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).
14 *
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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 G1HeapSizingPolicy;
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 friend class G1HeapSizingPolicy;
58 private:
59
60 static G1IHOPControl* create_ihop_control(const G1Predictions* predictor);
61 // Update the IHOP control with necessary statistics.
62 void update_ihop_prediction(double mutator_time_s,
63 size_t mutator_alloc_bytes,
64 size_t young_gen_size,
65 bool this_gc_was_young_only);
66 void report_ihop_statistics();
67
68 G1Predictions _predictor;
69 G1Analytics* _analytics;
70 G1RemSetTrackingPolicy _remset_tracker;
71 G1MMUTracker* _mmu_tracker;
72 G1IHOPControl* _ihop_control;
73
74 GCPolicyCounters* _policy_counters;
75
76 double _full_collection_start_sec;
77
78 jlong _collection_pause_end_millis;
79
80 uint _young_list_target_length;
81 uint _young_list_fixed_length;
82
83 // The max number of regions we can extend the eden by while the GC
84 // locker is active. This should be >= _young_list_target_length;
85 uint _young_list_max_length;
86
87 // The survivor rate groups below must be initialized after the predictor because they
88 // indirectly use it through the "this" object passed to their constructor.
89 G1SurvRateGroup* _eden_surv_rate_group;
90 G1SurvRateGroup* _survivor_surv_rate_group;
91
92 double _reserve_factor;
93 // This will be set when the heap is expanded
94 // for the first time during initialization.
95 uint _reserve_regions;
96
97 G1YoungGenSizer* _young_gen_sizer;
98
99 uint _free_regions_at_end_of_collection;
100
101 size_t _rs_length;
102
103 size_t _rs_length_prediction;
104
105 size_t _pending_cards_at_gc_start;
106 size_t _pending_cards_at_prev_gc_end;
107 size_t _total_mutator_refined_cards;
108 size_t _total_concurrent_refined_cards;
109 Tickspan _total_concurrent_refinement_time;
110
111 // The amount of allocated bytes in old gen during the last mutator and the following
112 // young GC phase.
113 size_t _bytes_allocated_in_old_since_last_gc;
114
115 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
116
117 bool should_update_surv_rate_group_predictors() {
118 return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
119 }
120
121 double logged_cards_processing_time() const;
122 public:
123 const G1Predictions& predictor() const { return _predictor; }
124 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
125
126 G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
127
128 // Add the given number of bytes to the total number of allocated bytes in the old gen.
129 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
130
131 void set_region_eden(HeapRegion* hr) {
132 hr->set_eden();
133 hr->install_surv_rate_group(_eden_surv_rate_group);
134 }
135
136 void set_region_survivor(HeapRegion* hr) {
137 assert(hr->is_survivor(), "pre-condition");
138 hr->install_surv_rate_group(_survivor_surv_rate_group);
139 }
140
141 void record_rs_length(size_t rs_length) {
142 _rs_length = rs_length;
143 }
144
145 double predict_base_elapsed_time_ms(size_t num_pending_cards) const;
146
147 private:
148 double predict_base_elapsed_time_ms(size_t num_pending_cards, size_t rs_length) const;
149
150 double predict_region_copy_time_ms(HeapRegion* hr) const;
151
152 public:
153
154 double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = NULL) const;
155 double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_gc) const;
156 double predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const;
157
158 void cset_regions_freed() {
159 bool update = should_update_surv_rate_group_predictors();
160
161 _eden_surv_rate_group->all_surviving_words_recorded(predictor(), update);
162 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
163 }
164
165 G1MMUTracker* mmu_tracker() {
166 return _mmu_tracker;
167 }
168
169 const G1MMUTracker* mmu_tracker() const {
170 return _mmu_tracker;
171 }
172
173 double max_pause_time_ms() const {
174 return _mmu_tracker->max_gc_time() * 1000.0;
175 }
176
177 private:
178 G1CollectionSet* _collection_set;
179 double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
180 double other_time_ms(double pause_time_ms) const;
181
182 double young_other_time_ms() const;
183 double non_young_other_time_ms() const;
184 double constant_other_time_ms(double pause_time_ms) const;
185
186 G1CollectionSetChooser* cset_chooser() const;
187
188 // Stash a pointer to the g1 heap.
189 G1CollectedHeap* _g1h;
190
191 G1GCPhaseTimes* _phase_times;
192
193 // This set of variables tracks the collector efficiency, in order to
194 // determine whether we should initiate a new marking.
195 double _mark_remark_start_sec;
196 double _mark_cleanup_start_sec;
197
198 // Updates the internal young list maximum and target lengths. Returns the
199 // unbounded young list target length. If no rs_length parameter is passed,
200 // predict the RS length using the prediction model, otherwise use the
201 // given rs_length as the prediction.
202 uint update_young_list_max_and_target_length();
203 uint update_young_list_max_and_target_length(size_t rs_length);
204
205 // Update the young list target length either by setting it to the
206 // desired fixed value or by calculating it using G1's pause
207 // prediction model.
208 // Returns the unbounded young list target length.
209 uint update_young_list_target_length(size_t rs_length);
210
211 // Calculate and return the minimum desired young list target
212 // length. This is the minimum desired young list length according
213 // to the user's inputs.
214 uint calculate_young_list_desired_min_length(uint base_min_length) const;
215
216 // Calculate and return the maximum desired young list target
217 // length. This is the maximum desired young list length according
218 // to the user's inputs.
219 uint calculate_young_list_desired_max_length() const;
220
221 // Calculate and return the maximum young list target length that
222 // can fit into the pause time goal. The parameters are: rs_length
223 // represent the prediction of how large the young RSet lengths will
224 // be, base_min_length is the already existing number of regions in
225 // the young list, min_length and max_length are the desired min and
226 // max young list length according to the user's inputs.
227 uint calculate_young_list_target_length(size_t rs_length,
228 uint base_min_length,
229 uint desired_min_length,
230 uint desired_max_length) const;
231
232 // Result of the bounded_young_list_target_length() method, containing both the
233 // bounded as well as the unbounded young list target lengths in this order.
234 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
235 YoungTargetLengths young_list_target_lengths(size_t rs_length) const;
236
237 void update_rs_length_prediction();
238 void update_rs_length_prediction(size_t prediction);
239
240 size_t predict_bytes_to_copy(HeapRegion* hr) const;
241 double predict_survivor_regions_evac_time() const;
242
243 // Check whether a given young length (young_length) fits into the
244 // given target pause time and whether the prediction for the amount
245 // of objects to be copied for the given length will fit into the
246 // given free space (expressed by base_free_regions). It is used by
247 // calculate_young_list_target_length().
248 bool predict_will_fit(uint young_length, double base_time_ms,
249 uint base_free_regions, double target_pause_time_ms) const;
250
251 public:
252 size_t pending_cards_at_gc_start() const { return _pending_cards_at_gc_start; }
253
254 // Calculate the minimum number of old regions we'll add to the CSet
255 // during a mixed GC.
256 uint calc_min_old_cset_length() const;
257
258 // Calculate the maximum number of old regions we'll add to the CSet
259 // during a mixed GC.
260 uint calc_max_old_cset_length() const;
261
262 // Returns the given amount of reclaimable bytes (that represents
263 // the amount of reclaimable space still to be collected) as a
264 // percentage of the current heap capacity.
265 double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
266
267 jlong collection_pause_end_millis() { return _collection_pause_end_millis; }
268
269 private:
270 void clear_collection_set_candidates();
271 // Sets up marking if proper conditions are met.
272 void maybe_start_marking();
273
274 // The kind of STW pause.
275 enum PauseKind {
276 FullGC,
277 YoungOnlyGC,
278 MixedGC,
279 LastYoungGC,
280 InitialMarkGC,
281 Cleanup,
282 Remark
283 };
284
285 // Calculate PauseKind from internal state.
286 PauseKind young_gc_pause_kind() const;
287 // Record the given STW pause with the given start and end times (in s).
288 void record_pause(PauseKind kind, double start, double end);
289 // Indicate that we aborted marking before doing any mixed GCs.
290 void abort_time_to_mixed_tracking();
291
292 void record_concurrent_refinement_data(bool is_full_collection);
293
294 public:
295
296 G1Policy(STWGCTimer* gc_timer);
297
298 virtual ~G1Policy();
299
300 static G1Policy* create_policy(STWGCTimer* gc_timer_stw);
301
302 G1CollectorState* collector_state() const;
303
304 G1GCPhaseTimes* phase_times() const { return _phase_times; }
305
306 // Check the current value of the young list RSet length and
307 // compare it against the last prediction. If the current value is
308 // higher, recalculate the young list target length prediction.
309 void revise_young_list_target_length_if_necessary(size_t rs_length);
310
311 // This should be called after the heap is resized.
312 void record_new_heap_size(uint new_number_of_regions);
313
314 virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
315
316 void note_gc_start();
317
318 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
319
320 bool about_to_start_mixed_phase() const;
321
322 // Record the start and end of an evacuation pause.
323 void record_collection_pause_start(double start_time_sec);
324 virtual void record_collection_pause_end(double pause_time_ms);
325
326 // Record the start and end of a full collection.
327 void record_full_collection_start();
328 virtual void record_full_collection_end();
329
330 // Must currently be called while the world is stopped.
331 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
332
333 // Record start and end of remark.
334 void record_concurrent_mark_remark_start();
335 void record_concurrent_mark_remark_end();
336
337 // Record start, end, and completion of cleanup.
338 void record_concurrent_mark_cleanup_start();
339 void record_concurrent_mark_cleanup_end();
340
341 void print_phases();
342
343 bool next_gc_should_be_mixed(const char* true_action_str,
344 const char* false_action_str) const;
345
346 // Calculate and return the number of initial and optional old gen regions from
347 // the given collection set candidates and the remaining time.
348 void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
349 double time_remaining_ms,
350 uint& num_initial_regions,
351 uint& num_optional_regions);
352
353 // Calculate the number of optional regions from the given collection set candidates,
354 // the remaining time and the maximum number of these regions and return the number
355 // of actually selected regions in num_optional_regions.
356 void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
357 uint const max_optional_regions,
358 double time_remaining_ms,
359 uint& num_optional_regions);
360
361 private:
362 // Set the state to start a concurrent marking cycle and clear
363 // _initiate_conc_mark_if_possible because it has now been
364 // acted on.
365 void initiate_conc_mark();
366
367 public:
368 // This sets the initiate_conc_mark_if_possible() flag to start a
369 // new cycle, as long as we are not already in one. It's best if it
370 // is called during a safepoint when the test whether a cycle is in
371 // progress or not is stable.
372 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
373
374 // This is called at the very beginning of an evacuation pause (it
375 // has to be the first thing that the pause does). If
376 // initiate_conc_mark_if_possible() is true, and the concurrent
377 // marking thread has completed its work during the previous cycle,
378 // it will set in_initial_mark_gc() to so that the pause does
379 // the initial-mark work and start a marking cycle.
380 void decide_on_conc_mark_initiation();
381
382 size_t young_list_target_length() const { return _young_list_target_length; }
383
384 bool should_allocate_mutator_region() const;
385
386 bool can_expand_young_list() const;
387
388 uint young_list_max_length() const {
389 return _young_list_max_length;
390 }
391
392 bool use_adaptive_young_list_length() const;
393
394 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
395
396 private:
397 //
398 // Survivor regions policy.
399 //
400
401 // Current tenuring threshold, set to 0 if the collector reaches the
402 // maximum amount of survivors regions.
403 uint _tenuring_threshold;
404
405 // The limit on the number of regions allocated for survivors.
406 uint _max_survivor_regions;
407
408 AgeTable _survivors_age_table;
409
410 size_t desired_survivor_size(uint max_regions) const;
411
412 // Fraction used when predicting how many optional regions to include in
413 // the CSet. This fraction of the available time is used for optional regions,
414 // the rest is used to add old regions to the normal CSet.
415 double optional_prediction_fraction() { return 0.2; }
416
417 public:
418 // Fraction used when evacuating the optional regions. This fraction of the
419 // remaining time is used to choose what regions to include in the evacuation.
420 double optional_evacuation_fraction() { return 0.75; }
421
422 uint tenuring_threshold() const { return _tenuring_threshold; }
423
424 uint max_survivor_regions() {
425 return _max_survivor_regions;
426 }
427
428 void note_start_adding_survivor_regions() {
429 _survivor_surv_rate_group->start_adding_regions();
430 }
431
432 void note_stop_adding_survivor_regions() {
433 _survivor_surv_rate_group->stop_adding_regions();
434 }
435
436 void record_age_table(AgeTable* age_table) {
437 _survivors_age_table.merge(age_table);
438 }
439
440 void print_age_table();
441
442 void update_max_gc_locker_expansion();
443
444 void update_survivors_policy();
445
446 virtual bool force_upgrade_to_full() {
447 return false;
448 }
449 };
450
451 #endif // SHARE_GC_G1_G1POLICY_HPP