1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
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  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
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  24 
  25 #ifndef SHARE_GC_G1_G1POLICY_HPP
  26 #define SHARE_GC_G1_G1POLICY_HPP
  27 
  28 #include "gc/g1/g1CollectorState.hpp"
  29 #include "gc/g1/g1GCPhaseTimes.hpp"
  30 #include "gc/g1/g1HeapRegionAttr.hpp"
  31 #include "gc/g1/g1InitialMarkToMixedTimeTracker.hpp"
  32 #include "gc/g1/g1MMUTracker.hpp"
  33 #include "gc/g1/g1RemSetTrackingPolicy.hpp"
  34 #include "gc/g1/g1Predictions.hpp"
  35 #include "gc/g1/g1YoungGenSizer.hpp"
  36 #include "gc/shared/gcCause.hpp"
  37 #include "utilities/pair.hpp"
  38 
  39 // A G1Policy makes policy decisions that determine the
  40 // characteristics of the collector.  Examples include:
  41 //   * choice of collection set.
  42 //   * when to collect.
  43 
  44 class HeapRegion;
  45 class G1CollectionSet;
  46 class G1CollectionSetCandidates;
  47 class G1CollectionSetChooser;
  48 class G1IHOPControl;
  49 class G1Analytics;
  50 class G1SurvivorRegions;
  51 class G1YoungGenSizer;
  52 class GCPolicyCounters;
  53 class STWGCTimer;
  54 
  55 class G1Policy: public CHeapObj<mtGC> {
  56  private:
  57 
  58   static G1IHOPControl* create_ihop_control(const G1Predictions* predictor);
  59   // Update the IHOP control with necessary statistics.
  60   void update_ihop_prediction(double mutator_time_s,
  61                               size_t mutator_alloc_bytes,
  62                               size_t young_gen_size,
  63                               bool this_gc_was_young_only);
  64   void report_ihop_statistics();
  65 
  66   G1Predictions _predictor;
  67   G1Analytics* _analytics;
  68   G1RemSetTrackingPolicy _remset_tracker;
  69   G1MMUTracker* _mmu_tracker;
  70   G1IHOPControl* _ihop_control;
  71 
  72   GCPolicyCounters* _policy_counters;
  73 
  74   double _full_collection_start_sec;
  75 
  76   jlong _collection_pause_end_millis;
  77 
  78   uint _young_list_target_length;
  79   uint _young_list_fixed_length;
  80 
  81   // The max number of regions we can extend the eden by while the GC
  82   // locker is active. This should be >= _young_list_target_length;
  83   uint _young_list_max_length;
  84 
  85   // SurvRateGroups below must be initialized after the predictor because they
  86   // indirectly use it through this object passed to their constructor.
  87   SurvRateGroup* _short_lived_surv_rate_group;
  88   SurvRateGroup* _survivor_surv_rate_group;
  89 
  90   double _reserve_factor;
  91   // This will be set when the heap is expanded
  92   // for the first time during initialization.
  93   uint   _reserve_regions;
  94 
  95   G1YoungGenSizer* _young_gen_sizer;
  96 
  97   uint _free_regions_at_end_of_collection;
  98 
  99   size_t _max_rs_lengths;
 100 
 101   size_t _rs_lengths_prediction;
 102 
 103   size_t _pending_cards;
 104 
 105   // The amount of allocated bytes in old gen during the last mutator and the following
 106   // young GC phase.
 107   size_t _bytes_allocated_in_old_since_last_gc;
 108 
 109   G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
 110 
 111   bool should_update_surv_rate_group_predictors() {
 112     return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
 113   }
 114 public:
 115   const G1Predictions& predictor() const { return _predictor; }
 116   const G1Analytics* analytics()   const { return const_cast<const G1Analytics*>(_analytics); }
 117 
 118   G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
 119 
 120   // Add the given number of bytes to the total number of allocated bytes in the old gen.
 121   void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
 122 
 123   void set_region_eden(HeapRegion* hr) {
 124     hr->set_eden();
 125     hr->install_surv_rate_group(_short_lived_surv_rate_group);
 126   }
 127 
 128   void set_region_survivor(HeapRegion* hr) {
 129     assert(hr->is_survivor(), "pre-condition");
 130     hr->install_surv_rate_group(_survivor_surv_rate_group);
 131   }
 132 
 133   void record_max_rs_lengths(size_t rs_lengths) {
 134     _max_rs_lengths = rs_lengths;
 135   }
 136 
 137   double predict_base_elapsed_time_ms(size_t pending_cards) const;
 138   double predict_base_elapsed_time_ms(size_t pending_cards,
 139                                       size_t scanned_cards) const;
 140   size_t predict_bytes_to_copy(HeapRegion* hr) const;
 141   double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;
 142 
 143   double predict_survivor_regions_evac_time() const;
 144 
 145   void cset_regions_freed() {
 146     bool update = should_update_surv_rate_group_predictors();
 147 
 148     _short_lived_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 149     _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 150   }
 151 
 152   G1MMUTracker* mmu_tracker() {
 153     return _mmu_tracker;
 154   }
 155 
 156   const G1MMUTracker* mmu_tracker() const {
 157     return _mmu_tracker;
 158   }
 159 
 160   double max_pause_time_ms() const {
 161     return _mmu_tracker->max_gc_time() * 1000.0;
 162   }
 163 
 164   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;
 165 
 166   double predict_yg_surv_rate(int age) const;
 167 
 168   double accum_yg_surv_rate_pred(int age) const;
 169 
 170 private:
 171   G1CollectionSet* _collection_set;
 172   double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
 173   double other_time_ms(double pause_time_ms) const;
 174 
 175   double young_other_time_ms() const;
 176   double non_young_other_time_ms() const;
 177   double constant_other_time_ms(double pause_time_ms) const;
 178 
 179   G1CollectionSetChooser* cset_chooser() const;
 180 
 181   // The number of bytes copied during the GC.
 182   size_t _bytes_copied_during_gc;
 183 
 184   // Stash a pointer to the g1 heap.
 185   G1CollectedHeap* _g1h;
 186 
 187   G1GCPhaseTimes* _phase_times;
 188 
 189   // This set of variables tracks the collector efficiency, in order to
 190   // determine whether we should initiate a new marking.
 191   double _mark_remark_start_sec;
 192   double _mark_cleanup_start_sec;
 193 
 194   // Updates the internal young list maximum and target lengths. Returns the
 195   // unbounded young list target length.
 196   uint update_young_list_max_and_target_length();
 197   uint update_young_list_max_and_target_length(size_t rs_lengths);
 198 
 199   // Update the young list target length either by setting it to the
 200   // desired fixed value or by calculating it using G1's pause
 201   // prediction model. If no rs_lengths parameter is passed, predict
 202   // the RS lengths using the prediction model, otherwise use the
 203   // given rs_lengths as the prediction.
 204   // Returns the unbounded young list target length.
 205   uint update_young_list_target_length(size_t rs_lengths);
 206 
 207   // Calculate and return the minimum desired young list target
 208   // length. This is the minimum desired young list length according
 209   // to the user's inputs.
 210   uint calculate_young_list_desired_min_length(uint base_min_length) const;
 211 
 212   // Calculate and return the maximum desired young list target
 213   // length. This is the maximum desired young list length according
 214   // to the user's inputs.
 215   uint calculate_young_list_desired_max_length() const;
 216 
 217   // Calculate and return the maximum young list target length that
 218   // can fit into the pause time goal. The parameters are: rs_lengths
 219   // represent the prediction of how large the young RSet lengths will
 220   // be, base_min_length is the already existing number of regions in
 221   // the young list, min_length and max_length are the desired min and
 222   // max young list length according to the user's inputs.
 223   uint calculate_young_list_target_length(size_t rs_lengths,
 224                                           uint base_min_length,
 225                                           uint desired_min_length,
 226                                           uint desired_max_length) const;
 227 
 228   // Result of the bounded_young_list_target_length() method, containing both the
 229   // bounded as well as the unbounded young list target lengths in this order.
 230   typedef Pair<uint, uint, StackObj> YoungTargetLengths;
 231   YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
 232 
 233   void update_rs_lengths_prediction();
 234   void update_rs_lengths_prediction(size_t prediction);
 235 
 236   // Check whether a given young length (young_length) fits into the
 237   // given target pause time and whether the prediction for the amount
 238   // of objects to be copied for the given length will fit into the
 239   // given free space (expressed by base_free_regions).  It is used by
 240   // calculate_young_list_target_length().
 241   bool predict_will_fit(uint young_length, double base_time_ms,
 242                         uint base_free_regions, double target_pause_time_ms) const;
 243 
 244 public:
 245   size_t pending_cards() const { return _pending_cards; }
 246 
 247   // Calculate the minimum number of old regions we'll add to the CSet
 248   // during a mixed GC.
 249   uint calc_min_old_cset_length() const;
 250 
 251   // Calculate the maximum number of old regions we'll add to the CSet
 252   // during a mixed GC.
 253   uint calc_max_old_cset_length() const;
 254 
 255   // Returns the given amount of reclaimable bytes (that represents
 256   // the amount of reclaimable space still to be collected) as a
 257   // percentage of the current heap capacity.
 258   double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
 259 
 260   jlong collection_pause_end_millis() { return _collection_pause_end_millis; }
 261 
 262 private:
 263   void clear_collection_set_candidates();
 264   // Sets up marking if proper conditions are met.
 265   void maybe_start_marking();
 266 
 267   // The kind of STW pause.
 268   enum PauseKind {
 269     FullGC,
 270     YoungOnlyGC,
 271     MixedGC,
 272     LastYoungGC,
 273     InitialMarkGC,
 274     Cleanup,
 275     Remark
 276   };
 277 
 278   // Calculate PauseKind from internal state.
 279   PauseKind young_gc_pause_kind() const;
 280   // Record the given STW pause with the given start and end times (in s).
 281   void record_pause(PauseKind kind, double start, double end);
 282   // Indicate that we aborted marking before doing any mixed GCs.
 283   void abort_time_to_mixed_tracking();
 284 public:
 285 
 286   G1Policy(STWGCTimer* gc_timer);
 287 
 288   virtual ~G1Policy();
 289 
 290   static G1Policy* create_policy(STWGCTimer* gc_timer_stw);
 291 
 292   G1CollectorState* collector_state() const;
 293 
 294   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 295 
 296   // Check the current value of the young list RSet lengths and
 297   // compare it against the last prediction. If the current value is
 298   // higher, recalculate the young list target length prediction.
 299   void revise_young_list_target_length_if_necessary(size_t rs_lengths);
 300 
 301   // This should be called after the heap is resized.
 302   void record_new_heap_size(uint new_number_of_regions);
 303 
 304   virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
 305 
 306   void note_gc_start();
 307 
 308   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 309 
 310   bool about_to_start_mixed_phase() const;
 311 
 312   // Record the start and end of an evacuation pause.
 313   void record_collection_pause_start(double start_time_sec);
 314   virtual void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
 315 
 316   // Record the start and end of a full collection.
 317   void record_full_collection_start();
 318   virtual void record_full_collection_end();
 319 
 320   // Must currently be called while the world is stopped.
 321   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 322 
 323   // Record start and end of remark.
 324   void record_concurrent_mark_remark_start();
 325   void record_concurrent_mark_remark_end();
 326 
 327   // Record start, end, and completion of cleanup.
 328   void record_concurrent_mark_cleanup_start();
 329   void record_concurrent_mark_cleanup_end();
 330 
 331   void print_phases();
 332 
 333   // Record how much space we copied during a GC. This is typically
 334   // called when a GC alloc region is being retired.
 335   void record_bytes_copied_during_gc(size_t bytes) {
 336     _bytes_copied_during_gc += bytes;
 337   }
 338 
 339   // The amount of space we copied during a GC.
 340   size_t bytes_copied_during_gc() const {
 341     return _bytes_copied_during_gc;
 342   }
 343 
 344   bool next_gc_should_be_mixed(const char* true_action_str,
 345                                const char* false_action_str) const;
 346 
 347   // Calculate and return the number of initial and optional old gen regions from
 348   // the given collection set candidates and the remaining time.
 349   void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
 350                                             double time_remaining_ms,
 351                                             uint& num_initial_regions,
 352                                             uint& num_optional_regions);
 353 
 354   // Calculate the number of optional regions from the given collection set candidates,
 355   // the remaining time and the maximum number of these regions and return the number
 356   // of actually selected regions in num_optional_regions.
 357   void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
 358                                                  uint const max_optional_regions,
 359                                                  double time_remaining_ms,
 360                                                  uint& num_optional_regions);
 361 
 362 private:
 363   // Set the state to start a concurrent marking cycle and clear
 364   // _initiate_conc_mark_if_possible because it has now been
 365   // acted on.
 366   void initiate_conc_mark();
 367 
 368 public:
 369   // This sets the initiate_conc_mark_if_possible() flag to start a
 370   // new cycle, as long as we are not already in one. It's best if it
 371   // is called during a safepoint when the test whether a cycle is in
 372   // progress or not is stable.
 373   bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
 374 
 375   // This is called at the very beginning of an evacuation pause (it
 376   // has to be the first thing that the pause does). If
 377   // initiate_conc_mark_if_possible() is true, and the concurrent
 378   // marking thread has completed its work during the previous cycle,
 379   // it will set in_initial_mark_gc() to so that the pause does
 380   // the initial-mark work and start a marking cycle.
 381   void decide_on_conc_mark_initiation();
 382 
 383   void finished_recalculating_age_indexes(bool is_survivors) {
 384     if (is_survivors) {
 385       _survivor_surv_rate_group->finished_recalculating_age_indexes();
 386     } else {
 387       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
 388     }
 389   }
 390 
 391   size_t young_list_target_length() const { return _young_list_target_length; }
 392 
 393   bool should_allocate_mutator_region() const;
 394 
 395   bool can_expand_young_list() const;
 396 
 397   uint young_list_max_length() const {
 398     return _young_list_max_length;
 399   }
 400 
 401   bool use_adaptive_young_list_length() const;
 402 
 403   void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
 404 
 405 private:
 406   //
 407   // Survivor regions policy.
 408   //
 409 
 410   // Current tenuring threshold, set to 0 if the collector reaches the
 411   // maximum amount of survivors regions.
 412   uint _tenuring_threshold;
 413 
 414   // The limit on the number of regions allocated for survivors.
 415   uint _max_survivor_regions;
 416 
 417   AgeTable _survivors_age_table;
 418 
 419   size_t desired_survivor_size(uint max_regions) const;
 420 
 421   // Fraction used when predicting how many optional regions to include in
 422   // the CSet. This fraction of the available time is used for optional regions,
 423   // the rest is used to add old regions to the normal CSet.
 424   double optional_prediction_fraction() { return 0.2; }
 425 
 426 public:
 427   // Fraction used when evacuating the optional regions. This fraction of the
 428   // remaining time is used to choose what regions to include in the evacuation.
 429   double optional_evacuation_fraction() { return 0.75; }
 430 
 431   uint tenuring_threshold() const { return _tenuring_threshold; }
 432 
 433   uint max_survivor_regions() {
 434     return _max_survivor_regions;
 435   }
 436 
 437   void note_start_adding_survivor_regions() {
 438     _survivor_surv_rate_group->start_adding_regions();
 439   }
 440 
 441   void note_stop_adding_survivor_regions() {
 442     _survivor_surv_rate_group->stop_adding_regions();
 443   }
 444 
 445   void record_age_table(AgeTable* age_table) {
 446     _survivors_age_table.merge(age_table);
 447   }
 448 
 449   void print_age_table();
 450 
 451   void update_max_gc_locker_expansion();
 452 
 453   void update_survivors_policy();
 454 
 455   virtual bool force_upgrade_to_full() {
 456     return false;
 457   }
 458 };
 459 
 460 #endif // SHARE_GC_G1_G1POLICY_HPP