1 /*
2 * Copyright (c) 2001, 2017, 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.
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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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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 {
75 friend class HeapRegionRemSetIterator;
76
77 G1CollectedHeap* _g1h;
78 Mutex* _m;
79 HeapRegion* _hr;
80
81 // These are protected by "_m".
82 CHeapBitMap _coarse_map;
83 size_t _n_coarse_entries;
84 static jint _n_coarsenings;
85
86 PerRegionTable** _fine_grain_regions;
87 size_t _n_fine_entries;
88
89 // The fine grain remembered sets are doubly linked together using
90 // their 'next' and 'prev' fields.
91 // This allows fast bulk freeing of all the fine grain remembered
92 // set entries, and fast finding of all of them without iterating
93 // over the _fine_grain_regions table.
94 PerRegionTable * _first_all_fine_prts;
95 PerRegionTable * _last_all_fine_prts;
96
97 // Used to sample a subset of the fine grain PRTs to determine which
98 // PRT to evict and coarsen.
99 size_t _fine_eviction_start;
100 static size_t _fine_eviction_stride;
101 static size_t _fine_eviction_sample_size;
102
103 SparsePRT _sparse_table;
104
105 // These are static after init.
106 static size_t _max_fine_entries;
107 static size_t _mod_max_fine_entries_mask;
108
109 // Requires "prt" to be the first element of the bucket list appropriate
110 // for "hr". If this list contains an entry for "hr", return it,
111 // otherwise return "NULL".
112 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
113
114 // Find, delete, and return a candidate PerRegionTable, if any exists,
115 // adding the deleted region to the coarse bitmap. Requires the caller
116 // to hold _m, and the fine-grain table to be full.
117 PerRegionTable* delete_region_table();
118
119 // link/add the given fine grain remembered set into the "all" list
120 void link_to_all(PerRegionTable * prt);
121 // unlink/remove the given fine grain remembered set into the "all" list
122 void unlink_from_all(PerRegionTable * prt);
123
124 bool contains_reference_locked(OopOrNarrowOopStar from) const;
125
126 // Clear the from_card_cache entries for this region.
127 void clear_fcc();
128 public:
129 // Create a new remembered set for the given heap region. The given mutex should
130 // be used to ensure consistency.
131 OtherRegionsTable(HeapRegion* hr, Mutex* m);
132
133 // For now. Could "expand" some tables in the future, so that this made
134 // sense.
135 void add_reference(OopOrNarrowOopStar from, uint tid);
136
137 // Returns whether the remembered set contains the given reference.
138 bool contains_reference(OopOrNarrowOopStar from) const;
139
140 // Returns whether this remembered set (and all sub-sets) have an occupancy
141 // that is less or equal than the given occupancy.
142 bool occupancy_less_or_equal_than(size_t limit) const;
143
144 // Removes any entries shown by the given bitmaps to contain only dead
145 // objects. Not thread safe.
146 // Set bits in the bitmaps indicate that the given region or card is live.
147 void scrub(G1CardLiveData* live_data);
148
149 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
150 bool is_empty() const;
151
152 // Returns the number of cards contained in this remembered set.
153 size_t occupied() const;
154 size_t occ_fine() const;
155 size_t occ_coarse() const;
156 size_t occ_sparse() const;
157
158 static jint n_coarsenings() { return _n_coarsenings; }
159
160 // Returns size of the actual remembered set containers in bytes.
161 size_t mem_size() const;
162 // Returns the size of static data in bytes.
163 static size_t static_mem_size();
164 // Returns the size of the free list content in bytes.
165 static size_t fl_mem_size();
166
167 // Clear the entire contents of this remembered set.
168 void clear();
169
170 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
171 };
172
173 class HeapRegionRemSet : public CHeapObj<mtGC> {
174 friend class VMStructs;
175 friend class HeapRegionRemSetIterator;
176
177 private:
178 G1BlockOffsetTable* _bot;
179
180 // A set of code blobs (nmethods) whose code contains pointers into
181 // the region that owns this RSet.
182 G1CodeRootSet _code_roots;
183
184 Mutex _m;
185
186 OtherRegionsTable _other_regions;
187
188 public:
189 HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
190
191 static void setup_remset_size();
192
193 bool is_empty() const {
194 return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
195 }
196
197 bool occupancy_less_or_equal_than(size_t occ) const {
198 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
199 }
200
201 size_t occupied() {
202 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
203 return occupied_locked();
204 }
205 size_t occupied_locked() {
206 return _other_regions.occupied();
207 }
208 size_t occ_fine() const {
209 return _other_regions.occ_fine();
210 }
211 size_t occ_coarse() const {
212 return _other_regions.occ_coarse();
213 }
214 size_t occ_sparse() const {
215 return _other_regions.occ_sparse();
216 }
217
218 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
219
220 // Used in the sequential case.
221 void add_reference(OopOrNarrowOopStar from) {
222 _other_regions.add_reference(from, 0);
223 }
224
225 // Used in the parallel case.
226 void add_reference(OopOrNarrowOopStar from, uint tid) {
227 _other_regions.add_reference(from, tid);
228 }
229
230 // Removes any entries in the remembered set shown by the given card live data to
231 // contain only dead objects. Not thread safe.
232 void scrub(G1CardLiveData* live_data);
233
234 // The region is being reclaimed; clear its remset, and any mention of
235 // entries for this region in other remsets.
236 void clear();
237 void clear_locked();
238
239 // The actual # of bytes this hr_remset takes up.
240 // Note also includes the strong code root set.
241 size_t mem_size() {
242 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
243 return _other_regions.mem_size()
244 // This correction is necessary because the above includes the second
245 // part.
246 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
247 + strong_code_roots_mem_size();
248 }
249
250 // Returns the memory occupancy of all static data structures associated
251 // with remembered sets.
252 static size_t static_mem_size() {
253 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
254 }
255
256 // Returns the memory occupancy of all free_list data structures associated
257 // with remembered sets.
258 static size_t fl_mem_size() {
259 return OtherRegionsTable::fl_mem_size();
260 }
261
262 bool contains_reference(OopOrNarrowOopStar from) const {
263 return _other_regions.contains_reference(from);
264 }
265
266 // Routines for managing the list of code roots that point into
267 // the heap region that owns this RSet.
268 void add_strong_code_root(nmethod* nm);
269 void add_strong_code_root_locked(nmethod* nm);
270 void remove_strong_code_root(nmethod* nm);
271
272 // Applies blk->do_code_blob() to each of the entries in
273 // the strong code roots list
274 void strong_code_roots_do(CodeBlobClosure* blk) const;
275
276 void clean_strong_code_roots(HeapRegion* hr);
277
278 // Returns the number of elements in the strong code roots list
279 size_t strong_code_roots_list_length() const {
280 return _code_roots.length();
281 }
282
283 // Returns true if the strong code roots contains the given
284 // nmethod.
285 bool strong_code_roots_list_contains(nmethod* nm) {
286 return _code_roots.contains(nm);
287 }
288
289 // Returns the amount of memory, in bytes, currently
290 // consumed by the strong code roots.
291 size_t strong_code_roots_mem_size();
292
293 // Called during a stop-world phase to perform any deferred cleanups.
294 static void cleanup();
295
296 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
297 G1FromCardCache::invalidate(start_idx, num_regions);
298 }
299
300 #ifndef PRODUCT
301 static void print_from_card_cache() {
302 G1FromCardCache::print();
303 }
304 #endif
305
306 // These are wrappers for the similarly-named methods on
307 // SparsePRT. Look at sparsePRT.hpp for more details.
308 static void reset_for_cleanup_tasks();
309 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
310 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
311
312 // Run unit tests.
313 #ifndef PRODUCT
314 static void test();
315 #endif
316 };
317
318 class HeapRegionRemSetIterator : public StackObj {
319 private:
320 // The region RSet over which we are iterating.
321 HeapRegionRemSet* _hrrs;
322
323 // Local caching of HRRS fields.
324 const BitMap* _coarse_map;
325
326 G1BlockOffsetTable* _bot;
327 G1CollectedHeap* _g1h;
328
329 // The number of cards yielded since initialization.
330 size_t _n_yielded_fine;
331 size_t _n_yielded_coarse;
332 size_t _n_yielded_sparse;
333
334 // Indicates what granularity of table that we are currently iterating over.
335 // We start iterating over the sparse table, progress to the fine grain
336 // table, and then finish with the coarse table.
337 enum IterState {
338 Sparse,
339 Fine,
340 Coarse
341 };
342 IterState _is;
343
344 // For both Coarse and Fine remembered set iteration this contains the
345 // first card number of the heap region we currently iterate over.
346 size_t _cur_region_card_offset;
347
348 // Current region index for the Coarse remembered set iteration.
349 int _coarse_cur_region_index;
350 size_t _coarse_cur_region_cur_card;
351
352 bool coarse_has_next(size_t& card_index);
353
354 // The PRT we are currently iterating over.
355 PerRegionTable* _fine_cur_prt;
356 // Card offset within the current PRT.
357 size_t _cur_card_in_prt;
358
359 // Update internal variables when switching to the given PRT.
360 void switch_to_prt(PerRegionTable* prt);
361 bool fine_has_next();
362 bool fine_has_next(size_t& card_index);
363
364 // The Sparse remembered set iterator.
365 SparsePRTIter _sparse_iter;
366
367 public:
368 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
369
370 // If there remains one or more cards to be yielded, returns true and
371 // sets "card_index" to one of those cards (which is then considered
372 // yielded.) Otherwise, returns false (and leaves "card_index"
373 // undefined.)
374 bool has_next(size_t& card_index);
375
376 size_t n_yielded_fine() { return _n_yielded_fine; }
377 size_t n_yielded_coarse() { return _n_yielded_coarse; }
378 size_t n_yielded_sparse() { return _n_yielded_sparse; }
379 size_t n_yielded() {
380 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
381 }
382 };
383
384 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP