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1a6f708ec5
Our benchmarking efforts indicate that the reasons for splitting the
buf_pool in commit c18084f71b
have mostly gone away, possibly as a result of
mysql/mysql-server@ce6109ebfd
or similar work.
Only in one write-heavy benchmark where the working set size is
ten times the buffer pool size, the buf_pool->mutex would be
less contended with 4 buffer pool instances than with 1 instance,
in buf_page_io_complete(). That contention could be alleviated
further by making more use of std::atomic and by splitting
buf_pool_t::mutex further (MDEV-15053).
We will deprecate and ignore the following parameters:
innodb_buffer_pool_instances
innodb_page_cleaners
There will be only one buffer pool and one page cleaner task.
In a number of INFORMATION_SCHEMA views, columns that indicated
the buffer pool instance will be removed:
information_schema.innodb_buffer_page.pool_id
information_schema.innodb_buffer_page_lru.pool_id
information_schema.innodb_buffer_pool_stats.pool_id
information_schema.innodb_cmpmem.buffer_pool_instance
information_schema.innodb_cmpmem_reset.buffer_pool_instance
125 lines
5.8 KiB
C
125 lines
5.8 KiB
C
/*****************************************************************************
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Copyright (c) 1995, 2015, Oracle and/or its affiliates. All Rights Reserved.
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Copyright (c) 2015, 2020, MariaDB Corporation.
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
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*****************************************************************************/
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/**************************************************//**
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@file include/buf0rea.h
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The database buffer read
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Created 11/5/1995 Heikki Tuuri
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*******************************************************/
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#ifndef buf0rea_h
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#define buf0rea_h
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#include "buf0buf.h"
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/** High-level function which reads a page asynchronously from a file to the
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buffer buf_pool if it is not already there. Sets the io_fix flag and sets
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an exclusive lock on the buffer frame. The flag is cleared and the x-lock
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released by the i/o-handler thread.
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@param[in] page_id page id
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@param[in] zip_size ROW_FORMAT=COMPRESSED page size, or 0
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@retval DB_SUCCESS if the page was read and is not corrupted,
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@retval DB_PAGE_CORRUPTED if page based on checksum check is corrupted,
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@retval DB_DECRYPTION_FAILED if page post encryption checksum matches but
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after decryption normal page checksum does not match.
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@retval DB_TABLESPACE_DELETED if tablespace .ibd file is missing */
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dberr_t buf_read_page(const page_id_t page_id, ulint zip_size);
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/** High-level function which reads a page asynchronously from a file to the
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buffer buf_pool if it is not already there. Sets the io_fix flag and sets
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an exclusive lock on the buffer frame. The flag is cleared and the x-lock
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released by the i/o-handler thread.
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@param[in] page_id page id
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@param[in] zip_size ROW_FORMAT=COMPRESSED page size, or 0
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@param[in] sync true if synchronous aio is desired */
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void
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buf_read_page_background(const page_id_t page_id, ulint zip_size, bool sync);
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/** Applies a random read-ahead in buf_pool if there are at least a threshold
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value of accessed pages from the random read-ahead area. Does not read any
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page, not even the one at the position (space, offset), if the read-ahead
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mechanism is not activated. NOTE 1: the calling thread may own latches on
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pages: to avoid deadlocks this function must be written such that it cannot
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end up waiting for these latches! NOTE 2: the calling thread must want
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access to the page given: this rule is set to prevent unintended read-aheads
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performed by ibuf routines, a situation which could result in a deadlock if
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the OS does not support asynchronous i/o.
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@param[in] page_id page id of a page which the current thread
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wants to access
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@param[in] zip_size ROW_FORMAT=COMPRESSED page size, or 0
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@param[in] ibuf whether we are inside ibuf routine
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@return number of page read requests issued; NOTE that if we read ibuf
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pages, it may happen that the page at the given page number does not
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get read even if we return a positive value! */
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ulint
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buf_read_ahead_random(const page_id_t page_id, ulint zip_size, bool ibuf);
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/** Applies linear read-ahead if in the buf_pool the page is a border page of
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a linear read-ahead area and all the pages in the area have been accessed.
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Does not read any page if the read-ahead mechanism is not activated. Note
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that the algorithm looks at the 'natural' adjacent successor and
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predecessor of the page, which on the leaf level of a B-tree are the next
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and previous page in the chain of leaves. To know these, the page specified
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in (space, offset) must already be present in the buf_pool. Thus, the
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natural way to use this function is to call it when a page in the buf_pool
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is accessed the first time, calling this function just after it has been
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bufferfixed.
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NOTE 1: as this function looks at the natural predecessor and successor
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fields on the page, what happens, if these are not initialized to any
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sensible value? No problem, before applying read-ahead we check that the
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area to read is within the span of the space, if not, read-ahead is not
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applied. An uninitialized value may result in a useless read operation, but
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only very improbably.
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NOTE 2: the calling thread may own latches on pages: to avoid deadlocks this
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function must be written such that it cannot end up waiting for these
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latches!
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NOTE 3: the calling thread must want access to the page given: this rule is
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set to prevent unintended read-aheads performed by ibuf routines, a situation
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which could result in a deadlock if the OS does not support asynchronous io.
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@param[in] page_id page id; see NOTE 3 above
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@param[in] zip_size ROW_FORMAT=COMPRESSED page size, or 0
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@param[in] ibuf whether if we are inside ibuf routine
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@return number of page read requests issued */
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ulint
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buf_read_ahead_linear(const page_id_t page_id, ulint zip_size, bool ibuf);
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/** Issues read requests for pages which recovery wants to read in.
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@param[in] sync true if the caller wants this function to wait
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for the highest address page to get read in, before this function returns
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@param[in] space_id tablespace id
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@param[in] page_nos array of page numbers to read, with the
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highest page number the last in the array
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@param[in] n_stored number of page numbers in the array */
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void
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buf_read_recv_pages(
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bool sync,
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ulint space_id,
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const ulint* page_nos,
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ulint n_stored);
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/** @name Modes used in read-ahead @{ */
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/** read only pages belonging to the insert buffer tree */
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#define BUF_READ_IBUF_PAGES_ONLY 131
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/** read any page */
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#define BUF_READ_ANY_PAGE 132
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/* @} */
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#endif
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