/*

 * Copyright (c) 2004, 2019, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "gc/shared/adaptiveSizePolicy.hpp"

#include "gc/shared/gcCause.hpp"

#include "gc/shared/gcUtil.inline.hpp"

#include "logging/log.hpp"

#include "runtime/timer.hpp"

elapsedTimer AdaptiveSizePolicy::_minor_timer;

elapsedTimer AdaptiveSizePolicy::_major_timer;

// The throughput goal is implemented as

//      _throughput_goal = 1 - ( 1 / (1 + gc_cost_ratio))

// gc_cost_ratio is the ratio

//      application cost / gc cost

// For example a gc_cost_ratio of 4 translates into a

// throughput goal of .80

AdaptiveSizePolicy::AdaptiveSizePolicy(size_t init_eden_size,

                                       size_t init_promo_size,

                                       size_t init_survivor_size,

                                       double gc_pause_goal_sec,

                                       uint gc_cost_ratio) :

    _throughput_goal(1.0 - double(1.0 / (1.0 + (double) gc_cost_ratio))),

    _eden_size(init_eden_size),

    _promo_size(init_promo_size),

    _survivor_size(init_survivor_size),

    _avg_minor_pause(new AdaptivePaddedAverage(AdaptiveTimeWeight, PausePadding)),

    _avg_minor_interval(new AdaptiveWeightedAverage(AdaptiveTimeWeight)),

    _avg_minor_gc_cost(new AdaptiveWeightedAverage(AdaptiveTimeWeight)),

    _avg_major_interval(new AdaptiveWeightedAverage(AdaptiveTimeWeight)),

    _avg_major_gc_cost(new AdaptiveWeightedAverage(AdaptiveTimeWeight)),

    _avg_young_live(new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight)),

    _avg_eden_live(new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight)),

    _avg_old_live(new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight)),

    _avg_survived(new AdaptivePaddedAverage(AdaptiveSizePolicyWeight, SurvivorPadding)),

    _avg_pretenured(new AdaptivePaddedNoZeroDevAverage(AdaptiveSizePolicyWeight, SurvivorPadding)),

    _minor_pause_old_estimator(new LinearLeastSquareFit(AdaptiveSizePolicyWeight)),

    _minor_pause_young_estimator(new LinearLeastSquareFit(AdaptiveSizePolicyWeight)),

    _minor_collection_estimator(new LinearLeastSquareFit(AdaptiveSizePolicyWeight)),

    _major_collection_estimator(new LinearLeastSquareFit(AdaptiveSizePolicyWeight)),

    _latest_minor_mutator_interval_seconds(0),

    _threshold_tolerance_percent(1.0 + ThresholdTolerance/100.0),

    _gc_pause_goal_sec(gc_pause_goal_sec),

    _young_gen_policy_is_ready(false),

    _change_young_gen_for_min_pauses(0),

    _change_old_gen_for_maj_pauses(0),

    _change_old_gen_for_throughput(0),

    _change_young_gen_for_throughput(0),

    _increment_tenuring_threshold_for_gc_cost(false),

    _decrement_tenuring_threshold_for_gc_cost(false),

    _decrement_tenuring_threshold_for_survivor_limit(false),

    _decrease_for_footprint(0),

    _decide_at_full_gc(0),

    _young_gen_change_for_minor_throughput(0),

    _old_gen_change_for_major_throughput(0) {

  // Start the timers

  _minor_timer.start();

}

bool AdaptiveSizePolicy::tenuring_threshold_change() const {

  return decrement_tenuring_threshold_for_gc_cost() ||

         increment_tenuring_threshold_for_gc_cost() ||

         decrement_tenuring_threshold_for_survivor_limit();

}

void AdaptiveSizePolicy::minor_collection_begin() {

  // Update the interval time

  _minor_timer.stop();

  // Save most recent collection time

  _latest_minor_mutator_interval_seconds = _minor_timer.seconds();

  _minor_timer.reset();

  _minor_timer.start();

}

void AdaptiveSizePolicy::update_minor_pause_young_estimator(

    double minor_pause_in_ms) {

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

  _minor_pause_young_estimator->update(eden_size_in_mbytes,

    minor_pause_in_ms);

}

void AdaptiveSizePolicy::minor_collection_end(GCCause::Cause gc_cause) {

  // Update the pause time.

  _minor_timer.stop();

  if (!GCCause::is_user_requested_gc(gc_cause) ||

      UseAdaptiveSizePolicyWithSystemGC) {

    double minor_pause_in_seconds = _minor_timer.seconds();

    double minor_pause_in_ms = minor_pause_in_seconds * MILLIUNITS;

    // Sample for performance counter

    _avg_minor_pause->sample(minor_pause_in_seconds);

    // Cost of collection (unit-less)

    double collection_cost = 0.0;

    if ((_latest_minor_mutator_interval_seconds > 0.0) &&

        (minor_pause_in_seconds > 0.0)) {

      double interval_in_seconds =

        _latest_minor_mutator_interval_seconds + minor_pause_in_seconds;

      collection_cost =

        minor_pause_in_seconds / interval_in_seconds;

      _avg_minor_gc_cost->sample(collection_cost);

      // Sample for performance counter

      _avg_minor_interval->sample(interval_in_seconds);

    }

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

    // young collections have been done.

    _young_gen_policy_is_ready =

      (_avg_minor_gc_cost->count() >= AdaptiveSizePolicyReadyThreshold);

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

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

    update_minor_pause_young_estimator(minor_pause_in_ms);

    update_minor_pause_old_estimator(minor_pause_in_ms);

    log_trace(gc, ergo)("AdaptiveSizePolicy::minor_collection_end: minor gc cost: %f  average: %f",

                        collection_cost, _avg_minor_gc_cost->average());

    log_trace(gc, ergo)("  minor pause: %f minor period %f",

                        minor_pause_in_ms, _latest_minor_mutator_interval_seconds * MILLIUNITS);

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

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

    _minor_collection_estimator->update(eden_size_in_mbytes, collection_cost);

  }

  // Interval times use this timer to measure the mutator time.

  // Reset the timer after the GC pause.

  _minor_timer.reset();

  _minor_timer.start();

}

size_t AdaptiveSizePolicy::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 AdaptiveSizePolicy::eden_increment(size_t cur_eden) {

  return eden_increment(cur_eden, YoungGenerationSizeIncrement);

}

size_t AdaptiveSizePolicy::eden_decrement(size_t cur_eden) {

  size_t eden_heap_delta = eden_increment(cur_eden) /

    AdaptiveSizeDecrementScaleFactor;

  return eden_heap_delta;

}

size_t AdaptiveSizePolicy::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 AdaptiveSizePolicy::promo_increment(size_t cur_promo) {

  return promo_increment(cur_promo, TenuredGenerationSizeIncrement);

}

size_t AdaptiveSizePolicy::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;

}

double AdaptiveSizePolicy::time_since_major_gc() const {

  _major_timer.stop();

  double result = _major_timer.seconds();

  _major_timer.start();

  return result;

}

// Linear decay of major gc cost

double AdaptiveSizePolicy::decaying_major_gc_cost() const {

  double major_interval = major_gc_interval_average_for_decay();

  double major_gc_cost_average = major_gc_cost();

  double decayed_major_gc_cost = major_gc_cost_average;

  if(time_since_major_gc() > 0.0) {

    decayed_major_gc_cost = major_gc_cost() *

      (((double) AdaptiveSizeMajorGCDecayTimeScale) * major_interval)

      / time_since_major_gc();

  }

  // The decayed cost should always be smaller than the

  // average cost but the vagaries of finite arithmetic could

  // produce a larger value in decayed_major_gc_cost so protect

  // against that.

  return MIN2(major_gc_cost_average, decayed_major_gc_cost);

}

// Use a value of the major gc cost that has been decayed

// by the factor

//

//      average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale /

//        time-since-last-major-gc

//

// if the average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale

// is less than time-since-last-major-gc.

//

// In cases where there are initial major gc's that

// are of a relatively high cost but no later major

// gc's, the total gc cost can remain high because

// the major gc cost remains unchanged (since there are no major

// gc's).  In such a situation the value of the unchanging

// major gc cost can keep the mutator throughput below

// the goal when in fact the major gc cost is becoming diminishingly

// small.  Use the decaying gc cost only to decide whether to

// adjust for throughput.  Using it also to determine the adjustment

// to be made for throughput also seems reasonable but there is

// no test case to use to decide if it is the right thing to do

// don't do it yet.

double AdaptiveSizePolicy::decaying_gc_cost() const {

  double decayed_major_gc_cost = major_gc_cost();

  double avg_major_interval = major_gc_interval_average_for_decay();

  if (UseAdaptiveSizeDecayMajorGCCost &&

      (AdaptiveSizeMajorGCDecayTimeScale > 0) &&

      (avg_major_interval > 0.00)) {

    double time_since_last_major_gc = time_since_major_gc();

    // Decay the major gc cost?

    if (time_since_last_major_gc >

        ((double) AdaptiveSizeMajorGCDecayTimeScale) * avg_major_interval) {

      // Decay using the time-since-last-major-gc

      decayed_major_gc_cost = decaying_major_gc_cost();

      log_trace(gc, ergo)("decaying_gc_cost: major interval average: %f  time since last major gc: %f",

                    avg_major_interval, time_since_last_major_gc);

      log_trace(gc, ergo)("  major gc cost: %f  decayed major gc cost: %f",

                    major_gc_cost(), decayed_major_gc_cost);

    }

  }

  double result = MIN2(1.0, decayed_major_gc_cost + minor_gc_cost());

  return result;

}

void AdaptiveSizePolicy::clear_generation_free_space_flags() {

  set_change_young_gen_for_min_pauses(0);

  set_change_old_gen_for_maj_pauses(0);

  set_change_old_gen_for_throughput(0);

  set_change_young_gen_for_throughput(0);

  set_decrease_for_footprint(0);

  set_decide_at_full_gc(0);

}

class AdaptiveSizePolicyTimeOverheadTester: public GCOverheadTester {

  double _gc_cost;

 public:

  AdaptiveSizePolicyTimeOverheadTester(double gc_cost) : _gc_cost(gc_cost) {}

  bool is_exceeded() {

    return _gc_cost > (GCTimeLimit / 100.0);

  }

};

class AdaptiveSizePolicySpaceOverheadTester: public GCOverheadTester {

  size_t _eden_live;

  size_t _max_old_gen_size;

  size_t _max_eden_size;

  size_t _promo_size;

  double _avg_eden_live;

  double _avg_old_live;

 public:

  AdaptiveSizePolicySpaceOverheadTester(size_t eden_live,

                                        size_t max_old_gen_size,

                                        size_t max_eden_size,

                                        size_t promo_size,

                                        double avg_eden_live,

                                        double avg_old_live) :

    _eden_live(eden_live),

    _max_old_gen_size(max_old_gen_size),

    _max_eden_size(max_eden_size),

    _promo_size(promo_size),

    _avg_eden_live(avg_eden_live),

    _avg_old_live(avg_old_live) {}

  bool is_exceeded() {

    // _max_eden_size is the upper limit on the size of eden based on

    // the maximum size of the young generation and the sizes

    // of the survivor space.

    // The question being asked is whether the space being recovered by

    // a collection is low.

    // free_in_eden is the free space in eden after a collection and

    // free_in_old_gen is the free space in the old generation after

    // a collection.

    //

    // Use the minimum of the current value of the live in eden

    // or the average of the live in eden.

    // If the current value drops quickly, that should be taken

    // into account (i.e., don't trigger if the amount of free

    // space has suddenly jumped up).  If the current is much

    // higher than the average, use the average since it represents

    // the longer term behavior.

    const size_t live_in_eden =

      MIN2(_eden_live, (size_t)_avg_eden_live);

    const size_t free_in_eden = _max_eden_size > live_in_eden ?

      _max_eden_size - live_in_eden : 0;

    const size_t free_in_old_gen = (size_t)(_max_old_gen_size - _avg_old_live);

    const size_t total_free_limit = free_in_old_gen + free_in_eden;

    const size_t total_mem = _max_old_gen_size + _max_eden_size;

    const double free_limit_ratio = GCHeapFreeLimit / 100.0;

    const double mem_free_limit = total_mem * free_limit_ratio;

    const double mem_free_old_limit = _max_old_gen_size * free_limit_ratio;

    const double mem_free_eden_limit = _max_eden_size * free_limit_ratio;

    size_t promo_limit = (size_t)(_max_old_gen_size - _avg_old_live);

    // 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);

    log_trace(gc, ergo)(

          "AdaptiveSizePolicySpaceOverheadTester::is_exceeded:"

          " promo_limit: " SIZE_FORMAT

          " max_eden_size: " SIZE_FORMAT

          " total_free_limit: " SIZE_FORMAT

          " max_old_gen_size: " SIZE_FORMAT

          " max_eden_size: " SIZE_FORMAT

          " mem_free_limit: " SIZE_FORMAT,

          promo_limit, _max_eden_size, total_free_limit,

          _max_old_gen_size, _max_eden_size,

          (size_t)mem_free_limit);

    return free_in_old_gen < (size_t)mem_free_old_limit &&

           free_in_eden < (size_t)mem_free_eden_limit;

  }

};

void AdaptiveSizePolicy::check_gc_overhead_limit(

                                          size_t eden_live,

                                          size_t max_old_gen_size,

                                          size_t max_eden_size,

                                          bool   is_full_gc,

                                          GCCause::Cause gc_cause,

                                          SoftRefPolicy* soft_ref_policy) {

  AdaptiveSizePolicyTimeOverheadTester time_overhead(gc_cost());

  AdaptiveSizePolicySpaceOverheadTester space_overhead(eden_live,

                                                       max_old_gen_size,

                                                       max_eden_size,

                                                       _promo_size,

                                                       avg_eden_live()->average(),

                                                       avg_old_live()->average());

  _overhead_checker.check_gc_overhead_limit(&time_overhead,

                                            &space_overhead,

                                            is_full_gc,

                                            gc_cause,

                                            soft_ref_policy);

}

// Printing

bool AdaptiveSizePolicy::print() const {

  assert(UseAdaptiveSizePolicy, "UseAdaptiveSizePolicy need to be enabled.");

  if (!log_is_enabled(Debug, gc, ergo)) {

    return false;

  }

  // Print goal for which action is needed.

  char* action = NULL;

  bool change_for_pause = false;

  if ((change_old_gen_for_maj_pauses() ==

         decrease_old_gen_for_maj_pauses_true) ||

      (change_young_gen_for_min_pauses() ==

         decrease_young_gen_for_min_pauses_true)) {

    action = (char*) " *** pause time goal ***";

    change_for_pause = true;

  } else if ((change_old_gen_for_throughput() ==

               increase_old_gen_for_throughput_true) ||

            (change_young_gen_for_throughput() ==

               increase_young_gen_for_througput_true)) {

    action = (char*) " *** throughput goal ***";

  } else if (decrease_for_footprint()) {

    action = (char*) " *** reduced footprint ***";

  } else {

    // No actions were taken.  This can legitimately be the

    // situation if not enough data has been gathered to make

    // decisions.

    return false;

  }

  // Pauses

  // Currently the size of the old gen is only adjusted to

  // change the major pause times.

  char* young_gen_action = NULL;

  char* tenured_gen_action = NULL;

  char* shrink_msg = (char*) "(attempted to shrink)";

  char* grow_msg = (char*) "(attempted to grow)";

  char* no_change_msg = (char*) "(no change)";

  if (change_young_gen_for_min_pauses() ==

      decrease_young_gen_for_min_pauses_true) {

    young_gen_action = shrink_msg;

  } else if (change_for_pause) {

    young_gen_action = no_change_msg;

  }

  if (change_old_gen_for_maj_pauses() == decrease_old_gen_for_maj_pauses_true) {

    tenured_gen_action = shrink_msg;

  } else if (change_for_pause) {

    tenured_gen_action = no_change_msg;

  }

  // Throughput

  if (change_old_gen_for_throughput() == increase_old_gen_for_throughput_true) {

    assert(change_young_gen_for_throughput() ==

           increase_young_gen_for_througput_true,

           "Both generations should be growing");

    young_gen_action = grow_msg;

    tenured_gen_action = grow_msg;

  } else if (change_young_gen_for_throughput() ==

             increase_young_gen_for_througput_true) {

    // Only the young generation may grow at start up (before

    // enough full collections have been done to grow the old generation).

    young_gen_action = grow_msg;

    tenured_gen_action = no_change_msg;

  }

  // Minimum footprint

  if (decrease_for_footprint() != 0) {

    young_gen_action = shrink_msg;

    tenured_gen_action = shrink_msg;

  }

  log_debug(gc, ergo)("UseAdaptiveSizePolicy actions to meet %s", action);

  log_debug(gc, ergo)("                       GC overhead (%%)");

  log_debug(gc, ergo)("    Young generation:     %7.2f\t  %s",

                      100.0 * avg_minor_gc_cost()->average(), young_gen_action);

  log_debug(gc, ergo)("    Tenured generation:   %7.2f\t  %s",

                      100.0 * avg_major_gc_cost()->average(), tenured_gen_action);

  return true;

}

void AdaptiveSizePolicy::print_tenuring_threshold( uint new_tenuring_threshold_arg) const {

  // Tenuring threshold

  if (decrement_tenuring_threshold_for_survivor_limit()) {

    log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to avoid survivor space overflow) = %u", new_tenuring_threshold_arg);

  } else if (decrement_tenuring_threshold_for_gc_cost()) {

    log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to balance GC costs) = %u", new_tenuring_threshold_arg);

  } else if (increment_tenuring_threshold_for_gc_cost()) {

    log_debug(gc, ergo)("Tenuring threshold: (attempted to increase to balance GC costs) = %u", new_tenuring_threshold_arg);

  } else {

    assert(!tenuring_threshold_change(), "(no change was attempted)");

  }

}