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_length;
 100 
 101   size_t _rs_length_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 
 115   double log_buffer_processing_time() const;
 116 public:
 117   const G1Predictions& predictor() const { return _predictor; }
 118   const G1Analytics* analytics()   const { return const_cast<const G1Analytics*>(_analytics); }
 119 
 120   G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
 121 
 122   // Add the given number of bytes to the total number of allocated bytes in the old gen.
 123   void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
 124 
 125   void set_region_eden(HeapRegion* hr) {
 126     hr->set_eden();
 127     hr->install_surv_rate_group(_short_lived_surv_rate_group);
 128   }
 129 
 130   void set_region_survivor(HeapRegion* hr) {
 131     assert(hr->is_survivor(), "pre-condition");
 132     hr->install_surv_rate_group(_survivor_surv_rate_group);
 133   }
 134 
 135   void record_max_rs_length(size_t rs_length) {
 136     _max_rs_length = rs_length;
 137   }
 138 
 139   double predict_base_elapsed_time_ms(size_t pending_cards) const;
 140   double predict_base_elapsed_time_ms(size_t pending_cards,
 141                                       size_t scanned_cards) const;
 142   size_t predict_bytes_to_copy(HeapRegion* hr) const;
 143   double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;
 144 
 145   double predict_survivor_regions_evac_time() const;
 146 
 147   void cset_regions_freed() {
 148     bool update = should_update_surv_rate_group_predictors();
 149 
 150     _short_lived_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 151     _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 152   }
 153 
 154   G1MMUTracker* mmu_tracker() {
 155     return _mmu_tracker;
 156   }
 157 
 158   const G1MMUTracker* mmu_tracker() const {
 159     return _mmu_tracker;
 160   }
 161 
 162   double max_pause_time_ms() const {
 163     return _mmu_tracker->max_gc_time() * 1000.0;
 164   }
 165 
 166   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;
 167 
 168   double predict_yg_surv_rate(int age) const;
 169 
 170   double accum_yg_surv_rate_pred(int age) const;
 171 
 172 private:
 173   G1CollectionSet* _collection_set;
 174   double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
 175   double other_time_ms(double pause_time_ms) const;
 176 
 177   double young_other_time_ms() const;
 178   double non_young_other_time_ms() const;
 179   double constant_other_time_ms(double pause_time_ms) const;
 180 
 181   G1CollectionSetChooser* cset_chooser() const;
 182 
 183   // The number of bytes copied during the GC.
 184   size_t _bytes_copied_during_gc;
 185 
 186   // Stash a pointer to the g1 heap.
 187   G1CollectedHeap* _g1h;
 188 
 189   G1GCPhaseTimes* _phase_times;
 190 
 191   // This set of variables tracks the collector efficiency, in order to
 192   // determine whether we should initiate a new marking.
 193   double _mark_remark_start_sec;
 194   double _mark_cleanup_start_sec;
 195 
 196   // Updates the internal young list maximum and target lengths. Returns the
 197   // unbounded young list target length. If no rs_length parameter is passed,
 198   // predict the RS length using the prediction model, otherwise use the
 199   // given rs_length as the prediction.
 200   uint update_young_list_max_and_target_length();
 201   uint update_young_list_max_and_target_length(size_t rs_length);
 202 
 203   // Update the young list target length either by setting it to the
 204   // desired fixed value or by calculating it using G1's pause
 205   // prediction model.
 206   // Returns the unbounded young list target length.
 207   uint update_young_list_target_length(size_t rs_length);
 208 
 209   // Calculate and return the minimum desired young list target
 210   // length. This is the minimum desired young list length according
 211   // to the user's inputs.
 212   uint calculate_young_list_desired_min_length(uint base_min_length) const;
 213 
 214   // Calculate and return the maximum desired young list target
 215   // length. This is the maximum desired young list length according
 216   // to the user's inputs.
 217   uint calculate_young_list_desired_max_length() const;
 218 
 219   // Calculate and return the maximum young list target length that
 220   // can fit into the pause time goal. The parameters are: rs_length
 221   // represent the prediction of how large the young RSet lengths will
 222   // be, base_min_length is the already existing number of regions in
 223   // the young list, min_length and max_length are the desired min and
 224   // max young list length according to the user's inputs.
 225   uint calculate_young_list_target_length(size_t rs_length,
 226                                           uint base_min_length,
 227                                           uint desired_min_length,
 228                                           uint desired_max_length) const;
 229 
 230   // Result of the bounded_young_list_target_length() method, containing both the
 231   // bounded as well as the unbounded young list target lengths in this order.
 232   typedef Pair<uint, uint, StackObj> YoungTargetLengths;
 233   YoungTargetLengths young_list_target_lengths(size_t rs_length) const;
 234 
 235   void update_rs_length_prediction();
 236   void update_rs_length_prediction(size_t prediction);
 237 
 238   // Check whether a given young length (young_length) fits into the
 239   // given target pause time and whether the prediction for the amount
 240   // of objects to be copied for the given length will fit into the
 241   // given free space (expressed by base_free_regions).  It is used by
 242   // calculate_young_list_target_length().
 243   bool predict_will_fit(uint young_length, double base_time_ms,
 244                         uint base_free_regions, double target_pause_time_ms) const;
 245 
 246 public:
 247   size_t pending_cards() const { return _pending_cards; }
 248 
 249   // Calculate the minimum number of old regions we'll add to the CSet
 250   // during a mixed GC.
 251   uint calc_min_old_cset_length() const;
 252 
 253   // Calculate the maximum number of old regions we'll add to the CSet
 254   // during a mixed GC.
 255   uint calc_max_old_cset_length() const;
 256 
 257   // Returns the given amount of reclaimable bytes (that represents
 258   // the amount of reclaimable space still to be collected) as a
 259   // percentage of the current heap capacity.
 260   double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
 261 
 262   jlong collection_pause_end_millis() { return _collection_pause_end_millis; }
 263 
 264 private:
 265   void clear_collection_set_candidates();
 266   // Sets up marking if proper conditions are met.
 267   void maybe_start_marking();
 268 
 269   // The kind of STW pause.
 270   enum PauseKind {
 271     FullGC,
 272     YoungOnlyGC,
 273     MixedGC,
 274     LastYoungGC,
 275     InitialMarkGC,
 276     Cleanup,
 277     Remark
 278   };
 279 
 280   // Calculate PauseKind from internal state.
 281   PauseKind young_gc_pause_kind() const;
 282   // Record the given STW pause with the given start and end times (in s).
 283   void record_pause(PauseKind kind, double start, double end);
 284   // Indicate that we aborted marking before doing any mixed GCs.
 285   void abort_time_to_mixed_tracking();
 286 public:
 287 
 288   G1Policy(STWGCTimer* gc_timer);
 289 
 290   virtual ~G1Policy();
 291 
 292   static G1Policy* create_policy(STWGCTimer* gc_timer_stw);
 293 
 294   G1CollectorState* collector_state() const;
 295 
 296   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 297 
 298   // Check the current value of the young list RSet length and
 299   // compare it against the last prediction. If the current value is
 300   // higher, recalculate the young list target length prediction.
 301   void revise_young_list_target_length_if_necessary(size_t rs_length);
 302 
 303   // This should be called after the heap is resized.
 304   void record_new_heap_size(uint new_number_of_regions);
 305 
 306   virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
 307 
 308   void note_gc_start();
 309 
 310   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 311 
 312   bool about_to_start_mixed_phase() const;
 313 
 314   // Record the start and end of an evacuation pause.
 315   void record_collection_pause_start(double start_time_sec);
 316   virtual void record_collection_pause_end(double pause_time_ms, size_t heap_used_bytes_before_gc);
 317 
 318   // Record the start and end of a full collection.
 319   void record_full_collection_start();
 320   virtual void record_full_collection_end();
 321 
 322   // Must currently be called while the world is stopped.
 323   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 324 
 325   // Record start and end of remark.
 326   void record_concurrent_mark_remark_start();
 327   void record_concurrent_mark_remark_end();
 328 
 329   // Record start, end, and completion of cleanup.
 330   void record_concurrent_mark_cleanup_start();
 331   void record_concurrent_mark_cleanup_end();
 332 
 333   void print_phases();
 334 
 335   // Record how much space we copied during a GC. This is typically
 336   // called when a GC alloc region is being retired.
 337   void record_bytes_copied_during_gc(size_t bytes) {
 338     _bytes_copied_during_gc += bytes;
 339   }
 340 
 341   // The amount of space we copied during a GC.
 342   size_t bytes_copied_during_gc() const {
 343     return _bytes_copied_during_gc;
 344   }
 345 
 346   bool next_gc_should_be_mixed(const char* true_action_str,
 347                                const char* false_action_str) const;
 348 
 349   // Calculate and return the number of initial and optional old gen regions from
 350   // the given collection set candidates and the remaining time.
 351   void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
 352                                             double time_remaining_ms,
 353                                             uint& num_initial_regions,
 354                                             uint& num_optional_regions);
 355 
 356   // Calculate the number of optional regions from the given collection set candidates,
 357   // the remaining time and the maximum number of these regions and return the number
 358   // of actually selected regions in num_optional_regions.
 359   void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
 360                                                  uint const max_optional_regions,
 361                                                  double time_remaining_ms,
 362                                                  uint& num_optional_regions);
 363 
 364 private:
 365   // Set the state to start a concurrent marking cycle and clear
 366   // _initiate_conc_mark_if_possible because it has now been
 367   // acted on.
 368   void initiate_conc_mark();
 369 
 370 public:
 371   // This sets the initiate_conc_mark_if_possible() flag to start a
 372   // new cycle, as long as we are not already in one. It's best if it
 373   // is called during a safepoint when the test whether a cycle is in
 374   // progress or not is stable.
 375   bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
 376 
 377   // This is called at the very beginning of an evacuation pause (it
 378   // has to be the first thing that the pause does). If
 379   // initiate_conc_mark_if_possible() is true, and the concurrent
 380   // marking thread has completed its work during the previous cycle,
 381   // it will set in_initial_mark_gc() to so that the pause does
 382   // the initial-mark work and start a marking cycle.
 383   void decide_on_conc_mark_initiation();
 384 
 385   void finished_recalculating_age_indexes(bool is_survivors) {
 386     if (is_survivors) {
 387       _survivor_surv_rate_group->finished_recalculating_age_indexes();
 388     } else {
 389       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
 390     }
 391   }
 392 
 393   size_t young_list_target_length() const { return _young_list_target_length; }
 394 
 395   bool should_allocate_mutator_region() const;
 396 
 397   bool can_expand_young_list() const;
 398 
 399   uint young_list_max_length() const {
 400     return _young_list_max_length;
 401   }
 402 
 403   bool use_adaptive_young_list_length() const;
 404 
 405   void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
 406 
 407 private:
 408   //
 409   // Survivor regions policy.
 410   //
 411 
 412   // Current tenuring threshold, set to 0 if the collector reaches the
 413   // maximum amount of survivors regions.
 414   uint _tenuring_threshold;
 415 
 416   // The limit on the number of regions allocated for survivors.
 417   uint _max_survivor_regions;
 418 
 419   AgeTable _survivors_age_table;
 420 
 421   size_t desired_survivor_size(uint max_regions) const;
 422 
 423   // Fraction used when predicting how many optional regions to include in
 424   // the CSet. This fraction of the available time is used for optional regions,
 425   // the rest is used to add old regions to the normal CSet.
 426   double optional_prediction_fraction() { return 0.2; }
 427 
 428 public:
 429   // Fraction used when evacuating the optional regions. This fraction of the
 430   // remaining time is used to choose what regions to include in the evacuation.
 431   double optional_evacuation_fraction() { return 0.75; }
 432 
 433   uint tenuring_threshold() const { return _tenuring_threshold; }
 434 
 435   uint max_survivor_regions() {
 436     return _max_survivor_regions;
 437   }
 438 
 439   void note_start_adding_survivor_regions() {
 440     _survivor_surv_rate_group->start_adding_regions();
 441   }
 442 
 443   void note_stop_adding_survivor_regions() {
 444     _survivor_surv_rate_group->stop_adding_regions();
 445   }
 446 
 447   void record_age_table(AgeTable* age_table) {
 448     _survivors_age_table.merge(age_table);
 449   }
 450 
 451   void print_age_table();
 452 
 453   void update_max_gc_locker_expansion();
 454 
 455   void update_survivors_policy();
 456 
 457   virtual bool force_upgrade_to_full() {
 458     return false;
 459   }
 460 };
 461 
 462 #endif // SHARE_GC_G1_G1POLICY_HPP