1 /*
   2  * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/concurrentG1Refine.hpp"
  27 #include "gc/g1/concurrentG1RefineThread.hpp"
  28 #include "gc/g1/g1BlockOffsetTable.inline.hpp"
  29 #include "gc/g1/g1CollectedHeap.inline.hpp"
  30 #include "gc/g1/g1CollectorPolicy.hpp"
  31 #include "gc/g1/g1GCPhaseTimes.hpp"
  32 #include "gc/g1/g1HotCardCache.hpp"
  33 #include "gc/g1/g1OopClosures.inline.hpp"
  34 #include "gc/g1/g1RemSet.inline.hpp"
  35 #include "gc/g1/heapRegionManager.inline.hpp"
  36 #include "gc/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 #include "utilities/stack.inline.hpp"
  42 
  43 G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs)
  44   : _g1(g1), _conc_refine_cards(0),
  45     _ct_bs(ct_bs), _g1p(_g1->g1_policy()),
  46     _cg1r(g1->concurrent_g1_refine()),
  47     _cset_rs_update_cl(NULL),
  48     _prev_period_summary(),
  49     _into_cset_dirty_card_queue_set(false)
  50 {
  51   _cset_rs_update_cl = NEW_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, n_workers(), mtGC);
  52   for (uint i = 0; i < n_workers(); i++) {
  53     _cset_rs_update_cl[i] = NULL;
  54   }
  55   if (log_is_enabled(Trace, gc, remset)) {
  56     _prev_period_summary.initialize(this);
  57   }
  58   // Initialize the card queue set used to hold cards containing
  59   // references into the collection set.
  60   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
  61                                              DirtyCardQ_CBL_mon,
  62                                              DirtyCardQ_FL_lock,
  63                                              -1, // never trigger processing
  64                                              -1, // no limit on length
  65                                              Shared_DirtyCardQ_lock,
  66                                              &JavaThread::dirty_card_queue_set());
  67 }
  68 
  69 G1RemSet::~G1RemSet() {
  70   for (uint i = 0; i < n_workers(); i++) {
  71     assert(_cset_rs_update_cl[i] == NULL, "it should be");
  72   }
  73   FREE_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, _cset_rs_update_cl);
  74 }
  75 
  76 ScanRSClosure::ScanRSClosure(G1ParPushHeapRSClosure* oc,
  77                              CodeBlobClosure* code_root_cl,
  78                              uint worker_i) :
  79     _oc(oc),
  80     _code_root_cl(code_root_cl),
  81     _strong_code_root_scan_time_sec(0.0),
  82     _cards(0),
  83     _cards_done(0),
  84     _worker_i(worker_i),
  85     _try_claimed(false) {
  86   _g1h = G1CollectedHeap::heap();
  87   _bot_shared = _g1h->bot_shared();
  88   _ct_bs = _g1h->g1_barrier_set();
  89   _block_size = MAX2<size_t>(G1RSetScanBlockSize, 1);
  90 }
  91 
  92 void ScanRSClosure::scanCard(size_t index, HeapRegion *r) {
  93   // Stack allocate the DirtyCardToOopClosure instance
  94   HeapRegionDCTOC cl(_g1h, r, _oc,
  95       CardTableModRefBS::Precise);
  96 
  97   // Set the "from" region in the closure.
  98   _oc->set_region(r);
  99   MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words);
 100   MemRegion pre_gc_allocated(r->bottom(), r->scan_top());
 101   MemRegion mr = pre_gc_allocated.intersection(card_region);
 102   if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
 103     // We make the card as "claimed" lazily (so races are possible
 104     // but they're benign), which reduces the number of duplicate
 105     // scans (the rsets of the regions in the cset can intersect).
 106     _ct_bs->set_card_claimed(index);
 107     _cards_done++;
 108     cl.do_MemRegion(mr);
 109   }
 110 }
 111 
 112 void ScanRSClosure::scan_strong_code_roots(HeapRegion* r) {
 113   double scan_start = os::elapsedTime();
 114   r->strong_code_roots_do(_code_root_cl);
 115   _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
 116 }
 117 
 118 bool ScanRSClosure::doHeapRegion(HeapRegion* r) {
 119   assert(r->in_collection_set(), "should only be called on elements of CS.");
 120   HeapRegionRemSet* hrrs = r->rem_set();
 121   if (hrrs->iter_is_complete()) return false; // All done.
 122   if (!_try_claimed && !hrrs->claim_iter()) return false;
 123   // If we ever free the collection set concurrently, we should also
 124   // clear the card table concurrently therefore we won't need to
 125   // add regions of the collection set to the dirty cards region.
 126   _g1h->push_dirty_cards_region(r);
 127   // If we didn't return above, then
 128   //   _try_claimed || r->claim_iter()
 129   // is true: either we're supposed to work on claimed-but-not-complete
 130   // regions, or we successfully claimed the region.
 131 
 132   HeapRegionRemSetIterator iter(hrrs);
 133   size_t card_index;
 134 
 135   // We claim cards in block so as to reduce the contention. The block size is determined by
 136   // the G1RSetScanBlockSize parameter.
 137   size_t jump_to_card = hrrs->iter_claimed_next(_block_size);
 138   for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
 139     if (current_card >= jump_to_card + _block_size) {
 140       jump_to_card = hrrs->iter_claimed_next(_block_size);
 141     }
 142     if (current_card < jump_to_card) continue;
 143     HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);
 144 
 145     HeapRegion* card_region = _g1h->heap_region_containing(card_start);
 146     _cards++;
 147 
 148     if (!card_region->is_on_dirty_cards_region_list()) {
 149       _g1h->push_dirty_cards_region(card_region);
 150     }
 151 
 152     // If the card is dirty, then we will scan it during updateRS.
 153     if (!card_region->in_collection_set() &&
 154         !_ct_bs->is_card_dirty(card_index)) {
 155       scanCard(card_index, card_region);
 156     }
 157   }
 158   if (!_try_claimed) {
 159     // Scan the strong code root list attached to the current region
 160     scan_strong_code_roots(r);
 161 
 162     hrrs->set_iter_complete();
 163   }
 164   return false;
 165 }
 166 
 167 size_t G1RemSet::scanRS(G1ParPushHeapRSClosure* oc,
 168                         CodeBlobClosure* heap_region_codeblobs,
 169                         uint worker_i) {
 170   double rs_time_start = os::elapsedTime();
 171 
 172   HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);
 173 
 174   ScanRSClosure scanRScl(oc, heap_region_codeblobs, worker_i);
 175 
 176   _g1->collection_set_iterate_from(startRegion, &scanRScl);
 177   scanRScl.set_try_claimed();
 178   _g1->collection_set_iterate_from(startRegion, &scanRScl);
 179 
 180   double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)
 181                             - scanRScl.strong_code_root_scan_time_sec();
 182 
 183   _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, scan_rs_time_sec);
 184   _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::CodeRoots, worker_i, scanRScl.strong_code_root_scan_time_sec());
 185 
 186   return scanRScl.cards_done();
 187 }
 188 
 189 // Closure used for updating RSets and recording references that
 190 // point into the collection set. Only called during an
 191 // evacuation pause.
 192 
 193 class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {
 194   G1RemSet* _g1rs;
 195   DirtyCardQueue* _into_cset_dcq;
 196 public:
 197   RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,
 198                                               DirtyCardQueue* into_cset_dcq) :
 199     _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)
 200   {}
 201 
 202   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 203     // The only time we care about recording cards that
 204     // contain references that point into the collection set
 205     // is during RSet updating within an evacuation pause.
 206     // In this case worker_i should be the id of a GC worker thread.
 207     assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
 208     assert(worker_i < ParallelGCThreads, "should be a GC worker");
 209 
 210     if (_g1rs->refine_card(card_ptr, worker_i, true)) {
 211       // 'card_ptr' contains references that point into the collection
 212       // set. We need to record the card in the DCQS
 213       // (_into_cset_dirty_card_queue_set)
 214       // that's used for that purpose.
 215       //
 216       // Enqueue the card
 217       _into_cset_dcq->enqueue(card_ptr);
 218     }
 219     return true;
 220   }
 221 };
 222 
 223 void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {
 224   RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);
 225 
 226   G1GCParPhaseTimesTracker x(_g1p->phase_times(), G1GCPhaseTimes::UpdateRS, worker_i);
 227   {
 228     // Apply the closure to the entries of the hot card cache.
 229     G1GCParPhaseTimesTracker y(_g1p->phase_times(), G1GCPhaseTimes::ScanHCC, worker_i);
 230     _g1->iterate_hcc_closure(&into_cset_update_rs_cl, worker_i);
 231   }
 232   // Apply the closure to all remaining log entries.
 233   _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, worker_i);
 234 }
 235 
 236 void G1RemSet::cleanupHRRS() {
 237   HeapRegionRemSet::cleanup();
 238 }
 239 
 240 size_t G1RemSet::oops_into_collection_set_do(G1ParPushHeapRSClosure* oc,
 241                                              CodeBlobClosure* heap_region_codeblobs,
 242                                              uint worker_i) {
 243   // We cache the value of 'oc' closure into the appropriate slot in the
 244   // _cset_rs_update_cl for this worker
 245   assert(worker_i < n_workers(), "sanity");
 246   _cset_rs_update_cl[worker_i] = oc;
 247 
 248   // A DirtyCardQueue that is used to hold cards containing references
 249   // that point into the collection set. This DCQ is associated with a
 250   // special DirtyCardQueueSet (see g1CollectedHeap.hpp).  Under normal
 251   // circumstances (i.e. the pause successfully completes), these cards
 252   // are just discarded (there's no need to update the RSets of regions
 253   // that were in the collection set - after the pause these regions
 254   // are wholly 'free' of live objects. In the event of an evacuation
 255   // failure the cards/buffers in this queue set are passed to the
 256   // DirtyCardQueueSet that is used to manage RSet updates
 257   DirtyCardQueue into_cset_dcq(&_into_cset_dirty_card_queue_set);
 258 
 259   updateRS(&into_cset_dcq, worker_i);
 260   size_t cards_scanned = scanRS(oc, heap_region_codeblobs, worker_i);
 261 
 262   // We now clear the cached values of _cset_rs_update_cl for this worker
 263   _cset_rs_update_cl[worker_i] = NULL;
 264   return cards_scanned;
 265 }
 266 
 267 void G1RemSet::prepare_for_oops_into_collection_set_do() {
 268   _g1->set_refine_cte_cl_concurrency(false);
 269   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 270   dcqs.concatenate_logs();
 271 }
 272 
 273 void G1RemSet::cleanup_after_oops_into_collection_set_do() {
 274   // Cleanup after copy
 275   _g1->set_refine_cte_cl_concurrency(true);
 276   // Set all cards back to clean.
 277   _g1->cleanUpCardTable();
 278 
 279   DirtyCardQueueSet& into_cset_dcqs = _into_cset_dirty_card_queue_set;
 280   int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();
 281 
 282   if (_g1->evacuation_failed()) {
 283     double restore_remembered_set_start = os::elapsedTime();
 284 
 285     // Restore remembered sets for the regions pointing into the collection set.
 286     // We just need to transfer the completed buffers from the DirtyCardQueueSet
 287     // used to hold cards that contain references that point into the collection set
 288     // to the DCQS used to hold the deferred RS updates.
 289     _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);
 290     _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);
 291   }
 292 
 293   // Free any completed buffers in the DirtyCardQueueSet used to hold cards
 294   // which contain references that point into the collection.
 295   _into_cset_dirty_card_queue_set.clear();
 296   assert(_into_cset_dirty_card_queue_set.completed_buffers_num() == 0,
 297          "all buffers should be freed");
 298   _into_cset_dirty_card_queue_set.clear_n_completed_buffers();
 299 }
 300 
 301 class ScrubRSClosure: public HeapRegionClosure {
 302   G1CollectedHeap* _g1h;
 303   BitMap* _region_bm;
 304   BitMap* _card_bm;
 305   CardTableModRefBS* _ctbs;
 306 public:
 307   ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :
 308     _g1h(G1CollectedHeap::heap()),
 309     _region_bm(region_bm), _card_bm(card_bm),
 310     _ctbs(_g1h->g1_barrier_set()) {}
 311 
 312   bool doHeapRegion(HeapRegion* r) {
 313     if (!r->is_continues_humongous()) {
 314       r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);
 315     }
 316     return false;
 317   }
 318 };
 319 
 320 void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm, uint worker_num, HeapRegionClaimer *hrclaimer) {
 321   ScrubRSClosure scrub_cl(region_bm, card_bm);
 322   _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
 323 }
 324 
 325 G1TriggerClosure::G1TriggerClosure() :
 326   _triggered(false) { }
 327 
 328 G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,
 329                                                              OopClosure* oop_cl)  :
 330   _trigger_cl(t_cl), _oop_cl(oop_cl) { }
 331 
 332 G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :
 333   _c1(c1), _c2(c2) { }
 334 
 335 G1UpdateRSOrPushRefOopClosure::
 336 G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,
 337                               G1RemSet* rs,
 338                               G1ParPushHeapRSClosure* push_ref_cl,
 339                               bool record_refs_into_cset,
 340                               uint worker_i) :
 341   _g1(g1h), _g1_rem_set(rs), _from(NULL),
 342   _record_refs_into_cset(record_refs_into_cset),
 343   _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }
 344 
 345 // Returns true if the given card contains references that point
 346 // into the collection set, if we're checking for such references;
 347 // false otherwise.
 348 
 349 bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,
 350                            bool check_for_refs_into_cset) {
 351   assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),
 352          "Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap",
 353          p2i(card_ptr),
 354          _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),
 355          p2i(_ct_bs->addr_for(card_ptr)),
 356          _g1->addr_to_region(_ct_bs->addr_for(card_ptr)));
 357 
 358   // If the card is no longer dirty, nothing to do.
 359   if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 360     // No need to return that this card contains refs that point
 361     // into the collection set.
 362     return false;
 363   }
 364 
 365   // Construct the region representing the card.
 366   HeapWord* start = _ct_bs->addr_for(card_ptr);
 367   // And find the region containing it.
 368   HeapRegion* r = _g1->heap_region_containing(start);
 369 
 370   // Why do we have to check here whether a card is on a young region,
 371   // given that we dirty young regions and, as a result, the
 372   // post-barrier is supposed to filter them out and never to enqueue
 373   // them? When we allocate a new region as the "allocation region" we
 374   // actually dirty its cards after we release the lock, since card
 375   // dirtying while holding the lock was a performance bottleneck. So,
 376   // as a result, it is possible for other threads to actually
 377   // allocate objects in the region (after the acquire the lock)
 378   // before all the cards on the region are dirtied. This is unlikely,
 379   // and it doesn't happen often, but it can happen. So, the extra
 380   // check below filters out those cards.
 381   if (r->is_young()) {
 382     return false;
 383   }
 384 
 385   // While we are processing RSet buffers during the collection, we
 386   // actually don't want to scan any cards on the collection set,
 387   // since we don't want to update remembered sets with entries that
 388   // point into the collection set, given that live objects from the
 389   // collection set are about to move and such entries will be stale
 390   // very soon. This change also deals with a reliability issue which
 391   // involves scanning a card in the collection set and coming across
 392   // an array that was being chunked and looking malformed. Note,
 393   // however, that if evacuation fails, we have to scan any objects
 394   // that were not moved and create any missing entries.
 395   if (r->in_collection_set()) {
 396     return false;
 397   }
 398 
 399   // The result from the hot card cache insert call is either:
 400   //   * pointer to the current card
 401   //     (implying that the current card is not 'hot'),
 402   //   * null
 403   //     (meaning we had inserted the card ptr into the "hot" card cache,
 404   //     which had some headroom),
 405   //   * a pointer to a "hot" card that was evicted from the "hot" cache.
 406   //
 407 
 408   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 409   if (hot_card_cache->use_cache()) {
 410     assert(!check_for_refs_into_cset, "sanity");
 411     assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
 412 
 413     card_ptr = hot_card_cache->insert(card_ptr);
 414     if (card_ptr == NULL) {
 415       // There was no eviction. Nothing to do.
 416       return false;
 417     }
 418 
 419     start = _ct_bs->addr_for(card_ptr);
 420     r = _g1->heap_region_containing(start);
 421 
 422     // Checking whether the region we got back from the cache
 423     // is young here is inappropriate. The region could have been
 424     // freed, reallocated and tagged as young while in the cache.
 425     // Hence we could see its young type change at any time.
 426   }
 427 
 428   // Don't use addr_for(card_ptr + 1) which can ask for
 429   // a card beyond the heap.  This is not safe without a perm
 430   // gen at the upper end of the heap.
 431   HeapWord* end   = start + CardTableModRefBS::card_size_in_words;
 432   MemRegion dirtyRegion(start, end);
 433 
 434   G1ParPushHeapRSClosure* oops_in_heap_closure = NULL;
 435   if (check_for_refs_into_cset) {
 436     // ConcurrentG1RefineThreads have worker numbers larger than what
 437     // _cset_rs_update_cl[] is set up to handle. But those threads should
 438     // only be active outside of a collection which means that when they
 439     // reach here they should have check_for_refs_into_cset == false.
 440     assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");
 441     oops_in_heap_closure = _cset_rs_update_cl[worker_i];
 442   }
 443   G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
 444                                                  _g1->g1_rem_set(),
 445                                                  oops_in_heap_closure,
 446                                                  check_for_refs_into_cset,
 447                                                  worker_i);
 448   update_rs_oop_cl.set_from(r);
 449 
 450   G1TriggerClosure trigger_cl;
 451   FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
 452   G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
 453   G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);
 454 
 455   FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,
 456                         (check_for_refs_into_cset ?
 457                                 (OopClosure*)&mux :
 458                                 (OopClosure*)&update_rs_oop_cl));
 459 
 460   // The region for the current card may be a young region. The
 461   // current card may have been a card that was evicted from the
 462   // card cache. When the card was inserted into the cache, we had
 463   // determined that its region was non-young. While in the cache,
 464   // the region may have been freed during a cleanup pause, reallocated
 465   // and tagged as young.
 466   //
 467   // We wish to filter out cards for such a region but the current
 468   // thread, if we're running concurrently, may "see" the young type
 469   // change at any time (so an earlier "is_young" check may pass or
 470   // fail arbitrarily). We tell the iteration code to perform this
 471   // filtering when it has been determined that there has been an actual
 472   // allocation in this region and making it safe to check the young type.
 473   bool filter_young = true;
 474 
 475   HeapWord* stop_point =
 476     r->oops_on_card_seq_iterate_careful(dirtyRegion,
 477                                         &filter_then_update_rs_oop_cl,
 478                                         filter_young,
 479                                         card_ptr);
 480 
 481   // If stop_point is non-null, then we encountered an unallocated region
 482   // (perhaps the unfilled portion of a TLAB.)  For now, we'll dirty the
 483   // card and re-enqueue: if we put off the card until a GC pause, then the
 484   // unallocated portion will be filled in.  Alternatively, we might try
 485   // the full complexity of the technique used in "regular" precleaning.
 486   if (stop_point != NULL) {
 487     // The card might have gotten re-dirtied and re-enqueued while we
 488     // worked.  (In fact, it's pretty likely.)
 489     if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
 490       *card_ptr = CardTableModRefBS::dirty_card_val();
 491       MutexLockerEx x(Shared_DirtyCardQ_lock,
 492                       Mutex::_no_safepoint_check_flag);
 493       DirtyCardQueue* sdcq =
 494         JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
 495       sdcq->enqueue(card_ptr);
 496     }
 497   } else {
 498     _conc_refine_cards++;
 499   }
 500 
 501   // This gets set to true if the card being refined has
 502   // references that point into the collection set.
 503   bool has_refs_into_cset = trigger_cl.triggered();
 504 
 505   // We should only be detecting that the card contains references
 506   // that point into the collection set if the current thread is
 507   // a GC worker thread.
 508   assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
 509            "invalid result at non safepoint");
 510 
 511   return has_refs_into_cset;
 512 }
 513 
 514 void G1RemSet::print_periodic_summary_info(const char* header, uint period_count) {
 515   if ((G1SummarizeRSetStatsPeriod > 0) && log_is_enabled(Trace, gc, remset) &&
 516       (period_count % G1SummarizeRSetStatsPeriod == 0)) {
 517 
 518     if (!_prev_period_summary.initialized()) {
 519       _prev_period_summary.initialize(this);
 520     }
 521 
 522     G1RemSetSummary current;
 523     current.initialize(this);
 524     _prev_period_summary.subtract_from(&current);
 525 
 526     LogHandle(gc, remset) log;
 527     log.trace("%s", header);
 528     ResourceMark rm;
 529     _prev_period_summary.print_on(log.trace_stream());
 530 
 531     _prev_period_summary.set(&current);
 532   }
 533 }
 534 
 535 void G1RemSet::print_summary_info() {
 536   LogHandle(gc, remset, exit) log;
 537   if (log.is_trace()) {
 538     log.trace(" Cumulative RS summary");
 539     G1RemSetSummary current;
 540     current.initialize(this);
 541     ResourceMark rm;
 542     current.print_on(log.trace_stream());
 543   }
 544 }
 545 
 546 void G1RemSet::prepare_for_verify() {
 547   if (G1HRRSFlushLogBuffersOnVerify &&
 548       (VerifyBeforeGC || VerifyAfterGC)
 549       &&  (!_g1->collector_state()->full_collection() || G1VerifyRSetsDuringFullGC)) {
 550     cleanupHRRS();
 551     _g1->set_refine_cte_cl_concurrency(false);
 552     if (SafepointSynchronize::is_at_safepoint()) {
 553       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 554       dcqs.concatenate_logs();
 555     }
 556 
 557     G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
 558     bool use_hot_card_cache = hot_card_cache->use_cache();
 559     hot_card_cache->set_use_cache(false);
 560 
 561     DirtyCardQueue into_cset_dcq(&_into_cset_dirty_card_queue_set);
 562     updateRS(&into_cset_dcq, 0);
 563     _into_cset_dirty_card_queue_set.clear();
 564 
 565     hot_card_cache->set_use_cache(use_hot_card_cache);
 566     assert(JavaThread::dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
 567   }
 568 }