1 /* 2 * Copyright (c) 2001, 2018, 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/g1CollectedHeap.inline.hpp" 28 #include "gc/g1/g1CollectionSet.hpp" 29 #include "gc/g1/g1ConcurrentMark.hpp" 30 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 31 #include "gc/g1/g1ConcurrentRefine.hpp" 32 #include "gc/g1/g1HotCardCache.hpp" 33 #include "gc/g1/g1IHOPControl.hpp" 34 #include "gc/g1/g1GCPhaseTimes.hpp" 35 #include "gc/g1/g1Policy.hpp" 36 #include "gc/g1/g1SurvivorRegions.hpp" 37 #include "gc/g1/g1YoungGenSizer.hpp" 38 #include "gc/g1/heapRegion.inline.hpp" 39 #include "gc/g1/heapRegionRemSet.hpp" 40 #include "gc/shared/gcPolicyCounters.hpp" 41 #include "logging/logStream.hpp" 42 #include "runtime/arguments.hpp" 43 #include "runtime/java.hpp" 44 #include "runtime/mutexLocker.hpp" 45 #include "utilities/debug.hpp" 46 #include "utilities/growableArray.hpp" 47 #include "utilities/pair.hpp" 48 49 G1Policy::G1Policy(STWGCTimer* gc_timer) : 50 _predictor(G1ConfidencePercent / 100.0), 51 _analytics(new G1Analytics(&_predictor)), 52 _remset_tracker(), 53 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)), 54 _ihop_control(create_ihop_control(&_predictor)), 55 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)), 56 _young_list_fixed_length(0), 57 _short_lived_surv_rate_group(new SurvRateGroup()), 58 _survivor_surv_rate_group(new SurvRateGroup()), 59 _reserve_factor((double) G1ReservePercent / 100.0), 60 _reserve_regions(0), 61 _rs_lengths_prediction(0), 62 _bytes_allocated_in_old_since_last_gc(0), 63 _initial_mark_to_mixed(), 64 _collection_set(NULL), 65 _g1h(NULL), 66 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)), 67 _tenuring_threshold(MaxTenuringThreshold), 68 _max_survivor_regions(0), 69 _survivors_age_table(true), 70 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC) { 71 } 72 73 G1Policy::~G1Policy() { 74 delete _ihop_control; 75 } 76 77 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); } 78 79 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) { 80 _g1h = g1h; 81 _collection_set = collection_set; 82 83 assert(Heap_lock->owned_by_self(), "Locking discipline."); 84 85 if (!adaptive_young_list_length()) { 86 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length(); 87 } 88 _young_gen_sizer.adjust_max_new_size(_g1h->max_regions()); 89 90 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 91 92 update_young_list_max_and_target_length(); 93 // We may immediately start allocating regions and placing them on the 94 // collection set list. Initialize the per-collection set info 95 _collection_set->start_incremental_building(); 96 } 97 98 void G1Policy::note_gc_start() { 99 phase_times()->note_gc_start(); 100 } 101 102 class G1YoungLengthPredictor { 103 const bool _during_cm; 104 const double _base_time_ms; 105 const double _base_free_regions; 106 const double _target_pause_time_ms; 107 const G1Policy* const _policy; 108 109 public: 110 G1YoungLengthPredictor(bool during_cm, 111 double base_time_ms, 112 double base_free_regions, 113 double target_pause_time_ms, 114 const G1Policy* policy) : 115 _during_cm(during_cm), 116 _base_time_ms(base_time_ms), 117 _base_free_regions(base_free_regions), 118 _target_pause_time_ms(target_pause_time_ms), 119 _policy(policy) {} 120 121 bool will_fit(uint young_length) const { 122 if (young_length >= _base_free_regions) { 123 // end condition 1: not enough space for the young regions 124 return false; 125 } 126 127 const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1); 128 const size_t bytes_to_copy = 129 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes); 130 const double copy_time_ms = 131 _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm); 132 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length); 133 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms; 134 if (pause_time_ms > _target_pause_time_ms) { 135 // end condition 2: prediction is over the target pause time 136 return false; 137 } 138 139 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes; 140 141 // When copying, we will likely need more bytes free than is live in the region. 142 // Add some safety margin to factor in the confidence of our guess, and the 143 // natural expected waste. 144 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 145 // of the calculation: the lower the confidence, the more headroom. 146 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 147 // copying due to anticipated waste in the PLABs. 148 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 149 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 150 151 if (expected_bytes_to_copy > free_bytes) { 152 // end condition 3: out-of-space 153 return false; 154 } 155 156 // success! 157 return true; 158 } 159 }; 160 161 void G1Policy::record_new_heap_size(uint new_number_of_regions) { 162 // re-calculate the necessary reserve 163 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 164 // We use ceiling so that if reserve_regions_d is > 0.0 (but 165 // smaller than 1.0) we'll get 1. 166 _reserve_regions = (uint) ceil(reserve_regions_d); 167 168 _young_gen_sizer.heap_size_changed(new_number_of_regions); 169 170 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 171 } 172 173 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const { 174 uint desired_min_length = 0; 175 if (adaptive_young_list_length()) { 176 if (_analytics->num_alloc_rate_ms() > 3) { 177 double now_sec = os::elapsedTime(); 178 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 179 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 180 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 181 } else { 182 // otherwise we don't have enough info to make the prediction 183 } 184 } 185 desired_min_length += base_min_length; 186 // make sure we don't go below any user-defined minimum bound 187 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length); 188 } 189 190 uint G1Policy::calculate_young_list_desired_max_length() const { 191 // Here, we might want to also take into account any additional 192 // constraints (i.e., user-defined minimum bound). Currently, we 193 // effectively don't set this bound. 194 return _young_gen_sizer.max_desired_young_length(); 195 } 196 197 uint G1Policy::update_young_list_max_and_target_length() { 198 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths()); 199 } 200 201 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) { 202 uint unbounded_target_length = update_young_list_target_length(rs_lengths); 203 update_max_gc_locker_expansion(); 204 return unbounded_target_length; 205 } 206 207 uint G1Policy::update_young_list_target_length(size_t rs_lengths) { 208 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths); 209 _young_list_target_length = young_lengths.first; 210 return young_lengths.second; 211 } 212 213 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const { 214 YoungTargetLengths result; 215 216 // Calculate the absolute and desired min bounds first. 217 218 // This is how many young regions we already have (currently: the survivors). 219 const uint base_min_length = _g1h->survivor_regions_count(); 220 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 221 // This is the absolute minimum young length. Ensure that we 222 // will at least have one eden region available for allocation. 223 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1); 224 // If we shrank the young list target it should not shrink below the current size. 225 desired_min_length = MAX2(desired_min_length, absolute_min_length); 226 // Calculate the absolute and desired max bounds. 227 228 uint desired_max_length = calculate_young_list_desired_max_length(); 229 230 uint young_list_target_length = 0; 231 if (adaptive_young_list_length()) { 232 if (collector_state()->in_young_only_phase()) { 233 young_list_target_length = 234 calculate_young_list_target_length(rs_lengths, 235 base_min_length, 236 desired_min_length, 237 desired_max_length); 238 } else { 239 // Don't calculate anything and let the code below bound it to 240 // the desired_min_length, i.e., do the next GC as soon as 241 // possible to maximize how many old regions we can add to it. 242 } 243 } else { 244 // The user asked for a fixed young gen so we'll fix the young gen 245 // whether the next GC is young or mixed. 246 young_list_target_length = _young_list_fixed_length; 247 } 248 249 result.second = young_list_target_length; 250 251 // We will try our best not to "eat" into the reserve. 252 uint absolute_max_length = 0; 253 if (_free_regions_at_end_of_collection > _reserve_regions) { 254 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 255 } 256 if (desired_max_length > absolute_max_length) { 257 desired_max_length = absolute_max_length; 258 } 259 260 // Make sure we don't go over the desired max length, nor under the 261 // desired min length. In case they clash, desired_min_length wins 262 // which is why that test is second. 263 if (young_list_target_length > desired_max_length) { 264 young_list_target_length = desired_max_length; 265 } 266 if (young_list_target_length < desired_min_length) { 267 young_list_target_length = desired_min_length; 268 } 269 270 assert(young_list_target_length > base_min_length, 271 "we should be able to allocate at least one eden region"); 272 assert(young_list_target_length >= absolute_min_length, "post-condition"); 273 274 result.first = young_list_target_length; 275 return result; 276 } 277 278 uint 279 G1Policy::calculate_young_list_target_length(size_t rs_lengths, 280 uint base_min_length, 281 uint desired_min_length, 282 uint desired_max_length) const { 283 assert(adaptive_young_list_length(), "pre-condition"); 284 assert(collector_state()->in_young_only_phase(), "only call this for young GCs"); 285 286 // In case some edge-condition makes the desired max length too small... 287 if (desired_max_length <= desired_min_length) { 288 return desired_min_length; 289 } 290 291 // We'll adjust min_young_length and max_young_length not to include 292 // the already allocated young regions (i.e., so they reflect the 293 // min and max eden regions we'll allocate). The base_min_length 294 // will be reflected in the predictions by the 295 // survivor_regions_evac_time prediction. 296 assert(desired_min_length > base_min_length, "invariant"); 297 uint min_young_length = desired_min_length - base_min_length; 298 assert(desired_max_length > base_min_length, "invariant"); 299 uint max_young_length = desired_max_length - base_min_length; 300 301 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 302 const double survivor_regions_evac_time = predict_survivor_regions_evac_time(); 303 const size_t pending_cards = _analytics->predict_pending_cards(); 304 const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff(); 305 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, true /* for_young_gc */); 306 const double base_time_ms = 307 predict_base_elapsed_time_ms(pending_cards, scanned_cards) + 308 survivor_regions_evac_time; 309 const uint available_free_regions = _free_regions_at_end_of_collection; 310 const uint base_free_regions = 311 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0; 312 313 // Here, we will make sure that the shortest young length that 314 // makes sense fits within the target pause time. 315 316 G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(), 317 base_time_ms, 318 base_free_regions, 319 target_pause_time_ms, 320 this); 321 if (p.will_fit(min_young_length)) { 322 // The shortest young length will fit into the target pause time; 323 // we'll now check whether the absolute maximum number of young 324 // regions will fit in the target pause time. If not, we'll do 325 // a binary search between min_young_length and max_young_length. 326 if (p.will_fit(max_young_length)) { 327 // The maximum young length will fit into the target pause time. 328 // We are done so set min young length to the maximum length (as 329 // the result is assumed to be returned in min_young_length). 330 min_young_length = max_young_length; 331 } else { 332 // The maximum possible number of young regions will not fit within 333 // the target pause time so we'll search for the optimal 334 // length. The loop invariants are: 335 // 336 // min_young_length < max_young_length 337 // min_young_length is known to fit into the target pause time 338 // max_young_length is known not to fit into the target pause time 339 // 340 // Going into the loop we know the above hold as we've just 341 // checked them. Every time around the loop we check whether 342 // the middle value between min_young_length and 343 // max_young_length fits into the target pause time. If it 344 // does, it becomes the new min. If it doesn't, it becomes 345 // the new max. This way we maintain the loop invariants. 346 347 assert(min_young_length < max_young_length, "invariant"); 348 uint diff = (max_young_length - min_young_length) / 2; 349 while (diff > 0) { 350 uint young_length = min_young_length + diff; 351 if (p.will_fit(young_length)) { 352 min_young_length = young_length; 353 } else { 354 max_young_length = young_length; 355 } 356 assert(min_young_length < max_young_length, "invariant"); 357 diff = (max_young_length - min_young_length) / 2; 358 } 359 // The results is min_young_length which, according to the 360 // loop invariants, should fit within the target pause time. 361 362 // These are the post-conditions of the binary search above: 363 assert(min_young_length < max_young_length, 364 "otherwise we should have discovered that max_young_length " 365 "fits into the pause target and not done the binary search"); 366 assert(p.will_fit(min_young_length), 367 "min_young_length, the result of the binary search, should " 368 "fit into the pause target"); 369 assert(!p.will_fit(min_young_length + 1), 370 "min_young_length, the result of the binary search, should be " 371 "optimal, so no larger length should fit into the pause target"); 372 } 373 } else { 374 // Even the minimum length doesn't fit into the pause time 375 // target, return it as the result nevertheless. 376 } 377 return base_min_length + min_young_length; 378 } 379 380 double G1Policy::predict_survivor_regions_evac_time() const { 381 double survivor_regions_evac_time = 0.0; 382 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions(); 383 384 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin(); 385 it != survivor_regions->end(); 386 ++it) { 387 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase()); 388 } 389 return survivor_regions_evac_time; 390 } 391 392 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) { 393 guarantee( adaptive_young_list_length(), "should not call this otherwise" ); 394 395 if (rs_lengths > _rs_lengths_prediction) { 396 // add 10% to avoid having to recalculate often 397 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000; 398 update_rs_lengths_prediction(rs_lengths_prediction); 399 400 update_young_list_max_and_target_length(rs_lengths_prediction); 401 } 402 } 403 404 void G1Policy::update_rs_lengths_prediction() { 405 update_rs_lengths_prediction(_analytics->predict_rs_lengths()); 406 } 407 408 void G1Policy::update_rs_lengths_prediction(size_t prediction) { 409 if (collector_state()->in_young_only_phase() && adaptive_young_list_length()) { 410 _rs_lengths_prediction = prediction; 411 } 412 } 413 414 void G1Policy::record_full_collection_start() { 415 _full_collection_start_sec = os::elapsedTime(); 416 // Release the future to-space so that it is available for compaction into. 417 collector_state()->set_in_young_only_phase(false); 418 collector_state()->set_in_full_gc(true); 419 cset_chooser()->clear(); 420 } 421 422 void G1Policy::record_full_collection_end() { 423 // Consider this like a collection pause for the purposes of allocation 424 // since last pause. 425 double end_sec = os::elapsedTime(); 426 double full_gc_time_sec = end_sec - _full_collection_start_sec; 427 double full_gc_time_ms = full_gc_time_sec * 1000.0; 428 429 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 430 431 collector_state()->set_in_full_gc(false); 432 433 // "Nuke" the heuristics that control the young/mixed GC 434 // transitions and make sure we start with young GCs after the Full GC. 435 collector_state()->set_in_young_only_phase(true); 436 collector_state()->set_in_young_gc_before_mixed(false); 437 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 438 collector_state()->set_in_initial_mark_gc(false); 439 collector_state()->set_mark_or_rebuild_in_progress(false); 440 collector_state()->set_clearing_next_bitmap(false); 441 442 _short_lived_surv_rate_group->start_adding_regions(); 443 // also call this on any additional surv rate groups 444 445 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 446 // Reset survivors SurvRateGroup. 447 _survivor_surv_rate_group->reset(); 448 update_young_list_max_and_target_length(); 449 update_rs_lengths_prediction(); 450 451 _bytes_allocated_in_old_since_last_gc = 0; 452 453 record_pause(FullGC, _full_collection_start_sec, end_sec); 454 } 455 456 void G1Policy::record_collection_pause_start(double start_time_sec) { 457 // We only need to do this here as the policy will only be applied 458 // to the GC we're about to start. so, no point is calculating this 459 // every time we calculate / recalculate the target young length. 460 update_survivors_policy(); 461 462 assert(_g1h->used() == _g1h->recalculate_used(), 463 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT, 464 _g1h->used(), _g1h->recalculate_used()); 465 466 phase_times()->record_cur_collection_start_sec(start_time_sec); 467 _pending_cards = _g1h->pending_card_num(); 468 469 _collection_set->reset_bytes_used_before(); 470 _bytes_copied_during_gc = 0; 471 472 // do that for any other surv rate groups 473 _short_lived_surv_rate_group->stop_adding_regions(); 474 _survivors_age_table.clear(); 475 476 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed"); 477 } 478 479 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 480 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 481 collector_state()->set_in_initial_mark_gc(false); 482 } 483 484 void G1Policy::record_concurrent_mark_remark_start() { 485 _mark_remark_start_sec = os::elapsedTime(); 486 } 487 488 void G1Policy::record_concurrent_mark_remark_end() { 489 double end_time_sec = os::elapsedTime(); 490 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 491 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 492 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 493 494 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 495 } 496 497 void G1Policy::record_concurrent_mark_cleanup_start() { 498 _mark_cleanup_start_sec = os::elapsedTime(); 499 } 500 501 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 502 return phase_times()->average_time_ms(phase); 503 } 504 505 double G1Policy::young_other_time_ms() const { 506 return phase_times()->young_cset_choice_time_ms() + 507 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet); 508 } 509 510 double G1Policy::non_young_other_time_ms() const { 511 return phase_times()->non_young_cset_choice_time_ms() + 512 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet); 513 } 514 515 double G1Policy::other_time_ms(double pause_time_ms) const { 516 return pause_time_ms - phase_times()->cur_collection_par_time_ms(); 517 } 518 519 double G1Policy::constant_other_time_ms(double pause_time_ms) const { 520 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms(); 521 } 522 523 CollectionSetChooser* G1Policy::cset_chooser() const { 524 return _collection_set->cset_chooser(); 525 } 526 527 bool G1Policy::about_to_start_mixed_phase() const { 528 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed(); 529 } 530 531 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 532 if (about_to_start_mixed_phase()) { 533 return false; 534 } 535 536 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 537 538 size_t cur_used_bytes = _g1h->non_young_capacity_bytes(); 539 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 540 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 541 542 bool result = false; 543 if (marking_request_bytes > marking_initiating_used_threshold) { 544 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed(); 545 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 546 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 547 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source); 548 } 549 550 return result; 551 } 552 553 // Anything below that is considered to be zero 554 #define MIN_TIMER_GRANULARITY 0.0000001 555 556 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) { 557 double end_time_sec = os::elapsedTime(); 558 559 size_t cur_used_bytes = _g1h->used(); 560 assert(cur_used_bytes == _g1h->recalculate_used(), "It should!"); 561 bool this_pause_included_initial_mark = false; 562 bool this_pause_was_young_only = collector_state()->in_young_only_phase(); 563 564 bool update_stats = !_g1h->evacuation_failed(); 565 566 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 567 568 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 569 570 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc(); 571 if (this_pause_included_initial_mark) { 572 record_concurrent_mark_init_end(0.0); 573 } else { 574 maybe_start_marking(); 575 } 576 577 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 578 if (app_time_ms < MIN_TIMER_GRANULARITY) { 579 // This usually happens due to the timer not having the required 580 // granularity. Some Linuxes are the usual culprits. 581 // We'll just set it to something (arbitrarily) small. 582 app_time_ms = 1.0; 583 } 584 585 if (update_stats) { 586 // We maintain the invariant that all objects allocated by mutator 587 // threads will be allocated out of eden regions. So, we can use 588 // the eden region number allocated since the previous GC to 589 // calculate the application's allocate rate. The only exception 590 // to that is humongous objects that are allocated separately. But 591 // given that humongous object allocations do not really affect 592 // either the pause's duration nor when the next pause will take 593 // place we can safely ignore them here. 594 uint regions_allocated = _collection_set->eden_region_length(); 595 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 596 _analytics->report_alloc_rate_ms(alloc_rate_ms); 597 598 double interval_ms = 599 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; 600 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 601 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms); 602 } 603 604 if (collector_state()->in_young_gc_before_mixed()) { 605 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC"); 606 // This has been the young GC before we start doing mixed GCs. We already 607 // decided to start mixed GCs much earlier, so there is nothing to do except 608 // advancing the state. 609 collector_state()->set_in_young_only_phase(false); 610 collector_state()->set_in_young_gc_before_mixed(false); 611 } else if (!this_pause_was_young_only) { 612 // This is a mixed GC. Here we decide whether to continue doing more 613 // mixed GCs or not. 614 if (!next_gc_should_be_mixed("continue mixed GCs", 615 "do not continue mixed GCs")) { 616 collector_state()->set_in_young_only_phase(true); 617 618 clear_collection_set_candidates(); 619 maybe_start_marking(); 620 } 621 } 622 623 _short_lived_surv_rate_group->start_adding_regions(); 624 // Do that for any other surv rate groups 625 626 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0; 627 628 if (update_stats) { 629 double cost_per_card_ms = 0.0; 630 if (_pending_cards > 0) { 631 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards; 632 _analytics->report_cost_per_card_ms(cost_per_card_ms); 633 } 634 _analytics->report_cost_scan_hcc(scan_hcc_time_ms); 635 636 double cost_per_entry_ms = 0.0; 637 if (cards_scanned > 10) { 638 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned; 639 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only); 640 } 641 642 if (_max_rs_lengths > 0) { 643 double cards_per_entry_ratio = 644 (double) cards_scanned / (double) _max_rs_lengths; 645 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only); 646 } 647 648 // This is defensive. For a while _max_rs_lengths could get 649 // smaller than _recorded_rs_lengths which was causing 650 // rs_length_diff to get very large and mess up the RSet length 651 // predictions. The reason was unsafe concurrent updates to the 652 // _inc_cset_recorded_rs_lengths field which the code below guards 653 // against (see CR 7118202). This bug has now been fixed (see CR 654 // 7119027). However, I'm still worried that 655 // _inc_cset_recorded_rs_lengths might still end up somewhat 656 // inaccurate. The concurrent refinement thread calculates an 657 // RSet's length concurrently with other CR threads updating it 658 // which might cause it to calculate the length incorrectly (if, 659 // say, it's in mid-coarsening). So I'll leave in the defensive 660 // conditional below just in case. 661 size_t rs_length_diff = 0; 662 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths(); 663 if (_max_rs_lengths > recorded_rs_lengths) { 664 rs_length_diff = _max_rs_lengths - recorded_rs_lengths; 665 } 666 _analytics->report_rs_length_diff((double) rs_length_diff); 667 668 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes; 669 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes; 670 double cost_per_byte_ms = 0.0; 671 672 if (copied_bytes > 0) { 673 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes; 674 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress()); 675 } 676 677 if (_collection_set->young_region_length() > 0) { 678 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 679 _collection_set->young_region_length()); 680 } 681 682 if (_collection_set->old_region_length() > 0) { 683 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 684 _collection_set->old_region_length()); 685 } 686 687 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 688 689 // Do not update RS lengths and the number of pending cards with information from mixed gc: 690 // these are is wildly different to during young only gc and mess up young gen sizing right 691 // after the mixed gc phase. 692 // During mixed gc we do not use them for young gen sizing. 693 if (this_pause_was_young_only) { 694 _analytics->report_pending_cards((double) _pending_cards); 695 _analytics->report_rs_lengths((double) _max_rs_lengths); 696 } 697 } 698 699 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()), 700 "If the last pause has been an initial mark, we should not have been in the marking window"); 701 if (this_pause_included_initial_mark) { 702 collector_state()->set_mark_or_rebuild_in_progress(true); 703 } 704 705 _free_regions_at_end_of_collection = _g1h->num_free_regions(); 706 // IHOP control wants to know the expected young gen length if it were not 707 // restrained by the heap reserve. Using the actual length would make the 708 // prediction too small and the limit the young gen every time we get to the 709 // predicted target occupancy. 710 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 711 update_rs_lengths_prediction(); 712 713 update_ihop_prediction(app_time_ms / 1000.0, 714 _bytes_allocated_in_old_since_last_gc, 715 last_unrestrained_young_length * HeapRegion::GrainBytes, 716 this_pause_was_young_only); 717 _bytes_allocated_in_old_since_last_gc = 0; 718 719 _ihop_control->send_trace_event(_g1h->gc_tracer_stw()); 720 721 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 722 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 723 724 if (update_rs_time_goal_ms < scan_hcc_time_ms) { 725 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 726 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms", 727 update_rs_time_goal_ms, scan_hcc_time_ms); 728 729 update_rs_time_goal_ms = 0; 730 } else { 731 update_rs_time_goal_ms -= scan_hcc_time_ms; 732 } 733 _g1h->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms, 734 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS), 735 update_rs_time_goal_ms); 736 737 cset_chooser()->verify(); 738 } 739 740 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){ 741 if (G1UseAdaptiveIHOP) { 742 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 743 predictor, 744 G1ReservePercent, 745 G1HeapWastePercent); 746 } else { 747 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 748 } 749 } 750 751 void G1Policy::update_ihop_prediction(double mutator_time_s, 752 size_t mutator_alloc_bytes, 753 size_t young_gen_size, 754 bool this_gc_was_young_only) { 755 // Always try to update IHOP prediction. Even evacuation failures give information 756 // about e.g. whether to start IHOP earlier next time. 757 758 // Avoid using really small application times that might create samples with 759 // very high or very low values. They may be caused by e.g. back-to-back gcs. 760 double const min_valid_time = 1e-6; 761 762 bool report = false; 763 764 double marking_to_mixed_time = -1.0; 765 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) { 766 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 767 assert(marking_to_mixed_time > 0.0, 768 "Initial mark to mixed time must be larger than zero but is %.3f", 769 marking_to_mixed_time); 770 if (marking_to_mixed_time > min_valid_time) { 771 _ihop_control->update_marking_length(marking_to_mixed_time); 772 report = true; 773 } 774 } 775 776 // As an approximation for the young gc promotion rates during marking we use 777 // all of them. In many applications there are only a few if any young gcs during 778 // marking, which makes any prediction useless. This increases the accuracy of the 779 // prediction. 780 if (this_gc_was_young_only && mutator_time_s > min_valid_time) { 781 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 782 report = true; 783 } 784 785 if (report) { 786 report_ihop_statistics(); 787 } 788 } 789 790 void G1Policy::report_ihop_statistics() { 791 _ihop_control->print(); 792 } 793 794 void G1Policy::print_phases() { 795 phase_times()->print(); 796 } 797 798 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { 799 TruncatedSeq* seq = surv_rate_group->get_seq(age); 800 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); 801 double pred = _predictor.get_new_prediction(seq); 802 if (pred > 1.0) { 803 pred = 1.0; 804 } 805 return pred; 806 } 807 808 double G1Policy::accum_yg_surv_rate_pred(int age) const { 809 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 810 } 811 812 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards, 813 size_t scanned_cards) const { 814 return 815 _analytics->predict_rs_update_time_ms(pending_cards) + 816 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) + 817 _analytics->predict_constant_other_time_ms(); 818 } 819 820 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const { 821 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff(); 822 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase()); 823 return predict_base_elapsed_time_ms(pending_cards, card_num); 824 } 825 826 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const { 827 size_t bytes_to_copy; 828 if (hr->is_marked()) 829 bytes_to_copy = hr->max_live_bytes(); 830 else { 831 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant"); 832 int age = hr->age_in_surv_rate_group(); 833 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); 834 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); 835 } 836 return bytes_to_copy; 837 } 838 839 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr, 840 bool for_young_gc) const { 841 size_t rs_length = hr->rem_set()->occupied(); 842 // Predicting the number of cards is based on which type of GC 843 // we're predicting for. 844 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc); 845 size_t bytes_to_copy = predict_bytes_to_copy(hr); 846 847 double region_elapsed_time_ms = 848 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) + 849 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress()); 850 851 // The prediction of the "other" time for this region is based 852 // upon the region type and NOT the GC type. 853 if (hr->is_young()) { 854 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 855 } else { 856 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 857 } 858 return region_elapsed_time_ms; 859 } 860 861 bool G1Policy::should_allocate_mutator_region() const { 862 uint young_list_length = _g1h->young_regions_count(); 863 uint young_list_target_length = _young_list_target_length; 864 return young_list_length < young_list_target_length; 865 } 866 867 bool G1Policy::can_expand_young_list() const { 868 uint young_list_length = _g1h->young_regions_count(); 869 uint young_list_max_length = _young_list_max_length; 870 return young_list_length < young_list_max_length; 871 } 872 873 bool G1Policy::adaptive_young_list_length() const { 874 return _young_gen_sizer.adaptive_young_list_length(); 875 } 876 877 size_t G1Policy::desired_survivor_size() const { 878 size_t const survivor_capacity = HeapRegion::GrainWords * _max_survivor_regions; 879 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 880 } 881 882 void G1Policy::print_age_table() { 883 _survivors_age_table.print_age_table(_tenuring_threshold); 884 } 885 886 void G1Policy::update_max_gc_locker_expansion() { 887 uint expansion_region_num = 0; 888 if (GCLockerEdenExpansionPercent > 0) { 889 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 890 double expansion_region_num_d = perc * (double) _young_list_target_length; 891 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 892 // less than 1.0) we'll get 1. 893 expansion_region_num = (uint) ceil(expansion_region_num_d); 894 } else { 895 assert(expansion_region_num == 0, "sanity"); 896 } 897 _young_list_max_length = _young_list_target_length + expansion_region_num; 898 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 899 } 900 901 // Calculates survivor space parameters. 902 void G1Policy::update_survivors_policy() { 903 double max_survivor_regions_d = 904 (double) _young_list_target_length / (double) SurvivorRatio; 905 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but 906 // smaller than 1.0) we'll get 1. 907 _max_survivor_regions = (uint) ceil(max_survivor_regions_d); 908 909 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(desired_survivor_size()); 910 if (UsePerfData) { 911 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold); 912 _policy_counters->desired_survivor_size()->set_value(desired_survivor_size() * oopSize); 913 } 914 } 915 916 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 917 // We actually check whether we are marking here and not if we are in a 918 // reclamation phase. This means that we will schedule a concurrent mark 919 // even while we are still in the process of reclaiming memory. 920 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle(); 921 if (!during_cycle) { 922 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 923 collector_state()->set_initiate_conc_mark_if_possible(true); 924 return true; 925 } else { 926 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 927 return false; 928 } 929 } 930 931 void G1Policy::initiate_conc_mark() { 932 collector_state()->set_in_initial_mark_gc(true); 933 collector_state()->set_initiate_conc_mark_if_possible(false); 934 } 935 936 void G1Policy::decide_on_conc_mark_initiation() { 937 // We are about to decide on whether this pause will be an 938 // initial-mark pause. 939 940 // First, collector_state()->in_initial_mark_gc() should not be already set. We 941 // will set it here if we have to. However, it should be cleared by 942 // the end of the pause (it's only set for the duration of an 943 // initial-mark pause). 944 assert(!collector_state()->in_initial_mark_gc(), "pre-condition"); 945 946 if (collector_state()->initiate_conc_mark_if_possible()) { 947 // We had noticed on a previous pause that the heap occupancy has 948 // gone over the initiating threshold and we should start a 949 // concurrent marking cycle. So we might initiate one. 950 951 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) { 952 // Initiate a new initial mark if there is no marking or reclamation going on. 953 initiate_conc_mark(); 954 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 955 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) { 956 // Initiate a user requested initial mark. An initial mark must be young only 957 // GC, so the collector state must be updated to reflect this. 958 collector_state()->set_in_young_only_phase(true); 959 collector_state()->set_in_young_gc_before_mixed(false); 960 961 // We might have ended up coming here about to start a mixed phase with a collection set 962 // active. The following remark might change the change the "evacuation efficiency" of 963 // the regions in this set, leading to failing asserts later. 964 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here. 965 clear_collection_set_candidates(); 966 abort_time_to_mixed_tracking(); 967 initiate_conc_mark(); 968 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 969 } else { 970 // The concurrent marking thread is still finishing up the 971 // previous cycle. If we start one right now the two cycles 972 // overlap. In particular, the concurrent marking thread might 973 // be in the process of clearing the next marking bitmap (which 974 // we will use for the next cycle if we start one). Starting a 975 // cycle now will be bad given that parts of the marking 976 // information might get cleared by the marking thread. And we 977 // cannot wait for the marking thread to finish the cycle as it 978 // periodically yields while clearing the next marking bitmap 979 // and, if it's in a yield point, it's waiting for us to 980 // finish. So, at this point we will not start a cycle and we'll 981 // let the concurrent marking thread complete the last one. 982 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 983 } 984 } 985 } 986 987 void G1Policy::record_concurrent_mark_cleanup_end() { 988 cset_chooser()->rebuild(_g1h->workers(), _g1h->num_regions()); 989 990 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs"); 991 if (!mixed_gc_pending) { 992 clear_collection_set_candidates(); 993 abort_time_to_mixed_tracking(); 994 } 995 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending); 996 collector_state()->set_mark_or_rebuild_in_progress(false); 997 998 double end_sec = os::elapsedTime(); 999 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1000 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1001 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1002 1003 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1004 } 1005 1006 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const { 1007 return percent_of(reclaimable_bytes, _g1h->capacity()); 1008 } 1009 1010 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure { 1011 virtual bool do_heap_region(HeapRegion* r) { 1012 r->rem_set()->clear_locked(true /* only_cardset */); 1013 return false; 1014 } 1015 }; 1016 1017 void G1Policy::clear_collection_set_candidates() { 1018 // Clear remembered sets of remaining candidate regions and the actual candidate 1019 // list. 1020 G1ClearCollectionSetCandidateRemSets cl; 1021 cset_chooser()->iterate(&cl); 1022 cset_chooser()->clear(); 1023 } 1024 1025 void G1Policy::maybe_start_marking() { 1026 if (need_to_start_conc_mark("end of GC")) { 1027 // Note: this might have already been set, if during the last 1028 // pause we decided to start a cycle but at the beginning of 1029 // this pause we decided to postpone it. That's OK. 1030 collector_state()->set_initiate_conc_mark_if_possible(true); 1031 } 1032 } 1033 1034 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const { 1035 assert(!collector_state()->in_full_gc(), "must be"); 1036 if (collector_state()->in_initial_mark_gc()) { 1037 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1038 return InitialMarkGC; 1039 } else if (collector_state()->in_young_gc_before_mixed()) { 1040 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1041 return LastYoungGC; 1042 } else if (collector_state()->in_mixed_phase()) { 1043 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1044 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1045 return MixedGC; 1046 } else { 1047 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1048 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1049 return YoungOnlyGC; 1050 } 1051 } 1052 1053 void G1Policy::record_pause(PauseKind kind, double start, double end) { 1054 // Manage the MMU tracker. For some reason it ignores Full GCs. 1055 if (kind != FullGC) { 1056 _mmu_tracker->add_pause(start, end); 1057 } 1058 // Manage the mutator time tracking from initial mark to first mixed gc. 1059 switch (kind) { 1060 case FullGC: 1061 abort_time_to_mixed_tracking(); 1062 break; 1063 case Cleanup: 1064 case Remark: 1065 case YoungOnlyGC: 1066 case LastYoungGC: 1067 _initial_mark_to_mixed.add_pause(end - start); 1068 break; 1069 case InitialMarkGC: 1070 _initial_mark_to_mixed.record_initial_mark_end(end); 1071 break; 1072 case MixedGC: 1073 _initial_mark_to_mixed.record_mixed_gc_start(start); 1074 break; 1075 default: 1076 ShouldNotReachHere(); 1077 } 1078 } 1079 1080 void G1Policy::abort_time_to_mixed_tracking() { 1081 _initial_mark_to_mixed.reset(); 1082 } 1083 1084 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str, 1085 const char* false_action_str) const { 1086 if (cset_chooser()->is_empty()) { 1087 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1088 return false; 1089 } 1090 1091 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1092 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); 1093 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1094 double threshold = (double) G1HeapWastePercent; 1095 if (reclaimable_percent <= threshold) { 1096 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1097 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1098 return false; 1099 } 1100 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1101 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1102 return true; 1103 } 1104 1105 uint G1Policy::calc_min_old_cset_length() const { 1106 // The min old CSet region bound is based on the maximum desired 1107 // number of mixed GCs after a cycle. I.e., even if some old regions 1108 // look expensive, we should add them to the CSet anyway to make 1109 // sure we go through the available old regions in no more than the 1110 // maximum desired number of mixed GCs. 1111 // 1112 // The calculation is based on the number of marked regions we added 1113 // to the CSet chooser in the first place, not how many remain, so 1114 // that the result is the same during all mixed GCs that follow a cycle. 1115 1116 const size_t region_num = (size_t) cset_chooser()->length(); 1117 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1118 size_t result = region_num / gc_num; 1119 // emulate ceiling 1120 if (result * gc_num < region_num) { 1121 result += 1; 1122 } 1123 return (uint) result; 1124 } 1125 1126 uint G1Policy::calc_max_old_cset_length() const { 1127 // The max old CSet region bound is based on the threshold expressed 1128 // as a percentage of the heap size. I.e., it should bound the 1129 // number of old regions added to the CSet irrespective of how many 1130 // of them are available. 1131 1132 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1133 const size_t region_num = g1h->num_regions(); 1134 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1135 size_t result = region_num * perc / 100; 1136 // emulate ceiling 1137 if (100 * result < region_num * perc) { 1138 result += 1; 1139 } 1140 return (uint) result; 1141 } 1142 1143 void G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) { 1144 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor); 1145 _collection_set->finalize_old_part(time_remaining_ms); 1146 } 1147 1148 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) { 1149 1150 // Add survivor regions to SurvRateGroup. 1151 note_start_adding_survivor_regions(); 1152 finished_recalculating_age_indexes(true /* is_survivors */); 1153 1154 HeapRegion* last = NULL; 1155 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin(); 1156 it != survivors->regions()->end(); 1157 ++it) { 1158 HeapRegion* curr = *it; 1159 set_region_survivor(curr); 1160 1161 // The region is a non-empty survivor so let's add it to 1162 // the incremental collection set for the next evacuation 1163 // pause. 1164 _collection_set->add_survivor_regions(curr); 1165 1166 last = curr; 1167 } 1168 note_stop_adding_survivor_regions(); 1169 1170 // Don't clear the survivor list handles until the start of 1171 // the next evacuation pause - we need it in order to re-tag 1172 // the survivor regions from this evacuation pause as 'young' 1173 // at the start of the next. 1174 1175 finished_recalculating_age_indexes(false /* is_survivors */); 1176 }