1 /*
2 * Copyright (c) 2001, 2019, 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,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
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 "utilities/bitMap.hpp"
32
33 // Remembered set for a heap region. Represent a set of "cards" that
34 // contain pointers into the owner heap region. Cards are defined somewhat
35 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
36
37 class G1CollectedHeap;
38 class G1BlockOffsetTable;
39 class G1CardLiveData;
40 class HeapRegion;
41 class PerRegionTable;
42 class SparsePRT;
43 class nmethod;
44
45 // The "_coarse_map" is a bitmap with one bit for each region, where set
46 // bits indicate that the corresponding region may contain some pointer
47 // into the owning region.
48
49 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
50 // (PRTs), indicating regions for which we're keeping the RS as a set of
51 // cards. The strategy is to cap the size of the fine-grain table,
52 // deleting an entry and setting the corresponding coarse-grained bit when
53 // we would overflow this cap.
54
55 // We use a mixture of locking and lock-free techniques here. We allow
56 // threads to locate PRTs without locking, but threads attempting to alter
57 // a bucket list obtain a lock. This means that any failing attempt to
58 // find a PRT must be retried with the lock. It might seem dangerous that
59 // a read can find a PRT that is concurrently deleted. This is all right,
60 // because:
61 //
62 // 1) We only actually free PRT's at safe points (though we reuse them at
63 // other times).
64 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
65 // it's _coarse_map bit is set, so the that we were attempting to add
66 // is represented. If a deleted PRT is re-used, a thread adding a bit,
67 // thinking the PRT is for a different region, does no harm.
68
69 class OtherRegionsTable {
70 G1CollectedHeap* _g1h;
71 Mutex* _m;
72
73 // These are protected by "_m".
74 CHeapBitMap _coarse_map;
75 size_t _n_coarse_entries;
76 static jint _n_coarsenings;
77
78 PerRegionTable** _fine_grain_regions;
79 size_t _n_fine_entries;
80
81 // The fine grain remembered sets are doubly linked together using
82 // their 'next' and 'prev' fields.
83 // This allows fast bulk freeing of all the fine grain remembered
84 // set entries, and fast finding of all of them without iterating
85 // over the _fine_grain_regions table.
86 PerRegionTable * _first_all_fine_prts;
87 PerRegionTable * _last_all_fine_prts;
88
89 // Used to sample a subset of the fine grain PRTs to determine which
90 // PRT to evict and coarsen.
91 size_t _fine_eviction_start;
92 static size_t _fine_eviction_stride;
93 static size_t _fine_eviction_sample_size;
94
95 SparsePRT _sparse_table;
96
97 // These are static after init.
98 static size_t _max_fine_entries;
99 static size_t _mod_max_fine_entries_mask;
100
101 // Requires "prt" to be the first element of the bucket list appropriate
102 // for "hr". If this list contains an entry for "hr", return it,
103 // otherwise return "NULL".
104 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
105
106 // Find, delete, and return a candidate PerRegionTable, if any exists,
107 // adding the deleted region to the coarse bitmap. Requires the caller
108 // to hold _m, and the fine-grain table to be full.
109 PerRegionTable* delete_region_table();
110
111 // link/add the given fine grain remembered set into the "all" list
112 void link_to_all(PerRegionTable * prt);
113 // unlink/remove the given fine grain remembered set into the "all" list
114 void unlink_from_all(PerRegionTable * prt);
115
116 bool contains_reference_locked(OopOrNarrowOopStar from) const;
117
118 size_t occ_fine() const;
119 size_t occ_coarse() const;
120 size_t occ_sparse() const;
121
122 public:
123 // Create a new remembered set. The given mutex is used to ensure consistency.
124 OtherRegionsTable(Mutex* m);
125
126 template <class Closure>
127 void iterate(Closure& v);
128
129 // Returns the card index of the given within_region pointer relative to the bottom
130 // of the given heap region.
131 static CardIdx_t card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr);
132 // Adds the reference from "from to this remembered set.
133 void add_reference(OopOrNarrowOopStar from, uint tid);
134
135 // Returns whether the remembered set contains the given reference.
136 bool contains_reference(OopOrNarrowOopStar from) const;
137
138 // Returns whether this remembered set (and all sub-sets) have an occupancy
139 // that is less or equal than the given occupancy.
140 bool occupancy_less_or_equal_than(size_t limit) const;
141
142 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
143 bool is_empty() const;
144
145 // Returns the number of cards contained in this remembered set.
146 size_t occupied() const;
147
148 static jint n_coarsenings() { return _n_coarsenings; }
149
150 // Returns size of the actual remembered set containers in bytes.
151 size_t mem_size() const;
152 // Returns the size of static data in bytes.
153 static size_t static_mem_size();
154 // Returns the size of the free list content in bytes.
155 static size_t fl_mem_size();
156
157 // Clear the entire contents of this remembered set.
158 void clear();
159 };
160
161 class PerRegionTable: public CHeapObj<mtGC> {
162 friend class OtherRegionsTable;
163
164 HeapRegion* _hr;
165 CHeapBitMap _bm;
166 jint _occupied;
167
168 // next pointer for free/allocated 'all' list
169 PerRegionTable* _next;
170
171 // prev pointer for the allocated 'all' list
172 PerRegionTable* _prev;
173
174 // next pointer in collision list
175 PerRegionTable * _collision_list_next;
176
177 // Global free list of PRTs
178 static PerRegionTable* volatile _free_list;
179
180 protected:
181 PerRegionTable(HeapRegion* hr) :
182 _hr(hr),
183 _bm(HeapRegion::CardsPerRegion, mtGC),
184 _occupied(0),
185 _next(NULL), _prev(NULL),
186 _collision_list_next(NULL)
187 {}
188
189 inline void add_card_work(CardIdx_t from_card, bool par);
190
191 inline void add_reference_work(OopOrNarrowOopStar from, bool par);
192
193 public:
194 // We need access in order to union things into the base table.
195 BitMap* bm() { return &_bm; }
196
197 HeapRegion* hr() const { return OrderAccess::load_acquire(&_hr); }
198
199 jint occupied() const {
200 // Overkill, but if we ever need it...
201 // guarantee(_occupied == _bm.count_one_bits(), "Check");
202 return _occupied;
203 }
204
205 void init(HeapRegion* hr, bool clear_links_to_all_list);
206
207 inline void add_reference(OopOrNarrowOopStar from);
208
209 inline void seq_add_reference(OopOrNarrowOopStar from);
210
211 inline void add_card(CardIdx_t from_card_index);
212
213 void seq_add_card(CardIdx_t from_card_index);
214
215 // (Destructively) union the bitmap of the current table into the given
216 // bitmap (which is assumed to be of the same size.)
217 void union_bitmap_into(BitMap* bm) {
218 bm->set_union(_bm);
219 }
220
221 // Mem size in bytes.
222 size_t mem_size() const {
223 return sizeof(PerRegionTable) + _bm.size_in_words() * HeapWordSize;
224 }
225
226 // Requires "from" to be in "hr()".
227 bool contains_reference(OopOrNarrowOopStar from) const {
228 assert(hr()->is_in_reserved(from), "Precondition.");
229 size_t card_ind = pointer_delta(from, hr()->bottom(),
230 G1CardTable::card_size);
231 return _bm.at(card_ind);
232 }
233
234 // Bulk-free the PRTs from prt to last, assumes that they are
235 // linked together using their _next field.
236 static void bulk_free(PerRegionTable* prt, PerRegionTable* last) {
237 while (true) {
238 PerRegionTable* fl = _free_list;
239 last->set_next(fl);
240 PerRegionTable* res = Atomic::cmpxchg(prt, &_free_list, fl);
241 if (res == fl) {
242 return;
243 }
244 }
245 ShouldNotReachHere();
246 }
247
248 static void free(PerRegionTable* prt) {
249 bulk_free(prt, prt);
250 }
251
252 // Returns an initialized PerRegionTable instance.
253 static PerRegionTable* alloc(HeapRegion* hr);
254
255 PerRegionTable* next() const { return _next; }
256 void set_next(PerRegionTable* next) { _next = next; }
257 PerRegionTable* prev() const { return _prev; }
258 void set_prev(PerRegionTable* prev) { _prev = prev; }
259
260 // Accessor and Modification routines for the pointer for the
261 // singly linked collision list that links the PRTs within the
262 // OtherRegionsTable::_fine_grain_regions hash table.
263 //
264 // It might be useful to also make the collision list doubly linked
265 // to avoid iteration over the collisions list during scrubbing/deletion.
266 // OTOH there might not be many collisions.
267
268 PerRegionTable* collision_list_next() const {
269 return _collision_list_next;
270 }
271
272 void set_collision_list_next(PerRegionTable* next) {
273 _collision_list_next = next;
274 }
275
276 PerRegionTable** collision_list_next_addr() {
277 return &_collision_list_next;
278 }
279
280 static size_t fl_mem_size() {
281 PerRegionTable* cur = _free_list;
282 size_t res = 0;
283 while (cur != NULL) {
284 res += cur->mem_size();
285 cur = cur->next();
286 }
287 return res;
288 }
289
290 static void test_fl_mem_size();
291 };
292
293 class HeapRegionRemSet : public CHeapObj<mtGC> {
294 friend class VMStructs;
295
296 private:
297 G1BlockOffsetTable* _bot;
298
299 // A set of code blobs (nmethods) whose code contains pointers into
300 // the region that owns this RSet.
301 G1CodeRootSet _code_roots;
302
303 Mutex _m;
304
305 OtherRegionsTable _other_regions;
306
307 HeapRegion* _hr;
308
309 void clear_fcc();
310
311 public:
312 HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
313
314 // Setup sparse and fine-grain tables sizes.
315 static void setup_remset_size();
316
317 bool is_empty() const {
318 return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
319 }
320
321 bool occupancy_less_or_equal_than(size_t occ) const {
322 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
323 }
324
325 // For each PRT in the card (remembered) set call one of the following methods
326 // of the given closure:
327 //
328 // set_full_region_dirty(uint region_idx) - pass the region index for coarse PRTs
329 // set_bitmap_dirty(uint region_idx, BitMap* bitmap) - pass the region index and bitmap for fine PRTs
330 // set_cards_dirty(uint region_idx, elem_t* cards, uint num_cards) - pass region index and cards for sparse PRTs
331 template <class Closure>
332 inline void iterate_prts(Closure& cl);
333
334 size_t occupied() {
335 MutexLocker x(&_m, Mutex::_no_safepoint_check_flag);
336 return occupied_locked();
337 }
338 size_t occupied_locked() {
339 return _other_regions.occupied();
340 }
341
342 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
343
344 private:
345 enum RemSetState {
346 Untracked,
347 Updating,
348 Complete
349 };
350
351 RemSetState _state;
352
353 static const char* _state_strings[];
354 static const char* _short_state_strings[];
355 public:
356
357 const char* get_state_str() const { return _state_strings[_state]; }
358 const char* get_short_state_str() const { return _short_state_strings[_state]; }
359
360 bool is_tracked() { return _state != Untracked; }
361 bool is_updating() { return _state == Updating; }
362 bool is_complete() { return _state == Complete; }
363
364 void set_state_empty() {
365 guarantee(SafepointSynchronize::is_at_safepoint() || !is_tracked(), "Should only set to Untracked during safepoint but is %s.", get_state_str());
366 if (_state == Untracked) {
367 return;
368 }
369 clear_fcc();
370 _state = Untracked;
371 }
372
373 void set_state_updating() {
374 guarantee(SafepointSynchronize::is_at_safepoint() && !is_tracked(), "Should only set to Updating from Untracked during safepoint but is %s", get_state_str());
375 clear_fcc();
376 _state = Updating;
377 }
378
379 void set_state_complete() {
380 clear_fcc();
381 _state = Complete;
382 }
383
384 // Used in the sequential case.
385 void add_reference(OopOrNarrowOopStar from) {
386 add_reference(from, 0);
387 }
388
389 // Used in the parallel case.
390 void add_reference(OopOrNarrowOopStar from, uint tid) {
391 RemSetState state = _state;
392 if (state == Untracked) {
393 return;
394 }
395
396 uint cur_idx = _hr->hrm_index();
397 uintptr_t from_card = uintptr_t(from) >> CardTable::card_shift;
398
399 if (G1FromCardCache::contains_or_replace(tid, cur_idx, from_card)) {
400 assert(contains_reference(from), "We just found " PTR_FORMAT " in the FromCardCache", p2i(from));
401 return;
402 }
403
404 _other_regions.add_reference(from, tid);
405 }
406
407 // The region is being reclaimed; clear its remset, and any mention of
408 // entries for this region in other remsets.
409 void clear(bool only_cardset = false);
410 void clear_locked(bool only_cardset = false);
411
412 // The actual # of bytes this hr_remset takes up.
413 // Note also includes the strong code root set.
414 size_t mem_size() {
415 MutexLocker x(&_m, Mutex::_no_safepoint_check_flag);
416 return _other_regions.mem_size()
417 // This correction is necessary because the above includes the second
418 // part.
419 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
420 + strong_code_roots_mem_size();
421 }
422
423 // Returns the memory occupancy of all static data structures associated
424 // with remembered sets.
425 static size_t static_mem_size() {
426 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
427 }
428
429 // Returns the memory occupancy of all free_list data structures associated
430 // with remembered sets.
431 static size_t fl_mem_size() {
432 return OtherRegionsTable::fl_mem_size();
433 }
434
435 bool contains_reference(OopOrNarrowOopStar from) const {
436 return _other_regions.contains_reference(from);
437 }
438
439 // Routines for managing the list of code roots that point into
440 // the heap region that owns this RSet.
441 void add_strong_code_root(nmethod* nm);
442 void add_strong_code_root_locked(nmethod* nm);
443 void remove_strong_code_root(nmethod* nm);
444
445 // Applies blk->do_code_blob() to each of the entries in
446 // the strong code roots list
447 void strong_code_roots_do(CodeBlobClosure* blk) const;
448
449 void clean_strong_code_roots(HeapRegion* hr);
450
451 // Returns the number of elements in the strong code roots list
452 size_t strong_code_roots_list_length() const {
453 return _code_roots.length();
454 }
455
456 // Returns true if the strong code roots contains the given
457 // nmethod.
458 bool strong_code_roots_list_contains(nmethod* nm) {
459 return _code_roots.contains(nm);
460 }
461
462 // Returns the amount of memory, in bytes, currently
463 // consumed by the strong code roots.
464 size_t strong_code_roots_mem_size();
465
466 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
467 G1FromCardCache::invalidate(start_idx, num_regions);
468 }
469
470 #ifndef PRODUCT
471 static void print_from_card_cache() {
472 G1FromCardCache::print();
473 }
474
475 static void test();
476 #endif
477 };
478
479 #endif // SHARE_GC_G1_HEAPREGIONREMSET_HPP