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
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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 cardset_is_empty() const {
191 return _other_regions.is_empty();
192 }
193
194 bool is_empty() const {
195 return (strong_code_roots_list_length() == 0) && cardset_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 private:
222 enum RemSetState {
223 Untracked,
224 Updating,
225 Complete
226 };
227
228 RemSetState _state;
229
230 static const char* _state_strings[];
231 static const char* _short_state_strings[];
232 public:
233
234 const char* get_state_str() const { return _state_strings[_state]; }
235 const char* get_short_state_str() const { return _short_state_strings[_state]; }
236
237 bool is_tracked() { return _state != Untracked; }
238 bool is_updating() { return _state == Updating; }
239 bool is_complete() { return _state == Complete; }
240
241 void set_state_empty() {
242 guarantee(SafepointSynchronize::is_at_safepoint() || !is_tracked(), "Should only set to Untracked during safepoint but is %s.", get_state_str());
243 if (_state == Untracked) {
244 return;
245 }
246 _other_regions.clear_fcc();
247 _state = Untracked;
248 }
249
250 void set_state_updating() {
251 guarantee(SafepointSynchronize::is_at_safepoint() && !is_tracked(), "Should only set to Updating from Untracked during safepoint but is %s", get_state_str());
252 _other_regions.clear_fcc();
253 _state = Updating;
254 }
255
256 void set_state_complete() {
257 _other_regions.clear_fcc();
258 _state = Complete;
259 }
260
261 // Used in the sequential case.
262 void add_reference(OopOrNarrowOopStar from) {
263 add_reference(from, 0);
264 }
265
266 // Used in the parallel case.
267 void add_reference(OopOrNarrowOopStar from, uint tid) {
268 RemSetState state = _state;
269 if (state == Untracked) {
270 return;
271 }
272 _other_regions.add_reference(from, tid);
273 }
274
275 // The region is being reclaimed; clear its remset, and any mention of
276 // entries for this region in other remsets.
277 void clear(bool only_cardset = false);
278 void clear_locked(bool only_cardset = false);
279
280 // The actual # of bytes this hr_remset takes up.
281 // Note also includes the strong code root set.
282 size_t mem_size() {
283 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
284 return _other_regions.mem_size()
285 // This correction is necessary because the above includes the second
286 // part.
287 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
288 + strong_code_roots_mem_size();
289 }
290
291 // Returns the memory occupancy of all static data structures associated
292 // with remembered sets.
293 static size_t static_mem_size() {
294 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
295 }
296
297 // Returns the memory occupancy of all free_list data structures associated
298 // with remembered sets.
299 static size_t fl_mem_size() {
300 return OtherRegionsTable::fl_mem_size();
301 }
302
303 bool contains_reference(OopOrNarrowOopStar from) const {
304 return _other_regions.contains_reference(from);
305 }
306
307 // Routines for managing the list of code roots that point into
308 // the heap region that owns this RSet.
309 void add_strong_code_root(nmethod* nm);
310 void add_strong_code_root_locked(nmethod* nm);
311 void remove_strong_code_root(nmethod* nm);
312
313 // Applies blk->do_code_blob() to each of the entries in
314 // the strong code roots list
315 void strong_code_roots_do(CodeBlobClosure* blk) const;
316
317 void clean_strong_code_roots(HeapRegion* hr);
318
319 // Returns the number of elements in the strong code roots list
320 size_t strong_code_roots_list_length() const {
321 return _code_roots.length();
322 }
323
324 // Returns true if the strong code roots contains the given
325 // nmethod.
326 bool strong_code_roots_list_contains(nmethod* nm) {
327 return _code_roots.contains(nm);
328 }
329
330 // Returns the amount of memory, in bytes, currently
331 // consumed by the strong code roots.
332 size_t strong_code_roots_mem_size();
333
334 // Called during a stop-world phase to perform any deferred cleanups.
335 static void cleanup();
336
337 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
338 G1FromCardCache::invalidate(start_idx, num_regions);
339 }
340
341 #ifndef PRODUCT
342 static void print_from_card_cache() {
343 G1FromCardCache::print();
344 }
345 #endif
346
347 // These are wrappers for the similarly-named methods on
348 // SparsePRT. Look at sparsePRT.hpp for more details.
349 static void reset_for_cleanup_tasks();
350 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
351 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
352
353 // Run unit tests.
354 #ifndef PRODUCT
355 static void test();
356 #endif
357 };
358
359 class HeapRegionRemSetIterator : public StackObj {
360 private:
361 // The region RSet over which we are iterating.
362 HeapRegionRemSet* _hrrs;
363
364 // Local caching of HRRS fields.
365 const BitMap* _coarse_map;
366
367 G1BlockOffsetTable* _bot;
368 G1CollectedHeap* _g1h;
369
370 // The number of cards yielded since initialization.
371 size_t _n_yielded_fine;
372 size_t _n_yielded_coarse;
373 size_t _n_yielded_sparse;
374
375 // Indicates what granularity of table that we are currently iterating over.
376 // We start iterating over the sparse table, progress to the fine grain
377 // table, and then finish with the coarse table.
378 enum IterState {
379 Sparse,
380 Fine,
381 Coarse
382 };
383 IterState _is;
384
385 // For both Coarse and Fine remembered set iteration this contains the
386 // first card number of the heap region we currently iterate over.
387 size_t _cur_region_card_offset;
388
389 // Current region index for the Coarse remembered set iteration.
390 int _coarse_cur_region_index;
391 size_t _coarse_cur_region_cur_card;
392
393 bool coarse_has_next(size_t& card_index);
394
395 // The PRT we are currently iterating over.
396 PerRegionTable* _fine_cur_prt;
397 // Card offset within the current PRT.
398 size_t _cur_card_in_prt;
399
400 // Update internal variables when switching to the given PRT.
401 void switch_to_prt(PerRegionTable* prt);
402 bool fine_has_next();
403 bool fine_has_next(size_t& card_index);
404
405 // The Sparse remembered set iterator.
406 SparsePRTIter _sparse_iter;
407
408 public:
409 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
410
411 // If there remains one or more cards to be yielded, returns true and
412 // sets "card_index" to one of those cards (which is then considered
413 // yielded.) Otherwise, returns false (and leaves "card_index"
414 // undefined.)
415 bool has_next(size_t& card_index);
416
417 size_t n_yielded_fine() { return _n_yielded_fine; }
418 size_t n_yielded_coarse() { return _n_yielded_coarse; }
419 size_t n_yielded_sparse() { return _n_yielded_sparse; }
420 size_t n_yielded() {
421 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
422 }
423 };
424
425 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP