1 /* 2 * Copyright (c) 2001, 2025, 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 #ifndef SHARE_GC_G1_G1BARRIERSET_HPP 26 #define SHARE_GC_G1_G1BARRIERSET_HPP 27 28 #include "gc/g1/g1SATBMarkQueueSet.hpp" 29 #include "gc/shared/bufferNode.hpp" 30 #include "gc/shared/cardTable.hpp" 31 #include "gc/shared/cardTableBarrierSet.hpp" 32 33 class G1CardTable; 34 class Thread; 35 36 // This barrier set is specialized to manage two card tables: 37 // * one the mutator is currently working on ("card table") 38 // * one the refinement threads or GC during pause are working on ("refinement table") 39 // 40 // The card table acts like a regular card table where the mutator dirties cards 41 // containing potentially interesting references. 42 // 43 // When the amount of dirty cards on the card table exceeds a threshold, G1 swaps 44 // the card tables and has the refinement threads reduce them by "refining" 45 // them. 46 // I.e. refinement looks at all dirty cards on the refinement table, and updates 47 // the remembered sets accordingly, clearing the cards on the refinement table. 48 // 49 // Meanwhile the mutator continues dirtying the now empty card table. 50 // 51 // This separation of data the mutator and refinement threads are working on 52 // removes the need for any fine-grained (per mutator write) synchronization between 53 // them, keeping the write barrier simple. 54 // 55 // The refinement threads mark cards in the current collection set specially on the 56 // card table - this is fine wrt synchronization with the mutator, because at 57 // most the mutator will overwrite it again if there is a race, as G1 will scan the 58 // entire card either way during the GC pause. 59 // 60 // During garbage collection, if the refinement table is known to be non-empty, G1 61 // merges it back (and cleaning it) to the card table which is scanned for dirty 62 // cards. 63 // 64 class G1BarrierSet: public CardTableBarrierSet { 65 friend class VMStructs; 66 private: 67 BufferNode::Allocator _satb_mark_queue_buffer_allocator; 68 G1SATBMarkQueueSet _satb_mark_queue_set; 69 70 G1CardTable* _refinement_table; 71 72 public: 73 G1BarrierSet(G1CardTable* card_table, G1CardTable* refinement_table); 74 virtual ~G1BarrierSet(); 75 76 static G1BarrierSet* g1_barrier_set() { 77 return barrier_set_cast<G1BarrierSet>(BarrierSet::barrier_set()); 78 } 79 80 G1CardTable* refinement_table() const { return _refinement_table; } 81 82 // Swap the global card table references, without synchronization. 83 void swap_global_card_table(); 84 85 // Update the given thread's card table (byte map) base to the current card table's. 86 void update_card_table_base(Thread* thread); 87 88 virtual bool card_mark_must_follow_store() const { 89 return true; 90 } 91 92 // Add "pre_val" to a set of objects that may have been disconnected from the 93 // pre-marking object graph. Prefer the version that takes location, as it 94 // can avoid touching the heap unnecessarily. 95 template <class T> static void enqueue(T* dst); 96 static void enqueue_preloaded(oop pre_val); 97 98 static void enqueue_preloaded_if_weak(DecoratorSet decorators, oop value); 99 100 template <class T> void write_ref_array_pre_work(T* dst, size_t count); 101 virtual void write_ref_array_pre(oop* dst, size_t count, bool dest_uninitialized); 102 virtual void write_ref_array_pre(narrowOop* dst, size_t count, bool dest_uninitialized); 103 104 template <DecoratorSet decorators, typename T> 105 void write_ref_field_pre(T* field); 106 107 inline void write_region(MemRegion mr); 108 void write_region(JavaThread* thread, MemRegion mr); 109 110 template <DecoratorSet decorators = DECORATORS_NONE, typename T> 111 void write_ref_field_post(T* field); 112 113 virtual void on_thread_create(Thread* thread); 114 virtual void on_thread_destroy(Thread* thread); 115 virtual void on_thread_attach(Thread* thread); 116 virtual void on_thread_detach(Thread* thread); 117 118 static G1SATBMarkQueueSet& satb_mark_queue_set() { 119 return g1_barrier_set()->_satb_mark_queue_set; 120 } 121 122 virtual void print_on(outputStream* st) const; 123 124 // Callbacks for runtime accesses. 125 template <DecoratorSet decorators, typename BarrierSetT = G1BarrierSet> 126 class AccessBarrier: public ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> { 127 typedef ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> ModRef; 128 typedef BarrierSet::AccessBarrier<decorators, BarrierSetT> Raw; 129 130 public: 131 // Needed for loads on non-heap weak references 132 template <typename T> 133 static oop oop_load_not_in_heap(T* addr); 134 135 // Needed for non-heap stores 136 template <typename T> 137 static void oop_store_not_in_heap(T* addr, oop new_value); 138 139 // Needed for weak references 140 static oop oop_load_in_heap_at(oop base, ptrdiff_t offset); 141 142 // Defensive: will catch weak oops at addresses in heap 143 template <typename T> 144 static oop oop_load_in_heap(T* addr); 145 146 template <typename T> 147 static oop oop_atomic_cmpxchg_not_in_heap(T* addr, oop compare_value, oop new_value); 148 template <typename T> 149 static oop oop_atomic_xchg_not_in_heap(T* addr, oop new_value); 150 }; 151 }; 152 153 template<> 154 struct BarrierSet::GetName<G1BarrierSet> { 155 static const BarrierSet::Name value = BarrierSet::G1BarrierSet; 156 }; 157 158 template<> 159 struct BarrierSet::GetType<BarrierSet::G1BarrierSet> { 160 typedef ::G1BarrierSet type; 161 }; 162 163 #endif // SHARE_GC_G1_G1BARRIERSET_HPP