1 /*
   2  * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1CARDCOUNTS_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1CARDCOUNTS_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "runtime/virtualspace.hpp"
  30 #include "utilities/globalDefinitions.hpp"
  31 
  32 class CardTableModRefBS;
  33 class G1CollectedHeap;
  34 class HeapRegion;
  35 
  36 class G1CardCounts: public CHeapObj<mtGC> {
  37   // Table to track the number of times a card has been refined.
  38   // Once a card has been refined a certain number of times, it
  39   // is considered 'hot' and its refinement is delayed by inserting
  40   // the card into the hot card cache. The card will then be refined
  41   // when it is evicted from the hot card cache, or when the
  42   // hot card cache is 'drained' during the next evacuation pause.
  43 
  44   G1CollectedHeap* _g1h;
  45 
  46   // The table of counts
  47   jbyte* _card_counts;
  48 
  49   // Max capacity of the reserved space for the counts table
  50   size_t _reserved_max_card_num;
  51 
  52   // Max capacity of the committed space for the counts table
  53   size_t _committed_max_card_num;
  54 
  55   // Size of committed space for the counts table
  56   size_t _committed_size;
  57 
  58   // CardTable bottom.
  59   const jbyte* _ct_bot;
  60 
  61   // Barrier set
  62   CardTableModRefBS* _ct_bs;
  63 
  64   // The virtual memory backing the counts table
  65   VirtualSpace _card_counts_storage;
  66 
  67   void check_card_num(size_t card_num, const char* msg) {
  68     assert(card_num >= 0 && card_num < _committed_max_card_num, msg);
  69   }
  70 
  71   size_t ptr_2_card_num(jbyte* card_ptr) {
  72     size_t card_num = (size_t) (card_ptr - _ct_bot);
  73     check_card_num(card_num,
  74                    err_msg("card pointer out of range: "PTR_FORMAT, card_ptr));
  75     return card_num;
  76   }
  77 
  78   jbyte* card_num_2_ptr(size_t card_num) {
  79     check_card_num(card_num,
  80                    err_msg("card num out of range: "SIZE_FORMAT, card_num));
  81     return (jbyte*) (_ct_bot + card_num);
  82   }
  83 
  84   // Clear the counts table for the given (exclusive) index range.
  85   void clear_range(size_t from_card_num, size_t to_card_num);
  86 
  87   // Returns the count of this card after incrementing it.
  88   int add_card_count(jbyte* card_ptr);
  89   
  90  public:
  91   G1CardCounts(G1CollectedHeap* g1h);
  92   ~G1CardCounts();
  93 
  94   void initialize();
  95 
  96   // Resize the committed space for the card counts table in
  97   // response to a resize of the committed space for the heap.
  98   void resize(size_t heap_capacity);
  99 
 100   // Updates the refinment count for the given card.
 101   // Returns true if the card is considered 'hot'; false otherwise.
 102   bool is_hot(jbyte* card_ptr);
 103 
 104   // Clears the card counts for the cards spanned by the region
 105   void clear_region(HeapRegion* hr);
 106 
 107   // Clear the entire card counts table during GC.
 108   // Updates the policy stats with the duration.
 109   void clear_all();
 110 };
 111 
 112 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1CARDCOUNTS_HPP