[quote]If you're high in 'user', then you might find that you've not got your web server tuned adequately and it's killing the rest of the server.[/quote]
We also have this issue of high user CPU load when submitting assignments. We had 33 users online of which around 20 were uploading small Word documents for "Assignment - upload a single file" type submission.
Our setup is:
4 core CPU
PHP 5 / mySQL 5
RAM is only 3GB used and no swap at all, but our CPU usage and overall load is very high - it got to over 20 just now.
We anticipate much higher usage from our Moodle config, but are concerned that when users are all submitting files the load grinds the box to a halt.
What aspects of tuning the web server could address this specific issue?