1 /*
2 * Copyright (c) 2014, 2021, Red Hat, Inc. All rights reserved.
3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
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
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/shenandoahCollectorPolicy.hpp"
38 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
39 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
40 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
41 #include "gc/shenandoah/shenandoahFreeSet.hpp"
42 #include "gc/shenandoah/shenandoahFullGC.hpp"
43 #include "gc/shenandoah/shenandoahGenerationalFullGC.hpp"
44 #include "gc/shenandoah/shenandoahGlobalGeneration.hpp"
45 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
46 #include "gc/shenandoah/shenandoahMark.inline.hpp"
47 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
48 #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp"
49 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
50 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
51 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
52 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
53 #include "gc/shenandoah/shenandoahMetrics.hpp"
54 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
55 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
56 #include "gc/shenandoah/shenandoahSTWMark.hpp"
57 #include "gc/shenandoah/shenandoahUtils.hpp"
58 #include "gc/shenandoah/shenandoahVerifier.hpp"
59 #include "gc/shenandoah/shenandoahVMOperations.hpp"
60 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
61 #include "memory/metaspaceUtils.hpp"
62 #include "memory/universe.hpp"
63 #include "oops/compressedOops.inline.hpp"
64 #include "oops/oop.inline.hpp"
65 #include "runtime/orderAccess.hpp"
66 #include "runtime/vmThread.hpp"
67 #include "utilities/copy.hpp"
68 #include "utilities/events.hpp"
69 #include "utilities/growableArray.hpp"
70
71 ShenandoahFullGC::ShenandoahFullGC() :
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 ShenandoahMetricsSnapshot metrics;
109 metrics.snap_before();
110
111 // Perform full GC
112 do_it(cause);
113
114 ShenandoahHeap* const heap = ShenandoahHeap::heap();
115
116 if (heap->mode()->is_generational()) {
117 ShenandoahGenerationalFullGC::handle_completion(heap);
118 }
119
120 metrics.snap_after();
121
122 if (metrics.is_good_progress()) {
123 heap->notify_gc_progress();
124 } else {
125 // Nothing to do. Tell the allocation path that we have failed to make
126 // progress, and it can finally fail.
127 heap->notify_gc_no_progress();
128 }
129
130 // Regardless if progress was made, we record that we completed a "successful" full GC.
131 heap->global_generation()->heuristics()->record_success_full();
132 heap->shenandoah_policy()->record_success_full();
133 }
134
135 void ShenandoahFullGC::do_it(GCCause::Cause gc_cause) {
136 ShenandoahHeap* heap = ShenandoahHeap::heap();
137
138 if (heap->mode()->is_generational()) {
139 ShenandoahGenerationalFullGC::prepare();
140 }
141
142 if (ShenandoahVerify) {
143 heap->verifier()->verify_before_fullgc();
144 }
145
146 if (VerifyBeforeGC) {
147 Universe::verify();
148 }
149
150 // Degenerated GC may carry concurrent root flags when upgrading to
151 // full GC. We need to reset it before mutators resume.
152 heap->set_concurrent_strong_root_in_progress(false);
153 heap->set_concurrent_weak_root_in_progress(false);
154
155 heap->set_full_gc_in_progress(true);
156
157 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint");
158 assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped");
159
160 {
161 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdump_pre);
162 heap->pre_full_gc_dump(_gc_timer);
163 }
164
165 {
166 ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare);
167 // Full GC is supposed to recover from any GC state:
168
169 // a0. Remember if we have forwarded objects
170 bool has_forwarded_objects = heap->has_forwarded_objects();
171
172 // a1. Cancel evacuation, if in progress
173 if (heap->is_evacuation_in_progress()) {
174 heap->set_evacuation_in_progress(false);
175 }
176 assert(!heap->is_evacuation_in_progress(), "sanity");
177
178 // a2. Cancel update-refs, if in progress
179 if (heap->is_update_refs_in_progress()) {
180 heap->set_update_refs_in_progress(false);
181 }
182 assert(!heap->is_update_refs_in_progress(), "sanity");
183
184 // b. Cancel all concurrent marks, if in progress
185 if (heap->is_concurrent_mark_in_progress()) {
186 heap->cancel_concurrent_mark();
187 }
188 assert(!heap->is_concurrent_mark_in_progress(), "sanity");
189
190 // c. Update roots if this full GC is due to evac-oom, which may carry from-space pointers in roots.
191 if (has_forwarded_objects) {
192 update_roots(true /*full_gc*/);
193 }
194
195 // d. Reset the bitmaps for new marking
196 heap->global_generation()->reset_mark_bitmap();
197 assert(heap->marking_context()->is_bitmap_clear(), "sanity");
198 assert(!heap->global_generation()->is_mark_complete(), "sanity");
199
200 // e. Abandon reference discovery and clear all discovered references.
201 ShenandoahReferenceProcessor* rp = heap->global_generation()->ref_processor();
202 rp->abandon_partial_discovery();
203
204 // f. Sync pinned region status from the CP marks
205 heap->sync_pinned_region_status();
206
207 if (heap->mode()->is_generational()) {
208 ShenandoahGenerationalFullGC::restore_top_before_promote(heap);
209 }
210
211 // The rest of prologue:
212 _preserved_marks->init(heap->workers()->active_workers());
213
214 assert(heap->has_forwarded_objects() == has_forwarded_objects, "This should not change");
215 }
216
217 if (UseTLAB) {
218 // Note: PLABs are also retired with GCLABs in generational mode.
219 heap->gclabs_retire(ResizeTLAB);
220 heap->tlabs_retire(ResizeTLAB);
221 }
222
223 OrderAccess::fence();
224
225 phase1_mark_heap();
226
227 // Once marking is done, which may have fixed up forwarded objects, we can drop it.
228 // Coming out of Full GC, we would not have any forwarded objects.
229 // This also prevents resolves with fwdptr from kicking in while adjusting pointers in phase3.
230 heap->set_has_forwarded_objects(false);
231
232 heap->set_full_gc_move_in_progress(true);
233
234 // Setup workers for the rest
235 OrderAccess::fence();
236
237 // Initialize worker slices
238 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
239 for (uint i = 0; i < heap->max_workers(); i++) {
240 worker_slices[i] = new ShenandoahHeapRegionSet();
241 }
242
243 {
244 // The rest of code performs region moves, where region status is undefined
245 // until all phases run together.
246 ShenandoahHeapLocker lock(heap->lock());
247
248 FullGCForwarding::begin();
249
250 phase2_calculate_target_addresses(worker_slices);
251
252 OrderAccess::fence();
253
254 phase3_update_references();
255
256 phase4_compact_objects(worker_slices);
257
258 phase5_epilog();
259
260 FullGCForwarding::end();
261 }
262
263 // Resize metaspace
264 MetaspaceGC::compute_new_size();
265
266 // Free worker slices
267 for (uint i = 0; i < heap->max_workers(); i++) {
268 delete worker_slices[i];
269 }
270 FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices);
271
272 heap->set_full_gc_move_in_progress(false);
273 heap->set_full_gc_in_progress(false);
274
275 if (ShenandoahVerify) {
276 heap->verifier()->verify_after_fullgc();
277 }
278
279 if (VerifyAfterGC) {
280 Universe::verify();
281 }
282
283 {
284 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdump_post);
285 heap->post_full_gc_dump(_gc_timer);
286 }
287 }
288
289 class ShenandoahPrepareForMarkClosure: public ShenandoahHeapRegionClosure {
290 private:
291 ShenandoahMarkingContext* const _ctx;
292
293 public:
294 ShenandoahPrepareForMarkClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
295
296 void heap_region_do(ShenandoahHeapRegion *r) override {
297 _ctx->capture_top_at_mark_start(r);
298 r->clear_live_data();
299 }
300
301 bool is_thread_safe() override { return true; }
302 };
303
304 void ShenandoahFullGC::phase1_mark_heap() {
305 GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer);
306 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
307
308 ShenandoahHeap* heap = ShenandoahHeap::heap();
309
310 ShenandoahPrepareForMarkClosure prepare_for_mark;
311 ShenandoahExcludeRegionClosure<FREE> cl(&prepare_for_mark);
312 heap->parallel_heap_region_iterate(&cl);
313
314 heap->set_unload_classes(heap->global_generation()->heuristics()->can_unload_classes());
315
316 ShenandoahReferenceProcessor* rp = heap->global_generation()->ref_processor();
317 // enable ("weak") refs discovery
318 rp->set_soft_reference_policy(true); // forcefully purge all soft references
319
320 ShenandoahSTWMark mark(heap->global_generation(), true /*full_gc*/);
321 mark.mark();
322 heap->parallel_cleaning(true /* full_gc */);
323
324 if (ShenandoahHeap::heap()->mode()->is_generational()) {
325 ShenandoahGenerationalFullGC::log_live_in_old(heap);
326 }
327 }
328
329 class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
330 private:
331 PreservedMarks* const _preserved_marks;
332 ShenandoahHeap* const _heap;
333 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
334 int _empty_regions_pos;
335 ShenandoahHeapRegion* _to_region;
336 ShenandoahHeapRegion* _from_region;
337 HeapWord* _compact_point;
338
339 public:
340 ShenandoahPrepareForCompactionObjectClosure(PreservedMarks* preserved_marks,
341 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
342 ShenandoahHeapRegion* to_region) :
343 _preserved_marks(preserved_marks),
344 _heap(ShenandoahHeap::heap()),
345 _empty_regions(empty_regions),
346 _empty_regions_pos(0),
347 _to_region(to_region),
348 _from_region(nullptr),
349 _compact_point(to_region->bottom()) {}
350
351 void set_from_region(ShenandoahHeapRegion* from_region) {
352 _from_region = from_region;
353 }
354
355 void finish() {
356 assert(_to_region != nullptr, "should not happen");
357 _to_region->set_new_top(_compact_point);
358 }
359
360 bool is_compact_same_region() {
361 return _from_region == _to_region;
362 }
363
364 int empty_regions_pos() {
365 return _empty_regions_pos;
366 }
367
368 void do_object(oop p) {
369 assert(_from_region != nullptr, "must set before work");
370 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
371 assert(!_heap->complete_marking_context()->allocated_after_mark_start(p), "must be truly marked");
372
373 size_t old_size = p->size();
374 size_t new_size = p->copy_size(old_size, p->mark());
375 size_t obj_size = _compact_point == cast_from_oop<HeapWord*>(p) ? old_size : new_size;
376 if (_compact_point + obj_size > _to_region->end()) {
377 finish();
378
379 // Object doesn't fit. Pick next empty region and start compacting there.
380 ShenandoahHeapRegion* new_to_region;
381 if (_empty_regions_pos < _empty_regions.length()) {
382 new_to_region = _empty_regions.at(_empty_regions_pos);
383 _empty_regions_pos++;
384 } else {
385 // Out of empty region? Compact within the same region.
386 new_to_region = _from_region;
387 }
388
389 assert(new_to_region != _to_region, "must not reuse same to-region");
390 assert(new_to_region != nullptr, "must not be null");
391 _to_region = new_to_region;
392 _compact_point = _to_region->bottom();
393 obj_size = _compact_point == cast_from_oop<HeapWord*>(p) ? old_size : new_size;
394 }
395
396 // Object fits into current region, record new location, if object does not move:
397 assert(_compact_point + obj_size <= _to_region->end(), "must fit");
398 shenandoah_assert_not_forwarded(nullptr, p);
399 if (_compact_point != cast_from_oop<HeapWord*>(p)) {
400 _preserved_marks->push_if_necessary(p, p->mark());
401 FullGCForwarding::forward_to(p, cast_to_oop(_compact_point));
402 }
403 _compact_point += obj_size;
404 }
405 };
406
407 class ShenandoahPrepareForCompactionTask : public WorkerTask {
408 private:
409 PreservedMarksSet* const _preserved_marks;
410 ShenandoahHeap* const _heap;
411 ShenandoahHeapRegionSet** const _worker_slices;
412
413 public:
414 ShenandoahPrepareForCompactionTask(PreservedMarksSet *preserved_marks, ShenandoahHeapRegionSet **worker_slices) :
415 WorkerTask("Shenandoah Prepare For Compaction"),
416 _preserved_marks(preserved_marks),
417 _heap(ShenandoahHeap::heap()), _worker_slices(worker_slices) {
418 }
419
420 static bool is_candidate_region(ShenandoahHeapRegion* r) {
421 // Empty region: get it into the slice to defragment the slice itself.
422 // We could have skipped this without violating correctness, but we really
423 // want to compact all live regions to the start of the heap, which sometimes
424 // means moving them into the fully empty regions.
425 if (r->is_empty()) return true;
426
427 // Can move the region, and this is not the humongous region. Humongous
428 // moves are special cased here, because their moves are handled separately.
429 return r->is_stw_move_allowed() && !r->is_humongous();
430 }
431
432 void work(uint worker_id) override;
433 private:
434 template<typename ClosureType>
435 void prepare_for_compaction(ClosureType& cl,
436 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
437 ShenandoahHeapRegionSetIterator& it,
438 ShenandoahHeapRegion* from_region);
439 };
440
441 void ShenandoahPrepareForCompactionTask::work(uint worker_id) {
442 ShenandoahParallelWorkerSession worker_session(worker_id);
443 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
444 ShenandoahHeapRegionSetIterator it(slice);
445 ShenandoahHeapRegion* from_region = it.next();
446 // No work?
447 if (from_region == nullptr) {
448 return;
449 }
450
451 // Sliding compaction. Walk all regions in the slice, and compact them.
452 // Remember empty regions and reuse them as needed.
453 ResourceMark rm;
454
455 GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions());
456
457 if (_heap->mode()->is_generational()) {
458 ShenandoahPrepareForGenerationalCompactionObjectClosure cl(_preserved_marks->get(worker_id),
459 empty_regions, from_region, worker_id);
460 prepare_for_compaction(cl, empty_regions, it, from_region);
461 } else {
462 ShenandoahPrepareForCompactionObjectClosure cl(_preserved_marks->get(worker_id), empty_regions, from_region);
463 prepare_for_compaction(cl, empty_regions, it, from_region);
464 }
465 }
466
467 template<typename ClosureType>
468 void ShenandoahPrepareForCompactionTask::prepare_for_compaction(ClosureType& cl,
469 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
470 ShenandoahHeapRegionSetIterator& it,
471 ShenandoahHeapRegion* from_region) {
472 while (from_region != nullptr) {
473 assert(is_candidate_region(from_region), "Sanity");
474 cl.set_from_region(from_region);
475 if (from_region->has_live()) {
476 _heap->marked_object_iterate(from_region, &cl);
477 }
478
479 // Compacted the region to somewhere else? From-region is empty then.
480 if (!cl.is_compact_same_region()) {
481 empty_regions.append(from_region);
482 }
483 from_region = it.next();
484 }
485 cl.finish();
486
487 // Mark all remaining regions as empty
488 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
489 ShenandoahHeapRegion* r = empty_regions.at(pos);
490 r->set_new_top(r->bottom());
491 }
492 }
493
494 void ShenandoahFullGC::calculate_target_humongous_objects() {
495 ShenandoahHeap* heap = ShenandoahHeap::heap();
496
497 // Compute the new addresses for humongous objects. We need to do this after addresses
498 // for regular objects are calculated, and we know what regions in heap suffix are
499 // available for humongous moves.
500 //
501 // Scan the heap backwards, because we are compacting humongous regions towards the end.
502 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
503 // humongous start there.
504 //
505 // The complication is potential non-movable regions during the scan. If such region is
506 // detected, then sliding restarts towards that non-movable region.
507
508 size_t to_begin = heap->num_regions();
509 size_t to_end = heap->num_regions();
510
511 log_debug(gc)("Full GC calculating target humongous objects from end " SIZE_FORMAT, to_end);
512 for (size_t c = heap->num_regions(); c > 0; c--) {
513 ShenandoahHeapRegion *r = heap->get_region(c - 1);
514 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
515 // To-region candidate: record this, and continue scan
516 to_begin = r->index();
517 continue;
518 }
519
520 if (r->is_humongous_start() && r->is_stw_move_allowed()) {
521 // From-region candidate: movable humongous region
522 oop old_obj = cast_to_oop(r->bottom());
523 size_t words_size = old_obj->size();
524 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
525
526 size_t start = to_end - num_regions;
527
528 if (start >= to_begin && start != r->index()) {
529 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
530 _preserved_marks->get(0)->push_if_necessary(old_obj, old_obj->mark());
531 FullGCForwarding::forward_to(old_obj, cast_to_oop(heap->get_region(start)->bottom()));
532 to_end = start;
533 continue;
534 }
535 }
536
537 // Failed to fit. Scan starting from current region.
538 to_begin = r->index();
539 to_end = r->index();
540 }
541 }
542
543 class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
544 private:
545 ShenandoahHeap* const _heap;
546
547 public:
548 ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {}
549 void heap_region_do(ShenandoahHeapRegion* r) {
550 if (r->is_trash()) {
551 r->recycle();
552 }
553 if (r->is_cset()) {
554 // Leave affiliation unchanged
555 r->make_regular_bypass();
556 }
557 if (r->is_empty_uncommitted()) {
558 r->make_committed_bypass();
559 }
560 assert (r->is_committed(), "only committed regions in heap now, see region " SIZE_FORMAT, r->index());
561
562 // Record current region occupancy: this communicates empty regions are free
563 // to the rest of Full GC code.
564 r->set_new_top(r->top());
565 }
566 };
567
568 class ShenandoahTrashImmediateGarbageClosure: public ShenandoahHeapRegionClosure {
569 private:
570 ShenandoahHeap* const _heap;
571 ShenandoahMarkingContext* const _ctx;
572
573 public:
574 ShenandoahTrashImmediateGarbageClosure() :
575 _heap(ShenandoahHeap::heap()),
576 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
577
578 void heap_region_do(ShenandoahHeapRegion* r) override {
579 if (r->is_humongous_start()) {
580 oop humongous_obj = cast_to_oop(r->bottom());
581 if (!_ctx->is_marked(humongous_obj)) {
582 assert(!r->has_live(), "Region " SIZE_FORMAT " is not marked, should not have live", r->index());
583 _heap->trash_humongous_region_at(r);
584 } else {
585 assert(r->has_live(), "Region " SIZE_FORMAT " should have live", r->index());
586 }
587 } else if (r->is_humongous_continuation()) {
588 // If we hit continuation, the non-live humongous starts should have been trashed already
589 assert(r->humongous_start_region()->has_live(), "Region " SIZE_FORMAT " should have live", r->index());
590 } else if (r->is_regular()) {
591 if (!r->has_live()) {
592 r->make_trash_immediate();
593 }
594 }
595 }
596 };
597
598 void ShenandoahFullGC::distribute_slices(ShenandoahHeapRegionSet** worker_slices) {
599 ShenandoahHeap* heap = ShenandoahHeap::heap();
600
601 uint n_workers = heap->workers()->active_workers();
602 size_t n_regions = heap->num_regions();
603
604 // What we want to accomplish: have the dense prefix of data, while still balancing
605 // out the parallel work.
606 //
607 // Assuming the amount of work is driven by the live data that needs moving, we can slice
608 // the entire heap into equal-live-sized prefix slices, and compact into them. So, each
609 // thread takes all regions in its prefix subset, and then it takes some regions from
610 // the tail.
611 //
612 // Tail region selection becomes interesting.
613 //
614 // First, we want to distribute the regions fairly between the workers, and those regions
615 // might have different amount of live data. So, until we sure no workers need live data,
616 // we need to only take what the worker needs.
617 //
618 // Second, since we slide everything to the left in each slice, the most busy regions
619 // would be the ones on the left. Which means we want to have all workers have their after-tail
620 // regions as close to the left as possible.
621 //
622 // The easiest way to do this is to distribute after-tail regions in round-robin between
623 // workers that still need live data.
624 //
625 // Consider parallel workers A, B, C, then the target slice layout would be:
626 //
627 // AAAAAAAABBBBBBBBCCCCCCCC|ABCABCABCABCABCABCABCABABABABABABABABABABAAAAA
628 //
629 // (.....dense-prefix.....) (.....................tail...................)
630 // [all regions fully live] [left-most regions are fuller that right-most]
631 //
632
633 // Compute how much live data is there. This would approximate the size of dense prefix
634 // we target to create.
635 size_t total_live = 0;
636 for (size_t idx = 0; idx < n_regions; idx++) {
637 ShenandoahHeapRegion *r = heap->get_region(idx);
638 if (ShenandoahPrepareForCompactionTask::is_candidate_region(r)) {
639 total_live += r->get_live_data_words();
640 }
641 }
642
643 // Estimate the size for the dense prefix. Note that we specifically count only the
644 // "full" regions, so there would be some non-full regions in the slice tail.
645 size_t live_per_worker = total_live / n_workers;
646 size_t prefix_regions_per_worker = live_per_worker / ShenandoahHeapRegion::region_size_words();
647 size_t prefix_regions_total = prefix_regions_per_worker * n_workers;
648 prefix_regions_total = MIN2(prefix_regions_total, n_regions);
649 assert(prefix_regions_total <= n_regions, "Sanity");
650
651 // There might be non-candidate regions in the prefix. To compute where the tail actually
652 // ends up being, we need to account those as well.
653 size_t prefix_end = prefix_regions_total;
654 for (size_t idx = 0; idx < prefix_regions_total; idx++) {
655 ShenandoahHeapRegion *r = heap->get_region(idx);
656 if (!ShenandoahPrepareForCompactionTask::is_candidate_region(r)) {
657 prefix_end++;
658 }
659 }
660 prefix_end = MIN2(prefix_end, n_regions);
661 assert(prefix_end <= n_regions, "Sanity");
662
663 // Distribute prefix regions per worker: each thread definitely gets its own same-sized
664 // subset of dense prefix.
665 size_t prefix_idx = 0;
666
667 size_t* live = NEW_C_HEAP_ARRAY(size_t, n_workers, mtGC);
668
669 for (size_t wid = 0; wid < n_workers; wid++) {
670 ShenandoahHeapRegionSet* slice = worker_slices[wid];
671
672 live[wid] = 0;
673 size_t regs = 0;
674
675 // Add all prefix regions for this worker
676 while (prefix_idx < prefix_end && regs < prefix_regions_per_worker) {
677 ShenandoahHeapRegion *r = heap->get_region(prefix_idx);
678 if (ShenandoahPrepareForCompactionTask::is_candidate_region(r)) {
679 slice->add_region(r);
680 live[wid] += r->get_live_data_words();
681 regs++;
682 }
683 prefix_idx++;
684 }
685 }
686
687 // Distribute the tail among workers in round-robin fashion.
688 size_t wid = n_workers - 1;
689
690 for (size_t tail_idx = prefix_end; tail_idx < n_regions; tail_idx++) {
691 ShenandoahHeapRegion *r = heap->get_region(tail_idx);
692 if (ShenandoahPrepareForCompactionTask::is_candidate_region(r)) {
693 assert(wid < n_workers, "Sanity");
694
695 size_t live_region = r->get_live_data_words();
696
697 // Select next worker that still needs live data.
698 size_t old_wid = wid;
699 do {
700 wid++;
701 if (wid == n_workers) wid = 0;
702 } while (live[wid] + live_region >= live_per_worker && old_wid != wid);
703
704 if (old_wid == wid) {
705 // Circled back to the same worker? This means liveness data was
706 // miscalculated. Bump the live_per_worker limit so that
707 // everyone gets a piece of the leftover work.
708 live_per_worker += ShenandoahHeapRegion::region_size_words();
709 }
710
711 worker_slices[wid]->add_region(r);
712 live[wid] += live_region;
713 }
714 }
715
716 FREE_C_HEAP_ARRAY(size_t, live);
717
718 #ifdef ASSERT
719 ResourceBitMap map(n_regions);
720 for (size_t wid = 0; wid < n_workers; wid++) {
721 ShenandoahHeapRegionSetIterator it(worker_slices[wid]);
722 ShenandoahHeapRegion* r = it.next();
723 while (r != nullptr) {
724 size_t idx = r->index();
725 assert(ShenandoahPrepareForCompactionTask::is_candidate_region(r), "Sanity: " SIZE_FORMAT, idx);
726 assert(!map.at(idx), "No region distributed twice: " SIZE_FORMAT, idx);
727 map.at_put(idx, true);
728 r = it.next();
729 }
730 }
731
732 for (size_t rid = 0; rid < n_regions; rid++) {
733 bool is_candidate = ShenandoahPrepareForCompactionTask::is_candidate_region(heap->get_region(rid));
734 bool is_distributed = map.at(rid);
735 assert(is_distributed || !is_candidate, "All candidates are distributed: " SIZE_FORMAT, rid);
736 }
737 #endif
738 }
739
740 void ShenandoahFullGC::phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices) {
741 GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer);
742 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
743
744 ShenandoahHeap* heap = ShenandoahHeap::heap();
745
746 // About to figure out which regions can be compacted, make sure pinning status
747 // had been updated in GC prologue.
748 heap->assert_pinned_region_status();
749
750 {
751 // Trash the immediately collectible regions before computing addresses
752 ShenandoahTrashImmediateGarbageClosure trash_immediate_garbage;
753 ShenandoahExcludeRegionClosure<FREE> cl(&trash_immediate_garbage);
754 heap->heap_region_iterate(&cl);
755
756 // Make sure regions are in good state: committed, active, clean.
757 // This is needed because we are potentially sliding the data through them.
758 ShenandoahEnsureHeapActiveClosure ecl;
759 heap->heap_region_iterate(&ecl);
760 }
761
762 // Compute the new addresses for regular objects
763 {
764 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
765
766 distribute_slices(worker_slices);
767
768 ShenandoahPrepareForCompactionTask task(_preserved_marks, worker_slices);
769 heap->workers()->run_task(&task);
770 }
771
772 // Compute the new addresses for humongous objects
773 {
774 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
775 calculate_target_humongous_objects();
776 }
777 }
778
779 class ShenandoahAdjustPointersClosure : public MetadataVisitingOopIterateClosure {
780 private:
781 ShenandoahHeap* const _heap;
782 ShenandoahMarkingContext* const _ctx;
783
784 template <class T>
785 inline void do_oop_work(T* p) {
786 T o = RawAccess<>::oop_load(p);
787 if (!CompressedOops::is_null(o)) {
788 oop obj = CompressedOops::decode_not_null(o);
789 assert(_ctx->is_marked(obj), "must be marked");
790 if (FullGCForwarding::is_forwarded(obj)) {
791 oop forw = FullGCForwarding::forwardee(obj);
792 RawAccess<IS_NOT_NULL>::oop_store(p, forw);
793 }
794 }
795 }
796
797 public:
798 ShenandoahAdjustPointersClosure() :
799 _heap(ShenandoahHeap::heap()),
800 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
801
802 void do_oop(oop* p) { do_oop_work(p); }
803 void do_oop(narrowOop* p) { do_oop_work(p); }
804 void do_method(Method* m) {}
805 void do_nmethod(nmethod* nm) {}
806 };
807
808 class ShenandoahAdjustPointersObjectClosure : public ObjectClosure {
809 private:
810 ShenandoahHeap* const _heap;
811 ShenandoahAdjustPointersClosure _cl;
812
813 public:
814 ShenandoahAdjustPointersObjectClosure() :
815 _heap(ShenandoahHeap::heap()) {
816 }
817 void do_object(oop p) {
818 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
819 p->oop_iterate(&_cl);
820 }
821 };
822
823 class ShenandoahAdjustPointersTask : public WorkerTask {
824 private:
825 ShenandoahHeap* const _heap;
826 ShenandoahRegionIterator _regions;
827
828 public:
829 ShenandoahAdjustPointersTask() :
830 WorkerTask("Shenandoah Adjust Pointers"),
831 _heap(ShenandoahHeap::heap()) {
832 }
833
834 void work(uint worker_id) {
835 ShenandoahParallelWorkerSession worker_session(worker_id);
836 ShenandoahAdjustPointersObjectClosure obj_cl;
837 ShenandoahHeapRegion* r = _regions.next();
838 while (r != nullptr) {
839 if (!r->is_humongous_continuation() && r->has_live()) {
840 _heap->marked_object_iterate(r, &obj_cl);
841 }
842 if (_heap->mode()->is_generational()) {
843 ShenandoahGenerationalFullGC::maybe_coalesce_and_fill_region(r);
844 }
845 r = _regions.next();
846 }
847 }
848 };
849
850 class ShenandoahAdjustRootPointersTask : public WorkerTask {
851 private:
852 ShenandoahRootAdjuster* _rp;
853 PreservedMarksSet* _preserved_marks;
854 public:
855 ShenandoahAdjustRootPointersTask(ShenandoahRootAdjuster* rp, PreservedMarksSet* preserved_marks) :
856 WorkerTask("Shenandoah Adjust Root Pointers"),
857 _rp(rp),
858 _preserved_marks(preserved_marks) {}
859
860 void work(uint worker_id) {
861 ShenandoahParallelWorkerSession worker_session(worker_id);
862 ShenandoahAdjustPointersClosure cl;
863 _rp->roots_do(worker_id, &cl);
864 _preserved_marks->get(worker_id)->adjust_during_full_gc();
865 }
866 };
867
868 void ShenandoahFullGC::phase3_update_references() {
869 GCTraceTime(Info, gc, phases) time("Phase 3: Adjust pointers", _gc_timer);
870 ShenandoahGCPhase adjust_pointer_phase(ShenandoahPhaseTimings::full_gc_adjust_pointers);
871
872 ShenandoahHeap* heap = ShenandoahHeap::heap();
873
874 WorkerThreads* workers = heap->workers();
875 uint nworkers = workers->active_workers();
876 {
877 #if COMPILER2_OR_JVMCI
878 DerivedPointerTable::clear();
879 #endif
880 ShenandoahRootAdjuster rp(nworkers, ShenandoahPhaseTimings::full_gc_adjust_roots);
881 ShenandoahAdjustRootPointersTask task(&rp, _preserved_marks);
882 workers->run_task(&task);
883 #if COMPILER2_OR_JVMCI
884 DerivedPointerTable::update_pointers();
885 #endif
886 }
887
888 ShenandoahAdjustPointersTask adjust_pointers_task;
889 workers->run_task(&adjust_pointers_task);
890 }
891
892 class ShenandoahCompactObjectsClosure : public ObjectClosure {
893 private:
894 ShenandoahHeap* const _heap;
895 uint const _worker_id;
896
897 public:
898 ShenandoahCompactObjectsClosure(uint worker_id) :
899 _heap(ShenandoahHeap::heap()), _worker_id(worker_id) {}
900
901 void do_object(oop p) {
902 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
903 size_t size = p->size();
904 if (FullGCForwarding::is_forwarded(p)) {
905 HeapWord* compact_from = cast_from_oop<HeapWord*>(p);
906 HeapWord* compact_to = cast_from_oop<HeapWord*>(FullGCForwarding::forwardee(p));
907 assert(compact_from != compact_to, "Forwarded object should move");
908 Copy::aligned_conjoint_words(compact_from, compact_to, size);
909 oop new_obj = cast_to_oop(compact_to);
910
911 ContinuationGCSupport::relativize_stack_chunk(new_obj);
912 new_obj->init_mark();
913 new_obj->initialize_hash_if_necessary(p);
914 }
915 }
916 };
917
918 class ShenandoahCompactObjectsTask : public WorkerTask {
919 private:
920 ShenandoahHeap* const _heap;
921 ShenandoahHeapRegionSet** const _worker_slices;
922
923 public:
924 ShenandoahCompactObjectsTask(ShenandoahHeapRegionSet** worker_slices) :
925 WorkerTask("Shenandoah Compact Objects"),
926 _heap(ShenandoahHeap::heap()),
927 _worker_slices(worker_slices) {
928 }
929
930 void work(uint worker_id) {
931 ShenandoahParallelWorkerSession worker_session(worker_id);
932 ShenandoahHeapRegionSetIterator slice(_worker_slices[worker_id]);
933
934 ShenandoahCompactObjectsClosure cl(worker_id);
935 ShenandoahHeapRegion* r = slice.next();
936 while (r != nullptr) {
937 assert(!r->is_humongous(), "must not get humongous regions here");
938 if (r->has_live()) {
939 _heap->marked_object_iterate(r, &cl);
940 }
941 r->set_top(r->new_top());
942 r = slice.next();
943 }
944 }
945 };
946
947 class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
948 private:
949 ShenandoahHeap* const _heap;
950 bool _is_generational;
951 size_t _young_regions, _young_usage, _young_humongous_waste;
952 size_t _old_regions, _old_usage, _old_humongous_waste;
953
954 public:
955 ShenandoahPostCompactClosure() : _heap(ShenandoahHeap::heap()),
956 _is_generational(_heap->mode()->is_generational()),
957 _young_regions(0),
958 _young_usage(0),
959 _young_humongous_waste(0),
960 _old_regions(0),
961 _old_usage(0),
962 _old_humongous_waste(0)
963 {
964 _heap->free_set()->clear();
965 }
966
967 void heap_region_do(ShenandoahHeapRegion* r) {
968 assert (!r->is_cset(), "cset regions should have been demoted already");
969
970 // Need to reset the complete-top-at-mark-start pointer here because
971 // the complete marking bitmap is no longer valid. This ensures
972 // size-based iteration in marked_object_iterate().
973 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
974 // pinned regions.
975 if (!r->is_pinned()) {
976 _heap->complete_marking_context()->reset_top_at_mark_start(r);
977 }
978
979 size_t live = r->used();
980
981 // Make empty regions that have been allocated into regular
982 if (r->is_empty() && live > 0) {
983 if (!_is_generational) {
984 r->make_affiliated_maybe();
985 }
986 // else, generational mode compaction has already established affiliation.
987 r->make_regular_bypass();
988 if (ZapUnusedHeapArea) {
989 SpaceMangler::mangle_region(MemRegion(r->top(), r->end()));
990 }
991 }
992
993 // Reclaim regular regions that became empty
994 if (r->is_regular() && live == 0) {
995 r->make_trash();
996 }
997
998 // Recycle all trash regions
999 if (r->is_trash()) {
1000 live = 0;
1001 r->recycle();
1002 } else {
1003 if (r->is_old()) {
1004 ShenandoahGenerationalFullGC::account_for_region(r, _old_regions, _old_usage, _old_humongous_waste);
1005 } else if (r->is_young()) {
1006 ShenandoahGenerationalFullGC::account_for_region(r, _young_regions, _young_usage, _young_humongous_waste);
1007 }
1008 }
1009 r->set_live_data(live);
1010 r->reset_alloc_metadata();
1011 }
1012
1013 void update_generation_usage() {
1014 if (_is_generational) {
1015 _heap->old_generation()->establish_usage(_old_regions, _old_usage, _old_humongous_waste);
1016 _heap->young_generation()->establish_usage(_young_regions, _young_usage, _young_humongous_waste);
1017 } else {
1018 assert(_old_regions == 0, "Old regions only expected in generational mode");
1019 assert(_old_usage == 0, "Old usage only expected in generational mode");
1020 assert(_old_humongous_waste == 0, "Old humongous waste only expected in generational mode");
1021 }
1022
1023 // In generational mode, global usage should be the sum of young and old. This is also true
1024 // for non-generational modes except that there are no old regions.
1025 _heap->global_generation()->establish_usage(_old_regions + _young_regions,
1026 _old_usage + _young_usage,
1027 _old_humongous_waste + _young_humongous_waste);
1028 }
1029 };
1030
1031 void ShenandoahFullGC::compact_humongous_objects() {
1032 // Compact humongous regions, based on their fwdptr objects.
1033 //
1034 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
1035 // humongous regions are already compacted, and do not require further moves, which alleviates
1036 // sliding costs. We may consider doing this in parallel in the future.
1037
1038 ShenandoahHeap* heap = ShenandoahHeap::heap();
1039
1040 for (size_t c = heap->num_regions(); c > 0; c--) {
1041 ShenandoahHeapRegion* r = heap->get_region(c - 1);
1042 if (r->is_humongous_start()) {
1043 oop old_obj = cast_to_oop(r->bottom());
1044 if (!FullGCForwarding::is_forwarded(old_obj)) {
1045 // No need to move the object, it stays at the same slot
1046 continue;
1047 }
1048 size_t words_size = old_obj->size();
1049 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
1050
1051 size_t old_start = r->index();
1052 size_t old_end = old_start + num_regions - 1;
1053 size_t new_start = heap->heap_region_index_containing(FullGCForwarding::forwardee(old_obj));
1054 size_t new_end = new_start + num_regions - 1;
1055 assert(old_start != new_start, "must be real move");
1056 assert(r->is_stw_move_allowed(), "Region " SIZE_FORMAT " should be movable", r->index());
1057
1058 log_debug(gc)("Full GC compaction moves humongous object from region " SIZE_FORMAT " to region " SIZE_FORMAT, old_start, new_start);
1059 Copy::aligned_conjoint_words(r->bottom(), heap->get_region(new_start)->bottom(), words_size);
1060 ContinuationGCSupport::relativize_stack_chunk(cast_to_oop<HeapWord*>(r->bottom()));
1061
1062 oop new_obj = cast_to_oop(heap->get_region(new_start)->bottom());
1063 new_obj->init_mark();
1064
1065 {
1066 ShenandoahAffiliation original_affiliation = r->affiliation();
1067 for (size_t c = old_start; c <= old_end; c++) {
1068 ShenandoahHeapRegion* r = heap->get_region(c);
1069 // Leave humongous region affiliation unchanged.
1070 r->make_regular_bypass();
1071 r->set_top(r->bottom());
1072 }
1073
1074 for (size_t c = new_start; c <= new_end; c++) {
1075 ShenandoahHeapRegion* r = heap->get_region(c);
1076 if (c == new_start) {
1077 r->make_humongous_start_bypass(original_affiliation);
1078 } else {
1079 r->make_humongous_cont_bypass(original_affiliation);
1080 }
1081
1082 // Trailing region may be non-full, record the remainder there
1083 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
1084 if ((c == new_end) && (remainder != 0)) {
1085 r->set_top(r->bottom() + remainder);
1086 } else {
1087 r->set_top(r->end());
1088 }
1089
1090 r->reset_alloc_metadata();
1091 }
1092 }
1093 }
1094 }
1095 }
1096
1097 // This is slightly different to ShHeap::reset_next_mark_bitmap:
1098 // we need to remain able to walk pinned regions.
1099 // Since pinned region do not move and don't get compacted, we will get holes with
1100 // unreachable objects in them (which may have pointers to unloaded Klasses and thus
1101 // cannot be iterated over using oop->size(). The only way to safely iterate over those is using
1102 // a valid marking bitmap and valid TAMS pointer. This class only resets marking
1103 // bitmaps for un-pinned regions, and later we only reset TAMS for unpinned regions.
1104 class ShenandoahMCResetCompleteBitmapTask : public WorkerTask {
1105 private:
1106 ShenandoahRegionIterator _regions;
1107
1108 public:
1109 ShenandoahMCResetCompleteBitmapTask() :
1110 WorkerTask("Shenandoah Reset Bitmap") {
1111 }
1112
1113 void work(uint worker_id) {
1114 ShenandoahParallelWorkerSession worker_session(worker_id);
1115 ShenandoahHeapRegion* region = _regions.next();
1116 ShenandoahHeap* heap = ShenandoahHeap::heap();
1117 ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
1118 while (region != nullptr) {
1119 if (heap->is_bitmap_slice_committed(region) && !region->is_pinned() && region->has_live()) {
1120 ctx->clear_bitmap(region);
1121 }
1122 region = _regions.next();
1123 }
1124 }
1125 };
1126
1127 void ShenandoahFullGC::phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices) {
1128 GCTraceTime(Info, gc, phases) time("Phase 4: Move objects", _gc_timer);
1129 ShenandoahGCPhase compaction_phase(ShenandoahPhaseTimings::full_gc_copy_objects);
1130
1131 ShenandoahHeap* heap = ShenandoahHeap::heap();
1132
1133 // Compact regular objects first
1134 {
1135 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_regular);
1136 ShenandoahCompactObjectsTask compact_task(worker_slices);
1137 heap->workers()->run_task(&compact_task);
1138 }
1139
1140 // Compact humongous objects after regular object moves
1141 {
1142 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
1143 compact_humongous_objects();
1144 }
1145 }
1146
1147 void ShenandoahFullGC::phase5_epilog() {
1148 GCTraceTime(Info, gc, phases) time("Phase 5: Full GC epilog", _gc_timer);
1149 ShenandoahHeap* heap = ShenandoahHeap::heap();
1150
1151 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
1152 // and must ensure the bitmap is in sync.
1153 {
1154 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_reset_complete);
1155 ShenandoahMCResetCompleteBitmapTask task;
1156 heap->workers()->run_task(&task);
1157 }
1158
1159 // Bring regions in proper states after the collection, and set heap properties.
1160 {
1161 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_rebuild);
1162 ShenandoahPostCompactClosure post_compact;
1163 heap->heap_region_iterate(&post_compact);
1164 post_compact.update_generation_usage();
1165
1166 if (heap->mode()->is_generational()) {
1167 ShenandoahGenerationalFullGC::balance_generations_after_gc(heap);
1168 }
1169
1170 heap->collection_set()->clear();
1171 size_t young_cset_regions, old_cset_regions;
1172 size_t first_old, last_old, num_old;
1173 heap->free_set()->prepare_to_rebuild(young_cset_regions, old_cset_regions, first_old, last_old, num_old);
1174
1175 // We also do not expand old generation size following Full GC because we have scrambled age populations and
1176 // no longer have objects separated by age into distinct regions.
1177 if (heap->mode()->is_generational()) {
1178 ShenandoahGenerationalFullGC::compute_balances();
1179 }
1180
1181 heap->free_set()->finish_rebuild(young_cset_regions, old_cset_regions, num_old);
1182
1183 heap->clear_cancelled_gc(true /* clear oom handler */);
1184 }
1185
1186 _preserved_marks->restore(heap->workers());
1187 _preserved_marks->reclaim();
1188
1189 // We defer generation resizing actions until after cset regions have been recycled. We do this even following an
1190 // abbreviated cycle.
1191 if (heap->mode()->is_generational()) {
1192 ShenandoahGenerationalFullGC::balance_generations_after_rebuilding_free_set();
1193 ShenandoahGenerationalFullGC::rebuild_remembered_set(heap);
1194 }
1195 }