[Mesa-dev] [PATCH v2 6/7] radeonsi: Add DCC decompress.

[Marek Olšák]

On Mon, Oct 12, 2015 at 5:05 PM, Bas Nieuwenhuizen
<bas at basnieuwenhuizen.nl> wrote:
> Hi Marek,
>
> Thanks for the quick review.
>
> I do not think I understand the sharing semantics. We currently have
> fast clear for scanout surfaces with the CMASK and eliminate it on
> flush resource. I would think we could do that similarly with DCC fast
> clear. Both require a flush_resource after modifying the resource
> before other applications can use it.

I meant not using fast clear for shared textures, so flush_resource
would be a no-op. We can't use fast clear for shared textures, because
we can't communicate clear color changes between processes.

>
> Furthermore, if we disable DCC for image stores, we also need to
> communicate that. We could leave DCC enabled for sampling as long as
> the DCC buffer stays in decompressed state. But we would need to
> communicate that DCC should not be used anymore for rendering.

Image stores are the only big problem preventing DCC sharing. If we
share textures with DCC enabled, we can't disable it, which means we
have to decompress before image stores are used, which can result in
performance that is worse than without DCC.

>
> Do we still want patch 6 and 7 or should I drop them until we have an
> actual user?

I'd like to keep them and put them in a branch somewhere. I'll be
maintaining them.

Marek