rev 60542 : [mq]: 8245511-rev.3

   1 /*
   2  * Copyright (c) 2001, 2020, 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/g1ConcurrentRefineStats.hpp"
  35 #include "gc/g1/g1CollectionSetChooser.hpp"
  36 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
  37 #include "gc/g1/g1HotCardCache.hpp"
  38 #include "gc/g1/g1IHOPControl.hpp"
  39 #include "gc/g1/g1GCPhaseTimes.hpp"
  40 #include "gc/g1/g1Policy.hpp"
  41 #include "gc/g1/g1SurvivorRegions.hpp"
  42 #include "gc/g1/g1YoungGenSizer.hpp"
  43 #include "gc/g1/heapRegion.inline.hpp"
  44 #include "gc/g1/heapRegionRemSet.hpp"
  45 #include "gc/shared/concurrentGCBreakpoints.hpp"
  46 #include "gc/shared/gcPolicyCounters.hpp"
  47 #include "logging/log.hpp"
  48 #include "runtime/arguments.hpp"
  49 #include "runtime/java.hpp"
  50 #include "runtime/mutexLocker.hpp"
  51 #include "utilities/debug.hpp"
  52 #include "utilities/growableArray.hpp"
  53 #include "utilities/pair.hpp"
  54 
  55 G1Policy::G1Policy(STWGCTimer* gc_timer) :
  56   _predictor(G1ConfidencePercent / 100.0),
  57   _analytics(new G1Analytics(&_predictor)),
  58   _remset_tracker(),
  59   _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
  60   _old_gen_alloc_tracker(),
  61   _ihop_control(create_ihop_control(&_old_gen_alloc_tracker, &_predictor)),
  62   _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
  63   _full_collection_start_sec(0.0),
  64   _young_list_target_length(0),
  65   _young_list_fixed_length(0),
  66   _young_list_max_length(0),
  67   _eden_surv_rate_group(new G1SurvRateGroup()),
  68   _survivor_surv_rate_group(new G1SurvRateGroup()),
  69   _reserve_factor((double) G1ReservePercent / 100.0),
  70   _reserve_regions(0),
  71   _young_gen_sizer(G1YoungGenSizer::create_gen_sizer()),
  72   _free_regions_at_end_of_collection(0),
  73   _rs_length(0),
  74   _rs_length_prediction(0),
  75   _pending_cards_at_gc_start(0),

  76   _concurrent_start_to_mixed(),
  77   _collection_set(NULL),
  78   _g1h(NULL),
  79   _phase_times_timer(gc_timer),
  80   _phase_times(NULL),
  81   _mark_remark_start_sec(0),
  82   _mark_cleanup_start_sec(0),
  83   _tenuring_threshold(MaxTenuringThreshold),
  84   _max_survivor_regions(0),
  85   _survivors_age_table(true)
  86 {
  87 }
  88 
  89 G1Policy::~G1Policy() {
  90   delete _ihop_control;
  91   delete _young_gen_sizer;
  92 }
  93 
  94 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) {
  95   if (G1Arguments::is_heterogeneous_heap()) {
  96     return new G1HeterogeneousHeapPolicy(gc_timer_stw);
  97   } else {
  98     return new G1Policy(gc_timer_stw);
  99   }
 100 }
 101 
 102 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
 103 
 104 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
 105   _g1h = g1h;
 106   _collection_set = collection_set;
 107 
 108   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 109 
 110   if (!use_adaptive_young_list_length()) {
 111     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 112   }
 113   _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
 114 
 115   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 116 
 117   update_young_list_max_and_target_length();
 118   // We may immediately start allocating regions and placing them on the
 119   // collection set list. Initialize the per-collection set info
 120   _collection_set->start_incremental_building();
 121 }
 122 
 123 void G1Policy::note_gc_start() {
 124   phase_times()->note_gc_start();
 125 }
 126 
 127 class G1YoungLengthPredictor {
 128   const double _base_time_ms;
 129   const double _base_free_regions;
 130   const double _target_pause_time_ms;
 131   const G1Policy* const _policy;
 132 
 133  public:
 134   G1YoungLengthPredictor(double base_time_ms,
 135                          double base_free_regions,
 136                          double target_pause_time_ms,
 137                          const G1Policy* policy) :
 138     _base_time_ms(base_time_ms),
 139     _base_free_regions(base_free_regions),
 140     _target_pause_time_ms(target_pause_time_ms),
 141     _policy(policy) {}
 142 
 143   bool will_fit(uint young_length) const {
 144     if (young_length >= _base_free_regions) {
 145       // end condition 1: not enough space for the young regions
 146       return false;
 147     }
 148 
 149     size_t bytes_to_copy = 0;
 150     const double copy_time_ms = _policy->predict_eden_copy_time_ms(young_length, &bytes_to_copy);
 151     const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
 152     const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
 153     if (pause_time_ms > _target_pause_time_ms) {
 154       // end condition 2: prediction is over the target pause time
 155       return false;
 156     }
 157 
 158     const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
 159 
 160     // When copying, we will likely need more bytes free than is live in the region.
 161     // Add some safety margin to factor in the confidence of our guess, and the
 162     // natural expected waste.
 163     // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
 164     // of the calculation: the lower the confidence, the more headroom.
 165     // (100 + TargetPLABWastePct) represents the increase in expected bytes during
 166     // copying due to anticipated waste in the PLABs.
 167     const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
 168     const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
 169 
 170     if (expected_bytes_to_copy > free_bytes) {
 171       // end condition 3: out-of-space
 172       return false;
 173     }
 174 
 175     // success!
 176     return true;
 177   }
 178 };
 179 
 180 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
 181   // re-calculate the necessary reserve
 182   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 183   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 184   // smaller than 1.0) we'll get 1.
 185   _reserve_regions = (uint) ceil(reserve_regions_d);
 186 
 187   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 188 
 189   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
 190 }
 191 
 192 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
 193   uint desired_min_length = 0;
 194   if (use_adaptive_young_list_length()) {
 195     if (_analytics->num_alloc_rate_ms() > 3) {
 196       double now_sec = os::elapsedTime();
 197       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 198       double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
 199       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 200     } else {
 201       // otherwise we don't have enough info to make the prediction
 202     }
 203   }
 204   desired_min_length += base_min_length;
 205   // make sure we don't go below any user-defined minimum bound
 206   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 207 }
 208 
 209 uint G1Policy::calculate_young_list_desired_max_length() const {
 210   // Here, we might want to also take into account any additional
 211   // constraints (i.e., user-defined minimum bound). Currently, we
 212   // effectively don't set this bound.
 213   return _young_gen_sizer->max_desired_young_length();
 214 }
 215 
 216 uint G1Policy::update_young_list_max_and_target_length() {
 217   return update_young_list_max_and_target_length(_analytics->predict_rs_length());
 218 }
 219 
 220 uint G1Policy::update_young_list_max_and_target_length(size_t rs_length) {
 221   uint unbounded_target_length = update_young_list_target_length(rs_length);
 222   update_max_gc_locker_expansion();
 223   return unbounded_target_length;
 224 }
 225 
 226 uint G1Policy::update_young_list_target_length(size_t rs_length) {
 227   YoungTargetLengths young_lengths = young_list_target_lengths(rs_length);
 228   _young_list_target_length = young_lengths.first;
 229 
 230   return young_lengths.second;
 231 }
 232 
 233 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_length) const {
 234   YoungTargetLengths result;
 235 
 236   // Calculate the absolute and desired min bounds first.
 237 
 238   // This is how many young regions we already have (currently: the survivors).
 239   const uint base_min_length = _g1h->survivor_regions_count();
 240   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 241   // This is the absolute minimum young length. Ensure that we
 242   // will at least have one eden region available for allocation.
 243   uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
 244   // If we shrank the young list target it should not shrink below the current size.
 245   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 246   // Calculate the absolute and desired max bounds.
 247 
 248   uint desired_max_length = calculate_young_list_desired_max_length();
 249 
 250   uint young_list_target_length = 0;
 251   if (use_adaptive_young_list_length()) {
 252     if (collector_state()->in_young_only_phase()) {
 253       young_list_target_length =
 254                         calculate_young_list_target_length(rs_length,
 255                                                            base_min_length,
 256                                                            desired_min_length,
 257                                                            desired_max_length);
 258     } else {
 259       // Don't calculate anything and let the code below bound it to
 260       // the desired_min_length, i.e., do the next GC as soon as
 261       // possible to maximize how many old regions we can add to it.
 262     }
 263   } else {
 264     // The user asked for a fixed young gen so we'll fix the young gen
 265     // whether the next GC is young or mixed.
 266     young_list_target_length = _young_list_fixed_length;
 267   }
 268 
 269   result.second = young_list_target_length;
 270 
 271   // We will try our best not to "eat" into the reserve.
 272   uint absolute_max_length = 0;
 273   if (_free_regions_at_end_of_collection > _reserve_regions) {
 274     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 275   }
 276   if (desired_max_length > absolute_max_length) {
 277     desired_max_length = absolute_max_length;
 278   }
 279 
 280   // Make sure we don't go over the desired max length, nor under the
 281   // desired min length. In case they clash, desired_min_length wins
 282   // which is why that test is second.
 283   if (young_list_target_length > desired_max_length) {
 284     young_list_target_length = desired_max_length;
 285   }
 286   if (young_list_target_length < desired_min_length) {
 287     young_list_target_length = desired_min_length;
 288   }
 289 
 290   assert(young_list_target_length > base_min_length,
 291          "we should be able to allocate at least one eden region");
 292   assert(young_list_target_length >= absolute_min_length, "post-condition");
 293 
 294   result.first = young_list_target_length;
 295   return result;
 296 }
 297 
 298 uint G1Policy::calculate_young_list_target_length(size_t rs_length,
 299                                                   uint base_min_length,
 300                                                   uint desired_min_length,
 301                                                   uint desired_max_length) const {
 302   assert(use_adaptive_young_list_length(), "pre-condition");
 303   assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
 304 
 305   // In case some edge-condition makes the desired max length too small...
 306   if (desired_max_length <= desired_min_length) {
 307     return desired_min_length;
 308   }
 309 
 310   // We'll adjust min_young_length and max_young_length not to include
 311   // the already allocated young regions (i.e., so they reflect the
 312   // min and max eden regions we'll allocate). The base_min_length
 313   // will be reflected in the predictions by the
 314   // survivor_regions_evac_time prediction.
 315   assert(desired_min_length > base_min_length, "invariant");
 316   uint min_young_length = desired_min_length - base_min_length;
 317   assert(desired_max_length > base_min_length, "invariant");
 318   uint max_young_length = desired_max_length - base_min_length;
 319 
 320   const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 321   const size_t pending_cards = _analytics->predict_pending_cards();
 322   const double base_time_ms = predict_base_elapsed_time_ms(pending_cards, rs_length);
 323   const uint available_free_regions = _free_regions_at_end_of_collection;
 324   const uint base_free_regions =
 325     available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
 326 
 327   // Here, we will make sure that the shortest young length that
 328   // makes sense fits within the target pause time.
 329 
 330   G1YoungLengthPredictor p(base_time_ms,
 331                            base_free_regions,
 332                            target_pause_time_ms,
 333                            this);
 334   if (p.will_fit(min_young_length)) {
 335     // The shortest young length will fit into the target pause time;
 336     // we'll now check whether the absolute maximum number of young
 337     // regions will fit in the target pause time. If not, we'll do
 338     // a binary search between min_young_length and max_young_length.
 339     if (p.will_fit(max_young_length)) {
 340       // The maximum young length will fit into the target pause time.
 341       // We are done so set min young length to the maximum length (as
 342       // the result is assumed to be returned in min_young_length).
 343       min_young_length = max_young_length;
 344     } else {
 345       // The maximum possible number of young regions will not fit within
 346       // the target pause time so we'll search for the optimal
 347       // length. The loop invariants are:
 348       //
 349       // min_young_length < max_young_length
 350       // min_young_length is known to fit into the target pause time
 351       // max_young_length is known not to fit into the target pause time
 352       //
 353       // Going into the loop we know the above hold as we've just
 354       // checked them. Every time around the loop we check whether
 355       // the middle value between min_young_length and
 356       // max_young_length fits into the target pause time. If it
 357       // does, it becomes the new min. If it doesn't, it becomes
 358       // the new max. This way we maintain the loop invariants.
 359 
 360       assert(min_young_length < max_young_length, "invariant");
 361       uint diff = (max_young_length - min_young_length) / 2;
 362       while (diff > 0) {
 363         uint young_length = min_young_length + diff;
 364         if (p.will_fit(young_length)) {
 365           min_young_length = young_length;
 366         } else {
 367           max_young_length = young_length;
 368         }
 369         assert(min_young_length <  max_young_length, "invariant");
 370         diff = (max_young_length - min_young_length) / 2;
 371       }
 372       // The results is min_young_length which, according to the
 373       // loop invariants, should fit within the target pause time.
 374 
 375       // These are the post-conditions of the binary search above:
 376       assert(min_young_length < max_young_length,
 377              "otherwise we should have discovered that max_young_length "
 378              "fits into the pause target and not done the binary search");
 379       assert(p.will_fit(min_young_length),
 380              "min_young_length, the result of the binary search, should "
 381              "fit into the pause target");
 382       assert(!p.will_fit(min_young_length + 1),
 383              "min_young_length, the result of the binary search, should be "
 384              "optimal, so no larger length should fit into the pause target");
 385     }
 386   } else {
 387     // Even the minimum length doesn't fit into the pause time
 388     // target, return it as the result nevertheless.
 389   }
 390   return base_min_length + min_young_length;
 391 }
 392 
 393 double G1Policy::predict_survivor_regions_evac_time() const {
 394   double survivor_regions_evac_time = 0.0;
 395   const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
 396   for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
 397        it != survivor_regions->end();
 398        ++it) {
 399     survivor_regions_evac_time += predict_region_total_time_ms(*it, collector_state()->in_young_only_phase());
 400   }
 401   return survivor_regions_evac_time;
 402 }
 403 
 404 G1GCPhaseTimes* G1Policy::phase_times() const {
 405   // Lazy allocation because it must follow initialization of all the
 406   // OopStorage objects by various other subsystems.
 407   if (_phase_times == NULL) {
 408     _phase_times = new G1GCPhaseTimes(_phase_times_timer, ParallelGCThreads);
 409   }
 410   return _phase_times;
 411 }
 412 
 413 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_length) {
 414   guarantee(use_adaptive_young_list_length(), "should not call this otherwise" );
 415 
 416   if (rs_length > _rs_length_prediction) {
 417     // add 10% to avoid having to recalculate often
 418     size_t rs_length_prediction = rs_length * 1100 / 1000;
 419     update_rs_length_prediction(rs_length_prediction);
 420 
 421     update_young_list_max_and_target_length(rs_length_prediction);
 422   }
 423 }
 424 
 425 void G1Policy::update_rs_length_prediction() {
 426   update_rs_length_prediction(_analytics->predict_rs_length());
 427 }
 428 
 429 void G1Policy::update_rs_length_prediction(size_t prediction) {
 430   if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) {
 431     _rs_length_prediction = prediction;
 432   }
 433 }
 434 
 435 void G1Policy::record_full_collection_start() {
 436   _full_collection_start_sec = os::elapsedTime();
 437   // Release the future to-space so that it is available for compaction into.
 438   collector_state()->set_in_young_only_phase(false);
 439   collector_state()->set_in_full_gc(true);
 440   _collection_set->clear_candidates();
 441   _pending_cards_at_gc_start = 0;
 442 }
 443 
 444 void G1Policy::record_full_collection_end() {
 445   // Consider this like a collection pause for the purposes of allocation
 446   // since last pause.
 447   double end_sec = os::elapsedTime();
 448   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 449   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 450 
 451   _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
 452 
 453   collector_state()->set_in_full_gc(false);
 454 
 455   // "Nuke" the heuristics that control the young/mixed GC
 456   // transitions and make sure we start with young GCs after the Full GC.
 457   collector_state()->set_in_young_only_phase(true);
 458   collector_state()->set_in_young_gc_before_mixed(false);
 459   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
 460   collector_state()->set_in_concurrent_start_gc(false);
 461   collector_state()->set_mark_or_rebuild_in_progress(false);
 462   collector_state()->set_clearing_next_bitmap(false);
 463 
 464   _eden_surv_rate_group->start_adding_regions();
 465   // also call this on any additional surv rate groups
 466 
 467   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 468   _survivor_surv_rate_group->reset();
 469   update_young_list_max_and_target_length();
 470   update_rs_length_prediction();
 471 
 472   _old_gen_alloc_tracker.reset_after_gc(_g1h->humongous_regions_count() * HeapRegion::GrainBytes);
 473 
 474   record_pause(FullGC, _full_collection_start_sec, end_sec);
 475 }
 476 
 477 static void log_refinement_stats(const char* kind, const G1ConcurrentRefineStats& stats) {
 478   log_debug(gc, refine, stats)
 479            ("%s refinement: %.2fms, refined: " SIZE_FORMAT
 480             ", precleaned: " SIZE_FORMAT ", dirtied: " SIZE_FORMAT,
 481             kind,
 482             stats.refinement_time().seconds() * MILLIUNITS,
 483             stats.refined_cards(),
 484             stats.precleaned_cards(),
 485             stats.dirtied_cards());
 486 }
 487 
 488 void G1Policy::record_concurrent_refinement_stats() {
 489   G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
 490   _pending_cards_at_gc_start = dcqs.num_cards();
 491 
 492   // Collect per-thread stats, mostly from mutator activity.
 493   G1ConcurrentRefineStats mut_stats = dcqs.get_and_reset_refinement_stats();
 494 
 495   // Collect specialized concurrent refinement thread stats.
 496   G1ConcurrentRefine* cr = _g1h->concurrent_refine();
 497   G1ConcurrentRefineStats cr_stats = cr->get_and_reset_refinement_stats();
 498 
 499   G1ConcurrentRefineStats total_stats = mut_stats + cr_stats;
 500 
 501   log_refinement_stats("Mutator", mut_stats);
 502   log_refinement_stats("Concurrent", cr_stats);
 503   log_refinement_stats("Total", total_stats);
 504 
 505   // Record the rate at which cards were refined.
 506   // Don't update the rate if the current sample is empty or time is zero.
 507   Tickspan refinement_time = total_stats.refinement_time();
 508   size_t refined_cards = total_stats.refined_cards();
 509   if ((refined_cards > 0) && (refinement_time > Tickspan())) {
 510     double rate = refined_cards / (refinement_time.seconds() * MILLIUNITS);
 511     _analytics->report_concurrent_refine_rate_ms(rate);
 512     log_debug(gc, refine, stats)("Concurrent refinement rate: %.2f cards/ms", rate);
 513   }
 514 
 515   // Record mutator's card logging rate.
 516   double mut_start_time = _analytics->prev_collection_pause_end_ms();
 517   double mut_end_time = phase_times()->cur_collection_start_sec() * MILLIUNITS;
 518   double mut_time = mut_end_time - mut_start_time;
 519   // Unlike above for conc-refine rate, here we should not require a
 520   // non-empty sample, since an application could go some time with only
 521   // young-gen or filtered out writes.  But we'll ignore unusually short
 522   // sample periods, as they may just pollute the predictions.
 523   if (mut_time > 1.0) {   // Require > 1ms sample time.
 524     double dirtied_rate = total_stats.dirtied_cards() / mut_time;
 525     _analytics->report_dirtied_cards_rate_ms(dirtied_rate);
 526     log_debug(gc, refine, stats)("Generate dirty cards rate: %.2f cards/ms", dirtied_rate);
 527   }
 528 }
 529 
 530 void G1Policy::record_collection_pause_start(double start_time_sec) {
 531   // We only need to do this here as the policy will only be applied
 532   // to the GC we're about to start. so, no point is calculating this
 533   // every time we calculate / recalculate the target young length.
 534   update_survivors_policy();
 535 
 536   assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
 537          "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
 538          max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
 539   assert_used_and_recalculate_used_equal(_g1h);
 540 
 541   phase_times()->record_cur_collection_start_sec(start_time_sec);
 542 
 543   record_concurrent_refinement_stats();
 544 
 545   _collection_set->reset_bytes_used_before();
 546 
 547   // do that for any other surv rate groups
 548   _eden_surv_rate_group->stop_adding_regions();
 549   _survivors_age_table.clear();
 550 
 551   assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
 552 }
 553 
 554 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
 555   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 556   collector_state()->set_in_concurrent_start_gc(false);
 557 }
 558 
 559 void G1Policy::record_concurrent_mark_remark_start() {
 560   _mark_remark_start_sec = os::elapsedTime();
 561 }
 562 
 563 void G1Policy::record_concurrent_mark_remark_end() {
 564   double end_time_sec = os::elapsedTime();
 565   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 566   _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
 567   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
 568 
 569   record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 570 }
 571 
 572 void G1Policy::record_concurrent_mark_cleanup_start() {
 573   _mark_cleanup_start_sec = os::elapsedTime();
 574 }
 575 
 576 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
 577   return phase_times()->average_time_ms(phase);
 578 }
 579 
 580 double G1Policy::young_other_time_ms() const {
 581   return phase_times()->young_cset_choice_time_ms() +
 582          phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
 583 }
 584 
 585 double G1Policy::non_young_other_time_ms() const {
 586   return phase_times()->non_young_cset_choice_time_ms() +
 587          phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
 588 }
 589 
 590 double G1Policy::other_time_ms(double pause_time_ms) const {
 591   return pause_time_ms - phase_times()->cur_collection_par_time_ms();
 592 }
 593 
 594 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
 595   return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms() - phase_times()->total_rebuild_freelist_time_ms();
 596 }
 597 
 598 bool G1Policy::about_to_start_mixed_phase() const {
 599   return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
 600 }
 601 
 602 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
 603   if (about_to_start_mixed_phase()) {
 604     return false;
 605   }
 606 
 607   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
 608 
 609   size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
 610   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 611   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 612 
 613   bool result = false;
 614   if (marking_request_bytes > marking_initiating_used_threshold) {
 615     result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
 616     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
 617                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
 618                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
 619   }
 620 
 621   return result;
 622 }
 623 
 624 double G1Policy::logged_cards_processing_time() const {
 625   double all_cards_processing_time = average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR);
 626   size_t logged_dirty_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
 627   size_t scan_heap_roots_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
 628                                  phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
 629   // This may happen if there are duplicate cards in different log buffers.
 630   if (logged_dirty_cards > scan_heap_roots_cards) {
 631     return all_cards_processing_time + average_time_ms(G1GCPhaseTimes::MergeLB);
 632   }
 633   return (all_cards_processing_time * logged_dirty_cards / scan_heap_roots_cards) + average_time_ms(G1GCPhaseTimes::MergeLB);
 634 }
 635 
 636 // Anything below that is considered to be zero
 637 #define MIN_TIMER_GRANULARITY 0.0000001
 638 
 639 void G1Policy::record_collection_pause_end(double pause_time_ms) {
 640   G1GCPhaseTimes* p = phase_times();
 641 
 642   double end_time_sec = os::elapsedTime();
 643 
 644   PauseKind this_pause = young_gc_pause_kind();
 645 
 646   bool update_stats = !_g1h->evacuation_failed();
 647 
 648   record_pause(this_pause, end_time_sec - pause_time_ms / 1000.0, end_time_sec);
 649 
 650   if (is_concurrent_start_pause(this_pause)) {
 651     record_concurrent_mark_init_end(0.0);
 652   } else {
 653     maybe_start_marking();
 654   }
 655 
 656   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
 657   if (app_time_ms < MIN_TIMER_GRANULARITY) {
 658     // This usually happens due to the timer not having the required
 659     // granularity. Some Linuxes are the usual culprits.
 660     // We'll just set it to something (arbitrarily) small.
 661     app_time_ms = 1.0;
 662   }
 663 
 664   if (update_stats) {
 665     // We maintain the invariant that all objects allocated by mutator
 666     // threads will be allocated out of eden regions. So, we can use
 667     // the eden region number allocated since the previous GC to
 668     // calculate the application's allocate rate. The only exception
 669     // to that is humongous objects that are allocated separately. But
 670     // given that humongous object allocations do not really affect
 671     // either the pause's duration nor when the next pause will take
 672     // place we can safely ignore them here.
 673     uint regions_allocated = _collection_set->eden_region_length();
 674     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
 675     _analytics->report_alloc_rate_ms(alloc_rate_ms);
 676 
 677     _analytics->compute_pause_time_ratios(end_time_sec, pause_time_ms);
 678     _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
 679   }
 680 
 681   if (is_last_young_pause(this_pause)) {
 682     assert(!is_concurrent_start_pause(this_pause),
 683            "The young GC before mixed is not allowed to be concurrent start 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 (is_mixed_pause(this_pause)) {
 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   } else {
 700     assert(is_young_only_pause(this_pause), "must be");
 701   }
 702 
 703   _eden_surv_rate_group->start_adding_regions();
 704 
 705   double merge_hcc_time_ms = average_time_ms(G1GCPhaseTimes::MergeHCC);
 706   if (update_stats) {
 707     size_t const total_log_buffer_cards = p->sum_thread_work_items(G1GCPhaseTimes::MergeHCC, G1GCPhaseTimes::MergeHCCDirtyCards) +
 708                                           p->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
 709     // Update prediction for card merge; MergeRSDirtyCards includes the cards from the Eager Reclaim phase.
 710     size_t const total_cards_merged = p->sum_thread_work_items(G1GCPhaseTimes::MergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
 711                                       p->sum_thread_work_items(G1GCPhaseTimes::OptMergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
 712                                       total_log_buffer_cards;
 713 
 714     // The threshold for the number of cards in a given sampling which we consider
 715     // large enough so that the impact from setup and other costs is negligible.
 716     size_t const CardsNumSamplingThreshold = 10;
 717 
 718     if (total_cards_merged > CardsNumSamplingThreshold) {
 719       double avg_time_merge_cards = average_time_ms(G1GCPhaseTimes::MergeER) +
 720                                     average_time_ms(G1GCPhaseTimes::MergeRS) +
 721                                     average_time_ms(G1GCPhaseTimes::MergeHCC) +
 722                                     average_time_ms(G1GCPhaseTimes::MergeLB) +
 723                                     average_time_ms(G1GCPhaseTimes::OptMergeRS);
 724       _analytics->report_cost_per_card_merge_ms(avg_time_merge_cards / total_cards_merged,
 725                                                 is_young_only_pause(this_pause));
 726     }
 727 
 728     // Update prediction for card scan
 729     size_t const total_cards_scanned = p->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
 730                                        p->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
 731 
 732     if (total_cards_scanned > CardsNumSamplingThreshold) {
 733       double avg_time_dirty_card_scan = average_time_ms(G1GCPhaseTimes::ScanHR) +
 734                                         average_time_ms(G1GCPhaseTimes::OptScanHR);
 735 
 736       _analytics->report_cost_per_card_scan_ms(avg_time_dirty_card_scan / total_cards_scanned,
 737                                                is_young_only_pause(this_pause));
 738     }
 739 
 740     // Update prediction for the ratio between cards from the remembered
 741     // sets and actually scanned cards from the remembered sets.
 742     // Cards from the remembered sets are all cards not duplicated by cards from
 743     // the logs.
 744     // Due to duplicates in the log buffers, the number of actually scanned cards
 745     // can be smaller than the cards in the log buffers.
 746     const size_t from_rs_length_cards = (total_cards_scanned > total_log_buffer_cards) ? total_cards_scanned - total_log_buffer_cards : 0;
 747     double merge_to_scan_ratio = 0.0;
 748     if (total_cards_scanned > 0) {
 749       merge_to_scan_ratio = (double) from_rs_length_cards / total_cards_scanned;
 750     }
 751     _analytics->report_card_merge_to_scan_ratio(merge_to_scan_ratio,
 752                                                 is_young_only_pause(this_pause));
 753 
 754     const size_t recorded_rs_length = _collection_set->recorded_rs_length();
 755     const size_t rs_length_diff = _rs_length > recorded_rs_length ? _rs_length - recorded_rs_length : 0;
 756     _analytics->report_rs_length_diff(rs_length_diff);
 757 
 758     // Update prediction for copy cost per byte
 759     size_t copied_bytes = p->sum_thread_work_items(G1GCPhaseTimes::MergePSS, G1GCPhaseTimes::MergePSSCopiedBytes);
 760 
 761     if (copied_bytes > 0) {
 762       double cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / copied_bytes;
 763       _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
 764     }
 765 
 766     if (_collection_set->young_region_length() > 0) {
 767       _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
 768                                                         _collection_set->young_region_length());
 769     }
 770 
 771     if (_collection_set->old_region_length() > 0) {
 772       _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
 773                                                             _collection_set->old_region_length());
 774     }
 775 
 776     _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
 777 
 778     // Do not update RS lengths and the number of pending cards with information from mixed gc:
 779     // these are is wildly different to during young only gc and mess up young gen sizing right
 780     // after the mixed gc phase.
 781     // During mixed gc we do not use them for young gen sizing.
 782     if (is_young_only_pause(this_pause)) {
 783       _analytics->report_pending_cards((double) _pending_cards_at_gc_start);
 784       _analytics->report_rs_length((double) _rs_length);
 785     }
 786   }
 787 
 788   assert(!(is_concurrent_start_pause(this_pause) && collector_state()->mark_or_rebuild_in_progress()),
 789          "If the last pause has been concurrent start, we should not have been in the marking window");
 790   if (is_concurrent_start_pause(this_pause)) {
 791     collector_state()->set_mark_or_rebuild_in_progress(true);
 792   }
 793 
 794   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 795 
 796   update_rs_length_prediction();
 797 
 798   // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely
 799   // that in this case we are not running in a "normal" operating mode.
 800   if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
 801     // IHOP control wants to know the expected young gen length if it were not
 802     // restrained by the heap reserve. Using the actual length would make the
 803     // prediction too small and the limit the young gen every time we get to the
 804     // predicted target occupancy.
 805     size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
 806 
 807     _old_gen_alloc_tracker.reset_after_gc(_g1h->humongous_regions_count() * HeapRegion::GrainBytes);
 808     update_ihop_prediction(app_time_ms / 1000.0,
 809                            last_unrestrained_young_length * HeapRegion::GrainBytes,
 810                            is_young_only_pause(this_pause));
 811 
 812     _ihop_control->send_trace_event(_g1h->gc_tracer_stw());
 813   } else {
 814     // Any garbage collection triggered as periodic collection resets the time-to-mixed
 815     // measurement. Periodic collection typically means that the application is "inactive", i.e.
 816     // the marking threads may have received an uncharacterisic amount of cpu time
 817     // for completing the marking, i.e. are faster than expected.
 818     // This skews the predicted marking length towards smaller values which might cause
 819     // the mark start being too late.
 820     _concurrent_start_to_mixed.reset();
 821   }
 822 
 823   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
 824   double scan_logged_cards_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
 825 
 826   if (scan_logged_cards_time_goal_ms < merge_hcc_time_ms) {
 827     log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
 828                                 "Logged Cards Scan time goal: %1.2fms Scan HCC time: %1.2fms",
 829                                 scan_logged_cards_time_goal_ms, merge_hcc_time_ms);
 830 
 831     scan_logged_cards_time_goal_ms = 0;
 832   } else {
 833     scan_logged_cards_time_goal_ms -= merge_hcc_time_ms;
 834   }
 835 
 836   double const logged_cards_time = logged_cards_processing_time();
 837 
 838   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",
 839                               scan_logged_cards_time_goal_ms, logged_cards_time, merge_hcc_time_ms);
 840 
 841   _g1h->concurrent_refine()->adjust(logged_cards_time,
 842                                     phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards),
 843                                     scan_logged_cards_time_goal_ms);
 844 }
 845 
 846 G1IHOPControl* G1Policy::create_ihop_control(const G1OldGenAllocationTracker* old_gen_alloc_tracker,
 847                                              const G1Predictions* predictor) {
 848   if (G1UseAdaptiveIHOP) {
 849     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
 850                                      old_gen_alloc_tracker,
 851                                      predictor,
 852                                      G1ReservePercent,
 853                                      G1HeapWastePercent);
 854   } else {
 855     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent, old_gen_alloc_tracker);
 856   }
 857 }
 858 
 859 void G1Policy::update_ihop_prediction(double mutator_time_s,
 860                                       size_t young_gen_size,
 861                                       bool this_gc_was_young_only) {
 862   // Always try to update IHOP prediction. Even evacuation failures give information
 863   // about e.g. whether to start IHOP earlier next time.
 864 
 865   // Avoid using really small application times that might create samples with
 866   // very high or very low values. They may be caused by e.g. back-to-back gcs.
 867   double const min_valid_time = 1e-6;
 868 
 869   bool report = false;
 870 
 871   double marking_to_mixed_time = -1.0;
 872   if (!this_gc_was_young_only && _concurrent_start_to_mixed.has_result()) {
 873     marking_to_mixed_time = _concurrent_start_to_mixed.last_marking_time();
 874     assert(marking_to_mixed_time > 0.0,
 875            "Concurrent start to mixed time must be larger than zero but is %.3f",
 876            marking_to_mixed_time);
 877     if (marking_to_mixed_time > min_valid_time) {
 878       _ihop_control->update_marking_length(marking_to_mixed_time);
 879       report = true;
 880     }
 881   }
 882 
 883   // As an approximation for the young gc promotion rates during marking we use
 884   // all of them. In many applications there are only a few if any young gcs during
 885   // marking, which makes any prediction useless. This increases the accuracy of the
 886   // prediction.
 887   if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
 888     _ihop_control->update_allocation_info(mutator_time_s, young_gen_size);
 889     report = true;
 890   }
 891 
 892   if (report) {
 893     report_ihop_statistics();
 894   }
 895 }
 896 
 897 void G1Policy::report_ihop_statistics() {
 898   _ihop_control->print();
 899 }
 900 
 901 void G1Policy::print_phases() {
 902   phase_times()->print();
 903 }
 904 
 905 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
 906                                               size_t rs_length) const {
 907   size_t effective_scanned_cards = _analytics->predict_scan_card_num(rs_length, collector_state()->in_young_only_phase());
 908   return
 909     _analytics->predict_card_merge_time_ms(pending_cards + rs_length, collector_state()->in_young_only_phase()) +
 910     _analytics->predict_card_scan_time_ms(effective_scanned_cards, collector_state()->in_young_only_phase()) +
 911     _analytics->predict_constant_other_time_ms() +
 912     predict_survivor_regions_evac_time();
 913 }
 914 
 915 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
 916   size_t rs_length = _analytics->predict_rs_length();
 917   return predict_base_elapsed_time_ms(pending_cards, rs_length);
 918 }
 919 
 920 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
 921   size_t bytes_to_copy;
 922   if (!hr->is_young()) {
 923     bytes_to_copy = hr->max_live_bytes();
 924   } else {
 925     bytes_to_copy = (size_t) (hr->used() * hr->surv_rate_prediction(_predictor));
 926   }
 927   return bytes_to_copy;
 928 }
 929 
 930 double G1Policy::predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy) const {
 931   if (count == 0) {
 932     return 0.0;
 933   }
 934   size_t const expected_bytes = _eden_surv_rate_group->accum_surv_rate_pred(count) * HeapRegion::GrainBytes;
 935   if (bytes_to_copy != NULL) {
 936     *bytes_to_copy = expected_bytes;
 937   }
 938   return _analytics->predict_object_copy_time_ms(expected_bytes, collector_state()->mark_or_rebuild_in_progress());
 939 }
 940 
 941 double G1Policy::predict_region_copy_time_ms(HeapRegion* hr) const {
 942   size_t const bytes_to_copy = predict_bytes_to_copy(hr);
 943   return _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
 944 }
 945 
 946 double G1Policy::predict_region_non_copy_time_ms(HeapRegion* hr,
 947                                                  bool for_young_gc) const {
 948   size_t rs_length = hr->rem_set()->occupied();
 949   size_t scan_card_num = _analytics->predict_scan_card_num(rs_length, for_young_gc);
 950 
 951   double region_elapsed_time_ms =
 952     _analytics->predict_card_merge_time_ms(rs_length, collector_state()->in_young_only_phase()) +
 953     _analytics->predict_card_scan_time_ms(scan_card_num, collector_state()->in_young_only_phase());
 954 
 955   // The prediction of the "other" time for this region is based
 956   // upon the region type and NOT the GC type.
 957   if (hr->is_young()) {
 958     region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
 959   } else {
 960     region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
 961   }
 962   return region_elapsed_time_ms;
 963 }
 964 
 965 double G1Policy::predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const {
 966   return predict_region_non_copy_time_ms(hr, for_young_gc) + predict_region_copy_time_ms(hr);
 967 }
 968 
 969 bool G1Policy::should_allocate_mutator_region() const {
 970   uint young_list_length = _g1h->young_regions_count();
 971   uint young_list_target_length = _young_list_target_length;
 972   return young_list_length < young_list_target_length;
 973 }
 974 
 975 bool G1Policy::can_expand_young_list() const {
 976   uint young_list_length = _g1h->young_regions_count();
 977   uint young_list_max_length = _young_list_max_length;
 978   return young_list_length < young_list_max_length;
 979 }
 980 
 981 bool G1Policy::use_adaptive_young_list_length() const {
 982   return _young_gen_sizer->use_adaptive_young_list_length();
 983 }
 984 
 985 size_t G1Policy::desired_survivor_size(uint max_regions) const {
 986   size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
 987   return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 988 }
 989 
 990 void G1Policy::print_age_table() {
 991   _survivors_age_table.print_age_table(_tenuring_threshold);
 992 }
 993 
 994 void G1Policy::update_max_gc_locker_expansion() {
 995   uint expansion_region_num = 0;
 996   if (GCLockerEdenExpansionPercent > 0) {
 997     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
 998     double expansion_region_num_d = perc * (double) _young_list_target_length;
 999     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1000     // less than 1.0) we'll get 1.
1001     expansion_region_num = (uint) ceil(expansion_region_num_d);
1002   } else {
1003     assert(expansion_region_num == 0, "sanity");
1004   }
1005   _young_list_max_length = _young_list_target_length + expansion_region_num;
1006   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1007 }
1008 
1009 // Calculates survivor space parameters.
1010 void G1Policy::update_survivors_policy() {
1011   double max_survivor_regions_d =
1012                  (double) _young_list_target_length / (double) SurvivorRatio;
1013 
1014   // Calculate desired survivor size based on desired max survivor regions (unconstrained
1015   // by remaining heap). Otherwise we may cause undesired promotions as we are
1016   // already getting close to end of the heap, impacting performance even more.
1017   uint const desired_max_survivor_regions = ceil(max_survivor_regions_d);
1018   size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions);
1019 
1020   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size);
1021   if (UsePerfData) {
1022     _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
1023     _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize);
1024   }
1025   // The real maximum survivor size is bounded by the number of regions that can
1026   // be allocated into.
1027   _max_survivor_regions = MIN2(desired_max_survivor_regions,
1028                                _g1h->num_free_or_available_regions());
1029 }
1030 
1031 bool G1Policy::force_concurrent_start_if_outside_cycle(GCCause::Cause gc_cause) {
1032   // We actually check whether we are marking here and not if we are in a
1033   // reclamation phase. This means that we will schedule a concurrent mark
1034   // even while we are still in the process of reclaiming memory.
1035   bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
1036   if (!during_cycle) {
1037     log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). "
1038                         "GC cause: %s",
1039                         GCCause::to_string(gc_cause));
1040     collector_state()->set_initiate_conc_mark_if_possible(true);
1041     return true;
1042   } else {
1043     log_debug(gc, ergo)("Do not request concurrent cycle initiation "
1044                         "(concurrent cycle already in progress). GC cause: %s",
1045                         GCCause::to_string(gc_cause));
1046     return false;
1047   }
1048 }
1049 
1050 void G1Policy::initiate_conc_mark() {
1051   collector_state()->set_in_concurrent_start_gc(true);
1052   collector_state()->set_initiate_conc_mark_if_possible(false);
1053 }
1054 
1055 void G1Policy::decide_on_conc_mark_initiation() {
1056   // We are about to decide on whether this pause will be a
1057   // concurrent start pause.
1058 
1059   // First, collector_state()->in_concurrent_start_gc() should not be already set. We
1060   // will set it here if we have to. However, it should be cleared by
1061   // the end of the pause (it's only set for the duration of a
1062   // concurrent start pause).
1063   assert(!collector_state()->in_concurrent_start_gc(), "pre-condition");
1064 
1065   if (collector_state()->initiate_conc_mark_if_possible()) {
1066     // We had noticed on a previous pause that the heap occupancy has
1067     // gone over the initiating threshold and we should start a
1068     // concurrent marking cycle.  Or we've been explicitly requested
1069     // to start a concurrent marking cycle.  Either way, we initiate
1070     // one if not inhibited for some reason.
1071 
1072     GCCause::Cause cause = _g1h->gc_cause();
1073     if ((cause != GCCause::_wb_breakpoint) &&
1074         ConcurrentGCBreakpoints::is_controlled()) {
1075       log_debug(gc, ergo)("Do not initiate concurrent cycle (whitebox controlled)");
1076     } else if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
1077       // Initiate a new concurrent start if there is no marking or reclamation going on.
1078       initiate_conc_mark();
1079       log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1080     } else if (_g1h->is_user_requested_concurrent_full_gc(cause) ||
1081                (cause == GCCause::_wb_breakpoint)) {
1082       // Initiate a user requested concurrent start or run to a breakpoint.
1083       // A concurrent start must be young only GC, so the collector state
1084       // must be updated to reflect this.
1085       collector_state()->set_in_young_only_phase(true);
1086       collector_state()->set_in_young_gc_before_mixed(false);
1087 
1088       // We might have ended up coming here about to start a mixed phase with a collection set
1089       // active. The following remark might change the change the "evacuation efficiency" of
1090       // the regions in this set, leading to failing asserts later.
1091       // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
1092       clear_collection_set_candidates();
1093       abort_time_to_mixed_tracking();
1094       initiate_conc_mark();
1095       log_debug(gc, ergo)("Initiate concurrent cycle (%s requested concurrent cycle)",
1096                           (cause == GCCause::_wb_breakpoint) ? "run_to breakpoint" : "user");
1097     } else {
1098       // The concurrent marking thread is still finishing up the
1099       // previous cycle. If we start one right now the two cycles
1100       // overlap. In particular, the concurrent marking thread might
1101       // be in the process of clearing the next marking bitmap (which
1102       // we will use for the next cycle if we start one). Starting a
1103       // cycle now will be bad given that parts of the marking
1104       // information might get cleared by the marking thread. And we
1105       // cannot wait for the marking thread to finish the cycle as it
1106       // periodically yields while clearing the next marking bitmap
1107       // and, if it's in a yield point, it's waiting for us to
1108       // finish. So, at this point we will not start a cycle and we'll
1109       // let the concurrent marking thread complete the last one.
1110       log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1111     }
1112   }
1113 }
1114 
1115 void G1Policy::record_concurrent_mark_cleanup_end() {
1116   G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions());
1117   _collection_set->set_candidates(candidates);
1118 
1119   bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1120   if (!mixed_gc_pending) {
1121     clear_collection_set_candidates();
1122     abort_time_to_mixed_tracking();
1123   }
1124   collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1125   collector_state()->set_mark_or_rebuild_in_progress(false);
1126 
1127   double end_sec = os::elapsedTime();
1128   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1129   _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1130   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1131 
1132   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1133 }
1134 
1135 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1136   return percent_of(reclaimable_bytes, _g1h->capacity());
1137 }
1138 
1139 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1140   virtual bool do_heap_region(HeapRegion* r) {
1141     r->rem_set()->clear_locked(true /* only_cardset */);
1142     return false;
1143   }
1144 };
1145 
1146 void G1Policy::clear_collection_set_candidates() {
1147   // Clear remembered sets of remaining candidate regions and the actual candidate
1148   // set.
1149   G1ClearCollectionSetCandidateRemSets cl;
1150   _collection_set->candidates()->iterate(&cl);
1151   _collection_set->clear_candidates();
1152 }
1153 
1154 void G1Policy::maybe_start_marking() {
1155   if (need_to_start_conc_mark("end of GC")) {
1156     // Note: this might have already been set, if during the last
1157     // pause we decided to start a cycle but at the beginning of
1158     // this pause we decided to postpone it. That's OK.
1159     collector_state()->set_initiate_conc_mark_if_possible(true);
1160   }
1161 }
1162 
1163 bool G1Policy::is_young_only_pause(PauseKind kind) {
1164   assert(kind != FullGC, "must be");
1165   assert(kind != Remark, "must be");
1166   assert(kind != Cleanup, "must be");
1167   return kind == ConcurrentStartGC || kind == LastYoungGC || kind == YoungOnlyGC;
1168 }
1169 
1170 bool G1Policy::is_mixed_pause(PauseKind kind) {
1171   assert(kind != FullGC, "must be");
1172   assert(kind != Remark, "must be");
1173   assert(kind != Cleanup, "must be");
1174   return kind == MixedGC;
1175 }
1176 
1177 bool G1Policy::is_last_young_pause(PauseKind kind) {
1178   return kind == LastYoungGC;
1179 }
1180 
1181 bool G1Policy::is_concurrent_start_pause(PauseKind kind) {
1182   return kind == ConcurrentStartGC;
1183 }
1184 
1185 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1186   assert(!collector_state()->in_full_gc(), "must be");
1187   if (collector_state()->in_concurrent_start_gc()) {
1188     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1189     return ConcurrentStartGC;
1190   } else if (collector_state()->in_young_gc_before_mixed()) {
1191     assert(!collector_state()->in_concurrent_start_gc(), "must be");
1192     return LastYoungGC;
1193   } else if (collector_state()->in_mixed_phase()) {
1194     assert(!collector_state()->in_concurrent_start_gc(), "must be");
1195     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1196     return MixedGC;
1197   } else {
1198     assert(!collector_state()->in_concurrent_start_gc(), "must be");
1199     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1200     return YoungOnlyGC;
1201   }
1202 }
1203 
1204 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1205   // Manage the MMU tracker. For some reason it ignores Full GCs.
1206   if (kind != FullGC) {
1207     _mmu_tracker->add_pause(start, end);
1208   }
1209   // Manage the mutator time tracking from concurrent start to first mixed gc.
1210   switch (kind) {
1211     case FullGC:
1212       abort_time_to_mixed_tracking();
1213       break;
1214     case Cleanup:
1215     case Remark:
1216     case YoungOnlyGC:
1217     case LastYoungGC:
1218       _concurrent_start_to_mixed.add_pause(end - start);
1219       break;
1220     case ConcurrentStartGC:
1221       if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
1222         _concurrent_start_to_mixed.record_concurrent_start_end(end);
1223       }
1224       break;
1225     case MixedGC:
1226       _concurrent_start_to_mixed.record_mixed_gc_start(start);
1227       break;
1228     default:
1229       ShouldNotReachHere();
1230   }
1231 }
1232 
1233 void G1Policy::abort_time_to_mixed_tracking() {
1234   _concurrent_start_to_mixed.reset();
1235 }
1236 
1237 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1238                                        const char* false_action_str) const {
1239   G1CollectionSetCandidates* candidates = _collection_set->candidates();
1240 
1241   if (candidates->is_empty()) {
1242     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1243     return false;
1244   }
1245 
1246   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1247   size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1248   double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1249   double threshold = (double) G1HeapWastePercent;
1250   if (reclaimable_percent <= threshold) {
1251     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1252                         false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1253     return false;
1254   }
1255   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1256                       true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1257   return true;
1258 }
1259 
1260 uint G1Policy::calc_min_old_cset_length() const {
1261   // The min old CSet region bound is based on the maximum desired
1262   // number of mixed GCs after a cycle. I.e., even if some old regions
1263   // look expensive, we should add them to the CSet anyway to make
1264   // sure we go through the available old regions in no more than the
1265   // maximum desired number of mixed GCs.
1266   //
1267   // The calculation is based on the number of marked regions we added
1268   // to the CSet candidates in the first place, not how many remain, so
1269   // that the result is the same during all mixed GCs that follow a cycle.
1270 
1271   const size_t region_num = _collection_set->candidates()->num_regions();
1272   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1273   size_t result = region_num / gc_num;
1274   // emulate ceiling
1275   if (result * gc_num < region_num) {
1276     result += 1;
1277   }
1278   return (uint) result;
1279 }
1280 
1281 uint G1Policy::calc_max_old_cset_length() const {
1282   // The max old CSet region bound is based on the threshold expressed
1283   // as a percentage of the heap size. I.e., it should bound the
1284   // number of old regions added to the CSet irrespective of how many
1285   // of them are available.
1286 
1287   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1288   const size_t region_num = g1h->num_regions();
1289   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1290   size_t result = region_num * perc / 100;
1291   // emulate ceiling
1292   if (100 * result < region_num * perc) {
1293     result += 1;
1294   }
1295   return (uint) result;
1296 }
1297 
1298 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
1299                                                     double time_remaining_ms,
1300                                                     uint& num_initial_regions,
1301                                                     uint& num_optional_regions) {
1302   assert(candidates != NULL, "Must be");
1303 
1304   num_initial_regions = 0;
1305   num_optional_regions = 0;
1306   uint num_expensive_regions = 0;
1307 
1308   double predicted_old_time_ms = 0.0;
1309   double predicted_initial_time_ms = 0.0;
1310   double predicted_optional_time_ms = 0.0;
1311 
1312   double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction();
1313 
1314   const uint min_old_cset_length = calc_min_old_cset_length();
1315   const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length());
1316   const uint max_optional_regions = max_old_cset_length - min_old_cset_length;
1317   bool check_time_remaining = use_adaptive_young_list_length();
1318 
1319   uint candidate_idx = candidates->cur_idx();
1320 
1321   log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, "
1322                             "time remaining %1.2fms, optional threshold %1.2fms",
1323                             min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms);
1324 
1325   HeapRegion* hr = candidates->at(candidate_idx);
1326   while (hr != NULL) {
1327     if (num_initial_regions + num_optional_regions >= max_old_cset_length) {
1328       // Added maximum number of old regions to the CSet.
1329       log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). "
1330                                 "Initial %u regions, optional %u regions",
1331                                 num_initial_regions, num_optional_regions);
1332       break;
1333     }
1334 
1335     // Stop adding regions if the remaining reclaimable space is
1336     // not above G1HeapWastePercent.
1337     size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1338     double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1339     double threshold = (double) G1HeapWastePercent;
1340     if (reclaimable_percent <= threshold) {
1341       // We've added enough old regions that the amount of uncollected
1342       // reclaimable space is at or below the waste threshold. Stop
1343       // adding old regions to the CSet.
1344       log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). "
1345                                 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%",
1346                                 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes),
1347                                 reclaimable_percent, G1HeapWastePercent);
1348       break;
1349     }
1350 
1351     double predicted_time_ms = predict_region_total_time_ms(hr, false);
1352     time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
1353     // Add regions to old set until we reach the minimum amount
1354     if (num_initial_regions < min_old_cset_length) {
1355       predicted_old_time_ms += predicted_time_ms;
1356       num_initial_regions++;
1357       // Record the number of regions added with no time remaining
1358       if (time_remaining_ms == 0.0) {
1359         num_expensive_regions++;
1360       }
1361     } else if (!check_time_remaining) {
1362       // In the non-auto-tuning case, we'll finish adding regions
1363       // to the CSet if we reach the minimum.
1364       log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min).");
1365       break;
1366     } else {
1367       // Keep adding regions to old set until we reach the optional threshold
1368       if (time_remaining_ms > optional_threshold_ms) {
1369         predicted_old_time_ms += predicted_time_ms;
1370         num_initial_regions++;
1371       } else if (time_remaining_ms > 0) {
1372         // Keep adding optional regions until time is up.
1373         assert(num_optional_regions < max_optional_regions, "Should not be possible.");
1374         predicted_optional_time_ms += predicted_time_ms;
1375         num_optional_regions++;
1376       } else {
1377         log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high).");
1378         break;
1379       }
1380     }
1381     hr = candidates->at(++candidate_idx);
1382   }
1383   if (hr == NULL) {
1384     log_debug(gc, ergo, cset)("Old candidate collection set empty.");
1385   }
1386 
1387   if (num_expensive_regions > 0) {
1388     log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.",
1389                               num_expensive_regions);
1390   }
1391 
1392   log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, "
1393                             "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f",
1394                             num_initial_regions, num_optional_regions,
1395                             predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms);
1396 }
1397 
1398 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
1399                                                          uint const max_optional_regions,
1400                                                          double time_remaining_ms,
1401                                                          uint& num_optional_regions) {
1402   assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase");
1403 
1404   num_optional_regions = 0;
1405   double prediction_ms = 0;
1406   uint candidate_idx = candidates->cur_idx();
1407 
1408   HeapRegion* r = candidates->at(candidate_idx);
1409   while (num_optional_regions < max_optional_regions) {
1410     assert(r != NULL, "Region must exist");
1411     prediction_ms += predict_region_total_time_ms(r, false);
1412 
1413     if (prediction_ms > time_remaining_ms) {
1414       log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.",
1415                                 prediction_ms, r->hrm_index(), time_remaining_ms);
1416       break;
1417     }
1418     // This region will be included in the next optional evacuation.
1419 
1420     time_remaining_ms -= prediction_ms;
1421     num_optional_regions++;
1422     r = candidates->at(++candidate_idx);
1423   }
1424 
1425   log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms",
1426                             num_optional_regions, max_optional_regions, prediction_ms);
1427 }
1428 
1429 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1430   note_start_adding_survivor_regions();
1431 
1432   HeapRegion* last = NULL;
1433   for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1434        it != survivors->regions()->end();
1435        ++it) {
1436     HeapRegion* curr = *it;
1437     set_region_survivor(curr);
1438 
1439     // The region is a non-empty survivor so let's add it to
1440     // the incremental collection set for the next evacuation
1441     // pause.
1442     _collection_set->add_survivor_regions(curr);
1443 
1444     last = curr;
1445   }
1446   note_stop_adding_survivor_regions();
1447 
1448   // Don't clear the survivor list handles until the start of
1449   // the next evacuation pause - we need it in order to re-tag
1450   // the survivor regions from this evacuation pause as 'young'
1451   // at the start of the next.
1452 }
--- EOF ---