com.orientechnologies.common.directmemory

Class OByteBufferPool

java.lang.Object

com.orientechnologies.common.directmemory.OByteBufferPool

All Implemented Interfaces:

OByteBufferPoolMXBean, OOrientShutdownListener

public class OByteBufferPool
extends Object
implements OOrientShutdownListener, OByteBufferPoolMXBean

Object of this class works at the same time as factory for DirectByteBuffer objects and pool for DirectByteBuffer objects which were used and now are free to be reused by other parts of the code.

All DirectByteBuffer objects have the same size which is specified in objects constructor as "page size". Despite of the fact that size of page is relatively small memory may be acquired from OS in relatively big chunks. It is done to optimize memory usage inside of database.

See Also:

OGlobalConfiguration.MEMORY_CHUNK_SIZE

Field Summary

Fields

Modifier and Type	Field and Description
static String	MBEAN_NAME OByteBufferPool's MBean name.

Constructor Summary

Constructors

Constructor and Description
OByteBufferPool(int pageSize)
OByteBufferPool(int pageSize, int maxChunkSize, long preAllocationLimit)

Method Summary

Modifier and Type	Method and Description
ByteBuffer	acquireDirect(boolean clear) Acquires direct memory buffer.
long	getAllocatedMemory()
double	getAllocatedMemoryInGB()
long	getAllocatedMemoryInMB()
int	getBuffersInThePool()
int	getBufferSize()
int	getMaxPagesPerChunk()
int	getMaxPagesPerSingleArea()
long	getOverflowBufferCount()
int	getPoolSize()
long	getPreAllocatedBufferCount()
long	getPreAllocationLimit()
int	getSize()
static OByteBufferPool	instance() Pool returned by this method is used in all components of storage.
void	logTrackedBufferInfo(String prefix, ByteBuffer buffer) Logs all known tracking information about the given buffer.
void	onShutdown()
void	registerMBean() Registers the MBean for this byte buffer pool.
void	release(ByteBuffer buffer) Put buffer which is not used any more back to the pool.
void	unregisterMBean() Unregisters the MBean for this byte buffer pool.
void	verifyState() Verifies the state of this byte buffer pool for a consistency, leaks, etc.

Methods inherited from class java.lang.Object

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

Field Detail

MBEAN_NAME

public static final String MBEAN_NAME

OByteBufferPool's MBean name.

See Also:

Constant Field Values

Constructor Detail

OByteBufferPool

public OByteBufferPool(int pageSize)

Parameters:

pageSize - Size of single page (instance of DirectByteBuffer) returned by pool.

OByteBufferPool

public OByteBufferPool(int pageSize,
                       int maxChunkSize,
                       long preAllocationLimit)

Parameters:

pageSize - Size of single page (DirectByteBuffer) returned by pool.

maxChunkSize - Maximum allocation chunk size

preAllocationLimit - Limit of memory which will be allocated by big chunks

Method Detail

instance

public static OByteBufferPool instance()

Pool returned by this method is used in all components of storage. Memory used by this pool is preallocated by chunks with size not more than OGlobalConfiguration.MEMORY_CHUNK_SIZE Amount of maximum memory preallocated by this pool equals to sum of OGlobalConfiguration.DISK_CACHE_SIZE and OGlobalConfiguration.WAL_CACHE_SIZE and one.

Size of single page equals to OGlobalConfiguration.DISK_CACHE_PAGE_SIZE.

Returns:

Global instance is used inside of storage.

getSize

public int getSize()

Returns:

Amount of pages which are available in pool. Pages which were allocated and now not used.

getMaxPagesPerChunk

public int getMaxPagesPerChunk()

Returns:

Maximum amount of pages in single preallocate memory chunk.

acquireDirect

public ByteBuffer acquireDirect(boolean clear)

Acquires direct memory buffer. If there is free (already released) direct memory buffer we reuse it, otherwise either new memory chunk is allocated from direct memory or slice of already preallocated memory chunk is used as new byte buffer instance.

If we reached maximum amount of preallocated memory chunks then small portion of direct memory equals to page size is allocated. Byte order of returned direct memory buffer equals to native byte order.

Position of returned buffer is always zero.

Parameters:

clear - Whether returned buffer should be filled with zeros before return.

Returns:

Direct memory buffer instance.

release

public void release(ByteBuffer buffer)

Put buffer which is not used any more back to the pool.

Parameters:

buffer - Not used instance of buffer.

getBufferSize

public int getBufferSize()

Specified by:

getBufferSize in interface OByteBufferPoolMXBean

Returns:

the buffer AKA page size in bytes of the associated OByteBufferPool.

getPreAllocatedBufferCount

public long getPreAllocatedBufferCount()

Specified by:

getPreAllocatedBufferCount in interface OByteBufferPoolMXBean

Returns:

the number of the allocated buffers of the associated OByteBufferPool, this does not include the overflow buffers.

getOverflowBufferCount

public long getOverflowBufferCount()

Specified by:

getOverflowBufferCount in interface OByteBufferPoolMXBean

Returns:

the number of the allocated overflow buffers of the associated OByteBufferPool.

getBuffersInThePool

public int getBuffersInThePool()

Specified by:

getBuffersInThePool in interface OByteBufferPoolMXBean

Returns:

the number of the free buffers currently in the pool of the associated OByteBufferPool.

getAllocatedMemory

public long getAllocatedMemory()

Specified by:

getAllocatedMemory in interface OByteBufferPoolMXBean

Returns:

the current total memory allocation size in bytes of the the associated OByteBufferPool, including the overflow buffer allocations.

getAllocatedMemoryInMB

public long getAllocatedMemoryInMB()

Specified by:

getAllocatedMemoryInMB in interface OByteBufferPoolMXBean

Returns:

the current total memory allocation size in megabytes of the the associated OByteBufferPool, including the overflow buffer allocations.

getAllocatedMemoryInGB

public double getAllocatedMemoryInGB()

Specified by:

getAllocatedMemoryInGB in interface OByteBufferPoolMXBean

Returns:

the current total memory allocation size in gigabytes of the the associated OByteBufferPool, including the overflow buffer allocations.

getPreAllocationLimit

public long getPreAllocationLimit()

Specified by:

getPreAllocationLimit in interface OByteBufferPoolMXBean

Returns:

Maximum amount of bytes which may be allocated using big chunks of memory

getMaxPagesPerSingleArea

public int getMaxPagesPerSingleArea()

Specified by:

getMaxPagesPerSingleArea in interface OByteBufferPoolMXBean

Returns:

Amount of pages which fit in single big chunk of memory preallocated during page allocation request.

getPoolSize

public int getPoolSize()

Specified by:

getPoolSize in interface OByteBufferPoolMXBean

Returns:

Size of the pool which contains records which were allocated but now were fried to the pool by database.

registerMBean

public void registerMBean()

Registers the MBean for this byte buffer pool.

See Also:

OByteBufferPoolMXBean

unregisterMBean

public void unregisterMBean()

Unregisters the MBean for this byte buffer pool.

See Also:

OByteBufferPoolMXBean

verifyState

public void verifyState()

Verifies the state of this byte buffer pool for a consistency, leaks, etc. OGlobalConfiguration.DIRECT_MEMORY_TRACK_MODE must be on, otherwise this method does nothing. Detected problems will be printed to the error log. If assertions are on and erroneous state is detected, verification will fail with AssertionError exception.

logTrackedBufferInfo

public void logTrackedBufferInfo(String prefix,
                                 ByteBuffer buffer)

Logs all known tracking information about the given buffer. OGlobalConfiguration.DIRECT_MEMORY_TRACK_MODE must be on, otherwise this method does nothing.

Parameters:

prefix - the log message prefix

buffer - the buffer to print information about

onShutdown

public void onShutdown()

Specified by:

onShutdown in interface OOrientShutdownListener