1 /*
2 * Copyright (c) 2000, 2015, 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/cardTableModRefBSCodeGen.hpp"
27 #include "gc/shared/c1CardTableModRefBSCodeGen.hpp"
28 #include "gc/shared/c2CardTableModRefBSCodeGen.hpp"
29 #include "gc/shared/cardTableModRefBS.inline.hpp"
30
31 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
32 // enumerate ref fields that have been modified (since the last
33 // enumeration.)
34
35 void CardTableModRefBS::write_region(MemRegion mr) {
36 _card_table->dirty_MemRegion(mr);
37 }
38
39 void CardTableModRefBS::write_ref_array_region(MemRegion mr) {
40 _card_table->dirty_MemRegion(mr);
41 }
42
43 BarrierSetCodeGen* CardTableModRefBS::make_code_gen() {
44 return new CardTableModRefBSCodeGen();
45 }
46
47 C1BarrierSetCodeGen* CardTableModRefBS::make_c1_code_gen() {
48 return new C1CardTableModRefBSCodeGen();
49 }
50
51 C2BarrierSetCodeGen* CardTableModRefBS::make_c2_code_gen() {
52 return new C2CardTableModRefBSCodeGen();
53 }
54
55 void CardTableModRefBS::initialize() {
56 ModRefBarrierSet::initialize();
57 // Used for ReduceInitialCardMarks (when COMPILER2 or JVMCI is used);
58 // otherwise remains unused.
59 #if defined(COMPILER2) || INCLUDE_JVMCI
60 _can_elide_tlab_store_barriers = can_elide_tlab_store_barriers();
61 _defer_initial_card_mark = is_server_compilation_mode_vm() && ReduceInitialCardMarks && _can_elide_tlab_store_barriers
62 && (DeferInitialCardMark || card_mark_must_follow_store());
63 #else
64 assert(_defer_initial_card_mark == false, "Who would set it?");
65 assert(_can_elide_tlab_store_barriers == false, "Who would set it?");
66 #endif
67 }
68
69 CardTableModRefBS::CardTableModRefBS(
70 CardTable* card_table,
71 const BarrierSet::FakeRtti& fake_rtti) :
72 ModRefBarrierSet(fake_rtti.add_tag(BarrierSet::CardTableModRef)),
73 _defer_initial_card_mark(false),
74 _can_elide_tlab_store_barriers(false),
75 _card_table(card_table)
76 {}
77
78 CardTableModRefBS::CardTableModRefBS(CardTable* card_table) :
79 ModRefBarrierSet(BarrierSet::FakeRtti(BarrierSet::CardTableModRef)),
80 _defer_initial_card_mark(false),
81 _can_elide_tlab_store_barriers(false),
82 _card_table(card_table)
83 {}
84
85 CardTableModRefBS::~CardTableModRefBS() {
86 delete _card_table;
87 }
88
89 void CardTableModRefBS::invalidate(MemRegion mr) {
90 _card_table->invalidate(mr);
91 }
92
93 void CardTableModRefBS::print_on(outputStream* st) const {
94 _card_table->print_on(st);
95 }
96
97 // Helper for ReduceInitialCardMarks. For performance,
98 // compiled code may elide card-marks for initializing stores
99 // to a newly allocated object along the fast-path. We
100 // compensate for such elided card-marks as follows:
101 // (a) Generational, non-concurrent collectors, such as
102 // GenCollectedHeap(ParNew,DefNew,Tenured) and
103 // ParallelScavengeHeap(ParallelGC, ParallelOldGC)
104 // need the card-mark if and only if the region is
105 // in the old gen, and do not care if the card-mark
106 // succeeds or precedes the initializing stores themselves,
107 // so long as the card-mark is completed before the next
108 // scavenge. For all these cases, we can do a card mark
109 // at the point at which we do a slow path allocation
110 // in the old gen, i.e. in this call.
111 // (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
112 // in addition that the card-mark for an old gen allocated
113 // object strictly follow any associated initializing stores.
114 // In these cases, the memRegion remembered below is
115 // used to card-mark the entire region either just before the next
116 // slow-path allocation by this thread or just before the next scavenge or
117 // CMS-associated safepoint, whichever of these events happens first.
118 // (The implicit assumption is that the object has been fully
119 // initialized by this point, a fact that we assert when doing the
120 // card-mark.)
121 // (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
122 // G1 concurrent marking is in progress an SATB (pre-write-)barrier
123 // is used to remember the pre-value of any store. Initializing
124 // stores will not need this barrier, so we need not worry about
125 // compensating for the missing pre-barrier here. Turning now
126 // to the post-barrier, we note that G1 needs a RS update barrier
127 // which simply enqueues a (sequence of) dirty cards which may
128 // optionally be refined by the concurrent update threads. Note
129 // that this barrier need only be applied to a non-young write,
130 // but, like in CMS, because of the presence of concurrent refinement
131 // (much like CMS' precleaning), must strictly follow the oop-store.
132 // Thus, using the same protocol for maintaining the intended
133 // invariants turns out, serendepitously, to be the same for both
134 // G1 and CMS.
135 //
136 // For any future collector, this code should be reexamined with
137 // that specific collector in mind, and the documentation above suitably
138 // extended and updated.
139 void CardTableModRefBS::new_deferred_store_barrier(JavaThread* thread, oop new_obj) {
140 // If a previous card-mark was deferred, flush it now.
141 flush_deferred_store_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 write_region(mr);
156 }
157 }
158 }
159
160 void CardTableModRefBS::flush_deferred_store_barrier(JavaThread* thread) {
161 MemRegion deferred = thread->deferred_card_mark();
162 if (!deferred.is_empty()) {
163 assert(_defer_initial_card_mark, "Otherwise should be empty");
164 {
165 // Verify that the storage points to a parsable object in heap
166 DEBUG_ONLY(oop old_obj = oop(deferred.start());)
167 assert(!_card_table->is_in_young(old_obj),
168 "Else should have been filtered in new_deferred_store_barrier()");
169 assert(old_obj->is_oop(true), "Not an oop");
170 assert(deferred.word_size() == (size_t)(old_obj->size()),
171 "Mismatch: multiple objects?");
172 }
173 write_region(deferred);
174 // "Clear" the deferred_card_mark field
175 thread->set_deferred_card_mark(MemRegion());
176 }
177 assert(thread->deferred_card_mark().is_empty(), "invariant");
178 }
179
180 void CardTableModRefBS::on_destroy_thread(JavaThread* thread) {
181 ModRefBarrierSet::on_destroy_thread(thread);
182 flush_deferred_store_barrier(thread);
183 }
184
185 void CardTableModRefBS::make_parsable(JavaThread* thread) {
186 ModRefBarrierSet::make_parsable(thread);
187 #if defined(COMPILER2) || INCLUDE_JVMCI
188 // The deferred store barriers must all have been flushed to the
189 // card-table (or other remembered set structure) before GC starts
190 // processing the card-table (or other remembered set).
191 if (_defer_initial_card_mark) flush_deferred_store_barrier(thread);
192 #else
193 assert(!_defer_initial_card_mark, "Should be false");
194 assert(thread->deferred_card_mark().is_empty(), "Should be empty");
195 #endif
196 }
197
198 bool CardTableModRefBS::card_mark_must_follow_store() const {
199 return _card_table->scanned_concurrently();
200 }