/*

 * Copyright (c) 2004, 2016, 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

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 */

#include "precompiled.hpp"

#include "gc/shared/adaptiveSizePolicy.hpp"

#include "gc/shared/collectorPolicy.hpp"

#include "gc/shared/gcCause.hpp"

#include "gc/shared/workgroup.hpp"

#include "logging/log.hpp"

#include "runtime/timer.hpp"

#include "utilities/ostream.hpp"

elapsedTimer AdaptiveSizePolicy::_minor_timer;

elapsedTimer AdaptiveSizePolicy::_major_timer;

bool AdaptiveSizePolicy::_debug_perturbation = false;

// 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) :

    _eden_size(init_eden_size),

    _promo_size(init_promo_size),

    _survivor_size(init_survivor_size),

    _gc_pause_goal_sec(gc_pause_goal_sec),

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

    _gc_overhead_limit_exceeded(false),

    _print_gc_overhead_limit_would_be_exceeded(false),

    _gc_overhead_limit_count(0),

    _latest_minor_mutator_interval_seconds(0),

    _threshold_tolerance_percent(1.0 + ThresholdTolerance/100.0),

    _young_gen_change_for_minor_throughput(0),

    _old_gen_change_for_major_throughput(0) {

  assert(AdaptiveSizePolicyGCTimeLimitThreshold > 0,

    "No opportunity to clear SoftReferences before GC overhead limit");

  _avg_minor_pause    =

    new AdaptivePaddedAverage(AdaptiveTimeWeight, PausePadding);

  _avg_minor_interval = new AdaptiveWeightedAverage(AdaptiveTimeWeight);

  _avg_minor_gc_cost  = new AdaptiveWeightedAverage(AdaptiveTimeWeight);

  _avg_major_gc_cost  = new AdaptiveWeightedAverage(AdaptiveTimeWeight);

  _avg_young_live     = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);

  _avg_old_live       = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);

  _avg_eden_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);

  // Start the timers

  _minor_timer.start();

  _young_gen_policy_is_ready = false;

}

//  If the number of GC threads was set on the command line,

// use it.

//  Else

//    Calculate the number of GC threads based on the number of Java threads.

//    Calculate the number of GC threads based on the size of the heap.

//    Use the larger.

uint AdaptiveSizePolicy::calc_default_active_workers(uintx total_workers,

                                                     const uintx min_workers,

                                                     uintx active_workers,

                                                     uintx application_workers) {

  // If the user has specifically set the number of

  // GC threads, use them.

  // If the user has turned off using a dynamic number of GC threads

  // or the users has requested a specific number, set the active

  // number of workers to all the workers.

  uintx new_active_workers = total_workers;

  uintx prev_active_workers = active_workers;

  uintx active_workers_by_JT = 0;

  uintx active_workers_by_heap_size = 0;

  // Always use at least min_workers but use up to

  // GCThreadsPerJavaThreads * application threads.

  active_workers_by_JT =

    MAX2((uintx) GCWorkersPerJavaThread * application_workers,

         min_workers);

  // Choose a number of GC threads based on the current size

  // of the heap.  This may be complicated because the size of

  // the heap depends on factors such as the throughput goal.

  // Still a large heap should be collected by more GC threads.

  active_workers_by_heap_size =

      MAX2((size_t) 2U, Universe::heap()->capacity() / HeapSizePerGCThread);

  uintx max_active_workers =

    MAX2(active_workers_by_JT, active_workers_by_heap_size);

  new_active_workers = MIN2(max_active_workers, (uintx) total_workers);

  // Increase GC workers instantly but decrease them more

  // slowly.

  if (new_active_workers < prev_active_workers) {

    new_active_workers =

      MAX2(min_workers, (prev_active_workers + new_active_workers) / 2);

  }

  // Check once more that the number of workers is within the limits.

  assert(min_workers <= total_workers, "Minimum workers not consistent with total workers");

  assert(new_active_workers >= min_workers, "Minimum workers not observed");

  assert(new_active_workers <= total_workers, "Total workers not observed");

  if (ForceDynamicNumberOfGCThreads) {

    // Assume this is debugging and jiggle the number of GC threads.

    if (new_active_workers == prev_active_workers) {

      if (new_active_workers < total_workers) {

        new_active_workers++;

      } else if (new_active_workers > min_workers) {

        new_active_workers--;

      }

    }

    if (new_active_workers == total_workers) {

      if (_debug_perturbation) {

        new_active_workers =  min_workers;

      }

      _debug_perturbation = !_debug_perturbation;

    }

    assert((new_active_workers <= ParallelGCThreads) &&

           (new_active_workers >= min_workers),

      "Jiggled active workers too much");

  }

  log_trace(gc, task)("GCTaskManager::calc_default_active_workers() : "

     "active_workers(): " UINTX_FORMAT "  new_active_workers: " UINTX_FORMAT "  "

     "prev_active_workers: " UINTX_FORMAT "\n"

     " active_workers_by_JT: " UINTX_FORMAT "  active_workers_by_heap_size: " UINTX_FORMAT,

     active_workers, new_active_workers, prev_active_workers,

     active_workers_by_JT, active_workers_by_heap_size);

  assert(new_active_workers > 0, "Always need at least 1");

  return new_active_workers;

}

uint AdaptiveSizePolicy::calc_active_workers(uintx total_workers,

                                             uintx active_workers,

                                             uintx application_workers) {

  // If the user has specifically set the number of

  // GC threads, use them.

  // If the user has turned off using a dynamic number of GC threads

  // or the users has requested a specific number, set the active

  // number of workers to all the workers.

  uint new_active_workers;

  if (!UseDynamicNumberOfGCThreads ||

     (!FLAG_IS_DEFAULT(ParallelGCThreads) && !ForceDynamicNumberOfGCThreads)) {

    new_active_workers = total_workers;

  } else {

    uintx min_workers = (total_workers == 1) ? 1 : 2;

    new_active_workers = calc_default_active_workers(total_workers,

                                                     min_workers,

                                                     active_workers,

                                                     application_workers);

  }

  assert(new_active_workers > 0, "Always need at least 1");

  return new_active_workers;

}

uint AdaptiveSizePolicy::calc_active_conc_workers(uintx total_workers,

                                                  uintx active_workers,

                                                  uintx application_workers) {

  if (!UseDynamicNumberOfGCThreads ||

     (!FLAG_IS_DEFAULT(ConcGCThreads) && !ForceDynamicNumberOfGCThreads)) {

    return ConcGCThreads;

  } else {

    uint no_of_gc_threads = calc_default_active_workers(total_workers,

                                                        1, /* Minimum number of workers */

                                                        active_workers,

                                                        application_workers);

    return no_of_gc_threads;

  }

}

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);

}

void AdaptiveSizePolicy::check_gc_overhead_limit(

                                          size_t young_live,

                                          size_t eden_live,

                                          size_t max_old_gen_size,

                                          size_t max_eden_size,

                                          bool   is_full_gc,

                                          GCCause::Cause gc_cause,

                                          CollectorPolicy* collector_policy) {

  // Ignore explicit GC's.  Exiting here does not set the flag and

  // does not reset the count.  Updating of the averages for system

  // GC's is still controlled by UseAdaptiveSizePolicyWithSystemGC.

  if (GCCause::is_user_requested_gc(gc_cause) ||

      GCCause::is_serviceability_requested_gc(gc_cause)) {

    return;

  }

  // eden_limit 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 gc costs are high

  // and the space being recovered by a collection is low.

  // free_in_young_gen is the free space in the young generation

  // after a collection and promo_live is the free space in the old

  // generation after a collection.

  //

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

  // young gen or the average of the live in the young gen.

  // 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()->average());

  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()->average());

  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 mem_free_limit = total_mem * (GCHeapFreeLimit/100.0);

  const double mem_free_old_limit = max_old_gen_size * (GCHeapFreeLimit/100.0);

  const double mem_free_eden_limit = max_eden_size * (GCHeapFreeLimit/100.0);

  const double gc_cost_limit = GCTimeLimit/100.0;

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

  // 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)(

        "PSAdaptiveSizePolicy::check_gc_overhead_limit:"

        " 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);

  bool print_gc_overhead_limit_would_be_exceeded = false;

  if (is_full_gc) {

    if (gc_cost() > gc_cost_limit &&

      free_in_old_gen < (size_t) mem_free_old_limit &&

      free_in_eden < (size_t) mem_free_eden_limit) {

      // Collections, on average, are taking too much time, and

      //      gc_cost() > gc_cost_limit

      // we have too little space available after a full gc.

      //      total_free_limit < mem_free_limit

      // where

      //   total_free_limit is the free space available in

      //     both generations

      //   total_mem is the total space available for allocation

      //     in both generations (survivor spaces are not included

      //     just as they are not included in eden_limit).

      //   mem_free_limit is a fraction of total_mem judged to be an

      //     acceptable amount that is still unused.

      // The heap can ask for the value of this variable when deciding

      // whether to thrown an OutOfMemory error.

      // Note that the gc time limit test only works for the collections

      // of the young gen + tenured gen and not for collections of the

      // permanent gen.  That is because the calculation of the space

      // freed by the collection is the free space in the young gen +

      // tenured gen.

      // At this point the GC overhead limit is being exceeded.

      inc_gc_overhead_limit_count();

      if (UseGCOverheadLimit) {

        if (gc_overhead_limit_count() >=

            AdaptiveSizePolicyGCTimeLimitThreshold){

          // All conditions have been met for throwing an out-of-memory

          set_gc_overhead_limit_exceeded(true);

          // Avoid consecutive OOM due to the gc time limit by resetting

          // the counter.

          reset_gc_overhead_limit_count();

        } else {

          // The required consecutive collections which exceed the

          // GC time limit may or may not have been reached. We

          // are approaching that condition and so as not to

          // throw an out-of-memory before all SoftRef's have been

          // cleared, set _should_clear_all_soft_refs in CollectorPolicy.

          // The clearing will be done on the next GC.

          bool near_limit = gc_overhead_limit_near();

          if (near_limit) {