1 /*
2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/g1/concurrentG1Refine.hpp"
27 #include "gc/g1/dirtyCardQueue.hpp"
28 #include "gc/g1/g1BlockOffsetTable.inline.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1FromCardCache.hpp"
31 #include "gc/g1/g1GCPhaseTimes.hpp"
32 #include "gc/g1/g1HotCardCache.hpp"
33 #include "gc/g1/g1OopClosures.inline.hpp"
34 #include "gc/g1/g1RemSet.inline.hpp"
35 #include "gc/g1/g1SATBCardTableModRefBS.inline.hpp"
36 #include "gc/g1/heapRegion.inline.hpp"
37 #include "gc/g1/heapRegionManager.inline.hpp"
38 #include "gc/g1/heapRegionRemSet.hpp"
39 #include "gc/g1/suspendibleThreadSet.hpp"
40 #include "gc/shared/gcTraceTime.inline.hpp"
41 #include "memory/iterator.hpp"
42 #include "memory/resourceArea.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "utilities/align.hpp"
45 #include "utilities/globalDefinitions.hpp"
46 #include "utilities/intHisto.hpp"
47 #include "utilities/stack.inline.hpp"
48
49 // Collects information about the overall remembered set scan progress during an evacuation.
50 class G1RemSetScanState : public CHeapObj<mtGC> {
51 private:
52 class G1ClearCardTableTask : public AbstractGangTask {
53 G1CollectedHeap* _g1h;
54 uint* _dirty_region_list;
55 size_t _num_dirty_regions;
56 size_t _chunk_length;
57
58 size_t volatile _cur_dirty_regions;
59 public:
60 G1ClearCardTableTask(G1CollectedHeap* g1h,
61 uint* dirty_region_list,
62 size_t num_dirty_regions,
63 size_t chunk_length) :
64 AbstractGangTask("G1 Clear Card Table Task"),
65 _g1h(g1h),
66 _dirty_region_list(dirty_region_list),
67 _num_dirty_regions(num_dirty_regions),
68 _chunk_length(chunk_length),
69 _cur_dirty_regions(0) {
70
71 assert(chunk_length > 0, "must be");
72 }
73
74 static size_t chunk_size() { return M; }
75
76 void work(uint worker_id) {
77 G1SATBCardTableModRefBS* ct_bs = _g1h->g1_barrier_set();
78
79 while (_cur_dirty_regions < _num_dirty_regions) {
80 size_t next = Atomic::add(_chunk_length, &_cur_dirty_regions) - _chunk_length;
81 size_t max = MIN2(next + _chunk_length, _num_dirty_regions);
82
83 for (size_t i = next; i < max; i++) {
84 HeapRegion* r = _g1h->region_at(_dirty_region_list[i]);
85 if (!r->is_survivor()) {
86 ct_bs->clear(MemRegion(r->bottom(), r->end()));
87 }
88 }
89 }
90 }
91 };
92
93 size_t _max_regions;
94
95 // Scan progress for the remembered set of a single region. Transitions from
96 // Unclaimed -> Claimed -> Complete.
97 // At each of the transitions the thread that does the transition needs to perform
98 // some special action once. This is the reason for the extra "Claimed" state.
99 typedef jint G1RemsetIterState;
100
101 static const G1RemsetIterState Unclaimed = 0; // The remembered set has not been scanned yet.
102 static const G1RemsetIterState Claimed = 1; // The remembered set is currently being scanned.
103 static const G1RemsetIterState Complete = 2; // The remembered set has been completely scanned.
104
105 G1RemsetIterState volatile* _iter_states;
106 // The current location where the next thread should continue scanning in a region's
107 // remembered set.
108 size_t volatile* _iter_claims;
109
110 // Temporary buffer holding the regions we used to store remembered set scan duplicate
111 // information. These are also called "dirty". Valid entries are from [0.._cur_dirty_region)
112 uint* _dirty_region_buffer;
113
114 typedef jbyte IsDirtyRegionState;
115 static const IsDirtyRegionState Clean = 0;
116 static const IsDirtyRegionState Dirty = 1;
117 // Holds a flag for every region whether it is in the _dirty_region_buffer already
118 // to avoid duplicates. Uses jbyte since there are no atomic instructions for bools.
119 IsDirtyRegionState* _in_dirty_region_buffer;
120 size_t _cur_dirty_region;
121
122 // Creates a snapshot of the current _top values at the start of collection to
123 // filter out card marks that we do not want to scan.
124 class G1ResetScanTopClosure : public HeapRegionClosure {
125 private:
126 HeapWord** _scan_top;
127 public:
128 G1ResetScanTopClosure(HeapWord** scan_top) : _scan_top(scan_top) { }
129
130 virtual bool doHeapRegion(HeapRegion* r) {
131 uint hrm_index = r->hrm_index();
132 if (!r->in_collection_set() && r->is_old_or_humongous()) {
133 _scan_top[hrm_index] = r->top();
134 } else {
135 _scan_top[hrm_index] = r->bottom();
136 }
137 return false;
138 }
139 };
140
141 // For each region, contains the maximum top() value to be used during this garbage
142 // collection. Subsumes common checks like filtering out everything but old and
143 // humongous regions outside the collection set.
144 // This is valid because we are not interested in scanning stray remembered set
145 // entries from free or archive regions.
146 HeapWord** _scan_top;
147 public:
148 G1RemSetScanState() :
149 _max_regions(0),
150 _iter_states(NULL),
151 _iter_claims(NULL),
152 _dirty_region_buffer(NULL),
153 _in_dirty_region_buffer(NULL),
154 _cur_dirty_region(0),
155 _scan_top(NULL) {
156 }
157
158 ~G1RemSetScanState() {
159 if (_iter_states != NULL) {
160 FREE_C_HEAP_ARRAY(G1RemsetIterState, _iter_states);
161 }
162 if (_iter_claims != NULL) {
163 FREE_C_HEAP_ARRAY(size_t, _iter_claims);
164 }
165 if (_dirty_region_buffer != NULL) {
166 FREE_C_HEAP_ARRAY(uint, _dirty_region_buffer);
167 }
168 if (_in_dirty_region_buffer != NULL) {
169 FREE_C_HEAP_ARRAY(IsDirtyRegionState, _in_dirty_region_buffer);
170 }
171 if (_scan_top != NULL) {
172 FREE_C_HEAP_ARRAY(HeapWord*, _scan_top);
173 }
174 }
175
176 void initialize(uint max_regions) {
177 assert(_iter_states == NULL, "Must not be initialized twice");
178 assert(_iter_claims == NULL, "Must not be initialized twice");
179 _max_regions = max_regions;
180 _iter_states = NEW_C_HEAP_ARRAY(G1RemsetIterState, max_regions, mtGC);
181 _iter_claims = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
182 _dirty_region_buffer = NEW_C_HEAP_ARRAY(uint, max_regions, mtGC);
183 _in_dirty_region_buffer = NEW_C_HEAP_ARRAY(IsDirtyRegionState, max_regions, mtGC);
184 _scan_top = NEW_C_HEAP_ARRAY(HeapWord*, max_regions, mtGC);
185 }
186
187 void reset() {
188 for (uint i = 0; i < _max_regions; i++) {
189 _iter_states[i] = Unclaimed;
190 }
191
192 G1ResetScanTopClosure cl(_scan_top);
193 G1CollectedHeap::heap()->heap_region_iterate(&cl);
194
195 memset((void*)_iter_claims, 0, _max_regions * sizeof(size_t));
196 memset(_in_dirty_region_buffer, Clean, _max_regions * sizeof(IsDirtyRegionState));
197 _cur_dirty_region = 0;
198 }
199
200 // Attempt to claim the remembered set of the region for iteration. Returns true
201 // if this call caused the transition from Unclaimed to Claimed.
202 inline bool claim_iter(uint region) {
203 assert(region < _max_regions, "Tried to access invalid region %u", region);
204 if (_iter_states[region] != Unclaimed) {
205 return false;
206 }
207 jint res = Atomic::cmpxchg(Claimed, (jint*)(&_iter_states[region]), Unclaimed);
208 return (res == Unclaimed);
209 }
210
211 // Try to atomically sets the iteration state to "complete". Returns true for the
212 // thread that caused the transition.
213 inline bool set_iter_complete(uint region) {
214 if (iter_is_complete(region)) {
215 return false;
216 }
217 jint res = Atomic::cmpxchg(Complete, (jint*)(&_iter_states[region]), Claimed);
218 return (res == Claimed);
219 }
220
221 // Returns true if the region's iteration is complete.
222 inline bool iter_is_complete(uint region) const {
223 assert(region < _max_regions, "Tried to access invalid region %u", region);
224 return _iter_states[region] == Complete;
225 }
226
227 // The current position within the remembered set of the given region.
228 inline size_t iter_claimed(uint region) const {
229 assert(region < _max_regions, "Tried to access invalid region %u", region);
230 return _iter_claims[region];
231 }
232
233 // Claim the next block of cards within the remembered set of the region with
234 // step size.
235 inline size_t iter_claimed_next(uint region, size_t step) {
236 return Atomic::add(step, &_iter_claims[region]) - step;
237 }
238
239 void add_dirty_region(uint region) {
240 if (_in_dirty_region_buffer[region] == Dirty) {
241 return;
242 }
243
244 bool marked_as_dirty = Atomic::cmpxchg(Dirty, &_in_dirty_region_buffer[region], Clean) == Clean;
245 if (marked_as_dirty) {
246 size_t allocated = Atomic::add(1, &_cur_dirty_region) - 1;
247 _dirty_region_buffer[allocated] = region;
248 }
249 }
250
251 HeapWord* scan_top(uint region_idx) const {
252 return _scan_top[region_idx];
253 }
254
255 // Clear the card table of "dirty" regions.
256 void clear_card_table(WorkGang* workers) {
257 if (_cur_dirty_region == 0) {
258 return;
259 }
260
261 size_t const num_chunks = align_up(_cur_dirty_region * HeapRegion::CardsPerRegion, G1ClearCardTableTask::chunk_size()) / G1ClearCardTableTask::chunk_size();
262 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
263 size_t const chunk_length = G1ClearCardTableTask::chunk_size() / HeapRegion::CardsPerRegion;
264
265 // Iterate over the dirty cards region list.
266 G1ClearCardTableTask cl(G1CollectedHeap::heap(), _dirty_region_buffer, _cur_dirty_region, chunk_length);
267
268 log_debug(gc, ergo)("Running %s using %u workers for " SIZE_FORMAT " "
269 "units of work for " SIZE_FORMAT " regions.",
270 cl.name(), num_workers, num_chunks, _cur_dirty_region);
271 workers->run_task(&cl, num_workers);
272
273 #ifndef PRODUCT
274 // Need to synchronize with concurrent cleanup since it needs to
275 // finish its card table clearing before we can verify.
276 G1CollectedHeap::heap()->wait_while_free_regions_coming();
277 G1CollectedHeap::heap()->verifier()->verify_card_table_cleanup();
278 #endif
279 }
280 };
281
282 G1RemSet::G1RemSet(G1CollectedHeap* g1,
283 CardTableModRefBS* ct_bs,
284 G1HotCardCache* hot_card_cache) :
285 _g1(g1),
286 _scan_state(new G1RemSetScanState()),
287 _refine_card_concurrently_cl(),
288 _num_conc_refined_cards(0),
289 _ct_bs(ct_bs),
290 _g1p(_g1->g1_policy()),
291 _hot_card_cache(hot_card_cache),
292 _prev_period_summary(),
293 _into_cset_dirty_card_queue_set(false)
294 {
295 // Initialize the card queue set used to hold cards containing
296 // references into the collection set.
297 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
298 DirtyCardQ_CBL_mon,
299 DirtyCardQ_FL_lock,
300 -1, // never trigger processing
301 -1, // no limit on length
302 Shared_DirtyCardQ_lock,
303 &JavaThread::dirty_card_queue_set());
304 }
305
306 G1RemSet::~G1RemSet() {
307 if (_scan_state != NULL) {
308 delete _scan_state;
309 }
310 }
311
312 uint G1RemSet::num_par_rem_sets() {
313 return MAX2(DirtyCardQueueSet::num_par_ids() + ConcurrentG1Refine::thread_num(), ParallelGCThreads);
314 }
315
316 void G1RemSet::initialize(size_t capacity, uint max_regions) {
317 G1FromCardCache::initialize(num_par_rem_sets(), max_regions);
318 _scan_state->initialize(max_regions);
319 {
320 GCTraceTime(Debug, gc, marking)("Initialize Card Live Data");
321 _card_live_data.initialize(capacity, max_regions);
322 }
323 if (G1PretouchAuxiliaryMemory) {
324 GCTraceTime(Debug, gc, marking)("Pre-Touch Card Live Data");
325 _card_live_data.pretouch();
326 }
327 }
328
329 G1ScanRSForRegionClosure::G1ScanRSForRegionClosure(G1RemSetScanState* scan_state,
330 G1ScanObjsDuringScanRSClosure* scan_obj_on_card,
331 CodeBlobClosure* code_root_cl,
332 uint worker_i) :
333 _scan_state(scan_state),
334 _scan_objs_on_card_cl(scan_obj_on_card),
335 _code_root_cl(code_root_cl),
336 _strong_code_root_scan_time_sec(0.0),
337 _cards_claimed(0),
338 _cards_scanned(0),
339 _cards_skipped(0),
340 _worker_i(worker_i) {
341 _g1h = G1CollectedHeap::heap();
342 _bot = _g1h->bot();
343 _ct_bs = _g1h->g1_barrier_set();
344 }
345
346 void G1ScanRSForRegionClosure::scan_card(MemRegion mr, uint region_idx_for_card) {
347 HeapRegion* const card_region = _g1h->region_at(region_idx_for_card);
348 _scan_objs_on_card_cl->set_region(card_region);
349 card_region->oops_on_card_seq_iterate_careful<true>(mr, _scan_objs_on_card_cl);
350 _cards_scanned++;
351 }
352
353 void G1ScanRSForRegionClosure::scan_strong_code_roots(HeapRegion* r) {
354 double scan_start = os::elapsedTime();
355 r->strong_code_roots_do(_code_root_cl);
356 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
357 }
358
359 void G1ScanRSForRegionClosure::claim_card(size_t card_index, const uint region_idx_for_card){
360 _ct_bs->set_card_claimed(card_index);
361 _scan_state->add_dirty_region(region_idx_for_card);
362 }
363
364 bool G1ScanRSForRegionClosure::doHeapRegion(HeapRegion* r) {
365 assert(r->in_collection_set(), "should only be called on elements of CS.");
366 uint region_idx = r->hrm_index();
367
368 if (_scan_state->iter_is_complete(region_idx)) {
369 return false;
370 }
371 if (_scan_state->claim_iter(region_idx)) {
372 // If we ever free the collection set concurrently, we should also
373 // clear the card table concurrently therefore we won't need to
374 // add regions of the collection set to the dirty cards region.
375 _scan_state->add_dirty_region(region_idx);
376 }
377
378 // We claim cards in blocks so as to reduce the contention.
379 size_t const block_size = G1RSetScanBlockSize;
380
381 HeapRegionRemSetIterator iter(r->rem_set());
382 size_t card_index;
383
384 size_t claimed_card_block = _scan_state->iter_claimed_next(region_idx, block_size);
385 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
386 if (current_card >= claimed_card_block + block_size) {
387 claimed_card_block = _scan_state->iter_claimed_next(region_idx, block_size);
388 }
389 if (current_card < claimed_card_block) {
390 _cards_skipped++;
391 continue;
392 }
393 _cards_claimed++;
394
395 // If the card is dirty, then G1 will scan it during Update RS.
396 if (_ct_bs->is_card_claimed(card_index) || _ct_bs->is_card_dirty(card_index)) {
397 continue;
398 }
399
400 HeapWord* const card_start = _g1h->bot()->address_for_index(card_index);
401 uint const region_idx_for_card = _g1h->addr_to_region(card_start);
402
403 assert(_g1h->region_at(region_idx_for_card)->is_in_reserved(card_start),
404 "Card start " PTR_FORMAT " to scan outside of region %u", p2i(card_start), _g1h->region_at(region_idx_for_card)->hrm_index());
405 HeapWord* const top = _scan_state->scan_top(region_idx_for_card);
406 if (card_start >= top) {
407 continue;
408 }
409
410 // We claim lazily (so races are possible but they're benign), which reduces the
411 // number of duplicate scans (the rsets of the regions in the cset can intersect).
412 // Claim the card after checking bounds above: the remembered set may contain
413 // random cards into current survivor, and we would then have an incorrectly
414 // claimed card in survivor space. Card table clear does not reset the card table
415 // of survivor space regions.
416 claim_card(card_index, region_idx_for_card);
417
418 MemRegion const mr(card_start, MIN2(card_start + BOTConstants::N_words, top));
419
420 scan_card(mr, region_idx_for_card);
421 }
422 if (_scan_state->set_iter_complete(region_idx)) {
423 // Scan the strong code root list attached to the current region
424 scan_strong_code_roots(r);
425 }
426 return false;
427 }
428
429 void G1RemSet::scan_rem_set(G1ParScanThreadState* pss,
430 CodeBlobClosure* heap_region_codeblobs,
431 uint worker_i) {
432 double rs_time_start = os::elapsedTime();
433
434 G1ScanObjsDuringScanRSClosure scan_cl(_g1, pss);
435 G1ScanRSForRegionClosure cl(_scan_state, &scan_cl, heap_region_codeblobs, worker_i);
436 _g1->collection_set_iterate_from(&cl, worker_i);
437
438 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start) -
439 cl.strong_code_root_scan_time_sec();
440
441 G1GCPhaseTimes* p = _g1p->phase_times();
442
443 p->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, scan_rs_time_sec);
444 p->record_thread_work_item(G1GCPhaseTimes::ScanRS, worker_i, cl.cards_scanned(), G1GCPhaseTimes::ScannedCards);
445 p->record_thread_work_item(G1GCPhaseTimes::ScanRS, worker_i, cl.cards_claimed(), G1GCPhaseTimes::ClaimedCards);
446 p->record_thread_work_item(G1GCPhaseTimes::ScanRS, worker_i, cl.cards_skipped(), G1GCPhaseTimes::SkippedCards);
447
448 p->record_time_secs(G1GCPhaseTimes::CodeRoots, worker_i, cl.strong_code_root_scan_time_sec());
449 }
450
451 bool G1RefineCardConcurrentlyClosure::do_card_ptr(jbyte* card_ptr, uint worker_i) {
452 G1CollectedHeap::heap()->g1_rem_set()->refine_card_concurrently(card_ptr, worker_i);
453
454 if (SuspendibleThreadSet::should_yield()) {
455 // Caller will actually yield.
456 return false;
457 }
458 // Otherwise, we finished successfully; return true.
459 return true;
460 }
461
462 // Closure used for updating RSets and recording references that
463 // point into the collection set. Only called during an
464 // evacuation pause.
465 class G1RefineCardClosure: public CardTableEntryClosure {
466 G1RemSet* _g1rs;
467 DirtyCardQueue* _into_cset_dcq;
468 G1ScanObjsDuringUpdateRSClosure* _update_rs_cl;
469 public:
470 G1RefineCardClosure(G1CollectedHeap* g1h,
471 DirtyCardQueue* into_cset_dcq,
472 G1ScanObjsDuringUpdateRSClosure* update_rs_cl) :
473 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq), _update_rs_cl(update_rs_cl)
474 {}
475
476 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
477 // The only time we care about recording cards that
478 // contain references that point into the collection set
479 // is during RSet updating within an evacuation pause.
480 // In this case worker_i should be the id of a GC worker thread.
481 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
482
483 if (_g1rs->refine_card_during_gc(card_ptr, _update_rs_cl)) {
484 // 'card_ptr' contains references that point into the collection
485 // set. We need to record the card in the DCQS
486 // (_into_cset_dirty_card_queue_set)
487 // that's used for that purpose.
488 //
489 // Enqueue the card
490 _into_cset_dcq->enqueue(card_ptr);
491 }
492 return true;
493 }
494 };
495
496 void G1RemSet::update_rem_set(DirtyCardQueue* into_cset_dcq,
497 G1ParScanThreadState* pss,
498 uint worker_i) {
499 G1ScanObjsDuringUpdateRSClosure update_rs_cl(_g1, pss, worker_i);
500 G1RefineCardClosure refine_card_cl(_g1, into_cset_dcq, &update_rs_cl);
501
502 G1GCParPhaseTimesTracker x(_g1p->phase_times(), G1GCPhaseTimes::UpdateRS, worker_i);
503 if (G1HotCardCache::default_use_cache()) {
504 // Apply the closure to the entries of the hot card cache.
505 G1GCParPhaseTimesTracker y(_g1p->phase_times(), G1GCPhaseTimes::ScanHCC, worker_i);
506 _g1->iterate_hcc_closure(&refine_card_cl, worker_i);
507 }
508 // Apply the closure to all remaining log entries.
509 _g1->iterate_dirty_card_closure(&refine_card_cl, worker_i);
510 }
511
512 void G1RemSet::cleanupHRRS() {
513 HeapRegionRemSet::cleanup();
514 }
515
516 void G1RemSet::oops_into_collection_set_do(G1ParScanThreadState* pss,
517 CodeBlobClosure* heap_region_codeblobs,
518 uint worker_i) {
519 // A DirtyCardQueue that is used to hold cards containing references
520 // that point into the collection set. This DCQ is associated with a
521 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
522 // circumstances (i.e. the pause successfully completes), these cards
523 // are just discarded (there's no need to update the RSets of regions
524 // that were in the collection set - after the pause these regions
525 // are wholly 'free' of live objects. In the event of an evacuation
526 // failure the cards/buffers in this queue set are passed to the
527 // DirtyCardQueueSet that is used to manage RSet updates
528 DirtyCardQueue into_cset_dcq(&_into_cset_dirty_card_queue_set);
529
530 update_rem_set(&into_cset_dcq, pss, worker_i);
531 scan_rem_set(pss, heap_region_codeblobs, worker_i);;
532 }
533
534 void G1RemSet::prepare_for_oops_into_collection_set_do() {
535 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
536 dcqs.concatenate_logs();
537
538 _scan_state->reset();
539 }
540
541 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
542 G1GCPhaseTimes* phase_times = _g1->g1_policy()->phase_times();
543
544 // Set all cards back to clean.
545 double start = os::elapsedTime();
546 _scan_state->clear_card_table(_g1->workers());
547 phase_times->record_clear_ct_time((os::elapsedTime() - start) * 1000.0);
548
549 DirtyCardQueueSet& into_cset_dcqs = _into_cset_dirty_card_queue_set;
550
551 if (_g1->evacuation_failed()) {
552 double restore_remembered_set_start = os::elapsedTime();
553
554 // Restore remembered sets for the regions pointing into the collection set.
555 // We just need to transfer the completed buffers from the DirtyCardQueueSet
556 // used to hold cards that contain references that point into the collection set
557 // to the DCQS used to hold the deferred RS updates.
558 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
559 phase_times->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
560 }
561
562 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
563 // which contain references that point into the collection.
564 _into_cset_dirty_card_queue_set.clear();
565 assert(_into_cset_dirty_card_queue_set.completed_buffers_num() == 0,
566 "all buffers should be freed");
567 _into_cset_dirty_card_queue_set.clear_n_completed_buffers();
568 }
569
570 class G1ScrubRSClosure: public HeapRegionClosure {
571 G1CollectedHeap* _g1h;
572 G1CardLiveData* _live_data;
573 public:
574 G1ScrubRSClosure(G1CardLiveData* live_data) :
575 _g1h(G1CollectedHeap::heap()),
576 _live_data(live_data) { }
577
578 bool doHeapRegion(HeapRegion* r) {
579 if (!r->is_continues_humongous()) {
580 r->rem_set()->scrub(_live_data);
581 }
582 return false;
583 }
584 };
585
586 void G1RemSet::scrub(uint worker_num, HeapRegionClaimer *hrclaimer) {
587 G1ScrubRSClosure scrub_cl(&_card_live_data);
588 _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
589 }
590
591 inline void check_card_ptr(jbyte* card_ptr, CardTableModRefBS* ct_bs) {
592 #ifdef ASSERT
593 G1CollectedHeap* g1 = G1CollectedHeap::heap();
594 assert(g1->is_in_exact(ct_bs->addr_for(card_ptr)),
595 "Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap",
596 p2i(card_ptr),
597 ct_bs->index_for(ct_bs->addr_for(card_ptr)),
598 p2i(ct_bs->addr_for(card_ptr)),
599 g1->addr_to_region(ct_bs->addr_for(card_ptr)));
600 #endif
601 }
602
603 void G1RemSet::refine_card_concurrently(jbyte* card_ptr,
604 uint worker_i) {
605 assert(!_g1->is_gc_active(), "Only call concurrently");
606
607 check_card_ptr(card_ptr, _ct_bs);
608
609 // If the card is no longer dirty, nothing to do.
610 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
611 return;
612 }
613
614 // Construct the region representing the card.
615 HeapWord* start = _ct_bs->addr_for(card_ptr);
616 // And find the region containing it.
617 HeapRegion* r = _g1->heap_region_containing(start);
618
619 // This check is needed for some uncommon cases where we should
620 // ignore the card.
621 //
622 // The region could be young. Cards for young regions are
623 // distinctly marked (set to g1_young_gen), so the post-barrier will
624 // filter them out. However, that marking is performed
625 // concurrently. A write to a young object could occur before the
626 // card has been marked young, slipping past the filter.
627 //
628 // The card could be stale, because the region has been freed since
629 // the card was recorded. In this case the region type could be
630 // anything. If (still) free or (reallocated) young, just ignore
631 // it. If (reallocated) old or humongous, the later card trimming
632 // and additional checks in iteration may detect staleness. At
633 // worst, we end up processing a stale card unnecessarily.
634 //
635 // In the normal (non-stale) case, the synchronization between the
636 // enqueueing of the card and processing it here will have ensured
637 // we see the up-to-date region type here.
638 if (!r->is_old_or_humongous()) {
639 return;
640 }
641
642 // While we are processing RSet buffers during the collection, we
643 // actually don't want to scan any cards on the collection set,
644 // since we don't want to update remembered sets with entries that
645 // point into the collection set, given that live objects from the
646 // collection set are about to move and such entries will be stale
647 // very soon. This change also deals with a reliability issue which
648 // involves scanning a card in the collection set and coming across
649 // an array that was being chunked and looking malformed. Note,
650 // however, that if evacuation fails, we have to scan any objects
651 // that were not moved and create any missing entries.
652 if (r->in_collection_set()) {
653 return;
654 }
655
656 // The result from the hot card cache insert call is either:
657 // * pointer to the current card
658 // (implying that the current card is not 'hot'),
659 // * null
660 // (meaning we had inserted the card ptr into the "hot" card cache,
661 // which had some headroom),
662 // * a pointer to a "hot" card that was evicted from the "hot" cache.
663 //
664
665 if (_hot_card_cache->use_cache()) {
666 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
667
668 const jbyte* orig_card_ptr = card_ptr;
669 card_ptr = _hot_card_cache->insert(card_ptr);
670 if (card_ptr == NULL) {
671 // There was no eviction. Nothing to do.
672 return;
673 } else if (card_ptr != orig_card_ptr) {
674 // Original card was inserted and an old card was evicted.
675 start = _ct_bs->addr_for(card_ptr);
676 r = _g1->heap_region_containing(start);
677
678 // Check whether the region formerly in the cache should be
679 // ignored, as discussed earlier for the original card. The
680 // region could have been freed while in the cache. The cset is
681 // not relevant here, since we're in concurrent phase.
682 if (!r->is_old_or_humongous()) {
683 return;
684 }
685 } // Else we still have the original card.
686 }
687
688 // Trim the region designated by the card to what's been allocated
689 // in the region. The card could be stale, or the card could cover
690 // (part of) an object at the end of the allocated space and extend
691 // beyond the end of allocation.
692
693 // Non-humongous objects are only allocated in the old-gen during
694 // GC, so if region is old then top is stable. Humongous object
695 // allocation sets top last; if top has not yet been set, this is
696 // a stale card and we'll end up with an empty intersection. If
697 // this is not a stale card, the synchronization between the
698 // enqueuing of the card and processing it here will have ensured
699 // we see the up-to-date top here.
700 HeapWord* scan_limit = r->top();
701
702 if (scan_limit <= start) {
703 // If the trimmed region is empty, the card must be stale.
704 return;
705 }
706
707 // Okay to clean and process the card now. There are still some
708 // stale card cases that may be detected by iteration and dealt with
709 // as iteration failure.
710 *const_cast<volatile jbyte*>(card_ptr) = CardTableModRefBS::clean_card_val();
711
712 // This fence serves two purposes. First, the card must be cleaned
713 // before processing the contents. Second, we can't proceed with
714 // processing until after the read of top, for synchronization with
715 // possibly concurrent humongous object allocation. It's okay that
716 // reading top and reading type were racy wrto each other. We need
717 // both set, in any order, to proceed.
718 OrderAccess::fence();
719
720 // Don't use addr_for(card_ptr + 1) which can ask for
721 // a card beyond the heap.
722 HeapWord* end = start + CardTableModRefBS::card_size_in_words;
723 MemRegion dirty_region(start, MIN2(scan_limit, end));
724 assert(!dirty_region.is_empty(), "sanity");
725
726 G1ConcurrentRefineOopClosure conc_refine_cl(_g1, worker_i);
727
728 bool card_processed =
729 r->oops_on_card_seq_iterate_careful<false>(dirty_region, &conc_refine_cl);
730
731 // If unable to process the card then we encountered an unparsable
732 // part of the heap (e.g. a partially allocated object) while
733 // processing a stale card. Despite the card being stale, redirty
734 // and re-enqueue, because we've already cleaned the card. Without
735 // this we could incorrectly discard a non-stale card.
736 if (!card_processed) {
737 // The card might have gotten re-dirtied and re-enqueued while we
738 // worked. (In fact, it's pretty likely.)
739 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
740 *card_ptr = CardTableModRefBS::dirty_card_val();
741 MutexLockerEx x(Shared_DirtyCardQ_lock,
742 Mutex::_no_safepoint_check_flag);
743 DirtyCardQueue* sdcq =
744 JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
745 sdcq->enqueue(card_ptr);
746 }
747 } else {
748 _num_conc_refined_cards++; // Unsynchronized update, only used for logging.
749 }
750 }
751
752 bool G1RemSet::refine_card_during_gc(jbyte* card_ptr,
753 G1ScanObjsDuringUpdateRSClosure* update_rs_cl) {
754 assert(_g1->is_gc_active(), "Only call during GC");
755
756 check_card_ptr(card_ptr, _ct_bs);
757
758 // If the card is no longer dirty, nothing to do. This covers cards that were already
759 // scanned as parts of the remembered sets.
760 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
761 // No need to return that this card contains refs that point
762 // into the collection set.
763 return false;
764 }
765
766 // During GC we can immediately clean the card since we will not re-enqueue stale
767 // cards as we know they can be disregarded.
768 *card_ptr = CardTableModRefBS::clean_card_val();
769
770 // Construct the region representing the card.
771 HeapWord* card_start = _ct_bs->addr_for(card_ptr);
772 // And find the region containing it.
773 HeapRegion* r = _g1->heap_region_containing(card_start);
774
775 HeapWord* scan_limit = _scan_state->scan_top(r->hrm_index());
776 if (scan_limit <= card_start) {
777 // If the card starts above the area in the region containing objects to scan, skip it.
778 return false;
779 }
780
781 // Don't use addr_for(card_ptr + 1) which can ask for
782 // a card beyond the heap.
783 HeapWord* card_end = card_start + CardTableModRefBS::card_size_in_words;
784 MemRegion dirty_region(card_start, MIN2(scan_limit, card_end));
785 assert(!dirty_region.is_empty(), "sanity");
786
787 update_rs_cl->set_region(r);
788 update_rs_cl->reset_has_refs_into_cset();
789
790 bool card_processed = r->oops_on_card_seq_iterate_careful<true>(dirty_region, update_rs_cl);
791 assert(card_processed, "must be");
792
793 return update_rs_cl->has_refs_into_cset();
794 }
795
796 void G1RemSet::print_periodic_summary_info(const char* header, uint period_count) {
797 if ((G1SummarizeRSetStatsPeriod > 0) && log_is_enabled(Trace, gc, remset) &&
798 (period_count % G1SummarizeRSetStatsPeriod == 0)) {
799
800 G1RemSetSummary current;
801 _prev_period_summary.subtract_from(¤t);
802
803 Log(gc, remset) log;
804 log.trace("%s", header);
805 ResourceMark rm;
806 _prev_period_summary.print_on(log.trace_stream());
807
808 _prev_period_summary.set(¤t);
809 }
810 }
811
812 void G1RemSet::print_summary_info() {
813 Log(gc, remset, exit) log;
814 if (log.is_trace()) {
815 log.trace(" Cumulative RS summary");
816 G1RemSetSummary current;
817 ResourceMark rm;
818 current.print_on(log.trace_stream());
819 }
820 }
821
822 void G1RemSet::create_card_live_data(WorkGang* workers, G1CMBitMap* mark_bitmap) {
823 _card_live_data.create(workers, mark_bitmap);
824 }
825
826 void G1RemSet::finalize_card_live_data(WorkGang* workers, G1CMBitMap* mark_bitmap) {
827 _card_live_data.finalize(workers, mark_bitmap);
828 }
829
830 void G1RemSet::verify_card_live_data(WorkGang* workers, G1CMBitMap* bitmap) {
831 _card_live_data.verify(workers, bitmap);
832 }
833
834 void G1RemSet::clear_card_live_data(WorkGang* workers) {
835 _card_live_data.clear(workers);
836 }
837
838 #ifdef ASSERT
839 void G1RemSet::verify_card_live_data_is_clear() {
840 _card_live_data.verify_is_clear();
841 }
842 #endif