1 /*
   2  * Copyright (c) 2016, 2019, 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/g1CollectionSet.hpp"
  28 #include "gc/g1/g1CollectionSetCandidates.hpp"
  29 #include "gc/g1/g1CollectorState.hpp"
  30 #include "gc/g1/g1HotCardCache.hpp"
  31 #include "gc/g1/g1ParScanThreadState.hpp"
  32 #include "gc/g1/g1Policy.hpp"
  33 #include "gc/g1/heapRegion.inline.hpp"
  34 #include "gc/g1/heapRegionRemSet.hpp"
  35 #include "gc/g1/heapRegionSet.hpp"
  36 #include "logging/logStream.hpp"
  37 #include "runtime/orderAccess.hpp"
  38 #include "utilities/debug.hpp"
  39 #include "utilities/globalDefinitions.hpp"
  40 #include "utilities/quickSort.hpp"
  41 
  42 G1CollectorState* G1CollectionSet::collector_state() const {
  43   return _g1h->collector_state();
  44 }
  45 
  46 G1GCPhaseTimes* G1CollectionSet::phase_times() {
  47   return _policy->phase_times();
  48 }
  49 
  50 double G1CollectionSet::predict_region_non_copy_time_ms(HeapRegion* hr) const {
  51   return _policy->predict_region_non_copy_time_ms(hr, collector_state()->in_young_only_phase());
  52 }
  53 
  54 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :
  55   _g1h(g1h),
  56   _policy(policy),
  57   _candidates(NULL),
  58   _eden_region_length(0),
  59   _survivor_region_length(0),
  60   _old_region_length(0),
  61   _collection_set_regions(NULL),
  62   _collection_set_cur_length(0),
  63   _collection_set_max_length(0),
  64   _num_optional_regions(0),
  65   _bytes_used_before(0),
  66   _recorded_rs_length(0),
  67   _inc_build_state(Inactive),
  68   _inc_part_start(0),
  69   _inc_collection_set_stats(NULL),
  70   _inc_bytes_used_before(0),
  71   _inc_recorded_rs_length(0),
  72   _inc_recorded_rs_length_diff(0),
  73   _inc_predicted_non_copy_time_ms(0.0),
  74   _inc_predicted_non_copy_time_ms_diff(0.0) {
  75 }
  76 
  77 G1CollectionSet::~G1CollectionSet() {
  78   FREE_C_HEAP_ARRAY(uint, _collection_set_regions);
  79   FREE_C_HEAP_ARRAY(IncCollectionSetRegionStat, _inc_collection_set_stats);
  80   free_optional_regions();
  81   clear_candidates();
  82 }
  83 
  84 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
  85                                           uint survivor_cset_region_length) {
  86   assert_at_safepoint_on_vm_thread();
  87 
  88   _eden_region_length     = eden_cset_region_length;
  89   _survivor_region_length = survivor_cset_region_length;
  90 
  91   assert((size_t) young_region_length() == _collection_set_cur_length,
  92          "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length);
  93 
  94   _old_region_length = 0;
  95   free_optional_regions();
  96 }
  97 
  98 void G1CollectionSet::initialize(uint max_region_length) {
  99   guarantee(_collection_set_regions == NULL, "Must only initialize once.");
 100   _collection_set_max_length = max_region_length;
 101   _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC);
 102   _inc_collection_set_stats = NEW_C_HEAP_ARRAY(IncCollectionSetRegionStat, max_region_length, mtGC);
 103 }
 104 
 105 void G1CollectionSet::free_optional_regions() {
 106   _num_optional_regions = 0;
 107 }
 108 
 109 void G1CollectionSet::clear_candidates() {
 110   delete _candidates;
 111   _candidates = NULL;
 112 }
 113 
 114 void G1CollectionSet::set_recorded_rs_length(size_t rs_length) {
 115   _recorded_rs_length = rs_length;
 116 }
 117 
 118 // Add the heap region at the head of the non-incremental collection set
 119 void G1CollectionSet::add_old_region(HeapRegion* hr) {
 120   assert_at_safepoint_on_vm_thread();
 121 
 122   assert(_inc_build_state == Active,
 123          "Precondition, actively building cset or adding optional later on");
 124   assert(hr->is_old(), "the region should be old");
 125 
 126   assert(!hr->in_collection_set(), "should not already be in the collection set");
 127   _g1h->register_old_region_with_region_attr(hr);
 128 
 129   _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();
 130   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size.");
 131 
 132   _bytes_used_before += hr->used();
 133   _recorded_rs_length += hr->rem_set()->occupied();
 134   _old_region_length++;
 135 
 136   _g1h->old_set_remove(hr);
 137 }
 138 
 139 void G1CollectionSet::add_optional_region(HeapRegion* hr) {
 140   assert(hr->is_old(), "the region should be old");
 141   assert(!hr->in_collection_set(), "should not already be in the CSet");
 142 
 143   _g1h->register_optional_region_with_region_attr(hr);
 144 
 145   hr->set_index_in_opt_cset(_num_optional_regions++);
 146 }
 147 
 148 void G1CollectionSet::start_incremental_building() {
 149   assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");
 150   assert(_inc_build_state == Inactive, "Precondition");
 151 #ifdef ASSERT
 152   for (size_t i = 0; i < _collection_set_max_length; i++) {
 153     _inc_collection_set_stats[i].reset();
 154   }
 155 #endif
 156 
 157   _inc_bytes_used_before = 0;
 158 
 159   _inc_recorded_rs_length = 0;
 160   _inc_recorded_rs_length_diff = 0;
 161   _inc_predicted_non_copy_time_ms = 0.0;
 162   _inc_predicted_non_copy_time_ms_diff = 0.0;
 163 
 164   update_incremental_marker();
 165 }
 166 
 167 void G1CollectionSet::finalize_incremental_building() {
 168   assert(_inc_build_state == Active, "Precondition");
 169   assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
 170 
 171   // The two "main" fields, _inc_recorded_rs_length and
 172   // _inc_predicted_non_copy_time_ms, are updated by the thread
 173   // that adds a new region to the CSet. Further updates by the
 174   // concurrent refinement thread that samples the young RSet lengths
 175   // are accumulated in the *_diff fields. Here we add the diffs to
 176   // the "main" fields.
 177 
 178   _inc_recorded_rs_length += _inc_recorded_rs_length_diff;
 179   _inc_predicted_non_copy_time_ms += _inc_predicted_non_copy_time_ms_diff;
 180 
 181   _inc_recorded_rs_length_diff = 0;
 182   _inc_predicted_non_copy_time_ms_diff = 0.0;
 183 }
 184 
 185 void G1CollectionSet::clear() {
 186   assert_at_safepoint_on_vm_thread();
 187   _collection_set_cur_length = 0;
 188 }
 189 
 190 void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
 191   size_t len = _collection_set_cur_length;
 192   OrderAccess::loadload();
 193 
 194   for (uint i = 0; i < len; i++) {
 195     HeapRegion* r = _g1h->region_at(_collection_set_regions[i]);
 196     bool result = cl->do_heap_region(r);
 197     if (result) {
 198       cl->set_incomplete();
 199       return;
 200     }
 201   }
 202 }
 203 
 204 void G1CollectionSet::iterate_optional(HeapRegionClosure* cl) const {
 205   assert_at_safepoint();
 206 
 207   for (uint i = 0; i < _num_optional_regions; i++) {
 208     HeapRegion* r = _candidates->at(i);
 209     bool result = cl->do_heap_region(r);
 210     guarantee(!result, "Must not cancel iteration");
 211   }
 212 }
 213 
 214 void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl,
 215                                                     HeapRegionClaimer* hr_claimer,
 216                                                     uint worker_id,
 217                                                     uint total_workers) const {
 218   assert_at_safepoint();
 219 
 220   size_t len = increment_length();
 221   if (len == 0) {
 222     return;
 223   }
 224 
 225   size_t start_pos = (worker_id * len) / total_workers;
 226   size_t cur_pos = start_pos;
 227 
 228   do {
 229     uint region_idx = _collection_set_regions[cur_pos + _inc_part_start];
 230     if (hr_claimer == NULL || hr_claimer->claim_region(region_idx)) {
 231       HeapRegion* r = _g1h->region_at(region_idx);
 232       bool result = cl->do_heap_region(r);
 233       guarantee(!result, "Must not cancel iteration");
 234     }
 235 
 236     cur_pos++;
 237     if (cur_pos == len) {
 238       cur_pos = 0;
 239     }
 240   } while (cur_pos != start_pos);
 241 }
 242 
 243 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
 244                                                      size_t new_rs_length) {
 245   // Update the CSet information that is dependent on the new RS length
 246   assert(hr->is_young(), "Precondition");
 247   assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
 248 
 249   IncCollectionSetRegionStat* stat = &_inc_collection_set_stats[hr->hrm_index()];
 250 
 251   size_t old_rs_length = stat->_rs_length;
 252   assert(old_rs_length <= new_rs_length,
 253          "Remembered set decreased (changed from " SIZE_FORMAT " to " SIZE_FORMAT " region %u type %s)",
 254          old_rs_length, new_rs_length, hr->hrm_index(), hr->get_short_type_str());
 255   size_t rs_length_diff = new_rs_length - old_rs_length;
 256   stat->_rs_length = new_rs_length;
 257   _inc_recorded_rs_length_diff += rs_length_diff;
 258 
 259   double old_non_copy_time = stat->_non_copy_time_ms;
 260   assert(old_non_copy_time >= 0.0, "Non copy time for region %u not initialized yet, is %.3f", hr->hrm_index(), old_non_copy_time);
 261   double new_non_copy_time = predict_region_non_copy_time_ms(hr);
 262   double non_copy_time_ms_diff = new_non_copy_time - old_non_copy_time;
 263 
 264   stat->_non_copy_time_ms = new_non_copy_time;
 265   _inc_predicted_non_copy_time_ms_diff += non_copy_time_ms_diff;
 266 }
 267 
 268 void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
 269   assert(hr->is_young(), "invariant");
 270   assert(_inc_build_state == Active, "Precondition");
 271 
 272   // This routine is used when:
 273   // * adding survivor regions to the incremental cset at the end of an
 274   //   evacuation pause or
 275   // * adding the current allocation region to the incremental cset
 276   //   when it is retired.
 277   // Therefore this routine may be called at a safepoint by the
 278   // VM thread, or in-between safepoints by mutator threads (when
 279   // retiring the current allocation region)
 280   // We need to clear and set the cached recorded/cached collection set
 281   // information in the heap region here (before the region gets added
 282   // to the collection set). An individual heap region's cached values
 283   // are calculated, aggregated with the policy collection set info,
 284   // and cached in the heap region here (initially) and (subsequently)
 285   // by the Young List sampling code.
 286   // Ignore calls to this due to retirement during full gc.
 287 
 288   if (!_g1h->collector_state()->in_full_gc()) {
 289     size_t rs_length = hr->rem_set()->occupied();
 290     double non_copy_time = predict_region_non_copy_time_ms(hr);
 291 
 292     // Cache the values we have added to the aggregated information
 293     // in the heap region in case we have to remove this region from
 294     // the incremental collection set, or it is updated by the
 295     // rset sampling code
 296 
 297     IncCollectionSetRegionStat* stat = &_inc_collection_set_stats[hr->hrm_index()];
 298     stat->_rs_length = rs_length;
 299     stat->_non_copy_time_ms = non_copy_time;
 300 
 301     _inc_recorded_rs_length += rs_length;
 302     _inc_predicted_non_copy_time_ms += non_copy_time;
 303     _inc_bytes_used_before += hr->used();
 304   }
 305 
 306   assert(!hr->in_collection_set(), "invariant");
 307   _g1h->register_young_region_with_region_attr(hr);
 308 
 309   // We use UINT_MAX as "invalid" marker in verification.
 310   assert(_collection_set_cur_length < (UINT_MAX - 1),
 311          "Collection set is too large with " SIZE_FORMAT " entries", _collection_set_cur_length);
 312   hr->set_young_index_in_cset((uint)_collection_set_cur_length + 1);
 313 
 314   _collection_set_regions[_collection_set_cur_length] = hr->hrm_index();
 315   // Concurrent readers must observe the store of the value in the array before an
 316   // update to the length field.
 317   OrderAccess::storestore();
 318   _collection_set_cur_length++;
 319   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
 320 }
 321 
 322 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
 323   assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
 324   add_young_region_common(hr);
 325 }
 326 
 327 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
 328   assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
 329   add_young_region_common(hr);
 330 }
 331 
 332 #ifndef PRODUCT
 333 class G1VerifyYoungAgesClosure : public HeapRegionClosure {
 334 public:
 335   bool _valid;
 336 
 337   G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }
 338 
 339   virtual bool do_heap_region(HeapRegion* r) {
 340     guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());
 341 
 342     if (!r->has_surv_rate_group()) {
 343       log_error(gc, verify)("## encountered young region without surv_rate_group");
 344       _valid = false;
 345     }
 346 
 347     if (!r->has_valid_age_in_surv_rate()) {
 348       log_error(gc, verify)("## encountered invalid age in young region");
 349       _valid = false;
 350     }
 351 
 352     return false;
 353   }
 354 
 355   bool valid() const { return _valid; }
 356 };
 357 
 358 bool G1CollectionSet::verify_young_ages() {
 359   assert_at_safepoint_on_vm_thread();
 360 
 361   G1VerifyYoungAgesClosure cl;
 362   iterate(&cl);
 363 
 364   if (!cl.valid()) {
 365     LogStreamHandle(Error, gc, verify) log;
 366     print(&log);
 367   }
 368 
 369   return cl.valid();
 370 }
 371 
 372 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {
 373   outputStream* _st;
 374 public:
 375   G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
 376 
 377   virtual bool do_heap_region(HeapRegion* r) {
 378     assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
 379     _st->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
 380                   HR_FORMAT_PARAMS(r),
 381                   p2i(r->prev_top_at_mark_start()),
 382                   p2i(r->next_top_at_mark_start()),
 383                   r->has_surv_rate_group() ? r->age_in_surv_rate_group() : -1);
 384     return false;
 385   }
 386 };
 387 
 388 void G1CollectionSet::print(outputStream* st) {
 389   st->print_cr("\nCollection_set:");
 390 
 391   G1PrintCollectionSetDetailClosure cl(st);
 392   iterate(&cl);
 393 }
 394 #endif // !PRODUCT
 395 
 396 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
 397   Ticks start_time = Ticks::now();
 398 
 399   finalize_incremental_building();
 400 
 401   guarantee(target_pause_time_ms > 0.0,
 402             "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
 403 
 404   size_t pending_cards = _policy->pending_cards_at_gc_start() + _g1h->hot_card_cache()->num_entries();
 405 
 406   log_trace(gc, ergo, cset)("Start choosing CSet. Pending cards: " SIZE_FORMAT " target pause time: %1.2fms",
 407                             pending_cards, target_pause_time_ms);
 408 
 409   // The young list is laid with the survivor regions from the previous
 410   // pause are appended to the RHS of the young list, i.e.
 411   //   [Newly Young Regions ++ Survivors from last pause].
 412 
 413   uint eden_region_length = _g1h->eden_regions_count();
 414   uint survivor_region_length = survivors->length();
 415   init_region_lengths(eden_region_length, survivor_region_length);
 416 
 417   verify_young_cset_indices();
 418 
 419   // Clear the fields that point to the survivor list - they are all young now.
 420   survivors->convert_to_eden();
 421 
 422   _bytes_used_before = _inc_bytes_used_before;
 423 
 424   // The number of recorded young regions is the incremental
 425   // collection set's current size
 426   set_recorded_rs_length(_inc_recorded_rs_length);
 427 
 428   double predicted_base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
 429   double predicted_eden_time = _inc_predicted_non_copy_time_ms + _policy->predict_eden_copy_time_ms(eden_region_length);
 430   double remaining_time_ms = MAX2(target_pause_time_ms - (predicted_base_time_ms + predicted_eden_time), 0.0);
 431 
 432   log_trace(gc, ergo, cset)("Added young regions to CSet. Eden: %u regions, Survivors: %u regions, "
 433                             "predicted eden time: %1.2fms, predicted base time: %1.2fms, target pause time: %1.2fms, remaining time: %1.2fms",
 434                             eden_region_length, survivor_region_length,
 435                             predicted_eden_time, predicted_base_time_ms, target_pause_time_ms, remaining_time_ms);
 436 
 437   phase_times()->record_young_cset_choice_time_ms((Ticks::now() - start_time).seconds() * 1000.0);
 438 
 439   return remaining_time_ms;
 440 }
 441 
 442 static int compare_region_idx(const uint a, const uint b) {
 443   if (a > b) {
 444     return 1;
 445   } else if (a == b) {
 446     return 0;
 447   } else {
 448     return -1;
 449   }
 450 }
 451 
 452 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
 453   double non_young_start_time_sec = os::elapsedTime();
 454 
 455   if (collector_state()->in_mixed_phase()) {
 456     candidates()->verify();
 457 
 458     uint num_initial_old_regions;
 459     uint num_optional_old_regions;
 460 
 461     _policy->calculate_old_collection_set_regions(candidates(),
 462                                                   time_remaining_ms,
 463                                                   num_initial_old_regions,
 464                                                   num_optional_old_regions);
 465 
 466     // Prepare initial old regions.
 467     move_candidates_to_collection_set(num_initial_old_regions);
 468 
 469     // Prepare optional old regions for evacuation.
 470     uint candidate_idx = candidates()->cur_idx();
 471     for (uint i = 0; i < num_optional_old_regions; i++) {
 472       add_optional_region(candidates()->at(candidate_idx + i));
 473     }
 474 
 475     candidates()->verify();
 476   }
 477 
 478   stop_incremental_building();
 479 
 480   double non_young_end_time_sec = os::elapsedTime();
 481   phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
 482 
 483   QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);
 484 }
 485 
 486 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) {
 487   if (num_old_candidate_regions == 0) {
 488     return;
 489   }
 490   uint candidate_idx = candidates()->cur_idx();
 491   for (uint i = 0; i < num_old_candidate_regions; i++) {
 492     HeapRegion* r = candidates()->at(candidate_idx + i);
 493     // This potentially optional candidate region is going to be an actual collection
 494     // set region. Clear cset marker.
 495     _g1h->clear_region_attr(r);
 496     add_old_region(r);
 497   }
 498   candidates()->remove(num_old_candidate_regions);
 499 
 500   candidates()->verify();
 501 }
 502 
 503 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
 504   double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor);
 505   finalize_old_part(time_remaining_ms);
 506 }
 507 
 508 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) {
 509   update_incremental_marker();
 510 
 511   uint num_selected_regions;
 512   _policy->calculate_optional_collection_set_regions(candidates(),
 513                                                      _num_optional_regions,
 514                                                      remaining_pause_time,
 515                                                      num_selected_regions);
 516 
 517   move_candidates_to_collection_set(num_selected_regions);
 518 
 519   _num_optional_regions -= num_selected_regions;
 520 
 521   stop_incremental_building();
 522 
 523   _g1h->verify_region_attr_remset_update();
 524 
 525   return num_selected_regions > 0;
 526 }
 527 
 528 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) {
 529   for (uint i = 0; i < _num_optional_regions; i++) {
 530     HeapRegion* r = candidates()->at(candidates()->cur_idx() + i);
 531     pss->record_unused_optional_region(r);
 532     // Clear collection set marker and make sure that the remembered set information
 533     // is correct as we still need it later.
 534     _g1h->clear_region_attr(r);
 535     _g1h->register_region_with_region_attr(r);
 536     r->clear_index_in_opt_cset();
 537   }
 538   free_optional_regions();
 539 
 540   _g1h->verify_region_attr_remset_update();
 541 }
 542 
 543 #ifdef ASSERT
 544 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
 545 private:
 546   size_t _young_length;
 547   uint* _heap_region_indices;
 548 public:
 549   G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
 550     _heap_region_indices = NEW_C_HEAP_ARRAY(uint, young_length + 1, mtGC);
 551     for (size_t i = 0; i < young_length + 1; i++) {
 552       _heap_region_indices[i] = UINT_MAX;
 553     }
 554   }
 555   ~G1VerifyYoungCSetIndicesClosure() {
 556     FREE_C_HEAP_ARRAY(int, _heap_region_indices);
 557   }
 558 
 559   virtual bool do_heap_region(HeapRegion* r) {
 560     const uint idx = r->young_index_in_cset();
 561 
 562     assert(idx > 0, "Young index must be set for all regions in the incremental collection set but is not for region %u.", r->hrm_index());
 563     assert(idx <= _young_length, "Young cset index %u too large for region %u", idx, r->hrm_index());
 564 
 565     assert(_heap_region_indices[idx] == UINT_MAX,
 566            "Index %d used by multiple regions, first use by region %u, second by region %u",
 567            idx, _heap_region_indices[idx], r->hrm_index());
 568 
 569     _heap_region_indices[idx] = r->hrm_index();
 570 
 571     return false;
 572   }
 573 };
 574 
 575 void G1CollectionSet::verify_young_cset_indices() const {
 576   assert_at_safepoint_on_vm_thread();
 577 
 578   G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
 579   iterate(&cl);
 580 }
 581 #endif