1 /*
2 * Copyright (c) 2014, 2018, 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/shenandoah/shenandoahBrooksPointer.hpp"
29 #include "gc/shenandoah/shenandoahConcurrentMark.inline.hpp"
30 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
31 #include "gc/shenandoah/shenandoahFreeSet.hpp"
32 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
33 #include "gc/shenandoah/shenandoahMarkCompact.hpp"
34 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
35 #include "gc/shenandoah/shenandoahHeap.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.hpp"
40 #include "gc/shenandoah/shenandoahTraversalGC.hpp"
41 #include "gc/shenandoah/shenandoahTaskqueue.hpp"
42 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
43 #include "gc/shenandoah/shenandoahUtils.hpp"
44 #include "gc/shenandoah/shenandoahVerifier.hpp"
45 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
46 #include "gc/shenandoah/vm_operations_shenandoah.hpp"
47 #include "memory/metaspace.hpp"
48 #include "oops/oop.inline.hpp"
49 #include "runtime/thread.hpp"
50 #include "utilities/copy.hpp"
51 #include "utilities/growableArray.hpp"
52 #include "gc/shared/workgroup.hpp"
53
54 void ShenandoahMarkCompact::initialize(GCTimer* gc_timer) {
55 _gc_timer = gc_timer;
56 }
57
58 void ShenandoahMarkCompact::do_it(GCCause::Cause gc_cause) {
59 ShenandoahHeap* heap = ShenandoahHeap::heap();
60
61 if (ShenandoahVerify) {
62 heap->verifier()->verify_before_fullgc();
63 }
64
65 if (VerifyBeforeGC) {
66 Universe::verify();
67 }
68
69 heap->set_full_gc_in_progress(true);
70
71 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint");
72 assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped");
73
74 {
75 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
76 heap->pre_full_gc_dump(_gc_timer);
77 }
78
79 {
80 ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare);
81 // Full GC is supposed to recover from any GC state:
82
83 // a0. Remember if we have forwarded objects
84 bool has_forwarded_objects = heap->has_forwarded_objects();
85
86 // a1. Cancel evacuation, if in progress
87 if (heap->is_evacuation_in_progress()) {
88 heap->set_evacuation_in_progress(false);
89 }
90 assert(!heap->is_evacuation_in_progress(), "sanity");
91
92 // a2. Cancel update-refs, if in progress
93 if (heap->is_update_refs_in_progress()) {
94 heap->set_update_refs_in_progress(false);
95 }
96 assert(!heap->is_update_refs_in_progress(), "sanity");
97
98 // a3. Cancel concurrent traversal GC, if in progress
99 if (heap->is_concurrent_traversal_in_progress()) {
100 heap->traversal_gc()->reset();
101 heap->set_concurrent_traversal_in_progress(false);
102 }
103
104 // b. Cancel concurrent mark, if in progress
105 if (heap->is_concurrent_mark_in_progress()) {
106 heap->concurrent_mark()->cancel();
107 heap->stop_concurrent_marking();
108 }
109 assert(!heap->is_concurrent_mark_in_progress(), "sanity");
110
111 // c. Reset the bitmaps for new marking
112 heap->reset_mark_bitmap();
113 assert(heap->marking_context()->is_bitmap_clear(), "sanity");
114 assert(!heap->marking_context()->is_complete(), "sanity");
115
116 // d. Abandon reference discovery and clear all discovered references.
117 ReferenceProcessor* rp = heap->ref_processor();
118 rp->disable_discovery();
119 rp->abandon_partial_discovery();
120 rp->verify_no_references_recorded();
121
122 // e. Set back forwarded objects bit back, in case some steps above dropped it.
123 heap->set_has_forwarded_objects(has_forwarded_objects);
124 }
125
126 heap->make_parsable(true);
127
128 CodeCache::gc_prologue();
129
130 OrderAccess::fence();
131
132 phase1_mark_heap();
133
134 // Once marking is done, which may have fixed up forwarded objects, we can drop it.
135 // Coming out of Full GC, we would not have any forwarded objects.
136 // This also prevents read barrier from kicking in while adjusting pointers in phase3.
137 heap->set_has_forwarded_objects(false);
138
139 heap->set_full_gc_move_in_progress(true);
140
141 // Setup workers for the rest
142 OrderAccess::fence();
143
144 // Initialize worker slices
145 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
146 for (uint i = 0; i < heap->max_workers(); i++) {
147 worker_slices[i] = new ShenandoahHeapRegionSet();
148 }
149
150 {
151 // The rest of code performs region moves, where region status is undefined
152 // until all phases run together.
153 ShenandoahHeapLocker lock(heap->lock());
154
155 phase2_calculate_target_addresses(worker_slices);
156
157 OrderAccess::fence();
158
159 phase3_update_references();
160
161 phase4_compact_objects(worker_slices);
162 }
163
164 // Resize metaspace
165 MetaspaceGC::compute_new_size();
166
167 // Free worker slices
168 for (uint i = 0; i < heap->max_workers(); i++) {
169 delete worker_slices[i];
170 }
171 FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices);
172
173 CodeCache::gc_epilogue();
174 JvmtiExport::gc_epilogue();
175
176 heap->set_full_gc_move_in_progress(false);
177 heap->set_full_gc_in_progress(false);
178
179 if (ShenandoahVerify) {
180 heap->verifier()->verify_after_fullgc();
181 }
182
183 if (VerifyAfterGC) {
184 Universe::verify();
185 }
186
187 {
188 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
189 heap->post_full_gc_dump(_gc_timer);
190 }
191 }
192
193 class ShenandoahPrepareForMarkClosure: public ShenandoahHeapRegionClosure {
194 private:
195 ShenandoahMarkingContext* const _ctx;
196
197 public:
198 ShenandoahPrepareForMarkClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
199
200 void heap_region_do(ShenandoahHeapRegion *r) {
201 _ctx->capture_top_at_mark_start(r);
202 r->clear_live_data();
203 r->set_concurrent_iteration_safe_limit(r->top());
204 }
205 };
206
207 void ShenandoahMarkCompact::phase1_mark_heap() {
208 GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer);
209 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
210
211 ShenandoahHeap* heap = ShenandoahHeap::heap();
212
213 ShenandoahPrepareForMarkClosure cl;
214 heap->heap_region_iterate(&cl);
215
216 ShenandoahConcurrentMark* cm = heap->concurrent_mark();
217
218 heap->set_process_references(heap->heuristics()->can_process_references());
219 heap->set_unload_classes(heap->heuristics()->can_unload_classes());
220
221 ReferenceProcessor* rp = heap->ref_processor();
222 // enable ("weak") refs discovery
223 rp->enable_discovery(true /*verify_no_refs*/);
224 rp->setup_policy(true); // forcefully purge all soft references
225 rp->set_active_mt_degree(heap->workers()->active_workers());
226
227 cm->update_roots(ShenandoahPhaseTimings::full_gc_roots);
228 cm->mark_roots(ShenandoahPhaseTimings::full_gc_roots);
229 cm->finish_mark_from_roots(/* full_gc = */ true);
230
231 heap->mark_complete_marking_context();
232 }
233
234 class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
235 private:
236 ShenandoahHeap* const _heap;
237 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
238 int _empty_regions_pos;
239 ShenandoahHeapRegion* _to_region;
240 ShenandoahHeapRegion* _from_region;
241 HeapWord* _compact_point;
242
243 public:
244 ShenandoahPrepareForCompactionObjectClosure(GrowableArray<ShenandoahHeapRegion*>& empty_regions, ShenandoahHeapRegion* to_region) :
245 _heap(ShenandoahHeap::heap()),
246 _empty_regions(empty_regions),
247 _empty_regions_pos(0),
248 _to_region(to_region),
249 _from_region(NULL),
250 _compact_point(to_region->bottom()) {}
251
252 void set_from_region(ShenandoahHeapRegion* from_region) {
253 _from_region = from_region;
254 }
255
256 void finish_region() {
257 assert(_to_region != NULL, "should not happen");
258 _to_region->set_new_top(_compact_point);
259 }
260
261 bool is_compact_same_region() {
262 return _from_region == _to_region;
263 }
264
265 int empty_regions_pos() {
266 return _empty_regions_pos;
267 }
268
269 void do_object(oop p) {
270 assert(_from_region != NULL, "must set before work");
271 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
272 assert(!_heap->complete_marking_context()->allocated_after_mark_start((HeapWord*) p), "must be truly marked");
273
274 size_t obj_size = p->size() + ShenandoahBrooksPointer::word_size();
275 if (_compact_point + obj_size > _to_region->end()) {
276 finish_region();
277
278 // Object doesn't fit. Pick next empty region and start compacting there.
279 ShenandoahHeapRegion* new_to_region;
280 if (_empty_regions_pos < _empty_regions.length()) {
281 new_to_region = _empty_regions.at(_empty_regions_pos);
282 _empty_regions_pos++;
283 } else {
284 // Out of empty region? Compact within the same region.
285 new_to_region = _from_region;
286 }
287
288 assert(new_to_region != _to_region, "must not reuse same to-region");
289 assert(new_to_region != NULL, "must not be NULL");
290 _to_region = new_to_region;
291 _compact_point = _to_region->bottom();
292 }
293
294 // Object fits into current region, record new location:
295 assert(_compact_point + obj_size <= _to_region->end(), "must fit");
296 shenandoah_assert_not_forwarded(NULL, p);
297 ShenandoahBrooksPointer::set_raw(p, _compact_point + ShenandoahBrooksPointer::word_size());
298 _compact_point += obj_size;
299 }
300 };
301
302 class ShenandoahPrepareForCompactionTask : public AbstractGangTask {
303 private:
304 ShenandoahHeap* const _heap;
305 ShenandoahHeapRegionSet** const _worker_slices;
306 ShenandoahRegionIterator _heap_regions;
307
308 ShenandoahHeapRegion* next_from_region(ShenandoahHeapRegionSet* slice) {
309 ShenandoahHeapRegion* from_region = _heap_regions.next();
310
311 while (from_region != NULL && (!from_region->is_move_allowed() || from_region->is_humongous())) {
312 from_region = _heap_regions.next();
313 }
314
315 if (from_region != NULL) {
316 assert(slice != NULL, "sanity");
317 assert(!from_region->is_humongous(), "this path cannot handle humongous regions");
318 assert(from_region->is_move_allowed(), "only regions that can be moved in mark-compact");
319 slice->add_region(from_region);
320 }
321
322 return from_region;
323 }
324
325 public:
326 ShenandoahPrepareForCompactionTask(ShenandoahHeapRegionSet** worker_slices) :
327 AbstractGangTask("Shenandoah Prepare For Compaction Task"),
328 _heap(ShenandoahHeap::heap()), _worker_slices(worker_slices) {
329 }
330
331 void work(uint worker_id) {
332 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
333 ShenandoahHeapRegion* from_region = next_from_region(slice);
334 // No work?
335 if (from_region == NULL) {
336 return;
337 }
338
339 // Sliding compaction. Walk all regions in the slice, and compact them.
340 // Remember empty regions and reuse them as needed.
341 ResourceMark rm;
342 GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions());
343 ShenandoahPrepareForCompactionObjectClosure cl(empty_regions, from_region);
344 while (from_region != NULL) {
345 cl.set_from_region(from_region);
346 if (from_region->has_live()) {
347 _heap->marked_object_iterate(from_region, &cl);
348 }
349
350 // Compacted the region to somewhere else? From-region is empty then.
351 if (!cl.is_compact_same_region()) {
352 empty_regions.append(from_region);
353 }
354 from_region = next_from_region(slice);
355 }
356 cl.finish_region();
357
358 // Mark all remaining regions as empty
359 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
360 ShenandoahHeapRegion* r = empty_regions.at(pos);
361 r->set_new_top(r->bottom());
362 }
363 }
364 };
365
366 void ShenandoahMarkCompact::calculate_target_humongous_objects() {
367 ShenandoahHeap* heap = ShenandoahHeap::heap();
368
369 // Compute the new addresses for humongous objects. We need to do this after addresses
370 // for regular objects are calculated, and we know what regions in heap suffix are
371 // available for humongous moves.
372 //
373 // Scan the heap backwards, because we are compacting humongous regions towards the end.
374 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
375 // humongous start there.
376 //
377 // The complication is potential non-movable regions during the scan. If such region is
378 // detected, then sliding restarts towards that non-movable region.
379
380 size_t to_begin = heap->num_regions();
381 size_t to_end = heap->num_regions();
382
383 for (size_t c = heap->num_regions() - 1; c > 0; c--) {
384 ShenandoahHeapRegion *r = heap->get_region(c);
385 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
386 // To-region candidate: record this, and continue scan
387 to_begin = r->region_number();
388 continue;
389 }
390
391 if (r->is_humongous_start() && r->is_move_allowed()) {
392 // From-region candidate: movable humongous region
393 oop old_obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size());
394 size_t words_size = old_obj->size() + ShenandoahBrooksPointer::word_size();
395 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
396
397 size_t start = to_end - num_regions;
398
399 if (start >= to_begin && start != r->region_number()) {
400 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
401 ShenandoahBrooksPointer::set_raw(old_obj, heap->get_region(start)->bottom() + ShenandoahBrooksPointer::word_size());
402 to_end = start;
403 continue;
404 }
405 }
406
407 // Failed to fit. Scan starting from current region.
408 to_begin = r->region_number();
409 to_end = r->region_number();
410 }
411 }
412
413 class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
414 private:
415 ShenandoahHeap* const _heap;
416
417 public:
418 ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {}
419 void heap_region_do(ShenandoahHeapRegion* r) {
420 if (r->is_trash()) {
421 r->recycle();
422 }
423 if (r->is_cset()) {
424 r->make_regular_bypass();
425 }
426 if (r->is_empty_uncommitted()) {
427 r->make_committed_bypass();
428 }
429 assert (r->is_committed(), "only committed regions in heap now, see region " SIZE_FORMAT, r->region_number());
430
431 // Record current region occupancy: this communicates empty regions are free
432 // to the rest of Full GC code.
433 r->set_new_top(r->top());
434 }
435 };
436
437 class ShenandoahTrashImmediateGarbageClosure: public ShenandoahHeapRegionClosure {
438 private:
439 ShenandoahHeap* const _heap;
440 ShenandoahMarkingContext* const _ctx;
441
442 public:
443 ShenandoahTrashImmediateGarbageClosure() :
444 _heap(ShenandoahHeap::heap()),
445 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
446
447 void heap_region_do(ShenandoahHeapRegion* r) {
448 if (r->is_humongous_start()) {
449 oop humongous_obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size());
450 if (!_ctx->is_marked(humongous_obj)) {
451 assert(!r->has_live(),
452 "Region " SIZE_FORMAT " is not marked, should not have live", r->region_number());
453 _heap->trash_humongous_region_at(r);
454 } else {
455 assert(r->has_live(),
456 "Region " SIZE_FORMAT " should have live", r->region_number());
457 }
458 } else if (r->is_humongous_continuation()) {
459 // If we hit continuation, the non-live humongous starts should have been trashed already
460 assert(r->humongous_start_region()->has_live(),
461 "Region " SIZE_FORMAT " should have live", r->region_number());
462 } else if (r->is_regular()) {
463 if (!r->has_live()) {
464 r->make_trash_immediate();
465 }
466 }
467 }
468 };
469
470 void ShenandoahMarkCompact::phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices) {
471 GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer);
472 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
473
474 ShenandoahHeap* heap = ShenandoahHeap::heap();
475
476 {
477 // Trash the immediately collectible regions before computing addresses
478 ShenandoahTrashImmediateGarbageClosure tigcl;
479 heap->heap_region_iterate(&tigcl);
480
481 // Make sure regions are in good state: committed, active, clean.
482 // This is needed because we are potentially sliding the data through them.
483 ShenandoahEnsureHeapActiveClosure ecl;
484 heap->heap_region_iterate(&ecl);
485 }
486
487 // Compute the new addresses for regular objects
488 {
489 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
490 ShenandoahPrepareForCompactionTask prepare_task(worker_slices);
491 heap->workers()->run_task(&prepare_task);
492 }
493
494 // Compute the new addresses for humongous objects
495 {
496 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
497 calculate_target_humongous_objects();
498 }
499 }
500
501 class ShenandoahAdjustPointersClosure : public MetadataVisitingOopIterateClosure {
502 private:
503 ShenandoahHeap* const _heap;
504 ShenandoahMarkingContext* const _ctx;
505
506 template <class T>
507 inline void do_oop_work(T* p) {
508 T o = RawAccess<>::oop_load(p);
509 if (!CompressedOops::is_null(o)) {
510 oop obj = CompressedOops::decode_not_null(o);
511 assert(_ctx->is_marked(obj), "must be marked");
512 oop forw = oop(ShenandoahBrooksPointer::get_raw(obj));
513 RawAccess<IS_NOT_NULL>::oop_store(p, forw);
514 }
515 }
516
517 public:
518 ShenandoahAdjustPointersClosure() :
519 _heap(ShenandoahHeap::heap()),
520 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
521
522 void do_oop(oop* p) { do_oop_work(p); }
523 void do_oop(narrowOop* p) { do_oop_work(p); }
524 };
525
526 class ShenandoahAdjustPointersObjectClosure : public ObjectClosure {
527 private:
528 ShenandoahHeap* const _heap;
529 ShenandoahAdjustPointersClosure _cl;
530
531 public:
532 ShenandoahAdjustPointersObjectClosure() :
533 _heap(ShenandoahHeap::heap()) {
534 }
535 void do_object(oop p) {
536 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
537 HeapWord* forw = ShenandoahBrooksPointer::get_raw(p);
538 p->oop_iterate(&_cl);
539 }
540 };
541
542 class ShenandoahAdjustPointersTask : public AbstractGangTask {
543 private:
544 ShenandoahHeap* const _heap;
545 ShenandoahRegionIterator _regions;
546
547 public:
548 ShenandoahAdjustPointersTask() :
549 AbstractGangTask("Shenandoah Adjust Pointers Task"),
550 _heap(ShenandoahHeap::heap()) {
551 }
552
553 void work(uint worker_id) {
554 ShenandoahAdjustPointersObjectClosure obj_cl;
555 ShenandoahHeapRegion* r = _regions.next();
556 while (r != NULL) {
557 if (!r->is_humongous_continuation() && r->has_live()) {
558 _heap->marked_object_iterate(r, &obj_cl);
559 }
560 r = _regions.next();
561 }
562 }
563 };
564
565 class ShenandoahAdjustRootPointersTask : public AbstractGangTask {
566 private:
567 ShenandoahRootProcessor* _rp;
568
569 public:
570 ShenandoahAdjustRootPointersTask(ShenandoahRootProcessor* rp) :
571 AbstractGangTask("Shenandoah Adjust Root Pointers Task"),
572 _rp(rp) {}
573
574 void work(uint worker_id) {
575 ShenandoahAdjustPointersClosure cl;
576 CLDToOopClosure adjust_cld_closure(&cl, ClassLoaderData::_claim_strong);
577 MarkingCodeBlobClosure adjust_code_closure(&cl,
578 CodeBlobToOopClosure::FixRelocations);
579
580 _rp->process_all_roots(&cl, &cl,
581 &adjust_cld_closure,
582 &adjust_code_closure, NULL, worker_id);
583 }
584 };
585
586 void ShenandoahMarkCompact::phase3_update_references() {
587 GCTraceTime(Info, gc, phases) time("Phase 3: Adjust pointers", _gc_timer);
588 ShenandoahGCPhase adjust_pointer_phase(ShenandoahPhaseTimings::full_gc_adjust_pointers);
589
590 ShenandoahHeap* heap = ShenandoahHeap::heap();
591
592 WorkGang* workers = heap->workers();
593 uint nworkers = workers->active_workers();
594 {
595 #if COMPILER2_OR_JVMCI
596 DerivedPointerTable::clear();
597 #endif
598 ShenandoahRootProcessor rp(heap, nworkers, ShenandoahPhaseTimings::full_gc_roots);
599 ShenandoahAdjustRootPointersTask task(&rp);
600 workers->run_task(&task);
601 #if COMPILER2_OR_JVMCI
602 DerivedPointerTable::update_pointers();
603 #endif
604 }
605
606 ShenandoahAdjustPointersTask adjust_pointers_task;
607 workers->run_task(&adjust_pointers_task);
608 }
609
610 class ShenandoahCompactObjectsClosure : public ObjectClosure {
611 private:
612 ShenandoahHeap* const _heap;
613 uint const _worker_id;
614
615 public:
616 ShenandoahCompactObjectsClosure(uint worker_id) :
617 _heap(ShenandoahHeap::heap()), _worker_id(worker_id) {}
618
619 void do_object(oop p) {
620 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
621 size_t size = (size_t)p->size();
622 HeapWord* compact_to = ShenandoahBrooksPointer::get_raw(p);
623 HeapWord* compact_from = (HeapWord*) p;
624 if (compact_from != compact_to) {
625 Copy::aligned_conjoint_words(compact_from, compact_to, size);
626 }
627 oop new_obj = oop(compact_to);
628 ShenandoahBrooksPointer::initialize(new_obj);
629 }
630 };
631
632 class ShenandoahCompactObjectsTask : public AbstractGangTask {
633 private:
634 ShenandoahHeap* const _heap;
635 ShenandoahHeapRegionSet** const _worker_slices;
636
637 public:
638 ShenandoahCompactObjectsTask(ShenandoahHeapRegionSet** worker_slices) :
639 AbstractGangTask("Shenandoah Compact Objects Task"),
640 _heap(ShenandoahHeap::heap()),
641 _worker_slices(worker_slices) {
642 }
643
644 void work(uint worker_id) {
645 ShenandoahHeapRegionSetIterator slice(_worker_slices[worker_id]);
646
647 ShenandoahCompactObjectsClosure cl(worker_id);
648 ShenandoahHeapRegion* r = slice.next();
649 while (r != NULL) {
650 assert(!r->is_humongous(), "must not get humongous regions here");
651 if (r->has_live()) {
652 _heap->marked_object_iterate(r, &cl);
653 }
654 r->set_top(r->new_top());
655 r = slice.next();
656 }
657 }
658 };
659
660 class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
661 private:
662 ShenandoahHeap* const _heap;
663 size_t _live;
664
665 public:
666 ShenandoahPostCompactClosure() : _heap(ShenandoahHeap::heap()), _live(0) {
667 _heap->free_set()->clear();
668 }
669
670 void heap_region_do(ShenandoahHeapRegion* r) {
671 assert (!r->is_cset(), "cset regions should have been demoted already");
672
673 // Need to reset the complete-top-at-mark-start pointer here because
674 // the complete marking bitmap is no longer valid. This ensures
675 // size-based iteration in marked_object_iterate().
676 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
677 // pinned regions.
678 if (!r->is_pinned()) {
679 _heap->complete_marking_context()->reset_top_at_mark_start(r);
680 }
681
682 size_t live = r->used();
683
684 // Make empty regions that have been allocated into regular
685 if (r->is_empty() && live > 0) {
686 r->make_regular_bypass();
687 }
688
689 // Reclaim regular regions that became empty
690 if (r->is_regular() && live == 0) {
691 r->make_trash();
692 }
693
694 // Recycle all trash regions
695 if (r->is_trash()) {
696 live = 0;
697 r->recycle();
698 }
699
700 r->set_live_data(live);
701 r->reset_alloc_metadata_to_shared();
702 _live += live;
703 }
704
705 size_t get_live() {
706 return _live;
707 }
708 };
709
710 void ShenandoahMarkCompact::compact_humongous_objects() {
711 // Compact humongous regions, based on their fwdptr objects.
712 //
713 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
714 // humongous regions are already compacted, and do not require further moves, which alleviates
715 // sliding costs. We may consider doing this in parallel in future.
716
717 ShenandoahHeap* heap = ShenandoahHeap::heap();
718
719 for (size_t c = heap->num_regions() - 1; c > 0; c--) {
720 ShenandoahHeapRegion* r = heap->get_region(c);
721 if (r->is_humongous_start()) {
722 oop old_obj = oop(r->bottom() + ShenandoahBrooksPointer::word_size());
723 size_t words_size = old_obj->size() + ShenandoahBrooksPointer::word_size();
724 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
725
726 size_t old_start = r->region_number();
727 size_t old_end = old_start + num_regions - 1;
728 size_t new_start = heap->heap_region_index_containing(ShenandoahBrooksPointer::get_raw(old_obj));
729 size_t new_end = new_start + num_regions - 1;
730
731 if (old_start == new_start) {
732 // No need to move the object, it stays at the same slot
733 continue;
734 }
735
736 assert (r->is_move_allowed(), "should be movable");
737
738 Copy::aligned_conjoint_words(heap->get_region(old_start)->bottom(),
739 heap->get_region(new_start)->bottom(),
740 ShenandoahHeapRegion::region_size_words()*num_regions);
741
742 oop new_obj = oop(heap->get_region(new_start)->bottom() + ShenandoahBrooksPointer::word_size());
743 ShenandoahBrooksPointer::initialize(new_obj);
744
745 {
746 for (size_t c = old_start; c <= old_end; c++) {
747 ShenandoahHeapRegion* r = heap->get_region(c);
748 r->make_regular_bypass();
749 r->set_top(r->bottom());
750 }
751
752 for (size_t c = new_start; c <= new_end; c++) {
753 ShenandoahHeapRegion* r = heap->get_region(c);
754 if (c == new_start) {
755 r->make_humongous_start_bypass();
756 } else {
757 r->make_humongous_cont_bypass();
758 }
759
760 // Trailing region may be non-full, record the remainder there
761 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
762 if ((c == new_end) && (remainder != 0)) {
763 r->set_top(r->bottom() + remainder);
764 } else {
765 r->set_top(r->end());
766 }
767
768 r->reset_alloc_metadata_to_shared();
769 }
770 }
771 }
772 }
773 }
774
775 // This is slightly different to ShHeap::reset_next_mark_bitmap:
776 // we need to remain able to walk pinned regions.
777 // Since pinned region do not move and don't get compacted, we will get holes with
778 // unreachable objects in them (which may have pointers to unloaded Klasses and thus
779 // cannot be iterated over using oop->size(). The only way to safely iterate over those is using
780 // a valid marking bitmap and valid TAMS pointer. This class only resets marking
781 // bitmaps for un-pinned regions, and later we only reset TAMS for unpinned regions.
782 class ShenandoahMCResetCompleteBitmapTask : public AbstractGangTask {
783 private:
784 ShenandoahRegionIterator _regions;
785
786 public:
787 ShenandoahMCResetCompleteBitmapTask() :
788 AbstractGangTask("Parallel Reset Bitmap Task") {
789 }
790
791 void work(uint worker_id) {
792 ShenandoahHeapRegion* region = _regions.next();
793 ShenandoahHeap* heap = ShenandoahHeap::heap();
794 ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
795 while (region != NULL) {
796 if (heap->is_bitmap_slice_committed(region) && !region->is_pinned() && region->has_live()) {
797 ctx->clear_bitmap(region);
798 }
799 region = _regions.next();
800 }
801 }
802 };
803
804 void ShenandoahMarkCompact::phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices) {
805 GCTraceTime(Info, gc, phases) time("Phase 4: Move objects", _gc_timer);
806 ShenandoahGCPhase compaction_phase(ShenandoahPhaseTimings::full_gc_copy_objects);
807
808 ShenandoahHeap* heap = ShenandoahHeap::heap();
809
810 // Compact regular objects first
811 {
812 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_regular);
813 ShenandoahCompactObjectsTask compact_task(worker_slices);
814 heap->workers()->run_task(&compact_task);
815 }
816
817 // Compact humongous objects after regular object moves
818 {
819 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
820 compact_humongous_objects();
821 }
822
823 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
824 // and must ensure the bitmap is in sync.
825 {
826 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_reset_complete);
827 ShenandoahMCResetCompleteBitmapTask task;
828 heap->workers()->run_task(&task);
829 }
830
831 // Bring regions in proper states after the collection, and set heap properties.
832 {
833 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_rebuild);
834
835 ShenandoahPostCompactClosure post_compact;
836 heap->heap_region_iterate(&post_compact);
837 heap->set_used(post_compact.get_live());
838
839 heap->collection_set()->clear();
840 heap->free_set()->rebuild();
841 }
842
843 heap->clear_cancelled_gc();
844 }