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