1 /*
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   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.
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   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).
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
  27 
  28 #include "gc_implementation/g1/collectionSetChooser.hpp"
  29 #include "gc_implementation/g1/g1MMUTracker.hpp"
  30 #include "memory/collectorPolicy.hpp"
  31 
  32 // A G1CollectorPolicy makes policy decisions that determine the
  33 // characteristics of the collector.  Examples include:
  34 //   * choice of collection set.
  35 //   * when to collect.
  36 
  37 class HeapRegion;
  38 class CollectionSetChooser;
  39 class G1GCPhaseTimes;
  40 
  41 // TraceGen0Time collects data on _both_ young and mixed evacuation pauses
  42 // (the latter may contain non-young regions - i.e. regions that are
  43 // technically in Gen1) while TraceGen1Time collects data about full GCs.
  44 class TraceGen0TimeData : public CHeapObj<mtGC> {
  45  private:
  46   unsigned  _young_pause_num;
  47   unsigned  _mixed_pause_num;
  48 
  49   NumberSeq _all_stop_world_times_ms;
  50   NumberSeq _all_yield_times_ms;
  51 
  52   NumberSeq _total;
  53   NumberSeq _other;
  54   NumberSeq _root_region_scan_wait;
  55   NumberSeq _parallel;
  56   NumberSeq _ext_root_scan;
  57   NumberSeq _satb_filtering;
  58   NumberSeq _update_rs;
  59   NumberSeq _scan_rs;
  60   NumberSeq _obj_copy;
  61   NumberSeq _termination;
  62   NumberSeq _parallel_other;
  63   NumberSeq _clear_ct;
  64 
  65   void print_summary(const char* str, const NumberSeq* seq) const;
  66   void print_summary_sd(const char* str, const NumberSeq* seq) const;
  67 
  68 public:
  69    TraceGen0TimeData() : _young_pause_num(0), _mixed_pause_num(0) {};
  70   void record_start_collection(double time_to_stop_the_world_ms);
  71   void record_yield_time(double yield_time_ms);
  72   void record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times);
  73   void increment_young_collection_count();
  74   void increment_mixed_collection_count();
  75   void print() const;
  76 };
  77 
  78 class TraceGen1TimeData : public CHeapObj<mtGC> {
  79  private:
  80   NumberSeq _all_full_gc_times;
  81 
  82  public:
  83   void record_full_collection(double full_gc_time_ms);
  84   void print() const;
  85 };
  86 
  87 // There are three command line options related to the young gen size:
  88 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
  89 // just a short form for NewSize==MaxNewSize). G1 will use its internal
  90 // heuristics to calculate the actual young gen size, so these options
  91 // basically only limit the range within which G1 can pick a young gen
  92 // size. Also, these are general options taking byte sizes. G1 will
  93 // internally work with a number of regions instead. So, some rounding
  94 // will occur.
  95 //
  96 // If nothing related to the the young gen size is set on the command
  97 // line we should allow the young gen to be between G1NewSizePercent
  98 // and G1MaxNewSizePercent of the heap size. This means that every time
  99 // the heap size changes, the limits for the young gen size will be
 100 // recalculated.
 101 //
 102 // If only -XX:NewSize is set we should use the specified value as the
 103 // minimum size for young gen. Still using G1MaxNewSizePercent of the
 104 // heap as maximum.
 105 //
 106 // If only -XX:MaxNewSize is set we should use the specified value as the
 107 // maximum size for young gen. Still using G1NewSizePercent of the heap
 108 // as minimum.
 109 //
 110 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
 111 // No updates when the heap size changes. There is a special case when
 112 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
 113 // different heuristic for calculating the collection set when we do mixed
 114 // collection.
 115 //
 116 // If only -XX:NewRatio is set we should use the specified ratio of the heap
 117 // as both min and max. This will be interpreted as "fixed" just like the
 118 // NewSize==MaxNewSize case above. But we will update the min and max
 119 // everytime the heap size changes.
 120 //
 121 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
 122 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
 123 class G1YoungGenSizer : public CHeapObj<mtGC> {
 124 private:
 125   enum SizerKind {
 126     SizerDefaults,
 127     SizerNewSizeOnly,
 128     SizerMaxNewSizeOnly,
 129     SizerMaxAndNewSize,
 130     SizerNewRatio
 131   };
 132   SizerKind _sizer_kind;
 133   uint _min_desired_young_length;
 134   uint _max_desired_young_length;
 135   bool _adaptive_size;
 136   uint calculate_default_min_length(uint new_number_of_heap_regions);
 137   uint calculate_default_max_length(uint new_number_of_heap_regions);
 138 
 139 public:
 140   G1YoungGenSizer();
 141   void heap_size_changed(uint new_number_of_heap_regions);
 142   uint min_desired_young_length() {
 143     return _min_desired_young_length;
 144   }
 145   uint max_desired_young_length() {
 146     return _max_desired_young_length;
 147   }
 148   bool adaptive_young_list_length() {
 149     return _adaptive_size;
 150   }
 151 };
 152 
 153 class G1CollectorPolicy: public CollectorPolicy {
 154 private:
 155   // either equal to the number of parallel threads, if ParallelGCThreads
 156   // has been set, or 1 otherwise
 157   int _parallel_gc_threads;
 158 
 159   // The number of GC threads currently active.
 160   uintx _no_of_gc_threads;
 161 
 162   enum SomePrivateConstants {
 163     NumPrevPausesForHeuristics = 10
 164   };
 165 
 166   G1MMUTracker* _mmu_tracker;
 167 
 168   void initialize_flags();
 169 
 170   void initialize_all() {
 171     initialize_flags();
 172     initialize_size_info();
 173   }
 174 
 175   CollectionSetChooser* _collectionSetChooser;
 176 
 177   double _full_collection_start_sec;
 178   uint   _cur_collection_pause_used_regions_at_start;
 179 
 180   // These exclude marking times.
 181   TruncatedSeq* _recent_gc_times_ms;
 182 
 183   TruncatedSeq* _concurrent_mark_remark_times_ms;
 184   TruncatedSeq* _concurrent_mark_cleanup_times_ms;
 185 
 186   TraceGen0TimeData _trace_gen0_time_data;
 187   TraceGen1TimeData _trace_gen1_time_data;
 188 
 189   double _stop_world_start;
 190 
 191   // indicates whether we are in young or mixed GC mode
 192   bool _gcs_are_young;
 193 
 194   uint _young_list_target_length;
 195   uint _young_list_fixed_length;
 196 
 197   // The max number of regions we can extend the eden by while the GC
 198   // locker is active. This should be >= _young_list_target_length;
 199   uint _young_list_max_length;
 200 
 201   bool                  _last_gc_was_young;
 202 
 203   bool                  _during_marking;
 204   bool                  _in_marking_window;
 205   bool                  _in_marking_window_im;
 206 
 207   SurvRateGroup*        _short_lived_surv_rate_group;
 208   SurvRateGroup*        _survivor_surv_rate_group;
 209   // add here any more surv rate groups
 210 
 211   double                _gc_overhead_perc;
 212 
 213   double _reserve_factor;
 214   uint _reserve_regions;
 215 
 216   bool during_marking() {
 217     return _during_marking;
 218   }
 219 
 220 private:
 221   enum PredictionConstants {
 222     TruncatedSeqLength = 10
 223   };
 224 
 225   TruncatedSeq* _alloc_rate_ms_seq;
 226   double        _prev_collection_pause_end_ms;
 227 
 228   TruncatedSeq* _rs_length_diff_seq;
 229   TruncatedSeq* _cost_per_card_ms_seq;
 230   TruncatedSeq* _young_cards_per_entry_ratio_seq;
 231   TruncatedSeq* _mixed_cards_per_entry_ratio_seq;
 232   TruncatedSeq* _cost_per_entry_ms_seq;
 233   TruncatedSeq* _mixed_cost_per_entry_ms_seq;
 234   TruncatedSeq* _cost_per_byte_ms_seq;
 235   TruncatedSeq* _constant_other_time_ms_seq;
 236   TruncatedSeq* _young_other_cost_per_region_ms_seq;
 237   TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
 238 
 239   TruncatedSeq* _pending_cards_seq;
 240   TruncatedSeq* _rs_lengths_seq;
 241 
 242   TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
 243 
 244   G1YoungGenSizer* _young_gen_sizer;
 245 
 246   uint _eden_cset_region_length;
 247   uint _survivor_cset_region_length;
 248   uint _old_cset_region_length;
 249 
 250   void init_cset_region_lengths(uint eden_cset_region_length,
 251                                 uint survivor_cset_region_length);
 252 
 253   uint eden_cset_region_length()     { return _eden_cset_region_length;     }
 254   uint survivor_cset_region_length() { return _survivor_cset_region_length; }
 255   uint old_cset_region_length()      { return _old_cset_region_length;      }
 256 
 257   uint _free_regions_at_end_of_collection;
 258 
 259   size_t _recorded_rs_lengths;
 260   size_t _max_rs_lengths;
 261   double _sigma;
 262 
 263   size_t _rs_lengths_prediction;
 264 
 265   double sigma() { return _sigma; }
 266 
 267   // A function that prevents us putting too much stock in small sample
 268   // sets.  Returns a number between 2.0 and 1.0, depending on the number
 269   // of samples.  5 or more samples yields one; fewer scales linearly from
 270   // 2.0 at 1 sample to 1.0 at 5.
 271   double confidence_factor(int samples) {
 272     if (samples > 4) return 1.0;
 273     else return  1.0 + sigma() * ((double)(5 - samples))/2.0;
 274   }
 275 
 276   double get_new_neg_prediction(TruncatedSeq* seq) {
 277     return seq->davg() - sigma() * seq->dsd();
 278   }
 279 
 280 #ifndef PRODUCT
 281   bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
 282 #endif // PRODUCT
 283 
 284   void adjust_concurrent_refinement(double update_rs_time,
 285                                     double update_rs_processed_buffers,
 286                                     double goal_ms);
 287 
 288   uintx no_of_gc_threads() { return _no_of_gc_threads; }
 289   void set_no_of_gc_threads(uintx v) { _no_of_gc_threads = v; }
 290 
 291   double _pause_time_target_ms;
 292 
 293   size_t _pending_cards;
 294 
 295 public:
 296   // Accessors
 297 
 298   void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
 299     hr->set_young();
 300     hr->install_surv_rate_group(_short_lived_surv_rate_group);
 301     hr->set_young_index_in_cset(young_index_in_cset);
 302   }
 303 
 304   void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
 305     assert(hr->is_young() && hr->is_survivor(), "pre-condition");
 306     hr->install_surv_rate_group(_survivor_surv_rate_group);
 307     hr->set_young_index_in_cset(young_index_in_cset);
 308   }
 309 
 310 #ifndef PRODUCT
 311   bool verify_young_ages();
 312 #endif // PRODUCT
 313 
 314   double get_new_prediction(TruncatedSeq* seq) {
 315     return MAX2(seq->davg() + sigma() * seq->dsd(),
 316                 seq->davg() * confidence_factor(seq->num()));
 317   }
 318 
 319   void record_max_rs_lengths(size_t rs_lengths) {
 320     _max_rs_lengths = rs_lengths;
 321   }
 322 
 323   size_t predict_rs_length_diff() {
 324     return (size_t) get_new_prediction(_rs_length_diff_seq);
 325   }
 326 
 327   double predict_alloc_rate_ms() {
 328     return get_new_prediction(_alloc_rate_ms_seq);
 329   }
 330 
 331   double predict_cost_per_card_ms() {
 332     return get_new_prediction(_cost_per_card_ms_seq);
 333   }
 334 
 335   double predict_rs_update_time_ms(size_t pending_cards) {
 336     return (double) pending_cards * predict_cost_per_card_ms();
 337   }
 338 
 339   double predict_young_cards_per_entry_ratio() {
 340     return get_new_prediction(_young_cards_per_entry_ratio_seq);
 341   }
 342 
 343   double predict_mixed_cards_per_entry_ratio() {
 344     if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
 345       return predict_young_cards_per_entry_ratio();
 346     } else {
 347       return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
 348     }
 349   }
 350 
 351   size_t predict_young_card_num(size_t rs_length) {
 352     return (size_t) ((double) rs_length *
 353                      predict_young_cards_per_entry_ratio());
 354   }
 355 
 356   size_t predict_non_young_card_num(size_t rs_length) {
 357     return (size_t) ((double) rs_length *
 358                      predict_mixed_cards_per_entry_ratio());
 359   }
 360 
 361   double predict_rs_scan_time_ms(size_t card_num) {
 362     if (gcs_are_young()) {
 363       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 364     } else {
 365       return predict_mixed_rs_scan_time_ms(card_num);
 366     }
 367   }
 368 
 369   double predict_mixed_rs_scan_time_ms(size_t card_num) {
 370     if (_mixed_cost_per_entry_ms_seq->num() < 3) {
 371       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 372     } else {
 373       return (double) (card_num *
 374                        get_new_prediction(_mixed_cost_per_entry_ms_seq));
 375     }
 376   }
 377 
 378   double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
 379     if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
 380       return (1.1 * (double) bytes_to_copy) *
 381               get_new_prediction(_cost_per_byte_ms_seq);
 382     } else {
 383       return (double) bytes_to_copy *
 384              get_new_prediction(_cost_per_byte_ms_during_cm_seq);
 385     }
 386   }
 387 
 388   double predict_object_copy_time_ms(size_t bytes_to_copy) {
 389     if (_in_marking_window && !_in_marking_window_im) {
 390       return predict_object_copy_time_ms_during_cm(bytes_to_copy);
 391     } else {
 392       return (double) bytes_to_copy *
 393               get_new_prediction(_cost_per_byte_ms_seq);
 394     }
 395   }
 396 
 397   double predict_constant_other_time_ms() {
 398     return get_new_prediction(_constant_other_time_ms_seq);
 399   }
 400 
 401   double predict_young_other_time_ms(size_t young_num) {
 402     return (double) young_num *
 403            get_new_prediction(_young_other_cost_per_region_ms_seq);
 404   }
 405 
 406   double predict_non_young_other_time_ms(size_t non_young_num) {
 407     return (double) non_young_num *
 408            get_new_prediction(_non_young_other_cost_per_region_ms_seq);
 409   }
 410 
 411   double predict_base_elapsed_time_ms(size_t pending_cards);
 412   double predict_base_elapsed_time_ms(size_t pending_cards,
 413                                       size_t scanned_cards);
 414   size_t predict_bytes_to_copy(HeapRegion* hr);
 415   double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc);
 416 
 417   void set_recorded_rs_lengths(size_t rs_lengths);
 418 
 419   uint cset_region_length()       { return young_cset_region_length() +
 420                                            old_cset_region_length(); }
 421   uint young_cset_region_length() { return eden_cset_region_length() +
 422                                            survivor_cset_region_length(); }
 423 
 424   double predict_survivor_regions_evac_time();
 425 
 426   void cset_regions_freed() {
 427     bool propagate = _last_gc_was_young && !_in_marking_window;
 428     _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
 429     _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
 430     // also call it on any more surv rate groups
 431   }
 432 
 433   G1MMUTracker* mmu_tracker() {
 434     return _mmu_tracker;
 435   }
 436 
 437   double max_pause_time_ms() {
 438     return _mmu_tracker->max_gc_time() * 1000.0;
 439   }
 440 
 441   double predict_remark_time_ms() {
 442     return get_new_prediction(_concurrent_mark_remark_times_ms);
 443   }
 444 
 445   double predict_cleanup_time_ms() {
 446     return get_new_prediction(_concurrent_mark_cleanup_times_ms);
 447   }
 448 
 449   // Returns an estimate of the survival rate of the region at yg-age
 450   // "yg_age".
 451   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
 452     TruncatedSeq* seq = surv_rate_group->get_seq(age);
 453     if (seq->num() == 0)
 454       gclog_or_tty->print("BARF! age is %d", age);
 455     guarantee( seq->num() > 0, "invariant" );
 456     double pred = get_new_prediction(seq);
 457     if (pred > 1.0)
 458       pred = 1.0;
 459     return pred;
 460   }
 461 
 462   double predict_yg_surv_rate(int age) {
 463     return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
 464   }
 465 
 466   double accum_yg_surv_rate_pred(int age) {
 467     return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
 468   }
 469 
 470 private:
 471   // Statistics kept per GC stoppage, pause or full.
 472   TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
 473 
 474   // Add a new GC of the given duration and end time to the record.
 475   void update_recent_gc_times(double end_time_sec, double elapsed_ms);
 476 
 477   // The head of the list (via "next_in_collection_set()") representing the
 478   // current collection set. Set from the incrementally built collection
 479   // set at the start of the pause.
 480   HeapRegion* _collection_set;
 481 
 482   // The number of bytes in the collection set before the pause. Set from
 483   // the incrementally built collection set at the start of an evacuation
 484   // pause, and incremented in finalize_cset() when adding old regions
 485   // (if any) to the collection set.
 486   size_t _collection_set_bytes_used_before;
 487 
 488   // The number of bytes copied during the GC.
 489   size_t _bytes_copied_during_gc;
 490 
 491   // The associated information that is maintained while the incremental
 492   // collection set is being built with young regions. Used to populate
 493   // the recorded info for the evacuation pause.
 494 
 495   enum CSetBuildType {
 496     Active,             // We are actively building the collection set
 497     Inactive            // We are not actively building the collection set
 498   };
 499 
 500   CSetBuildType _inc_cset_build_state;
 501 
 502   // The head of the incrementally built collection set.
 503   HeapRegion* _inc_cset_head;
 504 
 505   // The tail of the incrementally built collection set.
 506   HeapRegion* _inc_cset_tail;
 507 
 508   // The number of bytes in the incrementally built collection set.
 509   // Used to set _collection_set_bytes_used_before at the start of
 510   // an evacuation pause.
 511   size_t _inc_cset_bytes_used_before;
 512 
 513   // Used to record the highest end of heap region in collection set
 514   HeapWord* _inc_cset_max_finger;
 515 
 516   // The RSet lengths recorded for regions in the CSet. It is updated
 517   // by the thread that adds a new region to the CSet. We assume that
 518   // only one thread can be allocating a new CSet region (currently,
 519   // it does so after taking the Heap_lock) hence no need to
 520   // synchronize updates to this field.
 521   size_t _inc_cset_recorded_rs_lengths;
 522 
 523   // A concurrent refinement thread periodcially samples the young
 524   // region RSets and needs to update _inc_cset_recorded_rs_lengths as
 525   // the RSets grow. Instead of having to syncronize updates to that
 526   // field we accumulate them in this field and add it to
 527   // _inc_cset_recorded_rs_lengths_diffs at the start of a GC.
 528   ssize_t _inc_cset_recorded_rs_lengths_diffs;
 529 
 530   // The predicted elapsed time it will take to collect the regions in
 531   // the CSet. This is updated by the thread that adds a new region to
 532   // the CSet. See the comment for _inc_cset_recorded_rs_lengths about
 533   // MT-safety assumptions.
 534   double _inc_cset_predicted_elapsed_time_ms;
 535 
 536   // See the comment for _inc_cset_recorded_rs_lengths_diffs.
 537   double _inc_cset_predicted_elapsed_time_ms_diffs;
 538 
 539   // Stash a pointer to the g1 heap.
 540   G1CollectedHeap* _g1;
 541 
 542   G1GCPhaseTimes* _phase_times;
 543 
 544   // The ratio of gc time to elapsed time, computed over recent pauses.
 545   double _recent_avg_pause_time_ratio;
 546 
 547   double recent_avg_pause_time_ratio() {
 548     return _recent_avg_pause_time_ratio;
 549   }
 550 
 551   // At the end of a pause we check the heap occupancy and we decide
 552   // whether we will start a marking cycle during the next pause. If
 553   // we decide that we want to do that, we will set this parameter to
 554   // true. So, this parameter will stay true between the end of a
 555   // pause and the beginning of a subsequent pause (not necessarily
 556   // the next one, see the comments on the next field) when we decide
 557   // that we will indeed start a marking cycle and do the initial-mark
 558   // work.
 559   volatile bool _initiate_conc_mark_if_possible;
 560 
 561   // If initiate_conc_mark_if_possible() is set at the beginning of a
 562   // pause, it is a suggestion that the pause should start a marking
 563   // cycle by doing the initial-mark work. However, it is possible
 564   // that the concurrent marking thread is still finishing up the
 565   // previous marking cycle (e.g., clearing the next marking
 566   // bitmap). If that is the case we cannot start a new cycle and
 567   // we'll have to wait for the concurrent marking thread to finish
 568   // what it is doing. In this case we will postpone the marking cycle
 569   // initiation decision for the next pause. When we eventually decide
 570   // to start a cycle, we will set _during_initial_mark_pause which
 571   // will stay true until the end of the initial-mark pause and it's
 572   // the condition that indicates that a pause is doing the
 573   // initial-mark work.
 574   volatile bool _during_initial_mark_pause;
 575 
 576   bool _last_young_gc;
 577 
 578   // This set of variables tracks the collector efficiency, in order to
 579   // determine whether we should initiate a new marking.
 580   double _cur_mark_stop_world_time_ms;
 581   double _mark_remark_start_sec;
 582   double _mark_cleanup_start_sec;
 583 
 584   // Update the young list target length either by setting it to the
 585   // desired fixed value or by calculating it using G1's pause
 586   // prediction model. If no rs_lengths parameter is passed, predict
 587   // the RS lengths using the prediction model, otherwise use the
 588   // given rs_lengths as the prediction.
 589   void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
 590 
 591   // Calculate and return the minimum desired young list target
 592   // length. This is the minimum desired young list length according
 593   // to the user's inputs.
 594   uint calculate_young_list_desired_min_length(uint base_min_length);
 595 
 596   // Calculate and return the maximum desired young list target
 597   // length. This is the maximum desired young list length according
 598   // to the user's inputs.
 599   uint calculate_young_list_desired_max_length();
 600 
 601   // Calculate and return the maximum young list target length that
 602   // can fit into the pause time goal. The parameters are: rs_lengths
 603   // represent the prediction of how large the young RSet lengths will
 604   // be, base_min_length is the alreay existing number of regions in
 605   // the young list, min_length and max_length are the desired min and
 606   // max young list length according to the user's inputs.
 607   uint calculate_young_list_target_length(size_t rs_lengths,
 608                                           uint base_min_length,
 609                                           uint desired_min_length,
 610                                           uint desired_max_length);
 611 
 612   // Check whether a given young length (young_length) fits into the
 613   // given target pause time and whether the prediction for the amount
 614   // of objects to be copied for the given length will fit into the
 615   // given free space (expressed by base_free_regions).  It is used by
 616   // calculate_young_list_target_length().
 617   bool predict_will_fit(uint young_length, double base_time_ms,
 618                         uint base_free_regions, double target_pause_time_ms);
 619 
 620   // Calculate the minimum number of old regions we'll add to the CSet
 621   // during a mixed GC.
 622   uint calc_min_old_cset_length();
 623 
 624   // Calculate the maximum number of old regions we'll add to the CSet
 625   // during a mixed GC.
 626   uint calc_max_old_cset_length();
 627 
 628   // Returns the given amount of uncollected reclaimable space
 629   // as a percentage of the current heap capacity.
 630   double reclaimable_bytes_perc(size_t reclaimable_bytes);
 631 
 632 public:
 633 
 634   G1CollectorPolicy();
 635 
 636   virtual G1CollectorPolicy* as_g1_policy() { return this; }
 637 
 638   virtual CollectorPolicy::Name kind() {
 639     return CollectorPolicy::G1CollectorPolicyKind;
 640   }
 641 
 642   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 643 
 644   // Check the current value of the young list RSet lengths and
 645   // compare it against the last prediction. If the current value is
 646   // higher, recalculate the young list target length prediction.
 647   void revise_young_list_target_length_if_necessary();
 648 
 649   // This should be called after the heap is resized.
 650   void record_new_heap_size(uint new_number_of_regions);
 651 
 652   void init();
 653 
 654   // Create jstat counters for the policy.
 655   virtual void initialize_gc_policy_counters();
 656 
 657   virtual HeapWord* mem_allocate_work(size_t size,
 658                                       bool is_tlab,
 659                                       bool* gc_overhead_limit_was_exceeded);
 660 
 661   // This method controls how a collector handles one or more
 662   // of its generations being fully allocated.
 663   virtual HeapWord* satisfy_failed_allocation(size_t size,
 664                                               bool is_tlab);
 665 
 666   BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
 667 
 668   GenRemSet::Name  rem_set_name()     { return GenRemSet::CardTable; }
 669 
 670   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 671 
 672   // Record the start and end of an evacuation pause.
 673   void record_collection_pause_start(double start_time_sec);
 674   void record_collection_pause_end(double pause_time_ms);
 675 
 676   // Record the start and end of a full collection.
 677   void record_full_collection_start();
 678   void record_full_collection_end();
 679 
 680   // Must currently be called while the world is stopped.
 681   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 682 
 683   // Record start and end of remark.
 684   void record_concurrent_mark_remark_start();
 685   void record_concurrent_mark_remark_end();
 686 
 687   // Record start, end, and completion of cleanup.
 688   void record_concurrent_mark_cleanup_start();
 689   void record_concurrent_mark_cleanup_end(int no_of_gc_threads);
 690   void record_concurrent_mark_cleanup_completed();
 691 
 692   // Records the information about the heap size for reporting in
 693   // print_detailed_heap_transition
 694   void record_heap_size_info_at_start(bool full);
 695 
 696   // Print heap sizing transition (with less and more detail).
 697   void print_heap_transition();
 698   void print_detailed_heap_transition(bool full = false);
 699 
 700   void record_stop_world_start();
 701   void record_concurrent_pause();
 702 
 703   // Record how much space we copied during a GC. This is typically
 704   // called when a GC alloc region is being retired.
 705   void record_bytes_copied_during_gc(size_t bytes) {
 706     _bytes_copied_during_gc += bytes;
 707   }
 708 
 709   // The amount of space we copied during a GC.
 710   size_t bytes_copied_during_gc() {
 711     return _bytes_copied_during_gc;
 712   }
 713 
 714   // Determine whether there are candidate regions so that the
 715   // next GC should be mixed. The two action strings are used
 716   // in the ergo output when the method returns true or false.
 717   bool next_gc_should_be_mixed(const char* true_action_str,
 718                                const char* false_action_str);
 719 
 720   // Choose a new collection set.  Marks the chosen regions as being
 721   // "in_collection_set", and links them together.  The head and number of
 722   // the collection set are available via access methods.
 723   void finalize_cset(double target_pause_time_ms);
 724 
 725   // The head of the list (via "next_in_collection_set()") representing the
 726   // current collection set.
 727   HeapRegion* collection_set() { return _collection_set; }
 728 
 729   void clear_collection_set() { _collection_set = NULL; }
 730 
 731   // Add old region "hr" to the CSet.
 732   void add_old_region_to_cset(HeapRegion* hr);
 733 
 734   // Incremental CSet Support
 735 
 736   // The head of the incrementally built collection set.
 737   HeapRegion* inc_cset_head() { return _inc_cset_head; }
 738 
 739   // The tail of the incrementally built collection set.
 740   HeapRegion* inc_set_tail() { return _inc_cset_tail; }
 741 
 742   // Initialize incremental collection set info.
 743   void start_incremental_cset_building();
 744 
 745   // Perform any final calculations on the incremental CSet fields
 746   // before we can use them.
 747   void finalize_incremental_cset_building();
 748 
 749   void clear_incremental_cset() {
 750     _inc_cset_head = NULL;
 751     _inc_cset_tail = NULL;
 752   }
 753 
 754   // Stop adding regions to the incremental collection set
 755   void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
 756 
 757   // Add information about hr to the aggregated information for the
 758   // incrementally built collection set.
 759   void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
 760 
 761   // Update information about hr in the aggregated information for
 762   // the incrementally built collection set.
 763   void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
 764 
 765 private:
 766   // Update the incremental cset information when adding a region
 767   // (should not be called directly).
 768   void add_region_to_incremental_cset_common(HeapRegion* hr);
 769 
 770 public:
 771   // Add hr to the LHS of the incremental collection set.
 772   void add_region_to_incremental_cset_lhs(HeapRegion* hr);
 773 
 774   // Add hr to the RHS of the incremental collection set.
 775   void add_region_to_incremental_cset_rhs(HeapRegion* hr);
 776 
 777 #ifndef PRODUCT
 778   void print_collection_set(HeapRegion* list_head, outputStream* st);
 779 #endif // !PRODUCT
 780 
 781   bool initiate_conc_mark_if_possible()       { return _initiate_conc_mark_if_possible;  }
 782   void set_initiate_conc_mark_if_possible()   { _initiate_conc_mark_if_possible = true;  }
 783   void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
 784 
 785   bool during_initial_mark_pause()      { return _during_initial_mark_pause;  }
 786   void set_during_initial_mark_pause()  { _during_initial_mark_pause = true;  }
 787   void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
 788 
 789   // This sets the initiate_conc_mark_if_possible() flag to start a
 790   // new cycle, as long as we are not already in one. It's best if it
 791   // is called during a safepoint when the test whether a cycle is in
 792   // progress or not is stable.
 793   bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
 794 
 795   // This is called at the very beginning of an evacuation pause (it
 796   // has to be the first thing that the pause does). If
 797   // initiate_conc_mark_if_possible() is true, and the concurrent
 798   // marking thread has completed its work during the previous cycle,
 799   // it will set during_initial_mark_pause() to so that the pause does
 800   // the initial-mark work and start a marking cycle.
 801   void decide_on_conc_mark_initiation();
 802 
 803   // If an expansion would be appropriate, because recent GC overhead had
 804   // exceeded the desired limit, return an amount to expand by.
 805   size_t expansion_amount();
 806 
 807   // Print tracing information.
 808   void print_tracing_info() const;
 809 
 810   // Print stats on young survival ratio
 811   void print_yg_surv_rate_info() const;
 812 
 813   void finished_recalculating_age_indexes(bool is_survivors) {
 814     if (is_survivors) {
 815       _survivor_surv_rate_group->finished_recalculating_age_indexes();
 816     } else {
 817       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
 818     }
 819     // do that for any other surv rate groups
 820   }
 821 
 822   bool is_young_list_full() {
 823     uint young_list_length = _g1->young_list()->length();
 824     uint young_list_target_length = _young_list_target_length;
 825     return young_list_length >= young_list_target_length;
 826   }
 827 
 828   bool can_expand_young_list() {
 829     uint young_list_length = _g1->young_list()->length();
 830     uint young_list_max_length = _young_list_max_length;
 831     return young_list_length < young_list_max_length;
 832   }
 833 
 834   uint young_list_max_length() {
 835     return _young_list_max_length;
 836   }
 837 
 838   bool gcs_are_young() {
 839     return _gcs_are_young;
 840   }
 841   void set_gcs_are_young(bool gcs_are_young) {
 842     _gcs_are_young = gcs_are_young;
 843   }
 844 
 845   bool adaptive_young_list_length() {
 846     return _young_gen_sizer->adaptive_young_list_length();
 847   }
 848 
 849 private:
 850   //
 851   // Survivor regions policy.
 852   //
 853 
 854   // Current tenuring threshold, set to 0 if the collector reaches the
 855   // maximum amount of survivors regions.
 856   uint _tenuring_threshold;
 857 
 858   // The limit on the number of regions allocated for survivors.
 859   uint _max_survivor_regions;
 860 
 861   // For reporting purposes.
 862   // The value of _heap_bytes_before_gc is also used to calculate
 863   // the cost of copying.
 864 
 865   size_t _eden_used_bytes_before_gc;         // Eden occupancy before GC
 866   size_t _survivor_used_bytes_before_gc;     // Survivor occupancy before GC
 867   size_t _heap_used_bytes_before_gc;         // Heap occupancy before GC
 868   size_t _metaspace_used_bytes_before_gc;    // Metaspace occupancy before GC
 869 
 870   size_t _eden_capacity_bytes_before_gc;     // Eden capacity before GC
 871   size_t _heap_capacity_bytes_before_gc;     // Heap capacity before GC
 872 
 873   // The amount of survivor regions after a collection.
 874   uint _recorded_survivor_regions;
 875   // List of survivor regions.
 876   HeapRegion* _recorded_survivor_head;
 877   HeapRegion* _recorded_survivor_tail;
 878 
 879   ageTable _survivors_age_table;
 880 
 881 public:
 882 
 883   inline GCAllocPurpose
 884     evacuation_destination(HeapRegion* src_region, uint age, size_t word_sz) {
 885       if (age < _tenuring_threshold && src_region->is_young()) {
 886         return GCAllocForSurvived;
 887       } else {
 888         return GCAllocForTenured;
 889       }
 890   }
 891 
 892   inline bool track_object_age(GCAllocPurpose purpose) {
 893     return purpose == GCAllocForSurvived;
 894   }
 895 
 896   static const uint REGIONS_UNLIMITED = (uint) -1;
 897 
 898   uint max_regions(int purpose);
 899 
 900   // The limit on regions for a particular purpose is reached.
 901   void note_alloc_region_limit_reached(int purpose) {
 902     if (purpose == GCAllocForSurvived) {
 903       _tenuring_threshold = 0;
 904     }
 905   }
 906 
 907   void note_start_adding_survivor_regions() {
 908     _survivor_surv_rate_group->start_adding_regions();
 909   }
 910 
 911   void note_stop_adding_survivor_regions() {
 912     _survivor_surv_rate_group->stop_adding_regions();
 913   }
 914 
 915   void record_survivor_regions(uint regions,
 916                                HeapRegion* head,
 917                                HeapRegion* tail) {
 918     _recorded_survivor_regions = regions;
 919     _recorded_survivor_head    = head;
 920     _recorded_survivor_tail    = tail;
 921   }
 922 
 923   uint recorded_survivor_regions() {
 924     return _recorded_survivor_regions;
 925   }
 926 
 927   void record_thread_age_table(ageTable* age_table) {
 928     _survivors_age_table.merge_par(age_table);
 929   }
 930 
 931   void update_max_gc_locker_expansion();
 932 
 933   // Calculates survivor space parameters.
 934   void update_survivors_policy();
 935 
 936 };
 937 
 938 // This should move to some place more general...
 939 
 940 // If we have "n" measurements, and we've kept track of their "sum" and the
 941 // "sum_of_squares" of the measurements, this returns the variance of the
 942 // sequence.
 943 inline double variance(int n, double sum_of_squares, double sum) {
 944   double n_d = (double)n;
 945   double avg = sum/n_d;
 946   return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
 947 }
 948 
 949 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP