GC.java revision 2289:1c9b94ce045e 
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
24package sun.hotspot.gc;
25
26import java.util.ArrayList;
27import java.util.List;
28import sun.hotspot.WhiteBox;
29
30/**
31 * API to obtain information about selected and supported Garbage Collectors
32 * retrieved from the VM with the WhiteBox API.
33 */
34public enum GC {
35    Serial(1),
36    Parallel(2),
37    ConcMarkSweep(4),
38    G1(8);
39
40    private static final GC CURRENT_GC;
41    private static final int ALL_GC_CODES;
42    private static final boolean IS_BY_ERGO;
43    static {
44        WhiteBox WB = WhiteBox.getWhiteBox();
45        ALL_GC_CODES = WB.allSupportedGC();
46        IS_BY_ERGO = WB.gcSelectedByErgo();
47
48        int currentCode = WB.currentGC();
49        GC tmp = null;
50        for (GC gc: GC.values()) {
51            if (gc.code == currentCode) {
52                tmp = gc;
53                break;
54            }
55        }
56        if (tmp == null) {
57            throw new Error("Unknown current GC code " + currentCode);
58        }
59        CURRENT_GC = tmp;
60    }
61
62    private final int code;
63    private GC(int code) {
64        this.code = code;
65    }
66
67    /**
68     * @return true if the collector is supported by the VM, false otherwise.
69     */
70    public boolean isSupported() {
71        return (ALL_GC_CODES & code) != 0;
72    }
73
74
75    /**
76     * @return the current collector used by VM.
77     */
78    public static GC current() {
79        return CURRENT_GC;
80    }
81
82    /**
83     * @return true if GC was selected by ergonomic, false if specified
84     * explicitly by the command line flag.
85     */
86    public static boolean currentSetByErgo() {
87        return IS_BY_ERGO;
88    }
89
90    /**
91     * @return List of collectors supported by the VM.
92     */
93    public static List<GC> allSupported() {
94        List<GC> list = new ArrayList<>();
95        for (GC gc: GC.values()) {
96            if (gc.isSupported()) {
97                list.add(gc);
98            }
99        }
100        return list;
101    }
102}
103
104