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_implementation/shenandoah/shenandoahGCTraceTime.hpp"
28 #include "gc_implementation/shared/gcTimer.hpp"
29 #include "gc_implementation/shenandoah/preservedMarks.inline.hpp"
30 #include "gc_implementation/shenandoah/shenandoahForwarding.hpp"
31 #include "gc_implementation/shenandoah/shenandoahCollectorPolicy.hpp"
32 #include "gc_implementation/shenandoah/shenandoahConcurrentMark.inline.hpp"
33 #include "gc_implementation/shenandoah/shenandoahCollectionSet.hpp"
34 #include "gc_implementation/shenandoah/shenandoahFreeSet.hpp"
35 #include "gc_implementation/shenandoah/shenandoahPhaseTimings.hpp"
36 #include "gc_implementation/shenandoah/shenandoahMarkCompact.hpp"
37 #include "gc_implementation/shenandoah/shenandoahHeapRegionSet.hpp"
38 #include "gc_implementation/shenandoah/shenandoahHeap.inline.hpp"
39 #include "gc_implementation/shenandoah/shenandoahHeuristics.hpp"
40 #include "gc_implementation/shenandoah/shenandoahMarkingContext.inline.hpp"
41 #include "gc_implementation/shenandoah/shenandoahRootProcessor.hpp"
42 #include "gc_implementation/shenandoah/shenandoahTaskqueue.inline.hpp"
43 #include "gc_implementation/shenandoah/shenandoahUtils.hpp"
44 #include "gc_implementation/shenandoah/shenandoahVerifier.hpp"
45 #include "gc_implementation/shenandoah/shenandoahVMOperations.hpp"
46 #include "gc_implementation/shenandoah/shenandoahWorkGroup.hpp"
47 #include "gc_implementation/shenandoah/shenandoahWorkerPolicy.hpp"
48 #include "memory/metaspace.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 "utilities/workgroup.hpp"
55
56 ShenandoahMarkCompact::ShenandoahMarkCompact() :
57 _gc_timer(NULL),
58 _preserved_marks(new PreservedMarksSet(true)) {}
59
60 void ShenandoahMarkCompact::initialize(GCTimer* gc_timer) {
61 _gc_timer = gc_timer;
62 }
63
64 void 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 phase(ShenandoahPhaseTimings::full_gc_prepare);
87 // Full GC is supposed to recover from any GC state:
88
89 // 0. Remember if we have forwarded objects
90 bool has_forwarded_objects = heap->has_forwarded_objects();
91
92 // a. Cancel concurrent mark, if in progress
93 if (heap->is_concurrent_mark_in_progress()) {
94 heap->concurrent_mark()->cancel();
95 heap->stop_concurrent_marking();
96 }
97 assert(!heap->is_concurrent_mark_in_progress(), "sanity");
98
99 // b1. Cancel evacuation, if in progress
100 if (heap->is_evacuation_in_progress()) {
101 heap->set_evacuation_in_progress(false);
102 }
103 assert(!heap->is_evacuation_in_progress(), "sanity");
104
105 // b2. Cancel update-refs, if in progress
106 if (heap->is_update_refs_in_progress()) {
107 heap->set_update_refs_in_progress(false);
108 }
109 assert(!heap->is_update_refs_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 // f. Sync pinned region status from the CP marks
126 heap->sync_pinned_region_status();
127
128 // The rest of prologue:
129 BiasedLocking::preserve_marks();
130 _preserved_marks->init(heap->workers()->active_workers());
131 }
132
133 heap->make_parsable(true);
134
135 CodeCache::gc_prologue();
136
137 OrderAccess::fence();
138
139 phase1_mark_heap();
140
141 // Once marking is done, which may have fixed up forwarded objects, we can drop it.
142 // Coming out of Full GC, we would not have any forwarded objects.
143 // This also prevents read barrier from kicking in while adjusting pointers in phase3.
144 heap->set_has_forwarded_objects(false);
145
146 heap->set_full_gc_move_in_progress(true);
147
148 // Setup workers for the rest
149 OrderAccess::fence();
150
151 // Initialize worker slices
152 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
153 for (uint i = 0; i < heap->max_workers(); i++) {
154 worker_slices[i] = new ShenandoahHeapRegionSet();
155 }
156
157 {
158 // The rest of code performs region moves, where region status is undefined
159 // until all phases run together.
160 ShenandoahHeapLocker lock(heap->lock());
161
162 phase2_calculate_target_addresses(worker_slices);
163
164 OrderAccess::fence();
165
166 phase3_update_references();
167
168 phase4_compact_objects(worker_slices);
169 }
170
171 {
172 // Epilogue
173 SharedRestorePreservedMarksTaskExecutor exec(heap->workers());
174 _preserved_marks->restore(&exec);
175 BiasedLocking::restore_marks();
176 _preserved_marks->reclaim();
177
178 JvmtiExport::gc_epilogue();
179 }
180
181 // Resize metaspace
182 MetaspaceGC::compute_new_size();
183
184 // Free worker slices
185 for (uint i = 0; i < heap->max_workers(); i++) {
186 delete worker_slices[i];
187 }
188 FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices, mtGC);
189
190 CodeCache::gc_epilogue();
191 JvmtiExport::gc_epilogue();
192
193 heap->set_full_gc_move_in_progress(false);
194 heap->set_full_gc_in_progress(false);
195
196 if (ShenandoahVerify) {
197 heap->verifier()->verify_after_fullgc();
198 }
199
200 if (VerifyAfterGC) {
201 Universe::verify();
202 }
203
204 {
205 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
206 heap->post_full_gc_dump(_gc_timer);
207 }
208
209 if (UseTLAB) {
210 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_resize_tlabs);
211 heap->resize_all_tlabs();
212 }
213 }
214
215 class ShenandoahPrepareForMarkClosure: public ShenandoahHeapRegionClosure {
216 private:
217 ShenandoahMarkingContext* const _ctx;
218
219 public:
220 ShenandoahPrepareForMarkClosure() : _ctx(ShenandoahHeap::heap()->marking_context()) {}
221
222 void heap_region_do(ShenandoahHeapRegion *r) {
223 _ctx->capture_top_at_mark_start(r);
224 r->clear_live_data();
225 r->set_concurrent_iteration_safe_limit(r->top());
226 }
227 };
228
229 void ShenandoahMarkCompact::phase1_mark_heap() {
230 ShenandoahHeap* heap = ShenandoahHeap::heap();
231 GCTraceTime time("Phase 1: Mark live objects", ShenandoahLogDebug, _gc_timer, heap->tracer()->gc_id());
232 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
233
234 ShenandoahPrepareForMarkClosure cl;
235 heap->heap_region_iterate(&cl);
236
237 ShenandoahConcurrentMark* cm = heap->concurrent_mark();
238
239 heap->set_process_references(heap->heuristics()->can_process_references());
240 heap->set_unload_classes(heap->heuristics()->can_unload_classes());
241
242 ReferenceProcessor* rp = heap->ref_processor();
243 // enable ("weak") refs discovery
244 rp->enable_discovery(true /*verify_no_refs*/, true);
245 rp->setup_policy(true); // forcefully purge all soft references
246 rp->set_active_mt_degree(heap->workers()->active_workers());
247
248 cm->update_roots(ShenandoahPhaseTimings::full_gc_roots);
249 cm->mark_roots(ShenandoahPhaseTimings::full_gc_roots);
250 cm->finish_mark_from_roots(/* full_gc = */ true);
251
252 heap->mark_complete_marking_context();
253 }
254
255 class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
256 private:
257 PreservedMarks* const _preserved_marks;
258 ShenandoahHeap* const _heap;
259 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
260 int _empty_regions_pos;
261 ShenandoahHeapRegion* _to_region;
262 ShenandoahHeapRegion* _from_region;
263 HeapWord* _compact_point;
264
265 public:
266 ShenandoahPrepareForCompactionObjectClosure(PreservedMarks* preserved_marks,
267 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
268 ShenandoahHeapRegion* to_region) :
269 _preserved_marks(preserved_marks),
270 _heap(ShenandoahHeap::heap()),
271 _empty_regions(empty_regions),
272 _empty_regions_pos(0),
273 _to_region(to_region),
274 _from_region(NULL),
275 _compact_point(to_region->bottom()) {}
276
277 void set_from_region(ShenandoahHeapRegion* from_region) {
278 _from_region = from_region;
279 }
280
281 void finish_region() {
282 assert(_to_region != NULL, "should not happen");
283 _to_region->set_new_top(_compact_point);
284 }
285
286 bool is_compact_same_region() {
287 return _from_region == _to_region;
288 }
289
290 int empty_regions_pos() {
291 return _empty_regions_pos;
292 }
293
294 void do_object(oop p) {
295 assert(_from_region != NULL, "must set before work");
296 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
297 assert(!_heap->complete_marking_context()->allocated_after_mark_start((HeapWord*) p), "must be truly marked");
298
299 size_t obj_size = p->size();
300 if (_compact_point + obj_size > _to_region->end()) {
301 finish_region();
302
303 // Object doesn't fit. Pick next empty region and start compacting there.
304 ShenandoahHeapRegion* new_to_region;
305 if (_empty_regions_pos < _empty_regions.length()) {
306 new_to_region = _empty_regions.at(_empty_regions_pos);
307 _empty_regions_pos++;
308 } else {
309 // Out of empty region? Compact within the same region.
310 new_to_region = _from_region;
311 }
312
313 assert(new_to_region != _to_region, "must not reuse same to-region");
314 assert(new_to_region != NULL, "must not be NULL");
315 _to_region = new_to_region;
316 _compact_point = _to_region->bottom();
317 }
318
319 // Object fits into current region, record new location:
320 assert(_compact_point + obj_size <= _to_region->end(), "must fit");
321 shenandoah_assert_not_forwarded(NULL, p);
322 _preserved_marks->push_if_necessary(p, p->mark());
323 p->forward_to(oop(_compact_point));
324 _compact_point += obj_size;
325 }
326 };
327
328 class ShenandoahPrepareForCompactionTask : public AbstractGangTask {
329 private:
330 PreservedMarksSet* const _preserved_marks;
331 ShenandoahHeap* const _heap;
332 ShenandoahHeapRegionSet** const _worker_slices;
333 ShenandoahRegionIterator _heap_regions;
334
335 ShenandoahHeapRegion* next_from_region(ShenandoahHeapRegionSet* slice) {
336 ShenandoahHeapRegion* from_region = _heap_regions.next();
337
338 // Look for next candidate for this slice:
339 while (from_region != NULL) {
340 // Empty region: get it into the slice to defragment the slice itself.
341 // We could have skipped this without violating correctness, but we really
342 // want to compact all live regions to the start of the heap, which sometimes
343 // means moving them into the fully empty regions.
344 if (from_region->is_empty()) break;
345
346 // Can move the region, and this is not the humongous region. Humongous
347 // moves are special cased here, because their moves are handled separately.
348 if (from_region->is_stw_move_allowed() && !from_region->is_humongous()) break;
349
350 from_region = _heap_regions.next();
351 }
352
353 if (from_region != NULL) {
354 assert(slice != NULL, "sanity");
355 assert(!from_region->is_humongous(), "this path cannot handle humongous regions");
356 assert(from_region->is_empty() || from_region->is_stw_move_allowed(), "only regions that can be moved in mark-compact");
357 slice->add_region(from_region);
358 }
359
360 return from_region;
361 }
362
363 public:
364 ShenandoahPrepareForCompactionTask(PreservedMarksSet* preserved_marks, ShenandoahHeapRegionSet** worker_slices) :
365 AbstractGangTask("Shenandoah Prepare For Compaction Task"),
366 _preserved_marks(preserved_marks),
367 _heap(ShenandoahHeap::heap()), _worker_slices(worker_slices) {
368 }
369
370 void work(uint worker_id) {
371 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
372 ShenandoahHeapRegion* from_region = next_from_region(slice);
373
374 // No work?
375 if (from_region == NULL) {
376 return;
377 }
378
379 // Sliding compaction. Walk all regions in the slice, and compact them.
380 // Remember empty regions and reuse them as needed.
381 ResourceMark rm;
382 GrowableArray<ShenandoahHeapRegion*> empty_regions((int)_heap->num_regions());
383 ShenandoahPrepareForCompactionObjectClosure cl(_preserved_marks->get(worker_id), empty_regions, from_region);
384 while (from_region != NULL) {
385 cl.set_from_region(from_region);
386 if (from_region->has_live()) {
387 _heap->marked_object_iterate(from_region, &cl);
388 }
389
390 // Compacted the region to somewhere else? From-region is empty then.
391 if (!cl.is_compact_same_region()) {
392 empty_regions.append(from_region);
393 }
394 from_region = next_from_region(slice);
395 }
396 cl.finish_region();
397
398 // Mark all remaining regions as empty
399 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
400 ShenandoahHeapRegion* r = empty_regions.at(pos);
401 r->set_new_top(r->bottom());
402 }
403 }
404 };
405
406 void ShenandoahMarkCompact::calculate_target_humongous_objects() {
407 ShenandoahHeap* heap = ShenandoahHeap::heap();
408
409 // Compute the new addresses for humongous objects. We need to do this after addresses
410 // for regular objects are calculated, and we know what regions in heap suffix are
411 // available for humongous moves.
412 //
413 // Scan the heap backwards, because we are compacting humongous regions towards the end.
414 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
415 // humongous start there.
416 //
417 // The complication is potential non-movable regions during the scan. If such region is
418 // detected, then sliding restarts towards that non-movable region.
419
420 size_t to_begin = heap->num_regions();
421 size_t to_end = heap->num_regions();
422
423 for (size_t c = heap->num_regions(); c > 0; c--) {
424 ShenandoahHeapRegion *r = heap->get_region(c - 1);
425 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
426 // To-region candidate: record this, and continue scan
427 to_begin = r->region_number();
428 continue;
429 }
430
431 if (r->is_humongous_start() && r->is_stw_move_allowed()) {
432 // From-region candidate: movable humongous region
433 oop old_obj = oop(r->bottom());
434 size_t words_size = old_obj->size();
435 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
436
437 size_t start = to_end - num_regions;
438
439 if (start >= to_begin && start != r->region_number()) {
440 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
441 _preserved_marks->get(0)->push_if_necessary(old_obj, old_obj->mark());
442 old_obj->forward_to(oop(heap->get_region(start)->bottom()));
443 to_end = start;
444 continue;
445 }
446 }
447
448 // Failed to fit. Scan starting from current region.
449 to_begin = r->region_number();
450 to_end = r->region_number();
451 }
452 }
453
454 class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
455 private:
456 ShenandoahHeap* const _heap;
457
458 public:
459 ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {}
460 void heap_region_do(ShenandoahHeapRegion* r) {
461 if (r->is_trash()) {
462 r->recycle();
463 }
464 if (r->is_cset()) {
465 r->make_regular_bypass();
466 }
467 if (r->is_empty_uncommitted()) {
468 r->make_committed_bypass();
469 }
470 assert (r->is_committed(), err_msg("only committed regions in heap now, see region " SIZE_FORMAT, r->region_number()));
471
472 // Record current region occupancy: this communicates empty regions are free
473 // to the rest of Full GC code.
474 r->set_new_top(r->top());
475 }
476 };
477
478 class ShenandoahTrashImmediateGarbageClosure: public ShenandoahHeapRegionClosure {
479 private:
480 ShenandoahHeap* const _heap;
481 ShenandoahMarkingContext* const _ctx;
482
483 public:
484 ShenandoahTrashImmediateGarbageClosure() :
485 _heap(ShenandoahHeap::heap()),
486 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
487
488 void heap_region_do(ShenandoahHeapRegion* r) {
489 if (r->is_humongous_start()) {
490 oop humongous_obj = oop(r->bottom());
491 if (!_ctx->is_marked(humongous_obj)) {
492 assert(!r->has_live(),
493 err_msg("Region " SIZE_FORMAT " is not marked, should not have live", r->region_number()));
494 _heap->trash_humongous_region_at(r);
495 } else {
496 assert(r->has_live(),
497 err_msg("Region " SIZE_FORMAT " should have live", r->region_number()));
498 }
499 } else if (r->is_humongous_continuation()) {
500 // If we hit continuation, the non-live humongous starts should have been trashed already
501 assert(r->humongous_start_region()->has_live(),
502 err_msg("Region " SIZE_FORMAT " should have live", r->region_number()));
503 } else if (r->is_regular()) {
504 if (!r->has_live()) {
505 r->make_trash_immediate();
506 }
507 }
508 }
509 };
510
511 void ShenandoahMarkCompact::phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices) {
512 ShenandoahHeap* heap = ShenandoahHeap::heap();
513 GCTraceTime time("Phase 2: Compute new object addresses", ShenandoahLogDebug, _gc_timer, heap->tracer()->gc_id());
514 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
515
516 // About to figure out which regions can be compacted, make sure pinning status
517 // had been updated in GC prologue.
518 heap->assert_pinned_region_status();
519
520 {
521 // Trash the immediately collectible regions before computing addresses
522 ShenandoahTrashImmediateGarbageClosure tigcl;
523 heap->heap_region_iterate(&tigcl);
524
525 // Make sure regions are in good state: committed, active, clean.
526 // This is needed because we are potentially sliding the data through them.
527 ShenandoahEnsureHeapActiveClosure ecl;
528 heap->heap_region_iterate(&ecl);
529 }
530
531 // Compute the new addresses for regular objects
532 {
533 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
534 ShenandoahPrepareForCompactionTask prepare_task(_preserved_marks, worker_slices);
535 heap->workers()->run_task(&prepare_task);
536 }
537
538 // Compute the new addresses for humongous objects
539 {
540 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
541 calculate_target_humongous_objects();
542 }
543 }
544
545 class ShenandoahAdjustPointersClosure : public MetadataAwareOopClosure {
546 private:
547 ShenandoahHeap* const _heap;
548 ShenandoahMarkingContext* const _ctx;
549
550 template <class T>
551 inline void do_oop_work(T* p) {
552 T o = oopDesc::load_heap_oop(p);
553 if (! oopDesc::is_null(o)) {
554 oop obj = oopDesc::decode_heap_oop_not_null(o);
555 assert(_ctx->is_marked(obj), "must be marked");
556 if (obj->is_forwarded()) {
557 oop forw = obj->forwardee();
558 oopDesc::encode_store_heap_oop(p, forw);
559 }
560 }
561 }
562
563 public:
564 ShenandoahAdjustPointersClosure() :
565 _heap(ShenandoahHeap::heap()),
566 _ctx(ShenandoahHeap::heap()->complete_marking_context()) {}
567
568 void do_oop(oop* p) { do_oop_work(p); }
569 void do_oop(narrowOop* p) { do_oop_work(p); }
570 };
571
572 class ShenandoahAdjustPointersObjectClosure : public ObjectClosure {
573 private:
574 ShenandoahHeap* const _heap;
575 ShenandoahAdjustPointersClosure _cl;
576
577 public:
578 ShenandoahAdjustPointersObjectClosure() :
579 _heap(ShenandoahHeap::heap()) {
580 }
581 void do_object(oop p) {
582 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
583 p->oop_iterate(&_cl);
584 }
585 };
586
587 class ShenandoahAdjustPointersTask : public AbstractGangTask {
588 private:
589 ShenandoahHeap* const _heap;
590 ShenandoahRegionIterator _regions;
591
592 public:
593 ShenandoahAdjustPointersTask() :
594 AbstractGangTask("Shenandoah Adjust Pointers Task"),
595 _heap(ShenandoahHeap::heap()) {
596 }
597
598 void work(uint worker_id) {
599 ShenandoahAdjustPointersObjectClosure obj_cl;
600 ShenandoahHeapRegion* r = _regions.next();
601 while (r != NULL) {
602 if (!r->is_humongous_continuation() && r->has_live()) {
603 _heap->marked_object_iterate(r, &obj_cl);
604 }
605 r = _regions.next();
606 }
607 }
608 };
609
610 class ShenandoahAdjustRootPointersTask : public AbstractGangTask {
611 private:
612 ShenandoahRootProcessor* _rp;
613 PreservedMarksSet* _preserved_marks;
614 public:
615 ShenandoahAdjustRootPointersTask(ShenandoahRootProcessor* rp, PreservedMarksSet* preserved_marks) :
616 AbstractGangTask("Shenandoah Adjust Root Pointers Task"),
617 _rp(rp),
618 _preserved_marks(preserved_marks) {}
619
620 void work(uint worker_id) {
621 ShenandoahAdjustPointersClosure cl;
622 CLDToOopClosure adjust_cld_closure(&cl, true);
623 MarkingCodeBlobClosure adjust_code_closure(&cl,
624 CodeBlobToOopClosure::FixRelocations);
625
626 _rp->process_all_roots(&cl, &cl,
627 &adjust_cld_closure,
628 &adjust_code_closure, NULL, worker_id);
629 _preserved_marks->get(worker_id)->adjust_during_full_gc();
630 }
631 };
632
633 void ShenandoahMarkCompact::phase3_update_references() {
634 ShenandoahHeap* heap = ShenandoahHeap::heap();
635 GCTraceTime time("Phase 3: Adjust pointers", ShenandoahLogDebug, _gc_timer, heap->tracer()->gc_id());
636 ShenandoahGCPhase adjust_pointer_phase(ShenandoahPhaseTimings::full_gc_adjust_pointers);
637
638 WorkGang* workers = heap->workers();
639 uint nworkers = workers->active_workers();
640 {
641 COMPILER2_PRESENT(DerivedPointerTable::clear());
642 ShenandoahRootProcessor rp(heap, nworkers, ShenandoahPhaseTimings::full_gc_roots);
643 ShenandoahAdjustRootPointersTask task(&rp, _preserved_marks);
644 workers->run_task(&task);
645 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
646 }
647
648 ShenandoahAdjustPointersTask adjust_pointers_task;
649 workers->run_task(&adjust_pointers_task);
650 }
651
652 class ShenandoahCompactObjectsClosure : public ObjectClosure {
653 private:
654 ShenandoahHeap* const _heap;
655
656 public:
657 ShenandoahCompactObjectsClosure() : _heap(ShenandoahHeap::heap()) {}
658
659 void do_object(oop p) {
660 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
661 size_t size = (size_t)p->size();
662 if (p->is_forwarded()) {
663 HeapWord* compact_from = (HeapWord*) p;
664 HeapWord* compact_to = (HeapWord*) p->forwardee();
665 Copy::aligned_conjoint_words(compact_from, compact_to, size);
666 oop new_obj = oop(compact_to);
667 new_obj->init_mark();
668 }
669 }
670 };
671
672 class ShenandoahCompactObjectsTask : public AbstractGangTask {
673 private:
674 ShenandoahHeap* const _heap;
675 ShenandoahHeapRegionSet** const _worker_slices;
676
677 public:
678 ShenandoahCompactObjectsTask(ShenandoahHeapRegionSet** worker_slices) :
679 AbstractGangTask("Shenandoah Compact Objects Task"),
680 _heap(ShenandoahHeap::heap()),
681 _worker_slices(worker_slices) {
682 }
683
684 void work(uint worker_id) {
685 ShenandoahHeapRegionSetIterator slice(_worker_slices[worker_id]);
686
687 ShenandoahCompactObjectsClosure cl;
688 ShenandoahHeapRegion* r = slice.next();
689 while (r != NULL) {
690 assert(!r->is_humongous(), "must not get humongous regions here");
691 if (r->has_live()) {
692 _heap->marked_object_iterate(r, &cl);
693 }
694 r->set_top(r->new_top());
695 r = slice.next();
696 }
697 }
698 };
699
700 class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
701 private:
702 ShenandoahHeap* const _heap;
703 size_t _live;
704
705 public:
706 ShenandoahPostCompactClosure() : _heap(ShenandoahHeap::heap()), _live(0) {
707 _heap->free_set()->clear();
708 }
709
710 void heap_region_do(ShenandoahHeapRegion* r) {
711 assert (!r->is_cset(), "cset regions should have been demoted already");
712
713 // Need to reset the complete-top-at-mark-start pointer here because
714 // the complete marking bitmap is no longer valid. This ensures
715 // size-based iteration in marked_object_iterate().
716 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
717 // pinned regions.
718 if (!r->is_pinned()) {
719 _heap->complete_marking_context()->reset_top_at_mark_start(r);
720 }
721
722 size_t live = r->used();
723
724 // Make empty regions that have been allocated into regular
725 if (r->is_empty() && live > 0) {
726 r->make_regular_bypass();
727 }
728
729 // Reclaim regular regions that became empty
730 if (r->is_regular() && live == 0) {
731 r->make_trash();
732 }
733
734 // Recycle all trash regions
735 if (r->is_trash()) {
736 live = 0;
737 r->recycle();
738 }
739
740 r->set_live_data(live);
741 r->reset_alloc_metadata_to_shared();
742 _live += live;
743 }
744
745 size_t get_live() {
746 return _live;
747 }
748 };
749
750 void ShenandoahMarkCompact::compact_humongous_objects() {
751 // Compact humongous regions, based on their fwdptr objects.
752 //
753 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
754 // humongous regions are already compacted, and do not require further moves, which alleviates
755 // sliding costs. We may consider doing this in parallel in future.
756
757 ShenandoahHeap* heap = ShenandoahHeap::heap();
758
759 for (size_t c = heap->num_regions(); c > 0; c--) {
760 ShenandoahHeapRegion* r = heap->get_region(c - 1);
761 if (r->is_humongous_start()) {
762 oop old_obj = oop(r->bottom());
763 if (!old_obj->is_forwarded()) {
764 // No need to move the object, it stays at the same slot
765 continue;
766 }
767 size_t words_size = old_obj->size();
768 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
769
770 size_t old_start = r->region_number();
771 size_t old_end = old_start + num_regions - 1;
772 size_t new_start = heap->heap_region_index_containing(old_obj->forwardee());
773 size_t new_end = new_start + num_regions - 1;
774 assert(old_start != new_start, "must be real move");
775 assert(r->is_stw_move_allowed(), err_msg("Region " SIZE_FORMAT " should be movable", r->region_number()));
776
777 Copy::aligned_conjoint_words(heap->get_region(old_start)->bottom(),
778 heap->get_region(new_start)->bottom(),
779 ShenandoahHeapRegion::region_size_words()*num_regions);
780
781 oop new_obj = oop(heap->get_region(new_start)->bottom());
782 new_obj->init_mark();
783
784 {
785 for (size_t c = old_start; c <= old_end; c++) {
786 ShenandoahHeapRegion* r = heap->get_region(c);
787 r->make_regular_bypass();
788 r->set_top(r->bottom());
789 }
790
791 for (size_t c = new_start; c <= new_end; c++) {
792 ShenandoahHeapRegion* r = heap->get_region(c);
793 if (c == new_start) {
794 r->make_humongous_start_bypass();
795 } else {
796 r->make_humongous_cont_bypass();
797 }
798
799 // Trailing region may be non-full, record the remainder there
800 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
801 if ((c == new_end) && (remainder != 0)) {
802 r->set_top(r->bottom() + remainder);
803 } else {
804 r->set_top(r->end());
805 }
806
807 r->reset_alloc_metadata_to_shared();
808 }
809 }
810 }
811 }
812 }
813
814 // This is slightly different to ShHeap::reset_next_mark_bitmap:
815 // we need to remain able to walk pinned regions.
816 // Since pinned region do not move and don't get compacted, we will get holes with
817 // unreachable objects in them (which may have pointers to unloaded Klasses and thus
818 // cannot be iterated over using oop->size(). The only way to safely iterate over those is using
819 // a valid marking bitmap and valid TAMS pointer. This class only resets marking
820 // bitmaps for un-pinned regions, and later we only reset TAMS for unpinned regions.
821 class ShenandoahMCResetCompleteBitmapTask : public AbstractGangTask {
822 private:
823 ShenandoahRegionIterator _regions;
824
825 public:
826 ShenandoahMCResetCompleteBitmapTask() :
827 AbstractGangTask("Parallel Reset Bitmap Task") {
828 }
829
830 void work(uint worker_id) {
831 ShenandoahHeapRegion* region = _regions.next();
832 ShenandoahHeap* heap = ShenandoahHeap::heap();
833 ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
834 while (region != NULL) {
835 if (heap->is_bitmap_slice_committed(region) && !region->is_pinned() && region->has_live()) {
836 ctx->clear_bitmap(region);
837 }
838 region = _regions.next();
839 }
840 }
841 };
842
843 void ShenandoahMarkCompact::phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices) {
844 ShenandoahHeap* heap = ShenandoahHeap::heap();
845 GCTraceTime time("Phase 4: Move objects", ShenandoahLogDebug, _gc_timer, heap->tracer()->gc_id());
846 ShenandoahGCPhase compaction_phase(ShenandoahPhaseTimings::full_gc_copy_objects);
847
848 // Compact regular objects first
849 {
850 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_regular);
851 ShenandoahCompactObjectsTask compact_task(worker_slices);
852 heap->workers()->run_task(&compact_task);
853 }
854
855 // Compact humongous objects after regular object moves
856 {
857 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
858 compact_humongous_objects();
859 }
860
861 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
862 // and must ensure the bitmap is in sync.
863 {
864 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_reset_complete);
865 ShenandoahMCResetCompleteBitmapTask task;
866 heap->workers()->run_task(&task);
867 }
868
869 // Bring regions in proper states after the collection, and set heap properties.
870 {
871 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_rebuild);
872
873 ShenandoahPostCompactClosure post_compact;
874 heap->heap_region_iterate(&post_compact);
875 heap->set_used(post_compact.get_live());
876
877 heap->collection_set()->clear();
878 heap->free_set()->rebuild();
879 }
880
881 heap->clear_cancelled_gc();
882 }