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_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/g1Predictions.hpp"

    34 #include "gc/g1/g1YoungGenSizer.hpp"

    35 #include "gc/shared/gcCause.hpp"

    36 #include "utilities/pair.hpp"

    37 

    38 // A G1Policy makes policy decisions that determine the

    39 // characteristics of the collector.  Examples include:

    40 //   * choice of collection set.

    41 //   * when to collect.

    42 

    43 class HeapRegion;

    44 class G1CollectionSet;

    45 class CollectionSetChooser;

    46 class G1IHOPControl;

    47 class G1Analytics;

    48 class G1YoungGenSizer;

    49 

    50 class G1Policy: public CHeapObj<mtGC> {

    51  private:

    52   G1IHOPControl* _ihop_control;

    53 

    54   G1IHOPControl* create_ihop_control() const;

    55   // Update the IHOP control with necessary statistics.

    56   void update_ihop_prediction(double mutator_time_s,

    57                               size_t mutator_alloc_bytes,

    58                               size_t young_gen_size);

    59   void report_ihop_statistics();

    60 

    61   G1Predictions _predictor;

    62   G1Analytics* _analytics;

    63   G1MMUTracker* _mmu_tracker;

    64 

    65   double _full_collection_start_sec;

    66 

    67   uint _young_list_target_length;

    68   uint _young_list_fixed_length;

    69 

    70   // The max number of regions we can extend the eden by while the GC

    71   // locker is active. This should be >= _young_list_target_length;

    72   uint _young_list_max_length;

    73 

    74   SurvRateGroup* _short_lived_surv_rate_group;

    75   SurvRateGroup* _survivor_surv_rate_group;

    76 

    77   double _reserve_factor;

    78   uint   _reserve_regions;

    79 

    80   G1YoungGenSizer _young_gen_sizer;

    81 

    82   uint _free_regions_at_end_of_collection;

    83 

    84   size_t _max_rs_lengths;

    85 

    86   size_t _rs_lengths_prediction;

    87 

    88 #ifndef PRODUCT

    89   bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);

    90 #endif // PRODUCT

    91 

    92   double _pause_time_target_ms;

    93 

    94   size_t _pending_cards;

    95 

    96   // The amount of allocated bytes in old gen during the last mutator and the following

    97   // young GC phase.

    98   size_t _bytes_allocated_in_old_since_last_gc;

    99 

   100   G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;

   101 public:

   102   const G1Predictions& predictor() const { return _predictor; }

   103   const G1Analytics* analytics()   const { return const_cast<const G1Analytics*>(_analytics); }

   104 

   105   // Add the given number of bytes to the total number of allocated bytes in the old gen.

   106   void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }

   107 

   108   // Accessors

   109 

   110   void set_region_eden(HeapRegion* hr, int young_index_in_cset) {

   111     hr->set_eden();

   112     hr->install_surv_rate_group(_short_lived_surv_rate_group);

   113     hr->set_young_index_in_cset(young_index_in_cset);

   114   }

   115 

   116   void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {

   117     assert(hr->is_survivor(), "pre-condition");

   118     hr->install_surv_rate_group(_survivor_surv_rate_group);

   119     hr->set_young_index_in_cset(young_index_in_cset);

   120   }

   121 

   122 #ifndef PRODUCT

   123   bool verify_young_ages();

   124 #endif // PRODUCT

   125 

   126   void record_max_rs_lengths(size_t rs_lengths) {

   127     _max_rs_lengths = rs_lengths;

   128   }

   129 

   130 

   131   double predict_base_elapsed_time_ms(size_t pending_cards) const;

   132   double predict_base_elapsed_time_ms(size_t pending_cards,

   133                                       size_t scanned_cards) const;

   134   size_t predict_bytes_to_copy(HeapRegion* hr) const;

   135   double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;

   136 

   137   double predict_survivor_regions_evac_time() const;

   138 

   139   bool should_update_surv_rate_group_predictors() {

   140     return collector_state()->last_gc_was_young() && !collector_state()->in_marking_window();

   141   }

   142 

   143   void cset_regions_freed() {

   144     bool update = should_update_surv_rate_group_predictors();

   145 

   146     _short_lived_surv_rate_group->all_surviving_words_recorded(update);

   147     _survivor_surv_rate_group->all_surviving_words_recorded(update);

   148   }

   149 

   150   G1MMUTracker* mmu_tracker() {

   151     return _mmu_tracker;

   152   }

   153 

   154   const G1MMUTracker* mmu_tracker() const {

   155     return _mmu_tracker;

   156   }

   157 

   158   double max_pause_time_ms() const {

   159     return _mmu_tracker->max_gc_time() * 1000.0;

   160   }

   161 

   162   // Returns an estimate of the survival rate of the region at yg-age

   163   // "yg_age".

   164   double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;

   165 

   166   double predict_yg_surv_rate(int age) const;

   167 

   168   double accum_yg_surv_rate_pred(int age) const;

   169 

   170 protected:

   171   G1CollectionSet* _collection_set;

   172   virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;

   173   virtual double other_time_ms(double pause_time_ms) const;

   174 

   175   double young_other_time_ms() const;

   176   double non_young_other_time_ms() const;

   177   double constant_other_time_ms(double pause_time_ms) const;

   178 

   179   CollectionSetChooser* cset_chooser() const;

   180 private:

   181 

   182   // The number of bytes copied during the GC.

   183   size_t _bytes_copied_during_gc;

   184 

   185   // Stash a pointer to the g1 heap.

   186   G1CollectedHeap* _g1;

   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 list maximum and target lengths. Returns the

   196   // unbounded young list target length.

   197   uint update_young_list_max_and_target_length();

   198   uint update_young_list_max_and_target_length(size_t rs_lengths);

   199 

   200   // Update the young list target length either by setting it to the

   201   // desired fixed value or by calculating it using G1's pause

   202   // prediction model. If no rs_lengths parameter is passed, predict

   203   // the RS lengths using the prediction model, otherwise use the

   204   // given rs_lengths as the prediction.

   205   // Returns the unbounded young list target length.

   206   uint update_young_list_target_length(size_t rs_lengths);

   207 

   208   // Calculate and return the minimum desired young list target

   209   // length. This is the minimum desired young list length according

   210   // to the user's inputs.

   211   uint calculate_young_list_desired_min_length(uint base_min_length) const;

   212 

   213   // Calculate and return the maximum desired young list target

   214   // length. This is the maximum desired young list length according

   215   // to the user's inputs.

   216   uint calculate_young_list_desired_max_length() const;

   217 

   218   // Calculate and return the maximum young list target length that

   219   // can fit into the pause time goal. The parameters are: rs_lengths

   220   // represent the prediction of how large the young RSet lengths will

   221   // be, base_min_length is the already existing number of regions in

   222   // the young list, min_length and max_length are the desired min and

   223   // max young list length according to the user's inputs.

   224   uint calculate_young_list_target_length(size_t rs_lengths,

   225                                           uint base_min_length,

   226                                           uint desired_min_length,

   227                                           uint desired_max_length) const;

   228 

   229   // Result of the bounded_young_list_target_length() method, containing both the

   230   // bounded as well as the unbounded young list target lengths in this order.

   231   typedef Pair<uint, uint, StackObj> YoungTargetLengths;

   232   YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;

   233 

   234   void update_rs_lengths_prediction();

   235   void update_rs_lengths_prediction(size_t prediction);

   236 

   237   // Check whether a given young length (young_length) fits into the

   238   // given target pause time and whether the prediction for the amount

   239   // of objects to be copied for the given length will fit into the

   240   // given free space (expressed by base_free_regions).  It is used by

   241   // calculate_young_list_target_length().

   242   bool predict_will_fit(uint young_length, double base_time_ms,

   243                         uint base_free_regions, double target_pause_time_ms) const;

   244 

   245 public:

   246   size_t pending_cards() const { return _pending_cards; }

   247 

   248   // Calculate the minimum number of old regions we'll add to the CSet

   249   // during a mixed GC.

   250   uint calc_min_old_cset_length() const;

   251 

   252   // Calculate the maximum number of old regions we'll add to the CSet

   253   // during a mixed GC.

   254   uint calc_max_old_cset_length() const;

   255 

   256   // Returns the given amount of uncollected reclaimable space

   257   // as a percentage of the current heap capacity.

   258   double reclaimable_bytes_perc(size_t reclaimable_bytes) const;

   259 

   260 private:

   261   // Sets up marking if proper conditions are met.

   262   void maybe_start_marking();

   263 

   264   // The kind of STW pause.

   265   enum PauseKind {

   266     FullGC,

   267     YoungOnlyGC,

   268     MixedGC,

   269     LastYoungGC,

   270     InitialMarkGC,

   271     Cleanup,

   272     Remark

   273   };

   274 

   275   // Calculate PauseKind from internal state.

   276   PauseKind young_gc_pause_kind() const;

   277   // Record the given STW pause with the given start and end times (in s).

   278   void record_pause(PauseKind kind, double start, double end);

   279   // Indicate that we aborted marking before doing any mixed GCs.

   280   void abort_time_to_mixed_tracking();

   281 public:

   282 

   283   G1Policy();

   284 

   285   virtual ~G1Policy();

   286 

   287   G1CollectorState* collector_state() const;

   288 

   289   G1GCPhaseTimes* phase_times() const { return _phase_times; }

   290 

   291   // Check the current value of the young list RSet lengths and

   292   // compare it against the last prediction. If the current value is

   293   // higher, recalculate the young list target length prediction.

   294   void revise_young_list_target_length_if_necessary(size_t rs_lengths);

   295 

   296   // This should be called after the heap is resized.

   297   void record_new_heap_size(uint new_number_of_regions);

   298 

   299   void init();

   300 

   301   virtual void note_gc_start();

   302 

   303   bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);

   304 

   305   bool about_to_start_mixed_phase() const;

   306 

   307   // Record the start and end of an evacuation pause.

   308   void record_collection_pause_start(double start_time_sec);

   309   void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);

   310 

   311   // Record the start and end of a full collection.

   312   void record_full_collection_start();

   313   void record_full_collection_end();

   314 

   315   // Must currently be called while the world is stopped.

   316   void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);

   317 

   318   // Record start and end of remark.

   319   void record_concurrent_mark_remark_start();

   320   void record_concurrent_mark_remark_end();

   321 

   322   // Record start, end, and completion of cleanup.

   323   void record_concurrent_mark_cleanup_start();

   324   void record_concurrent_mark_cleanup_end();

   325   void record_concurrent_mark_cleanup_completed();

   326 

   327   virtual void print_phases();

   328 

   329   // Record how much space we copied during a GC. This is typically

   330   // called when a GC alloc region is being retired.

   331   void record_bytes_copied_during_gc(size_t bytes) {

   332     _bytes_copied_during_gc += bytes;

   333   }

   334 

   335   // The amount of space we copied during a GC.

   336   size_t bytes_copied_during_gc() const {

   337     return _bytes_copied_during_gc;

   338   }

   339 

   340   // Determine whether there are candidate regions so that the

   341   // next GC should be mixed. The two action strings are used

   342   // in the ergo output when the method returns true or false.

   343   bool next_gc_should_be_mixed(const char* true_action_str,

   344                                const char* false_action_str) const;

   345 

   346   virtual void finalize_collection_set(double target_pause_time_ms);

   347 private:

   348   // Set the state to start a concurrent marking cycle and clear

   349   // _initiate_conc_mark_if_possible because it has now been

   350   // acted on.

   351   void initiate_conc_mark();

   352 

   353 public:

   354   // This sets the initiate_conc_mark_if_possible() flag to start a

   355   // new cycle, as long as we are not already in one. It's best if it

   356   // is called during a safepoint when the test whether a cycle is in

   357   // progress or not is stable.

   358   bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);

   359 

   360   // This is called at the very beginning of an evacuation pause (it

   361   // has to be the first thing that the pause does). If

   362   // initiate_conc_mark_if_possible() is true, and the concurrent

   363   // marking thread has completed its work during the previous cycle,

   364   // it will set during_initial_mark_pause() to so that the pause does

   365   // the initial-mark work and start a marking cycle.

   366   void decide_on_conc_mark_initiation();

   367 

   368   // Print stats on young survival ratio

   369   void print_yg_surv_rate_info() const;

   370 

   371   void finished_recalculating_age_indexes(bool is_survivors) {

   372     if (is_survivors) {

   373       _survivor_surv_rate_group->finished_recalculating_age_indexes();

   374     } else {

   375       _short_lived_surv_rate_group->finished_recalculating_age_indexes();

   376     }

   377   }

   378 

   379   size_t young_list_target_length() const { return _young_list_target_length; }

   380 

   381   bool is_young_list_full() const;

   382 

   383   bool can_expand_young_list() const;

   384 

   385   uint young_list_max_length() const {

   386     return _young_list_max_length;

   387   }

   388 

   389   bool adaptive_young_list_length() const;

   390 

   391   virtual bool should_process_references() const {

   392     return true;

   393   }

   394 

   395 private:

   396   //

   397   // Survivor regions policy.

   398   //

   399 

   400   // Current tenuring threshold, set to 0 if the collector reaches the

   401   // maximum amount of survivors regions.

   402   uint _tenuring_threshold;

   403 

   404   // The limit on the number of regions allocated for survivors.

   405   uint _max_survivor_regions;

   406 

   407   AgeTable _survivors_age_table;

   408 

   409 public:

   410   uint tenuring_threshold() const { return _tenuring_threshold; }

   411 

   412   uint max_survivor_regions() {

   413     return _max_survivor_regions;

   414   }

   415 

   416   void note_start_adding_survivor_regions() {

   417     _survivor_surv_rate_group->start_adding_regions();

   418   }

   419 

   420   void note_stop_adding_survivor_regions() {

   421     _survivor_surv_rate_group->stop_adding_regions();

   422   }

   423 

   424   void record_age_table(AgeTable* age_table) {

   425     _survivors_age_table.merge(age_table);

   426   }

   427 

   428   void update_max_gc_locker_expansion();

   429 

   430   // Calculates survivor space parameters.

   431   void update_survivors_policy();

   432 };

   433 

   434 #endif // SHARE_VM_GC_G1_G1POLICY_HPP