glGetTexImage with PBO is not accelerated on Gallium
Submitted by Andrew Wesie
Assigned to mes..@..op.org
Created attachment 141925 Mesa patch for accelerated PBO texture downloads
In May 2016, a patchset (https://lists.freedesktop.org/archives/mesa-dev/2016-May/117294.html) added acceleration for glReadPixels PBO downloads. Support for glGetTexImage and friends was left as future work.
As part of my efforts to find and fix performance hot spots in Wine's directx layer, I submitted patches to support texture downloads using PBOs in Wine. Unfortunately, on Mesa, this does not improve performance for the reason stated above.
It would be great if Mesa could add support for accelerated texture downloads using PBOs. In order to facilitate this, I put together a patch based on glReadPixels and a test case in piglit. I am not familiar with the Mesa code or conventions, but the patch passes the test case so it is probably close to correct.
Patch 141925, "Mesa patch for accelerated PBO texture downloads":