org.apache.hadoop.hbase.regionserver

类 HeapMemStoreLAB

java.lang.Object

org.apache.hadoop.hbase.regionserver.HeapMemStoreLAB

所有已实现的接口:

MemStoreLAB

@InterfaceAudience.Private
public class HeapMemStoreLAB
extends Object
implements MemStoreLAB

A memstore-local allocation buffer.

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

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

Without the MSLAB, 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.

TODO: we should probably benchmark whether word-aligning the allocations would provide a performance improvement - probably would speed up the Bytes.toLong/Bytes.toInt calls in KeyValue, but some of those are cached anyway

构造器概要

构造器

构造器和说明
HeapMemStoreLAB()
HeapMemStoreLAB(org.apache.hadoop.conf.Configuration conf)

方法概要

方法

限定符和类型	方法和说明
ByteRange	allocateBytes(int size) Allocate a slice of the given length.
void	close() Close this instance since it won't be used any more, try to put the chunks back to pool
void	decScannerCount() Called when closing a scanner on the data of this MemStoreLAB
void	incScannerCount() Called when opening a scanner on the data of this MemStoreLAB

从类继承的方法 java.lang.Object

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

构造器详细资料

HeapMemStoreLAB

public HeapMemStoreLAB()

HeapMemStoreLAB

public HeapMemStoreLAB(org.apache.hadoop.conf.Configuration conf)

方法详细资料

allocateBytes

public ByteRange 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.

指定者:

allocateBytes 在接口中 MemStoreLAB

返回:

ByteRange

close

public void close()

Close this instance since it won't be used any more, try to put the chunks back to pool

指定者:

close 在接口中 MemStoreLAB

incScannerCount

public void incScannerCount()

Called when opening a scanner on the data of this MemStoreLAB

指定者:

incScannerCount 在接口中 MemStoreLAB

decScannerCount

public void decScannerCount()

Called when closing a scanner on the data of this MemStoreLAB

指定者:

decScannerCount 在接口中 MemStoreLAB