I think that glxgears isn't exactly the best software to use when comparing drivers.
Have you tried out Tomb Raider and its benchmark?

Ok, I missed some important things as I see now :).

1. I don't even start steam with mesa, less the Tomb Rider (steam.sh runs, but no GUI is loading)
2. felt like HW rendering with Mesa was not simply there (but got direct rendering: yes in glxinfo), even YT videos had lower framerate (not that they need HW rendering!), If game started (unlike Tomb Rider), I didn't get past menu and framerate was very low (like 1 FPS at best)
I used padoka ppa which is now Mesa 13.1 with same result in all described aspects

To me it seems like I forget some extremely important detail like setting DRI in XOrg or something else? I am not that familiar with Mesa, but googling didn't really help me understand what might be the problem (before when trying Padoka PPA, I was able to get nice results on AMD 280x though with no extra steps).

Thanks a ton mirv, I uninstalled AMDGPU PRO again and installed Padoku PPA.

glxinfo: [http://pastebin.com/de2npDgh](http://pastebin.com/de2npDgh)
Xorg.0.log: [http://pastebin.com/m0gWiHNF](http://pastebin.com/m0gWiHNF)

Glxinfo looks good to me (showing 13.1 devel Mesa + direct rendering - yes. XOrg I am not that sure about, see several errors but I am unable to tell if they are 'sorta ok'.

This one looks sorta explain why there is poor performance though:

[    14.330] (EE) AIGLX: reverting to software rendering

Thanks again for any ideas!

Not sure about *buntu based but on Mageia (RedHat) you need to remove a few libs from the steam folder.

libstdc++ and a few others.

Might be wise to wait for a *buntu guy to clarify first though

Edit:

To clarify, that's to use Mesa.

Now I am utterly confused.

EE about fallback to software rendering is gone from todays Xorg.0.log.

vblank_mode=0 glxgears 
ATTENTION: default value of option vblank_mode overridden by environment.
51401 frames in 5.0 seconds = 10279.994 FPS
52630 frames in 5.0 seconds = 10525.814 FPS
53456 frames in 5.0 seconds = 10691.200 FPS

glxinfo | grep LLVM
    Device: AMD POLARIS10 (DRM 3.3.0 / 4.8.0-040800rc5-generic, LLVM 4.0.0) (0x67df)
OpenGL renderer string: Gallium 0.4 on AMD POLARIS10 (DRM 3.3.0 / 4.8.0-040800rc5-generic, LLVM 4.0.0)

That's after one more reboot (I was rebooting after AMDGPU PRO driver uninstall, and after Mesa Padoka PPA + upgrade install).

Also Steam was fixed with following (renaming some obsolete libraries ):

[http://askubuntu.com/questions/762219/steam-wont-start-on-ubuntu-16-04](http://askubuntu.com/questions/762219/steam-wont-start-on-ubuntu-16-04)

Tomb Rider runs, there are some texture glitches, but I guess that's as far as we can get! :)

Thanks a TON to all you guys, I'd not be able to move forward without your help!