1 /*
   2  * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/g1Analytics.hpp"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1CollectionSet.hpp"
  29 #include "gc/g1/g1ConcurrentMark.hpp"
  30 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  31 #include "gc/g1/g1ConcurrentRefine.hpp"
  32 #include "gc/g1/g1HotCardCache.hpp"
  33 #include "gc/g1/g1IHOPControl.hpp"
  34 #include "gc/g1/g1GCPhaseTimes.hpp"
  35 #include "gc/g1/g1Policy.hpp"
  36 #include "gc/g1/g1SurvivorRegions.hpp"
  37 #include "gc/g1/g1YoungGenSizer.hpp"
  38 #include "gc/g1/heapRegion.inline.hpp"
  39 #include "gc/g1/heapRegionRemSet.hpp"
  40 #include "gc/shared/gcPolicyCounters.hpp"
  41 #include "logging/logStream.hpp"
  42 #include "runtime/arguments.hpp"
  43 #include "runtime/java.hpp"
  44 #include "runtime/mutexLocker.hpp"
  45 #include "utilities/debug.hpp"
  46 #include "utilities/growableArray.hpp"
  47 #include "utilities/pair.hpp"
  48 
  49 G1Policy::G1Policy(STWGCTimer* gc_timer) :
  50   _predictor(G1ConfidencePercent / 100.0),
  51   _analytics(new G1Analytics(&_predictor)),
  52   _remset_tracker(),
  53   _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
  54   _ihop_control(create_ihop_control(&_predictor)),
  55   _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
  56   _young_list_fixed_length(0),
  57   _short_lived_surv_rate_group(new SurvRateGroup()),
  58   _survivor_surv_rate_group(new SurvRateGroup()),
  59   _reserve_factor((double) G1ReservePercent / 100.0),
  60   _reserve_regions(0),
  61   _rs_lengths_prediction(0),
  62   _bytes_allocated_in_old_since_last_gc(0),
  63   _initial_mark_to_mixed(),
  64   _collection_set(NULL),
  65   _g1(NULL),
  66   _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
  67   _tenuring_threshold(MaxTenuringThreshold),
  68   _max_survivor_regions(0),
  69   _survivors_age_table(true),
  70   _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC) {
  71 }
  72 
  73 G1Policy::~G1Policy() {
  74   delete _ihop_control;
  75 }
  76 
  77 G1CollectorState* G1Policy::collector_state() const { return _g1->collector_state(); }
  78 
  79 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
  80   _g1 = g1h;
  81   _collection_set = collection_set;
  82 
  83   assert(Heap_lock->owned_by_self(), "Locking discipline.");
  84 
  85   if (!adaptive_young_list_length()) {
  86     _young_list_fixed_length = _young_gen_sizer.min_desired_young_length();
  87   }
  88   _young_gen_sizer.adjust_max_new_size(_g1->max_regions());
  89 
  90   _free_regions_at_end_of_collection = _g1->num_free_regions();
  91 
  92   update_young_list_max_and_target_length();
  93   // We may immediately start allocating regions and placing them on the
  94   // collection set list. Initialize the per-collection set info
  95   _collection_set->start_incremental_building();
  96 }
  97 
  98 void G1Policy::note_gc_start() {
  99   phase_times()->note_gc_start();
 100 }
 101 
 102 class G1YoungLengthPredictor {
 103   const bool _during_cm;
 104   const double _base_time_ms;
 105   const double _base_free_regions;
 106   const double _target_pause_time_ms;
 107   const G1Policy* const _policy;
 108 
 109  public:
 110   G1YoungLengthPredictor(bool during_cm,
 111                          double base_time_ms,
 112                          double base_free_regions,
 113                          double target_pause_time_ms,
 114                          const G1Policy* policy) :
 115     _during_cm(during_cm),
 116     _base_time_ms(base_time_ms),
 117     _base_free_regions(base_free_regions),
 118     _target_pause_time_ms(target_pause_time_ms),
 119     _policy(policy) {}
 120 
 121   bool will_fit(uint young_length) const {
 122     if (young_length >= _base_free_regions) {
 123       // end condition 1: not enough space for the young regions
 124       return false;
 125     }
 126 
 127     const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1);
 128     const size_t bytes_to_copy =
 129                  (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
 130     const double copy_time_ms =
 131       _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm);
 132     const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
 133     const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
 134     if (pause_time_ms > _target_pause_time_ms) {
 135       // end condition 2: prediction is over the target pause time
 136       return false;
 137     }
 138 
 139     const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
 140 
 141     // When copying, we will likely need more bytes free than is live in the region.
 142     // Add some safety margin to factor in the confidence of our guess, and the
 143     // natural expected waste.
 144     // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
 145     // of the calculation: the lower the confidence, the more headroom.
 146     // (100 + TargetPLABWastePct) represents the increase in expected bytes during
 147     // copying due to anticipated waste in the PLABs.
 148     const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
 149     const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
 150 
 151     if (expected_bytes_to_copy > free_bytes) {
 152       // end condition 3: out-of-space
 153       return false;
 154     }
 155 
 156     // success!
 157     return true;
 158   }
 159 };
 160 
 161 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
 162   // re-calculate the necessary reserve
 163   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 164   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 165   // smaller than 1.0) we'll get 1.
 166   _reserve_regions = (uint) ceil(reserve_regions_d);
 167 
 168   _young_gen_sizer.heap_size_changed(new_number_of_regions);
 169 
 170   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
 171 }
 172 
 173 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
 174   uint desired_min_length = 0;
 175   if (adaptive_young_list_length()) {
 176     if (_analytics->num_alloc_rate_ms() > 3) {
 177       double now_sec = os::elapsedTime();
 178       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 179       double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
 180       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 181     } else {
 182       // otherwise we don't have enough info to make the prediction
 183     }
 184   }
 185   desired_min_length += base_min_length;
 186   // make sure we don't go below any user-defined minimum bound
 187   return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length);
 188 }
 189 
 190 uint G1Policy::calculate_young_list_desired_max_length() const {
 191   // Here, we might want to also take into account any additional
 192   // constraints (i.e., user-defined minimum bound). Currently, we
 193   // effectively don't set this bound.
 194   return _young_gen_sizer.max_desired_young_length();
 195 }
 196 
 197 uint G1Policy::update_young_list_max_and_target_length() {
 198   return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
 199 }
 200 
 201 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) {
 202   uint unbounded_target_length = update_young_list_target_length(rs_lengths);
 203   update_max_gc_locker_expansion();
 204   return unbounded_target_length;
 205 }
 206 
 207 uint G1Policy::update_young_list_target_length(size_t rs_lengths) {
 208   YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
 209   _young_list_target_length = young_lengths.first;
 210   return young_lengths.second;
 211 }
 212 
 213 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const {
 214   YoungTargetLengths result;
 215 
 216   // Calculate the absolute and desired min bounds first.
 217 
 218   // This is how many young regions we already have (currently: the survivors).
 219   const uint base_min_length = _g1->survivor_regions_count();
 220   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 221   // This is the absolute minimum young length. Ensure that we
 222   // will at least have one eden region available for allocation.
 223   uint absolute_min_length = base_min_length + MAX2(_g1->eden_regions_count(), (uint)1);
 224   // If we shrank the young list target it should not shrink below the current size.
 225   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 226   // Calculate the absolute and desired max bounds.
 227 
 228   uint desired_max_length = calculate_young_list_desired_max_length();
 229 
 230   uint young_list_target_length = 0;
 231   if (adaptive_young_list_length()) {
 232     if (collector_state()->in_young_only_phase()) {
 233       young_list_target_length =
 234                         calculate_young_list_target_length(rs_lengths,
 235                                                            base_min_length,
 236                                                            desired_min_length,
 237                                                            desired_max_length);
 238     } else {
 239       // Don't calculate anything and let the code below bound it to
 240       // the desired_min_length, i.e., do the next GC as soon as
 241       // possible to maximize how many old regions we can add to it.
 242     }
 243   } else {
 244     // The user asked for a fixed young gen so we'll fix the young gen
 245     // whether the next GC is young or mixed.
 246     young_list_target_length = _young_list_fixed_length;
 247   }
 248 
 249   result.second = young_list_target_length;
 250 
 251   // We will try our best not to "eat" into the reserve.
 252   uint absolute_max_length = 0;
 253   if (_free_regions_at_end_of_collection > _reserve_regions) {
 254     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 255   }
 256   if (desired_max_length > absolute_max_length) {
 257     desired_max_length = absolute_max_length;
 258   }
 259 
 260   // Make sure we don't go over the desired max length, nor under the
 261   // desired min length. In case they clash, desired_min_length wins
 262   // which is why that test is second.
 263   if (young_list_target_length > desired_max_length) {
 264     young_list_target_length = desired_max_length;
 265   }
 266   if (young_list_target_length < desired_min_length) {
 267     young_list_target_length = desired_min_length;
 268   }
 269 
 270   assert(young_list_target_length > base_min_length,
 271          "we should be able to allocate at least one eden region");
 272   assert(young_list_target_length >= absolute_min_length, "post-condition");
 273 
 274   result.first = young_list_target_length;
 275   return result;
 276 }
 277 
 278 uint
 279 G1Policy::calculate_young_list_target_length(size_t rs_lengths,
 280                                                     uint base_min_length,
 281                                                     uint desired_min_length,
 282                                                     uint desired_max_length) const {
 283   assert(adaptive_young_list_length(), "pre-condition");
 284   assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
 285 
 286   // In case some edge-condition makes the desired max length too small...
 287   if (desired_max_length <= desired_min_length) {
 288     return desired_min_length;
 289   }
 290 
 291   // We'll adjust min_young_length and max_young_length not to include
 292   // the already allocated young regions (i.e., so they reflect the
 293   // min and max eden regions we'll allocate). The base_min_length
 294   // will be reflected in the predictions by the
 295   // survivor_regions_evac_time prediction.
 296   assert(desired_min_length > base_min_length, "invariant");
 297   uint min_young_length = desired_min_length - base_min_length;
 298   assert(desired_max_length > base_min_length, "invariant");
 299   uint max_young_length = desired_max_length - base_min_length;
 300 
 301   const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 302   const double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 303   const size_t pending_cards = _analytics->predict_pending_cards();
 304   const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
 305   const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, true /* for_young_gc */);
 306   const double base_time_ms =
 307     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
 308     survivor_regions_evac_time;
 309   const uint available_free_regions = _free_regions_at_end_of_collection;
 310   const uint base_free_regions =
 311     available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
 312 
 313   // Here, we will make sure that the shortest young length that
 314   // makes sense fits within the target pause time.
 315 
 316   G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(),
 317                            base_time_ms,
 318                            base_free_regions,
 319                            target_pause_time_ms,
 320                            this);
 321   if (p.will_fit(min_young_length)) {
 322     // The shortest young length will fit into the target pause time;
 323     // we'll now check whether the absolute maximum number of young
 324     // regions will fit in the target pause time. If not, we'll do
 325     // a binary search between min_young_length and max_young_length.
 326     if (p.will_fit(max_young_length)) {
 327       // The maximum young length will fit into the target pause time.
 328       // We are done so set min young length to the maximum length (as
 329       // the result is assumed to be returned in min_young_length).
 330       min_young_length = max_young_length;
 331     } else {
 332       // The maximum possible number of young regions will not fit within
 333       // the target pause time so we'll search for the optimal
 334       // length. The loop invariants are:
 335       //
 336       // min_young_length < max_young_length
 337       // min_young_length is known to fit into the target pause time
 338       // max_young_length is known not to fit into the target pause time
 339       //
 340       // Going into the loop we know the above hold as we've just
 341       // checked them. Every time around the loop we check whether
 342       // the middle value between min_young_length and
 343       // max_young_length fits into the target pause time. If it
 344       // does, it becomes the new min. If it doesn't, it becomes
 345       // the new max. This way we maintain the loop invariants.
 346 
 347       assert(min_young_length < max_young_length, "invariant");
 348       uint diff = (max_young_length - min_young_length) / 2;
 349       while (diff > 0) {
 350         uint young_length = min_young_length + diff;
 351         if (p.will_fit(young_length)) {
 352           min_young_length = young_length;
 353         } else {
 354           max_young_length = young_length;
 355         }
 356         assert(min_young_length <  max_young_length, "invariant");
 357         diff = (max_young_length - min_young_length) / 2;
 358       }
 359       // The results is min_young_length which, according to the
 360       // loop invariants, should fit within the target pause time.
 361 
 362       // These are the post-conditions of the binary search above:
 363       assert(min_young_length < max_young_length,
 364              "otherwise we should have discovered that max_young_length "
 365              "fits into the pause target and not done the binary search");
 366       assert(p.will_fit(min_young_length),
 367              "min_young_length, the result of the binary search, should "
 368              "fit into the pause target");
 369       assert(!p.will_fit(min_young_length + 1),
 370              "min_young_length, the result of the binary search, should be "
 371              "optimal, so no larger length should fit into the pause target");
 372     }
 373   } else {
 374     // Even the minimum length doesn't fit into the pause time
 375     // target, return it as the result nevertheless.
 376   }
 377   return base_min_length + min_young_length;
 378 }
 379 
 380 double G1Policy::predict_survivor_regions_evac_time() const {
 381   double survivor_regions_evac_time = 0.0;
 382   const GrowableArray<HeapRegion*>* survivor_regions = _g1->survivor()->regions();
 383 
 384   for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
 385        it != survivor_regions->end();
 386        ++it) {
 387     survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase());
 388   }
 389   return survivor_regions_evac_time;
 390 }
 391 
 392 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
 393   guarantee( adaptive_young_list_length(), "should not call this otherwise" );
 394 
 395   if (rs_lengths > _rs_lengths_prediction) {
 396     // add 10% to avoid having to recalculate often
 397     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 398     update_rs_lengths_prediction(rs_lengths_prediction);
 399 
 400     update_young_list_max_and_target_length(rs_lengths_prediction);
 401   }
 402 }
 403 
 404 void G1Policy::update_rs_lengths_prediction() {
 405   update_rs_lengths_prediction(_analytics->predict_rs_lengths());
 406 }
 407 
 408 void G1Policy::update_rs_lengths_prediction(size_t prediction) {
 409   if (collector_state()->in_young_only_phase() && adaptive_young_list_length()) {
 410     _rs_lengths_prediction = prediction;
 411   }
 412 }
 413 
 414 void G1Policy::record_full_collection_start() {
 415   _full_collection_start_sec = os::elapsedTime();
 416   // Release the future to-space so that it is available for compaction into.
 417   collector_state()->set_in_young_only_phase(false);
 418   collector_state()->set_in_full_gc(true);
 419   cset_chooser()->clear();
 420 }
 421 
 422 void G1Policy::record_full_collection_end() {
 423   // Consider this like a collection pause for the purposes of allocation
 424   // since last pause.
 425   double end_sec = os::elapsedTime();
 426   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 427   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 428 
 429   _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
 430 
 431   collector_state()->set_in_full_gc(false);
 432 
 433   // "Nuke" the heuristics that control the young/mixed GC
 434   // transitions and make sure we start with young GCs after the Full GC.
 435   collector_state()->set_in_young_only_phase(true);
 436   collector_state()->set_in_young_gc_before_mixed(false);
 437   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
 438   collector_state()->set_in_initial_mark_gc(false);
 439   collector_state()->set_mark_or_rebuild_in_progress(false);
 440   collector_state()->set_clearing_next_bitmap(false);
 441 
 442   _short_lived_surv_rate_group->start_adding_regions();
 443   // also call this on any additional surv rate groups
 444 
 445   _free_regions_at_end_of_collection = _g1->num_free_regions();
 446   // Reset survivors SurvRateGroup.
 447   _survivor_surv_rate_group->reset();
 448   update_young_list_max_and_target_length();
 449   update_rs_lengths_prediction();
 450 
 451   _bytes_allocated_in_old_since_last_gc = 0;
 452 
 453   record_pause(FullGC, _full_collection_start_sec, end_sec);
 454 }
 455 
 456 void G1Policy::record_collection_pause_start(double start_time_sec) {
 457   // We only need to do this here as the policy will only be applied
 458   // to the GC we're about to start. so, no point is calculating this
 459   // every time we calculate / recalculate the target young length.
 460   update_survivors_policy();
 461 
 462   assert(_g1->used() == _g1->recalculate_used(),
 463          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
 464          _g1->used(), _g1->recalculate_used());
 465 
 466   phase_times()->record_cur_collection_start_sec(start_time_sec);
 467   _pending_cards = _g1->pending_card_num();
 468 
 469   _collection_set->reset_bytes_used_before();
 470   _bytes_copied_during_gc = 0;
 471 
 472   // do that for any other surv rate groups
 473   _short_lived_surv_rate_group->stop_adding_regions();
 474   _survivors_age_table.clear();
 475 
 476   assert(_g1->collection_set()->verify_young_ages(), "region age verification failed");
 477 }
 478 
 479 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
 480   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 481   collector_state()->set_in_initial_mark_gc(false);
 482 }
 483 
 484 void G1Policy::record_concurrent_mark_remark_start() {
 485   _mark_remark_start_sec = os::elapsedTime();
 486 }
 487 
 488 void G1Policy::record_concurrent_mark_remark_end() {
 489   double end_time_sec = os::elapsedTime();
 490   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 491   _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
 492   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
 493 
 494   record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 495 }
 496 
 497 void G1Policy::record_concurrent_mark_cleanup_start() {
 498   _mark_cleanup_start_sec = os::elapsedTime();
 499 }
 500 
 501 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
 502   return phase_times()->average_time_ms(phase);
 503 }
 504 
 505 double G1Policy::young_other_time_ms() const {
 506   return phase_times()->young_cset_choice_time_ms() +
 507          phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
 508 }
 509 
 510 double G1Policy::non_young_other_time_ms() const {
 511   return phase_times()->non_young_cset_choice_time_ms() +
 512          phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
 513 }
 514 
 515 double G1Policy::other_time_ms(double pause_time_ms) const {
 516   return pause_time_ms - phase_times()->cur_collection_par_time_ms();
 517 }
 518 
 519 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
 520   return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms();
 521 }
 522 
 523 CollectionSetChooser* G1Policy::cset_chooser() const {
 524   return _collection_set->cset_chooser();
 525 }
 526 
 527 bool G1Policy::about_to_start_mixed_phase() const {
 528   return _g1->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
 529 }
 530 
 531 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
 532   if (about_to_start_mixed_phase()) {
 533     return false;
 534   }
 535 
 536   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
 537 
 538   size_t cur_used_bytes = _g1->non_young_capacity_bytes();
 539   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 540   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 541 
 542   bool result = false;
 543   if (marking_request_bytes > marking_initiating_used_threshold) {
 544     result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
 545     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
 546                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
 547                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
 548   }
 549 
 550   return result;
 551 }
 552 
 553 // Anything below that is considered to be zero
 554 #define MIN_TIMER_GRANULARITY 0.0000001
 555 
 556 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
 557   double end_time_sec = os::elapsedTime();
 558 
 559   size_t cur_used_bytes = _g1->used();
 560   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
 561   bool this_pause_included_initial_mark = false;
 562   bool this_pause_was_young_only = collector_state()->in_young_only_phase();
 563 
 564   bool update_stats = !_g1->evacuation_failed();
 565 
 566   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
 567 
 568   _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 569 
 570   this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
 571   if (this_pause_included_initial_mark) {
 572     record_concurrent_mark_init_end(0.0);
 573   } else {
 574     maybe_start_marking();
 575   }
 576 
 577   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
 578   if (app_time_ms < MIN_TIMER_GRANULARITY) {
 579     // This usually happens due to the timer not having the required
 580     // granularity. Some Linuxes are the usual culprits.
 581     // We'll just set it to something (arbitrarily) small.
 582     app_time_ms = 1.0;
 583   }
 584 
 585   if (update_stats) {
 586     // We maintain the invariant that all objects allocated by mutator
 587     // threads will be allocated out of eden regions. So, we can use
 588     // the eden region number allocated since the previous GC to
 589     // calculate the application's allocate rate. The only exception
 590     // to that is humongous objects that are allocated separately. But
 591     // given that humongous object allocations do not really affect
 592     // either the pause's duration nor when the next pause will take
 593     // place we can safely ignore them here.
 594     uint regions_allocated = _collection_set->eden_region_length();
 595     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
 596     _analytics->report_alloc_rate_ms(alloc_rate_ms);
 597 
 598     double interval_ms =
 599       (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
 600     _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
 601     _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
 602   }
 603 
 604   if (collector_state()->in_young_gc_before_mixed()) {
 605     assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
 606     // This has been the young GC before we start doing mixed GCs. We already
 607     // decided to start mixed GCs much earlier, so there is nothing to do except
 608     // advancing the state.
 609     collector_state()->set_in_young_only_phase(false);
 610     collector_state()->set_in_young_gc_before_mixed(false);
 611   } else if (!this_pause_was_young_only) {
 612     // This is a mixed GC. Here we decide whether to continue doing more
 613     // mixed GCs or not.
 614     if (!next_gc_should_be_mixed("continue mixed GCs",
 615                                  "do not continue mixed GCs")) {
 616       collector_state()->set_in_young_only_phase(true);
 617 
 618       clear_collection_set_candidates();
 619       maybe_start_marking();
 620     }
 621   }
 622 
 623   _short_lived_surv_rate_group->start_adding_regions();
 624   // Do that for any other surv rate groups
 625 
 626   double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
 627 
 628   if (update_stats) {
 629     double cost_per_card_ms = 0.0;
 630     if (_pending_cards > 0) {
 631       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
 632       _analytics->report_cost_per_card_ms(cost_per_card_ms);
 633     }
 634     _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
 635 
 636     double cost_per_entry_ms = 0.0;
 637     if (cards_scanned > 10) {
 638       cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
 639       _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only);
 640     }
 641 
 642     if (_max_rs_lengths > 0) {
 643       double cards_per_entry_ratio =
 644         (double) cards_scanned / (double) _max_rs_lengths;
 645       _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only);
 646     }
 647 
 648     // This is defensive. For a while _max_rs_lengths could get
 649     // smaller than _recorded_rs_lengths which was causing
 650     // rs_length_diff to get very large and mess up the RSet length
 651     // predictions. The reason was unsafe concurrent updates to the
 652     // _inc_cset_recorded_rs_lengths field which the code below guards
 653     // against (see CR 7118202). This bug has now been fixed (see CR
 654     // 7119027). However, I'm still worried that
 655     // _inc_cset_recorded_rs_lengths might still end up somewhat
 656     // inaccurate. The concurrent refinement thread calculates an
 657     // RSet's length concurrently with other CR threads updating it
 658     // which might cause it to calculate the length incorrectly (if,
 659     // say, it's in mid-coarsening). So I'll leave in the defensive
 660     // conditional below just in case.
 661     size_t rs_length_diff = 0;
 662     size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
 663     if (_max_rs_lengths > recorded_rs_lengths) {
 664       rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
 665     }
 666     _analytics->report_rs_length_diff((double) rs_length_diff);
 667 
 668     size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
 669     size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
 670     double cost_per_byte_ms = 0.0;
 671 
 672     if (copied_bytes > 0) {
 673       cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
 674       _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
 675     }
 676 
 677     if (_collection_set->young_region_length() > 0) {
 678       _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
 679                                                         _collection_set->young_region_length());
 680     }
 681 
 682     if (_collection_set->old_region_length() > 0) {
 683       _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
 684                                                             _collection_set->old_region_length());
 685     }
 686 
 687     _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
 688 
 689     _analytics->report_pending_cards((double) _pending_cards);
 690     _analytics->report_rs_lengths((double) _max_rs_lengths);
 691   }
 692 
 693   assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()),
 694          "If the last pause has been an initial mark, we should not have been in the marking window");
 695   if (this_pause_included_initial_mark) {
 696     collector_state()->set_mark_or_rebuild_in_progress(true);
 697   }
 698 
 699   _free_regions_at_end_of_collection = _g1->num_free_regions();
 700   // IHOP control wants to know the expected young gen length if it were not
 701   // restrained by the heap reserve. Using the actual length would make the
 702   // prediction too small and the limit the young gen every time we get to the
 703   // predicted target occupancy.
 704   size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
 705   update_rs_lengths_prediction();
 706 
 707   update_ihop_prediction(app_time_ms / 1000.0,
 708                          _bytes_allocated_in_old_since_last_gc,
 709                          last_unrestrained_young_length * HeapRegion::GrainBytes,
 710                          this_pause_was_young_only);
 711   _bytes_allocated_in_old_since_last_gc = 0;
 712 
 713   _ihop_control->send_trace_event(_g1->gc_tracer_stw());
 714 
 715   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
 716   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
 717 
 718   if (update_rs_time_goal_ms < scan_hcc_time_ms) {
 719     log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
 720                                 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
 721                                 update_rs_time_goal_ms, scan_hcc_time_ms);
 722 
 723     update_rs_time_goal_ms = 0;
 724   } else {
 725     update_rs_time_goal_ms -= scan_hcc_time_ms;
 726   }
 727   _g1->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
 728                                    phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
 729                                    update_rs_time_goal_ms);
 730 
 731   cset_chooser()->verify();
 732 }
 733 
 734 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
 735   if (G1UseAdaptiveIHOP) {
 736     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
 737                                      predictor,
 738                                      G1ReservePercent,
 739                                      G1HeapWastePercent);
 740   } else {
 741     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
 742   }
 743 }
 744 
 745 void G1Policy::update_ihop_prediction(double mutator_time_s,
 746                                       size_t mutator_alloc_bytes,
 747                                       size_t young_gen_size,
 748                                       bool this_gc_was_young_only) {
 749   // Always try to update IHOP prediction. Even evacuation failures give information
 750   // about e.g. whether to start IHOP earlier next time.
 751 
 752   // Avoid using really small application times that might create samples with
 753   // very high or very low values. They may be caused by e.g. back-to-back gcs.
 754   double const min_valid_time = 1e-6;
 755 
 756   bool report = false;
 757 
 758   double marking_to_mixed_time = -1.0;
 759   if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
 760     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
 761     assert(marking_to_mixed_time > 0.0,
 762            "Initial mark to mixed time must be larger than zero but is %.3f",
 763            marking_to_mixed_time);
 764     if (marking_to_mixed_time > min_valid_time) {
 765       _ihop_control->update_marking_length(marking_to_mixed_time);
 766       report = true;
 767     }
 768   }
 769 
 770   // As an approximation for the young gc promotion rates during marking we use
 771   // all of them. In many applications there are only a few if any young gcs during
 772   // marking, which makes any prediction useless. This increases the accuracy of the
 773   // prediction.
 774   if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
 775     _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
 776     report = true;
 777   }
 778 
 779   if (report) {
 780     report_ihop_statistics();
 781   }
 782 }
 783 
 784 void G1Policy::report_ihop_statistics() {
 785   _ihop_control->print();
 786 }
 787 
 788 void G1Policy::print_phases() {
 789   phase_times()->print();
 790 }
 791 
 792 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
 793   TruncatedSeq* seq = surv_rate_group->get_seq(age);
 794   guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
 795   double pred = _predictor.get_new_prediction(seq);
 796   if (pred > 1.0) {
 797     pred = 1.0;
 798   }
 799   return pred;
 800 }
 801 
 802 double G1Policy::accum_yg_surv_rate_pred(int age) const {
 803   return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
 804 }
 805 
 806 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
 807                                               size_t scanned_cards) const {
 808   return
 809     _analytics->predict_rs_update_time_ms(pending_cards) +
 810     _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) +
 811     _analytics->predict_constant_other_time_ms();
 812 }
 813 
 814 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
 815   size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
 816   size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase());
 817   return predict_base_elapsed_time_ms(pending_cards, card_num);
 818 }
 819 
 820 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
 821   size_t bytes_to_copy;
 822   if (hr->is_marked())
 823     bytes_to_copy = hr->max_live_bytes();
 824   else {
 825     assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
 826     int age = hr->age_in_surv_rate_group();
 827     double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
 828     bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
 829   }
 830   return bytes_to_copy;
 831 }
 832 
 833 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr,
 834                                                 bool for_young_gc) const {
 835   size_t rs_length = hr->rem_set()->occupied();
 836   // Predicting the number of cards is based on which type of GC
 837   // we're predicting for.
 838   size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
 839   size_t bytes_to_copy = predict_bytes_to_copy(hr);
 840 
 841   double region_elapsed_time_ms =
 842     _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) +
 843     _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
 844 
 845   // The prediction of the "other" time for this region is based
 846   // upon the region type and NOT the GC type.
 847   if (hr->is_young()) {
 848     region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
 849   } else {
 850     region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
 851   }
 852   return region_elapsed_time_ms;
 853 }
 854 
 855 bool G1Policy::should_allocate_mutator_region() const {
 856   uint young_list_length = _g1->young_regions_count();
 857   uint young_list_target_length = _young_list_target_length;
 858   return young_list_length < young_list_target_length;
 859 }
 860 
 861 bool G1Policy::can_expand_young_list() const {
 862   uint young_list_length = _g1->young_regions_count();
 863   uint young_list_max_length = _young_list_max_length;
 864   return young_list_length < young_list_max_length;
 865 }
 866 
 867 bool G1Policy::adaptive_young_list_length() const {
 868   return _young_gen_sizer.adaptive_young_list_length();
 869 }
 870 
 871 size_t G1Policy::desired_survivor_size() const {
 872   size_t const survivor_capacity = HeapRegion::GrainWords * _max_survivor_regions;
 873   return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 874 }
 875 
 876 void G1Policy::print_age_table() {
 877   _survivors_age_table.print_age_table(_tenuring_threshold);
 878 }
 879 
 880 void G1Policy::update_max_gc_locker_expansion() {
 881   uint expansion_region_num = 0;
 882   if (GCLockerEdenExpansionPercent > 0) {
 883     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
 884     double expansion_region_num_d = perc * (double) _young_list_target_length;
 885     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
 886     // less than 1.0) we'll get 1.
 887     expansion_region_num = (uint) ceil(expansion_region_num_d);
 888   } else {
 889     assert(expansion_region_num == 0, "sanity");
 890   }
 891   _young_list_max_length = _young_list_target_length + expansion_region_num;
 892   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
 893 }
 894 
 895 // Calculates survivor space parameters.
 896 void G1Policy::update_survivors_policy() {
 897   double max_survivor_regions_d =
 898                  (double) _young_list_target_length / (double) SurvivorRatio;
 899   // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
 900   // smaller than 1.0) we'll get 1.
 901   _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
 902 
 903   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(desired_survivor_size());
 904   if (UsePerfData) {
 905     _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
 906     _policy_counters->desired_survivor_size()->set_value(desired_survivor_size() * oopSize);
 907   }
 908 }
 909 
 910 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
 911   // We actually check whether we are marking here and not if we are in a
 912   // reclamation phase. This means that we will schedule a concurrent mark
 913   // even while we are still in the process of reclaiming memory.
 914   bool during_cycle = _g1->concurrent_mark()->cm_thread()->during_cycle();
 915   if (!during_cycle) {
 916     log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
 917     collector_state()->set_initiate_conc_mark_if_possible(true);
 918     return true;
 919   } else {
 920     log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
 921     return false;
 922   }
 923 }
 924 
 925 void G1Policy::initiate_conc_mark() {
 926   collector_state()->set_in_initial_mark_gc(true);
 927   collector_state()->set_initiate_conc_mark_if_possible(false);
 928 }
 929 
 930 void G1Policy::decide_on_conc_mark_initiation() {
 931   // We are about to decide on whether this pause will be an
 932   // initial-mark pause.
 933 
 934   // First, collector_state()->in_initial_mark_gc() should not be already set. We
 935   // will set it here if we have to. However, it should be cleared by
 936   // the end of the pause (it's only set for the duration of an
 937   // initial-mark pause).
 938   assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
 939 
 940   if (collector_state()->initiate_conc_mark_if_possible()) {
 941     // We had noticed on a previous pause that the heap occupancy has
 942     // gone over the initiating threshold and we should start a
 943     // concurrent marking cycle. So we might initiate one.
 944 
 945     if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
 946       // Initiate a new initial mark if there is no marking or reclamation going on.
 947       initiate_conc_mark();
 948       log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
 949     } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
 950       // Initiate a user requested initial mark. An initial mark must be young only
 951       // GC, so the collector state must be updated to reflect this.
 952       collector_state()->set_in_young_only_phase(true);
 953       collector_state()->set_in_young_gc_before_mixed(false);
 954 
 955       // We might have ended up coming here about to start a mixed phase with a collection set
 956       // active. The following remark might change the change the "evacuation efficiency" of
 957       // the regions in this set, leading to failing asserts later.
 958       // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
 959       clear_collection_set_candidates();
 960       abort_time_to_mixed_tracking();
 961       initiate_conc_mark();
 962       log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
 963     } else {
 964       // The concurrent marking thread is still finishing up the
 965       // previous cycle. If we start one right now the two cycles
 966       // overlap. In particular, the concurrent marking thread might
 967       // be in the process of clearing the next marking bitmap (which
 968       // we will use for the next cycle if we start one). Starting a
 969       // cycle now will be bad given that parts of the marking
 970       // information might get cleared by the marking thread. And we
 971       // cannot wait for the marking thread to finish the cycle as it
 972       // periodically yields while clearing the next marking bitmap
 973       // and, if it's in a yield point, it's waiting for us to
 974       // finish. So, at this point we will not start a cycle and we'll
 975       // let the concurrent marking thread complete the last one.
 976       log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
 977     }
 978   }
 979 }
 980 
 981 void G1Policy::record_concurrent_mark_cleanup_end() {
 982   cset_chooser()->rebuild(_g1->workers(), _g1->num_regions());
 983 
 984   bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
 985   if (!mixed_gc_pending) {
 986     clear_collection_set_candidates();
 987     abort_time_to_mixed_tracking();
 988   }
 989   collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
 990   collector_state()->set_mark_or_rebuild_in_progress(false);
 991 
 992   double end_sec = os::elapsedTime();
 993   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
 994   _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
 995   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
 996 
 997   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
 998 }
 999 
1000 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1001   return percent_of(reclaimable_bytes, _g1->capacity());
1002 }
1003 
1004 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1005   virtual bool do_heap_region(HeapRegion* r) {
1006     r->rem_set()->clear_locked(true /* only_cardset */);
1007     return false;
1008   }
1009 };
1010 
1011 void G1Policy::clear_collection_set_candidates() {
1012   // Clear remembered sets of remaining candidate regions and the actual candidate
1013   // list.
1014   G1ClearCollectionSetCandidateRemSets cl;
1015   cset_chooser()->iterate(&cl);
1016   cset_chooser()->clear();
1017 }
1018 
1019 void G1Policy::maybe_start_marking() {
1020   if (need_to_start_conc_mark("end of GC")) {
1021     // Note: this might have already been set, if during the last
1022     // pause we decided to start a cycle but at the beginning of
1023     // this pause we decided to postpone it. That's OK.
1024     collector_state()->set_initiate_conc_mark_if_possible(true);
1025   }
1026 }
1027 
1028 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1029   assert(!collector_state()->in_full_gc(), "must be");
1030   if (collector_state()->in_initial_mark_gc()) {
1031     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1032     return InitialMarkGC;
1033   } else if (collector_state()->in_young_gc_before_mixed()) {
1034     assert(!collector_state()->in_initial_mark_gc(), "must be");
1035     return LastYoungGC;
1036   } else if (collector_state()->in_mixed_phase()) {
1037     assert(!collector_state()->in_initial_mark_gc(), "must be");
1038     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1039     return MixedGC;
1040   } else {
1041     assert(!collector_state()->in_initial_mark_gc(), "must be");
1042     assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1043     return YoungOnlyGC;
1044   }
1045 }
1046 
1047 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1048   // Manage the MMU tracker. For some reason it ignores Full GCs.
1049   if (kind != FullGC) {
1050     _mmu_tracker->add_pause(start, end);
1051   }
1052   // Manage the mutator time tracking from initial mark to first mixed gc.
1053   switch (kind) {
1054     case FullGC:
1055       abort_time_to_mixed_tracking();
1056       break;
1057     case Cleanup:
1058     case Remark:
1059     case YoungOnlyGC:
1060     case LastYoungGC:
1061       _initial_mark_to_mixed.add_pause(end - start);
1062       break;
1063     case InitialMarkGC:
1064       _initial_mark_to_mixed.record_initial_mark_end(end);
1065       break;
1066     case MixedGC:
1067       _initial_mark_to_mixed.record_mixed_gc_start(start);
1068       break;
1069     default:
1070       ShouldNotReachHere();
1071   }
1072 }
1073 
1074 void G1Policy::abort_time_to_mixed_tracking() {
1075   _initial_mark_to_mixed.reset();
1076 }
1077 
1078 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1079                                        const char* false_action_str) const {
1080   if (cset_chooser()->is_empty()) {
1081     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1082     return false;
1083   }
1084 
1085   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1086   size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1087   double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1088   double threshold = (double) G1HeapWastePercent;
1089   if (reclaimable_percent <= threshold) {
1090     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1091                         false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1092     return false;
1093   }
1094   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1095                       true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1096   return true;
1097 }
1098 
1099 uint G1Policy::calc_min_old_cset_length() const {
1100   // The min old CSet region bound is based on the maximum desired
1101   // number of mixed GCs after a cycle. I.e., even if some old regions
1102   // look expensive, we should add them to the CSet anyway to make
1103   // sure we go through the available old regions in no more than the
1104   // maximum desired number of mixed GCs.
1105   //
1106   // The calculation is based on the number of marked regions we added
1107   // to the CSet chooser in the first place, not how many remain, so
1108   // that the result is the same during all mixed GCs that follow a cycle.
1109 
1110   const size_t region_num = (size_t) cset_chooser()->length();
1111   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1112   size_t result = region_num / gc_num;
1113   // emulate ceiling
1114   if (result * gc_num < region_num) {
1115     result += 1;
1116   }
1117   return (uint) result;
1118 }
1119 
1120 uint G1Policy::calc_max_old_cset_length() const {
1121   // The max old CSet region bound is based on the threshold expressed
1122   // as a percentage of the heap size. I.e., it should bound the
1123   // number of old regions added to the CSet irrespective of how many
1124   // of them are available.
1125 
1126   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1127   const size_t region_num = g1h->num_regions();
1128   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1129   size_t result = region_num * perc / 100;
1130   // emulate ceiling
1131   if (100 * result < region_num * perc) {
1132     result += 1;
1133   }
1134   return (uint) result;
1135 }
1136 
1137 void G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
1138   double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor);
1139   _collection_set->finalize_old_part(time_remaining_ms);
1140 }
1141 
1142 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1143 
1144   // Add survivor regions to SurvRateGroup.
1145   note_start_adding_survivor_regions();
1146   finished_recalculating_age_indexes(true /* is_survivors */);
1147 
1148   HeapRegion* last = NULL;
1149   for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1150        it != survivors->regions()->end();
1151        ++it) {
1152     HeapRegion* curr = *it;
1153     set_region_survivor(curr);
1154 
1155     // The region is a non-empty survivor so let's add it to
1156     // the incremental collection set for the next evacuation
1157     // pause.
1158     _collection_set->add_survivor_regions(curr);
1159 
1160     last = curr;
1161   }
1162   note_stop_adding_survivor_regions();
1163 
1164   // Don't clear the survivor list handles until the start of
1165   // the next evacuation pause - we need it in order to re-tag
1166   // the survivor regions from this evacuation pause as 'young'
1167   // at the start of the next.
1168 
1169   finished_recalculating_age_indexes(false /* is_survivors */);
1170 }