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