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 _initial_mark_to_mixed() { 56 57 // SurvRateGroups below must be initialized after the predictor because they 58 // indirectly use it through this object passed to their constructor. 59 _short_lived_surv_rate_group = 60 new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary); 61 _survivor_surv_rate_group = 62 new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary); 63 64 _phase_times = new G1GCPhaseTimes(ParallelGCThreads); 65 66 double max_gc_time = (double) MaxGCPauseMillis / 1000.0; 67 double time_slice = (double) GCPauseIntervalMillis / 1000.0; 68 _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time); 69 70 _tenuring_threshold = MaxTenuringThreshold; 71 72 73 guarantee(G1ReservePercent <= 50, "Range checking should not allow values over 50."); 74 _reserve_factor = (double) G1ReservePercent / 100.0; 75 // This will be set when the heap is expanded 76 // for the first time during initialization. 77 _reserve_regions = 0; 78 79 _ihop_control = create_ihop_control(); 80 } 81 82 G1Policy::~G1Policy() { 83 delete _ihop_control; 84 } 85 86 G1CollectorState* G1Policy::collector_state() const { return _g1->collector_state(); } 87 88 void G1Policy::init() { 89 // Set aside an initial future to_space. 90 _g1 = G1CollectedHeap::heap(); 91 _collection_set = _g1->collection_set(); 92 93 assert(Heap_lock->owned_by_self(), "Locking discipline."); 94 95 _g1->collector_policy()->initialize_gc_policy_counters(); 96 97 if (adaptive_young_list_length()) { 98 _young_list_fixed_length = 0; 99 } else { 100 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length(); 101 } 102 _young_gen_sizer.adjust_max_new_size(_g1->max_regions()); 103 104 _free_regions_at_end_of_collection = _g1->num_free_regions(); 105 106 update_young_list_max_and_target_length(); 107 // We may immediately start allocating regions and placing them on the 108 // collection set list. Initialize the per-collection set info 109 _collection_set->start_incremental_building(); 110 } 111 112 void G1Policy::note_gc_start() { 113 phase_times()->note_gc_start(); 114 } 115 116 bool G1Policy::predict_will_fit(uint young_length, 117 double base_time_ms, 118 uint base_free_regions, 119 double target_pause_time_ms) const { 120 if (young_length >= base_free_regions) { 121 // end condition 1: not enough space for the young regions 122 return false; 123 } 124 125 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1); 126 size_t bytes_to_copy = 127 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes); 128 double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy, 129 collector_state()->during_concurrent_mark()); 130 double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length); 131 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms; 132 if (pause_time_ms > target_pause_time_ms) { 133 // end condition 2: prediction is over the target pause time 134 return false; 135 } 136 137 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes; 138 139 // When copying, we will likely need more bytes free than is live in the region. 140 // Add some safety margin to factor in the confidence of our guess, and the 141 // natural expected waste. 142 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 143 // of the calculation: the lower the confidence, the more headroom. 144 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 145 // copying due to anticipated waste in the PLABs. 146 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 147 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 148 149 if (expected_bytes_to_copy > free_bytes) { 150 // end condition 3: out-of-space 151 return false; 152 } 153 154 // success! 155 return true; 156 } 157 158 void G1Policy::record_new_heap_size(uint new_number_of_regions) { 159 // re-calculate the necessary reserve 160 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 161 // We use ceiling so that if reserve_regions_d is > 0.0 (but 162 // smaller than 1.0) we'll get 1. 163 _reserve_regions = (uint) ceil(reserve_regions_d); 164 165 _young_gen_sizer.heap_size_changed(new_number_of_regions); 166 167 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 168 } 169 170 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const { 171 uint desired_min_length = 0; 172 if (adaptive_young_list_length()) { 173 if (_analytics->num_alloc_rate_ms() > 3) { 174 double now_sec = os::elapsedTime(); 175 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 176 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 177 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 178 } else { 179 // otherwise we don't have enough info to make the prediction 180 } 181 } 182 desired_min_length += base_min_length; 183 // make sure we don't go below any user-defined minimum bound 184 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length); 185 } 186 187 uint G1Policy::calculate_young_list_desired_max_length() const { 188 // Here, we might want to also take into account any additional 189 // constraints (i.e., user-defined minimum bound). Currently, we 190 // effectively don't set this bound. 191 return _young_gen_sizer.max_desired_young_length(); 192 } 193 194 uint G1Policy::update_young_list_max_and_target_length() { 195 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths()); 196 } 197 198 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) { 199 uint unbounded_target_length = update_young_list_target_length(rs_lengths); 200 update_max_gc_locker_expansion(); 201 return unbounded_target_length; 202 } 203 204 uint G1Policy::update_young_list_target_length(size_t rs_lengths) { 205 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths); 206 _young_list_target_length = young_lengths.first; 207 return young_lengths.second; 208 } 209 210 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const { 211 YoungTargetLengths result; 212 213 // Calculate the absolute and desired min bounds first. 214 215 // This is how many young regions we already have (currently: the survivors). 216 const uint base_min_length = _g1->young_list()->survivor_length(); 217 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 218 // This is the absolute minimum young length. Ensure that we 219 // will at least have one eden region available for allocation. 220 uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1); 221 // If we shrank the young list target it should not shrink below the current size. 222 desired_min_length = MAX2(desired_min_length, absolute_min_length); 223 // Calculate the absolute and desired max bounds. 224 225 uint desired_max_length = calculate_young_list_desired_max_length(); 226 227 uint young_list_target_length = 0; 228 if (adaptive_young_list_length()) { 229 if (collector_state()->gcs_are_young()) { 230 young_list_target_length = 231 calculate_young_list_target_length(rs_lengths, 232 base_min_length, 233 desired_min_length, 234 desired_max_length); 235 } else { 236 // Don't calculate anything and let the code below bound it to 237 // the desired_min_length, i.e., do the next GC as soon as 238 // possible to maximize how many old regions we can add to it. 239 } 240 } else { 241 // The user asked for a fixed young gen so we'll fix the young gen 242 // whether the next GC is young or mixed. 243 young_list_target_length = _young_list_fixed_length; 244 } 245 246 result.second = young_list_target_length; 247 248 // We will try our best not to "eat" into the reserve. 249 uint absolute_max_length = 0; 250 if (_free_regions_at_end_of_collection > _reserve_regions) { 251 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 252 } 253 if (desired_max_length > absolute_max_length) { 254 desired_max_length = absolute_max_length; 255 } 256 257 // Make sure we don't go over the desired max length, nor under the 258 // desired min length. In case they clash, desired_min_length wins 259 // which is why that test is second. 260 if (young_list_target_length > desired_max_length) { 261 young_list_target_length = desired_max_length; 262 } 263 if (young_list_target_length < desired_min_length) { 264 young_list_target_length = desired_min_length; 265 } 266 267 assert(young_list_target_length > base_min_length, 268 "we should be able to allocate at least one eden region"); 269 assert(young_list_target_length >= absolute_min_length, "post-condition"); 270 271 result.first = young_list_target_length; 272 return result; 273 } 274 275 uint 276 G1Policy::calculate_young_list_target_length(size_t rs_lengths, 277 uint base_min_length, 278 uint desired_min_length, 279 uint desired_max_length) const { 280 assert(adaptive_young_list_length(), "pre-condition"); 281 assert(collector_state()->gcs_are_young(), "only call this for young GCs"); 282 283 // In case some edge-condition makes the desired max length too small... 284 if (desired_max_length <= desired_min_length) { 285 return desired_min_length; 286 } 287 288 // We'll adjust min_young_length and max_young_length not to include 289 // the already allocated young regions (i.e., so they reflect the 290 // min and max eden regions we'll allocate). The base_min_length 291 // will be reflected in the predictions by the 292 // survivor_regions_evac_time prediction. 293 assert(desired_min_length > base_min_length, "invariant"); 294 uint min_young_length = desired_min_length - base_min_length; 295 assert(desired_max_length > base_min_length, "invariant"); 296 uint max_young_length = desired_max_length - base_min_length; 297 298 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 299 double survivor_regions_evac_time = predict_survivor_regions_evac_time(); 300 size_t pending_cards = _analytics->predict_pending_cards(); 301 size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff(); 302 size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true); 303 double base_time_ms = 304 predict_base_elapsed_time_ms(pending_cards, scanned_cards) + 305 survivor_regions_evac_time; 306 uint available_free_regions = _free_regions_at_end_of_collection; 307 uint base_free_regions = 0; 308 if (available_free_regions > _reserve_regions) { 309 base_free_regions = available_free_regions - _reserve_regions; 310 } 311 312 // Here, we will make sure that the shortest young length that 313 // makes sense fits within the target pause time. 314 315 if (predict_will_fit(min_young_length, base_time_ms, 316 base_free_regions, target_pause_time_ms)) { 317 // The shortest young length will fit into the target pause time; 318 // we'll now check whether the absolute maximum number of young 319 // regions will fit in the target pause time. If not, we'll do 320 // a binary search between min_young_length and max_young_length. 321 if (predict_will_fit(max_young_length, base_time_ms, 322 base_free_regions, target_pause_time_ms)) { 323 // The maximum young length will fit into the target pause time. 324 // We are done so set min young length to the maximum length (as 325 // the result is assumed to be returned in min_young_length). 326 min_young_length = max_young_length; 327 } else { 328 // The maximum possible number of young regions will not fit within 329 // the target pause time so we'll search for the optimal 330 // length. The loop invariants are: 331 // 332 // min_young_length < max_young_length 333 // min_young_length is known to fit into the target pause time 334 // max_young_length is known not to fit into the target pause time 335 // 336 // Going into the loop we know the above hold as we've just 337 // checked them. Every time around the loop we check whether 338 // the middle value between min_young_length and 339 // max_young_length fits into the target pause time. If it 340 // does, it becomes the new min. If it doesn't, it becomes 341 // the new max. This way we maintain the loop invariants. 342 343 assert(min_young_length < max_young_length, "invariant"); 344 uint diff = (max_young_length - min_young_length) / 2; 345 while (diff > 0) { 346 uint young_length = min_young_length + diff; 347 if (predict_will_fit(young_length, base_time_ms, 348 base_free_regions, target_pause_time_ms)) { 349 min_young_length = young_length; 350 } else { 351 max_young_length = young_length; 352 } 353 assert(min_young_length < max_young_length, "invariant"); 354 diff = (max_young_length - min_young_length) / 2; 355 } 356 // The results is min_young_length which, according to the 357 // loop invariants, should fit within the target pause time. 358 359 // These are the post-conditions of the binary search above: 360 assert(min_young_length < max_young_length, 361 "otherwise we should have discovered that max_young_length " 362 "fits into the pause target and not done the binary search"); 363 assert(predict_will_fit(min_young_length, base_time_ms, 364 base_free_regions, target_pause_time_ms), 365 "min_young_length, the result of the binary search, should " 366 "fit into the pause target"); 367 assert(!predict_will_fit(min_young_length + 1, base_time_ms, 368 base_free_regions, target_pause_time_ms), 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 G1Policy::predict_survivor_regions_evac_time() const { 380 double survivor_regions_evac_time = 0.0; 381 for (HeapRegion * r = _g1->young_list()->first_survivor_region(); 382 r != NULL && r != _g1->young_list()->last_survivor_region()->get_next_young_region(); 383 r = r->get_next_young_region()) { 384 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young()); 385 } 386 return survivor_regions_evac_time; 387 } 388 389 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) { 390 guarantee( adaptive_young_list_length(), "should not call this otherwise" ); 391 392 if (rs_lengths > _rs_lengths_prediction) { 393 // add 10% to avoid having to recalculate often 394 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000; 395 update_rs_lengths_prediction(rs_lengths_prediction); 396 397 update_young_list_max_and_target_length(rs_lengths_prediction); 398 } 399 } 400 401 void G1Policy::update_rs_lengths_prediction() { 402 update_rs_lengths_prediction(_analytics->predict_rs_lengths()); 403 } 404 405 void G1Policy::update_rs_lengths_prediction(size_t prediction) { 406 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) { 407 _rs_lengths_prediction = prediction; 408 } 409 } 410 411 #ifndef PRODUCT 412 bool G1Policy::verify_young_ages() { 413 HeapRegion* head = _g1->young_list()->first_region(); 414 return 415 verify_young_ages(head, _short_lived_surv_rate_group); 416 // also call verify_young_ages on any additional surv rate groups 417 } 418 419 bool G1Policy::verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group) { 420 guarantee( surv_rate_group != NULL, "pre-condition" ); 421 422 const char* name = surv_rate_group->name(); 423 bool ret = true; 424 int prev_age = -1; 425 426 for (HeapRegion* curr = head; 427 curr != NULL; 428 curr = curr->get_next_young_region()) { 429 SurvRateGroup* group = curr->surv_rate_group(); 430 if (group == NULL && !curr->is_survivor()) { 431 log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name); 432 ret = false; 433 } 434 435 if (surv_rate_group == group) { 436 int age = curr->age_in_surv_rate_group(); 437 438 if (age < 0) { 439 log_error(gc, verify)("## %s: encountered negative age", name); 440 ret = false; 441 } 442 443 if (age <= prev_age) { 444 log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age); 445 ret = false; 446 } 447 prev_age = age; 448 } 449 } 450 451 return ret; 452 } 453 #endif // PRODUCT 454 455 void G1Policy::record_full_collection_start() { 456 _full_collection_start_sec = os::elapsedTime(); 457 // Release the future to-space so that it is available for compaction into. 458 collector_state()->set_full_collection(true); 459 } 460 461 void G1Policy::record_full_collection_end() { 462 // Consider this like a collection pause for the purposes of allocation 463 // since last pause. 464 double end_sec = os::elapsedTime(); 465 double full_gc_time_sec = end_sec - _full_collection_start_sec; 466 double full_gc_time_ms = full_gc_time_sec * 1000.0; 467 468 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 469 470 collector_state()->set_full_collection(false); 471 472 // "Nuke" the heuristics that control the young/mixed GC 473 // transitions and make sure we start with young GCs after the Full GC. 474 collector_state()->set_gcs_are_young(true); 475 collector_state()->set_last_young_gc(false); 476 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 477 collector_state()->set_during_initial_mark_pause(false); 478 collector_state()->set_in_marking_window(false); 479 collector_state()->set_in_marking_window_im(false); 480 481 _short_lived_surv_rate_group->start_adding_regions(); 482 // also call this on any additional surv rate groups 483 484 _free_regions_at_end_of_collection = _g1->num_free_regions(); 485 // Reset survivors SurvRateGroup. 486 _survivor_surv_rate_group->reset(); 487 update_young_list_max_and_target_length(); 488 update_rs_lengths_prediction(); 489 cset_chooser()->clear(); 490 491 _bytes_allocated_in_old_since_last_gc = 0; 492 493 record_pause(FullGC, _full_collection_start_sec, end_sec); 494 } 495 496 void G1Policy::record_collection_pause_start(double start_time_sec) { 497 // We only need to do this here as the policy will only be applied 498 // to the GC we're about to start. so, no point is calculating this 499 // every time we calculate / recalculate the target young length. 500 update_survivors_policy(); 501 502 assert(_g1->used() == _g1->recalculate_used(), 503 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT, 504 _g1->used(), _g1->recalculate_used()); 505 506 phase_times()->record_cur_collection_start_sec(start_time_sec); 507 _pending_cards = _g1->pending_card_num(); 508 509 _collection_set->reset_bytes_used_before(); 510 _bytes_copied_during_gc = 0; 511 512 collector_state()->set_last_gc_was_young(false); 513 514 // do that for any other surv rate groups 515 _short_lived_surv_rate_group->stop_adding_regions(); 516 _survivors_age_table.clear(); 517 518 assert( verify_young_ages(), "region age verification" ); 519 } 520 521 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 522 collector_state()->set_during_marking(true); 523 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 524 collector_state()->set_during_initial_mark_pause(false); 525 } 526 527 void G1Policy::record_concurrent_mark_remark_start() { 528 _mark_remark_start_sec = os::elapsedTime(); 529 collector_state()->set_during_marking(false); 530 } 531 532 void G1Policy::record_concurrent_mark_remark_end() { 533 double end_time_sec = os::elapsedTime(); 534 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 535 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 536 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 537 538 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 539 } 540 541 void G1Policy::record_concurrent_mark_cleanup_start() { 542 _mark_cleanup_start_sec = os::elapsedTime(); 543 } 544 545 void G1Policy::record_concurrent_mark_cleanup_completed() { 546 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc", 547 "skip last young-only gc"); 548 collector_state()->set_last_young_gc(should_continue_with_reclaim); 549 // We skip the marking phase. 550 if (!should_continue_with_reclaim) { 551 abort_time_to_mixed_tracking(); 552 } 553 collector_state()->set_in_marking_window(false); 554 } 555 556 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 557 return phase_times()->average_time_ms(phase); 558 } 559 560 double G1Policy::young_other_time_ms() const { 561 return phase_times()->young_cset_choice_time_ms() + 562 phase_times()->young_free_cset_time_ms(); 563 } 564 565 double G1Policy::non_young_other_time_ms() const { 566 return phase_times()->non_young_cset_choice_time_ms() + 567 phase_times()->non_young_free_cset_time_ms(); 568 569 } 570 571 double G1Policy::other_time_ms(double pause_time_ms) const { 572 return pause_time_ms - 573 average_time_ms(G1GCPhaseTimes::UpdateRS) - 574 average_time_ms(G1GCPhaseTimes::ScanRS) - 575 average_time_ms(G1GCPhaseTimes::ObjCopy) - 576 average_time_ms(G1GCPhaseTimes::Termination); 577 } 578 579 double G1Policy::constant_other_time_ms(double pause_time_ms) const { 580 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms(); 581 } 582 583 CollectionSetChooser* G1Policy::cset_chooser() const { 584 return _collection_set->cset_chooser(); 585 } 586 587 bool G1Policy::about_to_start_mixed_phase() const { 588 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc(); 589 } 590 591 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 592 if (about_to_start_mixed_phase()) { 593 return false; 594 } 595 596 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 597 598 size_t cur_used_bytes = _g1->non_young_capacity_bytes(); 599 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 600 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 601 602 bool result = false; 603 if (marking_request_bytes > marking_initiating_used_threshold) { 604 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc(); 605 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 606 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 607 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source); 608 } 609 610 return result; 611 } 612 613 // Anything below that is considered to be zero 614 #define MIN_TIMER_GRANULARITY 0.0000001 615 616 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) { 617 double end_time_sec = os::elapsedTime(); 618 619 size_t cur_used_bytes = _g1->used(); 620 assert(cur_used_bytes == _g1->recalculate_used(), "It should!"); 621 bool last_pause_included_initial_mark = false; 622 bool update_stats = !_g1->evacuation_failed(); 623 624 NOT_PRODUCT(_short_lived_surv_rate_group->print()); 625 626 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 627 628 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause(); 629 if (last_pause_included_initial_mark) { 630 record_concurrent_mark_init_end(0.0); 631 } else { 632 maybe_start_marking(); 633 } 634 635 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 636 if (app_time_ms < MIN_TIMER_GRANULARITY) { 637 // This usually happens due to the timer not having the required 638 // granularity. Some Linuxes are the usual culprits. 639 // We'll just set it to something (arbitrarily) small. 640 app_time_ms = 1.0; 641 } 642 643 if (update_stats) { 644 // We maintain the invariant that all objects allocated by mutator 645 // threads will be allocated out of eden regions. So, we can use 646 // the eden region number allocated since the previous GC to 647 // calculate the application's allocate rate. The only exception 648 // to that is humongous objects that are allocated separately. But 649 // given that humongous object allocations do not really affect 650 // either the pause's duration nor when the next pause will take 651 // place we can safely ignore them here. 652 uint regions_allocated = _collection_set->eden_region_length(); 653 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 654 _analytics->report_alloc_rate_ms(alloc_rate_ms); 655 656 double interval_ms = 657 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; 658 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 659 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms); 660 } 661 662 bool new_in_marking_window = collector_state()->in_marking_window(); 663 bool new_in_marking_window_im = false; 664 if (last_pause_included_initial_mark) { 665 new_in_marking_window = true; 666 new_in_marking_window_im = true; 667 } 668 669 if (collector_state()->last_young_gc()) { 670 // This is supposed to to be the "last young GC" before we start 671 // doing mixed GCs. Here we decide whether to start mixed GCs or not. 672 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC"); 673 674 if (next_gc_should_be_mixed("start mixed GCs", 675 "do not start mixed GCs")) { 676 collector_state()->set_gcs_are_young(false); 677 } else { 678 // We aborted the mixed GC phase early. 679 abort_time_to_mixed_tracking(); 680 } 681 682 collector_state()->set_last_young_gc(false); 683 } 684 685 if (!collector_state()->last_gc_was_young()) { 686 // This is a mixed GC. Here we decide whether to continue doing 687 // mixed GCs or not. 688 if (!next_gc_should_be_mixed("continue mixed GCs", 689 "do not continue mixed GCs")) { 690 collector_state()->set_gcs_are_young(true); 691 692 maybe_start_marking(); 693 } 694 } 695 696 _short_lived_surv_rate_group->start_adding_regions(); 697 // Do that for any other surv rate groups 698 699 double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0; 700 701 if (update_stats) { 702 double cost_per_card_ms = 0.0; 703 if (_pending_cards > 0) { 704 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards; 705 _analytics->report_cost_per_card_ms(cost_per_card_ms); 706 } 707 _analytics->report_cost_scan_hcc(scan_hcc_time_ms); 708 709 double cost_per_entry_ms = 0.0; 710 if (cards_scanned > 10) { 711 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned; 712 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young()); 713 } 714 715 if (_max_rs_lengths > 0) { 716 double cards_per_entry_ratio = 717 (double) cards_scanned / (double) _max_rs_lengths; 718 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young()); 719 } 720 721 // This is defensive. For a while _max_rs_lengths could get 722 // smaller than _recorded_rs_lengths which was causing 723 // rs_length_diff to get very large and mess up the RSet length 724 // predictions. The reason was unsafe concurrent updates to the 725 // _inc_cset_recorded_rs_lengths field which the code below guards 726 // against (see CR 7118202). This bug has now been fixed (see CR 727 // 7119027). However, I'm still worried that 728 // _inc_cset_recorded_rs_lengths might still end up somewhat 729 // inaccurate. The concurrent refinement thread calculates an 730 // RSet's length concurrently with other CR threads updating it 731 // which might cause it to calculate the length incorrectly (if, 732 // say, it's in mid-coarsening). So I'll leave in the defensive 733 // conditional below just in case. 734 size_t rs_length_diff = 0; 735 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths(); 736 if (_max_rs_lengths > recorded_rs_lengths) { 737 rs_length_diff = _max_rs_lengths - recorded_rs_lengths; 738 } 739 _analytics->report_rs_length_diff((double) rs_length_diff); 740 741 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes; 742 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes; 743 double cost_per_byte_ms = 0.0; 744 745 if (copied_bytes > 0) { 746 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes; 747 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window()); 748 } 749 750 if (_collection_set->young_region_length() > 0) { 751 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 752 _collection_set->young_region_length()); 753 } 754 755 if (_collection_set->old_region_length() > 0) { 756 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 757 _collection_set->old_region_length()); 758 } 759 760 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 761 762 _analytics->report_pending_cards((double) _pending_cards); 763 _analytics->report_rs_lengths((double) _max_rs_lengths); 764 } 765 766 collector_state()->set_in_marking_window(new_in_marking_window); 767 collector_state()->set_in_marking_window_im(new_in_marking_window_im); 768 _free_regions_at_end_of_collection = _g1->num_free_regions(); 769 // IHOP control wants to know the expected young gen length if it were not 770 // restrained by the heap reserve. Using the actual length would make the 771 // prediction too small and the limit the young gen every time we get to the 772 // predicted target occupancy. 773 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 774 update_rs_lengths_prediction(); 775 776 update_ihop_prediction(app_time_ms / 1000.0, 777 _bytes_allocated_in_old_since_last_gc, 778 last_unrestrained_young_length * HeapRegion::GrainBytes); 779 _bytes_allocated_in_old_since_last_gc = 0; 780 781 _ihop_control->send_trace_event(_g1->gc_tracer_stw()); 782 783 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 784 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 785 786 if (update_rs_time_goal_ms < scan_hcc_time_ms) { 787 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 788 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms", 789 update_rs_time_goal_ms, scan_hcc_time_ms); 790 791 update_rs_time_goal_ms = 0; 792 } else { 793 update_rs_time_goal_ms -= scan_hcc_time_ms; 794 } 795 _g1->concurrent_g1_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms, 796 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS), 797 update_rs_time_goal_ms); 798 799 cset_chooser()->verify(); 800 } 801 802 G1IHOPControl* G1Policy::create_ihop_control() const { 803 if (G1UseAdaptiveIHOP) { 804 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 805 &_predictor, 806 G1ReservePercent, 807 G1HeapWastePercent); 808 } else { 809 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 810 } 811 } 812 813 void G1Policy::update_ihop_prediction(double mutator_time_s, 814 size_t mutator_alloc_bytes, 815 size_t young_gen_size) { 816 // Always try to update IHOP prediction. Even evacuation failures give information 817 // about e.g. whether to start IHOP earlier next time. 818 819 // Avoid using really small application times that might create samples with 820 // very high or very low values. They may be caused by e.g. back-to-back gcs. 821 double const min_valid_time = 1e-6; 822 823 bool report = false; 824 825 double marking_to_mixed_time = -1.0; 826 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) { 827 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 828 assert(marking_to_mixed_time > 0.0, 829 "Initial mark to mixed time must be larger than zero but is %.3f", 830 marking_to_mixed_time); 831 if (marking_to_mixed_time > min_valid_time) { 832 _ihop_control->update_marking_length(marking_to_mixed_time); 833 report = true; 834 } 835 } 836 837 // As an approximation for the young gc promotion rates during marking we use 838 // all of them. In many applications there are only a few if any young gcs during 839 // marking, which makes any prediction useless. This increases the accuracy of the 840 // prediction. 841 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) { 842 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 843 report = true; 844 } 845 846 if (report) { 847 report_ihop_statistics(); 848 } 849 } 850 851 void G1Policy::report_ihop_statistics() { 852 _ihop_control->print(); 853 } 854 855 void G1Policy::print_phases() { 856 phase_times()->print(); 857 } 858 859 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { 860 TruncatedSeq* seq = surv_rate_group->get_seq(age); 861 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); 862 double pred = _predictor.get_new_prediction(seq); 863 if (pred > 1.0) { 864 pred = 1.0; 865 } 866 return pred; 867 } 868 869 double G1Policy::predict_yg_surv_rate(int age) const { 870 return predict_yg_surv_rate(age, _short_lived_surv_rate_group); 871 } 872 873 double G1Policy::accum_yg_surv_rate_pred(int age) const { 874 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 875 } 876 877 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards, 878 size_t scanned_cards) const { 879 return 880 _analytics->predict_rs_update_time_ms(pending_cards) + 881 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) + 882 _analytics->predict_constant_other_time_ms(); 883 } 884 885 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const { 886 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff(); 887 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young()); 888 return predict_base_elapsed_time_ms(pending_cards, card_num); 889 } 890 891 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const { 892 size_t bytes_to_copy; 893 if (hr->is_marked()) 894 bytes_to_copy = hr->max_live_bytes(); 895 else { 896 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant"); 897 int age = hr->age_in_surv_rate_group(); 898 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); 899 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); 900 } 901 return bytes_to_copy; 902 } 903 904 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr, 905 bool for_young_gc) const { 906 size_t rs_length = hr->rem_set()->occupied(); 907 // Predicting the number of cards is based on which type of GC 908 // we're predicting for. 909 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc); 910 size_t bytes_to_copy = predict_bytes_to_copy(hr); 911 912 double region_elapsed_time_ms = 913 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) + 914 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark()); 915 916 // The prediction of the "other" time for this region is based 917 // upon the region type and NOT the GC type. 918 if (hr->is_young()) { 919 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 920 } else { 921 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 922 } 923 return region_elapsed_time_ms; 924 } 925 926 927 void G1Policy::print_yg_surv_rate_info() const { 928 #ifndef PRODUCT 929 _short_lived_surv_rate_group->print_surv_rate_summary(); 930 // add this call for any other surv rate groups 931 #endif // PRODUCT 932 } 933 934 bool G1Policy::is_young_list_full() const { 935 uint young_list_length = _g1->young_list()->length(); 936 uint young_list_target_length = _young_list_target_length; 937 return young_list_length >= young_list_target_length; 938 } 939 940 bool G1Policy::can_expand_young_list() const { 941 uint young_list_length = _g1->young_list()->length(); 942 uint young_list_max_length = _young_list_max_length; 943 return young_list_length < young_list_max_length; 944 } 945 946 bool G1Policy::adaptive_young_list_length() const { 947 return _young_gen_sizer.adaptive_young_list_length(); 948 } 949 950 void G1Policy::update_max_gc_locker_expansion() { 951 uint expansion_region_num = 0; 952 if (GCLockerEdenExpansionPercent > 0) { 953 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 954 double expansion_region_num_d = perc * (double) _young_list_target_length; 955 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 956 // less than 1.0) we'll get 1. 957 expansion_region_num = (uint) ceil(expansion_region_num_d); 958 } else { 959 assert(expansion_region_num == 0, "sanity"); 960 } 961 _young_list_max_length = _young_list_target_length + expansion_region_num; 962 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 963 } 964 965 // Calculates survivor space parameters. 966 void G1Policy::update_survivors_policy() { 967 double max_survivor_regions_d = 968 (double) _young_list_target_length / (double) SurvivorRatio; 969 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but 970 // smaller than 1.0) we'll get 1. 971 _max_survivor_regions = (uint) ceil(max_survivor_regions_d); 972 973 GCPolicyCounters* counters = _g1->collector_policy()->counters(); 974 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold( 975 HeapRegion::GrainWords * _max_survivor_regions, counters); 976 } 977 978 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 979 // We actually check whether we are marking here and not if we are in a 980 // reclamation phase. This means that we will schedule a concurrent mark 981 // even while we are still in the process of reclaiming memory. 982 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle(); 983 if (!during_cycle) { 984 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 985 collector_state()->set_initiate_conc_mark_if_possible(true); 986 return true; 987 } else { 988 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 989 return false; 990 } 991 } 992 993 void G1Policy::initiate_conc_mark() { 994 collector_state()->set_during_initial_mark_pause(true); 995 collector_state()->set_initiate_conc_mark_if_possible(false); 996 } 997 998 void G1Policy::decide_on_conc_mark_initiation() { 999 // We are about to decide on whether this pause will be an 1000 // initial-mark pause. 1001 1002 // First, collector_state()->during_initial_mark_pause() should not be already set. We 1003 // will set it here if we have to. However, it should be cleared by 1004 // the end of the pause (it's only set for the duration of an 1005 // initial-mark pause). 1006 assert(!collector_state()->during_initial_mark_pause(), "pre-condition"); 1007 1008 if (collector_state()->initiate_conc_mark_if_possible()) { 1009 // We had noticed on a previous pause that the heap occupancy has 1010 // gone over the initiating threshold and we should start a 1011 // concurrent marking cycle. So we might initiate one. 1012 1013 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) { 1014 // Initiate a new initial mark if there is no marking or reclamation going on. 1015 initiate_conc_mark(); 1016 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 1017 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) { 1018 // Initiate a user requested initial mark. An initial mark must be young only 1019 // GC, so the collector state must be updated to reflect this. 1020 collector_state()->set_gcs_are_young(true); 1021 collector_state()->set_last_young_gc(false); 1022 1023 abort_time_to_mixed_tracking(); 1024 initiate_conc_mark(); 1025 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 1026 } else { 1027 // The concurrent marking thread is still finishing up the 1028 // previous cycle. If we start one right now the two cycles 1029 // overlap. In particular, the concurrent marking thread might 1030 // be in the process of clearing the next marking bitmap (which 1031 // we will use for the next cycle if we start one). Starting a 1032 // cycle now will be bad given that parts of the marking 1033 // information might get cleared by the marking thread. And we 1034 // cannot wait for the marking thread to finish the cycle as it 1035 // periodically yields while clearing the next marking bitmap 1036 // and, if it's in a yield point, it's waiting for us to 1037 // finish. So, at this point we will not start a cycle and we'll 1038 // let the concurrent marking thread complete the last one. 1039 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 1040 } 1041 } 1042 } 1043 1044 void G1Policy::record_concurrent_mark_cleanup_end() { 1045 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions()); 1046 1047 double end_sec = os::elapsedTime(); 1048 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1049 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1050 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1051 1052 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1053 } 1054 1055 double G1Policy::reclaimable_bytes_perc(size_t reclaimable_bytes) const { 1056 // Returns the given amount of reclaimable bytes (that represents 1057 // the amount of reclaimable space still to be collected) as a 1058 // percentage of the current heap capacity. 1059 size_t capacity_bytes = _g1->capacity(); 1060 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes; 1061 } 1062 1063 void G1Policy::maybe_start_marking() { 1064 if (need_to_start_conc_mark("end of GC")) { 1065 // Note: this might have already been set, if during the last 1066 // pause we decided to start a cycle but at the beginning of 1067 // this pause we decided to postpone it. That's OK. 1068 collector_state()->set_initiate_conc_mark_if_possible(true); 1069 } 1070 } 1071 1072 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const { 1073 assert(!collector_state()->full_collection(), "must be"); 1074 if (collector_state()->during_initial_mark_pause()) { 1075 assert(collector_state()->last_gc_was_young(), "must be"); 1076 assert(!collector_state()->last_young_gc(), "must be"); 1077 return InitialMarkGC; 1078 } else if (collector_state()->last_young_gc()) { 1079 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1080 assert(collector_state()->last_gc_was_young(), "must be"); 1081 return LastYoungGC; 1082 } else if (!collector_state()->last_gc_was_young()) { 1083 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1084 assert(!collector_state()->last_young_gc(), "must be"); 1085 return MixedGC; 1086 } else { 1087 assert(collector_state()->last_gc_was_young(), "must be"); 1088 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1089 assert(!collector_state()->last_young_gc(), "must be"); 1090 return YoungOnlyGC; 1091 } 1092 } 1093 1094 void G1Policy::record_pause(PauseKind kind, double start, double end) { 1095 // Manage the MMU tracker. For some reason it ignores Full GCs. 1096 if (kind != FullGC) { 1097 _mmu_tracker->add_pause(start, end); 1098 } 1099 // Manage the mutator time tracking from initial mark to first mixed gc. 1100 switch (kind) { 1101 case FullGC: 1102 abort_time_to_mixed_tracking(); 1103 break; 1104 case Cleanup: 1105 case Remark: 1106 case YoungOnlyGC: 1107 case LastYoungGC: 1108 _initial_mark_to_mixed.add_pause(end - start); 1109 break; 1110 case InitialMarkGC: 1111 _initial_mark_to_mixed.record_initial_mark_end(end); 1112 break; 1113 case MixedGC: 1114 _initial_mark_to_mixed.record_mixed_gc_start(start); 1115 break; 1116 default: 1117 ShouldNotReachHere(); 1118 } 1119 } 1120 1121 void G1Policy::abort_time_to_mixed_tracking() { 1122 _initial_mark_to_mixed.reset(); 1123 } 1124 1125 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str, 1126 const char* false_action_str) const { 1127 if (cset_chooser()->is_empty()) { 1128 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1129 return false; 1130 } 1131 1132 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1133 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); 1134 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes); 1135 double threshold = (double) G1HeapWastePercent; 1136 if (reclaimable_perc <= threshold) { 1137 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1138 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); 1139 return false; 1140 } 1141 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1142 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); 1143 return true; 1144 } 1145 1146 uint G1Policy::calc_min_old_cset_length() const { 1147 // The min old CSet region bound is based on the maximum desired 1148 // number of mixed GCs after a cycle. I.e., even if some old regions 1149 // look expensive, we should add them to the CSet anyway to make 1150 // sure we go through the available old regions in no more than the 1151 // maximum desired number of mixed GCs. 1152 // 1153 // The calculation is based on the number of marked regions we added 1154 // to the CSet chooser in the first place, not how many remain, so 1155 // that the result is the same during all mixed GCs that follow a cycle. 1156 1157 const size_t region_num = (size_t) cset_chooser()->length(); 1158 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1159 size_t result = region_num / gc_num; 1160 // emulate ceiling 1161 if (result * gc_num < region_num) { 1162 result += 1; 1163 } 1164 return (uint) result; 1165 } 1166 1167 uint G1Policy::calc_max_old_cset_length() const { 1168 // The max old CSet region bound is based on the threshold expressed 1169 // as a percentage of the heap size. I.e., it should bound the 1170 // number of old regions added to the CSet irrespective of how many 1171 // of them are available. 1172 1173 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1174 const size_t region_num = g1h->num_regions(); 1175 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1176 size_t result = region_num * perc / 100; 1177 // emulate ceiling 1178 if (100 * result < region_num * perc) { 1179 result += 1; 1180 } 1181 return (uint) result; 1182 } 1183 1184 void G1Policy::finalize_collection_set(double target_pause_time_ms) { 1185 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms); 1186 _collection_set->finalize_old_part(time_remaining_ms); 1187 }