Thu, 22 Apr 2010 10:02:38 -0700
6819061: G1: eliminate serial Other times that are proportional to the collection set length
6871109: G1: remove the concept of the scan only prefix
Summary: Removed scan only regions and associated code. The young portion of the collection set is now constructed incrementally - when a young region is retired as the current allocation region it is added to the collection set.
Reviewed-by: apetrusenko, iveresov, tonyp
1 /*
2 * Copyright 2001-2009 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 // Sparse remembered set for a heap region (the "owning" region). Maps
26 // indices of other regions to short sequences of cards in the other region
27 // that might contain pointers into the owner region.
29 // These tables only expand while they are accessed in parallel --
30 // deletions may be done in single-threaded code. This allows us to allow
31 // unsynchronized reads/iterations, as long as expansions caused by
32 // insertions only enqueue old versions for deletions, but do not delete
33 // old versions synchronously.
35 class SparsePRTEntry: public CHeapObj {
36 public:
37 enum SomePublicConstants {
38 NullEntry = -1,
39 UnrollFactor = 4
40 };
41 private:
42 RegionIdx_t _region_ind;
43 int _next_index;
44 CardIdx_t _cards[1];
45 // WARNING: Don't put any data members beyond this line. Card array has, in fact, variable length.
46 // It should always be the last data member.
47 public:
48 // Returns the size of the entry, used for entry allocation.
49 static size_t size() { return sizeof(SparsePRTEntry) + sizeof(CardIdx_t) * (cards_num() - 1); }
50 // Returns the size of the card array.
51 static int cards_num() {
52 // The number of cards should be a multiple of 4, because that's our current
53 // unrolling factor.
54 static const int s = MAX2<int>(G1RSetSparseRegionEntries & ~(UnrollFactor - 1), UnrollFactor);
55 return s;
56 }
58 // Set the region_ind to the given value, and delete all cards.
59 inline void init(RegionIdx_t region_ind);
61 RegionIdx_t r_ind() const { return _region_ind; }
62 bool valid_entry() const { return r_ind() >= 0; }
63 void set_r_ind(RegionIdx_t rind) { _region_ind = rind; }
65 int next_index() const { return _next_index; }
66 int* next_index_addr() { return &_next_index; }
67 void set_next_index(int ni) { _next_index = ni; }
69 // Returns "true" iff the entry contains the given card index.
70 inline bool contains_card(CardIdx_t card_index) const;
72 // Returns the number of non-NULL card entries.
73 inline int num_valid_cards() const;
75 // Requires that the entry not contain the given card index. If there is
76 // space available, add the given card index to the entry and return
77 // "true"; otherwise, return "false" to indicate that the entry is full.
78 enum AddCardResult {
79 overflow,
80 found,
81 added
82 };
83 inline AddCardResult add_card(CardIdx_t card_index);
85 // Copy the current entry's cards into "cards".
86 inline void copy_cards(CardIdx_t* cards) const;
87 // Copy the current entry's cards into the "_card" array of "e."
88 inline void copy_cards(SparsePRTEntry* e) const;
90 inline CardIdx_t card(int i) const { return _cards[i]; }
91 };
94 class RSHashTable : public CHeapObj {
96 friend class RSHashTableIter;
98 enum SomePrivateConstants {
99 NullEntry = -1
100 };
102 size_t _capacity;
103 size_t _capacity_mask;
104 size_t _occupied_entries;
105 size_t _occupied_cards;
107 SparsePRTEntry* _entries;
108 int* _buckets;
109 int _free_region;
110 int _free_list;
112 // Requires that the caller hold a lock preventing parallel modifying
113 // operations, and that the the table be less than completely full. If
114 // an entry for "region_ind" is already in the table, finds it and
115 // returns its address; otherwise returns "NULL."
116 SparsePRTEntry* entry_for_region_ind(RegionIdx_t region_ind) const;
118 // Requires that the caller hold a lock preventing parallel modifying
119 // operations, and that the the table be less than completely full. If
120 // an entry for "region_ind" is already in the table, finds it and
121 // returns its address; otherwise allocates, initializes, inserts and
122 // returns a new entry for "region_ind".
123 SparsePRTEntry* entry_for_region_ind_create(RegionIdx_t region_ind);
125 // Returns the index of the next free entry in "_entries".
126 int alloc_entry();
127 // Declares the entry "fi" to be free. (It must have already been
128 // deleted from any bucket lists.
129 void free_entry(int fi);
131 public:
132 RSHashTable(size_t capacity);
133 ~RSHashTable();
135 // Attempts to ensure that the given card_index in the given region is in
136 // the sparse table. If successful (because the card was already
137 // present, or because it was successfullly added) returns "true".
138 // Otherwise, returns "false" to indicate that the addition would
139 // overflow the entry for the region. The caller must transfer these
140 // entries to a larger-capacity representation.
141 bool add_card(RegionIdx_t region_id, CardIdx_t card_index);
143 bool get_cards(RegionIdx_t region_id, CardIdx_t* cards);
145 bool delete_entry(RegionIdx_t region_id);
147 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const;
149 void add_entry(SparsePRTEntry* e);
151 SparsePRTEntry* get_entry(RegionIdx_t region_id);
153 void clear();
155 size_t capacity() const { return _capacity; }
156 size_t capacity_mask() const { return _capacity_mask; }
157 size_t occupied_entries() const { return _occupied_entries; }
158 size_t occupied_cards() const { return _occupied_cards; }
159 size_t mem_size() const;
161 SparsePRTEntry* entry(int i) const { return (SparsePRTEntry*)((char*)_entries + SparsePRTEntry::size() * i); }
163 void print();
164 };
166 // ValueObj because will be embedded in HRRS iterator.
167 class RSHashTableIter VALUE_OBJ_CLASS_SPEC {
168 int _tbl_ind; // [-1, 0.._rsht->_capacity)
169 int _bl_ind; // [-1, 0.._rsht->_capacity)
170 short _card_ind; // [0..SparsePRTEntry::cards_num())
171 RSHashTable* _rsht;
172 size_t _heap_bot_card_ind;
174 // If the bucket list pointed to by _bl_ind contains a card, sets
175 // _bl_ind to the index of that entry, and returns the card.
176 // Otherwise, returns SparseEntry::NullEntry.
177 CardIdx_t find_first_card_in_list();
179 // Computes the proper card index for the card whose offset in the
180 // current region (as indicated by _bl_ind) is "ci".
181 // This is subject to errors when there is iteration concurrent with
182 // modification, but these errors should be benign.
183 size_t compute_card_ind(CardIdx_t ci);
185 public:
186 RSHashTableIter(size_t heap_bot_card_ind) :
187 _tbl_ind(RSHashTable::NullEntry),
188 _bl_ind(RSHashTable::NullEntry),
189 _card_ind((SparsePRTEntry::cards_num() - 1)),
190 _rsht(NULL),
191 _heap_bot_card_ind(heap_bot_card_ind)
192 {}
194 void init(RSHashTable* rsht) {
195 _rsht = rsht;
196 _tbl_ind = -1; // So that first increment gets to 0.
197 _bl_ind = RSHashTable::NullEntry;
198 _card_ind = (SparsePRTEntry::cards_num() - 1);
199 }
201 bool has_next(size_t& card_index);
202 };
204 // Concurrent accesss to a SparsePRT must be serialized by some external
205 // mutex.
207 class SparsePRTIter;
209 class SparsePRT VALUE_OBJ_CLASS_SPEC {
210 // Iterations are done on the _cur hash table, since they only need to
211 // see entries visible at the start of a collection pause.
212 // All other operations are done using the _next hash table.
213 RSHashTable* _cur;
214 RSHashTable* _next;
216 HeapRegion* _hr;
218 enum SomeAdditionalPrivateConstants {
219 InitialCapacity = 16
220 };
222 void expand();
224 bool _expanded;
226 bool expanded() { return _expanded; }
227 void set_expanded(bool b) { _expanded = b; }
229 SparsePRT* _next_expanded;
231 SparsePRT* next_expanded() { return _next_expanded; }
232 void set_next_expanded(SparsePRT* nxt) { _next_expanded = nxt; }
234 static SparsePRT* _head_expanded_list;
236 public:
237 SparsePRT(HeapRegion* hr);
239 ~SparsePRT();
241 size_t occupied() const { return _next->occupied_cards(); }
242 size_t mem_size() const;
244 // Attempts to ensure that the given card_index in the given region is in
245 // the sparse table. If successful (because the card was already
246 // present, or because it was successfullly added) returns "true".
247 // Otherwise, returns "false" to indicate that the addition would
248 // overflow the entry for the region. The caller must transfer these
249 // entries to a larger-capacity representation.
250 bool add_card(RegionIdx_t region_id, CardIdx_t card_index);
252 // If the table hold an entry for "region_ind", Copies its
253 // cards into "cards", which must be an array of length at least
254 // "SparePRTEntry::cards_num()", and returns "true"; otherwise,
255 // returns "false".
256 bool get_cards(RegionIdx_t region_ind, CardIdx_t* cards);
258 // Return the pointer to the entry associated with the given region.
259 SparsePRTEntry* get_entry(RegionIdx_t region_ind);
261 // If there is an entry for "region_ind", removes it and return "true";
262 // otherwise returns "false."
263 bool delete_entry(RegionIdx_t region_ind);
265 // Clear the table, and reinitialize to initial capacity.
266 void clear();
268 // Ensure that "_cur" and "_next" point to the same table.
269 void cleanup();
271 // Clean up all tables on the expanded list. Called single threaded.
272 static void cleanup_all();
273 RSHashTable* cur() const { return _cur; }
275 void init_iterator(SparsePRTIter* sprt_iter);
277 static void add_to_expanded_list(SparsePRT* sprt);
278 static SparsePRT* get_from_expanded_list();
280 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const {
281 return _next->contains_card(region_id, card_index);
282 }
284 #if 0
285 void verify_is_cleared();
286 void print();
287 #endif
288 };
291 class SparsePRTIter: public /* RSHashTable:: */RSHashTableIter {
292 public:
293 SparsePRTIter(size_t heap_bot_card_ind) :
294 /* RSHashTable:: */RSHashTableIter(heap_bot_card_ind)
295 {}
297 void init(const SparsePRT* sprt) {
298 RSHashTableIter::init(sprt->cur());
299 }
300 bool has_next(size_t& card_index) {
301 return RSHashTableIter::has_next(card_index);
302 }
303 };