/*

 * Copyright (c) 2014, 2015, 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

 * published by the Free Software Foundation.

 *

 * 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.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

/**

 * @test TestDynShrinkHeap

 * @bug 8016479

 * @requires vm.gc=="Parallel" | vm.gc=="null"

 * @summary Verify that the heap shrinks after full GC according to the current values of the Min/MaxHeapFreeRatio flags

 * @library /testlibrary

 * @run main/othervm -XX:+UseAdaptiveSizePolicyWithSystemGC -XX:+UseParallelGC -XX:MinHeapFreeRatio=0 -XX:MaxHeapFreeRatio=100 -Xmx1g -verbose:gc TestDynShrinkHeap

 */

import com.oracle.java.testlibrary.DynamicVMOption;

import java.lang.management.ManagementFactory;

import java.lang.management.MemoryUsage;

import java.util.ArrayList;

import static com.oracle.java.testlibrary.Asserts.assertLessThan;

import com.sun.management.HotSpotDiagnosticMXBean;

public class TestDynShrinkHeap {

    public static final String MIN_FREE_RATIO_FLAG_NAME = "MinHeapFreeRatio";

    public static final String MAX_FREE_RATIO_FLAG_NAME = "MaxHeapFreeRatio";

    private static ArrayList<byte[]> list = new ArrayList<>(0);

    private static final int LEN = 512 * 1024 + 1;

    public TestDynShrinkHeap() {

    }

    private final void test() {

        System.gc();

        MemoryUsagePrinter.printMemoryUsage("init");

        eat();

        MemoryUsagePrinter.printMemoryUsage("eaten");

        MemoryUsage muFull = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();

        free();

        MemoryUsagePrinter.printMemoryUsage("free");

        MemoryUsage muFree = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();

        assertLessThan(muFree.getCommitted(), muFull.getCommitted(), String.format(

                "committed free heap size is not less than committed full heap size, heap hasn't been shrunk?%n"

                + "%s = %s%n%s = %s",

                MIN_FREE_RATIO_FLAG_NAME,

                ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class)

                    .getVMOption(MIN_FREE_RATIO_FLAG_NAME).getValue(),

                MAX_FREE_RATIO_FLAG_NAME,

                ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class)

                    .getVMOption(MAX_FREE_RATIO_FLAG_NAME).getValue()

        ));

    }

    private void eat() {

        for (int i = 0; i < LEN; i++) {

            list.add(new byte[1024]);

        }

        MemoryUsagePrinter.printMemoryUsage("allocated " + LEN + " arrays");

        list.subList(0, LEN / 2).clear();

        System.gc();

        MemoryUsagePrinter.printMemoryUsage("array halved");

    }

    private void free() {

        int min = DynamicVMOption.getInt(MIN_FREE_RATIO_FLAG_NAME);

        DynamicVMOption.setInt(MAX_FREE_RATIO_FLAG_NAME, min);

        System.gc();

        MemoryUsagePrinter.printMemoryUsage("under pressure");

    }

    public static void main(String[] args) {

        new TestDynShrinkHeap().test();

    }

}

/**

 * Prints memory usage to standard output

 */

class MemoryUsagePrinter {

    public static String humanReadableByteCount(long bytes, boolean si) {

        int unit = si ? 1000 : 1024;

        if (bytes < unit) {

            return bytes + " B";

        }

        int exp = (int) (Math.log(bytes) / Math.log(unit));

        String pre = (si ? "kMGTPE" : "KMGTPE").charAt(exp - 1) + (si ? "" : "i");

        return String.format("%.1f %sB", bytes / Math.pow(unit, exp), pre);

    }

    public static void printMemoryUsage(String label) {

        MemoryUsage memusage = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();

        float freeratio = 1f - (float) memusage.getUsed() / memusage.getCommitted();

        System.out.format("[%-24s] init: %-7s, used: %-7s, comm: %-7s, freeRatio ~= %.1f%%%n",

                label,

                humanReadableByteCount(memusage.getInit(), true),

                humanReadableByteCount(memusage.getUsed(), true),

                humanReadableByteCount(memusage.getCommitted(), true),

                freeratio * 100

        );

    }

}