1 /*
   2  * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/concurrentG1Refine.hpp"
  27 #include "gc/g1/concurrentMarkThread.inline.hpp"
  28 #include "gc/g1/g1CollectedHeap.inline.hpp"
  29 #include "gc/g1/g1CollectorPolicy.hpp"
  30 #include "gc/g1/g1ConcurrentMark.hpp"
  31 #include "gc/g1/g1IHOPControl.hpp"
  32 #include "gc/g1/g1GCPhaseTimes.hpp"
  33 #include "gc/g1/heapRegion.inline.hpp"
  34 #include "gc/g1/heapRegionRemSet.hpp"
  35 #include "gc/shared/gcPolicyCounters.hpp"
  36 #include "runtime/arguments.hpp"
  37 #include "runtime/java.hpp"
  38 #include "runtime/mutexLocker.hpp"
  39 #include "utilities/debug.hpp"
  40 #include "utilities/pair.hpp"
  41 
  42 // Different defaults for different number of GC threads
  43 // They were chosen by running GCOld and SPECjbb on debris with different
  44 //   numbers of GC threads and choosing them based on the results
  45 
  46 // all the same
  47 static double rs_length_diff_defaults[] = {
  48   0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
  49 };
  50 
  51 static double cost_per_card_ms_defaults[] = {
  52   0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
  53 };
  54 
  55 // all the same
  56 static double young_cards_per_entry_ratio_defaults[] = {
  57   1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
  58 };
  59 
  60 static double cost_per_entry_ms_defaults[] = {
  61   0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
  62 };
  63 
  64 static double cost_per_byte_ms_defaults[] = {
  65   0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
  66 };
  67 
  68 // these should be pretty consistent
  69 static double constant_other_time_ms_defaults[] = {
  70   5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
  71 };
  72 
  73 
  74 static double young_other_cost_per_region_ms_defaults[] = {
  75   0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
  76 };
  77 
  78 static double non_young_other_cost_per_region_ms_defaults[] = {
  79   1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
  80 };
  81 
  82 G1CollectorPolicy::G1CollectorPolicy() :
  83   _predictor(G1ConfidencePercent / 100.0),
  84   _parallel_gc_threads(ParallelGCThreads),
  85 
  86   _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  87   _stop_world_start(0.0),
  88 
  89   _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  90   _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  91 
  92   _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  93   _prev_collection_pause_end_ms(0.0),
  94   _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
  95   _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  96   _cost_scan_hcc_seq(new TruncatedSeq(TruncatedSeqLength)),
  97   _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
  98   _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
  99   _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 100   _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 101   _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 102   _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
 103   _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 104   _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 105   _non_young_other_cost_per_region_ms_seq(
 106                                          new TruncatedSeq(TruncatedSeqLength)),
 107 
 108   _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
 109   _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
 110 
 111   _pause_time_target_ms((double) MaxGCPauseMillis),
 112 
 113   _recent_prev_end_times_for_all_gcs_sec(
 114                                 new TruncatedSeq(NumPrevPausesForHeuristics)),
 115 
 116   _recent_avg_pause_time_ratio(0.0),
 117   _rs_lengths_prediction(0),
 118   _max_survivor_regions(0),
 119 
 120   _eden_cset_region_length(0),
 121   _survivor_cset_region_length(0),
 122   _old_cset_region_length(0),
 123 
 124   _collection_set(NULL),
 125   _collection_set_bytes_used_before(0),
 126 
 127   // Incremental CSet attributes
 128   _inc_cset_build_state(Inactive),
 129   _inc_cset_head(NULL),
 130   _inc_cset_tail(NULL),
 131   _inc_cset_bytes_used_before(0),
 132   _inc_cset_max_finger(NULL),
 133   _inc_cset_recorded_rs_lengths(0),
 134   _inc_cset_recorded_rs_lengths_diffs(0),
 135   _inc_cset_predicted_elapsed_time_ms(0.0),
 136   _inc_cset_predicted_elapsed_time_ms_diffs(0.0),
 137 
 138   // add here any more surv rate groups
 139   _recorded_survivor_regions(0),
 140   _recorded_survivor_head(NULL),
 141   _recorded_survivor_tail(NULL),
 142   _survivors_age_table(true),
 143 
 144   _gc_overhead_perc(0.0),
 145 
 146   _bytes_allocated_in_old_since_last_gc(0),
 147   _ihop_control(NULL),
 148   _initial_mark_to_mixed() {
 149 
 150   // SurvRateGroups below must be initialized after the predictor because they
 151   // indirectly use it through this object passed to their constructor.
 152   _short_lived_surv_rate_group =
 153     new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
 154   _survivor_surv_rate_group =
 155     new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
 156 
 157   // Set up the region size and associated fields. Given that the
 158   // policy is created before the heap, we have to set this up here,
 159   // so it's done as soon as possible.
 160 
 161   // It would have been natural to pass initial_heap_byte_size() and
 162   // max_heap_byte_size() to setup_heap_region_size() but those have
 163   // not been set up at this point since they should be aligned with
 164   // the region size. So, there is a circular dependency here. We base
 165   // the region size on the heap size, but the heap size should be
 166   // aligned with the region size. To get around this we use the
 167   // unaligned values for the heap.
 168   HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
 169   HeapRegionRemSet::setup_remset_size();
 170 
 171   _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
 172   _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
 173   clear_ratio_check_data();
 174 
 175   _phase_times = new G1GCPhaseTimes(_parallel_gc_threads);
 176 
 177   int index = MIN2(_parallel_gc_threads - 1, 7);
 178 
 179   _rs_length_diff_seq->add(rs_length_diff_defaults[index]);
 180   _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
 181   _cost_scan_hcc_seq->add(0.0);
 182   _young_cards_per_entry_ratio_seq->add(
 183                                   young_cards_per_entry_ratio_defaults[index]);
 184   _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
 185   _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
 186   _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
 187   _young_other_cost_per_region_ms_seq->add(
 188                                young_other_cost_per_region_ms_defaults[index]);
 189   _non_young_other_cost_per_region_ms_seq->add(
 190                            non_young_other_cost_per_region_ms_defaults[index]);
 191 
 192   // Below, we might need to calculate the pause time target based on
 193   // the pause interval. When we do so we are going to give G1 maximum
 194   // flexibility and allow it to do pauses when it needs to. So, we'll
 195   // arrange that the pause interval to be pause time target + 1 to
 196   // ensure that a) the pause time target is maximized with respect to
 197   // the pause interval and b) we maintain the invariant that pause
 198   // time target < pause interval. If the user does not want this
 199   // maximum flexibility, they will have to set the pause interval
 200   // explicitly.
 201 
 202   // First make sure that, if either parameter is set, its value is
 203   // reasonable.
 204   if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 205     if (MaxGCPauseMillis < 1) {
 206       vm_exit_during_initialization("MaxGCPauseMillis should be "
 207                                     "greater than 0");
 208     }
 209   }
 210   if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 211     if (GCPauseIntervalMillis < 1) {
 212       vm_exit_during_initialization("GCPauseIntervalMillis should be "
 213                                     "greater than 0");
 214     }
 215   }
 216 
 217   // Then, if the pause time target parameter was not set, set it to
 218   // the default value.
 219   if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 220     if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 221       // The default pause time target in G1 is 200ms
 222       FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
 223     } else {
 224       // We do not allow the pause interval to be set without the
 225       // pause time target
 226       vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
 227                                     "without setting MaxGCPauseMillis");
 228     }
 229   }
 230 
 231   // Then, if the interval parameter was not set, set it according to
 232   // the pause time target (this will also deal with the case when the
 233   // pause time target is the default value).
 234   if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 235     FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
 236   }
 237 
 238   // Finally, make sure that the two parameters are consistent.
 239   if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
 240     char buffer[256];
 241     jio_snprintf(buffer, 256,
 242                  "MaxGCPauseMillis (%u) should be less than "
 243                  "GCPauseIntervalMillis (%u)",
 244                  MaxGCPauseMillis, GCPauseIntervalMillis);
 245     vm_exit_during_initialization(buffer);
 246   }
 247 
 248   double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
 249   double time_slice  = (double) GCPauseIntervalMillis / 1000.0;
 250   _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
 251 
 252   // start conservatively (around 50ms is about right)
 253   _concurrent_mark_remark_times_ms->add(0.05);
 254   _concurrent_mark_cleanup_times_ms->add(0.20);
 255   _tenuring_threshold = MaxTenuringThreshold;
 256 
 257   assert(GCTimeRatio > 0,
 258          "we should have set it to a default value set_g1_gc_flags() "
 259          "if a user set it to 0");
 260   _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
 261 
 262   uintx reserve_perc = G1ReservePercent;
 263   // Put an artificial ceiling on this so that it's not set to a silly value.
 264   if (reserve_perc > 50) {
 265     reserve_perc = 50;
 266     warning("G1ReservePercent is set to a value that is too large, "
 267             "it's been updated to " UINTX_FORMAT, reserve_perc);
 268   }
 269   _reserve_factor = (double) reserve_perc / 100.0;
 270   // This will be set when the heap is expanded
 271   // for the first time during initialization.
 272   _reserve_regions = 0;
 273 
 274   _cset_chooser = new CollectionSetChooser();
 275 }
 276 
 277 G1CollectorPolicy::~G1CollectorPolicy() {
 278   delete _ihop_control;
 279 }
 280 
 281 double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const {
 282   return _predictor.get_new_prediction(seq);
 283 }
 284 
 285 size_t G1CollectorPolicy::get_new_size_prediction(TruncatedSeq const* seq) const {
 286   return (size_t)get_new_prediction(seq);
 287 }
 288 
 289 void G1CollectorPolicy::initialize_alignments() {
 290   _space_alignment = HeapRegion::GrainBytes;
 291   size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
 292   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
 293   _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
 294 }
 295 
 296 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
 297 
 298 // There are three command line options related to the young gen size:
 299 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
 300 // just a short form for NewSize==MaxNewSize). G1 will use its internal
 301 // heuristics to calculate the actual young gen size, so these options
 302 // basically only limit the range within which G1 can pick a young gen
 303 // size. Also, these are general options taking byte sizes. G1 will
 304 // internally work with a number of regions instead. So, some rounding
 305 // will occur.
 306 //
 307 // If nothing related to the the young gen size is set on the command
 308 // line we should allow the young gen to be between G1NewSizePercent
 309 // and G1MaxNewSizePercent of the heap size. This means that every time
 310 // the heap size changes, the limits for the young gen size will be
 311 // recalculated.
 312 //
 313 // If only -XX:NewSize is set we should use the specified value as the
 314 // minimum size for young gen. Still using G1MaxNewSizePercent of the
 315 // heap as maximum.
 316 //
 317 // If only -XX:MaxNewSize is set we should use the specified value as the
 318 // maximum size for young gen. Still using G1NewSizePercent of the heap
 319 // as minimum.
 320 //
 321 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
 322 // No updates when the heap size changes. There is a special case when
 323 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
 324 // different heuristic for calculating the collection set when we do mixed
 325 // collection.
 326 //
 327 // If only -XX:NewRatio is set we should use the specified ratio of the heap
 328 // as both min and max. This will be interpreted as "fixed" just like the
 329 // NewSize==MaxNewSize case above. But we will update the min and max
 330 // every time the heap size changes.
 331 //
 332 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
 333 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
 334 class G1YoungGenSizer : public CHeapObj<mtGC> {
 335 private:
 336   enum SizerKind {
 337     SizerDefaults,
 338     SizerNewSizeOnly,
 339     SizerMaxNewSizeOnly,
 340     SizerMaxAndNewSize,
 341     SizerNewRatio
 342   };
 343   SizerKind _sizer_kind;
 344   uint _min_desired_young_length;
 345   uint _max_desired_young_length;
 346   bool _adaptive_size;
 347   uint calculate_default_min_length(uint new_number_of_heap_regions);
 348   uint calculate_default_max_length(uint new_number_of_heap_regions);
 349 
 350   // Update the given values for minimum and maximum young gen length in regions
 351   // given the number of heap regions depending on the kind of sizing algorithm.
 352   void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
 353 
 354 public:
 355   G1YoungGenSizer();
 356   // Calculate the maximum length of the young gen given the number of regions
 357   // depending on the sizing algorithm.
 358   uint max_young_length(uint number_of_heap_regions);
 359 
 360   void heap_size_changed(uint new_number_of_heap_regions);
 361   uint min_desired_young_length() {
 362     return _min_desired_young_length;
 363   }
 364   uint max_desired_young_length() {
 365     return _max_desired_young_length;
 366   }
 367 
 368   bool adaptive_young_list_length() const {
 369     return _adaptive_size;
 370   }
 371 };
 372 
 373 
 374 G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true),
 375         _min_desired_young_length(0), _max_desired_young_length(0) {
 376   if (FLAG_IS_CMDLINE(NewRatio)) {
 377     if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
 378       warning("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio");
 379     } else {
 380       _sizer_kind = SizerNewRatio;
 381       _adaptive_size = false;
 382       return;
 383     }
 384   }
 385 
 386   if (NewSize > MaxNewSize) {
 387     if (FLAG_IS_CMDLINE(MaxNewSize)) {
 388       warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
 389               "A new max generation size of " SIZE_FORMAT "k will be used.",
 390               NewSize/K, MaxNewSize/K, NewSize/K);
 391     }
 392     MaxNewSize = NewSize;
 393   }
 394 
 395   if (FLAG_IS_CMDLINE(NewSize)) {
 396     _min_desired_young_length = MAX2((uint) (NewSize / HeapRegion::GrainBytes),
 397                                      1U);
 398     if (FLAG_IS_CMDLINE(MaxNewSize)) {
 399       _max_desired_young_length =
 400                              MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
 401                                   1U);
 402       _sizer_kind = SizerMaxAndNewSize;
 403       _adaptive_size = _min_desired_young_length == _max_desired_young_length;
 404     } else {
 405       _sizer_kind = SizerNewSizeOnly;
 406     }
 407   } else if (FLAG_IS_CMDLINE(MaxNewSize)) {
 408     _max_desired_young_length =
 409                              MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
 410                                   1U);
 411     _sizer_kind = SizerMaxNewSizeOnly;
 412   }
 413 }
 414 
 415 uint G1YoungGenSizer::calculate_default_min_length(uint new_number_of_heap_regions) {
 416   uint default_value = (new_number_of_heap_regions * G1NewSizePercent) / 100;
 417   return MAX2(1U, default_value);
 418 }
 419 
 420 uint G1YoungGenSizer::calculate_default_max_length(uint new_number_of_heap_regions) {
 421   uint default_value = (new_number_of_heap_regions * G1MaxNewSizePercent) / 100;
 422   return MAX2(1U, default_value);
 423 }
 424 
 425 void G1YoungGenSizer::recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length) {
 426   assert(number_of_heap_regions > 0, "Heap must be initialized");
 427 
 428   switch (_sizer_kind) {
 429     case SizerDefaults:
 430       *min_young_length = calculate_default_min_length(number_of_heap_regions);
 431       *max_young_length = calculate_default_max_length(number_of_heap_regions);
 432       break;
 433     case SizerNewSizeOnly:
 434       *max_young_length = calculate_default_max_length(number_of_heap_regions);
 435       *max_young_length = MAX2(*min_young_length, *max_young_length);
 436       break;
 437     case SizerMaxNewSizeOnly:
 438       *min_young_length = calculate_default_min_length(number_of_heap_regions);
 439       *min_young_length = MIN2(*min_young_length, *max_young_length);
 440       break;
 441     case SizerMaxAndNewSize:
 442       // Do nothing. Values set on the command line, don't update them at runtime.
 443       break;
 444     case SizerNewRatio:
 445       *min_young_length = number_of_heap_regions / (NewRatio + 1);
 446       *max_young_length = *min_young_length;
 447       break;
 448     default:
 449       ShouldNotReachHere();
 450   }
 451 
 452   assert(*min_young_length <= *max_young_length, "Invalid min/max young gen size values");
 453 }
 454 
 455 uint G1YoungGenSizer::max_young_length(uint number_of_heap_regions) {
 456   // We need to pass the desired values because recalculation may not update these
 457   // values in some cases.
 458   uint temp = _min_desired_young_length;
 459   uint result = _max_desired_young_length;
 460   recalculate_min_max_young_length(number_of_heap_regions, &temp, &result);
 461   return result;
 462 }
 463 
 464 void G1YoungGenSizer::heap_size_changed(uint new_number_of_heap_regions) {
 465   recalculate_min_max_young_length(new_number_of_heap_regions, &_min_desired_young_length,
 466           &_max_desired_young_length);
 467 }
 468 
 469 void G1CollectorPolicy::post_heap_initialize() {
 470   uintx max_regions = G1CollectedHeap::heap()->max_regions();
 471   size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
 472   if (max_young_size != MaxNewSize) {
 473     FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
 474   }
 475 
 476   _ihop_control = create_ihop_control();
 477 }
 478 
 479 void G1CollectorPolicy::initialize_flags() {
 480   if (G1HeapRegionSize != HeapRegion::GrainBytes) {
 481     FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
 482   }
 483 
 484   if (SurvivorRatio < 1) {
 485     vm_exit_during_initialization("Invalid survivor ratio specified");
 486   }
 487   CollectorPolicy::initialize_flags();
 488   _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
 489 }
 490 
 491 
 492 void G1CollectorPolicy::init() {
 493   // Set aside an initial future to_space.
 494   _g1 = G1CollectedHeap::heap();
 495 
 496   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 497 
 498   initialize_gc_policy_counters();
 499 
 500   if (adaptive_young_list_length()) {
 501     _young_list_fixed_length = 0;
 502   } else {
 503     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 504   }
 505   _free_regions_at_end_of_collection = _g1->num_free_regions();
 506 
 507   update_young_list_max_and_target_length();
 508   // We may immediately start allocating regions and placing them on the
 509   // collection set list. Initialize the per-collection set info
 510   start_incremental_cset_building();
 511 }
 512 
 513 void G1CollectorPolicy::note_gc_start(uint num_active_workers) {
 514   phase_times()->note_gc_start(num_active_workers);
 515 }
 516 
 517 // Create the jstat counters for the policy.
 518 void G1CollectorPolicy::initialize_gc_policy_counters() {
 519   _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
 520 }
 521 
 522 bool G1CollectorPolicy::predict_will_fit(uint young_length,
 523                                          double base_time_ms,
 524                                          uint base_free_regions,
 525                                          double target_pause_time_ms) const {
 526   if (young_length >= base_free_regions) {
 527     // end condition 1: not enough space for the young regions
 528     return false;
 529   }
 530 
 531   double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
 532   size_t bytes_to_copy =
 533                (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
 534   double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
 535   double young_other_time_ms = predict_young_other_time_ms(young_length);
 536   double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
 537   if (pause_time_ms > target_pause_time_ms) {
 538     // end condition 2: prediction is over the target pause time
 539     return false;
 540   }
 541 
 542   size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
 543 
 544   // When copying, we will likely need more bytes free than is live in the region.
 545   // Add some safety margin to factor in the confidence of our guess, and the
 546   // natural expected waste.
 547   // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
 548   // of the calculation: the lower the confidence, the more headroom.
 549   // (100 + TargetPLABWastePct) represents the increase in expected bytes during
 550   // copying due to anticipated waste in the PLABs.
 551   double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
 552   size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
 553 
 554   if (expected_bytes_to_copy > free_bytes) {
 555     // end condition 3: out-of-space
 556     return false;
 557   }
 558 
 559   // success!
 560   return true;
 561 }
 562 
 563 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
 564   // re-calculate the necessary reserve
 565   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 566   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 567   // smaller than 1.0) we'll get 1.
 568   _reserve_regions = (uint) ceil(reserve_regions_d);
 569 
 570   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 571 }
 572 
 573 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
 574                                                        uint base_min_length) const {
 575   uint desired_min_length = 0;
 576   if (adaptive_young_list_length()) {
 577     if (_alloc_rate_ms_seq->num() > 3) {
 578       double now_sec = os::elapsedTime();
 579       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 580       double alloc_rate_ms = predict_alloc_rate_ms();
 581       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 582     } else {
 583       // otherwise we don't have enough info to make the prediction
 584     }
 585   }
 586   desired_min_length += base_min_length;
 587   // make sure we don't go below any user-defined minimum bound
 588   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 589 }
 590 
 591 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
 592   // Here, we might want to also take into account any additional
 593   // constraints (i.e., user-defined minimum bound). Currently, we
 594   // effectively don't set this bound.
 595   return _young_gen_sizer->max_desired_young_length();
 596 }
 597 
 598 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
 599   return update_young_list_max_and_target_length(get_new_size_prediction(_rs_lengths_seq));
 600 }
 601 
 602 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
 603   uint unbounded_target_length = update_young_list_target_length(rs_lengths);
 604   update_max_gc_locker_expansion();
 605   return unbounded_target_length;
 606 }
 607 
 608 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
 609   YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
 610   _young_list_target_length = young_lengths.first;
 611   return young_lengths.second;
 612 }
 613 
 614 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
 615   YoungTargetLengths result;
 616 
 617   // Calculate the absolute and desired min bounds first.
 618 
 619   // This is how many young regions we already have (currently: the survivors).
 620   uint base_min_length = recorded_survivor_regions();
 621   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 622   // This is the absolute minimum young length. Ensure that we
 623   // will at least have one eden region available for allocation.
 624   uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
 625   // If we shrank the young list target it should not shrink below the current size.
 626   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 627   // Calculate the absolute and desired max bounds.
 628 
 629   uint desired_max_length = calculate_young_list_desired_max_length();
 630 
 631   uint young_list_target_length = 0;
 632   if (adaptive_young_list_length()) {
 633     if (collector_state()->gcs_are_young()) {
 634       young_list_target_length =
 635                         calculate_young_list_target_length(rs_lengths,
 636                                                            base_min_length,
 637                                                            desired_min_length,
 638                                                            desired_max_length);
 639     } else {
 640       // Don't calculate anything and let the code below bound it to
 641       // the desired_min_length, i.e., do the next GC as soon as
 642       // possible to maximize how many old regions we can add to it.
 643     }
 644   } else {
 645     // The user asked for a fixed young gen so we'll fix the young gen
 646     // whether the next GC is young or mixed.
 647     young_list_target_length = _young_list_fixed_length;
 648   }
 649 
 650   result.second = young_list_target_length;
 651 
 652   // We will try our best not to "eat" into the reserve.
 653   uint absolute_max_length = 0;
 654   if (_free_regions_at_end_of_collection > _reserve_regions) {
 655     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 656   }
 657   if (desired_max_length > absolute_max_length) {
 658     desired_max_length = absolute_max_length;
 659   }
 660 
 661   // Make sure we don't go over the desired max length, nor under the
 662   // desired min length. In case they clash, desired_min_length wins
 663   // which is why that test is second.
 664   if (young_list_target_length > desired_max_length) {
 665     young_list_target_length = desired_max_length;
 666   }
 667   if (young_list_target_length < desired_min_length) {
 668     young_list_target_length = desired_min_length;
 669   }
 670 
 671   assert(young_list_target_length > recorded_survivor_regions(),
 672          "we should be able to allocate at least one eden region");
 673   assert(young_list_target_length >= absolute_min_length, "post-condition");
 674 
 675   result.first = young_list_target_length;
 676   return result;
 677 }
 678 
 679 uint
 680 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
 681                                                      uint base_min_length,
 682                                                      uint desired_min_length,
 683                                                      uint desired_max_length) const {
 684   assert(adaptive_young_list_length(), "pre-condition");
 685   assert(collector_state()->gcs_are_young(), "only call this for young GCs");
 686 
 687   // In case some edge-condition makes the desired max length too small...
 688   if (desired_max_length <= desired_min_length) {
 689     return desired_min_length;
 690   }
 691 
 692   // We'll adjust min_young_length and max_young_length not to include
 693   // the already allocated young regions (i.e., so they reflect the
 694   // min and max eden regions we'll allocate). The base_min_length
 695   // will be reflected in the predictions by the
 696   // survivor_regions_evac_time prediction.
 697   assert(desired_min_length > base_min_length, "invariant");
 698   uint min_young_length = desired_min_length - base_min_length;
 699   assert(desired_max_length > base_min_length, "invariant");
 700   uint max_young_length = desired_max_length - base_min_length;
 701 
 702   double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 703   double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 704   size_t pending_cards = get_new_size_prediction(_pending_cards_seq);
 705   size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
 706   size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
 707   double base_time_ms =
 708     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
 709     survivor_regions_evac_time;
 710   uint available_free_regions = _free_regions_at_end_of_collection;
 711   uint base_free_regions = 0;
 712   if (available_free_regions > _reserve_regions) {
 713     base_free_regions = available_free_regions - _reserve_regions;
 714   }
 715 
 716   // Here, we will make sure that the shortest young length that
 717   // makes sense fits within the target pause time.
 718 
 719   if (predict_will_fit(min_young_length, base_time_ms,
 720                        base_free_regions, target_pause_time_ms)) {
 721     // The shortest young length will fit into the target pause time;
 722     // we'll now check whether the absolute maximum number of young
 723     // regions will fit in the target pause time. If not, we'll do
 724     // a binary search between min_young_length and max_young_length.
 725     if (predict_will_fit(max_young_length, base_time_ms,
 726                          base_free_regions, target_pause_time_ms)) {
 727       // The maximum young length will fit into the target pause time.
 728       // We are done so set min young length to the maximum length (as
 729       // the result is assumed to be returned in min_young_length).
 730       min_young_length = max_young_length;
 731     } else {
 732       // The maximum possible number of young regions will not fit within
 733       // the target pause time so we'll search for the optimal
 734       // length. The loop invariants are:
 735       //
 736       // min_young_length < max_young_length
 737       // min_young_length is known to fit into the target pause time
 738       // max_young_length is known not to fit into the target pause time
 739       //
 740       // Going into the loop we know the above hold as we've just
 741       // checked them. Every time around the loop we check whether
 742       // the middle value between min_young_length and
 743       // max_young_length fits into the target pause time. If it
 744       // does, it becomes the new min. If it doesn't, it becomes
 745       // the new max. This way we maintain the loop invariants.
 746 
 747       assert(min_young_length < max_young_length, "invariant");
 748       uint diff = (max_young_length - min_young_length) / 2;
 749       while (diff > 0) {
 750         uint young_length = min_young_length + diff;
 751         if (predict_will_fit(young_length, base_time_ms,
 752                              base_free_regions, target_pause_time_ms)) {
 753           min_young_length = young_length;
 754         } else {
 755           max_young_length = young_length;
 756         }
 757         assert(min_young_length <  max_young_length, "invariant");
 758         diff = (max_young_length - min_young_length) / 2;
 759       }
 760       // The results is min_young_length which, according to the
 761       // loop invariants, should fit within the target pause time.
 762 
 763       // These are the post-conditions of the binary search above:
 764       assert(min_young_length < max_young_length,
 765              "otherwise we should have discovered that max_young_length "
 766              "fits into the pause target and not done the binary search");
 767       assert(predict_will_fit(min_young_length, base_time_ms,
 768                               base_free_regions, target_pause_time_ms),
 769              "min_young_length, the result of the binary search, should "
 770              "fit into the pause target");
 771       assert(!predict_will_fit(min_young_length + 1, base_time_ms,
 772                                base_free_regions, target_pause_time_ms),
 773              "min_young_length, the result of the binary search, should be "
 774              "optimal, so no larger length should fit into the pause target");
 775     }
 776   } else {
 777     // Even the minimum length doesn't fit into the pause time
 778     // target, return it as the result nevertheless.
 779   }
 780   return base_min_length + min_young_length;
 781 }
 782 
 783 double G1CollectorPolicy::predict_survivor_regions_evac_time() const {
 784   double survivor_regions_evac_time = 0.0;
 785   for (HeapRegion * r = _recorded_survivor_head;
 786        r != NULL && r != _recorded_survivor_tail->get_next_young_region();
 787        r = r->get_next_young_region()) {
 788     survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
 789   }
 790   return survivor_regions_evac_time;
 791 }
 792 
 793 void G1CollectorPolicy::revise_young_list_target_length_if_necessary() {
 794   guarantee( adaptive_young_list_length(), "should not call this otherwise" );
 795 
 796   size_t rs_lengths = _g1->young_list()->sampled_rs_lengths();
 797   if (rs_lengths > _rs_lengths_prediction) {
 798     // add 10% to avoid having to recalculate often
 799     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 800     update_rs_lengths_prediction(rs_lengths_prediction);
 801 
 802     update_young_list_max_and_target_length(rs_lengths_prediction);
 803   }
 804 }
 805 
 806 void G1CollectorPolicy::update_rs_lengths_prediction() {
 807   update_rs_lengths_prediction(get_new_size_prediction(_rs_lengths_seq));
 808 }
 809 
 810 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
 811   if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
 812     _rs_lengths_prediction = prediction;
 813   }
 814 }
 815 
 816 #ifndef PRODUCT
 817 bool G1CollectorPolicy::verify_young_ages() {
 818   HeapRegion* head = _g1->young_list()->first_region();
 819   return
 820     verify_young_ages(head, _short_lived_surv_rate_group);
 821   // also call verify_young_ages on any additional surv rate groups
 822 }
 823 
 824 bool
 825 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
 826                                      SurvRateGroup *surv_rate_group) {
 827   guarantee( surv_rate_group != NULL, "pre-condition" );
 828 
 829   const char* name = surv_rate_group->name();
 830   bool ret = true;
 831   int prev_age = -1;
 832 
 833   for (HeapRegion* curr = head;
 834        curr != NULL;
 835        curr = curr->get_next_young_region()) {
 836     SurvRateGroup* group = curr->surv_rate_group();
 837     if (group == NULL && !curr->is_survivor()) {
 838       log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);
 839       ret = false;
 840     }
 841 
 842     if (surv_rate_group == group) {
 843       int age = curr->age_in_surv_rate_group();
 844 
 845       if (age < 0) {
 846         log_error(gc, verify)("## %s: encountered negative age", name);
 847         ret = false;
 848       }
 849 
 850       if (age <= prev_age) {
 851         log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
 852         ret = false;
 853       }
 854       prev_age = age;
 855     }
 856   }
 857 
 858   return ret;
 859 }
 860 #endif // PRODUCT
 861 
 862 void G1CollectorPolicy::record_full_collection_start() {
 863   _full_collection_start_sec = os::elapsedTime();
 864   // Release the future to-space so that it is available for compaction into.
 865   collector_state()->set_full_collection(true);
 866 }
 867 
 868 void G1CollectorPolicy::record_full_collection_end() {
 869   // Consider this like a collection pause for the purposes of allocation
 870   // since last pause.
 871   double end_sec = os::elapsedTime();
 872   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 873   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 874 
 875   _trace_old_gen_time_data.record_full_collection(full_gc_time_ms);
 876 
 877   update_recent_gc_times(end_sec, full_gc_time_ms);
 878 
 879   collector_state()->set_full_collection(false);
 880 
 881   // "Nuke" the heuristics that control the young/mixed GC
 882   // transitions and make sure we start with young GCs after the Full GC.
 883   collector_state()->set_gcs_are_young(true);
 884   collector_state()->set_last_young_gc(false);
 885   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
 886   collector_state()->set_during_initial_mark_pause(false);
 887   collector_state()->set_in_marking_window(false);
 888   collector_state()->set_in_marking_window_im(false);
 889 
 890   _short_lived_surv_rate_group->start_adding_regions();
 891   // also call this on any additional surv rate groups
 892 
 893   record_survivor_regions(0, NULL, NULL);
 894 
 895   _free_regions_at_end_of_collection = _g1->num_free_regions();
 896   // Reset survivors SurvRateGroup.
 897   _survivor_surv_rate_group->reset();
 898   update_young_list_max_and_target_length();
 899   update_rs_lengths_prediction();
 900   cset_chooser()->clear();
 901 
 902   _bytes_allocated_in_old_since_last_gc = 0;
 903 
 904   record_pause(FullGC, _full_collection_start_sec, end_sec);
 905 }
 906 
 907 void G1CollectorPolicy::record_stop_world_start() {
 908   _stop_world_start = os::elapsedTime();
 909 }
 910 
 911 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) {
 912   // We only need to do this here as the policy will only be applied
 913   // to the GC we're about to start. so, no point is calculating this
 914   // every time we calculate / recalculate the target young length.
 915   update_survivors_policy();
 916 
 917   assert(_g1->used() == _g1->recalculate_used(),
 918          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
 919          _g1->used(), _g1->recalculate_used());
 920 
 921   double s_w_t_ms = (start_time_sec - _stop_world_start) * 1000.0;
 922   _trace_young_gen_time_data.record_start_collection(s_w_t_ms);
 923   _stop_world_start = 0.0;
 924 
 925   phase_times()->record_cur_collection_start_sec(start_time_sec);
 926   _pending_cards = _g1->pending_card_num();
 927 
 928   _collection_set_bytes_used_before = 0;
 929   _bytes_copied_during_gc = 0;
 930 
 931   collector_state()->set_last_gc_was_young(false);
 932 
 933   // do that for any other surv rate groups
 934   _short_lived_surv_rate_group->stop_adding_regions();
 935   _survivors_age_table.clear();
 936 
 937   assert( verify_young_ages(), "region age verification" );
 938 }
 939 
 940 void G1CollectorPolicy::record_concurrent_mark_init_end(double
 941                                                    mark_init_elapsed_time_ms) {
 942   collector_state()->set_during_marking(true);
 943   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 944   collector_state()->set_during_initial_mark_pause(false);
 945 }
 946 
 947 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
 948   _mark_remark_start_sec = os::elapsedTime();
 949   collector_state()->set_during_marking(false);
 950 }
 951 
 952 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
 953   double end_time_sec = os::elapsedTime();
 954   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 955   _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
 956   _prev_collection_pause_end_ms += elapsed_time_ms;
 957 
 958   record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 959 }
 960 
 961 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
 962   _mark_cleanup_start_sec = os::elapsedTime();
 963 }
 964 
 965 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
 966   bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
 967                                                               "skip last young-only gc");
 968   collector_state()->set_last_young_gc(should_continue_with_reclaim);
 969   // We skip the marking phase.
 970   if (!should_continue_with_reclaim) {
 971     abort_time_to_mixed_tracking();
 972   }
 973   collector_state()->set_in_marking_window(false);
 974 }
 975 
 976 void G1CollectorPolicy::record_concurrent_pause() {
 977   if (_stop_world_start > 0.0) {
 978     double yield_ms = (os::elapsedTime() - _stop_world_start) * 1000.0;
 979     _trace_young_gen_time_data.record_yield_time(yield_ms);
 980   }
 981 }
 982 
 983 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
 984   return phase_times()->average_time_ms(phase);
 985 }
 986 
 987 double G1CollectorPolicy::young_other_time_ms() const {
 988   return phase_times()->young_cset_choice_time_ms() +
 989          phase_times()->young_free_cset_time_ms();
 990 }
 991 
 992 double G1CollectorPolicy::non_young_other_time_ms() const {
 993   return phase_times()->non_young_cset_choice_time_ms() +
 994          phase_times()->non_young_free_cset_time_ms();
 995 
 996 }
 997 
 998 double G1CollectorPolicy::other_time_ms(double pause_time_ms) const {
 999   return pause_time_ms -
1000          average_time_ms(G1GCPhaseTimes::UpdateRS) -
1001          average_time_ms(G1GCPhaseTimes::ScanRS) -
1002          average_time_ms(G1GCPhaseTimes::ObjCopy) -
1003          average_time_ms(G1GCPhaseTimes::Termination);
1004 }
1005 
1006 double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const {
1007   return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
1008 }
1009 
1010 bool G1CollectorPolicy::about_to_start_mixed_phase() const {
1011   return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
1012 }
1013 
1014 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
1015   if (about_to_start_mixed_phase()) {
1016     return false;
1017   }
1018 
1019   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
1020 
1021   size_t cur_used_bytes = _g1->non_young_capacity_bytes();
1022   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
1023   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
1024 
1025   bool result = false;
1026   if (marking_request_bytes > marking_initiating_used_threshold) {
1027     result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
1028     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
1029                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
1030                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
1031   }
1032 
1033   return result;
1034 }
1035 
1036 // Anything below that is considered to be zero
1037 #define MIN_TIMER_GRANULARITY 0.0000001
1038 
1039 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
1040   double end_time_sec = os::elapsedTime();
1041 
1042   size_t cur_used_bytes = _g1->used();
1043   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
1044   bool last_pause_included_initial_mark = false;
1045   bool update_stats = !_g1->evacuation_failed();
1046 
1047   NOT_PRODUCT(_short_lived_surv_rate_group->print());
1048 
1049   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
1050 
1051   last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
1052   if (last_pause_included_initial_mark) {
1053     record_concurrent_mark_init_end(0.0);
1054   } else {
1055     maybe_start_marking();
1056   }
1057 
1058   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
1059   if (app_time_ms < MIN_TIMER_GRANULARITY) {
1060     // This usually happens due to the timer not having the required
1061     // granularity. Some Linuxes are the usual culprits.
1062     // We'll just set it to something (arbitrarily) small.
1063     app_time_ms = 1.0;
1064   }
1065 
1066   if (update_stats) {
1067     _trace_young_gen_time_data.record_end_collection(pause_time_ms, phase_times());
1068     // We maintain the invariant that all objects allocated by mutator
1069     // threads will be allocated out of eden regions. So, we can use
1070     // the eden region number allocated since the previous GC to
1071     // calculate the application's allocate rate. The only exception
1072     // to that is humongous objects that are allocated separately. But
1073     // given that humongous object allocations do not really affect
1074     // either the pause's duration nor when the next pause will take
1075     // place we can safely ignore them here.
1076     uint regions_allocated = eden_cset_region_length();
1077     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
1078     _alloc_rate_ms_seq->add(alloc_rate_ms);
1079 
1080     double interval_ms =
1081       (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
1082     update_recent_gc_times(end_time_sec, pause_time_ms);
1083     _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
1084     if (recent_avg_pause_time_ratio() < 0.0 ||
1085         (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
1086       // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
1087       // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
1088       if (_recent_avg_pause_time_ratio < 0.0) {
1089         _recent_avg_pause_time_ratio = 0.0;
1090       } else {
1091         assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
1092         _recent_avg_pause_time_ratio = 1.0;
1093       }
1094     }
1095 
1096     // Compute the ratio of just this last pause time to the entire time range stored
1097     // in the vectors. Comparing this pause to the entire range, rather than only the
1098     // most recent interval, has the effect of smoothing over a possible transient 'burst'
1099     // of more frequent pauses that don't really reflect a change in heap occupancy.
1100     // This reduces the likelihood of a needless heap expansion being triggered.
1101     _last_pause_time_ratio =
1102       (pause_time_ms * _recent_prev_end_times_for_all_gcs_sec->num()) / interval_ms;
1103   }
1104 
1105   bool new_in_marking_window = collector_state()->in_marking_window();
1106   bool new_in_marking_window_im = false;
1107   if (last_pause_included_initial_mark) {
1108     new_in_marking_window = true;
1109     new_in_marking_window_im = true;
1110   }
1111 
1112   if (collector_state()->last_young_gc()) {
1113     // This is supposed to to be the "last young GC" before we start
1114     // doing mixed GCs. Here we decide whether to start mixed GCs or not.
1115     assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
1116 
1117     if (next_gc_should_be_mixed("start mixed GCs",
1118                                 "do not start mixed GCs")) {
1119       collector_state()->set_gcs_are_young(false);
1120     } else {
1121       // We aborted the mixed GC phase early.
1122       abort_time_to_mixed_tracking();
1123     }
1124 
1125     collector_state()->set_last_young_gc(false);
1126   }
1127 
1128   if (!collector_state()->last_gc_was_young()) {
1129     // This is a mixed GC. Here we decide whether to continue doing
1130     // mixed GCs or not.
1131     if (!next_gc_should_be_mixed("continue mixed GCs",
1132                                  "do not continue mixed GCs")) {
1133       collector_state()->set_gcs_are_young(true);
1134 
1135       maybe_start_marking();
1136     }
1137   }
1138 
1139   _short_lived_surv_rate_group->start_adding_regions();
1140   // Do that for any other surv rate groups
1141 
1142   if (update_stats) {
1143     double cost_per_card_ms = 0.0;
1144     double cost_scan_hcc = average_time_ms(G1GCPhaseTimes::ScanHCC);
1145     if (_pending_cards > 0) {
1146       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - cost_scan_hcc) / (double) _pending_cards;
1147       _cost_per_card_ms_seq->add(cost_per_card_ms);
1148     }
1149     _cost_scan_hcc_seq->add(cost_scan_hcc);
1150 
1151     double cost_per_entry_ms = 0.0;
1152     if (cards_scanned > 10) {
1153       cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
1154       if (collector_state()->last_gc_was_young()) {
1155         _cost_per_entry_ms_seq->add(cost_per_entry_ms);
1156       } else {
1157         _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
1158       }
1159     }
1160 
1161     if (_max_rs_lengths > 0) {
1162       double cards_per_entry_ratio =
1163         (double) cards_scanned / (double) _max_rs_lengths;
1164       if (collector_state()->last_gc_was_young()) {
1165         _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1166       } else {
1167         _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1168       }
1169     }
1170 
1171     // This is defensive. For a while _max_rs_lengths could get
1172     // smaller than _recorded_rs_lengths which was causing
1173     // rs_length_diff to get very large and mess up the RSet length
1174     // predictions. The reason was unsafe concurrent updates to the
1175     // _inc_cset_recorded_rs_lengths field which the code below guards
1176     // against (see CR 7118202). This bug has now been fixed (see CR
1177     // 7119027). However, I'm still worried that
1178     // _inc_cset_recorded_rs_lengths might still end up somewhat
1179     // inaccurate. The concurrent refinement thread calculates an
1180     // RSet's length concurrently with other CR threads updating it
1181     // which might cause it to calculate the length incorrectly (if,
1182     // say, it's in mid-coarsening). So I'll leave in the defensive
1183     // conditional below just in case.
1184     size_t rs_length_diff = 0;
1185     if (_max_rs_lengths > _recorded_rs_lengths) {
1186       rs_length_diff = _max_rs_lengths - _recorded_rs_lengths;
1187     }
1188     _rs_length_diff_seq->add((double) rs_length_diff);
1189 
1190     size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
1191     size_t copied_bytes = _collection_set_bytes_used_before - freed_bytes;
1192     double cost_per_byte_ms = 0.0;
1193 
1194     if (copied_bytes > 0) {
1195       cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
1196       if (collector_state()->in_marking_window()) {
1197         _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
1198       } else {
1199         _cost_per_byte_ms_seq->add(cost_per_byte_ms);
1200       }
1201     }
1202 
1203     if (young_cset_region_length() > 0) {
1204       _young_other_cost_per_region_ms_seq->add(young_other_time_ms() /
1205                                                young_cset_region_length());
1206     }
1207 
1208     if (old_cset_region_length() > 0) {
1209       _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() /
1210                                                    old_cset_region_length());
1211     }
1212 
1213     _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms));
1214 
1215     _pending_cards_seq->add((double) _pending_cards);
1216     _rs_lengths_seq->add((double) _max_rs_lengths);
1217   }
1218 
1219   collector_state()->set_in_marking_window(new_in_marking_window);
1220   collector_state()->set_in_marking_window_im(new_in_marking_window_im);
1221   _free_regions_at_end_of_collection = _g1->num_free_regions();
1222   // IHOP control wants to know the expected young gen length if it were not
1223   // restrained by the heap reserve. Using the actual length would make the
1224   // prediction too small and the limit the young gen every time we get to the
1225   // predicted target occupancy.
1226   size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
1227   update_rs_lengths_prediction();
1228 
1229   update_ihop_prediction(app_time_ms / 1000.0,
1230                          _bytes_allocated_in_old_since_last_gc,
1231                          last_unrestrained_young_length * HeapRegion::GrainBytes);
1232   _bytes_allocated_in_old_since_last_gc = 0;
1233 
1234   _ihop_control->send_trace_event(_g1->gc_tracer_stw());
1235 
1236   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1237   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
1238 
1239   double scan_hcc_time_ms = average_time_ms(G1GCPhaseTimes::ScanHCC);
1240 
1241   if (update_rs_time_goal_ms < scan_hcc_time_ms) {
1242     log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
1243                                 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
1244                                 update_rs_time_goal_ms, scan_hcc_time_ms);
1245 
1246     update_rs_time_goal_ms = 0;
1247   } else {
1248     update_rs_time_goal_ms -= scan_hcc_time_ms;
1249   }
1250   adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
1251                                phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
1252                                update_rs_time_goal_ms);
1253 
1254   cset_chooser()->verify();
1255 }
1256 
1257 G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
1258   if (G1UseAdaptiveIHOP) {
1259     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
1260                                      G1CollectedHeap::heap()->max_capacity(),
1261                                      &_predictor,
1262                                      G1ReservePercent,
1263                                      G1HeapWastePercent);
1264   } else {
1265     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent,
1266                                    G1CollectedHeap::heap()->max_capacity());
1267   }
1268 }
1269 
1270 void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s,
1271                                                size_t mutator_alloc_bytes,
1272                                                size_t young_gen_size) {
1273   // Always try to update IHOP prediction. Even evacuation failures give information
1274   // about e.g. whether to start IHOP earlier next time.
1275 
1276   // Avoid using really small application times that might create samples with
1277   // very high or very low values. They may be caused by e.g. back-to-back gcs.
1278   double const min_valid_time = 1e-6;
1279 
1280   bool report = false;
1281 
1282   double marking_to_mixed_time = -1.0;
1283   if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
1284     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
1285     assert(marking_to_mixed_time > 0.0,
1286            "Initial mark to mixed time must be larger than zero but is %.3f",
1287            marking_to_mixed_time);
1288     if (marking_to_mixed_time > min_valid_time) {
1289       _ihop_control->update_marking_length(marking_to_mixed_time);
1290       report = true;
1291     }
1292   }
1293 
1294   // As an approximation for the young gc promotion rates during marking we use
1295   // all of them. In many applications there are only a few if any young gcs during
1296   // marking, which makes any prediction useless. This increases the accuracy of the
1297   // prediction.
1298   if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
1299     _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
1300     report = true;
1301   }
1302 
1303   if (report) {
1304     report_ihop_statistics();
1305   }
1306 }
1307 
1308 void G1CollectorPolicy::report_ihop_statistics() {
1309   _ihop_control->print();
1310 }
1311 
1312 void G1CollectorPolicy::print_phases() {
1313   phase_times()->print();
1314 }
1315 
1316 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
1317                                                      double update_rs_processed_buffers,
1318                                                      double goal_ms) {
1319   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1320   ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
1321 
1322   if (G1UseAdaptiveConcRefinement) {
1323     const int k_gy = 3, k_gr = 6;
1324     const double inc_k = 1.1, dec_k = 0.9;
1325 
1326     size_t g = cg1r->green_zone();
1327     if (update_rs_time > goal_ms) {
1328       g = (size_t)(g * dec_k);  // Can become 0, that's OK. That would mean a mutator-only processing.
1329     } else {
1330       if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
1331         g = (size_t)MAX2(g * inc_k, g + 1.0);
1332       }
1333     }
1334     // Change the refinement threads params
1335     cg1r->set_green_zone(g);
1336     cg1r->set_yellow_zone(g * k_gy);
1337     cg1r->set_red_zone(g * k_gr);
1338     cg1r->reinitialize_threads();
1339 
1340     size_t processing_threshold_delta = MAX2<size_t>(cg1r->green_zone() * _predictor.sigma(), 1);
1341     size_t processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1342                                     cg1r->yellow_zone());
1343     // Change the barrier params
1344     dcqs.set_process_completed_threshold(processing_threshold);
1345     dcqs.set_max_completed_queue(cg1r->red_zone());
1346   }
1347 
1348   size_t curr_queue_size = dcqs.completed_buffers_num();
1349   if (curr_queue_size >= cg1r->yellow_zone()) {
1350     dcqs.set_completed_queue_padding(curr_queue_size);
1351   } else {
1352     dcqs.set_completed_queue_padding(0);
1353   }
1354   dcqs.notify_if_necessary();
1355 }
1356 
1357 size_t G1CollectorPolicy::predict_rs_length_diff() const {
1358   return get_new_size_prediction(_rs_length_diff_seq);
1359 }
1360 
1361 double G1CollectorPolicy::predict_alloc_rate_ms() const {
1362   return get_new_prediction(_alloc_rate_ms_seq);
1363 }
1364 
1365 double G1CollectorPolicy::predict_cost_per_card_ms() const {
1366   return get_new_prediction(_cost_per_card_ms_seq);
1367 }
1368 
1369 double G1CollectorPolicy::predict_scan_hcc_ms() const {
1370   return get_new_prediction(_cost_scan_hcc_seq);
1371 }
1372 
1373 double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const {
1374   return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms();
1375 }
1376 
1377 double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const {
1378   return get_new_prediction(_young_cards_per_entry_ratio_seq);
1379 }
1380 
1381 double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const {
1382   if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
1383     return predict_young_cards_per_entry_ratio();
1384   } else {
1385     return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
1386   }
1387 }
1388 
1389 size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const {
1390   return (size_t) (rs_length * predict_young_cards_per_entry_ratio());
1391 }
1392 
1393 size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const {
1394   return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio());
1395 }
1396 
1397 double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const {
1398   if (collector_state()->gcs_are_young()) {
1399     return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1400   } else {
1401     return predict_mixed_rs_scan_time_ms(card_num);
1402   }
1403 }
1404 
1405 double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const {
1406   if (_mixed_cost_per_entry_ms_seq->num() < 3) {
1407     return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1408   } else {
1409     return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq);
1410   }
1411 }
1412 
1413 double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const {
1414   if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
1415     return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq);
1416   } else {
1417     return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq);
1418   }
1419 }
1420 
1421 double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const {
1422   if (collector_state()->during_concurrent_mark()) {
1423     return predict_object_copy_time_ms_during_cm(bytes_to_copy);
1424   } else {
1425     return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq);
1426   }
1427 }
1428 
1429 double G1CollectorPolicy::predict_constant_other_time_ms() const {
1430   return get_new_prediction(_constant_other_time_ms_seq);
1431 }
1432 
1433 double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const {
1434   return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq);
1435 }
1436 
1437 double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const {
1438   return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq);
1439 }
1440 
1441 double G1CollectorPolicy::predict_remark_time_ms() const {
1442   return get_new_prediction(_concurrent_mark_remark_times_ms);
1443 }
1444 
1445 double G1CollectorPolicy::predict_cleanup_time_ms() const {
1446   return get_new_prediction(_concurrent_mark_cleanup_times_ms);
1447 }
1448 
1449 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1450   TruncatedSeq* seq = surv_rate_group->get_seq(age);
1451   guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1452   double pred = get_new_prediction(seq);
1453   if (pred > 1.0) {
1454     pred = 1.0;
1455   }
1456   return pred;
1457 }
1458 
1459 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1460   return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1461 }
1462 
1463 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1464   return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1465 }
1466 
1467 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1468                                                        size_t scanned_cards) const {
1469   return
1470     predict_rs_update_time_ms(pending_cards) +
1471     predict_rs_scan_time_ms(scanned_cards) +
1472     predict_constant_other_time_ms();
1473 }
1474 
1475 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1476   size_t rs_length = predict_rs_length_diff();
1477   size_t card_num;
1478   if (collector_state()->gcs_are_young()) {
1479     card_num = predict_young_card_num(rs_length);
1480   } else {
1481     card_num = predict_non_young_card_num(rs_length);
1482   }
1483   return predict_base_elapsed_time_ms(pending_cards, card_num);
1484 }
1485 
1486 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1487   size_t bytes_to_copy;
1488   if (hr->is_marked())
1489     bytes_to_copy = hr->max_live_bytes();
1490   else {
1491     assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1492     int age = hr->age_in_surv_rate_group();
1493     double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1494     bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1495   }
1496   return bytes_to_copy;
1497 }
1498 
1499 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1500                                                          bool for_young_gc) const {
1501   size_t rs_length = hr->rem_set()->occupied();
1502   size_t card_num;
1503 
1504   // Predicting the number of cards is based on which type of GC
1505   // we're predicting for.
1506   if (for_young_gc) {
1507     card_num = predict_young_card_num(rs_length);
1508   } else {
1509     card_num = predict_non_young_card_num(rs_length);
1510   }
1511   size_t bytes_to_copy = predict_bytes_to_copy(hr);
1512 
1513   double region_elapsed_time_ms =
1514     predict_rs_scan_time_ms(card_num) +
1515     predict_object_copy_time_ms(bytes_to_copy);
1516 
1517   // The prediction of the "other" time for this region is based
1518   // upon the region type and NOT the GC type.
1519   if (hr->is_young()) {
1520     region_elapsed_time_ms += predict_young_other_time_ms(1);
1521   } else {
1522     region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1523   }
1524   return region_elapsed_time_ms;
1525 }
1526 
1527 void G1CollectorPolicy::init_cset_region_lengths(uint eden_cset_region_length,
1528                                                  uint survivor_cset_region_length) {
1529   _eden_cset_region_length     = eden_cset_region_length;
1530   _survivor_cset_region_length = survivor_cset_region_length;
1531   _old_cset_region_length      = 0;
1532 }
1533 
1534 void G1CollectorPolicy::set_recorded_rs_lengths(size_t rs_lengths) {
1535   _recorded_rs_lengths = rs_lengths;
1536 }
1537 
1538 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1539                                                double elapsed_ms) {
1540   _recent_gc_times_ms->add(elapsed_ms);
1541   _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1542   _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1543 }
1544 
1545 void G1CollectorPolicy::clear_ratio_check_data() {
1546   _ratio_over_threshold_count = 0;
1547   _ratio_over_threshold_sum = 0.0;
1548   _pauses_since_start = 0;
1549 }
1550 
1551 size_t G1CollectorPolicy::expansion_amount() {
1552   double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1553   double last_gc_overhead = _last_pause_time_ratio * 100.0;
1554   double threshold = _gc_overhead_perc;
1555   size_t expand_bytes = 0;
1556 
1557   // If the heap is at less than half its maximum size, scale the threshold down,
1558   // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1559   // though the scaling code will likely keep the increase small.
1560   if (_g1->capacity() <= _g1->max_capacity() / 2) {
1561     threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1562     threshold = MAX2(threshold, 1.0);
1563   }
1564 
1565   // If the last GC time ratio is over the threshold, increment the count of
1566   // times it has been exceeded, and add this ratio to the sum of exceeded
1567   // ratios.
1568   if (last_gc_overhead > threshold) {
1569     _ratio_over_threshold_count++;
1570     _ratio_over_threshold_sum += last_gc_overhead;
1571   }
1572 
1573   // Check if we've had enough GC time ratio checks that were over the
1574   // threshold to trigger an expansion. We'll also expand if we've
1575   // reached the end of the history buffer and the average of all entries
1576   // is still over the threshold. This indicates a smaller number of GCs were
1577   // long enough to make the average exceed the threshold.
1578   bool filled_history_buffer = _pauses_since_start == NumPrevPausesForHeuristics;
1579   if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) ||
1580       (filled_history_buffer && (recent_gc_overhead > threshold))) {
1581     size_t min_expand_bytes = HeapRegion::GrainBytes;
1582     size_t reserved_bytes = _g1->max_capacity();
1583     size_t committed_bytes = _g1->capacity();
1584     size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1585     size_t expand_bytes_via_pct =
1586       uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1587     double scale_factor = 1.0;
1588 
1589     // If the current size is less than 1/4 of the Initial heap size, expand
1590     // by half of the delta between the current and Initial sizes. IE, grow
1591     // back quickly.
1592     //
1593     // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of
1594     // the available expansion space, whichever is smaller, as the base
1595     // expansion size. Then possibly scale this size according to how much the
1596     // threshold has (on average) been exceeded by. If the delta is small
1597     // (less than the StartScaleDownAt value), scale the size down linearly, but
1598     // not by less than MinScaleDownFactor. If the delta is large (greater than
1599     // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor
1600     // times the base size. The scaling will be linear in the range from
1601     // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words,
1602     // ScaleUpRange sets the rate of scaling up.
1603     if (committed_bytes < InitialHeapSize / 4) {
1604       expand_bytes = (InitialHeapSize - committed_bytes) / 2;
1605     } else {
1606       double const MinScaleDownFactor = 0.2;
1607       double const MaxScaleUpFactor = 2;
1608       double const StartScaleDownAt = _gc_overhead_perc;
1609       double const StartScaleUpAt = _gc_overhead_perc * 1.5;
1610       double const ScaleUpRange = _gc_overhead_perc * 2.0;
1611 
1612       double ratio_delta;
1613       if (filled_history_buffer) {
1614         ratio_delta = recent_gc_overhead - threshold;
1615       } else {
1616         ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold;
1617       }
1618 
1619       expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1620       if (ratio_delta < StartScaleDownAt) {
1621         scale_factor = ratio_delta / StartScaleDownAt;
1622         scale_factor = MAX2(scale_factor, MinScaleDownFactor);
1623       } else if (ratio_delta > StartScaleUpAt) {
1624         scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange);
1625         scale_factor = MIN2(scale_factor, MaxScaleUpFactor);
1626       }
1627     }
1628 
1629     log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) "
1630                               "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)",
1631                               recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100);
1632 
1633     expand_bytes = static_cast<size_t>(expand_bytes * scale_factor);
1634 
1635     // Ensure the expansion size is at least the minimum growth amount
1636     // and at most the remaining uncommitted byte size.
1637     expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1638     expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1639 
1640     clear_ratio_check_data();
1641   } else {
1642     // An expansion was not triggered. If we've started counting, increment
1643     // the number of checks we've made in the current window.  If we've
1644     // reached the end of the window without resizing, clear the counters to
1645     // start again the next time we see a ratio above the threshold.
1646     if (_ratio_over_threshold_count > 0) {
1647       _pauses_since_start++;
1648       if (_pauses_since_start > NumPrevPausesForHeuristics) {
1649         clear_ratio_check_data();
1650       }
1651     }
1652   }
1653 
1654   return expand_bytes;
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 bool G1CollectorPolicy::adaptive_young_list_length() const {
1682   return _young_gen_sizer->adaptive_young_list_length();
1683 }
1684 
1685 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1686   uint expansion_region_num = 0;
1687   if (GCLockerEdenExpansionPercent > 0) {
1688     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1689     double expansion_region_num_d = perc * (double) _young_list_target_length;
1690     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1691     // less than 1.0) we'll get 1.
1692     expansion_region_num = (uint) ceil(expansion_region_num_d);
1693   } else {
1694     assert(expansion_region_num == 0, "sanity");
1695   }
1696   _young_list_max_length = _young_list_target_length + expansion_region_num;
1697   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1698 }
1699 
1700 // Calculates survivor space parameters.
1701 void G1CollectorPolicy::update_survivors_policy() {
1702   double max_survivor_regions_d =
1703                  (double) _young_list_target_length / (double) SurvivorRatio;
1704   // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1705   // smaller than 1.0) we'll get 1.
1706   _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1707 
1708   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1709         HeapRegion::GrainWords * _max_survivor_regions, counters());
1710 }
1711 
1712 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1713   // We actually check whether we are marking here and not if we are in a
1714   // reclamation phase. This means that we will schedule a concurrent mark
1715   // even while we are still in the process of reclaiming memory.
1716   bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1717   if (!during_cycle) {
1718     log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1719     collector_state()->set_initiate_conc_mark_if_possible(true);
1720     return true;
1721   } else {
1722     log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1723     return false;
1724   }
1725 }
1726 
1727 void G1CollectorPolicy::initiate_conc_mark() {
1728   collector_state()->set_during_initial_mark_pause(true);
1729   collector_state()->set_initiate_conc_mark_if_possible(false);
1730 }
1731 
1732 void G1CollectorPolicy::decide_on_conc_mark_initiation() {
1733   // We are about to decide on whether this pause will be an
1734   // initial-mark pause.
1735 
1736   // First, collector_state()->during_initial_mark_pause() should not be already set. We
1737   // will set it here if we have to. However, it should be cleared by
1738   // the end of the pause (it's only set for the duration of an
1739   // initial-mark pause).
1740   assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1741 
1742   if (collector_state()->initiate_conc_mark_if_possible()) {
1743     // We had noticed on a previous pause that the heap occupancy has
1744     // gone over the initiating threshold and we should start a
1745     // concurrent marking cycle. So we might initiate one.
1746 
1747     if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1748       // Initiate a new initial mark if there is no marking or reclamation going on.
1749       initiate_conc_mark();
1750       log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1751     } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
1752       // Initiate a user requested initial mark. An initial mark must be young only
1753       // GC, so the collector state must be updated to reflect this.
1754       collector_state()->set_gcs_are_young(true);
1755       collector_state()->set_last_young_gc(false);
1756 
1757       abort_time_to_mixed_tracking();
1758       initiate_conc_mark();
1759       log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1760     } else {
1761       // The concurrent marking thread is still finishing up the
1762       // previous cycle. If we start one right now the two cycles
1763       // overlap. In particular, the concurrent marking thread might
1764       // be in the process of clearing the next marking bitmap (which
1765       // we will use for the next cycle if we start one). Starting a
1766       // cycle now will be bad given that parts of the marking
1767       // information might get cleared by the marking thread. And we
1768       // cannot wait for the marking thread to finish the cycle as it
1769       // periodically yields while clearing the next marking bitmap
1770       // and, if it's in a yield point, it's waiting for us to
1771       // finish. So, at this point we will not start a cycle and we'll
1772       // let the concurrent marking thread complete the last one.
1773       log_debug(gc, ergo)("Do not initiate concurrent cycle (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   cset_chooser()->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   cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1836   ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers);
1837   workers->run_task(&par_known_garbage_task);
1838 
1839   cset_chooser()->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   _prev_collection_pause_end_ms += elapsed_time_ms;
1845 
1846   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1847 }
1848 
1849 // Add the heap region at the head of the non-incremental collection set
1850 void G1CollectorPolicy::add_old_region_to_cset(HeapRegion* hr) {
1851   assert(_inc_cset_build_state == Active, "Precondition");
1852   assert(hr->is_old(), "the region should be old");
1853 
1854   assert(!hr->in_collection_set(), "should not already be in the CSet");
1855   _g1->register_old_region_with_cset(hr);
1856   hr->set_next_in_collection_set(_collection_set);
1857   _collection_set = hr;
1858   _collection_set_bytes_used_before += hr->used();
1859   size_t rs_length = hr->rem_set()->occupied();
1860   _recorded_rs_lengths += rs_length;
1861   _old_cset_region_length += 1;
1862 }
1863 
1864 // Initialize the per-collection-set information
1865 void G1CollectorPolicy::start_incremental_cset_building() {
1866   assert(_inc_cset_build_state == Inactive, "Precondition");
1867 
1868   _inc_cset_head = NULL;
1869   _inc_cset_tail = NULL;
1870   _inc_cset_bytes_used_before = 0;
1871 
1872   _inc_cset_max_finger = 0;
1873   _inc_cset_recorded_rs_lengths = 0;
1874   _inc_cset_recorded_rs_lengths_diffs = 0;
1875   _inc_cset_predicted_elapsed_time_ms = 0.0;
1876   _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1877   _inc_cset_build_state = Active;
1878 }
1879 
1880 void G1CollectorPolicy::finalize_incremental_cset_building() {
1881   assert(_inc_cset_build_state == Active, "Precondition");
1882   assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1883 
1884   // The two "main" fields, _inc_cset_recorded_rs_lengths and
1885   // _inc_cset_predicted_elapsed_time_ms, are updated by the thread
1886   // that adds a new region to the CSet. Further updates by the
1887   // concurrent refinement thread that samples the young RSet lengths
1888   // are accumulated in the *_diffs fields. Here we add the diffs to
1889   // the "main" fields.
1890 
1891   if (_inc_cset_recorded_rs_lengths_diffs >= 0) {
1892     _inc_cset_recorded_rs_lengths += _inc_cset_recorded_rs_lengths_diffs;
1893   } else {
1894     // This is defensive. The diff should in theory be always positive
1895     // as RSets can only grow between GCs. However, given that we
1896     // sample their size concurrently with other threads updating them
1897     // it's possible that we might get the wrong size back, which
1898     // could make the calculations somewhat inaccurate.
1899     size_t diffs = (size_t) (-_inc_cset_recorded_rs_lengths_diffs);
1900     if (_inc_cset_recorded_rs_lengths >= diffs) {
1901       _inc_cset_recorded_rs_lengths -= diffs;
1902     } else {
1903       _inc_cset_recorded_rs_lengths = 0;
1904     }
1905   }
1906   _inc_cset_predicted_elapsed_time_ms +=
1907                                      _inc_cset_predicted_elapsed_time_ms_diffs;
1908 
1909   _inc_cset_recorded_rs_lengths_diffs = 0;
1910   _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1911 }
1912 
1913 void G1CollectorPolicy::add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length) {
1914   // This routine is used when:
1915   // * adding survivor regions to the incremental cset at the end of an
1916   //   evacuation pause,
1917   // * adding the current allocation region to the incremental cset
1918   //   when it is retired, and
1919   // * updating existing policy information for a region in the
1920   //   incremental cset via young list RSet sampling.
1921   // Therefore this routine may be called at a safepoint by the
1922   // VM thread, or in-between safepoints by mutator threads (when
1923   // retiring the current allocation region) or a concurrent
1924   // refine thread (RSet sampling).
1925 
1926   double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1927   size_t used_bytes = hr->used();
1928   _inc_cset_recorded_rs_lengths += rs_length;
1929   _inc_cset_predicted_elapsed_time_ms += region_elapsed_time_ms;
1930   _inc_cset_bytes_used_before += used_bytes;
1931 
1932   // Cache the values we have added to the aggregated information
1933   // in the heap region in case we have to remove this region from
1934   // the incremental collection set, or it is updated by the
1935   // rset sampling code
1936   hr->set_recorded_rs_length(rs_length);
1937   hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
1938 }
1939 
1940 void G1CollectorPolicy::update_incremental_cset_info(HeapRegion* hr,
1941                                                      size_t new_rs_length) {
1942   // Update the CSet information that is dependent on the new RS length
1943   assert(hr->is_young(), "Precondition");
1944   assert(!SafepointSynchronize::is_at_safepoint(),
1945                                                "should not be at a safepoint");
1946 
1947   // We could have updated _inc_cset_recorded_rs_lengths and
1948   // _inc_cset_predicted_elapsed_time_ms directly but we'd need to do
1949   // that atomically, as this code is executed by a concurrent
1950   // refinement thread, potentially concurrently with a mutator thread
1951   // allocating a new region and also updating the same fields. To
1952   // avoid the atomic operations we accumulate these updates on two
1953   // separate fields (*_diffs) and we'll just add them to the "main"
1954   // fields at the start of a GC.
1955 
1956   ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
1957   ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
1958   _inc_cset_recorded_rs_lengths_diffs += rs_lengths_diff;
1959 
1960   double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
1961   double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1962   double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
1963   _inc_cset_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
1964 
1965   hr->set_recorded_rs_length(new_rs_length);
1966   hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
1967 }
1968 
1969 void G1CollectorPolicy::add_region_to_incremental_cset_common(HeapRegion* hr) {
1970   assert(hr->is_young(), "invariant");
1971   assert(hr->young_index_in_cset() > -1, "should have already been set");
1972   assert(_inc_cset_build_state == Active, "Precondition");
1973 
1974   // We need to clear and set the cached recorded/cached collection set
1975   // information in the heap region here (before the region gets added
1976   // to the collection set). An individual heap region's cached values
1977   // are calculated, aggregated with the policy collection set info,
1978   // and cached in the heap region here (initially) and (subsequently)
1979   // by the Young List sampling code.
1980 
1981   size_t rs_length = hr->rem_set()->occupied();
1982   add_to_incremental_cset_info(hr, rs_length);
1983 
1984   HeapWord* hr_end = hr->end();
1985   _inc_cset_max_finger = MAX2(_inc_cset_max_finger, hr_end);
1986 
1987   assert(!hr->in_collection_set(), "invariant");
1988   _g1->register_young_region_with_cset(hr);
1989   assert(hr->next_in_collection_set() == NULL, "invariant");
1990 }
1991 
1992 // Add the region at the RHS of the incremental cset
1993 void G1CollectorPolicy::add_region_to_incremental_cset_rhs(HeapRegion* hr) {
1994   // We should only ever be appending survivors at the end of a pause
1995   assert(hr->is_survivor(), "Logic");
1996 
1997   // Do the 'common' stuff
1998   add_region_to_incremental_cset_common(hr);
1999 
2000   // Now add the region at the right hand side
2001   if (_inc_cset_tail == NULL) {
2002     assert(_inc_cset_head == NULL, "invariant");
2003     _inc_cset_head = hr;
2004   } else {
2005     _inc_cset_tail->set_next_in_collection_set(hr);
2006   }
2007   _inc_cset_tail = hr;
2008 }
2009 
2010 // Add the region to the LHS of the incremental cset
2011 void G1CollectorPolicy::add_region_to_incremental_cset_lhs(HeapRegion* hr) {
2012   // Survivors should be added to the RHS at the end of a pause
2013   assert(hr->is_eden(), "Logic");
2014 
2015   // Do the 'common' stuff
2016   add_region_to_incremental_cset_common(hr);
2017 
2018   // Add the region at the left hand side
2019   hr->set_next_in_collection_set(_inc_cset_head);
2020   if (_inc_cset_head == NULL) {
2021     assert(_inc_cset_tail == NULL, "Invariant");
2022     _inc_cset_tail = hr;
2023   }
2024   _inc_cset_head = hr;
2025 }
2026 
2027 #ifndef PRODUCT
2028 void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream* st) {
2029   assert(list_head == inc_cset_head() || list_head == collection_set(), "must be");
2030 
2031   st->print_cr("\nCollection_set:");
2032   HeapRegion* csr = list_head;
2033   while (csr != NULL) {
2034     HeapRegion* next = csr->next_in_collection_set();
2035     assert(csr->in_collection_set(), "bad CS");
2036     st->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
2037                  HR_FORMAT_PARAMS(csr),
2038                  p2i(csr->prev_top_at_mark_start()), p2i(csr->next_top_at_mark_start()),
2039                  csr->age_in_surv_rate_group_cond());
2040     csr = next;
2041   }
2042 }
2043 #endif // !PRODUCT
2044 
2045 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
2046   // Returns the given amount of reclaimable bytes (that represents
2047   // the amount of reclaimable space still to be collected) as a
2048   // percentage of the current heap capacity.
2049   size_t capacity_bytes = _g1->capacity();
2050   return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
2051 }
2052 
2053 void G1CollectorPolicy::maybe_start_marking() {
2054   if (need_to_start_conc_mark("end of GC")) {
2055     // Note: this might have already been set, if during the last
2056     // pause we decided to start a cycle but at the beginning of
2057     // this pause we decided to postpone it. That's OK.
2058     collector_state()->set_initiate_conc_mark_if_possible(true);
2059   }
2060 }
2061 
2062 G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
2063   assert(!collector_state()->full_collection(), "must be");
2064   if (collector_state()->during_initial_mark_pause()) {
2065     assert(collector_state()->last_gc_was_young(), "must be");
2066     assert(!collector_state()->last_young_gc(), "must be");
2067     return InitialMarkGC;
2068   } else if (collector_state()->last_young_gc()) {
2069     assert(!collector_state()->during_initial_mark_pause(), "must be");
2070     assert(collector_state()->last_gc_was_young(), "must be");
2071     return LastYoungGC;
2072   } else if (!collector_state()->last_gc_was_young()) {
2073     assert(!collector_state()->during_initial_mark_pause(), "must be");
2074     assert(!collector_state()->last_young_gc(), "must be");
2075     return MixedGC;
2076   } else {
2077     assert(collector_state()->last_gc_was_young(), "must be");
2078     assert(!collector_state()->during_initial_mark_pause(), "must be");
2079     assert(!collector_state()->last_young_gc(), "must be");
2080     return YoungOnlyGC;
2081   }
2082 }
2083 
2084 void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
2085   // Manage the MMU tracker. For some reason it ignores Full GCs.
2086   if (kind != FullGC) {
2087     _mmu_tracker->add_pause(start, end);
2088   }
2089   // Manage the mutator time tracking from initial mark to first mixed gc.
2090   switch (kind) {
2091     case FullGC:
2092       abort_time_to_mixed_tracking();
2093       break;
2094     case Cleanup:
2095     case Remark:
2096     case YoungOnlyGC:
2097     case LastYoungGC:
2098       _initial_mark_to_mixed.add_pause(end - start);
2099       break;
2100     case InitialMarkGC:
2101       _initial_mark_to_mixed.record_initial_mark_end(end);
2102       break;
2103     case MixedGC:
2104       _initial_mark_to_mixed.record_mixed_gc_start(start);
2105       break;
2106     default:
2107       ShouldNotReachHere();
2108   }
2109 }
2110 
2111 void G1CollectorPolicy::abort_time_to_mixed_tracking() {
2112   _initial_mark_to_mixed.reset();
2113 }
2114 
2115 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
2116                                                 const char* false_action_str) const {
2117   if (cset_chooser()->is_empty()) {
2118     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
2119     return false;
2120   }
2121 
2122   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
2123   size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
2124   double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2125   double threshold = (double) G1HeapWastePercent;
2126   if (reclaimable_perc <= threshold) {
2127     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
2128                         false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2129     return false;
2130   }
2131   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
2132                       true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2133   return true;
2134 }
2135 
2136 uint G1CollectorPolicy::calc_min_old_cset_length() const {
2137   // The min old CSet region bound is based on the maximum desired
2138   // number of mixed GCs after a cycle. I.e., even if some old regions
2139   // look expensive, we should add them to the CSet anyway to make
2140   // sure we go through the available old regions in no more than the
2141   // maximum desired number of mixed GCs.
2142   //
2143   // The calculation is based on the number of marked regions we added
2144   // to the CSet chooser in the first place, not how many remain, so
2145   // that the result is the same during all mixed GCs that follow a cycle.
2146 
2147   const size_t region_num = (size_t) cset_chooser()->length();
2148   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
2149   size_t result = region_num / gc_num;
2150   // emulate ceiling
2151   if (result * gc_num < region_num) {
2152     result += 1;
2153   }
2154   return (uint) result;
2155 }
2156 
2157 uint G1CollectorPolicy::calc_max_old_cset_length() const {
2158   // The max old CSet region bound is based on the threshold expressed
2159   // as a percentage of the heap size. I.e., it should bound the
2160   // number of old regions added to the CSet irrespective of how many
2161   // of them are available.
2162 
2163   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
2164   const size_t region_num = g1h->num_regions();
2165   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
2166   size_t result = region_num * perc / 100;
2167   // emulate ceiling
2168   if (100 * result < region_num * perc) {
2169     result += 1;
2170   }
2171   return (uint) result;
2172 }
2173 
2174 
2175 double G1CollectorPolicy::finalize_young_cset_part(double target_pause_time_ms) {
2176   double young_start_time_sec = os::elapsedTime();
2177 
2178   YoungList* young_list = _g1->young_list();
2179   finalize_incremental_cset_building();
2180 
2181   guarantee(target_pause_time_ms > 0.0,
2182             "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
2183   guarantee(_collection_set == NULL, "Precondition");
2184 
2185   double base_time_ms = predict_base_elapsed_time_ms(_pending_cards);
2186   double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
2187 
2188   log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms",
2189                             _pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
2190 
2191   collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young());
2192 
2193   if (collector_state()->last_gc_was_young()) {
2194     _trace_young_gen_time_data.increment_young_collection_count();
2195   } else {
2196     _trace_young_gen_time_data.increment_mixed_collection_count();
2197   }
2198 
2199   // The young list is laid with the survivor regions from the previous
2200   // pause are appended to the RHS of the young list, i.e.
2201   //   [Newly Young Regions ++ Survivors from last pause].
2202 
2203   uint survivor_region_length = young_list->survivor_length();
2204   uint eden_region_length = young_list->eden_length();
2205   init_cset_region_lengths(eden_region_length, survivor_region_length);
2206 
2207   HeapRegion* hr = young_list->first_survivor_region();
2208   while (hr != NULL) {
2209     assert(hr->is_survivor(), "badly formed young list");
2210     // There is a convention that all the young regions in the CSet
2211     // are tagged as "eden", so we do this for the survivors here. We
2212     // use the special set_eden_pre_gc() as it doesn't check that the
2213     // region is free (which is not the case here).
2214     hr->set_eden_pre_gc();
2215     hr = hr->get_next_young_region();
2216   }
2217 
2218   // Clear the fields that point to the survivor list - they are all young now.
2219   young_list->clear_survivors();
2220 
2221   _collection_set = _inc_cset_head;
2222   _collection_set_bytes_used_before = _inc_cset_bytes_used_before;
2223   time_remaining_ms = MAX2(time_remaining_ms - _inc_cset_predicted_elapsed_time_ms, 0.0);
2224 
2225   log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",
2226                             eden_region_length, survivor_region_length, _inc_cset_predicted_elapsed_time_ms, target_pause_time_ms);
2227 
2228   // The number of recorded young regions is the incremental
2229   // collection set's current size
2230   set_recorded_rs_lengths(_inc_cset_recorded_rs_lengths);
2231 
2232   double young_end_time_sec = os::elapsedTime();
2233   phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
2234 
2235   return time_remaining_ms;
2236 }
2237 
2238 void G1CollectorPolicy::finalize_old_cset_part(double time_remaining_ms) {
2239   double non_young_start_time_sec = os::elapsedTime();
2240   double predicted_old_time_ms = 0.0;
2241 
2242 
2243   if (!collector_state()->gcs_are_young()) {
2244     cset_chooser()->verify();
2245     const uint min_old_cset_length = calc_min_old_cset_length();
2246     const uint max_old_cset_length = calc_max_old_cset_length();
2247 
2248     uint expensive_region_num = 0;
2249     bool check_time_remaining = adaptive_young_list_length();
2250 
2251     HeapRegion* hr = cset_chooser()->peek();
2252     while (hr != NULL) {
2253       if (old_cset_region_length() >= max_old_cset_length) {
2254         // Added maximum number of old regions to the CSet.
2255         log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions",
2256                                   old_cset_region_length(), max_old_cset_length);
2257         break;
2258       }
2259 
2260 
2261       // Stop adding regions if the remaining reclaimable space is
2262       // not above G1HeapWastePercent.
2263       size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
2264       double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2265       double threshold = (double) G1HeapWastePercent;
2266       if (reclaimable_perc <= threshold) {
2267         // We've added enough old regions that the amount of uncollected
2268         // reclaimable space is at or below the waste threshold. Stop
2269         // adding old regions to the CSet.
2270         log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). "
2271                                   "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%",
2272                                   old_cset_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2273         break;
2274       }
2275 
2276       double predicted_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
2277       if (check_time_remaining) {
2278         if (predicted_time_ms > time_remaining_ms) {
2279           // Too expensive for the current CSet.
2280 
2281           if (old_cset_region_length() >= min_old_cset_length) {
2282             // We have added the minimum number of old regions to the CSet,
2283             // we are done with this CSet.
2284             log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). "
2285                                       "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions",
2286                                       predicted_time_ms, time_remaining_ms, old_cset_region_length(), min_old_cset_length);
2287             break;
2288           }
2289 
2290           // We'll add it anyway given that we haven't reached the
2291           // minimum number of old regions.
2292           expensive_region_num += 1;
2293         }
2294       } else {
2295         if (old_cset_region_length() >= min_old_cset_length) {
2296           // In the non-auto-tuning case, we'll finish adding regions
2297           // to the CSet if we reach the minimum.
2298 
2299           log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions",
2300                                     old_cset_region_length(), min_old_cset_length);
2301           break;
2302         }
2303       }
2304 
2305       // We will add this region to the CSet.
2306       time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
2307       predicted_old_time_ms += predicted_time_ms;
2308       cset_chooser()->pop(); // already have region via peek()
2309       _g1->old_set_remove(hr);
2310       add_old_region_to_cset(hr);
2311 
2312       hr = cset_chooser()->peek();
2313     }
2314     if (hr == NULL) {
2315       log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)");
2316     }
2317 
2318     if (expensive_region_num > 0) {
2319       // We print the information once here at the end, predicated on
2320       // whether we added any apparently expensive regions or not, to
2321       // avoid generating output per region.
2322       log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)."
2323                                 "old: %u regions, expensive: %u regions, min: %u regions, remaining time: %1.2fms",
2324                                 old_cset_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms);
2325     }
2326 
2327     cset_chooser()->verify();
2328   }
2329 
2330   stop_incremental_cset_building();
2331 
2332   log_debug(gc, ergo, cset)("Finish choosing CSet. old: %u regions, predicted old region time: %1.2fms, time remaining: %1.2f",
2333                             old_cset_region_length(), predicted_old_time_ms, time_remaining_ms);
2334 
2335   double non_young_end_time_sec = os::elapsedTime();
2336   phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
2337 }
2338 
2339 void TraceYoungGenTimeData::record_start_collection(double time_to_stop_the_world_ms) {
2340   if(TraceYoungGenTime) {
2341     _all_stop_world_times_ms.add(time_to_stop_the_world_ms);
2342   }
2343 }
2344 
2345 void TraceYoungGenTimeData::record_yield_time(double yield_time_ms) {
2346   if(TraceYoungGenTime) {
2347     _all_yield_times_ms.add(yield_time_ms);
2348   }
2349 }
2350 
2351 void TraceYoungGenTimeData::record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times) {
2352   if(TraceYoungGenTime) {
2353     _total.add(pause_time_ms);
2354     _other.add(pause_time_ms - phase_times->accounted_time_ms());
2355     _root_region_scan_wait.add(phase_times->root_region_scan_wait_time_ms());
2356     _parallel.add(phase_times->cur_collection_par_time_ms());
2357     _ext_root_scan.add(phase_times->average_time_ms(G1GCPhaseTimes::ExtRootScan));
2358     _satb_filtering.add(phase_times->average_time_ms(G1GCPhaseTimes::SATBFiltering));
2359     _update_rs.add(phase_times->average_time_ms(G1GCPhaseTimes::UpdateRS));
2360     _scan_rs.add(phase_times->average_time_ms(G1GCPhaseTimes::ScanRS));
2361     _obj_copy.add(phase_times->average_time_ms(G1GCPhaseTimes::ObjCopy));
2362     _termination.add(phase_times->average_time_ms(G1GCPhaseTimes::Termination));
2363 
2364     double parallel_known_time = phase_times->average_time_ms(G1GCPhaseTimes::ExtRootScan) +
2365       phase_times->average_time_ms(G1GCPhaseTimes::SATBFiltering) +
2366       phase_times->average_time_ms(G1GCPhaseTimes::UpdateRS) +
2367       phase_times->average_time_ms(G1GCPhaseTimes::ScanRS) +
2368       phase_times->average_time_ms(G1GCPhaseTimes::ObjCopy) +
2369       phase_times->average_time_ms(G1GCPhaseTimes::Termination);
2370 
2371     double parallel_other_time = phase_times->cur_collection_par_time_ms() - parallel_known_time;
2372     _parallel_other.add(parallel_other_time);
2373     _clear_ct.add(phase_times->cur_clear_ct_time_ms());
2374   }
2375 }
2376 
2377 void TraceYoungGenTimeData::increment_young_collection_count() {
2378   if(TraceYoungGenTime) {
2379     ++_young_pause_num;
2380   }
2381 }
2382 
2383 void TraceYoungGenTimeData::increment_mixed_collection_count() {
2384   if(TraceYoungGenTime) {
2385     ++_mixed_pause_num;
2386   }
2387 }
2388 
2389 void TraceYoungGenTimeData::print_summary(const char* str,
2390                                           const NumberSeq* seq) const {
2391   double sum = seq->sum();
2392   tty->print_cr("%-27s = %8.2lf s (avg = %8.2lf ms)",
2393                 str, sum / 1000.0, seq->avg());
2394 }
2395 
2396 void TraceYoungGenTimeData::print_summary_sd(const char* str,
2397                                              const NumberSeq* seq) const {
2398   print_summary(str, seq);
2399   tty->print_cr("%45s = %5d, std dev = %8.2lf ms, max = %8.2lf ms)",
2400                 "(num", seq->num(), seq->sd(), seq->maximum());
2401 }
2402 
2403 void TraceYoungGenTimeData::print() const {
2404   if (!TraceYoungGenTime) {
2405     return;
2406   }
2407 
2408   tty->print_cr("ALL PAUSES");
2409   print_summary_sd("   Total", &_total);
2410   tty->cr();
2411   tty->cr();
2412   tty->print_cr("   Young GC Pauses: %8d", _young_pause_num);
2413   tty->print_cr("   Mixed GC Pauses: %8d", _mixed_pause_num);
2414   tty->cr();
2415 
2416   tty->print_cr("EVACUATION PAUSES");
2417 
2418   if (_young_pause_num == 0 && _mixed_pause_num == 0) {
2419     tty->print_cr("none");
2420   } else {
2421     print_summary_sd("   Evacuation Pauses", &_total);
2422     print_summary("      Root Region Scan Wait", &_root_region_scan_wait);
2423     print_summary("      Parallel Time", &_parallel);
2424     print_summary("         Ext Root Scanning", &_ext_root_scan);
2425     print_summary("         SATB Filtering", &_satb_filtering);
2426     print_summary("         Update RS", &_update_rs);
2427     print_summary("         Scan RS", &_scan_rs);
2428     print_summary("         Object Copy", &_obj_copy);
2429     print_summary("         Termination", &_termination);
2430     print_summary("         Parallel Other", &_parallel_other);
2431     print_summary("      Clear CT", &_clear_ct);
2432     print_summary("      Other", &_other);
2433   }
2434   tty->cr();
2435 
2436   tty->print_cr("MISC");
2437   print_summary_sd("   Stop World", &_all_stop_world_times_ms);
2438   print_summary_sd("   Yields", &_all_yield_times_ms);
2439 }
2440 
2441 void TraceOldGenTimeData::record_full_collection(double full_gc_time_ms) {
2442   if (TraceOldGenTime) {
2443     _all_full_gc_times.add(full_gc_time_ms);
2444   }
2445 }
2446 
2447 void TraceOldGenTimeData::print() const {
2448   if (!TraceOldGenTime) {
2449     return;
2450   }
2451 
2452   if (_all_full_gc_times.num() > 0) {
2453     tty->print("\n%4d full_gcs: total time = %8.2f s",
2454       _all_full_gc_times.num(),
2455       _all_full_gc_times.sum() / 1000.0);
2456     tty->print_cr(" (avg = %8.2fms).", _all_full_gc_times.avg());
2457     tty->print_cr("                     [std. dev = %8.2f ms, max = %8.2f ms]",
2458       _all_full_gc_times.sd(),
2459       _all_full_gc_times.maximum());
2460   }
2461 }