1 /*
2 * Copyright (c) 2014, 2017, Red Hat, Inc. and/or its affiliates.
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 "classfile/javaClasses.inline.hpp"
27 #include "code/codeCache.hpp"
28 #include "gc/shared/gcTraceTime.inline.hpp"
29 #include "gc/shenandoah/brooksPointer.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/shenandoahBarrierSet.hpp"
36 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
37 #include "gc/shenandoah/shenandoahHeap.hpp"
38 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
39 #include "gc/shenandoah/shenandoahRootProcessor.hpp"
40 #include "gc/shenandoah/shenandoahTraversalGC.hpp"
41 #include "gc/shenandoah/shenandoahUtils.hpp"
42 #include "gc/shenandoah/shenandoahVerifier.hpp"
43 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
44 #include "gc/shenandoah/vm_operations_shenandoah.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "runtime/biasedLocking.hpp"
47 #include "runtime/thread.hpp"
48 #include "utilities/copy.hpp"
49 #include "utilities/growableArray.hpp"
50 #include "gc/shared/taskqueue.inline.hpp"
51 #include "gc/shared/workgroup.hpp"
52
53 class ShenandoahClearRegionStatusClosure: public ShenandoahHeapRegionClosure {
54 private:
55 ShenandoahHeap* const _heap;
56
57 public:
58 ShenandoahClearRegionStatusClosure() : _heap(ShenandoahHeap::heap()) {}
59
60 bool heap_region_do(ShenandoahHeapRegion *r) {
61 _heap->set_next_top_at_mark_start(r->bottom(), r->top());
62 r->clear_live_data();
63 r->set_concurrent_iteration_safe_limit(r->top());
64 return false;
65 }
66 };
67
68 class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
69 private:
70 ShenandoahHeap* const _heap;
71
72 public:
73 ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {}
74 bool heap_region_do(ShenandoahHeapRegion* r) {
75 if (r->is_trash()) {
76 r->recycle();
77 }
78 if (r->is_cset()) {
79 r->make_regular_bypass();
80 }
81 if (r->is_empty_uncommitted()) {
82 r->make_committed_bypass();
83 }
84 assert (r->is_committed(), "only committed regions in heap now, see region " SIZE_FORMAT, r->region_number());
85
86 // Record current region occupancy: this communicates empty regions are free
87 // to the rest of Full GC code.
88 r->set_new_top(r->top());
89 return false;
90 }
91 };
92
93 void ShenandoahMarkCompact::initialize(GCTimer* gc_timer) {
94 _gc_timer = gc_timer;
95 }
96
97 void ShenandoahMarkCompact::do_it(GCCause::Cause gc_cause) {
98 ShenandoahHeap* heap = ShenandoahHeap::heap();
99
100 {
101 if (ShenandoahVerify) {
102 heap->verifier()->verify_before_fullgc();
103 }
104
105 heap->set_full_gc_in_progress(true);
106
107 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint");
108 assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped");
109
110 {
111 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
112 heap->pre_full_gc_dump(_gc_timer);
113 }
114
115 {
116 ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare);
117 // Full GC is supposed to recover from any GC state:
118
119 // a1. Cancel evacuation, if in progress
120 if (heap->is_evacuation_in_progress()) {
121 heap->set_evacuation_in_progress(false);
122 }
123 assert(!heap->is_evacuation_in_progress(), "sanity");
124
125 // a2. Cancel update-refs, if in progress
126 if (heap->is_update_refs_in_progress()) {
127 heap->set_update_refs_in_progress(false);
128 }
129 assert(!heap->is_update_refs_in_progress(), "sanity");
130
131 // a3. Cancel concurrent traversal GC, if in progress
132 if (heap->is_concurrent_traversal_in_progress()) {
133 heap->traversal_gc()->reset();
134 heap->set_concurrent_traversal_in_progress(false);
135 }
136
137 // b. Cancel concurrent mark, if in progress
138 if (heap->is_concurrent_mark_in_progress()) {
139 heap->concurrentMark()->cancel();
140 heap->stop_concurrent_marking();
141 }
142 assert(!heap->is_concurrent_mark_in_progress(), "sanity");
143
144 // c. Reset the bitmaps for new marking
145 heap->reset_next_mark_bitmap();
146 assert(heap->is_next_bitmap_clear(), "sanity");
147
148 // d. Abandon reference discovery and clear all discovered references.
149 ReferenceProcessor* rp = heap->ref_processor();
150 rp->disable_discovery();
151 rp->abandon_partial_discovery();
152 rp->verify_no_references_recorded();
153
154 {
155 ShenandoahHeapLocker lock(heap->lock());
156
157 // f. Make sure all regions are active. This is needed because we are potentially
158 // sliding the data through them
159 ShenandoahEnsureHeapActiveClosure ecl;
160 heap->heap_region_iterate(&ecl, false, false);
161
162 // g. Clear region statuses, including collection set status
163 ShenandoahClearRegionStatusClosure cl;
164 heap->heap_region_iterate(&cl, false, false);
165 }
166 }
167
168 {
169 if (UseTLAB) {
170 heap->make_tlabs_parsable(true);
171 }
172
173 CodeCache::gc_prologue();
174
175 // TODO: We don't necessarily need to update refs. We might want to clean
176 // up managing has_forwarded_objects when diving into degen/full-gc.
177 heap->set_has_forwarded_objects(true);
178
179 OrderAccess::fence();
180
181 phase1_mark_heap();
182
183 // Prevent read-barrier from kicking in while adjusting pointers in phase3.
184 heap->set_has_forwarded_objects(false);
185
186 heap->set_full_gc_move_in_progress(true);
187
188 // Setup workers for the rest
189 {
190 OrderAccess::fence();
191
192 // Initialize worker slices
193 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
194 for (uint i = 0; i < heap->max_workers(); i++) {
195 worker_slices[i] = new ShenandoahHeapRegionSet();
196 }
197
198 phase2_calculate_target_addresses(worker_slices);
199
200 OrderAccess::fence();
201
202 phase3_update_references();
203
204 phase4_compact_objects(worker_slices);
205
206 // Free worker slices
207 for (uint i = 0; i < heap->max_workers(); i++) {
208 delete worker_slices[i];
209 }
210 FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices);
211
212 CodeCache::gc_epilogue();
213 JvmtiExport::gc_epilogue();
214 }
215
216 heap->set_full_gc_move_in_progress(false);
217 heap->set_full_gc_in_progress(false);
218
219 if (ShenandoahVerify) {
220 heap->verifier()->verify_after_fullgc();
221 }
222 }
223
224 {
225 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
226 heap->post_full_gc_dump(_gc_timer);
227 }
228 }
229
230
231 if (UseShenandoahMatrix && PrintShenandoahMatrix) {
232 LogTarget(Info, gc) lt;
233 LogStream ls(lt);
234 heap->connection_matrix()->print_on(&ls);
235 }
236 }
237
238 void ShenandoahMarkCompact::phase1_mark_heap() {
239 GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer);
240 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
241
242 ShenandoahHeap* heap = ShenandoahHeap::heap();
243
244 ShenandoahConcurrentMark* cm = heap->concurrentMark();
245
246 // Do not trust heuristics, because this can be our last resort collection.
247 // Only ignore processing references and class unloading if explicitly disabled.
248 heap->set_process_references(ShenandoahRefProcFrequency != 0);
249 heap->set_unload_classes(ShenandoahUnloadClassesFrequency != 0);
250
251 ReferenceProcessor* rp = heap->ref_processor();
252 // enable ("weak") refs discovery
253 rp->enable_discovery(true /*verify_no_refs*/);
254 rp->setup_policy(true); // snapshot the soft ref policy to be used in this cycle
255 rp->set_active_mt_degree(heap->workers()->active_workers());
256
257 cm->update_roots(ShenandoahPhaseTimings::full_gc_roots);
258 cm->mark_roots(ShenandoahPhaseTimings::full_gc_roots);
259 cm->shared_finish_mark_from_roots(/* full_gc = */ true);
260
261 heap->swap_mark_bitmaps();
262
263 if (UseShenandoahMatrix && PrintShenandoahMatrix) {
264 LogTarget(Info, gc) lt;
265 LogStream ls(lt);
266 heap->connection_matrix()->print_on(&ls);
267 }
268 }
269
270 class ShenandoahMCReclaimHumongousRegionClosure : public ShenandoahHeapRegionClosure {
271 private:
272 ShenandoahHeap* const _heap;
273 public:
274 ShenandoahMCReclaimHumongousRegionClosure() : _heap(ShenandoahHeap::heap()) {}
275
276 bool heap_region_do(ShenandoahHeapRegion* r) {
277 if (r->is_humongous_start()) {
278 oop humongous_obj = oop(r->bottom() + BrooksPointer::word_size());
279 if (!_heap->is_marked_complete(humongous_obj)) {
280 _heap->trash_humongous_region_at(r);
281 }
282 }
283 return false;
284 }
285 };
286
287 class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
288 private:
289 ShenandoahHeap* const _heap;
290 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
291 int _empty_regions_pos;
292 ShenandoahHeapRegion* _to_region;
293 ShenandoahHeapRegion* _from_region;
294 HeapWord* _compact_point;
295
296 public:
297 ShenandoahPrepareForCompactionObjectClosure(GrowableArray<ShenandoahHeapRegion*>& empty_regions, ShenandoahHeapRegion* to_region) :
298 _heap(ShenandoahHeap::heap()),
299 _empty_regions(empty_regions),
300 _empty_regions_pos(0),
301 _to_region(to_region),
302 _from_region(NULL),
303 _compact_point(to_region->bottom()) {}
304
305 void set_from_region(ShenandoahHeapRegion* from_region) {
306 _from_region = from_region;
307 }
308
309 void finish_region() {
310 assert(_to_region != NULL, "should not happen");
311 _to_region->set_new_top(_compact_point);
312 }
313
314 bool is_compact_same_region() {
315 return _from_region == _to_region;
316 }
317
318 int empty_regions_pos() {
319 return _empty_regions_pos;
320 }
321
322 void do_object(oop p) {
323 assert(_from_region != NULL, "must set before work");
324 assert(_heap->is_marked_complete(p), "must be marked");
325 assert(!_heap->allocated_after_complete_mark_start((HeapWord*) p), "must be truly marked");
326
327 size_t obj_size = p->size() + BrooksPointer::word_size();
328 if (_compact_point + obj_size > _to_region->end()) {
329 finish_region();
330
331 // Object doesn't fit. Pick next empty region and start compacting there.
332 ShenandoahHeapRegion* new_to_region;
333 if (_empty_regions_pos < _empty_regions.length()) {
334 new_to_region = _empty_regions.at(_empty_regions_pos);
335 _empty_regions_pos++;
336 } else {
337 // Out of empty region? Compact within the same region.
338 new_to_region = _from_region;
339 }
340
341 assert(new_to_region != _to_region, "must not reuse same to-region");
342 assert(new_to_region != NULL, "must not be NULL");
343 _to_region = new_to_region;
344 _compact_point = _to_region->bottom();
345 }
346
347 // Object fits into current region, record new location:
348 assert(_compact_point + obj_size <= _to_region->end(), "must fit");
349 shenandoah_assert_not_forwarded(NULL, p);
350 BrooksPointer::set_raw(p, _compact_point + BrooksPointer::word_size());
351 _compact_point += obj_size;
352 }
353 };
354
355 class ShenandoahPrepareForCompactionTask : public AbstractGangTask {
356 private:
357 ShenandoahHeap* const _heap;
358 ShenandoahHeapRegionSet** const _worker_slices;
359 ShenandoahRegionIterator _heap_regions;
360
361 ShenandoahHeapRegion* next_from_region(ShenandoahHeapRegionSet* slice) {
362 ShenandoahHeapRegion* from_region = _heap_regions.next();
363
364 while (from_region != NULL && (!from_region->is_move_allowed() || from_region->is_humongous())) {
365 from_region = _heap_regions.next();
366 }
367
368 if (from_region != NULL) {
369 assert(slice != NULL, "sanity");
370 assert(!from_region->is_humongous(), "this path cannot handle humongous regions");
371 assert(from_region->is_move_allowed(), "only regions that can be moved in mark-compact");
372 slice->add_region(from_region);
373 }
374
375 return from_region;
376 }
377
378 public:
379 ShenandoahPrepareForCompactionTask(ShenandoahHeapRegionSet** worker_slices) :
380 AbstractGangTask("Shenandoah Prepare For Compaction Task"),
381 _heap(ShenandoahHeap::heap()), _worker_slices(worker_slices) {
382 }
383
384 void work(uint worker_id) {
385 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
386 ShenandoahHeapRegion* from_region = next_from_region(slice);
387 // No work?
388 if (from_region == NULL) {
389 return;
390 }
391
392 // Sliding compaction. Walk all regions in the slice, and compact them.
393 // Remember empty regions and reuse them as needed.
394 ResourceMark rm;
395 GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions());
396 ShenandoahPrepareForCompactionObjectClosure cl(empty_regions, from_region);
397 while (from_region != NULL) {
398 cl.set_from_region(from_region);
399 _heap->marked_object_iterate(from_region, &cl);
400
401 // Compacted the region to somewhere else? From-region is empty then.
402 if (!cl.is_compact_same_region()) {
403 empty_regions.append(from_region);
404 }
405 from_region = next_from_region(slice);
406 }
407 cl.finish_region();
408
409 // Mark all remaining regions as empty
410 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
411 ShenandoahHeapRegion* r = empty_regions.at(pos);
412 r->set_new_top(r->bottom());
413 }
414 }
415 };
416
417 void ShenandoahMarkCompact::calculate_target_humongous_objects() {
418 ShenandoahHeap* heap = ShenandoahHeap::heap();
419
420 // Compute the new addresses for humongous objects. We need to do this after addresses
421 // for regular objects are calculated, and we know what regions in heap suffix are
422 // available for humongous moves.
423 //
424 // Scan the heap backwards, because we are compacting humongous regions towards the end.
425 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
426 // humongous start there.
427 //
428 // The complication is potential non-movable regions during the scan. If such region is
429 // detected, then sliding restarts towards that non-movable region.
430
431 size_t to_begin = heap->num_regions();
432 size_t to_end = heap->num_regions();
433
434 for (size_t c = heap->num_regions() - 1; c > 0; c--) {
435 ShenandoahHeapRegion *r = heap->get_region(c);
436 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
437 // To-region candidate: record this, and continue scan
438 to_begin = r->region_number();
439 continue;
440 }
441
442 if (r->is_humongous_start() && r->is_move_allowed()) {
443 // From-region candidate: movable humongous region
444 oop old_obj = oop(r->bottom() + BrooksPointer::word_size());
445 size_t words_size = old_obj->size() + BrooksPointer::word_size();
446 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
447
448 size_t start = to_end - num_regions;
449
450 if (start >= to_begin && start != r->region_number()) {
451 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
452 BrooksPointer::set_raw(old_obj, heap->get_region(start)->bottom() + BrooksPointer::word_size());
453 to_end = start;
454 continue;
455 }
456 }
457
458 // Failed to fit. Scan starting from current region.
459 to_begin = r->region_number();
460 to_end = r->region_number();
461 }
462 }
463
464 void ShenandoahMarkCompact::phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices) {
465 GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer);
466 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
467
468 ShenandoahHeap* heap = ShenandoahHeap::heap();
469
470 {
471 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
472
473 {
474 ShenandoahHeapLocker lock(heap->lock());
475
476 ShenandoahMCReclaimHumongousRegionClosure cl;
477 heap->heap_region_iterate(&cl);
478
479 // After some humongous regions were reclaimed, we need to ensure their
480 // backing storage is active. This is needed because we are potentially
481 // sliding the data through them.
482 ShenandoahEnsureHeapActiveClosure ecl;
483 heap->heap_region_iterate(&ecl, false, false);
484 }
485
486 // Compute the new addresses for regular objects
487 ShenandoahPrepareForCompactionTask prepare_task(worker_slices);
488 heap->workers()->run_task(&prepare_task);
489 }
490
491 // Compute the new addresses for humongous objects
492 {
493 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
494 calculate_target_humongous_objects();
495 }
496 }
497
498 class ShenandoahAdjustPointersClosure : public MetadataAwareOopClosure {
499 private:
500 ShenandoahHeap* const _heap;
501 size_t _new_obj_offset;
502
503 template <class T>
504 inline void do_oop_work(T* p) {
505 T o = oopDesc::load_heap_oop(p);
506 if (! oopDesc::is_null(o)) {
507 oop obj = oopDesc::decode_heap_oop_not_null(o);
508 assert(_heap->is_marked_complete(obj), "must be marked");
509 oop forw = oop(BrooksPointer::get_raw(obj));
510 oopDesc::encode_store_heap_oop(p, forw);
511 if (UseShenandoahMatrix) {
512 if (_heap->is_in_reserved(p)) {
513 assert(_heap->is_in_reserved(forw), "must be in heap");
514 assert(_new_obj_offset != SIZE_MAX, "should be set");
515 // We're moving a to a', which points to b, about to be moved to b'.
516 // We already know b' from the fwd pointer of b.
517 // In the object closure, we see a, and we know a' (by looking at its
518 // fwd ptr). We store the offset in the OopClosure, which is going
519 // to visit all of a's fields, and then, when we see each field, we
520 // subtract the offset from each field address to get the final ptr.
521 _heap->connection_matrix()->set_connected(((HeapWord*) p) - _new_obj_offset, forw);
522 }
523 }
524 }
525 }
526
527 public:
528 ShenandoahAdjustPointersClosure() : _heap(ShenandoahHeap::heap()), _new_obj_offset(SIZE_MAX) {}
529
530 void do_oop(oop* p) { do_oop_work(p); }
531 void do_oop(narrowOop* p) { do_oop_work(p); }
532
533 void set_new_obj_offset(size_t new_obj_offset) {
534 _new_obj_offset = new_obj_offset;
535 }
536 };
537
538 class ShenandoahAdjustPointersObjectClosure : public ObjectClosure {
539 private:
540 ShenandoahHeap* const _heap;
541 ShenandoahAdjustPointersClosure _cl;
542
543 public:
544 ShenandoahAdjustPointersObjectClosure() :
545 _heap(ShenandoahHeap::heap()) {
546 }
547 void do_object(oop p) {
548 assert(_heap->is_marked_complete(p), "must be marked");
549 HeapWord* forw = BrooksPointer::get_raw(p);
550 _cl.set_new_obj_offset(pointer_delta((HeapWord*) p, forw));
551 p->oop_iterate(&_cl);
552 }
553 };
554
555 class ShenandoahAdjustPointersTask : public AbstractGangTask {
556 private:
557 ShenandoahHeap* const _heap;
558 ShenandoahRegionIterator _regions;
559
560 public:
561 ShenandoahAdjustPointersTask() :
562 AbstractGangTask("Shenandoah Adjust Pointers Task"),
563 _heap(ShenandoahHeap::heap()) {
564 }
565
566 void work(uint worker_id) {
567 ShenandoahAdjustPointersObjectClosure obj_cl;
568 ShenandoahHeapRegion* r = _regions.next();
569 while (r != NULL) {
570 if (!r->is_humongous_continuation()) {
571 _heap->marked_object_iterate(r, &obj_cl);
572 }
573 r = _regions.next();
574 }
575 }
576 };
577
578 class ShenandoahAdjustRootPointersTask : public AbstractGangTask {
579 private:
580 ShenandoahRootProcessor* _rp;
581
582 public:
583 ShenandoahAdjustRootPointersTask(ShenandoahRootProcessor* rp) :
584 AbstractGangTask("Shenandoah Adjust Root Pointers Task"),
585 _rp(rp) {}
586
587 void work(uint worker_id) {
588 ShenandoahAdjustPointersClosure cl;
589 CLDToOopClosure adjust_cld_closure(&cl, true);
590 MarkingCodeBlobClosure adjust_code_closure(&cl,
591 CodeBlobToOopClosure::FixRelocations);
592
593 _rp->process_all_roots(&cl, &cl,
594 &adjust_cld_closure,
595 &adjust_code_closure, NULL, worker_id);
596 }
597 };
598
599 void ShenandoahMarkCompact::phase3_update_references() {
600 GCTraceTime(Info, gc, phases) time("Phase 3: Adjust pointers", _gc_timer);
601 ShenandoahGCPhase adjust_pointer_phase(ShenandoahPhaseTimings::full_gc_adjust_pointers);
602
603 ShenandoahHeap* heap = ShenandoahHeap::heap();
604
605 if (UseShenandoahMatrix) {
606 heap->connection_matrix()->clear_all();
607 }
608
609 WorkGang* workers = heap->workers();
610 uint nworkers = workers->active_workers();
611 {
612 #if COMPILER2_OR_JVMCI
613 DerivedPointerTable::clear();
614 #endif
615 ShenandoahRootProcessor rp(heap, nworkers, ShenandoahPhaseTimings::full_gc_roots);
616 ShenandoahAdjustRootPointersTask task(&rp);
617 workers->run_task(&task);
618 #if COMPILER2_OR_JVMCI
619 DerivedPointerTable::update_pointers();
620 #endif
621 }
622
623 ShenandoahAdjustPointersTask adjust_pointers_task;
624 workers->run_task(&adjust_pointers_task);
625 }
626
627 class ShenandoahCompactObjectsClosure : public ObjectClosure {
628 private:
629 ShenandoahHeap* const _heap;
630 uint const _worker_id;
631
632 public:
633 ShenandoahCompactObjectsClosure(uint worker_id) :
634 _heap(ShenandoahHeap::heap()), _worker_id(worker_id) {}
635
636 void do_object(oop p) {
637 assert(_heap->is_marked_complete(p), "must be marked");
638 size_t size = (size_t)p->size();
639 HeapWord* compact_to = BrooksPointer::get_raw(p);
640 HeapWord* compact_from = (HeapWord*) p;
641 if (compact_from != compact_to) {
642 Copy::aligned_conjoint_words(compact_from, compact_to, size);
643 }
644 oop new_obj = oop(compact_to);
645 BrooksPointer::initialize(new_obj);
646 }
647 };
648
649 class ShenandoahCompactObjectsTask : public AbstractGangTask {
650 private:
651 ShenandoahHeap* const _heap;
652 ShenandoahHeapRegionSet** const _worker_slices;
653
654 public:
655 ShenandoahCompactObjectsTask(ShenandoahHeapRegionSet** worker_slices) :
656 AbstractGangTask("Shenandoah Compact Objects Task"),
657 _heap(ShenandoahHeap::heap()),
658 _worker_slices(worker_slices) {
659 }
660
661 void work(uint worker_id) {
662 ShenandoahHeapRegionSetIterator slice(_worker_slices[worker_id]);
663
664 ShenandoahCompactObjectsClosure cl(worker_id);
665 ShenandoahHeapRegion* r = slice.next();
666 while (r != NULL) {
667 assert(!r->is_humongous(), "must not get humongous regions here");
668 _heap->marked_object_iterate(r, &cl);
669 r->set_top(r->new_top());
670 r = slice.next();
671 }
672 }
673 };
674
675 class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
676 private:
677 ShenandoahHeap* const _heap;
678 size_t _live;
679
680 public:
681 ShenandoahPostCompactClosure() : _live(0), _heap(ShenandoahHeap::heap()) {
682 _heap->free_set()->clear();
683 }
684
685 bool heap_region_do(ShenandoahHeapRegion* r) {
686 assert (!r->is_cset(), "cset regions should have been demoted already");
687
688 // Need to reset the complete-top-at-mark-start pointer here because
689 // the complete marking bitmap is no longer valid. This ensures
690 // size-based iteration in marked_object_iterate().
691 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
692 // pinned regions.
693 if (!r->is_pinned()) {
694 _heap->set_complete_top_at_mark_start(r->bottom(), r->bottom());
695 }
696
697 size_t live = r->used();
698
699 // Make empty regions that have been allocated into regular
700 if (r->is_empty() && live > 0) {
701 r->make_regular_bypass();
702 }
703
704 // Reclaim regular regions that became empty
705 if (r->is_regular() && live == 0) {
706 r->make_trash();
707 }
708
709 // Recycle all trash regions
710 if (r->is_trash()) {
711 live = 0;
712 r->recycle();
713 }
714
715 r->set_live_data(live);
716 r->reset_alloc_metadata_to_shared();
717 _live += live;
718 return false;
719 }
720
721 size_t get_live() {
722 return _live;
723 }
724 };
725
726 void ShenandoahMarkCompact::compact_humongous_objects() {
727 // Compact humongous regions, based on their fwdptr objects.
728 //
729 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
730 // humongous regions are already compacted, and do not require further moves, which alleviates
731 // sliding costs. We may consider doing this in parallel in future.
732
733 ShenandoahHeap* heap = ShenandoahHeap::heap();
734
735 for (size_t c = heap->num_regions() - 1; c > 0; c--) {
736 ShenandoahHeapRegion* r = heap->get_region(c);
737 if (r->is_humongous_start()) {
738 oop old_obj = oop(r->bottom() + BrooksPointer::word_size());
739 size_t words_size = old_obj->size() + BrooksPointer::word_size();
740 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
741
742 size_t old_start = r->region_number();
743 size_t old_end = old_start + num_regions - 1;
744 size_t new_start = heap->heap_region_index_containing(BrooksPointer::get_raw(old_obj));
745 size_t new_end = new_start + num_regions - 1;
746
747 if (old_start == new_start) {
748 // No need to move the object, it stays at the same slot
749 continue;
750 }
751
752 assert (r->is_move_allowed(), "should be movable");
753
754 Copy::aligned_conjoint_words(heap->get_region(old_start)->bottom(),
755 heap->get_region(new_start)->bottom(),
756 ShenandoahHeapRegion::region_size_words()*num_regions);
757
758 oop new_obj = oop(heap->get_region(new_start)->bottom() + BrooksPointer::word_size());
759 BrooksPointer::initialize(new_obj);
760
761 {
762 ShenandoahHeapLocker lock(heap->lock());
763
764 for (size_t c = old_start; c <= old_end; c++) {
765 ShenandoahHeapRegion* r = heap->get_region(c);
766 r->make_regular_bypass();
767 r->set_top(r->bottom());
768 }
769
770 for (size_t c = new_start; c <= new_end; c++) {
771 ShenandoahHeapRegion* r = heap->get_region(c);
772 if (c == new_start) {
773 r->make_humongous_start_bypass();
774 } else {
775 r->make_humongous_cont_bypass();
776 }
777
778 // Trailing region may be non-full, record the remainder there
779 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
780 if ((c == new_end) && (remainder != 0)) {
781 r->set_top(r->bottom() + remainder);
782 } else {
783 r->set_top(r->end());
784 }
785
786 r->reset_alloc_metadata_to_shared();
787 }
788 }
789 }
790 }
791 }
792
793 // This is slightly different to ShHeap::reset_next_mark_bitmap:
794 // we need to remain able to walk pinned regions.
795 // Since pinned region do not move and don't get compacted, we will get holes with
796 // unreachable objects in them (which may have pointers to unloaded Klasses and thus
797 // cannot be iterated over using oop->size(). The only way to safely iterate over those is using
798 // a valid marking bitmap and valid TAMS pointer. This class only resets marking
799 // bitmaps for un-pinned regions, and later we only reset TAMS for unpinned regions.
800 class ShenandoahMCResetCompleteBitmapTask : public AbstractGangTask {
801 private:
802 ShenandoahRegionIterator _regions;
803
804 public:
805 ShenandoahMCResetCompleteBitmapTask() :
806 AbstractGangTask("Parallel Reset Bitmap Task") {
807 }
808
809 void work(uint worker_id) {
810 ShenandoahHeapRegion* region = _regions.next();
811 ShenandoahHeap* heap = ShenandoahHeap::heap();
812 while (region != NULL) {
813 if (heap->is_bitmap_slice_committed(region) && !region->is_pinned()) {
814 HeapWord* bottom = region->bottom();
815 HeapWord* top = heap->complete_top_at_mark_start(region->bottom());
816 if (top > bottom) {
817 heap->complete_mark_bit_map()->clear_range_large(MemRegion(bottom, top));
818 }
819 assert(heap->is_complete_bitmap_clear_range(bottom, region->end()), "must be clear");
820 }
821 region = _regions.next();
822 }
823 }
824 };
825
826 void ShenandoahMarkCompact::phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices) {
827 GCTraceTime(Info, gc, phases) time("Phase 4: Move objects", _gc_timer);
828 ShenandoahGCPhase compaction_phase(ShenandoahPhaseTimings::full_gc_copy_objects);
829
830 ShenandoahHeap* heap = ShenandoahHeap::heap();
831
832 // Compact regular objects first
833 {
834 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_regular);
835 ShenandoahCompactObjectsTask compact_task(worker_slices);
836 heap->workers()->run_task(&compact_task);
837 }
838
839 // Compact humongous objects after regular object moves
840 {
841 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
842 compact_humongous_objects();
843 }
844
845 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
846 // and must ensure the bitmap is in sync.
847 ShenandoahMCResetCompleteBitmapTask task;
848 heap->workers()->run_task(&task);
849
850 // Bring regions in proper states after the collection, and set heap properties.
851 {
852 ShenandoahHeapLocker lock(heap->lock());
853 ShenandoahPostCompactClosure post_compact;
854 heap->heap_region_iterate(&post_compact);
855 heap->set_used(post_compact.get_live());
856
857 heap->collection_set()->clear();
858 heap->free_set()->rebuild();
859 }
860
861 heap->clear_cancelled_concgc();
862
863 // Also clear the next bitmap in preparation for next marking.
864 heap->reset_next_mark_bitmap();
865 }