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

类 SharedMemoryMmapIOEngine

java.lang.Object

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

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

所有已实现的接口:

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.

字段概要

从类继承的字段 org.apache.hadoop.hbase.io.hfile.bucket.FileMmapIOEngine

bufferArray, path, size

构造器概要

构造器

构造器和说明
SharedMemoryMmapIOEngine(String filePath, long capacity)

方法概要

限定符和类型	方法和说明
Cacheable	read(long offset, int length, CacheableDeserializer<Cacheable> deserializer) 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.

从类继承的方法 org.apache.hadoop.hbase.io.hfile.bucket.FileMmapIOEngine

isPersistent, shutdown, sync, toString, write, write

从类继承的方法 java.lang.Object

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

构造器详细资料

SharedMemoryMmapIOEngine

public SharedMemoryMmapIOEngine(String filePath,
                                long capacity)
                         throws IOException

抛出:

IOException

方法详细资料

usesSharedMemory

public boolean usesSharedMemory()

从接口复制的说明: 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.

返回:

true when IOEngine using shared memory.

read

public Cacheable read(long offset,
                      int length,
                      CacheableDeserializer<Cacheable> deserializer)
               throws IOException

从接口复制的说明: IOEngine

Transfers data from IOEngine to a Cacheable object.

指定者:

read 在接口中 IOEngine

指定者:

read 在类中 FileMmapIOEngine

参数:

offset - The offset in the IO engine where the first byte to be read

length - How many bytes to be read from the offset

deserializer - The deserializer to be used to make a Cacheable from the data.

返回:

Cacheable

抛出:

IOException