1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_GC_G1_G1BARRIERSET_HPP
26 #define SHARE_GC_G1_G1BARRIERSET_HPP
27
28 #include "gc/g1/g1HeapRegion.hpp"
29 #include "gc/g1/g1SATBMarkQueueSet.hpp"
30 #include "gc/shared/bufferNode.hpp"
31 #include "gc/shared/cardTable.hpp"
32 #include "gc/shared/cardTableBarrierSet.hpp"
33
34 class G1CardTable;
35 class Thread;
36
37 // This barrier set is specialized to manage two card tables:
38 // * one the mutator is currently working on ("card table")
39 // * one the refinement threads or GC during pause are working on ("refinement table")
40 //
41 // The card table acts like a regular card table where the mutator dirties cards
42 // containing potentially interesting references.
43 //
44 // When the amount of dirty cards on the card table exceeds a threshold, G1 swaps
45 // the card tables and has the refinement threads reduce them by "refining"
46 // them.
47 // I.e. refinement looks at all dirty cards on the refinement table, and updates
48 // the remembered sets accordingly, clearing the cards on the refinement table.
49 //
50 // Meanwhile the mutator continues dirtying the now empty card table.
51 //
52 // This separation of data the mutator and refinement threads are working on
53 // removes the need for any fine-grained (per mutator write) synchronization between
54 // them, keeping the write barrier simple.
55 //
56 // The refinement threads mark cards in the current collection set specially on the
57 // card table - this is fine wrt synchronization with the mutator, because at
58 // most the mutator will overwrite it again if there is a race, as G1 will scan the
59 // entire card either way during the GC pause.
60 //
61 // During garbage collection, if the refinement table is known to be non-empty, G1
62 // merges it back (and cleaning it) to the card table which is scanned for dirty
63 // cards.
64 //
65 class G1BarrierSet: public CardTableBarrierSet {
66 friend class VMStructs;
67 private:
68 BufferNode::Allocator _satb_mark_queue_buffer_allocator;
69 G1SATBMarkQueueSet _satb_mark_queue_set;
70
71 G1CardTable* _refinement_table;
72
73 public:
74 G1BarrierSet(G1CardTable* card_table, G1CardTable* refinement_table);
75 virtual ~G1BarrierSet();
76
77 static G1BarrierSet* g1_barrier_set() {
78 return barrier_set_cast<G1BarrierSet>(BarrierSet::barrier_set());
79 }
80
81 G1CardTable* refinement_table() const { return _refinement_table; }
82
83 // Swap the global card table references, without synchronization.
84 void swap_global_card_table();
85
86 // Update the given thread's card table (byte map) base to the current card table's.
87 void update_card_table_base(Thread* thread);
88
89 virtual bool card_mark_must_follow_store() const {
90 return true;
91 }
92
93 // Add "pre_val" to a set of objects that may have been disconnected from the
94 // pre-marking object graph. Prefer the version that takes location, as it
95 // can avoid touching the heap unnecessarily.
96 template <class T> static void enqueue(T* dst);
97 static void enqueue_preloaded(oop pre_val);
98
99 static void enqueue_preloaded_if_weak(DecoratorSet decorators, oop value);
100
101 template <class T> void write_ref_array_pre_work(T* dst, size_t count);
102 virtual void write_ref_array_pre(oop* dst, size_t count, bool dest_uninitialized);
103 virtual void write_ref_array_pre(narrowOop* dst, size_t count, bool dest_uninitialized);
104
105 template <DecoratorSet decorators, typename T>
106 void write_ref_field_pre(T* field);
107
108 inline void write_region(MemRegion mr);
109 void write_region(JavaThread* thread, MemRegion mr);
110
111 template <DecoratorSet decorators = DECORATORS_NONE, typename T>
112 void write_ref_field_post(T* field);
113
114 virtual void on_thread_create(Thread* thread);
115 virtual void on_thread_destroy(Thread* thread);
116 virtual void on_thread_attach(Thread* thread);
117 virtual void on_thread_detach(Thread* thread);
118
119 static G1SATBMarkQueueSet& satb_mark_queue_set() {
120 return g1_barrier_set()->_satb_mark_queue_set;
121 }
122
123 virtual void print_on(outputStream* st) const;
124
125 virtual uint grain_shift() { return G1HeapRegion::LogOfHRGrainBytes; }
126
127 // Callbacks for runtime accesses.
128 template <DecoratorSet decorators, typename BarrierSetT = G1BarrierSet>
129 class AccessBarrier: public ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> {
130 typedef ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> ModRef;
131 typedef BarrierSet::AccessBarrier<decorators, BarrierSetT> Raw;
132
133 public:
134 // Needed for loads on non-heap weak references
135 template <typename T>
136 static oop oop_load_not_in_heap(T* addr);
137
138 // Needed for non-heap stores
139 template <typename T>
140 static void oop_store_not_in_heap(T* addr, oop new_value);
141
142 // Needed for weak references
143 static oop oop_load_in_heap_at(oop base, ptrdiff_t offset);
144
145 // Defensive: will catch weak oops at addresses in heap
146 template <typename T>
147 static oop oop_load_in_heap(T* addr);
148
149 template <typename T>
150 static oop oop_atomic_cmpxchg_not_in_heap(T* addr, oop compare_value, oop new_value);
151 template <typename T>
152 static oop oop_atomic_xchg_not_in_heap(T* addr, oop new_value);
153 };
154 };
155
156 template<>
157 struct BarrierSet::GetName<G1BarrierSet> {
158 static const BarrierSet::Name value = BarrierSet::G1BarrierSet;
159 };
160
161 template<>
162 struct BarrierSet::GetType<BarrierSet::G1BarrierSet> {
163 typedef ::G1BarrierSet type;
164 };
165
166 #endif // SHARE_GC_G1_G1BARRIERSET_HPP