.. _buff_read_ahead_area: ==================================== Fixed Size for the Read Ahead Area ==================================== |InnoDB| dynamically calculates the size of the read-ahead area in case it has to trigger its read-ahead algorithm. When the workload involves heavy I/O operations, this size is computed so frequently that it has a non-negligeable impact on the CPU usage. This variable only depends on the size of the buffer pool set by the :variable:`innodb_buffer_pool_size` variable, and as soon as the buffer pool has a size properly greater than 1024 pages (or 16 MB), it is always 64. With this change, its value is fixed to 64, thus removing a bottleneck experienced by some users. Please note that the minimum allowed value for the |InnoDB| buffer pool is de facto set to 32 MB. This change is a port of the feature from Facebook: * http://bazaar.launchpad.net/~mysqlatfacebook/mysqlatfacebook/5.1/revision/3538 Version Specific Information ============================ * :rn:`5.5.8-20.0` : Full functionality available. Other Information ================= * Author/Origin: Facebook * Bugs fixed: :bug:`606811` Other Reading ============= * `BUF_READ_AHEAD_AREA Bottleneck `_