Working on large upgrade of MySQL 4.1 running Innodb to MySQL 5.0 and doing oprofile analyzes we found very interesting issue … the gotchas. The second issue we ran into is number of Threads_Running being much higher for MySQL 5.0 compared to MySQL 4.1 It was something like 2-3 for MySQL 4.1 vs 40-60 for MySQL 5.0…