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/shenandoahPartialGC.hpp"
40 #include "gc/shenandoah/shenandoahRootProcessor.hpp"
41 #include "gc/shenandoah/shenandoahTraversalGC.hpp"
42 #include "gc/shenandoah/shenandoahUtils.hpp"
43 #include "gc/shenandoah/shenandoahVerifier.hpp"
44 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
45 #include "gc/shenandoah/vm_operations_shenandoah.hpp"
46 #include "oops/oop.inline.hpp"
47 #include "runtime/biasedLocking.hpp"
48 #include "runtime/thread.hpp"
49 #include "utilities/copy.hpp"
50 #include "utilities/growableArray.hpp"
51 #include "gc/shared/taskqueue.inline.hpp"
52 #include "gc/shared/workgroup.hpp"
53
54 class ShenandoahMarkCompactBarrierSet : public ShenandoahBarrierSet {
55 public:
56 ShenandoahMarkCompactBarrierSet(ShenandoahHeap* heap) : ShenandoahBarrierSet(heap) {}
57
58 oop read_barrier(oop src) {
59 return src;
60 }
61
62 #ifdef ASSERT
63 void verify_safe_oop(oop o) {}
64 void verify_safe_oop(narrowOop o) {}
65 #endif
66 };
67
68 class ShenandoahClearRegionStatusClosure: public ShenandoahHeapRegionClosure {
69 private:
70 ShenandoahHeap* const _heap;
71
72 public:
73 ShenandoahClearRegionStatusClosure() : _heap(ShenandoahHeap::heap()) {}
74
75 bool heap_region_do(ShenandoahHeapRegion *r) {
76 _heap->set_next_top_at_mark_start(r->bottom(), r->top());
77 r->clear_live_data();
78 r->set_concurrent_iteration_safe_limit(r->top());
79 return false;
80 }
81 };
82
83 class ShenandoahEnsureHeapActiveClosure: public ShenandoahHeapRegionClosure {
84 private:
85 ShenandoahHeap* const _heap;
86
87 public:
88 ShenandoahEnsureHeapActiveClosure() : _heap(ShenandoahHeap::heap()) {}
89 bool heap_region_do(ShenandoahHeapRegion* r) {
90 if (r->is_trash()) {
91 r->recycle();
92 }
93 if (r->is_cset()) {
94 r->make_regular_bypass();
95 }
96 if (r->is_empty_uncommitted()) {
97 r->make_committed_bypass();
98 }
99 assert (r->is_committed(), "only committed regions in heap now, see region " SIZE_FORMAT, r->region_number());
100
101 // Record current region occupancy: this communicates empty regions are free
102 // to the rest of Full GC code.
103 r->set_new_top(r->top());
104 return false;
105 }
106 };
107
108 void ShenandoahMarkCompact::initialize(GCTimer* gc_timer) {
109 _gc_timer = gc_timer;
110 }
111
112 void ShenandoahMarkCompact::do_it(GCCause::Cause gc_cause) {
113 ShenandoahHeap* heap = ShenandoahHeap::heap();
114
115 {
116 if (ShenandoahVerify) {
117 heap->verifier()->verify_before_fullgc();
118 }
119
120 heap->set_full_gc_in_progress(true);
121
122 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint");
123 assert(Thread::current()->is_VM_thread(), "Do full GC only while world is stopped");
124
125 {
126 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
127 heap->pre_full_gc_dump(_gc_timer);
128 }
129
130 {
131 ShenandoahGCPhase prepare_phase(ShenandoahPhaseTimings::full_gc_prepare);
132 // Full GC is supposed to recover from any GC state:
133
134 // a1. Cancel evacuation, if in progress
135 if (heap->is_evacuation_in_progress()) {
136 heap->set_evacuation_in_progress(false);
137 }
138 assert(!heap->is_evacuation_in_progress(), "sanity");
139
140 // a2. Cancel update-refs, if in progress
141 if (heap->is_update_refs_in_progress()) {
142 heap->set_update_refs_in_progress(false);
143 }
144 assert(!heap->is_update_refs_in_progress(), "sanity");
145
146 // a3. Cancel concurrent partial GC, if in progress
147 if (heap->is_concurrent_partial_in_progress()) {
148 heap->partial_gc()->reset();
149 heap->set_concurrent_partial_in_progress(false);
150 }
151
152 // a3. Cancel concurrent traversal GC, if in progress
153 if (heap->is_concurrent_traversal_in_progress()) {
154 heap->traversal_gc()->reset();
155 heap->set_concurrent_traversal_in_progress(false);
156 }
157
158 // b. Cancel concurrent mark, if in progress
159 if (heap->is_concurrent_mark_in_progress()) {
160 heap->concurrentMark()->cancel();
161 heap->stop_concurrent_marking();
162 }
163 assert(!heap->is_concurrent_mark_in_progress(), "sanity");
164
165 // c. Reset the bitmaps for new marking
166 heap->reset_next_mark_bitmap();
167 assert(heap->is_next_bitmap_clear(), "sanity");
168
169 // d. Abandon reference discovery and clear all discovered references.
170 ReferenceProcessor* rp = heap->ref_processor();
171 rp->disable_discovery();
172 rp->abandon_partial_discovery();
173 rp->verify_no_references_recorded();
174
175 {
176 ShenandoahHeapLocker lock(heap->lock());
177
178 // f. Make sure all regions are active. This is needed because we are potentially
179 // sliding the data through them
180 ShenandoahEnsureHeapActiveClosure ecl;
181 heap->heap_region_iterate(&ecl, false, false);
182
183 // g. Clear region statuses, including collection set status
184 ShenandoahClearRegionStatusClosure cl;
185 heap->heap_region_iterate(&cl, false, false);
186 }
187 }
188
189 BarrierSet* old_bs = BarrierSet::barrier_set();
190 ShenandoahMarkCompactBarrierSet bs(heap);
191 BarrierSet::set_bs(&bs);
192
193 {
194 if (UseTLAB) {
195 heap->make_tlabs_parsable(true);
196 }
197
198 CodeCache::gc_prologue();
199
200 // We should save the marks of the currently locked biased monitors.
201 // The marking doesn't preserve the marks of biased objects.
202 //BiasedLocking::preserve_marks();
203
204 heap->set_has_forwarded_objects(true);
205
206 OrderAccess::fence();
207
208 phase1_mark_heap();
209
210 heap->set_full_gc_move_in_progress(true);
211
212 // Setup workers for the rest
213 {
214 OrderAccess::fence();
215
216 // Initialize worker slices
217 ShenandoahHeapRegionSet** worker_slices = NEW_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, heap->max_workers(), mtGC);
218 for (uint i = 0; i < heap->max_workers(); i++) {
219 worker_slices[i] = new ShenandoahHeapRegionSet();
220 }
221
222 phase2_calculate_target_addresses(worker_slices);
223
224 OrderAccess::fence();
225
226 phase3_update_references();
227
228 phase4_compact_objects(worker_slices);
229
230 // Free worker slices
231 for (uint i = 0; i < heap->max_workers(); i++) {
232 delete worker_slices[i];
233 }
234 FREE_C_HEAP_ARRAY(ShenandoahHeapRegionSet*, worker_slices);
235
236 CodeCache::gc_epilogue();
237 JvmtiExport::gc_epilogue();
238 }
239
240 heap->set_has_forwarded_objects(false);
241 heap->set_full_gc_move_in_progress(false);
242 heap->set_full_gc_in_progress(false);
243
244 if (ShenandoahVerify) {
245 heap->verifier()->verify_after_fullgc();
246 }
247 }
248
249 {
250 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_heapdumps);
251 heap->post_full_gc_dump(_gc_timer);
252 }
253
254 if (UseTLAB) {
255 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_resize_tlabs);
256 heap->resize_all_tlabs();
257 }
258
259 BarrierSet::set_bs(old_bs);
260 }
261
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 void ShenandoahMarkCompact::phase1_mark_heap() {
271 GCTraceTime(Info, gc, phases) time("Phase 1: Mark live objects", _gc_timer);
272 ShenandoahGCPhase mark_phase(ShenandoahPhaseTimings::full_gc_mark);
273
274 ShenandoahHeap* heap = ShenandoahHeap::heap();
275
276 ShenandoahConcurrentMark* cm = heap->concurrentMark();
277
278 // Do not trust heuristics, because this can be our last resort collection.
279 // Only ignore processing references and class unloading if explicitly disabled.
280 heap->set_process_references(ShenandoahRefProcFrequency != 0);
281 heap->set_unload_classes(ShenandoahUnloadClassesFrequency != 0);
282
283 ReferenceProcessor* rp = heap->ref_processor();
284 // enable ("weak") refs discovery
285 rp->enable_discovery(true /*verify_no_refs*/);
286 rp->setup_policy(true); // snapshot the soft ref policy to be used in this cycle
287 rp->set_active_mt_degree(heap->workers()->active_workers());
288
289 cm->update_roots(ShenandoahPhaseTimings::full_gc_roots);
290 cm->mark_roots(ShenandoahPhaseTimings::full_gc_roots);
291 cm->shared_finish_mark_from_roots(/* full_gc = */ true);
292
293 heap->swap_mark_bitmaps();
294
295 if (UseShenandoahMatrix && PrintShenandoahMatrix) {
296 LogTarget(Info, gc) lt;
297 LogStream ls(lt);
298 heap->connection_matrix()->print_on(&ls);
299 }
300 }
301
302 class ShenandoahMCReclaimHumongousRegionClosure : public ShenandoahHeapRegionClosure {
303 private:
304 ShenandoahHeap* const _heap;
305 public:
306 ShenandoahMCReclaimHumongousRegionClosure() : _heap(ShenandoahHeap::heap()) {}
307
308 bool heap_region_do(ShenandoahHeapRegion* r) {
309 if (r->is_humongous_start()) {
310 oop humongous_obj = oop(r->bottom() + BrooksPointer::word_size());
311 if (!_heap->is_marked_complete(humongous_obj)) {
312 _heap->trash_humongous_region_at(r);
313 }
314 }
315 return false;
316 }
317 };
318
319 class ShenandoahPrepareForCompactionObjectClosure : public ObjectClosure {
320 private:
321 ShenandoahHeap* const _heap;
322 GrowableArray<ShenandoahHeapRegion*>& _empty_regions;
323 int _empty_regions_pos;
324 ShenandoahHeapRegion* _to_region;
325 ShenandoahHeapRegion* _from_region;
326 HeapWord* _compact_point;
327
328 public:
329 ShenandoahPrepareForCompactionObjectClosure(GrowableArray<ShenandoahHeapRegion*>& empty_regions, ShenandoahHeapRegion* to_region) :
330 _heap(ShenandoahHeap::heap()),
331 _empty_regions(empty_regions),
332 _empty_regions_pos(0),
333 _to_region(to_region),
334 _from_region(NULL),
335 _compact_point(to_region->bottom()) {}
336
337 void set_from_region(ShenandoahHeapRegion* from_region) {
338 _from_region = from_region;
339 }
340
341 void finish_region() {
342 assert(_to_region != NULL, "should not happen");
343 _to_region->set_new_top(_compact_point);
344 }
345
346 bool is_compact_same_region() {
347 return _from_region == _to_region;
348 }
349
350 int empty_regions_pos() {
351 return _empty_regions_pos;
352 }
353
354 void do_object(oop p) {
355 assert(_from_region != NULL, "must set before work");
356 assert(_heap->is_marked_complete(p), "must be marked");
357 assert(!_heap->allocated_after_complete_mark_start((HeapWord*) p), "must be truly marked");
358
359 size_t obj_size = p->size() + BrooksPointer::word_size();
360 if (_compact_point + obj_size > _to_region->end()) {
361 finish_region();
362
363 // Object doesn't fit. Pick next empty region and start compacting there.
364 ShenandoahHeapRegion* new_to_region;
365 if (_empty_regions_pos < _empty_regions.length()) {
366 new_to_region = _empty_regions.at(_empty_regions_pos);
367 _empty_regions_pos++;
368 } else {
369 // Out of empty region? Compact within the same region.
370 new_to_region = _from_region;
371 }
372
373 assert(new_to_region != _to_region, "must not reuse same to-region");
374 assert(new_to_region != NULL, "must not be NULL");
375 _to_region = new_to_region;
376 _compact_point = _to_region->bottom();
377 }
378
379 // Object fits into current region, record new location:
380 assert(_compact_point + obj_size <= _to_region->end(), "must fit");
381 shenandoah_assert_not_forwarded(NULL, p);
382 BrooksPointer::set_raw(p, _compact_point + BrooksPointer::word_size());
383 _compact_point += obj_size;
384 }
385 };
386
387 class ShenandoahPrepareForCompactionTask : public AbstractGangTask {
388 private:
389 ShenandoahHeap* const _heap;
390 ShenandoahHeapRegionSet** const _worker_slices;
391 ShenandoahRegionIterator _heap_regions;
392
393 ShenandoahHeapRegion* next_from_region(ShenandoahHeapRegionSet* slice) {
394 ShenandoahHeapRegion* from_region = _heap_regions.next();
395
396 while (from_region != NULL && (!from_region->is_move_allowed() || from_region->is_humongous())) {
397 from_region = _heap_regions.next();
398 }
399
400 if (from_region != NULL) {
401 assert(slice != NULL, "sanity");
402 assert(!from_region->is_humongous(), "this path cannot handle humongous regions");
403 assert(from_region->is_move_allowed(), "only regions that can be moved in mark-compact");
404 slice->add_region(from_region);
405 }
406
407 return from_region;
408 }
409
410 public:
411 ShenandoahPrepareForCompactionTask(ShenandoahHeapRegionSet** worker_slices) :
412 AbstractGangTask("Shenandoah Prepare For Compaction Task"),
413 _heap(ShenandoahHeap::heap()), _heap_regions(_heap->region_iterator()), _worker_slices(worker_slices) {
414 }
415
416 void work(uint worker_id) {
417 ShenandoahHeapRegionSet* slice = _worker_slices[worker_id];
418 ShenandoahHeapRegion* from_region = next_from_region(slice);
419 // No work?
420 if (from_region == NULL) {
421 return;
422 }
423
424 // Sliding compaction. Walk all regions in the slice, and compact them.
425 // Remember empty regions and reuse them as needed.
426 ResourceMark rm;
427 GrowableArray<ShenandoahHeapRegion*> empty_regions(_heap->num_regions());
428 ShenandoahPrepareForCompactionObjectClosure cl(empty_regions, from_region);
429 while (from_region != NULL) {
430 cl.set_from_region(from_region);
431 _heap->marked_object_iterate(from_region, &cl);
432
433 // Compacted the region to somewhere else? From-region is empty then.
434 if (!cl.is_compact_same_region()) {
435 empty_regions.append(from_region);
436 }
437 from_region = next_from_region(slice);
438 }
439 cl.finish_region();
440
441 // Mark all remaining regions as empty
442 for (int pos = cl.empty_regions_pos(); pos < empty_regions.length(); ++pos) {
443 ShenandoahHeapRegion* r = empty_regions.at(pos);
444 r->set_new_top(r->bottom());
445 }
446 }
447 };
448
449 void ShenandoahMarkCompact::calculate_target_humongous_objects() {
450 ShenandoahHeap* heap = ShenandoahHeap::heap();
451
452 // Compute the new addresses for humongous objects. We need to do this after addresses
453 // for regular objects are calculated, and we know what regions in heap suffix are
454 // available for humongous moves.
455 //
456 // Scan the heap backwards, because we are compacting humongous regions towards the end.
457 // Maintain the contiguous compaction window in [to_begin; to_end), so that we can slide
458 // humongous start there.
459 //
460 // The complication is potential non-movable regions during the scan. If such region is
461 // detected, then sliding restarts towards that non-movable region.
462
463 size_t to_begin = heap->num_regions();
464 size_t to_end = heap->num_regions();
465
466 for (size_t c = heap->num_regions() - 1; c > 0; c--) {
467 ShenandoahHeapRegion *r = heap->get_region(c);
468 if (r->is_humongous_continuation() || (r->new_top() == r->bottom())) {
469 // To-region candidate: record this, and continue scan
470 to_begin = r->region_number();
471 continue;
472 }
473
474 if (r->is_humongous_start() && r->is_move_allowed()) {
475 // From-region candidate: movable humongous region
476 oop old_obj = oop(r->bottom() + BrooksPointer::word_size());
477 size_t words_size = old_obj->size() + BrooksPointer::word_size();
478 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
479
480 size_t start = to_end - num_regions;
481
482 if (start >= to_begin && start != r->region_number()) {
483 // Fits into current window, and the move is non-trivial. Record the move then, and continue scan.
484 BrooksPointer::set_raw(old_obj, heap->get_region(start)->bottom() + BrooksPointer::word_size());
485 to_end = start;
486 continue;
487 }
488 }
489
490 // Failed to fit. Scan starting from current region.
491 to_begin = r->region_number();
492 to_end = r->region_number();
493 }
494 }
495
496 void ShenandoahMarkCompact::phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices) {
497 GCTraceTime(Info, gc, phases) time("Phase 2: Compute new object addresses", _gc_timer);
498 ShenandoahGCPhase calculate_address_phase(ShenandoahPhaseTimings::full_gc_calculate_addresses);
499
500 ShenandoahHeap* heap = ShenandoahHeap::heap();
501
502 {
503 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_regular);
504
505 {
506 ShenandoahHeapLocker lock(heap->lock());
507
508 ShenandoahMCReclaimHumongousRegionClosure cl;
509 heap->heap_region_iterate(&cl);
510
511 // After some humongous regions were reclaimed, we need to ensure their
512 // backing storage is active. This is needed because we are potentially
513 // sliding the data through them.
514 ShenandoahEnsureHeapActiveClosure ecl;
515 heap->heap_region_iterate(&ecl, false, false);
516 }
517
518 // Compute the new addresses for regular objects
519 ShenandoahPrepareForCompactionTask prepare_task(worker_slices);
520 heap->workers()->run_task(&prepare_task);
521 }
522
523 // Compute the new addresses for humongous objects
524 {
525 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_calculate_addresses_humong);
526 calculate_target_humongous_objects();
527 }
528 }
529
530 class ShenandoahAdjustPointersClosure : public MetadataAwareOopClosure {
531 private:
532 ShenandoahHeap* const _heap;
533 size_t _new_obj_offset;
534
535 template <class T>
536 inline void do_oop_work(T* p) {
537 T o = oopDesc::load_heap_oop(p);
538 if (! oopDesc::is_null(o)) {
539 oop obj = oopDesc::decode_heap_oop_not_null(o);
540 assert(_heap->is_marked_complete(obj), "must be marked");
541 oop forw = oop(BrooksPointer::get_raw(obj));
542 oopDesc::encode_store_heap_oop(p, forw);
543 if (UseShenandoahMatrix) {
544 if (_heap->is_in_reserved(p)) {
545 assert(_heap->is_in_reserved(forw), "must be in heap");
546 assert(_new_obj_offset != SIZE_MAX, "should be set");
547 // We're moving a to a', which points to b, about to be moved to b'.
548 // We already know b' from the fwd pointer of b.
549 // In the object closure, we see a, and we know a' (by looking at its
550 // fwd ptr). We store the offset in the OopClosure, which is going
551 // to visit all of a's fields, and then, when we see each field, we
552 // subtract the offset from each field address to get the final ptr.
553 _heap->connection_matrix()->set_connected(((HeapWord*) p) - _new_obj_offset, forw);
554 }
555 }
556 }
557 }
558
559 public:
560 ShenandoahAdjustPointersClosure() : _heap(ShenandoahHeap::heap()), _new_obj_offset(SIZE_MAX) {}
561
562 void do_oop(oop* p) { do_oop_work(p); }
563 void do_oop(narrowOop* p) { do_oop_work(p); }
564
565 void set_new_obj_offset(size_t new_obj_offset) {
566 _new_obj_offset = new_obj_offset;
567 }
568 };
569
570 class ShenandoahAdjustPointersObjectClosure : public ObjectClosure {
571 private:
572 ShenandoahHeap* const _heap;
573 ShenandoahAdjustPointersClosure _cl;
574
575 public:
576 ShenandoahAdjustPointersObjectClosure() :
577 _heap(ShenandoahHeap::heap()) {
578 }
579 void do_object(oop p) {
580 assert(_heap->is_marked_complete(p), "must be marked");
581 HeapWord* forw = BrooksPointer::get_raw(p);
582 _cl.set_new_obj_offset(pointer_delta((HeapWord*) p, forw));
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()), _regions(_heap->region_iterator()) {
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()) {
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
614 public:
615 ShenandoahAdjustRootPointersTask(ShenandoahRootProcessor* rp) :
616 AbstractGangTask("Shenandoah Adjust Root Pointers Task"),
617 _rp(rp) {}
618
619 void work(uint worker_id) {
620 ShenandoahAdjustPointersClosure cl;
621 CLDToOopClosure adjust_cld_closure(&cl, true);
622 MarkingCodeBlobClosure adjust_code_closure(&cl,
623 CodeBlobToOopClosure::FixRelocations);
624
625 _rp->process_all_roots(&cl, &cl,
626 &adjust_cld_closure,
627 &adjust_code_closure, NULL, worker_id);
628 }
629 };
630
631 void ShenandoahMarkCompact::phase3_update_references() {
632 GCTraceTime(Info, gc, phases) time("Phase 3: Adjust pointers", _gc_timer);
633 ShenandoahGCPhase adjust_pointer_phase(ShenandoahPhaseTimings::full_gc_adjust_pointers);
634
635 ShenandoahHeap* heap = ShenandoahHeap::heap();
636
637 if (UseShenandoahMatrix) {
638 heap->connection_matrix()->clear_all();
639 }
640
641 WorkGang* workers = heap->workers();
642 uint nworkers = workers->active_workers();
643 {
644 #if COMPILER2_OR_JVMCI
645 DerivedPointerTable::clear();
646 #endif
647 ShenandoahRootProcessor rp(heap, nworkers, ShenandoahPhaseTimings::full_gc_roots);
648 ShenandoahAdjustRootPointersTask task(&rp);
649 workers->run_task(&task);
650 #if COMPILER2_OR_JVMCI
651 DerivedPointerTable::update_pointers();
652 #endif
653 }
654
655 ShenandoahAdjustPointersTask adjust_pointers_task;
656 workers->run_task(&adjust_pointers_task);
657 }
658
659 class ShenandoahCompactObjectsClosure : public ObjectClosure {
660 private:
661 ShenandoahHeap* const _heap;
662 uint const _worker_id;
663
664 public:
665 ShenandoahCompactObjectsClosure(uint worker_id) :
666 _heap(ShenandoahHeap::heap()), _worker_id(worker_id) {}
667
668 void do_object(oop p) {
669 assert(_heap->is_marked_complete(p), "must be marked");
670 size_t size = (size_t)p->size();
671 HeapWord* compact_to = BrooksPointer::get_raw(p);
672 HeapWord* compact_from = (HeapWord*) p;
673 if (compact_from != compact_to) {
674 Copy::aligned_conjoint_words(compact_from, compact_to, size);
675 }
676 oop new_obj = oop(compact_to);
677 BrooksPointer::initialize(new_obj);
678 }
679 };
680
681 class ShenandoahCompactObjectsTask : public AbstractGangTask {
682 private:
683 ShenandoahHeap* const _heap;
684 ShenandoahHeapRegionSet** const _worker_slices;
685
686 public:
687 ShenandoahCompactObjectsTask(ShenandoahHeapRegionSet** worker_slices) :
688 AbstractGangTask("Shenandoah Compact Objects Task"),
689 _heap(ShenandoahHeap::heap()),
690 _worker_slices(worker_slices) {
691 }
692
693 void work(uint worker_id) {
694 ShenandoahHeapRegionSetIterator slice = _worker_slices[worker_id]->iterator();
695
696 ShenandoahCompactObjectsClosure cl(worker_id);
697 ShenandoahHeapRegion* r = slice.next();
698 while (r != NULL) {
699 assert(!r->is_humongous(), "must not get humongous regions here");
700 _heap->marked_object_iterate(r, &cl);
701 r->set_top(r->new_top());
702 r = slice.next();
703 }
704 }
705 };
706
707 class ShenandoahPostCompactClosure : public ShenandoahHeapRegionClosure {
708 private:
709 ShenandoahHeap* const _heap;
710 size_t _live;
711
712 public:
713 ShenandoahPostCompactClosure() : _live(0), _heap(ShenandoahHeap::heap()) {
714 _heap->free_set()->clear();
715 }
716
717 bool heap_region_do(ShenandoahHeapRegion* r) {
718 assert (!r->is_cset(), "cset regions should have been demoted already");
719
720 // Need to reset the complete-top-at-mark-start pointer here because
721 // the complete marking bitmap is no longer valid. This ensures
722 // size-based iteration in marked_object_iterate().
723 // NOTE: See blurb at ShenandoahMCResetCompleteBitmapTask on why we need to skip
724 // pinned regions.
725 if (!r->is_pinned()) {
726 _heap->set_complete_top_at_mark_start(r->bottom(), r->bottom());
727 }
728
729 size_t live = r->used();
730
731 // Make empty regions that have been allocated into regular
732 if (r->is_empty() && live > 0) {
733 r->make_regular_bypass();
734 }
735
736 // Reclaim regular regions that became empty
737 if (r->is_regular() && live == 0) {
738 r->make_trash();
739 }
740
741 // Recycle all trash regions
742 if (r->is_trash()) {
743 live = 0;
744 r->recycle();
745 }
746
747 r->set_live_data(live);
748 r->reset_alloc_metadata_to_shared();
749 _live += live;
750 return false;
751 }
752
753 size_t get_live() {
754 return _live;
755 }
756 };
757
758 void ShenandoahMarkCompact::compact_humongous_objects() {
759 // Compact humongous regions, based on their fwdptr objects.
760 //
761 // This code is serial, because doing the in-slice parallel sliding is tricky. In most cases,
762 // humongous regions are already compacted, and do not require further moves, which alleviates
763 // sliding costs. We may consider doing this in parallel in future.
764
765 ShenandoahHeap* heap = ShenandoahHeap::heap();
766
767 for (size_t c = heap->num_regions() - 1; c > 0; c--) {
768 ShenandoahHeapRegion* r = heap->get_region(c);
769 if (r->is_humongous_start()) {
770 oop old_obj = oop(r->bottom() + BrooksPointer::word_size());
771 size_t words_size = old_obj->size() + BrooksPointer::word_size();
772 size_t num_regions = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
773
774 size_t old_start = r->region_number();
775 size_t old_end = old_start + num_regions - 1;
776 size_t new_start = heap->heap_region_index_containing(BrooksPointer::get_raw(old_obj));
777 size_t new_end = new_start + num_regions - 1;
778
779 if (old_start == new_start) {
780 // No need to move the object, it stays at the same slot
781 continue;
782 }
783
784 assert (r->is_move_allowed(), "should be movable");
785
786 Copy::aligned_conjoint_words(heap->get_region(old_start)->bottom(),
787 heap->get_region(new_start)->bottom(),
788 ShenandoahHeapRegion::region_size_words()*num_regions);
789
790 oop new_obj = oop(heap->get_region(new_start)->bottom() + BrooksPointer::word_size());
791 BrooksPointer::initialize(new_obj);
792
793 {
794 ShenandoahHeapLocker lock(heap->lock());
795
796 for (size_t c = old_start; c <= old_end; c++) {
797 ShenandoahHeapRegion* r = heap->get_region(c);
798 r->make_regular_bypass();
799 r->set_top(r->bottom());
800 }
801
802 for (size_t c = new_start; c <= new_end; c++) {
803 ShenandoahHeapRegion* r = heap->get_region(c);
804 if (c == new_start) {
805 r->make_humongous_start_bypass();
806 } else {
807 r->make_humongous_cont_bypass();
808 }
809
810 // Trailing region may be non-full, record the remainder there
811 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
812 if ((c == new_end) && (remainder != 0)) {
813 r->set_top(r->bottom() + remainder);
814 } else {
815 r->set_top(r->end());
816 }
817
818 r->reset_alloc_metadata_to_shared();
819 }
820 }
821 }
822 }
823 }
824
825 // This is slightly different to ShHeap::reset_next_mark_bitmap:
826 // we need to remain able to walk pinned regions.
827 // Since pinned region do not move and don't get compacted, we will get holes with
828 // unreachable objects in them (which may have pointers to unloaded Klasses and thus
829 // cannot be iterated over using oop->size(). The only way to safely iterate over those is using
830 // a valid marking bitmap and valid TAMS pointer. This class only resets marking
831 // bitmaps for un-pinned regions, and later we only reset TAMS for unpinned regions.
832 class ShenandoahMCResetCompleteBitmapTask : public AbstractGangTask {
833 private:
834 ShenandoahRegionIterator _regions;
835
836 public:
837 ShenandoahMCResetCompleteBitmapTask(ShenandoahRegionIterator regions) :
838 AbstractGangTask("Parallel Reset Bitmap Task"),
839 _regions(regions) {
840 }
841
842 void work(uint worker_id) {
843 ShenandoahHeapRegion* region = _regions.next();
844 ShenandoahHeap* heap = ShenandoahHeap::heap();
845 while (region != NULL) {
846 if (heap->is_bitmap_slice_committed(region) && !region->is_pinned()) {
847 HeapWord* bottom = region->bottom();
848 HeapWord* top = heap->complete_top_at_mark_start(region->bottom());
849 if (top > bottom) {
850 heap->complete_mark_bit_map()->clear_range_large(MemRegion(bottom, top));
851 }
852 assert(heap->is_complete_bitmap_clear_range(bottom, region->end()), "must be clear");
853 }
854 region = _regions.next();
855 }
856 }
857 };
858
859 void ShenandoahMarkCompact::phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices) {
860 GCTraceTime(Info, gc, phases) time("Phase 4: Move objects", _gc_timer);
861 ShenandoahGCPhase compaction_phase(ShenandoahPhaseTimings::full_gc_copy_objects);
862
863 ShenandoahHeap* heap = ShenandoahHeap::heap();
864
865 // Compact regular objects first
866 {
867 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_regular);
868 ShenandoahCompactObjectsTask compact_task(worker_slices);
869 heap->workers()->run_task(&compact_task);
870 }
871
872 // Compact humongous objects after regular object moves
873 {
874 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_copy_objects_humong);
875 compact_humongous_objects();
876 }
877
878 // Reset complete bitmap. We're about to reset the complete-top-at-mark-start pointer
879 // and must ensure the bitmap is in sync.
880 ShenandoahMCResetCompleteBitmapTask task(heap->region_iterator());
881 heap->workers()->run_task(&task);
882
883 // Bring regions in proper states after the collection, and set heap properties.
884 {
885 ShenandoahHeapLocker lock(heap->lock());
886 ShenandoahPostCompactClosure post_compact;
887 heap->heap_region_iterate(&post_compact);
888 heap->set_used(post_compact.get_live());
889
890 heap->collection_set()->clear();
891 heap->free_set()->rebuild();
892 }
893
894 heap->clear_cancelled_concgc();
895
896 // Also clear the next bitmap in preparation for next marking.
897 heap->reset_next_mark_bitmap();
898 }