1 /* 2 * Copyright (c) 2001, 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 #include "precompiled.hpp" 26 #include "gc/g1/g1Analytics.hpp" 27 #include "gc/g1/g1CollectedHeap.inline.hpp" 28 #include "gc/g1/g1CollectionSet.hpp" 29 #include "gc/g1/g1CollectionSetCandidates.hpp" 30 #include "gc/g1/g1ConcurrentMark.hpp" 31 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 32 #include "gc/g1/g1ConcurrentRefine.hpp" 33 #include "gc/g1/g1CollectionSetChooser.hpp" 34 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp" 35 #include "gc/g1/g1HotCardCache.hpp" 36 #include "gc/g1/g1IHOPControl.hpp" 37 #include "gc/g1/g1GCPhaseTimes.hpp" 38 #include "gc/g1/g1Policy.hpp" 39 #include "gc/g1/g1SurvivorRegions.hpp" 40 #include "gc/g1/g1YoungGenSizer.hpp" 41 #include "gc/g1/heapRegion.inline.hpp" 42 #include "gc/g1/heapRegionRemSet.hpp" 43 #include "gc/shared/gcPolicyCounters.hpp" 44 #include "logging/logStream.hpp" 45 #include "runtime/arguments.hpp" 46 #include "runtime/java.hpp" 47 #include "runtime/mutexLocker.hpp" 48 #include "utilities/debug.hpp" 49 #include "utilities/growableArray.hpp" 50 #include "utilities/pair.hpp" 51 52 G1Policy::G1Policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer) : 53 _predictor(G1ConfidencePercent / 100.0), 54 _analytics(new G1Analytics(&_predictor)), 55 _remset_tracker(), 56 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)), 57 _ihop_control(create_ihop_control(&_predictor)), 58 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)), 59 _full_collection_start_sec(0.0), 60 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC), 61 _young_list_target_length(0), 62 _young_list_fixed_length(0), 63 _young_list_max_length(0), 64 _short_lived_surv_rate_group(new SurvRateGroup()), 65 _survivor_surv_rate_group(new SurvRateGroup()), 66 _reserve_factor((double) G1ReservePercent / 100.0), 67 _reserve_regions(0), 68 _young_gen_sizer(G1YoungGenSizer::create_gen_sizer(policy)), 69 _free_regions_at_end_of_collection(0), 70 _max_rs_lengths(0), 71 _rs_lengths_prediction(0), 72 _pending_cards(0), 73 _bytes_allocated_in_old_since_last_gc(0), 74 _initial_mark_to_mixed(), 75 _collection_set(NULL), 76 _bytes_copied_during_gc(0), 77 _g1h(NULL), 78 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)), 79 _mark_remark_start_sec(0), 80 _mark_cleanup_start_sec(0), 81 _tenuring_threshold(MaxTenuringThreshold), 82 _max_survivor_regions(0), 83 _survivors_age_table(true) 84 { 85 } 86 87 G1Policy::~G1Policy() { 88 delete _ihop_control; 89 delete _young_gen_sizer; 90 } 91 92 G1Policy* G1Policy::create_policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer_stw) { 93 if (policy->is_heterogeneous_heap()) { 94 return new G1HeterogeneousHeapPolicy(policy, gc_timer_stw); 95 } else { 96 return new G1Policy(policy, gc_timer_stw); 97 } 98 } 99 100 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); } 101 102 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) { 103 _g1h = g1h; 104 _collection_set = collection_set; 105 106 assert(Heap_lock->owned_by_self(), "Locking discipline."); 107 108 if (!use_adaptive_young_list_length()) { 109 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length(); 110 } 111 _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions()); 112 113 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 114 115 update_young_list_max_and_target_length(); 116 // We may immediately start allocating regions and placing them on the 117 // collection set list. Initialize the per-collection set info 118 _collection_set->start_incremental_building(); 119 } 120 121 void G1Policy::note_gc_start() { 122 phase_times()->note_gc_start(); 123 } 124 125 class G1YoungLengthPredictor { 126 const bool _during_cm; 127 const double _base_time_ms; 128 const double _base_free_regions; 129 const double _target_pause_time_ms; 130 const G1Policy* const _policy; 131 132 public: 133 G1YoungLengthPredictor(bool during_cm, 134 double base_time_ms, 135 double base_free_regions, 136 double target_pause_time_ms, 137 const G1Policy* policy) : 138 _during_cm(during_cm), 139 _base_time_ms(base_time_ms), 140 _base_free_regions(base_free_regions), 141 _target_pause_time_ms(target_pause_time_ms), 142 _policy(policy) {} 143 144 bool will_fit(uint young_length) const { 145 if (young_length >= _base_free_regions) { 146 // end condition 1: not enough space for the young regions 147 return false; 148 } 149 150 const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1); 151 const size_t bytes_to_copy = 152 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes); 153 const double copy_time_ms = 154 _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm); 155 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length); 156 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms; 157 if (pause_time_ms > _target_pause_time_ms) { 158 // end condition 2: prediction is over the target pause time 159 return false; 160 } 161 162 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes; 163 164 // When copying, we will likely need more bytes free than is live in the region. 165 // Add some safety margin to factor in the confidence of our guess, and the 166 // natural expected waste. 167 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 168 // of the calculation: the lower the confidence, the more headroom. 169 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 170 // copying due to anticipated waste in the PLABs. 171 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 172 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 173 174 if (expected_bytes_to_copy > free_bytes) { 175 // end condition 3: out-of-space 176 return false; 177 } 178 179 // success! 180 return true; 181 } 182 }; 183 184 void G1Policy::record_new_heap_size(uint new_number_of_regions) { 185 // re-calculate the necessary reserve 186 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 187 // We use ceiling so that if reserve_regions_d is > 0.0 (but 188 // smaller than 1.0) we'll get 1. 189 _reserve_regions = (uint) ceil(reserve_regions_d); 190 191 _young_gen_sizer->heap_size_changed(new_number_of_regions); 192 193 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 194 } 195 196 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const { 197 uint desired_min_length = 0; 198 if (use_adaptive_young_list_length()) { 199 if (_analytics->num_alloc_rate_ms() > 3) { 200 double now_sec = os::elapsedTime(); 201 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 202 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 203 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 204 } else { 205 // otherwise we don't have enough info to make the prediction 206 } 207 } 208 desired_min_length += base_min_length; 209 // make sure we don't go below any user-defined minimum bound 210 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length); 211 } 212 213 uint G1Policy::calculate_young_list_desired_max_length() const { 214 // Here, we might want to also take into account any additional 215 // constraints (i.e., user-defined minimum bound). Currently, we 216 // effectively don't set this bound. 217 return _young_gen_sizer->max_desired_young_length(); 218 } 219 220 uint G1Policy::update_young_list_max_and_target_length() { 221 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths()); 222 } 223 224 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) { 225 uint unbounded_target_length = update_young_list_target_length(rs_lengths); 226 update_max_gc_locker_expansion(); 227 return unbounded_target_length; 228 } 229 230 uint G1Policy::update_young_list_target_length(size_t rs_lengths) { 231 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths); 232 _young_list_target_length = young_lengths.first; 233 234 return young_lengths.second; 235 } 236 237 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const { 238 YoungTargetLengths result; 239 240 // Calculate the absolute and desired min bounds first. 241 242 // This is how many young regions we already have (currently: the survivors). 243 const uint base_min_length = _g1h->survivor_regions_count(); 244 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 245 // This is the absolute minimum young length. Ensure that we 246 // will at least have one eden region available for allocation. 247 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1); 248 // If we shrank the young list target it should not shrink below the current size. 249 desired_min_length = MAX2(desired_min_length, absolute_min_length); 250 // Calculate the absolute and desired max bounds. 251 252 uint desired_max_length = calculate_young_list_desired_max_length(); 253 254 uint young_list_target_length = 0; 255 if (use_adaptive_young_list_length()) { 256 if (collector_state()->in_young_only_phase()) { 257 young_list_target_length = 258 calculate_young_list_target_length(rs_lengths, 259 base_min_length, 260 desired_min_length, 261 desired_max_length); 262 } else { 263 // Don't calculate anything and let the code below bound it to 264 // the desired_min_length, i.e., do the next GC as soon as 265 // possible to maximize how many old regions we can add to it. 266 } 267 } else { 268 // The user asked for a fixed young gen so we'll fix the young gen 269 // whether the next GC is young or mixed. 270 young_list_target_length = _young_list_fixed_length; 271 } 272 273 result.second = young_list_target_length; 274 275 // We will try our best not to "eat" into the reserve. 276 uint absolute_max_length = 0; 277 if (_free_regions_at_end_of_collection > _reserve_regions) { 278 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 279 } 280 if (desired_max_length > absolute_max_length) { 281 desired_max_length = absolute_max_length; 282 } 283 284 // Make sure we don't go over the desired max length, nor under the 285 // desired min length. In case they clash, desired_min_length wins 286 // which is why that test is second. 287 if (young_list_target_length > desired_max_length) { 288 young_list_target_length = desired_max_length; 289 } 290 if (young_list_target_length < desired_min_length) { 291 young_list_target_length = desired_min_length; 292 } 293 294 assert(young_list_target_length > base_min_length, 295 "we should be able to allocate at least one eden region"); 296 assert(young_list_target_length >= absolute_min_length, "post-condition"); 297 298 result.first = young_list_target_length; 299 return result; 300 } 301 302 uint 303 G1Policy::calculate_young_list_target_length(size_t rs_lengths, 304 uint base_min_length, 305 uint desired_min_length, 306 uint desired_max_length) const { 307 assert(use_adaptive_young_list_length(), "pre-condition"); 308 assert(collector_state()->in_young_only_phase(), "only call this for young GCs"); 309 310 // In case some edge-condition makes the desired max length too small... 311 if (desired_max_length <= desired_min_length) { 312 return desired_min_length; 313 } 314 315 // We'll adjust min_young_length and max_young_length not to include 316 // the already allocated young regions (i.e., so they reflect the 317 // min and max eden regions we'll allocate). The base_min_length 318 // will be reflected in the predictions by the 319 // survivor_regions_evac_time prediction. 320 assert(desired_min_length > base_min_length, "invariant"); 321 uint min_young_length = desired_min_length - base_min_length; 322 assert(desired_max_length > base_min_length, "invariant"); 323 uint max_young_length = desired_max_length - base_min_length; 324 325 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 326 const double survivor_regions_evac_time = predict_survivor_regions_evac_time(); 327 const size_t pending_cards = _analytics->predict_pending_cards(); 328 const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff(); 329 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, true /* for_young_gc */); 330 const double base_time_ms = 331 predict_base_elapsed_time_ms(pending_cards, scanned_cards) + 332 survivor_regions_evac_time; 333 const uint available_free_regions = _free_regions_at_end_of_collection; 334 const uint base_free_regions = 335 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0; 336 337 // Here, we will make sure that the shortest young length that 338 // makes sense fits within the target pause time. 339 340 G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(), 341 base_time_ms, 342 base_free_regions, 343 target_pause_time_ms, 344 this); 345 if (p.will_fit(min_young_length)) { 346 // The shortest young length will fit into the target pause time; 347 // we'll now check whether the absolute maximum number of young 348 // regions will fit in the target pause time. If not, we'll do 349 // a binary search between min_young_length and max_young_length. 350 if (p.will_fit(max_young_length)) { 351 // The maximum young length will fit into the target pause time. 352 // We are done so set min young length to the maximum length (as 353 // the result is assumed to be returned in min_young_length). 354 min_young_length = max_young_length; 355 } else { 356 // The maximum possible number of young regions will not fit within 357 // the target pause time so we'll search for the optimal 358 // length. The loop invariants are: 359 // 360 // min_young_length < max_young_length 361 // min_young_length is known to fit into the target pause time 362 // max_young_length is known not to fit into the target pause time 363 // 364 // Going into the loop we know the above hold as we've just 365 // checked them. Every time around the loop we check whether 366 // the middle value between min_young_length and 367 // max_young_length fits into the target pause time. If it 368 // does, it becomes the new min. If it doesn't, it becomes 369 // the new max. This way we maintain the loop invariants. 370 371 assert(min_young_length < max_young_length, "invariant"); 372 uint diff = (max_young_length - min_young_length) / 2; 373 while (diff > 0) { 374 uint young_length = min_young_length + diff; 375 if (p.will_fit(young_length)) { 376 min_young_length = young_length; 377 } else { 378 max_young_length = young_length; 379 } 380 assert(min_young_length < max_young_length, "invariant"); 381 diff = (max_young_length - min_young_length) / 2; 382 } 383 // The results is min_young_length which, according to the 384 // loop invariants, should fit within the target pause time. 385 386 // These are the post-conditions of the binary search above: 387 assert(min_young_length < max_young_length, 388 "otherwise we should have discovered that max_young_length " 389 "fits into the pause target and not done the binary search"); 390 assert(p.will_fit(min_young_length), 391 "min_young_length, the result of the binary search, should " 392 "fit into the pause target"); 393 assert(!p.will_fit(min_young_length + 1), 394 "min_young_length, the result of the binary search, should be " 395 "optimal, so no larger length should fit into the pause target"); 396 } 397 } else { 398 // Even the minimum length doesn't fit into the pause time 399 // target, return it as the result nevertheless. 400 } 401 return base_min_length + min_young_length; 402 } 403 404 double G1Policy::predict_survivor_regions_evac_time() const { 405 double survivor_regions_evac_time = 0.0; 406 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions(); 407 408 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin(); 409 it != survivor_regions->end(); 410 ++it) { 411 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase()); 412 } 413 return survivor_regions_evac_time; 414 } 415 416 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) { 417 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" ); 418 419 if (rs_lengths > _rs_lengths_prediction) { 420 // add 10% to avoid having to recalculate often 421 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000; 422 update_rs_lengths_prediction(rs_lengths_prediction); 423 424 update_young_list_max_and_target_length(rs_lengths_prediction); 425 } 426 } 427 428 void G1Policy::update_rs_lengths_prediction() { 429 update_rs_lengths_prediction(_analytics->predict_rs_lengths()); 430 } 431 432 void G1Policy::update_rs_lengths_prediction(size_t prediction) { 433 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) { 434 _rs_lengths_prediction = prediction; 435 } 436 } 437 438 void G1Policy::record_full_collection_start() { 439 _full_collection_start_sec = os::elapsedTime(); 440 // Release the future to-space so that it is available for compaction into. 441 collector_state()->set_in_young_only_phase(false); 442 collector_state()->set_in_full_gc(true); 443 _collection_set->clear_candidates(); 444 } 445 446 void G1Policy::record_full_collection_end() { 447 // Consider this like a collection pause for the purposes of allocation 448 // since last pause. 449 double end_sec = os::elapsedTime(); 450 double full_gc_time_sec = end_sec - _full_collection_start_sec; 451 double full_gc_time_ms = full_gc_time_sec * 1000.0; 452 453 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 454 455 collector_state()->set_in_full_gc(false); 456 457 // "Nuke" the heuristics that control the young/mixed GC 458 // transitions and make sure we start with young GCs after the Full GC. 459 collector_state()->set_in_young_only_phase(true); 460 collector_state()->set_in_young_gc_before_mixed(false); 461 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 462 collector_state()->set_in_initial_mark_gc(false); 463 collector_state()->set_mark_or_rebuild_in_progress(false); 464 collector_state()->set_clearing_next_bitmap(false); 465 466 _short_lived_surv_rate_group->start_adding_regions(); 467 // also call this on any additional surv rate groups 468 469 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 470 // Reset survivors SurvRateGroup. 471 _survivor_surv_rate_group->reset(); 472 update_young_list_max_and_target_length(); 473 update_rs_lengths_prediction(); 474 475 _bytes_allocated_in_old_since_last_gc = 0; 476 477 record_pause(FullGC, _full_collection_start_sec, end_sec); 478 } 479 480 void G1Policy::record_collection_pause_start(double start_time_sec) { 481 // We only need to do this here as the policy will only be applied 482 // to the GC we're about to start. so, no point is calculating this 483 // every time we calculate / recalculate the target young length. 484 update_survivors_policy(); 485 486 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(), 487 "Maximum survivor regions %u plus used regions %u exceeds max regions %u", 488 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions()); 489 490 assert(_g1h->used() == _g1h->recalculate_used(), 491 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT, 492 _g1h->used(), _g1h->recalculate_used()); 493 494 phase_times()->record_cur_collection_start_sec(start_time_sec); 495 _pending_cards = _g1h->pending_card_num(); 496 497 _collection_set->reset_bytes_used_before(); 498 _bytes_copied_during_gc = 0; 499 500 // do that for any other surv rate groups 501 _short_lived_surv_rate_group->stop_adding_regions(); 502 _survivors_age_table.clear(); 503 504 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed"); 505 } 506 507 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 508 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 509 collector_state()->set_in_initial_mark_gc(false); 510 } 511 512 void G1Policy::record_concurrent_mark_remark_start() { 513 _mark_remark_start_sec = os::elapsedTime(); 514 } 515 516 void G1Policy::record_concurrent_mark_remark_end() { 517 double end_time_sec = os::elapsedTime(); 518 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 519 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 520 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 521 522 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 523 } 524 525 void G1Policy::record_concurrent_mark_cleanup_start() { 526 _mark_cleanup_start_sec = os::elapsedTime(); 527 } 528 529 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 530 return phase_times()->average_time_ms(phase); 531 } 532 533 double G1Policy::young_other_time_ms() const { 534 return phase_times()->young_cset_choice_time_ms() + 535 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet); 536 } 537 538 double G1Policy::non_young_other_time_ms() const { 539 return phase_times()->non_young_cset_choice_time_ms() + 540 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet); 541 } 542 543 double G1Policy::other_time_ms(double pause_time_ms) const { 544 return pause_time_ms - phase_times()->cur_collection_par_time_ms(); 545 } 546 547 double G1Policy::constant_other_time_ms(double pause_time_ms) const { 548 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms(); 549 } 550 551 bool G1Policy::about_to_start_mixed_phase() const { 552 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed(); 553 } 554 555 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 556 if (about_to_start_mixed_phase()) { 557 return false; 558 } 559 560 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 561 562 size_t cur_used_bytes = _g1h->non_young_capacity_bytes(); 563 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 564 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 565 566 bool result = false; 567 if (marking_request_bytes > marking_initiating_used_threshold) { 568 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed(); 569 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 570 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 571 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source); 572 } 573 574 return result; 575 } 576 577 // Anything below that is considered to be zero 578 #define MIN_TIMER_GRANULARITY 0.0000001 579 580 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) { 581 double end_time_sec = os::elapsedTime(); 582 583 size_t cur_used_bytes = _g1h->used(); 584 assert(cur_used_bytes == _g1h->recalculate_used(), "It should!"); 585 bool this_pause_included_initial_mark = false; 586 bool this_pause_was_young_only = collector_state()->in_young_only_phase(); 587 588 bool update_stats = !_g1h->evacuation_failed(); 589 590 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 591 592 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 593 594 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc(); 595 if (this_pause_included_initial_mark) { 596 record_concurrent_mark_init_end(0.0); 597 } else { 598 maybe_start_marking(); 599 } 600 601 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 602 if (app_time_ms < MIN_TIMER_GRANULARITY) { 603 // This usually happens due to the timer not having the required 604 // granularity. Some Linuxes are the usual culprits. 605 // We'll just set it to something (arbitrarily) small. 606 app_time_ms = 1.0; 607 } 608 609 if (update_stats) { 610 // We maintain the invariant that all objects allocated by mutator 611 // threads will be allocated out of eden regions. So, we can use 612 // the eden region number allocated since the previous GC to 613 // calculate the application's allocate rate. The only exception 614 // to that is humongous objects that are allocated separately. But 615 // given that humongous object allocations do not really affect 616 // either the pause's duration nor when the next pause will take 617 // place we can safely ignore them here. 618 uint regions_allocated = _collection_set->eden_region_length(); 619 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 620 _analytics->report_alloc_rate_ms(alloc_rate_ms); 621 622 double interval_ms = 623 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; 624 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 625 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms); 626 } 627 628 if (collector_state()->in_young_gc_before_mixed()) { 629 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC"); 630 // This has been the young GC before we start doing mixed GCs. We already 631 // decided to start mixed GCs much earlier, so there is nothing to do except 632 // advancing the state. 633 collector_state()->set_in_young_only_phase(false); 634 collector_state()->set_in_young_gc_before_mixed(false); 635 } else if (!this_pause_was_young_only) { 636 // This is a mixed GC. Here we decide whether to continue doing more 637 // mixed GCs or not. 638 if (!next_gc_should_be_mixed("continue mixed GCs", 639 "do not continue mixed GCs")) { 640 collector_state()->set_in_young_only_phase(true); 641 642 clear_collection_set_candidates(); 643 maybe_start_marking(); 644 } 645 } 646 647 _short_lived_surv_rate_group->start_adding_regions(); 648 // Do that for any other surv rate groups 649 650 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0; 651 652 if (update_stats) { 653 double cost_per_card_ms = 0.0; 654 if (_pending_cards > 0) { 655 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS)) / (double) _pending_cards; 656 _analytics->report_cost_per_card_ms(cost_per_card_ms); 657 } 658 _analytics->report_cost_scan_hcc(scan_hcc_time_ms); 659 660 double cost_per_entry_ms = 0.0; 661 if (cards_scanned > 10) { 662 double avg_time_scan_rs = average_time_ms(G1GCPhaseTimes::ScanRS); 663 if (this_pause_was_young_only) { 664 avg_time_scan_rs += average_time_ms(G1GCPhaseTimes::OptScanRS); 665 } 666 cost_per_entry_ms = avg_time_scan_rs / cards_scanned; 667 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only); 668 } 669 670 if (_max_rs_lengths > 0) { 671 double cards_per_entry_ratio = 672 (double) cards_scanned / (double) _max_rs_lengths; 673 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only); 674 } 675 676 // This is defensive. For a while _max_rs_lengths could get 677 // smaller than _recorded_rs_lengths which was causing 678 // rs_length_diff to get very large and mess up the RSet length 679 // predictions. The reason was unsafe concurrent updates to the 680 // _inc_cset_recorded_rs_lengths field which the code below guards 681 // against (see CR 7118202). This bug has now been fixed (see CR 682 // 7119027). However, I'm still worried that 683 // _inc_cset_recorded_rs_lengths might still end up somewhat 684 // inaccurate. The concurrent refinement thread calculates an 685 // RSet's length concurrently with other CR threads updating it 686 // which might cause it to calculate the length incorrectly (if, 687 // say, it's in mid-coarsening). So I'll leave in the defensive 688 // conditional below just in case. 689 size_t rs_length_diff = 0; 690 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths(); 691 if (_max_rs_lengths > recorded_rs_lengths) { 692 rs_length_diff = _max_rs_lengths - recorded_rs_lengths; 693 } 694 _analytics->report_rs_length_diff((double) rs_length_diff); 695 696 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes; 697 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes; 698 double cost_per_byte_ms = 0.0; 699 700 if (copied_bytes > 0) { 701 cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / (double) copied_bytes; 702 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress()); 703 } 704 705 if (_collection_set->young_region_length() > 0) { 706 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 707 _collection_set->young_region_length()); 708 } 709 710 if (_collection_set->old_region_length() > 0) { 711 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 712 _collection_set->old_region_length()); 713 } 714 715 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 716 717 // Do not update RS lengths and the number of pending cards with information from mixed gc: 718 // these are is wildly different to during young only gc and mess up young gen sizing right 719 // after the mixed gc phase. 720 // During mixed gc we do not use them for young gen sizing. 721 if (this_pause_was_young_only) { 722 _analytics->report_pending_cards((double) _pending_cards); 723 _analytics->report_rs_lengths((double) _max_rs_lengths); 724 } 725 } 726 727 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()), 728 "If the last pause has been an initial mark, we should not have been in the marking window"); 729 if (this_pause_included_initial_mark) { 730 collector_state()->set_mark_or_rebuild_in_progress(true); 731 } 732 733 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 734 735 update_rs_lengths_prediction(); 736 737 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely 738 // that in this case we are not running in a "normal" operating mode. 739 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 740 // IHOP control wants to know the expected young gen length if it were not 741 // restrained by the heap reserve. Using the actual length would make the 742 // prediction too small and the limit the young gen every time we get to the 743 // predicted target occupancy. 744 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 745 746 update_ihop_prediction(app_time_ms / 1000.0, 747 _bytes_allocated_in_old_since_last_gc, 748 last_unrestrained_young_length * HeapRegion::GrainBytes, 749 this_pause_was_young_only); 750 _bytes_allocated_in_old_since_last_gc = 0; 751 752 _ihop_control->send_trace_event(_g1h->gc_tracer_stw()); 753 } else { 754 // Any garbage collection triggered as periodic collection resets the time-to-mixed 755 // measurement. Periodic collection typically means that the application is "inactive", i.e. 756 // the marking threads may have received an uncharacterisic amount of cpu time 757 // for completing the marking, i.e. are faster than expected. 758 // This skews the predicted marking length towards smaller values which might cause 759 // the mark start being too late. 760 _initial_mark_to_mixed.reset(); 761 } 762 763 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 764 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 765 766 if (update_rs_time_goal_ms < scan_hcc_time_ms) { 767 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 768 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms", 769 update_rs_time_goal_ms, scan_hcc_time_ms); 770 771 update_rs_time_goal_ms = 0; 772 } else { 773 update_rs_time_goal_ms -= scan_hcc_time_ms; 774 } 775 _g1h->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS), 776 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS), 777 update_rs_time_goal_ms); 778 } 779 780 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){ 781 if (G1UseAdaptiveIHOP) { 782 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 783 predictor, 784 G1ReservePercent, 785 G1HeapWastePercent); 786 } else { 787 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 788 } 789 } 790 791 void G1Policy::update_ihop_prediction(double mutator_time_s, 792 size_t mutator_alloc_bytes, 793 size_t young_gen_size, 794 bool this_gc_was_young_only) { 795 // Always try to update IHOP prediction. Even evacuation failures give information 796 // about e.g. whether to start IHOP earlier next time. 797 798 // Avoid using really small application times that might create samples with 799 // very high or very low values. They may be caused by e.g. back-to-back gcs. 800 double const min_valid_time = 1e-6; 801 802 bool report = false; 803 804 double marking_to_mixed_time = -1.0; 805 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) { 806 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 807 assert(marking_to_mixed_time > 0.0, 808 "Initial mark to mixed time must be larger than zero but is %.3f", 809 marking_to_mixed_time); 810 if (marking_to_mixed_time > min_valid_time) { 811 _ihop_control->update_marking_length(marking_to_mixed_time); 812 report = true; 813 } 814 } 815 816 // As an approximation for the young gc promotion rates during marking we use 817 // all of them. In many applications there are only a few if any young gcs during 818 // marking, which makes any prediction useless. This increases the accuracy of the 819 // prediction. 820 if (this_gc_was_young_only && mutator_time_s > min_valid_time) { 821 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 822 report = true; 823 } 824 825 if (report) { 826 report_ihop_statistics(); 827 } 828 } 829 830 void G1Policy::report_ihop_statistics() { 831 _ihop_control->print(); 832 } 833 834 void G1Policy::print_phases() { 835 phase_times()->print(); 836 } 837 838 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { 839 TruncatedSeq* seq = surv_rate_group->get_seq(age); 840 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); 841 double pred = _predictor.get_new_prediction(seq); 842 if (pred > 1.0) { 843 pred = 1.0; 844 } 845 return pred; 846 } 847 848 double G1Policy::accum_yg_surv_rate_pred(int age) const { 849 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 850 } 851 852 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards, 853 size_t scanned_cards) const { 854 return 855 _analytics->predict_rs_update_time_ms(pending_cards) + 856 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) + 857 _analytics->predict_constant_other_time_ms(); 858 } 859 860 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const { 861 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff(); 862 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase()); 863 return predict_base_elapsed_time_ms(pending_cards, card_num); 864 } 865 866 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const { 867 size_t bytes_to_copy; 868 if (!hr->is_young()) { 869 bytes_to_copy = hr->max_live_bytes(); 870 } else { 871 assert(hr->age_in_surv_rate_group() != -1, "invariant"); 872 int age = hr->age_in_surv_rate_group(); 873 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); 874 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); 875 } 876 return bytes_to_copy; 877 } 878 879 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr, 880 bool for_young_gc) const { 881 size_t rs_length = hr->rem_set()->occupied(); 882 // Predicting the number of cards is based on which type of GC 883 // we're predicting for. 884 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc); 885 size_t bytes_to_copy = predict_bytes_to_copy(hr); 886 887 double region_elapsed_time_ms = 888 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) + 889 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress()); 890 891 // The prediction of the "other" time for this region is based 892 // upon the region type and NOT the GC type. 893 if (hr->is_young()) { 894 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 895 } else { 896 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 897 } 898 return region_elapsed_time_ms; 899 } 900 901 bool G1Policy::should_allocate_mutator_region() const { 902 uint young_list_length = _g1h->young_regions_count(); 903 uint young_list_target_length = _young_list_target_length; 904 return young_list_length < young_list_target_length; 905 } 906 907 bool G1Policy::can_expand_young_list() const { 908 uint young_list_length = _g1h->young_regions_count(); 909 uint young_list_max_length = _young_list_max_length; 910 return young_list_length < young_list_max_length; 911 } 912 913 bool G1Policy::use_adaptive_young_list_length() const { 914 return _young_gen_sizer->use_adaptive_young_list_length(); 915 } 916 917 size_t G1Policy::desired_survivor_size(uint max_regions) const { 918 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions; 919 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 920 } 921 922 void G1Policy::print_age_table() { 923 _survivors_age_table.print_age_table(_tenuring_threshold); 924 } 925 926 void G1Policy::update_max_gc_locker_expansion() { 927 uint expansion_region_num = 0; 928 if (GCLockerEdenExpansionPercent > 0) { 929 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 930 double expansion_region_num_d = perc * (double) _young_list_target_length; 931 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 932 // less than 1.0) we'll get 1. 933 expansion_region_num = (uint) ceil(expansion_region_num_d); 934 } else { 935 assert(expansion_region_num == 0, "sanity"); 936 } 937 _young_list_max_length = _young_list_target_length + expansion_region_num; 938 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 939 } 940 941 // Calculates survivor space parameters. 942 void G1Policy::update_survivors_policy() { 943 double max_survivor_regions_d = 944 (double) _young_list_target_length / (double) SurvivorRatio; 945 946 // Calculate desired survivor size based on desired max survivor regions (unconstrained 947 // by remaining heap). Otherwise we may cause undesired promotions as we are 948 // already getting close to end of the heap, impacting performance even more. 949 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d); 950 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions); 951 952 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size); 953 if (UsePerfData) { 954 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold); 955 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize); 956 } 957 // The real maximum survivor size is bounded by the number of regions that can 958 // be allocated into. 959 _max_survivor_regions = MIN2(desired_max_survivor_regions, 960 _g1h->num_free_or_available_regions()); 961 } 962 963 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 964 // We actually check whether we are marking here and not if we are in a 965 // reclamation phase. This means that we will schedule a concurrent mark 966 // even while we are still in the process of reclaiming memory. 967 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle(); 968 if (!during_cycle) { 969 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 970 collector_state()->set_initiate_conc_mark_if_possible(true); 971 return true; 972 } else { 973 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 974 return false; 975 } 976 } 977 978 void G1Policy::initiate_conc_mark() { 979 collector_state()->set_in_initial_mark_gc(true); 980 collector_state()->set_initiate_conc_mark_if_possible(false); 981 } 982 983 void G1Policy::decide_on_conc_mark_initiation() { 984 // We are about to decide on whether this pause will be an 985 // initial-mark pause. 986 987 // First, collector_state()->in_initial_mark_gc() should not be already set. We 988 // will set it here if we have to. However, it should be cleared by 989 // the end of the pause (it's only set for the duration of an 990 // initial-mark pause). 991 assert(!collector_state()->in_initial_mark_gc(), "pre-condition"); 992 993 if (collector_state()->initiate_conc_mark_if_possible()) { 994 // We had noticed on a previous pause that the heap occupancy has 995 // gone over the initiating threshold and we should start a 996 // concurrent marking cycle. So we might initiate one. 997 998 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) { 999 // Initiate a new initial mark if there is no marking or reclamation going on. 1000 initiate_conc_mark(); 1001 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 1002 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) { 1003 // Initiate a user requested initial mark. An initial mark must be young only 1004 // GC, so the collector state must be updated to reflect this. 1005 collector_state()->set_in_young_only_phase(true); 1006 collector_state()->set_in_young_gc_before_mixed(false); 1007 1008 // We might have ended up coming here about to start a mixed phase with a collection set 1009 // active. The following remark might change the change the "evacuation efficiency" of 1010 // the regions in this set, leading to failing asserts later. 1011 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here. 1012 clear_collection_set_candidates(); 1013 abort_time_to_mixed_tracking(); 1014 initiate_conc_mark(); 1015 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 1016 } else { 1017 // The concurrent marking thread is still finishing up the 1018 // previous cycle. If we start one right now the two cycles 1019 // overlap. In particular, the concurrent marking thread might 1020 // be in the process of clearing the next marking bitmap (which 1021 // we will use for the next cycle if we start one). Starting a 1022 // cycle now will be bad given that parts of the marking 1023 // information might get cleared by the marking thread. And we 1024 // cannot wait for the marking thread to finish the cycle as it 1025 // periodically yields while clearing the next marking bitmap 1026 // and, if it's in a yield point, it's waiting for us to 1027 // finish. So, at this point we will not start a cycle and we'll 1028 // let the concurrent marking thread complete the last one. 1029 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 1030 } 1031 } 1032 } 1033 1034 void G1Policy::record_concurrent_mark_cleanup_end() { 1035 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions()); 1036 _collection_set->set_candidates(candidates); 1037 1038 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs"); 1039 if (!mixed_gc_pending) { 1040 clear_collection_set_candidates(); 1041 abort_time_to_mixed_tracking(); 1042 } 1043 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending); 1044 collector_state()->set_mark_or_rebuild_in_progress(false); 1045 1046 double end_sec = os::elapsedTime(); 1047 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1048 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1049 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1050 1051 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1052 } 1053 1054 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const { 1055 return percent_of(reclaimable_bytes, _g1h->capacity()); 1056 } 1057 1058 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure { 1059 virtual bool do_heap_region(HeapRegion* r) { 1060 r->rem_set()->clear_locked(true /* only_cardset */); 1061 return false; 1062 } 1063 }; 1064 1065 void G1Policy::clear_collection_set_candidates() { 1066 // Clear remembered sets of remaining candidate regions and the actual candidate 1067 // set. 1068 G1ClearCollectionSetCandidateRemSets cl; 1069 _collection_set->candidates()->iterate(&cl); 1070 _collection_set->clear_candidates(); 1071 } 1072 1073 void G1Policy::maybe_start_marking() { 1074 if (need_to_start_conc_mark("end of GC")) { 1075 // Note: this might have already been set, if during the last 1076 // pause we decided to start a cycle but at the beginning of 1077 // this pause we decided to postpone it. That's OK. 1078 collector_state()->set_initiate_conc_mark_if_possible(true); 1079 } 1080 } 1081 1082 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const { 1083 assert(!collector_state()->in_full_gc(), "must be"); 1084 if (collector_state()->in_initial_mark_gc()) { 1085 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1086 return InitialMarkGC; 1087 } else if (collector_state()->in_young_gc_before_mixed()) { 1088 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1089 return LastYoungGC; 1090 } else if (collector_state()->in_mixed_phase()) { 1091 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1092 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1093 return MixedGC; 1094 } else { 1095 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1096 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1097 return YoungOnlyGC; 1098 } 1099 } 1100 1101 void G1Policy::record_pause(PauseKind kind, double start, double end) { 1102 // Manage the MMU tracker. For some reason it ignores Full GCs. 1103 if (kind != FullGC) { 1104 _mmu_tracker->add_pause(start, end); 1105 } 1106 // Manage the mutator time tracking from initial mark to first mixed gc. 1107 switch (kind) { 1108 case FullGC: 1109 abort_time_to_mixed_tracking(); 1110 break; 1111 case Cleanup: 1112 case Remark: 1113 case YoungOnlyGC: 1114 case LastYoungGC: 1115 _initial_mark_to_mixed.add_pause(end - start); 1116 break; 1117 case InitialMarkGC: 1118 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 1119 _initial_mark_to_mixed.record_initial_mark_end(end); 1120 } 1121 break; 1122 case MixedGC: 1123 _initial_mark_to_mixed.record_mixed_gc_start(start); 1124 break; 1125 default: 1126 ShouldNotReachHere(); 1127 } 1128 } 1129 1130 void G1Policy::abort_time_to_mixed_tracking() { 1131 _initial_mark_to_mixed.reset(); 1132 } 1133 1134 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str, 1135 const char* false_action_str) const { 1136 G1CollectionSetCandidates* candidates = _collection_set->candidates(); 1137 1138 if (candidates->is_empty()) { 1139 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1140 return false; 1141 } 1142 1143 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1144 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1145 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1146 double threshold = (double) G1HeapWastePercent; 1147 if (reclaimable_percent <= threshold) { 1148 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1149 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1150 return false; 1151 } 1152 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1153 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1154 return true; 1155 } 1156 1157 uint G1Policy::calc_min_old_cset_length() const { 1158 // The min old CSet region bound is based on the maximum desired 1159 // number of mixed GCs after a cycle. I.e., even if some old regions 1160 // look expensive, we should add them to the CSet anyway to make 1161 // sure we go through the available old regions in no more than the 1162 // maximum desired number of mixed GCs. 1163 // 1164 // The calculation is based on the number of marked regions we added 1165 // to the CSet candidates in the first place, not how many remain, so 1166 // that the result is the same during all mixed GCs that follow a cycle. 1167 1168 const size_t region_num = _collection_set->candidates()->num_regions(); 1169 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1170 size_t result = region_num / gc_num; 1171 // emulate ceiling 1172 if (result * gc_num < region_num) { 1173 result += 1; 1174 } 1175 return (uint) result; 1176 } 1177 1178 uint G1Policy::calc_max_old_cset_length() const { 1179 // The max old CSet region bound is based on the threshold expressed 1180 // as a percentage of the heap size. I.e., it should bound the 1181 // number of old regions added to the CSet irrespective of how many 1182 // of them are available. 1183 1184 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1185 const size_t region_num = g1h->num_regions(); 1186 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1187 size_t result = region_num * perc / 100; 1188 // emulate ceiling 1189 if (100 * result < region_num * perc) { 1190 result += 1; 1191 } 1192 return (uint) result; 1193 } 1194 1195 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates, 1196 double time_remaining_ms, 1197 uint& num_initial_regions, 1198 uint& num_optional_regions) { 1199 assert(candidates != NULL, "Must be"); 1200 1201 num_initial_regions = 0; 1202 num_optional_regions = 0; 1203 uint num_expensive_regions = 0; 1204 1205 double predicted_old_time_ms = 0.0; 1206 double predicted_initial_time_ms = 0.0; 1207 double predicted_optional_time_ms = 0.0; 1208 1209 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction(); 1210 1211 const uint min_old_cset_length = calc_min_old_cset_length(); 1212 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length()); 1213 const uint max_optional_regions = max_old_cset_length - min_old_cset_length; 1214 bool check_time_remaining = use_adaptive_young_list_length(); 1215 1216 uint candidate_idx = candidates->cur_idx(); 1217 1218 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, " 1219 "time remaining %1.2fms, optional threshold %1.2fms", 1220 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms); 1221 1222 HeapRegion* hr = candidates->at(candidate_idx); 1223 while (hr != NULL) { 1224 if (num_initial_regions + num_optional_regions >= max_old_cset_length) { 1225 // Added maximum number of old regions to the CSet. 1226 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). " 1227 "Initial %u regions, optional %u regions", 1228 num_initial_regions, num_optional_regions); 1229 break; 1230 } 1231 1232 // Stop adding regions if the remaining reclaimable space is 1233 // not above G1HeapWastePercent. 1234 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1235 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1236 double threshold = (double) G1HeapWastePercent; 1237 if (reclaimable_percent <= threshold) { 1238 // We've added enough old regions that the amount of uncollected 1239 // reclaimable space is at or below the waste threshold. Stop 1240 // adding old regions to the CSet. 1241 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). " 1242 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%", 1243 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes), 1244 reclaimable_percent, G1HeapWastePercent); 1245 break; 1246 } 1247 1248 double predicted_time_ms = predict_region_elapsed_time_ms(hr, false); 1249 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0); 1250 // Add regions to old set until we reach the minimum amount 1251 if (num_initial_regions < min_old_cset_length) { 1252 predicted_old_time_ms += predicted_time_ms; 1253 num_initial_regions++; 1254 // Record the number of regions added with no time remaining 1255 if (time_remaining_ms == 0.0) { 1256 num_expensive_regions++; 1257 } 1258 } else if (!check_time_remaining) { 1259 // In the non-auto-tuning case, we'll finish adding regions 1260 // to the CSet if we reach the minimum. 1261 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min)."); 1262 break; 1263 } else { 1264 // Keep adding regions to old set until we reach the optional threshold 1265 if (time_remaining_ms > optional_threshold_ms) { 1266 predicted_old_time_ms += predicted_time_ms; 1267 num_initial_regions++; 1268 } else if (time_remaining_ms > 0) { 1269 // Keep adding optional regions until time is up. 1270 assert(num_optional_regions < max_optional_regions, "Should not be possible."); 1271 predicted_optional_time_ms += predicted_time_ms; 1272 num_optional_regions++; 1273 } else { 1274 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high)."); 1275 break; 1276 } 1277 } 1278 hr = candidates->at(++candidate_idx); 1279 } 1280 if (hr == NULL) { 1281 log_debug(gc, ergo, cset)("Old candidate collection set empty."); 1282 } 1283 1284 if (num_expensive_regions > 0) { 1285 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.", 1286 num_expensive_regions); 1287 } 1288 1289 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, " 1290 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f", 1291 num_initial_regions, num_optional_regions, 1292 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms); 1293 } 1294 1295 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates, 1296 uint const max_optional_regions, 1297 double time_remaining_ms, 1298 uint& num_optional_regions) { 1299 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase"); 1300 1301 num_optional_regions = 0; 1302 double prediction_ms = 0; 1303 uint candidate_idx = candidates->cur_idx(); 1304 1305 HeapRegion* r = candidates->at(candidate_idx); 1306 while (num_optional_regions < max_optional_regions) { 1307 assert(r != NULL, "Region must exist"); 1308 prediction_ms += predict_region_elapsed_time_ms(r, false); 1309 1310 if (prediction_ms > time_remaining_ms) { 1311 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.", 1312 prediction_ms, r->hrm_index(), time_remaining_ms); 1313 break; 1314 } 1315 // This region will be included in the next optional evacuation. 1316 1317 time_remaining_ms -= prediction_ms; 1318 num_optional_regions++; 1319 r = candidates->at(++candidate_idx); 1320 } 1321 1322 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms", 1323 num_optional_regions, max_optional_regions, prediction_ms); 1324 } 1325 1326 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) { 1327 1328 // Add survivor regions to SurvRateGroup. 1329 note_start_adding_survivor_regions(); 1330 finished_recalculating_age_indexes(true /* is_survivors */); 1331 1332 HeapRegion* last = NULL; 1333 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin(); 1334 it != survivors->regions()->end(); 1335 ++it) { 1336 HeapRegion* curr = *it; 1337 set_region_survivor(curr); 1338 1339 // The region is a non-empty survivor so let's add it to 1340 // the incremental collection set for the next evacuation 1341 // pause. 1342 _collection_set->add_survivor_regions(curr); 1343 1344 last = curr; 1345 } 1346 note_stop_adding_survivor_regions(); 1347 1348 // Don't clear the survivor list handles until the start of 1349 // the next evacuation pause - we need it in order to re-tag 1350 // the survivor regions from this evacuation pause as 'young' 1351 // at the start of the next. 1352 1353 finished_recalculating_age_indexes(false /* is_survivors */); 1354 }