1 /*
2 * Copyright (c) 2001, 2011, 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.
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23 */
24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
27
28 #include "gc_implementation/g1/sparsePRT.hpp"
29
30 // Remembered set for a heap region. Represent a set of "cards" that
31 // contain pointers into the owner heap region. Cards are defined somewhat
32 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
33
34 class G1CollectedHeap;
35 class G1BlockOffsetSharedArray;
36 class HeapRegion;
37 class HeapRegionRemSetIterator;
38 class PosParPRT;
39 class SparsePRT;
40
41 // Essentially a wrapper around SparsePRTCleanupTask. See
42 // sparsePRT.hpp for more details.
43 class HRRSCleanupTask : public SparsePRTCleanupTask {
44 };
45
46 // The "_coarse_map" is a bitmap with one bit for each region, where set
47 // bits indicate that the corresponding region may contain some pointer
48 // into the owning region.
49
50 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
51 // (PRTs), indicating regions for which we're keeping the RS as a set of
52 // cards. The strategy is to cap the size of the fine-grain table,
53 // deleting an entry and setting the corresponding coarse-grained bit when
54 // we would overflow this cap.
55
56 // We use a mixture of locking and lock-free techniques here. We allow
57 // threads to locate PRTs without locking, but threads attempting to alter
58 // a bucket list obtain a lock. This means that any failing attempt to
59 // find a PRT must be retried with the lock. It might seem dangerous that
60 // a read can find a PRT that is concurrently deleted. This is all right,
61 // because:
62 //
63 // 1) We only actually free PRT's at safe points (though we reuse them at
64 // other times).
65 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
66 // it's _coarse_map bit is set, so the that we were attempting to add
67 // is represented. If a deleted PRT is re-used, a thread adding a bit,
68 // thinking the PRT is for a different region, does no harm.
69
70 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
71 friend class HeapRegionRemSetIterator;
72
73 G1CollectedHeap* _g1h;
74 Mutex _m;
75 HeapRegion* _hr;
76
77 // These are protected by "_m".
78 BitMap _coarse_map;
79 size_t _n_coarse_entries;
80 static jint _n_coarsenings;
81
82 PosParPRT** _fine_grain_regions;
83 size_t _n_fine_entries;
84
85 #define SAMPLE_FOR_EVICTION 1
86 #if SAMPLE_FOR_EVICTION
87 size_t _fine_eviction_start;
88 static size_t _fine_eviction_stride;
89 static size_t _fine_eviction_sample_size;
90 #endif
91
92 SparsePRT _sparse_table;
93
94 // These are static after init.
95 static size_t _max_fine_entries;
96 static size_t _mod_max_fine_entries_mask;
97
98 // Requires "prt" to be the first element of the bucket list appropriate
99 // for "hr". If this list contains an entry for "hr", return it,
100 // otherwise return "NULL".
101 PosParPRT* find_region_table(size_t ind, HeapRegion* hr) const;
102
103 // Find, delete, and return a candidate PosParPRT, if any exists,
104 // adding the deleted region to the coarse bitmap. Requires the caller
105 // to hold _m, and the fine-grain table to be full.
106 PosParPRT* delete_region_table();
107
108 // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
109 // be the correct index for "hr"), delete it and return true; else return
110 // false.
111 bool del_single_region_table(size_t ind, HeapRegion* hr);
112
113 static jint _cache_probes;
114 static jint _cache_hits;
115
116 // Indexed by thread X heap region, to minimize thread contention.
117 static int** _from_card_cache;
118 static size_t _from_card_cache_max_regions;
119 static size_t _from_card_cache_mem_size;
120
121 public:
122 OtherRegionsTable(HeapRegion* hr);
123
124 HeapRegion* hr() const { return _hr; }
125
126 // For now. Could "expand" some tables in the future, so that this made
127 // sense.
128 void add_reference(OopOrNarrowOopStar from, int tid);
129
130 void add_reference(OopOrNarrowOopStar from) {
131 return add_reference(from, 0);
132 }
133
134 // Removes any entries shown by the given bitmaps to contain only dead
135 // objects.
136 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
137
138 // Not const because it takes a lock.
139 size_t occupied() const;
140 size_t occ_fine() const;
141 size_t occ_coarse() const;
142 size_t occ_sparse() const;
143
144 static jint n_coarsenings() { return _n_coarsenings; }
145
146 // Returns size in bytes.
147 // Not const because it takes a lock.
148 size_t mem_size() const;
149 static size_t static_mem_size();
150 static size_t fl_mem_size();
151
152 bool contains_reference(OopOrNarrowOopStar from) const;
153 bool contains_reference_locked(OopOrNarrowOopStar from) const;
154
155 void clear();
156
157 // Specifically clear the from_card_cache.
158 void clear_fcc();
159
160 // "from_hr" is being cleared; remove any entries from it.
161 void clear_incoming_entry(HeapRegion* from_hr);
162
163 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
164
165 // Declare the heap size (in # of regions) to the OtherRegionsTable.
166 // (Uses it to initialize from_card_cache).
167 static void init_from_card_cache(size_t max_regions);
168
169 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
170 // Make sure any entries for higher regions are invalid.
171 static void shrink_from_card_cache(size_t new_n_regs);
172
173 static void print_from_card_cache();
174 };
175
176 class HeapRegionRemSet : public CHeapObj {
177 friend class VMStructs;
178 friend class HeapRegionRemSetIterator;
179
180 public:
181 enum Event {
182 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
183 };
184
185 private:
186 G1BlockOffsetSharedArray* _bosa;
187 G1BlockOffsetSharedArray* bosa() const { return _bosa; }
188
189 OtherRegionsTable _other_regions;
190
191 enum ParIterState { Unclaimed, Claimed, Complete };
192 volatile ParIterState _iter_state;
193 volatile jlong _iter_claimed;
194
195 // Unused unless G1RecordHRRSOops is true.
196
197 static const int MaxRecorded = 1000000;
198 static OopOrNarrowOopStar* _recorded_oops;
199 static HeapWord** _recorded_cards;
200 static HeapRegion** _recorded_regions;
201 static int _n_recorded;
202
203 static const int MaxRecordedEvents = 1000;
204 static Event* _recorded_events;
205 static int* _recorded_event_index;
206 static int _n_recorded_events;
207
208 static void print_event(outputStream* str, Event evnt);
209
210 public:
211 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
212 HeapRegion* hr);
213
214 static int num_par_rem_sets();
215 static void setup_remset_size();
216
217 HeapRegion* hr() const {
218 return _other_regions.hr();
219 }
220
221 size_t occupied() const {
222 return _other_regions.occupied();
223 }
224 size_t occ_fine() const {
225 return _other_regions.occ_fine();
226 }
227 size_t occ_coarse() const {
228 return _other_regions.occ_coarse();
229 }
230 size_t occ_sparse() const {
231 return _other_regions.occ_sparse();
232 }
233
234 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
235
236 /* Used in the sequential case. Returns "true" iff this addition causes
237 the size limit to be reached. */
238 void add_reference(OopOrNarrowOopStar from) {
239 _other_regions.add_reference(from);
240 }
241
242 /* Used in the parallel case. Returns "true" iff this addition causes
243 the size limit to be reached. */
244 void add_reference(OopOrNarrowOopStar from, int tid) {
245 _other_regions.add_reference(from, tid);
246 }
247
248 // Removes any entries shown by the given bitmaps to contain only dead
249 // objects.
250 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
251
252 // The region is being reclaimed; clear its remset, and any mention of
253 // entries for this region in other remsets.
254 void clear();
255
256 // Forget any entries due to pointers from "from_hr".
257 void clear_incoming_entry(HeapRegion* from_hr) {
258 _other_regions.clear_incoming_entry(from_hr);
259 }
260
261 #if 0
262 virtual void cleanup() = 0;
263 #endif
264
265 // Attempt to claim the region. Returns true iff this call caused an
266 // atomic transition from Unclaimed to Claimed.
267 bool claim_iter();
268 // Sets the iteration state to "complete".
269 void set_iter_complete();
270 // Returns "true" iff the region's iteration is complete.
271 bool iter_is_complete();
272
273 // Support for claiming blocks of cards during iteration
274 size_t iter_claimed() const { return (size_t)_iter_claimed; }
275 // Claim the next block of cards
276 size_t iter_claimed_next(size_t step) {
277 size_t current, next;
278 do {
279 current = iter_claimed();
280 next = current + step;
281 } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);
282 return current;
283 }
284 void reset_for_par_iteration();
285
286 bool verify_ready_for_par_iteration() {
287 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
288 }
289
290 // Initialize the given iterator to iterate over this rem set.
291 void init_iterator(HeapRegionRemSetIterator* iter) const;
292
293 #if 0
294 // Apply the "do_card" method to the start address of every card in the
295 // rem set. Returns false if some application of the closure aborted.
296 virtual bool card_iterate(CardClosure* iter) = 0;
297 #endif
298
299 // The actual # of bytes this hr_remset takes up.
300 size_t mem_size() {
301 return _other_regions.mem_size()
302 // This correction is necessary because the above includes the second
303 // part.
304 + sizeof(this) - sizeof(OtherRegionsTable);
305 }
306
307 // Returns the memory occupancy of all static data structures associated
308 // with remembered sets.
309 static size_t static_mem_size() {
310 return OtherRegionsTable::static_mem_size();
311 }
312
313 // Returns the memory occupancy of all free_list data structures associated
314 // with remembered sets.
315 static size_t fl_mem_size() {
316 return OtherRegionsTable::fl_mem_size();
317 }
318
319 bool contains_reference(OopOrNarrowOopStar from) const {
320 return _other_regions.contains_reference(from);
321 }
322 void print() const;
323
324 // Called during a stop-world phase to perform any deferred cleanups.
325 // The second version may be called by parallel threads after then finish
326 // collection work.
327 static void cleanup();
328 static void par_cleanup();
329
330 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
331 // (Uses it to initialize from_card_cache).
332 static void init_heap(size_t max_regions) {
333 OtherRegionsTable::init_from_card_cache(max_regions);
334 }
335
336 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
337 static void shrink_heap(size_t new_n_regs) {
338 OtherRegionsTable::shrink_from_card_cache(new_n_regs);
339 }
340
341 #ifndef PRODUCT
342 static void print_from_card_cache() {
343 OtherRegionsTable::print_from_card_cache();
344 }
345 #endif
346
347 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
348 static void print_recorded();
349 static void record_event(Event evnt);
350
351 // These are wrappers for the similarly-named methods on
352 // SparsePRT. Look at sparsePRT.hpp for more details.
353 static void reset_for_cleanup_tasks();
354 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
355 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
356
357 // Run unit tests.
358 #ifndef PRODUCT
359 static void test();
360 #endif
361 };
362
363 class HeapRegionRemSetIterator : public CHeapObj {
364
365 // The region over which we're iterating.
366 const HeapRegionRemSet* _hrrs;
367
368 // Local caching of HRRS fields.
369 const BitMap* _coarse_map;
370 PosParPRT** _fine_grain_regions;
371
372 G1BlockOffsetSharedArray* _bosa;
373 G1CollectedHeap* _g1h;
374
375 // The number yielded since initialization.
376 size_t _n_yielded_fine;
377 size_t _n_yielded_coarse;
378 size_t _n_yielded_sparse;
379
380 // If true we're iterating over the coarse table; if false the fine
381 // table.
382 enum IterState {
383 Sparse,
384 Fine,
385 Coarse
386 };
387 IterState _is;
388
389 // In both kinds of iteration, heap offset of first card of current
390 // region.
391 size_t _cur_region_card_offset;
392 // Card offset within cur region.
393 size_t _cur_region_cur_card;
394
395 // Coarse table iteration fields:
396
397 // Current region index;
398 int _coarse_cur_region_index;
399 int _coarse_cur_region_cur_card;
400
401 bool coarse_has_next(size_t& card_index);
402
403 // Fine table iteration fields:
404
405 // Index of bucket-list we're working on.
406 int _fine_array_index;
407 // Per Region Table we're doing within current bucket list.
408 PosParPRT* _fine_cur_prt;
409
410 /* SparsePRT::*/ SparsePRTIter _sparse_iter;
411
412 void fine_find_next_non_null_prt();
413
414 bool fine_has_next();
415 bool fine_has_next(size_t& card_index);
416
417 public:
418 // We require an iterator to be initialized before use, so the
419 // constructor does little.
420 HeapRegionRemSetIterator();
421
422 void initialize(const HeapRegionRemSet* hrrs);
423
424 // If there remains one or more cards to be yielded, returns true and
425 // sets "card_index" to one of those cards (which is then considered
426 // yielded.) Otherwise, returns false (and leaves "card_index"
427 // undefined.)
428 bool has_next(size_t& card_index);
429
430 size_t n_yielded_fine() { return _n_yielded_fine; }
431 size_t n_yielded_coarse() { return _n_yielded_coarse; }
432 size_t n_yielded_sparse() { return _n_yielded_sparse; }
433 size_t n_yielded() {
434 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
435 }
436 };
437
438 #if 0
439 class CardClosure: public Closure {
440 public:
441 virtual void do_card(HeapWord* card_start) = 0;
442 };
443
444 #endif
445
446 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP