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/g1CollectedHeap.inline.hpp"
  29 #include "gc/g1/g1CollectionSet.hpp"
  30 #include "gc/g1/g1CollectorPolicy.hpp"
  31 #include "gc/g1/g1ConcurrentMark.hpp"
  32 #include "gc/g1/g1IHOPControl.hpp"
  33 #include "gc/g1/g1GCPhaseTimes.hpp"
  34 #include "gc/g1/g1YoungGenSizer.hpp"
  35 #include "gc/g1/heapRegion.inline.hpp"
  36 #include "gc/g1/heapRegionRemSet.hpp"
  37 #include "gc/shared/gcPolicyCounters.hpp"
  38 #include "runtime/arguments.hpp"
  39 #include "runtime/java.hpp"
  40 #include "runtime/mutexLocker.hpp"
  41 #include "utilities/debug.hpp"
  42 #include "utilities/pair.hpp"
  43 
  44 // Different defaults for different number of GC threads
  45 // They were chosen by running GCOld and SPECjbb on debris with different
  46 //   numbers of GC threads and choosing them based on the results
  47 
  48 // all the same
  49 static double rs_length_diff_defaults[] = {
  50   0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
  51 };
  52 
  53 static double cost_per_card_ms_defaults[] = {
  54   0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
  55 };
  56 
  57 // all the same
  58 static double young_cards_per_entry_ratio_defaults[] = {
  59   1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
  60 };
  61 
  62 static double cost_per_entry_ms_defaults[] = {
  63   0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
  64 };
  65 
  66 static double cost_per_byte_ms_defaults[] = {
  67   0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
  68 };
  69 
  70 // these should be pretty consistent
  71 static double constant_other_time_ms_defaults[] = {
  72   5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
  73 };
  74 
  75 
  76 static double young_other_cost_per_region_ms_defaults[] = {
  77   0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
  78 };
  79 
  80 static double non_young_other_cost_per_region_ms_defaults[] = {
  81   1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
  82 };
  83 
  84 G1CollectorPolicy::G1CollectorPolicy() :
  85   _predictor(G1ConfidencePercent / 100.0),
  86 
  87   _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  88 
  89   _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  90   _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  91 
  92   _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  93   _prev_collection_pause_end_ms(0.0),
  94   _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
  95   _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  96   _cost_scan_hcc_seq(new TruncatedSeq(TruncatedSeqLength)),
  97   _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
  98   _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
  99   _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 100   _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 101   _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 102   _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
 103   _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 104   _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 105   _non_young_other_cost_per_region_ms_seq(
 106                                          new TruncatedSeq(TruncatedSeqLength)),
 107 
 108   _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
 109   _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
 110 
 111   _pause_time_target_ms((double) MaxGCPauseMillis),
 112 
 113   _recent_prev_end_times_for_all_gcs_sec(
 114                                 new TruncatedSeq(NumPrevPausesForHeuristics)),
 115 
 116   _recent_avg_pause_time_ratio(0.0),
 117   _rs_lengths_prediction(0),
 118   _max_survivor_regions(0),
 119 
 120   // add here any more surv rate groups
 121   _recorded_survivor_regions(0),
 122   _recorded_survivor_head(NULL),
 123   _recorded_survivor_tail(NULL),
 124   _survivors_age_table(true),
 125 
 126   _gc_overhead_perc(0.0),
 127 
 128   _bytes_allocated_in_old_since_last_gc(0),
 129   _ihop_control(NULL),
 130   _initial_mark_to_mixed() {
 131 
 132   // SurvRateGroups below must be initialized after the predictor because they
 133   // indirectly use it through this object passed to their constructor.
 134   _short_lived_surv_rate_group =
 135     new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
 136   _survivor_surv_rate_group =
 137     new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
 138 
 139   // Set up the region size and associated fields. Given that the
 140   // policy is created before the heap, we have to set this up here,
 141   // so it's done as soon as possible.
 142 
 143   // It would have been natural to pass initial_heap_byte_size() and
 144   // max_heap_byte_size() to setup_heap_region_size() but those have
 145   // not been set up at this point since they should be aligned with
 146   // the region size. So, there is a circular dependency here. We base
 147   // the region size on the heap size, but the heap size should be
 148   // aligned with the region size. To get around this we use the
 149   // unaligned values for the heap.
 150   HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
 151   HeapRegionRemSet::setup_remset_size();
 152 
 153   _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
 154   _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
 155   clear_ratio_check_data();
 156 
 157   _phase_times = new G1GCPhaseTimes(ParallelGCThreads);
 158 
 159   int index = MIN2(ParallelGCThreads - 1, 7u);
 160 
 161   _rs_length_diff_seq->add(rs_length_diff_defaults[index]);
 162   _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
 163   _cost_scan_hcc_seq->add(0.0);
 164   _young_cards_per_entry_ratio_seq->add(
 165                                   young_cards_per_entry_ratio_defaults[index]);
 166   _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
 167   _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
 168   _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
 169   _young_other_cost_per_region_ms_seq->add(
 170                                young_other_cost_per_region_ms_defaults[index]);
 171   _non_young_other_cost_per_region_ms_seq->add(
 172                            non_young_other_cost_per_region_ms_defaults[index]);
 173 
 174   // Below, we might need to calculate the pause time target based on
 175   // the pause interval. When we do so we are going to give G1 maximum
 176   // flexibility and allow it to do pauses when it needs to. So, we'll
 177   // arrange that the pause interval to be pause time target + 1 to
 178   // ensure that a) the pause time target is maximized with respect to
 179   // the pause interval and b) we maintain the invariant that pause
 180   // time target < pause interval. If the user does not want this
 181   // maximum flexibility, they will have to set the pause interval
 182   // explicitly.
 183 
 184   // First make sure that, if either parameter is set, its value is
 185   // reasonable.
 186   if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 187     if (MaxGCPauseMillis < 1) {
 188       vm_exit_during_initialization("MaxGCPauseMillis should be "
 189                                     "greater than 0");
 190     }
 191   }
 192   if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 193     if (GCPauseIntervalMillis < 1) {
 194       vm_exit_during_initialization("GCPauseIntervalMillis should be "
 195                                     "greater than 0");
 196     }
 197   }
 198 
 199   // Then, if the pause time target parameter was not set, set it to
 200   // the default value.
 201   if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 202     if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 203       // The default pause time target in G1 is 200ms
 204       FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
 205     } else {
 206       // We do not allow the pause interval to be set without the
 207       // pause time target
 208       vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
 209                                     "without setting MaxGCPauseMillis");
 210     }
 211   }
 212 
 213   // Then, if the interval parameter was not set, set it according to
 214   // the pause time target (this will also deal with the case when the
 215   // pause time target is the default value).
 216   if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 217     FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
 218   }
 219 
 220   // Finally, make sure that the two parameters are consistent.
 221   if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
 222     char buffer[256];
 223     jio_snprintf(buffer, 256,
 224                  "MaxGCPauseMillis (%u) should be less than "
 225                  "GCPauseIntervalMillis (%u)",
 226                  MaxGCPauseMillis, GCPauseIntervalMillis);
 227     vm_exit_during_initialization(buffer);
 228   }
 229 
 230   double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
 231   double time_slice  = (double) GCPauseIntervalMillis / 1000.0;
 232   _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
 233 
 234   // start conservatively (around 50ms is about right)
 235   _concurrent_mark_remark_times_ms->add(0.05);
 236   _concurrent_mark_cleanup_times_ms->add(0.20);
 237   _tenuring_threshold = MaxTenuringThreshold;
 238 
 239   assert(GCTimeRatio > 0,
 240          "we should have set it to a default value set_g1_gc_flags() "
 241          "if a user set it to 0");
 242   _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
 243 
 244   guarantee(G1ReservePercent <= 50, "Range checking should not allow values over 50.");
 245   _reserve_factor = (double) G1ReservePercent / 100.0;
 246   // This will be set when the heap is expanded
 247   // for the first time during initialization.
 248   _reserve_regions = 0;
 249 
 250   _ihop_control = create_ihop_control();
 251 }
 252 
 253 G1CollectorPolicy::~G1CollectorPolicy() {
 254   delete _ihop_control;
 255 }
 256 
 257 double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const {
 258   return _predictor.get_new_prediction(seq);
 259 }
 260 
 261 size_t G1CollectorPolicy::get_new_size_prediction(TruncatedSeq const* seq) const {
 262   return (size_t)get_new_prediction(seq);
 263 }
 264 
 265 void G1CollectorPolicy::initialize_alignments() {
 266   _space_alignment = HeapRegion::GrainBytes;
 267   size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
 268   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 269   _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
 270 }
 271 
 272 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
 273 
 274 void G1CollectorPolicy::post_heap_initialize() {
 275   uintx max_regions = G1CollectedHeap::heap()->max_regions();
 276   size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
 277   if (max_young_size != MaxNewSize) {
 278     FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
 279   }
 280 }
 281 
 282 void G1CollectorPolicy::initialize_flags() {
 283   if (G1HeapRegionSize != HeapRegion::GrainBytes) {
 284     FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
 285   }
 286 
 287   if (SurvivorRatio < 1) {
 288     vm_exit_during_initialization("Invalid survivor ratio specified");
 289   }
 290   CollectorPolicy::initialize_flags();
 291   _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
 292 }
 293 
 294 
 295 void G1CollectorPolicy::init() {
 296   // Set aside an initial future to_space.
 297   _g1 = G1CollectedHeap::heap();
 298   _collection_set = _g1->collection_set();
 299   _collection_set->set_policy(this);
 300 
 301   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 302 
 303   initialize_gc_policy_counters();
 304 
 305   if (adaptive_young_list_length()) {
 306     _young_list_fixed_length = 0;
 307   } else {
 308     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 309   }
 310   _free_regions_at_end_of_collection = _g1->num_free_regions();
 311 
 312   update_young_list_max_and_target_length();
 313   // We may immediately start allocating regions and placing them on the
 314   // collection set list. Initialize the per-collection set info
 315   _collection_set->start_incremental_building();
 316 }
 317 
 318 void G1CollectorPolicy::note_gc_start(uint num_active_workers) {
 319   phase_times()->note_gc_start(num_active_workers);
 320 }
 321 
 322 // Create the jstat counters for the policy.
 323 void G1CollectorPolicy::initialize_gc_policy_counters() {
 324   _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
 325 }
 326 
 327 bool G1CollectorPolicy::predict_will_fit(uint young_length,
 328                                          double base_time_ms,
 329                                          uint base_free_regions,
 330                                          double target_pause_time_ms) const {
 331   if (young_length >= base_free_regions) {
 332     // end condition 1: not enough space for the young regions
 333     return false;
 334   }
 335 
 336   double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
 337   size_t bytes_to_copy =
 338                (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
 339   double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
 340   double young_other_time_ms = predict_young_other_time_ms(young_length);
 341   double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
 342   if (pause_time_ms > target_pause_time_ms) {
 343     // end condition 2: prediction is over the target pause time
 344     return false;
 345   }
 346 
 347   size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
 348 
 349   // When copying, we will likely need more bytes free than is live in the region.
 350   // Add some safety margin to factor in the confidence of our guess, and the
 351   // natural expected waste.
 352   // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
 353   // of the calculation: the lower the confidence, the more headroom.
 354   // (100 + TargetPLABWastePct) represents the increase in expected bytes during
 355   // copying due to anticipated waste in the PLABs.
 356   double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
 357   size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
 358 
 359   if (expected_bytes_to_copy > free_bytes) {
 360     // end condition 3: out-of-space
 361     return false;
 362   }
 363 
 364   // success!
 365   return true;
 366 }
 367 
 368 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
 369   // re-calculate the necessary reserve
 370   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 371   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 372   // smaller than 1.0) we'll get 1.
 373   _reserve_regions = (uint) ceil(reserve_regions_d);
 374 
 375   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 376 
 377   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
 378 }
 379 
 380 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
 381                                                        uint base_min_length) const {
 382   uint desired_min_length = 0;
 383   if (adaptive_young_list_length()) {
 384     if (_alloc_rate_ms_seq->num() > 3) {
 385       double now_sec = os::elapsedTime();
 386       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 387       double alloc_rate_ms = predict_alloc_rate_ms();
 388       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 389     } else {
 390       // otherwise we don't have enough info to make the prediction
 391     }
 392   }
 393   desired_min_length += base_min_length;
 394   // make sure we don't go below any user-defined minimum bound
 395   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 396 }
 397 
 398 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
 399   // Here, we might want to also take into account any additional
 400   // constraints (i.e., user-defined minimum bound). Currently, we
 401   // effectively don't set this bound.
 402   return _young_gen_sizer->max_desired_young_length();
 403 }
 404 
 405 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
 406   return update_young_list_max_and_target_length(predict_rs_lengths());
 407 }
 408 
 409 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
 410   uint unbounded_target_length = update_young_list_target_length(rs_lengths);
 411   update_max_gc_locker_expansion();
 412   return unbounded_target_length;
 413 }
 414 
 415 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
 416   YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
 417   _young_list_target_length = young_lengths.first;
 418   return young_lengths.second;
 419 }
 420 
 421 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
 422   YoungTargetLengths result;
 423 
 424   // Calculate the absolute and desired min bounds first.
 425 
 426   // This is how many young regions we already have (currently: the survivors).
 427   uint base_min_length = recorded_survivor_regions();
 428   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 429   // This is the absolute minimum young length. Ensure that we
 430   // will at least have one eden region available for allocation.
 431   uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
 432   // If we shrank the young list target it should not shrink below the current size.
 433   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 434   // Calculate the absolute and desired max bounds.
 435 
 436   uint desired_max_length = calculate_young_list_desired_max_length();
 437 
 438   uint young_list_target_length = 0;
 439   if (adaptive_young_list_length()) {
 440     if (collector_state()->gcs_are_young()) {
 441       young_list_target_length =
 442                         calculate_young_list_target_length(rs_lengths,
 443                                                            base_min_length,
 444                                                            desired_min_length,
 445                                                            desired_max_length);
 446     } else {
 447       // Don't calculate anything and let the code below bound it to
 448       // the desired_min_length, i.e., do the next GC as soon as
 449       // possible to maximize how many old regions we can add to it.
 450     }
 451   } else {
 452     // The user asked for a fixed young gen so we'll fix the young gen
 453     // whether the next GC is young or mixed.
 454     young_list_target_length = _young_list_fixed_length;
 455   }
 456 
 457   result.second = young_list_target_length;
 458 
 459   // We will try our best not to "eat" into the reserve.
 460   uint absolute_max_length = 0;
 461   if (_free_regions_at_end_of_collection > _reserve_regions) {
 462     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 463   }
 464   if (desired_max_length > absolute_max_length) {
 465     desired_max_length = absolute_max_length;
 466   }
 467 
 468   // Make sure we don't go over the desired max length, nor under the
 469   // desired min length. In case they clash, desired_min_length wins
 470   // which is why that test is second.
 471   if (young_list_target_length > desired_max_length) {
 472     young_list_target_length = desired_max_length;
 473   }
 474   if (young_list_target_length < desired_min_length) {
 475     young_list_target_length = desired_min_length;
 476   }
 477 
 478   assert(young_list_target_length > recorded_survivor_regions(),
 479          "we should be able to allocate at least one eden region");
 480   assert(young_list_target_length >= absolute_min_length, "post-condition");
 481 
 482   result.first = young_list_target_length;
 483   return result;
 484 }
 485 
 486 uint
 487 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
 488                                                      uint base_min_length,
 489                                                      uint desired_min_length,
 490                                                      uint desired_max_length) const {
 491   assert(adaptive_young_list_length(), "pre-condition");
 492   assert(collector_state()->gcs_are_young(), "only call this for young GCs");
 493 
 494   // In case some edge-condition makes the desired max length too small...
 495   if (desired_max_length <= desired_min_length) {
 496     return desired_min_length;
 497   }
 498 
 499   // We'll adjust min_young_length and max_young_length not to include
 500   // the already allocated young regions (i.e., so they reflect the
 501   // min and max eden regions we'll allocate). The base_min_length
 502   // will be reflected in the predictions by the
 503   // survivor_regions_evac_time prediction.
 504   assert(desired_min_length > base_min_length, "invariant");
 505   uint min_young_length = desired_min_length - base_min_length;
 506   assert(desired_max_length > base_min_length, "invariant");
 507   uint max_young_length = desired_max_length - base_min_length;
 508 
 509   double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 510   double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 511   size_t pending_cards = get_new_size_prediction(_pending_cards_seq);
 512   size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
 513   size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
 514   double base_time_ms =
 515     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
 516     survivor_regions_evac_time;
 517   uint available_free_regions = _free_regions_at_end_of_collection;
 518   uint base_free_regions = 0;
 519   if (available_free_regions > _reserve_regions) {
 520     base_free_regions = available_free_regions - _reserve_regions;
 521   }
 522 
 523   // Here, we will make sure that the shortest young length that
 524   // makes sense fits within the target pause time.
 525 
 526   if (predict_will_fit(min_young_length, base_time_ms,
 527                        base_free_regions, target_pause_time_ms)) {
 528     // The shortest young length will fit into the target pause time;
 529     // we'll now check whether the absolute maximum number of young
 530     // regions will fit in the target pause time. If not, we'll do
 531     // a binary search between min_young_length and max_young_length.
 532     if (predict_will_fit(max_young_length, base_time_ms,
 533                          base_free_regions, target_pause_time_ms)) {
 534       // The maximum young length will fit into the target pause time.
 535       // We are done so set min young length to the maximum length (as
 536       // the result is assumed to be returned in min_young_length).
 537       min_young_length = max_young_length;
 538     } else {
 539       // The maximum possible number of young regions will not fit within
 540       // the target pause time so we'll search for the optimal
 541       // length. The loop invariants are:
 542       //
 543       // min_young_length < max_young_length
 544       // min_young_length is known to fit into the target pause time
 545       // max_young_length is known not to fit into the target pause time
 546       //
 547       // Going into the loop we know the above hold as we've just
 548       // checked them. Every time around the loop we check whether
 549       // the middle value between min_young_length and
 550       // max_young_length fits into the target pause time. If it
 551       // does, it becomes the new min. If it doesn't, it becomes
 552       // the new max. This way we maintain the loop invariants.
 553 
 554       assert(min_young_length < max_young_length, "invariant");
 555       uint diff = (max_young_length - min_young_length) / 2;
 556       while (diff > 0) {
 557         uint young_length = min_young_length + diff;
 558         if (predict_will_fit(young_length, base_time_ms,
 559                              base_free_regions, target_pause_time_ms)) {
 560           min_young_length = young_length;
 561         } else {
 562           max_young_length = young_length;
 563         }
 564         assert(min_young_length <  max_young_length, "invariant");
 565         diff = (max_young_length - min_young_length) / 2;
 566       }
 567       // The results is min_young_length which, according to the
 568       // loop invariants, should fit within the target pause time.
 569 
 570       // These are the post-conditions of the binary search above:
 571       assert(min_young_length < max_young_length,
 572              "otherwise we should have discovered that max_young_length "
 573              "fits into the pause target and not done the binary search");
 574       assert(predict_will_fit(min_young_length, base_time_ms,
 575                               base_free_regions, target_pause_time_ms),
 576              "min_young_length, the result of the binary search, should "
 577              "fit into the pause target");
 578       assert(!predict_will_fit(min_young_length + 1, base_time_ms,
 579                                base_free_regions, target_pause_time_ms),
 580              "min_young_length, the result of the binary search, should be "
 581              "optimal, so no larger length should fit into the pause target");
 582     }
 583   } else {
 584     // Even the minimum length doesn't fit into the pause time
 585     // target, return it as the result nevertheless.
 586   }
 587   return base_min_length + min_young_length;
 588 }
 589 
 590 double G1CollectorPolicy::predict_survivor_regions_evac_time() const {
 591   double survivor_regions_evac_time = 0.0;
 592   for (HeapRegion * r = _recorded_survivor_head;
 593        r != NULL && r != _recorded_survivor_tail->get_next_young_region();
 594        r = r->get_next_young_region()) {
 595     survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
 596   }
 597   return survivor_regions_evac_time;
 598 }
 599 
 600 void G1CollectorPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
 601   guarantee( adaptive_young_list_length(), "should not call this otherwise" );
 602 
 603   if (rs_lengths > _rs_lengths_prediction) {
 604     // add 10% to avoid having to recalculate often
 605     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 606     update_rs_lengths_prediction(rs_lengths_prediction);
 607 
 608     update_young_list_max_and_target_length(rs_lengths_prediction);
 609   }
 610 }
 611 
 612 void G1CollectorPolicy::update_rs_lengths_prediction() {
 613   update_rs_lengths_prediction(predict_rs_lengths());
 614 }
 615 
 616 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
 617   if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
 618     _rs_lengths_prediction = prediction;
 619   }
 620 }
 621 
 622 #ifndef PRODUCT
 623 bool G1CollectorPolicy::verify_young_ages() {
 624   HeapRegion* head = _g1->young_list()->first_region();
 625   return
 626     verify_young_ages(head, _short_lived_surv_rate_group);
 627   // also call verify_young_ages on any additional surv rate groups
 628 }
 629 
 630 bool
 631 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
 632                                      SurvRateGroup *surv_rate_group) {
 633   guarantee( surv_rate_group != NULL, "pre-condition" );
 634 
 635   const char* name = surv_rate_group->name();
 636   bool ret = true;
 637   int prev_age = -1;
 638 
 639   for (HeapRegion* curr = head;
 640        curr != NULL;
 641        curr = curr->get_next_young_region()) {
 642     SurvRateGroup* group = curr->surv_rate_group();
 643     if (group == NULL && !curr->is_survivor()) {
 644       log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);
 645       ret = false;
 646     }
 647 
 648     if (surv_rate_group == group) {
 649       int age = curr->age_in_surv_rate_group();
 650 
 651       if (age < 0) {
 652         log_error(gc, verify)("## %s: encountered negative age", name);
 653         ret = false;
 654       }
 655 
 656       if (age <= prev_age) {
 657         log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
 658         ret = false;
 659       }
 660       prev_age = age;
 661     }
 662   }
 663 
 664   return ret;
 665 }
 666 #endif // PRODUCT
 667 
 668 void G1CollectorPolicy::record_full_collection_start() {
 669   _full_collection_start_sec = os::elapsedTime();
 670   // Release the future to-space so that it is available for compaction into.
 671   collector_state()->set_full_collection(true);
 672 }
 673 
 674 void G1CollectorPolicy::record_full_collection_end() {
 675   // Consider this like a collection pause for the purposes of allocation
 676   // since last pause.
 677   double end_sec = os::elapsedTime();
 678   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 679   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 680 
 681   update_recent_gc_times(end_sec, full_gc_time_ms);
 682 
 683   collector_state()->set_full_collection(false);
 684 
 685   // "Nuke" the heuristics that control the young/mixed GC
 686   // transitions and make sure we start with young GCs after the Full GC.
 687   collector_state()->set_gcs_are_young(true);
 688   collector_state()->set_last_young_gc(false);
 689   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
 690   collector_state()->set_during_initial_mark_pause(false);
 691   collector_state()->set_in_marking_window(false);
 692   collector_state()->set_in_marking_window_im(false);
 693 
 694   _short_lived_surv_rate_group->start_adding_regions();
 695   // also call this on any additional surv rate groups
 696 
 697   record_survivor_regions(0, NULL, NULL);
 698 
 699   _free_regions_at_end_of_collection = _g1->num_free_regions();
 700   // Reset survivors SurvRateGroup.
 701   _survivor_surv_rate_group->reset();
 702   update_young_list_max_and_target_length();
 703   update_rs_lengths_prediction();
 704   cset_chooser()->clear();
 705 
 706   _bytes_allocated_in_old_since_last_gc = 0;
 707 
 708   record_pause(FullGC, _full_collection_start_sec, end_sec);
 709 }
 710 
 711 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) {
 712   // We only need to do this here as the policy will only be applied
 713   // to the GC we're about to start. so, no point is calculating this
 714   // every time we calculate / recalculate the target young length.
 715   update_survivors_policy();
 716 
 717   assert(_g1->used() == _g1->recalculate_used(),
 718          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
 719          _g1->used(), _g1->recalculate_used());
 720 
 721   phase_times()->record_cur_collection_start_sec(start_time_sec);
 722   _pending_cards = _g1->pending_card_num();
 723 
 724   _collection_set->reset_bytes_used_before();
 725   _bytes_copied_during_gc = 0;
 726 
 727   collector_state()->set_last_gc_was_young(false);
 728 
 729   // do that for any other surv rate groups
 730   _short_lived_surv_rate_group->stop_adding_regions();
 731   _survivors_age_table.clear();
 732 
 733   assert( verify_young_ages(), "region age verification" );
 734 }
 735 
 736 void G1CollectorPolicy::record_concurrent_mark_init_end(double
 737                                                    mark_init_elapsed_time_ms) {
 738   collector_state()->set_during_marking(true);
 739   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 740   collector_state()->set_during_initial_mark_pause(false);
 741 }
 742 
 743 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
 744   _mark_remark_start_sec = os::elapsedTime();
 745   collector_state()->set_during_marking(false);
 746 }
 747 
 748 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
 749   double end_time_sec = os::elapsedTime();
 750   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 751   _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
 752   _prev_collection_pause_end_ms += elapsed_time_ms;
 753 
 754   record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 755 }
 756 
 757 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
 758   _mark_cleanup_start_sec = os::elapsedTime();
 759 }
 760 
 761 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
 762   bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
 763                                                               "skip last young-only gc");
 764   collector_state()->set_last_young_gc(should_continue_with_reclaim);
 765   // We skip the marking phase.
 766   if (!should_continue_with_reclaim) {
 767     abort_time_to_mixed_tracking();
 768   }
 769   collector_state()->set_in_marking_window(false);
 770 }
 771 
 772 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
 773   return phase_times()->average_time_ms(phase);
 774 }
 775 
 776 double G1CollectorPolicy::young_other_time_ms() const {
 777   return phase_times()->young_cset_choice_time_ms() +
 778          phase_times()->young_free_cset_time_ms();
 779 }
 780 
 781 double G1CollectorPolicy::non_young_other_time_ms() const {
 782   return phase_times()->non_young_cset_choice_time_ms() +
 783          phase_times()->non_young_free_cset_time_ms();
 784 
 785 }
 786 
 787 double G1CollectorPolicy::other_time_ms(double pause_time_ms) const {
 788   return pause_time_ms -
 789          average_time_ms(G1GCPhaseTimes::UpdateRS) -
 790          average_time_ms(G1GCPhaseTimes::ScanRS) -
 791          average_time_ms(G1GCPhaseTimes::ObjCopy) -
 792          average_time_ms(G1GCPhaseTimes::Termination);
 793 }
 794 
 795 double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const {
 796   return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
 797 }
 798 
 799 CollectionSetChooser* G1CollectorPolicy::cset_chooser() const {
 800   return _collection_set->cset_chooser();
 801 }
 802 
 803 bool G1CollectorPolicy::about_to_start_mixed_phase() const {
 804   return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
 805 }
 806 
 807 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
 808   if (about_to_start_mixed_phase()) {
 809     return false;
 810   }
 811 
 812   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
 813 
 814   size_t cur_used_bytes = _g1->non_young_capacity_bytes();
 815   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 816   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 817 
 818   bool result = false;
 819   if (marking_request_bytes > marking_initiating_used_threshold) {
 820     result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
 821     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
 822                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
 823                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
 824   }
 825 
 826   return result;
 827 }
 828 
 829 // Anything below that is considered to be zero
 830 #define MIN_TIMER_GRANULARITY 0.0000001
 831 
 832 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
 833   double end_time_sec = os::elapsedTime();
 834 
 835   size_t cur_used_bytes = _g1->used();
 836   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
 837   bool last_pause_included_initial_mark = false;
 838   bool update_stats = !_g1->evacuation_failed();
 839 
 840   NOT_PRODUCT(_short_lived_surv_rate_group->print());
 841 
 842   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
 843 
 844   last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
 845   if (last_pause_included_initial_mark) {
 846     record_concurrent_mark_init_end(0.0);
 847   } else {
 848     maybe_start_marking();
 849   }
 850 
 851   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
 852   if (app_time_ms < MIN_TIMER_GRANULARITY) {
 853     // This usually happens due to the timer not having the required
 854     // granularity. Some Linuxes are the usual culprits.
 855     // We'll just set it to something (arbitrarily) small.
 856     app_time_ms = 1.0;
 857   }
 858 
 859   if (update_stats) {
 860     // We maintain the invariant that all objects allocated by mutator
 861     // threads will be allocated out of eden regions. So, we can use
 862     // the eden region number allocated since the previous GC to
 863     // calculate the application's allocate rate. The only exception
 864     // to that is humongous objects that are allocated separately. But
 865     // given that humongous object allocations do not really affect
 866     // either the pause's duration nor when the next pause will take
 867     // place we can safely ignore them here.
 868     uint regions_allocated = _collection_set->eden_region_length();
 869     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
 870     _alloc_rate_ms_seq->add(alloc_rate_ms);
 871 
 872     double interval_ms =
 873       (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
 874     update_recent_gc_times(end_time_sec, pause_time_ms);
 875     _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
 876     if (recent_avg_pause_time_ratio() < 0.0 ||
 877         (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
 878       // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
 879       // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
 880       if (_recent_avg_pause_time_ratio < 0.0) {
 881         _recent_avg_pause_time_ratio = 0.0;
 882       } else {
 883         assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
 884         _recent_avg_pause_time_ratio = 1.0;
 885       }
 886     }
 887 
 888     // Compute the ratio of just this last pause time to the entire time range stored
 889     // in the vectors. Comparing this pause to the entire range, rather than only the
 890     // most recent interval, has the effect of smoothing over a possible transient 'burst'
 891     // of more frequent pauses that don't really reflect a change in heap occupancy.
 892     // This reduces the likelihood of a needless heap expansion being triggered.
 893     _last_pause_time_ratio =
 894       (pause_time_ms * _recent_prev_end_times_for_all_gcs_sec->num()) / interval_ms;
 895   }
 896 
 897   bool new_in_marking_window = collector_state()->in_marking_window();
 898   bool new_in_marking_window_im = false;
 899   if (last_pause_included_initial_mark) {
 900     new_in_marking_window = true;
 901     new_in_marking_window_im = true;
 902   }
 903 
 904   if (collector_state()->last_young_gc()) {
 905     // This is supposed to to be the "last young GC" before we start
 906     // doing mixed GCs. Here we decide whether to start mixed GCs or not.
 907     assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
 908 
 909     if (next_gc_should_be_mixed("start mixed GCs",
 910                                 "do not start mixed GCs")) {
 911       collector_state()->set_gcs_are_young(false);
 912     } else {
 913       // We aborted the mixed GC phase early.
 914       abort_time_to_mixed_tracking();
 915     }
 916 
 917     collector_state()->set_last_young_gc(false);
 918   }
 919 
 920   if (!collector_state()->last_gc_was_young()) {
 921     // This is a mixed GC. Here we decide whether to continue doing
 922     // mixed GCs or not.
 923     if (!next_gc_should_be_mixed("continue mixed GCs",
 924                                  "do not continue mixed GCs")) {
 925       collector_state()->set_gcs_are_young(true);
 926 
 927       maybe_start_marking();
 928     }
 929   }
 930 
 931   _short_lived_surv_rate_group->start_adding_regions();
 932   // Do that for any other surv rate groups
 933 
 934   double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
 935 
 936   if (update_stats) {
 937     double cost_per_card_ms = 0.0;
 938     if (_pending_cards > 0) {
 939       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
 940       _cost_per_card_ms_seq->add(cost_per_card_ms);
 941     }
 942     _cost_scan_hcc_seq->add(scan_hcc_time_ms);
 943 
 944     double cost_per_entry_ms = 0.0;
 945     if (cards_scanned > 10) {
 946       cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
 947       if (collector_state()->last_gc_was_young()) {
 948         _cost_per_entry_ms_seq->add(cost_per_entry_ms);
 949       } else {
 950         _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
 951       }
 952     }
 953 
 954     if (_max_rs_lengths > 0) {
 955       double cards_per_entry_ratio =
 956         (double) cards_scanned / (double) _max_rs_lengths;
 957       if (collector_state()->last_gc_was_young()) {
 958         _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
 959       } else {
 960         _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
 961       }
 962     }
 963 
 964     // This is defensive. For a while _max_rs_lengths could get
 965     // smaller than _recorded_rs_lengths which was causing
 966     // rs_length_diff to get very large and mess up the RSet length
 967     // predictions. The reason was unsafe concurrent updates to the
 968     // _inc_cset_recorded_rs_lengths field which the code below guards
 969     // against (see CR 7118202). This bug has now been fixed (see CR
 970     // 7119027). However, I'm still worried that
 971     // _inc_cset_recorded_rs_lengths might still end up somewhat
 972     // inaccurate. The concurrent refinement thread calculates an
 973     // RSet's length concurrently with other CR threads updating it
 974     // which might cause it to calculate the length incorrectly (if,
 975     // say, it's in mid-coarsening). So I'll leave in the defensive
 976     // conditional below just in case.
 977     size_t rs_length_diff = 0;
 978     size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
 979     if (_max_rs_lengths > recorded_rs_lengths) {
 980       rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
 981     }
 982     _rs_length_diff_seq->add((double) rs_length_diff);
 983 
 984     size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
 985     size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
 986     double cost_per_byte_ms = 0.0;
 987 
 988     if (copied_bytes > 0) {
 989       cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
 990       if (collector_state()->in_marking_window()) {
 991         _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
 992       } else {
 993         _cost_per_byte_ms_seq->add(cost_per_byte_ms);
 994       }
 995     }
 996 
 997     if (_collection_set->young_region_length() > 0) {
 998       _young_other_cost_per_region_ms_seq->add(young_other_time_ms() /
 999                                                _collection_set->young_region_length());
1000     }
1001 
1002     if (_collection_set->old_region_length() > 0) {
1003       _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() /
1004                                                    _collection_set->old_region_length());
1005     }
1006 
1007     _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms));
1008 
1009     _pending_cards_seq->add((double) _pending_cards);
1010     _rs_lengths_seq->add((double) _max_rs_lengths);
1011   }
1012 
1013   collector_state()->set_in_marking_window(new_in_marking_window);
1014   collector_state()->set_in_marking_window_im(new_in_marking_window_im);
1015   _free_regions_at_end_of_collection = _g1->num_free_regions();
1016   // IHOP control wants to know the expected young gen length if it were not
1017   // restrained by the heap reserve. Using the actual length would make the
1018   // prediction too small and the limit the young gen every time we get to the
1019   // predicted target occupancy.
1020   size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
1021   update_rs_lengths_prediction();
1022 
1023   update_ihop_prediction(app_time_ms / 1000.0,
1024                          _bytes_allocated_in_old_since_last_gc,
1025                          last_unrestrained_young_length * HeapRegion::GrainBytes);
1026   _bytes_allocated_in_old_since_last_gc = 0;
1027 
1028   _ihop_control->send_trace_event(_g1->gc_tracer_stw());
1029 
1030   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1031   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
1032 
1033   if (update_rs_time_goal_ms < scan_hcc_time_ms) {
1034     log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
1035                                 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
1036                                 update_rs_time_goal_ms, scan_hcc_time_ms);
1037 
1038     update_rs_time_goal_ms = 0;
1039   } else {
1040     update_rs_time_goal_ms -= scan_hcc_time_ms;
1041   }
1042   adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
1043                                phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
1044                                update_rs_time_goal_ms);
1045 
1046   cset_chooser()->verify();
1047 }
1048 
1049 G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
1050   if (G1UseAdaptiveIHOP) {
1051     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
1052                                      &_predictor,
1053                                      G1ReservePercent,
1054                                      G1HeapWastePercent);
1055   } else {
1056     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
1057   }
1058 }
1059 
1060 void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s,
1061                                                size_t mutator_alloc_bytes,
1062                                                size_t young_gen_size) {
1063   // Always try to update IHOP prediction. Even evacuation failures give information
1064   // about e.g. whether to start IHOP earlier next time.
1065 
1066   // Avoid using really small application times that might create samples with
1067   // very high or very low values. They may be caused by e.g. back-to-back gcs.
1068   double const min_valid_time = 1e-6;
1069 
1070   bool report = false;
1071 
1072   double marking_to_mixed_time = -1.0;
1073   if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
1074     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
1075     assert(marking_to_mixed_time > 0.0,
1076            "Initial mark to mixed time must be larger than zero but is %.3f",
1077            marking_to_mixed_time);
1078     if (marking_to_mixed_time > min_valid_time) {
1079       _ihop_control->update_marking_length(marking_to_mixed_time);
1080       report = true;
1081     }
1082   }
1083 
1084   // As an approximation for the young gc promotion rates during marking we use
1085   // all of them. In many applications there are only a few if any young gcs during
1086   // marking, which makes any prediction useless. This increases the accuracy of the
1087   // prediction.
1088   if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
1089     _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
1090     report = true;
1091   }
1092 
1093   if (report) {
1094     report_ihop_statistics();
1095   }
1096 }
1097 
1098 void G1CollectorPolicy::report_ihop_statistics() {
1099   _ihop_control->print();
1100 }
1101 
1102 void G1CollectorPolicy::print_phases() {
1103   phase_times()->print();
1104 }
1105 
1106 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
1107                                                      double update_rs_processed_buffers,
1108                                                      double goal_ms) {
1109   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1110   ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
1111 
1112   if (G1UseAdaptiveConcRefinement) {
1113     const int k_gy = 3, k_gr = 6;
1114     const double inc_k = 1.1, dec_k = 0.9;
1115 
1116     size_t g = cg1r->green_zone();
1117     if (update_rs_time > goal_ms) {
1118       g = (size_t)(g * dec_k);  // Can become 0, that's OK. That would mean a mutator-only processing.
1119     } else {
1120       if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
1121         g = (size_t)MAX2(g * inc_k, g + 1.0);
1122       }
1123     }
1124     // Change the refinement threads params
1125     cg1r->set_green_zone(g);
1126     cg1r->set_yellow_zone(g * k_gy);
1127     cg1r->set_red_zone(g * k_gr);
1128     cg1r->reinitialize_threads();
1129 
1130     size_t processing_threshold_delta = MAX2<size_t>(cg1r->green_zone() * _predictor.sigma(), 1);
1131     size_t processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1132                                     cg1r->yellow_zone());
1133     // Change the barrier params
1134     dcqs.set_process_completed_threshold((int)processing_threshold);
1135     dcqs.set_max_completed_queue((int)cg1r->red_zone());
1136   }
1137 
1138   size_t curr_queue_size = dcqs.completed_buffers_num();
1139   if (curr_queue_size >= cg1r->yellow_zone()) {
1140     dcqs.set_completed_queue_padding(curr_queue_size);
1141   } else {
1142     dcqs.set_completed_queue_padding(0);
1143   }
1144   dcqs.notify_if_necessary();
1145 }
1146 
1147 size_t G1CollectorPolicy::predict_rs_lengths() const {
1148   return get_new_size_prediction(_rs_lengths_seq);
1149 }
1150 
1151 size_t G1CollectorPolicy::predict_rs_length_diff() const {
1152   return get_new_size_prediction(_rs_length_diff_seq);
1153 }
1154 
1155 double G1CollectorPolicy::predict_alloc_rate_ms() const {
1156   return get_new_prediction(_alloc_rate_ms_seq);
1157 }
1158 
1159 double G1CollectorPolicy::predict_cost_per_card_ms() const {
1160   return get_new_prediction(_cost_per_card_ms_seq);
1161 }
1162 
1163 double G1CollectorPolicy::predict_scan_hcc_ms() const {
1164   return get_new_prediction(_cost_scan_hcc_seq);
1165 }
1166 
1167 double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const {
1168   return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms();
1169 }
1170 
1171 double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const {
1172   return get_new_prediction(_young_cards_per_entry_ratio_seq);
1173 }
1174 
1175 double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const {
1176   if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
1177     return predict_young_cards_per_entry_ratio();
1178   } else {
1179     return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
1180   }
1181 }
1182 
1183 size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const {
1184   return (size_t) (rs_length * predict_young_cards_per_entry_ratio());
1185 }
1186 
1187 size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const {
1188   return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio());
1189 }
1190 
1191 double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const {
1192   if (collector_state()->gcs_are_young()) {
1193     return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1194   } else {
1195     return predict_mixed_rs_scan_time_ms(card_num);
1196   }
1197 }
1198 
1199 double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const {
1200   if (_mixed_cost_per_entry_ms_seq->num() < 3) {
1201     return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1202   } else {
1203     return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq);
1204   }
1205 }
1206 
1207 double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const {
1208   if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
1209     return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq);
1210   } else {
1211     return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq);
1212   }
1213 }
1214 
1215 double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const {
1216   if (collector_state()->during_concurrent_mark()) {
1217     return predict_object_copy_time_ms_during_cm(bytes_to_copy);
1218   } else {
1219     return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq);
1220   }
1221 }
1222 
1223 double G1CollectorPolicy::predict_constant_other_time_ms() const {
1224   return get_new_prediction(_constant_other_time_ms_seq);
1225 }
1226 
1227 double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const {
1228   return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq);
1229 }
1230 
1231 double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const {
1232   return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq);
1233 }
1234 
1235 double G1CollectorPolicy::predict_remark_time_ms() const {
1236   return get_new_prediction(_concurrent_mark_remark_times_ms);
1237 }
1238 
1239 double G1CollectorPolicy::predict_cleanup_time_ms() const {
1240   return get_new_prediction(_concurrent_mark_cleanup_times_ms);
1241 }
1242 
1243 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1244   TruncatedSeq* seq = surv_rate_group->get_seq(age);
1245   guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1246   double pred = get_new_prediction(seq);
1247   if (pred > 1.0) {
1248     pred = 1.0;
1249   }
1250   return pred;
1251 }
1252 
1253 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1254   return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1255 }
1256 
1257 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1258   return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1259 }
1260 
1261 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1262                                                        size_t scanned_cards) const {
1263   return
1264     predict_rs_update_time_ms(pending_cards) +
1265     predict_rs_scan_time_ms(scanned_cards) +
1266     predict_constant_other_time_ms();
1267 }
1268 
1269 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1270   size_t rs_length = predict_rs_lengths() + predict_rs_length_diff();
1271   size_t card_num;
1272   if (collector_state()->gcs_are_young()) {
1273     card_num = predict_young_card_num(rs_length);
1274   } else {
1275     card_num = predict_non_young_card_num(rs_length);
1276   }
1277   return predict_base_elapsed_time_ms(pending_cards, card_num);
1278 }
1279 
1280 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1281   size_t bytes_to_copy;
1282   if (hr->is_marked())
1283     bytes_to_copy = hr->max_live_bytes();
1284   else {
1285     assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1286     int age = hr->age_in_surv_rate_group();
1287     double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1288     bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1289   }
1290   return bytes_to_copy;
1291 }
1292 
1293 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1294                                                          bool for_young_gc) const {
1295   size_t rs_length = hr->rem_set()->occupied();
1296   size_t card_num;
1297 
1298   // Predicting the number of cards is based on which type of GC
1299   // we're predicting for.
1300   if (for_young_gc) {
1301     card_num = predict_young_card_num(rs_length);
1302   } else {
1303     card_num = predict_non_young_card_num(rs_length);
1304   }
1305   size_t bytes_to_copy = predict_bytes_to_copy(hr);
1306 
1307   double region_elapsed_time_ms =
1308     predict_rs_scan_time_ms(card_num) +
1309     predict_object_copy_time_ms(bytes_to_copy);
1310 
1311   // The prediction of the "other" time for this region is based
1312   // upon the region type and NOT the GC type.
1313   if (hr->is_young()) {
1314     region_elapsed_time_ms += predict_young_other_time_ms(1);
1315   } else {
1316     region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1317   }
1318   return region_elapsed_time_ms;
1319 }
1320 
1321 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1322                                                double elapsed_ms) {
1323   _recent_gc_times_ms->add(elapsed_ms);
1324   _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1325   _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1326 }
1327 
1328 void G1CollectorPolicy::clear_ratio_check_data() {
1329   _ratio_over_threshold_count = 0;
1330   _ratio_over_threshold_sum = 0.0;
1331   _pauses_since_start = 0;
1332 }
1333 
1334 size_t G1CollectorPolicy::expansion_amount() {
1335   double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1336   double last_gc_overhead = _last_pause_time_ratio * 100.0;
1337   double threshold = _gc_overhead_perc;
1338   size_t expand_bytes = 0;
1339 
1340   // If the heap is at less than half its maximum size, scale the threshold down,
1341   // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1342   // though the scaling code will likely keep the increase small.
1343   if (_g1->capacity() <= _g1->max_capacity() / 2) {
1344     threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1345     threshold = MAX2(threshold, 1.0);
1346   }
1347 
1348   // If the last GC time ratio is over the threshold, increment the count of
1349   // times it has been exceeded, and add this ratio to the sum of exceeded
1350   // ratios.
1351   if (last_gc_overhead > threshold) {
1352     _ratio_over_threshold_count++;
1353     _ratio_over_threshold_sum += last_gc_overhead;
1354   }
1355 
1356   // Check if we've had enough GC time ratio checks that were over the
1357   // threshold to trigger an expansion. We'll also expand if we've
1358   // reached the end of the history buffer and the average of all entries
1359   // is still over the threshold. This indicates a smaller number of GCs were
1360   // long enough to make the average exceed the threshold.
1361   bool filled_history_buffer = _pauses_since_start == NumPrevPausesForHeuristics;
1362   if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) ||
1363       (filled_history_buffer && (recent_gc_overhead > threshold))) {
1364     size_t min_expand_bytes = HeapRegion::GrainBytes;
1365     size_t reserved_bytes = _g1->max_capacity();
1366     size_t committed_bytes = _g1->capacity();
1367     size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1368     size_t expand_bytes_via_pct =
1369       uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1370     double scale_factor = 1.0;
1371 
1372     // If the current size is less than 1/4 of the Initial heap size, expand
1373     // by half of the delta between the current and Initial sizes. IE, grow
1374     // back quickly.
1375     //
1376     // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of
1377     // the available expansion space, whichever is smaller, as the base
1378     // expansion size. Then possibly scale this size according to how much the
1379     // threshold has (on average) been exceeded by. If the delta is small
1380     // (less than the StartScaleDownAt value), scale the size down linearly, but
1381     // not by less than MinScaleDownFactor. If the delta is large (greater than
1382     // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor
1383     // times the base size. The scaling will be linear in the range from
1384     // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words,
1385     // ScaleUpRange sets the rate of scaling up.
1386     if (committed_bytes < InitialHeapSize / 4) {
1387       expand_bytes = (InitialHeapSize - committed_bytes) / 2;
1388     } else {
1389       double const MinScaleDownFactor = 0.2;
1390       double const MaxScaleUpFactor = 2;
1391       double const StartScaleDownAt = _gc_overhead_perc;
1392       double const StartScaleUpAt = _gc_overhead_perc * 1.5;
1393       double const ScaleUpRange = _gc_overhead_perc * 2.0;
1394 
1395       double ratio_delta;
1396       if (filled_history_buffer) {
1397         ratio_delta = recent_gc_overhead - threshold;
1398       } else {
1399         ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold;
1400       }
1401 
1402       expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1403       if (ratio_delta < StartScaleDownAt) {
1404         scale_factor = ratio_delta / StartScaleDownAt;
1405         scale_factor = MAX2(scale_factor, MinScaleDownFactor);
1406       } else if (ratio_delta > StartScaleUpAt) {
1407         scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange);
1408         scale_factor = MIN2(scale_factor, MaxScaleUpFactor);
1409       }
1410     }
1411 
1412     log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) "
1413                               "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)",
1414                               recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100);
1415 
1416     expand_bytes = static_cast<size_t>(expand_bytes * scale_factor);
1417 
1418     // Ensure the expansion size is at least the minimum growth amount
1419     // and at most the remaining uncommitted byte size.
1420     expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1421     expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1422 
1423     clear_ratio_check_data();
1424   } else {
1425     // An expansion was not triggered. If we've started counting, increment
1426     // the number of checks we've made in the current window.  If we've
1427     // reached the end of the window without resizing, clear the counters to
1428     // start again the next time we see a ratio above the threshold.
1429     if (_ratio_over_threshold_count > 0) {
1430       _pauses_since_start++;
1431       if (_pauses_since_start > NumPrevPausesForHeuristics) {
1432         clear_ratio_check_data();
1433       }
1434     }
1435   }
1436 
1437   return expand_bytes;
1438 }
1439 
1440 void G1CollectorPolicy::print_yg_surv_rate_info() const {
1441 #ifndef PRODUCT
1442   _short_lived_surv_rate_group->print_surv_rate_summary();
1443   // add this call for any other surv rate groups
1444 #endif // PRODUCT
1445 }
1446 
1447 bool G1CollectorPolicy::is_young_list_full() const {
1448   uint young_list_length = _g1->young_list()->length();
1449   uint young_list_target_length = _young_list_target_length;
1450   return young_list_length >= young_list_target_length;
1451 }
1452 
1453 bool G1CollectorPolicy::can_expand_young_list() const {
1454   uint young_list_length = _g1->young_list()->length();
1455   uint young_list_max_length = _young_list_max_length;
1456   return young_list_length < young_list_max_length;
1457 }
1458 
1459 bool G1CollectorPolicy::adaptive_young_list_length() const {
1460   return _young_gen_sizer->adaptive_young_list_length();
1461 }
1462 
1463 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1464   uint expansion_region_num = 0;
1465   if (GCLockerEdenExpansionPercent > 0) {
1466     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1467     double expansion_region_num_d = perc * (double) _young_list_target_length;
1468     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1469     // less than 1.0) we'll get 1.
1470     expansion_region_num = (uint) ceil(expansion_region_num_d);
1471   } else {
1472     assert(expansion_region_num == 0, "sanity");
1473   }
1474   _young_list_max_length = _young_list_target_length + expansion_region_num;
1475   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1476 }
1477 
1478 // Calculates survivor space parameters.
1479 void G1CollectorPolicy::update_survivors_policy() {
1480   double max_survivor_regions_d =
1481                  (double) _young_list_target_length / (double) SurvivorRatio;
1482   // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1483   // smaller than 1.0) we'll get 1.
1484   _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1485 
1486   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1487         HeapRegion::GrainWords * _max_survivor_regions, counters());
1488 }
1489 
1490 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1491   // We actually check whether we are marking here and not if we are in a
1492   // reclamation phase. This means that we will schedule a concurrent mark
1493   // even while we are still in the process of reclaiming memory.
1494   bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1495   if (!during_cycle) {
1496     log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1497     collector_state()->set_initiate_conc_mark_if_possible(true);
1498     return true;
1499   } else {
1500     log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1501     return false;
1502   }
1503 }
1504 
1505 void G1CollectorPolicy::initiate_conc_mark() {
1506   collector_state()->set_during_initial_mark_pause(true);
1507   collector_state()->set_initiate_conc_mark_if_possible(false);
1508 }
1509 
1510 void G1CollectorPolicy::decide_on_conc_mark_initiation() {
1511   // We are about to decide on whether this pause will be an
1512   // initial-mark pause.
1513 
1514   // First, collector_state()->during_initial_mark_pause() should not be already set. We
1515   // will set it here if we have to. However, it should be cleared by
1516   // the end of the pause (it's only set for the duration of an
1517   // initial-mark pause).
1518   assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1519 
1520   if (collector_state()->initiate_conc_mark_if_possible()) {
1521     // We had noticed on a previous pause that the heap occupancy has
1522     // gone over the initiating threshold and we should start a
1523     // concurrent marking cycle. So we might initiate one.
1524 
1525     if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1526       // Initiate a new initial mark if there is no marking or reclamation going on.
1527       initiate_conc_mark();
1528       log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1529     } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
1530       // Initiate a user requested initial mark. An initial mark must be young only
1531       // GC, so the collector state must be updated to reflect this.
1532       collector_state()->set_gcs_are_young(true);
1533       collector_state()->set_last_young_gc(false);
1534 
1535       abort_time_to_mixed_tracking();
1536       initiate_conc_mark();
1537       log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1538     } else {
1539       // The concurrent marking thread is still finishing up the
1540       // previous cycle. If we start one right now the two cycles
1541       // overlap. In particular, the concurrent marking thread might
1542       // be in the process of clearing the next marking bitmap (which
1543       // we will use for the next cycle if we start one). Starting a
1544       // cycle now will be bad given that parts of the marking
1545       // information might get cleared by the marking thread. And we
1546       // cannot wait for the marking thread to finish the cycle as it
1547       // periodically yields while clearing the next marking bitmap
1548       // and, if it's in a yield point, it's waiting for us to
1549       // finish. So, at this point we will not start a cycle and we'll
1550       // let the concurrent marking thread complete the last one.
1551       log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1552     }
1553   }
1554 }
1555 
1556 class ParKnownGarbageHRClosure: public HeapRegionClosure {
1557   G1CollectedHeap* _g1h;
1558   CSetChooserParUpdater _cset_updater;
1559 
1560 public:
1561   ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
1562                            uint chunk_size) :
1563     _g1h(G1CollectedHeap::heap()),
1564     _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
1565 
1566   bool doHeapRegion(HeapRegion* r) {
1567     // Do we have any marking information for this region?
1568     if (r->is_marked()) {
1569       // We will skip any region that's currently used as an old GC
1570       // alloc region (we should not consider those for collection
1571       // before we fill them up).
1572       if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
1573         _cset_updater.add_region(r);
1574       }
1575     }
1576     return false;
1577   }
1578 };
1579 
1580 class ParKnownGarbageTask: public AbstractGangTask {
1581   CollectionSetChooser* _hrSorted;
1582   uint _chunk_size;
1583   G1CollectedHeap* _g1;
1584   HeapRegionClaimer _hrclaimer;
1585 
1586 public:
1587   ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size, uint n_workers) :
1588       AbstractGangTask("ParKnownGarbageTask"),
1589       _hrSorted(hrSorted), _chunk_size(chunk_size),
1590       _g1(G1CollectedHeap::heap()), _hrclaimer(n_workers) {}
1591 
1592   void work(uint worker_id) {
1593     ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
1594     _g1->heap_region_par_iterate(&parKnownGarbageCl, worker_id, &_hrclaimer);
1595   }
1596 };
1597 
1598 uint G1CollectorPolicy::calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const {
1599   assert(n_workers > 0, "Active gc workers should be greater than 0");
1600   const uint overpartition_factor = 4;
1601   const uint min_chunk_size = MAX2(n_regions / n_workers, 1U);
1602   return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
1603 }
1604 
1605 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1606   cset_chooser()->clear();
1607 
1608   WorkGang* workers = _g1->workers();
1609   uint n_workers = workers->active_workers();
1610 
1611   uint n_regions = _g1->num_regions();
1612   uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions);
1613   cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1614   ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers);
1615   workers->run_task(&par_known_garbage_task);
1616 
1617   cset_chooser()->sort_regions();
1618 
1619   double end_sec = os::elapsedTime();
1620   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1621   _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
1622   _prev_collection_pause_end_ms += elapsed_time_ms;
1623 
1624   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1625 }
1626 
1627 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1628   // Returns the given amount of reclaimable bytes (that represents
1629   // the amount of reclaimable space still to be collected) as a
1630   // percentage of the current heap capacity.
1631   size_t capacity_bytes = _g1->capacity();
1632   return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1633 }
1634 
1635 void G1CollectorPolicy::maybe_start_marking() {
1636   if (need_to_start_conc_mark("end of GC")) {
1637     // Note: this might have already been set, if during the last
1638     // pause we decided to start a cycle but at the beginning of
1639     // this pause we decided to postpone it. That's OK.
1640     collector_state()->set_initiate_conc_mark_if_possible(true);
1641   }
1642 }
1643 
1644 G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
1645   assert(!collector_state()->full_collection(), "must be");
1646   if (collector_state()->during_initial_mark_pause()) {
1647     assert(collector_state()->last_gc_was_young(), "must be");
1648     assert(!collector_state()->last_young_gc(), "must be");
1649     return InitialMarkGC;
1650   } else if (collector_state()->last_young_gc()) {
1651     assert(!collector_state()->during_initial_mark_pause(), "must be");
1652     assert(collector_state()->last_gc_was_young(), "must be");
1653     return LastYoungGC;
1654   } else if (!collector_state()->last_gc_was_young()) {
1655     assert(!collector_state()->during_initial_mark_pause(), "must be");
1656     assert(!collector_state()->last_young_gc(), "must be");
1657     return MixedGC;
1658   } else {
1659     assert(collector_state()->last_gc_was_young(), "must be");
1660     assert(!collector_state()->during_initial_mark_pause(), "must be");
1661     assert(!collector_state()->last_young_gc(), "must be");
1662     return YoungOnlyGC;
1663   }
1664 }
1665 
1666 void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
1667   // Manage the MMU tracker. For some reason it ignores Full GCs.
1668   if (kind != FullGC) {
1669     _mmu_tracker->add_pause(start, end);
1670   }
1671   // Manage the mutator time tracking from initial mark to first mixed gc.
1672   switch (kind) {
1673     case FullGC:
1674       abort_time_to_mixed_tracking();
1675       break;
1676     case Cleanup:
1677     case Remark:
1678     case YoungOnlyGC:
1679     case LastYoungGC:
1680       _initial_mark_to_mixed.add_pause(end - start);
1681       break;
1682     case InitialMarkGC:
1683       _initial_mark_to_mixed.record_initial_mark_end(end);
1684       break;
1685     case MixedGC:
1686       _initial_mark_to_mixed.record_mixed_gc_start(start);
1687       break;
1688     default:
1689       ShouldNotReachHere();
1690   }
1691 }
1692 
1693 void G1CollectorPolicy::abort_time_to_mixed_tracking() {
1694   _initial_mark_to_mixed.reset();
1695 }
1696 
1697 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
1698                                                 const char* false_action_str) const {
1699   if (cset_chooser()->is_empty()) {
1700     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1701     return false;
1702   }
1703 
1704   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1705   size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1706   double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
1707   double threshold = (double) G1HeapWastePercent;
1708   if (reclaimable_perc <= threshold) {
1709     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1710                         false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1711     return false;
1712   }
1713   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1714                       true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1715   return true;
1716 }
1717 
1718 uint G1CollectorPolicy::calc_min_old_cset_length() const {
1719   // The min old CSet region bound is based on the maximum desired
1720   // number of mixed GCs after a cycle. I.e., even if some old regions
1721   // look expensive, we should add them to the CSet anyway to make
1722   // sure we go through the available old regions in no more than the
1723   // maximum desired number of mixed GCs.
1724   //
1725   // The calculation is based on the number of marked regions we added
1726   // to the CSet chooser in the first place, not how many remain, so
1727   // that the result is the same during all mixed GCs that follow a cycle.
1728 
1729   const size_t region_num = (size_t) cset_chooser()->length();
1730   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1731   size_t result = region_num / gc_num;
1732   // emulate ceiling
1733   if (result * gc_num < region_num) {
1734     result += 1;
1735   }
1736   return (uint) result;
1737 }
1738 
1739 uint G1CollectorPolicy::calc_max_old_cset_length() const {
1740   // The max old CSet region bound is based on the threshold expressed
1741   // as a percentage of the heap size. I.e., it should bound the
1742   // number of old regions added to the CSet irrespective of how many
1743   // of them are available.
1744 
1745   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1746   const size_t region_num = g1h->num_regions();
1747   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1748   size_t result = region_num * perc / 100;
1749   // emulate ceiling
1750   if (100 * result < region_num * perc) {
1751     result += 1;
1752   }
1753   return (uint) result;
1754 }
1755 
1756 void G1CollectorPolicy::finalize_collection_set(double target_pause_time_ms) {
1757   double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
1758   _collection_set->finalize_old_part(time_remaining_ms);
1759 }
1760