test/hotspot/jtreg/gc/x/TestRelocateInPlace.java

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package gc.x;

/*
 * @test TestRelocateInPlace
 * @requires vm.gc.ZSinglegen
 * @summary Test ZGC in-place relocateion
 * @run main/othervm -XX:+UseZGC -XX:-ZGenerational -Xlog:gc*,gc+stats=off -Xmx256M -XX:+UnlockDiagnosticVMOptions -XX:+ZStressRelocateInPlace gc.x.TestRelocateInPlace
 */

import java.util.ArrayList;

public class TestRelocateInPlace {
    private static final int allocSize = 100 * 1024 * 1024; // 100M
    private static final int smallObjectSize = 4 * 1024; // 4K
    private static final int mediumObjectSize = 2 * 1024 * 1024; // 2M

    private static volatile ArrayList<byte[]> keepAlive;

    private static void allocate(int objectSize) {
        keepAlive = new ArrayList<>();
        for (int i = 0; i < allocSize; i+= objectSize) {
            keepAlive.add(new byte[objectSize]);
        }
    }

    private static void fragment() {
        // Release every other reference to cause lots of fragmentation
        for (int i = 0; i < keepAlive.size(); i += 2) {
            keepAlive.set(i, null);
        }
    }

    private static void test(int objectSize) throws Exception {
        System.out.println("Allocating");
        allocate(objectSize);

        System.out.println("Fragmenting");
        fragment();

        System.out.println("Reclaiming");
        System.gc();
    }

    public static void main(String[] args) throws Exception {
        for (int i = 0; i < 10; i++) {
            System.out.println("Iteration " + i);
            test(smallObjectSize);
            test(mediumObjectSize);
        }
    }
}