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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.
73 lines
2.2 KiB
C++
73 lines
2.2 KiB
C++
#ifndef HA_HANDLER_STATS_INCLUDED
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#define HA_HANDLER_STATS_INCLUDED
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/*
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Copyright (c) 2023, MariaDB Foundation
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; version 2 of
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the License.
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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 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 02110-1335 USA
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*/
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/* Definitions for parameters to do with handler-routines */
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class ha_handler_stats
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{
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public:
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ulonglong pages_accessed; /* Pages accessed from page cache */
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ulonglong pages_updated; /* Pages changed in page cache */
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ulonglong pages_read_count; /* Pages read from disk */
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/* Time spent reading pages, in timer_tracker_frequency() units */
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ulonglong pages_read_time;
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/*
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Number of pages that we've requested to prefetch while running the query.
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Note that we don't know:
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- how much time was spent reading these pages (and how to count the time
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if reading was done in parallel)
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- whether the pages were read by "us" or somebody else...
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*/
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ulonglong pages_prefetched;
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ulonglong undo_records_read;
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/* Time spent in engine, in timer_tracker_frequency() units */
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ulonglong engine_time;
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uint active; /* <> 0 if status has to be updated */
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#define first_stat pages_accessed
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#define last_stat engine_time
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inline void reset()
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{
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bzero((void*) this, sizeof(*this));
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}
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inline void add(ha_handler_stats *stats)
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{
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ulonglong *to= &first_stat;
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ulonglong *from= &stats->first_stat;
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do
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{
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(*to)+= *from++;
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} while (to++ != &last_stat);
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}
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inline bool has_stats()
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{
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ulonglong *to= &first_stat;
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do
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{
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if (*to)
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return 1;
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} while (to++ != &last_stat);
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return 0;
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}
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};
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#endif /* HA_HANDLER_STATS_INCLUDED */
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