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513c827041
The symptoms were: take a server with no activity and a table that's not in the buffer pool. Run a query that reads the whole table and observe that r_engine_stats.pages_read_count shows about 2% of the table was read. Who reads the rest? The cause was that page prefetching done inside InnoDB was not counted. This counts page prefetch requests made in buf_read_ahead_random() and buf_read_ahead_linear() and makes them visible in: - ANALYZE: r_engine_stats.pages_prefetch_read_count - Slow Query Log: Pages_prefetched: This patch intentionally doesn't attempt to count the time to read the prefetched pages: * there's no obvious place where one can do it * prefetch reads may be done in parallel (right?), it is not clear how to count the time in this case.
135 lines
3.3 KiB
C++
135 lines
3.3 KiB
C++
/*****************************************************************************
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Copyright (c) 2023, MariaDB Foundation
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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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#pragma once
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#include "ha_handler_stats.h"
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#include "my_rdtsc.h"
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/* We do not want a dynamic initialization function to be
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conditionally invoked on each access to a C++11 extern thread_local. */
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#if __cplusplus >= 202002L
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# define simple_thread_local constinit thread_local
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#else
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# define simple_thread_local IF_WIN(__declspec(thread),__thread)
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#endif
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/** Pointer to handler::active_handler_stats or nullptr (via .tbss) */
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extern simple_thread_local ha_handler_stats *mariadb_stats;
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/*
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Returns nonzero if MariaDB wants engine status
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*/
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inline uint mariadb_stats_active()
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{
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if (ha_handler_stats *stats= mariadb_stats)
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return stats->active;
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return 0;
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}
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/* The following functions increment different engine status */
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inline void mariadb_increment_pages_accessed(ha_handler_stats *stats)
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{
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if (stats)
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stats->pages_accessed++;
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}
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inline void mariadb_increment_pages_accessed()
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{
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mariadb_increment_pages_accessed(mariadb_stats);
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}
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inline void mariadb_increment_pages_updated(ulonglong count)
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{
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if (ha_handler_stats *stats= mariadb_stats)
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stats->pages_updated+= count;
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}
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inline void mariadb_increment_pages_read(ha_handler_stats *stats)
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{
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if (stats)
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stats->pages_read_count++;
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}
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inline void mariadb_increment_pages_read()
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{
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mariadb_increment_pages_read(mariadb_stats);
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}
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inline void mariadb_increment_undo_records_read()
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{
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if (ha_handler_stats *stats= mariadb_stats)
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stats->undo_records_read++;
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}
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inline void mariadb_increment_pages_prefetched(ulint n_pages)
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{
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if (ha_handler_stats *stats= mariadb_stats)
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stats->pages_prefetched += n_pages;
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}
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/*
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The following has to be identical code as measure() in sql_analyze_stmt.h
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One should only call this if mariadb_stats_active() is true.
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*/
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inline ulonglong mariadb_measure()
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{
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#if (MY_TIMER_ROUTINE_CYCLES)
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return my_timer_cycles();
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#else
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return my_timer_microseconds();
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#endif
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}
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/*
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Call this only of start_time != 0
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See buf0rea.cc for an example of how to use it efficiently
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*/
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inline void mariadb_increment_pages_read_time(ulonglong start_time)
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{
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ha_handler_stats *stats= mariadb_stats;
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ulonglong end_time= mariadb_measure();
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/* Check that we only call this if active, see example! */
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DBUG_ASSERT(start_time);
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DBUG_ASSERT(stats->active);
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stats->pages_read_time+= (end_time - start_time);
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}
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/*
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Helper class to set mariadb_stats temporarly for one call in handler.cc
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*/
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class mariadb_set_stats
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{
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public:
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mariadb_set_stats(ha_handler_stats *stats)
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{
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mariadb_stats= stats;
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}
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~mariadb_set_stats()
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{
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mariadb_stats= nullptr;
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}
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};
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