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 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:

Version Specific Information

Other Information

  • Author/Origin: Facebook
  • Bugs fixed: #606811
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