1 /* 2 * Copyright (c) 2001, 2016, 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_VM_GC_G1_G1COLLECTORPOLICY_HPP 26 #define SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP 27 28 #include "gc/g1/g1CollectorState.hpp" 29 #include "gc/g1/g1GCPhaseTimes.hpp" 30 #include "gc/g1/g1InCSetState.hpp" 31 #include "gc/g1/g1InitialMarkToMixedTimeTracker.hpp" 32 #include "gc/g1/g1MMUTracker.hpp" 33 #include "gc/g1/g1Predictions.hpp" 34 #include "gc/shared/collectorPolicy.hpp" 35 #include "utilities/pair.hpp" 36 37 // A G1CollectorPolicy makes policy decisions that determine the 38 // characteristics of the collector. Examples include: 39 // * choice of collection set. 40 // * when to collect. 41 42 class HeapRegion; 43 class G1CollectionSet; 44 class CollectionSetChooser; 45 class G1IHOPControl; 46 class G1YoungGenSizer; 47 48 class G1CollectorPolicy: public CollectorPolicy { 49 private: 50 G1IHOPControl* _ihop_control; 51 52 G1IHOPControl* create_ihop_control() const; 53 // Update the IHOP control with necessary statistics. 54 void update_ihop_prediction(double mutator_time_s, 55 size_t mutator_alloc_bytes, 56 size_t young_gen_size); 57 void report_ihop_statistics(); 58 59 G1Predictions _predictor; 60 61 double get_new_prediction(TruncatedSeq const* seq) const; 62 size_t get_new_size_prediction(TruncatedSeq const* seq) const; 63 64 G1MMUTracker* _mmu_tracker; 65 66 void initialize_alignments(); 67 void initialize_flags(); 68 69 double _full_collection_start_sec; 70 71 // These exclude marking times. 72 TruncatedSeq* _recent_gc_times_ms; 73 74 TruncatedSeq* _concurrent_mark_remark_times_ms; 75 TruncatedSeq* _concurrent_mark_cleanup_times_ms; 76 77 // Ratio check data for determining if heap growth is necessary. 78 uint _ratio_over_threshold_count; 79 double _ratio_over_threshold_sum; 80 uint _pauses_since_start; 81 82 uint _young_list_target_length; 83 uint _young_list_fixed_length; 84 85 // The max number of regions we can extend the eden by while the GC 86 // locker is active. This should be >= _young_list_target_length; 87 uint _young_list_max_length; 88 89 SurvRateGroup* _short_lived_surv_rate_group; 90 SurvRateGroup* _survivor_surv_rate_group; 91 // add here any more surv rate groups 92 93 double _gc_overhead_perc; 94 95 double _reserve_factor; 96 uint _reserve_regions; 97 98 enum PredictionConstants { 99 TruncatedSeqLength = 10, 100 NumPrevPausesForHeuristics = 10, 101 // MinOverThresholdForGrowth must be less than NumPrevPausesForHeuristics, 102 // representing the minimum number of pause time ratios that exceed 103 // GCTimeRatio before a heap expansion will be triggered. 104 MinOverThresholdForGrowth = 4 105 }; 106 107 TruncatedSeq* _alloc_rate_ms_seq; 108 double _prev_collection_pause_end_ms; 109 110 TruncatedSeq* _rs_length_diff_seq; 111 TruncatedSeq* _cost_per_card_ms_seq; 112 TruncatedSeq* _cost_scan_hcc_seq; 113 TruncatedSeq* _young_cards_per_entry_ratio_seq; 114 TruncatedSeq* _mixed_cards_per_entry_ratio_seq; 115 TruncatedSeq* _cost_per_entry_ms_seq; 116 TruncatedSeq* _mixed_cost_per_entry_ms_seq; 117 TruncatedSeq* _cost_per_byte_ms_seq; 118 TruncatedSeq* _constant_other_time_ms_seq; 119 TruncatedSeq* _young_other_cost_per_region_ms_seq; 120 TruncatedSeq* _non_young_other_cost_per_region_ms_seq; 121 122 TruncatedSeq* _pending_cards_seq; 123 TruncatedSeq* _rs_lengths_seq; 124 125 TruncatedSeq* _cost_per_byte_ms_during_cm_seq; 126 127 G1YoungGenSizer* _young_gen_sizer; 128 129 uint _free_regions_at_end_of_collection; 130 131 size_t _max_rs_lengths; 132 133 size_t _rs_lengths_prediction; 134 135 #ifndef PRODUCT 136 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group); 137 #endif // PRODUCT 138 139 void adjust_concurrent_refinement(double update_rs_time, 140 double update_rs_processed_buffers, 141 double goal_ms); 142 143 double _pause_time_target_ms; 144 145 size_t _pending_cards; 146 147 // The amount of allocated bytes in old gen during the last mutator and the following 148 // young GC phase. 149 size_t _bytes_allocated_in_old_since_last_gc; 150 151 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed; 152 public: 153 const G1Predictions& predictor() const { return _predictor; } 154 155 // Add the given number of bytes to the total number of allocated bytes in the old gen. 156 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; } 157 158 // Accessors 159 160 void set_region_eden(HeapRegion* hr, int young_index_in_cset) { 161 hr->set_eden(); 162 hr->install_surv_rate_group(_short_lived_surv_rate_group); 163 hr->set_young_index_in_cset(young_index_in_cset); 164 } 165 166 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) { 167 assert(hr->is_survivor(), "pre-condition"); 168 hr->install_surv_rate_group(_survivor_surv_rate_group); 169 hr->set_young_index_in_cset(young_index_in_cset); 170 } 171 172 #ifndef PRODUCT 173 bool verify_young_ages(); 174 #endif // PRODUCT 175 176 void record_max_rs_lengths(size_t rs_lengths) { 177 _max_rs_lengths = rs_lengths; 178 } 179 180 size_t predict_rs_lengths() const; 181 182 size_t predict_rs_length_diff() const; 183 184 double predict_alloc_rate_ms() const; 185 186 double predict_cost_per_card_ms() const; 187 188 double predict_scan_hcc_ms() const; 189 190 double predict_rs_update_time_ms(size_t pending_cards) const; 191 192 double predict_young_cards_per_entry_ratio() const; 193 194 double predict_mixed_cards_per_entry_ratio() const; 195 196 size_t predict_young_card_num(size_t rs_length) const; 197 198 size_t predict_non_young_card_num(size_t rs_length) const; 199 200 double predict_rs_scan_time_ms(size_t card_num) const; 201 202 double predict_mixed_rs_scan_time_ms(size_t card_num) const; 203 204 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const; 205 206 double predict_object_copy_time_ms(size_t bytes_to_copy) const; 207 208 double predict_constant_other_time_ms() const; 209 210 double predict_young_other_time_ms(size_t young_num) const; 211 212 double predict_non_young_other_time_ms(size_t non_young_num) const; 213 214 double predict_base_elapsed_time_ms(size_t pending_cards) const; 215 double predict_base_elapsed_time_ms(size_t pending_cards, 216 size_t scanned_cards) const; 217 size_t predict_bytes_to_copy(HeapRegion* hr) const; 218 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const; 219 220 double predict_survivor_regions_evac_time() const; 221 222 bool should_update_surv_rate_group_predictors() { 223 return collector_state()->last_gc_was_young() && !collector_state()->in_marking_window(); 224 } 225 226 void cset_regions_freed() { 227 bool update = should_update_surv_rate_group_predictors(); 228 229 _short_lived_surv_rate_group->all_surviving_words_recorded(update); 230 _survivor_surv_rate_group->all_surviving_words_recorded(update); 231 } 232 233 G1MMUTracker* mmu_tracker() { 234 return _mmu_tracker; 235 } 236 237 const G1MMUTracker* mmu_tracker() const { 238 return _mmu_tracker; 239 } 240 241 double max_pause_time_ms() const { 242 return _mmu_tracker->max_gc_time() * 1000.0; 243 } 244 245 double predict_remark_time_ms() const; 246 247 double predict_cleanup_time_ms() const; 248 249 // Returns an estimate of the survival rate of the region at yg-age 250 // "yg_age". 251 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const; 252 253 double predict_yg_surv_rate(int age) const; 254 255 double accum_yg_surv_rate_pred(int age) const; 256 257 protected: 258 G1CollectionSet* _collection_set; 259 virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const; 260 virtual double other_time_ms(double pause_time_ms) const; 261 262 double young_other_time_ms() const; 263 double non_young_other_time_ms() const; 264 double constant_other_time_ms(double pause_time_ms) const; 265 266 CollectionSetChooser* cset_chooser() const; 267 private: 268 // Statistics kept per GC stoppage, pause or full. 269 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec; 270 271 // Add a new GC of the given duration and end time to the record. 272 void update_recent_gc_times(double end_time_sec, double elapsed_ms); 273 274 // The number of bytes copied during the GC. 275 size_t _bytes_copied_during_gc; 276 277 // Stash a pointer to the g1 heap. 278 G1CollectedHeap* _g1; 279 280 G1GCPhaseTimes* _phase_times; 281 282 // The ratio of gc time to elapsed time, computed over recent pauses, 283 // and the ratio for just the last pause. 284 double _recent_avg_pause_time_ratio; 285 double _last_pause_time_ratio; 286 287 double recent_avg_pause_time_ratio() const { 288 return _recent_avg_pause_time_ratio; 289 } 290 291 // This set of variables tracks the collector efficiency, in order to 292 // determine whether we should initiate a new marking. 293 double _mark_remark_start_sec; 294 double _mark_cleanup_start_sec; 295 296 // Updates the internal young list maximum and target lengths. Returns the 297 // unbounded young list target length. 298 uint update_young_list_max_and_target_length(); 299 uint update_young_list_max_and_target_length(size_t rs_lengths); 300 301 // Update the young list target length either by setting it to the 302 // desired fixed value or by calculating it using G1's pause 303 // prediction model. If no rs_lengths parameter is passed, predict 304 // the RS lengths using the prediction model, otherwise use the 305 // given rs_lengths as the prediction. 306 // Returns the unbounded young list target length. 307 uint update_young_list_target_length(size_t rs_lengths); 308 309 // Calculate and return the minimum desired young list target 310 // length. This is the minimum desired young list length according 311 // to the user's inputs. 312 uint calculate_young_list_desired_min_length(uint base_min_length) const; 313 314 // Calculate and return the maximum desired young list target 315 // length. This is the maximum desired young list length according 316 // to the user's inputs. 317 uint calculate_young_list_desired_max_length() const; 318 319 // Calculate and return the maximum young list target length that 320 // can fit into the pause time goal. The parameters are: rs_lengths 321 // represent the prediction of how large the young RSet lengths will 322 // be, base_min_length is the already existing number of regions in 323 // the young list, min_length and max_length are the desired min and 324 // max young list length according to the user's inputs. 325 uint calculate_young_list_target_length(size_t rs_lengths, 326 uint base_min_length, 327 uint desired_min_length, 328 uint desired_max_length) const; 329 330 // Result of the bounded_young_list_target_length() method, containing both the 331 // bounded as well as the unbounded young list target lengths in this order. 332 typedef Pair<uint, uint, StackObj> YoungTargetLengths; 333 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const; 334 335 void update_rs_lengths_prediction(); 336 void update_rs_lengths_prediction(size_t prediction); 337 338 // Calculate and return chunk size (in number of regions) for parallel 339 // concurrent mark cleanup. 340 uint calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const; 341 342 // Check whether a given young length (young_length) fits into the 343 // given target pause time and whether the prediction for the amount 344 // of objects to be copied for the given length will fit into the 345 // given free space (expressed by base_free_regions). It is used by 346 // calculate_young_list_target_length(). 347 bool predict_will_fit(uint young_length, double base_time_ms, 348 uint base_free_regions, double target_pause_time_ms) const; 349 350 public: 351 size_t pending_cards() const { return _pending_cards; } 352 353 // Calculate the minimum number of old regions we'll add to the CSet 354 // during a mixed GC. 355 uint calc_min_old_cset_length() const; 356 357 // Calculate the maximum number of old regions we'll add to the CSet 358 // during a mixed GC. 359 uint calc_max_old_cset_length() const; 360 361 // Returns the given amount of uncollected reclaimable space 362 // as a percentage of the current heap capacity. 363 double reclaimable_bytes_perc(size_t reclaimable_bytes) const; 364 365 private: 366 // Sets up marking if proper conditions are met. 367 void maybe_start_marking(); 368 369 // The kind of STW pause. 370 enum PauseKind { 371 FullGC, 372 YoungOnlyGC, 373 MixedGC, 374 LastYoungGC, 375 InitialMarkGC, 376 Cleanup, 377 Remark 378 }; 379 380 // Calculate PauseKind from internal state. 381 PauseKind young_gc_pause_kind() const; 382 // Record the given STW pause with the given start and end times (in s). 383 void record_pause(PauseKind kind, double start, double end); 384 // Indicate that we aborted marking before doing any mixed GCs. 385 void abort_time_to_mixed_tracking(); 386 public: 387 388 G1CollectorPolicy(); 389 390 virtual ~G1CollectorPolicy(); 391 392 virtual G1CollectorPolicy* as_g1_policy() { return this; } 393 394 G1CollectorState* collector_state() const; 395 396 G1GCPhaseTimes* phase_times() const { return _phase_times; } 397 398 // Check the current value of the young list RSet lengths and 399 // compare it against the last prediction. If the current value is 400 // higher, recalculate the young list target length prediction. 401 void revise_young_list_target_length_if_necessary(size_t rs_lengths); 402 403 // This should be called after the heap is resized. 404 void record_new_heap_size(uint new_number_of_regions); 405 406 void init(); 407 408 virtual void note_gc_start(uint num_active_workers); 409 410 // Create jstat counters for the policy. 411 virtual void initialize_gc_policy_counters(); 412 413 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0); 414 415 bool about_to_start_mixed_phase() const; 416 417 // Record the start and end of an evacuation pause. 418 void record_collection_pause_start(double start_time_sec); 419 void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc); 420 421 // Record the start and end of a full collection. 422 void record_full_collection_start(); 423 void record_full_collection_end(); 424 425 // Must currently be called while the world is stopped. 426 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms); 427 428 // Record start and end of remark. 429 void record_concurrent_mark_remark_start(); 430 void record_concurrent_mark_remark_end(); 431 432 // Record start, end, and completion of cleanup. 433 void record_concurrent_mark_cleanup_start(); 434 void record_concurrent_mark_cleanup_end(); 435 void record_concurrent_mark_cleanup_completed(); 436 437 virtual void print_phases(); 438 439 // Record how much space we copied during a GC. This is typically 440 // called when a GC alloc region is being retired. 441 void record_bytes_copied_during_gc(size_t bytes) { 442 _bytes_copied_during_gc += bytes; 443 } 444 445 // The amount of space we copied during a GC. 446 size_t bytes_copied_during_gc() const { 447 return _bytes_copied_during_gc; 448 } 449 450 // Determine whether there are candidate regions so that the 451 // next GC should be mixed. The two action strings are used 452 // in the ergo output when the method returns true or false. 453 bool next_gc_should_be_mixed(const char* true_action_str, 454 const char* false_action_str) const; 455 456 virtual void finalize_collection_set(double target_pause_time_ms); 457 private: 458 // Set the state to start a concurrent marking cycle and clear 459 // _initiate_conc_mark_if_possible because it has now been 460 // acted on. 461 void initiate_conc_mark(); 462 463 public: 464 // This sets the initiate_conc_mark_if_possible() flag to start a 465 // new cycle, as long as we are not already in one. It's best if it 466 // is called during a safepoint when the test whether a cycle is in 467 // progress or not is stable. 468 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause); 469 470 // This is called at the very beginning of an evacuation pause (it 471 // has to be the first thing that the pause does). If 472 // initiate_conc_mark_if_possible() is true, and the concurrent 473 // marking thread has completed its work during the previous cycle, 474 // it will set during_initial_mark_pause() to so that the pause does 475 // the initial-mark work and start a marking cycle. 476 void decide_on_conc_mark_initiation(); 477 478 // If an expansion would be appropriate, because recent GC overhead had 479 // exceeded the desired limit, return an amount to expand by. 480 virtual size_t expansion_amount(); 481 482 // Clear ratio tracking data used by expansion_amount(). 483 void clear_ratio_check_data(); 484 485 // Print stats on young survival ratio 486 void print_yg_surv_rate_info() const; 487 488 void finished_recalculating_age_indexes(bool is_survivors) { 489 if (is_survivors) { 490 _survivor_surv_rate_group->finished_recalculating_age_indexes(); 491 } else { 492 _short_lived_surv_rate_group->finished_recalculating_age_indexes(); 493 } 494 // do that for any other surv rate groups 495 } 496 497 size_t young_list_target_length() const { return _young_list_target_length; } 498 499 bool is_young_list_full() const; 500 501 bool can_expand_young_list() const; 502 503 uint young_list_max_length() const { 504 return _young_list_max_length; 505 } 506 507 bool adaptive_young_list_length() const; 508 509 virtual bool should_process_references() const { 510 return true; 511 } 512 513 private: 514 // 515 // Survivor regions policy. 516 // 517 518 // Current tenuring threshold, set to 0 if the collector reaches the 519 // maximum amount of survivors regions. 520 uint _tenuring_threshold; 521 522 // The limit on the number of regions allocated for survivors. 523 uint _max_survivor_regions; 524 525 AgeTable _survivors_age_table; 526 527 public: 528 uint tenuring_threshold() const { return _tenuring_threshold; } 529 530 uint max_survivor_regions() { 531 return _max_survivor_regions; 532 } 533 534 static const uint REGIONS_UNLIMITED = (uint) -1; 535 536 uint max_regions(InCSetState dest) const { 537 switch (dest.value()) { 538 case InCSetState::Young: 539 return _max_survivor_regions; 540 case InCSetState::Old: 541 return REGIONS_UNLIMITED; 542 default: 543 assert(false, "Unknown dest state: " CSETSTATE_FORMAT, dest.value()); 544 break; 545 } 546 // keep some compilers happy 547 return 0; 548 } 549 550 void note_start_adding_survivor_regions() { 551 _survivor_surv_rate_group->start_adding_regions(); 552 } 553 554 void note_stop_adding_survivor_regions() { 555 _survivor_surv_rate_group->stop_adding_regions(); 556 } 557 558 void record_age_table(AgeTable* age_table) { 559 _survivors_age_table.merge(age_table); 560 } 561 562 void update_max_gc_locker_expansion(); 563 564 // Calculates survivor space parameters. 565 void update_survivors_policy(); 566 567 virtual void post_heap_initialize(); 568 }; 569 570 #endif // SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP