1 /*
   2  * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
   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.
   8  *
   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  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  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 
  40 // Yes, this is a bit unpleasant... but it saves replicating the same thing
  41 // over and over again and introducing subtle problems through small typos and
  42 // cutting and pasting mistakes. The macros below introduces a number
  43 // sequnce into the following two classes and the methods that access it.
  44 
  45 #define define_num_seq(name)                                                  \
  46 private:                                                                      \
  47   NumberSeq _all_##name##_times_ms;                                           \
  48 public:                                                                       \
  49   void record_##name##_time_ms(double ms) {                                   \
  50     _all_##name##_times_ms.add(ms);                                           \
  51   }                                                                           \
  52   NumberSeq* get_##name##_seq() {                                             \
  53     return &_all_##name##_times_ms;                                           \
  54   }
  55 
  56 class MainBodySummary;
  57 
  58 class PauseSummary: public CHeapObj {
  59   define_num_seq(total)
  60     define_num_seq(other)
  61 
  62 public:
  63   virtual MainBodySummary*    main_body_summary()    { return NULL; }
  64 };
  65 
  66 class MainBodySummary: public CHeapObj {
  67   define_num_seq(satb_drain) // optional
  68   define_num_seq(parallel) // parallel only
  69     define_num_seq(ext_root_scan)
  70     define_num_seq(mark_stack_scan)
  71     define_num_seq(update_rs)
  72     define_num_seq(scan_rs)
  73     define_num_seq(obj_copy)
  74     define_num_seq(termination) // parallel only
  75     define_num_seq(parallel_other) // parallel only
  76   define_num_seq(mark_closure)
  77   define_num_seq(clear_ct)  // parallel only
  78 };
  79 
  80 class Summary: public PauseSummary,
  81                public MainBodySummary {
  82 public:
  83   virtual MainBodySummary*    main_body_summary()    { return this; }
  84 };
  85 
  86 class G1CollectorPolicy: public CollectorPolicy {
  87 protected:
  88   // The number of pauses during the execution.
  89   long _n_pauses;
  90 
  91   // either equal to the number of parallel threads, if ParallelGCThreads
  92   // has been set, or 1 otherwise
  93   int _parallel_gc_threads;
  94 
  95   enum SomePrivateConstants {
  96     NumPrevPausesForHeuristics = 10
  97   };
  98 
  99   G1MMUTracker* _mmu_tracker;
 100 
 101   void initialize_flags();
 102 
 103   void initialize_all() {
 104     initialize_flags();
 105     initialize_size_info();
 106     initialize_perm_generation(PermGen::MarkSweepCompact);
 107   }
 108 
 109   virtual size_t default_init_heap_size() {
 110     // Pick some reasonable default.
 111     return 8*M;
 112   }
 113 
 114   double _cur_collection_start_sec;
 115   size_t _cur_collection_pause_used_at_start_bytes;
 116   size_t _cur_collection_pause_used_regions_at_start;
 117   size_t _prev_collection_pause_used_at_end_bytes;
 118   double _cur_collection_par_time_ms;
 119   double _cur_satb_drain_time_ms;
 120   double _cur_clear_ct_time_ms;
 121   bool   _satb_drain_time_set;
 122 
 123 #ifndef PRODUCT
 124   // Card Table Count Cache stats
 125   double _min_clear_cc_time_ms;         // min
 126   double _max_clear_cc_time_ms;         // max
 127   double _cur_clear_cc_time_ms;         // clearing time during current pause
 128   double _cum_clear_cc_time_ms;         // cummulative clearing time
 129   jlong  _num_cc_clears;                // number of times the card count cache has been cleared
 130 #endif
 131 
 132   double _cur_CH_strong_roots_end_sec;
 133   double _cur_CH_strong_roots_dur_ms;
 134   double _cur_G1_strong_roots_end_sec;
 135   double _cur_G1_strong_roots_dur_ms;
 136 
 137   // Statistics for recent GC pauses.  See below for how indexed.
 138   TruncatedSeq* _recent_CH_strong_roots_times_ms;
 139   TruncatedSeq* _recent_G1_strong_roots_times_ms;
 140   TruncatedSeq* _recent_evac_times_ms;
 141   // These exclude marking times.
 142   TruncatedSeq* _recent_pause_times_ms;
 143   TruncatedSeq* _recent_gc_times_ms;
 144 
 145   TruncatedSeq* _recent_CS_bytes_used_before;
 146   TruncatedSeq* _recent_CS_bytes_surviving;
 147 
 148   TruncatedSeq* _recent_rs_sizes;
 149 
 150   TruncatedSeq* _concurrent_mark_init_times_ms;
 151   TruncatedSeq* _concurrent_mark_remark_times_ms;
 152   TruncatedSeq* _concurrent_mark_cleanup_times_ms;
 153 
 154   Summary*           _summary;
 155 
 156   NumberSeq* _all_pause_times_ms;
 157   NumberSeq* _all_full_gc_times_ms;
 158   double _stop_world_start;
 159   NumberSeq* _all_stop_world_times_ms;
 160   NumberSeq* _all_yield_times_ms;
 161 
 162   size_t     _region_num_young;
 163   size_t     _region_num_tenured;
 164   size_t     _prev_region_num_young;
 165   size_t     _prev_region_num_tenured;
 166 
 167   NumberSeq* _all_mod_union_times_ms;
 168 
 169   int        _aux_num;
 170   NumberSeq* _all_aux_times_ms;
 171   double*    _cur_aux_start_times_ms;
 172   double*    _cur_aux_times_ms;
 173   bool*      _cur_aux_times_set;
 174 
 175   double* _par_last_gc_worker_start_times_ms;
 176   double* _par_last_ext_root_scan_times_ms;
 177   double* _par_last_mark_stack_scan_times_ms;
 178   double* _par_last_update_rs_times_ms;
 179   double* _par_last_update_rs_processed_buffers;
 180   double* _par_last_scan_rs_times_ms;
 181   double* _par_last_obj_copy_times_ms;
 182   double* _par_last_termination_times_ms;
 183   double* _par_last_termination_attempts;
 184   double* _par_last_gc_worker_end_times_ms;
 185   double* _par_last_gc_worker_times_ms;
 186 
 187   // indicates that we are in young GC mode
 188   bool _in_young_gc_mode;
 189 
 190   // indicates whether we are in full young or partially young GC mode
 191   bool _full_young_gcs;
 192 
 193   // if true, then it tries to dynamically adjust the length of the
 194   // young list
 195   bool _adaptive_young_list_length;
 196   size_t _young_list_min_length;
 197   size_t _young_list_target_length;
 198   size_t _young_list_fixed_length;
 199 
 200   // The max number of regions we can extend the eden by while the GC
 201   // locker is active. This should be >= _young_list_target_length;
 202   size_t _young_list_max_length;
 203 
 204   size_t _young_cset_length;
 205   bool   _last_young_gc_full;
 206 
 207   unsigned              _full_young_pause_num;
 208   unsigned              _partial_young_pause_num;
 209 
 210   bool                  _during_marking;
 211   bool                  _in_marking_window;
 212   bool                  _in_marking_window_im;
 213 
 214   SurvRateGroup*        _short_lived_surv_rate_group;
 215   SurvRateGroup*        _survivor_surv_rate_group;
 216   // add here any more surv rate groups
 217 
 218   double                _gc_overhead_perc;
 219 
 220   bool during_marking() {
 221     return _during_marking;
 222   }
 223 
 224   // <NEW PREDICTION>
 225 
 226 private:
 227   enum PredictionConstants {
 228     TruncatedSeqLength = 10
 229   };
 230 
 231   TruncatedSeq* _alloc_rate_ms_seq;
 232   double        _prev_collection_pause_end_ms;
 233 
 234   TruncatedSeq* _pending_card_diff_seq;
 235   TruncatedSeq* _rs_length_diff_seq;
 236   TruncatedSeq* _cost_per_card_ms_seq;
 237   TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;
 238   TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;
 239   TruncatedSeq* _cost_per_entry_ms_seq;
 240   TruncatedSeq* _partially_young_cost_per_entry_ms_seq;
 241   TruncatedSeq* _cost_per_byte_ms_seq;
 242   TruncatedSeq* _constant_other_time_ms_seq;
 243   TruncatedSeq* _young_other_cost_per_region_ms_seq;
 244   TruncatedSeq* _non_young_other_cost_per_region_ms_seq;
 245 
 246   TruncatedSeq* _pending_cards_seq;
 247   TruncatedSeq* _scanned_cards_seq;
 248   TruncatedSeq* _rs_lengths_seq;
 249 
 250   TruncatedSeq* _cost_per_byte_ms_during_cm_seq;
 251 
 252   TruncatedSeq* _young_gc_eff_seq;
 253 
 254   TruncatedSeq* _max_conc_overhead_seq;
 255 
 256   size_t _recorded_young_regions;
 257   size_t _recorded_non_young_regions;
 258   size_t _recorded_region_num;
 259 
 260   size_t _free_regions_at_end_of_collection;
 261 
 262   size_t _recorded_rs_lengths;
 263   size_t _max_rs_lengths;
 264 
 265   size_t _recorded_marked_bytes;
 266   size_t _recorded_young_bytes;
 267 
 268   size_t _predicted_pending_cards;
 269   size_t _predicted_cards_scanned;
 270   size_t _predicted_rs_lengths;
 271   size_t _predicted_bytes_to_copy;
 272 
 273   double _predicted_survival_ratio;
 274   double _predicted_rs_update_time_ms;
 275   double _predicted_rs_scan_time_ms;
 276   double _predicted_object_copy_time_ms;
 277   double _predicted_constant_other_time_ms;
 278   double _predicted_young_other_time_ms;
 279   double _predicted_non_young_other_time_ms;
 280   double _predicted_pause_time_ms;
 281 
 282   double _vtime_diff_ms;
 283 
 284   double _recorded_young_free_cset_time_ms;
 285   double _recorded_non_young_free_cset_time_ms;
 286 
 287   double _sigma;
 288   double _expensive_region_limit_ms;
 289 
 290   size_t _rs_lengths_prediction;
 291 
 292   size_t _known_garbage_bytes;
 293   double _known_garbage_ratio;
 294 
 295   double sigma() {
 296     return _sigma;
 297   }
 298 
 299   // A function that prevents us putting too much stock in small sample
 300   // sets.  Returns a number between 2.0 and 1.0, depending on the number
 301   // of samples.  5 or more samples yields one; fewer scales linearly from
 302   // 2.0 at 1 sample to 1.0 at 5.
 303   double confidence_factor(int samples) {
 304     if (samples > 4) return 1.0;
 305     else return  1.0 + sigma() * ((double)(5 - samples))/2.0;
 306   }
 307 
 308   double get_new_neg_prediction(TruncatedSeq* seq) {
 309     return seq->davg() - sigma() * seq->dsd();
 310   }
 311 
 312 #ifndef PRODUCT
 313   bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
 314 #endif // PRODUCT
 315 
 316   void adjust_concurrent_refinement(double update_rs_time,
 317                                     double update_rs_processed_buffers,
 318                                     double goal_ms);
 319 
 320 protected:
 321   double _pause_time_target_ms;
 322   double _recorded_young_cset_choice_time_ms;
 323   double _recorded_non_young_cset_choice_time_ms;
 324   bool   _within_target;
 325   size_t _pending_cards;
 326   size_t _max_pending_cards;
 327 
 328 public:
 329 
 330   void set_region_short_lived(HeapRegion* hr) {
 331     hr->install_surv_rate_group(_short_lived_surv_rate_group);
 332   }
 333 
 334   void set_region_survivors(HeapRegion* hr) {
 335     hr->install_surv_rate_group(_survivor_surv_rate_group);
 336   }
 337 
 338 #ifndef PRODUCT
 339   bool verify_young_ages();
 340 #endif // PRODUCT
 341 
 342   double get_new_prediction(TruncatedSeq* seq) {
 343     return MAX2(seq->davg() + sigma() * seq->dsd(),
 344                 seq->davg() * confidence_factor(seq->num()));
 345   }
 346 
 347   size_t young_cset_length() {
 348     return _young_cset_length;
 349   }
 350 
 351   void record_max_rs_lengths(size_t rs_lengths) {
 352     _max_rs_lengths = rs_lengths;
 353   }
 354 
 355   size_t predict_pending_card_diff() {
 356     double prediction = get_new_neg_prediction(_pending_card_diff_seq);
 357     if (prediction < 0.00001)
 358       return 0;
 359     else
 360       return (size_t) prediction;
 361   }
 362 
 363   size_t predict_pending_cards() {
 364     size_t max_pending_card_num = _g1->max_pending_card_num();
 365     size_t diff = predict_pending_card_diff();
 366     size_t prediction;
 367     if (diff > max_pending_card_num)
 368       prediction = max_pending_card_num;
 369     else
 370       prediction = max_pending_card_num - diff;
 371 
 372     return prediction;
 373   }
 374 
 375   size_t predict_rs_length_diff() {
 376     return (size_t) get_new_prediction(_rs_length_diff_seq);
 377   }
 378 
 379   double predict_alloc_rate_ms() {
 380     return get_new_prediction(_alloc_rate_ms_seq);
 381   }
 382 
 383   double predict_cost_per_card_ms() {
 384     return get_new_prediction(_cost_per_card_ms_seq);
 385   }
 386 
 387   double predict_rs_update_time_ms(size_t pending_cards) {
 388     return (double) pending_cards * predict_cost_per_card_ms();
 389   }
 390 
 391   double predict_fully_young_cards_per_entry_ratio() {
 392     return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);
 393   }
 394 
 395   double predict_partially_young_cards_per_entry_ratio() {
 396     if (_partially_young_cards_per_entry_ratio_seq->num() < 2)
 397       return predict_fully_young_cards_per_entry_ratio();
 398     else
 399       return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);
 400   }
 401 
 402   size_t predict_young_card_num(size_t rs_length) {
 403     return (size_t) ((double) rs_length *
 404                      predict_fully_young_cards_per_entry_ratio());
 405   }
 406 
 407   size_t predict_non_young_card_num(size_t rs_length) {
 408     return (size_t) ((double) rs_length *
 409                      predict_partially_young_cards_per_entry_ratio());
 410   }
 411 
 412   double predict_rs_scan_time_ms(size_t card_num) {
 413     if (full_young_gcs())
 414       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 415     else
 416       return predict_partially_young_rs_scan_time_ms(card_num);
 417   }
 418 
 419   double predict_partially_young_rs_scan_time_ms(size_t card_num) {
 420     if (_partially_young_cost_per_entry_ms_seq->num() < 3)
 421       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);
 422     else
 423       return (double) card_num *
 424         get_new_prediction(_partially_young_cost_per_entry_ms_seq);
 425   }
 426 
 427   double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {
 428     if (_cost_per_byte_ms_during_cm_seq->num() < 3)
 429       return 1.1 * (double) bytes_to_copy *
 430         get_new_prediction(_cost_per_byte_ms_seq);
 431     else
 432       return (double) bytes_to_copy *
 433         get_new_prediction(_cost_per_byte_ms_during_cm_seq);
 434   }
 435 
 436   double predict_object_copy_time_ms(size_t bytes_to_copy) {
 437     if (_in_marking_window && !_in_marking_window_im)
 438       return predict_object_copy_time_ms_during_cm(bytes_to_copy);
 439     else
 440       return (double) bytes_to_copy *
 441         get_new_prediction(_cost_per_byte_ms_seq);
 442   }
 443 
 444   double predict_constant_other_time_ms() {
 445     return get_new_prediction(_constant_other_time_ms_seq);
 446   }
 447 
 448   double predict_young_other_time_ms(size_t young_num) {
 449     return
 450       (double) young_num *
 451       get_new_prediction(_young_other_cost_per_region_ms_seq);
 452   }
 453 
 454   double predict_non_young_other_time_ms(size_t non_young_num) {
 455     return
 456       (double) non_young_num *
 457       get_new_prediction(_non_young_other_cost_per_region_ms_seq);
 458   }
 459 
 460   void check_if_region_is_too_expensive(double predicted_time_ms);
 461 
 462   double predict_young_collection_elapsed_time_ms(size_t adjustment);
 463   double predict_base_elapsed_time_ms(size_t pending_cards);
 464   double predict_base_elapsed_time_ms(size_t pending_cards,
 465                                       size_t scanned_cards);
 466   size_t predict_bytes_to_copy(HeapRegion* hr);
 467   double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
 468 
 469     // for use by: calculate_young_list_target_length(rs_length)
 470   bool predict_will_fit(size_t young_region_num,
 471                         double base_time_ms,
 472                         size_t init_free_regions,
 473                         double target_pause_time_ms);
 474 
 475   void start_recording_regions();
 476   void record_cset_region_info(HeapRegion* hr, bool young);
 477   void record_non_young_cset_region(HeapRegion* hr);
 478 
 479   void set_recorded_young_regions(size_t n_regions);
 480   void set_recorded_young_bytes(size_t bytes);
 481   void set_recorded_rs_lengths(size_t rs_lengths);
 482   void set_predicted_bytes_to_copy(size_t bytes);
 483 
 484   void end_recording_regions();
 485 
 486   void record_vtime_diff_ms(double vtime_diff_ms) {
 487     _vtime_diff_ms = vtime_diff_ms;
 488   }
 489 
 490   void record_young_free_cset_time_ms(double time_ms) {
 491     _recorded_young_free_cset_time_ms = time_ms;
 492   }
 493 
 494   void record_non_young_free_cset_time_ms(double time_ms) {
 495     _recorded_non_young_free_cset_time_ms = time_ms;
 496   }
 497 
 498   double predict_young_gc_eff() {
 499     return get_new_neg_prediction(_young_gc_eff_seq);
 500   }
 501 
 502   double predict_survivor_regions_evac_time();
 503 
 504   // </NEW PREDICTION>
 505 
 506 public:
 507   void cset_regions_freed() {
 508     bool propagate = _last_young_gc_full && !_in_marking_window;
 509     _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);
 510     _survivor_surv_rate_group->all_surviving_words_recorded(propagate);
 511     // also call it on any more surv rate groups
 512   }
 513 
 514   void set_known_garbage_bytes(size_t known_garbage_bytes) {
 515     _known_garbage_bytes = known_garbage_bytes;
 516     size_t heap_bytes = _g1->capacity();
 517     _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
 518   }
 519 
 520   void decrease_known_garbage_bytes(size_t known_garbage_bytes) {
 521     guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );
 522 
 523     _known_garbage_bytes -= known_garbage_bytes;
 524     size_t heap_bytes = _g1->capacity();
 525     _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;
 526   }
 527 
 528   G1MMUTracker* mmu_tracker() {
 529     return _mmu_tracker;
 530   }
 531 
 532   double max_pause_time_ms() {
 533     return _mmu_tracker->max_gc_time() * 1000.0;
 534   }
 535 
 536   double predict_init_time_ms() {
 537     return get_new_prediction(_concurrent_mark_init_times_ms);
 538   }
 539 
 540   double predict_remark_time_ms() {
 541     return get_new_prediction(_concurrent_mark_remark_times_ms);
 542   }
 543 
 544   double predict_cleanup_time_ms() {
 545     return get_new_prediction(_concurrent_mark_cleanup_times_ms);
 546   }
 547 
 548   // Returns an estimate of the survival rate of the region at yg-age
 549   // "yg_age".
 550   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) {
 551     TruncatedSeq* seq = surv_rate_group->get_seq(age);
 552     if (seq->num() == 0)
 553       gclog_or_tty->print("BARF! age is %d", age);
 554     guarantee( seq->num() > 0, "invariant" );
 555     double pred = get_new_prediction(seq);
 556     if (pred > 1.0)
 557       pred = 1.0;
 558     return pred;
 559   }
 560 
 561   double predict_yg_surv_rate(int age) {
 562     return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
 563   }
 564 
 565   double accum_yg_surv_rate_pred(int age) {
 566     return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
 567   }
 568 
 569 protected:
 570   void print_stats(int level, const char* str, double value);
 571   void print_stats(int level, const char* str, int value);
 572 
 573   void print_par_stats(int level, const char* str, double* data);
 574   void print_par_sizes(int level, const char* str, double* data);
 575 
 576   void check_other_times(int level,
 577                          NumberSeq* other_times_ms,
 578                          NumberSeq* calc_other_times_ms) const;
 579 
 580   void print_summary (PauseSummary* stats) const;
 581 
 582   void print_summary (int level, const char* str, NumberSeq* seq) const;
 583   void print_summary_sd (int level, const char* str, NumberSeq* seq) const;
 584 
 585   double avg_value (double* data);
 586   double max_value (double* data);
 587   double sum_of_values (double* data);
 588   double max_sum (double* data1, double* data2);
 589 
 590   int _last_satb_drain_processed_buffers;
 591   int _last_update_rs_processed_buffers;
 592   double _last_pause_time_ms;
 593 
 594   size_t _bytes_in_to_space_before_gc;
 595   size_t _bytes_in_to_space_after_gc;
 596   size_t bytes_in_to_space_during_gc() {
 597     return
 598       _bytes_in_to_space_after_gc - _bytes_in_to_space_before_gc;
 599   }
 600   size_t _bytes_in_collection_set_before_gc;
 601   // Used to count used bytes in CS.
 602   friend class CountCSClosure;
 603 
 604   // Statistics kept per GC stoppage, pause or full.
 605   TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;
 606 
 607   // We track markings.
 608   int _num_markings;
 609   double _mark_thread_startup_sec;       // Time at startup of marking thread
 610 
 611   // Add a new GC of the given duration and end time to the record.
 612   void update_recent_gc_times(double end_time_sec, double elapsed_ms);
 613 
 614   // The head of the list (via "next_in_collection_set()") representing the
 615   // current collection set. Set from the incrementally built collection
 616   // set at the start of the pause.
 617   HeapRegion* _collection_set;
 618 
 619   // The number of regions in the collection set. Set from the incrementally
 620   // built collection set at the start of an evacuation pause.
 621   size_t _collection_set_size;
 622 
 623   // The number of bytes in the collection set before the pause. Set from
 624   // the incrementally built collection set at the start of an evacuation
 625   // pause.
 626   size_t _collection_set_bytes_used_before;
 627 
 628   // The associated information that is maintained while the incremental
 629   // collection set is being built with young regions. Used to populate
 630   // the recorded info for the evacuation pause.
 631 
 632   enum CSetBuildType {
 633     Active,             // We are actively building the collection set
 634     Inactive            // We are not actively building the collection set
 635   };
 636 
 637   CSetBuildType _inc_cset_build_state;
 638 
 639   // The head of the incrementally built collection set.
 640   HeapRegion* _inc_cset_head;
 641 
 642   // The tail of the incrementally built collection set.
 643   HeapRegion* _inc_cset_tail;
 644 
 645   // The number of regions in the incrementally built collection set.
 646   // Used to set _collection_set_size at the start of an evacuation
 647   // pause.
 648   size_t _inc_cset_size;
 649 
 650   // Used as the index in the surving young words structure
 651   // which tracks the amount of space, for each young region,
 652   // that survives the pause.
 653   size_t _inc_cset_young_index;
 654 
 655   // The number of bytes in the incrementally built collection set.
 656   // Used to set _collection_set_bytes_used_before at the start of
 657   // an evacuation pause.
 658   size_t _inc_cset_bytes_used_before;
 659 
 660   // Used to record the highest end of heap region in collection set
 661   HeapWord* _inc_cset_max_finger;
 662 
 663   // The number of recorded used bytes in the young regions
 664   // of the collection set. This is the sum of the used() bytes
 665   // of retired young regions in the collection set.
 666   size_t _inc_cset_recorded_young_bytes;
 667 
 668   // The RSet lengths recorded for regions in the collection set
 669   // (updated by the periodic sampling of the regions in the
 670   // young list/collection set).
 671   size_t _inc_cset_recorded_rs_lengths;
 672 
 673   // The predicted elapsed time it will take to collect the regions
 674   // in the collection set (updated by the periodic sampling of the
 675   // regions in the young list/collection set).
 676   double _inc_cset_predicted_elapsed_time_ms;
 677 
 678   // The predicted bytes to copy for the regions in the collection
 679   // set (updated by the periodic sampling of the regions in the
 680   // young list/collection set).
 681   size_t _inc_cset_predicted_bytes_to_copy;
 682 
 683   // Info about marking.
 684   int _n_marks; // Sticky at 2, so we know when we've done at least 2.
 685 
 686   // The number of collection pauses at the end of the last mark.
 687   size_t _n_pauses_at_mark_end;
 688 
 689   // Stash a pointer to the g1 heap.
 690   G1CollectedHeap* _g1;
 691 
 692   // The average time in ms per collection pause, averaged over recent pauses.
 693   double recent_avg_time_for_pauses_ms();
 694 
 695   // The average time in ms for processing CollectedHeap strong roots, per
 696   // collection pause, averaged over recent pauses.
 697   double recent_avg_time_for_CH_strong_ms();
 698 
 699   // The average time in ms for processing the G1 remembered set, per
 700   // pause, averaged over recent pauses.
 701   double recent_avg_time_for_G1_strong_ms();
 702 
 703   // The average time in ms for "evacuating followers", per pause, averaged
 704   // over recent pauses.
 705   double recent_avg_time_for_evac_ms();
 706 
 707   // The number of "recent" GCs recorded in the number sequences
 708   int number_of_recent_gcs();
 709 
 710   // The average survival ratio, computed by the total number of bytes
 711   // suriviving / total number of bytes before collection over the last
 712   // several recent pauses.
 713   double recent_avg_survival_fraction();
 714   // The survival fraction of the most recent pause; if there have been no
 715   // pauses, returns 1.0.
 716   double last_survival_fraction();
 717 
 718   // Returns a "conservative" estimate of the recent survival rate, i.e.,
 719   // one that may be higher than "recent_avg_survival_fraction".
 720   // This is conservative in several ways:
 721   //   If there have been few pauses, it will assume a potential high
 722   //     variance, and err on the side of caution.
 723   //   It puts a lower bound (currently 0.1) on the value it will return.
 724   //   To try to detect phase changes, if the most recent pause ("latest") has a
 725   //     higher-than average ("avg") survival rate, it returns that rate.
 726   // "work" version is a utility function; young is restricted to young regions.
 727   double conservative_avg_survival_fraction_work(double avg,
 728                                                  double latest);
 729 
 730   // The arguments are the two sequences that keep track of the number of bytes
 731   //   surviving and the total number of bytes before collection, resp.,
 732   //   over the last evereal recent pauses
 733   // Returns the survival rate for the category in the most recent pause.
 734   // If there have been no pauses, returns 1.0.
 735   double last_survival_fraction_work(TruncatedSeq* surviving,
 736                                      TruncatedSeq* before);
 737 
 738   // The arguments are the two sequences that keep track of the number of bytes
 739   //   surviving and the total number of bytes before collection, resp.,
 740   //   over the last several recent pauses
 741   // Returns the average survival ration over the last several recent pauses
 742   // If there have been no pauses, return 1.0
 743   double recent_avg_survival_fraction_work(TruncatedSeq* surviving,
 744                                            TruncatedSeq* before);
 745 
 746   double conservative_avg_survival_fraction() {
 747     double avg = recent_avg_survival_fraction();
 748     double latest = last_survival_fraction();
 749     return conservative_avg_survival_fraction_work(avg, latest);
 750   }
 751 
 752   // The ratio of gc time to elapsed time, computed over recent pauses.
 753   double _recent_avg_pause_time_ratio;
 754 
 755   double recent_avg_pause_time_ratio() {
 756     return _recent_avg_pause_time_ratio;
 757   }
 758 
 759   // Number of pauses between concurrent marking.
 760   size_t _pauses_btwn_concurrent_mark;
 761 
 762   size_t _n_marks_since_last_pause;
 763 
 764   // At the end of a pause we check the heap occupancy and we decide
 765   // whether we will start a marking cycle during the next pause. If
 766   // we decide that we want to do that, we will set this parameter to
 767   // true. So, this parameter will stay true between the end of a
 768   // pause and the beginning of a subsequent pause (not necessarily
 769   // the next one, see the comments on the next field) when we decide
 770   // that we will indeed start a marking cycle and do the initial-mark
 771   // work.
 772   volatile bool _initiate_conc_mark_if_possible;
 773 
 774   // If initiate_conc_mark_if_possible() is set at the beginning of a
 775   // pause, it is a suggestion that the pause should start a marking
 776   // cycle by doing the initial-mark work. However, it is possible
 777   // that the concurrent marking thread is still finishing up the
 778   // previous marking cycle (e.g., clearing the next marking
 779   // bitmap). If that is the case we cannot start a new cycle and
 780   // we'll have to wait for the concurrent marking thread to finish
 781   // what it is doing. In this case we will postpone the marking cycle
 782   // initiation decision for the next pause. When we eventually decide
 783   // to start a cycle, we will set _during_initial_mark_pause which
 784   // will stay true until the end of the initial-mark pause and it's
 785   // the condition that indicates that a pause is doing the
 786   // initial-mark work.
 787   volatile bool _during_initial_mark_pause;
 788 
 789   bool _should_revert_to_full_young_gcs;
 790   bool _last_full_young_gc;
 791 
 792   // This set of variables tracks the collector efficiency, in order to
 793   // determine whether we should initiate a new marking.
 794   double _cur_mark_stop_world_time_ms;
 795   double _mark_init_start_sec;
 796   double _mark_remark_start_sec;
 797   double _mark_cleanup_start_sec;
 798   double _mark_closure_time_ms;
 799 
 800   void   calculate_young_list_min_length();
 801   void   calculate_young_list_target_length();
 802   void   calculate_young_list_target_length(size_t rs_lengths);
 803 
 804 public:
 805 
 806   G1CollectorPolicy();
 807 
 808   virtual G1CollectorPolicy* as_g1_policy() { return this; }
 809 
 810   virtual CollectorPolicy::Name kind() {
 811     return CollectorPolicy::G1CollectorPolicyKind;
 812   }
 813 
 814   void check_prediction_validity();
 815 
 816   size_t bytes_in_collection_set() {
 817     return _bytes_in_collection_set_before_gc;
 818   }
 819 
 820   size_t bytes_in_to_space() {
 821     return bytes_in_to_space_during_gc();
 822   }
 823 
 824   unsigned calc_gc_alloc_time_stamp() {
 825     return _all_pause_times_ms->num() + 1;
 826   }
 827 
 828 protected:
 829 
 830   // Count the number of bytes used in the CS.
 831   void count_CS_bytes_used();
 832 
 833   // Together these do the base cleanup-recording work.  Subclasses might
 834   // want to put something between them.
 835   void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,
 836                                                 size_t max_live_bytes);
 837   void record_concurrent_mark_cleanup_end_work2();
 838 
 839 public:
 840 
 841   virtual void init();
 842 
 843   // Create jstat counters for the policy.
 844   virtual void initialize_gc_policy_counters();
 845 
 846   virtual HeapWord* mem_allocate_work(size_t size,
 847                                       bool is_tlab,
 848                                       bool* gc_overhead_limit_was_exceeded);
 849 
 850   // This method controls how a collector handles one or more
 851   // of its generations being fully allocated.
 852   virtual HeapWord* satisfy_failed_allocation(size_t size,
 853                                               bool is_tlab);
 854 
 855   BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }
 856 
 857   GenRemSet::Name  rem_set_name()     { return GenRemSet::CardTable; }
 858 
 859   // The number of collection pauses so far.
 860   long n_pauses() const { return _n_pauses; }
 861 
 862   // Update the heuristic info to record a collection pause of the given
 863   // start time, where the given number of bytes were used at the start.
 864   // This may involve changing the desired size of a collection set.
 865 
 866   virtual void record_stop_world_start();
 867 
 868   virtual void record_collection_pause_start(double start_time_sec,
 869                                              size_t start_used);
 870 
 871   // Must currently be called while the world is stopped.
 872   virtual void record_concurrent_mark_init_start();
 873   virtual void record_concurrent_mark_init_end();
 874   void record_concurrent_mark_init_end_pre(double
 875                                            mark_init_elapsed_time_ms);
 876 
 877   void record_mark_closure_time(double mark_closure_time_ms);
 878 
 879   virtual void record_concurrent_mark_remark_start();
 880   virtual void record_concurrent_mark_remark_end();
 881 
 882   virtual void record_concurrent_mark_cleanup_start();
 883   virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
 884                                                   size_t max_live_bytes);
 885   virtual void record_concurrent_mark_cleanup_completed();
 886 
 887   virtual void record_concurrent_pause();
 888   virtual void record_concurrent_pause_end();
 889 
 890   virtual void record_collection_pause_end_CH_strong_roots();
 891   virtual void record_collection_pause_end_G1_strong_roots();
 892 
 893   virtual void record_collection_pause_end();
 894   void print_heap_transition();
 895 
 896   // Record the fact that a full collection occurred.
 897   virtual void record_full_collection_start();
 898   virtual void record_full_collection_end();
 899 
 900   void record_gc_worker_start_time(int worker_i, double ms) {
 901     _par_last_gc_worker_start_times_ms[worker_i] = ms;
 902   }
 903 
 904   void record_ext_root_scan_time(int worker_i, double ms) {
 905     _par_last_ext_root_scan_times_ms[worker_i] = ms;
 906   }
 907 
 908   void record_mark_stack_scan_time(int worker_i, double ms) {
 909     _par_last_mark_stack_scan_times_ms[worker_i] = ms;
 910   }
 911 
 912   void record_satb_drain_time(double ms) {
 913     _cur_satb_drain_time_ms = ms;
 914     _satb_drain_time_set    = true;
 915   }
 916 
 917   void record_satb_drain_processed_buffers (int processed_buffers) {
 918     _last_satb_drain_processed_buffers = processed_buffers;
 919   }
 920 
 921   void record_mod_union_time(double ms) {
 922     _all_mod_union_times_ms->add(ms);
 923   }
 924 
 925   void record_update_rs_time(int thread, double ms) {
 926     _par_last_update_rs_times_ms[thread] = ms;
 927   }
 928 
 929   void record_update_rs_processed_buffers (int thread,
 930                                            double processed_buffers) {
 931     _par_last_update_rs_processed_buffers[thread] = processed_buffers;
 932   }
 933 
 934   void record_scan_rs_time(int thread, double ms) {
 935     _par_last_scan_rs_times_ms[thread] = ms;
 936   }
 937 
 938   void reset_obj_copy_time(int thread) {
 939     _par_last_obj_copy_times_ms[thread] = 0.0;
 940   }
 941 
 942   void reset_obj_copy_time() {
 943     reset_obj_copy_time(0);
 944   }
 945 
 946   void record_obj_copy_time(int thread, double ms) {
 947     _par_last_obj_copy_times_ms[thread] += ms;
 948   }
 949 
 950   void record_termination(int thread, double ms, size_t attempts) {
 951     _par_last_termination_times_ms[thread] = ms;
 952     _par_last_termination_attempts[thread] = (double) attempts;
 953   }
 954 
 955   void record_gc_worker_end_time(int worker_i, double ms) {
 956     _par_last_gc_worker_end_times_ms[worker_i] = ms;
 957   }
 958 
 959   void record_pause_time_ms(double ms) {
 960     _last_pause_time_ms = ms;
 961   }
 962 
 963   void record_clear_ct_time(double ms) {
 964     _cur_clear_ct_time_ms = ms;
 965   }
 966 
 967   void record_par_time(double ms) {
 968     _cur_collection_par_time_ms = ms;
 969   }
 970 
 971   void record_aux_start_time(int i) {
 972     guarantee(i < _aux_num, "should be within range");
 973     _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;
 974   }
 975 
 976   void record_aux_end_time(int i) {
 977     guarantee(i < _aux_num, "should be within range");
 978     double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];
 979     _cur_aux_times_set[i] = true;
 980     _cur_aux_times_ms[i] += ms;
 981   }
 982 
 983 #ifndef PRODUCT
 984   void record_cc_clear_time(double ms) {
 985     if (_min_clear_cc_time_ms < 0.0 || ms <= _min_clear_cc_time_ms)
 986       _min_clear_cc_time_ms = ms;
 987     if (_max_clear_cc_time_ms < 0.0 || ms >= _max_clear_cc_time_ms)
 988       _max_clear_cc_time_ms = ms;
 989     _cur_clear_cc_time_ms = ms;
 990     _cum_clear_cc_time_ms += ms;
 991     _num_cc_clears++;
 992   }
 993 #endif
 994 
 995   // Record the fact that "bytes" bytes allocated in a region.
 996   void record_before_bytes(size_t bytes);
 997   void record_after_bytes(size_t bytes);
 998 
 999   // Choose a new collection set.  Marks the chosen regions as being
1000   // "in_collection_set", and links them together.  The head and number of
1001   // the collection set are available via access methods.
1002   virtual void choose_collection_set(double target_pause_time_ms) = 0;
1003 
1004   // The head of the list (via "next_in_collection_set()") representing the
1005   // current collection set.
1006   HeapRegion* collection_set() { return _collection_set; }
1007 
1008   void clear_collection_set() { _collection_set = NULL; }
1009 
1010   // The number of elements in the current collection set.
1011   size_t collection_set_size() { return _collection_set_size; }
1012 
1013   // Add "hr" to the CS.
1014   void add_to_collection_set(HeapRegion* hr);
1015 
1016   // Incremental CSet Support
1017 
1018   // The head of the incrementally built collection set.
1019   HeapRegion* inc_cset_head() { return _inc_cset_head; }
1020 
1021   // The tail of the incrementally built collection set.
1022   HeapRegion* inc_set_tail() { return _inc_cset_tail; }
1023 
1024   // The number of elements in the incrementally built collection set.
1025   size_t inc_cset_size() { return _inc_cset_size; }
1026 
1027   // Initialize incremental collection set info.
1028   void start_incremental_cset_building();
1029 
1030   void clear_incremental_cset() {
1031     _inc_cset_head = NULL;
1032     _inc_cset_tail = NULL;
1033   }
1034 
1035   // Stop adding regions to the incremental collection set
1036   void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; }
1037 
1038   // Add/remove information about hr to the aggregated information
1039   // for the incrementally built collection set.
1040   void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length);
1041   void remove_from_incremental_cset_info(HeapRegion* hr);
1042 
1043   // Update information about hr in the aggregated information for
1044   // the incrementally built collection set.
1045   void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length);
1046 
1047 private:
1048   // Update the incremental cset information when adding a region
1049   // (should not be called directly).
1050   void add_region_to_incremental_cset_common(HeapRegion* hr);
1051 
1052 public:
1053   // Add hr to the LHS of the incremental collection set.
1054   void add_region_to_incremental_cset_lhs(HeapRegion* hr);
1055 
1056   // Add hr to the RHS of the incremental collection set.
1057   void add_region_to_incremental_cset_rhs(HeapRegion* hr);
1058 
1059 #ifndef PRODUCT
1060   void print_collection_set(HeapRegion* list_head, outputStream* st);
1061 #endif // !PRODUCT
1062 
1063   bool initiate_conc_mark_if_possible()       { return _initiate_conc_mark_if_possible;  }
1064   void set_initiate_conc_mark_if_possible()   { _initiate_conc_mark_if_possible = true;  }
1065   void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; }
1066 
1067   bool during_initial_mark_pause()      { return _during_initial_mark_pause;  }
1068   void set_during_initial_mark_pause()  { _during_initial_mark_pause = true;  }
1069   void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; }
1070 
1071   // This sets the initiate_conc_mark_if_possible() flag to start a
1072   // new cycle, as long as we are not already in one. It's best if it
1073   // is called during a safepoint when the test whether a cycle is in
1074   // progress or not is stable.
1075   bool force_initial_mark_if_outside_cycle();
1076 
1077   // This is called at the very beginning of an evacuation pause (it
1078   // has to be the first thing that the pause does). If
1079   // initiate_conc_mark_if_possible() is true, and the concurrent
1080   // marking thread has completed its work during the previous cycle,
1081   // it will set during_initial_mark_pause() to so that the pause does
1082   // the initial-mark work and start a marking cycle.
1083   void decide_on_conc_mark_initiation();
1084 
1085   // If an expansion would be appropriate, because recent GC overhead had
1086   // exceeded the desired limit, return an amount to expand by.
1087   virtual size_t expansion_amount();
1088 
1089   // note start of mark thread
1090   void note_start_of_mark_thread();
1091 
1092   // The marked bytes of the "r" has changed; reclassify it's desirability
1093   // for marking.  Also asserts that "r" is eligible for a CS.
1094   virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;
1095 
1096 #ifndef PRODUCT
1097   // Check any appropriate marked bytes info, asserting false if
1098   // something's wrong, else returning "true".
1099   virtual bool assertMarkedBytesDataOK() = 0;
1100 #endif
1101 
1102   // Print tracing information.
1103   void print_tracing_info() const;
1104 
1105   // Print stats on young survival ratio
1106   void print_yg_surv_rate_info() const;
1107 
1108   void finished_recalculating_age_indexes(bool is_survivors) {
1109     if (is_survivors) {
1110       _survivor_surv_rate_group->finished_recalculating_age_indexes();
1111     } else {
1112       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
1113     }
1114     // do that for any other surv rate groups
1115   }
1116 
1117   bool is_young_list_full() {
1118     size_t young_list_length = _g1->young_list()->length();
1119     size_t young_list_target_length = _young_list_target_length;
1120     if (G1FixedEdenSize) {
1121       young_list_target_length -= _max_survivor_regions;
1122     }
1123     return young_list_length >= young_list_target_length;
1124   }
1125 
1126   bool can_expand_young_list() {
1127     size_t young_list_length = _g1->young_list()->length();
1128     size_t young_list_max_length = _young_list_max_length;
1129     if (G1FixedEdenSize) {
1130       young_list_max_length -= _max_survivor_regions;
1131     }
1132     return young_list_length < young_list_max_length;
1133   }
1134 
1135   void update_region_num(bool young);
1136 
1137   bool in_young_gc_mode() {
1138     return _in_young_gc_mode;
1139   }
1140   void set_in_young_gc_mode(bool in_young_gc_mode) {
1141     _in_young_gc_mode = in_young_gc_mode;
1142   }
1143 
1144   bool full_young_gcs() {
1145     return _full_young_gcs;
1146   }
1147   void set_full_young_gcs(bool full_young_gcs) {
1148     _full_young_gcs = full_young_gcs;
1149   }
1150 
1151   bool adaptive_young_list_length() {
1152     return _adaptive_young_list_length;
1153   }
1154   void set_adaptive_young_list_length(bool adaptive_young_list_length) {
1155     _adaptive_young_list_length = adaptive_young_list_length;
1156   }
1157 
1158   inline double get_gc_eff_factor() {
1159     double ratio = _known_garbage_ratio;
1160 
1161     double square = ratio * ratio;
1162     // square = square * square;
1163     double ret = square * 9.0 + 1.0;
1164 #if 0
1165     gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);
1166 #endif // 0
1167     guarantee(0.0 <= ret && ret < 10.0, "invariant!");
1168     return ret;
1169   }
1170 
1171   //
1172   // Survivor regions policy.
1173   //
1174 protected:
1175 
1176   // Current tenuring threshold, set to 0 if the collector reaches the
1177   // maximum amount of suvivors regions.
1178   int _tenuring_threshold;
1179 
1180   // The limit on the number of regions allocated for survivors.
1181   size_t _max_survivor_regions;
1182 
1183   // For reporting purposes.
1184   size_t _eden_bytes_before_gc;
1185   size_t _survivor_bytes_before_gc;
1186   size_t _capacity_before_gc;
1187 
1188   // The amount of survor regions after a collection.
1189   size_t _recorded_survivor_regions;
1190   // List of survivor regions.
1191   HeapRegion* _recorded_survivor_head;
1192   HeapRegion* _recorded_survivor_tail;
1193 
1194   ageTable _survivors_age_table;
1195 
1196 public:
1197 
1198   inline GCAllocPurpose
1199     evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {
1200       if (age < _tenuring_threshold && src_region->is_young()) {
1201         return GCAllocForSurvived;
1202       } else {
1203         return GCAllocForTenured;
1204       }
1205   }
1206 
1207   inline bool track_object_age(GCAllocPurpose purpose) {
1208     return purpose == GCAllocForSurvived;
1209   }
1210 
1211   inline GCAllocPurpose alternative_purpose(int purpose) {
1212     return GCAllocForTenured;
1213   }
1214 
1215   static const size_t REGIONS_UNLIMITED = ~(size_t)0;
1216 
1217   size_t max_regions(int purpose);
1218 
1219   // The limit on regions for a particular purpose is reached.
1220   void note_alloc_region_limit_reached(int purpose) {
1221     if (purpose == GCAllocForSurvived) {
1222       _tenuring_threshold = 0;
1223     }
1224   }
1225 
1226   void note_start_adding_survivor_regions() {
1227     _survivor_surv_rate_group->start_adding_regions();
1228   }
1229 
1230   void note_stop_adding_survivor_regions() {
1231     _survivor_surv_rate_group->stop_adding_regions();
1232   }
1233 
1234   void record_survivor_regions(size_t      regions,
1235                                HeapRegion* head,
1236                                HeapRegion* tail) {
1237     _recorded_survivor_regions = regions;
1238     _recorded_survivor_head    = head;
1239     _recorded_survivor_tail    = tail;
1240   }
1241 
1242   size_t recorded_survivor_regions() {
1243     return _recorded_survivor_regions;
1244   }
1245 
1246   void record_thread_age_table(ageTable* age_table)
1247   {
1248     _survivors_age_table.merge_par(age_table);
1249   }
1250 
1251   void calculate_max_gc_locker_expansion();
1252 
1253   // Calculates survivor space parameters.
1254   void calculate_survivors_policy();
1255 
1256 };
1257 
1258 // This encapsulates a particular strategy for a g1 Collector.
1259 //
1260 //      Start a concurrent mark when our heap size is n bytes
1261 //            greater then our heap size was at the last concurrent
1262 //            mark.  Where n is a function of the CMSTriggerRatio
1263 //            and the MinHeapFreeRatio.
1264 //
1265 //      Start a g1 collection pause when we have allocated the
1266 //            average number of bytes currently being freed in
1267 //            a collection, but only if it is at least one region
1268 //            full
1269 //
1270 //      Resize Heap based on desired
1271 //      allocation space, where desired allocation space is
1272 //      a function of survival rate and desired future to size.
1273 //
1274 //      Choose collection set by first picking all older regions
1275 //      which have a survival rate which beats our projected young
1276 //      survival rate.  Then fill out the number of needed regions
1277 //      with young regions.
1278 
1279 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {
1280   CollectionSetChooser* _collectionSetChooser;
1281   // If the estimated is less then desirable, resize if possible.
1282   void expand_if_possible(size_t numRegions);
1283 
1284   virtual void choose_collection_set(double target_pause_time_ms);
1285   virtual void record_collection_pause_start(double start_time_sec,
1286                                              size_t start_used);
1287   virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,
1288                                                   size_t max_live_bytes);
1289   virtual void record_full_collection_end();
1290 
1291 public:
1292   G1CollectorPolicy_BestRegionsFirst() {
1293     _collectionSetChooser = new CollectionSetChooser();
1294   }
1295   void record_collection_pause_end();
1296   // This is not needed any more, after the CSet choosing code was
1297   // changed to use the pause prediction work. But let's leave the
1298   // hook in just in case.
1299   void note_change_in_marked_bytes(HeapRegion* r) { }
1300 #ifndef PRODUCT
1301   bool assertMarkedBytesDataOK();
1302 #endif
1303 };
1304 
1305 // This should move to some place more general...
1306 
1307 // If we have "n" measurements, and we've kept track of their "sum" and the
1308 // "sum_of_squares" of the measurements, this returns the variance of the
1309 // sequence.
1310 inline double variance(int n, double sum_of_squares, double sum) {
1311   double n_d = (double)n;
1312   double avg = sum/n_d;
1313   return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;
1314 }
1315 
1316 // Local Variables: ***
1317 // c-indentation-style: gnu ***
1318 // End: ***
1319 
1320 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP