1 /*
2 * Copyright (c) 2001, 2015, 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
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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 G1BlockOffsetSharedArray;
38 class HeapRegion;
39 class HeapRegionRemSetIterator;
40 class PerRegionTable;
41 class SparsePRT;
42 class nmethod;
43
44 // Essentially a wrapper around SparsePRTCleanupTask. See
45 // sparsePRT.hpp for more details.
46 class HRRSCleanupTask : public SparsePRTCleanupTask {
47 };
48
49 // The "_coarse_map" is a bitmap with one bit for each region, where set
50 // bits indicate that the corresponding region may contain some pointer
51 // into the owning region.
52
53 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
54 // (PRTs), indicating regions for which we're keeping the RS as a set of
55 // cards. The strategy is to cap the size of the fine-grain table,
56 // deleting an entry and setting the corresponding coarse-grained bit when
57 // we would overflow this cap.
58
59 // We use a mixture of locking and lock-free techniques here. We allow
60 // threads to locate PRTs without locking, but threads attempting to alter
61 // a bucket list obtain a lock. This means that any failing attempt to
62 // find a PRT must be retried with the lock. It might seem dangerous that
63 // a read can find a PRT that is concurrently deleted. This is all right,
64 // because:
65 //
66 // 1) We only actually free PRT's at safe points (though we reuse them at
67 // other times).
68 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
69 // it's _coarse_map bit is set, so the that we were attempting to add
70 // is represented. If a deleted PRT is re-used, a thread adding a bit,
71 // thinking the PRT is for a different region, does no harm.
72
73 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
74 friend class HeapRegionRemSetIterator;
75
76 G1CollectedHeap* _g1h;
77 Mutex* _m;
78 HeapRegion* _hr;
79
80 // These are protected by "_m".
81 BitMap _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 // Clear the from_card_cache entries for this region.
126 void clear_fcc();
127 public:
128 // Create a new remembered set for the given heap region. The given mutex should
129 // be used to ensure consistency.
130 OtherRegionsTable(HeapRegion* hr, Mutex* m);
131
132 // For now. Could "expand" some tables in the future, so that this made
133 // sense.
134 void add_reference(OopOrNarrowOopStar from, uint tid);
135
136 // Returns whether the remembered set contains the given reference.
137 bool contains_reference(OopOrNarrowOopStar from) const;
138
139 // Returns whether this remembered set (and all sub-sets) have an occupancy
140 // that is less or equal than the given occupancy.
141 bool occupancy_less_or_equal_than(size_t limit) const;
142
143 // Removes any entries shown by the given bitmaps to contain only dead
144 // objects. Not thread safe.
145 // Set bits in the bitmaps indicate that the given region or card is live.
146 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
147
148 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
149 bool is_empty() const;
150
151 // Returns the number of cards contained in this remembered set.
152 size_t occupied() const;
153 size_t occ_fine() const;
154 size_t occ_coarse() const;
155 size_t occ_sparse() const;
156
157 static jint n_coarsenings() { return _n_coarsenings; }
158
159 // Returns size of the actual remembered set containers in bytes.
160 size_t mem_size() const;
161 // Returns the size of static data in bytes.
162 static size_t static_mem_size();
163 // Returns the size of the free list content in bytes.
164 static size_t fl_mem_size();
165
166 // Clear the entire contents of this remembered set.
167 void clear();
168
169 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
170 };
171
172 class HeapRegionRemSet : public CHeapObj<mtGC> {
173 friend class VMStructs;
174 friend class HeapRegionRemSetIterator;
175
176 private:
177 G1BlockOffsetSharedArray* _bosa;
178
179 // A set of code blobs (nmethods) whose code contains pointers into
180 // the region that owns this RSet.
181 G1CodeRootSet _code_roots;
182
183 Mutex _m;
184
185 OtherRegionsTable _other_regions;
186
187 enum ParIterState { Unclaimed, Claimed, Complete };
188 volatile ParIterState _iter_state;
189 volatile size_t _iter_claimed;
190
191 public:
192 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa, HeapRegion* hr);
193
194 static uint num_par_rem_sets();
195 static void setup_remset_size();
196
197 bool is_empty() const {
198 return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
199 }
200
201 bool occupancy_less_or_equal_than(size_t occ) const {
202 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
203 }
204
205 size_t occupied() {
206 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
207 return occupied_locked();
208 }
209 size_t occupied_locked() {
210 return _other_regions.occupied();
211 }
212 size_t occ_fine() const {
213 return _other_regions.occ_fine();
214 }
215 size_t occ_coarse() const {
216 return _other_regions.occ_coarse();
217 }
218 size_t occ_sparse() const {
219 return _other_regions.occ_sparse();
220 }
221
222 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
223
224 // Used in the sequential case.
225 void add_reference(OopOrNarrowOopStar from) {
226 _other_regions.add_reference(from, 0);
227 }
228
229 // Used in the parallel case.
230 void add_reference(OopOrNarrowOopStar from, uint tid) {
231 _other_regions.add_reference(from, tid);
232 }
233
234 // Removes any entries in the remembered set shown by the given bitmaps to
235 // contain only dead objects. Not thread safe.
236 // One bits in the bitmaps indicate that the given region or card is live.
237 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
238
239 // The region is being reclaimed; clear its remset, and any mention of
240 // entries for this region in other remsets.
241 void clear();
242 void clear_locked();
243
244 // Attempt to claim the region. Returns true iff this call caused an
245 // atomic transition from Unclaimed to Claimed.
246 bool claim_iter();
247 // Sets the iteration state to "complete".
248 void set_iter_complete();
249 // Returns "true" iff the region's iteration is complete.
250 bool iter_is_complete();
251
252 // Support for claiming blocks of cards during iteration
253 size_t iter_claimed() const { return _iter_claimed; }
254 // Claim the next block of cards
255 size_t iter_claimed_next(size_t step) {
256 return Atomic::add(step, &_iter_claimed) - step;
257 }
258
259 void reset_for_par_iteration();
260
261 bool verify_ready_for_par_iteration() {
262 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
263 }
264
265 // The actual # of bytes this hr_remset takes up.
266 // Note also includes the strong code root set.
267 size_t mem_size() {
268 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
269 return _other_regions.mem_size()
270 // This correction is necessary because the above includes the second
271 // part.
272 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
273 + strong_code_roots_mem_size();
274 }
275
276 // Returns the memory occupancy of all static data structures associated
277 // with remembered sets.
278 static size_t static_mem_size() {
279 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
280 }
281
282 // Returns the memory occupancy of all free_list data structures associated
283 // with remembered sets.
284 static size_t fl_mem_size() {
285 return OtherRegionsTable::fl_mem_size();
286 }
287
288 bool contains_reference(OopOrNarrowOopStar from) const {
289 return _other_regions.contains_reference(from);
290 }
291
292 // Routines for managing the list of code roots that point into
293 // the heap region that owns this RSet.
294 void add_strong_code_root(nmethod* nm);
295 void add_strong_code_root_locked(nmethod* nm);
296 void remove_strong_code_root(nmethod* nm);
297
298 // Applies blk->do_code_blob() to each of the entries in
299 // the strong code roots list
300 void strong_code_roots_do(CodeBlobClosure* blk) const;
301
302 void clean_strong_code_roots(HeapRegion* hr);
303
304 // Returns the number of elements in the strong code roots list
305 size_t strong_code_roots_list_length() const {
306 return _code_roots.length();
307 }
308
309 // Returns true if the strong code roots contains the given
310 // nmethod.
311 bool strong_code_roots_list_contains(nmethod* nm) {
312 return _code_roots.contains(nm);
313 }
314
315 // Returns the amount of memory, in bytes, currently
316 // consumed by the strong code roots.
317 size_t strong_code_roots_mem_size();
318
319 void print() PRODUCT_RETURN;
320
321 // Called during a stop-world phase to perform any deferred cleanups.
322 static void cleanup();
323
324 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
325 // (Uses it to initialize from_card_cache).
326 static void init_heap(uint max_regions) {
327 G1FromCardCache::initialize(num_par_rem_sets(), max_regions);
328 }
329
330 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
331 G1FromCardCache::invalidate(start_idx, num_regions);
332 }
333
334 #ifndef PRODUCT
335 static void print_from_card_cache() {
336 G1FromCardCache::print();
337 }
338 #endif
339
340 // These are wrappers for the similarly-named methods on
341 // SparsePRT. Look at sparsePRT.hpp for more details.
342 static void reset_for_cleanup_tasks();
343 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
344 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
345
346 // Run unit tests.
347 #ifndef PRODUCT
348 static void test();
349 #endif
350 };
351
352 class HeapRegionRemSetIterator : public StackObj {
353 private:
354 // The region RSet over which we are iterating.
355 HeapRegionRemSet* _hrrs;
356
357 // Local caching of HRRS fields.
358 const BitMap* _coarse_map;
359
360 G1BlockOffsetSharedArray* _bosa;
361 G1CollectedHeap* _g1h;
362
363 // The number of cards yielded since initialization.
364 size_t _n_yielded_fine;
365 size_t _n_yielded_coarse;
366 size_t _n_yielded_sparse;
367
368 // Indicates what granularity of table that we are currently iterating over.
369 // We start iterating over the sparse table, progress to the fine grain
370 // table, and then finish with the coarse table.
371 enum IterState {
372 Sparse,
373 Fine,
374 Coarse
375 };
376 IterState _is;
377
378 // For both Coarse and Fine remembered set iteration this contains the
379 // first card number of the heap region we currently iterate over.
380 size_t _cur_region_card_offset;
381
382 // Current region index for the Coarse remembered set iteration.
383 int _coarse_cur_region_index;
384 size_t _coarse_cur_region_cur_card;
385
386 bool coarse_has_next(size_t& card_index);
387
388 // The PRT we are currently iterating over.
389 PerRegionTable* _fine_cur_prt;
390 // Card offset within the current PRT.
391 size_t _cur_card_in_prt;
392
393 // Update internal variables when switching to the given PRT.
394 void switch_to_prt(PerRegionTable* prt);
395 bool fine_has_next();
396 bool fine_has_next(size_t& card_index);
397
398 // The Sparse remembered set iterator.
399 SparsePRTIter _sparse_iter;
400
401 public:
402 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
403
404 // If there remains one or more cards to be yielded, returns true and
405 // sets "card_index" to one of those cards (which is then considered
406 // yielded.) Otherwise, returns false (and leaves "card_index"
407 // undefined.)
408 bool has_next(size_t& card_index);
409
410 size_t n_yielded_fine() { return _n_yielded_fine; }
411 size_t n_yielded_coarse() { return _n_yielded_coarse; }
412 size_t n_yielded_sparse() { return _n_yielded_sparse; }
413 size_t n_yielded() {
414 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
415 }
416 };
417
418 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP