1 /* 2 * Copyright (c) 2016, 2020, 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/g1ConcurrentStartToMixedTimeTracker.hpp" 32 #include "gc/g1/g1MMUTracker.hpp" 33 #include "gc/g1/g1OldGenAllocationTracker.hpp" 34 #include "gc/g1/g1RemSetTrackingPolicy.hpp" 35 #include "gc/g1/g1Predictions.hpp" 36 #include "gc/g1/g1YoungGenSizer.hpp" 37 #include "gc/shared/gcCause.hpp" 38 #include "utilities/pair.hpp" 39 40 // A G1Policy makes policy decisions that determine the 41 // characteristics of the collector. Examples include: 42 // * choice of collection set. 43 // * when to collect. 44 45 class HeapRegion; 46 class G1CollectionSet; 47 class G1CollectionSetCandidates; 48 class G1CollectionSetChooser; 49 class G1IHOPControl; 50 class G1Analytics; 51 class G1SurvivorRegions; 52 class G1YoungGenSizer; 53 class GCPolicyCounters; 54 class STWGCTimer; 55 56 class G1Policy: public CHeapObj<mtGC> { 57 private: 58 59 static G1IHOPControl* create_ihop_control(const G1Predictions* predictor); 60 // Update the IHOP control with necessary statistics. 61 void update_ihop_prediction(double mutator_time_s, 62 size_t mutator_alloc_bytes, 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_desired_length; 79 uint _young_list_target_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 // The survivor rate groups below must be initialized after the predictor because they 86 // indirectly use it through the "this" object passed to their constructor. 87 G1SurvRateGroup* _eden_surv_rate_group; 88 G1SurvRateGroup* _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 _rs_length; 100 101 size_t _rs_length_prediction; 102 103 size_t _pending_cards_at_gc_start; 104 105 // Tracking the allocation in the old generation between 106 // two GCs. 107 G1OldGenAllocationTracker _old_gen_alloc_tracker; 108 109 G1ConcurrentStartToMixedTimeTracker _concurrent_start_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 logged_cards_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 G1OldGenAllocationTracker* old_gen_alloc_tracker() { return &_old_gen_alloc_tracker; } 123 124 void set_region_eden(HeapRegion* hr) { 125 hr->set_eden(); 126 hr->install_surv_rate_group(_eden_surv_rate_group); 127 } 128 129 void set_region_survivor(HeapRegion* hr) { 130 assert(hr->is_survivor(), "pre-condition"); 131 hr->install_surv_rate_group(_survivor_surv_rate_group); 132 } 133 134 void record_rs_length(size_t rs_length) { 135 _rs_length = rs_length; 136 } 137 138 double predict_base_elapsed_time_ms(size_t num_pending_cards) const; 139 140 private: 141 double predict_base_elapsed_time_ms(size_t num_pending_cards, size_t rs_length) const; 142 143 double predict_region_copy_time_ms(HeapRegion* hr) const; 144 145 public: 146 147 double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = NULL) const; 148 double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_gc) const; 149 double predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const; 150 151 void cset_regions_freed() { 152 bool update = should_update_surv_rate_group_predictors(); 153 154 _eden_surv_rate_group->all_surviving_words_recorded(predictor(), update); 155 _survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update); 156 } 157 158 G1MMUTracker* mmu_tracker() { 159 return _mmu_tracker; 160 } 161 162 const G1MMUTracker* mmu_tracker() const { 163 return _mmu_tracker; 164 } 165 166 double max_pause_time_ms() const { 167 return _mmu_tracker->max_gc_time() * 1000.0; 168 } 169 170 private: 171 G1CollectionSet* _collection_set; 172 173 bool next_gc_should_be_mixed(const char* true_action_str, 174 const char* false_action_str) const; 175 176 double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const; 177 double other_time_ms(double pause_time_ms) const; 178 179 double young_other_time_ms() const; 180 double non_young_other_time_ms() const; 181 double constant_other_time_ms(double pause_time_ms) const; 182 183 G1CollectionSetChooser* cset_chooser() const; 184 185 // Stash a pointer to the g1 heap. 186 G1CollectedHeap* _g1h; 187 188 G1GCPhaseTimes* _phase_times; 189 190 // This set of variables tracks the collector efficiency, in order to 191 // determine whether we should initiate a new marking. 192 double _mark_remark_start_sec; 193 double _mark_cleanup_start_sec; 194 195 // Updates the internal young gen maximum and target and desired lengths. 196 // If no rs_length parameter is passed, predict the RS length using the 197 // prediction model, otherwise use the given rs_length as the prediction. 198 void update_young_length_bounds(); 199 void update_young_length_bounds(size_t rs_length); 200 201 // Calculate and return the minimum desired eden length based on the MMU target. 202 uint calculate_desired_eden_length_by_mmu() const; 203 204 // Calculate and return the desired eden length that can fit into the pause time goal. 205 // The parameters are: rs_length represents the prediction of how large the 206 // young RSet lengths will be, min_eden_length and max_eden_length are the bounds 207 // (inclusive) within eden can grow. 208 uint calculate_desired_eden_length_by_pause(double base_time_ms, 209 uint min_eden_length, 210 uint max_eden_length) const; 211 212 // Calculates the desired eden length before mixed gc so that after adding the 213 // minimum amount of old gen regions from the collection set, the eden fits into 214 // the pause time goal. 215 uint calculate_desired_eden_length_before_mixed(double survivor_base_time_ms, 216 uint min_eden_length, 217 uint max_eden_length) const; 218 219 // Calculate desired young length based on current situation without taking actually 220 // available free regions into account. 221 uint calculate_young_desired_length(size_t rs_length) const; 222 // Limit the given desired young length to available free regions. 223 uint calculate_young_target_length(uint desired_young_length) const; 224 // The GCLocker might cause us to need more regions than the target. Calculate 225 // the maximum number of regions to use in that case. 226 uint calculate_young_max_length(uint target_young_length) const; 227 228 void update_rs_length_prediction(); 229 void update_rs_length_prediction(size_t prediction); 230 231 size_t predict_bytes_to_copy(HeapRegion* hr) const; 232 double predict_survivor_regions_evac_time() const; 233 234 // Check whether a given young length (young_length) fits into the 235 // given target pause time and whether the prediction for the amount 236 // of objects to be copied for the given length will fit into the 237 // given free space (expressed by base_free_regions). It is used by 238 // calculate_young_list_target_length(). 239 bool predict_will_fit(uint young_length, double base_time_ms, 240 uint base_free_regions, double target_pause_time_ms) const; 241 242 public: 243 size_t pending_cards_at_gc_start() const { return _pending_cards_at_gc_start; } 244 245 // Calculate the minimum number of old regions we'll add to the CSet 246 // during a mixed GC. 247 uint calc_min_old_cset_length() const; 248 249 // Calculate the maximum number of old regions we'll add to the CSet 250 // during a mixed GC. 251 uint calc_max_old_cset_length() const; 252 253 // Returns the given amount of reclaimable bytes (that represents 254 // the amount of reclaimable space still to be collected) as a 255 // percentage of the current heap capacity. 256 double reclaimable_bytes_percent(size_t reclaimable_bytes) const; 257 258 jlong collection_pause_end_millis() { return _collection_pause_end_millis; } 259 260 private: 261 void clear_collection_set_candidates(); 262 // Sets up marking if proper conditions are met. 263 void maybe_start_marking(); 264 265 // The kind of STW pause. 266 enum PauseKind { 267 FullGC, 268 YoungOnlyGC, 269 MixedGC, 270 LastYoungGC, 271 ConcurrentStartGC, 272 Cleanup, 273 Remark 274 }; 275 276 static bool is_young_only_pause(PauseKind kind); 277 static bool is_last_young_pause(PauseKind kind); 278 static bool is_concurrent_start_pause(PauseKind kind); 279 // Calculate PauseKind from internal state. 280 PauseKind young_gc_pause_kind() const; 281 // Record the given STW pause with the given start and end times (in s). 282 void record_pause(PauseKind kind, double start, double end); 283 // Indicate that we aborted marking before doing any mixed GCs. 284 void abort_time_to_mixed_tracking(); 285 286 // Record and log stats before not-full collection. 287 void record_concurrent_refinement_stats(); 288 289 public: 290 291 G1Policy(STWGCTimer* gc_timer); 292 293 virtual ~G1Policy(); 294 295 static G1Policy* create_policy(STWGCTimer* gc_timer_stw); 296 297 G1CollectorState* collector_state() const; 298 299 G1GCPhaseTimes* phase_times() const { return _phase_times; } 300 301 // Check the current value of the young list RSet length and 302 // compare it against the last prediction. If the current value is 303 // higher, recalculate the young list target length prediction. 304 void revise_young_list_target_length_if_necessary(size_t rs_length); 305 306 // This should be called after the heap is resized. 307 void record_new_heap_size(uint new_number_of_regions); 308 309 virtual void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set); 310 311 void note_gc_start(); 312 313 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0); 314 315 bool about_to_start_mixed_phase() const; 316 317 // Record the start and end of an evacuation pause. 318 void record_collection_pause_start(double start_time_sec); 319 virtual void record_collection_pause_end(double pause_time_ms); 320 321 // Record the start and end of a full collection. 322 void record_full_collection_start(); 323 virtual void record_full_collection_end(); 324 325 // Must currently be called while the world is stopped. 326 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms); 327 328 // Record start and end of remark. 329 void record_concurrent_mark_remark_start(); 330 void record_concurrent_mark_remark_end(); 331 332 // Record start, end, and completion of cleanup. 333 void record_concurrent_mark_cleanup_start(); 334 void record_concurrent_mark_cleanup_end(); 335 336 void print_phases(); 337 338 // Calculate and return the number of initial and optional old gen regions from 339 // the given collection set candidates and the remaining time. 340 void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates, 341 double time_remaining_ms, 342 uint& num_initial_regions, 343 uint& num_optional_regions); 344 345 // Calculate the number of optional regions from the given collection set candidates, 346 // the remaining time and the maximum number of these regions and return the number 347 // of actually selected regions in num_optional_regions. 348 void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates, 349 uint const max_optional_regions, 350 double time_remaining_ms, 351 uint& num_optional_regions); 352 353 private: 354 // Set the state to start a concurrent marking cycle and clear 355 // _initiate_conc_mark_if_possible because it has now been 356 // acted on. 357 void initiate_conc_mark(); 358 359 public: 360 // This sets the initiate_conc_mark_if_possible() flag to start a 361 // new cycle, as long as we are not already in one. It's best if it 362 // is called during a safepoint when the test whether a cycle is in 363 // progress or not is stable. 364 bool force_concurrent_start_if_outside_cycle(GCCause::Cause gc_cause); 365 366 // This is called at the very beginning of an evacuation pause (it 367 // has to be the first thing that the pause does). If 368 // initiate_conc_mark_if_possible() is true, and the concurrent 369 // marking thread has completed its work during the previous cycle, 370 // it will set in_concurrent_start_gc() to so that the pause does 371 // the concurrent start work and start a marking cycle. 372 void decide_on_conc_mark_initiation(); 373 374 uint young_list_desired_length() const { return _young_list_desired_length; } 375 size_t young_list_target_length() const { return _young_list_target_length; } 376 377 bool should_allocate_mutator_region() const; 378 379 bool can_expand_young_list() const; 380 381 uint young_list_max_length() const { 382 return _young_list_max_length; 383 } 384 385 bool use_adaptive_young_list_length() const; 386 387 void transfer_survivors_to_cset(const G1SurvivorRegions* survivors); 388 389 private: 390 // 391 // Survivor regions policy. 392 // 393 394 // Current tenuring threshold, set to 0 if the collector reaches the 395 // maximum amount of survivors regions. 396 uint _tenuring_threshold; 397 398 // The limit on the number of regions allocated for survivors. 399 uint _max_survivor_regions; 400 401 AgeTable _survivors_age_table; 402 403 size_t desired_survivor_size(uint max_regions) const; 404 405 // Fraction used when predicting how many optional regions to include in 406 // the CSet. This fraction of the available time is used for optional regions, 407 // the rest is used to add old regions to the normal CSet. 408 double optional_prediction_fraction() { return 0.2; } 409 410 public: 411 // Fraction used when evacuating the optional regions. This fraction of the 412 // remaining time is used to choose what regions to include in the evacuation. 413 double optional_evacuation_fraction() { return 0.75; } 414 415 uint tenuring_threshold() const { return _tenuring_threshold; } 416 417 uint max_survivor_regions() { 418 return _max_survivor_regions; 419 } 420 421 void note_start_adding_survivor_regions() { 422 _survivor_surv_rate_group->start_adding_regions(); 423 } 424 425 void note_stop_adding_survivor_regions() { 426 _survivor_surv_rate_group->stop_adding_regions(); 427 } 428 429 void record_age_table(AgeTable* age_table) { 430 _survivors_age_table.merge(age_table); 431 } 432 433 void print_age_table(); 434 435 void update_survivors_policy(); 436 437 virtual bool force_upgrade_to_full() { 438 return false; 439 } 440 }; 441 442 #endif // SHARE_GC_G1_G1POLICY_HPP