1 /*
2 * Copyright (c) 2016, 2019, 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.
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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).
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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23 */
24
25 #ifndef SHARE_GC_G1_G1POLICY_HPP
26 #define SHARE_GC_G1_G1POLICY_HPP
27
28 #include "gc/g1/g1CollectorState.hpp"
29 #include "gc/g1/g1GCPhaseTimes.hpp"
30 #include "gc/g1/g1HeapRegionAttr.hpp"
31 #include "gc/g1/g1InitialMarkToMixedTimeTracker.hpp"
32 #include "gc/g1/g1MMUTracker.hpp"
33 #include "gc/g1/g1RemSetTrackingPolicy.hpp"
34 #include "gc/g1/g1Predictions.hpp"
35 #include "gc/g1/g1YoungGenSizer.hpp"
36 #include "gc/shared/gcCause.hpp"
37 #include "utilities/pair.hpp"
38
39 // A G1Policy makes policy decisions that determine the
40 // characteristics of the collector. Examples include:
41 // * choice of collection set.
42 // * when to collect.
43
44 class HeapRegion;
45 class G1CollectionSet;
46 class G1CollectionSetCandidates;
47 class G1CollectionSetChooser;
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 // The survivor rate groups below must be initialized after the predictor because they
86 // indirectly use it through the "this" object passed to their constructor.
87 G1SurvRateGroup* _eden_surv_rate_group;
88 G1SurvRateGroup* _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 _rs_length;
100
101 size_t _rs_length_prediction;
102
103 size_t _pending_cards_at_gc_start;
104 size_t _pending_cards_at_prev_gc_end;
105 size_t _total_mutator_refined_cards;
106 size_t _total_concurrent_refined_cards;
107 Tickspan _total_concurrent_refinement_time;
108
109 // The amount of allocated bytes in old gen during the last mutator and the following
110 // young GC phase.
111 size_t _bytes_allocated_in_old_since_last_gc;
112
113 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
114
115 bool should_update_surv_rate_group_predictors() {
116 return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
117 }
118
119 double logged_cards_processing_time() const;
120 public:
121 const G1Predictions& predictor() const { return _predictor; }
122 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
123
124 G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
125
126 // Add the given number of bytes to the total number of allocated bytes in the old gen.
127 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
128
129 void set_region_eden(HeapRegion* hr) {
130 hr->set_eden();
131 hr->install_surv_rate_group(_eden_surv_rate_group);
132 }
133
134 void set_region_survivor(HeapRegion* hr) {
135 assert(hr->is_survivor(), "pre-condition");
136 hr->install_surv_rate_group(_survivor_surv_rate_group);
137 }
138
139 void record_rs_length(size_t rs_length) {
140 _rs_length = rs_length;
141 }
142
143 double predict_base_elapsed_time_ms(size_t num_pending_cards) const;
144
145 private:
146 double predict_base_elapsed_time_ms(size_t num_pending_cards, size_t rs_length) const;
147
148 double predict_region_copy_time_ms(HeapRegion* hr) const;
149
150 public:
151
152 double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = NULL) const;
153 double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_gc) const;
154 double predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const;
155
156 void cset_regions_freed() {
157 bool update = should_update_surv_rate_group_predictors();
158
159 _eden_surv_rate_group->all_surviving_words_recorded(predictor(), update);
160 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
161 }
162
163 G1MMUTracker* mmu_tracker() {
164 return _mmu_tracker;
165 }
166
167 const G1MMUTracker* mmu_tracker() const {
168 return _mmu_tracker;
169 }
170
171 double max_pause_time_ms() const {
172 return _mmu_tracker->max_gc_time() * 1000.0;
173 }
174
175 private:
176 G1CollectionSet* _collection_set;
177 double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
178 double other_time_ms(double pause_time_ms) const;
179
180 double young_other_time_ms() const;
181 double non_young_other_time_ms() const;
182 double constant_other_time_ms(double pause_time_ms) const;
183
184 G1CollectionSetChooser* cset_chooser() const;
185
186 // Stash a pointer to the g1 heap.
187 G1CollectedHeap* _g1h;
188
189 G1GCPhaseTimes* _phase_times;
190
191 // This set of variables tracks the collector efficiency, in order to
192 // determine whether we should initiate a new marking.
193 double _mark_remark_start_sec;
194 double _mark_cleanup_start_sec;
195
196 // Updates the internal young list maximum and target lengths. Returns the
197 // unbounded young list target length. If no rs_length parameter is passed,
198 // predict the RS length using the prediction model, otherwise use the
199 // given rs_length as the prediction.
200 uint update_young_list_max_and_target_length();
201 uint update_young_list_max_and_target_length(size_t rs_length);
202
203 // Update the young list target length either by setting it to the
204 // desired fixed value or by calculating it using G1's pause
205 // prediction model.
206 // Returns the unbounded young list target length.
207 uint update_young_list_target_length(size_t rs_length);
208
209 // Calculate and return the minimum desired young list target
210 // length. This is the minimum desired young list length according
211 // to the user's inputs.
212 uint calculate_young_list_desired_min_length(uint base_min_length) const;
213
214 // Calculate and return the maximum desired young list target
215 // length. This is the maximum desired young list length according
216 // to the user's inputs.
217 uint calculate_young_list_desired_max_length() const;
218
219 // Calculate and return the maximum young list target length that
220 // can fit into the pause time goal. The parameters are: rs_length
221 // represent the prediction of how large the young RSet lengths will
222 // be, base_min_length is the already existing number of regions in
223 // the young list, min_length and max_length are the desired min and
224 // max young list length according to the user's inputs.
225 uint calculate_young_list_target_length(size_t rs_length,
226 uint base_min_length,
227 uint desired_min_length,
228 uint desired_max_length) const;
229
230 // Result of the bounded_young_list_target_length() method, containing both the
231 // bounded as well as the unbounded young list target lengths in this order.
232 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
233 YoungTargetLengths young_list_target_lengths(size_t rs_length) const;
234
235 void update_rs_length_prediction();
236 void update_rs_length_prediction(size_t prediction);
237
238 size_t predict_bytes_to_copy(HeapRegion* hr) const;
239 double predict_survivor_regions_evac_time() const;
240
241 // Check whether a given young length (young_length) fits into the
242 // given target pause time and whether the prediction for the amount
243 // of objects to be copied for the given length will fit into the
244 // given free space (expressed by base_free_regions). It is used by
245 // calculate_young_list_target_length().
246 bool predict_will_fit(uint young_length, double base_time_ms,
247 uint base_free_regions, double target_pause_time_ms) const;
248
249 public:
250 size_t pending_cards_at_gc_start() const { return _pending_cards_at_gc_start; }
251
252 // Calculate the minimum number of old regions we'll add to the CSet
253 // during a mixed GC.
254 uint calc_min_old_cset_length() const;
255
256 // Calculate the maximum number of old regions we'll add to the CSet
257 // during a mixed GC.
258 uint calc_max_old_cset_length() const;
259
260 // Returns the given amount of reclaimable bytes (that represents
261 // the amount of reclaimable space still to be collected) as a
262 // percentage of the current heap capacity.
263 double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
264
265 jlong collection_pause_end_millis() { return _collection_pause_end_millis; }
266
267 private:
268 void clear_collection_set_candidates();
269 // Sets up marking if proper conditions are met.
270 void maybe_start_marking();
271
272 // The kind of STW pause.
273 enum PauseKind {
274 FullGC,
275 YoungOnlyGC,
276 MixedGC,
277 LastYoungGC,
278 InitialMarkGC,
279 Cleanup,
280 Remark
281 };
282
283 // Calculate PauseKind from internal state.
284 PauseKind young_gc_pause_kind() const;
285 // Record the given STW pause with the given start and end times (in s).
286 void record_pause(PauseKind kind, double start, double end);
287 // Indicate that we aborted marking before doing any mixed GCs.
288 void abort_time_to_mixed_tracking();
289
290 void record_concurrent_refinement_data(bool is_full_collection);
291
292 public:
293
294 G1Policy(STWGCTimer* gc_timer);
295
296 virtual ~G1Policy();
297
298 static G1Policy* create_policy(STWGCTimer* gc_timer_stw);
299
300 G1CollectorState* collector_state() const;
301
302 G1GCPhaseTimes* phase_times() const { return _phase_times; }
303
304 // Check the current value of the young list RSet length and
305 // compare it against the last prediction. If the current value is
306 // higher, recalculate the young list target length prediction.
307 void revise_young_list_target_length_if_necessary(size_t rs_length);
308
309 // This should be called after the heap is resized.
310 void record_new_heap_size(uint new_number_of_regions);
311
312 virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
313
314 void note_gc_start();
315
316 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
317
318 bool about_to_start_mixed_phase() const;
319
320 // Record the start and end of an evacuation pause.
321 void record_collection_pause_start(double start_time_sec);
322 virtual void record_collection_pause_end(double pause_time_ms);
323
324 // Record the start and end of a full collection.
325 void record_full_collection_start();
326 virtual void record_full_collection_end();
327
328 // Must currently be called while the world is stopped.
329 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
330
331 // Record start and end of remark.
332 void record_concurrent_mark_remark_start();
333 void record_concurrent_mark_remark_end();
334
335 // Record start, end, and completion of cleanup.
336 void record_concurrent_mark_cleanup_start();
337 void record_concurrent_mark_cleanup_end();
338
339 void print_phases();
340
341 bool next_gc_should_be_mixed(const char* true_action_str,
342 const char* false_action_str) const;
343
344 // Calculate and return the number of initial and optional old gen regions from
345 // the given collection set candidates and the remaining time.
346 void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
347 double time_remaining_ms,
348 uint& num_initial_regions,
349 uint& num_optional_regions);
350
351 // Calculate the number of optional regions from the given collection set candidates,
352 // the remaining time and the maximum number of these regions and return the number
353 // of actually selected regions in num_optional_regions.
354 void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
355 uint const max_optional_regions,
356 double time_remaining_ms,
357 uint& num_optional_regions);
358
359 private:
360 // Set the state to start a concurrent marking cycle and clear
361 // _initiate_conc_mark_if_possible because it has now been
362 // acted on.
363 void initiate_conc_mark();
364
365 public:
366 // This sets the initiate_conc_mark_if_possible() flag to start a
367 // new cycle, as long as we are not already in one. It's best if it
368 // is called during a safepoint when the test whether a cycle is in
369 // progress or not is stable.
370 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
371
372 // This is called at the very beginning of an evacuation pause (it
373 // has to be the first thing that the pause does). If
374 // initiate_conc_mark_if_possible() is true, and the concurrent
375 // marking thread has completed its work during the previous cycle,
376 // it will set in_initial_mark_gc() to so that the pause does
377 // the initial-mark work and start a marking cycle.
378 void decide_on_conc_mark_initiation();
379
380 size_t young_list_target_length() const { return _young_list_target_length; }
381
382 bool should_allocate_mutator_region() const;
383
384 bool can_expand_young_list() const;
385
386 uint young_list_max_length() const {
387 return _young_list_max_length;
388 }
389
390 bool use_adaptive_young_list_length() const;
391
392 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
393
394 private:
395 //
396 // Survivor regions policy.
397 //
398
399 // Current tenuring threshold, set to 0 if the collector reaches the
400 // maximum amount of survivors regions.
401 uint _tenuring_threshold;
402
403 // The limit on the number of regions allocated for survivors.
404 uint _max_survivor_regions;
405
406 AgeTable _survivors_age_table;
407
408 size_t desired_survivor_size(uint max_regions) const;
409
410 // Fraction used when predicting how many optional regions to include in
411 // the CSet. This fraction of the available time is used for optional regions,
412 // the rest is used to add old regions to the normal CSet.
413 double optional_prediction_fraction() { return 0.2; }
414
415 public:
416 // Fraction used when evacuating the optional regions. This fraction of the
417 // remaining time is used to choose what regions to include in the evacuation.
418 double optional_evacuation_fraction() { return 0.75; }
419
420 uint tenuring_threshold() const { return _tenuring_threshold; }
421
422 uint max_survivor_regions() {
423 return _max_survivor_regions;
424 }
425
426 void note_start_adding_survivor_regions() {
427 _survivor_surv_rate_group->start_adding_regions();
428 }
429
430 void note_stop_adding_survivor_regions() {
431 _survivor_surv_rate_group->stop_adding_regions();
432 }
433
434 void record_age_table(AgeTable* age_table) {
435 _survivors_age_table.merge(age_table);
436 }
437
438 void print_age_table();
439
440 void update_max_gc_locker_expansion();
441
442 void update_survivors_policy();
443
444 virtual bool force_upgrade_to_full() {
445 return false;
446 }
447 };
448
449 #endif // SHARE_GC_G1_G1POLICY_HPP