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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7 * published by the Free Software Foundation.
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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_GC_G1_HEAPREGIONREMSET_HPP
26 #define SHARE_GC_G1_HEAPREGIONREMSET_HPP
27
28 #include "gc/g1/g1CodeCacheRemSet.hpp"
29 #include "gc/g1/g1FromCardCache.hpp"
30 #include "gc/g1/sparsePRT.hpp"
31 #include "runtime/mutexLocker.inline.hpp"
32 #include "utilities/bitMap.hpp"
33
34 // Remembered set for a heap region. Represent a set of "cards" that
35 // contain pointers into the owner heap region. Cards are defined somewhat
36 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
37
38 class G1CollectedHeap;
39 class G1BlockOffsetTable;
40 class G1CardLiveData;
41 class HeapRegion;
42 class PerRegionTable;
43 class SparsePRT;
44 class nmethod;
45
46 // The "_coarse_map" is a bitmap with one bit for each region, where set
47 // bits indicate that the corresponding region may contain some pointer
48 // into the owning region.
49
50 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
51 // (PRTs), indicating regions for which we're keeping the RS as a set of
52 // cards. The strategy is to cap the size of the fine-grain table,
53 // deleting an entry and setting the corresponding coarse-grained bit when
54 // we would overflow this cap.
55
56 // We use a mixture of locking and lock-free techniques here. We allow
57 // threads to locate PRTs without locking, but threads attempting to alter
58 // a bucket list obtain a lock. This means that any failing attempt to
59 // find a PRT must be retried with the lock. It might seem dangerous that
60 // a read can find a PRT that is concurrently deleted. This is all right,
61 // because:
62 //
63 // 1) We only actually free PRT's at safe points (though we reuse them at
64 // other times).
65 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
66 // it's _coarse_map bit is set, so the that we were attempting to add
67 // is represented. If a deleted PRT is re-used, a thread adding a bit,
68 // thinking the PRT is for a different region, does no harm.
69
70 class OtherRegionsTable {
71 G1CollectedHeap* _g1h;
72 Mutex* _m;
73
74 // These are protected by "_m".
75 CHeapBitMap _coarse_map;
76 size_t _n_coarse_entries;
77 static jint _n_coarsenings;
78
79 PerRegionTable** _fine_grain_regions;
80 size_t _n_fine_entries;
81
82 // The fine grain remembered sets are doubly linked together using
83 // their 'next' and 'prev' fields.
84 // This allows fast bulk freeing of all the fine grain remembered
85 // set entries, and fast finding of all of them without iterating
86 // over the _fine_grain_regions table.
87 PerRegionTable * _first_all_fine_prts;
88 PerRegionTable * _last_all_fine_prts;
89
90 // Used to sample a subset of the fine grain PRTs to determine which
91 // PRT to evict and coarsen.
92 size_t _fine_eviction_start;
93 static size_t _fine_eviction_stride;
94 static size_t _fine_eviction_sample_size;
95
96 SparsePRT _sparse_table;
97
98 // These are static after init.
99 static size_t _max_fine_entries;
100 static size_t _mod_max_fine_entries_mask;
101
102 // Requires "prt" to be the first element of the bucket list appropriate
103 // for "hr". If this list contains an entry for "hr", return it,
104 // otherwise return "NULL".
105 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
106
107 // Find, delete, and return a candidate PerRegionTable, if any exists,
108 // adding the deleted region to the coarse bitmap. Requires the caller
109 // to hold _m, and the fine-grain table to be full.
110 PerRegionTable* delete_region_table();
111
112 // link/add the given fine grain remembered set into the "all" list
113 void link_to_all(PerRegionTable * prt);
114 // unlink/remove the given fine grain remembered set into the "all" list
115 void unlink_from_all(PerRegionTable * prt);
116
117 bool contains_reference_locked(OopOrNarrowOopStar from) const;
118
119 size_t occ_fine() const;
120 size_t occ_coarse() const;
121 size_t occ_sparse() const;
122
123 public:
124 // Create a new remembered set. The given mutex is used to ensure consistency.
125 OtherRegionsTable(Mutex* m);
126
127 template <class Closure>
128 void iterate(Closure& v);
129
130 // Returns the card index of the given within_region pointer relative to the bottom
131 // of the given heap region.
132 static CardIdx_t card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr);
133 // Adds the reference from "from to this remembered set.
134 void add_reference(OopOrNarrowOopStar from, uint tid);
135
136 // Returns whether the remembered set contains the given reference.
137 bool contains_reference(OopOrNarrowOopStar from) const;
138
139 // Returns whether this remembered set (and all sub-sets) have an occupancy
140 // that is less or equal than the given occupancy.
141 bool occupancy_less_or_equal_than(size_t limit) const;
142
143 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
144 bool is_empty() const;
145
146 // Returns the number of cards contained in this remembered set.
147 size_t occupied() const;
148
149 static jint n_coarsenings() { return _n_coarsenings; }
150
151 // Returns size of the actual remembered set containers in bytes.
152 size_t mem_size() const;
153 // Returns the size of static data in bytes.
154 static size_t static_mem_size();
155 // Returns the size of the free list content in bytes.
156 static size_t fl_mem_size();
157
158 // Clear the entire contents of this remembered set.
159 void clear();
160 };
161
162 class PerRegionTable: public CHeapObj<mtGC> {
163 friend class OtherRegionsTable;
164
165 HeapRegion* _hr;
166 CHeapBitMap _bm;
167 jint _occupied;
168
169 // next pointer for free/allocated 'all' list
170 PerRegionTable* _next;
171
172 // prev pointer for the allocated 'all' list
173 PerRegionTable* _prev;
174
175 // next pointer in collision list
176 PerRegionTable * _collision_list_next;
177
178 // Global free list of PRTs
179 static PerRegionTable* volatile _free_list;
180
181 protected:
182 PerRegionTable(HeapRegion* hr) :
183 _hr(hr),
184 _bm(HeapRegion::CardsPerRegion, mtGC),
185 _occupied(0),
186 _next(NULL), _prev(NULL),
187 _collision_list_next(NULL)
188 {}
189
190 inline void add_card_work(CardIdx_t from_card, bool par);
191
192 inline void add_reference_work(OopOrNarrowOopStar from, bool par);
193
194 public:
195 // We need access in order to union things into the base table.
196 BitMap* bm() { return &_bm; }
197
198 HeapRegion* hr() const { return OrderAccess::load_acquire(&_hr); }
199
200 jint occupied() const {
201 // Overkill, but if we ever need it...
202 // guarantee(_occupied == _bm.count_one_bits(), "Check");
203 return _occupied;
204 }
205
206 void init(HeapRegion* hr, bool clear_links_to_all_list);
207
208 inline void add_reference(OopOrNarrowOopStar from);
209
210 inline void seq_add_reference(OopOrNarrowOopStar from);
211
212 inline void add_card(CardIdx_t from_card_index);
213
214 void seq_add_card(CardIdx_t from_card_index);
215
216 // (Destructively) union the bitmap of the current table into the given
217 // bitmap (which is assumed to be of the same size.)
218 void union_bitmap_into(BitMap* bm) {
219 bm->set_union(_bm);
220 }
221
222 // Mem size in bytes.
223 size_t mem_size() const {
224 return sizeof(PerRegionTable) + _bm.size_in_words() * HeapWordSize;
225 }
226
227 // Requires "from" to be in "hr()".
228 bool contains_reference(OopOrNarrowOopStar from) const {
229 assert(hr()->is_in_reserved(from), "Precondition.");
230 size_t card_ind = pointer_delta(from, hr()->bottom(),
231 G1CardTable::card_size);
232 return _bm.at(card_ind);
233 }
234
235 // Bulk-free the PRTs from prt to last, assumes that they are
236 // linked together using their _next field.
237 static void bulk_free(PerRegionTable* prt, PerRegionTable* last) {
238 while (true) {
239 PerRegionTable* fl = _free_list;
240 last->set_next(fl);
241 PerRegionTable* res = Atomic::cmpxchg(prt, &_free_list, fl);
242 if (res == fl) {
243 return;
244 }
245 }
246 ShouldNotReachHere();
247 }
248
249 static void free(PerRegionTable* prt) {
250 bulk_free(prt, prt);
251 }
252
253 // Returns an initialized PerRegionTable instance.
254 static PerRegionTable* alloc(HeapRegion* hr);
255
256 PerRegionTable* next() const { return _next; }
257 void set_next(PerRegionTable* next) { _next = next; }
258 PerRegionTable* prev() const { return _prev; }
259 void set_prev(PerRegionTable* prev) { _prev = prev; }
260
261 // Accessor and Modification routines for the pointer for the
262 // singly linked collision list that links the PRTs within the
263 // OtherRegionsTable::_fine_grain_regions hash table.
264 //
265 // It might be useful to also make the collision list doubly linked
266 // to avoid iteration over the collisions list during scrubbing/deletion.
267 // OTOH there might not be many collisions.
268
269 PerRegionTable* collision_list_next() const {
270 return _collision_list_next;
271 }
272
273 void set_collision_list_next(PerRegionTable* next) {
274 _collision_list_next = next;
275 }
276
277 PerRegionTable** collision_list_next_addr() {
278 return &_collision_list_next;
279 }
280
281 static size_t fl_mem_size() {
282 PerRegionTable* cur = _free_list;
283 size_t res = 0;
284 while (cur != NULL) {
285 res += cur->mem_size();
286 cur = cur->next();
287 }
288 return res;
289 }
290
291 static void test_fl_mem_size();
292 };
293
294 class HeapRegionRemSet : public CHeapObj<mtGC> {
295 friend class VMStructs;
296
297 private:
298 G1BlockOffsetTable* _bot;
299
300 // A set of code blobs (nmethods) whose code contains pointers into
301 // the region that owns this RSet.
302 G1CodeRootSet _code_roots;
303
304 Mutex _m;
305
306 OtherRegionsTable _other_regions;
307
308 HeapRegion* _hr;
309
310 void clear_fcc();
311
312 public:
313 HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
314
315 // Setup sparse and fine-grain tables sizes.
316 static void setup_remset_size();
317
318 bool is_empty() const {
319 return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
320 }
321
322 bool occupancy_less_or_equal_than(size_t occ) const {
323 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
324 }
325
326 // For each PRT in the card (remembered) set call one of the following methods
327 // of the given closure:
328 //
329 // set_full_region_dirty(uint region_idx) - pass the region index for coarse PRTs
330 // set_bitmap_dirty(uint region_idx, BitMap* bitmap) - pass the region index and bitmap for fine PRTs
331 // set_cards_dirty(uint region_idx, elem_t* cards, uint num_cards) - pass region index and cards for sparse PRTs
332 template <class Closure>
333 inline void iterate_prts(Closure& cl);
334
335 size_t occupied() {
336 MutexLocker x(&_m, Mutex::_no_safepoint_check_flag);
337 return occupied_locked();
338 }
339 size_t occupied_locked() {
340 return _other_regions.occupied();
341 }
342
343 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
344
345 private:
346 enum RemSetState {
347 Untracked,
348 Updating,
349 Complete
350 };
351
352 RemSetState _state;
353
354 static const char* _state_strings[];
355 static const char* _short_state_strings[];
356 public:
357
358 const char* get_state_str() const { return _state_strings[_state]; }
359 const char* get_short_state_str() const { return _short_state_strings[_state]; }
360
361 bool is_tracked() { return _state != Untracked; }
362 bool is_updating() { return _state == Updating; }
363 bool is_complete() { return _state == Complete; }
364
365 void set_state_empty() {
366 guarantee(SafepointSynchronize::is_at_safepoint() || !is_tracked(), "Should only set to Untracked during safepoint but is %s.", get_state_str());
367 if (_state == Untracked) {
368 return;
369 }
370 clear_fcc();
371 _state = Untracked;
372 }
373
374 void set_state_updating() {
375 guarantee(SafepointSynchronize::is_at_safepoint() && !is_tracked(), "Should only set to Updating from Untracked during safepoint but is %s", get_state_str());
376 clear_fcc();
377 _state = Updating;
378 }
379
380 void set_state_complete() {
381 clear_fcc();
382 _state = Complete;
383 }
384
385 // Used in the sequential case.
386 void add_reference(OopOrNarrowOopStar from) {
387 add_reference(from, 0);
388 }
389
390 // Used in the parallel case.
391 void add_reference(OopOrNarrowOopStar from, uint tid) {
392 RemSetState state = _state;
393 if (state == Untracked) {
394 return;
395 }
396
397 uint cur_idx = _hr->hrm_index();
398 uintptr_t from_card = uintptr_t(from) >> CardTable::card_shift;
399
400 if (G1FromCardCache::contains_or_replace(tid, cur_idx, from_card)) {
401 assert(contains_reference(from), "We just found " PTR_FORMAT " in the FromCardCache", p2i(from));
402 return;
403 }
404
405 _other_regions.add_reference(from, tid);
406 }
407
408 // The region is being reclaimed; clear its remset, and any mention of
409 // entries for this region in other remsets.
410 void clear(bool only_cardset = false);
411 void clear_locked(bool only_cardset = false);
412
413 // The actual # of bytes this hr_remset takes up.
414 // Note also includes the strong code root set.
415 size_t mem_size() {
416 MutexLocker x(&_m, Mutex::_no_safepoint_check_flag);
417 return _other_regions.mem_size()
418 // This correction is necessary because the above includes the second
419 // part.
420 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
421 + strong_code_roots_mem_size();
422 }
423
424 // Returns the memory occupancy of all static data structures associated
425 // with remembered sets.
426 static size_t static_mem_size() {
427 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
428 }
429
430 // Returns the memory occupancy of all free_list data structures associated
431 // with remembered sets.
432 static size_t fl_mem_size() {
433 return OtherRegionsTable::fl_mem_size();
434 }
435
436 bool contains_reference(OopOrNarrowOopStar from) const {
437 return _other_regions.contains_reference(from);
438 }
439
440 // Routines for managing the list of code roots that point into
441 // the heap region that owns this RSet.
442 void add_strong_code_root(nmethod* nm);
443 void add_strong_code_root_locked(nmethod* nm);
444 void remove_strong_code_root(nmethod* nm);
445
446 // Applies blk->do_code_blob() to each of the entries in
447 // the strong code roots list
448 void strong_code_roots_do(CodeBlobClosure* blk) const;
449
450 void clean_strong_code_roots(HeapRegion* hr);
451
452 // Returns the number of elements in the strong code roots list
453 size_t strong_code_roots_list_length() const {
454 return _code_roots.length();
455 }
456
457 // Returns true if the strong code roots contains the given
458 // nmethod.
459 bool strong_code_roots_list_contains(nmethod* nm) {
460 return _code_roots.contains(nm);
461 }
462
463 // Returns the amount of memory, in bytes, currently
464 // consumed by the strong code roots.
465 size_t strong_code_roots_mem_size();
466
467 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
468 G1FromCardCache::invalidate(start_idx, num_regions);
469 }
470
471 #ifndef PRODUCT
472 static void print_from_card_cache() {
473 G1FromCardCache::print();
474 }
475
476 static void test();
477 #endif
478 };
479
480 #endif // SHARE_GC_G1_HEAPREGIONREMSET_HPP