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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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).
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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/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
163 // Specifically clear the from_card_cache.
164 void clear_fcc();
165
166 // "from_hr" is being cleared; remove any entries from it.
167 void clear_incoming_entry(HeapRegion* from_hr);
168
169 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
170
171 // Declare the heap size (in # of regions) to the OtherRegionsTable.
172 // (Uses it to initialize from_card_cache).
173 static void init_from_card_cache(size_t max_regions);
174
175 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
176 // Make sure any entries for higher regions are invalid.
177 static void shrink_from_card_cache(size_t new_n_regs);
178
179 static void print_from_card_cache();
180 };
181
182 class HeapRegionRemSet : public CHeapObj<mtGC> {
183 friend class VMStructs;
184 friend class HeapRegionRemSetIterator;
185
186 public:
187 enum Event {
188 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
189 };
190
191 private:
192 G1BlockOffsetSharedArray* _bosa;
193 G1BlockOffsetSharedArray* bosa() const { return _bosa; }
194
195 // A set of code blobs (nmethods) whose code contains pointers into
196 // the region that owns this RSet.
197 G1CodeRootSet _code_roots;
198
199 Mutex _m;
200
201 OtherRegionsTable _other_regions;
202
203 enum ParIterState { Unclaimed, Claimed, Complete };
204 volatile ParIterState _iter_state;
205 volatile jlong _iter_claimed;
206
207 // Unused unless G1RecordHRRSOops is true.
208
209 static const int MaxRecorded = 1000000;
210 static OopOrNarrowOopStar* _recorded_oops;
211 static HeapWord** _recorded_cards;
212 static HeapRegion** _recorded_regions;
213 static int _n_recorded;
214
215 static const int MaxRecordedEvents = 1000;
216 static Event* _recorded_events;
217 static int* _recorded_event_index;
218 static int _n_recorded_events;
219
220 static void print_event(outputStream* str, Event evnt);
221
222 public:
223 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa, HeapRegion* hr);
224
225 static int num_par_rem_sets();
226 static void setup_remset_size();
227
228 HeapRegion* hr() const {
229 return _other_regions.hr();
230 }
231
232 size_t occupied() {
233 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
234 return occupied_locked();
235 }
236 size_t occupied_locked() {
237 return _other_regions.occupied();
238 }
239 size_t occ_fine() const {
240 return _other_regions.occ_fine();
241 }
242 size_t occ_coarse() const {
243 return _other_regions.occ_coarse();
244 }
245 size_t occ_sparse() const {
246 return _other_regions.occ_sparse();
247 }
248
249 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
250
251 // Used in the sequential case.
252 void add_reference(OopOrNarrowOopStar from) {
253 _other_regions.add_reference(from, 0);
254 }
255
256 // Used in the parallel case.
257 void add_reference(OopOrNarrowOopStar from, int tid) {
258 _other_regions.add_reference(from, tid);
259 }
260
261 // Removes any entries shown by the given bitmaps to contain only dead
262 // objects.
263 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
264
265 // The region is being reclaimed; clear its remset, and any mention of
266 // entries for this region in other remsets.
267 void clear();
268 void clear_locked();
269
270 // Attempt to claim the region. Returns true iff this call caused an
271 // atomic transition from Unclaimed to Claimed.
272 bool claim_iter();
273 // Sets the iteration state to "complete".
274 void set_iter_complete();
275 // Returns "true" iff the region's iteration is complete.
276 bool iter_is_complete();
277
278 // Support for claiming blocks of cards during iteration
279 size_t iter_claimed() const { return (size_t)_iter_claimed; }
280 // Claim the next block of cards
281 size_t iter_claimed_next(size_t step) {
282 size_t current, next;
283 do {
284 current = iter_claimed();
285 next = current + step;
286 } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);
287 return current;
288 }
289 void reset_for_par_iteration();
290
291 bool verify_ready_for_par_iteration() {
292 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
293 }
294
295 // The actual # of bytes this hr_remset takes up.
296 // Note also includes the strong code root set.
297 size_t mem_size() {
298 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
299 return _other_regions.mem_size()
300 // This correction is necessary because the above includes the second
301 // part.
302 + (sizeof(this) - sizeof(OtherRegionsTable))
303 + strong_code_roots_mem_size();
304 }
305
306 // Returns the memory occupancy of all static data structures associated
307 // with remembered sets.
308 static size_t static_mem_size() {
309 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
310 }
311
312 // Returns the memory occupancy of all free_list data structures associated
313 // with remembered sets.
314 static size_t fl_mem_size() {
315 return OtherRegionsTable::fl_mem_size() + G1CodeRootSet::fl_mem_size();
316 }
317
318 bool contains_reference(OopOrNarrowOopStar from) const {
319 return _other_regions.contains_reference(from);
320 }
321
322 // Routines for managing the list of code roots that point into
323 // the heap region that owns this RSet.
324 void add_strong_code_root(nmethod* nm);
325 void remove_strong_code_root(nmethod* nm);
326
327 // During a collection, migrate the successfully evacuated strong
328 // code roots that referenced into the region that owns this RSet
329 // to the RSets of the new regions that they now point into.
330 // Unsuccessfully evacuated code roots are not migrated.
331 void migrate_strong_code_roots();
332
333 // Applies blk->do_code_blob() to each of the entries in
334 // the strong code roots list
335 void strong_code_roots_do(CodeBlobClosure* blk) const;
336
337 // Returns the number of elements in the strong code roots list
338 size_t strong_code_roots_list_length() {
339 return _code_roots.length();
340 }
341
342 // Returns true if the strong code roots contains the given
343 // nmethod.
344 bool strong_code_roots_list_contains(nmethod* nm) {
345 return _code_roots.contains(nm);
346 }
347
348 // Returns the amount of memory, in bytes, currently
349 // consumed by the strong code roots.
350 size_t strong_code_roots_mem_size();
351
352 void print() PRODUCT_RETURN;
353
354 // Called during a stop-world phase to perform any deferred cleanups.
355 static void cleanup();
356
357 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
358 // (Uses it to initialize from_card_cache).
359 static void init_heap(uint max_regions) {
360 G1CodeRootSet::initialize();
361 OtherRegionsTable::init_from_card_cache((size_t) max_regions);
362 }
363
364 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
365 static void shrink_heap(uint new_n_regs) {
366 OtherRegionsTable::shrink_from_card_cache((size_t) new_n_regs);
367 }
368
369 #ifndef PRODUCT
370 static void print_from_card_cache() {
371 OtherRegionsTable::print_from_card_cache();
372 }
373 #endif
374
375 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
376 static void print_recorded();
377 static void record_event(Event evnt);
378
379 // These are wrappers for the similarly-named methods on
380 // SparsePRT. Look at sparsePRT.hpp for more details.
381 static void reset_for_cleanup_tasks();
382 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
383 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
384
385 // Run unit tests.
386 #ifndef PRODUCT
387 static void test_prt();
388 static void test();
389 #endif
390 };
391
392 class HeapRegionRemSetIterator : public StackObj {
393
394 // The region RSet over which we're iterating.
395 HeapRegionRemSet* _hrrs;
396
397 // Local caching of HRRS fields.
398 const BitMap* _coarse_map;
399 PerRegionTable** _fine_grain_regions;
400
401 G1BlockOffsetSharedArray* _bosa;
402 G1CollectedHeap* _g1h;
403
404 // The number yielded since initialization.
405 size_t _n_yielded_fine;
406 size_t _n_yielded_coarse;
407 size_t _n_yielded_sparse;
408
409 // Indicates what granularity of table that we're currently iterating over.
410 // We start iterating over the sparse table, progress to the fine grain
411 // table, and then finish with the coarse table.
412 // See HeapRegionRemSetIterator::has_next().
413 enum IterState {
414 Sparse,
415 Fine,
416 Coarse
417 };
418 IterState _is;
419
420 // In both kinds of iteration, heap offset of first card of current
421 // region.
422 size_t _cur_region_card_offset;
423 // Card offset within cur region.
424 size_t _cur_region_cur_card;
425
426 // Coarse table iteration fields:
427
428 // Current region index;
429 int _coarse_cur_region_index;
430 size_t _coarse_cur_region_cur_card;
431
432 bool coarse_has_next(size_t& card_index);
433
434 // Fine table iteration fields:
435
436 // Index of bucket-list we're working on.
437 int _fine_array_index;
438
439 // Per Region Table we're doing within current bucket list.
440 PerRegionTable* _fine_cur_prt;
441
442 /* SparsePRT::*/ SparsePRTIter _sparse_iter;
443
444 void fine_find_next_non_null_prt();
445
446 bool fine_has_next();
447 bool fine_has_next(size_t& card_index);
448
449 public:
450 // We require an iterator to be initialized before use, so the
451 // constructor does little.
452 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
453
454 // If there remains one or more cards to be yielded, returns true and
455 // sets "card_index" to one of those cards (which is then considered
456 // yielded.) Otherwise, returns false (and leaves "card_index"
457 // undefined.)
458 bool has_next(size_t& card_index);
459
460 size_t n_yielded_fine() { return _n_yielded_fine; }
461 size_t n_yielded_coarse() { return _n_yielded_coarse; }
462 size_t n_yielded_sparse() { return _n_yielded_sparse; }
463 size_t n_yielded() {
464 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
465 }
466 };
467
468 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP