1 /*
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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  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   virtual uint grain_shift() { return G1HeapRegion::LogOfHRGrainBytes; }
125 
126   // Callbacks for runtime accesses.
127   template <DecoratorSet decorators, typename BarrierSetT = G1BarrierSet>
128   class AccessBarrier: public ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> {
129     typedef ModRefBarrierSet::AccessBarrier<decorators, BarrierSetT> ModRef;
130     typedef BarrierSet::AccessBarrier<decorators, BarrierSetT> Raw;
131 
132   public:
133     // Needed for loads on non-heap weak references
134     template <typename T>
135     static oop oop_load_not_in_heap(T* addr);
136 
137     // Needed for non-heap stores
138     template <typename T>
139     static void oop_store_not_in_heap(T* addr, oop new_value);
140 
141     // Needed for weak references
142     static oop oop_load_in_heap_at(oop base, ptrdiff_t offset);
143 
144     // Defensive: will catch weak oops at addresses in heap
145     template <typename T>
146     static oop oop_load_in_heap(T* addr);
147 
148     template <typename T>
149     static oop oop_atomic_cmpxchg_not_in_heap(T* addr, oop compare_value, oop new_value);
150     template <typename T>
151     static oop oop_atomic_xchg_not_in_heap(T* addr, oop new_value);
152   };
153 };
154 
155 template<>
156 struct BarrierSet::GetName<G1BarrierSet> {
157   static const BarrierSet::Name value = BarrierSet::G1BarrierSet;
158 };
159 
160 template<>
161 struct BarrierSet::GetType<BarrierSet::G1BarrierSet> {
162   typedef ::G1BarrierSet type;
163 };
164 
165 #endif // SHARE_GC_G1_G1BARRIERSET_HPP