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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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 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 G1BlockOffsetTable* _bot;
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(G1BlockOffsetTable* bot, HeapRegion* hr);
193
194 static void setup_remset_size();
195
196 bool is_empty() const {
197 return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
198 }
199
200 bool occupancy_less_or_equal_than(size_t occ) const {
201 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
202 }
203
204 size_t occupied() {
205 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
206 return occupied_locked();
207 }
208 size_t occupied_locked() {
209 return _other_regions.occupied();
210 }
211 size_t occ_fine() const {
212 return _other_regions.occ_fine();
213 }
214 size_t occ_coarse() const {
215 return _other_regions.occ_coarse();
216 }
217 size_t occ_sparse() const {
218 return _other_regions.occ_sparse();
219 }
220
221 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
222
223 // Used in the sequential case.
224 void add_reference(OopOrNarrowOopStar from) {
225 _other_regions.add_reference(from, 0);
226 }
227
228 // Used in the parallel case.
229 void add_reference(OopOrNarrowOopStar from, uint tid) {
230 _other_regions.add_reference(from, tid);
231 }
232
233 // Removes any entries in the remembered set shown by the given bitmaps to
234 // contain only dead objects. Not thread safe.
235 // One bits in the bitmaps indicate that the given region or card is live.
236 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
237
238 // The region is being reclaimed; clear its remset, and any mention of
239 // entries for this region in other remsets.
240 void clear();
241 void clear_locked();
242
243 // Attempt to claim the region. Returns true iff this call caused an
244 // atomic transition from Unclaimed to Claimed.
245 bool claim_iter();
246 // Sets the iteration state to "complete".
247 void set_iter_complete();
248 // Returns "true" iff the region's iteration is complete.
249 bool iter_is_complete();
250
251 // Support for claiming blocks of cards during iteration
252 size_t iter_claimed() const { return _iter_claimed; }
253 // Claim the next block of cards
254 size_t iter_claimed_next(size_t step) {
255 return Atomic::add(step, &_iter_claimed) - step;
256 }
257
258 void reset_for_par_iteration();
259
260 bool verify_ready_for_par_iteration() {
261 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
262 }
263
264 // The actual # of bytes this hr_remset takes up.
265 // Note also includes the strong code root set.
266 size_t mem_size() {
267 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
268 return _other_regions.mem_size()
269 // This correction is necessary because the above includes the second
270 // part.
271 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
272 + strong_code_roots_mem_size();
273 }
274
275 // Returns the memory occupancy of all static data structures associated
276 // with remembered sets.
277 static size_t static_mem_size() {
278 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
279 }
280
281 // Returns the memory occupancy of all free_list data structures associated
282 // with remembered sets.
283 static size_t fl_mem_size() {
284 return OtherRegionsTable::fl_mem_size();
285 }
286
287 bool contains_reference(OopOrNarrowOopStar from) const {
288 return _other_regions.contains_reference(from);
289 }
290
291 // Routines for managing the list of code roots that point into
292 // the heap region that owns this RSet.
293 void add_strong_code_root(nmethod* nm);
294 void add_strong_code_root_locked(nmethod* nm);
295 void remove_strong_code_root(nmethod* nm);
296
297 // Applies blk->do_code_blob() to each of the entries in
298 // the strong code roots list
299 void strong_code_roots_do(CodeBlobClosure* blk) const;
300
301 void clean_strong_code_roots(HeapRegion* hr);
302
303 // Returns the number of elements in the strong code roots list
304 size_t strong_code_roots_list_length() const {
305 return _code_roots.length();
306 }
307
308 // Returns true if the strong code roots contains the given
309 // nmethod.
310 bool strong_code_roots_list_contains(nmethod* nm) {
311 return _code_roots.contains(nm);
312 }
313
314 // Returns the amount of memory, in bytes, currently
315 // consumed by the strong code roots.
316 size_t strong_code_roots_mem_size();
317
318 void print() PRODUCT_RETURN;
319
320 // Called during a stop-world phase to perform any deferred cleanups.
321 static void cleanup();
322
323 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
324 G1FromCardCache::invalidate(start_idx, num_regions);
325 }
326
327 #ifndef PRODUCT
328 static void print_from_card_cache() {
329 G1FromCardCache::print();
330 }
331 #endif
332
333 // These are wrappers for the similarly-named methods on
334 // SparsePRT. Look at sparsePRT.hpp for more details.
335 static void reset_for_cleanup_tasks();
336 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
337 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
338
339 // Run unit tests.
340 #ifndef PRODUCT
341 static void test();
342 #endif
343 };
344
345 class HeapRegionRemSetIterator : public StackObj {
346 private:
347 // The region RSet over which we are iterating.
348 HeapRegionRemSet* _hrrs;
349
350 // Local caching of HRRS fields.
351 const BitMap* _coarse_map;
352
353 G1BlockOffsetTable* _bot;
354 G1CollectedHeap* _g1h;
355
356 // The number of cards yielded since initialization.
357 size_t _n_yielded_fine;
358 size_t _n_yielded_coarse;
359 size_t _n_yielded_sparse;
360
361 // Indicates what granularity of table that we are currently iterating over.
362 // We start iterating over the sparse table, progress to the fine grain
363 // table, and then finish with the coarse table.
364 enum IterState {
365 Sparse,
366 Fine,
367 Coarse
368 };
369 IterState _is;
370
371 // For both Coarse and Fine remembered set iteration this contains the
372 // first card number of the heap region we currently iterate over.
373 size_t _cur_region_card_offset;
374
375 // Current region index for the Coarse remembered set iteration.
376 int _coarse_cur_region_index;
377 size_t _coarse_cur_region_cur_card;
378
379 bool coarse_has_next(size_t& card_index);
380
381 // The PRT we are currently iterating over.
382 PerRegionTable* _fine_cur_prt;
383 // Card offset within the current PRT.
384 size_t _cur_card_in_prt;
385
386 // Update internal variables when switching to the given PRT.
387 void switch_to_prt(PerRegionTable* prt);
388 bool fine_has_next();
389 bool fine_has_next(size_t& card_index);
390
391 // The Sparse remembered set iterator.
392 SparsePRTIter _sparse_iter;
393
394 public:
395 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
396
397 // If there remains one or more cards to be yielded, returns true and
398 // sets "card_index" to one of those cards (which is then considered
399 // yielded.) Otherwise, returns false (and leaves "card_index"
400 // undefined.)
401 bool has_next(size_t& card_index);
402
403 size_t n_yielded_fine() { return _n_yielded_fine; }
404 size_t n_yielded_coarse() { return _n_yielded_coarse; }
405 size_t n_yielded_sparse() { return _n_yielded_sparse; }
406 size_t n_yielded() {
407 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
408 }
409 };
410
411 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP