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.
   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_G1COLLECTIONSET_HPP
  26 #define SHARE_VM_GC_G1_G1COLLECTIONSET_HPP
  27 
  28 #include "gc/g1/collectionSetChooser.hpp"
  29 #include "utilities/debug.hpp"
  30 #include "utilities/globalDefinitions.hpp"
  31 
  32 class G1CollectedHeap;
  33 class G1CollectorState;
  34 class G1GCPhaseTimes;
  35 class G1Policy;
  36 class G1SurvivorRegions;
  37 class HeapRegion;
  38 
  39 class G1CollectionSet {
  40   G1CollectedHeap* _g1;
  41   G1Policy* _policy;
  42 
  43   CollectionSetChooser* _cset_chooser;
  44 
  45   uint _eden_region_length;
  46   uint _survivor_region_length;
  47   uint _old_region_length;
  48 
  49   // The actual collection set as a set of region indices.
  50   // All entries in _collection_set_regions below _collection_set_cur_length are
  51   // assumed to be valid entries.
  52   // We assume that at any time there is at most only one writer and (one or more)
  53   // concurrent readers. This means we are good with using storestore and loadload
  54   // barriers on the writer and reader respectively only.
  55   uint* _collection_set_regions;
  56   volatile size_t _collection_set_cur_length;
  57   size_t _collection_set_max_length;
  58 
  59   // The number of bytes in the collection set before the pause. Set from
  60   // the incrementally built collection set at the start of an evacuation
  61   // pause, and incremented in finalize_old_part() when adding old regions
  62   // (if any) to the collection set.
  63   size_t _bytes_used_before;
  64 
  65   size_t _recorded_rs_lengths;
  66 
  67   // The associated information that is maintained while the incremental
  68   // collection set is being built with young regions. Used to populate
  69   // the recorded info for the evacuation pause.
  70 
  71   enum CSetBuildType {
  72     Active,             // We are actively building the collection set
  73     Inactive            // We are not actively building the collection set
  74   };
  75 
  76   CSetBuildType _inc_build_state;
  77 
  78   // The number of bytes in the incrementally built collection set.
  79   // Used to set _collection_set_bytes_used_before at the start of
  80   // an evacuation pause.
  81   size_t _inc_bytes_used_before;
  82 
  83   // The RSet lengths recorded for regions in the CSet. It is updated
  84   // by the thread that adds a new region to the CSet. We assume that
  85   // only one thread can be allocating a new CSet region (currently,
  86   // it does so after taking the Heap_lock) hence no need to
  87   // synchronize updates to this field.
  88   size_t _inc_recorded_rs_lengths;
  89 
  90   // A concurrent refinement thread periodically samples the young
  91   // region RSets and needs to update _inc_recorded_rs_lengths as
  92   // the RSets grow. Instead of having to synchronize updates to that
  93   // field we accumulate them in this field and add it to
  94   // _inc_recorded_rs_lengths_diffs at the start of a GC.
  95   ssize_t _inc_recorded_rs_lengths_diffs;
  96 
  97   // The predicted elapsed time it will take to collect the regions in
  98   // the CSet. This is updated by the thread that adds a new region to
  99   // the CSet. See the comment for _inc_recorded_rs_lengths about
 100   // MT-safety assumptions.
 101   double _inc_predicted_elapsed_time_ms;
 102 
 103   // See the comment for _inc_recorded_rs_lengths_diffs.
 104   double _inc_predicted_elapsed_time_ms_diffs;
 105 
 106   G1CollectorState* collector_state();
 107   G1GCPhaseTimes* phase_times();
 108 
 109   double predict_region_elapsed_time_ms(HeapRegion* hr);
 110 
 111   void verify_young_cset_indices() const NOT_DEBUG_RETURN;
 112 public:
 113   G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy);
 114   ~G1CollectionSet();
 115 
 116   // Initializes the collection set giving the maximum possible length of the collection set.
 117   void initialize(uint max_region_length);
 118 
 119   CollectionSetChooser* cset_chooser();
 120 
 121   void init_region_lengths(uint eden_cset_region_length,
 122                            uint survivor_cset_region_length);
 123 
 124   void set_recorded_rs_lengths(size_t rs_lengths);
 125 
 126   uint region_length() const       { return young_region_length() +
 127                                             old_region_length(); }
 128   uint young_region_length() const { return eden_region_length() +
 129                                             survivor_region_length(); }
 130 
 131   uint eden_region_length() const     { return _eden_region_length;     }
 132   uint survivor_region_length() const { return _survivor_region_length; }
 133   uint old_region_length() const      { return _old_region_length;      }
 134 
 135   // Incremental collection set support
 136 
 137   // Initialize incremental collection set info.
 138   void start_incremental_building();
 139 
 140   // Perform any final calculations on the incremental collection set fields
 141   // before we can use them.
 142   void finalize_incremental_building();
 143 
 144   // Reset the contents of the collection set.
 145   void clear();
 146 
 147   // Iterate over the collection set, applying the given HeapRegionClosure on all of them.
 148   // If may_be_aborted is true, iteration may be aborted using the return value of the
 149   // called closure method.
 150   void iterate(HeapRegionClosure* cl) const;
 151 
 152   // Iterate over the collection set, applying the given HeapRegionClosure on all of them,
 153   // trying to optimally spread out starting position of total_workers workers given the
 154   // caller's worker_id.
 155   void iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const;
 156 
 157   // Stop adding regions to the incremental collection set.
 158   void stop_incremental_building() { _inc_build_state = Inactive; }
 159 
 160   size_t recorded_rs_lengths() { return _recorded_rs_lengths; }
 161 
 162   size_t bytes_used_before() const {
 163     return _bytes_used_before;
 164   }
 165 
 166   void reset_bytes_used_before() {
 167     _bytes_used_before = 0;
 168   }
 169 
 170   // Choose a new collection set.  Marks the chosen regions as being
 171   // "in_collection_set".
 172   double finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors);
 173   void finalize_old_part(double time_remaining_ms);
 174 
 175   // Add old region "hr" to the collection set.
 176   void add_old_region(HeapRegion* hr);
 177 
 178   // Update information about hr in the aggregated information for
 179   // the incrementally built collection set.
 180   void update_young_region_prediction(HeapRegion* hr, size_t new_rs_length);
 181 
 182   // Add eden region to the collection set.
 183   void add_eden_region(HeapRegion* hr);
 184 
 185   // Add survivor region to the collection set.
 186   void add_survivor_regions(HeapRegion* hr);
 187 
 188 #ifndef PRODUCT
 189   bool verify_young_ages();
 190 
 191   void print(outputStream* st);
 192 #endif // !PRODUCT
 193 
 194 private:
 195   // Update the incremental collection set information when adding a region.
 196   void add_young_region_common(HeapRegion* hr);
 197 };
 198 
 199 #endif // SHARE_VM_GC_G1_G1COLLECTIONSET_HPP
 200