I'm getting severely slowed down performance under Linux (Ubuntu 12.04 64bit) with HD 7790 Catalyst Performance Driver. It ran fine under Windows on the same GPU (about 4 to 8 times faster).
When I tried profiling with CodeXL - the slow down went away. I then realized that setting CL_QUEUE_PROFILING_ENABLE made it run a lot faster, just like under Windows.
Since it's a 7790, I installed the driver from here http://support.amd.com/us/kbarticles/Pages/RadeonHD7790CatalystPerformanceDriver.aspx
I later ran the 7xxx Catalyst 13.4 installer with --force.
I can't reproduce this problem on another PC with a HD 7870 with 13.4. Only on the HD 7790.
Yeah, I saw the special release for 7790...but I think it is more from the gaming side...
So, from what I understand -- you have a problem with both the special driver for 7790 and also for the generic 7xxx series driver. Is that right?
Can you post a quick case for reproduction here?