Bad graphics performances with femtovg on Linux 6.7.0 with nouveau drivers and mesa 23.3.3 on Wayland

[abique]

Hi,

I can observe that llvm-pipe's thread pool is blasting my cpu for not doing much actually while all my gnome desktop is smooth.

Linux knot 6.7.0-arch3-1 #1 SMP PREEMPT_DYNAMIC Sat, 13 Jan 2024 14:37:14 +0000 x86_64 GNU/Linux
Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz
01:00.0 VGA compatible controller: NVIDIA Corporation TU116 [GeForce GTX 1660 SUPER] (rev a1)
mesa 23.3.3-1
archlinux up to date

I'm compiling slint with:

slint = { version = "1.3.2", default-features = false, features = [
        "compat-1-2",
        "std",
        "serde",
        "backend-winit",
        "backend-winit-wayland",
        "backend-winit-x11",
        "renderer-femtovg",
] }

I wonder if there are some problems in femtovg maybe?

[tronical]

That's not good :(. Are there animations running? Are you using X11 or Wayland? Could you try with the master branch from git?

[abique]

It is on Wayland, I have one image that I rotate continuously, but I think even without it the problem shows up.

[abique]

That's not good :(. Are there animations running? Are you using X11 or Wayland? Could you try with the master branch from git?

How to tell cargo to use slint's git branch?

[abique]

I've switched to skia and it works fine now.

[tronical]

That's not good :(. Are there animations running? Are you using X11 or Wayland? Could you try with the master branch from git?

How to tell cargo to use slint's git branch?

Something like this:

slint = { version = "1.4.0", git = "https://github.com/slint-ui/slint", branch = "master" }

(and the same for slint-build if you're using that)

[tronical]

The FemtoVG renderer isn't thaaat crazy in what it does, but it's a little heavy on the fragment shader side. Perhaps this triggers a bad code path in the nouveau drivers :(. If it works well with Skia, then I'm not sure that there's much that we can do in Slint itself :-(.

Unless something actionable surfaces, I'll close this for now. Would be nice to switch to a different default renderer in the future.

[abique]

@tronical I think I'm happy with skia :+1:

[abique]

Do you want me to give a try to the master branch or it isn't needed?

[tronical]

If you have time, that would be greatly appreciated :)

[abique]

OK

[abique]

On the first run only, gnome said that the window isn't responding for a while. This is maybe related to a shader cache? Could it be that the 1.3.2 version did overflow the shader cache and needed to recompute everything all the time?

Then on every run, the linear gradient is incorrectly rendered. I get this on the console:

MESA: error: ZINK: failed to choose pdev
libEGL warning: egl: failed to create dri2 screen

While it seems to work a bit better, it stills blows the cpu in llvm pipe even if nothing happens and nothing needs to be redrawn.