On Tue, Dec 07, 2021 at 06:32:06PM +0100, Karol Herbst wrote: > On Tue, Dec 7, 2021 at 10:52 AM Christian König > <christian.koenig@xxxxxxx> wrote: > > > > Am 06.12.21 um 19:37 schrieb Dan Moulding: > > > On 04.12.21 17:40, Stefan Fritsch wrote: > > >> Hi, > > >> > > >> when updating from 5.14 to 5.15 on a system with NVIDIA GP108 [GeForce > > >> GT 1030] (NV138) and Ryzen 9 3900XT using kde/plasma on X (not wayland), > > >> there is a regression: There is now some annoying black flickering in > > >> some applications, for example thunderbird, firefox, or mpv. It mostly > > >> happens when scrolling or when playing video. Only the window of the > > >> application flickers, not the whole screen. But the flickering is not > > >> limited to the scrolled area: for example in firefox the url and > > >> bookmark bars flicker, too, not only the web site. I have bisected the > > >> issue to this commit: > > >> > > >> commit 3e1ad79bf66165bdb2baca3989f9227939241f11 (HEAD) > > > I have been experiencing this same issue since switching to 5.15. I > > > can confirm that reverting the above mentioned commit fixes the issue > > > for me. I'm on GP104 hardware (GeForce GTX 1070), also running KDE > > > Plasma on X. > > > > I'm still scratching my head what's going wrong here. > > > > Either we trigger some performance problem because we now wait twice for > > submissions or nouveau is doing something very nasty and not syncing > > it's memory accesses correctly. > > > > Attached is an only compile tested patch which might mitigate the first > > problem. > > > > But if it's the second then nouveau has a really nasty design issue here > > and somebody with more background on that driver design needs to take a > > look. > > > > Ben mentioned a few times that fences might be busted but we all have > no idea what's actually wrong. So it might be that your change is > indeed triggering something which was always broken or something else. Description sounds a bit like we're doing a clear before Xorg has had a chance to copy the pixmap to the frontbuffer perhaps? That would point to a fencing issue in userspace, and somehow ignoring fences ensures that the Xorg copy/blt completes before we get around to clearing stuff. I'm assuming we're rendering with glamour, so is nouveau relying on kernel implicit sync or doing it's own fencing in userspace? -Daniel > > > Please test if that patch changes anything. > > > > Thanks, > > Christian. > > > > > > > > Cheers, > > > > > > -- Dan > > > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
