Phoronix: Linux 3.12 Can Change AMD's Catalyst Performance
Due to a change found in the Linux 3.12 kernel, the AMD Radeon GPU performance is a lot faster with the open-source driver for certain configurations and the Nouveau driver performance is also faster depending upon the CPU and GPU. Now the latest in comparing the Linux 3.11 and 3.12 kernel performance, I can confirm some small performance changes with the binary Catalyst driver.
Ignoring the issue of which governor is in use, I actually have a question for Marek and Alex... R600g saw jumps of anywhere between 7% and like 50% with this governor change. Catalyst didn't. All other things being equal, including the card being used and only changing the driver... why is R600g so CPU-tempermental? I know that Gallium has overhead, and that it was a point of concern originally, but I thought the developers found ways to make the overhead be negligible?
If its not the Gallium-architecture, then it seems like the open source driver is leveraging the CPU in ways Catalyst isn't, in which case the question becomes: Whats being shoved to the CPU under R600g that Catalyst is having the GPU do?
Due to the CPUfreq changes within Linux 3.12, depending upon the GPU, CPU, governor, and OpenGL workload, the performance can be improved compared to Linux 3.11 and prior. For the quick Catalyst testing done this morning, the Intel Core i7 4770K Haswell system was again used and an AMD Radeon HD 7950 graphics card
The effect of the governor change on SI is interesting in its own right, but perhaps you should have stayed consistent with the earlier investigations by, say, using the same HD 6950 .... and then afterwards (or simultaneously) added on a look at the SI hardware.