1 /* 2 * Copyright (c) 2001, 2017, 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/g1DefaultPolicy.hpp" 33 #include "gc/g1/g1HotCardCache.hpp" 34 #include "gc/g1/g1IHOPControl.hpp" 35 #include "gc/g1/g1GCPhaseTimes.hpp" 36 #include "gc/g1/g1Policy.hpp" 37 #include "gc/g1/g1SurvivorRegions.hpp" 38 #include "gc/g1/g1YoungGenSizer.hpp" 39 #include "gc/g1/heapRegion.inline.hpp" 40 #include "gc/g1/heapRegionRemSet.hpp" 41 #include "gc/shared/gcPolicyCounters.hpp" 42 #include "logging/logStream.hpp" 43 #include "runtime/arguments.hpp" 44 #include "runtime/java.hpp" 45 #include "runtime/mutexLocker.hpp" 46 #include "utilities/debug.hpp" 47 #include "utilities/growableArray.hpp" 48 #include "utilities/pair.hpp" 49 50 G1DefaultPolicy::G1DefaultPolicy(STWGCTimer* gc_timer) : 51 _predictor(G1ConfidencePercent / 100.0), 52 _analytics(new G1Analytics(&_predictor)), 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 G1DefaultPolicy::~G1DefaultPolicy() { 73 delete _ihop_control; 74 } 75 76 G1CollectorState* G1DefaultPolicy::collector_state() const { return _g1->collector_state(); } 77 78 void G1DefaultPolicy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) { 79 _g1 = g1h; 80 _collection_set = collection_set; 81 82 assert(Heap_lock->owned_by_self(), "Locking discipline."); 83 84 if (!adaptive_young_list_length()) { 85 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length(); 86 } 87 _young_gen_sizer.adjust_max_new_size(_g1->max_regions()); 88 89 _free_regions_at_end_of_collection = _g1->num_free_regions(); 90 91 update_young_list_max_and_target_length(); 92 // We may immediately start allocating regions and placing them on the 93 // collection set list. Initialize the per-collection set info 94 _collection_set->start_incremental_building(); 95 } 96 97 void G1DefaultPolicy::note_gc_start() { 98 phase_times()->note_gc_start(); 99 } 100 101 class G1YoungLengthPredictor VALUE_OBJ_CLASS_SPEC { 102 const bool _during_cm; 103 const double _base_time_ms; 104 const double _base_free_regions; 105 const double _target_pause_time_ms; 106 const G1DefaultPolicy* const _policy; 107 108 public: 109 G1YoungLengthPredictor(bool during_cm, 110 double base_time_ms, 111 double base_free_regions, 112 double target_pause_time_ms, 113 const G1DefaultPolicy* policy) : 114 _during_cm(during_cm), 115 _base_time_ms(base_time_ms), 116 _base_free_regions(base_free_regions), 117 _target_pause_time_ms(target_pause_time_ms), 118 _policy(policy) {} 119 120 bool will_fit(uint young_length) const { 121 if (young_length >= _base_free_regions) { 122 // end condition 1: not enough space for the young regions 123 return false; 124 } 125 126 const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1); 127 const size_t bytes_to_copy = 128 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes); 129 const double copy_time_ms = 130 _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm); 131 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length); 132 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms; 133 if (pause_time_ms > _target_pause_time_ms) { 134 // end condition 2: prediction is over the target pause time 135 return false; 136 } 137 138 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes; 139 140 // When copying, we will likely need more bytes free than is live in the region. 141 // Add some safety margin to factor in the confidence of our guess, and the 142 // natural expected waste. 143 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 144 // of the calculation: the lower the confidence, the more headroom. 145 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 146 // copying due to anticipated waste in the PLABs. 147 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 148 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 149 150 if (expected_bytes_to_copy > free_bytes) { 151 // end condition 3: out-of-space 152 return false; 153 } 154 155 // success! 156 return true; 157 } 158 }; 159 160 void G1DefaultPolicy::record_new_heap_size(uint new_number_of_regions) { 161 // re-calculate the necessary reserve 162 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 163 // We use ceiling so that if reserve_regions_d is > 0.0 (but 164 // smaller than 1.0) we'll get 1. 165 _reserve_regions = (uint) ceil(reserve_regions_d); 166 167 _young_gen_sizer.heap_size_changed(new_number_of_regions); 168 169 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 170 } 171 172 uint G1DefaultPolicy::calculate_young_list_desired_min_length(uint base_min_length) const { 173 uint desired_min_length = 0; 174 if (adaptive_young_list_length()) { 175 if (_analytics->num_alloc_rate_ms() > 3) { 176 double now_sec = os::elapsedTime(); 177 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 178 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 179 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 180 } else { 181 // otherwise we don't have enough info to make the prediction 182 } 183 } 184 desired_min_length += base_min_length; 185 // make sure we don't go below any user-defined minimum bound 186 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length); 187 } 188 189 uint G1DefaultPolicy::calculate_young_list_desired_max_length() const { 190 // Here, we might want to also take into account any additional 191 // constraints (i.e., user-defined minimum bound). Currently, we 192 // effectively don't set this bound. 193 return _young_gen_sizer.max_desired_young_length(); 194 } 195 196 uint G1DefaultPolicy::update_young_list_max_and_target_length() { 197 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths()); 198 } 199 200 uint G1DefaultPolicy::update_young_list_max_and_target_length(size_t rs_lengths) { 201 uint unbounded_target_length = update_young_list_target_length(rs_lengths); 202 update_max_gc_locker_expansion(); 203 return unbounded_target_length; 204 } 205 206 uint G1DefaultPolicy::update_young_list_target_length(size_t rs_lengths) { 207 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths); 208 _young_list_target_length = young_lengths.first; 209 return young_lengths.second; 210 } 211 212 G1DefaultPolicy::YoungTargetLengths G1DefaultPolicy::young_list_target_lengths(size_t rs_lengths) const { 213 YoungTargetLengths result; 214 215 // Calculate the absolute and desired min bounds first. 216 217 // This is how many young regions we already have (currently: the survivors). 218 const uint base_min_length = _g1->survivor_regions_count(); 219 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 220 // This is the absolute minimum young length. Ensure that we 221 // will at least have one eden region available for allocation. 222 uint absolute_min_length = base_min_length + MAX2(_g1->eden_regions_count(), (uint)1); 223 // If we shrank the young list target it should not shrink below the current size. 224 desired_min_length = MAX2(desired_min_length, absolute_min_length); 225 // Calculate the absolute and desired max bounds. 226 227 uint desired_max_length = calculate_young_list_desired_max_length(); 228 229 uint young_list_target_length = 0; 230 if (adaptive_young_list_length()) { 231 if (collector_state()->gcs_are_young()) { 232 young_list_target_length = 233 calculate_young_list_target_length(rs_lengths, 234 base_min_length, 235 desired_min_length, 236 desired_max_length); 237 } else { 238 // Don't calculate anything and let the code below bound it to 239 // the desired_min_length, i.e., do the next GC as soon as 240 // possible to maximize how many old regions we can add to it. 241 } 242 } else { 243 // The user asked for a fixed young gen so we'll fix the young gen 244 // whether the next GC is young or mixed. 245 young_list_target_length = _young_list_fixed_length; 246 } 247 248 result.second = young_list_target_length; 249 250 // We will try our best not to "eat" into the reserve. 251 uint absolute_max_length = 0; 252 if (_free_regions_at_end_of_collection > _reserve_regions) { 253 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 254 } 255 if (desired_max_length > absolute_max_length) { 256 desired_max_length = absolute_max_length; 257 } 258 259 // Make sure we don't go over the desired max length, nor under the 260 // desired min length. In case they clash, desired_min_length wins 261 // which is why that test is second. 262 if (young_list_target_length > desired_max_length) { 263 young_list_target_length = desired_max_length; 264 } 265 if (young_list_target_length < desired_min_length) { 266 young_list_target_length = desired_min_length; 267 } 268 269 assert(young_list_target_length > base_min_length, 270 "we should be able to allocate at least one eden region"); 271 assert(young_list_target_length >= absolute_min_length, "post-condition"); 272 273 result.first = young_list_target_length; 274 return result; 275 } 276 277 uint 278 G1DefaultPolicy::calculate_young_list_target_length(size_t rs_lengths, 279 uint base_min_length, 280 uint desired_min_length, 281 uint desired_max_length) const { 282 assert(adaptive_young_list_length(), "pre-condition"); 283 assert(collector_state()->gcs_are_young(), "only call this for young GCs"); 284 285 // In case some edge-condition makes the desired max length too small... 286 if (desired_max_length <= desired_min_length) { 287 return desired_min_length; 288 } 289 290 // We'll adjust min_young_length and max_young_length not to include 291 // the already allocated young regions (i.e., so they reflect the 292 // min and max eden regions we'll allocate). The base_min_length 293 // will be reflected in the predictions by the 294 // survivor_regions_evac_time prediction. 295 assert(desired_min_length > base_min_length, "invariant"); 296 uint min_young_length = desired_min_length - base_min_length; 297 assert(desired_max_length > base_min_length, "invariant"); 298 uint max_young_length = desired_max_length - base_min_length; 299 300 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 301 const double survivor_regions_evac_time = predict_survivor_regions_evac_time(); 302 const size_t pending_cards = _analytics->predict_pending_cards(); 303 const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff(); 304 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true); 305 const double base_time_ms = 306 predict_base_elapsed_time_ms(pending_cards, scanned_cards) + 307 survivor_regions_evac_time; 308 const uint available_free_regions = _free_regions_at_end_of_collection; 309 const uint base_free_regions = 310 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0; 311 312 // Here, we will make sure that the shortest young length that 313 // makes sense fits within the target pause time. 314 315 G1YoungLengthPredictor p(collector_state()->during_concurrent_mark(), 316 base_time_ms, 317 base_free_regions, 318 target_pause_time_ms, 319 this); 320 if (p.will_fit(min_young_length)) { 321 // The shortest young length will fit into the target pause time; 322 // we'll now check whether the absolute maximum number of young 323 // regions will fit in the target pause time. If not, we'll do 324 // a binary search between min_young_length and max_young_length. 325 if (p.will_fit(max_young_length)) { 326 // The maximum young length will fit into the target pause time. 327 // We are done so set min young length to the maximum length (as 328 // the result is assumed to be returned in min_young_length). 329 min_young_length = max_young_length; 330 } else { 331 // The maximum possible number of young regions will not fit within 332 // the target pause time so we'll search for the optimal 333 // length. The loop invariants are: 334 // 335 // min_young_length < max_young_length 336 // min_young_length is known to fit into the target pause time 337 // max_young_length is known not to fit into the target pause time 338 // 339 // Going into the loop we know the above hold as we've just 340 // checked them. Every time around the loop we check whether 341 // the middle value between min_young_length and 342 // max_young_length fits into the target pause time. If it 343 // does, it becomes the new min. If it doesn't, it becomes 344 // the new max. This way we maintain the loop invariants. 345 346 assert(min_young_length < max_young_length, "invariant"); 347 uint diff = (max_young_length - min_young_length) / 2; 348 while (diff > 0) { 349 uint young_length = min_young_length + diff; 350 if (p.will_fit(young_length)) { 351 min_young_length = young_length; 352 } else { 353 max_young_length = young_length; 354 } 355 assert(min_young_length < max_young_length, "invariant"); 356 diff = (max_young_length - min_young_length) / 2; 357 } 358 // The results is min_young_length which, according to the 359 // loop invariants, should fit within the target pause time. 360 361 // These are the post-conditions of the binary search above: 362 assert(min_young_length < max_young_length, 363 "otherwise we should have discovered that max_young_length " 364 "fits into the pause target and not done the binary search"); 365 assert(p.will_fit(min_young_length), 366 "min_young_length, the result of the binary search, should " 367 "fit into the pause target"); 368 assert(!p.will_fit(min_young_length + 1), 369 "min_young_length, the result of the binary search, should be " 370 "optimal, so no larger length should fit into the pause target"); 371 } 372 } else { 373 // Even the minimum length doesn't fit into the pause time 374 // target, return it as the result nevertheless. 375 } 376 return base_min_length + min_young_length; 377 } 378 379 double G1DefaultPolicy::predict_survivor_regions_evac_time() const { 380 double survivor_regions_evac_time = 0.0; 381 const GrowableArray<HeapRegion*>* survivor_regions = _g1->survivor()->regions(); 382 383 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin(); 384 it != survivor_regions->end(); 385 ++it) { 386 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->gcs_are_young()); 387 } 388 return survivor_regions_evac_time; 389 } 390 391 void G1DefaultPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) { 392 guarantee( adaptive_young_list_length(), "should not call this otherwise" ); 393 394 if (rs_lengths > _rs_lengths_prediction) { 395 // add 10% to avoid having to recalculate often 396 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000; 397 update_rs_lengths_prediction(rs_lengths_prediction); 398 399 update_young_list_max_and_target_length(rs_lengths_prediction); 400 } 401 } 402 403 void G1DefaultPolicy::update_rs_lengths_prediction() { 404 update_rs_lengths_prediction(_analytics->predict_rs_lengths()); 405 } 406 407 void G1DefaultPolicy::update_rs_lengths_prediction(size_t prediction) { 408 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) { 409 _rs_lengths_prediction = prediction; 410 } 411 } 412 413 void G1DefaultPolicy::record_full_collection_start() { 414 _full_collection_start_sec = os::elapsedTime(); 415 // Release the future to-space so that it is available for compaction into. 416 collector_state()->set_full_collection(true); 417 } 418 419 void G1DefaultPolicy::record_full_collection_end() { 420 // Consider this like a collection pause for the purposes of allocation 421 // since last pause. 422 double end_sec = os::elapsedTime(); 423 double full_gc_time_sec = end_sec - _full_collection_start_sec; 424 double full_gc_time_ms = full_gc_time_sec * 1000.0; 425 426 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 427 428 collector_state()->set_full_collection(false); 429 430 // "Nuke" the heuristics that control the young/mixed GC 431 // transitions and make sure we start with young GCs after the Full GC. 432 collector_state()->set_gcs_are_young(true); 433 collector_state()->set_last_young_gc(false); 434 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 435 collector_state()->set_during_initial_mark_pause(false); 436 collector_state()->set_in_marking_window(false); 437 collector_state()->set_in_marking_window_im(false); 438 439 _short_lived_surv_rate_group->start_adding_regions(); 440 // also call this on any additional surv rate groups 441 442 _free_regions_at_end_of_collection = _g1->num_free_regions(); 443 // Reset survivors SurvRateGroup. 444 _survivor_surv_rate_group->reset(); 445 update_young_list_max_and_target_length(); 446 update_rs_lengths_prediction(); 447 cset_chooser()->clear(); 448 449 _bytes_allocated_in_old_since_last_gc = 0; 450 451 record_pause(FullGC, _full_collection_start_sec, end_sec); 452 } 453 454 void G1DefaultPolicy::record_collection_pause_start(double start_time_sec) { 455 // We only need to do this here as the policy will only be applied 456 // to the GC we're about to start. so, no point is calculating this 457 // every time we calculate / recalculate the target young length. 458 update_survivors_policy(); 459 460 assert(_g1->used() == _g1->recalculate_used(), 461 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT, 462 _g1->used(), _g1->recalculate_used()); 463 464 phase_times()->record_cur_collection_start_sec(start_time_sec); 465 _pending_cards = _g1->pending_card_num(); 466 467 _collection_set->reset_bytes_used_before(); 468 _bytes_copied_during_gc = 0; 469 470 collector_state()->set_last_gc_was_young(false); 471 472 // do that for any other surv rate groups 473 _short_lived_surv_rate_group->stop_adding_regions(); 474 _survivors_age_table.clear(); 475 476 assert(_g1->collection_set()->verify_young_ages(), "region age verification failed"); 477 } 478 479 void G1DefaultPolicy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 480 collector_state()->set_during_marking(true); 481 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 482 collector_state()->set_during_initial_mark_pause(false); 483 } 484 485 void G1DefaultPolicy::record_concurrent_mark_remark_start() { 486 _mark_remark_start_sec = os::elapsedTime(); 487 collector_state()->set_during_marking(false); 488 } 489 490 void G1DefaultPolicy::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 G1DefaultPolicy::record_concurrent_mark_cleanup_start() { 500 _mark_cleanup_start_sec = os::elapsedTime(); 501 } 502 503 void G1DefaultPolicy::record_concurrent_mark_cleanup_completed() { 504 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc", 505 "skip last young-only gc"); 506 collector_state()->set_last_young_gc(should_continue_with_reclaim); 507 // We skip the marking phase. 508 if (!should_continue_with_reclaim) { 509 abort_time_to_mixed_tracking(); 510 } 511 collector_state()->set_in_marking_window(false); 512 } 513 514 double G1DefaultPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 515 return phase_times()->average_time_ms(phase); 516 } 517 518 double G1DefaultPolicy::young_other_time_ms() const { 519 return phase_times()->young_cset_choice_time_ms() + 520 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet); 521 } 522 523 double G1DefaultPolicy::non_young_other_time_ms() const { 524 return phase_times()->non_young_cset_choice_time_ms() + 525 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet); 526 } 527 528 double G1DefaultPolicy::other_time_ms(double pause_time_ms) const { 529 return pause_time_ms - phase_times()->cur_collection_par_time_ms(); 530 } 531 532 double G1DefaultPolicy::constant_other_time_ms(double pause_time_ms) const { 533 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms(); 534 } 535 536 CollectionSetChooser* G1DefaultPolicy::cset_chooser() const { 537 return _collection_set->cset_chooser(); 538 } 539 540 bool G1DefaultPolicy::about_to_start_mixed_phase() const { 541 return _g1->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->last_young_gc(); 542 } 543 544 bool G1DefaultPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 545 if (about_to_start_mixed_phase()) { 546 return false; 547 } 548 549 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 550 551 size_t cur_used_bytes = _g1->non_young_capacity_bytes(); 552 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 553 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 554 555 bool result = false; 556 if (marking_request_bytes > marking_initiating_used_threshold) { 557 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc(); 558 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 559 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 560 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source); 561 } 562 563 return result; 564 } 565 566 // Anything below that is considered to be zero 567 #define MIN_TIMER_GRANULARITY 0.0000001 568 569 void G1DefaultPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) { 570 double end_time_sec = os::elapsedTime(); 571 572 size_t cur_used_bytes = _g1->used(); 573 assert(cur_used_bytes == _g1->recalculate_used(), "It should!"); 574 bool last_pause_included_initial_mark = false; 575 bool update_stats = !_g1->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 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause(); 582 if (last_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 bool new_in_marking_window = collector_state()->in_marking_window(); 616 bool new_in_marking_window_im = false; 617 if (last_pause_included_initial_mark) { 618 new_in_marking_window = true; 619 new_in_marking_window_im = true; 620 } 621 622 if (collector_state()->last_young_gc()) { 623 // This is supposed to to be the "last young GC" before we start 624 // doing mixed GCs. Here we decide whether to start mixed GCs or not. 625 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC"); 626 627 if (next_gc_should_be_mixed("start mixed GCs", 628 "do not start mixed GCs")) { 629 collector_state()->set_gcs_are_young(false); 630 } else { 631 // We aborted the mixed GC phase early. 632 abort_time_to_mixed_tracking(); 633 } 634 635 collector_state()->set_last_young_gc(false); 636 } 637 638 if (!collector_state()->last_gc_was_young()) { 639 // This is a mixed GC. Here we decide whether to continue doing 640 // mixed GCs or not. 641 if (!next_gc_should_be_mixed("continue mixed GCs", 642 "do not continue mixed GCs")) { 643 collector_state()->set_gcs_are_young(true); 644 645 maybe_start_marking(); 646 } 647 } 648 649 _short_lived_surv_rate_group->start_adding_regions(); 650 // Do that for any other surv rate groups 651 652 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0; 653 654 if (update_stats) { 655 double cost_per_card_ms = 0.0; 656 if (_pending_cards > 0) { 657 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards; 658 _analytics->report_cost_per_card_ms(cost_per_card_ms); 659 } 660 _analytics->report_cost_scan_hcc(scan_hcc_time_ms); 661 662 double cost_per_entry_ms = 0.0; 663 if (cards_scanned > 10) { 664 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned; 665 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young()); 666 } 667 668 if (_max_rs_lengths > 0) { 669 double cards_per_entry_ratio = 670 (double) cards_scanned / (double) _max_rs_lengths; 671 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young()); 672 } 673 674 // This is defensive. For a while _max_rs_lengths could get 675 // smaller than _recorded_rs_lengths which was causing 676 // rs_length_diff to get very large and mess up the RSet length 677 // predictions. The reason was unsafe concurrent updates to the 678 // _inc_cset_recorded_rs_lengths field which the code below guards 679 // against (see CR 7118202). This bug has now been fixed (see CR 680 // 7119027). However, I'm still worried that 681 // _inc_cset_recorded_rs_lengths might still end up somewhat 682 // inaccurate. The concurrent refinement thread calculates an 683 // RSet's length concurrently with other CR threads updating it 684 // which might cause it to calculate the length incorrectly (if, 685 // say, it's in mid-coarsening). So I'll leave in the defensive 686 // conditional below just in case. 687 size_t rs_length_diff = 0; 688 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths(); 689 if (_max_rs_lengths > recorded_rs_lengths) { 690 rs_length_diff = _max_rs_lengths - recorded_rs_lengths; 691 } 692 _analytics->report_rs_length_diff((double) rs_length_diff); 693 694 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes; 695 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes; 696 double cost_per_byte_ms = 0.0; 697 698 if (copied_bytes > 0) { 699 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes; 700 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window()); 701 } 702 703 if (_collection_set->young_region_length() > 0) { 704 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 705 _collection_set->young_region_length()); 706 } 707 708 if (_collection_set->old_region_length() > 0) { 709 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 710 _collection_set->old_region_length()); 711 } 712 713 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 714 715 _analytics->report_pending_cards((double) _pending_cards); 716 _analytics->report_rs_lengths((double) _max_rs_lengths); 717 } 718 719 collector_state()->set_in_marking_window(new_in_marking_window); 720 collector_state()->set_in_marking_window_im(new_in_marking_window_im); 721 _free_regions_at_end_of_collection = _g1->num_free_regions(); 722 // IHOP control wants to know the expected young gen length if it were not 723 // restrained by the heap reserve. Using the actual length would make the 724 // prediction too small and the limit the young gen every time we get to the 725 // predicted target occupancy. 726 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 727 update_rs_lengths_prediction(); 728 729 update_ihop_prediction(app_time_ms / 1000.0, 730 _bytes_allocated_in_old_since_last_gc, 731 last_unrestrained_young_length * HeapRegion::GrainBytes); 732 _bytes_allocated_in_old_since_last_gc = 0; 733 734 _ihop_control->send_trace_event(_g1->gc_tracer_stw()); 735 736 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 737 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 738 739 if (update_rs_time_goal_ms < scan_hcc_time_ms) { 740 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 741 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms", 742 update_rs_time_goal_ms, scan_hcc_time_ms); 743 744 update_rs_time_goal_ms = 0; 745 } else { 746 update_rs_time_goal_ms -= scan_hcc_time_ms; 747 } 748 _g1->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms, 749 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS), 750 update_rs_time_goal_ms); 751 752 cset_chooser()->verify(); 753 } 754 755 G1IHOPControl* G1DefaultPolicy::create_ihop_control(const G1Predictions* predictor){ 756 if (G1UseAdaptiveIHOP) { 757 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 758 predictor, 759 G1ReservePercent, 760 G1HeapWastePercent); 761 } else { 762 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 763 } 764 } 765 766 void G1DefaultPolicy::update_ihop_prediction(double mutator_time_s, 767 size_t mutator_alloc_bytes, 768 size_t young_gen_size) { 769 // Always try to update IHOP prediction. Even evacuation failures give information 770 // about e.g. whether to start IHOP earlier next time. 771 772 // Avoid using really small application times that might create samples with 773 // very high or very low values. They may be caused by e.g. back-to-back gcs. 774 double const min_valid_time = 1e-6; 775 776 bool report = false; 777 778 double marking_to_mixed_time = -1.0; 779 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) { 780 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 781 assert(marking_to_mixed_time > 0.0, 782 "Initial mark to mixed time must be larger than zero but is %.3f", 783 marking_to_mixed_time); 784 if (marking_to_mixed_time > min_valid_time) { 785 _ihop_control->update_marking_length(marking_to_mixed_time); 786 report = true; 787 } 788 } 789 790 // As an approximation for the young gc promotion rates during marking we use 791 // all of them. In many applications there are only a few if any young gcs during 792 // marking, which makes any prediction useless. This increases the accuracy of the 793 // prediction. 794 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) { 795 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 796 report = true; 797 } 798 799 if (report) { 800 report_ihop_statistics(); 801 } 802 } 803 804 void G1DefaultPolicy::report_ihop_statistics() { 805 _ihop_control->print(); 806 } 807 808 void G1DefaultPolicy::print_phases() { 809 phase_times()->print(); 810 } 811 812 double G1DefaultPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { 813 TruncatedSeq* seq = surv_rate_group->get_seq(age); 814 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); 815 double pred = _predictor.get_new_prediction(seq); 816 if (pred > 1.0) { 817 pred = 1.0; 818 } 819 return pred; 820 } 821 822 double G1DefaultPolicy::accum_yg_surv_rate_pred(int age) const { 823 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 824 } 825 826 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards, 827 size_t scanned_cards) const { 828 return 829 _analytics->predict_rs_update_time_ms(pending_cards) + 830 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) + 831 _analytics->predict_constant_other_time_ms(); 832 } 833 834 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const { 835 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff(); 836 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young()); 837 return predict_base_elapsed_time_ms(pending_cards, card_num); 838 } 839 840 size_t G1DefaultPolicy::predict_bytes_to_copy(HeapRegion* hr) const { 841 size_t bytes_to_copy; 842 if (hr->is_marked()) 843 bytes_to_copy = hr->max_live_bytes(); 844 else { 845 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant"); 846 int age = hr->age_in_surv_rate_group(); 847 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); 848 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); 849 } 850 return bytes_to_copy; 851 } 852 853 double G1DefaultPolicy::predict_region_elapsed_time_ms(HeapRegion* hr, 854 bool for_young_gc) const { 855 size_t rs_length = hr->rem_set()->occupied(); 856 // Predicting the number of cards is based on which type of GC 857 // we're predicting for. 858 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc); 859 size_t bytes_to_copy = predict_bytes_to_copy(hr); 860 861 double region_elapsed_time_ms = 862 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) + 863 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark()); 864 865 // The prediction of the "other" time for this region is based 866 // upon the region type and NOT the GC type. 867 if (hr->is_young()) { 868 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 869 } else { 870 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 871 } 872 return region_elapsed_time_ms; 873 } 874 875 bool G1DefaultPolicy::should_allocate_mutator_region() const { 876 uint young_list_length = _g1->young_regions_count(); 877 uint young_list_target_length = _young_list_target_length; 878 return young_list_length < young_list_target_length; 879 } 880 881 bool G1DefaultPolicy::can_expand_young_list() const { 882 uint young_list_length = _g1->young_regions_count(); 883 uint young_list_max_length = _young_list_max_length; 884 return young_list_length < young_list_max_length; 885 } 886 887 bool G1DefaultPolicy::adaptive_young_list_length() const { 888 return _young_gen_sizer.adaptive_young_list_length(); 889 } 890 891 size_t G1DefaultPolicy::desired_survivor_size() const { 892 size_t const survivor_capacity = HeapRegion::GrainWords * _max_survivor_regions; 893 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100); 894 } 895 896 void G1DefaultPolicy::print_age_table() { 897 _survivors_age_table.print_age_table(_tenuring_threshold); 898 } 899 900 void G1DefaultPolicy::update_max_gc_locker_expansion() { 901 uint expansion_region_num = 0; 902 if (GCLockerEdenExpansionPercent > 0) { 903 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 904 double expansion_region_num_d = perc * (double) _young_list_target_length; 905 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 906 // less than 1.0) we'll get 1. 907 expansion_region_num = (uint) ceil(expansion_region_num_d); 908 } else { 909 assert(expansion_region_num == 0, "sanity"); 910 } 911 _young_list_max_length = _young_list_target_length + expansion_region_num; 912 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 913 } 914 915 // Calculates survivor space parameters. 916 void G1DefaultPolicy::update_survivors_policy() { 917 double max_survivor_regions_d = 918 (double) _young_list_target_length / (double) SurvivorRatio; 919 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but 920 // smaller than 1.0) we'll get 1. 921 _max_survivor_regions = (uint) ceil(max_survivor_regions_d); 922 923 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(desired_survivor_size()); 924 if (UsePerfData) { 925 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold); 926 _policy_counters->desired_survivor_size()->set_value(desired_survivor_size() * oopSize); 927 } 928 } 929 930 bool G1DefaultPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 931 // We actually check whether we are marking here and not if we are in a 932 // reclamation phase. This means that we will schedule a concurrent mark 933 // even while we are still in the process of reclaiming memory. 934 bool during_cycle = _g1->concurrent_mark()->cm_thread()->during_cycle(); 935 if (!during_cycle) { 936 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 937 collector_state()->set_initiate_conc_mark_if_possible(true); 938 return true; 939 } else { 940 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 941 return false; 942 } 943 } 944 945 void G1DefaultPolicy::initiate_conc_mark() { 946 collector_state()->set_during_initial_mark_pause(true); 947 collector_state()->set_initiate_conc_mark_if_possible(false); 948 } 949 950 void G1DefaultPolicy::decide_on_conc_mark_initiation() { 951 // We are about to decide on whether this pause will be an 952 // initial-mark pause. 953 954 // First, collector_state()->during_initial_mark_pause() should not be already set. We 955 // will set it here if we have to. However, it should be cleared by 956 // the end of the pause (it's only set for the duration of an 957 // initial-mark pause). 958 assert(!collector_state()->during_initial_mark_pause(), "pre-condition"); 959 960 if (collector_state()->initiate_conc_mark_if_possible()) { 961 // We had noticed on a previous pause that the heap occupancy has 962 // gone over the initiating threshold and we should start a 963 // concurrent marking cycle. So we might initiate one. 964 965 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) { 966 // Initiate a new initial mark if there is no marking or reclamation going on. 967 initiate_conc_mark(); 968 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 969 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) { 970 // Initiate a user requested initial mark. An initial mark must be young only 971 // GC, so the collector state must be updated to reflect this. 972 collector_state()->set_gcs_are_young(true); 973 collector_state()->set_last_young_gc(false); 974 975 abort_time_to_mixed_tracking(); 976 initiate_conc_mark(); 977 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 978 } else { 979 // The concurrent marking thread is still finishing up the 980 // previous cycle. If we start one right now the two cycles 981 // overlap. In particular, the concurrent marking thread might 982 // be in the process of clearing the next marking bitmap (which 983 // we will use for the next cycle if we start one). Starting a 984 // cycle now will be bad given that parts of the marking 985 // information might get cleared by the marking thread. And we 986 // cannot wait for the marking thread to finish the cycle as it 987 // periodically yields while clearing the next marking bitmap 988 // and, if it's in a yield point, it's waiting for us to 989 // finish. So, at this point we will not start a cycle and we'll 990 // let the concurrent marking thread complete the last one. 991 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 992 } 993 } 994 } 995 996 void G1DefaultPolicy::record_concurrent_mark_cleanup_end() { 997 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions()); 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 G1DefaultPolicy::reclaimable_bytes_percent(size_t reclaimable_bytes) const { 1008 return percent_of(reclaimable_bytes, _g1->capacity()); 1009 } 1010 1011 void G1DefaultPolicy::maybe_start_marking() { 1012 if (need_to_start_conc_mark("end of GC")) { 1013 // Note: this might have already been set, if during the last 1014 // pause we decided to start a cycle but at the beginning of 1015 // this pause we decided to postpone it. That's OK. 1016 collector_state()->set_initiate_conc_mark_if_possible(true); 1017 } 1018 } 1019 1020 G1DefaultPolicy::PauseKind G1DefaultPolicy::young_gc_pause_kind() const { 1021 assert(!collector_state()->full_collection(), "must be"); 1022 if (collector_state()->during_initial_mark_pause()) { 1023 assert(collector_state()->last_gc_was_young(), "must be"); 1024 assert(!collector_state()->last_young_gc(), "must be"); 1025 return InitialMarkGC; 1026 } else if (collector_state()->last_young_gc()) { 1027 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1028 assert(collector_state()->last_gc_was_young(), "must be"); 1029 return LastYoungGC; 1030 } else if (!collector_state()->last_gc_was_young()) { 1031 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1032 assert(!collector_state()->last_young_gc(), "must be"); 1033 return MixedGC; 1034 } else { 1035 assert(collector_state()->last_gc_was_young(), "must be"); 1036 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1037 assert(!collector_state()->last_young_gc(), "must be"); 1038 return YoungOnlyGC; 1039 } 1040 } 1041 1042 void G1DefaultPolicy::record_pause(PauseKind kind, double start, double end) { 1043 // Manage the MMU tracker. For some reason it ignores Full GCs. 1044 if (kind != FullGC) { 1045 _mmu_tracker->add_pause(start, end); 1046 } 1047 // Manage the mutator time tracking from initial mark to first mixed gc. 1048 switch (kind) { 1049 case FullGC: 1050 abort_time_to_mixed_tracking(); 1051 break; 1052 case Cleanup: 1053 case Remark: 1054 case YoungOnlyGC: 1055 case LastYoungGC: 1056 _initial_mark_to_mixed.add_pause(end - start); 1057 break; 1058 case InitialMarkGC: 1059 _initial_mark_to_mixed.record_initial_mark_end(end); 1060 break; 1061 case MixedGC: 1062 _initial_mark_to_mixed.record_mixed_gc_start(start); 1063 break; 1064 default: 1065 ShouldNotReachHere(); 1066 } 1067 } 1068 1069 void G1DefaultPolicy::abort_time_to_mixed_tracking() { 1070 _initial_mark_to_mixed.reset(); 1071 } 1072 1073 bool G1DefaultPolicy::next_gc_should_be_mixed(const char* true_action_str, 1074 const char* false_action_str) const { 1075 if (cset_chooser()->is_empty()) { 1076 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1077 return false; 1078 } 1079 1080 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1081 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); 1082 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes); 1083 double threshold = (double) G1HeapWastePercent; 1084 if (reclaimable_percent <= threshold) { 1085 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1086 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1087 return false; 1088 } 1089 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1090 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent); 1091 return true; 1092 } 1093 1094 uint G1DefaultPolicy::calc_min_old_cset_length() const { 1095 // The min old CSet region bound is based on the maximum desired 1096 // number of mixed GCs after a cycle. I.e., even if some old regions 1097 // look expensive, we should add them to the CSet anyway to make 1098 // sure we go through the available old regions in no more than the 1099 // maximum desired number of mixed GCs. 1100 // 1101 // The calculation is based on the number of marked regions we added 1102 // to the CSet chooser in the first place, not how many remain, so 1103 // that the result is the same during all mixed GCs that follow a cycle. 1104 1105 const size_t region_num = (size_t) cset_chooser()->length(); 1106 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1107 size_t result = region_num / gc_num; 1108 // emulate ceiling 1109 if (result * gc_num < region_num) { 1110 result += 1; 1111 } 1112 return (uint) result; 1113 } 1114 1115 uint G1DefaultPolicy::calc_max_old_cset_length() const { 1116 // The max old CSet region bound is based on the threshold expressed 1117 // as a percentage of the heap size. I.e., it should bound the 1118 // number of old regions added to the CSet irrespective of how many 1119 // of them are available. 1120 1121 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1122 const size_t region_num = g1h->num_regions(); 1123 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1124 size_t result = region_num * perc / 100; 1125 // emulate ceiling 1126 if (100 * result < region_num * perc) { 1127 result += 1; 1128 } 1129 return (uint) result; 1130 } 1131 1132 void G1DefaultPolicy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) { 1133 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor); 1134 _collection_set->finalize_old_part(time_remaining_ms); 1135 } 1136 1137 void G1DefaultPolicy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) { 1138 1139 // Add survivor regions to SurvRateGroup. 1140 note_start_adding_survivor_regions(); 1141 finished_recalculating_age_indexes(true /* is_survivors */); 1142 1143 HeapRegion* last = NULL; 1144 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin(); 1145 it != survivors->regions()->end(); 1146 ++it) { 1147 HeapRegion* curr = *it; 1148 set_region_survivor(curr); 1149 1150 // The region is a non-empty survivor so let's add it to 1151 // the incremental collection set for the next evacuation 1152 // pause. 1153 _collection_set->add_survivor_regions(curr); 1154 1155 last = curr; 1156 } 1157 note_stop_adding_survivor_regions(); 1158 1159 // Don't clear the survivor list handles until the start of 1160 // the next evacuation pause - we need it in order to re-tag 1161 // the survivor regions from this evacuation pause as 'young' 1162 // at the start of the next. 1163 1164 finished_recalculating_age_indexes(false /* is_survivors */); 1165 }