Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 2001-2007 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 // A G1CollectorPolicy makes policy decisions that determine the

 // characteristics of the collector.  Examples include:

 //   * choice of collection set.

 //   * when to collect.

 class HeapRegion;

 class CollectionSetChooser;

 // Yes, this is a bit unpleasant... but it saves replicating the same thing

 // over and over again and introducing subtle problems through small typos and

 // cutting and pasting mistakes. The macros below introduces a number

 // sequnce into the following two classes and the methods that access it.

 #define define_num_seq(name)                                                  \

 private:                                                                      \

   NumberSeq _all_##name##_times_ms;                                           \

 public:                                                                       \

   void record_##name##_time_ms(double ms) {                                   \

     _all_##name##_times_ms.add(ms);                                           \

   }                                                                           \

   NumberSeq* get_##name##_seq() {                                             \

     return &_all_##name##_times_ms;                                           \

   }

 class MainBodySummary;

 class PopPreambleSummary;

 class PauseSummary {

   define_num_seq(total)

     define_num_seq(other)

 public:

   virtual MainBodySummary*    main_body_summary()    { return NULL; }

   virtual PopPreambleSummary* pop_preamble_summary() { return NULL; }

 };

 class MainBodySummary {

   define_num_seq(satb_drain) // optional

   define_num_seq(parallel) // parallel only

     define_num_seq(ext_root_scan)

     define_num_seq(mark_stack_scan)

     define_num_seq(scan_only)

     define_num_seq(update_rs)

     define_num_seq(scan_rs)

     define_num_seq(scan_new_refs) // Only for temp use; added to

                                   // in parallel case.

     define_num_seq(obj_copy)

     define_num_seq(termination) // parallel only

     define_num_seq(parallel_other) // parallel only

   define_num_seq(mark_closure)

   define_num_seq(clear_ct)  // parallel only

 };

 class PopPreambleSummary {

   define_num_seq(pop_preamble)

     define_num_seq(pop_update_rs)

     define_num_seq(pop_scan_rs)

     define_num_seq(pop_closure_app)

     define_num_seq(pop_evacuation)

     define_num_seq(pop_other)

 };

 class NonPopSummary: public PauseSummary,

                      public MainBodySummary {

 public:

   virtual MainBodySummary*    main_body_summary()    { return this; }

 };

 class PopSummary: public PauseSummary,

                   public MainBodySummary,

                   public PopPreambleSummary {

 public:

   virtual MainBodySummary*    main_body_summary()    { return this; }

   virtual PopPreambleSummary* pop_preamble_summary() { return this; }

 };

 class NonPopAbandonedSummary: public PauseSummary {

 };

 class PopAbandonedSummary: public PauseSummary,

                            public PopPreambleSummary {

 public:

   virtual PopPreambleSummary* pop_preamble_summary() { return this; }

 };

 class G1CollectorPolicy: public CollectorPolicy {

 protected:

   // The number of pauses during the execution.

   long _n_pauses;

   // either equal to the number of parallel threads, if ParallelGCThreads

   // has been set, or 1 otherwise

   int _parallel_gc_threads;

   enum SomePrivateConstants {

     NumPrevPausesForHeuristics = 10,

     NumPrevGCsForHeuristics = 10,

     NumAPIs = HeapRegion::MaxAge

   };

   G1MMUTracker* _mmu_tracker;

   void initialize_flags();

   void initialize_all() {

     initialize_flags();

     initialize_size_info();

     initialize_perm_generation(PermGen::MarkSweepCompact);

   }

   virtual size_t default_init_heap_size() {

     // Pick some reasonable default.

     return 8*M;

   }

   double _cur_collection_start_sec;

   size_t _cur_collection_pause_used_at_start_bytes;

   size_t _cur_collection_pause_used_regions_at_start;

   size_t _prev_collection_pause_used_at_end_bytes;

   double _cur_collection_par_time_ms;

   double _cur_satb_drain_time_ms;

   double _cur_clear_ct_time_ms;

   bool   _satb_drain_time_set;

   double _cur_popular_preamble_start_ms;

   double _cur_popular_preamble_time_ms;

   double _cur_popular_compute_rc_time_ms;

   double _cur_popular_evac_time_ms;

   double _cur_CH_strong_roots_end_sec;

   double _cur_CH_strong_roots_dur_ms;

   double _cur_G1_strong_roots_end_sec;

   double _cur_G1_strong_roots_dur_ms;

   // Statistics for recent GC pauses.  See below for how indexed.

   TruncatedSeq* _recent_CH_strong_roots_times_ms;

   TruncatedSeq* _recent_G1_strong_roots_times_ms;

   TruncatedSeq* _recent_evac_times_ms;

   // These exclude marking times.

   TruncatedSeq* _recent_pause_times_ms;

   TruncatedSeq* _recent_gc_times_ms;

   TruncatedSeq* _recent_CS_bytes_used_before;

   TruncatedSeq* _recent_CS_bytes_surviving;

   TruncatedSeq* _recent_rs_sizes;

   TruncatedSeq* _concurrent_mark_init_times_ms;

   TruncatedSeq* _concurrent_mark_remark_times_ms;

   TruncatedSeq* _concurrent_mark_cleanup_times_ms;

   NonPopSummary*           _non_pop_summary;

   PopSummary*              _pop_summary;

   NonPopAbandonedSummary*  _non_pop_abandoned_summary;

   PopAbandonedSummary*     _pop_abandoned_summary;

   NumberSeq* _all_pause_times_ms;

   NumberSeq* _all_full_gc_times_ms;

   double _stop_world_start;

   NumberSeq* _all_stop_world_times_ms;

   NumberSeq* _all_yield_times_ms;

   size_t     _region_num_young;

   size_t     _region_num_tenured;

   size_t     _prev_region_num_young;

   size_t     _prev_region_num_tenured;

   NumberSeq* _all_mod_union_times_ms;

   int        _aux_num;

   NumberSeq* _all_aux_times_ms;

   double*    _cur_aux_start_times_ms;

   double*    _cur_aux_times_ms;

   bool*      _cur_aux_times_set;

   double* _par_last_ext_root_scan_times_ms;

   double* _par_last_mark_stack_scan_times_ms;

   double* _par_last_scan_only_times_ms;

   double* _par_last_scan_only_regions_scanned;

   double* _par_last_update_rs_start_times_ms;

   double* _par_last_update_rs_times_ms;

   double* _par_last_update_rs_processed_buffers;

   double* _par_last_scan_rs_start_times_ms;

   double* _par_last_scan_rs_times_ms;

   double* _par_last_scan_new_refs_times_ms;

   double* _par_last_obj_copy_times_ms;

   double* _par_last_termination_times_ms;

   // there are two pases during popular pauses, so we need to store

   // somewhere the results of the first pass

   double* _pop_par_last_update_rs_start_times_ms;

   double* _pop_par_last_update_rs_times_ms;

   double* _pop_par_last_update_rs_processed_buffers;

   double* _pop_par_last_scan_rs_start_times_ms;

   double* _pop_par_last_scan_rs_times_ms;

   double* _pop_par_last_closure_app_times_ms;

   double _pop_compute_rc_start;

   double _pop_evac_start;

   // indicates that we are in young GC mode

   bool _in_young_gc_mode;

   // indicates whether we are in full young or partially young GC mode

   bool _full_young_gcs;

   // if true, then it tries to dynamically adjust the length of the

   // young list

   bool _adaptive_young_list_length;

   size_t _young_list_min_length;

   size_t _young_list_target_length;

   size_t _young_list_so_prefix_length;

   size_t _young_list_fixed_length;

   size_t _young_cset_length;

   bool   _last_young_gc_full;

   double _target_pause_time_ms;

   unsigned              _full_young_pause_num;

   unsigned              _partial_young_pause_num;

   bool                  _during_marking;

   bool                  _in_marking_window;

   bool                  _in_marking_window_im;

   SurvRateGroup*        _short_lived_surv_rate_group;

   SurvRateGroup*        _survivor_surv_rate_group;

   // add here any more surv rate groups

   bool during_marking() {

     return _during_marking;

   }

   // <NEW PREDICTION>

 private:

   enum PredictionConstants {

     TruncatedSeqLength = 10

   };

   TruncatedSeq* _alloc_rate_ms_seq;

   double        _prev_collection_pause_end_ms;

   TruncatedSeq* _pending_card_diff_seq;

   TruncatedSeq* _rs_length_diff_seq;

   TruncatedSeq* _cost_per_card_ms_seq;

   TruncatedSeq* _cost_per_scan_only_region_ms_seq;

   TruncatedSeq* _fully_young_cards_per_entry_ratio_seq;

   TruncatedSeq* _partially_young_cards_per_entry_ratio_seq;

   TruncatedSeq* _cost_per_entry_ms_seq;

   TruncatedSeq* _partially_young_cost_per_entry_ms_seq;

   TruncatedSeq* _cost_per_byte_ms_seq;

   TruncatedSeq* _constant_other_time_ms_seq;

   TruncatedSeq* _young_other_cost_per_region_ms_seq;

   TruncatedSeq* _non_young_other_cost_per_region_ms_seq;

   TruncatedSeq* _pending_cards_seq;

   TruncatedSeq* _scanned_cards_seq;

   TruncatedSeq* _rs_lengths_seq;

   TruncatedSeq* _cost_per_byte_ms_during_cm_seq;

   TruncatedSeq* _cost_per_scan_only_region_ms_during_cm_seq;

   TruncatedSeq* _young_gc_eff_seq;

   TruncatedSeq* _max_conc_overhead_seq;

   size_t _recorded_young_regions;

   size_t _recorded_scan_only_regions;

   size_t _recorded_non_young_regions;

   size_t _recorded_region_num;

   size_t _free_regions_at_end_of_collection;

   size_t _scan_only_regions_at_end_of_collection;

   size_t _recorded_rs_lengths;

   size_t _max_rs_lengths;

   size_t _recorded_marked_bytes;

   size_t _recorded_young_bytes;

   size_t _predicted_pending_cards;

   size_t _predicted_cards_scanned;

   size_t _predicted_rs_lengths;

   size_t _predicted_bytes_to_copy;

   double _predicted_survival_ratio;

   double _predicted_rs_update_time_ms;

   double _predicted_rs_scan_time_ms;

   double _predicted_scan_only_scan_time_ms;

   double _predicted_object_copy_time_ms;

   double _predicted_constant_other_time_ms;

   double _predicted_young_other_time_ms;

   double _predicted_non_young_other_time_ms;

   double _predicted_pause_time_ms;

   double _vtime_diff_ms;

   double _recorded_young_free_cset_time_ms;

   double _recorded_non_young_free_cset_time_ms;

   double _sigma;

   double _expensive_region_limit_ms;

   size_t _rs_lengths_prediction;

   size_t _known_garbage_bytes;

   double _known_garbage_ratio;

   double sigma() {

     return _sigma;

   }

   // A function that prevents us putting too much stock in small sample

   // sets.  Returns a number between 2.0 and 1.0, depending on the number

   // of samples.  5 or more samples yields one; fewer scales linearly from

   // 2.0 at 1 sample to 1.0 at 5.

   double confidence_factor(int samples) {

     if (samples > 4) return 1.0;

     else return  1.0 + sigma() * ((double)(5 - samples))/2.0;

   }

   double get_new_neg_prediction(TruncatedSeq* seq) {

     return seq->davg() - sigma() * seq->dsd();

   }

 #ifndef PRODUCT

   bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);

 #endif // PRODUCT

 protected:

   double _pause_time_target_ms;

   double _recorded_young_cset_choice_time_ms;

   double _recorded_non_young_cset_choice_time_ms;

   bool   _within_target;

   size_t _pending_cards;

   size_t _max_pending_cards;

 public:

   void set_region_short_lived(HeapRegion* hr) {

     hr->install_surv_rate_group(_short_lived_surv_rate_group);

   }

   void set_region_survivors(HeapRegion* hr) {

     hr->install_surv_rate_group(_survivor_surv_rate_group);

   }

 #ifndef PRODUCT

   bool verify_young_ages();

 #endif // PRODUCT

   void tag_scan_only(size_t short_lived_scan_only_length);

   double get_new_prediction(TruncatedSeq* seq) {

     return MAX2(seq->davg() + sigma() * seq->dsd(),

                 seq->davg() * confidence_factor(seq->num()));

   }

   size_t young_cset_length() {

     return _young_cset_length;

   }

   void record_max_rs_lengths(size_t rs_lengths) {

     _max_rs_lengths = rs_lengths;

   }

   size_t predict_pending_card_diff() {

     double prediction = get_new_neg_prediction(_pending_card_diff_seq);

     if (prediction < 0.00001)

       return 0;

     else

       return (size_t) prediction;

   }

   size_t predict_pending_cards() {

     size_t max_pending_card_num = _g1->max_pending_card_num();

     size_t diff = predict_pending_card_diff();

     size_t prediction;

     if (diff > max_pending_card_num)

       prediction = max_pending_card_num;

     else

       prediction = max_pending_card_num - diff;

     return prediction;

   }

   size_t predict_rs_length_diff() {

     return (size_t) get_new_prediction(_rs_length_diff_seq);

   }

   double predict_alloc_rate_ms() {

     return get_new_prediction(_alloc_rate_ms_seq);

   }

   double predict_cost_per_card_ms() {

     return get_new_prediction(_cost_per_card_ms_seq);

   }

   double predict_rs_update_time_ms(size_t pending_cards) {

     return (double) pending_cards * predict_cost_per_card_ms();

   }

   double predict_fully_young_cards_per_entry_ratio() {

     return get_new_prediction(_fully_young_cards_per_entry_ratio_seq);

   }

   double predict_partially_young_cards_per_entry_ratio() {

     if (_partially_young_cards_per_entry_ratio_seq->num() < 2)

       return predict_fully_young_cards_per_entry_ratio();

     else

       return get_new_prediction(_partially_young_cards_per_entry_ratio_seq);

   }

   size_t predict_young_card_num(size_t rs_length) {

     return (size_t) ((double) rs_length *

                      predict_fully_young_cards_per_entry_ratio());

   }

   size_t predict_non_young_card_num(size_t rs_length) {

     return (size_t) ((double) rs_length *

                      predict_partially_young_cards_per_entry_ratio());

   }

   double predict_rs_scan_time_ms(size_t card_num) {

     if (full_young_gcs())

       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);

     else

       return predict_partially_young_rs_scan_time_ms(card_num);

   }

   double predict_partially_young_rs_scan_time_ms(size_t card_num) {

     if (_partially_young_cost_per_entry_ms_seq->num() < 3)

       return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq);

     else

       return (double) card_num *

         get_new_prediction(_partially_young_cost_per_entry_ms_seq);

   }

   double predict_scan_only_time_ms_during_cm(size_t scan_only_region_num) {

     if (_cost_per_scan_only_region_ms_during_cm_seq->num() < 3)

       return 1.5 * (double) scan_only_region_num *

         get_new_prediction(_cost_per_scan_only_region_ms_seq);

     else

       return (double) scan_only_region_num *

         get_new_prediction(_cost_per_scan_only_region_ms_during_cm_seq);

   }

   double predict_scan_only_time_ms(size_t scan_only_region_num) {

     if (_in_marking_window_im)

       return predict_scan_only_time_ms_during_cm(scan_only_region_num);

     else

       return (double) scan_only_region_num *

         get_new_prediction(_cost_per_scan_only_region_ms_seq);

   }

   double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) {

     if (_cost_per_byte_ms_during_cm_seq->num() < 3)

       return 1.1 * (double) bytes_to_copy *

         get_new_prediction(_cost_per_byte_ms_seq);

     else

       return (double) bytes_to_copy *

         get_new_prediction(_cost_per_byte_ms_during_cm_seq);

   }

   double predict_object_copy_time_ms(size_t bytes_to_copy) {

     if (_in_marking_window && !_in_marking_window_im)

       return predict_object_copy_time_ms_during_cm(bytes_to_copy);

     else

       return (double) bytes_to_copy *

         get_new_prediction(_cost_per_byte_ms_seq);

   }

   double predict_constant_other_time_ms() {

     return get_new_prediction(_constant_other_time_ms_seq);

   }

   double predict_young_other_time_ms(size_t young_num) {

     return

       (double) young_num *

       get_new_prediction(_young_other_cost_per_region_ms_seq);

   }

   double predict_non_young_other_time_ms(size_t non_young_num) {

     return

       (double) non_young_num *

       get_new_prediction(_non_young_other_cost_per_region_ms_seq);

   }

   void check_if_region_is_too_expensive(double predicted_time_ms);

   double predict_young_collection_elapsed_time_ms(size_t adjustment);

   double predict_base_elapsed_time_ms(size_t pending_cards);

   double predict_base_elapsed_time_ms(size_t pending_cards,

                                       size_t scanned_cards);

   size_t predict_bytes_to_copy(HeapRegion* hr);

   double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);

   // for use by: calculate_optimal_so_length(length)

   void predict_gc_eff(size_t young_region_num,

                       size_t so_length,

                       double base_time_ms,

                       double *gc_eff,

                       double *pause_time_ms);

   // for use by: calculate_young_list_target_config(rs_length)

   bool predict_gc_eff(size_t young_region_num,

                       size_t so_length,

                       double base_time_with_so_ms,

                       size_t init_free_regions,

                       double target_pause_time_ms,

                       double* gc_eff);

   void start_recording_regions();

   void record_cset_region(HeapRegion* hr, bool young);

   void record_scan_only_regions(size_t scan_only_length);

   void end_recording_regions();

   void record_vtime_diff_ms(double vtime_diff_ms) {

     _vtime_diff_ms = vtime_diff_ms;

   }

   void record_young_free_cset_time_ms(double time_ms) {

     _recorded_young_free_cset_time_ms = time_ms;

   }

   void record_non_young_free_cset_time_ms(double time_ms) {

     _recorded_non_young_free_cset_time_ms = time_ms;

   }

   double predict_young_gc_eff() {

     return get_new_neg_prediction(_young_gc_eff_seq);

   }

   // </NEW PREDICTION>

 public:

   void cset_regions_freed() {

     bool propagate = _last_young_gc_full && !_in_marking_window;

     _short_lived_surv_rate_group->all_surviving_words_recorded(propagate);

     _survivor_surv_rate_group->all_surviving_words_recorded(propagate);

     // also call it on any more surv rate groups

   }

   void set_known_garbage_bytes(size_t known_garbage_bytes) {

     _known_garbage_bytes = known_garbage_bytes;

     size_t heap_bytes = _g1->capacity();

     _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;

   }

   void decrease_known_garbage_bytes(size_t known_garbage_bytes) {

     guarantee( _known_garbage_bytes >= known_garbage_bytes, "invariant" );

     _known_garbage_bytes -= known_garbage_bytes;

     size_t heap_bytes = _g1->capacity();

     _known_garbage_ratio = (double) _known_garbage_bytes / (double) heap_bytes;

   }

   G1MMUTracker* mmu_tracker() {

     return _mmu_tracker;

   }

   double predict_init_time_ms() {

     return get_new_prediction(_concurrent_mark_init_times_ms);

   }

   double predict_remark_time_ms() {

     return get_new_prediction(_concurrent_mark_remark_times_ms);

   }

   double predict_cleanup_time_ms() {

     return get_new_prediction(_concurrent_mark_cleanup_times_ms);

   }

   // Returns an estimate of the survival rate of the region at yg-age

   // "yg_age".

   double predict_yg_surv_rate(int age) {

     TruncatedSeq* seq = _short_lived_surv_rate_group->get_seq(age);

     if (seq->num() == 0)

       gclog_or_tty->print("BARF! age is %d", age);

     guarantee( seq->num() > 0, "invariant" );

     double pred = get_new_prediction(seq);

     if (pred > 1.0)

       pred = 1.0;

     return pred;

   }

   double accum_yg_surv_rate_pred(int age) {

     return _short_lived_surv_rate_group->accum_surv_rate_pred(age);

   }

 protected:

   void print_stats (int level, const char* str, double value);

   void print_stats (int level, const char* str, int value);

   void print_par_stats (int level, const char* str, double* data) {

     print_par_stats(level, str, data, true);

   }

   void print_par_stats (int level, const char* str, double* data, bool summary);

   void print_par_buffers (int level, const char* str, double* data, bool summary);

   void check_other_times(int level,

                          NumberSeq* other_times_ms,

                          NumberSeq* calc_other_times_ms) const;

   void print_summary (PauseSummary* stats) const;

   void print_abandoned_summary(PauseSummary* non_pop_summary,

                                PauseSummary* pop_summary) const;

   void print_summary (int level, const char* str, NumberSeq* seq) const;

   void print_summary_sd (int level, const char* str, NumberSeq* seq) const;

   double avg_value (double* data);

   double max_value (double* data);

   double sum_of_values (double* data);

   double max_sum (double* data1, double* data2);

   int _last_satb_drain_processed_buffers;

   int _last_update_rs_processed_buffers;

   double _last_pause_time_ms;

   size_t _bytes_in_to_space_before_gc;

   size_t _bytes_in_to_space_after_gc;

   size_t bytes_in_to_space_during_gc() {

     return

       _bytes_in_to_space_after_gc - _bytes_in_to_space_before_gc;

   }

   size_t _bytes_in_collection_set_before_gc;

   // Used to count used bytes in CS.

   friend class CountCSClosure;

   // Statistics kept per GC stoppage, pause or full.

   TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec;

   // We track markings.

   int _num_markings;

   double _mark_thread_startup_sec;       // Time at startup of marking thread

   // Add a new GC of the given duration and end time to the record.

   void update_recent_gc_times(double end_time_sec, double elapsed_ms);

   // The head of the list (via "next_in_collection_set()") representing the

   // current collection set.

   HeapRegion* _collection_set;

   size_t _collection_set_size;

   size_t _collection_set_bytes_used_before;

   // Info about marking.

   int _n_marks; // Sticky at 2, so we know when we've done at least 2.

   // The number of collection pauses at the end of the last mark.

   size_t _n_pauses_at_mark_end;

   // ==== This section is for stats related to starting Conc Refinement on time.

   size_t _conc_refine_enabled;

   size_t _conc_refine_zero_traversals;

   size_t _conc_refine_max_traversals;

   // In # of heap regions.

   size_t _conc_refine_current_delta;

   // At the beginning of a collection pause, update the variables above,

   // especially the "delta".

   void update_conc_refine_data();

   // ====

   // Stash a pointer to the g1 heap.

   G1CollectedHeap* _g1;

   // The average time in ms per collection pause, averaged over recent pauses.

   double recent_avg_time_for_pauses_ms();

   // The average time in ms for processing CollectedHeap strong roots, per

   // collection pause, averaged over recent pauses.

   double recent_avg_time_for_CH_strong_ms();

   // The average time in ms for processing the G1 remembered set, per

   // pause, averaged over recent pauses.

   double recent_avg_time_for_G1_strong_ms();

   // The average time in ms for "evacuating followers", per pause, averaged

   // over recent pauses.

   double recent_avg_time_for_evac_ms();

   // The number of "recent" GCs recorded in the number sequences

   int number_of_recent_gcs();

   // The average survival ratio, computed by the total number of bytes

   // suriviving / total number of bytes before collection over the last

   // several recent pauses.

   double recent_avg_survival_fraction();

   // The survival fraction of the most recent pause; if there have been no

   // pauses, returns 1.0.

   double last_survival_fraction();

   // Returns a "conservative" estimate of the recent survival rate, i.e.,

   // one that may be higher than "recent_avg_survival_fraction".

   // This is conservative in several ways:

   //   If there have been few pauses, it will assume a potential high

   //     variance, and err on the side of caution.

   //   It puts a lower bound (currently 0.1) on the value it will return.

   //   To try to detect phase changes, if the most recent pause ("latest") has a

   //     higher-than average ("avg") survival rate, it returns that rate.

   // "work" version is a utility function; young is restricted to young regions.

   double conservative_avg_survival_fraction_work(double avg,

                                                  double latest);

   // The arguments are the two sequences that keep track of the number of bytes

   //   surviving and the total number of bytes before collection, resp.,

   //   over the last evereal recent pauses

   // Returns the survival rate for the category in the most recent pause.

   // If there have been no pauses, returns 1.0.

   double last_survival_fraction_work(TruncatedSeq* surviving,

                                      TruncatedSeq* before);

   // The arguments are the two sequences that keep track of the number of bytes

   //   surviving and the total number of bytes before collection, resp.,

   //   over the last several recent pauses

   // Returns the average survival ration over the last several recent pauses

   // If there have been no pauses, return 1.0

   double recent_avg_survival_fraction_work(TruncatedSeq* surviving,

                                            TruncatedSeq* before);

   double conservative_avg_survival_fraction() {

     double avg = recent_avg_survival_fraction();

     double latest = last_survival_fraction();

     return conservative_avg_survival_fraction_work(avg, latest);

   }

   // The ratio of gc time to elapsed time, computed over recent pauses.

   double _recent_avg_pause_time_ratio;

   double recent_avg_pause_time_ratio() {

     return _recent_avg_pause_time_ratio;

   }

   // Number of pauses between concurrent marking.

   size_t _pauses_btwn_concurrent_mark;

   size_t _n_marks_since_last_pause;

   // True iff CM has been initiated.

   bool _conc_mark_initiated;

   // True iff CM should be initiated

   bool _should_initiate_conc_mark;

   bool _should_revert_to_full_young_gcs;

   bool _last_full_young_gc;

   // This set of variables tracks the collector efficiency, in order to

   // determine whether we should initiate a new marking.

   double _cur_mark_stop_world_time_ms;

   double _mark_init_start_sec;

   double _mark_remark_start_sec;

   double _mark_cleanup_start_sec;

   double _mark_closure_time_ms;

   void   calculate_young_list_min_length();

   void   calculate_young_list_target_config();

   void   calculate_young_list_target_config(size_t rs_lengths);

   size_t calculate_optimal_so_length(size_t young_list_length);

 public:

   G1CollectorPolicy();

   virtual G1CollectorPolicy* as_g1_policy() { return this; }

   virtual CollectorPolicy::Name kind() {

     return CollectorPolicy::G1CollectorPolicyKind;

   }

   void check_prediction_validity();

   size_t bytes_in_collection_set() {

     return _bytes_in_collection_set_before_gc;

   }

   size_t bytes_in_to_space() {

     return bytes_in_to_space_during_gc();

   }

   unsigned calc_gc_alloc_time_stamp() {

     return _all_pause_times_ms->num() + 1;

   }

 protected:

   // Count the number of bytes used in the CS.

   void count_CS_bytes_used();

   // Together these do the base cleanup-recording work.  Subclasses might

   // want to put something between them.

   void record_concurrent_mark_cleanup_end_work1(size_t freed_bytes,

                                                 size_t max_live_bytes);

   void record_concurrent_mark_cleanup_end_work2();

 public:

   virtual void init();

   virtual HeapWord* mem_allocate_work(size_t size,

                                       bool is_tlab,

                                       bool* gc_overhead_limit_was_exceeded);

   // This method controls how a collector handles one or more

   // of its generations being fully allocated.

   virtual HeapWord* satisfy_failed_allocation(size_t size,

                                               bool is_tlab);

   BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; }

   GenRemSet::Name  rem_set_name()     { return GenRemSet::CardTable; }

   // The number of collection pauses so far.

   long n_pauses() const { return _n_pauses; }

   // Update the heuristic info to record a collection pause of the given

   // start time, where the given number of bytes were used at the start.

   // This may involve changing the desired size of a collection set.

   virtual void record_stop_world_start();

   virtual void record_collection_pause_start(double start_time_sec,

                                              size_t start_used);

   virtual void record_popular_pause_preamble_start();

   virtual void record_popular_pause_preamble_end();

   // Must currently be called while the world is stopped.

   virtual void record_concurrent_mark_init_start();

   virtual void record_concurrent_mark_init_end();

   void record_concurrent_mark_init_end_pre(double

                                            mark_init_elapsed_time_ms);

   void record_mark_closure_time(double mark_closure_time_ms);

   virtual void record_concurrent_mark_remark_start();

   virtual void record_concurrent_mark_remark_end();

   virtual void record_concurrent_mark_cleanup_start();

   virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,

                                                   size_t max_live_bytes);

   virtual void record_concurrent_mark_cleanup_completed();

   virtual void record_concurrent_pause();

   virtual void record_concurrent_pause_end();

   virtual void record_collection_pause_end_CH_strong_roots();

   virtual void record_collection_pause_end_G1_strong_roots();

   virtual void record_collection_pause_end(bool popular, bool abandoned);

   // Record the fact that a full collection occurred.

   virtual void record_full_collection_start();

   virtual void record_full_collection_end();

   void record_ext_root_scan_time(int worker_i, double ms) {

     _par_last_ext_root_scan_times_ms[worker_i] = ms;

   }

   void record_mark_stack_scan_time(int worker_i, double ms) {

     _par_last_mark_stack_scan_times_ms[worker_i] = ms;

   }

   void record_scan_only_time(int worker_i, double ms, int n) {

     _par_last_scan_only_times_ms[worker_i] = ms;

     _par_last_scan_only_regions_scanned[worker_i] = (double) n;

   }

   void record_satb_drain_time(double ms) {

     _cur_satb_drain_time_ms = ms;

     _satb_drain_time_set    = true;

   }

   void record_satb_drain_processed_buffers (int processed_buffers) {

     _last_satb_drain_processed_buffers = processed_buffers;

   }

   void record_mod_union_time(double ms) {

     _all_mod_union_times_ms->add(ms);

   }

   void record_update_rs_start_time(int thread, double ms) {

     _par_last_update_rs_start_times_ms[thread] = ms;

   }

   void record_update_rs_time(int thread, double ms) {

     _par_last_update_rs_times_ms[thread] = ms;

   }

   void record_update_rs_processed_buffers (int thread,

                                            double processed_buffers) {

     _par_last_update_rs_processed_buffers[thread] = processed_buffers;

   }

   void record_scan_rs_start_time(int thread, double ms) {

     _par_last_scan_rs_start_times_ms[thread] = ms;

   }

   void record_scan_rs_time(int thread, double ms) {

     _par_last_scan_rs_times_ms[thread] = ms;

   }

   void record_scan_new_refs_time(int thread, double ms) {

     _par_last_scan_new_refs_times_ms[thread] = ms;

   }

   double get_scan_new_refs_time(int thread) {

     return _par_last_scan_new_refs_times_ms[thread];

   }

   void reset_obj_copy_time(int thread) {

     _par_last_obj_copy_times_ms[thread] = 0.0;

   }

   void reset_obj_copy_time() {

     reset_obj_copy_time(0);

   }

   void record_obj_copy_time(int thread, double ms) {

     _par_last_obj_copy_times_ms[thread] += ms;

   }

   void record_obj_copy_time(double ms) {

     record_obj_copy_time(0, ms);

   }

   void record_termination_time(int thread, double ms) {

     _par_last_termination_times_ms[thread] = ms;

   }

   void record_termination_time(double ms) {

     record_termination_time(0, ms);

   }

   void record_pause_time(double ms) {

     _last_pause_time_ms = ms;

   }

   void record_clear_ct_time(double ms) {

     _cur_clear_ct_time_ms = ms;

   }

   void record_par_time(double ms) {

     _cur_collection_par_time_ms = ms;

   }

   void record_aux_start_time(int i) {

     guarantee(i < _aux_num, "should be within range");

     _cur_aux_start_times_ms[i] = os::elapsedTime() * 1000.0;

   }

   void record_aux_end_time(int i) {

     guarantee(i < _aux_num, "should be within range");

     double ms = os::elapsedTime() * 1000.0 - _cur_aux_start_times_ms[i];

     _cur_aux_times_set[i] = true;

     _cur_aux_times_ms[i] += ms;

   }

   void record_pop_compute_rc_start();

   void record_pop_compute_rc_end();

   void record_pop_evac_start();

   void record_pop_evac_end();

   // Record the fact that "bytes" bytes allocated in a region.

   void record_before_bytes(size_t bytes);

   void record_after_bytes(size_t bytes);

   // Returns "true" if this is a good time to do a collection pause.

   // The "word_size" argument, if non-zero, indicates the size of an

   // allocation request that is prompting this query.

   virtual bool should_do_collection_pause(size_t word_size) = 0;

   // Choose a new collection set.  Marks the chosen regions as being

   // "in_collection_set", and links them together.  The head and number of

   // the collection set are available via access methods.

   // If "pop_region" is non-NULL, it is a popular region that has already

   // been added to the collection set.

   virtual void choose_collection_set(HeapRegion* pop_region = NULL) = 0;

   void clear_collection_set() { _collection_set = NULL; }

   // The head of the list (via "next_in_collection_set()") representing the

   // current collection set.

   HeapRegion* collection_set() { return _collection_set; }

   // Sets the collection set to the given single region.

   virtual void set_single_region_collection_set(HeapRegion* hr);

   // The number of elements in the current collection set.

   size_t collection_set_size() { return _collection_set_size; }

   // Add "hr" to the CS.

   void add_to_collection_set(HeapRegion* hr);

   bool should_initiate_conc_mark()      { return _should_initiate_conc_mark; }

   void set_should_initiate_conc_mark()  { _should_initiate_conc_mark = true; }

   void unset_should_initiate_conc_mark(){ _should_initiate_conc_mark = false; }

   void checkpoint_conc_overhead();

   // If an expansion would be appropriate, because recent GC overhead had

   // exceeded the desired limit, return an amount to expand by.

   virtual size_t expansion_amount();

   // note start of mark thread

   void note_start_of_mark_thread();

   // The marked bytes of the "r" has changed; reclassify it's desirability

   // for marking.  Also asserts that "r" is eligible for a CS.

   virtual void note_change_in_marked_bytes(HeapRegion* r) = 0;

 #ifndef PRODUCT

   // Check any appropriate marked bytes info, asserting false if

   // something's wrong, else returning "true".

   virtual bool assertMarkedBytesDataOK() = 0;

 #endif

   // Print tracing information.

   void print_tracing_info() const;

   // Print stats on young survival ratio

   void print_yg_surv_rate_info() const;

   void finished_recalculating_age_indexes() {

     _short_lived_surv_rate_group->finished_recalculating_age_indexes();

     // do that for any other surv rate groups

   }

   bool should_add_next_region_to_young_list();

   bool in_young_gc_mode() {

     return _in_young_gc_mode;

   }

   void set_in_young_gc_mode(bool in_young_gc_mode) {

     _in_young_gc_mode = in_young_gc_mode;

   }

   bool full_young_gcs() {

     return _full_young_gcs;

   }

   void set_full_young_gcs(bool full_young_gcs) {

     _full_young_gcs = full_young_gcs;

   }

   bool adaptive_young_list_length() {

     return _adaptive_young_list_length;

   }

   void set_adaptive_young_list_length(bool adaptive_young_list_length) {

     _adaptive_young_list_length = adaptive_young_list_length;

   }

   inline double get_gc_eff_factor() {

     double ratio = _known_garbage_ratio;

     double square = ratio * ratio;

     // square = square * square;

     double ret = square * 9.0 + 1.0;

 #if 0

     gclog_or_tty->print_cr("ratio = %1.2lf, ret = %1.2lf", ratio, ret);

 #endif // 0

     guarantee(0.0 <= ret && ret < 10.0, "invariant!");

     return ret;

   }

   //

   // Survivor regions policy.

   //

 protected:

   // Current tenuring threshold, set to 0 if the collector reaches the

   // maximum amount of suvivors regions.

   int _tenuring_threshold;

 public:

   inline GCAllocPurpose

     evacuation_destination(HeapRegion* src_region, int age, size_t word_sz) {

       if (age < _tenuring_threshold && src_region->is_young()) {

         return GCAllocForSurvived;

       } else {

         return GCAllocForTenured;

       }

   }

   inline bool track_object_age(GCAllocPurpose purpose) {

     return purpose == GCAllocForSurvived;

   }

   inline GCAllocPurpose alternative_purpose(int purpose) {

     return GCAllocForTenured;

   }

   uint max_regions(int purpose);

   // The limit on regions for a particular purpose is reached.

   void note_alloc_region_limit_reached(int purpose) {

     if (purpose == GCAllocForSurvived) {

       _tenuring_threshold = 0;

     }

   }

   void note_start_adding_survivor_regions() {

     _survivor_surv_rate_group->start_adding_regions();

   }

   void note_stop_adding_survivor_regions() {

     _survivor_surv_rate_group->stop_adding_regions();

   }

 };

 // This encapsulates a particular strategy for a g1 Collector.

 //

 //      Start a concurrent mark when our heap size is n bytes

 //            greater then our heap size was at the last concurrent

 //            mark.  Where n is a function of the CMSTriggerRatio

 //            and the MinHeapFreeRatio.

 //

 //      Start a g1 collection pause when we have allocated the

 //            average number of bytes currently being freed in

 //            a collection, but only if it is at least one region

 //            full

 //

 //      Resize Heap based on desired

 //      allocation space, where desired allocation space is

 //      a function of survival rate and desired future to size.

 //

 //      Choose collection set by first picking all older regions

 //      which have a survival rate which beats our projected young

 //      survival rate.  Then fill out the number of needed regions

 //      with young regions.

 class G1CollectorPolicy_BestRegionsFirst: public G1CollectorPolicy {

   CollectionSetChooser* _collectionSetChooser;

   // If the estimated is less then desirable, resize if possible.

   void expand_if_possible(size_t numRegions);

   virtual void choose_collection_set(HeapRegion* pop_region = NULL);

   virtual void record_collection_pause_start(double start_time_sec,

                                              size_t start_used);

   virtual void record_concurrent_mark_cleanup_end(size_t freed_bytes,

                                                   size_t max_live_bytes);

   virtual void record_full_collection_end();

 public:

   G1CollectorPolicy_BestRegionsFirst() {

     _collectionSetChooser = new CollectionSetChooser();

   }

   void record_collection_pause_end(bool popular, bool abandoned);

   bool should_do_collection_pause(size_t word_size);

   virtual void set_single_region_collection_set(HeapRegion* hr);

   // This is not needed any more, after the CSet choosing code was

   // changed to use the pause prediction work. But let's leave the

   // hook in just in case.

   void note_change_in_marked_bytes(HeapRegion* r) { }

 #ifndef PRODUCT

   bool assertMarkedBytesDataOK();

 #endif

 };

 // This should move to some place more general...

 // If we have "n" measurements, and we've kept track of their "sum" and the

 // "sum_of_squares" of the measurements, this returns the variance of the

 // sequence.

 inline double variance(int n, double sum_of_squares, double sum) {

   double n_d = (double)n;

   double avg = sum/n_d;

   return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d;

 }

 // Local Variables: ***

 // c-indentation-style: gnu ***

 // End: ***