1 /*
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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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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 PerRegionTable;
39 class SparsePRT;
40 class nmethod;
41
42 // Essentially a wrapper around SparsePRTCleanupTask. See
43 // sparsePRT.hpp for more details.
44 class HRRSCleanupTask : public SparsePRTCleanupTask {
45 };
46
47 // The "_coarse_map" is a bitmap with one bit for each region, where set
48 // bits indicate that the corresponding region may contain some pointer
49 // into the owning region.
50
51 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
52 // (PRTs), indicating regions for which we're keeping the RS as a set of
53 // cards. The strategy is to cap the size of the fine-grain table,
54 // deleting an entry and setting the corresponding coarse-grained bit when
55 // we would overflow this cap.
56
57 // We use a mixture of locking and lock-free techniques here. We allow
58 // threads to locate PRTs without locking, but threads attempting to alter
59 // a bucket list obtain a lock. This means that any failing attempt to
60 // find a PRT must be retried with the lock. It might seem dangerous that
61 // a read can find a PRT that is concurrently deleted. This is all right,
62 // because:
63 //
64 // 1) We only actually free PRT's at safe points (though we reuse them at
65 // other times).
66 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
67 // it's _coarse_map bit is set, so the that we were attempting to add
68 // is represented. If a deleted PRT is re-used, a thread adding a bit,
69 // thinking the PRT is for a different region, does no harm.
70
71 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
72 friend class HeapRegionRemSetIterator;
73
74 G1CollectedHeap* _g1h;
75 Mutex _m;
76 HeapRegion* _hr;
77
78 // These are protected by "_m".
79 BitMap _coarse_map;
80 size_t _n_coarse_entries;
81 static jint _n_coarsenings;
82
83 PerRegionTable** _fine_grain_regions;
84 size_t _n_fine_entries;
85
86 // The fine grain remembered sets are doubly linked together using
87 // their 'next' and 'prev' fields.
88 // This allows fast bulk freeing of all the fine grain remembered
89 // set entries, and fast finding of all of them without iterating
90 // over the _fine_grain_regions table.
91 PerRegionTable * _first_all_fine_prts;
92 PerRegionTable * _last_all_fine_prts;
93
94 // Used to sample a subset of the fine grain PRTs to determine which
95 // PRT to evict and coarsen.
96 size_t _fine_eviction_start;
97 static size_t _fine_eviction_stride;
98 static size_t _fine_eviction_sample_size;
99
100 SparsePRT _sparse_table;
101
102 // These are static after init.
103 static size_t _max_fine_entries;
104 static size_t _mod_max_fine_entries_mask;
105
106 // Requires "prt" to be the first element of the bucket list appropriate
107 // for "hr". If this list contains an entry for "hr", return it,
108 // otherwise return "NULL".
109 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
110
111 // Find, delete, and return a candidate PerRegionTable, if any exists,
112 // adding the deleted region to the coarse bitmap. Requires the caller
113 // to hold _m, and the fine-grain table to be full.
114 PerRegionTable* delete_region_table();
115
116 // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
117 // be the correct index for "hr"), delete it and return true; else return
118 // false.
119 bool del_single_region_table(size_t ind, HeapRegion* hr);
120
121 // Indexed by thread X heap region, to minimize thread contention.
122 static int** _from_card_cache;
123 static size_t _from_card_cache_max_regions;
124 static size_t _from_card_cache_mem_size;
125
126 // link/add the given fine grain remembered set into the "all" list
127 void link_to_all(PerRegionTable * prt);
128 // unlink/remove the given fine grain remembered set into the "all" list
129 void unlink_from_all(PerRegionTable * prt);
130
131 public:
132 OtherRegionsTable(HeapRegion* hr);
133
134 HeapRegion* hr() const { return _hr; }
135
136 // For now. Could "expand" some tables in the future, so that this made
137 // sense.
138 void add_reference(OopOrNarrowOopStar from, int tid);
139
140 // Removes any entries shown by the given bitmaps to contain only dead
141 // objects.
142 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
143
144 // Not const because it takes a lock.
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 list of code blobs (nmethods) whose code contains pointers into
196 // the region that owns this RSet.
197 GrowableArray<nmethod*>* _strong_code_roots_list;
198
199 OtherRegionsTable _other_regions;
200
201 enum ParIterState { Unclaimed, Claimed, Complete };
202 volatile ParIterState _iter_state;
203 volatile jlong _iter_claimed;
204
205 // Unused unless G1RecordHRRSOops is true.
206
207 static const int MaxRecorded = 1000000;
208 static OopOrNarrowOopStar* _recorded_oops;
209 static HeapWord** _recorded_cards;
210 static HeapRegion** _recorded_regions;
211 static int _n_recorded;
212
213 static const int MaxRecordedEvents = 1000;
214 static Event* _recorded_events;
215 static int* _recorded_event_index;
216 static int _n_recorded_events;
217
218 static void print_event(outputStream* str, Event evnt);
219
220 public:
221 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
222 HeapRegion* hr);
223
224 static int num_par_rem_sets();
225 static void setup_remset_size();
226
227 HeapRegion* hr() const {
228 return _other_regions.hr();
229 }
230
231 size_t occupied() const {
232 return _other_regions.occupied();
233 }
234 size_t occ_fine() const {
235 return _other_regions.occ_fine();
236 }
237 size_t occ_coarse() const {
238 return _other_regions.occ_coarse();
239 }
240 size_t occ_sparse() const {
241 return _other_regions.occ_sparse();
242 }
243
244 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
245
246 // Used in the sequential case.
247 void add_reference(OopOrNarrowOopStar from) {
248 _other_regions.add_reference(from, 0);
249 }
250
251 // Used in the parallel case.
252 void add_reference(OopOrNarrowOopStar from, int tid) {
253 _other_regions.add_reference(from, tid);
254 }
255
256 // Removes any entries shown by the given bitmaps to contain only dead
257 // objects.
258 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
259
260 // The region is being reclaimed; clear its remset, and any mention of
261 // entries for this region in other remsets.
262 void clear();
263
264 // Attempt to claim the region. Returns true iff this call caused an
265 // atomic transition from Unclaimed to Claimed.
266 bool claim_iter();
267 // Sets the iteration state to "complete".
268 void set_iter_complete();
269 // Returns "true" iff the region's iteration is complete.
270 bool iter_is_complete();
271
272 // Support for claiming blocks of cards during iteration
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 void reset_for_par_iteration();
284
285 bool verify_ready_for_par_iteration() {
286 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
287 }
288
289 // The actual # of bytes this hr_remset takes up.
290 // Note also includes the strong code root set.
291 size_t mem_size() {
292 return _other_regions.mem_size()
293 // This correction is necessary because the above includes the second
294 // part.
295 + (sizeof(this) - sizeof(OtherRegionsTable))
296 + strong_code_roots_mem_size();
297 }
298
299 // Returns the memory occupancy of all static data structures associated
300 // with remembered sets.
301 static size_t static_mem_size() {
302 return OtherRegionsTable::static_mem_size();
303 }
304
305 // Returns the memory occupancy of all free_list data structures associated
306 // with remembered sets.
307 static size_t fl_mem_size() {
308 return OtherRegionsTable::fl_mem_size();
309 }
310
311 bool contains_reference(OopOrNarrowOopStar from) const {
312 return _other_regions.contains_reference(from);
313 }
314
315 // Routines for managing the list of code roots that point into
316 // the heap region that owns this RSet.
317 void add_strong_code_root(nmethod* nm);
318 void remove_strong_code_root(nmethod* nm);
319
320 // During a collection, migrate the successfully evacuated strong
321 // code roots that referenced into the region that owns this RSet
322 // to the RSets of the new regions that they now point into.
323 // Unsuccessfully evacuated code roots are not migrated.
324 void migrate_strong_code_roots();
325
326 // Applies blk->do_code_blob() to each of the entries in
327 // the strong code roots list
328 void strong_code_roots_do(CodeBlobClosure* blk) const;
329
330 // Returns the number of elements in the strong code roots list
331 int strong_code_roots_list_length() {
332 return _strong_code_roots_list->length();
333 }
334
335 // Returns true if the strong code roots contains the given
336 // nmethod.
337 bool strong_code_roots_list_contains(nmethod* nm) {
338 return _strong_code_roots_list->contains(nm);
339 }
340
341 // Returns the amount of memory, in bytes, currently
342 // consumed by the strong code roots.
343 size_t strong_code_roots_mem_size();
344
345 void print() const;
346
347 // Called during a stop-world phase to perform any deferred cleanups.
348 static void cleanup();
349
350 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
351 // (Uses it to initialize from_card_cache).
352 static void init_heap(uint max_regions) {
353 OtherRegionsTable::init_from_card_cache((size_t) max_regions);
354 }
355
356 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
357 static void shrink_heap(uint new_n_regs) {
358 OtherRegionsTable::shrink_from_card_cache((size_t) new_n_regs);
359 }
360
361 #ifndef PRODUCT
362 static void print_from_card_cache() {
363 OtherRegionsTable::print_from_card_cache();
364 }
365 #endif
366
367 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
368 static void print_recorded();
369 static void record_event(Event evnt);
370
371 // These are wrappers for the similarly-named methods on
372 // SparsePRT. Look at sparsePRT.hpp for more details.
373 static void reset_for_cleanup_tasks();
374 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
375 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
376
377 // Run unit tests.
378 #ifndef PRODUCT
379 static void test_prt();
380 static void test();
381 #endif
382 };
383
384 class HeapRegionRemSetIterator : public StackObj {
385
386 // The region RSet over which we're iterating.
387 const HeapRegionRemSet* _hrrs;
388
389 // Local caching of HRRS fields.
390 const BitMap* _coarse_map;
391 PerRegionTable** _fine_grain_regions;
392
393 G1BlockOffsetSharedArray* _bosa;
394 G1CollectedHeap* _g1h;
395
396 // The number yielded since initialization.
397 size_t _n_yielded_fine;
398 size_t _n_yielded_coarse;
399 size_t _n_yielded_sparse;
400
401 // Indicates what granularity of table that we're currently iterating over.
402 // We start iterating over the sparse table, progress to the fine grain
403 // table, and then finish with the coarse table.
404 // See HeapRegionRemSetIterator::has_next().
405 enum IterState {
406 Sparse,
407 Fine,
408 Coarse
409 };
410 IterState _is;
411
412 // In both kinds of iteration, heap offset of first card of current
413 // region.
414 size_t _cur_region_card_offset;
415 // Card offset within cur region.
416 size_t _cur_region_cur_card;
417
418 // Coarse table iteration fields:
419
420 // Current region index;
421 int _coarse_cur_region_index;
422 size_t _coarse_cur_region_cur_card;
423
424 bool coarse_has_next(size_t& card_index);
425
426 // Fine table iteration fields:
427
428 // Index of bucket-list we're working on.
429 int _fine_array_index;
430
431 // Per Region Table we're doing within current bucket list.
432 PerRegionTable* _fine_cur_prt;
433
434 /* SparsePRT::*/ SparsePRTIter _sparse_iter;
435
436 void fine_find_next_non_null_prt();
437
438 bool fine_has_next();
439 bool fine_has_next(size_t& card_index);
440
441 public:
442 // We require an iterator to be initialized before use, so the
443 // constructor does little.
444 HeapRegionRemSetIterator(const HeapRegionRemSet* hrrs);
445
446 // If there remains one or more cards to be yielded, returns true and
447 // sets "card_index" to one of those cards (which is then considered
448 // yielded.) Otherwise, returns false (and leaves "card_index"
449 // undefined.)
450 bool has_next(size_t& card_index);
451
452 size_t n_yielded_fine() { return _n_yielded_fine; }
453 size_t n_yielded_coarse() { return _n_yielded_coarse; }
454 size_t n_yielded_sparse() { return _n_yielded_sparse; }
455 size_t n_yielded() {
456 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
457 }
458 };
459
460 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP