18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "compiler/oopMap.hpp"
28 #include "gc/shared/continuationGCSupport.hpp"
29 #include "gc/shared/gcTraceTime.inline.hpp"
30 #include "gc/shared/preservedMarks.inline.hpp"
31 #include "gc/shared/tlab_globals.hpp"
32 #include "gc/shared/workerThread.hpp"
33 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
34 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
35 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
36 #include "gc/shenandoah/shenandoahFreeSet.hpp"
37 #include "gc/shenandoah/shenandoahFullGC.hpp"
38 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
39 #include "gc/shenandoah/shenandoahMark.inline.hpp"
40 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
41 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
42 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
43 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
44 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
45 #include "gc/shenandoah/shenandoahMetrics.hpp"
46 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
47 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
48 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
49 #include "gc/shenandoah/shenandoahSTWMark.hpp"
50 #include "gc/shenandoah/shenandoahUtils.hpp"
51 #include "gc/shenandoah/shenandoahVerifier.hpp"
52 #include "gc/shenandoah/shenandoahVMOperations.hpp"
53 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
54 #include "memory/metaspaceUtils.hpp"
55 #include "memory/universe.hpp"
56 #include "oops/compressedOops.inline.hpp"
57 #include "oops/oop.inline.hpp"
58 #include "runtime/javaThread.hpp"
59 #include "runtime/orderAccess.hpp"
60 #include "runtime/vmThread.hpp"
61 #include "utilities/copy.hpp"
62 #include "utilities/events.hpp"
63 #include "utilities/growableArray.hpp"
64
65 ShenandoahFullGC::ShenandoahFullGC() :
66 _gc_timer(ShenandoahHeap::heap()->gc_timer()),
67 _preserved_marks(new PreservedMarksSet(true)) {}
68
69 bool ShenandoahFullGC::collect(GCCause::Cause cause) {
70 vmop_entry_full(cause);
71 // Always success
72 return true;
73 }
74
75 void ShenandoahFullGC::vmop_entry_full(GCCause::Cause cause) {
76 ShenandoahHeap* const heap = ShenandoahHeap::heap();
77 TraceCollectorStats tcs(heap->monitoring_support()->full_stw_collection_counters());
78 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::full_gc_gross);
79
80 heap->try_inject_alloc_failure();
81 VM_ShenandoahFullGC op(cause, this);
82 VMThread::execute(&op);
83 }
84
85 void ShenandoahFullGC::entry_full(GCCause::Cause cause) {
86 static const char* msg = "Pause Full";
87 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::full_gc, true /* log_heap_usage */);
88 EventMark em("%s", msg);
89
90 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
91 ShenandoahWorkerPolicy::calc_workers_for_fullgc(),
92 "full gc");
93
94 op_full(cause);
95 }
96
97 void ShenandoahFullGC::op_full(GCCause::Cause cause) {
98 ShenandoahMetricsSnapshot metrics;
99 metrics.snap_before();
100
101 // Perform full GC
102 do_it(cause);
103
104 metrics.snap_after();
105
106 if (metrics.is_good_progress()) {
107 ShenandoahHeap::heap()->notify_gc_progress();
108 } else {
109 // Nothing to do. Tell the allocation path that we have failed to make
110 // progress, and it can finally fail.
111 ShenandoahHeap::heap()->notify_gc_no_progress();
112 }
113 }
114
115 void ShenandoahFullGC::do_it(GCCause::Cause gc_cause) {
116 ShenandoahHeap* heap = ShenandoahHeap::heap();
117
118 if (ShenandoahVerify) {
119 heap->verifier()->verify_before_fullgc();
120 }
121
122 if (VerifyBeforeGC) {
123 Universe::verify();
124 }
125
126 // Degenerated GC may carry concurrent root flags when upgrading to
127 // full GC. We need to reset it before mutators resume.
128 heap->set_concurrent_strong_root_in_progress(false);
129 heap->set_concurrent_weak_root_in_progress(false);
130
131 heap->set_full_gc_in_progress(true);
132
133 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint");
134 assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped");
135
136 {
140
141 {
142 ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare);
143 // Full GC is supposed to recover from any GC state:
144
145 // a0. Remember if we have forwarded objects
146 bool has_forwarded_objects = heap->has_forwarded_objects();
147
148 // a1. Cancel evacuation, if in progress
149 if (heap->is_evacuation_in_progress()) {
150 heap->set_evacuation_in_progress(false);
151 }
152 assert(!heap->is_evacuation_in_progress(), "sanity");
153
154 // a2. Cancel update-refs, if in progress
155 if (heap->is_update_refs_in_progress()) {
156 heap->set_update_refs_in_progress(false);
157 }
158 assert(!heap->is_update_refs_in_progress(), "sanity");
159
160 // b. Cancel concurrent mark, if in progress
161 if (heap->is_concurrent_mark_in_progress()) {
162 ShenandoahConcurrentGC::cancel();
163 heap->set_concurrent_mark_in_progress(false);
164 }
165 assert(!heap->is_concurrent_mark_in_progress(), "sanity");
166
167 // c. Update roots if this full GC is due to evac-oom, which may carry from-space pointers in roots.
168 if (has_forwarded_objects) {
169 update_roots(true /*full_gc*/);
170 }
171
172 // d. Reset the bitmaps for new marking
173 heap->reset_mark_bitmap();
174 assert(heap->marking_context()->is_bitmap_clear(), "sanity");
175 assert(!heap->marking_context()->is_complete(), "sanity");
176
177 // e. Abandon reference discovery and clear all discovered references.
178 ShenandoahReferenceProcessor* rp = heap->ref_processor();
179 rp->abandon_partial_discovery();
180
181 // f. Sync pinned region status from the CP marks
182 heap->sync_pinned_region_status();
183
184 // The rest of prologue:
185 _preserved_marks->init(heap->workers()->active_workers());
186
187 assert(heap->has_forwarded_objects() == has_forwarded_objects, "This should not change");
188 }
189
190 if (UseTLAB) {
191 heap->gclabs_retire(ResizeTLAB);
192 heap->tlabs_retire(ResizeTLAB);
193 }
194
195 OrderAccess::fence();
196
197 phase1_mark_heap();
198
199 // Once marking is done, which may have fixed up forwarded objects, we can drop it.
200 // Coming out of Full GC, we would not have any forwarded objects.
201 // This also prevents resolves with fwdptr from kicking in while adjusting pointers in phase3.
202 heap->set_has_forwarded_objects(false);
203
204 heap->set_full_gc_move_in_progress(true);
205
206 // Setup workers for the rest
207 OrderAccess::fence();
208
209 // Initialize worker slices
210 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
213 }
214
215 {
216 // The rest of code performs region moves, where region status is undefined
217 // until all phases run together.
218 ShenandoahHeapLocker lock(heap->lock());
219
220 phase2_calculate_target_addresses(worker_slices);
221
222 OrderAccess::fence();
223
224 phase3_update_references();
225
226 phase4_compact_objects(worker_slices);
227 }
228
229 {
230 // Epilogue
231 _preserved_marks->restore(heap->workers());
232 _preserved_marks->reclaim();
233 }
234
235 // Resize metaspace
236 MetaspaceGC::compute_new_size();
237
238 // Free worker slices
239 for (uint i = 0; i < heap->max_workers(); i++) {
240 delete worker_slices[i];
241 }
242 FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices);
243
244 heap->set_full_gc_move_in_progress(false);
245 heap->set_full_gc_in_progress(false);
246
247 if (ShenandoahVerify) {
248 heap->verifier()->verify_after_fullgc();
249 }
250
251 if (VerifyAfterGC) {
252 Universe::verify();
253 }
254
255 {
256 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdump_post);
257 heap->post_full_gc_dump(_gc_timer);
258 }
259 }
260
261 class ShenandoahPrepareForMarkClosure: public ShenandoahHeapRegionClosure {
262 private:
263 ShenandoahMarkingContext* const _ctx;
264
265 public:
266 ShenandoahPrepareForMarkClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
267
268 void heap_region_do(ShenandoahHeapRegion *r) {
269 _ctx->capture_top_at_mark_start(r);
270 r->clear_live_data();
271 }
272 };
273
274 void ShenandoahFullGC::phase1_mark_heap() {
275 GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer);
276 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
277
278 ShenandoahHeap* heap = ShenandoahHeap::heap();
279
280 ShenandoahPrepareForMarkClosure cl;
281 heap->heap_region_iterate(&cl);
282
283 heap->set_unload_classes(heap->heuristics()->can_unload_classes());
284
285 ShenandoahReferenceProcessor* rp = heap->ref_processor();
286 // enable ("weak") refs discovery
287 rp->set_soft_reference_policy(true); // forcefully purge all soft references
288
289 ShenandoahSTWMark mark(true /*full_gc*/);
290 mark.mark();
291 heap->parallel_cleaning(true /* full_gc */);
292 }
293
294 class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
295 private:
296 PreservedMarks* const _preserved_marks;
297 ShenandoahHeap* const _heap;
298 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
299 int _empty_regions_pos;
300 ShenandoahHeapRegion* _to_region;
301 ShenandoahHeapRegion* _from_region;
302 HeapWord* _compact_point;
303
304 public:
305 ShenandoahPrepareForCompactionObjectClosure(PreservedMarks* preserved_marks,
306 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
307 ShenandoahHeapRegion* to_region) :
308 _preserved_marks(preserved_marks),
309 _heap(ShenandoahHeap::heap()),
310 _empty_regions(empty_regions),
311 _empty_regions_pos(0),
312 _to_region(to_region),
313 _from_region(NULL),
314 _compact_point(to_region->bottom()) {}
315
316 void set_from_region(ShenandoahHeapRegion* from_region) {
317 _from_region = from_region;
318 }
319
320 void finish_region() {
321 assert(_to_region != NULL, "should not happen");
322 _to_region->set_new_top(_compact_point);
323 }
324
325 bool is_compact_same_region() {
326 return _from_region == _to_region;
327 }
328
329 int empty_regions_pos() {
330 return _empty_regions_pos;
331 }
332
333 void do_object(oop p) {
334 assert(_from_region != NULL, "must set before work");
335 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
336 assert(!_heap->complete_marking_context()->allocated_after_mark_start(p), "must be truly marked");
337
338 size_t obj_size = p->size();
339 if (_compact_point + obj_size > _to_region->end()) {
340 finish_region();
341
347 } else {
348 // Out of empty region? Compact within the same region.
349 new_to_region = _from_region;
350 }
351
352 assert(new_to_region != _to_region, "must not reuse same to-region");
353 assert(new_to_region != NULL, "must not be NULL");
354 _to_region = new_to_region;
355 _compact_point = _to_region->bottom();
356 }
357
358 // Object fits into current region, record new location:
359 assert(_compact_point + obj_size <= _to_region->end(), "must fit");
360 shenandoah_assert_not_forwarded(NULL, p);
361 _preserved_marks->push_if_necessary(p, p->mark());
362 p->forward_to(cast_to_oop(_compact_point));
363 _compact_point += obj_size;
364 }
365 };
366
367 class ShenandoahPrepareForCompactionTask : public WorkerTask {
368 private:
369 PreservedMarksSet* const _preserved_marks;
370 ShenandoahHeap* const _heap;
371 ShenandoahHeapRegionSet** const _worker_slices;
372
373 public:
374 ShenandoahPrepareForCompactionTask(PreservedMarksSet *preserved_marks, ShenandoahHeapRegionSet **worker_slices) :
375 WorkerTask("Shenandoah Prepare For Compaction"),
376 _preserved_marks(preserved_marks),
377 _heap(ShenandoahHeap::heap()), _worker_slices(worker_slices) {
378 }
379
380 static bool is_candidate_region(ShenandoahHeapRegion* r) {
381 // Empty region: get it into the slice to defragment the slice itself.
382 // We could have skipped this without violating correctness, but we really
383 // want to compact all live regions to the start of the heap, which sometimes
384 // means moving them into the fully empty regions.
385 if (r->is_empty()) return true;
386
387 // Can move the region, and this is not the humongous region. Humongous
388 // moves are special cased here, because their moves are handled separately.
389 return r->is_stw_move_allowed() && !r->is_humongous();
390 }
391
392 void work(uint worker_id) {
393 ShenandoahParallelWorkerSession worker_session(worker_id);
394 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
395 ShenandoahHeapRegionSetIterator it(slice);
396 ShenandoahHeapRegion* from_region = it.next();
397 // No work?
398 if (from_region == NULL) {
399 return;
400 }
401
402 // Sliding compaction. Walk all regions in the slice, and compact them.
403 // Remember empty regions and reuse them as needed.
404 ResourceMark rm;
405
406 GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions());
407
408 ShenandoahPrepareForCompactionObjectClosure cl(_preserved_marks->get(worker_id), empty_regions, from_region);
409
410 while (from_region != NULL) {
411 assert(is_candidate_region(from_region), "Sanity");
412
413 cl.set_from_region(from_region);
414 if (from_region->has_live()) {
415 _heap->marked_object_iterate(from_region, &cl);
416 }
417
418 // Compacted the region to somewhere else? From-region is empty then.
419 if (!cl.is_compact_same_region()) {
420 empty_regions.append(from_region);
421 }
422 from_region = it.next();
423 }
424 cl.finish_region();
425
426 // Mark all remaining regions as empty
427 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
428 ShenandoahHeapRegion* r = empty_regions.at(pos);
429 r->set_new_top(r->bottom());
430 }
431 }
432 };
433
434 void ShenandoahFullGC::calculate_target_humongous_objects() {
435 ShenandoahHeap* heap = ShenandoahHeap::heap();
436
437 // Compute the new addresses for humongous objects. We need to do this after addresses
438 // for regular objects are calculated, and we know what regions in heap suffix are
439 // available for humongous moves.
440 //
441 // Scan the heap backwards, because we are compacting humongous regions towards the end.
442 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
443 // humongous start there.
444 //
445 // The complication is potential non-movable regions during the scan. If such region is
446 // detected, then sliding restarts towards that non-movable region.
447
448 size_t to_begin = heap->num_regions();
449 size_t to_end = heap->num_regions();
450
451 for (size_t c = heap->num_regions(); c > 0; c--) {
452 ShenandoahHeapRegion *r = heap->get_region(c - 1);
453 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
454 // To-region candidate: record this, and continue scan
455 to_begin = r->index();
456 continue;
457 }
458
459 if (r->is_humongous_start() && r->is_stw_move_allowed()) {
460 // From-region candidate: movable humongous region
461 oop old_obj = cast_to_oop(r->bottom());
462 size_t words_size = old_obj->size();
463 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
464
465 size_t start = to_end - num_regions;
466
467 if (start >= to_begin && start != r->index()) {
468 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
469 _preserved_marks->get(0)->push_if_necessary(old_obj, old_obj->mark());
470 old_obj->forward_to(cast_to_oop(heap->get_region(start)->bottom()));
471 to_end = start;
472 continue;
473 }
474 }
475
476 // Failed to fit. Scan starting from current region.
477 to_begin = r->index();
478 to_end = r->index();
479 }
480 }
481
482 class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
483 private:
484 ShenandoahHeap* const _heap;
485
486 public:
487 ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {}
488 void heap_region_do(ShenandoahHeapRegion* r) {
489 if (r->is_trash()) {
490 r->recycle();
491 }
492 if (r->is_cset()) {
493 r->make_regular_bypass();
494 }
495 if (r->is_empty_uncommitted()) {
496 r->make_committed_bypass();
497 }
498 assert (r->is_committed(), "only committed regions in heap now, see region " SIZE_FORMAT, r->index());
499
500 // Record current region occupancy: this communicates empty regions are free
501 // to the rest of Full GC code.
502 r->set_new_top(r->top());
503 }
504 };
505
506 class ShenandoahTrashImmediateGarbageClosure: public ShenandoahHeapRegionClosure {
507 private:
508 ShenandoahHeap* const _heap;
509 ShenandoahMarkingContext* const _ctx;
510
511 public:
512 ShenandoahTrashImmediateGarbageClosure() :
513 _heap(ShenandoahHeap::heap()),
514 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
515
516 void heap_region_do(ShenandoahHeapRegion* r) {
517 if (r->is_humongous_start()) {
518 oop humongous_obj = cast_to_oop(r->bottom());
519 if (!_ctx->is_marked(humongous_obj)) {
520 assert(!r->has_live(),
521 "Region " SIZE_FORMAT " is not marked, should not have live", r->index());
522 _heap->trash_humongous_region_at(r);
523 } else {
524 assert(r->has_live(),
525 "Region " SIZE_FORMAT " should have live", r->index());
526 }
527 } else if (r->is_humongous_continuation()) {
528 // If we hit continuation, the non-live humongous starts should have been trashed already
529 assert(r->humongous_start_region()->has_live(),
530 "Region " SIZE_FORMAT " should have live", r->index());
531 } else if (r->is_regular()) {
532 if (!r->has_live()) {
533 r->make_trash_immediate();
534 }
535 }
536 }
537 };
538
539 void ShenandoahFullGC::distribute_slices(ShenandoahHeapRegionSet** worker_slices) {
540 ShenandoahHeap* heap = ShenandoahHeap::heap();
541
542 uint n_workers = heap->workers()->active_workers();
543 size_t n_regions = heap->num_regions();
544
545 // What we want to accomplish: have the dense prefix of data, while still balancing
546 // out the parallel work.
547 //
548 // Assuming the amount of work is driven by the live data that needs moving, we can slice
549 // the entire heap into equal-live-sized prefix slices, and compact into them. So, each
550 // thread takes all regions in its prefix subset, and then it takes some regions from
551 // the tail.
552 //
553 // Tail region selection becomes interesting.
554 //
555 // First, we want to distribute the regions fairly between the workers, and those regions
682 GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer);
683 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
684
685 ShenandoahHeap* heap = ShenandoahHeap::heap();
686
687 // About to figure out which regions can be compacted, make sure pinning status
688 // had been updated in GC prologue.
689 heap->assert_pinned_region_status();
690
691 {
692 // Trash the immediately collectible regions before computing addresses
693 ShenandoahTrashImmediateGarbageClosure tigcl;
694 heap->heap_region_iterate(&tigcl);
695
696 // Make sure regions are in good state: committed, active, clean.
697 // This is needed because we are potentially sliding the data through them.
698 ShenandoahEnsureHeapActiveClosure ecl;
699 heap->heap_region_iterate(&ecl);
700 }
701
702 // Compute the new addresses for regular objects
703 {
704 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
705
706 distribute_slices(worker_slices);
707
708 ShenandoahPrepareForCompactionTask task(_preserved_marks, worker_slices);
709 heap->workers()->run_task(&task);
710 }
711
712 // Compute the new addresses for humongous objects
713 {
714 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
715 calculate_target_humongous_objects();
716 }
717 }
718
719 class ShenandoahAdjustPointersClosure : public MetadataVisitingOopIterateClosure {
720 private:
721 ShenandoahHeap* const _heap;
722 ShenandoahMarkingContext* const _ctx;
723
724 template <class T>
725 inline void do_oop_work(T* p) {
726 T o = RawAccess<>::oop_load(p);
727 if (!CompressedOops::is_null(o)) {
728 oop obj = CompressedOops::decode_not_null(o);
762
763 class ShenandoahAdjustPointersTask : public WorkerTask {
764 private:
765 ShenandoahHeap* const _heap;
766 ShenandoahRegionIterator _regions;
767
768 public:
769 ShenandoahAdjustPointersTask() :
770 WorkerTask("Shenandoah Adjust Pointers"),
771 _heap(ShenandoahHeap::heap()) {
772 }
773
774 void work(uint worker_id) {
775 ShenandoahParallelWorkerSession worker_session(worker_id);
776 ShenandoahAdjustPointersObjectClosure obj_cl;
777 ShenandoahHeapRegion* r = _regions.next();
778 while (r != NULL) {
779 if (!r->is_humongous_continuation() && r->has_live()) {
780 _heap->marked_object_iterate(r, &obj_cl);
781 }
782 r = _regions.next();
783 }
784 }
785 };
786
787 class ShenandoahAdjustRootPointersTask : public WorkerTask {
788 private:
789 ShenandoahRootAdjuster* _rp;
790 PreservedMarksSet* _preserved_marks;
791 public:
792 ShenandoahAdjustRootPointersTask(ShenandoahRootAdjuster* rp, PreservedMarksSet* preserved_marks) :
793 WorkerTask("Shenandoah Adjust Root Pointers"),
794 _rp(rp),
795 _preserved_marks(preserved_marks) {}
796
797 void work(uint worker_id) {
798 ShenandoahParallelWorkerSession worker_session(worker_id);
799 ShenandoahAdjustPointersClosure cl;
800 _rp->roots_do(worker_id, &cl);
801 _preserved_marks->get(worker_id)->adjust_during_full_gc();
874 _heap->marked_object_iterate(r, &cl);
875 }
876 r->set_top(r->new_top());
877 r = slice.next();
878 }
879 }
880 };
881
882 class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
883 private:
884 ShenandoahHeap* const _heap;
885 size_t _live;
886
887 public:
888 ShenandoahPostCompactClosure() : _heap(ShenandoahHeap::heap()), _live(0) {
889 _heap->free_set()->clear();
890 }
891
892 void heap_region_do(ShenandoahHeapRegion* r) {
893 assert (!r->is_cset(), "cset regions should have been demoted already");
894
895 // Need to reset the complete-top-at-mark-start pointer here because
896 // the complete marking bitmap is no longer valid. This ensures
897 // size-based iteration in marked_object_iterate().
898 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
899 // pinned regions.
900 if (!r->is_pinned()) {
901 _heap->complete_marking_context()->reset_top_at_mark_start(r);
902 }
903
904 size_t live = r->used();
905
906 // Make empty regions that have been allocated into regular
907 if (r->is_empty() && live > 0) {
908 r->make_regular_bypass();
909 }
910
911 // Reclaim regular regions that became empty
912 if (r->is_regular() && live == 0) {
913 r->make_trash();
914 }
915
916 // Recycle all trash regions
917 if (r->is_trash()) {
918 live = 0;
919 r->recycle();
920 }
921
922 r->set_live_data(live);
923 r->reset_alloc_metadata();
924 _live += live;
925 }
926
927 size_t get_live() {
928 return _live;
929 }
930 };
931
932 void ShenandoahFullGC::compact_humongous_objects() {
933 // Compact humongous regions, based on their fwdptr objects.
934 //
935 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
936 // humongous regions are already compacted, and do not require further moves, which alleviates
937 // sliding costs. We may consider doing this in parallel in future.
938
939 ShenandoahHeap* heap = ShenandoahHeap::heap();
940
941 for (size_t c = heap->num_regions(); c > 0; c--) {
942 ShenandoahHeapRegion* r = heap->get_region(c - 1);
943 if (r->is_humongous_start()) {
944 oop old_obj = cast_to_oop(r->bottom());
945 if (!old_obj->is_forwarded()) {
946 // No need to move the object, it stays at the same slot
947 continue;
948 }
949 size_t words_size = old_obj->size();
950 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
951
952 size_t old_start = r->index();
953 size_t old_end = old_start + num_regions - 1;
954 size_t new_start = heap->heap_region_index_containing(old_obj->forwardee());
955 size_t new_end = new_start + num_regions - 1;
956 assert(old_start != new_start, "must be real move");
957 assert(r->is_stw_move_allowed(), "Region " SIZE_FORMAT " should be movable", r->index());
958
959 Copy::aligned_conjoint_words(r->bottom(), heap->get_region(new_start)->bottom(), words_size);
960 ContinuationGCSupport::relativize_stack_chunk(cast_to_oop<HeapWord*>(r->bottom()));
961
962 oop new_obj = cast_to_oop(heap->get_region(new_start)->bottom());
963 new_obj->init_mark();
964
965 {
966 for (size_t c = old_start; c <= old_end; c++) {
967 ShenandoahHeapRegion* r = heap->get_region(c);
968 r->make_regular_bypass();
969 r->set_top(r->bottom());
970 }
971
972 for (size_t c = new_start; c <= new_end; c++) {
973 ShenandoahHeapRegion* r = heap->get_region(c);
974 if (c == new_start) {
975 r->make_humongous_start_bypass();
976 } else {
977 r->make_humongous_cont_bypass();
978 }
979
980 // Trailing region may be non-full, record the remainder there
981 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
982 if ((c == new_end) && (remainder != 0)) {
983 r->set_top(r->bottom() + remainder);
984 } else {
985 r->set_top(r->end());
986 }
987
988 r->reset_alloc_metadata();
989 }
990 }
991 }
992 }
993 }
994
995 // This is slightly different to ShHeap::reset_next_mark_bitmap:
996 // we need to remain able to walk pinned regions.
997 // Since pinned region do not move and don't get compacted, we will get holes with
1036 }
1037
1038 // Compact humongous objects after regular object moves
1039 {
1040 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
1041 compact_humongous_objects();
1042 }
1043
1044 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
1045 // and must ensure the bitmap is in sync.
1046 {
1047 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_reset_complete);
1048 ShenandoahMCResetCompleteBitmapTask task;
1049 heap->workers()->run_task(&task);
1050 }
1051
1052 // Bring regions in proper states after the collection, and set heap properties.
1053 {
1054 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_rebuild);
1055
1056 ShenandoahPostCompactClosure post_compact;
1057 heap->heap_region_iterate(&post_compact);
1058 heap->set_used(post_compact.get_live());
1059
1060 heap->collection_set()->clear();
1061 heap->free_set()->rebuild();
1062 }
1063
1064 heap->clear_cancelled_gc();
1065 }
|
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "compiler/oopMap.hpp"
28 #include "gc/shared/continuationGCSupport.hpp"
29 #include "gc/shared/gcTraceTime.inline.hpp"
30 #include "gc/shared/preservedMarks.inline.hpp"
31 #include "gc/shared/tlab_globals.hpp"
32 #include "gc/shared/workerThread.hpp"
33 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
34 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
35 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
36 #include "gc/shenandoah/shenandoahFreeSet.hpp"
37 #include "gc/shenandoah/shenandoahFullGC.hpp"
38 #include "gc/shenandoah/shenandoahGeneration.hpp"
39 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
40 #include "gc/shenandoah/shenandoahMark.inline.hpp"
41 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
42 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
43 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
44 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
45 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
46 #include "gc/shenandoah/shenandoahMetrics.hpp"
47 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
48 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
49 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
50 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
51 #include "gc/shenandoah/shenandoahSTWMark.hpp"
52 #include "gc/shenandoah/shenandoahUtils.hpp"
53 #include "gc/shenandoah/shenandoahVerifier.hpp"
54 #include "gc/shenandoah/shenandoahVMOperations.hpp"
55 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
56 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
57 #include "memory/metaspaceUtils.hpp"
58 #include "memory/universe.hpp"
59 #include "oops/compressedOops.inline.hpp"
60 #include "oops/oop.inline.hpp"
61 #include "runtime/javaThread.hpp"
62 #include "runtime/orderAccess.hpp"
63 #include "runtime/vmThread.hpp"
64 #include "utilities/copy.hpp"
65 #include "utilities/events.hpp"
66 #include "utilities/growableArray.hpp"
67
68 // After Full GC is done, reconstruct the remembered set by iterating over OLD regions,
69 // registering all objects between bottom() and top(), and setting remembered set cards to
70 // DIRTY if they hold interesting pointers.
71 class ShenandoahReconstructRememberedSetTask : public WorkerTask {
72 private:
73 ShenandoahRegionIterator _regions;
74
75 public:
76 ShenandoahReconstructRememberedSetTask() :
77 WorkerTask("Shenandoah Reset Bitmap") { }
78
79 void work(uint worker_id) {
80 ShenandoahParallelWorkerSession worker_session(worker_id);
81 ShenandoahHeapRegion* r = _regions.next();
82 ShenandoahHeap* heap = ShenandoahHeap::heap();
83 RememberedScanner* scanner = heap->card_scan();
84 ShenandoahSetRememberedCardsToDirtyClosure dirty_cards_for_interesting_pointers;
85
86 while (r != NULL) {
87 if (r->is_old() && r->is_active()) {
88 HeapWord* obj_addr = r->bottom();
89 if (r->is_humongous_start()) {
90 // First, clear the remembered set
91 oop obj = cast_to_oop(obj_addr);
92 size_t size = obj->size();
93 HeapWord* end_object = r->bottom() + size;
94
95 // First, clear the remembered set for all spanned humongous regions
96 size_t num_regions = (size + ShenandoahHeapRegion::region_size_words() - 1) / ShenandoahHeapRegion::region_size_words();
97 size_t region_span = num_regions * ShenandoahHeapRegion::region_size_words();
98 scanner->reset_remset(r->bottom(), region_span);
99 size_t region_index = r->index();
100 ShenandoahHeapRegion* humongous_region = heap->get_region(region_index);
101 while (num_regions-- != 0) {
102 scanner->reset_object_range(humongous_region->bottom(), humongous_region->end());
103 region_index++;
104 humongous_region = heap->get_region(region_index);
105 }
106
107 // Then register the humongous object and DIRTY relevant remembered set cards
108 scanner->register_object_wo_lock(obj_addr);
109 obj->oop_iterate(&dirty_cards_for_interesting_pointers);
110 } else if (!r->is_humongous()) {
111 // First, clear the remembered set
112 scanner->reset_remset(r->bottom(), ShenandoahHeapRegion::region_size_words());
113 scanner->reset_object_range(r->bottom(), r->end());
114
115 // Then iterate over all objects, registering object and DIRTYing relevant remembered set cards
116 HeapWord* t = r->top();
117 while (obj_addr < t) {
118 oop obj = cast_to_oop(obj_addr);
119 size_t size = obj->size();
120 scanner->register_object_wo_lock(obj_addr);
121 obj_addr += obj->oop_iterate_size(&dirty_cards_for_interesting_pointers);
122 }
123 } // else, ignore humongous continuation region
124 }
125 // else, this region is FREE or YOUNG or inactive and we can ignore it.
126 r = _regions.next();
127 }
128 }
129 };
130
131 ShenandoahFullGC::ShenandoahFullGC() :
132 _gc_timer(ShenandoahHeap::heap()->gc_timer()),
133 _preserved_marks(new PreservedMarksSet(true)) {}
134
135 bool ShenandoahFullGC::collect(GCCause::Cause cause) {
136 vmop_entry_full(cause);
137 // Always success
138 return true;
139 }
140
141 void ShenandoahFullGC::vmop_entry_full(GCCause::Cause cause) {
142 ShenandoahHeap* const heap = ShenandoahHeap::heap();
143 TraceCollectorStats tcs(heap->monitoring_support()->full_stw_collection_counters());
144 ShenandoahTimingsTracker timing(ShenandoahPhaseTimings::full_gc_gross);
145
146 heap->try_inject_alloc_failure();
147 VM_ShenandoahFullGC op(cause, this);
148 VMThread::execute(&op);
149 }
150
151 void ShenandoahFullGC::entry_full(GCCause::Cause cause) {
152 static const char* msg = "Pause Full";
153 ShenandoahPausePhase gc_phase(msg, ShenandoahPhaseTimings::full_gc, true /* log_heap_usage */);
154 EventMark em("%s", msg);
155
156 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
157 ShenandoahWorkerPolicy::calc_workers_for_fullgc(),
158 "full gc");
159
160 op_full(cause);
161 }
162
163 void ShenandoahFullGC::op_full(GCCause::Cause cause) {
164 ShenandoahHeap* const heap = ShenandoahHeap::heap();
165 ShenandoahMetricsSnapshot metrics;
166 metrics.snap_before();
167
168 // Perform full GC
169 do_it(cause);
170
171 metrics.snap_after();
172 if (heap->mode()->is_generational()) {
173 size_t old_available = heap->old_generation()->available();
174 size_t young_available = heap->young_generation()->available();
175 log_info(gc, ergo)("At end of Full GC, old_available: " SIZE_FORMAT "%s, young_available: " SIZE_FORMAT "%s",
176 byte_size_in_proper_unit(old_available), proper_unit_for_byte_size(old_available),
177 byte_size_in_proper_unit(young_available), proper_unit_for_byte_size(young_available));
178 }
179 if (metrics.is_good_progress()) {
180 ShenandoahHeap::heap()->notify_gc_progress();
181 } else {
182 // Nothing to do. Tell the allocation path that we have failed to make
183 // progress, and it can finally fail.
184 ShenandoahHeap::heap()->notify_gc_no_progress();
185 }
186 }
187
188 void ShenandoahFullGC::do_it(GCCause::Cause gc_cause) {
189 ShenandoahHeap* heap = ShenandoahHeap::heap();
190 // Since we may arrive here from degenerated GC failure of either young or old, establish generation as GLOBAL.
191 heap->set_gc_generation(heap->global_generation());
192
193 if (heap->mode()->is_generational()) {
194 // There will be no concurrent allocations during full GC so reset these coordination variables.
195 heap->young_generation()->unadjust_available();
196 heap->old_generation()->unadjust_available();
197 // No need to old_gen->increase_used(). That was done when plabs were allocated, accounting for both old evacs and promotions.
198
199 heap->set_alloc_supplement_reserve(0);
200 heap->set_young_evac_reserve(0);
201 heap->set_old_evac_reserve(0);
202 heap->reset_old_evac_expended();
203 heap->set_promoted_reserve(0);
204
205 // Full GC supersedes any marking or coalescing in old generation.
206 heap->cancel_old_gc();
207 }
208
209 if (ShenandoahVerify) {
210 heap->verifier()->verify_before_fullgc();
211 }
212
213 if (VerifyBeforeGC) {
214 Universe::verify();
215 }
216
217 // Degenerated GC may carry concurrent root flags when upgrading to
218 // full GC. We need to reset it before mutators resume.
219 heap->set_concurrent_strong_root_in_progress(false);
220 heap->set_concurrent_weak_root_in_progress(false);
221
222 heap->set_full_gc_in_progress(true);
223
224 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint");
225 assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped");
226
227 {
231
232 {
233 ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare);
234 // Full GC is supposed to recover from any GC state:
235
236 // a0. Remember if we have forwarded objects
237 bool has_forwarded_objects = heap->has_forwarded_objects();
238
239 // a1. Cancel evacuation, if in progress
240 if (heap->is_evacuation_in_progress()) {
241 heap->set_evacuation_in_progress(false);
242 }
243 assert(!heap->is_evacuation_in_progress(), "sanity");
244
245 // a2. Cancel update-refs, if in progress
246 if (heap->is_update_refs_in_progress()) {
247 heap->set_update_refs_in_progress(false);
248 }
249 assert(!heap->is_update_refs_in_progress(), "sanity");
250
251 // b. Cancel all concurrent marks, if in progress
252 if (heap->is_concurrent_mark_in_progress()) {
253 heap->cancel_concurrent_mark();
254 }
255 assert(!heap->is_concurrent_mark_in_progress(), "sanity");
256
257 // c. Update roots if this full GC is due to evac-oom, which may carry from-space pointers in roots.
258 if (has_forwarded_objects) {
259 update_roots(true /*full_gc*/);
260 }
261
262 // d. Reset the bitmaps for new marking
263 heap->global_generation()->reset_mark_bitmap();
264 assert(heap->marking_context()->is_bitmap_clear(), "sanity");
265 assert(!heap->global_generation()->is_mark_complete(), "sanity");
266
267 // e. Abandon reference discovery and clear all discovered references.
268 ShenandoahReferenceProcessor* rp = heap->global_generation()->ref_processor();
269 rp->abandon_partial_discovery();
270
271 // f. Sync pinned region status from the CP marks
272 heap->sync_pinned_region_status();
273
274 // The rest of prologue:
275 _preserved_marks->init(heap->workers()->active_workers());
276
277 assert(heap->has_forwarded_objects() == has_forwarded_objects, "This should not change");
278 }
279
280 if (UseTLAB) {
281 // TODO: Do we need to explicitly retire PLABs?
282 heap->gclabs_retire(ResizeTLAB);
283 heap->tlabs_retire(ResizeTLAB);
284 }
285
286 OrderAccess::fence();
287
288 phase1_mark_heap();
289
290 // Once marking is done, which may have fixed up forwarded objects, we can drop it.
291 // Coming out of Full GC, we would not have any forwarded objects.
292 // This also prevents resolves with fwdptr from kicking in while adjusting pointers in phase3.
293 heap->set_has_forwarded_objects(false);
294
295 heap->set_full_gc_move_in_progress(true);
296
297 // Setup workers for the rest
298 OrderAccess::fence();
299
300 // Initialize worker slices
301 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
304 }
305
306 {
307 // The rest of code performs region moves, where region status is undefined
308 // until all phases run together.
309 ShenandoahHeapLocker lock(heap->lock());
310
311 phase2_calculate_target_addresses(worker_slices);
312
313 OrderAccess::fence();
314
315 phase3_update_references();
316
317 phase4_compact_objects(worker_slices);
318 }
319
320 {
321 // Epilogue
322 _preserved_marks->restore(heap->workers());
323 _preserved_marks->reclaim();
324
325 if (heap->mode()->is_generational()) {
326 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_reconstruct_remembered_set);
327 ShenandoahReconstructRememberedSetTask task;
328 heap->workers()->run_task(&task);
329 }
330 }
331
332 // Resize metaspace
333 MetaspaceGC::compute_new_size();
334
335 // Free worker slices
336 for (uint i = 0; i < heap->max_workers(); i++) {
337 delete worker_slices[i];
338 }
339 FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices);
340
341 heap->set_full_gc_move_in_progress(false);
342 heap->set_full_gc_in_progress(false);
343
344 if (ShenandoahVerify) {
345 if (heap->mode()->is_generational()) {
346 heap->verifier()->verify_after_generational_fullgc();
347 } else {
348 heap->verifier()->verify_after_fullgc();
349 }
350 }
351
352 if (VerifyAfterGC) {
353 Universe::verify();
354 }
355
356 {
357 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdump_post);
358 heap->post_full_gc_dump(_gc_timer);
359 }
360 }
361
362 class ShenandoahPrepareForMarkClosure: public ShenandoahHeapRegionClosure {
363 private:
364 ShenandoahMarkingContext* const _ctx;
365
366 public:
367 ShenandoahPrepareForMarkClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
368
369 void heap_region_do(ShenandoahHeapRegion *r) {
370 if (r->affiliation() != FREE) {
371 _ctx->capture_top_at_mark_start(r);
372 r->clear_live_data();
373 }
374 }
375
376 bool is_thread_safe() { return true; }
377 };
378
379 void ShenandoahFullGC::phase1_mark_heap() {
380 GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer);
381 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
382
383 ShenandoahHeap* heap = ShenandoahHeap::heap();
384
385 ShenandoahPrepareForMarkClosure cl;
386 heap->parallel_heap_region_iterate(&cl);
387
388 heap->set_unload_classes(heap->global_generation()->heuristics()->can_unload_classes());
389
390 ShenandoahReferenceProcessor* rp = heap->global_generation()->ref_processor();
391 // enable ("weak") refs discovery
392 rp->set_soft_reference_policy(true); // forcefully purge all soft references
393
394 ShenandoahSTWMark mark(heap->global_generation(), true /*full_gc*/);
395 mark.mark();
396 heap->parallel_cleaning(true /* full_gc */);
397 }
398
399 class ShenandoahPrepareForCompactionTask : public WorkerTask {
400 private:
401 PreservedMarksSet* const _preserved_marks;
402 ShenandoahHeap* const _heap;
403 ShenandoahHeapRegionSet** const _worker_slices;
404 size_t const _num_workers;
405
406 public:
407 ShenandoahPrepareForCompactionTask(PreservedMarksSet *preserved_marks, ShenandoahHeapRegionSet **worker_slices,
408 size_t num_workers);
409
410 static bool is_candidate_region(ShenandoahHeapRegion* r) {
411 // Empty region: get it into the slice to defragment the slice itself.
412 // We could have skipped this without violating correctness, but we really
413 // want to compact all live regions to the start of the heap, which sometimes
414 // means moving them into the fully empty regions.
415 if (r->is_empty()) return true;
416
417 // Can move the region, and this is not the humongous region. Humongous
418 // moves are special cased here, because their moves are handled separately.
419 return r->is_stw_move_allowed() && !r->is_humongous();
420 }
421
422 void work(uint worker_id);
423 };
424
425 class ShenandoahPrepareForGenerationalCompactionObjectClosure : public ObjectClosure {
426 private:
427 ShenandoahPrepareForCompactionTask* _compactor;
428 PreservedMarks* const _preserved_marks;
429 ShenandoahHeap* const _heap;
430
431 // _empty_regions is a thread-local list of heap regions that have been completely emptied by this worker thread's
432 // compaction efforts. The worker thread that drives these efforts adds compacted regions to this list if the
433 // region has not been compacted onto itself.
434 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
435 int _empty_regions_pos;
436 ShenandoahHeapRegion* _old_to_region;
437 ShenandoahHeapRegion* _young_to_region;
438 ShenandoahHeapRegion* _from_region;
439 ShenandoahRegionAffiliation _from_affiliation;
440 HeapWord* _old_compact_point;
441 HeapWord* _young_compact_point;
442 uint _worker_id;
443
444 public:
445 ShenandoahPrepareForGenerationalCompactionObjectClosure(ShenandoahPrepareForCompactionTask* compactor,
446 PreservedMarks* preserved_marks,
447 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
448 ShenandoahHeapRegion* old_to_region,
449 ShenandoahHeapRegion* young_to_region, uint worker_id) :
450 _compactor(compactor),
451 _preserved_marks(preserved_marks),
452 _heap(ShenandoahHeap::heap()),
453 _empty_regions(empty_regions),
454 _empty_regions_pos(0),
455 _old_to_region(old_to_region),
456 _young_to_region(young_to_region),
457 _from_region(NULL),
458 _old_compact_point((old_to_region != nullptr)? old_to_region->bottom(): nullptr),
459 _young_compact_point((young_to_region != nullptr)? young_to_region->bottom(): nullptr),
460 _worker_id(worker_id) {}
461
462 void set_from_region(ShenandoahHeapRegion* from_region) {
463 _from_region = from_region;
464 _from_affiliation = from_region->affiliation();
465 if (_from_region->has_live()) {
466 if (_from_affiliation == ShenandoahRegionAffiliation::OLD_GENERATION) {
467 if (_old_to_region == nullptr) {
468 _old_to_region = from_region;
469 _old_compact_point = from_region->bottom();
470 }
471 } else {
472 assert(_from_affiliation == ShenandoahRegionAffiliation::YOUNG_GENERATION, "from_region must be OLD or YOUNG");
473 if (_young_to_region == nullptr) {
474 _young_to_region = from_region;
475 _young_compact_point = from_region->bottom();
476 }
477 }
478 } // else, we won't iterate over this _from_region so we don't need to set up to region to hold copies
479 }
480
481 void finish() {
482 finish_old_region();
483 finish_young_region();
484 }
485
486 void finish_old_region() {
487 if (_old_to_region != nullptr) {
488 log_debug(gc)("Planned compaction into Old Region " SIZE_FORMAT ", used: " SIZE_FORMAT " tabulated by worker %u",
489 _old_to_region->index(), _old_compact_point - _old_to_region->bottom(), _worker_id);
490 _old_to_region->set_new_top(_old_compact_point);
491 _old_to_region = nullptr;
492 }
493 }
494
495 void finish_young_region() {
496 if (_young_to_region != nullptr) {
497 log_debug(gc)("Worker %u planned compaction into Young Region " SIZE_FORMAT ", used: " SIZE_FORMAT,
498 _worker_id, _young_to_region->index(), _young_compact_point - _young_to_region->bottom());
499 _young_to_region->set_new_top(_young_compact_point);
500 _young_to_region = nullptr;
501 }
502 }
503
504 bool is_compact_same_region() {
505 return (_from_region == _old_to_region) || (_from_region == _young_to_region);
506 }
507
508 int empty_regions_pos() {
509 return _empty_regions_pos;
510 }
511
512 void do_object(oop p) {
513 assert(_from_region != NULL, "must set before work");
514 assert((_from_region->bottom() <= cast_from_oop<HeapWord*>(p)) && (cast_from_oop<HeapWord*>(p) < _from_region->top()),
515 "Object must reside in _from_region");
516 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
517 assert(!_heap->complete_marking_context()->allocated_after_mark_start(p), "must be truly marked");
518
519 size_t obj_size = p->size();
520 uint from_region_age = _from_region->age();
521 uint object_age = p->age();
522
523 bool promote_object = false;
524 if ((_from_affiliation == ShenandoahRegionAffiliation::YOUNG_GENERATION) &&
525 (from_region_age + object_age >= InitialTenuringThreshold)) {
526 if ((_old_to_region != nullptr) && (_old_compact_point + obj_size > _old_to_region->end())) {
527 finish_old_region();
528 _old_to_region = nullptr;
529 }
530 if (_old_to_region == nullptr) {
531 if (_empty_regions_pos < _empty_regions.length()) {
532 ShenandoahHeapRegion* new_to_region = _empty_regions.at(_empty_regions_pos);
533 _empty_regions_pos++;
534 new_to_region->set_affiliation(OLD_GENERATION);
535 _old_to_region = new_to_region;
536 _old_compact_point = _old_to_region->bottom();
537 promote_object = true;
538 }
539 // Else this worker thread does not yet have any empty regions into which this aged object can be promoted so
540 // we leave promote_object as false, deferring the promotion.
541 } else {
542 promote_object = true;
543 }
544 }
545
546 if (promote_object || (_from_affiliation == ShenandoahRegionAffiliation::OLD_GENERATION)) {
547 assert(_old_to_region != nullptr, "_old_to_region should not be NULL when evacuating to OLD region");
548 if (_old_compact_point + obj_size > _old_to_region->end()) {
549 ShenandoahHeapRegion* new_to_region;
550
551 log_debug(gc)("Worker %u finishing old region " SIZE_FORMAT ", compact_point: " PTR_FORMAT ", obj_size: " SIZE_FORMAT
552 ", &compact_point[obj_size]: " PTR_FORMAT ", region end: " PTR_FORMAT, _worker_id, _old_to_region->index(),
553 p2i(_old_compact_point), obj_size, p2i(_old_compact_point + obj_size), p2i(_old_to_region->end()));
554
555 // Object does not fit. Get a new _old_to_region.
556 finish_old_region();
557 if (_empty_regions_pos < _empty_regions.length()) {
558 new_to_region = _empty_regions.at(_empty_regions_pos);
559 _empty_regions_pos++;
560 new_to_region->set_affiliation(OLD_GENERATION);
561 } else {
562 // If we've exhausted the previously selected _old_to_region, we know that the _old_to_region is distinct
563 // from _from_region. That's because there is always room for _from_region to be compacted into itself.
564 // Since we're out of empty regions, let's use _from_region to hold the results of its own compaction.
565 new_to_region = _from_region;
566 }
567
568 assert(new_to_region != _old_to_region, "must not reuse same OLD to-region");
569 assert(new_to_region != NULL, "must not be NULL");
570 _old_to_region = new_to_region;
571 _old_compact_point = _old_to_region->bottom();
572 }
573
574 // Object fits into current region, record new location:
575 assert(_old_compact_point + obj_size <= _old_to_region->end(), "must fit");
576 shenandoah_assert_not_forwarded(NULL, p);
577 _preserved_marks->push_if_necessary(p, p->mark());
578 p->forward_to(cast_to_oop(_old_compact_point));
579 _old_compact_point += obj_size;
580 } else {
581 assert(_from_affiliation == ShenandoahRegionAffiliation::YOUNG_GENERATION,
582 "_from_region must be OLD_GENERATION or YOUNG_GENERATION");
583 assert(_young_to_region != nullptr, "_young_to_region should not be NULL when compacting YOUNG _from_region");
584
585 // After full gc compaction, all regions have age 0. Embed the region's age into the object's age in order to preserve
586 // tenuring progress.
587 _heap->increase_object_age(p, from_region_age + 1);
588
589 if (_young_compact_point + obj_size > _young_to_region->end()) {
590 ShenandoahHeapRegion* new_to_region;
591
592 log_debug(gc)("Worker %u finishing young region " SIZE_FORMAT ", compact_point: " PTR_FORMAT ", obj_size: " SIZE_FORMAT
593 ", &compact_point[obj_size]: " PTR_FORMAT ", region end: " PTR_FORMAT, _worker_id, _young_to_region->index(),
594 p2i(_young_compact_point), obj_size, p2i(_young_compact_point + obj_size), p2i(_young_to_region->end()));
595
596 // Object does not fit. Get a new _young_to_region.
597 finish_young_region();
598 if (_empty_regions_pos < _empty_regions.length()) {
599 new_to_region = _empty_regions.at(_empty_regions_pos);
600 _empty_regions_pos++;
601 new_to_region->set_affiliation(YOUNG_GENERATION);
602 } else {
603 // If we've exhausted the previously selected _young_to_region, we know that the _young_to_region is distinct
604 // from _from_region. That's because there is always room for _from_region to be compacted into itself.
605 // Since we're out of empty regions, let's use _from_region to hold the results of its own compaction.
606 new_to_region = _from_region;
607 }
608
609 assert(new_to_region != _young_to_region, "must not reuse same OLD to-region");
610 assert(new_to_region != NULL, "must not be NULL");
611 _young_to_region = new_to_region;
612 _young_compact_point = _young_to_region->bottom();
613 }
614
615 // Object fits into current region, record new location:
616 assert(_young_compact_point + obj_size <= _young_to_region->end(), "must fit");
617 shenandoah_assert_not_forwarded(NULL, p);
618 _preserved_marks->push_if_necessary(p, p->mark());
619 p->forward_to(cast_to_oop(_young_compact_point));
620 _young_compact_point += obj_size;
621 }
622 }
623 };
624
625
626 class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
627 private:
628 PreservedMarks* const _preserved_marks;
629 ShenandoahHeap* const _heap;
630 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
631 int _empty_regions_pos;
632 ShenandoahHeapRegion* _to_region;
633 ShenandoahHeapRegion* _from_region;
634 HeapWord* _compact_point;
635
636 public:
637 ShenandoahPrepareForCompactionObjectClosure(PreservedMarks* preserved_marks,
638 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
639 ShenandoahHeapRegion* to_region) :
640 _preserved_marks(preserved_marks),
641 _heap(ShenandoahHeap::heap()),
642 _empty_regions(empty_regions),
643 _empty_regions_pos(0),
644 _to_region(to_region),
645 _from_region(NULL),
646 _compact_point(to_region->bottom()) {}
647
648 void set_from_region(ShenandoahHeapRegion* from_region) {
649 _from_region = from_region;
650 }
651
652 void finish_region() {
653 assert(_to_region != NULL, "should not happen");
654 assert(!_heap->mode()->is_generational(), "Generational GC should use different Closure");
655 _to_region->set_new_top(_compact_point);
656 }
657
658 bool is_compact_same_region() {
659 return _from_region == _to_region;
660 }
661
662 int empty_regions_pos() {
663 return _empty_regions_pos;
664 }
665
666 void do_object(oop p) {
667 assert(_from_region != NULL, "must set before work");
668 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
669 assert(!_heap->complete_marking_context()->allocated_after_mark_start(p), "must be truly marked");
670
671 size_t obj_size = p->size();
672 if (_compact_point + obj_size > _to_region->end()) {
673 finish_region();
674
680 } else {
681 // Out of empty region? Compact within the same region.
682 new_to_region = _from_region;
683 }
684
685 assert(new_to_region != _to_region, "must not reuse same to-region");
686 assert(new_to_region != NULL, "must not be NULL");
687 _to_region = new_to_region;
688 _compact_point = _to_region->bottom();
689 }
690
691 // Object fits into current region, record new location:
692 assert(_compact_point + obj_size <= _to_region->end(), "must fit");
693 shenandoah_assert_not_forwarded(NULL, p);
694 _preserved_marks->push_if_necessary(p, p->mark());
695 p->forward_to(cast_to_oop(_compact_point));
696 _compact_point += obj_size;
697 }
698 };
699
700
701 ShenandoahPrepareForCompactionTask::ShenandoahPrepareForCompactionTask(PreservedMarksSet *preserved_marks,
702 ShenandoahHeapRegionSet **worker_slices,
703 size_t num_workers) :
704 WorkerTask("Shenandoah Prepare For Compaction"),
705 _preserved_marks(preserved_marks), _heap(ShenandoahHeap::heap()),
706 _worker_slices(worker_slices), _num_workers(num_workers) { }
707
708
709 void ShenandoahPrepareForCompactionTask::work(uint worker_id) {
710 ShenandoahParallelWorkerSession worker_session(worker_id);
711 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
712 ShenandoahHeapRegionSetIterator it(slice);
713 ShenandoahHeapRegion* from_region = it.next();
714 // No work?
715 if (from_region == NULL) {
716 return;
717 }
718
719 // Sliding compaction. Walk all regions in the slice, and compact them.
720 // Remember empty regions and reuse them as needed.
721 ResourceMark rm;
722
723 GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions());
724
725 if (_heap->mode()->is_generational()) {
726 ShenandoahHeapRegion* old_to_region = (from_region->is_old())? from_region: nullptr;
727 ShenandoahHeapRegion* young_to_region = (from_region->is_young())? from_region: nullptr;
728 ShenandoahPrepareForGenerationalCompactionObjectClosure cl(this, _preserved_marks->get(worker_id), empty_regions,
729 old_to_region, young_to_region, worker_id);
730 while (from_region != NULL) {
731 assert(is_candidate_region(from_region), "Sanity");
732 log_debug(gc)("Worker %u compacting %s Region " SIZE_FORMAT " which had used " SIZE_FORMAT " and %s live",
733 worker_id, affiliation_name(from_region->affiliation()),
734 from_region->index(), from_region->used(), from_region->has_live()? "has": "does not have");
735 cl.set_from_region(from_region);
736 if (from_region->has_live()) {
737 _heap->marked_object_iterate(from_region, &cl);
738 }
739
740 // Compacted the region to somewhere else? From-region is empty then.
741 if (!cl.is_compact_same_region()) {
742 empty_regions.append(from_region);
743 }
744 from_region = it.next();
745 }
746 cl.finish();
747
748 // Mark all remaining regions as empty
749 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
750 ShenandoahHeapRegion* r = empty_regions.at(pos);
751 r->set_new_top(r->bottom());
752 }
753 } else {
754 ShenandoahPrepareForCompactionObjectClosure cl(_preserved_marks->get(worker_id), empty_regions, from_region);
755 while (from_region != NULL) {
756 assert(is_candidate_region(from_region), "Sanity");
757 cl.set_from_region(from_region);
758 if (from_region->has_live()) {
759 _heap->marked_object_iterate(from_region, &cl);
760 }
761
762 // Compacted the region to somewhere else? From-region is empty then.
763 if (!cl.is_compact_same_region()) {
764 empty_regions.append(from_region);
765 }
766 from_region = it.next();
767 }
768 cl.finish_region();
769
770 // Mark all remaining regions as empty
771 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
772 ShenandoahHeapRegion* r = empty_regions.at(pos);
773 r->set_new_top(r->bottom());
774 }
775 }
776 }
777
778 void ShenandoahFullGC::calculate_target_humongous_objects() {
779 ShenandoahHeap* heap = ShenandoahHeap::heap();
780
781 // Compute the new addresses for humongous objects. We need to do this after addresses
782 // for regular objects are calculated, and we know what regions in heap suffix are
783 // available for humongous moves.
784 //
785 // Scan the heap backwards, because we are compacting humongous regions towards the end.
786 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
787 // humongous start there.
788 //
789 // The complication is potential non-movable regions during the scan. If such region is
790 // detected, then sliding restarts towards that non-movable region.
791
792 size_t to_begin = heap->num_regions();
793 size_t to_end = heap->num_regions();
794
795 log_debug(gc)("Full GC calculating target humongous objects from end " SIZE_FORMAT, to_end);
796 for (size_t c = heap->num_regions(); c > 0; c--) {
797 ShenandoahHeapRegion *r = heap->get_region(c - 1);
798 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
799 // To-region candidate: record this, and continue scan
800 to_begin = r->index();
801 continue;
802 }
803
804 if (r->is_humongous_start() && r->is_stw_move_allowed()) {
805 // From-region candidate: movable humongous region
806 oop old_obj = cast_to_oop(r->bottom());
807 size_t words_size = old_obj->size();
808 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
809
810 size_t start = to_end - num_regions;
811
812 if (start >= to_begin && start != r->index()) {
813 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
814 _preserved_marks->get(0)->push_if_necessary(old_obj, old_obj->mark());
815 old_obj->forward_to(cast_to_oop(heap->get_region(start)->bottom()));
816 to_end = start;
817 continue;
818 }
819 }
820
821 // Failed to fit. Scan starting from current region.
822 to_begin = r->index();
823 to_end = r->index();
824 }
825 }
826
827 class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
828 private:
829 ShenandoahHeap* const _heap;
830
831 public:
832 ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {}
833 void heap_region_do(ShenandoahHeapRegion* r) {
834 bool is_generational = _heap->mode()->is_generational();
835 if (r->is_trash()) {
836 r->recycle();
837 }
838 if (r->is_cset()) {
839 // Leave afffiliation unchanged.
840 r->make_regular_bypass();
841 }
842 if (r->is_empty_uncommitted()) {
843 r->make_committed_bypass();
844 }
845 assert (r->is_committed(), "only committed regions in heap now, see region " SIZE_FORMAT, r->index());
846
847 // Record current region occupancy: this communicates empty regions are free
848 // to the rest of Full GC code.
849 r->set_new_top(r->top());
850 }
851 };
852
853 class ShenandoahTrashImmediateGarbageClosure: public ShenandoahHeapRegionClosure {
854 private:
855 ShenandoahHeap* const _heap;
856 ShenandoahMarkingContext* const _ctx;
857
858 public:
859 ShenandoahTrashImmediateGarbageClosure() :
860 _heap(ShenandoahHeap::heap()),
861 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
862
863 void heap_region_do(ShenandoahHeapRegion* r) {
864 if (r->affiliation() != FREE) {
865 if (r->is_humongous_start()) {
866 oop humongous_obj = cast_to_oop(r->bottom());
867 if (!_ctx->is_marked(humongous_obj)) {
868 assert(!r->has_live(),
869 "Humongous Start %s Region " SIZE_FORMAT " is not marked, should not have live",
870 affiliation_name(r->affiliation()), r->index());
871 log_debug(gc)("Trashing immediate humongous region " SIZE_FORMAT " because not marked", r->index());
872 _heap->trash_humongous_region_at(r);
873 } else {
874 assert(r->has_live(),
875 "Humongous Start %s Region " SIZE_FORMAT " should have live", affiliation_name(r->affiliation()), r->index());
876 }
877 } else if (r->is_humongous_continuation()) {
878 // If we hit continuation, the non-live humongous starts should have been trashed already
879 assert(r->humongous_start_region()->has_live(),
880 "Humongous Continuation %s Region " SIZE_FORMAT " should have live", affiliation_name(r->affiliation()), r->index());
881 } else if (r->is_regular()) {
882 if (!r->has_live()) {
883 log_debug(gc)("Trashing immediate regular region " SIZE_FORMAT " because has no live", r->index());
884 r->make_trash_immediate();
885 }
886 }
887 }
888 // else, ignore this FREE region.
889 // TODO: change iterators so they do not process FREE regions.
890 }
891 };
892
893 void ShenandoahFullGC::distribute_slices(ShenandoahHeapRegionSet** worker_slices) {
894 ShenandoahHeap* heap = ShenandoahHeap::heap();
895
896 uint n_workers = heap->workers()->active_workers();
897 size_t n_regions = heap->num_regions();
898
899 // What we want to accomplish: have the dense prefix of data, while still balancing
900 // out the parallel work.
901 //
902 // Assuming the amount of work is driven by the live data that needs moving, we can slice
903 // the entire heap into equal-live-sized prefix slices, and compact into them. So, each
904 // thread takes all regions in its prefix subset, and then it takes some regions from
905 // the tail.
906 //
907 // Tail region selection becomes interesting.
908 //
909 // First, we want to distribute the regions fairly between the workers, and those regions
1036 GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer);
1037 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
1038
1039 ShenandoahHeap* heap = ShenandoahHeap::heap();
1040
1041 // About to figure out which regions can be compacted, make sure pinning status
1042 // had been updated in GC prologue.
1043 heap->assert_pinned_region_status();
1044
1045 {
1046 // Trash the immediately collectible regions before computing addresses
1047 ShenandoahTrashImmediateGarbageClosure tigcl;
1048 heap->heap_region_iterate(&tigcl);
1049
1050 // Make sure regions are in good state: committed, active, clean.
1051 // This is needed because we are potentially sliding the data through them.
1052 ShenandoahEnsureHeapActiveClosure ecl;
1053 heap->heap_region_iterate(&ecl);
1054 }
1055
1056 if (heap->mode()->is_generational()) {
1057 heap->young_generation()->clear_used();
1058 heap->old_generation()->clear_used();
1059 }
1060
1061 // Compute the new addresses for regular objects
1062 {
1063 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
1064
1065 distribute_slices(worker_slices);
1066
1067 size_t num_workers = heap->max_workers();
1068
1069 ResourceMark rm;
1070 ShenandoahPrepareForCompactionTask task(_preserved_marks, worker_slices, num_workers);
1071 heap->workers()->run_task(&task);
1072 }
1073
1074 // Compute the new addresses for humongous objects
1075 {
1076 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
1077 calculate_target_humongous_objects();
1078 }
1079 }
1080
1081 class ShenandoahAdjustPointersClosure : public MetadataVisitingOopIterateClosure {
1082 private:
1083 ShenandoahHeap* const _heap;
1084 ShenandoahMarkingContext* const _ctx;
1085
1086 template <class T>
1087 inline void do_oop_work(T* p) {
1088 T o = RawAccess<>::oop_load(p);
1089 if (!CompressedOops::is_null(o)) {
1090 oop obj = CompressedOops::decode_not_null(o);
1124
1125 class ShenandoahAdjustPointersTask : public WorkerTask {
1126 private:
1127 ShenandoahHeap* const _heap;
1128 ShenandoahRegionIterator _regions;
1129
1130 public:
1131 ShenandoahAdjustPointersTask() :
1132 WorkerTask("Shenandoah Adjust Pointers"),
1133 _heap(ShenandoahHeap::heap()) {
1134 }
1135
1136 void work(uint worker_id) {
1137 ShenandoahParallelWorkerSession worker_session(worker_id);
1138 ShenandoahAdjustPointersObjectClosure obj_cl;
1139 ShenandoahHeapRegion* r = _regions.next();
1140 while (r != NULL) {
1141 if (!r->is_humongous_continuation() && r->has_live()) {
1142 _heap->marked_object_iterate(r, &obj_cl);
1143 }
1144 if (r->is_pinned() && r->is_old() && r->is_active() && !r->is_humongous()) {
1145 // Pinned regions are not compacted so they may still hold unmarked objects with
1146 // reference to reclaimed memory. Remembered set scanning will crash if it attempts
1147 // to iterate the oops in these objects.
1148 r->begin_preemptible_coalesce_and_fill();
1149 r->oop_fill_and_coalesce_wo_cancel();
1150 }
1151 r = _regions.next();
1152 }
1153 }
1154 };
1155
1156 class ShenandoahAdjustRootPointersTask : public WorkerTask {
1157 private:
1158 ShenandoahRootAdjuster* _rp;
1159 PreservedMarksSet* _preserved_marks;
1160 public:
1161 ShenandoahAdjustRootPointersTask(ShenandoahRootAdjuster* rp, PreservedMarksSet* preserved_marks) :
1162 WorkerTask("Shenandoah Adjust Root Pointers"),
1163 _rp(rp),
1164 _preserved_marks(preserved_marks) {}
1165
1166 void work(uint worker_id) {
1167 ShenandoahParallelWorkerSession worker_session(worker_id);
1168 ShenandoahAdjustPointersClosure cl;
1169 _rp->roots_do(worker_id, &cl);
1170 _preserved_marks->get(worker_id)->adjust_during_full_gc();
1243 _heap->marked_object_iterate(r, &cl);
1244 }
1245 r->set_top(r->new_top());
1246 r = slice.next();
1247 }
1248 }
1249 };
1250
1251 class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
1252 private:
1253 ShenandoahHeap* const _heap;
1254 size_t _live;
1255
1256 public:
1257 ShenandoahPostCompactClosure() : _heap(ShenandoahHeap::heap()), _live(0) {
1258 _heap->free_set()->clear();
1259 }
1260
1261 void heap_region_do(ShenandoahHeapRegion* r) {
1262 assert (!r->is_cset(), "cset regions should have been demoted already");
1263 bool is_generational = _heap->mode()->is_generational();
1264
1265 // Need to reset the complete-top-at-mark-start pointer here because
1266 // the complete marking bitmap is no longer valid. This ensures
1267 // size-based iteration in marked_object_iterate().
1268 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
1269 // pinned regions.
1270 if (!r->is_pinned()) {
1271 _heap->complete_marking_context()->reset_top_at_mark_start(r);
1272 }
1273
1274 size_t live = r->used();
1275
1276 // Make empty regions that have been allocated into regular
1277 if (r->is_empty() && live > 0) {
1278 if (!is_generational) {
1279 r->make_young_maybe();
1280 }
1281 // else, generational mode compaction has already established affiliation.
1282 r->make_regular_bypass();
1283 }
1284
1285 // Reclaim regular regions that became empty
1286 if (r->is_regular() && live == 0) {
1287 r->make_trash();
1288 }
1289
1290 // Recycle all trash regions
1291 if (r->is_trash()) {
1292 live = 0;
1293 r->recycle();
1294 }
1295
1296 // Update final usage for generations
1297 if (is_generational && live != 0) {
1298 if (r->is_young()) {
1299 _heap->young_generation()->increase_used(live);
1300 } else if (r->is_old()) {
1301 _heap->old_generation()->increase_used(live);
1302 }
1303 }
1304
1305 r->set_live_data(live);
1306 r->reset_alloc_metadata();
1307 _live += live;
1308 }
1309
1310 size_t get_live() {
1311 return _live;
1312 }
1313 };
1314
1315 void ShenandoahFullGC::compact_humongous_objects() {
1316 // Compact humongous regions, based on their fwdptr objects.
1317 //
1318 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
1319 // humongous regions are already compacted, and do not require further moves, which alleviates
1320 // sliding costs. We may consider doing this in parallel in future.
1321
1322 ShenandoahHeap* heap = ShenandoahHeap::heap();
1323
1324 for (size_t c = heap->num_regions(); c > 0; c--) {
1325 ShenandoahHeapRegion* r = heap->get_region(c - 1);
1326 if (r->is_humongous_start()) {
1327 oop old_obj = cast_to_oop(r->bottom());
1328 if (!old_obj->is_forwarded()) {
1329 // No need to move the object, it stays at the same slot
1330 continue;
1331 }
1332 size_t words_size = old_obj->size();
1333 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
1334
1335 size_t old_start = r->index();
1336 size_t old_end = old_start + num_regions - 1;
1337 size_t new_start = heap->heap_region_index_containing(old_obj->forwardee());
1338 size_t new_end = new_start + num_regions - 1;
1339 assert(old_start != new_start, "must be real move");
1340 assert(r->is_stw_move_allowed(), "Region " SIZE_FORMAT " should be movable", r->index());
1341
1342 ContinuationGCSupport::relativize_stack_chunk(cast_to_oop<HeapWord*>(heap->get_region(old_start)->bottom()));
1343 log_debug(gc)("Full GC compaction moves humongous object from region " SIZE_FORMAT " to region " SIZE_FORMAT,
1344 old_start, new_start);
1345
1346 Copy::aligned_conjoint_words(heap->get_region(old_start)->bottom(),
1347 heap->get_region(new_start)->bottom(),
1348 words_size);
1349
1350 oop new_obj = cast_to_oop(heap->get_region(new_start)->bottom());
1351 new_obj->init_mark();
1352
1353 {
1354 ShenandoahRegionAffiliation original_affiliation = r->affiliation();
1355 for (size_t c = old_start; c <= old_end; c++) {
1356 ShenandoahHeapRegion* r = heap->get_region(c);
1357 // Leave humongous region affiliation unchanged.
1358 r->make_regular_bypass();
1359 r->set_top(r->bottom());
1360 }
1361
1362 for (size_t c = new_start; c <= new_end; c++) {
1363 ShenandoahHeapRegion* r = heap->get_region(c);
1364 if (c == new_start) {
1365 r->make_humongous_start_bypass(original_affiliation);
1366 } else {
1367 r->make_humongous_cont_bypass(original_affiliation);
1368 }
1369
1370 // Trailing region may be non-full, record the remainder there
1371 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
1372 if ((c == new_end) && (remainder != 0)) {
1373 r->set_top(r->bottom() + remainder);
1374 } else {
1375 r->set_top(r->end());
1376 }
1377
1378 r->reset_alloc_metadata();
1379 }
1380 }
1381 }
1382 }
1383 }
1384
1385 // This is slightly different to ShHeap::reset_next_mark_bitmap:
1386 // we need to remain able to walk pinned regions.
1387 // Since pinned region do not move and don't get compacted, we will get holes with
1426 }
1427
1428 // Compact humongous objects after regular object moves
1429 {
1430 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
1431 compact_humongous_objects();
1432 }
1433
1434 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
1435 // and must ensure the bitmap is in sync.
1436 {
1437 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_reset_complete);
1438 ShenandoahMCResetCompleteBitmapTask task;
1439 heap->workers()->run_task(&task);
1440 }
1441
1442 // Bring regions in proper states after the collection, and set heap properties.
1443 {
1444 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_rebuild);
1445
1446 if (heap->mode()->is_generational()) {
1447 heap->young_generation()->clear_used();
1448 heap->old_generation()->clear_used();
1449 }
1450
1451 ShenandoahPostCompactClosure post_compact;
1452 heap->heap_region_iterate(&post_compact);
1453 heap->set_used(post_compact.get_live());
1454 if (heap->mode()->is_generational()) {
1455 log_info(gc)("FullGC done: GLOBAL usage: " SIZE_FORMAT ", young usage: " SIZE_FORMAT ", old usage: " SIZE_FORMAT,
1456 post_compact.get_live(), heap->young_generation()->used(), heap->old_generation()->used());
1457 }
1458
1459 heap->collection_set()->clear();
1460 heap->free_set()->rebuild();
1461 }
1462
1463 heap->clear_cancelled_gc(true /* clear oom handler */);
1464 }
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