1/*
2 * Copyright (c) 2000, 2019, 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/cardTable.hpp"
27#include "gc/shared/cardTableBarrierSetAssembler.hpp"
28#include "gc/shared/cardTableBarrierSet.inline.hpp"
29#include "gc/shared/collectedHeap.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#ifdef COMPILER1
39#include "gc/shared/c1/cardTableBarrierSetC1.hpp"
40#endif
41#ifdef COMPILER2
42#include "gc/shared/c2/cardTableBarrierSetC2.hpp"
43#endif
44
45class CardTableBarrierSetC1;
46class CardTableBarrierSetC2;
47
48// This kind of "BarrierSet" allows a "CollectedHeap" to detect and
49// enumerate ref fields that have been modified (since the last
50// enumeration.)
51
52CardTableBarrierSet::CardTableBarrierSet(BarrierSetAssembler* barrier_set_assembler,
53 BarrierSetC1* barrier_set_c1,
54 BarrierSetC2* barrier_set_c2,
55 CardTable* card_table,
56 const BarrierSet::FakeRtti& fake_rtti) :
57 ModRefBarrierSet(barrier_set_assembler,
58 barrier_set_c1,
59 barrier_set_c2,
60 fake_rtti.add_tag(BarrierSet::CardTableBarrierSet)),
61 _defer_initial_card_mark(false),
62 _card_table(card_table)
63{}
64
65CardTableBarrierSet::CardTableBarrierSet(CardTable* card_table) :
66 ModRefBarrierSet(make_barrier_set_assembler<CardTableBarrierSetAssembler>(),
67 make_barrier_set_c1<CardTableBarrierSetC1>(),
68 make_barrier_set_c2<CardTableBarrierSetC2>(),
69 BarrierSet::FakeRtti(BarrierSet::CardTableBarrierSet)),
70 _defer_initial_card_mark(false),
71 _card_table(card_table)
72{}
73
74void CardTableBarrierSet::initialize() {
75 initialize_deferred_card_mark_barriers();
76}
77
78CardTableBarrierSet::~CardTableBarrierSet() {
79 delete _card_table;
80}
81
82void CardTableBarrierSet::write_ref_array_work(MemRegion mr) {
83 _card_table->dirty_MemRegion(mr);
84}
85
86void CardTableBarrierSet::invalidate(MemRegion mr) {
87 _card_table->invalidate(mr);
88}
89
90void CardTableBarrierSet::print_on(outputStream* st) const {
91 _card_table->print_on(st);
92}
93
94// Helper for ReduceInitialCardMarks. For performance,
95// compiled code may elide card-marks for initializing stores
96// to a newly allocated object along the fast-path. We
97// compensate for such elided card-marks as follows:
98// (a) Generational, non-concurrent collectors, such as
99// GenCollectedHeap(ParNew,DefNew,Tenured) and
100// ParallelScavengeHeap(ParallelGC, ParallelOldGC)
101// need the card-mark if and only if the region is
102// in the old gen, and do not care if the card-mark
103// succeeds or precedes the initializing stores themselves,
104// so long as the card-mark is completed before the next
105// scavenge. For all these cases, we can do a card mark
106// at the point at which we do a slow path allocation
107// in the old gen, i.e. in this call.
108// (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
109// in addition that the card-mark for an old gen allocated
110// object strictly follow any associated initializing stores.
111// In these cases, the memRegion remembered below is
112// used to card-mark the entire region either just before the next
113// slow-path allocation by this thread or just before the next scavenge or
114// CMS-associated safepoint, whichever of these events happens first.
115// (The implicit assumption is that the object has been fully
116// initialized by this point, a fact that we assert when doing the
117// card-mark.)
118// (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
119// G1 concurrent marking is in progress an SATB (pre-write-)barrier
120// is used to remember the pre-value of any store. Initializing
121// stores will not need this barrier, so we need not worry about
122// compensating for the missing pre-barrier here. Turning now
123// to the post-barrier, we note that G1 needs a RS update barrier
124// which simply enqueues a (sequence of) dirty cards which may
125// optionally be refined by the concurrent update threads. Note
126// that this barrier need only be applied to a non-young write,
127// but, like in CMS, because of the presence of concurrent refinement
128// (much like CMS' precleaning), must strictly follow the oop-store.
129// Thus, using the same protocol for maintaining the intended
130// invariants turns out, serendepitously, to be the same for both
131// G1 and CMS.
132//
133// For any future collector, this code should be reexamined with
134// that specific collector in mind, and the documentation above suitably
135// extended and updated.
136void CardTableBarrierSet::on_slowpath_allocation_exit(JavaThread* thread, oop new_obj) {
137#if COMPILER2_OR_JVMCI
138 if (!ReduceInitialCardMarks) {
139 return;
140 }
141 // If a previous card-mark was deferred, flush it now.
142 flush_deferred_card_mark_barrier(thread);
143 if (new_obj->is_typeArray() || _card_table->is_in_young(new_obj)) {
144 // Arrays of non-references don't need a post-barrier.
145 // The deferred_card_mark region should be empty
146 // following the flush above.
147 assert(thread->deferred_card_mark().is_empty(), "Error");
148 } else {
149 MemRegion mr((HeapWord*)new_obj, new_obj->size());
150 assert(!mr.is_empty(), "Error");
151 if (_defer_initial_card_mark) {
152 // Defer the card mark
153 thread->set_deferred_card_mark(mr);
154 } else {
155 // Do the card mark
156 invalidate(mr);
157 }
158 }
159#endif // COMPILER2_OR_JVMCI
160}
161
162void CardTableBarrierSet::initialize_deferred_card_mark_barriers() {
163 // Used for ReduceInitialCardMarks (when COMPILER2 or JVMCI is used);
164 // otherwise remains unused.
165#if COMPILER2_OR_JVMCI
166 _defer_initial_card_mark = is_server_compilation_mode_vm() && ReduceInitialCardMarks
167 && (DeferInitialCardMark || card_mark_must_follow_store());
168#else
169 assert(_defer_initial_card_mark == false, "Who would set it?");
170#endif
171}
172
173void CardTableBarrierSet::flush_deferred_card_mark_barrier(JavaThread* thread) {
174#if COMPILER2_OR_JVMCI
175 MemRegion deferred = thread->deferred_card_mark();
176 if (!deferred.is_empty()) {
177 assert(_defer_initial_card_mark, "Otherwise should be empty");
178 {
179 // Verify that the storage points to a parsable object in heap
180 DEBUG_ONLY(oop old_obj = oop(deferred.start());)
181 assert(!_card_table->is_in_young(old_obj),
182 "Else should have been filtered in on_slowpath_allocation_exit()");
183 assert(oopDesc::is_oop(old_obj, true), "Not an oop");
184 assert(deferred.word_size() == (size_t)(old_obj->size()),
185 "Mismatch: multiple objects?");
186 }
187 write_region(deferred);
188 // "Clear" the deferred_card_mark field
189 thread->set_deferred_card_mark(MemRegion());
190 }
191 assert(thread->deferred_card_mark().is_empty(), "invariant");
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
198void CardTableBarrierSet::on_thread_detach(Thread* thread) {
199 // The deferred store barriers must all have been flushed to the
200 // card-table (or other remembered set structure) before GC starts
201 // processing the card-table (or other remembered set).
202 if (thread->is_Java_thread()) { // Only relevant for Java threads.
203 flush_deferred_card_mark_barrier((JavaThread*)thread);
204 }
205}
206
207bool CardTableBarrierSet::card_mark_must_follow_store() const {
208 return _card_table->scanned_concurrently();
209}
210