[Discuss] issue with mysql in a VM on Ubuntu 14.04.4 LTS

[smallm at sdf.org (Mike Small)]

Jerry Feldman <gaf at blu.org> writes:

> My friend got back with some information.
>
> This is a dedicated web server VM (virtual machine) running Ubuntu 14.04
> LTS.  This is only running a single site, yet CPU usage reaches 100%
> with only a few simultaneous users viewing the site.  Looking deeper it
> appears that MySQL is using the majority of the CPU resources.  When
> this happens, the hosted website is extremely slow or unavailable. 
> Restarting the Apache and MySQL services temporarily helps, but a reboot
> seems to have a longer effect. 
>
> In troubleshooting the issue we have made several changes to various
> conf files to increase buffers, caches, memory limitations, etc.

What about DB level stuff?  Can you narrow it to a particular query?
Have indexes changed?  Does MySQL have some concept of statistics that
help the query optimizer and can get stale?