[DOC] Missing explanation for the innodb_thread_concurrency_timer_based variable

Bug #1034305 reported by Volans on 2012-08-08
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Percona Server moved to https://jira.percona.com/projects/PS
Fix Released
Hrvoje Matijakovic
Fix Released
Hrvoje Matijakovic
Fix Released
Hrvoje Matijakovic

Bug Description

[In:Percona Server Documentation]

In the "InnoDB timer-based Concurrency Throttling" ( http://www.percona.com/doc/percona-server/5.5/performance/innodb_thread_concurrency_timer_based.html ) page the explanation of the variable "innodb_thread_concurrency_timer_based" is missing.

Is this variable used in some way, maybe the same explained in the MySQL 5.4 older documentation (see http://mysql.localhost.net.ar/doc/mysql-5.4-features/en/smp-improvements.html ) or it is not used anymore as indicated in bug #695911 ?

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Related branches

That variable is still there (it was not removed in 695911) but its validity is slightly different from the 5.4 documentatation. Innodb_have_sync_atomic is no longer there, but Innodb_have_atomic_builtins is ON or OFF based on whether the InnoDB has been built with atomic builtins or not. If Innodb_have_atomic_builtins is OFF, then innodb_thread_concurrency_timer_based won't have any effect, otherwise turning it OFF / ON changes the algorithm when dealing with multiple threads in InnoDB kernel.

The other detail about "The lock-free concurrency method also requires that innodb_thread_concurrency be set to a value greater than 0 (the default value in 5.4). " still holds though.

All interesting platforms do have the atomic builtins, we can only consider that case for performance. The explanation should be expanded what the variable actually does.

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-1930

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