Thinking about this a bit longer I must recall a small, 'unsuited' program I wrote in mysql (an implementation of the Dijkstra, or star algorithm). I had a couple of JOIN statements that were taking 30 seconds - lots and lots of i/o.

Using the SQL statement DESCRIBE SELECT ....; I was able to find which indexes I needed for the queries, and finally, I learned how to apply the "LEFT JOIN" statement so that a SELECT statement that had been taking about 25 seconds dropped back to less than 0.2 seconds.

As is almost nearly the issue, performance problems are not really caused by OS settings, but by application code - misusing system resources.