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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  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 // TraceYoungGenTime 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 old) while TraceOldGenTime collects data about full GCs.
  44 class TraceYoungGenTimeData : 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    TraceYoungGenTimeData() : _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 TraceOldGenTimeData : 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 // every time 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   // Update the given values for minimum and maximum young gen length in regions
 140   // given the number of heap regions depending on the kind of sizing algorithm.
 141   void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
 142 
 143 public:
 144   G1YoungGenSizer();
 145   // Calculate the maximum length of the young gen given the number of regions
 146   // depending on the sizing algorithm.
 147   uint max_young_length(uint number_of_heap_regions);
 148 
 149   void heap_size_changed(uint new_number_of_heap_regions);
 150   uint min_desired_young_length() {
 151     return _min_desired_young_length;
 152   }
 153   uint max_desired_young_length() {
 154     return _max_desired_young_length;
 155   }
 156   bool adaptive_young_list_length() {
 157     return _adaptive_size;
 158   }
 159 };
 160 
 161 class G1CollectorPolicy: public CollectorPolicy {
 162 private:
 163   // either equal to the number of parallel threads, if ParallelGCThreads
 164   // has been set, or 1 otherwise
 165   int _parallel_gc_threads;
 166 
 167   // The number of GC threads currently active.
 168   uintx _no_of_gc_threads;
 169 
 170   enum SomePrivateConstants {
 171     NumPrevPausesForHeuristics = 10
 172   };
 173 
 174   G1MMUTracker* _mmu_tracker;
 175 
 176   void initialize_alignments();
 177   void initialize_flags();
 178 
 179   CollectionSetChooser* _collectionSetChooser;
 180 
 181   double _full_collection_start_sec;
 182   uint   _cur_collection_pause_used_regions_at_start;
 183 
 184   // These exclude marking times.
 185   TruncatedSeq* _recent_gc_times_ms;
 186 
 187   TruncatedSeq* _concurrent_mark_remark_times_ms;
 188   TruncatedSeq* _concurrent_mark_cleanup_times_ms;
 189 
 190   TraceYoungGenTimeData _trace_young_gen_time_data;
 191   TraceOldGenTimeData   _trace_old_gen_time_data;
 192 
 193   double _stop_world_start;
 194 
 195   // indicates whether we are in young or mixed GC mode
 196   bool _gcs_are_young;
 197 
 198   uint _young_list_target_length;
 199   uint _young_list_fixed_length;
 200 
 201   // The max number of regions we can extend the eden by while the GC
 202   // locker is active. This should be >= _young_list_target_length;
 203   uint _young_list_max_length;
 204 
 205   bool _last_gc_was_young;
 206 
 207   bool _during_marking;
 208   bool _in_marking_window;
 209   bool _in_marking_window_im;
 210 
 211   SurvRateGroup* _short_lived_surv_rate_group;
 212   SurvRateGroup* _survivor_surv_rate_group;
 213   // add here any more surv rate groups
 214 
 215   double _gc_overhead_perc;
 216 
 217   double _reserve_factor;
 218   uint   _reserve_regions;
 219 
 220   bool during_marking() {
 221     return _during_marking;
 222   }
 223 
 224   enum PredictionConstants {
 225     TruncatedSeqLength = 10
 226   };
 227 
 228   TruncatedSeq* _alloc_rate_ms_seq;
 229   double        _prev_collection_pause_end_ms;
 230 
 231   TruncatedSeq* _rs_length_diff_seq;
 232   TruncatedSeq* _cost_per_card_ms_seq;
 233   TruncatedSeq* _young_cards_per_entry_ratio_seq;
 234   TruncatedSeq* _mixed_cards_per_entry_ratio_seq;
 235   TruncatedSeq* _cost_per_entry_ms_seq;
 236   TruncatedSeq* _mixed_cost_per_entry_ms_seq;
 237   TruncatedSeq* _cost_per_byte_ms_seq;
 238   TruncatedSeq* _constant_other_time_ms_seq;
 239   TruncatedSeq* _young_other_cost_per_region_ms_seq;
 240   TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
 241 
 242   TruncatedSeq* _pending_cards_seq;
 243   TruncatedSeq* _rs_lengths_seq;
 244 
 245   TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
 246 
 247   G1YoungGenSizer* _young_gen_sizer;
 248 
 249   uint _eden_cset_region_length;
 250   uint _survivor_cset_region_length;
 251   uint _old_cset_region_length;
 252 
 253   void init_cset_region_lengths(uint eden_cset_region_length,
 254                                 uint survivor_cset_region_length);
 255 
 256   uint eden_cset_region_length()     { return _eden_cset_region_length;     }
 257   uint survivor_cset_region_length() { return _survivor_cset_region_length; }
 258   uint old_cset_region_length()      { return _old_cset_region_length;      }
 259 
 260   uint _free_regions_at_end_of_collection;
 261 
 262   size_t _recorded_rs_lengths;
 263   size_t _max_rs_lengths;
 264   double _sigma;
 265 
 266   size_t _rs_lengths_prediction;
 267 
 268   double sigma() { return _sigma; }
 269 
 270   // A function that prevents us putting too much stock in small sample
 271   // sets.  Returns a number between 2.0 and 1.0, depending on the number
 272   // of samples.  5 or more samples yields one; fewer scales linearly from
 273   // 2.0 at 1 sample to 1.0 at 5.
 274   double confidence_factor(int samples) {
 275     if (samples > 4) return 1.0;
 276     else return  1.0 + sigma() * ((double)(5 - samples))/2.0;
 277   }
 278 
 279   double get_new_neg_prediction(TruncatedSeq* seq) {
 280     return seq->davg() - sigma() * seq->dsd();
 281   }
 282 
 283 #ifndef PRODUCT
 284   bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
 285 #endif // PRODUCT
 286 
 287   void adjust_concurrent_refinement(double update_rs_time,
 288                                     double update_rs_processed_buffers,
 289                                     double goal_ms);
 290 
 291   uintx no_of_gc_threads() { return _no_of_gc_threads; }
 292   void set_no_of_gc_threads(uintx v) { _no_of_gc_threads = v; }
 293 
 294   double _pause_time_target_ms;
 295 
 296   size_t _pending_cards;
 297 
 298 public:
 299   // Accessors
 300 
 301   void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
 302     hr->set_young();
 303     hr->install_surv_rate_group(_short_lived_surv_rate_group);
 304     hr->set_young_index_in_cset(young_index_in_cset);
 305   }
 306 
 307   void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
 308     assert(hr->is_young() && hr->is_survivor(), "pre-condition");
 309     hr->install_surv_rate_group(_survivor_surv_rate_group);
 310     hr->set_young_index_in_cset(young_index_in_cset);
 311   }
 312 
 313 #ifndef PRODUCT
 314   bool verify_young_ages();
 315 #endif // PRODUCT
 316 
 317   double get_new_prediction(TruncatedSeq* seq) {
 318     return MAX2(seq->davg() + sigma() * seq->dsd(),
 319                 seq->davg() * confidence_factor(seq->num()));
 320   }
 321 
 322   void record_max_rs_lengths(size_t rs_lengths) {
 323     _max_rs_lengths = rs_lengths;
 324   }
 325 
 326   size_t predict_rs_length_diff() {
 327     return (size_t) get_new_prediction(_rs_length_diff_seq);
 328   }
 329 
 330   double predict_alloc_rate_ms() {
 331     return get_new_prediction(_alloc_rate_ms_seq);
 332   }
 333 
 334   double predict_cost_per_card_ms() {
 335     return get_new_prediction(_cost_per_card_ms_seq);
 336   }
 337 
 338   double predict_rs_update_time_ms(size_t pending_cards) {
 339     return (double) pending_cards * predict_cost_per_card_ms();
 340   }
 341 
 342   double predict_young_cards_per_entry_ratio() {
 343     return get_new_prediction(_young_cards_per_entry_ratio_seq);
 344   }
 345 
 346   double predict_mixed_cards_per_entry_ratio() {
 347     if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
 348       return predict_young_cards_per_entry_ratio();
 349     } else {
 350       return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
 351     }
 352   }
 353 
 354   size_t predict_young_card_num(size_t rs_length) {
 355     return (size_t) ((double) rs_length *
 356                      predict_young_cards_per_entry_ratio());
 357   }
 358 
 359   size_t predict_non_young_card_num(size_t rs_length) {
 360     return (size_t) ((double) rs_length *
 361                      predict_mixed_cards_per_entry_ratio());
 362   }
 363 
 364   double predict_rs_scan_time_ms(size_t card_num) {
 365     if (gcs_are_young()) {
 366       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 367     } else {
 368       return predict_mixed_rs_scan_time_ms(card_num);
 369     }
 370   }
 371 
 372   double predict_mixed_rs_scan_time_ms(size_t card_num) {
 373     if (_mixed_cost_per_entry_ms_seq->num() < 3) {
 374       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 375     } else {
 376       return (double) (card_num *
 377                        get_new_prediction(_mixed_cost_per_entry_ms_seq));
 378     }
 379   }
 380 
 381   double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
 382     if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
 383       return (1.1 * (double) bytes_to_copy) *
 384               get_new_prediction(_cost_per_byte_ms_seq);
 385     } else {
 386       return (double) bytes_to_copy *
 387              get_new_prediction(_cost_per_byte_ms_during_cm_seq);
 388     }
 389   }
 390 
 391   double predict_object_copy_time_ms(size_t bytes_to_copy) {
 392     if (_in_marking_window && !_in_marking_window_im) {
 393       return predict_object_copy_time_ms_during_cm(bytes_to_copy);
 394     } else {
 395       return (double) bytes_to_copy *
 396               get_new_prediction(_cost_per_byte_ms_seq);
 397     }
 398   }
 399 
 400   double predict_constant_other_time_ms() {
 401     return get_new_prediction(_constant_other_time_ms_seq);
 402   }
 403 
 404   double predict_young_other_time_ms(size_t young_num) {
 405     return (double) young_num *
 406            get_new_prediction(_young_other_cost_per_region_ms_seq);
 407   }
 408 
 409   double predict_non_young_other_time_ms(size_t non_young_num) {
 410     return (double) non_young_num *
 411            get_new_prediction(_non_young_other_cost_per_region_ms_seq);
 412   }
 413 
 414   double predict_base_elapsed_time_ms(size_t pending_cards);
 415   double predict_base_elapsed_time_ms(size_t pending_cards,
 416                                       size_t scanned_cards);
 417   size_t predict_bytes_to_copy(HeapRegion* hr);
 418   double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc);
 419 
 420   void set_recorded_rs_lengths(size_t rs_lengths);
 421 
 422   uint cset_region_length()       { return young_cset_region_length() +
 423                                            old_cset_region_length(); }
 424   uint young_cset_region_length() { return eden_cset_region_length() +
 425                                            survivor_cset_region_length(); }
 426 
 427   double predict_survivor_regions_evac_time();
 428 
 429   void cset_regions_freed() {
 430     bool propagate = _last_gc_was_young && !_in_marking_window;
 431     _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
 432     _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
 433     // also call it on any more surv rate groups
 434   }
 435 
 436   G1MMUTracker* mmu_tracker() {
 437     return _mmu_tracker;
 438   }
 439 
 440   double max_pause_time_ms() {
 441     return _mmu_tracker->max_gc_time() * 1000.0;
 442   }
 443 
 444   double predict_remark_time_ms() {
 445     return get_new_prediction(_concurrent_mark_remark_times_ms);
 446   }
 447 
 448   double predict_cleanup_time_ms() {
 449     return get_new_prediction(_concurrent_mark_cleanup_times_ms);
 450   }
 451 
 452   // Returns an estimate of the survival rate of the region at yg-age
 453   // "yg_age".
 454   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
 455     TruncatedSeq* seq = surv_rate_group->get_seq(age);
 456     if (seq->num() == 0)
 457       gclog_or_tty->print("BARF! age is %d", age);
 458     guarantee( seq->num() > 0, "invariant" );
 459     double pred = get_new_prediction(seq);
 460     if (pred > 1.0)
 461       pred = 1.0;
 462     return pred;
 463   }
 464 
 465   double predict_yg_surv_rate(int age) {
 466     return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
 467   }
 468 
 469   double accum_yg_surv_rate_pred(int age) {
 470     return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
 471   }
 472 
 473 private:
 474   // Statistics kept per GC stoppage, pause or full.
 475   TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
 476 
 477   // Add a new GC of the given duration and end time to the record.
 478   void update_recent_gc_times(double end_time_sec, double elapsed_ms);
 479 
 480   // The head of the list (via "next_in_collection_set()") representing the
 481   // current collection set. Set from the incrementally built collection
 482   // set at the start of the pause.
 483   HeapRegion* _collection_set;
 484 
 485   // The number of bytes in the collection set before the pause. Set from
 486   // the incrementally built collection set at the start of an evacuation
 487   // pause, and incremented in finalize_cset() when adding old regions
 488   // (if any) to the collection set.
 489   size_t _collection_set_bytes_used_before;
 490 
 491   // The number of bytes copied during the GC.
 492   size_t _bytes_copied_during_gc;
 493 
 494   // The associated information that is maintained while the incremental
 495   // collection set is being built with young regions. Used to populate
 496   // the recorded info for the evacuation pause.
 497 
 498   enum CSetBuildType {
 499     Active,             // We are actively building the collection set
 500     Inactive            // We are not actively building the collection set
 501   };
 502 
 503   CSetBuildType _inc_cset_build_state;
 504 
 505   // The head of the incrementally built collection set.
 506   HeapRegion* _inc_cset_head;
 507 
 508   // The tail of the incrementally built collection set.
 509   HeapRegion* _inc_cset_tail;
 510 
 511   // The number of bytes in the incrementally built collection set.
 512   // Used to set _collection_set_bytes_used_before at the start of
 513   // an evacuation pause.
 514   size_t _inc_cset_bytes_used_before;
 515 
 516   // Used to record the highest end of heap region in collection set
 517   HeapWord* _inc_cset_max_finger;
 518 
 519   // The RSet lengths recorded for regions in the CSet. It is updated
 520   // by the thread that adds a new region to the CSet. We assume that
 521   // only one thread can be allocating a new CSet region (currently,
 522   // it does so after taking the Heap_lock) hence no need to
 523   // synchronize updates to this field.
 524   size_t _inc_cset_recorded_rs_lengths;
 525 
 526   // A concurrent refinement thread periodically samples the young
 527   // region RSets and needs to update _inc_cset_recorded_rs_lengths as
 528   // the RSets grow. Instead of having to synchronize updates to that
 529   // field we accumulate them in this field and add it to
 530   // _inc_cset_recorded_rs_lengths_diffs at the start of a GC.
 531   ssize_t _inc_cset_recorded_rs_lengths_diffs;
 532 
 533   // The predicted elapsed time it will take to collect the regions in
 534   // the CSet. This is updated by the thread that adds a new region to
 535   // the CSet. See the comment for _inc_cset_recorded_rs_lengths about
 536   // MT-safety assumptions.
 537   double _inc_cset_predicted_elapsed_time_ms;
 538 
 539   // See the comment for _inc_cset_recorded_rs_lengths_diffs.
 540   double _inc_cset_predicted_elapsed_time_ms_diffs;
 541 
 542   // Stash a pointer to the g1 heap.
 543   G1CollectedHeap* _g1;
 544 
 545   G1GCPhaseTimes* _phase_times;
 546 
 547   // The ratio of gc time to elapsed time, computed over recent pauses.
 548   double _recent_avg_pause_time_ratio;
 549 
 550   double recent_avg_pause_time_ratio() {
 551     return _recent_avg_pause_time_ratio;
 552   }
 553 
 554   // At the end of a pause we check the heap occupancy and we decide
 555   // whether we will start a marking cycle during the next pause. If
 556   // we decide that we want to do that, we will set this parameter to
 557   // true. So, this parameter will stay true between the end of a
 558   // pause and the beginning of a subsequent pause (not necessarily
 559   // the next one, see the comments on the next field) when we decide
 560   // that we will indeed start a marking cycle and do the initial-mark
 561   // work.
 562   volatile bool _initiate_conc_mark_if_possible;
 563 
 564   // If initiate_conc_mark_if_possible() is set at the beginning of a
 565   // pause, it is a suggestion that the pause should start a marking
 566   // cycle by doing the initial-mark work. However, it is possible
 567   // that the concurrent marking thread is still finishing up the
 568   // previous marking cycle (e.g., clearing the next marking
 569   // bitmap). If that is the case we cannot start a new cycle and
 570   // we'll have to wait for the concurrent marking thread to finish
 571   // what it is doing. In this case we will postpone the marking cycle
 572   // initiation decision for the next pause. When we eventually decide
 573   // to start a cycle, we will set _during_initial_mark_pause which
 574   // will stay true until the end of the initial-mark pause and it's
 575   // the condition that indicates that a pause is doing the
 576   // initial-mark work.
 577   volatile bool _during_initial_mark_pause;
 578 
 579   bool _last_young_gc;
 580 
 581   // This set of variables tracks the collector efficiency, in order to
 582   // determine whether we should initiate a new marking.
 583   double _cur_mark_stop_world_time_ms;
 584   double _mark_remark_start_sec;
 585   double _mark_cleanup_start_sec;
 586 
 587   // Update the young list target length either by setting it to the
 588   // desired fixed value or by calculating it using G1's pause
 589   // prediction model. If no rs_lengths parameter is passed, predict
 590   // the RS lengths using the prediction model, otherwise use the
 591   // given rs_lengths as the prediction.
 592   void update_young_list_target_length(size_t rs_lengths = (size_t) -1);
 593 
 594   // Calculate and return the minimum desired young list target
 595   // length. This is the minimum desired young list length according
 596   // to the user's inputs.
 597   uint calculate_young_list_desired_min_length(uint base_min_length);
 598 
 599   // Calculate and return the maximum desired young list target
 600   // length. This is the maximum desired young list length according
 601   // to the user's inputs.
 602   uint calculate_young_list_desired_max_length();
 603 
 604   // Calculate and return the maximum young list target length that
 605   // can fit into the pause time goal. The parameters are: rs_lengths
 606   // represent the prediction of how large the young RSet lengths will
 607   // be, base_min_length is the already existing number of regions in
 608   // the young list, min_length and max_length are the desired min and
 609   // max young list length according to the user's inputs.
 610   uint calculate_young_list_target_length(size_t rs_lengths,
 611                                           uint base_min_length,
 612                                           uint desired_min_length,
 613                                           uint desired_max_length);
 614 
 615   // Calculate and return chunk size (in number of regions) for parallel
 616   // concurrent mark cleanup.
 617   uint calculate_parallel_work_chunk_size(int n_workers, uint n_regions);
 618 
 619   // Check whether a given young length (young_length) fits into the
 620   // given target pause time and whether the prediction for the amount
 621   // of objects to be copied for the given length will fit into the
 622   // given free space (expressed by base_free_regions).  It is used by
 623   // calculate_young_list_target_length().
 624   bool predict_will_fit(uint young_length, double base_time_ms,
 625                         uint base_free_regions, double target_pause_time_ms);
 626 
 627   // Calculate the minimum number of old regions we'll add to the CSet
 628   // during a mixed GC.
 629   uint calc_min_old_cset_length();
 630 
 631   // Calculate the maximum number of old regions we'll add to the CSet
 632   // during a mixed GC.
 633   uint calc_max_old_cset_length();
 634 
 635   // Returns the given amount of uncollected reclaimable space
 636   // as a percentage of the current heap capacity.
 637   double reclaimable_bytes_perc(size_t reclaimable_bytes);
 638 
 639 public:
 640 
 641   G1CollectorPolicy();
 642 
 643   virtual G1CollectorPolicy* as_g1_policy() { return this; }
 644 
 645   virtual CollectorPolicy::Name kind() {
 646     return CollectorPolicy::G1CollectorPolicyKind;
 647   }
 648 
 649   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 650 
 651   // Check the current value of the young list RSet lengths and
 652   // compare it against the last prediction. If the current value is
 653   // higher, recalculate the young list target length prediction.
 654   void revise_young_list_target_length_if_necessary();
 655 
 656   // This should be called after the heap is resized.
 657   void record_new_heap_size(uint new_number_of_regions);
 658 
 659   void init();
 660 
 661   // Create jstat counters for the policy.
 662   virtual void initialize_gc_policy_counters();
 663 
 664   virtual HeapWord* mem_allocate_work(size_t size,
 665                                       bool is_tlab,
 666                                       bool* gc_overhead_limit_was_exceeded);
 667 
 668   // This method controls how a collector handles one or more
 669   // of its generations being fully allocated.
 670   virtual HeapWord* satisfy_failed_allocation(size_t size,
 671                                               bool is_tlab);
 672 
 673   BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
 674 
 675   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 676 
 677   // Record the start and end of an evacuation pause.
 678   void record_collection_pause_start(double start_time_sec);
 679   void record_collection_pause_end(double pause_time_ms, EvacuationInfo& evacuation_info);
 680 
 681   // Record the start and end of a full collection.
 682   void record_full_collection_start();
 683   void record_full_collection_end();
 684 
 685   // Must currently be called while the world is stopped.
 686   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 687 
 688   // Record start and end of remark.
 689   void record_concurrent_mark_remark_start();
 690   void record_concurrent_mark_remark_end();
 691 
 692   // Record start, end, and completion of cleanup.
 693   void record_concurrent_mark_cleanup_start();
 694   void record_concurrent_mark_cleanup_end(int n_workers);
 695   void record_concurrent_mark_cleanup_completed();
 696 
 697   // Records the information about the heap size for reporting in
 698   // print_detailed_heap_transition
 699   void record_heap_size_info_at_start(bool full);
 700 
 701   // Print heap sizing transition (with less and more detail).
 702   void print_heap_transition();
 703   void print_detailed_heap_transition(bool full = false);
 704 
 705   void record_stop_world_start();
 706   void record_concurrent_pause();
 707 
 708   // Record how much space we copied during a GC. This is typically
 709   // called when a GC alloc region is being retired.
 710   void record_bytes_copied_during_gc(size_t bytes) {
 711     _bytes_copied_during_gc += bytes;
 712   }
 713 
 714   // The amount of space we copied during a GC.
 715   size_t bytes_copied_during_gc() {
 716     return _bytes_copied_during_gc;
 717   }
 718 
 719   // Determine whether there are candidate regions so that the
 720   // next GC should be mixed. The two action strings are used
 721   // in the ergo output when the method returns true or false.
 722   bool next_gc_should_be_mixed(const char* true_action_str,
 723                                const char* false_action_str);
 724 
 725   // Choose a new collection set.  Marks the chosen regions as being
 726   // "in_collection_set", and links them together.  The head and number of
 727   // the collection set are available via access methods.
 728   void finalize_cset(double target_pause_time_ms, EvacuationInfo& evacuation_info);
 729 
 730   // The head of the list (via "next_in_collection_set()") representing the
 731   // current collection set.
 732   HeapRegion* collection_set() { return _collection_set; }
 733 
 734   void clear_collection_set() { _collection_set = NULL; }
 735 
 736   // Add old region "hr" to the CSet.
 737   void add_old_region_to_cset(HeapRegion* hr);
 738 
 739   // Incremental CSet Support
 740 
 741   // The head of the incrementally built collection set.
 742   HeapRegion* inc_cset_head() { return _inc_cset_head; }
 743 
 744   // The tail of the incrementally built collection set.
 745   HeapRegion* inc_set_tail() { return _inc_cset_tail; }
 746 
 747   // Initialize incremental collection set info.
 748   void start_incremental_cset_building();
 749 
 750   // Perform any final calculations on the incremental CSet fields
 751   // before we can use them.
 752   void finalize_incremental_cset_building();
 753 
 754   void clear_incremental_cset() {
 755     _inc_cset_head = NULL;
 756     _inc_cset_tail = NULL;
 757   }
 758 
 759   // Stop adding regions to the incremental collection set
 760   void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
 761 
 762   // Add information about hr to the aggregated information for the
 763   // incrementally built collection set.
 764   void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
 765 
 766   // Update information about hr in the aggregated information for
 767   // the incrementally built collection set.
 768   void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
 769 
 770 private:
 771   // Update the incremental cset information when adding a region
 772   // (should not be called directly).
 773   void add_region_to_incremental_cset_common(HeapRegion* hr);
 774 
 775 public:
 776   // Add hr to the LHS of the incremental collection set.
 777   void add_region_to_incremental_cset_lhs(HeapRegion* hr);
 778 
 779   // Add hr to the RHS of the incremental collection set.
 780   void add_region_to_incremental_cset_rhs(HeapRegion* hr);
 781 
 782 #ifndef PRODUCT
 783   void print_collection_set(HeapRegion* list_head, outputStream* st);
 784 #endif // !PRODUCT
 785 
 786   bool initiate_conc_mark_if_possible()       { return _initiate_conc_mark_if_possible;  }
 787   void set_initiate_conc_mark_if_possible()   { _initiate_conc_mark_if_possible = true;  }
 788   void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
 789 
 790   bool during_initial_mark_pause()      { return _during_initial_mark_pause;  }
 791   void set_during_initial_mark_pause()  { _during_initial_mark_pause = true;  }
 792   void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
 793 
 794   // This sets the initiate_conc_mark_if_possible() flag to start a
 795   // new cycle, as long as we are not already in one. It's best if it
 796   // is called during a safepoint when the test whether a cycle is in
 797   // progress or not is stable.
 798   bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
 799 
 800   // This is called at the very beginning of an evacuation pause (it
 801   // has to be the first thing that the pause does). If
 802   // initiate_conc_mark_if_possible() is true, and the concurrent
 803   // marking thread has completed its work during the previous cycle,
 804   // it will set during_initial_mark_pause() to so that the pause does
 805   // the initial-mark work and start a marking cycle.
 806   void decide_on_conc_mark_initiation();
 807 
 808   // If an expansion would be appropriate, because recent GC overhead had
 809   // exceeded the desired limit, return an amount to expand by.
 810   size_t expansion_amount();
 811 
 812   // Print tracing information.
 813   void print_tracing_info() const;
 814 
 815   // Print stats on young survival ratio
 816   void print_yg_surv_rate_info() const;
 817 
 818   void finished_recalculating_age_indexes(bool is_survivors) {
 819     if (is_survivors) {
 820       _survivor_surv_rate_group->finished_recalculating_age_indexes();
 821     } else {
 822       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
 823     }
 824     // do that for any other surv rate groups
 825   }
 826 
 827   size_t young_list_target_length() const { return _young_list_target_length; }
 828 
 829   bool is_young_list_full() {
 830     uint young_list_length = _g1->young_list()->length();
 831     uint young_list_target_length = _young_list_target_length;
 832     return young_list_length >= young_list_target_length;
 833   }
 834 
 835   bool can_expand_young_list() {
 836     uint young_list_length = _g1->young_list()->length();
 837     uint young_list_max_length = _young_list_max_length;
 838     return young_list_length < young_list_max_length;
 839   }
 840 
 841   uint young_list_max_length() {
 842     return _young_list_max_length;
 843   }
 844 
 845   bool gcs_are_young() {
 846     return _gcs_are_young;
 847   }
 848   void set_gcs_are_young(bool gcs_are_young) {
 849     _gcs_are_young = gcs_are_young;
 850   }
 851 
 852   bool adaptive_young_list_length() {
 853     return _young_gen_sizer->adaptive_young_list_length();
 854   }
 855 
 856 private:
 857   //
 858   // Survivor regions policy.
 859   //
 860 
 861   // Current tenuring threshold, set to 0 if the collector reaches the
 862   // maximum amount of survivors regions.
 863   uint _tenuring_threshold;
 864 
 865   // The limit on the number of regions allocated for survivors.
 866   uint _max_survivor_regions;
 867 
 868   // For reporting purposes.
 869   // The value of _heap_bytes_before_gc is also used to calculate
 870   // the cost of copying.
 871 
 872   size_t _eden_used_bytes_before_gc;         // Eden occupancy before GC
 873   size_t _survivor_used_bytes_before_gc;     // Survivor occupancy before GC
 874   size_t _heap_used_bytes_before_gc;         // Heap occupancy before GC
 875   size_t _metaspace_used_bytes_before_gc;    // Metaspace occupancy before GC
 876 
 877   size_t _eden_capacity_bytes_before_gc;     // Eden capacity before GC
 878   size_t _heap_capacity_bytes_before_gc;     // Heap capacity before GC
 879 
 880   // The amount of survivor regions after a collection.
 881   uint _recorded_survivor_regions;
 882   // List of survivor regions.
 883   HeapRegion* _recorded_survivor_head;
 884   HeapRegion* _recorded_survivor_tail;
 885 
 886   ageTable _survivors_age_table;
 887 
 888 public:
 889   uint tenuring_threshold() const { return _tenuring_threshold; }
 890 
 891   inline GCAllocPurpose
 892     evacuation_destination(HeapRegion* src_region, uint age, size_t word_sz) {
 893       if (age < _tenuring_threshold && src_region->is_young()) {
 894         return GCAllocForSurvived;
 895       } else {
 896         return GCAllocForTenured;
 897       }
 898   }
 899 
 900   inline bool track_object_age(GCAllocPurpose purpose) {
 901     return purpose == GCAllocForSurvived;
 902   }
 903 
 904   static const uint REGIONS_UNLIMITED = (uint) -1;
 905 
 906   uint max_regions(int purpose);
 907 
 908   // The limit on regions for a particular purpose is reached.
 909   void note_alloc_region_limit_reached(int purpose) {
 910     if (purpose == GCAllocForSurvived) {
 911       _tenuring_threshold = 0;
 912     }
 913   }
 914 
 915   void note_start_adding_survivor_regions() {
 916     _survivor_surv_rate_group->start_adding_regions();
 917   }
 918 
 919   void note_stop_adding_survivor_regions() {
 920     _survivor_surv_rate_group->stop_adding_regions();
 921   }
 922 
 923   void record_survivor_regions(uint regions,
 924                                HeapRegion* head,
 925                                HeapRegion* tail) {
 926     _recorded_survivor_regions = regions;
 927     _recorded_survivor_head    = head;
 928     _recorded_survivor_tail    = tail;
 929   }
 930 
 931   uint recorded_survivor_regions() {
 932     return _recorded_survivor_regions;
 933   }
 934 
 935   void record_thread_age_table(ageTable* age_table) {
 936     _survivors_age_table.merge_par(age_table);
 937   }
 938 
 939   void update_max_gc_locker_expansion();
 940 
 941   // Calculates survivor space parameters.
 942   void update_survivors_policy();
 943 
 944   virtual void post_heap_initialize();
 945 };
 946 
 947 // This should move to some place more general...
 948 
 949 // If we have "n" measurements, and we've kept track of their "sum" and the
 950 // "sum_of_squares" of the measurements, this returns the variance of the
 951 // sequence.
 952 inline double variance(int n, double sum_of_squares, double sum) {
 953   double n_d = (double)n;
 954   double avg = sum/n_d;
 955   return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
 956 }
 957 
 958 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP