Custom memory allocator. More...

#include <allocator.h>

Classes
struct	rebind

Public Types
typedef T *	pointer

typedef const T *	const_pointer

typedef T &	reference

typedef const T &	const_reference

typedef T	value_type

typedef size_t	size_type

typedef ptrdiff_t	difference_type

Public Member Functions
	Allocator (Block *shared_block, TableResourceMonitor &table_resource_monitor)
	Constructor. More...

template<class U >
	Allocator (const Allocator< U > &other)
	Constructor from allocator of another type. More...

template<class U >
	Allocator (Allocator< U > &&other) noexcept
	Move constructor from allocator of another type. More...

	~Allocator ()
	Destructor. More...

	Allocator (const Allocator &)=default

template<class U >
void	operator= (const Allocator< U > &)=delete
	Assignment operator, not used, thus disabled. More...

template<class U >
void	operator= (const Allocator< U > &&)=delete
	Move operator, not used, thus disabled. More...

template<class U >
bool	operator== (const Allocator< U > &rhs) const
	Equality operator. More...

template<class U >
bool	operator!= (const Allocator< U > &rhs) const
	Inequality operator. More...

T *	allocate (size_t n_elements)
	Allocate memory for storing `n_elements` number of elements. More...

void	deallocate (T *ptr, size_t n_elements)
	Free a memory allocated by allocate(). More...

template<class U , class... Args>
void	construct (U *mem, Args &&... args)
	Construct one object of type `U` on an already allocated chunk of memory, which must be large enough to store it. More...

template<class U >
void	destroy (U *p)
	Destroy an object of type `U`. More...

Static Public Member Functions
static void	init ()
	Initialize necessary structures. More...

Public Attributes
std::shared_ptr< AllocatorState >	m_state
	Shared state between all the copies and rebinds of this allocator. More...

Block *	m_shared_block
	A block of memory which is a state external to this allocator and can be shared among different instances of the allocator (not simultaneously). More...

TableResourceMonitor &	m_table_resource_monitor
	Table resource monitor control mechanism that limits the amount of resources that can be consumed at the per-table level. More...

Detailed Description

template<class T, class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>
class temptable::Allocator< T, AllocationScheme >

Custom memory allocator.

All dynamic memory used by the TempTable engine is allocated through this allocator.

The purpose of this allocator is to minimize the number of calls to the OS for allocating new memory (e.g. malloc()) and to improve the spatial locality of reference. It is able to do so quite easily thanks to the Block/Chunk entities it is implemented in terms of. Due to the design of these entities, it is also able to feed allocations and deallocations in (amortized) constant-time and keep being CPU memory-access friendly because of the internal self-adjustment to word-size memory alignment. To learn even more about specifics and more properties please have a look at the respective header files of Header/Block/Chunk class declarations.

The most common use case, for which it is optimized, is to have the following performed by a single thread:

allocate many times (creation of a temp table and inserting data into it).
use the allocated memory (selects on the temp table).
free all the pieces (drop of the temp table).

The allocator allocates memory from the OS in large blocks (e.g. a few MiB) whose size also increases progressively by the increasing number of allocation requests. Exact block-size increase progress is defined by the block allocation scheme which, by default, is set to AllocationScheme::Exponential.

Allocator does not store a list of all allocated blocks but only keeps track of the current block which has not yet been entirely filled up and the overall number of allocated blocks. When current block gets filled up, new one is created and immediately made current.

Furthermore, it always keeps the last block alive. It cannot be deallocated by the user. Last block is automatically deallocated at the thread exit.

Allocator will also keep track of RAM-consumption and in case it reaches the threshold defined by temptable_max_ram, it will switch to MMAP-backed block allocations. It will switch back once RAM consumption is again below the threshold.

Member Typedef Documentation

◆ const_pointer

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

typedef const T* temptable::Allocator< T, AllocationScheme >::const_pointer

◆ const_reference

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

typedef const T& temptable::Allocator< T, AllocationScheme >::const_reference

◆ difference_type

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

typedef ptrdiff_t temptable::Allocator< T, AllocationScheme >::difference_type

◆ pointer

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

typedef T* temptable::Allocator< T, AllocationScheme >::pointer

◆ reference

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

typedef T& temptable::Allocator< T, AllocationScheme >::reference

◆ size_type

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

typedef size_t temptable::Allocator< T, AllocationScheme >::size_type

◆ value_type

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

typedef T temptable::Allocator< T, AllocationScheme >::value_type

Constructor & Destructor Documentation

◆ Allocator() [1/4]

template<class T , class AllocationScheme >

temptable::Allocator< T, AllocationScheme >::Allocator	(	Block *	shared_block,
		TableResourceMonitor &	table_resource_monitor
	)

inline

Constructor.

◆ Allocator() [2/4]

template<class T , class AllocationScheme >

template<class U >

temptable::Allocator< T, AllocationScheme >::Allocator ( const Allocator & other )

inline

Constructor from allocator of another type.

The state is copied into the new object.

Parameters

[in] other Source Allocator object.

◆ Allocator() [3/4]

template<class T , class AllocationScheme >

template<class U >

temptable::Allocator< T, AllocationScheme >::Allocator ( Allocator && other )

inlinenoexcept

Move constructor from allocator of another type.

Parameters

[in,out] other Source Allocator object.

◆ ~Allocator()

template<class T , class AllocationScheme >

temptable::Allocator< T, AllocationScheme >::~Allocator ( )

inlinedefault

Destructor.

◆ Allocator() [4/4]

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

temptable::Allocator< T, AllocationScheme >::Allocator ( const Allocator< T, AllocationScheme > & )

default

Member Function Documentation

◆ allocate()

template<class T , class AllocationScheme >

T * temptable::Allocator< T, AllocationScheme >::allocate ( size_t n_elements )

inline

Allocate memory for storing n_elements number of elements.

Parameters

[in] n_elements Number of elements that must be allocated.

◆ construct()

template<class T , class AllocationScheme >

template<class U , class... Args>

void temptable::Allocator< T, AllocationScheme >::construct	(	U *	mem,
		Args &&...	args
	)

inline

Construct one object of type U on an already allocated chunk of memory, which must be large enough to store it.

Parameters

[in]	mem	Memory where to create the object.
	args	Arguments to pass to U's constructor.

◆ deallocate()

template<class T , class AllocationScheme >

void temptable::Allocator< T, AllocationScheme >::deallocate	(	T *	ptr,
		size_t	n_elements
	)

inline

Free a memory allocated by allocate().

Parameters

[in,out]	ptr	Pointer to memory to free.
[in]	n_elements	Number of elements allocated.

◆ destroy()

template<class T , class AllocationScheme >

template<class U >

void temptable::Allocator< T, AllocationScheme >::destroy ( U * p )

inline

Destroy an object of type U.

The memory is not returned to the OS, this is the counterpart of construct().

Parameters

[in,out] p Object to destroy.

◆ init()

template<class T , class AllocationScheme >

void temptable::Allocator< T, AllocationScheme >::init ( void )

inlinestatic

Initialize necessary structures.

Called once in the OS process lifetime, before other methods.

◆ operator!=()

template<class T , class AllocationScheme >

template<class U >

bool temptable::Allocator< T, AllocationScheme >::operator!= ( const Allocator & rhs ) const

inline

Inequality operator.

Returns: true if not equal

Parameters

[in] rhs Object to compare with.

◆ operator=() [1/2]

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

template<class U >

void temptable::Allocator< T, AllocationScheme >::operator= ( const Allocator && )

delete

Move operator, not used, thus disabled.

◆ operator=() [2/2]

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

template<class U >

void temptable::Allocator< T, AllocationScheme >::operator= ( const Allocator & )

delete

Assignment operator, not used, thus disabled.

◆ operator==()

template<class T , class AllocationScheme >

template<class U >

bool temptable::Allocator< T, AllocationScheme >::operator== ( const Allocator & rhs ) const

inline

Equality operator.

Returns: true if equal

Parameters

[in] rhs Object to compare with.

Member Data Documentation

◆ m_shared_block

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

Block* temptable::Allocator< T, AllocationScheme >::m_shared_block

A block of memory which is a state external to this allocator and can be shared among different instances of the allocator (not simultaneously).

In order to speed up its operations, allocator may decide to consume the memory of this shared block.

◆ m_state

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

std::shared_ptr<AllocatorState> temptable::Allocator< T, AllocationScheme >::m_state

Shared state between all the copies and rebinds of this allocator.

See AllocatorState for details.

◆ m_table_resource_monitor

template<class T , class AllocationScheme = Exponential_growth_preferring_RAM_over_MMAP>

TableResourceMonitor& temptable::Allocator< T, AllocationScheme >::m_table_resource_monitor

Table resource monitor control mechanism that limits the amount of resources that can be consumed at the per-table level.

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

storage/temptable/include/temptable/allocator.h

Classes

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Detailed Description

Member Typedef Documentation

◆ const_pointer

◆ const_reference

◆ difference_type

◆ pointer

◆ reference

◆ size_type

◆ value_type

Constructor & Destructor Documentation

◆ Allocator() [1/4]

◆ Allocator() [2/4]

◆ Allocator() [3/4]

◆ ~Allocator()

◆ Allocator() [4/4]

Member Function Documentation

◆ allocate()

◆ construct()

◆ deallocate()

◆ destroy()

◆ init()

◆ operator!=()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ operator==()

Member Data Documentation

◆ m_shared_block

◆ m_state

◆ m_table_resource_monitor