110 lines
4.3 KiB
C++
110 lines
4.3 KiB
C++
/*
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* Copyright (c) 2016, 2018, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_VM_GC_G1_G1YOUNGGENSIZER_HPP
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#define SHARE_VM_GC_G1_G1YOUNGGENSIZER_HPP
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#include "utilities/globalDefinitions.hpp"
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// There are three command line options related to the young gen size:
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// NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
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// just a short form for NewSize==MaxNewSize). G1 will use its internal
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// heuristics to calculate the actual young gen size, so these options
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// basically only limit the range within which G1 can pick a young gen
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// size. Also, these are general options taking byte sizes. G1 will
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// internally work with a number of regions instead. So, some rounding
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// will occur.
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//
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// If nothing related to the the young gen size is set on the command
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// line we should allow the young gen to be between G1NewSizePercent
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// and G1MaxNewSizePercent of the heap size. This means that every time
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// the heap size changes, the limits for the young gen size will be
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// recalculated.
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//
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// If only -XX:NewSize is set we should use the specified value as the
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// minimum size for young gen. Still using G1MaxNewSizePercent of the
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// heap as maximum.
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//
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// If only -XX:MaxNewSize is set we should use the specified value as the
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// maximum size for young gen. Still using G1NewSizePercent of the heap
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// as minimum.
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//
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// If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
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// No updates when the heap size changes. There is a special case when
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// NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
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// different heuristic for calculating the collection set when we do mixed
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// collection.
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//
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// If only -XX:NewRatio is set we should use the specified ratio of the heap
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// as both min and max. This will be interpreted as "fixed" just like the
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// NewSize==MaxNewSize case above. But we will update the min and max
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// every time the heap size changes.
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//
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// NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
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// combined with either NewSize or MaxNewSize. (A warning message is printed.)
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class G1YoungGenSizer {
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private:
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enum SizerKind {
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SizerDefaults,
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SizerNewSizeOnly,
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SizerMaxNewSizeOnly,
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SizerMaxAndNewSize,
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SizerNewRatio
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};
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SizerKind _sizer_kind;
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uint _min_desired_young_length;
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uint _max_desired_young_length;
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// False when using a fixed young generation size due to command-line options,
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// true otherwise.
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bool _adaptive_size;
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uint calculate_default_min_length(uint new_number_of_heap_regions);
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uint calculate_default_max_length(uint new_number_of_heap_regions);
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// Update the given values for minimum and maximum young gen length in regions
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// given the number of heap regions depending on the kind of sizing algorithm.
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void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
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public:
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G1YoungGenSizer();
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// Calculate the maximum length of the young gen given the number of regions
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// depending on the sizing algorithm.
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void adjust_max_new_size(uint number_of_heap_regions);
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void heap_size_changed(uint new_number_of_heap_regions);
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uint min_desired_young_length() const {
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return _min_desired_young_length;
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}
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uint max_desired_young_length() const {
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return _max_desired_young_length;
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}
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bool adaptive_young_list_length() const {
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return _adaptive_size;
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}
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};
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#endif // SHARE_VM_GC_G1_G1YOUNGGENSIZER_HPP
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