https://bugs.freedesktop.org/show_bug.cgi?id=38800
--- Comment #15 from Simon Farnsworth simon.farnsworth@onelan.co.uk 2011-07-05 09:56:41 PDT --- Redoing my benchmarking with the resolution knowledge in mind:
Whatever resolution I choose, perf top shows me that 50% of my used CPU time is spent in r600_fence_finish from the r600g DRI driver.
At 1920x1200, I see my test program using approximately 27% CPU, and I have about 80% idle time across both cores of the Fusion APU.
These numbers are unchanged at 1024x768.
I also see about 5% of my used CPU time in radeon_fp_native_mode from the kernel driver; again, this is resolution independent.
I'm forced to conclude that it's not CPU-side slowdown - is there any way (like Intel's intel_gpu_top and intel_gpu_dump) to see roughly what the GPU is up to? Or is my best bet at this point to instrument something so that I can see the GPU command stream (where?), and use http://developer.amd.com/gpu_assets/r600isa.pdf to decode what's going on?