1 /* 2 * Copyright (c) 2001, 2014, 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_implementation/g1/concurrentG1Refine.hpp" 27 #include "gc_implementation/g1/concurrentG1RefineThread.hpp" 28 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp" 29 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 30 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 31 #include "gc_implementation/g1/g1HotCardCache.hpp" 32 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 33 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 34 #include "gc_implementation/g1/g1RemSet.inline.hpp" 35 #include "gc_implementation/g1/heapRegionSeq.inline.hpp" 36 #include "gc_implementation/g1/heapRegionRemSet.hpp" 37 #include "memory/iterator.hpp" 38 #include "oops/oop.inline.hpp" 39 #include "utilities/globalDefinitions.hpp" 40 #include "utilities/intHisto.hpp" 41 42 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 43 44 #define CARD_REPEAT_HISTO 0 45 46 #if CARD_REPEAT_HISTO 47 static size_t ct_freq_sz; 48 static jbyte* ct_freq = NULL; 49 50 void init_ct_freq_table(size_t heap_sz_bytes) { 51 if (ct_freq == NULL) { 52 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size; 53 ct_freq = new jbyte[ct_freq_sz]; 54 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0; 55 } 56 } 57 58 void ct_freq_note_card(size_t index) { 59 assert(0 <= index && index < ct_freq_sz, "Bounds error."); 60 if (ct_freq[index] < 100) { ct_freq[index]++; } 61 } 62 63 static IntHistogram card_repeat_count(10, 10); 64 65 void ct_freq_update_histo_and_reset() { 66 for (size_t j = 0; j < ct_freq_sz; j++) { 67 card_repeat_count.add_entry(ct_freq[j]); 68 ct_freq[j] = 0; 69 } 70 71 } 72 #endif 73 74 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs) 75 : _g1(g1), _conc_refine_cards(0), 76 _ct_bs(ct_bs), _g1p(_g1->g1_policy()), 77 _cg1r(g1->concurrent_g1_refine()), 78 _cset_rs_update_cl(NULL), 79 _cards_scanned(NULL), _total_cards_scanned(0), 80 _prev_period_summary() 81 { 82 _seq_task = new SubTasksDone(NumSeqTasks); 83 guarantee(n_workers() > 0, "There should be some workers"); 84 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC); 85 for (uint i = 0; i < n_workers(); i++) { 86 _cset_rs_update_cl[i] = NULL; 87 } 88 if (G1SummarizeRSetStats) { 89 _prev_period_summary.initialize(this); 90 } 91 } 92 93 G1RemSet::~G1RemSet() { 94 delete _seq_task; 95 for (uint i = 0; i < n_workers(); i++) { 96 assert(_cset_rs_update_cl[i] == NULL, "it should be"); 97 } 98 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC); 99 } 100 101 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) { 102 if (_g1->is_in_g1_reserved(mr.start())) { 103 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size)); 104 if (_start_first == NULL) _start_first = mr.start(); 105 } 106 } 107 108 class ScanRSClosure : public HeapRegionClosure { 109 size_t _cards_done, _cards; 110 G1CollectedHeap* _g1h; 111 112 OopsInHeapRegionClosure* _oc; 113 CodeBlobToOopClosure* _code_root_cl; 114 115 G1BlockOffsetSharedArray* _bot_shared; 116 G1SATBCardTableModRefBS *_ct_bs; 117 118 double _strong_code_root_scan_time_sec; 119 uint _worker_i; 120 int _block_size; 121 bool _try_claimed; 122 123 public: 124 ScanRSClosure(OopsInHeapRegionClosure* oc, 125 CodeBlobToOopClosure* code_root_cl, 126 uint worker_i) : 127 _oc(oc), 128 _code_root_cl(code_root_cl), 129 _strong_code_root_scan_time_sec(0.0), 130 _cards(0), 131 _cards_done(0), 132 _worker_i(worker_i), 133 _try_claimed(false) 134 { 135 _g1h = G1CollectedHeap::heap(); 136 _bot_shared = _g1h->bot_shared(); 137 _ct_bs = _g1h->g1_barrier_set(); 138 _block_size = MAX2<int>(G1RSetScanBlockSize, 1); 139 } 140 141 void set_try_claimed() { _try_claimed = true; } 142 143 void scanCard(size_t index, HeapRegion *r) { 144 // Stack allocate the DirtyCardToOopClosure instance 145 HeapRegionDCTOC cl(_g1h, r, _oc, 146 CardTableModRefBS::Precise, 147 HeapRegionDCTOC::IntoCSFilterKind); 148 149 // Set the "from" region in the closure. 150 _oc->set_region(r); 151 HeapWord* card_start = _bot_shared->address_for_index(index); 152 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words; 153 Space *sp = SharedHeap::heap()->space_containing(card_start); 154 MemRegion sm_region = sp->used_region_at_save_marks(); 155 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end)); 156 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) { 157 // We make the card as "claimed" lazily (so races are possible 158 // but they're benign), which reduces the number of duplicate 159 // scans (the rsets of the regions in the cset can intersect). 160 _ct_bs->set_card_claimed(index); 161 _cards_done++; 162 cl.do_MemRegion(mr); 163 } 164 } 165 166 void printCard(HeapRegion* card_region, size_t card_index, 167 HeapWord* card_start) { 168 gclog_or_tty->print_cr("T %u Region [" PTR_FORMAT ", " PTR_FORMAT ") " 169 "RS names card " SIZE_FORMAT_HEX ": " 170 "[" PTR_FORMAT ", " PTR_FORMAT ")", 171 _worker_i, 172 card_region->bottom(), card_region->end(), 173 card_index, 174 card_start, card_start + G1BlockOffsetSharedArray::N_words); 175 } 176 177 void scan_strong_code_roots(HeapRegion* r) { 178 double scan_start = os::elapsedTime(); 179 r->strong_code_roots_do(_code_root_cl); 180 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start); 181 } 182 183 bool doHeapRegion(HeapRegion* r) { 184 assert(r->in_collection_set(), "should only be called on elements of CS."); 185 HeapRegionRemSet* hrrs = r->rem_set(); 186 if (hrrs->iter_is_complete()) return false; // All done. 187 if (!_try_claimed && !hrrs->claim_iter()) return false; 188 // If we ever free the collection set concurrently, we should also 189 // clear the card table concurrently therefore we won't need to 190 // add regions of the collection set to the dirty cards region. 191 _g1h->push_dirty_cards_region(r); 192 // If we didn't return above, then 193 // _try_claimed || r->claim_iter() 194 // is true: either we're supposed to work on claimed-but-not-complete 195 // regions, or we successfully claimed the region. 196 197 HeapRegionRemSetIterator iter(hrrs); 198 size_t card_index; 199 200 // We claim cards in block so as to reduce the contention. The block size is determined by 201 // the G1RSetScanBlockSize parameter. 202 size_t jump_to_card = hrrs->iter_claimed_next(_block_size); 203 for (size_t current_card = 0; iter.has_next(card_index); current_card++) { 204 if (current_card >= jump_to_card + _block_size) { 205 jump_to_card = hrrs->iter_claimed_next(_block_size); 206 } 207 if (current_card < jump_to_card) continue; 208 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index); 209 #if 0 210 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n", 211 card_start, card_start + CardTableModRefBS::card_size_in_words); 212 #endif 213 214 HeapRegion* card_region = _g1h->heap_region_containing(card_start); 215 _cards++; 216 217 if (!card_region->is_on_dirty_cards_region_list()) { 218 _g1h->push_dirty_cards_region(card_region); 219 } 220 221 // If the card is dirty, then we will scan it during updateRS. 222 if (!card_region->in_collection_set() && 223 !_ct_bs->is_card_dirty(card_index)) { 224 scanCard(card_index, card_region); 225 } 226 } 227 if (!_try_claimed) { 228 // Scan the strong code root list attached to the current region 229 scan_strong_code_roots(r); 230 231 hrrs->set_iter_complete(); 232 } 233 return false; 234 } 235 236 double strong_code_root_scan_time_sec() { 237 return _strong_code_root_scan_time_sec; 238 } 239 240 size_t cards_done() { return _cards_done;} 241 size_t cards_looked_up() { return _cards;} 242 }; 243 244 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, 245 CodeBlobToOopClosure* code_root_cl, 246 uint worker_i) { 247 double rs_time_start = os::elapsedTime(); 248 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i); 249 250 ScanRSClosure scanRScl(oc, code_root_cl, worker_i); 251 252 _g1->collection_set_iterate_from(startRegion, &scanRScl); 253 scanRScl.set_try_claimed(); 254 _g1->collection_set_iterate_from(startRegion, &scanRScl); 255 256 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start) 257 - scanRScl.strong_code_root_scan_time_sec(); 258 259 assert(_cards_scanned != NULL, "invariant"); 260 _cards_scanned[worker_i] = scanRScl.cards_done(); 261 262 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0); 263 _g1p->phase_times()->record_strong_code_root_scan_time(worker_i, 264 scanRScl.strong_code_root_scan_time_sec() * 1000.0); 265 } 266 267 // Closure used for updating RSets and recording references that 268 // point into the collection set. Only called during an 269 // evacuation pause. 270 271 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure { 272 G1RemSet* _g1rs; 273 DirtyCardQueue* _into_cset_dcq; 274 public: 275 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h, 276 DirtyCardQueue* into_cset_dcq) : 277 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq) 278 {} 279 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 280 // The only time we care about recording cards that 281 // contain references that point into the collection set 282 // is during RSet updating within an evacuation pause. 283 // In this case worker_i should be the id of a GC worker thread. 284 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause"); 285 assert(worker_i < (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker"); 286 287 if (_g1rs->refine_card(card_ptr, worker_i, true)) { 288 // 'card_ptr' contains references that point into the collection 289 // set. We need to record the card in the DCQS 290 // (G1CollectedHeap::into_cset_dirty_card_queue_set()) 291 // that's used for that purpose. 292 // 293 // Enqueue the card 294 _into_cset_dcq->enqueue(card_ptr); 295 } 296 return true; 297 } 298 }; 299 300 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) { 301 double start = os::elapsedTime(); 302 // Apply the given closure to all remaining log entries. 303 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq); 304 305 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i); 306 307 // Now there should be no dirty cards. 308 if (G1RSLogCheckCardTable) { 309 CountNonCleanMemRegionClosure cl(_g1); 310 _ct_bs->mod_card_iterate(&cl); 311 // XXX This isn't true any more: keeping cards of young regions 312 // marked dirty broke it. Need some reasonable fix. 313 guarantee(cl.n() == 0, "Card table should be clean."); 314 } 315 316 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0); 317 } 318 319 void G1RemSet::cleanupHRRS() { 320 HeapRegionRemSet::cleanup(); 321 } 322 323 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc, 324 CodeBlobToOopClosure* code_root_cl, 325 uint worker_i) { 326 #if CARD_REPEAT_HISTO 327 ct_freq_update_histo_and_reset(); 328 #endif 329 330 // We cache the value of 'oc' closure into the appropriate slot in the 331 // _cset_rs_update_cl for this worker 332 assert(worker_i < n_workers(), "sanity"); 333 _cset_rs_update_cl[worker_i] = oc; 334 335 // A DirtyCardQueue that is used to hold cards containing references 336 // that point into the collection set. This DCQ is associated with a 337 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal 338 // circumstances (i.e. the pause successfully completes), these cards 339 // are just discarded (there's no need to update the RSets of regions 340 // that were in the collection set - after the pause these regions 341 // are wholly 'free' of live objects. In the event of an evacuation 342 // failure the cards/buffers in this queue set are: 343 // * passed to the DirtyCardQueueSet that is used to manage deferred 344 // RSet updates, or 345 // * scanned for references that point into the collection set 346 // and the RSet of the corresponding region in the collection set 347 // is updated immediately. 348 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); 349 350 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant"); 351 352 // The two flags below were introduced temporarily to serialize 353 // the updating and scanning of remembered sets. There are some 354 // race conditions when these two operations are done in parallel 355 // and they are causing failures. When we resolve said race 356 // conditions, we'll revert back to parallel remembered set 357 // updating and scanning. See CRs 6677707 and 6677708. 358 if (G1UseParallelRSetUpdating || (worker_i == 0)) { 359 updateRS(&into_cset_dcq, worker_i); 360 } else { 361 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0); 362 _g1p->phase_times()->record_update_rs_time(worker_i, 0.0); 363 } 364 if (G1UseParallelRSetScanning || (worker_i == 0)) { 365 scanRS(oc, code_root_cl, worker_i); 366 } else { 367 _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0); 368 } 369 370 // We now clear the cached values of _cset_rs_update_cl for this worker 371 _cset_rs_update_cl[worker_i] = NULL; 372 } 373 374 void G1RemSet::prepare_for_oops_into_collection_set_do() { 375 cleanupHRRS(); 376 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine(); 377 _g1->set_refine_cte_cl_concurrency(false); 378 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 379 dcqs.concatenate_logs(); 380 381 guarantee( _cards_scanned == NULL, "invariant" ); 382 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC); 383 for (uint i = 0; i < n_workers(); ++i) { 384 _cards_scanned[i] = 0; 385 } 386 _total_cards_scanned = 0; 387 } 388 389 390 // This closure, applied to a DirtyCardQueueSet, is used to immediately 391 // update the RSets for the regions in the CSet. For each card it iterates 392 // through the oops which coincide with that card. It scans the reference 393 // fields in each oop; when it finds an oop that points into the collection 394 // set, the RSet for the region containing the referenced object is updated. 395 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure { 396 G1CollectedHeap* _g1; 397 CardTableModRefBS* _ct_bs; 398 public: 399 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1, 400 CardTableModRefBS* bs): 401 _g1(g1), _ct_bs(bs) 402 { } 403 404 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 405 // Construct the region representing the card. 406 HeapWord* start = _ct_bs->addr_for(card_ptr); 407 // And find the region containing it. 408 HeapRegion* r = _g1->heap_region_containing(start); 409 410 // Scan oops in the card looking for references into the collection set 411 // Don't use addr_for(card_ptr + 1) which can ask for 412 // a card beyond the heap. This is not safe without a perm 413 // gen. 414 HeapWord* end = start + CardTableModRefBS::card_size_in_words; 415 MemRegion scanRegion(start, end); 416 417 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set()); 418 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl); 419 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl); 420 421 // We can pass false as the "filter_young" parameter here as: 422 // * we should be in a STW pause, 423 // * the DCQS to which this closure is applied is used to hold 424 // references that point into the collection set from the prior 425 // RSet updating, 426 // * the post-write barrier shouldn't be logging updates to young 427 // regions (but there is a situation where this can happen - see 428 // the comment in G1RemSet::refine_card() below - 429 // that should not be applicable here), and 430 // * during actual RSet updating, the filtering of cards in young 431 // regions in HeapRegion::oops_on_card_seq_iterate_careful is 432 // employed. 433 // As a result, when this closure is applied to "refs into cset" 434 // DCQS, we shouldn't see any cards in young regions. 435 update_rs_cl.set_region(r); 436 HeapWord* stop_point = 437 r->oops_on_card_seq_iterate_careful(scanRegion, 438 &filter_then_update_rs_cset_oop_cl, 439 false /* filter_young */, 440 NULL /* card_ptr */); 441 442 // Since this is performed in the event of an evacuation failure, we 443 // we shouldn't see a non-null stop point 444 assert(stop_point == NULL, "saw an unallocated region"); 445 return true; 446 } 447 }; 448 449 void G1RemSet::cleanup_after_oops_into_collection_set_do() { 450 guarantee( _cards_scanned != NULL, "invariant" ); 451 _total_cards_scanned = 0; 452 for (uint i = 0; i < n_workers(); ++i) { 453 _total_cards_scanned += _cards_scanned[i]; 454 } 455 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC); 456 _cards_scanned = NULL; 457 // Cleanup after copy 458 _g1->set_refine_cte_cl_concurrency(true); 459 // Set all cards back to clean. 460 _g1->cleanUpCardTable(); 461 462 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set(); 463 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num(); 464 465 if (_g1->evacuation_failed()) { 466 double restore_remembered_set_start = os::elapsedTime(); 467 468 // Restore remembered sets for the regions pointing into the collection set. 469 if (G1DeferredRSUpdate) { 470 // If deferred RS updates are enabled then we just need to transfer 471 // the completed buffers from (a) the DirtyCardQueueSet used to hold 472 // cards that contain references that point into the collection set 473 // to (b) the DCQS used to hold the deferred RS updates 474 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs); 475 } else { 476 477 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set(); 478 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs); 479 480 int n_completed_buffers = 0; 481 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate, 482 0, 0, true)) { 483 n_completed_buffers++; 484 } 485 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers"); 486 } 487 488 _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0); 489 } 490 491 // Free any completed buffers in the DirtyCardQueueSet used to hold cards 492 // which contain references that point into the collection. 493 _g1->into_cset_dirty_card_queue_set().clear(); 494 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0, 495 "all buffers should be freed"); 496 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers(); 497 } 498 499 class ScrubRSClosure: public HeapRegionClosure { 500 G1CollectedHeap* _g1h; 501 BitMap* _region_bm; 502 BitMap* _card_bm; 503 CardTableModRefBS* _ctbs; 504 public: 505 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) : 506 _g1h(G1CollectedHeap::heap()), 507 _region_bm(region_bm), _card_bm(card_bm), 508 _ctbs(_g1h->g1_barrier_set()) {} 509 510 bool doHeapRegion(HeapRegion* r) { 511 if (!r->continuesHumongous()) { 512 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm); 513 } 514 return false; 515 } 516 }; 517 518 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) { 519 ScrubRSClosure scrub_cl(region_bm, card_bm); 520 _g1->heap_region_iterate(&scrub_cl); 521 } 522 523 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm, 524 uint worker_num, int claim_val) { 525 ScrubRSClosure scrub_cl(region_bm, card_bm); 526 _g1->heap_region_par_iterate_chunked(&scrub_cl, 527 worker_num, 528 n_workers(), 529 claim_val); 530 } 531 532 G1TriggerClosure::G1TriggerClosure() : 533 _triggered(false) { } 534 535 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl, 536 OopClosure* oop_cl) : 537 _trigger_cl(t_cl), _oop_cl(oop_cl) { } 538 539 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) : 540 _c1(c1), _c2(c2) { } 541 542 G1UpdateRSOrPushRefOopClosure:: 543 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h, 544 G1RemSet* rs, 545 OopsInHeapRegionClosure* push_ref_cl, 546 bool record_refs_into_cset, 547 uint worker_i) : 548 _g1(g1h), _g1_rem_set(rs), _from(NULL), 549 _record_refs_into_cset(record_refs_into_cset), 550 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { } 551 552 // Returns true if the given card contains references that point 553 // into the collection set, if we're checking for such references; 554 // false otherwise. 555 556 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i, 557 bool check_for_refs_into_cset) { 558 559 // If the card is no longer dirty, nothing to do. 560 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 561 // No need to return that this card contains refs that point 562 // into the collection set. 563 return false; 564 } 565 566 // Construct the region representing the card. 567 HeapWord* start = _ct_bs->addr_for(card_ptr); 568 // And find the region containing it. 569 HeapRegion* r = _g1->heap_region_containing(start); 570 571 // Why do we have to check here whether a card is on a young region, 572 // given that we dirty young regions and, as a result, the 573 // post-barrier is supposed to filter them out and never to enqueue 574 // them? When we allocate a new region as the "allocation region" we 575 // actually dirty its cards after we release the lock, since card 576 // dirtying while holding the lock was a performance bottleneck. So, 577 // as a result, it is possible for other threads to actually 578 // allocate objects in the region (after the acquire the lock) 579 // before all the cards on the region are dirtied. This is unlikely, 580 // and it doesn't happen often, but it can happen. So, the extra 581 // check below filters out those cards. 582 if (r->is_young()) { 583 return false; 584 } 585 586 // While we are processing RSet buffers during the collection, we 587 // actually don't want to scan any cards on the collection set, 588 // since we don't want to update remembered sets with entries that 589 // point into the collection set, given that live objects from the 590 // collection set are about to move and such entries will be stale 591 // very soon. This change also deals with a reliability issue which 592 // involves scanning a card in the collection set and coming across 593 // an array that was being chunked and looking malformed. Note, 594 // however, that if evacuation fails, we have to scan any objects 595 // that were not moved and create any missing entries. 596 if (r->in_collection_set()) { 597 return false; 598 } 599 600 // The result from the hot card cache insert call is either: 601 // * pointer to the current card 602 // (implying that the current card is not 'hot'), 603 // * null 604 // (meaning we had inserted the card ptr into the "hot" card cache, 605 // which had some headroom), 606 // * a pointer to a "hot" card that was evicted from the "hot" cache. 607 // 608 609 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 610 if (hot_card_cache->use_cache()) { 611 assert(!check_for_refs_into_cset, "sanity"); 612 assert(!SafepointSynchronize::is_at_safepoint(), "sanity"); 613 614 card_ptr = hot_card_cache->insert(card_ptr); 615 if (card_ptr == NULL) { 616 // There was no eviction. Nothing to do. 617 return false; 618 } 619 620 start = _ct_bs->addr_for(card_ptr); 621 r = _g1->heap_region_containing(start); 622 623 // Checking whether the region we got back from the cache 624 // is young here is inappropriate. The region could have been 625 // freed, reallocated and tagged as young while in the cache. 626 // Hence we could see its young type change at any time. 627 } 628 629 // Don't use addr_for(card_ptr + 1) which can ask for 630 // a card beyond the heap. This is not safe without a perm 631 // gen at the upper end of the heap. 632 HeapWord* end = start + CardTableModRefBS::card_size_in_words; 633 MemRegion dirtyRegion(start, end); 634 635 #if CARD_REPEAT_HISTO 636 init_ct_freq_table(_g1->max_capacity()); 637 ct_freq_note_card(_ct_bs->index_for(start)); 638 #endif 639 640 OopsInHeapRegionClosure* oops_in_heap_closure = NULL; 641 if (check_for_refs_into_cset) { 642 // ConcurrentG1RefineThreads have worker numbers larger than what 643 // _cset_rs_update_cl[] is set up to handle. But those threads should 644 // only be active outside of a collection which means that when they 645 // reach here they should have check_for_refs_into_cset == false. 646 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length"); 647 oops_in_heap_closure = _cset_rs_update_cl[worker_i]; 648 } 649 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1, 650 _g1->g1_rem_set(), 651 oops_in_heap_closure, 652 check_for_refs_into_cset, 653 worker_i); 654 update_rs_oop_cl.set_from(r); 655 656 G1TriggerClosure trigger_cl; 657 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl); 658 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl); 659 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl); 660 661 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r, 662 (check_for_refs_into_cset ? 663 (OopClosure*)&mux : 664 (OopClosure*)&update_rs_oop_cl)); 665 666 // The region for the current card may be a young region. The 667 // current card may have been a card that was evicted from the 668 // card cache. When the card was inserted into the cache, we had 669 // determined that its region was non-young. While in the cache, 670 // the region may have been freed during a cleanup pause, reallocated 671 // and tagged as young. 672 // 673 // We wish to filter out cards for such a region but the current 674 // thread, if we're running concurrently, may "see" the young type 675 // change at any time (so an earlier "is_young" check may pass or 676 // fail arbitrarily). We tell the iteration code to perform this 677 // filtering when it has been determined that there has been an actual 678 // allocation in this region and making it safe to check the young type. 679 bool filter_young = true; 680 681 HeapWord* stop_point = 682 r->oops_on_card_seq_iterate_careful(dirtyRegion, 683 &filter_then_update_rs_oop_cl, 684 filter_young, 685 card_ptr); 686 687 // If stop_point is non-null, then we encountered an unallocated region 688 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the 689 // card and re-enqueue: if we put off the card until a GC pause, then the 690 // unallocated portion will be filled in. Alternatively, we might try 691 // the full complexity of the technique used in "regular" precleaning. 692 if (stop_point != NULL) { 693 // The card might have gotten re-dirtied and re-enqueued while we 694 // worked. (In fact, it's pretty likely.) 695 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 696 *card_ptr = CardTableModRefBS::dirty_card_val(); 697 MutexLockerEx x(Shared_DirtyCardQ_lock, 698 Mutex::_no_safepoint_check_flag); 699 DirtyCardQueue* sdcq = 700 JavaThread::dirty_card_queue_set().shared_dirty_card_queue(); 701 sdcq->enqueue(card_ptr); 702 } 703 } else { 704 _conc_refine_cards++; 705 } 706 707 // This gets set to true if the card being refined has 708 // references that point into the collection set. 709 bool has_refs_into_cset = trigger_cl.triggered(); 710 711 // We should only be detecting that the card contains references 712 // that point into the collection set if the current thread is 713 // a GC worker thread. 714 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(), 715 "invalid result at non safepoint"); 716 717 return has_refs_into_cset; 718 } 719 720 void G1RemSet::print_periodic_summary_info(const char* header) { 721 G1RemSetSummary current; 722 current.initialize(this); 723 724 _prev_period_summary.subtract_from(¤t); 725 print_summary_info(&_prev_period_summary, header); 726 727 _prev_period_summary.set(¤t); 728 } 729 730 void G1RemSet::print_summary_info() { 731 G1RemSetSummary current; 732 current.initialize(this); 733 734 print_summary_info(¤t, " Cumulative RS summary"); 735 } 736 737 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) { 738 assert(summary != NULL, "just checking"); 739 740 if (header != NULL) { 741 gclog_or_tty->print_cr("%s", header); 742 } 743 744 #if CARD_REPEAT_HISTO 745 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: "); 746 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number."); 747 card_repeat_count.print_on(gclog_or_tty); 748 #endif 749 750 summary->print_on(gclog_or_tty); 751 } 752 753 void G1RemSet::prepare_for_verify() { 754 if (G1HRRSFlushLogBuffersOnVerify && 755 (VerifyBeforeGC || VerifyAfterGC) 756 && (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) { 757 cleanupHRRS(); 758 _g1->set_refine_cte_cl_concurrency(false); 759 if (SafepointSynchronize::is_at_safepoint()) { 760 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 761 dcqs.concatenate_logs(); 762 } 763 764 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 765 bool use_hot_card_cache = hot_card_cache->use_cache(); 766 hot_card_cache->set_use_cache(false); 767 768 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); 769 updateRS(&into_cset_dcq, 0); 770 _g1->into_cset_dirty_card_queue_set().clear(); 771 772 hot_card_cache->set_use_cache(use_hot_card_cache); 773 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 774 } 775 }