1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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 bool this_gc_included_initial_mark);
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
82 // The max number of regions we can extend the eden by while the GC
83 // locker is active. This should be >= _young_list_target_length;
84 uint _young_list_max_length;
85
86 // The survivor rate groups below must be initialized after the predictor because they
87 // indirectly use it through the "this" object passed to their constructor.
88 G1SurvRateGroup* _eden_surv_rate_group;
89 G1SurvRateGroup* _survivor_surv_rate_group;
90
91 double _reserve_factor;
92 // This will be set when the heap is expanded
93 // for the first time during initialization.
94 uint _reserve_regions;
95
96 G1YoungGenSizer* _young_gen_sizer;
97
98 uint _free_regions_at_end_of_collection;
99
100 size_t _rs_length;
101
102 size_t _rs_length_prediction;
103
104 size_t _pending_cards_at_gc_start;
105
106 // Tracking the allocation in the old generation between
107 // two GCs.
108 G1OldGenAllocationTracker _old_gen_alloc_tracker;
109
110 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
111
112 bool should_update_surv_rate_group_predictors() {
113 return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
114 }
115
116 double logged_cards_processing_time() const;
117 public:
118 const G1Predictions& predictor() const { return _predictor; }
119 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
120
121 G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
122
123 G1OldGenAllocationTracker* old_gen_alloc_tracker() { return &_old_gen_alloc_tracker; }
124
125 void set_region_eden(HeapRegion* hr) {
126 hr->set_eden();
127 hr->install_surv_rate_group(_eden_surv_rate_group);
128 }
129
130 void set_region_survivor(HeapRegion* hr) {
131 assert(hr->is_survivor(), "pre-condition");
132 hr->install_surv_rate_group(_survivor_surv_rate_group);
133 }
134
135 void record_rs_length(size_t rs_length) {
136 _rs_length = rs_length;
137 }
138
139 double predict_base_elapsed_time_ms(size_t num_pending_cards) const;
140
141 private:
142 double predict_base_elapsed_time_ms(size_t num_pending_cards, size_t rs_length) const;
143
144 double predict_region_copy_time_ms(HeapRegion* hr) const;
145
146 public:
147
148 double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = NULL) const;
149 double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_gc) const;
150 double predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const;
151
152 void cset_regions_freed() {
153 bool update = should_update_surv_rate_group_predictors();
154
155 _eden_surv_rate_group->all_surviving_words_recorded(predictor(), update);
156 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
157 }
158
159 G1MMUTracker* mmu_tracker() {
160 return _mmu_tracker;
161 }
162
163 const G1MMUTracker* mmu_tracker() const {
164 return _mmu_tracker;
165 }
166
167 double max_pause_time_ms() const {
168 return _mmu_tracker->max_gc_time() * 1000.0;
169 }
170
171 private:
172 G1CollectionSet* _collection_set;
173
174 bool next_gc_should_be_mixed(const char* true_action_str,
175 const char* false_action_str) const;
176
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 gen maximum and target lengths. Returns the
197 // unbounded young 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_max_and_target_length();
201 uint update_young_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_target_length(size_t rs_length);
208
209 // Calculate and return the minimum desired eden length based on the MMU target.
210 uint calculate_desired_eden_length_by_mmu() const;
211
212 // Calculate and return the desired eden length that can fit into the pause time goal.
213 // The parameters are: rs_length represents the prediction of how large the
214 // young RSet lengths will be, min_eden_length and max_eden_length are the bounds
215 // (inclusive) within eden can grow.
216 uint calculate_desired_eden_length_by_pause(double base_time_ms,
217 uint min_eden_length,
218 uint max_eden_length) const;
219
220 // Calculates the desired eden length before mixed gc so that after adding the
221 // minimum amount of old gen regions from the collection set, the eden fits into
222 // the pause time goal.
223 uint calculate_desired_eden_length_before_mixed(double survivor_base_time_ms,
224 uint min_eden_length,
225 uint max_eden_length) const;
226
227 // Calculate desired young length based on current situation without taking actually
228 // available free regions into account.
229 uint calculate_young_desired_length(size_t rs_length) const;
230 // Limit the given desired young length to available free regions.
231 uint calculate_young_target_length(uint desired_young_length) const;
232
233 void update_rs_length_prediction();
234 void update_rs_length_prediction(size_t prediction);
235
236 size_t predict_bytes_to_copy(HeapRegion* hr) const;
237 double predict_survivor_regions_evac_time() const;
238
239 // Check whether a given young length (young_length) fits into the
240 // given target pause time and whether the prediction for the amount
241 // of objects to be copied for the given length will fit into the
242 // given free space (expressed by base_free_regions). It is used by
243 // calculate_young_list_target_length().
244 bool predict_will_fit(uint young_length, double base_time_ms,
245 uint base_free_regions, double target_pause_time_ms) const;
246
247 public:
248 size_t pending_cards_at_gc_start() const { return _pending_cards_at_gc_start; }
249
250 // Calculate the minimum number of old regions we'll add to the CSet
251 // during a mixed GC.
252 uint calc_min_old_cset_length() const;
253
254 // Calculate the maximum number of old regions we'll add to the CSet
255 // during a mixed GC.
256 uint calc_max_old_cset_length() const;
257
258 // Returns the given amount of reclaimable bytes (that represents
259 // the amount of reclaimable space still to be collected) as a
260 // percentage of the current heap capacity.
261 double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
262
263 jlong collection_pause_end_millis() { return _collection_pause_end_millis; }
264
265 private:
266 void clear_collection_set_candidates();
267 // Sets up marking if proper conditions are met.
268 void maybe_start_marking();
269
270 // The kind of STW pause.
271 enum PauseKind {
272 FullGC,
273 YoungOnlyGC,
274 MixedGC,
275 LastYoungGC,
276 InitialMarkGC,
277 Cleanup,
278 Remark
279 };
280
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 { return _phase_times; }
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 // Calculate and return the number of initial and optional old gen regions from
341 // the given collection set candidates and the remaining time.
342 void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
343 double time_remaining_ms,
344 uint& num_initial_regions,
345 uint& num_optional_regions);
346
347 // Calculate the number of optional regions from the given collection set candidates,
348 // the remaining time and the maximum number of these regions and return the number
349 // of actually selected regions in num_optional_regions.
350 void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
351 uint const max_optional_regions,
352 double time_remaining_ms,
353 uint& num_optional_regions);
354
355 private:
356 // Set the state to start a concurrent marking cycle and clear
357 // _initiate_conc_mark_if_possible because it has now been
358 // acted on.
359 void initiate_conc_mark();
360
361 public:
362 // This sets the initiate_conc_mark_if_possible() flag to start a
363 // new cycle, as long as we are not already in one. It's best if it
364 // is called during a safepoint when the test whether a cycle is in
365 // progress or not is stable.
366 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
367
368 // This is called at the very beginning of an evacuation pause (it
369 // has to be the first thing that the pause does). If
370 // initiate_conc_mark_if_possible() is true, and the concurrent
371 // marking thread has completed its work during the previous cycle,
372 // it will set in_initial_mark_gc() to so that the pause does
373 // the initial-mark work and start a marking cycle.
374 void decide_on_conc_mark_initiation();
375
376 size_t young_list_target_length() const { return _young_list_target_length; }
377
378 bool should_allocate_mutator_region() const;
379
380 bool can_expand_young_list() const;
381
382 uint young_list_max_length() const {
383 return _young_list_max_length;
384 }
385
386 bool use_adaptive_young_list_length() const;
387
388 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
389
390 private:
391 //
392 // Survivor regions policy.
393 //
394
395 // Current tenuring threshold, set to 0 if the collector reaches the
396 // maximum amount of survivors regions.
397 uint _tenuring_threshold;
398
399 // The limit on the number of regions allocated for survivors.
400 uint _max_survivor_regions;
401
402 AgeTable _survivors_age_table;
403
404 size_t desired_survivor_size(uint max_regions) const;
405
406 // Fraction used when predicting how many optional regions to include in
407 // the CSet. This fraction of the available time is used for optional regions,
408 // the rest is used to add old regions to the normal CSet.
409 double optional_prediction_fraction() { return 0.2; }
410
411 public:
412 // Fraction used when evacuating the optional regions. This fraction of the
413 // remaining time is used to choose what regions to include in the evacuation.
414 double optional_evacuation_fraction() { return 0.75; }
415
416 uint tenuring_threshold() const { return _tenuring_threshold; }
417
418 uint max_survivor_regions() {
419 return _max_survivor_regions;
420 }
421
422 void note_start_adding_survivor_regions() {
423 _survivor_surv_rate_group->start_adding_regions();
424 }
425
426 void note_stop_adding_survivor_regions() {
427 _survivor_surv_rate_group->stop_adding_regions();
428 }
429
430 void record_age_table(AgeTable* age_table) {
431 _survivors_age_table.merge(age_table);
432 }
433
434 void print_age_table();
435
436 void update_max_gc_locker_expansion();
437
438 void update_survivors_policy();
439
440 virtual bool force_upgrade_to_full() {
441 return false;
442 }
443 };
444
445 #endif // SHARE_GC_G1_G1POLICY_HPP