| /* |
| * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.lang.ref; |
| |
| |
| import java.util.Map; |
| import java.util.HashMap; |
| import java.util.Arrays; |
| import java.util.Comparator; |
| |
| /** |
| * This FinalizerHistogram class is for GC.finalizer_info diagnostic command support. |
| * It is invoked by the VM. |
| */ |
| |
| final class FinalizerHistogram { |
| |
| private static final class Entry { |
| private int instanceCount; |
| private final String className; |
| |
| int getInstanceCount() { |
| return instanceCount; |
| } |
| |
| void increment() { |
| instanceCount += 1; |
| } |
| |
| Entry(String className) { |
| this.className = className; |
| } |
| } |
| |
| // Method below is called by VM and VM expect certain |
| // entry class layout. |
| |
| static Entry[] getFinalizerHistogram() { |
| Map<String, Entry> countMap = new HashMap<>(); |
| ReferenceQueue<Object> queue = Finalizer.getQueue(); |
| queue.forEach(r -> { |
| Object referent = r.get(); |
| if (referent != null) { |
| countMap.computeIfAbsent( |
| referent.getClass().getName(), Entry::new).increment(); |
| /* Clear stack slot containing this variable, to decrease |
| the chances of false retention with a conservative GC */ |
| referent = null; |
| } |
| }); |
| |
| Entry fhe[] = countMap.values().toArray(new Entry[countMap.size()]); |
| Arrays.sort(fhe, |
| Comparator.comparingInt(Entry::getInstanceCount).reversed()); |
| return fhe; |
| } |
| } |