In all my days at working at MySQL the
LOCK_open mutex have always been a
key mutex to understand, now that I'm
working on scalability improvements of
the server it's as important to change
this mutex into something less contentious.

So last week I finally decided to start
thinking about how we can resolve this
mutex which is at the heart of the MySQL
Server. In principle the idea is that
LOCK_open has been used to protect a
hash table with all the open tables in
the MySQL Server. However it has been
used for many other purposes as well.
So it's not trivial to move around it.

However the main scalability problem
with LOCK_open is the hash lock it
provides. So what to do about it?

My current thinking is that a four-thronged
approach will do the trick.

1) Divide and concquer, perform the …