Am 31.07.2014 um 11:57 schrieb Michel D?nzer: > On 31.07.2014 18:52, Christian K?nig wrote: >> Am 31.07.2014 um 11:43 schrieb Michel D?nzer: >>> From: Michel D?nzer <michel.daenzer at amd.com> >>> >>> Signed-off-by: Michel D?nzer <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.
Forget what I've wrote, we do this handling by letting the driver copy the bitmap content to a staging texture. All other use case indeed use PIPE_USAGE_STAGING. Christian.
