view jol-samples/src/main/java/org/openjdk/jol/samples/JOLSample_24_Colocation.java @ 110:018c0e12f70f

7901973: JOL would not build with JDK EA 9b168
author shade
date Mon, 08 May 2017 20:26:33 +0200
parents 78ff957bc500
children fae3dfa61b12
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/*
 * Copyright (c) 2014, Oracle America, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 *  * Neither the name of Oracle nor the names of its contributors may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.openjdk.jol.samples;

import org.openjdk.jol.info.GraphLayout;
import org.openjdk.jol.vm.VM;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static java.lang.System.out;

/**
 * @author Aleksey Shipilev
 */
public class JOLSample_24_Colocation {

    /*
     * This is the example how VM colocates the objects allocated
     * by different threads.
     *
     * In this example, the ConcurrentHashMap is being populated
     * by several threads. We can see that after a few GCs it is
     * densely packed, regardless of the fact it was allocated by
     * multiple threads.
     *
     * This example generates PNG images in your current directory.
     */

    public static volatile Object sink;

    public static void main(String[] args) throws Exception {
        out.println(VM.current().details());

        // allocate some objects to beef up generations
        for (int c = 0; c < 1000000; c++) {
            sink = new Object();
        }
        System.gc();

        final int COUNT = 1000;

        ConcurrentHashMap<Object, Object> chm = new ConcurrentHashMap<Object, Object>();

        addElements(COUNT, chm);

        GraphLayout.parseInstance(chm).toImage("chm-1-new.png");

        for (int c = 2; c <= 5; c++) {
            GraphLayout.parseInstance(chm).toImage("chm-" + c + "-gc.png");
            System.gc();
        }

        addElements(COUNT, chm);

        for (int c = 6; c <= 10; c++) {
            GraphLayout.parseInstance(chm).toImage("chm-" + c + "-more-gc.png");
            System.gc();
        }

    }

    private static void addElements(final int count, final Map<Object, Object> chm) throws InterruptedException {
        ExecutorService pool = Executors.newCachedThreadPool();

        Runnable task = new Runnable() {
            @Override
            public void run() {
                for (int c = 0; c < count; c++) {
                    Object o = new Object();
                    chm.put(o, o);
                }
            }
        };

        for (int t = 0; t < Runtime.getRuntime().availableProcessors() * 2; t++) {
            pool.submit(task);
        }

        pool.shutdown();
        pool.awaitTermination(1, TimeUnit.DAYS);
    }

}