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/g1Arguments.hpp"
  28 #include "gc/g1/g1CollectedHeap.inline.hpp"
  29 #include "gc/g1/g1CollectionSet.hpp"
  30 #include "gc/g1/g1CollectionSetCandidates.hpp"
  31 #include "gc/g1/g1ConcurrentMark.hpp"
  32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  33 #include "gc/g1/g1ConcurrentRefine.hpp"
  34 #include "gc/g1/g1CollectionSetChooser.hpp"
  35 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
  36 #include "gc/g1/g1HotCardCache.hpp"
  37 #include "gc/g1/g1IHOPControl.hpp"
  38 #include "gc/g1/g1GCPhaseTimes.hpp"
  39 #include "gc/g1/g1Policy.hpp"
  40 #include "gc/g1/g1SurvivorRegions.hpp"
  41 #include "gc/g1/g1YoungGenSizer.hpp"
  42 #include "gc/g1/heapRegion.inline.hpp"
  43 #include "gc/g1/heapRegionRemSet.hpp"
  44 #include "gc/shared/gcPolicyCounters.hpp"
  45 #include "logging/logStream.hpp"
  46 #include "runtime/arguments.hpp"
  47 #include "runtime/java.hpp"
  48 #include "runtime/mutexLocker.hpp"
  49 #include "utilities/debug.hpp"
  50 #include "utilities/growableArray.hpp"
  51 #include "utilities/pair.hpp"
  52 
  53 G1Policy::G1Policy(STWGCTimer* gc_timer) :
  54   _predictor(G1ConfidencePercent / 100.0),
  55   _analytics(new G1Analytics(&_predictor)),
  56   _remset_tracker(),
  57   _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
  58   _ihop_control(create_ihop_control(&_predictor)),
  59   _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
  60   _full_collection_start_sec(0.0),
  61   _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
  62   _young_list_target_length(0),
  63   _young_list_fixed_length(0),
  64   _young_list_max_length(0),
  65   _eden_surv_rate_group(new G1SurvRateGroup()),
  66   _survivor_surv_rate_group(new G1SurvRateGroup()),
  67   _reserve_factor((double) G1ReservePercent / 100.0),
  68   _reserve_regions(0),
  69   _young_gen_sizer(G1YoungGenSizer::create_gen_sizer()),
  70   _free_regions_at_end_of_collection(0),
  71   _rs_length(0),
  72   _rs_length_prediction(0),
  73   _pending_cards_at_gc_start(0),
  74   _pending_cards_at_prev_gc_end(0),
  75   _total_mutator_refined_cards(0),
  76   _total_concurrent_refined_cards(0),
  77   _total_concurrent_refinement_time(),
  78   _bytes_allocated_in_old_since_last_gc(0),
  79   _initial_mark_to_mixed(),
  80   _collection_set(NULL),
  81   _g1h(NULL),
  82   _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
  83   _mark_remark_start_sec(0),
  84   _mark_cleanup_start_sec(0),
  85   _tenuring_threshold(MaxTenuringThreshold),
  86   _max_survivor_regions(0),
  87   _survivors_age_table(true)
  88 {
  89 }
  90 
  91 G1Policy::~G1Policy() {
  92   delete _ihop_control;
  93   delete _young_gen_sizer;
  94 }
  95 
  96 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) {
  97   if (G1Arguments::is_heterogeneous_heap()) {
  98     return new G1HeterogeneousHeapPolicy(gc_timer_stw);
  99   } else {
 100     return new G1Policy(gc_timer_stw);
 101   }
 102 }
 103 
 104 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
 105 
 106 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
 107   _g1h = g1h;
 108   _collection_set = collection_set;
 109 
 110   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 111 
 112   if (!use_adaptive_young_list_length()) {
 113     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 114   }
 115   _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
 116 
 117   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 118 
 119   update_young_list_max_and_target_length();
 120   // We may immediately start allocating regions and placing them on the
 121   // collection set list. Initialize the per-collection set info
 122   _collection_set->start_incremental_building();
 123 }
 124 
 125 void G1Policy::note_gc_start() {
 126   phase_times()->note_gc_start();
 127 }
 128 
 129 class G1YoungLengthPredictor {
 130   const double _base_time_ms;
 131   const double _base_free_regions;
 132   const double _target_pause_time_ms;
 133   const G1Policy* const _policy;
 134 
 135  public:
 136   G1YoungLengthPredictor(double base_time_ms,
 137                          double base_free_regions,
 138                          double target_pause_time_ms,
 139                          const G1Policy* policy) :
 140     _base_time_ms(base_time_ms),
 141     _base_free_regions(base_free_regions),
 142     _target_pause_time_ms(target_pause_time_ms),
 143     _policy(policy) {}
 144 
 145   bool will_fit(uint young_length) const {
 146     if (young_length >= _base_free_regions) {
 147       // end condition 1: not enough space for the young regions
 148       return false;
 149     }
 150 
 151     size_t bytes_to_copy = 0;
 152     const double copy_time_ms = _policy->predict_eden_copy_time_ms(young_length, &bytes_to_copy);
 153     const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
 154     const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
 155     if (pause_time_ms > _target_pause_time_ms) {
 156       // end condition 2: prediction is over the target pause time
 157       return false;
 158     }
 159 
 160     const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
 161 
 162     // When copying, we will likely need more bytes free than is live in the region.
 163     // Add some safety margin to factor in the confidence of our guess, and the
 164     // natural expected waste.
 165     // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
 166     // of the calculation: the lower the confidence, the more headroom.
 167     // (100 + TargetPLABWastePct) represents the increase in expected bytes during
 168     // copying due to anticipated waste in the PLABs.
 169     const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
 170     const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
 171 
 172     if (expected_bytes_to_copy > free_bytes) {
 173       // end condition 3: out-of-space
 174       return false;
 175     }
 176 
 177     // success!
 178     return true;
 179   }
 180 };
 181 
 182 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
 183   // re-calculate the necessary reserve
 184   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 185   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 186   // smaller than 1.0) we'll get 1.
 187   _reserve_regions = (uint) ceil(reserve_regions_d);
 188 
 189   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 190 
 191   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
 192 }
 193 
 194 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
 195   uint desired_min_length = 0;
 196   if (use_adaptive_young_list_length()) {
 197     if (_analytics->num_alloc_rate_ms() > 3) {
 198       double now_sec = os::elapsedTime();
 199       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 200       double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
 201       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 202     } else {
 203       // otherwise we don't have enough info to make the prediction
 204     }
 205   }
 206   desired_min_length += base_min_length;
 207   // make sure we don't go below any user-defined minimum bound
 208   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 209 }
 210 
 211 uint G1Policy::calculate_young_list_desired_max_length() const {
 212   // Here, we might want to also take into account any additional
 213   // constraints (i.e., user-defined minimum bound). Currently, we
 214   // effectively don't set this bound.
 215   return _young_gen_sizer->max_desired_young_length();
 216 }
 217 
 218 uint G1Policy::update_young_list_max_and_target_length() {
 219   return update_young_list_max_and_target_length(_analytics->predict_rs_length());
 220 }
 221 
 222 uint G1Policy::update_young_list_max_and_target_length(size_t rs_length) {
 223   uint unbounded_target_length = update_young_list_target_length(rs_length);
 224   update_max_gc_locker_expansion();
 225   return unbounded_target_length;
 226 }
 227 
 228 uint G1Policy::update_young_list_target_length(size_t rs_length) {
 229   YoungTargetLengths young_lengths = young_list_target_lengths(rs_length);
 230   _young_list_target_length = young_lengths.first;
 231 
 232   return young_lengths.second;
 233 }
 234 
 235 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_length) const {
 236   YoungTargetLengths result;
 237 
 238   // Calculate the absolute and desired min bounds first.
 239 
 240   // This is how many young regions we already have (currently: the survivors).
 241   const uint base_min_length = _g1h->survivor_regions_count();
 242   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 243   // This is the absolute minimum young length. Ensure that we
 244   // will at least have one eden region available for allocation.
 245   uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
 246   // If we shrank the young list target it should not shrink below the current size.
 247   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 248   // Calculate the absolute and desired max bounds.
 249 
 250   uint desired_max_length = calculate_young_list_desired_max_length();
 251 
 252   uint young_list_target_length = 0;
 253   if (use_adaptive_young_list_length()) {
 254     if (collector_state()->in_young_only_phase()) {
 255       young_list_target_length =
 256                         calculate_young_list_target_length(rs_length,
 257                                                            base_min_length,
 258                                                            desired_min_length,
 259                                                            desired_max_length);
 260     } else {
 261       // Don't calculate anything and let the code below bound it to
 262       // the desired_min_length, i.e., do the next GC as soon as
 263       // possible to maximize how many old regions we can add to it.
 264     }
 265   } else {
 266     // The user asked for a fixed young gen so we'll fix the young gen
 267     // whether the next GC is young or mixed.
 268     young_list_target_length = _young_list_fixed_length;
 269   }
 270 
 271   result.second = young_list_target_length;
 272 
 273   // We will try our best not to "eat" into the reserve.
 274   uint absolute_max_length = 0;
 275   if (_free_regions_at_end_of_collection > _reserve_regions) {
 276     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 277   }
 278   if (desired_max_length > absolute_max_length) {
 279     desired_max_length = absolute_max_length;
 280   }
 281 
 282   // Make sure we don't go over the desired max length, nor under the
 283   // desired min length. In case they clash, desired_min_length wins
 284   // which is why that test is second.
 285   if (young_list_target_length > desired_max_length) {
 286     young_list_target_length = desired_max_length;
 287   }
 288   if (young_list_target_length < desired_min_length) {
 289     young_list_target_length = desired_min_length;
 290   }
 291 
 292   assert(young_list_target_length > base_min_length,
 293          "we should be able to allocate at least one eden region");
 294   assert(young_list_target_length >= absolute_min_length, "post-condition");
 295 
 296   result.first = young_list_target_length;
 297   return result;
 298 }
 299 
 300 uint G1Policy::calculate_young_list_target_length(size_t rs_length,
 301                                                   uint base_min_length,
 302                                                   uint desired_min_length,
 303                                                   uint desired_max_length) const {
 304   assert(use_adaptive_young_list_length(), "pre-condition");
 305   assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
 306 
 307   // In case some edge-condition makes the desired max length too small...
 308   if (desired_max_length <= desired_min_length) {
 309     return desired_min_length;
 310   }
 311 
 312   // We'll adjust min_young_length and max_young_length not to include
 313   // the already allocated young regions (i.e., so they reflect the
 314   // min and max eden regions we'll allocate). The base_min_length
 315   // will be reflected in the predictions by the
 316   // survivor_regions_evac_time prediction.
 317   assert(desired_min_length > base_min_length, "invariant");
 318   uint min_young_length = desired_min_length - base_min_length;
 319   assert(desired_max_length > base_min_length, "invariant");
 320   uint max_young_length = desired_max_length - base_min_length;
 321 
 322   const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 323   const size_t pending_cards = _analytics->predict_pending_cards();
 324   const double base_time_ms = predict_base_elapsed_time_ms(pending_cards, rs_length);
 325   const uint available_free_regions = _free_regions_at_end_of_collection;
 326   const uint base_free_regions =
 327     available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
 328 
 329   // Here, we will make sure that the shortest young length that
 330   // makes sense fits within the target pause time.
 331 
 332   G1YoungLengthPredictor p(base_time_ms,
 333                            base_free_regions,
 334                            target_pause_time_ms,
 335                            this);
 336   if (p.will_fit(min_young_length)) {
 337     // The shortest young length will fit into the target pause time;
 338     // we'll now check whether the absolute maximum number of young
 339     // regions will fit in the target pause time. If not, we'll do
 340     // a binary search between min_young_length and max_young_length.
 341     if (p.will_fit(max_young_length)) {
 342       // The maximum young length will fit into the target pause time.
 343       // We are done so set min young length to the maximum length (as
 344       // the result is assumed to be returned in min_young_length).
 345       min_young_length = max_young_length;
 346     } else {
 347       // The maximum possible number of young regions will not fit within
 348       // the target pause time so we'll search for the optimal
 349       // length. The loop invariants are:
 350       //
 351       // min_young_length < max_young_length
 352       // min_young_length is known to fit into the target pause time
 353       // max_young_length is known not to fit into the target pause time
 354       //
 355       // Going into the loop we know the above hold as we've just
 356       // checked them. Every time around the loop we check whether
 357       // the middle value between min_young_length and
 358       // max_young_length fits into the target pause time. If it
 359       // does, it becomes the new min. If it doesn't, it becomes
 360       // the new max. This way we maintain the loop invariants.
 361 
 362       assert(min_young_length < max_young_length, "invariant");
 363       uint diff = (max_young_length - min_young_length) / 2;
 364       while (diff > 0) {
 365         uint young_length = min_young_length + diff;
 366         if (p.will_fit(young_length)) {
 367           min_young_length = young_length;
 368         } else {
 369           max_young_length = young_length;
 370         }
 371         assert(min_young_length <  max_young_length, "invariant");
 372         diff = (max_young_length - min_young_length) / 2;
 373       }
 374       // The results is min_young_length which, according to the
 375       // loop invariants, should fit within the target pause time.
 376 
 377       // These are the post-conditions of the binary search above:
 378       assert(min_young_length < max_young_length,
 379              "otherwise we should have discovered that max_young_length "
 380              "fits into the pause target and not done the binary search");
 381       assert(p.will_fit(min_young_length),
 382              "min_young_length, the result of the binary search, should "
 383              "fit into the pause target");
 384       assert(!p.will_fit(min_young_length + 1),
 385              "min_young_length, the result of the binary search, should be "
 386              "optimal, so no larger length should fit into the pause target");
 387     }
 388   } else {
 389     // Even the minimum length doesn't fit into the pause time
 390     // target, return it as the result nevertheless.
 391   }
 392   return base_min_length + min_young_length;
 393 }
 394 
 395 double G1Policy::predict_survivor_regions_evac_time() const {
 396   double survivor_regions_evac_time = 0.0;
 397   const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
 398   for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
 399        it != survivor_regions->end();
 400        ++it) {
 401     survivor_regions_evac_time += predict_region_total_time_ms(*it, collector_state()->in_young_only_phase());
 402   }
 403   return survivor_regions_evac_time;
 404 }
 405 
 406 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_length) {
 407   guarantee(use_adaptive_young_list_length(), "should not call this otherwise" );
 408 
 409   if (rs_length > _rs_length_prediction) {
 410     // add 10% to avoid having to recalculate often
 411     size_t rs_length_prediction = rs_length * 1100 / 1000;
 412     update_rs_length_prediction(rs_length_prediction);
 413 
 414     update_young_list_max_and_target_length(rs_length_prediction);
 415   }
 416 }
 417 
 418 void G1Policy::update_rs_length_prediction() {
 419   update_rs_length_prediction(_analytics->predict_rs_length());
 420 }
 421 
 422 void G1Policy::update_rs_length_prediction(size_t prediction) {
 423   if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) {
 424     _rs_length_prediction = prediction;
 425   }
 426 }
 427 
 428 void G1Policy::record_full_collection_start() {
 429   _full_collection_start_sec = os::elapsedTime();
 430   // Release the future to-space so that it is available for compaction into.
 431   collector_state()->set_in_young_only_phase(false);
 432   collector_state()->set_in_full_gc(true);
 433   _collection_set->clear_candidates();
 434   record_concurrent_refinement_data(true /* is_full_collection */);
 435 }
 436 
 437 void G1Policy::record_full_collection_end() {
 438   // Consider this like a collection pause for the purposes of allocation
 439   // since last pause.
 440   double end_sec = os::elapsedTime();
 441   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 442   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 443 
 444   _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
 445 
 446   collector_state()->set_in_full_gc(false);
 447 
 448   // "Nuke" the heuristics that control the young/mixed GC
 449   // transitions and make sure we start with young GCs after the Full GC.
 450   collector_state()->set_in_young_only_phase(true);
 451   collector_state()->set_in_young_gc_before_mixed(false);
 452   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
 453   collector_state()->set_in_initial_mark_gc(false);
 454   collector_state()->set_mark_or_rebuild_in_progress(false);
 455   collector_state()->set_clearing_next_bitmap(false);
 456 
 457   _eden_surv_rate_group->start_adding_regions();
 458   // also call this on any additional surv rate groups
 459 
 460   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 461   _survivor_surv_rate_group->reset();
 462   update_young_list_max_and_target_length();
 463   update_rs_length_prediction();
 464   _pending_cards_at_prev_gc_end = _g1h->pending_card_num();
 465 
 466   _bytes_allocated_in_old_since_last_gc = 0;
 467 
 468   record_pause(FullGC, _full_collection_start_sec, end_sec);
 469 }
 470 
 471 void G1Policy::record_concurrent_refinement_data(bool is_full_collection) {
 472   _pending_cards_at_gc_start = _g1h->pending_card_num();
 473 
 474   // Record info about concurrent refinement thread processing.
 475   G1ConcurrentRefine* cr = _g1h->concurrent_refine();
 476   G1ConcurrentRefine::RefinementStats cr_stats = cr->total_refinement_stats();
 477 
 478   Tickspan cr_time = cr_stats._time - _total_concurrent_refinement_time;
 479   _total_concurrent_refinement_time = cr_stats._time;
 480 
 481   size_t cr_cards = cr_stats._cards - _total_concurrent_refined_cards;
 482   _total_concurrent_refined_cards = cr_stats._cards;
 483 
 484   // Don't update rate if full collection.  We could be in an implicit full
 485   // collection after a non-full collection failure, in which case there
 486   // wasn't any mutator/cr-thread activity since last recording.  And if
 487   // we're in an explicit full collection, the time since the last GC can
 488   // be arbitrarily short, so not a very good sample.  Similarly, don't
 489   // update the rate if the current sample is empty or time is zero.
 490   if (!is_full_collection && (cr_cards > 0) && (cr_time > Tickspan())) {
 491     double rate = cr_cards / (cr_time.seconds() * MILLIUNITS);
 492     _analytics->report_concurrent_refine_rate_ms(rate);
 493   }
 494 
 495   // Record info about mutator thread processing.
 496   G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
 497   size_t mut_total_cards = dcqs.total_mutator_refined_cards();
 498   size_t mut_cards = mut_total_cards - _total_mutator_refined_cards;
 499   _total_mutator_refined_cards = mut_total_cards;
 500 
 501   // Record mutator's card logging rate.
 502   // Don't update if full collection; see above.
 503   if (!is_full_collection) {
 504     size_t total_cards = _pending_cards_at_gc_start + cr_cards + mut_cards;
 505     assert(_pending_cards_at_prev_gc_end <= total_cards,
 506            "untracked cards: last pending: " SIZE_FORMAT
 507            ", pending: " SIZE_FORMAT ", conc refine: " SIZE_FORMAT
 508            ", mut refine:" SIZE_FORMAT,
 509            _pending_cards_at_prev_gc_end, _pending_cards_at_gc_start,
 510            cr_cards, mut_cards);
 511     size_t logged_cards = total_cards - _pending_cards_at_prev_gc_end;
 512     double logging_start_time = _analytics->prev_collection_pause_end_ms();
 513     double logging_end_time = Ticks::now().seconds() * MILLIUNITS;
 514     double logging_time = logging_end_time - logging_start_time;
 515     // Unlike above for conc-refine rate, here we should not require a
 516     // non-empty sample, since an application could go some time with only
 517     // young-gen or filtered out writes.  But we'll ignore unusually short
 518     // sample periods, as they may just pollute the predictions.
 519     if (logging_time > 1.0) {   // Require > 1ms sample time.
 520       _analytics->report_logged_cards_rate_ms(logged_cards / logging_time);
 521     }
 522   }
 523 }
 524 
 525 void G1Policy::record_collection_pause_start(double start_time_sec) {
 526   // We only need to do this here as the policy will only be applied
 527   // to the GC we're about to start. so, no point is calculating this
 528   // every time we calculate / recalculate the target young length.
 529   update_survivors_policy();
 530 
 531   assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
 532          "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
 533          max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
 534   assert_used_and_recalculate_used_equal(_g1h);
 535 
 536   phase_times()->record_cur_collection_start_sec(start_time_sec);
 537 
 538   record_concurrent_refinement_data(false /* is_full_collection */);
 539 
 540   _collection_set->reset_bytes_used_before();
 541 
 542   // do that for any other surv rate groups
 543   _eden_surv_rate_group->stop_adding_regions();
 544   _survivors_age_table.clear();
 545 
 546   assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
 547 }
 548 
 549 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
 550   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 551   collector_state()->set_in_initial_mark_gc(false);
 552 }
 553 
 554 void G1Policy::record_concurrent_mark_remark_start() {
 555   _mark_remark_start_sec = os::elapsedTime();
 556 }
 557 
 558 void G1Policy::record_concurrent_mark_remark_end() {
 559   double end_time_sec = os::elapsedTime();
 560   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 561   _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
 562   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
 563 
 564   record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 565 }
 566 
 567 void G1Policy::record_concurrent_mark_cleanup_start() {
 568   _mark_cleanup_start_sec = os::elapsedTime();
 569 }
 570 
 571 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
 572   return phase_times()->average_time_ms(phase);
 573 }
 574 
 575 double G1Policy::young_other_time_ms() const {
 576   return phase_times()->young_cset_choice_time_ms() +
 577          phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
 578 }
 579 
 580 double G1Policy::non_young_other_time_ms() const {
 581   return phase_times()->non_young_cset_choice_time_ms() +
 582          phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
 583 }
 584 
 585 double G1Policy::other_time_ms(double pause_time_ms) const {
 586   return pause_time_ms - phase_times()->cur_collection_par_time_ms();
 587 }
 588 
 589 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
 590   return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms() - phase_times()->total_rebuild_freelist_time_ms();
 591 }
 592 
 593 bool G1Policy::about_to_start_mixed_phase() const {
 594   return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
 595 }
 596 
 597 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
 598   if (about_to_start_mixed_phase()) {
 599     return false;
 600   }
 601 
 602   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
 603 
 604   size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
 605   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 606   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 607 
 608   bool result = false;
 609   if (marking_request_bytes > marking_initiating_used_threshold) {
 610     result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
 611     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
 612                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
 613                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
 614   }
 615 
 616   return result;
 617 }
 618 
 619 double G1Policy::logged_cards_processing_time() const {
 620   double all_cards_processing_time = average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR);
 621   size_t logged_dirty_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
 622   size_t scan_heap_roots_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
 623                                  phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
 624   // This may happen if there are duplicate cards in different log buffers.
 625   if (logged_dirty_cards > scan_heap_roots_cards) {
 626     return all_cards_processing_time + average_time_ms(G1GCPhaseTimes::MergeLB);
 627   }
 628   return (all_cards_processing_time * logged_dirty_cards / scan_heap_roots_cards) + average_time_ms(G1GCPhaseTimes::MergeLB);
 629 }
 630 
 631 // Anything below that is considered to be zero
 632 #define MIN_TIMER_GRANULARITY 0.0000001
 633 
 634 void G1Policy::record_collection_pause_end(double pause_time_ms) {
 635   G1GCPhaseTimes* p = phase_times();
 636 
 637   double end_time_sec = os::elapsedTime();
 638 
 639   bool this_pause_included_initial_mark = false;
 640   bool this_pause_was_young_only = collector_state()->in_young_only_phase();
 641 
 642   bool update_stats = !_g1h->evacuation_failed();
 643 
 644   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
 645 
 646   _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 647 
 648   this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
 649   if (this_pause_included_initial_mark) {
 650     record_concurrent_mark_init_end(0.0);
 651   } else {
 652     maybe_start_marking();
 653   }
 654 
 655   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
 656   if (app_time_ms < MIN_TIMER_GRANULARITY) {
 657     // This usually happens due to the timer not having the required
 658     // granularity. Some Linuxes are the usual culprits.
 659     // We'll just set it to something (arbitrarily) small.
 660     app_time_ms = 1.0;
 661   }
 662 
 663   if (update_stats) {
 664     // We maintain the invariant that all objects allocated by mutator
 665     // threads will be allocated out of eden regions. So, we can use
 666     // the eden region number allocated since the previous GC to
 667     // calculate the application's allocate rate. The only exception
 668     // to that is humongous objects that are allocated separately. But
 669     // given that humongous object allocations do not really affect
 670     // either the pause's duration nor when the next pause will take
 671     // place we can safely ignore them here.
 672     uint regions_allocated = _collection_set->eden_region_length();
 673     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
 674     _analytics->report_alloc_rate_ms(alloc_rate_ms);
 675 
 676     double interval_ms =
 677       (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
 678     _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
 679     _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
 680   }
 681 
 682   if (collector_state()->in_young_gc_before_mixed()) {
 683     assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
 684     // This has been the young GC before we start doing mixed GCs. We already
 685     // decided to start mixed GCs much earlier, so there is nothing to do except
 686     // advancing the state.
 687     collector_state()->set_in_young_only_phase(false);
 688     collector_state()->set_in_young_gc_before_mixed(false);
 689   } else if (!this_pause_was_young_only) {
 690     // This is a mixed GC. Here we decide whether to continue doing more
 691     // mixed GCs or not.
 692     if (!next_gc_should_be_mixed("continue mixed GCs",
 693                                  "do not continue mixed GCs")) {
 694       collector_state()->set_in_young_only_phase(true);
 695 
 696       clear_collection_set_candidates();
 697       maybe_start_marking();
 698     }
 699   }
 700 
 701   _eden_surv_rate_group->start_adding_regions();
 702 
 703   double merge_hcc_time_ms = average_time_ms(G1GCPhaseTimes::MergeHCC);
 704   if (update_stats) {
 705     size_t const total_log_buffer_cards = p->sum_thread_work_items(G1GCPhaseTimes::MergeHCC, G1GCPhaseTimes::MergeHCCDirtyCards) +
 706                                           p->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
 707     // Update prediction for card merge; MergeRSDirtyCards includes the cards from the Eager Reclaim phase.
 708     size_t const total_cards_merged = p->sum_thread_work_items(G1GCPhaseTimes::MergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
 709                                       p->sum_thread_work_items(G1GCPhaseTimes::OptMergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
 710                                       total_log_buffer_cards;
 711 
 712     // The threshold for the number of cards in a given sampling which we consider
 713     // large enough so that the impact from setup and other costs is negligible.
 714     size_t const CardsNumSamplingThreshold = 10;
 715 
 716     if (total_cards_merged > CardsNumSamplingThreshold) {
 717       double avg_time_merge_cards = average_time_ms(G1GCPhaseTimes::MergeER) +
 718                                     average_time_ms(G1GCPhaseTimes::MergeRS) +
 719                                     average_time_ms(G1GCPhaseTimes::MergeHCC) +
 720                                     average_time_ms(G1GCPhaseTimes::MergeLB) +
 721                                     average_time_ms(G1GCPhaseTimes::OptMergeRS);
 722       _analytics->report_cost_per_card_merge_ms(avg_time_merge_cards / total_cards_merged, this_pause_was_young_only);
 723     }
 724 
 725     // Update prediction for card scan
 726     size_t const total_cards_scanned = p->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
 727                                        p->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
 728 
 729     if (total_cards_scanned > CardsNumSamplingThreshold) {
 730       double avg_time_dirty_card_scan = average_time_ms(G1GCPhaseTimes::ScanHR) +
 731                                         average_time_ms(G1GCPhaseTimes::OptScanHR);
 732 
 733       _analytics->report_cost_per_card_scan_ms(avg_time_dirty_card_scan / total_cards_scanned, this_pause_was_young_only);
 734     }
 735 
 736     // Update prediction for the ratio between cards from the remembered
 737     // sets and actually scanned cards from the remembered sets.
 738     // Cards from the remembered sets are all cards not duplicated by cards from
 739     // the logs.
 740     // Due to duplicates in the log buffers, the number of actually scanned cards
 741     // can be smaller than the cards in the log buffers.
 742     const size_t from_rs_length_cards = (total_cards_scanned > total_log_buffer_cards) ? total_cards_scanned - total_log_buffer_cards : 0;
 743     double merge_to_scan_ratio = 0.0;
 744     if (total_cards_scanned > 0) {
 745       merge_to_scan_ratio = (double) from_rs_length_cards / total_cards_scanned;
 746     }
 747     _analytics->report_card_merge_to_scan_ratio(merge_to_scan_ratio, this_pause_was_young_only);
 748 
 749     const size_t recorded_rs_length = _collection_set->recorded_rs_length();
 750     const size_t rs_length_diff = _rs_length > recorded_rs_length ? _rs_length - recorded_rs_length : 0;
 751     _analytics->report_rs_length_diff(rs_length_diff);
 752 
 753     // Update prediction for copy cost per byte
 754     size_t copied_bytes = p->sum_thread_work_items(G1GCPhaseTimes::MergePSS, G1GCPhaseTimes::MergePSSCopiedBytes);
 755 
 756     if (copied_bytes > 0) {
 757       double cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / copied_bytes;
 758       _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
 759     }
 760 
 761     if (_collection_set->young_region_length() > 0) {
 762       _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
 763                                                         _collection_set->young_region_length());
 764     }
 765 
 766     if (_collection_set->old_region_length() > 0) {
 767       _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
 768                                                             _collection_set->old_region_length());
 769     }
 770 
 771     _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
 772 
 773     // Do not update RS lengths and the number of pending cards with information from mixed gc:
 774     // these are is wildly different to during young only gc and mess up young gen sizing right
 775     // after the mixed gc phase.
 776     // During mixed gc we do not use them for young gen sizing.
 777     if (this_pause_was_young_only) {
 778       _analytics->report_pending_cards((double) _pending_cards_at_gc_start);
 779       _analytics->report_rs_length((double) _rs_length);
 780     }
 781   }
 782 
 783   assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()),
 784          "If the last pause has been an initial mark, we should not have been in the marking window");
 785   if (this_pause_included_initial_mark) {
 786     collector_state()->set_mark_or_rebuild_in_progress(true);
 787   }
 788 
 789   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 790 
 791   update_rs_length_prediction();
 792 
 793   // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely
 794   // that in this case we are not running in a "normal" operating mode.
 795   if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
 796     // IHOP control wants to know the expected young gen length if it were not
 797     // restrained by the heap reserve. Using the actual length would make the
 798     // prediction too small and the limit the young gen every time we get to the
 799     // predicted target occupancy.
 800     size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
 801 
 802     update_ihop_prediction(app_time_ms / 1000.0,
 803                            _bytes_allocated_in_old_since_last_gc,
 804                            last_unrestrained_young_length * HeapRegion::GrainBytes,
 805                            this_pause_was_young_only);
 806     _bytes_allocated_in_old_since_last_gc = 0;
 807 
 808     _ihop_control->send_trace_event(_g1h->gc_tracer_stw());
 809   } else {
 810     // Any garbage collection triggered as periodic collection resets the time-to-mixed
 811     // measurement. Periodic collection typically means that the application is "inactive", i.e.
 812     // the marking threads may have received an uncharacterisic amount of cpu time
 813     // for completing the marking, i.e. are faster than expected.
 814     // This skews the predicted marking length towards smaller values which might cause
 815     // the mark start being too late.
 816     _initial_mark_to_mixed.reset();
 817   }
 818 
 819   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
 820   double scan_logged_cards_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
 821 
 822   if (scan_logged_cards_time_goal_ms < merge_hcc_time_ms) {
 823     log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
 824                                 "Logged Cards Scan time goal: %1.2fms Scan HCC time: %1.2fms",
 825                                 scan_logged_cards_time_goal_ms, merge_hcc_time_ms);
 826 
 827     scan_logged_cards_time_goal_ms = 0;
 828   } else {
 829     scan_logged_cards_time_goal_ms -= merge_hcc_time_ms;
 830   }
 831 
 832   _pending_cards_at_prev_gc_end = _g1h->pending_card_num();
 833   double const logged_cards_time = logged_cards_processing_time();
 834 
 835   log_debug(gc, ergo, refine)("Concurrent refinement times: Logged Cards Scan time goal: %1.2fms Logged Cards Scan time: %1.2fms HCC time: %1.2fms",
 836                               scan_logged_cards_time_goal_ms, logged_cards_time, merge_hcc_time_ms);
 837 
 838   _g1h->concurrent_refine()->adjust(logged_cards_time,
 839                                     phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards),
 840                                     scan_logged_cards_time_goal_ms);
 841 }
 842 
 843 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
 844   if (G1UseAdaptiveIHOP) {
 845     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
 846                                      predictor,
 847                                      G1ReservePercent,
 848                                      G1HeapWastePercent);
 849   } else {
 850     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
 851   }
 852 }
 853 
 854 void G1Policy::update_ihop_prediction(double mutator_time_s,
 855                                       size_t mutator_alloc_bytes,
 856                                       size_t young_gen_size,
 857                                       bool this_gc_was_young_only) {
 858   // Always try to update IHOP prediction. Even evacuation failures give information
 859   // about e.g. whether to start IHOP earlier next time.
 860 
 861   // Avoid using really small application times that might create samples with
 862   // very high or very low values. They may be caused by e.g. back-to-back gcs.
 863   double const min_valid_time = 1e-6;
 864 
 865   bool report = false;
 866 
 867   double marking_to_mixed_time = -1.0;
 868   if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
 869     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
 870     assert(marking_to_mixed_time > 0.0,
 871            "Initial mark to mixed time must be larger than zero but is %.3f",
 872            marking_to_mixed_time);
 873     if (marking_to_mixed_time > min_valid_time) {
 874       _ihop_control->update_marking_length(marking_to_mixed_time);
 875       report = true;
 876     }
 877   }
 878 
 879   // As an approximation for the young gc promotion rates during marking we use
 880   // all of them. In many applications there are only a few if any young gcs during
 881   // marking, which makes any prediction useless. This increases the accuracy of the
 882   // prediction.
 883   if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
 884     _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
 885     report = true;
 886   }
 887 
 888   if (report) {
 889     report_ihop_statistics();
 890   }
 891 }
 892 
 893 void G1Policy::report_ihop_statistics() {
 894   _ihop_control->print();
 895 }
 896 
 897 void G1Policy::print_phases() {
 898   phase_times()->print();
 899 }
 900 
 901 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
 902                                               size_t rs_length) const {
 903   size_t effective_scanned_cards = _analytics->predict_scan_card_num(rs_length, collector_state()->in_young_only_phase());
 904   return
 905     _analytics->predict_card_merge_time_ms(pending_cards + rs_length, collector_state()->in_young_only_phase()) +
 906     _analytics->predict_card_scan_time_ms(effective_scanned_cards, collector_state()->in_young_only_phase()) +
 907     _analytics->predict_constant_other_time_ms() +
 908     predict_survivor_regions_evac_time();
 909 }
 910 
 911 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
 912   size_t rs_length = _analytics->predict_rs_length();
 913   return predict_base_elapsed_time_ms(pending_cards, rs_length);
 914 }
 915 
 916 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
 917   size_t bytes_to_copy;
 918   if (!hr->is_young()) {
 919     bytes_to_copy = hr->max_live_bytes();
 920   } else {
 921     bytes_to_copy = (size_t) (hr->used() * hr->surv_rate_prediction(_predictor));
 922   }
 923   return bytes_to_copy;
 924 }
 925 
 926 double G1Policy::predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy) const {
 927   if (count == 0) {
 928     return 0.0;
 929   }
 930   size_t const expected_bytes = _eden_surv_rate_group->accum_surv_rate_pred(count) * HeapRegion::GrainBytes;
 931   if (bytes_to_copy != NULL) {
 932     *bytes_to_copy = expected_bytes;
 933   }
 934   return _analytics->predict_object_copy_time_ms(expected_bytes, collector_state()->mark_or_rebuild_in_progress());
 935 }
 936 
 937 double G1Policy::predict_region_copy_time_ms(HeapRegion* hr) const {
 938   size_t const bytes_to_copy = predict_bytes_to_copy(hr);
 939   return _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
 940 }
 941 
 942 double G1Policy::predict_region_non_copy_time_ms(HeapRegion* hr,
 943                                                  bool for_young_gc) const {
 944   size_t rs_length = hr->rem_set()->occupied();
 945   size_t scan_card_num = _analytics->predict_scan_card_num(rs_length, for_young_gc);
 946 
 947   double region_elapsed_time_ms =
 948     _analytics->predict_card_merge_time_ms(rs_length, collector_state()->in_young_only_phase()) +
 949     _analytics->predict_card_scan_time_ms(scan_card_num, collector_state()->in_young_only_phase());
 950 
 951   // The prediction of the "other" time for this region is based
 952   // upon the region type and NOT the GC type.
 953   if (hr->is_young()) {
 954     region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
 955   } else {
 956     region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
 957   }
 958   return region_elapsed_time_ms;
 959 }
 960 
 961 double G1Policy::predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const {
 962   return predict_region_non_copy_time_ms(hr, for_young_gc) + predict_region_copy_time_ms(hr);
 963 }
 964 
 965 bool G1Policy::should_allocate_mutator_region() const {
 966   uint young_list_length = _g1h->young_regions_count();
 967   uint young_list_target_length = _young_list_target_length;
 968   return young_list_length < young_list_target_length;
 969 }
 970 
 971 bool G1Policy::can_expand_young_list() const {
 972   uint young_list_length = _g1h->young_regions_count();
 973   uint young_list_max_length = _young_list_max_length;
 974   return young_list_length < young_list_max_length;
 975 }
 976 
 977 bool G1Policy::use_adaptive_young_list_length() const {
 978   return _young_gen_sizer->use_adaptive_young_list_length();
 979 }
 980 
 981 size_t G1Policy::desired_survivor_size(uint max_regions) const {
 982   size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
 983   return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 984 }
 985 
 986 void G1Policy::print_age_table() {
 987   _survivors_age_table.print_age_table(_tenuring_threshold);
 988 }
 989 
 990 void G1Policy::update_max_gc_locker_expansion() {
 991   uint expansion_region_num = 0;
 992   if (GCLockerEdenExpansionPercent > 0) {
 993     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
 994     double expansion_region_num_d = perc * (double) _young_list_target_length;
 995     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
 996     // less than 1.0) we'll get 1.
 997     expansion_region_num = (uint) ceil(expansion_region_num_d);
 998   } else {
 999     assert(expansion_region_num == 0, "sanity");
1000   }
1001   _young_list_max_length = _young_list_target_length + expansion_region_num;
1002   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1003 }
1004 
1005 // Calculates survivor space parameters.
1006 void G1Policy::update_survivors_policy() {
1007   double max_survivor_regions_d =
1008                  (double) _young_list_target_length / (double) SurvivorRatio;
1009 
1010   // Calculate desired survivor size based on desired max survivor regions (unconstrained
1011   // by remaining heap). Otherwise we may cause undesired promotions as we are
1012   // already getting close to end of the heap, impacting performance even more.
1013   uint const desired_max_survivor_regions = ceil(max_survivor_regions_d);
1014   size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions);
1015 
1016   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size);
1017   if (UsePerfData) {
1018     _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
1019     _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize);
1020   }
1021   // The real maximum survivor size is bounded by the number of regions that can
1022   // be allocated into.
1023   _max_survivor_regions = MIN2(desired_max_survivor_regions,
1024                                _g1h->num_free_or_available_regions());
1025 }
1026 
1027 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1028   // We actually check whether we are marking here and not if we are in a
1029   // reclamation phase. This means that we will schedule a concurrent mark
1030   // even while we are still in the process of reclaiming memory.
1031   bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
1032   if (!during_cycle) {
1033     log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1034     collector_state()->set_initiate_conc_mark_if_possible(true);
1035     return true;
1036   } else {
1037     log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1038     return false;
1039   }
1040 }
1041 
1042 void G1Policy::initiate_conc_mark() {
1043   collector_state()->set_in_initial_mark_gc(true);
1044   collector_state()->set_initiate_conc_mark_if_possible(false);
1045 }
1046 
1047 void G1Policy::decide_on_conc_mark_initiation() {
1048   // We are about to decide on whether this pause will be an
1049   // initial-mark pause.
1050 
1051   // First, collector_state()->in_initial_mark_gc() should not be already set. We
1052   // will set it here if we have to. However, it should be cleared by
1053   // the end of the pause (it's only set for the duration of an
1054   // initial-mark pause).
1055   assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
1056 
1057   if (collector_state()->initiate_conc_mark_if_possible()) {
1058     // We had noticed on a previous pause that the heap occupancy has
1059     // gone over the initiating threshold and we should start a
1060     // concurrent marking cycle. So we might initiate one.
1061 
1062     if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
1063       // Initiate a new initial mark if there is no marking or reclamation going on.
1064       initiate_conc_mark();
1065       log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1066     } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) {
1067       // Initiate a user requested initial mark. An initial mark must be young only
1068       // GC, so the collector state must be updated to reflect this.
1069       collector_state()->set_in_young_only_phase(true);
1070       collector_state()->set_in_young_gc_before_mixed(false);
1071 
1072       // We might have ended up coming here about to start a mixed phase with a collection set
1073       // active. The following remark might change the change the "evacuation efficiency" of
1074       // the regions in this set, leading to failing asserts later.
1075       // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
1076       clear_collection_set_candidates();
1077       abort_time_to_mixed_tracking();
1078       initiate_conc_mark();
1079       log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1080     } else {
1081       // The concurrent marking thread is still finishing up the
1082       // previous cycle. If we start one right now the two cycles
1083       // overlap. In particular, the concurrent marking thread might
1084       // be in the process of clearing the next marking bitmap (which
1085       // we will use for the next cycle if we start one). Starting a
1086       // cycle now will be bad given that parts of the marking
1087       // information might get cleared by the marking thread. And we
1088       // cannot wait for the marking thread to finish the cycle as it
1089       // periodically yields while clearing the next marking bitmap
1090       // and, if it's in a yield point, it's waiting for us to
1091       // finish. So, at this point we will not start a cycle and we'll
1092       // let the concurrent marking thread complete the last one.
1093       log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1094     }
1095   }
1096 }
1097 
1098 void G1Policy::record_concurrent_mark_cleanup_end() {
1099   G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions());
1100   _collection_set->set_candidates(candidates);
1101 
1102   bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1103   if (!mixed_gc_pending) {
1104     clear_collection_set_candidates();
1105     abort_time_to_mixed_tracking();
1106   }
1107   collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1108   collector_state()->set_mark_or_rebuild_in_progress(false);
1109 
1110   double end_sec = os::elapsedTime();
1111   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1112   _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1113   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1114 
1115   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1116 }
1117 
1118 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1119   return percent_of(reclaimable_bytes, _g1h->capacity());
1120 }
1121 
1122 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1123   virtual bool do_heap_region(HeapRegion* r) {
1124     r->rem_set()->clear_locked(true /* only_cardset */);
1125     return false;
1126   }
1127 };
1128 
1129 void G1Policy::clear_collection_set_candidates() {
1130   // Clear remembered sets of remaining candidate regions and the actual candidate
1131   // set.
1132   G1ClearCollectionSetCandidateRemSets cl;
1133   _collection_set->candidates()->iterate(&cl);
1134   _collection_set->clear_candidates();
1135 }
1136 
1137 void G1Policy::maybe_start_marking() {
1138   if (need_to_start_conc_mark("end of GC")) {
1139     // Note: this might have already been set, if during the last
1140     // pause we decided to start a cycle but at the beginning of
1141     // this pause we decided to postpone it. That's OK.
1142     collector_state()->set_initiate_conc_mark_if_possible(true);
1143   }
1144 }
1145 
1146 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1147   assert(!collector_state()->in_full_gc(), "must be");
1148   if (collector_state()->in_initial_mark_gc()) {
1149     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1150     return InitialMarkGC;
1151   } else if (collector_state()->in_young_gc_before_mixed()) {
1152     assert(!collector_state()->in_initial_mark_gc(), "must be");
1153     return LastYoungGC;
1154   } else if (collector_state()->in_mixed_phase()) {
1155     assert(!collector_state()->in_initial_mark_gc(), "must be");
1156     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1157     return MixedGC;
1158   } else {
1159     assert(!collector_state()->in_initial_mark_gc(), "must be");
1160     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1161     return YoungOnlyGC;
1162   }
1163 }
1164 
1165 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1166   // Manage the MMU tracker. For some reason it ignores Full GCs.
1167   if (kind != FullGC) {
1168     _mmu_tracker->add_pause(start, end);
1169   }
1170   // Manage the mutator time tracking from initial mark to first mixed gc.
1171   switch (kind) {
1172     case FullGC:
1173       abort_time_to_mixed_tracking();
1174       break;
1175     case Cleanup:
1176     case Remark:
1177     case YoungOnlyGC:
1178     case LastYoungGC:
1179       _initial_mark_to_mixed.add_pause(end - start);
1180       break;
1181     case InitialMarkGC:
1182       if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
1183         _initial_mark_to_mixed.record_initial_mark_end(end);
1184       }
1185       break;
1186     case MixedGC:
1187       _initial_mark_to_mixed.record_mixed_gc_start(start);
1188       break;
1189     default:
1190       ShouldNotReachHere();
1191   }
1192 }
1193 
1194 void G1Policy::abort_time_to_mixed_tracking() {
1195   _initial_mark_to_mixed.reset();
1196 }
1197 
1198 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1199                                        const char* false_action_str) const {
1200   G1CollectionSetCandidates* candidates = _collection_set->candidates();
1201 
1202   if (candidates->is_empty()) {
1203     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1204     return false;
1205   }
1206 
1207   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1208   size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1209   double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1210   double threshold = (double) G1HeapWastePercent;
1211   if (reclaimable_percent <= threshold) {
1212     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1213                         false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1214     return false;
1215   }
1216   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1217                       true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1218   return true;
1219 }
1220 
1221 uint G1Policy::calc_min_old_cset_length() const {
1222   // The min old CSet region bound is based on the maximum desired
1223   // number of mixed GCs after a cycle. I.e., even if some old regions
1224   // look expensive, we should add them to the CSet anyway to make
1225   // sure we go through the available old regions in no more than the
1226   // maximum desired number of mixed GCs.
1227   //
1228   // The calculation is based on the number of marked regions we added
1229   // to the CSet candidates in the first place, not how many remain, so
1230   // that the result is the same during all mixed GCs that follow a cycle.
1231 
1232   const size_t region_num = _collection_set->candidates()->num_regions();
1233   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1234   size_t result = region_num / gc_num;
1235   // emulate ceiling
1236   if (result * gc_num < region_num) {
1237     result += 1;
1238   }
1239   return (uint) result;
1240 }
1241 
1242 uint G1Policy::calc_max_old_cset_length() const {
1243   // The max old CSet region bound is based on the threshold expressed
1244   // as a percentage of the heap size. I.e., it should bound the
1245   // number of old regions added to the CSet irrespective of how many
1246   // of them are available.
1247 
1248   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1249   const size_t region_num = g1h->num_regions();
1250   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1251   size_t result = region_num * perc / 100;
1252   // emulate ceiling
1253   if (100 * result < region_num * perc) {
1254     result += 1;
1255   }
1256   return (uint) result;
1257 }
1258 
1259 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
1260                                                     double time_remaining_ms,
1261                                                     uint& num_initial_regions,
1262                                                     uint& num_optional_regions) {
1263   assert(candidates != NULL, "Must be");
1264 
1265   num_initial_regions = 0;
1266   num_optional_regions = 0;
1267   uint num_expensive_regions = 0;
1268 
1269   double predicted_old_time_ms = 0.0;
1270   double predicted_initial_time_ms = 0.0;
1271   double predicted_optional_time_ms = 0.0;
1272 
1273   double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction();
1274 
1275   const uint min_old_cset_length = calc_min_old_cset_length();
1276   const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length());
1277   const uint max_optional_regions = max_old_cset_length - min_old_cset_length;
1278   bool check_time_remaining = use_adaptive_young_list_length();
1279 
1280   uint candidate_idx = candidates->cur_idx();
1281 
1282   log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, "
1283                             "time remaining %1.2fms, optional threshold %1.2fms",
1284                             min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms);
1285 
1286   HeapRegion* hr = candidates->at(candidate_idx);
1287   while (hr != NULL) {
1288     if (num_initial_regions + num_optional_regions >= max_old_cset_length) {
1289       // Added maximum number of old regions to the CSet.
1290       log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). "
1291                                 "Initial %u regions, optional %u regions",
1292                                 num_initial_regions, num_optional_regions);
1293       break;
1294     }
1295 
1296     // Stop adding regions if the remaining reclaimable space is
1297     // not above G1HeapWastePercent.
1298     size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1299     double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1300     double threshold = (double) G1HeapWastePercent;
1301     if (reclaimable_percent <= threshold) {
1302       // We've added enough old regions that the amount of uncollected
1303       // reclaimable space is at or below the waste threshold. Stop
1304       // adding old regions to the CSet.
1305       log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). "
1306                                 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%",
1307                                 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes),
1308                                 reclaimable_percent, G1HeapWastePercent);
1309       break;
1310     }
1311 
1312     double predicted_time_ms = predict_region_total_time_ms(hr, false);
1313     time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
1314     // Add regions to old set until we reach the minimum amount
1315     if (num_initial_regions < min_old_cset_length) {
1316       predicted_old_time_ms += predicted_time_ms;
1317       num_initial_regions++;
1318       // Record the number of regions added with no time remaining
1319       if (time_remaining_ms == 0.0) {
1320         num_expensive_regions++;
1321       }
1322     } else if (!check_time_remaining) {
1323       // In the non-auto-tuning case, we'll finish adding regions
1324       // to the CSet if we reach the minimum.
1325       log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min).");
1326       break;
1327     } else {
1328       // Keep adding regions to old set until we reach the optional threshold
1329       if (time_remaining_ms > optional_threshold_ms) {
1330         predicted_old_time_ms += predicted_time_ms;
1331         num_initial_regions++;
1332       } else if (time_remaining_ms > 0) {
1333         // Keep adding optional regions until time is up.
1334         assert(num_optional_regions < max_optional_regions, "Should not be possible.");
1335         predicted_optional_time_ms += predicted_time_ms;
1336         num_optional_regions++;
1337       } else {
1338         log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high).");
1339         break;
1340       }
1341     }
1342     hr = candidates->at(++candidate_idx);
1343   }
1344   if (hr == NULL) {
1345     log_debug(gc, ergo, cset)("Old candidate collection set empty.");
1346   }
1347 
1348   if (num_expensive_regions > 0) {
1349     log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.",
1350                               num_expensive_regions);
1351   }
1352 
1353   log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, "
1354                             "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f",
1355                             num_initial_regions, num_optional_regions,
1356                             predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms);
1357 }
1358 
1359 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
1360                                                          uint const max_optional_regions,
1361                                                          double time_remaining_ms,
1362                                                          uint& num_optional_regions) {
1363   assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase");
1364 
1365   num_optional_regions = 0;
1366   double prediction_ms = 0;
1367   uint candidate_idx = candidates->cur_idx();
1368 
1369   HeapRegion* r = candidates->at(candidate_idx);
1370   while (num_optional_regions < max_optional_regions) {
1371     assert(r != NULL, "Region must exist");
1372     prediction_ms += predict_region_total_time_ms(r, false);
1373 
1374     if (prediction_ms > time_remaining_ms) {
1375       log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.",
1376                                 prediction_ms, r->hrm_index(), time_remaining_ms);
1377       break;
1378     }
1379     // This region will be included in the next optional evacuation.
1380 
1381     time_remaining_ms -= prediction_ms;
1382     num_optional_regions++;
1383     r = candidates->at(++candidate_idx);
1384   }
1385 
1386   log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms",
1387                             num_optional_regions, max_optional_regions, prediction_ms);
1388 }
1389 
1390 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1391   note_start_adding_survivor_regions();
1392 
1393   HeapRegion* last = NULL;
1394   for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1395        it != survivors->regions()->end();
1396        ++it) {
1397     HeapRegion* curr = *it;
1398     set_region_survivor(curr);
1399 
1400     // The region is a non-empty survivor so let's add it to
1401     // the incremental collection set for the next evacuation
1402     // pause.
1403     _collection_set->add_survivor_regions(curr);
1404 
1405     last = curr;
1406   }
1407   note_stop_adding_survivor_regions();
1408 
1409   // Don't clear the survivor list handles until the start of
1410   // the next evacuation pause - we need it in order to re-tag
1411   // the survivor regions from this evacuation pause as 'young'
1412   // at the start of the next.
1413 }