[Mesa-dev] [PATCH 2/2] r600g/radeonsi: Prefer VRAM for CPU -> GPU streaming buffers

[Michel Dänzer]

On 31.07.2014 18:52, Christian König wrote:
> Am 31.07.2014 um 11:43 schrieb Michel Dänzer:
>> From: Michel Dänzer <michel.daenzer at amd.com>
>>
>> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
> 
> At least for PIPE_USAGE_STREAM buffers that's a bad idea, cause they are
> used by VDPAU to read back to data to a CPU buffer and that's really
> slow from VRAM.

>From src/gallium/docs/source/screen.rst:

* ``PIPE_USAGE_DEFAULT``: Optimized for fast GPU access.
* ``PIPE_USAGE_IMMUTABLE``: Optimized for fast GPU access and the resource is
  not expected to be mapped or changed (even by the GPU) after the first upload.
* ``PIPE_USAGE_DYNAMIC``: Expect frequent write-only CPU access. What is
  uploaded is expected to be used at least several times by the GPU.
* ``PIPE_USAGE_STREAM``: Expect frequent write-only CPU access. What is
  uploaded is expected to be used only once by the GPU.
* ``PIPE_USAGE_STAGING``: Optimized for fast CPU access.

That reads to me like only PIPE_USAGE_STAGING is expected to provide fast
CPU reads.


-- 
Earthling Michel Dänzer            |                  http://www.amd.com
Libre software enthusiast          |                Mesa and X developer