/*

 * Copyright (c) 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 "memory/allocation.hpp"

// There are three command line options related to the young gen size:

// NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is

// just a short form for NewSize==MaxNewSize). G1 will use its internal

// heuristics to calculate the actual young gen size, so these options

// basically only limit the range within which G1 can pick a young gen

// size. Also, these are general options taking byte sizes. G1 will

// internally work with a number of regions instead. So, some rounding

// will occur.

//

// If nothing related to the the young gen size is set on the command

// line we should allow the young gen to be between G1NewSizePercent

// and G1MaxNewSizePercent of the heap size. This means that every time

// the heap size changes, the limits for the young gen size will be

// recalculated.

//

// If only -XX:NewSize is set we should use the specified value as the

// minimum size for young gen. Still using G1MaxNewSizePercent of the

// heap as maximum.

//

// If only -XX:MaxNewSize is set we should use the specified value as the

// maximum size for young gen. Still using G1NewSizePercent of the heap

// as minimum.

//

// If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.

// No updates when the heap size changes. There is a special case when

// NewSize==MaxNewSize. This is interpreted as "fixed" and will use a

// different heuristic for calculating the collection set when we do mixed

// collection.

//

// If only -XX:NewRatio is set we should use the specified ratio of the heap

// as both min and max. This will be interpreted as "fixed" just like the

// NewSize==MaxNewSize case above. But we will update the min and max

// every time the heap size changes.

//

// NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is

// combined with either NewSize or MaxNewSize. (A warning message is printed.)

class G1YoungGenSizer : public CHeapObj<mtGC> {

private:

  enum SizerKind {

    SizerDefaults,

    SizerNewSizeOnly,

    SizerMaxNewSizeOnly,

    SizerMaxAndNewSize,

    SizerNewRatio

  };

  SizerKind _sizer_kind;

  uint _min_desired_young_length;

  uint _max_desired_young_length;

  bool _adaptive_size;

  uint calculate_default_min_length(uint new_number_of_heap_regions);

  uint calculate_default_max_length(uint new_number_of_heap_regions);

  // Update the given values for minimum and maximum young gen length in regions

  // given the number of heap regions depending on the kind of sizing algorithm.

  void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);

public:

  G1YoungGenSizer();

  // Calculate the maximum length of the young gen given the number of regions

  // depending on the sizing algorithm.

  uint max_young_length(uint number_of_heap_regions);

  void heap_size_changed(uint new_number_of_heap_regions);

  uint min_desired_young_length() {

    return _min_desired_young_length;

  }

  uint max_desired_young_length() {

    return _max_desired_young_length;

  }

  bool adaptive_young_list_length() const {

    return _adaptive_size;

  }

};