C# Class GSF.IO.Unmanaged.MemoryPool

This class allocates and pools unmanaged memory. Designed to be internally thread safe.

Be careful how this class is referenced. Deadlocks can occur when registering to event RequestCollection and when calling AllocatePage. See comments for these methods for considerations.

Inheritance: IDisposable

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Public Properties

Property	Type	Description
PageMask	int
PageShiftBits	int
PageSize	int

Public Methods

Method	Description
AllocatePage ( int &index, IntPtr &addressPointer ) : void	Requests a page from the buffered pool. If there is not a free one available, method will block and request a collection of unused pages by raising RequestCollection event. IMPORTANT NOTICE: Be careful when calling this method as the calling thread will block if no memory is available to have a background collection to occur. There is a possiblity for a deadlock if calling this method from within a lock. The page allocated will not be initialized, so assume that the data is garbage.
Dispose ( ) : void	Releases all the resources used by the MemoryPool object.
MemoryPool ( int pageSize = 64*1024, long maximumBufferSize = -1, TargetUtilizationLevels utilizationLevel = TargetUtilizationLevels.Low ) : System	Creates a new MemoryPool.
ReleasePage ( int pageIndex ) : void	Releases the page back to the buffer pool for reallocation. The page released will not be initialized. Releasing a page is on the honor system. Rereferencing a released page will most certainly cause unexpected crashing or data corruption or any other unexplained behavior.
ReleasePages ( IEnumerable pageIndexes ) : void	Releases all of the supplied pages
SetMaximumBufferSize ( long value ) : long	Changes the allowable buffer size
SetTargetUtilizationLevel ( TargetUtilizationLevels utilizationLevel ) : void	Changes the utilization level

Private Methods

Method	Description
CalculateStopShrinkingLimit ( long size ) : long	Calculates at what point a collection cycle will cease prematurely.
CalculateThresholds ( long maximumBufferSize, TargetUtilizationLevels levels ) : void
GetCollectionLevelBasedOnSize ( long size ) : int	Gets the number of collection rounds base on the size.
GetCollectionLevelString ( int iterations ) : string
RemoveDeadEvents ( ) : void	Searches the collection events and removes any events that have been collected by the garbage collector.
RequestMoreFreeBlocks ( ) : void	Determines whether to allocate more memory or to do a collection cycle on the existing pool.

Method Details

AllocatePage() public method

Requests a page from the buffered pool. If there is not a free one available, method will block and request a collection of unused pages by raising RequestCollection event.

IMPORTANT NOTICE: Be careful when calling this method as the calling thread will block if no memory is available to have a background collection to occur. There is a possiblity for a deadlock if calling this method from within a lock. The page allocated will not be initialized, so assume that the data is garbage.

public AllocatePage ( int &index, IntPtr &addressPointer ) : void
index	int	the index id of the page that was allocated
addressPointer	System.IntPtr	outputs a address that can be used /// to access this memory address. You cannot call release with this parameter. /// Use the returned index to release pages.
return	void

Dispose() public method

Releases all the resources used by the MemoryPool object.

public Dispose ( ) : void
return	void

MemoryPool() public method

Creates a new MemoryPool.

public MemoryPool ( int pageSize = 64*1024, long maximumBufferSize = -1, TargetUtilizationLevels utilizationLevel = TargetUtilizationLevels.Low ) : System
pageSize	int	The desired page size. Must be between 4KB and 256KB
maximumBufferSize	long	The desired maximum size of the allocation. Note: could be less if there is not enough system memory.
utilizationLevel	TargetUtilizationLevels	Specifies the desired utilization level of the allocated space.
return	System

ReleasePage() public method

Releases the page back to the buffer pool for reallocation.

The page released will not be initialized. Releasing a page is on the honor system. Rereferencing a released page will most certainly cause unexpected crashing or data corruption or any other unexplained behavior.

public ReleasePage ( int pageIndex ) : void
pageIndex	int	A value of zero or less will return silently
return	void

ReleasePages() public method

Releases all of the supplied pages

public ReleasePages ( IEnumerable pageIndexes ) : void
pageIndexes	IEnumerable	A collection of pages.
return	void

SetMaximumBufferSize() public method

Changes the allowable buffer size

public SetMaximumBufferSize ( long value ) : long
value	long	the number of bytes to set.
return	long

SetTargetUtilizationLevel() public method

Changes the utilization level

public SetTargetUtilizationLevel ( TargetUtilizationLevels utilizationLevel ) : void
utilizationLevel	TargetUtilizationLevels
return	void

Property Details

PageMask public_oe property

Provides a mask that the user can apply that can be used to get the offset position of a page.

public int PageMask
return	int

PageShiftBits public_oe property

Gets the number of bits that must be shifted to calculate an index of a position. This is not the same as a page index that is returned by the allocate functions.

public int PageShiftBits
return	int

PageSize public_oe property

Each page will be exactly this size (Based on RAM)

public int PageSize
return	int