Standard_MMgrOpt Class Reference

Open CASCADE memory manager optimized for speed. More...

#include <Standard_MMgrOpt.hxx>

Inheritance diagram for Standard_MMgrOpt:

Public Types
typedef void(*	TPCallBackFunc) (const bool theIsAlloc, void *const theStorage, const size_t theRoundSize, const size_t theSize)
	Declaration of a type pointer to the callback function that should accept the following arguments:

Public Member Functions
	Standard_MMgrOpt (const bool aClear=true, const bool aMMap=true, const size_t aCellSize=200, const int aNbPages=10000, const size_t aThreshold=40000)
	Constructor. If aClear is True, the allocated emmory will be nullified. For description of other parameters, see description of the class above.
	~Standard_MMgrOpt () override
	Frees all free lists and pools allocated for small blocks.
void *	Allocate (const size_t aSize) override
	Allocate aSize bytes; see class description above.
void *	Reallocate (void *thePtr, const size_t theSize) override
	Reallocate previously allocated aPtr to a new size; new address is returned. In case that aPtr is null, the function behaves exactly as Allocate.
void	Free (void *thePtr) override
	Free previously allocated block. Note that block can not all blocks are released to the OS by this method (see class description)
int	Purge (bool isDestroyed) override
	Release medium-sized blocks of memory in free lists to the system. Returns number of actually freed blocks.
Public Member Functions inherited from Standard_MMgrRoot
virtual	~Standard_MMgrRoot ()
	Virtual destructor; required for correct inheritance.

Static Public Member Functions
static void	SetCallBackFunction (TPCallBackFunc pFunc)
	Set the callback function. You may pass 0 there to turn off the callback. The callback function, if set, will be automatically called from within Allocate and Free methods.

Protected Member Functions
void	Initialize ()
	Internal - initialization of buffers.
size_t *	AllocMemory (size_t &aSize)
	Internal - allocation of memory using either malloc or memory mapped files. The size of the actually allocated block may be greater than requested one when memory mapping is used, since it is aligned to page size.
void	FreeMemory (void *aPtr, const size_t aSize)
	Internal - deallocation of memory taken by AllocMemory.
void	FreePools ()
	Internal - free memory pools allocated for small size blocks.

Protected Attributes
bool	myClear
	option to clear allocated memory
size_t	myFreeListMax
	last allocated index in the free blocks list
size_t **	myFreeList
	free blocks list
size_t	myCellSize
	small blocks size
int	myNbPages
	size (pages) for small block memory pools
size_t	myPageSize
	system-dependent memory page size
size_t *	myAllocList
	list of memory pools for small blocks
size_t *	myNextAddr
	next free address in the active memory pool
size_t *	myEndBlock
	end of the active memory pool
int	myMMap
	non-null if using memory mapped files for allocation of large blocks
size_t	myThreshold
	large block size
std::mutex	myMutex
	Mutex to protect free lists data.
std::mutex	myMutexPools
	Mutex to protect small block pools data.

Detailed Description

Open CASCADE memory manager optimized for speed.

The behaviour is different for memory blocks of different sizes, according to specified options provided to constructor:

• Small blocks with size less than or equal to aCellSize are allocated in big pools of memory. The parameter aNbPages specifies size of these pools in pages (operating system-dependent). When freed, small block is not returned to the system but added into free blocks list and reused when block of the same size is requested.
• Medium size blocks with size less than aThreshold are allocated using malloc() or calloc() function but not returned to the system when method Free() is called; instead they are put into free list and reused when block of the same size is requested. Blocks of medium size stored in free lists can be released to the system (by free()) by calling method Purge().
• Large blocks with size greater than or equal to aThreshold are allocated and freed directly: either using malloc()/calloc() and free(), or using memory mapped files (if option aMMap is True)

Thus the optimization of memory allocation/deallocation is reached for small and medium size blocks using free lists method; note that space allocated for small blocks cannot be (currently) released to the system while space for medium size blocks can be released by method Purge().

Note that destructor of that class frees all free lists and memory pools allocated for small blocks.

Note that size of memory blocks allocated by this memory manager is always rounded up to 16 bytes. In addition, 8 bytes are added at the beginning of the memory block to hold auxiliary information (size of the block when in use, or pointer to the next free block when in free list). This the expense of speed optimization. At the same time, allocating small blocks is usually less costly than directly by malloc since allocation is made once (when allocating a pool) and overheads induced by malloc are minimized.

Member Typedef Documentation

TPCallBackFunc

typedef void(* Standard_MMgrOpt::TPCallBackFunc) (const bool theIsAlloc, void *const theStorage, const size_t theRoundSize, const size_t theSize)

Declaration of a type pointer to the callback function that should accept the following arguments:

Parameters

theIsAlloc	true if the data is allocated, false if it is freed
theStorage	address of the allocated/freed block
theRoundSize	the real rounded size of the block
theSize	the size of the block that was requested by application (this value is correct only if theIsAlloc is true)

Constructor & Destructor Documentation

Standard_MMgrOpt()

Standard_MMgrOpt::Standard_MMgrOpt	(	const bool	aClear = true,
		const bool	aMMap = true,
		const size_t	aCellSize = 200,
		const int	aNbPages = 10000,
		const size_t	aThreshold = 40000 )

Constructor. If aClear is True, the allocated emmory will be nullified. For description of other parameters, see description of the class above.

~Standard_MMgrOpt()

Standard_MMgrOpt::~Standard_MMgrOpt ( )

override

Frees all free lists and pools allocated for small blocks.

Member Function Documentation

Allocate()

void * Standard_MMgrOpt::Allocate ( const size_t aSize )

overridevirtual

Allocate aSize bytes; see class description above.

Implements Standard_MMgrRoot.

AllocMemory()

size_t * Standard_MMgrOpt::AllocMemory ( size_t & aSize )

protected

Internal - allocation of memory using either malloc or memory mapped files. The size of the actually allocated block may be greater than requested one when memory mapping is used, since it is aligned to page size.

Free()

void Standard_MMgrOpt::Free ( void * thePtr )

overridevirtual

Free previously allocated block. Note that block can not all blocks are released to the OS by this method (see class description)

Implements Standard_MMgrRoot.

FreeMemory()

void Standard_MMgrOpt::FreeMemory ( void * aPtr, const size_t aSize )

protected

Internal - deallocation of memory taken by AllocMemory.

FreePools()

void Standard_MMgrOpt::FreePools ( )

protected

Internal - free memory pools allocated for small size blocks.

Initialize()

void Standard_MMgrOpt::Initialize ( )

protected

Internal - initialization of buffers.

Purge()

int Standard_MMgrOpt::Purge ( bool isDestroyed )

overridevirtual

Release medium-sized blocks of memory in free lists to the system. Returns number of actually freed blocks.

Reimplemented from Standard_MMgrRoot.

Reallocate()

void * Standard_MMgrOpt::Reallocate ( void * thePtr, const size_t theSize )

overridevirtual

Reallocate previously allocated aPtr to a new size; new address is returned. In case that aPtr is null, the function behaves exactly as Allocate.

Implements Standard_MMgrRoot.

SetCallBackFunction()

static void Standard_MMgrOpt::SetCallBackFunction ( TPCallBackFunc pFunc )

static

Set the callback function. You may pass 0 there to turn off the callback. The callback function, if set, will be automatically called from within Allocate and Free methods.

Field Documentation

myAllocList

size_t* Standard_MMgrOpt::myAllocList

protected

list of memory pools for small blocks

myCellSize

size_t Standard_MMgrOpt::myCellSize

protected

small blocks size

myClear

bool Standard_MMgrOpt::myClear

protected

option to clear allocated memory

myEndBlock

size_t* Standard_MMgrOpt::myEndBlock

protected

end of the active memory pool

myFreeList

size_t** Standard_MMgrOpt::myFreeList

protected

free blocks list

myFreeListMax

size_t Standard_MMgrOpt::myFreeListMax

protected

last allocated index in the free blocks list

myMMap

int Standard_MMgrOpt::myMMap

protected

non-null if using memory mapped files for allocation of large blocks

myMutex

std::mutex Standard_MMgrOpt::myMutex

protected

Mutex to protect free lists data.

myMutexPools

std::mutex Standard_MMgrOpt::myMutexPools

protected

Mutex to protect small block pools data.

myNbPages

int Standard_MMgrOpt::myNbPages

protected

size (pages) for small block memory pools

myNextAddr

size_t* Standard_MMgrOpt::myNextAddr

protected

next free address in the active memory pool

myPageSize

size_t Standard_MMgrOpt::myPageSize

protected

system-dependent memory page size

myThreshold

size_t Standard_MMgrOpt::myThreshold

protected

large block size

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The documentation for this class was generated from the following file:

• Standard_MMgrOpt.hxx