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.
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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).
14 *
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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 {
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 public:
127 // Clear the from_card_cache entries for this region.
128 void clear_fcc();
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 // Returns the card index of the given within_region pointer relative to the bottom
134 // of the given heap region.
135 static CardIdx_t card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr);
136 // Adds the reference from "from to this remembered set.
137 void add_reference(OopOrNarrowOopStar from, uint tid);
138
139 // Returns whether the remembered set contains the given reference.
140 bool contains_reference(OopOrNarrowOopStar from) const;
141
142 // Returns whether this remembered set (and all sub-sets) have an occupancy
143 // that is less or equal than the given occupancy.
144 bool occupancy_less_or_equal_than(size_t limit) const;
145
146 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
147 bool is_empty() const;
148
149 // Returns the number of cards contained in this remembered set.
150 size_t occupied() const;
151 size_t occ_fine() const;
152 size_t occ_coarse() const;
153 size_t occ_sparse() const;
154
155 static jint n_coarsenings() { return _n_coarsenings; }
156
157 // Returns size of the actual remembered set containers in bytes.
158 size_t mem_size() const;
159 // Returns the size of static data in bytes.
160 static size_t static_mem_size();
161 // Returns the size of the free list content in bytes.
162 static size_t fl_mem_size();
163
164 // Clear the entire contents of this remembered set.
165 void clear();
166
167 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
168 };
169
170 class HeapRegionRemSet : public CHeapObj<mtGC> {
171 friend class VMStructs;
172 friend class HeapRegionRemSetIterator;
173
174 private:
175 G1BlockOffsetTable* _bot;
176
177 // A set of code blobs (nmethods) whose code contains pointers into
178 // the region that owns this RSet.
179 G1CodeRootSet _code_roots;
180
181 Mutex _m;
182
183 OtherRegionsTable _other_regions;
184
185 public:
186 HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
187
188 static void setup_remset_size();
189
190 bool is_empty() const {
191 return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
192 }
193
194 bool occupancy_less_or_equal_than(size_t occ) const {
195 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
196 }
197
198 size_t occupied() {
199 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
200 return occupied_locked();
201 }
202 size_t occupied_locked() {
203 return _other_regions.occupied();
204 }
205 size_t occ_fine() const {
206 return _other_regions.occ_fine();
207 }
208 size_t occ_coarse() const {
209 return _other_regions.occ_coarse();
210 }
211 size_t occ_sparse() const {
212 return _other_regions.occ_sparse();
213 }
214
215 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
216
217 private:
218 enum RemSetState {
219 Untracked,
220 Updating,
221 Complete
222 };
223
224 RemSetState _state;
225
226 static const char* _state_strings[];
227 static const char* _short_state_strings[];
228 public:
229
230 const char* get_state_str() const { return _state_strings[_state]; }
231 const char* get_short_state_str() const { return _short_state_strings[_state]; }
232
233 bool is_tracked() { return _state != Untracked; }
234 bool is_updating() { return _state == Updating; }
235 bool is_complete() { return _state == Complete; }
236
237 void set_state_empty() {
238 guarantee(SafepointSynchronize::is_at_safepoint() || !is_tracked(), "Should only set to Untracked during safepoint but is %s.", get_state_str());
239 if (_state == Untracked) {
240 return;
241 }
242 _other_regions.clear_fcc();
243 _state = Untracked;
244 }
245
246 void set_state_updating() {
247 guarantee(SafepointSynchronize::is_at_safepoint() && !is_tracked(), "Should only set to Updating from Untracked during safepoint but is %s", get_state_str());
248 _other_regions.clear_fcc();
249 _state = Updating;
250 }
251
252 void set_state_complete() {
253 _other_regions.clear_fcc();
254 _state = Complete;
255 }
256
257 // Used in the sequential case.
258 void add_reference(OopOrNarrowOopStar from) {
259 add_reference(from, 0);
260 }
261
262 // Used in the parallel case.
263 void add_reference(OopOrNarrowOopStar from, uint tid) {
264 RemSetState state = _state;
265 if (state == Untracked) {
266 return;
267 }
268 _other_regions.add_reference(from, tid);
269 }
270
271 // The region is being reclaimed; clear its remset, and any mention of
272 // entries for this region in other remsets.
273 void clear(bool only_cardset = false);
274 void clear_locked(bool only_cardset = false);
275
276 // The actual # of bytes this hr_remset takes up.
277 // Note also includes the strong code root set.
278 size_t mem_size() {
279 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
280 return _other_regions.mem_size()
281 // This correction is necessary because the above includes the second
282 // part.
283 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
284 + strong_code_roots_mem_size();
285 }
286
287 // Returns the memory occupancy of all static data structures associated
288 // with remembered sets.
289 static size_t static_mem_size() {
290 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
291 }
292
293 // Returns the memory occupancy of all free_list data structures associated
294 // with remembered sets.
295 static size_t fl_mem_size() {
296 return OtherRegionsTable::fl_mem_size();
297 }
298
299 bool contains_reference(OopOrNarrowOopStar from) const {
300 return _other_regions.contains_reference(from);
301 }
302
303 // Routines for managing the list of code roots that point into
304 // the heap region that owns this RSet.
305 void add_strong_code_root(nmethod* nm);
306 void add_strong_code_root_locked(nmethod* nm);
307 void remove_strong_code_root(nmethod* nm);
308
309 // Applies blk->do_code_blob() to each of the entries in
310 // the strong code roots list
311 void strong_code_roots_do(CodeBlobClosure* blk) const;
312
313 void clean_strong_code_roots(HeapRegion* hr);
314
315 // Returns the number of elements in the strong code roots list
316 size_t strong_code_roots_list_length() const {
317 return _code_roots.length();
318 }
319
320 // Returns true if the strong code roots contains the given
321 // nmethod.
322 bool strong_code_roots_list_contains(nmethod* nm) {
323 return _code_roots.contains(nm);
324 }
325
326 // Returns the amount of memory, in bytes, currently
327 // consumed by the strong code roots.
328 size_t strong_code_roots_mem_size();
329
330 // Called during a stop-world phase to perform any deferred cleanups.
331 static void cleanup();
332
333 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
334 G1FromCardCache::invalidate(start_idx, num_regions);
335 }
336
337 #ifndef PRODUCT
338 static void print_from_card_cache() {
339 G1FromCardCache::print();
340 }
341 #endif
342
343 // These are wrappers for the similarly-named methods on
344 // SparsePRT. Look at sparsePRT.hpp for more details.
345 static void reset_for_cleanup_tasks();
346 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
347 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
348
349 // Run unit tests.
350 #ifndef PRODUCT
351 static void test();
352 #endif
353 };
354
355 class HeapRegionRemSetIterator : public StackObj {
356 private:
357 // The region RSet over which we are iterating.
358 HeapRegionRemSet* _hrrs;
359
360 // Local caching of HRRS fields.
361 const BitMap* _coarse_map;
362
363 G1BlockOffsetTable* _bot;
364 G1CollectedHeap* _g1h;
365
366 // The number of cards yielded since initialization.
367 size_t _n_yielded_fine;
368 size_t _n_yielded_coarse;
369 size_t _n_yielded_sparse;
370
371 // Indicates what granularity of table that we are currently iterating over.
372 // We start iterating over the sparse table, progress to the fine grain
373 // table, and then finish with the coarse table.
374 enum IterState {
375 Sparse,
376 Fine,
377 Coarse
378 };
379 IterState _is;
380
381 // For both Coarse and Fine remembered set iteration this contains the
382 // first card number of the heap region we currently iterate over.
383 size_t _cur_region_card_offset;
384
385 // Current region index for the Coarse remembered set iteration.
386 int _coarse_cur_region_index;
387 size_t _coarse_cur_region_cur_card;
388
389 bool coarse_has_next(size_t& card_index);
390
391 // The PRT we are currently iterating over.
392 PerRegionTable* _fine_cur_prt;
393 // Card offset within the current PRT.
394 size_t _cur_card_in_prt;
395
396 // Update internal variables when switching to the given PRT.
397 void switch_to_prt(PerRegionTable* prt);
398 bool fine_has_next();
399 bool fine_has_next(size_t& card_index);
400
401 // The Sparse remembered set iterator.
402 SparsePRTIter _sparse_iter;
403
404 public:
405 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
406
407 // If there remains one or more cards to be yielded, returns true and
408 // sets "card_index" to one of those cards (which is then considered
409 // yielded.) Otherwise, returns false (and leaves "card_index"
410 // undefined.)
411 bool has_next(size_t& card_index);
412
413 size_t n_yielded_fine() { return _n_yielded_fine; }
414 size_t n_yielded_coarse() { return _n_yielded_coarse; }
415 size_t n_yielded_sparse() { return _n_yielded_sparse; }
416 size_t n_yielded() {
417 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
418 }
419 };
420
421 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP