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