GC.java revision 2103:112989d7c3c0 
1/*
2 * Copyright (c) 2016, 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.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25package sun.hotspot.gc;
26
27import java.util.ArrayList;
28import java.util.List;
29import sun.hotspot.WhiteBox;
30
31/**
32 * API to obtain information about selected and supported Garbage Collectors
33 * retrieved from the VM with the WhiteBox API.
34 */
35public enum GC {
36    Serial(1),
37    Parallel(2),
38    ConcMarkSweep(4),
39    G1(8);
40
41    private static final GC CURRENT_GC;
42    private static final int ALL_GC_CODES;
43    private static final boolean IS_BY_ERGO;
44    static {
45        WhiteBox WB = WhiteBox.getWhiteBox();
46        ALL_GC_CODES = WB.allSupportedGC();
47        IS_BY_ERGO = WB.gcSelectedByErgo();
48
49        int currentCode = WB.currentGC();
50        GC tmp = null;
51        for (GC gc: GC.values()) {
52            if (gc.code == currentCode) {
53                tmp = gc;
54                break;
55            }
56        }
57        if (tmp == null) {
58            throw new Error("Unknown current GC code " + currentCode);
59        }
60        CURRENT_GC = tmp;
61    }
62
63    private final int code;
64    private GC(int code) {
65        this.code = code;
66    }
67
68    /**
69     * @return true if the collector is supported by the VM, false otherwise.
70     */
71    public boolean isSupported() {
72        return (ALL_GC_CODES & code) != 0;
73    }
74
75
76    /**
77     * @return the current collector used by VM.
78     */
79    public static GC current() {
80        return CURRENT_GC;
81    }
82
83    /**
84     * @return true if GC was selected by ergonomic, false if specified
85     * explicitly by the command line flag.
86     */
87    public static boolean currentSetByErgo() {
88        return IS_BY_ERGO;
89    }
90
91    /**
92     * @return List of collectors supported by the VM.
93     */
94    public static List<GC> allSupported() {
95        List<GC> list = new ArrayList<>();
96        for (GC gc: GC.values()) {
97            if (gc.isSupported()) {
98                list.add(gc);
99            }
100        }
101        return list;
102    }
103}
104
105