1 /*
2 * Copyright (c) 2001, 2010, 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 *
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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
42 // The "_coarse_map" is a bitmap with one bit for each region, where set
43 // bits indicate that the corresponding region may contain some pointer
44 // into the owning region.
45
46 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
47 // (PRTs), indicating regions for which we're keeping the RS as a set of
48 // cards. The strategy is to cap the size of the fine-grain table,
49 // deleting an entry and setting the corresponding coarse-grained bit when
50 // we would overflow this cap.
51
52 // We use a mixture of locking and lock-free techniques here. We allow
53 // threads to locate PRTs without locking, but threads attempting to alter
54 // a bucket list obtain a lock. This means that any failing attempt to
55 // find a PRT must be retried with the lock. It might seem dangerous that
56 // a read can find a PRT that is concurrently deleted. This is all right,
57 // because:
58 //
59 // 1) We only actually free PRT's at safe points (though we reuse them at
60 // other times).
61 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
62 // it's _coarse_map bit is set, so the that we were attempting to add
63 // is represented. If a deleted PRT is re-used, a thread adding a bit,
64 // thinking the PRT is for a different region, does no harm.
65
66 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
67 friend class HeapRegionRemSetIterator;
68
69 G1CollectedHeap* _g1h;
70 Mutex _m;
71 HeapRegion* _hr;
72
73 // These are protected by "_m".
74 BitMap _coarse_map;
75 size_t _n_coarse_entries;
76 static jint _n_coarsenings;
77
78 PosParPRT** _fine_grain_regions;
79 size_t _n_fine_entries;
80
81 #define SAMPLE_FOR_EVICTION 1
82 #if SAMPLE_FOR_EVICTION
83 size_t _fine_eviction_start;
84 static size_t _fine_eviction_stride;
85 static size_t _fine_eviction_sample_size;
86 #endif
87
88 SparsePRT _sparse_table;
89
90 // These are static after init.
91 static size_t _max_fine_entries;
92 static size_t _mod_max_fine_entries_mask;
93
94 // Requires "prt" to be the first element of the bucket list appropriate
95 // for "hr". If this list contains an entry for "hr", return it,
96 // otherwise return "NULL".
97 PosParPRT* find_region_table(size_t ind, HeapRegion* hr) const;
98
99 // Find, delete, and return a candidate PosParPRT, if any exists,
100 // adding the deleted region to the coarse bitmap. Requires the caller
101 // to hold _m, and the fine-grain table to be full.
102 PosParPRT* delete_region_table();
103
104 // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
105 // be the correct index for "hr"), delete it and return true; else return
106 // false.
107 bool del_single_region_table(size_t ind, HeapRegion* hr);
108
109 static jint _cache_probes;
110 static jint _cache_hits;
111
112 // Indexed by thread X heap region, to minimize thread contention.
113 static int** _from_card_cache;
114 static size_t _from_card_cache_max_regions;
115 static size_t _from_card_cache_mem_size;
116
117 public:
118 OtherRegionsTable(HeapRegion* hr);
119
120 HeapRegion* hr() const { return _hr; }
121
122 // For now. Could "expand" some tables in the future, so that this made
123 // sense.
124 void add_reference(OopOrNarrowOopStar from, int tid);
125
126 void add_reference(OopOrNarrowOopStar from) {
127 return add_reference(from, 0);
128 }
129
130 // Removes any entries shown by the given bitmaps to contain only dead
131 // objects.
132 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
133
134 // Not const because it takes a lock.
135 size_t occupied() const;
136 size_t occ_fine() const;
137 size_t occ_coarse() const;
138 size_t occ_sparse() const;
139
140 static jint n_coarsenings() { return _n_coarsenings; }
141
142 // Returns size in bytes.
143 // Not const because it takes a lock.
144 size_t mem_size() const;
145 static size_t static_mem_size();
146 static size_t fl_mem_size();
147
148 bool contains_reference(OopOrNarrowOopStar from) const;
149 bool contains_reference_locked(OopOrNarrowOopStar from) const;
150
151 void clear();
152
153 // Specifically clear the from_card_cache.
154 void clear_fcc();
155
156 // "from_hr" is being cleared; remove any entries from it.
157 void clear_incoming_entry(HeapRegion* from_hr);
158
159 // Declare the heap size (in # of regions) to the OtherRegionsTable.
160 // (Uses it to initialize from_card_cache).
161 static void init_from_card_cache(size_t max_regions);
162
163 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
164 // Make sure any entries for higher regions are invalid.
165 static void shrink_from_card_cache(size_t new_n_regs);
166
167 static void print_from_card_cache();
168
169 };
170
171
172 class HeapRegionRemSet : public CHeapObj {
173 friend class VMStructs;
174 friend class HeapRegionRemSetIterator;
175
176 public:
177 enum Event {
178 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
179 };
180
181 private:
182 G1BlockOffsetSharedArray* _bosa;
183 G1BlockOffsetSharedArray* bosa() const { return _bosa; }
184
185 OtherRegionsTable _other_regions;
186
187 enum ParIterState { Unclaimed, Claimed, Complete };
188 volatile ParIterState _iter_state;
189 volatile jlong _iter_claimed;
190
191 // Unused unless G1RecordHRRSOops is true.
192
193 static const int MaxRecorded = 1000000;
194 static OopOrNarrowOopStar* _recorded_oops;
195 static HeapWord** _recorded_cards;
196 static HeapRegion** _recorded_regions;
197 static int _n_recorded;
198
199 static const int MaxRecordedEvents = 1000;
200 static Event* _recorded_events;
201 static int* _recorded_event_index;
202 static int _n_recorded_events;
203
204 static void print_event(outputStream* str, Event evnt);
205
206 public:
207 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
208 HeapRegion* hr);
209
210 static int num_par_rem_sets();
211 static void setup_remset_size();
212
213 HeapRegion* hr() const {
214 return _other_regions.hr();
215 }
216
217 size_t occupied() const {
218 return _other_regions.occupied();
219 }
220 size_t occ_fine() const {
221 return _other_regions.occ_fine();
222 }
223 size_t occ_coarse() const {
224 return _other_regions.occ_coarse();
225 }
226 size_t occ_sparse() const {
227 return _other_regions.occ_sparse();
228 }
229
230 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
231
232 /* Used in the sequential case. Returns "true" iff this addition causes
233 the size limit to be reached. */
234 void add_reference(OopOrNarrowOopStar from) {
235 _other_regions.add_reference(from);
236 }
237
238 /* Used in the parallel case. Returns "true" iff this addition causes
239 the size limit to be reached. */
240 void add_reference(OopOrNarrowOopStar from, int tid) {
241 _other_regions.add_reference(from, tid);
242 }
243
244 // Removes any entries shown by the given bitmaps to contain only dead
245 // objects.
246 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
247
248 // The region is being reclaimed; clear its remset, and any mention of
249 // entries for this region in other remsets.
250 void clear();
251
252 // Forget any entries due to pointers from "from_hr".
253 void clear_incoming_entry(HeapRegion* from_hr) {
254 _other_regions.clear_incoming_entry(from_hr);
255 }
256
257 #if 0
258 virtual void cleanup() = 0;
259 #endif
260
261 // Should be called from single-threaded code.
262 void init_for_par_iteration();
263 // Attempt to claim the region. Returns true iff this call caused an
264 // atomic transition from Unclaimed to Claimed.
265 bool claim_iter();
266 // Sets the iteration state to "complete".
267 void set_iter_complete();
268 // Returns "true" iff the region's iteration is complete.
269 bool iter_is_complete();
270
271 // Support for claiming blocks of cards during iteration
272 void set_iter_claimed(size_t x) { _iter_claimed = (jlong)x; }
273 size_t iter_claimed() const { return (size_t)_iter_claimed; }
274 // Claim the next block of cards
275 size_t iter_claimed_next(size_t step) {
276 size_t current, next;
277 do {
278 current = iter_claimed();
279 next = current + step;
280 } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);
281 return current;
282 }
283
284 // Initialize the given iterator to iterate over this rem set.
285 void init_iterator(HeapRegionRemSetIterator* iter) const;
286
287 #if 0
288 // Apply the "do_card" method to the start address of every card in the
289 // rem set. Returns false if some application of the closure aborted.
290 virtual bool card_iterate(CardClosure* iter) = 0;
291 #endif
292
293 // The actual # of bytes this hr_remset takes up.
294 size_t mem_size() {
295 return _other_regions.mem_size()
296 // This correction is necessary because the above includes the second
297 // part.
298 + sizeof(this) - sizeof(OtherRegionsTable);
299 }
300
301 // Returns the memory occupancy of all static data structures associated
302 // with remembered sets.
303 static size_t static_mem_size() {
304 return OtherRegionsTable::static_mem_size();
305 }
306
307 // Returns the memory occupancy of all free_list data structures associated
308 // with remembered sets.
309 static size_t fl_mem_size() {
310 return OtherRegionsTable::fl_mem_size();
311 }
312
313 bool contains_reference(OopOrNarrowOopStar from) const {
314 return _other_regions.contains_reference(from);
315 }
316 void print() const;
317
318 // Called during a stop-world phase to perform any deferred cleanups.
319 // The second version may be called by parallel threads after then finish
320 // collection work.
321 static void cleanup();
322 static void par_cleanup();
323
324 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
325 // (Uses it to initialize from_card_cache).
326 static void init_heap(size_t max_regions) {
327 OtherRegionsTable::init_from_card_cache(max_regions);
328 }
329
330 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
331 static void shrink_heap(size_t new_n_regs) {
332 OtherRegionsTable::shrink_from_card_cache(new_n_regs);
333 }
334
335 #ifndef PRODUCT
336 static void print_from_card_cache() {
337 OtherRegionsTable::print_from_card_cache();
338 }
339 #endif
340
341 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
342 static void print_recorded();
343 static void record_event(Event evnt);
344
345 // Run unit tests.
346 #ifndef PRODUCT
347 static void test();
348 #endif
349
350 };
351
352 class HeapRegionRemSetIterator : public CHeapObj {
353
354 // The region over which we're iterating.
355 const HeapRegionRemSet* _hrrs;
356
357 // Local caching of HRRS fields.
358 const BitMap* _coarse_map;
359 PosParPRT** _fine_grain_regions;
360
361 G1BlockOffsetSharedArray* _bosa;
362 G1CollectedHeap* _g1h;
363
364 // The number yielded since initialization.
365 size_t _n_yielded_fine;
366 size_t _n_yielded_coarse;
367 size_t _n_yielded_sparse;
368
369 // If true we're iterating over the coarse table; if false the fine
370 // table.
371 enum IterState {
372 Sparse,
373 Fine,
374 Coarse
375 };
376 IterState _is;
377
378 // In both kinds of iteration, heap offset of first card of current
379 // region.
380 size_t _cur_region_card_offset;
381 // Card offset within cur region.
382 size_t _cur_region_cur_card;
383
384 // Coarse table iteration fields:
385
386 // Current region index;
387 int _coarse_cur_region_index;
388 int _coarse_cur_region_cur_card;
389
390 bool coarse_has_next(size_t& card_index);
391
392 // Fine table iteration fields:
393
394 // Index of bucket-list we're working on.
395 int _fine_array_index;
396 // Per Region Table we're doing within current bucket list.
397 PosParPRT* _fine_cur_prt;
398
399 /* SparsePRT::*/ SparsePRTIter _sparse_iter;
400
401 void fine_find_next_non_null_prt();
402
403 bool fine_has_next();
404 bool fine_has_next(size_t& card_index);
405
406 public:
407 // We require an iterator to be initialized before use, so the
408 // constructor does little.
409 HeapRegionRemSetIterator();
410
411 void initialize(const HeapRegionRemSet* hrrs);
412
413 // If there remains one or more cards to be yielded, returns true and
414 // sets "card_index" to one of those cards (which is then considered
415 // yielded.) Otherwise, returns false (and leaves "card_index"
416 // undefined.)
417 bool has_next(size_t& card_index);
418
419 size_t n_yielded_fine() { return _n_yielded_fine; }
420 size_t n_yielded_coarse() { return _n_yielded_coarse; }
421 size_t n_yielded_sparse() { return _n_yielded_sparse; }
422 size_t n_yielded() {
423 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
424 }
425 };
426
427 #if 0
428 class CardClosure: public Closure {
429 public:
430 virtual void do_card(HeapWord* card_start) = 0;
431 };
432
433 #endif
434
435 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP