Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 2002-2010 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 #include "incls/_precompiled.incl"

 #include "incls/_psAdaptiveSizePolicy.cpp.incl"

 #include <math.h>

 PSAdaptiveSizePolicy::PSAdaptiveSizePolicy(size_t init_eden_size,

                                            size_t init_promo_size,

                                            size_t init_survivor_size,

                                            size_t intra_generation_alignment,

                                            double gc_pause_goal_sec,

                                            double gc_minor_pause_goal_sec,

                                            uint gc_cost_ratio) :

      AdaptiveSizePolicy(init_eden_size,

                         init_promo_size,

                         init_survivor_size,

                         gc_pause_goal_sec,

                         gc_cost_ratio),

      _collection_cost_margin_fraction(AdaptiveSizePolicyCollectionCostMargin/

        100.0),

      _intra_generation_alignment(intra_generation_alignment),

      _live_at_last_full_gc(init_promo_size),

      _gc_minor_pause_goal_sec(gc_minor_pause_goal_sec),

      _latest_major_mutator_interval_seconds(0),

      _young_gen_change_for_major_pause_count(0)

 {

   // Sizing policy statistics

   _avg_major_pause    =

     new AdaptivePaddedAverage(AdaptiveTimeWeight, PausePadding);

   _avg_minor_interval = new AdaptiveWeightedAverage(AdaptiveTimeWeight);

   _avg_major_interval = new AdaptiveWeightedAverage(AdaptiveTimeWeight);

   _avg_base_footprint = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);

   _major_pause_old_estimator =

     new LinearLeastSquareFit(AdaptiveSizePolicyWeight);

   _major_pause_young_estimator =

     new LinearLeastSquareFit(AdaptiveSizePolicyWeight);

   _major_collection_estimator =

     new LinearLeastSquareFit(AdaptiveSizePolicyWeight);

   _young_gen_size_increment_supplement = YoungGenerationSizeSupplement;

   _old_gen_size_increment_supplement = TenuredGenerationSizeSupplement;

   // Start the timers

   _major_timer.start();

   _old_gen_policy_is_ready = false;

 }

 void PSAdaptiveSizePolicy::major_collection_begin() {

   // Update the interval time

   _major_timer.stop();

   // Save most recent collection time

   _latest_major_mutator_interval_seconds = _major_timer.seconds();

   _major_timer.reset();

   _major_timer.start();

 }

 void PSAdaptiveSizePolicy::update_minor_pause_old_estimator(

     double minor_pause_in_ms) {

   double promo_size_in_mbytes = ((double)_promo_size)/((double)M);

   _minor_pause_old_estimator->update(promo_size_in_mbytes,

     minor_pause_in_ms);

 }

 void PSAdaptiveSizePolicy::major_collection_end(size_t amount_live,

   GCCause::Cause gc_cause) {

   // Update the pause time.

   _major_timer.stop();

   if (gc_cause != GCCause::_java_lang_system_gc ||

       UseAdaptiveSizePolicyWithSystemGC) {

     double major_pause_in_seconds = _major_timer.seconds();

     double major_pause_in_ms = major_pause_in_seconds * MILLIUNITS;

     // Sample for performance counter

     _avg_major_pause->sample(major_pause_in_seconds);

     // Cost of collection (unit-less)

     double collection_cost = 0.0;

     if ((_latest_major_mutator_interval_seconds > 0.0) &&

         (major_pause_in_seconds > 0.0)) {

       double interval_in_seconds =

         _latest_major_mutator_interval_seconds + major_pause_in_seconds;

       collection_cost =

         major_pause_in_seconds / interval_in_seconds;

       avg_major_gc_cost()->sample(collection_cost);

       // Sample for performance counter

       _avg_major_interval->sample(interval_in_seconds);

     }

     // Calculate variables used to estimate pause time vs. gen sizes

     double eden_size_in_mbytes = ((double)_eden_size)/((double)M);

     double promo_size_in_mbytes = ((double)_promo_size)/((double)M);

     _major_pause_old_estimator->update(promo_size_in_mbytes,

       major_pause_in_ms);

     _major_pause_young_estimator->update(eden_size_in_mbytes,

       major_pause_in_ms);

     if (PrintAdaptiveSizePolicy && Verbose) {

       gclog_or_tty->print("psAdaptiveSizePolicy::major_collection_end: "

         "major gc cost: %f  average: %f", collection_cost,

         avg_major_gc_cost()->average());

       gclog_or_tty->print_cr("  major pause: %f major period %f",

         major_pause_in_ms,

         _latest_major_mutator_interval_seconds * MILLIUNITS);

     }

     // Calculate variable used to estimate collection cost vs. gen sizes

     assert(collection_cost >= 0.0, "Expected to be non-negative");

     _major_collection_estimator->update(promo_size_in_mbytes,

         collection_cost);

   }

   // Update the amount live at the end of a full GC

   _live_at_last_full_gc = amount_live;

   // The policy does not have enough data until at least some major collections

   // have been done.

   if (_avg_major_pause->count() >= AdaptiveSizePolicyReadyThreshold) {

     _old_gen_policy_is_ready = true;

   }

   // Interval times use this timer to measure the interval that

   // the mutator runs.  Reset after the GC pause has been measured.

   _major_timer.reset();

   _major_timer.start();

 }

 // If the remaining free space in the old generation is less that

 // that expected to be needed by the next collection, do a full

 // collection now.

 bool PSAdaptiveSizePolicy::should_full_GC(size_t old_free_in_bytes) {

   // A similar test is done in the scavenge's should_attempt_scavenge().  If

   // this is changed, decide if that test should also be changed.

   bool result = padded_average_promoted_in_bytes() > (float) old_free_in_bytes;

   if (PrintGCDetails && Verbose) {

     if (result) {

       gclog_or_tty->print("  full after scavenge: ");

     } else {

       gclog_or_tty->print("  no full after scavenge: ");

     }

     gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT

       " padded_average_promoted " SIZE_FORMAT

       " free in old gen " SIZE_FORMAT,

       (size_t) average_promoted_in_bytes(),

       (size_t) padded_average_promoted_in_bytes(),

       old_free_in_bytes);

   }

   return result;

 }

 void PSAdaptiveSizePolicy::clear_generation_free_space_flags() {

   AdaptiveSizePolicy::clear_generation_free_space_flags();

   set_change_old_gen_for_min_pauses(0);

   set_change_young_gen_for_maj_pauses(0);

 }

 // If this is not a full GC, only test and modify the young generation.

 void PSAdaptiveSizePolicy::compute_generation_free_space(

                                            size_t young_live,

                                            size_t eden_live,

                                            size_t old_live,

                                            size_t perm_live,

                                            size_t cur_eden,

                                            size_t max_old_gen_size,

                                            size_t max_eden_size,

                                            bool   is_full_gc,

                                            GCCause::Cause gc_cause,

                                            CollectorPolicy* collector_policy) {

   // Update statistics

   // Time statistics are updated as we go, update footprint stats here

   _avg_base_footprint->sample(BaseFootPrintEstimate + perm_live);

   avg_young_live()->sample(young_live);

   avg_eden_live()->sample(eden_live);

   if (is_full_gc) {

     // old_live is only accurate after a full gc

     avg_old_live()->sample(old_live);

   }

   // This code used to return if the policy was not ready , i.e.,

   // policy_is_ready() returning false.  The intent was that

   // decisions below needed major collection times and so could

   // not be made before two major collections.  A consequence was

   // adjustments to the young generation were not done until after

   // two major collections even if the minor collections times

   // exceeded the requested goals.  Now let the young generation

   // adjust for the minor collection times.  Major collection times

   // will be zero for the first collection and will naturally be

   // ignored.  Tenured generation adjustments are only made at the

   // full collections so until the second major collection has

   // been reached, no tenured generation adjustments will be made.

   // Until we know better, desired promotion size uses the last calculation

   size_t desired_promo_size = _promo_size;

   // Start eden at the current value.  The desired value that is stored

   // in _eden_size is not bounded by constraints of the heap and can

   // run away.

   //

   // As expected setting desired_eden_size to the current

   // value of desired_eden_size as a starting point

   // caused desired_eden_size to grow way too large and caused

   // an overflow down stream.  It may have improved performance in

   // some case but is dangerous.

   size_t desired_eden_size = cur_eden;

 #ifdef ASSERT

   size_t original_promo_size = desired_promo_size;

   size_t original_eden_size = desired_eden_size;

 #endif

   // Cache some values. There's a bit of work getting these, so

   // we might save a little time.

   const double major_cost = major_gc_cost();

   const double minor_cost = minor_gc_cost();

   // Used for diagnostics

   clear_generation_free_space_flags();

   // Limits on our growth

   size_t promo_limit = (size_t)(max_old_gen_size - avg_old_live()->average());

   // This method sets the desired eden size.  That plus the

   // desired survivor space sizes sets the desired young generation

   // size.  This methods does not know what the desired survivor

   // size is but expects that other policy will attempt to make

   // the survivor sizes compatible with the live data in the

   // young generation.  This limit is an estimate of the space left

   // in the young generation after the survivor spaces have been

   // subtracted out.

   size_t eden_limit = max_eden_size;

   // But don't force a promo size below the current promo size. Otherwise,

   // the promo size will shrink for no good reason.

   promo_limit = MAX2(promo_limit, _promo_size);

   const double gc_cost_limit = GCTimeLimit/100.0;

   // Which way should we go?

   // if pause requirement is not met

   //   adjust size of any generation with average paus exceeding

   //   the pause limit.  Adjust one pause at a time (the larger)

   //   and only make adjustments for the major pause at full collections.

   // else if throughput requirement not met

   //   adjust the size of the generation with larger gc time.  Only

   //   adjust one generation at a time.

   // else

   //   adjust down the total heap size.  Adjust down the larger of the

   //   generations.

   // Add some checks for a threshhold for a change.  For example,

   // a change less than the necessary alignment is probably not worth

   // attempting.

   if ((_avg_minor_pause->padded_average() > gc_pause_goal_sec()) ||

       (_avg_major_pause->padded_average() > gc_pause_goal_sec())) {

     //

     // Check pauses

     //

     // Make changes only to affect one of the pauses (the larger)

     // at a time.

     adjust_for_pause_time(is_full_gc, &desired_promo_size, &desired_eden_size);

   } else if (_avg_minor_pause->padded_average() > gc_minor_pause_goal_sec()) {

     // Adjust only for the minor pause time goal

     adjust_for_minor_pause_time(is_full_gc, &desired_promo_size, &desired_eden_size);

   } else if(adjusted_mutator_cost() < _throughput_goal) {

     // This branch used to require that (mutator_cost() > 0.0 in 1.4.2.

     // This sometimes resulted in skipping to the minimize footprint

     // code.  Change this to try and reduce GC time if mutator time is

     // negative for whatever reason.  Or for future consideration,

     // bail out of the code if mutator time is negative.

     //

     // Throughput

     //

     assert(major_cost >= 0.0, "major cost is < 0.0");

     assert(minor_cost >= 0.0, "minor cost is < 0.0");

     // Try to reduce the GC times.

     adjust_for_throughput(is_full_gc, &desired_promo_size, &desired_eden_size);

   } else {

     // Be conservative about reducing the footprint.

     //   Do a minimum number of major collections first.

     //   Have reasonable averages for major and minor collections costs.

     if (UseAdaptiveSizePolicyFootprintGoal &&

         young_gen_policy_is_ready() &&

         avg_major_gc_cost()->average() >= 0.0 &&

         avg_minor_gc_cost()->average() >= 0.0) {

       size_t desired_sum = desired_eden_size + desired_promo_size;

       desired_eden_size = adjust_eden_for_footprint(desired_eden_size,

                                                     desired_sum);

       if (is_full_gc) {

         set_decide_at_full_gc(decide_at_full_gc_true);

         desired_promo_size = adjust_promo_for_footprint(desired_promo_size,

                                                         desired_sum);

       }

     }

   }

   // Note we make the same tests as in the code block below;  the code

   // seems a little easier to read with the printing in another block.

   if (PrintAdaptiveSizePolicy) {

     if (desired_promo_size > promo_limit)  {

       // "free_in_old_gen" was the original value for used for promo_limit

       size_t free_in_old_gen = (size_t)(max_old_gen_size - avg_old_live()->average());

       gclog_or_tty->print_cr(

             "PSAdaptiveSizePolicy::compute_generation_free_space limits:"

             " desired_promo_size: " SIZE_FORMAT

             " promo_limit: " SIZE_FORMAT

             " free_in_old_gen: " SIZE_FORMAT

             " max_old_gen_size: " SIZE_FORMAT

             " avg_old_live: " SIZE_FORMAT,

             desired_promo_size, promo_limit, free_in_old_gen,

             max_old_gen_size, (size_t) avg_old_live()->average());

     }

     if (desired_eden_size > eden_limit) {

       gclog_or_tty->print_cr(

             "AdaptiveSizePolicy::compute_generation_free_space limits:"

             " desired_eden_size: " SIZE_FORMAT

             " old_eden_size: " SIZE_FORMAT

             " eden_limit: " SIZE_FORMAT

             " cur_eden: " SIZE_FORMAT

             " max_eden_size: " SIZE_FORMAT

             " avg_young_live: " SIZE_FORMAT,

             desired_eden_size, _eden_size, eden_limit, cur_eden,

             max_eden_size, (size_t)avg_young_live()->average());

     }

     if (gc_cost() > gc_cost_limit) {

       gclog_or_tty->print_cr(

             "AdaptiveSizePolicy::compute_generation_free_space: gc time limit"

             " gc_cost: %f "

             " GCTimeLimit: %d",

             gc_cost(), GCTimeLimit);

     }

   }

   // Align everything and make a final limit check

   const size_t alignment = _intra_generation_alignment;

   desired_eden_size  = align_size_up(desired_eden_size, alignment);

   desired_eden_size  = MAX2(desired_eden_size, alignment);

   desired_promo_size = align_size_up(desired_promo_size, alignment);

   desired_promo_size = MAX2(desired_promo_size, alignment);

   eden_limit  = align_size_down(eden_limit, alignment);

   promo_limit = align_size_down(promo_limit, alignment);

   // Is too much time being spent in GC?

   //   Is the heap trying to grow beyond it's limits?

   const size_t free_in_old_gen =

     (size_t)(max_old_gen_size - avg_old_live()->average());

   if (desired_promo_size > free_in_old_gen && desired_eden_size > eden_limit) {

     check_gc_overhead_limit(young_live,

                             eden_live,

                             max_old_gen_size,

                             max_eden_size,

                             is_full_gc,

                             gc_cause,

                             collector_policy);

   }

   // And one last limit check, now that we've aligned things.

   if (desired_eden_size > eden_limit) {

     // If the policy says to get a larger eden but

     // is hitting the limit, don't decrease eden.

     // This can lead to a general drifting down of the

     // eden size.  Let the tenuring calculation push more

     // into the old gen.

     desired_eden_size = MAX2(eden_limit, cur_eden);

   }

   desired_promo_size = MIN2(desired_promo_size, promo_limit);

   if (PrintAdaptiveSizePolicy) {

     // Timing stats

     gclog_or_tty->print(

                "PSAdaptiveSizePolicy::compute_generation_free_space: costs"

                " minor_time: %f"

                " major_cost: %f"

                " mutator_cost: %f"

                " throughput_goal: %f",

                minor_gc_cost(), major_gc_cost(), mutator_cost(),

                _throughput_goal);

     // We give more details if Verbose is set

     if (Verbose) {

       gclog_or_tty->print( " minor_pause: %f"

                   " major_pause: %f"

                   " minor_interval: %f"

                   " major_interval: %f"

                   " pause_goal: %f",

                   _avg_minor_pause->padded_average(),

                   _avg_major_pause->padded_average(),

                   _avg_minor_interval->average(),

                   _avg_major_interval->average(),

                   gc_pause_goal_sec());

     }

     // Footprint stats

     gclog_or_tty->print( " live_space: " SIZE_FORMAT

                 " free_space: " SIZE_FORMAT,

                 live_space(), free_space());

     // More detail

     if (Verbose) {

       gclog_or_tty->print( " base_footprint: " SIZE_FORMAT

                   " avg_young_live: " SIZE_FORMAT

                   " avg_old_live: " SIZE_FORMAT,

                   (size_t)_avg_base_footprint->average(),

                   (size_t)avg_young_live()->average(),

                   (size_t)avg_old_live()->average());

     }

     // And finally, our old and new sizes.

     gclog_or_tty->print(" old_promo_size: " SIZE_FORMAT

                " old_eden_size: " SIZE_FORMAT

                " desired_promo_size: " SIZE_FORMAT

                " desired_eden_size: " SIZE_FORMAT,

                _promo_size, _eden_size,

                desired_promo_size, desired_eden_size);

     gclog_or_tty->cr();

   }

   decay_supplemental_growth(is_full_gc);

   set_promo_size(desired_promo_size);

   set_eden_size(desired_eden_size);

 };

 void PSAdaptiveSizePolicy::decay_supplemental_growth(bool is_full_gc) {

   // Decay the supplemental increment?  Decay the supplement growth

   // factor even if it is not used.  It is only meant to give a boost

   // to the initial growth and if it is not used, then it was not

   // needed.

   if (is_full_gc) {

     // Don't wait for the threshold value for the major collections.  If

     // here, the supplemental growth term was used and should decay.

     if ((_avg_major_pause->count() % TenuredGenerationSizeSupplementDecay)

         == 0) {

       _old_gen_size_increment_supplement =

         _old_gen_size_increment_supplement >> 1;

     }

   } else {

     if ((_avg_minor_pause->count() >= AdaptiveSizePolicyReadyThreshold) &&

         (_avg_minor_pause->count() % YoungGenerationSizeSupplementDecay) == 0) {

       _young_gen_size_increment_supplement =

         _young_gen_size_increment_supplement >> 1;

     }

   }

 }

 void PSAdaptiveSizePolicy::adjust_for_minor_pause_time(bool is_full_gc,

     size_t* desired_promo_size_ptr, size_t* desired_eden_size_ptr) {

   // Adjust the young generation size to reduce pause time of

   // of collections.

   //

   // The AdaptiveSizePolicyInitializingSteps test is not used

   // here.  It has not seemed to be needed but perhaps should

   // be added for consistency.

   if (minor_pause_young_estimator()->decrement_will_decrease()) {

         // reduce eden size

     set_change_young_gen_for_min_pauses(

           decrease_young_gen_for_min_pauses_true);

     *desired_eden_size_ptr = *desired_eden_size_ptr -

       eden_decrement_aligned_down(*desired_eden_size_ptr);

     } else {

       // EXPERIMENTAL ADJUSTMENT

       // Only record that the estimator indicated such an action.

       // *desired_eden_size_ptr = *desired_eden_size_ptr + eden_heap_delta;

       set_change_young_gen_for_min_pauses(

           increase_young_gen_for_min_pauses_true);

   }

   if (PSAdjustTenuredGenForMinorPause) {

     // If the desired eden size is as small as it will get,

     // try to adjust the old gen size.

     if (*desired_eden_size_ptr <= _intra_generation_alignment) {

       // Vary the old gen size to reduce the young gen pause.  This

       // may not be a good idea.  This is just a test.

       if (minor_pause_old_estimator()->decrement_will_decrease()) {

         set_change_old_gen_for_min_pauses(

           decrease_old_gen_for_min_pauses_true);

         *desired_promo_size_ptr =

           _promo_size - promo_decrement_aligned_down(*desired_promo_size_ptr);

       } else {

         set_change_old_gen_for_min_pauses(

           increase_old_gen_for_min_pauses_true);

         size_t promo_heap_delta =

           promo_increment_with_supplement_aligned_up(*desired_promo_size_ptr);

         if ((*desired_promo_size_ptr + promo_heap_delta) >

             *desired_promo_size_ptr) {

           *desired_promo_size_ptr =

             _promo_size + promo_heap_delta;

         }

       }

     }

   }

 }

 void PSAdaptiveSizePolicy::adjust_for_pause_time(bool is_full_gc,

                                              size_t* desired_promo_size_ptr,

                                              size_t* desired_eden_size_ptr) {

   size_t promo_heap_delta = 0;

   size_t eden_heap_delta = 0;

   // Add some checks for a threshhold for a change.  For example,

   // a change less than the required alignment is probably not worth

   // attempting.

   if (is_full_gc) {

     set_decide_at_full_gc(decide_at_full_gc_true);

   }

   if (_avg_minor_pause->padded_average() > _avg_major_pause->padded_average()) {

     adjust_for_minor_pause_time(is_full_gc,

                                 desired_promo_size_ptr,

                                 desired_eden_size_ptr);

     // major pause adjustments

   } else if (is_full_gc) {

     // Adjust for the major pause time only at full gc's because the

     // affects of a change can only be seen at full gc's.

     // Reduce old generation size to reduce pause?

     if (major_pause_old_estimator()->decrement_will_decrease()) {

       // reduce old generation size

       set_change_old_gen_for_maj_pauses(decrease_old_gen_for_maj_pauses_true);

       promo_heap_delta = promo_decrement_aligned_down(*desired_promo_size_ptr);

       *desired_promo_size_ptr = _promo_size - promo_heap_delta;

     } else {

       // EXPERIMENTAL ADJUSTMENT

       // Only record that the estimator indicated such an action.

       // *desired_promo_size_ptr = _promo_size +

       //   promo_increment_aligned_up(*desired_promo_size_ptr);

       set_change_old_gen_for_maj_pauses(increase_old_gen_for_maj_pauses_true);

     }

     if (PSAdjustYoungGenForMajorPause) {

       // If the promo size is at the minimum (i.e., the old gen

       // size will not actually decrease), consider changing the

       // young gen size.

       if (*desired_promo_size_ptr < _intra_generation_alignment) {

         // If increasing the young generation will decrease the old gen

         // pause, do it.

         // During startup there is noise in the statistics for deciding

         // on whether to increase or decrease the young gen size.  For

         // some number of iterations, just try to increase the young

         // gen size if the major pause is too long to try and establish

         // good statistics for later decisions.

         if (major_pause_young_estimator()->increment_will_decrease() ||

           (_young_gen_change_for_major_pause_count

             <= AdaptiveSizePolicyInitializingSteps)) {

           set_change_young_gen_for_maj_pauses(

           increase_young_gen_for_maj_pauses_true);

           eden_heap_delta = eden_increment_aligned_up(*desired_eden_size_ptr);

           *desired_eden_size_ptr = _eden_size + eden_heap_delta;

           _young_gen_change_for_major_pause_count++;

         } else {

           // Record that decreasing the young gen size would decrease

           // the major pause

           set_change_young_gen_for_maj_pauses(

             decrease_young_gen_for_maj_pauses_true);

           eden_heap_delta = eden_decrement_aligned_down(*desired_eden_size_ptr);

           *desired_eden_size_ptr = _eden_size - eden_heap_delta;

         }

       }

     }

   }

   if (PrintAdaptiveSizePolicy && Verbose) {

     gclog_or_tty->print_cr(

       "AdaptiveSizePolicy::compute_generation_free_space "

       "adjusting gen sizes for major pause (avg %f goal %f). "

       "desired_promo_size " SIZE_FORMAT "desired_eden_size "

        SIZE_FORMAT

       " promo delta " SIZE_FORMAT  " eden delta " SIZE_FORMAT,

       _avg_major_pause->average(), gc_pause_goal_sec(),

       *desired_promo_size_ptr, *desired_eden_size_ptr,

       promo_heap_delta, eden_heap_delta);

   }

 }

 void PSAdaptiveSizePolicy::adjust_for_throughput(bool is_full_gc,

                                              size_t* desired_promo_size_ptr,

                                              size_t* desired_eden_size_ptr) {

   // Add some checks for a threshhold for a change.  For example,

   // a change less than the required alignment is probably not worth

   // attempting.

   if (is_full_gc) {

     set_decide_at_full_gc(decide_at_full_gc_true);

   }

   if ((gc_cost() + mutator_cost()) == 0.0) {

     return;

   }

   if (PrintAdaptiveSizePolicy && Verbose) {

     gclog_or_tty->print("\nPSAdaptiveSizePolicy::adjust_for_throughput("

       "is_full: %d, promo: " SIZE_FORMAT ",  cur_eden: " SIZE_FORMAT "): ",

       is_full_gc, *desired_promo_size_ptr, *desired_eden_size_ptr);

     gclog_or_tty->print_cr("mutator_cost %f  major_gc_cost %f "

       "minor_gc_cost %f", mutator_cost(), major_gc_cost(), minor_gc_cost());

   }

   // Tenured generation

   if (is_full_gc) {

     // Calculate the change to use for the tenured gen.

     size_t scaled_promo_heap_delta = 0;

     // Can the increment to the generation be scaled?

     if (gc_cost() >= 0.0 && major_gc_cost() >= 0.0) {

       size_t promo_heap_delta =

         promo_increment_with_supplement_aligned_up(*desired_promo_size_ptr);

       double scale_by_ratio = major_gc_cost() / gc_cost();

       scaled_promo_heap_delta =

         (size_t) (scale_by_ratio * (double) promo_heap_delta);

       if (PrintAdaptiveSizePolicy && Verbose) {

         gclog_or_tty->print_cr(

           "Scaled tenured increment: " SIZE_FORMAT " by %f down to "

           SIZE_FORMAT,

           promo_heap_delta, scale_by_ratio, scaled_promo_heap_delta);

       }

     } else if (major_gc_cost() >= 0.0) {

       // Scaling is not going to work.  If the major gc time is the

       // larger, give it a full increment.

       if (major_gc_cost() >= minor_gc_cost()) {

         scaled_promo_heap_delta =

           promo_increment_with_supplement_aligned_up(*desired_promo_size_ptr);

       }

     } else {

       // Don't expect to get here but it's ok if it does

       // in the product build since the delta will be 0

       // and nothing will change.

       assert(false, "Unexpected value for gc costs");

     }

     switch (AdaptiveSizeThroughPutPolicy) {

       case 1:

         // Early in the run the statistics might not be good.  Until

         // a specific number of collections have been, use the heuristic

         // that a larger generation size means lower collection costs.

         if (major_collection_estimator()->increment_will_decrease() ||

            (_old_gen_change_for_major_throughput

             <= AdaptiveSizePolicyInitializingSteps)) {

           // Increase tenured generation size to reduce major collection cost

           if ((*desired_promo_size_ptr + scaled_promo_heap_delta) >

               *desired_promo_size_ptr) {

             *desired_promo_size_ptr = _promo_size + scaled_promo_heap_delta;

           }

           set_change_old_gen_for_throughput(

               increase_old_gen_for_throughput_true);

               _old_gen_change_for_major_throughput++;

         } else {

           // EXPERIMENTAL ADJUSTMENT

           // Record that decreasing the old gen size would decrease

           // the major collection cost but don't do it.

           // *desired_promo_size_ptr = _promo_size -

           //   promo_decrement_aligned_down(*desired_promo_size_ptr);

           set_change_old_gen_for_throughput(

                 decrease_old_gen_for_throughput_true);

         }

         break;

       default:

         // Simplest strategy

         if ((*desired_promo_size_ptr + scaled_promo_heap_delta) >

             *desired_promo_size_ptr) {

           *desired_promo_size_ptr = *desired_promo_size_ptr +

             scaled_promo_heap_delta;

         }

         set_change_old_gen_for_throughput(

           increase_old_gen_for_throughput_true);

         _old_gen_change_for_major_throughput++;

     }

     if (PrintAdaptiveSizePolicy && Verbose) {

       gclog_or_tty->print_cr(

           "adjusting tenured gen for throughput (avg %f goal %f). "

           "desired_promo_size " SIZE_FORMAT " promo_delta " SIZE_FORMAT ,

           mutator_cost(), _throughput_goal,

           *desired_promo_size_ptr, scaled_promo_heap_delta);

     }

   }

   // Young generation

   size_t scaled_eden_heap_delta = 0;

   // Can the increment to the generation be scaled?

   if (gc_cost() >= 0.0 && minor_gc_cost() >= 0.0) {

     size_t eden_heap_delta =

       eden_increment_with_supplement_aligned_up(*desired_eden_size_ptr);

     double scale_by_ratio = minor_gc_cost() / gc_cost();

     assert(scale_by_ratio <= 1.0 && scale_by_ratio >= 0.0, "Scaling is wrong");

     scaled_eden_heap_delta =

       (size_t) (scale_by_ratio * (double) eden_heap_delta);

     if (PrintAdaptiveSizePolicy && Verbose) {

       gclog_or_tty->print_cr(

         "Scaled eden increment: " SIZE_FORMAT " by %f down to "

         SIZE_FORMAT,

         eden_heap_delta, scale_by_ratio, scaled_eden_heap_delta);

     }

   } else if (minor_gc_cost() >= 0.0) {

     // Scaling is not going to work.  If the minor gc time is the

     // larger, give it a full increment.

     if (minor_gc_cost() > major_gc_cost()) {

       scaled_eden_heap_delta =

         eden_increment_with_supplement_aligned_up(*desired_eden_size_ptr);

     }

   } else {

     // Don't expect to get here but it's ok if it does

     // in the product build since the delta will be 0

     // and nothing will change.

     assert(false, "Unexpected value for gc costs");

   }

   // Use a heuristic for some number of collections to give

   // the averages time to settle down.

   switch (AdaptiveSizeThroughPutPolicy) {

     case 1:

       if (minor_collection_estimator()->increment_will_decrease() ||

         (_young_gen_change_for_minor_throughput

           <= AdaptiveSizePolicyInitializingSteps)) {

         // Expand young generation size to reduce frequency of

         // of collections.

         if ((*desired_eden_size_ptr + scaled_eden_heap_delta) >

             *desired_eden_size_ptr) {

           *desired_eden_size_ptr =

             *desired_eden_size_ptr + scaled_eden_heap_delta;

         }

         set_change_young_gen_for_throughput(

           increase_young_gen_for_througput_true);

         _young_gen_change_for_minor_throughput++;

       } else {

         // EXPERIMENTAL ADJUSTMENT

         // Record that decreasing the young gen size would decrease

         // the minor collection cost but don't do it.

         // *desired_eden_size_ptr = _eden_size -

         //   eden_decrement_aligned_down(*desired_eden_size_ptr);

         set_change_young_gen_for_throughput(

           decrease_young_gen_for_througput_true);

       }

           break;

     default:

       if ((*desired_eden_size_ptr + scaled_eden_heap_delta) >

           *desired_eden_size_ptr) {

         *desired_eden_size_ptr =

           *desired_eden_size_ptr + scaled_eden_heap_delta;

       }

       set_change_young_gen_for_throughput(

         increase_young_gen_for_througput_true);

       _young_gen_change_for_minor_throughput++;

   }

   if (PrintAdaptiveSizePolicy && Verbose) {

     gclog_or_tty->print_cr(

         "adjusting eden for throughput (avg %f goal %f). desired_eden_size "

         SIZE_FORMAT " eden delta " SIZE_FORMAT "\n",

       mutator_cost(), _throughput_goal,

         *desired_eden_size_ptr, scaled_eden_heap_delta);

   }

 }

 size_t PSAdaptiveSizePolicy::adjust_promo_for_footprint(

     size_t desired_promo_size, size_t desired_sum) {

   assert(desired_promo_size <= desired_sum, "Inconsistent parameters");

   set_decrease_for_footprint(decrease_old_gen_for_footprint_true);

   size_t change = promo_decrement(desired_promo_size);

   change = scale_down(change, desired_promo_size, desired_sum);

   size_t reduced_size = desired_promo_size - change;

   if (PrintAdaptiveSizePolicy && Verbose) {

     gclog_or_tty->print_cr(

       "AdaptiveSizePolicy::compute_generation_free_space "

       "adjusting tenured gen for footprint. "

       "starting promo size " SIZE_FORMAT

       " reduced promo size " SIZE_FORMAT,

       " promo delta " SIZE_FORMAT,

       desired_promo_size, reduced_size, change );

   }

   assert(reduced_size <= desired_promo_size, "Inconsistent result");

   return reduced_size;

 }

 size_t PSAdaptiveSizePolicy::adjust_eden_for_footprint(

   size_t desired_eden_size, size_t desired_sum) {

   assert(desired_eden_size <= desired_sum, "Inconsistent parameters");

   set_decrease_for_footprint(decrease_young_gen_for_footprint_true);

   size_t change = eden_decrement(desired_eden_size);

   change = scale_down(change, desired_eden_size, desired_sum);

   size_t reduced_size = desired_eden_size - change;

   if (PrintAdaptiveSizePolicy && Verbose) {

     gclog_or_tty->print_cr(

       "AdaptiveSizePolicy::compute_generation_free_space "

       "adjusting eden for footprint. "

       " starting eden size " SIZE_FORMAT

       " reduced eden size " SIZE_FORMAT

       " eden delta " SIZE_FORMAT,

       desired_eden_size, reduced_size, change);

   }

   assert(reduced_size <= desired_eden_size, "Inconsistent result");

   return reduced_size;

 }

 // Scale down "change" by the factor

 //      part / total

 // Don't align the results.

 size_t PSAdaptiveSizePolicy::scale_down(size_t change,

                                         double part,

                                         double total) {

   assert(part <= total, "Inconsistent input");

   size_t reduced_change = change;

   if (total > 0) {

     double fraction =  part / total;

     reduced_change = (size_t) (fraction * (double) change);

   }

   assert(reduced_change <= change, "Inconsistent result");

   return reduced_change;

 }

 size_t PSAdaptiveSizePolicy::eden_increment(size_t cur_eden,

                                             uint percent_change) {

   size_t eden_heap_delta;

   eden_heap_delta = cur_eden / 100 * percent_change;

   return eden_heap_delta;

 }

 size_t PSAdaptiveSizePolicy::eden_increment(size_t cur_eden) {

   return eden_increment(cur_eden, YoungGenerationSizeIncrement);

 }

 size_t PSAdaptiveSizePolicy::eden_increment_aligned_up(size_t cur_eden) {

   size_t result = eden_increment(cur_eden, YoungGenerationSizeIncrement);

   return align_size_up(result, _intra_generation_alignment);

 }

 size_t PSAdaptiveSizePolicy::eden_increment_aligned_down(size_t cur_eden) {

   size_t result = eden_increment(cur_eden);

   return align_size_down(result, _intra_generation_alignment);

 }

 size_t PSAdaptiveSizePolicy::eden_increment_with_supplement_aligned_up(

   size_t cur_eden) {

   size_t result = eden_increment(cur_eden,

     YoungGenerationSizeIncrement + _young_gen_size_increment_supplement);

   return align_size_up(result, _intra_generation_alignment);

 }

 size_t PSAdaptiveSizePolicy::eden_decrement_aligned_down(size_t cur_eden) {

   size_t eden_heap_delta = eden_decrement(cur_eden);

   return align_size_down(eden_heap_delta, _intra_generation_alignment);

 }

 size_t PSAdaptiveSizePolicy::eden_decrement(size_t cur_eden) {

   size_t eden_heap_delta = eden_increment(cur_eden) /

     AdaptiveSizeDecrementScaleFactor;

   return eden_heap_delta;

 }

 size_t PSAdaptiveSizePolicy::promo_increment(size_t cur_promo,

                                              uint percent_change) {

   size_t promo_heap_delta;

   promo_heap_delta = cur_promo / 100 * percent_change;

   return promo_heap_delta;

 }

 size_t PSAdaptiveSizePolicy::promo_increment(size_t cur_promo) {

   return promo_increment(cur_promo, TenuredGenerationSizeIncrement);

 }

 size_t PSAdaptiveSizePolicy::promo_increment_aligned_up(size_t cur_promo) {

   size_t result =  promo_increment(cur_promo, TenuredGenerationSizeIncrement);

   return align_size_up(result, _intra_generation_alignment);

 }

 size_t PSAdaptiveSizePolicy::promo_increment_aligned_down(size_t cur_promo) {

   size_t result =  promo_increment(cur_promo, TenuredGenerationSizeIncrement);

   return align_size_down(result, _intra_generation_alignment);

 }

 size_t PSAdaptiveSizePolicy::promo_increment_with_supplement_aligned_up(

   size_t cur_promo) {

   size_t result =  promo_increment(cur_promo,

     TenuredGenerationSizeIncrement + _old_gen_size_increment_supplement);

   return align_size_up(result, _intra_generation_alignment);

 }

 size_t PSAdaptiveSizePolicy::promo_decrement_aligned_down(size_t cur_promo) {

   size_t promo_heap_delta = promo_decrement(cur_promo);

   return align_size_down(promo_heap_delta, _intra_generation_alignment);

 }

 size_t PSAdaptiveSizePolicy::promo_decrement(size_t cur_promo) {

   size_t promo_heap_delta = promo_increment(cur_promo);

   promo_heap_delta = promo_heap_delta / AdaptiveSizeDecrementScaleFactor;

   return promo_heap_delta;

 }

 int PSAdaptiveSizePolicy::compute_survivor_space_size_and_threshold(

                                              bool is_survivor_overflow,

                                              int tenuring_threshold,

                                              size_t survivor_limit) {

   assert(survivor_limit >= _intra_generation_alignment,

          "survivor_limit too small");

   assert((size_t)align_size_down(survivor_limit, _intra_generation_alignment)

          == survivor_limit, "survivor_limit not aligned");

   // This method is called even if the tenuring threshold and survivor

   // spaces are not adjusted so that the averages are sampled above.

   if (!UsePSAdaptiveSurvivorSizePolicy ||

       !young_gen_policy_is_ready()) {

     return tenuring_threshold;

   }

   // We'll decide whether to increase or decrease the tenuring

   // threshold based partly on the newly computed survivor size

   // (if we hit the maximum limit allowed, we'll always choose to

   // decrement the threshold).

   bool incr_tenuring_threshold = false;

   bool decr_tenuring_threshold = false;

   set_decrement_tenuring_threshold_for_gc_cost(false);

   set_increment_tenuring_threshold_for_gc_cost(false);

   set_decrement_tenuring_threshold_for_survivor_limit(false);

   if (!is_survivor_overflow) {

     // Keep running averages on how much survived

     // We use the tenuring threshold to equalize the cost of major

     // and minor collections.

     // ThresholdTolerance is used to indicate how sensitive the

     // tenuring threshold is to differences in cost betweent the

     // collection types.

     // Get the times of interest. This involves a little work, so

     // we cache the values here.

     const double major_cost = major_gc_cost();

     const double minor_cost = minor_gc_cost();

     if (minor_cost > major_cost * _threshold_tolerance_percent) {

       // Minor times are getting too long;  lower the threshold so

       // less survives and more is promoted.

       decr_tenuring_threshold = true;

       set_decrement_tenuring_threshold_for_gc_cost(true);

     } else if (major_cost > minor_cost * _threshold_tolerance_percent) {

       // Major times are too long, so we want less promotion.

       incr_tenuring_threshold = true;

       set_increment_tenuring_threshold_for_gc_cost(true);

     }

   } else {

     // Survivor space overflow occurred, so promoted and survived are

     // not accurate. We'll make our best guess by combining survived

     // and promoted and count them as survivors.

     //

     // We'll lower the tenuring threshold to see if we can correct

     // things. Also, set the survivor size conservatively. We're

     // trying to avoid many overflows from occurring if defnew size

     // is just too small.

     decr_tenuring_threshold = true;

   }

   // The padded average also maintains a deviation from the average;

   // we use this to see how good of an estimate we have of what survived.

   // We're trying to pad the survivor size as little as possible without

   // overflowing the survivor spaces.

   size_t target_size = align_size_up((size_t)_avg_survived->padded_average(),

                                      _intra_generation_alignment);

   target_size = MAX2(target_size, _intra_generation_alignment);

   if (target_size > survivor_limit) {

     // Target size is bigger than we can handle. Let's also reduce

     // the tenuring threshold.

     target_size = survivor_limit;

     decr_tenuring_threshold = true;

     set_decrement_tenuring_threshold_for_survivor_limit(true);

   }

   // Finally, increment or decrement the tenuring threshold, as decided above.

   // We test for decrementing first, as we might have hit the target size

   // limit.

   if (decr_tenuring_threshold && !(AlwaysTenure || NeverTenure)) {

     if (tenuring_threshold > 1) {

       tenuring_threshold--;

     }

   } else if (incr_tenuring_threshold && !(AlwaysTenure || NeverTenure)) {

     if (tenuring_threshold < MaxTenuringThreshold) {

       tenuring_threshold++;

     }

   }

   // We keep a running average of the amount promoted which is used

   // to decide when we should collect the old generation (when

   // the amount of old gen free space is less than what we expect to

   // promote).

   if (PrintAdaptiveSizePolicy) {

     // A little more detail if Verbose is on

     if (Verbose) {

       gclog_or_tty->print( "  avg_survived: %f"

                   "  avg_deviation: %f",

                   _avg_survived->average(),

                   _avg_survived->deviation());

     }

     gclog_or_tty->print( "  avg_survived_padded_avg: %f",

                 _avg_survived->padded_average());

     if (Verbose) {

       gclog_or_tty->print( "  avg_promoted_avg: %f"

                   "  avg_promoted_dev: %f",

                   avg_promoted()->average(),

                   avg_promoted()->deviation());

     }

     gclog_or_tty->print( "  avg_promoted_padded_avg: %f"

                 "  avg_pretenured_padded_avg: %f"

                 "  tenuring_thresh: %d"

                 "  target_size: " SIZE_FORMAT,

                 avg_promoted()->padded_average(),

                 _avg_pretenured->padded_average(),

                 tenuring_threshold, target_size);

     tty->cr();

   }

   set_survivor_size(target_size);

   return tenuring_threshold;

 }

 void PSAdaptiveSizePolicy::update_averages(bool is_survivor_overflow,

                                            size_t survived,

                                            size_t promoted) {

   // Update averages

   if (!is_survivor_overflow) {

     // Keep running averages on how much survived

     _avg_survived->sample(survived);

   } else {

     size_t survived_guess = survived + promoted;

     _avg_survived->sample(survived_guess);

   }

   avg_promoted()->sample(promoted + _avg_pretenured->padded_average());

   if (PrintAdaptiveSizePolicy) {

     gclog_or_tty->print(

                   "AdaptiveSizePolicy::compute_survivor_space_size_and_thresh:"

                   "  survived: "  SIZE_FORMAT

                   "  promoted: "  SIZE_FORMAT

                   "  overflow: %s",

                   survived, promoted, is_survivor_overflow ? "true" : "false");

   }

 }

 bool PSAdaptiveSizePolicy::print_adaptive_size_policy_on(outputStream* st)

   const {

   if (!UseAdaptiveSizePolicy) return false;

   return AdaptiveSizePolicy::print_adaptive_size_policy_on(

                           st,

                           PSScavenge::tenuring_threshold());

 }