1 /* 2 * Copyright (c) 2001, 2013, 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/bufferingOopClosure.hpp" 27 #include "gc_implementation/g1/concurrentG1Refine.hpp" 28 #include "gc_implementation/g1/concurrentG1RefineThread.hpp" 29 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp" 30 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp" 31 #include "gc_implementation/g1/g1CollectorPolicy.hpp" 32 #include "gc_implementation/g1/g1HotCardCache.hpp" 33 #include "gc_implementation/g1/g1GCPhaseTimes.hpp" 34 #include "gc_implementation/g1/g1OopClosures.inline.hpp" 35 #include "gc_implementation/g1/g1RemSet.inline.hpp" 36 #include "gc_implementation/g1/heapRegionSeq.inline.hpp" 37 #include "gc_implementation/g1/heapRegionRemSet.hpp" 38 #include "memory/iterator.hpp" 39 #include "oops/oop.inline.hpp" 40 #include "utilities/intHisto.hpp" 41 42 #define CARD_REPEAT_HISTO 0 43 44 #if CARD_REPEAT_HISTO 45 static size_t ct_freq_sz; 46 static jbyte* ct_freq = NULL; 47 48 void init_ct_freq_table(size_t heap_sz_bytes) { 49 if (ct_freq == NULL) { 50 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size; 51 ct_freq = new jbyte[ct_freq_sz]; 52 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0; 53 } 54 } 55 56 void ct_freq_note_card(size_t index) { 57 assert(0 <= index && index < ct_freq_sz, "Bounds error."); 58 if (ct_freq[index] < 100) { ct_freq[index]++; } 59 } 60 61 static IntHistogram card_repeat_count(10, 10); 62 63 void ct_freq_update_histo_and_reset() { 64 for (size_t j = 0; j < ct_freq_sz; j++) { 65 card_repeat_count.add_entry(ct_freq[j]); 66 ct_freq[j] = 0; 67 } 68 69 } 70 #endif 71 72 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs) 73 : _g1(g1), _conc_refine_cards(0), 74 _ct_bs(ct_bs), _g1p(_g1->g1_policy()), 75 _cg1r(g1->concurrent_g1_refine()), 76 _cset_rs_update_cl(NULL), 77 _cards_scanned(NULL), _total_cards_scanned(0), 78 _prev_period_summary() 79 { 80 _seq_task = new SubTasksDone(NumSeqTasks); 81 guarantee(n_workers() > 0, "There should be some workers"); 82 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC); 83 for (uint i = 0; i < n_workers(); i++) { 84 _cset_rs_update_cl[i] = NULL; 85 } 86 if (G1SummarizeRSetStats) { 87 _prev_period_summary.initialize(this); 88 } 89 } 90 91 G1RemSet::~G1RemSet() { 92 delete _seq_task; 93 for (uint i = 0; i < n_workers(); i++) { 94 assert(_cset_rs_update_cl[i] == NULL, "it should be"); 95 } 96 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC); 97 } 98 99 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) { 100 if (_g1->is_in_g1_reserved(mr.start())) { 101 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size)); 102 if (_start_first == NULL) _start_first = mr.start(); 103 } 104 } 105 106 class ScanRSClosure : public HeapRegionClosure { 107 size_t _cards_done, _cards; 108 G1CollectedHeap* _g1h; 109 110 OopsInHeapRegionClosure* _oc; 111 CodeBlobToOopClosure* _code_root_cl; 112 113 G1BlockOffsetSharedArray* _bot_shared; 114 G1SATBCardTableModRefBS *_ct_bs; 115 116 double _strong_code_root_scan_time_sec; 117 int _worker_i; 118 int _block_size; 119 bool _try_claimed; 120 121 public: 122 ScanRSClosure(OopsInHeapRegionClosure* oc, 123 CodeBlobToOopClosure* code_root_cl, 124 int worker_i) : 125 _oc(oc), 126 _code_root_cl(code_root_cl), 127 _strong_code_root_scan_time_sec(0.0), 128 _cards(0), 129 _cards_done(0), 130 _worker_i(worker_i), 131 _try_claimed(false) 132 { 133 _g1h = G1CollectedHeap::heap(); 134 _bot_shared = _g1h->bot_shared(); 135 _ct_bs = _g1h->g1_barrier_set(); 136 _block_size = MAX2<int>(G1RSetScanBlockSize, 1); 137 } 138 139 void set_try_claimed() { _try_claimed = true; } 140 141 void scanCard(size_t index, HeapRegion *r) { 142 // Stack allocate the DirtyCardToOopClosure instance 143 HeapRegionDCTOC cl(_g1h, r, _oc, 144 CardTableModRefBS::Precise, 145 HeapRegionDCTOC::IntoCSFilterKind); 146 147 // Set the "from" region in the closure. 148 _oc->set_region(r); 149 HeapWord* card_start = _bot_shared->address_for_index(index); 150 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words; 151 Space *sp = SharedHeap::heap()->space_containing(card_start); 152 MemRegion sm_region = sp->used_region_at_save_marks(); 153 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end)); 154 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) { 155 // We make the card as "claimed" lazily (so races are possible 156 // but they're benign), which reduces the number of duplicate 157 // scans (the rsets of the regions in the cset can intersect). 158 _ct_bs->set_card_claimed(index); 159 _cards_done++; 160 cl.do_MemRegion(mr); 161 } 162 } 163 164 void printCard(HeapRegion* card_region, size_t card_index, 165 HeapWord* card_start) { 166 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") " 167 "RS names card %p: " 168 "[" PTR_FORMAT ", " PTR_FORMAT ")", 169 _worker_i, 170 card_region->bottom(), card_region->end(), 171 card_index, 172 card_start, card_start + G1BlockOffsetSharedArray::N_words); 173 } 174 175 void scan_strong_code_roots(HeapRegion* r) { 176 double scan_start = os::elapsedTime(); 177 r->strong_code_roots_do(_code_root_cl); 178 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start); 179 } 180 181 bool doHeapRegion(HeapRegion* r) { 182 assert(r->in_collection_set(), "should only be called on elements of CS."); 183 HeapRegionRemSet* hrrs = r->rem_set(); 184 if (hrrs->iter_is_complete()) return false; // All done. 185 if (!_try_claimed && !hrrs->claim_iter()) return false; 186 // If we ever free the collection set concurrently, we should also 187 // clear the card table concurrently therefore we won't need to 188 // add regions of the collection set to the dirty cards region. 189 _g1h->push_dirty_cards_region(r); 190 // If we didn't return above, then 191 // _try_claimed || r->claim_iter() 192 // is true: either we're supposed to work on claimed-but-not-complete 193 // regions, or we successfully claimed the region. 194 195 HeapRegionRemSetIterator iter(hrrs); 196 size_t card_index; 197 198 // We claim cards in block so as to recude the contention. The block size is determined by 199 // the G1RSetScanBlockSize parameter. 200 size_t jump_to_card = hrrs->iter_claimed_next(_block_size); 201 for (size_t current_card = 0; iter.has_next(card_index); current_card++) { 202 if (current_card >= jump_to_card + _block_size) { 203 jump_to_card = hrrs->iter_claimed_next(_block_size); 204 } 205 if (current_card < jump_to_card) continue; 206 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index); 207 #if 0 208 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n", 209 card_start, card_start + CardTableModRefBS::card_size_in_words); 210 #endif 211 212 HeapRegion* card_region = _g1h->heap_region_containing(card_start); 213 assert(card_region != NULL, "Yielding cards not in the heap?"); 214 _cards++; 215 216 if (!card_region->is_on_dirty_cards_region_list()) { 217 _g1h->push_dirty_cards_region(card_region); 218 } 219 220 // If the card is dirty, then we will scan it during updateRS. 221 if (!card_region->in_collection_set() && 222 !_ct_bs->is_card_dirty(card_index)) { 223 scanCard(card_index, card_region); 224 } 225 } 226 if (!_try_claimed) { 227 // Scan the strong code root list attached to the current region 228 scan_strong_code_roots(r); 229 230 hrrs->set_iter_complete(); 231 } 232 return false; 233 } 234 235 double strong_code_root_scan_time_sec() { 236 return _strong_code_root_scan_time_sec; 237 } 238 239 size_t cards_done() { return _cards_done;} 240 size_t cards_looked_up() { return _cards;} 241 }; 242 243 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, 244 CodeBlobToOopClosure* code_root_cl, 245 int worker_i) { 246 double rs_time_start = os::elapsedTime(); 247 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i); 248 249 ScanRSClosure scanRScl(oc, code_root_cl, worker_i); 250 251 _g1->collection_set_iterate_from(startRegion, &scanRScl); 252 scanRScl.set_try_claimed(); 253 _g1->collection_set_iterate_from(startRegion, &scanRScl); 254 255 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start) 256 - scanRScl.strong_code_root_scan_time_sec(); 257 258 assert(_cards_scanned != NULL, "invariant"); 259 _cards_scanned[worker_i] = scanRScl.cards_done(); 260 261 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0); 262 _g1p->phase_times()->record_strong_code_root_scan_time(worker_i, 263 scanRScl.strong_code_root_scan_time_sec() * 1000.0); 264 } 265 266 // Closure used for updating RSets and recording references that 267 // point into the collection set. Only called during an 268 // evacuation pause. 269 270 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure { 271 G1RemSet* _g1rs; 272 DirtyCardQueue* _into_cset_dcq; 273 public: 274 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h, 275 DirtyCardQueue* into_cset_dcq) : 276 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq) 277 {} 278 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 279 // The only time we care about recording cards that 280 // contain references that point into the collection set 281 // is during RSet updating within an evacuation pause. 282 // In this case worker_i should be the id of a GC worker thread. 283 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause"); 284 assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker"); 285 286 if (_g1rs->refine_card(card_ptr, worker_i, true)) { 287 // 'card_ptr' contains references that point into the collection 288 // set. We need to record the card in the DCQS 289 // (G1CollectedHeap::into_cset_dirty_card_queue_set()) 290 // that's used for that purpose. 291 // 292 // Enqueue the card 293 _into_cset_dcq->enqueue(card_ptr); 294 } 295 return true; 296 } 297 }; 298 299 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) { 300 double start = os::elapsedTime(); 301 // Apply the given closure to all remaining log entries. 302 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq); 303 304 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i); 305 306 // Now there should be no dirty cards. 307 if (G1RSLogCheckCardTable) { 308 CountNonCleanMemRegionClosure cl(_g1); 309 _ct_bs->mod_card_iterate(&cl); 310 // XXX This isn't true any more: keeping cards of young regions 311 // marked dirty broke it. Need some reasonable fix. 312 guarantee(cl.n() == 0, "Card table should be clean."); 313 } 314 315 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0); 316 } 317 318 void G1RemSet::cleanupHRRS() { 319 HeapRegionRemSet::cleanup(); 320 } 321 322 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc, 323 CodeBlobToOopClosure* code_root_cl, 324 int worker_i) { 325 #if CARD_REPEAT_HISTO 326 ct_freq_update_histo_and_reset(); 327 #endif 328 329 // We cache the value of 'oc' closure into the appropriate slot in the 330 // _cset_rs_update_cl for this worker 331 assert(worker_i < (int)n_workers(), "sanity"); 332 _cset_rs_update_cl[worker_i] = oc; 333 334 // A DirtyCardQueue that is used to hold cards containing references 335 // that point into the collection set. This DCQ is associated with a 336 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal 337 // circumstances (i.e. the pause successfully completes), these cards 338 // are just discarded (there's no need to update the RSets of regions 339 // that were in the collection set - after the pause these regions 340 // are wholly 'free' of live objects. In the event of an evacuation 341 // failure the cards/buffers in this queue set are: 342 // * passed to the DirtyCardQueueSet that is used to manage deferred 343 // RSet updates, or 344 // * scanned for references that point into the collection set 345 // and the RSet of the corresponding region in the collection set 346 // is updated immediately. 347 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); 348 349 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant"); 350 351 // The two flags below were introduced temporarily to serialize 352 // the updating and scanning of remembered sets. There are some 353 // race conditions when these two operations are done in parallel 354 // and they are causing failures. When we resolve said race 355 // conditions, we'll revert back to parallel remembered set 356 // updating and scanning. See CRs 6677707 and 6677708. 357 if (G1UseParallelRSetUpdating || (worker_i == 0)) { 358 updateRS(&into_cset_dcq, worker_i); 359 } else { 360 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0); 361 _g1p->phase_times()->record_update_rs_time(worker_i, 0.0); 362 } 363 if (G1UseParallelRSetScanning || (worker_i == 0)) { 364 scanRS(oc, code_root_cl, worker_i); 365 } else { 366 _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0); 367 } 368 369 // We now clear the cached values of _cset_rs_update_cl for this worker 370 _cset_rs_update_cl[worker_i] = NULL; 371 } 372 373 void G1RemSet::prepare_for_oops_into_collection_set_do() { 374 cleanupHRRS(); 375 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine(); 376 _g1->set_refine_cte_cl_concurrency(false); 377 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 378 dcqs.concatenate_logs(); 379 380 if (G1CollectedHeap::use_parallel_gc_threads()) { 381 // Don't set the number of workers here. It will be set 382 // when the task is run 383 // _seq_task->set_n_termination((int)n_workers()); 384 } 385 guarantee( _cards_scanned == NULL, "invariant" ); 386 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC); 387 for (uint i = 0; i < n_workers(); ++i) { 388 _cards_scanned[i] = 0; 389 } 390 _total_cards_scanned = 0; 391 } 392 393 394 // This closure, applied to a DirtyCardQueueSet, is used to immediately 395 // update the RSets for the regions in the CSet. For each card it iterates 396 // through the oops which coincide with that card. It scans the reference 397 // fields in each oop; when it finds an oop that points into the collection 398 // set, the RSet for the region containing the referenced object is updated. 399 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure { 400 G1CollectedHeap* _g1; 401 CardTableModRefBS* _ct_bs; 402 public: 403 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1, 404 CardTableModRefBS* bs): 405 _g1(g1), _ct_bs(bs) 406 { } 407 408 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 409 // Construct the region representing the card. 410 HeapWord* start = _ct_bs->addr_for(card_ptr); 411 // And find the region containing it. 412 HeapRegion* r = _g1->heap_region_containing(start); 413 assert(r != NULL, "unexpected null"); 414 415 // Scan oops in the card looking for references into the collection set 416 // Don't use addr_for(card_ptr + 1) which can ask for 417 // a card beyond the heap. This is not safe without a perm 418 // gen. 419 HeapWord* end = start + CardTableModRefBS::card_size_in_words; 420 MemRegion scanRegion(start, end); 421 422 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set()); 423 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl); 424 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl); 425 426 // We can pass false as the "filter_young" parameter here as: 427 // * we should be in a STW pause, 428 // * the DCQS to which this closure is applied is used to hold 429 // references that point into the collection set from the prior 430 // RSet updating, 431 // * the post-write barrier shouldn't be logging updates to young 432 // regions (but there is a situation where this can happen - see 433 // the comment in G1RemSet::refine_card() below - 434 // that should not be applicable here), and 435 // * during actual RSet updating, the filtering of cards in young 436 // regions in HeapRegion::oops_on_card_seq_iterate_careful is 437 // employed. 438 // As a result, when this closure is applied to "refs into cset" 439 // DCQS, we shouldn't see any cards in young regions. 440 update_rs_cl.set_region(r); 441 HeapWord* stop_point = 442 r->oops_on_card_seq_iterate_careful(scanRegion, 443 &filter_then_update_rs_cset_oop_cl, 444 false /* filter_young */, 445 NULL /* card_ptr */); 446 447 // Since this is performed in the event of an evacuation failure, we 448 // we shouldn't see a non-null stop point 449 assert(stop_point == NULL, "saw an unallocated region"); 450 return true; 451 } 452 }; 453 454 void G1RemSet::cleanup_after_oops_into_collection_set_do() { 455 guarantee( _cards_scanned != NULL, "invariant" ); 456 _total_cards_scanned = 0; 457 for (uint i = 0; i < n_workers(); ++i) { 458 _total_cards_scanned += _cards_scanned[i]; 459 } 460 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC); 461 _cards_scanned = NULL; 462 // Cleanup after copy 463 _g1->set_refine_cte_cl_concurrency(true); 464 // Set all cards back to clean. 465 _g1->cleanUpCardTable(); 466 467 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set(); 468 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num(); 469 470 if (_g1->evacuation_failed()) { 471 // Restore remembered sets for the regions pointing into the collection set. 472 473 if (G1DeferredRSUpdate) { 474 // If deferred RS updates are enabled then we just need to transfer 475 // the completed buffers from (a) the DirtyCardQueueSet used to hold 476 // cards that contain references that point into the collection set 477 // to (b) the DCQS used to hold the deferred RS updates 478 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs); 479 } else { 480 481 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set(); 482 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs); 483 484 int n_completed_buffers = 0; 485 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate, 486 0, 0, true)) { 487 n_completed_buffers++; 488 } 489 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers"); 490 } 491 } 492 493 // Free any completed buffers in the DirtyCardQueueSet used to hold cards 494 // which contain references that point into the collection. 495 _g1->into_cset_dirty_card_queue_set().clear(); 496 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0, 497 "all buffers should be freed"); 498 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers(); 499 } 500 501 class ScrubRSClosure: public HeapRegionClosure { 502 G1CollectedHeap* _g1h; 503 BitMap* _region_bm; 504 BitMap* _card_bm; 505 CardTableModRefBS* _ctbs; 506 public: 507 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) : 508 _g1h(G1CollectedHeap::heap()), 509 _region_bm(region_bm), _card_bm(card_bm), 510 _ctbs(_g1h->g1_barrier_set()) {} 511 512 bool doHeapRegion(HeapRegion* r) { 513 if (!r->continuesHumongous()) { 514 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm); 515 } 516 return false; 517 } 518 }; 519 520 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) { 521 ScrubRSClosure scrub_cl(region_bm, card_bm); 522 _g1->heap_region_iterate(&scrub_cl); 523 } 524 525 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm, 526 uint worker_num, int claim_val) { 527 ScrubRSClosure scrub_cl(region_bm, card_bm); 528 _g1->heap_region_par_iterate_chunked(&scrub_cl, 529 worker_num, 530 n_workers(), 531 claim_val); 532 } 533 534 G1TriggerClosure::G1TriggerClosure() : 535 _triggered(false) { } 536 537 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl, 538 OopClosure* oop_cl) : 539 _trigger_cl(t_cl), _oop_cl(oop_cl) { } 540 541 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) : 542 _c1(c1), _c2(c2) { } 543 544 G1UpdateRSOrPushRefOopClosure:: 545 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h, 546 G1RemSet* rs, 547 OopsInHeapRegionClosure* push_ref_cl, 548 bool record_refs_into_cset, 549 int worker_i) : 550 _g1(g1h), _g1_rem_set(rs), _from(NULL), 551 _record_refs_into_cset(record_refs_into_cset), 552 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { } 553 554 // Returns true if the given card contains references that point 555 // into the collection set, if we're checking for such references; 556 // false otherwise. 557 558 bool G1RemSet::refine_card(jbyte* card_ptr, int worker_i, 559 bool check_for_refs_into_cset) { 560 561 // If the card is no longer dirty, nothing to do. 562 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 563 // No need to return that this card contains refs that point 564 // into the collection set. 565 return false; 566 } 567 568 // Construct the region representing the card. 569 HeapWord* start = _ct_bs->addr_for(card_ptr); 570 // And find the region containing it. 571 HeapRegion* r = _g1->heap_region_containing(start); 572 if (r == NULL) { 573 // Again no need to return that this card contains refs that 574 // point into the collection set. 575 return false; // Not in the G1 heap (might be in perm, for example.) 576 } 577 578 // Why do we have to check here whether a card is on a young region, 579 // given that we dirty young regions and, as a result, the 580 // post-barrier is supposed to filter them out and never to enqueue 581 // them? When we allocate a new region as the "allocation region" we 582 // actually dirty its cards after we release the lock, since card 583 // dirtying while holding the lock was a performance bottleneck. So, 584 // as a result, it is possible for other threads to actually 585 // allocate objects in the region (after the acquire the lock) 586 // before all the cards on the region are dirtied. This is unlikely, 587 // and it doesn't happen often, but it can happen. So, the extra 588 // check below filters out those cards. 589 if (r->is_young()) { 590 return false; 591 } 592 593 // While we are processing RSet buffers during the collection, we 594 // actually don't want to scan any cards on the collection set, 595 // since we don't want to update remebered sets with entries that 596 // point into the collection set, given that live objects from the 597 // collection set are about to move and such entries will be stale 598 // very soon. This change also deals with a reliability issue which 599 // involves scanning a card in the collection set and coming across 600 // an array that was being chunked and looking malformed. Note, 601 // however, that if evacuation fails, we have to scan any objects 602 // that were not moved and create any missing entries. 603 if (r->in_collection_set()) { 604 return false; 605 } 606 607 // The result from the hot card cache insert call is either: 608 // * pointer to the current card 609 // (implying that the current card is not 'hot'), 610 // * null 611 // (meaning we had inserted the card ptr into the "hot" card cache, 612 // which had some headroom), 613 // * a pointer to a "hot" card that was evicted from the "hot" cache. 614 // 615 616 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 617 if (hot_card_cache->use_cache()) { 618 assert(!check_for_refs_into_cset, "sanity"); 619 assert(!SafepointSynchronize::is_at_safepoint(), "sanity"); 620 621 card_ptr = hot_card_cache->insert(card_ptr); 622 if (card_ptr == NULL) { 623 // There was no eviction. Nothing to do. 624 return false; 625 } 626 627 start = _ct_bs->addr_for(card_ptr); 628 r = _g1->heap_region_containing(start); 629 if (r == NULL) { 630 // Not in the G1 heap 631 return false; 632 } 633 634 // Checking whether the region we got back from the cache 635 // is young here is inappropriate. The region could have been 636 // freed, reallocated and tagged as young while in the cache. 637 // Hence we could see its young type change at any time. 638 } 639 640 // Don't use addr_for(card_ptr + 1) which can ask for 641 // a card beyond the heap. This is not safe without a perm 642 // gen at the upper end of the heap. 643 HeapWord* end = start + CardTableModRefBS::card_size_in_words; 644 MemRegion dirtyRegion(start, end); 645 646 #if CARD_REPEAT_HISTO 647 init_ct_freq_table(_g1->max_capacity()); 648 ct_freq_note_card(_ct_bs->index_for(start)); 649 #endif 650 651 OopsInHeapRegionClosure* oops_in_heap_closure = NULL; 652 if (check_for_refs_into_cset) { 653 // ConcurrentG1RefineThreads have worker numbers larger than what 654 // _cset_rs_update_cl[] is set up to handle. But those threads should 655 // only be active outside of a collection which means that when they 656 // reach here they should have check_for_refs_into_cset == false. 657 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length"); 658 oops_in_heap_closure = _cset_rs_update_cl[worker_i]; 659 } 660 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1, 661 _g1->g1_rem_set(), 662 oops_in_heap_closure, 663 check_for_refs_into_cset, 664 worker_i); 665 update_rs_oop_cl.set_from(r); 666 667 G1TriggerClosure trigger_cl; 668 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl); 669 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl); 670 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl); 671 672 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r, 673 (check_for_refs_into_cset ? 674 (OopClosure*)&mux : 675 (OopClosure*)&update_rs_oop_cl)); 676 677 // The region for the current card may be a young region. The 678 // current card may have been a card that was evicted from the 679 // card cache. When the card was inserted into the cache, we had 680 // determined that its region was non-young. While in the cache, 681 // the region may have been freed during a cleanup pause, reallocated 682 // and tagged as young. 683 // 684 // We wish to filter out cards for such a region but the current 685 // thread, if we're running concurrently, may "see" the young type 686 // change at any time (so an earlier "is_young" check may pass or 687 // fail arbitrarily). We tell the iteration code to perform this 688 // filtering when it has been determined that there has been an actual 689 // allocation in this region and making it safe to check the young type. 690 bool filter_young = true; 691 692 HeapWord* stop_point = 693 r->oops_on_card_seq_iterate_careful(dirtyRegion, 694 &filter_then_update_rs_oop_cl, 695 filter_young, 696 card_ptr); 697 698 // If stop_point is non-null, then we encountered an unallocated region 699 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the 700 // card and re-enqueue: if we put off the card until a GC pause, then the 701 // unallocated portion will be filled in. Alternatively, we might try 702 // the full complexity of the technique used in "regular" precleaning. 703 if (stop_point != NULL) { 704 // The card might have gotten re-dirtied and re-enqueued while we 705 // worked. (In fact, it's pretty likely.) 706 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 707 *card_ptr = CardTableModRefBS::dirty_card_val(); 708 MutexLockerEx x(Shared_DirtyCardQ_lock, 709 Mutex::_no_safepoint_check_flag); 710 DirtyCardQueue* sdcq = 711 JavaThread::dirty_card_queue_set().shared_dirty_card_queue(); 712 sdcq->enqueue(card_ptr); 713 } 714 } else { 715 _conc_refine_cards++; 716 } 717 718 // This gets set to true if the card being refined has 719 // references that point into the collection set. 720 bool has_refs_into_cset = trigger_cl.triggered(); 721 722 // We should only be detecting that the card contains references 723 // that point into the collection set if the current thread is 724 // a GC worker thread. 725 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(), 726 "invalid result at non safepoint"); 727 728 return has_refs_into_cset; 729 } 730 731 void G1RemSet::print_periodic_summary_info(const char* header) { 732 G1RemSetSummary current; 733 current.initialize(this); 734 735 _prev_period_summary.subtract_from(¤t); 736 print_summary_info(&_prev_period_summary, header); 737 738 _prev_period_summary.set(¤t); 739 } 740 741 void G1RemSet::print_summary_info() { 742 G1RemSetSummary current; 743 current.initialize(this); 744 745 print_summary_info(¤t, " Cumulative RS summary"); 746 } 747 748 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) { 749 assert(summary != NULL, "just checking"); 750 751 if (header != NULL) { 752 gclog_or_tty->print_cr("%s", header); 753 } 754 755 #if CARD_REPEAT_HISTO 756 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: "); 757 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number."); 758 card_repeat_count.print_on(gclog_or_tty); 759 #endif 760 761 summary->print_on(gclog_or_tty); 762 } 763 764 void G1RemSet::prepare_for_verify() { 765 if (G1HRRSFlushLogBuffersOnVerify && 766 (VerifyBeforeGC || VerifyAfterGC) 767 && (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) { 768 cleanupHRRS(); 769 _g1->set_refine_cte_cl_concurrency(false); 770 if (SafepointSynchronize::is_at_safepoint()) { 771 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 772 dcqs.concatenate_logs(); 773 } 774 775 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 776 bool use_hot_card_cache = hot_card_cache->use_cache(); 777 hot_card_cache->set_use_cache(false); 778 779 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); 780 updateRS(&into_cset_dcq, 0); 781 _g1->into_cset_dirty_card_queue_set().clear(); 782 783 hot_card_cache->set_use_cache(use_hot_card_cache); 784 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 785 } 786 }