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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * 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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import java.io.IOException;

import java.lang.management.BufferPoolMXBean;

import java.lang.management.ManagementFactory;

import java.nio.ByteBuffer;

import java.nio.channels.FileChannel;

import java.nio.file.Path;

import java.nio.file.Paths;

import static java.nio.file.StandardOpenOption.CREATE;

import static java.nio.file.StandardOpenOption.TRUNCATE_EXISTING;

import static java.nio.file.StandardOpenOption.WRITE;

import java.util.List;

import java.util.Random;

/*

 * @test

 * @requires sun.arch.data.model == "64"

 * @modules java.management

 * @build TestMaxCachedBufferSize

 * @run main/othervm TestMaxCachedBufferSize

 * @run main/othervm -Djdk.nio.maxCachedBufferSize=0 TestMaxCachedBufferSize

 * @run main/othervm -Djdk.nio.maxCachedBufferSize=2000 TestMaxCachedBufferSize

 * @run main/othervm -Djdk.nio.maxCachedBufferSize=100000 TestMaxCachedBufferSize

 * @run main/othervm -Djdk.nio.maxCachedBufferSize=10000000 TestMaxCachedBufferSize

 * @summary Test the implementation of the jdk.nio.maxCachedBufferSize property.

 */

public class TestMaxCachedBufferSize {

    private static final int DEFAULT_ITERS = 10 * 1000;

    private static final int DEFAULT_THREAD_NUM = 4;

    private static final int SMALL_BUFFER_MIN_SIZE =  4 * 1024;

    private static final int SMALL_BUFFER_MAX_SIZE = 64 * 1024;

    private static final int SMALL_BUFFER_DIFF_SIZE =

                                 SMALL_BUFFER_MAX_SIZE - SMALL_BUFFER_MIN_SIZE;

    private static final int LARGE_BUFFER_MIN_SIZE =      512 * 1024;

    private static final int LARGE_BUFFER_MAX_SIZE = 4 * 1024 * 1024;

    private static final int LARGE_BUFFER_DIFF_SIZE =

                                 LARGE_BUFFER_MAX_SIZE - LARGE_BUFFER_MIN_SIZE;

    private static final int LARGE_BUFFER_FREQUENCY = 100;

    private static final String FILE_NAME_PREFIX = "nio-out-file-";

    private static final int VERBOSE_PERIOD = 5 * 1000;

    private static int iters = DEFAULT_ITERS;

    private static int threadNum = DEFAULT_THREAD_NUM;

    private static BufferPoolMXBean getDirectPool() {

        final List<BufferPoolMXBean> pools =

                  ManagementFactory.getPlatformMXBeans(BufferPoolMXBean.class);

        for (BufferPoolMXBean pool : pools) {

            if (pool.getName().equals("direct")) {

                return pool;

            }

        }

        throw new Error("could not find direct pool");

    }

    private static final BufferPoolMXBean directPool = getDirectPool();

    // Each worker will do write operations on a file channel using

    // buffers of various sizes. The buffer size is randomly chosen to

    // be within a small or a large range. This way we can control

    // which buffers can be cached (all, only the small ones, or none)

    // by setting the jdk.nio.maxCachedBufferSize property.

    private static class Worker implements Runnable {

        private final int id;

        private final Random random = new Random();

        private long smallBufferCount = 0;

        private long largeBufferCount = 0;

        private int getWriteSize() {

            int minSize = 0;

            int diff = 0;

            if (random.nextInt() % LARGE_BUFFER_FREQUENCY != 0) {

                // small buffer

                minSize = SMALL_BUFFER_MIN_SIZE;

                diff = SMALL_BUFFER_DIFF_SIZE;

                smallBufferCount += 1;

            } else {

                // large buffer

                minSize = LARGE_BUFFER_MIN_SIZE;

                diff = LARGE_BUFFER_DIFF_SIZE;

                largeBufferCount += 1;

            }

            return minSize + random.nextInt(diff);

        }

        private void loop() {

            final String fileName = String.format("%s%d", FILE_NAME_PREFIX, id);

            try {

                for (int i = 0; i < iters; i += 1) {

                    final int writeSize = getWriteSize();

                    // This will allocate a HeapByteBuffer. It should not

                    // be a direct buffer, otherwise the write() method on

                    // the channel below will not create a temporary

                    // direct buffer for the write.

                    final ByteBuffer buffer = ByteBuffer.allocate(writeSize);

                    // Put some random data on it.

                    while (buffer.hasRemaining()) {

                        buffer.put((byte) random.nextInt());

                    }

                    buffer.rewind();

                    final Path file = Paths.get(fileName);

                    try (FileChannel outChannel = FileChannel.open(file, CREATE, TRUNCATE_EXISTING, WRITE)) {

                        // The write() method will create a temporary

                        // direct buffer for the write and attempt to cache

                        // it. It's important that buffer is not a

                        // direct buffer, otherwise the temporary buffer

                        // will not be created.

                        long res = outChannel.write(buffer);

                    }

                    if ((i + 1) % VERBOSE_PERIOD == 0) {

                        System.out.printf(

                          " Worker %3d | %8d Iters | Small %8d Large %8d | Direct %4d / %7dK\n",

                          id, i + 1, smallBufferCount, largeBufferCount,

                          directPool.getCount(), directPool.getTotalCapacity() / 1024);

                    }

                }

            } catch (IOException e) {

                throw new Error("I/O error", e);

            }

        }

        @Override

        public void run() {

            loop();

        }

        public Worker(int id) {

            this.id = id;

        }

    }

    public static void checkDirectBuffers(long expectedCount, long expectedMax) {

        final long directCount = directPool.getCount();

        final long directTotalCapacity = directPool.getTotalCapacity();

        System.out.printf("Direct %d / %dK\n",

                          directCount, directTotalCapacity / 1024);

        // Note that directCount could be < expectedCount. This can

        // happen if a GC occurs after one of the worker threads exits

        // since its thread-local DirectByteBuffer could be cleaned up

        // before we reach here.

        if (directCount > expectedCount) {

            throw new Error(String.format(

                "inconsistent direct buffer total count, expected = %d, found = %d",

                expectedCount, directCount));

        }

        if (directTotalCapacity > expectedMax) {

            throw new Error(String.format(

                "inconsistent direct buffer total capacity, expectex max = %d, found = %d",

                expectedMax, directTotalCapacity));

        }

    }

    public static void main(String[] args) {

        final String maxBufferSizeStr = System.getProperty("jdk.nio.maxCachedBufferSize");

        final long maxBufferSize =

            (maxBufferSizeStr != null) ? Long.valueOf(maxBufferSizeStr) : Long.MAX_VALUE;

        // We assume that the max cannot be equal to a size of a

        // buffer that can be allocated (makes sanity checking at the

        // end easier).

        if ((SMALL_BUFFER_MIN_SIZE <= maxBufferSize &&

                                     maxBufferSize <= SMALL_BUFFER_MAX_SIZE) ||

            (LARGE_BUFFER_MIN_SIZE <= maxBufferSize &&

                                     maxBufferSize <= LARGE_BUFFER_MAX_SIZE)) {

            throw new Error(String.format("max buffer size = %d not allowed",

                                          maxBufferSize));

        }

        System.out.printf("Threads %d | Iterations %d | MaxBufferSize %d\n",

                          threadNum, iters, maxBufferSize);

        System.out.println();

        final Thread[] threads = new Thread[threadNum];

        for (int i = 0; i < threadNum; i += 1) {

            threads[i] = new Thread(new Worker(i));

            threads[i].start();

        }

        try {

            for (int i = 0; i < threadNum; i += 1) {

                threads[i].join();

            }

        } catch (InterruptedException e) {

            throw new Error("join() interrupted!", e);

        }

        // There is an assumption here that, at this point, only the

        // cached DirectByteBuffers should be active. Given we

        // haven't used any other DirectByteBuffers in this test, this

        // should hold.

        //

        // Also note that we can only do the sanity checking at the

        // end and not during the run given that, at any time, there

        // could be buffers currently in use by some of the workers

        // that will not be cached.

        System.out.println();

        if (maxBufferSize < SMALL_BUFFER_MAX_SIZE) {

            // The max buffer size is smaller than all buffers that

            // were allocated. No buffers should have been cached.

            checkDirectBuffers(0, 0);

        } else if (maxBufferSize < LARGE_BUFFER_MIN_SIZE) {

            // The max buffer size is larger than all small buffers

            // but smaller than all large buffers that were

            // allocated. Only small buffers could have been cached.

            checkDirectBuffers(threadNum,

                               (long) threadNum * (long) SMALL_BUFFER_MAX_SIZE);

        } else {

            // The max buffer size is larger than all buffers that

            // were allocated. All buffers could have been cached.

            checkDirectBuffers(threadNum,

                               (long) threadNum * (long) LARGE_BUFFER_MAX_SIZE);

        }

    }

}