1/*
2 * Copyright (c) 2014, 2019, Red Hat, Inc. All rights reserved.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24#include "precompiled.hpp"
25
26#include "code/codeCache.hpp"
27#include "gc/shared/gcTraceTime.inline.hpp"
28#include "gc/shared/preservedMarks.inline.hpp"
29#include "gc/shenandoah/shenandoahForwarding.inline.hpp"
30#include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
31#include "gc/shenandoah/shenandoahCollectionSet.hpp"
32#include "gc/shenandoah/shenandoahFreeSet.hpp"
33#include "gc/shenandoah/shenandoahPhaseTimings.hpp"
34#include "gc/shenandoah/shenandoahMarkCompact.hpp"
35#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
36#include "gc/shenandoah/shenandoahHeap.inline.hpp"
37#include "gc/shenandoah/shenandoahHeuristics.hpp"
38#include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
39#include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
40#include "gc/shenandoah/shenandoahTraversalGC.hpp"
41#include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
42#include "gc/shenandoah/shenandoahUtils.hpp"
43#include "gc/shenandoah/shenandoahVerifier.hpp"
44#include "gc/shenandoah/shenandoahVMOperations.hpp"
45#include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
46#include "memory/metaspace.hpp"
47#include "memory/universe.hpp"
48#include "oops/compressedOops.inline.hpp"
49#include "oops/oop.inline.hpp"
50#include "runtime/biasedLocking.hpp"
51#include "runtime/thread.hpp"
52#include "utilities/copy.hpp"
53#include "utilities/growableArray.hpp"
54#include "gc/shared/workgroup.hpp"
55
56ShenandoahMarkCompact::ShenandoahMarkCompact() :
57 _gc_timer(NULL),
58 _preserved_marks(new PreservedMarksSet(true)) {}
59
60void ShenandoahMarkCompact::initialize(GCTimer* gc_timer) {
61 _gc_timer = gc_timer;
62}
63
64void ShenandoahMarkCompact::do_it(GCCause::Cause gc_cause) {
65 ShenandoahHeap* heap = ShenandoahHeap::heap();
66
67 if (ShenandoahVerify) {
68 heap->verifier()->verify_before_fullgc();
69 }
70
71 if (VerifyBeforeGC) {
72 Universe::verify();
73 }
74
75 heap->set_full_gc_in_progress(true);
76
77 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint");
78 assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped");
79
80 {
81 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
82 heap->pre_full_gc_dump(_gc_timer);
83 }
84
85 {
86 ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare);
87 // Full GC is supposed to recover from any GC state:
88
89 // a0. Remember if we have forwarded objects
90 bool has_forwarded_objects = heap->has_forwarded_objects();
91
92 // a1. Cancel evacuation, if in progress
93 if (heap->is_evacuation_in_progress()) {
94 heap->set_evacuation_in_progress(false);
95 }
96 assert(!heap->is_evacuation_in_progress(), "sanity");
97
98 // a2. Cancel update-refs, if in progress
99 if (heap->is_update_refs_in_progress()) {
100 heap->set_update_refs_in_progress(false);
101 }
102 assert(!heap->is_update_refs_in_progress(), "sanity");
103
104 // a3. Cancel concurrent traversal GC, if in progress
105 if (heap->is_concurrent_traversal_in_progress()) {
106 heap->traversal_gc()->reset();
107 heap->set_concurrent_traversal_in_progress(false);
108 }
109
110 // b. Cancel concurrent mark, if in progress
111 if (heap->is_concurrent_mark_in_progress()) {
112 heap->concurrent_mark()->cancel();
113 heap->stop_concurrent_marking();
114 }
115 assert(!heap->is_concurrent_mark_in_progress(), "sanity");
116
117 // c. Reset the bitmaps for new marking
118 heap->reset_mark_bitmap();
119 assert(heap->marking_context()->is_bitmap_clear(), "sanity");
120 assert(!heap->marking_context()->is_complete(), "sanity");
121
122 // d. Abandon reference discovery and clear all discovered references.
123 ReferenceProcessor* rp = heap->ref_processor();
124 rp->disable_discovery();
125 rp->abandon_partial_discovery();
126 rp->verify_no_references_recorded();
127
128 // e. Set back forwarded objects bit back, in case some steps above dropped it.
129 heap->set_has_forwarded_objects(has_forwarded_objects);
130
131 // The rest of prologue:
132 BiasedLocking::preserve_marks();
133 _preserved_marks->init(heap->workers()->active_workers());
134 }
135
136 heap->make_parsable(true);
137
138 OrderAccess::fence();
139
140 phase1_mark_heap();
141
142 // Once marking is done, which may have fixed up forwarded objects, we can drop it.
143 // Coming out of Full GC, we would not have any forwarded objects.
144 // This also prevents resolves with fwdptr from kicking in while adjusting pointers in phase3.
145 heap->set_has_forwarded_objects(false);
146
147 heap->set_full_gc_move_in_progress(true);
148
149 // Setup workers for the rest
150 OrderAccess::fence();
151
152 // Initialize worker slices
153 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
154 for (uint i = 0; i < heap->max_workers(); i++) {
155 worker_slices[i] = new ShenandoahHeapRegionSet();
156 }
157
158 {
159 // The rest of code performs region moves, where region status is undefined
160 // until all phases run together.
161 ShenandoahHeapLocker lock(heap->lock());
162
163 phase2_calculate_target_addresses(worker_slices);
164
165 OrderAccess::fence();
166
167 phase3_update_references();
168
169 phase4_compact_objects(worker_slices);
170 }
171
172 {
173 // Epilogue
174 SharedRestorePreservedMarksTaskExecutor exec(heap->workers());
175 _preserved_marks->restore(&exec);
176 BiasedLocking::restore_marks();
177 _preserved_marks->reclaim();
178
179 JvmtiExport::gc_epilogue();
180 }
181
182 // Resize metaspace
183 MetaspaceGC::compute_new_size();
184
185 // Free worker slices
186 for (uint i = 0; i < heap->max_workers(); i++) {
187 delete worker_slices[i];
188 }
189 FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices);
190
191 heap->set_full_gc_move_in_progress(false);
192 heap->set_full_gc_in_progress(false);
193
194 if (ShenandoahVerify) {
195 heap->verifier()->verify_after_fullgc();
196 }
197
198 if (VerifyAfterGC) {
199 Universe::verify();
200 }
201
202 {
203 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
204 heap->post_full_gc_dump(_gc_timer);
205 }
206}
207
208class ShenandoahPrepareForMarkClosure: public ShenandoahHeapRegionClosure {
209private:
210 ShenandoahMarkingContext* const _ctx;
211
212public:
213 ShenandoahPrepareForMarkClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
214
215 void heap_region_do(ShenandoahHeapRegion *r) {
216 _ctx->capture_top_at_mark_start(r);
217 r->clear_live_data();
218 r->set_concurrent_iteration_safe_limit(r->top());
219 }
220};
221
222void ShenandoahMarkCompact::phase1_mark_heap() {
223 GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer);
224 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
225
226 ShenandoahHeap* heap = ShenandoahHeap::heap();
227
228 ShenandoahPrepareForMarkClosure cl;
229 heap->heap_region_iterate(&cl);
230
231 ShenandoahConcurrentMark* cm = heap->concurrent_mark();
232
233 heap->set_process_references(heap->heuristics()->can_process_references());
234 heap->set_unload_classes(heap->heuristics()->can_unload_classes());
235
236 ReferenceProcessor* rp = heap->ref_processor();
237 // enable ("weak") refs discovery
238 rp->enable_discovery(true /*verify_no_refs*/);
239 rp->setup_policy(true); // forcefully purge all soft references
240 rp->set_active_mt_degree(heap->workers()->active_workers());
241
242 cm->update_roots(ShenandoahPhaseTimings::full_gc_roots);
243 cm->mark_roots(ShenandoahPhaseTimings::full_gc_roots);
244 cm->finish_mark_from_roots(/* full_gc = */ true);
245
246 heap->mark_complete_marking_context();
247}
248
249class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
250private:
251 PreservedMarks* const _preserved_marks;
252 ShenandoahHeap* const _heap;
253 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
254 int _empty_regions_pos;
255 ShenandoahHeapRegion* _to_region;
256 ShenandoahHeapRegion* _from_region;
257 HeapWord* _compact_point;
258
259public:
260 ShenandoahPrepareForCompactionObjectClosure(PreservedMarks* preserved_marks,
261 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
262 ShenandoahHeapRegion* to_region) :
263 _preserved_marks(preserved_marks),
264 _heap(ShenandoahHeap::heap()),
265 _empty_regions(empty_regions),
266 _empty_regions_pos(0),
267 _to_region(to_region),
268 _from_region(NULL),
269 _compact_point(to_region->bottom()) {}
270
271 void set_from_region(ShenandoahHeapRegion* from_region) {
272 _from_region = from_region;
273 }
274
275 void finish_region() {
276 assert(_to_region != NULL, "should not happen");
277 _to_region->set_new_top(_compact_point);
278 }
279
280 bool is_compact_same_region() {
281 return _from_region == _to_region;
282 }
283
284 int empty_regions_pos() {
285 return _empty_regions_pos;
286 }
287
288 void do_object(oop p) {
289 assert(_from_region != NULL, "must set before work");
290 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
291 assert(!_heap->complete_marking_context()->allocated_after_mark_start((HeapWord*) p), "must be truly marked");
292
293 size_t obj_size = p->size();
294 if (_compact_point + obj_size > _to_region->end()) {
295 finish_region();
296
297 // Object doesn't fit. Pick next empty region and start compacting there.
298 ShenandoahHeapRegion* new_to_region;
299 if (_empty_regions_pos < _empty_regions.length()) {
300 new_to_region = _empty_regions.at(_empty_regions_pos);
301 _empty_regions_pos++;
302 } else {
303 // Out of empty region? Compact within the same region.
304 new_to_region = _from_region;
305 }
306
307 assert(new_to_region != _to_region, "must not reuse same to-region");
308 assert(new_to_region != NULL, "must not be NULL");
309 _to_region = new_to_region;
310 _compact_point = _to_region->bottom();
311 }
312
313 // Object fits into current region, record new location:
314 assert(_compact_point + obj_size <= _to_region->end(), "must fit");
315 shenandoah_assert_not_forwarded(NULL, p);
316 _preserved_marks->push_if_necessary(p, p->mark_raw());
317 p->forward_to(oop(_compact_point));
318 _compact_point += obj_size;
319 }
320};
321
322class ShenandoahPrepareForCompactionTask : public AbstractGangTask {
323private:
324 PreservedMarksSet* const _preserved_marks;
325 ShenandoahHeap* const _heap;
326 ShenandoahHeapRegionSet** const _worker_slices;
327 ShenandoahRegionIterator _heap_regions;
328
329 ShenandoahHeapRegion* next_from_region(ShenandoahHeapRegionSet* slice) {
330 ShenandoahHeapRegion* from_region = _heap_regions.next();
331
332 while (from_region != NULL && (!from_region->is_move_allowed() || from_region->is_humongous())) {
333 from_region = _heap_regions.next();
334 }
335
336 if (from_region != NULL) {
337 assert(slice != NULL, "sanity");
338 assert(!from_region->is_humongous(), "this path cannot handle humongous regions");
339 assert(from_region->is_move_allowed(), "only regions that can be moved in mark-compact");
340 slice->add_region(from_region);
341 }
342
343 return from_region;
344 }
345
346public:
347 ShenandoahPrepareForCompactionTask(PreservedMarksSet* preserved_marks, ShenandoahHeapRegionSet** worker_slices) :
348 AbstractGangTask("Shenandoah Prepare For Compaction Task"),
349 _preserved_marks(preserved_marks),
350 _heap(ShenandoahHeap::heap()), _worker_slices(worker_slices) {
351 }
352
353 void work(uint worker_id) {
354 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
355 ShenandoahHeapRegion* from_region = next_from_region(slice);
356 // No work?
357 if (from_region == NULL) {
358 return;
359 }
360
361 // Sliding compaction. Walk all regions in the slice, and compact them.
362 // Remember empty regions and reuse them as needed.
363 ResourceMark rm;
364 GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions());
365 ShenandoahPrepareForCompactionObjectClosure cl(_preserved_marks->get(worker_id), empty_regions, from_region);
366 while (from_region != NULL) {
367 cl.set_from_region(from_region);
368 if (from_region->has_live()) {
369 _heap->marked_object_iterate(from_region, &cl);
370 }
371
372 // Compacted the region to somewhere else? From-region is empty then.
373 if (!cl.is_compact_same_region()) {
374 empty_regions.append(from_region);
375 }
376 from_region = next_from_region(slice);
377 }
378 cl.finish_region();
379
380 // Mark all remaining regions as empty
381 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
382 ShenandoahHeapRegion* r = empty_regions.at(pos);
383 r->set_new_top(r->bottom());
384 }
385 }
386};
387
388void ShenandoahMarkCompact::calculate_target_humongous_objects() {
389 ShenandoahHeap* heap = ShenandoahHeap::heap();
390
391 // Compute the new addresses for humongous objects. We need to do this after addresses
392 // for regular objects are calculated, and we know what regions in heap suffix are
393 // available for humongous moves.
394 //
395 // Scan the heap backwards, because we are compacting humongous regions towards the end.
396 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
397 // humongous start there.
398 //
399 // The complication is potential non-movable regions during the scan. If such region is
400 // detected, then sliding restarts towards that non-movable region.
401
402 size_t to_begin = heap->num_regions();
403 size_t to_end = heap->num_regions();
404
405 for (size_t c = heap->num_regions(); c > 0; c--) {
406 ShenandoahHeapRegion *r = heap->get_region(c - 1);
407 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
408 // To-region candidate: record this, and continue scan
409 to_begin = r->region_number();
410 continue;
411 }
412
413 if (r->is_humongous_start() && r->is_move_allowed()) {
414 // From-region candidate: movable humongous region
415 oop old_obj = oop(r->bottom());
416 size_t words_size = old_obj->size();
417 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
418
419 size_t start = to_end - num_regions;
420
421 if (start >= to_begin && start != r->region_number()) {
422 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
423 _preserved_marks->get(0)->push_if_necessary(old_obj, old_obj->mark_raw());
424 old_obj->forward_to(oop(heap->get_region(start)->bottom()));
425 to_end = start;
426 continue;
427 }
428 }
429
430 // Failed to fit. Scan starting from current region.
431 to_begin = r->region_number();
432 to_end = r->region_number();
433 }
434}
435
436class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
437private:
438 ShenandoahHeap* const _heap;
439
440public:
441 ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {}
442 void heap_region_do(ShenandoahHeapRegion* r) {
443 if (r->is_trash()) {
444 r->recycle();
445 }
446 if (r->is_cset()) {
447 r->make_regular_bypass();
448 }
449 if (r->is_empty_uncommitted()) {
450 r->make_committed_bypass();
451 }
452 assert (r->is_committed(), "only committed regions in heap now, see region " SIZE_FORMAT, r->region_number());
453
454 // Record current region occupancy: this communicates empty regions are free
455 // to the rest of Full GC code.
456 r->set_new_top(r->top());
457 }
458};
459
460class ShenandoahTrashImmediateGarbageClosure: public ShenandoahHeapRegionClosure {
461private:
462 ShenandoahHeap* const _heap;
463 ShenandoahMarkingContext* const _ctx;
464
465public:
466 ShenandoahTrashImmediateGarbageClosure() :
467 _heap(ShenandoahHeap::heap()),
468 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
469
470 void heap_region_do(ShenandoahHeapRegion* r) {
471 if (r->is_humongous_start()) {
472 oop humongous_obj = oop(r->bottom());
473 if (!_ctx->is_marked(humongous_obj)) {
474 assert(!r->has_live(),
475 "Region " SIZE_FORMAT " is not marked, should not have live", r->region_number());
476 _heap->trash_humongous_region_at(r);
477 } else {
478 assert(r->has_live(),
479 "Region " SIZE_FORMAT " should have live", r->region_number());
480 }
481 } else if (r->is_humongous_continuation()) {
482 // If we hit continuation, the non-live humongous starts should have been trashed already
483 assert(r->humongous_start_region()->has_live(),
484 "Region " SIZE_FORMAT " should have live", r->region_number());
485 } else if (r->is_regular()) {
486 if (!r->has_live()) {
487 r->make_trash_immediate();
488 }
489 }
490 }
491};
492
493void ShenandoahMarkCompact::phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices) {
494 GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer);
495 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
496
497 ShenandoahHeap* heap = ShenandoahHeap::heap();
498
499 {
500 // Trash the immediately collectible regions before computing addresses
501 ShenandoahTrashImmediateGarbageClosure tigcl;
502 heap->heap_region_iterate(&tigcl);
503
504 // Make sure regions are in good state: committed, active, clean.
505 // This is needed because we are potentially sliding the data through them.
506 ShenandoahEnsureHeapActiveClosure ecl;
507 heap->heap_region_iterate(&ecl);
508 }
509
510 // Compute the new addresses for regular objects
511 {
512 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
513 ShenandoahPrepareForCompactionTask prepare_task(_preserved_marks, worker_slices);
514 heap->workers()->run_task(&prepare_task);
515 }
516
517 // Compute the new addresses for humongous objects
518 {
519 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
520 calculate_target_humongous_objects();
521 }
522}
523
524class ShenandoahAdjustPointersClosure : public MetadataVisitingOopIterateClosure {
525private:
526 ShenandoahHeap* const _heap;
527 ShenandoahMarkingContext* const _ctx;
528
529 template <class T>
530 inline void do_oop_work(T* p) {
531 T o = RawAccess<>::oop_load(p);
532 if (!CompressedOops::is_null(o)) {
533 oop obj = CompressedOops::decode_not_null(o);
534 assert(_ctx->is_marked(obj), "must be marked");
535 if (obj->is_forwarded()) {
536 oop forw = obj->forwardee();
537 RawAccess<IS_NOT_NULL>::oop_store(p, forw);
538 }
539 }
540 }
541
542public:
543 ShenandoahAdjustPointersClosure() :
544 _heap(ShenandoahHeap::heap()),
545 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
546
547 void do_oop(oop* p) { do_oop_work(p); }
548 void do_oop(narrowOop* p) { do_oop_work(p); }
549};
550
551class ShenandoahAdjustPointersObjectClosure : public ObjectClosure {
552private:
553 ShenandoahHeap* const _heap;
554 ShenandoahAdjustPointersClosure _cl;
555
556public:
557 ShenandoahAdjustPointersObjectClosure() :
558 _heap(ShenandoahHeap::heap()) {
559 }
560 void do_object(oop p) {
561 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
562 p->oop_iterate(&_cl);
563 }
564};
565
566class ShenandoahAdjustPointersTask : public AbstractGangTask {
567private:
568 ShenandoahHeap* const _heap;
569 ShenandoahRegionIterator _regions;
570
571public:
572 ShenandoahAdjustPointersTask() :
573 AbstractGangTask("Shenandoah Adjust Pointers Task"),
574 _heap(ShenandoahHeap::heap()) {
575 }
576
577 void work(uint worker_id) {
578 ShenandoahAdjustPointersObjectClosure obj_cl;
579 ShenandoahHeapRegion* r = _regions.next();
580 while (r != NULL) {
581 if (!r->is_humongous_continuation() && r->has_live()) {
582 _heap->marked_object_iterate(r, &obj_cl);
583 }
584 r = _regions.next();
585 }
586 }
587};
588
589class ShenandoahAdjustRootPointersTask : public AbstractGangTask {
590private:
591 ShenandoahRootAdjuster* _rp;
592 PreservedMarksSet* _preserved_marks;
593public:
594 ShenandoahAdjustRootPointersTask(ShenandoahRootAdjuster* rp, PreservedMarksSet* preserved_marks) :
595 AbstractGangTask("Shenandoah Adjust Root Pointers Task"),
596 _rp(rp),
597 _preserved_marks(preserved_marks) {}
598
599 void work(uint worker_id) {
600 ShenandoahAdjustPointersClosure cl;
601 _rp->roots_do(worker_id, &cl);
602 _preserved_marks->get(worker_id)->adjust_during_full_gc();
603 }
604};
605
606void ShenandoahMarkCompact::phase3_update_references() {
607 GCTraceTime(Info, gc, phases) time("Phase 3: Adjust pointers", _gc_timer);
608 ShenandoahGCPhase adjust_pointer_phase(ShenandoahPhaseTimings::full_gc_adjust_pointers);
609
610 ShenandoahHeap* heap = ShenandoahHeap::heap();
611
612 WorkGang* workers = heap->workers();
613 uint nworkers = workers->active_workers();
614 {
615#if COMPILER2_OR_JVMCI
616 DerivedPointerTable::clear();
617#endif
618 ShenandoahRootAdjuster rp(nworkers, ShenandoahPhaseTimings::full_gc_roots);
619 ShenandoahAdjustRootPointersTask task(&rp, _preserved_marks);
620 workers->run_task(&task);
621#if COMPILER2_OR_JVMCI
622 DerivedPointerTable::update_pointers();
623#endif
624 }
625
626 ShenandoahAdjustPointersTask adjust_pointers_task;
627 workers->run_task(&adjust_pointers_task);
628}
629
630class ShenandoahCompactObjectsClosure : public ObjectClosure {
631private:
632 ShenandoahHeap* const _heap;
633 uint const _worker_id;
634
635public:
636 ShenandoahCompactObjectsClosure(uint worker_id) :
637 _heap(ShenandoahHeap::heap()), _worker_id(worker_id) {}
638
639 void do_object(oop p) {
640 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
641 size_t size = (size_t)p->size();
642 if (p->is_forwarded()) {
643 HeapWord* compact_from = (HeapWord*) p;
644 HeapWord* compact_to = (HeapWord*) p->forwardee();
645 Copy::aligned_conjoint_words(compact_from, compact_to, size);
646 oop new_obj = oop(compact_to);
647 new_obj->init_mark_raw();
648 }
649 }
650};
651
652class ShenandoahCompactObjectsTask : public AbstractGangTask {
653private:
654 ShenandoahHeap* const _heap;
655 ShenandoahHeapRegionSet** const _worker_slices;
656
657public:
658 ShenandoahCompactObjectsTask(ShenandoahHeapRegionSet** worker_slices) :
659 AbstractGangTask("Shenandoah Compact Objects Task"),
660 _heap(ShenandoahHeap::heap()),
661 _worker_slices(worker_slices) {
662 }
663
664 void work(uint worker_id) {
665 ShenandoahHeapRegionSetIterator slice(_worker_slices[worker_id]);
666
667 ShenandoahCompactObjectsClosure cl(worker_id);
668 ShenandoahHeapRegion* r = slice.next();
669 while (r != NULL) {
670 assert(!r->is_humongous(), "must not get humongous regions here");
671 if (r->has_live()) {
672 _heap->marked_object_iterate(r, &cl);
673 }
674 r->set_top(r->new_top());
675 r = slice.next();
676 }
677 }
678};
679
680class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
681private:
682 ShenandoahHeap* const _heap;
683 size_t _live;
684
685public:
686 ShenandoahPostCompactClosure() : _heap(ShenandoahHeap::heap()), _live(0) {
687 _heap->free_set()->clear();
688 }
689
690 void heap_region_do(ShenandoahHeapRegion* r) {
691 assert (!r->is_cset(), "cset regions should have been demoted already");
692
693 // Need to reset the complete-top-at-mark-start pointer here because
694 // the complete marking bitmap is no longer valid. This ensures
695 // size-based iteration in marked_object_iterate().
696 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
697 // pinned regions.
698 if (!r->is_pinned()) {
699 _heap->complete_marking_context()->reset_top_at_mark_start(r);
700 }
701
702 size_t live = r->used();
703
704 // Make empty regions that have been allocated into regular
705 if (r->is_empty() && live > 0) {
706 r->make_regular_bypass();
707 }
708
709 // Reclaim regular regions that became empty
710 if (r->is_regular() && live == 0) {
711 r->make_trash();
712 }
713
714 // Recycle all trash regions
715 if (r->is_trash()) {
716 live = 0;
717 r->recycle();
718 }
719
720 r->set_live_data(live);
721 r->reset_alloc_metadata_to_shared();
722 _live += live;
723 }
724
725 size_t get_live() {
726 return _live;
727 }
728};
729
730void ShenandoahMarkCompact::compact_humongous_objects() {
731 // Compact humongous regions, based on their fwdptr objects.
732 //
733 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
734 // humongous regions are already compacted, and do not require further moves, which alleviates
735 // sliding costs. We may consider doing this in parallel in future.
736
737 ShenandoahHeap* heap = ShenandoahHeap::heap();
738
739 for (size_t c = heap->num_regions(); c > 0; c--) {
740 ShenandoahHeapRegion* r = heap->get_region(c - 1);
741 if (r->is_humongous_start()) {
742 oop old_obj = oop(r->bottom());
743 if (!old_obj->is_forwarded()) {
744 // No need to move the object, it stays at the same slot
745 continue;
746 }
747 size_t words_size = old_obj->size();
748 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
749
750 size_t old_start = r->region_number();
751 size_t old_end = old_start + num_regions - 1;
752 size_t new_start = heap->heap_region_index_containing(old_obj->forwardee());
753 size_t new_end = new_start + num_regions - 1;
754 assert(old_start != new_start, "must be real move");
755 assert (r->is_move_allowed(), "should be movable");
756
757 Copy::aligned_conjoint_words(heap->get_region(old_start)->bottom(),
758 heap->get_region(new_start)->bottom(),
759 ShenandoahHeapRegion::region_size_words()*num_regions);
760
761 oop new_obj = oop(heap->get_region(new_start)->bottom());
762 new_obj->init_mark_raw();
763
764 {
765 for (size_t c = old_start; c <= old_end; c++) {
766 ShenandoahHeapRegion* r = heap->get_region(c);
767 r->make_regular_bypass();
768 r->set_top(r->bottom());
769 }
770
771 for (size_t c = new_start; c <= new_end; c++) {
772 ShenandoahHeapRegion* r = heap->get_region(c);
773 if (c == new_start) {
774 r->make_humongous_start_bypass();
775 } else {
776 r->make_humongous_cont_bypass();
777 }
778
779 // Trailing region may be non-full, record the remainder there
780 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
781 if ((c == new_end) && (remainder != 0)) {
782 r->set_top(r->bottom() + remainder);
783 } else {
784 r->set_top(r->end());
785 }
786
787 r->reset_alloc_metadata_to_shared();
788 }
789 }
790 }
791 }
792}
793
794// This is slightly different to ShHeap::reset_next_mark_bitmap:
795// we need to remain able to walk pinned regions.
796// Since pinned region do not move and don't get compacted, we will get holes with
797// unreachable objects in them (which may have pointers to unloaded Klasses and thus
798// cannot be iterated over using oop->size(). The only way to safely iterate over those is using
799// a valid marking bitmap and valid TAMS pointer. This class only resets marking
800// bitmaps for un-pinned regions, and later we only reset TAMS for unpinned regions.
801class ShenandoahMCResetCompleteBitmapTask : public AbstractGangTask {
802private:
803 ShenandoahRegionIterator _regions;
804
805public:
806 ShenandoahMCResetCompleteBitmapTask() :
807 AbstractGangTask("Parallel Reset Bitmap Task") {
808 }
809
810 void work(uint worker_id) {
811 ShenandoahHeapRegion* region = _regions.next();
812 ShenandoahHeap* heap = ShenandoahHeap::heap();
813 ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
814 while (region != NULL) {
815 if (heap->is_bitmap_slice_committed(region) && !region->is_pinned() && region->has_live()) {
816 ctx->clear_bitmap(region);
817 }
818 region = _regions.next();
819 }
820 }
821};
822
823void ShenandoahMarkCompact::phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices) {
824 GCTraceTime(Info, gc, phases) time("Phase 4: Move objects", _gc_timer);
825 ShenandoahGCPhase compaction_phase(ShenandoahPhaseTimings::full_gc_copy_objects);
826
827 ShenandoahHeap* heap = ShenandoahHeap::heap();
828
829 // Compact regular objects first
830 {
831 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_regular);
832 ShenandoahCompactObjectsTask compact_task(worker_slices);
833 heap->workers()->run_task(&compact_task);
834 }
835
836 // Compact humongous objects after regular object moves
837 {
838 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
839 compact_humongous_objects();
840 }
841
842 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
843 // and must ensure the bitmap is in sync.
844 {
845 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_reset_complete);
846 ShenandoahMCResetCompleteBitmapTask task;
847 heap->workers()->run_task(&task);
848 }
849
850 // Bring regions in proper states after the collection, and set heap properties.
851 {
852 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_rebuild);
853
854 ShenandoahPostCompactClosure post_compact;
855 heap->heap_region_iterate(&post_compact);
856 heap->set_used(post_compact.get_live());
857
858 heap->collection_set()->clear();
859 heap->free_set()->rebuild();
860 }
861
862 heap->clear_cancelled_gc();
863}
864