1 /*
  2  * Copyright (c) 2017, 2025, 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 "gc/g1/g1CollectedHeap.hpp"
 26 #include "gc/g1/g1ConcurrentMarkBitMap.inline.hpp"
 27 #include "gc/g1/g1FullCollector.inline.hpp"
 28 #include "gc/g1/g1FullGCCompactionPoint.hpp"
 29 #include "gc/g1/g1FullGCCompactTask.hpp"
 30 #include "gc/g1/g1HeapRegion.inline.hpp"
 31 #include "gc/shared/fullGCForwarding.inline.hpp"
 32 #include "gc/shared/gcTraceTime.inline.hpp"
 33 #include "logging/log.hpp"
 34 #include "oops/oop.inline.hpp"
 35 #include "utilities/ticks.hpp"
 36 
 37 void G1FullGCCompactTask::G1CompactRegionClosure::clear_in_bitmap(oop obj) {
 38   assert(_bitmap->is_marked(obj), "Should only compact marked objects");
 39   _bitmap->clear(obj);
 40 }
 41 
 42 size_t G1FullGCCompactTask::G1CompactRegionClosure::apply(oop obj) {
 43   size_t size = obj->size();
 44   if (FullGCForwarding::is_forwarded(obj)) {
 45     G1FullGCCompactTask::copy_object_to_new_location(obj);
 46   }
 47 
 48   // Clear the mark for the compacted object to allow reuse of the
 49   // bitmap without an additional clearing step.
 50   clear_in_bitmap(obj);
 51   return size;
 52 }
 53 
 54 void G1FullGCCompactTask::copy_object_to_new_location(oop obj) {
 55   assert(FullGCForwarding::is_forwarded(obj), "Sanity!");
 56   assert(FullGCForwarding::forwardee(obj) != obj, "Object must have a new location");
 57 
 58   size_t size = obj->size();
 59   // Copy object and reinit its mark.
 60   HeapWord* obj_addr = cast_from_oop<HeapWord*>(obj);
 61   HeapWord* destination = cast_from_oop<HeapWord*>(FullGCForwarding::forwardee(obj));
 62   assert(obj_addr != destination, "only copy actually-moving objects");
 63   Copy::aligned_conjoint_words(obj_addr, destination, size);
 64 
 65   // There is no need to transform stack chunks - marking already did that.
 66   cast_to_oop(destination)->init_mark();
 67   cast_to_oop(destination)->initialize_hash_if_necessary(obj);
 68   assert(cast_to_oop(destination)->klass() != nullptr, "should have a class");
 69 }
 70 
 71 void G1FullGCCompactTask::compact_region(G1HeapRegion* hr) {
 72   assert(!hr->has_pinned_objects(), "Should be no region with pinned objects in compaction queue");
 73   assert(!hr->is_humongous(), "Should be no humongous regions in compaction queue");
 74 
 75   if (!collector()->is_free(hr->hrm_index())) {
 76     // The compaction closure not only copies the object to the new
 77     // location, but also clears the bitmap for it. This is needed
 78     // for bitmap verification and to be able to use the bitmap
 79     // for evacuation failures in the next young collection. Testing
 80     // showed that it was better overall to clear bit by bit, compared
 81     // to clearing the whole region at the end. This difference was
 82     // clearly seen for regions with few marks.
 83     G1CompactRegionClosure compact(collector()->mark_bitmap());
 84     hr->apply_to_marked_objects(collector()->mark_bitmap(), &compact);
 85   }
 86 
 87   hr->reset_compacted_after_full_gc(_collector->compaction_top(hr));
 88 }
 89 
 90 void G1FullGCCompactTask::work(uint worker_id) {
 91   Ticks start = Ticks::now();
 92   GrowableArray<G1HeapRegion*>* compaction_queue = collector()->compaction_point(worker_id)->regions();
 93   for (GrowableArrayIterator<G1HeapRegion*> it = compaction_queue->begin();
 94        it != compaction_queue->end();
 95        ++it) {
 96     compact_region(*it);
 97   }
 98 }
 99 
100 void G1FullGCCompactTask::serial_compaction() {
101   GCTraceTime(Debug, gc, phases) tm("Phase 4: Serial Compaction", collector()->scope()->timer());
102   GrowableArray<G1HeapRegion*>* compaction_queue = collector()->serial_compaction_point()->regions();
103   for (GrowableArrayIterator<G1HeapRegion*> it = compaction_queue->begin();
104        it != compaction_queue->end();
105        ++it) {
106     compact_region(*it);
107   }
108 }
109 
110 void G1FullGCCompactTask::humongous_compaction() {
111   GCTraceTime(Debug, gc, phases) tm("Phase 4: Humonguous Compaction", collector()->scope()->timer());
112 
113   for (G1HeapRegion* hr : collector()->humongous_compaction_regions()) {
114     assert(collector()->is_compaction_target(hr->hrm_index()), "Sanity");
115     compact_humongous_obj(hr);
116   }
117 }
118 
119 void G1FullGCCompactTask::compact_humongous_obj(G1HeapRegion* src_hr) {
120   assert(src_hr->is_starts_humongous(), "Should be start region of the humongous object");
121 
122   oop obj = cast_to_oop(src_hr->bottom());
123   size_t word_size = obj->size();
124 
125   uint num_regions = (uint)G1CollectedHeap::humongous_obj_size_in_regions(word_size);
126   HeapWord* destination = cast_from_oop<HeapWord*>(FullGCForwarding::forwardee(obj));
127 
128   assert(collector()->mark_bitmap()->is_marked(obj), "Should only compact marked objects");
129   collector()->mark_bitmap()->clear(obj);
130 
131   copy_object_to_new_location(obj);
132 
133   uint dest_start_idx = _g1h->addr_to_region(destination);
134   // Update the metadata for the destination regions.
135   _g1h->set_humongous_metadata(_g1h->region_at(dest_start_idx), num_regions, word_size, false);
136 
137   // Free the source regions that do not overlap with the destination regions.
138   uint src_start_idx = src_hr->hrm_index();
139   free_non_overlapping_regions(src_start_idx, dest_start_idx, num_regions);
140 }
141 
142 void G1FullGCCompactTask::free_non_overlapping_regions(uint src_start_idx, uint dest_start_idx, uint num_regions) {
143   uint dest_end_idx = dest_start_idx + num_regions -1;
144   uint src_end_idx  = src_start_idx + num_regions - 1;
145 
146   uint non_overlapping_start = dest_end_idx < src_start_idx ?
147                                src_start_idx :
148                                dest_end_idx + 1;
149 
150   for (uint i = non_overlapping_start; i <= src_end_idx; ++i) {
151     G1HeapRegion* hr = _g1h->region_at(i);
152     _g1h->free_humongous_region(hr, nullptr);
153   }
154 }