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* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 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);
}
}
}