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/g1Arguments.hpp" 28 #include "gc/g1/g1CollectedHeap.inline.hpp" 29 #include "gc/g1/g1CollectionSet.hpp" 30 #include "gc/g1/g1CollectionSetCandidates.hpp" 31 #include "gc/g1/g1ConcurrentMark.hpp" 32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 33 #include "gc/g1/g1ConcurrentRefine.hpp" 34 #include "gc/g1/g1CollectionSetChooser.hpp" 35 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp" 36 #include "gc/g1/g1HotCardCache.hpp" 37 #include "gc/g1/g1IHOPControl.hpp" 38 #include "gc/g1/g1GCPhaseTimes.hpp" 39 #include "gc/g1/g1Policy.hpp" 40 #include "gc/g1/g1SurvivorRegions.hpp" 41 #include "gc/g1/g1YoungGenSizer.hpp" 42 #include "gc/g1/heapRegion.inline.hpp" 43 #include "gc/g1/heapRegionRemSet.hpp" 44 #include "gc/shared/gcPolicyCounters.hpp" 45 #include "logging/logStream.hpp" 46 #include "runtime/arguments.hpp" 47 #include "runtime/java.hpp" 48 #include "runtime/mutexLocker.hpp" 49 #include "utilities/debug.hpp" 50 #include "utilities/growableArray.hpp" 51 #include "utilities/pair.hpp" 52 53 G1Policy::G1Policy(STWGCTimer* gc_timer) : 54 _predictor(G1ConfidencePercent / 100.0), 55 _analytics(new G1Analytics(&_predictor)), 56 _remset_tracker(), 57 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)), 58 _ihop_control(create_ihop_control(&_predictor)), 59 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)), 60 _full_collection_start_sec(0.0), 61 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC), 62 _young_list_target_length(0), 63 _young_list_fixed_length(0), 64 _young_list_max_length(0), 65 _short_lived_surv_rate_group(new SurvRateGroup()), 66 _survivor_surv_rate_group(new SurvRateGroup()), 67 _reserve_factor((double) G1ReservePercent / 100.0), 68 _reserve_regions(0), 69 _young_gen_sizer(G1YoungGenSizer::create_gen_sizer()), 70 _free_regions_at_end_of_collection(0), 71 _max_rs_lengths(0), 72 _rs_lengths_prediction(0), 73 _pending_cards(0), 74 _bytes_allocated_in_old_since_last_gc(0), 75 _initial_mark_to_mixed(), 76 _collection_set(NULL), 77 _bytes_copied_during_gc(0), 78 _g1h(NULL), 79 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)), 80 _mark_remark_start_sec(0), 81 _mark_cleanup_start_sec(0), 82 _tenuring_threshold(MaxTenuringThreshold), 83 _max_survivor_regions(0), 84 _survivors_age_table(true) 85 { 86 } 87 88 G1Policy::~G1Policy() { 89 delete _ihop_control; 90 delete _young_gen_sizer; 91 } 92 93 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) { 94 if (G1Arguments::is_heterogeneous_heap()) { 95 return new G1HeterogeneousHeapPolicy(gc_timer_stw); 96 } else { 97 return new G1Policy(gc_timer_stw); 98 } 99 } 100 101 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); } 102 103 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) { 104 _g1h = g1h; 105 _collection_set = collection_set; 106 107 assert(Heap_lock->owned_by_self(), "Locking discipline."); 108 109 if (!use_adaptive_young_list_length()) { 110 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length(); 111 } 112 _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions()); 113 114 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 115 116 update_young_list_max_and_target_length(); 117 // We may immediately start allocating regions and placing them on the 118 // collection set list. Initialize the per-collection set info 119 _collection_set->start_incremental_building(); 120 } 121 122 void G1Policy::note_gc_start() { 123 phase_times()->note_gc_start(); 124 } 125 126 class G1YoungLengthPredictor { 127 const bool _during_cm; 128 const double _base_time_ms; 129 const double _base_free_regions; 130 const double _target_pause_time_ms; 131 const G1Policy* const _policy; 132 133 public: 134 G1YoungLengthPredictor(bool during_cm, 135 double base_time_ms, 136 double base_free_regions, 137 double target_pause_time_ms, 138 const G1Policy* policy) : 139 _during_cm(during_cm), 140 _base_time_ms(base_time_ms), 141 _base_free_regions(base_free_regions), 142 _target_pause_time_ms(target_pause_time_ms), 143 _policy(policy) {} 144 145 bool will_fit(uint young_length) const { 146 if (young_length >= _base_free_regions) { 147 // end condition 1: not enough space for the young regions 148 return false; 149 } 150 151 const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1); 152 const size_t bytes_to_copy = 153 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes); 154 const double copy_time_ms = 155 _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm); 156 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length); 157 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms; 158 if (pause_time_ms > _target_pause_time_ms) { 159 // end condition 2: prediction is over the target pause time 160 return false; 161 } 162 163 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes; 164 165 // When copying, we will likely need more bytes free than is live in the region. 166 // Add some safety margin to factor in the confidence of our guess, and the 167 // natural expected waste. 168 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 169 // of the calculation: the lower the confidence, the more headroom. 170 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 171 // copying due to anticipated waste in the PLABs. 172 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 173 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 174 175 if (expected_bytes_to_copy > free_bytes) { 176 // end condition 3: out-of-space 177 return false; 178 } 179 180 // success! 181 return true; 182 } 183 }; 184 185 void G1Policy::record_new_heap_size(uint new_number_of_regions) { 186 // re-calculate the necessary reserve 187 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 188 // We use ceiling so that if reserve_regions_d is > 0.0 (but 189 // smaller than 1.0) we'll get 1. 190 _reserve_regions = (uint) ceil(reserve_regions_d); 191 192 _young_gen_sizer->heap_size_changed(new_number_of_regions); 193 194 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 195 } 196 197 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const { 198 uint desired_min_length = 0; 199 if (use_adaptive_young_list_length()) { 200 if (_analytics->num_alloc_rate_ms() > 3) { 201 double now_sec = os::elapsedTime(); 202 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 203 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 204 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 205 } else { 206 // otherwise we don't have enough info to make the prediction 207 } 208 } 209 desired_min_length += base_min_length; 210 // make sure we don't go below any user-defined minimum bound 211 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length); 212 } 213 214 uint G1Policy::calculate_young_list_desired_max_length() const { 215 // Here, we might want to also take into account any additional 216 // constraints (i.e., user-defined minimum bound). Currently, we 217 // effectively don't set this bound. 218 return _young_gen_sizer->max_desired_young_length(); 219 } 220 221 uint G1Policy::update_young_list_max_and_target_length() { 222 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths()); 223 } 224 225 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) { 226 uint unbounded_target_length = update_young_list_target_length(rs_lengths); 227 update_max_gc_locker_expansion(); 228 return unbounded_target_length; 229 } 230 231 uint G1Policy::update_young_list_target_length(size_t rs_lengths) { 232 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths); 233 _young_list_target_length = young_lengths.first; 234 235 return young_lengths.second; 236 } 237 238 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const { 239 YoungTargetLengths result; 240 241 // Calculate the absolute and desired min bounds first. 242 243 // This is how many young regions we already have (currently: the survivors). 244 const uint base_min_length = _g1h->survivor_regions_count(); 245 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 246 // This is the absolute minimum young length. Ensure that we 247 // will at least have one eden region available for allocation. 248 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1); 249 // If we shrank the young list target it should not shrink below the current size. 250 desired_min_length = MAX2(desired_min_length, absolute_min_length); 251 // Calculate the absolute and desired max bounds. 252 253 uint desired_max_length = calculate_young_list_desired_max_length(); 254 255 uint young_list_target_length = 0; 256 if (use_adaptive_young_list_length()) { 257 if (collector_state()->in_young_only_phase()) { 258 young_list_target_length = 259 calculate_young_list_target_length(rs_lengths, 260 base_min_length, 261 desired_min_length, 262 desired_max_length); 263 } else { 264 // Don't calculate anything and let the code below bound it to 265 // the desired_min_length, i.e., do the next GC as soon as 266 // possible to maximize how many old regions we can add to it. 267 } 268 } else { 269 // The user asked for a fixed young gen so we'll fix the young gen 270 // whether the next GC is young or mixed. 271 young_list_target_length = _young_list_fixed_length; 272 } 273 274 result.second = young_list_target_length; 275 276 // We will try our best not to "eat" into the reserve. 277 uint absolute_max_length = 0; 278 if (_free_regions_at_end_of_collection > _reserve_regions) { 279 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 280 } 281 if (desired_max_length > absolute_max_length) { 282 desired_max_length = absolute_max_length; 283 } 284 285 // Make sure we don't go over the desired max length, nor under the 286 // desired min length. In case they clash, desired_min_length wins 287 // which is why that test is second. 288 if (young_list_target_length > desired_max_length) { 289 young_list_target_length = desired_max_length; 290 } 291 if (young_list_target_length < desired_min_length) { 292 young_list_target_length = desired_min_length; 293 } 294 295 assert(young_list_target_length > base_min_length, 296 "we should be able to allocate at least one eden region"); 297 assert(young_list_target_length >= absolute_min_length, "post-condition"); 298 299 result.first = young_list_target_length; 300 return result; 301 } 302 303 uint 304 G1Policy::calculate_young_list_target_length(size_t rs_lengths, 305 uint base_min_length, 306 uint desired_min_length, 307 uint desired_max_length) const { 308 assert(use_adaptive_young_list_length(), "pre-condition"); 309 assert(collector_state()->in_young_only_phase(), "only call this for young GCs"); 310 311 // In case some edge-condition makes the desired max length too small... 312 if (desired_max_length <= desired_min_length) { 313 return desired_min_length; 314 } 315 316 // We'll adjust min_young_length and max_young_length not to include 317 // the already allocated young regions (i.e., so they reflect the 318 // min and max eden regions we'll allocate). The base_min_length 319 // will be reflected in the predictions by the 320 // survivor_regions_evac_time prediction. 321 assert(desired_min_length > base_min_length, "invariant"); 322 uint min_young_length = desired_min_length - base_min_length; 323 assert(desired_max_length > base_min_length, "invariant"); 324 uint max_young_length = desired_max_length - base_min_length; 325 326 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 327 const double survivor_regions_evac_time = predict_survivor_regions_evac_time(); 328 const size_t pending_cards = _analytics->predict_pending_cards(); 329 const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff(); 330 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, true /* for_young_gc */); 331 const double base_time_ms = 332 predict_base_elapsed_time_ms(pending_cards, scanned_cards) + 333 survivor_regions_evac_time; 334 const uint available_free_regions = _free_regions_at_end_of_collection; 335 const uint base_free_regions = 336 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0; 337 338 // Here, we will make sure that the shortest young length that 339 // makes sense fits within the target pause time. 340 341 G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(), 342 base_time_ms, 343 base_free_regions, 344 target_pause_time_ms, 345 this); 346 if (p.will_fit(min_young_length)) { 347 // The shortest young length will fit into the target pause time; 348 // we'll now check whether the absolute maximum number of young 349 // regions will fit in the target pause time. If not, we'll do 350 // a binary search between min_young_length and max_young_length. 351 if (p.will_fit(max_young_length)) { 352 // The maximum young length will fit into the target pause time. 353 // We are done so set min young length to the maximum length (as 354 // the result is assumed to be returned in min_young_length). 355 min_young_length = max_young_length; 356 } else { 357 // The maximum possible number of young regions will not fit within 358 // the target pause time so we'll search for the optimal 359 // length. The loop invariants are: 360 // 361 // min_young_length < max_young_length 362 // min_young_length is known to fit into the target pause time 363 // max_young_length is known not to fit into the target pause time 364 // 365 // Going into the loop we know the above hold as we've just 366 // checked them. Every time around the loop we check whether 367 // the middle value between min_young_length and 368 // max_young_length fits into the target pause time. If it 369 // does, it becomes the new min. If it doesn't, it becomes 370 // the new max. This way we maintain the loop invariants. 371 372 assert(min_young_length < max_young_length, "invariant"); 373 uint diff = (max_young_length - min_young_length) / 2; 374 while (diff > 0) { 375 uint young_length = min_young_length + diff; 376 if (p.will_fit(young_length)) { 377 min_young_length = young_length; 378 } else { 379 max_young_length = young_length; 380 } 381 assert(min_young_length < max_young_length, "invariant"); 382 diff = (max_young_length - min_young_length) / 2; 383 } 384 // The results is min_young_length which, according to the 385 // loop invariants, should fit within the target pause time. 386 387 // These are the post-conditions of the binary search above: 388 assert(min_young_length < max_young_length, 389 "otherwise we should have discovered that max_young_length " 390 "fits into the pause target and not done the binary search"); 391 assert(p.will_fit(min_young_length), 392 "min_young_length, the result of the binary search, should " 393 "fit into the pause target"); 394 assert(!p.will_fit(min_young_length + 1), 395 "min_young_length, the result of the binary search, should be " 396 "optimal, so no larger length should fit into the pause target"); 397 } 398 } else { 399 // Even the minimum length doesn't fit into the pause time 400 // target, return it as the result nevertheless. 401 } 402 return base_min_length + min_young_length; 403 } 404 405 double G1Policy::predict_survivor_regions_evac_time() const { 406 double survivor_regions_evac_time = 0.0; 407 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions(); 408 409 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin(); 410 it != survivor_regions->end(); 411 ++it) { 412 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase()); 413 } 414 return survivor_regions_evac_time; 415 } 416 417 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) { 418 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" ); 419 420 if (rs_lengths > _rs_lengths_prediction) { 421 // add 10% to avoid having to recalculate often 422 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000; 423 update_rs_lengths_prediction(rs_lengths_prediction); 424 425 update_young_list_max_and_target_length(rs_lengths_prediction); 426 } 427 } 428 429 void G1Policy::update_rs_lengths_prediction() { 430 update_rs_lengths_prediction(_analytics->predict_rs_lengths()); 431 } 432 433 void G1Policy::update_rs_lengths_prediction(size_t prediction) { 434 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) { 435 _rs_lengths_prediction = prediction; 436 } 437 } 438 439 void G1Policy::record_full_collection_start() { 440 _full_collection_start_sec = os::elapsedTime(); 441 // Release the future to-space so that it is available for compaction into. 442 collector_state()->set_in_young_only_phase(false); 443 collector_state()->set_in_full_gc(true); 444 _collection_set->clear_candidates(); 445 } 446 447 void G1Policy::record_full_collection_end() { 448 // Consider this like a collection pause for the purposes of allocation 449 // since last pause. 450 double end_sec = os::elapsedTime(); 451 double full_gc_time_sec = end_sec - _full_collection_start_sec; 452 double full_gc_time_ms = full_gc_time_sec * 1000.0; 453 454 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 455 456 collector_state()->set_in_full_gc(false); 457 458 // "Nuke" the heuristics that control the young/mixed GC 459 // transitions and make sure we start with young GCs after the Full GC. 460 collector_state()->set_in_young_only_phase(true); 461 collector_state()->set_in_young_gc_before_mixed(false); 462 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 463 collector_state()->set_in_initial_mark_gc(false); 464 collector_state()->set_mark_or_rebuild_in_progress(false); 465 collector_state()->set_clearing_next_bitmap(false); 466 467 _short_lived_surv_rate_group->start_adding_regions(); 468 // also call this on any additional surv rate groups 469 470 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 471 // Reset survivors SurvRateGroup. 472 _survivor_surv_rate_group->reset(); 473 update_young_list_max_and_target_length(); 474 update_rs_lengths_prediction(); 475 476 _bytes_allocated_in_old_since_last_gc = 0; 477 478 record_pause(FullGC, _full_collection_start_sec, end_sec); 479 } 480 481 void G1Policy::record_collection_pause_start(double start_time_sec) { 482 // We only need to do this here as the policy will only be applied 483 // to the GC we're about to start. so, no point is calculating this 484 // every time we calculate / recalculate the target young length. 485 update_survivors_policy(); 486 487 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(), 488 "Maximum survivor regions %u plus used regions %u exceeds max regions %u", 489 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions()); 490 assert_used_and_recalculate_used_equal(_g1h); 491 492 phase_times()->record_cur_collection_start_sec(start_time_sec); 493 _pending_cards = _g1h->pending_card_num(); 494 495 _collection_set->reset_bytes_used_before(); 496 _bytes_copied_during_gc = 0; 497 498 // do that for any other surv rate groups 499 _short_lived_surv_rate_group->stop_adding_regions(); 500 _survivors_age_table.clear(); 501 502 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed"); 503 } 504 505 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 506 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 507 collector_state()->set_in_initial_mark_gc(false); 508 } 509 510 void G1Policy::record_concurrent_mark_remark_start() { 511 _mark_remark_start_sec = os::elapsedTime(); 512 } 513 514 void G1Policy::record_concurrent_mark_remark_end() { 515 double end_time_sec = os::elapsedTime(); 516 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 517 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 518 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 519 520 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 521 } 522 523 void G1Policy::record_concurrent_mark_cleanup_start() { 524 _mark_cleanup_start_sec = os::elapsedTime(); 525 } 526 527 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 528 return phase_times()->average_time_ms(phase); 529 } 530 531 double G1Policy::young_other_time_ms() const { 532 return phase_times()->young_cset_choice_time_ms() + 533 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet); 534 } 535 536 double G1Policy::non_young_other_time_ms() const { 537 return phase_times()->non_young_cset_choice_time_ms() + 538 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet); 539 } 540 541 double G1Policy::other_time_ms(double pause_time_ms) const { 542 return pause_time_ms - phase_times()->cur_collection_par_time_ms(); 543 } 544 545 double G1Policy::constant_other_time_ms(double pause_time_ms) const { 546 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms(); 547 } 548 549 bool G1Policy::about_to_start_mixed_phase() const { 550 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed(); 551 } 552 553 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 554 if (about_to_start_mixed_phase()) { 555 return false; 556 } 557 558 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 559 560 size_t cur_used_bytes = _g1h->non_young_capacity_bytes(); 561 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 562 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 563 564 bool result = false; 565 if (marking_request_bytes > marking_initiating_used_threshold) { 566 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed(); 567 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 568 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 569 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source); 570 } 571 572 return result; 573 } 574 575 // Anything below that is considered to be zero 576 #define MIN_TIMER_GRANULARITY 0.0000001 577 578 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) { 579 double end_time_sec = os::elapsedTime(); 580 581 assert_used_and_recalculate_used_equal(_g1h); 582 size_t cur_used_bytes = _g1h->used(); 583 bool this_pause_included_initial_mark = false; 584 bool this_pause_was_young_only = collector_state()->in_young_only_phase(); 585 586 bool update_stats = !_g1h->evacuation_failed(); 587 588 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 589 590 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 591 592 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc(); 593 if (this_pause_included_initial_mark) { 594 record_concurrent_mark_init_end(0.0); 595 } else { 596 maybe_start_marking(); 597 } 598 599 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 600 if (app_time_ms < MIN_TIMER_GRANULARITY) { 601 // This usually happens due to the timer not having the required 602 // granularity. Some Linuxes are the usual culprits. 603 // We'll just set it to something (arbitrarily) small. 604 app_time_ms = 1.0; 605 } 606 607 if (update_stats) { 608 // We maintain the invariant that all objects allocated by mutator 609 // threads will be allocated out of eden regions. So, we can use 610 // the eden region number allocated since the previous GC to 611 // calculate the application's allocate rate. The only exception 612 // to that is humongous objects that are allocated separately. But 613 // given that humongous object allocations do not really affect 614 // either the pause's duration nor when the next pause will take 615 // place we can safely ignore them here. 616 uint regions_allocated = _collection_set->eden_region_length(); 617 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 618 _analytics->report_alloc_rate_ms(alloc_rate_ms); 619 620 double interval_ms = 621 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; 622 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 623 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms); 624 } 625 626 if (collector_state()->in_young_gc_before_mixed()) { 627 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC"); 628 // This has been the young GC before we start doing mixed GCs. We already 629 // decided to start mixed GCs much earlier, so there is nothing to do except 630 // advancing the state. 631 collector_state()->set_in_young_only_phase(false); 632 collector_state()->set_in_young_gc_before_mixed(false); 633 } else if (!this_pause_was_young_only) { 634 // This is a mixed GC. Here we decide whether to continue doing more 635 // mixed GCs or not. 636 if (!next_gc_should_be_mixed("continue mixed GCs", 637 "do not continue mixed GCs")) { 638 collector_state()->set_in_young_only_phase(true); 639 640 clear_collection_set_candidates(); 641 maybe_start_marking(); 642 } 643 } 644 645 _short_lived_surv_rate_group->start_adding_regions(); 646 // Do that for any other surv rate groups 647 648 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0; 649 650 if (update_stats) { 651 double cost_per_card_ms = 0.0; 652 if (_pending_cards > 0) { 653 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS)) / (double) _pending_cards; 654 _analytics->report_cost_per_card_ms(cost_per_card_ms); 655 } 656 _analytics->report_cost_scan_hcc(scan_hcc_time_ms); 657 658 double cost_per_entry_ms = 0.0; 659 if (cards_scanned > 10) { 660 double avg_time_scan_rs = average_time_ms(G1GCPhaseTimes::ScanRS); 661 if (this_pause_was_young_only) { 662 avg_time_scan_rs += average_time_ms(G1GCPhaseTimes::OptScanRS); 663 } 664 cost_per_entry_ms = avg_time_scan_rs / cards_scanned; 665 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only); 666 } 667 668 if (_max_rs_lengths > 0) { 669 double cards_per_entry_ratio = 670 (double) cards_scanned / (double) _max_rs_lengths; 671 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only); 672 } 673 674 // This is defensive. For a while _max_rs_lengths could get 675 // smaller than _recorded_rs_lengths which was causing 676 // rs_length_diff to get very large and mess up the RSet length 677 // predictions. The reason was unsafe concurrent updates to the 678 // _inc_cset_recorded_rs_lengths field which the code below guards 679 // against (see CR 7118202). This bug has now been fixed (see CR 680 // 7119027). However, I'm still worried that 681 // _inc_cset_recorded_rs_lengths might still end up somewhat 682 // inaccurate. The concurrent refinement thread calculates an 683 // RSet's length concurrently with other CR threads updating it 684 // which might cause it to calculate the length incorrectly (if, 685 // say, it's in mid-coarsening). So I'll leave in the defensive 686 // conditional below just in case. 687 size_t rs_length_diff = 0; 688 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths(); 689 if (_max_rs_lengths > recorded_rs_lengths) { 690 rs_length_diff = _max_rs_lengths - recorded_rs_lengths; 691 } 692 _analytics->report_rs_length_diff((double) rs_length_diff); 693 694 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes; 695 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes; 696 double cost_per_byte_ms = 0.0; 697 698 if (copied_bytes > 0) { 699 cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / (double) copied_bytes; 700 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress()); 701 } 702 703 if (_collection_set->young_region_length() > 0) { 704 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 705 _collection_set->young_region_length()); 706 } 707 708 if (_collection_set->old_region_length() > 0) { 709 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 710 _collection_set->old_region_length()); 711 } 712 713 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 714 715 // Do not update RS lengths and the number of pending cards with information from mixed gc: 716 // these are is wildly different to during young only gc and mess up young gen sizing right 717 // after the mixed gc phase. 718 // During mixed gc we do not use them for young gen sizing. 719 if (this_pause_was_young_only) { 720 _analytics->report_pending_cards((double) _pending_cards); 721 _analytics->report_rs_lengths((double) _max_rs_lengths); 722 } 723 } 724 725 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()), 726 "If the last pause has been an initial mark, we should not have been in the marking window"); 727 if (this_pause_included_initial_mark) { 728 collector_state()->set_mark_or_rebuild_in_progress(true); 729 } 730 731 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 732 733 update_rs_lengths_prediction(); 734 735 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely 736 // that in this case we are not running in a "normal" operating mode. 737 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 738 // IHOP control wants to know the expected young gen length if it were not 739 // restrained by the heap reserve. Using the actual length would make the 740 // prediction too small and the limit the young gen every time we get to the 741 // predicted target occupancy. 742 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 743 744 update_ihop_prediction(app_time_ms / 1000.0, 745 _bytes_allocated_in_old_since_last_gc, 746 last_unrestrained_young_length * HeapRegion::GrainBytes, 747 this_pause_was_young_only); 748 _bytes_allocated_in_old_since_last_gc = 0; 749 750 _ihop_control->send_trace_event(_g1h->gc_tracer_stw()); 751 } else { 752 // Any garbage collection triggered as periodic collection resets the time-to-mixed 753 // measurement. Periodic collection typically means that the application is "inactive", i.e. 754 // the marking threads may have received an uncharacterisic amount of cpu time 755 // for completing the marking, i.e. are faster than expected. 756 // This skews the predicted marking length towards smaller values which might cause 757 // the mark start being too late. 758 _initial_mark_to_mixed.reset(); 759 } 760 761 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 762 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 763 764 if (update_rs_time_goal_ms < scan_hcc_time_ms) { 765 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 766 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms", 767 update_rs_time_goal_ms, scan_hcc_time_ms); 768 769 update_rs_time_goal_ms = 0; 770 } else { 771 update_rs_time_goal_ms -= scan_hcc_time_ms; 772 } 773 _g1h->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS), 774 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS), 775 update_rs_time_goal_ms); 776 } 777 778 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){ 779 if (G1UseAdaptiveIHOP) { 780 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 781 predictor, 782 G1ReservePercent, 783 G1HeapWastePercent); 784 } else { 785 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 786 } 787 } 788 789 void G1Policy::update_ihop_prediction(double mutator_time_s, 790 size_t mutator_alloc_bytes, 791 size_t young_gen_size, 792 bool this_gc_was_young_only) { 793 // Always try to update IHOP prediction. Even evacuation failures give information 794 // about e.g. whether to start IHOP earlier next time. 795 796 // Avoid using really small application times that might create samples with 797 // very high or very low values. They may be caused by e.g. back-to-back gcs. 798 double const min_valid_time = 1e-6; 799 800 bool report = false; 801 802 double marking_to_mixed_time = -1.0; 803 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) { 804 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 805 assert(marking_to_mixed_time > 0.0, 806 "Initial mark to mixed time must be larger than zero but is %.3f", 807 marking_to_mixed_time); 808 if (marking_to_mixed_time > min_valid_time) { 809 _ihop_control->update_marking_length(marking_to_mixed_time); 810 report = true; 811 } 812 } 813 814 // As an approximation for the young gc promotion rates during marking we use 815 // all of them. In many applications there are only a few if any young gcs during 816 // marking, which makes any prediction useless. This increases the accuracy of the 817 // prediction. 818 if (this_gc_was_young_only && mutator_time_s > min_valid_time) { 819 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 820 report = true; 821 } 822 823 if (report) { 824 report_ihop_statistics(); 825 } 826 } 827 828 void G1Policy::report_ihop_statistics() { 829 _ihop_control->print(); 830 } 831 832 void G1Policy::print_phases() { 833 phase_times()->print(); 834 } 835 836 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { 837 TruncatedSeq* seq = surv_rate_group->get_seq(age); 838 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); 839 double pred = _predictor.get_new_prediction(seq); 840 if (pred > 1.0) { 841 pred = 1.0; 842 } 843 return pred; 844 } 845 846 double G1Policy::accum_yg_surv_rate_pred(int age) const { 847 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 848 } 849 850 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards, 851 size_t scanned_cards) const { 852 return 853 _analytics->predict_rs_update_time_ms(pending_cards) + 854 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) + 855 _analytics->predict_constant_other_time_ms(); 856 } 857 858 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const { 859 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff(); 860 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase()); 861 return predict_base_elapsed_time_ms(pending_cards, card_num); 862 } 863 864 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const { 865 size_t bytes_to_copy; 866 if (!hr->is_young()) { 867 bytes_to_copy = hr->max_live_bytes(); 868 } else { 869 assert(hr->age_in_surv_rate_group() != -1, "invariant"); 870 int age = hr->age_in_surv_rate_group(); 871 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); 872 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); 873 } 874 return bytes_to_copy; 875 } 876 877 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr, 878 bool for_young_gc) const { 879 size_t rs_length = hr->rem_set()->occupied(); 880 // Predicting the number of cards is based on which type of GC 881 // we're predicting for. 882 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc); 883 size_t bytes_to_copy = predict_bytes_to_copy(hr); 884 885 double region_elapsed_time_ms = 886 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) + 887 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress()); 888 889 // The prediction of the "other" time for this region is based 890 // upon the region type and NOT the GC type. 891 if (hr->is_young()) { 892 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 893 } else { 894 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 895 } 896 return region_elapsed_time_ms; 897 } 898 899 bool G1Policy::should_allocate_mutator_region() const { 900 uint young_list_length = _g1h->young_regions_count(); 901 uint young_list_target_length = _young_list_target_length; 902 return young_list_length < young_list_target_length; 903 } 904 905 bool G1Policy::can_expand_young_list() const { 906 uint young_list_length = _g1h->young_regions_count(); 907 uint young_list_max_length = _young_list_max_length; 908 return young_list_length < young_list_max_length; 909 } 910 911 bool G1Policy::use_adaptive_young_list_length() const { 912 return _young_gen_sizer->use_adaptive_young_list_length(); 913 } 914 915 size_t G1Policy::desired_survivor_size(uint max_regions) const { 916 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions; 917 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 918 } 919 920 void G1Policy::print_age_table() { 921 _survivors_age_table.print_age_table(_tenuring_threshold); 922 } 923 924 void G1Policy::update_max_gc_locker_expansion() { 925 uint expansion_region_num = 0; 926 if (GCLockerEdenExpansionPercent > 0) { 927 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 928 double expansion_region_num_d = perc * (double) _young_list_target_length; 929 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 930 // less than 1.0) we'll get 1. 931 expansion_region_num = (uint) ceil(expansion_region_num_d); 932 } else { 933 assert(expansion_region_num == 0, "sanity"); 934 } 935 _young_list_max_length = _young_list_target_length + expansion_region_num; 936 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 937 } 938 939 // Calculates survivor space parameters. 940 void G1Policy::update_survivors_policy() { 941 double max_survivor_regions_d = 942 (double) _young_list_target_length / (double) SurvivorRatio; 943 944 // Calculate desired survivor size based on desired max survivor regions (unconstrained 945 // by remaining heap). Otherwise we may cause undesired promotions as we are 946 // already getting close to end of the heap, impacting performance even more. 947 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d); 948 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions); 949 950 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size); 951 if (UsePerfData) { 952 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold); 953 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize); 954 } 955 // The real maximum survivor size is bounded by the number of regions that can 956 // be allocated into. 957 _max_survivor_regions = MIN2(desired_max_survivor_regions, 958 _g1h->num_free_or_available_regions()); 959 } 960 961 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 962 // We actually check whether we are marking here and not if we are in a 963 // reclamation phase. This means that we will schedule a concurrent mark 964 // even while we are still in the process of reclaiming memory. 965 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle(); 966 if (!during_cycle) { 967 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 968 collector_state()->set_initiate_conc_mark_if_possible(true); 969 return true; 970 } else { 971 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 972 return false; 973 } 974 } 975 976 void G1Policy::initiate_conc_mark() { 977 collector_state()->set_in_initial_mark_gc(true); 978 collector_state()->set_initiate_conc_mark_if_possible(false); 979 } 980 981 void G1Policy::decide_on_conc_mark_initiation() { 982 // We are about to decide on whether this pause will be an 983 // initial-mark pause. 984 985 // First, collector_state()->in_initial_mark_gc() should not be already set. We 986 // will set it here if we have to. However, it should be cleared by 987 // the end of the pause (it's only set for the duration of an 988 // initial-mark pause). 989 assert(!collector_state()->in_initial_mark_gc(), "pre-condition"); 990 991 if (collector_state()->initiate_conc_mark_if_possible()) { 992 // We had noticed on a previous pause that the heap occupancy has 993 // gone over the initiating threshold and we should start a 994 // concurrent marking cycle. So we might initiate one. 995 996 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) { 997 // Initiate a new initial mark if there is no marking or reclamation going on. 998 initiate_conc_mark(); 999 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 1000 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) { 1001 // Initiate a user requested initial mark. An initial mark must be young only 1002 // GC, so the collector state must be updated to reflect this. 1003 collector_state()->set_in_young_only_phase(true); 1004 collector_state()->set_in_young_gc_before_mixed(false); 1005 1006 // We might have ended up coming here about to start a mixed phase with a collection set 1007 // active. The following remark might change the change the "evacuation efficiency" of 1008 // the regions in this set, leading to failing asserts later. 1009 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here. 1010 clear_collection_set_candidates(); 1011 abort_time_to_mixed_tracking(); 1012 initiate_conc_mark(); 1013 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 1014 } else { 1015 // The concurrent marking thread is still finishing up the 1016 // previous cycle. If we start one right now the two cycles 1017 // overlap. In particular, the concurrent marking thread might 1018 // be in the process of clearing the next marking bitmap (which 1019 // we will use for the next cycle if we start one). Starting a 1020 // cycle now will be bad given that parts of the marking 1021 // information might get cleared by the marking thread. And we 1022 // cannot wait for the marking thread to finish the cycle as it 1023 // periodically yields while clearing the next marking bitmap 1024 // and, if it's in a yield point, it's waiting for us to 1025 // finish. So, at this point we will not start a cycle and we'll 1026 // let the concurrent marking thread complete the last one. 1027 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 1028 } 1029 } 1030 } 1031 1032 void G1Policy::record_concurrent_mark_cleanup_end() { 1033 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions()); 1034 _collection_set->set_candidates(candidates); 1035 1036 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs"); 1037 if (!mixed_gc_pending) { 1038 clear_collection_set_candidates(); 1039 abort_time_to_mixed_tracking(); 1040 } 1041 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending); 1042 collector_state()->set_mark_or_rebuild_in_progress(false); 1043 1044 double end_sec = os::elapsedTime(); 1045 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1046 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1047 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1048 1049 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1050 } 1051 1052 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const { 1053 return percent_of(reclaimable_bytes, _g1h->capacity()); 1054 } 1055 1056 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure { 1057 virtual bool do_heap_region(HeapRegion* r) { 1058 r->rem_set()->clear_locked(true /* only_cardset */); 1059 return false; 1060 } 1061 }; 1062 1063 void G1Policy::clear_collection_set_candidates() { 1064 // Clear remembered sets of remaining candidate regions and the actual candidate 1065 // set. 1066 G1ClearCollectionSetCandidateRemSets cl; 1067 _collection_set->candidates()->iterate(&cl); 1068 _collection_set->clear_candidates(); 1069 } 1070 1071 void G1Policy::maybe_start_marking() { 1072 if (need_to_start_conc_mark("end of GC")) { 1073 // Note: this might have already been set, if during the last 1074 // pause we decided to start a cycle but at the beginning of 1075 // this pause we decided to postpone it. That's OK. 1076 collector_state()->set_initiate_conc_mark_if_possible(true); 1077 } 1078 } 1079 1080 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const { 1081 assert(!collector_state()->in_full_gc(), "must be"); 1082 if (collector_state()->in_initial_mark_gc()) { 1083 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1084 return InitialMarkGC; 1085 } else if (collector_state()->in_young_gc_before_mixed()) { 1086 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1087 return LastYoungGC; 1088 } else if (collector_state()->in_mixed_phase()) { 1089 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1090 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1091 return MixedGC; 1092 } else { 1093 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1094 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1095 return YoungOnlyGC; 1096 } 1097 } 1098 1099 void G1Policy::record_pause(PauseKind kind, double start, double end) { 1100 // Manage the MMU tracker. For some reason it ignores Full GCs. 1101 if (kind != FullGC) { 1102 _mmu_tracker->add_pause(start, end); 1103 } 1104 // Manage the mutator time tracking from initial mark to first mixed gc. 1105 switch (kind) { 1106 case FullGC: 1107 abort_time_to_mixed_tracking(); 1108 break; 1109 case Cleanup: 1110 case Remark: 1111 case YoungOnlyGC: 1112 case LastYoungGC: 1113 _initial_mark_to_mixed.add_pause(end - start); 1114 break; 1115 case InitialMarkGC: 1116 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 1117 _initial_mark_to_mixed.record_initial_mark_end(end); 1118 } 1119 break; 1120 case MixedGC: 1121 _initial_mark_to_mixed.record_mixed_gc_start(start); 1122 break; 1123 default: 1124 ShouldNotReachHere(); 1125 } 1126 } 1127 1128 void G1Policy::abort_time_to_mixed_tracking() { 1129 _initial_mark_to_mixed.reset(); 1130 } 1131 1132 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str, 1133 const char* false_action_str) const { 1134 G1CollectionSetCandidates* candidates = _collection_set->candidates(); 1135 1136 if (candidates->is_empty()) { 1137 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1138 return false; 1139 } 1140 1141 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1142 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1143 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1144 double threshold = (double) G1HeapWastePercent; 1145 if (reclaimable_percent <= threshold) { 1146 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1147 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1148 return false; 1149 } 1150 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1151 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1152 return true; 1153 } 1154 1155 uint G1Policy::calc_min_old_cset_length() const { 1156 // The min old CSet region bound is based on the maximum desired 1157 // number of mixed GCs after a cycle. I.e., even if some old regions 1158 // look expensive, we should add them to the CSet anyway to make 1159 // sure we go through the available old regions in no more than the 1160 // maximum desired number of mixed GCs. 1161 // 1162 // The calculation is based on the number of marked regions we added 1163 // to the CSet candidates in the first place, not how many remain, so 1164 // that the result is the same during all mixed GCs that follow a cycle. 1165 1166 const size_t region_num = _collection_set->candidates()->num_regions(); 1167 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1168 size_t result = region_num / gc_num; 1169 // emulate ceiling 1170 if (result * gc_num < region_num) { 1171 result += 1; 1172 } 1173 return (uint) result; 1174 } 1175 1176 uint G1Policy::calc_max_old_cset_length() const { 1177 // The max old CSet region bound is based on the threshold expressed 1178 // as a percentage of the heap size. I.e., it should bound the 1179 // number of old regions added to the CSet irrespective of how many 1180 // of them are available. 1181 1182 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1183 const size_t region_num = g1h->num_regions(); 1184 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1185 size_t result = region_num * perc / 100; 1186 // emulate ceiling 1187 if (100 * result < region_num * perc) { 1188 result += 1; 1189 } 1190 return (uint) result; 1191 } 1192 1193 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates, 1194 double time_remaining_ms, 1195 uint& num_initial_regions, 1196 uint& num_optional_regions) { 1197 assert(candidates != NULL, "Must be"); 1198 1199 num_initial_regions = 0; 1200 num_optional_regions = 0; 1201 uint num_expensive_regions = 0; 1202 1203 double predicted_old_time_ms = 0.0; 1204 double predicted_initial_time_ms = 0.0; 1205 double predicted_optional_time_ms = 0.0; 1206 1207 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction(); 1208 1209 const uint min_old_cset_length = calc_min_old_cset_length(); 1210 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length()); 1211 const uint max_optional_regions = max_old_cset_length - min_old_cset_length; 1212 bool check_time_remaining = use_adaptive_young_list_length(); 1213 1214 uint candidate_idx = candidates->cur_idx(); 1215 1216 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, " 1217 "time remaining %1.2fms, optional threshold %1.2fms", 1218 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms); 1219 1220 HeapRegion* hr = candidates->at(candidate_idx); 1221 while (hr != NULL) { 1222 if (num_initial_regions + num_optional_regions >= max_old_cset_length) { 1223 // Added maximum number of old regions to the CSet. 1224 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). " 1225 "Initial %u regions, optional %u regions", 1226 num_initial_regions, num_optional_regions); 1227 break; 1228 } 1229 1230 // Stop adding regions if the remaining reclaimable space is 1231 // not above G1HeapWastePercent. 1232 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1233 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1234 double threshold = (double) G1HeapWastePercent; 1235 if (reclaimable_percent <= threshold) { 1236 // We've added enough old regions that the amount of uncollected 1237 // reclaimable space is at or below the waste threshold. Stop 1238 // adding old regions to the CSet. 1239 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). " 1240 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%", 1241 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes), 1242 reclaimable_percent, G1HeapWastePercent); 1243 break; 1244 } 1245 1246 double predicted_time_ms = predict_region_elapsed_time_ms(hr, false); 1247 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0); 1248 // Add regions to old set until we reach the minimum amount 1249 if (num_initial_regions < min_old_cset_length) { 1250 predicted_old_time_ms += predicted_time_ms; 1251 num_initial_regions++; 1252 // Record the number of regions added with no time remaining 1253 if (time_remaining_ms == 0.0) { 1254 num_expensive_regions++; 1255 } 1256 } else if (!check_time_remaining) { 1257 // In the non-auto-tuning case, we'll finish adding regions 1258 // to the CSet if we reach the minimum. 1259 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min)."); 1260 break; 1261 } else { 1262 // Keep adding regions to old set until we reach the optional threshold 1263 if (time_remaining_ms > optional_threshold_ms) { 1264 predicted_old_time_ms += predicted_time_ms; 1265 num_initial_regions++; 1266 } else if (time_remaining_ms > 0) { 1267 // Keep adding optional regions until time is up. 1268 assert(num_optional_regions < max_optional_regions, "Should not be possible."); 1269 predicted_optional_time_ms += predicted_time_ms; 1270 num_optional_regions++; 1271 } else { 1272 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high)."); 1273 break; 1274 } 1275 } 1276 hr = candidates->at(++candidate_idx); 1277 } 1278 if (hr == NULL) { 1279 log_debug(gc, ergo, cset)("Old candidate collection set empty."); 1280 } 1281 1282 if (num_expensive_regions > 0) { 1283 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.", 1284 num_expensive_regions); 1285 } 1286 1287 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, " 1288 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f", 1289 num_initial_regions, num_optional_regions, 1290 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms); 1291 } 1292 1293 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates, 1294 uint const max_optional_regions, 1295 double time_remaining_ms, 1296 uint& num_optional_regions) { 1297 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase"); 1298 1299 num_optional_regions = 0; 1300 double prediction_ms = 0; 1301 uint candidate_idx = candidates->cur_idx(); 1302 1303 HeapRegion* r = candidates->at(candidate_idx); 1304 while (num_optional_regions < max_optional_regions) { 1305 assert(r != NULL, "Region must exist"); 1306 prediction_ms += predict_region_elapsed_time_ms(r, false); 1307 1308 if (prediction_ms > time_remaining_ms) { 1309 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.", 1310 prediction_ms, r->hrm_index(), time_remaining_ms); 1311 break; 1312 } 1313 // This region will be included in the next optional evacuation. 1314 1315 time_remaining_ms -= prediction_ms; 1316 num_optional_regions++; 1317 r = candidates->at(++candidate_idx); 1318 } 1319 1320 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms", 1321 num_optional_regions, max_optional_regions, prediction_ms); 1322 } 1323 1324 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) { 1325 1326 // Add survivor regions to SurvRateGroup. 1327 note_start_adding_survivor_regions(); 1328 finished_recalculating_age_indexes(true /* is_survivors */); 1329 1330 HeapRegion* last = NULL; 1331 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin(); 1332 it != survivors->regions()->end(); 1333 ++it) { 1334 HeapRegion* curr = *it; 1335 set_region_survivor(curr); 1336 1337 // The region is a non-empty survivor so let's add it to 1338 // the incremental collection set for the next evacuation 1339 // pause. 1340 _collection_set->add_survivor_regions(curr); 1341 1342 last = curr; 1343 } 1344 note_stop_adding_survivor_regions(); 1345 1346 // Don't clear the survivor list handles until the start of 1347 // the next evacuation pause - we need it in order to re-tag 1348 // the survivor regions from this evacuation pause as 'young' 1349 // at the start of the next. 1350 1351 finished_recalculating_age_indexes(false /* is_survivors */); 1352 }