122 lines
4.2 KiB
C
122 lines
4.2 KiB
C
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/* Copyright (c) 2010, 2022, Oracle and/or its affiliates.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License, version 2.0, for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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#ifndef MYSQL_SERVICE_THD_WAIT_INCLUDED
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#define MYSQL_SERVICE_THD_WAIT_INCLUDED
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/**
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@file include/mysql/service_thd_wait.h
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This service provides functions for plugins and storage engines to report
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when they are going to sleep/stall.
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SYNOPSIS
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thd_wait_begin() - call just before a wait begins
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thd Thread object
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Use NULL if the thd is NOT known.
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wait_type Type of wait
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1 -- short wait (e.g. for mutex)
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2 -- medium wait (e.g. for disk io)
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3 -- large wait (e.g. for locked row/table)
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NOTES
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This is used by the threadpool to have better knowledge of which
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threads that currently are actively running on CPUs. When a thread
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reports that it's going to sleep/stall, the threadpool scheduler is
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free to start another thread in the pool most likely. The expected wait
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time is simply an indication of how long the wait is expected to
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become, the real wait time could be very different.
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thd_wait_end() called immediately after the wait is complete
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thd_wait_end() MUST be called if thd_wait_begin() was called.
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Using thd_wait_...() service is optional but recommended. Using it will
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improve performance as the thread pool will be more active at managing the
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thread workload.
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*/
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#ifdef __cplusplus
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class THD;
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#define MYSQL_THD THD*
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#else
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#define MYSQL_THD void*
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#endif
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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One should only report wait events that could potentially block for a
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long time. A mutex wait is too short of an event to report. The reason
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is that an event which is reported leads to a new thread starts
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executing a query and this has a negative impact of usage of CPU caches
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and thus the expected gain of starting a new thread must be higher than
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the expected cost of lost performance due to starting a new thread.
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Good examples of events that should be reported are waiting for row locks
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that could easily be for many milliseconds or even seconds and the same
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holds true for global read locks, table locks and other meta data locks.
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Another event of interest is going to sleep for an extended time.
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Note that user-level locks no longer use THD_WAIT_USER_LOCK wait type.
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Since their implementation relies on metadata locks manager it uses
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THD_WAIT_META_DATA_LOCK instead.
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*/
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typedef enum _thd_wait_type_e {
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THD_WAIT_SLEEP= 1,
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THD_WAIT_DISKIO= 2,
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THD_WAIT_ROW_LOCK= 3,
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THD_WAIT_GLOBAL_LOCK= 4,
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THD_WAIT_META_DATA_LOCK= 5,
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THD_WAIT_TABLE_LOCK= 6,
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THD_WAIT_USER_LOCK= 7,
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THD_WAIT_BINLOG= 8,
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THD_WAIT_GROUP_COMMIT= 9,
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THD_WAIT_SYNC= 10,
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THD_WAIT_LAST= 11
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} thd_wait_type;
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extern struct thd_wait_service_st {
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void (*thd_wait_begin_func)(MYSQL_THD, int);
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void (*thd_wait_end_func)(MYSQL_THD);
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} *thd_wait_service;
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#ifdef MYSQL_DYNAMIC_PLUGIN
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#define thd_wait_begin(_THD, _WAIT_TYPE) \
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thd_wait_service->thd_wait_begin_func(_THD, _WAIT_TYPE)
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#define thd_wait_end(_THD) thd_wait_service->thd_wait_end_func(_THD)
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#else
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void thd_wait_begin(MYSQL_THD thd, int wait_type);
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void thd_wait_end(MYSQL_THD thd);
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#endif
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#ifdef __cplusplus
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}
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#endif
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#endif
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