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 25 package sun.hotspot.gc; 26 27 import java.util.ArrayList; 28 import java.util.List; 29 import 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 */ 35 public 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