1 /*
   2  * Copyright (c) 2016, 2018, 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/g1CollectorState.hpp"
  29 #include "gc/g1/g1ParScanThreadState.hpp"
  30 #include "gc/g1/g1Policy.hpp"
  31 #include "gc/g1/heapRegion.inline.hpp"
  32 #include "gc/g1/heapRegionRemSet.hpp"
  33 #include "gc/g1/heapRegionSet.hpp"
  34 #include "logging/logStream.hpp"
  35 #include "utilities/debug.hpp"
  36 #include "utilities/globalDefinitions.hpp"
  37 #include "utilities/quickSort.hpp"
  38 
  39 G1CollectorState* G1CollectionSet::collector_state() {
  40   return _g1h->collector_state();
  41 }
  42 
  43 G1GCPhaseTimes* G1CollectionSet::phase_times() {
  44   return _policy->phase_times();
  45 }
  46 
  47 CollectionSetChooser* G1CollectionSet::cset_chooser() {
  48   return _cset_chooser;
  49 }
  50 
  51 double G1CollectionSet::predict_region_elapsed_time_ms(HeapRegion* hr) {
  52   return _policy->predict_region_elapsed_time_ms(hr, collector_state()->in_young_only_phase());
  53 }
  54 
  55 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :
  56   _g1h(g1h),
  57   _policy(policy),
  58   _cset_chooser(new CollectionSetChooser()),
  59   _eden_region_length(0),
  60   _survivor_region_length(0),
  61   _old_region_length(0),
  62   _collection_set_regions(NULL),
  63   _collection_set_cur_length(0),
  64   _collection_set_max_length(0),
  65   _optional_regions(NULL),
  66   _optional_region_length(0),
  67   _optional_region_max_length(0),
  68   _bytes_used_before(0),
  69   _recorded_rs_lengths(0),
  70   _inc_build_state(Inactive),
  71   _inc_bytes_used_before(0),
  72   _inc_recorded_rs_lengths(0),
  73   _inc_recorded_rs_lengths_diffs(0),
  74   _inc_predicted_elapsed_time_ms(0.0),
  75   _inc_predicted_elapsed_time_ms_diffs(0.0) {
  76 }
  77 
  78 G1CollectionSet::~G1CollectionSet() {
  79   if (_collection_set_regions != NULL) {
  80     FREE_C_HEAP_ARRAY(uint, _collection_set_regions);
  81   }
  82   free_optional_regions();
  83   delete _cset_chooser;
  84 }
  85 
  86 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
  87                                           uint survivor_cset_region_length) {
  88   assert_at_safepoint_on_vm_thread();
  89 
  90   _eden_region_length     = eden_cset_region_length;
  91   _survivor_region_length = survivor_cset_region_length;
  92 
  93   assert((size_t) young_region_length() == _collection_set_cur_length,
  94          "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length);
  95 
  96   _old_region_length      = 0;
  97   _optional_region_length = 0;
  98 }
  99 
 100 void G1CollectionSet::initialize(uint max_region_length) {
 101   guarantee(_collection_set_regions == NULL, "Must only initialize once.");
 102   _collection_set_max_length = max_region_length;
 103   _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC);
 104 }
 105 
 106 void G1CollectionSet::initialize_optional(uint max_length) {
 107   assert(_optional_regions == NULL, "Already initialized");
 108   assert(_optional_region_length == 0, "Already initialized");
 109   assert(_optional_region_max_length == 0, "Already initialized");
 110   _optional_region_max_length = max_length;
 111   _optional_regions = NEW_C_HEAP_ARRAY(HeapRegion*, _optional_region_max_length, mtGC);
 112 }
 113 
 114 void G1CollectionSet::free_optional_regions() {
 115   _optional_region_length = 0;
 116   _optional_region_max_length = 0;
 117   if (_optional_regions != NULL) {
 118     FREE_C_HEAP_ARRAY(HeapRegion*, _optional_regions);
 119     _optional_regions = NULL;
 120   }
 121 }
 122 
 123 void G1CollectionSet::set_recorded_rs_lengths(size_t rs_lengths) {
 124   _recorded_rs_lengths = rs_lengths;
 125 }
 126 
 127 // Add the heap region at the head of the non-incremental collection set
 128 void G1CollectionSet::add_old_region(HeapRegion* hr) {
 129   assert_at_safepoint_on_vm_thread();
 130 
 131   assert(_inc_build_state == Active || hr->index_in_opt_cset() != G1OptionalCSet::InvalidCSetIndex,
 132          "Precondition, actively building cset or adding optional later on");
 133   assert(hr->is_old(), "the region should be old");
 134 
 135   assert(!hr->in_collection_set(), "should not already be in the CSet");
 136   _g1h->register_old_region_with_cset(hr);
 137 
 138   _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();
 139   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size.");
 140 
 141   _bytes_used_before += hr->used();
 142   size_t rs_length = hr->rem_set()->occupied();
 143   _recorded_rs_lengths += rs_length;
 144   _old_region_length += 1;
 145 
 146   log_trace(gc, cset)("Added old region %d to collection set", hr->hrm_index());
 147 }
 148 
 149 void G1CollectionSet::add_optional_region(HeapRegion* hr) {
 150   assert(!optional_is_full(), "Precondition, must have room left for this region");
 151   assert(hr->is_old(), "the region should be old");
 152   assert(!hr->in_collection_set(), "should not already be in the CSet");
 153 
 154   _g1h->register_optional_region_with_cset(hr);
 155 
 156   _optional_regions[_optional_region_length] = hr;
 157   uint index = _optional_region_length++;
 158   hr->set_index_in_opt_cset(index);
 159 
 160   log_trace(gc, cset)("Added region %d to optional collection set (%u)", hr->hrm_index(), _optional_region_length);
 161 }
 162 
 163 // Initialize the per-collection-set information
 164 void G1CollectionSet::start_incremental_building() {
 165   assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");
 166   assert(_inc_build_state == Inactive, "Precondition");
 167 
 168   _inc_bytes_used_before = 0;
 169 
 170   _inc_recorded_rs_lengths = 0;
 171   _inc_recorded_rs_lengths_diffs = 0;
 172   _inc_predicted_elapsed_time_ms = 0.0;
 173   _inc_predicted_elapsed_time_ms_diffs = 0.0;
 174   _inc_build_state = Active;
 175 }
 176 
 177 void G1CollectionSet::finalize_incremental_building() {
 178   assert(_inc_build_state == Active, "Precondition");
 179   assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
 180 
 181   // The two "main" fields, _inc_recorded_rs_lengths and
 182   // _inc_predicted_elapsed_time_ms, are updated by the thread
 183   // that adds a new region to the CSet. Further updates by the
 184   // concurrent refinement thread that samples the young RSet lengths
 185   // are accumulated in the *_diffs fields. Here we add the diffs to
 186   // the "main" fields.
 187 
 188   if (_inc_recorded_rs_lengths_diffs >= 0) {
 189     _inc_recorded_rs_lengths += _inc_recorded_rs_lengths_diffs;
 190   } else {
 191     // This is defensive. The diff should in theory be always positive
 192     // as RSets can only grow between GCs. However, given that we
 193     // sample their size concurrently with other threads updating them
 194     // it's possible that we might get the wrong size back, which
 195     // could make the calculations somewhat inaccurate.
 196     size_t diffs = (size_t) (-_inc_recorded_rs_lengths_diffs);
 197     if (_inc_recorded_rs_lengths >= diffs) {
 198       _inc_recorded_rs_lengths -= diffs;
 199     } else {
 200       _inc_recorded_rs_lengths = 0;
 201     }
 202   }
 203   _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diffs;
 204 
 205   _inc_recorded_rs_lengths_diffs = 0;
 206   _inc_predicted_elapsed_time_ms_diffs = 0.0;
 207 }
 208 
 209 void G1CollectionSet::clear() {
 210   assert_at_safepoint_on_vm_thread();
 211   _collection_set_cur_length = 0;
 212   _optional_region_length = 0;
 213 }
 214 
 215 void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
 216   iterate_from(cl, 0, 1);
 217 }
 218 
 219 void G1CollectionSet::iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const {
 220   size_t len = _collection_set_cur_length;
 221   OrderAccess::loadload();
 222   if (len == 0) {
 223     return;
 224   }
 225   size_t start_pos = (worker_id * len) / total_workers;
 226   size_t cur_pos = start_pos;
 227 
 228   do {
 229     HeapRegion* r = _g1h->region_at(_collection_set_regions[cur_pos]);
 230     bool result = cl->do_heap_region(r);
 231     if (result) {
 232       cl->set_incomplete();
 233       return;
 234     }
 235     cur_pos++;
 236     if (cur_pos == len) {
 237       cur_pos = 0;
 238     }
 239   } while (cur_pos != start_pos);
 240 }
 241 
 242 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
 243                                                      size_t new_rs_length) {
 244   // Update the CSet information that is dependent on the new RS length
 245   assert(hr->is_young(), "Precondition");
 246   assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
 247 
 248   // We could have updated _inc_recorded_rs_lengths and
 249   // _inc_predicted_elapsed_time_ms directly but we'd need to do
 250   // that atomically, as this code is executed by a concurrent
 251   // refinement thread, potentially concurrently with a mutator thread
 252   // allocating a new region and also updating the same fields. To
 253   // avoid the atomic operations we accumulate these updates on two
 254   // separate fields (*_diffs) and we'll just add them to the "main"
 255   // fields at the start of a GC.
 256 
 257   ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
 258   ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
 259   _inc_recorded_rs_lengths_diffs += rs_lengths_diff;
 260 
 261   double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
 262   double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
 263   double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
 264   _inc_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
 265 
 266   hr->set_recorded_rs_length(new_rs_length);
 267   hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
 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   size_t collection_set_length = _collection_set_cur_length;
 275   assert(collection_set_length <= INT_MAX, "Collection set is too large with %d entries", (int)collection_set_length);
 276   hr->set_young_index_in_cset((int)collection_set_length);
 277 
 278   _collection_set_regions[collection_set_length] = hr->hrm_index();
 279   // Concurrent readers must observe the store of the value in the array before an
 280   // update to the length field.
 281   OrderAccess::storestore();
 282   _collection_set_cur_length++;
 283   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
 284 
 285   // This routine is used when:
 286   // * adding survivor regions to the incremental cset at the end of an
 287   //   evacuation pause or
 288   // * adding the current allocation region to the incremental cset
 289   //   when it is retired.
 290   // Therefore this routine may be called at a safepoint by the
 291   // VM thread, or in-between safepoints by mutator threads (when
 292   // retiring the current allocation region)
 293   // We need to clear and set the cached recorded/cached collection set
 294   // information in the heap region here (before the region gets added
 295   // to the collection set). An individual heap region's cached values
 296   // are calculated, aggregated with the policy collection set info,
 297   // and cached in the heap region here (initially) and (subsequently)
 298   // by the Young List sampling code.
 299   // Ignore calls to this due to retirement during full gc.
 300 
 301   if (!_g1h->collector_state()->in_full_gc()) {
 302     size_t rs_length = hr->rem_set()->occupied();
 303     double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
 304 
 305     // Cache the values we have added to the aggregated information
 306     // in the heap region in case we have to remove this region from
 307     // the incremental collection set, or it is updated by the
 308     // rset sampling code
 309     hr->set_recorded_rs_length(rs_length);
 310     hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
 311 
 312     _inc_recorded_rs_lengths += rs_length;
 313     _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
 314     _inc_bytes_used_before += hr->used();
 315   }
 316 
 317   assert(!hr->in_collection_set(), "invariant");
 318   _g1h->register_young_region_with_cset(hr);
 319 }
 320 
 321 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
 322   assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
 323   add_young_region_common(hr);
 324 }
 325 
 326 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
 327   assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
 328   add_young_region_common(hr);
 329 }
 330 
 331 #ifndef PRODUCT
 332 class G1VerifyYoungAgesClosure : public HeapRegionClosure {
 333 public:
 334   bool _valid;
 335 public:
 336   G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }
 337 
 338   virtual bool do_heap_region(HeapRegion* r) {
 339     guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());
 340 
 341     SurvRateGroup* group = r->surv_rate_group();
 342 
 343     if (group == NULL) {
 344       log_error(gc, verify)("## encountered NULL surv_rate_group in young region");
 345       _valid = false;
 346     }
 347 
 348     if (r->age_in_surv_rate_group() < 0) {
 349       log_error(gc, verify)("## encountered negative age in young region");
 350       _valid = false;
 351     }
 352 
 353     return false;
 354   }
 355 
 356   bool valid() const { return _valid; }
 357 };
 358 
 359 bool G1CollectionSet::verify_young_ages() {
 360   assert_at_safepoint_on_vm_thread();
 361 
 362   G1VerifyYoungAgesClosure cl;
 363   iterate(&cl);
 364 
 365   if (!cl.valid()) {
 366     LogStreamHandle(Error, gc, verify) log;
 367     print(&log);
 368   }
 369 
 370   return cl.valid();
 371 }
 372 
 373 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {
 374   outputStream* _st;
 375 public:
 376   G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
 377 
 378   virtual bool do_heap_region(HeapRegion* r) {
 379     assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
 380     _st->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
 381                   HR_FORMAT_PARAMS(r),
 382                   p2i(r->prev_top_at_mark_start()),
 383                   p2i(r->next_top_at_mark_start()),
 384                   r->age_in_surv_rate_group_cond());
 385     return false;
 386   }
 387 };
 388 
 389 void G1CollectionSet::print(outputStream* st) {
 390   st->print_cr("\nCollection_set:");
 391 
 392   G1PrintCollectionSetDetailClosure cl(st);
 393   iterate(&cl);
 394 }
 395 #endif // !PRODUCT
 396 
 397 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
 398   double young_start_time_sec = os::elapsedTime();
 399 
 400   finalize_incremental_building();
 401 
 402   guarantee(target_pause_time_ms > 0.0,
 403             "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
 404 
 405   size_t pending_cards = _policy->pending_cards();
 406   double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
 407   double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
 408 
 409   log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms",
 410                             pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
 411 
 412   // The young list is laid with the survivor regions from the previous
 413   // pause are appended to the RHS of the young list, i.e.
 414   //   [Newly Young Regions ++ Survivors from last pause].
 415 
 416   uint survivor_region_length = survivors->length();
 417   uint eden_region_length = _g1h->eden_regions_count();
 418   init_region_lengths(eden_region_length, survivor_region_length);
 419 
 420   verify_young_cset_indices();
 421 
 422   // Clear the fields that point to the survivor list - they are all young now.
 423   survivors->convert_to_eden();
 424 
 425   _bytes_used_before = _inc_bytes_used_before;
 426   time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
 427 
 428   log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",
 429                             eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);
 430 
 431   // The number of recorded young regions is the incremental
 432   // collection set's current size
 433   set_recorded_rs_lengths(_inc_recorded_rs_lengths);
 434 
 435   double young_end_time_sec = os::elapsedTime();
 436   phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
 437 
 438   return time_remaining_ms;
 439 }
 440 
 441 void G1CollectionSet::add_as_old(HeapRegion* hr) {
 442   cset_chooser()->pop(); // already have region via peek()
 443   _g1h->old_set_remove(hr);
 444   add_old_region(hr);
 445 }
 446 
 447 void G1CollectionSet::add_as_optional(HeapRegion* hr) {
 448   assert(_optional_regions != NULL, "Must not be called before array is allocated");
 449   cset_chooser()->pop(); // already have region via peek()
 450   _g1h->old_set_remove(hr);
 451   add_optional_region(hr);
 452 }
 453 
 454 bool G1CollectionSet::optional_is_full() {
 455   assert(_optional_region_length <= _optional_region_max_length, "Invariant");
 456   return _optional_region_length == _optional_region_max_length;
 457 }
 458 
 459 void G1CollectionSet::clear_optional_region(const HeapRegion* hr) {
 460   assert(_optional_regions != NULL, "Must not be called before array is allocated");
 461   uint index = hr->index_in_opt_cset();
 462   _optional_regions[index] = NULL;
 463 }
 464 
 465 static int compare_region_idx(const uint a, const uint b) {
 466   if (a > b) {
 467     return 1;
 468   } else if (a == b) {
 469     return 0;
 470   } else {
 471     return -1;
 472   }
 473 }
 474 
 475 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
 476   double non_young_start_time_sec = os::elapsedTime();
 477   double predicted_old_time_ms = 0.0;
 478   double predicted_optional_time_ms = 0.0;
 479   double optional_threshold_ms = time_remaining_ms * _policy->optional_prediction_fraction();
 480   uint expensive_region_num = 0;
 481 
 482   if (collector_state()->in_mixed_phase()) {
 483     cset_chooser()->verify();
 484     const uint min_old_cset_length = _policy->calc_min_old_cset_length();
 485     const uint max_old_cset_length = MAX2(min_old_cset_length, _policy->calc_max_old_cset_length());
 486     bool check_time_remaining = _policy->adaptive_young_list_length();
 487 
 488     initialize_optional(max_old_cset_length - min_old_cset_length);
 489     log_debug(gc, ergo, cset)("Start adding old regions for mixed gc. min %u regions, max %u regions, "
 490                               "time remaining %1.2fms, optional threshold %1.2fms",
 491                               min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms);
 492 
 493     HeapRegion* hr = cset_chooser()->peek();
 494     while (hr != NULL) {
 495       if (old_region_length() + optional_region_length() >= max_old_cset_length) {
 496         // Added maximum number of old regions to the CSet.
 497         log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). "
 498                                   "old %u regions, optional %u regions",
 499                                   old_region_length(), optional_region_length());
 500         break;
 501       }
 502 
 503       // Stop adding regions if the remaining reclaimable space is
 504       // not above G1HeapWastePercent.
 505       size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
 506       double reclaimable_percent = _policy->reclaimable_bytes_percent(reclaimable_bytes);
 507       double threshold = (double) G1HeapWastePercent;
 508       if (reclaimable_percent <= threshold) {
 509         // We've added enough old regions that the amount of uncollected
 510         // reclaimable space is at or below the waste threshold. Stop
 511         // adding old regions to the CSet.
 512         log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). "
 513                                   "reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%",
 514                                   byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes),
 515                                   reclaimable_percent, G1HeapWastePercent);
 516         break;
 517       }
 518 
 519       double predicted_time_ms = predict_region_elapsed_time_ms(hr);
 520       time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
 521       // Add regions to old set until we reach minimum amount
 522       if (old_region_length() < min_old_cset_length) {
 523         predicted_old_time_ms += predicted_time_ms;
 524         add_as_old(hr);
 525         // Record the number of regions added when no time remaining
 526         if (time_remaining_ms == 0.0) {
 527           expensive_region_num++;
 528         }
 529       } else {
 530         // In the non-auto-tuning case, we'll finish adding regions
 531         // to the CSet if we reach the minimum.
 532         if (!check_time_remaining) {
 533           log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min).");
 534           break;
 535         }
 536         // Keep adding regions to old set until we reach optional threshold
 537         if (time_remaining_ms > optional_threshold_ms) {
 538           predicted_old_time_ms += predicted_time_ms;
 539           add_as_old(hr);
 540         } else if (time_remaining_ms > 0) {
 541           // Keep adding optional regions until time is up
 542           if (!optional_is_full()) {
 543             predicted_optional_time_ms += predicted_time_ms;
 544             add_as_optional(hr);
 545           } else {
 546             log_debug(gc, ergo, cset)("Finish adding old regions to CSet (optional set full).");
 547             break;
 548           }
 549         } else {
 550           log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high).");
 551           break;
 552         }
 553       }
 554       hr = cset_chooser()->peek();
 555     }
 556     if (hr == NULL) {
 557       log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)");
 558     }
 559 
 560     cset_chooser()->verify();
 561   }
 562 
 563   stop_incremental_building();
 564 
 565   log_debug(gc, ergo, cset)("Finish choosing CSet regions old: %u, optional: %u, "
 566                             "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f",
 567                             old_region_length(), optional_region_length(),
 568                             predicted_old_time_ms, predicted_optional_time_ms, time_remaining_ms);
 569   if (expensive_region_num > 0) {
 570     log_debug(gc, ergo, cset)("CSet contains %u old regions that were added although the predicted time was too high.",
 571                               expensive_region_num);
 572   }
 573 
 574   double non_young_end_time_sec = os::elapsedTime();
 575   phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
 576 
 577   QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);
 578 }
 579 
 580 HeapRegion* G1OptionalCSet::region_at(uint index) {
 581   return _cset->optional_region_at(index);
 582 }
 583 
 584 void G1OptionalCSet::prepare_evacuation(double time_limit) {
 585   assert(_current_index == _current_limit, "Before prepare no regions should be ready for evac");
 586 
 587   uint prepared_regions = 0;
 588   double prediction_ms = 0;
 589 
 590   _prepare_failed = true;
 591   for (uint i = _current_index; i < _cset->optional_region_length(); i++) {
 592     HeapRegion* hr = region_at(i);
 593     prediction_ms += _cset->predict_region_elapsed_time_ms(hr);
 594     if (prediction_ms > time_limit) {
 595       log_debug(gc, cset)("Prepared %u regions for optional evacuation. Predicted time: %.3fms", prepared_regions, prediction_ms);
 596       return;
 597     }
 598 
 599     // This region will be included in the next optional evacuation.
 600     prepare_to_evacuate_optional_region(hr);
 601     prepared_regions++;
 602     _current_limit++;
 603     _prepare_failed = false;
 604   }
 605 
 606   log_debug(gc, cset)("Prepared all %u regions for optional evacuation. Predicted time: %.3fms",
 607                       prepared_regions, prediction_ms);
 608 }
 609 
 610 bool G1OptionalCSet::prepare_failed() {
 611   return _prepare_failed;
 612 }
 613 
 614 void G1OptionalCSet::complete_evacuation() {
 615   _evacuation_failed = false;
 616   for (uint i = _current_index; i < _current_limit; i++) {
 617     HeapRegion* hr = region_at(i);
 618     _cset->clear_optional_region(hr);
 619     if (hr->evacuation_failed()){
 620       _evacuation_failed = true;
 621     }
 622   }
 623   _current_index = _current_limit;
 624 }
 625 
 626 bool G1OptionalCSet::evacuation_failed() {
 627   return _evacuation_failed;
 628 }
 629 
 630 G1OptionalCSet::~G1OptionalCSet() {
 631   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 632   while (!is_empty()) {
 633     // We want to return regions not evacuated to the
 634     // chooser in reverse order to maintain the old order.
 635     HeapRegion* hr = _cset->remove_last_optional_region();
 636     assert(hr != NULL, "Should be valid region left");
 637     _pset->free_unused_optional_region(hr);
 638     g1h->old_set_add(hr);
 639     g1h->clear_in_cset(hr);
 640     hr->set_index_in_opt_cset(InvalidCSetIndex);
 641     _cset->cset_chooser()->push(hr);
 642   }
 643   _cset->free_optional_regions();
 644 }
 645 
 646 uint G1OptionalCSet::size() {
 647   return _cset->optional_region_length() - _current_index;
 648 }
 649 
 650 bool G1OptionalCSet::is_empty() {
 651   return size() == 0;
 652 }
 653 
 654 void G1OptionalCSet::prepare_to_evacuate_optional_region(HeapRegion* hr) {
 655   log_trace(gc, cset)("Adding region %u for optional evacuation", hr->hrm_index());
 656   G1CollectedHeap::heap()->clear_in_cset(hr);
 657   _cset->add_old_region(hr);
 658 }
 659 
 660 #ifdef ASSERT
 661 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
 662 private:
 663   size_t _young_length;
 664   int* _heap_region_indices;
 665 public:
 666   G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
 667     _heap_region_indices = NEW_C_HEAP_ARRAY(int, young_length, mtGC);
 668     for (size_t i = 0; i < young_length; i++) {
 669       _heap_region_indices[i] = -1;
 670     }
 671   }
 672   ~G1VerifyYoungCSetIndicesClosure() {
 673     FREE_C_HEAP_ARRAY(int, _heap_region_indices);
 674   }
 675 
 676   virtual bool do_heap_region(HeapRegion* r) {
 677     const int idx = r->young_index_in_cset();
 678 
 679     assert(idx > -1, "Young index must be set for all regions in the incremental collection set but is not for region %u.", r->hrm_index());
 680     assert((size_t)idx < _young_length, "Young cset index too large for region %u", r->hrm_index());
 681 
 682     assert(_heap_region_indices[idx] == -1,
 683            "Index %d used by multiple regions, first use by region %u, second by region %u",
 684            idx, _heap_region_indices[idx], r->hrm_index());
 685 
 686     _heap_region_indices[idx] = r->hrm_index();
 687 
 688     return false;
 689   }
 690 };
 691 
 692 void G1CollectionSet::verify_young_cset_indices() const {
 693   assert_at_safepoint_on_vm_thread();
 694 
 695   G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
 696   iterate(&cl);
 697 }
 698 #endif