1 /*
   2  * Copyright (c) 2001, 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/g1Analytics.hpp"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1CollectionSet.hpp"
  29 #include "gc/g1/g1CollectionSetCandidates.hpp"
  30 #include "gc/g1/g1ConcurrentMark.hpp"
  31 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  32 #include "gc/g1/g1ConcurrentRefine.hpp"
  33 #include "gc/g1/g1CollectionSetChooser.hpp"
  34 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
  35 #include "gc/g1/g1HotCardCache.hpp"
  36 #include "gc/g1/g1IHOPControl.hpp"
  37 #include "gc/g1/g1GCPhaseTimes.hpp"
  38 #include "gc/g1/g1Policy.hpp"
  39 #include "gc/g1/g1SurvivorRegions.hpp"
  40 #include "gc/g1/g1YoungGenSizer.hpp"
  41 #include "gc/g1/heapRegion.inline.hpp"
  42 #include "gc/g1/heapRegionRemSet.hpp"
  43 #include "gc/shared/gcPolicyCounters.hpp"
  44 #include "logging/logStream.hpp"
  45 #include "runtime/arguments.hpp"
  46 #include "runtime/java.hpp"
  47 #include "runtime/mutexLocker.hpp"
  48 #include "utilities/debug.hpp"
  49 #include "utilities/growableArray.hpp"
  50 #include "utilities/pair.hpp"
  51 
  52 G1Policy::G1Policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer) :
  53   _predictor(G1ConfidencePercent / 100.0),
  54   _analytics(new G1Analytics(&_predictor)),
  55   _remset_tracker(),
  56   _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
  57   _ihop_control(create_ihop_control(&_predictor)),
  58   _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
  59   _full_collection_start_sec(0.0),
  60   _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
  61   _young_list_target_length(0),
  62   _young_list_fixed_length(0),
  63   _young_list_max_length(0),
  64   _short_lived_surv_rate_group(new SurvRateGroup()),
  65   _survivor_surv_rate_group(new SurvRateGroup()),
  66   _reserve_factor((double) G1ReservePercent / 100.0),
  67   _reserve_regions(0),
  68   _young_gen_sizer(G1YoungGenSizer::create_gen_sizer(policy)),
  69   _free_regions_at_end_of_collection(0),
  70   _max_rs_lengths(0),
  71   _rs_lengths_prediction(0),
  72   _pending_cards(0),
  73   _bytes_allocated_in_old_since_last_gc(0),
  74   _initial_mark_to_mixed(),
  75   _collection_set(NULL),
  76   _bytes_copied_during_gc(0),
  77   _g1h(NULL),
  78   _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
  79   _mark_remark_start_sec(0),
  80   _mark_cleanup_start_sec(0),
  81   _tenuring_threshold(MaxTenuringThreshold),
  82   _max_survivor_regions(0),
  83   _survivors_age_table(true)
  84 {
  85 }
  86 
  87 G1Policy::~G1Policy() {
  88   delete _ihop_control;
  89   delete _young_gen_sizer;
  90 }
  91 
  92 G1Policy* G1Policy::create_policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer_stw) {
  93   if (policy->is_heterogeneous_heap()) {
  94     return new G1HeterogeneousHeapPolicy(policy, gc_timer_stw);
  95   } else {
  96     return new G1Policy(policy, gc_timer_stw);
  97   }
  98 }
  99 
 100 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
 101 
 102 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
 103   _g1h = g1h;
 104   _collection_set = collection_set;
 105 
 106   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 107 
 108   if (!adaptive_young_list_length()) {
 109     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 110   }
 111   _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
 112 
 113   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 114 
 115   update_young_list_max_and_target_length();
 116   // We may immediately start allocating regions and placing them on the
 117   // collection set list. Initialize the per-collection set info
 118   _collection_set->start_incremental_building();
 119 }
 120 
 121 void G1Policy::note_gc_start() {
 122   phase_times()->note_gc_start();
 123 }
 124 
 125 class G1YoungLengthPredictor {
 126   const bool _during_cm;
 127   const double _base_time_ms;
 128   const double _base_free_regions;
 129   const double _target_pause_time_ms;
 130   const G1Policy* const _policy;
 131 
 132  public:
 133   G1YoungLengthPredictor(bool during_cm,
 134                          double base_time_ms,
 135                          double base_free_regions,
 136                          double target_pause_time_ms,
 137                          const G1Policy* policy) :
 138     _during_cm(during_cm),
 139     _base_time_ms(base_time_ms),
 140     _base_free_regions(base_free_regions),
 141     _target_pause_time_ms(target_pause_time_ms),
 142     _policy(policy) {}
 143 
 144   bool will_fit(uint young_length) const {
 145     if (young_length >= _base_free_regions) {
 146       // end condition 1: not enough space for the young regions
 147       return false;
 148     }
 149 
 150     const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1);
 151     const size_t bytes_to_copy =
 152                  (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
 153     const double copy_time_ms =
 154       _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm);
 155     const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
 156     const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
 157     if (pause_time_ms > _target_pause_time_ms) {
 158       // end condition 2: prediction is over the target pause time
 159       return false;
 160     }
 161 
 162     const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
 163 
 164     // When copying, we will likely need more bytes free than is live in the region.
 165     // Add some safety margin to factor in the confidence of our guess, and the
 166     // natural expected waste.
 167     // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
 168     // of the calculation: the lower the confidence, the more headroom.
 169     // (100 + TargetPLABWastePct) represents the increase in expected bytes during
 170     // copying due to anticipated waste in the PLABs.
 171     const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
 172     const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
 173 
 174     if (expected_bytes_to_copy > free_bytes) {
 175       // end condition 3: out-of-space
 176       return false;
 177     }
 178 
 179     // success!
 180     return true;
 181   }
 182 };
 183 
 184 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
 185   // re-calculate the necessary reserve
 186   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 187   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 188   // smaller than 1.0) we'll get 1.
 189   _reserve_regions = (uint) ceil(reserve_regions_d);
 190 
 191   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 192 
 193   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
 194 }
 195 
 196 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
 197   uint desired_min_length = 0;
 198   if (adaptive_young_list_length()) {
 199     if (_analytics->num_alloc_rate_ms() > 3) {
 200       double now_sec = os::elapsedTime();
 201       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 202       double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
 203       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 204     } else {
 205       // otherwise we don't have enough info to make the prediction
 206     }
 207   }
 208   desired_min_length += base_min_length;
 209   // make sure we don't go below any user-defined minimum bound
 210   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 211 }
 212 
 213 uint G1Policy::calculate_young_list_desired_max_length() const {
 214   // Here, we might want to also take into account any additional
 215   // constraints (i.e., user-defined minimum bound). Currently, we
 216   // effectively don't set this bound.
 217   return _young_gen_sizer->max_desired_young_length();
 218 }
 219 
 220 uint G1Policy::update_young_list_max_and_target_length() {
 221   return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
 222 }
 223 
 224 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) {
 225   uint unbounded_target_length = update_young_list_target_length(rs_lengths);
 226   update_max_gc_locker_expansion();
 227   return unbounded_target_length;
 228 }
 229 
 230 uint G1Policy::update_young_list_target_length(size_t rs_lengths) {
 231   YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
 232   _young_list_target_length = young_lengths.first;
 233 
 234   return young_lengths.second;
 235 }
 236 
 237 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const {
 238   YoungTargetLengths result;
 239 
 240   // Calculate the absolute and desired min bounds first.
 241 
 242   // This is how many young regions we already have (currently: the survivors).
 243   const uint base_min_length = _g1h->survivor_regions_count();
 244   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 245   // This is the absolute minimum young length. Ensure that we
 246   // will at least have one eden region available for allocation.
 247   uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
 248   // If we shrank the young list target it should not shrink below the current size.
 249   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 250   // Calculate the absolute and desired max bounds.
 251 
 252   uint desired_max_length = calculate_young_list_desired_max_length();
 253 
 254   uint young_list_target_length = 0;
 255   if (adaptive_young_list_length()) {
 256     if (collector_state()->in_young_only_phase()) {
 257       young_list_target_length =
 258                         calculate_young_list_target_length(rs_lengths,
 259                                                            base_min_length,
 260                                                            desired_min_length,
 261                                                            desired_max_length);
 262     } else {
 263       // Don't calculate anything and let the code below bound it to
 264       // the desired_min_length, i.e., do the next GC as soon as
 265       // possible to maximize how many old regions we can add to it.
 266     }
 267   } else {
 268     // The user asked for a fixed young gen so we'll fix the young gen
 269     // whether the next GC is young or mixed.
 270     young_list_target_length = _young_list_fixed_length;
 271   }
 272 
 273   result.second = young_list_target_length;
 274 
 275   // We will try our best not to "eat" into the reserve.
 276   uint absolute_max_length = 0;
 277   if (_free_regions_at_end_of_collection > _reserve_regions) {
 278     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 279   }
 280   if (desired_max_length > absolute_max_length) {
 281     desired_max_length = absolute_max_length;
 282   }
 283 
 284   // Make sure we don't go over the desired max length, nor under the
 285   // desired min length. In case they clash, desired_min_length wins
 286   // which is why that test is second.
 287   if (young_list_target_length > desired_max_length) {
 288     young_list_target_length = desired_max_length;
 289   }
 290   if (young_list_target_length < desired_min_length) {
 291     young_list_target_length = desired_min_length;
 292   }
 293 
 294   assert(young_list_target_length > base_min_length,
 295          "we should be able to allocate at least one eden region");
 296   assert(young_list_target_length >= absolute_min_length, "post-condition");
 297 
 298   result.first = young_list_target_length;
 299   return result;
 300 }
 301 
 302 uint
 303 G1Policy::calculate_young_list_target_length(size_t rs_lengths,
 304                                                     uint base_min_length,
 305                                                     uint desired_min_length,
 306                                                     uint desired_max_length) const {
 307   assert(adaptive_young_list_length(), "pre-condition");
 308   assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
 309 
 310   // In case some edge-condition makes the desired max length too small...
 311   if (desired_max_length <= desired_min_length) {
 312     return desired_min_length;
 313   }
 314 
 315   // We'll adjust min_young_length and max_young_length not to include
 316   // the already allocated young regions (i.e., so they reflect the
 317   // min and max eden regions we'll allocate). The base_min_length
 318   // will be reflected in the predictions by the
 319   // survivor_regions_evac_time prediction.
 320   assert(desired_min_length > base_min_length, "invariant");
 321   uint min_young_length = desired_min_length - base_min_length;
 322   assert(desired_max_length > base_min_length, "invariant");
 323   uint max_young_length = desired_max_length - base_min_length;
 324 
 325   const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 326   const double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 327   const size_t pending_cards = _analytics->predict_pending_cards();
 328   const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
 329   const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, true /* for_young_gc */);
 330   const double base_time_ms =
 331     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
 332     survivor_regions_evac_time;
 333   const uint available_free_regions = _free_regions_at_end_of_collection;
 334   const uint base_free_regions =
 335     available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
 336 
 337   // Here, we will make sure that the shortest young length that
 338   // makes sense fits within the target pause time.
 339 
 340   G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(),
 341                            base_time_ms,
 342                            base_free_regions,
 343                            target_pause_time_ms,
 344                            this);
 345   if (p.will_fit(min_young_length)) {
 346     // The shortest young length will fit into the target pause time;
 347     // we'll now check whether the absolute maximum number of young
 348     // regions will fit in the target pause time. If not, we'll do
 349     // a binary search between min_young_length and max_young_length.
 350     if (p.will_fit(max_young_length)) {
 351       // The maximum young length will fit into the target pause time.
 352       // We are done so set min young length to the maximum length (as
 353       // the result is assumed to be returned in min_young_length).
 354       min_young_length = max_young_length;
 355     } else {
 356       // The maximum possible number of young regions will not fit within
 357       // the target pause time so we'll search for the optimal
 358       // length. The loop invariants are:
 359       //
 360       // min_young_length < max_young_length
 361       // min_young_length is known to fit into the target pause time
 362       // max_young_length is known not to fit into the target pause time
 363       //
 364       // Going into the loop we know the above hold as we've just
 365       // checked them. Every time around the loop we check whether
 366       // the middle value between min_young_length and
 367       // max_young_length fits into the target pause time. If it
 368       // does, it becomes the new min. If it doesn't, it becomes
 369       // the new max. This way we maintain the loop invariants.
 370 
 371       assert(min_young_length < max_young_length, "invariant");
 372       uint diff = (max_young_length - min_young_length) / 2;
 373       while (diff > 0) {
 374         uint young_length = min_young_length + diff;
 375         if (p.will_fit(young_length)) {
 376           min_young_length = young_length;
 377         } else {
 378           max_young_length = young_length;
 379         }
 380         assert(min_young_length <  max_young_length, "invariant");
 381         diff = (max_young_length - min_young_length) / 2;
 382       }
 383       // The results is min_young_length which, according to the
 384       // loop invariants, should fit within the target pause time.
 385 
 386       // These are the post-conditions of the binary search above:
 387       assert(min_young_length < max_young_length,
 388              "otherwise we should have discovered that max_young_length "
 389              "fits into the pause target and not done the binary search");
 390       assert(p.will_fit(min_young_length),
 391              "min_young_length, the result of the binary search, should "
 392              "fit into the pause target");
 393       assert(!p.will_fit(min_young_length + 1),
 394              "min_young_length, the result of the binary search, should be "
 395              "optimal, so no larger length should fit into the pause target");
 396     }
 397   } else {
 398     // Even the minimum length doesn't fit into the pause time
 399     // target, return it as the result nevertheless.
 400   }
 401   return base_min_length + min_young_length;
 402 }
 403 
 404 double G1Policy::predict_survivor_regions_evac_time() const {
 405   double survivor_regions_evac_time = 0.0;
 406   const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
 407 
 408   for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
 409        it != survivor_regions->end();
 410        ++it) {
 411     survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase());
 412   }
 413   return survivor_regions_evac_time;
 414 }
 415 
 416 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
 417   guarantee( adaptive_young_list_length(), "should not call this otherwise" );
 418 
 419   if (rs_lengths > _rs_lengths_prediction) {
 420     // add 10% to avoid having to recalculate often
 421     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 422     update_rs_lengths_prediction(rs_lengths_prediction);
 423 
 424     update_young_list_max_and_target_length(rs_lengths_prediction);
 425   }
 426 }
 427 
 428 void G1Policy::update_rs_lengths_prediction() {
 429   update_rs_lengths_prediction(_analytics->predict_rs_lengths());
 430 }
 431 
 432 void G1Policy::update_rs_lengths_prediction(size_t prediction) {
 433   if (collector_state()->in_young_only_phase() && adaptive_young_list_length()) {
 434     _rs_lengths_prediction = prediction;
 435   }
 436 }
 437 
 438 void G1Policy::record_full_collection_start() {
 439   _full_collection_start_sec = os::elapsedTime();
 440   // Release the future to-space so that it is available for compaction into.
 441   collector_state()->set_in_young_only_phase(false);
 442   collector_state()->set_in_full_gc(true);
 443   _collection_set->clear_candidates();
 444 }
 445 
 446 void G1Policy::record_full_collection_end() {
 447   // Consider this like a collection pause for the purposes of allocation
 448   // since last pause.
 449   double end_sec = os::elapsedTime();
 450   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 451   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 452 
 453   _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
 454 
 455   collector_state()->set_in_full_gc(false);
 456 
 457   // "Nuke" the heuristics that control the young/mixed GC
 458   // transitions and make sure we start with young GCs after the Full GC.
 459   collector_state()->set_in_young_only_phase(true);
 460   collector_state()->set_in_young_gc_before_mixed(false);
 461   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
 462   collector_state()->set_in_initial_mark_gc(false);
 463   collector_state()->set_mark_or_rebuild_in_progress(false);
 464   collector_state()->set_clearing_next_bitmap(false);
 465 
 466   _short_lived_surv_rate_group->start_adding_regions();
 467   // also call this on any additional surv rate groups
 468 
 469   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 470   // Reset survivors SurvRateGroup.
 471   _survivor_surv_rate_group->reset();
 472   update_young_list_max_and_target_length();
 473   update_rs_lengths_prediction();
 474 
 475   _bytes_allocated_in_old_since_last_gc = 0;
 476 
 477   record_pause(FullGC, _full_collection_start_sec, end_sec);
 478 }
 479 
 480 void G1Policy::record_collection_pause_start(double start_time_sec) {
 481   // We only need to do this here as the policy will only be applied
 482   // to the GC we're about to start. so, no point is calculating this
 483   // every time we calculate / recalculate the target young length.
 484   update_survivors_policy();
 485 
 486   assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
 487          "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
 488          max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
 489 
 490   assert(_g1h->used() == _g1h->recalculate_used(),
 491          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
 492          _g1h->used(), _g1h->recalculate_used());
 493 
 494   phase_times()->record_cur_collection_start_sec(start_time_sec);
 495   _pending_cards = _g1h->pending_card_num();
 496 
 497   _collection_set->reset_bytes_used_before();
 498   _bytes_copied_during_gc = 0;
 499 
 500   // do that for any other surv rate groups
 501   _short_lived_surv_rate_group->stop_adding_regions();
 502   _survivors_age_table.clear();
 503 
 504   assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
 505 }
 506 
 507 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
 508   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 509   collector_state()->set_in_initial_mark_gc(false);
 510 }
 511 
 512 void G1Policy::record_concurrent_mark_remark_start() {
 513   _mark_remark_start_sec = os::elapsedTime();
 514 }
 515 
 516 void G1Policy::record_concurrent_mark_remark_end() {
 517   double end_time_sec = os::elapsedTime();
 518   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 519   _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
 520   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
 521 
 522   record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 523 }
 524 
 525 void G1Policy::record_concurrent_mark_cleanup_start() {
 526   _mark_cleanup_start_sec = os::elapsedTime();
 527 }
 528 
 529 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
 530   return phase_times()->average_time_ms(phase);
 531 }
 532 
 533 double G1Policy::young_other_time_ms() const {
 534   return phase_times()->young_cset_choice_time_ms() +
 535          phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
 536 }
 537 
 538 double G1Policy::non_young_other_time_ms() const {
 539   return phase_times()->non_young_cset_choice_time_ms() +
 540          phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
 541 }
 542 
 543 double G1Policy::other_time_ms(double pause_time_ms) const {
 544   return pause_time_ms - phase_times()->cur_collection_par_time_ms();
 545 }
 546 
 547 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
 548   return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms();
 549 }
 550 
 551 bool G1Policy::about_to_start_mixed_phase() const {
 552   return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
 553 }
 554 
 555 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
 556   if (about_to_start_mixed_phase()) {
 557     return false;
 558   }
 559 
 560   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
 561 
 562   size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
 563   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 564   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 565 
 566   bool result = false;
 567   if (marking_request_bytes > marking_initiating_used_threshold) {
 568     result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
 569     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
 570                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
 571                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
 572   }
 573 
 574   return result;
 575 }
 576 
 577 // Anything below that is considered to be zero
 578 #define MIN_TIMER_GRANULARITY 0.0000001
 579 
 580 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
 581   double end_time_sec = os::elapsedTime();
 582 
 583   size_t cur_used_bytes = _g1h->used();
 584   assert(cur_used_bytes == _g1h->recalculate_used(), "It should!");
 585   bool this_pause_included_initial_mark = false;
 586   bool this_pause_was_young_only = collector_state()->in_young_only_phase();
 587 
 588   bool update_stats = !_g1h->evacuation_failed();
 589 
 590   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
 591 
 592   _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 593 
 594   this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
 595   if (this_pause_included_initial_mark) {
 596     record_concurrent_mark_init_end(0.0);
 597   } else {
 598     maybe_start_marking();
 599   }
 600 
 601   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
 602   if (app_time_ms < MIN_TIMER_GRANULARITY) {
 603     // This usually happens due to the timer not having the required
 604     // granularity. Some Linuxes are the usual culprits.
 605     // We'll just set it to something (arbitrarily) small.
 606     app_time_ms = 1.0;
 607   }
 608 
 609   if (update_stats) {
 610     // We maintain the invariant that all objects allocated by mutator
 611     // threads will be allocated out of eden regions. So, we can use
 612     // the eden region number allocated since the previous GC to
 613     // calculate the application's allocate rate. The only exception
 614     // to that is humongous objects that are allocated separately. But
 615     // given that humongous object allocations do not really affect
 616     // either the pause's duration nor when the next pause will take
 617     // place we can safely ignore them here.
 618     uint regions_allocated = _collection_set->eden_region_length();
 619     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
 620     _analytics->report_alloc_rate_ms(alloc_rate_ms);
 621 
 622     double interval_ms =
 623       (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
 624     _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
 625     _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
 626   }
 627 
 628   if (collector_state()->in_young_gc_before_mixed()) {
 629     assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
 630     // This has been the young GC before we start doing mixed GCs. We already
 631     // decided to start mixed GCs much earlier, so there is nothing to do except
 632     // advancing the state.
 633     collector_state()->set_in_young_only_phase(false);
 634     collector_state()->set_in_young_gc_before_mixed(false);
 635   } else if (!this_pause_was_young_only) {
 636     // This is a mixed GC. Here we decide whether to continue doing more
 637     // mixed GCs or not.
 638     if (!next_gc_should_be_mixed("continue mixed GCs",
 639                                  "do not continue mixed GCs")) {
 640       collector_state()->set_in_young_only_phase(true);
 641 
 642       clear_collection_set_candidates();
 643       maybe_start_marking();
 644     }
 645   }
 646 
 647   _short_lived_surv_rate_group->start_adding_regions();
 648   // Do that for any other surv rate groups
 649 
 650   double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
 651 
 652   if (update_stats) {
 653     double cost_per_card_ms = 0.0;
 654     if (_pending_cards > 0) {
 655       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS)) / (double) _pending_cards;
 656       _analytics->report_cost_per_card_ms(cost_per_card_ms);
 657     }
 658     _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
 659 
 660     double cost_per_entry_ms = 0.0;
 661     if (cards_scanned > 10) {
 662       cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
 663       _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only);
 664     }
 665 
 666     if (_max_rs_lengths > 0) {
 667       double cards_per_entry_ratio =
 668         (double) cards_scanned / (double) _max_rs_lengths;
 669       _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only);
 670     }
 671 
 672     // This is defensive. For a while _max_rs_lengths could get
 673     // smaller than _recorded_rs_lengths which was causing
 674     // rs_length_diff to get very large and mess up the RSet length
 675     // predictions. The reason was unsafe concurrent updates to the
 676     // _inc_cset_recorded_rs_lengths field which the code below guards
 677     // against (see CR 7118202). This bug has now been fixed (see CR
 678     // 7119027). However, I'm still worried that
 679     // _inc_cset_recorded_rs_lengths might still end up somewhat
 680     // inaccurate. The concurrent refinement thread calculates an
 681     // RSet's length concurrently with other CR threads updating it
 682     // which might cause it to calculate the length incorrectly (if,
 683     // say, it's in mid-coarsening). So I'll leave in the defensive
 684     // conditional below just in case.
 685     size_t rs_length_diff = 0;
 686     size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
 687     if (_max_rs_lengths > recorded_rs_lengths) {
 688       rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
 689     }
 690     _analytics->report_rs_length_diff((double) rs_length_diff);
 691 
 692     size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
 693     size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
 694     double cost_per_byte_ms = 0.0;
 695 
 696     if (copied_bytes > 0) {
 697       cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
 698       _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
 699     }
 700 
 701     if (_collection_set->young_region_length() > 0) {
 702       _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
 703                                                         _collection_set->young_region_length());
 704     }
 705 
 706     if (_collection_set->old_region_length() > 0) {
 707       _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
 708                                                             _collection_set->old_region_length());
 709     }
 710 
 711     _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
 712 
 713     // Do not update RS lengths and the number of pending cards with information from mixed gc:
 714     // these are is wildly different to during young only gc and mess up young gen sizing right
 715     // after the mixed gc phase.
 716     // During mixed gc we do not use them for young gen sizing.
 717     if (this_pause_was_young_only) {
 718       _analytics->report_pending_cards((double) _pending_cards);
 719       _analytics->report_rs_lengths((double) _max_rs_lengths);
 720     }
 721   }
 722 
 723   assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()),
 724          "If the last pause has been an initial mark, we should not have been in the marking window");
 725   if (this_pause_included_initial_mark) {
 726     collector_state()->set_mark_or_rebuild_in_progress(true);
 727   }
 728 
 729   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 730 
 731   update_rs_lengths_prediction();
 732 
 733   // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely
 734   // that in this case we are not running in a "normal" operating mode.
 735   if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
 736     // IHOP control wants to know the expected young gen length if it were not
 737     // restrained by the heap reserve. Using the actual length would make the
 738     // prediction too small and the limit the young gen every time we get to the
 739     // predicted target occupancy.
 740     size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
 741 
 742     update_ihop_prediction(app_time_ms / 1000.0,
 743                            _bytes_allocated_in_old_since_last_gc,
 744                            last_unrestrained_young_length * HeapRegion::GrainBytes,
 745                            this_pause_was_young_only);
 746     _bytes_allocated_in_old_since_last_gc = 0;
 747 
 748     _ihop_control->send_trace_event(_g1h->gc_tracer_stw());
 749   } else {
 750     // Any garbage collection triggered as periodic collection resets the time-to-mixed
 751     // measurement. Periodic collection typically means that the application is "inactive", i.e.
 752     // the marking threads may have received an uncharacterisic amount of cpu time
 753     // for completing the marking, i.e. are faster than expected.
 754     // This skews the predicted marking length towards smaller values which might cause
 755     // the mark start being too late.
 756     _initial_mark_to_mixed.reset();
 757   }
 758 
 759   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
 760   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
 761 
 762   if (update_rs_time_goal_ms < scan_hcc_time_ms) {
 763     log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
 764                                 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
 765                                 update_rs_time_goal_ms, scan_hcc_time_ms);
 766 
 767     update_rs_time_goal_ms = 0;
 768   } else {
 769     update_rs_time_goal_ms -= scan_hcc_time_ms;
 770   }
 771   _g1h->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS),
 772                                     phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
 773                                     update_rs_time_goal_ms);
 774 }
 775 
 776 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
 777   if (G1UseAdaptiveIHOP) {
 778     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
 779                                      predictor,
 780                                      G1ReservePercent,
 781                                      G1HeapWastePercent);
 782   } else {
 783     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
 784   }
 785 }
 786 
 787 void G1Policy::update_ihop_prediction(double mutator_time_s,
 788                                       size_t mutator_alloc_bytes,
 789                                       size_t young_gen_size,
 790                                       bool this_gc_was_young_only) {
 791   // Always try to update IHOP prediction. Even evacuation failures give information
 792   // about e.g. whether to start IHOP earlier next time.
 793 
 794   // Avoid using really small application times that might create samples with
 795   // very high or very low values. They may be caused by e.g. back-to-back gcs.
 796   double const min_valid_time = 1e-6;
 797 
 798   bool report = false;
 799 
 800   double marking_to_mixed_time = -1.0;
 801   if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
 802     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
 803     assert(marking_to_mixed_time > 0.0,
 804            "Initial mark to mixed time must be larger than zero but is %.3f",
 805            marking_to_mixed_time);
 806     if (marking_to_mixed_time > min_valid_time) {
 807       _ihop_control->update_marking_length(marking_to_mixed_time);
 808       report = true;
 809     }
 810   }
 811 
 812   // As an approximation for the young gc promotion rates during marking we use
 813   // all of them. In many applications there are only a few if any young gcs during
 814   // marking, which makes any prediction useless. This increases the accuracy of the
 815   // prediction.
 816   if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
 817     _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
 818     report = true;
 819   }
 820 
 821   if (report) {
 822     report_ihop_statistics();
 823   }
 824 }
 825 
 826 void G1Policy::report_ihop_statistics() {
 827   _ihop_control->print();
 828 }
 829 
 830 void G1Policy::print_phases() {
 831   phase_times()->print();
 832 }
 833 
 834 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
 835   TruncatedSeq* seq = surv_rate_group->get_seq(age);
 836   guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
 837   double pred = _predictor.get_new_prediction(seq);
 838   if (pred > 1.0) {
 839     pred = 1.0;
 840   }
 841   return pred;
 842 }
 843 
 844 double G1Policy::accum_yg_surv_rate_pred(int age) const {
 845   return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
 846 }
 847 
 848 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
 849                                               size_t scanned_cards) const {
 850   return
 851     _analytics->predict_rs_update_time_ms(pending_cards) +
 852     _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) +
 853     _analytics->predict_constant_other_time_ms();
 854 }
 855 
 856 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
 857   size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
 858   size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase());
 859   return predict_base_elapsed_time_ms(pending_cards, card_num);
 860 }
 861 
 862 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
 863   size_t bytes_to_copy;
 864   if (!hr->is_young()) {
 865     bytes_to_copy = hr->max_live_bytes();
 866   } else {
 867     assert(hr->age_in_surv_rate_group() != -1, "invariant");
 868     int age = hr->age_in_surv_rate_group();
 869     double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
 870     bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
 871   }
 872   return bytes_to_copy;
 873 }
 874 
 875 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr,
 876                                                 bool for_young_gc) const {
 877   size_t rs_length = hr->rem_set()->occupied();
 878   // Predicting the number of cards is based on which type of GC
 879   // we're predicting for.
 880   size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
 881   size_t bytes_to_copy = predict_bytes_to_copy(hr);
 882 
 883   double region_elapsed_time_ms =
 884     _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) +
 885     _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
 886 
 887   // The prediction of the "other" time for this region is based
 888   // upon the region type and NOT the GC type.
 889   if (hr->is_young()) {
 890     region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
 891   } else {
 892     region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
 893   }
 894   return region_elapsed_time_ms;
 895 }
 896 
 897 bool G1Policy::should_allocate_mutator_region() const {
 898   uint young_list_length = _g1h->young_regions_count();
 899   uint young_list_target_length = _young_list_target_length;
 900   return young_list_length < young_list_target_length;
 901 }
 902 
 903 bool G1Policy::can_expand_young_list() const {
 904   uint young_list_length = _g1h->young_regions_count();
 905   uint young_list_max_length = _young_list_max_length;
 906   return young_list_length < young_list_max_length;
 907 }
 908 
 909 bool G1Policy::adaptive_young_list_length() const {
 910   return _young_gen_sizer->adaptive_young_list_length();
 911 }
 912 
 913 size_t G1Policy::desired_survivor_size(uint max_regions) const {
 914   size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
 915   return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 916 }
 917 
 918 void G1Policy::print_age_table() {
 919   _survivors_age_table.print_age_table(_tenuring_threshold);
 920 }
 921 
 922 void G1Policy::update_max_gc_locker_expansion() {
 923   uint expansion_region_num = 0;
 924   if (GCLockerEdenExpansionPercent > 0) {
 925     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
 926     double expansion_region_num_d = perc * (double) _young_list_target_length;
 927     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
 928     // less than 1.0) we'll get 1.
 929     expansion_region_num = (uint) ceil(expansion_region_num_d);
 930   } else {
 931     assert(expansion_region_num == 0, "sanity");
 932   }
 933   _young_list_max_length = _young_list_target_length + expansion_region_num;
 934   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
 935 }
 936 
 937 // Calculates survivor space parameters.
 938 void G1Policy::update_survivors_policy() {
 939   double max_survivor_regions_d =
 940                  (double) _young_list_target_length / (double) SurvivorRatio;
 941 
 942   // Calculate desired survivor size based on desired max survivor regions (unconstrained
 943   // by remaining heap). Otherwise we may cause undesired promotions as we are
 944   // already getting close to end of the heap, impacting performance even more.
 945   uint const desired_max_survivor_regions = ceil(max_survivor_regions_d);
 946   size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions);
 947 
 948   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size);
 949   if (UsePerfData) {
 950     _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
 951     _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize);
 952   }
 953   // The real maximum survivor size is bounded by the number of regions that can
 954   // be allocated into.
 955   _max_survivor_regions = MIN2(desired_max_survivor_regions,
 956                                _g1h->num_free_or_available_regions());
 957 }
 958 
 959 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
 960   // We actually check whether we are marking here and not if we are in a
 961   // reclamation phase. This means that we will schedule a concurrent mark
 962   // even while we are still in the process of reclaiming memory.
 963   bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
 964   if (!during_cycle) {
 965     log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
 966     collector_state()->set_initiate_conc_mark_if_possible(true);
 967     return true;
 968   } else {
 969     log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
 970     return false;
 971   }
 972 }
 973 
 974 void G1Policy::initiate_conc_mark() {
 975   collector_state()->set_in_initial_mark_gc(true);
 976   collector_state()->set_initiate_conc_mark_if_possible(false);
 977 }
 978 
 979 void G1Policy::decide_on_conc_mark_initiation() {
 980   // We are about to decide on whether this pause will be an
 981   // initial-mark pause.
 982 
 983   // First, collector_state()->in_initial_mark_gc() should not be already set. We
 984   // will set it here if we have to. However, it should be cleared by
 985   // the end of the pause (it's only set for the duration of an
 986   // initial-mark pause).
 987   assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
 988 
 989   if (collector_state()->initiate_conc_mark_if_possible()) {
 990     // We had noticed on a previous pause that the heap occupancy has
 991     // gone over the initiating threshold and we should start a
 992     // concurrent marking cycle. So we might initiate one.
 993 
 994     if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
 995       // Initiate a new initial mark if there is no marking or reclamation going on.
 996       initiate_conc_mark();
 997       log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
 998     } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) {
 999       // Initiate a user requested initial mark. An initial mark must be young only
1000       // GC, so the collector state must be updated to reflect this.
1001       collector_state()->set_in_young_only_phase(true);
1002       collector_state()->set_in_young_gc_before_mixed(false);
1003 
1004       // We might have ended up coming here about to start a mixed phase with a collection set
1005       // active. The following remark might change the change the "evacuation efficiency" of
1006       // the regions in this set, leading to failing asserts later.
1007       // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
1008       clear_collection_set_candidates();
1009       abort_time_to_mixed_tracking();
1010       initiate_conc_mark();
1011       log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1012     } else {
1013       // The concurrent marking thread is still finishing up the
1014       // previous cycle. If we start one right now the two cycles
1015       // overlap. In particular, the concurrent marking thread might
1016       // be in the process of clearing the next marking bitmap (which
1017       // we will use for the next cycle if we start one). Starting a
1018       // cycle now will be bad given that parts of the marking
1019       // information might get cleared by the marking thread. And we
1020       // cannot wait for the marking thread to finish the cycle as it
1021       // periodically yields while clearing the next marking bitmap
1022       // and, if it's in a yield point, it's waiting for us to
1023       // finish. So, at this point we will not start a cycle and we'll
1024       // let the concurrent marking thread complete the last one.
1025       log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1026     }
1027   }
1028 }
1029 
1030 void G1Policy::record_concurrent_mark_cleanup_end() {
1031   G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions());
1032   _collection_set->set_candidates(candidates);
1033 
1034   bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1035   if (!mixed_gc_pending) {
1036     clear_collection_set_candidates();
1037     abort_time_to_mixed_tracking();
1038   }
1039   collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1040   collector_state()->set_mark_or_rebuild_in_progress(false);
1041 
1042   double end_sec = os::elapsedTime();
1043   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1044   _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1045   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1046 
1047   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1048 }
1049 
1050 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1051   return percent_of(reclaimable_bytes, _g1h->capacity());
1052 }
1053 
1054 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1055   virtual bool do_heap_region(HeapRegion* r) {
1056     r->rem_set()->clear_locked(true /* only_cardset */);
1057     return false;
1058   }
1059 };
1060 
1061 void G1Policy::clear_collection_set_candidates() {
1062   // Clear remembered sets of remaining candidate regions and the actual candidate
1063   // set.
1064   G1ClearCollectionSetCandidateRemSets cl;
1065   _collection_set->candidates()->iterate(&cl);
1066   _collection_set->clear_candidates();
1067 }
1068 
1069 void G1Policy::maybe_start_marking() {
1070   if (need_to_start_conc_mark("end of GC")) {
1071     // Note: this might have already been set, if during the last
1072     // pause we decided to start a cycle but at the beginning of
1073     // this pause we decided to postpone it. That's OK.
1074     collector_state()->set_initiate_conc_mark_if_possible(true);
1075   }
1076 }
1077 
1078 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1079   assert(!collector_state()->in_full_gc(), "must be");
1080   if (collector_state()->in_initial_mark_gc()) {
1081     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1082     return InitialMarkGC;
1083   } else if (collector_state()->in_young_gc_before_mixed()) {
1084     assert(!collector_state()->in_initial_mark_gc(), "must be");
1085     return LastYoungGC;
1086   } else if (collector_state()->in_mixed_phase()) {
1087     assert(!collector_state()->in_initial_mark_gc(), "must be");
1088     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1089     return MixedGC;
1090   } else {
1091     assert(!collector_state()->in_initial_mark_gc(), "must be");
1092     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1093     return YoungOnlyGC;
1094   }
1095 }
1096 
1097 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1098   // Manage the MMU tracker. For some reason it ignores Full GCs.
1099   if (kind != FullGC) {
1100     _mmu_tracker->add_pause(start, end);
1101   }
1102   // Manage the mutator time tracking from initial mark to first mixed gc.
1103   switch (kind) {
1104     case FullGC:
1105       abort_time_to_mixed_tracking();
1106       break;
1107     case Cleanup:
1108     case Remark:
1109     case YoungOnlyGC:
1110     case LastYoungGC:
1111       _initial_mark_to_mixed.add_pause(end - start);
1112       break;
1113     case InitialMarkGC:
1114       if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
1115         _initial_mark_to_mixed.record_initial_mark_end(end);
1116       }
1117       break;
1118     case MixedGC:
1119       _initial_mark_to_mixed.record_mixed_gc_start(start);
1120       break;
1121     default:
1122       ShouldNotReachHere();
1123   }
1124 }
1125 
1126 void G1Policy::abort_time_to_mixed_tracking() {
1127   _initial_mark_to_mixed.reset();
1128 }
1129 
1130 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1131                                        const char* false_action_str) const {
1132   G1CollectionSetCandidates* candidates = _collection_set->candidates();
1133 
1134   if (candidates->is_empty()) {
1135     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1136     return false;
1137   }
1138 
1139   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1140   size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1141   double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1142   double threshold = (double) G1HeapWastePercent;
1143   if (reclaimable_percent <= threshold) {
1144     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1145                         false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1146     return false;
1147   }
1148   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1149                       true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1150   return true;
1151 }
1152 
1153 uint G1Policy::calc_min_old_cset_length() const {
1154   // The min old CSet region bound is based on the maximum desired
1155   // number of mixed GCs after a cycle. I.e., even if some old regions
1156   // look expensive, we should add them to the CSet anyway to make
1157   // sure we go through the available old regions in no more than the
1158   // maximum desired number of mixed GCs.
1159   //
1160   // The calculation is based on the number of marked regions we added
1161   // to the CSet candidates in the first place, not how many remain, so
1162   // that the result is the same during all mixed GCs that follow a cycle.
1163 
1164   const size_t region_num = _collection_set->candidates()->num_regions();
1165   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1166   size_t result = region_num / gc_num;
1167   // emulate ceiling
1168   if (result * gc_num < region_num) {
1169     result += 1;
1170   }
1171   return (uint) result;
1172 }
1173 
1174 uint G1Policy::calc_max_old_cset_length() const {
1175   // The max old CSet region bound is based on the threshold expressed
1176   // as a percentage of the heap size. I.e., it should bound the
1177   // number of old regions added to the CSet irrespective of how many
1178   // of them are available.
1179 
1180   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1181   const size_t region_num = g1h->num_regions();
1182   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1183   size_t result = region_num * perc / 100;
1184   // emulate ceiling
1185   if (100 * result < region_num * perc) {
1186     result += 1;
1187   }
1188   return (uint) result;
1189 }
1190 
1191 uint G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
1192   double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor);
1193   _collection_set->finalize_old_part(time_remaining_ms);
1194 
1195   return _collection_set->region_length();
1196 }
1197 
1198 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1199 
1200   // Add survivor regions to SurvRateGroup.
1201   note_start_adding_survivor_regions();
1202   finished_recalculating_age_indexes(true /* is_survivors */);
1203 
1204   HeapRegion* last = NULL;
1205   for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1206        it != survivors->regions()->end();
1207        ++it) {
1208     HeapRegion* curr = *it;
1209     set_region_survivor(curr);
1210 
1211     // The region is a non-empty survivor so let's add it to
1212     // the incremental collection set for the next evacuation
1213     // pause.
1214     _collection_set->add_survivor_regions(curr);
1215 
1216     last = curr;
1217   }
1218   note_stop_adding_survivor_regions();
1219 
1220   // Don't clear the survivor list handles until the start of
1221   // the next evacuation pause - we need it in order to re-tag
1222   // the survivor regions from this evacuation pause as 'young'
1223   // at the start of the next.
1224 
1225   finished_recalculating_age_indexes(false /* is_survivors */);
1226 }