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