1 /* 2 * Copyright (c) 2001, 2013, 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_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP 27 28 #include "gc_implementation/g1/collectionSetChooser.hpp" 29 #include "gc_implementation/g1/g1MMUTracker.hpp" 30 #include "memory/collectorPolicy.hpp" 31 32 // A G1CollectorPolicy makes policy decisions that determine the 33 // characteristics of the collector. Examples include: 34 // * choice of collection set. 35 // * when to collect. 36 37 class HeapRegion; 38 class CollectionSetChooser; 39 class G1GCPhaseTimes; 40 41 // TraceGen0Time collects data on _both_ young and mixed evacuation pauses 42 // (the latter may contain non-young regions - i.e. regions that are 43 // technically in Gen1) while TraceGen1Time collects data about full GCs. 44 class TraceGen0TimeData : public CHeapObj<mtGC> { 45 private: 46 unsigned _young_pause_num; 47 unsigned _mixed_pause_num; 48 49 NumberSeq _all_stop_world_times_ms; 50 NumberSeq _all_yield_times_ms; 51 52 NumberSeq _total; 53 NumberSeq _other; 54 NumberSeq _root_region_scan_wait; 55 NumberSeq _parallel; 56 NumberSeq _ext_root_scan; 57 NumberSeq _satb_filtering; 58 NumberSeq _update_rs; 59 NumberSeq _scan_rs; 60 NumberSeq _obj_copy; 61 NumberSeq _termination; 62 NumberSeq _parallel_other; 63 NumberSeq _clear_ct; 64 65 void print_summary(const char* str, const NumberSeq* seq) const; 66 void print_summary_sd(const char* str, const NumberSeq* seq) const; 67 68 public: 69 TraceGen0TimeData() : _young_pause_num(0), _mixed_pause_num(0) {}; 70 void record_start_collection(double time_to_stop_the_world_ms); 71 void record_yield_time(double yield_time_ms); 72 void record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times); 73 void increment_young_collection_count(); 74 void increment_mixed_collection_count(); 75 void print() const; 76 }; 77 78 class TraceGen1TimeData : public CHeapObj<mtGC> { 79 private: 80 NumberSeq _all_full_gc_times; 81 82 public: 83 void record_full_collection(double full_gc_time_ms); 84 void print() const; 85 }; 86 87 // There are three command line options related to the young gen size: 88 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is 89 // just a short form for NewSize==MaxNewSize). G1 will use its internal 90 // heuristics to calculate the actual young gen size, so these options 91 // basically only limit the range within which G1 can pick a young gen 92 // size. Also, these are general options taking byte sizes. G1 will 93 // internally work with a number of regions instead. So, some rounding 94 // will occur. 95 // 96 // If nothing related to the the young gen size is set on the command 97 // line we should allow the young gen to be between G1NewSizePercent 98 // and G1MaxNewSizePercent of the heap size. This means that every time 99 // the heap size changes, the limits for the young gen size will be 100 // recalculated. 101 // 102 // If only -XX:NewSize is set we should use the specified value as the 103 // minimum size for young gen. Still using G1MaxNewSizePercent of the 104 // heap as maximum. 105 // 106 // If only -XX:MaxNewSize is set we should use the specified value as the 107 // maximum size for young gen. Still using G1NewSizePercent of the heap 108 // as minimum. 109 // 110 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values. 111 // No updates when the heap size changes. There is a special case when 112 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a 113 // different heuristic for calculating the collection set when we do mixed 114 // collection. 115 // 116 // If only -XX:NewRatio is set we should use the specified ratio of the heap 117 // as both min and max. This will be interpreted as "fixed" just like the 118 // NewSize==MaxNewSize case above. But we will update the min and max 119 // everytime the heap size changes. 120 // 121 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is 122 // combined with either NewSize or MaxNewSize. (A warning message is printed.) 123 class G1YoungGenSizer : public CHeapObj<mtGC> { 124 private: 125 enum SizerKind { 126 SizerDefaults, 127 SizerNewSizeOnly, 128 SizerMaxNewSizeOnly, 129 SizerMaxAndNewSize, 130 SizerNewRatio 131 }; 132 SizerKind _sizer_kind; 133 uint _min_desired_young_length; 134 uint _max_desired_young_length; 135 bool _adaptive_size; 136 uint calculate_default_min_length(uint new_number_of_heap_regions); 137 uint calculate_default_max_length(uint new_number_of_heap_regions); 138 139 public: 140 G1YoungGenSizer(); 141 void heap_size_changed(uint new_number_of_heap_regions); 142 uint min_desired_young_length() { 143 return _min_desired_young_length; 144 } 145 uint max_desired_young_length() { 146 return _max_desired_young_length; 147 } 148 bool adaptive_young_list_length() { 149 return _adaptive_size; 150 } 151 }; 152 153 class G1CollectorPolicy: public CollectorPolicy { 154 private: 155 // either equal to the number of parallel threads, if ParallelGCThreads 156 // has been set, or 1 otherwise 157 int _parallel_gc_threads; 158 159 // The number of GC threads currently active. 160 uintx _no_of_gc_threads; 161 162 enum SomePrivateConstants { 163 NumPrevPausesForHeuristics = 10 164 }; 165 166 G1MMUTracker* _mmu_tracker; 167 168 void initialize_flags(); 169 170 void initialize_all() { 171 initialize_flags(); 172 initialize_size_info(); 173 } 174 175 CollectionSetChooser* _collectionSetChooser; 176 177 double _full_collection_start_sec; 178 uint _cur_collection_pause_used_regions_at_start; 179 180 // These exclude marking times. 181 TruncatedSeq* _recent_gc_times_ms; 182 183 TruncatedSeq* _concurrent_mark_remark_times_ms; 184 TruncatedSeq* _concurrent_mark_cleanup_times_ms; 185 186 TraceGen0TimeData _trace_gen0_time_data; 187 TraceGen1TimeData _trace_gen1_time_data; 188 189 double _stop_world_start; 190 191 // indicates whether we are in young or mixed GC mode 192 bool _gcs_are_young; 193 194 uint _young_list_target_length; 195 uint _young_list_fixed_length; 196 197 // The max number of regions we can extend the eden by while the GC 198 // locker is active. This should be >= _young_list_target_length; 199 uint _young_list_max_length; 200 201 bool _last_gc_was_young; 202 203 bool _during_marking; 204 bool _in_marking_window; 205 bool _in_marking_window_im; 206 207 SurvRateGroup* _short_lived_surv_rate_group; 208 SurvRateGroup* _survivor_surv_rate_group; 209 // add here any more surv rate groups 210 211 double _gc_overhead_perc; 212 213 double _reserve_factor; 214 uint _reserve_regions; 215 216 bool during_marking() { 217 return _during_marking; 218 } 219 220 enum PredictionConstants { 221 TruncatedSeqLength = 10 222 }; 223 224 TruncatedSeq* _alloc_rate_ms_seq; 225 double _prev_collection_pause_end_ms; 226 227 TruncatedSeq* _rs_length_diff_seq; 228 TruncatedSeq* _cost_per_card_ms_seq; 229 TruncatedSeq* _young_cards_per_entry_ratio_seq; 230 TruncatedSeq* _mixed_cards_per_entry_ratio_seq; 231 TruncatedSeq* _cost_per_entry_ms_seq; 232 TruncatedSeq* _mixed_cost_per_entry_ms_seq; 233 TruncatedSeq* _cost_per_byte_ms_seq; 234 TruncatedSeq* _constant_other_time_ms_seq; 235 TruncatedSeq* _young_other_cost_per_region_ms_seq; 236 TruncatedSeq* _non_young_other_cost_per_region_ms_seq; 237 238 TruncatedSeq* _pending_cards_seq; 239 TruncatedSeq* _rs_lengths_seq; 240 241 TruncatedSeq* _cost_per_byte_ms_during_cm_seq; 242 243 G1YoungGenSizer* _young_gen_sizer; 244 245 uint _eden_cset_region_length; 246 uint _survivor_cset_region_length; 247 uint _old_cset_region_length; 248 249 void init_cset_region_lengths(uint eden_cset_region_length, 250 uint survivor_cset_region_length); 251 252 uint eden_cset_region_length() { return _eden_cset_region_length; } 253 uint survivor_cset_region_length() { return _survivor_cset_region_length; } 254 uint old_cset_region_length() { return _old_cset_region_length; } 255 256 uint _free_regions_at_end_of_collection; 257 258 size_t _recorded_rs_lengths; 259 size_t _max_rs_lengths; 260 double _sigma; 261 262 size_t _rs_lengths_prediction; 263 264 double sigma() { return _sigma; } 265 266 // A function that prevents us putting too much stock in small sample 267 // sets. Returns a number between 2.0 and 1.0, depending on the number 268 // of samples. 5 or more samples yields one; fewer scales linearly from 269 // 2.0 at 1 sample to 1.0 at 5. 270 double confidence_factor(int samples) { 271 if (samples > 4) return 1.0; 272 else return 1.0 + sigma() * ((double)(5 - samples))/2.0; 273 } 274 275 double get_new_neg_prediction(TruncatedSeq* seq) { 276 return seq->davg() - sigma() * seq->dsd(); 277 } 278 279 #ifndef PRODUCT 280 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group); 281 #endif // PRODUCT 282 283 void adjust_concurrent_refinement(double update_rs_time, 284 double update_rs_processed_buffers, 285 double goal_ms); 286 287 uintx no_of_gc_threads() { return _no_of_gc_threads; } 288 void set_no_of_gc_threads(uintx v) { _no_of_gc_threads = v; } 289 290 double _pause_time_target_ms; 291 292 size_t _pending_cards; 293 294 public: 295 // Accessors 296 297 void set_region_eden(HeapRegion* hr, int young_index_in_cset) { 298 hr->set_young(); 299 hr->install_surv_rate_group(_short_lived_surv_rate_group); 300 hr->set_young_index_in_cset(young_index_in_cset); 301 } 302 303 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) { 304 assert(hr->is_young() && hr->is_survivor(), "pre-condition"); 305 hr->install_surv_rate_group(_survivor_surv_rate_group); 306 hr->set_young_index_in_cset(young_index_in_cset); 307 } 308 309 #ifndef PRODUCT 310 bool verify_young_ages(); 311 #endif // PRODUCT 312 313 double get_new_prediction(TruncatedSeq* seq) { 314 return MAX2(seq->davg() + sigma() * seq->dsd(), 315 seq->davg() * confidence_factor(seq->num())); 316 } 317 318 void record_max_rs_lengths(size_t rs_lengths) { 319 _max_rs_lengths = rs_lengths; 320 } 321 322 size_t predict_rs_length_diff() { 323 return (size_t) get_new_prediction(_rs_length_diff_seq); 324 } 325 326 double predict_alloc_rate_ms() { 327 return get_new_prediction(_alloc_rate_ms_seq); 328 } 329 330 double predict_cost_per_card_ms() { 331 return get_new_prediction(_cost_per_card_ms_seq); 332 } 333 334 double predict_rs_update_time_ms(size_t pending_cards) { 335 return (double) pending_cards * predict_cost_per_card_ms(); 336 } 337 338 double predict_young_cards_per_entry_ratio() { 339 return get_new_prediction(_young_cards_per_entry_ratio_seq); 340 } 341 342 double predict_mixed_cards_per_entry_ratio() { 343 if (_mixed_cards_per_entry_ratio_seq->num() < 2) { 344 return predict_young_cards_per_entry_ratio(); 345 } else { 346 return get_new_prediction(_mixed_cards_per_entry_ratio_seq); 347 } 348 } 349 350 size_t predict_young_card_num(size_t rs_length) { 351 return (size_t) ((double) rs_length * 352 predict_young_cards_per_entry_ratio()); 353 } 354 355 size_t predict_non_young_card_num(size_t rs_length) { 356 return (size_t) ((double) rs_length * 357 predict_mixed_cards_per_entry_ratio()); 358 } 359 360 double predict_rs_scan_time_ms(size_t card_num) { 361 if (gcs_are_young()) { 362 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq); 363 } else { 364 return predict_mixed_rs_scan_time_ms(card_num); 365 } 366 } 367 368 double predict_mixed_rs_scan_time_ms(size_t card_num) { 369 if (_mixed_cost_per_entry_ms_seq->num() < 3) { 370 return (double) card_num * get_new_prediction(_cost_per_entry_ms_seq); 371 } else { 372 return (double) (card_num * 373 get_new_prediction(_mixed_cost_per_entry_ms_seq)); 374 } 375 } 376 377 double predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) { 378 if (_cost_per_byte_ms_during_cm_seq->num() < 3) { 379 return (1.1 * (double) bytes_to_copy) * 380 get_new_prediction(_cost_per_byte_ms_seq); 381 } else { 382 return (double) bytes_to_copy * 383 get_new_prediction(_cost_per_byte_ms_during_cm_seq); 384 } 385 } 386 387 double predict_object_copy_time_ms(size_t bytes_to_copy) { 388 if (_in_marking_window && !_in_marking_window_im) { 389 return predict_object_copy_time_ms_during_cm(bytes_to_copy); 390 } else { 391 return (double) bytes_to_copy * 392 get_new_prediction(_cost_per_byte_ms_seq); 393 } 394 } 395 396 double predict_constant_other_time_ms() { 397 return get_new_prediction(_constant_other_time_ms_seq); 398 } 399 400 double predict_young_other_time_ms(size_t young_num) { 401 return (double) young_num * 402 get_new_prediction(_young_other_cost_per_region_ms_seq); 403 } 404 405 double predict_non_young_other_time_ms(size_t non_young_num) { 406 return (double) non_young_num * 407 get_new_prediction(_non_young_other_cost_per_region_ms_seq); 408 } 409 410 double predict_base_elapsed_time_ms(size_t pending_cards); 411 double predict_base_elapsed_time_ms(size_t pending_cards, 412 size_t scanned_cards); 413 size_t predict_bytes_to_copy(HeapRegion* hr); 414 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc); 415 416 void set_recorded_rs_lengths(size_t rs_lengths); 417 418 uint cset_region_length() { return young_cset_region_length() + 419 old_cset_region_length(); } 420 uint young_cset_region_length() { return eden_cset_region_length() + 421 survivor_cset_region_length(); } 422 423 double predict_survivor_regions_evac_time(); 424 425 void cset_regions_freed() { 426 bool propagate = _last_gc_was_young && !_in_marking_window; 427 _short_lived_surv_rate_group->all_surviving_words_recorded(propagate); 428 _survivor_surv_rate_group->all_surviving_words_recorded(propagate); 429 // also call it on any more surv rate groups 430 } 431 432 G1MMUTracker* mmu_tracker() { 433 return _mmu_tracker; 434 } 435 436 double max_pause_time_ms() { 437 return _mmu_tracker->max_gc_time() * 1000.0; 438 } 439 440 double predict_remark_time_ms() { 441 return get_new_prediction(_concurrent_mark_remark_times_ms); 442 } 443 444 double predict_cleanup_time_ms() { 445 return get_new_prediction(_concurrent_mark_cleanup_times_ms); 446 } 447 448 // Returns an estimate of the survival rate of the region at yg-age 449 // "yg_age". 450 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) { 451 TruncatedSeq* seq = surv_rate_group->get_seq(age); 452 if (seq->num() == 0) 453 gclog_or_tty->print("BARF! age is %d", age); 454 guarantee( seq->num() > 0, "invariant" ); 455 double pred = get_new_prediction(seq); 456 if (pred > 1.0) 457 pred = 1.0; 458 return pred; 459 } 460 461 double predict_yg_surv_rate(int age) { 462 return predict_yg_surv_rate(age, _short_lived_surv_rate_group); 463 } 464 465 double accum_yg_surv_rate_pred(int age) { 466 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 467 } 468 469 private: 470 // Statistics kept per GC stoppage, pause or full. 471 TruncatedSeq* _recent_prev_end_times_for_all_gcs_sec; 472 473 // Add a new GC of the given duration and end time to the record. 474 void update_recent_gc_times(double end_time_sec, double elapsed_ms); 475 476 // The head of the list (via "next_in_collection_set()") representing the 477 // current collection set. Set from the incrementally built collection 478 // set at the start of the pause. 479 HeapRegion* _collection_set; 480 481 // The number of bytes in the collection set before the pause. Set from 482 // the incrementally built collection set at the start of an evacuation 483 // pause, and incremented in finalize_cset() when adding old regions 484 // (if any) to the collection set. 485 size_t _collection_set_bytes_used_before; 486 487 // The number of bytes copied during the GC. 488 size_t _bytes_copied_during_gc; 489 490 // The associated information that is maintained while the incremental 491 // collection set is being built with young regions. Used to populate 492 // the recorded info for the evacuation pause. 493 494 enum CSetBuildType { 495 Active, // We are actively building the collection set 496 Inactive // We are not actively building the collection set 497 }; 498 499 CSetBuildType _inc_cset_build_state; 500 501 // The head of the incrementally built collection set. 502 HeapRegion* _inc_cset_head; 503 504 // The tail of the incrementally built collection set. 505 HeapRegion* _inc_cset_tail; 506 507 // The number of bytes in the incrementally built collection set. 508 // Used to set _collection_set_bytes_used_before at the start of 509 // an evacuation pause. 510 size_t _inc_cset_bytes_used_before; 511 512 // Used to record the highest end of heap region in collection set 513 HeapWord* _inc_cset_max_finger; 514 515 // The RSet lengths recorded for regions in the CSet. It is updated 516 // by the thread that adds a new region to the CSet. We assume that 517 // only one thread can be allocating a new CSet region (currently, 518 // it does so after taking the Heap_lock) hence no need to 519 // synchronize updates to this field. 520 size_t _inc_cset_recorded_rs_lengths; 521 522 // A concurrent refinement thread periodcially samples the young 523 // region RSets and needs to update _inc_cset_recorded_rs_lengths as 524 // the RSets grow. Instead of having to syncronize updates to that 525 // field we accumulate them in this field and add it to 526 // _inc_cset_recorded_rs_lengths_diffs at the start of a GC. 527 ssize_t _inc_cset_recorded_rs_lengths_diffs; 528 529 // The predicted elapsed time it will take to collect the regions in 530 // the CSet. This is updated by the thread that adds a new region to 531 // the CSet. See the comment for _inc_cset_recorded_rs_lengths about 532 // MT-safety assumptions. 533 double _inc_cset_predicted_elapsed_time_ms; 534 535 // See the comment for _inc_cset_recorded_rs_lengths_diffs. 536 double _inc_cset_predicted_elapsed_time_ms_diffs; 537 538 // Stash a pointer to the g1 heap. 539 G1CollectedHeap* _g1; 540 541 G1GCPhaseTimes* _phase_times; 542 543 // The ratio of gc time to elapsed time, computed over recent pauses. 544 double _recent_avg_pause_time_ratio; 545 546 double recent_avg_pause_time_ratio() { 547 return _recent_avg_pause_time_ratio; 548 } 549 550 // At the end of a pause we check the heap occupancy and we decide 551 // whether we will start a marking cycle during the next pause. If 552 // we decide that we want to do that, we will set this parameter to 553 // true. So, this parameter will stay true between the end of a 554 // pause and the beginning of a subsequent pause (not necessarily 555 // the next one, see the comments on the next field) when we decide 556 // that we will indeed start a marking cycle and do the initial-mark 557 // work. 558 volatile bool _initiate_conc_mark_if_possible; 559 560 // If initiate_conc_mark_if_possible() is set at the beginning of a 561 // pause, it is a suggestion that the pause should start a marking 562 // cycle by doing the initial-mark work. However, it is possible 563 // that the concurrent marking thread is still finishing up the 564 // previous marking cycle (e.g., clearing the next marking 565 // bitmap). If that is the case we cannot start a new cycle and 566 // we'll have to wait for the concurrent marking thread to finish 567 // what it is doing. In this case we will postpone the marking cycle 568 // initiation decision for the next pause. When we eventually decide 569 // to start a cycle, we will set _during_initial_mark_pause which 570 // will stay true until the end of the initial-mark pause and it's 571 // the condition that indicates that a pause is doing the 572 // initial-mark work. 573 volatile bool _during_initial_mark_pause; 574 575 bool _last_young_gc; 576 577 // This set of variables tracks the collector efficiency, in order to 578 // determine whether we should initiate a new marking. 579 double _cur_mark_stop_world_time_ms; 580 double _mark_remark_start_sec; 581 double _mark_cleanup_start_sec; 582 583 // Update the young list target length either by setting it to the 584 // desired fixed value or by calculating it using G1's pause 585 // prediction model. If no rs_lengths parameter is passed, predict 586 // the RS lengths using the prediction model, otherwise use the 587 // given rs_lengths as the prediction. 588 void update_young_list_target_length(size_t rs_lengths = (size_t) -1); 589 590 // Calculate and return the minimum desired young list target 591 // length. This is the minimum desired young list length according 592 // to the user's inputs. 593 uint calculate_young_list_desired_min_length(uint base_min_length); 594 595 // Calculate and return the maximum desired young list target 596 // length. This is the maximum desired young list length according 597 // to the user's inputs. 598 uint calculate_young_list_desired_max_length(); 599 600 // Calculate and return the maximum young list target length that 601 // can fit into the pause time goal. The parameters are: rs_lengths 602 // represent the prediction of how large the young RSet lengths will 603 // be, base_min_length is the alreay existing number of regions in 604 // the young list, min_length and max_length are the desired min and 605 // max young list length according to the user's inputs. 606 uint calculate_young_list_target_length(size_t rs_lengths, 607 uint base_min_length, 608 uint desired_min_length, 609 uint desired_max_length); 610 611 // Check whether a given young length (young_length) fits into the 612 // given target pause time and whether the prediction for the amount 613 // of objects to be copied for the given length will fit into the 614 // given free space (expressed by base_free_regions). It is used by 615 // calculate_young_list_target_length(). 616 bool predict_will_fit(uint young_length, double base_time_ms, 617 uint base_free_regions, double target_pause_time_ms); 618 619 // Calculate the minimum number of old regions we'll add to the CSet 620 // during a mixed GC. 621 uint calc_min_old_cset_length(); 622 623 // Calculate the maximum number of old regions we'll add to the CSet 624 // during a mixed GC. 625 uint calc_max_old_cset_length(); 626 627 // Returns the given amount of uncollected reclaimable space 628 // as a percentage of the current heap capacity. 629 double reclaimable_bytes_perc(size_t reclaimable_bytes); 630 631 public: 632 633 G1CollectorPolicy(); 634 635 virtual G1CollectorPolicy* as_g1_policy() { return this; } 636 637 virtual CollectorPolicy::Name kind() { 638 return CollectorPolicy::G1CollectorPolicyKind; 639 } 640 641 G1GCPhaseTimes* phase_times() const { return _phase_times; } 642 643 // Check the current value of the young list RSet lengths and 644 // compare it against the last prediction. If the current value is 645 // higher, recalculate the young list target length prediction. 646 void revise_young_list_target_length_if_necessary(); 647 648 // This should be called after the heap is resized. 649 void record_new_heap_size(uint new_number_of_regions); 650 651 void init(); 652 653 // Create jstat counters for the policy. 654 virtual void initialize_gc_policy_counters(); 655 656 virtual HeapWord* mem_allocate_work(size_t size, 657 bool is_tlab, 658 bool* gc_overhead_limit_was_exceeded); 659 660 // This method controls how a collector handles one or more 661 // of its generations being fully allocated. 662 virtual HeapWord* satisfy_failed_allocation(size_t size, 663 bool is_tlab); 664 665 BarrierSet::Name barrier_set_name() { return BarrierSet::G1SATBCTLogging; } 666 667 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0); 668 669 // Record the start and end of an evacuation pause. 670 void record_collection_pause_start(double start_time_sec); 671 void record_collection_pause_end(double pause_time_ms, EvacuationInfo& evacuation_info); 672 673 // Record the start and end of a full collection. 674 void record_full_collection_start(); 675 void record_full_collection_end(); 676 677 // Must currently be called while the world is stopped. 678 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms); 679 680 // Record start and end of remark. 681 void record_concurrent_mark_remark_start(); 682 void record_concurrent_mark_remark_end(); 683 684 // Record start, end, and completion of cleanup. 685 void record_concurrent_mark_cleanup_start(); 686 void record_concurrent_mark_cleanup_end(int no_of_gc_threads); 687 void record_concurrent_mark_cleanup_completed(); 688 689 // Records the information about the heap size for reporting in 690 // print_detailed_heap_transition 691 void record_heap_size_info_at_start(bool full); 692 693 // Print heap sizing transition (with less and more detail). 694 void print_heap_transition(); 695 void print_detailed_heap_transition(bool full = false); 696 697 void record_stop_world_start(); 698 void record_concurrent_pause(); 699 700 // Record how much space we copied during a GC. This is typically 701 // called when a GC alloc region is being retired. 702 void record_bytes_copied_during_gc(size_t bytes) { 703 _bytes_copied_during_gc += bytes; 704 } 705 706 // The amount of space we copied during a GC. 707 size_t bytes_copied_during_gc() { 708 return _bytes_copied_during_gc; 709 } 710 711 // Determine whether there are candidate regions so that the 712 // next GC should be mixed. The two action strings are used 713 // in the ergo output when the method returns true or false. 714 bool next_gc_should_be_mixed(const char* true_action_str, 715 const char* false_action_str); 716 717 // Choose a new collection set. Marks the chosen regions as being 718 // "in_collection_set", and links them together. The head and number of 719 // the collection set are available via access methods. 720 void finalize_cset(double target_pause_time_ms, EvacuationInfo& evacuation_info); 721 722 // The head of the list (via "next_in_collection_set()") representing the 723 // current collection set. 724 HeapRegion* collection_set() { return _collection_set; } 725 726 void clear_collection_set() { _collection_set = NULL; } 727 728 // Add old region "hr" to the CSet. 729 void add_old_region_to_cset(HeapRegion* hr); 730 731 // Incremental CSet Support 732 733 // The head of the incrementally built collection set. 734 HeapRegion* inc_cset_head() { return _inc_cset_head; } 735 736 // The tail of the incrementally built collection set. 737 HeapRegion* inc_set_tail() { return _inc_cset_tail; } 738 739 // Initialize incremental collection set info. 740 void start_incremental_cset_building(); 741 742 // Perform any final calculations on the incremental CSet fields 743 // before we can use them. 744 void finalize_incremental_cset_building(); 745 746 void clear_incremental_cset() { 747 _inc_cset_head = NULL; 748 _inc_cset_tail = NULL; 749 } 750 751 // Stop adding regions to the incremental collection set 752 void stop_incremental_cset_building() { _inc_cset_build_state = Inactive; } 753 754 // Add information about hr to the aggregated information for the 755 // incrementally built collection set. 756 void add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length); 757 758 // Update information about hr in the aggregated information for 759 // the incrementally built collection set. 760 void update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length); 761 762 private: 763 // Update the incremental cset information when adding a region 764 // (should not be called directly). 765 void add_region_to_incremental_cset_common(HeapRegion* hr); 766 767 public: 768 // Add hr to the LHS of the incremental collection set. 769 void add_region_to_incremental_cset_lhs(HeapRegion* hr); 770 771 // Add hr to the RHS of the incremental collection set. 772 void add_region_to_incremental_cset_rhs(HeapRegion* hr); 773 774 #ifndef PRODUCT 775 void print_collection_set(HeapRegion* list_head, outputStream* st); 776 #endif // !PRODUCT 777 778 bool initiate_conc_mark_if_possible() { return _initiate_conc_mark_if_possible; } 779 void set_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = true; } 780 void clear_initiate_conc_mark_if_possible() { _initiate_conc_mark_if_possible = false; } 781 782 bool during_initial_mark_pause() { return _during_initial_mark_pause; } 783 void set_during_initial_mark_pause() { _during_initial_mark_pause = true; } 784 void clear_during_initial_mark_pause(){ _during_initial_mark_pause = false; } 785 786 // This sets the initiate_conc_mark_if_possible() flag to start a 787 // new cycle, as long as we are not already in one. It's best if it 788 // is called during a safepoint when the test whether a cycle is in 789 // progress or not is stable. 790 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause); 791 792 // This is called at the very beginning of an evacuation pause (it 793 // has to be the first thing that the pause does). If 794 // initiate_conc_mark_if_possible() is true, and the concurrent 795 // marking thread has completed its work during the previous cycle, 796 // it will set during_initial_mark_pause() to so that the pause does 797 // the initial-mark work and start a marking cycle. 798 void decide_on_conc_mark_initiation(); 799 800 // If an expansion would be appropriate, because recent GC overhead had 801 // exceeded the desired limit, return an amount to expand by. 802 size_t expansion_amount(); 803 804 // Print tracing information. 805 void print_tracing_info() const; 806 807 // Print stats on young survival ratio 808 void print_yg_surv_rate_info() const; 809 810 void finished_recalculating_age_indexes(bool is_survivors) { 811 if (is_survivors) { 812 _survivor_surv_rate_group->finished_recalculating_age_indexes(); 813 } else { 814 _short_lived_surv_rate_group->finished_recalculating_age_indexes(); 815 } 816 // do that for any other surv rate groups 817 } 818 819 bool is_young_list_full() { 820 uint young_list_length = _g1->young_list()->length(); 821 uint young_list_target_length = _young_list_target_length; 822 return young_list_length >= young_list_target_length; 823 } 824 825 bool can_expand_young_list() { 826 uint young_list_length = _g1->young_list()->length(); 827 uint young_list_max_length = _young_list_max_length; 828 return young_list_length < young_list_max_length; 829 } 830 831 uint young_list_max_length() { 832 return _young_list_max_length; 833 } 834 835 bool gcs_are_young() { 836 return _gcs_are_young; 837 } 838 void set_gcs_are_young(bool gcs_are_young) { 839 _gcs_are_young = gcs_are_young; 840 } 841 842 bool adaptive_young_list_length() { 843 return _young_gen_sizer->adaptive_young_list_length(); 844 } 845 846 private: 847 // 848 // Survivor regions policy. 849 // 850 851 // Current tenuring threshold, set to 0 if the collector reaches the 852 // maximum amount of survivors regions. 853 uint _tenuring_threshold; 854 855 // The limit on the number of regions allocated for survivors. 856 uint _max_survivor_regions; 857 858 // For reporting purposes. 859 // The value of _heap_bytes_before_gc is also used to calculate 860 // the cost of copying. 861 862 size_t _eden_used_bytes_before_gc; // Eden occupancy before GC 863 size_t _survivor_used_bytes_before_gc; // Survivor occupancy before GC 864 size_t _heap_used_bytes_before_gc; // Heap occupancy before GC 865 size_t _metaspace_used_bytes_before_gc; // Metaspace occupancy before GC 866 867 size_t _eden_capacity_bytes_before_gc; // Eden capacity before GC 868 size_t _heap_capacity_bytes_before_gc; // Heap capacity before GC 869 870 // The amount of survivor regions after a collection. 871 uint _recorded_survivor_regions; 872 // List of survivor regions. 873 HeapRegion* _recorded_survivor_head; 874 HeapRegion* _recorded_survivor_tail; 875 876 ageTable _survivors_age_table; 877 878 public: 879 uint tenuring_threshold() const { return _tenuring_threshold; } 880 881 inline GCAllocPurpose 882 evacuation_destination(HeapRegion* src_region, uint age, size_t word_sz) { 883 if (age < _tenuring_threshold && src_region->is_young()) { 884 return GCAllocForSurvived; 885 } else { 886 return GCAllocForTenured; 887 } 888 } 889 890 inline bool track_object_age(GCAllocPurpose purpose) { 891 return purpose == GCAllocForSurvived; 892 } 893 894 static const uint REGIONS_UNLIMITED = (uint) -1; 895 896 uint max_regions(int purpose); 897 898 // The limit on regions for a particular purpose is reached. 899 void note_alloc_region_limit_reached(int purpose) { 900 if (purpose == GCAllocForSurvived) { 901 _tenuring_threshold = 0; 902 } 903 } 904 905 void note_start_adding_survivor_regions() { 906 _survivor_surv_rate_group->start_adding_regions(); 907 } 908 909 void note_stop_adding_survivor_regions() { 910 _survivor_surv_rate_group->stop_adding_regions(); 911 } 912 913 void record_survivor_regions(uint regions, 914 HeapRegion* head, 915 HeapRegion* tail) { 916 _recorded_survivor_regions = regions; 917 _recorded_survivor_head = head; 918 _recorded_survivor_tail = tail; 919 } 920 921 uint recorded_survivor_regions() { 922 return _recorded_survivor_regions; 923 } 924 925 void record_thread_age_table(ageTable* age_table) { 926 _survivors_age_table.merge_par(age_table); 927 } 928 929 void update_max_gc_locker_expansion(); 930 931 // Calculates survivor space parameters. 932 void update_survivors_policy(); 933 934 }; 935 936 // This should move to some place more general... 937 938 // If we have "n" measurements, and we've kept track of their "sum" and the 939 // "sum_of_squares" of the measurements, this returns the variance of the 940 // sequence. 941 inline double variance(int n, double sum_of_squares, double sum) { 942 double n_d = (double)n; 943 double avg = sum/n_d; 944 return (sum_of_squares - 2.0 * avg * sum + n_d * avg * avg) / n_d; 945 } 946 947 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTORPOLICY_HPP