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
64 template <class T> void MarkSweep::KeepAliveClosure::do_oop_work(T* p) {
65 mark_and_push(p);
66 }
67
68 void MarkSweep::push_objarray(oop obj, size_t index) {
69 ObjArrayTask task(obj, index);
70 assert(task.is_valid(), "bad ObjArrayTask");
71 _objarray_stack.push(task);
72 }
73
74 void MarkSweep::follow_array(objArrayOop array) {
75 mark_and_push_closure.do_klass(array->klass());
76 // Don't push empty arrays to avoid unnecessary work.
77 if (array->length() > 0) {
78 MarkSweep::push_objarray(array, 0);
79 }
80 }
81
82 void MarkSweep::follow_object(oop obj) {
83 assert(obj->is_gc_marked(), "should be marked");
84 if (obj->is_objArray()) {
85 // Handle object arrays explicitly to allow them to
86 // be split into chunks if needed.
87 MarkSweep::follow_array((objArrayOop)obj);
88 } else {
89 obj->oop_iterate(&mark_and_push_closure);
90 }
91 }
92
93 void MarkSweep::follow_array_chunk(objArrayOop array, int index) {
94 const int len = array->length();
95 const int beg_index = index;
96 assert(beg_index < len || len == 0, "index too large");
97
98 const int stride = MIN2(len - beg_index, (int) ObjArrayMarkingStride);
99 const int end_index = beg_index + stride;
100
101 array->oop_iterate_range(&mark_and_push_closure, beg_index, end_index);
102
103 if (end_index < len) {
104 MarkSweep::push_objarray(array, end_index); // Push the continuation.
105 }
106 }
107
108 void MarkSweep::follow_stack() {
109 do {
110 while (!_marking_stack.is_empty()) {
111 oop obj = _marking_stack.pop();
112 assert (obj->is_gc_marked(), "p must be marked");
113 follow_object(obj);
114 }
115 // Process ObjArrays one at a time to avoid marking stack bloat.
116 if (!_objarray_stack.is_empty()) {
117 ObjArrayTask task = _objarray_stack.pop();
118 follow_array_chunk(objArrayOop(task.obj()), task.index());
119 }
120 } while (!_marking_stack.is_empty() || !_objarray_stack.is_empty());
121 }
122
123 MarkSweep::FollowStackClosure MarkSweep::follow_stack_closure;
124
125 void MarkSweep::FollowStackClosure::do_void() { follow_stack(); }
126
127 template <class T> void MarkSweep::follow_root(T* p) {
128 assert(!Universe::heap()->is_in(p),
129 "roots shouldn't be things within the heap");
130 T heap_oop = RawAccess<>::oop_load(p);
131 if (!CompressedOops::is_null(heap_oop)) {
132 oop obj = CompressedOops::decode_not_null(heap_oop);
133 if (!obj->mark().is_marked()) {
134 mark_object(obj);
135 follow_object(obj);
136 }
137 }
138 follow_stack();
139 }
140
141 void MarkSweep::FollowRootClosure::do_oop(oop* p) { follow_root(p); }
142 void MarkSweep::FollowRootClosure::do_oop(narrowOop* p) { follow_root(p); }
143
144 template <bool ALT_FWD>
145 void PreservedMark::adjust_pointer() {
146 MarkSweep::adjust_pointer<ALT_FWD>(&_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 // Do the transform while we still have the header intact,
176 // which might include important class information.
177 ContinuationGCSupport::transform_stack_chunk(obj);
178
179 // some marks may contain information we need to preserve so we store them away
180 // and overwrite the mark. We'll restore it at the end of markSweep.
181 markWord mark = obj->mark();
182 obj->set_mark(obj->prototype_mark().set_marked());
183
184 if (obj->mark_must_be_preserved(mark)) {
185 preserve_mark(obj, mark);
186 }
187 }
188
189 template <class T> void MarkSweep::mark_and_push(T* p) {
190 T heap_oop = RawAccess<>::oop_load(p);
191 if (!CompressedOops::is_null(heap_oop)) {
192 oop obj = CompressedOops::decode_not_null(heap_oop);
193 if (!obj->mark().is_marked()) {
194 mark_object(obj);
195 _marking_stack.push(obj);
196 }
197 }
198 }
199
200 template <typename T>
201 void MarkAndPushClosure::do_oop_work(T* p) { MarkSweep::mark_and_push(p); }
202 void MarkAndPushClosure::do_oop( oop* p) { do_oop_work(p); }
203 void MarkAndPushClosure::do_oop(narrowOop* p) { do_oop_work(p); }
204
205 template <bool ALT_FWD>
206 void MarkSweep::adjust_marks_impl() {
207 // adjust the oops we saved earlier
208 for (size_t i = 0; i < _preserved_count; i++) {
209 _preserved_marks[i].adjust_pointer<ALT_FWD>();
210 }
211
212 // deal with the overflow stack
213 StackIterator<PreservedMark, mtGC> iter(_preserved_overflow_stack);
214 while (!iter.is_empty()) {
215 PreservedMark* p = iter.next_addr();
216 p->adjust_pointer<ALT_FWD>();
217 }
218 }
219
220 void MarkSweep::adjust_marks() {
221 if (UseAltGCForwarding) {
222 adjust_marks_impl<true>();
223 } else {
224 adjust_marks_impl<false>();
225 }
226 }
227
228 void MarkSweep::restore_marks() {
229 log_trace(gc)("Restoring " SIZE_FORMAT " marks", _preserved_count + _preserved_overflow_stack.size());
230
231 // restore the marks we saved earlier
232 for (size_t i = 0; i < _preserved_count; i++) {
233 _preserved_marks[i].restore();
234 }
235
236 // deal with the overflow
237 while (!_preserved_overflow_stack.is_empty()) {
238 PreservedMark p = _preserved_overflow_stack.pop();
239 p.restore();
240 }
241 }
242
243 MarkSweep::IsAliveClosure MarkSweep::is_alive;
244
245 bool MarkSweep::IsAliveClosure::do_object_b(oop p) { return p->is_gc_marked(); }
246
247 MarkSweep::KeepAliveClosure MarkSweep::keep_alive;
248
249 void MarkSweep::KeepAliveClosure::do_oop(oop* p) { MarkSweep::KeepAliveClosure::do_oop_work(p); }
250 void MarkSweep::KeepAliveClosure::do_oop(narrowOop* p) { MarkSweep::KeepAliveClosure::do_oop_work(p); }
251
252 void MarkSweep::initialize() {
253 MarkSweep::_gc_timer = new STWGCTimer();
254 MarkSweep::_gc_tracer = new SerialOldTracer();
255 MarkSweep::_string_dedup_requests = new StringDedup::Requests();
256
257 // The Full GC operates on the entire heap so all objects should be subject
258 // to discovery, hence the _always_true_closure.
259 MarkSweep::_ref_processor = new ReferenceProcessor(&_always_true_closure);
260 mark_and_push_closure.set_ref_discoverer(_ref_processor);
261 }