The asynchronous i/o array structure. More...

Public Member Functions
	AIO (latch_id_t id, ulint n, ulint segments)
	Constructor. More...

	~AIO ()
	Destructor. More...

dberr_t	init ()
	Initialize the instance. More...

Slot *	reserve_slot (IORequest &type, fil_node_t m1, void m2, pfs_os_file_t file, const char name, void buf, os_offset_t offset, ulint len, const file::Block *e_block)
	Requests for a slot in the aio array. More...

ulint	pending_io_count () const
	Count the number of free slots. More...

const Slot *	at (ulint i) const
	Returns a pointer to the nth slot in the aio array. More...

Slot *	at (ulint i)
	Non const version. More...

void	release (Slot *slot)
	Frees a slot in the aio array. More...

void	release_with_mutex (Slot *slot)
	Frees a slot in the AIO array. More...

void	print (FILE *file)
	Prints info about the aio array. More...

ulint	slots_per_segment () const

ulint	get_n_segments () const

bool	is_mutex_owned () const

void	acquire () const
	Acquire the mutex. More...

void	release () const
	Release the mutex. More...

void	to_file (FILE *file) const
	Prints all pending IO for the array. More...

Static Public Member Functions
static AIO *	create (latch_id_t id, ulint n, ulint n_segments)
	Creates an aio wait array. More...

static bool	start (ulint n_per_seg, ulint n_readers, ulint n_writers)
	Initializes the asynchronous io system. More...

static void	start_threads ()
	Starts a thread for each segment. More...

static void	shutdown ()
	Free the AIO arrays. More...

static void	print_all (FILE *file)
	Print all the AIO segments. More...

static ulint	get_array_and_local_segment (AIO *&array, ulint segment)
	Calculates local segment number and aio array from global segment number. More...

static AIO *	select_slot_array (IORequest &type, bool read_only, AIO_mode aio_mode)
	Select the IO slot array. More...

static ulint	get_segment_no_from_slot (const AIO array, const Slot slot)
	Calculates segment number for a slot. More...

static void	wake_simulated_handler_thread (ulint global_segment)
	Wakes up a simulated AIO I/O handler thread if it has something to do. More...

static bool	is_read (const AIO *aio)
	Check if it is a read request. More...

static void	wait_until_no_pending_writes ()
	Wait on an event until no pending writes. More...

static void	print_to_file (FILE *file)
	Print to file. More...

static ulint	total_pending_io_count ()
	Check for pending IO. More...

Private Types
typedef std::vector< Slot >	Slots

Private Member Functions
dberr_t	init_slots ()
	Initialise the slots. More...

void	wake_simulated_handler_thread (ulint global_segment, ulint segment)
	Wakes up a simulated AIO I/O-handler thread if it has something to do for a local segment in the AIO array. More...

void	print_segment_info (FILE file, const ulint segments)
	Prints pending IO requests per segment of an aio array. More...

Static Private Member Functions
static size_t	number_of_extra_threads ()
	Returns the number of arrays other than n_readers and n_writers that start() will create. More...

Private Attributes
SysMutex	m_mutex
	the mutex protecting the aio array More...

Slots	m_slots
	Pointer to the slots in the array. More...

ulint	m_n_segments
	Number of segments in the aio array of pending aio requests. More...

os_event_t	m_not_full
	The event which is set to the signaled state when there is space in the aio outside the ibuf segment. More...

os_event_t	m_is_empty
	The event which is set to the signaled state when there are no pending i/os in this array. More...

ulint	m_n_reserved
	Number of reserved slots in the AIO array outside the ibuf segment. More...

std::atomic_size_t	m_last_slot_used
	The index of last slot used to reserve. More...

Static Private Attributes
static AIO *	s_ibuf
	The aio arrays for non-ibuf i/o and ibuf i/o. More...

static AIO *	s_reads
	Reads. More...

static AIO *	s_writes
	Writes. More...

Detailed Description

The asynchronous i/o array structure.

Member Typedef Documentation

◆ Slots

typedef std::vector<Slot> AIO::Slots

private

Constructor & Destructor Documentation

◆ AIO()

AIO::AIO	(	latch_id_t	id,
		ulint	n,
		ulint	segments
	)

Constructor.

Parameters

[in]	id	The latch ID
[in]	n	Number of AIO slots
[in]	segments	Number of segments

◆ ~AIO()

AIO::~AIO ( )

Destructor.

AIO destructor.

Member Function Documentation

◆ acquire()

void AIO::acquire ( ) const

inline

Acquire the mutex.

◆ at() [1/2]

Slot * AIO::at ( ulint i )

inline

Non const version.

◆ at() [2/2]

const Slot * AIO::at ( ulint i ) const

inline

Returns a pointer to the nth slot in the aio array.

Parameters

[in] i Index of the slot in the array

Returns: pointer to slot

◆ create()

AIO * AIO::create	(	latch_id_t	id,
		ulint	n,
		ulint	n_segments
	)

static

Creates an aio wait array.

Note that we return NULL in case of failure. We don't care about freeing memory here because we assume that a failure will result in server refusing to start up.

Parameters

[in]	id	Latch ID
[in]	n	maximum number of pending AIO operations allowed; n must be divisible by m_n_segments
[in]	n_segments	number of segments in the AIO array

Returns: own: AIO array, NULL on failure

◆ get_array_and_local_segment()

ulint AIO::get_array_and_local_segment	(	AIO *&	array,
		ulint	segment
	)

static

Calculates local segment number and aio array from global segment number.

Parameters

[out]	array	AIO wait array
[in]	segment	global segment number

Returns: local segment number within the aio array

◆ get_n_segments()

ulint AIO::get_n_segments ( ) const

inline

Returns: accessor for n_segments

◆ get_segment_no_from_slot()

ulint AIO::get_segment_no_from_slot	(	const AIO *	array,
		const Slot *	slot
	)

static

Calculates segment number for a slot.

Parameters

[in]	array	AIO wait array
[in]	slot	slot in this array

Returns: segment number (which is the number used by, for example, I/O handler threads)

◆ init()

dberr_t AIO::init ( void )

Initialize the instance.

Initialise the array.

Returns: DB_SUCCESS or error code

◆ init_slots()

dberr_t AIO::init_slots ( )

private

Initialise the slots.

Returns: DB_SUCCESS or error code

◆ is_mutex_owned()

bool AIO::is_mutex_owned ( ) const

inline

Returns: true if the thread owns the mutex

◆ is_read()

static bool AIO::is_read ( const AIO * aio )

inlinestatic

Check if it is a read request.

Parameters

[in] aio The AIO instance to check

Returns: true if the AIO instance is for reading.

◆ number_of_extra_threads()

size_t AIO::number_of_extra_threads ( )

staticprivate

Returns the number of arrays other than n_readers and n_writers that start() will create.

In srv_read_only_mode this is 0. Otherwise this is just one for ibuf i/o.

◆ pending_io_count()

ulint AIO::pending_io_count ( ) const

Count the number of free slots.

Returns: number of reserved slots

◆ print()

void AIO::print ( FILE * file )

Prints info about the aio array.

Parameters

[in,out] file Where to print

◆ print_all()

void AIO::print_all ( FILE * file )

static

Print all the AIO segments.

Parameters

[in,out] file Where to print

◆ print_segment_info()

void AIO::print_segment_info	(	FILE *	file,
		const ulint *	segments
	)

private

Prints pending IO requests per segment of an aio array.

We probably don't need per segment statistics but they can help us during development phase to see if the IO requests are being distributed as expected.

Parameters

[in,out]	file	File where to print
[in]	segments	Pending IO array

◆ print_to_file()

void AIO::print_to_file ( FILE * file )

static

Print to file.

Print pending IOs for all arrays.

Parameters

[in] file File to write to

◆ release() [1/2]

void AIO::release ( ) const

inline

Release the mutex.

◆ release() [2/2]

void AIO::release ( Slot * slot )

Frees a slot in the aio array.

Assumes caller owns the mutex.

Parameters

[in,out] slot Slot to release

◆ release_with_mutex()

void AIO::release_with_mutex ( Slot * slot )

Frees a slot in the AIO array.

Assumes caller doesn't own the mutex.

Parameters

[in,out] slot Slot to release

◆ reserve_slot()

Slot * AIO::reserve_slot	(	IORequest &	type,
		fil_node_t *	m1,
		void *	m2,
		pfs_os_file_t	file,
		const char *	name,
		void *	buf,
		os_offset_t	offset,
		ulint	len,
		const file::Block *	e_block
	)

Requests for a slot in the aio array.

If no slot is available, waits until not_full-event becomes signaled.

Parameters

[in,out]	type	IO context
[in,out]	m1	message to be passed along with AIO operation
[in,out]	m2	message to be passed along with AIO operation
[in]	file	file handle
[in]	name	name of the file or path as a null-terminated string
[in,out]	buf	buffer where to read or from which to write
[in]	offset	file offset, where to read from or start writing
[in]	len	length of the block to read or write
[in]	e_block	Encrypted block or nullptr.

Returns: pointer to slot

◆ select_slot_array()

AIO * AIO::select_slot_array	(	IORequest &	type,
		bool	read_only,
		AIO_mode	aio_mode
	)

static

Select the IO slot array.

Parameters

[in,out]	type	Type of IO, READ or WRITE
[in]	read_only	true if running in read-only mode
[in]	aio_mode	IO mode

Returns: slot array or NULL if invalid mode specified

◆ shutdown()

void AIO::shutdown ( )

static

Free the AIO arrays.

◆ slots_per_segment()

ulint AIO::slots_per_segment ( ) const

inline

Returns: the number of slots per segment

◆ start()

bool AIO::start	(	ulint	n_per_seg,
		ulint	n_readers,
		ulint	n_writers
	)

static

Initializes the asynchronous io system.

Creates one array for ibuf I/O. Also creates one array each for read and write where each array is divided logically into n_readers and n_writers respectively. The caller must create an i/o handler thread for each segment in these arrays by calling start_threads().

Parameters

[in]	n_per_seg	maximum number of pending aio operations allowed per segment
[in]	n_readers	number of reader threads
[in]	n_writers	number of writer threads

Returns: true if AIO sub-system was started successfully

◆ start_threads()

void AIO::start_threads ( )

static

Starts a thread for each segment.

◆ to_file()

void AIO::to_file ( FILE * file ) const

Prints all pending IO for the array.

Parameters

[in,out] file file where to print

◆ total_pending_io_count()

ulint AIO::total_pending_io_count ( )

static

Check for pending IO.

Get the total number of pending IOs.

Gets the count and also validates the data structures.

Returns: count of pending IO requests; the total number of pending IOs

◆ wait_until_no_pending_writes()

static void AIO::wait_until_no_pending_writes ( )

inlinestatic

Wait on an event until no pending writes.

◆ wake_simulated_handler_thread() [1/2]

void AIO::wake_simulated_handler_thread ( ulint global_segment )

static

Wakes up a simulated AIO I/O handler thread if it has something to do.

Parameters

[in] global_segment The number of the segment in the AIO arrays

◆ wake_simulated_handler_thread() [2/2]

void AIO::wake_simulated_handler_thread	(	ulint	global_segment,
		ulint	segment
	)

private

Wakes up a simulated AIO I/O-handler thread if it has something to do for a local segment in the AIO array.

Parameters

[in]	global_segment	The number of the segment in the AIO arrays
[in]	segment	The local segment in the AIO array

Member Data Documentation

◆ m_is_empty

os_event_t AIO::m_is_empty

private

The event which is set to the signaled state when there are no pending i/os in this array.

◆ m_last_slot_used

std::atomic_size_t AIO::m_last_slot_used

private

The index of last slot used to reserve.

This is used to balance the incoming requests more evenly throughout the segments. This field is not guarded by any lock. This is only used as a heuristic and any value read or written to it is OK. It is atomic as it is accesses without any latches from multiple threads.

◆ m_mutex

SysMutex AIO::m_mutex

mutableprivate

the mutex protecting the aio array

◆ m_n_reserved

ulint AIO::m_n_reserved

private

Number of reserved slots in the AIO array outside the ibuf segment.

◆ m_n_segments

ulint AIO::m_n_segments

private

Number of segments in the aio array of pending aio requests.

A thread can wait separately for any one of the segments.

◆ m_not_full

os_event_t AIO::m_not_full

private

The event which is set to the signaled state when there is space in the aio outside the ibuf segment.

◆ m_slots

Slots AIO::m_slots

private

Pointer to the slots in the array.

Number of elements must be divisible by n_threads.

◆ s_ibuf

AIO * AIO::s_ibuf

staticprivate

The aio arrays for non-ibuf i/o and ibuf i/o.

These are NULL when the module has not yet been initialized. Insert buffer

◆ s_reads

AIO * AIO::s_reads

staticprivate

Reads.

Static declarations.

◆ s_writes

AIO * AIO::s_writes

staticprivate

Writes.

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

storage/innobase/os/os0file.cc

Public Member Functions

Static Public Member Functions

Private Types

Private Member Functions

Static Private Member Functions

Private Attributes

Static Private Attributes

Detailed Description

Member Typedef Documentation

◆ Slots

Constructor & Destructor Documentation

◆ AIO()

◆ ~AIO()

Member Function Documentation

◆ acquire()

◆ at() [1/2]

◆ at() [2/2]

◆ create()

◆ get_array_and_local_segment()

◆ get_n_segments()

◆ get_segment_no_from_slot()

◆ init()

◆ init_slots()

◆ is_mutex_owned()

◆ is_read()

◆ number_of_extra_threads()

◆ pending_io_count()

◆ print()

◆ print_all()

◆ print_segment_info()

◆ print_to_file()

◆ release() [1/2]

◆ release() [2/2]

◆ release_with_mutex()

◆ reserve_slot()

◆ select_slot_array()

◆ shutdown()

◆ slots_per_segment()

◆ start()

◆ start_threads()

◆ to_file()

◆ total_pending_io_count()

◆ wait_until_no_pending_writes()

◆ wake_simulated_handler_thread() [1/2]

◆ wake_simulated_handler_thread() [2/2]

Member Data Documentation

◆ m_is_empty

◆ m_last_slot_used

◆ m_mutex

◆ m_n_reserved

◆ m_n_segments

◆ m_not_full

◆ m_slots

◆ s_ibuf

◆ s_reads

◆ s_writes