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 PreservedMarksSet       MarkSweep::_preserved_overflow_stack_set(false /* in_c_heap */);
 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 // We preserve the mark which should be replaced at the end and the location
146 // that it will go.  Note that the object that this markWord belongs to isn't
147 // currently at that address but it will be after phase4
148 void MarkSweep::preserve_mark(oop obj, markWord mark) {
149   // We try to store preserved marks in the to space of the new generation since
150   // this is storage which should be available.  Most of the time this should be
151   // sufficient space for the marks we need to preserve but if it isn't we fall
152   // back to using Stacks to keep track of the overflow.
153   if (_preserved_count < _preserved_count_max) {
154     _preserved_marks[_preserved_count++] = PreservedMark(obj, mark);
155   } else {
156     _preserved_overflow_stack_set.get()->push_always(obj, mark);
157   }
158 }
159 
160 void MarkSweep::mark_object(oop obj) {
161   if (StringDedup::is_enabled() &&
162       java_lang_String::is_instance(obj) &&
163       SerialStringDedup::is_candidate_from_mark(obj)) {
164     _string_dedup_requests->add(obj);
165   }
166 
167   // some marks may contain information we need to preserve so we store them away
168   // and overwrite the mark.  We'll restore it at the end of markSweep.
169   markWord mark = obj->mark();
170   obj->set_mark(markWord::prototype().set_marked());
171 
172   ContinuationGCSupport::transform_stack_chunk(obj);
173 
174   if (obj->mark_must_be_preserved(mark)) {
175     preserve_mark(obj, mark);
176   }
177 }
178 
179 template <class T> void MarkSweep::mark_and_push(T* p) {
180   T heap_oop = RawAccess<>::oop_load(p);
181   if (!CompressedOops::is_null(heap_oop)) {
182     oop obj = CompressedOops::decode_not_null(heap_oop);
183     if (!obj->mark().is_marked()) {
184       mark_object(obj);
185       _marking_stack.push(obj);
186     }
187   }
188 }
189 
190 template <typename T>
191 void MarkAndPushClosure::do_oop_work(T* p)            { MarkSweep::mark_and_push(p); }
192 void MarkAndPushClosure::do_oop(      oop* p)         { do_oop_work(p); }
193 void MarkAndPushClosure::do_oop(narrowOop* p)         { do_oop_work(p); }
194 
195 AdjustPointerClosure MarkSweep::adjust_pointer_closure;
196 
197 void MarkSweep::adjust_marks() {
198   // adjust the oops we saved earlier
199   for (size_t i = 0; i < _preserved_count; i++) {
200     PreservedMarks::adjust_preserved_mark(_preserved_marks + i);
201   }
202 
203   // deal with the overflow stack
204   _preserved_overflow_stack_set.get()->adjust_during_full_gc();
205 }
206 
207 void MarkSweep::restore_marks() {
208   log_trace(gc)("Restoring " SIZE_FORMAT " marks", _preserved_count + _preserved_overflow_stack_set.get()->size());
209 
210   // restore the marks we saved earlier
211   for (size_t i = 0; i < _preserved_count; i++) {
212     _preserved_marks[i].set_mark();
213   }
214 
215   // deal with the overflow
216   _preserved_overflow_stack_set.restore(nullptr);
217 }
218 
219 MarkSweep::IsAliveClosure   MarkSweep::is_alive;
220 
221 bool MarkSweep::IsAliveClosure::do_object_b(oop p) { return p->is_gc_marked(); }
222 
223 MarkSweep::KeepAliveClosure MarkSweep::keep_alive;
224 
225 void MarkSweep::KeepAliveClosure::do_oop(oop* p)       { MarkSweep::KeepAliveClosure::do_oop_work(p); }
226 void MarkSweep::KeepAliveClosure::do_oop(narrowOop* p) { MarkSweep::KeepAliveClosure::do_oop_work(p); }
227 
228 void MarkSweep::initialize() {
229   MarkSweep::_gc_timer = new STWGCTimer();
230   MarkSweep::_gc_tracer = new SerialOldTracer();
231   MarkSweep::_string_dedup_requests = new StringDedup::Requests();
232 
233   // The Full GC operates on the entire heap so all objects should be subject
234   // to discovery, hence the _always_true_closure.
235   MarkSweep::_ref_processor = new ReferenceProcessor(&_always_true_closure);
236   mark_and_push_closure.set_ref_discoverer(_ref_processor);
237 }