Hi, Is that a MariaDB table_cache improvement? MySQL 5.6 has partitioned table cache to overcome the negative scalability aspect of increasing table cache.
--Justin On Tue, Apr 21, 2015 at 10:34 AM, Sergey Vojtovich <[email protected]> wrote: > Hi! > > On Tue, Apr 21, 2015 at 10:11:12AM -0700, Justin Swanhart wrote: > > Hi, > > > > If a MyISAM table is not in the table_open_cache, it will be opened by > the > > query that needs the table. To increase the chances of the table being > in > > the table_open_cache, increase the size to 4000 for a start (1/10 of your > > current open files). > Same applies to InnoDB tables, especially with low innodb_file_per_table > and > innodb_open_files. But MyISAM needs to open a 2x more files indeed. > > > > > Be careful though. Increasing the table_open_cache increases the amount > of > > time it takes to search the table cache, as the search is linear through > > the structure that holds the table_cache. It also increases the time > for a > > flush tables operation. > Table cache is doubly-linked list, but there is no table cache search as > such: > we either take front element or push front element. So increased > table_open_cache > doesn't have any negative effect on table cache performance. FLUSH TABLES > will be > slower indeed. > > To get best performance table_open_cache should be something like: > number of hot tables * average number of concurrent connections. > > > > > Also increase table_definition_cache. This value is hash backed, so the > > performance impact of increasing it is minimal. I would increase it to > > 40000 since you have 40000 open files. > A good value for table_definition_cache is number of hot tables + some > reserve > (e.g. 100). > > Regards, > Sergey > > > > > These value changes can be made online. > > > > On Tue, Apr 21, 2015 at 9:14 AM, Honza Horak <[email protected]> wrote: > > > > > On 04/21/2015 05:07 PM, Justin Swanhart wrote: > > > > > >> Hi, > > >> > > >> Are you using MyISAM or InnoDB? What are the values of > > >> table_open_cache, table_definition_cache and innodb_open_files? > > >> > > > > > > It is a mixture of MyISAM and InnoDB, but we got complaints especially > > > about the MyISAM tables. > > > > > > Options table_open_cache, table_definition_cache have default values, > so > > > 400, innodb_open_files is changed to 128. > > > > > > Honza > > > > > > --justin > > >> > > >> On Tue, Apr 21, 2015 at 6:26 AM, Honza Horak <[email protected] > > >> <mailto:[email protected]>> wrote: > > >> > > >> Hey, with limited experiences with mariadb deployments, I'm > > >> wondering how many open files by the mysqld daemon is still sane > > >> (expected). > > >> > > >> We have a customer that reports hundreds of thousands of open > files > > >> with 600 connections (thread_pool_max_threads is used). Those > > >> processes seem rather stalled, but files in the datadir are often > > >> opened 40.000 times. > > >> > > >> Is it even possible that one file is opened several times during > > >> processing one query? Or does it mean there are ~40.000 queries > > >> running? > > >> > > >> Version of MariaDB: 5.5.40 > > >> > > >> Honza > > >> > > >> _______________________________________________ > > >> Mailing list: https://launchpad.net/~maria-discuss > > >> Post to : [email protected] > > >> <mailto:[email protected]> > > >> Unsubscribe : https://launchpad.net/~maria-discuss > > >> More help : https://help.launchpad.net/ListHelp > > >> > > >> > > >> > > > _______________________________________________ > > Mailing list: https://launchpad.net/~maria-discuss > > Post to : [email protected] > > Unsubscribe : https://launchpad.net/~maria-discuss > > More help : https://help.launchpad.net/ListHelp > >
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