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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  private:
 66   BufferNode::Allocator _satb_mark_queue_buffer_allocator;
 67   G1SATBMarkQueueSet _satb_mark_queue_set;
 68 
 69   G1CardTable* _refinement_table;
 70 
 71  public:
 72   G1BarrierSet(G1CardTable* card_table, G1CardTable* refinement_table);
 73   virtual ~G1BarrierSet();
 74 
 75   static G1BarrierSet* g1_barrier_set() {
 76     return barrier_set_cast<G1BarrierSet>(BarrierSet::barrier_set());
 77   }
 78 
 79   G1CardTable* refinement_table() const { return _refinement_table; }
 80 
 81   // Swap the global card table references, without synchronization.
 82   void swap_global_card_table();
 83 
 84   // Update the given thread's card table (byte map) base to the current card table's.
 85   void update_card_table_base(Thread* thread);
 86 
 87   virtual bool card_mark_must_follow_store() const {
 88     return true;
 89   }
 90 
 91   // Add "pre_val" to a set of objects that may have been disconnected from the
 92   // pre-marking object graph. Prefer the version that takes location, as it
 93   // can avoid touching the heap unnecessarily.
 94   template <class T> static void enqueue(T* dst);
 95   static void enqueue_preloaded(oop pre_val);
 96 
 97   static void enqueue_preloaded_if_weak(DecoratorSet decorators, oop value);
 98 
 99   template <class T> void write_ref_array_pre_work(T* dst, size_t count);
100   virtual void write_ref_array_pre(oop* dst, size_t count, bool dest_uninitialized);
101   virtual void write_ref_array_pre(narrowOop* dst, size_t count, bool dest_uninitialized);
102 
103   template <DecoratorSet decorators, typename T>
104   void write_ref_field_pre(T* field);
105 
106   inline void write_region(MemRegion mr);
107   void write_region(JavaThread* thread, MemRegion mr);
108 
109   template <DecoratorSet decorators = DECORATORS_NONE, typename T>
110   void write_ref_field_post(T* field);
111 
112   virtual void on_thread_create(Thread* thread);
113   virtual void on_thread_destroy(Thread* thread);
114   virtual void on_thread_attach(Thread* thread);
115   virtual void on_thread_detach(Thread* thread);
116 
117   static G1SATBMarkQueueSet& satb_mark_queue_set() {
118     return g1_barrier_set()->_satb_mark_queue_set;
119   }
120 
121   virtual void print_on(outputStream* st) const;
122 
123   // Callbacks for runtime accesses.
124   template <DecoratorSet decorators, typename BarrierSetT = G1BarrierSet>
125   class AccessBarrier: public ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> {
126     typedef ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> ModRef;
127     typedef BarrierSet::AccessBarrier<decorators, BarrierSetT> Raw;
128 
129   public:
130     // Needed for loads on non-heap weak references
131     template <typename T>
132     static oop oop_load_not_in_heap(T* addr);
133 
134     // Needed for non-heap stores
135     template <typename T>
136     static void oop_store_not_in_heap(T* addr, oop new_value);
137 
138     // Needed for weak references
139     static oop oop_load_in_heap_at(oop base, ptrdiff_t offset);
140 
141     // Defensive: will catch weak oops at addresses in heap
142     template <typename T>
143     static oop oop_load_in_heap(T* addr);
144 
145     template <typename T>
146     static oop oop_atomic_cmpxchg_not_in_heap(T* addr, oop compare_value, oop new_value);
147     template <typename T>
148     static oop oop_atomic_xchg_not_in_heap(T* addr, oop new_value);
149   };
150 };
151 
152 template<>
153 struct BarrierSet::GetName<G1BarrierSet> {
154   static const BarrierSet::Name value = BarrierSet::G1BarrierSet;
155 };
156 
157 template<>
158 struct BarrierSet::GetType<BarrierSet::G1BarrierSet> {
159   typedef ::G1BarrierSet type;
160 };
161 
162 #endif // SHARE_GC_G1_G1BARRIERSET_HPP