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,
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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
80 // These are protected by "_m".
81 CHeapBitMap _coarse_map;
82 size_t _n_coarse_entries;
83 static jint _n_coarsenings;
84
85 PerRegionTable** _fine_grain_regions;
86 size_t _n_fine_entries;
87
88 // The fine grain remembered sets are doubly linked together using
89 // their 'next' and 'prev' fields.
90 // This allows fast bulk freeing of all the fine grain remembered
91 // set entries, and fast finding of all of them without iterating
92 // over the _fine_grain_regions table.
93 PerRegionTable * _first_all_fine_prts;
94 PerRegionTable * _last_all_fine_prts;
95
96 // Used to sample a subset of the fine grain PRTs to determine which
97 // PRT to evict and coarsen.
98 size_t _fine_eviction_start;
99 static size_t _fine_eviction_stride;
100 static size_t _fine_eviction_sample_size;
101
102 SparsePRT _sparse_table;
103
104 // These are static after init.
105 static size_t _max_fine_entries;
106 static size_t _mod_max_fine_entries_mask;
107
108 // Requires "prt" to be the first element of the bucket list appropriate
109 // for "hr". If this list contains an entry for "hr", return it,
110 // otherwise return "NULL".
111 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
112
113 // Find, delete, and return a candidate PerRegionTable, if any exists,
114 // adding the deleted region to the coarse bitmap. Requires the caller
115 // to hold _m, and the fine-grain table to be full.
116 PerRegionTable* delete_region_table();
117
118 // link/add the given fine grain remembered set into the "all" list
119 void link_to_all(PerRegionTable * prt);
120 // unlink/remove the given fine grain remembered set into the "all" list
121 void unlink_from_all(PerRegionTable * prt);
122
123 bool contains_reference_locked(OopOrNarrowOopStar from) const;
124
125 public:
126 // Create a new remembered set. The given mutex is used to ensure consistency.
127 OtherRegionsTable(Mutex* m);
128
129 // Returns the card index of the given within_region pointer relative to the bottom
130 // of the given heap region.
131 static CardIdx_t card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr);
132 // Adds the reference from "from to this remembered set.
133 void add_reference(OopOrNarrowOopStar from, uint tid);
134
135 // Returns whether the remembered set contains the given reference.
136 bool contains_reference(OopOrNarrowOopStar from) const;
137
138 // Returns whether this remembered set (and all sub-sets) have an occupancy
139 // that is less or equal than the given occupancy.
140 bool occupancy_less_or_equal_than(size_t limit) const;
141
142 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
143 bool is_empty() const;
144
145 // Returns the number of cards contained in this remembered set.
146 size_t occupied() const;
147 size_t occ_fine() const;
148 size_t occ_coarse() const;
149 size_t occ_sparse() const;
150
151 static jint n_coarsenings() { return _n_coarsenings; }
152
153 // Returns size of the actual remembered set containers in bytes.
154 size_t mem_size() const;
155 // Returns the size of static data in bytes.
156 static size_t static_mem_size();
157 // Returns the size of the free list content in bytes.
158 static size_t fl_mem_size();
159
160 // Clear the entire contents of this remembered set.
161 void clear();
162
163 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
164 };
165
166 class HeapRegionRemSet : public CHeapObj<mtGC> {
167 friend class VMStructs;
168 friend class HeapRegionRemSetIterator;
169
170 private:
171 G1BlockOffsetTable* _bot;
172
173 // A set of code blobs (nmethods) whose code contains pointers into
174 // the region that owns this RSet.
175 G1CodeRootSet _code_roots;
176
177 Mutex _m;
178
179 OtherRegionsTable _other_regions;
180
181 HeapRegion* _hr;
182
183 void clear_fcc();
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 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 clear_fcc();
253 _state = Updating;
254 }
255
256 void set_state_complete() {
257 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
273 uint cur_idx = _hr->hrm_index();
274 uintptr_t from_card = uintptr_t(from) >> CardTable::card_shift;
275
276 if (G1FromCardCache::contains_or_replace(tid, cur_idx, from_card)) {
277 assert(contains_reference(from), "We just found " PTR_FORMAT " in the FromCardCache", p2i(from));
278 return;
279 }
280
281 _other_regions.add_reference(from, tid);
282 }
283
284 // The region is being reclaimed; clear its remset, and any mention of
285 // entries for this region in other remsets.
286 void clear(bool only_cardset = false);
287 void clear_locked(bool only_cardset = false);
288
289 // The actual # of bytes this hr_remset takes up.
290 // Note also includes the strong code root set.
291 size_t mem_size() {
292 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
293 return _other_regions.mem_size()
294 // This correction is necessary because the above includes the second
295 // part.
296 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
297 + strong_code_roots_mem_size();
298 }
299
300 // Returns the memory occupancy of all static data structures associated
301 // with remembered sets.
302 static size_t static_mem_size() {
303 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
304 }
305
306 // Returns the memory occupancy of all free_list data structures associated
307 // with remembered sets.
308 static size_t fl_mem_size() {
309 return OtherRegionsTable::fl_mem_size();
310 }
311
312 bool contains_reference(OopOrNarrowOopStar from) const {
313 return _other_regions.contains_reference(from);
314 }
315
316 // Routines for managing the list of code roots that point into
317 // the heap region that owns this RSet.
318 void add_strong_code_root(nmethod* nm);
319 void add_strong_code_root_locked(nmethod* nm);
320 void remove_strong_code_root(nmethod* nm);
321
322 // Applies blk->do_code_blob() to each of the entries in
323 // the strong code roots list
324 void strong_code_roots_do(CodeBlobClosure* blk) const;
325
326 void clean_strong_code_roots(HeapRegion* hr);
327
328 // Returns the number of elements in the strong code roots list
329 size_t strong_code_roots_list_length() const {
330 return _code_roots.length();
331 }
332
333 // Returns true if the strong code roots contains the given
334 // nmethod.
335 bool strong_code_roots_list_contains(nmethod* nm) {
336 return _code_roots.contains(nm);
337 }
338
339 // Returns the amount of memory, in bytes, currently
340 // consumed by the strong code roots.
341 size_t strong_code_roots_mem_size();
342
343 // Called during a stop-world phase to perform any deferred cleanups.
344 static void cleanup();
345
346 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
347 G1FromCardCache::invalidate(start_idx, num_regions);
348 }
349
350 #ifndef PRODUCT
351 static void print_from_card_cache() {
352 G1FromCardCache::print();
353 }
354 #endif
355
356 // These are wrappers for the similarly-named methods on
357 // SparsePRT. Look at sparsePRT.hpp for more details.
358 static void reset_for_cleanup_tasks();
359 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
360 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
361
362 // Run unit tests.
363 #ifndef PRODUCT
364 static void test();
365 #endif
366 };
367
368 class HeapRegionRemSetIterator : public StackObj {
369 private:
370 // The region RSet over which we are iterating.
371 HeapRegionRemSet* _hrrs;
372
373 // Local caching of HRRS fields.
374 const BitMap* _coarse_map;
375
376 G1BlockOffsetTable* _bot;
377 G1CollectedHeap* _g1h;
378
379 // The number of cards yielded since initialization.
380 size_t _n_yielded_fine;
381 size_t _n_yielded_coarse;
382 size_t _n_yielded_sparse;
383
384 // Indicates what granularity of table that we are currently iterating over.
385 // We start iterating over the sparse table, progress to the fine grain
386 // table, and then finish with the coarse table.
387 enum IterState {
388 Sparse,
389 Fine,
390 Coarse
391 };
392 IterState _is;
393
394 // For both Coarse and Fine remembered set iteration this contains the
395 // first card number of the heap region we currently iterate over.
396 size_t _cur_region_card_offset;
397
398 // Current region index for the Coarse remembered set iteration.
399 int _coarse_cur_region_index;
400 size_t _coarse_cur_region_cur_card;
401
402 bool coarse_has_next(size_t& card_index);
403
404 // The PRT we are currently iterating over.
405 PerRegionTable* _fine_cur_prt;
406 // Card offset within the current PRT.
407 size_t _cur_card_in_prt;
408
409 // Update internal variables when switching to the given PRT.
410 void switch_to_prt(PerRegionTable* prt);
411 bool fine_has_next();
412 bool fine_has_next(size_t& card_index);
413
414 // The Sparse remembered set iterator.
415 SparsePRTIter _sparse_iter;
416
417 public:
418 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
419
420 // If there remains one or more cards to be yielded, returns true and
421 // sets "card_index" to one of those cards (which is then considered
422 // yielded.) Otherwise, returns false (and leaves "card_index"
423 // undefined.)
424 bool has_next(size_t& card_index);
425
426 size_t n_yielded_fine() { return _n_yielded_fine; }
427 size_t n_yielded_coarse() { return _n_yielded_coarse; }
428 size_t n_yielded_sparse() { return _n_yielded_sparse; }
429 size_t n_yielded() {
430 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
431 }
432 };
433
434 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP