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