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-negligible impact on the CPU usage. With this fix, buffer read-ahead area size is precalculated once per buffer pool instance initialization, and this value is used each time read-ahead is invoked. This implementation should remove a bottleneck experienced by some users.