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src/hotspot/share/gc/g1/g1Policy.cpp

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   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/g1Analytics.hpp"
  27 #include "gc/g1/g1Arguments.hpp"
  28 #include "gc/g1/g1CollectedHeap.inline.hpp"
  29 #include "gc/g1/g1CollectionSet.hpp"
  30 #include "gc/g1/g1CollectionSetCandidates.hpp"
  31 #include "gc/g1/g1ConcurrentMark.hpp"
  32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  33 #include "gc/g1/g1ConcurrentRefine.hpp"
  34 #include "gc/g1/g1CollectionSetChooser.hpp"
  35 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
  36 #include "gc/g1/g1HotCardCache.hpp"
  37 #include "gc/g1/g1IHOPControl.hpp"
  38 #include "gc/g1/g1GCPhaseTimes.hpp"
  39 #include "gc/g1/g1Policy.hpp"
  40 #include "gc/g1/g1SurvivorRegions.hpp"
  41 #include "gc/g1/g1YoungGenSizer.hpp"
  42 #include "gc/g1/heapRegion.inline.hpp"
  43 #include "gc/g1/heapRegionRemSet.hpp"
  44 #include "gc/shared/gcPolicyCounters.hpp"
  45 #include "logging/logStream.hpp"
  46 #include "runtime/arguments.hpp"
  47 #include "runtime/java.hpp"
  48 #include "runtime/mutexLocker.hpp"
  49 #include "utilities/debug.hpp"
  50 #include "utilities/growableArray.hpp"
  51 #include "utilities/pair.hpp"
  52 
  53 G1Policy::G1Policy(STWGCTimer* gc_timer) :
  54   _predictor(G1ConfidencePercent / 100.0),
  55   _analytics(new G1Analytics(&_predictor)),
  56   _remset_tracker(),
  57   _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
  58   _ihop_control(create_ihop_control(&_predictor)),
  59   _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
  60   _full_collection_start_sec(0.0),
  61   _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
  62   _young_list_target_length(0),
  63   _young_list_fixed_length(0),
  64   _young_list_max_length(0),
  65   _short_lived_surv_rate_group(new SurvRateGroup()),
  66   _survivor_surv_rate_group(new SurvRateGroup()),
  67   _reserve_factor((double) G1ReservePercent / 100.0),
  68   _reserve_regions(0),
  69   _young_gen_sizer(G1YoungGenSizer::create_gen_sizer()),
  70   _free_regions_at_end_of_collection(0),
  71   _max_rs_lengths(0),
  72   _rs_lengths_prediction(0),
  73   _pending_cards(0),
  74   _bytes_allocated_in_old_since_last_gc(0),
  75   _initial_mark_to_mixed(),
  76   _collection_set(NULL),
  77   _bytes_copied_during_gc(0),
  78   _g1h(NULL),
  79   _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
  80   _mark_remark_start_sec(0),
  81   _mark_cleanup_start_sec(0),
  82   _tenuring_threshold(MaxTenuringThreshold),
  83   _max_survivor_regions(0),
  84   _survivors_age_table(true)
  85 {
  86 }
  87 
  88 G1Policy::~G1Policy() {
  89   delete _ihop_control;
  90   delete _young_gen_sizer;
  91 }
  92 
  93 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) {
  94   if (G1Arguments::is_heterogeneous_heap()) {
  95     return new G1HeterogeneousHeapPolicy(gc_timer_stw);
  96   } else {
  97     return new G1Policy(gc_timer_stw);
  98   }
  99 }
 100 
 101 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
 102 
 103 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
 104   _g1h = g1h;
 105   _collection_set = collection_set;
 106 
 107   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 108 
 109   if (!use_adaptive_young_list_length()) {
 110     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 111   }
 112   _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
 113 
 114   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 115 
 116   update_young_list_max_and_target_length();
 117   // We may immediately start allocating regions and placing them on the
 118   // collection set list. Initialize the per-collection set info
 119   _collection_set->start_incremental_building();
 120 }
 121 
 122 void G1Policy::note_gc_start() {
 123   phase_times()->note_gc_start();
 124 }
 125 
 126 class G1YoungLengthPredictor {
 127   const bool _during_cm;
 128   const double _base_time_ms;
 129   const double _base_free_regions;


 179 
 180     // success!
 181     return true;
 182   }
 183 };
 184 
 185 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
 186   // re-calculate the necessary reserve
 187   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 188   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 189   // smaller than 1.0) we'll get 1.
 190   _reserve_regions = (uint) ceil(reserve_regions_d);
 191 
 192   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 193 
 194   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
 195 }
 196 
 197 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
 198   uint desired_min_length = 0;
 199   if (use_adaptive_young_list_length()) {
 200     if (_analytics->num_alloc_rate_ms() > 3) {
 201       double now_sec = os::elapsedTime();
 202       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 203       double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
 204       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 205     } else {
 206       // otherwise we don't have enough info to make the prediction
 207     }
 208   }
 209   desired_min_length += base_min_length;
 210   // make sure we don't go below any user-defined minimum bound
 211   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 212 }
 213 
 214 uint G1Policy::calculate_young_list_desired_max_length() const {
 215   // Here, we might want to also take into account any additional
 216   // constraints (i.e., user-defined minimum bound). Currently, we
 217   // effectively don't set this bound.
 218   return _young_gen_sizer->max_desired_young_length();
 219 }


 236 }
 237 
 238 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const {
 239   YoungTargetLengths result;
 240 
 241   // Calculate the absolute and desired min bounds first.
 242 
 243   // This is how many young regions we already have (currently: the survivors).
 244   const uint base_min_length = _g1h->survivor_regions_count();
 245   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 246   // This is the absolute minimum young length. Ensure that we
 247   // will at least have one eden region available for allocation.
 248   uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
 249   // If we shrank the young list target it should not shrink below the current size.
 250   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 251   // Calculate the absolute and desired max bounds.
 252 
 253   uint desired_max_length = calculate_young_list_desired_max_length();
 254 
 255   uint young_list_target_length = 0;
 256   if (use_adaptive_young_list_length()) {
 257     if (collector_state()->in_young_only_phase()) {
 258       young_list_target_length =
 259                         calculate_young_list_target_length(rs_lengths,
 260                                                            base_min_length,
 261                                                            desired_min_length,
 262                                                            desired_max_length);
 263     } else {
 264       // Don't calculate anything and let the code below bound it to
 265       // the desired_min_length, i.e., do the next GC as soon as
 266       // possible to maximize how many old regions we can add to it.
 267     }
 268   } else {
 269     // The user asked for a fixed young gen so we'll fix the young gen
 270     // whether the next GC is young or mixed.
 271     young_list_target_length = _young_list_fixed_length;
 272   }
 273 
 274   result.second = young_list_target_length;
 275 
 276   // We will try our best not to "eat" into the reserve.


 288   if (young_list_target_length > desired_max_length) {
 289     young_list_target_length = desired_max_length;
 290   }
 291   if (young_list_target_length < desired_min_length) {
 292     young_list_target_length = desired_min_length;
 293   }
 294 
 295   assert(young_list_target_length > base_min_length,
 296          "we should be able to allocate at least one eden region");
 297   assert(young_list_target_length >= absolute_min_length, "post-condition");
 298 
 299   result.first = young_list_target_length;
 300   return result;
 301 }
 302 
 303 uint
 304 G1Policy::calculate_young_list_target_length(size_t rs_lengths,
 305                                                     uint base_min_length,
 306                                                     uint desired_min_length,
 307                                                     uint desired_max_length) const {
 308   assert(use_adaptive_young_list_length(), "pre-condition");
 309   assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
 310 
 311   // In case some edge-condition makes the desired max length too small...
 312   if (desired_max_length <= desired_min_length) {
 313     return desired_min_length;
 314   }
 315 
 316   // We'll adjust min_young_length and max_young_length not to include
 317   // the already allocated young regions (i.e., so they reflect the
 318   // min and max eden regions we'll allocate). The base_min_length
 319   // will be reflected in the predictions by the
 320   // survivor_regions_evac_time prediction.
 321   assert(desired_min_length > base_min_length, "invariant");
 322   uint min_young_length = desired_min_length - base_min_length;
 323   assert(desired_max_length > base_min_length, "invariant");
 324   uint max_young_length = desired_max_length - base_min_length;
 325 
 326   const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 327   const double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 328   const size_t pending_cards = _analytics->predict_pending_cards();


 398   } else {
 399     // Even the minimum length doesn't fit into the pause time
 400     // target, return it as the result nevertheless.
 401   }
 402   return base_min_length + min_young_length;
 403 }
 404 
 405 double G1Policy::predict_survivor_regions_evac_time() const {
 406   double survivor_regions_evac_time = 0.0;
 407   const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
 408 
 409   for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
 410        it != survivor_regions->end();
 411        ++it) {
 412     survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase());
 413   }
 414   return survivor_regions_evac_time;
 415 }
 416 
 417 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
 418   guarantee(use_adaptive_young_list_length(), "should not call this otherwise" );
 419 
 420   if (rs_lengths > _rs_lengths_prediction) {
 421     // add 10% to avoid having to recalculate often
 422     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 423     update_rs_lengths_prediction(rs_lengths_prediction);
 424 
 425     update_young_list_max_and_target_length(rs_lengths_prediction);
 426   }
 427 }
 428 
 429 void G1Policy::update_rs_lengths_prediction() {
 430   update_rs_lengths_prediction(_analytics->predict_rs_lengths());
 431 }
 432 
 433 void G1Policy::update_rs_lengths_prediction(size_t prediction) {
 434   if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) {
 435     _rs_lengths_prediction = prediction;
 436   }
 437 }
 438 
 439 void G1Policy::record_full_collection_start() {
 440   _full_collection_start_sec = os::elapsedTime();
 441   // Release the future to-space so that it is available for compaction into.
 442   collector_state()->set_in_young_only_phase(false);
 443   collector_state()->set_in_full_gc(true);
 444   _collection_set->clear_candidates();
 445 }
 446 
 447 void G1Policy::record_full_collection_end() {
 448   // Consider this like a collection pause for the purposes of allocation
 449   // since last pause.
 450   double end_sec = os::elapsedTime();
 451   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 452   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 453 
 454   _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);


 470   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 471   // Reset survivors SurvRateGroup.
 472   _survivor_surv_rate_group->reset();
 473   update_young_list_max_and_target_length();
 474   update_rs_lengths_prediction();
 475 
 476   _bytes_allocated_in_old_since_last_gc = 0;
 477 
 478   record_pause(FullGC, _full_collection_start_sec, end_sec);
 479 }
 480 
 481 void G1Policy::record_collection_pause_start(double start_time_sec) {
 482   // We only need to do this here as the policy will only be applied
 483   // to the GC we're about to start. so, no point is calculating this
 484   // every time we calculate / recalculate the target young length.
 485   update_survivors_policy();
 486 
 487   assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
 488          "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
 489          max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
 490   assert_used_and_recalculate_used_equal(_g1h);



 491 
 492   phase_times()->record_cur_collection_start_sec(start_time_sec);
 493   _pending_cards = _g1h->pending_card_num();
 494 
 495   _collection_set->reset_bytes_used_before();
 496   _bytes_copied_during_gc = 0;
 497 
 498   // do that for any other surv rate groups
 499   _short_lived_surv_rate_group->stop_adding_regions();
 500   _survivors_age_table.clear();
 501 
 502   assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
 503 }
 504 
 505 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
 506   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 507   collector_state()->set_in_initial_mark_gc(false);
 508 }
 509 
 510 void G1Policy::record_concurrent_mark_remark_start() {


 561   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 562   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 563 
 564   bool result = false;
 565   if (marking_request_bytes > marking_initiating_used_threshold) {
 566     result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
 567     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
 568                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
 569                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
 570   }
 571 
 572   return result;
 573 }
 574 
 575 // Anything below that is considered to be zero
 576 #define MIN_TIMER_GRANULARITY 0.0000001
 577 
 578 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
 579   double end_time_sec = os::elapsedTime();
 580 
 581   assert_used_and_recalculate_used_equal(_g1h);
 582   size_t cur_used_bytes = _g1h->used();

 583   bool this_pause_included_initial_mark = false;
 584   bool this_pause_was_young_only = collector_state()->in_young_only_phase();
 585 
 586   bool update_stats = !_g1h->evacuation_failed();
 587 
 588   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
 589 
 590   _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 591 
 592   this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
 593   if (this_pause_included_initial_mark) {
 594     record_concurrent_mark_init_end(0.0);
 595   } else {
 596     maybe_start_marking();
 597   }
 598 
 599   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
 600   if (app_time_ms < MIN_TIMER_GRANULARITY) {
 601     // This usually happens due to the timer not having the required
 602     // granularity. Some Linuxes are the usual culprits.


 640       clear_collection_set_candidates();
 641       maybe_start_marking();
 642     }
 643   }
 644 
 645   _short_lived_surv_rate_group->start_adding_regions();
 646   // Do that for any other surv rate groups
 647 
 648   double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
 649 
 650   if (update_stats) {
 651     double cost_per_card_ms = 0.0;
 652     if (_pending_cards > 0) {
 653       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS)) / (double) _pending_cards;
 654       _analytics->report_cost_per_card_ms(cost_per_card_ms);
 655     }
 656     _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
 657 
 658     double cost_per_entry_ms = 0.0;
 659     if (cards_scanned > 10) {
 660       double avg_time_scan_rs = average_time_ms(G1GCPhaseTimes::ScanRS);
 661       if (this_pause_was_young_only) {
 662         avg_time_scan_rs += average_time_ms(G1GCPhaseTimes::OptScanRS);
 663       }
 664       cost_per_entry_ms = avg_time_scan_rs / cards_scanned;
 665       _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only);
 666     }
 667 
 668     if (_max_rs_lengths > 0) {
 669       double cards_per_entry_ratio =
 670         (double) cards_scanned / (double) _max_rs_lengths;
 671       _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only);
 672     }
 673 
 674     // This is defensive. For a while _max_rs_lengths could get
 675     // smaller than _recorded_rs_lengths which was causing
 676     // rs_length_diff to get very large and mess up the RSet length
 677     // predictions. The reason was unsafe concurrent updates to the
 678     // _inc_cset_recorded_rs_lengths field which the code below guards
 679     // against (see CR 7118202). This bug has now been fixed (see CR
 680     // 7119027). However, I'm still worried that
 681     // _inc_cset_recorded_rs_lengths might still end up somewhat
 682     // inaccurate. The concurrent refinement thread calculates an
 683     // RSet's length concurrently with other CR threads updating it
 684     // which might cause it to calculate the length incorrectly (if,
 685     // say, it's in mid-coarsening). So I'll leave in the defensive
 686     // conditional below just in case.
 687     size_t rs_length_diff = 0;
 688     size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
 689     if (_max_rs_lengths > recorded_rs_lengths) {
 690       rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
 691     }
 692     _analytics->report_rs_length_diff((double) rs_length_diff);
 693 
 694     size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
 695     size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
 696     double cost_per_byte_ms = 0.0;
 697 
 698     if (copied_bytes > 0) {
 699       cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / (double) copied_bytes;
 700       _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
 701     }
 702 
 703     if (_collection_set->young_region_length() > 0) {
 704       _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
 705                                                         _collection_set->young_region_length());
 706     }
 707 
 708     if (_collection_set->old_region_length() > 0) {
 709       _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
 710                                                             _collection_set->old_region_length());
 711     }
 712 
 713     _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
 714 
 715     // Do not update RS lengths and the number of pending cards with information from mixed gc:
 716     // these are is wildly different to during young only gc and mess up young gen sizing right
 717     // after the mixed gc phase.
 718     // During mixed gc we do not use them for young gen sizing.
 719     if (this_pause_was_young_only) {


 891   if (hr->is_young()) {
 892     region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
 893   } else {
 894     region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
 895   }
 896   return region_elapsed_time_ms;
 897 }
 898 
 899 bool G1Policy::should_allocate_mutator_region() const {
 900   uint young_list_length = _g1h->young_regions_count();
 901   uint young_list_target_length = _young_list_target_length;
 902   return young_list_length < young_list_target_length;
 903 }
 904 
 905 bool G1Policy::can_expand_young_list() const {
 906   uint young_list_length = _g1h->young_regions_count();
 907   uint young_list_max_length = _young_list_max_length;
 908   return young_list_length < young_list_max_length;
 909 }
 910 
 911 bool G1Policy::use_adaptive_young_list_length() const {
 912   return _young_gen_sizer->use_adaptive_young_list_length();
 913 }
 914 
 915 size_t G1Policy::desired_survivor_size(uint max_regions) const {
 916   size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
 917   return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 918 }
 919 
 920 void G1Policy::print_age_table() {
 921   _survivors_age_table.print_age_table(_tenuring_threshold);
 922 }
 923 
 924 void G1Policy::update_max_gc_locker_expansion() {
 925   uint expansion_region_num = 0;
 926   if (GCLockerEdenExpansionPercent > 0) {
 927     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
 928     double expansion_region_num_d = perc * (double) _young_list_target_length;
 929     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
 930     // less than 1.0) we'll get 1.
 931     expansion_region_num = (uint) ceil(expansion_region_num_d);
 932   } else {


1173   return (uint) result;
1174 }
1175 
1176 uint G1Policy::calc_max_old_cset_length() const {
1177   // The max old CSet region bound is based on the threshold expressed
1178   // as a percentage of the heap size. I.e., it should bound the
1179   // number of old regions added to the CSet irrespective of how many
1180   // of them are available.
1181 
1182   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1183   const size_t region_num = g1h->num_regions();
1184   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1185   size_t result = region_num * perc / 100;
1186   // emulate ceiling
1187   if (100 * result < region_num * perc) {
1188     result += 1;
1189   }
1190   return (uint) result;
1191 }
1192 
1193 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
1194                                                     double time_remaining_ms,
1195                                                     uint& num_initial_regions,
1196                                                     uint& num_optional_regions) {
1197   assert(candidates != NULL, "Must be");
1198 
1199   num_initial_regions = 0;
1200   num_optional_regions = 0;
1201   uint num_expensive_regions = 0;
1202 
1203   double predicted_old_time_ms = 0.0;
1204   double predicted_initial_time_ms = 0.0;
1205   double predicted_optional_time_ms = 0.0;
1206 
1207   double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction();
1208 
1209   const uint min_old_cset_length = calc_min_old_cset_length();
1210   const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length());
1211   const uint max_optional_regions = max_old_cset_length - min_old_cset_length;
1212   bool check_time_remaining = use_adaptive_young_list_length();
1213 
1214   uint candidate_idx = candidates->cur_idx();
1215 
1216   log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, "
1217                             "time remaining %1.2fms, optional threshold %1.2fms",
1218                             min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms);
1219 
1220   HeapRegion* hr = candidates->at(candidate_idx);
1221   while (hr != NULL) {
1222     if (num_initial_regions + num_optional_regions >= max_old_cset_length) {
1223       // Added maximum number of old regions to the CSet.
1224       log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). "
1225                                 "Initial %u regions, optional %u regions",
1226                                 num_initial_regions, num_optional_regions);
1227       break;
1228     }
1229 
1230     // Stop adding regions if the remaining reclaimable space is
1231     // not above G1HeapWastePercent.
1232     size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1233     double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1234     double threshold = (double) G1HeapWastePercent;
1235     if (reclaimable_percent <= threshold) {
1236       // We've added enough old regions that the amount of uncollected
1237       // reclaimable space is at or below the waste threshold. Stop
1238       // adding old regions to the CSet.
1239       log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). "
1240                                 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%",
1241                                 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes),
1242                                 reclaimable_percent, G1HeapWastePercent);
1243       break;
1244     }
1245 
1246     double predicted_time_ms = predict_region_elapsed_time_ms(hr, false);
1247     time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
1248     // Add regions to old set until we reach the minimum amount
1249     if (num_initial_regions < min_old_cset_length) {
1250       predicted_old_time_ms += predicted_time_ms;
1251       num_initial_regions++;
1252       // Record the number of regions added with no time remaining
1253       if (time_remaining_ms == 0.0) {
1254         num_expensive_regions++;
1255       }
1256     } else if (!check_time_remaining) {
1257       // In the non-auto-tuning case, we'll finish adding regions
1258       // to the CSet if we reach the minimum.
1259       log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min).");
1260       break;
1261     } else {
1262       // Keep adding regions to old set until we reach the optional threshold
1263       if (time_remaining_ms > optional_threshold_ms) {
1264         predicted_old_time_ms += predicted_time_ms;
1265         num_initial_regions++;
1266       } else if (time_remaining_ms > 0) {
1267         // Keep adding optional regions until time is up.
1268         assert(num_optional_regions < max_optional_regions, "Should not be possible.");
1269         predicted_optional_time_ms += predicted_time_ms;
1270         num_optional_regions++;
1271       } else {
1272         log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high).");
1273         break;
1274       }
1275     }
1276     hr = candidates->at(++candidate_idx);
1277   }
1278   if (hr == NULL) {
1279     log_debug(gc, ergo, cset)("Old candidate collection set empty.");
1280   }
1281 
1282   if (num_expensive_regions > 0) {
1283     log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.",
1284                               num_expensive_regions);
1285   }
1286 
1287   log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, "
1288                             "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f",
1289                             num_initial_regions, num_optional_regions,
1290                             predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms);
1291 }
1292 
1293 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
1294                                                          uint const max_optional_regions,
1295                                                          double time_remaining_ms,
1296                                                          uint& num_optional_regions) {
1297   assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase");
1298 
1299   num_optional_regions = 0;
1300   double prediction_ms = 0;
1301   uint candidate_idx = candidates->cur_idx();
1302 
1303   HeapRegion* r = candidates->at(candidate_idx);
1304   while (num_optional_regions < max_optional_regions) {
1305     assert(r != NULL, "Region must exist");
1306     prediction_ms += predict_region_elapsed_time_ms(r, false);
1307 
1308     if (prediction_ms > time_remaining_ms) {
1309       log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.",
1310                                 prediction_ms, r->hrm_index(), time_remaining_ms);
1311       break;
1312     }
1313     // This region will be included in the next optional evacuation.
1314 
1315     time_remaining_ms -= prediction_ms;
1316     num_optional_regions++;
1317     r = candidates->at(++candidate_idx);
1318   }
1319 
1320   log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms",
1321                             num_optional_regions, max_optional_regions, prediction_ms);
1322 }
1323 
1324 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1325 
1326   // Add survivor regions to SurvRateGroup.
1327   note_start_adding_survivor_regions();
1328   finished_recalculating_age_indexes(true /* is_survivors */);
1329 
1330   HeapRegion* last = NULL;
1331   for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1332        it != survivors->regions()->end();
1333        ++it) {
1334     HeapRegion* curr = *it;
1335     set_region_survivor(curr);
1336 
1337     // The region is a non-empty survivor so let's add it to
1338     // the incremental collection set for the next evacuation
1339     // pause.
1340     _collection_set->add_survivor_regions(curr);
1341 


   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/g1Analytics.hpp"

  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1CollectionSet.hpp"
  29 #include "gc/g1/g1CollectionSetCandidates.hpp"
  30 #include "gc/g1/g1ConcurrentMark.hpp"
  31 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  32 #include "gc/g1/g1ConcurrentRefine.hpp"
  33 #include "gc/g1/g1CollectionSetChooser.hpp"
  34 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
  35 #include "gc/g1/g1HotCardCache.hpp"
  36 #include "gc/g1/g1IHOPControl.hpp"
  37 #include "gc/g1/g1GCPhaseTimes.hpp"
  38 #include "gc/g1/g1Policy.hpp"
  39 #include "gc/g1/g1SurvivorRegions.hpp"
  40 #include "gc/g1/g1YoungGenSizer.hpp"
  41 #include "gc/g1/heapRegion.inline.hpp"
  42 #include "gc/g1/heapRegionRemSet.hpp"
  43 #include "gc/shared/gcPolicyCounters.hpp"
  44 #include "logging/logStream.hpp"
  45 #include "runtime/arguments.hpp"
  46 #include "runtime/java.hpp"
  47 #include "runtime/mutexLocker.hpp"
  48 #include "utilities/debug.hpp"
  49 #include "utilities/growableArray.hpp"
  50 #include "utilities/pair.hpp"
  51 
  52 G1Policy::G1Policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer) :
  53   _predictor(G1ConfidencePercent / 100.0),
  54   _analytics(new G1Analytics(&_predictor)),
  55   _remset_tracker(),
  56   _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
  57   _ihop_control(create_ihop_control(&_predictor)),
  58   _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
  59   _full_collection_start_sec(0.0),
  60   _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
  61   _young_list_target_length(0),
  62   _young_list_fixed_length(0),
  63   _young_list_max_length(0),
  64   _short_lived_surv_rate_group(new SurvRateGroup()),
  65   _survivor_surv_rate_group(new SurvRateGroup()),
  66   _reserve_factor((double) G1ReservePercent / 100.0),
  67   _reserve_regions(0),
  68   _young_gen_sizer(G1YoungGenSizer::create_gen_sizer(policy)),
  69   _free_regions_at_end_of_collection(0),
  70   _max_rs_lengths(0),
  71   _rs_lengths_prediction(0),
  72   _pending_cards(0),
  73   _bytes_allocated_in_old_since_last_gc(0),
  74   _initial_mark_to_mixed(),
  75   _collection_set(NULL),
  76   _bytes_copied_during_gc(0),
  77   _g1h(NULL),
  78   _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
  79   _mark_remark_start_sec(0),
  80   _mark_cleanup_start_sec(0),
  81   _tenuring_threshold(MaxTenuringThreshold),
  82   _max_survivor_regions(0),
  83   _survivors_age_table(true)
  84 {
  85 }
  86 
  87 G1Policy::~G1Policy() {
  88   delete _ihop_control;
  89   delete _young_gen_sizer;
  90 }
  91 
  92 G1Policy* G1Policy::create_policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer_stw) {
  93   if (policy->is_heterogeneous_heap()) {
  94     return new G1HeterogeneousHeapPolicy(policy, gc_timer_stw);
  95   } else {
  96     return new G1Policy(policy, gc_timer_stw);
  97   }
  98 }
  99 
 100 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
 101 
 102 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
 103   _g1h = g1h;
 104   _collection_set = collection_set;
 105 
 106   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 107 
 108   if (!adaptive_young_list_length()) {
 109     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 110   }
 111   _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
 112 
 113   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 114 
 115   update_young_list_max_and_target_length();
 116   // We may immediately start allocating regions and placing them on the
 117   // collection set list. Initialize the per-collection set info
 118   _collection_set->start_incremental_building();
 119 }
 120 
 121 void G1Policy::note_gc_start() {
 122   phase_times()->note_gc_start();
 123 }
 124 
 125 class G1YoungLengthPredictor {
 126   const bool _during_cm;
 127   const double _base_time_ms;
 128   const double _base_free_regions;


 178 
 179     // success!
 180     return true;
 181   }
 182 };
 183 
 184 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
 185   // re-calculate the necessary reserve
 186   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 187   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 188   // smaller than 1.0) we'll get 1.
 189   _reserve_regions = (uint) ceil(reserve_regions_d);
 190 
 191   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 192 
 193   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
 194 }
 195 
 196 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
 197   uint desired_min_length = 0;
 198   if (adaptive_young_list_length()) {
 199     if (_analytics->num_alloc_rate_ms() > 3) {
 200       double now_sec = os::elapsedTime();
 201       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 202       double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
 203       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 204     } else {
 205       // otherwise we don't have enough info to make the prediction
 206     }
 207   }
 208   desired_min_length += base_min_length;
 209   // make sure we don't go below any user-defined minimum bound
 210   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 211 }
 212 
 213 uint G1Policy::calculate_young_list_desired_max_length() const {
 214   // Here, we might want to also take into account any additional
 215   // constraints (i.e., user-defined minimum bound). Currently, we
 216   // effectively don't set this bound.
 217   return _young_gen_sizer->max_desired_young_length();
 218 }


 235 }
 236 
 237 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const {
 238   YoungTargetLengths result;
 239 
 240   // Calculate the absolute and desired min bounds first.
 241 
 242   // This is how many young regions we already have (currently: the survivors).
 243   const uint base_min_length = _g1h->survivor_regions_count();
 244   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 245   // This is the absolute minimum young length. Ensure that we
 246   // will at least have one eden region available for allocation.
 247   uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
 248   // If we shrank the young list target it should not shrink below the current size.
 249   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 250   // Calculate the absolute and desired max bounds.
 251 
 252   uint desired_max_length = calculate_young_list_desired_max_length();
 253 
 254   uint young_list_target_length = 0;
 255   if (adaptive_young_list_length()) {
 256     if (collector_state()->in_young_only_phase()) {
 257       young_list_target_length =
 258                         calculate_young_list_target_length(rs_lengths,
 259                                                            base_min_length,
 260                                                            desired_min_length,
 261                                                            desired_max_length);
 262     } else {
 263       // Don't calculate anything and let the code below bound it to
 264       // the desired_min_length, i.e., do the next GC as soon as
 265       // possible to maximize how many old regions we can add to it.
 266     }
 267   } else {
 268     // The user asked for a fixed young gen so we'll fix the young gen
 269     // whether the next GC is young or mixed.
 270     young_list_target_length = _young_list_fixed_length;
 271   }
 272 
 273   result.second = young_list_target_length;
 274 
 275   // We will try our best not to "eat" into the reserve.


 287   if (young_list_target_length > desired_max_length) {
 288     young_list_target_length = desired_max_length;
 289   }
 290   if (young_list_target_length < desired_min_length) {
 291     young_list_target_length = desired_min_length;
 292   }
 293 
 294   assert(young_list_target_length > base_min_length,
 295          "we should be able to allocate at least one eden region");
 296   assert(young_list_target_length >= absolute_min_length, "post-condition");
 297 
 298   result.first = young_list_target_length;
 299   return result;
 300 }
 301 
 302 uint
 303 G1Policy::calculate_young_list_target_length(size_t rs_lengths,
 304                                                     uint base_min_length,
 305                                                     uint desired_min_length,
 306                                                     uint desired_max_length) const {
 307   assert(adaptive_young_list_length(), "pre-condition");
 308   assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
 309 
 310   // In case some edge-condition makes the desired max length too small...
 311   if (desired_max_length <= desired_min_length) {
 312     return desired_min_length;
 313   }
 314 
 315   // We'll adjust min_young_length and max_young_length not to include
 316   // the already allocated young regions (i.e., so they reflect the
 317   // min and max eden regions we'll allocate). The base_min_length
 318   // will be reflected in the predictions by the
 319   // survivor_regions_evac_time prediction.
 320   assert(desired_min_length > base_min_length, "invariant");
 321   uint min_young_length = desired_min_length - base_min_length;
 322   assert(desired_max_length > base_min_length, "invariant");
 323   uint max_young_length = desired_max_length - base_min_length;
 324 
 325   const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 326   const double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 327   const size_t pending_cards = _analytics->predict_pending_cards();


 397   } else {
 398     // Even the minimum length doesn't fit into the pause time
 399     // target, return it as the result nevertheless.
 400   }
 401   return base_min_length + min_young_length;
 402 }
 403 
 404 double G1Policy::predict_survivor_regions_evac_time() const {
 405   double survivor_regions_evac_time = 0.0;
 406   const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
 407 
 408   for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
 409        it != survivor_regions->end();
 410        ++it) {
 411     survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase());
 412   }
 413   return survivor_regions_evac_time;
 414 }
 415 
 416 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
 417   guarantee( adaptive_young_list_length(), "should not call this otherwise" );
 418 
 419   if (rs_lengths > _rs_lengths_prediction) {
 420     // add 10% to avoid having to recalculate often
 421     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 422     update_rs_lengths_prediction(rs_lengths_prediction);
 423 
 424     update_young_list_max_and_target_length(rs_lengths_prediction);
 425   }
 426 }
 427 
 428 void G1Policy::update_rs_lengths_prediction() {
 429   update_rs_lengths_prediction(_analytics->predict_rs_lengths());
 430 }
 431 
 432 void G1Policy::update_rs_lengths_prediction(size_t prediction) {
 433   if (collector_state()->in_young_only_phase() && adaptive_young_list_length()) {
 434     _rs_lengths_prediction = prediction;
 435   }
 436 }
 437 
 438 void G1Policy::record_full_collection_start() {
 439   _full_collection_start_sec = os::elapsedTime();
 440   // Release the future to-space so that it is available for compaction into.
 441   collector_state()->set_in_young_only_phase(false);
 442   collector_state()->set_in_full_gc(true);
 443   _collection_set->clear_candidates();
 444 }
 445 
 446 void G1Policy::record_full_collection_end() {
 447   // Consider this like a collection pause for the purposes of allocation
 448   // since last pause.
 449   double end_sec = os::elapsedTime();
 450   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 451   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 452 
 453   _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);


 469   _free_regions_at_end_of_collection = _g1h->num_free_regions();
 470   // Reset survivors SurvRateGroup.
 471   _survivor_surv_rate_group->reset();
 472   update_young_list_max_and_target_length();
 473   update_rs_lengths_prediction();
 474 
 475   _bytes_allocated_in_old_since_last_gc = 0;
 476 
 477   record_pause(FullGC, _full_collection_start_sec, end_sec);
 478 }
 479 
 480 void G1Policy::record_collection_pause_start(double start_time_sec) {
 481   // We only need to do this here as the policy will only be applied
 482   // to the GC we're about to start. so, no point is calculating this
 483   // every time we calculate / recalculate the target young length.
 484   update_survivors_policy();
 485 
 486   assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
 487          "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
 488          max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
 489 
 490   assert(_g1h->used() == _g1h->recalculate_used(),
 491          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
 492          _g1h->used(), _g1h->recalculate_used());
 493 
 494   phase_times()->record_cur_collection_start_sec(start_time_sec);
 495   _pending_cards = _g1h->pending_card_num();
 496 
 497   _collection_set->reset_bytes_used_before();
 498   _bytes_copied_during_gc = 0;
 499 
 500   // do that for any other surv rate groups
 501   _short_lived_surv_rate_group->stop_adding_regions();
 502   _survivors_age_table.clear();
 503 
 504   assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
 505 }
 506 
 507 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
 508   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 509   collector_state()->set_in_initial_mark_gc(false);
 510 }
 511 
 512 void G1Policy::record_concurrent_mark_remark_start() {


 563   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 564   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 565 
 566   bool result = false;
 567   if (marking_request_bytes > marking_initiating_used_threshold) {
 568     result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
 569     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
 570                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
 571                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
 572   }
 573 
 574   return result;
 575 }
 576 
 577 // Anything below that is considered to be zero
 578 #define MIN_TIMER_GRANULARITY 0.0000001
 579 
 580 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
 581   double end_time_sec = os::elapsedTime();
 582 

 583   size_t cur_used_bytes = _g1h->used();
 584   assert(cur_used_bytes == _g1h->recalculate_used(), "It should!");
 585   bool this_pause_included_initial_mark = false;
 586   bool this_pause_was_young_only = collector_state()->in_young_only_phase();
 587 
 588   bool update_stats = !_g1h->evacuation_failed();
 589 
 590   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
 591 
 592   _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
 593 
 594   this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
 595   if (this_pause_included_initial_mark) {
 596     record_concurrent_mark_init_end(0.0);
 597   } else {
 598     maybe_start_marking();
 599   }
 600 
 601   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
 602   if (app_time_ms < MIN_TIMER_GRANULARITY) {
 603     // This usually happens due to the timer not having the required
 604     // granularity. Some Linuxes are the usual culprits.


 642       clear_collection_set_candidates();
 643       maybe_start_marking();
 644     }
 645   }
 646 
 647   _short_lived_surv_rate_group->start_adding_regions();
 648   // Do that for any other surv rate groups
 649 
 650   double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
 651 
 652   if (update_stats) {
 653     double cost_per_card_ms = 0.0;
 654     if (_pending_cards > 0) {
 655       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS)) / (double) _pending_cards;
 656       _analytics->report_cost_per_card_ms(cost_per_card_ms);
 657     }
 658     _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
 659 
 660     double cost_per_entry_ms = 0.0;
 661     if (cards_scanned > 10) {
 662       cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;




 663       _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only);
 664     }
 665 
 666     if (_max_rs_lengths > 0) {
 667       double cards_per_entry_ratio =
 668         (double) cards_scanned / (double) _max_rs_lengths;
 669       _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only);
 670     }
 671 
 672     // This is defensive. For a while _max_rs_lengths could get
 673     // smaller than _recorded_rs_lengths which was causing
 674     // rs_length_diff to get very large and mess up the RSet length
 675     // predictions. The reason was unsafe concurrent updates to the
 676     // _inc_cset_recorded_rs_lengths field which the code below guards
 677     // against (see CR 7118202). This bug has now been fixed (see CR
 678     // 7119027). However, I'm still worried that
 679     // _inc_cset_recorded_rs_lengths might still end up somewhat
 680     // inaccurate. The concurrent refinement thread calculates an
 681     // RSet's length concurrently with other CR threads updating it
 682     // which might cause it to calculate the length incorrectly (if,
 683     // say, it's in mid-coarsening). So I'll leave in the defensive
 684     // conditional below just in case.
 685     size_t rs_length_diff = 0;
 686     size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
 687     if (_max_rs_lengths > recorded_rs_lengths) {
 688       rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
 689     }
 690     _analytics->report_rs_length_diff((double) rs_length_diff);
 691 
 692     size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
 693     size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
 694     double cost_per_byte_ms = 0.0;
 695 
 696     if (copied_bytes > 0) {
 697       cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
 698       _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
 699     }
 700 
 701     if (_collection_set->young_region_length() > 0) {
 702       _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
 703                                                         _collection_set->young_region_length());
 704     }
 705 
 706     if (_collection_set->old_region_length() > 0) {
 707       _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
 708                                                             _collection_set->old_region_length());
 709     }
 710 
 711     _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
 712 
 713     // Do not update RS lengths and the number of pending cards with information from mixed gc:
 714     // these are is wildly different to during young only gc and mess up young gen sizing right
 715     // after the mixed gc phase.
 716     // During mixed gc we do not use them for young gen sizing.
 717     if (this_pause_was_young_only) {


 889   if (hr->is_young()) {
 890     region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
 891   } else {
 892     region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
 893   }
 894   return region_elapsed_time_ms;
 895 }
 896 
 897 bool G1Policy::should_allocate_mutator_region() const {
 898   uint young_list_length = _g1h->young_regions_count();
 899   uint young_list_target_length = _young_list_target_length;
 900   return young_list_length < young_list_target_length;
 901 }
 902 
 903 bool G1Policy::can_expand_young_list() const {
 904   uint young_list_length = _g1h->young_regions_count();
 905   uint young_list_max_length = _young_list_max_length;
 906   return young_list_length < young_list_max_length;
 907 }
 908 
 909 bool G1Policy::adaptive_young_list_length() const {
 910   return _young_gen_sizer->adaptive_young_list_length();
 911 }
 912 
 913 size_t G1Policy::desired_survivor_size(uint max_regions) const {
 914   size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
 915   return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
 916 }
 917 
 918 void G1Policy::print_age_table() {
 919   _survivors_age_table.print_age_table(_tenuring_threshold);
 920 }
 921 
 922 void G1Policy::update_max_gc_locker_expansion() {
 923   uint expansion_region_num = 0;
 924   if (GCLockerEdenExpansionPercent > 0) {
 925     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
 926     double expansion_region_num_d = perc * (double) _young_list_target_length;
 927     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
 928     // less than 1.0) we'll get 1.
 929     expansion_region_num = (uint) ceil(expansion_region_num_d);
 930   } else {


1171   return (uint) result;
1172 }
1173 
1174 uint G1Policy::calc_max_old_cset_length() const {
1175   // The max old CSet region bound is based on the threshold expressed
1176   // as a percentage of the heap size. I.e., it should bound the
1177   // number of old regions added to the CSet irrespective of how many
1178   // of them are available.
1179 
1180   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1181   const size_t region_num = g1h->num_regions();
1182   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1183   size_t result = region_num * perc / 100;
1184   // emulate ceiling
1185   if (100 * result < region_num * perc) {
1186     result += 1;
1187   }
1188   return (uint) result;
1189 }
1190 
1191 uint G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
1192   double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor);
1193   _collection_set->finalize_old_part(time_remaining_ms);



























































































































1194 
1195   return _collection_set->region_length();

1196 }
1197 
1198 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1199 
1200   // Add survivor regions to SurvRateGroup.
1201   note_start_adding_survivor_regions();
1202   finished_recalculating_age_indexes(true /* is_survivors */);
1203 
1204   HeapRegion* last = NULL;
1205   for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1206        it != survivors->regions()->end();
1207        ++it) {
1208     HeapRegion* curr = *it;
1209     set_region_survivor(curr);
1210 
1211     // The region is a non-empty survivor so let's add it to
1212     // the incremental collection set for the next evacuation
1213     // pause.
1214     _collection_set->add_survivor_regions(curr);
1215 
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