On Wed, Jun 25, 2014 at 12:46:57PM +0100, Siluvery, Arun wrote: > On 25/06/2014 12:14, Damien Lespiau wrote: > >On Wed, Jun 25, 2014 at 11:51:33AM +0100, Damien Lespiau wrote: > >>(This is not necessarily things one would need to take into account for > >>this work, just a few thoughts). > >> > >>One thing I'm wondering is how fitting the "size" parameter really is > >>when talking about inherently 2D buffers. > >> > >>For instance, let's take a Y-tiled texture with MIPLAYOUT_RIGHT, if we > >>want to allocate mip map levels 0 and 1, and use the ioctl "naively" to > >>reserve the LOD1 region in one go, we'll end up over allocating the > >>space below LOD1 (if I'm not mistaken that is). > >> > >>This can be mitigated by several calls to this fallocate ioctl, to > >>reserve columns of pages (in the case above, columns for the LOD1 > >>region). > >> > >>So, how about trying to reduce this ioctl overhead by providing a list > >>of (start, length) in the ioctl structure? > > > >One more thing to factor in is (let's assume one future hardware will > >support that): > >https://www.opengl.org/registry/specs/ARB/sparse_texture.txt > > > >So maybe what we really want is to be able to specify region of pages > >that could be specified in (x, y, width, height, stride) ? (idea popped > >when talking to Neil Roberts (I now have someone working on Mesa in the > >office). > > > > Hi Damien, > > Thank you for your comments and the idea to improve this ioctl. > At the moment start, end of a region are expected to be > page-aligned; ioctl can be modified to accept a multiple ranges and > modify them in one go to reduce the overhead of the ioctl. > > We can define how we want to specify multiple ranges, if userspace > can provide the list as (start, end) pairs kernel can directly use > them but what would be the preferred way from the user point of > view? That's a good question to ask a GL team. In the light of sparse textures I think the region idea would be better. We would need to define what the coordinates mean, for instance: - 2D view of the buffer, and the kernel takes care of translating what it means for the underlying pages? - See the buffer object as an array of pages, and those numbers define a region of pages. -- Damien _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
