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24
25#ifndef SHARE_GC_G1_SPARSEPRT_HPP
26#define SHARE_GC_G1_SPARSEPRT_HPP
27
28#include "gc/g1/g1CollectedHeap.hpp"
29#include "gc/g1/heapRegion.hpp"
30#include "gc/shared/cardTableBarrierSet.hpp"
31#include "memory/allocation.hpp"
32#include "runtime/mutex.hpp"
33#include "utilities/align.hpp"
34#include "utilities/globalDefinitions.hpp"
35
36// Sparse remembered set for a heap region (the "owning" region). Maps
37// indices of other regions to short sequences of cards in the other region
38// that might contain pointers into the owner region.
39
40class SparsePRTEntry: public CHeapObj<mtGC> {
41private:
42 // The type of a card entry.
43 typedef uint16_t card_elem_t;
44
45 // We need to make sizeof(SparsePRTEntry) an even multiple of maximum member size,
46 // in order to force correct alignment that could otherwise cause SIGBUS errors
47 // when reading the member variables. This calculates the minimum number of card
48 // array elements required to get that alignment.
49 static const size_t card_array_alignment = sizeof(int) / sizeof(card_elem_t);
50
51 RegionIdx_t _region_ind;
52 int _next_index;
53 int _next_null;
54 // The actual cards stored in this array.
55 // WARNING: Don't put any data members beyond this line. Card array has, in fact, variable length.
56 // It should always be the last data member.
57 card_elem_t _cards[card_array_alignment];
58
59 // Copy the current entry's cards into "cards".
60 inline void copy_cards(card_elem_t* cards) const;
61public:
62 // Returns the size of the entry, used for entry allocation.
63 static size_t size() { return sizeof(SparsePRTEntry) + sizeof(card_elem_t) * (cards_num() - card_array_alignment); }
64 // Returns the size of the card array.
65 static int cards_num() {
66 return align_up((int)G1RSetSparseRegionEntries, (int)card_array_alignment);
67 }
68
69 // Set the region_ind to the given value, and delete all cards.
70 inline void init(RegionIdx_t region_ind);
71
72 RegionIdx_t r_ind() const { return _region_ind; }
73 bool valid_entry() const { return r_ind() >= 0; }
74 void set_r_ind(RegionIdx_t rind) { _region_ind = rind; }
75
76 int next_index() const { return _next_index; }
77 int* next_index_addr() { return &_next_index; }
78 void set_next_index(int ni) { _next_index = ni; }
79
80 // Returns "true" iff the entry contains the given card index.
81 inline bool contains_card(CardIdx_t card_index) const;
82
83 // Returns the number of non-NULL card entries.
84 inline int num_valid_cards() const { return _next_null; }
85
86 // Requires that the entry not contain the given card index. If there is
87 // space available, add the given card index to the entry and return
88 // "true"; otherwise, return "false" to indicate that the entry is full.
89 enum AddCardResult {
90 overflow,
91 found,
92 added
93 };
94 inline AddCardResult add_card(CardIdx_t card_index);
95
96 // Copy the current entry's cards into the "_card" array of "e."
97 inline void copy_cards(SparsePRTEntry* e) const;
98
99 inline CardIdx_t card(int i) const {
100 assert(i >= 0, "must be nonnegative");
101 assert(i < cards_num(), "range checking");
102 return (CardIdx_t)_cards[i];
103 }
104};
105
106class RSHashTable : public CHeapObj<mtGC> {
107
108 friend class RSHashTableIter;
109
110
111 // Inverse maximum hash table occupancy used.
112 static float TableOccupancyFactor;
113
114 size_t _num_entries;
115
116 size_t _capacity;
117 size_t _capacity_mask;
118 size_t _occupied_entries;
119 size_t _occupied_cards;
120
121 SparsePRTEntry* _entries;
122 int* _buckets;
123 int _free_region;
124 int _free_list;
125
126 // Requires that the caller hold a lock preventing parallel modifying
127 // operations, and that the the table be less than completely full. If
128 // an entry for "region_ind" is already in the table, finds it and
129 // returns its address; otherwise allocates, initializes, inserts and
130 // returns a new entry for "region_ind".
131 SparsePRTEntry* entry_for_region_ind_create(RegionIdx_t region_ind);
132
133 // Returns the index of the next free entry in "_entries".
134 int alloc_entry();
135 // Declares the entry "fi" to be free. (It must have already been
136 // deleted from any bucket lists.
137 void free_entry(int fi);
138
139public:
140 RSHashTable(size_t capacity);
141 ~RSHashTable();
142
143 static const int NullEntry = -1;
144
145 bool should_expand() const { return _occupied_entries == _num_entries; }
146
147 // Attempts to ensure that the given card_index in the given region is in
148 // the sparse table. If successful (because the card was already
149 // present, or because it was successfully added) returns "true".
150 // Otherwise, returns "false" to indicate that the addition would
151 // overflow the entry for the region. The caller must transfer these
152 // entries to a larger-capacity representation.
153 bool add_card(RegionIdx_t region_id, CardIdx_t card_index);
154
155 bool delete_entry(RegionIdx_t region_id);
156
157 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const;
158
159 void add_entry(SparsePRTEntry* e);
160
161 SparsePRTEntry* get_entry(RegionIdx_t region_id) const;
162
163 void clear();
164
165 size_t capacity() const { return _capacity; }
166 size_t capacity_mask() const { return _capacity_mask; }
167 size_t occupied_entries() const { return _occupied_entries; }
168 size_t occupied_cards() const { return _occupied_cards; }
169 size_t mem_size() const;
170 // The number of SparsePRTEntry instances available.
171 size_t num_entries() const { return _num_entries; }
172
173 SparsePRTEntry* entry(int i) const {
174 assert(i >= 0 && (size_t)i < _num_entries, "precondition");
175 return (SparsePRTEntry*)((char*)_entries + SparsePRTEntry::size() * i);
176 }
177
178 void print();
179};
180
181// This is embedded in HRRS iterator.
182class RSHashTableIter {
183 // Return value indicating "invalid/no card".
184 static const int NoCardFound = -1;
185
186 int _tbl_ind; // [-1, 0.._rsht->_capacity)
187 int _bl_ind; // [-1, 0.._rsht->_capacity)
188 short _card_ind; // [0..SparsePRTEntry::cards_num())
189 RSHashTable* _rsht;
190
191 // If the bucket list pointed to by _bl_ind contains a card, sets
192 // _bl_ind to the index of that entry,
193 // Returns the card found if there is, otherwise returns InvalidCard.
194 CardIdx_t find_first_card_in_list();
195
196 // Computes the proper card index for the card whose offset in the
197 // current region (as indicated by _bl_ind) is "ci".
198 // This is subject to errors when there is iteration concurrent with
199 // modification, but these errors should be benign.
200 size_t compute_card_ind(CardIdx_t ci);
201
202public:
203 RSHashTableIter(RSHashTable* rsht) :
204 _tbl_ind(RSHashTable::NullEntry), // So that first increment gets to 0.
205 _bl_ind(RSHashTable::NullEntry),
206 _card_ind((SparsePRTEntry::cards_num() - 1)),
207 _rsht(rsht) {}
208
209 bool has_next(size_t& card_index);
210};
211
212// Concurrent access to a SparsePRT must be serialized by some external mutex.
213
214class SparsePRTIter;
215
216class SparsePRT {
217 friend class SparsePRTIter;
218
219 RSHashTable* _table;
220
221 static const size_t InitialCapacity = 8;
222
223 void expand();
224
225public:
226 SparsePRT();
227 ~SparsePRT();
228
229 size_t occupied() const { return _table->occupied_cards(); }
230 size_t mem_size() const;
231
232 // Attempts to ensure that the given card_index in the given region is in
233 // the sparse table. If successful (because the card was already
234 // present, or because it was successfully added) returns "true".
235 // Otherwise, returns "false" to indicate that the addition would
236 // overflow the entry for the region. The caller must transfer these
237 // entries to a larger-capacity representation.
238 bool add_card(RegionIdx_t region_id, CardIdx_t card_index);
239
240 // Return the pointer to the entry associated with the given region.
241 SparsePRTEntry* get_entry(RegionIdx_t region_ind);
242
243 // If there is an entry for "region_ind", removes it and return "true";
244 // otherwise returns "false."
245 bool delete_entry(RegionIdx_t region_ind);
246
247 // Clear the table, and reinitialize to initial capacity.
248 void clear();
249
250 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const {
251 return _table->contains_card(region_id, card_index);
252 }
253};
254
255class SparsePRTIter: public RSHashTableIter {
256public:
257 SparsePRTIter(const SparsePRT* sprt) :
258 RSHashTableIter(sprt->_table) { }
259
260 bool has_next(size_t& card_index) {
261 return RSHashTableIter::has_next(card_index);
262 }
263};
264
265#endif // SHARE_GC_G1_SPARSEPRT_HPP
266