On Wed, May 25, 2022 at 04:22:48PM +0200, Christian König wrote: > Am 25.05.22 um 16:15 schrieb Daniel Stone: > > Hi, > > > > On Wed, 25 May 2022 at 15:07, Simon Ser <contact@xxxxxxxxxxx> wrote: > > > On Wednesday, May 25th, 2022 at 15:51, Daniel Vetter <daniel@xxxxxxxx> wrote: > > > > > You can add that to the list of reasons why compositors need to stop > > > > > using buffers with unsignaled fences. There's plenty of other reasons > > > > > there already (the big one being that otherwise slow clients can slow > > > > > down the compositor, even if the compositor uses a high priority context > > > > > and the HW supports preemption). > > > > > > > > Yeah that's tbh another reason why I think we shouldn't do umf as a > > > > transparent thing - compositors need to get better anyway, so we might as > > > > well take this as a chance to do this right. > > > As a compositor dev, I agree -- we should definitely be smarter about > > > this. Note, it would help a lot to have a good way to integrate the > > > waits into a poll(2) event loop. > > The same holds for Weston. We're currently working through a bunch of > > internal infrastructure to be able to handle this. Mutter (aka GNOME) > > is also really well-placed to be able to do this. > > > > Having pollable waits would be really useful, but I don't think it's > > essential. In my strawman I'm just waking up at the usual > > just-before-repaint point and checking; if it doesn't make it for this > > frame then we'll wait for the next frame. If someone submits buffers > > which take 4 repaint periods to clear then we'll have 3 'unnecessary' > > wakeups, but given the GPU is already slammed then it's not an > > efficiency problem I don't think. (I don't know if all the other > > compositor people share this view.) > > Oh, well you should already have pollable waits, at least on DMA-buf. > > If you are saying you want to have that for drm_syncobj timelines as well > then that's certainly something we could do. The pollable wait isn't enough because the client could keep issuing more rendering. So what you actually want is - dma-buf export to get a sync_file (should land any minute now) - poll on that (it works, as it doesn on dma-buf) - tell egl to no do implicit sync or (maybe better) just have a vk renderer in your compositor But interim you can poll on the dma-buf and it'll dtrt for at least cooperative clients already. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
