1 /*
   2  * Copyright (c) 2016, 2020, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_GC_G1_G1POLICY_HPP
  26 #define SHARE_GC_G1_G1POLICY_HPP
  27 
  28 #include "gc/g1/g1CollectorState.hpp"
  29 #include "gc/g1/g1ConcurrentStartToMixedTimeTracker.hpp"
  30 #include "gc/g1/g1GCPhaseTimes.hpp"
  31 #include "gc/g1/g1HeapRegionAttr.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   uint _young_list_desired_length;
  77   uint _young_list_target_length;
  78 
  79   // The max number of regions we can extend the eden by while the GC
  80   // locker is active. This should be >= _young_list_target_length;
  81   uint _young_list_max_length;
  82 
  83   // The survivor rate groups below must be initialized after the predictor because they
  84   // indirectly use it through the "this" object passed to their constructor.
  85   G1SurvRateGroup* _eden_surv_rate_group;
  86   G1SurvRateGroup* _survivor_surv_rate_group;
  87 
  88   double _reserve_factor;
  89   // This will be set when the heap is expanded
  90   // for the first time during initialization.
  91   uint   _reserve_regions;
  92 
  93   G1YoungGenSizer* _young_gen_sizer;
  94 
  95   uint _free_regions_at_end_of_collection;
  96 
  97   size_t _rs_length;
  98 
  99   size_t _rs_length_prediction;
 100 
 101   size_t _pending_cards_at_gc_start;
 102 
 103   // Tracking the allocation in the old generation between
 104   // two GCs.
 105   G1OldGenAllocationTracker _old_gen_alloc_tracker;
 106 
 107   G1ConcurrentStartToMixedTimeTracker _concurrent_start_to_mixed;
 108 
 109   bool should_update_surv_rate_group_predictors() {
 110     return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
 111   }
 112 
 113   double logged_cards_processing_time() const;
 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   G1OldGenAllocationTracker* old_gen_alloc_tracker() { return &_old_gen_alloc_tracker; }
 121 
 122   void set_region_eden(HeapRegion* hr) {
 123     hr->set_eden();
 124     hr->install_surv_rate_group(_eden_surv_rate_group);
 125   }
 126 
 127   void set_region_survivor(HeapRegion* hr) {
 128     assert(hr->is_survivor(), "pre-condition");
 129     hr->install_surv_rate_group(_survivor_surv_rate_group);
 130   }
 131 
 132   void record_rs_length(size_t rs_length) {
 133     _rs_length = rs_length;
 134   }
 135 
 136   double predict_base_elapsed_time_ms(size_t num_pending_cards) const;
 137 
 138 private:
 139   double predict_base_elapsed_time_ms(size_t num_pending_cards, size_t rs_length) const;
 140 
 141   double predict_region_copy_time_ms(HeapRegion* hr) const;
 142 
 143 public:
 144 
 145   double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = NULL) const;
 146   double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_gc) const;
 147   double predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const;
 148 
 149   void cset_regions_freed() {
 150     bool update = should_update_surv_rate_group_predictors();
 151 
 152     _eden_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 153     _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 154   }
 155 
 156   G1MMUTracker* mmu_tracker() {
 157     return _mmu_tracker;
 158   }
 159 
 160   const G1MMUTracker* mmu_tracker() const {
 161     return _mmu_tracker;
 162   }
 163 
 164   double max_pause_time_ms() const {
 165     return _mmu_tracker->max_gc_time() * 1000.0;
 166   }
 167 
 168 private:
 169   G1CollectionSet* _collection_set;
 170 
 171   bool next_gc_should_be_mixed(const char* true_action_str,
 172                                const char* false_action_str) const;
 173 
 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   // Stash a pointer to the g1 heap.
 184   G1CollectedHeap* _g1h;
 185 
 186   STWGCTimer*     _phase_times_timer;
 187   // Lazily initialized
 188   mutable 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 private:
 259   void clear_collection_set_candidates();
 260   // Sets up marking if proper conditions are met.
 261   void maybe_start_marking();
 262 
 263   // The kind of STW pause.
 264   enum PauseKind {
 265     FullGC,
 266     YoungOnlyGC,
 267     MixedGC,
 268     LastYoungGC,
 269     ConcurrentStartGC,
 270     Cleanup,
 271     Remark
 272   };
 273 
 274   static bool is_young_only_pause(PauseKind kind);
 275   static bool is_mixed_pause(PauseKind kind);
 276   static bool is_last_young_pause(PauseKind kind);
 277   static bool is_concurrent_start_pause(PauseKind kind);
 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 
 285   // Record and log stats before not-full collection.
 286   void record_concurrent_refinement_stats();
 287 
 288 public:
 289 
 290   G1Policy(STWGCTimer* gc_timer);
 291 
 292   virtual ~G1Policy();
 293 
 294   static G1Policy* create_policy(STWGCTimer* gc_timer_stw);
 295 
 296   G1CollectorState* collector_state() const;
 297 
 298   G1GCPhaseTimes* phase_times() const;
 299 
 300   // Check the current value of the young list RSet length and
 301   // compare it against the last prediction. If the current value is
 302   // higher, recalculate the young list target length prediction.
 303   void revise_young_list_target_length_if_necessary(size_t rs_length);
 304 
 305   // This should be called after the heap is resized.
 306   void record_new_heap_size(uint new_number_of_regions);
 307 
 308   virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
 309 
 310   void note_gc_start();
 311 
 312   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 313 
 314   bool about_to_start_mixed_phase() const;
 315 
 316   // Record the start and end of an evacuation pause.
 317   void record_collection_pause_start(double start_time_sec);
 318   virtual void record_collection_pause_end(double pause_time_ms);
 319 
 320   // Record the start and end of a full collection.
 321   void record_full_collection_start();
 322   virtual void record_full_collection_end();
 323 
 324   // Must currently be called while the world is stopped.
 325   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 326 
 327   // Record start and end of remark.
 328   void record_concurrent_mark_remark_start();
 329   void record_concurrent_mark_remark_end();
 330 
 331   // Record start, end, and completion of cleanup.
 332   void record_concurrent_mark_cleanup_start();
 333   void record_concurrent_mark_cleanup_end();
 334 
 335   void print_phases();
 336 
 337   // Calculate and return the number of initial and optional old gen regions from
 338   // the given collection set candidates and the remaining time.
 339   void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
 340                                             double time_remaining_ms,
 341                                             uint& num_initial_regions,
 342                                             uint& num_optional_regions);
 343 
 344   // Calculate the number of optional regions from the given collection set candidates,
 345   // the remaining time and the maximum number of these regions and return the number
 346   // of actually selected regions in num_optional_regions.
 347   void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
 348                                                  uint const max_optional_regions,
 349                                                  double time_remaining_ms,
 350                                                  uint& num_optional_regions);
 351 
 352 private:
 353   // Set the state to start a concurrent marking cycle and clear
 354   // _initiate_conc_mark_if_possible because it has now been
 355   // acted on.
 356   void initiate_conc_mark();
 357 
 358 public:
 359   // This sets the initiate_conc_mark_if_possible() flag to start a
 360   // new cycle, as long as we are not already in one. It's best if it
 361   // is called during a safepoint when the test whether a cycle is in
 362   // progress or not is stable.
 363   bool force_concurrent_start_if_outside_cycle(GCCause::Cause gc_cause);
 364 
 365   // This is called at the very beginning of an evacuation pause (it
 366   // has to be the first thing that the pause does). If
 367   // initiate_conc_mark_if_possible() is true, and the concurrent
 368   // marking thread has completed its work during the previous cycle,
 369   // it will set in_concurrent_start_gc() to so that the pause does
 370   // the concurrent start work and start a marking cycle.
 371   void decide_on_conc_mark_initiation();
 372 
 373   uint young_list_desired_length() const { return _young_list_desired_length; }
 374   size_t young_list_target_length() const { return _young_list_target_length; }
 375 
 376   bool should_allocate_mutator_region() const;
 377 
 378   bool can_expand_young_list() const;
 379 
 380   uint young_list_max_length() const {
 381     return _young_list_max_length;
 382   }
 383 
 384   bool use_adaptive_young_list_length() const;
 385 
 386   void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
 387 
 388 private:
 389   //
 390   // Survivor regions policy.
 391   //
 392 
 393   // Current tenuring threshold, set to 0 if the collector reaches the
 394   // maximum amount of survivors regions.
 395   uint _tenuring_threshold;
 396 
 397   // The limit on the number of regions allocated for survivors.
 398   uint _max_survivor_regions;
 399 
 400   AgeTable _survivors_age_table;
 401 
 402   size_t desired_survivor_size(uint max_regions) const;
 403 
 404   // Fraction used when predicting how many optional regions to include in
 405   // the CSet. This fraction of the available time is used for optional regions,
 406   // the rest is used to add old regions to the normal CSet.
 407   double optional_prediction_fraction() { return 0.2; }
 408 
 409 public:
 410   // Fraction used when evacuating the optional regions. This fraction of the
 411   // remaining time is used to choose what regions to include in the evacuation.
 412   double optional_evacuation_fraction() { return 0.75; }
 413 
 414   uint tenuring_threshold() const { return _tenuring_threshold; }
 415 
 416   uint max_survivor_regions() {
 417     return _max_survivor_regions;
 418   }
 419 
 420   void note_start_adding_survivor_regions() {
 421     _survivor_surv_rate_group->start_adding_regions();
 422   }
 423 
 424   void note_stop_adding_survivor_regions() {
 425     _survivor_surv_rate_group->stop_adding_regions();
 426   }
 427 
 428   void record_age_table(AgeTable* age_table) {
 429     _survivors_age_table.merge(age_table);
 430   }
 431 
 432   void print_age_table();
 433 
 434   void update_survivors_policy();
 435 
 436   virtual bool force_upgrade_to_full() {
 437     return false;
 438   }
 439 };
 440 
 441 #endif // SHARE_GC_G1_G1POLICY_HPP