1/*
2 * Copyright (c) 2000, 2019, 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_GC_SHARED_REFERENCEPOLICY_HPP
26#define SHARE_GC_SHARED_REFERENCEPOLICY_HPP
27
28#include "oops/oopsHierarchy.hpp"
29
30// referencePolicy is used to determine when soft reference objects
31// should be cleared.
32
33
34class ReferencePolicy : public CHeapObj<mtGC> {
35 public:
36 virtual bool should_clear_reference(oop p, jlong timestamp_clock) {
37 ShouldNotReachHere();
38 return true;
39 }
40
41 // Capture state (of-the-VM) information needed to evaluate the policy
42 virtual void setup() { /* do nothing */ }
43};
44
45class NeverClearPolicy : public ReferencePolicy {
46 public:
47 virtual bool should_clear_reference(oop p, jlong timestamp_clock) {
48 return false;
49 }
50};
51
52class AlwaysClearPolicy : public ReferencePolicy {
53 public:
54 virtual bool should_clear_reference(oop p, jlong timestamp_clock) {
55 return true;
56 }
57};
58
59class LRUCurrentHeapPolicy : public ReferencePolicy {
60 private:
61 jlong _max_interval;
62
63 public:
64 LRUCurrentHeapPolicy();
65
66 // Capture state (of-the-VM) information needed to evaluate the policy
67 void setup();
68 virtual bool should_clear_reference(oop p, jlong timestamp_clock);
69};
70
71class LRUMaxHeapPolicy : public ReferencePolicy {
72 private:
73 jlong _max_interval;
74
75 public:
76 LRUMaxHeapPolicy();
77
78 // Capture state (of-the-VM) information needed to evaluate the policy
79 void setup();
80 virtual bool should_clear_reference(oop p, jlong timestamp_clock);
81};
82
83#endif // SHARE_GC_SHARED_REFERENCEPOLICY_HPP
84