1 /* 2 * Copyright (c) 2001, 2016, 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/concurrentG1Refine.hpp" 27 #include "gc/g1/concurrentMarkThread.inline.hpp" 28 #include "gc/g1/g1Analytics.hpp" 29 #include "gc/g1/g1CollectedHeap.inline.hpp" 30 #include "gc/g1/g1CollectionSet.hpp" 31 #include "gc/g1/g1ConcurrentMark.hpp" 32 #include "gc/g1/g1IHOPControl.hpp" 33 #include "gc/g1/g1GCPhaseTimes.hpp" 34 #include "gc/g1/g1Policy.hpp" 35 #include "gc/g1/g1YoungGenSizer.hpp" 36 #include "gc/g1/heapRegion.inline.hpp" 37 #include "gc/g1/heapRegionRemSet.hpp" 38 #include "gc/shared/gcPolicyCounters.hpp" 39 #include "runtime/arguments.hpp" 40 #include "runtime/java.hpp" 41 #include "runtime/mutexLocker.hpp" 42 #include "utilities/debug.hpp" 43 #include "utilities/pair.hpp" 44 45 G1Policy::G1Policy() : 46 _predictor(G1ConfidencePercent / 100.0), 47 _analytics(new G1Analytics(&_predictor)), 48 _pause_time_target_ms((double) MaxGCPauseMillis), 49 _rs_lengths_prediction(0), 50 _max_survivor_regions(0), 51 _survivors_age_table(true), 52 53 _bytes_allocated_in_old_since_last_gc(0), 54 _ihop_control(NULL), 55 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 3)), 56 _initial_mark_to_mixed() { 57 58 // SurvRateGroups below must be initialized after the predictor because they 59 // indirectly use it through this object passed to their constructor. 60 _short_lived_surv_rate_group = 61 new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary); 62 _survivor_surv_rate_group = 63 new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary); 64 65 _phase_times = new G1GCPhaseTimes(ParallelGCThreads); 66 67 double max_gc_time = (double) MaxGCPauseMillis / 1000.0; 68 double time_slice = (double) GCPauseIntervalMillis / 1000.0; 69 _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time); 70 71 _tenuring_threshold = MaxTenuringThreshold; 72 73 74 guarantee(G1ReservePercent <= 50, "Range checking should not allow values over 50."); 75 _reserve_factor = (double) G1ReservePercent / 100.0; 76 // This will be set when the heap is expanded 77 // for the first time during initialization. 78 _reserve_regions = 0; 79 80 _ihop_control = create_ihop_control(); 81 } 82 83 G1Policy::~G1Policy() { 84 delete _ihop_control; 85 } 86 87 G1CollectorState* G1Policy::collector_state() const { return _g1->collector_state(); } 88 89 void G1Policy::init() { 90 // Set aside an initial future to_space. 91 _g1 = G1CollectedHeap::heap(); 92 _collection_set = _g1->collection_set(); 93 94 assert(Heap_lock->owned_by_self(), "Locking discipline."); 95 96 if (adaptive_young_list_length()) { 97 _young_list_fixed_length = 0; 98 } else { 99 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length(); 100 } 101 _young_gen_sizer.adjust_max_new_size(_g1->max_regions()); 102 103 _free_regions_at_end_of_collection = _g1->num_free_regions(); 104 105 update_young_list_max_and_target_length(); 106 // We may immediately start allocating regions and placing them on the 107 // collection set list. Initialize the per-collection set info 108 _collection_set->start_incremental_building(); 109 } 110 111 void G1Policy::note_gc_start() { 112 phase_times()->note_gc_start(); 113 } 114 115 bool G1Policy::predict_will_fit(uint young_length, 116 double base_time_ms, 117 uint base_free_regions, 118 double target_pause_time_ms) const { 119 if (young_length >= base_free_regions) { 120 // end condition 1: not enough space for the young regions 121 return false; 122 } 123 124 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1); 125 size_t bytes_to_copy = 126 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes); 127 double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy, 128 collector_state()->during_concurrent_mark()); 129 double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length); 130 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms; 131 if (pause_time_ms > target_pause_time_ms) { 132 // end condition 2: prediction is over the target pause time 133 return false; 134 } 135 136 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes; 137 138 // When copying, we will likely need more bytes free than is live in the region. 139 // Add some safety margin to factor in the confidence of our guess, and the 140 // natural expected waste. 141 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 142 // of the calculation: the lower the confidence, the more headroom. 143 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 144 // copying due to anticipated waste in the PLABs. 145 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 146 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 147 148 if (expected_bytes_to_copy > free_bytes) { 149 // end condition 3: out-of-space 150 return false; 151 } 152 153 // success! 154 return true; 155 } 156 157 void G1Policy::record_new_heap_size(uint new_number_of_regions) { 158 // re-calculate the necessary reserve 159 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 160 // We use ceiling so that if reserve_regions_d is > 0.0 (but 161 // smaller than 1.0) we'll get 1. 162 _reserve_regions = (uint) ceil(reserve_regions_d); 163 164 _young_gen_sizer.heap_size_changed(new_number_of_regions); 165 166 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 167 } 168 169 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const { 170 uint desired_min_length = 0; 171 if (adaptive_young_list_length()) { 172 if (_analytics->num_alloc_rate_ms() > 3) { 173 double now_sec = os::elapsedTime(); 174 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 175 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 176 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 177 } else { 178 // otherwise we don't have enough info to make the prediction 179 } 180 } 181 desired_min_length += base_min_length; 182 // make sure we don't go below any user-defined minimum bound 183 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length); 184 } 185 186 uint G1Policy::calculate_young_list_desired_max_length() const { 187 // Here, we might want to also take into account any additional 188 // constraints (i.e., user-defined minimum bound). Currently, we 189 // effectively don't set this bound. 190 return _young_gen_sizer.max_desired_young_length(); 191 } 192 193 uint G1Policy::update_young_list_max_and_target_length() { 194 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths()); 195 } 196 197 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) { 198 uint unbounded_target_length = update_young_list_target_length(rs_lengths); 199 update_max_gc_locker_expansion(); 200 return unbounded_target_length; 201 } 202 203 uint G1Policy::update_young_list_target_length(size_t rs_lengths) { 204 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths); 205 _young_list_target_length = young_lengths.first; 206 return young_lengths.second; 207 } 208 209 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const { 210 YoungTargetLengths result; 211 212 // Calculate the absolute and desired min bounds first. 213 214 // This is how many young regions we already have (currently: the survivors). 215 const uint base_min_length = _g1->young_list()->survivor_length(); 216 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 217 // This is the absolute minimum young length. Ensure that we 218 // will at least have one eden region available for allocation. 219 uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1); 220 // If we shrank the young list target it should not shrink below the current size. 221 desired_min_length = MAX2(desired_min_length, absolute_min_length); 222 // Calculate the absolute and desired max bounds. 223 224 uint desired_max_length = calculate_young_list_desired_max_length(); 225 226 uint young_list_target_length = 0; 227 if (adaptive_young_list_length()) { 228 if (collector_state()->gcs_are_young()) { 229 young_list_target_length = 230 calculate_young_list_target_length(rs_lengths, 231 base_min_length, 232 desired_min_length, 233 desired_max_length); 234 } else { 235 // Don't calculate anything and let the code below bound it to 236 // the desired_min_length, i.e., do the next GC as soon as 237 // possible to maximize how many old regions we can add to it. 238 } 239 } else { 240 // The user asked for a fixed young gen so we'll fix the young gen 241 // whether the next GC is young or mixed. 242 young_list_target_length = _young_list_fixed_length; 243 } 244 245 result.second = young_list_target_length; 246 247 // We will try our best not to "eat" into the reserve. 248 uint absolute_max_length = 0; 249 if (_free_regions_at_end_of_collection > _reserve_regions) { 250 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 251 } 252 if (desired_max_length > absolute_max_length) { 253 desired_max_length = absolute_max_length; 254 } 255 256 // Make sure we don't go over the desired max length, nor under the 257 // desired min length. In case they clash, desired_min_length wins 258 // which is why that test is second. 259 if (young_list_target_length > desired_max_length) { 260 young_list_target_length = desired_max_length; 261 } 262 if (young_list_target_length < desired_min_length) { 263 young_list_target_length = desired_min_length; 264 } 265 266 assert(young_list_target_length > base_min_length, 267 "we should be able to allocate at least one eden region"); 268 assert(young_list_target_length >= absolute_min_length, "post-condition"); 269 270 result.first = young_list_target_length; 271 return result; 272 } 273 274 uint 275 G1Policy::calculate_young_list_target_length(size_t rs_lengths, 276 uint base_min_length, 277 uint desired_min_length, 278 uint desired_max_length) const { 279 assert(adaptive_young_list_length(), "pre-condition"); 280 assert(collector_state()->gcs_are_young(), "only call this for young GCs"); 281 282 // In case some edge-condition makes the desired max length too small... 283 if (desired_max_length <= desired_min_length) { 284 return desired_min_length; 285 } 286 287 // We'll adjust min_young_length and max_young_length not to include 288 // the already allocated young regions (i.e., so they reflect the 289 // min and max eden regions we'll allocate). The base_min_length 290 // will be reflected in the predictions by the 291 // survivor_regions_evac_time prediction. 292 assert(desired_min_length > base_min_length, "invariant"); 293 uint min_young_length = desired_min_length - base_min_length; 294 assert(desired_max_length > base_min_length, "invariant"); 295 uint max_young_length = desired_max_length - base_min_length; 296 297 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 298 double survivor_regions_evac_time = predict_survivor_regions_evac_time(); 299 size_t pending_cards = _analytics->predict_pending_cards(); 300 size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff(); 301 size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true); 302 double base_time_ms = 303 predict_base_elapsed_time_ms(pending_cards, scanned_cards) + 304 survivor_regions_evac_time; 305 uint available_free_regions = _free_regions_at_end_of_collection; 306 uint base_free_regions = 0; 307 if (available_free_regions > _reserve_regions) { 308 base_free_regions = available_free_regions - _reserve_regions; 309 } 310 311 // Here, we will make sure that the shortest young length that 312 // makes sense fits within the target pause time. 313 314 if (predict_will_fit(min_young_length, base_time_ms, 315 base_free_regions, target_pause_time_ms)) { 316 // The shortest young length will fit into the target pause time; 317 // we'll now check whether the absolute maximum number of young 318 // regions will fit in the target pause time. If not, we'll do 319 // a binary search between min_young_length and max_young_length. 320 if (predict_will_fit(max_young_length, base_time_ms, 321 base_free_regions, target_pause_time_ms)) { 322 // The maximum young length will fit into the target pause time. 323 // We are done so set min young length to the maximum length (as 324 // the result is assumed to be returned in min_young_length). 325 min_young_length = max_young_length; 326 } else { 327 // The maximum possible number of young regions will not fit within 328 // the target pause time so we'll search for the optimal 329 // length. The loop invariants are: 330 // 331 // min_young_length < max_young_length 332 // min_young_length is known to fit into the target pause time 333 // max_young_length is known not to fit into the target pause time 334 // 335 // Going into the loop we know the above hold as we've just 336 // checked them. Every time around the loop we check whether 337 // the middle value between min_young_length and 338 // max_young_length fits into the target pause time. If it 339 // does, it becomes the new min. If it doesn't, it becomes 340 // the new max. This way we maintain the loop invariants. 341 342 assert(min_young_length < max_young_length, "invariant"); 343 uint diff = (max_young_length - min_young_length) / 2; 344 while (diff > 0) { 345 uint young_length = min_young_length + diff; 346 if (predict_will_fit(young_length, base_time_ms, 347 base_free_regions, target_pause_time_ms)) { 348 min_young_length = young_length; 349 } else { 350 max_young_length = young_length; 351 } 352 assert(min_young_length < max_young_length, "invariant"); 353 diff = (max_young_length - min_young_length) / 2; 354 } 355 // The results is min_young_length which, according to the 356 // loop invariants, should fit within the target pause time. 357 358 // These are the post-conditions of the binary search above: 359 assert(min_young_length < max_young_length, 360 "otherwise we should have discovered that max_young_length " 361 "fits into the pause target and not done the binary search"); 362 assert(predict_will_fit(min_young_length, base_time_ms, 363 base_free_regions, target_pause_time_ms), 364 "min_young_length, the result of the binary search, should " 365 "fit into the pause target"); 366 assert(!predict_will_fit(min_young_length + 1, base_time_ms, 367 base_free_regions, target_pause_time_ms), 368 "min_young_length, the result of the binary search, should be " 369 "optimal, so no larger length should fit into the pause target"); 370 } 371 } else { 372 // Even the minimum length doesn't fit into the pause time 373 // target, return it as the result nevertheless. 374 } 375 return base_min_length + min_young_length; 376 } 377 378 double G1Policy::predict_survivor_regions_evac_time() const { 379 double survivor_regions_evac_time = 0.0; 380 for (HeapRegion * r = _g1->young_list()->first_survivor_region(); 381 r != NULL && r != _g1->young_list()->last_survivor_region()->get_next_young_region(); 382 r = r->get_next_young_region()) { 383 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young()); 384 } 385 return survivor_regions_evac_time; 386 } 387 388 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) { 389 guarantee( adaptive_young_list_length(), "should not call this otherwise" ); 390 391 if (rs_lengths > _rs_lengths_prediction) { 392 // add 10% to avoid having to recalculate often 393 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000; 394 update_rs_lengths_prediction(rs_lengths_prediction); 395 396 update_young_list_max_and_target_length(rs_lengths_prediction); 397 } 398 } 399 400 void G1Policy::update_rs_lengths_prediction() { 401 update_rs_lengths_prediction(_analytics->predict_rs_lengths()); 402 } 403 404 void G1Policy::update_rs_lengths_prediction(size_t prediction) { 405 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) { 406 _rs_lengths_prediction = prediction; 407 } 408 } 409 410 #ifndef PRODUCT 411 bool G1Policy::verify_young_ages() { 412 HeapRegion* head = _g1->young_list()->first_region(); 413 return 414 verify_young_ages(head, _short_lived_surv_rate_group); 415 // also call verify_young_ages on any additional surv rate groups 416 } 417 418 bool G1Policy::verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group) { 419 guarantee( surv_rate_group != NULL, "pre-condition" ); 420 421 const char* name = surv_rate_group->name(); 422 bool ret = true; 423 int prev_age = -1; 424 425 for (HeapRegion* curr = head; 426 curr != NULL; 427 curr = curr->get_next_young_region()) { 428 SurvRateGroup* group = curr->surv_rate_group(); 429 if (group == NULL && !curr->is_survivor()) { 430 log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name); 431 ret = false; 432 } 433 434 if (surv_rate_group == group) { 435 int age = curr->age_in_surv_rate_group(); 436 437 if (age < 0) { 438 log_error(gc, verify)("## %s: encountered negative age", name); 439 ret = false; 440 } 441 442 if (age <= prev_age) { 443 log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age); 444 ret = false; 445 } 446 prev_age = age; 447 } 448 } 449 450 return ret; 451 } 452 #endif // PRODUCT 453 454 void G1Policy::record_full_collection_start() { 455 _full_collection_start_sec = os::elapsedTime(); 456 // Release the future to-space so that it is available for compaction into. 457 collector_state()->set_full_collection(true); 458 } 459 460 void G1Policy::record_full_collection_end() { 461 // Consider this like a collection pause for the purposes of allocation 462 // since last pause. 463 double end_sec = os::elapsedTime(); 464 double full_gc_time_sec = end_sec - _full_collection_start_sec; 465 double full_gc_time_ms = full_gc_time_sec * 1000.0; 466 467 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 468 469 collector_state()->set_full_collection(false); 470 471 // "Nuke" the heuristics that control the young/mixed GC 472 // transitions and make sure we start with young GCs after the Full GC. 473 collector_state()->set_gcs_are_young(true); 474 collector_state()->set_last_young_gc(false); 475 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 476 collector_state()->set_during_initial_mark_pause(false); 477 collector_state()->set_in_marking_window(false); 478 collector_state()->set_in_marking_window_im(false); 479 480 _short_lived_surv_rate_group->start_adding_regions(); 481 // also call this on any additional surv rate groups 482 483 _free_regions_at_end_of_collection = _g1->num_free_regions(); 484 // Reset survivors SurvRateGroup. 485 _survivor_surv_rate_group->reset(); 486 update_young_list_max_and_target_length(); 487 update_rs_lengths_prediction(); 488 cset_chooser()->clear(); 489 490 _bytes_allocated_in_old_since_last_gc = 0; 491 492 record_pause(FullGC, _full_collection_start_sec, end_sec); 493 } 494 495 void G1Policy::record_collection_pause_start(double start_time_sec) { 496 // We only need to do this here as the policy will only be applied 497 // to the GC we're about to start. so, no point is calculating this 498 // every time we calculate / recalculate the target young length. 499 update_survivors_policy(); 500 501 assert(_g1->used() == _g1->recalculate_used(), 502 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT, 503 _g1->used(), _g1->recalculate_used()); 504 505 phase_times()->record_cur_collection_start_sec(start_time_sec); 506 _pending_cards = _g1->pending_card_num(); 507 508 _collection_set->reset_bytes_used_before(); 509 _bytes_copied_during_gc = 0; 510 511 collector_state()->set_last_gc_was_young(false); 512 513 // do that for any other surv rate groups 514 _short_lived_surv_rate_group->stop_adding_regions(); 515 _survivors_age_table.clear(); 516 517 assert( verify_young_ages(), "region age verification" ); 518 } 519 520 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 521 collector_state()->set_during_marking(true); 522 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 523 collector_state()->set_during_initial_mark_pause(false); 524 } 525 526 void G1Policy::record_concurrent_mark_remark_start() { 527 _mark_remark_start_sec = os::elapsedTime(); 528 collector_state()->set_during_marking(false); 529 } 530 531 void G1Policy::record_concurrent_mark_remark_end() { 532 double end_time_sec = os::elapsedTime(); 533 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 534 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 535 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 536 537 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 538 } 539 540 void G1Policy::record_concurrent_mark_cleanup_start() { 541 _mark_cleanup_start_sec = os::elapsedTime(); 542 } 543 544 void G1Policy::record_concurrent_mark_cleanup_completed() { 545 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc", 546 "skip last young-only gc"); 547 collector_state()->set_last_young_gc(should_continue_with_reclaim); 548 // We skip the marking phase. 549 if (!should_continue_with_reclaim) { 550 abort_time_to_mixed_tracking(); 551 } 552 collector_state()->set_in_marking_window(false); 553 } 554 555 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 556 return phase_times()->average_time_ms(phase); 557 } 558 559 double G1Policy::young_other_time_ms() const { 560 return phase_times()->young_cset_choice_time_ms() + 561 phase_times()->young_free_cset_time_ms(); 562 } 563 564 double G1Policy::non_young_other_time_ms() const { 565 return phase_times()->non_young_cset_choice_time_ms() + 566 phase_times()->non_young_free_cset_time_ms(); 567 568 } 569 570 double G1Policy::other_time_ms(double pause_time_ms) const { 571 return pause_time_ms - 572 average_time_ms(G1GCPhaseTimes::UpdateRS) - 573 average_time_ms(G1GCPhaseTimes::ScanRS) - 574 average_time_ms(G1GCPhaseTimes::ObjCopy) - 575 average_time_ms(G1GCPhaseTimes::Termination); 576 } 577 578 double G1Policy::constant_other_time_ms(double pause_time_ms) const { 579 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms(); 580 } 581 582 CollectionSetChooser* G1Policy::cset_chooser() const { 583 return _collection_set->cset_chooser(); 584 } 585 586 bool G1Policy::about_to_start_mixed_phase() const { 587 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc(); 588 } 589 590 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 591 if (about_to_start_mixed_phase()) { 592 return false; 593 } 594 595 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 596 597 size_t cur_used_bytes = _g1->non_young_capacity_bytes(); 598 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 599 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 600 601 bool result = false; 602 if (marking_request_bytes > marking_initiating_used_threshold) { 603 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc(); 604 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 605 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 606 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source); 607 } 608 609 return result; 610 } 611 612 // Anything below that is considered to be zero 613 #define MIN_TIMER_GRANULARITY 0.0000001 614 615 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) { 616 double end_time_sec = os::elapsedTime(); 617 618 size_t cur_used_bytes = _g1->used(); 619 assert(cur_used_bytes == _g1->recalculate_used(), "It should!"); 620 bool last_pause_included_initial_mark = false; 621 bool update_stats = !_g1->evacuation_failed(); 622 623 NOT_PRODUCT(_short_lived_surv_rate_group->print()); 624 625 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 626 627 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause(); 628 if (last_pause_included_initial_mark) { 629 record_concurrent_mark_init_end(0.0); 630 } else { 631 maybe_start_marking(); 632 } 633 634 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 635 if (app_time_ms < MIN_TIMER_GRANULARITY) { 636 // This usually happens due to the timer not having the required 637 // granularity. Some Linuxes are the usual culprits. 638 // We'll just set it to something (arbitrarily) small. 639 app_time_ms = 1.0; 640 } 641 642 if (update_stats) { 643 // We maintain the invariant that all objects allocated by mutator 644 // threads will be allocated out of eden regions. So, we can use 645 // the eden region number allocated since the previous GC to 646 // calculate the application's allocate rate. The only exception 647 // to that is humongous objects that are allocated separately. But 648 // given that humongous object allocations do not really affect 649 // either the pause's duration nor when the next pause will take 650 // place we can safely ignore them here. 651 uint regions_allocated = _collection_set->eden_region_length(); 652 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 653 _analytics->report_alloc_rate_ms(alloc_rate_ms); 654 655 double interval_ms = 656 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; 657 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 658 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms); 659 } 660 661 bool new_in_marking_window = collector_state()->in_marking_window(); 662 bool new_in_marking_window_im = false; 663 if (last_pause_included_initial_mark) { 664 new_in_marking_window = true; 665 new_in_marking_window_im = true; 666 } 667 668 if (collector_state()->last_young_gc()) { 669 // This is supposed to to be the "last young GC" before we start 670 // doing mixed GCs. Here we decide whether to start mixed GCs or not. 671 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC"); 672 673 if (next_gc_should_be_mixed("start mixed GCs", 674 "do not start mixed GCs")) { 675 collector_state()->set_gcs_are_young(false); 676 } else { 677 // We aborted the mixed GC phase early. 678 abort_time_to_mixed_tracking(); 679 } 680 681 collector_state()->set_last_young_gc(false); 682 } 683 684 if (!collector_state()->last_gc_was_young()) { 685 // This is a mixed GC. Here we decide whether to continue doing 686 // mixed GCs or not. 687 if (!next_gc_should_be_mixed("continue mixed GCs", 688 "do not continue mixed GCs")) { 689 collector_state()->set_gcs_are_young(true); 690 691 maybe_start_marking(); 692 } 693 } 694 695 _short_lived_surv_rate_group->start_adding_regions(); 696 // Do that for any other surv rate groups 697 698 double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0; 699 700 if (update_stats) { 701 double cost_per_card_ms = 0.0; 702 if (_pending_cards > 0) { 703 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards; 704 _analytics->report_cost_per_card_ms(cost_per_card_ms); 705 } 706 _analytics->report_cost_scan_hcc(scan_hcc_time_ms); 707 708 double cost_per_entry_ms = 0.0; 709 if (cards_scanned > 10) { 710 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned; 711 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young()); 712 } 713 714 if (_max_rs_lengths > 0) { 715 double cards_per_entry_ratio = 716 (double) cards_scanned / (double) _max_rs_lengths; 717 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young()); 718 } 719 720 // This is defensive. For a while _max_rs_lengths could get 721 // smaller than _recorded_rs_lengths which was causing 722 // rs_length_diff to get very large and mess up the RSet length 723 // predictions. The reason was unsafe concurrent updates to the 724 // _inc_cset_recorded_rs_lengths field which the code below guards 725 // against (see CR 7118202). This bug has now been fixed (see CR 726 // 7119027). However, I'm still worried that 727 // _inc_cset_recorded_rs_lengths might still end up somewhat 728 // inaccurate. The concurrent refinement thread calculates an 729 // RSet's length concurrently with other CR threads updating it 730 // which might cause it to calculate the length incorrectly (if, 731 // say, it's in mid-coarsening). So I'll leave in the defensive 732 // conditional below just in case. 733 size_t rs_length_diff = 0; 734 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths(); 735 if (_max_rs_lengths > recorded_rs_lengths) { 736 rs_length_diff = _max_rs_lengths - recorded_rs_lengths; 737 } 738 _analytics->report_rs_length_diff((double) rs_length_diff); 739 740 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes; 741 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes; 742 double cost_per_byte_ms = 0.0; 743 744 if (copied_bytes > 0) { 745 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes; 746 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window()); 747 } 748 749 if (_collection_set->young_region_length() > 0) { 750 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 751 _collection_set->young_region_length()); 752 } 753 754 if (_collection_set->old_region_length() > 0) { 755 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 756 _collection_set->old_region_length()); 757 } 758 759 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 760 761 _analytics->report_pending_cards((double) _pending_cards); 762 _analytics->report_rs_lengths((double) _max_rs_lengths); 763 } 764 765 collector_state()->set_in_marking_window(new_in_marking_window); 766 collector_state()->set_in_marking_window_im(new_in_marking_window_im); 767 _free_regions_at_end_of_collection = _g1->num_free_regions(); 768 // IHOP control wants to know the expected young gen length if it were not 769 // restrained by the heap reserve. Using the actual length would make the 770 // prediction too small and the limit the young gen every time we get to the 771 // predicted target occupancy. 772 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 773 update_rs_lengths_prediction(); 774 775 update_ihop_prediction(app_time_ms / 1000.0, 776 _bytes_allocated_in_old_since_last_gc, 777 last_unrestrained_young_length * HeapRegion::GrainBytes); 778 _bytes_allocated_in_old_since_last_gc = 0; 779 780 _ihop_control->send_trace_event(_g1->gc_tracer_stw()); 781 782 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 783 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 784 785 if (update_rs_time_goal_ms < scan_hcc_time_ms) { 786 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 787 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms", 788 update_rs_time_goal_ms, scan_hcc_time_ms); 789 790 update_rs_time_goal_ms = 0; 791 } else { 792 update_rs_time_goal_ms -= scan_hcc_time_ms; 793 } 794 _g1->concurrent_g1_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms, 795 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS), 796 update_rs_time_goal_ms); 797 798 cset_chooser()->verify(); 799 } 800 801 G1IHOPControl* G1Policy::create_ihop_control() const { 802 if (G1UseAdaptiveIHOP) { 803 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 804 &_predictor, 805 G1ReservePercent, 806 G1HeapWastePercent); 807 } else { 808 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 809 } 810 } 811 812 void G1Policy::update_ihop_prediction(double mutator_time_s, 813 size_t mutator_alloc_bytes, 814 size_t young_gen_size) { 815 // Always try to update IHOP prediction. Even evacuation failures give information 816 // about e.g. whether to start IHOP earlier next time. 817 818 // Avoid using really small application times that might create samples with 819 // very high or very low values. They may be caused by e.g. back-to-back gcs. 820 double const min_valid_time = 1e-6; 821 822 bool report = false; 823 824 double marking_to_mixed_time = -1.0; 825 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) { 826 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 827 assert(marking_to_mixed_time > 0.0, 828 "Initial mark to mixed time must be larger than zero but is %.3f", 829 marking_to_mixed_time); 830 if (marking_to_mixed_time > min_valid_time) { 831 _ihop_control->update_marking_length(marking_to_mixed_time); 832 report = true; 833 } 834 } 835 836 // As an approximation for the young gc promotion rates during marking we use 837 // all of them. In many applications there are only a few if any young gcs during 838 // marking, which makes any prediction useless. This increases the accuracy of the 839 // prediction. 840 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) { 841 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 842 report = true; 843 } 844 845 if (report) { 846 report_ihop_statistics(); 847 } 848 } 849 850 void G1Policy::report_ihop_statistics() { 851 _ihop_control->print(); 852 } 853 854 void G1Policy::print_phases() { 855 phase_times()->print(); 856 } 857 858 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { 859 TruncatedSeq* seq = surv_rate_group->get_seq(age); 860 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); 861 double pred = _predictor.get_new_prediction(seq); 862 if (pred > 1.0) { 863 pred = 1.0; 864 } 865 return pred; 866 } 867 868 double G1Policy::predict_yg_surv_rate(int age) const { 869 return predict_yg_surv_rate(age, _short_lived_surv_rate_group); 870 } 871 872 double G1Policy::accum_yg_surv_rate_pred(int age) const { 873 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 874 } 875 876 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards, 877 size_t scanned_cards) const { 878 return 879 _analytics->predict_rs_update_time_ms(pending_cards) + 880 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) + 881 _analytics->predict_constant_other_time_ms(); 882 } 883 884 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const { 885 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff(); 886 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young()); 887 return predict_base_elapsed_time_ms(pending_cards, card_num); 888 } 889 890 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const { 891 size_t bytes_to_copy; 892 if (hr->is_marked()) 893 bytes_to_copy = hr->max_live_bytes(); 894 else { 895 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant"); 896 int age = hr->age_in_surv_rate_group(); 897 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); 898 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); 899 } 900 return bytes_to_copy; 901 } 902 903 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr, 904 bool for_young_gc) const { 905 size_t rs_length = hr->rem_set()->occupied(); 906 // Predicting the number of cards is based on which type of GC 907 // we're predicting for. 908 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc); 909 size_t bytes_to_copy = predict_bytes_to_copy(hr); 910 911 double region_elapsed_time_ms = 912 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) + 913 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark()); 914 915 // The prediction of the "other" time for this region is based 916 // upon the region type and NOT the GC type. 917 if (hr->is_young()) { 918 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 919 } else { 920 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 921 } 922 return region_elapsed_time_ms; 923 } 924 925 926 void G1Policy::print_yg_surv_rate_info() const { 927 #ifndef PRODUCT 928 _short_lived_surv_rate_group->print_surv_rate_summary(); 929 // add this call for any other surv rate groups 930 #endif // PRODUCT 931 } 932 933 bool G1Policy::is_young_list_full() const { 934 uint young_list_length = _g1->young_list()->length(); 935 uint young_list_target_length = _young_list_target_length; 936 return young_list_length >= young_list_target_length; 937 } 938 939 bool G1Policy::can_expand_young_list() const { 940 uint young_list_length = _g1->young_list()->length(); 941 uint young_list_max_length = _young_list_max_length; 942 return young_list_length < young_list_max_length; 943 } 944 945 bool G1Policy::adaptive_young_list_length() const { 946 return _young_gen_sizer.adaptive_young_list_length(); 947 } 948 949 void G1Policy::update_max_gc_locker_expansion() { 950 uint expansion_region_num = 0; 951 if (GCLockerEdenExpansionPercent > 0) { 952 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 953 double expansion_region_num_d = perc * (double) _young_list_target_length; 954 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 955 // less than 1.0) we'll get 1. 956 expansion_region_num = (uint) ceil(expansion_region_num_d); 957 } else { 958 assert(expansion_region_num == 0, "sanity"); 959 } 960 _young_list_max_length = _young_list_target_length + expansion_region_num; 961 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 962 } 963 964 // Calculates survivor space parameters. 965 void G1Policy::update_survivors_policy() { 966 double max_survivor_regions_d = 967 (double) _young_list_target_length / (double) SurvivorRatio; 968 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but 969 // smaller than 1.0) we'll get 1. 970 _max_survivor_regions = (uint) ceil(max_survivor_regions_d); 971 972 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold( 973 HeapRegion::GrainWords * _max_survivor_regions, _policy_counters); 974 } 975 976 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 977 // We actually check whether we are marking here and not if we are in a 978 // reclamation phase. This means that we will schedule a concurrent mark 979 // even while we are still in the process of reclaiming memory. 980 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle(); 981 if (!during_cycle) { 982 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 983 collector_state()->set_initiate_conc_mark_if_possible(true); 984 return true; 985 } else { 986 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 987 return false; 988 } 989 } 990 991 void G1Policy::initiate_conc_mark() { 992 collector_state()->set_during_initial_mark_pause(true); 993 collector_state()->set_initiate_conc_mark_if_possible(false); 994 } 995 996 void G1Policy::decide_on_conc_mark_initiation() { 997 // We are about to decide on whether this pause will be an 998 // initial-mark pause. 999 1000 // First, collector_state()->during_initial_mark_pause() should not be already set. We 1001 // will set it here if we have to. However, it should be cleared by 1002 // the end of the pause (it's only set for the duration of an 1003 // initial-mark pause). 1004 assert(!collector_state()->during_initial_mark_pause(), "pre-condition"); 1005 1006 if (collector_state()->initiate_conc_mark_if_possible()) { 1007 // We had noticed on a previous pause that the heap occupancy has 1008 // gone over the initiating threshold and we should start a 1009 // concurrent marking cycle. So we might initiate one. 1010 1011 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) { 1012 // Initiate a new initial mark if there is no marking or reclamation going on. 1013 initiate_conc_mark(); 1014 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 1015 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) { 1016 // Initiate a user requested initial mark. An initial mark must be young only 1017 // GC, so the collector state must be updated to reflect this. 1018 collector_state()->set_gcs_are_young(true); 1019 collector_state()->set_last_young_gc(false); 1020 1021 abort_time_to_mixed_tracking(); 1022 initiate_conc_mark(); 1023 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 1024 } else { 1025 // The concurrent marking thread is still finishing up the 1026 // previous cycle. If we start one right now the two cycles 1027 // overlap. In particular, the concurrent marking thread might 1028 // be in the process of clearing the next marking bitmap (which 1029 // we will use for the next cycle if we start one). Starting a 1030 // cycle now will be bad given that parts of the marking 1031 // information might get cleared by the marking thread. And we 1032 // cannot wait for the marking thread to finish the cycle as it 1033 // periodically yields while clearing the next marking bitmap 1034 // and, if it's in a yield point, it's waiting for us to 1035 // finish. So, at this point we will not start a cycle and we'll 1036 // let the concurrent marking thread complete the last one. 1037 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 1038 } 1039 } 1040 } 1041 1042 void G1Policy::record_concurrent_mark_cleanup_end() { 1043 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions()); 1044 1045 double end_sec = os::elapsedTime(); 1046 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1047 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1048 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1049 1050 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1051 } 1052 1053 double G1Policy::reclaimable_bytes_perc(size_t reclaimable_bytes) const { 1054 // Returns the given amount of reclaimable bytes (that represents 1055 // the amount of reclaimable space still to be collected) as a 1056 // percentage of the current heap capacity. 1057 size_t capacity_bytes = _g1->capacity(); 1058 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes; 1059 } 1060 1061 void G1Policy::maybe_start_marking() { 1062 if (need_to_start_conc_mark("end of GC")) { 1063 // Note: this might have already been set, if during the last 1064 // pause we decided to start a cycle but at the beginning of 1065 // this pause we decided to postpone it. That's OK. 1066 collector_state()->set_initiate_conc_mark_if_possible(true); 1067 } 1068 } 1069 1070 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const { 1071 assert(!collector_state()->full_collection(), "must be"); 1072 if (collector_state()->during_initial_mark_pause()) { 1073 assert(collector_state()->last_gc_was_young(), "must be"); 1074 assert(!collector_state()->last_young_gc(), "must be"); 1075 return InitialMarkGC; 1076 } else if (collector_state()->last_young_gc()) { 1077 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1078 assert(collector_state()->last_gc_was_young(), "must be"); 1079 return LastYoungGC; 1080 } else if (!collector_state()->last_gc_was_young()) { 1081 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1082 assert(!collector_state()->last_young_gc(), "must be"); 1083 return MixedGC; 1084 } else { 1085 assert(collector_state()->last_gc_was_young(), "must be"); 1086 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1087 assert(!collector_state()->last_young_gc(), "must be"); 1088 return YoungOnlyGC; 1089 } 1090 } 1091 1092 void G1Policy::record_pause(PauseKind kind, double start, double end) { 1093 // Manage the MMU tracker. For some reason it ignores Full GCs. 1094 if (kind != FullGC) { 1095 _mmu_tracker->add_pause(start, end); 1096 } 1097 // Manage the mutator time tracking from initial mark to first mixed gc. 1098 switch (kind) { 1099 case FullGC: 1100 abort_time_to_mixed_tracking(); 1101 break; 1102 case Cleanup: 1103 case Remark: 1104 case YoungOnlyGC: 1105 case LastYoungGC: 1106 _initial_mark_to_mixed.add_pause(end - start); 1107 break; 1108 case InitialMarkGC: 1109 _initial_mark_to_mixed.record_initial_mark_end(end); 1110 break; 1111 case MixedGC: 1112 _initial_mark_to_mixed.record_mixed_gc_start(start); 1113 break; 1114 default: 1115 ShouldNotReachHere(); 1116 } 1117 } 1118 1119 void G1Policy::abort_time_to_mixed_tracking() { 1120 _initial_mark_to_mixed.reset(); 1121 } 1122 1123 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str, 1124 const char* false_action_str) const { 1125 if (cset_chooser()->is_empty()) { 1126 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1127 return false; 1128 } 1129 1130 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1131 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); 1132 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes); 1133 double threshold = (double) G1HeapWastePercent; 1134 if (reclaimable_perc <= threshold) { 1135 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1136 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); 1137 return false; 1138 } 1139 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1140 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); 1141 return true; 1142 } 1143 1144 uint G1Policy::calc_min_old_cset_length() const { 1145 // The min old CSet region bound is based on the maximum desired 1146 // number of mixed GCs after a cycle. I.e., even if some old regions 1147 // look expensive, we should add them to the CSet anyway to make 1148 // sure we go through the available old regions in no more than the 1149 // maximum desired number of mixed GCs. 1150 // 1151 // The calculation is based on the number of marked regions we added 1152 // to the CSet chooser in the first place, not how many remain, so 1153 // that the result is the same during all mixed GCs that follow a cycle. 1154 1155 const size_t region_num = (size_t) cset_chooser()->length(); 1156 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1157 size_t result = region_num / gc_num; 1158 // emulate ceiling 1159 if (result * gc_num < region_num) { 1160 result += 1; 1161 } 1162 return (uint) result; 1163 } 1164 1165 uint G1Policy::calc_max_old_cset_length() const { 1166 // The max old CSet region bound is based on the threshold expressed 1167 // as a percentage of the heap size. I.e., it should bound the 1168 // number of old regions added to the CSet irrespective of how many 1169 // of them are available. 1170 1171 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1172 const size_t region_num = g1h->num_regions(); 1173 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1174 size_t result = region_num * perc / 100; 1175 // emulate ceiling 1176 if (100 * result < region_num * perc) { 1177 result += 1; 1178 } 1179 return (uint) result; 1180 } 1181 1182 void G1Policy::finalize_collection_set(double target_pause_time_ms) { 1183 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms); 1184 _collection_set->finalize_old_part(time_remaining_ms); 1185 }