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 "memory/iterator.hpp" 38 #include "oops/oop.inline.hpp" 39 #include "utilities/intHisto.hpp" 40 41 #define CARD_REPEAT_HISTO 0 42 43 #if CARD_REPEAT_HISTO 44 static size_t ct_freq_sz; 45 static jbyte* ct_freq = NULL; 46 47 void init_ct_freq_table(size_t heap_sz_bytes) { 48 if (ct_freq == NULL) { 49 ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size; 50 ct_freq = new jbyte[ct_freq_sz]; 51 for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0; 52 } 53 } 54 55 void ct_freq_note_card(size_t index) { 56 assert(0 <= index && index < ct_freq_sz, "Bounds error."); 57 if (ct_freq[index] < 100) { ct_freq[index]++; } 58 } 59 60 static IntHistogram card_repeat_count(10, 10); 61 62 void ct_freq_update_histo_and_reset() { 63 for (size_t j = 0; j < ct_freq_sz; j++) { 64 card_repeat_count.add_entry(ct_freq[j]); 65 ct_freq[j] = 0; 66 } 67 68 } 69 #endif 70 71 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs) 72 : _g1(g1), _conc_refine_cards(0), 73 _ct_bs(ct_bs), _g1p(_g1->g1_policy()), 74 _cg1r(g1->concurrent_g1_refine()), 75 _cset_rs_update_cl(NULL), 76 _cards_scanned(NULL), _total_cards_scanned(0) 77 { 78 _seq_task = new SubTasksDone(NumSeqTasks); 79 guarantee(n_workers() > 0, "There should be some workers"); 80 _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers(), mtGC); 81 for (uint i = 0; i < n_workers(); i++) { 82 _cset_rs_update_cl[i] = NULL; 83 } 84 } 85 86 G1RemSet::~G1RemSet() { 87 delete _seq_task; 88 for (uint i = 0; i < n_workers(); i++) { 89 assert(_cset_rs_update_cl[i] == NULL, "it should be"); 90 } 91 FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl, mtGC); 92 } 93 94 void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) { 95 if (_g1->is_in_g1_reserved(mr.start())) { 96 _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size)); 97 if (_start_first == NULL) _start_first = mr.start(); 98 } 99 } 100 101 class ScanRSClosure : public HeapRegionClosure { 102 size_t _cards_done, _cards; 103 G1CollectedHeap* _g1h; 104 OopsInHeapRegionClosure* _oc; 105 G1BlockOffsetSharedArray* _bot_shared; 106 CardTableModRefBS *_ct_bs; 107 int _worker_i; 108 int _block_size; 109 bool _try_claimed; 110 public: 111 ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) : 112 _oc(oc), 113 _cards(0), 114 _cards_done(0), 115 _worker_i(worker_i), 116 _try_claimed(false) 117 { 118 _g1h = G1CollectedHeap::heap(); 119 _bot_shared = _g1h->bot_shared(); 120 _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set()); 121 _block_size = MAX2<int>(G1RSetScanBlockSize, 1); 122 } 123 124 void set_try_claimed() { _try_claimed = true; } 125 126 void scanCard(size_t index, HeapRegion *r) { 127 // Stack allocate the DirtyCardToOopClosure instance 128 HeapRegionDCTOC cl(_g1h, r, _oc, 129 CardTableModRefBS::Precise, 130 HeapRegionDCTOC::IntoCSFilterKind); 131 132 // Set the "from" region in the closure. 133 _oc->set_region(r); 134 HeapWord* card_start = _bot_shared->address_for_index(index); 135 HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words; 136 Space *sp = SharedHeap::heap()->space_containing(card_start); 137 MemRegion sm_region = sp->used_region_at_save_marks(); 138 MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end)); 139 if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) { 140 // We make the card as "claimed" lazily (so races are possible 141 // but they're benign), which reduces the number of duplicate 142 // scans (the rsets of the regions in the cset can intersect). 143 _ct_bs->set_card_claimed(index); 144 _cards_done++; 145 cl.do_MemRegion(mr); 146 } 147 } 148 149 void printCard(HeapRegion* card_region, size_t card_index, 150 HeapWord* card_start) { 151 gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") " 152 "RS names card %p: " 153 "[" PTR_FORMAT ", " PTR_FORMAT ")", 154 _worker_i, 155 card_region->bottom(), card_region->end(), 156 card_index, 157 card_start, card_start + G1BlockOffsetSharedArray::N_words); 158 } 159 160 bool doHeapRegion(HeapRegion* r) { 161 assert(r->in_collection_set(), "should only be called on elements of CS."); 162 HeapRegionRemSet* hrrs = r->rem_set(); 163 if (hrrs->iter_is_complete()) return false; // All done. 164 if (!_try_claimed && !hrrs->claim_iter()) return false; 165 // If we ever free the collection set concurrently, we should also 166 // clear the card table concurrently therefore we won't need to 167 // add regions of the collection set to the dirty cards region. 168 _g1h->push_dirty_cards_region(r); 169 // If we didn't return above, then 170 // _try_claimed || r->claim_iter() 171 // is true: either we're supposed to work on claimed-but-not-complete 172 // regions, or we successfully claimed the region. 173 HeapRegionRemSetIterator iter(hrrs); 174 size_t card_index; 175 176 // We claim cards in block so as to recude the contention. The block size is determined by 177 // the G1RSetScanBlockSize parameter. 178 size_t jump_to_card = hrrs->iter_claimed_next(_block_size); 179 for (size_t current_card = 0; iter.has_next(card_index); current_card++) { 180 if (current_card >= jump_to_card + _block_size) { 181 jump_to_card = hrrs->iter_claimed_next(_block_size); 182 } 183 if (current_card < jump_to_card) continue; 184 HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index); 185 #if 0 186 gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n", 187 card_start, card_start + CardTableModRefBS::card_size_in_words); 188 #endif 189 190 HeapRegion* card_region = _g1h->heap_region_containing(card_start); 191 assert(card_region != NULL, "Yielding cards not in the heap?"); 192 _cards++; 193 194 if (!card_region->is_on_dirty_cards_region_list()) { 195 _g1h->push_dirty_cards_region(card_region); 196 } 197 198 // If the card is dirty, then we will scan it during updateRS. 199 if (!card_region->in_collection_set() && 200 !_ct_bs->is_card_dirty(card_index)) { 201 scanCard(card_index, card_region); 202 } 203 } 204 if (!_try_claimed) { 205 hrrs->set_iter_complete(); 206 } 207 return false; 208 } 209 size_t cards_done() { return _cards_done;} 210 size_t cards_looked_up() { return _cards;} 211 }; 212 213 void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) { 214 double rs_time_start = os::elapsedTime(); 215 HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i); 216 217 ScanRSClosure scanRScl(oc, worker_i); 218 219 _g1->collection_set_iterate_from(startRegion, &scanRScl); 220 scanRScl.set_try_claimed(); 221 _g1->collection_set_iterate_from(startRegion, &scanRScl); 222 223 double scan_rs_time_sec = os::elapsedTime() - rs_time_start; 224 225 assert( _cards_scanned != NULL, "invariant" ); 226 _cards_scanned[worker_i] = scanRScl.cards_done(); 227 228 _g1p->phase_times()->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0); 229 } 230 231 // Closure used for updating RSets and recording references that 232 // point into the collection set. Only called during an 233 // evacuation pause. 234 235 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure { 236 G1RemSet* _g1rs; 237 DirtyCardQueue* _into_cset_dcq; 238 public: 239 RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h, 240 DirtyCardQueue* into_cset_dcq) : 241 _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq) 242 {} 243 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 244 // The only time we care about recording cards that 245 // contain references that point into the collection set 246 // is during RSet updating within an evacuation pause. 247 // In this case worker_i should be the id of a GC worker thread. 248 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause"); 249 assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker"); 250 251 if (_g1rs->refine_card(card_ptr, worker_i, true)) { 252 // 'card_ptr' contains references that point into the collection 253 // set. We need to record the card in the DCQS 254 // (G1CollectedHeap::into_cset_dirty_card_queue_set()) 255 // that's used for that purpose. 256 // 257 // Enqueue the card 258 _into_cset_dcq->enqueue(card_ptr); 259 } 260 return true; 261 } 262 }; 263 264 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, int worker_i) { 265 double start = os::elapsedTime(); 266 // Apply the given closure to all remaining log entries. 267 RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq); 268 269 _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i); 270 271 // Now there should be no dirty cards. 272 if (G1RSLogCheckCardTable) { 273 CountNonCleanMemRegionClosure cl(_g1); 274 _ct_bs->mod_card_iterate(&cl); 275 // XXX This isn't true any more: keeping cards of young regions 276 // marked dirty broke it. Need some reasonable fix. 277 guarantee(cl.n() == 0, "Card table should be clean."); 278 } 279 280 _g1p->phase_times()->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0); 281 } 282 283 void G1RemSet::cleanupHRRS() { 284 HeapRegionRemSet::cleanup(); 285 } 286 287 void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc, 288 int worker_i) { 289 #if CARD_REPEAT_HISTO 290 ct_freq_update_histo_and_reset(); 291 #endif 292 293 // We cache the value of 'oc' closure into the appropriate slot in the 294 // _cset_rs_update_cl for this worker 295 assert(worker_i < (int)n_workers(), "sanity"); 296 _cset_rs_update_cl[worker_i] = oc; 297 298 // A DirtyCardQueue that is used to hold cards containing references 299 // that point into the collection set. This DCQ is associated with a 300 // special DirtyCardQueueSet (see g1CollectedHeap.hpp). Under normal 301 // circumstances (i.e. the pause successfully completes), these cards 302 // are just discarded (there's no need to update the RSets of regions 303 // that were in the collection set - after the pause these regions 304 // are wholly 'free' of live objects. In the event of an evacuation 305 // failure the cards/buffers in this queue set are: 306 // * passed to the DirtyCardQueueSet that is used to manage deferred 307 // RSet updates, or 308 // * scanned for references that point into the collection set 309 // and the RSet of the corresponding region in the collection set 310 // is updated immediately. 311 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); 312 313 assert((ParallelGCThreads > 0) || worker_i == 0, "invariant"); 314 315 // The two flags below were introduced temporarily to serialize 316 // the updating and scanning of remembered sets. There are some 317 // race conditions when these two operations are done in parallel 318 // and they are causing failures. When we resolve said race 319 // conditions, we'll revert back to parallel remembered set 320 // updating and scanning. See CRs 6677707 and 6677708. 321 if (G1UseParallelRSetUpdating || (worker_i == 0)) { 322 updateRS(&into_cset_dcq, worker_i); 323 } else { 324 _g1p->phase_times()->record_update_rs_processed_buffers(worker_i, 0); 325 _g1p->phase_times()->record_update_rs_time(worker_i, 0.0); 326 } 327 if (G1UseParallelRSetScanning || (worker_i == 0)) { 328 scanRS(oc, worker_i); 329 } else { 330 _g1p->phase_times()->record_scan_rs_time(worker_i, 0.0); 331 } 332 333 // We now clear the cached values of _cset_rs_update_cl for this worker 334 _cset_rs_update_cl[worker_i] = NULL; 335 } 336 337 void G1RemSet::prepare_for_oops_into_collection_set_do() { 338 cleanupHRRS(); 339 ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine(); 340 _g1->set_refine_cte_cl_concurrency(false); 341 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 342 dcqs.concatenate_logs(); 343 344 if (G1CollectedHeap::use_parallel_gc_threads()) { 345 // Don't set the number of workers here. It will be set 346 // when the task is run 347 // _seq_task->set_n_termination((int)n_workers()); 348 } 349 guarantee( _cards_scanned == NULL, "invariant" ); 350 _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers(), mtGC); 351 for (uint i = 0; i < n_workers(); ++i) { 352 _cards_scanned[i] = 0; 353 } 354 _total_cards_scanned = 0; 355 } 356 357 358 // This closure, applied to a DirtyCardQueueSet, is used to immediately 359 // update the RSets for the regions in the CSet. For each card it iterates 360 // through the oops which coincide with that card. It scans the reference 361 // fields in each oop; when it finds an oop that points into the collection 362 // set, the RSet for the region containing the referenced object is updated. 363 class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure { 364 G1CollectedHeap* _g1; 365 CardTableModRefBS* _ct_bs; 366 public: 367 UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1, 368 CardTableModRefBS* bs): 369 _g1(g1), _ct_bs(bs) 370 { } 371 372 bool do_card_ptr(jbyte* card_ptr, int worker_i) { 373 // Construct the region representing the card. 374 HeapWord* start = _ct_bs->addr_for(card_ptr); 375 // And find the region containing it. 376 HeapRegion* r = _g1->heap_region_containing(start); 377 assert(r != NULL, "unexpected null"); 378 379 // Scan oops in the card looking for references into the collection set 380 // Don't use addr_for(card_ptr + 1) which can ask for 381 // a card beyond the heap. This is not safe without a perm 382 // gen. 383 HeapWord* end = start + CardTableModRefBS::card_size_in_words; 384 MemRegion scanRegion(start, end); 385 386 UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set()); 387 FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl); 388 FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl); 389 390 // We can pass false as the "filter_young" parameter here as: 391 // * we should be in a STW pause, 392 // * the DCQS to which this closure is applied is used to hold 393 // references that point into the collection set from the prior 394 // RSet updating, 395 // * the post-write barrier shouldn't be logging updates to young 396 // regions (but there is a situation where this can happen - see 397 // the comment in G1RemSet::refine_card() below - 398 // that should not be applicable here), and 399 // * during actual RSet updating, the filtering of cards in young 400 // regions in HeapRegion::oops_on_card_seq_iterate_careful is 401 // employed. 402 // As a result, when this closure is applied to "refs into cset" 403 // DCQS, we shouldn't see any cards in young regions. 404 update_rs_cl.set_region(r); 405 HeapWord* stop_point = 406 r->oops_on_card_seq_iterate_careful(scanRegion, 407 &filter_then_update_rs_cset_oop_cl, 408 false /* filter_young */, 409 NULL /* card_ptr */); 410 411 // Since this is performed in the event of an evacuation failure, we 412 // we shouldn't see a non-null stop point 413 assert(stop_point == NULL, "saw an unallocated region"); 414 return true; 415 } 416 }; 417 418 void G1RemSet::cleanup_after_oops_into_collection_set_do() { 419 guarantee( _cards_scanned != NULL, "invariant" ); 420 _total_cards_scanned = 0; 421 for (uint i = 0; i < n_workers(); ++i) { 422 _total_cards_scanned += _cards_scanned[i]; 423 } 424 FREE_C_HEAP_ARRAY(size_t, _cards_scanned, mtGC); 425 _cards_scanned = NULL; 426 // Cleanup after copy 427 _g1->set_refine_cte_cl_concurrency(true); 428 // Set all cards back to clean. 429 _g1->cleanUpCardTable(); 430 431 DirtyCardQueueSet& into_cset_dcqs = _g1->into_cset_dirty_card_queue_set(); 432 int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num(); 433 434 if (_g1->evacuation_failed()) { 435 // Restore remembered sets for the regions pointing into the collection set. 436 437 if (G1DeferredRSUpdate) { 438 // If deferred RS updates are enabled then we just need to transfer 439 // the completed buffers from (a) the DirtyCardQueueSet used to hold 440 // cards that contain references that point into the collection set 441 // to (b) the DCQS used to hold the deferred RS updates 442 _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs); 443 } else { 444 445 CardTableModRefBS* bs = (CardTableModRefBS*)_g1->barrier_set(); 446 UpdateRSetCardTableEntryIntoCSetClosure update_rs_cset_immediate(_g1, bs); 447 448 int n_completed_buffers = 0; 449 while (into_cset_dcqs.apply_closure_to_completed_buffer(&update_rs_cset_immediate, 450 0, 0, true)) { 451 n_completed_buffers++; 452 } 453 assert(n_completed_buffers == into_cset_n_buffers, "missed some buffers"); 454 } 455 } 456 457 // Free any completed buffers in the DirtyCardQueueSet used to hold cards 458 // which contain references that point into the collection. 459 _g1->into_cset_dirty_card_queue_set().clear(); 460 assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0, 461 "all buffers should be freed"); 462 _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers(); 463 } 464 465 class ScrubRSClosure: public HeapRegionClosure { 466 G1CollectedHeap* _g1h; 467 BitMap* _region_bm; 468 BitMap* _card_bm; 469 CardTableModRefBS* _ctbs; 470 public: 471 ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) : 472 _g1h(G1CollectedHeap::heap()), 473 _region_bm(region_bm), _card_bm(card_bm), 474 _ctbs(NULL) 475 { 476 ModRefBarrierSet* bs = _g1h->mr_bs(); 477 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition"); 478 _ctbs = (CardTableModRefBS*)bs; 479 } 480 481 bool doHeapRegion(HeapRegion* r) { 482 if (!r->continuesHumongous()) { 483 r->rem_set()->scrub(_ctbs, _region_bm, _card_bm); 484 } 485 return false; 486 } 487 }; 488 489 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm) { 490 ScrubRSClosure scrub_cl(region_bm, card_bm); 491 _g1->heap_region_iterate(&scrub_cl); 492 } 493 494 void G1RemSet::scrub_par(BitMap* region_bm, BitMap* card_bm, 495 uint worker_num, int claim_val) { 496 ScrubRSClosure scrub_cl(region_bm, card_bm); 497 _g1->heap_region_par_iterate_chunked(&scrub_cl, 498 worker_num, 499 n_workers(), 500 claim_val); 501 } 502 503 G1TriggerClosure::G1TriggerClosure() : 504 _triggered(false) { } 505 506 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl, 507 OopClosure* oop_cl) : 508 _trigger_cl(t_cl), _oop_cl(oop_cl) { } 509 510 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) : 511 _c1(c1), _c2(c2) { } 512 513 G1UpdateRSOrPushRefOopClosure:: 514 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h, 515 G1RemSet* rs, 516 OopsInHeapRegionClosure* push_ref_cl, 517 bool record_refs_into_cset, 518 int worker_i) : 519 _g1(g1h), _g1_rem_set(rs), _from(NULL), 520 _record_refs_into_cset(record_refs_into_cset), 521 _push_ref_cl(push_ref_cl), _worker_i(worker_i) { } 522 523 // Returns true if the given card contains references that point 524 // into the collection set, if we're checking for such references; 525 // false otherwise. 526 527 bool G1RemSet::refine_card(jbyte* card_ptr, int worker_i, 528 bool check_for_refs_into_cset) { 529 530 // If the card is no longer dirty, nothing to do. 531 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 532 // No need to return that this card contains refs that point 533 // into the collection set. 534 return false; 535 } 536 537 // Construct the region representing the card. 538 HeapWord* start = _ct_bs->addr_for(card_ptr); 539 // And find the region containing it. 540 HeapRegion* r = _g1->heap_region_containing(start); 541 if (r == NULL) { 542 // Again no need to return that this card contains refs that 543 // point into the collection set. 544 return false; // Not in the G1 heap (might be in perm, for example.) 545 } 546 547 // Why do we have to check here whether a card is on a young region, 548 // given that we dirty young regions and, as a result, the 549 // post-barrier is supposed to filter them out and never to enqueue 550 // them? When we allocate a new region as the "allocation region" we 551 // actually dirty its cards after we release the lock, since card 552 // dirtying while holding the lock was a performance bottleneck. So, 553 // as a result, it is possible for other threads to actually 554 // allocate objects in the region (after the acquire the lock) 555 // before all the cards on the region are dirtied. This is unlikely, 556 // and it doesn't happen often, but it can happen. So, the extra 557 // check below filters out those cards. 558 if (r->is_young()) { 559 return false; 560 } 561 562 // While we are processing RSet buffers during the collection, we 563 // actually don't want to scan any cards on the collection set, 564 // since we don't want to update remebered sets with entries that 565 // point into the collection set, given that live objects from the 566 // collection set are about to move and such entries will be stale 567 // very soon. This change also deals with a reliability issue which 568 // involves scanning a card in the collection set and coming across 569 // an array that was being chunked and looking malformed. Note, 570 // however, that if evacuation fails, we have to scan any objects 571 // that were not moved and create any missing entries. 572 if (r->in_collection_set()) { 573 return false; 574 } 575 576 // The result from the hot card cache insert call is either: 577 // * pointer to the current card 578 // (implying that the current card is not 'hot'), 579 // * null 580 // (meaning we had inserted the card ptr into the "hot" card cache, 581 // which had some headroom), 582 // * a pointer to a "hot" card that was evicted from the "hot" cache. 583 // 584 585 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 586 if (hot_card_cache->use_cache()) { 587 assert(!check_for_refs_into_cset, "sanity"); 588 assert(!SafepointSynchronize::is_at_safepoint(), "sanity"); 589 590 card_ptr = hot_card_cache->insert(card_ptr); 591 if (card_ptr == NULL) { 592 // There was no eviction. Nothing to do. 593 return false; 594 } 595 596 start = _ct_bs->addr_for(card_ptr); 597 r = _g1->heap_region_containing(start); 598 if (r == NULL) { 599 // Not in the G1 heap 600 return false; 601 } 602 603 // Checking whether the region we got back from the cache 604 // is young here is inappropriate. The region could have been 605 // freed, reallocated and tagged as young while in the cache. 606 // Hence we could see its young type change at any time. 607 } 608 609 // Don't use addr_for(card_ptr + 1) which can ask for 610 // a card beyond the heap. This is not safe without a perm 611 // gen at the upper end of the heap. 612 HeapWord* end = start + CardTableModRefBS::card_size_in_words; 613 MemRegion dirtyRegion(start, end); 614 615 #if CARD_REPEAT_HISTO 616 init_ct_freq_table(_g1->max_capacity()); 617 ct_freq_note_card(_ct_bs->index_for(start)); 618 #endif 619 620 OopsInHeapRegionClosure* oops_in_heap_closure = NULL; 621 if (check_for_refs_into_cset) { 622 // ConcurrentG1RefineThreads have worker numbers larger than what 623 // _cset_rs_update_cl[] is set up to handle. But those threads should 624 // only be active outside of a collection which means that when they 625 // reach here they should have check_for_refs_into_cset == false. 626 assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length"); 627 oops_in_heap_closure = _cset_rs_update_cl[worker_i]; 628 } 629 G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1, 630 _g1->g1_rem_set(), 631 oops_in_heap_closure, 632 check_for_refs_into_cset, 633 worker_i); 634 update_rs_oop_cl.set_from(r); 635 636 G1TriggerClosure trigger_cl; 637 FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl); 638 G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl); 639 G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl); 640 641 FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r, 642 (check_for_refs_into_cset ? 643 (OopClosure*)&mux : 644 (OopClosure*)&update_rs_oop_cl)); 645 646 // The region for the current card may be a young region. The 647 // current card may have been a card that was evicted from the 648 // card cache. When the card was inserted into the cache, we had 649 // determined that its region was non-young. While in the cache, 650 // the region may have been freed during a cleanup pause, reallocated 651 // and tagged as young. 652 // 653 // We wish to filter out cards for such a region but the current 654 // thread, if we're running concurrently, may "see" the young type 655 // change at any time (so an earlier "is_young" check may pass or 656 // fail arbitrarily). We tell the iteration code to perform this 657 // filtering when it has been determined that there has been an actual 658 // allocation in this region and making it safe to check the young type. 659 bool filter_young = true; 660 661 HeapWord* stop_point = 662 r->oops_on_card_seq_iterate_careful(dirtyRegion, 663 &filter_then_update_rs_oop_cl, 664 filter_young, 665 card_ptr); 666 667 // If stop_point is non-null, then we encountered an unallocated region 668 // (perhaps the unfilled portion of a TLAB.) For now, we'll dirty the 669 // card and re-enqueue: if we put off the card until a GC pause, then the 670 // unallocated portion will be filled in. Alternatively, we might try 671 // the full complexity of the technique used in "regular" precleaning. 672 if (stop_point != NULL) { 673 // The card might have gotten re-dirtied and re-enqueued while we 674 // worked. (In fact, it's pretty likely.) 675 if (*card_ptr != CardTableModRefBS::dirty_card_val()) { 676 *card_ptr = CardTableModRefBS::dirty_card_val(); 677 MutexLockerEx x(Shared_DirtyCardQ_lock, 678 Mutex::_no_safepoint_check_flag); 679 DirtyCardQueue* sdcq = 680 JavaThread::dirty_card_queue_set().shared_dirty_card_queue(); 681 sdcq->enqueue(card_ptr); 682 } 683 } else { 684 _conc_refine_cards++; 685 } 686 687 // This gets set to true if the card being refined has 688 // references that point into the collection set. 689 bool has_refs_into_cset = trigger_cl.triggered(); 690 691 // We should only be detecting that the card contains references 692 // that point into the collection set if the current thread is 693 // a GC worker thread. 694 assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(), 695 "invalid result at non safepoint"); 696 697 return has_refs_into_cset; 698 } 699 700 class HRRSStatsIter: public HeapRegionClosure { 701 size_t _occupied; 702 size_t _total_mem_sz; 703 size_t _max_mem_sz; 704 HeapRegion* _max_mem_sz_region; 705 public: 706 HRRSStatsIter() : 707 _occupied(0), 708 _total_mem_sz(0), 709 _max_mem_sz(0), 710 _max_mem_sz_region(NULL) 711 {} 712 713 bool doHeapRegion(HeapRegion* r) { 714 if (r->continuesHumongous()) return false; 715 size_t mem_sz = r->rem_set()->mem_size(); 716 if (mem_sz > _max_mem_sz) { 717 _max_mem_sz = mem_sz; 718 _max_mem_sz_region = r; 719 } 720 _total_mem_sz += mem_sz; 721 size_t occ = r->rem_set()->occupied(); 722 _occupied += occ; 723 return false; 724 } 725 size_t total_mem_sz() { return _total_mem_sz; } 726 size_t max_mem_sz() { return _max_mem_sz; } 727 size_t occupied() { return _occupied; } 728 HeapRegion* max_mem_sz_region() { return _max_mem_sz_region; } 729 }; 730 731 class PrintRSThreadVTimeClosure : public ThreadClosure { 732 public: 733 virtual void do_thread(Thread *t) { 734 ConcurrentG1RefineThread* crt = (ConcurrentG1RefineThread*) t; 735 gclog_or_tty->print(" %5.2f", crt->vtime_accum()); 736 } 737 }; 738 739 void G1RemSet::print_summary_info() { 740 G1CollectedHeap* g1 = G1CollectedHeap::heap(); 741 742 #if CARD_REPEAT_HISTO 743 gclog_or_tty->print_cr("\nG1 card_repeat count histogram: "); 744 gclog_or_tty->print_cr(" # of repeats --> # of cards with that number."); 745 card_repeat_count.print_on(gclog_or_tty); 746 #endif 747 748 gclog_or_tty->print_cr("\n Concurrent RS processed %d cards", 749 _conc_refine_cards); 750 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 751 jint tot_processed_buffers = 752 dcqs.processed_buffers_mut() + dcqs.processed_buffers_rs_thread(); 753 gclog_or_tty->print_cr(" Of %d completed buffers:", tot_processed_buffers); 754 gclog_or_tty->print_cr(" %8d (%5.1f%%) by conc RS threads.", 755 dcqs.processed_buffers_rs_thread(), 756 100.0*(float)dcqs.processed_buffers_rs_thread()/ 757 (float)tot_processed_buffers); 758 gclog_or_tty->print_cr(" %8d (%5.1f%%) by mutator threads.", 759 dcqs.processed_buffers_mut(), 760 100.0*(float)dcqs.processed_buffers_mut()/ 761 (float)tot_processed_buffers); 762 gclog_or_tty->print_cr(" Conc RS threads times(s)"); 763 PrintRSThreadVTimeClosure p; 764 gclog_or_tty->print(" "); 765 g1->concurrent_g1_refine()->threads_do(&p); 766 gclog_or_tty->print_cr(""); 767 768 HRRSStatsIter blk; 769 g1->heap_region_iterate(&blk); 770 gclog_or_tty->print_cr(" Total heap region rem set sizes = "SIZE_FORMAT"K." 771 " Max = "SIZE_FORMAT"K.", 772 blk.total_mem_sz()/K, blk.max_mem_sz()/K); 773 gclog_or_tty->print_cr(" Static structures = "SIZE_FORMAT"K," 774 " free_lists = "SIZE_FORMAT"K.", 775 HeapRegionRemSet::static_mem_size() / K, 776 HeapRegionRemSet::fl_mem_size() / K); 777 gclog_or_tty->print_cr(" "SIZE_FORMAT" occupied cards represented.", 778 blk.occupied()); 779 HeapRegion* max_mem_sz_region = blk.max_mem_sz_region(); 780 HeapRegionRemSet* rem_set = max_mem_sz_region->rem_set(); 781 gclog_or_tty->print_cr(" Max size region = "HR_FORMAT", " 782 "size = "SIZE_FORMAT "K, occupied = "SIZE_FORMAT"K.", 783 HR_FORMAT_PARAMS(max_mem_sz_region), 784 (rem_set->mem_size() + K - 1)/K, 785 (rem_set->occupied() + K - 1)/K); 786 gclog_or_tty->print_cr(" Did %d coarsenings.", 787 HeapRegionRemSet::n_coarsenings()); 788 } 789 790 void G1RemSet::prepare_for_verify() { 791 if (G1HRRSFlushLogBuffersOnVerify && 792 (VerifyBeforeGC || VerifyAfterGC) 793 && !_g1->full_collection()) { 794 cleanupHRRS(); 795 _g1->set_refine_cte_cl_concurrency(false); 796 if (SafepointSynchronize::is_at_safepoint()) { 797 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); 798 dcqs.concatenate_logs(); 799 } 800 801 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache(); 802 bool use_hot_card_cache = hot_card_cache->use_cache(); 803 hot_card_cache->set_use_cache(false); 804 805 DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set()); 806 updateRS(&into_cset_dcq, 0); 807 _g1->into_cset_dirty_card_queue_set().clear(); 808 809 hot_card_cache->set_use_cache(use_hot_card_cache); 810 assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed"); 811 } 812 }