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* _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 // When doing mixed collections we can add old regions to the collection, which
60 // can be collected if there is enough time. We call these optional regions and
61 // the pointer to these regions are stored in the array below.
62 HeapRegion** _optional_regions;
63 uint _optional_region_length;
64 uint _optional_region_max_length;
65
66 // The number of bytes in the collection set before the pause. Set from
67 // the incrementally built collection set at the start of an evacuation
68 // pause, and incremented in finalize_old_part() when adding old regions
69 // (if any) to the collection set.
70 size_t _bytes_used_before;
71
72 size_t _recorded_rs_lengths;
73
74 // The associated information that is maintained while the incremental
75 // collection set is being built with young regions. Used to populate
76 // the recorded info for the evacuation pause.
77
78 enum CSetBuildType {
79 Active, // We are actively building the collection set
80 Inactive // We are not actively building the collection set
81 };
82
83 CSetBuildType _inc_build_state;
84
85 // The number of bytes in the incrementally built collection set.
86 // Used to set _collection_set_bytes_used_before at the start of
87 // an evacuation pause.
88 size_t _inc_bytes_used_before;
89
90 // The RSet lengths recorded for regions in the CSet. It is updated
91 // by the thread that adds a new region to the CSet. We assume that
92 // only one thread can be allocating a new CSet region (currently,
93 // it does so after taking the Heap_lock) hence no need to
94 // synchronize updates to this field.
95 size_t _inc_recorded_rs_lengths;
96
97 // A concurrent refinement thread periodically samples the young
98 // region RSets and needs to update _inc_recorded_rs_lengths as
99 // the RSets grow. Instead of having to synchronize updates to that
100 // field we accumulate them in this field and add it to
101 // _inc_recorded_rs_lengths_diffs at the start of a GC.
102 ssize_t _inc_recorded_rs_lengths_diffs;
103
104 // The predicted elapsed time it will take to collect the regions in
105 // the CSet. This is updated by the thread that adds a new region to
106 // the CSet. See the comment for _inc_recorded_rs_lengths about
107 // MT-safety assumptions.
108 double _inc_predicted_elapsed_time_ms;
109
110 // See the comment for _inc_recorded_rs_lengths_diffs.
111 double _inc_predicted_elapsed_time_ms_diffs;
112
113 G1CollectorState* collector_state();
114 G1GCPhaseTimes* phase_times();
115
116 void verify_young_cset_indices() const NOT_DEBUG_RETURN;
117 void add_as_optional(HeapRegion* hr);
118 void add_as_old(HeapRegion* hr);
119 bool optional_is_full();
120
121 public:
122 G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy);
123 ~G1CollectionSet();
124
125 // Initializes the collection set giving the maximum possible length of the collection set.
126 void initialize(uint max_region_length);
127 void initialize_optional(uint max_length);
128 void free_optional_regions();
129
130 CollectionSetChooser* cset_chooser();
131
132 void init_region_lengths(uint eden_cset_region_length,
133 uint survivor_cset_region_length);
134
135 void set_recorded_rs_lengths(size_t rs_lengths);
136
137 uint region_length() const { return young_region_length() +
138 old_region_length(); }
139 uint young_region_length() const { return eden_region_length() +
140 survivor_region_length(); }
141
142 uint eden_region_length() const { return _eden_region_length; }
143 uint survivor_region_length() const { return _survivor_region_length; }
144 uint old_region_length() const { return _old_region_length; }
145 uint optional_region_length() const { return _optional_region_length; }
146
147 // Incremental collection set support
148
149 // Initialize incremental collection set info.
150 void start_incremental_building();
151
152 // Perform any final calculations on the incremental collection set fields
153 // before we can use them.
154 void finalize_incremental_building();
155
156 // Reset the contents of the collection set.
157 void clear();
158
159 // Iterate over the collection set, applying the given HeapRegionClosure on all of them.
160 // If may_be_aborted is true, iteration may be aborted using the return value of the
161 // called closure method.
162 void iterate(HeapRegionClosure* cl) const;
163
164 // Iterate over the collection set, applying the given HeapRegionClosure on all of them,
165 // trying to optimally spread out starting position of total_workers workers given the
166 // caller's worker_id.
167 void iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const;
168
169 // Stop adding regions to the incremental collection set.
170 void stop_incremental_building() { _inc_build_state = Inactive; }
171
172 size_t recorded_rs_lengths() { return _recorded_rs_lengths; }
173
174 size_t bytes_used_before() const {
175 return _bytes_used_before;
176 }
177
178 void reset_bytes_used_before() {
179 _bytes_used_before = 0;
180 }
181
182 // Choose a new collection set. Marks the chosen regions as being
183 // "in_collection_set".
184 double finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors);
185 void finalize_old_part(double time_remaining_ms);
186
187 // Add old region "hr" to the collection set.
188 void add_old_region(HeapRegion* hr);
189
190 // Add old region "hr" to optional collection set.
191 void add_optional_region(HeapRegion* hr);
192
193 // Update information about hr in the aggregated information for
194 // the incrementally built collection set.
195 void update_young_region_prediction(HeapRegion* hr, size_t new_rs_length);
196
197 // Add eden region to the collection set.
198 void add_eden_region(HeapRegion* hr);
199
200 // Add survivor region to the collection set.
201 void add_survivor_regions(HeapRegion* hr);
202
203 #ifndef PRODUCT
204 bool verify_young_ages();
205
206 void print(outputStream* st);
207 #endif // !PRODUCT
208
209 double predict_region_elapsed_time_ms(HeapRegion* hr);
210
211 void clear_optional_region(const HeapRegion* hr);
212
213 HeapRegion* optional_region_at(uint i) const {
214 assert(_optional_regions != NULL, "Not yet initialized");
215 assert(i < _optional_region_length, "index %u out of bounds (%u)", i, _optional_region_length);
216 return _optional_regions[i];
217 }
218
219 HeapRegion* remove_last_optional_region() {
220 assert(_optional_regions != NULL, "Not yet initialized");
221 assert(_optional_region_length != 0, "No region to remove");
222 _optional_region_length--;
223 HeapRegion* removed = _optional_regions[_optional_region_length];
224 _optional_regions[_optional_region_length] = NULL;
225 return removed;
226 }
227
228 private:
229 // Update the incremental collection set information when adding a region.
230 void add_young_region_common(HeapRegion* hr);
231 };
232
233 // Helper class to manage the optional regions in a Mixed collection.
234 class G1OptionalCSet : public StackObj {
235 private:
236 G1CollectionSet* _cset;
237 uint _current_index;
238 uint _current_limit;
239 bool _prepare_failed;
240 bool _evacuation_failed;
241
242 void prepare_to_evacuate_optional_region(HeapRegion* hr);
243
244 public:
245 static const uint InvalidCSetIndex = UINT_MAX;
246
247 G1OptionalCSet(G1CollectionSet* cset) :
248 _cset(cset),
249 _current_index(0),
250 _current_limit(0),
251 _prepare_failed(false),
252 _evacuation_failed(false) { }
253 // The destructor returns regions to the cset-chooser and
254 // frees the optional structure in the cset.
255 ~G1OptionalCSet();
256
257 uint current_index() { return _current_index; }
258 uint current_limit() { return _current_limit; }
259
260 uint size();
261 bool is_empty();
262
263 HeapRegion* region_at(uint index);
264
265 // Prepare a set of regions for optional evacuation.
266 void prepare_evacuation(double time_left_ms);
267 bool prepare_failed();
268
269 // Complete the evacuation of the previously prepared
270 // regions by updating their state and check for failures.
271 void complete_evacuation();
272 bool evacuation_failed();
273 };
274
275 #endif // SHARE_VM_GC_G1_G1COLLECTIONSET_HPP
276