1 /* 2 * Copyright (c) 2001, 2020, 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/g1ConcurrentRefineStats.hpp" 35 #include "gc/g1/g1CollectionSetChooser.hpp" 36 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp" 37 #include "gc/g1/g1HotCardCache.hpp" 38 #include "gc/g1/g1IHOPControl.hpp" 39 #include "gc/g1/g1GCPhaseTimes.hpp" 40 #include "gc/g1/g1Policy.hpp" 41 #include "gc/g1/g1SurvivorRegions.hpp" 42 #include "gc/g1/g1YoungGenSizer.hpp" 43 #include "gc/g1/heapRegion.inline.hpp" 44 #include "gc/g1/heapRegionRemSet.hpp" 45 #include "gc/shared/concurrentGCBreakpoints.hpp" 46 #include "gc/shared/gcPolicyCounters.hpp" 47 #include "logging/log.hpp" 48 #include "runtime/arguments.hpp" 49 #include "runtime/java.hpp" 50 #include "runtime/mutexLocker.hpp" 51 #include "utilities/debug.hpp" 52 #include "utilities/growableArray.hpp" 53 #include "utilities/pair.hpp" 54 55 G1Policy::G1Policy(STWGCTimer* gc_timer) : 56 _predictor(G1ConfidencePercent / 100.0), 57 _analytics(new G1Analytics(&_predictor)), 58 _remset_tracker(), 59 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)), 60 _ihop_control(create_ihop_control(&_predictor)), 61 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)), 62 _full_collection_start_sec(0.0), 63 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC), 64 _young_list_target_length(0), 65 _young_list_fixed_length(0), 66 _young_list_max_length(0), 67 _eden_surv_rate_group(new G1SurvRateGroup()), 68 _survivor_surv_rate_group(new G1SurvRateGroup()), 69 _reserve_factor((double) G1ReservePercent / 100.0), 70 _reserve_regions(0), 71 _young_gen_sizer(G1YoungGenSizer::create_gen_sizer()), 72 _free_regions_at_end_of_collection(0), 73 _rs_length(0), 74 _rs_length_prediction(0), 75 _pending_cards_at_gc_start(0), 76 _bytes_allocated_in_old_since_last_gc(0), 77 _initial_mark_to_mixed(), 78 _collection_set(NULL), 79 _g1h(NULL), 80 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)), 81 _mark_remark_start_sec(0), 82 _mark_cleanup_start_sec(0), 83 _tenuring_threshold(MaxTenuringThreshold), 84 _max_survivor_regions(0), 85 _survivors_age_table(true) 86 { 87 } 88 89 G1Policy::~G1Policy() { 90 delete _ihop_control; 91 delete _young_gen_sizer; 92 } 93 94 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) { 95 if (G1Arguments::is_heterogeneous_heap()) { 96 return new G1HeterogeneousHeapPolicy(gc_timer_stw); 97 } else { 98 return new G1Policy(gc_timer_stw); 99 } 100 } 101 102 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); } 103 104 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) { 105 _g1h = g1h; 106 _collection_set = collection_set; 107 108 assert(Heap_lock->owned_by_self(), "Locking discipline."); 109 110 if (!use_adaptive_young_list_length()) { 111 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length(); 112 } 113 _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions()); 114 115 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 116 117 update_young_list_max_and_target_length(); 118 // We may immediately start allocating regions and placing them on the 119 // collection set list. Initialize the per-collection set info 120 _collection_set->start_incremental_building(); 121 122 double now = os::elapsedTime(); 123 _analytics->update_recent_gc_times(now, 0.0); 124 } 125 126 void G1Policy::note_gc_start() { 127 phase_times()->note_gc_start(); 128 } 129 130 class G1YoungLengthPredictor { 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(double base_time_ms, 138 double base_free_regions, 139 double target_pause_time_ms, 140 const G1Policy* policy) : 141 _base_time_ms(base_time_ms), 142 _base_free_regions(base_free_regions), 143 _target_pause_time_ms(target_pause_time_ms), 144 _policy(policy) {} 145 146 bool will_fit(uint young_length) const { 147 if (young_length >= _base_free_regions) { 148 // end condition 1: not enough space for the young regions 149 return false; 150 } 151 152 size_t bytes_to_copy = 0; 153 const double copy_time_ms = _policy->predict_eden_copy_time_ms(young_length, &bytes_to_copy); 154 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length); 155 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms; 156 if (pause_time_ms > _target_pause_time_ms) { 157 // end condition 2: prediction is over the target pause time 158 return false; 159 } 160 161 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes; 162 163 // When copying, we will likely need more bytes free than is live in the region. 164 // Add some safety margin to factor in the confidence of our guess, and the 165 // natural expected waste. 166 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 167 // of the calculation: the lower the confidence, the more headroom. 168 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 169 // copying due to anticipated waste in the PLABs. 170 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 171 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 172 173 if (expected_bytes_to_copy > free_bytes) { 174 // end condition 3: out-of-space 175 return false; 176 } 177 178 // success! 179 return true; 180 } 181 }; 182 183 void G1Policy::record_new_heap_size(uint new_number_of_regions) { 184 // re-calculate the necessary reserve 185 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 186 // We use ceiling so that if reserve_regions_d is > 0.0 (but 187 // smaller than 1.0) we'll get 1. 188 _reserve_regions = (uint) ceil(reserve_regions_d); 189 190 _young_gen_sizer->heap_size_changed(new_number_of_regions); 191 192 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 193 } 194 195 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const { 196 uint desired_min_length = 0; 197 if (use_adaptive_young_list_length()) { 198 if (_analytics->num_alloc_rate_ms() > 3) { 199 double now_sec = os::elapsedTime(); 200 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 201 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 202 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 203 } else { 204 // otherwise we don't have enough info to make the prediction 205 } 206 } 207 desired_min_length += base_min_length; 208 // make sure we don't go below any user-defined minimum bound 209 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length); 210 } 211 212 uint G1Policy::calculate_young_list_desired_max_length() const { 213 // Here, we might want to also take into account any additional 214 // constraints (i.e., user-defined minimum bound). Currently, we 215 // effectively don't set this bound. 216 return _young_gen_sizer->max_desired_young_length(); 217 } 218 219 uint G1Policy::update_young_list_max_and_target_length() { 220 return update_young_list_max_and_target_length(_analytics->predict_rs_length()); 221 } 222 223 uint G1Policy::update_young_list_max_and_target_length(size_t rs_length) { 224 uint unbounded_target_length = update_young_list_target_length(rs_length); 225 update_max_gc_locker_expansion(); 226 return unbounded_target_length; 227 } 228 229 uint G1Policy::update_young_list_target_length(size_t rs_length) { 230 YoungTargetLengths young_lengths = young_list_target_lengths(rs_length); 231 _young_list_target_length = young_lengths.first; 232 233 return young_lengths.second; 234 } 235 236 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_length) const { 237 YoungTargetLengths result; 238 239 // Calculate the absolute and desired min bounds first. 240 241 // This is how many young regions we already have (currently: the survivors). 242 const uint base_min_length = _g1h->survivor_regions_count(); 243 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 244 // This is the absolute minimum young length. Ensure that we 245 // will at least have one eden region available for allocation. 246 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1); 247 // If we shrank the young list target it should not shrink below the current size. 248 desired_min_length = MAX2(desired_min_length, absolute_min_length); 249 // Calculate the absolute and desired max bounds. 250 251 uint desired_max_length = calculate_young_list_desired_max_length(); 252 253 uint young_list_target_length = 0; 254 if (use_adaptive_young_list_length()) { 255 if (collector_state()->in_young_only_phase()) { 256 young_list_target_length = 257 calculate_young_list_target_length(rs_length, 258 base_min_length, 259 desired_min_length, 260 desired_max_length); 261 } else { 262 // Don't calculate anything and let the code below bound it to 263 // the desired_min_length, i.e., do the next GC as soon as 264 // possible to maximize how many old regions we can add to it. 265 } 266 } else { 267 // The user asked for a fixed young gen so we'll fix the young gen 268 // whether the next GC is young or mixed. 269 young_list_target_length = _young_list_fixed_length; 270 } 271 272 result.second = young_list_target_length; 273 274 // We will try our best not to "eat" into the reserve. 275 uint absolute_max_length = 0; 276 if (_free_regions_at_end_of_collection > _reserve_regions) { 277 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 278 } 279 if (desired_max_length > absolute_max_length) { 280 desired_max_length = absolute_max_length; 281 } 282 283 // Make sure we don't go over the desired max length, nor under the 284 // desired min length. In case they clash, desired_min_length wins 285 // which is why that test is second. 286 if (young_list_target_length > desired_max_length) { 287 young_list_target_length = desired_max_length; 288 } 289 if (young_list_target_length < desired_min_length) { 290 young_list_target_length = desired_min_length; 291 } 292 293 assert(young_list_target_length > base_min_length, 294 "we should be able to allocate at least one eden region"); 295 assert(young_list_target_length >= absolute_min_length, "post-condition"); 296 297 result.first = young_list_target_length; 298 return result; 299 } 300 301 uint G1Policy::calculate_young_list_target_length(size_t rs_length, 302 uint base_min_length, 303 uint desired_min_length, 304 uint desired_max_length) const { 305 assert(use_adaptive_young_list_length(), "pre-condition"); 306 assert(collector_state()->in_young_only_phase(), "only call this for young GCs"); 307 308 // In case some edge-condition makes the desired max length too small... 309 if (desired_max_length <= desired_min_length) { 310 return desired_min_length; 311 } 312 313 // We'll adjust min_young_length and max_young_length not to include 314 // the already allocated young regions (i.e., so they reflect the 315 // min and max eden regions we'll allocate). The base_min_length 316 // will be reflected in the predictions by the 317 // survivor_regions_evac_time prediction. 318 assert(desired_min_length > base_min_length, "invariant"); 319 uint min_young_length = desired_min_length - base_min_length; 320 assert(desired_max_length > base_min_length, "invariant"); 321 uint max_young_length = desired_max_length - base_min_length; 322 323 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 324 const size_t pending_cards = _analytics->predict_pending_cards(); 325 const double base_time_ms = predict_base_elapsed_time_ms(pending_cards, rs_length); 326 const uint available_free_regions = _free_regions_at_end_of_collection; 327 const uint base_free_regions = 328 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0; 329 330 // Here, we will make sure that the shortest young length that 331 // makes sense fits within the target pause time. 332 333 G1YoungLengthPredictor p(base_time_ms, 334 base_free_regions, 335 target_pause_time_ms, 336 this); 337 if (p.will_fit(min_young_length)) { 338 // The shortest young length will fit into the target pause time; 339 // we'll now check whether the absolute maximum number of young 340 // regions will fit in the target pause time. If not, we'll do 341 // a binary search between min_young_length and max_young_length. 342 if (p.will_fit(max_young_length)) { 343 // The maximum young length will fit into the target pause time. 344 // We are done so set min young length to the maximum length (as 345 // the result is assumed to be returned in min_young_length). 346 min_young_length = max_young_length; 347 } else { 348 // The maximum possible number of young regions will not fit within 349 // the target pause time so we'll search for the optimal 350 // length. The loop invariants are: 351 // 352 // min_young_length < max_young_length 353 // min_young_length is known to fit into the target pause time 354 // max_young_length is known not to fit into the target pause time 355 // 356 // Going into the loop we know the above hold as we've just 357 // checked them. Every time around the loop we check whether 358 // the middle value between min_young_length and 359 // max_young_length fits into the target pause time. If it 360 // does, it becomes the new min. If it doesn't, it becomes 361 // the new max. This way we maintain the loop invariants. 362 363 assert(min_young_length < max_young_length, "invariant"); 364 uint diff = (max_young_length - min_young_length) / 2; 365 while (diff > 0) { 366 uint young_length = min_young_length + diff; 367 if (p.will_fit(young_length)) { 368 min_young_length = young_length; 369 } else { 370 max_young_length = young_length; 371 } 372 assert(min_young_length < max_young_length, "invariant"); 373 diff = (max_young_length - min_young_length) / 2; 374 } 375 // The results is min_young_length which, according to the 376 // loop invariants, should fit within the target pause time. 377 378 // These are the post-conditions of the binary search above: 379 assert(min_young_length < max_young_length, 380 "otherwise we should have discovered that max_young_length " 381 "fits into the pause target and not done the binary search"); 382 assert(p.will_fit(min_young_length), 383 "min_young_length, the result of the binary search, should " 384 "fit into the pause target"); 385 assert(!p.will_fit(min_young_length + 1), 386 "min_young_length, the result of the binary search, should be " 387 "optimal, so no larger length should fit into the pause target"); 388 } 389 } else { 390 // Even the minimum length doesn't fit into the pause time 391 // target, return it as the result nevertheless. 392 } 393 return base_min_length + min_young_length; 394 } 395 396 double G1Policy::predict_survivor_regions_evac_time() const { 397 double survivor_regions_evac_time = 0.0; 398 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions(); 399 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin(); 400 it != survivor_regions->end(); 401 ++it) { 402 survivor_regions_evac_time += predict_region_total_time_ms(*it, collector_state()->in_young_only_phase()); 403 } 404 return survivor_regions_evac_time; 405 } 406 407 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_length) { 408 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" ); 409 410 if (rs_length > _rs_length_prediction) { 411 // add 10% to avoid having to recalculate often 412 size_t rs_length_prediction = rs_length * 1100 / 1000; 413 update_rs_length_prediction(rs_length_prediction); 414 415 update_young_list_max_and_target_length(rs_length_prediction); 416 } 417 } 418 419 void G1Policy::update_rs_length_prediction() { 420 update_rs_length_prediction(_analytics->predict_rs_length()); 421 } 422 423 void G1Policy::update_rs_length_prediction(size_t prediction) { 424 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) { 425 _rs_length_prediction = prediction; 426 } 427 } 428 429 void G1Policy::record_full_collection_start() { 430 _full_collection_start_sec = os::elapsedTime(); 431 // Release the future to-space so that it is available for compaction into. 432 collector_state()->set_in_young_only_phase(false); 433 collector_state()->set_in_full_gc(true); 434 _collection_set->clear_candidates(); 435 _pending_cards_at_gc_start = 0; 436 } 437 438 void G1Policy::record_full_collection_end() { 439 // Consider this like a collection pause for the purposes of allocation 440 // since last pause. 441 double end_sec = os::elapsedTime(); 442 double full_gc_time_sec = end_sec - _full_collection_start_sec; 443 double full_gc_time_ms = full_gc_time_sec * 1000.0; 444 445 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 446 447 collector_state()->set_in_full_gc(false); 448 449 // "Nuke" the heuristics that control the young/mixed GC 450 // transitions and make sure we start with young GCs after the Full GC. 451 collector_state()->set_in_young_only_phase(true); 452 collector_state()->set_in_young_gc_before_mixed(false); 453 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 454 collector_state()->set_in_initial_mark_gc(false); 455 collector_state()->set_mark_or_rebuild_in_progress(false); 456 collector_state()->set_clearing_next_bitmap(false); 457 458 _eden_surv_rate_group->start_adding_regions(); 459 // also call this on any additional surv rate groups 460 461 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 462 _survivor_surv_rate_group->reset(); 463 update_young_list_max_and_target_length(); 464 update_rs_length_prediction(); 465 466 _bytes_allocated_in_old_since_last_gc = 0; 467 468 record_pause(FullGC, _full_collection_start_sec, end_sec); 469 } 470 471 static void log_refinement_stats(const char* kind, const G1ConcurrentRefineStats& stats) { 472 log_debug(gc, refine, stats) 473 ("%s refinement: %.2fms, refined: " SIZE_FORMAT 474 ", precleaned: " SIZE_FORMAT ", dirtied: " SIZE_FORMAT, 475 kind, 476 stats.refinement_time().seconds() * MILLIUNITS, 477 stats.refined_cards(), 478 stats.precleaned_cards(), 479 stats.dirtied_cards()); 480 } 481 482 void G1Policy::record_concurrent_refinement_stats() { 483 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 484 _pending_cards_at_gc_start = dcqs.num_cards(); 485 486 // Collect per-thread stats, mostly from mutator activity. 487 G1ConcurrentRefineStats mut_stats = dcqs.get_and_reset_refinement_stats(); 488 489 // Collect specialized concurrent refinement thread stats. 490 G1ConcurrentRefine* cr = _g1h->concurrent_refine(); 491 G1ConcurrentRefineStats cr_stats = cr->get_and_reset_refinement_stats(); 492 493 G1ConcurrentRefineStats total_stats = mut_stats + cr_stats; 494 495 log_refinement_stats("Mutator", mut_stats); 496 log_refinement_stats("Concurrent", cr_stats); 497 log_refinement_stats("Total", total_stats); 498 499 // Record the rate at which cards were refined. 500 // Don't update the rate if the current sample is empty or time is zero. 501 Tickspan refinement_time = total_stats.refinement_time(); 502 size_t refined_cards = total_stats.refined_cards(); 503 if ((refined_cards > 0) && (refinement_time > Tickspan())) { 504 double rate = refined_cards / (refinement_time.seconds() * MILLIUNITS); 505 _analytics->report_concurrent_refine_rate_ms(rate); 506 log_debug(gc, refine, stats)("Concurrent refinement rate: %.2f cards/ms", rate); 507 } 508 509 // Record mutator's card logging rate. 510 double mut_start_time = _analytics->prev_collection_pause_end_ms(); 511 double mut_end_time = phase_times()->cur_collection_start_sec() * MILLIUNITS; 512 double mut_time = mut_end_time - mut_start_time; 513 // Unlike above for conc-refine rate, here we should not require a 514 // non-empty sample, since an application could go some time with only 515 // young-gen or filtered out writes. But we'll ignore unusually short 516 // sample periods, as they may just pollute the predictions. 517 if (mut_time > 1.0) { // Require > 1ms sample time. 518 double dirtied_rate = total_stats.dirtied_cards() / mut_time; 519 _analytics->report_dirtied_cards_rate_ms(dirtied_rate); 520 log_debug(gc, refine, stats)("Generate dirty cards rate: %.2f cards/ms", dirtied_rate); 521 } 522 } 523 524 void G1Policy::record_collection_pause_start(double start_time_sec) { 525 // We only need to do this here as the policy will only be applied 526 // to the GC we're about to start. so, no point is calculating this 527 // every time we calculate / recalculate the target young length. 528 update_survivors_policy(); 529 530 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(), 531 "Maximum survivor regions %u plus used regions %u exceeds max regions %u", 532 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions()); 533 assert_used_and_recalculate_used_equal(_g1h); 534 535 phase_times()->record_cur_collection_start_sec(start_time_sec); 536 537 record_concurrent_refinement_stats(); 538 539 _collection_set->reset_bytes_used_before(); 540 541 // do that for any other surv rate groups 542 _eden_surv_rate_group->stop_adding_regions(); 543 _survivors_age_table.clear(); 544 545 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed"); 546 } 547 548 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 549 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 550 collector_state()->set_in_initial_mark_gc(false); 551 } 552 553 void G1Policy::record_concurrent_mark_remark_start() { 554 _mark_remark_start_sec = os::elapsedTime(); 555 } 556 557 void G1Policy::record_concurrent_mark_remark_end() { 558 double end_time_sec = os::elapsedTime(); 559 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 560 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 561 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 562 563 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 564 } 565 566 void G1Policy::record_concurrent_mark_cleanup_start() { 567 _mark_cleanup_start_sec = os::elapsedTime(); 568 } 569 570 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 571 return phase_times()->average_time_ms(phase); 572 } 573 574 double G1Policy::young_other_time_ms() const { 575 return phase_times()->young_cset_choice_time_ms() + 576 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet); 577 } 578 579 double G1Policy::non_young_other_time_ms() const { 580 return phase_times()->non_young_cset_choice_time_ms() + 581 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet); 582 } 583 584 double G1Policy::other_time_ms(double pause_time_ms) const { 585 return pause_time_ms - phase_times()->cur_collection_par_time_ms(); 586 } 587 588 double G1Policy::constant_other_time_ms(double pause_time_ms) const { 589 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms() - phase_times()->total_rebuild_freelist_time_ms(); 590 } 591 592 bool G1Policy::about_to_start_mixed_phase() const { 593 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed(); 594 } 595 596 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 597 if (about_to_start_mixed_phase()) { 598 return false; 599 } 600 601 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 602 603 size_t cur_used_bytes = _g1h->non_young_capacity_bytes(); 604 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 605 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 606 607 bool result = false; 608 if (marking_request_bytes > marking_initiating_used_threshold) { 609 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed(); 610 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 611 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 612 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source); 613 } 614 615 return result; 616 } 617 618 double G1Policy::logged_cards_processing_time() const { 619 double all_cards_processing_time = average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR); 620 size_t logged_dirty_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards); 621 size_t scan_heap_roots_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) + 622 phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards); 623 // This may happen if there are duplicate cards in different log buffers. 624 if (logged_dirty_cards > scan_heap_roots_cards) { 625 return all_cards_processing_time + average_time_ms(G1GCPhaseTimes::MergeLB); 626 } 627 return (all_cards_processing_time * logged_dirty_cards / scan_heap_roots_cards) + average_time_ms(G1GCPhaseTimes::MergeLB); 628 } 629 630 // Anything below that is considered to be zero 631 #define MIN_TIMER_GRANULARITY 0.0000001 632 633 void G1Policy::record_collection_pause_end(double pause_time_ms) { 634 G1GCPhaseTimes* p = phase_times(); 635 636 double end_time_sec = os::elapsedTime(); 637 638 bool this_pause_included_initial_mark = false; 639 bool this_pause_was_young_only = collector_state()->in_young_only_phase(); 640 641 bool update_stats = !_g1h->evacuation_failed(); 642 643 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 644 645 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 646 647 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc(); 648 if (this_pause_included_initial_mark) { 649 record_concurrent_mark_init_end(0.0); 650 } else { 651 maybe_start_marking(); 652 } 653 654 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 655 if (app_time_ms < MIN_TIMER_GRANULARITY) { 656 // This usually happens due to the timer not having the required 657 // granularity. Some Linuxes are the usual culprits. 658 // We'll just set it to something (arbitrarily) small. 659 app_time_ms = 1.0; 660 } 661 662 if (update_stats) { 663 // We maintain the invariant that all objects allocated by mutator 664 // threads will be allocated out of eden regions. So, we can use 665 // the eden region number allocated since the previous GC to 666 // calculate the application's allocate rate. The only exception 667 // to that is humongous objects that are allocated separately. But 668 // given that humongous object allocations do not really affect 669 // either the pause's duration nor when the next pause will take 670 // place we can safely ignore them here. 671 uint regions_allocated = _collection_set->eden_region_length(); 672 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 673 _analytics->report_alloc_rate_ms(alloc_rate_ms); 674 675 _analytics->compute_pause_time_ratios(end_time_sec, pause_time_ms); 676 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 677 } 678 679 if (collector_state()->in_young_gc_before_mixed()) { 680 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC"); 681 // This has been the young GC before we start doing mixed GCs. We already 682 // decided to start mixed GCs much earlier, so there is nothing to do except 683 // advancing the state. 684 collector_state()->set_in_young_only_phase(false); 685 collector_state()->set_in_young_gc_before_mixed(false); 686 } else if (!this_pause_was_young_only) { 687 // This is a mixed GC. Here we decide whether to continue doing more 688 // mixed GCs or not. 689 if (!next_gc_should_be_mixed("continue mixed GCs", 690 "do not continue mixed GCs")) { 691 collector_state()->set_in_young_only_phase(true); 692 693 clear_collection_set_candidates(); 694 maybe_start_marking(); 695 } 696 } 697 698 _eden_surv_rate_group->start_adding_regions(); 699 700 double merge_hcc_time_ms = average_time_ms(G1GCPhaseTimes::MergeHCC); 701 if (update_stats) { 702 size_t const total_log_buffer_cards = p->sum_thread_work_items(G1GCPhaseTimes::MergeHCC, G1GCPhaseTimes::MergeHCCDirtyCards) + 703 p->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards); 704 // Update prediction for card merge; MergeRSDirtyCards includes the cards from the Eager Reclaim phase. 705 size_t const total_cards_merged = p->sum_thread_work_items(G1GCPhaseTimes::MergeRS, G1GCPhaseTimes::MergeRSDirtyCards) + 706 p->sum_thread_work_items(G1GCPhaseTimes::OptMergeRS, G1GCPhaseTimes::MergeRSDirtyCards) + 707 total_log_buffer_cards; 708 709 // The threshold for the number of cards in a given sampling which we consider 710 // large enough so that the impact from setup and other costs is negligible. 711 size_t const CardsNumSamplingThreshold = 10; 712 713 if (total_cards_merged > CardsNumSamplingThreshold) { 714 double avg_time_merge_cards = average_time_ms(G1GCPhaseTimes::MergeER) + 715 average_time_ms(G1GCPhaseTimes::MergeRS) + 716 average_time_ms(G1GCPhaseTimes::MergeHCC) + 717 average_time_ms(G1GCPhaseTimes::MergeLB) + 718 average_time_ms(G1GCPhaseTimes::OptMergeRS); 719 _analytics->report_cost_per_card_merge_ms(avg_time_merge_cards / total_cards_merged, this_pause_was_young_only); 720 } 721 722 // Update prediction for card scan 723 size_t const total_cards_scanned = p->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) + 724 p->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards); 725 726 if (total_cards_scanned > CardsNumSamplingThreshold) { 727 double avg_time_dirty_card_scan = average_time_ms(G1GCPhaseTimes::ScanHR) + 728 average_time_ms(G1GCPhaseTimes::OptScanHR); 729 730 _analytics->report_cost_per_card_scan_ms(avg_time_dirty_card_scan / total_cards_scanned, this_pause_was_young_only); 731 } 732 733 // Update prediction for the ratio between cards from the remembered 734 // sets and actually scanned cards from the remembered sets. 735 // Cards from the remembered sets are all cards not duplicated by cards from 736 // the logs. 737 // Due to duplicates in the log buffers, the number of actually scanned cards 738 // can be smaller than the cards in the log buffers. 739 const size_t from_rs_length_cards = (total_cards_scanned > total_log_buffer_cards) ? total_cards_scanned - total_log_buffer_cards : 0; 740 double merge_to_scan_ratio = 0.0; 741 if (total_cards_scanned > 0) { 742 merge_to_scan_ratio = (double) from_rs_length_cards / total_cards_scanned; 743 } 744 _analytics->report_card_merge_to_scan_ratio(merge_to_scan_ratio, this_pause_was_young_only); 745 746 const size_t recorded_rs_length = _collection_set->recorded_rs_length(); 747 const size_t rs_length_diff = _rs_length > recorded_rs_length ? _rs_length - recorded_rs_length : 0; 748 _analytics->report_rs_length_diff(rs_length_diff); 749 750 // Update prediction for copy cost per byte 751 size_t copied_bytes = p->sum_thread_work_items(G1GCPhaseTimes::MergePSS, G1GCPhaseTimes::MergePSSCopiedBytes); 752 753 if (copied_bytes > 0) { 754 double cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / copied_bytes; 755 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress()); 756 } 757 758 if (_collection_set->young_region_length() > 0) { 759 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 760 _collection_set->young_region_length()); 761 } 762 763 if (_collection_set->old_region_length() > 0) { 764 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 765 _collection_set->old_region_length()); 766 } 767 768 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 769 770 // Do not update RS lengths and the number of pending cards with information from mixed gc: 771 // these are is wildly different to during young only gc and mess up young gen sizing right 772 // after the mixed gc phase. 773 // During mixed gc we do not use them for young gen sizing. 774 if (this_pause_was_young_only) { 775 _analytics->report_pending_cards((double) _pending_cards_at_gc_start); 776 _analytics->report_rs_length((double) _rs_length); 777 } 778 } 779 780 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()), 781 "If the last pause has been an initial mark, we should not have been in the marking window"); 782 if (this_pause_included_initial_mark) { 783 collector_state()->set_mark_or_rebuild_in_progress(true); 784 } 785 786 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 787 788 update_rs_length_prediction(); 789 790 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely 791 // that in this case we are not running in a "normal" operating mode. 792 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 793 // IHOP control wants to know the expected young gen length if it were not 794 // restrained by the heap reserve. Using the actual length would make the 795 // prediction too small and the limit the young gen every time we get to the 796 // predicted target occupancy. 797 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 798 799 update_ihop_prediction(app_time_ms / 1000.0, 800 _bytes_allocated_in_old_since_last_gc, 801 last_unrestrained_young_length * HeapRegion::GrainBytes, 802 this_pause_was_young_only); 803 _bytes_allocated_in_old_since_last_gc = 0; 804 805 _ihop_control->send_trace_event(_g1h->gc_tracer_stw()); 806 } else { 807 // Any garbage collection triggered as periodic collection resets the time-to-mixed 808 // measurement. Periodic collection typically means that the application is "inactive", i.e. 809 // the marking threads may have received an uncharacterisic amount of cpu time 810 // for completing the marking, i.e. are faster than expected. 811 // This skews the predicted marking length towards smaller values which might cause 812 // the mark start being too late. 813 _initial_mark_to_mixed.reset(); 814 } 815 816 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 817 double scan_logged_cards_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 818 819 if (scan_logged_cards_time_goal_ms < merge_hcc_time_ms) { 820 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 821 "Logged Cards Scan time goal: %1.2fms Scan HCC time: %1.2fms", 822 scan_logged_cards_time_goal_ms, merge_hcc_time_ms); 823 824 scan_logged_cards_time_goal_ms = 0; 825 } else { 826 scan_logged_cards_time_goal_ms -= merge_hcc_time_ms; 827 } 828 829 double const logged_cards_time = logged_cards_processing_time(); 830 831 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", 832 scan_logged_cards_time_goal_ms, logged_cards_time, merge_hcc_time_ms); 833 834 _g1h->concurrent_refine()->adjust(logged_cards_time, 835 phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards), 836 scan_logged_cards_time_goal_ms); 837 } 838 839 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){ 840 if (G1UseAdaptiveIHOP) { 841 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 842 predictor, 843 G1ReservePercent, 844 G1HeapWastePercent); 845 } else { 846 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 847 } 848 } 849 850 void G1Policy::update_ihop_prediction(double mutator_time_s, 851 size_t mutator_alloc_bytes, 852 size_t young_gen_size, 853 bool this_gc_was_young_only) { 854 // Always try to update IHOP prediction. Even evacuation failures give information 855 // about e.g. whether to start IHOP earlier next time. 856 857 // Avoid using really small application times that might create samples with 858 // very high or very low values. They may be caused by e.g. back-to-back gcs. 859 double const min_valid_time = 1e-6; 860 861 bool report = false; 862 863 double marking_to_mixed_time = -1.0; 864 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) { 865 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 866 assert(marking_to_mixed_time > 0.0, 867 "Initial mark to mixed time must be larger than zero but is %.3f", 868 marking_to_mixed_time); 869 if (marking_to_mixed_time > min_valid_time) { 870 _ihop_control->update_marking_length(marking_to_mixed_time); 871 report = true; 872 } 873 } 874 875 // As an approximation for the young gc promotion rates during marking we use 876 // all of them. In many applications there are only a few if any young gcs during 877 // marking, which makes any prediction useless. This increases the accuracy of the 878 // prediction. 879 if (this_gc_was_young_only && mutator_time_s > min_valid_time) { 880 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 881 report = true; 882 } 883 884 if (report) { 885 report_ihop_statistics(); 886 } 887 } 888 889 void G1Policy::report_ihop_statistics() { 890 _ihop_control->print(); 891 } 892 893 void G1Policy::print_phases() { 894 phase_times()->print(); 895 } 896 897 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards, 898 size_t rs_length) const { 899 size_t effective_scanned_cards = _analytics->predict_scan_card_num(rs_length, collector_state()->in_young_only_phase()); 900 return 901 _analytics->predict_card_merge_time_ms(pending_cards + rs_length, collector_state()->in_young_only_phase()) + 902 _analytics->predict_card_scan_time_ms(effective_scanned_cards, collector_state()->in_young_only_phase()) + 903 _analytics->predict_constant_other_time_ms() + 904 predict_survivor_regions_evac_time(); 905 } 906 907 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const { 908 size_t rs_length = _analytics->predict_rs_length(); 909 return predict_base_elapsed_time_ms(pending_cards, rs_length); 910 } 911 912 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const { 913 size_t bytes_to_copy; 914 if (!hr->is_young()) { 915 bytes_to_copy = hr->max_live_bytes(); 916 } else { 917 bytes_to_copy = (size_t) (hr->used() * hr->surv_rate_prediction(_predictor)); 918 } 919 return bytes_to_copy; 920 } 921 922 double G1Policy::predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy) const { 923 if (count == 0) { 924 return 0.0; 925 } 926 size_t const expected_bytes = _eden_surv_rate_group->accum_surv_rate_pred(count) * HeapRegion::GrainBytes; 927 if (bytes_to_copy != NULL) { 928 *bytes_to_copy = expected_bytes; 929 } 930 return _analytics->predict_object_copy_time_ms(expected_bytes, collector_state()->mark_or_rebuild_in_progress()); 931 } 932 933 double G1Policy::predict_region_copy_time_ms(HeapRegion* hr) const { 934 size_t const bytes_to_copy = predict_bytes_to_copy(hr); 935 return _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress()); 936 } 937 938 double G1Policy::predict_region_non_copy_time_ms(HeapRegion* hr, 939 bool for_young_gc) const { 940 size_t rs_length = hr->rem_set()->occupied(); 941 size_t scan_card_num = _analytics->predict_scan_card_num(rs_length, for_young_gc); 942 943 double region_elapsed_time_ms = 944 _analytics->predict_card_merge_time_ms(rs_length, collector_state()->in_young_only_phase()) + 945 _analytics->predict_card_scan_time_ms(scan_card_num, collector_state()->in_young_only_phase()); 946 947 // The prediction of the "other" time for this region is based 948 // upon the region type and NOT the GC type. 949 if (hr->is_young()) { 950 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 951 } else { 952 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 953 } 954 return region_elapsed_time_ms; 955 } 956 957 double G1Policy::predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const { 958 return predict_region_non_copy_time_ms(hr, for_young_gc) + predict_region_copy_time_ms(hr); 959 } 960 961 bool G1Policy::should_allocate_mutator_region() const { 962 uint young_list_length = _g1h->young_regions_count(); 963 uint young_list_target_length = _young_list_target_length; 964 return young_list_length < young_list_target_length; 965 } 966 967 bool G1Policy::can_expand_young_list() const { 968 uint young_list_length = _g1h->young_regions_count(); 969 uint young_list_max_length = _young_list_max_length; 970 return young_list_length < young_list_max_length; 971 } 972 973 bool G1Policy::use_adaptive_young_list_length() const { 974 return _young_gen_sizer->use_adaptive_young_list_length(); 975 } 976 977 size_t G1Policy::desired_survivor_size(uint max_regions) const { 978 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions; 979 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 980 } 981 982 void G1Policy::print_age_table() { 983 _survivors_age_table.print_age_table(_tenuring_threshold); 984 } 985 986 void G1Policy::update_max_gc_locker_expansion() { 987 uint expansion_region_num = 0; 988 if (GCLockerEdenExpansionPercent > 0) { 989 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 990 double expansion_region_num_d = perc * (double) _young_list_target_length; 991 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 992 // less than 1.0) we'll get 1. 993 expansion_region_num = (uint) ceil(expansion_region_num_d); 994 } else { 995 assert(expansion_region_num == 0, "sanity"); 996 } 997 _young_list_max_length = _young_list_target_length + expansion_region_num; 998 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 999 } 1000 1001 // Calculates survivor space parameters. 1002 void G1Policy::update_survivors_policy() { 1003 double max_survivor_regions_d = 1004 (double) _young_list_target_length / (double) SurvivorRatio; 1005 1006 // Calculate desired survivor size based on desired max survivor regions (unconstrained 1007 // by remaining heap). Otherwise we may cause undesired promotions as we are 1008 // already getting close to end of the heap, impacting performance even more. 1009 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d); 1010 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions); 1011 1012 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size); 1013 if (UsePerfData) { 1014 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold); 1015 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize); 1016 } 1017 // The real maximum survivor size is bounded by the number of regions that can 1018 // be allocated into. 1019 _max_survivor_regions = MIN2(desired_max_survivor_regions, 1020 _g1h->num_free_or_available_regions()); 1021 } 1022 1023 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 1024 // We actually check whether we are marking here and not if we are in a 1025 // reclamation phase. This means that we will schedule a concurrent mark 1026 // even while we are still in the process of reclaiming memory. 1027 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle(); 1028 if (!during_cycle) { 1029 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 1030 collector_state()->set_initiate_conc_mark_if_possible(true); 1031 return true; 1032 } else { 1033 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 1034 return false; 1035 } 1036 } 1037 1038 void G1Policy::initiate_conc_mark() { 1039 collector_state()->set_in_initial_mark_gc(true); 1040 collector_state()->set_initiate_conc_mark_if_possible(false); 1041 } 1042 1043 void G1Policy::decide_on_conc_mark_initiation() { 1044 // We are about to decide on whether this pause will be an 1045 // initial-mark pause. 1046 1047 // First, collector_state()->in_initial_mark_gc() should not be already set. We 1048 // will set it here if we have to. However, it should be cleared by 1049 // the end of the pause (it's only set for the duration of an 1050 // initial-mark pause). 1051 assert(!collector_state()->in_initial_mark_gc(), "pre-condition"); 1052 1053 if (collector_state()->initiate_conc_mark_if_possible()) { 1054 // We had noticed on a previous pause that the heap occupancy has 1055 // gone over the initiating threshold and we should start a 1056 // concurrent marking cycle. Or we've been explicitly requested 1057 // to start a concurrent marking cycle. Either way, we initiate 1058 // one if not inhibited for some reason. 1059 1060 GCCause::Cause cause = _g1h->gc_cause(); 1061 if ((cause != GCCause::_wb_breakpoint) && 1062 ConcurrentGCBreakpoints::is_controlled()) { 1063 log_debug(gc, ergo)("Do not initiate concurrent cycle (whitebox controlled)"); 1064 } else if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) { 1065 // Initiate a new initial mark if there is no marking or reclamation going on. 1066 initiate_conc_mark(); 1067 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 1068 } else if (_g1h->is_user_requested_concurrent_full_gc(cause) || 1069 (cause == GCCause::_wb_breakpoint)) { 1070 // Initiate a user requested initial mark or run_to a breakpoint. 1071 // An initial mark must be young only GC, so the collector state 1072 // 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 (%s requested concurrent cycle)", 1084 (cause == GCCause::_wb_breakpoint) ? "run_to breakpoint" : "user"); 1085 } else { 1086 // The concurrent marking thread is still finishing up the 1087 // previous cycle. If we start one right now the two cycles 1088 // overlap. In particular, the concurrent marking thread might 1089 // be in the process of clearing the next marking bitmap (which 1090 // we will use for the next cycle if we start one). Starting a 1091 // cycle now will be bad given that parts of the marking 1092 // information might get cleared by the marking thread. And we 1093 // cannot wait for the marking thread to finish the cycle as it 1094 // periodically yields while clearing the next marking bitmap 1095 // and, if it's in a yield point, it's waiting for us to 1096 // finish. So, at this point we will not start a cycle and we'll 1097 // let the concurrent marking thread complete the last one. 1098 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 1099 } 1100 } 1101 } 1102 1103 void G1Policy::record_concurrent_mark_cleanup_end() { 1104 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions()); 1105 _collection_set->set_candidates(candidates); 1106 1107 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs"); 1108 if (!mixed_gc_pending) { 1109 clear_collection_set_candidates(); 1110 abort_time_to_mixed_tracking(); 1111 } 1112 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending); 1113 collector_state()->set_mark_or_rebuild_in_progress(false); 1114 1115 double end_sec = os::elapsedTime(); 1116 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1117 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1118 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1119 1120 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1121 } 1122 1123 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const { 1124 return percent_of(reclaimable_bytes, _g1h->capacity()); 1125 } 1126 1127 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure { 1128 virtual bool do_heap_region(HeapRegion* r) { 1129 r->rem_set()->clear_locked(true /* only_cardset */); 1130 return false; 1131 } 1132 }; 1133 1134 void G1Policy::clear_collection_set_candidates() { 1135 // Clear remembered sets of remaining candidate regions and the actual candidate 1136 // set. 1137 G1ClearCollectionSetCandidateRemSets cl; 1138 _collection_set->candidates()->iterate(&cl); 1139 _collection_set->clear_candidates(); 1140 } 1141 1142 void G1Policy::maybe_start_marking() { 1143 if (need_to_start_conc_mark("end of GC")) { 1144 // Note: this might have already been set, if during the last 1145 // pause we decided to start a cycle but at the beginning of 1146 // this pause we decided to postpone it. That's OK. 1147 collector_state()->set_initiate_conc_mark_if_possible(true); 1148 } 1149 } 1150 1151 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const { 1152 assert(!collector_state()->in_full_gc(), "must be"); 1153 if (collector_state()->in_initial_mark_gc()) { 1154 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1155 return InitialMarkGC; 1156 } else if (collector_state()->in_young_gc_before_mixed()) { 1157 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1158 return LastYoungGC; 1159 } else if (collector_state()->in_mixed_phase()) { 1160 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1161 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1162 return MixedGC; 1163 } else { 1164 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1165 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1166 return YoungOnlyGC; 1167 } 1168 } 1169 1170 void G1Policy::record_pause(PauseKind kind, double start, double end) { 1171 // Manage the MMU tracker. For some reason it ignores Full GCs. 1172 if (kind != FullGC) { 1173 _mmu_tracker->add_pause(start, end); 1174 } 1175 // Manage the mutator time tracking from initial mark to first mixed gc. 1176 switch (kind) { 1177 case FullGC: 1178 abort_time_to_mixed_tracking(); 1179 break; 1180 case Cleanup: 1181 case Remark: 1182 case YoungOnlyGC: 1183 case LastYoungGC: 1184 _initial_mark_to_mixed.add_pause(end - start); 1185 break; 1186 case InitialMarkGC: 1187 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) { 1188 _initial_mark_to_mixed.record_initial_mark_end(end); 1189 } 1190 break; 1191 case MixedGC: 1192 _initial_mark_to_mixed.record_mixed_gc_start(start); 1193 break; 1194 default: 1195 ShouldNotReachHere(); 1196 } 1197 } 1198 1199 void G1Policy::abort_time_to_mixed_tracking() { 1200 _initial_mark_to_mixed.reset(); 1201 } 1202 1203 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str, 1204 const char* false_action_str) const { 1205 G1CollectionSetCandidates* candidates = _collection_set->candidates(); 1206 1207 if (candidates->is_empty()) { 1208 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1209 return false; 1210 } 1211 1212 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1213 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1214 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1215 double threshold = (double) G1HeapWastePercent; 1216 if (reclaimable_percent <= threshold) { 1217 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1218 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1219 return false; 1220 } 1221 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1222 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1223 return true; 1224 } 1225 1226 uint G1Policy::calc_min_old_cset_length() const { 1227 // The min old CSet region bound is based on the maximum desired 1228 // number of mixed GCs after a cycle. I.e., even if some old regions 1229 // look expensive, we should add them to the CSet anyway to make 1230 // sure we go through the available old regions in no more than the 1231 // maximum desired number of mixed GCs. 1232 // 1233 // The calculation is based on the number of marked regions we added 1234 // to the CSet candidates in the first place, not how many remain, so 1235 // that the result is the same during all mixed GCs that follow a cycle. 1236 1237 const size_t region_num = _collection_set->candidates()->num_regions(); 1238 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1239 size_t result = region_num / gc_num; 1240 // emulate ceiling 1241 if (result * gc_num < region_num) { 1242 result += 1; 1243 } 1244 return (uint) result; 1245 } 1246 1247 uint G1Policy::calc_max_old_cset_length() const { 1248 // The max old CSet region bound is based on the threshold expressed 1249 // as a percentage of the heap size. I.e., it should bound the 1250 // number of old regions added to the CSet irrespective of how many 1251 // of them are available. 1252 1253 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1254 const size_t region_num = g1h->num_regions(); 1255 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1256 size_t result = region_num * perc / 100; 1257 // emulate ceiling 1258 if (100 * result < region_num * perc) { 1259 result += 1; 1260 } 1261 return (uint) result; 1262 } 1263 1264 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates, 1265 double time_remaining_ms, 1266 uint& num_initial_regions, 1267 uint& num_optional_regions) { 1268 assert(candidates != NULL, "Must be"); 1269 1270 num_initial_regions = 0; 1271 num_optional_regions = 0; 1272 uint num_expensive_regions = 0; 1273 1274 double predicted_old_time_ms = 0.0; 1275 double predicted_initial_time_ms = 0.0; 1276 double predicted_optional_time_ms = 0.0; 1277 1278 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction(); 1279 1280 const uint min_old_cset_length = calc_min_old_cset_length(); 1281 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length()); 1282 const uint max_optional_regions = max_old_cset_length - min_old_cset_length; 1283 bool check_time_remaining = use_adaptive_young_list_length(); 1284 1285 uint candidate_idx = candidates->cur_idx(); 1286 1287 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, " 1288 "time remaining %1.2fms, optional threshold %1.2fms", 1289 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms); 1290 1291 HeapRegion* hr = candidates->at(candidate_idx); 1292 while (hr != NULL) { 1293 if (num_initial_regions + num_optional_regions >= max_old_cset_length) { 1294 // Added maximum number of old regions to the CSet. 1295 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). " 1296 "Initial %u regions, optional %u regions", 1297 num_initial_regions, num_optional_regions); 1298 break; 1299 } 1300 1301 // Stop adding regions if the remaining reclaimable space is 1302 // not above G1HeapWastePercent. 1303 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes(); 1304 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1305 double threshold = (double) G1HeapWastePercent; 1306 if (reclaimable_percent <= threshold) { 1307 // We've added enough old regions that the amount of uncollected 1308 // reclaimable space is at or below the waste threshold. Stop 1309 // adding old regions to the CSet. 1310 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). " 1311 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%", 1312 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes), 1313 reclaimable_percent, G1HeapWastePercent); 1314 break; 1315 } 1316 1317 double predicted_time_ms = predict_region_total_time_ms(hr, false); 1318 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0); 1319 // Add regions to old set until we reach the minimum amount 1320 if (num_initial_regions < min_old_cset_length) { 1321 predicted_old_time_ms += predicted_time_ms; 1322 num_initial_regions++; 1323 // Record the number of regions added with no time remaining 1324 if (time_remaining_ms == 0.0) { 1325 num_expensive_regions++; 1326 } 1327 } else if (!check_time_remaining) { 1328 // In the non-auto-tuning case, we'll finish adding regions 1329 // to the CSet if we reach the minimum. 1330 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min)."); 1331 break; 1332 } else { 1333 // Keep adding regions to old set until we reach the optional threshold 1334 if (time_remaining_ms > optional_threshold_ms) { 1335 predicted_old_time_ms += predicted_time_ms; 1336 num_initial_regions++; 1337 } else if (time_remaining_ms > 0) { 1338 // Keep adding optional regions until time is up. 1339 assert(num_optional_regions < max_optional_regions, "Should not be possible."); 1340 predicted_optional_time_ms += predicted_time_ms; 1341 num_optional_regions++; 1342 } else { 1343 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high)."); 1344 break; 1345 } 1346 } 1347 hr = candidates->at(++candidate_idx); 1348 } 1349 if (hr == NULL) { 1350 log_debug(gc, ergo, cset)("Old candidate collection set empty."); 1351 } 1352 1353 if (num_expensive_regions > 0) { 1354 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.", 1355 num_expensive_regions); 1356 } 1357 1358 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, " 1359 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f", 1360 num_initial_regions, num_optional_regions, 1361 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms); 1362 } 1363 1364 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates, 1365 uint const max_optional_regions, 1366 double time_remaining_ms, 1367 uint& num_optional_regions) { 1368 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase"); 1369 1370 num_optional_regions = 0; 1371 double prediction_ms = 0; 1372 uint candidate_idx = candidates->cur_idx(); 1373 1374 HeapRegion* r = candidates->at(candidate_idx); 1375 while (num_optional_regions < max_optional_regions) { 1376 assert(r != NULL, "Region must exist"); 1377 prediction_ms += predict_region_total_time_ms(r, false); 1378 1379 if (prediction_ms > time_remaining_ms) { 1380 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.", 1381 prediction_ms, r->hrm_index(), time_remaining_ms); 1382 break; 1383 } 1384 // This region will be included in the next optional evacuation. 1385 1386 time_remaining_ms -= prediction_ms; 1387 num_optional_regions++; 1388 r = candidates->at(++candidate_idx); 1389 } 1390 1391 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms", 1392 num_optional_regions, max_optional_regions, prediction_ms); 1393 } 1394 1395 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) { 1396 note_start_adding_survivor_regions(); 1397 1398 HeapRegion* last = NULL; 1399 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin(); 1400 it != survivors->regions()->end(); 1401 ++it) { 1402 HeapRegion* curr = *it; 1403 set_region_survivor(curr); 1404 1405 // The region is a non-empty survivor so let's add it to 1406 // the incremental collection set for the next evacuation 1407 // pause. 1408 _collection_set->add_survivor_regions(curr); 1409 1410 last = curr; 1411 } 1412 note_stop_adding_survivor_regions(); 1413 1414 // Don't clear the survivor list handles until the start of 1415 // the next evacuation pause - we need it in order to re-tag 1416 // the survivor regions from this evacuation pause as 'young' 1417 // at the start of the next. 1418 }