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
12 * version 2 for more details (a copy is included in the LICENSE file that
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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/g1ConcurrentStartToMixedTimeTracker.hpp"
30 #include "gc/g1/g1GCPhaseTimes.hpp"
31 #include "gc/g1/g1HeapRegionAttr.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 uint _young_list_target_length;
78 uint _young_list_fixed_length;
79
80 // The max number of regions we can extend the eden by while the GC
81 // locker is active. This should be >= _young_list_target_length;
82 uint _young_list_max_length;
83
84 // The survivor rate groups below must be initialized after the predictor because they
85 // indirectly use it through the "this" object passed to their constructor.
86 G1SurvRateGroup* _eden_surv_rate_group;
87 G1SurvRateGroup* _survivor_surv_rate_group;
88
89 double _reserve_factor;
90 // This will be set when the heap is expanded
91 // for the first time during initialization.
92 uint _reserve_regions;
93
94 G1YoungGenSizer* _young_gen_sizer;
95
96 uint _free_regions_at_end_of_collection;
97
98 size_t _rs_length;
99
100 size_t _rs_length_prediction;
101
102 size_t _pending_cards_at_gc_start;
103
104 // Tracking the allocation in the old generation between
105 // two GCs.
106 G1OldGenAllocationTracker _old_gen_alloc_tracker;
107
108 G1ConcurrentStartToMixedTimeTracker _concurrent_start_to_mixed;
109
110 bool should_update_surv_rate_group_predictors() {
111 return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
112 }
113
114 double logged_cards_processing_time() const;
115 public:
116 const G1Predictions& predictor() const { return _predictor; }
117 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
118
119 G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
120
121 G1OldGenAllocationTracker* old_gen_alloc_tracker() { return &_old_gen_alloc_tracker; }
122
123 void set_region_eden(HeapRegion* hr) {
124 hr->set_eden();
125 hr->install_surv_rate_group(_eden_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_rs_length(size_t rs_length) {
134 _rs_length = rs_length;
135 }
136
137 double predict_base_elapsed_time_ms(size_t num_pending_cards) const;
138
139 private:
140 double predict_base_elapsed_time_ms(size_t num_pending_cards, size_t rs_length) const;
141
142 double predict_region_copy_time_ms(HeapRegion* hr) const;
143
144 public:
145
146 double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = NULL) const;
147 double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_gc) const;
148 double predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const;
149
150 void cset_regions_freed() {
151 bool update = should_update_surv_rate_group_predictors();
152
153 _eden_surv_rate_group->all_surviving_words_recorded(predictor(), update);
154 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
155 }
156
157 G1MMUTracker* mmu_tracker() {
158 return _mmu_tracker;
159 }
160
161 const G1MMUTracker* mmu_tracker() const {
162 return _mmu_tracker;
163 }
164
165 double max_pause_time_ms() const {
166 return _mmu_tracker->max_gc_time() * 1000.0;
167 }
168
169 private:
170 G1CollectionSet* _collection_set;
171 double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
172 double other_time_ms(double pause_time_ms) const;
173
174 double young_other_time_ms() const;
175 double non_young_other_time_ms() const;
176 double constant_other_time_ms(double pause_time_ms) const;
177
178 G1CollectionSetChooser* cset_chooser() const;
179
180 // Stash a pointer to the g1 heap.
181 G1CollectedHeap* _g1h;
182
183 STWGCTimer* _phase_times_timer;
184 // Lazily initialized
185 mutable G1GCPhaseTimes* _phase_times;
186
187 // This set of variables tracks the collector efficiency, in order to
188 // determine whether we should initiate a new marking.
189 double _mark_remark_start_sec;
190 double _mark_cleanup_start_sec;
191
192 // Updates the internal young list maximum and target lengths. Returns the
193 // unbounded young list target length. If no rs_length parameter is passed,
194 // predict the RS length using the prediction model, otherwise use the
195 // given rs_length as the prediction.
196 uint update_young_list_max_and_target_length();
197 uint update_young_list_max_and_target_length(size_t rs_length);
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.
202 // Returns the unbounded young list target length.
203 uint update_young_list_target_length(size_t rs_length);
204
205 // Calculate and return the minimum desired young list target
206 // length. This is the minimum desired young list length according
207 // to the user's inputs.
208 uint calculate_young_list_desired_min_length(uint base_min_length) const;
209
210 // Calculate and return the maximum desired young list target
211 // length. This is the maximum desired young list length according
212 // to the user's inputs.
213 uint calculate_young_list_desired_max_length() const;
214
215 // Calculate and return the maximum young list target length that
216 // can fit into the pause time goal. The parameters are: rs_length
217 // represent the prediction of how large the young RSet lengths will
218 // be, base_min_length is the already existing number of regions in
219 // the young list, min_length and max_length are the desired min and
220 // max young list length according to the user's inputs.
221 uint calculate_young_list_target_length(size_t rs_length,
222 uint base_min_length,
223 uint desired_min_length,
224 uint desired_max_length) const;
225
226 // Result of the bounded_young_list_target_length() method, containing both the
227 // bounded as well as the unbounded young list target lengths in this order.
228 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
229 YoungTargetLengths young_list_target_lengths(size_t rs_length) const;
230
231 void update_rs_length_prediction();
232 void update_rs_length_prediction(size_t prediction);
233
234 size_t predict_bytes_to_copy(HeapRegion* hr) const;
235 double predict_survivor_regions_evac_time() const;
236
237 // Check whether a given young length (young_length) fits into the
238 // given target pause time and whether the prediction for the amount
239 // of objects to be copied for the given length will fit into the
240 // given free space (expressed by base_free_regions). It is used by
241 // calculate_young_list_target_length().
242 bool predict_will_fit(uint young_length, double base_time_ms,
243 uint base_free_regions, double target_pause_time_ms) const;
244
245 public:
246 size_t pending_cards_at_gc_start() const { return _pending_cards_at_gc_start; }
247
248 // Calculate the minimum number of old regions we'll add to the CSet
249 // during a mixed GC.
250 uint calc_min_old_cset_length() const;
251
252 // Calculate the maximum number of old regions we'll add to the CSet
253 // during a mixed GC.
254 uint calc_max_old_cset_length() const;
255
256 // Returns the given amount of reclaimable bytes (that represents
257 // the amount of reclaimable space still to be collected) as a
258 // percentage of the current heap capacity.
259 double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
260
261 private:
262 void clear_collection_set_candidates();
263 // Sets up marking if proper conditions are met.
264 void maybe_start_marking();
265
266 // The kind of STW pause.
267 enum PauseKind {
268 FullGC,
269 YoungOnlyGC,
270 MixedGC,
271 LastYoungGC,
272 ConcurrentStartGC,
273 Cleanup,
274 Remark
275 };
276
277 static bool is_young_only_pause(PauseKind kind);
278 static bool is_mixed_pause(PauseKind kind);
279 static bool is_last_young_pause(PauseKind kind);
280 static bool is_concurrent_start_pause(PauseKind kind);
281 // Calculate PauseKind from internal state.
282 PauseKind young_gc_pause_kind() const;
283 // Record the given STW pause with the given start and end times (in s).
284 void record_pause(PauseKind kind, double start, double end);
285 // Indicate that we aborted marking before doing any mixed GCs.
286 void abort_time_to_mixed_tracking();
287
288 // Record and log stats before not-full collection.
289 void record_concurrent_refinement_stats();
290
291 public:
292
293 G1Policy(STWGCTimer* gc_timer);
294
295 virtual ~G1Policy();
296
297 static G1Policy* create_policy(STWGCTimer* gc_timer_stw);
298
299 G1CollectorState* collector_state() const;
300
301 G1GCPhaseTimes* phase_times() const;
302
303 // Check the current value of the young list RSet length and
304 // compare it against the last prediction. If the current value is
305 // higher, recalculate the young list target length prediction.
306 void revise_young_list_target_length_if_necessary(size_t rs_length);
307
308 // This should be called after the heap is resized.
309 void record_new_heap_size(uint new_number_of_regions);
310
311 virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
312
313 void note_gc_start();
314
315 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
316
317 bool about_to_start_mixed_phase() const;
318
319 // Record the start and end of an evacuation pause.
320 void record_collection_pause_start(double start_time_sec);
321 virtual void record_collection_pause_end(double pause_time_ms);
322
323 // Record the start and end of a full collection.
324 void record_full_collection_start();
325 virtual void record_full_collection_end();
326
327 // Must currently be called while the world is stopped.
328 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
329
330 // Record start and end of remark.
331 void record_concurrent_mark_remark_start();
332 void record_concurrent_mark_remark_end();
333
334 // Record start, end, and completion of cleanup.
335 void record_concurrent_mark_cleanup_start();
336 void record_concurrent_mark_cleanup_end();
337
338 void print_phases();
339
340 bool next_gc_should_be_mixed(const char* true_action_str,
341 const char* false_action_str) const;
342
343 // Calculate and return the number of initial and optional old gen regions from
344 // the given collection set candidates and the remaining time.
345 void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
346 double time_remaining_ms,
347 uint& num_initial_regions,
348 uint& num_optional_regions);
349
350 // Calculate the number of optional regions from the given collection set candidates,
351 // the remaining time and the maximum number of these regions and return the number
352 // of actually selected regions in num_optional_regions.
353 void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
354 uint const max_optional_regions,
355 double time_remaining_ms,
356 uint& num_optional_regions);
357
358 private:
359 // Set the state to start a concurrent marking cycle and clear
360 // _initiate_conc_mark_if_possible because it has now been
361 // acted on.
362 void initiate_conc_mark();
363
364 public:
365 // This sets the initiate_conc_mark_if_possible() flag to start a
366 // new cycle, as long as we are not already in one. It's best if it
367 // is called during a safepoint when the test whether a cycle is in
368 // progress or not is stable.
369 bool force_concurrent_start_if_outside_cycle(GCCause::Cause gc_cause);
370
371 // This is called at the very beginning of an evacuation pause (it
372 // has to be the first thing that the pause does). If
373 // initiate_conc_mark_if_possible() is true, and the concurrent
374 // marking thread has completed its work during the previous cycle,
375 // it will set in_concurrent_start_gc() to so that the pause does
376 // the concurrent start work and start a marking cycle.
377 void decide_on_conc_mark_initiation();
378
379 size_t young_list_target_length() const { return _young_list_target_length; }
380
381 bool should_allocate_mutator_region() const;
382
383 bool can_expand_young_list() const;
384
385 uint young_list_max_length() const {
386 return _young_list_max_length;
387 }
388
389 bool use_adaptive_young_list_length() const;
390
391 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
392
393 private:
394 //
395 // Survivor regions policy.
396 //
397
398 // Current tenuring threshold, set to 0 if the collector reaches the
399 // maximum amount of survivors regions.
400 uint _tenuring_threshold;
401
402 // The limit on the number of regions allocated for survivors.
403 uint _max_survivor_regions;
404
405 AgeTable _survivors_age_table;
406
407 size_t desired_survivor_size(uint max_regions) const;
408
409 // Fraction used when predicting how many optional regions to include in
410 // the CSet. This fraction of the available time is used for optional regions,
411 // the rest is used to add old regions to the normal CSet.
412 double optional_prediction_fraction() { return 0.2; }
413
414 public:
415 // Fraction used when evacuating the optional regions. This fraction of the
416 // remaining time is used to choose what regions to include in the evacuation.
417 double optional_evacuation_fraction() { return 0.75; }
418
419 uint tenuring_threshold() const { return _tenuring_threshold; }
420
421 uint max_survivor_regions() {
422 return _max_survivor_regions;
423 }
424
425 void note_start_adding_survivor_regions() {
426 _survivor_surv_rate_group->start_adding_regions();
427 }
428
429 void note_stop_adding_survivor_regions() {
430 _survivor_surv_rate_group->stop_adding_regions();
431 }
432
433 void record_age_table(AgeTable* age_table) {
434 _survivors_age_table.merge(age_table);
435 }
436
437 void print_age_table();
438
439 void update_max_gc_locker_expansion();
440
441 void update_survivors_policy();
442
443 virtual bool force_upgrade_to_full() {
444 return false;
445 }
446 };
447
448 #endif // SHARE_GC_G1_G1POLICY_HPP