Pool Class Reference

#include <Pool.H>

List of all members.

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Detailed Description

Pool is a class to optimize memory allocation.

Pool is a class to optimize memory allocation. It is specialized to allocate fixed size chunks of memory specified by ptrSize in the constructor. Its operation is analogous to malloc, not new. It does not initialize the memory in any way. The constructor can optionally specify an initial pool size, and memory alignment. The pool size will grow as needed by calling new. The pool size never shrinks. Memory will be reclaimed at ~Pool(). The units of poolSize are number-of-ptrSize-chunks. The units of alignment are bytes.

Pool can only be used for objects of fixed size. Typically used in situations where a class or struct is being constantly constructed and deleted. Objects returned by value from functions, elements in a database, etc. Pool's tend to be allocated statically.

(from Copier.cpp)

    // static data member s_motionIemPool getting constructed
    Pool Copier::s_motionItemPool(sizeof(MotionItem), "Copier::MotionItem");

    // note the use of a 'placement new'
    MotionItem* item = new (s_motionItemPool.getPtr()) MotionItem(fromdi, todi, box);

    // if your object does requires it's destructor to be called.
    item->~MotionItem();

    // then return the memory chunk to your pool
    s_motionItemPool.returnPtr(item)

Technical note In the event of multi-threading Chombo, we will have to make pool access serialized (locks, single thread access, etc) or implement a fast lock-free version, or go back to new/delete and let the OS be clever again about memory management.

Public Member Functions
	Pool (int a_ptrSize, const char *a_name="unnamed", int a_poolSize=100, int a_alignment=sizeof(int), bool a_allowUnalignedAlloc=false)
	~Pool ()
void *	getPtr ()
	request a section of memory of ptrSize_ contiguous bytes.
void	returnPtr (void *a_ptr)
	return memory previous acquired with the getPtr() function.
long	memUsage () const
	report how much memory this Pool is currently using.
void	clear ()
Public Attributes
char	m_name_ [64]
Static Public Attributes
static PoolList *	m_poolList_
Private Member Functions
void *	getMoreMemory ()
void *	getMore ()
	Pool (const Pool &a_rhs)
const Pool &	operator= (const Pool &a_rhs)
	Not implemented. Compiler will not let you copy a Pool.
Static Private Member Functions
static void	clearAllPools ()
Private Attributes
std::vector< char * >	m_pool_
int	m_ptrSize_
int	m_poolSize_
int	m_alignment_
bool	m_allowUnalignedAlloc
void *	m_next_
Friends
void	dumpmemoryatexit ()

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Constructor & Destructor Documentation

Pool::Pool	(	int	a_ptrSize,
		const char *	a_name = "unnamed",
		int	a_poolSize = 100,
		int	a_alignment = sizeof(int),
		bool	a_allowUnalignedAlloc = false
	)

Parameters:

	a_ptrSize	Size of fixed memory allocations needed
	a_poolSize	Size of allocations (a_ptrSize*a_poolSize) made of the operating system. This controls the granularity of the Pool allocations. Smaller values result in less wasted memory, at the cost of more calls to the operating system for heap memory.
	a_name	optional name for this Pool. Used in reporting memory by the memory tracking system in Chombo.

Pool::~Pool

(

)

Pool::Pool

(

const Pool &

a_rhs

)

[private]

Not implemented. Compiler will not let you copy a Pool

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Member Function Documentation

void * Pool::getPtr

(

)

[inline]

request a section of memory of ptrSize_ contiguous bytes.

getPtr and returnPtr must be as fast as possible!

References getMoreMemory(), m_next_, and m_ptrSize_.

Referenced by List< T >::addAfter(), and List< T >::addBefore().

void Pool::returnPtr

(

void *

a_ptr

)

return memory previous acquired with the getPtr() function.

Referenced by List< T >::clear(), and List< T >::remove().

long Pool::memUsage

(

)

const

report how much memory this Pool is currently using.

memUsage for a Pool only grows until Pool destruction. The Pool object has no knowledge of what pieces of memory it has parcelled out to a user, so it keeps it all available. The user is responsible for not leaking Pool memory.

void Pool::clear

(

)

undocumented function, call this at own risk. You must be absolutely positive that you have returned all the ptr's you've asked for, or you can have major seg faults.

void* Pool::getMoreMemory

(

)

[private]

Referenced by getPtr().

void* Pool::getMore

(

)

[private]

const Pool& Pool::operator=

(

const Pool &

a_rhs

)

[private]

Not implemented. Compiler will not let you copy a Pool.

static void Pool::clearAllPools

(

)

[static, private]

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Friends And Related Function Documentation

void dumpmemoryatexit

(

)

[friend]

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Member Data Documentation

PoolList* Pool::m_poolList_ [static]

char Pool::m_name_[64]

std::vector<char*> Pool::m_pool_ [private]

int Pool::m_ptrSize_ [private]

Referenced by getPtr().

int Pool::m_poolSize_ [private]

int Pool::m_alignment_ [private]

bool Pool::m_allowUnalignedAlloc [private]

T - Allows unaligned allocations (> sizof(double) if it is not known how to allocate aligned memory F - Otherwise abort

void* Pool::m_next_ [private]

Referenced by getPtr().

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

• Pool.H