jdk-24/hotspot/src/share/vm/gc_implementation/g1/g1CardCounts.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1CARDCOUNTS_HPP
#define SHARE_VM_GC_IMPLEMENTATION_G1_G1CARDCOUNTS_HPP

#include "memory/allocation.hpp"
#include "runtime/virtualspace.hpp"
#include "utilities/globalDefinitions.hpp"

class CardTableModRefBS;
class G1CollectedHeap;
class HeapRegion;

// Table to track the number of times a card has been refined. Once
// a card has been refined a certain number of times, it is
// considered 'hot' and its refinement is delayed by inserting the
// card into the hot card cache. The card will then be refined when
// it is evicted from the hot card cache, or when the hot card cache
// is 'drained' during the next evacuation pause.

class G1CardCounts: public CHeapObj<mtGC> {
  G1CollectedHeap* _g1h;

  // The table of counts
  jubyte* _card_counts;

  // Max capacity of the reserved space for the counts table
  size_t _reserved_max_card_num;

  // Max capacity of the committed space for the counts table
  size_t _committed_max_card_num;

  // Size of committed space for the counts table
  size_t _committed_size;

  // CardTable bottom.
  const jbyte* _ct_bot;

  // Barrier set
  CardTableModRefBS* _ct_bs;

  // The virtual memory backing the counts table
  VirtualSpace _card_counts_storage;

  // Returns true if the card counts table has been reserved.
  bool has_reserved_count_table() { return _card_counts != NULL; }

  // Returns true if the card counts table has been reserved and committed.
  bool has_count_table() {
    return has_reserved_count_table() && _committed_max_card_num > 0;
  }

  size_t ptr_2_card_num(const jbyte* card_ptr) {
    assert(card_ptr >= _ct_bot,
           err_msg("Invalid card pointer: "
                   "card_ptr: " PTR_FORMAT ", "
                   "_ct_bot: " PTR_FORMAT,
                   p2i(card_ptr), p2i(_ct_bot)));
    size_t card_num = pointer_delta(card_ptr, _ct_bot, sizeof(jbyte));
    assert(card_num >= 0 && card_num < _committed_max_card_num,
           err_msg("card pointer out of range: " PTR_FORMAT, p2i(card_ptr)));
    return card_num;
  }

  jbyte* card_num_2_ptr(size_t card_num) {
    assert(card_num >= 0 && card_num < _committed_max_card_num,
           err_msg("card num out of range: "SIZE_FORMAT, card_num));
    return (jbyte*) (_ct_bot + card_num);
  }

  // Helper routine.
  // Returns the number of cards that can be counted by the given committed
  // table size, with a maximum of the number of cards spanned by the max
  // capacity of the heap.
  size_t committed_to_card_num(size_t committed_size) {
    return MIN2(_reserved_max_card_num, committed_size / sizeof(jbyte));
  }

  // Clear the counts table for the given (exclusive) index range.
  void clear_range(size_t from_card_num, size_t to_card_num);

 public:
  G1CardCounts(G1CollectedHeap* g1h);
  ~G1CardCounts();

  void initialize();

  // Resize the committed space for the card counts table in
  // response to a resize of the committed space for the heap.
  void resize(size_t heap_capacity);

  // Increments the refinement count for the given card.
  // Returns the pre-increment count value.
  uint add_card_count(jbyte* card_ptr);

  // Returns true if the given count is high enough to be considered
  // 'hot'; false otherwise.
  bool is_hot(uint count);

  // Clears the card counts for the cards spanned by the region
  void clear_region(HeapRegion* hr);

  // Clear the entire card counts table during GC.
  // Updates the policy stats with the duration.
  void clear_all();
};

#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1CARDCOUNTS_HPP