1 /*
2 * Copyright (c) 2017, 2023, 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/g1FullCollector.inline.hpp"
27 #include "gc/g1/g1FullGCCompactionPoint.hpp"
28 #include "gc/g1/g1HeapRegion.hpp"
29 #include "gc/shared/preservedMarks.inline.hpp"
30 #include "gc/shared/slidingForwarding.inline.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "utilities/debug.hpp"
33
34 G1FullGCCompactionPoint::G1FullGCCompactionPoint(G1FullCollector* collector, PreservedMarks* preserved_stack) :
35 _collector(collector),
36 _current_region(nullptr),
37 _compaction_top(nullptr),
38 _preserved_stack(preserved_stack) {
39 _compaction_regions = new (mtGC) GrowableArray<G1HeapRegion*>(32, mtGC);
40 _compaction_region_iterator = _compaction_regions->begin();
41 }
42
43 G1FullGCCompactionPoint::~G1FullGCCompactionPoint() {
44 delete _compaction_regions;
45 }
46
47 void G1FullGCCompactionPoint::update() {
48 if (is_initialized()) {
49 _collector->set_compaction_top(_current_region, _compaction_top);
50 }
51 }
52
53 void G1FullGCCompactionPoint::initialize_values() {
54 _compaction_top = _collector->compaction_top(_current_region);
55 }
56
57 bool G1FullGCCompactionPoint::has_regions() {
58 return !_compaction_regions->is_empty();
59 }
60
61 bool G1FullGCCompactionPoint::is_initialized() {
62 return _current_region != nullptr;
63 }
64
65 void G1FullGCCompactionPoint::initialize(G1HeapRegion* hr) {
66 _current_region = hr;
67 initialize_values();
68 }
69
70 G1HeapRegion* G1FullGCCompactionPoint::current_region() {
71 return *_compaction_region_iterator;
72 }
73
74 G1HeapRegion* G1FullGCCompactionPoint::next_region() {
75 G1HeapRegion* next = *(++_compaction_region_iterator);
76 assert(next != nullptr, "Must return valid region");
77 return next;
78 }
79
80 GrowableArray<G1HeapRegion*>* G1FullGCCompactionPoint::regions() {
81 return _compaction_regions;
82 }
83
84 bool G1FullGCCompactionPoint::object_will_fit(size_t size) {
85 size_t space_left = pointer_delta(_current_region->end(), _compaction_top);
86 return size <= space_left;
87 }
88
89 void G1FullGCCompactionPoint::switch_region() {
90 // Save compaction top in the region.
91 _collector->set_compaction_top(_current_region, _compaction_top);
92 // Get the next region and re-initialize the values.
93 _current_region = next_region();
94 initialize_values();
95 }
96
97 void G1FullGCCompactionPoint::forward(oop object, size_t size) {
98 assert(_current_region != nullptr, "Must have been initialized");
99
100 // Ensure the object fit in the current region.
101 while (!object_will_fit(size)) {
102 switch_region();
103 }
104
105 // Store a forwarding pointer if the object should be moved.
106 if (cast_from_oop<HeapWord*>(object) != _compaction_top) {
107 if (!object->is_forwarded()) {
108 preserved_stack()->push_if_necessary(object, object->mark());
109 }
110 SlidingForwarding::forward_to(object, cast_to_oop(_compaction_top));
111 assert(SlidingForwarding::is_forwarded(object), "must be forwarded");
112 } else {
113 assert(SlidingForwarding::is_not_forwarded(object), "must not be forwarded");
114 }
115
116 // Update compaction values.
117 _compaction_top += size;
118 _current_region->update_bot_for_block(_compaction_top - size, _compaction_top);
119 }
120
121 void G1FullGCCompactionPoint::add(G1HeapRegion* hr) {
122 _compaction_regions->append(hr);
123 }
124
125 void G1FullGCCompactionPoint::remove_at_or_above(uint bottom) {
126 G1HeapRegion* cur = current_region();
127 assert(cur->hrm_index() >= bottom, "Sanity!");
128
129 int start_index = 0;
130 for (G1HeapRegion* r : *_compaction_regions) {
131 if (r->hrm_index() < bottom) {
132 start_index++;
133 }
134 }
135
136 assert(start_index >= 0, "Should have at least one region");
137 _compaction_regions->trunc_to(start_index);
138 }
139
140 void G1FullGCCompactionPoint::add_humongous(G1HeapRegion* hr) {
141 assert(hr->is_starts_humongous(), "Sanity!");
142
143 _collector->add_humongous_region(hr);
144
145 G1CollectedHeap* g1h = G1CollectedHeap::heap();
146 g1h->humongous_obj_regions_iterate(hr,
147 [&] (G1HeapRegion* r) {
148 add(r);
149 _collector->update_from_skip_compacting_to_compacting(r->hrm_index());
150 });
151 }
152
153 void G1FullGCCompactionPoint::forward_humongous(G1HeapRegion* hr) {
154 assert(hr->is_starts_humongous(), "Sanity!");
155
156 oop obj = cast_to_oop(hr->bottom());
157 size_t obj_size = obj->size();
158 uint num_regions = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size);
159
160 if (!has_regions()) {
161 return;
162 }
163
164 // Find contiguous compaction target regions for the humongous object.
165 uint range_begin = find_contiguous_before(hr, num_regions);
166
167 if (range_begin == UINT_MAX) {
168 // No contiguous compaction target regions found, so the object cannot be moved.
169 return;
170 }
171
172 // Preserve the mark for the humongous object as the region was initially not compacting.
173 preserved_stack()->push_if_necessary(obj, obj->mark());
174
175 G1HeapRegion* dest_hr = _compaction_regions->at(range_begin);
176 SlidingForwarding::forward_to(obj, cast_to_oop(dest_hr->bottom()));
177 assert(SlidingForwarding::is_forwarded(obj), "Object must be forwarded!");
178
179 // Add the humongous object regions to the compaction point.
180 add_humongous(hr);
181
182 // Remove covered regions from compaction target candidates.
183 _compaction_regions->remove_range(range_begin, (range_begin + num_regions));
184
185 return;
186 }
187
188 uint G1FullGCCompactionPoint::find_contiguous_before(G1HeapRegion* hr, uint num_regions) {
189 assert(num_regions > 0, "Sanity!");
190 assert(has_regions(), "Sanity!");
191
192 if (num_regions == 1) {
193 // If only one region, return the first region.
194 return 0;
195 }
196
197 uint contiguous_region_count = 1;
198
199 uint range_end = 1;
200 uint range_limit = (uint)_compaction_regions->length();
201
202 for (; range_end < range_limit; range_end++) {
203 if (contiguous_region_count == num_regions) {
204 break;
205 }
206 // Check if the current region and the previous region are contiguous.
207 bool regions_are_contiguous = (_compaction_regions->at(range_end)->hrm_index() - _compaction_regions->at(range_end - 1)->hrm_index()) == 1;
208 contiguous_region_count = regions_are_contiguous ? contiguous_region_count + 1 : 1;
209 }
210
211 if (contiguous_region_count < num_regions &&
212 hr->hrm_index() - _compaction_regions->at(range_end-1)->hrm_index() != 1) {
213 // We reached the end but the final region is not contiguous with the target region;
214 // no contiguous regions to move to.
215 return UINT_MAX;
216 }
217 // Return the index of the first region in the range of contiguous regions.
218 return range_end - contiguous_region_count;
219 }