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81 lines
1.7 KiB
81 lines
1.7 KiB
/*
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* Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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package java.lang.ref;
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import java.util.Map;
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import java.util.HashMap;
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import java.util.Arrays;
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import java.util.Comparator;
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/**
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* This FinalizerHistogram class is for GC.finalizer_info diagnostic command support.
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* It is invoked by the VM.
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*/
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final class FinalizerHistogram {
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private static final class Entry {
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private int instanceCount;
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private final String className;
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int getInstanceCount() {
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return instanceCount;
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}
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void increment() {
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instanceCount += 1;
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}
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Entry(String className) {
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this.className = className;
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}
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}
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// Method below is called by VM and VM expect certain
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// entry class layout.
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static Entry[] getFinalizerHistogram() {
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Map<String, Entry> countMap = new HashMap<>();
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ReferenceQueue<Object> queue = Finalizer.getQueue();
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queue.forEach(r -> {
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Object referent = r.get();
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if (referent != null) {
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countMap.computeIfAbsent(
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referent.getClass().getName(), Entry::new).increment();
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/* Clear stack slot containing this variable, to decrease
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the chances of false retention with a conservative GC */
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referent = null;
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}
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});
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Entry fhe[] = countMap.values().toArray(new Entry[countMap.size()]);
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Arrays.sort(fhe,
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Comparator.comparingInt(Entry::getInstanceCount).reversed());
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return fhe;
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}
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}
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