1 /*
2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
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.
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).
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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 // Essentially a wrapper around SparsePRTCleanupTask. See
46 // sparsePRT.hpp for more details.
47 class HRRSCleanupTask : public SparsePRTCleanupTask {
48 };
49
50 // The "_coarse_map" is a bitmap with one bit for each region, where set
51 // bits indicate that the corresponding region may contain some pointer
52 // into the owning region.
53
54 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
55 // (PRTs), indicating regions for which we're keeping the RS as a set of
56 // cards. The strategy is to cap the size of the fine-grain table,
57 // deleting an entry and setting the corresponding coarse-grained bit when
58 // we would overflow this cap.
59
60 // We use a mixture of locking and lock-free techniques here. We allow
61 // threads to locate PRTs without locking, but threads attempting to alter
62 // a bucket list obtain a lock. This means that any failing attempt to
63 // find a PRT must be retried with the lock. It might seem dangerous that
64 // a read can find a PRT that is concurrently deleted. This is all right,
65 // because:
66 //
67 // 1) We only actually free PRT's at safe points (though we reuse them at
68 // other times).
69 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
70 // it's _coarse_map bit is set, so the that we were attempting to add
71 // is represented. If a deleted PRT is re-used, a thread adding a bit,
72 // thinking the PRT is for a different region, does no harm.
73
74 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
75 friend class HeapRegionRemSetIterator;
76
77 G1CollectedHeap* _g1h;
78 Mutex* _m;
79 HeapRegion* _hr;
80
81 // These are protected by "_m".
82 bool _coarse_dirty;
83 BitMap _coarse_map;
84 size_t _n_coarse_entries;
85 static jint _n_coarsenings;
86
87 PerRegionTable** _fine_grain_regions;
88 size_t _n_fine_entries;
89
90 // The fine grain remembered sets are doubly linked together using
91 // their 'next' and 'prev' fields.
92 // This allows fast bulk freeing of all the fine grain remembered
93 // set entries, and fast finding of all of them without iterating
94 // over the _fine_grain_regions table.
95 PerRegionTable * _first_all_fine_prts;
96 PerRegionTable * _last_all_fine_prts;
97
98 // Used to sample a subset of the fine grain PRTs to determine which
99 // PRT to evict and coarsen.
100 size_t _fine_eviction_start;
101 static size_t _fine_eviction_stride;
102 static size_t _fine_eviction_sample_size;
103
104 SparsePRT _sparse_table;
105
106 // These are static after init.
107 static size_t _max_fine_entries;
108 static size_t _mod_max_fine_entries_mask;
109
110 // Requires "prt" to be the first element of the bucket list appropriate
111 // for "hr". If this list contains an entry for "hr", return it,
112 // otherwise return "NULL".
113 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
114
115 // Find, delete, and return a candidate PerRegionTable, if any exists,
116 // adding the deleted region to the coarse bitmap. Requires the caller
117 // to hold _m, and the fine-grain table to be full.
118 PerRegionTable* delete_region_table();
119
120 // link/add the given fine grain remembered set into the "all" list
121 void link_to_all(PerRegionTable * prt);
122 // unlink/remove the given fine grain remembered set into the "all" list
123 void unlink_from_all(PerRegionTable * prt);
124
125 bool contains_reference_locked(OopOrNarrowOopStar from) const;
126
127 // Clear the from_card_cache entries for this region.
128 void clear_fcc();
129 public:
130 // Create a new remembered set for the given heap region. The given mutex should
131 // be used to ensure consistency.
132 OtherRegionsTable(HeapRegion* hr, Mutex* m);
133
134 // For now. Could "expand" some tables in the future, so that this made
135 // sense.
136 void add_reference(OopOrNarrowOopStar from, uint tid);
137
138 // Returns whether the remembered set contains the given reference.
139 bool contains_reference(OopOrNarrowOopStar from) const;
140
141 // Returns whether this remembered set (and all sub-sets) have an occupancy
142 // that is less or equal than the given occupancy.
143 bool occupancy_less_or_equal_than(size_t limit) const;
144
145 // Removes any entries shown by the given bitmaps to contain only dead
146 // objects. Not thread safe.
147 // Set bits in the bitmaps indicate that the given region or card is live.
148 void scrub(G1CardLiveData* live_data);
149
150 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
151 bool is_empty() const;
152
153 // Returns the number of cards contained in this remembered set.
154 size_t occupied() const;
155 size_t occ_fine() const;
156 size_t occ_coarse() const;
157 size_t occ_sparse() const;
158
159 static jint n_coarsenings() { return _n_coarsenings; }
160
161 // Returns size of the actual remembered set containers in bytes.
162 size_t mem_size() const;
163 // Returns the size of static data in bytes.
164 static size_t static_mem_size();
165 // Returns the size of the free list content in bytes.
166 static size_t fl_mem_size();
167
168 // Clear the entire contents of this remembered set.
169 void clear();
170
171 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
172 };
173
174 class HeapRegionRemSet : public CHeapObj<mtGC> {
175 friend class VMStructs;
176 friend class HeapRegionRemSetIterator;
177
178 private:
179 G1BlockOffsetTable* _bot;
180
181 // A set of code blobs (nmethods) whose code contains pointers into
182 // the region that owns this RSet.
183 G1CodeRootSet _code_roots;
184
185 Mutex _m;
186
187 OtherRegionsTable _other_regions;
188
189 public:
190 HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
191
192 static void setup_remset_size();
193
194 bool is_empty() const {
195 return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
196 }
197
198 bool occupancy_less_or_equal_than(size_t occ) const {
199 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
200 }
201
202 size_t occupied() {
203 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
204 return occupied_locked();
205 }
206 size_t occupied_locked() {
207 return _other_regions.occupied();
208 }
209 size_t occ_fine() const {
210 return _other_regions.occ_fine();
211 }
212 size_t occ_coarse() const {
213 return _other_regions.occ_coarse();
214 }
215 size_t occ_sparse() const {
216 return _other_regions.occ_sparse();
217 }
218
219 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
220
221 // Used in the sequential case.
222 void add_reference(OopOrNarrowOopStar from) {
223 _other_regions.add_reference(from, 0);
224 }
225
226 // Used in the parallel case.
227 void add_reference(OopOrNarrowOopStar from, uint tid) {
228 _other_regions.add_reference(from, tid);
229 }
230
231 // Removes any entries in the remembered set shown by the given card live data to
232 // contain only dead objects. Not thread safe.
233 void scrub(G1CardLiveData* live_data);
234
235 // The region is being reclaimed; clear its remset, and any mention of
236 // entries for this region in other remsets.
237 void clear();
238 void clear_locked();
239
240 // The actual # of bytes this hr_remset takes up.
241 // Note also includes the strong code root set.
242 size_t mem_size() {
243 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
244 return _other_regions.mem_size()
245 // This correction is necessary because the above includes the second
246 // part.
247 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
248 + strong_code_roots_mem_size();
249 }
250
251 // Returns the memory occupancy of all static data structures associated
252 // with remembered sets.
253 static size_t static_mem_size() {
254 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
255 }
256
257 // Returns the memory occupancy of all free_list data structures associated
258 // with remembered sets.
259 static size_t fl_mem_size() {
260 return OtherRegionsTable::fl_mem_size();
261 }
262
263 bool contains_reference(OopOrNarrowOopStar from) const {
264 return _other_regions.contains_reference(from);
265 }
266
267 // Routines for managing the list of code roots that point into
268 // the heap region that owns this RSet.
269 void add_strong_code_root(nmethod* nm);
270 void add_strong_code_root_locked(nmethod* nm);
271 void remove_strong_code_root(nmethod* nm);
272
273 // Applies blk->do_code_blob() to each of the entries in
274 // the strong code roots list
275 void strong_code_roots_do(CodeBlobClosure* blk) const;
276
277 void clean_strong_code_roots(HeapRegion* hr);
278
279 // Returns the number of elements in the strong code roots list
280 size_t strong_code_roots_list_length() const {
281 return _code_roots.length();
282 }
283
284 // Returns true if the strong code roots contains the given
285 // nmethod.
286 bool strong_code_roots_list_contains(nmethod* nm) {
287 return _code_roots.contains(nm);
288 }
289
290 // Returns the amount of memory, in bytes, currently
291 // consumed by the strong code roots.
292 size_t strong_code_roots_mem_size();
293
294 void print() PRODUCT_RETURN;
295
296 // Called during a stop-world phase to perform any deferred cleanups.
297 static void cleanup();
298
299 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
300 G1FromCardCache::invalidate(start_idx, num_regions);
301 }
302
303 #ifndef PRODUCT
304 static void print_from_card_cache() {
305 G1FromCardCache::print();
306 }
307 #endif
308
309 // These are wrappers for the similarly-named methods on
310 // SparsePRT. Look at sparsePRT.hpp for more details.
311 static void reset_for_cleanup_tasks();
312 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
313 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
314
315 // Run unit tests.
316 #ifndef PRODUCT
317 static void test();
318 #endif
319 };
320
321 class HeapRegionRemSetIterator : public StackObj {
322 private:
323 // The region RSet over which we are iterating.
324 HeapRegionRemSet* _hrrs;
325
326 // Local caching of HRRS fields.
327 const BitMap* _coarse_map;
328
329 G1BlockOffsetTable* _bot;
330 G1CollectedHeap* _g1h;
331
332 // The number of cards yielded since initialization.
333 size_t _n_yielded_fine;
334 size_t _n_yielded_coarse;
335 size_t _n_yielded_sparse;
336
337 // Indicates what granularity of table that we are currently iterating over.
338 // We start iterating over the sparse table, progress to the fine grain
339 // table, and then finish with the coarse table.
340 enum IterState {
341 Sparse,
342 Fine,
343 Coarse
344 };
345 IterState _is;
346
347 // For both Coarse and Fine remembered set iteration this contains the
348 // first card number of the heap region we currently iterate over.
349 size_t _cur_region_card_offset;
350
351 // Current region index for the Coarse remembered set iteration.
352 int _coarse_cur_region_index;
353 size_t _coarse_cur_region_cur_card;
354
355 bool coarse_has_next(size_t& card_index);
356
357 // The PRT we are currently iterating over.
358 PerRegionTable* _fine_cur_prt;
359 // Card offset within the current PRT.
360 size_t _cur_card_in_prt;
361
362 // Update internal variables when switching to the given PRT.
363 void switch_to_prt(PerRegionTable* prt);
364 bool fine_has_next();
365 bool fine_has_next(size_t& card_index);
366
367 // The Sparse remembered set iterator.
368 SparsePRTIter _sparse_iter;
369
370 public:
371 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
372
373 // If there remains one or more cards to be yielded, returns true and
374 // sets "card_index" to one of those cards (which is then considered
375 // yielded.) Otherwise, returns false (and leaves "card_index"
376 // undefined.)
377 bool has_next(size_t& card_index);
378
379 size_t n_yielded_fine() { return _n_yielded_fine; }
380 size_t n_yielded_coarse() { return _n_yielded_coarse; }
381 size_t n_yielded_sparse() { return _n_yielded_sparse; }
382 size_t n_yielded() {
383 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
384 }
385 };
386
387 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP