Package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl

Class FsDatasetCache

java.lang.Object

org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetCache

@Private
@Unstable
public class FsDatasetCache
extends Object

Manages caching for an FsDatasetImpl by using the mmap(2) and mlock(2) system calls to lock blocks into memory. Block checksums are verified upon entry into the cache.

Constructor Summary

Constructors

Constructor	Description
FsDatasetCache(org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl dataset)

Method Summary

Modifier and Type	Method	Description
long	getCacheCapacity()	Get the maximum amount of bytes we can cache either on DRAM or on persistent memory.
long	getCacheUsed()	Get the approximate amount of cache space used either on DRAM or on persistent memory.
long	getMemCacheCapacity()	Get the maximum amount of bytes we can cache on DRAM.
long	getMemCacheUsed()	Get the approximate amount of DRAM cache space used.
long	getNumBlocksCached()
long	getNumBlocksFailedToCache()
long	getNumBlocksFailedToUncache()
void	initCache(String bpid)	For persistent memory cache, create cache subdirectory specified with blockPoolId to store cache data.
boolean	isCached(String bpid, long blockId)

Methods inherited from class java.lang.Object

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

Constructor Details

FsDatasetCache

public FsDatasetCache(org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl dataset)
               throws IOException

Throws:

IOException

Method Details

initCache

public void initCache(String bpid)
               throws IOException

For persistent memory cache, create cache subdirectory specified with blockPoolId to store cache data. Recover the status of cache in persistent memory, if any.

Throws:

IOException

getMemCacheUsed

public long getMemCacheUsed()

Get the approximate amount of DRAM cache space used.

getCacheUsed

public long getCacheUsed()

Get the approximate amount of cache space used either on DRAM or on persistent memory.

Returns:

getMemCacheCapacity

public long getMemCacheCapacity()

Get the maximum amount of bytes we can cache on DRAM. This is a constant.

getCacheCapacity

public long getCacheCapacity()

Get the maximum amount of bytes we can cache either on DRAM or on persistent memory. This is a constant.

getNumBlocksFailedToCache

public long getNumBlocksFailedToCache()

getNumBlocksFailedToUncache

public long getNumBlocksFailedToUncache()

getNumBlocksCached

public long getNumBlocksCached()

isCached

public boolean isCached(String bpid,
 long blockId)