1 /*
2 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1IHOPCONTROL_HPP
26 #define SHARE_VM_GC_G1_G1IHOPCONTROL_HPP
27
28 #include "memory/allocation.hpp"
29 #include "utilities/numberSeq.hpp"
30
31 class G1Predictions;
32
33 // Base class for algorithms that calculate the heap occupancy at which
34 // concurrent marking should start. This heap usage threshold should be relative
35 // to old gen size.
36 class G1IHOPControl : public CHeapObj<mtGC> {
37 protected:
38 // The initial IHOP value relative to the target occupancy.
39 double _initial_ihop_percent;
40 // The target maximum occupancy of the heap.
41 size_t _target_occupancy;
42
43 // Initialize an instance with the initial IHOP value in percent and the target
44 // occupancy. The target occupancy is the number of bytes when marking should
45 // be finished and reclaim started.
46 G1IHOPControl(double initial_ihop_percent, size_t target_occupancy);
47 public:
48 virtual ~G1IHOPControl() { }
49
50 // Get the current non-young occupancy at which concurrent marking should start.
51 virtual size_t get_conc_mark_start_threshold() = 0;
52
53 // Update information about time during which allocations in the Java heap occurred,
54 // how large these allocations were in bytes, and an additional buffer.
55 // The allocations should contain any amount of space made unusable for further
56 // allocation, e.g. any waste caused by TLAB allocation, space at the end of
57 // humongous objects that can not be used for allocation, etc.
58 // Together with the target occupancy, this additional buffer should contain the
59 // difference between old gen size and total heap size at the start of reclamation,
60 // and space required for that reclamation.
61 virtual void update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size) = 0;
62 // Update the time spent in the mutator beginning from the end of initial mark to
63 // the first mixed gc.
64 virtual void update_marking_length(double marking_length_s) = 0;
65
66 virtual void print() = 0;
67 };
68
69 // The returned concurrent mark starting occupancy threshold is a fixed value
70 // relative to the maximum heap size.
71 class G1StaticIHOPControl : public G1IHOPControl {
72 // Most recent complete mutator allocation period in seconds.
73 double _last_allocation_time_s;
74 // Amount of bytes allocated during _last_allocation_time_s.
75 size_t _last_allocated_bytes;
76 // Most recent mutator time between the end of initial mark to the start of the
77 // first mixed gc.
78 double _last_marking_length_s;
79 public:
80 G1StaticIHOPControl(double ihop_percent, size_t target_occupancy);
81
82 size_t get_conc_mark_start_threshold() { return (size_t) (_initial_ihop_percent * _target_occupancy / 100.0); }
83
84 virtual void update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size) {
85 assert(allocation_time_s >= 0.0, "Allocation time must be positive but is %.3f", allocation_time_s);
86 _last_allocation_time_s = allocation_time_s;
87 _last_allocated_bytes = allocated_bytes;
88 }
89
90 virtual void update_marking_length(double marking_length_s) {
91 assert(marking_length_s > 0.0, "Marking length must be larger than zero but is %.3f", marking_length_s);
92 _last_marking_length_s = marking_length_s;
93 }
94
95 virtual void print();
96 #ifndef PRODUCT
97 static void test();
98 #endif
99 };
100
101 // This algorithm tries to return a concurrent mark starting occupancy value that
102 // makes sure that during marking the given target occupancy is never exceeded,
103 // depending on predictions of current allocation rate and time periods between
104 // initial mark and the first mixed gc.
105 class G1AdaptiveIHOPControl : public G1IHOPControl {
106 size_t _heap_reserve_percent; // Percentage of maximum heap capacity we should avoid to touch
107 size_t _heap_waste_percent; // Percentage of free heap that should be considered as waste.
108
109 G1Predictions const * _predictor;
110
111 TruncatedSeq _marking_times_s;
112 TruncatedSeq _allocation_rate_s;
113
114 size_t _last_allocation_bytes; // Most recent mutator allocation since last GC.
115 // The most recent unrestrained size of the young gen. This is used as an additional
116 // factor in the calculation of the threshold, as the threshold is based on
117 // non-young gen occupancy compared against at the end of GC, but we need to
118 // accommodate the young gen too during that time.
119 // Since we cannot know what young gen sizes are used in the future, we will just
120 // use the current one. We expect that this one will be one with a fairly large size,
121 // as there is no marking or mixed gc that could impact its size too much.
122 size_t _last_unrestrained_young_size;
123
124 size_t _current_threshold; // Save the most recently calculated threshold value here.
125
126 // Updates _current_threshold according to internal state.
127 void calculate();
128
129 bool have_enough_data_for_prediction() const;
130
131 // The "actual" target threshold the algorithm wants to keep during and at the
132 // end of marking. This is typically lower than the requested threshold, as the
133 // algorithm needs to consider restrictions by the environment.
134 size_t actual_target_threshold() const;
135 public:
136 G1AdaptiveIHOPControl(double ihop_percent,
137 size_t initial_target_occupancy,
138 G1Predictions const* predictor,
139 size_t heap_reserve_percent, // The percentage of total heap capacity that should not be tapped into.
140 size_t heap_waste_percent); // The percentage of the free space in the heap that we think is not usable for allocation.
141
142 virtual void set_target_occupancy(size_t target_occupancy);
143
144 virtual size_t get_conc_mark_start_threshold();
145
146 virtual void update_allocation_info(double allocation_time_s, size_t allocated_bytes, size_t additional_buffer_size);
147 virtual void update_marking_length(double marking_length_s);
148
149 virtual void print();
150 #ifndef PRODUCT
151 static void test();
152 #endif
153 };
154
155 #endif // SHARE_VM_GC_G1_G1IHOPCONTROL_HPP