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MySQL 8.0 Reference Manual  /  ...  /  Configuring Multiple Buffer Pool Instances

Pre-General Availability Draft: 2017-12-15

15.6.3.3 Configuring Multiple Buffer Pool Instances

For systems with buffer pools in the multi-gigabyte range, dividing the buffer pool into separate instances can improve concurrency, by reducing contention as different threads read and write to cached pages. This feature is typically intended for systems with a buffer pool size in the multi-gigabyte range. Multiple buffer pool instances are configured using the innodb_buffer_pool_instances configuration option, and you might also adjust the innodb_buffer_pool_size value.

When the InnoDB buffer pool is large, many data requests can be satisfied by retrieving from memory. You might encounter bottlenecks from multiple threads trying to access the buffer pool at once. You can enable multiple buffer pools to minimize this contention. Each page that is stored in or read from the buffer pool is assigned to one of the buffer pools randomly, using a hashing function. Each buffer pool manages its own free lists, flush lists, LRUs, and all other data structures connected to a buffer pool. Prior to MySQL 8.0, each buffer pool was protected by its own buffer pool mutex. In MySQL 8.0 and later, the buffer pool mutex was replaced by several list and hash protecting mutexes, to reduce contention.

To enable multiple buffer pool instances, set the innodb_buffer_pool_instances configuration option to a value greater than 1 (the default) up to 64 (the maximum). This option takes effect only when you set innodb_buffer_pool_size to a size of 1GB or more. The total size you specify is divided among all the buffer pools. For best efficiency, specify a combination of innodb_buffer_pool_instances and innodb_buffer_pool_size so that each buffer pool instance is at least 1GB.

For information about modifying InnoDB buffer pool size, see Section 15.6.3.2, “Configuring InnoDB Buffer Pool Size”.


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