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 * 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

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 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

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 * 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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 */

/**

 * @test TestHumongousShrinkHeap

 * @bug 8036025 8056043

 * @requires vm.gc=="G1" | vm.gc=="null"

 * @summary Verify that heap shrinks after GC in the presence of fragmentation

 * due to humongous objects

 * @library /testlibrary

 * @modules java.management/sun.management

 * @run main/othervm -XX:-ExplicitGCInvokesConcurrent -XX:MinHeapFreeRatio=10

 * -XX:MaxHeapFreeRatio=12 -XX:+UseG1GC -XX:G1HeapRegionSize=1M -verbose:gc

 * TestHumongousShrinkHeap

 */

import com.sun.management.HotSpotDiagnosticMXBean;

import java.lang.management.ManagementFactory;

import java.lang.management.MemoryUsage;

import java.util.ArrayList;

import java.util.List;

import static jdk.test.lib.Asserts.*;

public class TestHumongousShrinkHeap {

    public static final String MIN_FREE_RATIO_FLAG_NAME = "MinHeapFreeRatio";

    public static final String MAX_FREE_RATIO_FLAG_NAME = "MaxHeapFreeRatio";

    private static final List<List<byte[]>> garbage = new ArrayList();

    private static final int REGION_SIZE = 1024 * 1024; // 1M

    private static final int LISTS_COUNT = 10;

    private static final int HUMON_SIZE = Math.round(.9f * REGION_SIZE);

    private static final long AVAILABLE_MEMORY

                              = Runtime.getRuntime().freeMemory();

    private static final int HUMON_COUNT

                             = (int) ((AVAILABLE_MEMORY / HUMON_SIZE)

            / LISTS_COUNT);

    public static void main(String[] args) {

        System.out.format("Running with %s max heap size. "

                + "Will allocate humongous object of %s size %d times.%n",

                MemoryUsagePrinter.humanReadableByteCount(AVAILABLE_MEMORY, false),

                MemoryUsagePrinter.humanReadableByteCount(HUMON_SIZE, false),

                HUMON_COUNT

        );

        new TestHumongousShrinkHeap().test();

    }

    private final void test() {

        System.gc();

        MemoryUsagePrinter.printMemoryUsage("init");

        allocate();

        MemoryUsagePrinter.printMemoryUsage("allocated");

        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 allocate() {

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

            List<byte[]> stuff = new ArrayList();

            allocateList(stuff, HUMON_COUNT, HUMON_SIZE);

            MemoryUsagePrinter.printMemoryUsage("allocate #" + (i+1));

            garbage.add(stuff);

        }

    }

    private void free() {

        // do not free last one list

        garbage.subList(0, garbage.size() - 1).clear();

        // do not free last one element from last list

        List stuff = garbage.get(garbage.size() - 1);

        stuff.subList(0, stuff.size() - 1).clear();

        System.gc();

    }

    private static void allocateList(List garbage, int count, int size) {

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

            garbage.add(new byte[size]);

        }

    }

}

/**

 * 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(), false),

                humanReadableByteCount(memusage.getUsed(), false),

                humanReadableByteCount(memusage.getCommitted(), false),

                freeratio * 100

        );

    }

}