1 /*
2 * Copyright (c) 2000, 2018, 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 "gc/shared/cardTableBarrierSetAssembler.hpp"
27 #include "gc/shared/cardTableBarrierSet.inline.hpp"
28 #include "gc/shared/collectedHeap.hpp"
29 #include "gc/shared/space.inline.hpp"
30 #include "logging/log.hpp"
31 #include "memory/virtualspace.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "runtime/thread.hpp"
34 #include "services/memTracker.hpp"
35 #include "utilities/align.hpp"
36 #include "utilities/macros.hpp"
37 #ifdef COMPILER1
38 #include "gc/shared/c1/cardTableBarrierSetC1.hpp"
39 #endif
40 #ifdef COMPILER2
41 #include "gc/shared/c2/cardTableBarrierSetC2.hpp"
42 #endif
43
44 class CardTableBarrierSetC1;
45 class CardTableBarrierSetC2;
46
47 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
48 // enumerate ref fields that have been modified (since the last
49 // enumeration.)
50
51 CardTableBarrierSet::CardTableBarrierSet(BarrierSetAssembler* barrier_set_assembler,
52 BarrierSetC1* barrier_set_c1,
53 BarrierSetC2* barrier_set_c2,
54 CardTable* card_table,
55 const BarrierSet::FakeRtti& fake_rtti) :
56 ModRefBarrierSet(barrier_set_assembler,
57 barrier_set_c1,
58 barrier_set_c2,
59 fake_rtti.add_tag(BarrierSet::CardTableBarrierSet)),
60 _defer_initial_card_mark(false),
61 _card_table(card_table)
62 {}
63
64 CardTableBarrierSet::CardTableBarrierSet(CardTable* card_table) :
65 ModRefBarrierSet(make_barrier_set_assembler<CardTableBarrierSetAssembler>(),
66 make_barrier_set_c1<CardTableBarrierSetC1>(),
67 make_barrier_set_c2<CardTableBarrierSetC2>(),
68 BarrierSet::FakeRtti(BarrierSet::CardTableBarrierSet)),
69 _defer_initial_card_mark(false),
70 _card_table(card_table)
71 {}
72
73 void CardTableBarrierSet::initialize() {
74 initialize_deferred_card_mark_barriers();
75 }
76
77 CardTableBarrierSet::~CardTableBarrierSet() {
78 delete _card_table;
79 }
80
81 void CardTableBarrierSet::write_ref_array_work(MemRegion mr) {
82 _card_table->dirty_MemRegion(mr);
83 }
84
85 void CardTableBarrierSet::invalidate(MemRegion mr) {
86 _card_table->invalidate(mr);
87 }
88
89 void CardTableBarrierSet::print_on(outputStream* st) const {
90 _card_table->print_on(st);
91 }
92
93 // Helper for ReduceInitialCardMarks. For performance,
94 // compiled code may elide card-marks for initializing stores
95 // to a newly allocated object along the fast-path. We
96 // compensate for such elided card-marks as follows:
97 // (a) Generational, non-concurrent collectors, such as
98 // GenCollectedHeap(ParNew,DefNew,Tenured) and
99 // ParallelScavengeHeap(ParallelGC, ParallelOldGC)
100 // need the card-mark if and only if the region is
101 // in the old gen, and do not care if the card-mark
102 // succeeds or precedes the initializing stores themselves,
103 // so long as the card-mark is completed before the next
104 // scavenge. For all these cases, we can do a card mark
105 // at the point at which we do a slow path allocation
106 // in the old gen, i.e. in this call.
107 // (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
108 // in addition that the card-mark for an old gen allocated
109 // object strictly follow any associated initializing stores.
110 // In these cases, the memRegion remembered below is
111 // used to card-mark the entire region either just before the next
112 // slow-path allocation by this thread or just before the next scavenge or
113 // CMS-associated safepoint, whichever of these events happens first.
114 // (The implicit assumption is that the object has been fully
115 // initialized by this point, a fact that we assert when doing the
116 // card-mark.)
117 // (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
118 // G1 concurrent marking is in progress an SATB (pre-write-)barrier
119 // is used to remember the pre-value of any store. Initializing
120 // stores will not need this barrier, so we need not worry about
121 // compensating for the missing pre-barrier here. Turning now
122 // to the post-barrier, we note that G1 needs a RS update barrier
123 // which simply enqueues a (sequence of) dirty cards which may
124 // optionally be refined by the concurrent update threads. Note
125 // that this barrier need only be applied to a non-young write,
126 // but, like in CMS, because of the presence of concurrent refinement
127 // (much like CMS' precleaning), must strictly follow the oop-store.
128 // Thus, using the same protocol for maintaining the intended
129 // invariants turns out, serendepitously, to be the same for both
130 // G1 and CMS.
131 //
132 // For any future collector, this code should be reexamined with
133 // that specific collector in mind, and the documentation above suitably
134 // extended and updated.
135 void CardTableBarrierSet::on_slowpath_allocation_exit(JavaThread* thread, oop new_obj) {
136 #if COMPILER2_OR_JVMCI
137 if (!ReduceInitialCardMarks) {
138 return;
139 }
140 // If a previous card-mark was deferred, flush it now.
141 flush_deferred_card_mark_barrier(thread);
142 if (new_obj->is_typeArray() || _card_table->is_in_young(new_obj)) {
143 // Arrays of non-references don't need a post-barrier.
144 // The deferred_card_mark region should be empty
145 // following the flush above.
146 assert(thread->deferred_card_mark().is_empty(), "Error");
147 } else {
148 MemRegion mr((HeapWord*)new_obj, new_obj->size());
149 assert(!mr.is_empty(), "Error");
150 if (_defer_initial_card_mark) {
151 // Defer the card mark
152 thread->set_deferred_card_mark(mr);
153 } else {
154 // Do the card mark
155 invalidate(mr);
156 }
157 }
158 #endif // COMPILER2_OR_JVMCI
159 }
160
161 void CardTableBarrierSet::initialize_deferred_card_mark_barriers() {
162 // Used for ReduceInitialCardMarks (when COMPILER2 or JVMCI is used);
163 // otherwise remains unused.
164 #if COMPILER2_OR_JVMCI
165 _defer_initial_card_mark = is_server_compilation_mode_vm() && ReduceInitialCardMarks
166 && (DeferInitialCardMark || card_mark_must_follow_store());
167 #else
168 assert(_defer_initial_card_mark == false, "Who would set it?");
169 #endif
170 }
171
172 void CardTableBarrierSet::flush_deferred_card_mark_barrier(JavaThread* thread) {
173 #if COMPILER2_OR_JVMCI
174 MemRegion deferred = thread->deferred_card_mark();
175 if (!deferred.is_empty()) {
176 assert(_defer_initial_card_mark, "Otherwise should be empty");
177 {
178 // Verify that the storage points to a parsable object in heap
179 DEBUG_ONLY(oop old_obj = oop(deferred.start());)
180 assert(!_card_table->is_in_young(old_obj),
181 "Else should have been filtered in on_slowpath_allocation_exit()");
182 assert(oopDesc::is_oop(old_obj, true), "Not an oop");
183 assert(deferred.word_size() == (size_t)(old_obj->size()),
184 "Mismatch: multiple objects?");
185 }
186 write_region(deferred);
187 // "Clear" the deferred_card_mark field
188 thread->set_deferred_card_mark(MemRegion());
189 }
190 assert(thread->deferred_card_mark().is_empty(), "invariant");
191 #else
192 assert(!_defer_initial_card_mark, "Should be false");
193 assert(thread->deferred_card_mark().is_empty(), "Should be empty");
194 #endif
195 }
196
197 void CardTableBarrierSet::on_thread_detach(Thread* thread) {
198 // The deferred store barriers must all have been flushed to the
199 // card-table (or other remembered set structure) before GC starts
200 // processing the card-table (or other remembered set).
201 if (thread->is_Java_thread()) { // Only relevant for Java threads.
202 flush_deferred_card_mark_barrier((JavaThread*)thread);
203 }
204 }
205
206 bool CardTableBarrierSet::card_mark_must_follow_store() const {
207 return _card_table->scanned_concurrently();
208 }