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_SHARED_CARDTABLEBARRIERSET_HPP
26 #define SHARE_GC_SHARED_CARDTABLEBARRIERSET_HPP
27
28 #include "gc/shared/barrierSet.hpp"
29 #include "gc/shared/cardTable.hpp"
30 #include "gc/shared/gc_globals.hpp"
31 #include "memory/memRegion.hpp"
32 #include "runtime/atomic.hpp"
33 #include "utilities/align.hpp"
34
35 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
36 // enumerate ref fields that have been modified (since the last
37 // enumeration.)
38
39 // As it currently stands, this barrier is *imprecise*: when a ref field in
40 // an object "o" is modified, the card table entry for the card containing
41 // the head of "o" is dirtied, not necessarily the card containing the
42 // modified field itself. For object arrays, however, the barrier *is*
43 // precise; only the card containing the modified element is dirtied.
44 // Closures used to scan dirty cards should take these
45 // considerations into account.
46
47 class CardTableBarrierSet: public BarrierSet {
48 // Some classes get to look at some private stuff.
49 friend class VMStructs;
50
51 protected:
52 typedef CardTable::CardValue CardValue;
53 Atomic<CardTable*> _card_table;
54
55 CardTableBarrierSet(BarrierSetAssembler* barrier_set_assembler,
56 BarrierSetC1* barrier_set_c1,
57 BarrierSetC2* barrier_set_c2,
58 CardTable* card_table,
59 const BarrierSet::FakeRtti& fake_rtti);
60
61 public:
62 CardTableBarrierSet(CardTable* card_table);
63 virtual ~CardTableBarrierSet();
64
65 inline static CardTableBarrierSet* barrier_set() {
66 return barrier_set_cast<CardTableBarrierSet>(BarrierSet::barrier_set());
67 }
68
69 template <DecoratorSet decorators, typename T>
70 inline void write_ref_field_pre(T* addr) {}
71
72 // Record a reference update. Note that these versions are precise!
73 // The scanning code has to handle the fact that the write barrier may be
74 // either precise or imprecise. We make non-virtual inline variants of
75 // these functions here for performance.
76 template <DecoratorSet decorators, typename T>
77 inline void write_ref_field_post(T *addr);
78
79 // Causes all refs in "mr" to be assumed to be modified (by this JavaThread).
80 virtual void write_region(MemRegion mr);
81
82 // Operations on arrays, or general regions (e.g., for "clone") may be
83 // optimized by some barriers.
84
85 // Below length is the # array elements being written
86 virtual void write_ref_array_pre(oop* dst, size_t length,
87 bool dest_uninitialized) {}
88 virtual void write_ref_array_pre(narrowOop* dst, size_t length,
89 bool dest_uninitialized) {}
90 // Below count is the # array elements being written, starting
91 // at the address "start", which may not necessarily be HeapWord-aligned
92 inline void write_ref_array(HeapWord* start, size_t count);
93
94 CardTable* card_table() { return _card_table.load_relaxed(); }
95 CardTable* card_table() const { return _card_table.load_relaxed(); }
96
97 CardValue* card_table_base_const() const {
98 assert(UseSerialGC || UseParallelGC, "Only these GCs have constant card table base");
99 return card_table()->byte_map_base();
100 }
101
102 virtual void on_slowpath_allocation_exit(JavaThread* thread, oop new_obj);
103
104 virtual void print_on(outputStream* st) const;
105
106 template <DecoratorSet decorators, typename BarrierSetT = CardTableBarrierSet>
107 class AccessBarrier: public BarrierSet::AccessBarrier<decorators, BarrierSetT> {
108 typedef BarrierSet::AccessBarrier<decorators, BarrierSetT> Raw;
109
110 public:
111 template <typename T>
112 static void oop_store_in_heap(T* addr, oop value);
113 template <typename T>
114 static oop oop_atomic_cmpxchg_in_heap(T* addr, oop compare_value, oop new_value);
115 template <typename T>
116 static oop oop_atomic_xchg_in_heap(T* addr, oop new_value);
117
118 template <typename T>
119 static OopCopyResult oop_arraycopy_in_heap(arrayOop src_obj, size_t src_offset_in_bytes, T* src_raw,
120 arrayOop dst_obj, size_t dst_offset_in_bytes, T* dst_raw,
121 size_t length);
122
123 static void clone_in_heap(oop src, oop dst, size_t size);
124
125 static void oop_store_in_heap_at(oop base, ptrdiff_t offset, oop value) {
126 oop_store_in_heap(AccessInternal::oop_field_addr<decorators>(base, offset), value);
127 }
128
129 static oop oop_atomic_xchg_in_heap_at(oop base, ptrdiff_t offset, oop new_value) {
130 return oop_atomic_xchg_in_heap(AccessInternal::oop_field_addr<decorators>(base, offset), new_value);
131 }
132
133 static oop oop_atomic_cmpxchg_in_heap_at(oop base, ptrdiff_t offset, oop compare_value, oop new_value) {
134 return oop_atomic_cmpxchg_in_heap(AccessInternal::oop_field_addr<decorators>(base, offset), compare_value, new_value);
135 }
136 };
137 };
138
139 template<>
140 struct BarrierSet::GetName<CardTableBarrierSet> {
141 static const BarrierSet::Name value = BarrierSet::CardTableBarrierSet;
142 };
143
144 template<>
145 struct BarrierSet::GetType<BarrierSet::CardTableBarrierSet> {
146 typedef ::CardTableBarrierSet type;
147 };
148
149 #endif // SHARE_GC_SHARED_CARDTABLEBARRIERSET_HPP