org.apache.hadoop.hbase.util

Class DirectMemoryUtils

java.lang.Object

org.apache.hadoop.hbase.util.DirectMemoryUtils

@InterfaceAudience.Private
 @InterfaceStability.Evolving
public class DirectMemoryUtils
extends Object

Utilities for interacting with and monitoring DirectByteBuffer allocations.

Field Summary

Fields

Modifier and Type	Field and Description
private static MBeanServer	BEAN_SERVER
private static boolean	HAS_MEMORY_USED_ATTRIBUTE
private static org.slf4j.Logger	LOG
private static String	MEMORY_USED
private static ObjectName	NIO_DIRECT_POOL

Constructor Summary

Constructors

Constructor and Description
DirectMemoryUtils()

Method Summary

Modifier and Type	Method and Description
static void	destroyDirectByteBuffer(ByteBuffer toBeDestroyed) DirectByteBuffers are garbage collected by using a phantom reference and a reference queue.
static long	getDirectMemorySize()
static long	getDirectMemoryUsage()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LOG

private static final org.slf4j.Logger LOG

MEMORY_USED

private static final String MEMORY_USED

See Also:

Constant Field Values

BEAN_SERVER

private static final MBeanServer BEAN_SERVER

NIO_DIRECT_POOL

private static final ObjectName NIO_DIRECT_POOL

HAS_MEMORY_USED_ATTRIBUTE

private static final boolean HAS_MEMORY_USED_ATTRIBUTE

Constructor Detail

DirectMemoryUtils

public DirectMemoryUtils()

Method Detail

getDirectMemorySize

public static long getDirectMemorySize()

Returns:

the setting of -XX:MaxDirectMemorySize as a long. Returns 0 if -XX:MaxDirectMemorySize is not set.

getDirectMemoryUsage

public static long getDirectMemoryUsage()

Returns:

the current amount of direct memory used.

destroyDirectByteBuffer

public static void destroyDirectByteBuffer(ByteBuffer toBeDestroyed)
                                    throws IllegalArgumentException,
                                           IllegalAccessException,
                                           InvocationTargetException,
                                           SecurityException,
                                           NoSuchMethodException

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.

Parameters:

toBeDestroyed - The DirectByteBuffer that will be "cleaned". Utilizes reflection.

Throws:

IllegalArgumentException

IllegalAccessException

InvocationTargetException

SecurityException

NoSuchMethodException