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 _rs_length(0), 72 _rs_length_prediction(0), 73 _pending_cards_at_gc_start(0), 74 _pending_cards_at_prev_gc_end(0), 75 _total_mutator_refined_cards(0), 76 _total_concurrent_refined_cards(0), 77 _total_concurrent_refinement_time(), 78 _bytes_allocated_in_old_since_last_gc(0), 79 _initial_mark_to_mixed(), 80 _collection_set(NULL), 81 _g1h(NULL), 82 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)), 83 _mark_remark_start_sec(0), 84 _mark_cleanup_start_sec(0), 85 _tenuring_threshold(MaxTenuringThreshold), 86 _max_survivor_regions(0), 87 _survivors_age_table(true) 88 { 89 } 90 91 G1Policy::~G1Policy() { 92 delete _ihop_control; 93 delete _young_gen_sizer; 94 } 95 96 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) { 97 if (G1Arguments::is_heterogeneous_heap()) { 98 return new G1HeterogeneousHeapPolicy(gc_timer_stw); 99 } else { 100 return new G1Policy(gc_timer_stw); 101 } 102 } 103 104 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); } 105 106 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) { 107 _g1h = g1h; 108 _collection_set = collection_set; 109 110 assert(Heap_lock->owned_by_self(), "Locking discipline."); 111 112 if (!use_adaptive_young_list_length()) { 113 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length(); 114 } 115 _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions()); 116 117 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 118 119 update_young_list_max_and_target_length(); 120 // We may immediately start allocating regions and placing them on the 121 // collection set list. Initialize the per-collection set info 122 _collection_set->start_incremental_building(); 123 } 124 125 void G1Policy::note_gc_start() { 126 phase_times()->note_gc_start(); 127 } 128 129 class G1YoungLengthPredictor { 130 const bool _during_cm; 131 const double _base_time_ms; 132 const double _base_free_regions; 133 const double _target_pause_time_ms; 134 const G1Policy* const _policy; 135 136 public: 137 G1YoungLengthPredictor(bool during_cm, 138 double base_time_ms, 139 double base_free_regions, 140 double target_pause_time_ms, 141 const G1Policy* policy) : 142 _during_cm(during_cm), 143 _base_time_ms(base_time_ms), 144 _base_free_regions(base_free_regions), 145 _target_pause_time_ms(target_pause_time_ms), 146 _policy(policy) {} 147 148 bool will_fit(uint young_length) const { 149 if (young_length >= _base_free_regions) { 150 // end condition 1: not enough space for the young regions 151 return false; 152 } 153 154 const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1); 155 const size_t bytes_to_copy = 156 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes); 157 const double copy_time_ms = 158 _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm); 159 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length); 160 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms; 161 if (pause_time_ms > _target_pause_time_ms) { 162 // end condition 2: prediction is over the target pause time 163 return false; 164 } 165 166 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes; 167 168 // When copying, we will likely need more bytes free than is live in the region. 169 // Add some safety margin to factor in the confidence of our guess, and the 170 // natural expected waste. 171 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 172 // of the calculation: the lower the confidence, the more headroom. 173 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 174 // copying due to anticipated waste in the PLABs. 175 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 176 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 177 178 if (expected_bytes_to_copy > free_bytes) { 179 // end condition 3: out-of-space 180 return false; 181 } 182 183 // success! 184 return true; 185 } 186 }; 187 188 void G1Policy::record_new_heap_size(uint new_number_of_regions) { 189 // re-calculate the necessary reserve 190 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 191 // We use ceiling so that if reserve_regions_d is > 0.0 (but 192 // smaller than 1.0) we'll get 1. 193 _reserve_regions = (uint) ceil(reserve_regions_d); 194 195 _young_gen_sizer->heap_size_changed(new_number_of_regions); 196 197 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 198 } 199 200 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const { 201 uint desired_min_length = 0; 202 if (use_adaptive_young_list_length()) { 203 if (_analytics->num_alloc_rate_ms() > 3) { 204 double now_sec = os::elapsedTime(); 205 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 206 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 207 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 208 } else { 209 // otherwise we don't have enough info to make the prediction 210 } 211 } 212 desired_min_length += base_min_length; 213 // make sure we don't go below any user-defined minimum bound 214 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length); 215 } 216 217 uint G1Policy::calculate_young_list_desired_max_length() const { 218 // Here, we might want to also take into account any additional 219 // constraints (i.e., user-defined minimum bound). Currently, we 220 // effectively don't set this bound. 221 return _young_gen_sizer->max_desired_young_length(); 222 } 223 224 uint G1Policy::update_young_list_max_and_target_length() { 225 return update_young_list_max_and_target_length(_analytics->predict_rs_length()); 226 } 227 228 uint G1Policy::update_young_list_max_and_target_length(size_t rs_length) { 229 uint unbounded_target_length = update_young_list_target_length(rs_length); 230 update_max_gc_locker_expansion(); 231 return unbounded_target_length; 232 } 233 234 uint G1Policy::update_young_list_target_length(size_t rs_length) { 235 YoungTargetLengths young_lengths = young_list_target_lengths(rs_length); 236 _young_list_target_length = young_lengths.first; 237 238 return young_lengths.second; 239 } 240 241 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_length) const { 242 YoungTargetLengths result; 243 244 // Calculate the absolute and desired min bounds first. 245 246 // This is how many young regions we already have (currently: the survivors). 247 const uint base_min_length = _g1h->survivor_regions_count(); 248 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 249 // This is the absolute minimum young length. Ensure that we 250 // will at least have one eden region available for allocation. 251 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1); 252 // If we shrank the young list target it should not shrink below the current size. 253 desired_min_length = MAX2(desired_min_length, absolute_min_length); 254 // Calculate the absolute and desired max bounds. 255 256 uint desired_max_length = calculate_young_list_desired_max_length(); 257 258 uint young_list_target_length = 0; 259 if (use_adaptive_young_list_length()) { 260 if (collector_state()->in_young_only_phase()) { 261 young_list_target_length = 262 calculate_young_list_target_length(rs_length, 263 base_min_length, 264 desired_min_length, 265 desired_max_length); 266 } else { 267 // Don't calculate anything and let the code below bound it to 268 // the desired_min_length, i.e., do the next GC as soon as 269 // possible to maximize how many old regions we can add to it. 270 } 271 } else { 272 // The user asked for a fixed young gen so we'll fix the young gen 273 // whether the next GC is young or mixed. 274 young_list_target_length = _young_list_fixed_length; 275 } 276 277 result.second = young_list_target_length; 278 279 // We will try our best not to "eat" into the reserve. 280 uint absolute_max_length = 0; 281 if (_free_regions_at_end_of_collection > _reserve_regions) { 282 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 283 } 284 if (desired_max_length > absolute_max_length) { 285 desired_max_length = absolute_max_length; 286 } 287 288 // Make sure we don't go over the desired max length, nor under the 289 // desired min length. In case they clash, desired_min_length wins 290 // which is why that test is second. 291 if (young_list_target_length > desired_max_length) { 292 young_list_target_length = desired_max_length; 293 } 294 if (young_list_target_length < desired_min_length) { 295 young_list_target_length = desired_min_length; 296 } 297 298 assert(young_list_target_length > base_min_length, 299 "we should be able to allocate at least one eden region"); 300 assert(young_list_target_length >= absolute_min_length, "post-condition"); 301 302 result.first = young_list_target_length; 303 return result; 304 } 305 306 uint 307 G1Policy::calculate_young_list_target_length(size_t rs_length, 308 uint base_min_length, 309 uint desired_min_length, 310 uint desired_max_length) const { 311 assert(use_adaptive_young_list_length(), "pre-condition"); 312 assert(collector_state()->in_young_only_phase(), "only call this for young GCs"); 313 314 // In case some edge-condition makes the desired max length too small... 315 if (desired_max_length <= desired_min_length) { 316 return desired_min_length; 317 } 318 319 // We'll adjust min_young_length and max_young_length not to include 320 // the already allocated young regions (i.e., so they reflect the 321 // min and max eden regions we'll allocate). The base_min_length 322 // will be reflected in the predictions by the 323 // survivor_regions_evac_time prediction. 324 assert(desired_min_length > base_min_length, "invariant"); 325 uint min_young_length = desired_min_length - base_min_length; 326 assert(desired_max_length > base_min_length, "invariant"); 327 uint max_young_length = desired_max_length - base_min_length; 328 329 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 330 const double survivor_regions_evac_time = predict_survivor_regions_evac_time(); 331 const size_t pending_cards = _analytics->predict_pending_cards(); 332 const double base_time_ms = 333 predict_base_elapsed_time_ms(pending_cards, rs_length) + 334 survivor_regions_evac_time; 335 const uint available_free_regions = _free_regions_at_end_of_collection; 336 const uint base_free_regions = 337 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0; 338 339 // Here, we will make sure that the shortest young length that 340 // makes sense fits within the target pause time. 341 342 G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(), 343 base_time_ms, 344 base_free_regions, 345 target_pause_time_ms, 346 this); 347 if (p.will_fit(min_young_length)) { 348 // The shortest young length will fit into the target pause time; 349 // we'll now check whether the absolute maximum number of young 350 // regions will fit in the target pause time. If not, we'll do 351 // a binary search between min_young_length and max_young_length. 352 if (p.will_fit(max_young_length)) { 353 // The maximum young length will fit into the target pause time. 354 // We are done so set min young length to the maximum length (as 355 // the result is assumed to be returned in min_young_length). 356 min_young_length = max_young_length; 357 } else { 358 // The maximum possible number of young regions will not fit within 359 // the target pause time so we'll search for the optimal 360 // length. The loop invariants are: 361 // 362 // min_young_length < max_young_length 363 // min_young_length is known to fit into the target pause time 364 // max_young_length is known not to fit into the target pause time 365 // 366 // Going into the loop we know the above hold as we've just 367 // checked them. Every time around the loop we check whether 368 // the middle value between min_young_length and 369 // max_young_length fits into the target pause time. If it 370 // does, it becomes the new min. If it doesn't, it becomes 371 // the new max. This way we maintain the loop invariants. 372 373 assert(min_young_length < max_young_length, "invariant"); 374 uint diff = (max_young_length - min_young_length) / 2; 375 while (diff > 0) { 376 uint young_length = min_young_length + diff; 377 if (p.will_fit(young_length)) { 378 min_young_length = young_length; 379 } else { 380 max_young_length = young_length; 381 } 382 assert(min_young_length < max_young_length, "invariant"); 383 diff = (max_young_length - min_young_length) / 2; 384 } 385 // The results is min_young_length which, according to the 386 // loop invariants, should fit within the target pause time. 387 388 // These are the post-conditions of the binary search above: 389 assert(min_young_length < max_young_length, 390 "otherwise we should have discovered that max_young_length " 391 "fits into the pause target and not done the binary search"); 392 assert(p.will_fit(min_young_length), 393 "min_young_length, the result of the binary search, should " 394 "fit into the pause target"); 395 assert(!p.will_fit(min_young_length + 1), 396 "min_young_length, the result of the binary search, should be " 397 "optimal, so no larger length should fit into the pause target"); 398 } 399 } else { 400 // Even the minimum length doesn't fit into the pause time 401 // target, return it as the result nevertheless. 402 } 403 return base_min_length + min_young_length; 404 } 405 406 double G1Policy::predict_survivor_regions_evac_time() const { 407 double survivor_regions_evac_time = 0.0; 408 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions(); 409 410 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin(); 411 it != survivor_regions->end(); 412 ++it) { 413 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase()); 414 } 415 return survivor_regions_evac_time; 416 } 417 418 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_length) { 419 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" ); 420 421 if (rs_length > _rs_length_prediction) { 422 // add 10% to avoid having to recalculate often 423 size_t rs_length_prediction = rs_length * 1100 / 1000; 424 update_rs_length_prediction(rs_length_prediction); 425 426 update_young_list_max_and_target_length(rs_length_prediction); 427 } 428 } 429 430 void G1Policy::update_rs_length_prediction() { 431 update_rs_length_prediction(_analytics->predict_rs_length()); 432 } 433 434 void G1Policy::update_rs_length_prediction(size_t prediction) { 435 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) { 436 _rs_length_prediction = prediction; 437 } 438 } 439 440 void G1Policy::record_full_collection_start() { 441 _full_collection_start_sec = os::elapsedTime(); 442 // Release the future to-space so that it is available for compaction into. 443 collector_state()->set_in_young_only_phase(false); 444 collector_state()->set_in_full_gc(true); 445 _collection_set->clear_candidates(); 446 record_concurrent_refinement_data(true /* is_full_collection */); 447 } 448 449 void G1Policy::record_full_collection_end() { 450 // Consider this like a collection pause for the purposes of allocation 451 // since last pause. 452 double end_sec = os::elapsedTime(); 453 double full_gc_time_sec = end_sec - _full_collection_start_sec; 454 double full_gc_time_ms = full_gc_time_sec * 1000.0; 455 456 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 457 458 collector_state()->set_in_full_gc(false); 459 460 // "Nuke" the heuristics that control the young/mixed GC 461 // transitions and make sure we start with young GCs after the Full GC. 462 collector_state()->set_in_young_only_phase(true); 463 collector_state()->set_in_young_gc_before_mixed(false); 464 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 465 collector_state()->set_in_initial_mark_gc(false); 466 collector_state()->set_mark_or_rebuild_in_progress(false); 467 collector_state()->set_clearing_next_bitmap(false); 468 469 _short_lived_surv_rate_group->start_adding_regions(); 470 // also call this on any additional surv rate groups 471 472 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 473 // Reset survivors SurvRateGroup. 474 _survivor_surv_rate_group->reset(); 475 update_young_list_max_and_target_length(); 476 update_rs_length_prediction(); 477 _pending_cards_at_prev_gc_end = _g1h->pending_card_num(); 478 479 _bytes_allocated_in_old_since_last_gc = 0; 480 481 record_pause(FullGC, _full_collection_start_sec, end_sec); 482 } 483 484 void G1Policy::record_concurrent_refinement_data(bool is_full_collection) { 485 _pending_cards_at_gc_start = _g1h->pending_card_num(); 486 487 // Record info about concurrent refinement thread processing. 488 G1ConcurrentRefine* cr = _g1h->concurrent_refine(); 489 G1ConcurrentRefine::RefinementStats cr_stats = cr->total_refinement_stats(); 490 491 Tickspan cr_time = cr_stats._time - _total_concurrent_refinement_time; 492 _total_concurrent_refinement_time = cr_stats._time; 493 494 size_t cr_cards = cr_stats._cards - _total_concurrent_refined_cards; 495 _total_concurrent_refined_cards = cr_stats._cards; 496 497 // Don't update rate if full collection. We could be in an implicit full 498 // collection after a non-full collection failure, in which case there 499 // wasn't any mutator/cr-thread activity since last recording. And if 500 // we're in an explicit full collection, the time since the last GC can 501 // be arbitrarily short, so not a very good sample. Similarly, don't 502 // update the rate if the current sample is empty or time is zero. 503 if (!is_full_collection && (cr_cards > 0) && (cr_time > Tickspan())) { 504 double rate = cr_cards / (cr_time.seconds() * MILLIUNITS); 505 _analytics->report_concurrent_refine_rate_ms(rate); 506 } 507 508 // Record info about mutator thread processing. 509 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 510 size_t mut_total_cards = dcqs.total_mutator_refined_cards(); 511 size_t mut_cards = mut_total_cards - _total_mutator_refined_cards; 512 _total_mutator_refined_cards = mut_total_cards; 513 514 // Record mutator's card logging rate. 515 // Don't update if full collection; see above. 516 if (!is_full_collection) { 517 size_t total_cards = _pending_cards_at_gc_start + cr_cards + mut_cards; 518 assert(_pending_cards_at_prev_gc_end <= total_cards, 519 "untracked cards: last pending: " SIZE_FORMAT 520 ", pending: " SIZE_FORMAT ", conc refine: " SIZE_FORMAT 521 ", mut refine:" SIZE_FORMAT, 522 _pending_cards_at_prev_gc_end, _pending_cards_at_gc_start, 523 cr_cards, mut_cards); 524 size_t logged_cards = total_cards - _pending_cards_at_prev_gc_end; 525 double logging_start_time = _analytics->prev_collection_pause_end_ms(); 526 double logging_end_time = Ticks::now().seconds() * MILLIUNITS; 527 double logging_time = logging_end_time - logging_start_time; 528 // Unlike above for conc-refine rate, here we should not require a 529 // non-empty sample, since an application could go some time with only 530 // young-gen or filtered out writes. But we'll ignore unusually short 531 // sample periods, as they may just pollute the predictions. 532 if (logging_time > 1.0) { // Require > 1ms sample time. 533 _analytics->report_logged_cards_rate_ms(logged_cards / logging_time); 534 } 535 } 536 } 537 538 void G1Policy::record_collection_pause_start(double start_time_sec) { 539 // We only need to do this here as the policy will only be applied 540 // to the GC we're about to start. so, no point is calculating this 541 // every time we calculate / recalculate the target young length. 542 update_survivors_policy(); 543 544 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(), 545 "Maximum survivor regions %u plus used regions %u exceeds max regions %u", 546 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions()); 547 assert_used_and_recalculate_used_equal(_g1h); 548 549 phase_times()->record_cur_collection_start_sec(start_time_sec); 550 551 record_concurrent_refinement_data(false /* is_full_collection */); 552 553 _collection_set->reset_bytes_used_before(); 554 555 // do that for any other surv rate groups 556 _short_lived_surv_rate_group->stop_adding_regions(); 557 _survivors_age_table.clear(); 558 559 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed"); 560 } 561 562 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 563 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 564 collector_state()->set_in_initial_mark_gc(false); 565 } 566 567 void G1Policy::record_concurrent_mark_remark_start() { 568 _mark_remark_start_sec = os::elapsedTime(); 569 } 570 571 void G1Policy::record_concurrent_mark_remark_end() { 572 double end_time_sec = os::elapsedTime(); 573 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 574 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 575 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 576 577 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 578 } 579 580 void G1Policy::record_concurrent_mark_cleanup_start() { 581 _mark_cleanup_start_sec = os::elapsedTime(); 582 } 583 584 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 585 return phase_times()->average_time_ms(phase); 586 } 587 588 double G1Policy::young_other_time_ms() const { 589 return phase_times()->young_cset_choice_time_ms() + 590 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet); 591 } 592 593 double G1Policy::non_young_other_time_ms() const { 594 return phase_times()->non_young_cset_choice_time_ms() + 595 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet); 596 } 597 598 double G1Policy::other_time_ms(double pause_time_ms) const { 599 return pause_time_ms - phase_times()->cur_collection_par_time_ms(); 600 } 601 602 double G1Policy::constant_other_time_ms(double pause_time_ms) const { 603 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms(); 604 } 605 606 bool G1Policy::about_to_start_mixed_phase() const { 607 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed(); 608 } 609 610 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 611 if (about_to_start_mixed_phase()) { 612 return false; 613 } 614 615 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 616 617 size_t cur_used_bytes = _g1h->non_young_capacity_bytes(); 618 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 619 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 620 621 bool result = false; 622 if (marking_request_bytes > marking_initiating_used_threshold) { 623 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed(); 624 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 625 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 626 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source); 627 } 628 629 return result; 630 } 631 632 double G1Policy::logged_cards_processing_time() const { 633 double all_cards_processing_time = average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR); 634 size_t logged_dirty_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards); 635 size_t scan_heap_roots_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) + 636 phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards); 637 // This may happen if there are duplicate cards in different log buffers. 638 if (logged_dirty_cards > scan_heap_roots_cards) { 639 return all_cards_processing_time + average_time_ms(G1GCPhaseTimes::MergeLB); 640 } 641 return (all_cards_processing_time * logged_dirty_cards / scan_heap_roots_cards) + average_time_ms(G1GCPhaseTimes::MergeLB); 642 } 643 644 // Anything below that is considered to be zero 645 #define MIN_TIMER_GRANULARITY 0.0000001 646 647 void G1Policy::record_collection_pause_end(double pause_time_ms) { 648 G1GCPhaseTimes* p = phase_times(); 649 650 double end_time_sec = os::elapsedTime(); 651 652 bool this_pause_included_initial_mark = false; 653 bool this_pause_was_young_only = collector_state()->in_young_only_phase(); 654 655 bool update_stats = !_g1h->evacuation_failed(); 656 657 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 658 659 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 660 661 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc(); 662 if (this_pause_included_initial_mark) { 663 record_concurrent_mark_init_end(0.0); 664 } else { 665 maybe_start_marking(); 666 } 667 668 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 669 if (app_time_ms < MIN_TIMER_GRANULARITY) { 670 // This usually happens due to the timer not having the required 671 // granularity. Some Linuxes are the usual culprits. 672 // We'll just set it to something (arbitrarily) small. 673 app_time_ms = 1.0; 674 } 675 676 if (update_stats) { 677 // We maintain the invariant that all objects allocated by mutator 678 // threads will be allocated out of eden regions. So, we can use 679 // the eden region number allocated since the previous GC to 680 // calculate the application's allocate rate. The only exception 681 // to that is humongous objects that are allocated separately. But 682 // given that humongous object allocations do not really affect 683 // either the pause's duration nor when the next pause will take 684 // place we can safely ignore them here. 685 uint regions_allocated = _collection_set->eden_region_length(); 686 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 687 _analytics->report_alloc_rate_ms(alloc_rate_ms); 688 689 double interval_ms = 690 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; 691 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 692 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms); 693 } 694 695 if (collector_state()->in_young_gc_before_mixed()) { 696 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC"); 697 // This has been the young GC before we start doing mixed GCs. We already 698 // decided to start mixed GCs much earlier, so there is nothing to do except 699 // advancing the state. 700 collector_state()->set_in_young_only_phase(false); 701 collector_state()->set_in_young_gc_before_mixed(false); 702 } else if (!this_pause_was_young_only) { 703 // This is a mixed GC. Here we decide whether to continue doing more 704 // mixed GCs or not. 705 if (!next_gc_should_be_mixed("continue mixed GCs", 706 "do not continue mixed GCs")) { 707 collector_state()->set_in_young_only_phase(true); 708 709 clear_collection_set_candidates(); 710 maybe_start_marking(); 711 } 712 } 713 714 _short_lived_surv_rate_group->start_adding_regions(); 715 716 double merge_hcc_time_ms = average_time_ms(G1GCPhaseTimes::MergeHCC); 717 if (update_stats) { 718 size_t const total_log_buffer_cards = p->sum_thread_work_items(G1GCPhaseTimes::MergeHCC, G1GCPhaseTimes::MergeHCCDirtyCards) + 719 p->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards); 720 // Update prediction for card merge; MergeRSDirtyCards includes the cards from the Eager Reclaim phase. 721 size_t const total_cards_merged = p->sum_thread_work_items(G1GCPhaseTimes::MergeRS, G1GCPhaseTimes::MergeRSDirtyCards) + 722 p->sum_thread_work_items(G1GCPhaseTimes::OptMergeRS, G1GCPhaseTimes::MergeRSDirtyCards) + 723 total_log_buffer_cards; 724 725 // The threshold for the number of cards in a given sampling which we consider 726 // large enough so that the impact from setup and other costs is negligible. 727 size_t const CardsNumSamplingThreshold = 10; 728 729 if (total_cards_merged > CardsNumSamplingThreshold) { 730 double avg_time_merge_cards = average_time_ms(G1GCPhaseTimes::MergeER) + 731 average_time_ms(G1GCPhaseTimes::MergeRS) + 732 average_time_ms(G1GCPhaseTimes::MergeHCC) + 733 average_time_ms(G1GCPhaseTimes::MergeLB) + 734 average_time_ms(G1GCPhaseTimes::OptMergeRS); 735 _analytics->report_cost_per_card_merge_ms(avg_time_merge_cards / total_cards_merged, this_pause_was_young_only); 736 } 737 738 // Update prediction for card scan 739 size_t const total_cards_scanned = p->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) + 740 p->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards); 741 742 if (total_cards_scanned > CardsNumSamplingThreshold) { 743 double avg_time_dirty_card_scan = average_time_ms(G1GCPhaseTimes::ScanHR) + 744 average_time_ms(G1GCPhaseTimes::OptScanHR); 745 746 _analytics->report_cost_per_card_scan_ms(avg_time_dirty_card_scan / total_cards_scanned, this_pause_was_young_only); 747 } 748 749 // Update prediction for the ratio between cards from the remembered 750 // sets and actually scanned cards from the remembered sets. 751 // Cards from the remembered sets are all cards not duplicated by cards from 752 // the logs. 753 // Due to duplicates in the log buffers, the number of actually scanned cards 754 // can be smaller than the cards in the log buffers. 755 const size_t from_rs_length_cards = (total_cards_scanned > total_log_buffer_cards) ? total_cards_scanned - total_log_buffer_cards : 0; 756 double merge_to_scan_ratio = 0.0; 757 if (total_cards_scanned > 0) { 758 merge_to_scan_ratio = (double) from_rs_length_cards / total_cards_scanned; 759 } 760 _analytics->report_card_merge_to_scan_ratio(merge_to_scan_ratio, this_pause_was_young_only); 761 762 const size_t recorded_rs_length = _collection_set->recorded_rs_length(); 763 const size_t rs_length_diff = _rs_length > recorded_rs_length ? _rs_length - recorded_rs_length : 0; 764 _analytics->report_rs_length_diff(rs_length_diff); 765 766 // Update prediction for copy cost per byte 767 size_t copied_bytes = p->sum_thread_work_items(G1GCPhaseTimes::MergePSS, G1GCPhaseTimes::MergePSSCopiedBytes); 768 769 if (copied_bytes > 0) { 770 double cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / copied_bytes; 771 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress()); 772 } 773 774 if (_collection_set->young_region_length() > 0) { 775 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 776 _collection_set->young_region_length()); 777 } 778 779 if (_collection_set->old_region_length() > 0) { 780 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 781 _collection_set->old_region_length()); 782 } 783 784 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 785 786 // Do not update RS lengths and the number of pending cards with information from mixed gc: 787 // these are is wildly different to during young only gc and mess up young gen sizing right 788 // after the mixed gc phase. 789 // During mixed gc we do not use them for young gen sizing. 790 if (this_pause_was_young_only) { 791 _analytics->report_pending_cards((double) _pending_cards_at_gc_start); 792 _analytics->report_rs_length((double) _rs_length); 793 } 794 } 795 796 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()), 797 "If the last pause has been an initial mark, we should not have been in the marking window"); 798 if (this_pause_included_initial_mark) { 799 collector_state()->set_mark_or_rebuild_in_progress(true); 800 } 801 802 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 803 804 update_rs_length_prediction(); 805 806 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely 807 // that in this case we are not running in a "normal" operating mode. 808 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 809 // IHOP control wants to know the expected young gen length if it were not 810 // restrained by the heap reserve. Using the actual length would make the 811 // prediction too small and the limit the young gen every time we get to the 812 // predicted target occupancy. 813 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 814 815 update_ihop_prediction(app_time_ms / 1000.0, 816 _bytes_allocated_in_old_since_last_gc, 817 last_unrestrained_young_length * HeapRegion::GrainBytes, 818 this_pause_was_young_only); 819 _bytes_allocated_in_old_since_last_gc = 0; 820 821 _ihop_control->send_trace_event(_g1h->gc_tracer_stw()); 822 } else { 823 // Any garbage collection triggered as periodic collection resets the time-to-mixed 824 // measurement. Periodic collection typically means that the application is "inactive", i.e. 825 // the marking threads may have received an uncharacterisic amount of cpu time 826 // for completing the marking, i.e. are faster than expected. 827 // This skews the predicted marking length towards smaller values which might cause 828 // the mark start being too late. 829 _initial_mark_to_mixed.reset(); 830 } 831 832 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 833 double scan_logged_cards_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 834 835 if (scan_logged_cards_time_goal_ms < merge_hcc_time_ms) { 836 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 837 "Logged Cards Scan time goal: %1.2fms Scan HCC time: %1.2fms", 838 scan_logged_cards_time_goal_ms, merge_hcc_time_ms); 839 840 scan_logged_cards_time_goal_ms = 0; 841 } else { 842 scan_logged_cards_time_goal_ms -= merge_hcc_time_ms; 843 } 844 845 _pending_cards_at_prev_gc_end = _g1h->pending_card_num(); 846 double const logged_cards_time = logged_cards_processing_time(); 847 848 log_debug(gc, ergo, refine)("Concurrent refinement times: Logged Cards Scan time goal: %1.2fms Logged Cards Scan time: %1.2fms HCC time: %1.2fms", 849 scan_logged_cards_time_goal_ms, logged_cards_time, merge_hcc_time_ms); 850 851 _g1h->concurrent_refine()->adjust(logged_cards_time, 852 phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards), 853 scan_logged_cards_time_goal_ms); 854 } 855 856 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){ 857 if (G1UseAdaptiveIHOP) { 858 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 859 predictor, 860 G1ReservePercent, 861 G1HeapWastePercent); 862 } else { 863 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 864 } 865 } 866 867 void G1Policy::update_ihop_prediction(double mutator_time_s, 868 size_t mutator_alloc_bytes, 869 size_t young_gen_size, 870 bool this_gc_was_young_only) { 871 // Always try to update IHOP prediction. Even evacuation failures give information 872 // about e.g. whether to start IHOP earlier next time. 873 874 // Avoid using really small application times that might create samples with 875 // very high or very low values. They may be caused by e.g. back-to-back gcs. 876 double const min_valid_time = 1e-6; 877 878 bool report = false; 879 880 double marking_to_mixed_time = -1.0; 881 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) { 882 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 883 assert(marking_to_mixed_time > 0.0, 884 "Initial mark to mixed time must be larger than zero but is %.3f", 885 marking_to_mixed_time); 886 if (marking_to_mixed_time > min_valid_time) { 887 _ihop_control->update_marking_length(marking_to_mixed_time); 888 report = true; 889 } 890 } 891 892 // As an approximation for the young gc promotion rates during marking we use 893 // all of them. In many applications there are only a few if any young gcs during 894 // marking, which makes any prediction useless. This increases the accuracy of the 895 // prediction. 896 if (this_gc_was_young_only && mutator_time_s > min_valid_time) { 897 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 898 report = true; 899 } 900 901 if (report) { 902 report_ihop_statistics(); 903 } 904 } 905 906 void G1Policy::report_ihop_statistics() { 907 _ihop_control->print(); 908 } 909 910 void G1Policy::print_phases() { 911 phase_times()->print(); 912 } 913 914 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { 915 TruncatedSeq* seq = surv_rate_group->get_seq(age); 916 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); 917 return _predictor.get_new_unit_prediction(seq); 918 } 919 920 double G1Policy::accum_yg_surv_rate_pred(int age) const { 921 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 922 } 923 924 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards, 925 size_t rs_length) const { 926 size_t effective_scanned_cards = _analytics->predict_scan_card_num(rs_length, collector_state()->in_young_only_phase()); 927 return 928 _analytics->predict_card_merge_time_ms(pending_cards + rs_length, collector_state()->in_young_only_phase()) + 929 _analytics->predict_card_scan_time_ms(effective_scanned_cards, collector_state()->in_young_only_phase()) + 930 _analytics->predict_constant_other_time_ms(); 931 } 932 933 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const { 934 size_t rs_length = _analytics->predict_rs_length(); 935 return predict_base_elapsed_time_ms(pending_cards, rs_length); 936 } 937 938 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const { 939 size_t bytes_to_copy; 940 if (!hr->is_young()) { 941 bytes_to_copy = hr->max_live_bytes(); 942 } else { 943 assert(hr->age_in_surv_rate_group() != -1, "invariant"); 944 int age = hr->age_in_surv_rate_group(); 945 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); 946 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); 947 } 948 return bytes_to_copy; 949 } 950 951 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr, 952 bool for_young_gc) const { 953 size_t rs_length = hr->rem_set()->occupied(); 954 size_t scan_card_num = _analytics->predict_scan_card_num(rs_length, for_young_gc); 955 956 size_t bytes_to_copy = predict_bytes_to_copy(hr); 957 958 double region_elapsed_time_ms = 959 _analytics->predict_card_merge_time_ms(rs_length, collector_state()->in_young_only_phase()) + 960 _analytics->predict_card_scan_time_ms(scan_card_num, collector_state()->in_young_only_phase()) + 961 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress()); 962 963 // The prediction of the "other" time for this region is based 964 // upon the region type and NOT the GC type. 965 if (hr->is_young()) { 966 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 967 } else { 968 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 969 } 970 return region_elapsed_time_ms; 971 } 972 973 bool G1Policy::should_allocate_mutator_region() const { 974 uint young_list_length = _g1h->young_regions_count(); 975 uint young_list_target_length = _young_list_target_length; 976 return young_list_length < young_list_target_length; 977 } 978 979 bool G1Policy::can_expand_young_list() const { 980 uint young_list_length = _g1h->young_regions_count(); 981 uint young_list_max_length = _young_list_max_length; 982 return young_list_length < young_list_max_length; 983 } 984 985 bool G1Policy::use_adaptive_young_list_length() const { 986 return _young_gen_sizer->use_adaptive_young_list_length(); 987 } 988 989 size_t G1Policy::desired_survivor_size(uint max_regions) const { 990 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions; 991 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 992 } 993 994 void G1Policy::print_age_table() { 995 _survivors_age_table.print_age_table(_tenuring_threshold); 996 } 997 998 void G1Policy::update_max_gc_locker_expansion() { 999 uint expansion_region_num = 0; 1000 if (GCLockerEdenExpansionPercent > 0) { 1001 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 1002 double expansion_region_num_d = perc * (double) _young_list_target_length; 1003 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 1004 // less than 1.0) we'll get 1. 1005 expansion_region_num = (uint) ceil(expansion_region_num_d); 1006 } else { 1007 assert(expansion_region_num == 0, "sanity"); 1008 } 1009 _young_list_max_length = _young_list_target_length + expansion_region_num; 1010 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 1011 } 1012 1013 // Calculates survivor space parameters. 1014 void G1Policy::update_survivors_policy() { 1015 double max_survivor_regions_d = 1016 (double) _young_list_target_length / (double) SurvivorRatio; 1017 1018 // Calculate desired survivor size based on desired max survivor regions (unconstrained 1019 // by remaining heap). Otherwise we may cause undesired promotions as we are 1020 // already getting close to end of the heap, impacting performance even more. 1021 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d); 1022 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions); 1023 1024 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size); 1025 if (UsePerfData) { 1026 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold); 1027 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize); 1028 } 1029 // The real maximum survivor size is bounded by the number of regions that can 1030 // be allocated into. 1031 _max_survivor_regions = MIN2(desired_max_survivor_regions, 1032 _g1h->num_free_or_available_regions()); 1033 } 1034 1035 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 1036 // We actually check whether we are marking here and not if we are in a 1037 // reclamation phase. This means that we will schedule a concurrent mark 1038 // even while we are still in the process of reclaiming memory. 1039 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle(); 1040 if (!during_cycle) { 1041 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 1042 collector_state()->set_initiate_conc_mark_if_possible(true); 1043 return true; 1044 } else { 1045 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 1046 return false; 1047 } 1048 } 1049 1050 void G1Policy::initiate_conc_mark() { 1051 collector_state()->set_in_initial_mark_gc(true); 1052 collector_state()->set_initiate_conc_mark_if_possible(false); 1053 } 1054 1055 void G1Policy::decide_on_conc_mark_initiation() { 1056 // We are about to decide on whether this pause will be an 1057 // initial-mark pause. 1058 1059 // First, collector_state()->in_initial_mark_gc() should not be already set. We 1060 // will set it here if we have to. However, it should be cleared by 1061 // the end of the pause (it's only set for the duration of an 1062 // initial-mark pause). 1063 assert(!collector_state()->in_initial_mark_gc(), "pre-condition"); 1064 1065 if (collector_state()->initiate_conc_mark_if_possible()) { 1066 // We had noticed on a previous pause that the heap occupancy has 1067 // gone over the initiating threshold and we should start a 1068 // concurrent marking cycle. So we might initiate one. 1069 1070 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) { 1071 // Initiate a new initial mark if there is no marking or reclamation going on. 1072 initiate_conc_mark(); 1073 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 1074 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) { 1075 // Initiate a user requested initial mark. An initial mark must be young only 1076 // GC, so the collector state must be updated to reflect this. 1077 collector_state()->set_in_young_only_phase(true); 1078 collector_state()->set_in_young_gc_before_mixed(false); 1079 1080 // We might have ended up coming here about to start a mixed phase with a collection set 1081 // active. The following remark might change the change the "evacuation efficiency" of 1082 // the regions in this set, leading to failing asserts later. 1083 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here. 1084 clear_collection_set_candidates(); 1085 abort_time_to_mixed_tracking(); 1086 initiate_conc_mark(); 1087 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 1088 } else { 1089 // The concurrent marking thread is still finishing up the 1090 // previous cycle. If we start one right now the two cycles 1091 // overlap. In particular, the concurrent marking thread might 1092 // be in the process of clearing the next marking bitmap (which 1093 // we will use for the next cycle if we start one). Starting a 1094 // cycle now will be bad given that parts of the marking 1095 // information might get cleared by the marking thread. And we 1096 // cannot wait for the marking thread to finish the cycle as it 1097 // periodically yields while clearing the next marking bitmap 1098 // and, if it's in a yield point, it's waiting for us to 1099 // finish. So, at this point we will not start a cycle and we'll 1100 // let the concurrent marking thread complete the last one. 1101 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 1102 } 1103 } 1104 } 1105 1106 void G1Policy::record_concurrent_mark_cleanup_end() { 1107 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions()); 1108 _collection_set->set_candidates(candidates); 1109 1110 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs"); 1111 if (!mixed_gc_pending) { 1112 clear_collection_set_candidates(); 1113 abort_time_to_mixed_tracking(); 1114 } 1115 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending); 1116 collector_state()->set_mark_or_rebuild_in_progress(false); 1117 1118 double end_sec = os::elapsedTime(); 1119 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1120 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1121 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1122 1123 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1124 } 1125 1126 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const { 1127 return percent_of(reclaimable_bytes, _g1h->capacity()); 1128 } 1129 1130 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure { 1131 virtual bool do_heap_region(HeapRegion* r) { 1132 r->rem_set()->clear_locked(true /* only_cardset */); 1133 return false; 1134 } 1135 }; 1136 1137 void G1Policy::clear_collection_set_candidates() { 1138 // Clear remembered sets of remaining candidate regions and the actual candidate 1139 // set. 1140 G1ClearCollectionSetCandidateRemSets cl; 1141 _collection_set->candidates()->iterate(&cl); 1142 _collection_set->clear_candidates(); 1143 } 1144 1145 void G1Policy::maybe_start_marking() { 1146 if (need_to_start_conc_mark("end of GC")) { 1147 // Note: this might have already been set, if during the last 1148 // pause we decided to start a cycle but at the beginning of 1149 // this pause we decided to postpone it. That's OK. 1150 collector_state()->set_initiate_conc_mark_if_possible(true); 1151 } 1152 } 1153 1154 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const { 1155 assert(!collector_state()->in_full_gc(), "must be"); 1156 if (collector_state()->in_initial_mark_gc()) { 1157 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1158 return InitialMarkGC; 1159 } else if (collector_state()->in_young_gc_before_mixed()) { 1160 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1161 return LastYoungGC; 1162 } else if (collector_state()->in_mixed_phase()) { 1163 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1164 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1165 return MixedGC; 1166 } else { 1167 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1168 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1169 return YoungOnlyGC; 1170 } 1171 } 1172 1173 void G1Policy::record_pause(PauseKind kind, double start, double end) { 1174 // Manage the MMU tracker. For some reason it ignores Full GCs. 1175 if (kind != FullGC) { 1176 _mmu_tracker->add_pause(start, end); 1177 } 1178 // Manage the mutator time tracking from initial mark to first mixed gc. 1179 switch (kind) { 1180 case FullGC: 1181 abort_time_to_mixed_tracking(); 1182 break; 1183 case Cleanup: 1184 case Remark: 1185 case YoungOnlyGC: 1186 case LastYoungGC: 1187 _initial_mark_to_mixed.add_pause(end - start); 1188 break; 1189 case InitialMarkGC: 1190 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 1191 _initial_mark_to_mixed.record_initial_mark_end(end); 1192 } 1193 break; 1194 case MixedGC: 1195 _initial_mark_to_mixed.record_mixed_gc_start(start); 1196 break; 1197 default: 1198 ShouldNotReachHere(); 1199 } 1200 } 1201 1202 void G1Policy::abort_time_to_mixed_tracking() { 1203 _initial_mark_to_mixed.reset(); 1204 } 1205 1206 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str, 1207 const char* false_action_str) const { 1208 G1CollectionSetCandidates* candidates = _collection_set->candidates(); 1209 1210 if (candidates->is_empty()) { 1211 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1212 return false; 1213 } 1214 1215 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1216 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1217 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1218 double threshold = (double) G1HeapWastePercent; 1219 if (reclaimable_percent <= threshold) { 1220 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1221 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1222 return false; 1223 } 1224 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1225 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1226 return true; 1227 } 1228 1229 uint G1Policy::calc_min_old_cset_length() const { 1230 // The min old CSet region bound is based on the maximum desired 1231 // number of mixed GCs after a cycle. I.e., even if some old regions 1232 // look expensive, we should add them to the CSet anyway to make 1233 // sure we go through the available old regions in no more than the 1234 // maximum desired number of mixed GCs. 1235 // 1236 // The calculation is based on the number of marked regions we added 1237 // to the CSet candidates in the first place, not how many remain, so 1238 // that the result is the same during all mixed GCs that follow a cycle. 1239 1240 const size_t region_num = _collection_set->candidates()->num_regions(); 1241 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1242 size_t result = region_num / gc_num; 1243 // emulate ceiling 1244 if (result * gc_num < region_num) { 1245 result += 1; 1246 } 1247 return (uint) result; 1248 } 1249 1250 uint G1Policy::calc_max_old_cset_length() const { 1251 // The max old CSet region bound is based on the threshold expressed 1252 // as a percentage of the heap size. I.e., it should bound the 1253 // number of old regions added to the CSet irrespective of how many 1254 // of them are available. 1255 1256 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1257 const size_t region_num = g1h->num_regions(); 1258 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1259 size_t result = region_num * perc / 100; 1260 // emulate ceiling 1261 if (100 * result < region_num * perc) { 1262 result += 1; 1263 } 1264 return (uint) result; 1265 } 1266 1267 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates, 1268 double time_remaining_ms, 1269 uint& num_initial_regions, 1270 uint& num_optional_regions) { 1271 assert(candidates != NULL, "Must be"); 1272 1273 num_initial_regions = 0; 1274 num_optional_regions = 0; 1275 uint num_expensive_regions = 0; 1276 1277 double predicted_old_time_ms = 0.0; 1278 double predicted_initial_time_ms = 0.0; 1279 double predicted_optional_time_ms = 0.0; 1280 1281 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction(); 1282 1283 const uint min_old_cset_length = calc_min_old_cset_length(); 1284 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length()); 1285 const uint max_optional_regions = max_old_cset_length - min_old_cset_length; 1286 bool check_time_remaining = use_adaptive_young_list_length(); 1287 1288 uint candidate_idx = candidates->cur_idx(); 1289 1290 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, " 1291 "time remaining %1.2fms, optional threshold %1.2fms", 1292 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms); 1293 1294 HeapRegion* hr = candidates->at(candidate_idx); 1295 while (hr != NULL) { 1296 if (num_initial_regions + num_optional_regions >= max_old_cset_length) { 1297 // Added maximum number of old regions to the CSet. 1298 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). " 1299 "Initial %u regions, optional %u regions", 1300 num_initial_regions, num_optional_regions); 1301 break; 1302 } 1303 1304 // Stop adding regions if the remaining reclaimable space is 1305 // not above G1HeapWastePercent. 1306 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1307 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1308 double threshold = (double) G1HeapWastePercent; 1309 if (reclaimable_percent <= threshold) { 1310 // We've added enough old regions that the amount of uncollected 1311 // reclaimable space is at or below the waste threshold. Stop 1312 // adding old regions to the CSet. 1313 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). " 1314 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%", 1315 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes), 1316 reclaimable_percent, G1HeapWastePercent); 1317 break; 1318 } 1319 1320 double predicted_time_ms = predict_region_elapsed_time_ms(hr, false); 1321 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0); 1322 // Add regions to old set until we reach the minimum amount 1323 if (num_initial_regions < min_old_cset_length) { 1324 predicted_old_time_ms += predicted_time_ms; 1325 num_initial_regions++; 1326 // Record the number of regions added with no time remaining 1327 if (time_remaining_ms == 0.0) { 1328 num_expensive_regions++; 1329 } 1330 } else if (!check_time_remaining) { 1331 // In the non-auto-tuning case, we'll finish adding regions 1332 // to the CSet if we reach the minimum. 1333 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min)."); 1334 break; 1335 } else { 1336 // Keep adding regions to old set until we reach the optional threshold 1337 if (time_remaining_ms > optional_threshold_ms) { 1338 predicted_old_time_ms += predicted_time_ms; 1339 num_initial_regions++; 1340 } else if (time_remaining_ms > 0) { 1341 // Keep adding optional regions until time is up. 1342 assert(num_optional_regions < max_optional_regions, "Should not be possible."); 1343 predicted_optional_time_ms += predicted_time_ms; 1344 num_optional_regions++; 1345 } else { 1346 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high)."); 1347 break; 1348 } 1349 } 1350 hr = candidates->at(++candidate_idx); 1351 } 1352 if (hr == NULL) { 1353 log_debug(gc, ergo, cset)("Old candidate collection set empty."); 1354 } 1355 1356 if (num_expensive_regions > 0) { 1357 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.", 1358 num_expensive_regions); 1359 } 1360 1361 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, " 1362 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f", 1363 num_initial_regions, num_optional_regions, 1364 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms); 1365 } 1366 1367 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates, 1368 uint const max_optional_regions, 1369 double time_remaining_ms, 1370 uint& num_optional_regions) { 1371 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase"); 1372 1373 num_optional_regions = 0; 1374 double prediction_ms = 0; 1375 uint candidate_idx = candidates->cur_idx(); 1376 1377 HeapRegion* r = candidates->at(candidate_idx); 1378 while (num_optional_regions < max_optional_regions) { 1379 assert(r != NULL, "Region must exist"); 1380 prediction_ms += predict_region_elapsed_time_ms(r, false); 1381 1382 if (prediction_ms > time_remaining_ms) { 1383 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.", 1384 prediction_ms, r->hrm_index(), time_remaining_ms); 1385 break; 1386 } 1387 // This region will be included in the next optional evacuation. 1388 1389 time_remaining_ms -= prediction_ms; 1390 num_optional_regions++; 1391 r = candidates->at(++candidate_idx); 1392 } 1393 1394 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms", 1395 num_optional_regions, max_optional_regions, prediction_ms); 1396 } 1397 1398 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) { 1399 1400 // Add survivor regions to SurvRateGroup. 1401 note_start_adding_survivor_regions(); 1402 finished_recalculating_age_indexes(true /* is_survivors */); 1403 1404 HeapRegion* last = NULL; 1405 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin(); 1406 it != survivors->regions()->end(); 1407 ++it) { 1408 HeapRegion* curr = *it; 1409 set_region_survivor(curr); 1410 1411 // The region is a non-empty survivor so let's add it to 1412 // the incremental collection set for the next evacuation 1413 // pause. 1414 _collection_set->add_survivor_regions(curr); 1415 1416 last = curr; 1417 } 1418 note_stop_adding_survivor_regions(); 1419 1420 // Don't clear the survivor list handles until the start of 1421 // the next evacuation pause - we need it in order to re-tag 1422 // the survivor regions from this evacuation pause as 'young' 1423 // at the start of the next. 1424 1425 finished_recalculating_age_indexes(false /* is_survivors */); 1426 }