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 G1Analytics; 47 class G1YoungGenSizer; 48 49 class G1CollectorPolicy: public CollectorPolicy { 50 private: 51 G1IHOPControl* _ihop_control; 52 53 G1IHOPControl* create_ihop_control() const; 54 // Update the IHOP control with necessary statistics. 55 void update_ihop_prediction(double mutator_time_s, 56 size_t mutator_alloc_bytes, 57 size_t young_gen_size); 58 void report_ihop_statistics(); 59 60 G1Predictions _predictor; 61 G1Analytics* _analytics; 62 G1MMUTracker* _mmu_tracker; 63 64 void initialize_alignments(); 65 void initialize_flags(); 66 67 double _full_collection_start_sec; 68 69 uint _young_list_target_length; 70 uint _young_list_fixed_length; 71 72 // The max number of regions we can extend the eden by while the GC 73 // locker is active. This should be >= _young_list_target_length; 74 uint _young_list_max_length; 75 76 SurvRateGroup* _short_lived_surv_rate_group; 77 SurvRateGroup* _survivor_surv_rate_group; 78 79 double _reserve_factor; 80 uint _reserve_regions; 81 82 G1YoungGenSizer* _young_gen_sizer; 83 84 uint _free_regions_at_end_of_collection; 85 86 size_t _max_rs_lengths; 87 88 size_t _rs_lengths_prediction; 89 90 #ifndef PRODUCT 91 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group); 92 #endif // PRODUCT 93 94 double _pause_time_target_ms; 95 96 size_t _pending_cards; 97 98 // The amount of allocated bytes in old gen during the last mutator and the following 99 // young GC phase. 100 size_t _bytes_allocated_in_old_since_last_gc; 101 102 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed; 103 public: 104 const G1Predictions& predictor() const { return _predictor; } 105 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); } 106 107 // Add the given number of bytes to the total number of allocated bytes in the old gen. 108 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; } 109 110 // Accessors 111 112 void set_region_eden(HeapRegion* hr, int young_index_in_cset) { 113 hr->set_eden(); 114 hr->install_surv_rate_group(_short_lived_surv_rate_group); 115 hr->set_young_index_in_cset(young_index_in_cset); 116 } 117 118 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) { 119 assert(hr->is_survivor(), "pre-condition"); 120 hr->install_surv_rate_group(_survivor_surv_rate_group); 121 hr->set_young_index_in_cset(young_index_in_cset); 122 } 123 124 #ifndef PRODUCT 125 bool verify_young_ages(); 126 #endif // PRODUCT 127 128 void record_max_rs_lengths(size_t rs_lengths) { 129 _max_rs_lengths = rs_lengths; 130 } 131 132 133 double predict_base_elapsed_time_ms(size_t pending_cards) const; 134 double predict_base_elapsed_time_ms(size_t pending_cards, 135 size_t scanned_cards) const; 136 size_t predict_bytes_to_copy(HeapRegion* hr) const; 137 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const; 138 139 double predict_survivor_regions_evac_time() const; 140 141 bool should_update_surv_rate_group_predictors() { 142 return collector_state()->last_gc_was_young() && !collector_state()->in_marking_window(); 143 } 144 145 void cset_regions_freed() { 146 bool update = should_update_surv_rate_group_predictors(); 147 148 _short_lived_surv_rate_group->all_surviving_words_recorded(update); 149 _survivor_surv_rate_group->all_surviving_words_recorded(update); 150 } 151 152 G1MMUTracker* mmu_tracker() { 153 return _mmu_tracker; 154 } 155 156 const G1MMUTracker* mmu_tracker() const { 157 return _mmu_tracker; 158 } 159 160 double max_pause_time_ms() const { 161 return _mmu_tracker->max_gc_time() * 1000.0; 162 } 163 164 // Returns an estimate of the survival rate of the region at yg-age 165 // "yg_age". 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 // When copying, we will likely need more bytes free than is live in the region. 173 // Add some safety margin to factor in the confidence of our guess, and the 174 // natural expected waste. 175 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 176 // of the calculation: the lower the confidence, the more headroom. 177 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 178 // copying due to anticipated waste in the PLABs. 179 double safety_factor() const { 180 return (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 181 } 182 183 // Returns an estimate of the available bytes at end of collection, adjusted by 184 // the safety factor. 185 size_t available_bytes_estimate(); 186 187 protected: 188 G1CollectionSet* _collection_set; 189 virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const; 190 virtual double other_time_ms(double pause_time_ms) const; 191 192 double young_other_time_ms() const; 193 double non_young_other_time_ms() const; 194 double constant_other_time_ms(double pause_time_ms) const; 195 196 CollectionSetChooser* cset_chooser() const; 197 private: 198 199 // The number of bytes copied during the GC. 200 size_t _bytes_copied_during_gc; 201 202 // Stash a pointer to the g1 heap. 203 G1CollectedHeap* _g1; 204 205 G1GCPhaseTimes* _phase_times; 206 207 // This set of variables tracks the collector efficiency, in order to 208 // determine whether we should initiate a new marking. 209 double _mark_remark_start_sec; 210 double _mark_cleanup_start_sec; 211 212 // Updates the internal young list maximum and target lengths. Returns the 213 // unbounded young list target length. 214 uint update_young_list_max_and_target_length(); 215 uint update_young_list_max_and_target_length(size_t rs_lengths); 216 217 // Update the young list target length either by setting it to the 218 // desired fixed value or by calculating it using G1's pause 219 // prediction model. If no rs_lengths parameter is passed, predict 220 // the RS lengths using the prediction model, otherwise use the 221 // given rs_lengths as the prediction. 222 // Returns the unbounded young list target length. 223 uint update_young_list_target_length(size_t rs_lengths); 224 225 // Calculate and return the minimum desired young list target 226 // length. This is the minimum desired young list length according 227 // to the user's inputs. 228 uint calculate_young_list_desired_min_length(uint base_min_length) const; 229 230 // Calculate and return the maximum desired young list target 231 // length. This is the maximum desired young list length according 232 // to the user's inputs. 233 uint calculate_young_list_desired_max_length() const; 234 235 // Calculate and return the maximum young list target length that 236 // can fit into the pause time goal. The parameters are: rs_lengths 237 // represent the prediction of how large the young RSet lengths will 238 // be, base_min_length is the already existing number of regions in 239 // the young list, min_length and max_length are the desired min and 240 // max young list length according to the user's inputs. 241 uint calculate_young_list_target_length(size_t rs_lengths, 242 uint base_min_length, 243 uint desired_min_length, 244 uint desired_max_length) const; 245 246 // Result of the bounded_young_list_target_length() method, containing both the 247 // bounded as well as the unbounded young list target lengths in this order. 248 typedef Pair<uint, uint, StackObj> YoungTargetLengths; 249 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const; 250 251 void update_rs_lengths_prediction(); 252 void update_rs_lengths_prediction(size_t prediction); 253 254 // Check whether a given young length (young_length) fits into the 255 // given target pause time and whether the prediction for the amount 256 // of objects to be copied for the given length will fit into the 257 // given free space (expressed by base_free_regions). It is used by 258 // calculate_young_list_target_length(). 259 bool predict_will_fit(uint young_length, double base_time_ms, 260 uint base_free_regions, double target_pause_time_ms) const; 261 262 public: 263 size_t pending_cards() const { return _pending_cards; } 264 265 // Calculate the minimum number of old regions we'll add to the CSet 266 // during a mixed GC. 267 uint calc_min_old_cset_length() const; 268 269 // Calculate the maximum number of old regions we'll add to the CSet 270 // during a mixed GC. 271 uint calc_max_old_cset_length() const; 272 273 // Returns the given amount of uncollected reclaimable space 274 // as a percentage of the current heap capacity. 275 double reclaimable_bytes_perc(size_t reclaimable_bytes) const; 276 277 private: 278 // Sets up marking if proper conditions are met. 279 void maybe_start_marking(); 280 281 // The kind of STW pause. 282 enum PauseKind { 283 FullGC, 284 YoungOnlyGC, 285 MixedGC, 286 LastYoungGC, 287 InitialMarkGC, 288 Cleanup, 289 Remark 290 }; 291 292 // Calculate PauseKind from internal state. 293 PauseKind young_gc_pause_kind() const; 294 // Record the given STW pause with the given start and end times (in s). 295 void record_pause(PauseKind kind, double start, double end); 296 // Indicate that we aborted marking before doing any mixed GCs. 297 void abort_time_to_mixed_tracking(); 298 public: 299 300 G1CollectorPolicy(); 301 302 virtual ~G1CollectorPolicy(); 303 304 virtual G1CollectorPolicy* as_g1_policy() { return this; } 305 306 G1CollectorState* collector_state() const; 307 308 G1GCPhaseTimes* phase_times() const { return _phase_times; } 309 310 // Check the current value of the young list RSet lengths and 311 // compare it against the last prediction. If the current value is 312 // higher, recalculate the young list target length prediction. 313 void revise_young_list_target_length_if_necessary(size_t rs_lengths); 314 315 // This should be called after the heap is resized. 316 void record_new_heap_size(uint new_number_of_regions); 317 318 void init(); 319 320 virtual void note_gc_start(uint num_active_workers); 321 322 // Create jstat counters for the policy. 323 virtual void initialize_gc_policy_counters(); 324 325 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0); 326 327 bool about_to_start_mixed_phase() const; 328 329 // Record the start and end of an evacuation pause. 330 void record_collection_pause_start(double start_time_sec); 331 void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc); 332 333 // Record the start and end of a full collection. 334 void record_full_collection_start(); 335 void record_full_collection_end(); 336 337 // Must currently be called while the world is stopped. 338 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms); 339 340 // Record start and end of remark. 341 void record_concurrent_mark_remark_start(); 342 void record_concurrent_mark_remark_end(); 343 344 // Record start, end, and completion of cleanup. 345 void record_concurrent_mark_cleanup_start(); 346 void record_concurrent_mark_cleanup_end(); 347 void record_concurrent_mark_cleanup_completed(); 348 349 virtual void print_phases(); 350 351 // Record how much space we copied during a GC. This is typically 352 // called when a GC alloc region is being retired. 353 void record_bytes_copied_during_gc(size_t bytes) { 354 _bytes_copied_during_gc += bytes; 355 } 356 357 // The amount of space we copied during a GC. 358 size_t bytes_copied_during_gc() const { 359 return _bytes_copied_during_gc; 360 } 361 362 // Determine whether there are candidate regions so that the 363 // next GC should be mixed. The two action strings are used 364 // in the ergo output when the method returns true or false. 365 bool next_gc_should_be_mixed(const char* true_action_str, 366 const char* false_action_str) const; 367 368 virtual void finalize_collection_set(double target_pause_time_ms); 369 private: 370 // Set the state to start a concurrent marking cycle and clear 371 // _initiate_conc_mark_if_possible because it has now been 372 // acted on. 373 void initiate_conc_mark(); 374 375 public: 376 // This sets the initiate_conc_mark_if_possible() flag to start a 377 // new cycle, as long as we are not already in one. It's best if it 378 // is called during a safepoint when the test whether a cycle is in 379 // progress or not is stable. 380 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause); 381 382 // This is called at the very beginning of an evacuation pause (it 383 // has to be the first thing that the pause does). If 384 // initiate_conc_mark_if_possible() is true, and the concurrent 385 // marking thread has completed its work during the previous cycle, 386 // it will set during_initial_mark_pause() to so that the pause does 387 // the initial-mark work and start a marking cycle. 388 void decide_on_conc_mark_initiation(); 389 390 // Print stats on young survival ratio 391 void print_yg_surv_rate_info() const; 392 393 void finished_recalculating_age_indexes(bool is_survivors) { 394 if (is_survivors) { 395 _survivor_surv_rate_group->finished_recalculating_age_indexes(); 396 } else { 397 _short_lived_surv_rate_group->finished_recalculating_age_indexes(); 398 } 399 } 400 401 size_t young_list_target_length() const { return _young_list_target_length; } 402 403 bool is_young_list_full() const; 404 405 bool can_expand_young_list() const; 406 407 uint young_list_max_length() const { 408 return _young_list_max_length; 409 } 410 411 bool adaptive_young_list_length() const; 412 413 virtual bool should_process_references() const { 414 return true; 415 } 416 417 private: 418 // 419 // Survivor regions policy. 420 // 421 422 // Current tenuring threshold, set to 0 if the collector reaches the 423 // maximum amount of survivors regions. 424 uint _tenuring_threshold; 425 426 // The limit on the number of regions allocated for survivors. 427 uint _max_survivor_regions; 428 429 AgeTable _survivors_age_table; 430 431 public: 432 uint tenuring_threshold() const { return _tenuring_threshold; } 433 434 uint max_survivor_regions() { 435 return _max_survivor_regions; 436 } 437 438 void note_start_adding_survivor_regions() { 439 _survivor_surv_rate_group->start_adding_regions(); 440 } 441 442 void note_stop_adding_survivor_regions() { 443 _survivor_surv_rate_group->stop_adding_regions(); 444 } 445 446 void record_age_table(AgeTable* age_table) { 447 _survivors_age_table.merge(age_table); 448 } 449 450 void update_max_gc_locker_expansion(); 451 452 // Calculates survivor space parameters. 453 void update_survivors_policy(); 454 455 virtual void post_heap_initialize(); 456 }; 457 458 #endif // SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP