All of the below being said, I'm fine with landing things with a BACK_TO_BACK layout and then making the switch to one isl_surf per miplevel later if that's an easier path.
On Tue, May 9, 2017 at 8:45 AM, Jason Ekstrand <ja...@jlekstrand.net> wrote: > On Mon, May 8, 2017 at 11:10 PM, Pohjolainen, Topi < > topi.pohjolai...@gmail.com> wrote: > >> On Mon, May 08, 2017 at 04:51:35PM -0700, Jason Ekstrand wrote: >> > On Wed, May 3, 2017 at 2:22 AM, Topi Pohjolainen < >> topi.pohjolai...@gmail.com >> > > wrote: >> > >> > > Patches 1-17 are revision that >> > > >> > > - rework hiz on gen6 to use on-demand offset calculator allowing >> > > one to drop dependency to miptree structure and >> > > - rework all auxiliary surfaces to be created against isl directly. >> > > >> > > Patches 18 and 19 introduce new surface layout in ISL. This is called >> > > back-to-back and similar to layout ALL_SLICES_AT_EACH_LOD found in >> > > i965 for gen6 hiz and stencil. This layout stacks slices for each >> level >> > > after one and other, or back to back. All slices ate each lod is >> almost >> > > the same except that it places levels one and two side-by-side trying >> > > to preserve space. Back-to-back wastes a little more memory but aligns >> > > each level on page boundary simplifying driver logic. >> > > >> > >> > My primary gripe here is that you seem to have half-added back-to-back >> to >> > ISL. If this layout is a long-term thing, then we should add a new >> > ISL_DIM_LAYOUT_GEN6_BACK_TO_BACK layout and plumb your offset function >> > through isl_surf_get_image_offset_sa. Is this intended to be a >> permanent >> > solution? I think eventually, I'd like us to go with one surf per >> miplevel >> > (which is almost the same) but I can see how this is easier at the >> moment. >> > However, I think this works sufficiently well that I'm ok with doing the >> > back-to-back thing for a while. >> >> I thought about adding new layout type but couldn't decide which way is >> better. It is easy to buy your arguments in favor, and I'm happy to give >> it >> a go. >> If miptree per level is your number one choice, then lets go with that. > > > I said "one surf per miplevel". I see no reason why we need N miptrees. > > >> I just >> need to check a few things first about the actual solution. I would see >> something in these lines: >> >> 1) Add a dynamically allocated array of miptrees into miptree. This would >> contain miptree instance per level. >> >> 2) Still uses one buffer object containing space for all levels. The >> instances >> in the array would either have their ::bo pointer zero or pointing to >> the >> parent ::bo. In both cases ::offset would point the start of the level. >> > > Yes > > >> 3) Instances in the array are not reference counted and therefore deleted >> simply by deallocating the malloced chunk underneath. >> > > If we have one isl_surf per miplevel and not a miptree per level, then I > don't think this is an issue. > > >> 4) Add similar dynamically allocated array of intel_miptree_aux_buffer >> instances for hiz. Here also use one ::bo which would need to added to >> miptree I think cause there ins't one in miptree. Or perhaps add the >> array of aux buffers to aux buffer? >> > > Looking at intel_miptree_aux_buffer, I think what we would end up with is > an array of aux_buffers > > >> 5) ISL doesn't need to know about this and hence we would add the total >> space >> calculator along with ::offset initialization in i965 (brw_tex_layout, >> I think). >> > > That's fine. We already do that in Vulkan with anv_surface. ::offset > calculation can be done easily enough by just adding sizes. > > >> 6) In Vulkan <-> GL interop, we'd pass single level arrays only as ISL >> didn't >> know about back-2-back. Or we simply don't care about gen6 as Vulkan >> doesn't support it anyhow? >> > > Yeah, we don't care about gen6. > > --Jason >
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