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 // Returns whether this remembered set (and all sub-sets) contain no entries.
189 bool is_empty() const;
190
191 size_t occupied() const;
192 size_t occ_fine() const;
193 size_t occ_coarse() const;
194 size_t occ_sparse() const;
195
196 static jint n_coarsenings() { return _n_coarsenings; }
197
198 // Returns size in bytes.
199 // Not const because it takes a lock.
200 size_t mem_size() const;
201 static size_t static_mem_size();
202 static size_t fl_mem_size();
203
204 bool contains_reference(OopOrNarrowOopStar from) const;
205 bool contains_reference_locked(OopOrNarrowOopStar from) const;
206
207 void clear();
208
209 // Specifically clear the from_card_cache.
210 void clear_fcc();
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 bool is_empty() const {
276 return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
277 }
278
279 size_t occupied() {
280 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
281 return occupied_locked();
282 }
283 size_t occupied_locked() {
284 return _other_regions.occupied();
285 }
286 size_t occ_fine() const {
287 return _other_regions.occ_fine();
288 }
289 size_t occ_coarse() const {
290 return _other_regions.occ_coarse();
291 }
292 size_t occ_sparse() const {
293 return _other_regions.occ_sparse();
294 }
295
296 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
297
298 // Used in the sequential case.
299 void add_reference(OopOrNarrowOopStar from) {
300 _other_regions.add_reference(from, 0);
301 }
302
303 // Used in the parallel case.
304 void add_reference(OopOrNarrowOopStar from, int tid) {
305 _other_regions.add_reference(from, tid);
306 }
307
308 // Removes any entries shown by the given bitmaps to contain only dead
309 // objects.
310 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
311
312 // The region is being reclaimed; clear its remset, and any mention of
313 // entries for this region in other remsets.
314 void clear();
315 void clear_locked();
316
317 // Attempt to claim the region. Returns true iff this call caused an
318 // atomic transition from Unclaimed to Claimed.
319 bool claim_iter();
320 // Sets the iteration state to "complete".
321 void set_iter_complete();
322 // Returns "true" iff the region's iteration is complete.
323 bool iter_is_complete();
324
325 // Support for claiming blocks of cards during iteration
326 size_t iter_claimed() const { return _iter_claimed; }
327 // Claim the next block of cards
328 size_t iter_claimed_next(size_t step) {
329 return Atomic::add(step, &_iter_claimed) - step;
330 }
331
332 void reset_for_par_iteration();
333
334 bool verify_ready_for_par_iteration() {
335 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
336 }
337
338 // The actual # of bytes this hr_remset takes up.
339 // Note also includes the strong code root set.
340 size_t mem_size() {
341 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
342 return _other_regions.mem_size()
343 // This correction is necessary because the above includes the second
344 // part.
345 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
346 + strong_code_roots_mem_size();
347 }
348
349 // Returns the memory occupancy of all static data structures associated
350 // with remembered sets.
351 static size_t static_mem_size() {
352 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::free_chunks_static_mem_size();
353 }
354
355 // Returns the memory occupancy of all free_list data structures associated
356 // with remembered sets.
357 static size_t fl_mem_size() {
358 return OtherRegionsTable::fl_mem_size() + G1CodeRootSet::free_chunks_mem_size();
359 }
360
361 bool contains_reference(OopOrNarrowOopStar from) const {
362 return _other_regions.contains_reference(from);
363 }
364
365 // Routines for managing the list of code roots that point into
366 // the heap region that owns this RSet.
367 void add_strong_code_root(nmethod* nm);
368 void remove_strong_code_root(nmethod* nm);
369
370 // During a collection, migrate the successfully evacuated strong
371 // code roots that referenced into the region that owns this RSet
372 // to the RSets of the new regions that they now point into.
373 // Unsuccessfully evacuated code roots are not migrated.
374 void migrate_strong_code_roots();
375
376 // Applies blk->do_code_blob() to each of the entries in
377 // the strong code roots list
378 void strong_code_roots_do(CodeBlobClosure* blk) const;
379
380 // Returns the number of elements in the strong code roots list
381 size_t strong_code_roots_list_length() const {
382 return _code_roots.length();
383 }
384
385 // Returns true if the strong code roots contains the given
386 // nmethod.
387 bool strong_code_roots_list_contains(nmethod* nm) {
388 return _code_roots.contains(nm);
389 }
390
391 // Returns the amount of memory, in bytes, currently
392 // consumed by the strong code roots.
393 size_t strong_code_roots_mem_size();
394
395 void print() PRODUCT_RETURN;
396
397 // Called during a stop-world phase to perform any deferred cleanups.
398 static void cleanup();
399
400 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
401 // (Uses it to initialize from_card_cache).
402 static void init_heap(uint max_regions) {
403 OtherRegionsTable::init_from_card_cache(max_regions);
404 }
405
406 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
407 static void shrink_heap(uint new_n_regs) {
408 OtherRegionsTable::shrink_from_card_cache(new_n_regs);
409 }
410
411 #ifndef PRODUCT
412 static void print_from_card_cache() {
413 OtherRegionsTable::print_from_card_cache();
414 }
415 #endif
416
417 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
418 static void print_recorded();
419 static void record_event(Event evnt);
420
421 // These are wrappers for the similarly-named methods on
422 // SparsePRT. Look at sparsePRT.hpp for more details.
423 static void reset_for_cleanup_tasks();
424 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
425 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
426
427 // Run unit tests.
428 #ifndef PRODUCT
429 static void test_prt();
430 static void test();
431 #endif
432 };
433
434 class HeapRegionRemSetIterator : public StackObj {
435 private:
436 // The region RSet over which we are iterating.
437 HeapRegionRemSet* _hrrs;
438
439 // Local caching of HRRS fields.
440 const BitMap* _coarse_map;
441
442 G1BlockOffsetSharedArray* _bosa;
443 G1CollectedHeap* _g1h;
444
445 // The number of cards yielded since initialization.
446 size_t _n_yielded_fine;
447 size_t _n_yielded_coarse;
448 size_t _n_yielded_sparse;
449
450 // Indicates what granularity of table that we are currently iterating over.
451 // We start iterating over the sparse table, progress to the fine grain
452 // table, and then finish with the coarse table.
453 enum IterState {
454 Sparse,
455 Fine,
456 Coarse
457 };
458 IterState _is;
459
460 // For both Coarse and Fine remembered set iteration this contains the
461 // first card number of the heap region we currently iterate over.
462 size_t _cur_region_card_offset;
463
464 // Current region index for the Coarse remembered set iteration.
465 int _coarse_cur_region_index;
466 size_t _coarse_cur_region_cur_card;
467
468 bool coarse_has_next(size_t& card_index);
469
470 // The PRT we are currently iterating over.
471 PerRegionTable* _fine_cur_prt;
472 // Card offset within the current PRT.
473 size_t _cur_card_in_prt;
474
475 // Update internal variables when switching to the given PRT.
476 void switch_to_prt(PerRegionTable* prt);
477 bool fine_has_next();
478 bool fine_has_next(size_t& card_index);
479
480 // The Sparse remembered set iterator.
481 SparsePRTIter _sparse_iter;
482
483 public:
484 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
485
486 // If there remains one or more cards to be yielded, returns true and
487 // sets "card_index" to one of those cards (which is then considered
488 // yielded.) Otherwise, returns false (and leaves "card_index"
489 // undefined.)
490 bool has_next(size_t& card_index);
491
492 size_t n_yielded_fine() { return _n_yielded_fine; }
493 size_t n_yielded_coarse() { return _n_yielded_coarse; }
494 size_t n_yielded_sparse() { return _n_yielded_sparse; }
495 size_t n_yielded() {
496 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
497 }
498 };
499
500 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP