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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* _g1h;
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 
region_length() const126   uint region_length() const       { return young_region_length() +
127                                             old_region_length(); }
young_region_length() const128   uint young_region_length() const { return eden_region_length() +
129                                             survivor_region_length(); }
130 
eden_region_length() const131   uint eden_region_length() const     { return _eden_region_length;     }
survivor_region_length() const132   uint survivor_region_length() const { return _survivor_region_length; }
old_region_length() const133   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.
stop_incremental_building()158   void stop_incremental_building() { _inc_build_state = Inactive; }
159 
recorded_rs_lengths()160   size_t recorded_rs_lengths() { return _recorded_rs_lengths; }
161 
bytes_used_before() const162   size_t bytes_used_before() const {
163     return _bytes_used_before;
164   }
165 
reset_bytes_used_before()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 
201