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.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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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).
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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 FromCardCache remembers the most recently processed card on the heap on
49 // a per-region and per-thread basis.
50 class FromCardCache : public AllStatic {
51 private:
52 // Array of card indices. Indexed by thread X and heap region to minimize
53 // thread contention.
54 static int** _cache;
55 static uint _max_regions;
56 static size_t _static_mem_size;
57
58 public:
59 enum {
60 InvalidCard = -1 // Card value of an invalid card, i.e. a card index not otherwise used.
61 };
62
63 static void clear(uint region_idx);
64
65 // Returns true if the given card is in the cache at the given location, or
66 // replaces the card at that location and returns false.
67 static bool contains_or_replace(uint worker_id, uint region_idx, int card) {
68 int card_in_cache = at(worker_id, region_idx);
69 if (card_in_cache == card) {
70 return true;
71 } else {
72 set(worker_id, region_idx, card);
73 return false;
74 }
75 }
76
77 static int at(uint worker_id, uint region_idx) {
78 return _cache[worker_id][region_idx];
79 }
80
81 static void set(uint worker_id, uint region_idx, int val) {
82 _cache[worker_id][region_idx] = val;
83 }
84
85 static void initialize(uint n_par_rs, uint max_num_regions);
86
87 static void shrink(uint new_num_regions);
88
89 static void print(outputStream* out = gclog_or_tty) PRODUCT_RETURN;
90
91 static size_t static_mem_size() {
92 return _static_mem_size;
93 }
94 };
95
96 // The "_coarse_map" is a bitmap with one bit for each region, where set
97 // bits indicate that the corresponding region may contain some pointer
98 // into the owning region.
99
100 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
101 // (PRTs), indicating regions for which we're keeping the RS as a set of
102 // cards. The strategy is to cap the size of the fine-grain table,
103 // deleting an entry and setting the corresponding coarse-grained bit when
104 // we would overflow this cap.
105
106 // We use a mixture of locking and lock-free techniques here. We allow
107 // threads to locate PRTs without locking, but threads attempting to alter
108 // a bucket list obtain a lock. This means that any failing attempt to
109 // find a PRT must be retried with the lock. It might seem dangerous that
110 // a read can find a PRT that is concurrently deleted. This is all right,
111 // because:
112 //
113 // 1) We only actually free PRT's at safe points (though we reuse them at
114 // other times).
115 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
116 // it's _coarse_map bit is set, so the that we were attempting to add
117 // is represented. If a deleted PRT is re-used, a thread adding a bit,
118 // thinking the PRT is for a different region, does no harm.
119
120 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
121 friend class HeapRegionRemSetIterator;
122
123 G1CollectedHeap* _g1h;
124 Mutex* _m;
125 HeapRegion* _hr;
126
127 // These are protected by "_m".
128 BitMap _coarse_map;
129 size_t _n_coarse_entries;
130 static jint _n_coarsenings;
131
132 PerRegionTable** _fine_grain_regions;
133 size_t _n_fine_entries;
134
135 // The fine grain remembered sets are doubly linked together using
136 // their 'next' and 'prev' fields.
137 // This allows fast bulk freeing of all the fine grain remembered
138 // set entries, and fast finding of all of them without iterating
139 // over the _fine_grain_regions table.
140 PerRegionTable * _first_all_fine_prts;
141 PerRegionTable * _last_all_fine_prts;
142
143 // Used to sample a subset of the fine grain PRTs to determine which
144 // PRT to evict and coarsen.
145 size_t _fine_eviction_start;
146 static size_t _fine_eviction_stride;
147 static size_t _fine_eviction_sample_size;
148
149 SparsePRT _sparse_table;
150
151 // These are static after init.
152 static size_t _max_fine_entries;
153 static size_t _mod_max_fine_entries_mask;
154
155 // Requires "prt" to be the first element of the bucket list appropriate
156 // for "hr". If this list contains an entry for "hr", return it,
157 // otherwise return "NULL".
158 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
159
160 // Find, delete, and return a candidate PerRegionTable, if any exists,
161 // adding the deleted region to the coarse bitmap. Requires the caller
162 // to hold _m, and the fine-grain table to be full.
163 PerRegionTable* delete_region_table();
164
165 // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
166 // be the correct index for "hr"), delete it and return true; else return
167 // false.
168 bool del_single_region_table(size_t ind, HeapRegion* hr);
169
170 // link/add the given fine grain remembered set into the "all" list
171 void link_to_all(PerRegionTable * prt);
172 // unlink/remove the given fine grain remembered set into the "all" list
173 void unlink_from_all(PerRegionTable * prt);
174
175 public:
176 OtherRegionsTable(HeapRegion* hr, Mutex* m);
177
178 HeapRegion* hr() const { return _hr; }
179
180 // For now. Could "expand" some tables in the future, so that this made
181 // sense.
182 void add_reference(OopOrNarrowOopStar from, int tid);
183
184 // Removes any entries shown by the given bitmaps to contain only dead
185 // objects.
186 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
187
188 size_t occupied() const;
189 size_t occ_fine() const;
190 size_t occ_coarse() const;
191 size_t occ_sparse() const;
192
193 static jint n_coarsenings() { return _n_coarsenings; }
194
195 // Returns size in bytes.
196 // Not const because it takes a lock.
197 size_t mem_size() const;
198 static size_t static_mem_size();
199 static size_t fl_mem_size();
200
201 bool contains_reference(OopOrNarrowOopStar from) const;
202 bool contains_reference_locked(OopOrNarrowOopStar from) const;
203
204 void clear();
205
206 // Specifically clear the from_card_cache.
207 void clear_fcc();
208
209 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
210
211 // Declare the heap size (in # of regions) to the OtherRegionsTable.
212 // (Uses it to initialize from_card_cache).
213 static void init_from_card_cache(uint max_regions);
214
215 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
216 // Make sure any entries for higher regions are invalid.
217 static void shrink_from_card_cache(uint new_num_regions);
218
219 static void print_from_card_cache();
220 };
221
222 class HeapRegionRemSet : public CHeapObj<mtGC> {
223 friend class VMStructs;
224 friend class HeapRegionRemSetIterator;
225
226 public:
227 enum Event {
228 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
229 };
230
231 private:
232 G1BlockOffsetSharedArray* _bosa;
233 G1BlockOffsetSharedArray* bosa() const { return _bosa; }
234
235 // A set of code blobs (nmethods) whose code contains pointers into
236 // the region that owns this RSet.
237 G1CodeRootSet _code_roots;
238
239 Mutex _m;
240
241 OtherRegionsTable _other_regions;
242
243 enum ParIterState { Unclaimed, Claimed, Complete };
244 volatile ParIterState _iter_state;
245 volatile jlong _iter_claimed;
246
247 // Unused unless G1RecordHRRSOops is true.
248
249 static const int MaxRecorded = 1000000;
250 static OopOrNarrowOopStar* _recorded_oops;
251 static HeapWord** _recorded_cards;
252 static HeapRegion** _recorded_regions;
253 static int _n_recorded;
254
255 static const int MaxRecordedEvents = 1000;
256 static Event* _recorded_events;
257 static int* _recorded_event_index;
258 static int _n_recorded_events;
259
260 static void print_event(outputStream* str, Event evnt);
261
262 public:
263 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa, HeapRegion* hr);
264
265 static uint num_par_rem_sets();
266 static void setup_remset_size();
267
268 HeapRegion* hr() const {
269 return _other_regions.hr();
270 }
271
272 size_t occupied() {
273 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
274 return occupied_locked();
275 }
276 size_t occupied_locked() {
277 return _other_regions.occupied();
278 }
279 size_t occ_fine() const {
280 return _other_regions.occ_fine();
281 }
282 size_t occ_coarse() const {
283 return _other_regions.occ_coarse();
284 }
285 size_t occ_sparse() const {
286 return _other_regions.occ_sparse();
287 }
288
289 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
290
291 // Used in the sequential case.
292 void add_reference(OopOrNarrowOopStar from) {
293 _other_regions.add_reference(from, 0);
294 }
295
296 // Used in the parallel case.
297 void add_reference(OopOrNarrowOopStar from, int tid) {
298 _other_regions.add_reference(from, tid);
299 }
300
301 // Removes any entries shown by the given bitmaps to contain only dead
302 // objects.
303 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
304
305 // The region is being reclaimed; clear its remset, and any mention of
306 // entries for this region in other remsets.
307 void clear();
308 void clear_locked();
309
310 // Attempt to claim the region. Returns true iff this call caused an
311 // atomic transition from Unclaimed to Claimed.
312 bool claim_iter();
313 // Sets the iteration state to "complete".
314 void set_iter_complete();
315 // Returns "true" iff the region's iteration is complete.
316 bool iter_is_complete();
317
318 // Support for claiming blocks of cards during iteration
319 size_t iter_claimed() const { return (size_t)_iter_claimed; }
320 // Claim the next block of cards
321 size_t iter_claimed_next(size_t step) {
322 size_t current, next;
323 do {
324 current = iter_claimed();
325 next = current + step;
326 } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);
327 return current;
328 }
329 void reset_for_par_iteration();
330
331 bool verify_ready_for_par_iteration() {
332 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
333 }
334
335 // The actual # of bytes this hr_remset takes up.
336 // Note also includes the strong code root set.
337 size_t mem_size() {
338 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
339 return _other_regions.mem_size()
340 // This correction is necessary because the above includes the second
341 // part.
342 + (sizeof(this) - sizeof(OtherRegionsTable))
343 + strong_code_roots_mem_size();
344 }
345
346 // Returns the memory occupancy of all static data structures associated
347 // with remembered sets.
348 static size_t static_mem_size() {
349 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
350 }
351
352 // Returns the memory occupancy of all free_list data structures associated
353 // with remembered sets.
354 static size_t fl_mem_size() {
355 return OtherRegionsTable::fl_mem_size() + G1CodeRootSet::free_chunks_mem_size();
356 }
357
358 bool contains_reference(OopOrNarrowOopStar from) const {
359 return _other_regions.contains_reference(from);
360 }
361
362 // Routines for managing the list of code roots that point into
363 // the heap region that owns this RSet.
364 void add_strong_code_root(nmethod* nm);
365 void remove_strong_code_root(nmethod* nm);
366
367 // During a collection, migrate the successfully evacuated strong
368 // code roots that referenced into the region that owns this RSet
369 // to the RSets of the new regions that they now point into.
370 // Unsuccessfully evacuated code roots are not migrated.
371 void migrate_strong_code_roots();
372
373 // Applies blk->do_code_blob() to each of the entries in
374 // the strong code roots list
375 void strong_code_roots_do(CodeBlobClosure* blk) const;
376
377 // Returns the number of elements in the strong code roots list
378 size_t strong_code_roots_list_length() {
379 return _code_roots.length();
380 }
381
382 // Returns true if the strong code roots contains the given
383 // nmethod.
384 bool strong_code_roots_list_contains(nmethod* nm) {
385 return _code_roots.contains(nm);
386 }
387
388 // Returns the amount of memory, in bytes, currently
389 // consumed by the strong code roots.
390 size_t strong_code_roots_mem_size();
391
392 void print() PRODUCT_RETURN;
393
394 // Called during a stop-world phase to perform any deferred cleanups.
395 static void cleanup();
396
397 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
398 // (Uses it to initialize from_card_cache).
399 static void init_heap(uint max_regions) {
400 OtherRegionsTable::init_from_card_cache(max_regions);
401 }
402
403 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
404 static void shrink_heap(uint new_n_regs) {
405 OtherRegionsTable::shrink_from_card_cache(new_n_regs);
406 }
407
408 #ifndef PRODUCT
409 static void print_from_card_cache() {
410 OtherRegionsTable::print_from_card_cache();
411 }
412 #endif
413
414 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
415 static void print_recorded();
416 static void record_event(Event evnt);
417
418 // These are wrappers for the similarly-named methods on
419 // SparsePRT. Look at sparsePRT.hpp for more details.
420 static void reset_for_cleanup_tasks();
421 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
422 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
423
424 // Run unit tests.
425 #ifndef PRODUCT
426 static void test_prt();
427 static void test();
428 #endif
429 };
430
431 class HeapRegionRemSetIterator : public StackObj {
432 private:
433 // The region RSet over which we are iterating.
434 HeapRegionRemSet* _hrrs;
435
436 // Local caching of HRRS fields.
437 const BitMap* _coarse_map;
438
439 G1BlockOffsetSharedArray* _bosa;
440 G1CollectedHeap* _g1h;
441
442 // The number of cards yielded since initialization.
443 size_t _n_yielded_fine;
444 size_t _n_yielded_coarse;
445 size_t _n_yielded_sparse;
446
447 // Indicates what granularity of table that we are currently iterating over.
448 // We start iterating over the sparse table, progress to the fine grain
449 // table, and then finish with the coarse table.
450 enum IterState {
451 Sparse,
452 Fine,
453 Coarse
454 };
455 IterState _is;
456
457 // For both Coarse and Fine remembered set iteration this contains the
458 // first card number of the heap region we currently iterate over.
459 size_t _cur_region_card_offset;
460
461 // Current region index for the Coarse remembered set iteration.
462 int _coarse_cur_region_index;
463 size_t _coarse_cur_region_cur_card;
464
465 bool coarse_has_next(size_t& card_index);
466
467 // The PRT we are currently iterating over.
468 PerRegionTable* _fine_cur_prt;
469 // Card offset within the current PRT.
470 size_t _cur_card_in_prt;
471
472 // Update internal variables when switching to the given PRT.
473 void switch_to_prt(PerRegionTable* prt);
474 bool fine_has_next();
475 bool fine_has_next(size_t& card_index);
476
477 // The Sparse remembered set iterator.
478 SparsePRTIter _sparse_iter;
479
480 public:
481 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
482
483 // If there remains one or more cards to be yielded, returns true and
484 // sets "card_index" to one of those cards (which is then considered
485 // yielded.) Otherwise, returns false (and leaves "card_index"
486 // undefined.)
487 bool has_next(size_t& card_index);
488
489 size_t n_yielded_fine() { return _n_yielded_fine; }
490 size_t n_yielded_coarse() { return _n_yielded_coarse; }
491 size_t n_yielded_sparse() { return _n_yielded_sparse; }
492 size_t n_yielded() {
493 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
494 }
495 };
496
497 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP