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/**

 * @test TestShrinkDefragmentedHeap

 * @bug 8038423 8129590

 * @summary Verify that heap shrinks after GC in the presence of fragmentation due to humongous objects

 *     1. allocate small objects mixed with humongous ones

 *        "ssssHssssHssssHssssHssssHssssHssssH"

 *     2. release all allocated object except the last humongous one

 *        "..................................H"

 *     3. invoke gc and check that memory returned to the system (amount of committed memory got down)

 *

 * @library /testlibrary

 * @modules java.base/jdk.internal.misc

 *          java.management/sun.management

 */

import java.lang.management.ManagementFactory;

import java.lang.management.MemoryUsage;

import java.util.ArrayList;

import java.util.List;

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

import jdk.test.lib.ProcessTools;

import jdk.test.lib.OutputAnalyzer;

import com.sun.management.HotSpotDiagnosticMXBean;

public class TestShrinkDefragmentedHeap {

    // Since we store all the small objects, they become old and old regions are also allocated at the bottom of the heap

    // together with humongous regions. So if there are a lot of old regions in the lower part of the heap,

    // the humongous regions will be allocated in the upper part of the heap anyway.

    // To avoid this the Eden needs to be big enough to fit all the small objects.

    private static final int INITIAL_HEAP_SIZE  = 200 * 1024 * 1024;

    private static final int MINIMAL_YOUNG_SIZE = 190 * 1024 * 1024;

    private static final int MAXIMUM_HEAP_SIZE  = 256 * 1024 * 1024;

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

    public static void main(String[] args) throws Exception, Throwable {

        ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(

                "-XX:InitialHeapSize=" + INITIAL_HEAP_SIZE,

                "-Xmn" + MINIMAL_YOUNG_SIZE,

                "-Xmx" + MAXIMUM_HEAP_SIZE,

                "-XX:MinHeapFreeRatio=10",

                "-XX:MaxHeapFreeRatio=11",

                "-XX:+UseG1GC",

                "-XX:G1HeapRegionSize=" + REGION_SIZE,

                "-XX:-ExplicitGCInvokesConcurrent",

                "-verbose:gc",

                GCTest.class.getName()

        );

        OutputAnalyzer output = ProcessTools.executeProcess(pb);

        output.shouldHaveExitValue(0);

    }

    static class GCTest {

        private static final String MIN_FREE_RATIO_FLAG_NAME = "MinHeapFreeRatio";

        private static final String MAX_FREE_RATIO_FLAG_NAME = "MaxHeapFreeRatio";

        private static final String NEW_SIZE_FLAG_NAME = "NewSize";

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

        private static final int SMALL_OBJS_SIZE  = 10 * 1024; // 10kB

        private static final int SMALL_OBJS_COUNT = MINIMAL_YOUNG_SIZE / (SMALL_OBJS_SIZE-1);

        private static final int ALLOCATE_COUNT = 3;

        // try to put all humongous object into gap between min young size and initial heap size

        // to avoid implicit GCs

        private static final int HUMONG_OBJS_SIZE = (int) Math.max(

                (INITIAL_HEAP_SIZE - MINIMAL_YOUNG_SIZE) / ALLOCATE_COUNT / 4,

                REGION_SIZE * 1.1

        );

        private static final long initialHeapSize = getHeapMemoryUsage().getUsed();

        public static void main(String[] args) throws InterruptedException {

            new GCTest().test();

        }

        private void test() throws InterruptedException {

            MemoryUsagePrinter.printMemoryUsage("init");

            allocate();

            System.gc();

            MemoryUsage muFull = getHeapMemoryUsage();

            MemoryUsagePrinter.printMemoryUsage("allocated");

            free();

            //Thread.sleep(1000); // sleep before measures due lags in JMX

            MemoryUsage muFree = getHeapMemoryUsage();

            MemoryUsagePrinter.printMemoryUsage("free");

            assertLessThan(muFree.getCommitted(), muFull.getCommitted(), prepareMessageCommittedIsNotLess() );

        }

        private void allocate() {

            System.out.format("Will allocate objects of small size = %s and humongous size = %s",

                    MemoryUsagePrinter.humanReadableByteCount(SMALL_OBJS_SIZE, false),

                    MemoryUsagePrinter.humanReadableByteCount(HUMONG_OBJS_SIZE, false)

            );

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

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

                allocateList(stuff, SMALL_OBJS_COUNT / ALLOCATE_COUNT, SMALL_OBJS_SIZE);

                garbage.add(stuff);

                ArrayList<byte[]> humongousStuff = new ArrayList<>();

                allocateList(humongousStuff, 4, HUMONG_OBJS_SIZE);

                garbage.add(humongousStuff);

            }

        }

        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

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

            if (stuff.size() > 1) {

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

            }

            System.gc();

        }

        private String prepareMessageCommittedIsNotLess() {

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

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

                garbage.add(new byte[size]);

            }

        }

    }

    static MemoryUsage getHeapMemoryUsage() {

        return ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();

    }

    /**

     * Prints memory usage to standard output

     */

    static 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

            );

        }

    }

}