How to measure current load of MySQL server?

Question

How to measure current load of MySQL server? I know I can measure different things like CPU usage, RAM usage, disk IO etc but is there a generic load measure for example the server is at 40% load etc?

Answer 1

mysql> SHOW GLOBAL STATUS;

Found here.

Answer 2

The notion of "40% load" is not really well-defined. Your particular application may react differently to constraints on different resources. Applications will typically be bound by one of three factors: available (physical) memory, available CPU time, and disk IO.

On Linux (or possibly other *NIX) systems, you can get a snapshot of these with vmstat, or iostat (which provides more detail on disk IO).

However, to connect these to "40% load", you need to understand your database's performance characteristics under typical load. The best way to do this is to test with typical queries under varying amounts of load, until you observe response times increasing dramatically (this will mean you've hit a bottleneck in memory, CPU, or disk). This load should be considered your critical level, which you do not want to exceed.