1 /*
   2  * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/concurrentG1Refine.hpp"
  27 #include "gc/g1/concurrentMarkThread.inline.hpp"
  28 #include "gc/g1/g1Analytics.hpp"
  29 #include "gc/g1/g1CollectedHeap.inline.hpp"
  30 #include "gc/g1/g1CollectionSet.hpp"
  31 #include "gc/g1/g1ConcurrentMark.hpp"
  32 #include "gc/g1/g1IHOPControl.hpp"
  33 #include "gc/g1/g1GCPhaseTimes.hpp"
  34 #include "gc/g1/g1Policy.hpp"
  35 #include "gc/g1/g1YoungGenSizer.hpp"
  36 #include "gc/g1/heapRegion.inline.hpp"
  37 #include "gc/g1/heapRegionRemSet.hpp"
  38 #include "gc/shared/gcPolicyCounters.hpp"
  39 #include "runtime/arguments.hpp"
  40 #include "runtime/java.hpp"
  41 #include "runtime/mutexLocker.hpp"
  42 #include "utilities/debug.hpp"
  43 #include "utilities/pair.hpp"
  44 
  45 G1Policy::G1Policy() :
  46   _predictor(G1ConfidencePercent / 100.0),
  47   _analytics(new G1Analytics(&_predictor)),
  48   _pause_time_target_ms((double) MaxGCPauseMillis),
  49   _rs_lengths_prediction(0),
  50   _max_survivor_regions(0),
  51   _survivors_age_table(true),
  52 
  53   _bytes_allocated_in_old_since_last_gc(0),
  54   _ihop_control(NULL),
  55   _initial_mark_to_mixed() {
  56 
  57   // SurvRateGroups below must be initialized after the predictor because they
  58   // indirectly use it through this object passed to their constructor.
  59   _short_lived_surv_rate_group =
  60     new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
  61   _survivor_surv_rate_group =
  62     new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
  63 
  64   _phase_times = new G1GCPhaseTimes(ParallelGCThreads);
  65 
  66   double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
  67   double time_slice  = (double) GCPauseIntervalMillis / 1000.0;
  68   _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
  69 
  70   _tenuring_threshold = MaxTenuringThreshold;
  71 
  72 
  73   guarantee(G1ReservePercent <= 50, "Range checking should not allow values over 50.");
  74   _reserve_factor = (double) G1ReservePercent / 100.0;
  75   // This will be set when the heap is expanded
  76   // for the first time during initialization.
  77   _reserve_regions = 0;
  78 
  79   _ihop_control = create_ihop_control();
  80 }
  81 
  82 G1Policy::~G1Policy() {
  83   delete _ihop_control;
  84 }
  85 
  86 G1CollectorState* G1Policy::collector_state() const { return _g1->collector_state(); }
  87 
  88 void G1Policy::init() {
  89   // Set aside an initial future to_space.
  90   _g1 = G1CollectedHeap::heap();
  91   _collection_set = _g1->collection_set();
  92 
  93   assert(Heap_lock->owned_by_self(), "Locking discipline.");
  94 
  95   _g1->collector_policy()->initialize_gc_policy_counters();
  96 
  97   if (adaptive_young_list_length()) {
  98     _young_list_fixed_length = 0;
  99   } else {
 100     _young_list_fixed_length = _young_gen_sizer.min_desired_young_length();
 101   }
 102   _young_gen_sizer.adjust_max_new_size(_g1->max_regions());
 103 
 104   _free_regions_at_end_of_collection = _g1->num_free_regions();
 105 
 106   update_young_list_max_and_target_length();
 107   // We may immediately start allocating regions and placing them on the
 108   // collection set list. Initialize the per-collection set info
 109   _collection_set->start_incremental_building();
 110 }
 111 
 112 void G1Policy::note_gc_start() {
 113   phase_times()->note_gc_start();
 114 }
 115 
 116 bool G1Policy::predict_will_fit(uint young_length,
 117                                 double base_time_ms,
 118                                 uint base_free_regions,
 119                                 double target_pause_time_ms) const {
 120   if (young_length >= base_free_regions) {
 121     // end condition 1: not enough space for the young regions
 122     return false;
 123   }
 124 
 125   double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
 126   size_t bytes_to_copy =
 127                (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
 128   double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy,
 129                                                                 collector_state()->during_concurrent_mark());
 130   double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length);
 131   double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
 132   if (pause_time_ms > target_pause_time_ms) {
 133     // end condition 2: prediction is over the target pause time
 134     return false;
 135   }
 136 
 137   size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
 138 
 139   // When copying, we will likely need more bytes free than is live in the region.
 140   // Add some safety margin to factor in the confidence of our guess, and the
 141   // natural expected waste.
 142   // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
 143   // of the calculation: the lower the confidence, the more headroom.
 144   // (100 + TargetPLABWastePct) represents the increase in expected bytes during
 145   // copying due to anticipated waste in the PLABs.
 146   double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
 147   size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
 148 
 149   if (expected_bytes_to_copy > free_bytes) {
 150     // end condition 3: out-of-space
 151     return false;
 152   }
 153 
 154   // success!
 155   return true;
 156 }
 157 
 158 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
 159   // re-calculate the necessary reserve
 160   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
 161   // We use ceiling so that if reserve_regions_d is > 0.0 (but
 162   // smaller than 1.0) we'll get 1.
 163   _reserve_regions = (uint) ceil(reserve_regions_d);
 164 
 165   _young_gen_sizer.heap_size_changed(new_number_of_regions);
 166 
 167   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
 168 }
 169 
 170 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
 171   uint desired_min_length = 0;
 172   if (adaptive_young_list_length()) {
 173     if (_analytics->num_alloc_rate_ms() > 3) {
 174       double now_sec = os::elapsedTime();
 175       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
 176       double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
 177       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
 178     } else {
 179       // otherwise we don't have enough info to make the prediction
 180     }
 181   }
 182   desired_min_length += base_min_length;
 183   // make sure we don't go below any user-defined minimum bound
 184   return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length);
 185 }
 186 
 187 uint G1Policy::calculate_young_list_desired_max_length() const {
 188   // Here, we might want to also take into account any additional
 189   // constraints (i.e., user-defined minimum bound). Currently, we
 190   // effectively don't set this bound.
 191   return _young_gen_sizer.max_desired_young_length();
 192 }
 193 
 194 uint G1Policy::update_young_list_max_and_target_length() {
 195   return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
 196 }
 197 
 198 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) {
 199   uint unbounded_target_length = update_young_list_target_length(rs_lengths);
 200   update_max_gc_locker_expansion();
 201   return unbounded_target_length;
 202 }
 203 
 204 uint G1Policy::update_young_list_target_length(size_t rs_lengths) {
 205   YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
 206   _young_list_target_length = young_lengths.first;
 207   return young_lengths.second;
 208 }
 209 
 210 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const {
 211   YoungTargetLengths result;
 212 
 213   // Calculate the absolute and desired min bounds first.
 214 
 215   // This is how many young regions we already have (currently: the survivors).
 216   const uint base_min_length = _g1->young_list()->survivor_length();
 217   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
 218   // This is the absolute minimum young length. Ensure that we
 219   // will at least have one eden region available for allocation.
 220   uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
 221   // If we shrank the young list target it should not shrink below the current size.
 222   desired_min_length = MAX2(desired_min_length, absolute_min_length);
 223   // Calculate the absolute and desired max bounds.
 224 
 225   uint desired_max_length = calculate_young_list_desired_max_length();
 226 
 227   uint young_list_target_length = 0;
 228   if (adaptive_young_list_length()) {
 229     if (collector_state()->gcs_are_young()) {
 230       young_list_target_length =
 231                         calculate_young_list_target_length(rs_lengths,
 232                                                            base_min_length,
 233                                                            desired_min_length,
 234                                                            desired_max_length);
 235     } else {
 236       // Don't calculate anything and let the code below bound it to
 237       // the desired_min_length, i.e., do the next GC as soon as
 238       // possible to maximize how many old regions we can add to it.
 239     }
 240   } else {
 241     // The user asked for a fixed young gen so we'll fix the young gen
 242     // whether the next GC is young or mixed.
 243     young_list_target_length = _young_list_fixed_length;
 244   }
 245 
 246   result.second = young_list_target_length;
 247 
 248   // We will try our best not to "eat" into the reserve.
 249   uint absolute_max_length = 0;
 250   if (_free_regions_at_end_of_collection > _reserve_regions) {
 251     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
 252   }
 253   if (desired_max_length > absolute_max_length) {
 254     desired_max_length = absolute_max_length;
 255   }
 256 
 257   // Make sure we don't go over the desired max length, nor under the
 258   // desired min length. In case they clash, desired_min_length wins
 259   // which is why that test is second.
 260   if (young_list_target_length > desired_max_length) {
 261     young_list_target_length = desired_max_length;
 262   }
 263   if (young_list_target_length < desired_min_length) {
 264     young_list_target_length = desired_min_length;
 265   }
 266 
 267   assert(young_list_target_length > base_min_length,
 268          "we should be able to allocate at least one eden region");
 269   assert(young_list_target_length >= absolute_min_length, "post-condition");
 270 
 271   result.first = young_list_target_length;
 272   return result;
 273 }
 274 
 275 uint
 276 G1Policy::calculate_young_list_target_length(size_t rs_lengths,
 277                                              uint base_min_length,
 278                                              uint desired_min_length,
 279                                              uint desired_max_length) const {
 280   assert(adaptive_young_list_length(), "pre-condition");
 281   assert(collector_state()->gcs_are_young(), "only call this for young GCs");
 282 
 283   // In case some edge-condition makes the desired max length too small...
 284   if (desired_max_length <= desired_min_length) {
 285     return desired_min_length;
 286   }
 287 
 288   // We'll adjust min_young_length and max_young_length not to include
 289   // the already allocated young regions (i.e., so they reflect the
 290   // min and max eden regions we'll allocate). The base_min_length
 291   // will be reflected in the predictions by the
 292   // survivor_regions_evac_time prediction.
 293   assert(desired_min_length > base_min_length, "invariant");
 294   uint min_young_length = desired_min_length - base_min_length;
 295   assert(desired_max_length > base_min_length, "invariant");
 296   uint max_young_length = desired_max_length - base_min_length;
 297 
 298   double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
 299   double survivor_regions_evac_time = predict_survivor_regions_evac_time();
 300   size_t pending_cards = _analytics->predict_pending_cards();
 301   size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
 302   size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);
 303   double base_time_ms =
 304     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
 305     survivor_regions_evac_time;
 306   uint available_free_regions = _free_regions_at_end_of_collection;
 307   uint base_free_regions = 0;
 308   if (available_free_regions > _reserve_regions) {
 309     base_free_regions = available_free_regions - _reserve_regions;
 310   }
 311 
 312   // Here, we will make sure that the shortest young length that
 313   // makes sense fits within the target pause time.
 314 
 315   if (predict_will_fit(min_young_length, base_time_ms,
 316                        base_free_regions, target_pause_time_ms)) {
 317     // The shortest young length will fit into the target pause time;
 318     // we'll now check whether the absolute maximum number of young
 319     // regions will fit in the target pause time. If not, we'll do
 320     // a binary search between min_young_length and max_young_length.
 321     if (predict_will_fit(max_young_length, base_time_ms,
 322                          base_free_regions, target_pause_time_ms)) {
 323       // The maximum young length will fit into the target pause time.
 324       // We are done so set min young length to the maximum length (as
 325       // the result is assumed to be returned in min_young_length).
 326       min_young_length = max_young_length;
 327     } else {
 328       // The maximum possible number of young regions will not fit within
 329       // the target pause time so we'll search for the optimal
 330       // length. The loop invariants are:
 331       //
 332       // min_young_length < max_young_length
 333       // min_young_length is known to fit into the target pause time
 334       // max_young_length is known not to fit into the target pause time
 335       //
 336       // Going into the loop we know the above hold as we've just
 337       // checked them. Every time around the loop we check whether
 338       // the middle value between min_young_length and
 339       // max_young_length fits into the target pause time. If it
 340       // does, it becomes the new min. If it doesn't, it becomes
 341       // the new max. This way we maintain the loop invariants.
 342 
 343       assert(min_young_length < max_young_length, "invariant");
 344       uint diff = (max_young_length - min_young_length) / 2;
 345       while (diff > 0) {
 346         uint young_length = min_young_length + diff;
 347         if (predict_will_fit(young_length, base_time_ms,
 348                              base_free_regions, target_pause_time_ms)) {
 349           min_young_length = young_length;
 350         } else {
 351           max_young_length = young_length;
 352         }
 353         assert(min_young_length <  max_young_length, "invariant");
 354         diff = (max_young_length - min_young_length) / 2;
 355       }
 356       // The results is min_young_length which, according to the
 357       // loop invariants, should fit within the target pause time.
 358 
 359       // These are the post-conditions of the binary search above:
 360       assert(min_young_length < max_young_length,
 361              "otherwise we should have discovered that max_young_length "
 362              "fits into the pause target and not done the binary search");
 363       assert(predict_will_fit(min_young_length, base_time_ms,
 364                               base_free_regions, target_pause_time_ms),
 365              "min_young_length, the result of the binary search, should "
 366              "fit into the pause target");
 367       assert(!predict_will_fit(min_young_length + 1, base_time_ms,
 368                                base_free_regions, target_pause_time_ms),
 369              "min_young_length, the result of the binary search, should be "
 370              "optimal, so no larger length should fit into the pause target");
 371     }
 372   } else {
 373     // Even the minimum length doesn't fit into the pause time
 374     // target, return it as the result nevertheless.
 375   }
 376   return base_min_length + min_young_length;
 377 }
 378 
 379 double G1Policy::predict_survivor_regions_evac_time() const {
 380   double survivor_regions_evac_time = 0.0;
 381   for (HeapRegion * r = _g1->young_list()->first_survivor_region();
 382        r != NULL && r != _g1->young_list()->last_survivor_region()->get_next_young_region();
 383        r = r->get_next_young_region()) {
 384     survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
 385   }
 386   return survivor_regions_evac_time;
 387 }
 388 
 389 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
 390   guarantee( adaptive_young_list_length(), "should not call this otherwise" );
 391 
 392   if (rs_lengths > _rs_lengths_prediction) {
 393     // add 10% to avoid having to recalculate often
 394     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
 395     update_rs_lengths_prediction(rs_lengths_prediction);
 396 
 397     update_young_list_max_and_target_length(rs_lengths_prediction);
 398   }
 399 }
 400 
 401 void G1Policy::update_rs_lengths_prediction() {
 402   update_rs_lengths_prediction(_analytics->predict_rs_lengths());
 403 }
 404 
 405 void G1Policy::update_rs_lengths_prediction(size_t prediction) {
 406   if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
 407     _rs_lengths_prediction = prediction;
 408   }
 409 }
 410 
 411 #ifndef PRODUCT
 412 bool G1Policy::verify_young_ages() {
 413   HeapRegion* head = _g1->young_list()->first_region();
 414   return
 415     verify_young_ages(head, _short_lived_surv_rate_group);
 416   // also call verify_young_ages on any additional surv rate groups
 417 }
 418 
 419 bool G1Policy::verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group) {
 420   guarantee( surv_rate_group != NULL, "pre-condition" );
 421 
 422   const char* name = surv_rate_group->name();
 423   bool ret = true;
 424   int prev_age = -1;
 425 
 426   for (HeapRegion* curr = head;
 427        curr != NULL;
 428        curr = curr->get_next_young_region()) {
 429     SurvRateGroup* group = curr->surv_rate_group();
 430     if (group == NULL && !curr->is_survivor()) {
 431       log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);
 432       ret = false;
 433     }
 434 
 435     if (surv_rate_group == group) {
 436       int age = curr->age_in_surv_rate_group();
 437 
 438       if (age < 0) {
 439         log_error(gc, verify)("## %s: encountered negative age", name);
 440         ret = false;
 441       }
 442 
 443       if (age <= prev_age) {
 444         log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
 445         ret = false;
 446       }
 447       prev_age = age;
 448     }
 449   }
 450 
 451   return ret;
 452 }
 453 #endif // PRODUCT
 454 
 455 void G1Policy::record_full_collection_start() {
 456   _full_collection_start_sec = os::elapsedTime();
 457   // Release the future to-space so that it is available for compaction into.
 458   collector_state()->set_full_collection(true);
 459 }
 460 
 461 void G1Policy::record_full_collection_end() {
 462   // Consider this like a collection pause for the purposes of allocation
 463   // since last pause.
 464   double end_sec = os::elapsedTime();
 465   double full_gc_time_sec = end_sec - _full_collection_start_sec;
 466   double full_gc_time_ms = full_gc_time_sec * 1000.0;
 467 
 468   _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
 469 
 470   collector_state()->set_full_collection(false);
 471 
 472   // "Nuke" the heuristics that control the young/mixed GC
 473   // transitions and make sure we start with young GCs after the Full GC.
 474   collector_state()->set_gcs_are_young(true);
 475   collector_state()->set_last_young_gc(false);
 476   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
 477   collector_state()->set_during_initial_mark_pause(false);
 478   collector_state()->set_in_marking_window(false);
 479   collector_state()->set_in_marking_window_im(false);
 480 
 481   _short_lived_surv_rate_group->start_adding_regions();
 482   // also call this on any additional surv rate groups
 483 
 484   _free_regions_at_end_of_collection = _g1->num_free_regions();
 485   // Reset survivors SurvRateGroup.
 486   _survivor_surv_rate_group->reset();
 487   update_young_list_max_and_target_length();
 488   update_rs_lengths_prediction();
 489   cset_chooser()->clear();
 490 
 491   _bytes_allocated_in_old_since_last_gc = 0;
 492 
 493   record_pause(FullGC, _full_collection_start_sec, end_sec);
 494 }
 495 
 496 void G1Policy::record_collection_pause_start(double start_time_sec) {
 497   // We only need to do this here as the policy will only be applied
 498   // to the GC we're about to start. so, no point is calculating this
 499   // every time we calculate / recalculate the target young length.
 500   update_survivors_policy();
 501 
 502   assert(_g1->used() == _g1->recalculate_used(),
 503          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
 504          _g1->used(), _g1->recalculate_used());
 505 
 506   phase_times()->record_cur_collection_start_sec(start_time_sec);
 507   _pending_cards = _g1->pending_card_num();
 508 
 509   _collection_set->reset_bytes_used_before();
 510   _bytes_copied_during_gc = 0;
 511 
 512   collector_state()->set_last_gc_was_young(false);
 513 
 514   // do that for any other surv rate groups
 515   _short_lived_surv_rate_group->stop_adding_regions();
 516   _survivors_age_table.clear();
 517 
 518   assert( verify_young_ages(), "region age verification" );
 519 }
 520 
 521 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
 522   collector_state()->set_during_marking(true);
 523   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
 524   collector_state()->set_during_initial_mark_pause(false);
 525 }
 526 
 527 void G1Policy::record_concurrent_mark_remark_start() {
 528   _mark_remark_start_sec = os::elapsedTime();
 529   collector_state()->set_during_marking(false);
 530 }
 531 
 532 void G1Policy::record_concurrent_mark_remark_end() {
 533   double end_time_sec = os::elapsedTime();
 534   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
 535   _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
 536   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
 537 
 538   record_pause(Remark, _mark_remark_start_sec, end_time_sec);
 539 }
 540 
 541 void G1Policy::record_concurrent_mark_cleanup_start() {
 542   _mark_cleanup_start_sec = os::elapsedTime();
 543 }
 544 
 545 void G1Policy::record_concurrent_mark_cleanup_completed() {
 546   bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
 547                                                               "skip last young-only gc");
 548   collector_state()->set_last_young_gc(should_continue_with_reclaim);
 549   // We skip the marking phase.
 550   if (!should_continue_with_reclaim) {
 551     abort_time_to_mixed_tracking();
 552   }
 553   collector_state()->set_in_marking_window(false);
 554 }
 555 
 556 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
 557   return phase_times()->average_time_ms(phase);
 558 }
 559 
 560 double G1Policy::young_other_time_ms() const {
 561   return phase_times()->young_cset_choice_time_ms() +
 562          phase_times()->young_free_cset_time_ms();
 563 }
 564 
 565 double G1Policy::non_young_other_time_ms() const {
 566   return phase_times()->non_young_cset_choice_time_ms() +
 567          phase_times()->non_young_free_cset_time_ms();
 568 
 569 }
 570 
 571 double G1Policy::other_time_ms(double pause_time_ms) const {
 572   return pause_time_ms -
 573          average_time_ms(G1GCPhaseTimes::UpdateRS) -
 574          average_time_ms(G1GCPhaseTimes::ScanRS) -
 575          average_time_ms(G1GCPhaseTimes::ObjCopy) -
 576          average_time_ms(G1GCPhaseTimes::Termination);
 577 }
 578 
 579 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
 580   return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
 581 }
 582 
 583 CollectionSetChooser* G1Policy::cset_chooser() const {
 584   return _collection_set->cset_chooser();
 585 }
 586 
 587 bool G1Policy::about_to_start_mixed_phase() const {
 588   return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
 589 }
 590 
 591 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
 592   if (about_to_start_mixed_phase()) {
 593     return false;
 594   }
 595 
 596   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
 597 
 598   size_t cur_used_bytes = _g1->non_young_capacity_bytes();
 599   size_t alloc_byte_size = alloc_word_size * HeapWordSize;
 600   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
 601 
 602   bool result = false;
 603   if (marking_request_bytes > marking_initiating_used_threshold) {
 604     result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
 605     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
 606                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
 607                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
 608   }
 609 
 610   return result;
 611 }
 612 
 613 // Anything below that is considered to be zero
 614 #define MIN_TIMER_GRANULARITY 0.0000001
 615 
 616 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
 617   double end_time_sec = os::elapsedTime();
 618 
 619   size_t cur_used_bytes = _g1->used();
 620   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
 621   bool last_pause_included_initial_mark = false;
 622   bool update_stats = !_g1->evacuation_failed();
 623 
 624   NOT_PRODUCT(_short_lived_surv_rate_group->print());
 625 
 626   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
 627 
 628   last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
 629   if (last_pause_included_initial_mark) {
 630     record_concurrent_mark_init_end(0.0);
 631   } else {
 632     maybe_start_marking();
 633   }
 634 
 635   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
 636   if (app_time_ms < MIN_TIMER_GRANULARITY) {
 637     // This usually happens due to the timer not having the required
 638     // granularity. Some Linuxes are the usual culprits.
 639     // We'll just set it to something (arbitrarily) small.
 640     app_time_ms = 1.0;
 641   }
 642 
 643   if (update_stats) {
 644     // We maintain the invariant that all objects allocated by mutator
 645     // threads will be allocated out of eden regions. So, we can use
 646     // the eden region number allocated since the previous GC to
 647     // calculate the application's allocate rate. The only exception
 648     // to that is humongous objects that are allocated separately. But
 649     // given that humongous object allocations do not really affect
 650     // either the pause's duration nor when the next pause will take
 651     // place we can safely ignore them here.
 652     uint regions_allocated = _collection_set->eden_region_length();
 653     double alloc_rate_ms = (double) regions_allocated / app_time_ms;
 654     _analytics->report_alloc_rate_ms(alloc_rate_ms);
 655 
 656     double interval_ms =
 657       (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
 658     _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
 659     _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
 660   }
 661 
 662   bool new_in_marking_window = collector_state()->in_marking_window();
 663   bool new_in_marking_window_im = false;
 664   if (last_pause_included_initial_mark) {
 665     new_in_marking_window = true;
 666     new_in_marking_window_im = true;
 667   }
 668 
 669   if (collector_state()->last_young_gc()) {
 670     // This is supposed to to be the "last young GC" before we start
 671     // doing mixed GCs. Here we decide whether to start mixed GCs or not.
 672     assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
 673 
 674     if (next_gc_should_be_mixed("start mixed GCs",
 675                                 "do not start mixed GCs")) {
 676       collector_state()->set_gcs_are_young(false);
 677     } else {
 678       // We aborted the mixed GC phase early.
 679       abort_time_to_mixed_tracking();
 680     }
 681 
 682     collector_state()->set_last_young_gc(false);
 683   }
 684 
 685   if (!collector_state()->last_gc_was_young()) {
 686     // This is a mixed GC. Here we decide whether to continue doing
 687     // mixed GCs or not.
 688     if (!next_gc_should_be_mixed("continue mixed GCs",
 689                                  "do not continue mixed GCs")) {
 690       collector_state()->set_gcs_are_young(true);
 691 
 692       maybe_start_marking();
 693     }
 694   }
 695 
 696   _short_lived_surv_rate_group->start_adding_regions();
 697   // Do that for any other surv rate groups
 698 
 699   double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
 700 
 701   if (update_stats) {
 702     double cost_per_card_ms = 0.0;
 703     if (_pending_cards > 0) {
 704       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
 705       _analytics->report_cost_per_card_ms(cost_per_card_ms);
 706     }
 707     _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
 708 
 709     double cost_per_entry_ms = 0.0;
 710     if (cards_scanned > 10) {
 711       cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
 712       _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young());
 713     }
 714 
 715     if (_max_rs_lengths > 0) {
 716       double cards_per_entry_ratio =
 717         (double) cards_scanned / (double) _max_rs_lengths;
 718       _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young());
 719     }
 720 
 721     // This is defensive. For a while _max_rs_lengths could get
 722     // smaller than _recorded_rs_lengths which was causing
 723     // rs_length_diff to get very large and mess up the RSet length
 724     // predictions. The reason was unsafe concurrent updates to the
 725     // _inc_cset_recorded_rs_lengths field which the code below guards
 726     // against (see CR 7118202). This bug has now been fixed (see CR
 727     // 7119027). However, I'm still worried that
 728     // _inc_cset_recorded_rs_lengths might still end up somewhat
 729     // inaccurate. The concurrent refinement thread calculates an
 730     // RSet's length concurrently with other CR threads updating it
 731     // which might cause it to calculate the length incorrectly (if,
 732     // say, it's in mid-coarsening). So I'll leave in the defensive
 733     // conditional below just in case.
 734     size_t rs_length_diff = 0;
 735     size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
 736     if (_max_rs_lengths > recorded_rs_lengths) {
 737       rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
 738     }
 739     _analytics->report_rs_length_diff((double) rs_length_diff);
 740 
 741     size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
 742     size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
 743     double cost_per_byte_ms = 0.0;
 744 
 745     if (copied_bytes > 0) {
 746       cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
 747       _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window());
 748     }
 749 
 750     if (_collection_set->young_region_length() > 0) {
 751       _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
 752                                                         _collection_set->young_region_length());
 753     }
 754 
 755     if (_collection_set->old_region_length() > 0) {
 756       _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
 757                                                             _collection_set->old_region_length());
 758     }
 759 
 760     _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
 761 
 762     _analytics->report_pending_cards((double) _pending_cards);
 763     _analytics->report_rs_lengths((double) _max_rs_lengths);
 764   }
 765 
 766   collector_state()->set_in_marking_window(new_in_marking_window);
 767   collector_state()->set_in_marking_window_im(new_in_marking_window_im);
 768   _free_regions_at_end_of_collection = _g1->num_free_regions();
 769   // IHOP control wants to know the expected young gen length if it were not
 770   // restrained by the heap reserve. Using the actual length would make the
 771   // prediction too small and the limit the young gen every time we get to the
 772   // predicted target occupancy.
 773   size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
 774   update_rs_lengths_prediction();
 775 
 776   update_ihop_prediction(app_time_ms / 1000.0,
 777                          _bytes_allocated_in_old_since_last_gc,
 778                          last_unrestrained_young_length * HeapRegion::GrainBytes);
 779   _bytes_allocated_in_old_since_last_gc = 0;
 780 
 781   _ihop_control->send_trace_event(_g1->gc_tracer_stw());
 782 
 783   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
 784   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
 785 
 786   if (update_rs_time_goal_ms < scan_hcc_time_ms) {
 787     log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
 788                                 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
 789                                 update_rs_time_goal_ms, scan_hcc_time_ms);
 790 
 791     update_rs_time_goal_ms = 0;
 792   } else {
 793     update_rs_time_goal_ms -= scan_hcc_time_ms;
 794   }
 795   _g1->concurrent_g1_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
 796                                       phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
 797                                       update_rs_time_goal_ms);
 798 
 799   cset_chooser()->verify();
 800 }
 801 
 802 G1IHOPControl* G1Policy::create_ihop_control() const {
 803   if (G1UseAdaptiveIHOP) {
 804     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
 805                                      &_predictor,
 806                                      G1ReservePercent,
 807                                      G1HeapWastePercent);
 808   } else {
 809     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
 810   }
 811 }
 812 
 813 void G1Policy::update_ihop_prediction(double mutator_time_s,
 814                                       size_t mutator_alloc_bytes,
 815                                       size_t young_gen_size) {
 816   // Always try to update IHOP prediction. Even evacuation failures give information
 817   // about e.g. whether to start IHOP earlier next time.
 818 
 819   // Avoid using really small application times that might create samples with
 820   // very high or very low values. They may be caused by e.g. back-to-back gcs.
 821   double const min_valid_time = 1e-6;
 822 
 823   bool report = false;
 824 
 825   double marking_to_mixed_time = -1.0;
 826   if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
 827     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
 828     assert(marking_to_mixed_time > 0.0,
 829            "Initial mark to mixed time must be larger than zero but is %.3f",
 830            marking_to_mixed_time);
 831     if (marking_to_mixed_time > min_valid_time) {
 832       _ihop_control->update_marking_length(marking_to_mixed_time);
 833       report = true;
 834     }
 835   }
 836 
 837   // As an approximation for the young gc promotion rates during marking we use
 838   // all of them. In many applications there are only a few if any young gcs during
 839   // marking, which makes any prediction useless. This increases the accuracy of the
 840   // prediction.
 841   if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
 842     _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
 843     report = true;
 844   }
 845 
 846   if (report) {
 847     report_ihop_statistics();
 848   }
 849 }
 850 
 851 void G1Policy::report_ihop_statistics() {
 852   _ihop_control->print();
 853 }
 854 
 855 void G1Policy::print_phases() {
 856   phase_times()->print();
 857 }
 858 
 859 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
 860   TruncatedSeq* seq = surv_rate_group->get_seq(age);
 861   guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
 862   double pred = _predictor.get_new_prediction(seq);
 863   if (pred > 1.0) {
 864     pred = 1.0;
 865   }
 866   return pred;
 867 }
 868 
 869 double G1Policy::predict_yg_surv_rate(int age) const {
 870   return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
 871 }
 872 
 873 double G1Policy::accum_yg_surv_rate_pred(int age) const {
 874   return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
 875 }
 876 
 877 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
 878                                               size_t scanned_cards) const {
 879   return
 880     _analytics->predict_rs_update_time_ms(pending_cards) +
 881     _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) +
 882     _analytics->predict_constant_other_time_ms();
 883 }
 884 
 885 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
 886   size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
 887   size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young());
 888   return predict_base_elapsed_time_ms(pending_cards, card_num);
 889 }
 890 
 891 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
 892   size_t bytes_to_copy;
 893   if (hr->is_marked())
 894     bytes_to_copy = hr->max_live_bytes();
 895   else {
 896     assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
 897     int age = hr->age_in_surv_rate_group();
 898     double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
 899     bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
 900   }
 901   return bytes_to_copy;
 902 }
 903 
 904 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr,
 905                                                 bool for_young_gc) const {
 906   size_t rs_length = hr->rem_set()->occupied();
 907   // Predicting the number of cards is based on which type of GC
 908   // we're predicting for.
 909   size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
 910   size_t bytes_to_copy = predict_bytes_to_copy(hr);
 911 
 912   double region_elapsed_time_ms =
 913     _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) +
 914     _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark());
 915 
 916   // The prediction of the "other" time for this region is based
 917   // upon the region type and NOT the GC type.
 918   if (hr->is_young()) {
 919     region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
 920   } else {
 921     region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
 922   }
 923   return region_elapsed_time_ms;
 924 }
 925 
 926 
 927 void G1Policy::print_yg_surv_rate_info() const {
 928 #ifndef PRODUCT
 929   _short_lived_surv_rate_group->print_surv_rate_summary();
 930   // add this call for any other surv rate groups
 931 #endif // PRODUCT
 932 }
 933 
 934 bool G1Policy::is_young_list_full() const {
 935   uint young_list_length = _g1->young_list()->length();
 936   uint young_list_target_length = _young_list_target_length;
 937   return young_list_length >= young_list_target_length;
 938 }
 939 
 940 bool G1Policy::can_expand_young_list() const {
 941   uint young_list_length = _g1->young_list()->length();
 942   uint young_list_max_length = _young_list_max_length;
 943   return young_list_length < young_list_max_length;
 944 }
 945 
 946 bool G1Policy::adaptive_young_list_length() const {
 947   return _young_gen_sizer.adaptive_young_list_length();
 948 }
 949 
 950 void G1Policy::update_max_gc_locker_expansion() {
 951   uint expansion_region_num = 0;
 952   if (GCLockerEdenExpansionPercent > 0) {
 953     double perc = (double) GCLockerEdenExpansionPercent / 100.0;
 954     double expansion_region_num_d = perc * (double) _young_list_target_length;
 955     // We use ceiling so that if expansion_region_num_d is > 0.0 (but
 956     // less than 1.0) we'll get 1.
 957     expansion_region_num = (uint) ceil(expansion_region_num_d);
 958   } else {
 959     assert(expansion_region_num == 0, "sanity");
 960   }
 961   _young_list_max_length = _young_list_target_length + expansion_region_num;
 962   assert(_young_list_target_length <= _young_list_max_length, "post-condition");
 963 }
 964 
 965 // Calculates survivor space parameters.
 966 void G1Policy::update_survivors_policy() {
 967   double max_survivor_regions_d =
 968                  (double) _young_list_target_length / (double) SurvivorRatio;
 969   // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
 970   // smaller than 1.0) we'll get 1.
 971   _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
 972 
 973   GCPolicyCounters* counters = _g1->collector_policy()->counters();
 974   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
 975         HeapRegion::GrainWords * _max_survivor_regions, counters);
 976 }
 977 
 978 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
 979   // We actually check whether we are marking here and not if we are in a
 980   // reclamation phase. This means that we will schedule a concurrent mark
 981   // even while we are still in the process of reclaiming memory.
 982   bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
 983   if (!during_cycle) {
 984     log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
 985     collector_state()->set_initiate_conc_mark_if_possible(true);
 986     return true;
 987   } else {
 988     log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
 989     return false;
 990   }
 991 }
 992 
 993 void G1Policy::initiate_conc_mark() {
 994   collector_state()->set_during_initial_mark_pause(true);
 995   collector_state()->set_initiate_conc_mark_if_possible(false);
 996 }
 997 
 998 void G1Policy::decide_on_conc_mark_initiation() {
 999   // We are about to decide on whether this pause will be an
1000   // initial-mark pause.
1001 
1002   // First, collector_state()->during_initial_mark_pause() should not be already set. We
1003   // will set it here if we have to. However, it should be cleared by
1004   // the end of the pause (it's only set for the duration of an
1005   // initial-mark pause).
1006   assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1007 
1008   if (collector_state()->initiate_conc_mark_if_possible()) {
1009     // We had noticed on a previous pause that the heap occupancy has
1010     // gone over the initiating threshold and we should start a
1011     // concurrent marking cycle. So we might initiate one.
1012 
1013     if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1014       // Initiate a new initial mark if there is no marking or reclamation going on.
1015       initiate_conc_mark();
1016       log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1017     } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
1018       // Initiate a user requested initial mark. An initial mark must be young only
1019       // GC, so the collector state must be updated to reflect this.
1020       collector_state()->set_gcs_are_young(true);
1021       collector_state()->set_last_young_gc(false);
1022 
1023       abort_time_to_mixed_tracking();
1024       initiate_conc_mark();
1025       log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1026     } else {
1027       // The concurrent marking thread is still finishing up the
1028       // previous cycle. If we start one right now the two cycles
1029       // overlap. In particular, the concurrent marking thread might
1030       // be in the process of clearing the next marking bitmap (which
1031       // we will use for the next cycle if we start one). Starting a
1032       // cycle now will be bad given that parts of the marking
1033       // information might get cleared by the marking thread. And we
1034       // cannot wait for the marking thread to finish the cycle as it
1035       // periodically yields while clearing the next marking bitmap
1036       // and, if it's in a yield point, it's waiting for us to
1037       // finish. So, at this point we will not start a cycle and we'll
1038       // let the concurrent marking thread complete the last one.
1039       log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1040     }
1041   }
1042 }
1043 
1044 void G1Policy::record_concurrent_mark_cleanup_end() {
1045   cset_chooser()->rebuild(_g1->workers(), _g1->num_regions());
1046 
1047   double end_sec = os::elapsedTime();
1048   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1049   _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1050   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1051 
1052   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1053 }
1054 
1055 double G1Policy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1056   // Returns the given amount of reclaimable bytes (that represents
1057   // the amount of reclaimable space still to be collected) as a
1058   // percentage of the current heap capacity.
1059   size_t capacity_bytes = _g1->capacity();
1060   return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1061 }
1062 
1063 void G1Policy::maybe_start_marking() {
1064   if (need_to_start_conc_mark("end of GC")) {
1065     // Note: this might have already been set, if during the last
1066     // pause we decided to start a cycle but at the beginning of
1067     // this pause we decided to postpone it. That's OK.
1068     collector_state()->set_initiate_conc_mark_if_possible(true);
1069   }
1070 }
1071 
1072 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1073   assert(!collector_state()->full_collection(), "must be");
1074   if (collector_state()->during_initial_mark_pause()) {
1075     assert(collector_state()->last_gc_was_young(), "must be");
1076     assert(!collector_state()->last_young_gc(), "must be");
1077     return InitialMarkGC;
1078   } else if (collector_state()->last_young_gc()) {
1079     assert(!collector_state()->during_initial_mark_pause(), "must be");
1080     assert(collector_state()->last_gc_was_young(), "must be");
1081     return LastYoungGC;
1082   } else if (!collector_state()->last_gc_was_young()) {
1083     assert(!collector_state()->during_initial_mark_pause(), "must be");
1084     assert(!collector_state()->last_young_gc(), "must be");
1085     return MixedGC;
1086   } else {
1087     assert(collector_state()->last_gc_was_young(), "must be");
1088     assert(!collector_state()->during_initial_mark_pause(), "must be");
1089     assert(!collector_state()->last_young_gc(), "must be");
1090     return YoungOnlyGC;
1091   }
1092 }
1093 
1094 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1095   // Manage the MMU tracker. For some reason it ignores Full GCs.
1096   if (kind != FullGC) {
1097     _mmu_tracker->add_pause(start, end);
1098   }
1099   // Manage the mutator time tracking from initial mark to first mixed gc.
1100   switch (kind) {
1101     case FullGC:
1102       abort_time_to_mixed_tracking();
1103       break;
1104     case Cleanup:
1105     case Remark:
1106     case YoungOnlyGC:
1107     case LastYoungGC:
1108       _initial_mark_to_mixed.add_pause(end - start);
1109       break;
1110     case InitialMarkGC:
1111       _initial_mark_to_mixed.record_initial_mark_end(end);
1112       break;
1113     case MixedGC:
1114       _initial_mark_to_mixed.record_mixed_gc_start(start);
1115       break;
1116     default:
1117       ShouldNotReachHere();
1118   }
1119 }
1120 
1121 void G1Policy::abort_time_to_mixed_tracking() {
1122   _initial_mark_to_mixed.reset();
1123 }
1124 
1125 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1126                                        const char* false_action_str) const {
1127   if (cset_chooser()->is_empty()) {
1128     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1129     return false;
1130   }
1131 
1132   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1133   size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1134   double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
1135   double threshold = (double) G1HeapWastePercent;
1136   if (reclaimable_perc <= threshold) {
1137     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1138                         false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1139     return false;
1140   }
1141   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1142                       true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1143   return true;
1144 }
1145 
1146 uint G1Policy::calc_min_old_cset_length() const {
1147   // The min old CSet region bound is based on the maximum desired
1148   // number of mixed GCs after a cycle. I.e., even if some old regions
1149   // look expensive, we should add them to the CSet anyway to make
1150   // sure we go through the available old regions in no more than the
1151   // maximum desired number of mixed GCs.
1152   //
1153   // The calculation is based on the number of marked regions we added
1154   // to the CSet chooser in the first place, not how many remain, so
1155   // that the result is the same during all mixed GCs that follow a cycle.
1156 
1157   const size_t region_num = (size_t) cset_chooser()->length();
1158   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1159   size_t result = region_num / gc_num;
1160   // emulate ceiling
1161   if (result * gc_num < region_num) {
1162     result += 1;
1163   }
1164   return (uint) result;
1165 }
1166 
1167 uint G1Policy::calc_max_old_cset_length() const {
1168   // The max old CSet region bound is based on the threshold expressed
1169   // as a percentage of the heap size. I.e., it should bound the
1170   // number of old regions added to the CSet irrespective of how many
1171   // of them are available.
1172 
1173   const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1174   const size_t region_num = g1h->num_regions();
1175   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1176   size_t result = region_num * perc / 100;
1177   // emulate ceiling
1178   if (100 * result < region_num * perc) {
1179     result += 1;
1180   }
1181   return (uint) result;
1182 }
1183 
1184 void G1Policy::finalize_collection_set(double target_pause_time_ms) {
1185   double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
1186   _collection_set->finalize_old_part(time_remaining_ms);
1187 }