Package org.apache.bookkeeper.bookie

Class SkipListArena

java.lang.Object

org.apache.bookkeeper.bookie.SkipListArena

public class SkipListArena
extends java.lang.Object

SkipList allocation buffer to reduce memory fragment. Adapted from HBase project.

The SkipListArena is basically a bump-the-pointer allocator that allocates big (default 2MB) byte[] chunks from and then handles it out to threads that request slices into the array.

The purpose of this class is to combat heap fragmentation in the bookie. By ensuring that all KeyValues in a given SkipList refer only to large chunks of contiguous memory, we ensure that large blocks get freed up when the SkipList is flushed.

Without the Arena, the byte array allocated during insertion end up interleaved throughout the heap, and the old generation gets progressively more fragmented until a stop-the-world compacting collection occurs.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	SkipListArena.MemorySlice	The result of a single allocation.

Field Summary

Fields

Modifier and Type	Field	Description
(package private) int	chunkSize
(package private) int	maxAlloc

Constructor Summary

Constructors

Constructor	Description
SkipListArena(ServerConfiguration cfg)

Method Summary

Modifier and Type	Method	Description
SkipListArena.MemorySlice	allocateBytes(int size)	Allocate a slice of the given length.

Methods inherited from class java.lang.Object

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

Field Detail

chunkSize

final int chunkSize

maxAlloc

final int maxAlloc

Constructor Detail

SkipListArena

public SkipListArena(ServerConfiguration cfg)

Method Detail

allocateBytes

public SkipListArena.MemorySlice allocateBytes(int size)

Allocate a slice of the given length.

If the size is larger than the maximum size specified for this allocator, returns null.