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24
25#ifndef SHARE_GC_SHARED_CARDTABLEBARRIERSET_HPP
26#define SHARE_GC_SHARED_CARDTABLEBARRIERSET_HPP
27
28#include "gc/shared/cardTable.hpp"
29#include "gc/shared/modRefBarrierSet.hpp"
30#include "utilities/align.hpp"
31
32// This kind of "BarrierSet" allows a "CollectedHeap" to detect and
33// enumerate ref fields that have been modified (since the last
34// enumeration.)
35
36// As it currently stands, this barrier is *imprecise*: when a ref field in
37// an object "o" is modified, the card table entry for the card containing
38// the head of "o" is dirtied, not necessarily the card containing the
39// modified field itself. For object arrays, however, the barrier *is*
40// precise; only the card containing the modified element is dirtied.
41// Closures used to scan dirty cards should take these
42// considerations into account.
43
44class CardTableBarrierSet: public ModRefBarrierSet {
45 // Some classes get to look at some private stuff.
46 friend class VMStructs;
47
48public:
49
50 typedef CardTable::CardValue CardValue;
51protected:
52 // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2
53 // or INCLUDE_JVMCI is being used
54 bool _defer_initial_card_mark;
55 CardTable* _card_table;
56
57 CardTableBarrierSet(BarrierSetAssembler* barrier_set_assembler,
58 BarrierSetC1* barrier_set_c1,
59 BarrierSetC2* barrier_set_c2,
60 CardTable* card_table,
61 const BarrierSet::FakeRtti& fake_rtti);
62
63 public:
64 CardTableBarrierSet(CardTable* card_table);
65 ~CardTableBarrierSet();
66
67 CardTable* card_table() const { return _card_table; }
68
69 virtual void initialize();
70
71 void write_region(MemRegion mr) {
72 invalidate(mr);
73 }
74
75 void write_ref_array_work(MemRegion mr);
76
77 public:
78 // Record a reference update. Note that these versions are precise!
79 // The scanning code has to handle the fact that the write barrier may be
80 // either precise or imprecise. We make non-virtual inline variants of
81 // these functions here for performance.
82 template <DecoratorSet decorators, typename T>
83 void write_ref_field_post(T* field, oop newVal);
84
85 virtual void invalidate(MemRegion mr);
86
87 // ReduceInitialCardMarks
88 void initialize_deferred_card_mark_barriers();
89
90 // If the CollectedHeap was asked to defer a store barrier above,
91 // this informs it to flush such a deferred store barrier to the
92 // remembered set.
93 void flush_deferred_card_mark_barrier(JavaThread* thread);
94
95 // If a compiler is eliding store barriers for TLAB-allocated objects,
96 // we will be informed of a slow-path allocation by a call
97 // to on_slowpath_allocation_exit() below. Such a call precedes the
98 // initialization of the object itself, and no post-store-barriers will
99 // be issued. Some heap types require that the barrier strictly follows
100 // the initializing stores. (This is currently implemented by deferring the
101 // barrier until the next slow-path allocation or gc-related safepoint.)
102 // This interface answers whether a particular barrier type needs the card
103 // mark to be thus strictly sequenced after the stores.
104 virtual bool card_mark_must_follow_store() const;
105
106 virtual void on_slowpath_allocation_exit(JavaThread* thread, oop new_obj);
107 virtual void on_thread_detach(Thread* thread);
108
109 virtual void make_parsable(JavaThread* thread) { flush_deferred_card_mark_barrier(thread); }
110
111 virtual void print_on(outputStream* st) const;
112
113 template <DecoratorSet decorators, typename BarrierSetT = CardTableBarrierSet>
114 class AccessBarrier: public ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> {};
115};
116
117template<>
118struct BarrierSet::GetName<CardTableBarrierSet> {
119 static const BarrierSet::Name value = BarrierSet::CardTableBarrierSet;
120};
121
122template<>
123struct BarrierSet::GetType<BarrierSet::CardTableBarrierSet> {
124 typedef ::CardTableBarrierSet type;
125};
126
127#endif // SHARE_GC_SHARED_CARDTABLEBARRIERSET_HPP
128