1 /*
2 * Copyright (c) 1997, 2026, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "classfile/classLoaderData.inline.hpp"
26 #include "classfile/classLoaderDataGraph.hpp"
27 #include "classfile/javaClasses.inline.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "classfile/vmSymbols.hpp"
32 #include "code/codeCache.hpp"
33 #include "compiler/compileBroker.hpp"
34 #include "compiler/oopMap.hpp"
35 #include "gc/serial/cardTableRS.hpp"
36 #include "gc/serial/defNewGeneration.hpp"
37 #include "gc/serial/serialFullGC.hpp"
38 #include "gc/serial/serialGcRefProcProxyTask.hpp"
39 #include "gc/serial/serialHeap.hpp"
40 #include "gc/serial/serialStringDedup.hpp"
41 #include "gc/serial/tenuredGeneration.inline.hpp"
42 #include "gc/shared/classUnloadingContext.hpp"
43 #include "gc/shared/collectedHeap.inline.hpp"
44 #include "gc/shared/continuationGCSupport.inline.hpp"
45 #include "gc/shared/fullGCForwarding.inline.hpp"
46 #include "gc/shared/gc_globals.hpp"
47 #include "gc/shared/gcHeapSummary.hpp"
48 #include "gc/shared/gcTimer.hpp"
49 #include "gc/shared/gcTrace.hpp"
50 #include "gc/shared/gcTraceTime.inline.hpp"
51 #include "gc/shared/oopStorageSet.inline.hpp"
52 #include "gc/shared/preservedMarks.inline.hpp"
53 #include "gc/shared/referencePolicy.hpp"
54 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
55 #include "gc/shared/space.hpp"
56 #include "gc/shared/weakProcessor.hpp"
57 #include "memory/iterator.inline.hpp"
58 #include "memory/universe.hpp"
59 #include "oops/access.inline.hpp"
60 #include "oops/compressedOops.inline.hpp"
61 #include "oops/instanceRefKlass.hpp"
62 #include "oops/markWord.hpp"
63 #include "oops/methodData.hpp"
64 #include "oops/objArrayKlass.inline.hpp"
65 #include "oops/oop.inline.hpp"
66 #include "oops/typeArrayOop.inline.hpp"
67 #include "runtime/prefetch.inline.hpp"
68 #include "runtime/threads.hpp"
69 #include "utilities/align.hpp"
70 #include "utilities/copy.hpp"
71 #include "utilities/events.hpp"
72 #include "utilities/stack.inline.hpp"
73
74 Stack<oop, mtGC> SerialFullGC::_marking_stack;
75 Stack<ObjArrayTask, mtGC> SerialFullGC::_objarray_stack;
76
77 PreservedMarksSet SerialFullGC::_preserved_overflow_stack_set(false /* in_c_heap */);
78 size_t SerialFullGC::_preserved_count = 0;
79 size_t SerialFullGC::_preserved_count_max = 0;
80 PreservedMark* SerialFullGC::_preserved_marks = nullptr;
81 STWGCTimer* SerialFullGC::_gc_timer = nullptr;
82 SerialOldTracer* SerialFullGC::_gc_tracer = nullptr;
83
84 AlwaysTrueClosure SerialFullGC::_always_true_closure;
85 ReferenceProcessor* SerialFullGC::_ref_processor;
86
87 StringDedup::Requests* SerialFullGC::_string_dedup_requests = nullptr;
88
89 SerialFullGC::FollowRootClosure SerialFullGC::follow_root_closure;
90
91 MarkAndPushClosure SerialFullGC::mark_and_push_closure(ClassLoaderData::_claim_stw_fullgc_mark);
92 CLDToOopClosure SerialFullGC::follow_cld_closure(&mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
93 CLDToOopClosure SerialFullGC::adjust_cld_closure(&adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
94
95 class DeadSpacer : StackObj {
96 size_t _allowed_deadspace_words;
97 bool _active;
98 ContiguousSpace* _space;
99
100 public:
101 DeadSpacer(ContiguousSpace* space) : _allowed_deadspace_words(0), _space(space) {
102 size_t ratio = (_space == SerialHeap::heap()->old_gen()->space())
103 ? MarkSweepDeadRatio : 0;
104 _active = ratio > 0;
105
106 if (_active) {
107 // We allow some amount of garbage towards the bottom of the space, so
108 // we don't start compacting before there is a significant gain to be made.
109 // Occasionally, we want to ensure a full compaction, which is determined
110 // by the MarkSweepAlwaysCompactCount parameter.
111 if ((SerialHeap::heap()->total_full_collections() % MarkSweepAlwaysCompactCount) != 0) {
112 _allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize;
113 } else {
114 _active = false;
115 }
116 }
117 }
118
119 bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) {
120 if (!_active) {
121 return false;
122 }
123
124 size_t dead_length = pointer_delta(dead_end, dead_start);
125 if (_allowed_deadspace_words >= dead_length) {
126 _allowed_deadspace_words -= dead_length;
127 CollectedHeap::fill_with_object(dead_start, dead_length);
128 oop obj = cast_to_oop(dead_start);
129 // obj->set_mark(obj->mark().set_marked());
130
131 assert(dead_length == obj->size(), "bad filler object size");
132 log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", %zub",
133 p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize);
134
135 return true;
136 } else {
137 _active = false;
138 return false;
139 }
140 }
141 };
142
143 // Implement the "compaction" part of the mark-compact GC algorithm.
144 class Compacter {
145 // There are four spaces in total, but only the first three can be used after
146 // compact. IOW, old and eden/from must be enough for all live objs
147 static constexpr uint max_num_spaces = 4;
148
149 struct CompactionSpace {
150 ContiguousSpace* _space;
151 // Will be the new top after compaction is complete.
152 HeapWord* _compaction_top;
153 // The first dead word in this contiguous space. It's an optimization to
154 // skip large chunk of live objects at the beginning.
155 HeapWord* _first_dead;
156
157 void init(ContiguousSpace* space) {
158 _space = space;
159 _compaction_top = space->bottom();
160 _first_dead = nullptr;
161 }
162 };
163
164 CompactionSpace _spaces[max_num_spaces];
165 // The num of spaces to be compacted, i.e. containing live objs.
166 uint _num_spaces;
167
168 uint _index;
169
170 // Used for BOT update
171 TenuredGeneration* _old_gen;
172
173 HeapWord* get_compaction_top(uint index) const {
174 return _spaces[index]._compaction_top;
175 }
176
177 HeapWord* get_first_dead(uint index) const {
178 return _spaces[index]._first_dead;
179 }
180
181 ContiguousSpace* get_space(uint index) const {
182 return _spaces[index]._space;
183 }
184
185 void record_first_dead(uint index, HeapWord* first_dead) {
186 assert(_spaces[index]._first_dead == nullptr, "should write only once");
187 _spaces[index]._first_dead = first_dead;
188 }
189
190 HeapWord* alloc(size_t words) {
191 while (true) {
192 if (words <= pointer_delta(_spaces[_index]._space->end(),
193 _spaces[_index]._compaction_top)) {
194 HeapWord* result = _spaces[_index]._compaction_top;
195 _spaces[_index]._compaction_top += words;
196 if (_index == 0) {
197 // old-gen requires BOT update
198 _old_gen->update_for_block(result, result + words);
199 }
200 return result;
201 }
202
203 // out-of-memory in this space
204 _index++;
205 assert(_index < max_num_spaces - 1, "the last space should not be used");
206 }
207 }
208
209 static void prefetch_read_scan(void* p) {
210 if (PrefetchScanIntervalInBytes >= 0) {
211 Prefetch::read(p, PrefetchScanIntervalInBytes);
212 }
213 }
214
215 static void prefetch_write_scan(void* p) {
216 if (PrefetchScanIntervalInBytes >= 0) {
217 Prefetch::write(p, PrefetchScanIntervalInBytes);
218 }
219 }
220
221 static void prefetch_write_copy(void* p) {
222 if (PrefetchCopyIntervalInBytes >= 0) {
223 Prefetch::write(p, PrefetchCopyIntervalInBytes);
224 }
225 }
226
227 static void forward_obj(oop obj, HeapWord* new_addr) {
228 prefetch_write_scan(obj);
229 if (cast_from_oop<HeapWord*>(obj) != new_addr) {
230 FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
231 } else {
232 assert(obj->is_gc_marked(), "inv");
233 // This obj will stay in-place. Fix the markword.
234 obj->init_mark();
235 }
236 }
237
238 static HeapWord* find_next_live_addr(HeapWord* start, HeapWord* end) {
239 for (HeapWord* i_addr = start; i_addr < end; /* empty */) {
240 prefetch_read_scan(i_addr);
241 oop obj = cast_to_oop(i_addr);
242 if (obj->is_gc_marked()) {
243 return i_addr;
244 }
245 i_addr += obj->size();
246 }
247 return end;
248 };
249
250 static size_t relocate(HeapWord* addr) {
251 // Prefetch source and destination
252 prefetch_read_scan(addr);
253
254 oop obj = cast_to_oop(addr);
255 oop new_obj = FullGCForwarding::forwardee(obj);
256 HeapWord* new_addr = cast_from_oop<HeapWord*>(new_obj);
257 assert(addr != new_addr, "inv");
258 prefetch_write_copy(new_addr);
259
260 size_t obj_size = obj->size();
261 Copy::aligned_conjoint_words(addr, new_addr, obj_size);
262 new_obj->init_mark();
263
264 return obj_size;
265 }
266
267 public:
268 explicit Compacter(SerialHeap* heap) {
269 // In this order so that heap is compacted towards old-gen.
270 _spaces[0].init(heap->old_gen()->space());
271 _spaces[1].init(heap->young_gen()->eden());
272 _spaces[2].init(heap->young_gen()->from());
273
274 bool is_promotion_failed = !heap->young_gen()->to()->is_empty();
275 if (is_promotion_failed) {
276 _spaces[3].init(heap->young_gen()->to());
277 _num_spaces = 4;
278 } else {
279 _num_spaces = 3;
280 }
281 _index = 0;
282 _old_gen = heap->old_gen();
283 }
284
285 void phase2_calculate_new_addr() {
286 for (uint i = 0; i < _num_spaces; ++i) {
287 ContiguousSpace* space = get_space(i);
288 HeapWord* cur_addr = space->bottom();
289 HeapWord* top = space->top();
290
291 bool record_first_dead_done = false;
292
293 DeadSpacer dead_spacer(space);
294
295 while (cur_addr < top) {
296 oop obj = cast_to_oop(cur_addr);
297 size_t obj_size = obj->size();
298 if (obj->is_gc_marked()) {
299 HeapWord* new_addr = alloc(obj_size);
300 forward_obj(obj, new_addr);
301 cur_addr += obj_size;
302 } else {
303 // Skipping the current known-unmarked obj
304 HeapWord* next_live_addr = find_next_live_addr(cur_addr + obj_size, top);
305 if (dead_spacer.insert_deadspace(cur_addr, next_live_addr)) {
306 // Register space for the filler obj
307 alloc(pointer_delta(next_live_addr, cur_addr));
308 } else {
309 if (!record_first_dead_done) {
310 record_first_dead(i, cur_addr);
311 record_first_dead_done = true;
312 }
313 *(HeapWord**)cur_addr = next_live_addr;
314 }
315 cur_addr = next_live_addr;
316 }
317 }
318
319 if (!record_first_dead_done) {
320 record_first_dead(i, top);
321 }
322 }
323 }
324
325 void phase3_adjust_pointers() {
326 for (uint i = 0; i < _num_spaces; ++i) {
327 ContiguousSpace* space = get_space(i);
328 HeapWord* cur_addr = space->bottom();
329 HeapWord* const top = space->top();
330 HeapWord* const first_dead = get_first_dead(i);
331
332 while (cur_addr < top) {
333 prefetch_write_scan(cur_addr);
334 if (cur_addr < first_dead || cast_to_oop(cur_addr)->is_gc_marked()) {
335 size_t size = cast_to_oop(cur_addr)->oop_iterate_size(&SerialFullGC::adjust_pointer_closure);
336 cur_addr += size;
337 } else {
338 assert(*(HeapWord**)cur_addr > cur_addr, "forward progress");
339 cur_addr = *(HeapWord**)cur_addr;
340 }
341 }
342 }
343 }
344
345 void phase4_compact() {
346 for (uint i = 0; i < _num_spaces; ++i) {
347 ContiguousSpace* space = get_space(i);
348 HeapWord* cur_addr = space->bottom();
349 HeapWord* top = space->top();
350
351 // Check if the first obj inside this space is forwarded.
352 if (!FullGCForwarding::is_forwarded(cast_to_oop(cur_addr))) {
353 // Jump over consecutive (in-place) live-objs-chunk
354 cur_addr = get_first_dead(i);
355 }
356
357 while (cur_addr < top) {
358 if (!FullGCForwarding::is_forwarded(cast_to_oop(cur_addr))) {
359 cur_addr = *(HeapWord**) cur_addr;
360 continue;
361 }
362 cur_addr += relocate(cur_addr);
363 }
364
365 // Reset top and unused memory
366 HeapWord* new_top = get_compaction_top(i);
367 space->set_top(new_top);
368 if (ZapUnusedHeapArea && new_top < top) {
369 space->mangle_unused_area(MemRegion(new_top, top));
370 }
371 }
372 }
373 };
374
375 template <class T> void SerialFullGC::KeepAliveClosure::do_oop_work(T* p) {
376 mark_and_push(p);
377 }
378
379 void SerialFullGC::push_objarray(oop obj, size_t index) {
380 ObjArrayTask task(obj, index);
381 assert(task.is_valid(), "bad ObjArrayTask");
382 _objarray_stack.push(task);
383 }
384
385 void SerialFullGC::follow_array(objArrayOop array) {
386 mark_and_push_closure.do_klass(array->klass());
387 // Don't push empty arrays to avoid unnecessary work.
388 if (array->length() > 0) {
389 SerialFullGC::push_objarray(array, 0);
390 }
391 }
392
393 void SerialFullGC::follow_object(oop obj) {
394 assert(obj->is_gc_marked(), "should be marked");
395 if (obj->is_objArray()) {
396 // Handle object arrays explicitly to allow them to
397 // be split into chunks if needed.
398 SerialFullGC::follow_array((objArrayOop)obj);
399 } else {
400 obj->oop_iterate(&mark_and_push_closure);
401 }
402 }
403
404 void SerialFullGC::follow_array_chunk(objArrayOop array, int index) {
405 const int len = array->length();
406 const int beg_index = index;
407 assert(beg_index < len || len == 0, "index too large");
408
409 const int stride = MIN2(len - beg_index, (int) ObjArrayMarkingStride);
410 const int end_index = beg_index + stride;
411
412 array->oop_iterate_elements_range(&mark_and_push_closure, beg_index, end_index);
413
414 if (end_index < len) {
415 SerialFullGC::push_objarray(array, end_index); // Push the continuation.
416 }
417 }
418
419 void SerialFullGC::follow_stack() {
420 do {
421 while (!_marking_stack.is_empty()) {
422 oop obj = _marking_stack.pop();
423 assert (obj->is_gc_marked(), "p must be marked");
424 follow_object(obj);
425 }
426 // Process ObjArrays one at a time to avoid marking stack bloat.
427 if (!_objarray_stack.is_empty()) {
428 ObjArrayTask task = _objarray_stack.pop();
429 follow_array_chunk(objArrayOop(task.obj()), task.index());
430 }
431 } while (!_marking_stack.is_empty() || !_objarray_stack.is_empty());
432 }
433
434 SerialFullGC::FollowStackClosure SerialFullGC::follow_stack_closure;
435
436 void SerialFullGC::FollowStackClosure::do_void() { follow_stack(); }
437
438 template <class T> void SerialFullGC::follow_root(T* p) {
439 assert(!Universe::heap()->is_in(p),
440 "roots shouldn't be things within the heap");
441 T heap_oop = RawAccess<>::oop_load(p);
442 if (!CompressedOops::is_null(heap_oop)) {
443 oop obj = CompressedOops::decode_not_null(heap_oop);
444 if (!obj->mark().is_marked()) {
445 mark_object(obj);
446 follow_object(obj);
447 }
448 }
449 follow_stack();
450 }
451
452 void SerialFullGC::FollowRootClosure::do_oop(oop* p) { follow_root(p); }
453 void SerialFullGC::FollowRootClosure::do_oop(narrowOop* p) { follow_root(p); }
454
455 // We preserve the mark which should be replaced at the end and the location
456 // that it will go. Note that the object that this markWord belongs to isn't
457 // currently at that address but it will be after phase4
458 void SerialFullGC::preserve_mark(oop obj, markWord mark) {
459 // We try to store preserved marks in the to space of the new generation since
460 // this is storage which should be available. Most of the time this should be
461 // sufficient space for the marks we need to preserve but if it isn't we fall
462 // back to using Stacks to keep track of the overflow.
463 if (_preserved_count < _preserved_count_max) {
464 _preserved_marks[_preserved_count++] = PreservedMark(obj, mark);
465 } else {
466 _preserved_overflow_stack_set.get()->push_always(obj, mark);
467 }
468 }
469
470 void SerialFullGC::phase1_mark(bool clear_all_softrefs) {
471 // Recursively traverse all live objects and mark them
472 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", _gc_timer);
473
474 SerialHeap* gch = SerialHeap::heap();
475
476 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
477
478 ref_processor()->start_discovery(clear_all_softrefs);
479
480 {
481 GCTraceTime(Debug, gc, phases) tm_m("Marking From Roots", gc_timer());
482
483 // Start tracing from roots, there are 3 kinds of roots in full-gc.
484 //
485 // 1. CLD. This method internally takes care of whether class loading is
486 // enabled or not, applying the closure to both strong and weak or only
487 // strong CLDs.
488 ClassLoaderDataGraph::always_strong_cld_do(&follow_cld_closure);
489
490 {
491 // 2. Threads stack frames and active nmethods in them.
492 NMethodMarkingScope nmethod_marking_scope;
493 MarkingNMethodClosure mark_code_closure(&follow_root_closure);
494
495 Threads::oops_do(&follow_root_closure, &mark_code_closure);
496 }
497
498 // 3. VM internal roots.
499 OopStorageSet::strong_oops_do(&follow_root_closure);
500 }
501
502 // Process reference objects found during marking
503 {
504 GCTraceTime(Debug, gc, phases) tm_m("Reference Processing", gc_timer());
505
506 ReferenceProcessorPhaseTimes pt(_gc_timer, ref_processor()->max_num_queues());
507 SerialGCRefProcProxyTask task(is_alive, keep_alive, follow_stack_closure);
508 const ReferenceProcessorStats& stats = ref_processor()->process_discovered_references(task, nullptr, pt);
509 pt.print_all_references();
510 gc_tracer()->report_gc_reference_stats(stats);
511 }
512
513 // This is the point where the entire marking should have completed.
514 assert(_marking_stack.is_empty(), "Marking should have completed");
515
516 {
517 GCTraceTime(Debug, gc, phases) tm_m("Weak Processing", gc_timer());
518 WeakProcessor::weak_oops_do(&is_alive, &do_nothing_cl);
519 }
520
521 {
522 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", gc_timer());
523
524 ClassUnloadingContext* ctx = ClassUnloadingContext::context();
525
526 bool unloading_occurred;
527 {
528 CodeCache::UnlinkingScope scope(&is_alive);
529
530 // Unload classes and purge the SystemDictionary.
531 unloading_occurred = SystemDictionary::do_unloading(gc_timer());
532
533 // Unload nmethods.
534 CodeCache::do_unloading(unloading_occurred);
535 }
536
537 {
538 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
539 // Release unloaded nmethod's memory.
540 ctx->purge_nmethods();
541 }
542 {
543 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", gc_timer());
544 gch->prune_unlinked_nmethods();
545 }
546 {
547 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
548 ctx->free_nmethods();
549 }
550
551 // Prune dead klasses from subklass/sibling/implementor lists.
552 Klass::clean_weak_klass_links(unloading_occurred);
553 }
554
555 {
556 GCTraceTime(Debug, gc, phases) tm_m("Report Object Count", gc_timer());
557 gc_tracer()->report_object_count_after_gc(&is_alive, nullptr);
558 }
559 }
560
561 void SerialFullGC::allocate_stacks() {
562 void* scratch = nullptr;
563 size_t num_words;
564 DefNewGeneration* young_gen = (DefNewGeneration*)SerialHeap::heap()->young_gen();
565 young_gen->contribute_scratch(scratch, num_words);
566
567 if (scratch != nullptr) {
568 _preserved_count_max = num_words * HeapWordSize / sizeof(PreservedMark);
569 } else {
570 _preserved_count_max = 0;
571 }
572
573 _preserved_marks = (PreservedMark*)scratch;
574 _preserved_count = 0;
575
576 _preserved_overflow_stack_set.init(1);
577 }
578
579 void SerialFullGC::deallocate_stacks() {
580 if (_preserved_count_max != 0) {
581 DefNewGeneration* young_gen = (DefNewGeneration*)SerialHeap::heap()->young_gen();
582 young_gen->reset_scratch();
583 }
584
585 _preserved_overflow_stack_set.reclaim();
586 _marking_stack.clear();
587 _objarray_stack.clear(true);
588 }
589
590 void SerialFullGC::mark_object(oop obj) {
591 if (StringDedup::is_enabled() &&
592 java_lang_String::is_instance(obj) &&
593 SerialStringDedup::is_candidate_from_mark(obj)) {
594 _string_dedup_requests->add(obj);
595 }
596
597 // some marks may contain information we need to preserve so we store them away
598 // and overwrite the mark. We'll restore it at the end of serial full GC.
599 markWord mark = obj->mark();
600 obj->set_mark(obj->prototype_mark().set_marked());
601
602 ContinuationGCSupport::transform_stack_chunk(obj);
603
604 if (obj->mark_must_be_preserved(mark)) {
605 preserve_mark(obj, mark);
606 }
607 }
608
609 template <class T> void SerialFullGC::mark_and_push(T* p) {
610 T heap_oop = RawAccess<>::oop_load(p);
611 if (!CompressedOops::is_null(heap_oop)) {
612 oop obj = CompressedOops::decode_not_null(heap_oop);
613 if (!obj->mark().is_marked()) {
614 mark_object(obj);
615 _marking_stack.push(obj);
616 }
617 }
618 }
619
620 template <typename T>
621 void MarkAndPushClosure::do_oop_work(T* p) { SerialFullGC::mark_and_push(p); }
622 void MarkAndPushClosure::do_oop( oop* p) { do_oop_work(p); }
623 void MarkAndPushClosure::do_oop(narrowOop* p) { do_oop_work(p); }
624
625 template <class T> void SerialFullGC::adjust_pointer(T* p) {
626 T heap_oop = RawAccess<>::oop_load(p);
627 if (!CompressedOops::is_null(heap_oop)) {
628 oop obj = CompressedOops::decode_not_null(heap_oop);
629 assert(Universe::heap()->is_in(obj), "should be in heap");
630
631 if (FullGCForwarding::is_forwarded(obj)) {
632 oop new_obj = FullGCForwarding::forwardee(obj);
633 assert(is_object_aligned(new_obj), "oop must be aligned");
634 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
635 }
636 }
637 }
638
639 template <typename T>
640 void AdjustPointerClosure::do_oop_work(T* p) { SerialFullGC::adjust_pointer(p); }
641 inline void AdjustPointerClosure::do_oop(oop* p) { do_oop_work(p); }
642 inline void AdjustPointerClosure::do_oop(narrowOop* p) { do_oop_work(p); }
643
644 AdjustPointerClosure SerialFullGC::adjust_pointer_closure;
645
646 void SerialFullGC::adjust_marks() {
647 // adjust the oops we saved earlier
648 for (size_t i = 0; i < _preserved_count; i++) {
649 PreservedMarks::adjust_preserved_mark(_preserved_marks + i);
650 }
651
652 // deal with the overflow stack
653 _preserved_overflow_stack_set.get()->adjust_during_full_gc();
654 }
655
656 void SerialFullGC::restore_marks() {
657 log_trace(gc)("Restoring %zu marks", _preserved_count + _preserved_overflow_stack_set.get()->size());
658
659 // restore the marks we saved earlier
660 for (size_t i = 0; i < _preserved_count; i++) {
661 _preserved_marks[i].set_mark();
662 }
663
664 // deal with the overflow
665 _preserved_overflow_stack_set.restore(nullptr);
666 }
667
668 SerialFullGC::IsAliveClosure SerialFullGC::is_alive;
669
670 bool SerialFullGC::IsAliveClosure::do_object_b(oop p) { return p->is_gc_marked(); }
671
672 SerialFullGC::KeepAliveClosure SerialFullGC::keep_alive;
673
674 void SerialFullGC::KeepAliveClosure::do_oop(oop* p) { SerialFullGC::KeepAliveClosure::do_oop_work(p); }
675 void SerialFullGC::KeepAliveClosure::do_oop(narrowOop* p) { SerialFullGC::KeepAliveClosure::do_oop_work(p); }
676
677 void SerialFullGC::initialize() {
678 SerialFullGC::_gc_timer = new STWGCTimer();
679 SerialFullGC::_gc_tracer = new SerialOldTracer();
680 SerialFullGC::_string_dedup_requests = new StringDedup::Requests();
681
682 // The Full GC operates on the entire heap so all objects should be subject
683 // to discovery, hence the _always_true_closure.
684 SerialFullGC::_ref_processor = new ReferenceProcessor(&_always_true_closure);
685 mark_and_push_closure.set_ref_discoverer(_ref_processor);
686 }
687
688 void SerialFullGC::invoke_at_safepoint(bool clear_all_softrefs) {
689 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
690
691 SerialHeap* gch = SerialHeap::heap();
692
693 gch->trace_heap_before_gc(_gc_tracer);
694
695 // Capture used regions for old-gen to reestablish old-to-young invariant
696 // after full-gc.
697 gch->old_gen()->save_used_region();
698
699 allocate_stacks();
700
701 // Usually, all class unloading work occurs at the end of phase 1, but Serial
702 // full-gc accesses dead-objs' klass to find out the start of next live-obj
703 // during phase 2. This requires klasses of dead-objs to be kept loaded.
704 // Therefore, we declare ClassUnloadingContext at the same level as
705 // full-gc phases, and purge dead classes (invoking
706 // ClassLoaderDataGraph::purge) after all phases of full-gc.
707 ClassUnloadingContext ctx(1 /* num_nmethod_unlink_workers */,
708 false /* unregister_nmethods_during_purge */,
709 false /* lock_nmethod_free_separately */);
710
711 phase1_mark(clear_all_softrefs);
712
713 Compacter compacter{gch};
714
715 {
716 // Now all live objects are marked, compute the new object addresses.
717 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", _gc_timer);
718
719 compacter.phase2_calculate_new_addr();
720 }
721
722 // Don't add any more derived pointers during phase3
723 #ifdef COMPILER2
724 assert(DerivedPointerTable::is_active(), "Sanity");
725 DerivedPointerTable::set_active(false);
726 #endif // COMPILER2
727
728 {
729 // Adjust the pointers to reflect the new locations
730 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
731
732 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
733
734 // Remap strong and weak roots in adjust phase.
735 // 1. All (strong and weak) CLDs.
736 ClassLoaderDataGraph::cld_do(&adjust_cld_closure);
737
738 // 2. Threads stack frames. No need to visit on-stack nmethods, because all
739 // nmethods are visited in one go via CodeCache::nmethods_do.
740 Threads::oops_do(&adjust_pointer_closure, nullptr);
741 NMethodToOopClosure nmethod_cl(&adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
742 CodeCache::nmethods_do(&nmethod_cl);
743
744 // 3. VM internal roots
745 OopStorageSet::strong_oops_do(&adjust_pointer_closure);
746
747 // 4. VM internal weak roots
748 WeakProcessor::oops_do(&adjust_pointer_closure);
749
750 adjust_marks();
751 compacter.phase3_adjust_pointers();
752 }
753
754 {
755 // All pointers are now adjusted, move objects accordingly
756 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", _gc_timer);
757
758 compacter.phase4_compact();
759 }
760
761 // Delete metaspaces for unloaded class loaders and clean up CLDG.
762 ClassLoaderDataGraph::purge(true /* at_safepoint */);
763 DEBUG_ONLY(MetaspaceUtils::verify();)
764
765 // Need to clear claim bits for the next full-gc (specifically phase 1 and 3).
766 ClassLoaderDataGraph::clear_claimed_marks();
767
768 restore_marks();
769
770 deallocate_stacks();
771
772 SerialFullGC::_string_dedup_requests->flush();
773
774 bool is_young_gen_empty = (gch->young_gen()->used() == 0);
775 gch->rem_set()->maintain_old_to_young_invariant(gch->old_gen(), is_young_gen_empty);
776
777 gch->prune_scavengable_nmethods();
778
779 // Update heap occupancy information which is used as
780 // input to soft ref clearing policy at the next gc.
781 Universe::heap()->update_capacity_and_used_at_gc();
782
783 // Signal that we have completed a visit to all live objects.
784 Universe::heap()->record_whole_heap_examined_timestamp();
785
786 gch->trace_heap_after_gc(_gc_tracer);
787 }