1 /*
2 * Copyright (c) 2016, 2019, 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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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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13 * accompanied this code).
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23 */
24
25 #ifndef SHARE_GC_G1_G1YOUNGGENSIZER_HPP
26 #define SHARE_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
67 // Forward declarations
68 class G1HeapSizingPolicy;
69
70 class G1YoungGenSizer : public CHeapObj<mtGC> {
71 friend class G1HeapSizingPolicy;
72 private:
73 enum SizerKind {
74 SizerDefaults,
75 SizerNewSizeOnly,
76 SizerMaxNewSizeOnly,
77 SizerMaxAndNewSize,
78 SizerNewRatio
79 };
80 SizerKind _sizer_kind;
81
82 // False when using a fixed young generation size due to command-line options,
83 // true otherwise.
84 bool _use_adaptive_sizing;
85
86 uint calculate_default_min_length(uint new_number_of_heap_regions);
87 uint calculate_default_max_length(uint new_number_of_heap_regions);
88
89 // Update the given values for minimum and maximum young gen length in regions
90 // given the number of heap regions depending on the kind of sizing algorithm.
91 void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
92
93 protected:
94 uint _min_desired_young_length;
95 uint _max_desired_young_length;
96
97 public:
98 G1YoungGenSizer();
99 // Calculate the maximum length of the young gen given the number of regions
100 // depending on the sizing algorithm.
101 virtual void adjust_max_new_size(uint number_of_heap_regions);
102
103 virtual void heap_size_changed(uint new_number_of_heap_regions);
104 uint min_desired_young_length() const {
105 return _min_desired_young_length;
106 }
107 uint max_desired_young_length() const {
108 return _max_desired_young_length;
109 }
110
111 bool use_adaptive_young_list_length() const {
112 return _use_adaptive_sizing;
113 }
114
115 static G1YoungGenSizer* create_gen_sizer();
116 };
117
118 #endif // SHARE_GC_G1_G1YOUNGGENSIZER_HPP