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24
25#ifndef SHARE_GC_G1_HEAPREGIONREMSET_HPP
26#define SHARE_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
36class G1CollectedHeap;
37class G1BlockOffsetTable;
38class G1CardLiveData;
39class HeapRegion;
40class HeapRegionRemSetIterator;
41class PerRegionTable;
42class SparsePRT;
43class nmethod;
44
45// The "_coarse_map" is a bitmap with one bit for each region, where set
46// bits indicate that the corresponding region may contain some pointer
47// into the owning region.
48
49// The "_fine_grain_entries" array is an open hash table of PerRegionTables
50// (PRTs), indicating regions for which we're keeping the RS as a set of
51// cards. The strategy is to cap the size of the fine-grain table,
52// deleting an entry and setting the corresponding coarse-grained bit when
53// we would overflow this cap.
54
55// We use a mixture of locking and lock-free techniques here. We allow
56// threads to locate PRTs without locking, but threads attempting to alter
57// a bucket list obtain a lock. This means that any failing attempt to
58// find a PRT must be retried with the lock. It might seem dangerous that
59// a read can find a PRT that is concurrently deleted. This is all right,
60// because:
61//
62// 1) We only actually free PRT's at safe points (though we reuse them at
63// other times).
64// 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
65// it's _coarse_map bit is set, so the that we were attempting to add
66// is represented. If a deleted PRT is re-used, a thread adding a bit,
67// thinking the PRT is for a different region, does no harm.
68
69class OtherRegionsTable {
70 friend class HeapRegionRemSetIterator;
71
72 G1CollectedHeap* _g1h;
73 Mutex* _m;
74
75 // These are protected by "_m".
76 CHeapBitMap _coarse_map;
77 size_t _n_coarse_entries;
78 static jint _n_coarsenings;
79
80 PerRegionTable** _fine_grain_regions;
81 size_t _n_fine_entries;
82
83 // The fine grain remembered sets are doubly linked together using
84 // their 'next' and 'prev' fields.
85 // This allows fast bulk freeing of all the fine grain remembered
86 // set entries, and fast finding of all of them without iterating
87 // over the _fine_grain_regions table.
88 PerRegionTable * _first_all_fine_prts;
89 PerRegionTable * _last_all_fine_prts;
90
91 // Used to sample a subset of the fine grain PRTs to determine which
92 // PRT to evict and coarsen.
93 size_t _fine_eviction_start;
94 static size_t _fine_eviction_stride;
95 static size_t _fine_eviction_sample_size;
96
97 SparsePRT _sparse_table;
98
99 // These are static after init.
100 static size_t _max_fine_entries;
101 static size_t _mod_max_fine_entries_mask;
102
103 // Requires "prt" to be the first element of the bucket list appropriate
104 // for "hr". If this list contains an entry for "hr", return it,
105 // otherwise return "NULL".
106 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
107
108 // Find, delete, and return a candidate PerRegionTable, if any exists,
109 // adding the deleted region to the coarse bitmap. Requires the caller
110 // to hold _m, and the fine-grain table to be full.
111 PerRegionTable* delete_region_table();
112
113 // link/add the given fine grain remembered set into the "all" list
114 void link_to_all(PerRegionTable * prt);
115 // unlink/remove the given fine grain remembered set into the "all" list
116 void unlink_from_all(PerRegionTable * prt);
117
118 bool contains_reference_locked(OopOrNarrowOopStar from) const;
119
120 size_t occ_fine() const;
121 size_t occ_coarse() const;
122 size_t occ_sparse() const;
123
124public:
125 // Create a new remembered set. The given mutex is used to ensure consistency.
126 OtherRegionsTable(Mutex* m);
127
128 // Returns the card index of the given within_region pointer relative to the bottom
129 // of the given heap region.
130 static CardIdx_t card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr);
131 // Adds the reference from "from to this remembered set.
132 void add_reference(OopOrNarrowOopStar from, uint tid);
133
134 // Returns whether the remembered set contains the given reference.
135 bool contains_reference(OopOrNarrowOopStar from) const;
136
137 // Returns whether this remembered set (and all sub-sets) have an occupancy
138 // that is less or equal than the given occupancy.
139 bool occupancy_less_or_equal_than(size_t limit) const;
140
141 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
142 bool is_empty() const;
143
144 // Returns the number of cards contained in this remembered set.
145 size_t occupied() const;
146
147 static jint n_coarsenings() { return _n_coarsenings; }
148
149 // Returns size of the actual remembered set containers in bytes.
150 size_t mem_size() const;
151 // Returns the size of static data in bytes.
152 static size_t static_mem_size();
153 // Returns the size of the free list content in bytes.
154 static size_t fl_mem_size();
155
156 // Clear the entire contents of this remembered set.
157 void clear();
158};
159
160class HeapRegionRemSet : public CHeapObj<mtGC> {
161 friend class VMStructs;
162 friend class HeapRegionRemSetIterator;
163
164private:
165 G1BlockOffsetTable* _bot;
166
167 // A set of code blobs (nmethods) whose code contains pointers into
168 // the region that owns this RSet.
169 G1CodeRootSet _code_roots;
170
171 Mutex _m;
172
173 OtherRegionsTable _other_regions;
174
175 HeapRegion* _hr;
176
177 void clear_fcc();
178
179public:
180 HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
181
182 // Setup sparse and fine-grain tables sizes.
183 static void setup_remset_size();
184
185 bool cardset_is_empty() const {
186 return _other_regions.is_empty();
187 }
188
189 bool is_empty() const {
190 return (strong_code_roots_list_length() == 0) && cardset_is_empty();
191 }
192
193 bool occupancy_less_or_equal_than(size_t occ) const {
194 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
195 }
196
197 size_t occupied() {
198 MutexLocker x(&_m, Mutex::_no_safepoint_check_flag);
199 return occupied_locked();
200 }
201 size_t occupied_locked() {
202 return _other_regions.occupied();
203 }
204
205 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
206
207private:
208 enum RemSetState {
209 Untracked,
210 Updating,
211 Complete
212 };
213
214 RemSetState _state;
215
216 static const char* _state_strings[];
217 static const char* _short_state_strings[];
218public:
219
220 const char* get_state_str() const { return _state_strings[_state]; }
221 const char* get_short_state_str() const { return _short_state_strings[_state]; }
222
223 bool is_tracked() { return _state != Untracked; }
224 bool is_updating() { return _state == Updating; }
225 bool is_complete() { return _state == Complete; }
226
227 void set_state_empty() {
228 guarantee(SafepointSynchronize::is_at_safepoint() || !is_tracked(), "Should only set to Untracked during safepoint but is %s.", get_state_str());
229 if (_state == Untracked) {
230 return;
231 }
232 clear_fcc();
233 _state = Untracked;
234 }
235
236 void set_state_updating() {
237 guarantee(SafepointSynchronize::is_at_safepoint() && !is_tracked(), "Should only set to Updating from Untracked during safepoint but is %s", get_state_str());
238 clear_fcc();
239 _state = Updating;
240 }
241
242 void set_state_complete() {
243 clear_fcc();
244 _state = Complete;
245 }
246
247 // Used in the sequential case.
248 void add_reference(OopOrNarrowOopStar from) {
249 add_reference(from, 0);
250 }
251
252 // Used in the parallel case.
253 void add_reference(OopOrNarrowOopStar from, uint tid) {
254 RemSetState state = _state;
255 if (state == Untracked) {
256 return;
257 }
258
259 uint cur_idx = _hr->hrm_index();
260 uintptr_t from_card = uintptr_t(from) >> CardTable::card_shift;
261
262 if (G1FromCardCache::contains_or_replace(tid, cur_idx, from_card)) {
263 assert(contains_reference(from), "We just found " PTR_FORMAT " in the FromCardCache", p2i(from));
264 return;
265 }
266
267 _other_regions.add_reference(from, tid);
268 }
269
270 // The region is being reclaimed; clear its remset, and any mention of
271 // entries for this region in other remsets.
272 void clear(bool only_cardset = false);
273 void clear_locked(bool only_cardset = false);
274
275 // The actual # of bytes this hr_remset takes up.
276 // Note also includes the strong code root set.
277 size_t mem_size() {
278 MutexLocker x(&_m, Mutex::_no_safepoint_check_flag);
279 return _other_regions.mem_size()
280 // This correction is necessary because the above includes the second
281 // part.
282 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
283 + strong_code_roots_mem_size();
284 }
285
286 // Returns the memory occupancy of all static data structures associated
287 // with remembered sets.
288 static size_t static_mem_size() {
289 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
290 }
291
292 // Returns the memory occupancy of all free_list data structures associated
293 // with remembered sets.
294 static size_t fl_mem_size() {
295 return OtherRegionsTable::fl_mem_size();
296 }
297
298 bool contains_reference(OopOrNarrowOopStar from) const {
299 return _other_regions.contains_reference(from);
300 }
301
302 // Routines for managing the list of code roots that point into
303 // the heap region that owns this RSet.
304 void add_strong_code_root(nmethod* nm);
305 void add_strong_code_root_locked(nmethod* nm);
306 void remove_strong_code_root(nmethod* nm);
307
308 // Applies blk->do_code_blob() to each of the entries in
309 // the strong code roots list
310 void strong_code_roots_do(CodeBlobClosure* blk) const;
311
312 void clean_strong_code_roots(HeapRegion* hr);
313
314 // Returns the number of elements in the strong code roots list
315 size_t strong_code_roots_list_length() const {
316 return _code_roots.length();
317 }
318
319 // Returns true if the strong code roots contains the given
320 // nmethod.
321 bool strong_code_roots_list_contains(nmethod* nm) {
322 return _code_roots.contains(nm);
323 }
324
325 // Returns the amount of memory, in bytes, currently
326 // consumed by the strong code roots.
327 size_t strong_code_roots_mem_size();
328
329 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
330 G1FromCardCache::invalidate(start_idx, num_regions);
331 }
332
333#ifndef PRODUCT
334 static void print_from_card_cache() {
335 G1FromCardCache::print();
336 }
337
338 static void test();
339#endif
340};
341
342class HeapRegionRemSetIterator : public StackObj {
343private:
344 // The region RSet over which we are iterating.
345 HeapRegionRemSet* _hrrs;
346
347 // Local caching of HRRS fields.
348 const BitMap* _coarse_map;
349
350 G1BlockOffsetTable* _bot;
351 G1CollectedHeap* _g1h;
352
353 // The number of cards yielded since initialization.
354 size_t _n_yielded_fine;
355 size_t _n_yielded_coarse;
356 size_t _n_yielded_sparse;
357
358 // Indicates what granularity of table that we are currently iterating over.
359 // We start iterating over the sparse table, progress to the fine grain
360 // table, and then finish with the coarse table.
361 enum IterState {
362 Sparse,
363 Fine,
364 Coarse
365 };
366 IterState _is;
367
368 // For both Coarse and Fine remembered set iteration this contains the
369 // first card number of the heap region we currently iterate over.
370 size_t _cur_region_card_offset;
371
372 // Current region index for the Coarse remembered set iteration.
373 int _coarse_cur_region_index;
374 size_t _coarse_cur_region_cur_card;
375
376 bool coarse_has_next(size_t& card_index);
377
378 // The PRT we are currently iterating over.
379 PerRegionTable* _fine_cur_prt;
380 // Card offset within the current PRT.
381 size_t _cur_card_in_prt;
382
383 // Update internal variables when switching to the given PRT.
384 void switch_to_prt(PerRegionTable* prt);
385 bool fine_has_next();
386 bool fine_has_next(size_t& card_index);
387
388 // The Sparse remembered set iterator.
389 SparsePRTIter _sparse_iter;
390
391public:
392 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
393
394 // If there remains one or more cards to be yielded, returns true and
395 // sets "card_index" to one of those cards (which is then considered
396 // yielded.) Otherwise, returns false (and leaves "card_index"
397 // undefined.)
398 bool has_next(size_t& card_index);
399
400 size_t n_yielded_fine() { return _n_yielded_fine; }
401 size_t n_yielded_coarse() { return _n_yielded_coarse; }
402 size_t n_yielded_sparse() { return _n_yielded_sparse; }
403 size_t n_yielded() {
404 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
405 }
406};
407
408#endif // SHARE_GC_G1_HEAPREGIONREMSET_HPP
409