1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  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).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_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/g1ConcurrentStartToMixedTimeTracker.hpp"
  32 #include "gc/g1/g1MMUTracker.hpp"
  33 #include "gc/g1/g1OldGenAllocationTracker.hpp"
  34 #include "gc/g1/g1RemSetTrackingPolicy.hpp"
  35 #include "gc/g1/g1Predictions.hpp"
  36 #include "gc/g1/g1YoungGenSizer.hpp"
  37 #include "gc/shared/gcCause.hpp"
  38 #include "utilities/pair.hpp"
  39 
  40 // A G1Policy makes policy decisions that determine the
  41 // characteristics of the collector.  Examples include:
  42 //   * choice of collection set.
  43 //   * when to collect.
  44 
  45 class HeapRegion;
  46 class G1CollectionSet;
  47 class G1CollectionSetCandidates;
  48 class G1CollectionSetChooser;
  49 class G1IHOPControl;
  50 class G1Analytics;
  51 class G1SurvivorRegions;
  52 class G1YoungGenSizer;
  53 class GCPolicyCounters;
  54 class STWGCTimer;
  55 
  56 class G1Policy: public CHeapObj<mtGC> {
  57  private:
  58 
  59   static G1IHOPControl* create_ihop_control(const G1Predictions* predictor);
  60   // Update the IHOP control with necessary statistics.
  61   void update_ihop_prediction(double mutator_time_s,
  62                               size_t mutator_alloc_bytes,
  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_desired_length;
  79   uint _young_list_target_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   // The survivor rate groups below must be initialized after the predictor because they
  86   // indirectly use it through the "this" object passed to their constructor.
  87   G1SurvRateGroup* _eden_surv_rate_group;
  88   G1SurvRateGroup* _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 _rs_length;
 100 
 101   size_t _rs_length_prediction;
 102 
 103   size_t _pending_cards_at_gc_start;
 104 
 105   // Tracking the allocation in the old generation between
 106   // two GCs.
 107   G1OldGenAllocationTracker _old_gen_alloc_tracker;
 108 
 109   G1ConcurrentStartToMixedTimeTracker _concurrent_start_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 logged_cards_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   G1OldGenAllocationTracker* old_gen_alloc_tracker() { return &_old_gen_alloc_tracker; }
 123 
 124   void set_region_eden(HeapRegion* hr) {
 125     hr->set_eden();
 126     hr->install_surv_rate_group(_eden_surv_rate_group);
 127   }
 128 
 129   void set_region_survivor(HeapRegion* hr) {
 130     assert(hr->is_survivor(), "pre-condition");
 131     hr->install_surv_rate_group(_survivor_surv_rate_group);
 132   }
 133 
 134   void record_rs_length(size_t rs_length) {
 135     _rs_length = rs_length;
 136   }
 137 
 138   double predict_base_elapsed_time_ms(size_t num_pending_cards) const;
 139 
 140 private:
 141   double predict_base_elapsed_time_ms(size_t num_pending_cards, size_t rs_length) const;
 142 
 143   double predict_region_copy_time_ms(HeapRegion* hr) const;
 144 
 145 public:
 146 
 147   double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = NULL) const;
 148   double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_gc) const;
 149   double predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const;
 150 
 151   void cset_regions_freed() {
 152     bool update = should_update_surv_rate_group_predictors();
 153 
 154     _eden_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 155     _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 156   }
 157 
 158   G1MMUTracker* mmu_tracker() {
 159     return _mmu_tracker;
 160   }
 161 
 162   const G1MMUTracker* mmu_tracker() const {
 163     return _mmu_tracker;
 164   }
 165 
 166   double max_pause_time_ms() const {
 167     return _mmu_tracker->max_gc_time() * 1000.0;
 168   }
 169 
 170 private:
 171   G1CollectionSet* _collection_set;
 172 
 173   bool next_gc_should_be_mixed(const char* true_action_str,
 174                                const char* false_action_str) const;
 175 
 176   double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
 177   double other_time_ms(double pause_time_ms) const;
 178 
 179   double young_other_time_ms() const;
 180   double non_young_other_time_ms() const;
 181   double constant_other_time_ms(double pause_time_ms) const;
 182 
 183   G1CollectionSetChooser* cset_chooser() const;
 184 
 185   // Stash a pointer to the g1 heap.
 186   G1CollectedHeap* _g1h;
 187 
 188   G1GCPhaseTimes* _phase_times;
 189 
 190   // This set of variables tracks the collector efficiency, in order to
 191   // determine whether we should initiate a new marking.
 192   double _mark_remark_start_sec;
 193   double _mark_cleanup_start_sec;
 194 
 195   // Updates the internal young gen maximum and target and desired lengths.
 196   // If no rs_length parameter is passed, predict the RS length using the
 197   // prediction model, otherwise use the given rs_length as the prediction.
 198   void update_young_length_bounds();
 199   void update_young_length_bounds(size_t rs_length);
 200 
 201   // Calculate and return the minimum desired eden length based on the MMU target.
 202   uint calculate_desired_eden_length_by_mmu() const;
 203 
 204   // Calculate and return the desired eden length that can fit into the pause time goal.
 205   // The parameters are: rs_length represents the prediction of how large the
 206   // young RSet lengths will be, min_eden_length and max_eden_length are the bounds
 207   // (inclusive) within eden can grow.
 208   uint calculate_desired_eden_length_by_pause(double base_time_ms,
 209                                               uint min_eden_length,
 210                                               uint max_eden_length) const;
 211 
 212   // Calculates the desired eden length before mixed gc so that after adding the
 213   // minimum amount of old gen regions from the collection set, the eden fits into
 214   // the pause time goal.
 215   uint calculate_desired_eden_length_before_mixed(double survivor_base_time_ms,
 216                                                   uint min_eden_length,
 217                                                   uint max_eden_length) const;
 218 
 219   // Calculate desired young length based on current situation without taking actually
 220   // available free regions into account.
 221   uint calculate_young_desired_length(size_t rs_length) const;
 222   // Limit the given desired young length to available free regions.
 223   uint calculate_young_target_length(uint desired_young_length) const;
 224   // The GCLocker might cause us to need more regions than the target. Calculate
 225   // the maximum number of regions to use in that case.
 226   uint calculate_young_max_length(uint target_young_length) const;
 227 
 228   void update_rs_length_prediction();
 229   void update_rs_length_prediction(size_t prediction);
 230 
 231   size_t predict_bytes_to_copy(HeapRegion* hr) const;
 232   double predict_survivor_regions_evac_time() const;
 233 
 234   // Check whether a given young length (young_length) fits into the
 235   // given target pause time and whether the prediction for the amount
 236   // of objects to be copied for the given length will fit into the
 237   // given free space (expressed by base_free_regions).  It is used by
 238   // calculate_young_list_target_length().
 239   bool predict_will_fit(uint young_length, double base_time_ms,
 240                         uint base_free_regions, double target_pause_time_ms) const;
 241 
 242 public:
 243   size_t pending_cards_at_gc_start() const { return _pending_cards_at_gc_start; }
 244 
 245   // Calculate the minimum number of old regions we'll add to the CSet
 246   // during a mixed GC.
 247   uint calc_min_old_cset_length() const;
 248 
 249   // Calculate the maximum number of old regions we'll add to the CSet
 250   // during a mixed GC.
 251   uint calc_max_old_cset_length() const;
 252 
 253   // Returns the given amount of reclaimable bytes (that represents
 254   // the amount of reclaimable space still to be collected) as a
 255   // percentage of the current heap capacity.
 256   double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
 257 
 258   jlong collection_pause_end_millis() { return _collection_pause_end_millis; }
 259 
 260 private:
 261   void clear_collection_set_candidates();
 262   // Sets up marking if proper conditions are met.
 263   void maybe_start_marking();
 264 
 265   // The kind of STW pause.
 266   enum PauseKind {
 267     FullGC,
 268     YoungOnlyGC,
 269     MixedGC,
 270     LastYoungGC,
 271     ConcurrentStartGC,
 272     Cleanup,
 273     Remark
 274   };
 275 
 276   static bool is_young_only_pause(PauseKind kind);
 277   static bool is_last_young_pause(PauseKind kind);
 278   static bool is_concurrent_start_pause(PauseKind kind);
 279   // Calculate PauseKind from internal state.
 280   PauseKind young_gc_pause_kind() const;
 281   // Record the given STW pause with the given start and end times (in s).
 282   void record_pause(PauseKind kind, double start, double end);
 283   // Indicate that we aborted marking before doing any mixed GCs.
 284   void abort_time_to_mixed_tracking();
 285 
 286   // Record and log stats before not-full collection.
 287   void record_concurrent_refinement_stats();
 288 
 289 public:
 290 
 291   G1Policy(STWGCTimer* gc_timer);
 292 
 293   virtual ~G1Policy();
 294 
 295   static G1Policy* create_policy(STWGCTimer* gc_timer_stw);
 296 
 297   G1CollectorState* collector_state() const;
 298 
 299   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 300 
 301   // Check the current value of the young list RSet length and
 302   // compare it against the last prediction. If the current value is
 303   // higher, recalculate the young list target length prediction.
 304   void revise_young_list_target_length_if_necessary(size_t rs_length);
 305 
 306   // This should be called after the heap is resized.
 307   void record_new_heap_size(uint new_number_of_regions);
 308 
 309   virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
 310 
 311   void note_gc_start();
 312 
 313   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 314 
 315   bool about_to_start_mixed_phase() const;
 316 
 317   // Record the start and end of an evacuation pause.
 318   void record_collection_pause_start(double start_time_sec);
 319   virtual void record_collection_pause_end(double pause_time_ms);
 320 
 321   // Record the start and end of a full collection.
 322   void record_full_collection_start();
 323   virtual void record_full_collection_end();
 324 
 325   // Must currently be called while the world is stopped.
 326   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 327 
 328   // Record start and end of remark.
 329   void record_concurrent_mark_remark_start();
 330   void record_concurrent_mark_remark_end();
 331 
 332   // Record start, end, and completion of cleanup.
 333   void record_concurrent_mark_cleanup_start();
 334   void record_concurrent_mark_cleanup_end();
 335 
 336   void print_phases();
 337 
 338   // Calculate and return the number of initial and optional old gen regions from
 339   // the given collection set candidates and the remaining time.
 340   void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
 341                                             double time_remaining_ms,
 342                                             uint& num_initial_regions,
 343                                             uint& num_optional_regions);
 344 
 345   // Calculate the number of optional regions from the given collection set candidates,
 346   // the remaining time and the maximum number of these regions and return the number
 347   // of actually selected regions in num_optional_regions.
 348   void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
 349                                                  uint const max_optional_regions,
 350                                                  double time_remaining_ms,
 351                                                  uint& num_optional_regions);
 352 
 353 private:
 354   // Set the state to start a concurrent marking cycle and clear
 355   // _initiate_conc_mark_if_possible because it has now been
 356   // acted on.
 357   void initiate_conc_mark();
 358 
 359 public:
 360   // This sets the initiate_conc_mark_if_possible() flag to start a
 361   // new cycle, as long as we are not already in one. It's best if it
 362   // is called during a safepoint when the test whether a cycle is in
 363   // progress or not is stable.
 364   bool force_concurrent_start_if_outside_cycle(GCCause::Cause gc_cause);
 365 
 366   // This is called at the very beginning of an evacuation pause (it
 367   // has to be the first thing that the pause does). If
 368   // initiate_conc_mark_if_possible() is true, and the concurrent
 369   // marking thread has completed its work during the previous cycle,
 370   // it will set in_concurrent_start_gc() to so that the pause does
 371   // the concurrent start work and start a marking cycle.
 372   void decide_on_conc_mark_initiation();
 373 
 374   uint young_list_desired_length() const { return _young_list_desired_length; }
 375   size_t young_list_target_length() const { return _young_list_target_length; }
 376 
 377   bool should_allocate_mutator_region() const;
 378 
 379   bool can_expand_young_list() const;
 380 
 381   uint young_list_max_length() const {
 382     return _young_list_max_length;
 383   }
 384 
 385   bool use_adaptive_young_list_length() const;
 386 
 387   void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
 388 
 389 private:
 390   //
 391   // Survivor regions policy.
 392   //
 393 
 394   // Current tenuring threshold, set to 0 if the collector reaches the
 395   // maximum amount of survivors regions.
 396   uint _tenuring_threshold;
 397 
 398   // The limit on the number of regions allocated for survivors.
 399   uint _max_survivor_regions;
 400 
 401   AgeTable _survivors_age_table;
 402 
 403   size_t desired_survivor_size(uint max_regions) const;
 404 
 405   // Fraction used when predicting how many optional regions to include in
 406   // the CSet. This fraction of the available time is used for optional regions,
 407   // the rest is used to add old regions to the normal CSet.
 408   double optional_prediction_fraction() { return 0.2; }
 409 
 410 public:
 411   // Fraction used when evacuating the optional regions. This fraction of the
 412   // remaining time is used to choose what regions to include in the evacuation.
 413   double optional_evacuation_fraction() { return 0.75; }
 414 
 415   uint tenuring_threshold() const { return _tenuring_threshold; }
 416 
 417   uint max_survivor_regions() {
 418     return _max_survivor_regions;
 419   }
 420 
 421   void note_start_adding_survivor_regions() {
 422     _survivor_surv_rate_group->start_adding_regions();
 423   }
 424 
 425   void note_stop_adding_survivor_regions() {
 426     _survivor_surv_rate_group->stop_adding_regions();
 427   }
 428 
 429   void record_age_table(AgeTable* age_table) {
 430     _survivors_age_table.merge(age_table);
 431   }
 432 
 433   void print_age_table();
 434 
 435   void update_survivors_policy();
 436 
 437   virtual bool force_upgrade_to_full() {
 438     return false;
 439   }
 440 };
 441 
 442 #endif // SHARE_GC_G1_G1POLICY_HPP