1 /*
2 * Copyright (c) 1997, 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 "compiler/compileBroker.hpp"
27 #include "gc/serial/markSweep.inline.hpp"
28 #include "gc/shared/collectedHeap.inline.hpp"
29 #include "gc/shared/gcTimer.hpp"
30 #include "gc/shared/gcTrace.hpp"
31 #include "gc/shared/gc_globals.hpp"
32 #include "memory/iterator.inline.hpp"
33 #include "memory/universe.hpp"
34 #include "oops/access.inline.hpp"
35 #include "oops/compressedOops.inline.hpp"
36 #include "oops/methodData.hpp"
37 #include "oops/objArrayKlass.inline.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "oops/typeArrayOop.inline.hpp"
40 #include "utilities/stack.inline.hpp"
41
42 uint MarkSweep::_total_invocations = 0;
43
44 Stack<oop, mtGC> MarkSweep::_marking_stack;
45 Stack<ObjArrayTask, mtGC> MarkSweep::_objarray_stack;
46
47 Stack<PreservedMark, mtGC> MarkSweep::_preserved_overflow_stack;
48 size_t MarkSweep::_preserved_count = 0;
49 size_t MarkSweep::_preserved_count_max = 0;
50 PreservedMark* MarkSweep::_preserved_marks = nullptr;
51 STWGCTimer* MarkSweep::_gc_timer = nullptr;
52 SerialOldTracer* MarkSweep::_gc_tracer = nullptr;
53
54 AlwaysTrueClosure MarkSweep::_always_true_closure;
55 ReferenceProcessor* MarkSweep::_ref_processor;
56
57 StringDedup::Requests* MarkSweep::_string_dedup_requests = nullptr;
58
59 MarkSweep::FollowRootClosure MarkSweep::follow_root_closure;
60
61 MarkAndPushClosure MarkSweep::mark_and_push_closure(ClassLoaderData::_claim_stw_fullgc_mark);
62 CLDToOopClosure MarkSweep::follow_cld_closure(&mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
63 CLDToOopClosure MarkSweep::adjust_cld_closure(&adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
64
65 template <class T> void MarkSweep::KeepAliveClosure::do_oop_work(T* p) {
66 mark_and_push(p);
67 }
68
69 void MarkSweep::push_objarray(oop obj, size_t index) {
70 ObjArrayTask task(obj, index);
71 assert(task.is_valid(), "bad ObjArrayTask");
72 _objarray_stack.push(task);
73 }
74
75 void MarkSweep::follow_array(objArrayOop array) {
76 mark_and_push_closure.do_klass(array->klass());
77 // Don't push empty arrays to avoid unnecessary work.
78 if (array->length() > 0) {
79 MarkSweep::push_objarray(array, 0);
80 }
81 }
82
83 void MarkSweep::follow_object(oop obj) {
84 assert(obj->is_gc_marked(), "should be marked");
85 if (obj->is_objArray()) {
86 // Handle object arrays explicitly to allow them to
87 // be split into chunks if needed.
88 MarkSweep::follow_array((objArrayOop)obj);
89 } else {
90 obj->oop_iterate(&mark_and_push_closure);
91 }
92 }
93
94 void MarkSweep::follow_array_chunk(objArrayOop array, int index) {
95 const int len = array->length();
96 const int beg_index = index;
97 assert(beg_index < len || len == 0, "index too large");
98
99 const int stride = MIN2(len - beg_index, (int) ObjArrayMarkingStride);
100 const int end_index = beg_index + stride;
101
102 array->oop_iterate_range(&mark_and_push_closure, beg_index, end_index);
103
104 if (end_index < len) {
105 MarkSweep::push_objarray(array, end_index); // Push the continuation.
106 }
107 }
108
109 void MarkSweep::follow_stack() {
110 do {
111 while (!_marking_stack.is_empty()) {
112 oop obj = _marking_stack.pop();
113 assert (obj->is_gc_marked(), "p must be marked");
114 follow_object(obj);
115 }
116 // Process ObjArrays one at a time to avoid marking stack bloat.
117 if (!_objarray_stack.is_empty()) {
118 ObjArrayTask task = _objarray_stack.pop();
119 follow_array_chunk(objArrayOop(task.obj()), task.index());
120 }
121 } while (!_marking_stack.is_empty() || !_objarray_stack.is_empty());
122 }
123
124 MarkSweep::FollowStackClosure MarkSweep::follow_stack_closure;
125
126 void MarkSweep::FollowStackClosure::do_void() { follow_stack(); }
127
128 template <class T> void MarkSweep::follow_root(T* p) {
129 assert(!Universe::heap()->is_in(p),
130 "roots shouldn't be things within the heap");
131 T heap_oop = RawAccess<>::oop_load(p);
132 if (!CompressedOops::is_null(heap_oop)) {
133 oop obj = CompressedOops::decode_not_null(heap_oop);
134 if (!obj->mark().is_marked()) {
135 mark_object(obj);
136 follow_object(obj);
137 }
138 }
139 follow_stack();
140 }
141
142 void MarkSweep::FollowRootClosure::do_oop(oop* p) { follow_root(p); }
143 void MarkSweep::FollowRootClosure::do_oop(narrowOop* p) { follow_root(p); }
144
145 void PreservedMark::adjust_pointer() {
146 MarkSweep::adjust_pointer(&_obj);
147 }
148
149 void PreservedMark::restore() {
150 _obj->set_mark(_mark);
151 }
152
153 // We preserve the mark which should be replaced at the end and the location
154 // that it will go. Note that the object that this markWord belongs to isn't
155 // currently at that address but it will be after phase4
156 void MarkSweep::preserve_mark(oop obj, markWord mark) {
157 // We try to store preserved marks in the to space of the new generation since
158 // this is storage which should be available. Most of the time this should be
159 // sufficient space for the marks we need to preserve but if it isn't we fall
160 // back to using Stacks to keep track of the overflow.
161 if (_preserved_count < _preserved_count_max) {
162 _preserved_marks[_preserved_count++] = PreservedMark(obj, mark);
163 } else {
164 _preserved_overflow_stack.push(PreservedMark(obj, mark));
165 }
166 }
167
168 void MarkSweep::mark_object(oop obj) {
169 if (StringDedup::is_enabled() &&
170 java_lang_String::is_instance(obj) &&
171 SerialStringDedup::is_candidate_from_mark(obj)) {
172 _string_dedup_requests->add(obj);
173 }
174
175 // some marks may contain information we need to preserve so we store them away
176 // and overwrite the mark. We'll restore it at the end of markSweep.
177 markWord mark = obj->mark();
178 obj->set_mark(markWord::prototype().set_marked());
179
180 ContinuationGCSupport::transform_stack_chunk(obj);
181
182 if (obj->mark_must_be_preserved(mark)) {
183 preserve_mark(obj, mark);
184 }
185 }
186
187 template <class T> void MarkSweep::mark_and_push(T* p) {
188 T heap_oop = RawAccess<>::oop_load(p);
189 if (!CompressedOops::is_null(heap_oop)) {
190 oop obj = CompressedOops::decode_not_null(heap_oop);
191 if (!obj->mark().is_marked()) {
192 mark_object(obj);
193 _marking_stack.push(obj);
194 }
195 }
196 }
197
198 template <typename T>
199 void MarkAndPushClosure::do_oop_work(T* p) { MarkSweep::mark_and_push(p); }
200 void MarkAndPushClosure::do_oop( oop* p) { do_oop_work(p); }
201 void MarkAndPushClosure::do_oop(narrowOop* p) { do_oop_work(p); }
202
203 AdjustPointerClosure MarkSweep::adjust_pointer_closure;
204
205 void MarkSweep::adjust_marks() {
206 // adjust the oops we saved earlier
207 for (size_t i = 0; i < _preserved_count; i++) {
208 _preserved_marks[i].adjust_pointer();
209 }
210
211 // deal with the overflow stack
212 StackIterator<PreservedMark, mtGC> iter(_preserved_overflow_stack);
213 while (!iter.is_empty()) {
214 PreservedMark* p = iter.next_addr();
215 p->adjust_pointer();
216 }
217 }
218
219 void MarkSweep::restore_marks() {
220 log_trace(gc)("Restoring " SIZE_FORMAT " marks", _preserved_count + _preserved_overflow_stack.size());
221
222 // restore the marks we saved earlier
223 for (size_t i = 0; i < _preserved_count; i++) {
224 _preserved_marks[i].restore();
225 }
226
227 // deal with the overflow
228 while (!_preserved_overflow_stack.is_empty()) {
229 PreservedMark p = _preserved_overflow_stack.pop();
230 p.restore();
231 }
232 }
233
234 MarkSweep::IsAliveClosure MarkSweep::is_alive;
235
236 bool MarkSweep::IsAliveClosure::do_object_b(oop p) { return p->is_gc_marked(); }
237
238 MarkSweep::KeepAliveClosure MarkSweep::keep_alive;
239
240 void MarkSweep::KeepAliveClosure::do_oop(oop* p) { MarkSweep::KeepAliveClosure::do_oop_work(p); }
241 void MarkSweep::KeepAliveClosure::do_oop(narrowOop* p) { MarkSweep::KeepAliveClosure::do_oop_work(p); }
242
243 void MarkSweep::initialize() {
244 MarkSweep::_gc_timer = new STWGCTimer();
245 MarkSweep::_gc_tracer = new SerialOldTracer();
246 MarkSweep::_string_dedup_requests = new StringDedup::Requests();
247
248 // The Full GC operates on the entire heap so all objects should be subject
249 // to discovery, hence the _always_true_closure.
250 MarkSweep::_ref_processor = new ReferenceProcessor(&_always_true_closure);
251 mark_and_push_closure.set_ref_discoverer(_ref_processor);
252 }