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/g1BarrierSet.hpp"
29 #include "gc/g1/g1BlockOffsetTable.inline.hpp"
30 #include "gc/g1/g1CardTable.inline.hpp"
31 #include "gc/g1/g1CollectedHeap.inline.hpp"
32 #include "gc/g1/g1FromCardCache.hpp"
33 #include "gc/g1/g1GCPhaseTimes.hpp"
34 #include "gc/g1/g1HotCardCache.hpp"
35 #include "gc/g1/g1OopClosures.inline.hpp"
36 #include "gc/g1/g1RemSet.inline.hpp"
37 #include "gc/g1/heapRegion.inline.hpp"
38 #include "gc/g1/heapRegionManager.inline.hpp"
39 #include "gc/g1/heapRegionRemSet.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/globalDefinitions.hpp"
45 #include "utilities/intHisto.hpp"
46 #include "utilities/stack.inline.hpp"
47
48 // Collects information about the overall remembered set scan progress during an evacuation.
49 class G1RemSetScanState : public CHeapObj<mtGC> {
50 private:
51 class G1ClearCardTableTask : public AbstractGangTask {
52 G1CollectedHeap* _g1h;
53 uint* _dirty_region_list;
54 size_t _num_dirty_regions;
55 size_t _chunk_length;
56
57 size_t volatile _cur_dirty_regions;
58 public:
59 G1ClearCardTableTask(G1CollectedHeap* g1h,
60 uint* dirty_region_list,
61 size_t num_dirty_regions,
62 size_t chunk_length) :
63 AbstractGangTask("G1 Clear Card Table Task"),
64 _g1h(g1h),
65 _dirty_region_list(dirty_region_list),
66 _num_dirty_regions(num_dirty_regions),
67 _chunk_length(chunk_length),
68 _cur_dirty_regions(0) {
69
70 assert(chunk_length > 0, "must be");
71 }
72
73 static size_t chunk_size() { return M; }
74
75 void work(uint worker_id) {
76 G1CardTable* ct = _g1h->g1_card_table();
77
78 while (_cur_dirty_regions < _num_dirty_regions) {
79 size_t next = Atomic::add(_chunk_length, &_cur_dirty_regions) - _chunk_length;
80 size_t max = MIN2(next + _chunk_length, _num_dirty_regions);
81
82 for (size_t i = next; i < max; i++) {
83 HeapRegion* r = _g1h->region_at(_dirty_region_list[i]);
84 if (!r->is_survivor()) {
85 ct->clear(MemRegion(r->bottom(), r->end()));
86 }
87 }
88 }
89 }
90 };
91
92 size_t _max_regions;
93
94 // Scan progress for the remembered set of a single region. Transitions from
95 // Unclaimed -> Claimed -> Complete.
96 // At each of the transitions the thread that does the transition needs to perform
97 // some special action once. This is the reason for the extra "Claimed" state.
98 typedef jint G1RemsetIterState;
99
100 static const G1RemsetIterState Unclaimed = 0; // The remembered set has not been scanned yet.
101 static const G1RemsetIterState Claimed = 1; // The remembered set is currently being scanned.
102 static const G1RemsetIterState Complete = 2; // The remembered set has been completely scanned.
103
104 G1RemsetIterState volatile* _iter_states;
105 // The current location where the next thread should continue scanning in a region's
106 // remembered set.
107 size_t volatile* _iter_claims;
108
109 // Temporary buffer holding the regions we used to store remembered set scan duplicate
110 // information. These are also called "dirty". Valid entries are from [0.._cur_dirty_region)
111 uint* _dirty_region_buffer;
112
113 typedef jbyte IsDirtyRegionState;
114 static const IsDirtyRegionState Clean = 0;
115 static const IsDirtyRegionState Dirty = 1;
116 // Holds a flag for every region whether it is in the _dirty_region_buffer already
117 // to avoid duplicates. Uses jbyte since there are no atomic instructions for bools.
118 IsDirtyRegionState* _in_dirty_region_buffer;
119 size_t _cur_dirty_region;
120 public:
121 G1RemSetScanState() :
122 _max_regions(0),
123 _iter_states(NULL),
124 _iter_claims(NULL),
125 _dirty_region_buffer(NULL),
126 _in_dirty_region_buffer(NULL),
127 _cur_dirty_region(0) {
128
129 }
130
131 ~G1RemSetScanState() {
132 if (_iter_states != NULL) {
133 FREE_C_HEAP_ARRAY(G1RemsetIterState, _iter_states);
134 }
135 if (_iter_claims != NULL) {
136 FREE_C_HEAP_ARRAY(size_t, _iter_claims);
137 }
138 if (_dirty_region_buffer != NULL) {
139 FREE_C_HEAP_ARRAY(uint, _dirty_region_buffer);
140 }
141 if (_in_dirty_region_buffer != NULL) {
142 FREE_C_HEAP_ARRAY(IsDirtyRegionState, _in_dirty_region_buffer);
143 }
144 }
145
146 void initialize(uint max_regions) {
147 assert(_iter_states == NULL, "Must not be initialized twice");
148 assert(_iter_claims == NULL, "Must not be initialized twice");
149 _max_regions = max_regions;
150 _iter_states = NEW_C_HEAP_ARRAY(G1RemsetIterState, max_regions, mtGC);
151 _iter_claims = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
152 _dirty_region_buffer = NEW_C_HEAP_ARRAY(uint, max_regions, mtGC);
153 _in_dirty_region_buffer = NEW_C_HEAP_ARRAY(IsDirtyRegionState, max_regions, mtGC);
154 }
155
156 void reset() {
157 for (uint i = 0; i < _max_regions; i++) {
158 _iter_states[i] = Unclaimed;
159 }
160 memset((void*)_iter_claims, 0, _max_regions * sizeof(size_t));
161 memset(_in_dirty_region_buffer, Clean, _max_regions * sizeof(IsDirtyRegionState));
162 _cur_dirty_region = 0;
163 }
164
165 // Attempt to claim the remembered set of the region for iteration. Returns true
166 // if this call caused the transition from Unclaimed to Claimed.
167 inline bool claim_iter(uint region) {
168 assert(region < _max_regions, "Tried to access invalid region %u", region);
169 if (_iter_states[region] != Unclaimed) {
170 return false;
171 }
172 jint res = Atomic::cmpxchg(Claimed, (jint*)(&_iter_states[region]), Unclaimed);
173 return (res == Unclaimed);
174 }
175
176 // Try to atomically sets the iteration state to "complete". Returns true for the
177 // thread that caused the transition.
178 inline bool set_iter_complete(uint region) {
179 if (iter_is_complete(region)) {
180 return false;
181 }
182 jint res = Atomic::cmpxchg(Complete, (jint*)(&_iter_states[region]), Claimed);
183 return (res == Claimed);
184 }
185
186 // Returns true if the region's iteration is complete.
187 inline bool iter_is_complete(uint region) const {
188 assert(region < _max_regions, "Tried to access invalid region %u", region);
189 return _iter_states[region] == Complete;
190 }
191
192 // The current position within the remembered set of the given region.
193 inline size_t iter_claimed(uint region) const {
194 assert(region < _max_regions, "Tried to access invalid region %u", region);
195 return _iter_claims[region];
196 }
197
198 // Claim the next block of cards within the remembered set of the region with
199 // step size.
200 inline size_t iter_claimed_next(uint region, size_t step) {
201 return Atomic::add(step, &_iter_claims[region]) - step;
202 }
203
204 void add_dirty_region(uint region) {
205 if (_in_dirty_region_buffer[region] == Dirty) {
206 return;
207 }
208
209 bool marked_as_dirty = Atomic::cmpxchg(Dirty, &_in_dirty_region_buffer[region], Clean) == Clean;
210 if (marked_as_dirty) {
211 size_t allocated = Atomic::add(1, &_cur_dirty_region) - 1;
212 _dirty_region_buffer[allocated] = region;
213 }
214 }
215
216 // Clear the card table of "dirty" regions.
217 void clear_card_table(WorkGang* workers) {
218 if (_cur_dirty_region == 0) {
219 return;
220 }
221
222 size_t const num_chunks = align_size_up(_cur_dirty_region * HeapRegion::CardsPerRegion, G1ClearCardTableTask::chunk_size()) / G1ClearCardTableTask::chunk_size();
223 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
224 size_t const chunk_length = G1ClearCardTableTask::chunk_size() / HeapRegion::CardsPerRegion;
225
226 // Iterate over the dirty cards region list.
227 G1ClearCardTableTask cl(G1CollectedHeap::heap(), _dirty_region_buffer, _cur_dirty_region, chunk_length);
228
229 log_debug(gc, ergo)("Running %s using %u workers for " SIZE_FORMAT " "
230 "units of work for " SIZE_FORMAT " regions.",
231 cl.name(), num_workers, num_chunks, _cur_dirty_region);
232 workers->run_task(&cl, num_workers);
233
234 #ifndef PRODUCT
235 // Need to synchronize with concurrent cleanup since it needs to
236 // finish its card table clearing before we can verify.
237 G1CollectedHeap::heap()->wait_while_free_regions_coming();
238 G1CollectedHeap::heap()->verifier()->verify_card_table_cleanup();
239 #endif
240 }
241 };
242
243 G1RemSet::G1RemSet(G1CollectedHeap* g1,
244 G1CardTable* ct,
245 G1HotCardCache* hot_card_cache) :
246 _g1(g1),
247 _scan_state(new G1RemSetScanState()),
248 _conc_refine_cards(0),
249 _ct(ct),
250 _g1p(_g1->g1_policy()),
251 _hot_card_cache(hot_card_cache),
252 _prev_period_summary(),
253 _into_cset_dirty_card_queue_set(false)
254 {
255 if (log_is_enabled(Trace, gc, remset)) {
256 _prev_period_summary.initialize(this);
257 }
258 // Initialize the card queue set used to hold cards containing
259 // references into the collection set.
260 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
261 DirtyCardQ_CBL_mon,
262 DirtyCardQ_FL_lock,
263 -1, // never trigger processing
264 -1, // no limit on length
265 Shared_DirtyCardQ_lock,
266 &G1BarrierSet::dirty_card_queue_set());
267 }
268
269 G1RemSet::~G1RemSet() {
270 if (_scan_state != NULL) {
271 delete _scan_state;
272 }
273 }
274
275 uint G1RemSet::num_par_rem_sets() {
276 return MAX2(DirtyCardQueueSet::num_par_ids() + ConcurrentG1Refine::thread_num(), ParallelGCThreads);
277 }
278
279 void G1RemSet::initialize(size_t capacity, uint max_regions) {
280 G1FromCardCache::initialize(num_par_rem_sets(), max_regions);
281 _scan_state->initialize(max_regions);
282 {
283 GCTraceTime(Debug, gc, marking)("Initialize Card Live Data");
284 _card_live_data.initialize(capacity, max_regions);
285 }
286 if (G1PretouchAuxiliaryMemory) {
287 GCTraceTime(Debug, gc, marking)("Pre-Touch Card Live Data");
288 _card_live_data.pretouch();
289 }
290 }
291
292 G1ScanRSClosure::G1ScanRSClosure(G1RemSetScanState* scan_state,
293 G1ParPushHeapRSClosure* push_heap_cl,
294 CodeBlobClosure* code_root_cl,
295 uint worker_i) :
296 _scan_state(scan_state),
297 _push_heap_cl(push_heap_cl),
298 _code_root_cl(code_root_cl),
299 _strong_code_root_scan_time_sec(0.0),
300 _cards(0),
301 _cards_done(0),
302 _worker_i(worker_i) {
303 _g1h = G1CollectedHeap::heap();
304 _bot = _g1h->bot();
305 _ct = _g1h->g1_card_table();
306 _block_size = MAX2<size_t>(G1RSetScanBlockSize, 1);
307 }
308
309 void G1ScanRSClosure::scan_card(size_t index, HeapRegion *r) {
310 // Stack allocate the DirtyCardToOopClosure instance
311 HeapRegionDCTOC cl(_g1h, r, _push_heap_cl, G1CardTable::Precise);
312
313 // Set the "from" region in the closure.
314 _push_heap_cl->set_region(r);
315 MemRegion card_region(_bot->address_for_index(index), BOTConstants::N_words);
316 MemRegion pre_gc_allocated(r->bottom(), r->scan_top());
317 MemRegion mr = pre_gc_allocated.intersection(card_region);
318 if (!mr.is_empty() && !_ct->is_card_claimed(index)) {
319 // We make the card as "claimed" lazily (so races are possible
320 // but they're benign), which reduces the number of duplicate
321 // scans (the rsets of the regions in the cset can intersect).
322 _ct->set_card_claimed(index);
323 _cards_done++;
324 cl.do_MemRegion(mr);
325 }
326 }
327
328 void G1ScanRSClosure::scan_strong_code_roots(HeapRegion* r) {
329 double scan_start = os::elapsedTime();
330 r->strong_code_roots_do(_code_root_cl);
331 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
332 }
333
334 bool G1ScanRSClosure::doHeapRegion(HeapRegion* r) {
335 assert(r->in_collection_set(), "should only be called on elements of CS.");
336 uint region_idx = r->hrm_index();
337
338 if (_scan_state->iter_is_complete(region_idx)) {
339 return false;
340 }
341 if (_scan_state->claim_iter(region_idx)) {
342 // If we ever free the collection set concurrently, we should also
343 // clear the card table concurrently therefore we won't need to
344 // add regions of the collection set to the dirty cards region.
345 _scan_state->add_dirty_region(region_idx);
346 }
347
348 HeapRegionRemSetIterator iter(r->rem_set());
349 size_t card_index;
350
351 // We claim cards in block so as to reduce the contention. The block size is determined by
352 // the G1RSetScanBlockSize parameter.
353 size_t claimed_card_block = _scan_state->iter_claimed_next(region_idx, _block_size);
354 for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
355 if (current_card >= claimed_card_block + _block_size) {
356 claimed_card_block = _scan_state->iter_claimed_next(region_idx, _block_size);
357 }
358 if (current_card < claimed_card_block) {
359 continue;
360 }
361 HeapWord* card_start = _g1h->bot()->address_for_index(card_index);
362
363 HeapRegion* card_region = _g1h->heap_region_containing(card_start);
364 _cards++;
365
366 _scan_state->add_dirty_region(card_region->hrm_index());
367
368 // If the card is dirty, then we will scan it during updateRS.
369 if (!card_region->in_collection_set() &&
370 !_ct->is_card_dirty(card_index)) {
371 scan_card(card_index, card_region);
372 }
373 }
374 if (_scan_state->set_iter_complete(region_idx)) {
375 // Scan the strong code root list attached to the current region
376 scan_strong_code_roots(r);
377 }
378 return false;
379 }
380
381 size_t G1RemSet::scan_rem_set(G1ParPushHeapRSClosure* oops_in_heap_closure,
382 CodeBlobClosure* heap_region_codeblobs,
383 uint worker_i) {
384 double rs_time_start = os::elapsedTime();
385
386 G1ScanRSClosure cl(_scan_state, oops_in_heap_closure, heap_region_codeblobs, worker_i);
387 _g1->collection_set_iterate_from(&cl, worker_i);
388
389 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start) -
390 cl.strong_code_root_scan_time_sec();
391
392 _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, scan_rs_time_sec);
393 _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::CodeRoots, worker_i, cl.strong_code_root_scan_time_sec());
394
395 return cl.cards_done();
396 }
397
398 // Closure used for updating RSets and recording references that
399 // point into the collection set. Only called during an
400 // evacuation pause.
401
402 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
403 G1RemSet* _g1rs;
404 DirtyCardQueue* _into_cset_dcq;
405 G1ParPushHeapRSClosure* _cl;
406 public:
407 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
408 DirtyCardQueue* into_cset_dcq,
409 G1ParPushHeapRSClosure* cl) :
410 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq), _cl(cl)
411 {}
412
413 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
414 // The only time we care about recording cards that
415 // contain references that point into the collection set
416 // is during RSet updating within an evacuation pause.
417 // In this case worker_i should be the id of a GC worker thread.
418 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
419 assert(worker_i < ParallelGCThreads, "should be a GC worker");
420
421 if (_g1rs->refine_card(card_ptr, worker_i, _cl)) {
422 // 'card_ptr' contains references that point into the collection
423 // set. We need to record the card in the DCQS
424 // (_into_cset_dirty_card_queue_set)
425 // that's used for that purpose.
426 //
427 // Enqueue the card
428 _into_cset_dcq->enqueue(card_ptr);
429 }
430 return true;
431 }
432 };
433
434 void G1RemSet::update_rem_set(DirtyCardQueue* into_cset_dcq,
435 G1ParPushHeapRSClosure* oops_in_heap_closure,
436 uint worker_i) {
437 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq, oops_in_heap_closure);
438
439 G1GCParPhaseTimesTracker x(_g1p->phase_times(), G1GCPhaseTimes::UpdateRS, worker_i);
440 if (G1HotCardCache::default_use_cache()) {
441 // Apply the closure to the entries of the hot card cache.
442 G1GCParPhaseTimesTracker y(_g1p->phase_times(), G1GCPhaseTimes::ScanHCC, worker_i);
443 _g1->iterate_hcc_closure(&into_cset_update_rs_cl, worker_i);
444 }
445 // Apply the closure to all remaining log entries.
446 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, worker_i);
447 }
448
449 void G1RemSet::cleanupHRRS() {
450 HeapRegionRemSet::cleanup();
451 }
452
453 size_t G1RemSet::oops_into_collection_set_do(G1ParPushHeapRSClosure* cl,
454 CodeBlobClosure* heap_region_codeblobs,
455 uint worker_i) {
456 // A DirtyCardQueue that is used to hold cards containing references
457 // that point into the collection set. This DCQ is associated with a
458 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal
459 // circumstances (i.e. the pause successfully completes), these cards
460 // are just discarded (there's no need to update the RSets of regions
461 // that were in the collection set - after the pause these regions
462 // are wholly 'free' of live objects. In the event of an evacuation
463 // failure the cards/buffers in this queue set are passed to the
464 // DirtyCardQueueSet that is used to manage RSet updates
465 DirtyCardQueue into_cset_dcq(&_into_cset_dirty_card_queue_set);
466
467 update_rem_set(&into_cset_dcq, cl, worker_i);
468 return scan_rem_set(cl, heap_region_codeblobs, worker_i);;
469 }
470
471 void G1RemSet::prepare_for_oops_into_collection_set_do() {
472 _g1->set_refine_cte_cl_concurrency(false);
473 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
474 dcqs.concatenate_logs();
475
476 _scan_state->reset();
477 }
478
479 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
480 G1GCPhaseTimes* phase_times = _g1->g1_policy()->phase_times();
481 // Cleanup after copy
482 _g1->set_refine_cte_cl_concurrency(true);
483
484 // Set all cards back to clean.
485 double start = os::elapsedTime();
486 _scan_state->clear_card_table(_g1->workers());
487 phase_times->record_clear_ct_time((os::elapsedTime() - start) * 1000.0);
488
489 DirtyCardQueueSet& into_cset_dcqs = _into_cset_dirty_card_queue_set;
490
491 if (_g1->evacuation_failed()) {
492 double restore_remembered_set_start = os::elapsedTime();
493
494 // Restore remembered sets for the regions pointing into the collection set.
495 // We just need to transfer the completed buffers from the DirtyCardQueueSet
496 // used to hold cards that contain references that point into the collection set
497 // to the DCQS used to hold the deferred RS updates.
498 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
499 phase_times->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
500 }
501
502 // Free any completed buffers in the DirtyCardQueueSet used to hold cards
503 // which contain references that point into the collection.
504 _into_cset_dirty_card_queue_set.clear();
505 assert(_into_cset_dirty_card_queue_set.completed_buffers_num() == 0,
506 "all buffers should be freed");
507 _into_cset_dirty_card_queue_set.clear_n_completed_buffers();
508 }
509
510 class G1ScrubRSClosure: public HeapRegionClosure {
511 G1CollectedHeap* _g1h;
512 G1CardLiveData* _live_data;
513 public:
514 G1ScrubRSClosure(G1CardLiveData* live_data) :
515 _g1h(G1CollectedHeap::heap()),
516 _live_data(live_data) { }
517
518 bool doHeapRegion(HeapRegion* r) {
519 if (!r->is_continues_humongous()) {
520 r->rem_set()->scrub(_live_data);
521 }
522 return false;
523 }
524 };
525
526 void G1RemSet::scrub(uint worker_num, HeapRegionClaimer *hrclaimer) {
527 G1ScrubRSClosure scrub_cl(&_card_live_data);
528 _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
529 }
530
531 G1UpdateRSOrPushRefOopClosure::G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
532 G1ParPushHeapRSClosure* push_ref_cl,
533 bool record_refs_into_cset,
534 uint worker_i) :
535 _g1(g1h),
536 _from(NULL),
537 _record_refs_into_cset(record_refs_into_cset),
538 _has_refs_into_cset(false),
539 _push_ref_cl(push_ref_cl),
540 _worker_i(worker_i) { }
541
542 // Returns true if the given card contains references that point
543 // into the collection set, if we're checking for such references;
544 // false otherwise.
545
546 bool G1RemSet::refine_card(jbyte* card_ptr,
547 uint worker_i,
548 G1ParPushHeapRSClosure* oops_in_heap_closure) {
549 assert(_g1->is_in_exact(_ct->addr_for(card_ptr)),
550 "Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap",
551 p2i(card_ptr),
552 _ct->index_for(_ct->addr_for(card_ptr)),
553 p2i(_ct->addr_for(card_ptr)),
554 _g1->addr_to_region(_ct->addr_for(card_ptr)));
555
556 bool check_for_refs_into_cset = oops_in_heap_closure != NULL;
557
558 // If the card is no longer dirty, nothing to do.
559 if (*card_ptr != G1CardTable::dirty_card_val()) {
560 // No need to return that this card contains refs that point
561 // into the collection set.
562 return false;
563 }
564
565 // Construct the region representing the card.
566 HeapWord* start = _ct->addr_for(card_ptr);
567 // And find the region containing it.
568 HeapRegion* r = _g1->heap_region_containing(start);
569
570 // This check is needed for some uncommon cases where we should
571 // ignore the card.
572 //
573 // The region could be young. Cards for young regions are
574 // distinctly marked (set to g1_young_gen), so the post-barrier will
575 // filter them out. However, that marking is performed
576 // concurrently. A write to a young object could occur before the
577 // card has been marked young, slipping past the filter.
578 //
579 // The card could be stale, because the region has been freed since
580 // the card was recorded. In this case the region type could be
581 // anything. If (still) free or (reallocated) young, just ignore
582 // it. If (reallocated) old or humongous, the later card trimming
583 // and additional checks in iteration may detect staleness. At
584 // worst, we end up processing a stale card unnecessarily.
585 //
586 // In the normal (non-stale) case, the synchronization between the
587 // enqueueing of the card and processing it here will have ensured
588 // we see the up-to-date region type here.
589 if (!r->is_old_or_humongous()) {
590 return false;
591 }
592
593 // While we are processing RSet buffers during the collection, we
594 // actually don't want to scan any cards on the collection set,
595 // since we don't want to update remembered sets with entries that
596 // point into the collection set, given that live objects from the
597 // collection set are about to move and such entries will be stale
598 // very soon. This change also deals with a reliability issue which
599 // involves scanning a card in the collection set and coming across
600 // an array that was being chunked and looking malformed. Note,
601 // however, that if evacuation fails, we have to scan any objects
602 // that were not moved and create any missing entries.
603 if (r->in_collection_set()) {
604 return false;
605 }
606
607 // The result from the hot card cache insert call is either:
608 // * pointer to the current card
609 // (implying that the current card is not 'hot'),
610 // * null
611 // (meaning we had inserted the card ptr into the "hot" card cache,
612 // which had some headroom),
613 // * a pointer to a "hot" card that was evicted from the "hot" cache.
614 //
615
616 if (_hot_card_cache->use_cache()) {
617 assert(!check_for_refs_into_cset, "sanity");
618 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
619
620 const jbyte* orig_card_ptr = card_ptr;
621 card_ptr = _hot_card_cache->insert(card_ptr);
622 if (card_ptr == NULL) {
623 // There was no eviction. Nothing to do.
624 return false;
625 } else if (card_ptr != orig_card_ptr) {
626 // Original card was inserted and an old card was evicted.
627 start = _ct->addr_for(card_ptr);
628 r = _g1->heap_region_containing(start);
629
630 // Check whether the region formerly in the cache should be
631 // ignored, as discussed earlier for the original card. The
632 // region could have been freed while in the cache. The cset is
633 // not relevant here, since we're in concurrent phase.
634 if (!r->is_old_or_humongous()) {
635 return false;
636 }
637 } // Else we still have the original card.
638 }
639
640 // Trim the region designated by the card to what's been allocated
641 // in the region. The card could be stale, or the card could cover
642 // (part of) an object at the end of the allocated space and extend
643 // beyond the end of allocation.
644 HeapWord* scan_limit;
645 if (_g1->is_gc_active()) {
646 // If we're in a STW GC, then a card might be in a GC alloc region
647 // and extend onto a GC LAB, which may not be parsable. Stop such
648 // at the "scan_top" of the region.
649 scan_limit = r->scan_top();
650 } else {
651 // Non-humongous objects are only allocated in the old-gen during
652 // GC, so if region is old then top is stable. Humongous object
653 // allocation sets top last; if top has not yet been set, this is
654 // a stale card and we'll end up with an empty intersection. If
655 // this is not a stale card, the synchronization between the
656 // enqueuing of the card and processing it here will have ensured
657 // we see the up-to-date top here.
658 scan_limit = r->top();
659 }
660 if (scan_limit <= start) {
661 // If the trimmed region is empty, the card must be stale.
662 return false;
663 }
664
665 // Okay to clean and process the card now. There are still some
666 // stale card cases that may be detected by iteration and dealt with
667 // as iteration failure.
668 *const_cast<volatile jbyte*>(card_ptr) = G1CardTable::clean_card_val();
669
670 // This fence serves two purposes. First, the card must be cleaned
671 // before processing the contents. Second, we can't proceed with
672 // processing until after the read of top, for synchronization with
673 // possibly concurrent humongous object allocation. It's okay that
674 // reading top and reading type were racy wrto each other. We need
675 // both set, in any order, to proceed.
676 OrderAccess::fence();
677
678 // Don't use addr_for(card_ptr + 1) which can ask for
679 // a card beyond the heap.
680 HeapWord* end = start + G1CardTable::card_size_in_words;
681 MemRegion dirty_region(start, MIN2(scan_limit, end));
682 assert(!dirty_region.is_empty(), "sanity");
683
684 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
685 oops_in_heap_closure,
686 check_for_refs_into_cset,
687 worker_i);
688 update_rs_oop_cl.set_from(r);
689
690 bool card_processed =
691 r->oops_on_card_seq_iterate_careful(dirty_region,
692 &update_rs_oop_cl);
693
694 // If unable to process the card then we encountered an unparsable
695 // part of the heap (e.g. a partially allocated object) while
696 // processing a stale card. Despite the card being stale, redirty
697 // and re-enqueue, because we've already cleaned the card. Without
698 // this we could incorrectly discard a non-stale card.
699 if (!card_processed) {
700 assert(!_g1->is_gc_active(), "Unparsable heap during GC");
701 // The card might have gotten re-dirtied and re-enqueued while we
702 // worked. (In fact, it's pretty likely.)
703 if (*card_ptr != G1CardTable::dirty_card_val()) {
704 *card_ptr = G1CardTable::dirty_card_val();
705 MutexLockerEx x(Shared_DirtyCardQ_lock,
706 Mutex::_no_safepoint_check_flag);
707 DirtyCardQueue* sdcq =
708 G1BarrierSet::dirty_card_queue_set().shared_dirty_card_queue();
709 sdcq->enqueue(card_ptr);
710 }
711 } else {
712 _conc_refine_cards++;
713 }
714
715 // This gets set to true if the card being refined has references that point
716 // into the collection set.
717 bool has_refs_into_cset = update_rs_oop_cl.has_refs_into_cset();
718
719 // We should only be detecting that the card contains references
720 // that point into the collection set if the current thread is
721 // a GC worker thread.
722 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
723 "invalid result at non safepoint");
724
725 return has_refs_into_cset;
726 }
727
728 void G1RemSet::print_periodic_summary_info(const char* header, uint period_count) {
729 if ((G1SummarizeRSetStatsPeriod > 0) && log_is_enabled(Trace, gc, remset) &&
730 (period_count % G1SummarizeRSetStatsPeriod == 0)) {
731
732 if (!_prev_period_summary.initialized()) {
733 _prev_period_summary.initialize(this);
734 }
735
736 G1RemSetSummary current;
737 current.initialize(this);
738 _prev_period_summary.subtract_from(¤t);
739
740 Log(gc, remset) log;
741 log.trace("%s", header);
742 ResourceMark rm;
743 _prev_period_summary.print_on(log.trace_stream());
744
745 _prev_period_summary.set(¤t);
746 }
747 }
748
749 void G1RemSet::print_summary_info() {
750 Log(gc, remset, exit) log;
751 if (log.is_trace()) {
752 log.trace(" Cumulative RS summary");
753 G1RemSetSummary current;
754 current.initialize(this);
755 ResourceMark rm;
756 current.print_on(log.trace_stream());
757 }
758 }
759
760 void G1RemSet::prepare_for_verify() {
761 if (G1HRRSFlushLogBuffersOnVerify &&
762 (VerifyBeforeGC || VerifyAfterGC)
763 && (!_g1->collector_state()->full_collection() || G1VerifyRSetsDuringFullGC)) {
764 cleanupHRRS();
765 _g1->set_refine_cte_cl_concurrency(false);
766 if (SafepointSynchronize::is_at_safepoint()) {
767 DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
768 dcqs.concatenate_logs();
769 }
770
771 bool use_hot_card_cache = _hot_card_cache->use_cache();
772 _hot_card_cache->set_use_cache(false);
773
774 DirtyCardQueue into_cset_dcq(&_into_cset_dirty_card_queue_set);
775 update_rem_set(&into_cset_dcq, NULL, 0);
776 _into_cset_dirty_card_queue_set.clear();
777
778 _hot_card_cache->set_use_cache(use_hot_card_cache);
779 assert(G1BarrierSet::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
780 }
781 }
782
783 void G1RemSet::create_card_live_data(WorkGang* workers, G1CMBitMap* mark_bitmap) {
784 _card_live_data.create(workers, mark_bitmap);
785 }
786
787 void G1RemSet::finalize_card_live_data(WorkGang* workers, G1CMBitMap* mark_bitmap) {
788 _card_live_data.finalize(workers, mark_bitmap);
789 }
790
791 void G1RemSet::verify_card_live_data(WorkGang* workers, G1CMBitMap* bitmap) {
792 _card_live_data.verify(workers, bitmap);
793 }
794
795 void G1RemSet::clear_card_live_data(WorkGang* workers) {
796 _card_live_data.clear(workers);
797 }
798
799 #ifdef ASSERT
800 void G1RemSet::verify_card_live_data_is_clear() {
801 _card_live_data.verify_is_clear();
802 }
803 #endif