rev 9277 : imported patch 8140597-forcing-initial-mark-causes-abort-mixed-collections
rev 9278 : imported patch 8139874-after-full-gc-next-gc-is-always-young-only
rev 9279 : imported patch 8138740-start-initial-mark-right-after-mixed-gc-if-needed
rev 9281 : imported patch 8140689-skip-last-young-if-nothing-to-do-in-mixed
rev 9282 : dihop-changes
rev 9284 : imported patch 8136678-implement-adaptive-sizing-algorithm-for-IHOP
rev 9286 : imported patch 8136679-jfr-event-for-dynamic-ihop

   1 /*
   2  * Copyright (c) 2001, 2015, 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/concurrentMark.hpp"
  28 #include "gc/g1/concurrentMarkThread.inline.hpp"
  29 #include "gc/g1/g1CollectedHeap.inline.hpp"
  30 #include "gc/g1/g1CollectorPolicy.hpp"
  31 #include "gc/g1/g1IHOPControl.hpp"
  32 #include "gc/g1/g1ErgoVerbose.hpp"
  33 #include "gc/g1/g1GCPhaseTimes.hpp"
  34 #include "gc/g1/g1Log.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 
  43 // Different defaults for different number of GC threads
  44 // They were chosen by running GCOld and SPECjbb on debris with different
  45 //   numbers of GC threads and choosing them based on the results
  46 
  47 // all the same
  48 static double rs_length_diff_defaults[] = {
  49   0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
  50 };
  51 
  52 static double cost_per_card_ms_defaults[] = {
  53   0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
  54 };
  55 
  56 // all the same
  57 static double young_cards_per_entry_ratio_defaults[] = {
  58   1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
  59 };
  60 
  61 static double cost_per_entry_ms_defaults[] = {
  62   0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
  63 };
  64 
  65 static double cost_per_byte_ms_defaults[] = {
  66   0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
  67 };
  68 
  69 // these should be pretty consistent
  70 static double constant_other_time_ms_defaults[] = {
  71   5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
  72 };
  73 
  74 
  75 static double young_other_cost_per_region_ms_defaults[] = {
  76   0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
  77 };
  78 
  79 static double non_young_other_cost_per_region_ms_defaults[] = {
  80   1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
  81 };
  82 
  83 G1CollectorPolicy::G1CollectorPolicy() :
  84   _predictor(G1ConfidencePercent / 100.0),
  85   _parallel_gc_threads(ParallelGCThreads),
  86 
  87   _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  88   _stop_world_start(0.0),
  89 
  90   _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  91   _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  92 
  93   _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  94   _prev_collection_pause_end_ms(0.0),
  95   _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
  96   _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  97   _cost_scan_hcc_seq(new TruncatedSeq(TruncatedSeqLength)),
  98   _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
  99   _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
 100   _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 101   _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 102   _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 103   _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
 104   _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 105   _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 106   _non_young_other_cost_per_region_ms_seq(
 107                                          new TruncatedSeq(TruncatedSeqLength)),
 108 
 109   _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
 110   _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
 111 
 112   _pause_time_target_ms((double) MaxGCPauseMillis),
 113 
 114   _recent_prev_end_times_for_all_gcs_sec(
 115                                 new TruncatedSeq(NumPrevPausesForHeuristics)),
 116 
 117   _recent_avg_pause_time_ratio(0.0),
 118   _rs_lengths_prediction(0),
 119   _max_survivor_regions(0),
 120 
 121   _eden_used_bytes_before_gc(0),
 122   _survivor_used_bytes_before_gc(0),
 123   _heap_used_bytes_before_gc(0),
 124   _metaspace_used_bytes_before_gc(0),
 125   _eden_capacity_bytes_before_gc(0),
 126   _heap_capacity_bytes_before_gc(0),
 127 
 128   _eden_cset_region_length(0),
 129   _survivor_cset_region_length(0),
 130   _old_cset_region_length(0),
 131 
 132   _collection_set(NULL),
 133   _collection_set_bytes_used_before(0),
 134 
 135   // Incremental CSet attributes
 136   _inc_cset_build_state(Inactive),
 137   _inc_cset_head(NULL),
 138   _inc_cset_tail(NULL),
 139   _inc_cset_bytes_used_before(0),
 140   _inc_cset_max_finger(NULL),
 141   _inc_cset_recorded_rs_lengths(0),
 142   _inc_cset_recorded_rs_lengths_diffs(0),
 143   _inc_cset_predicted_elapsed_time_ms(0.0),
 144   _inc_cset_predicted_elapsed_time_ms_diffs(0.0),
 145 
 146   // add here any more surv rate groups
 147   _recorded_survivor_regions(0),
 148   _recorded_survivor_head(NULL),
 149   _recorded_survivor_tail(NULL),
 150   _survivors_age_table(true),
 151 
 152   _gc_overhead_perc(0.0),
 153 
 154   _last_old_allocated_bytes(0),
 155   _ihop_control(NULL),
 156   _initial_mark_to_mixed() {
 157 
 158   // SurvRateGroups below must be initialized after the predictor because they
 159   // indirectly use it through this object passed to their constructor.
 160   _short_lived_surv_rate_group =
 161     new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
 162   _survivor_surv_rate_group =
 163     new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
 164 
 165   // Set up the region size and associated fields. Given that the
 166   // policy is created before the heap, we have to set this up here,
 167   // so it's done as soon as possible.
 168 
 169   // It would have been natural to pass initial_heap_byte_size() and
 170   // max_heap_byte_size() to setup_heap_region_size() but those have
 171   // not been set up at this point since they should be aligned with
 172   // the region size. So, there is a circular dependency here. We base
 173   // the region size on the heap size, but the heap size should be
 174   // aligned with the region size. To get around this we use the
 175   // unaligned values for the heap.
 176   HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
 177   HeapRegionRemSet::setup_remset_size();
 178 
 179   G1ErgoVerbose::initialize();
 180   if (PrintAdaptiveSizePolicy) {
 181     // Currently, we only use a single switch for all the heuristics.
 182     G1ErgoVerbose::set_enabled(true);
 183     // Given that we don't currently have a verboseness level
 184     // parameter, we'll hardcode this to high. This can be easily
 185     // changed in the future.
 186     G1ErgoVerbose::set_level(ErgoHigh);
 187   } else {
 188     G1ErgoVerbose::set_enabled(false);
 189   }
 190 
 191   _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
 192   _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
 193 
 194   _phase_times = new G1GCPhaseTimes(_parallel_gc_threads);
 195 
 196   int index = MIN2(_parallel_gc_threads - 1, 7);
 197 
 198   _rs_length_diff_seq->add(rs_length_diff_defaults[index]);
 199   _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
 200   _cost_scan_hcc_seq->add(0.0);
 201   _young_cards_per_entry_ratio_seq->add(
 202                                   young_cards_per_entry_ratio_defaults[index]);
 203   _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
 204   _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
 205   _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
 206   _young_other_cost_per_region_ms_seq->add(
 207                                young_other_cost_per_region_ms_defaults[index]);
 208   _non_young_other_cost_per_region_ms_seq->add(
 209                            non_young_other_cost_per_region_ms_defaults[index]);
 210 
 211   // Below, we might need to calculate the pause time target based on
 212   // the pause interval. When we do so we are going to give G1 maximum
 213   // flexibility and allow it to do pauses when it needs to. So, we'll
 214   // arrange that the pause interval to be pause time target + 1 to
 215   // ensure that a) the pause time target is maximized with respect to
 216   // the pause interval and b) we maintain the invariant that pause
 217   // time target < pause interval. If the user does not want this
 218   // maximum flexibility, they will have to set the pause interval
 219   // explicitly.
 220 
 221   // First make sure that, if either parameter is set, its value is
 222   // reasonable.
 223   if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 224     if (MaxGCPauseMillis < 1) {
 225       vm_exit_during_initialization("MaxGCPauseMillis should be "
 226                                     "greater than 0");
 227     }
 228   }
 229   if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 230     if (GCPauseIntervalMillis < 1) {
 231       vm_exit_during_initialization("GCPauseIntervalMillis should be "
 232                                     "greater than 0");
 233     }
 234   }
 235 
 236   // Then, if the pause time target parameter was not set, set it to
 237   // the default value.
 238   if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 239     if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 240       // The default pause time target in G1 is 200ms
 241       FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
 242     } else {
 243       // We do not allow the pause interval to be set without the
 244       // pause time target
 245       vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
 246                                     "without setting MaxGCPauseMillis");
 247     }
 248   }
 249 
 250   // Then, if the interval parameter was not set, set it according to
 251   // the pause time target (this will also deal with the case when the
 252   // pause time target is the default value).
 253   if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 254     FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
 255   }
 256 
 257   // Finally, make sure that the two parameters are consistent.
 258   if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
 259     char buffer[256];
 260     jio_snprintf(buffer, 256,
 261                  "MaxGCPauseMillis (%u) should be less than "
 262                  "GCPauseIntervalMillis (%u)",
 263                  MaxGCPauseMillis, GCPauseIntervalMillis);
 264     vm_exit_during_initialization(buffer);
 265   }
 266 
 267   double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
 268   double time_slice  = (double) GCPauseIntervalMillis / 1000.0;
 269   _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
 270 
 271   // start conservatively (around 50ms is about right)
 272   _concurrent_mark_remark_times_ms->add(0.05);
 273   _concurrent_mark_cleanup_times_ms->add(0.20);
 274   _tenuring_threshold = MaxTenuringThreshold;
 275 
 276   assert(GCTimeRatio > 0,
 277          "we should have set it to a default value set_g1_gc_flags() "
 278          "if a user set it to 0");
 279   _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
 280 
 281   uintx reserve_perc = G1ReservePercent;
 282   // Put an artificial ceiling on this so that it's not set to a silly value.
 283   if (reserve_perc > 50) {
 284     reserve_perc = 50;
 285     warning("G1ReservePercent is set to a value that is too large, "
 286             "it's been updated to " UINTX_FORMAT, reserve_perc);
 287   }
 288   _reserve_factor = (double) reserve_perc / 100.0;
 289   // This will be set when the heap is expanded
 290   // for the first time during initialization.
 291   _reserve_regions = 0;
 292 
 293   _collectionSetChooser = new CollectionSetChooser();
 294 }
 295 
 296 G1CollectorPolicy::~G1CollectorPolicy() {
 297   if (_ihop_control != NULL) {
 298     delete _ihop_control;
 299   }
 300 }
 301 
 302 double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const {
 303   return _predictor.get_new_prediction(seq);
 304 }
 305 
 306 void G1CollectorPolicy::initialize_alignments() {
 307   _space_alignment = HeapRegion::GrainBytes;
 308   size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
 309   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 310   _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
 311 }
 312 
 313 void G1CollectorPolicy::initialize_flags() {
 314   if (G1HeapRegionSize != HeapRegion::GrainBytes) {
 315     FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
 316   }
 317 
 318   if (SurvivorRatio < 1) {
 319     vm_exit_during_initialization("Invalid survivor ratio specified");
 320   }
 321   CollectorPolicy::initialize_flags();
 322   _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
 323 }
 324 
 325 void G1CollectorPolicy::post_heap_initialize() {
 326   uintx max_regions = G1CollectedHeap::heap()->max_regions();
 327   size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
 328   if (max_young_size != MaxNewSize) {
 329     FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
 330   }
 331 
 332   _ihop_control = create_ihop_control();
 333 }
 334 
 335 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
 336 
 337 G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true),
 338         _min_desired_young_length(0), _max_desired_young_length(0) {
 339   if (FLAG_IS_CMDLINE(NewRatio)) {
 340     if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
 341       warning("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio");
 342     } else {
 343       _sizer_kind = SizerNewRatio;
 344       _adaptive_size = false;
 345       return;
 346     }
 347   }
 348 
 349   if (NewSize > MaxNewSize) {
 350     if (FLAG_IS_CMDLINE(MaxNewSize)) {
 351       warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
 352               "A new max generation size of " SIZE_FORMAT "k will be used.",
 353               NewSize/K, MaxNewSize/K, NewSize/K);
 354     }
 355     MaxNewSize = NewSize;
 356   }
 357 
 358   if (FLAG_IS_CMDLINE(NewSize)) {
 359     _min_desired_young_length = MAX2((uint) (NewSize / HeapRegion::GrainBytes),
 360                                      1U);
 361     if (FLAG_IS_CMDLINE(MaxNewSize)) {
 362       _max_desired_young_length =
 363                              MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
 364                                   1U);
 365       _sizer_kind = SizerMaxAndNewSize;
 366       _adaptive_size = _min_desired_young_length == _max_desired_young_length;
 367     } else {
 368       _sizer_kind = SizerNewSizeOnly;
 369     }
 370   } else if (FLAG_IS_CMDLINE(MaxNewSize)) {
 371     _max_desired_young_length =
 372                              MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
 373                                   1U);
 374     _sizer_kind = SizerMaxNewSizeOnly;
 375   }
 376 }
 377 
 378 uint G1YoungGenSizer::calculate_default_min_length(uint new_number_of_heap_regions) {
 379   uint default_value = (new_number_of_heap_regions * G1NewSizePercent) / 100;
 380   return MAX2(1U, default_value);
 381 }
 382 
 383 uint G1YoungGenSizer::calculate_default_max_length(uint new_number_of_heap_regions) {
 384   uint default_value = (new_number_of_heap_regions * G1MaxNewSizePercent) / 100;
 385   return MAX2(1U, default_value);
 386 }
 387 
 388 void G1YoungGenSizer::recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length) {
 389   assert(number_of_heap_regions > 0, "Heap must be initialized");
 390 
 391   switch (_sizer_kind) {
 392     case SizerDefaults:
 393       *min_young_length = calculate_default_min_length(number_of_heap_regions);
 394       *max_young_length = calculate_default_max_length(number_of_heap_regions);
 395       break;
 396     case SizerNewSizeOnly:
 397       *max_young_length = calculate_default_max_length(number_of_heap_regions);
 398       *max_young_length = MAX2(*min_young_length, *max_young_length);
 399       break;
 400     case SizerMaxNewSizeOnly:
 401       *min_young_length = calculate_default_min_length(number_of_heap_regions);
 402       *min_young_length = MIN2(*min_young_length, *max_young_length);
 403       break;
 404     case SizerMaxAndNewSize:
 405       // Do nothing. Values set on the command line, don't update them at runtime.
 406       break;
 407     case SizerNewRatio:
 408       *min_young_length = number_of_heap_regions / (NewRatio + 1);
 409       *max_young_length = *min_young_length;
 410       break;
 411     default:
 412       ShouldNotReachHere();
 413   }
 414 
 415   assert(*min_young_length <= *max_young_length, "Invalid min/max young gen size values");
 416 }
 417 
 418 uint G1YoungGenSizer::max_young_length(uint number_of_heap_regions) {
 419   // We need to pass the desired values because recalculation may not update these
 420   // values in some cases.
 421   uint temp = _min_desired_young_length;
 422   uint result = _max_desired_young_length;
 423   recalculate_min_max_young_length(number_of_heap_regions, &temp, &result);
 424   return result;
 425 }
 426 
 427 void G1YoungGenSizer::heap_size_changed(uint new_number_of_heap_regions) {
 428   recalculate_min_max_young_length(new_number_of_heap_regions, &_min_desired_young_length,
 429           &_max_desired_young_length);
 430 }
 431 
 432 void G1CollectorPolicy::init() {
 433   // Set aside an initial future to_space.
 434   _g1 = G1CollectedHeap::heap();
 435 
 436   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 437 
 438   initialize_gc_policy_counters();
 439 
 440   if (adaptive_young_list_length()) {
 441     _young_list_fixed_length = 0;
 442   } else {
 443     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 444   }
 445   _free_regions_at_end_of_collection = _g1->num_free_regions();
 446 
 447   update_young_list_max_and_target_length();
 448   // We may immediately start allocating regions and placing them on the
 449   // collection set list. Initialize the per-collection set info
 450   start_incremental_cset_building();
 451 }
 452 
 453 void G1CollectorPolicy::note_gc_start(uint num_active_workers) {
 454   phase_times()->note_gc_start(num_active_workers);
 455 }
 456 
 457 // Create the jstat counters for the policy.
 458 void G1CollectorPolicy::initialize_gc_policy_counters() {
 459   _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
 460 }
 461 
 462 bool G1CollectorPolicy::predict_will_fit(uint young_length,
 463                                          double base_time_ms,
 464                                          uint base_free_regions,
 465                                          double target_pause_time_ms) const {
 466   if (young_length >= base_free_regions) {
 467     // end condition 1: not enough space for the young regions
 468     return false;
 469   }
 470 
 471   double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
 472   size_t bytes_to_copy =
 473                (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
 474   double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
 475   double young_other_time_ms = predict_young_other_time_ms(young_length);
 476   double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
 477   if (pause_time_ms > target_pause_time_ms) {
 478     // end condition 2: prediction is over the target pause time
 479     return false;
 480   }
 481 
 482   size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
 483   if ((2.0 /* magic */ * _predictor.sigma()) * bytes_to_copy > free_bytes) {
 484     // end condition 3: out-of-space (conservatively!)
 485     return false;
 486   }
 487 
 488   // success!
 489   return true;
 490 }
 491 
 492 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
 493   // re-calculate the necessary reserve
 494   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 495   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 496   // smaller than 1.0) we'll get 1.
 497   _reserve_regions = (uint) ceil(reserve_regions_d);
 498 
 499   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 500 }
 501 
 502 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
 503                                                        uint base_min_length) const {
 504   uint desired_min_length = 0;
 505   if (adaptive_young_list_length()) {
 506     if (_alloc_rate_ms_seq->num() > 3) {
 507       double now_sec = os::elapsedTime();
 508       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 509       double alloc_rate_ms = predict_alloc_rate_ms();
 510       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 511     } else {
 512       // otherwise we don't have enough info to make the prediction
 513     }
 514   }
 515   desired_min_length += base_min_length;
 516   // make sure we don't go below any user-defined minimum bound
 517   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 518 }
 519 
 520 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
 521   // Here, we might want to also take into account any additional
 522   // constraints (i.e., user-defined minimum bound). Currently, we
 523   // effectively don't set this bound.
 524   return _young_gen_sizer->max_desired_young_length();
 525 }
 526 
 527 void G1CollectorPolicy::update_young_list_max_and_target_length(size_t* unbounded_target_length) {
 528   update_young_list_max_and_target_length(get_new_prediction(_rs_lengths_seq), unbounded_target_length);
 529 }
 530 
 531 void G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths, size_t* unbounded_target_length) {
 532   update_young_list_target_length(rs_lengths, unbounded_target_length);
 533   update_max_gc_locker_expansion();
 534 }
 535 
 536 void G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths, size_t* unbounded_target_length) {
 537   _young_list_target_length = bounded_young_list_target_length(rs_lengths, unbounded_target_length);
 538 }
 539 
 540 void G1CollectorPolicy::update_young_list_target_length() {
 541   update_young_list_target_length(get_new_prediction(_rs_lengths_seq));
 542 }
 543 
 544 uint G1CollectorPolicy::bounded_young_list_target_length(size_t rs_lengths, size_t* unbounded_target_length) const {
 545   // Calculate the absolute and desired min bounds.
 546 
 547   // This is how many young regions we already have (currently: the survivors).
 548   uint base_min_length = recorded_survivor_regions();
 549   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 550   // This is the absolute minimum young length. Ensure that we
 551   // will at least have one eden region available for allocation.
 552   uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
 553   // If we shrank the young list target it should not shrink below the current size.
 554   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 555   // Calculate the absolute and desired max bounds.
 556 
 557   uint desired_max_length = calculate_young_list_desired_max_length();
 558 
 559   uint young_list_target_length = 0;
 560   if (adaptive_young_list_length()) {
 561     if (collector_state()->gcs_are_young()) {
 562       young_list_target_length =
 563                         calculate_young_list_target_length(rs_lengths,
 564                                                            base_min_length,
 565                                                            desired_min_length,
 566                                                            desired_max_length);
 567     } else {
 568       // Don't calculate anything and let the code below bound it to
 569       // the desired_min_length, i.e., do the next GC as soon as
 570       // possible to maximize how many old regions we can add to it.
 571     }
 572   } else {
 573     // The user asked for a fixed young gen so we'll fix the young gen
 574     // whether the next GC is young or mixed.
 575     young_list_target_length = _young_list_fixed_length;
 576   }
 577 
 578   if (unbounded_target_length != NULL) {
 579     *unbounded_target_length = young_list_target_length;    
 580   }
 581   
 582   // We will try our best not to "eat" into the reserve.
 583   uint absolute_max_length = 0;
 584   if (_free_regions_at_end_of_collection > _reserve_regions) {
 585     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 586   }
 587   if (desired_max_length > absolute_max_length) {
 588     desired_max_length = absolute_max_length;
 589   }
 590 
 591   // Make sure we don't go over the desired max length, nor under the
 592   // desired min length. In case they clash, desired_min_length wins
 593   // which is why that test is second.
 594   if (young_list_target_length > desired_max_length) {
 595     young_list_target_length = desired_max_length;
 596   }
 597   if (young_list_target_length < desired_min_length) {
 598     young_list_target_length = desired_min_length;
 599   }
 600 
 601   assert(young_list_target_length > recorded_survivor_regions(),
 602          "we should be able to allocate at least one eden region");
 603   assert(young_list_target_length >= absolute_min_length, "post-condition");
 604 
 605   return young_list_target_length;
 606 }
 607 
 608 uint
 609 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
 610                                                      uint base_min_length,
 611                                                      uint desired_min_length,
 612                                                      uint desired_max_length) const {
 613   assert(adaptive_young_list_length(), "pre-condition");
 614   assert(collector_state()->gcs_are_young(), "only call this for young GCs");
 615 
 616   // In case some edge-condition makes the desired max length too small...
 617   if (desired_max_length <= desired_min_length) {
 618     return desired_min_length;
 619   }
 620 
 621   // We'll adjust min_young_length and max_young_length not to include
 622   // the already allocated young regions (i.e., so they reflect the
 623   // min and max eden regions we'll allocate). The base_min_length
 624   // will be reflected in the predictions by the
 625   // survivor_regions_evac_time prediction.
 626   assert(desired_min_length > base_min_length, "invariant");
 627   uint min_young_length = desired_min_length - base_min_length;
 628   assert(desired_max_length > base_min_length, "invariant");
 629   uint max_young_length = desired_max_length - base_min_length;
 630 
 631   double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 632   double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 633   size_t pending_cards = (size_t) get_new_prediction(_pending_cards_seq);
 634   size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
 635   size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
 636   double base_time_ms =
 637     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
 638     survivor_regions_evac_time;
 639   uint available_free_regions = _free_regions_at_end_of_collection;
 640   uint base_free_regions = 0;
 641   if (available_free_regions > _reserve_regions) {
 642     base_free_regions = available_free_regions - _reserve_regions;
 643   }
 644 
 645   // Here, we will make sure that the shortest young length that
 646   // makes sense fits within the target pause time.
 647 
 648   if (predict_will_fit(min_young_length, base_time_ms,
 649                        base_free_regions, target_pause_time_ms)) {
 650     // The shortest young length will fit into the target pause time;
 651     // we'll now check whether the absolute maximum number of young
 652     // regions will fit in the target pause time. If not, we'll do
 653     // a binary search between min_young_length and max_young_length.
 654     if (predict_will_fit(max_young_length, base_time_ms,
 655                          base_free_regions, target_pause_time_ms)) {
 656       // The maximum young length will fit into the target pause time.
 657       // We are done so set min young length to the maximum length (as
 658       // the result is assumed to be returned in min_young_length).
 659       min_young_length = max_young_length;
 660     } else {
 661       // The maximum possible number of young regions will not fit within
 662       // the target pause time so we'll search for the optimal
 663       // length. The loop invariants are:
 664       //
 665       // min_young_length < max_young_length
 666       // min_young_length is known to fit into the target pause time
 667       // max_young_length is known not to fit into the target pause time
 668       //
 669       // Going into the loop we know the above hold as we've just
 670       // checked them. Every time around the loop we check whether
 671       // the middle value between min_young_length and
 672       // max_young_length fits into the target pause time. If it
 673       // does, it becomes the new min. If it doesn't, it becomes
 674       // the new max. This way we maintain the loop invariants.
 675 
 676       assert(min_young_length < max_young_length, "invariant");
 677       uint diff = (max_young_length - min_young_length) / 2;
 678       while (diff > 0) {
 679         uint young_length = min_young_length + diff;
 680         if (predict_will_fit(young_length, base_time_ms,
 681                              base_free_regions, target_pause_time_ms)) {
 682           min_young_length = young_length;
 683         } else {
 684           max_young_length = young_length;
 685         }
 686         assert(min_young_length <  max_young_length, "invariant");
 687         diff = (max_young_length - min_young_length) / 2;
 688       }
 689       // The results is min_young_length which, according to the
 690       // loop invariants, should fit within the target pause time.
 691 
 692       // These are the post-conditions of the binary search above:
 693       assert(min_young_length < max_young_length,
 694              "otherwise we should have discovered that max_young_length "
 695              "fits into the pause target and not done the binary search");
 696       assert(predict_will_fit(min_young_length, base_time_ms,
 697                               base_free_regions, target_pause_time_ms),
 698              "min_young_length, the result of the binary search, should "
 699              "fit into the pause target");
 700       assert(!predict_will_fit(min_young_length + 1, base_time_ms,
 701                                base_free_regions, target_pause_time_ms),
 702              "min_young_length, the result of the binary search, should be "
 703              "optimal, so no larger length should fit into the pause target");
 704     }
 705   } else {
 706     // Even the minimum length doesn't fit into the pause time
 707     // target, return it as the result nevertheless.
 708   }
 709   return base_min_length + min_young_length;
 710 }
 711 
 712 double G1CollectorPolicy::predict_survivor_regions_evac_time() const {
 713   double survivor_regions_evac_time = 0.0;
 714   for (HeapRegion * r = _recorded_survivor_head;
 715        r != NULL && r != _recorded_survivor_tail->get_next_young_region();
 716        r = r->get_next_young_region()) {
 717     survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
 718   }
 719   return survivor_regions_evac_time;
 720 }
 721 
 722 void G1CollectorPolicy::revise_young_list_target_length_if_necessary() {
 723   guarantee( adaptive_young_list_length(), "should not call this otherwise" );
 724 
 725   size_t rs_lengths = _g1->young_list()->sampled_rs_lengths();
 726   if (rs_lengths > _rs_lengths_prediction) {
 727     // add 10% to avoid having to recalculate often
 728     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 729     update_rs_lengths_prediction(rs_lengths_prediction);
 730 
 731     update_young_list_max_and_target_length(rs_lengths_prediction);
 732   }
 733 }
 734 
 735 void G1CollectorPolicy::update_rs_lengths_prediction() {
 736   update_rs_lengths_prediction(get_new_prediction(_rs_lengths_seq));
 737 }
 738 
 739 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
 740   if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
 741     _rs_lengths_prediction = prediction;
 742   }
 743 }
 744 
 745 HeapWord* G1CollectorPolicy::mem_allocate_work(size_t size,
 746                                                bool is_tlab,
 747                                                bool* gc_overhead_limit_was_exceeded) {
 748   guarantee(false, "Not using this policy feature yet.");
 749   return NULL;
 750 }
 751 
 752 // This method controls how a collector handles one or more
 753 // of its generations being fully allocated.
 754 HeapWord* G1CollectorPolicy::satisfy_failed_allocation(size_t size,
 755                                                        bool is_tlab) {
 756   guarantee(false, "Not using this policy feature yet.");
 757   return NULL;
 758 }
 759 
 760 
 761 #ifndef PRODUCT
 762 bool G1CollectorPolicy::verify_young_ages() {
 763   HeapRegion* head = _g1->young_list()->first_region();
 764   return
 765     verify_young_ages(head, _short_lived_surv_rate_group);
 766   // also call verify_young_ages on any additional surv rate groups
 767 }
 768 
 769 bool
 770 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
 771                                      SurvRateGroup *surv_rate_group) {
 772   guarantee( surv_rate_group != NULL, "pre-condition" );
 773 
 774   const char* name = surv_rate_group->name();
 775   bool ret = true;
 776   int prev_age = -1;
 777 
 778   for (HeapRegion* curr = head;
 779        curr != NULL;
 780        curr = curr->get_next_young_region()) {
 781     SurvRateGroup* group = curr->surv_rate_group();
 782     if (group == NULL && !curr->is_survivor()) {
 783       gclog_or_tty->print_cr("## %s: encountered NULL surv_rate_group", name);
 784       ret = false;
 785     }
 786 
 787     if (surv_rate_group == group) {
 788       int age = curr->age_in_surv_rate_group();
 789 
 790       if (age < 0) {
 791         gclog_or_tty->print_cr("## %s: encountered negative age", name);
 792         ret = false;
 793       }
 794 
 795       if (age <= prev_age) {
 796         gclog_or_tty->print_cr("## %s: region ages are not strictly increasing "
 797                                "(%d, %d)", name, age, prev_age);
 798         ret = false;
 799       }
 800       prev_age = age;
 801     }
 802   }
 803 
 804   return ret;
 805 }
 806 #endif // PRODUCT
 807 
 808 void G1CollectorPolicy::record_full_collection_start() {
 809   _full_collection_start_sec = os::elapsedTime();
 810   record_heap_size_info_at_start(true /* full */);
 811   // Release the future to-space so that it is available for compaction into.
 812   collector_state()->set_full_collection(true);
 813 }
 814 
 815 void G1CollectorPolicy::record_full_collection_end() {
 816   // Consider this like a collection pause for the purposes of allocation
 817   // since last pause.
 818   double end_sec = os::elapsedTime();
 819   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 820   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 821 
 822   _trace_old_gen_time_data.record_full_collection(full_gc_time_ms);
 823 
 824   update_recent_gc_times(end_sec, full_gc_time_ms);
 825 
 826   collector_state()->set_full_collection(false);
 827 
 828   // "Nuke" the heuristics that control the young/mixed GC
 829   // transitions and make sure we start with young GCs after the Full GC.
 830   collector_state()->set_gcs_are_young(true);
 831   collector_state()->set_last_young_gc(false);
 832   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
 833   collector_state()->set_during_initial_mark_pause(false);
 834   collector_state()->set_in_marking_window(false);
 835   collector_state()->set_in_marking_window_im(false);
 836 
 837   _short_lived_surv_rate_group->start_adding_regions();
 838   // also call this on any additional surv rate groups
 839 
 840   record_survivor_regions(0, NULL, NULL);
 841 
 842   _free_regions_at_end_of_collection = _g1->num_free_regions();
 843   // Reset survivors SurvRateGroup.
 844   _survivor_surv_rate_group->reset();
 845   update_young_list_max_and_target_length();
 846   update_rs_lengths_prediction();
 847   _collectionSetChooser->clear();
 848 
 849   _last_old_allocated_bytes = 0;
 850 
 851   record_pause(FullGC, _full_collection_start_sec, end_sec);
 852 }
 853 
 854 void G1CollectorPolicy::record_stop_world_start() {
 855   _stop_world_start = os::elapsedTime();
 856 }
 857 
 858 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) {
 859   // We only need to do this here as the policy will only be applied
 860   // to the GC we're about to start. so, no point is calculating this
 861   // every time we calculate / recalculate the target young length.
 862   update_survivors_policy();
 863 
 864   assert(_g1->used() == _g1->recalculate_used(),
 865          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
 866          _g1->used(), _g1->recalculate_used());
 867 
 868   double s_w_t_ms = (start_time_sec - _stop_world_start) * 1000.0;
 869   _trace_young_gen_time_data.record_start_collection(s_w_t_ms);
 870   _stop_world_start = 0.0;
 871 
 872   record_heap_size_info_at_start(false /* full */);
 873 
 874   phase_times()->record_cur_collection_start_sec(start_time_sec);
 875   _pending_cards = _g1->pending_card_num();
 876 
 877   _collection_set_bytes_used_before = 0;
 878   _bytes_copied_during_gc = 0;
 879 
 880   collector_state()->set_last_gc_was_young(false);
 881 
 882   // do that for any other surv rate groups
 883   _short_lived_surv_rate_group->stop_adding_regions();
 884   _survivors_age_table.clear();
 885 
 886   assert( verify_young_ages(), "region age verification" );
 887 }
 888 
 889 void G1CollectorPolicy::record_concurrent_mark_init_end(double
 890                                                    mark_init_elapsed_time_ms) {
 891   collector_state()->set_during_marking(true);
 892   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 893   collector_state()->set_during_initial_mark_pause(false);
 894   _cur_mark_stop_world_time_ms = mark_init_elapsed_time_ms;
 895 }
 896 
 897 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
 898   _mark_remark_start_sec = os::elapsedTime();
 899   collector_state()->set_during_marking(false);
 900 }
 901 
 902 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
 903   double end_time_sec = os::elapsedTime();
 904   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 905   _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
 906   _cur_mark_stop_world_time_ms += elapsed_time_ms;
 907   _prev_collection_pause_end_ms += elapsed_time_ms;
 908 
 909   record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 910 }
 911 
 912 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
 913   _mark_cleanup_start_sec = os::elapsedTime();
 914 }
 915 
 916 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
 917   bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
 918                                                               "skip last young-only gc");
 919   collector_state()->set_last_young_gc(should_continue_with_reclaim);
 920   // We abort the marking phase.
 921   if (!should_continue_with_reclaim) {
 922     abort_time_to_mixed_tracking();
 923   }
 924   collector_state()->set_in_marking_window(false);
 925 }
 926 
 927 void G1CollectorPolicy::record_concurrent_pause() {
 928   if (_stop_world_start > 0.0) {
 929     double yield_ms = (os::elapsedTime() - _stop_world_start) * 1000.0;
 930     _trace_young_gen_time_data.record_yield_time(yield_ms);
 931   }
 932 }
 933 
 934 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
 935   return phase_times()->average_time_ms(phase);
 936 }
 937 
 938 double G1CollectorPolicy::young_other_time_ms() const {
 939   return phase_times()->young_cset_choice_time_ms() +
 940          phase_times()->young_free_cset_time_ms();
 941 }
 942 
 943 double G1CollectorPolicy::non_young_other_time_ms() const {
 944   return phase_times()->non_young_cset_choice_time_ms() +
 945          phase_times()->non_young_free_cset_time_ms();
 946 
 947 }
 948 
 949 double G1CollectorPolicy::other_time_ms(double pause_time_ms) const {
 950   return pause_time_ms -
 951          average_time_ms(G1GCPhaseTimes::UpdateRS) -
 952          average_time_ms(G1GCPhaseTimes::ScanRS) -
 953          average_time_ms(G1GCPhaseTimes::ObjCopy) -
 954          average_time_ms(G1GCPhaseTimes::Termination);
 955 }
 956 
 957 double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const {
 958   return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
 959 }
 960 
 961 bool G1CollectorPolicy::about_to_start_mixed_phase() const {
 962   return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
 963 }
 964 
 965 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
 966   if (about_to_start_mixed_phase()) {
 967     return false;
 968   }
 969 
 970   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
 971 
 972   size_t cur_used_bytes = _g1->non_young_capacity_bytes();
 973   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 974   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 975 
 976   if (marking_request_bytes > marking_initiating_used_threshold) {
 977     if (collector_state()->gcs_are_young() && !collector_state()->last_young_gc()) {
 978       ergo_verbose5(ErgoConcCycles,
 979         "request concurrent cycle initiation",
 980         ergo_format_reason("occupancy higher than threshold")
 981         ergo_format_byte("occupancy")
 982         ergo_format_byte("allocation request")
 983         ergo_format_byte_perc("threshold")
 984         ergo_format_str("source"),
 985         cur_used_bytes,
 986         alloc_byte_size,
 987         marking_initiating_used_threshold,
 988         (double) marking_initiating_used_threshold / _g1->capacity() * 100,
 989         source);
 990       return true;
 991     } else {
 992       ergo_verbose5(ErgoConcCycles,
 993         "do not request concurrent cycle initiation",
 994         ergo_format_reason("still doing mixed collections")
 995         ergo_format_byte("occupancy")
 996         ergo_format_byte("allocation request")
 997         ergo_format_byte_perc("threshold")
 998         ergo_format_str("source"),
 999         cur_used_bytes,
1000         alloc_byte_size,
1001         marking_initiating_used_threshold,
1002         (double) InitiatingHeapOccupancyPercent,
1003         source);
1004     }
1005   }
1006 
1007   return false;
1008 }
1009 
1010 // Anything below that is considered to be zero
1011 #define MIN_TIMER_GRANULARITY 0.0000001
1012 
1013 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned) {
1014   double end_time_sec = os::elapsedTime();
1015   assert(_cur_collection_pause_used_regions_at_start >= cset_region_length(),
1016          "otherwise, the subtraction below does not make sense");
1017   size_t cur_used_bytes = _g1->used();
1018   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
1019   bool last_pause_included_initial_mark = false;
1020   bool update_stats = !_g1->evacuation_failed();
1021 
1022 #ifndef PRODUCT
1023   if (G1YoungSurvRateVerbose) {
1024     gclog_or_tty->cr();
1025     _short_lived_surv_rate_group->print();
1026     // do that for any other surv rate groups too
1027   }
1028 #endif // PRODUCT
1029 
1030   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
1031 
1032   last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
1033   if (last_pause_included_initial_mark) {
1034     record_concurrent_mark_init_end(0.0);
1035   } else {
1036     maybe_start_marking();
1037   }
1038 
1039   double app_time_ms = 1.0;
1040 
1041   if (update_stats) {
1042     _trace_young_gen_time_data.record_end_collection(pause_time_ms, phase_times());
1043     // this is where we update the allocation rate of the application
1044     app_time_ms =
1045       (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
1046     if (app_time_ms < MIN_TIMER_GRANULARITY) {
1047       // This usually happens due to the timer not having the required
1048       // granularity. Some Linuxes are the usual culprits.
1049       // We'll just set it to something (arbitrarily) small.
1050       app_time_ms = 1.0;
1051     }
1052     // We maintain the invariant that all objects allocated by mutator
1053     // threads will be allocated out of eden regions. So, we can use
1054     // the eden region number allocated since the previous GC to
1055     // calculate the application's allocate rate. The only exception
1056     // to that is humongous objects that are allocated separately. But
1057     // given that humongous object allocations do not really affect
1058     // either the pause's duration nor when the next pause will take
1059     // place we can safely ignore them here.
1060     uint regions_allocated = eden_cset_region_length();
1061     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
1062     _alloc_rate_ms_seq->add(alloc_rate_ms);
1063 
1064     double interval_ms =
1065       (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
1066     update_recent_gc_times(end_time_sec, pause_time_ms);
1067     _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
1068     if (recent_avg_pause_time_ratio() < 0.0 ||
1069         (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
1070 #ifndef PRODUCT
1071       // Dump info to allow post-facto debugging
1072       gclog_or_tty->print_cr("recent_avg_pause_time_ratio() out of bounds");
1073       gclog_or_tty->print_cr("-------------------------------------------");
1074       gclog_or_tty->print_cr("Recent GC Times (ms):");
1075       _recent_gc_times_ms->dump();
1076       gclog_or_tty->print_cr("(End Time=%3.3f) Recent GC End Times (s):", end_time_sec);
1077       _recent_prev_end_times_for_all_gcs_sec->dump();
1078       gclog_or_tty->print_cr("GC = %3.3f, Interval = %3.3f, Ratio = %3.3f",
1079                              _recent_gc_times_ms->sum(), interval_ms, recent_avg_pause_time_ratio());
1080       // In debug mode, terminate the JVM if the user wants to debug at this point.
1081       assert(!G1FailOnFPError, "Debugging data for CR 6898948 has been dumped above");
1082 #endif  // !PRODUCT
1083       // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
1084       // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
1085       if (_recent_avg_pause_time_ratio < 0.0) {
1086         _recent_avg_pause_time_ratio = 0.0;
1087       } else {
1088         assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
1089         _recent_avg_pause_time_ratio = 1.0;
1090       }
1091     }
1092   }
1093 
1094   bool new_in_marking_window = collector_state()->in_marking_window();
1095   bool new_in_marking_window_im = false;
1096   if (last_pause_included_initial_mark) {
1097     new_in_marking_window = true;
1098     new_in_marking_window_im = true;
1099   }
1100 
1101   if (collector_state()->last_young_gc()) {
1102     // This is supposed to to be the "last young GC" before we start
1103     // doing mixed GCs. Here we decide whether to start mixed GCs or not.
1104     assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
1105 
1106     if (next_gc_should_be_mixed("start mixed GCs",
1107                                 "do not start mixed GCs")) {
1108       collector_state()->set_gcs_are_young(false);
1109     } else {
1110       // We aborted the mixed GC phase early.
1111       abort_time_to_mixed_tracking();
1112     }
1113 
1114     collector_state()->set_last_young_gc(false);
1115   }
1116 
1117   if (!collector_state()->last_gc_was_young()) {
1118     // This is a mixed GC. Here we decide whether to continue doing
1119     // mixed GCs or not.
1120     if (!next_gc_should_be_mixed("continue mixed GCs",
1121                                  "do not continue mixed GCs")) {
1122       collector_state()->set_gcs_are_young(true);
1123 
1124       maybe_start_marking();
1125     }
1126   }
1127 
1128   _short_lived_surv_rate_group->start_adding_regions();
1129   // Do that for any other surv rate groups
1130 
1131   if (update_stats) {
1132     double cost_per_card_ms = 0.0;
1133     double cost_scan_hcc = average_time_ms(G1GCPhaseTimes::ScanHCC);
1134     if (_pending_cards > 0) {
1135       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - cost_scan_hcc) / (double) _pending_cards;
1136       _cost_per_card_ms_seq->add(cost_per_card_ms);
1137     }
1138     _cost_scan_hcc_seq->add(cost_scan_hcc);
1139 
1140     double cost_per_entry_ms = 0.0;
1141     if (cards_scanned > 10) {
1142       cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
1143       if (collector_state()->last_gc_was_young()) {
1144         _cost_per_entry_ms_seq->add(cost_per_entry_ms);
1145       } else {
1146         _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
1147       }
1148     }
1149 
1150     if (_max_rs_lengths > 0) {
1151       double cards_per_entry_ratio =
1152         (double) cards_scanned / (double) _max_rs_lengths;
1153       if (collector_state()->last_gc_was_young()) {
1154         _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1155       } else {
1156         _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1157       }
1158     }
1159 
1160     // This is defensive. For a while _max_rs_lengths could get
1161     // smaller than _recorded_rs_lengths which was causing
1162     // rs_length_diff to get very large and mess up the RSet length
1163     // predictions. The reason was unsafe concurrent updates to the
1164     // _inc_cset_recorded_rs_lengths field which the code below guards
1165     // against (see CR 7118202). This bug has now been fixed (see CR
1166     // 7119027). However, I'm still worried that
1167     // _inc_cset_recorded_rs_lengths might still end up somewhat
1168     // inaccurate. The concurrent refinement thread calculates an
1169     // RSet's length concurrently with other CR threads updating it
1170     // which might cause it to calculate the length incorrectly (if,
1171     // say, it's in mid-coarsening). So I'll leave in the defensive
1172     // conditional below just in case.
1173     size_t rs_length_diff = 0;
1174     if (_max_rs_lengths > _recorded_rs_lengths) {
1175       rs_length_diff = _max_rs_lengths - _recorded_rs_lengths;
1176     }
1177     _rs_length_diff_seq->add((double) rs_length_diff);
1178 
1179     size_t freed_bytes = _heap_used_bytes_before_gc - cur_used_bytes;
1180     size_t copied_bytes = _collection_set_bytes_used_before - freed_bytes;
1181     double cost_per_byte_ms = 0.0;
1182 
1183     if (copied_bytes > 0) {
1184       cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
1185       if (collector_state()->in_marking_window()) {
1186         _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
1187       } else {
1188         _cost_per_byte_ms_seq->add(cost_per_byte_ms);
1189       }
1190     }
1191 
1192     if (young_cset_region_length() > 0) {
1193       _young_other_cost_per_region_ms_seq->add(young_other_time_ms() /
1194                                                young_cset_region_length());
1195     }
1196 
1197     if (old_cset_region_length() > 0) {
1198       _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() /
1199                                                    old_cset_region_length());
1200     }
1201 
1202     _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms));
1203 
1204     _pending_cards_seq->add((double) _pending_cards);
1205     _rs_lengths_seq->add((double) _max_rs_lengths);
1206   }
1207 
1208   collector_state()->set_in_marking_window(new_in_marking_window);
1209   collector_state()->set_in_marking_window_im(new_in_marking_window_im);
1210   _free_regions_at_end_of_collection = _g1->num_free_regions();
1211   // IHOP control wants to know the expected young gen length if it were not
1212   // restrained by the heap reserve. Using the actual length would make the
1213   // prediction too small and the limit the young gen every time we get to the
1214   // predicted target occupancy.
1215   size_t last_unrestrained_young_length = 0;
1216   update_young_list_max_and_target_length(&last_unrestrained_young_length);
1217   update_rs_lengths_prediction();
1218 
1219   double marking_to_mixed_time = -1.0;
1220   if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
1221     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
1222     assert(marking_to_mixed_time > 0.0,
1223            "Initial mark to mixed time must be larger than zero but is %.3f",
1224            marking_to_mixed_time);
1225   }
1226   // Only update IHOP information on regular GCs.
1227   if (update_stats) {
1228     update_ihop_statistics(marking_to_mixed_time,
1229                            app_time_ms / 1000.0,
1230                            _last_old_allocated_bytes,
1231                            last_unrestrained_young_length * HeapRegion::GrainBytes);
1232   }
1233   _last_old_allocated_bytes = 0;
1234 


1235   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1236   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
1237 
1238   double scan_hcc_time_ms = average_time_ms(G1GCPhaseTimes::ScanHCC);
1239 
1240   if (update_rs_time_goal_ms < scan_hcc_time_ms) {
1241     ergo_verbose2(ErgoTiming,
1242                   "adjust concurrent refinement thresholds",
1243                   ergo_format_reason("Scanning the HCC expected to take longer than Update RS time goal")
1244                   ergo_format_ms("Update RS time goal")
1245                   ergo_format_ms("Scan HCC time"),
1246                   update_rs_time_goal_ms,
1247                   scan_hcc_time_ms);
1248 
1249     update_rs_time_goal_ms = 0;
1250   } else {
1251     update_rs_time_goal_ms -= scan_hcc_time_ms;
1252   }
1253   adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
1254                                phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
1255                                update_rs_time_goal_ms);
1256 
1257   _collectionSetChooser->verify();
1258 }
1259 
1260 G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
1261   if (G1UseAdaptiveIHOP) {
1262     // The target occupancy is the total heap occupancy we want to hit. First, we
1263     // want to avoid eating into the reserve intended for young GC (to avoid unnecessary
1264     // throughput loss). Additionally G1 is free to not clean out up to
1265     // G1HeapWastePercent of heap, that space also cannot be used for allocation
1266     // while marking.
1267     size_t safe_heap_percentage = (size_t) (G1ReservePercent + G1HeapWastePercent);
1268     size_t target_occupancy = 0;
1269 
1270     if (safe_heap_percentage < 100) {
1271       target_occupancy = G1CollectedHeap::heap()->max_capacity() * (100.0 - safe_heap_percentage) / 100.0;
1272     }
1273     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
1274                                      target_occupancy,
1275                                      &_predictor);
1276   } else {
1277     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent,
1278                                    G1CollectedHeap::heap()->max_capacity());
1279   }
1280 }
1281 
1282 void G1CollectorPolicy::update_ihop_statistics(double marking_time,
1283                                                double mutator_time_s,
1284                                                size_t mutator_alloc_bytes,
1285                                                size_t young_gen_size) {
1286   bool report = false;
1287 
1288   // To avoid using really small times that may be caused by e.g. back-to-back gcs
1289   // we filter them out.
1290   double const min_valid_time = 1e-6;
1291 
1292   if (marking_time > min_valid_time) {
1293     _ihop_control->update_time_to_mixed(marking_time);
1294     report = true;
1295   }
1296 
1297   // As an approximation for the young gc promotion rates during marking we use
1298   // all of them. In many applications there are only a few if any young gcs during
1299   // marking, which makes any prediction useless. This increases the accuracy of the
1300   // prediction.
1301   if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
1302     _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
1303     report = true;
1304   }
1305 
1306   if (report) {
1307     report_ihop_statistics();
1308   }
1309 }
1310 
1311 void G1CollectorPolicy::report_ihop_statistics() {
1312   _ihop_control->print();
1313 }
1314 
1315 #define EXT_SIZE_FORMAT "%.1f%s"
1316 #define EXT_SIZE_PARAMS(bytes)                                  \
1317   byte_size_in_proper_unit((double)(bytes)),                    \
1318   proper_unit_for_byte_size((bytes))
1319 
1320 void G1CollectorPolicy::record_heap_size_info_at_start(bool full) {
1321   YoungList* young_list = _g1->young_list();
1322   _eden_used_bytes_before_gc = young_list->eden_used_bytes();
1323   _survivor_used_bytes_before_gc = young_list->survivor_used_bytes();
1324   _heap_capacity_bytes_before_gc = _g1->capacity();
1325   _heap_used_bytes_before_gc = _g1->used();
1326   _cur_collection_pause_used_regions_at_start = _g1->num_used_regions();
1327 
1328   _eden_capacity_bytes_before_gc =
1329          (_young_list_target_length * HeapRegion::GrainBytes) - _survivor_used_bytes_before_gc;
1330 
1331   if (full) {
1332     _metaspace_used_bytes_before_gc = MetaspaceAux::used_bytes();
1333   }
1334 }
1335 
1336 void G1CollectorPolicy::print_heap_transition(size_t bytes_before) const {
1337   size_t bytes_after = _g1->used();
1338   size_t capacity = _g1->capacity();
1339 
1340   gclog_or_tty->print(" " SIZE_FORMAT "%s->" SIZE_FORMAT "%s(" SIZE_FORMAT "%s)",
1341       byte_size_in_proper_unit(bytes_before),
1342       proper_unit_for_byte_size(bytes_before),
1343       byte_size_in_proper_unit(bytes_after),
1344       proper_unit_for_byte_size(bytes_after),
1345       byte_size_in_proper_unit(capacity),
1346       proper_unit_for_byte_size(capacity));
1347 }
1348 
1349 void G1CollectorPolicy::print_heap_transition() const {
1350   print_heap_transition(_heap_used_bytes_before_gc);
1351 }
1352 
1353 void G1CollectorPolicy::print_detailed_heap_transition(bool full) const {
1354   YoungList* young_list = _g1->young_list();
1355 
1356   size_t eden_used_bytes_after_gc = young_list->eden_used_bytes();
1357   size_t survivor_used_bytes_after_gc = young_list->survivor_used_bytes();
1358   size_t heap_used_bytes_after_gc = _g1->used();
1359 
1360   size_t heap_capacity_bytes_after_gc = _g1->capacity();
1361   size_t eden_capacity_bytes_after_gc =
1362     (_young_list_target_length * HeapRegion::GrainBytes) - survivor_used_bytes_after_gc;
1363 
1364   gclog_or_tty->print(
1365     "   [Eden: " EXT_SIZE_FORMAT "(" EXT_SIZE_FORMAT ")->" EXT_SIZE_FORMAT "(" EXT_SIZE_FORMAT ") "
1366     "Survivors: " EXT_SIZE_FORMAT "->" EXT_SIZE_FORMAT " "
1367     "Heap: " EXT_SIZE_FORMAT "(" EXT_SIZE_FORMAT ")->"
1368     EXT_SIZE_FORMAT "(" EXT_SIZE_FORMAT ")]",
1369     EXT_SIZE_PARAMS(_eden_used_bytes_before_gc),
1370     EXT_SIZE_PARAMS(_eden_capacity_bytes_before_gc),
1371     EXT_SIZE_PARAMS(eden_used_bytes_after_gc),
1372     EXT_SIZE_PARAMS(eden_capacity_bytes_after_gc),
1373     EXT_SIZE_PARAMS(_survivor_used_bytes_before_gc),
1374     EXT_SIZE_PARAMS(survivor_used_bytes_after_gc),
1375     EXT_SIZE_PARAMS(_heap_used_bytes_before_gc),
1376     EXT_SIZE_PARAMS(_heap_capacity_bytes_before_gc),
1377     EXT_SIZE_PARAMS(heap_used_bytes_after_gc),
1378     EXT_SIZE_PARAMS(heap_capacity_bytes_after_gc));
1379 
1380   if (full) {
1381     MetaspaceAux::print_metaspace_change(_metaspace_used_bytes_before_gc);
1382   }
1383 
1384   gclog_or_tty->cr();
1385 }
1386 
1387 void G1CollectorPolicy::print_phases(double pause_time_sec) {
1388   phase_times()->print(pause_time_sec);
1389 }
1390 
1391 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
1392                                                      double update_rs_processed_buffers,
1393                                                      double goal_ms) {
1394   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1395   ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
1396 
1397   if (G1UseAdaptiveConcRefinement) {
1398     const int k_gy = 3, k_gr = 6;
1399     const double inc_k = 1.1, dec_k = 0.9;
1400 
1401     int g = cg1r->green_zone();
1402     if (update_rs_time > goal_ms) {
1403       g = (int)(g * dec_k);  // Can become 0, that's OK. That would mean a mutator-only processing.
1404     } else {
1405       if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
1406         g = (int)MAX2(g * inc_k, g + 1.0);
1407       }
1408     }
1409     // Change the refinement threads params
1410     cg1r->set_green_zone(g);
1411     cg1r->set_yellow_zone(g * k_gy);
1412     cg1r->set_red_zone(g * k_gr);
1413     cg1r->reinitialize_threads();
1414 
1415     int processing_threshold_delta = MAX2((int)(cg1r->green_zone() * _predictor.sigma()), 1);
1416     int processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1417                                     cg1r->yellow_zone());
1418     // Change the barrier params
1419     dcqs.set_process_completed_threshold(processing_threshold);
1420     dcqs.set_max_completed_queue(cg1r->red_zone());
1421   }
1422 
1423   int curr_queue_size = dcqs.completed_buffers_num();
1424   if (curr_queue_size >= cg1r->yellow_zone()) {
1425     dcqs.set_completed_queue_padding(curr_queue_size);
1426   } else {
1427     dcqs.set_completed_queue_padding(0);
1428   }
1429   dcqs.notify_if_necessary();
1430 }
1431 
1432 size_t G1CollectorPolicy::predict_rs_length_diff() const {
1433   return (size_t) get_new_prediction(_rs_length_diff_seq);
1434 }
1435 
1436 double G1CollectorPolicy::predict_alloc_rate_ms() const {
1437   return get_new_prediction(_alloc_rate_ms_seq);
1438 }
1439 
1440 double G1CollectorPolicy::predict_cost_per_card_ms() const {
1441   return get_new_prediction(_cost_per_card_ms_seq);
1442 }
1443 
1444 double G1CollectorPolicy::predict_scan_hcc_ms() const {
1445   return get_new_prediction(_cost_scan_hcc_seq);
1446 }
1447 
1448 double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const {
1449   return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms();
1450 }
1451 
1452 double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const {
1453   return get_new_prediction(_young_cards_per_entry_ratio_seq);
1454 }
1455 
1456 double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const {
1457   if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
1458     return predict_young_cards_per_entry_ratio();
1459   } else {
1460     return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
1461   }
1462 }
1463 
1464 size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const {
1465   return (size_t) (rs_length * predict_young_cards_per_entry_ratio());
1466 }
1467 
1468 size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const {
1469   return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio());
1470 }
1471 
1472 double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const {
1473   if (collector_state()->gcs_are_young()) {
1474     return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1475   } else {
1476     return predict_mixed_rs_scan_time_ms(card_num);
1477   }
1478 }
1479 
1480 double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const {
1481   if (_mixed_cost_per_entry_ms_seq->num() < 3) {
1482     return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1483   } else {
1484     return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq);
1485   }
1486 }
1487 
1488 double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const {
1489   if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
1490     return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq);
1491   } else {
1492     return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq);
1493   }
1494 }
1495 
1496 double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const {
1497   if (collector_state()->during_concurrent_mark()) {
1498     return predict_object_copy_time_ms_during_cm(bytes_to_copy);
1499   } else {
1500     return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq);
1501   }
1502 }
1503 
1504 double G1CollectorPolicy::predict_constant_other_time_ms() const {
1505   return get_new_prediction(_constant_other_time_ms_seq);
1506 }
1507 
1508 double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const {
1509   return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq);
1510 }
1511 
1512 double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const {
1513   return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq);
1514 }
1515 
1516 double G1CollectorPolicy::predict_remark_time_ms() const {
1517   return get_new_prediction(_concurrent_mark_remark_times_ms);
1518 }
1519 
1520 double G1CollectorPolicy::predict_cleanup_time_ms() const {
1521   return get_new_prediction(_concurrent_mark_cleanup_times_ms);
1522 }
1523 
1524 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1525   TruncatedSeq* seq = surv_rate_group->get_seq(age);
1526   guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1527   double pred = get_new_prediction(seq);
1528   if (pred > 1.0) {
1529     pred = 1.0;
1530   }
1531   return pred;
1532 }
1533 
1534 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1535   return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1536 }
1537 
1538 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1539   return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1540 }
1541 
1542 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1543                                                        size_t scanned_cards) const {
1544   return
1545     predict_rs_update_time_ms(pending_cards) +
1546     predict_rs_scan_time_ms(scanned_cards) +
1547     predict_constant_other_time_ms();
1548 }
1549 
1550 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1551   size_t rs_length = predict_rs_length_diff();
1552   size_t card_num;
1553   if (collector_state()->gcs_are_young()) {
1554     card_num = predict_young_card_num(rs_length);
1555   } else {
1556     card_num = predict_non_young_card_num(rs_length);
1557   }
1558   return predict_base_elapsed_time_ms(pending_cards, card_num);
1559 }
1560 
1561 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1562   size_t bytes_to_copy;
1563   if (hr->is_marked())
1564     bytes_to_copy = hr->max_live_bytes();
1565   else {
1566     assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1567     int age = hr->age_in_surv_rate_group();
1568     double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1569     bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1570   }
1571   return bytes_to_copy;
1572 }
1573 
1574 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1575                                                          bool for_young_gc) const {
1576   size_t rs_length = hr->rem_set()->occupied();
1577   size_t card_num;
1578 
1579   // Predicting the number of cards is based on which type of GC
1580   // we're predicting for.
1581   if (for_young_gc) {
1582     card_num = predict_young_card_num(rs_length);
1583   } else {
1584     card_num = predict_non_young_card_num(rs_length);
1585   }
1586   size_t bytes_to_copy = predict_bytes_to_copy(hr);
1587 
1588   double region_elapsed_time_ms =
1589     predict_rs_scan_time_ms(card_num) +
1590     predict_object_copy_time_ms(bytes_to_copy);
1591 
1592   // The prediction of the "other" time for this region is based
1593   // upon the region type and NOT the GC type.
1594   if (hr->is_young()) {
1595     region_elapsed_time_ms += predict_young_other_time_ms(1);
1596   } else {
1597     region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1598   }
1599   return region_elapsed_time_ms;
1600 }
1601 
1602 void G1CollectorPolicy::init_cset_region_lengths(uint eden_cset_region_length,
1603                                                  uint survivor_cset_region_length) {
1604   _eden_cset_region_length     = eden_cset_region_length;
1605   _survivor_cset_region_length = survivor_cset_region_length;
1606   _old_cset_region_length      = 0;
1607 }
1608 
1609 void G1CollectorPolicy::set_recorded_rs_lengths(size_t rs_lengths) {
1610   _recorded_rs_lengths = rs_lengths;
1611 }
1612 
1613 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1614                                                double elapsed_ms) {
1615   _recent_gc_times_ms->add(elapsed_ms);
1616   _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1617   _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1618 }
1619 
1620 size_t G1CollectorPolicy::expansion_amount() const {
1621   double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1622   double threshold = _gc_overhead_perc;
1623   if (recent_gc_overhead > threshold) {
1624     // We will double the existing space, or take
1625     // G1ExpandByPercentOfAvailable % of the available expansion
1626     // space, whichever is smaller, bounded below by a minimum
1627     // expansion (unless that's all that's left.)
1628     const size_t min_expand_bytes = 1*M;
1629     size_t reserved_bytes = _g1->max_capacity();
1630     size_t committed_bytes = _g1->capacity();
1631     size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1632     size_t expand_bytes;
1633     size_t expand_bytes_via_pct =
1634       uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1635     expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1636     expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1637     expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1638 
1639     ergo_verbose5(ErgoHeapSizing,
1640                   "attempt heap expansion",
1641                   ergo_format_reason("recent GC overhead higher than "
1642                                      "threshold after GC")
1643                   ergo_format_perc("recent GC overhead")
1644                   ergo_format_perc("threshold")
1645                   ergo_format_byte("uncommitted")
1646                   ergo_format_byte_perc("calculated expansion amount"),
1647                   recent_gc_overhead, threshold,
1648                   uncommitted_bytes,
1649                   expand_bytes_via_pct, (double) G1ExpandByPercentOfAvailable);
1650 
1651     return expand_bytes;
1652   } else {
1653     return 0;
1654   }
1655 }
1656 
1657 void G1CollectorPolicy::print_tracing_info() const {
1658   _trace_young_gen_time_data.print();
1659   _trace_old_gen_time_data.print();
1660 }
1661 
1662 void G1CollectorPolicy::print_yg_surv_rate_info() const {
1663 #ifndef PRODUCT
1664   _short_lived_surv_rate_group->print_surv_rate_summary();
1665   // add this call for any other surv rate groups
1666 #endif // PRODUCT
1667 }
1668 
1669 bool G1CollectorPolicy::is_young_list_full() const {
1670   uint young_list_length = _g1->young_list()->length();
1671   uint young_list_target_length = _young_list_target_length;
1672   return young_list_length >= young_list_target_length;
1673 }
1674 
1675 bool G1CollectorPolicy::can_expand_young_list() const {
1676   uint young_list_length = _g1->young_list()->length();
1677   uint young_list_max_length = _young_list_max_length;
1678   return young_list_length < young_list_max_length;
1679 }
1680 
1681 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1682   uint expansion_region_num = 0;
1683   if (GCLockerEdenExpansionPercent > 0) {
1684     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1685     double expansion_region_num_d = perc * (double) _young_list_target_length;
1686     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1687     // less than 1.0) we'll get 1.
1688     expansion_region_num = (uint) ceil(expansion_region_num_d);
1689   } else {
1690     assert(expansion_region_num == 0, "sanity");
1691   }
1692   _young_list_max_length = _young_list_target_length + expansion_region_num;
1693   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1694 }
1695 
1696 // Calculates survivor space parameters.
1697 void G1CollectorPolicy::update_survivors_policy() {
1698   double max_survivor_regions_d =
1699                  (double) _young_list_target_length / (double) SurvivorRatio;
1700   // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1701   // smaller than 1.0) we'll get 1.
1702   _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1703 
1704   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1705         HeapRegion::GrainWords * _max_survivor_regions, counters());
1706 }
1707 
1708 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1709   // We actually check whether we are marking here and not if we are in a
1710   // reclamation phase. This means that we will schedule a concurrent mark
1711   // even while we are still in the process of reclaiming memory.
1712   bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1713   if (!during_cycle) {
1714     ergo_verbose1(ErgoConcCycles,
1715                   "request concurrent cycle initiation",
1716                   ergo_format_reason("requested by GC cause")
1717                   ergo_format_str("GC cause"),
1718                   GCCause::to_string(gc_cause));
1719     collector_state()->set_initiate_conc_mark_if_possible(true);
1720     return true;
1721   } else {
1722     ergo_verbose1(ErgoConcCycles,
1723                   "do not request concurrent cycle initiation",
1724                   ergo_format_reason("concurrent cycle already in progress")
1725                   ergo_format_str("GC cause"),
1726                   GCCause::to_string(gc_cause));
1727     return false;
1728   }
1729 }
1730 
1731 void G1CollectorPolicy::decide_on_conc_mark_initiation() {
1732   // We are about to decide on whether this pause will be an
1733   // initial-mark pause.
1734 
1735   // First, collector_state()->during_initial_mark_pause() should not be already set. We
1736   // will set it here if we have to. However, it should be cleared by
1737   // the end of the pause (it's only set for the duration of an
1738   // initial-mark pause).
1739   assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1740 
1741   if (collector_state()->initiate_conc_mark_if_possible()) {
1742     // We had noticed on a previous pause that the heap occupancy has
1743     // gone over the initiating threshold and we should start a
1744     // concurrent marking cycle. So we might initiate one.
1745 
1746     if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1747       // Initiate a new initial mark only if there is no marking or reclamation going
1748       // on.
1749 
1750       collector_state()->set_during_initial_mark_pause(true);
1751       // And we can now clear initiate_conc_mark_if_possible() as
1752       // we've already acted on it.
1753       collector_state()->set_initiate_conc_mark_if_possible(false);
1754 
1755       ergo_verbose0(ErgoConcCycles,
1756                   "initiate concurrent cycle",
1757                   ergo_format_reason("concurrent cycle initiation requested"));
1758     } else {
1759       // The concurrent marking thread is still finishing up the
1760       // previous cycle. If we start one right now the two cycles
1761       // overlap. In particular, the concurrent marking thread might
1762       // be in the process of clearing the next marking bitmap (which
1763       // we will use for the next cycle if we start one). Starting a
1764       // cycle now will be bad given that parts of the marking
1765       // information might get cleared by the marking thread. And we
1766       // cannot wait for the marking thread to finish the cycle as it
1767       // periodically yields while clearing the next marking bitmap
1768       // and, if it's in a yield point, it's waiting for us to
1769       // finish. So, at this point we will not start a cycle and we'll
1770       // let the concurrent marking thread complete the last one.
1771       ergo_verbose0(ErgoConcCycles,
1772                     "do not initiate concurrent cycle",
1773                     ergo_format_reason("concurrent cycle already in progress"));
1774     }
1775   }
1776 }
1777 
1778 class ParKnownGarbageHRClosure: public HeapRegionClosure {
1779   G1CollectedHeap* _g1h;
1780   CSetChooserParUpdater _cset_updater;
1781 
1782 public:
1783   ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
1784                            uint chunk_size) :
1785     _g1h(G1CollectedHeap::heap()),
1786     _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
1787 
1788   bool doHeapRegion(HeapRegion* r) {
1789     // Do we have any marking information for this region?
1790     if (r->is_marked()) {
1791       // We will skip any region that's currently used as an old GC
1792       // alloc region (we should not consider those for collection
1793       // before we fill them up).
1794       if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
1795         _cset_updater.add_region(r);
1796       }
1797     }
1798     return false;
1799   }
1800 };
1801 
1802 class ParKnownGarbageTask: public AbstractGangTask {
1803   CollectionSetChooser* _hrSorted;
1804   uint _chunk_size;
1805   G1CollectedHeap* _g1;
1806   HeapRegionClaimer _hrclaimer;
1807 
1808 public:
1809   ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size, uint n_workers) :
1810       AbstractGangTask("ParKnownGarbageTask"),
1811       _hrSorted(hrSorted), _chunk_size(chunk_size),
1812       _g1(G1CollectedHeap::heap()), _hrclaimer(n_workers) {}
1813 
1814   void work(uint worker_id) {
1815     ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
1816     _g1->heap_region_par_iterate(&parKnownGarbageCl, worker_id, &_hrclaimer);
1817   }
1818 };
1819 
1820 uint G1CollectorPolicy::calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const {
1821   assert(n_workers > 0, "Active gc workers should be greater than 0");
1822   const uint overpartition_factor = 4;
1823   const uint min_chunk_size = MAX2(n_regions / n_workers, 1U);
1824   return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
1825 }
1826 
1827 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1828   _collectionSetChooser->clear();
1829 
1830   WorkGang* workers = _g1->workers();
1831   uint n_workers = workers->active_workers();
1832 
1833   uint n_regions = _g1->num_regions();
1834   uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions);
1835   _collectionSetChooser->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1836   ParKnownGarbageTask par_known_garbage_task(_collectionSetChooser, chunk_size, n_workers);
1837   workers->run_task(&par_known_garbage_task);
1838 
1839   _collectionSetChooser->sort_regions();
1840 
1841   double end_sec = os::elapsedTime();
1842   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1843   _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
1844   _cur_mark_stop_world_time_ms += elapsed_time_ms;
1845   _prev_collection_pause_end_ms += elapsed_time_ms;
1846 
1847   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1848 }
1849 
1850 // Add the heap region at the head of the non-incremental collection set
1851 void G1CollectorPolicy::add_old_region_to_cset(HeapRegion* hr) {
1852   assert(_inc_cset_build_state == Active, "Precondition");
1853   assert(hr->is_old(), "the region should be old");
1854 
1855   assert(!hr->in_collection_set(), "should not already be in the CSet");
1856   _g1->register_old_region_with_cset(hr);
1857   hr->set_next_in_collection_set(_collection_set);
1858   _collection_set = hr;
1859   _collection_set_bytes_used_before += hr->used();
1860   size_t rs_length = hr->rem_set()->occupied();
1861   _recorded_rs_lengths += rs_length;
1862   _old_cset_region_length += 1;
1863 }
1864 
1865 // Initialize the per-collection-set information
1866 void G1CollectorPolicy::start_incremental_cset_building() {
1867   assert(_inc_cset_build_state == Inactive, "Precondition");
1868 
1869   _inc_cset_head = NULL;
1870   _inc_cset_tail = NULL;
1871   _inc_cset_bytes_used_before = 0;
1872 
1873   _inc_cset_max_finger = 0;
1874   _inc_cset_recorded_rs_lengths = 0;
1875   _inc_cset_recorded_rs_lengths_diffs = 0;
1876   _inc_cset_predicted_elapsed_time_ms = 0.0;
1877   _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1878   _inc_cset_build_state = Active;
1879 }
1880 
1881 void G1CollectorPolicy::finalize_incremental_cset_building() {
1882   assert(_inc_cset_build_state == Active, "Precondition");
1883   assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1884 
1885   // The two "main" fields, _inc_cset_recorded_rs_lengths and
1886   // _inc_cset_predicted_elapsed_time_ms, are updated by the thread
1887   // that adds a new region to the CSet. Further updates by the
1888   // concurrent refinement thread that samples the young RSet lengths
1889   // are accumulated in the *_diffs fields. Here we add the diffs to
1890   // the "main" fields.
1891 
1892   if (_inc_cset_recorded_rs_lengths_diffs >= 0) {
1893     _inc_cset_recorded_rs_lengths += _inc_cset_recorded_rs_lengths_diffs;
1894   } else {
1895     // This is defensive. The diff should in theory be always positive
1896     // as RSets can only grow between GCs. However, given that we
1897     // sample their size concurrently with other threads updating them
1898     // it's possible that we might get the wrong size back, which
1899     // could make the calculations somewhat inaccurate.
1900     size_t diffs = (size_t) (-_inc_cset_recorded_rs_lengths_diffs);
1901     if (_inc_cset_recorded_rs_lengths >= diffs) {
1902       _inc_cset_recorded_rs_lengths -= diffs;
1903     } else {
1904       _inc_cset_recorded_rs_lengths = 0;
1905     }
1906   }
1907   _inc_cset_predicted_elapsed_time_ms +=
1908                                      _inc_cset_predicted_elapsed_time_ms_diffs;
1909 
1910   _inc_cset_recorded_rs_lengths_diffs = 0;
1911   _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1912 }
1913 
1914 void G1CollectorPolicy::add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length) {
1915   // This routine is used when:
1916   // * adding survivor regions to the incremental cset at the end of an
1917   //   evacuation pause,
1918   // * adding the current allocation region to the incremental cset
1919   //   when it is retired, and
1920   // * updating existing policy information for a region in the
1921   //   incremental cset via young list RSet sampling.
1922   // Therefore this routine may be called at a safepoint by the
1923   // VM thread, or in-between safepoints by mutator threads (when
1924   // retiring the current allocation region) or a concurrent
1925   // refine thread (RSet sampling).
1926 
1927   double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1928   size_t used_bytes = hr->used();
1929   _inc_cset_recorded_rs_lengths += rs_length;
1930   _inc_cset_predicted_elapsed_time_ms += region_elapsed_time_ms;
1931   _inc_cset_bytes_used_before += used_bytes;
1932 
1933   // Cache the values we have added to the aggregated information
1934   // in the heap region in case we have to remove this region from
1935   // the incremental collection set, or it is updated by the
1936   // rset sampling code
1937   hr->set_recorded_rs_length(rs_length);
1938   hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
1939 }
1940 
1941 void G1CollectorPolicy::update_incremental_cset_info(HeapRegion* hr,
1942                                                      size_t new_rs_length) {
1943   // Update the CSet information that is dependent on the new RS length
1944   assert(hr->is_young(), "Precondition");
1945   assert(!SafepointSynchronize::is_at_safepoint(),
1946                                                "should not be at a safepoint");
1947 
1948   // We could have updated _inc_cset_recorded_rs_lengths and
1949   // _inc_cset_predicted_elapsed_time_ms directly but we'd need to do
1950   // that atomically, as this code is executed by a concurrent
1951   // refinement thread, potentially concurrently with a mutator thread
1952   // allocating a new region and also updating the same fields. To
1953   // avoid the atomic operations we accumulate these updates on two
1954   // separate fields (*_diffs) and we'll just add them to the "main"
1955   // fields at the start of a GC.
1956 
1957   ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
1958   ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
1959   _inc_cset_recorded_rs_lengths_diffs += rs_lengths_diff;
1960 
1961   double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
1962   double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1963   double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
1964   _inc_cset_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
1965 
1966   hr->set_recorded_rs_length(new_rs_length);
1967   hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
1968 }
1969 
1970 void G1CollectorPolicy::add_region_to_incremental_cset_common(HeapRegion* hr) {
1971   assert(hr->is_young(), "invariant");
1972   assert(hr->young_index_in_cset() > -1, "should have already been set");
1973   assert(_inc_cset_build_state == Active, "Precondition");
1974 
1975   // We need to clear and set the cached recorded/cached collection set
1976   // information in the heap region here (before the region gets added
1977   // to the collection set). An individual heap region's cached values
1978   // are calculated, aggregated with the policy collection set info,
1979   // and cached in the heap region here (initially) and (subsequently)
1980   // by the Young List sampling code.
1981 
1982   size_t rs_length = hr->rem_set()->occupied();
1983   add_to_incremental_cset_info(hr, rs_length);
1984 
1985   HeapWord* hr_end = hr->end();
1986   _inc_cset_max_finger = MAX2(_inc_cset_max_finger, hr_end);
1987 
1988   assert(!hr->in_collection_set(), "invariant");
1989   _g1->register_young_region_with_cset(hr);
1990   assert(hr->next_in_collection_set() == NULL, "invariant");
1991 }
1992 
1993 // Add the region at the RHS of the incremental cset
1994 void G1CollectorPolicy::add_region_to_incremental_cset_rhs(HeapRegion* hr) {
1995   // We should only ever be appending survivors at the end of a pause
1996   assert(hr->is_survivor(), "Logic");
1997 
1998   // Do the 'common' stuff
1999   add_region_to_incremental_cset_common(hr);
2000 
2001   // Now add the region at the right hand side
2002   if (_inc_cset_tail == NULL) {
2003     assert(_inc_cset_head == NULL, "invariant");
2004     _inc_cset_head = hr;
2005   } else {
2006     _inc_cset_tail->set_next_in_collection_set(hr);
2007   }
2008   _inc_cset_tail = hr;
2009 }
2010 
2011 // Add the region to the LHS of the incremental cset
2012 void G1CollectorPolicy::add_region_to_incremental_cset_lhs(HeapRegion* hr) {
2013   // Survivors should be added to the RHS at the end of a pause
2014   assert(hr->is_eden(), "Logic");
2015 
2016   // Do the 'common' stuff
2017   add_region_to_incremental_cset_common(hr);
2018 
2019   // Add the region at the left hand side
2020   hr->set_next_in_collection_set(_inc_cset_head);
2021   if (_inc_cset_head == NULL) {
2022     assert(_inc_cset_tail == NULL, "Invariant");
2023     _inc_cset_tail = hr;
2024   }
2025   _inc_cset_head = hr;
2026 }
2027 
2028 #ifndef PRODUCT
2029 void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream* st) {
2030   assert(list_head == inc_cset_head() || list_head == collection_set(), "must be");
2031 
2032   st->print_cr("\nCollection_set:");
2033   HeapRegion* csr = list_head;
2034   while (csr != NULL) {
2035     HeapRegion* next = csr->next_in_collection_set();
2036     assert(csr->in_collection_set(), "bad CS");
2037     st->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
2038                  HR_FORMAT_PARAMS(csr),
2039                  p2i(csr->prev_top_at_mark_start()), p2i(csr->next_top_at_mark_start()),
2040                  csr->age_in_surv_rate_group_cond());
2041     csr = next;
2042   }
2043 }
2044 #endif // !PRODUCT
2045 
2046 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
2047   // Returns the given amount of reclaimable bytes (that represents
2048   // the amount of reclaimable space still to be collected) as a
2049   // percentage of the current heap capacity.
2050   size_t capacity_bytes = _g1->capacity();
2051   return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
2052 }
2053 
2054 void G1CollectorPolicy::maybe_start_marking() {
2055   if (need_to_start_conc_mark("end of GC")) {
2056     // Note: this might have already been set, if during the last
2057     // pause we decided to start a cycle but at the beginning of
2058     // this pause we decided to postpone it. That's OK.
2059     collector_state()->set_initiate_conc_mark_if_possible(true);
2060   }  
2061 }
2062 
2063 G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
2064   assert(!collector_state()->full_collection(), "must be");
2065   if (collector_state()->during_initial_mark_pause()) {
2066     assert(collector_state()->last_gc_was_young(), "must be");
2067     assert(!collector_state()->last_young_gc(), "must be");
2068     return InitialMarkGC;
2069   } else if (collector_state()->last_young_gc()) {
2070     assert(!collector_state()->during_initial_mark_pause(), "must be");
2071     assert(collector_state()->last_gc_was_young(), "must be");   
2072     return LastYoungGC;
2073   } else if (!collector_state()->last_gc_was_young()) {
2074     assert(!collector_state()->during_initial_mark_pause(), "must be");
2075     assert(!collector_state()->last_young_gc(), "must be");
2076     return MixedGC;
2077   } else {
2078     assert(collector_state()->last_gc_was_young(), "must be");
2079     assert(!collector_state()->during_initial_mark_pause(), "must be");
2080     assert(!collector_state()->last_young_gc(), "must be");
2081     return YoungOnlyGC;
2082   }
2083 }
2084 
2085 void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
2086   // Manage the MMU tracker. For some reason it ignores Full GCs.
2087   if (kind != FullGC) {
2088     _mmu_tracker->add_pause(start, end);
2089   }
2090   // Manage the mutator time tracking from initial mark to first mixed gc.
2091   switch (kind) {
2092     case FullGC:
2093       abort_time_to_mixed_tracking();
2094       break;
2095     case Cleanup:
2096     case Remark:
2097     case YoungOnlyGC:
2098     case LastYoungGC:
2099       _initial_mark_to_mixed.add_pause(end - start);
2100       break;
2101     case InitialMarkGC:
2102       _initial_mark_to_mixed.record_initial_mark_end(end);
2103       break;
2104     case MixedGC:
2105       _initial_mark_to_mixed.record_mixed_gc_start(start);
2106       break;
2107     default:
2108       ShouldNotReachHere();
2109   }
2110 }
2111 
2112 void G1CollectorPolicy::abort_time_to_mixed_tracking() {
2113   _initial_mark_to_mixed.reset();
2114 }
2115 
2116 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
2117                                                 const char* false_action_str) const {
2118   CollectionSetChooser* cset_chooser = _collectionSetChooser;
2119   if (cset_chooser->is_empty()) {
2120     ergo_verbose0(ErgoMixedGCs,
2121                   false_action_str,
2122                   ergo_format_reason("candidate old regions not available"));
2123     return false;
2124   }
2125 
2126   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
2127   size_t reclaimable_bytes = cset_chooser->remaining_reclaimable_bytes();
2128   double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2129   double threshold = (double) G1HeapWastePercent;
2130   if (reclaimable_perc <= threshold) {
2131     ergo_verbose4(ErgoMixedGCs,
2132               false_action_str,
2133               ergo_format_reason("reclaimable percentage not over threshold")
2134               ergo_format_region("candidate old regions")
2135               ergo_format_byte_perc("reclaimable")
2136               ergo_format_perc("threshold"),
2137               cset_chooser->remaining_regions(),
2138               reclaimable_bytes,
2139               reclaimable_perc, threshold);
2140     return false;
2141   }
2142 
2143   ergo_verbose4(ErgoMixedGCs,
2144                 true_action_str,
2145                 ergo_format_reason("candidate old regions available")
2146                 ergo_format_region("candidate old regions")
2147                 ergo_format_byte_perc("reclaimable")
2148                 ergo_format_perc("threshold"),
2149                 cset_chooser->remaining_regions(),
2150                 reclaimable_bytes,
2151                 reclaimable_perc, threshold);
2152   return true;
2153 }
2154 
2155 uint G1CollectorPolicy::calc_min_old_cset_length() const {
2156   // The min old CSet region bound is based on the maximum desired
2157   // number of mixed GCs after a cycle. I.e., even if some old regions
2158   // look expensive, we should add them to the CSet anyway to make
2159   // sure we go through the available old regions in no more than the
2160   // maximum desired number of mixed GCs.
2161   //
2162   // The calculation is based on the number of marked regions we added
2163   // to the CSet chooser in the first place, not how many remain, so
2164   // that the result is the same during all mixed GCs that follow a cycle.
2165 
2166   const size_t region_num = (size_t) _collectionSetChooser->length();
2167   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
2168   size_t result = region_num / gc_num;
2169   // emulate ceiling
2170   if (result * gc_num < region_num) {
2171     result += 1;
2172   }
2173   return (uint) result;
2174 }
2175 
2176 uint G1CollectorPolicy::calc_max_old_cset_length() const {
2177   // The max old CSet region bound is based on the threshold expressed
2178   // as a percentage of the heap size. I.e., it should bound the
2179   // number of old regions added to the CSet irrespective of how many
2180   // of them are available.
2181 
2182   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
2183   const size_t region_num = g1h->num_regions();
2184   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
2185   size_t result = region_num * perc / 100;
2186   // emulate ceiling
2187   if (100 * result < region_num * perc) {
2188     result += 1;
2189   }
2190   return (uint) result;
2191 }
2192 
2193 
2194 double G1CollectorPolicy::finalize_young_cset_part(double target_pause_time_ms) {
2195   double young_start_time_sec = os::elapsedTime();
2196 
2197   YoungList* young_list = _g1->young_list();
2198   finalize_incremental_cset_building();
2199 
2200   guarantee(target_pause_time_ms > 0.0,
2201             "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
2202   guarantee(_collection_set == NULL, "Precondition");
2203 
2204   double base_time_ms = predict_base_elapsed_time_ms(_pending_cards);
2205   double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
2206 
2207   ergo_verbose4(ErgoCSetConstruction | ErgoHigh,
2208                 "start choosing CSet",
2209                 ergo_format_size("_pending_cards")
2210                 ergo_format_ms("predicted base time")
2211                 ergo_format_ms("remaining time")
2212                 ergo_format_ms("target pause time"),
2213                 _pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
2214 
2215   collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young());
2216 
2217   if (collector_state()->last_gc_was_young()) {
2218     _trace_young_gen_time_data.increment_young_collection_count();
2219   } else {
2220     _trace_young_gen_time_data.increment_mixed_collection_count();
2221   }
2222 
2223   // The young list is laid with the survivor regions from the previous
2224   // pause are appended to the RHS of the young list, i.e.
2225   //   [Newly Young Regions ++ Survivors from last pause].
2226 
2227   uint survivor_region_length = young_list->survivor_length();
2228   uint eden_region_length = young_list->eden_length();
2229   init_cset_region_lengths(eden_region_length, survivor_region_length);
2230 
2231   HeapRegion* hr = young_list->first_survivor_region();
2232   while (hr != NULL) {
2233     assert(hr->is_survivor(), "badly formed young list");
2234     // There is a convention that all the young regions in the CSet
2235     // are tagged as "eden", so we do this for the survivors here. We
2236     // use the special set_eden_pre_gc() as it doesn't check that the
2237     // region is free (which is not the case here).
2238     hr->set_eden_pre_gc();
2239     hr = hr->get_next_young_region();
2240   }
2241 
2242   // Clear the fields that point to the survivor list - they are all young now.
2243   young_list->clear_survivors();
2244 
2245   _collection_set = _inc_cset_head;
2246   _collection_set_bytes_used_before = _inc_cset_bytes_used_before;
2247   time_remaining_ms = MAX2(time_remaining_ms - _inc_cset_predicted_elapsed_time_ms, 0.0);
2248 
2249   ergo_verbose4(ErgoCSetConstruction | ErgoHigh,
2250                 "add young regions to CSet",
2251                 ergo_format_region("eden")
2252                 ergo_format_region("survivors")
2253                 ergo_format_ms("predicted young region time")
2254                 ergo_format_ms("target pause time"),
2255                 eden_region_length, survivor_region_length,
2256                 _inc_cset_predicted_elapsed_time_ms,
2257                 target_pause_time_ms);
2258 
2259   // The number of recorded young regions is the incremental
2260   // collection set's current size
2261   set_recorded_rs_lengths(_inc_cset_recorded_rs_lengths);
2262 
2263   double young_end_time_sec = os::elapsedTime();
2264   phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
2265 
2266   return time_remaining_ms;
2267 }
2268 
2269 void G1CollectorPolicy::finalize_old_cset_part(double time_remaining_ms) {
2270   double non_young_start_time_sec = os::elapsedTime();
2271   double predicted_old_time_ms = 0.0;
2272 
2273 
2274   if (!collector_state()->gcs_are_young()) {
2275     CollectionSetChooser* cset_chooser = _collectionSetChooser;
2276     cset_chooser->verify();
2277     const uint min_old_cset_length = calc_min_old_cset_length();
2278     const uint max_old_cset_length = calc_max_old_cset_length();
2279 
2280     uint expensive_region_num = 0;
2281     bool check_time_remaining = adaptive_young_list_length();
2282 
2283     HeapRegion* hr = cset_chooser->peek();
2284     while (hr != NULL) {
2285       if (old_cset_region_length() >= max_old_cset_length) {
2286         // Added maximum number of old regions to the CSet.
2287         ergo_verbose2(ErgoCSetConstruction,
2288                       "finish adding old regions to CSet",
2289                       ergo_format_reason("old CSet region num reached max")
2290                       ergo_format_region("old")
2291                       ergo_format_region("max"),
2292                       old_cset_region_length(), max_old_cset_length);
2293         break;
2294       }
2295 
2296 
2297       // Stop adding regions if the remaining reclaimable space is
2298       // not above G1HeapWastePercent.
2299       size_t reclaimable_bytes = cset_chooser->remaining_reclaimable_bytes();
2300       double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2301       double threshold = (double) G1HeapWastePercent;
2302       if (reclaimable_perc <= threshold) {
2303         // We've added enough old regions that the amount of uncollected
2304         // reclaimable space is at or below the waste threshold. Stop
2305         // adding old regions to the CSet.
2306         ergo_verbose5(ErgoCSetConstruction,
2307                       "finish adding old regions to CSet",
2308                       ergo_format_reason("reclaimable percentage not over threshold")
2309                       ergo_format_region("old")
2310                       ergo_format_region("max")
2311                       ergo_format_byte_perc("reclaimable")
2312                       ergo_format_perc("threshold"),
2313                       old_cset_region_length(),
2314                       max_old_cset_length,
2315                       reclaimable_bytes,
2316                       reclaimable_perc, threshold);
2317         break;
2318       }
2319 
2320       double predicted_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
2321       if (check_time_remaining) {
2322         if (predicted_time_ms > time_remaining_ms) {
2323           // Too expensive for the current CSet.
2324 
2325           if (old_cset_region_length() >= min_old_cset_length) {
2326             // We have added the minimum number of old regions to the CSet,
2327             // we are done with this CSet.
2328             ergo_verbose4(ErgoCSetConstruction,
2329                           "finish adding old regions to CSet",
2330                           ergo_format_reason("predicted time is too high")
2331                           ergo_format_ms("predicted time")
2332                           ergo_format_ms("remaining time")
2333                           ergo_format_region("old")
2334                           ergo_format_region("min"),
2335                           predicted_time_ms, time_remaining_ms,
2336                           old_cset_region_length(), min_old_cset_length);
2337             break;
2338           }
2339 
2340           // We'll add it anyway given that we haven't reached the
2341           // minimum number of old regions.
2342           expensive_region_num += 1;
2343         }
2344       } else {
2345         if (old_cset_region_length() >= min_old_cset_length) {
2346           // In the non-auto-tuning case, we'll finish adding regions
2347           // to the CSet if we reach the minimum.
2348           ergo_verbose2(ErgoCSetConstruction,
2349                         "finish adding old regions to CSet",
2350                         ergo_format_reason("old CSet region num reached min")
2351                         ergo_format_region("old")
2352                         ergo_format_region("min"),
2353                         old_cset_region_length(), min_old_cset_length);
2354           break;
2355         }
2356       }
2357 
2358       // We will add this region to the CSet.
2359       time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
2360       predicted_old_time_ms += predicted_time_ms;
2361       cset_chooser->pop(); // already have region via peek()
2362       _g1->old_set_remove(hr);
2363       add_old_region_to_cset(hr);
2364 
2365       hr = cset_chooser->peek();
2366     }
2367     if (hr == NULL) {
2368       ergo_verbose0(ErgoCSetConstruction,
2369                     "finish adding old regions to CSet",
2370                     ergo_format_reason("candidate old regions not available"));
2371     }
2372 
2373     if (expensive_region_num > 0) {
2374       // We print the information once here at the end, predicated on
2375       // whether we added any apparently expensive regions or not, to
2376       // avoid generating output per region.
2377       ergo_verbose4(ErgoCSetConstruction,
2378                     "added expensive regions to CSet",
2379                     ergo_format_reason("old CSet region num not reached min")
2380                     ergo_format_region("old")
2381                     ergo_format_region("expensive")
2382                     ergo_format_region("min")
2383                     ergo_format_ms("remaining time"),
2384                     old_cset_region_length(),
2385                     expensive_region_num,
2386                     min_old_cset_length,
2387                     time_remaining_ms);
2388     }
2389 
2390     cset_chooser->verify();
2391   }
2392 
2393   stop_incremental_cset_building();
2394 
2395   ergo_verbose3(ErgoCSetConstruction,
2396                 "finish choosing CSet",
2397                 ergo_format_region("old")
2398                 ergo_format_ms("predicted old region time")
2399                 ergo_format_ms("time remaining"),
2400                 old_cset_region_length(),
2401                 predicted_old_time_ms, time_remaining_ms);
2402 
2403   double non_young_end_time_sec = os::elapsedTime();
2404   phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
2405 }
2406 
2407 void TraceYoungGenTimeData::record_start_collection(double time_to_stop_the_world_ms) {
2408   if(TraceYoungGenTime) {
2409     _all_stop_world_times_ms.add(time_to_stop_the_world_ms);
2410   }
2411 }
2412 
2413 void TraceYoungGenTimeData::record_yield_time(double yield_time_ms) {
2414   if(TraceYoungGenTime) {
2415     _all_yield_times_ms.add(yield_time_ms);
2416   }
2417 }
2418 
2419 void TraceYoungGenTimeData::record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times) {
2420   if(TraceYoungGenTime) {
2421     _total.add(pause_time_ms);
2422     _other.add(pause_time_ms - phase_times->accounted_time_ms());
2423     _root_region_scan_wait.add(phase_times->root_region_scan_wait_time_ms());
2424     _parallel.add(phase_times->cur_collection_par_time_ms());
2425     _ext_root_scan.add(phase_times->average_time_ms(G1GCPhaseTimes::ExtRootScan));
2426     _satb_filtering.add(phase_times->average_time_ms(G1GCPhaseTimes::SATBFiltering));
2427     _update_rs.add(phase_times->average_time_ms(G1GCPhaseTimes::UpdateRS));
2428     _scan_rs.add(phase_times->average_time_ms(G1GCPhaseTimes::ScanRS));
2429     _obj_copy.add(phase_times->average_time_ms(G1GCPhaseTimes::ObjCopy));
2430     _termination.add(phase_times->average_time_ms(G1GCPhaseTimes::Termination));
2431 
2432     double parallel_known_time = phase_times->average_time_ms(G1GCPhaseTimes::ExtRootScan) +
2433       phase_times->average_time_ms(G1GCPhaseTimes::SATBFiltering) +
2434       phase_times->average_time_ms(G1GCPhaseTimes::UpdateRS) +
2435       phase_times->average_time_ms(G1GCPhaseTimes::ScanRS) +
2436       phase_times->average_time_ms(G1GCPhaseTimes::ObjCopy) +
2437       phase_times->average_time_ms(G1GCPhaseTimes::Termination);
2438 
2439     double parallel_other_time = phase_times->cur_collection_par_time_ms() - parallel_known_time;
2440     _parallel_other.add(parallel_other_time);
2441     _clear_ct.add(phase_times->cur_clear_ct_time_ms());
2442   }
2443 }
2444 
2445 void TraceYoungGenTimeData::increment_young_collection_count() {
2446   if(TraceYoungGenTime) {
2447     ++_young_pause_num;
2448   }
2449 }
2450 
2451 void TraceYoungGenTimeData::increment_mixed_collection_count() {
2452   if(TraceYoungGenTime) {
2453     ++_mixed_pause_num;
2454   }
2455 }
2456 
2457 void TraceYoungGenTimeData::print_summary(const char* str,
2458                                           const NumberSeq* seq) const {
2459   double sum = seq->sum();
2460   gclog_or_tty->print_cr("%-27s = %8.2lf s (avg = %8.2lf ms)",
2461                 str, sum / 1000.0, seq->avg());
2462 }
2463 
2464 void TraceYoungGenTimeData::print_summary_sd(const char* str,
2465                                              const NumberSeq* seq) const {
2466   print_summary(str, seq);
2467   gclog_or_tty->print_cr("%45s = %5d, std dev = %8.2lf ms, max = %8.2lf ms)",
2468                 "(num", seq->num(), seq->sd(), seq->maximum());
2469 }
2470 
2471 void TraceYoungGenTimeData::print() const {
2472   if (!TraceYoungGenTime) {
2473     return;
2474   }
2475 
2476   gclog_or_tty->print_cr("ALL PAUSES");
2477   print_summary_sd("   Total", &_total);
2478   gclog_or_tty->cr();
2479   gclog_or_tty->cr();
2480   gclog_or_tty->print_cr("   Young GC Pauses: %8d", _young_pause_num);
2481   gclog_or_tty->print_cr("   Mixed GC Pauses: %8d", _mixed_pause_num);
2482   gclog_or_tty->cr();
2483 
2484   gclog_or_tty->print_cr("EVACUATION PAUSES");
2485 
2486   if (_young_pause_num == 0 && _mixed_pause_num == 0) {
2487     gclog_or_tty->print_cr("none");
2488   } else {
2489     print_summary_sd("   Evacuation Pauses", &_total);
2490     print_summary("      Root Region Scan Wait", &_root_region_scan_wait);
2491     print_summary("      Parallel Time", &_parallel);
2492     print_summary("         Ext Root Scanning", &_ext_root_scan);
2493     print_summary("         SATB Filtering", &_satb_filtering);
2494     print_summary("         Update RS", &_update_rs);
2495     print_summary("         Scan RS", &_scan_rs);
2496     print_summary("         Object Copy", &_obj_copy);
2497     print_summary("         Termination", &_termination);
2498     print_summary("         Parallel Other", &_parallel_other);
2499     print_summary("      Clear CT", &_clear_ct);
2500     print_summary("      Other", &_other);
2501   }
2502   gclog_or_tty->cr();
2503 
2504   gclog_or_tty->print_cr("MISC");
2505   print_summary_sd("   Stop World", &_all_stop_world_times_ms);
2506   print_summary_sd("   Yields", &_all_yield_times_ms);
2507 }
2508 
2509 void TraceOldGenTimeData::record_full_collection(double full_gc_time_ms) {
2510   if (TraceOldGenTime) {
2511     _all_full_gc_times.add(full_gc_time_ms);
2512   }
2513 }
2514 
2515 void TraceOldGenTimeData::print() const {
2516   if (!TraceOldGenTime) {
2517     return;
2518   }
2519 
2520   if (_all_full_gc_times.num() > 0) {
2521     gclog_or_tty->print("\n%4d full_gcs: total time = %8.2f s",
2522       _all_full_gc_times.num(),
2523       _all_full_gc_times.sum() / 1000.0);
2524     gclog_or_tty->print_cr(" (avg = %8.2fms).", _all_full_gc_times.avg());
2525     gclog_or_tty->print_cr("                     [std. dev = %8.2f ms, max = %8.2f ms]",
2526       _all_full_gc_times.sd(),
2527       _all_full_gc_times.maximum());
2528   }
2529 }
--- EOF ---