1 /*
2 * Copyright (c) 2017, 2021, 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 "gc/g1/g1CollectedHeap.hpp"
27 #include "gc/g1/g1ConcurrentMarkBitMap.inline.hpp"
28 #include "gc/g1/g1FullCollector.hpp"
29 #include "gc/g1/g1FullCollector.inline.hpp"
30 #include "gc/g1/g1FullGCCompactionPoint.hpp"
31 #include "gc/g1/g1FullGCCompactTask.hpp"
32 #include "gc/g1/heapRegion.inline.hpp"
33 #include "gc/shared/gcTraceTime.inline.hpp"
34 #include "logging/log.hpp"
35 #include "oops/oop.inline.hpp"
36 #include "utilities/ticks.hpp"
37
38 // Do work for all skip-compacting regions.
39 class G1ResetSkipCompactingClosure : public HeapRegionClosure {
40 G1FullCollector* _collector;
41
42 public:
43 G1ResetSkipCompactingClosure(G1FullCollector* collector) : _collector(collector) { }
44
45 bool do_heap_region(HeapRegion* r) {
46 uint region_index = r->hrm_index();
47 // Only for skip-compaction regions; early return otherwise.
48 if (!_collector->is_skip_compacting(region_index)) {
49 return false;
50 }
51 #ifdef ASSERT
52 if (r->is_humongous()) {
53 oop obj = cast_to_oop(r->humongous_start_region()->bottom());
54 assert(_collector->mark_bitmap()->is_marked(obj), "must be live");
55 } else if (r->is_open_archive()) {
56 bool is_empty = (_collector->live_words(r->hrm_index()) == 0);
57 assert(!is_empty, "should contain at least one live obj");
58 } else if (r->is_closed_archive()) {
59 // should early-return above
60 ShouldNotReachHere();
61 } else {
62 assert(_collector->live_words(region_index) > _collector->scope()->region_compaction_threshold(),
63 "should be quite full");
64 }
65 #endif
66 r->reset_skip_compacting_after_full_gc();
67 return false;
68 }
69 };
70
71 void G1FullGCCompactTask::G1CompactRegionClosure::clear_in_prev_bitmap(oop obj) {
72 assert(_bitmap->is_marked(obj), "Should only compact marked objects");
73 _bitmap->clear(obj);
74 }
75
76 size_t G1FullGCCompactTask::G1CompactRegionClosure::apply(oop obj) {
77 size_t size = obj->size();
78 if (!obj->is_forwarded()) {
79 // Object not moving, but clear the mark to allow reuse of the bitmap.
80 clear_in_prev_bitmap(obj);
81 return size;
82 }
83
84 HeapWord* destination = cast_from_oop<HeapWord*>(obj->forwardee());
85
86 // copy object and reinit its mark
87 HeapWord* obj_addr = cast_from_oop<HeapWord*>(obj);
88 assert(obj_addr != destination, "everything in this pass should be moving");
89 Copy::aligned_conjoint_words(obj_addr, destination, size);
90 cast_to_oop(destination)->init_mark();
91 assert(cast_to_oop(destination)->klass() != NULL, "should have a class");
92
93 // Clear the mark for the compacted object to allow reuse of the
94 // bitmap without an additional clearing step.
95 clear_in_prev_bitmap(obj);
96 return size;
97 }
98
99 void G1FullGCCompactTask::compact_region(HeapRegion* hr) {
100 assert(!hr->is_pinned(), "Should be no pinned region in compaction queue");
101 assert(!hr->is_humongous(), "Should be no humongous regions in compaction queue");
102
103 if (!collector()->is_free(hr->hrm_index())) {
104 // The compaction closure not only copies the object to the new
105 // location, but also clears the bitmap for it. This is needed
106 // for bitmap verification and to be able to use the prev_bitmap
107 // for evacuation failures in the next young collection. Testing
108 // showed that it was better overall to clear bit by bit, compared
109 // to clearing the whole region at the end. This difference was
110 // clearly seen for regions with few marks.
111 G1CompactRegionClosure compact(collector()->mark_bitmap());
112 hr->apply_to_marked_objects(collector()->mark_bitmap(), &compact);
113 }
114
115 hr->reset_compacted_after_full_gc();
116 }
117
118 void G1FullGCCompactTask::work(uint worker_id) {
119 Ticks start = Ticks::now();
120 GrowableArray<HeapRegion*>* compaction_queue = collector()->compaction_point(worker_id)->regions();
121 for (GrowableArrayIterator<HeapRegion*> it = compaction_queue->begin();
122 it != compaction_queue->end();
123 ++it) {
124 compact_region(*it);
125 }
126
127 G1ResetSkipCompactingClosure hc(collector());
128 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&hc, &_claimer, worker_id);
129 log_task("Compaction task", worker_id, start);
130 }
131
132 void G1FullGCCompactTask::serial_compaction() {
133 GCTraceTime(Debug, gc, phases) tm("Phase 4: Serial Compaction", collector()->scope()->timer());
134 GrowableArray<HeapRegion*>* compaction_queue = collector()->serial_compaction_point()->regions();
135 for (GrowableArrayIterator<HeapRegion*> it = compaction_queue->begin();
136 it != compaction_queue->end();
137 ++it) {
138 compact_region(*it);
139 }
140 }