We have been performance testing Moodle 2.5.2 at the OU, in preparation for deploying it in December. Here is a very brief summary of what we found.
Our test script tests the most common pages our students user, something like
- Visit course page
- Visit some resources
- Visit some forum threads
- Make a forum post
On the test hardware, Moodle 2.4.3 (the version we are currently running) was giving 0.33s average page-load times.
Our initial run with Moodle 2.5.2 gave 0.41s.
The basic issue there is that there are a lot of new caches, which default to being stored on disc in moodledata. In a clustered environmant, moodledata is on a networked file system, so quite slow.
So, as expected, we had to re-configure most of the new caches to use memcache. The singificant change came from moving the pluginlist cache to memcache. That brought the average times down to 0.36s. None of the other caching changes made a measureable difference.
That is about where we are at. We are going to have to live with our 2.5.x being 10% slower than 2.4.x.
Note that we are using Eric Merrill's clustered memcache implementation: MDL-42071 for some of the caches. (Thanks Eric.) However, it seems to be fractionally slower than the local memcache hack we were using before. We don't know why. If we can work out what is going on there, we will post in the tracker issue. It is still much faster than non-clustered memcache for read-heavy caches.
(As an aside, I think our results reinforce my point that in the testing that HQ do - e.g. http://docs.moodle.org/dev/Moodle_2.6_release_notes/Performance_tests - they really need a set-up with moodledata on a different box from their web server.)
Also, I should point out that I am just posting these results. I have not done any of the work to generate them.