is there a mutex around 'checking permissions' and 'open tables' code in mysql 5.1/xtradb 6?

Question

question comes up from some behavior i'm seeing.

we're using mysql 5.1.36, xtradb release 6 on an 8 core box. when dropping a database with a lot of tables, mysql takes a long time to check permissions for each table before dropping them. i understand this to be normal behavior, at least with recent versions of mysql. however, when doing this, all other queries on the database are blocking in the 'open table' state. top shows that 1 of the cores is pegged at 100%, and the other cores are not doing anything.

is this expected behavior? is there a mutex around the checking permissions and opening tables code?

thanks!

Answer 1

Yes, there is a mutex around opening/closing tables: http://www.mysqlperformanceblog.com/2009/06/16/slow-drop-table/