In this blog post, I’ll look at MySQL and Linux context switches and what is the normal number per second for a database environment.

You might have heard many times about the importance of looking at the number of context switches to indicate if MySQL is suffering from the internal contention issues. I often get the question of what is a “normal” or “acceptable” number, and at what point should you worry about the number of context switches per second?

First, let’s talk about what context switches are in Linux. This StackOverflow Thread provides a good discussion, with a lot of details, but basically it works like this:  

The process (or thread in MySQL’s case) is running its computations. Sooner or later, it has to do some blocking operation: disk IO, network IO, block waiting on a mutex …