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

[Marek Olšák]

On Mon, Oct 12, 2015 at 10:27 PM, Axel Davy <axel.davy at ens.fr> wrote:
> On 12/10/2015 17:05, Bas Nieuwenhuizen 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.
>>
>> 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.
>>
>> Do we still want patch 6 and 7 or should I drop them until we have an
>> actual user?
>>
>> Yours sincerely,
>> Bas Nieuwenhuizen
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
> Hi,
>
> I think it would be better perf wise to not disable DCC for the backbuffer
> (which
> is both shared and scanout currently). Decompressing anything that needs to
> be decompressed
> in flush_resource seems to me a good idea.

Bas found out that DCC decompression decreases performance and might
make the performance worse than without DCC. Eliminating fast clear is
typically pretty fast, DCC decompression is not.

That said, I haven't done any testing by myself to be able to say what
is and isn't good, so take it with a grain of salt.

Marek