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1 /*
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2 * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // Sparse remembered set for a heap region (the "owning" region). Maps
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26 // indices of other regions to short sequences of cards in the other region
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27 // that might contain pointers into the owner region.
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28
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29 // These tables only expand while they are accessed in parallel --
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30 // deletions may be done in single-threaded code. This allows us to allow
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31 // unsynchronized reads/iterations, as long as expansions caused by
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32 // insertions only enqueue old versions for deletions, but do not delete
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33 // old versions synchronously.
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34
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35
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36 class SparsePRTEntry {
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37 public:
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38 enum SomePublicConstants {
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39 CardsPerEntry = (short)4,
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40 NullEntry = (short)-1,
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41 DeletedEntry = (short)-2
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42 };
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43
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44 private:
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45 short _region_ind;
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46 short _next_index;
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47 short _cards[CardsPerEntry];
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48
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49 public:
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50
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51 // Set the region_ind to the given value, and delete all cards.
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52 inline void init(short region_ind);
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53
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54 short r_ind() const { return _region_ind; }
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55 bool valid_entry() const { return r_ind() >= 0; }
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56 void set_r_ind(short rind) { _region_ind = rind; }
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57
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58 short next_index() const { return _next_index; }
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59 short* next_index_addr() { return &_next_index; }
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60 void set_next_index(short ni) { _next_index = ni; }
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61
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62 // Returns "true" iff the entry contains the given card index.
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63 inline bool contains_card(short card_index) const;
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64
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65 // Returns the number of non-NULL card entries.
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66 inline int num_valid_cards() const;
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67
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68 // Requires that the entry not contain the given card index. If there is
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69 // space available, add the given card index to the entry and return
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70 // "true"; otherwise, return "false" to indicate that the entry is full.
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71 enum AddCardResult {
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72 overflow,
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73 found,
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74 added
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75 };
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76 inline AddCardResult add_card(short card_index);
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77
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78 // Copy the current entry's cards into "cards".
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79 inline void copy_cards(short* cards) const;
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80 // Copy the current entry's cards into the "_card" array of "e."
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81 inline void copy_cards(SparsePRTEntry* e) const;
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82
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83 inline short card(int i) const { return _cards[i]; }
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84 };
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85
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86
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87 class RSHashTable : public CHeapObj {
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88
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89 friend class RSHashTableIter;
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90
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91 enum SomePrivateConstants {
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92 NullEntry = -1
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93 };
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94
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95 size_t _capacity;
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96 size_t _capacity_mask;
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97 size_t _occupied_entries;
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98 size_t _occupied_cards;
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99
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100 SparsePRTEntry* _entries;
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101 short* _buckets;
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102 short _free_region;
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103 short _free_list;
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104
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105 static RSHashTable* _head_deleted_list;
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106 RSHashTable* _next_deleted;
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107 RSHashTable* next_deleted() { return _next_deleted; }
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108 void set_next_deleted(RSHashTable* rsht) { _next_deleted = rsht; }
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109 bool _deleted;
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110 void set_deleted(bool b) { _deleted = b; }
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111
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112 // Requires that the caller hold a lock preventing parallel modifying
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113 // operations, and that the the table be less than completely full. If
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114 // an entry for "region_ind" is already in the table, finds it and
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115 // returns its address; otherwise returns "NULL."
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116 SparsePRTEntry* entry_for_region_ind(short region_ind) const;
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117
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118 // Requires that the caller hold a lock preventing parallel modifying
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119 // operations, and that the the table be less than completely full. If
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120 // an entry for "region_ind" is already in the table, finds it and
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121 // returns its address; otherwise allocates, initializes, inserts and
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122 // returns a new entry for "region_ind".
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123 SparsePRTEntry* entry_for_region_ind_create(short region_ind);
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124
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125 // Returns the index of the next free entry in "_entries".
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126 short alloc_entry();
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127 // Declares the entry "fi" to be free. (It must have already been
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128 // deleted from any bucket lists.
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129 void free_entry(short fi);
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130
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131 public:
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132 RSHashTable(size_t capacity);
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133 ~RSHashTable();
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134
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135 // Attempts to ensure that the given card_index in the given region is in
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136 // the sparse table. If successful (because the card was already
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137 // present, or because it was successfullly added) returns "true".
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138 // Otherwise, returns "false" to indicate that the addition would
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139 // overflow the entry for the region. The caller must transfer these
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140 // entries to a larger-capacity representation.
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141 bool add_card(short region_id, short card_index);
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142
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143 bool get_cards(short region_id, short* cards);
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144 bool delete_entry(short region_id);
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145
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146 bool contains_card(short region_id, short card_index) const;
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147
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148 void add_entry(SparsePRTEntry* e);
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149
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150 void clear();
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151
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152 size_t capacity() const { return _capacity; }
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153 size_t capacity_mask() const { return _capacity_mask; }
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154 size_t occupied_entries() const { return _occupied_entries; }
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155 size_t occupied_cards() const { return _occupied_cards; }
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156 size_t mem_size() const;
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157 bool deleted() { return _deleted; }
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158
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159 SparsePRTEntry* entry(int i) const { return &_entries[i]; }
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160
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161 void print();
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162
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163 static void add_to_deleted_list(RSHashTable* rsht);
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164 static RSHashTable* get_from_deleted_list();
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165
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166
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167 };
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168
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169 // ValueObj because will be embedded in HRRS iterator.
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170 class RSHashTableIter: public CHeapObj {
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171 short _tbl_ind;
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172 short _bl_ind;
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173 short _card_ind;
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174 RSHashTable* _rsht;
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175 size_t _heap_bot_card_ind;
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176
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177 enum SomePrivateConstants {
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178 CardsPerRegion = HeapRegion::GrainBytes >> CardTableModRefBS::card_shift
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179 };
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180
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181 // If the bucket list pointed to by _bl_ind contains a card, sets
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182 // _bl_ind to the index of that entry, and returns the card.
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183 // Otherwise, returns SparseEntry::NullEnty.
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184 short find_first_card_in_list();
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185 // Computes the proper card index for the card whose offset in the
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186 // current region (as indicated by _bl_ind) is "ci".
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187 // This is subject to errors when there is iteration concurrent with
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188 // modification, but these errors should be benign.
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189 size_t compute_card_ind(short ci);
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190
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191 public:
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192 RSHashTableIter(size_t heap_bot_card_ind) :
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193 _tbl_ind(RSHashTable::NullEntry),
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194 _bl_ind(RSHashTable::NullEntry),
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195 _card_ind((SparsePRTEntry::CardsPerEntry-1)),
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196 _rsht(NULL),
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197 _heap_bot_card_ind(heap_bot_card_ind)
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198 {}
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199
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200 void init(RSHashTable* rsht) {
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201 _rsht = rsht;
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202 _tbl_ind = -1; // So that first increment gets to 0.
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203 _bl_ind = RSHashTable::NullEntry;
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204 _card_ind = (SparsePRTEntry::CardsPerEntry-1);
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205 }
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206
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207 bool has_next(size_t& card_index);
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208
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209 };
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210
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211 // Concurrent accesss to a SparsePRT must be serialized by some external
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212 // mutex.
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213
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214 class SparsePRTIter;
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215
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216 class SparsePRT : public CHeapObj {
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217 // Iterations are done on the _cur hash table, since they only need to
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218 // see entries visible at the start of a collection pause.
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219 // All other operations are done using the _next hash table.
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220 RSHashTable* _cur;
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221 RSHashTable* _next;
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222
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223 HeapRegion* _hr;
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224
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225 enum SomeAdditionalPrivateConstants {
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226 InitialCapacity = 16
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227 };
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228
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229 void expand();
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230
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231 bool _expanded;
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232
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233 bool expanded() { return _expanded; }
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234 void set_expanded(bool b) { _expanded = b; }
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235
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236 SparsePRT* _next_expanded;
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237
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238 SparsePRT* next_expanded() { return _next_expanded; }
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239 void set_next_expanded(SparsePRT* nxt) { _next_expanded = nxt; }
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240
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241
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242 static SparsePRT* _head_expanded_list;
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243
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244 public:
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245 SparsePRT(HeapRegion* hr);
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246
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247 ~SparsePRT();
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248
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249 size_t occupied() const { return _next->occupied_cards(); }
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250 size_t mem_size() const;
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251
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252 // Attempts to ensure that the given card_index in the given region is in
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253 // the sparse table. If successful (because the card was already
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254 // present, or because it was successfullly added) returns "true".
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255 // Otherwise, returns "false" to indicate that the addition would
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256 // overflow the entry for the region. The caller must transfer these
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257 // entries to a larger-capacity representation.
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258 bool add_card(short region_id, short card_index);
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259
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260 // If the table hold an entry for "region_ind", Copies its
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261 // cards into "cards", which must be an array of length at least
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262 // "CardsPerEntry", and returns "true"; otherwise, returns "false".
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263 bool get_cards(short region_ind, short* cards);
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264
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265 // If there is an entry for "region_ind", removes it and return "true";
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266 // otherwise returns "false."
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267 bool delete_entry(short region_ind);
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268
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269 // Clear the table, and reinitialize to initial capacity.
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270 void clear();
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271
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272 // Ensure that "_cur" and "_next" point to the same table.
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273 void cleanup();
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274
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275 // Clean up all tables on the expanded list. Called single threaded.
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276 static void cleanup_all();
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277 RSHashTable* next() const { return _next; }
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278
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279
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280 void init_iterator(SparsePRTIter* sprt_iter);
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281
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282 static void add_to_expanded_list(SparsePRT* sprt);
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283 static SparsePRT* get_from_expanded_list();
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284
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285 bool contains_card(short region_id, short card_index) const {
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286 return _next->contains_card(region_id, card_index);
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287 }
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288
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289 #if 0
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290 void verify_is_cleared();
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291 void print();
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292 #endif
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293 };
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294
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295
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296 class SparsePRTIter: public /* RSHashTable:: */RSHashTableIter {
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297 public:
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298 SparsePRTIter(size_t heap_bot_card_ind) :
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299 /* RSHashTable:: */RSHashTableIter(heap_bot_card_ind)
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300 {}
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301
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302 void init(const SparsePRT* sprt) {
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303 RSHashTableIter::init(sprt->next());
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304 }
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305 bool has_next(size_t& card_index) {
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306 return RSHashTableIter::has_next(card_index);
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307 }
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308 };
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