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