1 /*

     2  * Copyright (c) 2001, 2018, 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/concurrentMarkThread.inline.hpp"

    27 #include "gc/g1/g1Analytics.hpp"

    28 #include "gc/g1/g1CollectedHeap.inline.hpp"

    29 #include "gc/g1/g1CollectionSet.hpp"

    30 #include "gc/g1/g1ConcurrentMark.hpp"

    31 #include "gc/g1/g1ConcurrentRefine.hpp"

    32 #include "gc/g1/g1HotCardCache.hpp"

    33 #include "gc/g1/g1IHOPControl.hpp"

    34 #include "gc/g1/g1GCPhaseTimes.hpp"

    35 #include "gc/g1/g1Policy.hpp"

    36 #include "gc/g1/g1SurvivorRegions.hpp"

    37 #include "gc/g1/g1YoungGenSizer.hpp"

    38 #include "gc/g1/heapRegion.inline.hpp"

    39 #include "gc/g1/heapRegionRemSet.hpp"

    40 #include "gc/shared/gcPolicyCounters.hpp"

    41 #include "logging/logStream.hpp"

    42 #include "runtime/arguments.hpp"

    43 #include "runtime/java.hpp"

    44 #include "runtime/mutexLocker.hpp"

    45 #include "utilities/debug.hpp"

    46 #include "utilities/growableArray.hpp"

    47 #include "utilities/pair.hpp"

    48 

    49 G1Policy::G1Policy(STWGCTimer* gc_timer) :

    50   _predictor(G1ConfidencePercent / 100.0),

    51   _analytics(new G1Analytics(&_predictor)),

    52   _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),

    53   _ihop_control(create_ihop_control(&_predictor)),

    54   _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),

    55   _young_list_fixed_length(0),

    56   _short_lived_surv_rate_group(new SurvRateGroup()),

    57   _survivor_surv_rate_group(new SurvRateGroup()),

    58   _reserve_factor((double) G1ReservePercent / 100.0),

    59   _reserve_regions(0),

    60   _rs_lengths_prediction(0),

    61   _bytes_allocated_in_old_since_last_gc(0),

    62   _initial_mark_to_mixed(),

    63   _collection_set(NULL),

    64   _g1(NULL),

    65   _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),

    66   _tenuring_threshold(MaxTenuringThreshold),

    67   _max_survivor_regions(0),

    68   _survivors_age_table(true),

    69   _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC) { }

    70 

    71 G1Policy::~G1Policy() {

    72   delete _ihop_control;

    73 }

    74 

    75 G1CollectorState* G1Policy::collector_state() const { return _g1->collector_state(); }

    76 

    77 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {

    78   _g1 = g1h;

    79   _collection_set = collection_set;

    80 

    81   assert(Heap_lock->owned_by_self(), "Locking discipline.");

    82 

    83   if (!adaptive_young_list_length()) {

    84     _young_list_fixed_length = _young_gen_sizer.min_desired_young_length();

    85   }

    86   _young_gen_sizer.adjust_max_new_size(_g1->max_regions());

    87 

    88   _free_regions_at_end_of_collection = _g1->num_free_regions();

    89 

    90   update_young_list_max_and_target_length();

    91   // We may immediately start allocating regions and placing them on the

    92   // collection set list. Initialize the per-collection set info

    93   _collection_set->start_incremental_building();

    94 }

    95 

    96 void G1Policy::note_gc_start() {

    97   phase_times()->note_gc_start();

    98 }

    99 

   100 class G1YoungLengthPredictor {

   101   const bool _during_cm;

   102   const double _base_time_ms;

   103   const double _base_free_regions;

   104   const double _target_pause_time_ms;

   105   const G1Policy* const _policy;

   106 

   107  public:

   108   G1YoungLengthPredictor(bool during_cm,

   109                          double base_time_ms,

   110                          double base_free_regions,

   111                          double target_pause_time_ms,

   112                          const G1Policy* policy) :

   113     _during_cm(during_cm),

   114     _base_time_ms(base_time_ms),

   115     _base_free_regions(base_free_regions),

   116     _target_pause_time_ms(target_pause_time_ms),

   117     _policy(policy) {}

   118 

   119   bool will_fit(uint young_length) 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     const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1);

   126     const size_t bytes_to_copy =

   127                  (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);

   128     const double copy_time_ms =

   129       _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm);

   130     const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);

   131     const 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     const 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     const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;

   147     const 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 

   159 void G1Policy::record_new_heap_size(uint new_number_of_regions) {

   160   // re-calculate the necessary reserve

   161   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;

   162   // We use ceiling so that if reserve_regions_d is > 0.0 (but

   163   // smaller than 1.0) we'll get 1.

   164   _reserve_regions = (uint) ceil(reserve_regions_d);

   165 

   166   _young_gen_sizer.heap_size_changed(new_number_of_regions);

   167 

   168   _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);

   169 }

   170 

   171 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {

   172   uint desired_min_length = 0;

   173   if (adaptive_young_list_length()) {

   174     if (_analytics->num_alloc_rate_ms() > 3) {

   175       double now_sec = os::elapsedTime();

   176       double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;

   177       double alloc_rate_ms = _analytics->predict_alloc_rate_ms();

   178       desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);

   179     } else {

   180       // otherwise we don't have enough info to make the prediction

   181     }

   182   }

   183   desired_min_length += base_min_length;

   184   // make sure we don't go below any user-defined minimum bound

   185   return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length);

   186 }

   187 

   188 uint G1Policy::calculate_young_list_desired_max_length() const {

   189   // Here, we might want to also take into account any additional

   190   // constraints (i.e., user-defined minimum bound). Currently, we

   191   // effectively don't set this bound.

   192   return _young_gen_sizer.max_desired_young_length();

   193 }

   194 

   195 uint G1Policy::update_young_list_max_and_target_length() {

   196   return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());

   197 }

   198 

   199 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) {

   200   uint unbounded_target_length = update_young_list_target_length(rs_lengths);

   201   update_max_gc_locker_expansion();

   202   return unbounded_target_length;

   203 }

   204 

   205 uint G1Policy::update_young_list_target_length(size_t rs_lengths) {

   206   YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);

   207   _young_list_target_length = young_lengths.first;

   208   return young_lengths.second;

   209 }

   210 

   211 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const {

   212   YoungTargetLengths result;

   213 

   214   // Calculate the absolute and desired min bounds first.

   215 

   216   // This is how many young regions we already have (currently: the survivors).

   217   const uint base_min_length = _g1->survivor_regions_count();

   218   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);

   219   // This is the absolute minimum young length. Ensure that we

   220   // will at least have one eden region available for allocation.

   221   uint absolute_min_length = base_min_length + MAX2(_g1->eden_regions_count(), (uint)1);

   222   // If we shrank the young list target it should not shrink below the current size.

   223   desired_min_length = MAX2(desired_min_length, absolute_min_length);

   224   // Calculate the absolute and desired max bounds.

   225 

   226   uint desired_max_length = calculate_young_list_desired_max_length();

   227 

   228   uint young_list_target_length = 0;

   229   if (adaptive_young_list_length()) {

   230     if (collector_state()->gcs_are_young()) {

   231       young_list_target_length =

   232                         calculate_young_list_target_length(rs_lengths,

   233                                                            base_min_length,

   234                                                            desired_min_length,

   235                                                            desired_max_length);

   236     } else {

   237       // Don't calculate anything and let the code below bound it to

   238       // the desired_min_length, i.e., do the next GC as soon as

   239       // possible to maximize how many old regions we can add to it.

   240     }

   241   } else {

   242     // The user asked for a fixed young gen so we'll fix the young gen

   243     // whether the next GC is young or mixed.

   244     young_list_target_length = _young_list_fixed_length;

   245   }

   246 

   247   result.second = young_list_target_length;

   248 

   249   // We will try our best not to "eat" into the reserve.

   250   uint absolute_max_length = 0;

   251   if (_free_regions_at_end_of_collection > _reserve_regions) {

   252     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;

   253   }

   254   if (desired_max_length > absolute_max_length) {

   255     desired_max_length = absolute_max_length;

   256   }

   257 

   258   // Make sure we don't go over the desired max length, nor under the

   259   // desired min length. In case they clash, desired_min_length wins

   260   // which is why that test is second.

   261   if (young_list_target_length > desired_max_length) {

   262     young_list_target_length = desired_max_length;

   263   }

   264   if (young_list_target_length < desired_min_length) {

   265     young_list_target_length = desired_min_length;

   266   }

   267 

   268   assert(young_list_target_length > base_min_length,

   269          "we should be able to allocate at least one eden region");

   270   assert(young_list_target_length >= absolute_min_length, "post-condition");

   271 

   272   result.first = young_list_target_length;

   273   return result;

   274 }

   275 

   276 uint

   277 G1Policy::calculate_young_list_target_length(size_t rs_lengths,

   278                                                     uint base_min_length,

   279                                                     uint desired_min_length,

   280                                                     uint desired_max_length) const {

   281   assert(adaptive_young_list_length(), "pre-condition");

   282   assert(collector_state()->gcs_are_young(), "only call this for young GCs");

   283 

   284   // In case some edge-condition makes the desired max length too small...

   285   if (desired_max_length <= desired_min_length) {

   286     return desired_min_length;

   287   }

   288 

   289   // We'll adjust min_young_length and max_young_length not to include

   290   // the already allocated young regions (i.e., so they reflect the

   291   // min and max eden regions we'll allocate). The base_min_length

   292   // will be reflected in the predictions by the

   293   // survivor_regions_evac_time prediction.

   294   assert(desired_min_length > base_min_length, "invariant");

   295   uint min_young_length = desired_min_length - base_min_length;

   296   assert(desired_max_length > base_min_length, "invariant");

   297   uint max_young_length = desired_max_length - base_min_length;

   298 

   299   const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;

   300   const double survivor_regions_evac_time = predict_survivor_regions_evac_time();

   301   const size_t pending_cards = _analytics->predict_pending_cards();

   302   const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();

   303   const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);

   304   const double base_time_ms =

   305     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +

   306     survivor_regions_evac_time;

   307   const uint available_free_regions = _free_regions_at_end_of_collection;

   308   const uint base_free_regions =

   309     available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;

   310 

   311   // Here, we will make sure that the shortest young length that

   312   // makes sense fits within the target pause time.

   313 

   314   G1YoungLengthPredictor p(collector_state()->during_concurrent_mark(),

   315                            base_time_ms,

   316                            base_free_regions,

   317                            target_pause_time_ms,

   318                            this);

   319   if (p.will_fit(min_young_length)) {

   320     // The shortest young length will fit into the target pause time;

   321     // we'll now check whether the absolute maximum number of young

   322     // regions will fit in the target pause time. If not, we'll do

   323     // a binary search between min_young_length and max_young_length.

   324     if (p.will_fit(max_young_length)) {

   325       // The maximum young length will fit into the target pause time.

   326       // We are done so set min young length to the maximum length (as

   327       // the result is assumed to be returned in min_young_length).

   328       min_young_length = max_young_length;

   329     } else {

   330       // The maximum possible number of young regions will not fit within

   331       // the target pause time so we'll search for the optimal

   332       // length. The loop invariants are:

   333       //

   334       // min_young_length < max_young_length

   335       // min_young_length is known to fit into the target pause time

   336       // max_young_length is known not to fit into the target pause time

   337       //

   338       // Going into the loop we know the above hold as we've just

   339       // checked them. Every time around the loop we check whether

   340       // the middle value between min_young_length and

   341       // max_young_length fits into the target pause time. If it

   342       // does, it becomes the new min. If it doesn't, it becomes

   343       // the new max. This way we maintain the loop invariants.

   344 

   345       assert(min_young_length < max_young_length, "invariant");

   346       uint diff = (max_young_length - min_young_length) / 2;

   347       while (diff > 0) {

   348         uint young_length = min_young_length + diff;

   349         if (p.will_fit(young_length)) {

   350           min_young_length = young_length;

   351         } else {

   352           max_young_length = young_length;

   353         }

   354         assert(min_young_length <  max_young_length, "invariant");

   355         diff = (max_young_length - min_young_length) / 2;

   356       }

   357       // The results is min_young_length which, according to the

   358       // loop invariants, should fit within the target pause time.

   359 

   360       // These are the post-conditions of the binary search above:

   361       assert(min_young_length < max_young_length,

   362              "otherwise we should have discovered that max_young_length "

   363              "fits into the pause target and not done the binary search");

   364       assert(p.will_fit(min_young_length),

   365              "min_young_length, the result of the binary search, should "

   366              "fit into the pause target");

   367       assert(!p.will_fit(min_young_length + 1),

   368              "min_young_length, the result of the binary search, should be "

   369              "optimal, so no larger length should fit into the pause target");

   370     }

   371   } else {

   372     // Even the minimum length doesn't fit into the pause time

   373     // target, return it as the result nevertheless.

   374   }

   375   return base_min_length + min_young_length;

   376 }

   377 

   378 double G1Policy::predict_survivor_regions_evac_time() const {

   379   double survivor_regions_evac_time = 0.0;

   380   const GrowableArray<HeapRegion*>* survivor_regions = _g1->survivor()->regions();

   381 

   382   for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();

   383        it != survivor_regions->end();

   384        ++it) {

   385     survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->gcs_are_young());

   386   }

   387   return survivor_regions_evac_time;

   388 }

   389 

   390 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {

   391   guarantee( adaptive_young_list_length(), "should not call this otherwise" );

   392 

   393   if (rs_lengths > _rs_lengths_prediction) {

   394     // add 10% to avoid having to recalculate often

   395     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;

   396     update_rs_lengths_prediction(rs_lengths_prediction);

   397 

   398     update_young_list_max_and_target_length(rs_lengths_prediction);

   399   }

   400 }

   401 

   402 void G1Policy::update_rs_lengths_prediction() {

   403   update_rs_lengths_prediction(_analytics->predict_rs_lengths());

   404 }

   405 

   406 void G1Policy::update_rs_lengths_prediction(size_t prediction) {

   407   if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {

   408     _rs_lengths_prediction = prediction;

   409   }

   410 }

   411 

   412 void G1Policy::record_full_collection_start() {

   413   _full_collection_start_sec = os::elapsedTime();

   414   // Release the future to-space so that it is available for compaction into.

   415   collector_state()->set_full_collection(true);

   416 }

   417 

   418 void G1Policy::record_full_collection_end() {

   419   // Consider this like a collection pause for the purposes of allocation

   420   // since last pause.

   421   double end_sec = os::elapsedTime();

   422   double full_gc_time_sec = end_sec - _full_collection_start_sec;

   423   double full_gc_time_ms = full_gc_time_sec * 1000.0;

   424 

   425   _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);

   426 

   427   collector_state()->set_full_collection(false);

   428 

   429   // "Nuke" the heuristics that control the young/mixed GC

   430   // transitions and make sure we start with young GCs after the Full GC.

   431   collector_state()->set_gcs_are_young(true);

   432   collector_state()->set_last_young_gc(false);

   433   collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));

   434   collector_state()->set_during_initial_mark_pause(false);

   435   collector_state()->set_in_marking_window(false);

   436   collector_state()->set_in_marking_window_im(false);

   437 

   438   _short_lived_surv_rate_group->start_adding_regions();

   439   // also call this on any additional surv rate groups

   440 

   441   _free_regions_at_end_of_collection = _g1->num_free_regions();

   442   // Reset survivors SurvRateGroup.

   443   _survivor_surv_rate_group->reset();

   444   update_young_list_max_and_target_length();

   445   update_rs_lengths_prediction();

   446   cset_chooser()->clear();

   447 

   448   _bytes_allocated_in_old_since_last_gc = 0;

   449 

   450   record_pause(FullGC, _full_collection_start_sec, end_sec);

   451 }

   452 

   453 void G1Policy::record_collection_pause_start(double start_time_sec) {

   454   // We only need to do this here as the policy will only be applied

   455   // to the GC we're about to start. so, no point is calculating this

   456   // every time we calculate / recalculate the target young length.

   457   update_survivors_policy();

   458 

   459   assert(_g1->used() == _g1->recalculate_used(),

   460          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,

   461          _g1->used(), _g1->recalculate_used());

   462 

   463   phase_times()->record_cur_collection_start_sec(start_time_sec);

   464   _pending_cards = _g1->pending_card_num();

   465 

   466   _collection_set->reset_bytes_used_before();

   467   _bytes_copied_during_gc = 0;

   468 

   469   collector_state()->set_last_gc_was_young(false);

   470 

   471   // do that for any other surv rate groups

   472   _short_lived_surv_rate_group->stop_adding_regions();

   473   _survivors_age_table.clear();

   474 

   475   assert(_g1->collection_set()->verify_young_ages(), "region age verification failed");

   476 }

   477 

   478 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {

   479   collector_state()->set_during_marking(true);

   480   assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");

   481   collector_state()->set_during_initial_mark_pause(false);

   482 }

   483 

   484 void G1Policy::record_concurrent_mark_remark_start() {

   485   _mark_remark_start_sec = os::elapsedTime();

   486   collector_state()->set_during_marking(false);

   487 }

   488 

   489 void G1Policy::record_concurrent_mark_remark_end() {

   490   double end_time_sec = os::elapsedTime();

   491   double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;

   492   _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);

   493   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);

   494 

   495   record_pause(Remark, _mark_remark_start_sec, end_time_sec);

   496 }

   497 

   498 void G1Policy::record_concurrent_mark_cleanup_start() {

   499   _mark_cleanup_start_sec = os::elapsedTime();

   500 }

   501 

   502 void G1Policy::record_concurrent_mark_cleanup_completed() {

   503   bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",

   504                                                               "skip last young-only gc");

   505   collector_state()->set_last_young_gc(should_continue_with_reclaim);

   506   // We skip the marking phase.

   507   if (!should_continue_with_reclaim) {

   508     abort_time_to_mixed_tracking();

   509   }

   510   collector_state()->set_in_marking_window(false);

   511 }

   512 

   513 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {

   514   return phase_times()->average_time_ms(phase);

   515 }

   516 

   517 double G1Policy::young_other_time_ms() const {

   518   return phase_times()->young_cset_choice_time_ms() +

   519          phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);

   520 }

   521 

   522 double G1Policy::non_young_other_time_ms() const {

   523   return phase_times()->non_young_cset_choice_time_ms() +

   524          phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);

   525 }

   526 

   527 double G1Policy::other_time_ms(double pause_time_ms) const {

   528   return pause_time_ms - phase_times()->cur_collection_par_time_ms();

   529 }

   530 

   531 double G1Policy::constant_other_time_ms(double pause_time_ms) const {

   532   return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms();

   533 }

   534 

   535 CollectionSetChooser* G1Policy::cset_chooser() const {

   536   return _collection_set->cset_chooser();

   537 }

   538 

   539 bool G1Policy::about_to_start_mixed_phase() const {

   540   return _g1->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->last_young_gc();

   541 }

   542 

   543 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {

   544   if (about_to_start_mixed_phase()) {

   545     return false;

   546   }

   547 

   548   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();

   549 

   550   size_t cur_used_bytes = _g1->non_young_capacity_bytes();

   551   size_t alloc_byte_size = alloc_word_size * HeapWordSize;

   552   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;

   553 

   554   bool result = false;

   555   if (marking_request_bytes > marking_initiating_used_threshold) {

   556     result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();

   557     log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",

   558                               result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",

   559                               cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);

   560   }

   561 

   562   return result;

   563 }

   564 

   565 // Anything below that is considered to be zero

   566 #define MIN_TIMER_GRANULARITY 0.0000001

   567 

   568 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {

   569   double end_time_sec = os::elapsedTime();

   570 

   571   size_t cur_used_bytes = _g1->used();

   572   assert(cur_used_bytes == _g1->recalculate_used(), "It should!");

   573   bool last_pause_included_initial_mark = false;

   574   bool update_stats = !_g1->evacuation_failed();

   575 

   576   record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);

   577 

   578   _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;

   579 

   580   last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();

   581   if (last_pause_included_initial_mark) {

   582     record_concurrent_mark_init_end(0.0);

   583   } else {

   584     maybe_start_marking();

   585   }

   586 

   587   double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());

   588   if (app_time_ms < MIN_TIMER_GRANULARITY) {

   589     // This usually happens due to the timer not having the required

   590     // granularity. Some Linuxes are the usual culprits.

   591     // We'll just set it to something (arbitrarily) small.

   592     app_time_ms = 1.0;

   593   }

   594 

   595   if (update_stats) {

   596     // We maintain the invariant that all objects allocated by mutator

   597     // threads will be allocated out of eden regions. So, we can use

   598     // the eden region number allocated since the previous GC to

   599     // calculate the application's allocate rate. The only exception

   600     // to that is humongous objects that are allocated separately. But

   601     // given that humongous object allocations do not really affect

   602     // either the pause's duration nor when the next pause will take

   603     // place we can safely ignore them here.

   604     uint regions_allocated = _collection_set->eden_region_length();

   605     double alloc_rate_ms = (double) regions_allocated / app_time_ms;

   606     _analytics->report_alloc_rate_ms(alloc_rate_ms);

   607 

   608     double interval_ms =

   609       (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;

   610     _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);

   611     _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);

   612   }

   613 

   614   bool new_in_marking_window = collector_state()->in_marking_window();

   615   bool new_in_marking_window_im = false;

   616   if (last_pause_included_initial_mark) {

   617     new_in_marking_window = true;

   618     new_in_marking_window_im = true;

   619   }

   620 

   621   if (collector_state()->last_young_gc()) {

   622     // This is supposed to to be the "last young GC" before we start

   623     // doing mixed GCs. Here we decide whether to start mixed GCs or not.

   624     assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");

   625 

   626     if (next_gc_should_be_mixed("start mixed GCs",

   627                                 "do not start mixed GCs")) {

   628       collector_state()->set_gcs_are_young(false);

   629     } else {

   630       // We aborted the mixed GC phase early.

   631       abort_time_to_mixed_tracking();

   632     }

   633 

   634     collector_state()->set_last_young_gc(false);

   635   }

   636 

   637   if (!collector_state()->last_gc_was_young()) {

   638     // This is a mixed GC. Here we decide whether to continue doing

   639     // mixed GCs or not.

   640     if (!next_gc_should_be_mixed("continue mixed GCs",

   641                                  "do not continue mixed GCs")) {

   642       collector_state()->set_gcs_are_young(true);

   643 

   644       maybe_start_marking();

   645     }

   646   }

   647 

   648   _short_lived_surv_rate_group->start_adding_regions();

   649   // Do that for any other surv rate groups

   650 

   651   double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;

   652 

   653   if (update_stats) {

   654     double cost_per_card_ms = 0.0;

   655     if (_pending_cards > 0) {

   656       cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;

   657       _analytics->report_cost_per_card_ms(cost_per_card_ms);

   658     }

   659     _analytics->report_cost_scan_hcc(scan_hcc_time_ms);

   660 

   661     double cost_per_entry_ms = 0.0;

   662     if (cards_scanned > 10) {

   663       cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;

   664       _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young());

   665     }

   666 

   667     if (_max_rs_lengths > 0) {

   668       double cards_per_entry_ratio =

   669         (double) cards_scanned / (double) _max_rs_lengths;

   670       _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young());

   671     }

   672 

   673     // This is defensive. For a while _max_rs_lengths could get

   674     // smaller than _recorded_rs_lengths which was causing

   675     // rs_length_diff to get very large and mess up the RSet length

   676     // predictions. The reason was unsafe concurrent updates to the

   677     // _inc_cset_recorded_rs_lengths field which the code below guards

   678     // against (see CR 7118202). This bug has now been fixed (see CR

   679     // 7119027). However, I'm still worried that

   680     // _inc_cset_recorded_rs_lengths might still end up somewhat

   681     // inaccurate. The concurrent refinement thread calculates an

   682     // RSet's length concurrently with other CR threads updating it

   683     // which might cause it to calculate the length incorrectly (if,

   684     // say, it's in mid-coarsening). So I'll leave in the defensive

   685     // conditional below just in case.

   686     size_t rs_length_diff = 0;

   687     size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();

   688     if (_max_rs_lengths > recorded_rs_lengths) {

   689       rs_length_diff = _max_rs_lengths - recorded_rs_lengths;

   690     }

   691     _analytics->report_rs_length_diff((double) rs_length_diff);

   692 

   693     size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;

   694     size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;

   695     double cost_per_byte_ms = 0.0;

   696 

   697     if (copied_bytes > 0) {

   698       cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;

   699       _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window());

   700     }

   701 

   702     if (_collection_set->young_region_length() > 0) {

   703       _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /

   704                                                         _collection_set->young_region_length());

   705     }

   706 

   707     if (_collection_set->old_region_length() > 0) {

   708       _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /

   709                                                             _collection_set->old_region_length());

   710     }

   711 

   712     _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));

   713 

   714     _analytics->report_pending_cards((double) _pending_cards);

   715     _analytics->report_rs_lengths((double) _max_rs_lengths);

   716   }

   717 

   718   collector_state()->set_in_marking_window(new_in_marking_window);

   719   collector_state()->set_in_marking_window_im(new_in_marking_window_im);

   720   _free_regions_at_end_of_collection = _g1->num_free_regions();

   721   // IHOP control wants to know the expected young gen length if it were not

   722   // restrained by the heap reserve. Using the actual length would make the

   723   // prediction too small and the limit the young gen every time we get to the

   724   // predicted target occupancy.

   725   size_t last_unrestrained_young_length = update_young_list_max_and_target_length();

   726   update_rs_lengths_prediction();

   727 

   728   update_ihop_prediction(app_time_ms / 1000.0,

   729                          _bytes_allocated_in_old_since_last_gc,

   730                          last_unrestrained_young_length * HeapRegion::GrainBytes);

   731   _bytes_allocated_in_old_since_last_gc = 0;

   732 

   733   _ihop_control->send_trace_event(_g1->gc_tracer_stw());

   734 

   735   // Note that _mmu_tracker->max_gc_time() returns the time in seconds.

   736   double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;

   737 

   738   if (update_rs_time_goal_ms < scan_hcc_time_ms) {

   739     log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."

   740                                 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",

   741                                 update_rs_time_goal_ms, scan_hcc_time_ms);

   742 

   743     update_rs_time_goal_ms = 0;

   744   } else {

   745     update_rs_time_goal_ms -= scan_hcc_time_ms;

   746   }

   747   _g1->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,

   748                                       phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),

   749                                       update_rs_time_goal_ms);

   750 

   751   cset_chooser()->verify();

   752 }

   753 

   754 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){

   755   if (G1UseAdaptiveIHOP) {

   756     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,

   757                                      predictor,

   758                                      G1ReservePercent,

   759                                      G1HeapWastePercent);

   760   } else {

   761     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);

   762   }

   763 }

   764 

   765 void G1Policy::update_ihop_prediction(double mutator_time_s,

   766                                       size_t mutator_alloc_bytes,

   767                                       size_t young_gen_size) {

   768   // Always try to update IHOP prediction. Even evacuation failures give information

   769   // about e.g. whether to start IHOP earlier next time.

   770 

   771   // Avoid using really small application times that might create samples with

   772   // very high or very low values. They may be caused by e.g. back-to-back gcs.

   773   double const min_valid_time = 1e-6;

   774 

   775   bool report = false;

   776 

   777   double marking_to_mixed_time = -1.0;

   778   if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {

   779     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();

   780     assert(marking_to_mixed_time > 0.0,

   781            "Initial mark to mixed time must be larger than zero but is %.3f",

   782            marking_to_mixed_time);

   783     if (marking_to_mixed_time > min_valid_time) {

   784       _ihop_control->update_marking_length(marking_to_mixed_time);

   785       report = true;

   786     }

   787   }

   788 

   789   // As an approximation for the young gc promotion rates during marking we use

   790   // all of them. In many applications there are only a few if any young gcs during

   791   // marking, which makes any prediction useless. This increases the accuracy of the

   792   // prediction.

   793   if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {

   794     _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);

   795     report = true;

   796   }

   797 

   798   if (report) {

   799     report_ihop_statistics();

   800   }

   801 }

   802 

   803 void G1Policy::report_ihop_statistics() {

   804   _ihop_control->print();

   805 }

   806 

   807 void G1Policy::print_phases() {

   808   phase_times()->print();

   809 }

   810 

   811 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {

   812   TruncatedSeq* seq = surv_rate_group->get_seq(age);

   813   guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);

   814   double pred = _predictor.get_new_prediction(seq);

   815   if (pred > 1.0) {

   816     pred = 1.0;

   817   }

   818   return pred;

   819 }

   820 

   821 double G1Policy::accum_yg_surv_rate_pred(int age) const {

   822   return _short_lived_surv_rate_group->accum_surv_rate_pred(age);

   823 }

   824 

   825 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,

   826                                               size_t scanned_cards) const {

   827   return

   828     _analytics->predict_rs_update_time_ms(pending_cards) +

   829     _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) +

   830     _analytics->predict_constant_other_time_ms();

   831 }

   832 

   833 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {

   834   size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();

   835   size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young());

   836   return predict_base_elapsed_time_ms(pending_cards, card_num);

   837 }

   838 

   839 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {

   840   size_t bytes_to_copy;

   841   if (hr->is_marked())

   842     bytes_to_copy = hr->max_live_bytes();

   843   else {

   844     assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");

   845     int age = hr->age_in_surv_rate_group();

   846     double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());

   847     bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);

   848   }

   849   return bytes_to_copy;

   850 }

   851 

   852 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr,

   853                                                 bool for_young_gc) const {

   854   size_t rs_length = hr->rem_set()->occupied();

   855   // Predicting the number of cards is based on which type of GC

   856   // we're predicting for.

   857   size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);

   858   size_t bytes_to_copy = predict_bytes_to_copy(hr);

   859 

   860   double region_elapsed_time_ms =

   861     _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) +

   862     _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark());

   863 

   864   // The prediction of the "other" time for this region is based

   865   // upon the region type and NOT the GC type.

   866   if (hr->is_young()) {

   867     region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);

   868   } else {

   869     region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);

   870   }

   871   return region_elapsed_time_ms;

   872 }

   873 

   874 bool G1Policy::should_allocate_mutator_region() const {

   875   uint young_list_length = _g1->young_regions_count();

   876   uint young_list_target_length = _young_list_target_length;

   877   return young_list_length < young_list_target_length;

   878 }

   879 

   880 bool G1Policy::can_expand_young_list() const {

   881   uint young_list_length = _g1->young_regions_count();

   882   uint young_list_max_length = _young_list_max_length;

   883   return young_list_length < young_list_max_length;

   884 }

   885 

   886 bool G1Policy::adaptive_young_list_length() const {

   887   return _young_gen_sizer.adaptive_young_list_length();

   888 }

   889 

   890 size_t G1Policy::desired_survivor_size() const {

   891   size_t const survivor_capacity = HeapRegion::GrainWords * _max_survivor_regions;

   892   return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);

   893 }

   894 

   895 void G1Policy::print_age_table() {

   896   _survivors_age_table.print_age_table(_tenuring_threshold);

   897 }

   898 

   899 void G1Policy::update_max_gc_locker_expansion() {

   900   uint expansion_region_num = 0;

   901   if (GCLockerEdenExpansionPercent > 0) {

   902     double perc = (double) GCLockerEdenExpansionPercent / 100.0;

   903     double expansion_region_num_d = perc * (double) _young_list_target_length;

   904     // We use ceiling so that if expansion_region_num_d is > 0.0 (but

   905     // less than 1.0) we'll get 1.

   906     expansion_region_num = (uint) ceil(expansion_region_num_d);

   907   } else {

   908     assert(expansion_region_num == 0, "sanity");

   909   }

   910   _young_list_max_length = _young_list_target_length + expansion_region_num;

   911   assert(_young_list_target_length <= _young_list_max_length, "post-condition");

   912 }

   913 

   914 // Calculates survivor space parameters.

   915 void G1Policy::update_survivors_policy() {

   916   double max_survivor_regions_d =

   917                  (double) _young_list_target_length / (double) SurvivorRatio;

   918   // We use ceiling so that if max_survivor_regions_d is > 0.0 (but

   919   // smaller than 1.0) we'll get 1.

   920   _max_survivor_regions = (uint) ceil(max_survivor_regions_d);

   921 

   922   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(desired_survivor_size());

   923   if (UsePerfData) {

   924     _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);

   925     _policy_counters->desired_survivor_size()->set_value(desired_survivor_size() * oopSize);

   926   }

   927 }

   928 

   929 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {

   930   // We actually check whether we are marking here and not if we are in a

   931   // reclamation phase. This means that we will schedule a concurrent mark

   932   // even while we are still in the process of reclaiming memory.

   933   bool during_cycle = _g1->concurrent_mark()->cm_thread()->during_cycle();

   934   if (!during_cycle) {

   935     log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));

   936     collector_state()->set_initiate_conc_mark_if_possible(true);

   937     return true;

   938   } else {

   939     log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));

   940     return false;

   941   }

   942 }

   943 

   944 void G1Policy::initiate_conc_mark() {

   945   collector_state()->set_during_initial_mark_pause(true);

   946   collector_state()->set_initiate_conc_mark_if_possible(false);

   947 }

   948 

   949 void G1Policy::decide_on_conc_mark_initiation() {

   950   // We are about to decide on whether this pause will be an

   951   // initial-mark pause.

   952 

   953   // First, collector_state()->during_initial_mark_pause() should not be already set. We

   954   // will set it here if we have to. However, it should be cleared by

   955   // the end of the pause (it's only set for the duration of an

   956   // initial-mark pause).

   957   assert(!collector_state()->during_initial_mark_pause(), "pre-condition");

   958 

   959   if (collector_state()->initiate_conc_mark_if_possible()) {

   960     // We had noticed on a previous pause that the heap occupancy has

   961     // gone over the initiating threshold and we should start a

   962     // concurrent marking cycle. So we might initiate one.

   963 

   964     if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {

   965       // Initiate a new initial mark if there is no marking or reclamation going on.

   966       initiate_conc_mark();

   967       log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");

   968     } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {

   969       // Initiate a user requested initial mark. An initial mark must be young only

   970       // GC, so the collector state must be updated to reflect this.

   971       collector_state()->set_gcs_are_young(true);

   972       collector_state()->set_last_young_gc(false);

   973 

   974       abort_time_to_mixed_tracking();

   975       initiate_conc_mark();

   976       log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");

   977     } else {

   978       // The concurrent marking thread is still finishing up the

   979       // previous cycle. If we start one right now the two cycles

   980       // overlap. In particular, the concurrent marking thread might

   981       // be in the process of clearing the next marking bitmap (which

   982       // we will use for the next cycle if we start one). Starting a

   983       // cycle now will be bad given that parts of the marking

   984       // information might get cleared by the marking thread. And we

   985       // cannot wait for the marking thread to finish the cycle as it

   986       // periodically yields while clearing the next marking bitmap

   987       // and, if it's in a yield point, it's waiting for us to

   988       // finish. So, at this point we will not start a cycle and we'll

   989       // let the concurrent marking thread complete the last one.

   990       log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");

   991     }

   992   }

   993 }

   994 

   995 void G1Policy::record_concurrent_mark_cleanup_end() {

   996   cset_chooser()->rebuild(_g1->workers(), _g1->num_regions());

   997 

   998   double end_sec = os::elapsedTime();

   999   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;

  1000   _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);

  1001   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);

  1002 

  1003   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);

  1004 }

  1005 

  1006 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {

  1007   return percent_of(reclaimable_bytes, _g1->capacity());

  1008 }

  1009 

  1010 void G1Policy::maybe_start_marking() {

  1011   if (need_to_start_conc_mark("end of GC")) {

  1012     // Note: this might have already been set, if during the last

  1013     // pause we decided to start a cycle but at the beginning of

  1014     // this pause we decided to postpone it. That's OK.

  1015     collector_state()->set_initiate_conc_mark_if_possible(true);

  1016   }

  1017 }

  1018 

  1019 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {

  1020   assert(!collector_state()->full_collection(), "must be");

  1021   if (collector_state()->during_initial_mark_pause()) {

  1022     assert(collector_state()->last_gc_was_young(), "must be");

  1023     assert(!collector_state()->last_young_gc(), "must be");

  1024     return InitialMarkGC;

  1025   } else if (collector_state()->last_young_gc()) {

  1026     assert(!collector_state()->during_initial_mark_pause(), "must be");

  1027     assert(collector_state()->last_gc_was_young(), "must be");

  1028     return LastYoungGC;

  1029   } else if (!collector_state()->last_gc_was_young()) {

  1030     assert(!collector_state()->during_initial_mark_pause(), "must be");

  1031     assert(!collector_state()->last_young_gc(), "must be");

  1032     return MixedGC;

  1033   } else {

  1034     assert(collector_state()->last_gc_was_young(), "must be");

  1035     assert(!collector_state()->during_initial_mark_pause(), "must be");

  1036     assert(!collector_state()->last_young_gc(), "must be");

  1037     return YoungOnlyGC;

  1038   }

  1039 }

  1040 

  1041 void G1Policy::record_pause(PauseKind kind, double start, double end) {

  1042   // Manage the MMU tracker. For some reason it ignores Full GCs.

  1043   if (kind != FullGC) {

  1044     _mmu_tracker->add_pause(start, end);

  1045   }

  1046   // Manage the mutator time tracking from initial mark to first mixed gc.

  1047   switch (kind) {

  1048     case FullGC:

  1049       abort_time_to_mixed_tracking();

  1050       break;

  1051     case Cleanup:

  1052     case Remark:

  1053     case YoungOnlyGC:

  1054     case LastYoungGC:

  1055       _initial_mark_to_mixed.add_pause(end - start);

  1056       break;

  1057     case InitialMarkGC:

  1058       _initial_mark_to_mixed.record_initial_mark_end(end);

  1059       break;

  1060     case MixedGC:

  1061       _initial_mark_to_mixed.record_mixed_gc_start(start);

  1062       break;

  1063     default:

  1064       ShouldNotReachHere();

  1065   }

  1066 }

  1067 

  1068 void G1Policy::abort_time_to_mixed_tracking() {

  1069   _initial_mark_to_mixed.reset();

  1070 }

  1071 

  1072 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,

  1073                                        const char* false_action_str) const {

  1074   if (cset_chooser()->is_empty()) {

  1075     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);

  1076     return false;

  1077   }

  1078 

  1079   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?

  1080   size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();

  1081   double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);

  1082   double threshold = (double) G1HeapWastePercent;

  1083   if (reclaimable_percent <= threshold) {

  1084     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,

  1085                         false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);

  1086     return false;

  1087   }

  1088   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,

  1089                       true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);

  1090   return true;

  1091 }

  1092 

  1093 uint G1Policy::calc_min_old_cset_length() const {

  1094   // The min old CSet region bound is based on the maximum desired

  1095   // number of mixed GCs after a cycle. I.e., even if some old regions

  1096   // look expensive, we should add them to the CSet anyway to make

  1097   // sure we go through the available old regions in no more than the

  1098   // maximum desired number of mixed GCs.

  1099   //

  1100   // The calculation is based on the number of marked regions we added

  1101   // to the CSet chooser in the first place, not how many remain, so

  1102   // that the result is the same during all mixed GCs that follow a cycle.

  1103 

  1104   const size_t region_num = (size_t) cset_chooser()->length();

  1105   const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);

  1106   size_t result = region_num / gc_num;

  1107   // emulate ceiling

  1108   if (result * gc_num < region_num) {

  1109     result += 1;

  1110   }

  1111   return (uint) result;

  1112 }

  1113 

  1114 uint G1Policy::calc_max_old_cset_length() const {

  1115   // The max old CSet region bound is based on the threshold expressed

  1116   // as a percentage of the heap size. I.e., it should bound the

  1117   // number of old regions added to the CSet irrespective of how many

  1118   // of them are available.

  1119 

  1120   const G1CollectedHeap* g1h = G1CollectedHeap::heap();

  1121   const size_t region_num = g1h->num_regions();

  1122   const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;

  1123   size_t result = region_num * perc / 100;

  1124   // emulate ceiling

  1125   if (100 * result < region_num * perc) {

  1126     result += 1;

  1127   }

  1128   return (uint) result;

  1129 }

  1130 

  1131 void G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {

  1132   double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor);

  1133   _collection_set->finalize_old_part(time_remaining_ms);

  1134 }