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/concurrentMarkThread.inline.hpp" 27 #include "gc/g1/g1Analytics.hpp" 28 #include "gc/g1/g1CollectedHeap.inline.hpp" 29 #include "gc/g1/g1CollectionSet.hpp" 30 #include "gc/g1/g1ConcurrentMark.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 _g1(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 _g1->collector_state(); } 78 79 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) { 80 _g1 = 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(_g1->max_regions()); 89 90 _free_regions_at_end_of_collection = _g1->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 log_debug(gc)("younglengthpred: length %u base_time_ms %.3f accum_surv_rate %.3f bytes_to_copy " SIZE_FORMAT " copy_time_ms %.3f young_other_time_ms %.3f pause_time_ms %.3f", 135 young_length, _base_time_ms, accum_surv_rate, bytes_to_copy, copy_time_ms, young_other_time_ms, pause_time_ms); 136 if (pause_time_ms > _target_pause_time_ms) { 137 // end condition 2: prediction is over the target pause time 138 return false; 139 } 140 141 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes; 142 143 // When copying, we will likely need more bytes free than is live in the region. 144 // Add some safety margin to factor in the confidence of our guess, and the 145 // natural expected waste. 146 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 147 // of the calculation: the lower the confidence, the more headroom. 148 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 149 // copying due to anticipated waste in the PLABs. 150 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 151 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 152 153 if (expected_bytes_to_copy > free_bytes) { 154 // end condition 3: out-of-space 155 return false; 156 } 157 158 // success! 159 return true; 160 } 161 }; 162 163 void G1Policy::record_new_heap_size(uint new_number_of_regions) { 164 // re-calculate the necessary reserve 165 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 166 // We use ceiling so that if reserve_regions_d is > 0.0 (but 167 // smaller than 1.0) we'll get 1. 168 _reserve_regions = (uint) ceil(reserve_regions_d); 169 170 _young_gen_sizer.heap_size_changed(new_number_of_regions); 171 172 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 173 } 174 175 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const { 176 uint desired_min_length = 0; 177 if (adaptive_young_list_length()) { 178 if (_analytics->num_alloc_rate_ms() > 3) { 179 double now_sec = os::elapsedTime(); 180 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 181 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 182 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 183 } else { 184 // otherwise we don't have enough info to make the prediction 185 } 186 } 187 desired_min_length += base_min_length; 188 // make sure we don't go below any user-defined minimum bound 189 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length); 190 } 191 192 uint G1Policy::calculate_young_list_desired_max_length() const { 193 // Here, we might want to also take into account any additional 194 // constraints (i.e., user-defined minimum bound). Currently, we 195 // effectively don't set this bound. 196 return _young_gen_sizer.max_desired_young_length(); 197 } 198 199 uint G1Policy::update_young_list_max_and_target_length() { 200 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths()); 201 } 202 203 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) { 204 uint unbounded_target_length = update_young_list_target_length(rs_lengths); 205 update_max_gc_locker_expansion(); 206 return unbounded_target_length; 207 } 208 209 uint G1Policy::update_young_list_target_length(size_t rs_lengths) { 210 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths); 211 _young_list_target_length = young_lengths.first; 212 return young_lengths.second; 213 } 214 215 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const { 216 YoungTargetLengths result; 217 218 // Calculate the absolute and desired min bounds first. 219 220 // This is how many young regions we already have (currently: the survivors). 221 const uint base_min_length = _g1->survivor_regions_count(); 222 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 223 // This is the absolute minimum young length. Ensure that we 224 // will at least have one eden region available for allocation. 225 uint absolute_min_length = base_min_length + MAX2(_g1->eden_regions_count(), (uint)1); 226 // If we shrank the young list target it should not shrink below the current size. 227 desired_min_length = MAX2(desired_min_length, absolute_min_length); 228 // Calculate the absolute and desired max bounds. 229 230 uint desired_max_length = calculate_young_list_desired_max_length(); 231 232 uint young_list_target_length = 0; 233 if (adaptive_young_list_length()) { 234 if (collector_state()->in_young_only_phase()) { 235 young_list_target_length = 236 calculate_young_list_target_length(rs_lengths, 237 base_min_length, 238 desired_min_length, 239 desired_max_length); 240 } else { 241 // Don't calculate anything and let the code below bound it to 242 // the desired_min_length, i.e., do the next GC as soon as 243 // possible to maximize how many old regions we can add to it. 244 } 245 } else { 246 // The user asked for a fixed young gen so we'll fix the young gen 247 // whether the next GC is young or mixed. 248 young_list_target_length = _young_list_fixed_length; 249 } 250 251 result.second = young_list_target_length; 252 253 // We will try our best not to "eat" into the reserve. 254 uint absolute_max_length = 0; 255 if (_free_regions_at_end_of_collection > _reserve_regions) { 256 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 257 } 258 if (desired_max_length > absolute_max_length) { 259 desired_max_length = absolute_max_length; 260 } 261 262 // Make sure we don't go over the desired max length, nor under the 263 // desired min length. In case they clash, desired_min_length wins 264 // which is why that test is second. 265 if (young_list_target_length > desired_max_length) { 266 young_list_target_length = desired_max_length; 267 } 268 if (young_list_target_length < desired_min_length) { 269 young_list_target_length = desired_min_length; 270 } 271 272 assert(young_list_target_length > base_min_length, 273 "we should be able to allocate at least one eden region"); 274 assert(young_list_target_length >= absolute_min_length, "post-condition"); 275 276 result.first = young_list_target_length; 277 return result; 278 } 279 280 uint 281 G1Policy::calculate_young_list_target_length(size_t rs_lengths, 282 uint base_min_length, 283 uint desired_min_length, 284 uint desired_max_length) const { 285 assert(adaptive_young_list_length(), "pre-condition"); 286 assert(collector_state()->in_young_only_phase(), "only call this for young GCs"); 287 288 // In case some edge-condition makes the desired max length too small... 289 if (desired_max_length <= desired_min_length) { 290 return desired_min_length; 291 } 292 293 // We'll adjust min_young_length and max_young_length not to include 294 // the already allocated young regions (i.e., so they reflect the 295 // min and max eden regions we'll allocate). The base_min_length 296 // will be reflected in the predictions by the 297 // survivor_regions_evac_time prediction. 298 assert(desired_min_length > base_min_length, "invariant"); 299 uint min_young_length = desired_min_length - base_min_length; 300 assert(desired_max_length > base_min_length, "invariant"); 301 uint max_young_length = desired_max_length - base_min_length; 302 303 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 304 const double survivor_regions_evac_time = predict_survivor_regions_evac_time(); 305 const size_t pending_cards = _analytics->predict_pending_cards(); 306 const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff(); 307 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, true /* for_young_gc */); 308 const double base_time_ms = 309 predict_base_elapsed_time_ms(pending_cards, scanned_cards) + 310 survivor_regions_evac_time; 311 const uint available_free_regions = _free_regions_at_end_of_collection; 312 const uint base_free_regions = 313 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0; 314 315 // Here, we will make sure that the shortest young length that 316 // makes sense fits within the target pause time. 317 318 G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(), 319 base_time_ms, 320 base_free_regions, 321 target_pause_time_ms, 322 this); 323 if (p.will_fit(min_young_length)) { 324 // The shortest young length will fit into the target pause time; 325 // we'll now check whether the absolute maximum number of young 326 // regions will fit in the target pause time. If not, we'll do 327 // a binary search between min_young_length and max_young_length. 328 if (p.will_fit(max_young_length)) { 329 // The maximum young length will fit into the target pause time. 330 // We are done so set min young length to the maximum length (as 331 // the result is assumed to be returned in min_young_length). 332 min_young_length = max_young_length; 333 } else { 334 // The maximum possible number of young regions will not fit within 335 // the target pause time so we'll search for the optimal 336 // length. The loop invariants are: 337 // 338 // min_young_length < max_young_length 339 // min_young_length is known to fit into the target pause time 340 // max_young_length is known not to fit into the target pause time 341 // 342 // Going into the loop we know the above hold as we've just 343 // checked them. Every time around the loop we check whether 344 // the middle value between min_young_length and 345 // max_young_length fits into the target pause time. If it 346 // does, it becomes the new min. If it doesn't, it becomes 347 // the new max. This way we maintain the loop invariants. 348 349 assert(min_young_length < max_young_length, "invariant"); 350 uint diff = (max_young_length - min_young_length) / 2; 351 while (diff > 0) { 352 uint young_length = min_young_length + diff; 353 if (p.will_fit(young_length)) { 354 min_young_length = young_length; 355 } else { 356 max_young_length = young_length; 357 } 358 assert(min_young_length < max_young_length, "invariant"); 359 diff = (max_young_length - min_young_length) / 2; 360 } 361 // The results is min_young_length which, according to the 362 // loop invariants, should fit within the target pause time. 363 364 // These are the post-conditions of the binary search above: 365 assert(min_young_length < max_young_length, 366 "otherwise we should have discovered that max_young_length " 367 "fits into the pause target and not done the binary search"); 368 assert(p.will_fit(min_young_length), 369 "min_young_length, the result of the binary search, should " 370 "fit into the pause target"); 371 assert(!p.will_fit(min_young_length + 1), 372 "min_young_length, the result of the binary search, should be " 373 "optimal, so no larger length should fit into the pause target"); 374 } 375 } else { 376 // Even the minimum length doesn't fit into the pause time 377 // target, return it as the result nevertheless. 378 } 379 return base_min_length + min_young_length; 380 } 381 382 double G1Policy::predict_survivor_regions_evac_time() const { 383 double survivor_regions_evac_time = 0.0; 384 const GrowableArray<HeapRegion*>* survivor_regions = _g1->survivor()->regions(); 385 386 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin(); 387 it != survivor_regions->end(); 388 ++it) { 389 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase()); 390 } 391 return survivor_regions_evac_time; 392 } 393 394 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) { 395 guarantee( adaptive_young_list_length(), "should not call this otherwise" ); 396 397 if (rs_lengths > _rs_lengths_prediction) { 398 // add 10% to avoid having to recalculate often 399 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000; 400 update_rs_lengths_prediction(rs_lengths_prediction); 401 402 update_young_list_max_and_target_length(rs_lengths_prediction); 403 } 404 } 405 406 void G1Policy::update_rs_lengths_prediction() { 407 update_rs_lengths_prediction(_analytics->predict_rs_lengths()); 408 } 409 410 void G1Policy::update_rs_lengths_prediction(size_t prediction) { 411 if (collector_state()->in_young_only_phase() && adaptive_young_list_length()) { 412 _rs_lengths_prediction = prediction; 413 } 414 } 415 416 void G1Policy::record_full_collection_start() { 417 _full_collection_start_sec = os::elapsedTime(); 418 // Release the future to-space so that it is available for compaction into. 419 collector_state()->set_in_young_only_phase(false); 420 collector_state()->set_in_full_gc(true); 421 cset_chooser()->clear(); 422 } 423 424 void G1Policy::record_full_collection_end() { 425 // Consider this like a collection pause for the purposes of allocation 426 // since last pause. 427 double end_sec = os::elapsedTime(); 428 double full_gc_time_sec = end_sec - _full_collection_start_sec; 429 double full_gc_time_ms = full_gc_time_sec * 1000.0; 430 431 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 432 433 collector_state()->set_in_full_gc(false); 434 435 // "Nuke" the heuristics that control the young/mixed GC 436 // transitions and make sure we start with young GCs after the Full GC. 437 collector_state()->set_in_young_only_phase(true); 438 collector_state()->set_in_young_gc_before_mixed(false); 439 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 440 collector_state()->set_in_initial_mark_gc(false); 441 collector_state()->set_mark_or_rebuild_in_progress(false); 442 collector_state()->set_clearing_next_bitmap(false); 443 444 _short_lived_surv_rate_group->start_adding_regions(); 445 // also call this on any additional surv rate groups 446 447 _free_regions_at_end_of_collection = _g1->num_free_regions(); 448 // Reset survivors SurvRateGroup. 449 _survivor_surv_rate_group->reset(); 450 update_young_list_max_and_target_length(); 451 update_rs_lengths_prediction(); 452 453 _bytes_allocated_in_old_since_last_gc = 0; 454 455 record_pause(FullGC, _full_collection_start_sec, end_sec); 456 } 457 458 void G1Policy::record_collection_pause_start(double start_time_sec) { 459 // We only need to do this here as the policy will only be applied 460 // to the GC we're about to start. so, no point is calculating this 461 // every time we calculate / recalculate the target young length. 462 update_survivors_policy(); 463 464 assert(_g1->used() == _g1->recalculate_used(), 465 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT, 466 _g1->used(), _g1->recalculate_used()); 467 468 phase_times()->record_cur_collection_start_sec(start_time_sec); 469 _pending_cards = _g1->pending_card_num(); 470 471 _collection_set->reset_bytes_used_before(); 472 _bytes_copied_during_gc = 0; 473 474 // do that for any other surv rate groups 475 _short_lived_surv_rate_group->stop_adding_regions(); 476 _survivors_age_table.clear(); 477 478 assert(_g1->collection_set()->verify_young_ages(), "region age verification failed"); 479 } 480 481 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 482 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 483 collector_state()->set_in_initial_mark_gc(false); 484 } 485 486 void G1Policy::record_concurrent_mark_remark_start() { 487 _mark_remark_start_sec = os::elapsedTime(); 488 } 489 490 void G1Policy::record_concurrent_mark_remark_end() { 491 double end_time_sec = os::elapsedTime(); 492 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 493 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 494 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 495 496 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 497 } 498 499 void G1Policy::record_concurrent_mark_cleanup_start() { 500 _mark_cleanup_start_sec = os::elapsedTime(); 501 } 502 503 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 504 return phase_times()->average_time_ms(phase); 505 } 506 507 double G1Policy::young_other_time_ms() const { 508 return phase_times()->young_cset_choice_time_ms() + 509 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet); 510 } 511 512 double G1Policy::non_young_other_time_ms() const { 513 return phase_times()->non_young_cset_choice_time_ms() + 514 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet); 515 } 516 517 double G1Policy::other_time_ms(double pause_time_ms) const { 518 return pause_time_ms - phase_times()->cur_collection_par_time_ms(); 519 } 520 521 double G1Policy::constant_other_time_ms(double pause_time_ms) const { 522 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms(); 523 } 524 525 CollectionSetChooser* G1Policy::cset_chooser() const { 526 return _collection_set->cset_chooser(); 527 } 528 529 bool G1Policy::about_to_start_mixed_phase() const { 530 return _g1->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed(); 531 } 532 533 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 534 if (about_to_start_mixed_phase()) { 535 return false; 536 } 537 538 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 539 540 size_t cur_used_bytes = _g1->non_young_capacity_bytes(); 541 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 542 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 543 544 bool result = false; 545 if (marking_request_bytes > marking_initiating_used_threshold) { 546 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed(); 547 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 548 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 549 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source); 550 } 551 552 return result; 553 } 554 555 // Anything below that is considered to be zero 556 #define MIN_TIMER_GRANULARITY 0.0000001 557 558 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) { 559 double end_time_sec = os::elapsedTime(); 560 561 size_t cur_used_bytes = _g1->used(); 562 assert(cur_used_bytes == _g1->recalculate_used(), "It should!"); 563 bool this_pause_included_initial_mark = false; 564 bool this_pause_was_young_only = collector_state()->in_young_only_phase(); 565 566 bool update_stats = !_g1->evacuation_failed(); 567 568 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 569 570 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; 571 572 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc(); 573 if (this_pause_included_initial_mark) { 574 record_concurrent_mark_init_end(0.0); 575 } else { 576 maybe_start_marking(); 577 } 578 579 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 580 if (app_time_ms < MIN_TIMER_GRANULARITY) { 581 // This usually happens due to the timer not having the required 582 // granularity. Some Linuxes are the usual culprits. 583 // We'll just set it to something (arbitrarily) small. 584 app_time_ms = 1.0; 585 } 586 587 if (update_stats) { 588 // We maintain the invariant that all objects allocated by mutator 589 // threads will be allocated out of eden regions. So, we can use 590 // the eden region number allocated since the previous GC to 591 // calculate the application's allocate rate. The only exception 592 // to that is humongous objects that are allocated separately. But 593 // given that humongous object allocations do not really affect 594 // either the pause's duration nor when the next pause will take 595 // place we can safely ignore them here. 596 uint regions_allocated = _collection_set->eden_region_length(); 597 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 598 _analytics->report_alloc_rate_ms(alloc_rate_ms); 599 600 double interval_ms = 601 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; 602 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 603 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms); 604 } 605 606 if (collector_state()->in_young_gc_before_mixed()) { 607 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC"); 608 // This has been the young GC before we start doing mixed GCs. We already 609 // decided to start mixed GCs much earlier, so there is nothing to do except 610 // advancing the state. 611 collector_state()->set_in_young_only_phase(false); 612 collector_state()->set_in_young_gc_before_mixed(false); 613 } else if (!this_pause_was_young_only) { 614 // This is a mixed GC. Here we decide whether to continue doing more 615 // mixed GCs or not. 616 if (!next_gc_should_be_mixed("continue mixed GCs", 617 "do not continue mixed GCs")) { 618 collector_state()->set_in_young_only_phase(true); 619 620 clear_collection_set_candidates(); 621 maybe_start_marking(); 622 } 623 } 624 625 _short_lived_surv_rate_group->start_adding_regions(); 626 // Do that for any other surv rate groups 627 628 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0; 629 630 if (update_stats) { 631 double cost_per_card_ms = 0.0; 632 if (_pending_cards > 0) { 633 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards; 634 _analytics->report_cost_per_card_ms(cost_per_card_ms); 635 } 636 _analytics->report_cost_scan_hcc(scan_hcc_time_ms); 637 638 double cost_per_entry_ms = 0.0; 639 if (cards_scanned > 10) { 640 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned; 641 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only); 642 } 643 644 if (_max_rs_lengths > 0) { 645 double cards_per_entry_ratio = 646 (double) cards_scanned / (double) _max_rs_lengths; 647 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only); 648 } 649 650 // This is defensive. For a while _max_rs_lengths could get 651 // smaller than _recorded_rs_lengths which was causing 652 // rs_length_diff to get very large and mess up the RSet length 653 // predictions. The reason was unsafe concurrent updates to the 654 // _inc_cset_recorded_rs_lengths field which the code below guards 655 // against (see CR 7118202). This bug has now been fixed (see CR 656 // 7119027). However, I'm still worried that 657 // _inc_cset_recorded_rs_lengths might still end up somewhat 658 // inaccurate. The concurrent refinement thread calculates an 659 // RSet's length concurrently with other CR threads updating it 660 // which might cause it to calculate the length incorrectly (if, 661 // say, it's in mid-coarsening). So I'll leave in the defensive 662 // conditional below just in case. 663 size_t rs_length_diff = 0; 664 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths(); 665 if (_max_rs_lengths > recorded_rs_lengths) { 666 rs_length_diff = _max_rs_lengths - recorded_rs_lengths; 667 } 668 _analytics->report_rs_length_diff((double) rs_length_diff); 669 670 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes; 671 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes; 672 double cost_per_byte_ms = 0.0; 673 674 if (copied_bytes > 0) { 675 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes; 676 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress()); 677 } 678 679 if (_collection_set->young_region_length() > 0) { 680 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 681 _collection_set->young_region_length()); 682 } 683 684 if (_collection_set->old_region_length() > 0) { 685 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 686 _collection_set->old_region_length()); 687 } 688 689 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 690 691 // Do not update RS lengths with information from mixed gc: this one is wildly different 692 // to during young only gc and messes up young gen sizing right after the mixed gc phase. 693 // During mixed gc we do not use it anyway for young gen sizing. 694 if (this_pause_was_young_only) { 695 _analytics->report_pending_cards((double) _pending_cards); 696 _analytics->report_rs_lengths((double) _max_rs_lengths); 697 } 698 } 699 700 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()), 701 "If the last pause has been an initial mark, we should not have been in the marking window"); 702 if (this_pause_included_initial_mark) { 703 collector_state()->set_mark_or_rebuild_in_progress(true); 704 } 705 706 _free_regions_at_end_of_collection = _g1->num_free_regions(); 707 // IHOP control wants to know the expected young gen length if it were not 708 // restrained by the heap reserve. Using the actual length would make the 709 // prediction too small and the limit the young gen every time we get to the 710 // predicted target occupancy. 711 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 712 update_rs_lengths_prediction(); 713 714 update_ihop_prediction(app_time_ms / 1000.0, 715 _bytes_allocated_in_old_since_last_gc, 716 last_unrestrained_young_length * HeapRegion::GrainBytes, 717 this_pause_was_young_only); 718 _bytes_allocated_in_old_since_last_gc = 0; 719 720 _ihop_control->send_trace_event(_g1->gc_tracer_stw()); 721 722 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 723 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 724 725 if (update_rs_time_goal_ms < scan_hcc_time_ms) { 726 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 727 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms", 728 update_rs_time_goal_ms, scan_hcc_time_ms); 729 730 update_rs_time_goal_ms = 0; 731 } else { 732 update_rs_time_goal_ms -= scan_hcc_time_ms; 733 } 734 _g1->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms, 735 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS), 736 update_rs_time_goal_ms); 737 738 cset_chooser()->verify(); 739 } 740 741 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){ 742 if (G1UseAdaptiveIHOP) { 743 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 744 predictor, 745 G1ReservePercent, 746 G1HeapWastePercent); 747 } else { 748 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 749 } 750 } 751 752 void G1Policy::update_ihop_prediction(double mutator_time_s, 753 size_t mutator_alloc_bytes, 754 size_t young_gen_size, 755 bool this_gc_was_young_only) { 756 // Always try to update IHOP prediction. Even evacuation failures give information 757 // about e.g. whether to start IHOP earlier next time. 758 759 // Avoid using really small application times that might create samples with 760 // very high or very low values. They may be caused by e.g. back-to-back gcs. 761 double const min_valid_time = 1e-6; 762 763 bool report = false; 764 765 double marking_to_mixed_time = -1.0; 766 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) { 767 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 768 assert(marking_to_mixed_time > 0.0, 769 "Initial mark to mixed time must be larger than zero but is %.3f", 770 marking_to_mixed_time); 771 if (marking_to_mixed_time > min_valid_time) { 772 _ihop_control->update_marking_length(marking_to_mixed_time); 773 report = true; 774 } 775 } 776 777 // As an approximation for the young gc promotion rates during marking we use 778 // all of them. In many applications there are only a few if any young gcs during 779 // marking, which makes any prediction useless. This increases the accuracy of the 780 // prediction. 781 if (this_gc_was_young_only && mutator_time_s > min_valid_time) { 782 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 783 report = true; 784 } 785 786 if (report) { 787 report_ihop_statistics(); 788 } 789 } 790 791 void G1Policy::report_ihop_statistics() { 792 _ihop_control->print(); 793 } 794 795 void G1Policy::print_phases() { 796 phase_times()->print(); 797 } 798 799 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { 800 TruncatedSeq* seq = surv_rate_group->get_seq(age); 801 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); 802 double pred = _predictor.get_new_prediction(seq); 803 if (pred > 1.0) { 804 pred = 1.0; 805 } 806 return pred; 807 } 808 809 double G1Policy::accum_yg_surv_rate_pred(int age) const { 810 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 811 } 812 813 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards, 814 size_t scanned_cards) const { 815 return 816 _analytics->predict_rs_update_time_ms(pending_cards) + 817 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) + 818 _analytics->predict_constant_other_time_ms(); 819 } 820 821 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const { 822 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff(); 823 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase()); 824 return predict_base_elapsed_time_ms(pending_cards, card_num); 825 } 826 827 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const { 828 size_t bytes_to_copy; 829 if (hr->is_marked()) 830 bytes_to_copy = hr->max_live_bytes(); 831 else { 832 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant"); 833 int age = hr->age_in_surv_rate_group(); 834 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); 835 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); 836 } 837 return bytes_to_copy; 838 } 839 840 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr, 841 bool for_young_gc) const { 842 size_t rs_length = hr->rem_set()->occupied(); 843 // Predicting the number of cards is based on which type of GC 844 // we're predicting for. 845 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc); 846 size_t bytes_to_copy = predict_bytes_to_copy(hr); 847 848 double region_elapsed_time_ms = 849 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) + 850 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress()); 851 852 // The prediction of the "other" time for this region is based 853 // upon the region type and NOT the GC type. 854 if (hr->is_young()) { 855 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 856 } else { 857 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 858 } 859 return region_elapsed_time_ms; 860 } 861 862 bool G1Policy::should_allocate_mutator_region() const { 863 uint young_list_length = _g1->young_regions_count(); 864 uint young_list_target_length = _young_list_target_length; 865 return young_list_length < young_list_target_length; 866 } 867 868 bool G1Policy::can_expand_young_list() const { 869 uint young_list_length = _g1->young_regions_count(); 870 uint young_list_max_length = _young_list_max_length; 871 return young_list_length < young_list_max_length; 872 } 873 874 bool G1Policy::adaptive_young_list_length() const { 875 return _young_gen_sizer.adaptive_young_list_length(); 876 } 877 878 size_t G1Policy::desired_survivor_size() const { 879 size_t const survivor_capacity = HeapRegion::GrainWords * _max_survivor_regions; 880 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 881 } 882 883 void G1Policy::print_age_table() { 884 _survivors_age_table.print_age_table(_tenuring_threshold); 885 } 886 887 void G1Policy::update_max_gc_locker_expansion() { 888 uint expansion_region_num = 0; 889 if (GCLockerEdenExpansionPercent > 0) { 890 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 891 double expansion_region_num_d = perc * (double) _young_list_target_length; 892 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 893 // less than 1.0) we'll get 1. 894 expansion_region_num = (uint) ceil(expansion_region_num_d); 895 } else { 896 assert(expansion_region_num == 0, "sanity"); 897 } 898 _young_list_max_length = _young_list_target_length + expansion_region_num; 899 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 900 } 901 902 // Calculates survivor space parameters. 903 void G1Policy::update_survivors_policy() { 904 double max_survivor_regions_d = 905 (double) _young_list_target_length / (double) SurvivorRatio; 906 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but 907 // smaller than 1.0) we'll get 1. 908 _max_survivor_regions = (uint) ceil(max_survivor_regions_d); 909 910 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(desired_survivor_size()); 911 if (UsePerfData) { 912 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold); 913 _policy_counters->desired_survivor_size()->set_value(desired_survivor_size() * oopSize); 914 } 915 } 916 917 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 918 // We actually check whether we are marking here and not if we are in a 919 // reclamation phase. This means that we will schedule a concurrent mark 920 // even while we are still in the process of reclaiming memory. 921 bool during_cycle = _g1->concurrent_mark()->cm_thread()->during_cycle(); 922 if (!during_cycle) { 923 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 924 collector_state()->set_initiate_conc_mark_if_possible(true); 925 return true; 926 } else { 927 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 928 return false; 929 } 930 } 931 932 void G1Policy::initiate_conc_mark() { 933 collector_state()->set_in_initial_mark_gc(true); 934 collector_state()->set_initiate_conc_mark_if_possible(false); 935 } 936 937 void G1Policy::decide_on_conc_mark_initiation() { 938 // We are about to decide on whether this pause will be an 939 // initial-mark pause. 940 941 // First, collector_state()->in_initial_mark_gc() should not be already set. We 942 // will set it here if we have to. However, it should be cleared by 943 // the end of the pause (it's only set for the duration of an 944 // initial-mark pause). 945 assert(!collector_state()->in_initial_mark_gc(), "pre-condition"); 946 947 if (collector_state()->initiate_conc_mark_if_possible()) { 948 // We had noticed on a previous pause that the heap occupancy has 949 // gone over the initiating threshold and we should start a 950 // concurrent marking cycle. So we might initiate one. 951 952 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) { 953 // Initiate a new initial mark if there is no marking or reclamation going on. 954 initiate_conc_mark(); 955 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 956 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) { 957 // Initiate a user requested initial mark. An initial mark must be young only 958 // GC, so the collector state must be updated to reflect this. 959 collector_state()->set_in_young_only_phase(true); 960 collector_state()->set_in_young_gc_before_mixed(false); 961 962 // We might have ended up coming here about to start a mixed phase with a collection set 963 // active. The following remark might change the change the "evacuation efficiency" of 964 // the regions in this set, leading to failing asserts later. 965 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here. 966 clear_collection_set_candidates(); 967 abort_time_to_mixed_tracking(); 968 initiate_conc_mark(); 969 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 970 } else { 971 // The concurrent marking thread is still finishing up the 972 // previous cycle. If we start one right now the two cycles 973 // overlap. In particular, the concurrent marking thread might 974 // be in the process of clearing the next marking bitmap (which 975 // we will use for the next cycle if we start one). Starting a 976 // cycle now will be bad given that parts of the marking 977 // information might get cleared by the marking thread. And we 978 // cannot wait for the marking thread to finish the cycle as it 979 // periodically yields while clearing the next marking bitmap 980 // and, if it's in a yield point, it's waiting for us to 981 // finish. So, at this point we will not start a cycle and we'll 982 // let the concurrent marking thread complete the last one. 983 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 984 } 985 } 986 } 987 988 void G1Policy::record_concurrent_mark_cleanup_end() { 989 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions()); 990 991 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs"); 992 if (!mixed_gc_pending) { 993 clear_collection_set_candidates(); 994 abort_time_to_mixed_tracking(); 995 } 996 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending); 997 collector_state()->set_mark_or_rebuild_in_progress(false); 998 999 double end_sec = os::elapsedTime(); 1000 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1001 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1002 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1003 1004 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1005 } 1006 1007 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const { 1008 return percent_of(reclaimable_bytes, _g1->capacity()); 1009 } 1010 1011 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure { 1012 virtual bool do_heap_region(HeapRegion* r) { 1013 r->rem_set()->clear_locked(true /* only_cardset */); 1014 return false; 1015 } 1016 }; 1017 1018 void G1Policy::clear_collection_set_candidates() { 1019 // Clear remembered sets of remaining candidate regions and the actual candidate 1020 // list. 1021 G1ClearCollectionSetCandidateRemSets cl; 1022 cset_chooser()->iterate(&cl); 1023 cset_chooser()->clear(); 1024 } 1025 1026 void G1Policy::maybe_start_marking() { 1027 if (need_to_start_conc_mark("end of GC")) { 1028 // Note: this might have already been set, if during the last 1029 // pause we decided to start a cycle but at the beginning of 1030 // this pause we decided to postpone it. That's OK. 1031 collector_state()->set_initiate_conc_mark_if_possible(true); 1032 } 1033 } 1034 1035 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const { 1036 assert(!collector_state()->in_full_gc(), "must be"); 1037 if (collector_state()->in_initial_mark_gc()) { 1038 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1039 return InitialMarkGC; 1040 } else if (collector_state()->in_young_gc_before_mixed()) { 1041 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1042 return LastYoungGC; 1043 } else if (collector_state()->in_mixed_phase()) { 1044 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1045 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1046 return MixedGC; 1047 } else { 1048 assert(!collector_state()->in_initial_mark_gc(), "must be"); 1049 assert(!collector_state()->in_young_gc_before_mixed(), "must be"); 1050 return YoungOnlyGC; 1051 } 1052 } 1053 1054 void G1Policy::record_pause(PauseKind kind, double start, double end) { 1055 // Manage the MMU tracker. For some reason it ignores Full GCs. 1056 if (kind != FullGC) { 1057 _mmu_tracker->add_pause(start, end); 1058 } 1059 // Manage the mutator time tracking from initial mark to first mixed gc. 1060 switch (kind) { 1061 case FullGC: 1062 abort_time_to_mixed_tracking(); 1063 break; 1064 case Cleanup: 1065 case Remark: 1066 case YoungOnlyGC: 1067 case LastYoungGC: 1068 _initial_mark_to_mixed.add_pause(end - start); 1069 break; 1070 case InitialMarkGC: 1071 _initial_mark_to_mixed.record_initial_mark_end(end); 1072 break; 1073 case MixedGC: 1074 _initial_mark_to_mixed.record_mixed_gc_start(start); 1075 break; 1076 default: 1077 ShouldNotReachHere(); 1078 } 1079 } 1080 1081 void G1Policy::abort_time_to_mixed_tracking() { 1082 _initial_mark_to_mixed.reset(); 1083 } 1084 1085 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str, 1086 const char* false_action_str) const { 1087 if (cset_chooser()->is_empty()) { 1088 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1089 return false; 1090 } 1091 1092 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1093 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); 1094 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1095 double threshold = (double) G1HeapWastePercent; 1096 if (reclaimable_percent <= threshold) { 1097 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1098 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1099 return false; 1100 } 1101 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1102 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1103 return true; 1104 } 1105 1106 uint G1Policy::calc_min_old_cset_length() const { 1107 // The min old CSet region bound is based on the maximum desired 1108 // number of mixed GCs after a cycle. I.e., even if some old regions 1109 // look expensive, we should add them to the CSet anyway to make 1110 // sure we go through the available old regions in no more than the 1111 // maximum desired number of mixed GCs. 1112 // 1113 // The calculation is based on the number of marked regions we added 1114 // to the CSet chooser in the first place, not how many remain, so 1115 // that the result is the same during all mixed GCs that follow a cycle. 1116 1117 const size_t region_num = (size_t) cset_chooser()->length(); 1118 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1119 size_t result = region_num / gc_num; 1120 // emulate ceiling 1121 if (result * gc_num < region_num) { 1122 result += 1; 1123 } 1124 return (uint) result; 1125 } 1126 1127 uint G1Policy::calc_max_old_cset_length() const { 1128 // The max old CSet region bound is based on the threshold expressed 1129 // as a percentage of the heap size. I.e., it should bound the 1130 // number of old regions added to the CSet irrespective of how many 1131 // of them are available. 1132 1133 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1134 const size_t region_num = g1h->num_regions(); 1135 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1136 size_t result = region_num * perc / 100; 1137 // emulate ceiling 1138 if (100 * result < region_num * perc) { 1139 result += 1; 1140 } 1141 return (uint) result; 1142 } 1143 1144 void G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) { 1145 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor); 1146 _collection_set->finalize_old_part(time_remaining_ms); 1147 } 1148 1149 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) { 1150 1151 // Add survivor regions to SurvRateGroup. 1152 note_start_adding_survivor_regions(); 1153 finished_recalculating_age_indexes(true /* is_survivors */); 1154 1155 HeapRegion* last = NULL; 1156 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin(); 1157 it != survivors->regions()->end(); 1158 ++it) { 1159 HeapRegion* curr = *it; 1160 set_region_survivor(curr); 1161 1162 // The region is a non-empty survivor so let's add it to 1163 // the incremental collection set for the next evacuation 1164 // pause. 1165 _collection_set->add_survivor_regions(curr); 1166 1167 last = curr; 1168 } 1169 note_stop_adding_survivor_regions(); 1170 1171 // Don't clear the survivor list handles until the start of 1172 // the next evacuation pause - we need it in order to re-tag 1173 // the survivor regions from this evacuation pause as 'young' 1174 // at the start of the next. 1175 1176 finished_recalculating_age_indexes(false /* is_survivors */); 1177 }