1 /*
   2  * Copyright (c) 2016, 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/g1CollectedHeap.inline.hpp"
  27 #include "gc/g1/g1ConcurrentMark.inline.hpp"
  28 #include "gc/g1/g1CardLiveData.inline.hpp"
  29 #include "gc/g1/suspendibleThreadSet.hpp"
  30 #include "gc/shared/workgroup.hpp"
  31 #include "logging/log.hpp"
  32 #include "memory/universe.hpp"
  33 #include "runtime/atomic.hpp"
  34 #include "runtime/globals.hpp"
  35 #include "runtime/os.hpp"
  36 #include "utilities/bitMap.inline.hpp"
  37 #include "utilities/debug.hpp"
  38 
  39 G1CardLiveData::G1CardLiveData() :
  40   _max_capacity(0),
  41   _cards_per_region(0),
  42   _gc_timestamp_at_create(0),
  43   _live_regions(NULL),
  44   _live_regions_size_in_bits(0),
  45   _live_cards(NULL),
  46   _live_cards_size_in_bits(0) {
  47 }
  48 
  49 G1CardLiveData::~G1CardLiveData()  {
  50   free_large_bitmap(_live_cards, _live_cards_size_in_bits);
  51   free_large_bitmap(_live_regions, _live_regions_size_in_bits);
  52 }
  53 
  54 G1CardLiveData::bm_word_t* G1CardLiveData::allocate_large_bitmap(size_t size_in_bits) {
  55   size_t size_in_words = BitMap::calc_size_in_words(size_in_bits);
  56 
  57   bm_word_t* map = MmapArrayAllocator<bm_word_t, mtGC>::allocate(size_in_words);
  58 
  59   return map;
  60 }
  61 
  62 void G1CardLiveData::free_large_bitmap(bm_word_t* bitmap, size_t size_in_bits) {
  63   MmapArrayAllocator<bm_word_t, mtGC>::free(bitmap, BitMap::calc_size_in_words(size_in_bits));
  64 }
  65 
  66 void G1CardLiveData::initialize(size_t max_capacity, uint num_max_regions) {
  67   assert(max_capacity % num_max_regions == 0,
  68          "Given capacity must be evenly divisible by region size.");
  69   size_t region_size = max_capacity / num_max_regions;
  70   assert(region_size % (G1SATBCardTableModRefBS::card_size * BitsPerWord) == 0,
  71          "Region size must be evenly divisible by area covered by a single word.");
  72   _max_capacity = max_capacity;
  73   _cards_per_region = region_size / G1SATBCardTableModRefBS::card_size;
  74 
  75   _live_regions_size_in_bits = live_region_bitmap_size_in_bits();
  76   _live_regions = allocate_large_bitmap(_live_regions_size_in_bits);
  77   _live_cards_size_in_bits = live_card_bitmap_size_in_bits();
  78   _live_cards = allocate_large_bitmap(_live_cards_size_in_bits);
  79 }
  80 
  81 void G1CardLiveData::pretouch() {
  82   live_cards_bm().pretouch();
  83   live_regions_bm().pretouch();
  84 }
  85 
  86 size_t G1CardLiveData::live_region_bitmap_size_in_bits() const {
  87   return _max_capacity / (_cards_per_region << G1SATBCardTableModRefBS::card_shift);
  88 }
  89 
  90 size_t G1CardLiveData::live_card_bitmap_size_in_bits() const {
  91   return _max_capacity >> G1SATBCardTableModRefBS::card_shift;
  92 }
  93 
  94 // Helper class that provides functionality to generate the Live Data Count
  95 // information.
  96 class G1CardLiveDataHelper VALUE_OBJ_CLASS_SPEC {
  97 private:
  98   BitMapView _region_bm;
  99   BitMapView _card_bm;
 100 
 101   // The card number of the bottom of the G1 heap.
 102   // Used in biasing indices into accounting card bitmaps.
 103   BitMap::idx_t _heap_card_bias;
 104 
 105   // Utility routine to set an exclusive range of bits on the given
 106   // bitmap, optimized for very small ranges.
 107   // There must be at least one bit to set.
 108   void set_card_bitmap_range(BitMap::idx_t start_idx,
 109                              BitMap::idx_t end_idx) {
 110 
 111     // Set the exclusive bit range [start_idx, end_idx).
 112     assert((end_idx - start_idx) > 0, "at least one bit");
 113 
 114     // For small ranges use a simple loop; otherwise use set_range.
 115     // The range is made up of the cards that are spanned by an object/mem
 116     // region so 8 cards will allow up to object sizes up to 4K to be handled
 117     // using the loop.
 118     if ((end_idx - start_idx) <= 8) {
 119       for (BitMap::idx_t i = start_idx; i < end_idx; i += 1) {
 120         _card_bm.set_bit(i);
 121       }
 122     } else {
 123       _card_bm.set_range(start_idx, end_idx);
 124     }
 125   }
 126 
 127   // We cache the last mark set. This avoids setting the same bit multiple times.
 128   // This is particularly interesting for dense bitmaps, as this avoids doing
 129   // lots of work most of the time.
 130   BitMap::idx_t _last_marked_bit_idx;
 131 
 132   void clear_card_bitmap_range(HeapWord* start, HeapWord* end) {
 133     BitMap::idx_t start_idx = card_live_bitmap_index_for(start);
 134     BitMap::idx_t end_idx = card_live_bitmap_index_for(align_ptr_up(end, CardTableModRefBS::card_size));
 135 
 136     _card_bm.clear_range(start_idx, end_idx);
 137   }
 138 
 139   // Mark the card liveness bitmap for the object spanning from start to end.
 140   void mark_card_bitmap_range(HeapWord* start, HeapWord* end) {
 141     BitMap::idx_t start_idx = card_live_bitmap_index_for(start);
 142     BitMap::idx_t end_idx = card_live_bitmap_index_for(align_ptr_up(end, CardTableModRefBS::card_size));
 143 
 144     assert((end_idx - start_idx) > 0, "Trying to mark zero sized range.");
 145 
 146     if (start_idx == _last_marked_bit_idx) {
 147       start_idx++;
 148     }
 149     if (start_idx == end_idx) {
 150       return;
 151     }
 152 
 153     // Set the bits in the card bitmap for the cards spanned by this object.
 154     set_card_bitmap_range(start_idx, end_idx);
 155     _last_marked_bit_idx = end_idx - 1;
 156   }
 157 
 158   void reset_mark_cache() {
 159     _last_marked_bit_idx = (BitMap::idx_t)-1;
 160   }
 161 
 162 public:
 163   // Returns the index in the per-card liveness count bitmap
 164   // for the given address
 165   inline BitMap::idx_t card_live_bitmap_index_for(HeapWord* addr) {
 166     // Below, the term "card num" means the result of shifting an address
 167     // by the card shift -- address 0 corresponds to card number 0.  One
 168     // must subtract the card num of the bottom of the heap to obtain a
 169     // card table index.
 170     BitMap::idx_t card_num = uintptr_t(addr) >> CardTableModRefBS::card_shift;
 171     return card_num - _heap_card_bias;
 172   }
 173 
 174   // Takes a region that's not empty (i.e., it has at least one
 175   // live object in it and sets its corresponding bit on the region
 176   // bitmap to 1.
 177   void set_bit_for_region(HeapRegion* hr) {
 178     _region_bm.par_set_bit(hr->hrm_index());
 179   }
 180 
 181   void reset_live_data(HeapRegion* hr) {
 182     clear_card_bitmap_range(hr->next_top_at_mark_start(), hr->end());
 183   }
 184 
 185   // Mark the range of bits covered by allocations done since the last marking
 186   // in the given heap region, i.e. from NTAMS to top of the given region.
 187   // Returns if there has been some allocation in this region since the last marking.
 188   bool mark_allocated_since_marking(HeapRegion* hr) {
 189     reset_mark_cache();
 190 
 191     HeapWord* ntams = hr->next_top_at_mark_start();
 192     HeapWord* top   = hr->top();
 193 
 194     assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
 195 
 196     // Mark the allocated-since-marking portion...
 197     if (ntams < top) {
 198       mark_card_bitmap_range(ntams, top);
 199       return true;
 200     } else {
 201       return false;
 202     }
 203   }
 204 
 205   // Mark the range of bits covered by live objects on the mark bitmap between
 206   // bottom and NTAMS of the given region.
 207   // Returns the number of live bytes marked within that area for the given
 208   // heap region.
 209   size_t mark_marked_during_marking(G1CMBitMap* mark_bitmap, HeapRegion* hr) {
 210     reset_mark_cache();
 211 
 212     size_t marked_bytes = 0;
 213 
 214     HeapWord* ntams = hr->next_top_at_mark_start();
 215     HeapWord* start = hr->bottom();
 216 
 217     if (ntams <= start) {
 218       // Skip empty regions.
 219       return 0;
 220     }
 221     if (hr->is_humongous()) {
 222       HeapRegion* start_region = hr->humongous_start_region();
 223       if (mark_bitmap->isMarked(start_region->bottom())) {
 224         mark_card_bitmap_range(start, hr->top());
 225         return pointer_delta(hr->top(), start, 1);
 226       } else {
 227         // Humongous start object was actually dead.
 228         return 0;
 229       }
 230     }
 231 
 232     assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
 233            "Preconditions not met - "
 234            "start: " PTR_FORMAT ", ntams: " PTR_FORMAT ", end: " PTR_FORMAT,
 235            p2i(start), p2i(ntams), p2i(hr->end()));
 236 
 237     // Find the first marked object at or after "start".
 238     start = mark_bitmap->getNextMarkedWordAddress(start, ntams);
 239     while (start < ntams) {
 240       oop obj = oop(start);
 241       size_t obj_size = obj->size();
 242       HeapWord* obj_end = start + obj_size;
 243 
 244       assert(obj_end <= hr->end(), "Humongous objects must have been handled elsewhere.");
 245 
 246       mark_card_bitmap_range(start, obj_end);
 247 
 248       // Add the size of this object to the number of marked bytes.
 249       marked_bytes += obj_size * HeapWordSize;
 250 
 251       // Find the next marked object after this one.
 252       start = mark_bitmap->getNextMarkedWordAddress(obj_end, ntams);
 253     }
 254 
 255     return marked_bytes;
 256   }
 257 
 258   G1CardLiveDataHelper(G1CardLiveData* live_data, HeapWord* base_address) :
 259     _region_bm(live_data->live_regions_bm()),
 260     _card_bm(live_data->live_cards_bm()) {
 261     // Calculate the card number for the bottom of the heap. Used
 262     // in biasing indexes into the accounting card bitmaps.
 263     _heap_card_bias =
 264       uintptr_t(base_address) >> CardTableModRefBS::card_shift;
 265   }
 266 };
 267 
 268 class G1CreateCardLiveDataTask: public AbstractGangTask {
 269   // Aggregate the counting data that was constructed concurrently
 270   // with marking.
 271   class G1CreateLiveDataClosure : public HeapRegionClosure {
 272     G1CardLiveDataHelper _helper;
 273 
 274     G1CMBitMap* _mark_bitmap;
 275 
 276     G1ConcurrentMark* _cm;
 277   public:
 278     G1CreateLiveDataClosure(G1CollectedHeap* g1h,
 279                             G1ConcurrentMark* cm,
 280                             G1CMBitMap* mark_bitmap,
 281                             G1CardLiveData* live_data) :
 282       HeapRegionClosure(),
 283       _helper(live_data, g1h->reserved_region().start()),
 284       _mark_bitmap(mark_bitmap),
 285       _cm(cm) { }
 286 
 287     bool doHeapRegion(HeapRegion* hr) {
 288       size_t marked_bytes = _helper.mark_marked_during_marking(_mark_bitmap, hr);
 289       if (marked_bytes > 0) {
 290         hr->add_to_marked_bytes(marked_bytes);
 291       }
 292 
 293       return (_cm->do_yield_check() && _cm->has_aborted());
 294     }
 295   };
 296 
 297   G1ConcurrentMark* _cm;
 298   G1CardLiveData* _live_data;
 299   HeapRegionClaimer _hr_claimer;
 300 
 301 public:
 302   G1CreateCardLiveDataTask(G1CMBitMap* bitmap,
 303                            G1CardLiveData* live_data,
 304                            uint n_workers) :
 305       AbstractGangTask("G1 Create Live Data"),
 306       _live_data(live_data),
 307       _hr_claimer(n_workers) {
 308   }
 309 
 310   void work(uint worker_id) {
 311     SuspendibleThreadSetJoiner sts_join;
 312 
 313     G1CollectedHeap* g1h = G1CollectedHeap::heap();
 314     G1ConcurrentMark* cm = g1h->concurrent_mark();
 315     G1CreateLiveDataClosure cl(g1h, cm, cm->nextMarkBitMap(), _live_data);
 316     g1h->heap_region_par_iterate(&cl, worker_id, &_hr_claimer);
 317   }
 318 };
 319 
 320 void G1CardLiveData::create(WorkGang* workers, G1CMBitMap* mark_bitmap) {
 321   _gc_timestamp_at_create = G1CollectedHeap::heap()->get_gc_time_stamp();
 322 
 323   uint n_workers = workers->active_workers();
 324 
 325   G1CreateCardLiveDataTask cl(mark_bitmap,
 326                               this,
 327                               n_workers);
 328   workers->run_task(&cl);
 329 }
 330 
 331 class G1FinalizeCardLiveDataTask: public AbstractGangTask {
 332   // Finalizes the liveness counting data.
 333   // Sets the bits corresponding to the interval [NTAMS, top]
 334   // (which contains the implicitly live objects) in the
 335   // card liveness bitmap. Also sets the bit for each region
 336   // containing live data, in the region liveness bitmap.
 337   class G1FinalizeCardLiveDataClosure: public HeapRegionClosure {
 338   private:
 339     G1CardLiveDataHelper _helper;
 340 
 341     uint _gc_timestamp_at_create;
 342 
 343     bool has_been_reclaimed(HeapRegion* hr) const {
 344       return hr->get_gc_time_stamp() > _gc_timestamp_at_create;
 345     }
 346   public:
 347     G1FinalizeCardLiveDataClosure(G1CollectedHeap* g1h,
 348                                   G1CMBitMap* bitmap,
 349                                   G1CardLiveData* live_data) :
 350       HeapRegionClosure(),
 351       _helper(live_data, g1h->reserved_region().start()),
 352       _gc_timestamp_at_create(live_data->gc_timestamp_at_create()) { }
 353 
 354     bool doHeapRegion(HeapRegion* hr) {
 355       if (has_been_reclaimed(hr)) {
 356         _helper.reset_live_data(hr);
 357       }
 358       bool allocated_since_marking = _helper.mark_allocated_since_marking(hr);
 359       if (allocated_since_marking || hr->next_marked_bytes() > 0) {
 360         _helper.set_bit_for_region(hr);
 361       }
 362       return false;
 363     }
 364   };
 365 
 366   G1CMBitMap* _bitmap;
 367 
 368   G1CardLiveData* _live_data;
 369 
 370   HeapRegionClaimer _hr_claimer;
 371 
 372 public:
 373   G1FinalizeCardLiveDataTask(G1CMBitMap* bitmap, G1CardLiveData* live_data, uint n_workers) :
 374     AbstractGangTask("G1 Finalize Card Live Data"),
 375     _bitmap(bitmap),
 376     _live_data(live_data),
 377     _hr_claimer(n_workers) {
 378   }
 379 
 380   void work(uint worker_id) {
 381     G1FinalizeCardLiveDataClosure cl(G1CollectedHeap::heap(), _bitmap, _live_data);
 382 
 383     G1CollectedHeap::heap()->heap_region_par_iterate(&cl, worker_id, &_hr_claimer);
 384   }
 385 };
 386 
 387 void G1CardLiveData::finalize(WorkGang* workers, G1CMBitMap* mark_bitmap) {
 388   // Finalize the live data.
 389   G1FinalizeCardLiveDataTask cl(mark_bitmap,
 390                                 this,
 391                                 workers->active_workers());
 392   workers->run_task(&cl);
 393 }
 394 
 395 class G1ClearCardLiveDataTask : public AbstractGangTask {
 396   BitMapView _bitmap;
 397   size_t     _num_chunks;
 398   size_t     _cur_chunk;
 399 public:
 400   G1ClearCardLiveDataTask(const BitMapView& bitmap, size_t num_tasks) :
 401     AbstractGangTask("G1 Clear Card Live Data"),
 402     _bitmap(bitmap),
 403     _num_chunks(num_tasks),
 404     _cur_chunk(0) {
 405   }
 406 
 407   static size_t chunk_size() { return M; }
 408 
 409   virtual void work(uint worker_id) {
 410     while (true) {
 411       size_t to_process = Atomic::add(1, &_cur_chunk) - 1;
 412       if (to_process >= _num_chunks) {
 413         break;
 414       }
 415 
 416       BitMap::idx_t start = M * BitsPerByte * to_process;
 417       BitMap::idx_t end = MIN2(start + M * BitsPerByte, _bitmap.size());
 418       _bitmap.clear_range(start, end);
 419     }
 420   }
 421 };
 422 
 423 void G1CardLiveData::clear(WorkGang* workers) {
 424   guarantee(Universe::is_fully_initialized(), "Should not call this during initialization.");
 425 
 426   size_t const num_chunks = align_size_up(live_cards_bm().size_in_bytes(), G1ClearCardLiveDataTask::chunk_size()) / G1ClearCardLiveDataTask::chunk_size();
 427   uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
 428 
 429   G1ClearCardLiveDataTask cl(live_cards_bm(), num_chunks);
 430 
 431   log_debug(gc, ergo)("Running %s using %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
 432   workers->run_task(&cl, num_workers);
 433 
 434   // The region live bitmap is always very small, even for huge heaps. Clear
 435   // directly.
 436   live_regions_bm().clear();
 437 }
 438 
 439 class G1VerifyCardLiveDataTask: public AbstractGangTask {
 440   // Heap region closure used for verifying the live count data
 441   // that was created concurrently and finalized during
 442   // the remark pause. This closure is applied to the heap
 443   // regions during the STW cleanup pause.
 444   class G1VerifyCardLiveDataClosure: public HeapRegionClosure {
 445   private:
 446     G1CollectedHeap* _g1h;
 447     G1CMBitMap* _mark_bitmap;
 448     G1CardLiveDataHelper _helper;
 449 
 450     G1CardLiveData* _act_live_data;
 451 
 452     G1CardLiveData* _exp_live_data;
 453 
 454     int _failures;
 455 
 456     // Completely recreates the live data count for the given heap region and
 457     // returns the number of bytes marked.
 458     size_t create_live_data_count(HeapRegion* hr) {
 459       size_t bytes_marked = _helper.mark_marked_during_marking(_mark_bitmap, hr);
 460       bool allocated_since_marking = _helper.mark_allocated_since_marking(hr);
 461       if (allocated_since_marking || bytes_marked > 0) {
 462         _helper.set_bit_for_region(hr);
 463       }
 464       return bytes_marked;
 465     }
 466   public:
 467     G1VerifyCardLiveDataClosure(G1CollectedHeap* g1h,
 468                                 G1CMBitMap* mark_bitmap,
 469                                 G1CardLiveData* act_live_data,
 470                                 G1CardLiveData* exp_live_data) :
 471       _g1h(g1h),
 472       _mark_bitmap(mark_bitmap),
 473       _helper(exp_live_data, g1h->reserved_region().start()),
 474       _act_live_data(act_live_data),
 475       _exp_live_data(exp_live_data),
 476       _failures(0) { }
 477 
 478     int failures() const { return _failures; }
 479 
 480     bool doHeapRegion(HeapRegion* hr) {
 481       int failures = 0;
 482 
 483       // Walk the marking bitmap for this region and set the corresponding bits
 484       // in the expected region and card bitmaps.
 485       size_t exp_marked_bytes = create_live_data_count(hr);
 486       size_t act_marked_bytes = hr->next_marked_bytes();
 487       // Verify the marked bytes for this region.
 488 
 489       if (exp_marked_bytes != act_marked_bytes) {
 490         log_error(gc)("Expected marked bytes " SIZE_FORMAT " != actual marked bytes " SIZE_FORMAT " in region %u", exp_marked_bytes, act_marked_bytes, hr->hrm_index());
 491         failures += 1;
 492       } else if (exp_marked_bytes > HeapRegion::GrainBytes) {
 493         log_error(gc)("Expected marked bytes " SIZE_FORMAT " larger than possible " SIZE_FORMAT " in region %u", exp_marked_bytes, HeapRegion::GrainBytes, hr->hrm_index());
 494         failures += 1;
 495       }
 496 
 497       // Verify the bit, for this region, in the actual and expected
 498       // (which was just calculated) region bit maps.
 499       uint index = hr->hrm_index();
 500 
 501       bool expected = _exp_live_data->is_region_live(index);
 502       bool actual = _act_live_data->is_region_live(index);
 503       if (expected != actual) {
 504         log_error(gc)("Expected liveness %d not equal actual %d in region %u", expected, actual, hr->hrm_index());
 505         failures += 1;
 506       }
 507 
 508       // Verify that the card bit maps for the cards spanned by the current
 509       // region match.
 510       BitMap::idx_t start_idx = _helper.card_live_bitmap_index_for(hr->bottom());
 511       BitMap::idx_t end_idx = _helper.card_live_bitmap_index_for(hr->top());
 512 
 513       for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
 514         expected = _exp_live_data->is_card_live_at(i);
 515         actual = _act_live_data->is_card_live_at(i);
 516 
 517         if (expected != actual) {
 518           log_error(gc)("Expected card liveness %d not equal actual card liveness %d at card " SIZE_FORMAT " in region %u", expected, actual, i, hr->hrm_index());
 519           failures += 1;
 520         }
 521       }
 522 
 523       _failures += failures;
 524 
 525       // We could stop iteration over the heap when we
 526       // find the first violating region by returning true.
 527       return false;
 528     }
 529   };
 530 protected:
 531   G1CollectedHeap* _g1h;
 532   G1CMBitMap* _mark_bitmap;
 533 
 534   G1CardLiveData* _act_live_data;
 535 
 536   G1CardLiveData _exp_live_data;
 537 
 538   int  _failures;
 539 
 540   HeapRegionClaimer _hr_claimer;
 541 
 542 public:
 543   G1VerifyCardLiveDataTask(G1CMBitMap* bitmap,
 544                            G1CardLiveData* act_live_data,
 545                            uint n_workers)
 546   : AbstractGangTask("G1 Verify Card Live Data"),
 547     _g1h(G1CollectedHeap::heap()),
 548     _mark_bitmap(bitmap),
 549     _act_live_data(act_live_data),
 550     _exp_live_data(),
 551     _failures(0),
 552     _hr_claimer(n_workers) {
 553     assert(VerifyDuringGC, "don't call this otherwise");
 554     _exp_live_data.initialize(_g1h->max_capacity(), _g1h->max_regions());
 555   }
 556 
 557   void work(uint worker_id) {
 558     G1VerifyCardLiveDataClosure cl(_g1h,
 559                                    _mark_bitmap,
 560                                    _act_live_data,
 561                                    &_exp_live_data);
 562     _g1h->heap_region_par_iterate(&cl, worker_id, &_hr_claimer);
 563 
 564     Atomic::add(cl.failures(), &_failures);
 565   }
 566 
 567   int failures() const { return _failures; }
 568 };
 569 
 570 void G1CardLiveData::verify(WorkGang* workers, G1CMBitMap* actual_bitmap) {
 571     ResourceMark rm;
 572 
 573     G1VerifyCardLiveDataTask cl(actual_bitmap,
 574                                 this,
 575                                 workers->active_workers());
 576     workers->run_task(&cl);
 577 
 578     guarantee(cl.failures() == 0, "Unexpected accounting failures");
 579 }
 580 
 581 #ifndef PRODUCT
 582 void G1CardLiveData::verify_is_clear() {
 583   assert(live_cards_bm().count_one_bits() == 0, "Live cards bitmap must be clear.");
 584   assert(live_regions_bm().count_one_bits() == 0, "Live regions bitmap must be clear.");
 585 }
 586 #endif