1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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24
25 #ifndef SHARE_GC_G1_G1COLLECTIONSET_HPP
26 #define SHARE_GC_G1_G1COLLECTIONSET_HPP
27
28 #include "gc/g1/g1CollectionSetCandidates.hpp"
29 #include "utilities/debug.hpp"
30 #include "utilities/globalDefinitions.hpp"
31
32 class G1CollectedHeap;
33 class G1CollectorState;
34 class G1GCPhaseTimes;
35 class G1ParScanThreadStateSet;
36 class G1Policy;
37 class G1SurvivorRegions;
38 class HeapRegion;
39
40 class G1CollectionSet {
41 G1CollectedHeap* _g1h;
42 G1Policy* _policy;
43
44 // All old gen collection set candidate regions for the current mixed gc phase.
45 G1CollectionSetCandidates* _candidates;
46
47 uint _eden_region_length;
48 uint _survivor_region_length;
49 uint _old_region_length;
50
51 // The actual collection set as a set of region indices.
52 // All entries in _collection_set_regions below _collection_set_cur_length are
53 // assumed to be valid entries.
54 // We assume that at any time there is at most only one writer and (one or more)
55 // concurrent readers. This means we are good with using storestore and loadload
56 // barriers on the writer and reader respectively only.
57 uint* _collection_set_regions;
58 volatile size_t _collection_set_cur_length;
59 size_t _collection_set_max_length;
60
61 // When doing mixed collections we can add old regions to the collection, which
62 // can be collected if there is enough time. We call these optional regions and
63 // the pointer to these regions are stored in the array below.
64 HeapRegion** _optional_regions;
65 uint _optional_region_length;
66 uint _optional_region_max_length;
67
68 // The number of bytes in the collection set before the pause. Set from
69 // the incrementally built collection set at the start of an evacuation
70 // pause, and incremented in finalize_old_part() when adding old regions
71 // (if any) to the collection set.
72 size_t _bytes_used_before;
73
74 size_t _recorded_rs_lengths;
75
76 // The associated information that is maintained while the incremental
77 // collection set is being built with young regions. Used to populate
78 // the recorded info for the evacuation pause.
79
80 enum CSetBuildType {
81 Active, // We are actively building the collection set
82 Inactive // We are not actively building the collection set
83 };
84
85 CSetBuildType _inc_build_state;
86
87 // The number of bytes in the incrementally built collection set.
88 // Used to set _collection_set_bytes_used_before at the start of
89 // an evacuation pause.
90 size_t _inc_bytes_used_before;
91
92 // The RSet lengths recorded for regions in the CSet. It is updated
93 // by the thread that adds a new region to the CSet. We assume that
94 // only one thread can be allocating a new CSet region (currently,
95 // it does so after taking the Heap_lock) hence no need to
96 // synchronize updates to this field.
97 size_t _inc_recorded_rs_lengths;
98
99 // A concurrent refinement thread periodically samples the young
100 // region RSets and needs to update _inc_recorded_rs_lengths as
101 // the RSets grow. Instead of having to synchronize updates to that
102 // field we accumulate them in this field and add it to
103 // _inc_recorded_rs_lengths_diffs at the start of a GC.
104 ssize_t _inc_recorded_rs_lengths_diffs;
105
106 // The predicted elapsed time it will take to collect the regions in
107 // the CSet. This is updated by the thread that adds a new region to
108 // the CSet. See the comment for _inc_recorded_rs_lengths about
109 // MT-safety assumptions.
110 double _inc_predicted_elapsed_time_ms;
111
112 // See the comment for _inc_recorded_rs_lengths_diffs.
113 double _inc_predicted_elapsed_time_ms_diffs;
114
115 G1CollectorState* collector_state();
116 G1GCPhaseTimes* phase_times();
117
118 void verify_young_cset_indices() const NOT_DEBUG_RETURN;
119 void add_as_optional(HeapRegion* hr);
120 void add_as_old(HeapRegion* hr);
121 bool optional_is_full();
122
123 public:
124 G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy);
125 ~G1CollectionSet();
126
127 // Initializes the collection set giving the maximum possible length of the collection set.
128 void initialize(uint max_region_length);
129 void initialize_optional(uint max_length);
130 void free_optional_regions();
131
132 void clear_candidates() {
133 delete _candidates;
134 _candidates = NULL;
135 }
136 void set_candidates(G1CollectionSetCandidates* candidates) {
137 assert(_candidates == NULL, "Trying to replace collection set candidates.");
138 _candidates = candidates;
139 }
140 G1CollectionSetCandidates* candidates() { return _candidates; }
141
142 void init_region_lengths(uint eden_cset_region_length,
143 uint survivor_cset_region_length);
144
145 void set_recorded_rs_lengths(size_t rs_lengths);
146
147 uint region_length() const { return young_region_length() +
148 old_region_length(); }
149 uint young_region_length() const { return eden_region_length() +
150 survivor_region_length(); }
151
152 uint eden_region_length() const { return _eden_region_length; }
153 uint survivor_region_length() const { return _survivor_region_length; }
154 uint old_region_length() const { return _old_region_length; }
155 uint optional_region_length() const { return _optional_region_length; }
156
157 // Incremental collection set support
158
159 // Initialize incremental collection set info.
160 void start_incremental_building();
161
162 // Perform any final calculations on the incremental collection set fields
163 // before we can use them.
164 void finalize_incremental_building();
165
166 // Reset the contents of the collection set.
167 void clear();
168
169 // Iterate over the collection set, applying the given HeapRegionClosure on all of them.
170 // If may_be_aborted is true, iteration may be aborted using the return value of the
171 // called closure method.
172 void iterate(HeapRegionClosure* cl) const;
173
174 // Iterate over the collection set, applying the given HeapRegionClosure on all of them,
175 // trying to optimally spread out starting position of total_workers workers given the
176 // caller's worker_id.
177 void iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const;
178
179 // Stop adding regions to the incremental collection set.
180 void stop_incremental_building() { _inc_build_state = Inactive; }
181
182 size_t recorded_rs_lengths() { return _recorded_rs_lengths; }
183
184 size_t bytes_used_before() const {
185 return _bytes_used_before;
186 }
187
188 void reset_bytes_used_before() {
189 _bytes_used_before = 0;
190 }
191
192 // Choose a new collection set. Marks the chosen regions as being
193 // "in_collection_set".
194 double finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors);
195 void finalize_old_part(double time_remaining_ms);
196
197 // Add old region "hr" to the collection set.
198 void add_old_region(HeapRegion* hr);
199
200 // Add old region "hr" to optional collection set.
201 void add_optional_region(HeapRegion* hr);
202
203 // Update information about hr in the aggregated information for
204 // the incrementally built collection set.
205 void update_young_region_prediction(HeapRegion* hr, size_t new_rs_length);
206
207 // Add eden region to the collection set.
208 void add_eden_region(HeapRegion* hr);
209
210 // Add survivor region to the collection set.
211 void add_survivor_regions(HeapRegion* hr);
212
213 #ifndef PRODUCT
214 bool verify_young_ages();
215
216 void print(outputStream* st);
217 #endif // !PRODUCT
218
219 double predict_region_elapsed_time_ms(HeapRegion* hr);
220
221 void clear_optional_region(const HeapRegion* hr);
222
223 HeapRegion* optional_region_at(uint i) const {
224 assert(_optional_regions != NULL, "Not yet initialized");
225 assert(i < _optional_region_length, "index %u out of bounds (%u)", i, _optional_region_length);
226 return _optional_regions[i];
227 }
228
229 HeapRegion* remove_last_optional_region() {
230 assert(_optional_regions != NULL, "Not yet initialized");
231 assert(_optional_region_length != 0, "No region to remove");
232 _optional_region_length--;
233 HeapRegion* removed = _optional_regions[_optional_region_length];
234 _optional_regions[_optional_region_length] = NULL;
235 return removed;
236 }
237
238 private:
239 // Update the incremental collection set information when adding a region.
240 void add_young_region_common(HeapRegion* hr);
241 };
242
243 // Helper class to manage the optional regions in a Mixed collection.
244 class G1OptionalCSet : public StackObj {
245 private:
246 G1CollectionSet* _cset;
247 G1ParScanThreadStateSet* _pset;
248 uint _current_index;
249 uint _current_limit;
250 bool _prepare_failed;
251 bool _evacuation_failed;
252
253 void prepare_to_evacuate_optional_region(HeapRegion* hr);
254
255 public:
256 static const uint InvalidCSetIndex = UINT_MAX;
257
258 G1OptionalCSet(G1CollectionSet* cset, G1ParScanThreadStateSet* pset) :
259 _cset(cset),
260 _pset(pset),
261 _current_index(0),
262 _current_limit(0),
263 _prepare_failed(false),
264 _evacuation_failed(false) { }
265 // The destructor returns regions to the collection set candidates set and
266 // frees the optional structure in the collection set.
267 ~G1OptionalCSet();
268
269 uint current_index() { return _current_index; }
270 uint current_limit() { return _current_limit; }
271
272 uint size();
273 bool is_empty();
274
275 HeapRegion* region_at(uint index);
276
277 // Prepare a set of regions for optional evacuation.
278 void prepare_evacuation(double time_left_ms);
279 bool prepare_failed();
280
281 // Complete the evacuation of the previously prepared
282 // regions by updating their state and check for failures.
283 void complete_evacuation();
284 bool evacuation_failed();
285 };
286
287 #endif // SHARE_GC_G1_G1COLLECTIONSET_HPP