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).
  14  *
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP
  27 
  28 #include "gc_implementation/g1/collectionSetChooser.hpp"
  29 #include "gc_implementation/g1/g1MMUTracker.hpp"
  30 #include "memory/collectorPolicy.hpp"
  31 
  32 // A G1CollectorPolicy makes policy decisions that determine the
  33 // characteristics of the collector.  Examples include:
  34 //   * choice of collection set.
  35 //   * when to collect.
  36 
  37 class HeapRegion;
  38 class CollectionSetChooser;
  39 class G1GCPhaseTimes;
  40 
  41 // TraceGen0Time collects data on _both_ young and mixed evacuation pauses
  42 // (the latter may contain non-young regions - i.e. regions that are
  43 // technically in Gen1) while TraceGen1Time collects data about full GCs.
  44 class TraceGen0TimeData : public CHeapObj<mtGC> {
  45  private:
  46   unsigned  _young_pause_num;
  47   unsigned  _mixed_pause_num;
  48 
  49   NumberSeq _all_stop_world_times_ms;
  50   NumberSeq _all_yield_times_ms;
  51 
  52   NumberSeq _total;
  53   NumberSeq _other;
  54   NumberSeq _root_region_scan_wait;
  55   NumberSeq _parallel;
  56   NumberSeq _ext_root_scan;
  57   NumberSeq _satb_filtering;
  58   NumberSeq _update_rs;
  59   NumberSeq _scan_rs;
  60   NumberSeq _obj_copy;
  61   NumberSeq _termination;
  62   NumberSeq _parallel_other;
  63   NumberSeq _clear_ct;
  64 
  65   void print_summary(const char* str, const NumberSeq* seq) const;
  66   void print_summary_sd(const char* str, const NumberSeq* seq) const;
  67 
  68 public:
  69    TraceGen0TimeData() : _young_pause_num(0), _mixed_pause_num(0) {};
  70   void record_start_collection(double time_to_stop_the_world_ms);
  71   void record_yield_time(double yield_time_ms);
  72   void record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times);
  73   void increment_young_collection_count();
  74   void increment_mixed_collection_count();
  75   void print() const;
  76 };
  77 
  78 class TraceGen1TimeData : public CHeapObj<mtGC> {
  79  private:
  80   NumberSeq _all_full_gc_times;
  81 
  82  public:
  83   void record_full_collection(double full_gc_time_ms);
  84   void print() const;
  85 };
  86 
  87 // There are three command line options related to the young gen size:
  88 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
  89 // just a short form for NewSize==MaxNewSize). G1 will use its internal
  90 // heuristics to calculate the actual young gen size, so these options
  91 // basically only limit the range within which G1 can pick a young gen
  92 // size. Also, these are general options taking byte sizes. G1 will
  93 // internally work with a number of regions instead. So, some rounding
  94 // will occur.
  95 //
  96 // If nothing related to the the young gen size is set on the command
  97 // line we should allow the young gen to be between G1NewSizePercent
  98 // and G1MaxNewSizePercent of the heap size. This means that every time
  99 // the heap size changes, the limits for the young gen size will be
 100 // recalculated.
 101 //
 102 // If only -XX:NewSize is set we should use the specified value as the
 103 // minimum size for young gen. Still using G1MaxNewSizePercent of the
 104 // heap as maximum.
 105 //
 106 // If only -XX:MaxNewSize is set we should use the specified value as the
 107 // maximum size for young gen. Still using G1NewSizePercent of the heap
 108 // as minimum.
 109 //
 110 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
 111 // No updates when the heap size changes. There is a special case when
 112 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
 113 // different heuristic for calculating the collection set when we do mixed
 114 // collection.
 115 //
 116 // If only -XX:NewRatio is set we should use the specified ratio of the heap
 117 // as both min and max. This will be interpreted as "fixed" just like the
 118 // NewSize==MaxNewSize case above. But we will update the min and max
 119 // everytime the heap size changes.
 120 //
 121 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
 122 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
 123 class G1YoungGenSizer : public CHeapObj<mtGC> {
 124 private:
 125   enum SizerKind {
 126     SizerDefaults,
 127     SizerNewSizeOnly,
 128     SizerMaxNewSizeOnly,
 129     SizerMaxAndNewSize,
 130     SizerNewRatio
 131   };
 132   SizerKind _sizer_kind;
 133   uint _min_desired_young_length;
 134   uint _max_desired_young_length;
 135   bool _adaptive_size;
 136   uint calculate_default_min_length(uint new_number_of_heap_regions);
 137   uint calculate_default_max_length(uint new_number_of_heap_regions);
 138 
 139 public:
 140   G1YoungGenSizer();
 141   void heap_size_changed(uint new_number_of_heap_regions);
 142   uint min_desired_young_length() {
 143     return _min_desired_young_length;
 144   }
 145   uint max_desired_young_length() {
 146     return _max_desired_young_length;
 147   }
 148   bool adaptive_young_list_length() {
 149     return _adaptive_size;
 150   }
 151 };
 152 
 153 class G1CollectorPolicy: public CollectorPolicy {
 154 private:
 155   // either equal to the number of parallel threads, if ParallelGCThreads
 156   // has been set, or 1 otherwise
 157   int _parallel_gc_threads;
 158 
 159   // The number of GC threads currently active.
 160   uintx _no_of_gc_threads;
 161 
 162   enum SomePrivateConstants {
 163     NumPrevPausesForHeuristics = 10
 164   };
 165 
 166   G1MMUTracker* _mmu_tracker;
 167 
 168   void initialize_flags();
 169 
 170   void initialize_all() {
 171     initialize_flags();
 172     initialize_size_info();
 173     initialize_perm_generation(PermGen::MarkSweepCompact);
 174   }
 175 
 176   CollectionSetChooser* _collectionSetChooser;
 177 
 178   double _full_collection_start_sec;
 179   size_t _cur_collection_pause_used_at_start_bytes;
 180   uint   _cur_collection_pause_used_regions_at_start;
 181 
 182   // These exclude marking times.
 183   TruncatedSeq* _recent_gc_times_ms;
 184 
 185   TruncatedSeq* _concurrent_mark_remark_times_ms;
 186   TruncatedSeq* _concurrent_mark_cleanup_times_ms;
 187 
 188   TraceGen0TimeData _trace_gen0_time_data;
 189   TraceGen1TimeData _trace_gen1_time_data;
 190 
 191   double _stop_world_start;
 192 
 193   // indicates whether we are in young or mixed GC mode
 194   bool _gcs_are_young;
 195 
 196   uint _young_list_target_length;
 197   uint _young_list_fixed_length;
 198   size_t _prev_eden_capacity; // used for logging
 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   bool                  _last_gc_was_young;
 205 
 206   bool                  _during_marking;
 207   bool                  _in_marking_window;
 208   bool                  _in_marking_window_im;
 209 
 210   SurvRateGroup*        _short_lived_surv_rate_group;
 211   SurvRateGroup*        _survivor_surv_rate_group;
 212   // add here any more surv rate groups
 213 
 214   double                _gc_overhead_perc;
 215 
 216   double _reserve_factor;
 217   uint _reserve_regions;
 218 
 219   bool during_marking() {
 220     return _during_marking;
 221   }
 222 
 223 private:
 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 periodcially samples the young
 527   // region RSets and needs to update _inc_cset_recorded_rs_lengths as
 528   // the RSets grow. Instead of having to syncronize 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 alreay 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   // Check whether a given young length (young_length) fits into the
 616   // given target pause time and whether the prediction for the amount
 617   // of objects to be copied for the given length will fit into the
 618   // given free space (expressed by base_free_regions).  It is used by
 619   // calculate_young_list_target_length().
 620   bool predict_will_fit(uint young_length, double base_time_ms,
 621                         uint base_free_regions, double target_pause_time_ms);
 622 
 623   // Calculate the minimum number of old regions we'll add to the CSet
 624   // during a mixed GC.
 625   uint calc_min_old_cset_length();
 626 
 627   // Calculate the maximum number of old regions we'll add to the CSet
 628   // during a mixed GC.
 629   uint calc_max_old_cset_length();
 630 
 631   // Returns the given amount of uncollected reclaimable space
 632   // as a percentage of the current heap capacity.
 633   double reclaimable_bytes_perc(size_t reclaimable_bytes);
 634 
 635 public:
 636 
 637   G1CollectorPolicy();
 638 
 639   virtual G1CollectorPolicy* as_g1_policy() { return this; }
 640 
 641   virtual CollectorPolicy::Name kind() {
 642     return CollectorPolicy::G1CollectorPolicyKind;
 643   }
 644 
 645   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 646 
 647   // Check the current value of the young list RSet lengths and
 648   // compare it against the last prediction. If the current value is
 649   // higher, recalculate the young list target length prediction.
 650   void revise_young_list_target_length_if_necessary();
 651 
 652   // This should be called after the heap is resized.
 653   void record_new_heap_size(uint new_number_of_regions);
 654 
 655   void init();
 656 
 657   // Create jstat counters for the policy.
 658   virtual void initialize_gc_policy_counters();
 659 
 660   virtual HeapWord* mem_allocate_work(size_t size,
 661                                       bool is_tlab,
 662                                       bool* gc_overhead_limit_was_exceeded);
 663 
 664   // This method controls how a collector handles one or more
 665   // of its generations being fully allocated.
 666   virtual HeapWord* satisfy_failed_allocation(size_t size,
 667                                               bool is_tlab);
 668 
 669   BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
 670 
 671   GenRemSet::Name  rem_set_name()     { return GenRemSet::CardTable; }
 672 
 673   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 674 
 675   // Record the start and end of an evacuation pause.
 676   void record_collection_pause_start(double start_time_sec);
 677   void record_collection_pause_end(double pause_time_ms, EvacuationInfo& evacuation_info);
 678 
 679   // Record the start and end of a full collection.
 680   void record_full_collection_start();
 681   void record_full_collection_end();
 682 
 683   // Must currently be called while the world is stopped.
 684   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 685 
 686   // Record start and end of remark.
 687   void record_concurrent_mark_remark_start();
 688   void record_concurrent_mark_remark_end();
 689 
 690   // Record start, end, and completion of cleanup.
 691   void record_concurrent_mark_cleanup_start();
 692   void record_concurrent_mark_cleanup_end(int no_of_gc_threads);
 693   void record_concurrent_mark_cleanup_completed();
 694 
 695   // Records the information about the heap size for reporting in
 696   // print_detailed_heap_transition
 697   void record_heap_size_info_at_start();
 698 
 699   // Print heap sizing transition (with less and more detail).
 700   void print_heap_transition();
 701   void print_detailed_heap_transition();
 702 
 703   void record_stop_world_start();
 704   void record_concurrent_pause();
 705 
 706   // Record how much space we copied during a GC. This is typically
 707   // called when a GC alloc region is being retired.
 708   void record_bytes_copied_during_gc(size_t bytes) {
 709     _bytes_copied_during_gc += bytes;
 710   }
 711 
 712   // The amount of space we copied during a GC.
 713   size_t bytes_copied_during_gc() {
 714     return _bytes_copied_during_gc;
 715   }
 716 
 717   // Determine whether there are candidate regions so that the
 718   // next GC should be mixed. The two action strings are used
 719   // in the ergo output when the method returns true or false.
 720   bool next_gc_should_be_mixed(const char* true_action_str,
 721                                const char* false_action_str);
 722 
 723   // Choose a new collection set.  Marks the chosen regions as being
 724   // "in_collection_set", and links them together.  The head and number of
 725   // the collection set are available via access methods.
 726   void finalize_cset(double target_pause_time_ms, EvacuationInfo& evacuation_info);
 727 
 728   // The head of the list (via "next_in_collection_set()") representing the
 729   // current collection set.
 730   HeapRegion* collection_set() { return _collection_set; }
 731 
 732   void clear_collection_set() { _collection_set = NULL; }
 733 
 734   // Add old region "hr" to the CSet.
 735   void add_old_region_to_cset(HeapRegion* hr);
 736 
 737   // Incremental CSet Support
 738 
 739   // The head of the incrementally built collection set.
 740   HeapRegion* inc_cset_head() { return _inc_cset_head; }
 741 
 742   // The tail of the incrementally built collection set.
 743   HeapRegion* inc_set_tail() { return _inc_cset_tail; }
 744 
 745   // Initialize incremental collection set info.
 746   void start_incremental_cset_building();
 747 
 748   // Perform any final calculations on the incremental CSet fields
 749   // before we can use them.
 750   void finalize_incremental_cset_building();
 751 
 752   void clear_incremental_cset() {
 753     _inc_cset_head = NULL;
 754     _inc_cset_tail = NULL;
 755   }
 756 
 757   // Stop adding regions to the incremental collection set
 758   void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
 759 
 760   // Add information about hr to the aggregated information for the
 761   // incrementally built collection set.
 762   void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
 763 
 764   // Update information about hr in the aggregated information for
 765   // the incrementally built collection set.
 766   void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
 767 
 768 private:
 769   // Update the incremental cset information when adding a region
 770   // (should not be called directly).
 771   void add_region_to_incremental_cset_common(HeapRegion* hr);
 772 
 773 public:
 774   // Add hr to the LHS of the incremental collection set.
 775   void add_region_to_incremental_cset_lhs(HeapRegion* hr);
 776 
 777   // Add hr to the RHS of the incremental collection set.
 778   void add_region_to_incremental_cset_rhs(HeapRegion* hr);
 779 
 780 #ifndef PRODUCT
 781   void print_collection_set(HeapRegion* list_head, outputStream* st);
 782 #endif // !PRODUCT
 783 
 784   bool initiate_conc_mark_if_possible()       { return _initiate_conc_mark_if_possible;  }
 785   void set_initiate_conc_mark_if_possible()   { _initiate_conc_mark_if_possible = true;  }
 786   void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
 787 
 788   bool during_initial_mark_pause()      { return _during_initial_mark_pause;  }
 789   void set_during_initial_mark_pause()  { _during_initial_mark_pause = true;  }
 790   void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
 791 
 792   // This sets the initiate_conc_mark_if_possible() flag to start a
 793   // new cycle, as long as we are not already in one. It's best if it
 794   // is called during a safepoint when the test whether a cycle is in
 795   // progress or not is stable.
 796   bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
 797 
 798   // This is called at the very beginning of an evacuation pause (it
 799   // has to be the first thing that the pause does). If
 800   // initiate_conc_mark_if_possible() is true, and the concurrent
 801   // marking thread has completed its work during the previous cycle,
 802   // it will set during_initial_mark_pause() to so that the pause does
 803   // the initial-mark work and start a marking cycle.
 804   void decide_on_conc_mark_initiation();
 805 
 806   // If an expansion would be appropriate, because recent GC overhead had
 807   // exceeded the desired limit, return an amount to expand by.
 808   size_t expansion_amount();
 809 
 810   // Print tracing information.
 811   void print_tracing_info() const;
 812 
 813   // Print stats on young survival ratio
 814   void print_yg_surv_rate_info() const;
 815 
 816   void finished_recalculating_age_indexes(bool is_survivors) {
 817     if (is_survivors) {
 818       _survivor_surv_rate_group->finished_recalculating_age_indexes();
 819     } else {
 820       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
 821     }
 822     // do that for any other surv rate groups
 823   }
 824 
 825   bool is_young_list_full() {
 826     uint young_list_length = _g1->young_list()->length();
 827     uint young_list_target_length = _young_list_target_length;
 828     return young_list_length >= young_list_target_length;
 829   }
 830 
 831   bool can_expand_young_list() {
 832     uint young_list_length = _g1->young_list()->length();
 833     uint young_list_max_length = _young_list_max_length;
 834     return young_list_length < young_list_max_length;
 835   }
 836 
 837   uint young_list_max_length() {
 838     return _young_list_max_length;
 839   }
 840 
 841   bool gcs_are_young() {
 842     return _gcs_are_young;
 843   }
 844   void set_gcs_are_young(bool gcs_are_young) {
 845     _gcs_are_young = gcs_are_young;
 846   }
 847 
 848   bool adaptive_young_list_length() {
 849     return _young_gen_sizer->adaptive_young_list_length();
 850   }
 851 
 852 private:
 853   //
 854   // Survivor regions policy.
 855   //
 856 
 857   // Current tenuring threshold, set to 0 if the collector reaches the
 858   // maximum amount of suvivors regions.
 859   int _tenuring_threshold;
 860 
 861   // The limit on the number of regions allocated for survivors.
 862   uint _max_survivor_regions;
 863 
 864   // For reporting purposes.
 865   size_t _eden_bytes_before_gc;
 866   size_t _survivor_bytes_before_gc;
 867   size_t _capacity_before_gc;
 868 
 869   // The amount of survor regions after a collection.
 870   uint _recorded_survivor_regions;
 871   // List of survivor regions.
 872   HeapRegion* _recorded_survivor_head;
 873   HeapRegion* _recorded_survivor_tail;
 874 
 875   ageTable _survivors_age_table;
 876 
 877 public:
 878   uint tenuring_threshold() const { return _tenuring_threshold; }
 879 
 880   inline GCAllocPurpose
 881     evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
 882       if (age < _tenuring_threshold && src_region->is_young()) {
 883         return GCAllocForSurvived;
 884       } else {
 885         return GCAllocForTenured;
 886       }
 887   }
 888 
 889   inline bool track_object_age(GCAllocPurpose purpose) {
 890     return purpose == GCAllocForSurvived;
 891   }
 892 
 893   static const uint REGIONS_UNLIMITED = (uint) -1;
 894 
 895   uint max_regions(int purpose);
 896 
 897   // The limit on regions for a particular purpose is reached.
 898   void note_alloc_region_limit_reached(int purpose) {
 899     if (purpose == GCAllocForSurvived) {
 900       _tenuring_threshold = 0;
 901     }
 902   }
 903 
 904   void note_start_adding_survivor_regions() {
 905     _survivor_surv_rate_group->start_adding_regions();
 906   }
 907 
 908   void note_stop_adding_survivor_regions() {
 909     _survivor_surv_rate_group->stop_adding_regions();
 910   }
 911 
 912   void record_survivor_regions(uint regions,
 913                                HeapRegion* head,
 914                                HeapRegion* tail) {
 915     _recorded_survivor_regions = regions;
 916     _recorded_survivor_head    = head;
 917     _recorded_survivor_tail    = tail;
 918   }
 919 
 920   uint recorded_survivor_regions() {
 921     return _recorded_survivor_regions;
 922   }
 923 
 924   void record_thread_age_table(ageTable* age_table) {
 925     _survivors_age_table.merge_par(age_table);
 926   }
 927 
 928   void update_max_gc_locker_expansion();
 929 
 930   // Calculates survivor space parameters.
 931   void update_survivors_policy();
 932 
 933 };
 934 
 935 // This should move to some place more general...
 936 
 937 // If we have "n" measurements, and we've kept track of their "sum" and the
 938 // "sum_of_squares" of the measurements, this returns the variance of the
 939 // sequence.
 940 inline double variance(int n, double sum_of_squares, double sum) {
 941   double n_d = (double)n;
 942   double avg = sum/n_d;
 943   return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
 944 }
 945 
 946 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP