1 /*
   2  * Copyright (c) 2001, 2012, 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_implementation/g1/concurrentG1Refine.hpp"
  27 #include "gc_implementation/g1/concurrentMark.hpp"
  28 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  29 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  30 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  31 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  32 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  33 #include "gc_implementation/g1/g1Log.hpp"
  34 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  35 #include "gc_implementation/shared/gcPolicyCounters.hpp"
  36 #include "runtime/arguments.hpp"
  37 #include "runtime/java.hpp"
  38 #include "runtime/mutexLocker.hpp"
  39 #include "utilities/debug.hpp"
  40 
  41 // Different defaults for different number of GC threads
  42 // They were chosen by running GCOld and SPECjbb on debris with different
  43 //   numbers of GC threads and choosing them based on the results
  44 
  45 // all the same
  46 static double rs_length_diff_defaults[] = {
  47   0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
  48 };
  49 
  50 static double cost_per_card_ms_defaults[] = {
  51   0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
  52 };
  53 
  54 // all the same
  55 static double young_cards_per_entry_ratio_defaults[] = {
  56   1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
  57 };
  58 
  59 static double cost_per_entry_ms_defaults[] = {
  60   0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
  61 };
  62 
  63 static double cost_per_byte_ms_defaults[] = {
  64   0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
  65 };
  66 
  67 // these should be pretty consistent
  68 static double constant_other_time_ms_defaults[] = {
  69   5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
  70 };
  71 
  72 
  73 static double young_other_cost_per_region_ms_defaults[] = {
  74   0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
  75 };
  76 
  77 static double non_young_other_cost_per_region_ms_defaults[] = {
  78   1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
  79 };
  80 
  81 G1CollectorPolicy::G1CollectorPolicy() :
  82   _parallel_gc_threads(G1CollectedHeap::use_parallel_gc_threads()
  83                         ? ParallelGCThreads : 1),
  84 
  85   _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  86   _stop_world_start(0.0),
  87 
  88   _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  89   _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
  90 
  91   _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  92   _prev_collection_pause_end_ms(0.0),
  93   _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
  94   _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  95   _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
  96   _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
  97   _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  98   _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
  99   _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 100   _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
 101   _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 102   _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
 103   _non_young_other_cost_per_region_ms_seq(
 104                                          new TruncatedSeq(TruncatedSeqLength)),
 105 
 106   _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
 107   _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
 108 
 109   _pause_time_target_ms((double) MaxGCPauseMillis),
 110 
 111   _gcs_are_young(true),
 112 
 113   _during_marking(false),
 114   _in_marking_window(false),
 115   _in_marking_window_im(false),
 116 
 117   _recent_prev_end_times_for_all_gcs_sec(
 118                                 new TruncatedSeq(NumPrevPausesForHeuristics)),
 119 
 120   _recent_avg_pause_time_ratio(0.0),
 121 
 122   _initiate_conc_mark_if_possible(false),
 123   _during_initial_mark_pause(false),
 124   _last_young_gc(false),
 125   _last_gc_was_young(false),
 126 
 127   _eden_bytes_before_gc(0),
 128   _survivor_bytes_before_gc(0),
 129   _capacity_before_gc(0),
 130 
 131   _eden_cset_region_length(0),
 132   _survivor_cset_region_length(0),
 133   _old_cset_region_length(0),
 134 
 135   _collection_set(NULL),
 136   _collection_set_bytes_used_before(0),
 137 
 138   // Incremental CSet attributes
 139   _inc_cset_build_state(Inactive),
 140   _inc_cset_head(NULL),
 141   _inc_cset_tail(NULL),
 142   _inc_cset_bytes_used_before(0),
 143   _inc_cset_max_finger(NULL),
 144   _inc_cset_recorded_rs_lengths(0),
 145   _inc_cset_recorded_rs_lengths_diffs(0),
 146   _inc_cset_predicted_elapsed_time_ms(0.0),
 147   _inc_cset_predicted_elapsed_time_ms_diffs(0.0),
 148 
 149 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
 150 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 151 #endif // _MSC_VER
 152 
 153   _short_lived_surv_rate_group(new SurvRateGroup(this, "Short Lived",
 154                                                  G1YoungSurvRateNumRegionsSummary)),
 155   _survivor_surv_rate_group(new SurvRateGroup(this, "Survivor",
 156                                               G1YoungSurvRateNumRegionsSummary)),
 157   // add here any more surv rate groups
 158   _recorded_survivor_regions(0),
 159   _recorded_survivor_head(NULL),
 160   _recorded_survivor_tail(NULL),
 161   _survivors_age_table(true),
 162 
 163   _gc_overhead_perc(0.0) {
 164 
 165   // Set up the region size and associated fields. Given that the
 166   // policy is created before the heap, we have to set this up here,
 167   // so it's done as soon as possible.
 168   HeapRegion::setup_heap_region_size(Arguments::min_heap_size());
 169   HeapRegionRemSet::setup_remset_size();
 170 
 171   G1ErgoVerbose::initialize();
 172   if (PrintAdaptiveSizePolicy) {
 173     // Currently, we only use a single switch for all the heuristics.
 174     G1ErgoVerbose::set_enabled(true);
 175     // Given that we don't currently have a verboseness level
 176     // parameter, we'll hardcode this to high. This can be easily
 177     // changed in the future.
 178     G1ErgoVerbose::set_level(ErgoHigh);
 179   } else {
 180     G1ErgoVerbose::set_enabled(false);
 181   }
 182 
 183   // Verify PLAB sizes
 184   const size_t region_size = HeapRegion::GrainWords;
 185   if (YoungPLABSize > region_size || OldPLABSize > region_size) {
 186     char buffer[128];
 187     jio_snprintf(buffer, sizeof(buffer), "%sPLABSize should be at most "SIZE_FORMAT,
 188                  OldPLABSize > region_size ? "Old" : "Young", region_size);
 189     vm_exit_during_initialization(buffer);
 190   }
 191 
 192   _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
 193   _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
 194 
 195   _phase_times = new G1GCPhaseTimes(_parallel_gc_threads);
 196 
 197   int index = MIN2(_parallel_gc_threads - 1, 7);
 198 
 199   _rs_length_diff_seq->add(rs_length_diff_defaults[index]);
 200   _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
 201   _young_cards_per_entry_ratio_seq->add(
 202                                   young_cards_per_entry_ratio_defaults[index]);
 203   _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
 204   _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
 205   _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
 206   _young_other_cost_per_region_ms_seq->add(
 207                                young_other_cost_per_region_ms_defaults[index]);
 208   _non_young_other_cost_per_region_ms_seq->add(
 209                            non_young_other_cost_per_region_ms_defaults[index]);
 210 
 211   // Below, we might need to calculate the pause time target based on
 212   // the pause interval. When we do so we are going to give G1 maximum
 213   // flexibility and allow it to do pauses when it needs to. So, we'll
 214   // arrange that the pause interval to be pause time target + 1 to
 215   // ensure that a) the pause time target is maximized with respect to
 216   // the pause interval and b) we maintain the invariant that pause
 217   // time target < pause interval. If the user does not want this
 218   // maximum flexibility, they will have to set the pause interval
 219   // explicitly.
 220 
 221   // First make sure that, if either parameter is set, its value is
 222   // reasonable.
 223   if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 224     if (MaxGCPauseMillis < 1) {
 225       vm_exit_during_initialization("MaxGCPauseMillis should be "
 226                                     "greater than 0");
 227     }
 228   }
 229   if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 230     if (GCPauseIntervalMillis < 1) {
 231       vm_exit_during_initialization("GCPauseIntervalMillis should be "
 232                                     "greater than 0");
 233     }
 234   }
 235 
 236   // Then, if the pause time target parameter was not set, set it to
 237   // the default value.
 238   if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
 239     if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 240       // The default pause time target in G1 is 200ms
 241       FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
 242     } else {
 243       // We do not allow the pause interval to be set without the
 244       // pause time target
 245       vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
 246                                     "without setting MaxGCPauseMillis");
 247     }
 248   }
 249 
 250   // Then, if the interval parameter was not set, set it according to
 251   // the pause time target (this will also deal with the case when the
 252   // pause time target is the default value).
 253   if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
 254     FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
 255   }
 256 
 257   // Finally, make sure that the two parameters are consistent.
 258   if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
 259     char buffer[256];
 260     jio_snprintf(buffer, 256,
 261                  "MaxGCPauseMillis (%u) should be less than "
 262                  "GCPauseIntervalMillis (%u)",
 263                  MaxGCPauseMillis, GCPauseIntervalMillis);
 264     vm_exit_during_initialization(buffer);
 265   }
 266 
 267   double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
 268   double time_slice  = (double) GCPauseIntervalMillis / 1000.0;
 269   _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
 270   _sigma = (double) G1ConfidencePercent / 100.0;
 271 
 272   // start conservatively (around 50ms is about right)
 273   _concurrent_mark_remark_times_ms->add(0.05);
 274   _concurrent_mark_cleanup_times_ms->add(0.20);
 275   _tenuring_threshold = MaxTenuringThreshold;
 276   // _max_survivor_regions will be calculated by
 277   // update_young_list_target_length() during initialization.
 278   _max_survivor_regions = 0;
 279 
 280   assert(GCTimeRatio > 0,
 281          "we should have set it to a default value set_g1_gc_flags() "
 282          "if a user set it to 0");
 283   _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
 284 
 285   uintx reserve_perc = G1ReservePercent;
 286   // Put an artificial ceiling on this so that it's not set to a silly value.
 287   if (reserve_perc > 50) {
 288     reserve_perc = 50;
 289     warning("G1ReservePercent is set to a value that is too large, "
 290             "it's been updated to %u", reserve_perc);
 291   }
 292   _reserve_factor = (double) reserve_perc / 100.0;
 293   // This will be set when the heap is expanded
 294   // for the first time during initialization.
 295   _reserve_regions = 0;
 296 
 297   initialize_all();
 298   _collectionSetChooser = new CollectionSetChooser();
 299   _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
 300 }
 301 
 302 void G1CollectorPolicy::initialize_flags() {
 303   set_min_alignment(HeapRegion::GrainBytes);
 304   set_max_alignment(GenRemSet::max_alignment_constraint(rem_set_name()));
 305   if (SurvivorRatio < 1) {
 306     vm_exit_during_initialization("Invalid survivor ratio specified");
 307   }
 308   CollectorPolicy::initialize_flags();
 309 }
 310 
 311 G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true) {
 312   assert(G1NewSizePercent <= G1MaxNewSizePercent, "Min larger than max");
 313   assert(G1NewSizePercent > 0 && G1NewSizePercent < 100, "Min out of bounds");
 314   assert(G1MaxNewSizePercent > 0 && G1MaxNewSizePercent < 100, "Max out of bounds");
 315 
 316   if (FLAG_IS_CMDLINE(NewRatio)) {
 317     if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
 318       warning("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio");
 319     } else {
 320       _sizer_kind = SizerNewRatio;
 321       _adaptive_size = false;
 322       return;
 323     }
 324   }
 325 
 326   if (FLAG_IS_CMDLINE(NewSize)) {
 327     _min_desired_young_length = MAX2((uint) (NewSize / HeapRegion::GrainBytes),
 328                                      1U);
 329     if (FLAG_IS_CMDLINE(MaxNewSize)) {
 330       _max_desired_young_length =
 331                              MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
 332                                   1U);
 333       _sizer_kind = SizerMaxAndNewSize;
 334       _adaptive_size = _min_desired_young_length == _max_desired_young_length;
 335     } else {
 336       _sizer_kind = SizerNewSizeOnly;
 337     }
 338   } else if (FLAG_IS_CMDLINE(MaxNewSize)) {
 339     _max_desired_young_length =
 340                              MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
 341                                   1U);
 342     _sizer_kind = SizerMaxNewSizeOnly;
 343   }
 344 }
 345 
 346 uint G1YoungGenSizer::calculate_default_min_length(uint new_number_of_heap_regions) {
 347   uint default_value = (new_number_of_heap_regions * G1NewSizePercent) / 100;
 348   return MAX2(1U, default_value);
 349 }
 350 
 351 uint G1YoungGenSizer::calculate_default_max_length(uint new_number_of_heap_regions) {
 352   uint default_value = (new_number_of_heap_regions * G1MaxNewSizePercent) / 100;
 353   return MAX2(1U, default_value);
 354 }
 355 
 356 void G1YoungGenSizer::heap_size_changed(uint new_number_of_heap_regions) {
 357   assert(new_number_of_heap_regions > 0, "Heap must be initialized");
 358 
 359   switch (_sizer_kind) {
 360     case SizerDefaults:
 361       _min_desired_young_length = calculate_default_min_length(new_number_of_heap_regions);
 362       _max_desired_young_length = calculate_default_max_length(new_number_of_heap_regions);
 363       break;
 364     case SizerNewSizeOnly:
 365       _max_desired_young_length = calculate_default_max_length(new_number_of_heap_regions);
 366       _max_desired_young_length = MAX2(_min_desired_young_length, _max_desired_young_length);
 367       break;
 368     case SizerMaxNewSizeOnly:
 369       _min_desired_young_length = calculate_default_min_length(new_number_of_heap_regions);
 370       _min_desired_young_length = MIN2(_min_desired_young_length, _max_desired_young_length);
 371       break;
 372     case SizerMaxAndNewSize:
 373       // Do nothing. Values set on the command line, don't update them at runtime.
 374       break;
 375     case SizerNewRatio:
 376       _min_desired_young_length = new_number_of_heap_regions / (NewRatio + 1);
 377       _max_desired_young_length = _min_desired_young_length;
 378       break;
 379     default:
 380       ShouldNotReachHere();
 381   }
 382 
 383   assert(_min_desired_young_length <= _max_desired_young_length, "Invalid min/max young gen size values");
 384 }
 385 
 386 void G1CollectorPolicy::init() {
 387   // Set aside an initial future to_space.
 388   _g1 = G1CollectedHeap::heap();
 389 
 390   assert(Heap_lock->owned_by_self(), "Locking discipline.");
 391 
 392   initialize_gc_policy_counters();
 393 
 394   if (adaptive_young_list_length()) {
 395     _young_list_fixed_length = 0;
 396   } else {
 397     _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
 398   }
 399   _free_regions_at_end_of_collection = _g1->free_regions();
 400   update_young_list_target_length();
 401   _prev_eden_capacity = _young_list_target_length * HeapRegion::GrainBytes;
 402 
 403   // We may immediately start allocating regions and placing them on the
 404   // collection set list. Initialize the per-collection set info
 405   start_incremental_cset_building();
 406 }
 407 
 408 // Create the jstat counters for the policy.
 409 void G1CollectorPolicy::initialize_gc_policy_counters() {
 410   _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
 411 }
 412 
 413 bool G1CollectorPolicy::predict_will_fit(uint young_length,
 414                                          double base_time_ms,
 415                                          uint base_free_regions,
 416                                          double target_pause_time_ms) {
 417   if (young_length >= base_free_regions) {
 418     // end condition 1: not enough space for the young regions
 419     return false;
 420   }
 421 
 422   double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
 423   size_t bytes_to_copy =
 424                (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
 425   double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
 426   double young_other_time_ms = predict_young_other_time_ms(young_length);
 427   double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
 428   if (pause_time_ms > target_pause_time_ms) {
 429     // end condition 2: prediction is over the target pause time
 430     return false;
 431   }
 432 
 433   size_t free_bytes =
 434                    (base_free_regions - young_length) * HeapRegion::GrainBytes;
 435   if ((2.0 * sigma()) * (double) bytes_to_copy > (double) free_bytes) {
 436     // end condition 3: out-of-space (conservatively!)
 437     return false;
 438   }
 439 
 440   // success!
 441   return true;
 442 }
 443 
 444 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
 445   // re-calculate the necessary reserve
 446   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 447   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 448   // smaller than 1.0) we'll get 1.
 449   _reserve_regions = (uint) ceil(reserve_regions_d);
 450 
 451   _young_gen_sizer->heap_size_changed(new_number_of_regions);
 452 }
 453 
 454 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
 455                                                        uint base_min_length) {
 456   uint desired_min_length = 0;
 457   if (adaptive_young_list_length()) {
 458     if (_alloc_rate_ms_seq->num() > 3) {
 459       double now_sec = os::elapsedTime();
 460       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 461       double alloc_rate_ms = predict_alloc_rate_ms();
 462       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 463     } else {
 464       // otherwise we don't have enough info to make the prediction
 465     }
 466   }
 467   desired_min_length += base_min_length;
 468   // make sure we don't go below any user-defined minimum bound
 469   return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
 470 }
 471 
 472 uint G1CollectorPolicy::calculate_young_list_desired_max_length() {
 473   // Here, we might want to also take into account any additional
 474   // constraints (i.e., user-defined minimum bound). Currently, we
 475   // effectively don't set this bound.
 476   return _young_gen_sizer->max_desired_young_length();
 477 }
 478 
 479 void G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
 480   if (rs_lengths == (size_t) -1) {
 481     // if it's set to the default value (-1), we should predict it;
 482     // otherwise, use the given value.
 483     rs_lengths = (size_t) get_new_prediction(_rs_lengths_seq);
 484   }
 485 
 486   // Calculate the absolute and desired min bounds.
 487 
 488   // This is how many young regions we already have (currently: the survivors).
 489   uint base_min_length = recorded_survivor_regions();
 490   // This is the absolute minimum young length, which ensures that we
 491   // can allocate one eden region in the worst-case.
 492   uint absolute_min_length = base_min_length + 1;
 493   uint desired_min_length =
 494                      calculate_young_list_desired_min_length(base_min_length);
 495   if (desired_min_length < absolute_min_length) {
 496     desired_min_length = absolute_min_length;
 497   }
 498 
 499   // Calculate the absolute and desired max bounds.
 500 
 501   // We will try our best not to "eat" into the reserve.
 502   uint absolute_max_length = 0;
 503   if (_free_regions_at_end_of_collection > _reserve_regions) {
 504     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 505   }
 506   uint desired_max_length = calculate_young_list_desired_max_length();
 507   if (desired_max_length > absolute_max_length) {
 508     desired_max_length = absolute_max_length;
 509   }
 510 
 511   uint young_list_target_length = 0;
 512   if (adaptive_young_list_length()) {
 513     if (gcs_are_young()) {
 514       young_list_target_length =
 515                         calculate_young_list_target_length(rs_lengths,
 516                                                            base_min_length,
 517                                                            desired_min_length,
 518                                                            desired_max_length);
 519       _rs_lengths_prediction = rs_lengths;
 520     } else {
 521       // Don't calculate anything and let the code below bound it to
 522       // the desired_min_length, i.e., do the next GC as soon as
 523       // possible to maximize how many old regions we can add to it.
 524     }
 525   } else {
 526     // The user asked for a fixed young gen so we'll fix the young gen
 527     // whether the next GC is young or mixed.
 528     young_list_target_length = _young_list_fixed_length;
 529   }
 530 
 531   // Make sure we don't go over the desired max length, nor under the
 532   // desired min length. In case they clash, desired_min_length wins
 533   // which is why that test is second.
 534   if (young_list_target_length > desired_max_length) {
 535     young_list_target_length = desired_max_length;
 536   }
 537   if (young_list_target_length < desired_min_length) {
 538     young_list_target_length = desired_min_length;
 539   }
 540 
 541   assert(young_list_target_length > recorded_survivor_regions(),
 542          "we should be able to allocate at least one eden region");
 543   assert(young_list_target_length >= absolute_min_length, "post-condition");
 544   _young_list_target_length = young_list_target_length;
 545 
 546   update_max_gc_locker_expansion();
 547 }
 548 
 549 uint
 550 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
 551                                                      uint base_min_length,
 552                                                      uint desired_min_length,
 553                                                      uint desired_max_length) {
 554   assert(adaptive_young_list_length(), "pre-condition");
 555   assert(gcs_are_young(), "only call this for young GCs");
 556 
 557   // In case some edge-condition makes the desired max length too small...
 558   if (desired_max_length <= desired_min_length) {
 559     return desired_min_length;
 560   }
 561 
 562   // We'll adjust min_young_length and max_young_length not to include
 563   // the already allocated young regions (i.e., so they reflect the
 564   // min and max eden regions we'll allocate). The base_min_length
 565   // will be reflected in the predictions by the
 566   // survivor_regions_evac_time prediction.
 567   assert(desired_min_length > base_min_length, "invariant");
 568   uint min_young_length = desired_min_length - base_min_length;
 569   assert(desired_max_length > base_min_length, "invariant");
 570   uint max_young_length = desired_max_length - base_min_length;
 571 
 572   double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 573   double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 574   size_t pending_cards = (size_t) get_new_prediction(_pending_cards_seq);
 575   size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
 576   size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
 577   double base_time_ms =
 578     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
 579     survivor_regions_evac_time;
 580   uint available_free_regions = _free_regions_at_end_of_collection;
 581   uint base_free_regions = 0;
 582   if (available_free_regions > _reserve_regions) {
 583     base_free_regions = available_free_regions - _reserve_regions;
 584   }
 585 
 586   // Here, we will make sure that the shortest young length that
 587   // makes sense fits within the target pause time.
 588 
 589   if (predict_will_fit(min_young_length, base_time_ms,
 590                        base_free_regions, target_pause_time_ms)) {
 591     // The shortest young length will fit into the target pause time;
 592     // we'll now check whether the absolute maximum number of young
 593     // regions will fit in the target pause time. If not, we'll do
 594     // a binary search between min_young_length and max_young_length.
 595     if (predict_will_fit(max_young_length, base_time_ms,
 596                          base_free_regions, target_pause_time_ms)) {
 597       // The maximum young length will fit into the target pause time.
 598       // We are done so set min young length to the maximum length (as
 599       // the result is assumed to be returned in min_young_length).
 600       min_young_length = max_young_length;
 601     } else {
 602       // The maximum possible number of young regions will not fit within
 603       // the target pause time so we'll search for the optimal
 604       // length. The loop invariants are:
 605       //
 606       // min_young_length < max_young_length
 607       // min_young_length is known to fit into the target pause time
 608       // max_young_length is known not to fit into the target pause time
 609       //
 610       // Going into the loop we know the above hold as we've just
 611       // checked them. Every time around the loop we check whether
 612       // the middle value between min_young_length and
 613       // max_young_length fits into the target pause time. If it
 614       // does, it becomes the new min. If it doesn't, it becomes
 615       // the new max. This way we maintain the loop invariants.
 616 
 617       assert(min_young_length < max_young_length, "invariant");
 618       uint diff = (max_young_length - min_young_length) / 2;
 619       while (diff > 0) {
 620         uint young_length = min_young_length + diff;
 621         if (predict_will_fit(young_length, base_time_ms,
 622                              base_free_regions, target_pause_time_ms)) {
 623           min_young_length = young_length;
 624         } else {
 625           max_young_length = young_length;
 626         }
 627         assert(min_young_length <  max_young_length, "invariant");
 628         diff = (max_young_length - min_young_length) / 2;
 629       }
 630       // The results is min_young_length which, according to the
 631       // loop invariants, should fit within the target pause time.
 632 
 633       // These are the post-conditions of the binary search above:
 634       assert(min_young_length < max_young_length,
 635              "otherwise we should have discovered that max_young_length "
 636              "fits into the pause target and not done the binary search");
 637       assert(predict_will_fit(min_young_length, base_time_ms,
 638                               base_free_regions, target_pause_time_ms),
 639              "min_young_length, the result of the binary search, should "
 640              "fit into the pause target");
 641       assert(!predict_will_fit(min_young_length + 1, base_time_ms,
 642                                base_free_regions, target_pause_time_ms),
 643              "min_young_length, the result of the binary search, should be "
 644              "optimal, so no larger length should fit into the pause target");
 645     }
 646   } else {
 647     // Even the minimum length doesn't fit into the pause time
 648     // target, return it as the result nevertheless.
 649   }
 650   return base_min_length + min_young_length;
 651 }
 652 
 653 double G1CollectorPolicy::predict_survivor_regions_evac_time() {
 654   double survivor_regions_evac_time = 0.0;
 655   for (HeapRegion * r = _recorded_survivor_head;
 656        r != NULL && r != _recorded_survivor_tail->get_next_young_region();
 657        r = r->get_next_young_region()) {
 658     survivor_regions_evac_time += predict_region_elapsed_time_ms(r, gcs_are_young());
 659   }
 660   return survivor_regions_evac_time;
 661 }
 662 
 663 void G1CollectorPolicy::revise_young_list_target_length_if_necessary() {
 664   guarantee( adaptive_young_list_length(), "should not call this otherwise" );
 665 
 666   size_t rs_lengths = _g1->young_list()->sampled_rs_lengths();
 667   if (rs_lengths > _rs_lengths_prediction) {
 668     // add 10% to avoid having to recalculate often
 669     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 670     update_young_list_target_length(rs_lengths_prediction);
 671   }
 672 }
 673 
 674 
 675 
 676 HeapWord* G1CollectorPolicy::mem_allocate_work(size_t size,
 677                                                bool is_tlab,
 678                                                bool* gc_overhead_limit_was_exceeded) {
 679   guarantee(false, "Not using this policy feature yet.");
 680   return NULL;
 681 }
 682 
 683 // This method controls how a collector handles one or more
 684 // of its generations being fully allocated.
 685 HeapWord* G1CollectorPolicy::satisfy_failed_allocation(size_t size,
 686                                                        bool is_tlab) {
 687   guarantee(false, "Not using this policy feature yet.");
 688   return NULL;
 689 }
 690 
 691 
 692 #ifndef PRODUCT
 693 bool G1CollectorPolicy::verify_young_ages() {
 694   HeapRegion* head = _g1->young_list()->first_region();
 695   return
 696     verify_young_ages(head, _short_lived_surv_rate_group);
 697   // also call verify_young_ages on any additional surv rate groups
 698 }
 699 
 700 bool
 701 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
 702                                      SurvRateGroup *surv_rate_group) {
 703   guarantee( surv_rate_group != NULL, "pre-condition" );
 704 
 705   const char* name = surv_rate_group->name();
 706   bool ret = true;
 707   int prev_age = -1;
 708 
 709   for (HeapRegion* curr = head;
 710        curr != NULL;
 711        curr = curr->get_next_young_region()) {
 712     SurvRateGroup* group = curr->surv_rate_group();
 713     if (group == NULL && !curr->is_survivor()) {
 714       gclog_or_tty->print_cr("## %s: encountered NULL surv_rate_group", name);
 715       ret = false;
 716     }
 717 
 718     if (surv_rate_group == group) {
 719       int age = curr->age_in_surv_rate_group();
 720 
 721       if (age < 0) {
 722         gclog_or_tty->print_cr("## %s: encountered negative age", name);
 723         ret = false;
 724       }
 725 
 726       if (age <= prev_age) {
 727         gclog_or_tty->print_cr("## %s: region ages are not strictly increasing "
 728                                "(%d, %d)", name, age, prev_age);
 729         ret = false;
 730       }
 731       prev_age = age;
 732     }
 733   }
 734 
 735   return ret;
 736 }
 737 #endif // PRODUCT
 738 
 739 void G1CollectorPolicy::record_full_collection_start() {
 740   _full_collection_start_sec = os::elapsedTime();
 741   // Release the future to-space so that it is available for compaction into.
 742   _g1->set_full_collection();
 743 }
 744 
 745 void G1CollectorPolicy::record_full_collection_end() {
 746   // Consider this like a collection pause for the purposes of allocation
 747   // since last pause.
 748   double end_sec = os::elapsedTime();
 749   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 750   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 751 
 752   _trace_gen1_time_data.record_full_collection(full_gc_time_ms);
 753 
 754   update_recent_gc_times(end_sec, full_gc_time_ms);
 755 
 756   _g1->clear_full_collection();
 757 
 758   // "Nuke" the heuristics that control the young/mixed GC
 759   // transitions and make sure we start with young GCs after the Full GC.
 760   set_gcs_are_young(true);
 761   _last_young_gc = false;
 762   clear_initiate_conc_mark_if_possible();
 763   clear_during_initial_mark_pause();
 764   _in_marking_window = false;
 765   _in_marking_window_im = false;
 766 
 767   _short_lived_surv_rate_group->start_adding_regions();
 768   // also call this on any additional surv rate groups
 769 
 770   record_survivor_regions(0, NULL, NULL);
 771 
 772   _free_regions_at_end_of_collection = _g1->free_regions();
 773   // Reset survivors SurvRateGroup.
 774   _survivor_surv_rate_group->reset();
 775   update_young_list_target_length();
 776   _collectionSetChooser->clear();
 777 }
 778 
 779 void G1CollectorPolicy::record_stop_world_start() {
 780   _stop_world_start = os::elapsedTime();
 781 }
 782 
 783 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec,
 784                                                       size_t start_used) {
 785   // We only need to do this here as the policy will only be applied
 786   // to the GC we're about to start. so, no point is calculating this
 787   // every time we calculate / recalculate the target young length.
 788   update_survivors_policy();
 789 
 790   assert(_g1->used() == _g1->recalculate_used(),
 791          err_msg("sanity, used: "SIZE_FORMAT" recalculate_used: "SIZE_FORMAT,
 792                  _g1->used(), _g1->recalculate_used()));
 793 
 794   double s_w_t_ms = (start_time_sec - _stop_world_start) * 1000.0;
 795   _trace_gen0_time_data.record_start_collection(s_w_t_ms);
 796   _stop_world_start = 0.0;
 797 
 798   phase_times()->record_cur_collection_start_sec(start_time_sec);
 799   _cur_collection_pause_used_at_start_bytes = start_used;
 800   _cur_collection_pause_used_regions_at_start = _g1->used_regions();
 801   _pending_cards = _g1->pending_card_num();
 802 
 803   _collection_set_bytes_used_before = 0;
 804   _bytes_copied_during_gc = 0;
 805 
 806   YoungList* young_list = _g1->young_list();
 807   _eden_bytes_before_gc = young_list->eden_used_bytes();
 808   _survivor_bytes_before_gc = young_list->survivor_used_bytes();
 809   _capacity_before_gc = _g1->capacity();
 810 
 811   _last_gc_was_young = false;
 812 
 813   // do that for any other surv rate groups
 814   _short_lived_surv_rate_group->stop_adding_regions();
 815   _survivors_age_table.clear();
 816 
 817   assert( verify_young_ages(), "region age verification" );
 818 }
 819 
 820 void G1CollectorPolicy::record_concurrent_mark_init_end(double
 821                                                    mark_init_elapsed_time_ms) {
 822   _during_marking = true;
 823   assert(!initiate_conc_mark_if_possible(), "we should have cleared it by now");
 824   clear_during_initial_mark_pause();
 825   _cur_mark_stop_world_time_ms = mark_init_elapsed_time_ms;
 826 }
 827 
 828 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
 829   _mark_remark_start_sec = os::elapsedTime();
 830   _during_marking = false;
 831 }
 832 
 833 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
 834   double end_time_sec = os::elapsedTime();
 835   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 836   _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
 837   _cur_mark_stop_world_time_ms += elapsed_time_ms;
 838   _prev_collection_pause_end_ms += elapsed_time_ms;
 839 
 840   _mmu_tracker->add_pause(_mark_remark_start_sec, end_time_sec, true);
 841 }
 842 
 843 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
 844   _mark_cleanup_start_sec = os::elapsedTime();
 845 }
 846 
 847 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
 848   _last_young_gc = true;
 849   _in_marking_window = false;
 850 }
 851 
 852 void G1CollectorPolicy::record_concurrent_pause() {
 853   if (_stop_world_start > 0.0) {
 854     double yield_ms = (os::elapsedTime() - _stop_world_start) * 1000.0;
 855     _trace_gen0_time_data.record_yield_time(yield_ms);
 856   }
 857 }
 858 
 859 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
 860   if (_g1->concurrent_mark()->cmThread()->during_cycle()) {
 861     return false;
 862   }
 863 
 864   size_t marking_initiating_used_threshold =
 865     (_g1->capacity() / 100) * InitiatingHeapOccupancyPercent;
 866   size_t cur_used_bytes = _g1->non_young_capacity_bytes();
 867   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 868 
 869   if ((cur_used_bytes + alloc_byte_size) > marking_initiating_used_threshold) {
 870     if (gcs_are_young()) {
 871       ergo_verbose5(ErgoConcCycles,
 872         "request concurrent cycle initiation",
 873         ergo_format_reason("occupancy higher than threshold")
 874         ergo_format_byte("occupancy")
 875         ergo_format_byte("allocation request")
 876         ergo_format_byte_perc("threshold")
 877         ergo_format_str("source"),
 878         cur_used_bytes,
 879         alloc_byte_size,
 880         marking_initiating_used_threshold,
 881         (double) InitiatingHeapOccupancyPercent,
 882         source);
 883       return true;
 884     } else {
 885       ergo_verbose5(ErgoConcCycles,
 886         "do not request concurrent cycle initiation",
 887         ergo_format_reason("still doing mixed collections")
 888         ergo_format_byte("occupancy")
 889         ergo_format_byte("allocation request")
 890         ergo_format_byte_perc("threshold")
 891         ergo_format_str("source"),
 892         cur_used_bytes,
 893         alloc_byte_size,
 894         marking_initiating_used_threshold,
 895         (double) InitiatingHeapOccupancyPercent,
 896         source);
 897     }
 898   }
 899 
 900   return false;
 901 }
 902 
 903 // Anything below that is considered to be zero
 904 #define MIN_TIMER_GRANULARITY 0.0000001
 905 
 906 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms) {
 907   double end_time_sec = os::elapsedTime();
 908   assert(_cur_collection_pause_used_regions_at_start >= cset_region_length(),
 909          "otherwise, the subtraction below does not make sense");
 910   size_t rs_size =
 911             _cur_collection_pause_used_regions_at_start - cset_region_length();
 912   size_t cur_used_bytes = _g1->used();
 913   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
 914   bool last_pause_included_initial_mark = false;
 915   bool update_stats = !_g1->evacuation_failed();
 916 
 917 #ifndef PRODUCT
 918   if (G1YoungSurvRateVerbose) {
 919     gclog_or_tty->print_cr("");
 920     _short_lived_surv_rate_group->print();
 921     // do that for any other surv rate groups too
 922   }
 923 #endif // PRODUCT
 924 
 925   last_pause_included_initial_mark = during_initial_mark_pause();
 926   if (last_pause_included_initial_mark) {
 927     record_concurrent_mark_init_end(0.0);
 928   } else if (!_last_young_gc && need_to_start_conc_mark("end of GC")) {
 929     // Note: this might have already been set, if during the last
 930     // pause we decided to start a cycle but at the beginning of
 931     // this pause we decided to postpone it. That's OK.
 932     set_initiate_conc_mark_if_possible();
 933   }
 934 
 935   _mmu_tracker->add_pause(end_time_sec - pause_time_ms/1000.0,
 936                           end_time_sec, false);
 937 
 938   size_t freed_bytes =
 939     _cur_collection_pause_used_at_start_bytes - cur_used_bytes;
 940   size_t surviving_bytes = _collection_set_bytes_used_before - freed_bytes;
 941 
 942   double survival_fraction =
 943     (double)surviving_bytes/
 944     (double)_collection_set_bytes_used_before;
 945 
 946   if (update_stats) {
 947     _trace_gen0_time_data.record_end_collection(pause_time_ms, phase_times());
 948     // this is where we update the allocation rate of the application
 949     double app_time_ms =
 950       (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
 951     if (app_time_ms < MIN_TIMER_GRANULARITY) {
 952       // This usually happens due to the timer not having the required
 953       // granularity. Some Linuxes are the usual culprits.
 954       // We'll just set it to something (arbitrarily) small.
 955       app_time_ms = 1.0;
 956     }
 957     // We maintain the invariant that all objects allocated by mutator
 958     // threads will be allocated out of eden regions. So, we can use
 959     // the eden region number allocated since the previous GC to
 960     // calculate the application's allocate rate. The only exception
 961     // to that is humongous objects that are allocated separately. But
 962     // given that humongous object allocations do not really affect
 963     // either the pause's duration nor when the next pause will take
 964     // place we can safely ignore them here.
 965     uint regions_allocated = eden_cset_region_length();
 966     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
 967     _alloc_rate_ms_seq->add(alloc_rate_ms);
 968 
 969     double interval_ms =
 970       (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
 971     update_recent_gc_times(end_time_sec, pause_time_ms);
 972     _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
 973     if (recent_avg_pause_time_ratio() < 0.0 ||
 974         (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
 975 #ifndef PRODUCT
 976       // Dump info to allow post-facto debugging
 977       gclog_or_tty->print_cr("recent_avg_pause_time_ratio() out of bounds");
 978       gclog_or_tty->print_cr("-------------------------------------------");
 979       gclog_or_tty->print_cr("Recent GC Times (ms):");
 980       _recent_gc_times_ms->dump();
 981       gclog_or_tty->print_cr("(End Time=%3.3f) Recent GC End Times (s):", end_time_sec);
 982       _recent_prev_end_times_for_all_gcs_sec->dump();
 983       gclog_or_tty->print_cr("GC = %3.3f, Interval = %3.3f, Ratio = %3.3f",
 984                              _recent_gc_times_ms->sum(), interval_ms, recent_avg_pause_time_ratio());
 985       // In debug mode, terminate the JVM if the user wants to debug at this point.
 986       assert(!G1FailOnFPError, "Debugging data for CR 6898948 has been dumped above");
 987 #endif  // !PRODUCT
 988       // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
 989       // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
 990       if (_recent_avg_pause_time_ratio < 0.0) {
 991         _recent_avg_pause_time_ratio = 0.0;
 992       } else {
 993         assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
 994         _recent_avg_pause_time_ratio = 1.0;
 995       }
 996     }
 997   }
 998   bool new_in_marking_window = _in_marking_window;
 999   bool new_in_marking_window_im = false;
1000   if (during_initial_mark_pause()) {
1001     new_in_marking_window = true;
1002     new_in_marking_window_im = true;
1003   }
1004 
1005   if (_last_young_gc) {
1006     // This is supposed to to be the "last young GC" before we start
1007     // doing mixed GCs. Here we decide whether to start mixed GCs or not.
1008 
1009     if (!last_pause_included_initial_mark) {
1010       if (next_gc_should_be_mixed("start mixed GCs",
1011                                   "do not start mixed GCs")) {
1012         set_gcs_are_young(false);
1013       }
1014     } else {
1015       ergo_verbose0(ErgoMixedGCs,
1016                     "do not start mixed GCs",
1017                     ergo_format_reason("concurrent cycle is about to start"));
1018     }
1019     _last_young_gc = false;
1020   }
1021 
1022   if (!_last_gc_was_young) {
1023     // This is a mixed GC. Here we decide whether to continue doing
1024     // mixed GCs or not.
1025 
1026     if (!next_gc_should_be_mixed("continue mixed GCs",
1027                                  "do not continue mixed GCs")) {
1028       set_gcs_are_young(true);
1029     }
1030   }
1031 
1032   _short_lived_surv_rate_group->start_adding_regions();
1033   // do that for any other surv rate groupsx
1034 
1035   if (update_stats) {
1036     double cost_per_card_ms = 0.0;
1037     if (_pending_cards > 0) {
1038       cost_per_card_ms = phase_times()->average_last_update_rs_time() / (double) _pending_cards;
1039       _cost_per_card_ms_seq->add(cost_per_card_ms);
1040     }
1041 
1042     size_t cards_scanned = _g1->cards_scanned();
1043 
1044     double cost_per_entry_ms = 0.0;
1045     if (cards_scanned > 10) {
1046       cost_per_entry_ms = phase_times()->average_last_scan_rs_time() / (double) cards_scanned;
1047       if (_last_gc_was_young) {
1048         _cost_per_entry_ms_seq->add(cost_per_entry_ms);
1049       } else {
1050         _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
1051       }
1052     }
1053 
1054     if (_max_rs_lengths > 0) {
1055       double cards_per_entry_ratio =
1056         (double) cards_scanned / (double) _max_rs_lengths;
1057       if (_last_gc_was_young) {
1058         _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1059       } else {
1060         _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1061       }
1062     }
1063 
1064     // This is defensive. For a while _max_rs_lengths could get
1065     // smaller than _recorded_rs_lengths which was causing
1066     // rs_length_diff to get very large and mess up the RSet length
1067     // predictions. The reason was unsafe concurrent updates to the
1068     // _inc_cset_recorded_rs_lengths field which the code below guards
1069     // against (see CR 7118202). This bug has now been fixed (see CR
1070     // 7119027). However, I'm still worried that
1071     // _inc_cset_recorded_rs_lengths might still end up somewhat
1072     // inaccurate. The concurrent refinement thread calculates an
1073     // RSet's length concurrently with other CR threads updating it
1074     // which might cause it to calculate the length incorrectly (if,
1075     // say, it's in mid-coarsening). So I'll leave in the defensive
1076     // conditional below just in case.
1077     size_t rs_length_diff = 0;
1078     if (_max_rs_lengths > _recorded_rs_lengths) {
1079       rs_length_diff = _max_rs_lengths - _recorded_rs_lengths;
1080     }
1081     _rs_length_diff_seq->add((double) rs_length_diff);
1082 
1083     size_t copied_bytes = surviving_bytes;
1084     double cost_per_byte_ms = 0.0;
1085     if (copied_bytes > 0) {
1086       cost_per_byte_ms = phase_times()->average_last_obj_copy_time() / (double) copied_bytes;
1087       if (_in_marking_window) {
1088         _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
1089       } else {
1090         _cost_per_byte_ms_seq->add(cost_per_byte_ms);
1091       }
1092     }
1093 
1094     double all_other_time_ms = pause_time_ms -
1095       (phase_times()->average_last_update_rs_time() + phase_times()->average_last_scan_rs_time()
1096       + phase_times()->average_last_obj_copy_time() + phase_times()->average_last_termination_time());
1097 
1098     double young_other_time_ms = 0.0;
1099     if (young_cset_region_length() > 0) {
1100       young_other_time_ms =
1101         phase_times()->young_cset_choice_time_ms() +
1102         phase_times()->young_free_cset_time_ms();
1103       _young_other_cost_per_region_ms_seq->add(young_other_time_ms /
1104                                           (double) young_cset_region_length());
1105     }
1106     double non_young_other_time_ms = 0.0;
1107     if (old_cset_region_length() > 0) {
1108       non_young_other_time_ms =
1109         phase_times()->non_young_cset_choice_time_ms() +
1110         phase_times()->non_young_free_cset_time_ms();
1111 
1112       _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms /
1113                                             (double) old_cset_region_length());
1114     }
1115 
1116     double constant_other_time_ms = all_other_time_ms -
1117       (young_other_time_ms + non_young_other_time_ms);
1118     _constant_other_time_ms_seq->add(constant_other_time_ms);
1119 
1120     double survival_ratio = 0.0;
1121     if (_collection_set_bytes_used_before > 0) {
1122       survival_ratio = (double) _bytes_copied_during_gc /
1123                                    (double) _collection_set_bytes_used_before;
1124     }
1125 
1126     _pending_cards_seq->add((double) _pending_cards);
1127     _rs_lengths_seq->add((double) _max_rs_lengths);
1128   }
1129 
1130   _in_marking_window = new_in_marking_window;
1131   _in_marking_window_im = new_in_marking_window_im;
1132   _free_regions_at_end_of_collection = _g1->free_regions();
1133   update_young_list_target_length();
1134 
1135   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1136   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
1137   adjust_concurrent_refinement(phase_times()->average_last_update_rs_time(),
1138                                phase_times()->sum_last_update_rs_processed_buffers(), update_rs_time_goal_ms);
1139 
1140   _collectionSetChooser->verify();
1141 }
1142 
1143 #define EXT_SIZE_FORMAT "%.1f%s"
1144 #define EXT_SIZE_PARAMS(bytes)                                  \
1145   byte_size_in_proper_unit((double)(bytes)),                    \
1146   proper_unit_for_byte_size((bytes))
1147 
1148 void G1CollectorPolicy::print_heap_transition() {
1149   _g1->print_size_transition(gclog_or_tty,
1150     _cur_collection_pause_used_at_start_bytes, _g1->used(), _g1->capacity());
1151 }
1152 
1153 void G1CollectorPolicy::print_detailed_heap_transition() {
1154     YoungList* young_list = _g1->young_list();
1155     size_t eden_bytes = young_list->eden_used_bytes();
1156     size_t survivor_bytes = young_list->survivor_used_bytes();
1157     size_t used_before_gc = _cur_collection_pause_used_at_start_bytes;
1158     size_t used = _g1->used();
1159     size_t capacity = _g1->capacity();
1160     size_t eden_capacity =
1161       (_young_list_target_length * HeapRegion::GrainBytes) - survivor_bytes;
1162 
1163     gclog_or_tty->print_cr(
1164       "   [Eden: "EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT")->"EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT") "
1165       "Survivors: "EXT_SIZE_FORMAT"->"EXT_SIZE_FORMAT" "
1166       "Heap: "EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT")->"
1167       EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT")]",
1168       EXT_SIZE_PARAMS(_eden_bytes_before_gc),
1169       EXT_SIZE_PARAMS(_prev_eden_capacity),
1170       EXT_SIZE_PARAMS(eden_bytes),
1171       EXT_SIZE_PARAMS(eden_capacity),
1172       EXT_SIZE_PARAMS(_survivor_bytes_before_gc),
1173       EXT_SIZE_PARAMS(survivor_bytes),
1174       EXT_SIZE_PARAMS(used_before_gc),
1175       EXT_SIZE_PARAMS(_capacity_before_gc),
1176       EXT_SIZE_PARAMS(used),
1177       EXT_SIZE_PARAMS(capacity));
1178 
1179     _prev_eden_capacity = eden_capacity;
1180 }
1181 
1182 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
1183                                                      double update_rs_processed_buffers,
1184                                                      double goal_ms) {
1185   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1186   ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
1187 
1188   if (G1UseAdaptiveConcRefinement) {
1189     const int k_gy = 3, k_gr = 6;
1190     const double inc_k = 1.1, dec_k = 0.9;
1191 
1192     int g = cg1r->green_zone();
1193     if (update_rs_time > goal_ms) {
1194       g = (int)(g * dec_k);  // Can become 0, that's OK. That would mean a mutator-only processing.
1195     } else {
1196       if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
1197         g = (int)MAX2(g * inc_k, g + 1.0);
1198       }
1199     }
1200     // Change the refinement threads params
1201     cg1r->set_green_zone(g);
1202     cg1r->set_yellow_zone(g * k_gy);
1203     cg1r->set_red_zone(g * k_gr);
1204     cg1r->reinitialize_threads();
1205 
1206     int processing_threshold_delta = MAX2((int)(cg1r->green_zone() * sigma()), 1);
1207     int processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1208                                     cg1r->yellow_zone());
1209     // Change the barrier params
1210     dcqs.set_process_completed_threshold(processing_threshold);
1211     dcqs.set_max_completed_queue(cg1r->red_zone());
1212   }
1213 
1214   int curr_queue_size = dcqs.completed_buffers_num();
1215   if (curr_queue_size >= cg1r->yellow_zone()) {
1216     dcqs.set_completed_queue_padding(curr_queue_size);
1217   } else {
1218     dcqs.set_completed_queue_padding(0);
1219   }
1220   dcqs.notify_if_necessary();
1221 }
1222 
1223 double
1224 G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1225                                                 size_t scanned_cards) {
1226   return
1227     predict_rs_update_time_ms(pending_cards) +
1228     predict_rs_scan_time_ms(scanned_cards) +
1229     predict_constant_other_time_ms();
1230 }
1231 
1232 double
1233 G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) {
1234   size_t rs_length = predict_rs_length_diff();
1235   size_t card_num;
1236   if (gcs_are_young()) {
1237     card_num = predict_young_card_num(rs_length);
1238   } else {
1239     card_num = predict_non_young_card_num(rs_length);
1240   }
1241   return predict_base_elapsed_time_ms(pending_cards, card_num);
1242 }
1243 
1244 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) {
1245   size_t bytes_to_copy;
1246   if (hr->is_marked())
1247     bytes_to_copy = hr->max_live_bytes();
1248   else {
1249     assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1250     int age = hr->age_in_surv_rate_group();
1251     double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1252     bytes_to_copy = (size_t) ((double) hr->used() * yg_surv_rate);
1253   }
1254   return bytes_to_copy;
1255 }
1256 
1257 double
1258 G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1259                                                   bool for_young_gc) {
1260   size_t rs_length = hr->rem_set()->occupied();
1261   size_t card_num;
1262 
1263   // Predicting the number of cards is based on which type of GC
1264   // we're predicting for.
1265   if (for_young_gc) {
1266     card_num = predict_young_card_num(rs_length);
1267   } else {
1268     card_num = predict_non_young_card_num(rs_length);
1269   }
1270   size_t bytes_to_copy = predict_bytes_to_copy(hr);
1271 
1272   double region_elapsed_time_ms =
1273     predict_rs_scan_time_ms(card_num) +
1274     predict_object_copy_time_ms(bytes_to_copy);
1275 
1276   // The prediction of the "other" time for this region is based
1277   // upon the region type and NOT the GC type.
1278   if (hr->is_young()) {
1279     region_elapsed_time_ms += predict_young_other_time_ms(1);
1280   } else {
1281     region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1282   }
1283   return region_elapsed_time_ms;
1284 }
1285 
1286 void
1287 G1CollectorPolicy::init_cset_region_lengths(uint eden_cset_region_length,
1288                                             uint survivor_cset_region_length) {
1289   _eden_cset_region_length     = eden_cset_region_length;
1290   _survivor_cset_region_length = survivor_cset_region_length;
1291   _old_cset_region_length      = 0;
1292 }
1293 
1294 void G1CollectorPolicy::set_recorded_rs_lengths(size_t rs_lengths) {
1295   _recorded_rs_lengths = rs_lengths;
1296 }
1297 
1298 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1299                                                double elapsed_ms) {
1300   _recent_gc_times_ms->add(elapsed_ms);
1301   _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1302   _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1303 }
1304 
1305 size_t G1CollectorPolicy::expansion_amount() {
1306   double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1307   double threshold = _gc_overhead_perc;
1308   if (recent_gc_overhead > threshold) {
1309     // We will double the existing space, or take
1310     // G1ExpandByPercentOfAvailable % of the available expansion
1311     // space, whichever is smaller, bounded below by a minimum
1312     // expansion (unless that's all that's left.)
1313     const size_t min_expand_bytes = 1*M;
1314     size_t reserved_bytes = _g1->max_capacity();
1315     size_t committed_bytes = _g1->capacity();
1316     size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1317     size_t expand_bytes;
1318     size_t expand_bytes_via_pct =
1319       uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1320     expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1321     expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1322     expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1323 
1324     ergo_verbose5(ErgoHeapSizing,
1325                   "attempt heap expansion",
1326                   ergo_format_reason("recent GC overhead higher than "
1327                                      "threshold after GC")
1328                   ergo_format_perc("recent GC overhead")
1329                   ergo_format_perc("threshold")
1330                   ergo_format_byte("uncommitted")
1331                   ergo_format_byte_perc("calculated expansion amount"),
1332                   recent_gc_overhead, threshold,
1333                   uncommitted_bytes,
1334                   expand_bytes_via_pct, (double) G1ExpandByPercentOfAvailable);
1335 
1336     return expand_bytes;
1337   } else {
1338     return 0;
1339   }
1340 }
1341 
1342 void G1CollectorPolicy::print_tracing_info() const {
1343   _trace_gen0_time_data.print();
1344   _trace_gen1_time_data.print();
1345 }
1346 
1347 void G1CollectorPolicy::print_yg_surv_rate_info() const {
1348 #ifndef PRODUCT
1349   _short_lived_surv_rate_group->print_surv_rate_summary();
1350   // add this call for any other surv rate groups
1351 #endif // PRODUCT
1352 }
1353 
1354 #ifndef PRODUCT
1355 // for debugging, bit of a hack...
1356 static char*
1357 region_num_to_mbs(int length) {
1358   static char buffer[64];
1359   double bytes = (double) (length * HeapRegion::GrainBytes);
1360   double mbs = bytes / (double) (1024 * 1024);
1361   sprintf(buffer, "%7.2lfMB", mbs);
1362   return buffer;
1363 }
1364 #endif // PRODUCT
1365 
1366 uint G1CollectorPolicy::max_regions(int purpose) {
1367   switch (purpose) {
1368     case GCAllocForSurvived:
1369       return _max_survivor_regions;
1370     case GCAllocForTenured:
1371       return REGIONS_UNLIMITED;
1372     default:
1373       ShouldNotReachHere();
1374       return REGIONS_UNLIMITED;
1375   };
1376 }
1377 
1378 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1379   uint expansion_region_num = 0;
1380   if (GCLockerEdenExpansionPercent > 0) {
1381     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1382     double expansion_region_num_d = perc * (double) _young_list_target_length;
1383     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1384     // less than 1.0) we'll get 1.
1385     expansion_region_num = (uint) ceil(expansion_region_num_d);
1386   } else {
1387     assert(expansion_region_num == 0, "sanity");
1388   }
1389   _young_list_max_length = _young_list_target_length + expansion_region_num;
1390   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1391 }
1392 
1393 // Calculates survivor space parameters.
1394 void G1CollectorPolicy::update_survivors_policy() {
1395   double max_survivor_regions_d =
1396                  (double) _young_list_target_length / (double) SurvivorRatio;
1397   // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1398   // smaller than 1.0) we'll get 1.
1399   _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1400 
1401   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1402         HeapRegion::GrainWords * _max_survivor_regions);
1403 }
1404 
1405 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(
1406                                                      GCCause::Cause gc_cause) {
1407   bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1408   if (!during_cycle) {
1409     ergo_verbose1(ErgoConcCycles,
1410                   "request concurrent cycle initiation",
1411                   ergo_format_reason("requested by GC cause")
1412                   ergo_format_str("GC cause"),
1413                   GCCause::to_string(gc_cause));
1414     set_initiate_conc_mark_if_possible();
1415     return true;
1416   } else {
1417     ergo_verbose1(ErgoConcCycles,
1418                   "do not request concurrent cycle initiation",
1419                   ergo_format_reason("concurrent cycle already in progress")
1420                   ergo_format_str("GC cause"),
1421                   GCCause::to_string(gc_cause));
1422     return false;
1423   }
1424 }
1425 
1426 void
1427 G1CollectorPolicy::decide_on_conc_mark_initiation() {
1428   // We are about to decide on whether this pause will be an
1429   // initial-mark pause.
1430 
1431   // First, during_initial_mark_pause() should not be already set. We
1432   // will set it here if we have to. However, it should be cleared by
1433   // the end of the pause (it's only set for the duration of an
1434   // initial-mark pause).
1435   assert(!during_initial_mark_pause(), "pre-condition");
1436 
1437   if (initiate_conc_mark_if_possible()) {
1438     // We had noticed on a previous pause that the heap occupancy has
1439     // gone over the initiating threshold and we should start a
1440     // concurrent marking cycle. So we might initiate one.
1441 
1442     bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1443     if (!during_cycle) {
1444       // The concurrent marking thread is not "during a cycle", i.e.,
1445       // it has completed the last one. So we can go ahead and
1446       // initiate a new cycle.
1447 
1448       set_during_initial_mark_pause();
1449       // We do not allow mixed GCs during marking.
1450       if (!gcs_are_young()) {
1451         set_gcs_are_young(true);
1452         ergo_verbose0(ErgoMixedGCs,
1453                       "end mixed GCs",
1454                       ergo_format_reason("concurrent cycle is about to start"));
1455       }
1456 
1457       // And we can now clear initiate_conc_mark_if_possible() as
1458       // we've already acted on it.
1459       clear_initiate_conc_mark_if_possible();
1460 
1461       ergo_verbose0(ErgoConcCycles,
1462                   "initiate concurrent cycle",
1463                   ergo_format_reason("concurrent cycle initiation requested"));
1464     } else {
1465       // The concurrent marking thread is still finishing up the
1466       // previous cycle. If we start one right now the two cycles
1467       // overlap. In particular, the concurrent marking thread might
1468       // be in the process of clearing the next marking bitmap (which
1469       // we will use for the next cycle if we start one). Starting a
1470       // cycle now will be bad given that parts of the marking
1471       // information might get cleared by the marking thread. And we
1472       // cannot wait for the marking thread to finish the cycle as it
1473       // periodically yields while clearing the next marking bitmap
1474       // and, if it's in a yield point, it's waiting for us to
1475       // finish. So, at this point we will not start a cycle and we'll
1476       // let the concurrent marking thread complete the last one.
1477       ergo_verbose0(ErgoConcCycles,
1478                     "do not initiate concurrent cycle",
1479                     ergo_format_reason("concurrent cycle already in progress"));
1480     }
1481   }
1482 }
1483 
1484 class KnownGarbageClosure: public HeapRegionClosure {
1485   G1CollectedHeap* _g1h;
1486   CollectionSetChooser* _hrSorted;
1487 
1488 public:
1489   KnownGarbageClosure(CollectionSetChooser* hrSorted) :
1490     _g1h(G1CollectedHeap::heap()), _hrSorted(hrSorted) { }
1491 
1492   bool doHeapRegion(HeapRegion* r) {
1493     // We only include humongous regions in collection
1494     // sets when concurrent mark shows that their contained object is
1495     // unreachable.
1496 
1497     // Do we have any marking information for this region?
1498     if (r->is_marked()) {
1499       // We will skip any region that's currently used as an old GC
1500       // alloc region (we should not consider those for collection
1501       // before we fill them up).
1502       if (_hrSorted->should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
1503         _hrSorted->add_region(r);
1504       }
1505     }
1506     return false;
1507   }
1508 };
1509 
1510 class ParKnownGarbageHRClosure: public HeapRegionClosure {
1511   G1CollectedHeap* _g1h;
1512   CSetChooserParUpdater _cset_updater;
1513 
1514 public:
1515   ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
1516                            uint chunk_size) :
1517     _g1h(G1CollectedHeap::heap()),
1518     _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
1519 
1520   bool doHeapRegion(HeapRegion* r) {
1521     // Do we have any marking information for this region?
1522     if (r->is_marked()) {
1523       // We will skip any region that's currently used as an old GC
1524       // alloc region (we should not consider those for collection
1525       // before we fill them up).
1526       if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
1527         _cset_updater.add_region(r);
1528       }
1529     }
1530     return false;
1531   }
1532 };
1533 
1534 class ParKnownGarbageTask: public AbstractGangTask {
1535   CollectionSetChooser* _hrSorted;
1536   uint _chunk_size;
1537   G1CollectedHeap* _g1;
1538 public:
1539   ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size) :
1540     AbstractGangTask("ParKnownGarbageTask"),
1541     _hrSorted(hrSorted), _chunk_size(chunk_size),
1542     _g1(G1CollectedHeap::heap()) { }
1543 
1544   void work(uint worker_id) {
1545     ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
1546 
1547     // Back to zero for the claim value.
1548     _g1->heap_region_par_iterate_chunked(&parKnownGarbageCl, worker_id,
1549                                          _g1->workers()->active_workers(),
1550                                          HeapRegion::InitialClaimValue);
1551   }
1552 };
1553 
1554 void
1555 G1CollectorPolicy::record_concurrent_mark_cleanup_end(int no_of_gc_threads) {
1556   _collectionSetChooser->clear();
1557 
1558   uint region_num = _g1->n_regions();
1559   if (G1CollectedHeap::use_parallel_gc_threads()) {
1560     const uint OverpartitionFactor = 4;
1561     uint WorkUnit;
1562     // The use of MinChunkSize = 8 in the original code
1563     // causes some assertion failures when the total number of
1564     // region is less than 8.  The code here tries to fix that.
1565     // Should the original code also be fixed?
1566     if (no_of_gc_threads > 0) {
1567       const uint MinWorkUnit = MAX2(region_num / no_of_gc_threads, 1U);
1568       WorkUnit = MAX2(region_num / (no_of_gc_threads * OverpartitionFactor),
1569                       MinWorkUnit);
1570     } else {
1571       assert(no_of_gc_threads > 0,
1572         "The active gc workers should be greater than 0");
1573       // In a product build do something reasonable to avoid a crash.
1574       const uint MinWorkUnit = MAX2(region_num / (uint) ParallelGCThreads, 1U);
1575       WorkUnit =
1576         MAX2(region_num / (uint) (ParallelGCThreads * OverpartitionFactor),
1577              MinWorkUnit);
1578     }
1579     _collectionSetChooser->prepare_for_par_region_addition(_g1->n_regions(),
1580                                                            WorkUnit);
1581     ParKnownGarbageTask parKnownGarbageTask(_collectionSetChooser,
1582                                             (int) WorkUnit);
1583     _g1->workers()->run_task(&parKnownGarbageTask);
1584 
1585     assert(_g1->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
1586            "sanity check");
1587   } else {
1588     KnownGarbageClosure knownGarbagecl(_collectionSetChooser);
1589     _g1->heap_region_iterate(&knownGarbagecl);
1590   }
1591 
1592   _collectionSetChooser->sort_regions();
1593 
1594   double end_sec = os::elapsedTime();
1595   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1596   _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
1597   _cur_mark_stop_world_time_ms += elapsed_time_ms;
1598   _prev_collection_pause_end_ms += elapsed_time_ms;
1599   _mmu_tracker->add_pause(_mark_cleanup_start_sec, end_sec, true);
1600 }
1601 
1602 // Add the heap region at the head of the non-incremental collection set
1603 void G1CollectorPolicy::add_old_region_to_cset(HeapRegion* hr) {
1604   assert(_inc_cset_build_state == Active, "Precondition");
1605   assert(!hr->is_young(), "non-incremental add of young region");
1606 
1607   assert(!hr->in_collection_set(), "should not already be in the CSet");
1608   hr->set_in_collection_set(true);
1609   hr->set_next_in_collection_set(_collection_set);
1610   _collection_set = hr;
1611   _collection_set_bytes_used_before += hr->used();
1612   _g1->register_region_with_in_cset_fast_test(hr);
1613   size_t rs_length = hr->rem_set()->occupied();
1614   _recorded_rs_lengths += rs_length;
1615   _old_cset_region_length += 1;
1616 }
1617 
1618 // Initialize the per-collection-set information
1619 void G1CollectorPolicy::start_incremental_cset_building() {
1620   assert(_inc_cset_build_state == Inactive, "Precondition");
1621 
1622   _inc_cset_head = NULL;
1623   _inc_cset_tail = NULL;
1624   _inc_cset_bytes_used_before = 0;
1625 
1626   _inc_cset_max_finger = 0;
1627   _inc_cset_recorded_rs_lengths = 0;
1628   _inc_cset_recorded_rs_lengths_diffs = 0;
1629   _inc_cset_predicted_elapsed_time_ms = 0.0;
1630   _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1631   _inc_cset_build_state = Active;
1632 }
1633 
1634 void G1CollectorPolicy::finalize_incremental_cset_building() {
1635   assert(_inc_cset_build_state == Active, "Precondition");
1636   assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1637 
1638   // The two "main" fields, _inc_cset_recorded_rs_lengths and
1639   // _inc_cset_predicted_elapsed_time_ms, are updated by the thread
1640   // that adds a new region to the CSet. Further updates by the
1641   // concurrent refinement thread that samples the young RSet lengths
1642   // are accumulated in the *_diffs fields. Here we add the diffs to
1643   // the "main" fields.
1644 
1645   if (_inc_cset_recorded_rs_lengths_diffs >= 0) {
1646     _inc_cset_recorded_rs_lengths += _inc_cset_recorded_rs_lengths_diffs;
1647   } else {
1648     // This is defensive. The diff should in theory be always positive
1649     // as RSets can only grow between GCs. However, given that we
1650     // sample their size concurrently with other threads updating them
1651     // it's possible that we might get the wrong size back, which
1652     // could make the calculations somewhat inaccurate.
1653     size_t diffs = (size_t) (-_inc_cset_recorded_rs_lengths_diffs);
1654     if (_inc_cset_recorded_rs_lengths >= diffs) {
1655       _inc_cset_recorded_rs_lengths -= diffs;
1656     } else {
1657       _inc_cset_recorded_rs_lengths = 0;
1658     }
1659   }
1660   _inc_cset_predicted_elapsed_time_ms +=
1661                                      _inc_cset_predicted_elapsed_time_ms_diffs;
1662 
1663   _inc_cset_recorded_rs_lengths_diffs = 0;
1664   _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1665 }
1666 
1667 void G1CollectorPolicy::add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length) {
1668   // This routine is used when:
1669   // * adding survivor regions to the incremental cset at the end of an
1670   //   evacuation pause,
1671   // * adding the current allocation region to the incremental cset
1672   //   when it is retired, and
1673   // * updating existing policy information for a region in the
1674   //   incremental cset via young list RSet sampling.
1675   // Therefore this routine may be called at a safepoint by the
1676   // VM thread, or in-between safepoints by mutator threads (when
1677   // retiring the current allocation region) or a concurrent
1678   // refine thread (RSet sampling).
1679 
1680   double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, gcs_are_young());
1681   size_t used_bytes = hr->used();
1682   _inc_cset_recorded_rs_lengths += rs_length;
1683   _inc_cset_predicted_elapsed_time_ms += region_elapsed_time_ms;
1684   _inc_cset_bytes_used_before += used_bytes;
1685 
1686   // Cache the values we have added to the aggregated informtion
1687   // in the heap region in case we have to remove this region from
1688   // the incremental collection set, or it is updated by the
1689   // rset sampling code
1690   hr->set_recorded_rs_length(rs_length);
1691   hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
1692 }
1693 
1694 void G1CollectorPolicy::update_incremental_cset_info(HeapRegion* hr,
1695                                                      size_t new_rs_length) {
1696   // Update the CSet information that is dependent on the new RS length
1697   assert(hr->is_young(), "Precondition");
1698   assert(!SafepointSynchronize::is_at_safepoint(),
1699                                                "should not be at a safepoint");
1700 
1701   // We could have updated _inc_cset_recorded_rs_lengths and
1702   // _inc_cset_predicted_elapsed_time_ms directly but we'd need to do
1703   // that atomically, as this code is executed by a concurrent
1704   // refinement thread, potentially concurrently with a mutator thread
1705   // allocating a new region and also updating the same fields. To
1706   // avoid the atomic operations we accumulate these updates on two
1707   // separate fields (*_diffs) and we'll just add them to the "main"
1708   // fields at the start of a GC.
1709 
1710   ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
1711   ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
1712   _inc_cset_recorded_rs_lengths_diffs += rs_lengths_diff;
1713 
1714   double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
1715   double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, gcs_are_young());
1716   double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
1717   _inc_cset_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
1718 
1719   hr->set_recorded_rs_length(new_rs_length);
1720   hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
1721 }
1722 
1723 void G1CollectorPolicy::add_region_to_incremental_cset_common(HeapRegion* hr) {
1724   assert(hr->is_young(), "invariant");
1725   assert(hr->young_index_in_cset() > -1, "should have already been set");
1726   assert(_inc_cset_build_state == Active, "Precondition");
1727 
1728   // We need to clear and set the cached recorded/cached collection set
1729   // information in the heap region here (before the region gets added
1730   // to the collection set). An individual heap region's cached values
1731   // are calculated, aggregated with the policy collection set info,
1732   // and cached in the heap region here (initially) and (subsequently)
1733   // by the Young List sampling code.
1734 
1735   size_t rs_length = hr->rem_set()->occupied();
1736   add_to_incremental_cset_info(hr, rs_length);
1737 
1738   HeapWord* hr_end = hr->end();
1739   _inc_cset_max_finger = MAX2(_inc_cset_max_finger, hr_end);
1740 
1741   assert(!hr->in_collection_set(), "invariant");
1742   hr->set_in_collection_set(true);
1743   assert( hr->next_in_collection_set() == NULL, "invariant");
1744 
1745   _g1->register_region_with_in_cset_fast_test(hr);
1746 }
1747 
1748 // Add the region at the RHS of the incremental cset
1749 void G1CollectorPolicy::add_region_to_incremental_cset_rhs(HeapRegion* hr) {
1750   // We should only ever be appending survivors at the end of a pause
1751   assert( hr->is_survivor(), "Logic");
1752 
1753   // Do the 'common' stuff
1754   add_region_to_incremental_cset_common(hr);
1755 
1756   // Now add the region at the right hand side
1757   if (_inc_cset_tail == NULL) {
1758     assert(_inc_cset_head == NULL, "invariant");
1759     _inc_cset_head = hr;
1760   } else {
1761     _inc_cset_tail->set_next_in_collection_set(hr);
1762   }
1763   _inc_cset_tail = hr;
1764 }
1765 
1766 // Add the region to the LHS of the incremental cset
1767 void G1CollectorPolicy::add_region_to_incremental_cset_lhs(HeapRegion* hr) {
1768   // Survivors should be added to the RHS at the end of a pause
1769   assert(!hr->is_survivor(), "Logic");
1770 
1771   // Do the 'common' stuff
1772   add_region_to_incremental_cset_common(hr);
1773 
1774   // Add the region at the left hand side
1775   hr->set_next_in_collection_set(_inc_cset_head);
1776   if (_inc_cset_head == NULL) {
1777     assert(_inc_cset_tail == NULL, "Invariant");
1778     _inc_cset_tail = hr;
1779   }
1780   _inc_cset_head = hr;
1781 }
1782 
1783 #ifndef PRODUCT
1784 void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream* st) {
1785   assert(list_head == inc_cset_head() || list_head == collection_set(), "must be");
1786 
1787   st->print_cr("\nCollection_set:");
1788   HeapRegion* csr = list_head;
1789   while (csr != NULL) {
1790     HeapRegion* next = csr->next_in_collection_set();
1791     assert(csr->in_collection_set(), "bad CS");
1792     st->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
1793                  HR_FORMAT_PARAMS(csr),
1794                  csr->prev_top_at_mark_start(), csr->next_top_at_mark_start(),
1795                  csr->age_in_surv_rate_group_cond());
1796     csr = next;
1797   }
1798 }
1799 #endif // !PRODUCT
1800 
1801 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
1802                                                 const char* false_action_str) {
1803   CollectionSetChooser* cset_chooser = _collectionSetChooser;
1804   if (cset_chooser->is_empty()) {
1805     ergo_verbose0(ErgoMixedGCs,
1806                   false_action_str,
1807                   ergo_format_reason("candidate old regions not available"));
1808     return false;
1809   }
1810   size_t reclaimable_bytes = cset_chooser->remaining_reclaimable_bytes();
1811   size_t capacity_bytes = _g1->capacity();
1812   double perc = (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1813   double threshold = (double) G1HeapWastePercent;
1814   if (perc < threshold) {
1815     ergo_verbose4(ErgoMixedGCs,
1816               false_action_str,
1817               ergo_format_reason("reclaimable percentage lower than threshold")
1818               ergo_format_region("candidate old regions")
1819               ergo_format_byte_perc("reclaimable")
1820               ergo_format_perc("threshold"),
1821               cset_chooser->remaining_regions(),
1822               reclaimable_bytes, perc, threshold);
1823     return false;
1824   }
1825 
1826   ergo_verbose4(ErgoMixedGCs,
1827                 true_action_str,
1828                 ergo_format_reason("candidate old regions available")
1829                 ergo_format_region("candidate old regions")
1830                 ergo_format_byte_perc("reclaimable")
1831                 ergo_format_perc("threshold"),
1832                 cset_chooser->remaining_regions(),
1833                 reclaimable_bytes, perc, threshold);
1834   return true;
1835 }
1836 
1837 void G1CollectorPolicy::finalize_cset(double target_pause_time_ms) {
1838   double young_start_time_sec = os::elapsedTime();
1839 
1840   YoungList* young_list = _g1->young_list();
1841   finalize_incremental_cset_building();
1842 
1843   guarantee(target_pause_time_ms > 0.0,
1844             err_msg("target_pause_time_ms = %1.6lf should be positive",
1845                     target_pause_time_ms));
1846   guarantee(_collection_set == NULL, "Precondition");
1847 
1848   double base_time_ms = predict_base_elapsed_time_ms(_pending_cards);
1849   double predicted_pause_time_ms = base_time_ms;
1850   double time_remaining_ms = target_pause_time_ms - base_time_ms;
1851 
1852   ergo_verbose4(ErgoCSetConstruction | ErgoHigh,
1853                 "start choosing CSet",
1854                 ergo_format_size("_pending_cards")
1855                 ergo_format_ms("predicted base time")
1856                 ergo_format_ms("remaining time")
1857                 ergo_format_ms("target pause time"),
1858                 _pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
1859 
1860   _last_gc_was_young = gcs_are_young() ? true : false;
1861 
1862   if (_last_gc_was_young) {
1863     _trace_gen0_time_data.increment_young_collection_count();
1864   } else {
1865     _trace_gen0_time_data.increment_mixed_collection_count();
1866   }
1867 
1868   // The young list is laid with the survivor regions from the previous
1869   // pause are appended to the RHS of the young list, i.e.
1870   //   [Newly Young Regions ++ Survivors from last pause].
1871 
1872   uint survivor_region_length = young_list->survivor_length();
1873   uint eden_region_length = young_list->length() - survivor_region_length;
1874   init_cset_region_lengths(eden_region_length, survivor_region_length);
1875 
1876   HeapRegion* hr = young_list->first_survivor_region();
1877   while (hr != NULL) {
1878     assert(hr->is_survivor(), "badly formed young list");
1879     hr->set_young();
1880     hr = hr->get_next_young_region();
1881   }
1882 
1883   // Clear the fields that point to the survivor list - they are all young now.
1884   young_list->clear_survivors();
1885 
1886   _collection_set = _inc_cset_head;
1887   _collection_set_bytes_used_before = _inc_cset_bytes_used_before;
1888   time_remaining_ms -= _inc_cset_predicted_elapsed_time_ms;
1889   predicted_pause_time_ms += _inc_cset_predicted_elapsed_time_ms;
1890 
1891   ergo_verbose3(ErgoCSetConstruction | ErgoHigh,
1892                 "add young regions to CSet",
1893                 ergo_format_region("eden")
1894                 ergo_format_region("survivors")
1895                 ergo_format_ms("predicted young region time"),
1896                 eden_region_length, survivor_region_length,
1897                 _inc_cset_predicted_elapsed_time_ms);
1898 
1899   // The number of recorded young regions is the incremental
1900   // collection set's current size
1901   set_recorded_rs_lengths(_inc_cset_recorded_rs_lengths);
1902 
1903   double young_end_time_sec = os::elapsedTime();
1904   phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
1905 
1906   // Set the start of the non-young choice time.
1907   double non_young_start_time_sec = young_end_time_sec;
1908 
1909   if (!gcs_are_young()) {
1910     CollectionSetChooser* cset_chooser = _collectionSetChooser;
1911     cset_chooser->verify();
1912     const uint min_old_cset_length = cset_chooser->calc_min_old_cset_length();
1913     const uint max_old_cset_length = cset_chooser->calc_max_old_cset_length();
1914 
1915     uint expensive_region_num = 0;
1916     bool check_time_remaining = adaptive_young_list_length();
1917 
1918     HeapRegion* hr = cset_chooser->peek();
1919     while (hr != NULL) {
1920       if (old_cset_region_length() >= max_old_cset_length) {
1921         // Added maximum number of old regions to the CSet.
1922         ergo_verbose2(ErgoCSetConstruction,
1923                       "finish adding old regions to CSet",
1924                       ergo_format_reason("old CSet region num reached max")
1925                       ergo_format_region("old")
1926                       ergo_format_region("max"),
1927                       old_cset_region_length(), max_old_cset_length);
1928         break;
1929       }
1930 
1931       double predicted_time_ms = predict_region_elapsed_time_ms(hr, gcs_are_young());
1932       if (check_time_remaining) {
1933         if (predicted_time_ms > time_remaining_ms) {
1934           // Too expensive for the current CSet.
1935 
1936           if (old_cset_region_length() >= min_old_cset_length) {
1937             // We have added the minimum number of old regions to the CSet,
1938             // we are done with this CSet.
1939             ergo_verbose4(ErgoCSetConstruction,
1940                           "finish adding old regions to CSet",
1941                           ergo_format_reason("predicted time is too high")
1942                           ergo_format_ms("predicted time")
1943                           ergo_format_ms("remaining time")
1944                           ergo_format_region("old")
1945                           ergo_format_region("min"),
1946                           predicted_time_ms, time_remaining_ms,
1947                           old_cset_region_length(), min_old_cset_length);
1948             break;
1949           }
1950 
1951           // We'll add it anyway given that we haven't reached the
1952           // minimum number of old regions.
1953           expensive_region_num += 1;
1954         }
1955       } else {
1956         if (old_cset_region_length() >= min_old_cset_length) {
1957           // In the non-auto-tuning case, we'll finish adding regions
1958           // to the CSet if we reach the minimum.
1959           ergo_verbose2(ErgoCSetConstruction,
1960                         "finish adding old regions to CSet",
1961                         ergo_format_reason("old CSet region num reached min")
1962                         ergo_format_region("old")
1963                         ergo_format_region("min"),
1964                         old_cset_region_length(), min_old_cset_length);
1965           break;
1966         }
1967       }
1968 
1969       // We will add this region to the CSet.
1970       time_remaining_ms -= predicted_time_ms;
1971       predicted_pause_time_ms += predicted_time_ms;
1972       cset_chooser->remove_and_move_to_next(hr);
1973       _g1->old_set_remove(hr);
1974       add_old_region_to_cset(hr);
1975 
1976       hr = cset_chooser->peek();
1977     }
1978     if (hr == NULL) {
1979       ergo_verbose0(ErgoCSetConstruction,
1980                     "finish adding old regions to CSet",
1981                     ergo_format_reason("candidate old regions not available"));
1982     }
1983 
1984     if (expensive_region_num > 0) {
1985       // We print the information once here at the end, predicated on
1986       // whether we added any apparently expensive regions or not, to
1987       // avoid generating output per region.
1988       ergo_verbose4(ErgoCSetConstruction,
1989                     "added expensive regions to CSet",
1990                     ergo_format_reason("old CSet region num not reached min")
1991                     ergo_format_region("old")
1992                     ergo_format_region("expensive")
1993                     ergo_format_region("min")
1994                     ergo_format_ms("remaining time"),
1995                     old_cset_region_length(),
1996                     expensive_region_num,
1997                     min_old_cset_length,
1998                     time_remaining_ms);
1999     }
2000 
2001     cset_chooser->verify();
2002   }
2003 
2004   stop_incremental_cset_building();
2005 
2006   ergo_verbose5(ErgoCSetConstruction,
2007                 "finish choosing CSet",
2008                 ergo_format_region("eden")
2009                 ergo_format_region("survivors")
2010                 ergo_format_region("old")
2011                 ergo_format_ms("predicted pause time")
2012                 ergo_format_ms("target pause time"),
2013                 eden_region_length, survivor_region_length,
2014                 old_cset_region_length(),
2015                 predicted_pause_time_ms, target_pause_time_ms);
2016 
2017   double non_young_end_time_sec = os::elapsedTime();
2018   phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
2019 }
2020 
2021 void TraceGen0TimeData::record_start_collection(double time_to_stop_the_world_ms) {
2022   if(TraceGen0Time) {
2023     _all_stop_world_times_ms.add(time_to_stop_the_world_ms);
2024   }
2025 }
2026 
2027 void TraceGen0TimeData::record_yield_time(double yield_time_ms) {
2028   if(TraceGen0Time) {
2029     _all_yield_times_ms.add(yield_time_ms);
2030   }
2031 }
2032 
2033 void TraceGen0TimeData::record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times) {
2034   if(TraceGen0Time) {
2035     _total.add(pause_time_ms);
2036     _other.add(pause_time_ms - phase_times->accounted_time_ms());
2037     _root_region_scan_wait.add(phase_times->root_region_scan_wait_time_ms());
2038     _parallel.add(phase_times->cur_collection_par_time_ms());
2039     _ext_root_scan.add(phase_times->average_last_ext_root_scan_time());
2040     _satb_filtering.add(phase_times->average_last_satb_filtering_times_ms());
2041     _update_rs.add(phase_times->average_last_update_rs_time());
2042     _scan_rs.add(phase_times->average_last_scan_rs_time());
2043     _obj_copy.add(phase_times->average_last_obj_copy_time());
2044     _termination.add(phase_times->average_last_termination_time());
2045 
2046     double parallel_known_time = phase_times->average_last_ext_root_scan_time() +
2047       phase_times->average_last_satb_filtering_times_ms() +
2048       phase_times->average_last_update_rs_time() +
2049       phase_times->average_last_scan_rs_time() +
2050       phase_times->average_last_obj_copy_time() +
2051       + phase_times->average_last_termination_time();
2052 
2053     double parallel_other_time = phase_times->cur_collection_par_time_ms() - parallel_known_time;
2054     _parallel_other.add(parallel_other_time);
2055     _clear_ct.add(phase_times->cur_clear_ct_time_ms());
2056   }
2057 }
2058 
2059 void TraceGen0TimeData::increment_young_collection_count() {
2060   if(TraceGen0Time) {
2061     ++_young_pause_num;
2062   }
2063 }
2064 
2065 void TraceGen0TimeData::increment_mixed_collection_count() {
2066   if(TraceGen0Time) {
2067     ++_mixed_pause_num;
2068   }
2069 }
2070 
2071 void TraceGen0TimeData::print_summary(const char* str,
2072                                       const NumberSeq* seq) const {
2073   double sum = seq->sum();
2074   gclog_or_tty->print_cr("%-27s = %8.2lf s (avg = %8.2lf ms)",
2075                 str, sum / 1000.0, seq->avg());
2076 }
2077 
2078 void TraceGen0TimeData::print_summary_sd(const char* str,
2079                                          const NumberSeq* seq) const {
2080   print_summary(str, seq);
2081   gclog_or_tty->print_cr("%+45s = %5d, std dev = %8.2lf ms, max = %8.2lf ms)",
2082                 "(num", seq->num(), seq->sd(), seq->maximum());
2083 }
2084 
2085 void TraceGen0TimeData::print() const {
2086   if (!TraceGen0Time) {
2087     return;
2088   }
2089 
2090   gclog_or_tty->print_cr("ALL PAUSES");
2091   print_summary_sd("   Total", &_total);
2092   gclog_or_tty->print_cr("");
2093   gclog_or_tty->print_cr("");
2094   gclog_or_tty->print_cr("   Young GC Pauses: %8d", _young_pause_num);
2095   gclog_or_tty->print_cr("   Mixed GC Pauses: %8d", _mixed_pause_num);
2096   gclog_or_tty->print_cr("");
2097 
2098   gclog_or_tty->print_cr("EVACUATION PAUSES");
2099 
2100   if (_young_pause_num == 0 && _mixed_pause_num == 0) {
2101     gclog_or_tty->print_cr("none");
2102   } else {
2103     print_summary_sd("   Evacuation Pauses", &_total);
2104     print_summary("      Root Region Scan Wait", &_root_region_scan_wait);
2105     print_summary("      Parallel Time", &_parallel);
2106     print_summary("         Ext Root Scanning", &_ext_root_scan);
2107     print_summary("         SATB Filtering", &_satb_filtering);
2108     print_summary("         Update RS", &_update_rs);
2109     print_summary("         Scan RS", &_scan_rs);
2110     print_summary("         Object Copy", &_obj_copy);
2111     print_summary("         Termination", &_termination);
2112     print_summary("         Parallel Other", &_parallel_other);
2113     print_summary("      Clear CT", &_clear_ct);
2114     print_summary("      Other", &_other);
2115   }
2116   gclog_or_tty->print_cr("");
2117 
2118   gclog_or_tty->print_cr("MISC");
2119   print_summary_sd("   Stop World", &_all_stop_world_times_ms);
2120   print_summary_sd("   Yields", &_all_yield_times_ms);
2121 }
2122 
2123 void TraceGen1TimeData::record_full_collection(double full_gc_time_ms) {
2124   if (TraceGen1Time) {
2125     _all_full_gc_times.add(full_gc_time_ms);
2126   }
2127 }
2128 
2129 void TraceGen1TimeData::print() const {
2130   if (!TraceGen1Time) {
2131     return;
2132   }
2133 
2134   if (_all_full_gc_times.num() > 0) {
2135     gclog_or_tty->print("\n%4d full_gcs: total time = %8.2f s",
2136       _all_full_gc_times.num(),
2137       _all_full_gc_times.sum() / 1000.0);
2138     gclog_or_tty->print_cr(" (avg = %8.2fms).", _all_full_gc_times.avg());
2139     gclog_or_tty->print_cr("                     [std. dev = %8.2f ms, max = %8.2f ms]",
2140       _all_full_gc_times.sd(),
2141       _all_full_gc_times.maximum());
2142   }
2143 }