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
   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/g1Allocator.hpp"
  30 #include "gc_implementation/g1/g1MMUTracker.hpp"
  31 #include "memory/collectorPolicy.hpp"
  32 
  33 // A G1CollectorPolicy makes policy decisions that determine the
  34 // characteristics of the collector.  Examples include:
  35 //   * choice of collection set.
  36 //   * when to collect.
  37 
  38 class HeapRegion;
  39 class CollectionSetChooser;
  40 class G1GCPhaseTimes;
  41 
  42 // TraceYoungGenTime collects data on _both_ young and mixed evacuation pauses
  43 // (the latter may contain non-young regions - i.e. regions that are
  44 // technically in old) while TraceOldGenTime collects data about full GCs.
  45 class TraceYoungGenTimeData : public CHeapObj<mtGC> {
  46  private:
  47   unsigned  _young_pause_num;
  48   unsigned  _mixed_pause_num;
  49 
  50   NumberSeq _all_stop_world_times_ms;
  51   NumberSeq _all_yield_times_ms;
  52 
  53   NumberSeq _total;
  54   NumberSeq _other;
  55   NumberSeq _root_region_scan_wait;
  56   NumberSeq _parallel;
  57   NumberSeq _ext_root_scan;
  58   NumberSeq _satb_filtering;
  59   NumberSeq _update_rs;
  60   NumberSeq _scan_rs;
  61   NumberSeq _obj_copy;
  62   NumberSeq _termination;
  63   NumberSeq _parallel_other;
  64   NumberSeq _clear_ct;
  65 
  66   void print_summary(const char* str, const NumberSeq* seq) const;
  67   void print_summary_sd(const char* str, const NumberSeq* seq) const;
  68 
  69 public:
  70    TraceYoungGenTimeData() : _young_pause_num(0), _mixed_pause_num(0) {};
  71   void record_start_collection(double time_to_stop_the_world_ms);
  72   void record_yield_time(double yield_time_ms);
  73   void record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times);
  74   void increment_young_collection_count();
  75   void increment_mixed_collection_count();
  76   void print() const;
  77 };
  78 
  79 class TraceOldGenTimeData : public CHeapObj<mtGC> {
  80  private:
  81   NumberSeq _all_full_gc_times;
  82 
  83  public:
  84   void record_full_collection(double full_gc_time_ms);
  85   void print() const;
  86 };
  87 
  88 // There are three command line options related to the young gen size:
  89 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
  90 // just a short form for NewSize==MaxNewSize). G1 will use its internal
  91 // heuristics to calculate the actual young gen size, so these options
  92 // basically only limit the range within which G1 can pick a young gen
  93 // size. Also, these are general options taking byte sizes. G1 will
  94 // internally work with a number of regions instead. So, some rounding
  95 // will occur.
  96 //
  97 // If nothing related to the the young gen size is set on the command
  98 // line we should allow the young gen to be between G1NewSizePercent
  99 // and G1MaxNewSizePercent of the heap size. This means that every time
 100 // the heap size changes, the limits for the young gen size will be
 101 // recalculated.
 102 //
 103 // If only -XX:NewSize is set we should use the specified value as the
 104 // minimum size for young gen. Still using G1MaxNewSizePercent of the
 105 // heap as maximum.
 106 //
 107 // If only -XX:MaxNewSize is set we should use the specified value as the
 108 // maximum size for young gen. Still using G1NewSizePercent of the heap
 109 // as minimum.
 110 //
 111 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
 112 // No updates when the heap size changes. There is a special case when
 113 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
 114 // different heuristic for calculating the collection set when we do mixed
 115 // collection.
 116 //
 117 // If only -XX:NewRatio is set we should use the specified ratio of the heap
 118 // as both min and max. This will be interpreted as "fixed" just like the
 119 // NewSize==MaxNewSize case above. But we will update the min and max
 120 // every time the heap size changes.
 121 //
 122 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
 123 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
 124 class G1YoungGenSizer : public CHeapObj<mtGC> {
 125 private:
 126   enum SizerKind {
 127     SizerDefaults,
 128     SizerNewSizeOnly,
 129     SizerMaxNewSizeOnly,
 130     SizerMaxAndNewSize,
 131     SizerNewRatio
 132   };
 133   SizerKind _sizer_kind;
 134   uint _min_desired_young_length;
 135   uint _max_desired_young_length;
 136   bool _adaptive_size;
 137   uint calculate_default_min_length(uint new_number_of_heap_regions);
 138   uint calculate_default_max_length(uint new_number_of_heap_regions);
 139 
 140   // Update the given values for minimum and maximum young gen length in regions
 141   // given the number of heap regions depending on the kind of sizing algorithm.
 142   void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
 143 
 144 public:
 145   G1YoungGenSizer();
 146   // Calculate the maximum length of the young gen given the number of regions
 147   // depending on the sizing algorithm.
 148   uint max_young_length(uint number_of_heap_regions);
 149 
 150   void heap_size_changed(uint new_number_of_heap_regions);
 151   uint min_desired_young_length() {
 152     return _min_desired_young_length;
 153   }
 154   uint max_desired_young_length() {
 155     return _max_desired_young_length;
 156   }
 157   bool adaptive_young_list_length() {
 158     return _adaptive_size;
 159   }
 160 };
 161 
 162 class G1CollectorPolicy: public CollectorPolicy {
 163 private:
 164   // either equal to the number of parallel threads, if ParallelGCThreads
 165   // has been set, or 1 otherwise
 166   int _parallel_gc_threads;
 167 
 168   // The number of GC threads currently active.
 169   uintx _no_of_gc_threads;
 170 
 171   enum SomePrivateConstants {
 172     NumPrevPausesForHeuristics = 10
 173   };
 174 
 175   G1MMUTracker* _mmu_tracker;
 176 
 177   void initialize_alignments();
 178   void initialize_flags();
 179 
 180   CollectionSetChooser* _collectionSetChooser;
 181 
 182   double _full_collection_start_sec;
 183   uint   _cur_collection_pause_used_regions_at_start;
 184 
 185   // These exclude marking times.
 186   TruncatedSeq* _recent_gc_times_ms;
 187 
 188   TruncatedSeq* _concurrent_mark_remark_times_ms;
 189   TruncatedSeq* _concurrent_mark_cleanup_times_ms;
 190 
 191   TraceYoungGenTimeData _trace_young_gen_time_data;
 192   TraceOldGenTimeData   _trace_old_gen_time_data;
 193 
 194   double _stop_world_start;
 195 
 196   // indicates whether we are in young or mixed GC mode
 197   bool _gcs_are_young;
 198 
 199   uint _young_list_target_length;
 200   uint _young_list_fixed_length;
 201 
 202   // The max number of regions we can extend the eden by while the GC
 203   // locker is active. This should be >= _young_list_target_length;
 204   uint _young_list_max_length;
 205 
 206   bool _last_gc_was_young;
 207 
 208   bool _during_marking;
 209   bool _in_marking_window;
 210   bool _in_marking_window_im;
 211 
 212   SurvRateGroup* _short_lived_surv_rate_group;
 213   SurvRateGroup* _survivor_surv_rate_group;
 214   // add here any more surv rate groups
 215 
 216   double _gc_overhead_perc;
 217 
 218   double _reserve_factor;
 219   uint   _reserve_regions;
 220 
 221   bool during_marking() {
 222     return _during_marking;
 223   }
 224 
 225   enum PredictionConstants {
 226     TruncatedSeqLength = 10
 227   };
 228 
 229   TruncatedSeq* _alloc_rate_ms_seq;
 230   double        _prev_collection_pause_end_ms;
 231 
 232   TruncatedSeq* _rs_length_diff_seq;
 233   TruncatedSeq* _cost_per_card_ms_seq;
 234   TruncatedSeq* _young_cards_per_entry_ratio_seq;
 235   TruncatedSeq* _mixed_cards_per_entry_ratio_seq;
 236   TruncatedSeq* _cost_per_entry_ms_seq;
 237   TruncatedSeq* _mixed_cost_per_entry_ms_seq;
 238   TruncatedSeq* _cost_per_byte_ms_seq;
 239   TruncatedSeq* _constant_other_time_ms_seq;
 240   TruncatedSeq* _young_other_cost_per_region_ms_seq;
 241   TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
 242 
 243   TruncatedSeq* _pending_cards_seq;
 244   TruncatedSeq* _rs_lengths_seq;
 245 
 246   TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
 247 
 248   G1YoungGenSizer* _young_gen_sizer;
 249 
 250   uint _eden_cset_region_length;
 251   uint _survivor_cset_region_length;
 252   uint _old_cset_region_length;
 253 
 254   void init_cset_region_lengths(uint eden_cset_region_length,
 255                                 uint survivor_cset_region_length);
 256 
 257   uint eden_cset_region_length()     { return _eden_cset_region_length;     }
 258   uint survivor_cset_region_length() { return _survivor_cset_region_length; }
 259   uint old_cset_region_length()      { return _old_cset_region_length;      }
 260 
 261   uint _free_regions_at_end_of_collection;
 262 
 263   size_t _recorded_rs_lengths;
 264   size_t _max_rs_lengths;
 265   double _sigma;
 266 
 267   size_t _rs_lengths_prediction;
 268 
 269   double sigma() { return _sigma; }
 270 
 271   // A function that prevents us putting too much stock in small sample
 272   // sets.  Returns a number between 2.0 and 1.0, depending on the number
 273   // of samples.  5 or more samples yields one; fewer scales linearly from
 274   // 2.0 at 1 sample to 1.0 at 5.
 275   double confidence_factor(int samples) {
 276     if (samples > 4) return 1.0;
 277     else return  1.0 + sigma() * ((double)(5 - samples))/2.0;
 278   }
 279 
 280   double get_new_neg_prediction(TruncatedSeq* seq) {
 281     return seq->davg() - sigma() * seq->dsd();
 282   }
 283 
 284 #ifndef PRODUCT
 285   bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
 286 #endif // PRODUCT
 287 
 288   void adjust_concurrent_refinement(double update_rs_time,
 289                                     double update_rs_processed_buffers,
 290                                     double goal_ms);
 291 
 292   uintx no_of_gc_threads() { return _no_of_gc_threads; }
 293   void set_no_of_gc_threads(uintx v) { _no_of_gc_threads = v; }
 294 
 295   double _pause_time_target_ms;
 296 
 297   size_t _pending_cards;
 298 
 299 public:
 300   // Accessors
 301 
 302   void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
 303     hr->set_eden();
 304     hr->install_surv_rate_group(_short_lived_surv_rate_group);
 305     hr->set_young_index_in_cset(young_index_in_cset);
 306   }
 307 
 308   void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
 309     assert(hr->is_survivor(), "pre-condition");
 310     hr->install_surv_rate_group(_survivor_surv_rate_group);
 311     hr->set_young_index_in_cset(young_index_in_cset);
 312   }
 313 
 314 #ifndef PRODUCT
 315   bool verify_young_ages();
 316 #endif // PRODUCT
 317 
 318   double get_new_prediction(TruncatedSeq* seq) {
 319     return MAX2(seq->davg() + sigma() * seq->dsd(),
 320                 seq->davg() * confidence_factor(seq->num()));
 321   }
 322 
 323   void record_max_rs_lengths(size_t rs_lengths) {
 324     _max_rs_lengths = rs_lengths;
 325   }
 326 
 327   size_t predict_rs_length_diff() {
 328     return (size_t) get_new_prediction(_rs_length_diff_seq);
 329   }
 330 
 331   double predict_alloc_rate_ms() {
 332     return get_new_prediction(_alloc_rate_ms_seq);
 333   }
 334 
 335   double predict_cost_per_card_ms() {
 336     return get_new_prediction(_cost_per_card_ms_seq);
 337   }
 338 
 339   double predict_rs_update_time_ms(size_t pending_cards) {
 340     return (double) pending_cards * predict_cost_per_card_ms();
 341   }
 342 
 343   double predict_young_cards_per_entry_ratio() {
 344     return get_new_prediction(_young_cards_per_entry_ratio_seq);
 345   }
 346 
 347   double predict_mixed_cards_per_entry_ratio() {
 348     if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
 349       return predict_young_cards_per_entry_ratio();
 350     } else {
 351       return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
 352     }
 353   }
 354 
 355   size_t predict_young_card_num(size_t rs_length) {
 356     return (size_t) ((double) rs_length *
 357                      predict_young_cards_per_entry_ratio());
 358   }
 359 
 360   size_t predict_non_young_card_num(size_t rs_length) {
 361     return (size_t) ((double) rs_length *
 362                      predict_mixed_cards_per_entry_ratio());
 363   }
 364 
 365   double predict_rs_scan_time_ms(size_t card_num) {
 366     if (gcs_are_young()) {
 367       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 368     } else {
 369       return predict_mixed_rs_scan_time_ms(card_num);
 370     }
 371   }
 372 
 373   double predict_mixed_rs_scan_time_ms(size_t card_num) {
 374     if (_mixed_cost_per_entry_ms_seq->num() < 3) {
 375       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 376     } else {
 377       return (double) (card_num *
 378                        get_new_prediction(_mixed_cost_per_entry_ms_seq));
 379     }
 380   }
 381 
 382   double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
 383     if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
 384       return (1.1 * (double) bytes_to_copy) *
 385               get_new_prediction(_cost_per_byte_ms_seq);
 386     } else {
 387       return (double) bytes_to_copy *
 388              get_new_prediction(_cost_per_byte_ms_during_cm_seq);
 389     }
 390   }
 391 
 392   double predict_object_copy_time_ms(size_t bytes_to_copy) {
 393     if (_in_marking_window && !_in_marking_window_im) {
 394       return predict_object_copy_time_ms_during_cm(bytes_to_copy);
 395     } else {
 396       return (double) bytes_to_copy *
 397               get_new_prediction(_cost_per_byte_ms_seq);
 398     }
 399   }
 400 
 401   double predict_constant_other_time_ms() {
 402     return get_new_prediction(_constant_other_time_ms_seq);
 403   }
 404 
 405   double predict_young_other_time_ms(size_t young_num) {
 406     return (double) young_num *
 407            get_new_prediction(_young_other_cost_per_region_ms_seq);
 408   }
 409 
 410   double predict_non_young_other_time_ms(size_t non_young_num) {
 411     return (double) non_young_num *
 412            get_new_prediction(_non_young_other_cost_per_region_ms_seq);
 413   }
 414 
 415   double predict_base_elapsed_time_ms(size_t pending_cards);
 416   double predict_base_elapsed_time_ms(size_t pending_cards,
 417                                       size_t scanned_cards);
 418   size_t predict_bytes_to_copy(HeapRegion* hr);
 419   double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc);
 420 
 421   void set_recorded_rs_lengths(size_t rs_lengths);
 422 
 423   uint cset_region_length()       { return young_cset_region_length() +
 424                                            old_cset_region_length(); }
 425   uint young_cset_region_length() { return eden_cset_region_length() +
 426                                            survivor_cset_region_length(); }
 427 
 428   double predict_survivor_regions_evac_time();
 429 
 430   void cset_regions_freed() {
 431     bool propagate = _last_gc_was_young && !_in_marking_window;
 432     _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
 433     _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
 434     // also call it on any more surv rate groups
 435   }
 436 
 437   G1MMUTracker* mmu_tracker() {
 438     return _mmu_tracker;
 439   }
 440 
 441   double max_pause_time_ms() {
 442     return _mmu_tracker->max_gc_time() * 1000.0;
 443   }
 444 
 445   double predict_remark_time_ms() {
 446     return get_new_prediction(_concurrent_mark_remark_times_ms);
 447   }
 448 
 449   double predict_cleanup_time_ms() {
 450     return get_new_prediction(_concurrent_mark_cleanup_times_ms);
 451   }
 452 
 453   // Returns an estimate of the survival rate of the region at yg-age
 454   // "yg_age".
 455   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
 456     TruncatedSeq* seq = surv_rate_group->get_seq(age);
 457     if (seq->num() == 0)
 458       gclog_or_tty->print("BARF! age is %d", age);
 459     guarantee( seq->num() > 0, "invariant" );
 460     double pred = get_new_prediction(seq);
 461     if (pred > 1.0)
 462       pred = 1.0;
 463     return pred;
 464   }
 465 
 466   double predict_yg_surv_rate(int age) {
 467     return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
 468   }
 469 
 470   double accum_yg_surv_rate_pred(int age) {
 471     return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
 472   }
 473 
 474 private:
 475   // Statistics kept per GC stoppage, pause or full.
 476   TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
 477 
 478   // Add a new GC of the given duration and end time to the record.
 479   void update_recent_gc_times(double end_time_sec, double elapsed_ms);
 480 
 481   // The head of the list (via "next_in_collection_set()") representing the
 482   // current collection set. Set from the incrementally built collection
 483   // set at the start of the pause.
 484   HeapRegion* _collection_set;
 485 
 486   // The number of bytes in the collection set before the pause. Set from
 487   // the incrementally built collection set at the start of an evacuation
 488   // pause, and incremented in finalize_cset() when adding old regions
 489   // (if any) to the collection set.
 490   size_t _collection_set_bytes_used_before;
 491 
 492   // The number of bytes copied during the GC.
 493   size_t _bytes_copied_during_gc;
 494 
 495   // The associated information that is maintained while the incremental
 496   // collection set is being built with young regions. Used to populate
 497   // the recorded info for the evacuation pause.
 498 
 499   enum CSetBuildType {
 500     Active,             // We are actively building the collection set
 501     Inactive            // We are not actively building the collection set
 502   };
 503 
 504   CSetBuildType _inc_cset_build_state;
 505 
 506   // The head of the incrementally built collection set.
 507   HeapRegion* _inc_cset_head;
 508 
 509   // The tail of the incrementally built collection set.
 510   HeapRegion* _inc_cset_tail;
 511 
 512   // The number of bytes in the incrementally built collection set.
 513   // Used to set _collection_set_bytes_used_before at the start of
 514   // an evacuation pause.
 515   size_t _inc_cset_bytes_used_before;
 516 
 517   // Used to record the highest end of heap region in collection set
 518   HeapWord* _inc_cset_max_finger;
 519 
 520   // The RSet lengths recorded for regions in the CSet. It is updated
 521   // by the thread that adds a new region to the CSet. We assume that
 522   // only one thread can be allocating a new CSet region (currently,
 523   // it does so after taking the Heap_lock) hence no need to
 524   // synchronize updates to this field.
 525   size_t _inc_cset_recorded_rs_lengths;
 526 
 527   // A concurrent refinement thread periodically samples the young
 528   // region RSets and needs to update _inc_cset_recorded_rs_lengths as
 529   // the RSets grow. Instead of having to synchronize updates to that
 530   // field we accumulate them in this field and add it to
 531   // _inc_cset_recorded_rs_lengths_diffs at the start of a GC.
 532   ssize_t _inc_cset_recorded_rs_lengths_diffs;
 533 
 534   // The predicted elapsed time it will take to collect the regions in
 535   // the CSet. This is updated by the thread that adds a new region to
 536   // the CSet. See the comment for _inc_cset_recorded_rs_lengths about
 537   // MT-safety assumptions.
 538   double _inc_cset_predicted_elapsed_time_ms;
 539 
 540   // See the comment for _inc_cset_recorded_rs_lengths_diffs.
 541   double _inc_cset_predicted_elapsed_time_ms_diffs;
 542 
 543   // Stash a pointer to the g1 heap.
 544   G1CollectedHeap* _g1;
 545 
 546   G1GCPhaseTimes* _phase_times;
 547 
 548   // The ratio of gc time to elapsed time, computed over recent pauses.
 549   double _recent_avg_pause_time_ratio;
 550 
 551   double recent_avg_pause_time_ratio() {
 552     return _recent_avg_pause_time_ratio;
 553   }
 554 
 555   // At the end of a pause we check the heap occupancy and we decide
 556   // whether we will start a marking cycle during the next pause. If
 557   // we decide that we want to do that, we will set this parameter to
 558   // true. So, this parameter will stay true between the end of a
 559   // pause and the beginning of a subsequent pause (not necessarily
 560   // the next one, see the comments on the next field) when we decide
 561   // that we will indeed start a marking cycle and do the initial-mark
 562   // work.
 563   volatile bool _initiate_conc_mark_if_possible;
 564 
 565   // If initiate_conc_mark_if_possible() is set at the beginning of a
 566   // pause, it is a suggestion that the pause should start a marking
 567   // cycle by doing the initial-mark work. However, it is possible
 568   // that the concurrent marking thread is still finishing up the
 569   // previous marking cycle (e.g., clearing the next marking
 570   // bitmap). If that is the case we cannot start a new cycle and
 571   // we'll have to wait for the concurrent marking thread to finish
 572   // what it is doing. In this case we will postpone the marking cycle
 573   // initiation decision for the next pause. When we eventually decide
 574   // to start a cycle, we will set _during_initial_mark_pause which
 575   // will stay true until the end of the initial-mark pause and it's
 576   // the condition that indicates that a pause is doing the
 577   // initial-mark work.
 578   volatile bool _during_initial_mark_pause;
 579 
 580   bool _last_young_gc;
 581 
 582   // This set of variables tracks the collector efficiency, in order to
 583   // determine whether we should initiate a new marking.
 584   double _cur_mark_stop_world_time_ms;
 585   double _mark_remark_start_sec;
 586   double _mark_cleanup_start_sec;
 587 
 588   // Update the young list target length either by setting it to the
 589   // desired fixed value or by calculating it using G1's pause
 590   // prediction model. If no rs_lengths parameter is passed, predict
 591   // the RS lengths using the prediction model, otherwise use the
 592   // given rs_lengths as the prediction.
 593   void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
 594 
 595   // Calculate and return the minimum desired young list target
 596   // length. This is the minimum desired young list length according
 597   // to the user's inputs.
 598   uint calculate_young_list_desired_min_length(uint base_min_length);
 599 
 600   // Calculate and return the maximum desired young list target
 601   // length. This is the maximum desired young list length according
 602   // to the user's inputs.
 603   uint calculate_young_list_desired_max_length();
 604 
 605   // Calculate and return the maximum young list target length that
 606   // can fit into the pause time goal. The parameters are: rs_lengths
 607   // represent the prediction of how large the young RSet lengths will
 608   // be, base_min_length is the already existing number of regions in
 609   // the young list, min_length and max_length are the desired min and
 610   // max young list length according to the user's inputs.
 611   uint calculate_young_list_target_length(size_t rs_lengths,
 612                                           uint base_min_length,
 613                                           uint desired_min_length,
 614                                           uint desired_max_length);
 615 
 616   // Calculate and return chunk size (in number of regions) for parallel
 617   // concurrent mark cleanup.
 618   uint calculate_parallel_work_chunk_size(uint n_workers, uint n_regions);
 619 
 620   // Check whether a given young length (young_length) fits into the
 621   // given target pause time and whether the prediction for the amount
 622   // of objects to be copied for the given length will fit into the
 623   // given free space (expressed by base_free_regions).  It is used by
 624   // calculate_young_list_target_length().
 625   bool predict_will_fit(uint young_length, double base_time_ms,
 626                         uint base_free_regions, double target_pause_time_ms);
 627 
 628   // Calculate the minimum number of old regions we'll add to the CSet
 629   // during a mixed GC.
 630   uint calc_min_old_cset_length();
 631 
 632   // Calculate the maximum number of old regions we'll add to the CSet
 633   // during a mixed GC.
 634   uint calc_max_old_cset_length();
 635 
 636   // Returns the given amount of uncollected reclaimable space
 637   // as a percentage of the current heap capacity.
 638   double reclaimable_bytes_perc(size_t reclaimable_bytes);
 639 
 640 public:
 641 
 642   G1CollectorPolicy();
 643 
 644   virtual G1CollectorPolicy* as_g1_policy() { return this; }
 645 
 646   virtual CollectorPolicy::Name kind() {
 647     return CollectorPolicy::G1CollectorPolicyKind;
 648   }
 649 
 650   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 651 
 652   // Check the current value of the young list RSet lengths and
 653   // compare it against the last prediction. If the current value is
 654   // higher, recalculate the young list target length prediction.
 655   void revise_young_list_target_length_if_necessary();
 656 
 657   // This should be called after the heap is resized.
 658   void record_new_heap_size(uint new_number_of_regions);
 659 
 660   void init();
 661 
 662   // Create jstat counters for the policy.
 663   virtual void initialize_gc_policy_counters();
 664 
 665   virtual HeapWord* mem_allocate_work(size_t size,
 666                                       bool is_tlab,
 667                                       bool* gc_overhead_limit_was_exceeded);
 668 
 669   // This method controls how a collector handles one or more
 670   // of its generations being fully allocated.
 671   virtual HeapWord* satisfy_failed_allocation(size_t size,
 672                                               bool is_tlab);
 673 
 674   BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
 675 
 676   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 677 
 678   // Record the start and end of an evacuation pause.
 679   void record_collection_pause_start(double start_time_sec);
 680   void record_collection_pause_end(double pause_time_ms, EvacuationInfo& evacuation_info);
 681 
 682   // Record the start and end of a full collection.
 683   void record_full_collection_start();
 684   void record_full_collection_end();
 685 
 686   // Must currently be called while the world is stopped.
 687   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 688 
 689   // Record start and end of remark.
 690   void record_concurrent_mark_remark_start();
 691   void record_concurrent_mark_remark_end();
 692 
 693   // Record start, end, and completion of cleanup.
 694   void record_concurrent_mark_cleanup_start();
 695   void record_concurrent_mark_cleanup_end(uint n_workers);
 696   void record_concurrent_mark_cleanup_completed();
 697 
 698   // Records the information about the heap size for reporting in
 699   // print_detailed_heap_transition
 700   void record_heap_size_info_at_start(bool full);
 701 
 702   // Print heap sizing transition (with less and more detail).
 703 
 704   void print_heap_transition(size_t bytes_before);
 705   void print_heap_transition();
 706   void print_detailed_heap_transition(bool full = false);
 707 
 708   void record_stop_world_start();
 709   void record_concurrent_pause();
 710 
 711   // Record how much space we copied during a GC. This is typically
 712   // called when a GC alloc region is being retired.
 713   void record_bytes_copied_during_gc(size_t bytes) {
 714     _bytes_copied_during_gc += bytes;
 715   }
 716 
 717   // The amount of space we copied during a GC.
 718   size_t bytes_copied_during_gc() {
 719     return _bytes_copied_during_gc;
 720   }
 721 
 722   // Determine whether there are candidate regions so that the
 723   // next GC should be mixed. The two action strings are used
 724   // in the ergo output when the method returns true or false.
 725   bool next_gc_should_be_mixed(const char* true_action_str,
 726                                const char* false_action_str);
 727 
 728   // Choose a new collection set.  Marks the chosen regions as being
 729   // "in_collection_set", and links them together.  The head and number of
 730   // the collection set are available via access methods.
 731   void finalize_cset(double target_pause_time_ms, EvacuationInfo& evacuation_info);
 732 
 733   // The head of the list (via "next_in_collection_set()") representing the
 734   // current collection set.
 735   HeapRegion* collection_set() { return _collection_set; }
 736 
 737   void clear_collection_set() { _collection_set = NULL; }
 738 
 739   // Add old region "hr" to the CSet.
 740   void add_old_region_to_cset(HeapRegion* hr);
 741 
 742   // Incremental CSet Support
 743 
 744   // The head of the incrementally built collection set.
 745   HeapRegion* inc_cset_head() { return _inc_cset_head; }
 746 
 747   // The tail of the incrementally built collection set.
 748   HeapRegion* inc_set_tail() { return _inc_cset_tail; }
 749 
 750   // Initialize incremental collection set info.
 751   void start_incremental_cset_building();
 752 
 753   // Perform any final calculations on the incremental CSet fields
 754   // before we can use them.
 755   void finalize_incremental_cset_building();
 756 
 757   void clear_incremental_cset() {
 758     _inc_cset_head = NULL;
 759     _inc_cset_tail = NULL;
 760   }
 761 
 762   // Stop adding regions to the incremental collection set
 763   void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
 764 
 765   // Add information about hr to the aggregated information for the
 766   // incrementally built collection set.
 767   void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
 768 
 769   // Update information about hr in the aggregated information for
 770   // the incrementally built collection set.
 771   void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
 772 
 773 private:
 774   // Update the incremental cset information when adding a region
 775   // (should not be called directly).
 776   void add_region_to_incremental_cset_common(HeapRegion* hr);
 777 
 778 public:
 779   // Add hr to the LHS of the incremental collection set.
 780   void add_region_to_incremental_cset_lhs(HeapRegion* hr);
 781 
 782   // Add hr to the RHS of the incremental collection set.
 783   void add_region_to_incremental_cset_rhs(HeapRegion* hr);
 784 
 785 #ifndef PRODUCT
 786   void print_collection_set(HeapRegion* list_head, outputStream* st);
 787 #endif // !PRODUCT
 788 
 789   bool initiate_conc_mark_if_possible()       { return _initiate_conc_mark_if_possible;  }
 790   void set_initiate_conc_mark_if_possible()   { _initiate_conc_mark_if_possible = true;  }
 791   void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
 792 
 793   bool during_initial_mark_pause()      { return _during_initial_mark_pause;  }
 794   void set_during_initial_mark_pause()  { _during_initial_mark_pause = true;  }
 795   void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
 796 
 797   // This sets the initiate_conc_mark_if_possible() flag to start a
 798   // new cycle, as long as we are not already in one. It's best if it
 799   // is called during a safepoint when the test whether a cycle is in
 800   // progress or not is stable.
 801   bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
 802 
 803   // This is called at the very beginning of an evacuation pause (it
 804   // has to be the first thing that the pause does). If
 805   // initiate_conc_mark_if_possible() is true, and the concurrent
 806   // marking thread has completed its work during the previous cycle,
 807   // it will set during_initial_mark_pause() to so that the pause does
 808   // the initial-mark work and start a marking cycle.
 809   void decide_on_conc_mark_initiation();
 810 
 811   // If an expansion would be appropriate, because recent GC overhead had
 812   // exceeded the desired limit, return an amount to expand by.
 813   virtual size_t expansion_amount();
 814 
 815   // Print tracing information.
 816   void print_tracing_info() const;
 817 
 818   // Print stats on young survival ratio
 819   void print_yg_surv_rate_info() const;
 820 
 821   void finished_recalculating_age_indexes(bool is_survivors) {
 822     if (is_survivors) {
 823       _survivor_surv_rate_group->finished_recalculating_age_indexes();
 824     } else {
 825       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
 826     }
 827     // do that for any other surv rate groups
 828   }
 829 
 830   size_t young_list_target_length() const { return _young_list_target_length; }
 831 
 832   bool is_young_list_full();
 833 
 834   bool can_expand_young_list();
 835 
 836   uint young_list_max_length() {
 837     return _young_list_max_length;
 838   }
 839 
 840   bool gcs_are_young() {
 841     return _gcs_are_young;
 842   }
 843   void set_gcs_are_young(bool gcs_are_young) {
 844     _gcs_are_young = gcs_are_young;
 845   }
 846 
 847   bool adaptive_young_list_length() {
 848     return _young_gen_sizer->adaptive_young_list_length();
 849   }
 850 
 851 private:
 852   //
 853   // Survivor regions policy.
 854   //
 855 
 856   // Current tenuring threshold, set to 0 if the collector reaches the
 857   // maximum amount of survivors regions.
 858   uint _tenuring_threshold;
 859 
 860   // The limit on the number of regions allocated for survivors.
 861   uint _max_survivor_regions;
 862 
 863   // For reporting purposes.
 864   // The value of _heap_bytes_before_gc is also used to calculate
 865   // the cost of copying.
 866 
 867   size_t _eden_used_bytes_before_gc;         // Eden occupancy before GC
 868   size_t _survivor_used_bytes_before_gc;     // Survivor occupancy before GC
 869   size_t _heap_used_bytes_before_gc;         // Heap occupancy before GC
 870   size_t _metaspace_used_bytes_before_gc;    // Metaspace occupancy before GC
 871 
 872   size_t _eden_capacity_bytes_before_gc;     // Eden capacity before GC
 873   size_t _heap_capacity_bytes_before_gc;     // Heap capacity before GC
 874 
 875   // The amount of survivor regions after a collection.
 876   uint _recorded_survivor_regions;
 877   // List of survivor regions.
 878   HeapRegion* _recorded_survivor_head;
 879   HeapRegion* _recorded_survivor_tail;
 880 
 881   ageTable _survivors_age_table;
 882 
 883 public:
 884   uint tenuring_threshold() const { return _tenuring_threshold; }
 885 
 886   static const uint REGIONS_UNLIMITED = (uint) -1;
 887 
 888   uint max_regions(InCSetState dest) {
 889     switch (dest.value()) {
 890       case InCSetState::Young:
 891         return _max_survivor_regions;
 892       case InCSetState::Old:
 893         return REGIONS_UNLIMITED;
 894       default:
 895         assert(false, err_msg("Unknown dest state: " CSETSTATE_FORMAT, dest.value()));
 896         break;
 897     }
 898     // keep some compilers happy
 899     return 0;
 900   }
 901 
 902   void note_start_adding_survivor_regions() {
 903     _survivor_surv_rate_group->start_adding_regions();
 904   }
 905 
 906   void note_stop_adding_survivor_regions() {
 907     _survivor_surv_rate_group->stop_adding_regions();
 908   }
 909 
 910   void record_survivor_regions(uint regions,
 911                                HeapRegion* head,
 912                                HeapRegion* tail) {
 913     _recorded_survivor_regions = regions;
 914     _recorded_survivor_head    = head;
 915     _recorded_survivor_tail    = tail;
 916   }
 917 
 918   uint recorded_survivor_regions() {
 919     return _recorded_survivor_regions;
 920   }
 921 
 922   void record_thread_age_table(ageTable* age_table) {
 923     _survivors_age_table.merge_par(age_table);
 924   }
 925 
 926   void update_max_gc_locker_expansion();
 927 
 928   // Calculates survivor space parameters.
 929   void update_survivors_policy();
 930 
 931   virtual void post_heap_initialize();
 932 };
 933 
 934 // This should move to some place more general...
 935 
 936 // If we have "n" measurements, and we've kept track of their "sum" and the
 937 // "sum_of_squares" of the measurements, this returns the variance of the
 938 // sequence.
 939 inline double variance(int n, double sum_of_squares, double sum) {
 940   double n_d = (double)n;
 941   double avg = sum/n_d;
 942   return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
 943 }
 944 
 945 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
--- EOF ---