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

    49   _ihop_control(create_ihop_control(&_predictor)),

    50   _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 3)),

    51   _young_list_fixed_length(0),

    52   _short_lived_surv_rate_group(new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary)),

    53   _survivor_surv_rate_group(new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary)),

    54   _reserve_factor((double) G1ReservePercent / 100.0),

    55   _reserve_regions(0),

    56   _rs_lengths_prediction(0),

    57   _bytes_allocated_in_old_since_last_gc(0),

    58   _initial_mark_to_mixed(),

    59   _collection_set(NULL),

    60   _g1(NULL),

    61   _phase_times(new G1GCPhaseTimes(ParallelGCThreads)),

    62   _tenuring_threshold(MaxTenuringThreshold),

    63   _max_survivor_regions(0),

    64   _survivors_age_table(true) { }

    65 

    66 G1Policy::~G1Policy() {

    67   delete _ihop_control;

    68 }

    69 

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

    71 

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

    73   _g1 = g1h;

    74   _collection_set = collection_set;

    75 

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

    77 

    78   if (!adaptive_young_list_length()) {

    79     _young_list_fixed_length = _young_gen_sizer.min_desired_young_length();

    80   }

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

    82 

    83   _free_regions_at_end_of_collection = _g1->num_free_regions();

    84 

    85   update_young_list_max_and_target_length();

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

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

    88   _collection_set->start_incremental_building();

    89 }

    90 

    91 void G1Policy::note_gc_start() {

    92   phase_times()->note_gc_start();

    93 }

    94 

    95 bool G1Policy::predict_will_fit(uint young_length,

    96                                 double base_time_ms,

    97                                 uint base_free_regions,

    98                                 double target_pause_time_ms) const {

    99   if (young_length >= base_free_regions) {

   100     // end condition 1: not enough space for the young regions

   101     return false;

   102   }

   103 

   104   double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);

   105   size_t bytes_to_copy =

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

   107   double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy,

   108                                                                 collector_state()->during_concurrent_mark());

   109   double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length);

   110   double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;

   111   if (pause_time_ms > target_pause_time_ms) {

   112     // end condition 2: prediction is over the target pause time

   113     return false;

   114   }

   115 

   116   size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;

   117 

   118   // When copying, we will likely need more bytes free than is live in the region.

   119   // Add some safety margin to factor in the confidence of our guess, and the

   120   // natural expected waste.

   121   // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty

   122   // of the calculation: the lower the confidence, the more headroom.

   123   // (100 + TargetPLABWastePct) represents the increase in expected bytes during

   124   // copying due to anticipated waste in the PLABs.

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

   126   size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);

   127 

   128   if (expected_bytes_to_copy > free_bytes) {

   129     // end condition 3: out-of-space

   130     return false;

   131   }

   132 

   133   // success!

   134   return true;

   135 }

   136 

   137 void G1Policy::record_new_heap_size(uint new_number_of_regions) {

   138   // re-calculate the necessary reserve

   139   double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;

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

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

   142   _reserve_regions = (uint) ceil(reserve_regions_d);

   143 

   144   _young_gen_sizer.heap_size_changed(new_number_of_regions);

   145 

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

   147 }

   148 

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

   150   uint desired_min_length = 0;

   151   if (adaptive_young_list_length()) {

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

   153       double now_sec = os::elapsedTime();

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

   155       double alloc_rate_ms = _analytics->predict_alloc_rate_ms();

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

   157     } else {

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

   159     }

   160   }

   161   desired_min_length += base_min_length;

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

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

   164 }

   165 

   166 uint G1Policy::calculate_young_list_desired_max_length() const {

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

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

   169   // effectively don't set this bound.

   170   return _young_gen_sizer.max_desired_young_length();

   171 }

   172 

   173 uint G1Policy::update_young_list_max_and_target_length() {

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

   175 }

   176 

   177 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) {

   178   uint unbounded_target_length = update_young_list_target_length(rs_lengths);

   179   update_max_gc_locker_expansion();

   180   return unbounded_target_length;

   181 }

   182 

   183 uint G1Policy::update_young_list_target_length(size_t rs_lengths) {

   184   YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);

   185   _young_list_target_length = young_lengths.first;

   186   return young_lengths.second;

   187 }

   188 

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

   190   YoungTargetLengths result;

   191 

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

   193 

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

   195   const uint base_min_length = _g1->young_list()->survivor_length();

   196   uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);

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

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

   199   uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);

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

   201   desired_min_length = MAX2(desired_min_length, absolute_min_length);

   202   // Calculate the absolute and desired max bounds.

   203 

   204   uint desired_max_length = calculate_young_list_desired_max_length();

   205 

   206   uint young_list_target_length = 0;

   207   if (adaptive_young_list_length()) {

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

   209       young_list_target_length =

   210                         calculate_young_list_target_length(rs_lengths,

   211                                                            base_min_length,

   212                                                            desired_min_length,

   213                                                            desired_max_length);

   214     } else {

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

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

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

   218     }

   219   } else {

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

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

   222     young_list_target_length = _young_list_fixed_length;

   223   }

   224 

   225   result.second = young_list_target_length;

   226 

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

   228   uint absolute_max_length = 0;

   229   if (_free_regions_at_end_of_collection > _reserve_regions) {

   230     absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;

   231   }

   232   if (desired_max_length > absolute_max_length) {

   233     desired_max_length = absolute_max_length;

   234   }

   235 

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

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

   238   // which is why that test is second.

   239   if (young_list_target_length > desired_max_length) {

   240     young_list_target_length = desired_max_length;

   241   }

   242   if (young_list_target_length < desired_min_length) {

   243     young_list_target_length = desired_min_length;

   244   }

   245 

   246   assert(young_list_target_length > base_min_length,

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

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

   249 

   250   result.first = young_list_target_length;

   251   return result;

   252 }

   253 

   254 uint

   255 G1Policy::calculate_young_list_target_length(size_t rs_lengths,

   256                                              uint base_min_length,

   257                                              uint desired_min_length,

   258                                              uint desired_max_length) const {

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

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

   261 

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

   263   if (desired_max_length <= desired_min_length) {

   264     return desired_min_length;

   265   }

   266 

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

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

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

   270   // will be reflected in the predictions by the

   271   // survivor_regions_evac_time prediction.

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

   273   uint min_young_length = desired_min_length - base_min_length;

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

   275   uint max_young_length = desired_max_length - base_min_length;

   276 

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

   278   double survivor_regions_evac_time = predict_survivor_regions_evac_time();

   279   size_t pending_cards = _analytics->predict_pending_cards();

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

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

   282   double base_time_ms =

   283     predict_base_elapsed_time_ms(pending_cards, scanned_cards) +

   284     survivor_regions_evac_time;

   285   uint available_free_regions = _free_regions_at_end_of_collection;

   286   uint base_free_regions = 0;

   287   if (available_free_regions > _reserve_regions) {

   288     base_free_regions = available_free_regions - _reserve_regions;

   289   }

   290 

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

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

   293 

   294   if (predict_will_fit(min_young_length, base_time_ms,

   295                        base_free_regions, target_pause_time_ms)) {

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

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

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

   299     // a binary search between min_young_length and max_young_length.

   300     if (predict_will_fit(max_young_length, base_time_ms,

   301                          base_free_regions, target_pause_time_ms)) {

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

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

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

   305       min_young_length = max_young_length;

   306     } else {

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

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

   309       // length. The loop invariants are:

   310       //

   311       // min_young_length < max_young_length

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

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

   314       //

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

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

   317       // the middle value between min_young_length and

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

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

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

   321 

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

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

   324       while (diff > 0) {

   325         uint young_length = min_young_length + diff;

   326         if (predict_will_fit(young_length, base_time_ms,

   327                              base_free_regions, target_pause_time_ms)) {

   328           min_young_length = young_length;

   329         } else {

   330           max_young_length = young_length;

   331         }

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

   333         diff = (max_young_length - min_young_length) / 2;

   334       }

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

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

   337 

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

   339       assert(min_young_length < max_young_length,

   340              "otherwise we should have discovered that max_young_length "

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

   342       assert(predict_will_fit(min_young_length, base_time_ms,

   343                               base_free_regions, target_pause_time_ms),

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

   345              "fit into the pause target");

   346       assert(!predict_will_fit(min_young_length + 1, base_time_ms,

   347                                base_free_regions, target_pause_time_ms),

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

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

   350     }

   351   } else {

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

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

   354   }

   355   return base_min_length + min_young_length;

   356 }

   357 

   358 double G1Policy::predict_survivor_regions_evac_time() const {

   359   double survivor_regions_evac_time = 0.0;

   360   for (HeapRegion * r = _g1->young_list()->first_survivor_region();

   361        r != NULL && r != _g1->young_list()->last_survivor_region()->get_next_young_region();

   362        r = r->get_next_young_region()) {

   363     survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());

   364   }

   365   return survivor_regions_evac_time;

   366 }

   367 

   368 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {

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

   370 

   371   if (rs_lengths > _rs_lengths_prediction) {

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

   373     size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;

   374     update_rs_lengths_prediction(rs_lengths_prediction);

   375 

   376     update_young_list_max_and_target_length(rs_lengths_prediction);

   377   }

   378 }

   379 

   380 void G1Policy::update_rs_lengths_prediction() {

   381   update_rs_lengths_prediction(_analytics->predict_rs_lengths());

   382 }

   383 

   384 void G1Policy::update_rs_lengths_prediction(size_t prediction) {

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

   386     _rs_lengths_prediction = prediction;

   387   }

   388 }

   389 

   390 #ifndef PRODUCT

   391 bool G1Policy::verify_young_ages() {

   392   HeapRegion* head = _g1->young_list()->first_region();

   393   return

   394     verify_young_ages(head, _short_lived_surv_rate_group);

   395   // also call verify_young_ages on any additional surv rate groups

   396 }

   397 

   398 bool G1Policy::verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group) {

   399   guarantee( surv_rate_group != NULL, "pre-condition" );

   400 

   401   const char* name = surv_rate_group->name();

   402   bool ret = true;

   403   int prev_age = -1;

   404 

   405   for (HeapRegion* curr = head;

   406        curr != NULL;

   407        curr = curr->get_next_young_region()) {

   408     SurvRateGroup* group = curr->surv_rate_group();

   409     if (group == NULL && !curr->is_survivor()) {

   410       log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);

   411       ret = false;

   412     }

   413 

   414     if (surv_rate_group == group) {

   415       int age = curr->age_in_surv_rate_group();

   416 

   417       if (age < 0) {

   418         log_error(gc, verify)("## %s: encountered negative age", name);

   419         ret = false;

   420       }

   421 

   422       if (age <= prev_age) {

   423         log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);

   424         ret = false;

   425       }

   426       prev_age = age;

   427     }

   428   }

   429 

   430   return ret;

   431 }

   432 #endif // PRODUCT

   433 

   434 void G1Policy::record_full_collection_start() {

   435   _full_collection_start_sec = os::elapsedTime();

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

   437   collector_state()->set_full_collection(true);

   438 }

   439 

   440 void G1Policy::record_full_collection_end() {

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

   442   // since last pause.

   443   double end_sec = os::elapsedTime();

   444   double full_gc_time_sec = end_sec - _full_collection_start_sec;

   445   double full_gc_time_ms = full_gc_time_sec * 1000.0;

   446 

   447   _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);

   448 

   449   collector_state()->set_full_collection(false);

   450 

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

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

   453   collector_state()->set_gcs_are_young(true);

   454   collector_state()->set_last_young_gc(false);

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

   456   collector_state()->set_during_initial_mark_pause(false);

   457   collector_state()->set_in_marking_window(false);

   458   collector_state()->set_in_marking_window_im(false);

   459 

   460   _short_lived_surv_rate_group->start_adding_regions();

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

   462 

   463   _free_regions_at_end_of_collection = _g1->num_free_regions();

   464   // Reset survivors SurvRateGroup.

   465   _survivor_surv_rate_group->reset();

   466   update_young_list_max_and_target_length();

   467   update_rs_lengths_prediction();

   468   cset_chooser()->clear();

   469 

   470   _bytes_allocated_in_old_since_last_gc = 0;

   471 

   472   record_pause(FullGC, _full_collection_start_sec, end_sec);

   473 }

   474 

   475 void G1Policy::record_collection_pause_start(double start_time_sec) {

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

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

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

   479   update_survivors_policy();

   480 

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

   482          "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,

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

   484 

   485   phase_times()->record_cur_collection_start_sec(start_time_sec);

   486   _pending_cards = _g1->pending_card_num();

   487 

   488   _collection_set->reset_bytes_used_before();

   489   _bytes_copied_during_gc = 0;

   490 

   491   collector_state()->set_last_gc_was_young(false);

   492 

   493   // do that for any other surv rate groups

   494   _short_lived_surv_rate_group->stop_adding_regions();

   495   _survivors_age_table.clear();

   496 

   497   assert( verify_young_ages(), "region age verification" );

   498 }

   499 

   500 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {

   501   collector_state()->set_during_marking(true);

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

   503   collector_state()->set_during_initial_mark_pause(false);

   504 }

   505 

   506 void G1Policy::record_concurrent_mark_remark_start() {

   507   _mark_remark_start_sec = os::elapsedTime();

   508   collector_state()->set_during_marking(false);

   509 }

   510 

   511 void G1Policy::record_concurrent_mark_remark_end() {

   512   double end_time_sec = os::elapsedTime();

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

   514   _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);

   515   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);

   516 

   517   record_pause(Remark, _mark_remark_start_sec, end_time_sec);

   518 }

   519 

   520 void G1Policy::record_concurrent_mark_cleanup_start() {

   521   _mark_cleanup_start_sec = os::elapsedTime();

   522 }

   523 

   524 void G1Policy::record_concurrent_mark_cleanup_completed() {

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

   526                                                               "skip last young-only gc");

   527   collector_state()->set_last_young_gc(should_continue_with_reclaim);

   528   // We skip the marking phase.

   529   if (!should_continue_with_reclaim) {

   530     abort_time_to_mixed_tracking();

   531   }

   532   collector_state()->set_in_marking_window(false);

   533 }

   534 

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

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

   537 }

   538 

   539 double G1Policy::young_other_time_ms() const {

   540   return phase_times()->young_cset_choice_time_ms() +

   541          phase_times()->young_free_cset_time_ms();

   542 }

   543 

   544 double G1Policy::non_young_other_time_ms() const {

   545   return phase_times()->non_young_cset_choice_time_ms() +

   546          phase_times()->non_young_free_cset_time_ms();

   547 

   548 }

   549 

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

   551   return pause_time_ms -

   552          average_time_ms(G1GCPhaseTimes::UpdateRS) -

   553          average_time_ms(G1GCPhaseTimes::ScanRS) -

   554          average_time_ms(G1GCPhaseTimes::ObjCopy) -

   555          average_time_ms(G1GCPhaseTimes::Termination);

   556 }

   557 

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

   559   return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();

   560 }

   561 

   562 CollectionSetChooser* G1Policy::cset_chooser() const {

   563   return _collection_set->cset_chooser();

   564 }

   565 

   566 bool G1Policy::about_to_start_mixed_phase() const {

   567   return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();

   568 }

   569 

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

   571   if (about_to_start_mixed_phase()) {

   572     return false;

   573   }

   574 

   575   size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();

   576 

   577   size_t cur_used_bytes = _g1->non_young_capacity_bytes();

   578   size_t alloc_byte_size = alloc_word_size * HeapWordSize;

   579   size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;

   580 

   581   bool result = false;

   582   if (marking_request_bytes > marking_initiating_used_threshold) {

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

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

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

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

   587   }

   588 

   589   return result;

   590 }

   591 

   592 // Anything below that is considered to be zero

   593 #define MIN_TIMER_GRANULARITY 0.0000001

   594 

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

   596   double end_time_sec = os::elapsedTime();

   597 

   598   size_t cur_used_bytes = _g1->used();

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

   600   bool last_pause_included_initial_mark = false;

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

   602 

   603   NOT_PRODUCT(_short_lived_surv_rate_group->print());

   604 

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

   606 

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

   608   if (last_pause_included_initial_mark) {

   609     record_concurrent_mark_init_end(0.0);

   610   } else {

   611     maybe_start_marking();

   612   }

   613 

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

   615   if (app_time_ms < MIN_TIMER_GRANULARITY) {

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

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

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

   619     app_time_ms = 1.0;

   620   }

   621 

   622   if (update_stats) {

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

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

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

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

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

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

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

   630     // place we can safely ignore them here.

   631     uint regions_allocated = _collection_set->eden_region_length();

   632     double alloc_rate_ms = (double) regions_allocated / app_time_ms;

   633     _analytics->report_alloc_rate_ms(alloc_rate_ms);

   634 

   635     double interval_ms =

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

   637     _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);

   638     _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);

   639   }

   640 

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

   642   bool new_in_marking_window_im = false;

   643   if (last_pause_included_initial_mark) {

   644     new_in_marking_window = true;

   645     new_in_marking_window_im = true;

   646   }

   647 

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

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

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

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

   652 

   653     if (next_gc_should_be_mixed("start mixed GCs",

   654                                 "do not start mixed GCs")) {

   655       collector_state()->set_gcs_are_young(false);

   656     } else {

   657       // We aborted the mixed GC phase early.

   658       abort_time_to_mixed_tracking();

   659     }

   660 

   661     collector_state()->set_last_young_gc(false);

   662   }

   663 

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

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

   666     // mixed GCs or not.

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

   668                                  "do not continue mixed GCs")) {

   669       collector_state()->set_gcs_are_young(true);

   670 

   671       maybe_start_marking();

   672     }

   673   }

   674 

   675   _short_lived_surv_rate_group->start_adding_regions();

   676   // Do that for any other surv rate groups

   677 

   678   double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;

   679 

   680   if (update_stats) {

   681     double cost_per_card_ms = 0.0;

   682     if (_pending_cards > 0) {

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

   684       _analytics->report_cost_per_card_ms(cost_per_card_ms);

   685     }

   686     _analytics->report_cost_scan_hcc(scan_hcc_time_ms);

   687 

   688     double cost_per_entry_ms = 0.0;

   689     if (cards_scanned > 10) {

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

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

   692     }

   693 

   694     if (_max_rs_lengths > 0) {

   695       double cards_per_entry_ratio =

   696         (double) cards_scanned / (double) _max_rs_lengths;

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

   698     }

   699 

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

   701     // smaller than _recorded_rs_lengths which was causing

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

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

   704     // _inc_cset_recorded_rs_lengths field which the code below guards

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

   706     // 7119027). However, I'm still worried that

   707     // _inc_cset_recorded_rs_lengths might still end up somewhat

   708     // inaccurate. The concurrent refinement thread calculates an

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

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

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

   712     // conditional below just in case.

   713     size_t rs_length_diff = 0;

   714     size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();

   715     if (_max_rs_lengths > recorded_rs_lengths) {

   716       rs_length_diff = _max_rs_lengths - recorded_rs_lengths;

   717     }

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

   719 

   720     size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;

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

   722     double cost_per_byte_ms = 0.0;

   723 

   724     if (copied_bytes > 0) {

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

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

   727     }

   728 

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

   730       _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /

   731                                                         _collection_set->young_region_length());

   732     }

   733 

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

   735       _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /

   736                                                             _collection_set->old_region_length());

   737     }

   738 

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

   740 

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

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

   743   }

   744 

   745   collector_state()->set_in_marking_window(new_in_marking_window);

   746   collector_state()->set_in_marking_window_im(new_in_marking_window_im);

   747   _free_regions_at_end_of_collection = _g1->num_free_regions();

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

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

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

   751   // predicted target occupancy.

   752   size_t last_unrestrained_young_length = update_young_list_max_and_target_length();

   753   update_rs_lengths_prediction();

   754 

   755   update_ihop_prediction(app_time_ms / 1000.0,

   756                          _bytes_allocated_in_old_since_last_gc,

   757                          last_unrestrained_young_length * HeapRegion::GrainBytes);

   758   _bytes_allocated_in_old_since_last_gc = 0;

   759 

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

   761 

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

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

   764 

   765   if (update_rs_time_goal_ms < scan_hcc_time_ms) {

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

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

   768                                 update_rs_time_goal_ms, scan_hcc_time_ms);

   769 

   770     update_rs_time_goal_ms = 0;

   771   } else {

   772     update_rs_time_goal_ms -= scan_hcc_time_ms;

   773   }

   774   _g1->concurrent_g1_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,

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

   776                                       update_rs_time_goal_ms);

   777 

   778   cset_chooser()->verify();

   779 }

   780 

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

   782   if (G1UseAdaptiveIHOP) {

   783     return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,

   784                                      predictor,

   785                                      G1ReservePercent,

   786                                      G1HeapWastePercent);

   787   } else {

   788     return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);

   789   }

   790 }

   791 

   792 void G1Policy::update_ihop_prediction(double mutator_time_s,

   793                                       size_t mutator_alloc_bytes,

   794                                       size_t young_gen_size) {

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

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

   797 

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

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

   800   double const min_valid_time = 1e-6;

   801 

   802   bool report = false;

   803 

   804   double marking_to_mixed_time = -1.0;

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

   806     marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();

   807     assert(marking_to_mixed_time > 0.0,

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

   809            marking_to_mixed_time);

   810     if (marking_to_mixed_time > min_valid_time) {

   811       _ihop_control->update_marking_length(marking_to_mixed_time);

   812       report = true;

   813     }

   814   }

   815 

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

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

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

   819   // prediction.

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

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

   822     report = true;

   823   }

   824 

   825   if (report) {

   826     report_ihop_statistics();

   827   }

   828 }

   829 

   830 void G1Policy::report_ihop_statistics() {

   831   _ihop_control->print();

   832 }

   833 

   834 void G1Policy::print_phases() {

   835   phase_times()->print();

   836 }

   837 

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

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

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

   841   double pred = _predictor.get_new_prediction(seq);

   842   if (pred > 1.0) {

   843     pred = 1.0;

   844   }

   845   return pred;

   846 }

   847 

   848 double G1Policy::predict_yg_surv_rate(int age) const {

   849   return predict_yg_surv_rate(age, _short_lived_surv_rate_group);

   850 }

   851 

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

   853   return _short_lived_surv_rate_group->accum_surv_rate_pred(age);

   854 }

   855 

   856 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,

   857                                               size_t scanned_cards) const {

   858   return

   859     _analytics->predict_rs_update_time_ms(pending_cards) +

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

   861     _analytics->predict_constant_other_time_ms();

   862 }

   863 

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

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

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

   867   return predict_base_elapsed_time_ms(pending_cards, card_num);

   868 }

   869 

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

   871   size_t bytes_to_copy;

   872   if (hr->is_marked())

   873     bytes_to_copy = hr->max_live_bytes();

   874   else {

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

   876     int age = hr->age_in_surv_rate_group();

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

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

   879   }

   880   return bytes_to_copy;

   881 }

   882 

   883 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr,

   884                                                 bool for_young_gc) const {

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

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

   887   // we're predicting for.

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

   889   size_t bytes_to_copy = predict_bytes_to_copy(hr);

   890 

   891   double region_elapsed_time_ms =

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

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

   894 

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

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

   897   if (hr->is_young()) {

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

   899   } else {

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

   901   }

   902   return region_elapsed_time_ms;

   903 }

   904 

   905 

   906 void G1Policy::print_yg_surv_rate_info() const {

   907 #ifndef PRODUCT

   908   _short_lived_surv_rate_group->print_surv_rate_summary();

   909   // add this call for any other surv rate groups

   910 #endif // PRODUCT

   911 }

   912 

   913 bool G1Policy::is_young_list_full() const {

   914   uint young_list_length = _g1->young_list()->length();

   915   uint young_list_target_length = _young_list_target_length;

   916   return young_list_length >= young_list_target_length;

   917 }

   918 

   919 bool G1Policy::can_expand_young_list() const {

   920   uint young_list_length = _g1->young_list()->length();

   921   uint young_list_max_length = _young_list_max_length;

   922   return young_list_length < young_list_max_length;

   923 }

   924 

   925 bool G1Policy::adaptive_young_list_length() const {

   926   return _young_gen_sizer.adaptive_young_list_length();

   927 }

   928 

   929 void G1Policy::update_max_gc_locker_expansion() {

   930   uint expansion_region_num = 0;

   931   if (GCLockerEdenExpansionPercent > 0) {

   932     double perc = (double) GCLockerEdenExpansionPercent / 100.0;

   933     double expansion_region_num_d = perc * (double) _young_list_target_length;

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

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

   936     expansion_region_num = (uint) ceil(expansion_region_num_d);

   937   } else {

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

   939   }

   940   _young_list_max_length = _young_list_target_length + expansion_region_num;

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

   942 }

   943 

   944 // Calculates survivor space parameters.

   945 void G1Policy::update_survivors_policy() {

   946   double max_survivor_regions_d =

   947                  (double) _young_list_target_length / (double) SurvivorRatio;

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

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

   950   _max_survivor_regions = (uint) ceil(max_survivor_regions_d);

   951 

   952   _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(

   953       HeapRegion::GrainWords * _max_survivor_regions, _policy_counters);

   954 }

   955 

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

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

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

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

   960   bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();

   961   if (!during_cycle) {

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

   963     collector_state()->set_initiate_conc_mark_if_possible(true);

   964     return true;

   965   } else {

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

   967     return false;

   968   }

   969 }

   970 

   971 void G1Policy::initiate_conc_mark() {

   972   collector_state()->set_during_initial_mark_pause(true);

   973   collector_state()->set_initiate_conc_mark_if_possible(false);

   974 }

   975 

   976 void G1Policy::decide_on_conc_mark_initiation() {

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

   978   // initial-mark pause.

   979 

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

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

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

   983   // initial-mark pause).

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

   985 

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

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

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

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

   990 

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

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

   993       initiate_conc_mark();

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

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

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

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

   998       collector_state()->set_gcs_are_young(true);

   999       collector_state()->set_last_young_gc(false);

  1000 

  1001       abort_time_to_mixed_tracking();

  1002       initiate_conc_mark();

  1003       log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");

  1004     } else {

  1005       // The concurrent marking thread is still finishing up the

  1006       // previous cycle. If we start one right now the two cycles

  1007       // overlap. In particular, the concurrent marking thread might

  1008       // be in the process of clearing the next marking bitmap (which

  1009       // we will use for the next cycle if we start one). Starting a

  1010       // cycle now will be bad given that parts of the marking

  1011       // information might get cleared by the marking thread. And we

  1012       // cannot wait for the marking thread to finish the cycle as it

  1013       // periodically yields while clearing the next marking bitmap

  1014       // and, if it's in a yield point, it's waiting for us to

  1015       // finish. So, at this point we will not start a cycle and we'll

  1016       // let the concurrent marking thread complete the last one.

  1017       log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");

  1018     }

  1019   }

  1020 }

  1021 

  1022 void G1Policy::record_concurrent_mark_cleanup_end() {

  1023   cset_chooser()->rebuild(_g1->workers(), _g1->num_regions());

  1024 

  1025   double end_sec = os::elapsedTime();

  1026   double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;

  1027   _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);

  1028   _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);

  1029 

  1030   record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);

  1031 }

  1032 

  1033 double G1Policy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {

  1034   // Returns the given amount of reclaimable bytes (that represents

  1035   // the amount of reclaimable space still to be collected) as a

  1036   // percentage of the current heap capacity.

  1037   size_t capacity_bytes = _g1->capacity();

  1038   return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;

  1039 }

  1040 

  1041 void G1Policy::maybe_start_marking() {

  1042   if (need_to_start_conc_mark("end of GC")) {

  1043     // Note: this might have already been set, if during the last

  1044     // pause we decided to start a cycle but at the beginning of

  1045     // this pause we decided to postpone it. That's OK.

  1046     collector_state()->set_initiate_conc_mark_if_possible(true);

  1047   }

  1048 }

  1049 

  1050 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {

  1051   assert(!collector_state()->full_collection(), "must be");

  1052   if (collector_state()->during_initial_mark_pause()) {

  1053     assert(collector_state()->last_gc_was_young(), "must be");

  1054     assert(!collector_state()->last_young_gc(), "must be");

  1055     return InitialMarkGC;

  1056   } else if (collector_state()->last_young_gc()) {

  1057     assert(!collector_state()->during_initial_mark_pause(), "must be");

  1058     assert(collector_state()->last_gc_was_young(), "must be");

  1059     return LastYoungGC;

  1060   } else if (!collector_state()->last_gc_was_young()) {

  1061     assert(!collector_state()->during_initial_mark_pause(), "must be");

  1062     assert(!collector_state()->last_young_gc(), "must be");

  1063     return MixedGC;

  1064   } else {

  1065     assert(collector_state()->last_gc_was_young(), "must be");

  1066     assert(!collector_state()->during_initial_mark_pause(), "must be");

  1067     assert(!collector_state()->last_young_gc(), "must be");

  1068     return YoungOnlyGC;

  1069   }

  1070 }

  1071 

  1072 void G1Policy::record_pause(PauseKind kind, double start, double end) {

  1073   // Manage the MMU tracker. For some reason it ignores Full GCs.

  1074   if (kind != FullGC) {

  1075     _mmu_tracker->add_pause(start, end);

  1076   }

  1077   // Manage the mutator time tracking from initial mark to first mixed gc.

  1078   switch (kind) {

  1079     case FullGC:

  1080       abort_time_to_mixed_tracking();

  1081       break;

  1082     case Cleanup:

  1083     case Remark:

  1084     case YoungOnlyGC:

  1085     case LastYoungGC:

  1086       _initial_mark_to_mixed.add_pause(end - start);

  1087       break;

  1088     case InitialMarkGC:

  1089       _initial_mark_to_mixed.record_initial_mark_end(end);

  1090       break;

  1091     case MixedGC:

  1092       _initial_mark_to_mixed.record_mixed_gc_start(start);

  1093       break;

  1094     default:

  1095       ShouldNotReachHere();

  1096   }

  1097 }

  1098 

  1099 void G1Policy::abort_time_to_mixed_tracking() {

  1100   _initial_mark_to_mixed.reset();

  1101 }

  1102 

  1103 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,

  1104                                        const char* false_action_str) const {

  1105   if (cset_chooser()->is_empty()) {

  1106     log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);

  1107     return false;

  1108   }

  1109 

  1110   // Is the amount of uncollected reclaimable space above G1HeapWastePercent?

  1111   size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();

  1112   double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);

  1113   double threshold = (double) G1HeapWastePercent;

  1114   if (reclaimable_perc <= threshold) {

  1115     log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,

  1116                         false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);

  1117     return false;

  1118   }

  1119   log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,

  1120                       true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);

  1121   return true;

  1122 }

  1123 

  1124 uint G1Policy::calc_min_old_cset_length() const {

  1125   // The min old CSet region bound is based on the maximum desired

  1126   // number of mixed GCs after a cycle. I.e., even if some old regions

  1127   // look expensive, we should add them to the CSet anyway to make

  1128   // sure we go through the available old regions in no more than the

  1129   // maximum desired number of mixed GCs.

  1130   //

  1131   // The calculation is based on the number of marked regions we added

  1132   // to the CSet chooser in the first place, not how many remain, so

  1133   // that the result is the same during all mixed GCs that follow a cycle.

  1134