org.apache.hadoop.hbase.io.hfile.bucket

Class SharedMemoryMmapIOEngine

java.lang.Object

org.apache.hadoop.hbase.io.hfile.bucket.PersistentIOEngine

org.apache.hadoop.hbase.io.hfile.bucket.FileMmapIOEngine

org.apache.hadoop.hbase.io.hfile.bucket.SharedMemoryMmapIOEngine

All Implemented Interfaces:

IOEngine

@InterfaceAudience.Private
public class SharedMemoryMmapIOEngine
extends FileMmapIOEngine

IO engine that stores data in pmem devices such as DCPMM. This engine also mmaps the file from the given path. But note that this path has to be a path on the pmem device so that when mmapped the file's address is mapped to the Pmem's address space and not in the DRAM. Since this address space is exclusive for the Pmem device there is no swapping out of the mmapped contents that generally happens when DRAM's free space is not enough to hold the specified file's mmapped contents. This gives us the option of using the MemoryType#SHARED type when serving the data from this pmem address space. We need not copy the blocks to the onheap space as we need to do for the case of ExclusiveMemoryMmapIOEngine.

Field Summary

Fields inherited from class org.apache.hadoop.hbase.io.hfile.bucket.FileMmapIOEngine

bufferArray, LOG, path, size

Fields inherited from class org.apache.hadoop.hbase.io.hfile.bucket.PersistentIOEngine

filePaths

Constructor Summary

Constructors

Constructor and Description
SharedMemoryMmapIOEngine(String filePath, long capacity)

Method Summary

Modifier and Type	Method and Description
Cacheable	read(BucketEntry be) Transfers data from IOEngine to a Cacheable object.
boolean	usesSharedMemory() IOEngine uses shared memory means, when reading Cacheable from it, those refers to the same memory area as used by the Engine for caching it.

Methods inherited from class org.apache.hadoop.hbase.io.hfile.bucket.FileMmapIOEngine

isPersistent, shutdown, sync, toString, write, write

Methods inherited from class org.apache.hadoop.hbase.io.hfile.bucket.PersistentIOEngine

calculateChecksum, verifyFileIntegrity

Methods inherited from class java.lang.Object

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

Constructor Detail

SharedMemoryMmapIOEngine

public SharedMemoryMmapIOEngine(String filePath,
                                long capacity)
                         throws IOException

Throws:

IOException

Method Detail

usesSharedMemory

public boolean usesSharedMemory()

Description copied from interface: IOEngine

IOEngine uses shared memory means, when reading Cacheable from it, those refers to the same memory area as used by the Engine for caching it.

Returns:

true when IOEngine using shared memory.

read

public Cacheable read(BucketEntry be)
               throws IOException

Description copied from interface: IOEngine

Transfers data from IOEngine to a Cacheable object.

Specified by:

read in interface IOEngine

Specified by:

read in class FileMmapIOEngine

Parameters:

be - maintains an (offset,len,refCnt) inside.

Returns:

Cacheable which will wrap the NIO ByteBuffers from IOEngine.

Throws:

IOException - when any IO error happen