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/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/g1RemSetTrackingPolicy.hpp" 34 #include "gc/g1/g1Predictions.hpp" 35 #include "gc/g1/g1YoungGenSizer.hpp" 36 #include "gc/shared/gcCause.hpp" 37 #include "utilities/pair.hpp" 38 39 // A G1Policy makes policy decisions that determine the 40 // characteristics of the collector. Examples include: 41 // * choice of collection set. 42 // * when to collect. 43 44 class HeapRegion; 45 class G1CollectionSet; 46 class G1CollectionSetCandidates; 47 class G1CollectionSetChooser; 48 class G1IHOPControl; 49 class G1Analytics; 50 class G1SurvivorRegions; 51 class G1YoungGenSizer; 52 class GCPolicyCounters; 53 class STWGCTimer; 54 55 class G1Policy: public CHeapObj<mtGC> { 56 private: 57 58 static G1IHOPControl* create_ihop_control(const G1Predictions* predictor); 59 // Update the IHOP control with necessary statistics. 60 void update_ihop_prediction(double mutator_time_s, 61 size_t mutator_alloc_bytes, 62 size_t young_gen_size, 63 bool this_gc_was_young_only); 64 void report_ihop_statistics(); 65 66 G1Predictions _predictor; 67 G1Analytics* _analytics; 68 G1RemSetTrackingPolicy _remset_tracker; 69 G1MMUTracker* _mmu_tracker; 70 G1IHOPControl* _ihop_control; 71 72 GCPolicyCounters* _policy_counters; 73 74 double _full_collection_start_sec; 75 76 jlong _collection_pause_end_millis; 77 78 uint _young_list_target_length; 79 uint _young_list_fixed_length; 80 81 // The max number of regions we can extend the eden by while the GC 82 // locker is active. This should be >= _young_list_target_length; 83 uint _young_list_max_length; 84 85 // SurvRateGroups below must be initialized after the predictor because they 86 // indirectly use it through this object passed to their constructor. 87 SurvRateGroup* _short_lived_surv_rate_group; 88 SurvRateGroup* _survivor_surv_rate_group; 89 90 double _reserve_factor; 91 // This will be set when the heap is expanded 92 // for the first time during initialization. 93 uint _reserve_regions; 94 95 G1YoungGenSizer* _young_gen_sizer; 96 97 uint _free_regions_at_end_of_collection; 98 99 size_t _max_rs_length; 100 101 size_t _rs_length_prediction; 102 103 size_t _pending_cards; 104 105 // The amount of allocated bytes in old gen during the last mutator and the following 106 // young GC phase. 107 size_t _bytes_allocated_in_old_since_last_gc; 108 109 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed; 110 111 bool should_update_surv_rate_group_predictors() { 112 return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress(); 113 } 114 115 double log_buffer_processing_time() const; 116 public: 117 const G1Predictions& predictor() const { return _predictor; } 118 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); } 119 120 G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; } 121 122 // Add the given number of bytes to the total number of allocated bytes in the old gen. 123 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; } 124 125 void set_region_eden(HeapRegion* hr) { 126 hr->set_eden(); 127 hr->install_surv_rate_group(_short_lived_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_max_rs_length(size_t rs_length) { 136 _max_rs_length = rs_length; 137 } 138 139 double predict_base_elapsed_time_ms(size_t pending_cards) const; 140 double predict_base_elapsed_time_ms(size_t pending_cards, 141 size_t scanned_cards) const; 142 size_t predict_bytes_to_copy(HeapRegion* hr) const; 143 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const; 144 145 double predict_survivor_regions_evac_time() const; 146 147 void cset_regions_freed() { 148 bool update = should_update_surv_rate_group_predictors(); 149 150 _short_lived_surv_rate_group->all_surviving_words_recorded(predictor(), update); 151 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update); 152 } 153 154 G1MMUTracker* mmu_tracker() { 155 return _mmu_tracker; 156 } 157 158 const G1MMUTracker* mmu_tracker() const { 159 return _mmu_tracker; 160 } 161 162 double max_pause_time_ms() const { 163 return _mmu_tracker->max_gc_time() * 1000.0; 164 } 165 166 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const; 167 168 double predict_yg_surv_rate(int age) const; 169 170 double accum_yg_surv_rate_pred(int age) const; 171 172 private: 173 G1CollectionSet* _collection_set; 174 double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const; 175 double other_time_ms(double pause_time_ms) const; 176 177 double young_other_time_ms() const; 178 double non_young_other_time_ms() const; 179 double constant_other_time_ms(double pause_time_ms) const; 180 181 G1CollectionSetChooser* cset_chooser() const; 182 183 // The number of bytes copied during the GC. 184 size_t _bytes_copied_during_gc; 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 list maximum and target lengths. Returns the 197 // unbounded young list 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_list_max_and_target_length(); 201 uint update_young_list_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_list_target_length(size_t rs_length); 208 209 // Calculate and return the minimum desired young list target 210 // length. This is the minimum desired young list length according 211 // to the user's inputs. 212 uint calculate_young_list_desired_min_length(uint base_min_length) const; 213 214 // Calculate and return the maximum desired young list target 215 // length. This is the maximum desired young list length according 216 // to the user's inputs. 217 uint calculate_young_list_desired_max_length() const; 218 219 // Calculate and return the maximum young list target length that 220 // can fit into the pause time goal. The parameters are: rs_length 221 // represent the prediction of how large the young RSet lengths will 222 // be, base_min_length is the already existing number of regions in 223 // the young list, min_length and max_length are the desired min and 224 // max young list length according to the user's inputs. 225 uint calculate_young_list_target_length(size_t rs_length, 226 uint base_min_length, 227 uint desired_min_length, 228 uint desired_max_length) const; 229 230 // Result of the bounded_young_list_target_length() method, containing both the 231 // bounded as well as the unbounded young list target lengths in this order. 232 typedef Pair<uint, uint, StackObj> YoungTargetLengths; 233 YoungTargetLengths young_list_target_lengths(size_t rs_length) const; 234 235 void update_rs_length_prediction(); 236 void update_rs_length_prediction(size_t prediction); 237 238 // Check whether a given young length (young_length) fits into the 239 // given target pause time and whether the prediction for the amount 240 // of objects to be copied for the given length will fit into the 241 // given free space (expressed by base_free_regions). It is used by 242 // calculate_young_list_target_length(). 243 bool predict_will_fit(uint young_length, double base_time_ms, 244 uint base_free_regions, double target_pause_time_ms) const; 245 246 public: 247 size_t pending_cards() const { return _pending_cards; } 248 249 // Calculate the minimum number of old regions we'll add to the CSet 250 // during a mixed GC. 251 uint calc_min_old_cset_length() const; 252 253 // Calculate the maximum number of old regions we'll add to the CSet 254 // during a mixed GC. 255 uint calc_max_old_cset_length() const; 256 257 // Returns the given amount of reclaimable bytes (that represents 258 // the amount of reclaimable space still to be collected) as a 259 // percentage of the current heap capacity. 260 double reclaimable_bytes_percent(size_t reclaimable_bytes) const; 261 262 jlong collection_pause_end_millis() { return _collection_pause_end_millis; } 263 264 private: 265 void clear_collection_set_candidates(); 266 // Sets up marking if proper conditions are met. 267 void maybe_start_marking(); 268 269 // The kind of STW pause. 270 enum PauseKind { 271 FullGC, 272 YoungOnlyGC, 273 MixedGC, 274 LastYoungGC, 275 InitialMarkGC, 276 Cleanup, 277 Remark 278 }; 279 280 // Calculate PauseKind from internal state. 281 PauseKind young_gc_pause_kind() const; 282 // Record the given STW pause with the given start and end times (in s). 283 void record_pause(PauseKind kind, double start, double end); 284 // Indicate that we aborted marking before doing any mixed GCs. 285 void abort_time_to_mixed_tracking(); 286 public: 287 288 G1Policy(STWGCTimer* gc_timer); 289 290 virtual ~G1Policy(); 291 292 static G1Policy* create_policy(STWGCTimer* gc_timer_stw); 293 294 G1CollectorState* collector_state() const; 295 296 G1GCPhaseTimes* phase_times() const { return _phase_times; } 297 298 // Check the current value of the young list RSet length and 299 // compare it against the last prediction. If the current value is 300 // higher, recalculate the young list target length prediction. 301 void revise_young_list_target_length_if_necessary(size_t rs_length); 302 303 // This should be called after the heap is resized. 304 void record_new_heap_size(uint new_number_of_regions); 305 306 virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set); 307 308 void note_gc_start(); 309 310 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0); 311 312 bool about_to_start_mixed_phase() const; 313 314 // Record the start and end of an evacuation pause. 315 void record_collection_pause_start(double start_time_sec); 316 virtual void record_collection_pause_end(double pause_time_ms, size_t heap_used_bytes_before_gc); 317 318 // Record the start and end of a full collection. 319 void record_full_collection_start(); 320 virtual void record_full_collection_end(); 321 322 // Must currently be called while the world is stopped. 323 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms); 324 325 // Record start and end of remark. 326 void record_concurrent_mark_remark_start(); 327 void record_concurrent_mark_remark_end(); 328 329 // Record start, end, and completion of cleanup. 330 void record_concurrent_mark_cleanup_start(); 331 void record_concurrent_mark_cleanup_end(); 332 333 void print_phases(); 334 335 // Record how much space we copied during a GC. This is typically 336 // called when a GC alloc region is being retired. 337 void record_bytes_copied_during_gc(size_t bytes) { 338 _bytes_copied_during_gc += bytes; 339 } 340 341 // The amount of space we copied during a GC. 342 size_t bytes_copied_during_gc() const { 343 return _bytes_copied_during_gc; 344 } 345 346 bool next_gc_should_be_mixed(const char* true_action_str, 347 const char* false_action_str) const; 348 349 // Calculate and return the number of initial and optional old gen regions from 350 // the given collection set candidates and the remaining time. 351 void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates, 352 double time_remaining_ms, 353 uint& num_initial_regions, 354 uint& num_optional_regions); 355 356 // Calculate the number of optional regions from the given collection set candidates, 357 // the remaining time and the maximum number of these regions and return the number 358 // of actually selected regions in num_optional_regions. 359 void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates, 360 uint const max_optional_regions, 361 double time_remaining_ms, 362 uint& num_optional_regions); 363 364 private: 365 // Set the state to start a concurrent marking cycle and clear 366 // _initiate_conc_mark_if_possible because it has now been 367 // acted on. 368 void initiate_conc_mark(); 369 370 public: 371 // This sets the initiate_conc_mark_if_possible() flag to start a 372 // new cycle, as long as we are not already in one. It's best if it 373 // is called during a safepoint when the test whether a cycle is in 374 // progress or not is stable. 375 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause); 376 377 // This is called at the very beginning of an evacuation pause (it 378 // has to be the first thing that the pause does). If 379 // initiate_conc_mark_if_possible() is true, and the concurrent 380 // marking thread has completed its work during the previous cycle, 381 // it will set in_initial_mark_gc() to so that the pause does 382 // the initial-mark work and start a marking cycle. 383 void decide_on_conc_mark_initiation(); 384 385 void finished_recalculating_age_indexes(bool is_survivors) { 386 if (is_survivors) { 387 _survivor_surv_rate_group->finished_recalculating_age_indexes(); 388 } else { 389 _short_lived_surv_rate_group->finished_recalculating_age_indexes(); 390 } 391 } 392 393 size_t young_list_target_length() const { return _young_list_target_length; } 394 395 bool should_allocate_mutator_region() const; 396 397 bool can_expand_young_list() const; 398 399 uint young_list_max_length() const { 400 return _young_list_max_length; 401 } 402 403 bool use_adaptive_young_list_length() const; 404 405 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors); 406 407 private: 408 // 409 // Survivor regions policy. 410 // 411 412 // Current tenuring threshold, set to 0 if the collector reaches the 413 // maximum amount of survivors regions. 414 uint _tenuring_threshold; 415 416 // The limit on the number of regions allocated for survivors. 417 uint _max_survivor_regions; 418 419 AgeTable _survivors_age_table; 420 421 size_t desired_survivor_size(uint max_regions) const; 422 423 // Fraction used when predicting how many optional regions to include in 424 // the CSet. This fraction of the available time is used for optional regions, 425 // the rest is used to add old regions to the normal CSet. 426 double optional_prediction_fraction() { return 0.2; } 427 428 public: 429 // Fraction used when evacuating the optional regions. This fraction of the 430 // remaining time is used to choose what regions to include in the evacuation. 431 double optional_evacuation_fraction() { return 0.75; } 432 433 uint tenuring_threshold() const { return _tenuring_threshold; } 434 435 uint max_survivor_regions() { 436 return _max_survivor_regions; 437 } 438 439 void note_start_adding_survivor_regions() { 440 _survivor_surv_rate_group->start_adding_regions(); 441 } 442 443 void note_stop_adding_survivor_regions() { 444 _survivor_surv_rate_group->stop_adding_regions(); 445 } 446 447 void record_age_table(AgeTable* age_table) { 448 _survivors_age_table.merge(age_table); 449 } 450 451 void print_age_table(); 452 453 void update_max_gc_locker_expansion(); 454 455 void update_survivors_policy(); 456 457 virtual bool force_upgrade_to_full() { 458 return false; 459 } 460 }; 461 462 #endif // SHARE_GC_G1_G1POLICY_HPP