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.
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5 * This code is free software; you can redistribute it and/or modify it
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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
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1POLICY_HPP
26 #define SHARE_VM_GC_G1_G1POLICY_HPP
27
28 #include "gc/g1/g1CollectorPolicy.hpp"
29 #include "gc/g1/g1CollectorState.hpp"
30 #include "gc/g1/g1GCPhaseTimes.hpp"
31 #include "gc/g1/g1InCSetState.hpp"
32 #include "gc/g1/g1InitialMarkToMixedTimeTracker.hpp"
33 #include "gc/g1/g1MMUTracker.hpp"
34 #include "gc/g1/g1RemSetTrackingPolicy.hpp"
35 #include "gc/g1/g1Predictions.hpp"
36 #include "gc/g1/g1YoungGenSizer.hpp"
37 #include "gc/shared/gcCause.hpp"
38 #include "utilities/pair.hpp"
39
40 // A G1Policy makes policy decisions that determine the
41 // characteristics of the collector. Examples include:
42 // * choice of collection set.
43 // * when to collect.
44
45 class HeapRegion;
46 class G1CollectionSet;
47 class CollectionSetChooser;
48 class G1IHOPControl;
49 class G1Analytics;
50 class G1SurvivorRegions;
51 class G1YoungGenSizer;
52 class GCPolicyCounters;
53 class STWGCTimer;
54
55 class G1Policy: public CHeapObj<mtGC> {
56 private:
57
58 static G1IHOPControl* create_ihop_control(const G1Predictions* predictor);
59 // Update the IHOP control with necessary statistics.
60 void update_ihop_prediction(double mutator_time_s,
61 size_t mutator_alloc_bytes,
62 size_t young_gen_size,
63 bool this_gc_was_young_only);
64 void report_ihop_statistics();
65
66 G1Predictions _predictor;
67 G1Analytics* _analytics;
68 G1RemSetTrackingPolicy _remset_tracker;
69 G1MMUTracker* _mmu_tracker;
70 G1IHOPControl* _ihop_control;
71
72 GCPolicyCounters* _policy_counters;
73
74 double _full_collection_start_sec;
75
76 jlong _collection_pause_end_millis;
77
78 uint _young_list_target_length;
79 uint _young_list_fixed_length;
80
81 // The max number of regions we can extend the eden by while the GC
82 // locker is active. This should be >= _young_list_target_length;
83 uint _young_list_max_length;
84
85 // SurvRateGroups below must be initialized after the predictor because they
86 // indirectly use it through this object passed to their constructor.
87 SurvRateGroup* _short_lived_surv_rate_group;
88 SurvRateGroup* _survivor_surv_rate_group;
89
90 double _reserve_factor;
91 // This will be set when the heap is expanded
92 // for the first time during initialization.
93 uint _reserve_regions;
94
95 G1YoungGenSizer _young_gen_sizer;
96
97 uint _free_regions_at_end_of_collection;
98
99 size_t _max_rs_lengths;
100
101 size_t _rs_lengths_prediction;
102
103 size_t _pending_cards;
104
105 // The amount of allocated bytes in old gen during the last mutator and the following
106 // young GC phase.
107 size_t _bytes_allocated_in_old_since_last_gc;
108
109 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
110
111 bool should_update_surv_rate_group_predictors() {
112 return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
113 }
114 public:
115 const G1Predictions& predictor() const { return _predictor; }
116 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
117
118 G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
119
120 // Add the given number of bytes to the total number of allocated bytes in the old gen.
121 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
122
123 void set_region_eden(HeapRegion* hr) {
124 hr->set_eden();
125 hr->install_surv_rate_group(_short_lived_surv_rate_group);
126 }
127
128 void set_region_survivor(HeapRegion* hr) {
129 assert(hr->is_survivor(), "pre-condition");
130 hr->install_surv_rate_group(_survivor_surv_rate_group);
131 }
132
133 void record_max_rs_lengths(size_t rs_lengths) {
134 _max_rs_lengths = rs_lengths;
135 }
136
137 double predict_base_elapsed_time_ms(size_t pending_cards) const;
138 double predict_base_elapsed_time_ms(size_t pending_cards,
139 size_t scanned_cards) const;
140 size_t predict_bytes_to_copy(HeapRegion* hr) const;
141 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;
142
143 double predict_survivor_regions_evac_time() const;
144
145 void cset_regions_freed() {
146 bool update = should_update_surv_rate_group_predictors();
147
148 _short_lived_surv_rate_group->all_surviving_words_recorded(predictor(), update);
149 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
150 }
151
152 G1MMUTracker* mmu_tracker() {
153 return _mmu_tracker;
154 }
155
156 const G1MMUTracker* mmu_tracker() const {
157 return _mmu_tracker;
158 }
159
160 double max_pause_time_ms() const {
161 return _mmu_tracker->max_gc_time() * 1000.0;
162 }
163
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 private:
171 G1CollectionSet* _collection_set;
172 double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
173 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
181 // The number of bytes copied during the GC.
182 size_t _bytes_copied_during_gc;
183
184 // Stash a pointer to the g1 heap.
185 G1CollectedHeap* _g1h;
186
187 G1GCPhaseTimes* _phase_times;
188
189 // This set of variables tracks the collector efficiency, in order to
190 // determine whether we should initiate a new marking.
191 double _mark_remark_start_sec;
192 double _mark_cleanup_start_sec;
193
194 // Updates the internal young list maximum and target lengths. Returns the
195 // unbounded young list target length.
196 uint update_young_list_max_and_target_length();
197 uint update_young_list_max_and_target_length(size_t rs_lengths);
198
199 // Update the young list target length either by setting it to the
200 // desired fixed value or by calculating it using G1's pause
201 // prediction model. If no rs_lengths parameter is passed, predict
202 // the RS lengths using the prediction model, otherwise use the
203 // given rs_lengths as the prediction.
204 // Returns the unbounded young list target length.
205 uint update_young_list_target_length(size_t rs_lengths);
206
207 // Calculate and return the minimum desired young list target
208 // length. This is the minimum desired young list length according
209 // to the user's inputs.
210 uint calculate_young_list_desired_min_length(uint base_min_length) const;
211
212 // Calculate and return the maximum desired young list target
213 // length. This is the maximum desired young list length according
214 // to the user's inputs.
215 uint calculate_young_list_desired_max_length() const;
216
217 // Calculate and return the maximum young list target length that
218 // can fit into the pause time goal. The parameters are: rs_lengths
219 // represent the prediction of how large the young RSet lengths will
220 // be, base_min_length is the already existing number of regions in
221 // the young list, min_length and max_length are the desired min and
222 // max young list length according to the user's inputs.
223 uint calculate_young_list_target_length(size_t rs_lengths,
224 uint base_min_length,
225 uint desired_min_length,
226 uint desired_max_length) const;
227
228 // Result of the bounded_young_list_target_length() method, containing both the
229 // bounded as well as the unbounded young list target lengths in this order.
230 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
231 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
232
233 void update_rs_lengths_prediction();
234 void update_rs_lengths_prediction(size_t prediction);
235
236 // Check whether a given young length (young_length) fits into the
237 // given target pause time and whether the prediction for the amount
238 // of objects to be copied for the given length will fit into the
239 // given free space (expressed by base_free_regions). It is used by
240 // calculate_young_list_target_length().
241 bool predict_will_fit(uint young_length, double base_time_ms,
242 uint base_free_regions, double target_pause_time_ms) const;
243
244 public:
245 size_t pending_cards() const { return _pending_cards; }
246
247 // Calculate the minimum number of old regions we'll add to the CSet
248 // during a mixed GC.
249 uint calc_min_old_cset_length() const;
250
251 // Calculate the maximum number of old regions we'll add to the CSet
252 // during a mixed GC.
253 uint calc_max_old_cset_length() const;
254
255 // Returns the given amount of reclaimable bytes (that represents
256 // the amount of reclaimable space still to be collected) as a
257 // percentage of the current heap capacity.
258 double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
259
260 jlong collection_pause_end_millis() { return _collection_pause_end_millis; }
261
262 private:
263 void clear_collection_set_candidates();
264 // Sets up marking if proper conditions are met.
265 void maybe_start_marking();
266
267 // The kind of STW pause.
268 enum PauseKind {
269 FullGC,
270 YoungOnlyGC,
271 MixedGC,
272 LastYoungGC,
273 InitialMarkGC,
274 Cleanup,
275 Remark
276 };
277
278 // Calculate PauseKind from internal state.
279 PauseKind young_gc_pause_kind() const;
280 // Record the given STW pause with the given start and end times (in s).
281 void record_pause(PauseKind kind, double start, double end);
282 // Indicate that we aborted marking before doing any mixed GCs.
283 void abort_time_to_mixed_tracking();
284 public:
285
286 G1Policy(STWGCTimer* gc_timer);
287
288 virtual ~G1Policy();
289
290 static G1Policy* create_policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer_stw);
291
292 G1CollectorState* collector_state() const;
293
294 G1GCPhaseTimes* phase_times() const { return _phase_times; }
295
296 // Check the current value of the young list RSet lengths and
297 // compare it against the last prediction. If the current value is
298 // higher, recalculate the young list target length prediction.
299 void revise_young_list_target_length_if_necessary(size_t rs_lengths);
300
301 // This should be called after the heap is resized.
302 void record_new_heap_size(uint new_number_of_regions);
303
304 virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
305
306 void note_gc_start();
307
308 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
309
310 bool about_to_start_mixed_phase() const;
311
312 // Record the start and end of an evacuation pause.
313 void record_collection_pause_start(double start_time_sec);
314 virtual void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
315
316 // Record the start and end of a full collection.
317 void record_full_collection_start();
318 virtual void record_full_collection_end();
319
320 // Must currently be called while the world is stopped.
321 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
322
323 // Record start and end of remark.
324 void record_concurrent_mark_remark_start();
325 void record_concurrent_mark_remark_end();
326
327 // Record start, end, and completion of cleanup.
328 void record_concurrent_mark_cleanup_start();
329 void record_concurrent_mark_cleanup_end();
330
331 void print_phases();
332
333 // Record how much space we copied during a GC. This is typically
334 // called when a GC alloc region is being retired.
335 void record_bytes_copied_during_gc(size_t bytes) {
336 _bytes_copied_during_gc += bytes;
337 }
338
339 // The amount of space we copied during a GC.
340 size_t bytes_copied_during_gc() const {
341 return _bytes_copied_during_gc;
342 }
343
344 bool next_gc_should_be_mixed(const char* true_action_str,
345 const char* false_action_str) const;
346
347 void finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor);
348 private:
349 // Set the state to start a concurrent marking cycle and clear
350 // _initiate_conc_mark_if_possible because it has now been
351 // acted on.
352 void initiate_conc_mark();
353
354 public:
355 // This sets the initiate_conc_mark_if_possible() flag to start a
356 // new cycle, as long as we are not already in one. It's best if it
357 // is called during a safepoint when the test whether a cycle is in
358 // progress or not is stable.
359 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
360
361 // This is called at the very beginning of an evacuation pause (it
362 // has to be the first thing that the pause does). If
363 // initiate_conc_mark_if_possible() is true, and the concurrent
364 // marking thread has completed its work during the previous cycle,
365 // it will set in_initial_mark_gc() to so that the pause does
366 // the initial-mark work and start a marking cycle.
367 void decide_on_conc_mark_initiation();
368
369 void finished_recalculating_age_indexes(bool is_survivors) {
370 if (is_survivors) {
371 _survivor_surv_rate_group->finished_recalculating_age_indexes();
372 } else {
373 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
374 }
375 }
376
377 size_t young_list_target_length() const { return _young_list_target_length; }
378
379 bool should_allocate_mutator_region() const;
380
381 bool can_expand_young_list() const;
382
383 uint young_list_max_length() const {
384 return _young_list_max_length;
385 }
386
387 bool adaptive_young_list_length() const;
388
389 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
390
391 private:
392 //
393 // Survivor regions policy.
394 //
395
396 // Current tenuring threshold, set to 0 if the collector reaches the
397 // maximum amount of survivors regions.
398 uint _tenuring_threshold;
399
400 // The limit on the number of regions allocated for survivors.
401 uint _max_survivor_regions;
402
403 AgeTable _survivors_age_table;
404
405 size_t desired_survivor_size() const;
406 public:
407 // Fraction used when predicting how many optional regions to include in
408 // the CSet. This fraction of the available time is used for optional regions,
409 // the rest is used to add old regions to the normal CSet.
410 double optional_prediction_fraction() { return 0.2; }
411 // Fraction used when evacuating the optional regions. This fraction of the
412 // remaining time is used to choose what regions to include in the evacuation.
413 double optional_evacuation_fraction() { return 0.75; }
414
415 uint tenuring_threshold() const { return _tenuring_threshold; }
416
417 uint max_survivor_regions() {
418 return _max_survivor_regions;
419 }
420
421 void note_start_adding_survivor_regions() {
422 _survivor_surv_rate_group->start_adding_regions();
423 }
424
425 void note_stop_adding_survivor_regions() {
426 _survivor_surv_rate_group->stop_adding_regions();
427 }
428
429 void record_age_table(AgeTable* age_table) {
430 _survivors_age_table.merge(age_table);
431 }
432
433 void print_age_table();
434
435 void update_max_gc_locker_expansion();
436
437 void update_survivors_policy();
438 };
439
440 #endif // SHARE_VM_GC_G1_G1POLICY_HPP