1 /*
2 * Copyright (c) 2020, 2024, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2017, 2018, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
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20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24 */
25
26 #ifndef SHARE_GC_EPSILON_EPSILON_GLOBALS_HPP
27 #define SHARE_GC_EPSILON_EPSILON_GLOBALS_HPP
28
29 #include "runtime/globals_shared.hpp"
30
31 //
32 // Defines all globals flags used by the Epsilon GC.
33 //
34
35 #define GC_EPSILON_FLAGS(develop, \
36 develop_pd, \
37 product, \
38 product_pd, \
39 range, \
40 constraint) \
41 \
42 product(size_t, EpsilonPrintHeapSteps, 20, EXPERIMENTAL, \
43 "Print heap occupancy stats with this number of steps. " \
44 "0 turns the printing off.") \
45 range(0, max_intx) \
46 \
47 product(size_t, EpsilonUpdateCountersStep, 1 * M, EXPERIMENTAL, \
48 "Update heap occupancy counters after allocating this much " \
49 "memory. Higher values would make allocations faster at " \
50 "the expense of lower resolution in heap counters.") \
51 range(1, max_intx) \
52 \
53 product(size_t, EpsilonMaxTLABSize, 4 * M, EXPERIMENTAL, \
54 "Max TLAB size to use with Epsilon GC. Larger value improves " \
55 "performance at the expense of per-thread memory waste. This " \
56 "asks TLAB machinery to cap TLAB sizes at this value.") \
57 range(1, max_intx) \
58 \
59 product(bool, EpsilonElasticTLAB, true, EXPERIMENTAL, \
60 "Use elastic policy to manage TLAB sizes. This conserves memory " \
61 "for non-actively allocating threads, even when they request " \
62 "large TLABs for themselves. Active threads would experience " \
63 "smaller TLABs until policy catches up.") \
64 \
65 product(bool, EpsilonElasticTLABDecay, true, EXPERIMENTAL, \
66 "Use timed decays to shrink TLAB sizes. This conserves memory " \
67 "for the threads that allocate in bursts of different sizes, " \
68 "for example the small/rare allocations coming after the initial "\
69 "large burst.") \
70 \
71 product(double, EpsilonTLABElasticity, 1.1, EXPERIMENTAL, \
72 "Multiplier to use when deciding on next TLAB size. Larger value "\
73 "improves performance at the expense of per-thread memory waste. "\
74 "Lower value improves memory footprint, but penalizes actively " \
75 "allocating threads.") \
76 range(1.0, DBL_MAX) \
77 \
78 product(size_t, EpsilonTLABDecayTime, 1000, EXPERIMENTAL, \
79 "TLAB sizing policy decays to initial size after thread had not " \
80 "allocated for this long. Time is in milliseconds. Lower value " \
81 "improves memory footprint, but penalizes actively allocating " \
82 "threads.") \
83 range(1, max_intx) \
84 \
85 product(size_t, EpsilonMinHeapExpand, 128 * M, EXPERIMENTAL, \
86 "Min expansion step for heap. Larger value improves performance " \
87 "at the potential expense of memory waste.") \
88 range(1, max_intx) \
89 \
90 product(bool, EpsilonSlidingGC, false, EXPERIMENTAL, \
91 "Actually does sliding mark-compact GC.") \
92 \
93 product(bool, EpsilonImplicitGC, true, EXPERIMENTAL, \
94 "Does GC on implicit GC requests, e.g. for allocation failure.") \
95 \
96 product(bool, EpsilonUncommit, false, EXPERIMENTAL, \
97 "Uncommits all unneeded memory after GC.") \
98 \
99 product(bool, EpsilonVerify, false, EXPERIMENTAL, \
100 "Does the additional GC verification step.") \
101 \
102
103 // end of GC_EPSILON_FLAGS
104
105 #endif // SHARE_GC_EPSILON_EPSILON_GLOBALS_HPP