On Wed, Jan 28, 2015 at 10:50:18AM +0100, Daniel Vetter wrote: > On Wed, Jan 28, 2015 at 09:23:46AM +0000, Chris Wilson wrote: > > On Wed, Jan 28, 2015 at 10:22:15AM +0100, Daniel Vetter wrote: > > > On Mon, Jan 26, 2015 at 09:08:03AM +0000, Chris Wilson wrote: > > > > On Mon, Jan 26, 2015 at 08:52:39AM +0100, Daniel Vetter wrote: > > > > > I think the problem will be platforms that want full explicit fence (like > > > > > android) but allow delayed creation of the fence fd from a gl sync object > > > > > (like the android egl extension allows). > > > > > > > > > > I'm not sure yet how to best expose that really since just creating a > > > > > fence from the implicit request attached to the batch might upset the > > > > > interface purists with the mix in implicit and explicit fencing ;-) Hence > > > > > why I think for now we should just do the eager fd creation at execbuf > > > > > until ppl scream (well maybe not merge this patch until ppl scream ...). > > > > > > > > Everything we do is buffer centric. Even in the future with random bits > > > > of memory, we will still use buffers behind the scenes. From an > > > > interface perspective, it is clearer to me if we say "give me a fence for > > > > this buffer". Exactly the same way as we say "is this buffer busy" or > > > > "wait on this buffer". The change is that we now hand back an fd to slot > > > > into an event loop. That, to me, is a much smaller evolutionary step of > > > > the existing API, and yet more versatile than just attaching one to the > > > > execbuf. > > > > > > The problem is that big parts of the world do not subscribe to that buffer > > > centric view of gfx. Imo since those parts will be the primary users of > > > this interface we should try to fit their ideas as much as feasible. Later > > > on (if we need it) we can add some glue to tie in the buffer-centric > > > implicit model with the explicit model. > > > > They won't be using execbuffer either. So what's your point? > > Android very much will user execbuffer. And even the in-flight buffered > svm stuff will keep on using execbuf (just without any relocs). So still buffer-centric and would benefit from the more general and more explict fencing rather than just execbuf. If you look at the throttling in mesa, you can already see a place that would rather create a fence on a buffer rather than its very approximate execbuf tracking. > And once we indeed can make the case (plus have the hw) for direct > userspace submission I think the kernel shouldn't be in the business of > creating fence objects: The ring will be fully under control of > userspace, and that's the only place we could insert a seqno into. So > again the same trust issues. No buffers, no requests, nothing for the kernel to do. No impact on designing an API that is useful today. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
