Wed, 30 Sep 2009 14:50:51 -0400
6890137: G1: revamp reachable object dump
Summary: Revamp the reachable object dump debugging facility.
Reviewed-by: jmasa, apetrusenko
1 /*
2 * Copyright 2001-2009 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 // Remembered set for a heap region. Represent a set of "cards" that
26 // contain pointers into the owner heap region. Cards are defined somewhat
27 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
29 class G1CollectedHeap;
30 class G1BlockOffsetSharedArray;
31 class HeapRegion;
32 class HeapRegionRemSetIterator;
33 class PosParPRT;
34 class SparsePRT;
37 // The "_coarse_map" is a bitmap with one bit for each region, where set
38 // bits indicate that the corresponding region may contain some pointer
39 // into the owning region.
41 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
42 // (PRTs), indicating regions for which we're keeping the RS as a set of
43 // cards. The strategy is to cap the size of the fine-grain table,
44 // deleting an entry and setting the corresponding coarse-grained bit when
45 // we would overflow this cap.
47 // We use a mixture of locking and lock-free techniques here. We allow
48 // threads to locate PRTs without locking, but threads attempting to alter
49 // a bucket list obtain a lock. This means that any failing attempt to
50 // find a PRT must be retried with the lock. It might seem dangerous that
51 // a read can find a PRT that is concurrently deleted. This is all right,
52 // because:
53 //
54 // 1) We only actually free PRT's at safe points (though we reuse them at
55 // other times).
56 // 2) We find PRT's in an attempt to add entries. If a PRT is deleted,
57 // it's _coarse_map bit is set, so the that we were attempting to add
58 // is represented. If a deleted PRT is re-used, a thread adding a bit,
59 // thinking the PRT is for a different region, does no harm.
61 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
62 friend class HeapRegionRemSetIterator;
64 G1CollectedHeap* _g1h;
65 Mutex _m;
66 HeapRegion* _hr;
68 // These are protected by "_m".
69 BitMap _coarse_map;
70 size_t _n_coarse_entries;
71 static jint _n_coarsenings;
73 PosParPRT** _fine_grain_regions;
74 size_t _n_fine_entries;
76 #define SAMPLE_FOR_EVICTION 1
77 #if SAMPLE_FOR_EVICTION
78 size_t _fine_eviction_start;
79 static size_t _fine_eviction_stride;
80 static size_t _fine_eviction_sample_size;
81 #endif
83 SparsePRT _sparse_table;
85 // These are static after init.
86 static size_t _max_fine_entries;
87 static size_t _mod_max_fine_entries_mask;
89 // Requires "prt" to be the first element of the bucket list appropriate
90 // for "hr". If this list contains an entry for "hr", return it,
91 // otherwise return "NULL".
92 PosParPRT* find_region_table(size_t ind, HeapRegion* hr) const;
94 // Find, delete, and return a candidate PosParPRT, if any exists,
95 // adding the deleted region to the coarse bitmap. Requires the caller
96 // to hold _m, and the fine-grain table to be full.
97 PosParPRT* delete_region_table();
99 // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
100 // be the correct index for "hr"), delete it and return true; else return
101 // false.
102 bool del_single_region_table(size_t ind, HeapRegion* hr);
104 static jint _cache_probes;
105 static jint _cache_hits;
107 // Indexed by thread X heap region, to minimize thread contention.
108 static int** _from_card_cache;
109 static size_t _from_card_cache_max_regions;
110 static size_t _from_card_cache_mem_size;
112 public:
113 OtherRegionsTable(HeapRegion* hr);
115 HeapRegion* hr() const { return _hr; }
117 // For now. Could "expand" some tables in the future, so that this made
118 // sense.
119 void add_reference(OopOrNarrowOopStar from, int tid);
121 void add_reference(OopOrNarrowOopStar from) {
122 return add_reference(from, 0);
123 }
125 // Removes any entries shown by the given bitmaps to contain only dead
126 // objects.
127 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
129 // Not const because it takes a lock.
130 size_t occupied() const;
131 size_t occ_fine() const;
132 size_t occ_coarse() const;
133 size_t occ_sparse() const;
135 static jint n_coarsenings() { return _n_coarsenings; }
137 // Returns size in bytes.
138 // Not const because it takes a lock.
139 size_t mem_size() const;
140 static size_t static_mem_size();
141 static size_t fl_mem_size();
143 bool contains_reference(OopOrNarrowOopStar from) const;
144 bool contains_reference_locked(OopOrNarrowOopStar from) const;
146 void clear();
148 // Specifically clear the from_card_cache.
149 void clear_fcc();
151 // "from_hr" is being cleared; remove any entries from it.
152 void clear_incoming_entry(HeapRegion* from_hr);
154 // Declare the heap size (in # of regions) to the OtherRegionsTable.
155 // (Uses it to initialize from_card_cache).
156 static void init_from_card_cache(size_t max_regions);
158 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
159 // Make sure any entries for higher regions are invalid.
160 static void shrink_from_card_cache(size_t new_n_regs);
162 static void print_from_card_cache();
164 };
167 class HeapRegionRemSet : public CHeapObj {
168 friend class VMStructs;
169 friend class HeapRegionRemSetIterator;
171 public:
172 enum Event {
173 Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
174 };
176 private:
177 G1BlockOffsetSharedArray* _bosa;
178 G1BlockOffsetSharedArray* bosa() const { return _bosa; }
180 OtherRegionsTable _other_regions;
182 // One set bit for every region that has an entry for this one.
183 BitMap _outgoing_region_map;
185 // Clear entries for the current region in any rem sets named in
186 // the _outgoing_region_map.
187 void clear_outgoing_entries();
189 enum ParIterState { Unclaimed, Claimed, Complete };
190 ParIterState _iter_state;
192 // Unused unless G1RecordHRRSOops is true.
194 static const int MaxRecorded = 1000000;
195 static OopOrNarrowOopStar* _recorded_oops;
196 static HeapWord** _recorded_cards;
197 static HeapRegion** _recorded_regions;
198 static int _n_recorded;
200 static const int MaxRecordedEvents = 1000;
201 static Event* _recorded_events;
202 static int* _recorded_event_index;
203 static int _n_recorded_events;
205 static void print_event(outputStream* str, Event evnt);
207 public:
208 HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
209 HeapRegion* hr);
211 static int num_par_rem_sets();
213 HeapRegion* hr() const {
214 return _other_regions.hr();
215 }
217 size_t occupied() const {
218 return _other_regions.occupied();
219 }
220 size_t occ_fine() const {
221 return _other_regions.occ_fine();
222 }
223 size_t occ_coarse() const {
224 return _other_regions.occ_coarse();
225 }
226 size_t occ_sparse() const {
227 return _other_regions.occ_sparse();
228 }
230 static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
232 /* Used in the sequential case. Returns "true" iff this addition causes
233 the size limit to be reached. */
234 void add_reference(OopOrNarrowOopStar from) {
235 _other_regions.add_reference(from);
236 }
238 /* Used in the parallel case. Returns "true" iff this addition causes
239 the size limit to be reached. */
240 void add_reference(OopOrNarrowOopStar from, int tid) {
241 _other_regions.add_reference(from, tid);
242 }
244 // Records the fact that the current region contains an outgoing
245 // reference into "to_hr".
246 void add_outgoing_reference(HeapRegion* to_hr);
248 // Removes any entries shown by the given bitmaps to contain only dead
249 // objects.
250 void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
252 // The region is being reclaimed; clear its remset, and any mention of
253 // entries for this region in other remsets.
254 void clear();
256 // Forget any entries due to pointers from "from_hr".
257 void clear_incoming_entry(HeapRegion* from_hr) {
258 _other_regions.clear_incoming_entry(from_hr);
259 }
261 #if 0
262 virtual void cleanup() = 0;
263 #endif
265 // Should be called from single-threaded code.
266 void init_for_par_iteration();
267 // Attempt to claim the region. Returns true iff this call caused an
268 // atomic transition from Unclaimed to Claimed.
269 bool claim_iter();
270 // Sets the iteration state to "complete".
271 void set_iter_complete();
272 // Returns "true" iff the region's iteration is complete.
273 bool iter_is_complete();
275 // Initialize the given iterator to iterate over this rem set.
276 void init_iterator(HeapRegionRemSetIterator* iter) const;
278 #if 0
279 // Apply the "do_card" method to the start address of every card in the
280 // rem set. Returns false if some application of the closure aborted.
281 virtual bool card_iterate(CardClosure* iter) = 0;
282 #endif
284 // The actual # of bytes this hr_remset takes up.
285 size_t mem_size() {
286 return _other_regions.mem_size()
287 // This correction is necessary because the above includes the second
288 // part.
289 + sizeof(this) - sizeof(OtherRegionsTable);
290 }
292 // Returns the memory occupancy of all static data structures associated
293 // with remembered sets.
294 static size_t static_mem_size() {
295 return OtherRegionsTable::static_mem_size();
296 }
298 // Returns the memory occupancy of all free_list data structures associated
299 // with remembered sets.
300 static size_t fl_mem_size() {
301 return OtherRegionsTable::fl_mem_size();
302 }
304 bool contains_reference(OopOrNarrowOopStar from) const {
305 return _other_regions.contains_reference(from);
306 }
307 void print() const;
309 // Called during a stop-world phase to perform any deferred cleanups.
310 // The second version may be called by parallel threads after then finish
311 // collection work.
312 static void cleanup();
313 static void par_cleanup();
315 // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
316 // (Uses it to initialize from_card_cache).
317 static void init_heap(size_t max_regions) {
318 OtherRegionsTable::init_from_card_cache(max_regions);
319 }
321 // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
322 static void shrink_heap(size_t new_n_regs) {
323 OtherRegionsTable::shrink_from_card_cache(new_n_regs);
324 }
326 #ifndef PRODUCT
327 static void print_from_card_cache() {
328 OtherRegionsTable::print_from_card_cache();
329 }
330 #endif
332 static void record(HeapRegion* hr, OopOrNarrowOopStar f);
333 static void print_recorded();
334 static void record_event(Event evnt);
336 // Run unit tests.
337 #ifndef PRODUCT
338 static void test();
339 #endif
341 };
343 class HeapRegionRemSetIterator : public CHeapObj {
345 // The region over which we're iterating.
346 const HeapRegionRemSet* _hrrs;
348 // Local caching of HRRS fields.
349 const BitMap* _coarse_map;
350 PosParPRT** _fine_grain_regions;
352 G1BlockOffsetSharedArray* _bosa;
353 G1CollectedHeap* _g1h;
355 // The number yielded since initialization.
356 size_t _n_yielded_fine;
357 size_t _n_yielded_coarse;
358 size_t _n_yielded_sparse;
360 // If true we're iterating over the coarse table; if false the fine
361 // table.
362 enum IterState {
363 Sparse,
364 Fine,
365 Coarse
366 };
367 IterState _is;
369 // In both kinds of iteration, heap offset of first card of current
370 // region.
371 size_t _cur_region_card_offset;
372 // Card offset within cur region.
373 size_t _cur_region_cur_card;
375 // Coarse table iteration fields:
377 // Current region index;
378 int _coarse_cur_region_index;
379 int _coarse_cur_region_cur_card;
381 bool coarse_has_next(size_t& card_index);
383 // Fine table iteration fields:
385 // Index of bucket-list we're working on.
386 int _fine_array_index;
387 // Per Region Table we're doing within current bucket list.
388 PosParPRT* _fine_cur_prt;
390 /* SparsePRT::*/ SparsePRTIter _sparse_iter;
392 void fine_find_next_non_null_prt();
394 bool fine_has_next();
395 bool fine_has_next(size_t& card_index);
397 public:
398 // We require an iterator to be initialized before use, so the
399 // constructor does little.
400 HeapRegionRemSetIterator();
402 void initialize(const HeapRegionRemSet* hrrs);
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);
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 };
418 #if 0
419 class CardClosure: public Closure {
420 public:
421 virtual void do_card(HeapWord* card_start) = 0;
422 };
424 #endif