On 19.07.2014 00:47, Christian König wrote:
Am 18.07.2014 05:07, schrieb Michel Dänzer:
[PATCH 5/5] drm/radeon: Use VRAM for indirect buffers on >= SI
I'm still not very keen with this change since I still don't understand the reason why it's faster than with GTT. Definitely needs more testing on a wider range of systems.
Sure. If anyone wants to give this patch a spin and see if they can measure any performance difference, good or bad, that would be interesting.
Maybe limit it to APUs for now?
But IIRC, CPU writes to VRAM vs. write-combined GTT are actually an even bigger win with dedicated GPUs than with the Kaveri built-in GPU on my system. I suspect it may depend on the bandwidth available for PCIe vs. system memory though.
I've made a few tests today with the kernel part of the patches running Xonotic on Ultra in 1920 x 1080.
Without any patches I get around ~47.0fps on average with my dedicated HD7870.
Adding only "drm/radeon: Use write-combined CPU mappings of rings and IBs on >= SI" and that goes down to ~45.3fps.
Adding on to off that "drm/radeon: Use VRAM for indirect buffers on >= SI" and the frame rate goes down to ~27.74fps.
Hmm, looks like I'll need to do more benchmarking of 3D workloads as well.
Alex, given those numbers, it's probably best if you remove the "Use write-combined CPU mappings of rings and IBs on >= SI" change from your tree as well for now.