On Mon, Mar 11, 2013 at 6:49 PM, Ian Romanick <i...@freedesktop.org> wrote: > Once upon a time Matt Turner was talking about using pixman to accelerate > operations like this in Mesa. It has a lot of highly optimized paths for > just this sort of thing. Since it's used by other projects, it gets a lot > more testing, etc. It may be worth looking at using that to solve this > problem.
I think that using pixman or any other CPU-based solution is a waste of time (for dedicated GPUs at least). The OpenGL packing and unpacking can be implemented entirely on the GPU using streamout and TBOs, and we generally only want memcpy on the CPU side. That would also allow us to finally accelerate pixel buffer objects. For now, the easiest and fastest solution is to do a blit, which should cover swizzling and format conversions. We just need a lot of texture formats or do swizzling in the fragment shader. The destination of the blit can be a temporary texture allocated in GTT. The author of the patch (at least I think it's him) has actually started working on the blit-based solution for ReadPixels in st/mesa and the time spent in ReadPixels went from 2300 ms to 9 ms (so he can still use additional 7.6 ms for rendering and be at 60 fps). Marek _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
