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src/hotspot/share/gc/g1/g1CardTable.hpp

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rev 55404 : 8226197: Reducing G1?s CPU cost with simplified write post-barrier and disabling concurrent refinement
Summary: A prototype to add a mode for G1 to use a simplified write post-barrier. Guarded by new flag G1FastWriteBarrier.


  45 };
  46 
  47 class G1CardTable: public CardTable {
  48   friend class VMStructs;
  49   friend class G1CardTableChangedListener;
  50 
  51   G1CardTableChangedListener _listener;
  52 
  53   enum G1CardValues {
  54     g1_young_gen = CT_MR_BS_last_reserved << 1
  55   };
  56 
  57 public:
  58   G1CardTable(MemRegion whole_heap): CardTable(whole_heap, /* scanned concurrently */ true), _listener() {
  59     _listener.set_card_table(this);
  60   }
  61   bool is_card_dirty(size_t card_index) {
  62     return _byte_map[card_index] == dirty_card_val();
  63   }
  64 
  65   static CardValue g1_young_card_val() { return g1_young_gen; }



  66 
  67 /*
  68    Claimed and deferred bits are used together in G1 during the evacuation
  69    pause. These bits can have the following state transitions:
  70    1. The claimed bit can be put over any other card state. Except that
  71       the "dirty -> dirty and claimed" transition is checked for in
  72       G1 code and is not used.
  73    2. Deferred bit can be set only if the previous state of the card
  74       was either clean or claimed. mark_card_deferred() is wait-free.
  75       We do not care if the operation is be successful because if
  76       it does not it will only result in duplicate entry in the update
  77       buffer because of the "cache-miss". So it's not worth spinning.
  78  */
  79 
  80   bool is_card_claimed(size_t card_index) {
  81     CardValue val = _byte_map[card_index];
  82     return (val & (clean_card_mask_val() | claimed_card_val())) == claimed_card_val();
  83   }
  84 
  85   inline void set_card_claimed(size_t card_index);
  86 
  87   void verify_g1_young_region(MemRegion mr) PRODUCT_RETURN;

  88   void g1_mark_as_young(const MemRegion& mr);
  89 
  90   bool mark_card_deferred(size_t card_index);
  91 
  92   bool is_card_deferred(size_t card_index) {
  93     CardValue val = _byte_map[card_index];
  94     return (val & (clean_card_mask_val() | deferred_card_val())) == deferred_card_val();
  95   }
  96 
  97   static size_t compute_size(size_t mem_region_size_in_words) {
  98     size_t number_of_slots = (mem_region_size_in_words / card_size_in_words);
  99     return ReservedSpace::allocation_align_size_up(number_of_slots);
 100   }
 101 
 102   // Returns how many bytes of the heap a single byte of the Card Table corresponds to.
 103   static size_t heap_map_factor() { return card_size; }
 104 
 105   void initialize() {}
 106   void initialize(G1RegionToSpaceMapper* mapper);
 107 


  45 };
  46 
  47 class G1CardTable: public CardTable {
  48   friend class VMStructs;
  49   friend class G1CardTableChangedListener;
  50 
  51   G1CardTableChangedListener _listener;
  52 
  53   enum G1CardValues {
  54     g1_young_gen = CT_MR_BS_last_reserved << 1
  55   };
  56 
  57 public:
  58   G1CardTable(MemRegion whole_heap): CardTable(whole_heap, /* scanned concurrently */ true), _listener() {
  59     _listener.set_card_table(this);
  60   }
  61   bool is_card_dirty(size_t card_index) {
  62     return _byte_map[card_index] == dirty_card_val();
  63   }
  64 
  65   static CardValue g1_young_card_val() {
  66     assert(!G1FastWriteBarrier, "should not be called");
  67     return g1_young_gen;
  68   }
  69 
  70 /*
  71    Claimed and deferred bits are used together in G1 during the evacuation
  72    pause. These bits can have the following state transitions:
  73    1. The claimed bit can be put over any other card state. Except that
  74       the "dirty -> dirty and claimed" transition is checked for in
  75       G1 code and is not used.
  76    2. Deferred bit can be set only if the previous state of the card
  77       was either clean or claimed. mark_card_deferred() is wait-free.
  78       We do not care if the operation is be successful because if
  79       it does not it will only result in duplicate entry in the update
  80       buffer because of the "cache-miss". So it's not worth spinning.
  81  */
  82 
  83   bool is_card_claimed(size_t card_index) {
  84     CardValue val = _byte_map[card_index];
  85     return (val & (clean_card_mask_val() | claimed_card_val())) == claimed_card_val();
  86   }
  87 
  88   inline void set_card_claimed(size_t card_index);
  89 
  90   void verify_g1_young_region(MemRegion mr) PRODUCT_RETURN;
  91   void verfiy_claimed_dirty_region(MemRegion mr) PRODUCT_RETURN;
  92   void g1_mark_as_young(const MemRegion& mr);
  93 
  94   bool mark_card_deferred(size_t card_index);
  95 
  96   bool is_card_deferred(size_t card_index) {
  97     CardValue val = _byte_map[card_index];
  98     return (val & (clean_card_mask_val() | deferred_card_val())) == deferred_card_val();
  99   }
 100 
 101   static size_t compute_size(size_t mem_region_size_in_words) {
 102     size_t number_of_slots = (mem_region_size_in_words / card_size_in_words);
 103     return ReservedSpace::allocation_align_size_up(number_of_slots);
 104   }
 105 
 106   // Returns how many bytes of the heap a single byte of the Card Table corresponds to.
 107   static size_t heap_map_factor() { return card_size; }
 108 
 109   void initialize() {}
 110   void initialize(G1RegionToSpaceMapper* mapper);
 111 
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