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/*
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* Copyright 2002-2007 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*
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*/
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// This class keeps statistical information and computes the
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// optimal free space for both the young and old generation
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// based on current application characteristics (based on gc cost
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// and application footprint).
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//
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// It also computes an optimal tenuring threshold between the young
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// and old generations, so as to equalize the cost of collections
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// of those generations, as well as optimial survivor space sizes
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// for the young generation.
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//
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// While this class is specifically intended for a generational system
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// consisting of a young gen (containing an Eden and two semi-spaces)
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// and a tenured gen, as well as a perm gen for reflective data, it
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// makes NO references to specific generations.
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//
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// 05/02/2003 Update
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// The 1.5 policy makes use of data gathered for the costs of GC on
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// specific generations. That data does reference specific
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// generation. Also diagnostics specific to generations have
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// been added.
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// Forward decls
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class elapsedTimer;
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class PSAdaptiveSizePolicy : public AdaptiveSizePolicy {
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friend class PSGCAdaptivePolicyCounters;
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private:
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// These values are used to record decisions made during the
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// policy. For example, if the young generation was decreased
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// to decrease the GC cost of minor collections the value
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// decrease_young_gen_for_throughput_true is used.
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// Last calculated sizes, in bytes, and aligned
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// NEEDS_CLEANUP should use sizes.hpp, but it works in ints, not size_t's
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// Time statistics
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AdaptivePaddedAverage* _avg_major_pause;
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// Footprint statistics
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AdaptiveWeightedAverage* _avg_base_footprint;
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// Statistical data gathered for GC
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GCStats _gc_stats;
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size_t _survivor_size_limit; // Limit in bytes of survivor size
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const double _collection_cost_margin_fraction;
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// Variable for estimating the major and minor pause times.
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// These variables represent linear least-squares fits of
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// the data.
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// major pause time vs. old gen size
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LinearLeastSquareFit* _major_pause_old_estimator;
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// major pause time vs. young gen size
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LinearLeastSquareFit* _major_pause_young_estimator;
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// These record the most recent collection times. They
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// are available as an alternative to using the averages
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// for making ergonomic decisions.
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double _latest_major_mutator_interval_seconds;
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const size_t _intra_generation_alignment; // alignment for eden, survivors
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const double _gc_minor_pause_goal_sec; // goal for maximum minor gc pause
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// The amount of live data in the heap at the last full GC, used
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// as a baseline to help us determine when we need to perform the
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// next full GC.
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size_t _live_at_last_full_gc;
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// decrease/increase the old generation for minor pause time
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int _change_old_gen_for_min_pauses;
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// increase/decrease the young generation for major pause time
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int _change_young_gen_for_maj_pauses;
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// Flag indicating that the adaptive policy is ready to use
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bool _old_gen_policy_is_ready;
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// Changing the generation sizing depends on the data that is
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// gathered about the effects of changes on the pause times and
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// throughput. These variable count the number of data points
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// gathered. The policy may use these counters as a threshhold
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// for reliable data.
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julong _young_gen_change_for_major_pause_count;
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// To facilitate faster growth at start up, supplement the normal
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// growth percentage for the young gen eden and the
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// old gen space for promotion with these value which decay
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// with increasing collections.
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uint _young_gen_size_increment_supplement;
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uint _old_gen_size_increment_supplement;
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// The number of bytes absorbed from eden into the old gen by moving the
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// boundary over live data.
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size_t _bytes_absorbed_from_eden;
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private:
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// Accessors
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AdaptivePaddedAverage* avg_major_pause() const { return _avg_major_pause; }
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double gc_minor_pause_goal_sec() const { return _gc_minor_pause_goal_sec; }
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// Change the young generation size to achieve a minor GC pause time goal
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void adjust_for_minor_pause_time(bool is_full_gc,
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size_t* desired_promo_size_ptr,
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size_t* desired_eden_size_ptr);
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// Change the generation sizes to achieve a GC pause time goal
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// Returned sizes are not necessarily aligned.
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void adjust_for_pause_time(bool is_full_gc,
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size_t* desired_promo_size_ptr,
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size_t* desired_eden_size_ptr);
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// Change the generation sizes to achieve an application throughput goal
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// Returned sizes are not necessarily aligned.
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void adjust_for_throughput(bool is_full_gc,
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size_t* desired_promo_size_ptr,
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size_t* desired_eden_size_ptr);
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// Change the generation sizes to achieve minimum footprint
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// Returned sizes are not aligned.
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size_t adjust_promo_for_footprint(size_t desired_promo_size,
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size_t desired_total);
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size_t adjust_eden_for_footprint(size_t desired_promo_size,
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size_t desired_total);
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// Size in bytes for an increment or decrement of eden.
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virtual size_t eden_increment(size_t cur_eden, uint percent_change);
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virtual size_t eden_decrement(size_t cur_eden);
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size_t eden_decrement_aligned_down(size_t cur_eden);
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size_t eden_increment_with_supplement_aligned_up(size_t cur_eden);
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// Size in bytes for an increment or decrement of the promotion area
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virtual size_t promo_increment(size_t cur_promo, uint percent_change);
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virtual size_t promo_decrement(size_t cur_promo);
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size_t promo_decrement_aligned_down(size_t cur_promo);
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size_t promo_increment_with_supplement_aligned_up(size_t cur_promo);
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// Decay the supplemental growth additive.
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void decay_supplemental_growth(bool is_full_gc);
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// Returns a change that has been scaled down. Result
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// is not aligned. (If useful, move to some shared
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// location.)
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size_t scale_down(size_t change, double part, double total);
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protected:
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// Time accessors
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// Footprint accessors
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size_t live_space() const {
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return (size_t)(avg_base_footprint()->average() +
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avg_young_live()->average() +
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avg_old_live()->average());
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}
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size_t free_space() const {
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return _eden_size + _promo_size;
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}
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void set_promo_size(size_t new_size) {
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_promo_size = new_size;
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}
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void set_survivor_size(size_t new_size) {
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_survivor_size = new_size;
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}
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// Update estimators
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void update_minor_pause_old_estimator(double minor_pause_in_ms);
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virtual GCPolicyKind kind() const { return _gc_ps_adaptive_size_policy; }
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public:
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// Use by ASPSYoungGen and ASPSOldGen to limit boundary moving.
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size_t eden_increment_aligned_up(size_t cur_eden);
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size_t eden_increment_aligned_down(size_t cur_eden);
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size_t promo_increment_aligned_up(size_t cur_promo);
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size_t promo_increment_aligned_down(size_t cur_promo);
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virtual size_t eden_increment(size_t cur_eden);
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virtual size_t promo_increment(size_t cur_promo);
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// Accessors for use by performance counters
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AdaptivePaddedNoZeroDevAverage* avg_promoted() const {
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return _gc_stats.avg_promoted();
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}
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AdaptiveWeightedAverage* avg_base_footprint() const {
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return _avg_base_footprint;
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}
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// Input arguments are initial free space sizes for young and old
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// generations, the initial survivor space size, the
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// alignment values and the pause & throughput goals.
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//
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// NEEDS_CLEANUP this is a singleton object
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PSAdaptiveSizePolicy(size_t init_eden_size,
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size_t init_promo_size,
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size_t init_survivor_size,
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size_t intra_generation_alignment,
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double gc_pause_goal_sec,
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double gc_minor_pause_goal_sec,
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uint gc_time_ratio);
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// Methods indicating events of interest to the adaptive size policy,
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// called by GC algorithms. It is the responsibility of users of this
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// policy to call these methods at the correct times!
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void major_collection_begin();
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void major_collection_end(size_t amount_live, GCCause::Cause gc_cause);
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//
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void tenured_allocation(size_t size) {
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_avg_pretenured->sample(size);
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}
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// Accessors
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// NEEDS_CLEANUP should use sizes.hpp
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size_t calculated_old_free_size_in_bytes() const {
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return (size_t)(_promo_size + avg_promoted()->padded_average());
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}
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size_t average_old_live_in_bytes() const {
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return (size_t) avg_old_live()->average();
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}
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size_t average_promoted_in_bytes() const {
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return (size_t)avg_promoted()->average();
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}
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size_t padded_average_promoted_in_bytes() const {
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return (size_t)avg_promoted()->padded_average();
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}
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int change_young_gen_for_maj_pauses() {
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return _change_young_gen_for_maj_pauses;
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}
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void set_change_young_gen_for_maj_pauses(int v) {
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_change_young_gen_for_maj_pauses = v;
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}
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int change_old_gen_for_min_pauses() {
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return _change_old_gen_for_min_pauses;
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}
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void set_change_old_gen_for_min_pauses(int v) {
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_change_old_gen_for_min_pauses = v;
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}
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// Return true if the old generation size was changed
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// to try to reach a pause time goal.
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bool old_gen_changed_for_pauses() {
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bool result = _change_old_gen_for_maj_pauses != 0 ||
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_change_old_gen_for_min_pauses != 0;
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return result;
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}
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// Return true if the young generation size was changed
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// to try to reach a pause time goal.
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bool young_gen_changed_for_pauses() {
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bool result = _change_young_gen_for_min_pauses != 0 ||
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_change_young_gen_for_maj_pauses != 0;
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return result;
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}
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// end flags for pause goal
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// Return true if the old generation size was changed
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// to try to reach a throughput goal.
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bool old_gen_changed_for_throughput() {
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bool result = _change_old_gen_for_throughput != 0;
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return result;
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}
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// Return true if the young generation size was changed
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// to try to reach a throughput goal.
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bool young_gen_changed_for_throughput() {
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bool result = _change_young_gen_for_throughput != 0;
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return result;
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}
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int decrease_for_footprint() { return _decrease_for_footprint; }
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// Accessors for estimators. The slope of the linear fit is
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// currently all that is used for making decisions.
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LinearLeastSquareFit* major_pause_old_estimator() {
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return _major_pause_old_estimator;
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}
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LinearLeastSquareFit* major_pause_young_estimator() {
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return _major_pause_young_estimator;
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}
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virtual void clear_generation_free_space_flags();
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float major_pause_old_slope() { return _major_pause_old_estimator->slope(); }
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float major_pause_young_slope() {
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return _major_pause_young_estimator->slope();
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}
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float major_collection_slope() { return _major_collection_estimator->slope();}
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bool old_gen_policy_is_ready() { return _old_gen_policy_is_ready; }
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// Given the amount of live data in the heap, should we
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// perform a Full GC?
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bool should_full_GC(size_t live_in_old_gen);
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// Calculates optimial free space sizes for both the old and young
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// generations. Stores results in _eden_size and _promo_size.
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// Takes current used space in all generations as input, as well
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// as an indication if a full gc has just been performed, for use
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// in deciding if an OOM error should be thrown.
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void compute_generation_free_space(size_t young_live,
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size_t eden_live,
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size_t old_live,
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size_t perm_live,
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size_t cur_eden, // current eden in bytes
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size_t max_old_gen_size,
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size_t max_eden_size,
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bool is_full_gc,
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GCCause::Cause gc_cause);
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// Calculates new survivor space size; returns a new tenuring threshold
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// value. Stores new survivor size in _survivor_size.
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int compute_survivor_space_size_and_threshold(bool is_survivor_overflow,
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int tenuring_threshold,
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size_t survivor_limit);
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// Return the maximum size of a survivor space if the young generation were of
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// size gen_size.
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size_t max_survivor_size(size_t gen_size) {
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// Never allow the target survivor size to grow more than MinSurvivorRatio
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// of the young generation size. We cannot grow into a two semi-space
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// system, with Eden zero sized. Even if the survivor space grows, from()
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// might grow by moving the bottom boundary "down" -- so from space will
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// remain almost full anyway (top() will be near end(), but there will be a
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// large filler object at the bottom).
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const size_t sz = gen_size / MinSurvivorRatio;
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const size_t alignment = _intra_generation_alignment;
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return sz > alignment ? align_size_down(sz, alignment) : alignment;
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}
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size_t live_at_last_full_gc() {
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return _live_at_last_full_gc;
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}
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size_t bytes_absorbed_from_eden() const { return _bytes_absorbed_from_eden; }
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void reset_bytes_absorbed_from_eden() { _bytes_absorbed_from_eden = 0; }
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void set_bytes_absorbed_from_eden(size_t val) {
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_bytes_absorbed_from_eden = val;
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}
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// Update averages that are always used (even
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// if adaptive sizing is turned off).
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void update_averages(bool is_survivor_overflow,
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size_t survived,
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size_t promoted);
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// Printing support
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virtual bool print_adaptive_size_policy_on(outputStream* st) const;
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};
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