cfd44bb2cd
8293564: serviceability/tmtools/jstat/GcTest01.java fails with "Error in the percent calculation" Reviewed-by: sspitsyn, lmesnik, dcubed
95 lines
3.7 KiB
Java
95 lines
3.7 KiB
Java
/*
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* Copyright (c) 2015, 2022, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package utils;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* This is an class used to provoke GC and perform other GC-related
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* procedures
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*
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*/
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public class GcProvoker{
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// Uses fixed small objects to avoid Humongous objects allocation in G1
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private static final int MEMORY_CHUNK = 2048;
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private final Runtime runtime;
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private List<Object> allocateHeap(float targetUsage) {
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long maxMemory = runtime.maxMemory();
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List<Object> list = new ArrayList<>();
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long used = 0;
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long target = (long) (maxMemory * targetUsage);
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while (used < target) {
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try {
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list.add(new byte[MEMORY_CHUNK]);
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used += MEMORY_CHUNK;
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} catch (OutOfMemoryError e) {
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list = null;
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throw new RuntimeException("Unexpected OOME '" + e.getMessage() + "' while eating " + targetUsage + " of heap memory.");
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}
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}
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return list;
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}
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/**
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* This method provokes a GC
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*/
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public void provokeGc() {
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float targetFraction = 0;
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// Read sizes of eden and overall heap, to find eden size as a fraction of heap.
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// Recognise if heap is changing size, and retry (heap is expected to initially shrink).
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for (int i = 0; i < 3; i++) {
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// One retry is expected occasionally. More "should not happen":
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if (i == 2) {
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throw new RuntimeException("Cannot calculate targetFraction. Heap size not stable.");
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}
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long heapSize0 = Pools.getHeapCommittedSize();
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long edenSize = Pools.getEdenCommittedSize();
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long heapSize = Pools.getHeapCommittedSize();
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if (heapSize < heapSize0) {
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System.out.println("provokeGc: Heap shrinking, retry. eden: " + edenSize + ", heap0: " + heapSize0 + ", heap: " + heapSize);
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System.gc();
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continue;
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}
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targetFraction = ((float) edenSize) / (heapSize);
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if ((targetFraction < 0) || (targetFraction > 1.0)) {
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throw new RuntimeException("Error in fraction calculation" + " (eden size: " + edenSize + ", heap size: " + heapSize
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+ ", calculated eden fraction: " + targetFraction + ")");
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}
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break; // We have found eden as a fraction of heap.
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}
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// Previously these allocations and GC call were in a loop.
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// That appears unnecesary as the goal is simply to cause a GC:
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allocateHeap(targetFraction);
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allocateHeap(targetFraction);
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System.gc();
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}
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public GcProvoker() {
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runtime = Runtime.getRuntime();
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}
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}
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