1 /* 2 * Copyright (c) 2015, 2017, 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 package utils; 24 25 import java.util.ArrayList; 26 import java.util.List; 27 28 /** 29 * This is an class used to provoke GC and perform other GC-related 30 * procedures 31 * 32 */ 33 public class GcProvoker{ 34 35 // Uses fixed small objects to avoid Humongous objects allocation in G1 36 public static final int MEMORY_CHUNK = 2048; 37 38 private final Runtime runtime; 39 40 private List<Object> allocateHeap(float targetUsage) { 41 long maxMemory = runtime.maxMemory(); 42 List<Object> list = new ArrayList<>(); 43 long used = 0; 44 long target = (long) (maxMemory * targetUsage); 45 while (used < target) { 46 try { 47 list.add(new byte[MEMORY_CHUNK]); 48 used += MEMORY_CHUNK; 49 } catch (OutOfMemoryError e) { 50 list = null; 51 throw new RuntimeException("Unexpected OOME '" + e.getMessage() + "' while eating " + targetUsage + " of heap memory."); 52 } 53 } 54 return list; 55 } 56 57 /** 58 * This method provokes a GC 59 */ 60 public void provokeGc() { 61 for (int i = 0; i < 3; i++) { 62 long edenSize = Pools.getEdenCommittedSize(); 63 long heapSize = Pools.getHeapCommittedSize(); 64 float targetPercent = ((float) edenSize) / (heapSize); 65 if ((targetPercent < 0) || (targetPercent > 1.0)) { 66 throw new RuntimeException("Error in the percent calculation" + " (eden size: " + edenSize + ", heap size: " + heapSize + ", calculated eden percent: " + targetPercent + ")"); 67 } 68 allocateHeap(targetPercent); 69 allocateHeap(targetPercent); 70 System.gc(); 71 } 72 } 73 74 public GcProvoker() { 75 runtime = Runtime.getRuntime(); 76 } 77 }