On Fri, 14 Jun 2019 at 23:22, Rob Herring <robh@xxxxxxxxxx> wrote: > > On Wed, Jun 12, 2019 at 6:55 AM Tomeu Vizoso <tomeu@xxxxxxxxxxxxxxx> wrote: > > > > On Mon, 10 Jun 2019 at 19:06, Rob Herring <robh@xxxxxxxxxx> wrote: > > > > > > The midgard/bifrost GPUs need to allocate GPU memory which is allocated > > > on GPU page faults and not pinned in memory. The vendor driver calls > > > this functionality GROW_ON_GPF. > > > > > > This implementation assumes that BOs allocated with the > > > PANFROST_BO_NOMAP flag are never mmapped or exported. Both of those may > > > actually work, but I'm unsure if there's some interaction there. It > > > would cause the whole object to be pinned in memory which would defeat > > > the point of this. > > > > > > Issues/questions/thoughts: > > > > > > What's the difference between i_mapping and f_mapping? > > > > > > What kind of clean-up on close is needed? Based on vgem faults, there > > > doesn't seem to be any refcounting. Assume userspace is responsible for > > > not freeing the BO while a page fault can occur? > > > > Aren't we taking a reference on all BOs that a job relates to and > > unreferencing them once the job is done? I would think that that's > > enough, or am I missing something? > > No, I think we're fine. > > > > What about evictions? Need to call mapping_set_unevictable()? Maybe we > > > want these pages to be swappable, but then we need some notification to > > > unmap them. > > > > I'm not sure there's much point in swapping out pages with lifetimes > > of a few milliseconds. > > The lifetime is *forever* though. If we don't allow swapping, then the > heap is grow only until the FD is closed. IIRC, the maximum size is on > the order of 1GB. Seems like you'd want to shrink it with some > trigger. I thought that the lifetime of the *contents* of the heap was that of the job chain that wrote them? Otherwise, only the GPU would know what can be discarded. Cheers, Tomeu _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
