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24
25#ifndef SHARE_GC_G1_G1IHOPCONTROL_HPP
26#define SHARE_GC_G1_G1IHOPCONTROL_HPP
27
28#include "memory/allocation.hpp"
29#include "utilities/numberSeq.hpp"
30
31class G1Predictions;
32class G1NewTracer;
33
34// Base class for algorithms that calculate the heap occupancy at which
35// concurrent marking should start. This heap usage threshold should be relative
36// to old gen size.
37class G1IHOPControl : public CHeapObj<mtGC> {
38 protected:
39 // The initial IHOP value relative to the target occupancy.
40 double _initial_ihop_percent;
41 // The target maximum occupancy of the heap. The target occupancy is the number
42 // of bytes when marking should be finished and reclaim started.
43 size_t _target_occupancy;
44
45 // Most recent complete mutator allocation period in seconds.
46 double _last_allocation_time_s;
47 // Amount of bytes allocated during _last_allocation_time_s.
48 size_t _last_allocated_bytes;
49
50 // Initialize an instance with the initial IHOP value in percent. The target
51 // occupancy will be updated at the first heap expansion.
52 G1IHOPControl(double initial_ihop_percent);
53
54 // Most recent time from the end of the initial mark to the start of the first
55 // mixed gc.
56 virtual double last_marking_length_s() const = 0;
57 public:
58 virtual ~G1IHOPControl() { }
59
60 // Get the current non-young occupancy at which concurrent marking should start.
61 virtual size_t get_conc_mark_start_threshold() = 0;
62
63 // Adjust target occupancy.
64 virtual void update_target_occupancy(size_t new_target_occupancy);
65 // Update information about time during which allocations in the Java heap occurred,
66 // how large these allocations were in bytes, and an additional buffer.
67 // The allocations should contain any amount of space made unusable for further
68 // allocation, e.g. any waste caused by TLAB allocation, space at the end of
69 // humongous objects that can not be used for allocation, etc.
70 // Together with the target occupancy, this additional buffer should contain the
71 // difference between old gen size and total heap size at the start of reclamation,
72 // and space required for that reclamation.
73 virtual void update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size);
74 // Update the time spent in the mutator beginning from the end of initial mark to
75 // the first mixed gc.
76 virtual void update_marking_length(double marking_length_s) = 0;
77
78 virtual void print();
79 virtual void send_trace_event(G1NewTracer* tracer);
80};
81
82// The returned concurrent mark starting occupancy threshold is a fixed value
83// relative to the maximum heap size.
84class G1StaticIHOPControl : public G1IHOPControl {
85 // Most recent mutator time between the end of initial mark to the start of the
86 // first mixed gc.
87 double _last_marking_length_s;
88 protected:
89 double last_marking_length_s() const { return _last_marking_length_s; }
90 public:
91 G1StaticIHOPControl(double ihop_percent);
92
93 size_t get_conc_mark_start_threshold() {
94 guarantee(_target_occupancy > 0, "Target occupancy must have been initialized.");
95 return (size_t) (_initial_ihop_percent * _target_occupancy / 100.0);
96 }
97
98 virtual void update_marking_length(double marking_length_s) {
99 assert(marking_length_s > 0.0, "Marking length must be larger than zero but is %.3f", marking_length_s);
100 _last_marking_length_s = marking_length_s;
101 }
102};
103
104// This algorithm tries to return a concurrent mark starting occupancy value that
105// makes sure that during marking the given target occupancy is never exceeded,
106// based on predictions of current allocation rate and time periods between
107// initial mark and the first mixed gc.
108class G1AdaptiveIHOPControl : public G1IHOPControl {
109 size_t _heap_reserve_percent; // Percentage of maximum heap capacity we should avoid to touch
110 size_t _heap_waste_percent; // Percentage of free heap that should be considered as waste.
111
112 const G1Predictions * _predictor;
113
114 TruncatedSeq _marking_times_s;
115 TruncatedSeq _allocation_rate_s;
116
117 // The most recent unrestrained size of the young gen. This is used as an additional
118 // factor in the calculation of the threshold, as the threshold is based on
119 // non-young gen occupancy at the end of GC. For the IHOP threshold, we need to
120 // consider the young gen size during that time too.
121 // Since we cannot know what young gen sizes are used in the future, we will just
122 // use the current one. We expect that this one will be one with a fairly large size,
123 // as there is no marking or mixed gc that could impact its size too much.
124 size_t _last_unrestrained_young_size;
125
126 bool have_enough_data_for_prediction() const;
127
128 // The "actual" target threshold the algorithm wants to keep during and at the
129 // end of marking. This is typically lower than the requested threshold, as the
130 // algorithm needs to consider restrictions by the environment.
131 size_t actual_target_threshold() const;
132 protected:
133 virtual double last_marking_length_s() const { return _marking_times_s.last(); }
134 public:
135 G1AdaptiveIHOPControl(double ihop_percent,
136 G1Predictions const* predictor,
137 size_t heap_reserve_percent, // The percentage of total heap capacity that should not be tapped into.
138 size_t heap_waste_percent); // The percentage of the free space in the heap that we think is not usable for allocation.
139
140 virtual size_t get_conc_mark_start_threshold();
141
142 virtual void update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size);
143 virtual void update_marking_length(double marking_length_s);
144
145 virtual void print();
146 virtual void send_trace_event(G1NewTracer* tracer);
147};
148
149#endif // SHARE_GC_G1_G1IHOPCONTROL_HPP
150