The buffer pool structure. More...

#include <buf0buf.h>

Public Attributes
General fields
BufListMutex	chunks_mutex
	protects (de)allocation of chunks: More...

BufListMutex	LRU_list_mutex
	LRU list mutex. More...

BufListMutex	free_list_mutex
	free and withdraw list mutex More...

BufListMutex	zip_free_mutex
	buddy allocator mutex More...

BufListMutex	zip_hash_mutex
	zip_hash mutex More...

ib_mutex_t	flush_state_mutex
	Flush state protection mutex. More...

BufPoolZipMutex	zip_mutex
	Zip mutex of this buffer pool instance, protects compressed only pages (of type buf_page_t, not buf_block_t. More...

ulint	instance_no
	Array index of this buffer pool instance. More...

ulint	curr_pool_size
	Current pool size in bytes. More...

ulint	LRU_old_ratio
	Reserve this much of the buffer pool for "old" blocks. More...

ulint	buddy_n_frames
	Number of frames allocated from the buffer pool to the buddy system. More...

volatile ulint	n_chunks
	Number of buffer pool chunks. More...

volatile ulint	n_chunks_new
	New number of buffer pool chunks. More...

buf_chunk_t *	chunks
	buffer pool chunks More...

buf_chunk_t *	chunks_old
	old buffer pool chunks to be freed after resizing buffer pool More...

ulint	curr_size
	Current pool size in pages. More...

ulint	old_size
	Previous pool size in pages. More...

page_no_t	read_ahead_area
	Size in pages of the area which the read-ahead algorithms read if invoked. More...

hash_table_t *	page_hash
	Hash table of buf_page_t or buf_block_t file pages, buf_page_in_file() == true, indexed by (space_id, offset). More...

hash_table_t *	zip_hash
	Hash table of buf_block_t blocks whose frames are allocated to the zip buddy system, indexed by block->frame. More...

std::atomic< ulint >	n_pend_reads
	Number of pending read operations. More...

std::atomic< ulint >	n_pend_unzip
	number of pending decompressions. More...

std::chrono::steady_clock::time_point	last_printout_time
	when buf_print_io was last time called. More...

buf_buddy_stat_t	buddy_stat [BUF_BUDDY_SIZES_MAX+1]
	Statistics of buddy system, indexed by block size. More...

buf_pool_stat_t	stat
	Current statistics. More...

buf_pool_stat_t	old_stat
	Old statistics. More...

Page flushing algorithm fields
BufListMutex	flush_list_mutex
	Mutex protecting the flush list access. More...

FlushHp	flush_hp
	"Hazard pointer" used during scan of flush_list while doing flush list batch. More...

FlushHp	oldest_hp
	Entry pointer to scan the oldest page except for system temporary. More...

bool	init_flush [BUF_FLUSH_N_TYPES]
	This is true when a flush of the given type is being initialized. More...

std::array< size_t, BUF_FLUSH_N_TYPES >	n_flush
	This is the number of pending writes in the given flush type. More...

os_event_t	no_flush [BUF_FLUSH_N_TYPES]
	This is in the set state when there is no flush batch of the given type running. More...

ib_rbt_t *	flush_rbt
	A red-black tree is used exclusively during recovery to speed up insertions in the flush_list. More...

ulint	freed_page_clock
	A sequence number used to count the number of buffer blocks removed from the end of the LRU list; NOTE that this counter may wrap around at 4 billion! A thread is allowed to read this for heuristic purposes without holding any mutex or latch. More...

bool	try_LRU_scan
	Set to false when an LRU scan for free block fails. More...

lsn_t	track_page_lsn
	Page Tracking start LSN. More...

lsn_t	max_lsn_io
	Maximum LSN for which write io has already started. More...

	UT_LIST_BASE_NODE_T (buf_page_t, list) flush_list
	Base node of the modified block list. More...

bool	is_tracking ()
	Check if the page modifications are tracked. More...

LRU replacement algorithm fields
ulint	withdraw_target
	Target length of withdraw block list, when withdrawing. More...

LRUHp	lru_hp
	"hazard pointer" used during scan of LRU while doing LRU list batch. More...

LRUItr	lru_scan_itr
	Iterator used to scan the LRU list when searching for replaceable victim. More...

LRUItr	single_scan_itr
	Iterator used to scan the LRU list when searching for single page flushing victim. More...

buf_page_t *	LRU_old
	Pointer to the about LRU_old_ratio/BUF_LRU_OLD_RATIO_DIV oldest blocks in the LRU list; NULL if LRU length less than BUF_LRU_OLD_MIN_LEN; NOTE: when LRU_old != NULL, its length should always equal LRU_old_len. More...

ulint	LRU_old_len
	Length of the LRU list from the block to which LRU_old points onward, including that block; see buf0lru.cc for the restrictions on this value; 0 if LRU_old == NULL; NOTE: LRU_old_len must be adjusted whenever LRU_old shrinks or grows! More...

	UT_LIST_BASE_NODE_T (buf_page_t, list) free
	Base node of the free block list. More...

	UT_LIST_BASE_NODE_T (buf_page_t, list) withdraw
	base node of the withdraw block list. More...

	UT_LIST_BASE_NODE_T (buf_page_t, LRU) LRU
	Base node of the LRU list. More...

	UT_LIST_BASE_NODE_T (buf_block_t, unzip_LRU) unzip_LRU
	Base node of the unzip_LRU list. More...

Buddy allocator fields
The buddy allocator is used for allocating compressed page frames and buf_page_t descriptors of blocks that exist in the buffer pool only in compressed form.
buf_page_t *	watch
	Sentinel records for buffer pool watches. More...

	UT_LIST_BASE_NODE_T (buf_page_t, list) zip_clean
	Unmodified compressed pages. More...

	UT_LIST_BASE_NODE_T (buf_buddy_free_t, list) zip_free[BUF_BUDDY_SIZES_MAX]
	Buddy free lists. More...

bool	allocate_chunk (ulonglong mem_size, buf_chunk_t *chunk)
	A wrapper for buf_pool_t::allocator.alocate_large which also advices the OS that this chunk should not be dumped to a core file if that was requested. More...

void	deallocate_chunk (buf_chunk_t *chunk)
	A wrapper for buf_pool_t::allocator.deallocate_large which also advices the OS that this chunk can be dumped to a core file. More...

bool	madvise_dump ()
	Advices the OS that all chunks in this buffer pool instance can be dumped to a core file. More...

bool	madvise_dont_dump ()
	Advices the OS that all chunks in this buffer pool instance should not be dumped to a core file. More...

bool	is_flushing (buf_flush_t flush_type) const
	Checks if the batch is running, which is basically equivalent to !os_event_is_set(no_flush[type]) if you hold flush_state_mutex. More...

template<typename F >
void	change_flush_state (buf_flush_t flush_type, F &&change)
	Executes change() which modifies fields protected by flush_state_mutex. More...

Detailed Description

The buffer pool structure.

NOTE! The definition appears here only for other modules of this directory (buf) to see it. Do not use from outside!

Member Function Documentation

◆ allocate_chunk()

bool buf_pool_t::allocate_chunk	(	ulonglong	mem_size,
		buf_chunk_t *	chunk
	)

A wrapper for buf_pool_t::allocator.alocate_large which also advices the OS that this chunk should not be dumped to a core file if that was requested.

Emits a warning to the log and disables @global.core_file if advising was requested but could not be performed, but still return true as the allocation itself succeeded.

Parameters

[in]	mem_size	number of bytes to allocate
[in,out]	chunk	mem and mem_pfx fields of this chunk will be updated to contain information about allocated memory region

Returns: true iff allocated successfully

◆ change_flush_state()

template<typename F >

void buf_pool_t::change_flush_state	(	buf_flush_t	flush_type,
		F &&	change
	)

inline

Executes change() which modifies fields protected by flush_state_mutex.

If it caused a change to is_flushing(flush_type) then it sets or resets the no_flush[flush_type] to keep it in sync.

Parameters

[in]	flush_type	The type of the flush this change of state concerns
[in]	change	A callback to execute within flush_state_mutex

◆ deallocate_chunk()

void buf_pool_t::deallocate_chunk ( buf_chunk_t * chunk )

A wrapper for buf_pool_t::allocator.deallocate_large which also advices the OS that this chunk can be dumped to a core file.

Emits a warning to the log and disables @global.core_file if advising was requested but could not be performed.

Parameters

[in] chunk mem and mem_pfx fields of this chunk will be used to locate the memory region to free

◆ is_flushing()

bool buf_pool_t::is_flushing ( buf_flush_t flush_type ) const

inline

Checks if the batch is running, which is basically equivalent to !os_event_is_set(no_flush[type]) if you hold flush_state_mutex.

It is used as source of truth to know when to set or reset this event. Caller should hold flush_state_mutex.

Parameters

[in] flush_type The type of the flush we are interested in

Returns: Should no_flush[type] be in the "unset" state?

◆ is_tracking()

bool buf_pool_t::is_tracking ( )

inline

Check if the page modifications are tracked.

Returns: true if page modifications are tracked, false otherwise.

◆ madvise_dont_dump()

bool buf_pool_t::madvise_dont_dump ( )

Advices the OS that all chunks in this buffer pool instance should not be dumped to a core file.

Emits a warning to the log if could not succeed.

Returns: true iff succeeded, false if no OS support or failed

◆ madvise_dump()

bool buf_pool_t::madvise_dump ( )

Advices the OS that all chunks in this buffer pool instance can be dumped to a core file.

Emits a warning to the log if could not succeed.

Returns: true iff succeeded, false if no OS support or failed

◆ UT_LIST_BASE_NODE_T() [1/7]

buf_pool_t::UT_LIST_BASE_NODE_T	(	buf_block_t	,
		unzip_LRU
	)

Base node of the unzip_LRU list.

The list is protected by the LRU_list_mutex.

◆ UT_LIST_BASE_NODE_T() [2/7]

buf_pool_t::UT_LIST_BASE_NODE_T	(	buf_buddy_free_t	,
		list
	)

Buddy free lists.

◆ UT_LIST_BASE_NODE_T() [3/7]

buf_pool_t::UT_LIST_BASE_NODE_T	(	buf_page_t	,
		list
	)

Base node of the modified block list.

◆ UT_LIST_BASE_NODE_T() [4/7]

buf_pool_t::UT_LIST_BASE_NODE_T	(	buf_page_t	,
		list
	)

Base node of the free block list.

◆ UT_LIST_BASE_NODE_T() [5/7]

buf_pool_t::UT_LIST_BASE_NODE_T	(	buf_page_t	,
		list
	)

base node of the withdraw block list.

It is only used during shrinking buffer pool size, not to reuse the blocks will be removed. Protected by free_list_mutex

◆ UT_LIST_BASE_NODE_T() [6/7]

buf_pool_t::UT_LIST_BASE_NODE_T	(	buf_page_t	,
		list
	)

Unmodified compressed pages.

◆ UT_LIST_BASE_NODE_T() [7/7]

buf_pool_t::UT_LIST_BASE_NODE_T	(	buf_page_t	,
		LRU
	)

Base node of the LRU list.

Member Data Documentation

◆ buddy_n_frames

ulint buf_pool_t::buddy_n_frames

Number of frames allocated from the buffer pool to the buddy system.

Protected by zip_hash_mutex.

◆ buddy_stat

buf_buddy_stat_t buf_pool_t::buddy_stat[BUF_BUDDY_SIZES_MAX+1]

Statistics of buddy system, indexed by block size.

Protected by zip_free mutex, except for the used field, which is also accessed atomically

◆ chunks

buf_chunk_t* buf_pool_t::chunks

buffer pool chunks

◆ chunks_mutex

BufListMutex buf_pool_t::chunks_mutex

protects (de)allocation of chunks:

changes to chunks, n_chunks are performed while holding this latch,
reading buf_pool_should_madvise requires holding this latch for any buf_pool_t
writing to buf_pool_should_madvise requires holding these latches for all buf_pool_t-s

◆ chunks_old

buf_chunk_t* buf_pool_t::chunks_old

old buffer pool chunks to be freed after resizing buffer pool

◆ curr_pool_size

ulint buf_pool_t::curr_pool_size

Current pool size in bytes.

◆ curr_size

ulint buf_pool_t::curr_size

Current pool size in pages.

◆ flush_hp

FlushHp buf_pool_t::flush_hp

"Hazard pointer" used during scan of flush_list while doing flush list batch.

Protected by flush_list_mutex

◆ flush_list_mutex

BufListMutex buf_pool_t::flush_list_mutex

Mutex protecting the flush list access.

This mutex protects flush_list, flush_rbt and bpage::list pointers when the bpage is on flush_list. It also protects writes to bpage::oldest_modification and flush_list_hp

◆ flush_rbt

ib_rbt_t* buf_pool_t::flush_rbt

A red-black tree is used exclusively during recovery to speed up insertions in the flush_list.

This tree contains blocks in order of oldest_modification LSN and is kept in sync with the flush_list. Each member of the tree MUST also be on the flush_list. This tree is relevant only in recovery and is set to NULL once the recovery is over. Protected by flush_list_mutex

◆ flush_state_mutex

ib_mutex_t buf_pool_t::flush_state_mutex

Flush state protection mutex.

◆ free_list_mutex

BufListMutex buf_pool_t::free_list_mutex

free and withdraw list mutex

◆ freed_page_clock

ulint buf_pool_t::freed_page_clock

A sequence number used to count the number of buffer blocks removed from the end of the LRU list; NOTE that this counter may wrap around at 4 billion! A thread is allowed to read this for heuristic purposes without holding any mutex or latch.

For non-heuristic purposes protected by LRU_list_mutex

◆ init_flush

bool buf_pool_t::init_flush[BUF_FLUSH_N_TYPES]

This is true when a flush of the given type is being initialized.

Protected by flush_state_mutex.

◆ instance_no

ulint buf_pool_t::instance_no

Array index of this buffer pool instance.

◆ last_printout_time

std::chrono::steady_clock::time_point buf_pool_t::last_printout_time

when buf_print_io was last time called.

Accesses not protected.

◆ lru_hp

LRUHp buf_pool_t::lru_hp

"hazard pointer" used during scan of LRU while doing LRU list batch.

Protected by buf_pool::LRU_list_mutex

◆ LRU_list_mutex

BufListMutex buf_pool_t::LRU_list_mutex

LRU list mutex.

◆ LRU_old

buf_page_t* buf_pool_t::LRU_old

Pointer to the about LRU_old_ratio/BUF_LRU_OLD_RATIO_DIV oldest blocks in the LRU list; NULL if LRU length less than BUF_LRU_OLD_MIN_LEN; NOTE: when LRU_old != NULL, its length should always equal LRU_old_len.

◆ LRU_old_len

ulint buf_pool_t::LRU_old_len

Length of the LRU list from the block to which LRU_old points onward, including that block; see buf0lru.cc for the restrictions on this value; 0 if LRU_old == NULL; NOTE: LRU_old_len must be adjusted whenever LRU_old shrinks or grows!

◆ LRU_old_ratio

ulint buf_pool_t::LRU_old_ratio

Reserve this much of the buffer pool for "old" blocks.

◆ lru_scan_itr

LRUItr buf_pool_t::lru_scan_itr

Iterator used to scan the LRU list when searching for replaceable victim.

Protected by buf_pool::LRU_list_mutex.

◆ max_lsn_io

lsn_t buf_pool_t::max_lsn_io

Maximum LSN for which write io has already started.

◆ n_chunks

volatile ulint buf_pool_t::n_chunks

Number of buffer pool chunks.

◆ n_chunks_new

volatile ulint buf_pool_t::n_chunks_new

New number of buffer pool chunks.

◆ n_flush

std::array<size_t, BUF_FLUSH_N_TYPES> buf_pool_t::n_flush

This is the number of pending writes in the given flush type.

Protected by flush_state_mutex.

◆ n_pend_reads

std::atomic<ulint> buf_pool_t::n_pend_reads

Number of pending read operations.

Accessed atomically

◆ n_pend_unzip

std::atomic<ulint> buf_pool_t::n_pend_unzip

number of pending decompressions.

Accessed atomically.

◆ no_flush

os_event_t buf_pool_t::no_flush[BUF_FLUSH_N_TYPES]

This is in the set state when there is no flush batch of the given type running.

Protected by flush_state_mutex.

◆ old_size

ulint buf_pool_t::old_size

Previous pool size in pages.

◆ old_stat

buf_pool_stat_t buf_pool_t::old_stat

Old statistics.

◆ oldest_hp

FlushHp buf_pool_t::oldest_hp

Entry pointer to scan the oldest page except for system temporary.

◆ page_hash

hash_table_t* buf_pool_t::page_hash

Hash table of buf_page_t or buf_block_t file pages, buf_page_in_file() == true, indexed by (space_id, offset).

page_hash is protected by an array of mutexes.

◆ read_ahead_area

page_no_t buf_pool_t::read_ahead_area

Size in pages of the area which the read-ahead algorithms read if invoked.

◆ single_scan_itr

LRUItr buf_pool_t::single_scan_itr

Iterator used to scan the LRU list when searching for single page flushing victim.

Protected by buf_pool::LRU_list_mutex.

◆ stat

buf_pool_stat_t buf_pool_t::stat

Current statistics.

◆ track_page_lsn

lsn_t buf_pool_t::track_page_lsn

Page Tracking start LSN.

◆ try_LRU_scan

bool buf_pool_t::try_LRU_scan

Set to false when an LRU scan for free block fails.

This flag is used to avoid repeated scans of LRU list when we know that there is no free block available in the scan depth for eviction. Set to true whenever we flush a batch from the buffer pool. Accessed protected by memory barriers.

◆ watch

buf_page_t* buf_pool_t::watch

Sentinel records for buffer pool watches.

Scanning the array is protected by taking all page_hash latches in X. Updating or reading an individual watch page is protected by a corresponding individual page_hash latch.

◆ withdraw_target

ulint buf_pool_t::withdraw_target

Target length of withdraw block list, when withdrawing.

◆ zip_free_mutex

BufListMutex buf_pool_t::zip_free_mutex

buddy allocator mutex

◆ zip_hash

hash_table_t* buf_pool_t::zip_hash

Hash table of buf_block_t blocks whose frames are allocated to the zip buddy system, indexed by block->frame.

◆ zip_hash_mutex

BufListMutex buf_pool_t::zip_hash_mutex

zip_hash mutex

◆ zip_mutex

BufPoolZipMutex buf_pool_t::zip_mutex

Zip mutex of this buffer pool instance, protects compressed only pages (of type buf_page_t, not buf_block_t.

The documentation for this struct was generated from the following files:

storage/innobase/include/buf0buf.h
storage/innobase/buf/buf0buf.cc

Public Attributes

Page flushing algorithm fields

LRU replacement algorithm fields

Buddy allocator fields

Detailed Description

Member Function Documentation

◆ allocate_chunk()

◆ change_flush_state()

◆ deallocate_chunk()

◆ is_flushing()

◆ is_tracking()

◆ madvise_dont_dump()

◆ madvise_dump()

◆ UT_LIST_BASE_NODE_T() [1/7]

◆ UT_LIST_BASE_NODE_T() [2/7]

◆ UT_LIST_BASE_NODE_T() [3/7]

◆ UT_LIST_BASE_NODE_T() [4/7]

◆ UT_LIST_BASE_NODE_T() [5/7]

◆ UT_LIST_BASE_NODE_T() [6/7]

◆ UT_LIST_BASE_NODE_T() [7/7]

Member Data Documentation

◆ buddy_n_frames

◆ buddy_stat

◆ chunks

◆ chunks_mutex

◆ chunks_old

◆ curr_pool_size

◆ curr_size

◆ flush_hp

◆ flush_list_mutex

◆ flush_rbt

◆ flush_state_mutex

◆ free_list_mutex

◆ freed_page_clock

◆ init_flush

◆ instance_no

◆ last_printout_time

◆ lru_hp

◆ LRU_list_mutex

◆ LRU_old

◆ LRU_old_len

◆ LRU_old_ratio

◆ lru_scan_itr

◆ max_lsn_io

◆ n_chunks

◆ n_chunks_new

◆ n_flush

◆ n_pend_reads

◆ n_pend_unzip

◆ no_flush

◆ old_size

◆ old_stat

◆ oldest_hp

◆ page_hash

◆ read_ahead_area

◆ single_scan_itr

◆ stat

◆ track_page_lsn

◆ try_LRU_scan

◆ watch

◆ withdraw_target

◆ zip_free_mutex

◆ zip_hash

◆ zip_hash_mutex

◆ zip_mutex