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 * Copyright (c) 2017, 2025, 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
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 *
 * 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.
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package org.openjdk.bench.vm.gc.systemgc;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Level;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;

import java.util.concurrent.TimeUnit;

@BenchmarkMode(Mode.SingleShotTime)
@Warmup(iterations = 5)
@Measurement(iterations = 5)
@Fork(value=25, jvmArgs={"-Xmx5g", "-Xms5g", "-Xmn3g", "-XX:+AlwaysPreTouch"})
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@State(Scope.Benchmark)
public class DifferentObjectSizesArray {

    /*
     * Test the System GC when 2/3 of the objects are live
     * and kept reachable through an object array.
     *
     * The jvmArgs are provided to avoid GCs during object creation.
     */

    static Object[] largeObjArray;

    @Setup(Level.Trial)
    public void preRun() {
        // Compact right now, kicking out all unrelated objects
        System.gc();
    }

    @Setup(Level.Iteration)
    public void generateGarbage() {
        largeObjArray = GarbageGenerator.generateAndFillLargeObjArray(false);
        // Removing a third of the objects and keeping a good
        // distribution of sizes.
        for (int i = 0; i < largeObjArray.length; i++) {
            if (i%3 == 0) {
                largeObjArray[i] = null;
            }
        }
    }

    @Benchmark
    public void gc() {
        System.gc();
    }
}
