1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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
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  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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  24 
  25 #ifndef SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP
  26 #define SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP
  27 
  28 #include "gc/g1/collectionSetChooser.hpp"
  29 #include "gc/g1/g1CollectorState.hpp"
  30 #include "gc/g1/g1InCSetState.hpp"
  31 #include "gc/g1/g1MMUTracker.hpp"
  32 #include "gc/shared/collectorPolicy.hpp"
  33 
  34 // A G1CollectorPolicy makes policy decisions that determine the
  35 // characteristics of the collector.  Examples include:
  36 //   * choice of collection set.
  37 //   * when to collect.
  38 
  39 class HeapRegion;
  40 class CollectionSetChooser;
  41 class G1GCPhaseTimes;
  42 
  43 // TraceYoungGenTime collects data on _both_ young and mixed evacuation pauses
  44 // (the latter may contain non-young regions - i.e. regions that are
  45 // technically in old) while TraceOldGenTime collects data about full GCs.
  46 class TraceYoungGenTimeData : public CHeapObj<mtGC> {
  47  private:
  48   unsigned  _young_pause_num;
  49   unsigned  _mixed_pause_num;
  50 
  51   NumberSeq _all_stop_world_times_ms;
  52   NumberSeq _all_yield_times_ms;
  53 
  54   NumberSeq _total;
  55   NumberSeq _other;
  56   NumberSeq _root_region_scan_wait;
  57   NumberSeq _parallel;
  58   NumberSeq _ext_root_scan;
  59   NumberSeq _satb_filtering;
  60   NumberSeq _update_rs;
  61   NumberSeq _scan_rs;
  62   NumberSeq _obj_copy;
  63   NumberSeq _termination;
  64   NumberSeq _parallel_other;
  65   NumberSeq _clear_ct;
  66 
  67   void print_summary(const char* str, const NumberSeq* seq) const;
  68   void print_summary_sd(const char* str, const NumberSeq* seq) const;
  69 
  70 public:
  71    TraceYoungGenTimeData() : _young_pause_num(0), _mixed_pause_num(0) {};
  72   void record_start_collection(double time_to_stop_the_world_ms);
  73   void record_yield_time(double yield_time_ms);
  74   void record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times);
  75   void increment_young_collection_count();
  76   void increment_mixed_collection_count();
  77   void print() const;
  78 };
  79 
  80 class TraceOldGenTimeData : public CHeapObj<mtGC> {
  81  private:
  82   NumberSeq _all_full_gc_times;
  83 
  84  public:
  85   void record_full_collection(double full_gc_time_ms);
  86   void print() const;
  87 };
  88 
  89 // There are three command line options related to the young gen size:
  90 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
  91 // just a short form for NewSize==MaxNewSize). G1 will use its internal
  92 // heuristics to calculate the actual young gen size, so these options
  93 // basically only limit the range within which G1 can pick a young gen
  94 // size. Also, these are general options taking byte sizes. G1 will
  95 // internally work with a number of regions instead. So, some rounding
  96 // will occur.
  97 //
  98 // If nothing related to the the young gen size is set on the command
  99 // line we should allow the young gen to be between G1NewSizePercent
 100 // and G1MaxNewSizePercent of the heap size. This means that every time
 101 // the heap size changes, the limits for the young gen size will be
 102 // recalculated.
 103 //
 104 // If only -XX:NewSize is set we should use the specified value as the
 105 // minimum size for young gen. Still using G1MaxNewSizePercent of the
 106 // heap as maximum.
 107 //
 108 // If only -XX:MaxNewSize is set we should use the specified value as the
 109 // maximum size for young gen. Still using G1NewSizePercent of the heap
 110 // as minimum.
 111 //
 112 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
 113 // No updates when the heap size changes. There is a special case when
 114 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
 115 // different heuristic for calculating the collection set when we do mixed
 116 // collection.
 117 //
 118 // If only -XX:NewRatio is set we should use the specified ratio of the heap
 119 // as both min and max. This will be interpreted as "fixed" just like the
 120 // NewSize==MaxNewSize case above. But we will update the min and max
 121 // every time the heap size changes.
 122 //
 123 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
 124 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
 125 class G1YoungGenSizer : public CHeapObj<mtGC> {
 126 private:
 127   enum SizerKind {
 128     SizerDefaults,
 129     SizerNewSizeOnly,
 130     SizerMaxNewSizeOnly,
 131     SizerMaxAndNewSize,
 132     SizerNewRatio
 133   };
 134   SizerKind _sizer_kind;
 135   uint _min_desired_young_length;
 136   uint _max_desired_young_length;
 137   bool _adaptive_size;
 138   uint calculate_default_min_length(uint new_number_of_heap_regions);
 139   uint calculate_default_max_length(uint new_number_of_heap_regions);
 140 
 141   // Update the given values for minimum and maximum young gen length in regions
 142   // given the number of heap regions depending on the kind of sizing algorithm.
 143   void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
 144 
 145 public:
 146   G1YoungGenSizer();
 147   // Calculate the maximum length of the young gen given the number of regions
 148   // depending on the sizing algorithm.
 149   uint max_young_length(uint number_of_heap_regions);
 150 
 151   void heap_size_changed(uint new_number_of_heap_regions);
 152   uint min_desired_young_length() {
 153     return _min_desired_young_length;
 154   }
 155   uint max_desired_young_length() {
 156     return _max_desired_young_length;
 157   }
 158   bool adaptive_young_list_length() {
 159     return _adaptive_size;
 160   }
 161 };
 162 
 163 class G1CollectorPolicy: public CollectorPolicy {
 164 private:
 165   // either equal to the number of parallel threads, if ParallelGCThreads
 166   // has been set, or 1 otherwise
 167   int _parallel_gc_threads;
 168 
 169   // The number of GC threads currently active.
 170   uintx _no_of_gc_threads;
 171 
 172   enum SomePrivateConstants {
 173     NumPrevPausesForHeuristics = 10
 174   };
 175 
 176   G1MMUTracker* _mmu_tracker;
 177 
 178   void initialize_alignments();
 179   void initialize_flags();
 180 
 181   CollectionSetChooser* _collectionSetChooser;
 182 
 183   double _full_collection_start_sec;
 184   uint   _cur_collection_pause_used_regions_at_start;
 185 
 186   // These exclude marking times.
 187   TruncatedSeq* _recent_gc_times_ms;
 188 
 189   TruncatedSeq* _concurrent_mark_remark_times_ms;
 190   TruncatedSeq* _concurrent_mark_cleanup_times_ms;
 191 
 192   TraceYoungGenTimeData _trace_young_gen_time_data;
 193   TraceOldGenTimeData   _trace_old_gen_time_data;
 194 
 195   double _stop_world_start;
 196 
 197   uint _young_list_target_length;
 198   uint _young_list_fixed_length;
 199 
 200   // The max number of regions we can extend the eden by while the GC
 201   // locker is active. This should be >= _young_list_target_length;
 202   uint _young_list_max_length;
 203 
 204   SurvRateGroup* _short_lived_surv_rate_group;
 205   SurvRateGroup* _survivor_surv_rate_group;
 206   // add here any more surv rate groups
 207 
 208   double _gc_overhead_perc;
 209 
 210   double _reserve_factor;
 211   uint   _reserve_regions;
 212 
 213   enum PredictionConstants {
 214     TruncatedSeqLength = 10
 215   };
 216 
 217   TruncatedSeq* _alloc_rate_ms_seq;
 218   double        _prev_collection_pause_end_ms;
 219 
 220   TruncatedSeq* _rs_length_diff_seq;
 221   TruncatedSeq* _cost_per_card_ms_seq;
 222   TruncatedSeq* _young_cards_per_entry_ratio_seq;
 223   TruncatedSeq* _mixed_cards_per_entry_ratio_seq;
 224   TruncatedSeq* _cost_per_entry_ms_seq;
 225   TruncatedSeq* _mixed_cost_per_entry_ms_seq;
 226   TruncatedSeq* _cost_per_byte_ms_seq;
 227   TruncatedSeq* _constant_other_time_ms_seq;
 228   TruncatedSeq* _young_other_cost_per_region_ms_seq;
 229   TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
 230 
 231   TruncatedSeq* _pending_cards_seq;
 232   TruncatedSeq* _rs_lengths_seq;
 233 
 234   TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
 235 
 236   G1YoungGenSizer* _young_gen_sizer;
 237 
 238   uint _eden_cset_region_length;
 239   uint _survivor_cset_region_length;
 240   uint _old_cset_region_length;
 241 
 242   void init_cset_region_lengths(uint eden_cset_region_length,
 243                                 uint survivor_cset_region_length);
 244 
 245   uint eden_cset_region_length()     { return _eden_cset_region_length;     }
 246   uint survivor_cset_region_length() { return _survivor_cset_region_length; }
 247   uint old_cset_region_length()      { return _old_cset_region_length;      }
 248 
 249   uint _free_regions_at_end_of_collection;
 250 
 251   size_t _recorded_rs_lengths;
 252   size_t _max_rs_lengths;
 253   double _sigma;
 254 
 255   size_t _rs_lengths_prediction;
 256 
 257   double sigma() { return _sigma; }
 258 
 259   // A function that prevents us putting too much stock in small sample
 260   // sets.  Returns a number between 2.0 and 1.0, depending on the number
 261   // of samples.  5 or more samples yields one; fewer scales linearly from
 262   // 2.0 at 1 sample to 1.0 at 5.
 263   double confidence_factor(int samples) {
 264     if (samples > 4) return 1.0;
 265     else return  1.0 + sigma() * ((double)(5 - samples))/2.0;
 266   }
 267 
 268   double get_new_neg_prediction(TruncatedSeq* seq) {
 269     return seq->davg() - sigma() * seq->dsd();
 270   }
 271 
 272 #ifndef PRODUCT
 273   bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
 274 #endif // PRODUCT
 275 
 276   void adjust_concurrent_refinement(double update_rs_time,
 277                                     double update_rs_processed_buffers,
 278                                     double goal_ms);
 279 
 280   uintx no_of_gc_threads() { return _no_of_gc_threads; }
 281   void set_no_of_gc_threads(uintx v) { _no_of_gc_threads = v; }
 282 
 283   double _pause_time_target_ms;
 284 
 285   size_t _pending_cards;
 286 
 287 public:
 288   // Accessors
 289 
 290   void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
 291     hr->set_eden();
 292     hr->install_surv_rate_group(_short_lived_surv_rate_group);
 293     hr->set_young_index_in_cset(young_index_in_cset);
 294   }
 295 
 296   void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
 297     assert(hr->is_survivor(), "pre-condition");
 298     hr->install_surv_rate_group(_survivor_surv_rate_group);
 299     hr->set_young_index_in_cset(young_index_in_cset);
 300   }
 301 
 302 #ifndef PRODUCT
 303   bool verify_young_ages();
 304 #endif // PRODUCT
 305 
 306   double get_new_prediction(TruncatedSeq* seq) {
 307     return MAX2(seq->davg() + sigma() * seq->dsd(),
 308                 seq->davg() * confidence_factor(seq->num()));
 309   }
 310 
 311   void record_max_rs_lengths(size_t rs_lengths) {
 312     _max_rs_lengths = rs_lengths;
 313   }
 314 
 315   size_t predict_rs_length_diff() {
 316     return (size_t) get_new_prediction(_rs_length_diff_seq);
 317   }
 318 
 319   double predict_alloc_rate_ms() {
 320     return get_new_prediction(_alloc_rate_ms_seq);
 321   }
 322 
 323   double predict_cost_per_card_ms() {
 324     return get_new_prediction(_cost_per_card_ms_seq);
 325   }
 326 
 327   double predict_rs_update_time_ms(size_t pending_cards) {
 328     return (double) pending_cards * predict_cost_per_card_ms();
 329   }
 330 
 331   double predict_young_cards_per_entry_ratio() {
 332     return get_new_prediction(_young_cards_per_entry_ratio_seq);
 333   }
 334 
 335   double predict_mixed_cards_per_entry_ratio() {
 336     if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
 337       return predict_young_cards_per_entry_ratio();
 338     } else {
 339       return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
 340     }
 341   }
 342 
 343   size_t predict_young_card_num(size_t rs_length) {
 344     return (size_t) ((double) rs_length *
 345                      predict_young_cards_per_entry_ratio());
 346   }
 347 
 348   size_t predict_non_young_card_num(size_t rs_length) {
 349     return (size_t) ((double) rs_length *
 350                      predict_mixed_cards_per_entry_ratio());
 351   }
 352 
 353   double predict_rs_scan_time_ms(size_t card_num) {
 354     if (collector_state()->gcs_are_young()) {
 355       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 356     } else {
 357       return predict_mixed_rs_scan_time_ms(card_num);
 358     }
 359   }
 360 
 361   double predict_mixed_rs_scan_time_ms(size_t card_num) {
 362     if (_mixed_cost_per_entry_ms_seq->num() < 3) {
 363       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 364     } else {
 365       return (double) (card_num *
 366                        get_new_prediction(_mixed_cost_per_entry_ms_seq));
 367     }
 368   }
 369 
 370   double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
 371     if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
 372       return (1.1 * (double) bytes_to_copy) *
 373               get_new_prediction(_cost_per_byte_ms_seq);
 374     } else {
 375       return (double) bytes_to_copy *
 376              get_new_prediction(_cost_per_byte_ms_during_cm_seq);
 377     }
 378   }
 379 
 380   double predict_object_copy_time_ms(size_t bytes_to_copy) {
 381     if (collector_state()->during_concurrent_mark()) {
 382       return predict_object_copy_time_ms_during_cm(bytes_to_copy);
 383     } else {
 384       return (double) bytes_to_copy *
 385               get_new_prediction(_cost_per_byte_ms_seq);
 386     }
 387   }
 388 
 389   double predict_constant_other_time_ms() {
 390     return get_new_prediction(_constant_other_time_ms_seq);
 391   }
 392 
 393   double predict_young_other_time_ms(size_t young_num) {
 394     return (double) young_num *
 395            get_new_prediction(_young_other_cost_per_region_ms_seq);
 396   }
 397 
 398   double predict_non_young_other_time_ms(size_t non_young_num) {
 399     return (double) non_young_num *
 400            get_new_prediction(_non_young_other_cost_per_region_ms_seq);
 401   }
 402 
 403   double predict_base_elapsed_time_ms(size_t pending_cards);
 404   double predict_base_elapsed_time_ms(size_t pending_cards,
 405                                       size_t scanned_cards);
 406   size_t predict_bytes_to_copy(HeapRegion* hr);
 407   double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc);
 408 
 409   void set_recorded_rs_lengths(size_t rs_lengths);
 410 
 411   uint cset_region_length()       { return young_cset_region_length() +
 412                                            old_cset_region_length(); }
 413   uint young_cset_region_length() { return eden_cset_region_length() +
 414                                            survivor_cset_region_length(); }
 415 
 416   double predict_survivor_regions_evac_time();
 417 
 418   void cset_regions_freed() {
 419     bool propagate = collector_state()->should_propagate();
 420     _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
 421     _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
 422     // also call it on any more surv rate groups
 423   }
 424 
 425   G1MMUTracker* mmu_tracker() {
 426     return _mmu_tracker;
 427   }
 428 
 429   double max_pause_time_ms() {
 430     return _mmu_tracker->max_gc_time() * 1000.0;
 431   }
 432 
 433   double predict_remark_time_ms() {
 434     return get_new_prediction(_concurrent_mark_remark_times_ms);
 435   }
 436 
 437   double predict_cleanup_time_ms() {
 438     return get_new_prediction(_concurrent_mark_cleanup_times_ms);
 439   }
 440 
 441   // Returns an estimate of the survival rate of the region at yg-age
 442   // "yg_age".
 443   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
 444     TruncatedSeq* seq = surv_rate_group->get_seq(age);
 445     if (seq->num() == 0)
 446       gclog_or_tty->print("BARF! age is %d", age);
 447     guarantee( seq->num() > 0, "invariant" );
 448     double pred = get_new_prediction(seq);
 449     if (pred > 1.0)
 450       pred = 1.0;
 451     return pred;
 452   }
 453 
 454   double predict_yg_surv_rate(int age) {
 455     return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
 456   }
 457 
 458   double accum_yg_surv_rate_pred(int age) {
 459     return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
 460   }
 461 
 462 private:
 463   // Statistics kept per GC stoppage, pause or full.
 464   TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
 465 
 466   // Add a new GC of the given duration and end time to the record.
 467   void update_recent_gc_times(double end_time_sec, double elapsed_ms);
 468 
 469   // The head of the list (via "next_in_collection_set()") representing the
 470   // current collection set. Set from the incrementally built collection
 471   // set at the start of the pause.
 472   HeapRegion* _collection_set;
 473 
 474   // The number of bytes in the collection set before the pause. Set from
 475   // the incrementally built collection set at the start of an evacuation
 476   // pause, and incremented in finalize_old_cset_part() when adding old regions
 477   // (if any) to the collection set.
 478   size_t _collection_set_bytes_used_before;
 479 
 480   // The number of bytes copied during the GC.
 481   size_t _bytes_copied_during_gc;
 482 
 483   // The associated information that is maintained while the incremental
 484   // collection set is being built with young regions. Used to populate
 485   // the recorded info for the evacuation pause.
 486 
 487   enum CSetBuildType {
 488     Active,             // We are actively building the collection set
 489     Inactive            // We are not actively building the collection set
 490   };
 491 
 492   CSetBuildType _inc_cset_build_state;
 493 
 494   // The head of the incrementally built collection set.
 495   HeapRegion* _inc_cset_head;
 496 
 497   // The tail of the incrementally built collection set.
 498   HeapRegion* _inc_cset_tail;
 499 
 500   // The number of bytes in the incrementally built collection set.
 501   // Used to set _collection_set_bytes_used_before at the start of
 502   // an evacuation pause.
 503   size_t _inc_cset_bytes_used_before;
 504 
 505   // Used to record the highest end of heap region in collection set
 506   HeapWord* _inc_cset_max_finger;
 507 
 508   // The RSet lengths recorded for regions in the CSet. It is updated
 509   // by the thread that adds a new region to the CSet. We assume that
 510   // only one thread can be allocating a new CSet region (currently,
 511   // it does so after taking the Heap_lock) hence no need to
 512   // synchronize updates to this field.
 513   size_t _inc_cset_recorded_rs_lengths;
 514 
 515   // A concurrent refinement thread periodically samples the young
 516   // region RSets and needs to update _inc_cset_recorded_rs_lengths as
 517   // the RSets grow. Instead of having to synchronize updates to that
 518   // field we accumulate them in this field and add it to
 519   // _inc_cset_recorded_rs_lengths_diffs at the start of a GC.
 520   ssize_t _inc_cset_recorded_rs_lengths_diffs;
 521 
 522   // The predicted elapsed time it will take to collect the regions in
 523   // the CSet. This is updated by the thread that adds a new region to
 524   // the CSet. See the comment for _inc_cset_recorded_rs_lengths about
 525   // MT-safety assumptions.
 526   double _inc_cset_predicted_elapsed_time_ms;
 527 
 528   // See the comment for _inc_cset_recorded_rs_lengths_diffs.
 529   double _inc_cset_predicted_elapsed_time_ms_diffs;
 530 
 531   // Stash a pointer to the g1 heap.
 532   G1CollectedHeap* _g1;
 533 
 534   G1GCPhaseTimes* _phase_times;
 535 
 536   // The ratio of gc time to elapsed time, computed over recent pauses.
 537   double _recent_avg_pause_time_ratio;
 538 
 539   double recent_avg_pause_time_ratio() {
 540     return _recent_avg_pause_time_ratio;
 541   }
 542 
 543   // This set of variables tracks the collector efficiency, in order to
 544   // determine whether we should initiate a new marking.
 545   double _cur_mark_stop_world_time_ms;
 546   double _mark_remark_start_sec;
 547   double _mark_cleanup_start_sec;
 548 
 549   // Update the young list target length either by setting it to the
 550   // desired fixed value or by calculating it using G1's pause
 551   // prediction model. If no rs_lengths parameter is passed, predict
 552   // the RS lengths using the prediction model, otherwise use the
 553   // given rs_lengths as the prediction.
 554   void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
 555 
 556   // Calculate and return the minimum desired young list target
 557   // length. This is the minimum desired young list length according
 558   // to the user's inputs.
 559   uint calculate_young_list_desired_min_length(uint base_min_length);
 560 
 561   // Calculate and return the maximum desired young list target
 562   // length. This is the maximum desired young list length according
 563   // to the user's inputs.
 564   uint calculate_young_list_desired_max_length();
 565 
 566   // Calculate and return the maximum young list target length that
 567   // can fit into the pause time goal. The parameters are: rs_lengths
 568   // represent the prediction of how large the young RSet lengths will
 569   // be, base_min_length is the already existing number of regions in
 570   // the young list, min_length and max_length are the desired min and
 571   // max young list length according to the user's inputs.
 572   uint calculate_young_list_target_length(size_t rs_lengths,
 573                                           uint base_min_length,
 574                                           uint desired_min_length,
 575                                           uint desired_max_length);
 576 
 577   // Calculate and return chunk size (in number of regions) for parallel
 578   // concurrent mark cleanup.
 579   uint calculate_parallel_work_chunk_size(uint n_workers, uint n_regions);
 580 
 581   // Check whether a given young length (young_length) fits into the
 582   // given target pause time and whether the prediction for the amount
 583   // of objects to be copied for the given length will fit into the
 584   // given free space (expressed by base_free_regions).  It is used by
 585   // calculate_young_list_target_length().
 586   bool predict_will_fit(uint young_length, double base_time_ms,
 587                         uint base_free_regions, double target_pause_time_ms);
 588 
 589   // Calculate the minimum number of old regions we'll add to the CSet
 590   // during a mixed GC.
 591   uint calc_min_old_cset_length();
 592 
 593   // Calculate the maximum number of old regions we'll add to the CSet
 594   // during a mixed GC.
 595   uint calc_max_old_cset_length();
 596 
 597   // Returns the given amount of uncollected reclaimable space
 598   // as a percentage of the current heap capacity.
 599   double reclaimable_bytes_perc(size_t reclaimable_bytes);
 600 
 601 public:
 602 
 603   G1CollectorPolicy();
 604 
 605   virtual G1CollectorPolicy* as_g1_policy() { return this; }
 606 
 607   G1CollectorState* collector_state();
 608 
 609   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 610 
 611   // Check the current value of the young list RSet lengths and
 612   // compare it against the last prediction. If the current value is
 613   // higher, recalculate the young list target length prediction.
 614   void revise_young_list_target_length_if_necessary();
 615 
 616   // This should be called after the heap is resized.
 617   void record_new_heap_size(uint new_number_of_regions);
 618 
 619   void init();
 620 
 621   // Create jstat counters for the policy.
 622   virtual void initialize_gc_policy_counters();
 623 
 624   virtual HeapWord* mem_allocate_work(size_t size,
 625                                       bool is_tlab,
 626                                       bool* gc_overhead_limit_was_exceeded);
 627 
 628   // This method controls how a collector handles one or more
 629   // of its generations being fully allocated.
 630   virtual HeapWord* satisfy_failed_allocation(size_t size,
 631                                               bool is_tlab);
 632 
 633   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 634 
 635   // Record the start and end of an evacuation pause.
 636   void record_collection_pause_start(double start_time_sec);
 637   void record_collection_pause_end(double pause_time_ms, size_t cards_scanned);
 638 
 639   // Record the start and end of a full collection.
 640   void record_full_collection_start();
 641   void record_full_collection_end();
 642 
 643   // Must currently be called while the world is stopped.
 644   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 645 
 646   // Record start and end of remark.
 647   void record_concurrent_mark_remark_start();
 648   void record_concurrent_mark_remark_end();
 649 
 650   // Record start, end, and completion of cleanup.
 651   void record_concurrent_mark_cleanup_start();
 652   void record_concurrent_mark_cleanup_end();
 653   void record_concurrent_mark_cleanup_completed();
 654 
 655   // Records the information about the heap size for reporting in
 656   // print_detailed_heap_transition
 657   void record_heap_size_info_at_start(bool full);
 658 
 659   // Print heap sizing transition (with less and more detail).
 660 
 661   void print_heap_transition(size_t bytes_before);
 662   void print_heap_transition();
 663   void print_detailed_heap_transition(bool full = false);
 664 
 665   void record_stop_world_start();
 666   void record_concurrent_pause();
 667 
 668   // Record how much space we copied during a GC. This is typically
 669   // called when a GC alloc region is being retired.
 670   void record_bytes_copied_during_gc(size_t bytes) {
 671     _bytes_copied_during_gc += bytes;
 672   }
 673 
 674   // The amount of space we copied during a GC.
 675   size_t bytes_copied_during_gc() {
 676     return _bytes_copied_during_gc;
 677   }
 678 
 679   size_t collection_set_bytes_used_before() const {
 680     return _collection_set_bytes_used_before;
 681   }
 682 
 683   // Determine whether there are candidate regions so that the
 684   // next GC should be mixed. The two action strings are used
 685   // in the ergo output when the method returns true or false.
 686   bool next_gc_should_be_mixed(const char* true_action_str,
 687                                const char* false_action_str);
 688 
 689   // Choose a new collection set.  Marks the chosen regions as being
 690   // "in_collection_set", and links them together.  The head and number of
 691   // the collection set are available via access methods.
 692   double finalize_young_cset_part(double target_pause_time_ms);
 693   virtual void finalize_old_cset_part(double time_remaining_ms);
 694 
 695   // The head of the list (via "next_in_collection_set()") representing the
 696   // current collection set.
 697   HeapRegion* collection_set() { return _collection_set; }
 698 
 699   void clear_collection_set() { _collection_set = NULL; }
 700 
 701   // Add old region "hr" to the CSet.
 702   void add_old_region_to_cset(HeapRegion* hr);
 703 
 704   // Incremental CSet Support
 705 
 706   // The head of the incrementally built collection set.
 707   HeapRegion* inc_cset_head() { return _inc_cset_head; }
 708 
 709   // The tail of the incrementally built collection set.
 710   HeapRegion* inc_set_tail() { return _inc_cset_tail; }
 711 
 712   // Initialize incremental collection set info.
 713   void start_incremental_cset_building();
 714 
 715   // Perform any final calculations on the incremental CSet fields
 716   // before we can use them.
 717   void finalize_incremental_cset_building();
 718 
 719   void clear_incremental_cset() {
 720     _inc_cset_head = NULL;
 721     _inc_cset_tail = NULL;
 722   }
 723 
 724   // Stop adding regions to the incremental collection set
 725   void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
 726 
 727   // Add information about hr to the aggregated information for the
 728   // incrementally built collection set.
 729   void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
 730 
 731   // Update information about hr in the aggregated information for
 732   // the incrementally built collection set.
 733   void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
 734 
 735 private:
 736   // Update the incremental cset information when adding a region
 737   // (should not be called directly).
 738   void add_region_to_incremental_cset_common(HeapRegion* hr);
 739 
 740 public:
 741   // Add hr to the LHS of the incremental collection set.
 742   void add_region_to_incremental_cset_lhs(HeapRegion* hr);
 743 
 744   // Add hr to the RHS of the incremental collection set.
 745   void add_region_to_incremental_cset_rhs(HeapRegion* hr);
 746 
 747 #ifndef PRODUCT
 748   void print_collection_set(HeapRegion* list_head, outputStream* st);
 749 #endif // !PRODUCT
 750 
 751   // This sets the initiate_conc_mark_if_possible() flag to start a
 752   // new cycle, as long as we are not already in one. It's best if it
 753   // is called during a safepoint when the test whether a cycle is in
 754   // progress or not is stable.
 755   bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
 756 
 757   // This is called at the very beginning of an evacuation pause (it
 758   // has to be the first thing that the pause does). If
 759   // initiate_conc_mark_if_possible() is true, and the concurrent
 760   // marking thread has completed its work during the previous cycle,
 761   // it will set during_initial_mark_pause() to so that the pause does
 762   // the initial-mark work and start a marking cycle.
 763   void decide_on_conc_mark_initiation();
 764 
 765   // If an expansion would be appropriate, because recent GC overhead had
 766   // exceeded the desired limit, return an amount to expand by.
 767   virtual size_t expansion_amount();
 768 
 769   // Print tracing information.
 770   void print_tracing_info() const;
 771 
 772   // Print stats on young survival ratio
 773   void print_yg_surv_rate_info() const;
 774 
 775   void finished_recalculating_age_indexes(bool is_survivors) {
 776     if (is_survivors) {
 777       _survivor_surv_rate_group->finished_recalculating_age_indexes();
 778     } else {
 779       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
 780     }
 781     // do that for any other surv rate groups
 782   }
 783 
 784   size_t young_list_target_length() const { return _young_list_target_length; }
 785 
 786   bool is_young_list_full();
 787 
 788   bool can_expand_young_list();
 789 
 790   uint young_list_max_length() {
 791     return _young_list_max_length;
 792   }
 793 
 794   bool adaptive_young_list_length() {
 795     return _young_gen_sizer->adaptive_young_list_length();
 796   }
 797 
 798 private:
 799   //
 800   // Survivor regions policy.
 801   //
 802 
 803   // Current tenuring threshold, set to 0 if the collector reaches the
 804   // maximum amount of survivors regions.
 805   uint _tenuring_threshold;
 806 
 807   // The limit on the number of regions allocated for survivors.
 808   uint _max_survivor_regions;
 809 
 810   // For reporting purposes.
 811   // The value of _heap_bytes_before_gc is also used to calculate
 812   // the cost of copying.
 813 
 814   size_t _eden_used_bytes_before_gc;         // Eden occupancy before GC
 815   size_t _survivor_used_bytes_before_gc;     // Survivor occupancy before GC
 816   size_t _heap_used_bytes_before_gc;         // Heap occupancy before GC
 817   size_t _metaspace_used_bytes_before_gc;    // Metaspace occupancy before GC
 818 
 819   size_t _eden_capacity_bytes_before_gc;     // Eden capacity before GC
 820   size_t _heap_capacity_bytes_before_gc;     // Heap capacity before GC
 821 
 822   // The amount of survivor regions after a collection.
 823   uint _recorded_survivor_regions;
 824   // List of survivor regions.
 825   HeapRegion* _recorded_survivor_head;
 826   HeapRegion* _recorded_survivor_tail;
 827 
 828   ageTable _survivors_age_table;
 829 
 830 public:
 831   uint tenuring_threshold() const { return _tenuring_threshold; }
 832 
 833   static const uint REGIONS_UNLIMITED = (uint) -1;
 834 
 835   uint max_regions(InCSetState dest) {
 836     switch (dest.value()) {
 837       case InCSetState::Young:
 838         return _max_survivor_regions;
 839       case InCSetState::Old:
 840         return REGIONS_UNLIMITED;
 841       default:
 842         assert(false, "Unknown dest state: " CSETSTATE_FORMAT, dest.value());
 843         break;
 844     }
 845     // keep some compilers happy
 846     return 0;
 847   }
 848 
 849   void note_start_adding_survivor_regions() {
 850     _survivor_surv_rate_group->start_adding_regions();
 851   }
 852 
 853   void note_stop_adding_survivor_regions() {
 854     _survivor_surv_rate_group->stop_adding_regions();
 855   }
 856 
 857   void record_survivor_regions(uint regions,
 858                                HeapRegion* head,
 859                                HeapRegion* tail) {
 860     _recorded_survivor_regions = regions;
 861     _recorded_survivor_head    = head;
 862     _recorded_survivor_tail    = tail;
 863   }
 864 
 865   uint recorded_survivor_regions() {
 866     return _recorded_survivor_regions;
 867   }
 868 
 869   void record_age_table(ageTable* age_table) {
 870     _survivors_age_table.merge(age_table);
 871   }
 872 
 873   void update_max_gc_locker_expansion();
 874 
 875   // Calculates survivor space parameters.
 876   void update_survivors_policy();
 877 
 878   virtual void post_heap_initialize();
 879 };
 880 
 881 // This should move to some place more general...
 882 
 883 // If we have "n" measurements, and we've kept track of their "sum" and the
 884 // "sum_of_squares" of the measurements, this returns the variance of the
 885 // sequence.
 886 inline double variance(int n, double sum_of_squares, double sum) {
 887   double n_d = (double)n;
 888   double avg = sum/n_d;
 889   return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
 890 }
 891 
 892 #endif // SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP