org.apache.cassandra.utils

Class SlabAllocator

java.lang.Object

org.apache.cassandra.utils.Allocator

org.apache.cassandra.utils.SlabAllocator

public class SlabAllocator
extends Allocator

The SlabAllocator is a bump-the-pointer allocator that allocates large (2MB by default) regions and then doles them out to threads that request slices into the array.

The purpose of this class is to combat heap fragmentation in long lived objects: by ensuring that all allocations with similar lifetimes only to large regions of contiguous memory, we ensure that large blocks get freed up at the same time.

Otherwise, variable length byte arrays allocated end up interleaved throughout the heap, and the old generation gets progressively more fragmented until a stop-the-world compacting collection occurs.

Constructor Summary

Constructors

Constructor and Description
SlabAllocator()

Method Summary

Methods

Modifier and Type	Method and Description
java.nio.ByteBuffer	allocate(int size)
long	getMaximumSize()
long	getMinimumSize()

Methods inherited from class org.apache.cassandra.utils.Allocator

clone

Methods inherited from class java.lang.Object

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

Constructor Detail

SlabAllocator

public SlabAllocator()

Method Detail

allocate

public java.nio.ByteBuffer allocate(int size)

Specified by:

allocate in class Allocator

getMinimumSize

public long getMinimumSize()

Returns:

a lower bound on how much space has been allocated

getMaximumSize

public long getMaximumSize()

Returns:

an upper bound on how much space has been allocated