1 /* 2 * Copyright (c) 2016, 2018, 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_G1POLICY_HPP 26 #define SHARE_VM_GC_G1_G1POLICY_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/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 CollectionSetChooser; 47 class G1IHOPControl; 48 class G1Analytics; 49 class G1SurvivorRegions; 50 class G1YoungGenSizer; 51 class GCPolicyCounters; 52 class STWGCTimer; 53 54 class G1Policy: public CHeapObj<mtGC> { 55 private: 56 57 static G1IHOPControl* create_ihop_control(const G1Predictions* predictor); 58 // Update the IHOP control with necessary statistics. 59 void update_ihop_prediction(double mutator_time_s, 60 size_t mutator_alloc_bytes, 61 size_t young_gen_size, 62 bool this_gc_was_young_only); 63 void report_ihop_statistics(); 64 65 G1Predictions _predictor; 66 G1Analytics* _analytics; 67 G1RemSetTrackingPolicy _remset_tracker; 68 G1MMUTracker* _mmu_tracker; 69 G1IHOPControl* _ihop_control; 70 71 GCPolicyCounters* _policy_counters; 72 73 double _full_collection_start_sec; 74 75 jlong _collection_pause_end_millis; 76 77 uint _young_list_target_length; 78 uint _young_list_fixed_length; 79 80 // The max number of regions we can extend the eden by while the GC 81 // locker is active. This should be >= _young_list_target_length; 82 uint _young_list_max_length; 83 84 // SurvRateGroups below must be initialized after the predictor because they 85 // indirectly use it through this object passed to their constructor. 86 SurvRateGroup* _short_lived_surv_rate_group; 87 SurvRateGroup* _survivor_surv_rate_group; 88 89 double _reserve_factor; 90 // This will be set when the heap is expanded 91 // for the first time during initialization. 92 uint _reserve_regions; 93 94 G1YoungGenSizer _young_gen_sizer; 95 96 uint _free_regions_at_end_of_collection; 97 98 size_t _max_rs_lengths; 99 100 size_t _rs_lengths_prediction; 101 102 size_t _pending_cards; 103 104 // The amount of allocated bytes in old gen during the last mutator and the following 105 // young GC phase. 106 size_t _bytes_allocated_in_old_since_last_gc; 107 108 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed; 109 110 bool should_update_surv_rate_group_predictors() { 111 return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress(); 112 } 113 public: 114 const G1Predictions& predictor() const { return _predictor; } 115 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); } 116 117 G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; } 118 119 // Add the given number of bytes to the total number of allocated bytes in the old gen. 120 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; } 121 122 void set_region_eden(HeapRegion* hr) { 123 hr->set_eden(); 124 hr->install_surv_rate_group(_short_lived_surv_rate_group); 125 } 126 127 void set_region_survivor(HeapRegion* hr) { 128 assert(hr->is_survivor(), "pre-condition"); 129 hr->install_surv_rate_group(_survivor_surv_rate_group); 130 } 131 132 void record_max_rs_lengths(size_t rs_lengths) { 133 _max_rs_lengths = rs_lengths; 134 } 135 136 double predict_base_elapsed_time_ms(size_t pending_cards) const; 137 double predict_base_elapsed_time_ms(size_t pending_cards, 138 size_t scanned_cards) const; 139 size_t predict_bytes_to_copy(HeapRegion* hr) const; 140 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const; 141 142 double predict_survivor_regions_evac_time() const; 143 144 void cset_regions_freed() { 145 bool update = should_update_surv_rate_group_predictors(); 146 147 _short_lived_surv_rate_group->all_surviving_words_recorded(predictor(), update); 148 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update); 149 } 150 151 G1MMUTracker* mmu_tracker() { 152 return _mmu_tracker; 153 } 154 155 const G1MMUTracker* mmu_tracker() const { 156 return _mmu_tracker; 157 } 158 159 double max_pause_time_ms() const { 160 return _mmu_tracker->max_gc_time() * 1000.0; 161 } 162 163 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const; 164 165 double predict_yg_surv_rate(int age) const; 166 167 double accum_yg_surv_rate_pred(int age) const; 168 169 private: 170 G1CollectionSet* _collection_set; 171 double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const; 172 double other_time_ms(double pause_time_ms) const; 173 174 double young_other_time_ms() const; 175 double non_young_other_time_ms() const; 176 double constant_other_time_ms(double pause_time_ms) const; 177 178 CollectionSetChooser* cset_chooser() const; 179 180 // The number of bytes copied during the GC. 181 size_t _bytes_copied_during_gc; 182 183 // Stash a pointer to the g1 heap. 184 G1CollectedHeap* _g1h; 185 186 G1GCPhaseTimes* _phase_times; 187 188 // This set of variables tracks the collector efficiency, in order to 189 // determine whether we should initiate a new marking. 190 double _mark_remark_start_sec; 191 double _mark_cleanup_start_sec; 192 193 // Updates the internal young list maximum and target lengths. Returns the 194 // unbounded young list target length. 195 uint update_young_list_max_and_target_length(); 196 uint update_young_list_max_and_target_length(size_t rs_lengths); 197 198 // Update the young list target length either by setting it to the 199 // desired fixed value or by calculating it using G1's pause 200 // prediction model. If no rs_lengths parameter is passed, predict 201 // the RS lengths using the prediction model, otherwise use the 202 // given rs_lengths as the prediction. 203 // Returns the unbounded young list target length. 204 uint update_young_list_target_length(size_t rs_lengths); 205 206 // Calculate and return the minimum desired young list target 207 // length. This is the minimum desired young list length according 208 // to the user's inputs. 209 uint calculate_young_list_desired_min_length(uint base_min_length) const; 210 211 // Calculate and return the maximum desired young list target 212 // length. This is the maximum desired young list length according 213 // to the user's inputs. 214 uint calculate_young_list_desired_max_length() const; 215 216 // Calculate and return the maximum young list target length that 217 // can fit into the pause time goal. The parameters are: rs_lengths 218 // represent the prediction of how large the young RSet lengths will 219 // be, base_min_length is the already existing number of regions in 220 // the young list, min_length and max_length are the desired min and 221 // max young list length according to the user's inputs. 222 uint calculate_young_list_target_length(size_t rs_lengths, 223 uint base_min_length, 224 uint desired_min_length, 225 uint desired_max_length) const; 226 227 // Result of the bounded_young_list_target_length() method, containing both the 228 // bounded as well as the unbounded young list target lengths in this order. 229 typedef Pair<uint, uint, StackObj> YoungTargetLengths; 230 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const; 231 232 void update_rs_lengths_prediction(); 233 void update_rs_lengths_prediction(size_t prediction); 234 235 // Check whether a given young length (young_length) fits into the 236 // given target pause time and whether the prediction for the amount 237 // of objects to be copied for the given length will fit into the 238 // given free space (expressed by base_free_regions). It is used by 239 // calculate_young_list_target_length(). 240 bool predict_will_fit(uint young_length, double base_time_ms, 241 uint base_free_regions, double target_pause_time_ms) const; 242 243 public: 244 size_t pending_cards() const { return _pending_cards; } 245 246 // Calculate the minimum number of old regions we'll add to the CSet 247 // during a mixed GC. 248 uint calc_min_old_cset_length() const; 249 250 // Calculate the maximum number of old regions we'll add to the CSet 251 // during a mixed GC. 252 uint calc_max_old_cset_length() const; 253 254 // Returns the given amount of reclaimable bytes (that represents 255 // the amount of reclaimable space still to be collected) as a 256 // percentage of the current heap capacity. 257 double reclaimable_bytes_percent(size_t reclaimable_bytes) const; 258 259 jlong collection_pause_end_millis() { return _collection_pause_end_millis; } 260 261 private: 262 void clear_collection_set_candidates(); 263 // Sets up marking if proper conditions are met. 264 void maybe_start_marking(); 265 266 // The kind of STW pause. 267 enum PauseKind { 268 FullGC, 269 YoungOnlyGC, 270 MixedGC, 271 LastYoungGC, 272 InitialMarkGC, 273 Cleanup, 274 Remark 275 }; 276 277 // Calculate PauseKind from internal state. 278 PauseKind young_gc_pause_kind() const; 279 // Record the given STW pause with the given start and end times (in s). 280 void record_pause(PauseKind kind, double start, double end); 281 // Indicate that we aborted marking before doing any mixed GCs. 282 void abort_time_to_mixed_tracking(); 283 public: 284 285 G1Policy(STWGCTimer* gc_timer); 286 287 virtual ~G1Policy(); 288 289 G1CollectorState* collector_state() const; 290 291 G1GCPhaseTimes* phase_times() const { return _phase_times; } 292 293 // Check the current value of the young list RSet lengths and 294 // compare it against the last prediction. If the current value is 295 // higher, recalculate the young list target length prediction. 296 void revise_young_list_target_length_if_necessary(size_t rs_lengths); 297 298 // This should be called after the heap is resized. 299 void record_new_heap_size(uint new_number_of_regions); 300 301 void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set); 302 303 void note_gc_start(); 304 305 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0); 306 307 bool about_to_start_mixed_phase() const; 308 309 // Record the start and end of an evacuation pause. 310 void record_collection_pause_start(double start_time_sec); 311 void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc); 312 313 // Record the start and end of a full collection. 314 void record_full_collection_start(); 315 void record_full_collection_end(); 316 317 // Must currently be called while the world is stopped. 318 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms); 319 320 // Record start and end of remark. 321 void record_concurrent_mark_remark_start(); 322 void record_concurrent_mark_remark_end(); 323 324 // Record start, end, and completion of cleanup. 325 void record_concurrent_mark_cleanup_start(); 326 void record_concurrent_mark_cleanup_end(); 327 328 void print_phases(); 329 330 // Record how much space we copied during a GC. This is typically 331 // called when a GC alloc region is being retired. 332 void record_bytes_copied_during_gc(size_t bytes) { 333 _bytes_copied_during_gc += bytes; 334 } 335 336 // The amount of space we copied during a GC. 337 size_t bytes_copied_during_gc() const { 338 return _bytes_copied_during_gc; 339 } 340 341 bool next_gc_should_be_mixed(const char* true_action_str, 342 const char* false_action_str) const; 343 344 void finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor); 345 private: 346 // Set the state to start a concurrent marking cycle and clear 347 // _initiate_conc_mark_if_possible because it has now been 348 // acted on. 349 void initiate_conc_mark(); 350 351 public: 352 // This sets the initiate_conc_mark_if_possible() flag to start a 353 // new cycle, as long as we are not already in one. It's best if it 354 // is called during a safepoint when the test whether a cycle is in 355 // progress or not is stable. 356 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause); 357 358 // This is called at the very beginning of an evacuation pause (it 359 // has to be the first thing that the pause does). If 360 // initiate_conc_mark_if_possible() is true, and the concurrent 361 // marking thread has completed its work during the previous cycle, 362 // it will set in_initial_mark_gc() to so that the pause does 363 // the initial-mark work and start a marking cycle. 364 void decide_on_conc_mark_initiation(); 365 366 void finished_recalculating_age_indexes(bool is_survivors) { 367 if (is_survivors) { 368 _survivor_surv_rate_group->finished_recalculating_age_indexes(); 369 } else { 370 _short_lived_surv_rate_group->finished_recalculating_age_indexes(); 371 } 372 } 373 374 size_t young_list_target_length() const { return _young_list_target_length; } 375 376 bool should_allocate_mutator_region() const; 377 378 bool can_expand_young_list() const; 379 380 uint young_list_max_length() const { 381 return _young_list_max_length; 382 } 383 384 bool adaptive_young_list_length() const; 385 386 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors); 387 388 private: 389 // 390 // Survivor regions policy. 391 // 392 393 // Current tenuring threshold, set to 0 if the collector reaches the 394 // maximum amount of survivors regions. 395 uint _tenuring_threshold; 396 397 // The limit on the number of regions allocated for survivors. 398 uint _max_survivor_regions; 399 400 AgeTable _survivors_age_table; 401 402 size_t desired_survivor_size() const; 403 public: 404 // Fraction used when predicting how many optional regions to include in 405 // the CSet. This fraction of the available time is used for optional regions, 406 // the rest is used to add old regions to the normal CSet. 407 double optional_prediction_fraction() { return 0.2; } 408 // Fraction used when evacuating the optional regions. This fraction of the 409 // remaining time is used to choose what regions to include in the evacuation. 410 double optional_evacuation_fraction() { return 0.75; } 411 412 uint tenuring_threshold() const { return _tenuring_threshold; } 413 414 uint max_survivor_regions() { 415 return _max_survivor_regions; 416 } 417 418 void note_start_adding_survivor_regions() { 419 _survivor_surv_rate_group->start_adding_regions(); 420 } 421 422 void note_stop_adding_survivor_regions() { 423 _survivor_surv_rate_group->stop_adding_regions(); 424 } 425 426 void record_age_table(AgeTable* age_table) { 427 _survivors_age_table.merge(age_table); 428 } 429 430 void print_age_table(); 431 432 void update_max_gc_locker_expansion(); 433 434 void update_survivors_policy(); 435 }; 436 437 #endif // SHARE_VM_GC_G1_G1POLICY_HPP