Hello. I'm managing a RedHat VPS that is used for hosting a group of websites and I've been having some memory usage issues lately.

I've spoken with my hosting company and looked at some diagnostics and MySQL has a stranglehold on the system's memory. I have a total of 13 active databases (not counting the default "mysql" database), which are taking up 3% memory each. However, when I run the "top" command I see 18 instances of mysqld, each taking 3% memory.

My main question is about what exactly an instance of mysqld in the top listing entails-I thought it was one for each active database, but the are 5 more instances of mysqld than I have databases. Any idea what these are, and if so can I turn them off without losing any functionality?

Any help is greatly appreciated. Thanks.

I think your interpretation of the mysqld is incorrect. When mysqld starts, it does not create an instance for each database. It starts and listens for database connections, when a connection is requested mysqld forks and creates a new process to handle that connection. If you see 18 processes, then likely you have 17 active mysql connections. Some may be from users ODBC connections, others could be command line mysql connections. My system currently shows 30 mysqld processes, each with 2.7% of the system memory. Keep in mind that one single application instance could have several open odbc connections to the database, each will have it's own mysqld. One of our applications frequently has 4 simultaneous databases open at once.

-Nite

http://www.itslot.com/calculate_mysql_memory -> Calculate MySQL memory usage.

http://emergent.urbanpug.com/?p=61 -> Reduce MySQL memory Footprint.

Unless you are seeing degraded performance with the sites, why are you concerned about memory usage? Are the sites slow or unresponsive? I don't recall seeing anything like that in your post, only the concern that each process is using 3% of memory.

Yes, degraded performance with the sites is the memory usage problem I was referring to-sorry for not being specific.

Altering the server variables as mentioned has apparently solved the problem-thanks for the help.