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 _eden_surv_rate_group(new G1SurvRateGroup()), 66 _survivor_surv_rate_group(new G1SurvRateGroup()), 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 double _base_time_ms; 131 const double _base_free_regions; 132 const double _target_pause_time_ms; 133 const G1Policy* const _policy; 134 135 public: 136 G1YoungLengthPredictor(double base_time_ms, 137 double base_free_regions, 138 double target_pause_time_ms, 139 const G1Policy* policy) : 140 _base_time_ms(base_time_ms), 141 _base_free_regions(base_free_regions), 142 _target_pause_time_ms(target_pause_time_ms), 143 _policy(policy) {} 144 145 bool will_fit(uint young_length) const { 146 if (young_length >= _base_free_regions) { 147 // end condition 1: not enough space for the young regions 148 return false; 149 } 150 151 size_t bytes_to_copy = 0; 152 const double copy_time_ms = _policy->predict_eden_copy_time_ms(young_length, &bytes_to_copy); 153 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length); 154 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms; 155 if (pause_time_ms > _target_pause_time_ms) { 156 // end condition 2: prediction is over the target pause time 157 return false; 158 } 159 160 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes; 161 162 // When copying, we will likely need more bytes free than is live in the region. 163 // Add some safety margin to factor in the confidence of our guess, and the 164 // natural expected waste. 165 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 166 // of the calculation: the lower the confidence, the more headroom. 167 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 168 // copying due to anticipated waste in the PLABs. 169 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 170 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 171 172 if (expected_bytes_to_copy > free_bytes) { 173 // end condition 3: out-of-space 174 return false; 175 } 176 177 // success! 178 return true; 179 } 180 }; 181 182 void G1Policy::record_new_heap_size(uint new_number_of_regions) { 183 // re-calculate the necessary reserve 184 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 185 // We use ceiling so that if reserve_regions_d is > 0.0 (but 186 // smaller than 1.0) we'll get 1. 187 _reserve_regions = (uint) ceil(reserve_regions_d); 188 189 _young_gen_sizer->heap_size_changed(new_number_of_regions); 190 191 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 192 } 193 194 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const { 195 uint desired_min_length = 0; 196 if (use_adaptive_young_list_length()) { 197 if (_analytics->num_alloc_rate_ms() > 3) { 198 double now_sec = os::elapsedTime(); 199 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 200 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 201 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 202 } else { 203 // otherwise we don't have enough info to make the prediction 204 } 205 } 206 desired_min_length += base_min_length; 207 // make sure we don't go below any user-defined minimum bound 208 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length); 209 } 210 211 uint G1Policy::calculate_young_list_desired_max_length() const { 212 // Here, we might want to also take into account any additional 213 // constraints (i.e., user-defined minimum bound). Currently, we 214 // effectively don't set this bound. 215 return _young_gen_sizer->max_desired_young_length(); 216 } 217 218 uint G1Policy::update_young_list_max_and_target_length() { 219 return update_young_list_max_and_target_length(_analytics->predict_rs_length()); 220 } 221 222 uint G1Policy::update_young_list_max_and_target_length(size_t rs_length) { 223 uint unbounded_target_length = update_young_list_target_length(rs_length); 224 update_max_gc_locker_expansion(); 225 return unbounded_target_length; 226 } 227 228 uint G1Policy::update_young_list_target_length(size_t rs_length) { 229 YoungTargetLengths young_lengths = young_list_target_lengths(rs_length); 230 _young_list_target_length = young_lengths.first; 231 232 return young_lengths.second; 233 } 234 235 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_length) const { 236 YoungTargetLengths result; 237 238 // Calculate the absolute and desired min bounds first. 239 240 // This is how many young regions we already have (currently: the survivors). 241 const uint base_min_length = _g1h->survivor_regions_count(); 242 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 243 // This is the absolute minimum young length. Ensure that we 244 // will at least have one eden region available for allocation. 245 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1); 246 // If we shrank the young list target it should not shrink below the current size. 247 desired_min_length = MAX2(desired_min_length, absolute_min_length); 248 // Calculate the absolute and desired max bounds. 249 250 uint desired_max_length = calculate_young_list_desired_max_length(); 251 252 uint young_list_target_length = 0; 253 if (use_adaptive_young_list_length()) { 254 if (collector_state()->in_young_only_phase()) { 255 young_list_target_length = 256 calculate_young_list_target_length(rs_length, 257 base_min_length, 258 desired_min_length, 259 desired_max_length); 260 } else { 261 // Don't calculate anything and let the code below bound it to 262 // the desired_min_length, i.e., do the next GC as soon as 263 // possible to maximize how many old regions we can add to it. 264 } 265 } else { 266 // The user asked for a fixed young gen so we'll fix the young gen 267 // whether the next GC is young or mixed. 268 young_list_target_length = _young_list_fixed_length; 269 } 270 271 result.second = young_list_target_length; 272 273 // We will try our best not to "eat" into the reserve. 274 uint absolute_max_length = 0; 275 if (_free_regions_at_end_of_collection > _reserve_regions) { 276 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 277 } 278 if (desired_max_length > absolute_max_length) { 279 desired_max_length = absolute_max_length; 280 } 281 282 // Make sure we don't go over the desired max length, nor under the 283 // desired min length. In case they clash, desired_min_length wins 284 // which is why that test is second. 285 if (young_list_target_length > desired_max_length) { 286 young_list_target_length = desired_max_length; 287 } 288 if (young_list_target_length < desired_min_length) { 289 young_list_target_length = desired_min_length; 290 } 291 292 assert(young_list_target_length > base_min_length, 293 "we should be able to allocate at least one eden region"); 294 assert(young_list_target_length >= absolute_min_length, "post-condition"); 295 296 result.first = young_list_target_length; 297 return result; 298 } 299 300 uint G1Policy::calculate_young_list_target_length(size_t rs_length, 301 uint base_min_length, 302 uint desired_min_length, 303 uint desired_max_length) const { 304 assert(use_adaptive_young_list_length(), "pre-condition"); 305 assert(collector_state()->in_young_only_phase(), "only call this for young GCs"); 306 307 // In case some edge-condition makes the desired max length too small... 308 if (desired_max_length <= desired_min_length) { 309 return desired_min_length; 310 } 311 312 // We'll adjust min_young_length and max_young_length not to include 313 // the already allocated young regions (i.e., so they reflect the 314 // min and max eden regions we'll allocate). The base_min_length 315 // will be reflected in the predictions by the 316 // survivor_regions_evac_time prediction. 317 assert(desired_min_length > base_min_length, "invariant"); 318 uint min_young_length = desired_min_length - base_min_length; 319 assert(desired_max_length > base_min_length, "invariant"); 320 uint max_young_length = desired_max_length - base_min_length; 321 322 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 323 const size_t pending_cards = _analytics->predict_pending_cards(); 324 const double base_time_ms = predict_base_elapsed_time_ms(pending_cards, rs_length); 325 const uint available_free_regions = _free_regions_at_end_of_collection; 326 const uint base_free_regions = 327 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0; 328 329 // Here, we will make sure that the shortest young length that 330 // makes sense fits within the target pause time. 331 332 G1YoungLengthPredictor p(base_time_ms, 333 base_free_regions, 334 target_pause_time_ms, 335 this); 336 if (p.will_fit(min_young_length)) { 337 // The shortest young length will fit into the target pause time; 338 // we'll now check whether the absolute maximum number of young 339 // regions will fit in the target pause time. If not, we'll do 340 // a binary search between min_young_length and max_young_length. 341 if (p.will_fit(max_young_length)) { 342 // The maximum young length will fit into the target pause time. 343 // We are done so set min young length to the maximum length (as 344 // the result is assumed to be returned in min_young_length). 345 min_young_length = max_young_length; 346 } else { 347 // The maximum possible number of young regions will not fit within 348 // the target pause time so we'll search for the optimal 349 // length. The loop invariants are: 350 // 351 // min_young_length < max_young_length 352 // min_young_length is known to fit into the target pause time 353 // max_young_length is known not to fit into the target pause time 354 // 355 // Going into the loop we know the above hold as we've just 356 // checked them. Every time around the loop we check whether 357 // the middle value between min_young_length and 358 // max_young_length fits into the target pause time. If it 359 // does, it becomes the new min. If it doesn't, it becomes 360 // the new max. This way we maintain the loop invariants. 361 362 assert(min_young_length < max_young_length, "invariant"); 363 uint diff = (max_young_length - min_young_length) / 2; 364 while (diff > 0) { 365 uint young_length = min_young_length + diff; 366 if (p.will_fit(young_length)) { 367 min_young_length = young_length; 368 } else { 369 max_young_length = young_length; 370 } 371 assert(min_young_length < max_young_length, "invariant"); 372 diff = (max_young_length - min_young_length) / 2; 373 } 374 // The results is min_young_length which, according to the 375 // loop invariants, should fit within the target pause time. 376 377 // These are the post-conditions of the binary search above: 378 assert(min_young_length < max_young_length, 379 "otherwise we should have discovered that max_young_length " 380 "fits into the pause target and not done the binary search"); 381 assert(p.will_fit(min_young_length), 382 "min_young_length, the result of the binary search, should " 383 "fit into the pause target"); 384 assert(!p.will_fit(min_young_length + 1), 385 "min_young_length, the result of the binary search, should be " 386 "optimal, so no larger length should fit into the pause target"); 387 } 388 } else { 389 // Even the minimum length doesn't fit into the pause time 390 // target, return it as the result nevertheless. 391 } 392 return base_min_length + min_young_length; 393 } 394 395 double G1Policy::predict_survivor_regions_evac_time() const { 396 double survivor_regions_evac_time = 0.0; 397 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions(); 398 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin(); 399 it != survivor_regions->end(); 400 ++it) { 401 survivor_regions_evac_time += predict_region_total_time_ms(*it, collector_state()->in_young_only_phase()); 402 } 403 return survivor_regions_evac_time; 404 } 405 406 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_length) { 407 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" ); 408 409 if (rs_length > _rs_length_prediction) { 410 // add 10% to avoid having to recalculate often 411 size_t rs_length_prediction = rs_length * 1100 / 1000; 412 update_rs_length_prediction(rs_length_prediction); 413 414 update_young_list_max_and_target_length(rs_length_prediction); 415 } 416 } 417 418 void G1Policy::update_rs_length_prediction() { 419 update_rs_length_prediction(_analytics->predict_rs_length()); 420 } 421 422 void G1Policy::update_rs_length_prediction(size_t prediction) { 423 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) { 424 _rs_length_prediction = prediction; 425 } 426 } 427 428 void G1Policy::record_full_collection_start() { 429 _full_collection_start_sec = os::elapsedTime(); 430 // Release the future to-space so that it is available for compaction into. 431 collector_state()->set_in_young_only_phase(false); 432 collector_state()->set_in_full_gc(true); 433 _collection_set->clear_candidates(); 434 record_concurrent_refinement_data(true /* is_full_collection */); 435 } 436 437 void G1Policy::record_full_collection_end() { 438 // Consider this like a collection pause for the purposes of allocation 439 // since last pause. 440 double end_sec = os::elapsedTime(); 441 double full_gc_time_sec = end_sec - _full_collection_start_sec; 442 double full_gc_time_ms = full_gc_time_sec * 1000.0; 443 444 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 445 446 collector_state()->set_in_full_gc(false); 447 448 // "Nuke" the heuristics that control the young/mixed GC 449 // transitions and make sure we start with young GCs after the Full GC. 450 collector_state()->set_in_young_only_phase(true); 451 collector_state()->set_in_young_gc_before_mixed(false); 452 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 453 collector_state()->set_in_initial_mark_gc(false); 454 collector_state()->set_mark_or_rebuild_in_progress(false); 455 collector_state()->set_clearing_next_bitmap(false); 456 457 _eden_surv_rate_group->start_adding_regions(); 458 // also call this on any additional surv rate groups 459 460 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 461 _survivor_surv_rate_group->reset(); 462 update_young_list_max_and_target_length(); 463 update_rs_length_prediction(); 464 _pending_cards_at_prev_gc_end = _g1h->pending_card_num(); 465 466 _bytes_allocated_in_old_since_last_gc = 0; 467 468 record_pause(FullGC, _full_collection_start_sec, end_sec); 469 } 470 471 void G1Policy::record_concurrent_refinement_data(bool is_full_collection) { 472 _pending_cards_at_gc_start = _g1h->pending_card_num(); 473 474 // Record info about concurrent refinement thread processing. 475 G1ConcurrentRefine* cr = _g1h->concurrent_refine(); 476 G1ConcurrentRefine::RefinementStats cr_stats = cr->total_refinement_stats(); 477 478 Tickspan cr_time = cr_stats._time - _total_concurrent_refinement_time; 479 _total_concurrent_refinement_time = cr_stats._time; 480 481 size_t cr_cards = cr_stats._cards - _total_concurrent_refined_cards; 482 _total_concurrent_refined_cards = cr_stats._cards; 483 484 // Don't update rate if full collection. We could be in an implicit full 485 // collection after a non-full collection failure, in which case there 486 // wasn't any mutator/cr-thread activity since last recording. And if 487 // we're in an explicit full collection, the time since the last GC can 488 // be arbitrarily short, so not a very good sample. Similarly, don't 489 // update the rate if the current sample is empty or time is zero. 490 if (!is_full_collection && (cr_cards > 0) && (cr_time > Tickspan())) { 491 double rate = cr_cards / (cr_time.seconds() * MILLIUNITS); 492 _analytics->report_concurrent_refine_rate_ms(rate); 493 } 494 495 // Record info about mutator thread processing. 496 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 497 size_t mut_total_cards = dcqs.total_mutator_refined_cards(); 498 size_t mut_cards = mut_total_cards - _total_mutator_refined_cards; 499 _total_mutator_refined_cards = mut_total_cards; 500 501 // Record mutator's card logging rate. 502 // Don't update if full collection; see above. 503 if (!is_full_collection) { 504 size_t total_cards = _pending_cards_at_gc_start + cr_cards + mut_cards; 505 assert(_pending_cards_at_prev_gc_end <= total_cards, 506 "untracked cards: last pending: " SIZE_FORMAT 507 ", pending: " SIZE_FORMAT ", conc refine: " SIZE_FORMAT 508 ", mut refine:" SIZE_FORMAT, 509 _pending_cards_at_prev_gc_end, _pending_cards_at_gc_start, 510 cr_cards, mut_cards); 511 size_t logged_cards = total_cards - _pending_cards_at_prev_gc_end; 512 double logging_start_time = _analytics->prev_collection_pause_end_ms(); 513 double logging_end_time = Ticks::now().seconds() * MILLIUNITS; 514 double logging_time = logging_end_time - logging_start_time; 515 // Unlike above for conc-refine rate, here we should not require a 516 // non-empty sample, since an application could go some time with only 517 // young-gen or filtered out writes. But we'll ignore unusually short 518 // sample periods, as they may just pollute the predictions. 519 if (logging_time > 1.0) { // Require > 1ms sample time. 520 _analytics->report_logged_cards_rate_ms(logged_cards / logging_time); 521 } 522 } 523 } 524 525 void G1Policy::record_collection_pause_start(double start_time_sec) { 526 // We only need to do this here as the policy will only be applied 527 // to the GC we're about to start. so, no point is calculating this 528 // every time we calculate / recalculate the target young length. 529 update_survivors_policy(); 530 531 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(), 532 "Maximum survivor regions %u plus used regions %u exceeds max regions %u", 533 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions()); 534 assert_used_and_recalculate_used_equal(_g1h); 535 536 phase_times()->record_cur_collection_start_sec(start_time_sec); 537 538 record_concurrent_refinement_data(false /* is_full_collection */); 539 540 _collection_set->reset_bytes_used_before(); 541 542 // do that for any other surv rate groups 543 _eden_surv_rate_group->stop_adding_regions(); 544 _survivors_age_table.clear(); 545 546 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed"); 547 } 548 549 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 550 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 551 collector_state()->set_in_initial_mark_gc(false); 552 } 553 554 void G1Policy::record_concurrent_mark_remark_start() { 555 _mark_remark_start_sec = os::elapsedTime(); 556 } 557 558 void G1Policy::record_concurrent_mark_remark_end() { 559 double end_time_sec = os::elapsedTime(); 560 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 561 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 562 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 563 564 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 565 } 566 567 void G1Policy::record_concurrent_mark_cleanup_start() { 568 _mark_cleanup_start_sec = os::elapsedTime(); 569 } 570 571 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 572 return phase_times()->average_time_ms(phase); 573 } 574 575 double G1Policy::young_other_time_ms() const { 576 return phase_times()->young_cset_choice_time_ms() + 577 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet); 578 } 579 580 double G1Policy::non_young_other_time_ms() const { 581 return phase_times()->non_young_cset_choice_time_ms() + 582 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet); 583 } 584 585 double G1Policy::other_time_ms(double pause_time_ms) const { 586 return pause_time_ms - phase_times()->cur_collection_par_time_ms(); 587 } 588 589 double G1Policy::constant_other_time_ms(double pause_time_ms) const { 590 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms() - phase_times()->total_rebuild_freelist_time_ms(); 591 } 592 593 bool G1Policy::about_to_start_mixed_phase() const { 594 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed(); 595 } 596 597 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 598 if (about_to_start_mixed_phase()) { 599 return false; 600 } 601 602 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 603 604 size_t cur_used_bytes = _g1h->non_young_capacity_bytes(); 605 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 606 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 607 608 bool result = false; 609 if (marking_request_bytes > marking_initiating_used_threshold) { 610 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed(); 611 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 612 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 613 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source); 614 } 615 616 return result; 617 } 618 619 double G1Policy::logged_cards_processing_time() const { 620 double all_cards_processing_time = average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR); 621 size_t logged_dirty_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards); 622 size_t scan_heap_roots_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) + 623 phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards); 624 // This may happen if there are duplicate cards in different log buffers. 625 if (logged_dirty_cards > scan_heap_roots_cards) { 626 return all_cards_processing_time + average_time_ms(G1GCPhaseTimes::MergeLB); 627 } 628 return (all_cards_processing_time * logged_dirty_cards / scan_heap_roots_cards) + average_time_ms(G1GCPhaseTimes::MergeLB); 629 } 630 631 // Anything below that is considered to be zero 632 #define MIN_TIMER_GRANULARITY 0.0000001 633 634 void G1Policy::record_collection_pause_end(double pause_time_ms) { 635 G1GCPhaseTimes* p = phase_times(); 636 637 double end_time_sec = os::elapsedTime(); 638 639 bool this_pause_included_initial_mark = false; 640 bool this_pause_was_young_only = collector_state()->in_young_only_phase(); 641 642 bool update_stats = !_g1h->evacuation_failed(); 643 644 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 645 646 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 647 648 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc(); 649 if (this_pause_included_initial_mark) { 650 record_concurrent_mark_init_end(0.0); 651 } else { 652 maybe_start_marking(); 653 } 654 655 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 656 if (app_time_ms < MIN_TIMER_GRANULARITY) { 657 // This usually happens due to the timer not having the required 658 // granularity. Some Linuxes are the usual culprits. 659 // We'll just set it to something (arbitrarily) small. 660 app_time_ms = 1.0; 661 } 662 663 if (update_stats) { 664 // We maintain the invariant that all objects allocated by mutator 665 // threads will be allocated out of eden regions. So, we can use 666 // the eden region number allocated since the previous GC to 667 // calculate the application's allocate rate. The only exception 668 // to that is humongous objects that are allocated separately. But 669 // given that humongous object allocations do not really affect 670 // either the pause's duration nor when the next pause will take 671 // place we can safely ignore them here. 672 uint regions_allocated = _collection_set->eden_region_length(); 673 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 674 _analytics->report_alloc_rate_ms(alloc_rate_ms); 675 676 double interval_ms = 677 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; 678 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 679 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms); 680 } 681 682 if (collector_state()->finish_of_mixed_gc()) { 683 collector_state()->set_finish_of_mixed_gc(false); 684 } 685 if (collector_state()->in_young_gc_before_mixed()) { 686 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC"); 687 // This has been the young GC before we start doing mixed GCs. We already 688 // decided to start mixed GCs much earlier, so there is nothing to do except 689 // advancing the state. 690 collector_state()->set_in_young_only_phase(false); 691 collector_state()->set_in_young_gc_before_mixed(false); 692 } else if (!this_pause_was_young_only) { 693 // This is a mixed GC. Here we decide whether to continue doing more 694 // mixed GCs or not. 695 if (!next_gc_should_be_mixed("continue mixed GCs", 696 "do not continue mixed GCs")) { 697 collector_state()->set_in_young_only_phase(true); 698 collector_state()->set_finish_of_mixed_gc(true); 699 700 clear_collection_set_candidates(); 701 maybe_start_marking(); 702 } 703 } 704 705 _eden_surv_rate_group->start_adding_regions(); 706 707 double merge_hcc_time_ms = average_time_ms(G1GCPhaseTimes::MergeHCC); 708 if (update_stats) { 709 size_t const total_log_buffer_cards = p->sum_thread_work_items(G1GCPhaseTimes::MergeHCC, G1GCPhaseTimes::MergeHCCDirtyCards) + 710 p->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards); 711 // Update prediction for card merge; MergeRSDirtyCards includes the cards from the Eager Reclaim phase. 712 size_t const total_cards_merged = p->sum_thread_work_items(G1GCPhaseTimes::MergeRS, G1GCPhaseTimes::MergeRSDirtyCards) + 713 p->sum_thread_work_items(G1GCPhaseTimes::OptMergeRS, G1GCPhaseTimes::MergeRSDirtyCards) + 714 total_log_buffer_cards; 715 716 // The threshold for the number of cards in a given sampling which we consider 717 // large enough so that the impact from setup and other costs is negligible. 718 size_t const CardsNumSamplingThreshold = 10; 719 720 if (total_cards_merged > CardsNumSamplingThreshold) { 721 double avg_time_merge_cards = average_time_ms(G1GCPhaseTimes::MergeER) + 722 average_time_ms(G1GCPhaseTimes::MergeRS) + 723 average_time_ms(G1GCPhaseTimes::MergeHCC) + 724 average_time_ms(G1GCPhaseTimes::MergeLB) + 725 average_time_ms(G1GCPhaseTimes::OptMergeRS); 726 _analytics->report_cost_per_card_merge_ms(avg_time_merge_cards / total_cards_merged, this_pause_was_young_only); 727 } 728 729 // Update prediction for card scan 730 size_t const total_cards_scanned = p->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) + 731 p->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards); 732 733 if (total_cards_scanned > CardsNumSamplingThreshold) { 734 double avg_time_dirty_card_scan = average_time_ms(G1GCPhaseTimes::ScanHR) + 735 average_time_ms(G1GCPhaseTimes::OptScanHR); 736 737 _analytics->report_cost_per_card_scan_ms(avg_time_dirty_card_scan / total_cards_scanned, this_pause_was_young_only); 738 } 739 740 // Update prediction for the ratio between cards from the remembered 741 // sets and actually scanned cards from the remembered sets. 742 // Cards from the remembered sets are all cards not duplicated by cards from 743 // the logs. 744 // Due to duplicates in the log buffers, the number of actually scanned cards 745 // can be smaller than the cards in the log buffers. 746 const size_t from_rs_length_cards = (total_cards_scanned > total_log_buffer_cards) ? total_cards_scanned - total_log_buffer_cards : 0; 747 double merge_to_scan_ratio = 0.0; 748 if (total_cards_scanned > 0) { 749 merge_to_scan_ratio = (double) from_rs_length_cards / total_cards_scanned; 750 } 751 _analytics->report_card_merge_to_scan_ratio(merge_to_scan_ratio, this_pause_was_young_only); 752 753 const size_t recorded_rs_length = _collection_set->recorded_rs_length(); 754 const size_t rs_length_diff = _rs_length > recorded_rs_length ? _rs_length - recorded_rs_length : 0; 755 _analytics->report_rs_length_diff(rs_length_diff); 756 757 // Update prediction for copy cost per byte 758 size_t copied_bytes = p->sum_thread_work_items(G1GCPhaseTimes::MergePSS, G1GCPhaseTimes::MergePSSCopiedBytes); 759 760 if (copied_bytes > 0) { 761 double cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / copied_bytes; 762 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress()); 763 } 764 765 if (_collection_set->young_region_length() > 0) { 766 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 767 _collection_set->young_region_length()); 768 } 769 770 if (_collection_set->old_region_length() > 0) { 771 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 772 _collection_set->old_region_length()); 773 } 774 775 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 776 777 // Do not update RS lengths and the number of pending cards with information from mixed gc: 778 // these are is wildly different to during young only gc and mess up young gen sizing right 779 // after the mixed gc phase. 780 // During mixed gc we do not use them for young gen sizing. 781 if (this_pause_was_young_only) { 782 _analytics->report_pending_cards((double) _pending_cards_at_gc_start); 783 _analytics->report_rs_length((double) _rs_length); 784 } 785 } 786 787 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()), 788 "If the last pause has been an initial mark, we should not have been in the marking window"); 789 if (this_pause_included_initial_mark) { 790 collector_state()->set_mark_or_rebuild_in_progress(true); 791 } 792 793 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 794 795 update_rs_length_prediction(); 796 797 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely 798 // that in this case we are not running in a "normal" operating mode. 799 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 800 // IHOP control wants to know the expected young gen length if it were not 801 // restrained by the heap reserve. Using the actual length would make the 802 // prediction too small and the limit the young gen every time we get to the 803 // predicted target occupancy. 804 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 805 806 update_ihop_prediction(app_time_ms / 1000.0, 807 _bytes_allocated_in_old_since_last_gc, 808 last_unrestrained_young_length * HeapRegion::GrainBytes, 809 this_pause_was_young_only); 810 _bytes_allocated_in_old_since_last_gc = 0; 811 812 _ihop_control->send_trace_event(_g1h->gc_tracer_stw()); 813 } else { 814 // Any garbage collection triggered as periodic collection resets the time-to-mixed 815 // measurement. Periodic collection typically means that the application is "inactive", i.e. 816 // the marking threads may have received an uncharacterisic amount of cpu time 817 // for completing the marking, i.e. are faster than expected. 818 // This skews the predicted marking length towards smaller values which might cause 819 // the mark start being too late. 820 _initial_mark_to_mixed.reset(); 821 } 822 823 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 824 double scan_logged_cards_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 825 826 if (scan_logged_cards_time_goal_ms < merge_hcc_time_ms) { 827 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 828 "Logged Cards Scan time goal: %1.2fms Scan HCC time: %1.2fms", 829 scan_logged_cards_time_goal_ms, merge_hcc_time_ms); 830 831 scan_logged_cards_time_goal_ms = 0; 832 } else { 833 scan_logged_cards_time_goal_ms -= merge_hcc_time_ms; 834 } 835 836 _pending_cards_at_prev_gc_end = _g1h->pending_card_num(); 837 double const logged_cards_time = logged_cards_processing_time(); 838 839 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", 840 scan_logged_cards_time_goal_ms, logged_cards_time, merge_hcc_time_ms); 841 842 _g1h->concurrent_refine()->adjust(logged_cards_time, 843 phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards), 844 scan_logged_cards_time_goal_ms); 845 } 846 847 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){ 848 if (G1UseAdaptiveIHOP) { 849 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 850 predictor, 851 G1ReservePercent, 852 G1HeapWastePercent); 853 } else { 854 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 855 } 856 } 857 858 void G1Policy::update_ihop_prediction(double mutator_time_s, 859 size_t mutator_alloc_bytes, 860 size_t young_gen_size, 861 bool this_gc_was_young_only) { 862 // Always try to update IHOP prediction. Even evacuation failures give information 863 // about e.g. whether to start IHOP earlier next time. 864 865 // Avoid using really small application times that might create samples with 866 // very high or very low values. They may be caused by e.g. back-to-back gcs. 867 double const min_valid_time = 1e-6; 868 869 bool report = false; 870 871 double marking_to_mixed_time = -1.0; 872 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) { 873 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 874 assert(marking_to_mixed_time > 0.0, 875 "Initial mark to mixed time must be larger than zero but is %.3f", 876 marking_to_mixed_time); 877 if (marking_to_mixed_time > min_valid_time) { 878 _ihop_control->update_marking_length(marking_to_mixed_time); 879 report = true; 880 } 881 } 882 883 // As an approximation for the young gc promotion rates during marking we use 884 // all of them. In many applications there are only a few if any young gcs during 885 // marking, which makes any prediction useless. This increases the accuracy of the 886 // prediction. 887 if (this_gc_was_young_only && mutator_time_s > min_valid_time) { 888 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 889 report = true; 890 } 891 892 if (report) { 893 report_ihop_statistics(); 894 } 895 } 896 897 void G1Policy::report_ihop_statistics() { 898 _ihop_control->print(); 899 } 900 901 void G1Policy::print_phases() { 902 phase_times()->print(); 903 } 904 905 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards, 906 size_t rs_length) const { 907 size_t effective_scanned_cards = _analytics->predict_scan_card_num(rs_length, collector_state()->in_young_only_phase()); 908 return 909 _analytics->predict_card_merge_time_ms(pending_cards + rs_length, collector_state()->in_young_only_phase()) + 910 _analytics->predict_card_scan_time_ms(effective_scanned_cards, collector_state()->in_young_only_phase()) + 911 _analytics->predict_constant_other_time_ms() + 912 predict_survivor_regions_evac_time(); 913 } 914 915 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const { 916 size_t rs_length = _analytics->predict_rs_length(); 917 return predict_base_elapsed_time_ms(pending_cards, rs_length); 918 } 919 920 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const { 921 size_t bytes_to_copy; 922 if (!hr->is_young()) { 923 bytes_to_copy = hr->max_live_bytes(); 924 } else { 925 bytes_to_copy = (size_t) (hr->used() * hr->surv_rate_prediction(_predictor)); 926 } 927 return bytes_to_copy; 928 } 929 930 double G1Policy::predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy) const { 931 if (count == 0) { 932 return 0.0; 933 } 934 size_t const expected_bytes = _eden_surv_rate_group->accum_surv_rate_pred(count) * HeapRegion::GrainBytes; 935 if (bytes_to_copy != NULL) { 936 *bytes_to_copy = expected_bytes; 937 } 938 return _analytics->predict_object_copy_time_ms(expected_bytes, collector_state()->mark_or_rebuild_in_progress()); 939 } 940 941 double G1Policy::predict_region_copy_time_ms(HeapRegion* hr) const { 942 size_t const bytes_to_copy = predict_bytes_to_copy(hr); 943 return _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress()); 944 } 945 946 double G1Policy::predict_region_non_copy_time_ms(HeapRegion* hr, 947 bool for_young_gc) const { 948 size_t rs_length = hr->rem_set()->occupied(); 949 size_t scan_card_num = _analytics->predict_scan_card_num(rs_length, for_young_gc); 950 951 double region_elapsed_time_ms = 952 _analytics->predict_card_merge_time_ms(rs_length, collector_state()->in_young_only_phase()) + 953 _analytics->predict_card_scan_time_ms(scan_card_num, collector_state()->in_young_only_phase()); 954 955 // The prediction of the "other" time for this region is based 956 // upon the region type and NOT the GC type. 957 if (hr->is_young()) { 958 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 959 } else { 960 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 961 } 962 return region_elapsed_time_ms; 963 } 964 965 double G1Policy::predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const { 966 return predict_region_non_copy_time_ms(hr, for_young_gc) + predict_region_copy_time_ms(hr); 967 } 968 969 bool G1Policy::should_allocate_mutator_region() const { 970 uint young_list_length = _g1h->young_regions_count(); 971 uint young_list_target_length = _young_list_target_length; 972 return young_list_length < young_list_target_length; 973 } 974 975 bool G1Policy::can_expand_young_list() const { 976 uint young_list_length = _g1h->young_regions_count(); 977 uint young_list_max_length = _young_list_max_length; 978 return young_list_length < young_list_max_length; 979 } 980 981 bool G1Policy::use_adaptive_young_list_length() const { 982 return _young_gen_sizer->use_adaptive_young_list_length(); 983 } 984 985 size_t G1Policy::desired_survivor_size(uint max_regions) const { 986 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions; 987 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 988 } 989 990 void G1Policy::print_age_table() { 991 _survivors_age_table.print_age_table(_tenuring_threshold); 992 } 993 994 void G1Policy::update_max_gc_locker_expansion() { 995 uint expansion_region_num = 0; 996 if (GCLockerEdenExpansionPercent > 0) { 997 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 998 double expansion_region_num_d = perc * (double) _young_list_target_length; 999 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 1000 // less than 1.0) we'll get 1. 1001 expansion_region_num = (uint) ceil(expansion_region_num_d); 1002 } else { 1003 assert(expansion_region_num == 0, "sanity"); 1004 } 1005 _young_list_max_length = _young_list_target_length + expansion_region_num; 1006 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 1007 } 1008 1009 // Calculates survivor space parameters. 1010 void G1Policy::update_survivors_policy() { 1011 double max_survivor_regions_d = 1012 (double) _young_list_target_length / (double) SurvivorRatio; 1013 1014 // Calculate desired survivor size based on desired max survivor regions (unconstrained 1015 // by remaining heap). Otherwise we may cause undesired promotions as we are 1016 // already getting close to end of the heap, impacting performance even more. 1017 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d); 1018 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions); 1019 1020 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size); 1021 if (UsePerfData) { 1022 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold); 1023 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize); 1024 } 1025 // The real maximum survivor size is bounded by the number of regions that can 1026 // be allocated into. 1027 _max_survivor_regions = MIN2(desired_max_survivor_regions, 1028 _g1h->num_free_or_available_regions()); 1029 } 1030 1031 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 1032 // We actually check whether we are marking here and not if we are in a 1033 // reclamation phase. This means that we will schedule a concurrent mark 1034 // even while we are still in the process of reclaiming memory. 1035 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle(); 1036 if (!during_cycle) { 1037 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 1038 collector_state()->set_initiate_conc_mark_if_possible(true); 1039 return true; 1040 } else { 1041 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 1042 return false; 1043 } 1044 } 1045 1046 void G1Policy::initiate_conc_mark() { 1047 collector_state()->set_in_initial_mark_gc(true); 1048 collector_state()->set_initiate_conc_mark_if_possible(false); 1049 } 1050 1051 void G1Policy::decide_on_conc_mark_initiation() { 1052 // We are about to decide on whether this pause will be an 1053 // initial-mark pause. 1054 1055 // First, collector_state()->in_initial_mark_gc() should not be already set. We 1056 // will set it here if we have to. However, it should be cleared by 1057 // the end of the pause (it's only set for the duration of an 1058 // initial-mark pause). 1059 assert(!collector_state()->in_initial_mark_gc(), "pre-condition"); 1060 1061 if (collector_state()->initiate_conc_mark_if_possible()) { 1062 // We had noticed on a previous pause that the heap occupancy has 1063 // gone over the initiating threshold and we should start a 1064 // concurrent marking cycle. So we might initiate one. 1065 1066 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) { 1067 // Initiate a new initial mark if there is no marking or reclamation going on. 1068 initiate_conc_mark(); 1069 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 1070 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) { 1071 // Initiate a user requested initial mark. An initial mark must be young only 1072 // GC, so the collector state must be updated to reflect this. 1073 collector_state()->set_in_young_only_phase(true); 1074 collector_state()->set_in_young_gc_before_mixed(false); 1075 1076 // We might have ended up coming here about to start a mixed phase with a collection set 1077 // active. The following remark might change the change the "evacuation efficiency" of 1078 // the regions in this set, leading to failing asserts later. 1079 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here. 1080 clear_collection_set_candidates(); 1081 abort_time_to_mixed_tracking(); 1082 initiate_conc_mark(); 1083 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 1084 } else { 1085 // The concurrent marking thread is still finishing up the 1086 // previous cycle. If we start one right now the two cycles 1087 // overlap. In particular, the concurrent marking thread might 1088 // be in the process of clearing the next marking bitmap (which 1089 // we will use for the next cycle if we start one). Starting a 1090 // cycle now will be bad given that parts of the marking 1091 // information might get cleared by the marking thread. And we 1092 // cannot wait for the marking thread to finish the cycle as it 1093 // periodically yields while clearing the next marking bitmap 1094 // and, if it's in a yield point, it's waiting for us to 1095 // finish. So, at this point we will not start a cycle and we'll 1096 // let the concurrent marking thread complete the last one. 1097 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 1098 } 1099 } 1100 } 1101 1102 void G1Policy::record_concurrent_mark_cleanup_end() { 1103 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions()); 1104 _collection_set->set_candidates(candidates); 1105 1106 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs"); 1107 if (!mixed_gc_pending) { 1108 clear_collection_set_candidates(); 1109 abort_time_to_mixed_tracking(); 1110 } 1111 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending); 1112 collector_state()->set_mark_or_rebuild_in_progress(false); 1113 1114 double end_sec = os::elapsedTime(); 1115 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1116 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1117 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1118 1119 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1120 } 1121 1122 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const { 1123 return percent_of(reclaimable_bytes, _g1h->capacity()); 1124 } 1125 1126 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure { 1127 virtual bool do_heap_region(HeapRegion* r) { 1128 r->rem_set()->clear_locked(true /* only_cardset */); 1129 return false; 1130 } 1131 }; 1132 1133 void G1Policy::clear_collection_set_candidates() { 1134 // Clear remembered sets of remaining candidate regions and the actual candidate 1135 // set. 1136 G1ClearCollectionSetCandidateRemSets cl; 1137 _collection_set->candidates()->iterate(&cl); 1138 _collection_set->clear_candidates(); 1139 } 1140 1141 void G1Policy::maybe_start_marking() { 1142 if (need_to_start_conc_mark("end of GC")) { 1143 // Note: this might have already been set, if during the last 1144 // pause we decided to start a cycle but at the beginning of 1145 // this pause we decided to postpone it. That's OK. 1146 collector_state()->set_initiate_conc_mark_if_possible(true); 1147 } 1148 } 1149 1150 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const { 1151 assert(!collector_state()->in_full_gc(), "must be"); 1152 if (collector_state()->in_initial_mark_gc()) { 1153 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1154 return InitialMarkGC; 1155 } else if (collector_state()->in_young_gc_before_mixed()) { 1156 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1157 return LastYoungGC; 1158 } else if (collector_state()->in_mixed_phase()) { 1159 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1160 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1161 return MixedGC; 1162 } else { 1163 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1164 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1165 return YoungOnlyGC; 1166 } 1167 } 1168 1169 void G1Policy::record_pause(PauseKind kind, double start, double end) { 1170 // Manage the MMU tracker. For some reason it ignores Full GCs. 1171 if (kind != FullGC) { 1172 _mmu_tracker->add_pause(start, end); 1173 } 1174 // Manage the mutator time tracking from initial mark to first mixed gc. 1175 switch (kind) { 1176 case FullGC: 1177 abort_time_to_mixed_tracking(); 1178 break; 1179 case Cleanup: 1180 case Remark: 1181 case YoungOnlyGC: 1182 case LastYoungGC: 1183 _initial_mark_to_mixed.add_pause(end - start); 1184 break; 1185 case InitialMarkGC: 1186 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 1187 _initial_mark_to_mixed.record_initial_mark_end(end); 1188 } 1189 break; 1190 case MixedGC: 1191 _initial_mark_to_mixed.record_mixed_gc_start(start); 1192 break; 1193 default: 1194 ShouldNotReachHere(); 1195 } 1196 } 1197 1198 void G1Policy::abort_time_to_mixed_tracking() { 1199 _initial_mark_to_mixed.reset(); 1200 } 1201 1202 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str, 1203 const char* false_action_str) const { 1204 G1CollectionSetCandidates* candidates = _collection_set->candidates(); 1205 1206 if (candidates->is_empty()) { 1207 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1208 return false; 1209 } 1210 1211 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1212 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1213 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1214 double threshold = (double) G1HeapWastePercent; 1215 if (reclaimable_percent <= threshold) { 1216 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1217 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1218 return false; 1219 } 1220 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1221 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1222 return true; 1223 } 1224 1225 uint G1Policy::calc_min_old_cset_length() const { 1226 // The min old CSet region bound is based on the maximum desired 1227 // number of mixed GCs after a cycle. I.e., even if some old regions 1228 // look expensive, we should add them to the CSet anyway to make 1229 // sure we go through the available old regions in no more than the 1230 // maximum desired number of mixed GCs. 1231 // 1232 // The calculation is based on the number of marked regions we added 1233 // to the CSet candidates in the first place, not how many remain, so 1234 // that the result is the same during all mixed GCs that follow a cycle. 1235 1236 const size_t region_num = _collection_set->candidates()->num_regions(); 1237 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1238 size_t result = region_num / gc_num; 1239 // emulate ceiling 1240 if (result * gc_num < region_num) { 1241 result += 1; 1242 } 1243 return (uint) result; 1244 } 1245 1246 uint G1Policy::calc_max_old_cset_length() const { 1247 // The max old CSet region bound is based on the threshold expressed 1248 // as a percentage of the heap size. I.e., it should bound the 1249 // number of old regions added to the CSet irrespective of how many 1250 // of them are available. 1251 1252 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1253 const size_t region_num = g1h->num_regions(); 1254 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1255 size_t result = region_num * perc / 100; 1256 // emulate ceiling 1257 if (100 * result < region_num * perc) { 1258 result += 1; 1259 } 1260 return (uint) result; 1261 } 1262 1263 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates, 1264 double time_remaining_ms, 1265 uint& num_initial_regions, 1266 uint& num_optional_regions) { 1267 assert(candidates != NULL, "Must be"); 1268 1269 num_initial_regions = 0; 1270 num_optional_regions = 0; 1271 uint num_expensive_regions = 0; 1272 1273 double predicted_old_time_ms = 0.0; 1274 double predicted_initial_time_ms = 0.0; 1275 double predicted_optional_time_ms = 0.0; 1276 1277 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction(); 1278 1279 const uint min_old_cset_length = calc_min_old_cset_length(); 1280 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length()); 1281 const uint max_optional_regions = max_old_cset_length - min_old_cset_length; 1282 bool check_time_remaining = use_adaptive_young_list_length(); 1283 1284 uint candidate_idx = candidates->cur_idx(); 1285 1286 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, " 1287 "time remaining %1.2fms, optional threshold %1.2fms", 1288 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms); 1289 1290 HeapRegion* hr = candidates->at(candidate_idx); 1291 while (hr != NULL) { 1292 if (num_initial_regions + num_optional_regions >= max_old_cset_length) { 1293 // Added maximum number of old regions to the CSet. 1294 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). " 1295 "Initial %u regions, optional %u regions", 1296 num_initial_regions, num_optional_regions); 1297 break; 1298 } 1299 1300 // Stop adding regions if the remaining reclaimable space is 1301 // not above G1HeapWastePercent. 1302 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1303 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1304 double threshold = (double) G1HeapWastePercent; 1305 if (reclaimable_percent <= threshold) { 1306 // We've added enough old regions that the amount of uncollected 1307 // reclaimable space is at or below the waste threshold. Stop 1308 // adding old regions to the CSet. 1309 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). " 1310 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%", 1311 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes), 1312 reclaimable_percent, G1HeapWastePercent); 1313 break; 1314 } 1315 1316 double predicted_time_ms = predict_region_total_time_ms(hr, false); 1317 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0); 1318 // Add regions to old set until we reach the minimum amount 1319 if (num_initial_regions < min_old_cset_length) { 1320 predicted_old_time_ms += predicted_time_ms; 1321 num_initial_regions++; 1322 // Record the number of regions added with no time remaining 1323 if (time_remaining_ms == 0.0) { 1324 num_expensive_regions++; 1325 } 1326 } else if (!check_time_remaining) { 1327 // In the non-auto-tuning case, we'll finish adding regions 1328 // to the CSet if we reach the minimum. 1329 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min)."); 1330 break; 1331 } else { 1332 // Keep adding regions to old set until we reach the optional threshold 1333 if (time_remaining_ms > optional_threshold_ms) { 1334 predicted_old_time_ms += predicted_time_ms; 1335 num_initial_regions++; 1336 } else if (time_remaining_ms > 0) { 1337 // Keep adding optional regions until time is up. 1338 assert(num_optional_regions < max_optional_regions, "Should not be possible."); 1339 predicted_optional_time_ms += predicted_time_ms; 1340 num_optional_regions++; 1341 } else { 1342 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high)."); 1343 break; 1344 } 1345 } 1346 hr = candidates->at(++candidate_idx); 1347 } 1348 if (hr == NULL) { 1349 log_debug(gc, ergo, cset)("Old candidate collection set empty."); 1350 } 1351 1352 if (num_expensive_regions > 0) { 1353 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.", 1354 num_expensive_regions); 1355 } 1356 1357 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, " 1358 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f", 1359 num_initial_regions, num_optional_regions, 1360 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms); 1361 } 1362 1363 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates, 1364 uint const max_optional_regions, 1365 double time_remaining_ms, 1366 uint& num_optional_regions) { 1367 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase"); 1368 1369 num_optional_regions = 0; 1370 double prediction_ms = 0; 1371 uint candidate_idx = candidates->cur_idx(); 1372 1373 HeapRegion* r = candidates->at(candidate_idx); 1374 while (num_optional_regions < max_optional_regions) { 1375 assert(r != NULL, "Region must exist"); 1376 prediction_ms += predict_region_total_time_ms(r, false); 1377 1378 if (prediction_ms > time_remaining_ms) { 1379 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.", 1380 prediction_ms, r->hrm_index(), time_remaining_ms); 1381 break; 1382 } 1383 // This region will be included in the next optional evacuation. 1384 1385 time_remaining_ms -= prediction_ms; 1386 num_optional_regions++; 1387 r = candidates->at(++candidate_idx); 1388 } 1389 1390 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms", 1391 num_optional_regions, max_optional_regions, prediction_ms); 1392 } 1393 1394 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) { 1395 note_start_adding_survivor_regions(); 1396 1397 HeapRegion* last = NULL; 1398 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin(); 1399 it != survivors->regions()->end(); 1400 ++it) { 1401 HeapRegion* curr = *it; 1402 set_region_survivor(curr); 1403 1404 // The region is a non-empty survivor so let's add it to 1405 // the incremental collection set for the next evacuation 1406 // pause. 1407 _collection_set->add_survivor_regions(curr); 1408 1409 last = curr; 1410 } 1411 note_stop_adding_survivor_regions(); 1412 1413 // Don't clear the survivor list handles until the start of 1414 // the next evacuation pause - we need it in order to re-tag 1415 // the survivor regions from this evacuation pause as 'young' 1416 // at the start of the next. 1417 } 1418 1419 size_t G1Policy::minimum_desired_bytes_after_concurrent_mark(size_t used_bytes) { 1420 size_t minimum_desired_buffer_size = _ihop_control->predict_unstrained_buffer_size(); 1421 return minimum_desired_buffer_size != 0 ? 1422 minimum_desired_buffer_size : _young_list_max_length * HeapRegion::GrainBytes 1423 + _reserve_regions * HeapRegion::GrainBytes + used_bytes; 1424 }