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,
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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 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 // "from_hr" is being cleared; remove any entries from it.
210 void clear_incoming_entry(HeapRegion* from_hr);
211
212 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
213
214 // Declare the heap size (in # of regions) to the OtherRegionsTable.
215 // (Uses it to initialize from_card_cache).
216 static void init_from_card_cache(uint max_regions);
217
218 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
219 // Make sure any entries for higher regions are invalid.
220 static void shrink_from_card_cache(uint new_num_regions);
221
222 static void print_from_card_cache();
223 };
224
225 class HeapRegionRemSet : public CHeapObj<mtGC> {
226 friend class VMStructs;
227 friend class HeapRegionRemSetIterator;
228
229 public:
230 enum Event {
231 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
232 };
233
234 private:
235 G1BlockOffsetSharedArray* _bosa;
236 G1BlockOffsetSharedArray* bosa() const { return _bosa; }
237
238 // A set of code blobs (nmethods) whose code contains pointers into
239 // the region that owns this RSet.
240 G1CodeRootSet _code_roots;
241
242 Mutex _m;
243
244 OtherRegionsTable _other_regions;
245
246 enum ParIterState { Unclaimed, Claimed, Complete };
247 volatile ParIterState _iter_state;
248 volatile size_t _iter_claimed;
249
250 // Unused unless G1RecordHRRSOops is true.
251
252 static const int MaxRecorded = 1000000;
253 static OopOrNarrowOopStar* _recorded_oops;
254 static HeapWord** _recorded_cards;
255 static HeapRegion** _recorded_regions;
256 static int _n_recorded;
257
258 static const int MaxRecordedEvents = 1000;
259 static Event* _recorded_events;
260 static int* _recorded_event_index;
261 static int _n_recorded_events;
262
263 static void print_event(outputStream* str, Event evnt);
264
265 public:
266 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa, HeapRegion* hr);
267
268 static uint num_par_rem_sets();
269 static void setup_remset_size();
270
271 HeapRegion* hr() const {
272 return _other_regions.hr();
273 }
274
275 size_t occupied() {
276 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
277 return occupied_locked();
278 }
279 size_t occupied_locked() {
280 return _other_regions.occupied();
281 }
282 size_t occ_fine() const {
283 return _other_regions.occ_fine();
284 }
285 size_t occ_coarse() const {
286 return _other_regions.occ_coarse();
287 }
288 size_t occ_sparse() const {
289 return _other_regions.occ_sparse();
290 }
291
292 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
293
294 // Used in the sequential case.
295 void add_reference(OopOrNarrowOopStar from) {
296 _other_regions.add_reference(from, 0);
297 }
298
299 // Used in the parallel case.
300 void add_reference(OopOrNarrowOopStar from, int tid) {
301 _other_regions.add_reference(from, tid);
302 }
303
304 // Removes any entries shown by the given bitmaps to contain only dead
305 // objects.
306 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
307
308 // The region is being reclaimed; clear its remset, and any mention of
309 // entries for this region in other remsets.
310 void clear();
311 void clear_locked();
312
313 // Attempt to claim the region. Returns true iff this call caused an
314 // atomic transition from Unclaimed to Claimed.
315 bool claim_iter();
316 // Sets the iteration state to "complete".
317 void set_iter_complete();
318 // Returns "true" iff the region's iteration is complete.
319 bool iter_is_complete();
320
321 // Support for claiming blocks of cards during iteration
322 size_t iter_claimed() const { return _iter_claimed; }
323 // Claim the next block of cards
324 size_t iter_claimed_next(size_t step) {
325 return Atomic::add(step, &_iter_claimed) - step;
326 }
327
328 void reset_for_par_iteration();
329
330 bool verify_ready_for_par_iteration() {
331 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
332 }
333
334 // The actual # of bytes this hr_remset takes up.
335 // Note also includes the strong code root set.
336 size_t mem_size() {
337 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
338 return _other_regions.mem_size()
339 // This correction is necessary because the above includes the second
340 // part.
341 + (sizeof(this) - sizeof(OtherRegionsTable))
342 + strong_code_roots_mem_size();
343 }
344
345 // Returns the memory occupancy of all static data structures associated
346 // with remembered sets.
347 static size_t static_mem_size() {
348 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
349 }
350
351 // Returns the memory occupancy of all free_list data structures associated
352 // with remembered sets.
353 static size_t fl_mem_size() {
354 return OtherRegionsTable::fl_mem_size() + G1CodeRootSet::free_chunks_mem_size();
355 }
356
357 bool contains_reference(OopOrNarrowOopStar from) const {
358 return _other_regions.contains_reference(from);
359 }
360
361 // Routines for managing the list of code roots that point into
362 // the heap region that owns this RSet.
363 void add_strong_code_root(nmethod* nm);
364 void remove_strong_code_root(nmethod* nm);
365
366 // During a collection, migrate the successfully evacuated strong
367 // code roots that referenced into the region that owns this RSet
368 // to the RSets of the new regions that they now point into.
369 // Unsuccessfully evacuated code roots are not migrated.
370 void migrate_strong_code_roots();
371
372 // Applies blk->do_code_blob() to each of the entries in
373 // the strong code roots list
374 void strong_code_roots_do(CodeBlobClosure* blk) const;
375
376 // Returns the number of elements in the strong code roots list
377 size_t strong_code_roots_list_length() {
378 return _code_roots.length();
379 }
380
381 // Returns true if the strong code roots contains the given
382 // nmethod.
383 bool strong_code_roots_list_contains(nmethod* nm) {
384 return _code_roots.contains(nm);
385 }
386
387 // Returns the amount of memory, in bytes, currently
388 // consumed by the strong code roots.
389 size_t strong_code_roots_mem_size();
390
391 void print() PRODUCT_RETURN;
392
393 // Called during a stop-world phase to perform any deferred cleanups.
394 static void cleanup();
395
396 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
397 // (Uses it to initialize from_card_cache).
398 static void init_heap(uint max_regions) {
399 OtherRegionsTable::init_from_card_cache(max_regions);
400 }
401
402 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
403 static void shrink_heap(uint new_n_regs) {
404 OtherRegionsTable::shrink_from_card_cache(new_n_regs);
405 }
406
407 #ifndef PRODUCT
408 static void print_from_card_cache() {
409 OtherRegionsTable::print_from_card_cache();
410 }
411 #endif
412
413 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
414 static void print_recorded();
415 static void record_event(Event evnt);
416
417 // These are wrappers for the similarly-named methods on
418 // SparsePRT. Look at sparsePRT.hpp for more details.
419 static void reset_for_cleanup_tasks();
420 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
421 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
422
423 // Run unit tests.
424 #ifndef PRODUCT
425 static void test_prt();
426 static void test();
427 #endif
428 };
429
430 class HeapRegionRemSetIterator : public StackObj {
431
432 // The region RSet over which we're iterating.
433 HeapRegionRemSet* _hrrs;
434
435 // Local caching of HRRS fields.
436 const BitMap* _coarse_map;
437 PerRegionTable** _fine_grain_regions;
438
439 G1BlockOffsetSharedArray* _bosa;
440 G1CollectedHeap* _g1h;
441
442 // The number 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're 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 // See HeapRegionRemSetIterator::has_next().
451 enum IterState {
452 Sparse,
453 Fine,
454 Coarse
455 };
456 IterState _is;
457
458 // In both kinds of iteration, heap offset of first card of current
459 // region.
460 size_t _cur_region_card_offset;
461 // Card offset within cur region.
462 size_t _cur_region_cur_card;
463
464 // Coarse table iteration fields:
465
466 // Current region index;
467 int _coarse_cur_region_index;
468 size_t _coarse_cur_region_cur_card;
469
470 bool coarse_has_next(size_t& card_index);
471
472 // Fine table iteration fields:
473
474 // Index of bucket-list we're working on.
475 int _fine_array_index;
476
477 // Per Region Table we're doing within current bucket list.
478 PerRegionTable* _fine_cur_prt;
479
480 /* SparsePRT::*/ SparsePRTIter _sparse_iter;
481
482 void fine_find_next_non_null_prt();
483
484 bool fine_has_next();
485 bool fine_has_next(size_t& card_index);
486
487 public:
488 // We require an iterator to be initialized before use, so the
489 // constructor does little.
490 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
491
492 // If there remains one or more cards to be yielded, returns true and
493 // sets "card_index" to one of those cards (which is then considered
494 // yielded.) Otherwise, returns false (and leaves "card_index"
495 // undefined.)
496 bool has_next(size_t& card_index);
497
498 size_t n_yielded_fine() { return _n_yielded_fine; }
499 size_t n_yielded_coarse() { return _n_yielded_coarse; }
500 size_t n_yielded_sparse() { return _n_yielded_sparse; }
501 size_t n_yielded() {
502 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
503 }
504 };
505
506 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP