@Fabien fyi, you should be able to-do a truncate table xf_css_cache as this is a drop & recreate.
Also, this implies your MySQL instance and webserver (likely apache in pre-fork mode) are on the same box. A fixed size php worker pool and a webserver which doesn't use fork is generally...
That sounds like CentOS 6.x, I would recommend a 3rd party repository like remi or ius
I was hoping to finish the final testing this week but haven't had a chance to yet, so end of next week at the earliest.