Mon, 25 Jun 2012 16:00:55 -0700
6921087: G1: remove per-GC-thread expansion tables from the fine-grain remembered sets
Summary: Remove the per-thread expansion tables (PosParPRT) and associated expansion and compaction from the fine grain RSet entries. This code has been unused for a while.
Reviewed-by: johnc, brutisso
Contributed-by: Thomas Schatzl <thomas.schatzl@jku.at>
1 /*
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
28 #include "gc_implementation/g1/sparsePRT.hpp"
30 // Remembered set for a heap region. Represent a set of "cards" that
31 // contain pointers into the owner heap region. Cards are defined somewhat
32 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
34 class G1CollectedHeap;
35 class G1BlockOffsetSharedArray;
36 class HeapRegion;
37 class HeapRegionRemSetIterator;
38 class PerRegionTable;
39 class SparsePRT;
41 // Essentially a wrapper around SparsePRTCleanupTask. See
42 // sparsePRT.hpp for more details.
43 class HRRSCleanupTask : public SparsePRTCleanupTask {
44 };
46 // The "_coarse_map" is a bitmap with one bit for each region, where set
47 // bits indicate that the corresponding region may contain some pointer
48 // into the owning region.
50 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
51 // (PRTs), indicating regions for which we're keeping the RS as a set of
52 // cards. The strategy is to cap the size of the fine-grain table,
53 // deleting an entry and setting the corresponding coarse-grained bit when
54 // we would overflow this cap.
56 // We use a mixture of locking and lock-free techniques here. We allow
57 // threads to locate PRTs without locking, but threads attempting to alter
58 // a bucket list obtain a lock. This means that any failing attempt to
59 // find a PRT must be retried with the lock. It might seem dangerous that
60 // a read can find a PRT that is concurrently deleted. This is all right,
61 // because:
62 //
63 // 1) We only actually free PRT's at safe points (though we reuse them at
64 // other times).
65 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
66 // it's _coarse_map bit is set, so the that we were attempting to add
67 // is represented. If a deleted PRT is re-used, a thread adding a bit,
68 // thinking the PRT is for a different region, does no harm.
70 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
71 friend class HeapRegionRemSetIterator;
73 G1CollectedHeap* _g1h;
74 Mutex _m;
75 HeapRegion* _hr;
77 // These are protected by "_m".
78 BitMap _coarse_map;
79 size_t _n_coarse_entries;
80 static jint _n_coarsenings;
82 PerRegionTable** _fine_grain_regions;
83 size_t _n_fine_entries;
85 // Used to sample a subset of the fine grain PRTs to determine which
86 // PRT to evict and coarsen.
87 size_t _fine_eviction_start;
88 static size_t _fine_eviction_stride;
89 static size_t _fine_eviction_sample_size;
91 SparsePRT _sparse_table;
93 // These are static after init.
94 static size_t _max_fine_entries;
95 static size_t _mod_max_fine_entries_mask;
97 // Requires "prt" to be the first element of the bucket list appropriate
98 // for "hr". If this list contains an entry for "hr", return it,
99 // otherwise return "NULL".
100 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
102 // Find, delete, and return a candidate PerRegionTable, if any exists,
103 // adding the deleted region to the coarse bitmap. Requires the caller
104 // to hold _m, and the fine-grain table to be full.
105 PerRegionTable* delete_region_table();
107 // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
108 // be the correct index for "hr"), delete it and return true; else return
109 // false.
110 bool del_single_region_table(size_t ind, HeapRegion* hr);
112 // Indexed by thread X heap region, to minimize thread contention.
113 static int** _from_card_cache;
114 static size_t _from_card_cache_max_regions;
115 static size_t _from_card_cache_mem_size;
117 public:
118 OtherRegionsTable(HeapRegion* hr);
120 HeapRegion* hr() const { return _hr; }
122 // For now. Could "expand" some tables in the future, so that this made
123 // sense.
124 void add_reference(OopOrNarrowOopStar from, int tid);
126 // Removes any entries shown by the given bitmaps to contain only dead
127 // objects.
128 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
130 // Not const because it takes a lock.
131 size_t occupied() const;
132 size_t occ_fine() const;
133 size_t occ_coarse() const;
134 size_t occ_sparse() const;
136 static jint n_coarsenings() { return _n_coarsenings; }
138 // Returns size in bytes.
139 // Not const because it takes a lock.
140 size_t mem_size() const;
141 static size_t static_mem_size();
142 static size_t fl_mem_size();
144 bool contains_reference(OopOrNarrowOopStar from) const;
145 bool contains_reference_locked(OopOrNarrowOopStar from) const;
147 void clear();
149 // Specifically clear the from_card_cache.
150 void clear_fcc();
152 // "from_hr" is being cleared; remove any entries from it.
153 void clear_incoming_entry(HeapRegion* from_hr);
155 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
157 // Declare the heap size (in # of regions) to the OtherRegionsTable.
158 // (Uses it to initialize from_card_cache).
159 static void init_from_card_cache(size_t max_regions);
161 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
162 // Make sure any entries for higher regions are invalid.
163 static void shrink_from_card_cache(size_t new_n_regs);
165 static void print_from_card_cache();
166 };
168 class HeapRegionRemSet : public CHeapObj {
169 friend class VMStructs;
170 friend class HeapRegionRemSetIterator;
172 public:
173 enum Event {
174 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
175 };
177 private:
178 G1BlockOffsetSharedArray* _bosa;
179 G1BlockOffsetSharedArray* bosa() const { return _bosa; }
181 OtherRegionsTable _other_regions;
183 enum ParIterState { Unclaimed, Claimed, Complete };
184 volatile ParIterState _iter_state;
185 volatile jlong _iter_claimed;
187 // Unused unless G1RecordHRRSOops is true.
189 static const int MaxRecorded = 1000000;
190 static OopOrNarrowOopStar* _recorded_oops;
191 static HeapWord** _recorded_cards;
192 static HeapRegion** _recorded_regions;
193 static int _n_recorded;
195 static const int MaxRecordedEvents = 1000;
196 static Event* _recorded_events;
197 static int* _recorded_event_index;
198 static int _n_recorded_events;
200 static void print_event(outputStream* str, Event evnt);
202 public:
203 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
204 HeapRegion* hr);
206 static int num_par_rem_sets();
207 static void setup_remset_size();
209 HeapRegion* hr() const {
210 return _other_regions.hr();
211 }
213 size_t occupied() const {
214 return _other_regions.occupied();
215 }
216 size_t occ_fine() const {
217 return _other_regions.occ_fine();
218 }
219 size_t occ_coarse() const {
220 return _other_regions.occ_coarse();
221 }
222 size_t occ_sparse() const {
223 return _other_regions.occ_sparse();
224 }
226 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
228 // Used in the sequential case.
229 void add_reference(OopOrNarrowOopStar from) {
230 _other_regions.add_reference(from, 0);
231 }
233 // Used in the parallel case.
234 void add_reference(OopOrNarrowOopStar from, int tid) {
235 _other_regions.add_reference(from, tid);
236 }
238 // Removes any entries shown by the given bitmaps to contain only dead
239 // objects.
240 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
242 // The region is being reclaimed; clear its remset, and any mention of
243 // entries for this region in other remsets.
244 void clear();
246 // Attempt to claim the region. Returns true iff this call caused an
247 // atomic transition from Unclaimed to Claimed.
248 bool claim_iter();
249 // Sets the iteration state to "complete".
250 void set_iter_complete();
251 // Returns "true" iff the region's iteration is complete.
252 bool iter_is_complete();
254 // Support for claiming blocks of cards during iteration
255 size_t iter_claimed() const { return (size_t)_iter_claimed; }
256 // Claim the next block of cards
257 size_t iter_claimed_next(size_t step) {
258 size_t current, next;
259 do {
260 current = iter_claimed();
261 next = current + step;
262 } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);
263 return current;
264 }
265 void reset_for_par_iteration();
267 bool verify_ready_for_par_iteration() {
268 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
269 }
271 // Initialize the given iterator to iterate over this rem set.
272 void init_iterator(HeapRegionRemSetIterator* iter) const;
274 // The actual # of bytes this hr_remset takes up.
275 size_t mem_size() {
276 return _other_regions.mem_size()
277 // This correction is necessary because the above includes the second
278 // part.
279 + sizeof(this) - sizeof(OtherRegionsTable);
280 }
282 // Returns the memory occupancy of all static data structures associated
283 // with remembered sets.
284 static size_t static_mem_size() {
285 return OtherRegionsTable::static_mem_size();
286 }
288 // Returns the memory occupancy of all free_list data structures associated
289 // with remembered sets.
290 static size_t fl_mem_size() {
291 return OtherRegionsTable::fl_mem_size();
292 }
294 bool contains_reference(OopOrNarrowOopStar from) const {
295 return _other_regions.contains_reference(from);
296 }
297 void print() const;
299 // Called during a stop-world phase to perform any deferred cleanups.
300 static void cleanup();
302 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
303 // (Uses it to initialize from_card_cache).
304 static void init_heap(uint max_regions) {
305 OtherRegionsTable::init_from_card_cache((size_t) max_regions);
306 }
308 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
309 static void shrink_heap(uint new_n_regs) {
310 OtherRegionsTable::shrink_from_card_cache((size_t) new_n_regs);
311 }
313 #ifndef PRODUCT
314 static void print_from_card_cache() {
315 OtherRegionsTable::print_from_card_cache();
316 }
317 #endif
319 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
320 static void print_recorded();
321 static void record_event(Event evnt);
323 // These are wrappers for the similarly-named methods on
324 // SparsePRT. Look at sparsePRT.hpp for more details.
325 static void reset_for_cleanup_tasks();
326 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
327 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
329 // Run unit tests.
330 #ifndef PRODUCT
331 static void test();
332 #endif
333 };
335 class HeapRegionRemSetIterator : public CHeapObj {
337 // The region over which we're iterating.
338 const HeapRegionRemSet* _hrrs;
340 // Local caching of HRRS fields.
341 const BitMap* _coarse_map;
342 PerRegionTable** _fine_grain_regions;
344 G1BlockOffsetSharedArray* _bosa;
345 G1CollectedHeap* _g1h;
347 // The number yielded since initialization.
348 size_t _n_yielded_fine;
349 size_t _n_yielded_coarse;
350 size_t _n_yielded_sparse;
352 // If true we're iterating over the coarse table; if false the fine
353 // table.
354 enum IterState {
355 Sparse,
356 Fine,
357 Coarse
358 };
359 IterState _is;
361 // In both kinds of iteration, heap offset of first card of current
362 // region.
363 size_t _cur_region_card_offset;
364 // Card offset within cur region.
365 size_t _cur_region_cur_card;
367 // Coarse table iteration fields:
369 // Current region index;
370 int _coarse_cur_region_index;
371 size_t _coarse_cur_region_cur_card;
373 bool coarse_has_next(size_t& card_index);
375 // Fine table iteration fields:
377 // Index of bucket-list we're working on.
378 int _fine_array_index;
380 // Per Region Table we're doing within current bucket list.
381 PerRegionTable* _fine_cur_prt;
383 /* SparsePRT::*/ SparsePRTIter _sparse_iter;
385 void fine_find_next_non_null_prt();
387 bool fine_has_next();
388 bool fine_has_next(size_t& card_index);
390 public:
391 // We require an iterator to be initialized before use, so the
392 // constructor does little.
393 HeapRegionRemSetIterator();
395 void initialize(const HeapRegionRemSet* hrrs);
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);
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 };
411 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP