> Also, it sounds like you aren't using Mesa, but use AMD closed stack instead. Don't do that.
This is true, but needs a caveat: a lot of work has gone into improving Mesa and the rest of the Linux graphics stack recently and it's now pretty much caught up (performance-wise) to the proprietary AMD drivers. However, that's only happened in the past 6 months or so, so if you're not using a rolling-release distro like Arch or Gentoo you might still be better off with the proprietary drivers until your distro catches up.
Most stable distros including Ubuntu have repositories for backports, that provide recent Mesa. So I'd say there is no need to use closed AMD driver at all, unless someone needs full OpenCL or compat profile.
This is true, but needs a caveat: a lot of work has gone into improving Mesa and the rest of the Linux graphics stack recently and it's now pretty much caught up (performance-wise) to the proprietary AMD drivers. However, that's only happened in the past 6 months or so, so if you're not using a rolling-release distro like Arch or Gentoo you might still be better off with the proprietary drivers until your distro catches up.