1 /*
2 * Copyright (c) 2001, 2018, 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.
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20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25 #ifndef SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP
26 #define SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP
27
28 #include "gc/g1/g1CodeCacheRemSet.hpp"
29 #include "gc/g1/g1FromCardCache.hpp"
30 #include "gc/g1/sparsePRT.hpp"
31
32 // Remembered set for a heap region. Represent a set of "cards" that
33 // contain pointers into the owner heap region. Cards are defined somewhat
34 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
35
36 class G1CollectedHeap;
37 class G1BlockOffsetTable;
38 class G1CardLiveData;
39 class HeapRegion;
40 class HeapRegionRemSetIterator;
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 friend class HeapRegionRemSetIterator;
71
72 G1CollectedHeap* _g1h;
73 Mutex* _m;
74
75 // These are protected by "_m".
76 CHeapBitMap _coarse_map;
77 size_t _n_coarse_entries;
78 static jint _n_coarsenings;
79
80 PerRegionTable** _fine_grain_regions;
81 size_t _n_fine_entries;
82
83 // The fine grain remembered sets are doubly linked together using
84 // their 'next' and 'prev' fields.
85 // This allows fast bulk freeing of all the fine grain remembered
86 // set entries, and fast finding of all of them without iterating
87 // over the _fine_grain_regions table.
88 PerRegionTable * _first_all_fine_prts;
89 PerRegionTable * _last_all_fine_prts;
90
91 // Used to sample a subset of the fine grain PRTs to determine which
92 // PRT to evict and coarsen.
93 size_t _fine_eviction_start;
94 static size_t _fine_eviction_stride;
95 static size_t _fine_eviction_sample_size;
96
97 SparsePRT _sparse_table;
98
99 // These are static after init.
100 static size_t _max_fine_entries;
101 static size_t _mod_max_fine_entries_mask;
102
103 // Requires "prt" to be the first element of the bucket list appropriate
104 // for "hr". If this list contains an entry for "hr", return it,
105 // otherwise return "NULL".
106 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
107
108 // Find, delete, and return a candidate PerRegionTable, if any exists,
109 // adding the deleted region to the coarse bitmap. Requires the caller
110 // to hold _m, and the fine-grain table to be full.
111 PerRegionTable* delete_region_table();
112
113 // link/add the given fine grain remembered set into the "all" list
114 void link_to_all(PerRegionTable * prt);
115 // unlink/remove the given fine grain remembered set into the "all" list
116 void unlink_from_all(PerRegionTable * prt);
117
118 bool contains_reference_locked(OopOrNarrowOopStar from) const;
119
120 size_t occ_fine() const;
121 size_t occ_coarse() const;
122 size_t occ_sparse() const;
123
124 public:
125 // Create a new remembered set. The given mutex is used to ensure consistency.
126 OtherRegionsTable(Mutex* m);
127
128 // Returns the card index of the given within_region pointer relative to the bottom
129 // of the given heap region.
130 static CardIdx_t card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr);
131 // Adds the reference from "from to this remembered set.
132 void add_reference(OopOrNarrowOopStar from, uint tid);
133
134 // Returns whether the remembered set contains the given reference.
135 bool contains_reference(OopOrNarrowOopStar from) const;
136
137 // Returns whether this remembered set (and all sub-sets) have an occupancy
138 // that is less or equal than the given occupancy.
139 bool occupancy_less_or_equal_than(size_t limit) const;
140
141 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
142 bool is_empty() const;
143
144 // Returns the number of cards contained in this remembered set.
145 size_t occupied() const;
146
147 static jint n_coarsenings() { return _n_coarsenings; }
148
149 // Returns size of the actual remembered set containers in bytes.
150 size_t mem_size() const;
151 // Returns the size of static data in bytes.
152 static size_t static_mem_size();
153 // Returns the size of the free list content in bytes.
154 static size_t fl_mem_size();
155
156 // Clear the entire contents of this remembered set.
157 void clear();
158 };
159
160 class HeapRegionRemSet : public CHeapObj<mtGC> {
161 friend class VMStructs;
162 friend class HeapRegionRemSetIterator;
163
164 private:
165 G1BlockOffsetTable* _bot;
166
167 // A set of code blobs (nmethods) whose code contains pointers into
168 // the region that owns this RSet.
169 G1CodeRootSet _code_roots;
170
171 Mutex _m;
172
173 OtherRegionsTable _other_regions;
174
175 HeapRegion* _hr;
176
177 void clear_fcc();
178
179 public:
180 HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
181
182 static void setup_remset_size();
183
184 bool cardset_is_empty() const {
185 return _other_regions.is_empty();
186 }
187
188 bool is_empty() const {
189 return (strong_code_roots_list_length() == 0) && cardset_is_empty();
190 }
191
192 bool occupancy_less_or_equal_than(size_t occ) const {
193 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
194 }
195
196 size_t occupied() {
197 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
198 return occupied_locked();
199 }
200 size_t occupied_locked() {
201 return _other_regions.occupied();
202 }
203
204 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
205
206 private:
207 enum RemSetState {
208 Untracked,
209 Updating,
210 Complete
211 };
212
213 RemSetState _state;
214
215 static const char* _state_strings[];
216 static const char* _short_state_strings[];
217 public:
218
219 const char* get_state_str() const { return _state_strings[_state]; }
220 const char* get_short_state_str() const { return _short_state_strings[_state]; }
221
222 bool is_tracked() { return _state != Untracked; }
223 bool is_updating() { return _state == Updating; }
224 bool is_complete() { return _state == Complete; }
225
226 void set_state_empty() {
227 guarantee(SafepointSynchronize::is_at_safepoint() || !is_tracked(), "Should only set to Untracked during safepoint but is %s.", get_state_str());
228 if (_state == Untracked) {
229 return;
230 }
231 clear_fcc();
232 _state = Untracked;
233 }
234
235 void set_state_updating() {
236 guarantee(SafepointSynchronize::is_at_safepoint() && !is_tracked(), "Should only set to Updating from Untracked during safepoint but is %s", get_state_str());
237 clear_fcc();
238 _state = Updating;
239 }
240
241 void set_state_complete() {
242 clear_fcc();
243 _state = Complete;
244 }
245
246 // Used in the sequential case.
247 void add_reference(OopOrNarrowOopStar from) {
248 add_reference(from, 0);
249 }
250
251 // Used in the parallel case.
252 void add_reference(OopOrNarrowOopStar from, uint tid) {
253 RemSetState state = _state;
254 if (state == Untracked) {
255 return;
256 }
257
258 uint cur_idx = _hr->hrm_index();
259 uintptr_t from_card = uintptr_t(from) >> CardTable::card_shift;
260
261 if (G1FromCardCache::contains_or_replace(tid, cur_idx, from_card)) {
262 assert(contains_reference(from), "We just found " PTR_FORMAT " in the FromCardCache", p2i(from));
263 return;
264 }
265
266 _other_regions.add_reference(from, tid);
267 }
268
269 // The region is being reclaimed; clear its remset, and any mention of
270 // entries for this region in other remsets.
271 void clear(bool only_cardset = false);
272 void clear_locked(bool only_cardset = false);
273
274 // The actual # of bytes this hr_remset takes up.
275 // Note also includes the strong code root set.
276 size_t mem_size() {
277 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
278 return _other_regions.mem_size()
279 // This correction is necessary because the above includes the second
280 // part.
281 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
282 + strong_code_roots_mem_size();
283 }
284
285 // Returns the memory occupancy of all static data structures associated
286 // with remembered sets.
287 static size_t static_mem_size() {
288 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
289 }
290
291 // Returns the memory occupancy of all free_list data structures associated
292 // with remembered sets.
293 static size_t fl_mem_size() {
294 return OtherRegionsTable::fl_mem_size();
295 }
296
297 bool contains_reference(OopOrNarrowOopStar from) const {
298 return _other_regions.contains_reference(from);
299 }
300
301 // Routines for managing the list of code roots that point into
302 // the heap region that owns this RSet.
303 void add_strong_code_root(nmethod* nm);
304 void add_strong_code_root_locked(nmethod* nm);
305 void remove_strong_code_root(nmethod* nm);
306
307 // Applies blk->do_code_blob() to each of the entries in
308 // the strong code roots list
309 void strong_code_roots_do(CodeBlobClosure* blk) const;
310
311 void clean_strong_code_roots(HeapRegion* hr);
312
313 // Returns the number of elements in the strong code roots list
314 size_t strong_code_roots_list_length() const {
315 return _code_roots.length();
316 }
317
318 // Returns true if the strong code roots contains the given
319 // nmethod.
320 bool strong_code_roots_list_contains(nmethod* nm) {
321 return _code_roots.contains(nm);
322 }
323
324 // Returns the amount of memory, in bytes, currently
325 // consumed by the strong code roots.
326 size_t strong_code_roots_mem_size();
327
328 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
329 G1FromCardCache::invalidate(start_idx, num_regions);
330 }
331
332 #ifndef PRODUCT
333 static void print_from_card_cache() {
334 G1FromCardCache::print();
335 }
336
337 static void test();
338 #endif
339 };
340
341 class HeapRegionRemSetIterator : public StackObj {
342 private:
343 // The region RSet over which we are iterating.
344 HeapRegionRemSet* _hrrs;
345
346 // Local caching of HRRS fields.
347 const BitMap* _coarse_map;
348
349 G1BlockOffsetTable* _bot;
350 G1CollectedHeap* _g1h;
351
352 // The number of cards yielded since initialization.
353 size_t _n_yielded_fine;
354 size_t _n_yielded_coarse;
355 size_t _n_yielded_sparse;
356
357 // Indicates what granularity of table that we are currently iterating over.
358 // We start iterating over the sparse table, progress to the fine grain
359 // table, and then finish with the coarse table.
360 enum IterState {
361 Sparse,
362 Fine,
363 Coarse
364 };
365 IterState _is;
366
367 // For both Coarse and Fine remembered set iteration this contains the
368 // first card number of the heap region we currently iterate over.
369 size_t _cur_region_card_offset;
370
371 // Current region index for the Coarse remembered set iteration.
372 int _coarse_cur_region_index;
373 size_t _coarse_cur_region_cur_card;
374
375 bool coarse_has_next(size_t& card_index);
376
377 // The PRT we are currently iterating over.
378 PerRegionTable* _fine_cur_prt;
379 // Card offset within the current PRT.
380 size_t _cur_card_in_prt;
381
382 // Update internal variables when switching to the given PRT.
383 void switch_to_prt(PerRegionTable* prt);
384 bool fine_has_next();
385 bool fine_has_next(size_t& card_index);
386
387 // The Sparse remembered set iterator.
388 SparsePRTIter _sparse_iter;
389
390 public:
391 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
392
393 // If there remains one or more cards to be yielded, returns true and
394 // sets "card_index" to one of those cards (which is then considered
395 // yielded.) Otherwise, returns false (and leaves "card_index"
396 // undefined.)
397 bool has_next(size_t& card_index);
398
399 size_t n_yielded_fine() { return _n_yielded_fine; }
400 size_t n_yielded_coarse() { return _n_yielded_coarse; }
401 size_t n_yielded_sparse() { return _n_yielded_sparse; }
402 size_t n_yielded() {
403 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
404 }
405 };
406
407 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP