1 /*
2 * Copyright (c) 2001, 2019, 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/g1BarrierSet.hpp"
27 #include "gc/g1/g1BlockOffsetTable.inline.hpp"
28 #include "gc/g1/g1CardTable.inline.hpp"
29 #include "gc/g1/g1CardTableEntryClosure.hpp"
30 #include "gc/g1/g1CollectedHeap.inline.hpp"
31 #include "gc/g1/g1ConcurrentRefine.hpp"
32 #include "gc/g1/g1DirtyCardQueue.hpp"
33 #include "gc/g1/g1FromCardCache.hpp"
34 #include "gc/g1/g1GCPhaseTimes.hpp"
35 #include "gc/g1/g1HotCardCache.hpp"
36 #include "gc/g1/g1OopClosures.inline.hpp"
37 #include "gc/g1/g1RootClosures.hpp"
38 #include "gc/g1/g1RemSet.hpp"
39 #include "gc/g1/g1SharedDirtyCardQueue.hpp"
40 #include "gc/g1/heapRegion.inline.hpp"
41 #include "gc/g1/heapRegionManager.inline.hpp"
42 #include "gc/g1/heapRegionRemSet.inline.hpp"
43 #include "gc/g1/sparsePRT.hpp"
44 #include "gc/shared/gcTraceTime.inline.hpp"
45 #include "gc/shared/ptrQueue.hpp"
46 #include "gc/shared/suspendibleThreadSet.hpp"
47 #include "jfr/jfrEvents.hpp"
48 #include "memory/iterator.hpp"
49 #include "memory/resourceArea.hpp"
50 #include "oops/access.inline.hpp"
51 #include "oops/oop.inline.hpp"
52 #include "runtime/atomic.hpp"
53 #include "runtime/os.hpp"
54 #include "utilities/align.hpp"
55 #include "utilities/globalDefinitions.hpp"
56 #include "utilities/stack.inline.hpp"
57 #include "utilities/ticks.hpp"
58
59 // Collects information about the overall heap root scan progress during an evacuation.
60 //
61 // Scanning the remembered sets works by first merging all sources of cards to be
62 // scanned (log buffers, hcc, remembered sets) into a single data structure to remove
63 // duplicates and simplify work distribution.
64 //
65 // During the following card scanning we not only scan this combined set of cards, but
66 // also remember that these were completely scanned. The following evacuation passes
67 // do not scan these cards again, and so need to be preserved across increments.
68 //
69 // The representation for all the cards to scan is the card table: cards can have
70 // one of three states during GC:
71 // - clean: these cards will not be scanned in this pass
72 // - dirty: these cards will be scanned in this pass
73 // - scanned: these cards have already been scanned in a previous pass
74 //
75 // After all evacuation is done, we reset the card table to clean.
76 //
77 // Work distribution occurs on "chunk" basis, i.e. contiguous ranges of cards. As an
78 // additional optimization, during card merging we remember which regions and which
79 // chunks actually contain cards to be scanned. Threads iterate only across these
80 // regions, and only compete for chunks containing any cards.
81 //
82 // Within these chunks, a worker scans the card table on "blocks" of cards, i.e.
83 // contiguous ranges of dirty cards to be scanned. These blocks are converted to actual
84 // memory ranges and then passed on to actual scanning.
85 class G1RemSetScanState : public CHeapObj<mtGC> {
86 class G1DirtyRegions;
87
88 size_t _max_regions;
89
90 // Has this region that is part of the regions in the collection set been processed yet.
91 typedef bool G1RemsetIterState;
92
93 G1RemsetIterState volatile* _collection_set_iter_state;
94
95 // Card table iteration claim for each heap region, from 0 (completely unscanned)
96 // to (>=) HeapRegion::CardsPerRegion (completely scanned).
97 uint volatile* _card_table_scan_state;
98
99 // Return "optimal" number of chunks per region we want to use for claiming areas
100 // within a region to claim. Dependent on the region size as proxy for the heap
101 // size, we limit the total number of chunks to limit memory usage and maintenance
102 // effort of that table vs. granularity of distributing scanning work.
103 // Testing showed that 8 for 1M/2M region, 16 for 4M/8M regions, 32 for 16/32M regions
104 // seems to be such a good trade-off.
105 static uint get_chunks_per_region(uint log_region_size) {
106 // Limit the expected input values to current known possible values of the
107 // (log) region size. Adjust as necessary after testing if changing the permissible
108 // values for region size.
109 assert(log_region_size >= 20 && log_region_size <= 25,
110 "expected value in [20,25], but got %u", log_region_size);
111 return 1u << (log_region_size / 2 - 7);
112 }
113
114 uint _scan_chunks_per_region; // Number of chunks per region.
115 uint8_t _log_scan_chunks_per_region; // Log of number of chunks per region.
116 bool* _region_scan_chunks;
117 size_t _num_total_scan_chunks; // Total number of elements in _region_scan_chunks.
118 uint8_t _scan_chunks_shift; // For conversion between card index and chunk index.
119 public:
120 uint scan_chunk_size() const { return (uint)1 << _scan_chunks_shift; }
121
122 // Returns whether the chunk corresponding to the given region/card in region contain a
123 // dirty card, i.e. actually needs scanning.
124 bool chunk_needs_scan(uint const region_idx, uint const card_in_region) const {
125 size_t const idx = ((size_t)region_idx << _log_scan_chunks_per_region) + (card_in_region >> _scan_chunks_shift);
126 assert(idx < _num_total_scan_chunks, "Index " SIZE_FORMAT " out of bounds " SIZE_FORMAT,
127 idx, _num_total_scan_chunks);
128 return _region_scan_chunks[idx];
129 }
130
131 private:
132 // The complete set of regions which card table needs to be cleared at the end of GC because
133 // we scribbled all over them.
134 G1DirtyRegions* _all_dirty_regions;
135 // The set of regions which card table needs to be scanned for new dirty cards
136 // in the current evacuation pass.
137 G1DirtyRegions* _next_dirty_regions;
138
139 // Set of (unique) regions that can be added to concurrently.
140 class G1DirtyRegions : public CHeapObj<mtGC> {
141 uint* _buffer;
142 uint _cur_idx;
143 size_t _max_regions;
144
145 bool* _contains;
146
147 public:
148 G1DirtyRegions(size_t max_regions) :
149 _buffer(NEW_C_HEAP_ARRAY(uint, max_regions, mtGC)),
150 _cur_idx(0),
151 _max_regions(max_regions),
152 _contains(NEW_C_HEAP_ARRAY(bool, max_regions, mtGC)) {
153
154 reset();
155 }
156
157 static size_t chunk_size() { return M; }
158
159 ~G1DirtyRegions() {
160 FREE_C_HEAP_ARRAY(uint, _buffer);
161 FREE_C_HEAP_ARRAY(bool, _contains);
162 }
163
164 void reset() {
165 _cur_idx = 0;
166 ::memset(_contains, false, _max_regions * sizeof(bool));
167 }
168
169 uint size() const { return _cur_idx; }
170
171 uint at(uint idx) const {
172 assert(idx < _cur_idx, "Index %u beyond valid regions", idx);
173 return _buffer[idx];
174 }
175
176 void add_dirty_region(uint region) {
177 if (_contains[region]) {
178 return;
179 }
180
181 bool marked_as_dirty = Atomic::cmpxchg(&_contains[region], false, true) == false;
182 if (marked_as_dirty) {
183 uint allocated = Atomic::add(&_cur_idx, 1u) - 1;
184 _buffer[allocated] = region;
185 }
186 }
187
188 // Creates the union of this and the other G1DirtyRegions.
189 void merge(const G1DirtyRegions* other) {
190 for (uint i = 0; i < other->size(); i++) {
191 uint region = other->at(i);
192 if (!_contains[region]) {
193 _buffer[_cur_idx++] = region;
194 _contains[region] = true;
195 }
196 }
197 }
198 };
199
200 // For each region, contains the maximum top() value to be used during this garbage
201 // collection. Subsumes common checks like filtering out everything but old and
202 // humongous regions outside the collection set.
203 // This is valid because we are not interested in scanning stray remembered set
204 // entries from free or archive regions.
205 HeapWord** _scan_top;
206
207 class G1ClearCardTableTask : public AbstractGangTask {
208 G1CollectedHeap* _g1h;
209 G1DirtyRegions* _regions;
210 uint _chunk_length;
211
212 uint volatile _cur_dirty_regions;
213
214 G1RemSetScanState* _scan_state;
215
216 public:
217 G1ClearCardTableTask(G1CollectedHeap* g1h,
218 G1DirtyRegions* regions,
219 uint chunk_length,
220 G1RemSetScanState* scan_state) :
221 AbstractGangTask("G1 Clear Card Table Task"),
222 _g1h(g1h),
223 _regions(regions),
224 _chunk_length(chunk_length),
225 _cur_dirty_regions(0),
226 _scan_state(scan_state) {
227
228 assert(chunk_length > 0, "must be");
229 }
230
231 static uint chunk_size() { return M; }
232
233 void work(uint worker_id) {
234 while (_cur_dirty_regions < _regions->size()) {
235 uint next = Atomic::add(&_cur_dirty_regions, _chunk_length) - _chunk_length;
236 uint max = MIN2(next + _chunk_length, _regions->size());
237
238 for (uint i = next; i < max; i++) {
239 HeapRegion* r = _g1h->region_at(_regions->at(i));
240 if (!r->is_survivor()) {
241 r->clear_cardtable();
242 }
243 }
244 }
245 }
246 };
247
248 // Clear the card table of "dirty" regions.
249 void clear_card_table(WorkGang* workers) {
250 uint num_regions = _all_dirty_regions->size();
251
252 if (num_regions == 0) {
253 return;
254 }
255
256 uint const num_chunks = (uint)(align_up((size_t)num_regions << HeapRegion::LogCardsPerRegion, G1ClearCardTableTask::chunk_size()) / G1ClearCardTableTask::chunk_size());
257 uint const num_workers = MIN2(num_chunks, workers->active_workers());
258 uint const chunk_length = G1ClearCardTableTask::chunk_size() / (uint)HeapRegion::CardsPerRegion;
259
260 // Iterate over the dirty cards region list.
261 G1ClearCardTableTask cl(G1CollectedHeap::heap(), _all_dirty_regions, chunk_length, this);
262
263 log_debug(gc, ergo)("Running %s using %u workers for %u "
264 "units of work for %u regions.",
265 cl.name(), num_workers, num_chunks, num_regions);
266 workers->run_task(&cl, num_workers);
267
268 #ifndef PRODUCT
269 G1CollectedHeap::heap()->verifier()->verify_card_table_cleanup();
270 #endif
271 }
272
273 public:
274 G1RemSetScanState() :
275 _max_regions(0),
276 _collection_set_iter_state(NULL),
277 _card_table_scan_state(NULL),
278 _scan_chunks_per_region(get_chunks_per_region(HeapRegion::LogOfHRGrainBytes)),
279 _log_scan_chunks_per_region(log2_uint(_scan_chunks_per_region)),
280 _region_scan_chunks(NULL),
281 _num_total_scan_chunks(0),
282 _scan_chunks_shift(0),
283 _all_dirty_regions(NULL),
284 _next_dirty_regions(NULL),
285 _scan_top(NULL) {
286 }
287
288 ~G1RemSetScanState() {
289 FREE_C_HEAP_ARRAY(G1RemsetIterState, _collection_set_iter_state);
290 FREE_C_HEAP_ARRAY(uint, _card_table_scan_state);
291 FREE_C_HEAP_ARRAY(bool, _region_scan_chunks);
292 FREE_C_HEAP_ARRAY(HeapWord*, _scan_top);
293 }
294
295 void initialize(size_t max_regions) {
296 assert(_collection_set_iter_state == NULL, "Must not be initialized twice");
297 _max_regions = max_regions;
298 _collection_set_iter_state = NEW_C_HEAP_ARRAY(G1RemsetIterState, max_regions, mtGC);
299 _card_table_scan_state = NEW_C_HEAP_ARRAY(uint, max_regions, mtGC);
300 _num_total_scan_chunks = max_regions * _scan_chunks_per_region;
301 _region_scan_chunks = NEW_C_HEAP_ARRAY(bool, _num_total_scan_chunks, mtGC);
302
303 _scan_chunks_shift = (uint8_t)log2_intptr(HeapRegion::CardsPerRegion / _scan_chunks_per_region);
304 _scan_top = NEW_C_HEAP_ARRAY(HeapWord*, max_regions, mtGC);
305 }
306
307 void prepare() {
308 // Reset the claim and clear scan top for all regions, including
309 // regions currently not available or free. Since regions might
310 // become used during the collection these values must be valid
311 // for those regions as well.
312 for (size_t i = 0; i < _max_regions; i++) {
313 reset_region_claim((uint)i);
314 clear_scan_top((uint)i);
315 }
316
317 _all_dirty_regions = new G1DirtyRegions(_max_regions);
318 _next_dirty_regions = new G1DirtyRegions(_max_regions);
319 }
320
321 void prepare_for_merge_heap_roots() {
322 _all_dirty_regions->merge(_next_dirty_regions);
323
324 _next_dirty_regions->reset();
325 for (size_t i = 0; i < _max_regions; i++) {
326 _card_table_scan_state[i] = 0;
327 }
328
329 ::memset(_region_scan_chunks, false, _num_total_scan_chunks * sizeof(*_region_scan_chunks));
330 }
331
332 // Returns whether the given region contains cards we need to scan. The remembered
333 // set and other sources may contain cards that
334 // - are in uncommitted regions
335 // - are located in the collection set
336 // - are located in free regions
337 // as we do not clean up remembered sets before merging heap roots.
338 bool contains_cards_to_process(uint const region_idx) const {
339 HeapRegion* hr = G1CollectedHeap::heap()->region_at_or_null(region_idx);
340 return (hr != NULL && !hr->in_collection_set() && hr->is_old_or_humongous_or_archive());
341 }
342
343 size_t num_visited_cards() const {
344 size_t result = 0;
345 for (uint i = 0; i < _num_total_scan_chunks; i++) {
346 if (_region_scan_chunks[i]) {
347 result++;
348 }
349 }
350 return result * (HeapRegion::CardsPerRegion / _scan_chunks_per_region);
351 }
352
353 size_t num_cards_in_dirty_regions() const {
354 return _next_dirty_regions->size() * HeapRegion::CardsPerRegion;
355 }
356
357 void set_chunk_region_dirty(size_t const region_card_idx) {
358 size_t chunk_idx = region_card_idx >> _scan_chunks_shift;
359 for (uint i = 0; i < _scan_chunks_per_region; i++) {
360 _region_scan_chunks[chunk_idx++] = true;
361 }
362 }
363
364 void set_chunk_dirty(size_t const card_idx) {
365 assert((card_idx >> _scan_chunks_shift) < _num_total_scan_chunks,
366 "Trying to access index " SIZE_FORMAT " out of bounds " SIZE_FORMAT,
367 card_idx >> _scan_chunks_shift, _num_total_scan_chunks);
368 size_t const chunk_idx = card_idx >> _scan_chunks_shift;
369 if (!_region_scan_chunks[chunk_idx]) {
370 _region_scan_chunks[chunk_idx] = true;
371 }
372 }
373
374 void cleanup(WorkGang* workers) {
375 _all_dirty_regions->merge(_next_dirty_regions);
376
377 clear_card_table(workers);
378
379 delete _all_dirty_regions;
380 _all_dirty_regions = NULL;
381
382 delete _next_dirty_regions;
383 _next_dirty_regions = NULL;
384 }
385
386 void iterate_dirty_regions_from(HeapRegionClosure* cl, uint worker_id) {
387 uint num_regions = _next_dirty_regions->size();
388
389 if (num_regions == 0) {
390 return;
391 }
392
393 G1CollectedHeap* g1h = G1CollectedHeap::heap();
394
395 WorkGang* workers = g1h->workers();
396 uint const max_workers = workers->active_workers();
397
398 uint const start_pos = num_regions * worker_id / max_workers;
399 uint cur = start_pos;
400
401 do {
402 bool result = cl->do_heap_region(g1h->region_at(_next_dirty_regions->at(cur)));
403 guarantee(!result, "Not allowed to ask for early termination.");
404 cur++;
405 if (cur == _next_dirty_regions->size()) {
406 cur = 0;
407 }
408 } while (cur != start_pos);
409 }
410
411 void reset_region_claim(uint region_idx) {
412 _collection_set_iter_state[region_idx] = false;
413 }
414
415 // Attempt to claim the given region in the collection set for iteration. Returns true
416 // if this call caused the transition from Unclaimed to Claimed.
417 inline bool claim_collection_set_region(uint region) {
418 assert(region < _max_regions, "Tried to access invalid region %u", region);
419 if (_collection_set_iter_state[region]) {
420 return false;
421 }
422 return !Atomic::cmpxchg(&_collection_set_iter_state[region], false, true);
423 }
424
425 bool has_cards_to_scan(uint region) {
426 assert(region < _max_regions, "Tried to access invalid region %u", region);
427 return _card_table_scan_state[region] < HeapRegion::CardsPerRegion;
428 }
429
430 uint claim_cards_to_scan(uint region, uint increment) {
431 assert(region < _max_regions, "Tried to access invalid region %u", region);
432 return Atomic::add(&_card_table_scan_state[region], increment) - increment;
433 }
434
435 void add_dirty_region(uint const region) {
436 #ifdef ASSERT
437 HeapRegion* hr = G1CollectedHeap::heap()->region_at(region);
438 assert(!hr->in_collection_set() && hr->is_old_or_humongous_or_archive(),
439 "Region %u is not suitable for scanning, is %sin collection set or %s",
440 hr->hrm_index(), hr->in_collection_set() ? "" : "not ", hr->get_short_type_str());
441 #endif
442 _next_dirty_regions->add_dirty_region(region);
443 }
444
445 void add_all_dirty_region(uint region) {
446 #ifdef ASSERT
447 HeapRegion* hr = G1CollectedHeap::heap()->region_at(region);
448 assert(hr->in_collection_set(),
449 "Only add young regions to all dirty regions directly but %u is %s",
450 hr->hrm_index(), hr->get_short_type_str());
451 #endif
452 _all_dirty_regions->add_dirty_region(region);
453 }
454
455 void set_scan_top(uint region_idx, HeapWord* value) {
456 _scan_top[region_idx] = value;
457 }
458
459 HeapWord* scan_top(uint region_idx) const {
460 return _scan_top[region_idx];
461 }
462
463 void clear_scan_top(uint region_idx) {
464 set_scan_top(region_idx, NULL);
465 }
466 };
467
468 G1RemSet::G1RemSet(G1CollectedHeap* g1h,
469 G1CardTable* ct,
470 G1HotCardCache* hot_card_cache) :
471 _scan_state(new G1RemSetScanState()),
472 _prev_period_summary(false),
473 _g1h(g1h),
474 _ct(ct),
475 _g1p(_g1h->policy()),
476 _hot_card_cache(hot_card_cache) {
477 }
478
479 G1RemSet::~G1RemSet() {
480 delete _scan_state;
481 }
482
483 uint G1RemSet::num_par_rem_sets() {
484 return G1DirtyCardQueueSet::num_par_ids() + G1ConcurrentRefine::max_num_threads() + MAX2(ConcGCThreads, ParallelGCThreads);
485 }
486
487 void G1RemSet::initialize(size_t capacity, uint max_regions) {
488 G1FromCardCache::initialize(num_par_rem_sets(), max_regions);
489 _scan_state->initialize(max_regions);
490 }
491
492 // Helper class to scan and detect ranges of cards that need to be scanned on the
493 // card table.
494 class G1CardTableScanner : public StackObj {
495 public:
496 typedef CardTable::CardValue CardValue;
497
498 private:
499 CardValue* const _base_addr;
500
501 CardValue* _cur_addr;
502 CardValue* const _end_addr;
503
504 static const size_t ToScanMask = G1CardTable::g1_card_already_scanned;
505 static const size_t ExpandedToScanMask = G1CardTable::WordAlreadyScanned;
506
507 bool cur_addr_aligned() const {
508 return ((uintptr_t)_cur_addr) % sizeof(size_t) == 0;
509 }
510
511 bool cur_card_is_dirty() const {
512 CardValue value = *_cur_addr;
513 return (value & ToScanMask) == 0;
514 }
515
516 bool cur_word_of_cards_contains_any_dirty_card() const {
517 assert(cur_addr_aligned(), "Current address should be aligned");
518 size_t const value = *(size_t*)_cur_addr;
519 return (~value & ExpandedToScanMask) != 0;
520 }
521
522 bool cur_word_of_cards_all_dirty_cards() const {
523 size_t const value = *(size_t*)_cur_addr;
524 return value == G1CardTable::WordAllDirty;
525 }
526
527 size_t get_and_advance_pos() {
528 _cur_addr++;
529 return pointer_delta(_cur_addr, _base_addr, sizeof(CardValue)) - 1;
530 }
531
532 public:
533 G1CardTableScanner(CardValue* start_card, size_t size) :
534 _base_addr(start_card),
535 _cur_addr(start_card),
536 _end_addr(start_card + size) {
537
538 assert(is_aligned(start_card, sizeof(size_t)), "Unaligned start addr " PTR_FORMAT, p2i(start_card));
539 assert(is_aligned(size, sizeof(size_t)), "Unaligned size " SIZE_FORMAT, size);
540 }
541
542 size_t find_next_dirty() {
543 while (!cur_addr_aligned()) {
544 if (cur_card_is_dirty()) {
545 return get_and_advance_pos();
546 }
547 _cur_addr++;
548 }
549
550 assert(cur_addr_aligned(), "Current address should be aligned now.");
551 while (_cur_addr != _end_addr) {
552 if (cur_word_of_cards_contains_any_dirty_card()) {
553 for (size_t i = 0; i < sizeof(size_t); i++) {
554 if (cur_card_is_dirty()) {
555 return get_and_advance_pos();
556 }
557 _cur_addr++;
558 }
559 assert(false, "Should not reach here given we detected a dirty card in the word.");
560 }
561 _cur_addr += sizeof(size_t);
562 }
563 return get_and_advance_pos();
564 }
565
566 size_t find_next_non_dirty() {
567 assert(_cur_addr <= _end_addr, "Not allowed to search for marks after area.");
568
569 while (!cur_addr_aligned()) {
570 if (!cur_card_is_dirty()) {
571 return get_and_advance_pos();
572 }
573 _cur_addr++;
574 }
575
576 assert(cur_addr_aligned(), "Current address should be aligned now.");
577 while (_cur_addr != _end_addr) {
578 if (!cur_word_of_cards_all_dirty_cards()) {
579 for (size_t i = 0; i < sizeof(size_t); i++) {
580 if (!cur_card_is_dirty()) {
581 return get_and_advance_pos();
582 }
583 _cur_addr++;
584 }
585 assert(false, "Should not reach here given we detected a non-dirty card in the word.");
586 }
587 _cur_addr += sizeof(size_t);
588 }
589 return get_and_advance_pos();
590 }
591 };
592
593 // Helper class to claim dirty chunks within the card table.
594 class G1CardTableChunkClaimer {
595 G1RemSetScanState* _scan_state;
596 uint _region_idx;
597 uint _cur_claim;
598
599 public:
600 G1CardTableChunkClaimer(G1RemSetScanState* scan_state, uint region_idx) :
601 _scan_state(scan_state),
602 _region_idx(region_idx),
603 _cur_claim(0) {
604 guarantee(size() <= HeapRegion::CardsPerRegion, "Should not claim more space than possible.");
605 }
606
607 bool has_next() {
608 while (true) {
609 _cur_claim = _scan_state->claim_cards_to_scan(_region_idx, size());
610 if (_cur_claim >= HeapRegion::CardsPerRegion) {
611 return false;
612 }
613 if (_scan_state->chunk_needs_scan(_region_idx, _cur_claim)) {
614 return true;
615 }
616 }
617 }
618
619 uint value() const { return _cur_claim; }
620 uint size() const { return _scan_state->scan_chunk_size(); }
621 };
622
623 // Scans a heap region for dirty cards.
624 class G1ScanHRForRegionClosure : public HeapRegionClosure {
625 G1CollectedHeap* _g1h;
626 G1CardTable* _ct;
627 G1BlockOffsetTable* _bot;
628
629 G1ParScanThreadState* _pss;
630
631 G1RemSetScanState* _scan_state;
632
633 G1GCPhaseTimes::GCParPhases _phase;
634
635 uint _worker_id;
636
637 size_t _cards_scanned;
638 size_t _blocks_scanned;
639 size_t _chunks_claimed;
640
641 Tickspan _rem_set_root_scan_time;
642 Tickspan _rem_set_trim_partially_time;
643
644 // The address to which this thread already scanned (walked the heap) up to during
645 // card scanning (exclusive).
646 HeapWord* _scanned_to;
647
648 HeapWord* scan_memregion(uint region_idx_for_card, MemRegion mr) {
649 HeapRegion* const card_region = _g1h->region_at(region_idx_for_card);
650 G1ScanCardClosure card_cl(_g1h, _pss);
651
652 HeapWord* const scanned_to = card_region->oops_on_memregion_seq_iterate_careful<true>(mr, &card_cl);
653 assert(scanned_to != NULL, "Should be able to scan range");
654 assert(scanned_to >= mr.end(), "Scanned to " PTR_FORMAT " less than range " PTR_FORMAT, p2i(scanned_to), p2i(mr.end()));
655
656 _pss->trim_queue_partially();
657 return scanned_to;
658 }
659
660 void do_claimed_block(uint const region_idx_for_card, size_t const first_card, size_t const num_cards) {
661 HeapWord* const card_start = _bot->address_for_index_raw(first_card);
662 #ifdef ASSERT
663 HeapRegion* hr = _g1h->region_at_or_null(region_idx_for_card);
664 assert(hr == NULL || hr->is_in_reserved(card_start),
665 "Card start " PTR_FORMAT " to scan outside of region %u", p2i(card_start), _g1h->region_at(region_idx_for_card)->hrm_index());
666 #endif
667 HeapWord* const top = _scan_state->scan_top(region_idx_for_card);
668 if (card_start >= top) {
669 return;
670 }
671
672 HeapWord* scan_end = MIN2(card_start + (num_cards << BOTConstants::LogN_words), top);
673 if (_scanned_to >= scan_end) {
674 return;
675 }
676 MemRegion mr(MAX2(card_start, _scanned_to), scan_end);
677 _scanned_to = scan_memregion(region_idx_for_card, mr);
678
679 _cards_scanned += num_cards;
680 }
681
682 ALWAYSINLINE void do_card_block(uint const region_idx, size_t const first_card, size_t const num_cards) {
683 _ct->mark_as_scanned(first_card, num_cards);
684 do_claimed_block(region_idx, first_card, num_cards);
685 _blocks_scanned++;
686 }
687
688 void scan_heap_roots(HeapRegion* r) {
689 EventGCPhaseParallel event;
690 uint const region_idx = r->hrm_index();
691
692 ResourceMark rm;
693
694 G1CardTableChunkClaimer claim(_scan_state, region_idx);
695
696 // Set the current scan "finger" to NULL for every heap region to scan. Since
697 // the claim value is monotonically increasing, the check to not scan below this
698 // will filter out objects spanning chunks within the region too then, as opposed
699 // to resetting this value for every claim.
700 _scanned_to = NULL;
701
702 while (claim.has_next()) {
703 size_t const region_card_base_idx = ((size_t)region_idx << HeapRegion::LogCardsPerRegion) + claim.value();
704 CardTable::CardValue* const base_addr = _ct->byte_for_index(region_card_base_idx);
705
706 G1CardTableScanner scan(base_addr, claim.size());
707
708 size_t first_scan_idx = scan.find_next_dirty();
709 while (first_scan_idx != claim.size()) {
710 assert(*_ct->byte_for_index(region_card_base_idx + first_scan_idx) <= 0x1, "is %d at region %u idx " SIZE_FORMAT, *_ct->byte_for_index(region_card_base_idx + first_scan_idx), region_idx, first_scan_idx);
711
712 size_t const last_scan_idx = scan.find_next_non_dirty();
713 size_t const len = last_scan_idx - first_scan_idx;
714
715 do_card_block(region_idx, region_card_base_idx + first_scan_idx, len);
716
717 if (last_scan_idx == claim.size()) {
718 break;
719 }
720
721 first_scan_idx = scan.find_next_dirty();
722 }
723 _chunks_claimed++;
724 }
725
726 event.commit(GCId::current(), _worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ScanHR));
727 }
728
729 public:
730 G1ScanHRForRegionClosure(G1RemSetScanState* scan_state,
731 G1ParScanThreadState* pss,
732 uint worker_id,
733 G1GCPhaseTimes::GCParPhases phase) :
734 _g1h(G1CollectedHeap::heap()),
735 _ct(_g1h->card_table()),
736 _bot(_g1h->bot()),
737 _pss(pss),
738 _scan_state(scan_state),
739 _phase(phase),
740 _worker_id(worker_id),
741 _cards_scanned(0),
742 _blocks_scanned(0),
743 _chunks_claimed(0),
744 _rem_set_root_scan_time(),
745 _rem_set_trim_partially_time(),
746 _scanned_to(NULL) {
747 }
748
749 bool do_heap_region(HeapRegion* r) {
750 assert(!r->in_collection_set() && r->is_old_or_humongous_or_archive(),
751 "Should only be called on old gen non-collection set regions but region %u is not.",
752 r->hrm_index());
753 uint const region_idx = r->hrm_index();
754
755 if (_scan_state->has_cards_to_scan(region_idx)) {
756 G1EvacPhaseWithTrimTimeTracker timer(_pss, _rem_set_root_scan_time, _rem_set_trim_partially_time);
757 scan_heap_roots(r);
758 }
759 return false;
760 }
761
762 Tickspan rem_set_root_scan_time() const { return _rem_set_root_scan_time; }
763 Tickspan rem_set_trim_partially_time() const { return _rem_set_trim_partially_time; }
764
765 size_t cards_scanned() const { return _cards_scanned; }
766 size_t blocks_scanned() const { return _blocks_scanned; }
767 size_t chunks_claimed() const { return _chunks_claimed; }
768 };
769
770 void G1RemSet::scan_heap_roots(G1ParScanThreadState* pss,
771 uint worker_id,
772 G1GCPhaseTimes::GCParPhases scan_phase,
773 G1GCPhaseTimes::GCParPhases objcopy_phase) {
774 G1ScanHRForRegionClosure cl(_scan_state, pss, worker_id, scan_phase);
775 _scan_state->iterate_dirty_regions_from(&cl, worker_id);
776
777 G1GCPhaseTimes* p = _g1p->phase_times();
778
779 p->record_or_add_time_secs(objcopy_phase, worker_id, cl.rem_set_trim_partially_time().seconds());
780
781 p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_root_scan_time().seconds());
782 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.cards_scanned(), G1GCPhaseTimes::ScanHRScannedCards);
783 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.blocks_scanned(), G1GCPhaseTimes::ScanHRScannedBlocks);
784 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.chunks_claimed(), G1GCPhaseTimes::ScanHRClaimedChunks);
785 }
786
787 // Heap region closure to be applied to all regions in the current collection set
788 // increment to fix up non-card related roots.
789 class G1ScanCollectionSetRegionClosure : public HeapRegionClosure {
790 G1ParScanThreadState* _pss;
791 G1RemSetScanState* _scan_state;
792
793 G1GCPhaseTimes::GCParPhases _scan_phase;
794 G1GCPhaseTimes::GCParPhases _code_roots_phase;
795
796 uint _worker_id;
797
798 size_t _opt_refs_scanned;
799 size_t _opt_refs_memory_used;
800
801 Tickspan _strong_code_root_scan_time;
802 Tickspan _strong_code_trim_partially_time;
803
804 Tickspan _rem_set_opt_root_scan_time;
805 Tickspan _rem_set_opt_trim_partially_time;
806
807 void scan_opt_rem_set_roots(HeapRegion* r) {
808 EventGCPhaseParallel event;
809
810 G1OopStarChunkedList* opt_rem_set_list = _pss->oops_into_optional_region(r);
811
812 G1ScanCardClosure scan_cl(G1CollectedHeap::heap(), _pss);
813 G1ScanRSForOptionalClosure cl(G1CollectedHeap::heap(), &scan_cl);
814 _opt_refs_scanned += opt_rem_set_list->oops_do(&cl, _pss->closures()->strong_oops());
815 _opt_refs_memory_used += opt_rem_set_list->used_memory();
816
817 event.commit(GCId::current(), _worker_id, G1GCPhaseTimes::phase_name(_scan_phase));
818 }
819
820 public:
821 G1ScanCollectionSetRegionClosure(G1RemSetScanState* scan_state,
822 G1ParScanThreadState* pss,
823 uint worker_id,
824 G1GCPhaseTimes::GCParPhases scan_phase,
825 G1GCPhaseTimes::GCParPhases code_roots_phase) :
826 _pss(pss),
827 _scan_state(scan_state),
828 _scan_phase(scan_phase),
829 _code_roots_phase(code_roots_phase),
830 _worker_id(worker_id),
831 _opt_refs_scanned(0),
832 _opt_refs_memory_used(0),
833 _strong_code_root_scan_time(),
834 _strong_code_trim_partially_time(),
835 _rem_set_opt_root_scan_time(),
836 _rem_set_opt_trim_partially_time() { }
837
838 bool do_heap_region(HeapRegion* r) {
839 uint const region_idx = r->hrm_index();
840
841 // The individual references for the optional remembered set are per-worker, so we
842 // always need to scan them.
843 if (r->has_index_in_opt_cset()) {
844 G1EvacPhaseWithTrimTimeTracker timer(_pss, _rem_set_opt_root_scan_time, _rem_set_opt_trim_partially_time);
845 scan_opt_rem_set_roots(r);
846 }
847
848 if (_scan_state->claim_collection_set_region(region_idx)) {
849 EventGCPhaseParallel event;
850
851 G1EvacPhaseWithTrimTimeTracker timer(_pss, _strong_code_root_scan_time, _strong_code_trim_partially_time);
852 // Scan the strong code root list attached to the current region
853 r->strong_code_roots_do(_pss->closures()->weak_codeblobs());
854
855 event.commit(GCId::current(), _worker_id, G1GCPhaseTimes::phase_name(_code_roots_phase));
856 }
857
858 return false;
859 }
860
861 Tickspan strong_code_root_scan_time() const { return _strong_code_root_scan_time; }
862 Tickspan strong_code_root_trim_partially_time() const { return _strong_code_trim_partially_time; }
863
864 Tickspan rem_set_opt_root_scan_time() const { return _rem_set_opt_root_scan_time; }
865 Tickspan rem_set_opt_trim_partially_time() const { return _rem_set_opt_trim_partially_time; }
866
867 size_t opt_refs_scanned() const { return _opt_refs_scanned; }
868 size_t opt_refs_memory_used() const { return _opt_refs_memory_used; }
869 };
870
871 void G1RemSet::scan_collection_set_regions(G1ParScanThreadState* pss,
872 uint worker_id,
873 G1GCPhaseTimes::GCParPhases scan_phase,
874 G1GCPhaseTimes::GCParPhases coderoots_phase,
875 G1GCPhaseTimes::GCParPhases objcopy_phase) {
876 G1ScanCollectionSetRegionClosure cl(_scan_state, pss, worker_id, scan_phase, coderoots_phase);
877 _g1h->collection_set_iterate_increment_from(&cl, worker_id);
878
879 G1GCPhaseTimes* p = _g1h->phase_times();
880
881 p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_opt_root_scan_time().seconds());
882 p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_opt_trim_partially_time().seconds());
883
884 p->record_or_add_time_secs(coderoots_phase, worker_id, cl.strong_code_root_scan_time().seconds());
885 p->add_time_secs(objcopy_phase, worker_id, cl.strong_code_root_trim_partially_time().seconds());
886
887 // At this time we record some metrics only for the evacuations after the initial one.
888 if (scan_phase == G1GCPhaseTimes::OptScanHR) {
889 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_scanned(), G1GCPhaseTimes::ScanHRScannedOptRefs);
890 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_memory_used(), G1GCPhaseTimes::ScanHRUsedMemory);
891 }
892 }
893
894 void G1RemSet::prepare_region_for_scan(HeapRegion* region) {
895 uint hrm_index = region->hrm_index();
896
897 if (region->in_collection_set()) {
898 // Young regions had their card table marked as young at their allocation;
899 // we need to make sure that these marks are cleared at the end of GC, *but*
900 // they should not be scanned for cards.
901 // So directly add them to the "all_dirty_regions".
902 // Same for regions in the (initial) collection set: they may contain cards from
903 // the log buffers, make sure they are cleaned.
904 _scan_state->add_all_dirty_region(hrm_index);
905 } else if (region->is_old_or_humongous_or_archive()) {
906 _scan_state->set_scan_top(hrm_index, region->top());
907 } else {
908 assert(region->is_free(), "Should only be free region at this point %s", region->get_type_str());
909 }
910 }
911
912 void G1RemSet::prepare_for_scan_heap_roots() {
913 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
914 dcqs.concatenate_logs();
915
916 _scan_state->prepare();
917 }
918
919 class G1MergeHeapRootsTask : public AbstractGangTask {
920
921 // Visitor for remembered sets, dropping entries onto the card table.
922 class G1MergeCardSetClosure : public HeapRegionClosure {
923 G1RemSetScanState* _scan_state;
924 G1CardTable* _ct;
925
926 uint _merged_sparse;
927 uint _merged_fine;
928 uint _merged_coarse;
929
930 size_t _cards_dirty;
931
932 // Returns if the region contains cards we need to scan. If so, remember that
933 // region in the current set of dirty regions.
934 bool remember_if_interesting(uint const region_idx) {
935 if (!_scan_state->contains_cards_to_process(region_idx)) {
936 return false;
937 }
938 _scan_state->add_dirty_region(region_idx);
939 return true;
940 }
941 public:
942 G1MergeCardSetClosure(G1RemSetScanState* scan_state) :
943 _scan_state(scan_state),
944 _ct(G1CollectedHeap::heap()->card_table()),
945 _merged_sparse(0),
946 _merged_fine(0),
947 _merged_coarse(0),
948 _cards_dirty(0) { }
949
950 void next_coarse_prt(uint const region_idx) {
951 if (!remember_if_interesting(region_idx)) {
952 return;
953 }
954
955 _merged_coarse++;
956
957 size_t region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion;
958 _cards_dirty += _ct->mark_region_dirty(region_base_idx, HeapRegion::CardsPerRegion);
959 _scan_state->set_chunk_region_dirty(region_base_idx);
960 }
961
962 void next_fine_prt(uint const region_idx, BitMap* bm) {
963 if (!remember_if_interesting(region_idx)) {
964 return;
965 }
966
967 _merged_fine++;
968
969 size_t const region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion;
970 BitMap::idx_t cur = bm->get_next_one_offset(0);
971 while (cur != bm->size()) {
972 _cards_dirty += _ct->mark_clean_as_dirty(region_base_idx + cur);
973 _scan_state->set_chunk_dirty(region_base_idx + cur);
974 cur = bm->get_next_one_offset(cur + 1);
975 }
976 }
977
978 void next_sparse_prt(uint const region_idx, SparsePRTEntry::card_elem_t* cards, uint const num_cards) {
979 if (!remember_if_interesting(region_idx)) {
980 return;
981 }
982
983 _merged_sparse++;
984
985 size_t const region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion;
986 for (uint i = 0; i < num_cards; i++) {
987 size_t card_idx = region_base_idx + cards[i];
988 _cards_dirty += _ct->mark_clean_as_dirty(card_idx);
989 _scan_state->set_chunk_dirty(card_idx);
990 }
991 }
992
993 virtual bool do_heap_region(HeapRegion* r) {
994 assert(r->in_collection_set() || r->is_starts_humongous(), "must be");
995
996 HeapRegionRemSet* rem_set = r->rem_set();
997 if (!rem_set->is_empty()) {
998 rem_set->iterate_prts(*this);
999 }
1000
1001 return false;
1002 }
1003
1004 size_t merged_sparse() const { return _merged_sparse; }
1005 size_t merged_fine() const { return _merged_fine; }
1006 size_t merged_coarse() const { return _merged_coarse; }
1007
1008 size_t cards_dirty() const { return _cards_dirty; }
1009 };
1010
1011 // Visitor for the remembered sets of humongous candidate regions to merge their
1012 // remembered set into the card table.
1013 class G1FlushHumongousCandidateRemSets : public HeapRegionClosure {
1014 G1MergeCardSetClosure _cl;
1015
1016 public:
1017 G1FlushHumongousCandidateRemSets(G1RemSetScanState* scan_state) : _cl(scan_state) { }
1018
1019 virtual bool do_heap_region(HeapRegion* r) {
1020 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1021
1022 if (!r->is_starts_humongous() ||
1023 !g1h->region_attr(r->hrm_index()).is_humongous() ||
1024 r->rem_set()->is_empty()) {
1025 return false;
1026 }
1027
1028 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
1029 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
1030
1031 _cl.do_heap_region(r);
1032
1033 // We should only clear the card based remembered set here as we will not
1034 // implicitly rebuild anything else during eager reclaim. Note that at the moment
1035 // (and probably never) we do not enter this path if there are other kind of
1036 // remembered sets for this region.
1037 r->rem_set()->clear_locked(true /* only_cardset */);
1038 // Clear_locked() above sets the state to Empty. However we want to continue
1039 // collecting remembered set entries for humongous regions that were not
1040 // reclaimed.
1041 r->rem_set()->set_state_complete();
1042 #ifdef ASSERT
1043 G1HeapRegionAttr region_attr = g1h->region_attr(r->hrm_index());
1044 assert(region_attr.needs_remset_update(), "must be");
1045 #endif
1046 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
1047
1048 return false;
1049 }
1050
1051 size_t merged_sparse() const { return _cl.merged_sparse(); }
1052 size_t merged_fine() const { return _cl.merged_fine(); }
1053 size_t merged_coarse() const { return _cl.merged_coarse(); }
1054
1055 size_t cards_dirty() const { return _cl.cards_dirty(); }
1056 };
1057
1058 // Visitor for the log buffer entries to merge them into the card table.
1059 class G1MergeLogBufferCardsClosure : public G1CardTableEntryClosure {
1060 G1RemSetScanState* _scan_state;
1061 G1CardTable* _ct;
1062
1063 size_t _cards_dirty;
1064 size_t _cards_skipped;
1065 public:
1066 G1MergeLogBufferCardsClosure(G1CollectedHeap* g1h, G1RemSetScanState* scan_state) :
1067 _scan_state(scan_state), _ct(g1h->card_table()), _cards_dirty(0), _cards_skipped(0)
1068 {}
1069
1070 void do_card_ptr(CardValue* card_ptr, uint worker_id) {
1071 // The only time we care about recording cards that
1072 // contain references that point into the collection set
1073 // is during RSet updating within an evacuation pause.
1074 // In this case worker_id should be the id of a GC worker thread.
1075 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
1076
1077 uint const region_idx = _ct->region_idx_for(card_ptr);
1078
1079 // The second clause must come after - the log buffers might contain cards to uncommited
1080 // regions.
1081 // This code may count duplicate entries in the log buffers (even if rare) multiple
1082 // times.
1083 if (_scan_state->contains_cards_to_process(region_idx) && (*card_ptr == G1CardTable::dirty_card_val())) {
1084 _scan_state->add_dirty_region(region_idx);
1085 _scan_state->set_chunk_dirty(_ct->index_for_cardvalue(card_ptr));
1086 _cards_dirty++;
1087 } else {
1088 // We may have had dirty cards in the (initial) collection set (or the
1089 // young regions which are always in the initial collection set). We do
1090 // not fix their cards here: we already added these regions to the set of
1091 // regions to clear the card table at the end during the prepare() phase.
1092 _cards_skipped++;
1093 }
1094 }
1095
1096 size_t cards_dirty() const { return _cards_dirty; }
1097 size_t cards_skipped() const { return _cards_skipped; }
1098 };
1099
1100 HeapRegionClaimer _hr_claimer;
1101 G1RemSetScanState* _scan_state;
1102 BufferNode::Stack _dirty_card_buffers;
1103 bool _initial_evacuation;
1104
1105 volatile bool _fast_reclaim_handled;
1106
1107 void apply_closure_to_dirty_card_buffers(G1MergeLogBufferCardsClosure* cl, uint worker_id) {
1108 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1109 size_t buffer_size = dcqs.buffer_size();
1110 while (BufferNode* node = _dirty_card_buffers.pop()) {
1111 cl->apply_to_buffer(node, buffer_size, worker_id);
1112 dcqs.deallocate_buffer(node);
1113 }
1114 }
1115
1116 public:
1117 G1MergeHeapRootsTask(G1RemSetScanState* scan_state, uint num_workers, bool initial_evacuation) :
1118 AbstractGangTask("G1 Merge Heap Roots"),
1119 _hr_claimer(num_workers),
1120 _scan_state(scan_state),
1121 _dirty_card_buffers(),
1122 _initial_evacuation(initial_evacuation),
1123 _fast_reclaim_handled(false)
1124 {
1125 if (initial_evacuation) {
1126 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1127 G1BufferNodeList buffers = dcqs.take_all_completed_buffers();
1128 if (buffers._entry_count != 0) {
1129 _dirty_card_buffers.prepend(*buffers._head, *buffers._tail);
1130 }
1131 }
1132 }
1133
1134 virtual void work(uint worker_id) {
1135 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1136 G1GCPhaseTimes* p = g1h->phase_times();
1137
1138 G1GCPhaseTimes::GCParPhases merge_remset_phase = _initial_evacuation ?
1139 G1GCPhaseTimes::MergeRS :
1140 G1GCPhaseTimes::OptMergeRS;
1141
1142 // We schedule flushing the remembered sets of humongous fast reclaim candidates
1143 // onto the card table first to allow the remaining parallelized tasks hide it.
1144 if (_initial_evacuation &&
1145 p->fast_reclaim_humongous_candidates() > 0 &&
1146 !_fast_reclaim_handled &&
1147 !Atomic::cmpxchg(&_fast_reclaim_handled, false, true)) {
1148
1149 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeER, worker_id);
1150
1151 G1FlushHumongousCandidateRemSets cl(_scan_state);
1152 g1h->heap_region_iterate(&cl);
1153
1154 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_sparse(), G1GCPhaseTimes::MergeRSMergedSparse);
1155 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_fine(), G1GCPhaseTimes::MergeRSMergedFine);
1156 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_coarse(), G1GCPhaseTimes::MergeRSMergedCoarse);
1157 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeRSDirtyCards);
1158 }
1159
1160 // Merge remembered sets of current candidates.
1161 {
1162 G1GCParPhaseTimesTracker x(p, merge_remset_phase, worker_id, _initial_evacuation /* must_record */);
1163 G1MergeCardSetClosure cl(_scan_state);
1164 g1h->collection_set_iterate_increment_from(&cl, &_hr_claimer, worker_id);
1165
1166 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_sparse(), G1GCPhaseTimes::MergeRSMergedSparse);
1167 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_fine(), G1GCPhaseTimes::MergeRSMergedFine);
1168 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_coarse(), G1GCPhaseTimes::MergeRSMergedCoarse);
1169 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeRSDirtyCards);
1170 }
1171
1172 // Apply closure to log entries in the HCC.
1173 if (_initial_evacuation && G1HotCardCache::default_use_cache()) {
1174 assert(merge_remset_phase == G1GCPhaseTimes::MergeRS, "Wrong merge phase");
1175 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeHCC, worker_id);
1176 G1MergeLogBufferCardsClosure cl(g1h, _scan_state);
1177 g1h->iterate_hcc_closure(&cl, worker_id);
1178
1179 p->record_thread_work_item(G1GCPhaseTimes::MergeHCC, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeHCCDirtyCards);
1180 p->record_thread_work_item(G1GCPhaseTimes::MergeHCC, worker_id, cl.cards_skipped(), G1GCPhaseTimes::MergeHCCSkippedCards);
1181 }
1182
1183 // Now apply the closure to all remaining log entries.
1184 if (_initial_evacuation) {
1185 assert(merge_remset_phase == G1GCPhaseTimes::MergeRS, "Wrong merge phase");
1186 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeLB, worker_id);
1187
1188 G1MergeLogBufferCardsClosure cl(g1h, _scan_state);
1189 apply_closure_to_dirty_card_buffers(&cl, worker_id);
1190
1191 p->record_thread_work_item(G1GCPhaseTimes::MergeLB, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeLBDirtyCards);
1192 p->record_thread_work_item(G1GCPhaseTimes::MergeLB, worker_id, cl.cards_skipped(), G1GCPhaseTimes::MergeLBSkippedCards);
1193 }
1194 }
1195 };
1196
1197 void G1RemSet::print_merge_heap_roots_stats() {
1198 size_t num_visited_cards = _scan_state->num_visited_cards();
1199
1200 size_t total_dirty_region_cards = _scan_state->num_cards_in_dirty_regions();
1201
1202 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1203 size_t total_old_region_cards =
1204 (g1h->num_regions() - (g1h->num_free_regions() - g1h->collection_set()->cur_length())) * HeapRegion::CardsPerRegion;
1205
1206 log_debug(gc,remset)("Visited cards " SIZE_FORMAT " Total dirty " SIZE_FORMAT " (%.2lf%%) Total old " SIZE_FORMAT " (%.2lf%%)",
1207 num_visited_cards,
1208 total_dirty_region_cards,
1209 percent_of(num_visited_cards, total_dirty_region_cards),
1210 total_old_region_cards,
1211 percent_of(num_visited_cards, total_old_region_cards));
1212 }
1213
1214 void G1RemSet::merge_heap_roots(bool initial_evacuation) {
1215 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1216
1217 {
1218 Ticks start = Ticks::now();
1219
1220 _scan_state->prepare_for_merge_heap_roots();
1221
1222 Tickspan total = Ticks::now() - start;
1223 if (initial_evacuation) {
1224 g1h->phase_times()->record_prepare_merge_heap_roots_time(total.seconds() * 1000.0);
1225 } else {
1226 g1h->phase_times()->record_or_add_optional_prepare_merge_heap_roots_time(total.seconds() * 1000.0);
1227 }
1228 }
1229
1230 WorkGang* workers = g1h->workers();
1231 size_t const increment_length = g1h->collection_set()->increment_length();
1232
1233 uint const num_workers = initial_evacuation ? workers->active_workers() :
1234 MIN2(workers->active_workers(), (uint)increment_length);
1235
1236 {
1237 G1MergeHeapRootsTask cl(_scan_state, num_workers, initial_evacuation);
1238 log_debug(gc, ergo)("Running %s using %u workers for " SIZE_FORMAT " regions",
1239 cl.name(), num_workers, increment_length);
1240 workers->run_task(&cl, num_workers);
1241 }
1242
1243 if (log_is_enabled(Debug, gc, remset)) {
1244 print_merge_heap_roots_stats();
1245 }
1246 }
1247
1248 void G1RemSet::exclude_region_from_scan(uint region_idx) {
1249 _scan_state->clear_scan_top(region_idx);
1250 }
1251
1252 void G1RemSet::cleanup_after_scan_heap_roots() {
1253 G1GCPhaseTimes* phase_times = _g1h->phase_times();
1254
1255 // Set all cards back to clean.
1256 double start = os::elapsedTime();
1257 _scan_state->cleanup(_g1h->workers());
1258 phase_times->record_clear_ct_time((os::elapsedTime() - start) * 1000.0);
1259 }
1260
1261 inline void check_card_ptr(CardTable::CardValue* card_ptr, G1CardTable* ct) {
1262 #ifdef ASSERT
1263 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1264 assert(g1h->is_in_exact(ct->addr_for(card_ptr)),
1265 "Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap",
1266 p2i(card_ptr),
1267 ct->index_for(ct->addr_for(card_ptr)),
1268 p2i(ct->addr_for(card_ptr)),
1269 g1h->addr_to_region(ct->addr_for(card_ptr)));
1270 #endif
1271 }
1272
1273 bool G1RemSet::clean_card_before_refine(CardValue** const card_ptr_addr) {
1274 assert(!_g1h->is_gc_active(), "Only call concurrently");
1275
1276 CardValue* card_ptr = *card_ptr_addr;
1277 // Find the start address represented by the card.
1278 HeapWord* start = _ct->addr_for(card_ptr);
1279 // And find the region containing it.
1280 HeapRegion* r = _g1h->heap_region_containing_or_null(start);
1281
1282 // If this is a (stale) card into an uncommitted region, exit.
1283 if (r == NULL) {
1284 return false;
1285 }
1286
1287 check_card_ptr(card_ptr, _ct);
1288
1289 // If the card is no longer dirty, nothing to do.
1290 // We cannot load the card value before the "r == NULL" check, because G1
1291 // could uncommit parts of the card table covering uncommitted regions.
1292 if (*card_ptr != G1CardTable::dirty_card_val()) {
1293 return false;
1294 }
1295
1296 // This check is needed for some uncommon cases where we should
1297 // ignore the card.
1298 //
1299 // The region could be young. Cards for young regions are
1300 // distinctly marked (set to g1_young_gen), so the post-barrier will
1301 // filter them out. However, that marking is performed
1302 // concurrently. A write to a young object could occur before the
1303 // card has been marked young, slipping past the filter.
1304 //
1305 // The card could be stale, because the region has been freed since
1306 // the card was recorded. In this case the region type could be
1307 // anything. If (still) free or (reallocated) young, just ignore
1308 // it. If (reallocated) old or humongous, the later card trimming
1309 // and additional checks in iteration may detect staleness. At
1310 // worst, we end up processing a stale card unnecessarily.
1311 //
1312 // In the normal (non-stale) case, the synchronization between the
1313 // enqueueing of the card and processing it here will have ensured
1314 // we see the up-to-date region type here.
1315 if (!r->is_old_or_humongous_or_archive()) {
1316 return false;
1317 }
1318
1319 // The result from the hot card cache insert call is either:
1320 // * pointer to the current card
1321 // (implying that the current card is not 'hot'),
1322 // * null
1323 // (meaning we had inserted the card ptr into the "hot" card cache,
1324 // which had some headroom),
1325 // * a pointer to a "hot" card that was evicted from the "hot" cache.
1326 //
1327
1328 if (_hot_card_cache->use_cache()) {
1329 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
1330
1331 const CardValue* orig_card_ptr = card_ptr;
1332 card_ptr = _hot_card_cache->insert(card_ptr);
1333 if (card_ptr == NULL) {
1334 // There was no eviction. Nothing to do.
1335 return false;
1336 } else if (card_ptr != orig_card_ptr) {
1337 // Original card was inserted and an old card was evicted.
1338 start = _ct->addr_for(card_ptr);
1339 r = _g1h->heap_region_containing(start);
1340
1341 // Check whether the region formerly in the cache should be
1342 // ignored, as discussed earlier for the original card. The
1343 // region could have been freed while in the cache.
1344 if (!r->is_old_or_humongous_or_archive()) {
1345 return false;
1346 }
1347 *card_ptr_addr = card_ptr;
1348 } // Else we still have the original card.
1349 }
1350
1351 // Trim the region designated by the card to what's been allocated
1352 // in the region. The card could be stale, or the card could cover
1353 // (part of) an object at the end of the allocated space and extend
1354 // beyond the end of allocation.
1355
1356 // Non-humongous objects are either allocated in the old regions during GC,
1357 // or mapped in archive regions during startup. So if region is old or
1358 // archive then top is stable.
1359 // Humongous object allocation sets top last; if top has not yet been set,
1360 // this is a stale card and we'll end up with an empty intersection.
1361 // If this is not a stale card, the synchronization between the
1362 // enqueuing of the card and processing it here will have ensured
1363 // we see the up-to-date top here.
1364 HeapWord* scan_limit = r->top();
1365
1366 if (scan_limit <= start) {
1367 // If the trimmed region is empty, the card must be stale.
1368 return false;
1369 }
1370
1371 // Okay to clean and process the card now. There are still some
1372 // stale card cases that may be detected by iteration and dealt with
1373 // as iteration failure.
1374 *const_cast<volatile CardValue*>(card_ptr) = G1CardTable::clean_card_val();
1375
1376 return true;
1377 }
1378
1379 void G1RemSet::refine_card_concurrently(CardValue* const card_ptr,
1380 const uint worker_id) {
1381 assert(!_g1h->is_gc_active(), "Only call concurrently");
1382 check_card_ptr(card_ptr, _ct);
1383
1384 // Construct the MemRegion representing the card.
1385 HeapWord* start = _ct->addr_for(card_ptr);
1386 // And find the region containing it.
1387 HeapRegion* r = _g1h->heap_region_containing(start);
1388 // This reload of the top is safe even though it happens after the full
1389 // fence, because top is stable for old, archive and unfiltered humongous
1390 // regions, so it must return the same value as the previous load when
1391 // cleaning the card. Also cleaning the card and refinement of the card
1392 // cannot span across safepoint, so we don't need to worry about top being
1393 // changed during safepoint.
1394 HeapWord* scan_limit = r->top();
1395 assert(scan_limit > start, "sanity");
1396
1397 // Don't use addr_for(card_ptr + 1) which can ask for
1398 // a card beyond the heap.
1399 HeapWord* end = start + G1CardTable::card_size_in_words;
1400 MemRegion dirty_region(start, MIN2(scan_limit, end));
1401 assert(!dirty_region.is_empty(), "sanity");
1402
1403 G1ConcurrentRefineOopClosure conc_refine_cl(_g1h, worker_id);
1404 if (r->oops_on_memregion_seq_iterate_careful<false>(dirty_region, &conc_refine_cl) != NULL) {
1405 return;
1406 }
1407
1408 // If unable to process the card then we encountered an unparsable
1409 // part of the heap (e.g. a partially allocated object, so only
1410 // temporarily a problem) while processing a stale card. Despite
1411 // the card being stale, we can't simply ignore it, because we've
1412 // already marked the card cleaned, so taken responsibility for
1413 // ensuring the card gets scanned.
1414 //
1415 // However, the card might have gotten re-dirtied and re-enqueued
1416 // while we worked. (In fact, it's pretty likely.)
1417 if (*card_ptr == G1CardTable::dirty_card_val()) {
1418 return;
1419 }
1420
1421 // Re-dirty the card and enqueue in the *shared* queue. Can't use
1422 // the thread-local queue, because that might be the queue that is
1423 // being processed by us; we could be a Java thread conscripted to
1424 // perform refinement on our queue's current buffer.
1425 *card_ptr = G1CardTable::dirty_card_val();
1426 G1BarrierSet::shared_dirty_card_queue().enqueue(card_ptr);
1427 }
1428
1429 void G1RemSet::print_periodic_summary_info(const char* header, uint period_count) {
1430 if ((G1SummarizeRSetStatsPeriod > 0) && log_is_enabled(Trace, gc, remset) &&
1431 (period_count % G1SummarizeRSetStatsPeriod == 0)) {
1432
1433 G1RemSetSummary current;
1434 _prev_period_summary.subtract_from(¤t);
1435
1436 Log(gc, remset) log;
1437 log.trace("%s", header);
1438 ResourceMark rm;
1439 LogStream ls(log.trace());
1440 _prev_period_summary.print_on(&ls);
1441
1442 _prev_period_summary.set(¤t);
1443 }
1444 }
1445
1446 void G1RemSet::print_summary_info() {
1447 Log(gc, remset, exit) log;
1448 if (log.is_trace()) {
1449 log.trace(" Cumulative RS summary");
1450 G1RemSetSummary current;
1451 ResourceMark rm;
1452 LogStream ls(log.trace());
1453 current.print_on(&ls);
1454 }
1455 }
1456
1457 class G1RebuildRemSetTask: public AbstractGangTask {
1458 // Aggregate the counting data that was constructed concurrently
1459 // with marking.
1460 class G1RebuildRemSetHeapRegionClosure : public HeapRegionClosure {
1461 G1ConcurrentMark* _cm;
1462 G1RebuildRemSetClosure _update_cl;
1463
1464 // Applies _update_cl to the references of the given object, limiting objArrays
1465 // to the given MemRegion. Returns the amount of words actually scanned.
1466 size_t scan_for_references(oop const obj, MemRegion mr) {
1467 size_t const obj_size = obj->size();
1468 // All non-objArrays and objArrays completely within the mr
1469 // can be scanned without passing the mr.
1470 if (!obj->is_objArray() || mr.contains(MemRegion((HeapWord*)obj, obj_size))) {
1471 obj->oop_iterate(&_update_cl);
1472 return obj_size;
1473 }
1474 // This path is for objArrays crossing the given MemRegion. Only scan the
1475 // area within the MemRegion.
1476 obj->oop_iterate(&_update_cl, mr);
1477 return mr.intersection(MemRegion((HeapWord*)obj, obj_size)).word_size();
1478 }
1479
1480 // A humongous object is live (with respect to the scanning) either
1481 // a) it is marked on the bitmap as such
1482 // b) its TARS is larger than TAMS, i.e. has been allocated during marking.
1483 bool is_humongous_live(oop const humongous_obj, const G1CMBitMap* const bitmap, HeapWord* tams, HeapWord* tars) const {
1484 return bitmap->is_marked(humongous_obj) || (tars > tams);
1485 }
1486
1487 // Iterator over the live objects within the given MemRegion.
1488 class LiveObjIterator : public StackObj {
1489 const G1CMBitMap* const _bitmap;
1490 const HeapWord* _tams;
1491 const MemRegion _mr;
1492 HeapWord* _current;
1493
1494 bool is_below_tams() const {
1495 return _current < _tams;
1496 }
1497
1498 bool is_live(HeapWord* obj) const {
1499 return !is_below_tams() || _bitmap->is_marked(obj);
1500 }
1501
1502 HeapWord* bitmap_limit() const {
1503 return MIN2(const_cast<HeapWord*>(_tams), _mr.end());
1504 }
1505
1506 void move_if_below_tams() {
1507 if (is_below_tams() && has_next()) {
1508 _current = _bitmap->get_next_marked_addr(_current, bitmap_limit());
1509 }
1510 }
1511 public:
1512 LiveObjIterator(const G1CMBitMap* const bitmap, const HeapWord* tams, const MemRegion mr, HeapWord* first_oop_into_mr) :
1513 _bitmap(bitmap),
1514 _tams(tams),
1515 _mr(mr),
1516 _current(first_oop_into_mr) {
1517
1518 assert(_current <= _mr.start(),
1519 "First oop " PTR_FORMAT " should extend into mr [" PTR_FORMAT ", " PTR_FORMAT ")",
1520 p2i(first_oop_into_mr), p2i(mr.start()), p2i(mr.end()));
1521
1522 // Step to the next live object within the MemRegion if needed.
1523 if (is_live(_current)) {
1524 // Non-objArrays were scanned by the previous part of that region.
1525 if (_current < mr.start() && !oop(_current)->is_objArray()) {
1526 _current += oop(_current)->size();
1527 // We might have positioned _current on a non-live object. Reposition to the next
1528 // live one if needed.
1529 move_if_below_tams();
1530 }
1531 } else {
1532 // The object at _current can only be dead if below TAMS, so we can use the bitmap.
1533 // immediately.
1534 _current = _bitmap->get_next_marked_addr(_current, bitmap_limit());
1535 assert(_current == _mr.end() || is_live(_current),
1536 "Current " PTR_FORMAT " should be live (%s) or beyond the end of the MemRegion (" PTR_FORMAT ")",
1537 p2i(_current), BOOL_TO_STR(is_live(_current)), p2i(_mr.end()));
1538 }
1539 }
1540
1541 void move_to_next() {
1542 _current += next()->size();
1543 move_if_below_tams();
1544 }
1545
1546 oop next() const {
1547 oop result = oop(_current);
1548 assert(is_live(_current),
1549 "Object " PTR_FORMAT " must be live TAMS " PTR_FORMAT " below %d mr " PTR_FORMAT " " PTR_FORMAT " outside %d",
1550 p2i(_current), p2i(_tams), _tams > _current, p2i(_mr.start()), p2i(_mr.end()), _mr.contains(result));
1551 return result;
1552 }
1553
1554 bool has_next() const {
1555 return _current < _mr.end();
1556 }
1557 };
1558
1559 // Rebuild remembered sets in the part of the region specified by mr and hr.
1560 // Objects between the bottom of the region and the TAMS are checked for liveness
1561 // using the given bitmap. Objects between TAMS and TARS are assumed to be live.
1562 // Returns the number of live words between bottom and TAMS.
1563 size_t rebuild_rem_set_in_region(const G1CMBitMap* const bitmap,
1564 HeapWord* const top_at_mark_start,
1565 HeapWord* const top_at_rebuild_start,
1566 HeapRegion* hr,
1567 MemRegion mr) {
1568 size_t marked_words = 0;
1569
1570 if (hr->is_humongous()) {
1571 oop const humongous_obj = oop(hr->humongous_start_region()->bottom());
1572 if (is_humongous_live(humongous_obj, bitmap, top_at_mark_start, top_at_rebuild_start)) {
1573 // We need to scan both [bottom, TAMS) and [TAMS, top_at_rebuild_start);
1574 // however in case of humongous objects it is sufficient to scan the encompassing
1575 // area (top_at_rebuild_start is always larger or equal to TAMS) as one of the
1576 // two areas will be zero sized. I.e. TAMS is either
1577 // the same as bottom or top(_at_rebuild_start). There is no way TAMS has a different
1578 // value: this would mean that TAMS points somewhere into the object.
1579 assert(hr->top() == top_at_mark_start || hr->top() == top_at_rebuild_start,
1580 "More than one object in the humongous region?");
1581 humongous_obj->oop_iterate(&_update_cl, mr);
1582 return top_at_mark_start != hr->bottom() ? mr.intersection(MemRegion((HeapWord*)humongous_obj, humongous_obj->size())).byte_size() : 0;
1583 } else {
1584 return 0;
1585 }
1586 }
1587
1588 for (LiveObjIterator it(bitmap, top_at_mark_start, mr, hr->block_start(mr.start())); it.has_next(); it.move_to_next()) {
1589 oop obj = it.next();
1590 size_t scanned_size = scan_for_references(obj, mr);
1591 if ((HeapWord*)obj < top_at_mark_start) {
1592 marked_words += scanned_size;
1593 }
1594 }
1595
1596 return marked_words * HeapWordSize;
1597 }
1598 public:
1599 G1RebuildRemSetHeapRegionClosure(G1CollectedHeap* g1h,
1600 G1ConcurrentMark* cm,
1601 uint worker_id) :
1602 HeapRegionClosure(),
1603 _cm(cm),
1604 _update_cl(g1h, worker_id) { }
1605
1606 bool do_heap_region(HeapRegion* hr) {
1607 if (_cm->has_aborted()) {
1608 return true;
1609 }
1610
1611 uint const region_idx = hr->hrm_index();
1612 DEBUG_ONLY(HeapWord* const top_at_rebuild_start_check = _cm->top_at_rebuild_start(region_idx);)
1613 assert(top_at_rebuild_start_check == NULL ||
1614 top_at_rebuild_start_check > hr->bottom(),
1615 "A TARS (" PTR_FORMAT ") == bottom() (" PTR_FORMAT ") indicates the old region %u is empty (%s)",
1616 p2i(top_at_rebuild_start_check), p2i(hr->bottom()), region_idx, hr->get_type_str());
1617
1618 size_t total_marked_bytes = 0;
1619 size_t const chunk_size_in_words = G1RebuildRemSetChunkSize / HeapWordSize;
1620
1621 HeapWord* const top_at_mark_start = hr->prev_top_at_mark_start();
1622
1623 HeapWord* cur = hr->bottom();
1624 while (cur < hr->end()) {
1625 // After every iteration (yield point) we need to check whether the region's
1626 // TARS changed due to e.g. eager reclaim.
1627 HeapWord* const top_at_rebuild_start = _cm->top_at_rebuild_start(region_idx);
1628 if (top_at_rebuild_start == NULL) {
1629 return false;
1630 }
1631
1632 MemRegion next_chunk = MemRegion(hr->bottom(), top_at_rebuild_start).intersection(MemRegion(cur, chunk_size_in_words));
1633 if (next_chunk.is_empty()) {
1634 break;
1635 }
1636
1637 const Ticks start = Ticks::now();
1638 size_t marked_bytes = rebuild_rem_set_in_region(_cm->prev_mark_bitmap(),
1639 top_at_mark_start,
1640 top_at_rebuild_start,
1641 hr,
1642 next_chunk);
1643 Tickspan time = Ticks::now() - start;
1644
1645 log_trace(gc, remset, tracking)("Rebuilt region %u "
1646 "live " SIZE_FORMAT " "
1647 "time %.3fms "
1648 "marked bytes " SIZE_FORMAT " "
1649 "bot " PTR_FORMAT " "
1650 "TAMS " PTR_FORMAT " "
1651 "TARS " PTR_FORMAT,
1652 region_idx,
1653 _cm->liveness(region_idx) * HeapWordSize,
1654 time.seconds() * 1000.0,
1655 marked_bytes,
1656 p2i(hr->bottom()),
1657 p2i(top_at_mark_start),
1658 p2i(top_at_rebuild_start));
1659
1660 if (marked_bytes > 0) {
1661 total_marked_bytes += marked_bytes;
1662 }
1663 cur += chunk_size_in_words;
1664
1665 _cm->do_yield_check();
1666 if (_cm->has_aborted()) {
1667 return true;
1668 }
1669 }
1670 // In the final iteration of the loop the region might have been eagerly reclaimed.
1671 // Simply filter out those regions. We can not just use region type because there
1672 // might have already been new allocations into these regions.
1673 DEBUG_ONLY(HeapWord* const top_at_rebuild_start = _cm->top_at_rebuild_start(region_idx);)
1674 assert(top_at_rebuild_start == NULL ||
1675 total_marked_bytes == hr->marked_bytes(),
1676 "Marked bytes " SIZE_FORMAT " for region %u (%s) in [bottom, TAMS) do not match calculated marked bytes " SIZE_FORMAT " "
1677 "(" PTR_FORMAT " " PTR_FORMAT " " PTR_FORMAT ")",
1678 total_marked_bytes, hr->hrm_index(), hr->get_type_str(), hr->marked_bytes(),
1679 p2i(hr->bottom()), p2i(top_at_mark_start), p2i(top_at_rebuild_start));
1680 // Abort state may have changed after the yield check.
1681 return _cm->has_aborted();
1682 }
1683 };
1684
1685 HeapRegionClaimer _hr_claimer;
1686 G1ConcurrentMark* _cm;
1687
1688 uint _worker_id_offset;
1689 public:
1690 G1RebuildRemSetTask(G1ConcurrentMark* cm,
1691 uint n_workers,
1692 uint worker_id_offset) :
1693 AbstractGangTask("G1 Rebuild Remembered Set"),
1694 _hr_claimer(n_workers),
1695 _cm(cm),
1696 _worker_id_offset(worker_id_offset) {
1697 }
1698
1699 void work(uint worker_id) {
1700 SuspendibleThreadSetJoiner sts_join;
1701
1702 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1703
1704 G1RebuildRemSetHeapRegionClosure cl(g1h, _cm, _worker_id_offset + worker_id);
1705 g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hr_claimer, worker_id);
1706 }
1707 };
1708
1709 void G1RemSet::rebuild_rem_set(G1ConcurrentMark* cm,
1710 WorkGang* workers,
1711 uint worker_id_offset) {
1712 uint num_workers = workers->active_workers();
1713
1714 G1RebuildRemSetTask cl(cm,
1715 num_workers,
1716 worker_id_offset);
1717 workers->run_task(&cl, num_workers);
1718 }