1 /*
2 * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1YOUNGGENSIZER_HPP
26 #define SHARE_VM_GC_G1_G1YOUNGGENSIZER_HPP
27
28 #include "utilities/globalDefinitions.hpp"
29
30 // There are three command line options related to the young gen size:
31 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
32 // just a short form for NewSize==MaxNewSize). G1 will use its internal
33 // heuristics to calculate the actual young gen size, so these options
34 // basically only limit the range within which G1 can pick a young gen
35 // size. Also, these are general options taking byte sizes. G1 will
36 // internally work with a number of regions instead. So, some rounding
37 // will occur.
38 //
39 // If nothing related to the the young gen size is set on the command
40 // line we should allow the young gen to be between G1NewSizePercent
41 // and G1MaxNewSizePercent of the heap size. This means that every time
42 // the heap size changes, the limits for the young gen size will be
43 // recalculated.
44 //
45 // If only -XX:NewSize is set we should use the specified value as the
46 // minimum size for young gen. Still using G1MaxNewSizePercent of the
47 // heap as maximum.
48 //
49 // If only -XX:MaxNewSize is set we should use the specified value as the
50 // maximum size for young gen. Still using G1NewSizePercent of the heap
51 // as minimum.
52 //
53 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
54 // No updates when the heap size changes. There is a special case when
55 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
56 // different heuristic for calculating the collection set when we do mixed
57 // collection.
58 //
59 // If only -XX:NewRatio is set we should use the specified ratio of the heap
60 // as both min and max. This will be interpreted as "fixed" just like the
61 // NewSize==MaxNewSize case above. But we will update the min and max
62 // every time the heap size changes.
63 //
64 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
65 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
66 class G1YoungGenSizer : public CHeapObj<mtGC> {
67 private:
68 enum SizerKind {
69 SizerDefaults,
70 SizerNewSizeOnly,
71 SizerMaxNewSizeOnly,
72 SizerMaxAndNewSize,
73 SizerNewRatio
74 };
75 SizerKind _sizer_kind;
76
77 // False when using a fixed young generation size due to command-line options,
78 // true otherwise.
79 bool _adaptive_size;
80
81 uint calculate_default_min_length(uint new_number_of_heap_regions);
82 uint calculate_default_max_length(uint new_number_of_heap_regions);
83
84 // Update the given values for minimum and maximum young gen length in regions
85 // given the number of heap regions depending on the kind of sizing algorithm.
86 void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
87
88 protected:
89 uint _min_desired_young_length;
90 uint _max_desired_young_length;
91
92 public:
93 G1YoungGenSizer();
94 // Calculate the maximum length of the young gen given the number of regions
95 // depending on the sizing algorithm.
96 virtual void adjust_max_new_size(uint number_of_heap_regions);
97
98 virtual void heap_size_changed(uint new_number_of_heap_regions);
99 uint min_desired_young_length() const {
100 return _min_desired_young_length;
101 }
102 uint max_desired_young_length() const {
103 return _max_desired_young_length;
104 }
105
106 bool adaptive_young_list_length() const {
107 return _adaptive_size;
108 }
109
110 static G1YoungGenSizer* create_gen_sizer();
111 };
112
113 #endif // SHARE_VM_GC_G1_G1YOUNGGENSIZER_HPP