Thursday Aug 22, 2013

Remove on sight: thread_concurrency, innodb_additional_mem_pool_size, innodb_use_sys_malloc

If you have thread_concurrency, innodb_additional_mem_pool_size or innodb_use_sys_malloc in one of your my.cnf or my.ini files please remove it at your next opportunity unless one of the unlikely exceptions applies.

Thread_concurrency is a setting for only Solaris that has no effect in recent Solaris versions like 11. For Solaris 8 and earlier it gave the thread system a hint about how many threads to use for MySQL. Solaris 8 was last a supported platform for MySQL 5.1. We have deprecated this setting from 5.6.1 and removed it from 5.7.

Innodb_additional_mem_pool_size is used in any operating system to specify the initial size of a buffer used for InnoDB data dictionary information when the old InnoDB internal memory allocator is being used. InnoDB automatically increases this size on demand. Until late versions of MySQL 4.0, InnoDB would crash when trying to increase the size, so you needed this option. We have deprecated this setting from 5.6.3 and will remove it later.

The InnoDB internal memory allocator was only needed because when the InnoDB project was started the allocators in many operating systems did a bad job with many memory allocations happening concurrently. That situation persisted until sometime around the release of MySQL 4.1 through 5.1, with operating system allocators gradually getting better. The InnoDB internal allocator is no longer needed and we no longer use it by default in the InnoDB plugin in 5.1 or in 5.5 or 5.6, with innodb_use_sys_malloc set to 1. It is deprecated from 5.6.3 and we'll remove it in a future release because there is now no reason to have it turned off. If you use 5.1 with the InnoDB plugin, 5.5 or 5.6 it's best to remove this setting now and just use the default enabled setting.

Why remove them? If you remove them now you won't be inconvenienced when they go away and it's better to have only things that matter in your configuration files, not things that don't.

About

I'm James Day, one of the more senior support engineers in Oracle's MySQL team. A former developer, I've had the pleasure of being featured at a MySQL User Conference twice to receive awards, once in 2005 on behalf of Wikipedia as Application of the Year and in 2012 as one of the Community Contributors of the Year for my comments on the blog entries of other people.

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