1 /*
  2  * Copyright (c) 1997, 2021, 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/instanceClassLoaderKlass.inline.hpp"
 37 #include "oops/instanceKlass.inline.hpp"
 38 #include "oops/instanceMirrorKlass.inline.hpp"
 39 #include "oops/instanceRefKlass.inline.hpp"
 40 #include "oops/methodData.hpp"
 41 #include "oops/objArrayKlass.inline.hpp"
 42 #include "oops/oop.inline.hpp"
 43 #include "oops/typeArrayOop.inline.hpp"
 44 #include "utilities/macros.hpp"
 45 #include "utilities/stack.inline.hpp"
 46 
 47 uint                    MarkSweep::_total_invocations = 0;
 48 
 49 Stack<oop, mtGC>              MarkSweep::_marking_stack;
 50 Stack<ObjArrayTask, mtGC>     MarkSweep::_objarray_stack;
 51 
 52 Stack<PreservedMark, mtGC>    MarkSweep::_preserved_overflow_stack;
 53 size_t                  MarkSweep::_preserved_count = 0;
 54 size_t                  MarkSweep::_preserved_count_max = 0;
 55 PreservedMark*          MarkSweep::_preserved_marks = NULL;
 56 ReferenceProcessor*     MarkSweep::_ref_processor   = NULL;
 57 STWGCTimer*             MarkSweep::_gc_timer        = NULL;
 58 SerialOldTracer*        MarkSweep::_gc_tracer       = NULL;
 59 
 60 StringDedup::Requests*  MarkSweep::_string_dedup_requests = NULL;
 61 
 62 MarkSweep::FollowRootClosure  MarkSweep::follow_root_closure;
 63 
 64 MarkAndPushClosure MarkSweep::mark_and_push_closure;
 65 CLDToOopClosure    MarkSweep::follow_cld_closure(&mark_and_push_closure, ClassLoaderData::_claim_strong);
 66 CLDToOopClosure    MarkSweep::adjust_cld_closure(&adjust_pointer_closure, ClassLoaderData::_claim_strong);
 67 
 68 template <class T> inline void MarkSweep::KeepAliveClosure::do_oop_work(T* p) {
 69   mark_and_push(p);
 70 }
 71 
 72 void MarkSweep::push_objarray(oop obj, size_t index) {
 73   ObjArrayTask task(obj, index);
 74   assert(task.is_valid(), "bad ObjArrayTask");
 75   _objarray_stack.push(task);
 76 }
 77 
 78 inline void MarkSweep::follow_array(objArrayOop array) {
 79   MarkSweep::follow_klass(array->klass());
 80   // Don't push empty arrays to avoid unnecessary work.
 81   if (array->length() > 0) {
 82     MarkSweep::push_objarray(array, 0);
 83   }
 84 }
 85 
 86 inline void MarkSweep::follow_object(oop obj) {
 87   assert(obj->is_gc_marked(), "should be marked");
 88   if (obj->is_objArray()) {
 89     // Handle object arrays explicitly to allow them to
 90     // be split into chunks if needed.
 91     MarkSweep::follow_array((objArrayOop)obj);
 92   } else {
 93     obj->oop_iterate(&mark_and_push_closure);
 94   }
 95 }
 96 
 97 void MarkSweep::follow_array_chunk(objArrayOop array, int index) {
 98   const int len = array->length();
 99   const int beg_index = index;
100   assert(beg_index < len || len == 0, "index too large");
101 
102   const int stride = MIN2(len - beg_index, (int) ObjArrayMarkingStride);
103   const int end_index = beg_index + stride;
104 
105   array->oop_iterate_range(&mark_and_push_closure, beg_index, end_index);
106 
107   if (end_index < len) {
108     MarkSweep::push_objarray(array, end_index); // Push the continuation.
109   }
110 }
111 
112 void MarkSweep::follow_stack() {
113   do {
114     while (!_marking_stack.is_empty()) {
115       oop obj = _marking_stack.pop();
116       assert (obj->is_gc_marked(), "p must be marked");
117       follow_object(obj);
118     }
119     // Process ObjArrays one at a time to avoid marking stack bloat.
120     if (!_objarray_stack.is_empty()) {
121       ObjArrayTask task = _objarray_stack.pop();
122       follow_array_chunk(objArrayOop(task.obj()), task.index());
123     }
124   } while (!_marking_stack.is_empty() || !_objarray_stack.is_empty());
125 }
126 
127 MarkSweep::FollowStackClosure MarkSweep::follow_stack_closure;
128 
129 void MarkSweep::FollowStackClosure::do_void() { follow_stack(); }
130 
131 template <class T> inline void MarkSweep::follow_root(T* p) {
132   assert(!Universe::heap()->is_in(p),
133          "roots shouldn't be things within the heap");
134   T heap_oop = RawAccess<>::oop_load(p);
135   if (!CompressedOops::is_null(heap_oop)) {
136     oop obj = CompressedOops::decode_not_null(heap_oop);
137     if (!obj->mark().is_marked()) {
138       mark_object(obj);
139       follow_object(obj);
140     }
141   }
142   follow_stack();
143 }
144 
145 void MarkSweep::FollowRootClosure::do_oop(oop* p)       { follow_root(p); }
146 void MarkSweep::FollowRootClosure::do_oop(narrowOop* p) { follow_root(p); }
147 
148 void PreservedMark::adjust_pointer() {
149   MarkSweep::adjust_pointer(&_obj);
150 }
151 
152 void PreservedMark::restore() {
153   _obj->set_mark(_mark);
154 }
155 
156 // We preserve the mark which should be replaced at the end and the location
157 // that it will go.  Note that the object that this markWord belongs to isn't
158 // currently at that address but it will be after phase4
159 void MarkSweep::preserve_mark(oop obj, markWord mark) {
160   // We try to store preserved marks in the to space of the new generation since
161   // this is storage which should be available.  Most of the time this should be
162   // sufficient space for the marks we need to preserve but if it isn't we fall
163   // back to using Stacks to keep track of the overflow.
164   if (_preserved_count < _preserved_count_max) {
165     _preserved_marks[_preserved_count++] = PreservedMark(obj, mark);
166   } else {
167     _preserved_overflow_stack.push(PreservedMark(obj, mark));
168   }
169 }
170 
171 void MarkSweep::set_ref_processor(ReferenceProcessor* rp) {
172   _ref_processor = rp;
173   mark_and_push_closure.set_ref_discoverer(_ref_processor);
174 }
175 
176 AdjustPointerClosure MarkSweep::adjust_pointer_closure;
177 
178 void MarkSweep::adjust_marks() {
179   // adjust the oops we saved earlier
180   for (size_t i = 0; i < _preserved_count; i++) {
181     _preserved_marks[i].adjust_pointer();
182   }
183 
184   // deal with the overflow stack
185   StackIterator<PreservedMark, mtGC> iter(_preserved_overflow_stack);
186   while (!iter.is_empty()) {
187     PreservedMark* p = iter.next_addr();
188     p->adjust_pointer();
189   }
190 }
191 
192 void MarkSweep::restore_marks() {
193   log_trace(gc)("Restoring " SIZE_FORMAT " marks", _preserved_count + _preserved_overflow_stack.size());
194 
195   // restore the marks we saved earlier
196   for (size_t i = 0; i < _preserved_count; i++) {
197     _preserved_marks[i].restore();
198   }
199 
200   // deal with the overflow
201   while (!_preserved_overflow_stack.is_empty()) {
202     PreservedMark p = _preserved_overflow_stack.pop();
203     p.restore();
204   }
205 }
206 
207 MarkSweep::IsAliveClosure   MarkSweep::is_alive;
208 
209 bool MarkSweep::IsAliveClosure::do_object_b(oop p) { return p->is_gc_marked(); }
210 
211 MarkSweep::KeepAliveClosure MarkSweep::keep_alive;
212 
213 void MarkSweep::KeepAliveClosure::do_oop(oop* p)       { MarkSweep::KeepAliveClosure::do_oop_work(p); }
214 void MarkSweep::KeepAliveClosure::do_oop(narrowOop* p) { MarkSweep::KeepAliveClosure::do_oop_work(p); }
215 
216 void MarkSweep::initialize() {
217   MarkSweep::_gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
218   MarkSweep::_gc_tracer = new (ResourceObj::C_HEAP, mtGC) SerialOldTracer();
219   MarkSweep::_string_dedup_requests = new StringDedup::Requests();
220 }