/**
* Copyright 2011 The Apache Software Foundation
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.afewmoreamps.util;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.nio.ByteBuffer;
import java.util.List;
import com.google.common.base.Preconditions;
public class DirectMemoryUtils {
/**
* @return the setting of -XX:MaxDirectMemorySize as a long. Returns 0 if
* -XX:MaxDirectMemorySize is not set.
*/
public static long getDirectMemorySize() {
RuntimeMXBean RuntimemxBean = ManagementFactory.getRuntimeMXBean();
List<String> arguments = RuntimemxBean.getInputArguments();
long multiplier = 1; //for the byte case.
for (String s : arguments) {
if (s.contains("-XX:MaxDirectMemorySize=")) {
String memSize = s.toLowerCase()
.replace("-xx:maxdirectmemorysize=", "").trim();
if (memSize.contains("k")) {
multiplier = 1024;
}
else if (memSize.contains("m")) {
multiplier = 1048576;
}
else if (memSize.contains("g")) {
multiplier = 1073741824;
}
memSize = memSize.replaceAll("[^\\d]", "");
long retValue = Long.parseLong(memSize);
return retValue * multiplier;
}
}
return 0;
}
/**
* DirectByteBuffers are garbage collected by using a phantom reference and a
* reference queue. Every once a while, the JVM checks the reference queue and
* cleans the DirectByteBuffers. However, as this doesn't happen
* immediately after discarding all references to a DirectByteBuffer, it's
* easy to OutOfMemoryError yourself using DirectByteBuffers. This function
* explicitly calls the Cleaner method of a DirectByteBuffer.
*
* @param toBeDestroyed
* The DirectByteBuffer that will be "cleaned". Utilizes reflection.
*
*/
public static void destroyDirectByteBuffer(ByteBuffer toBeDestroyed)
throws IllegalArgumentException, IllegalAccessException,
InvocationTargetException, SecurityException, NoSuchMethodException {
Preconditions.checkArgument(toBeDestroyed.isDirect(),
"toBeDestroyed isn't direct!");
Method cleanerMethod = toBeDestroyed.getClass().getMethod("cleaner");
cleanerMethod.setAccessible(true);
Object cleaner = cleanerMethod.invoke(toBeDestroyed);
Method cleanMethod = cleaner.getClass().getMethod("clean");
cleanMethod.setAccessible(true);
cleanMethod.invoke(cleaner);
}
}