1 /*
2 * Copyright (c) 2001, 2009, 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 // Remembered set for a heap region. Represent a set of "cards" that
26 // contain pointers into the owner heap region. Cards are defined somewhat
27 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
28
29 class G1CollectedHeap;
30 class G1BlockOffsetSharedArray;
31 class HeapRegion;
32 class HeapRegionRemSetIterator;
33 class PosParPRT;
34 class SparsePRT;
35
36
37 // The "_coarse_map" is a bitmap with one bit for each region, where set
38 // bits indicate that the corresponding region may contain some pointer
39 // into the owning region.
40
41 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
42 // (PRTs), indicating regions for which we're keeping the RS as a set of
43 // cards. The strategy is to cap the size of the fine-grain table,
44 // deleting an entry and setting the corresponding coarse-grained bit when
45 // we would overflow this cap.
46
47 // We use a mixture of locking and lock-free techniques here. We allow
48 // threads to locate PRTs without locking, but threads attempting to alter
49 // a bucket list obtain a lock. This means that any failing attempt to
50 // find a PRT must be retried with the lock. It might seem dangerous that
51 // a read can find a PRT that is concurrently deleted. This is all right,
52 // because:
53 //
54 // 1) We only actually free PRT's at safe points (though we reuse them at
55 // other times).
56 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
57 // it's _coarse_map bit is set, so the that we were attempting to add
58 // is represented. If a deleted PRT is re-used, a thread adding a bit,
59 // thinking the PRT is for a different region, does no harm.
60
61 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
62 friend class HeapRegionRemSetIterator;
63
64 G1CollectedHeap* _g1h;
65 Mutex _m;
66 HeapRegion* _hr;
67
68 // These are protected by "_m".
69 BitMap _coarse_map;
70 size_t _n_coarse_entries;
71 static jint _n_coarsenings;
72
73 PosParPRT** _fine_grain_regions;
74 size_t _n_fine_entries;
75
76 #define SAMPLE_FOR_EVICTION 1
77 #if SAMPLE_FOR_EVICTION
78 size_t _fine_eviction_start;
79 static size_t _fine_eviction_stride;
80 static size_t _fine_eviction_sample_size;
81 #endif
82
83 SparsePRT _sparse_table;
84
85 // These are static after init.
86 static size_t _max_fine_entries;
87 static size_t _mod_max_fine_entries_mask;
88
89 // Requires "prt" to be the first element of the bucket list appropriate
90 // for "hr". If this list contains an entry for "hr", return it,
91 // otherwise return "NULL".
92 PosParPRT* find_region_table(size_t ind, HeapRegion* hr) const;
93
94 // Find, delete, and return a candidate PosParPRT, if any exists,
95 // adding the deleted region to the coarse bitmap. Requires the caller
96 // to hold _m, and the fine-grain table to be full.
97 PosParPRT* delete_region_table();
98
99 // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
100 // be the correct index for "hr"), delete it and return true; else return
101 // false.
102 bool del_single_region_table(size_t ind, HeapRegion* hr);
103
104 static jint _cache_probes;
105 static jint _cache_hits;
106
107 // Indexed by thread X heap region, to minimize thread contention.
108 static int** _from_card_cache;
109 static size_t _from_card_cache_max_regions;
110 static size_t _from_card_cache_mem_size;
111
112 public:
113 OtherRegionsTable(HeapRegion* hr);
114
115 HeapRegion* hr() const { return _hr; }
116
117 // For now. Could "expand" some tables in the future, so that this made
118 // sense.
119 void add_reference(OopOrNarrowOopStar from, int tid);
120
121 void add_reference(OopOrNarrowOopStar from) {
122 return add_reference(from, 0);
123 }
124
125 // Removes any entries shown by the given bitmaps to contain only dead
126 // objects.
127 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
128
129 // Not const because it takes a lock.
130 size_t occupied() const;
131 size_t occ_fine() const;
132 size_t occ_coarse() const;
133 size_t occ_sparse() const;
134
135 static jint n_coarsenings() { return _n_coarsenings; }
136
137 // Returns size in bytes.
138 // Not const because it takes a lock.
139 size_t mem_size() const;
140 static size_t static_mem_size();
141 static size_t fl_mem_size();
142
143 bool contains_reference(OopOrNarrowOopStar from) const;
144 bool contains_reference_locked(OopOrNarrowOopStar from) const;
145
146 void clear();
147
148 // Specifically clear the from_card_cache.
149 void clear_fcc();
150
151 // "from_hr" is being cleared; remove any entries from it.
152 void clear_incoming_entry(HeapRegion* from_hr);
153
154 // Declare the heap size (in # of regions) to the OtherRegionsTable.
155 // (Uses it to initialize from_card_cache).
156 static void init_from_card_cache(size_t max_regions);
157
158 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
159 // Make sure any entries for higher regions are invalid.
160 static void shrink_from_card_cache(size_t new_n_regs);
161
162 static void print_from_card_cache();
163
164 };
165
166
167 class HeapRegionRemSet : public CHeapObj {
168 friend class VMStructs;
169 friend class HeapRegionRemSetIterator;
170
171 public:
172 enum Event {
173 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
174 };
175
176 private:
177 G1BlockOffsetSharedArray* _bosa;
178 G1BlockOffsetSharedArray* bosa() const { return _bosa; }
179
180 OtherRegionsTable _other_regions;
181
182 enum ParIterState { Unclaimed, Claimed, Complete };
183 volatile ParIterState _iter_state;
184 volatile jlong _iter_claimed;
185
186 // Unused unless G1RecordHRRSOops is true.
187
188 static const int MaxRecorded = 1000000;
189 static OopOrNarrowOopStar* _recorded_oops;
190 static HeapWord** _recorded_cards;
191 static HeapRegion** _recorded_regions;
192 static int _n_recorded;
193
194 static const int MaxRecordedEvents = 1000;
195 static Event* _recorded_events;
196 static int* _recorded_event_index;
197 static int _n_recorded_events;
198
199 static void print_event(outputStream* str, Event evnt);
200
201 public:
202 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
203 HeapRegion* hr);
204
205 static int num_par_rem_sets();
206 static void setup_remset_size();
207
208 HeapRegion* hr() const {
209 return _other_regions.hr();
210 }
211
212 size_t occupied() const {
213 return _other_regions.occupied();
214 }
215 size_t occ_fine() const {
216 return _other_regions.occ_fine();
217 }
218 size_t occ_coarse() const {
219 return _other_regions.occ_coarse();
220 }
221 size_t occ_sparse() const {
222 return _other_regions.occ_sparse();
223 }
224
225 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
226
227 /* Used in the sequential case. Returns "true" iff this addition causes
228 the size limit to be reached. */
229 void add_reference(OopOrNarrowOopStar from) {
230 _other_regions.add_reference(from);
231 }
232
233 /* Used in the parallel case. Returns "true" iff this addition causes
234 the size limit to be reached. */
235 void add_reference(OopOrNarrowOopStar from, int tid) {
236 _other_regions.add_reference(from, tid);
237 }
238
239 // Removes any entries shown by the given bitmaps to contain only dead
240 // objects.
241 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
242
243 // The region is being reclaimed; clear its remset, and any mention of
244 // entries for this region in other remsets.
245 void clear();
246
247 // Forget any entries due to pointers from "from_hr".
248 void clear_incoming_entry(HeapRegion* from_hr) {
249 _other_regions.clear_incoming_entry(from_hr);
250 }
251
252 #if 0
253 virtual void cleanup() = 0;
254 #endif
255
256 // Should be called from single-threaded code.
257 void init_for_par_iteration();
258 // Attempt to claim the region. Returns true iff this call caused an
259 // atomic transition from Unclaimed to Claimed.
260 bool claim_iter();
261 // Sets the iteration state to "complete".
262 void set_iter_complete();
263 // Returns "true" iff the region's iteration is complete.
264 bool iter_is_complete();
265
266 // Support for claiming blocks of cards during iteration
267 void set_iter_claimed(size_t x) { _iter_claimed = (jlong)x; }
268 size_t iter_claimed() const { return (size_t)_iter_claimed; }
269 // Claim the next block of cards
270 size_t iter_claimed_next(size_t step) {
271 size_t current, next;
272 do {
273 current = iter_claimed();
274 next = current + step;
275 } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);
276 return current;
277 }
278
279 // Initialize the given iterator to iterate over this rem set.
280 void init_iterator(HeapRegionRemSetIterator* iter) const;
281
282 #if 0
283 // Apply the "do_card" method to the start address of every card in the
284 // rem set. Returns false if some application of the closure aborted.
285 virtual bool card_iterate(CardClosure* iter) = 0;
286 #endif
287
288 // The actual # of bytes this hr_remset takes up.
289 size_t mem_size() {
290 return _other_regions.mem_size()
291 // This correction is necessary because the above includes the second
292 // part.
293 + sizeof(this) - sizeof(OtherRegionsTable);
294 }
295
296 // Returns the memory occupancy of all static data structures associated
297 // with remembered sets.
298 static size_t static_mem_size() {
299 return OtherRegionsTable::static_mem_size();
300 }
301
302 // Returns the memory occupancy of all free_list data structures associated
303 // with remembered sets.
304 static size_t fl_mem_size() {
305 return OtherRegionsTable::fl_mem_size();
306 }
307
308 bool contains_reference(OopOrNarrowOopStar from) const {
309 return _other_regions.contains_reference(from);
310 }
311 void print() const;
312
313 // Called during a stop-world phase to perform any deferred cleanups.
314 // The second version may be called by parallel threads after then finish
315 // collection work.
316 static void cleanup();
317 static void par_cleanup();
318
319 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
320 // (Uses it to initialize from_card_cache).
321 static void init_heap(size_t max_regions) {
322 OtherRegionsTable::init_from_card_cache(max_regions);
323 }
324
325 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
326 static void shrink_heap(size_t new_n_regs) {
327 OtherRegionsTable::shrink_from_card_cache(new_n_regs);
328 }
329
330 #ifndef PRODUCT
331 static void print_from_card_cache() {
332 OtherRegionsTable::print_from_card_cache();
333 }
334 #endif
335
336 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
337 static void print_recorded();
338 static void record_event(Event evnt);
339
340 // Run unit tests.
341 #ifndef PRODUCT
342 static void test();
343 #endif
344
345 };
346
347 class HeapRegionRemSetIterator : public CHeapObj {
348
349 // The region over which we're iterating.
350 const HeapRegionRemSet* _hrrs;
351
352 // Local caching of HRRS fields.
353 const BitMap* _coarse_map;
354 PosParPRT** _fine_grain_regions;
355
356 G1BlockOffsetSharedArray* _bosa;
357 G1CollectedHeap* _g1h;
358
359 // The number yielded since initialization.
360 size_t _n_yielded_fine;
361 size_t _n_yielded_coarse;
362 size_t _n_yielded_sparse;
363
364 // If true we're iterating over the coarse table; if false the fine
365 // table.
366 enum IterState {
367 Sparse,
368 Fine,
369 Coarse
370 };
371 IterState _is;
372
373 // In both kinds of iteration, heap offset of first card of current
374 // region.
375 size_t _cur_region_card_offset;
376 // Card offset within cur region.
377 size_t _cur_region_cur_card;
378
379 // Coarse table iteration fields:
380
381 // Current region index;
382 int _coarse_cur_region_index;
383 int _coarse_cur_region_cur_card;
384
385 bool coarse_has_next(size_t& card_index);
386
387 // Fine table iteration fields:
388
389 // Index of bucket-list we're working on.
390 int _fine_array_index;
391 // Per Region Table we're doing within current bucket list.
392 PosParPRT* _fine_cur_prt;
393
394 /* SparsePRT::*/ SparsePRTIter _sparse_iter;
395
396 void fine_find_next_non_null_prt();
397
398 bool fine_has_next();
399 bool fine_has_next(size_t& card_index);
400
401 public:
402 // We require an iterator to be initialized before use, so the
403 // constructor does little.
404 HeapRegionRemSetIterator();
405
406 void initialize(const HeapRegionRemSet* hrrs);
407
408 // If there remains one or more cards to be yielded, returns true and
409 // sets "card_index" to one of those cards (which is then considered
410 // yielded.) Otherwise, returns false (and leaves "card_index"
411 // undefined.)
412 bool has_next(size_t& card_index);
413
414 size_t n_yielded_fine() { return _n_yielded_fine; }
415 size_t n_yielded_coarse() { return _n_yielded_coarse; }
416 size_t n_yielded_sparse() { return _n_yielded_sparse; }
417 size_t n_yielded() {
418 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
419 }
420 };
421
422 #if 0
423 class CardClosure: public Closure {
424 public:
425 virtual void do_card(HeapWord* card_start) = 0;
426 };
427
428 #endif