1 /*
2 * Copyright (c) 2001, 2014, 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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
27
28 #include "gc_implementation/g1/g1CodeCacheRemSet.hpp"
29 #include "gc_implementation/g1/sparsePRT.hpp"
30
31 // Remembered set for a heap region. Represent a set of "cards" that
32 // contain pointers into the owner heap region. Cards are defined somewhat
33 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
34
35 class G1CollectedHeap;
36 class G1BlockOffsetSharedArray;
37 class HeapRegion;
38 class HeapRegionRemSetIterator;
39 class PerRegionTable;
40 class SparsePRT;
41 class nmethod;
42
43 // Essentially a wrapper around SparsePRTCleanupTask. See
44 // sparsePRT.hpp for more details.
45 class HRRSCleanupTask : public SparsePRTCleanupTask {
46 };
47
48 // The "_coarse_map" is a bitmap with one bit for each region, where set
49 // bits indicate that the corresponding region may contain some pointer
50 // into the owning region.
51
52 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
53 // (PRTs), indicating regions for which we're keeping the RS as a set of
54 // cards. The strategy is to cap the size of the fine-grain table,
55 // deleting an entry and setting the corresponding coarse-grained bit when
56 // we would overflow this cap.
57
58 // We use a mixture of locking and lock-free techniques here. We allow
59 // threads to locate PRTs without locking, but threads attempting to alter
60 // a bucket list obtain a lock. This means that any failing attempt to
61 // find a PRT must be retried with the lock. It might seem dangerous that
62 // a read can find a PRT that is concurrently deleted. This is all right,
63 // because:
64 //
65 // 1) We only actually free PRT's at safe points (though we reuse them at
66 // other times).
67 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
68 // it's _coarse_map bit is set, so the that we were attempting to add
69 // is represented. If a deleted PRT is re-used, a thread adding a bit,
70 // thinking the PRT is for a different region, does no harm.
71
72 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
73 friend class HeapRegionRemSetIterator;
74
75 G1CollectedHeap* _g1h;
76 Mutex* _m;
77 HeapRegion* _hr;
78
79 // These are protected by "_m".
80 BitMap _coarse_map;
81 size_t _n_coarse_entries;
82 static jint _n_coarsenings;
83
84 PerRegionTable** _fine_grain_regions;
85 size_t _n_fine_entries;
86
87 // The fine grain remembered sets are doubly linked together using
88 // their 'next' and 'prev' fields.
89 // This allows fast bulk freeing of all the fine grain remembered
90 // set entries, and fast finding of all of them without iterating
91 // over the _fine_grain_regions table.
92 PerRegionTable * _first_all_fine_prts;
93 PerRegionTable * _last_all_fine_prts;
94
95 // Used to sample a subset of the fine grain PRTs to determine which
96 // PRT to evict and coarsen.
97 size_t _fine_eviction_start;
98 static size_t _fine_eviction_stride;
99 static size_t _fine_eviction_sample_size;
100
101 SparsePRT _sparse_table;
102
103 // These are static after init.
104 static size_t _max_fine_entries;
105 static size_t _mod_max_fine_entries_mask;
106
107 // Requires "prt" to be the first element of the bucket list appropriate
108 // for "hr". If this list contains an entry for "hr", return it,
109 // otherwise return "NULL".
110 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
111
112 // Find, delete, and return a candidate PerRegionTable, if any exists,
113 // adding the deleted region to the coarse bitmap. Requires the caller
114 // to hold _m, and the fine-grain table to be full.
115 PerRegionTable* delete_region_table();
116
117 // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
118 // be the correct index for "hr"), delete it and return true; else return
119 // false.
120 bool del_single_region_table(size_t ind, HeapRegion* hr);
121
122 // Indexed by thread X heap region, to minimize thread contention.
123 static int** _from_card_cache;
124 static size_t _from_card_cache_max_regions;
125 static size_t _from_card_cache_mem_size;
126
127 // link/add the given fine grain remembered set into the "all" list
128 void link_to_all(PerRegionTable * prt);
129 // unlink/remove the given fine grain remembered set into the "all" list
130 void unlink_from_all(PerRegionTable * prt);
131
132 public:
133 OtherRegionsTable(HeapRegion* hr, Mutex* m);
134
135 HeapRegion* hr() const { return _hr; }
136
137 // For now. Could "expand" some tables in the future, so that this made
138 // sense.
139 void add_reference(OopOrNarrowOopStar from, int tid);
140
141 // Removes any entries shown by the given bitmaps to contain only dead
142 // objects.
143 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
144
145 size_t occupied() const;
146 size_t occ_fine() const;
147 size_t occ_coarse() const;
148 size_t occ_sparse() const;
149
150 static jint n_coarsenings() { return _n_coarsenings; }
151
152 // Returns size in bytes.
153 // Not const because it takes a lock.
154 size_t mem_size() const;
155 static size_t static_mem_size();
156 static size_t fl_mem_size();
157
158 bool contains_reference(OopOrNarrowOopStar from) const;
159 bool contains_reference_locked(OopOrNarrowOopStar from) const;
160
161 void clear();
162 void clear_locked();
163
164 // Specifically clear the from_card_cache.
165 void clear_fcc();
166
167 // "from_hr" is being cleared; remove any entries from it.
168 void clear_incoming_entry(HeapRegion* from_hr);
169
170 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
171
172 // Declare the heap size (in # of regions) to the OtherRegionsTable.
173 // (Uses it to initialize from_card_cache).
174 static void init_from_card_cache(size_t max_regions);
175
176 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
177 // Make sure any entries for higher regions are invalid.
178 static void shrink_from_card_cache(size_t new_n_regs);
179
180 static void print_from_card_cache();
181 };
182
183 class HeapRegionRemSet : public CHeapObj<mtGC> {
184 friend class VMStructs;
185 friend class HeapRegionRemSetIterator;
186
187 public:
188 enum Event {
189 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
190 };
191
192 private:
193 G1BlockOffsetSharedArray* _bosa;
194 G1BlockOffsetSharedArray* bosa() const { return _bosa; }
195
196 // A set of code blobs (nmethods) whose code contains pointers into
197 // the region that owns this RSet.
198 G1CodeRootSet _code_roots;
199
200 Mutex _m;
201
202 OtherRegionsTable _other_regions;
203
204 enum ParIterState { Unclaimed, Claimed, Complete };
205 volatile ParIterState _iter_state;
206 volatile jlong _iter_claimed;
207
208 // Unused unless G1RecordHRRSOops is true.
209
210 static const int MaxRecorded = 1000000;
211 static OopOrNarrowOopStar* _recorded_oops;
212 static HeapWord** _recorded_cards;
213 static HeapRegion** _recorded_regions;
214 static int _n_recorded;
215
216 static const int MaxRecordedEvents = 1000;
217 static Event* _recorded_events;
218 static int* _recorded_event_index;
219 static int _n_recorded_events;
220
221 static void print_event(outputStream* str, Event evnt);
222
223 public:
224 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
225 HeapRegion* hr);
226
227 static int num_par_rem_sets();
228 static void setup_remset_size();
229
230 HeapRegion* hr() const {
231 return _other_regions.hr();
232 }
233
234 size_t occupied() {
235 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
236 return occupied_locked();
237 }
238 size_t occupied_locked() {
239 return _other_regions.occupied();
240 }
241 size_t occ_fine() const {
242 return _other_regions.occ_fine();
243 }
244 size_t occ_coarse() const {
245 return _other_regions.occ_coarse();
246 }
247 size_t occ_sparse() const {
248 return _other_regions.occ_sparse();
249 }
250
251 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
252
253 // Used in the sequential case.
254 void add_reference(OopOrNarrowOopStar from) {
255 _other_regions.add_reference(from, 0);
256 }
257
258 // Used in the parallel case.
259 void add_reference(OopOrNarrowOopStar from, int tid) {
260 _other_regions.add_reference(from, tid);
261 }
262
263 // Removes any entries shown by the given bitmaps to contain only dead
264 // objects.
265 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
266
267 // The region is being reclaimed; clear its remset, and any mention of
268 // entries for this region in other remsets.
269 void clear();
270 void clear_locked();
271
272 // Attempt to claim the region. Returns true iff this call caused an
273 // atomic transition from Unclaimed to Claimed.
274 bool claim_iter();
275 // Sets the iteration state to "complete".
276 void set_iter_complete();
277 // Returns "true" iff the region's iteration is complete.
278 bool iter_is_complete();
279
280 // Support for claiming blocks of cards during iteration
281 size_t iter_claimed() const { return (size_t)_iter_claimed; }
282 // Claim the next block of cards
283 size_t iter_claimed_next(size_t step) {
284 size_t current, next;
285 do {
286 current = iter_claimed();
287 next = current + step;
288 } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);
289 return current;
290 }
291 void reset_for_par_iteration();
292
293 bool verify_ready_for_par_iteration() {
294 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
295 }
296
297 // The actual # of bytes this hr_remset takes up.
298 // Note also includes the strong code root set.
299 size_t mem_size() {
300 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
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 + strong_code_roots_mem_size();
306 }
307
308 // Returns the memory occupancy of all static data structures associated
309 // with remembered sets.
310 static size_t static_mem_size() {
311 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
312 }
313
314 // Returns the memory occupancy of all free_list data structures associated
315 // with remembered sets.
316 static size_t fl_mem_size() {
317 return OtherRegionsTable::fl_mem_size() + G1CodeRootSet::fl_mem_size();
318 }
319
320 bool contains_reference(OopOrNarrowOopStar from) const {
321 return _other_regions.contains_reference(from);
322 }
323
324 // Routines for managing the list of code roots that point into
325 // the heap region that owns this RSet.
326 void add_strong_code_root(nmethod* nm);
327 void remove_strong_code_root(nmethod* nm);
328
329 // During a collection, migrate the successfully evacuated strong
330 // code roots that referenced into the region that owns this RSet
331 // to the RSets of the new regions that they now point into.
332 // Unsuccessfully evacuated code roots are not migrated.
333 void migrate_strong_code_roots();
334
335 // Applies blk->do_code_blob() to each of the entries in
336 // the strong code roots list
337 void strong_code_roots_do(CodeBlobClosure* blk) const;
338
339 // Returns the number of elements in the strong code roots list
340 size_t strong_code_roots_list_length() {
341 return _code_roots.length();
342 }
343
344 // Returns true if the strong code roots contains the given
345 // nmethod.
346 bool strong_code_roots_list_contains(nmethod* nm) {
347 return _code_roots.contains(nm);
348 }
349
350 // Returns the amount of memory, in bytes, currently
351 // consumed by the strong code roots.
352 size_t strong_code_roots_mem_size();
353
354 void print() PRODUCT_RETURN;
355
356 // Called during a stop-world phase to perform any deferred cleanups.
357 static void cleanup();
358
359 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
360 // (Uses it to initialize from_card_cache).
361 static void init_heap(uint max_regions) {
362 G1CodeRootSet::initialize();
363 OtherRegionsTable::init_from_card_cache((size_t) max_regions);
364 }
365
366 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
367 static void shrink_heap(uint new_n_regs) {
368 OtherRegionsTable::shrink_from_card_cache((size_t) new_n_regs);
369 }
370
371 #ifndef PRODUCT
372 static void print_from_card_cache() {
373 OtherRegionsTable::print_from_card_cache();
374 }
375 #endif
376
377 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
378 static void print_recorded();
379 static void record_event(Event evnt);
380
381 // These are wrappers for the similarly-named methods on
382 // SparsePRT. Look at sparsePRT.hpp for more details.
383 static void reset_for_cleanup_tasks();
384 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
385 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
386
387 // Run unit tests.
388 #ifndef PRODUCT
389 static void test_prt();
390 static void test();
391 #endif
392 };
393
394 class HeapRegionRemSetIterator : public StackObj {
395
396 // The region RSet over which we're iterating.
397 HeapRegionRemSet* _hrrs;
398
399 // Local caching of HRRS fields.
400 const BitMap* _coarse_map;
401 PerRegionTable** _fine_grain_regions;
402
403 G1BlockOffsetSharedArray* _bosa;
404 G1CollectedHeap* _g1h;
405
406 // The number yielded since initialization.
407 size_t _n_yielded_fine;
408 size_t _n_yielded_coarse;
409 size_t _n_yielded_sparse;
410
411 // Indicates what granularity of table that we're currently iterating over.
412 // We start iterating over the sparse table, progress to the fine grain
413 // table, and then finish with the coarse table.
414 // See HeapRegionRemSetIterator::has_next().
415 enum IterState {
416 Sparse,
417 Fine,
418 Coarse
419 };
420 IterState _is;
421
422 // In both kinds of iteration, heap offset of first card of current
423 // region.
424 size_t _cur_region_card_offset;
425 // Card offset within cur region.
426 size_t _cur_region_cur_card;
427
428 // Coarse table iteration fields:
429
430 // Current region index;
431 int _coarse_cur_region_index;
432 size_t _coarse_cur_region_cur_card;
433
434 bool coarse_has_next(size_t& card_index);
435
436 // Fine table iteration fields:
437
438 // Index of bucket-list we're working on.
439 int _fine_array_index;
440
441 // Per Region Table we're doing within current bucket list.
442 PerRegionTable* _fine_cur_prt;
443
444 /* SparsePRT::*/ SparsePRTIter _sparse_iter;
445
446 void fine_find_next_non_null_prt();
447
448 bool fine_has_next();
449 bool fine_has_next(size_t& card_index);
450
451 public:
452 // We require an iterator to be initialized before use, so the
453 // constructor does little.
454 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
455
456 // If there remains one or more cards to be yielded, returns true and
457 // sets "card_index" to one of those cards (which is then considered
458 // yielded.) Otherwise, returns false (and leaves "card_index"
459 // undefined.)
460 bool has_next(size_t& card_index);
461
462 size_t n_yielded_fine() { return _n_yielded_fine; }
463 size_t n_yielded_coarse() { return _n_yielded_coarse; }
464 size_t n_yielded_sparse() { return _n_yielded_sparse; }
465 size_t n_yielded() {
466 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
467 }
468 };
469
470 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP