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/g1FullCollector.inline.hpp"
26 #include "gc/g1/g1FullGCCompactionPoint.hpp"
27 #include "gc/g1/g1HeapRegion.hpp"
28 #include "gc/shared/fullGCForwarding.inline.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 size_t old_size = size;
100 size_t new_size = object->copy_size(old_size, object->mark());
101 size = cast_from_oop<HeapWord*>(object) != _compaction_top ? new_size : old_size;
102
103 // Ensure the object fit in the current region.
104 while (!object_will_fit(size)) {
105 switch_region();
106 size = cast_from_oop<HeapWord*>(object) != _compaction_top ? new_size : old_size;
107 }
108
109 // Store a forwarding pointer if the object should be moved.
110 if (cast_from_oop<HeapWord*>(object) != _compaction_top) {
111 if (!object->is_forwarded()) {
112 preserved_stack()->push_if_necessary(object, object->mark());
113 }
114 FullGCForwarding::forward_to(object, cast_to_oop(_compaction_top));
115 assert(FullGCForwarding::is_forwarded(object), "must be forwarded");
116 } else {
117 assert(!FullGCForwarding::is_forwarded(object), "must not be forwarded");
118 }
119
120 // Update compaction values.
121 _compaction_top += size;
122 _current_region->update_bot_for_block(_compaction_top - size, _compaction_top);
123 }
124
125 void G1FullGCCompactionPoint::add(G1HeapRegion* hr) {
126 _compaction_regions->append(hr);
127 }
128
129 void G1FullGCCompactionPoint::remove_at_or_above(uint bottom) {
130 G1HeapRegion* cur = current_region();
131 assert(cur->hrm_index() >= bottom, "Sanity!");
132
133 int start_index = 0;
134 for (G1HeapRegion* r : *_compaction_regions) {
135 if (r->hrm_index() < bottom) {
136 start_index++;
137 }
138 }
139
140 assert(start_index >= 0, "Should have at least one region");
141 _compaction_regions->trunc_to(start_index);
142 }
143
144 void G1FullGCCompactionPoint::add_humongous(G1HeapRegion* hr) {
145 assert(hr->is_starts_humongous(), "Sanity!");
146
147 _collector->add_humongous_region(hr);
148
149 G1CollectedHeap* g1h = G1CollectedHeap::heap();
150 g1h->humongous_obj_regions_iterate(hr,
151 [&] (G1HeapRegion* r) {
152 add(r);
153 _collector->update_from_skip_compacting_to_compacting(r->hrm_index());
154 });
155 }
156
157 void G1FullGCCompactionPoint::forward_humongous(G1HeapRegion* hr) {
158 assert(hr->is_starts_humongous(), "Sanity!");
159
160 oop obj = cast_to_oop(hr->bottom());
161 size_t old_size = obj->size();
162 size_t new_size = obj->copy_size(old_size, obj->mark());
163 uint num_regions = (uint)G1CollectedHeap::humongous_obj_size_in_regions(new_size);
164
165 if (!has_regions()) {
166 return;
167 }
168
169 // Find contiguous compaction target regions for the humongous object.
170 uint range_begin = find_contiguous_before(hr, num_regions);
171
172 if (range_begin == UINT_MAX) {
173 // No contiguous compaction target regions found, so the object cannot be moved.
174 return;
175 }
176
177 // Preserve the mark for the humongous object as the region was initially not compacting.
178 preserved_stack()->push_if_necessary(obj, obj->mark());
179
180 G1HeapRegion* dest_hr = _compaction_regions->at(range_begin);
181 assert(hr->bottom() != dest_hr->bottom(), "assuming actual humongous move");
182 FullGCForwarding::forward_to(obj, cast_to_oop(dest_hr->bottom()));
183 assert(FullGCForwarding::is_forwarded(obj), "Object must be forwarded!");
184
185 // Add the humongous object regions to the compaction point.
186 add_humongous(hr);
187
188 // Remove covered regions from compaction target candidates.
189 _compaction_regions->remove_range(range_begin, (range_begin + num_regions));
190
191 return;
192 }
193
194 uint G1FullGCCompactionPoint::find_contiguous_before(G1HeapRegion* hr, uint num_regions) {
195 assert(num_regions > 0, "Sanity!");
196 assert(has_regions(), "Sanity!");
197
198 if (num_regions == 1) {
199 // If only one region, return the first region.
200 return 0;
201 }
202
203 uint contiguous_region_count = 1;
204
205 uint range_end = 1;
206 uint range_limit = (uint)_compaction_regions->length();
207
208 for (; range_end < range_limit; range_end++) {
209 if (contiguous_region_count == num_regions) {
210 break;
211 }
212 // Check if the current region and the previous region are contiguous.
213 bool regions_are_contiguous = (_compaction_regions->at(range_end)->hrm_index() - _compaction_regions->at(range_end - 1)->hrm_index()) == 1;
214 contiguous_region_count = regions_are_contiguous ? contiguous_region_count + 1 : 1;
215 }
216
217 if (contiguous_region_count < num_regions &&
218 hr->hrm_index() - _compaction_regions->at(range_end-1)->hrm_index() != 1) {
219 // We reached the end but the final region is not contiguous with the target region;
220 // no contiguous regions to move to.
221 return UINT_MAX;
222 }
223 // Return the index of the first region in the range of contiguous regions.
224 return range_end - contiguous_region_count;
225 }