered_head)) {
356     refproc_data.set_discovered_list_head<T>(reference);
357     assert(refproc_data.discovered_list_head<T>() == reference, "reference must be new discovered head");
358     log_trace(gc, ref)("Discovered Reference: " PTR_FORMAT " (%s)", p2i(reference), reference_type_name(type));
359     _ref_proc_thread_locals[worker_id].inc_discovered(type);
360   }
361   return true;
362 }
363 
364 bool ShenandoahReferenceProcessor::discover_reference(oop reference, ReferenceType type) {
365   if (!RegisterReferences) {
366     // Reference processing disabled
367     return false;
368   }
369 
370   log_trace(gc, ref)("Encountered Reference: " PTR_FORMAT " (%s, %s)",
371           p2i(reference), reference_type_name(type), affiliation_name(reference));
372   uint worker_id = ShenandoahThreadLocalData::worker_id(Thread::current());
373   _ref_proc_thread_locals->inc_encountered(type);
374 
375   if (UseCompressedOops) {
376     return discover<narrowOop>(reference, type, worker_id);
377   } else {
378     return discover<oop>(reference, type, worker_id);
379   }
380 }
381 
382 template <typename T>
383 oop ShenandoahReferenceProcessor::drop(oop reference, ReferenceType type) {
384   log_trace(gc, ref)("Dropped Reference: " PTR_FORMAT " (%s)", p2i(reference), reference_type_name(type));
385 
386   ShenandoahHeap* heap = ShenandoahHeap::heap();
387   oop referent = reference_referent<T>(reference);
388   assert(referent == NULL || heap->marking_context()->is_marked(referent), "only drop references with alive referents");
389 
390   // Unlink and return next in list
391   oop next = reference_discovered<T>(reference);
392   reference_set_discovered<T>(reference, NULL);
393   // When this reference was discovered, it would not have been marked. If it ends up surviving
394   // the cycle, we need to dirty the card if the reference is old and the referent is young.  Note
395   // that if the reference is not dropped, then its pointer to the referent will be nulled before
396   // evacuation begins so card does not need to be dirtied.
397   if (heap->mode()->is_generational() && heap->is_in_old(reference) && heap->is_in_young(referent)) {
398     // Note: would be sufficient to mark only the card that holds the start of this Reference object.
399     heap->card_scan()->mark_range_as_dirty(cast_from_oop<HeapWord*>(reference), reference->size());
400   }
401   return next;
402 }
403 
404 template <typename T>
405 T* ShenandoahReferenceProcessor::keep(oop reference, ReferenceType type, uint worker_id) {
406   log_trace(gc, ref)("Enqueued Reference: " PTR_FORMAT " (%s)", p2i(reference), reference_type_name(type));
407 
408   // Update statistics
409   _ref_proc_thread_locals[worker_id].inc_enqueued(type);
410 
411   // Make reference inactive
412   make_inactive<T>(reference, type);
413 
414   // Return next in list
415   return reference_discovered_addr<T>(reference);
416 }
417 
418 template <typename T>
419 void ShenandoahReferenceProcessor::process_references(ShenandoahRefProcThreadLocal& refproc_data, uint worker_id) {;
420   log_trace(gc, ref)("Processing discovered list #%u : " PTR_FORMAT, worker_id, p2i(refproc_data.discovered_list_head<T>()));
421   T* list = refproc_data.discovered_list_addr<T>();
422   // The list head is basically a GC root, we need to resolve and update it,
423   // otherwise we will later swap a from-space ref into Universe::pending_list().
424   if (!CompressedOops::is_null(*list)) {
425     oop first_resolved = lrb(CompressedOops::decode_not_null(*list));
426     set_oop_field(list, first_resolved);
427   }
428   T* p = list;
429   while (true) {
430     const oop reference = lrb(CompressedOops::decode(*p));
431     if (reference == NULL) {
432       break;
433     }
434     log_trace(gc, ref)("Processing reference: " PTR_FORMAT, p2i(reference));
435     const ReferenceType type = reference_type(reference);
436 
437     if (should_drop<T>(reference, type)) {
438       set_oop_field(p, drop<T>(reference, type));
439     } else {
440       p = keep<T>(reference, type, worker_id);
441     }
442 
443     const oop discovered = lrb(reference_discovered<T>(reference));
444     if (reference == discovered) {
445       // Reset terminating self-loop to NULL
446       reference_set_discovered<T>(reference, oop(NULL));
447       break;
448     }
449   }
450 
451   // Prepend discovered references to internal pending list
452   if (!CompressedOops::is_null(*list)) {
453     oop head = lrb(CompressedOops::decode_not_null(*list));
454     shenandoah_assert_not_in_cset_except(&head, head, ShenandoahHeap::heap()->cancelled_gc() || !ShenandoahLoadRefBarrier);
455     oop prev = Atomic::xchg(&_pending_list, head);
456     RawAccess<>::oop_store(p, prev);
457     if (prev == NULL) {
458       // First to prepend to list, record tail
459       _pending_list_tail = reinterpret_cast<void*>(p);
460     }
461 
462     // Clear discovered list
463     set_oop_field(list, oop(NULL));
464   }
465 }
466 
467 void ShenandoahReferenceProcessor::work() {
468   // Process discovered references
469   uint max_workers = ShenandoahHeap::heap()->max_workers();
470   uint worker_id = Atomic::add(&_iterate_discovered_list_id, 1U) - 1;
471   while (worker_id < max_workers) {
472     if (UseCompressedOops) {
473       process_references<narrowOop>(_ref_proc_thread_locals[worker_id], worker_id);
474     } else {
475       process_references<oop>(_ref_proc_thread_locals[worker_id], worker_id);
476     }
477     worker_id = Atomic::add(&_iterate_discovered_list_id, 1U) - 1;
478   }
479 }
480 
481 class ShenandoahReferenceProcessorTask : public AbstractGangTask {
482 private:
483   bool const                          _concurrent;
484   ShenandoahPhaseTimings::Phase const _phase;
485   ShenandoahReferenceProcessor* const _reference_processor;
486 
487 public:
488   ShenandoahReferenceProcessorTask(ShenandoahPhaseTimings::Phase phase, bool concurrent, ShenandoahReferenceProcessor* reference_processor) :
489     AbstractGangTask("ShenandoahReferenceProcessorTask"),
490     _concurrent(concurrent),
491     _phase(phase),
492     _reference_processor(reference_processor) {
493   }
494 
495   virtual void work(uint worker_id) {
496     if (_concurrent) {
497       ShenandoahConcurrentWorkerSession worker_session(worker_id);
498       ShenandoahWorkerTimingsTracker x(_phase, ShenandoahPhaseTimings::WeakRefProc, worker_id);
499       _reference_processor->work();
500     } else {
501       ShenandoahParallelWorkerSession worker_session(worker_id);
502       ShenandoahWorkerTimingsTracker x(_phase, ShenandoahPhaseTimings::WeakRefProc, worker_id);
503       _reference_processor->work();
504     }
505   }
506 };
507 
508 void ShenandoahReferenceProcessor::process_references(ShenandoahPhaseTimings::Phase phase, WorkGang* workers, bool concurrent) {
509 
510   Atomic::release_store_fence(&_iterate_discovered_list_id, 0U);
511 
512   // Process discovered lists
513   ShenandoahReferenceProcessorTask task(phase, concurrent, this);
514   workers->run_task(&task);
515 
516   // Update SoftReference clock
517   soft_reference_update_clock();
518 
519   // Collect, log and trace statistics
520   collect_statistics();
521 
522   enqueue_references(concurrent);
523 }
524 
525 void ShenandoahReferenceProcessor::enqueue_references_locked() {
526   // Prepend internal pending list to external pending list
527   shenandoah_assert_not_in_cset_except(&_pending_list, _pending_list, ShenandoahHeap::heap()->cancelled_gc() || !ShenandoahLoadRefBarrier);
528   if (UseCompressedOops) {
529     *reinterpret_cast<narrowOop*>(_pending_list_tail) = CompressedOops::encode(Universe::swap_reference_pending_list(_pending_list));
530   } else {
531     *reinterpret_cast<oop*>(_pending_list_tail) = Universe::swap_reference_pending_list(_pending_list);
532   }
533 }
534 
535 void ShenandoahReferenceProcessor::enqueue_references(bool concurrent) {
536   if (_pending_list == NULL) {
537     // Nothing to enqueue
538     return;
539   }
540 
541   if (!concurrent) {
542     // When called from mark-compact or degen-GC, the locking is done by the VMOperation,
543     enqueue_references_locked();
544   } else {
545     // Heap_lock protects external pending list
546     MonitorLocker ml(Heap_lock);
547 
548     enqueue_references_locked();
549 
550     // Notify ReferenceHandler thread
551     ml.notify_all();
552   }
553 
554   // Reset internal pending list
555   _pending_list = NULL;
556   _pending_list_tail = &_pending_list;
557 }
558 
559 template<typename T>
560 void ShenandoahReferenceProcessor::clean_discovered_list(T* list) {
561   T discovered = *list;
562   while (!CompressedOops::is_null(discovered)) {
563     oop discovered_ref = CompressedOops::decode_not_null(discovered);
564     set_oop_field<T>(list, oop(NULL));
565     list = reference_discovered_addr<T>(discovered_ref);
566     discovered = *list;
567   }
568 }
569 
570 void ShenandoahReferenceProcessor::abandon_partial_discovery() {
571   uint max_workers = ShenandoahHeap::heap()->max_workers();
572   for (uint index = 0; index < max_workers; index++) {
573     if (UseCompressedOops) {
574       clean_discovered_list<narrowOop>(_ref_proc_thread_locals[index].discovered_list_addr<narrowOop>());
575     } else {
576       clean_discovered_list<oop>(_ref_proc_thread_locals[index].discovered_list_addr<oop>());
577     }
578   }
579   if (_pending_list != NULL) {
580     oop pending = _pending_list;
581     _pending_list = NULL;
582     if (UseCompressedOops) {
583       narrowOop* list = reference_discovered_addr<narrowOop>(pending);
584       clean_discovered_list<narrowOop>(list);
585     } else {
586       oop* list = reference_discovered_addr<oop>(pending);
587       clean_discovered_list<oop>(list);
588     }
589   }
590   _pending_list_tail = &_pending_list;
591 }
592 
593 void ShenandoahReferenceProcessor::collect_statistics() {
594   Counters encountered = {};
595   Counters discovered = {};
596   Counters enqueued = {};
597   uint max_workers = ShenandoahHeap::heap()->max_workers();
598   for (uint i = 0; i < max_workers; i++) {
599     for (size_t type = 0; type < reference_type_count; type++) {
600       encountered[type] += _ref_proc_thread_locals[i].encountered((ReferenceType)type);
601       discovered[type] += _ref_proc_thread_locals[i].discovered((ReferenceType)type);
602       enqueued[type] += _ref_proc_thread_locals[i].enqueued((ReferenceType)type);
603     }
604   }
605 
606   _stats = ReferenceProcessorStats(discovered[REF_SOFT],
607                                    discovered[REF_WEAK],
608                                    discovered[REF_FINAL],
609                                    discovered[REF_PHANTOM]);
610 
611   log_info(gc,ref)("Encountered references: Soft: " SIZE_FORMAT ", Weak: " SIZE_FORMAT ", Final: " SIZE_FORMAT ", Phantom: " SIZE_FORMAT,
612                    encountered[REF_SOFT], encountered[REF_WEAK], encountered[REF_FINAL], encountered[REF_PHANTOM]);
613   log_info(gc,ref)("Discovered  references: Soft: " SIZE_FORMAT ", Weak: " SIZE_FORMAT ", Final: " SIZE_FORMAT ", Phantom: " SIZE_FORMAT,
614                    discovered[REF_SOFT], discovered[REF_WEAK], discovered[REF_FINAL], discovered[REF_PHANTOM]);
615   log_info(gc,ref)("Enqueued    references: Soft: " SIZE_FORMAT ", Weak: " SIZE_FORMAT ", Final: " SIZE_FORMAT ", Phantom: " SIZE_FORMAT,
616                    enqueued[REF_SOFT], enqueued[REF_WEAK], enqueued[REF_FINAL], enqueued[REF_PHANTOM]);
617 }
618