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