rev 57223 : imported patch 8225484-changes-to-survivor-calculation

   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   _cur_eden_young_idx(0),
  70   _inc_collection_set_stats(NULL),
  71   _inc_bytes_used_before(0),
  72   _inc_recorded_rs_length(0),
  73   _inc_recorded_rs_length_diff(0),
  74   _inc_predicted_non_copy_time_ms(0.0),
  75   _inc_predicted_non_copy_time_ms_diff(0.0) {
  76 }
  77 
  78 G1CollectionSet::~G1CollectionSet() {
  79   FREE_C_HEAP_ARRAY(uint, _collection_set_regions);
  80   FREE_C_HEAP_ARRAY(IncCollectionSetRegionStat, _inc_collection_set_stats);
  81   free_optional_regions();
  82   clear_candidates();
  83 }
  84 
  85 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
  86                                           uint survivor_cset_region_length) {
  87   assert_at_safepoint_on_vm_thread();
  88 
  89   _eden_region_length     = eden_cset_region_length;
  90   _survivor_region_length = survivor_cset_region_length;
  91 
  92   assert((size_t) young_region_length() == _collection_set_cur_length,
  93          "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length);
  94 
  95   _old_region_length = 0;
  96   free_optional_regions();
  97 }
  98 
  99 void G1CollectionSet::initialize(uint max_region_length) {
 100   guarantee(_collection_set_regions == NULL, "Must only initialize once.");
 101   _collection_set_max_length = max_region_length;
 102   _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC);
 103   _inc_collection_set_stats = NEW_C_HEAP_ARRAY(IncCollectionSetRegionStat, max_region_length, mtGC);
 104 }
 105 
 106 void G1CollectionSet::free_optional_regions() {
 107   _num_optional_regions = 0;
 108 }
 109 
 110 void G1CollectionSet::clear_candidates() {
 111   delete _candidates;
 112   _candidates = NULL;
 113 }
 114 
 115 void G1CollectionSet::set_recorded_rs_length(size_t rs_length) {
 116   _recorded_rs_length = rs_length;
 117 }
 118 
 119 // Add the heap region at the head of the non-incremental collection set
 120 void G1CollectionSet::add_old_region(HeapRegion* hr) {
 121   assert_at_safepoint_on_vm_thread();
 122 
 123   assert(_inc_build_state == Active,
 124          "Precondition, actively building cset or adding optional later on");
 125   assert(hr->is_old(), "the region should be old");
 126 
 127   assert(!hr->in_collection_set(), "should not already be in the collection set");
 128   _g1h->register_old_region_with_region_attr(hr);
 129 
 130   _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();
 131   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size.");
 132 
 133   _bytes_used_before += hr->used();
 134   _recorded_rs_length += hr->rem_set()->occupied();
 135   _old_region_length++;
 136 
 137   _g1h->old_set_remove(hr);
 138 }
 139 
 140 void G1CollectionSet::add_optional_region(HeapRegion* hr) {
 141   assert(hr->is_old(), "the region should be old");
 142   assert(!hr->in_collection_set(), "should not already be in the CSet");
 143 
 144   _g1h->register_optional_region_with_region_attr(hr);
 145 
 146   hr->set_index_in_opt_cset(_num_optional_regions++);
 147 }
 148 
 149 void G1CollectionSet::start_incremental_building() {
 150   assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");
 151   assert(_inc_build_state == Inactive, "Precondition");
 152 #ifdef ASSERT
 153   for (size_t i = 0; i < _collection_set_max_length; i++) {
 154     _inc_collection_set_stats[i].reset();
 155   }
 156 #endif
 157 
 158   _inc_bytes_used_before = 0;
 159 
 160   _inc_recorded_rs_length = 0;
 161   _inc_recorded_rs_length_diff = 0;
 162   _inc_predicted_non_copy_time_ms = 0.0;
 163   _inc_predicted_non_copy_time_ms_diff = 0.0;
 164 
 165   update_incremental_marker();
 166   _cur_eden_young_idx = 0;
 167 }
 168 
 169 void G1CollectionSet::finalize_incremental_building() {
 170   assert(_inc_build_state == Active, "Precondition");
 171   assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
 172 
 173   // The two "main" fields, _inc_recorded_rs_length and
 174   // _inc_predicted_non_copy_time_ms, are updated by the thread
 175   // that adds a new region to the CSet. Further updates by the
 176   // concurrent refinement thread that samples the young RSet lengths
 177   // are accumulated in the *_diff fields. Here we add the diffs to
 178   // the "main" fields.
 179 
 180   _inc_recorded_rs_length += _inc_recorded_rs_length_diff;
 181   _inc_predicted_non_copy_time_ms += _inc_predicted_non_copy_time_ms_diff;
 182 
 183   _inc_recorded_rs_length_diff = 0;
 184   _inc_predicted_non_copy_time_ms_diff = 0.0;
 185 }
 186 
 187 void G1CollectionSet::clear() {
 188   assert_at_safepoint_on_vm_thread();
 189   _collection_set_cur_length = 0;
 190 }
 191 
 192 void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
 193   size_t len = _collection_set_cur_length;
 194   OrderAccess::loadload();
 195 
 196   for (uint i = 0; i < len; i++) {
 197     HeapRegion* r = _g1h->region_at(_collection_set_regions[i]);
 198     bool result = cl->do_heap_region(r);
 199     if (result) {
 200       cl->set_incomplete();
 201       return;
 202     }
 203   }
 204 }
 205 
 206 void G1CollectionSet::iterate_optional(HeapRegionClosure* cl) const {
 207   assert_at_safepoint();
 208 
 209   for (uint i = 0; i < _num_optional_regions; i++) {
 210     HeapRegion* r = _candidates->at(i);
 211     bool result = cl->do_heap_region(r);
 212     guarantee(!result, "Must not cancel iteration");
 213   }
 214 }
 215 
 216 void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl,
 217                                                     HeapRegionClaimer* hr_claimer,
 218                                                     uint worker_id,
 219                                                     uint total_workers) const {
 220   assert_at_safepoint();
 221 
 222   size_t len = increment_length();
 223   if (len == 0) {
 224     return;
 225   }
 226 
 227   size_t start_pos = (worker_id * len) / total_workers;
 228   size_t cur_pos = start_pos;
 229 
 230   do {
 231     uint region_idx = _collection_set_regions[cur_pos + _inc_part_start];
 232     if (hr_claimer == NULL || hr_claimer->claim_region(region_idx)) {
 233       HeapRegion* r = _g1h->region_at(region_idx);
 234       bool result = cl->do_heap_region(r);
 235       guarantee(!result, "Must not cancel iteration");
 236     }
 237 
 238     cur_pos++;
 239     if (cur_pos == len) {
 240       cur_pos = 0;
 241     }
 242   } while (cur_pos != start_pos);
 243 }
 244 
 245 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
 246                                                      size_t new_rs_length) {
 247   // Update the CSet information that is dependent on the new RS length
 248   assert(hr->is_young(), "Precondition");
 249   assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
 250 
 251   IncCollectionSetRegionStat* stat = &_inc_collection_set_stats[hr->hrm_index()];
 252 
 253   size_t old_rs_length = stat->_rs_length;
 254   assert(old_rs_length <= new_rs_length,
 255          "Remembered set decreased (changed from " SIZE_FORMAT " to " SIZE_FORMAT " region %u type %s)",
 256          old_rs_length, new_rs_length, hr->hrm_index(), hr->get_short_type_str());
 257   size_t rs_length_diff = new_rs_length - old_rs_length;
 258   stat->_rs_length = new_rs_length;
 259   _inc_recorded_rs_length_diff += rs_length_diff;
 260 
 261   double old_non_copy_time = stat->_non_copy_time_ms;
 262   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);
 263   double new_non_copy_time = predict_region_non_copy_time_ms(hr);
 264   double non_copy_time_ms_diff = new_non_copy_time - old_non_copy_time;
 265 
 266   stat->_non_copy_time_ms = new_non_copy_time;
 267   _inc_predicted_non_copy_time_ms_diff += non_copy_time_ms_diff;
 268 }
 269 
 270 void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
 271   assert(hr->is_young(), "invariant");
 272   assert(_inc_build_state == Active, "Precondition");
 273 
 274   // This routine is used when:
 275   // * adding survivor regions to the incremental cset at the end of an
 276   //   evacuation pause or
 277   // * adding the current allocation region to the incremental cset
 278   //   when it is retired.
 279   // Therefore this routine may be called at a safepoint by the
 280   // VM thread, or in-between safepoints by mutator threads (when
 281   // retiring the current allocation region)
 282   // We need to clear and set the cached recorded/cached collection set
 283   // information in the heap region here (before the region gets added
 284   // to the collection set). An individual heap region's cached values
 285   // are calculated, aggregated with the policy collection set info,
 286   // and cached in the heap region here (initially) and (subsequently)
 287   // by the Young List sampling code.
 288   // Ignore calls to this due to retirement during full gc.
 289 
 290   if (!_g1h->collector_state()->in_full_gc()) {
 291     size_t rs_length = hr->rem_set()->occupied();
 292     double non_copy_time = predict_region_non_copy_time_ms(hr);
 293 
 294     // Cache the values we have added to the aggregated information
 295     // in the heap region in case we have to remove this region from
 296     // the incremental collection set, or it is updated by the
 297     // rset sampling code
 298 
 299     IncCollectionSetRegionStat* stat = &_inc_collection_set_stats[hr->hrm_index()];
 300     stat->_rs_length = rs_length;
 301     stat->_non_copy_time_ms = non_copy_time;
 302 
 303     _inc_recorded_rs_length += rs_length;
 304     _inc_predicted_non_copy_time_ms += non_copy_time;
 305     _inc_bytes_used_before += hr->used();
 306   }
 307 
 308   assert(!hr->in_collection_set(), "invariant");
 309   _g1h->register_young_region_with_region_attr(hr);
 310 





 311   _collection_set_regions[_collection_set_cur_length] = hr->hrm_index();
 312   // Concurrent readers must observe the store of the value in the array before an
 313   // update to the length field.
 314   OrderAccess::storestore();
 315   _collection_set_cur_length++;
 316   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
 317 }
 318 
 319 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
 320   assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
 321   add_young_region_common(hr);
 322   _survivor_region_length++;
 323 }
 324 
 325 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
 326   assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
 327   assert(_collection_set_cur_length <= INT_MAX, "Collection set is too large with %d entries", (int)_collection_set_cur_length);
 328 
 329   // Young index for eden regions should start at 1. 0 is reserved for other region types.
 330   uint next_eden_young_idx = ++_cur_eden_young_idx;
 331   assert(next_eden_young_idx > 0, "Invalid next young region idx %d", next_eden_young_idx);
 332   hr->set_young_index_in_cset(next_eden_young_idx);
 333 
 334   add_young_region_common(hr);
 335 }
 336 
 337 #ifndef PRODUCT
 338 class G1VerifyYoungAgesClosure : public HeapRegionClosure {
 339 public:
 340   bool _valid;
 341 
 342   G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }
 343 
 344   virtual bool do_heap_region(HeapRegion* r) {
 345     guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());
 346 
 347     if (r->is_survivor()) {
 348       assert(r->survivor_bytes() > 0, "## encountered survivor region without contents");
 349       assert(!r->has_surv_rate_group(), "## encountered surv_rate_group in survivor region");
 350       return false;
 351     }
 352 
 353     if (!r->has_surv_rate_group()) {
 354       log_error(gc, verify)("## encountered eden region without surv_rate_group");
 355       _valid = false;
 356     }
 357 
 358     if (!r->has_valid_age_in_surv_rate()) {
 359       log_error(gc, verify)("## encountered invalid age in eden region");
 360       _valid = false;
 361     }
 362 
 363     return false;
 364   }
 365 
 366   bool valid() const { return _valid; }
 367 };
 368 
 369 bool G1CollectionSet::verify_young_ages() {
 370   assert_at_safepoint_on_vm_thread();
 371 
 372   G1VerifyYoungAgesClosure cl;
 373   iterate(&cl);
 374 
 375   if (!cl.valid()) {
 376     LogStreamHandle(Error, gc, verify) log;
 377     print(&log);
 378   }
 379 
 380   return cl.valid();
 381 }
 382 
 383 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {
 384   outputStream* _st;
 385 public:
 386   G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
 387 
 388   virtual bool do_heap_region(HeapRegion* r) {
 389     assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
 390     _st->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
 391                   HR_FORMAT_PARAMS(r),
 392                   p2i(r->prev_top_at_mark_start()),
 393                   p2i(r->next_top_at_mark_start()),
 394                   r->has_surv_rate_group() ? r->age_in_surv_rate_group() : -1);
 395     return false;
 396   }
 397 };
 398 
 399 void G1CollectionSet::print(outputStream* st) {
 400   st->print_cr("\nCollection_set:");
 401 
 402   G1PrintCollectionSetDetailClosure cl(st);
 403   iterate(&cl);
 404 }
 405 #endif // !PRODUCT
 406 
 407 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
 408   Ticks start_time = Ticks::now();
 409 
 410   finalize_incremental_building();
 411 
 412   guarantee(target_pause_time_ms > 0.0,
 413             "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
 414 
 415   size_t pending_cards = _policy->pending_cards_at_gc_start() + _g1h->hot_card_cache()->num_entries();
 416 
 417   log_trace(gc, ergo, cset)("Start choosing CSet. Pending cards: " SIZE_FORMAT " target pause time: %1.2fms",
 418                             pending_cards, target_pause_time_ms);
 419 
 420   // The young list is laid with the survivor regions from the previous
 421   // pause are appended to the RHS of the young list, i.e.
 422   //   [Newly Young Regions ++ Survivors from last pause].
 423 
 424   uint eden_region_length = _g1h->eden_regions_count();
 425   uint survivor_region_length = survivors->length();
 426   init_region_lengths(eden_region_length, survivor_region_length);
 427 
 428   verify_young_cset_indices();
 429 
 430   // Clear the fields that point to the survivor list - they are all young now.
 431   survivors->convert_to_eden();
 432 
 433   _bytes_used_before = _inc_bytes_used_before;
 434 
 435   // The number of recorded young regions is the incremental
 436   // collection set's current size
 437   set_recorded_rs_length(_inc_recorded_rs_length);
 438 
 439   double predicted_base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
 440   double predicted_eden_time = _inc_predicted_non_copy_time_ms + _policy->predict_eden_copy_time_ms(eden_region_length);
 441   double remaining_time_ms = MAX2(target_pause_time_ms - (predicted_base_time_ms + predicted_eden_time), 0.0);
 442 
 443   log_trace(gc, ergo, cset)("Added young regions to CSet. Eden: %u regions, Survivors: %u regions, "
 444                             "predicted eden time: %1.2fms, predicted base time: %1.2fms, target pause time: %1.2fms, remaining time: %1.2fms",
 445                             eden_region_length, survivor_region_length,
 446                             predicted_eden_time, predicted_base_time_ms, target_pause_time_ms, remaining_time_ms);
 447 
 448   phase_times()->record_young_cset_choice_time_ms((Ticks::now() - start_time).seconds() * 1000.0);
 449 
 450   return remaining_time_ms;
 451 }
 452 
 453 static int compare_region_idx(const uint a, const uint b) {
 454   if (a > b) {
 455     return 1;
 456   } else if (a == b) {
 457     return 0;
 458   } else {
 459     return -1;
 460   }
 461 }
 462 
 463 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
 464   double non_young_start_time_sec = os::elapsedTime();
 465 
 466   if (collector_state()->in_mixed_phase()) {
 467     candidates()->verify();
 468 
 469     uint num_initial_old_regions;
 470     uint num_optional_old_regions;
 471 
 472     _policy->calculate_old_collection_set_regions(candidates(),
 473                                                   time_remaining_ms,
 474                                                   num_initial_old_regions,
 475                                                   num_optional_old_regions);
 476 
 477     // Prepare initial old regions.
 478     move_candidates_to_collection_set(num_initial_old_regions);
 479 
 480     // Prepare optional old regions for evacuation.
 481     uint candidate_idx = candidates()->cur_idx();
 482     for (uint i = 0; i < num_optional_old_regions; i++) {
 483       add_optional_region(candidates()->at(candidate_idx + i));
 484     }
 485 
 486     candidates()->verify();
 487   }
 488 
 489   stop_incremental_building();
 490 
 491   double non_young_end_time_sec = os::elapsedTime();
 492   phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
 493 
 494   QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);
 495 }
 496 
 497 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) {
 498   if (num_old_candidate_regions == 0) {
 499     return;
 500   }
 501   uint candidate_idx = candidates()->cur_idx();
 502   for (uint i = 0; i < num_old_candidate_regions; i++) {
 503     HeapRegion* r = candidates()->at(candidate_idx + i);
 504     // This potentially optional candidate region is going to be an actual collection
 505     // set region. Clear cset marker.
 506     _g1h->clear_region_attr(r);
 507     add_old_region(r);
 508   }
 509   candidates()->remove(num_old_candidate_regions);
 510 
 511   candidates()->verify();
 512 }
 513 
 514 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
 515   double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor);
 516   finalize_old_part(time_remaining_ms);
 517 }
 518 
 519 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) {
 520   update_incremental_marker();
 521 
 522   uint num_selected_regions;
 523   _policy->calculate_optional_collection_set_regions(candidates(),
 524                                                      _num_optional_regions,
 525                                                      remaining_pause_time,
 526                                                      num_selected_regions);
 527 
 528   move_candidates_to_collection_set(num_selected_regions);
 529 
 530   _num_optional_regions -= num_selected_regions;
 531 
 532   stop_incremental_building();
 533 
 534   _g1h->verify_region_attr_remset_update();
 535 
 536   return num_selected_regions > 0;
 537 }
 538 
 539 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) {
 540   for (uint i = 0; i < _num_optional_regions; i++) {
 541     HeapRegion* r = candidates()->at(candidates()->cur_idx() + i);
 542     pss->record_unused_optional_region(r);
 543     // Clear collection set marker and make sure that the remembered set information
 544     // is correct as we still need it later.
 545     _g1h->clear_region_attr(r);
 546     _g1h->register_region_with_region_attr(r);
 547     r->clear_index_in_opt_cset();
 548   }
 549   free_optional_regions();
 550 
 551   _g1h->verify_region_attr_remset_update();
 552 }
 553 
 554 #ifdef ASSERT
 555 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
 556 private:
 557   size_t _young_length;
 558   uint* _heap_region_indices;
 559 public:
 560   G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
 561     _heap_region_indices = NEW_C_HEAP_ARRAY(uint, young_length + 1, mtGC);
 562     for (size_t i = 0; i < young_length + 1; i++) {
 563       _heap_region_indices[i] = UINT_MAX;
 564     }
 565   }
 566   ~G1VerifyYoungCSetIndicesClosure() {
 567     FREE_C_HEAP_ARRAY(int, _heap_region_indices);
 568   }
 569 
 570   virtual bool do_heap_region(HeapRegion* r) {
 571     const uint idx = r->young_index_in_cset();
 572 
 573     assert(idx > 0 || r->survivor_bytes() > 0,
 574            "Young index must be set for all regions not having survivor bytes but region %u.",
 575            r->hrm_index());
 576     assert(idx == 0 || idx <= _young_length, "Young cset index %u too large for region %u", idx, r->hrm_index());
 577 
 578     if (idx != 0) {
 579       assert(_heap_region_indices[idx] == UINT_MAX,
 580              "Index %d used by multiple regions, first use by region %u, second by region %u",
 581              idx, _heap_region_indices[idx], r->hrm_index());

 582       _heap_region_indices[idx] = r->hrm_index();
 583     }
 584 
 585     return false;
 586   }
 587 };
 588 
 589 void G1CollectionSet::verify_young_cset_indices() const {
 590   assert_at_safepoint_on_vm_thread();
 591 
 592   G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
 593   iterate(&cl);
 594 }
 595 #endif
--- EOF ---