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/heapRegionManager.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 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, n_workers(), mtGC); 84 for (uint i = 0; i < n_workers(); i++) { 85 _cset_rs_update_cl[i] = NULL; 86 } 87 if (G1SummarizeRSetStats) { 88 _prev_period_summary.initialize(this); 89 } 90 } 91 92 G1RemSet::~G1RemSet() { 93 delete _seq_task; 94 for (uint i = 0; i < n_workers(); i++) { 95 assert(_cset_rs_update_cl[i] == NULL, "it should be"); 96 } 97 FREE_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, _cset_rs_update_cl); 98 } 99 100 class ScanRSClosure : public HeapRegionClosure { 101 size_t _cards_done, _cards; 102 G1CollectedHeap* _g1h; 103 104 G1ParPushHeapRSClosure* _oc; 105 CodeBlobClosure* _code_root_cl; 106 107 G1BlockOffsetSharedArray* _bot_shared; 108 G1SATBCardTableModRefBS *_ct_bs; 109 110 double _strong_code_root_scan_time_sec; 111 uint _worker_i; 112 int _block_size; 113 bool _try_claimed; 114 115 public: 116 ScanRSClosure(G1ParPushHeapRSClosure* oc, 117 CodeBlobClosure* code_root_cl, 118 uint worker_i) : 119 _oc(oc), 120 _code_root_cl(code_root_cl), 121 _strong_code_root_scan_time_sec(0.0), 122 _cards(0), 123 _cards_done(0), 124 _worker_i(worker_i), 125 _try_claimed(false) 126 { 127 _g1h = G1CollectedHeap::heap(); 128 _bot_shared = _g1h->bot_shared(); 129 _ct_bs = _g1h->g1_barrier_set(); 130 _block_size = MAX2<int>(G1RSetScanBlockSize, 1); 131 } 132 133 void set_try_claimed() { _try_claimed = true; } 134 135 void scanCard(size_t index, HeapRegion *r) { 136 // Stack allocate the DirtyCardToOopClosure instance 137 HeapRegionDCTOC cl(_g1h, r, _oc, 138 CardTableModRefBS::Precise); 139 140 // Set the "from" region in the closure. 141 _oc->set_region(r); 142 MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words); 143 MemRegion pre_gc_allocated(r->bottom(), r->scan_top()); 144 MemRegion mr = pre_gc_allocated.intersection(card_region); 145 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) { 146 // We make the card as "claimed" lazily (so races are possible 147 // but they're benign), which reduces the number of duplicate 148 // scans (the rsets of the regions in the cset can intersect). 149 _ct_bs->set_card_claimed(index); 150 _cards_done++; 151 cl.do_MemRegion(mr); 152 } 153 } 154 155 void printCard(HeapRegion* card_region, size_t card_index, 156 HeapWord* card_start) { 157 gclog_or_tty->print_cr("T %u Region [" PTR_FORMAT ", " PTR_FORMAT ") " 158 "RS names card " SIZE_FORMAT_HEX ": " 159 "[" PTR_FORMAT ", " PTR_FORMAT ")", 160 _worker_i, 161 card_region->bottom(), card_region->end(), 162 card_index, 163 card_start, card_start + G1BlockOffsetSharedArray::N_words); 164 } 165 166 void scan_strong_code_roots(HeapRegion* r) { 167 double scan_start = os::elapsedTime(); 168 r->strong_code_roots_do(_code_root_cl); 169 _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start); 170 } 171 172 bool doHeapRegion(HeapRegion* r) { 173 assert(r->in_collection_set(), "should only be called on elements of CS."); 174 HeapRegionRemSet* hrrs = r->rem_set(); 175 if (hrrs->iter_is_complete()) return false; // All done. 176 if (!_try_claimed && !hrrs->claim_iter()) return false; 177 // If we ever free the collection set concurrently, we should also 178 // clear the card table concurrently therefore we won't need to 179 // add regions of the collection set to the dirty cards region. 180 _g1h->push_dirty_cards_region(r); 181 // If we didn't return above, then 182 // _try_claimed || r->claim_iter() 183 // is true: either we're supposed to work on claimed-but-not-complete 184 // regions, or we successfully claimed the region. 185 186 HeapRegionRemSetIterator iter(hrrs); 187 size_t card_index; 188 189 // We claim cards in block so as to reduce the contention. The block size is determined by 190 // the G1RSetScanBlockSize parameter. 191 size_t jump_to_card = hrrs->iter_claimed_next(_block_size); 192 for (size_t current_card = 0; iter.has_next(card_index); current_card++) { 193 if (current_card >= jump_to_card + _block_size) { 194 jump_to_card = hrrs->iter_claimed_next(_block_size); 195 } 196 if (current_card < jump_to_card) continue; 197 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index); 198 #if 0 199 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n", 200 card_start, card_start + CardTableModRefBS::card_size_in_words); 201 #endif 202 203 HeapRegion* card_region = _g1h->heap_region_containing(card_start); 204 _cards++; 205 206 if (!card_region->is_on_dirty_cards_region_list()) { 207 _g1h->push_dirty_cards_region(card_region); 208 } 209 210 // If the card is dirty, then we will scan it during updateRS. 211 if (!card_region->in_collection_set() && 212 !_ct_bs->is_card_dirty(card_index)) { 213 scanCard(card_index, card_region); 214 } 215 } 216 if (!_try_claimed) { 217 // Scan the strong code root list attached to the current region 218 scan_strong_code_roots(r); 219 220 hrrs->set_iter_complete(); 221 } 222 return false; 223 } 224 225 double strong_code_root_scan_time_sec() { 226 return _strong_code_root_scan_time_sec; 227 } 228 229 size_t cards_done() { return _cards_done;} 230 size_t cards_looked_up() { return _cards;} 231 }; 232 233 void G1RemSet::scanRS(G1ParPushHeapRSClosure* oc, 234 CodeBlobClosure* code_root_cl, 235 uint worker_i) { 236 double rs_time_start = os::elapsedTime(); 237 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i); 238 239 ScanRSClosure scanRScl(oc, code_root_cl, worker_i); 240 241 _g1->collection_set_iterate_from(startRegion, &scanRScl); 242 scanRScl.set_try_claimed(); 243 _g1->collection_set_iterate_from(startRegion, &scanRScl); 244 245 double scan_rs_time_sec = (os::elapsedTime() - rs_time_start) 246 - scanRScl.strong_code_root_scan_time_sec(); 247 248 assert(_cards_scanned != NULL, "invariant"); 249 _cards_scanned[worker_i] = scanRScl.cards_done(); 250 251 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0); 252 _g1p->phase_times()->record_strong_code_root_scan_time(worker_i, 253 scanRScl.strong_code_root_scan_time_sec() * 1000.0); 254 } 255 256 // Closure used for updating RSets and recording references that 257 // point into the collection set. Only called during an 258 // evacuation pause. 259 260 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure { 261 G1RemSet* _g1rs; 262 DirtyCardQueue* _into_cset_dcq; 263 public: 264 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h, 265 DirtyCardQueue* into_cset_dcq) : 266 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq) 267 {} 268 bool do_card_ptr(jbyte* card_ptr, uint worker_i) { 269 // The only time we care about recording cards that 270 // contain references that point into the collection set 271 // is during RSet updating within an evacuation pause. 272 // In this case worker_i should be the id of a GC worker thread. 273 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause"); 274 assert(worker_i < ParallelGCThreads, "should be a GC worker"); 275 276 if (_g1rs->refine_card(card_ptr, worker_i, true)) { 277 // 'card_ptr' contains references that point into the collection 278 // set. We need to record the card in the DCQS 279 // (G1CollectedHeap::into_cset_dirty_card_queue_set()) 280 // that's used for that purpose. 281 // 282 // Enqueue the card 283 _into_cset_dcq->enqueue(card_ptr); 284 } 285 return true; 286 } 287 }; 288 289 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) { 290 double start = os::elapsedTime(); 291 // Apply the given closure to all remaining log entries. 292 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq); 293 294 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i); 295 296 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0); 297 } 298 299 void G1RemSet::cleanupHRRS() { 300 HeapRegionRemSet::cleanup(); 301 } 302 303 void G1RemSet::oops_into_collection_set_do(G1ParPushHeapRSClosure* oc, 304 CodeBlobClosure* code_root_cl, 305 uint worker_i) { 306 #if CARD_REPEAT_HISTO 307 ct_freq_update_histo_and_reset(); 308 #endif 309 310 // We cache the value of 'oc' closure into the appropriate slot in the 311 // _cset_rs_update_cl for this worker 312 assert(worker_i < n_workers(), "sanity"); 313 _cset_rs_update_cl[worker_i] = oc; 314 315 // A DirtyCardQueue that is used to hold cards containing references 316 // that point into the collection set. This DCQ is associated with a 317 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal 318 // circumstances (i.e. the pause successfully completes), these cards 319 // are just discarded (there's no need to update the RSets of regions 320 // that were in the collection set - after the pause these regions 321 // are wholly 'free' of live objects. In the event of an evacuation 322 // failure the cards/buffers in this queue set are passed to the 323 // DirtyCardQueueSet that is used to manage RSet updates 324 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); 325 326 updateRS(&into_cset_dcq, worker_i); 327 scanRS(oc, code_root_cl, worker_i); 328 329 // We now clear the cached values of _cset_rs_update_cl for this worker 330 _cset_rs_update_cl[worker_i] = NULL; 331 } 332 333 void G1RemSet::prepare_for_oops_into_collection_set_do() { 334 cleanupHRRS(); 335 _g1->set_refine_cte_cl_concurrency(false); 336 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 337 dcqs.concatenate_logs(); 338 339 guarantee( _cards_scanned == NULL, "invariant" ); 340 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC); 341 for (uint i = 0; i < n_workers(); ++i) { 342 _cards_scanned[i] = 0; 343 } 344 _total_cards_scanned = 0; 345 } 346 347 void G1RemSet::cleanup_after_oops_into_collection_set_do() { 348 guarantee( _cards_scanned != NULL, "invariant" ); 349 _total_cards_scanned = 0; 350 for (uint i = 0; i < n_workers(); ++i) { 351 _total_cards_scanned += _cards_scanned[i]; 352 } 353 FREE_C_HEAP_ARRAY(size_t, _cards_scanned); 354 _cards_scanned = NULL; 355 // Cleanup after copy 356 _g1->set_refine_cte_cl_concurrency(true); 357 // Set all cards back to clean. 358 _g1->cleanUpCardTable(); 359 360 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set(); 361 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num(); 362 363 if (_g1->evacuation_failed()) { 364 double restore_remembered_set_start = os::elapsedTime(); 365 366 // Restore remembered sets for the regions pointing into the collection set. 367 // We just need to transfer the completed buffers from the DirtyCardQueueSet 368 // used to hold cards that contain references that point into the collection set 369 // to the DCQS used to hold the deferred RS updates. 370 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs); 371 _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0); 372 } 373 374 // Free any completed buffers in the DirtyCardQueueSet used to hold cards 375 // which contain references that point into the collection. 376 _g1->into_cset_dirty_card_queue_set().clear(); 377 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0, 378 "all buffers should be freed"); 379 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers(); 380 } 381 382 class ScrubRSClosure: public HeapRegionClosure { 383 G1CollectedHeap* _g1h; 384 BitMap* _region_bm; 385 BitMap* _card_bm; 386 CardTableModRefBS* _ctbs; 387 public: 388 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) : 389 _g1h(G1CollectedHeap::heap()), 390 _region_bm(region_bm), _card_bm(card_bm), 391 _ctbs(_g1h->g1_barrier_set()) {} 392 393 bool doHeapRegion(HeapRegion* r) { 394 if (!r->is_continues_humongous()) { 395 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm); 396 } 397 return false; 398 } 399 }; 400 401 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm, uint worker_num, HeapRegionClaimer *hrclaimer) { 402 ScrubRSClosure scrub_cl(region_bm, card_bm); 403 _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer); 404 } 405 406 G1TriggerClosure::G1TriggerClosure() : 407 _triggered(false) { } 408 409 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl, 410 OopClosure* oop_cl) : 411 _trigger_cl(t_cl), _oop_cl(oop_cl) { } 412 413 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) : 414 _c1(c1), _c2(c2) { } 415 416 G1UpdateRSOrPushRefOopClosure:: 417 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h, 418 G1RemSet* rs, 419 G1ParPushHeapRSClosure* push_ref_cl, 420 bool record_refs_into_cset, 421 uint worker_i) : 422 _g1(g1h), _g1_rem_set(rs), _from(NULL), 423 _record_refs_into_cset(record_refs_into_cset), 424 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { } 425 426 // Returns true if the given card contains references that point 427 // into the collection set, if we're checking for such references; 428 // false otherwise. 429 430 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i, 431 bool check_for_refs_into_cset) { 432 assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)), 433 err_msg("Card at "PTR_FORMAT" index "SIZE_FORMAT" representing heap at "PTR_FORMAT" (%u) must be in committed heap", 434 p2i(card_ptr), 435 _ct_bs->index_for(_ct_bs->addr_for(card_ptr)), 436 _ct_bs->addr_for(card_ptr), 437 _g1->addr_to_region(_ct_bs->addr_for(card_ptr)))); 438 439 // If the card is no longer dirty, nothing to do. 440 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 441 // No need to return that this card contains refs that point 442 // into the collection set. 443 return false; 444 } 445 446 // Construct the region representing the card. 447 HeapWord* start = _ct_bs->addr_for(card_ptr); 448 // And find the region containing it. 449 HeapRegion* r = _g1->heap_region_containing(start); 450 451 // Why do we have to check here whether a card is on a young region, 452 // given that we dirty young regions and, as a result, the 453 // post-barrier is supposed to filter them out and never to enqueue 454 // them? When we allocate a new region as the "allocation region" we 455 // actually dirty its cards after we release the lock, since card 456 // dirtying while holding the lock was a performance bottleneck. So, 457 // as a result, it is possible for other threads to actually 458 // allocate objects in the region (after the acquire the lock) 459 // before all the cards on the region are dirtied. This is unlikely, 460 // and it doesn't happen often, but it can happen. So, the extra 461 // check below filters out those cards. 462 if (r->is_young()) { 463 return false; 464 } 465 466 // While we are processing RSet buffers during the collection, we 467 // actually don't want to scan any cards on the collection set, 468 // since we don't want to update remembered sets with entries that 469 // point into the collection set, given that live objects from the 470 // collection set are about to move and such entries will be stale 471 // very soon. This change also deals with a reliability issue which 472 // involves scanning a card in the collection set and coming across 473 // an array that was being chunked and looking malformed. Note, 474 // however, that if evacuation fails, we have to scan any objects 475 // that were not moved and create any missing entries. 476 if (r->in_collection_set()) { 477 return false; 478 } 479 480 // The result from the hot card cache insert call is either: 481 // * pointer to the current card 482 // (implying that the current card is not 'hot'), 483 // * null 484 // (meaning we had inserted the card ptr into the "hot" card cache, 485 // which had some headroom), 486 // * a pointer to a "hot" card that was evicted from the "hot" cache. 487 // 488 489 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 490 if (hot_card_cache->use_cache()) { 491 assert(!check_for_refs_into_cset, "sanity"); 492 assert(!SafepointSynchronize::is_at_safepoint(), "sanity"); 493 494 card_ptr = hot_card_cache->insert(card_ptr); 495 if (card_ptr == NULL) { 496 // There was no eviction. Nothing to do. 497 return false; 498 } 499 500 start = _ct_bs->addr_for(card_ptr); 501 r = _g1->heap_region_containing(start); 502 503 // Checking whether the region we got back from the cache 504 // is young here is inappropriate. The region could have been 505 // freed, reallocated and tagged as young while in the cache. 506 // Hence we could see its young type change at any time. 507 } 508 509 // Don't use addr_for(card_ptr + 1) which can ask for 510 // a card beyond the heap. This is not safe without a perm 511 // gen at the upper end of the heap. 512 HeapWord* end = start + CardTableModRefBS::card_size_in_words; 513 MemRegion dirtyRegion(start, end); 514 515 #if CARD_REPEAT_HISTO 516 init_ct_freq_table(_g1->max_capacity()); 517 ct_freq_note_card(_ct_bs->index_for(start)); 518 #endif 519 520 G1ParPushHeapRSClosure* oops_in_heap_closure = NULL; 521 if (check_for_refs_into_cset) { 522 // ConcurrentG1RefineThreads have worker numbers larger than what 523 // _cset_rs_update_cl[] is set up to handle. But those threads should 524 // only be active outside of a collection which means that when they 525 // reach here they should have check_for_refs_into_cset == false. 526 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length"); 527 oops_in_heap_closure = _cset_rs_update_cl[worker_i]; 528 } 529 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1, 530 _g1->g1_rem_set(), 531 oops_in_heap_closure, 532 check_for_refs_into_cset, 533 worker_i); 534 update_rs_oop_cl.set_from(r); 535 536 G1TriggerClosure trigger_cl; 537 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl); 538 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl); 539 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl); 540 541 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r, 542 (check_for_refs_into_cset ? 543 (OopClosure*)&mux : 544 (OopClosure*)&update_rs_oop_cl)); 545 546 // The region for the current card may be a young region. The 547 // current card may have been a card that was evicted from the 548 // card cache. When the card was inserted into the cache, we had 549 // determined that its region was non-young. While in the cache, 550 // the region may have been freed during a cleanup pause, reallocated 551 // and tagged as young. 552 // 553 // We wish to filter out cards for such a region but the current 554 // thread, if we're running concurrently, may "see" the young type 555 // change at any time (so an earlier "is_young" check may pass or 556 // fail arbitrarily). We tell the iteration code to perform this 557 // filtering when it has been determined that there has been an actual 558 // allocation in this region and making it safe to check the young type. 559 bool filter_young = true; 560 561 HeapWord* stop_point = 562 r->oops_on_card_seq_iterate_careful(dirtyRegion, 563 &filter_then_update_rs_oop_cl, 564 filter_young, 565 card_ptr); 566 567 // If stop_point is non-null, then we encountered an unallocated region 568 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the 569 // card and re-enqueue: if we put off the card until a GC pause, then the 570 // unallocated portion will be filled in. Alternatively, we might try 571 // the full complexity of the technique used in "regular" precleaning. 572 if (stop_point != NULL) { 573 // The card might have gotten re-dirtied and re-enqueued while we 574 // worked. (In fact, it's pretty likely.) 575 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 576 *card_ptr = CardTableModRefBS::dirty_card_val(); 577 MutexLockerEx x(Shared_DirtyCardQ_lock, 578 Mutex::_no_safepoint_check_flag); 579 DirtyCardQueue* sdcq = 580 JavaThread::dirty_card_queue_set().shared_dirty_card_queue(); 581 sdcq->enqueue(card_ptr); 582 } 583 } else { 584 _conc_refine_cards++; 585 } 586 587 // This gets set to true if the card being refined has 588 // references that point into the collection set. 589 bool has_refs_into_cset = trigger_cl.triggered(); 590 591 // We should only be detecting that the card contains references 592 // that point into the collection set if the current thread is 593 // a GC worker thread. 594 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(), 595 "invalid result at non safepoint"); 596 597 return has_refs_into_cset; 598 } 599 600 void G1RemSet::print_periodic_summary_info(const char* header) { 601 G1RemSetSummary current; 602 current.initialize(this); 603 604 _prev_period_summary.subtract_from(¤t); 605 print_summary_info(&_prev_period_summary, header); 606 607 _prev_period_summary.set(¤t); 608 } 609 610 void G1RemSet::print_summary_info() { 611 G1RemSetSummary current; 612 current.initialize(this); 613 614 print_summary_info(¤t, " Cumulative RS summary"); 615 } 616 617 void G1RemSet::print_summary_info(G1RemSetSummary * summary, const char * header) { 618 assert(summary != NULL, "just checking"); 619 620 if (header != NULL) { 621 gclog_or_tty->print_cr("%s", header); 622 } 623 624 #if CARD_REPEAT_HISTO 625 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: "); 626 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number."); 627 card_repeat_count.print_on(gclog_or_tty); 628 #endif 629 630 summary->print_on(gclog_or_tty); 631 } 632 633 void G1RemSet::prepare_for_verify() { 634 if (G1HRRSFlushLogBuffersOnVerify && 635 (VerifyBeforeGC || VerifyAfterGC) 636 && (!_g1->full_collection() || G1VerifyRSetsDuringFullGC)) { 637 cleanupHRRS(); 638 _g1->set_refine_cte_cl_concurrency(false); 639 if (SafepointSynchronize::is_at_safepoint()) { 640 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 641 dcqs.concatenate_logs(); 642 } 643 644 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 645 bool use_hot_card_cache = hot_card_cache->use_cache(); 646 hot_card_cache->set_use_cache(false); 647 648 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); 649 updateRS(&into_cset_dcq, 0); 650 _g1->into_cset_dirty_card_queue_set().clear(); 651 652 hot_card_cache->set_use_cache(use_hot_card_cache); 653 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 654 } 655 }