The -c switch
instructs makemap to set the cache size for
hash or btree databases to the
number of bytes indicated:
% makemap -c 524288 hash outfile
The default cache size, if this switch is not specified, is 1,048,576
bytes (1k squared). Note that setting the cache size is an art, and
that the larger the cache, the better. The minimum cache size is
recommended to be no less than 10 pages, or about 40,960 bytes.