On Mon, Mar 9, 2020 at 11:21 AM Christian König <christian.koenig@xxxxxxx> wrote: > > Am 05.03.20 um 16:54 schrieb Jason Ekstrand: > > On Thu, Mar 5, 2020 at 7:06 AM Christian König <christian.koenig@xxxxxxx> wrote: > >> [SNIP] > >> Well as far as I can see this won't work because it would break the > >> semantics of the timeline sync. > > I'm not 100% convinced it has to. We already have support for the > > seqno regressing and we ensure that we still wait for all the fences. > > I thought maybe we could use that but I haven't spent enough time > > looking at the details to be sure. I may be missing something. > > That won't work. The seqno regression works by punishing userspace for > doing something stupid and undefined. > > Be we can't do that under normal circumstances. > > >> I can prototype that if you want, shouldn't be more than a few hours of > >> hacking anyway. > > If you'd like to, go for it. I'd be happy to give it a go as well but > > if you already know what you want, it may be easier for you to just > > write the patch for the cursor. > > Send you two patches for that a few minutes ago. But keep in mind that > those are completely untested. No worries. They were full of bugs but I think I've got them sorted out now. The v2's I'm about to send seem to work. I'm going to leave a Vulkan demo running all night long just to make sure I'm not leaking memory like mad. --Jason > > Two more questions: > > > > 1. Do you want this collapsing to happen every time we create a > > dma_fence_array or should it be a special entrypoint? Collapsing all > > the time likely means doing extra array calculations instead of the > > dma_fence_array taking ownership of the array that's passed in. My > > gut says that cost is ok; but my gut doesn't spend much time in kernel > > space. > > In my prototype implementation that is a dma_resv function you call and > get either a single fence or a dma_fence_array with the collapsed fences > in return. > > But I wouldn't add that to the general dma_fence_array_init function > since this is still a rather special case. Well see the patches, they > should be pretty self explaining. > > > 2. When we do the collapsing, should we call dma_fence_is_signaled() > > to avoid adding signaled fences to the array? It seems like avoiding > > adding references to fences that are already signaled would let the > > kernel clean them up faster and reduce the likelihood that a fence > > will hang around forever because it keeps getting added to arrays with > > other unsignaled fences. > > I think so. Can't think of a good reason why we would want to add > already signaled fences to the array. > > Christian. > > > > > --Jason >
