Package org.apache.hadoop.util

Class DirectBufferPool

java.lang.Object

org.apache.hadoop.util.DirectBufferPool

@LimitedPrivate({"HDFS","MapReduce"})
@Evolving
public class DirectBufferPool
extends Object

A simple class for pooling direct ByteBuffers. This is necessary because Direct Byte Buffers do not take up much space on the heap, and hence will not trigger GCs on their own. However, they do take native memory, and thus can cause high memory usage if not pooled. The pooled instances are referred to only via weak references, allowing them to be collected when a GC does run. This class only does effective pooling when many buffers will be allocated at the same size. There is no attempt to reuse larger buffers to satisfy smaller allocations.

Constructor Summary

Constructors

Constructor	Description
DirectBufferPool()

Method Summary

Modifier and Type	Method	Description
ByteBuffer	getBuffer(int size)	Allocate a direct buffer of the specified size, in bytes.
void	returnBuffer(ByteBuffer buf)	Return a buffer into the pool.

Methods inherited from class java.lang.Object

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

Constructor Details

DirectBufferPool

public DirectBufferPool()

Method Details

getBuffer

public ByteBuffer getBuffer(int size)

Allocate a direct buffer of the specified size, in bytes. If a pooled buffer is available, returns that. Otherwise allocates a new one.

Parameters:

size - size.

Returns:

ByteBuffer.

returnBuffer

public void returnBuffer(ByteBuffer buf)

Return a buffer into the pool. After being returned, the buffer may be recycled, so the user must not continue to use it in any way.

Parameters:

buf - the buffer to return