1 /*
2 * Copyright (c) 2016, 2020, 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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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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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/g1OldGenAllocationTracker.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 G1CollectionSetCandidates;
48 class G1CollectionSetChooser;
49 class G1IHOPControl;
50 class G1Analytics;
51 class G1SurvivorRegions;
52 class G1YoungGenSizer;
53 class GCPolicyCounters;
54 class STWGCTimer;
55
56 class G1Policy: public CHeapObj<mtGC> {
57 private:
58
59 static G1IHOPControl* create_ihop_control(const G1Predictions* predictor);
60 // Update the IHOP control with necessary statistics.
61 void update_ihop_prediction(double mutator_time_s,
62 size_t mutator_alloc_bytes,
63 size_t young_gen_size,
64 bool this_gc_was_young_only);
65 void report_ihop_statistics();
66
67 G1Predictions _predictor;
68 G1Analytics* _analytics;
69 G1RemSetTrackingPolicy _remset_tracker;
70 G1MMUTracker* _mmu_tracker;
71 G1IHOPControl* _ihop_control;
72
73 GCPolicyCounters* _policy_counters;
74
75 double _full_collection_start_sec;
76
77 jlong _collection_pause_end_millis;
78
79 uint _young_list_target_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
105 // Tracking the allocation in the old generation between
106 // two GCs.
107 G1OldGenAllocationTracker _old_gen_alloc_tracker;
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
115 double logged_cards_processing_time() const;
116 public:
117 const G1Predictions& predictor() const { return _predictor; }
118 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
119
120 G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
121
122 G1OldGenAllocationTracker* old_gen_alloc_tracker() { return &_old_gen_alloc_tracker; }
123
124 void set_region_eden(HeapRegion* hr) {
125 hr->set_eden();
126 hr->install_surv_rate_group(_eden_surv_rate_group);
127 }
128
129 void set_region_survivor(HeapRegion* hr) {
130 assert(hr->is_survivor(), "pre-condition");
131 hr->install_surv_rate_group(_survivor_surv_rate_group);
132 }
133
134 void record_rs_length(size_t rs_length) {
135 _rs_length = rs_length;
136 }
137
138 double predict_base_elapsed_time_ms(size_t num_pending_cards) const;
139
140 private:
141 double predict_base_elapsed_time_ms(size_t num_pending_cards, size_t rs_length) const;
142
143 double predict_region_copy_time_ms(HeapRegion* hr) const;
144
145 public:
146
147 double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = NULL) const;
148 double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_gc) const;
149 double predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const;
150
151 void cset_regions_freed() {
152 bool update = should_update_surv_rate_group_predictors();
153
154 _eden_surv_rate_group->all_surviving_words_recorded(predictor(), update);
155 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
156 }
157
158 G1MMUTracker* mmu_tracker() {
159 return _mmu_tracker;
160 }
161
162 const G1MMUTracker* mmu_tracker() const {
163 return _mmu_tracker;
164 }
165
166 double max_pause_time_ms() const {
167 return _mmu_tracker->max_gc_time() * 1000.0;
168 }
169
170 private:
171 G1CollectionSet* _collection_set;
172
173 bool next_gc_should_be_mixed(const char* true_action_str,
174 const char* false_action_str) const;
175
176 double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
177 double other_time_ms(double pause_time_ms) const;
178
179 double young_other_time_ms() const;
180 double non_young_other_time_ms() const;
181 double constant_other_time_ms(double pause_time_ms) const;
182
183 G1CollectionSetChooser* cset_chooser() const;
184
185 // Stash a pointer to the g1 heap.
186 G1CollectedHeap* _g1h;
187
188 G1GCPhaseTimes* _phase_times;
189
190 // This set of variables tracks the collector efficiency, in order to
191 // determine whether we should initiate a new marking.
192 double _mark_remark_start_sec;
193 double _mark_cleanup_start_sec;
194
195 // Updates the internal young gen maximum and target lengths. Returns the
196 // unbounded young target length. If no rs_length parameter is passed,
197 // predict the RS length using the prediction model, otherwise use the
198 // given rs_length as the prediction.
199 uint update_young_max_and_target_length();
200 uint update_young_max_and_target_length(size_t rs_length);
201
202 // Update the young list target length either by setting it to the
203 // desired fixed value or by calculating it using G1's pause
204 // prediction model.
205 // Returns the unbounded young list target length.
206 uint update_young_target_length(size_t rs_length);
207
208 // Calculate and return the minimum desired eden length based on the MMU target.
209 uint calculate_desired_eden_length_by_mmu() const;
210
211 // Calculate and return the desired eden length that can fit into the pause time goal.
212 // The parameters are: rs_length represents the prediction of how large the
213 // young RSet lengths will be, min_eden_length and max_eden_length are the bounds
214 // (inclusive) within eden can grow.
215 uint calculate_desired_eden_length_by_pause(double base_time_ms,
216 uint min_eden_length,
217 uint max_eden_length) const;
218
219 // Calculates the desired eden length before mixed gc so that after adding the
220 // minimum amount of old gen regions from the collection set, the eden fits into
221 // the pause time goal.
222 uint calculate_desired_eden_length_before_mixed(double survivor_base_time_ms,
223 uint min_eden_length,
224 uint max_eden_length) const;
225
226 // Calculate desired young length based on current situation without taking actually
227 // available free regions into account.
228 uint calculate_young_desired_length(size_t rs_length) const;
229 // Limit the given desired young length to available free regions.
230 uint calculate_young_target_length(uint desired_young_length) const;
231
232 void update_rs_length_prediction();
233 void update_rs_length_prediction(size_t prediction);
234
235 size_t predict_bytes_to_copy(HeapRegion* hr) const;
236 double predict_survivor_regions_evac_time() const;
237
238 // Check whether a given young length (young_length) fits into the
239 // given target pause time and whether the prediction for the amount
240 // of objects to be copied for the given length will fit into the
241 // given free space (expressed by base_free_regions). It is used by
242 // calculate_young_list_target_length().
243 bool predict_will_fit(uint young_length, double base_time_ms,
244 uint base_free_regions, double target_pause_time_ms) const;
245
246 public:
247 size_t pending_cards_at_gc_start() const { return _pending_cards_at_gc_start; }
248
249 // Calculate the minimum number of old regions we'll add to the CSet
250 // during a mixed GC.
251 uint calc_min_old_cset_length() const;
252
253 // Calculate the maximum number of old regions we'll add to the CSet
254 // during a mixed GC.
255 uint calc_max_old_cset_length() const;
256
257 // Returns the given amount of reclaimable bytes (that represents
258 // the amount of reclaimable space still to be collected) as a
259 // percentage of the current heap capacity.
260 double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
261
262 jlong collection_pause_end_millis() { return _collection_pause_end_millis; }
263
264 private:
265 void clear_collection_set_candidates();
266 // Sets up marking if proper conditions are met.
267 void maybe_start_marking();
268
269 // The kind of STW pause.
270 enum PauseKind {
271 FullGC,
272 YoungOnlyGC,
273 MixedGC,
274 LastYoungGC,
275 InitialMarkGC,
276 Cleanup,
277 Remark
278 };
279
280 // Calculate PauseKind from internal state.
281 PauseKind young_gc_pause_kind() const;
282 // Record the given STW pause with the given start and end times (in s).
283 void record_pause(PauseKind kind, double start, double end);
284 // Indicate that we aborted marking before doing any mixed GCs.
285 void abort_time_to_mixed_tracking();
286
287 // Record and log stats before not-full collection.
288 void record_concurrent_refinement_stats();
289
290 public:
291
292 G1Policy(STWGCTimer* gc_timer);
293
294 virtual ~G1Policy();
295
296 static G1Policy* create_policy(STWGCTimer* gc_timer_stw);
297
298 G1CollectorState* collector_state() const;
299
300 G1GCPhaseTimes* phase_times() const { return _phase_times; }
301
302 // Check the current value of the young list RSet length and
303 // compare it against the last prediction. If the current value is
304 // higher, recalculate the young list target length prediction.
305 void revise_young_list_target_length_if_necessary(size_t rs_length);
306
307 // This should be called after the heap is resized.
308 void record_new_heap_size(uint new_number_of_regions);
309
310 virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
311
312 void note_gc_start();
313
314 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
315
316 bool about_to_start_mixed_phase() const;
317
318 // Record the start and end of an evacuation pause.
319 void record_collection_pause_start(double start_time_sec);
320 virtual void record_collection_pause_end(double pause_time_ms);
321
322 // Record the start and end of a full collection.
323 void record_full_collection_start();
324 virtual void record_full_collection_end();
325
326 // Must currently be called while the world is stopped.
327 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
328
329 // Record start and end of remark.
330 void record_concurrent_mark_remark_start();
331 void record_concurrent_mark_remark_end();
332
333 // Record start, end, and completion of cleanup.
334 void record_concurrent_mark_cleanup_start();
335 void record_concurrent_mark_cleanup_end();
336
337 void print_phases();
338
339 // Calculate and return the number of initial and optional old gen regions from
340 // the given collection set candidates and the remaining time.
341 void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
342 double time_remaining_ms,
343 uint& num_initial_regions,
344 uint& num_optional_regions);
345
346 // Calculate the number of optional regions from the given collection set candidates,
347 // the remaining time and the maximum number of these regions and return the number
348 // of actually selected regions in num_optional_regions.
349 void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
350 uint const max_optional_regions,
351 double time_remaining_ms,
352 uint& num_optional_regions);
353
354 private:
355 // Set the state to start a concurrent marking cycle and clear
356 // _initiate_conc_mark_if_possible because it has now been
357 // acted on.
358 void initiate_conc_mark();
359
360 public:
361 // This sets the initiate_conc_mark_if_possible() flag to start a
362 // new cycle, as long as we are not already in one. It's best if it
363 // is called during a safepoint when the test whether a cycle is in
364 // progress or not is stable.
365 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
366
367 // This is called at the very beginning of an evacuation pause (it
368 // has to be the first thing that the pause does). If
369 // initiate_conc_mark_if_possible() is true, and the concurrent
370 // marking thread has completed its work during the previous cycle,
371 // it will set in_initial_mark_gc() to so that the pause does
372 // the initial-mark work and start a marking cycle.
373 void decide_on_conc_mark_initiation();
374
375 size_t young_list_target_length() const { return _young_list_target_length; }
376
377 bool should_allocate_mutator_region() const;
378
379 bool can_expand_young_list() const;
380
381 uint young_list_max_length() const {
382 return _young_list_max_length;
383 }
384
385 bool use_adaptive_young_list_length() const;
386
387 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
388
389 private:
390 //
391 // Survivor regions policy.
392 //
393
394 // Current tenuring threshold, set to 0 if the collector reaches the
395 // maximum amount of survivors regions.
396 uint _tenuring_threshold;
397
398 // The limit on the number of regions allocated for survivors.
399 uint _max_survivor_regions;
400
401 AgeTable _survivors_age_table;
402
403 size_t desired_survivor_size(uint max_regions) const;
404
405 // Fraction used when predicting how many optional regions to include in
406 // the CSet. This fraction of the available time is used for optional regions,
407 // the rest is used to add old regions to the normal CSet.
408 double optional_prediction_fraction() { return 0.2; }
409
410 public:
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 virtual bool force_upgrade_to_full() {
440 return false;
441 }
442 };
443
444 #endif // SHARE_GC_G1_G1POLICY_HPP