[Mesa-dev] [PATCH 1/7] gallium: add pipe_blend_state::srgb_enable and the CAP

[Marek Olšák]

On Mon, Jun 12, 2017 at 9:51 PM, Jose Fonseca <jfonseca at vmware.com> wrote:
> How does this help exactly?
>
> Are applications actually rendering to the same FBO w/ and w/o SRGB
> decoding?
>
> Or is the problem here GL_SRGB_WRITE state getting spuriously dirtied by the
> application?
>
> And even if they do, why is toggling surface views in framebuffer state so
> expensive?
>
> I don't object per se, but it looks like an unusual thing to optimize for.
>

set_framebuffer_state is basically a memory barrier. We have different
caches between FB and textures and we have to flush them when a
texture is unbound from the framebuffer and set as a sampler view. To
keep thing simple, set_framebuffer_state is the barrier. When we
change the blend state, the barrier is avoided. Note that the barrier
makes set_framebuffer_state a function that is always GPU-bound.

Marek