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/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