Hi Axel, Using DCC for scanout surfaces is problematic because as far as I understand the display hardware does not support it. We could solve that partially by decompressing when displaying.
However, the X server can also use these surfaces as a front buffer and for that case we cannot just use decompression without performance regressions for decompressing often. Furthermore, when using such a surface as back buffer, we would still need a single decompression before displaying it. It really depends on the application whether that improves performances or regresses it. For example, Xonotic regresses for me if I enable DCC for scanout surfaces. Yours sincerely, Bas Nieuwenhuizen On Mon, Oct 12, 2015 at 10:27 PM, Axel Davy <axel.d...@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@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. > > For dx9 apps, it seems the applications do render a lot of draw calls to the > backbuffer directly. > Likely having the backbuffer compressed with DCC (after it's been cleared), > and then decompressing > before sending it should - I guess - be faster than keeping it uncompressed. > I don't know for gl apps, but I guess it's the same than dx9. > > I tested the current serie, and it seems to boost some apps. > > Yours, > > Axel _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
