I am running WPMU with about 700+ blogs for a school district. I have noticed a huge spike in CPU utilization. We use only 4 plugins: WP-Gallery Remote, Google Translator, Podpress, and Events Calendar which may or may not be activated on each blog.
We are getting spikes from 2500 Mhz to 3500 Mhz. We are using Ubuntu Server and running it on a VMware server. The average during the school day is about 2600 Mhz and drops to near 200Mhz after 12pm until school starts the next day.
Because it is VM, we can give it more power but we are wondering if something else is going on that is causing the spikes during the day. We have other servers that hardly use so much power. One other thing of note: Each school website runs on Deki Wiki and utilizes Deki's built in RSS reader for displaying recent posts from teacher blogs on the school websites. So each time someone loads the Staff Pages from the school website, it hits the WPMU server and loads the Recent RSS feed items from the teachers blog. There can be anywhere from 12-20 RSS feeds it is processing when the staff page loads from the WPMU server.
Is this normal? Does WPMU require this much power for the larger sites? IF not, what can I do to cut down on the server CPU use?