rev 7558 : 8048179: Early reclaim of large objects that are referenced by a few objects
Summary:
Reviewed-by:
rev 7559 : imported patch bengt-review
rev 7560 : [mq]: bengt-review2
1 /*
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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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24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
27
28 #include "gc_implementation/g1/g1CodeCacheRemSet.hpp"
29 #include "gc_implementation/g1/sparsePRT.hpp"
30
31 // Remembered set for a heap region. Represent a set of "cards" that
32 // contain pointers into the owner heap region. Cards are defined somewhat
33 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
34
35 class G1CollectedHeap;
36 class G1BlockOffsetSharedArray;
37 class HeapRegion;
38 class HeapRegionRemSetIterator;
39 class PerRegionTable;
40 class SparsePRT;
41 class nmethod;
42
43 // Essentially a wrapper around SparsePRTCleanupTask. See
44 // sparsePRT.hpp for more details.
45 class HRRSCleanupTask : public SparsePRTCleanupTask {
46 };
47
48 // The FromCardCache remembers the most recently processed card on the heap on
49 // a per-region and per-thread basis.
50 class FromCardCache : public AllStatic {
51 private:
52 // Array of card indices. Indexed by thread X and heap region to minimize
53 // thread contention.
54 static int** _cache;
55 static uint _max_regions;
56 static size_t _static_mem_size;
57
58 public:
59 enum {
60 InvalidCard = -1 // Card value of an invalid card, i.e. a card index not otherwise used.
61 };
62
63 static void clear(uint region_idx);
64
65 // Returns true if the given card is in the cache at the given location, or
66 // replaces the card at that location and returns false.
67 static bool contains_or_replace(uint worker_id, uint region_idx, int card) {
68 int card_in_cache = at(worker_id, region_idx);
69 if (card_in_cache == card) {
70 return true;
71 } else {
72 set(worker_id, region_idx, card);
73 return false;
74 }
75 }
76
77 static int at(uint worker_id, uint region_idx) {
78 return _cache[worker_id][region_idx];
79 }
80
81 static void set(uint worker_id, uint region_idx, int val) {
82 _cache[worker_id][region_idx] = val;
83 }
84
85 static void initialize(uint n_par_rs, uint max_num_regions);
86
87 static void invalidate(uint start_idx, size_t num_regions);
88
89 static void print(outputStream* out = gclog_or_tty) PRODUCT_RETURN;
90
91 static size_t static_mem_size() {
92 return _static_mem_size;
93 }
94 };
95
96 // The "_coarse_map" is a bitmap with one bit for each region, where set
97 // bits indicate that the corresponding region may contain some pointer
98 // into the owning region.
99
100 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
101 // (PRTs), indicating regions for which we're keeping the RS as a set of
102 // cards. The strategy is to cap the size of the fine-grain table,
103 // deleting an entry and setting the corresponding coarse-grained bit when
104 // we would overflow this cap.
105
106 // We use a mixture of locking and lock-free techniques here. We allow
107 // threads to locate PRTs without locking, but threads attempting to alter
108 // a bucket list obtain a lock. This means that any failing attempt to
109 // find a PRT must be retried with the lock. It might seem dangerous that
110 // a read can find a PRT that is concurrently deleted. This is all right,
111 // because:
112 //
113 // 1) We only actually free PRT's at safe points (though we reuse them at
114 // other times).
115 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
116 // it's _coarse_map bit is set, so the that we were attempting to add
117 // is represented. If a deleted PRT is re-used, a thread adding a bit,
118 // thinking the PRT is for a different region, does no harm.
119
120 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
121 friend class HeapRegionRemSetIterator;
122
123 G1CollectedHeap* _g1h;
124 Mutex* _m;
125 HeapRegion* _hr;
126
127 // These are protected by "_m".
128 BitMap _coarse_map;
129 size_t _n_coarse_entries;
130 static jint _n_coarsenings;
131
132 PerRegionTable** _fine_grain_regions;
133 size_t _n_fine_entries;
134
135 // The fine grain remembered sets are doubly linked together using
136 // their 'next' and 'prev' fields.
137 // This allows fast bulk freeing of all the fine grain remembered
138 // set entries, and fast finding of all of them without iterating
139 // over the _fine_grain_regions table.
140 PerRegionTable * _first_all_fine_prts;
141 PerRegionTable * _last_all_fine_prts;
142
143 // Used to sample a subset of the fine grain PRTs to determine which
144 // PRT to evict and coarsen.
145 size_t _fine_eviction_start;
146 static size_t _fine_eviction_stride;
147 static size_t _fine_eviction_sample_size;
148
149 SparsePRT _sparse_table;
150
151 // These are static after init.
152 static size_t _max_fine_entries;
153 static size_t _mod_max_fine_entries_mask;
154
155 // Requires "prt" to be the first element of the bucket list appropriate
156 // for "hr". If this list contains an entry for "hr", return it,
157 // otherwise return "NULL".
158 PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
159
160 // Find, delete, and return a candidate PerRegionTable, if any exists,
161 // adding the deleted region to the coarse bitmap. Requires the caller
162 // to hold _m, and the fine-grain table to be full.
163 PerRegionTable* delete_region_table();
164
165 // link/add the given fine grain remembered set into the "all" list
166 void link_to_all(PerRegionTable * prt);
167 // unlink/remove the given fine grain remembered set into the "all" list
168 void unlink_from_all(PerRegionTable * prt);
169
170 bool contains_reference_locked(OopOrNarrowOopStar from) const;
171
172 // Clear the from_card_cache entries for this region.
173 void clear_fcc();
174 public:
175 // Create a new remembered set for the given heap region. The given mutex should
176 // be used to ensure consistency.
177 OtherRegionsTable(HeapRegion* hr, Mutex* m);
178
179 // For now. Could "expand" some tables in the future, so that this made
180 // sense.
181 void add_reference(OopOrNarrowOopStar from, uint tid);
182
183 // Returns whether the remembered set contains the given reference.
184 bool contains_reference(OopOrNarrowOopStar from) const;
185
186 // Returns whether this remembered set (and all sub-sets) have an occupancy
187 // that is less or equal than the given occupancy.
188 bool occupancy_less_or_equal_than(size_t occ) const;
189
190 // Removes any entries shown by the given bitmaps to contain only dead
191 // objects. Not thread safe.
192 // Set bits in the bitmaps indicate that the given region or card is live.
193 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
194
195 // Returns whether this remembered set (and all sub-sets) does not contain any entry.
196 bool is_empty() const;
197
198 // Returns the number of cards contained in this remembered set.
199 size_t occupied() const;
200 size_t occ_fine() const;
201 size_t occ_coarse() const;
202 size_t occ_sparse() const;
203
204 static jint n_coarsenings() { return _n_coarsenings; }
205
206 // Returns size of the actual remembered set containers in bytes.
207 size_t mem_size() const;
208 // Returns the size of static data in bytes.
209 static size_t static_mem_size();
210 // Returns the size of the free list content in bytes.
211 static size_t fl_mem_size();
212
213 // Clear the entire contents of this remembered set.
214 void clear();
215
216 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
217 };
218
219 class HeapRegionRemSet : public CHeapObj<mtGC> {
220 friend class VMStructs;
221 friend class HeapRegionRemSetIterator;
222
223 public:
224 enum Event {
225 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
226 };
227
228 private:
229 G1BlockOffsetSharedArray* _bosa;
230
231 // A set of code blobs (nmethods) whose code contains pointers into
232 // the region that owns this RSet.
233 G1CodeRootSet _code_roots;
234
235 Mutex _m;
236
237 OtherRegionsTable _other_regions;
238
239 enum ParIterState { Unclaimed, Claimed, Complete };
240 volatile ParIterState _iter_state;
241 volatile size_t _iter_claimed;
242
243 // Unused unless G1RecordHRRSOops is true.
244
245 static const int MaxRecorded = 1000000;
246 static OopOrNarrowOopStar* _recorded_oops;
247 static HeapWord** _recorded_cards;
248 static HeapRegion** _recorded_regions;
249 static int _n_recorded;
250
251 static const int MaxRecordedEvents = 1000;
252 static Event* _recorded_events;
253 static int* _recorded_event_index;
254 static int _n_recorded_events;
255
256 static void print_event(outputStream* str, Event evnt);
257
258 public:
259 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa, HeapRegion* hr);
260
261 static uint num_par_rem_sets();
262 static void setup_remset_size();
263
264 bool is_empty() const {
265 return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
266 }
267
268 bool occupancy_less_or_equal_than(size_t occ) const {
269 return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
270 }
271
272 size_t occupied() {
273 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
274 return occupied_locked();
275 }
276 size_t occupied_locked() {
277 return _other_regions.occupied();
278 }
279 size_t occ_fine() const {
280 return _other_regions.occ_fine();
281 }
282 size_t occ_coarse() const {
283 return _other_regions.occ_coarse();
284 }
285 size_t occ_sparse() const {
286 return _other_regions.occ_sparse();
287 }
288
289 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
290
291 // Used in the sequential case.
292 void add_reference(OopOrNarrowOopStar from) {
293 _other_regions.add_reference(from, 0);
294 }
295
296 // Used in the parallel case.
297 void add_reference(OopOrNarrowOopStar from, uint tid) {
298 _other_regions.add_reference(from, tid);
299 }
300
301 // Removes any entries in the remembered set shown by the given bitmaps to
302 // contain only dead objects. Not thread safe.
303 // One bits in the bitmaps indicate that the given region or card is live.
304 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
305
306 // The region is being reclaimed; clear its remset, and any mention of
307 // entries for this region in other remsets.
308 void clear();
309 void clear_locked();
310
311 // Attempt to claim the region. Returns true iff this call caused an
312 // atomic transition from Unclaimed to Claimed.
313 bool claim_iter();
314 // Sets the iteration state to "complete".
315 void set_iter_complete();
316 // Returns "true" iff the region's iteration is complete.
317 bool iter_is_complete();
318
319 // Support for claiming blocks of cards during iteration
320 size_t iter_claimed() const { return _iter_claimed; }
321 // Claim the next block of cards
322 size_t iter_claimed_next(size_t step) {
323 return Atomic::add(step, &_iter_claimed) - step;
324 }
325
326 void reset_for_par_iteration();
327
328 bool verify_ready_for_par_iteration() {
329 return (_iter_state == Unclaimed) && (_iter_claimed == 0);
330 }
331
332 // The actual # of bytes this hr_remset takes up.
333 // Note also includes the strong code root set.
334 size_t mem_size() {
335 MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
336 return _other_regions.mem_size()
337 // This correction is necessary because the above includes the second
338 // part.
339 + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
340 + strong_code_roots_mem_size();
341 }
342
343 // Returns the memory occupancy of all static data structures associated
344 // with remembered sets.
345 static size_t static_mem_size() {
346 return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
347 }
348
349 // Returns the memory occupancy of all free_list data structures associated
350 // with remembered sets.
351 static size_t fl_mem_size() {
352 return OtherRegionsTable::fl_mem_size();
353 }
354
355 bool contains_reference(OopOrNarrowOopStar from) const {
356 return _other_regions.contains_reference(from);
357 }
358
359 // Routines for managing the list of code roots that point into
360 // the heap region that owns this RSet.
361 void add_strong_code_root(nmethod* nm);
362 void add_strong_code_root_locked(nmethod* nm);
363 void remove_strong_code_root(nmethod* nm);
364
365 // Applies blk->do_code_blob() to each of the entries in
366 // the strong code roots list
367 void strong_code_roots_do(CodeBlobClosure* blk) const;
368
369 void clean_strong_code_roots(HeapRegion* hr);
370
371 // Returns the number of elements in the strong code roots list
372 size_t strong_code_roots_list_length() const {
373 return _code_roots.length();
374 }
375
376 // Returns true if the strong code roots contains the given
377 // nmethod.
378 bool strong_code_roots_list_contains(nmethod* nm) {
379 return _code_roots.contains(nm);
380 }
381
382 // Returns the amount of memory, in bytes, currently
383 // consumed by the strong code roots.
384 size_t strong_code_roots_mem_size();
385
386 void print() PRODUCT_RETURN;
387
388 // Called during a stop-world phase to perform any deferred cleanups.
389 static void cleanup();
390
391 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
392 // (Uses it to initialize from_card_cache).
393 static void init_heap(uint max_regions) {
394 FromCardCache::initialize(num_par_rem_sets(), max_regions);
395 }
396
397 static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
398 FromCardCache::invalidate(start_idx, num_regions);
399 }
400
401 #ifndef PRODUCT
402 static void print_from_card_cache() {
403 FromCardCache::print();
404 }
405 #endif
406
407 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
408 static void print_recorded();
409 static void record_event(Event evnt);
410
411 // These are wrappers for the similarly-named methods on
412 // SparsePRT. Look at sparsePRT.hpp for more details.
413 static void reset_for_cleanup_tasks();
414 void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
415 static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
416
417 // Run unit tests.
418 #ifndef PRODUCT
419 static void test_prt();
420 static void test();
421 #endif
422 };
423
424 class HeapRegionRemSetIterator : public StackObj {
425 private:
426 // The region RSet over which we are iterating.
427 HeapRegionRemSet* _hrrs;
428
429 // Local caching of HRRS fields.
430 const BitMap* _coarse_map;
431
432 G1BlockOffsetSharedArray* _bosa;
433 G1CollectedHeap* _g1h;
434
435 // The number of cards yielded since initialization.
436 size_t _n_yielded_fine;
437 size_t _n_yielded_coarse;
438 size_t _n_yielded_sparse;
439
440 // Indicates what granularity of table that we are currently iterating over.
441 // We start iterating over the sparse table, progress to the fine grain
442 // table, and then finish with the coarse table.
443 enum IterState {
444 Sparse,
445 Fine,
446 Coarse
447 };
448 IterState _is;
449
450 // For both Coarse and Fine remembered set iteration this contains the
451 // first card number of the heap region we currently iterate over.
452 size_t _cur_region_card_offset;
453
454 // Current region index for the Coarse remembered set iteration.
455 int _coarse_cur_region_index;
456 size_t _coarse_cur_region_cur_card;
457
458 bool coarse_has_next(size_t& card_index);
459
460 // The PRT we are currently iterating over.
461 PerRegionTable* _fine_cur_prt;
462 // Card offset within the current PRT.
463 size_t _cur_card_in_prt;
464
465 // Update internal variables when switching to the given PRT.
466 void switch_to_prt(PerRegionTable* prt);
467 bool fine_has_next();
468 bool fine_has_next(size_t& card_index);
469
470 // The Sparse remembered set iterator.
471 SparsePRTIter _sparse_iter;
472
473 public:
474 HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
475
476 // If there remains one or more cards to be yielded, returns true and
477 // sets "card_index" to one of those cards (which is then considered
478 // yielded.) Otherwise, returns false (and leaves "card_index"
479 // undefined.)
480 bool has_next(size_t& card_index);
481
482 size_t n_yielded_fine() { return _n_yielded_fine; }
483 size_t n_yielded_coarse() { return _n_yielded_coarse; }
484 size_t n_yielded_sparse() { return _n_yielded_sparse; }
485 size_t n_yielded() {
486 return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
487 }
488 };
489
490 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
--- EOF ---