1 /*
2 * Copyright (c) 2014, 2021, Red Hat, Inc. All rights reserved.
3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
4 * Copyright (c) 2025, 2026, Oracle and/or its affiliates. All rights reserved.
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27
28 #include "compiler/oopMap.hpp"
29 #include "gc/shared/continuationGCSupport.hpp"
30 #include "gc/shared/fullGCForwarding.inline.hpp"
31 #include "gc/shared/gcTraceTime.inline.hpp"
32 #include "gc/shared/preservedMarks.inline.hpp"
33 #include "gc/shared/tlab_globals.hpp"
34 #include "gc/shared/workerThread.hpp"
35 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
36 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
37 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
38 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
39 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
40 #include "gc/shenandoah/shenandoahFreeSet.hpp"
41 #include "gc/shenandoah/shenandoahFullGC.hpp"
42 #include "gc/shenandoah/shenandoahGenerationalFullGC.hpp"
43 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
44 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
45 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
46 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
47 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
48 #include "gc/shenandoah/shenandoahMark.inline.hpp"
49 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
50 #include "gc/shenandoah/shenandoahMetrics.hpp"
51 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
52 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
53 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
54 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
55 #include "gc/shenandoah/shenandoahSTWMark.hpp"
56 #include "gc/shenandoah/shenandoahUtils.hpp"
57 #include "gc/shenandoah/shenandoahVerifier.hpp"
58 #include "gc/shenandoah/shenandoahVMOperations.hpp"
59 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
60 #include "memory/metaspaceUtils.hpp"
61 #include "memory/universe.hpp"
62 #include "oops/compressedOops.inline.hpp"
63 #include "oops/oop.inline.hpp"
64 #include "runtime/orderAccess.hpp"
65 #include "runtime/vmThread.hpp"
66 #include "utilities/copy.hpp"
67 #include "utilities/events.hpp"
68 #include "utilities/growableArray.hpp"
69
70 ShenandoahFullGC::ShenandoahFullGC() :
71 ShenandoahGC(ShenandoahHeap::heap()->global_generation()),
72 _gc_timer(ShenandoahHeap::heap()->gc_timer()),
73 _preserved_marks(new PreservedMarksSet(true)) {}
74
75 ShenandoahFullGC::~ShenandoahFullGC() {
76 delete _preserved_marks;
77 }
78
79 bool ShenandoahFullGC::collect(GCCause::Cause cause) {
80 vmop_entry_full(cause);
81 // Always success
82 return true;
83 }
84
85 void ShenandoahFullGC::vmop_entry_full(GCCause::Cause cause) {
86 ShenandoahHeap* const heap = ShenandoahHeap::heap();
87 TraceCollectorStats tcs(heap->monitoring_support()->full_stw_collection_counters());
88 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::full_gc_gross);
89
90 heap->try_inject_alloc_failure();
91 VM_ShenandoahFullGC op(cause, this);
92 VMThread::execute(&op);
93 }
94
95 void ShenandoahFullGC::entry_full(GCCause::Cause cause) {
96 static const char* msg = "Pause Full";
97 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::full_gc, true /* log_heap_usage */);
98 EventMark em("%s", msg);
99
100 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
101 ShenandoahWorkerPolicy::calc_workers_for_fullgc(),
102 "full gc");
103
104 op_full(cause);
105 }
106
107 void ShenandoahFullGC::op_full(GCCause::Cause cause) {
108 ShenandoahHeap* const heap = ShenandoahHeap::heap();
109
110 ShenandoahMetricsSnapshot metrics(heap->free_set());
111
112 // Perform full GC
113 do_it(cause);
114
115 if (heap->mode()->is_generational()) {
116 ShenandoahGenerationalFullGC::handle_completion(heap);
117 }
118
119 if (metrics.is_good_progress()) {
120 heap->notify_gc_progress();
121 } else {
122 // Nothing to do. Tell the allocation path that we have failed to make
123 // progress, and it can finally fail.
124 heap->notify_gc_no_progress();
125 }
126
127 // Regardless if progress was made, we record that we completed a "successful" full GC.
128 _generation->heuristics()->record_success_full();
129 heap->shenandoah_policy()->record_success_full();
130
131 {
132 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::full_gc_propagate_gc_state);
133 heap->propagate_gc_state_to_all_threads();
134 }
135 }
136
137 void ShenandoahFullGC::do_it(GCCause::Cause gc_cause) {
138 ShenandoahHeap* heap = ShenandoahHeap::heap();
139
140 // A full GC may be entered directly, or as an upgrade from a failed
141 // degenerated GC. In the latter case, self-forwarded objects may be
142 // present from the failed evacuation. Drain those marks before any phase
143 // (verify, update_roots, phase1_mark_heap) walks headers.
144 {
145 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_un_self_forward);
146 heap->un_self_forward_cset_regions();
147 }
148
149 if (heap->mode()->is_generational()) {
150 ShenandoahGenerationalFullGC::prepare();
151 }
152
153 if (ShenandoahVerify) {
154 heap->verifier()->verify_before_fullgc(_generation);
155 }
156
157 if (VerifyBeforeGC) {
158 Universe::verify();
159 }
160
161 // Degenerated GC may carry concurrent root flags when upgrading to
162 // full GC. We need to reset it before mutators resume.
163 heap->set_concurrent_strong_root_in_progress(false);
164 heap->set_concurrent_weak_root_in_progress(false);
165
166 heap->set_full_gc_in_progress(true);
167
168 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint");
169 assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped");
170
171 {
172 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdump_pre);
173 heap->pre_full_gc_dump(_gc_timer);
174 }
175
176 {
177 ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare);
178 // Full GC is supposed to recover from any GC state:
179
180 // a0. Remember if we have forwarded objects
181 bool has_forwarded_objects = heap->has_forwarded_objects();
182
183 // a1. Cancel evacuation, if in progress
184 if (heap->is_evacuation_in_progress()) {
185 heap->set_evacuation_in_progress(false);
186 }
187 assert(!heap->is_evacuation_in_progress(), "sanity");
188
189 // a2. Cancel update-refs, if in progress
190 if (heap->is_update_refs_in_progress()) {
191 heap->set_update_refs_in_progress(false);
192 }
193 assert(!heap->is_update_refs_in_progress(), "sanity");
194
195 // b. Cancel all concurrent marks, if in progress
196 if (heap->is_concurrent_mark_in_progress()) {
197 heap->cancel_concurrent_mark();
198 }
199 assert(!heap->is_concurrent_mark_in_progress(), "sanity");
200
201 // c. Update roots if this full GC is due to evac-oom, which may carry from-space pointers in roots.
202 if (has_forwarded_objects) {
203 update_roots(true /*full_gc*/);
204 }
205
206 // d. Abandon reference discovery and clear all discovered references.
207 ShenandoahReferenceProcessor* rp = _generation->ref_processor();
208 rp->abandon_partial_discovery();
209
210 // e. Sync pinned region status from the CP marks
211 heap->sync_pinned_region_status();
212
213 if (heap->mode()->is_generational()) {
214 ShenandoahGenerationalFullGC::restore_top_before_promote(heap);
215 }
216
217 // The rest of prologue:
218 _preserved_marks->init(heap->workers()->active_workers());
219
220 assert(heap->has_forwarded_objects() == has_forwarded_objects, "This should not change");
221 }
222
223 if (UseTLAB) {
224 // Note: PLABs are also retired with GCLABs in generational mode.
225 heap->gclabs_retire(ResizeTLAB);
226 heap->tlabs_retire(ResizeTLAB);
227 }
228
229 OrderAccess::fence();
230
231 phase1_mark_heap();
232
233 // Once marking is done, which may have fixed up forwarded objects, we can drop it.
234 // Coming out of Full GC, we would not have any forwarded objects.
235 // This also prevents resolves with fwdptr from kicking in while adjusting pointers in phase3.
236 heap->set_has_forwarded_objects(false);
237
238 heap->set_full_gc_move_in_progress(true);
239
240 // Setup workers for the rest
241 OrderAccess::fence();
242
243 // Initialize worker slices
244 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
245 for (uint i = 0; i < heap->max_workers(); i++) {
246 worker_slices[i] = new ShenandoahHeapRegionSet();
247 }
248
249 {
250 // The rest of code performs region moves, where region status is undefined
251 // until all phases run together.
252 ShenandoahHeapLocker lock(heap->lock());
253
254 FullGCForwarding::begin();
255
256 phase2_calculate_target_addresses(worker_slices);
257
258 OrderAccess::fence();
259
260 phase3_update_references();
261
262 phase4_compact_objects(worker_slices);
263
264 phase5_epilog();
265
266 FullGCForwarding::end();
267 }
268 heap->start_idle_span();
269
270 // Resize metaspace
271 MetaspaceGC::compute_new_size();
272
273 // Free worker slices
274 for (uint i = 0; i < heap->max_workers(); i++) {
275 delete worker_slices[i];
276 }
277 FREE_C_HEAP_ARRAY(worker_slices);
278
279 heap->set_full_gc_move_in_progress(false);
280 heap->set_full_gc_in_progress(false);
281
282 DEBUG_ONLY(heap->assert_no_self_forwards());
283
284 if (ShenandoahVerify) {
285 heap->verifier()->verify_after_fullgc(_generation);
286 }
287
288 if (VerifyAfterGC) {
289 Universe::verify();
290 }
291
292 {
293 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdump_post);
294 heap->post_full_gc_dump(_gc_timer);
295 }
296 }
297
298 void ShenandoahFullGC::phase1_mark_heap() {
299 GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer);
300 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
301
302 ShenandoahHeap* heap = ShenandoahHeap::heap();
303
304 _generation->reset_mark_bitmap<true, true>();
305 assert(heap->marking_context()->is_bitmap_clear(), "sanity");
306 assert(!_generation->is_mark_complete(), "sanity");
307
308 heap->set_unload_classes(_generation->heuristics()->can_unload_classes());
309
310 ShenandoahReferenceProcessor* rp = _generation->ref_processor();
311 // enable ("weak") refs discovery
312 rp->set_soft_reference_policy(true); // forcefully purge all soft references
313
314 ShenandoahSTWMark mark(_generation, true /*full_gc*/);
315 mark.mark();
316 heap->parallel_cleaning(_generation, true /* full_gc */);
317
318 if (ShenandoahHeap::heap()->mode()->is_generational()) {
319 ShenandoahGenerationalFullGC::log_live_in_old(heap);
320 }
321 }
322
323 class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
324 private:
325 PreservedMarks* const _preserved_marks;
326 ShenandoahHeap* const _heap;
327 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
328 int _empty_regions_pos;
329 ShenandoahHeapRegion* _to_region;
330 ShenandoahHeapRegion* _from_region;
331 HeapWord* _compact_point;
332
333 public:
334 ShenandoahPrepareForCompactionObjectClosure(PreservedMarks* preserved_marks,
335 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
336 ShenandoahHeapRegion* to_region) :
337 _preserved_marks(preserved_marks),
338 _heap(ShenandoahHeap::heap()),
339 _empty_regions(empty_regions),
340 _empty_regions_pos(0),
341 _to_region(to_region),
342 _from_region(nullptr),
343 _compact_point(to_region->bottom()) {}
344
345 void set_from_region(ShenandoahHeapRegion* from_region) {
346 _from_region = from_region;
347 }
348
349 void finish() {
350 assert(_to_region != nullptr, "should not happen");
351 _to_region->set_new_top(_compact_point);
352 }
353
354 bool is_compact_same_region() {
355 return _from_region == _to_region;
356 }
357
358 int empty_regions_pos() {
359 return _empty_regions_pos;
360 }
361
362 void do_object(oop p) override {
363 shenandoah_assert_mark_complete(cast_from_oop<HeapWord*>(p));
364 assert(_from_region != nullptr, "must set before work");
365 assert(_heap->global_generation()->is_mark_complete(), "marking must be finished");
366 assert(_heap->marking_context()->is_marked(p), "must be marked");
367 assert(!_heap->marking_context()->allocated_after_mark_start(p), "must be truly marked");
368
369 size_t old_size = p->size();
370 size_t new_size = p->copy_size(old_size, p->mark());
371 size_t obj_size = _compact_point == cast_from_oop<HeapWord*>(p) ? old_size : new_size;
372 if (_compact_point + obj_size > _to_region->end()) {
373 finish();
374
375 // Object doesn't fit. Pick next empty region and start compacting there.
376 ShenandoahHeapRegion* new_to_region;
377 if (_empty_regions_pos < _empty_regions.length()) {
378 new_to_region = _empty_regions.at(_empty_regions_pos);
379 _empty_regions_pos++;
380 } else {
381 // Out of empty region? Compact within the same region.
382 new_to_region = _from_region;
383 }
384
385 assert(new_to_region != _to_region, "must not reuse same to-region");
386 assert(new_to_region != nullptr, "must not be null");
387 _to_region = new_to_region;
388 _compact_point = _to_region->bottom();
389 obj_size = _compact_point == cast_from_oop<HeapWord*>(p) ? old_size : new_size;
390 }
391
392 // Object fits into current region, record new location, if object does not move:
393 assert(_compact_point + obj_size <= _to_region->end(), "must fit");
394 shenandoah_assert_not_forwarded(nullptr, p);
395 if (_compact_point != cast_from_oop<HeapWord*>(p)) {
396 _preserved_marks->push_if_necessary(p, p->mark());
397 FullGCForwarding::forward_to(p, cast_to_oop(_compact_point));
398 }
399 _compact_point += obj_size;
400 }
401 };
402
403 class ShenandoahPrepareForCompactionTask : public WorkerTask {
404 private:
405 PreservedMarksSet* const _preserved_marks;
406 ShenandoahHeap* const _heap;
407 ShenandoahHeapRegionSet** const _worker_slices;
408
409 public:
410 ShenandoahPrepareForCompactionTask(PreservedMarksSet *preserved_marks, ShenandoahHeapRegionSet **worker_slices) :
411 WorkerTask("Shenandoah Prepare For Compaction"),
412 _preserved_marks(preserved_marks),
413 _heap(ShenandoahHeap::heap()), _worker_slices(worker_slices) {
414 }
415
416 static bool is_candidate_region(ShenandoahHeapRegion* r) {
417 // Empty region: get it into the slice to defragment the slice itself.
418 // We could have skipped this without violating correctness, but we really
419 // want to compact all live regions to the start of the heap, which sometimes
420 // means moving them into the fully empty regions.
421 if (r->is_empty()) return true;
422
423 // Can move the region, and this is not the humongous region. Humongous
424 // moves are special cased here, because their moves are handled separately.
425 return r->is_stw_move_allowed() && !r->is_humongous();
426 }
427
428 void work(uint worker_id) override;
429 private:
430 template<typename ClosureType>
431 void prepare_for_compaction(ClosureType& cl,
432 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
433 ShenandoahHeapRegionSetIterator& it,
434 ShenandoahHeapRegion* from_region);
435 };
436
437 void ShenandoahPrepareForCompactionTask::work(uint worker_id) {
438 ShenandoahParallelWorkerSession worker_session(worker_id);
439 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
440 ShenandoahHeapRegionSetIterator it(slice);
441 ShenandoahHeapRegion* from_region = it.next();
442 // No work?
443 if (from_region == nullptr) {
444 return;
445 }
446
447 // Sliding compaction. Walk all regions in the slice, and compact them.
448 // Remember empty regions and reuse them as needed.
449 ResourceMark rm;
450
451 GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions());
452
453 if (_heap->mode()->is_generational()) {
454 ShenandoahPrepareForGenerationalCompactionObjectClosure cl(_preserved_marks->get(worker_id),
455 empty_regions, from_region, worker_id);
456 prepare_for_compaction(cl, empty_regions, it, from_region);
457 } else {
458 ShenandoahPrepareForCompactionObjectClosure cl(_preserved_marks->get(worker_id), empty_regions, from_region);
459 prepare_for_compaction(cl, empty_regions, it, from_region);
460 }
461 }
462
463 template<typename ClosureType>
464 void ShenandoahPrepareForCompactionTask::prepare_for_compaction(ClosureType& cl,
465 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
466 ShenandoahHeapRegionSetIterator& it,
467 ShenandoahHeapRegion* from_region) {
468 while (from_region != nullptr) {
469 assert(is_candidate_region(from_region), "Sanity");
470 cl.set_from_region(from_region);
471 if (from_region->has_live()) {
472 _heap->marked_object_iterate(from_region, &cl);
473 }
474
475 // Compacted the region to somewhere else? From-region is empty then.
476 if (!cl.is_compact_same_region()) {
477 empty_regions.append(from_region);
478 }
479 from_region = it.next();
480 }
481 cl.finish();
482
483 // Mark all remaining regions as empty
484 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
485 ShenandoahHeapRegion* r = empty_regions.at(pos);
486 r->set_new_top(r->bottom());
487 }
488 }
489
490 void ShenandoahFullGC::calculate_target_humongous_objects() {
491 ShenandoahHeap* heap = ShenandoahHeap::heap();
492
493 // Compute the new addresses for humongous objects. We need to do this after addresses
494 // for regular objects are calculated, and we know what regions in heap suffix are
495 // available for humongous moves.
496 //
497 // Scan the heap backwards, because we are compacting humongous regions towards the end.
498 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
499 // humongous start there.
500 //
501 // The complication is potential non-movable regions during the scan. If such region is
502 // detected, then sliding restarts towards that non-movable region.
503
504 size_t to_begin = heap->num_regions();
505 size_t to_end = heap->num_regions();
506
507 log_debug(gc)("Full GC calculating target humongous objects from end %zu", to_end);
508 for (size_t c = heap->num_regions(); c > 0; c--) {
509 ShenandoahHeapRegion *r = heap->get_region(c - 1);
510 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
511 // To-region candidate: record this, and continue scan
512 to_begin = r->index();
513 continue;
514 }
515
516 if (r->is_humongous_start() && r->is_stw_move_allowed()) {
517 // From-region candidate: movable humongous region
518 oop old_obj = cast_to_oop(r->bottom());
519 size_t new_words_size = old_obj->copy_size(old_obj->size(), old_obj->mark());
520 size_t num_regions = ShenandoahHeapRegion::required_regions(new_words_size * HeapWordSize);
521
522 // Test the fit before computing the slide target. With compact object headers
523 // the expanded size can require one region more than the object currently
524 // occupies, so num_regions may exceed the available window. Comparing against
525 // the window size (to_end - to_begin) avoids the unsigned underflow that
526 // "to_end - num_regions" would suffer when the object does not fit.
527 if (num_regions <= to_end - to_begin) {
528 size_t start = to_end - num_regions;
529 if (start != r->index()) {
530 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
531 _preserved_marks->get(0)->push_if_necessary(old_obj, old_obj->mark());
532 FullGCForwarding::forward_to(old_obj, cast_to_oop(heap->get_region(start)->bottom()));
533 to_end = start;
534 continue;
535 }
536 }
537 }
538
539 // Failed to fit. Scan starting from current region.
540 to_begin = r->index();
541 to_end = r->index();
542 }
543 }
544
545 class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
546 public:
547 void heap_region_do(ShenandoahHeapRegion* r) override {
548 if (r->is_trash()) {
549 r->try_recycle_under_lock();
550 // No need to adjust_interval_for_recycled_old_region. That will be taken care of during freeset rebuild.
551 }
552 if (r->is_cset()) {
553 // Leave affiliation unchanged
554 r->make_regular_bypass();
555 }
556 if (r->is_empty_uncommitted()) {
557 r->make_committed_bypass();
558 }
559 assert (r->is_committed(), "only committed regions in heap now, see region %zu", r->index());
560
561 // Record current region occupancy: this communicates empty regions are free
562 // to the rest of Full GC code.
563 r->set_new_top(r->top());
564 }
565 };
566
567 class ShenandoahTrashImmediateGarbageClosure: public ShenandoahHeapRegionClosure {
568 private:
569 ShenandoahHeap* const _heap;
570 ShenandoahMarkingContext* const _ctx;
571
572 public:
573 ShenandoahTrashImmediateGarbageClosure() :
574 _heap(ShenandoahHeap::heap()),
575 _ctx(ShenandoahHeap::heap()->global_generation()->complete_marking_context()) {}
576
577 void heap_region_do(ShenandoahHeapRegion* r) override {
578 if (r->is_humongous_start()) {
579 oop humongous_obj = cast_to_oop(r->bottom());
580 if (!_ctx->is_marked(humongous_obj)) {
581 assert(!r->has_live(), "Region %zu is not marked, should not have live", r->index());
582 _heap->trash_humongous_region_at(r);
583 } else {
584 assert(r->has_live(), "Region %zu should have live", r->index());
585 }
586 } else if (r->is_humongous_continuation()) {
587 // If we hit continuation, the non-live humongous starts should have been trashed already
588 assert(r->humongous_start_region()->has_live(), "Region %zu should have live", r->index());
589 } else if (r->is_regular()) {
590 if (!r->has_live()) {
591 r->make_trash_immediate();
592 }
593 }
594 }
595 };
596
597 void ShenandoahFullGC::distribute_slices(ShenandoahHeapRegionSet** worker_slices) {
598 ShenandoahHeap* heap = ShenandoahHeap::heap();
599
600 uint n_workers = heap->workers()->active_workers();
601 size_t n_regions = heap->num_regions();
602
603 // What we want to accomplish: have the dense prefix of data, while still balancing
604 // out the parallel work.
605 //
606 // Assuming the amount of work is driven by the live data that needs moving, we can slice
607 // the entire heap into equal-live-sized prefix slices, and compact into them. So, each
608 // thread takes all regions in its prefix subset, and then it takes some regions from
609 // the tail.
610 //
611 // Tail region selection becomes interesting.
612 //
613 // First, we want to distribute the regions fairly between the workers, and those regions
614 // might have different amount of live data. So, until we sure no workers need live data,
615 // we need to only take what the worker needs.
616 //
617 // Second, since we slide everything to the left in each slice, the most busy regions
618 // would be the ones on the left. Which means we want to have all workers have their after-tail
619 // regions as close to the left as possible.
620 //
621 // The easiest way to do this is to distribute after-tail regions in round-robin between
622 // workers that still need live data.
623 //
624 // Consider parallel workers A, B, C, then the target slice layout would be:
625 //
626 // AAAAAAAABBBBBBBBCCCCCCCC|ABCABCABCABCABCABCABCABABABABABABABABABABAAAAA
627 //
628 // (.....dense-prefix.....) (.....................tail...................)
629 // [all regions fully live] [left-most regions are fuller that right-most]
630 //
631
632 // Compute how much live data is there. This would approximate the size of dense prefix
633 // we target to create.
634 size_t total_live = 0;
635 for (size_t idx = 0; idx < n_regions; idx++) {
636 ShenandoahHeapRegion *r = heap->get_region(idx);
637 if (ShenandoahPrepareForCompactionTask::is_candidate_region(r)) {
638 total_live += r->get_live_data_words();
639 }
640 }
641
642 // Estimate the size for the dense prefix. Note that we specifically count only the
643 // "full" regions, so there would be some non-full regions in the slice tail.
644 size_t live_per_worker = total_live / n_workers;
645 size_t prefix_regions_per_worker = live_per_worker / ShenandoahHeapRegion::region_size_words();
646 size_t prefix_regions_total = prefix_regions_per_worker * n_workers;
647 prefix_regions_total = MIN2(prefix_regions_total, n_regions);
648 assert(prefix_regions_total <= n_regions, "Sanity");
649
650 // There might be non-candidate regions in the prefix. To compute where the tail actually
651 // ends up being, we need to account those as well.
652 size_t prefix_end = prefix_regions_total;
653 for (size_t idx = 0; idx < prefix_regions_total; idx++) {
654 ShenandoahHeapRegion *r = heap->get_region(idx);
655 if (!ShenandoahPrepareForCompactionTask::is_candidate_region(r)) {
656 prefix_end++;
657 }
658 }
659 prefix_end = MIN2(prefix_end, n_regions);
660 assert(prefix_end <= n_regions, "Sanity");
661
662 // Distribute prefix regions per worker: each thread definitely gets its own same-sized
663 // subset of dense prefix.
664 size_t prefix_idx = 0;
665
666 size_t* live = NEW_C_HEAP_ARRAY(size_t, n_workers, mtGC);
667
668 for (size_t wid = 0; wid < n_workers; wid++) {
669 ShenandoahHeapRegionSet* slice = worker_slices[wid];
670
671 live[wid] = 0;
672 size_t regs = 0;
673
674 // Add all prefix regions for this worker
675 while (prefix_idx < prefix_end && regs < prefix_regions_per_worker) {
676 ShenandoahHeapRegion *r = heap->get_region(prefix_idx);
677 if (ShenandoahPrepareForCompactionTask::is_candidate_region(r)) {
678 slice->add_region(r);
679 live[wid] += r->get_live_data_words();
680 regs++;
681 }
682 prefix_idx++;
683 }
684 }
685
686 // Distribute the tail among workers in round-robin fashion.
687 size_t wid = n_workers - 1;
688
689 for (size_t tail_idx = prefix_end; tail_idx < n_regions; tail_idx++) {
690 ShenandoahHeapRegion *r = heap->get_region(tail_idx);
691 if (ShenandoahPrepareForCompactionTask::is_candidate_region(r)) {
692 assert(wid < n_workers, "Sanity");
693
694 size_t live_region = r->get_live_data_words();
695
696 // Select next worker that still needs live data.
697 size_t old_wid = wid;
698 do {
699 wid++;
700 if (wid == n_workers) wid = 0;
701 } while (live[wid] + live_region >= live_per_worker && old_wid != wid);
702
703 if (old_wid == wid) {
704 // Circled back to the same worker? This means liveness data was
705 // miscalculated. Bump the live_per_worker limit so that
706 // everyone gets a piece of the leftover work.
707 live_per_worker += ShenandoahHeapRegion::region_size_words();
708 }
709
710 worker_slices[wid]->add_region(r);
711 live[wid] += live_region;
712 }
713 }
714
715 FREE_C_HEAP_ARRAY(live);
716
717 #ifdef ASSERT
718 ResourceBitMap map(n_regions);
719 for (size_t wid = 0; wid < n_workers; wid++) {
720 ShenandoahHeapRegionSetIterator it(worker_slices[wid]);
721 ShenandoahHeapRegion* r = it.next();
722 while (r != nullptr) {
723 size_t idx = r->index();
724 assert(ShenandoahPrepareForCompactionTask::is_candidate_region(r), "Sanity: %zu", idx);
725 assert(!map.at(idx), "No region distributed twice: %zu", idx);
726 map.at_put(idx, true);
727 r = it.next();
728 }
729 }
730
731 for (size_t rid = 0; rid < n_regions; rid++) {
732 bool is_candidate = ShenandoahPrepareForCompactionTask::is_candidate_region(heap->get_region(rid));
733 bool is_distributed = map.at(rid);
734 assert(is_distributed || !is_candidate, "All candidates are distributed: %zu", rid);
735 }
736 #endif
737 }
738
739 void ShenandoahFullGC::phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices) {
740 GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer);
741 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
742
743 ShenandoahHeap* heap = ShenandoahHeap::heap();
744
745 // About to figure out which regions can be compacted, make sure pinning status
746 // had been updated in GC prologue.
747 heap->assert_pinned_region_status();
748
749 {
750 // Trash the immediately collectible regions before computing addresses
751 ShenandoahTrashImmediateGarbageClosure trash_immediate_garbage;
752 ShenandoahExcludeRegionClosure<FREE> cl(&trash_immediate_garbage);
753 heap->heap_region_iterate(&cl);
754
755 // Make sure regions are in good state: committed, active, clean.
756 // This is needed because we are potentially sliding the data through them.
757 ShenandoahEnsureHeapActiveClosure ecl;
758 heap->heap_region_iterate(&ecl);
759 }
760
761 // Compute the new addresses for regular objects
762 {
763 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
764
765 distribute_slices(worker_slices);
766
767 ShenandoahPrepareForCompactionTask task(_preserved_marks, worker_slices);
768 heap->workers()->run_task(&task);
769 }
770
771 // Compute the new addresses for humongous objects
772 {
773 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
774 calculate_target_humongous_objects();
775 }
776 }
777
778 class ShenandoahAdjustPointersClosure : public MetadataVisitingOopIterateClosure {
779 private:
780 ShenandoahMarkingContext* const _ctx;
781
782 template <class T>
783 inline void do_oop_work(T* p) {
784 T o = RawAccess<>::oop_load(p);
785 if (!CompressedOops::is_null(o)) {
786 oop obj = CompressedOops::decode_not_null(o);
787 assert(_ctx->is_marked(obj), "must be marked");
788 if (FullGCForwarding::is_forwarded(obj)) {
789 oop forw = FullGCForwarding::forwardee(obj);
790 RawAccess<IS_NOT_NULL>::oop_store(p, forw);
791 }
792 }
793 }
794
795 public:
796 ShenandoahAdjustPointersClosure() :
797 _ctx(ShenandoahHeap::heap()->global_generation()->complete_marking_context()) {}
798
799 void do_oop(oop* p) { do_oop_work(p); }
800 void do_oop(narrowOop* p) { do_oop_work(p); }
801 void do_method(Method* m) {}
802 void do_nmethod(nmethod* nm) {}
803 };
804
805 class ShenandoahAdjustPointersObjectClosure : public ObjectClosure {
806 private:
807 ShenandoahAdjustPointersClosure _cl;
808
809 public:
810 void do_object(oop p) override {
811 assert(ShenandoahHeap::heap()->global_generation()->is_mark_complete(), "marking must be complete");
812 assert(ShenandoahHeap::heap()->marking_context()->is_marked(p), "must be marked");
813 p->oop_iterate(&_cl);
814 }
815 };
816
817 class ShenandoahAdjustPointersTask : public WorkerTask {
818 private:
819 ShenandoahHeap* const _heap;
820 ShenandoahRegionIterator _regions;
821
822 public:
823 ShenandoahAdjustPointersTask() :
824 WorkerTask("Shenandoah Adjust Pointers"),
825 _heap(ShenandoahHeap::heap()) {
826 }
827
828 void work(uint worker_id) override {
829 ShenandoahParallelWorkerSession worker_session(worker_id);
830 ShenandoahAdjustPointersObjectClosure obj_cl;
831 ShenandoahHeapRegion* r = _regions.next();
832 while (r != nullptr) {
833 if (!r->is_humongous_continuation() && r->has_live()) {
834 _heap->marked_object_iterate(r, &obj_cl);
835 }
836 if (_heap->mode()->is_generational()) {
837 ShenandoahGenerationalFullGC::maybe_coalesce_and_fill_region(r);
838 }
839 r = _regions.next();
840 }
841 }
842 };
843
844 class ShenandoahAdjustRootPointersTask : public WorkerTask {
845 private:
846 ShenandoahRootAdjuster* _rp;
847 PreservedMarksSet* _preserved_marks;
848 public:
849 ShenandoahAdjustRootPointersTask(ShenandoahRootAdjuster* rp, PreservedMarksSet* preserved_marks) :
850 WorkerTask("Shenandoah Adjust Root Pointers"),
851 _rp(rp),
852 _preserved_marks(preserved_marks) {}
853
854 void work(uint worker_id) override {
855 ShenandoahParallelWorkerSession worker_session(worker_id);
856 ShenandoahAdjustPointersClosure cl;
857 _rp->roots_do(worker_id, &cl);
858 _preserved_marks->get(worker_id)->adjust_during_full_gc();
859 }
860 };
861
862 void ShenandoahFullGC::phase3_update_references() {
863 GCTraceTime(Info, gc, phases) time("Phase 3: Adjust pointers", _gc_timer);
864 ShenandoahGCPhase adjust_pointer_phase(ShenandoahPhaseTimings::full_gc_adjust_pointers);
865
866 ShenandoahHeap* heap = ShenandoahHeap::heap();
867
868 WorkerThreads* workers = heap->workers();
869 uint nworkers = workers->active_workers();
870 {
871 #ifdef COMPILER2
872 DerivedPointerTable::clear();
873 #endif // COMPILER2
874 ShenandoahRootAdjuster rp(nworkers, ShenandoahPhaseTimings::full_gc_adjust_roots);
875 ShenandoahAdjustRootPointersTask task(&rp, _preserved_marks);
876 workers->run_task(&task);
877 #ifdef COMPILER2
878 DerivedPointerTable::update_pointers();
879 #endif // COMPILER2
880 }
881
882 ShenandoahAdjustPointersTask adjust_pointers_task;
883 workers->run_task(&adjust_pointers_task);
884 }
885
886 class ShenandoahCompactObjectsClosure : public ObjectClosure {
887 private:
888 uint const _worker_id;
889
890 public:
891 explicit ShenandoahCompactObjectsClosure(uint worker_id) :
892 _worker_id(worker_id) {}
893
894 void do_object(oop p) override {
895 assert(ShenandoahHeap::heap()->global_generation()->is_mark_complete(), "marking must be finished");
896 assert(ShenandoahHeap::heap()->marking_context()->is_marked(p), "must be marked");
897 size_t size = p->size();
898 if (FullGCForwarding::is_forwarded(p)) {
899 HeapWord* compact_from = cast_from_oop<HeapWord*>(p);
900 HeapWord* compact_to = cast_from_oop<HeapWord*>(FullGCForwarding::forwardee(p));
901 assert(compact_from != compact_to, "Forwarded object should move");
902 Copy::aligned_conjoint_words(compact_from, compact_to, size);
903 oop new_obj = cast_to_oop(compact_to);
904
905 // Restore the mark word before relativizing the stack chunk. The copy's
906 // mark word contains the full GC forwarding encoding, which would cause
907 // is_stackChunk() to read garbage (especially with compact headers).
908 new_obj->reinit_mark();
909 new_obj->initialize_hash_if_necessary(p);
910 ContinuationGCSupport::relativize_stack_chunk(new_obj);
911 }
912 }
913 };
914
915 class ShenandoahCompactObjectsTask : public WorkerTask {
916 private:
917 ShenandoahHeap* const _heap;
918 ShenandoahHeapRegionSet** const _worker_slices;
919
920 public:
921 ShenandoahCompactObjectsTask(ShenandoahHeapRegionSet** worker_slices) :
922 WorkerTask("Shenandoah Compact Objects"),
923 _heap(ShenandoahHeap::heap()),
924 _worker_slices(worker_slices) {
925 }
926
927 void work(uint worker_id) override {
928 ShenandoahParallelWorkerSession worker_session(worker_id);
929 ShenandoahHeapRegionSetIterator slice(_worker_slices[worker_id]);
930
931 ShenandoahCompactObjectsClosure cl(worker_id);
932 ShenandoahHeapRegion* r = slice.next();
933 while (r != nullptr) {
934 assert(!r->is_humongous(), "must not get humongous regions here");
935 if (r->has_live()) {
936 _heap->marked_object_iterate(r, &cl);
937 }
938 r->set_top(r->new_top());
939 r = slice.next();
940 }
941 }
942 };
943
944 class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
945 private:
946 ShenandoahHeap* const _heap;
947 bool _is_generational;
948 size_t _young_regions, _young_usage, _young_humongous_waste;
949 size_t _old_regions, _old_usage, _old_humongous_waste;
950
951 public:
952 ShenandoahPostCompactClosure() : _heap(ShenandoahHeap::heap()),
953 _is_generational(_heap->mode()->is_generational()),
954 _young_regions(0),
955 _young_usage(0),
956 _young_humongous_waste(0),
957 _old_regions(0),
958 _old_usage(0),
959 _old_humongous_waste(0)
960 {
961 _heap->free_set()->clear();
962 }
963
964 void heap_region_do(ShenandoahHeapRegion* r) override {
965 assert (!r->is_cset(), "cset regions should have been demoted already");
966
967 // Need to reset the complete-top-at-mark-start pointer here because
968 // the complete marking bitmap is no longer valid. This ensures
969 // size-based iteration in marked_object_iterate().
970 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
971 // pinned regions.
972 if (!r->is_pinned()) {
973 _heap->marking_context()->reset_top_at_mark_start(r);
974 }
975
976 size_t live = r->used();
977
978 // Make empty regions that have been allocated into regular
979 if (r->is_empty() && live > 0) {
980 if (!_is_generational) {
981 r->make_affiliated_maybe();
982 }
983 // else, generational mode compaction has already established affiliation.
984 r->make_regular_bypass();
985 if (ZapUnusedHeapArea) {
986 SpaceMangler::mangle_region(MemRegion(r->top(), r->end()));
987 }
988 }
989
990 // Reclaim regular regions that became empty
991 if (r->is_regular() && live == 0) {
992 r->make_trash();
993 }
994
995 // Recycle all trash regions
996 if (r->is_trash()) {
997 live = 0;
998 r->try_recycle_under_lock();
999 // No need to adjust_interval_for_recycled_old_region. That will be taken care of during freeset rebuild.
1000 } else {
1001 if (r->is_old()) {
1002 ShenandoahGenerationalFullGC::account_for_region(r, _old_regions, _old_usage, _old_humongous_waste);
1003 } else if (r->is_young()) {
1004 ShenandoahGenerationalFullGC::account_for_region(r, _young_regions, _young_usage, _young_humongous_waste);
1005 }
1006 }
1007 r->set_live_data(live);
1008 r->reset_alloc_metadata();
1009 }
1010 };
1011
1012 void ShenandoahFullGC::compact_humongous_objects() {
1013 // Compact humongous regions, based on their fwdptr objects.
1014 //
1015 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
1016 // humongous regions are already compacted, and do not require further moves, which alleviates
1017 // sliding costs. We may consider doing this in parallel in the future.
1018
1019 ShenandoahHeap* heap = ShenandoahHeap::heap();
1020
1021 for (size_t c = heap->num_regions(); c > 0; c--) {
1022 ShenandoahHeapRegion* r = heap->get_region(c - 1);
1023 if (r->is_humongous_start()) {
1024 oop old_obj = cast_to_oop(r->bottom());
1025 if (!FullGCForwarding::is_forwarded(old_obj)) {
1026 // No need to move the object, it stays at the same slot
1027 continue;
1028 }
1029 size_t old_words_size = old_obj->size();
1030 size_t new_words_size = old_obj->copy_size(old_words_size, old_obj->mark());
1031 size_t old_num_regions = ShenandoahHeapRegion::required_regions(old_words_size * HeapWordSize);
1032 size_t new_num_regions = ShenandoahHeapRegion::required_regions(new_words_size * HeapWordSize);
1033
1034 size_t old_start = r->index();
1035 size_t old_end = old_start + old_num_regions - 1;
1036 size_t new_start = heap->heap_region_index_containing(FullGCForwarding::forwardee(old_obj));
1037 size_t new_end = new_start + new_num_regions - 1;
1038 assert(old_start != new_start, "must be real move");
1039 assert(r->is_stw_move_allowed(), "Region %zu should be movable", r->index());
1040
1041 log_debug(gc)("Full GC compaction moves humongous object from region %zu to region %zu", old_start, new_start);
1042 Copy::aligned_conjoint_words(r->bottom(), heap->get_region(new_start)->bottom(), old_words_size);
1043 ContinuationGCSupport::relativize_stack_chunk(cast_to_oop<HeapWord*>(r->bottom()));
1044
1045 oop new_obj = cast_to_oop(heap->get_region(new_start)->bottom());
1046 new_obj->reinit_mark();
1047 new_obj->initialize_hash_if_necessary(old_obj);
1048
1049 {
1050 ShenandoahAffiliation original_affiliation = r->affiliation();
1051 for (size_t c = old_start; c <= old_end; c++) {
1052 ShenandoahHeapRegion* r = heap->get_region(c);
1053 // Leave humongous region affiliation unchanged.
1054 r->make_regular_bypass();
1055 r->set_top(r->bottom());
1056 }
1057
1058 for (size_t c = new_start; c <= new_end; c++) {
1059 ShenandoahHeapRegion* r = heap->get_region(c);
1060 if (c == new_start) {
1061 r->make_humongous_start_bypass(original_affiliation);
1062 } else {
1063 r->make_humongous_cont_bypass(original_affiliation);
1064 }
1065
1066 // Trailing region may be non-full, record the remainder there
1067 size_t remainder = new_words_size & ShenandoahHeapRegion::region_size_words_mask();
1068 if ((c == new_end) && (remainder != 0)) {
1069 r->set_top(r->bottom() + remainder);
1070 } else {
1071 r->set_top(r->end());
1072 }
1073
1074 r->reset_alloc_metadata();
1075 }
1076 }
1077 }
1078 }
1079 }
1080
1081 // This is slightly different to ShHeap::reset_next_mark_bitmap:
1082 // we need to remain able to walk pinned regions.
1083 // Since pinned region do not move and don't get compacted, we will get holes with
1084 // unreachable objects in them (which may have pointers to unloaded Klasses and thus
1085 // cannot be iterated over using oop->size()). The only way to safely iterate over those is using
1086 // a valid marking bitmap and valid TAMS pointer. This class only resets marking
1087 // bitmaps for un-pinned regions, and later we only reset TAMS for unpinned regions.
1088 class ShenandoahMCResetCompleteBitmapTask : public WorkerTask {
1089 private:
1090 ShenandoahRegionIterator _regions;
1091
1092 public:
1093 ShenandoahMCResetCompleteBitmapTask() :
1094 WorkerTask("Shenandoah Reset Bitmap") {
1095 }
1096
1097 void work(uint worker_id) override {
1098 ShenandoahParallelWorkerSession worker_session(worker_id);
1099 ShenandoahHeapRegion* region = _regions.next();
1100 ShenandoahHeap* heap = ShenandoahHeap::heap();
1101 ShenandoahMarkingContext* const ctx = heap->marking_context();
1102 assert(heap->global_generation()->is_mark_complete(), "Marking must be complete");
1103 while (region != nullptr) {
1104 if (heap->is_bitmap_slice_committed(region) && !region->is_pinned() && region->has_live()) {
1105 ctx->clear_bitmap(region);
1106 }
1107 region = _regions.next();
1108 }
1109 }
1110 };
1111
1112 void ShenandoahFullGC::phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices) {
1113 GCTraceTime(Info, gc, phases) time("Phase 4: Move objects", _gc_timer);
1114 ShenandoahGCPhase compaction_phase(ShenandoahPhaseTimings::full_gc_copy_objects);
1115
1116 ShenandoahHeap* heap = ShenandoahHeap::heap();
1117
1118 // Compact regular objects first
1119 {
1120 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_regular);
1121 ShenandoahCompactObjectsTask compact_task(worker_slices);
1122 heap->workers()->run_task(&compact_task);
1123 }
1124
1125 // Compact humongous objects after regular object moves
1126 {
1127 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
1128 compact_humongous_objects();
1129 }
1130 }
1131
1132 void ShenandoahFullGC::phase5_epilog() {
1133 GCTraceTime(Info, gc, phases) time("Phase 5: Full GC epilog", _gc_timer);
1134 ShenandoahHeap* heap = ShenandoahHeap::heap();
1135
1136 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
1137 // and must ensure the bitmap is in sync.
1138 {
1139 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_reset_complete);
1140 ShenandoahMCResetCompleteBitmapTask task;
1141 heap->workers()->run_task(&task);
1142 }
1143
1144 // Bring regions in proper states after the collection, and set heap properties.
1145 {
1146 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_rebuild);
1147 ShenandoahPostCompactClosure post_compact;
1148 heap->heap_region_iterate(&post_compact);
1149 heap->collection_set()->clear();
1150 {
1151 ShenandoahFreeSet* free_set = heap->free_set();
1152 size_t young_trashed_regions, old_trashed_regions, first_old, last_old, num_old;
1153 free_set->prepare_to_rebuild(young_trashed_regions, old_trashed_regions, first_old, last_old, num_old);
1154 // We also do not expand old generation size following Full GC because we have scrambled age populations and
1155 // no longer have objects separated by age into distinct regions.
1156 if (heap->mode()->is_generational()) {
1157 ShenandoahGenerationalFullGC::compute_balances();
1158 }
1159 heap->free_set()->finish_rebuild(young_trashed_regions, old_trashed_regions, num_old);
1160 }
1161
1162 // Set mark incomplete because the marking bitmaps have been reset except pinned regions.
1163 _generation->set_mark_incomplete();
1164
1165 heap->clear_cancelled_gc();
1166 }
1167
1168 _preserved_marks->restore(heap->workers());
1169 _preserved_marks->reclaim();
1170
1171 if (heap->mode()->is_generational()) {
1172 ShenandoahGenerationalFullGC::rebuild_remembered_set(heap);
1173 }
1174 }