7.4.6.5. Key Cache Block Size
It is possible to specify the size of the block buffers for an
individual key cache using the
key_cache_block_size variable. This permits
tuning of the performance of I/O operations for index files.
The best performance for I/O operations is achieved when the
size of read buffers is equal to the size of the native
operating system I/O buffers. But setting the size of key
nodes equal to the size of the I/O buffer does not always
ensure the best overall performance. When reading the big leaf
nodes, the server pulls in a lot of unnecessary data,
effectively preventing reading other leaf nodes.
Currently, you cannot control the size of the index blocks in
a table. This size is set by the server when the
.MYI index file is created, depending on
the size of the keys in the indexes present in the table
definition. In most cases, it is set equal to the I/O buffer
size.
