1 /*
  2  * Copyright (c) 1997, 2024, 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 "precompiled.hpp"
 26 #include "classfile/classLoaderDataGraph.hpp"
 27 #include "classfile/classLoaderData.inline.hpp"
 28 #include "classfile/javaClasses.inline.hpp"
 29 #include "classfile/stringTable.hpp"
 30 #include "classfile/symbolTable.hpp"
 31 #include "classfile/systemDictionary.hpp"
 32 #include "classfile/vmSymbols.hpp"
 33 #include "code/codeCache.hpp"
 34 #include "compiler/compileBroker.hpp"
 35 #include "compiler/oopMap.hpp"
 36 #include "gc/serial/cardTableRS.hpp"
 37 #include "gc/serial/defNewGeneration.hpp"
 38 #include "gc/serial/serialFullGC.hpp"
 39 #include "gc/serial/serialGcRefProcProxyTask.hpp"
 40 #include "gc/serial/serialHeap.hpp"
 41 #include "gc/serial/serialStringDedup.hpp"
 42 #include "gc/serial/tenuredGeneration.inline.hpp"
 43 #include "gc/shared/classUnloadingContext.hpp"
 44 #include "gc/shared/collectedHeap.inline.hpp"
 45 #include "gc/shared/continuationGCSupport.inline.hpp"
 46 #include "gc/shared/gcHeapSummary.hpp"
 47 #include "gc/shared/gcTimer.hpp"
 48 #include "gc/shared/gcTrace.hpp"
 49 #include "gc/shared/gcTraceTime.inline.hpp"
 50 #include "gc/shared/gc_globals.hpp"
 51 #include "gc/shared/modRefBarrierSet.hpp"
 52 #include "gc/shared/preservedMarks.inline.hpp"
 53 #include "gc/shared/referencePolicy.hpp"
 54 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
 55 #include "gc/shared/slidingForwarding.inline.hpp"
 56 #include "gc/shared/space.hpp"
 57 #include "gc/shared/strongRootsScope.hpp"
 58 #include "gc/shared/weakProcessor.hpp"
 59 #include "memory/iterator.inline.hpp"
 60 #include "memory/universe.hpp"
 61 #include "oops/access.inline.hpp"
 62 #include "oops/compressedOops.inline.hpp"
 63 #include "oops/instanceRefKlass.hpp"
 64 #include "oops/markWord.hpp"
 65 #include "oops/methodData.hpp"
 66 #include "oops/objArrayKlass.inline.hpp"
 67 #include "oops/oop.inline.hpp"
 68 #include "oops/typeArrayOop.inline.hpp"
 69 #include "runtime/prefetch.inline.hpp"
 70 #include "utilities/align.hpp"
 71 #include "utilities/copy.hpp"
 72 #include "utilities/events.hpp"
 73 #include "utilities/stack.inline.hpp"
 74 #if INCLUDE_JVMCI
 75 #include "jvmci/jvmci.hpp"
 76 #endif
 77 
 78 Stack<oop, mtGC>              SerialFullGC::_marking_stack;
 79 Stack<ObjArrayTask, mtGC>     SerialFullGC::_objarray_stack;
 80 
 81 PreservedMarksSet       SerialFullGC::_preserved_overflow_stack_set(false /* in_c_heap */);
 82 size_t                  SerialFullGC::_preserved_count = 0;
 83 size_t                  SerialFullGC::_preserved_count_max = 0;
 84 PreservedMark*          SerialFullGC::_preserved_marks = nullptr;
 85 STWGCTimer*             SerialFullGC::_gc_timer        = nullptr;
 86 SerialOldTracer*        SerialFullGC::_gc_tracer       = nullptr;
 87 
 88 AlwaysTrueClosure   SerialFullGC::_always_true_closure;
 89 ReferenceProcessor* SerialFullGC::_ref_processor;
 90 
 91 StringDedup::Requests*  SerialFullGC::_string_dedup_requests = nullptr;
 92 
 93 SerialFullGC::FollowRootClosure  SerialFullGC::follow_root_closure;
 94 
 95 MarkAndPushClosure SerialFullGC::mark_and_push_closure(ClassLoaderData::_claim_stw_fullgc_mark);
 96 CLDToOopClosure    SerialFullGC::follow_cld_closure(&mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
 97 CLDToOopClosure    SerialFullGC::adjust_cld_closure(&adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
 98 
 99 class DeadSpacer : StackObj {
100   size_t _allowed_deadspace_words;
101   bool _active;
102   ContiguousSpace* _space;
103 
104 public:
105   DeadSpacer(ContiguousSpace* space) : _allowed_deadspace_words(0), _space(space) {
106     size_t ratio = (_space == SerialHeap::heap()->old_gen()->space())
107                    ? MarkSweepDeadRatio : 0;
108     _active = ratio > 0;
109 
110     if (_active) {
111       // We allow some amount of garbage towards the bottom of the space, so
112       // we don't start compacting before there is a significant gain to be made.
113       // Occasionally, we want to ensure a full compaction, which is determined
114       // by the MarkSweepAlwaysCompactCount parameter.
115       if ((SerialHeap::heap()->total_full_collections() % MarkSweepAlwaysCompactCount) != 0) {
116         _allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize;
117       } else {
118         _active = false;
119       }
120     }
121   }
122 
123   bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) {
124     if (!_active) {
125       return false;
126     }
127 
128     size_t dead_length = pointer_delta(dead_end, dead_start);
129     if (_allowed_deadspace_words >= dead_length) {
130       _allowed_deadspace_words -= dead_length;
131       CollectedHeap::fill_with_object(dead_start, dead_length);
132       oop obj = cast_to_oop(dead_start);
133       // obj->set_mark(obj->mark().set_marked());
134 
135       assert(dead_length == obj->size(), "bad filler object size");
136       log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", " SIZE_FORMAT "b",
137                                         p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize);
138 
139       return true;
140     } else {
141       _active = false;
142       return false;
143     }
144   }
145 };
146 
147 // Implement the "compaction" part of the mark-compact GC algorithm.
148 class Compacter {
149   // There are four spaces in total, but only the first three can be used after
150   // compact. IOW, old and eden/from must be enough for all live objs
151   static constexpr uint max_num_spaces = 4;
152 
153   struct CompactionSpace {
154     ContiguousSpace* _space;
155     // Will be the new top after compaction is complete.
156     HeapWord* _compaction_top;
157     // The first dead word in this contiguous space. It's an optimization to
158     // skip large chunk of live objects at the beginning.
159     HeapWord* _first_dead;
160 
161     void init(ContiguousSpace* space) {
162       _space = space;
163       _compaction_top = space->bottom();
164       _first_dead = nullptr;
165     }
166   };
167 
168   CompactionSpace _spaces[max_num_spaces];
169   // The num of spaces to be compacted, i.e. containing live objs.
170   uint _num_spaces;
171 
172   uint _index;
173 
174   // Used for BOT update
175   TenuredGeneration* _old_gen;
176 
177   HeapWord* get_compaction_top(uint index) const {
178     return _spaces[index]._compaction_top;
179   }
180 
181   HeapWord* get_first_dead(uint index) const {
182     return _spaces[index]._first_dead;
183   }
184 
185   ContiguousSpace* get_space(uint index) const {
186     return _spaces[index]._space;
187   }
188 
189   void record_first_dead(uint index, HeapWord* first_dead) {
190     assert(_spaces[index]._first_dead == nullptr, "should write only once");
191     _spaces[index]._first_dead = first_dead;
192   }
193 
194   HeapWord* alloc(size_t words) {
195     while (true) {
196       if (words <= pointer_delta(_spaces[_index]._space->end(),
197                                  _spaces[_index]._compaction_top)) {
198         HeapWord* result = _spaces[_index]._compaction_top;
199         _spaces[_index]._compaction_top += words;
200         if (_index == 0) {
201           // old-gen requires BOT update
202           _old_gen->update_for_block(result, result + words);
203         }
204         return result;
205       }
206 
207       // out-of-memory in this space
208       _index++;
209       assert(_index < max_num_spaces - 1, "the last space should not be used");
210     }
211   }
212 
213   static void prefetch_read_scan(void* p) {
214     if (PrefetchScanIntervalInBytes >= 0) {
215       Prefetch::read(p, PrefetchScanIntervalInBytes);
216     }
217   }
218 
219   static void prefetch_write_scan(void* p) {
220     if (PrefetchScanIntervalInBytes >= 0) {
221       Prefetch::write(p, PrefetchScanIntervalInBytes);
222     }
223   }
224 
225   static void prefetch_write_copy(void* p) {
226     if (PrefetchCopyIntervalInBytes >= 0) {
227       Prefetch::write(p, PrefetchCopyIntervalInBytes);
228     }
229   }
230 
231   static void forward_obj(oop obj, HeapWord* new_addr) {
232     prefetch_write_scan(obj);
233     if (cast_from_oop<HeapWord*>(obj) != new_addr) {
234       SlidingForwarding::forward_to(obj, cast_to_oop(new_addr));
235     } else {
236       assert(obj->is_gc_marked(), "inv");
237       // This obj will stay in-place. Fix the markword.
238       obj->init_mark();
239     }
240   }
241 
242   static HeapWord* find_next_live_addr(HeapWord* start, HeapWord* end) {
243     for (HeapWord* i_addr = start; i_addr < end; /* empty */) {
244       prefetch_read_scan(i_addr);
245       oop obj = cast_to_oop(i_addr);
246       if (obj->is_gc_marked()) {
247         return i_addr;
248       }
249       i_addr += obj->size();
250     }
251     return end;
252   };
253 
254   static size_t relocate(HeapWord* addr) {
255     // Prefetch source and destination
256     prefetch_read_scan(addr);
257 
258     oop obj = cast_to_oop(addr);
259     oop new_obj = SlidingForwarding::forwardee(obj);
260     HeapWord* new_addr = cast_from_oop<HeapWord*>(new_obj);
261     assert(addr != new_addr, "inv");
262     prefetch_write_copy(new_addr);
263 
264     size_t obj_size = obj->size();
265     Copy::aligned_conjoint_words(addr, new_addr, obj_size);
266     new_obj->init_mark();
267 
268     return obj_size;
269   }
270 
271 public:
272   explicit Compacter(SerialHeap* heap) {
273     // In this order so that heap is compacted towards old-gen.
274     _spaces[0].init(heap->old_gen()->space());
275     _spaces[1].init(heap->young_gen()->eden());
276     _spaces[2].init(heap->young_gen()->from());
277 
278     bool is_promotion_failed = !heap->young_gen()->to()->is_empty();
279     if (is_promotion_failed) {
280       _spaces[3].init(heap->young_gen()->to());
281       _num_spaces = 4;
282     } else {
283       _num_spaces = 3;
284     }
285     _index = 0;
286     _old_gen = heap->old_gen();
287   }
288 
289   void phase2_calculate_new_addr() {
290     for (uint i = 0; i < _num_spaces; ++i) {
291       ContiguousSpace* space = get_space(i);
292       HeapWord* cur_addr = space->bottom();
293       HeapWord* top = space->top();
294 
295       bool record_first_dead_done = false;
296 
297       DeadSpacer dead_spacer(space);
298 
299       while (cur_addr < top) {
300         oop obj = cast_to_oop(cur_addr);
301         size_t obj_size = obj->size();
302         if (obj->is_gc_marked()) {
303           HeapWord* new_addr = alloc(obj_size);
304           forward_obj(obj, new_addr);
305           cur_addr += obj_size;
306         } else {
307           // Skipping the current known-unmarked obj
308           HeapWord* next_live_addr = find_next_live_addr(cur_addr + obj_size, top);
309           if (dead_spacer.insert_deadspace(cur_addr, next_live_addr)) {
310             // Register space for the filler obj
311             alloc(pointer_delta(next_live_addr, cur_addr));
312           } else {
313             if (!record_first_dead_done) {
314               record_first_dead(i, cur_addr);
315               record_first_dead_done = true;
316             }
317             *(HeapWord**)cur_addr = next_live_addr;
318           }
319           cur_addr = next_live_addr;
320         }
321       }
322 
323       if (!record_first_dead_done) {
324         record_first_dead(i, top);
325       }
326     }
327   }
328 
329   void phase3_adjust_pointers() {
330     for (uint i = 0; i < _num_spaces; ++i) {
331       ContiguousSpace* space = get_space(i);
332       HeapWord* cur_addr = space->bottom();
333       HeapWord* const top = space->top();
334       HeapWord* const first_dead = get_first_dead(i);
335 
336       while (cur_addr < top) {
337         prefetch_write_scan(cur_addr);
338         if (cur_addr < first_dead || cast_to_oop(cur_addr)->is_gc_marked()) {
339           size_t size = cast_to_oop(cur_addr)->oop_iterate_size(&SerialFullGC::adjust_pointer_closure);
340           cur_addr += size;
341         } else {
342           assert(*(HeapWord**)cur_addr > cur_addr, "forward progress");
343           cur_addr = *(HeapWord**)cur_addr;
344         }
345       }
346     }
347   }
348 
349   void phase4_compact() {
350     for (uint i = 0; i < _num_spaces; ++i) {
351       ContiguousSpace* space = get_space(i);
352       HeapWord* cur_addr = space->bottom();
353       HeapWord* top = space->top();
354 
355       // Check if the first obj inside this space is forwarded.
356       if (SlidingForwarding::is_not_forwarded(cast_to_oop(cur_addr))) {
357         // Jump over consecutive (in-place) live-objs-chunk
358         cur_addr = get_first_dead(i);
359       }
360 
361       while (cur_addr < top) {
362         if (SlidingForwarding::is_not_forwarded(cast_to_oop(cur_addr))) {
363           cur_addr = *(HeapWord**) cur_addr;
364           continue;
365         }
366         cur_addr += relocate(cur_addr);
367       }
368 
369       // Reset top and unused memory
370       HeapWord* new_top = get_compaction_top(i);
371       space->set_top(new_top);
372       if (ZapUnusedHeapArea && new_top < top) {
373         space->mangle_unused_area(MemRegion(new_top, top));
374       }
375     }
376   }
377 };
378 
379 template <class T> void SerialFullGC::KeepAliveClosure::do_oop_work(T* p) {
380   mark_and_push(p);
381 }
382 
383 void SerialFullGC::push_objarray(oop obj, size_t index) {
384   ObjArrayTask task(obj, index);
385   assert(task.is_valid(), "bad ObjArrayTask");
386   _objarray_stack.push(task);
387 }
388 
389 void SerialFullGC::follow_array(objArrayOop array) {
390   mark_and_push_closure.do_klass(array->klass());
391   // Don't push empty arrays to avoid unnecessary work.
392   if (array->length() > 0) {
393     SerialFullGC::push_objarray(array, 0);
394   }
395 }
396 
397 void SerialFullGC::follow_object(oop obj) {
398   assert(obj->is_gc_marked(), "should be marked");
399   if (obj->is_objArray()) {
400     // Handle object arrays explicitly to allow them to
401     // be split into chunks if needed.
402     SerialFullGC::follow_array((objArrayOop)obj);
403   } else {
404     obj->oop_iterate(&mark_and_push_closure);
405   }
406 }
407 
408 void SerialFullGC::follow_array_chunk(objArrayOop array, int index) {
409   const int len = array->length();
410   const int beg_index = index;
411   assert(beg_index < len || len == 0, "index too large");
412 
413   const int stride = MIN2(len - beg_index, (int) ObjArrayMarkingStride);
414   const int end_index = beg_index + stride;
415 
416   array->oop_iterate_range(&mark_and_push_closure, beg_index, end_index);
417 
418   if (end_index < len) {
419     SerialFullGC::push_objarray(array, end_index); // Push the continuation.
420   }
421 }
422 
423 void SerialFullGC::follow_stack() {
424   do {
425     while (!_marking_stack.is_empty()) {
426       oop obj = _marking_stack.pop();
427       assert (obj->is_gc_marked(), "p must be marked");
428       follow_object(obj);
429     }
430     // Process ObjArrays one at a time to avoid marking stack bloat.
431     if (!_objarray_stack.is_empty()) {
432       ObjArrayTask task = _objarray_stack.pop();
433       follow_array_chunk(objArrayOop(task.obj()), task.index());
434     }
435   } while (!_marking_stack.is_empty() || !_objarray_stack.is_empty());
436 }
437 
438 SerialFullGC::FollowStackClosure SerialFullGC::follow_stack_closure;
439 
440 void SerialFullGC::FollowStackClosure::do_void() { follow_stack(); }
441 
442 template <class T> void SerialFullGC::follow_root(T* p) {
443   assert(!Universe::heap()->is_in(p),
444          "roots shouldn't be things within the heap");
445   T heap_oop = RawAccess<>::oop_load(p);
446   if (!CompressedOops::is_null(heap_oop)) {
447     oop obj = CompressedOops::decode_not_null(heap_oop);
448     if (!obj->mark().is_marked()) {
449       mark_object(obj);
450       follow_object(obj);
451     }
452   }
453   follow_stack();
454 }
455 
456 void SerialFullGC::FollowRootClosure::do_oop(oop* p)       { follow_root(p); }
457 void SerialFullGC::FollowRootClosure::do_oop(narrowOop* p) { follow_root(p); }
458 
459 // We preserve the mark which should be replaced at the end and the location
460 // that it will go.  Note that the object that this markWord belongs to isn't
461 // currently at that address but it will be after phase4
462 void SerialFullGC::preserve_mark(oop obj, markWord mark) {
463   // We try to store preserved marks in the to space of the new generation since
464   // this is storage which should be available.  Most of the time this should be
465   // sufficient space for the marks we need to preserve but if it isn't we fall
466   // back to using Stacks to keep track of the overflow.
467   if (_preserved_count < _preserved_count_max) {
468     _preserved_marks[_preserved_count++] = PreservedMark(obj, mark);
469   } else {
470     _preserved_overflow_stack_set.get()->push_always(obj, mark);
471   }
472 }
473 
474 void SerialFullGC::phase1_mark(bool clear_all_softrefs) {
475   // Recursively traverse all live objects and mark them
476   GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", _gc_timer);
477 
478   SerialHeap* gch = SerialHeap::heap();
479 
480   ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
481 
482   ref_processor()->start_discovery(clear_all_softrefs);
483 
484   {
485     StrongRootsScope srs(0);
486 
487     CLDClosure* weak_cld_closure = ClassUnloading ? nullptr : &follow_cld_closure;
488     MarkingNMethodClosure mark_code_closure(&follow_root_closure, !NMethodToOopClosure::FixRelocations, true);
489     gch->process_roots(SerialHeap::SO_None,
490                        &follow_root_closure,
491                        &follow_cld_closure,
492                        weak_cld_closure,
493                        &mark_code_closure);
494   }
495 
496   // Process reference objects found during marking
497   {
498     GCTraceTime(Debug, gc, phases) tm_m("Reference Processing", gc_timer());
499 
500     ReferenceProcessorPhaseTimes pt(_gc_timer, ref_processor()->max_num_queues());
501     SerialGCRefProcProxyTask task(is_alive, keep_alive, follow_stack_closure);
502     const ReferenceProcessorStats& stats = ref_processor()->process_discovered_references(task, pt);
503     pt.print_all_references();
504     gc_tracer()->report_gc_reference_stats(stats);
505   }
506 
507   // This is the point where the entire marking should have completed.
508   assert(_marking_stack.is_empty(), "Marking should have completed");
509 
510   {
511     GCTraceTime(Debug, gc, phases) tm_m("Weak Processing", gc_timer());
512     WeakProcessor::weak_oops_do(&is_alive, &do_nothing_cl);
513   }
514 
515   {
516     GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", gc_timer());
517 
518     ClassUnloadingContext* ctx = ClassUnloadingContext::context();
519 
520     bool unloading_occurred;
521     {
522       CodeCache::UnlinkingScope scope(&is_alive);
523 
524       // Unload classes and purge the SystemDictionary.
525       unloading_occurred = SystemDictionary::do_unloading(gc_timer());
526 
527       // Unload nmethods.
528       CodeCache::do_unloading(unloading_occurred);
529     }
530 
531     {
532       GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
533       // Release unloaded nmethod's memory.
534       ctx->purge_nmethods();
535     }
536     {
537       GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", gc_timer());
538       gch->prune_unlinked_nmethods();
539     }
540     {
541       GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
542       ctx->free_nmethods();
543     }
544 
545     // Prune dead klasses from subklass/sibling/implementor lists.
546     Klass::clean_weak_klass_links(unloading_occurred);
547 
548     // Clean JVMCI metadata handles.
549     JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
550   }
551 
552   {
553     GCTraceTime(Debug, gc, phases) tm_m("Report Object Count", gc_timer());
554     gc_tracer()->report_object_count_after_gc(&is_alive, nullptr);
555   }
556 }
557 
558 void SerialFullGC::allocate_stacks() {
559   void* scratch = nullptr;
560   size_t num_words;
561   DefNewGeneration* young_gen = (DefNewGeneration*)SerialHeap::heap()->young_gen();
562   young_gen->contribute_scratch(scratch, num_words);
563 
564   if (scratch != nullptr) {
565     _preserved_count_max = num_words * HeapWordSize / sizeof(PreservedMark);
566   } else {
567     _preserved_count_max = 0;
568   }
569 
570   _preserved_marks = (PreservedMark*)scratch;
571   _preserved_count = 0;
572 
573   _preserved_overflow_stack_set.init(1);
574 }
575 
576 void SerialFullGC::deallocate_stacks() {
577   if (_preserved_count_max != 0) {
578     DefNewGeneration* young_gen = (DefNewGeneration*)SerialHeap::heap()->young_gen();
579     young_gen->reset_scratch();
580   }
581 
582   _preserved_overflow_stack_set.reclaim();
583   _marking_stack.clear();
584   _objarray_stack.clear(true);
585 }
586 
587 void SerialFullGC::mark_object(oop obj) {
588   if (StringDedup::is_enabled() &&
589       java_lang_String::is_instance(obj) &&
590       SerialStringDedup::is_candidate_from_mark(obj)) {
591     _string_dedup_requests->add(obj);
592   }
593 
594   // Do the transform while we still have the header intact,
595   // which might include important class information.
596   ContinuationGCSupport::transform_stack_chunk(obj);
597 
598   // some marks may contain information we need to preserve so we store them away
599   // and overwrite the mark.  We'll restore it at the end of serial full GC.
600   markWord mark = obj->mark();
601   obj->set_mark(obj->prototype_mark().set_marked());


602 
603   if (obj->mark_must_be_preserved(mark)) {
604     preserve_mark(obj, mark);
605   }
606 }
607 
608 template <class T> void SerialFullGC::mark_and_push(T* p) {
609   T heap_oop = RawAccess<>::oop_load(p);
610   if (!CompressedOops::is_null(heap_oop)) {
611     oop obj = CompressedOops::decode_not_null(heap_oop);
612     if (!obj->mark().is_marked()) {
613       mark_object(obj);
614       _marking_stack.push(obj);
615     }
616   }
617 }
618 
619 template <typename T>
620 void MarkAndPushClosure::do_oop_work(T* p)            { SerialFullGC::mark_and_push(p); }
621 void MarkAndPushClosure::do_oop(      oop* p)         { do_oop_work(p); }
622 void MarkAndPushClosure::do_oop(narrowOop* p)         { do_oop_work(p); }
623 
624 template <class T> void SerialFullGC::adjust_pointer(T* p) {
625   T heap_oop = RawAccess<>::oop_load(p);
626   if (!CompressedOops::is_null(heap_oop)) {
627     oop obj = CompressedOops::decode_not_null(heap_oop);
628     assert(Universe::heap()->is_in(obj), "should be in heap");
629 
630     if (SlidingForwarding::is_forwarded(obj)) {
631       oop new_obj = SlidingForwarding::forwardee(obj);
632       assert(is_object_aligned(new_obj), "oop must be aligned");
633       RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
634     }
635   }
636 }
637 
638 template <typename T>
639 void AdjustPointerClosure::do_oop_work(T* p)           { SerialFullGC::adjust_pointer(p); }
640 inline void AdjustPointerClosure::do_oop(oop* p)       { do_oop_work(p); }
641 inline void AdjustPointerClosure::do_oop(narrowOop* p) { do_oop_work(p); }
642 
643 AdjustPointerClosure SerialFullGC::adjust_pointer_closure;
644 
645 void SerialFullGC::adjust_marks() {
646   // adjust the oops we saved earlier
647   for (size_t i = 0; i < _preserved_count; i++) {
648     PreservedMarks::adjust_preserved_mark(_preserved_marks + i);
649   }
650 
651   // deal with the overflow stack
652   _preserved_overflow_stack_set.get()->adjust_during_full_gc();
653 }
654 
655 void SerialFullGC::restore_marks() {
656   log_trace(gc)("Restoring " SIZE_FORMAT " marks", _preserved_count + _preserved_overflow_stack_set.get()->size());
657 
658   // restore the marks we saved earlier
659   for (size_t i = 0; i < _preserved_count; i++) {
660     _preserved_marks[i].set_mark();
661   }
662 
663   // deal with the overflow
664   _preserved_overflow_stack_set.restore(nullptr);
665 }
666 
667 SerialFullGC::IsAliveClosure   SerialFullGC::is_alive;
668 
669 bool SerialFullGC::IsAliveClosure::do_object_b(oop p) { return p->is_gc_marked(); }
670 
671 SerialFullGC::KeepAliveClosure SerialFullGC::keep_alive;
672 
673 void SerialFullGC::KeepAliveClosure::do_oop(oop* p)       { SerialFullGC::KeepAliveClosure::do_oop_work(p); }
674 void SerialFullGC::KeepAliveClosure::do_oop(narrowOop* p) { SerialFullGC::KeepAliveClosure::do_oop_work(p); }
675 
676 void SerialFullGC::initialize() {
677   SerialFullGC::_gc_timer = new STWGCTimer();
678   SerialFullGC::_gc_tracer = new SerialOldTracer();
679   SerialFullGC::_string_dedup_requests = new StringDedup::Requests();
680 
681   // The Full GC operates on the entire heap so all objects should be subject
682   // to discovery, hence the _always_true_closure.
683   SerialFullGC::_ref_processor = new ReferenceProcessor(&_always_true_closure);
684   mark_and_push_closure.set_ref_discoverer(_ref_processor);
685 }
686 
687 void SerialFullGC::invoke_at_safepoint(bool clear_all_softrefs) {
688   assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
689 
690   SerialHeap* gch = SerialHeap::heap();
691 
692   gch->trace_heap_before_gc(_gc_tracer);
693 
694   // Capture used regions for old-gen to reestablish old-to-young invariant
695   // after full-gc.
696   gch->old_gen()->save_used_region();
697 
698   allocate_stacks();
699 
700   phase1_mark(clear_all_softrefs);
701 
702   SlidingForwarding::begin();
703 
704   Compacter compacter{gch};
705 
706   {
707     // Now all live objects are marked, compute the new object addresses.
708     GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", _gc_timer);
709 
710     compacter.phase2_calculate_new_addr();
711   }
712 
713   // Don't add any more derived pointers during phase3
714 #if COMPILER2_OR_JVMCI
715   assert(DerivedPointerTable::is_active(), "Sanity");
716   DerivedPointerTable::set_active(false);
717 #endif
718 
719   {
720     // Adjust the pointers to reflect the new locations
721     GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
722 
723     ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
724 
725     NMethodToOopClosure code_closure(&adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
726     gch->process_roots(SerialHeap::SO_AllCodeCache,
727                        &adjust_pointer_closure,
728                        &adjust_cld_closure,
729                        &adjust_cld_closure,
730                        &code_closure);
731 
732     WeakProcessor::oops_do(&adjust_pointer_closure);
733 
734     adjust_marks();
735     compacter.phase3_adjust_pointers();
736   }
737 
738   {
739     // All pointers are now adjusted, move objects accordingly
740     GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", _gc_timer);
741 
742     compacter.phase4_compact();
743   }
744 
745   restore_marks();
746 
747   SlidingForwarding::end();
748 
749   deallocate_stacks();
750 
751   SerialFullGC::_string_dedup_requests->flush();
752 
753   bool is_young_gen_empty = (gch->young_gen()->used() == 0);
754   gch->rem_set()->maintain_old_to_young_invariant(gch->old_gen(), is_young_gen_empty);
755 
756   gch->prune_scavengable_nmethods();
757 
758   // Update heap occupancy information which is used as
759   // input to soft ref clearing policy at the next gc.
760   Universe::heap()->update_capacity_and_used_at_gc();
761 
762   // Signal that we have completed a visit to all live objects.
763   Universe::heap()->record_whole_heap_examined_timestamp();
764 
765   gch->trace_heap_after_gc(_gc_tracer);
766 }
--- EOF ---