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/g1DefaultPolicy.hpp" 33 #include "gc/g1/g1HotCardCache.hpp" 34 #include "gc/g1/g1IHOPControl.hpp" 35 #include "gc/g1/g1GCPhaseTimes.hpp" 36 #include "gc/g1/g1Policy.hpp" 37 #include "gc/g1/g1SurvivorRegions.hpp" 38 #include "gc/g1/g1YoungGenSizer.hpp" 39 #include "gc/g1/heapRegion.inline.hpp" 40 #include "gc/g1/heapRegionRemSet.hpp" 41 #include "gc/shared/gcPolicyCounters.hpp" 42 #include "logging/logStream.hpp" 43 #include "runtime/arguments.hpp" 44 #include "runtime/java.hpp" 45 #include "runtime/mutexLocker.hpp" 46 #include "utilities/debug.hpp" 47 #include "utilities/growableArray.hpp" 48 #include "utilities/pair.hpp" 49 50 G1DefaultPolicy::G1DefaultPolicy() : 51 _predictor(G1ConfidencePercent / 100.0), 52 _analytics(new G1Analytics(&_predictor)), 53 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)), 54 _ihop_control(create_ihop_control(&_predictor)), 55 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 3)), 56 _young_list_fixed_length(0), 57 _short_lived_surv_rate_group(new SurvRateGroup()), 58 _survivor_surv_rate_group(new SurvRateGroup()), 59 _reserve_factor((double) G1ReservePercent / 100.0), 60 _reserve_regions(0), 61 _rs_lengths_prediction(0), 62 _bytes_allocated_in_old_since_last_gc(0), 63 _initial_mark_to_mixed(), 64 _collection_set(NULL), 65 _g1(NULL), 66 _phase_times(new G1GCPhaseTimes(ParallelGCThreads)), 67 _tenuring_threshold(MaxTenuringThreshold), 68 _max_survivor_regions(0), 69 _survivors_age_table(true) { } 70 71 G1DefaultPolicy::~G1DefaultPolicy() { 72 delete _ihop_control; 73 } 74 75 G1CollectorState* G1DefaultPolicy::collector_state() const { return _g1->collector_state(); } 76 77 void G1DefaultPolicy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) { 78 _g1 = g1h; 79 _collection_set = collection_set; 80 81 assert(Heap_lock->owned_by_self(), "Locking discipline."); 82 83 if (!adaptive_young_list_length()) { 84 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length(); 85 } 86 _young_gen_sizer.adjust_max_new_size(_g1->max_regions()); 87 88 _free_regions_at_end_of_collection = _g1->num_free_regions(); 89 90 update_young_list_max_and_target_length(); 91 // We may immediately start allocating regions and placing them on the 92 // collection set list. Initialize the per-collection set info 93 _collection_set->start_incremental_building(); 94 } 95 96 void G1DefaultPolicy::note_gc_start() { 97 phase_times()->note_gc_start(); 98 } 99 100 bool G1DefaultPolicy::predict_will_fit(uint young_length, 101 double base_time_ms, 102 uint base_free_regions, 103 double target_pause_time_ms) const { 104 if (young_length >= base_free_regions) { 105 // end condition 1: not enough space for the young regions 106 return false; 107 } 108 109 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1); 110 size_t bytes_to_copy = 111 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes); 112 double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy, 113 collector_state()->during_concurrent_mark()); 114 double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length); 115 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms; 116 if (pause_time_ms > target_pause_time_ms) { 117 // end condition 2: prediction is over the target pause time 118 return false; 119 } 120 121 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes; 122 123 // When copying, we will likely need more bytes free than is live in the region. 124 // Add some safety margin to factor in the confidence of our guess, and the 125 // natural expected waste. 126 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty 127 // of the calculation: the lower the confidence, the more headroom. 128 // (100 + TargetPLABWastePct) represents the increase in expected bytes during 129 // copying due to anticipated waste in the PLABs. 130 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; 131 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); 132 133 if (expected_bytes_to_copy > free_bytes) { 134 // end condition 3: out-of-space 135 return false; 136 } 137 138 // success! 139 return true; 140 } 141 142 void G1DefaultPolicy::record_new_heap_size(uint new_number_of_regions) { 143 // re-calculate the necessary reserve 144 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; 145 // We use ceiling so that if reserve_regions_d is > 0.0 (but 146 // smaller than 1.0) we'll get 1. 147 _reserve_regions = (uint) ceil(reserve_regions_d); 148 149 _young_gen_sizer.heap_size_changed(new_number_of_regions); 150 151 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); 152 } 153 154 uint G1DefaultPolicy::calculate_young_list_desired_min_length(uint base_min_length) const { 155 uint desired_min_length = 0; 156 if (adaptive_young_list_length()) { 157 if (_analytics->num_alloc_rate_ms() > 3) { 158 double now_sec = os::elapsedTime(); 159 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; 160 double alloc_rate_ms = _analytics->predict_alloc_rate_ms(); 161 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); 162 } else { 163 // otherwise we don't have enough info to make the prediction 164 } 165 } 166 desired_min_length += base_min_length; 167 // make sure we don't go below any user-defined minimum bound 168 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length); 169 } 170 171 uint G1DefaultPolicy::calculate_young_list_desired_max_length() const { 172 // Here, we might want to also take into account any additional 173 // constraints (i.e., user-defined minimum bound). Currently, we 174 // effectively don't set this bound. 175 return _young_gen_sizer.max_desired_young_length(); 176 } 177 178 uint G1DefaultPolicy::update_young_list_max_and_target_length() { 179 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths()); 180 } 181 182 uint G1DefaultPolicy::update_young_list_max_and_target_length(size_t rs_lengths) { 183 uint unbounded_target_length = update_young_list_target_length(rs_lengths); 184 update_max_gc_locker_expansion(); 185 return unbounded_target_length; 186 } 187 188 uint G1DefaultPolicy::update_young_list_target_length(size_t rs_lengths) { 189 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths); 190 _young_list_target_length = young_lengths.first; 191 return young_lengths.second; 192 } 193 194 G1DefaultPolicy::YoungTargetLengths G1DefaultPolicy::young_list_target_lengths(size_t rs_lengths) const { 195 YoungTargetLengths result; 196 197 // Calculate the absolute and desired min bounds first. 198 199 // This is how many young regions we already have (currently: the survivors). 200 const uint base_min_length = _g1->survivor_regions_count(); 201 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); 202 // This is the absolute minimum young length. Ensure that we 203 // will at least have one eden region available for allocation. 204 uint absolute_min_length = base_min_length + MAX2(_g1->eden_regions_count(), (uint)1); 205 // If we shrank the young list target it should not shrink below the current size. 206 desired_min_length = MAX2(desired_min_length, absolute_min_length); 207 // Calculate the absolute and desired max bounds. 208 209 uint desired_max_length = calculate_young_list_desired_max_length(); 210 211 uint young_list_target_length = 0; 212 if (adaptive_young_list_length()) { 213 if (collector_state()->gcs_are_young()) { 214 young_list_target_length = 215 calculate_young_list_target_length(rs_lengths, 216 base_min_length, 217 desired_min_length, 218 desired_max_length); 219 } else { 220 // Don't calculate anything and let the code below bound it to 221 // the desired_min_length, i.e., do the next GC as soon as 222 // possible to maximize how many old regions we can add to it. 223 } 224 } else { 225 // The user asked for a fixed young gen so we'll fix the young gen 226 // whether the next GC is young or mixed. 227 young_list_target_length = _young_list_fixed_length; 228 } 229 230 result.second = young_list_target_length; 231 232 // We will try our best not to "eat" into the reserve. 233 uint absolute_max_length = 0; 234 if (_free_regions_at_end_of_collection > _reserve_regions) { 235 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; 236 } 237 if (desired_max_length > absolute_max_length) { 238 desired_max_length = absolute_max_length; 239 } 240 241 // Make sure we don't go over the desired max length, nor under the 242 // desired min length. In case they clash, desired_min_length wins 243 // which is why that test is second. 244 if (young_list_target_length > desired_max_length) { 245 young_list_target_length = desired_max_length; 246 } 247 if (young_list_target_length < desired_min_length) { 248 young_list_target_length = desired_min_length; 249 } 250 251 assert(young_list_target_length > base_min_length, 252 "we should be able to allocate at least one eden region"); 253 assert(young_list_target_length >= absolute_min_length, "post-condition"); 254 255 result.first = young_list_target_length; 256 return result; 257 } 258 259 uint 260 G1DefaultPolicy::calculate_young_list_target_length(size_t rs_lengths, 261 uint base_min_length, 262 uint desired_min_length, 263 uint desired_max_length) const { 264 assert(adaptive_young_list_length(), "pre-condition"); 265 assert(collector_state()->gcs_are_young(), "only call this for young GCs"); 266 267 // In case some edge-condition makes the desired max length too small... 268 if (desired_max_length <= desired_min_length) { 269 return desired_min_length; 270 } 271 272 // We'll adjust min_young_length and max_young_length not to include 273 // the already allocated young regions (i.e., so they reflect the 274 // min and max eden regions we'll allocate). The base_min_length 275 // will be reflected in the predictions by the 276 // survivor_regions_evac_time prediction. 277 assert(desired_min_length > base_min_length, "invariant"); 278 uint min_young_length = desired_min_length - base_min_length; 279 assert(desired_max_length > base_min_length, "invariant"); 280 uint max_young_length = desired_max_length - base_min_length; 281 282 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; 283 double survivor_regions_evac_time = predict_survivor_regions_evac_time(); 284 size_t pending_cards = _analytics->predict_pending_cards(); 285 size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff(); 286 size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true); 287 double base_time_ms = 288 predict_base_elapsed_time_ms(pending_cards, scanned_cards) + 289 survivor_regions_evac_time; 290 uint available_free_regions = _free_regions_at_end_of_collection; 291 uint base_free_regions = 0; 292 if (available_free_regions > _reserve_regions) { 293 base_free_regions = available_free_regions - _reserve_regions; 294 } 295 296 // Here, we will make sure that the shortest young length that 297 // makes sense fits within the target pause time. 298 299 if (predict_will_fit(min_young_length, base_time_ms, 300 base_free_regions, target_pause_time_ms)) { 301 // The shortest young length will fit into the target pause time; 302 // we'll now check whether the absolute maximum number of young 303 // regions will fit in the target pause time. If not, we'll do 304 // a binary search between min_young_length and max_young_length. 305 if (predict_will_fit(max_young_length, base_time_ms, 306 base_free_regions, target_pause_time_ms)) { 307 // The maximum young length will fit into the target pause time. 308 // We are done so set min young length to the maximum length (as 309 // the result is assumed to be returned in min_young_length). 310 min_young_length = max_young_length; 311 } else { 312 // The maximum possible number of young regions will not fit within 313 // the target pause time so we'll search for the optimal 314 // length. The loop invariants are: 315 // 316 // min_young_length < max_young_length 317 // min_young_length is known to fit into the target pause time 318 // max_young_length is known not to fit into the target pause time 319 // 320 // Going into the loop we know the above hold as we've just 321 // checked them. Every time around the loop we check whether 322 // the middle value between min_young_length and 323 // max_young_length fits into the target pause time. If it 324 // does, it becomes the new min. If it doesn't, it becomes 325 // the new max. This way we maintain the loop invariants. 326 327 assert(min_young_length < max_young_length, "invariant"); 328 uint diff = (max_young_length - min_young_length) / 2; 329 while (diff > 0) { 330 uint young_length = min_young_length + diff; 331 if (predict_will_fit(young_length, base_time_ms, 332 base_free_regions, target_pause_time_ms)) { 333 min_young_length = young_length; 334 } else { 335 max_young_length = young_length; 336 } 337 assert(min_young_length < max_young_length, "invariant"); 338 diff = (max_young_length - min_young_length) / 2; 339 } 340 // The results is min_young_length which, according to the 341 // loop invariants, should fit within the target pause time. 342 343 // These are the post-conditions of the binary search above: 344 assert(min_young_length < max_young_length, 345 "otherwise we should have discovered that max_young_length " 346 "fits into the pause target and not done the binary search"); 347 assert(predict_will_fit(min_young_length, base_time_ms, 348 base_free_regions, target_pause_time_ms), 349 "min_young_length, the result of the binary search, should " 350 "fit into the pause target"); 351 assert(!predict_will_fit(min_young_length + 1, base_time_ms, 352 base_free_regions, target_pause_time_ms), 353 "min_young_length, the result of the binary search, should be " 354 "optimal, so no larger length should fit into the pause target"); 355 } 356 } else { 357 // Even the minimum length doesn't fit into the pause time 358 // target, return it as the result nevertheless. 359 } 360 return base_min_length + min_young_length; 361 } 362 363 double G1DefaultPolicy::predict_survivor_regions_evac_time() const { 364 double survivor_regions_evac_time = 0.0; 365 const GrowableArray<HeapRegion*>* survivor_regions = _g1->survivor()->regions(); 366 367 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin(); 368 it != survivor_regions->end(); 369 ++it) { 370 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->gcs_are_young()); 371 } 372 return survivor_regions_evac_time; 373 } 374 375 void G1DefaultPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) { 376 guarantee( adaptive_young_list_length(), "should not call this otherwise" ); 377 378 if (rs_lengths > _rs_lengths_prediction) { 379 // add 10% to avoid having to recalculate often 380 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000; 381 update_rs_lengths_prediction(rs_lengths_prediction); 382 383 update_young_list_max_and_target_length(rs_lengths_prediction); 384 } 385 } 386 387 void G1DefaultPolicy::update_rs_lengths_prediction() { 388 update_rs_lengths_prediction(_analytics->predict_rs_lengths()); 389 } 390 391 void G1DefaultPolicy::update_rs_lengths_prediction(size_t prediction) { 392 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) { 393 _rs_lengths_prediction = prediction; 394 } 395 } 396 397 #ifndef PRODUCT 398 bool G1DefaultPolicy::verify_young_ages() { 399 bool ret = true; 400 401 for (HeapRegion* curr = _collection_set->inc_head(); 402 curr != NULL; 403 curr = curr->next_in_collection_set()) { 404 guarantee(curr->is_young(), "Region must be young"); 405 406 SurvRateGroup* group = curr->surv_rate_group(); 407 408 if (group == NULL) { 409 log_error(gc, verify)("## encountered NULL surv_rate_group in young region"); 410 ret = false; 411 } 412 413 if (curr->age_in_surv_rate_group() < 0) { 414 log_error(gc, verify)("## encountered negative age in young region"); 415 ret = false; 416 } 417 } 418 419 if (!ret) { 420 LogStreamHandle(Error, gc, verify) log; 421 _collection_set->print(_collection_set->inc_head(), &log); 422 } 423 424 return ret; 425 } 426 #endif // PRODUCT 427 428 void G1DefaultPolicy::record_full_collection_start() { 429 _full_collection_start_sec = os::elapsedTime(); 430 // Release the future to-space so that it is available for compaction into. 431 collector_state()->set_full_collection(true); 432 } 433 434 void G1DefaultPolicy::record_full_collection_end() { 435 // Consider this like a collection pause for the purposes of allocation 436 // since last pause. 437 double end_sec = os::elapsedTime(); 438 double full_gc_time_sec = end_sec - _full_collection_start_sec; 439 double full_gc_time_ms = full_gc_time_sec * 1000.0; 440 441 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms); 442 443 collector_state()->set_full_collection(false); 444 445 // "Nuke" the heuristics that control the young/mixed GC 446 // transitions and make sure we start with young GCs after the Full GC. 447 collector_state()->set_gcs_are_young(true); 448 collector_state()->set_last_young_gc(false); 449 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); 450 collector_state()->set_during_initial_mark_pause(false); 451 collector_state()->set_in_marking_window(false); 452 collector_state()->set_in_marking_window_im(false); 453 454 _short_lived_surv_rate_group->start_adding_regions(); 455 // also call this on any additional surv rate groups 456 457 _free_regions_at_end_of_collection = _g1->num_free_regions(); 458 // Reset survivors SurvRateGroup. 459 _survivor_surv_rate_group->reset(); 460 update_young_list_max_and_target_length(); 461 update_rs_lengths_prediction(); 462 cset_chooser()->clear(); 463 464 _bytes_allocated_in_old_since_last_gc = 0; 465 466 record_pause(FullGC, _full_collection_start_sec, end_sec); 467 } 468 469 void G1DefaultPolicy::record_collection_pause_start(double start_time_sec) { 470 // We only need to do this here as the policy will only be applied 471 // to the GC we're about to start. so, no point is calculating this 472 // every time we calculate / recalculate the target young length. 473 update_survivors_policy(); 474 475 assert(_g1->used() == _g1->recalculate_used(), 476 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT, 477 _g1->used(), _g1->recalculate_used()); 478 479 phase_times()->record_cur_collection_start_sec(start_time_sec); 480 _pending_cards = _g1->pending_card_num(); 481 482 _collection_set->reset_bytes_used_before(); 483 _bytes_copied_during_gc = 0; 484 485 collector_state()->set_last_gc_was_young(false); 486 487 // do that for any other surv rate groups 488 _short_lived_surv_rate_group->stop_adding_regions(); 489 _survivors_age_table.clear(); 490 491 assert( verify_young_ages(), "region age verification" ); 492 } 493 494 void G1DefaultPolicy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { 495 collector_state()->set_during_marking(true); 496 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); 497 collector_state()->set_during_initial_mark_pause(false); 498 } 499 500 void G1DefaultPolicy::record_concurrent_mark_remark_start() { 501 _mark_remark_start_sec = os::elapsedTime(); 502 collector_state()->set_during_marking(false); 503 } 504 505 void G1DefaultPolicy::record_concurrent_mark_remark_end() { 506 double end_time_sec = os::elapsedTime(); 507 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; 508 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); 509 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 510 511 record_pause(Remark, _mark_remark_start_sec, end_time_sec); 512 } 513 514 void G1DefaultPolicy::record_concurrent_mark_cleanup_start() { 515 _mark_cleanup_start_sec = os::elapsedTime(); 516 } 517 518 void G1DefaultPolicy::record_concurrent_mark_cleanup_completed() { 519 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc", 520 "skip last young-only gc"); 521 collector_state()->set_last_young_gc(should_continue_with_reclaim); 522 // We skip the marking phase. 523 if (!should_continue_with_reclaim) { 524 abort_time_to_mixed_tracking(); 525 } 526 collector_state()->set_in_marking_window(false); 527 } 528 529 double G1DefaultPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { 530 return phase_times()->average_time_ms(phase); 531 } 532 533 double G1DefaultPolicy::young_other_time_ms() const { 534 return phase_times()->young_cset_choice_time_ms() + 535 phase_times()->young_free_cset_time_ms(); 536 } 537 538 double G1DefaultPolicy::non_young_other_time_ms() const { 539 return phase_times()->non_young_cset_choice_time_ms() + 540 phase_times()->non_young_free_cset_time_ms(); 541 542 } 543 544 double G1DefaultPolicy::other_time_ms(double pause_time_ms) const { 545 return pause_time_ms - phase_times()->cur_collection_par_time_ms(); 546 } 547 548 double G1DefaultPolicy::constant_other_time_ms(double pause_time_ms) const { 549 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms(); 550 } 551 552 CollectionSetChooser* G1DefaultPolicy::cset_chooser() const { 553 return _collection_set->cset_chooser(); 554 } 555 556 bool G1DefaultPolicy::about_to_start_mixed_phase() const { 557 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc(); 558 } 559 560 bool G1DefaultPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { 561 if (about_to_start_mixed_phase()) { 562 return false; 563 } 564 565 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); 566 567 size_t cur_used_bytes = _g1->non_young_capacity_bytes(); 568 size_t alloc_byte_size = alloc_word_size * HeapWordSize; 569 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; 570 571 bool result = false; 572 if (marking_request_bytes > marking_initiating_used_threshold) { 573 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc(); 574 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", 575 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", 576 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source); 577 } 578 579 return result; 580 } 581 582 // Anything below that is considered to be zero 583 #define MIN_TIMER_GRANULARITY 0.0000001 584 585 void G1DefaultPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) { 586 double end_time_sec = os::elapsedTime(); 587 588 size_t cur_used_bytes = _g1->used(); 589 assert(cur_used_bytes == _g1->recalculate_used(), "It should!"); 590 bool last_pause_included_initial_mark = false; 591 bool update_stats = !_g1->evacuation_failed(); 592 593 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); 594 595 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause(); 596 if (last_pause_included_initial_mark) { 597 record_concurrent_mark_init_end(0.0); 598 } else { 599 maybe_start_marking(); 600 } 601 602 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms()); 603 if (app_time_ms < MIN_TIMER_GRANULARITY) { 604 // This usually happens due to the timer not having the required 605 // granularity. Some Linuxes are the usual culprits. 606 // We'll just set it to something (arbitrarily) small. 607 app_time_ms = 1.0; 608 } 609 610 if (update_stats) { 611 // We maintain the invariant that all objects allocated by mutator 612 // threads will be allocated out of eden regions. So, we can use 613 // the eden region number allocated since the previous GC to 614 // calculate the application's allocate rate. The only exception 615 // to that is humongous objects that are allocated separately. But 616 // given that humongous object allocations do not really affect 617 // either the pause's duration nor when the next pause will take 618 // place we can safely ignore them here. 619 uint regions_allocated = _collection_set->eden_region_length(); 620 double alloc_rate_ms = (double) regions_allocated / app_time_ms; 621 _analytics->report_alloc_rate_ms(alloc_rate_ms); 622 623 double interval_ms = 624 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; 625 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); 626 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms); 627 } 628 629 bool new_in_marking_window = collector_state()->in_marking_window(); 630 bool new_in_marking_window_im = false; 631 if (last_pause_included_initial_mark) { 632 new_in_marking_window = true; 633 new_in_marking_window_im = true; 634 } 635 636 if (collector_state()->last_young_gc()) { 637 // This is supposed to to be the "last young GC" before we start 638 // doing mixed GCs. Here we decide whether to start mixed GCs or not. 639 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC"); 640 641 if (next_gc_should_be_mixed("start mixed GCs", 642 "do not start mixed GCs")) { 643 collector_state()->set_gcs_are_young(false); 644 } else { 645 // We aborted the mixed GC phase early. 646 abort_time_to_mixed_tracking(); 647 } 648 649 collector_state()->set_last_young_gc(false); 650 } 651 652 if (!collector_state()->last_gc_was_young()) { 653 // This is a mixed GC. Here we decide whether to continue doing 654 // mixed GCs or not. 655 if (!next_gc_should_be_mixed("continue mixed GCs", 656 "do not continue mixed GCs")) { 657 collector_state()->set_gcs_are_young(true); 658 659 maybe_start_marking(); 660 } 661 } 662 663 _short_lived_surv_rate_group->start_adding_regions(); 664 // Do that for any other surv rate groups 665 666 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0; 667 668 if (update_stats) { 669 double cost_per_card_ms = 0.0; 670 if (_pending_cards > 0) { 671 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards; 672 _analytics->report_cost_per_card_ms(cost_per_card_ms); 673 } 674 _analytics->report_cost_scan_hcc(scan_hcc_time_ms); 675 676 double cost_per_entry_ms = 0.0; 677 if (cards_scanned > 10) { 678 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned; 679 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young()); 680 } 681 682 if (_max_rs_lengths > 0) { 683 double cards_per_entry_ratio = 684 (double) cards_scanned / (double) _max_rs_lengths; 685 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young()); 686 } 687 688 // This is defensive. For a while _max_rs_lengths could get 689 // smaller than _recorded_rs_lengths which was causing 690 // rs_length_diff to get very large and mess up the RSet length 691 // predictions. The reason was unsafe concurrent updates to the 692 // _inc_cset_recorded_rs_lengths field which the code below guards 693 // against (see CR 7118202). This bug has now been fixed (see CR 694 // 7119027). However, I'm still worried that 695 // _inc_cset_recorded_rs_lengths might still end up somewhat 696 // inaccurate. The concurrent refinement thread calculates an 697 // RSet's length concurrently with other CR threads updating it 698 // which might cause it to calculate the length incorrectly (if, 699 // say, it's in mid-coarsening). So I'll leave in the defensive 700 // conditional below just in case. 701 size_t rs_length_diff = 0; 702 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths(); 703 if (_max_rs_lengths > recorded_rs_lengths) { 704 rs_length_diff = _max_rs_lengths - recorded_rs_lengths; 705 } 706 _analytics->report_rs_length_diff((double) rs_length_diff); 707 708 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes; 709 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes; 710 double cost_per_byte_ms = 0.0; 711 712 if (copied_bytes > 0) { 713 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes; 714 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window()); 715 } 716 717 if (_collection_set->young_region_length() > 0) { 718 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / 719 _collection_set->young_region_length()); 720 } 721 722 if (_collection_set->old_region_length() > 0) { 723 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / 724 _collection_set->old_region_length()); 725 } 726 727 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); 728 729 _analytics->report_pending_cards((double) _pending_cards); 730 _analytics->report_rs_lengths((double) _max_rs_lengths); 731 } 732 733 collector_state()->set_in_marking_window(new_in_marking_window); 734 collector_state()->set_in_marking_window_im(new_in_marking_window_im); 735 _free_regions_at_end_of_collection = _g1->num_free_regions(); 736 // IHOP control wants to know the expected young gen length if it were not 737 // restrained by the heap reserve. Using the actual length would make the 738 // prediction too small and the limit the young gen every time we get to the 739 // predicted target occupancy. 740 size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); 741 update_rs_lengths_prediction(); 742 743 update_ihop_prediction(app_time_ms / 1000.0, 744 _bytes_allocated_in_old_since_last_gc, 745 last_unrestrained_young_length * HeapRegion::GrainBytes); 746 _bytes_allocated_in_old_since_last_gc = 0; 747 748 _ihop_control->send_trace_event(_g1->gc_tracer_stw()); 749 750 // Note that _mmu_tracker->max_gc_time() returns the time in seconds. 751 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; 752 753 if (update_rs_time_goal_ms < scan_hcc_time_ms) { 754 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." 755 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms", 756 update_rs_time_goal_ms, scan_hcc_time_ms); 757 758 update_rs_time_goal_ms = 0; 759 } else { 760 update_rs_time_goal_ms -= scan_hcc_time_ms; 761 } 762 _g1->concurrent_g1_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms, 763 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS), 764 update_rs_time_goal_ms); 765 766 cset_chooser()->verify(); 767 } 768 769 G1IHOPControl* G1DefaultPolicy::create_ihop_control(const G1Predictions* predictor){ 770 if (G1UseAdaptiveIHOP) { 771 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, 772 predictor, 773 G1ReservePercent, 774 G1HeapWastePercent); 775 } else { 776 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); 777 } 778 } 779 780 void G1DefaultPolicy::update_ihop_prediction(double mutator_time_s, 781 size_t mutator_alloc_bytes, 782 size_t young_gen_size) { 783 // Always try to update IHOP prediction. Even evacuation failures give information 784 // about e.g. whether to start IHOP earlier next time. 785 786 // Avoid using really small application times that might create samples with 787 // very high or very low values. They may be caused by e.g. back-to-back gcs. 788 double const min_valid_time = 1e-6; 789 790 bool report = false; 791 792 double marking_to_mixed_time = -1.0; 793 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) { 794 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); 795 assert(marking_to_mixed_time > 0.0, 796 "Initial mark to mixed time must be larger than zero but is %.3f", 797 marking_to_mixed_time); 798 if (marking_to_mixed_time > min_valid_time) { 799 _ihop_control->update_marking_length(marking_to_mixed_time); 800 report = true; 801 } 802 } 803 804 // As an approximation for the young gc promotion rates during marking we use 805 // all of them. In many applications there are only a few if any young gcs during 806 // marking, which makes any prediction useless. This increases the accuracy of the 807 // prediction. 808 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) { 809 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); 810 report = true; 811 } 812 813 if (report) { 814 report_ihop_statistics(); 815 } 816 } 817 818 void G1DefaultPolicy::report_ihop_statistics() { 819 _ihop_control->print(); 820 } 821 822 void G1DefaultPolicy::print_phases() { 823 phase_times()->print(); 824 } 825 826 double G1DefaultPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { 827 TruncatedSeq* seq = surv_rate_group->get_seq(age); 828 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); 829 double pred = _predictor.get_new_prediction(seq); 830 if (pred > 1.0) { 831 pred = 1.0; 832 } 833 return pred; 834 } 835 836 double G1DefaultPolicy::accum_yg_surv_rate_pred(int age) const { 837 return _short_lived_surv_rate_group->accum_surv_rate_pred(age); 838 } 839 840 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards, 841 size_t scanned_cards) const { 842 return 843 _analytics->predict_rs_update_time_ms(pending_cards) + 844 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) + 845 _analytics->predict_constant_other_time_ms(); 846 } 847 848 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const { 849 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff(); 850 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young()); 851 return predict_base_elapsed_time_ms(pending_cards, card_num); 852 } 853 854 size_t G1DefaultPolicy::predict_bytes_to_copy(HeapRegion* hr) const { 855 size_t bytes_to_copy; 856 if (hr->is_marked()) 857 bytes_to_copy = hr->max_live_bytes(); 858 else { 859 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant"); 860 int age = hr->age_in_surv_rate_group(); 861 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); 862 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); 863 } 864 return bytes_to_copy; 865 } 866 867 double G1DefaultPolicy::predict_region_elapsed_time_ms(HeapRegion* hr, 868 bool for_young_gc) const { 869 size_t rs_length = hr->rem_set()->occupied(); 870 // Predicting the number of cards is based on which type of GC 871 // we're predicting for. 872 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc); 873 size_t bytes_to_copy = predict_bytes_to_copy(hr); 874 875 double region_elapsed_time_ms = 876 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) + 877 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark()); 878 879 // The prediction of the "other" time for this region is based 880 // upon the region type and NOT the GC type. 881 if (hr->is_young()) { 882 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1); 883 } else { 884 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); 885 } 886 return region_elapsed_time_ms; 887 } 888 889 bool G1DefaultPolicy::should_allocate_mutator_region() const { 890 uint young_list_length = _g1->young_regions_count(); 891 uint young_list_target_length = _young_list_target_length; 892 return young_list_length < young_list_target_length; 893 } 894 895 bool G1DefaultPolicy::can_expand_young_list() const { 896 uint young_list_length = _g1->young_regions_count(); 897 uint young_list_max_length = _young_list_max_length; 898 return young_list_length < young_list_max_length; 899 } 900 901 bool G1DefaultPolicy::adaptive_young_list_length() const { 902 return _young_gen_sizer.adaptive_young_list_length(); 903 } 904 905 void G1DefaultPolicy::update_max_gc_locker_expansion() { 906 uint expansion_region_num = 0; 907 if (GCLockerEdenExpansionPercent > 0) { 908 double perc = (double) GCLockerEdenExpansionPercent / 100.0; 909 double expansion_region_num_d = perc * (double) _young_list_target_length; 910 // We use ceiling so that if expansion_region_num_d is > 0.0 (but 911 // less than 1.0) we'll get 1. 912 expansion_region_num = (uint) ceil(expansion_region_num_d); 913 } else { 914 assert(expansion_region_num == 0, "sanity"); 915 } 916 _young_list_max_length = _young_list_target_length + expansion_region_num; 917 assert(_young_list_target_length <= _young_list_max_length, "post-condition"); 918 } 919 920 // Calculates survivor space parameters. 921 void G1DefaultPolicy::update_survivors_policy() { 922 double max_survivor_regions_d = 923 (double) _young_list_target_length / (double) SurvivorRatio; 924 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but 925 // smaller than 1.0) we'll get 1. 926 _max_survivor_regions = (uint) ceil(max_survivor_regions_d); 927 928 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold( 929 HeapRegion::GrainWords * _max_survivor_regions, _policy_counters); 930 } 931 932 bool G1DefaultPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { 933 // We actually check whether we are marking here and not if we are in a 934 // reclamation phase. This means that we will schedule a concurrent mark 935 // even while we are still in the process of reclaiming memory. 936 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle(); 937 if (!during_cycle) { 938 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); 939 collector_state()->set_initiate_conc_mark_if_possible(true); 940 return true; 941 } else { 942 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); 943 return false; 944 } 945 } 946 947 void G1DefaultPolicy::initiate_conc_mark() { 948 collector_state()->set_during_initial_mark_pause(true); 949 collector_state()->set_initiate_conc_mark_if_possible(false); 950 } 951 952 void G1DefaultPolicy::decide_on_conc_mark_initiation() { 953 // We are about to decide on whether this pause will be an 954 // initial-mark pause. 955 956 // First, collector_state()->during_initial_mark_pause() should not be already set. We 957 // will set it here if we have to. However, it should be cleared by 958 // the end of the pause (it's only set for the duration of an 959 // initial-mark pause). 960 assert(!collector_state()->during_initial_mark_pause(), "pre-condition"); 961 962 if (collector_state()->initiate_conc_mark_if_possible()) { 963 // We had noticed on a previous pause that the heap occupancy has 964 // gone over the initiating threshold and we should start a 965 // concurrent marking cycle. So we might initiate one. 966 967 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) { 968 // Initiate a new initial mark if there is no marking or reclamation going on. 969 initiate_conc_mark(); 970 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); 971 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) { 972 // Initiate a user requested initial mark. An initial mark must be young only 973 // GC, so the collector state must be updated to reflect this. 974 collector_state()->set_gcs_are_young(true); 975 collector_state()->set_last_young_gc(false); 976 977 abort_time_to_mixed_tracking(); 978 initiate_conc_mark(); 979 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); 980 } else { 981 // The concurrent marking thread is still finishing up the 982 // previous cycle. If we start one right now the two cycles 983 // overlap. In particular, the concurrent marking thread might 984 // be in the process of clearing the next marking bitmap (which 985 // we will use for the next cycle if we start one). Starting a 986 // cycle now will be bad given that parts of the marking 987 // information might get cleared by the marking thread. And we 988 // cannot wait for the marking thread to finish the cycle as it 989 // periodically yields while clearing the next marking bitmap 990 // and, if it's in a yield point, it's waiting for us to 991 // finish. So, at this point we will not start a cycle and we'll 992 // let the concurrent marking thread complete the last one. 993 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); 994 } 995 } 996 } 997 998 void G1DefaultPolicy::record_concurrent_mark_cleanup_end() { 999 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions()); 1000 1001 double end_sec = os::elapsedTime(); 1002 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; 1003 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); 1004 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); 1005 1006 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); 1007 } 1008 1009 double G1DefaultPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const { 1010 // Returns the given amount of reclaimable bytes (that represents 1011 // the amount of reclaimable space still to be collected) as a 1012 // percentage of the current heap capacity. 1013 size_t capacity_bytes = _g1->capacity(); 1014 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes; 1015 } 1016 1017 void G1DefaultPolicy::maybe_start_marking() { 1018 if (need_to_start_conc_mark("end of GC")) { 1019 // Note: this might have already been set, if during the last 1020 // pause we decided to start a cycle but at the beginning of 1021 // this pause we decided to postpone it. That's OK. 1022 collector_state()->set_initiate_conc_mark_if_possible(true); 1023 } 1024 } 1025 1026 G1DefaultPolicy::PauseKind G1DefaultPolicy::young_gc_pause_kind() const { 1027 assert(!collector_state()->full_collection(), "must be"); 1028 if (collector_state()->during_initial_mark_pause()) { 1029 assert(collector_state()->last_gc_was_young(), "must be"); 1030 assert(!collector_state()->last_young_gc(), "must be"); 1031 return InitialMarkGC; 1032 } else if (collector_state()->last_young_gc()) { 1033 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1034 assert(collector_state()->last_gc_was_young(), "must be"); 1035 return LastYoungGC; 1036 } else if (!collector_state()->last_gc_was_young()) { 1037 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1038 assert(!collector_state()->last_young_gc(), "must be"); 1039 return MixedGC; 1040 } else { 1041 assert(collector_state()->last_gc_was_young(), "must be"); 1042 assert(!collector_state()->during_initial_mark_pause(), "must be"); 1043 assert(!collector_state()->last_young_gc(), "must be"); 1044 return YoungOnlyGC; 1045 } 1046 } 1047 1048 void G1DefaultPolicy::record_pause(PauseKind kind, double start, double end) { 1049 // Manage the MMU tracker. For some reason it ignores Full GCs. 1050 if (kind != FullGC) { 1051 _mmu_tracker->add_pause(start, end); 1052 } 1053 // Manage the mutator time tracking from initial mark to first mixed gc. 1054 switch (kind) { 1055 case FullGC: 1056 abort_time_to_mixed_tracking(); 1057 break; 1058 case Cleanup: 1059 case Remark: 1060 case YoungOnlyGC: 1061 case LastYoungGC: 1062 _initial_mark_to_mixed.add_pause(end - start); 1063 break; 1064 case InitialMarkGC: 1065 _initial_mark_to_mixed.record_initial_mark_end(end); 1066 break; 1067 case MixedGC: 1068 _initial_mark_to_mixed.record_mixed_gc_start(start); 1069 break; 1070 default: 1071 ShouldNotReachHere(); 1072 } 1073 } 1074 1075 void G1DefaultPolicy::abort_time_to_mixed_tracking() { 1076 _initial_mark_to_mixed.reset(); 1077 } 1078 1079 bool G1DefaultPolicy::next_gc_should_be_mixed(const char* true_action_str, 1080 const char* false_action_str) const { 1081 if (cset_chooser()->is_empty()) { 1082 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); 1083 return false; 1084 } 1085 1086 // Is the amount of uncollected reclaimable space above G1HeapWastePercent? 1087 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); 1088 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes); 1089 double threshold = (double) G1HeapWastePercent; 1090 if (reclaimable_perc <= threshold) { 1091 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1092 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); 1093 return false; 1094 } 1095 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, 1096 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); 1097 return true; 1098 } 1099 1100 uint G1DefaultPolicy::calc_min_old_cset_length() const { 1101 // The min old CSet region bound is based on the maximum desired 1102 // number of mixed GCs after a cycle. I.e., even if some old regions 1103 // look expensive, we should add them to the CSet anyway to make 1104 // sure we go through the available old regions in no more than the 1105 // maximum desired number of mixed GCs. 1106 // 1107 // The calculation is based on the number of marked regions we added 1108 // to the CSet chooser in the first place, not how many remain, so 1109 // that the result is the same during all mixed GCs that follow a cycle. 1110 1111 const size_t region_num = (size_t) cset_chooser()->length(); 1112 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); 1113 size_t result = region_num / gc_num; 1114 // emulate ceiling 1115 if (result * gc_num < region_num) { 1116 result += 1; 1117 } 1118 return (uint) result; 1119 } 1120 1121 uint G1DefaultPolicy::calc_max_old_cset_length() const { 1122 // The max old CSet region bound is based on the threshold expressed 1123 // as a percentage of the heap size. I.e., it should bound the 1124 // number of old regions added to the CSet irrespective of how many 1125 // of them are available. 1126 1127 const G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1128 const size_t region_num = g1h->num_regions(); 1129 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; 1130 size_t result = region_num * perc / 100; 1131 // emulate ceiling 1132 if (100 * result < region_num * perc) { 1133 result += 1; 1134 } 1135 return (uint) result; 1136 } 1137 1138 void G1DefaultPolicy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) { 1139 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor); 1140 _collection_set->finalize_old_part(time_remaining_ms); 1141 } 1142 1143 void G1DefaultPolicy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) { 1144 1145 // Add survivor regions to SurvRateGroup. 1146 note_start_adding_survivor_regions(); 1147 finished_recalculating_age_indexes(true /* is_survivors */); 1148 1149 HeapRegion* last = NULL; 1150 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin(); 1151 it != survivors->regions()->end(); 1152 ++it) { 1153 HeapRegion* curr = *it; 1154 set_region_survivor(curr); 1155 1156 // The region is a non-empty survivor so let's add it to 1157 // the incremental collection set for the next evacuation 1158 // pause. 1159 _collection_set->add_survivor_regions(curr); 1160 1161 last = curr; 1162 } 1163 note_stop_adding_survivor_regions(); 1164 1165 // Don't clear the survivor list handles until the start of 1166 // the next evacuation pause - we need it in order to re-tag 1167 // the survivor regions from this evacuation pause as 'young' 1168 // at the start of the next. 1169 1170 finished_recalculating_age_indexes(false /* is_survivors */); 1171 }