I'm using Moodle 2.5 and over the weekend it was seriously laggy. The Moodle instance runs on a remote VM in somebody's cloud somewhere, so I'm not entirely certain if the issue lies with the vmware hypervisor it's sitting on or if the problem lies with the database.
The first thing I tried of course was rebooting the server.
When I login via SSH it takes a while to load the ubuntu 12.04.01 server stats screen and then the bash shell prompt after that. The System load reads 2.89 when the server stats screen comes up.
Over the weekend I tried to login, there was nobody on the site except me and it was still really laggy with the browser timing out. I also tried running `ps aux | sort -rk 3,3 | head -n 6` during times of lag to see which processes were using the most CPU time. Mysqld comes up rather often as does Apache.
I also tried running mytop to see if the threads hitting the database were stuck. Some of the queries sleep and get stuck with their time field getting rather high and turn grey in mtop.
I cleared out the mdl_sessions table and that gave me some success, but it still runs really slow.
This is a massive issue because I need to setup some new courses this week, and synchronize some users over from our HR database.
We've been running Moodle 2.5 for a year straight now and haven't had any issues similar to this.
I checked the df and it looks a little bit full, we're using 77% of the space on / .