1 /*
   2  * Copyright (c) 2016, 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_VM_GC_G1_G1DEFAULTPOLICY_HPP
  26 #define SHARE_VM_GC_G1_G1DEFAULTPOLICY_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/g1Predictions.hpp"
  34 #include "gc/g1/g1Policy.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 G1YoungGenSizer;
  50 class GCPolicyCounters;
  51 
  52 class G1DefaultPolicy: public G1Policy {
  53  private:
  54 
  55   static G1IHOPControl* create_ihop_control(const G1Predictions* predictor);
  56   // Update the IHOP control with necessary statistics.
  57   void update_ihop_prediction(double mutator_time_s,
  58                               size_t mutator_alloc_bytes,
  59                               size_t young_gen_size);
  60   void report_ihop_statistics();
  61 
  62   G1Predictions _predictor;
  63   G1Analytics* _analytics;
  64   G1MMUTracker* _mmu_tracker;
  65   G1IHOPControl* _ihop_control;
  66 
  67   GCPolicyCounters* _policy_counters;
  68 
  69   double _full_collection_start_sec;
  70 
  71   uint _young_list_target_length;
  72   uint _young_list_fixed_length;
  73 
  74   // The max number of regions we can extend the eden by while the GC
  75   // locker is active. This should be >= _young_list_target_length;
  76   uint _young_list_max_length;
  77 
  78   // SurvRateGroups below must be initialized after the predictor because they
  79   // indirectly use it through this object passed to their constructor.
  80   SurvRateGroup* _short_lived_surv_rate_group;
  81   SurvRateGroup* _survivor_surv_rate_group;
  82 
  83   double _reserve_factor;
  84   // This will be set when the heap is expanded
  85   // for the first time during initialization.
  86   uint   _reserve_regions;
  87 
  88   G1YoungGenSizer _young_gen_sizer;
  89 
  90   uint _free_regions_at_end_of_collection;
  91 
  92   size_t _max_rs_lengths;
  93 
  94   size_t _rs_lengths_prediction;
  95 
  96 #ifndef PRODUCT
  97   bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
  98 #endif // PRODUCT
  99 
 100   size_t _pending_cards;
 101 
 102   // The amount of allocated bytes in old gen during the last mutator and the following
 103   // young GC phase.
 104   size_t _bytes_allocated_in_old_since_last_gc;
 105 
 106   G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
 107 public:
 108   const G1Predictions& predictor() const { return _predictor; }
 109   const G1Analytics* analytics()   const { return const_cast<const G1Analytics*>(_analytics); }
 110 
 111   // Add the given number of bytes to the total number of allocated bytes in the old gen.
 112   void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
 113 
 114   // Accessors
 115 
 116   void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
 117     hr->set_eden();
 118     hr->install_surv_rate_group(_short_lived_surv_rate_group);
 119     hr->set_young_index_in_cset(young_index_in_cset);
 120   }
 121 
 122   void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
 123     assert(hr->is_survivor(), "pre-condition");
 124     hr->install_surv_rate_group(_survivor_surv_rate_group);
 125     hr->set_young_index_in_cset(young_index_in_cset);
 126   }
 127 
 128 #ifndef PRODUCT
 129   bool verify_young_ages();
 130 #endif // PRODUCT
 131 
 132   void record_max_rs_lengths(size_t rs_lengths) {
 133     _max_rs_lengths = rs_lengths;
 134   }
 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   bool should_update_surv_rate_group_predictors() {
 146     return collector_state()->last_gc_was_young() && !collector_state()->in_marking_window();
 147   }
 148 
 149   void cset_regions_freed() {
 150     bool update = should_update_surv_rate_group_predictors();
 151 
 152     _short_lived_surv_rate_group->all_surviving_words_recorded(update);
 153     _survivor_surv_rate_group->all_surviving_words_recorded(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   // Returns an estimate of the survival rate of the region at yg-age
 169   // "yg_age".
 170   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;
 171 
 172   double predict_yg_surv_rate(int age) const;
 173 
 174   double accum_yg_surv_rate_pred(int age) const;
 175 
 176 protected:
 177   G1CollectionSet* _collection_set;
 178   virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
 179   virtual double other_time_ms(double pause_time_ms) const;
 180 
 181   double young_other_time_ms() const;
 182   double non_young_other_time_ms() const;
 183   double constant_other_time_ms(double pause_time_ms) const;
 184 
 185   CollectionSetChooser* cset_chooser() const;
 186 private:
 187 
 188   // The number of bytes copied during the GC.
 189   size_t _bytes_copied_during_gc;
 190 
 191   // Stash a pointer to the g1 heap.
 192   G1CollectedHeap* _g1;
 193 
 194   G1GCPhaseTimes* _phase_times;
 195 
 196   // This set of variables tracks the collector efficiency, in order to
 197   // determine whether we should initiate a new marking.
 198   double _mark_remark_start_sec;
 199   double _mark_cleanup_start_sec;
 200 
 201   // Updates the internal young list maximum and target lengths. Returns the
 202   // unbounded young list target length.
 203   uint update_young_list_max_and_target_length();
 204   uint update_young_list_max_and_target_length(size_t rs_lengths);
 205 
 206   // Update the young list target length either by setting it to the
 207   // desired fixed value or by calculating it using G1's pause
 208   // prediction model. If no rs_lengths parameter is passed, predict
 209   // the RS lengths using the prediction model, otherwise use the
 210   // given rs_lengths as the prediction.
 211   // Returns the unbounded young list target length.
 212   uint update_young_list_target_length(size_t rs_lengths);
 213 
 214   // Calculate and return the minimum desired young list target
 215   // length. This is the minimum desired young list length according
 216   // to the user's inputs.
 217   uint calculate_young_list_desired_min_length(uint base_min_length) const;
 218 
 219   // Calculate and return the maximum desired young list target
 220   // length. This is the maximum desired young list length according
 221   // to the user's inputs.
 222   uint calculate_young_list_desired_max_length() const;
 223 
 224   // Calculate and return the maximum young list target length that
 225   // can fit into the pause time goal. The parameters are: rs_lengths
 226   // represent the prediction of how large the young RSet lengths will
 227   // be, base_min_length is the already existing number of regions in
 228   // the young list, min_length and max_length are the desired min and
 229   // max young list length according to the user's inputs.
 230   uint calculate_young_list_target_length(size_t rs_lengths,
 231                                           uint base_min_length,
 232                                           uint desired_min_length,
 233                                           uint desired_max_length) const;
 234 
 235   // Result of the bounded_young_list_target_length() method, containing both the
 236   // bounded as well as the unbounded young list target lengths in this order.
 237   typedef Pair<uint, uint, StackObj> YoungTargetLengths;
 238   YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
 239 
 240   void update_rs_lengths_prediction();
 241   void update_rs_lengths_prediction(size_t prediction);
 242 
 243   // Check whether a given young length (young_length) fits into the
 244   // given target pause time and whether the prediction for the amount
 245   // of objects to be copied for the given length will fit into the
 246   // given free space (expressed by base_free_regions).  It is used by
 247   // calculate_young_list_target_length().
 248   bool predict_will_fit(uint young_length, double base_time_ms,
 249                         uint base_free_regions, double target_pause_time_ms) const;
 250 
 251 public:
 252   size_t pending_cards() const { return _pending_cards; }
 253 
 254   // Calculate the minimum number of old regions we'll add to the CSet
 255   // during a mixed GC.
 256   uint calc_min_old_cset_length() const;
 257 
 258   // Calculate the maximum number of old regions we'll add to the CSet
 259   // during a mixed GC.
 260   uint calc_max_old_cset_length() const;
 261 
 262   // Returns the given amount of uncollected reclaimable space
 263   // as a percentage of the current heap capacity.
 264   double reclaimable_bytes_perc(size_t reclaimable_bytes) const;
 265 
 266 private:
 267   // Sets up marking if proper conditions are met.
 268   void maybe_start_marking();
 269 
 270   // The kind of STW pause.
 271   enum PauseKind {
 272     FullGC,
 273     YoungOnlyGC,
 274     MixedGC,
 275     LastYoungGC,
 276     InitialMarkGC,
 277     Cleanup,
 278     Remark
 279   };
 280 
 281   // Calculate PauseKind from internal state.
 282   PauseKind young_gc_pause_kind() const;
 283   // Record the given STW pause with the given start and end times (in s).
 284   void record_pause(PauseKind kind, double start, double end);
 285   // Indicate that we aborted marking before doing any mixed GCs.
 286   void abort_time_to_mixed_tracking();
 287 public:
 288 
 289   G1DefaultPolicy();
 290 
 291   virtual ~G1DefaultPolicy();
 292 
 293   G1CollectorState* collector_state() const;
 294 
 295   G1GCPhaseTimes* phase_times() const { return _phase_times; }
 296 
 297   // Check the current value of the young list RSet lengths and
 298   // compare it against the last prediction. If the current value is
 299   // higher, recalculate the young list target length prediction.
 300   void revise_young_list_target_length_if_necessary(size_t rs_lengths);
 301 
 302   // This should be called after the heap is resized.
 303   void record_new_heap_size(uint new_number_of_regions);
 304 
 305   void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
 306 
 307   virtual void note_gc_start();
 308 
 309   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
 310 
 311   bool about_to_start_mixed_phase() const;
 312 
 313   // Record the start and end of an evacuation pause.
 314   void record_collection_pause_start(double start_time_sec);
 315   void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
 316 
 317   // Record the start and end of a full collection.
 318   void record_full_collection_start();
 319   void record_full_collection_end();
 320 
 321   // Must currently be called while the world is stopped.
 322   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
 323 
 324   // Record start and end of remark.
 325   void record_concurrent_mark_remark_start();
 326   void record_concurrent_mark_remark_end();
 327 
 328   // Record start, end, and completion of cleanup.
 329   void record_concurrent_mark_cleanup_start();
 330   void record_concurrent_mark_cleanup_end();
 331   void record_concurrent_mark_cleanup_completed();
 332 
 333   virtual 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   // Determine whether there are candidate regions so that the
 347   // next GC should be mixed. The two action strings are used
 348   // in the ergo output when the method returns true or false.
 349   bool next_gc_should_be_mixed(const char* true_action_str,
 350                                const char* false_action_str) const;
 351 
 352   virtual void finalize_collection_set(double target_pause_time_ms);
 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_initial_mark_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 during_initial_mark_pause() to so that the pause does
 371   // the initial-mark work and start a marking cycle.
 372   void decide_on_conc_mark_initiation();
 373 
 374   // Print stats on young survival ratio
 375   void print_yg_surv_rate_info() const;
 376 
 377   void finished_recalculating_age_indexes(bool is_survivors) {
 378     if (is_survivors) {
 379       _survivor_surv_rate_group->finished_recalculating_age_indexes();
 380     } else {
 381       _short_lived_surv_rate_group->finished_recalculating_age_indexes();
 382     }
 383   }
 384 
 385   size_t young_list_target_length() const { return _young_list_target_length; }
 386 
 387   bool is_young_list_full() const;
 388 
 389   bool can_expand_young_list() const;
 390 
 391   uint young_list_max_length() const {
 392     return _young_list_max_length;
 393   }
 394 
 395   bool adaptive_young_list_length() const;
 396 
 397   virtual bool should_process_references() const {
 398     return true;
 399   }
 400 
 401 private:
 402   //
 403   // Survivor regions policy.
 404   //
 405 
 406   // Current tenuring threshold, set to 0 if the collector reaches the
 407   // maximum amount of survivors regions.
 408   uint _tenuring_threshold;
 409 
 410   // The limit on the number of regions allocated for survivors.
 411   uint _max_survivor_regions;
 412 
 413   AgeTable _survivors_age_table;
 414 
 415 public:
 416   uint tenuring_threshold() const { return _tenuring_threshold; }
 417 
 418   uint max_survivor_regions() {
 419     return _max_survivor_regions;
 420   }
 421 
 422   void note_start_adding_survivor_regions() {
 423     _survivor_surv_rate_group->start_adding_regions();
 424   }
 425 
 426   void note_stop_adding_survivor_regions() {
 427     _survivor_surv_rate_group->stop_adding_regions();
 428   }
 429 
 430   void record_age_table(AgeTable* age_table) {
 431     _survivors_age_table.merge(age_table);
 432   }
 433 
 434   void update_max_gc_locker_expansion();
 435 
 436   // Calculates survivor space parameters.
 437   void update_survivors_policy();
 438 };
 439 
 440 #endif // SHARE_VM_GC_G1_G1DEFAULTPOLICY_HPP