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. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 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 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_GC_G1_G1POLICY_HPP 26 #define SHARE_GC_G1_G1POLICY_HPP 27 28 #include "gc/g1/g1CollectorPolicy.hpp" 29 #include "gc/g1/g1CollectorState.hpp" 30 #include "gc/g1/g1GCPhaseTimes.hpp" 31 #include "gc/g1/g1InCSetState.hpp" 32 #include "gc/g1/g1InitialMarkToMixedTimeTracker.hpp" 33 #include "gc/g1/g1MMUTracker.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 uint _young_list_fixed_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 // SurvRateGroups below must be initialized after the predictor because they 87 // indirectly use it through this object passed to their constructor. 88 SurvRateGroup* _short_lived_surv_rate_group; 89 SurvRateGroup* _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 _max_rs_lengths; 101 102 size_t _rs_lengths_prediction; 103 104 size_t _pending_cards; 105 106 // The amount of allocated bytes in old gen during the last mutator and the following 107 // young GC phase. 108 size_t _bytes_allocated_in_old_since_last_gc; 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 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 // Add the given number of bytes to the total number of allocated bytes in the old gen. 122 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; } 123 124 void set_region_eden(HeapRegion* hr) { 125 hr->set_eden(); 126 hr->install_surv_rate_group(_short_lived_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_max_rs_lengths(size_t rs_lengths) { 135 _max_rs_lengths = rs_lengths; 136 } 137 138 double predict_base_elapsed_time_ms(size_t pending_cards) const; 139 double predict_base_elapsed_time_ms(size_t pending_cards, 140 size_t scanned_cards) const; 141 size_t predict_bytes_to_copy(HeapRegion* hr) const; 142 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const; 143 144 double predict_survivor_regions_evac_time() const; 145 146 void cset_regions_freed() { 147 bool update = should_update_surv_rate_group_predictors(); 148 149 _short_lived_surv_rate_group->all_surviving_words_recorded(predictor(), update); 150 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update); 151 } 152 153 G1MMUTracker* mmu_tracker() { 154 return _mmu_tracker; 155 } 156 157 const G1MMUTracker* mmu_tracker() const { 158 return _mmu_tracker; 159 } 160 161 double max_pause_time_ms() const { 162 return _mmu_tracker->max_gc_time() * 1000.0; 163 } 164 165 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const; 166 167 double predict_yg_surv_rate(int age) const; 168 169 double accum_yg_surv_rate_pred(int age) const; 170 171 private: 172 G1CollectionSet* _collection_set; 173 double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const; 174 double other_time_ms(double pause_time_ms) const; 175 176 double young_other_time_ms() const; 177 double non_young_other_time_ms() const; 178 double constant_other_time_ms(double pause_time_ms) const; 179 180 G1CollectionSetChooser* cset_chooser() const; 181 182 // The number of bytes copied during the GC. 183 size_t _bytes_copied_during_gc; 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 list maximum and target lengths. Returns the 196 // unbounded young list target length. 197 uint update_young_list_max_and_target_length(); 198 uint update_young_list_max_and_target_length(size_t rs_lengths); 199 200 // Update the young list target length either by setting it to the 201 // desired fixed value or by calculating it using G1's pause 202 // prediction model. If no rs_lengths parameter is passed, predict 203 // the RS lengths using the prediction model, otherwise use the 204 // given rs_lengths as the prediction. 205 // Returns the unbounded young list target length. 206 uint update_young_list_target_length(size_t rs_lengths); 207 208 // Calculate and return the minimum desired young list target 209 // length. This is the minimum desired young list length according 210 // to the user's inputs. 211 uint calculate_young_list_desired_min_length(uint base_min_length) const; 212 213 // Calculate and return the maximum desired young list target 214 // length. This is the maximum desired young list length according 215 // to the user's inputs. 216 uint calculate_young_list_desired_max_length() const; 217 218 // Calculate and return the maximum young list target length that 219 // can fit into the pause time goal. The parameters are: rs_lengths 220 // represent the prediction of how large the young RSet lengths will 221 // be, base_min_length is the already existing number of regions in 222 // the young list, min_length and max_length are the desired min and 223 // max young list length according to the user's inputs. 224 uint calculate_young_list_target_length(size_t rs_lengths, 225 uint base_min_length, 226 uint desired_min_length, 227 uint desired_max_length) const; 228 229 // Result of the bounded_young_list_target_length() method, containing both the 230 // bounded as well as the unbounded young list target lengths in this order. 231 typedef Pair<uint, uint, StackObj> YoungTargetLengths; 232 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const; 233 234 void update_rs_lengths_prediction(); 235 void update_rs_lengths_prediction(size_t prediction); 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() const { return _pending_cards; } 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 jlong collection_pause_end_millis() { return _collection_pause_end_millis; } 262 263 private: 264 void clear_collection_set_candidates(); 265 // Sets up marking if proper conditions are met. 266 void maybe_start_marking(); 267 268 // The kind of STW pause. 269 enum PauseKind { 270 FullGC, 271 YoungOnlyGC, 272 MixedGC, 273 LastYoungGC, 274 InitialMarkGC, 275 Cleanup, 276 Remark 277 }; 278 279 // Calculate PauseKind from internal state. 280 PauseKind young_gc_pause_kind() const; 281 // Record the given STW pause with the given start and end times (in s). 282 void record_pause(PauseKind kind, double start, double end); 283 // Indicate that we aborted marking before doing any mixed GCs. 284 void abort_time_to_mixed_tracking(); 285 public: 286 287 G1Policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer); 288 289 virtual ~G1Policy(); 290 291 static G1Policy* create_policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer_stw); 292 293 G1CollectorState* collector_state() const; 294 295 G1GCPhaseTimes* phase_times() const { return _phase_times; } 296 297 // Check the current value of the young list RSet lengths and 298 // compare it against the last prediction. If the current value is 299 // higher, recalculate the young list target length prediction. 300 void revise_young_list_target_length_if_necessary(size_t rs_lengths); 301 302 // This should be called after the heap is resized. 303 void record_new_heap_size(uint new_number_of_regions); 304 305 virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set); 306 307 void note_gc_start(); 308 309 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0); 310 311 bool about_to_start_mixed_phase() const; 312 313 // Record the start and end of an evacuation pause. 314 void record_collection_pause_start(double start_time_sec); 315 virtual void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc); 316 317 // Record the start and end of a full collection. 318 void record_full_collection_start(); 319 virtual void record_full_collection_end(); 320 321 // Must currently be called while the world is stopped. 322 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms); 323 324 // Record start and end of remark. 325 void record_concurrent_mark_remark_start(); 326 void record_concurrent_mark_remark_end(); 327 328 // Record start, end, and completion of cleanup. 329 void record_concurrent_mark_cleanup_start(); 330 void record_concurrent_mark_cleanup_end(); 331 332 void print_phases(); 333 334 // Record how much space we copied during a GC. This is typically 335 // called when a GC alloc region is being retired. 336 void record_bytes_copied_during_gc(size_t bytes) { 337 _bytes_copied_during_gc += bytes; 338 } 339 340 // The amount of space we copied during a GC. 341 size_t bytes_copied_during_gc() const { 342 return _bytes_copied_during_gc; 343 } 344 345 bool next_gc_should_be_mixed(const char* true_action_str, 346 const char* false_action_str) const; 347 348 // Select and return the number of initial and optional old gen regions from 349 // the given collection set candidates and the remaining time. Num_expensive_regions 350 // returns the number of regions taken within the initial region count because of 351 // the minimum old gen region requirement. 352 void select_old_collection_set_regions(G1CollectionSetCandidates* candidates, 353 double time_remaining_ms, 354 uint& num_expensive_regions, 355 uint& num_initial_regions, 356 uint& num_optional_regions); 357 358 // Select the number of optional regions from the given collection set candidates, 359 // the remaining time and the maximum number of these regions and return in 360 // num_optional_regions. 361 void select_optional_collection_set_regions(G1CollectionSetCandidates* candidates, 362 uint const max_optional_regions, 363 double time_remaining_ms, 364 uint& num_optional_regions); 365 366 private: 367 // Set the state to start a concurrent marking cycle and clear 368 // _initiate_conc_mark_if_possible because it has now been 369 // acted on. 370 void initiate_conc_mark(); 371 372 public: 373 // This sets the initiate_conc_mark_if_possible() flag to start a 374 // new cycle, as long as we are not already in one. It's best if it 375 // is called during a safepoint when the test whether a cycle is in 376 // progress or not is stable. 377 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause); 378 379 // This is called at the very beginning of an evacuation pause (it 380 // has to be the first thing that the pause does). If 381 // initiate_conc_mark_if_possible() is true, and the concurrent 382 // marking thread has completed its work during the previous cycle, 383 // it will set in_initial_mark_gc() to so that the pause does 384 // the initial-mark work and start a marking cycle. 385 void decide_on_conc_mark_initiation(); 386 387 void finished_recalculating_age_indexes(bool is_survivors) { 388 if (is_survivors) { 389 _survivor_surv_rate_group->finished_recalculating_age_indexes(); 390 } else { 391 _short_lived_surv_rate_group->finished_recalculating_age_indexes(); 392 } 393 } 394 395 size_t young_list_target_length() const { return _young_list_target_length; } 396 397 bool should_allocate_mutator_region() const; 398 399 bool can_expand_young_list() const; 400 401 uint young_list_max_length() const { 402 return _young_list_max_length; 403 } 404 405 bool adaptive_young_list_length() const; 406 407 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors); 408 409 private: 410 // 411 // Survivor regions policy. 412 // 413 414 // Current tenuring threshold, set to 0 if the collector reaches the 415 // maximum amount of survivors regions. 416 uint _tenuring_threshold; 417 418 // The limit on the number of regions allocated for survivors. 419 uint _max_survivor_regions; 420 421 AgeTable _survivors_age_table; 422 423 size_t desired_survivor_size(uint max_regions) const; 424 425 // Fraction used when predicting how many optional regions to include in 426 // the CSet. This fraction of the available time is used for optional regions, 427 // the rest is used to add old regions to the normal CSet. 428 double optional_prediction_fraction() { return 0.2; } 429 430 public: 431 // Fraction used when evacuating the optional regions. This fraction of the 432 // remaining time is used to choose what regions to include in the evacuation. 433 double optional_evacuation_fraction() { return 0.75; } 434 435 uint tenuring_threshold() const { return _tenuring_threshold; } 436 437 uint max_survivor_regions() { 438 return _max_survivor_regions; 439 } 440 441 void note_start_adding_survivor_regions() { 442 _survivor_surv_rate_group->start_adding_regions(); 443 } 444 445 void note_stop_adding_survivor_regions() { 446 _survivor_surv_rate_group->stop_adding_regions(); 447 } 448 449 void record_age_table(AgeTable* age_table) { 450 _survivors_age_table.merge(age_table); 451 } 452 453 void print_age_table(); 454 455 void update_max_gc_locker_expansion(); 456 457 void update_survivors_policy(); 458 459 virtual bool force_upgrade_to_full() { 460 return false; 461 } 462 }; 463 464 #endif // SHARE_GC_G1_G1POLICY_HPP