OByteBufferPool (OrientDB 2.2.1-SNAPSHOT API)

java.lang.Object
- com.orientechnologies.common.directmemory.OByteBufferPool

All Implemented Interfaces:

OByteBufferPoolMXBean
```
public class OByteBufferPool
extends Object
implements 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.

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)

Constructors
Constructor and Description
`OByteBufferPool(int pageSize)`
`OByteBufferPool(int pageSize, int maxChunkSize)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`ByteBuffer`	`acquireDirect(boolean clear)` Acquires direct memory buffer.
`long`	`getAllocatedBufferCount()`
`long`	`getAllocatedMemory()`
`double`	`getAllocatedMemoryInGB()`
`long`	`getAllocatedMemoryInMB()`
`int`	`getBuffersInThePool()`
`int`	`getBufferSize()`
`int`	`getMaxPagesPerChunk()`
`long`	`getOverflowBufferCount()`
`int`	`getSize()`
`static OByteBufferPool`	`instance()` Pool returned by this method is used in all components of storage.
`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.

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)
```
    Parameters:
    
    pageSize - Size of single page (DirectByteBuffer) returned by pool.
    
    maxChunkSize -
- 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.
  - getAllocatedBufferCount
```
public long getAllocatedBufferCount()
```
    Specified by:
    
    getAllocatedBufferCount 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.
  - 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

Class OByteBufferPool

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MBEAN_NAME

Constructor Detail

OByteBufferPool

OByteBufferPool

Method Detail

instance

getSize

getMaxPagesPerChunk

acquireDirect

release

getBufferSize

getAllocatedBufferCount

getOverflowBufferCount

getBuffersInThePool

getAllocatedMemory

getAllocatedMemoryInMB

getAllocatedMemoryInGB

registerMBean

unregisterMBean