1 /*
   2  * Copyright (c) 2016, 2018, 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.
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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_VM_GC_G1_G1POLICY_HPP
  26 #define SHARE_VM_GC_G1_G1POLICY_HPP
  27 
  28 #include "gc/g1/g1CollectorState.hpp"
  29 #include "gc/g1/g1GCPhaseTimes.hpp"
  30 #include "gc/g1/g1InCSetState.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 CollectionSetChooser;
  47 class G1IHOPControl;
  48 class G1Analytics;
  49 class G1SurvivorRegions;
  50 class G1YoungGenSizer;
  51 class GCPolicyCounters;
  52 class STWGCTimer;
  53 
  54 class G1Policy: public CHeapObj<mtGC> {
  55  private:
  56 
  57   static G1IHOPControl* create_ihop_control(const G1Predictions* predictor);
  58   // Update the IHOP control with necessary statistics.
  59   void update_ihop_prediction(double mutator_time_s,
  60                               size_t mutator_alloc_bytes,
  61                               size_t young_gen_size,
  62                               bool this_gc_was_young_only);
  63   void report_ihop_statistics();
  64 
  65   G1Predictions _predictor;
  66   G1Analytics* _analytics;
  67   G1RemSetTrackingPolicy _remset_tracker;
  68   G1MMUTracker* _mmu_tracker;
  69   G1IHOPControl* _ihop_control;
  70 
  71   GCPolicyCounters* _policy_counters;
  72 
  73   double _full_collection_start_sec;
  74 
  75   jlong _collection_pause_end_millis;
  76 
  77   uint _young_list_target_length;
  78   uint _young_list_fixed_length;
  79 
  80   // The max number of regions we can extend the eden by while the GC
  81   // locker is active. This should be >= _young_list_target_length;
  82   uint _young_list_max_length;
  83 
  84   // SurvRateGroups below must be initialized after the predictor because they
  85   // indirectly use it through this object passed to their constructor.
  86   SurvRateGroup* _short_lived_surv_rate_group;
  87   SurvRateGroup* _survivor_surv_rate_group;
  88 
  89   double _reserve_factor;
  90   // This will be set when the heap is expanded
  91   // for the first time during initialization.
  92   uint   _reserve_regions;
  93 
  94   G1YoungGenSizer _young_gen_sizer;
  95 
  96   uint _free_regions_at_end_of_collection;
  97 
  98   size_t _max_rs_lengths;
  99 
 100   size_t _rs_lengths_prediction;
 101 
 102   size_t _pending_cards;
 103 
 104   // The amount of allocated bytes in old gen during the last mutator and the following
 105   // young GC phase.
 106   size_t _bytes_allocated_in_old_since_last_gc;
 107 
 108   G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
 109 
 110   bool should_update_surv_rate_group_predictors() {
 111     return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
 112   }
 113 public:
 114   const G1Predictions& predictor() const { return _predictor; }
 115   const G1Analytics* analytics()   const { return const_cast<const G1Analytics*>(_analytics); }
 116 
 117   G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
 118 
 119   // Add the given number of bytes to the total number of allocated bytes in the old gen.
 120   void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
 121 
 122   void set_region_eden(HeapRegion* hr) {
 123     hr->set_eden();
 124     hr->install_surv_rate_group(_short_lived_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_max_rs_lengths(size_t rs_lengths) {
 133     _max_rs_lengths = rs_lengths;
 134   }
 135 
 136   double predict_base_elapsed_time_ms(size_t pending_cards) const;
 137   double predict_base_elapsed_time_ms(size_t pending_cards,
 138                                       size_t scanned_cards) const;
 139   size_t predict_bytes_to_copy(HeapRegion* hr) const;
 140   double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;
 141 
 142   double predict_survivor_regions_evac_time() const;
 143 
 144   void cset_regions_freed() {
 145     bool update = should_update_surv_rate_group_predictors();
 146 
 147     _short_lived_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 148     _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
 149   }
 150 
 151   G1MMUTracker* mmu_tracker() {
 152     return _mmu_tracker;
 153   }
 154 
 155   const G1MMUTracker* mmu_tracker() const {
 156     return _mmu_tracker;
 157   }
 158 
 159   double max_pause_time_ms() const {
 160     return _mmu_tracker->max_gc_time() * 1000.0;
 161   }
 162 
 163   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;
 164 
 165   double predict_yg_surv_rate(int age) const;
 166 
 167   double accum_yg_surv_rate_pred(int age) const;
 168 
 169 private:
 170   G1CollectionSet* _collection_set;
 171   double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
 172   double other_time_ms(double pause_time_ms) const;
 173 
 174   double young_other_time_ms() const;
 175   double non_young_other_time_ms() const;
 176   double constant_other_time_ms(double pause_time_ms) const;
 177 
 178   CollectionSetChooser* cset_chooser() const;
 179 
 180   // The number of bytes copied during the GC.
 181   size_t _bytes_copied_during_gc;
 182 
 183   // Stash a pointer to the g1 heap.
 184   G1CollectedHeap* _g1h;
 185 
 186   G1GCPhaseTimes* _phase_times;
 187 
 188   // This set of variables tracks the collector efficiency, in order to
 189   // determine whether we should initiate a new marking.
 190   double _mark_remark_start_sec;
 191   double _mark_cleanup_start_sec;
 192 
 193   // Updates the internal young list maximum and target lengths. Returns the
 194   // unbounded young list target length.
 195   uint update_young_list_max_and_target_length();
 196   uint update_young_list_max_and_target_length(size_t rs_lengths);
 197 
 198   // Update the young list target length either by setting it to the
 199   // desired fixed value or by calculating it using G1's pause
 200   // prediction model. If no rs_lengths parameter is passed, predict
 201   // the RS lengths using the prediction model, otherwise use the
 202   // given rs_lengths as the prediction.
 203   // Returns the unbounded young list target length.
 204   uint update_young_list_target_length(size_t rs_lengths);
 205 
 206   // Calculate and return the minimum desired young list target
 207   // length. This is the minimum desired young list length according
 208   // to the user's inputs.
 209   uint calculate_young_list_desired_min_length(uint base_min_length) const;
 210 
 211   // Calculate and return the maximum desired young list target
 212   // length. This is the maximum desired young list length according
 213   // to the user's inputs.
 214   uint calculate_young_list_desired_max_length() const;
 215 
 216   // Calculate and return the maximum young list target length that
 217   // can fit into the pause time goal. The parameters are: rs_lengths
 218   // represent the prediction of how large the young RSet lengths will
 219   // be, base_min_length is the already existing number of regions in
 220   // the young list, min_length and max_length are the desired min and
 221   // max young list length according to the user's inputs.
 222   uint calculate_young_list_target_length(size_t rs_lengths,
 223                                           uint base_min_length,
 224                                           uint desired_min_length,
 225                                           uint desired_max_length) const;
 226 
 227   // Result of the bounded_young_list_target_length() method, containing both the
 228   // bounded as well as the unbounded young list target lengths in this order.
 229   typedef Pair<uint, uint, StackObj> YoungTargetLengths;
 230   YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
 231 
 232   void update_rs_lengths_prediction();
 233   void update_rs_lengths_prediction(size_t prediction);
 234 
 235   // Check whether a given young length (young_length) fits into the
 236   // given target pause time and whether the prediction for the amount
 237   // of objects to be copied for the given length will fit into the
 238   // given free space (expressed by base_free_regions).  It is used by
 239   // calculate_young_list_target_length().
 240   bool predict_will_fit(uint young_length, double base_time_ms,
 241                         uint base_free_regions, double target_pause_time_ms) const;
 242 
 243 public:
 244   size_t pending_cards() const { return _pending_cards; }
 245 
 246   // Calculate the minimum number of old regions we'll add to the CSet
 247   // during a mixed GC.
 248   uint calc_min_old_cset_length() const;
 249 
 250   // Calculate the maximum number of old regions we'll add to the CSet
 251   // during a mixed GC.
 252   uint calc_max_old_cset_length() const;
 253 
 254   // Returns the given amount of reclaimable bytes (that represents
 255   // the amount of reclaimable space still to be collected) as a
 256   // percentage of the current heap capacity.
 257   double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
 258 
 259   jlong collection_pause_end_millis() { return _collection_pause_end_millis; }
 260 
 261 private:
 262   void clear_collection_set_candidates();
 263   // Sets up marking if proper conditions are met.
 264   void maybe_start_marking();
 265 
 266   // The kind of STW pause.
 267   enum PauseKind {
 268     FullGC,
 269     YoungOnlyGC,
 270     MixedGC,
 271     LastYoungGC,
 272     InitialMarkGC,
 273     Cleanup,
 274     Remark
 275   };
 276 
 277   // Calculate PauseKind from internal state.
 278   PauseKind young_gc_pause_kind() const;
 279   // Record the given STW pause with the given start and end times (in s).
 280   void record_pause(PauseKind kind, double start, double end);
 281   // Indicate that we aborted marking before doing any mixed GCs.
 282   void abort_time_to_mixed_tracking();
 283 public:
 284 
 285   G1Policy(STWGCTimer* gc_timer);
 286 
 287   virtual ~G1Policy();
 288 
 289   G1CollectorState* collector_state() const;
 290 
 291   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 292 
 293   // Check the current value of the young list RSet lengths and
 294   // compare it against the last prediction. If the current value is
 295   // higher, recalculate the young list target length prediction.
 296   void revise_young_list_target_length_if_necessary(size_t rs_lengths);
 297 
 298   // This should be called after the heap is resized.
 299   void record_new_heap_size(uint new_number_of_regions);
 300 
 301   void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
 302 
 303   void note_gc_start();
 304 
 305   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 306 
 307   bool about_to_start_mixed_phase() const;
 308 
 309   // Record the start and end of an evacuation pause.
 310   void record_collection_pause_start(double start_time_sec);
 311   void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
 312 
 313   // Record the start and end of a full collection.
 314   void record_full_collection_start();
 315   void record_full_collection_end();
 316 
 317   // Must currently be called while the world is stopped.
 318   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 319 
 320   // Record start and end of remark.
 321   void record_concurrent_mark_remark_start();
 322   void record_concurrent_mark_remark_end();
 323 
 324   // Record start, end, and completion of cleanup.
 325   void record_concurrent_mark_cleanup_start();
 326   void record_concurrent_mark_cleanup_end();
 327 
 328   void print_phases();
 329 
 330   // Record how much space we copied during a GC. This is typically
 331   // called when a GC alloc region is being retired.
 332   void record_bytes_copied_during_gc(size_t bytes) {
 333     _bytes_copied_during_gc += bytes;
 334   }
 335 
 336   // The amount of space we copied during a GC.
 337   size_t bytes_copied_during_gc() const {
 338     return _bytes_copied_during_gc;
 339   }
 340 
 341   bool next_gc_should_be_mixed(const char* true_action_str,
 342                                const char* false_action_str) const;
 343 
 344   void finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor);
 345 private:
 346   // Set the state to start a concurrent marking cycle and clear
 347   // _initiate_conc_mark_if_possible because it has now been
 348   // acted on.
 349   void initiate_conc_mark();
 350 
 351 public:
 352   // This sets the initiate_conc_mark_if_possible() flag to start a
 353   // new cycle, as long as we are not already in one. It's best if it
 354   // is called during a safepoint when the test whether a cycle is in
 355   // progress or not is stable.
 356   bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
 357 
 358   // This is called at the very beginning of an evacuation pause (it
 359   // has to be the first thing that the pause does). If
 360   // initiate_conc_mark_if_possible() is true, and the concurrent
 361   // marking thread has completed its work during the previous cycle,
 362   // it will set in_initial_mark_gc() to so that the pause does
 363   // the initial-mark work and start a marking cycle.
 364   void decide_on_conc_mark_initiation();
 365 
 366   void finished_recalculating_age_indexes(bool is_survivors) {
 367     if (is_survivors) {
 368       _survivor_surv_rate_group->finished_recalculating_age_indexes();
 369     } else {
 370       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
 371     }
 372   }
 373 
 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 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() const;
 403 public:
 404   uint tenuring_threshold() const { return _tenuring_threshold; }
 405 
 406   uint max_survivor_regions() {
 407     return _max_survivor_regions;
 408   }
 409 
 410   void note_start_adding_survivor_regions() {
 411     _survivor_surv_rate_group->start_adding_regions();
 412   }
 413 
 414   void note_stop_adding_survivor_regions() {
 415     _survivor_surv_rate_group->stop_adding_regions();
 416   }
 417 
 418   void record_age_table(AgeTable* age_table) {
 419     _survivors_age_table.merge(age_table);
 420   }
 421 
 422   void print_age_table();
 423 
 424   void update_max_gc_locker_expansion();
 425 
 426   void update_survivors_policy();
 427 };
 428 
 429 #endif // SHARE_VM_GC_G1_G1POLICY_HPP